arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):259-267 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 259 original research article design and implementation of an arduino based light dependent alarm system h. ibrahim*, a. a. mohammed and i. a. aliyu (department of computer engineering, kaduna polytechnic, kaduna, nigeria) *corresponding author’s e-mail address: harunaebrahim@gmail.com article information submitted 10 november, 2018 revised 4 february, 2019 accepted 10 february, 2019 keywords: alarm arduino uno ldr microcontroller potentiometer abstract this paper is based on design and implementation of an arduino based alarm system which is capable of monitoring the illumination of the surrounding automatically. once the presence or absence of light is detected accordingly, a control device is activated which sends a sound alarm to a buzzer connected to the output of the system. waking up early from sleep has always become a challenge most especially after a very hectic and busy engagement during the previous day time, this makes waking up early the next morning to meet up with the activities of the day a challenge. the components used for carrying out this study include light dependent resistor, a control unit and an output buzzer unit. the ldr works on the principle of change of resistance based on the amount of luminous energy in its environment at that moment of time, once an illumination is detected, an arduino uno board was used to send a signal to the buzzer that generates sound when the intensity of light increases. the test conducted showed that the ldr resistance decreased as illuminance on the ldr increased; the illuminance ranges at which the buzzer was triggered was between 100-1000lux. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserve 1.0 introduction advancement in technology has made all aspects of life simpler and easier thereby making automated systems more preferred to manual systems (nikhil, 2016). automatic alarm systems are designed to alert an individual or group of individuals at specified times. the alarm system in this study uses sound and light devices. researchers have worked on techniques for light detection and sensing and had developed devices that offer excellent performance (busari et al., 2015). light is an electromagnetic radiation within a certain portion of the electromagnetic spectrum which is visible to the human eye and is responsible for the sense of sight (effend et al., 2014). the light sensor is a passive device that converts light energy into electrical signal that generates an output signal that is proportional to the intensity of the light (mavrya et al., 2012). the commonly used photo resistor is called cadmium sulphide light dependent resistor (ldr). mailto:harunaebrahim@gmail.com http://www.azojete.com.ng ibrahim et al.: design and implementation of an arduino based light dependent alarm system. azojete, vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 260 manual control of light is prone to errors and stressful. the introduction of automation and remote management solution for detecting light illuminations is vital and can be achieved by the used of programmed microcontroller. the alarm system in this article is designed to automatically detect the presence and absence of light. a buzzer is triggered once light, with illuminance between 100-1000lux, is detected. much effort and work have been done in this area of research but improvement on the drawbacks of past works is necessary in order to have maximum performance of their applications in domestic use which include: detection of the presence or absence of light, street light switching, security systems and as a triggered alarm system. some related works are therefore discussed. isah et al. (2015) designed an automatic street light control system. the work is based on ua741 operational amplifier which is configured as a schmitt trigger and a light dependent resistor. during the day, the ldr senses enough illumination and the street light goes off and comes on when there is darkness. a transistor is used as switch to provide the switching mechanism that activates the street lights. the transistor was not fully saturated and only switched on dc loads. this design overcame the challenge of streetlight system using a timer controller, and human intervention was completely removed. the drawback of this work is that discrete components were used in its implementation: this requires using many circuit components and thus not cost effective. similarly, an automatic street light control system was designed by sakshee (2013). this work exploits the working of a transistor, in saturation and cut-off region, to switch on and off the lights at the appropriate time with the help of an electromagnetically operated switch. it operates on a 12v dc supply and a photoconductive device whose resistance changes in proportion to light intensity. the work helped to reduce energy consumption, easy to operate and has low cost. the major drawback of this work is that the on and off timer controller circuit is easily affected during sunny or rainy days. mustafa et al, (2013) proposed an automatic street light control system using pic16f877a microcontroller. in the work, two sensors were used which are an ldr and a photoelectric sensor. the ldr is used to detect day/night time while the photoelectric sensor detects the movements on the street. the microcontroller is used as a brain, to control the street light system. the pic16f877a microcontroller used is not as flexible as arduino. arduino hardware components are cheaper in relation with the pic microcontroller, and the programming language is easy. arduino needs no separate compiler and programmer, and it also has greater academic applications because it is simple to learn. the objective of the study is to enable waking up from sleep early easier so as to meet up with responsibilities such as dropping of children in school and arriving in office on time a reality. with this study it makes meeting up with such responsibilities a reality. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 261 2. materials and methods 2.1 design of the arduino-based alarm system the arduino based alarm system using light sensor is designed in four working units which are the power supply unit, the ldr, the controller and the buzzer. the units are connected together to form a functional hardware system. the power supply unit powers the complete system. the second unit is the photo-sensor known as the light dependent resistor (ldr). the ldr resistance changes with the intensity of light. the ldr gives out an analog voltage when connected to vcc (5v), which varies in magnitude and is directly proportional to the intensity of the input light on it. the third unit is the arduino uno which serves as the control unit. the arduino, with its inbuilt adc (analog to digital converter) converts the analog voltage (from 05v) into digital voltage. thus, when there is sufficient light in its environment or on the surface of the ldr, the converted digital values are read from the ldr through the arduino. the buzzer is the last unit: it is connected to the arduino pin and produces sound as it is programmed. when the ldr detects a light beyond a certain threshold, the arduino triggers the buzzer and a sound is produced, but turned off when the intensity of light decreases. figure 1 shows the block diagram of the system and its component units. figure 1: block diagram of an arduino based alarm system. http://www.azojete.com.ng ibrahim et al.: design and implementation of an arduino based light dependent alarm system. azojete, vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 262 2.2 the software system in order to enable that the controller function appropriately, software that models the system operation is designed and implemented using c language. the flowchart is shown in figure 2. figure 2: the system flowchart. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 263 2.3 the hardware design the system hardware is implemented as shown in the figure 3: figure 3: circuit diagram of an arduino based alarm system the voltage out across the ldr and the variable resistor is implemented as shown in figure 4. figure 4: voltage divider between ldr and potentiometer. http://www.azojete.com.ng ibrahim et al.: design and implementation of an arduino based light dependent alarm system. azojete, vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 264 vout when light is detected; where: rldr is the resistance of the ldr, measured in ohm; vout is the output voltage from the voltage divider combination, measure in volt. vcc is the supply voltage , measure in volt. vout when light is not detected; vout = 4.95v it was deduced that, when light is detected, the resistance of the ldr decreases with a corresponding increase in voltage across the ldr as well as the variable resistor, and vice versa. figure 5 shows the light emitting resistor circuit. figure 5: the series connection between the miniature indicator light emitting resistor and a ballast resistor. the value of the current limiting resistor can be calculated from figure 5. the formula is shown below: ��im ���im � �⢈оᗐ⢈ 벨 ���� �⢈�� ⢈оᗐ⢈� (1) ��ૡ � 4.99 벨 �t��v r d r ⢈ � ��� � ��� � (2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 265 where; vs � power supply voltage vf � ledforward voltage /voltage drop across led i � desired current of led r � current limiting or ballast resistordesired current of led note: miniature indicator led (red led) from the manufacturer datasheet has the following parameters: i � 2tma led voltage � �.8v � 2v therefore, from equation (2), r is calculated as r � �5 � 2�v 2tma r � �5tω the value of the current resistor needed to be connected in series to the red led is 150ώ. 2.3 construction of arduino based light dependant alarm system the construction of the hardware and packaging was carried out as shown in figure 6 and 7 respectively. 3. results and discussions table 1 shows the testing of arduino based alarm system. when the system was subjected to darkness with the ldr having resistance of about 100kω, the light intensity is around 0lux and the alarm is in off-state. with decrease in the resistance of the ldr, at about 1269ω, the light intensity begins to increase gradually to about 100lux and the alarm comes “on”. the test conducted shows the ldr resistance decreases as light intensity increases. the light illuminance ranges at which the buzzer was triggered “on” is between 100-1000lux. the result obtained is as shown in a graph of resistance against light illuminance plot in figure 8. figure 6: construction of the system figure 7: packaging of the system http://www.azojete.com.ng ibrahim et al.: design and implementation of an arduino based light dependent alarm system. azojete, vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 266 table 1: testing of the arduino based alarm system. s/n light illuminance (lux) resistance (ώ) buzzer 1 0 11 900.90 off 2 100 1269.18 on 3 200 630.04 on 4 300 547.10 on 5 400 411.87 on 6 500 342.09 on 7 600 292.52 on 8 700 264.66 on 9 800 230.77 on 10 900 212.04 on 11 1000 190.30 on figure 8: result of plot for resistance against illuminance. 4. conclusion the arduino based alarm system was built, tested and found to be working in conformity to the design. it was found to be a versatile system capable of detecting the presence of light and triggering the buzzer. the ldr resistance decreases (to about100ώ) as incident of light falls on it and increases (to about 10mώ) in the dark. the range of illuminance at which the buzzer was triggered was between 100-1000 lux. the alarm is triggered at about 6.45 a.m., which is in http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):259-267 print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunaebrahim@gmail.com 267 conformity with the mean time of getting out of bed. such system can be produced locally with a minimum circuit complexity, resulting in a technological tool of utility and economy suited to the need of modern activities. the implementation (construction) is built around an open-source electronics platform which is based on an easy to use hardware and software. no need of a separate hardware programmer/burner for loading/burning of program on to the microcontroller. the arduino software is easy to use for beginners and very flexible for advance users. it is recommended that any other person working on this kind of design should make use of photodiode or phototransistor so as to improve on the response time of the system and increase the resistance needed to trigger the buzzer. a passive infrared (pir) sensor can also be used to detect motion when there is a variation of weather or light intensity. references busari, a., adebisi, o. and akanji, o. 2015. design and implementation of a microcontroller based alarm enabled dark activated switch. international journal of engineering and innovation technology, ibadan, nigeria, 4(12): 38-41 effendi, m., shayfull, z. and saad, m. 2014. design and implementation of an alarm reminder. locking security system. international journal of electronics and computer science engineering, 6(5): 465-472. isah, a., oshoma, a. and alexander, o. 2015, design and implementation of an automatic street light control system. international journal of emerging technology and advanced engineering, 4(3): 318-329. mavrya, k., singh, m. and jain, n. 2012. implementation of a real time vehicle tracking using gps technology. international journal of electronic and computer science engineering, 4(4): 277-289. mustafa, e., farij, a. and abdalroof, a. 2013. automatic street light control system using microcontroller. mathematical methods and optimization techniques in engineering isbn; 978960-474-339-1 pp 92 -96 nikhil, k. 2016. design and construction of an iot based intelligent home using smart devices. international journal of innovative research in electrical electronics and instrumentation engineering, 4(6): 12090-12097 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):279-284 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: monsoorakinleye@gmail.com 279 original research article evaluating the strength characteristics of claygravel mixtures m. t. akinleye1*, l. o. salami1 and m. o. salami2 (1department of civil engineering, adeleke university, ede, nigeria 2department of civil engineering, university of ibadan, ibadan, nigeria) *corresponding author’s email address: monsoorakinleye@gmail.com 1.0 introduction according to njoka et al. (2015) clay is a naturally occurring material that composed of layered structures of fine-grained materials which exhibit the property of plasticity at appropriate moisture content. it is chemically and structurally analogous to other phyllosilicates but contain varying amounts of water and allow more substitution of their cations. the clay material is formed from chemical weathering processes on the earth’s surface, and it contributes about 40% of the fine grained sedimentary rocks (ombaka, 2016). clayey soils have lower strength, lower permeability, higher compressibility, higher cracking potential and are apparently less susceptible to liquefaction. tijani et al. (2017) stated that it is necessary to obtain information on the properties of soils for engineering construction purposes so as to make improvement if it does not substantiate with internationally established standards. article information abstract shear strength is one of the most important soil properties in almost all geotechnical engineering problems. therefore, this study was aimed at investigating the effect of gravel on the shear strength of clayey soil. two clayey soil samples were obtained from a dug pit from different locations in osogbo, osun state and the gravels were collected locally. three different gradations of gravel (2-6mm, 6-12mm, and 12-20 mm) were mixed in a dry state in percentages of 5, 10, 15, 20, 30, 40 and 50% with the collected clay soil respectively. initially, some physical properties of clayey soil and the gravel, which include specific gravity, particle size analysis, liquid limit and plastic limit, were determined in accordance with bs 1377-3:2018. consequently, the california bearing ratio (cbr) and consolidated undrained (cu) triaxial compression tests at three different confining pressures of 50, 100 and 150 kn/m2, with a loading rate of 0.5 mm/min were carried out on the clay-gravel mixtures in accordance with bs 1377 (1990). the results from the cbr test indicated that the cbr value of the clay-gravel mixtures was higher than that of pure clay. the result of shear strength showed that the cohesion and effective angle of internal friction increases as the concentration of gravel increases from 0 to 50%. as the gravel size was increased from 6-12mm, effective cohesion reduces and angle of internal friction increases. it concluded that locally available gravel can be used to improve the strength properties of clayey soil for engineering construction. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 may, 2019 revised 17 july, 2019 accepted 23 july, 2019 keywords: clayey soil gravel clay-gravel mixtures shear strength california bearing ratio http://www.azojete.com.ng akinleye et al: evaluating the strength characteristics of claygravel mixtures. azojete,16(2):279-284. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: monsoorakinleye@gmail.com 280 mixing of clayey soils with granular materials (e.g. sand and gravel) is one of the methods to reduce the swell and shrinkage potential as well as improved strength. these soils with dominant part of clay are called mixed clayey soils (soltani and soroush, 2007). jafari and shafiee (2004) carried out consolidated undrained compression triaxial tests on mixtures of kaolin, sand/gravel and observed that the angle of shearing resistance at the critical state increases as the aggregate contents in the mixture increase. the study also observed that, during undrained loading, higher pore water pressures are induced in the mixtures with higher aggregate contents. soltani and soroush (2007) studied the behaviour of compacted clay-sand and clay-gravel mixtures by conducting undrained triaxial tests. the study suggested that critical sand/gravel contents, below which the shear strength and secant deformation modulus of the mixed soil (as compared to those of the pure clay) remain almost unchanged, and beyond which they increase considerably. also, the results revealed that adding sand/gravel to the clay increases pore water pressures during monotonic shearing. the clay-gravel mixtures, as opposed to the clay-sand mixtures showed a slightly higher strength and lower pore water pressure during shearing. ayininuola et al. (2018) investigated the influence of gravel on the geotechnical properties of clayey soil. the influence of gravel with grade sizes 2-6 mm, 6-12 mm and 12-20 mm on the geotechnical properties of two clayey soils were carried out. the result of particle size analysis shows that the addition of gravel to the clayey soil changed the class of the clayey soil from a5-7 to a-2-7. also, the addition of gravel to the clayey soil led to an increase in maximum dry density (mdd) and reduction in optimum moisture content (omc) as the concentration of gravel increases in the clay-gravel mixtures. further increase in mdd with a reduction in omc was also observed as the gravel sizes increases. vallejo and mawby (2000) revealed that the shear strength of clay-aggregate composites depends upon the relative concentrations of the aggregates and the clay by weight in such a way that if the content of the granular material in the composite is greater than 75%, the shear strength is controlled by the aggregate alone. in another study, kumar and wood (1999) noted that for clay contents above 35%, it is the clay matrix alone, which controls the mechanical behaviour of the mixture and the gravel only begins to influence the behaviour when the granular fraction reaches about 45%. iannacchione and vallejo (2000) reviewed 31 technical papers (comprised field case studies, laboratory investigations, and theoretical analysis) containing analysis of shear strength for clays and sands with varying mixtures of rock particles. the study concluded that the shear strength gradually increases with increase in percentages of floating particles in unsaturated clays. the present study, thus, aimed at evaluating the shear strength characteristics and california bearing ratio of clayey soil mixed with three different grades of gravel. the clayey soil-gravel mixtures were prepared by means of standard proctor compaction tests and the shear strength behaviour of the prepared samples was evaluated under consolidated-undrained (cu) triaxial test condition. results of the study will reveal the suitability of locally available gravel to improve the strength properties of clayey soil for engineering construction. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 279-284. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: monsoorakinleye@gmail.com 281 2. materials and method two clayey soil samples were collected at different locations. one at a dug pit for constructing a gantry located at gbongan road, ogo-oluwa, osogbo, osun state. the other sample was collected at a dug well located at oke-baale, osogbo, osun state. the gravel was collected locally around kasmo area, oke-baale, osogbo. california bearing ratio, and consolidated undrained triaxial, compaction tests,were determined in accordance with bs 1377-3 (2018).the gravel was separated into grades ranging from 2-6 mm, 6-12 mm and 12-20 mm in the laboratory. the gravel was mixed in a dry state in percentages of 5, 10, 15, 20, 30, 40 and 50% with the two clayey soils collected respectively. the clayey soil collected at ogo-oluwa was labeled as clayey soil a and the other collected at oke-baale was labeled as clayey soil b. 3. results and discussions the liquid limits for the clayey soils a and b were 49 and 58% respectively. the plastic limit was respectively found to be 30.6 and 31.18%, and the linear shrinkage was recorded as 9.3 and 10% respectively. particle size analysis revealed that clayey soil b contains more fine grain soil than clayey in soil a, with the percentage passing sieve size 0.075mm found to be 54%, which was higher than 52% of clayey soil a. the two clayey soils (a and b) were classified in accordance with the american association of state highway transportation officials (aashto). clayey soils a and b were classified as a-5-7 with a general subgrade rating of fair to poor. the results of geotechnical properties are similar to those obtained by kumar and muir (1999) who observed a sharp change in response when the clay content falls below about 40% and a change in character of response at clay contents below about 40% and for clay contents above about 35%, only the clay matrix controls the mechanical behaviour of the mixture. the results of the california bearing ratio (cbr) shown in tables 1 and 2 revealed that the value of the cbr of all the clay-gravel mixtures increased with increase in the concentration and sizes of gravels in clayey soils a and b from 0% to 50%. the increase was attributed to the presence of larger granular particles in the clay-gravel mixture, which will require a larger magnitude of forces at 2.5 and 5.0 mm penetration for cbr measurement. this is in agreement with the work of ayininuola et al. (2018) who reported that gravel addition to the clayey soil changed the soil class from a-5-7 to a-2-7, with general subgrade rating of excellent to good, the soil class changed when 40% of gravel size 2-6mm, 30% of gravel size 6-12 mm and 20% of gravel size 12-20mm were added respectively to each of the clayey soil a and b table1. average cbr in percentage values of clay-gravel soil samples a percentage of gravel size of gravel(mm) 2 – 6mm 6 – 12mm 12 – 20mm 0 65.00 65.0 65.0 5 66.5 67.5 68.8 10 68.0 69.0 70.5 15 70.5 72.0 74.6 20 71.2 74.6 78.2 30 74.4 78.2 81.6 40 76.0 80.0 85.7 50 78.0 82.0 87.0 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akinleye et al: evaluating the strength characteristics of claygravel mixtures. azojete,16(2):279-284. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: monsoorakinleye@gmail.com 282 table 2. average cbr in percentage values of clay-gravel soil samples b percentage of gravel size of gravel(mm) 2 – 6 mm 6 – 12 mm 12 – 20 mm 0 68.0 68.0 68.0 5 70.0 72.0 74.0 10 72.0 73.0 76.0 15 73.2 75.0 77.2 20 75.0 77.0 79.6 30 76.9 79.0 82.1 40 77.5 81.0 85.0 50 78.7 84.0 88.0 the shear strength parameters (effective cohesion c' and angle of internal friction φ') for the clay-gravel mixtures with gravel size 12-20mm cannot be obtained on the triaxial machine due to the presence of larger particle sizes than the values specified in the bs 1377-3 (2018 and reported also by bakhtiar et al. (2019); this could be solved by conducting sieve analysis before use. the variation of internal friction angle and the cohesion for clay-gravel mixtures for clayey soil a and b are shown in tables 3 and 4 for gravel size 2mm-6mm and 6mm-12mm respectively. an increase in shear strength of gravel content of approximately 50% was observed. this is undoubtedly in response to the significant inter-particle interaction occurring within this concentration. a corresponding reduction in the cohesion of the soil as the gravel size was increased from 6-12mm in the clay-gravel mixtures was apparent as the clay-gravel mixtures became more granular. table 3. the result of shear strength parameters c' and φ' for clay-gravel soil a size of gravel percentage of gravel c' (kn/m2) 2-6 mm φ' (0) 2-6 mm c' (kn/m2) 6-12 mm φ' (0) 6-12 mm 0 22.0 10.0 24.0 10.0 5 24.0 12.0 30.0 14.0 10 26.0 14.0 32.0 18.0 15 28.0 16.0 34.0 20.0 20 30.0 18.0 36.0 22.0 30 32.0 20.0 40.0 24.0 40 34.0 30.0 40.0 32.0 50 38.0 35.0 39.0 38.0 table 4. the result of shear strength parameters c' and φ' for clay-gravel soil b size of gravel percentage of gravel c' (kn/m2) 2 – 6mm φ' (0) 2– 6mm c' (kn/m2) 6-12mm φ' (0) 6 – 12mm 0 30.0 18.0 30.0 18.0 5 32.0 19.0 31.0 20.0 10 34.0 20.0 32.0 22.0 15 36.0 21.0 33.0 26.0 20 38.0 23.0 34.0 28.0 30 40.0 25.0 35.0 32.0 40 41.0 27.0 36.0 38.0 50 41.0 30.0 37.0 42.0 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 279-284. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: monsoorakinleye@gmail.com 283 4. conclusions the effects of gravel on the geotechnical and strength properties of clayey soils were evaluated using three different grades of gravel. the clayey soil-gravel mixtures were prepared by means of standard proctor compaction tests and the shear strength behaviour of the prepared samples was evaluated under consolidated-undrained (cu) triaxial test condition. the results revealed that, an addition of gravel to clayey soil contributes to the improvement in both its geotechnical and strength properties. the strength of the clay-gravel mixtures was influenced when the percentage of the gravel of sizes 6 – 12 mm, and 2 – 6 mm were 30 and 40% respectively. it was concluded that locally available gravels could be used to improve the strength properties of clayey soil for engineering construction. references ayininuola, gm., salami, mo. and salami, lo. 2018. investigating the geotechnical properties of clay-gravel mixtures. international research journal of advanced engineering and science, 4(1): 40-41. bakhtiar, ao., aminaton, m., nor, zmy., tan, cs. and faizal, p. 2019. the grading effect of coarse sand on consolidated undrained strength behaviour of sand matrix soils. international journal of recent technology and engineering (ijrte), 7 (5): 88 – 92. bs 1377-3 2018. methods of test for soils for civil engineering purposes. chemical and electrochemical testing. british standards institution, july 2020, london. pp. 1-7 iannacchione, at. and vallejo, le. 2000. shear strength evaluation of clay-rock mixtures. slope stability 2000, proceedings of sessions of geo-denver 2000 denver, colorado, august 5-8, geotechnical special publication no. 101, editors; griffiths dv., fenton ga. and martin tr., reston, va: american society of civil engineers, 209-223. jafari, mk. and shafiee, a. 2004. mechanical behaviour of compacted composite clays. canadian geotechnical journal, 41 (6): 1152-1167. kumar, gv and muir, wd. 1999. fall cone and compression tests on clay–gravel mixtures. geotechnique, 49(6): 727–739. njoka, en., ombaka, o., gichumbi, jm., kibaara, di. and nderi, om. 2015. characterization of clay from tharaka nithi country in kenya for industrial and agricultural applications. african journal of environmental science and technology, 9 (3): 228-243. ombaka, o. 2016. characterization and classification of clay minerals for potential applications in rugi ward, kenya. african journal of environmental science and technology, 10 (11): 415-431. soltani, jh. and soroush, a. 2007. the behaviour of mixed clayey soils under monotonic loading. international journal of science and technology-amirkabir (cmm), 18(67): 21-29 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akinleye et al: evaluating the strength characteristics of claygravel mixtures. azojete,16(2):279-284. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: monsoorakinleye@gmail.com 284 tijani, ma., akinleye, mt. and jaiyeoba, kf. 2017. engineering properties of laterites obtained in ede, southwestern nigeria. international journal of engineering and advanced technology, 7(1):160 – 162. vallejo, le. and mawby, r. 2000. porosity influence on the shear strength of granular materialclay mixtures. engineering geology, 58: 125–136 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 95-100 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng *corresponding author email: shuso@bpe.agr.hokudai.ac.jp 95 original research article practical application of near-infrared spectroscopy for determining rice amylose content at grain elevator m. matsuo1, s. kawamura*2, m. kato2, e. o. diaz2 and s. koseki2 1graduate school of global food resources, hokkaido university, sapporo, japan, 2 graduate school of agricultural science, hokkaido university, sapporo, japan article information received october, 2018 accepted december, 2018 keywords: rice quality evaluation amylose content rice grain elevator non-destructive method japan abstract the major chemical constituent contents of rice are moisture, protein and starch (amylose and amylopectin). those constituent contents associate with eating quality of rice. near-infrared (nir) spectroscopy is one of the non-destructive methods for determining grain chemical contents. at grain elevator, moisture and protein contents can be measured with high accuracy using an nir spectrometer by the effort of our research activities in japan. however, the accuracy to determine amylose content is not sufficient. thus, the objective of this study was to develop non-destructive method to determine rice amylose content for practical use at grain elevator. milled rice amylose content measurement was performed using an auto-analyzer for reference (chemical) analysis. spectra data of milled rice were obtained using an nir spectrometer with a wavelength range of 850 to 1048 nm. calibration model to determine amylose content was developed using non-waxy japonica-type rice samples. partial least squares (pls) regression analysis was used to develop calibration model. the accuracy of the model was validated and the validation statistics were shown: coefficient of determination (r2) was 0.72, bias was -0.04%, standard error of prediction (sep) was 0.92%, and ratio of sep to standard deviation of reference data (rpd) was 1.90. production year of the validation set (2017) was different from that of the calibration set (2008 to 2016). this means the same condition as practical use of this method at grain elevator. the result obtained in this study indicated that this calibration model enables non-destructive determination of rice amylose content at grain elevator. © 2018 faculty of engineering, university of maiduguri, nigeria, all rights reserved. http://www.azojete.com.ng mailto:shuso@bpe.agr.hokudai.ac.jp matsuo, et al. practical application of near-infrared spectroscopy for determining rice amylose content at grain elevator. azojete, 14(sp.i4):95-100 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 96 1.0 introduction rice is staple food for people in the large part of the world, especially in asian countries. the major chemical constituent contents of rice are moisture, protein and starch (amylose and amylopectin). those chemical constituents associate with eating quality of rice. the moisture content of rice is closely related to storage quality and milling characteristics. protein and amylose contents are important constituent contents associated with texture and eating quality of cooked rice (allahgholipour et al., 2006). texture of cooked rice greatly affects eating quality and is one of the most important quality factors of rice (natsuga, et al., 1999). environmental temperature during the ripening period of rice greatly affects amylose content in rice (matsue et al., 2002; kinoshita and sato, 2004; igarashi et al., 2009; tanno, 2010; yamaguchi et al., 2012; tsujii et al., 2015). lower environmental temperature during the ripening period of rice causes higher rice amylose content. hokkaido is the northernmost island in japan. in hokkaido, therefore, the temperature of rice ripening period is lower than that in the other areas in japan and rice amylose content increases than the other areas. east asian people including japanese, korean and most of chinese people prefer low amylose content rice, because it becomes soft and sticky cooked rice. thus, hokkaido makes effort in development of low amylose content rice cultivar. in hokkaido, we have bred low amylose rice cultivar called yumepirika from 2008.yumepirikais the original brand rice in hokkaido. we want to make higher quality of rice. thus, it was decided that the good taste combination of amylose and protein content about yumepirika. for example, when amylose content is less than 19%, protein content is less than 7.5%, or when amylose content is 19% or more, protein content is 6.8% or less (kawamura et al., 2013). the combination is selected finely. therefore, there is a need for the highly accurate measurement of rice protein and amylose content. near-infrared (nir) spectroscopy is one of the non-destructive methods for determining grain chemical contents. there have been many studies on the usefulness of nir spectroscopy as a non-destructive method for determining chemical constituent contents of agricultural products such as grain, fruits and vegetable. now, it has been shown that determination of moisture and protein contents of rice by nir spectrometer is sufficiently accurate for practical use at rice grain elevators (fujita et al., 2010; li et al., 2013). however, the accuracy for determination of rice amylose content by nir spectrometer is lower than those of moisture and protein contents. however, rice amylose content has great impacts on the eating quality of rice and farmer’s income. thus, there is a strong need for the highly accurate measurement of rice amylose content using non-destructive method such as nir spectroscopy. the overall objective of this study was to develop non-destructive and more accurate calibration model to determine rice amylose content for practical use at grain elevator. 2.0 materials and methods 2.1 rice samples for this study, a total number of 1069 milled rice samples were collected from hokkaido, japan. table 1 shows the detail of the rice samples collected. the rice samples consisted of 14 cultivars of non-waxy japonica-type rice grown in hokkaido, japan from 2008 to 2017. the cultivar names of the rice samples were aya, ayahime, daichinohoshi, fukkurinko, hoshimaru, hoshinoyume, kitakurin, kirara397, nanatsuboshi, oborozuki, sorayuki, yukihikari, yumepirika and yukisayaka. ayahime, aya, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):95-100. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 97 nir spectra reference (chemical) analysis pls regression analys is develop calibration model validate accuracy oborozuki, yumepirika and yukisayaka are low amylose content rice cultivars, and the others are ordinary amylose content rice cultivars. 2.2 reference (chemical) analysisof amylose content amylose content measurement was performed using an auto-analyzer (bran-luebbe, solid prep iii tokyo, japan) for reference (chemical) analysis following the protocol of williams et al. (1958) with modifications by inatsu (1988). the absorption of the amylose-iodine complex was measured at 620 nm with a spectrophotometer, and the apparent amylose content was quantified against a calibration curve. in this study, hoshinoyume cultivar of rice (moisture content: 13.09%, amylose content: 21.12%) grown in hokkaido and hakuchoumochi cultivar of glutinous rice (amylose content: 0%) grown in hokkaido were used as standard amylose contents to calculate the apparent amylose content (aac) of each sample. apparent amylose content was expressed as a percentage (%). table 1. rice sample used in this study production year a b c d e f g h i j k l m n total 2008 2 1 3 10 18 33 41 12 120 2009 16 9 14 12 11 13 45 120 2010 7 4 19 20 25 19 42 137 2011 1 10 6 18 25 8 42 110 2012 3 5 34 42 2013 9 13 7 6 18 27 5 15 100 2014 6 7 4 2 27 28 3 1 21 99 2015 10 11 9 11 8 36 12 14 32 144 2016 4 13 6 1 4 6 29 3 2 33 1 102 2017 2 20 5 1 4 25 2 2 33 1 95 total 2 1 58 100 12 78 24 147 252 77 18 1 297 2 1069 a=ayahime, b=aya, c=daichirinko, d=fukkurinko, e=hoshimaru, f=hoshiyome, g=kitakurinn, h=kirara 397, i=nanatuboshi, j=oborozuki, k=sorayuki, l=yukihikari, m=yumepirika, n=yukisayaka figure 1. nir spectrometer, model br-5000 2.3 calibration model from nir spectrometer spectra data of milled rice were obtained using an nir spectrometer (shizuoka seiki, br-5000, fukuroi, japan) (figure 1) with a wavelength range of850 to 1048 nm with 2-nm intervals. figure 2. flow chart of developing calibration model and validating the accuracy file:///c:/users/user/downloads/azojete143/www.azojete.com.ng matsuo, et al. practical application of near-infrared spectroscopy for determining rice amylose content at grain elevator. azojete, 14(sp.i4):95-100 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 98 calibtation set n (2017) r2 bias(%) sep(%) rpd regression 3 years (2008-2010) 95 0.25 0.26 1.94 0.90 y=0.41x+12.5 4 years (2008-2011) 94 0.46 -0.99 1.40 1.25 y=0.67x+7.50 5 years (2008-2012) 95 0.41 -0.89 1.55 1.12 y=0.58x+9.19 6 years (2008-2013) 95 0.50 -2.00 1.27 1.37 y=0.80x+5.75 7 years (2008-2014) 95 0.49 -1.79 1.29 1.35 y=0.78x+6.09 8 years (2008-2015) 95 0.65 0.41 1.03 1.69 y=1.01x-0.72 9 years (2008-2016) 94 0.72 -0.04 0.92 1.90 y=0.99x+0.20 the savitzky-golay derivative was used for pretreatment. the chemometric techniques partial least squares (pls) regression within the statistical software the unscrambler (version 10.3 upgrade 10.3.0r4) were used for processing the data. calibration model to determine amylose content was developed using the rice samples (calibration set, n=974, including 14 cultivars) grown from 2008 to 2016. and partial least squares (pls) regression analysis was used to develop calibration model. the accuracy of the calibration model was validated using the other rice samples (validation set, n=95, including 10 cultivars) grown in 2017. figure 2 shows the flow chart of developing calibration model and validating the accuracy. 3.0 results and discussion the accuracy for determining amylose content of milled rice was shown in the following. table 2 shows that when the production years for calibration set increased, standard error of prediction (sep) values decreased and ratio of sep to standard deviation of reference data (rpd) values increased. this means that the accuracy was improved by increasing production years of calibration sample set and this method got a step closer topractical use at grain elevator. amylose content of rice is affected by environmental temperature during the ripening period. in other words, the environmental temperature of each production years was different, amylose content of rice changed by each production year. natsuga (1995) reported that to obtain high accuracy of calibration model, it is necessary to use samples collected over a period of several years. by increasing production years of calibration set, the information of variation in temperature and amylose content was added to the calibration model, and then the accuracy of determination of milled rice amylose content was improved. this is the reason why the accuracy for calibration model increases when the production years for calibration set increases. the correlation between reference (chemical) amylose content of milled rice and predicted amylose content of milled rice (calibration set: 2008 to 2016, validation set: 2017) is shown in figure 3. the coefficient of determination (r2) was 0.72, bias was -0.04%, sep was 0.92% and rpd was 1.90.the production years of validation set (2017) was isolated from calibration set (2008 to 2016). this is the same condition in practical use of this non-destructive method at grain elevator. the result indicates that this method enables non-destructive determination of rice amylose content at grain elevator. table 2. change of accuracy for determining amylose content of milled rice http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):95-100. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 99 n: the number of validation set, r2: coefficient of determination, bias: difference of average values between predicted values and reference (chemical) values, sep: standard error of prediction, rpd: ratio of sep to standard deviation of reference data, regression line: regression line from predicted value (x) to reference value (y). figure 3 shows that the result which we validated the calibration model using 9-year production samples (2008-2016) for calibration set and 1-year production sample (2017) for validation set. regression line is y=0.99x+0.20, r2=0.72, bias=-0.042%, sep=0.92%, rpd=1.90, and n (the number of validation sample set)=94 (this result shown at the most bottom of table 2.) figure 3. correlation between reference (chemical) amylose content of milled rice and predicted amylose content of milled rice 4.0 conclusion the validation statistics between reference (chemical) amylose content and nir spectrometer-predicted amylose content indicate that when the production years for calibration set increase, the accuracy for determining amylose content of milled rice improves.and in this study, the production year of validation set was isolated from that of calibration set. thus, this is the same condition in practical use of this non-destructive method at grain elevator. the result obtained in this study indicates that the calibration model (developed using 9-year production samples (2008-2016)) enables non-destructive determination of rice amylose content at grain elevator. 5.0 acknowledgements we thank for the project of naro bio-oriented technology research advancement institution, japan (the special scheme project on vitalizing, management entities of agriculture, forestry and fisheries) for their grant support. references allahgholipour, m., ali, aj., alinia, f., nagamine, t. and kojima, y. 2006. relationship between rice grain amylose and pasting properties for breeding better quality rice varieties. plant breeding, 125(4), 357-362. 16 18 20 22 24 26 16 18 20 22 24 26 predicted amylose content using nir spectrometer（％） r ef er en ce (c he m ic al ) a m yl os e co nt en t（ ％ ） y = 0.99x+0.20 r2 = 0.72 bias = -0.042% sep = 0.92% rpd = 1.90 n = 94 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng matsuo, et al. practical application of near-infrared spectroscopy for determining rice amylose content at grain elevator. azojete, 14(sp.i4):95-100 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 100 fujita, h., kawamura, s. and yoshida, s. 2010. accuracy of determination of rice constituent contents by near-infrared spectroscopy at rice grain elevators. journal of hokkaido branch of the japanese society of agricultural machinery, 50, 53-60. igarashi, t., yanagihara, t., kanda, h., kawamoto, k. and masaki, k. 2009. the analysis (quality, processing) of the iodine absorption curve of the starch by the chemometrics technique for seasoning evaluations of rice. journal of the crop science society of japan, 78(1), 66-73. inatsu, o. 1988. studies on improving the eating quality of hokkaido rice. report of hokkaido prefectural agric. experiment stations, 66, 3-7. kawamura, s., iino, h. and fujikawa, s. 2013. a good sense of proportion makes a good sense of taste: effect of protein content and amylose content of rice on eating quality. in international food machinery and technology exhibition (pp. 273-276). the japan food machinery manufactures’ association. kinoshita, m. and sato, t. 2004. effects of difference in maturing period temperature to amylose contents of hokkaido rice varieties. journal of the crop science society of japan, 45, 19-20. matuse, y. and sato, h., uchimura, y. and ogata, t. 2002. influence of environmental temperature during the ripening period on the amylose content and whiteness of low-amylose rice. journal of the crop science society of japan, 71(4), 463-468. li, r., kawamura, s., fujita, h. and fujikawa, s. 2013. near-infraredspectoscopy for determining grain constituent contents at grain elevators. engineering in agriculture, environment and food, 6(1), 20-26. natsuga, m. 1995. grain quality determination by near-infrared spectroscopy (part 3) changes in the distribution of constituent contents of grain through the drying and preparation process, and changes in constituent contents of grain depending upon production districts and different harvest years. journal of the faculty of agriculture, hokkaido university,19(4), 377-409. natsuga, m. 1999. quality measurement of cereals by nir spectroscopy (part 4) the quality measurement of cereals by nir spectroscopy.journal of the faculty of agriculture, hokkaido university, 22(3), 127-168. tanno, h. 2010. yearly and regional variation in protein content in nonglutinous rice, and the factors affecting them in hokkaido in northern japan. journal of the crop science society of japan, 79 (1), 16-25. tsujii, y., kazami, m., goto, h., asanome, k. and takano, k. 2015. the influence that ripening temperature gives to quantity of rice endosperm enzyme activity.the japanese society for food science and technology. 62(11), 527-533. williams, vr., wu, wt., tsai, hy. and bates, hg. 1958. varietal differences in amylose content of rice starch. journal of agriculture and food chemistry, 6 (1), 47-48. yamaguchi, h., yoshinaga, s. and shiratsuchi, h. 2012. the estimated method of suitable cultivation filed and crop period for low amylose rice production with a little cloudiness by the estimation of the amylose content of polished rice.journal of the crop science society of japan, 81(3), 2 http://www.azojete.com.ng article information 1.0introduction arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):18-27 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 18 original research article mechanical and structural responses of low carbon steel to cold rolling and stress relief anneal treatments m. a. bodude1*, w.a. ayoola1, and a. oyetunji2 (1department of metallurgical and materials engineering, university of lagos, lagos, nigeria 2dept. of metallurgical and materials. eng., fed. univ. of technology akure, ondo state, nigeria) * corresponding author’s email address: mbodude@unilag.edu.ng 1.0 introduction plain carbon steels are widely used for many industrial applications and manufacturing on account of their low cost and ease of fabrication. in general, plain carbon steels are classified based on their carbon content, steels with carbon content varying from 0.3% to 0.6% are classified as medium carbon, while those with carbon content less than 0.25% are termed low carbon. those with high carbon content in the range 0.65-1.5% are classified as high carbon steels. low carbon steel has attracted a lot of research around the globe due to its numerous industrial applications. in industries, cold rolling is largely responsible for structural changes in engineering materials which often result in improved mechanical properties due to gradual extension of grains in the direction of the principal deformation stress with no recrystallization occurring. a low carbon steel subjected to intercritical annealing at 850oc exhibited a dual phase microstructure consisting of ferrite martensite and presented excellent mechanical properties in term of hardness, strength and elongation (phoumiphon et al., 2016). to further enhance the mechanical properties of engineering materials, heat treatment operation is carried out on low carbon steels to obtain desirable mechanical properties like hardness; toughness; ductility; strength. low carbon steel is the most common form of steel as its price is relatively low while it provides material properties that are acceptable for many applications. lcs has a article information abstract this study investigated the effect of deformation by cold rolling and stress relief anneal on the mechanical and structural properties of low carbon steel. the as-received steel samples were cold rolled at 20% – 40 % degrees of deformation using buhler rolling machine in metallurgical and materials engineering department university of lagos, nigeria. additionally, some of the cold rolled samples were annealed at a temperature of 650° c and soaked for 1 hour in a muffle furnace. the results revealed that the ultimate tensile strength (uts), percent elongation, hardness and impact strength of the cold rolled low carbon steel improved significantly after stress relief anneal due to the elimination of induced strain hardening caused by cold rolling. the micrographs show that cold rolled + stress relief anneal caused significant recrystallization of ferrite-austenite phase to refine martensite with reduction of dislocations. therefore, the low carbon steel can be used effectively for structural purposes in machines and equipment. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 02 april, 2018 revised 12 august, 2019 accepted 17 august, 2018 keywords: stress relief anneal degree of deformation residual stresses ultimate tensile strength recrystallization. mailto:mbodude@unilag.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 18-27. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 19 low carbon content (up to 0.3%) and is therefore neither extremely brittle nor ductile. it becomes malleable when heated, and so can be forged, rolled or machined into any shape. several studies have been conducted to examine the influence of cold rolling and heat treatment on the mechanical properties of engineering materials. the effect of soaking time on the mechanical properties of annealed cold drawn carbon steel has been conducted (raji and oluwole, 2012). similarly, rintaro et al. (2003) investigated the effect of the rolling reduction on the ultrafine grained structure and mechanical properties of plain low-carbon steel processed from martensite starting structure (ueji et al., 2004). in addition, the effect of severe plastic deformation on the mechanical properties of chosen material was studied. it was found that the microstructure was highly refined resulting in formation of nanosized grains that enhanced the tensile and hardness of the material. ayoola and oyetunji (2014) studied the effect of deformation and annealing processing on the texture and mechanical properties of aluminium alloy aa1200. the study found that ultimate tensile strength and hardness depends on the degree of deformation (ayoola and oyetunji,2014). furthermore, the influence of cold rolling and annealing on mechanical properties of steel qste420 was investigated (schindler et al., 2009). it was observed that combination of size of previous cold deformation and parameters of the following annealing, it was possible to influence mechanical properties of particular steel. phoumiphon et al. (2016) examined the effect of cold rolling and intercritical annealing on the mechanical properties of plain low carbon steel. many steel components failed in service due to residual stresses from previous processing and fabrication techniques such as forging, extrusion and rolling. therefore, this study aimed to investigate the effect of cold rolled deformation and stress relief anneal on the mechanical and structural properties of low carbon steel with a view to solving failures caused by plastic deformations during materials processing. 2. materials and methods 2.1 materials the steel used in this study was procured from finlab scientific store in lagos nigeria. the nominal chemical composition of the steel shown in table 1 indicated that the steel is a commercial grade low carbon steel rod with a diameter of 16 mm. table 1: chemical composition of as-procured plain carbon steel used (finlab scientific store, lagos. nigeria) 2.2 samples preparation the as-procured low carbon steel rod was cut into 250 mm long samples and cold rolled at room temperature (28° c) in a buhler two-high rolling machine 150 x 80a at metallurgical and materials engineering foundry unit, university of lagos, akoka, lagos nigeria. table 2 shows the deformation parameters used to produce samples in accordance with astm e8-8st standard (adeosun et al., 2011). the rolling was done by feeding the sample in the rolling machine, which is preset to allow for the required degree of deformation and number of passes. the deformed samples were heat treated in a muffle furnace at a temperature of 650 °c soaked for 1 hour and later cooled to room temperature in air. elements fe c si mn p s cr ni weight (%) 98.940 0.225 0.170 0.540 0.017 0.008 0.074 0.026 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng bodude et al: mechanical and structural responses of low carbon steel to cold rolling and stress relief anneal treatments. azojete, 16(1):18-27. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 20 table 2: the deformation parameters and their values (adeosun et.al, 2011) deformation parameters sample 1 sample 2 sample 3 sample 4 sample 5 sample diameter (mm) 12.80 12.0 11.20 10.40 9.60 degree of deformation (%) 20 25 30 35 40 reduction in diameter (mm) 3.20 4.00 4.80 5.60 6.40 number of passes 1 2 4 8 16 2.3 mechanical testing 2.3.1 tensile test the tensile test was conducted on instron universal testing machine model (usa). the tensile test pieces were prepared from the rolled and heat treated samples to astm e-8 standard (ayoola et al., 2012, tewary et al., 2015). figure 1 shows the standard dimensions of the specimen used in this study. from the tensile tests carried out, tensile strength and percentage elongations were determined. figure 1: cylindrical tensile test piece 2.3.2 flexural test the flexural test was done using m500 tensometer (usa) with a load of 25kn on samples. specimens of 120 mm long by 50 mm wide were cut and loaded in three point flexural with a recommended span of 100 mm and also with a test speed of 40 mm/min. 2.3.3 hardness test to evaluate the hardness of the material the rockwell hardness test was carried out according to astm e-18 specification (paul et al., 2007). 2.3.4 impact test impact test was carried out on the samples using the averydenison universal impact –testing machine. (usa) the energy absorbed by the machined sample was measured and recorded when the machine pendulum was released from the maximum position corresponding to charpy test, striking the test piece with a load of 300 j (paul et al., 2007). the same procedures were repeated on other samples 2.3.5 microstructural analysis microstructural examination of samples was conducted using a metallurgical optical microscope in line with gladkousky et al. (2016). the specimens for the optical microscopy were ground http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 18-27. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 21 using a series of emery papers of grit sizes ranging from 500 – 1500 μm while fine polishing was done afterwards. the specimens were etched with 2% nital solution for 5 seconds before observation in the optical microscope. 3. results and discussion this study investigated the effect of deformation by cold rolling and stress relief anneal on the mechanical and microstructural properties of low carbon steel. table 3 indicates the mechanical properties of the control sample while figure 2 shows the mechanical properties of the samples that were cold rolled with and without stress relief anneal at various degree of deformation. the ultimate tensile strength of the cold rolled samples without stress relief anneal increased with increasing degree of deformation and significantly higher than that of control and stress relief anneal samples. figure 2 also reveals that increase degree of deformation has no significant effect on the uts for the cold rolled + stress relieved samples. this implies that stress relief anneal at 650° c for 1 hour is sufficiently high enough to eliminate the strain hardening and induced residual stresses completely. this is because the recovery process, that is, stress relief anneal significantly allowed redefined and rearranged of large numbers of dislocations within grains resulted in reduce or complete elimination of residual stresses. the uts of rolled + stress relief anneal samples were approximately 2.5 higher than the cold rolled samples. this may be linked to the stress relief anneal temperature of 650° c investigated. at higher annealing temperatures, both recovery and recrystallization occur rapidly and resulted in grain growth which reduces the uts of the samples (ueji et al., 2004). table 3: mechanical properties of the as received low carbon steel. uts (mpa) impact energy (j) % elongation hardness 505.56 206 15.03 4.40 figure 2: variation of ultimate tensile strength with annealing and degree of deformation figure 3 shows the dependence of percent elongation on the degree of deformation. while the percent elongation increased with the degree of deformation for the cold rolled samples the rolled + stress relief anneal samples show some form of recovery. the percent elongation dropped at all levels of deformation after stress relief of the samples. figure 3 shows that 18% and 75 % reduction in elongation were obtained at 20% and 40 % degree of deformation, respectively. the elongation recovers when the samples are annealed at temperatures higher file:///c:/users/user/downloads/azojete143/www.azojete.com.ng bodude et al: mechanical and structural responses of low carbon steel to cold rolling and stress relief anneal treatments. azojete, 16(1):18-27. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 22 than 550° c (ueji et al., 2004). a gradual increase in the elongation was noticed beyond 30 % degree of deformation for the cold rolled + stress relief anneal. elongation of materials is a measure of its ductility. stress relief anneal improved the ductility of the low carbon steel investigated due to the elimination of residual stresses induced. between 20 and 30 % degree of deformation, percent elongation of cold rolled + stress relief anneal samples was observed to be closer to the original ductile of the as-received sample of 15 %. figure 3: variation of elongation with annealing and degree of deformation figure 4 shows the response of flexural strength to the degree of deformation. flexural strength decreases with increasing degree of deformation. the maximum flexural strength obtained for the rolled sample and rolled + stress relief anneal sample are 1900 mpa and 840 mpa respectively. similarly, the least flexural strength obtained for the rolled sample and rolled + stress relief anneal sample are 1260 mpa and 360 mpa respectively. figure 4: variation of flexural strength with annealing and degree of deformation figure 5 shows the effect of stress relieved annealing and degree of deformation on the sample hardness. as expected, the hardness value of the samples is a function of the processes the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 18-27. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 23 material is undergone. the rolled samples without stress relief anneal exshibited higher hardness compared to rolled + stress relief anneal samples. however, the slopes of the plots are similar. it can also be seeen that the hardness increased with increasing degree of deformation and dependent of stress relief anneal. cold rolled samples without stress relief anneal introduced commpressive residual stress, which is beneficial for parts that are subject to cyclical loads because it helps to prevent the initiation and propagation of cracks. however, with the annealed samples, compressive residual stress have been largely eliminated and tensile residual stress seems to have been introduced, which translated to drasstical reduction in hardness. the hardness of the stress relief anneal samples is higher than that of the control sample. figure 5: variation of hardness with annealing and degree of deformation the absorbed impact energy by the samples cold rolled with and without stress relief anneal is shown in figure 6. the trend of the two curves is similar. the linear regression lines fitted show that the impact strength is not enhanced by increasing the degree of deformation irrespective of treatment undergone. however, the influence of stress relief anneal can be seen. the impact energy of 220 j and 135 j were recorded for stress relieved and cold rolled samples, respectively. figure 6: variation of impact strength with annealing and degree of deformation file:///c:/users/user/downloads/azojete143/www.azojete.com.ng bodude et al: mechanical and structural responses of low carbon steel to cold rolling and stress relief anneal treatments. azojete, 16(1):18-27. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 24 figure 7 shows the micrograph of the as-received low carbon steel. figures 8, 9, 10, 11 and 12 show the micrographs of the samples deformed at 20, 25, 30, 35 and 40 %, respectively. interestingly, the micrographs are predominantly ferrite-austenite and martensite phases. it is noteworthy that large grains of the martensite phase of the as-received sample are regular in shape and well visible within the matrix of ferrite-austenite phase, as shown in figure 7. the volume fraction of the martensite and ferrite-austenite phases are well distributed. figures 8a, 9a, 10a, 11a and 12a are the micrographs of cold rolled samples while figures 8b, 9b, 10b, 11b and 12b are the micrographs of cold rolled + stress relief anneal samples at the same degree of deformation, in that order. the micrographs of the cold rolled samples contain deformed grains of smaller sizes which contain a very large number of dislocation than the cold rolled + stress relief anneal samples. the presence of these dislocations are largely responsible for the enhanced mechanical properties attained in the stress relieved samples. expectedly, stress relief anneal above 0.4*tm (tm, melting temperature of low carbon steel) caused recrysallisation of low carbon steel, elimination of the residual stresses and most dislocations, which subsequently reduce ultimate tensile strength with high ductility (ueji et al., 2004). application of stress relief anneal to the cold rolled samples caused major coalesence of the smaller martensite grains to larger grains of irregular shapes and increased the volume fraction due to recrystallisation. phoumiphon et al., 2016 reported that the ferrite-austenite dual phase region by referring to the lever rule, the volume fraction of austenite increases depends on annealing temperature, then will transform to martensite. also, gladkousky et al. (2016) revealed the possibility of the formation of an ultrfine grained structure in a steel layer during rolling. the stress relief anneal temperature is significantly high enough for recrytallisation of low carbon steel (knupfer and moore, 2010; phoumiphon et al., 2016). figure 12b shows that sample cold rolled at 40 % deformation and stress relief anneal exhibited highest presence of mentensite phase, which transilated to the highest hardness and uts. the higher hardness and uts recorded for the figure 12a over figure 12b was due to the large volume of dislocation present. the findings from this work is in agreement with most of the earlier studies cited and the results further revealed the adaptability and hence the effective utilisation of the low carbon steel for structural applications when rolled and stress relieved optimally. figure 7: micrograph of the control sample in as-received condition http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 18-27. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 25 figure 8: micrograph of samples at 20% deformation (a) rolled and (b) rolled + stress-relief anneal figure 9: micrograph of samples at 25% deformation (a) rolled and (b) rolled + stress-relief anneal figure 10: micrograph of samples at 30% deformation (a) rolled and (b) rolled + stress-relief anneal file:///c:/users/user/downloads/azojete143/www.azojete.com.ng bodude et al: mechanical and structural responses of low carbon steel to cold rolling and stress relief anneal treatments. azojete, 16(1):18-27. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 26 figure 11: micrograph of samples at 35% deformation (a) rolled and (b) rolled + stress-relief anneal figure 12: micrograph of samples at 40% deformation (a) rolled and (b) rolled + stress-relief anneal 4. conclusion the mechanical and microstructural characterizations of a low carbon steel subjected to cold rolling and annealing heat treatment was carried out in this work. the outcome of the study showed that the stress relief annealing heat treatment caused significant change in the grain size, distribution and volume fractions of the phases present in the resulting microstructure. this is therefore responsible for the significant increase in the ultimate tensile strength (uts), hardness, impact strength and percent elongation (ductility) of the low carbon steel. in addition, the heat treatment reduces the compressive residual stresses of the rolling, hence an increase in the degree of deformation has no significant effect on the uts for the rolled + stress-relieved samples due to complete elimination of the strain hardening and induced residual stresses. therefore, the outcome of the rolling and stress relief annealing in this work revealed the adaptability and hence the effective utilisation of the low carbon steel for structural applications when rolled and stress relieved. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 18-27. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mbodude@unilag.edu.ng 27 references adeosun, so., ayoola, wa., bodude, m. and sanni, so. 2011. strength and hardness of directionallyrolled aa1230 aluminum alloy. journal of emerging trends in engineering and applied sciences (jeteas), 2(3): 440-444. ayoola, wa., adeosun, so., sanni, so. and oyetunji, a. 2012. effect of casting mould on mechanical properties of 6063 allumium alloy. journal of engineering science and technology, 7(1): 9–96. ayoola, wa. and oyetunji, a. 2014. effect of deformation and annealing procesing on the texture and mechanical properties of a aluminium alloy aa1200. daffodil international university journal of science and technology, 9(2):.49–59. gladkousky, sv. 2016. effect of plastic deformation on the structure and mechanical properties of an ultra-low carbon interstial-free steel in the monolithic material and as a component of a sandwich composite. physics of metal metallurgy, 117(10): 1070-1077 knupfer, sm. and moore, aj. 2010. the effects of laser forming on the mechanical and metallurgical properties of low carbon steel and aluminium alloy samples. materials science and engineering a, 527(16–17): 4347–4359. paul, cp. 2007. investigating laser rapid manufacturing for inconel-625 components. optics and laser technology, 39(4):.800–805. phoumiphon, n., othman, r. and badri, a. 2016. improment in mechanical properties plain low carbon steel via cold rolling and intercritical annealing. procedia chemistry, 19: 822–827. raji, na. and oluwole, l. 2012. effect of soaking time on the mechanical properties of annealed cold-drawn low carbon steel effect of soaking time on the mechanical properties of annealed cold-drawn low carbon steel. materials science and applications, 3: 513–518. schindler, i., janosec, m., místecky, em., ruzicka, m., cizek, k., dobrzanski, la., rusz, s. and suchanek. p. 2009. effect of cold rolling and annealing on mechanical properties of hsla steel. archives of materials science and engineering , 36 (1): 41– 47. tewary, nk., ghush,sk. and chatterjee, s. 2015. effect of annealing on microstructure and mechanical behaviour of cold rolled low c, high mn twip steel. international journal of metallurgical engineering, 4(1): 12-23. ueji, r., tsuji, n., minamino, y. and koizumi, y. 2004. effect of rolling reduction on ultrafine grained structure and mechanical properties of low-carbon steel thermomechanically processed from martensite starting structure. scirnce and technology of advanced materials 5: 153-162 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4):1-7 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 1 1 original research article growth performance characteristics of okra (hibiscus esculentus) using improvised drip irrigation system m.o. amoo1, m.a. adedeji2, *a.m. oke3, t.e. aremu3 1department of agricultural and bio-environmental engineering, federal university of technology, akure, ondo state, nigeria. 2department of agricultural and bioenvironmental engineering technology, federal polytechnic, ede, osun state, nigeria 3department of agricultural engineering, adeleke university, p.m.b 250, ede, osun state, nigeria. article information received october, 2018 accepted december, 2018 keywords: okra irrigation drip marginal water quality nigeria abstract okra is a common and popular vegetable crop used in nigeria. irrigation method has very significant influence on okra (hibiscus esculentus) production. a careful effect of marginal water quality on idi and control system which were subjected to the same conditions was investigated. an experimental field area of 13.5 m2 by 6.0 m2 was properly cleared, stumped, ploughed, harrowed and leveled. high yielding and disease resistant okra variety seeds were carefully selected and planted at a regular interval of 0.6 m. the results of statistical analysis obtained using completely randomized blocked design (crbd) (p˂0.05) revealed that there were significant differences on water application which reflected an increase in some agronomic parameters such as growth, weight, yield and vegetative development of the okra. these selected okra agronomic parameters showed that the okra performed in idi. maximum fruit yield of 71.71% and water utilization efficiency of 55.49% was obtained by using idi system. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction okra (hibiscus esculentus) is indigenous crop which grows throughout the tropics and in some part of the sub-tropic (modupe 2015). the plant tropically grows to 180cm in height, but some indigenous varieties may grow to 360cm tall, with base stem of 6cm in diameter. the plant produces dark yellow flower that are about 5cm in diameter. the plant is cultivated in tropical, sub-tropical and warm temperate region around the world. (okunade et al., 2009). in nigeria, it is among the foremost vegetable crops in term of consumption and production (puneet and arun, 2015). okra is a hot weather crop with optimum soil temperature of 75of to 90of. it is tolerant to wide variation in rainfall (kamran et al., 2012). it will grow well on all types of soil but best performance is obtained on sandy loam soil with high organic matter content and optimum soil ph ranging from 6.0 to 7.0 (sexena et al., 2013). okra is propagated by seed; 2-3 seeds are sown at 1-2cm depth per hole with 60cm – 90cm inter row spacing and 30cm along the rows. irrigation is the artificial application of water to the soil for the purpose of supplying the essential moisture for plant growth to eliminate moisture deficiency at various stage of plant growth (michael, 2000). irrigation is necessary to provide enough water to fill the deficit arising http://www.azojete.com.ng amoo et al.: growth performance characteristics of okra (hibiscus esculentus) using improvised drip irrigation system. azojete, 14(sp.i4):1-7. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 2 2 from the depletion of soil moisture from combine action exist between two separate phenomena of evaporation and transpiration (fasina, 2008). ahmad et al., (2003) reported that the total amount of water that is used each year is utilized for the purpose of irrigation. water management by irrigation practices are t complement the available water from natural sources such as rainfall, flood, dew and ground water. therefore, irrigation is needed in most parts of west africa where there may be a prolonged drought period and mostly where water from natural sources is inadequate for effective crop germination and production. the available lands in the tropical regions need irrigation to improve economic returns from production of crops by more than 100%. (modupe et al., 2015). drip irrigation is the method whereby water is supplied to crop root zone at regulated rate and fertilizer application can be done. it is very importance to carry out a study on the best irrigation system for the production of okra in nigeria in order to maximize profit and reduce the cost of production. the main concern of productive agriculture is the effective and efficient supply of water and growing demand for crop production. it includes remunerative cropping which needs a systematic study of irrigation problem and method of efficient economic use of water since irrigation potential created and it utilization, and that makes the situation more serious. on the other hand, when it is limited as compound to available water, the aim would be to maximize production per unit of land without watching water. under irrigated condition, it is usually not possible to grow more than one crop in a year and the yield from a rain-fed crop may hardly be between 1-2 tonnes of food per hectare in dry areas. but irrigation makes it possible to grow more than one crop in a year. puneet and arun (2015). metin et al., (2006) reported that timely irrigation leads to high yield multiple cropping under irrigation farming which assure high crop production. high yield varieties have a high water requirement than ordinary varieties; the potential of okra varieties can be fully exploited if adequate amount of water is made available. irrigation is necessary for vegetable (okra) production in nigeria in order to make the crop available throughout the year. 2.0 materials and methods 2.1 study area and land clearing field experiments were located at teaching and research farm of agricultural and bioenvironmental engineering department, school of engineering technology, the federal polytechnic, ado ekiti, ekiti state, nigeria. it is located between longitude 40 5’ and 50 45’ east of the greenwch meridian and latitudes 70 5’ and 80 5’ north of the equator. it lies south of kwara and kogi state, east of kwara and bounded by ondo state in the east and in the kogi state. the plot has a flat topography and the area was chosen for its suitable soil structure, texture, water retention capacity, loamy fertile soil, nearness to water source (well) and availability of power supply to operate the electric water pump. land preparation involved the use of tractor for ploughing and harrowing to make it suitable for undisturbed, unobstructed free flow of water and good crop management. 2.2 experimental design and installation layout the consumptive water use of okra under improvised drip irrigation system were measured and recorded. these agronomic data collected were analyzed using completely randomized block design (crbd) anova method. total experimental plot of 13.5 m2 by 6.0 m2 was used. in drip irrigation system, the two drums 100 litres was placed on the raised platform that serve as water http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):1-7. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 3 reservoir, the main pipe, lateral (pvc) were measured and cut into different sizes with measuring tape and hacksaw respectively. the pipe was connected to the reservoir with a valve, the screen filter was attached, and then a quick coupling elbow was used in the coupling of the main line of the length 450 m. the lateral line of 210 m was fixed on the main line at equal interval from each other. typical okra farm planted in row and freshly harvested okra in plates 1a and 1b below, respectively, and the installation layout of improvised drip irrigation system in plate 2 plate 1a: typical okra farm planted in a row plate 1b: typical okra freshly fruits plate 2: installation layout of the idi system 2.3 irrigation design the purpose of irrigation layout is to transmit information from engineering plans to the irrigation field. this will locate the work and provide such lines and elevations as needed for the development of improvised drip irrigation system. pictorial details of idi layout is presented in plate 3. plate 3: improvised drip irrigation system layout 2.4 planting of okra and data collection 2.4.1 planting of okra before planting of the seeds, the irrigation system was tested by pre irrigation in order to locate and correct any high or low spots which can lead to uneven water supply to the plants. the okra seeds were planted at 0.02 m depth with 0.6 m interval, the weeding was carried out manually on the experimental plot of land. the same treatments and analysis were carried out on the improvised drip irrigation system and control at the same time on the same day to avoid predisposition of the results. the pesticide and npk fertilizer were applied to control the diseases and increase the quality and quantity of okra yields. 2.4.2 data collection the moisture content and soil temperature were measured by means of moisture meter and soil thermometers, respectively from the day of planting to the maturity. the agronomic parameters, height, girth, number of leaves, okra yield, and flowers stage were measured and recorded: using digital weighing balance (± 0.01g). kamran et al., (2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng amoo et al.: growth performance characteristics of okra (hibiscus esculentus) using improvised drip irrigation system. azojete, 14(sp.i4):1-7. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 4 4 3.0 results and discussion table 1 showed that the plant height (cm) for the readings after 5, 10, 15, 20, 25, 30, 35 and 40 days showed that there were a significant differences in idi when compared to control system. the mean plant height after 40 days under idi and control system were 151.68 and 63.32 cm, respectively choudhary et al., (2012) (figure 1). the results obtained for height of okra against dap and statistical analysis proved that there is significant difference in the methods used with respect to the height of okra for idi and control (okunade et al, 2009; choudhary et al., 2012). the mean plant diameter under idi after 99 days 328.79 and 99.45 cm respectively. from figure 2 results indicated that there is no significant difference in idi used with respect to the stem girth of okra against dap in control system. (babar et al., 2008). the increase stem girth (cm) under idi and control system for the eight reading after 5, 10, 15, 20, 25, 30, 35 and 40 days showed that there was a significant difference in idi in comparison to control system. (table 1). the mean plant stem girth after 40 days under idi and control system were 2.696 and 2.289 cm, respectively as indicated in results by (metin et al., 2006) in the studies of growth of okra fruits. figure 3 results showed a linear relationship in idi when compared to control between number of leave against dap from the results obtained there is significant differences at 0.05 percent. (pravukalyan et al., 2011; al-harbi et al., 2008). the number of leaves (cm) under idi and control system for the eight reading after 5, 10, 15, 20, 25, 30, 35 and 40 days showed that there was a significant difference in idi compare to control system. the mean plant height after 40 days under idi and control system was 936 and 598 cm, respectively as indicated in results by (alkaff, 2003) in the studies of growth of okra fruits. therefore, this result show that as the plant growth increased inline plant height and stem diameter as contributed to the conserved soil moisture, seedling emergence, and improved plant growth (okunade et al., 2009). figure 4, the results of yield for the eight days after planting showed a significant difference in dap 5, 10, 15, 20, and 25 days among the irrigation system. however, there were no significant in 30, 35, and 40 days from plant growth under idi as indicated by (sexena et al., 2013). the mean okra yield performance after 40 days under idi and control system was 3470 and 292 cm, respectively (table 1). based on the results in figure 4, the analysis carried out proved that there is significant difference in idi used with respect to the number of okra yield against dap in control. therefore, the number of okra increase based on the amount of rainfall. (jayapiratha, et al., 2010). from figure 5 displayed the relationship between the weights of okra against day after harvest, the relationship is linear and there is significant difference in idi respect of control systems (danso et al., 2015). the weight of okra production against days after planting (cm) for the eight reading after 5, 10, 15, 20, 25, 30, 35 and 40 days showed that there was a significant difference in idi compare to control system ahmad et al., (2013). the summation of weight of production after 40 days of planting under idi and control system was 45.61 and 10.60 kg, respectively (puneet et al., 2015). thus growth is not faster under the control system because no treatment was added. this system and results is in line with findings of ahmad et al., (2013). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):1-7. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 5 table 1: growth performance under improvised drip irrigation system (idi) dap height of okra (cm) stem girth (mm) number of leaves okra yield (kg) weight of okra (kg) idi control idi control idi control idi control idi control 5th 6.30 2.10 0.136 0.121 34 15 34 0 1.07 0 10th 12.20 6.30 0.171 0.141 50 30 344 0 5.07 0.84 15th 16.03 5.45 0.254 0.222 68 44 519 30 5.14 1.40 20th 17.49 9.54 0.264 0.330 101 99 415 37 5.20 1.20 25th 20.13 9.55 0.332 0.311 115 99 393 44 6.96 2.72 30th 22.13 9.56 0.394 0.324 201 101 650 72 6.18 1.72 35th 27.00 10.12 0.465 0.412 231 104 528 62 5.55 1.84 40th 30.40 10.70 0.680 0.430 251 106 587 47 10.45 0.88 figure 1: height of okra production (cm) against day after planting figure 2: stem girth of okra (cm) against days after planting (dap) figure 3: number of leaves (cm) against days after planting (dap). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng amoo et al.: growth performance characteristics of okra (hibiscus esculentus) using improvised drip irrigation system. azojete, 14(sp.i4):1-7. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 6 6 figure 4: number of okra yield performance (cm) against days after planting (dap) figure 5:weight of okra production (kg) against days after planting (dap) 4.0 conclusion and recommendation 4.1 conclusion the growth performance characteristic of okra on improvised drip irrigation system was investigated, this leads to minimized of water usage, fertilizers, land utilization and increased fruit yields as well as production of okra calls for an effective irrigation system. growth occurs through the effect of soil types and watering treatments had no significant different on its. therefore, okra may not require much water for maximum growth germination at the initial stage. 4.2 recommendation based on the results obtained from the study, improvised drip irrigation system (idi) is highly recommended for the effective cultivation of okra seeds and the amount of water required to irrigate is low compared to other irrigation systems. reference ahmad, sa., mahmood, aj., malik, a. and kumbhar, mb. 2013. response of okra to water stress, sarhad journal of agricultural 19: 73-79. al-harbi, ar., al-omran, am. and el-adgham, fl. 2008. effect of drip irrigation levels and emitters depth on okra (abelmoschus esculentus) growth. journals of applied sciences 8(15): 2764-2769. published by asian network for scientific information alkaff, sa. 2003. effect of organic fertilizer and foliar application of power 4 on growth and yield on okra plants. university of aden journals of water management science 7(1) 25-35 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):1-7. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oke.matthew@adelekeuniversity.edu.ng, amaomonsuru@gmail.com 7 babar, mm., shaikh, ah. and yaseen, sm. 2008. a comparative study on drip and furrow irrigation methods. mehran university j. engineering and technology, jamshoro. 27 oct. 2008, pp.413-418. choudhary, s., chandra, a. and yadav, pk. 2012. effect of crop geometry on okra (abelmoschus esculentus) cultivars under different irrigation levels and mulching, progressive horticulture, 44(2), 276-280. danso, oe., mickson, sa., sabi, eb., plauborg, f., abekoe, m., kugblenu, yo., jensen, cr. and andersen, mn. 2015. effect of different fertilization and irrigation methods on nitrogen uptake, intercepted radiation and yield of okra (abelmoschus esculentum l.) grown in the keta sand spit of southeast ghana, agricultural water management, 147, 34-42. fasina, as. 2008. irrigation suitability evaluation of asu river basin soils, south eastern nigeria. int. j. soil sci., 3(1): 35 – 41. jayapiratha, m., thushyanthy, v. and sivakumar, s. 2010. performance evaluation of okra under drip irrigation system.asian journal of agricultural research, 4:137-147. kamran, bs., hakim, as., javaid, ar., bhugro, m. and sakhawat, hk., 2012. effect of marginal quality water on okra. international journal of engineering research and technology. 4: 5667. metin, ss., yazar, a. and eker, s. 2006. effect of drip irrigation regimes on yield and quality of field grown bell pepper agricultural water management vol.4: pp 115-131. michael am. 2000. irrigation: theory and practice. 1st ed vikas publishing house ltd. new delhi, india modupe, ja., oluwakemi, ea. and joshua, k. 2015. effects of irrigation and soil types on the germination and growth of okra (abelmoschus esculentus l. moench). journal of plant sciences. vol. 3, pp. 59-63. okunade, da., olanusi, oa. and adekalu, ko. 2009. yield, and economics of okra and amaranth production under irrigation. international journal of vegetable science, vol. 15, 28–43. pravukalyan, p., narendra, ns. and sanatan, p. 2011. evaluating partial root-zone irrigation and mulching in okra (abelmoschus esculentus l.) under a sub-humid tropical climate. journal of agriculture and rural development in the tropics and subtropics. vol. 112 no. 2 169–175. published by jarts. puneet, s. and arun, k. 2015. economics of growing okra under drip fertigation. indian journal of science and technology vol. 8 pp 35. saxena, ck., gupta, sk., purohit, rc., bhaka, sr. and upadhyay, b. 2013. performance of okra under drip irrigation with saline water, journal of agricultural engineering, 50(4), 683-689. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng figure 4, the results of yield for the eight days arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):911-918 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 911 original research article implementation of vehicle accident monitoring device along beninwarri road g. i. efenedo1* and j.o. egwaile (1department of electrical and electronic engineering, delta state university abraka (oleh campus) 2department of electrical and electronic engineering, university of benin, benin-city) * corresponding author’s email address: efegabs@gmail.com 1.0 introduction on daily, monthly and yearly bases, death resulting from accidents is alarming. accident is an unexpected and unpleasant event (hornby, 2013). according to the world health organization. road accidents kill more than 1.2 million people every year, representing 21% of all deaths, and cause 50 million injuries. people, aged 15 to 44 years, who are the economically active adults, account for more than a half of the total road traffic deaths and about 30% to 86% of all trauma admissions as a result of road traffic crashes in some low-income and middle-income countries (peden et al., 2004). the problem of road traffic crashes and injuries is growing and this poses a serious developmental and public health problems. generally, the poorer population groups in developing countries bear a disproportionate burden of avoidable consequences from road traffic injuries. in the case of rich countries, children from relatively lower socio-economic classes also suffer a higher burden of morbidity and deaths from road crashes than their counterparts from high-income groups (akpoghomeh, 1998). the economic cost of road accidents and resulting injuries is estimated at $518 billion worldwide. irrespective of the numerous measures put in place to curb the menace, little or no success had been achieved. as article information abstract vehicle accident motoring system is a system that automatically senses an accident in real time and sends an sms alert to predetermined numbers for rescue of accident victims. the system comprises of a designed accident detecting device to be installed in vehicles that read and interpret geographical coordinates of various locations along benin-warri road and gsm mobile phone. the device has a vibration sensor, gsm/gps module with an embedded computer chip which was programmed with c language. the coordinates of the locations were collated using gps measuring instrument and serves as input to the device. the obtained data were subject to normality and correlation test for validation. the results show that the data are normally distributed and significant at 0.01 the device was programmed in such a way as to convert the latitude, longitude and altitude of a spot to its equivalent assigned or known name. if an accident occurs at any spot along the road, the device immediately sends the names of the location via sms alert to relevant numbers. it was tested for the route and various successful accident alert messages were registered. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 october, 2018 revised 15 june, 2019 accepted 19 june, 2019 keywords: vehicle accident location gps gsm monitoring. http://www.azojete.com.ng efenedo and egwaile: implementation of vehicle accident monitoring device along benin-warri road. azojete, 15(4):898-918 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 912 in other developing countries, road traffic accident in nigeria is one of the most serious problems in need of pragmatic solution. yet this problem has been difficult to address probably because of the country’s level of development. nigeria is said to have the highest road traffic accident rates in africa and the second in the world (nantulya and reich, 2003). according to statistics published by nigeria watch in 2015 on the trends and patterns of fatal vehicle accidents in nigeria (ukoji, 2015), approximately 61,090 people lost their lives in 14,087 events nationwide from year 2006 to 2014. the publication also revealed that lagos state recorded the highest number, with 1,543 car accident deaths, followed by edo with 1,201 deaths and fct (abuja) with 1,026 deaths. on the other hand, the statistics released by the federal road safety commission annual report 2015, shows that a total of 1,115,663 road traffic crashes were recorded from the year 1960 to 2015 that resulted to the death of 343,909 persons across the country. from the data, year 2015 alone recorded a total of 9734 traffic crashes with 5440 deaths. detailed review of the year 2015 in some states shows that. kaduna state recorded the highest number of fatalities with 474, followed by fct with 328 deaths, kogi with 310 deaths while edo and delta states recorded 184 and 151 deaths respectively. bayelsa (16 deaths), taraba (14 deaths) and borno (2 deaths) states recorded far fewer fatal road accidents. from the data, edo and delta states recorded a total of 2088 road crashes that led to 335 deaths in 2015 (frsc, 2016). 2. literature review 2.1 traffic monitoring and accident detection at intersections the traffic monitoring and accident detection at intersections is a modelled system based on local analysis of the behavior of a vehicle at intersection. it identifies a vehicle and track its behavior and to recognize situations or events that are likely to result from a chain of such behavior. in order to solve this problem an algorithm, referred to as spatio-temporal markov random field (mrf), for traffic images at intersections was formulated using blocks. this algorithm models a tracking problem by determining the state of each pixel in an image and its transit, and how such states transit along both the x-y image axes as well as the time axes. vehicles, of course, are of various shapes and they move in random fashion, thereby leading to full or partial occlusion at intersections. the following are models formulated in its realization (shunsuke et al., 2000). u12 yk) = u(yk = q1 −u(yk = q2) (1) where: y is label distribution of a vehicle, k is block number, q1 is vehicle label 1 and q2 is vehicle label 2. u12 (yk=q1) is the energy for a block of yk having a vehicle labeled q1 among two possible vehicles labeled as q1 and q2. the derivative of equation 1 is shown in equation 2. u12� yk = a ny yk = q1 − ny yk = q2 − {ny yk = q1 + ny yk = q2 − 2μny} + b mxy yk = q1 − mxy yk = q2 − {mxy yk = q1 +mxy yk = q2 − 2μmxy} + c{dxy (yk = q1)2 − dxy (yk = q2)2} (2) since the energy function ck is to confuse two blocks as the case of accident, ny yk = q1 + ny yk = q2 = 2μny (3) mxy yk = q1 +mxy yk = q2 = 2μmxy (4) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 911-918. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 913 where, ny is the number of neighbour blocks of a block ck, mxy is the goodness measure of the previous object while μ is a constant. the resultant effect to the energy function of equation 1 is shown in equation 5. u12 yk = α ny yk = q1 − ny yk = q2 + β mxy yk = q1 −mxy yk = q2 + γ{dxy (yk = q1)2 −dxy (yk = q2)2} (5) where: α, β and γ constants while dxy is energy function estimate. looking at equation 5, it is symmentrical with respect to q1 and q2. suppose u12(yk) is negative, the block ck will likely have more q1 than q2. again, if u12(yk) is positive, the block ck will likely have more q2 than q1 that indicates accident (shunsuke et al., 2000). 2.2 smartphones to detect car accidents that provide situational awareness to emergency responders the smartphones car accidents detecting and situational awareness to emergency responders is also called the wreck watch. it provides functionality similar to an accident/event data recorder by recording the path, speed, and forces of acceleration on a vehicle leading up to and during an accident. it can also notify emergency responders of accidents, aggregate images and video uploaded by bystanders at the scene of an accident and send prerecorded text and/or audio messages to emergency contacts. it is built using google android on the client and java/mysql with jetty and the spring framework on the server. the wreck watch is separated into two main components (the wreck watch server and the wreck watch client). the wreck watch client provides mapping functionality through google maps on the device to ensure that emergency responders continuously receive information about an accident. the wreck watch android client is written in java based on android 1.5 with google apis that consists of several android application activities for mapping, testing, and image upload. the background services detect accidents by polling smartphone system sensors, such as the gps receiver and accelerometers. as accident information becomes available, the wreck watch server posts location, route and severity information to a google map to aid emergency responders, as well as other drivers attempting to navigate the roads near the accident (chris et al., 2011). 2.3 development of automatic geofencing and accidental monitoring system based on gps technology the development of automatic geofencing and accidental monitoring system is based on gps technology embedded in vehicle to detect road accident for immediate medical help as well as for security purpose in theft prevention using single shock sensor. in case of accidental mode, the system informs automatically via text message to medical rescue team indicating the position of vehicle location. when the driver is out of the vehicle, the system automatically goes into security mode. at this mode, a theft attempt on the vehicle, this system sends an alert message to the owner. mobile text message is containing location from gps (latitude, longitude) will be sent if the device detects an accident. the major shortcoming in this work include detecting only a vehicle that exceeded its maximum speed limit, but incapable of detecting accident occurrence and reporting same with precise location (danish and jaspal, 2013). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng efenedo and egwaile: implementation of vehicle accident monitoring device along benin-warri road. azojete, 15(4):898-918 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 914 3. materials and methods 3.1 accident detecting device design figure 1 is the block diagram of the designed accident detecting device. it was implemented with the following major units/components namely; the vibration sensor model spm8667vc, the gps/gsm dual module sim808, lcd display lm018 (16x2) and the programmable microcontroller pic18f2550. the pic18f2550 microcontroller was chosen from the microchip technology 2006. it could communicate with gps/gsm module, drives the display, reads in real time picture date from camera, responds to motion detection signal from the pir, and drives the buzzer when necessary. it is a 28-pins, 8-bit, integrated circuit that has in-built universal asynchronous receiver transmitter (uart) module, pulse width modulation (pwm), in-circuit serial programmer (icsp) and runs at a high clock speed of 48mhz. it also has an internal program memory capacity of 32kilobytes, a 16384 single word instructions, data memory capacity of 2048 bytes and 256bytes of sram. in addition, it has an eeprom that can make it perform many functions almost at the same time. its power consumption is 5vmax. figure 2 is the ic representation of the pic18f2550 microcontroller. the accident detecting device is powered with a 12vdc which is the conventional battery rating of cars and vehicles. fgure 1: block diagram of proposed accident detecting device. figure 2: pic18f2550 microcontroller ic representation. (microchip 2006) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 911-918. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 915 3.2 accident detecting device input data implementation the accident reporting device inputs data are raw longitudes and latitudes obtained at interval of 150m along benin-warri road. the longitudes and latitudes data were obtained in degrees and minutes using a gps measuring device called garmin gpsmap78sc. the raw data were converted to their equivalent decimal values, a format for programming the microcontroller using the latlong converter software. furthermore, the data were validated by computing for the distance between each location along the benin -warri road. this was realized by programming the excel for ⧍d using the haversine formula in equation 6 (noel and montavont, 2006). haversin d r = haversin ϕ1 − ϕ2 + cos ϕ1 cos ϕ2 haversin ∆λ (6) where : haversin is the haversine function, d is the distance between the two points (along a great circle of the sphere) r is the radius of the sphere (earth) = about 6371km is the latitude of point 1 is the latitude of point 2 δλ is the longitude separation from equation 6, d can be solved for by applying the inverse haversine or by using the arcsin (inverse of sine) function, where: d = rhaversin−1 h = 2rarcsin √h and h = haversin d r 3.3 accident detecting device operation the accident detecting device starts its operation with a vibrating sensor that is set at optimum vibrating resonant frequency of 50 khz estimated for accident vibrations cases. when an accident occurs, the vibrating sensor converts the mechanical vibration to analog signal. this signal is in turn converted to digital signal with the aid of a/d converter. the signal is sent to the microcontroller chip which processes same and request at the same time for the spot where the accident occur from the gps module/receiver registering every spot coordinates of longitude, latitude and altitude with the aid of the gps satellite. the microcontroller then converts the raw data coordinates to its equivalent known nomenclature of the spots along warri-benin road. the location nomenclature is again processed and sends to registered numbers of rescue agencies, relatives and friends of the victim via gsm network. the major role of the microcontroller is to extract speed information from the gps satellites via the gps module and then display them on the lcd while constantly checking the vibration levels and comparing them with already predefined values so that once the measured vibration values fall off the safe range or rises above the safe zone, a message alert is sent to the emergency response personnel via the gsm modem. this is actualized by continuously analyzing digital signals from inputs from the vibrating sensor and gps controller circuits. the microcontroller output sends a high logic "1" signal to the sms controller circuit when a high is received at its input from the vibrating sensor. the signal from the microcontroller also drives the led indicators showing vibrating level and gps network status. it also receives signals from the gps, process same and send the appropriate codes to a mobile phone as sms alert of accident occurrence to predetermined receivers. to have an easy access to the satellite, the gps receiver file:///c:/users/user/downloads/azojete143/www.azojete.com.ng efenedo and egwaile: implementation of vehicle accident monitoring device along benin-warri road. azojete, 15(4):898-918 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 916 is placed on cars /vehicles dash boards. the raw data employed in programming the pic18f2550 microcontroller were obtained with the aid of gps measuring device and the authentication of the data were verified with the aid of a google maps coordinates of these selected spots along the route. c programming language was the software used for the device based on its compatibility and user friendly. 4. results and discussion the collated gps data of longitudes and latitudes obtained from benin-warri road were subjected to normality as well as correlation tests using the spss program and the results are shown in figures 3, 4 and table 1 respectively. figure 3: longitude normality distribution curve. figure 4: latitude normality distribution curve. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 911-918. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 917 table 1: correlation test for both longitude and latitude. correlations long(λcon) latt(φcon) long(λcon) pearson correlation 1 -.957** sig. (2-tailed) .000 n 608 608 latt(φcon) pearson correlation -.957** 1 sig. (2-tailed) .000 n 608 608 **. correlation is significant at the 0.01 level (2-tailed). analysis of figures 4 and 5 shows that the data are normally distributed with deviations of 0.2173892759 and 0.0519660452 respectively for the longitudes and latitudes while the relationship between longitudes and latitudes is significant at 0.01 level being less than standard 0.05 using two tail correlation test as shown in table 1. the vibration shock sensor, microcontroller and gps/gsm module were tested individually as well as with an integrated system. the assembled device was tested along benin-warri highway while in a vehicle on motion. testing results shows that the device performed satisfactorily as alert messages at various locations of accidents occurrence as manually simulated were automatically sent by the device at real time. output results generated in form of sms messages by the device were sent to programmed gsm numbers as designated safety personnel. example of such messages is "accident detected! location: ologbo town". 5. conclusion this paper presented an accident monitoring device that was designed based on gps technology. the major objective of this system is to reduce informative time of contacting rescue agencies and relative of accident victims when an accident occurs. manual callings which has many limitations that usually lead to time delay, before attending to accident victim(s) is drastically reduces. the data used in programming the microcontroller were validated and are significant at 0.01 less than 0.05 tolerance value. references akpoghomeh, os. 1998. temporal variations in road traffic accident parameters in the port harcourt metropolis. journal of transport studies, 2(1): 15-36. chris, t., white, j., dougherty, b., albright, a. and schmidt, dc. 2011. wreck watch: automatic traffic accident detection and notification with smartphones. international journal of mobile network and applications, 16(3): 285-303. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng efenedo and egwaile: implementation of vehicle accident monitoring device along benin-warri road. azojete, 15(4):898-918 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 918 danish, k. and jaspal, s. 2013. development of automatic geofencing and accidental monitoring system based on gps technology. international journal of computer science, engineering and applications, 3(4): 57-65. frsc. 2016. federal road safety commission annual report 2015. frsc abuja. issn: 24678759 pp 29 – 42. hornby, as. 2013, advance learner's dictionary. oxford university press, london. new 8th edition. isbn 978-0-19-479914-0 pp 08. microchip. 2006. pic18f4550/4455/2550/2455 data sheet. microchip. technology inc., pp 01 77. nantulya, vm. and reich, mr. 2003. equity dimensions of road traffic injuries in lowand middle-income countries. journal of transport studies, 10(1-2): 13-20. noel, j. and montavont, t. 2006. ieee 802.11 handovers assisted by gps information, wireless and mobile computing, networking and communications 2006, (wimob'2006). montreal canada, june 19-21, 2006. ieee international conference on wireless, montreal, pp. 166-172. peden, m., scurfield, r., sleet, d., mohan, d. and hyder, a.a, 2004. world report on road traffic injury prevention. world health organization, geneva, pp. 34 – 57. shunsuke, k., yasuyuki, m., katsushi, i. and masao, s. 2000. traffic monitoring and accident detection at intersections. ieee transaction on intelligent transportation system, 1(2): 108-119. ukoji, vn. 2014. trends and patterns of fatal road accidents in nigeria from 2006 to 2014. ifranigeria working papers series, no. 35. pp 01-35 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 725-732 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 725 original research article an assessment of some of the poisonous plant species to animals found in delta state, nigeria a.h. erhenhi1 and e.e. lemy2 (1department of botany, faculty of science, delta state university, abraka, nigeria 2department of animal and environmental biology, faculty of science, delta state university, abraka, nigeria) * corresponding author’s email address: aherhenhi@delsu.edu.ng article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: assessment poisonous plants phytochemicals delta state abstract this study investigated some poisonous plants to animals in three communities viz; ebor-orogun in ughelli north local government area; kwale in ndokwa west local government area and ozoro in isoko south local government area, all in delta state, nigeria. dried leaves, roots and tubers of dennettia tripetala, cola nitida, dracaena marginata, cucumis melo, terminalia catappa, persea americana, manihot esculenta, telfaira occidentalis and vernonia amygdalina were grounded to coarse powders and 16g of each powder was weighed into a conical flask. distilled water (120cm3) was added and the content was shaken and kept for 48hours at room temperature. filtration of the extract was carried out using whatman no1 filter paper and concentrated using vacuum evaporator. phytochemical analysis was carried out using standard methods. the results revealed that there were nine (9) indigenous plants with poisonous effects to animals as reported by the community dwellers, among the selected plants and these include: d. tripetala, c. nitida, d. marginata and c. melo, t. catappa, p. americana, m. esculenta (tuber), t. occidentalis (root) and v. amygdalina (root). qualitative analysis showed the presence of alkaloid, anthocyanines, cardiac glycoside, flavonoid, glycoside, phenol, reducing sugar, saponin, saponin, tannin and terpenoid in low, moderate and high level in the plants. the chemical quantification revealed the presence of tannin (26.90%, 22.95%, 27%) in c. melo, d. tripetala and c. nitida, saponin (13%) in n. laewis, cyanogenic glycoside (3.24mg/l, 1.11mg/l) in m. esculenta and v. amygdalina followed by hydrogen cyanide (0.76mg/l, 0.75mg/l, 6.41mg/l) in p. americana, t. catappa and t. occidentalisas the major cause of poisoning in the plants encountered.there is need for evaluation of the effects of these substances on the organs and systems of animals in order to ascertain the actual site of toxicity of these substances. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction animal husbandry is one of the integral agricultural practices in different parts of the world, although subsistent, it provides both food and income to the people. some of the inhabitants of these communities depend largely on these livestock for survival, hence the immense importance of the animals in their lives. forage crops may contain compounds that may inadvertently affect animals (birgit et al., 2006). in countries with higher plant biodiversity, the http://www.azojete.com.ng erhenhi and lemy: an assessment of some of the poisonous plant species to animals found in delta state, nigeria. azojete, 15(3):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 726 number of problematic toxic plants may be many (welelign and mekuriaw, 2016). however, land used for grazing contains both native and invasive plants which increase animal exposure to toxic plants with limited characterization (birgit et al., 2006). losses recorded in animals can be heavy if animals graze in field containing toxic and poisonous plants (usda, 2011). several plants of varying species and characteristics accumulate toxic substance in different concentrations. such plants include amaranthus species, solanum species and chenopodium species as reported elsewhere to contain some toxic nitrate at high concentration (puschner et al., 2006). prevention of loss from poisonous plants in general is a problem of range and livestock management (pfister et al., 2002). as these plants form are essential components of animal diets and at moderate grazing rate, they will result to no negative effects. consumption of these plants at excessive rate due to stress conditions and starvation may lead to poisoning. diagnosing a plant poisoning can be extremely difficult. in many cases, clinical signs are nonspecific (such as diarrhea) and post-mortem lesions are not characteristic (gupta, 2018). specialized veterinary toxicology laboratories may provide testing for plant toxins, but the assays do not cover the wide variety of plant toxins present in most countries (gwaltney-brant, 2016). there has been a major interest in rate of poisoning caused by consumption of plants; this has resulted in restriction in the consumption of certain plants by humans and animals (assi et al., 2016). this is a major concern to researchers and it is on this basis this study was developed. the objective of this study is therefore to determine the species of plants poisonous to animals in delta state, nigeria with a view to evaluating their chemical composition and toxicity to animals. 2. materials and methods 2.1 description of study area this study was conducted in three communities viz: ebor-orogun in ughelli north local government area; kwale in ndokwa west local government area and ozoro in isoko south local government area, all of delta state, nigeria (figure 1). delta state covers a landmass of about 18,050 km2 of which more than 60% is land. the state lies approximately between longitude 5°00 and 6°45' e. and latitude 5°00 and 6°30' n. it is bounded in the north east, south-east and on the southern flank by edo state, anambra state, bayelsa state and bight of benin respectively. the state is generally low-lying without remarkable hills. it has a wide coastal belt inter-lace with rivulets and streams, which form part of the niger-delta. delta state has a population of approximately 4,098,291 (federal republic of nigeria gazette, 2007) and an estimated area of 762km2. the state is ethnically diverse with people and different languages spoken in the state (national human development report, 2018). the whole ethnic groups that comprise the state are administratively grouped into three senatorial districts namely delta north, delta south and delta central and have respective human population of 1,229,074; 1,293,282 and 1,575,738. the state is made up of twenty-five local government areas. different animals including goat, dogs, sheep, pigs, birds and cattle grazes in the area. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):725-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 727 figure 1: map of delta state showing sampled areas source: osayande et al. (2016). 2.2 collection of poisonous plant plants with history and records of poisonous substances to animals were sorted within the selected local communities in delta state. information on the poisonous nature of the plants was obtained from the locals. all the species of plant were collected from the three different communities. leaves were collected using knife, stem were collected from the parent plant using cutlass while the root and tubers were collected by uprooting the plant from the soil with the aid of cutlass and hoe and used for analysis of major secondary metabolites. 2.3 extraction of the plant materials fresh leaves, roots and tubers of the collected plants were washed carefully in clean running tap water and dried at room temperature. dried leaves were grounded to coarse powder, and 16g of the powder was weighed into conical flask and distilled water (120cm3) was added and covered with aluminum foil. the content was shaken and kept for 48 h at room temperature. filtration of the extract was carried out using whatman no1 filter paper and the filtrate was concentrated using vacuum evaporator (auwal et al., 2012). 2.4 phytochemical screening of plant extract phytochemical screening of the plants samples were carried out using a modified method of auwal et al. (2012). tannins was determined by pouring 2.0 cm3 of the extract in a test tube and diluted with 5ml distilled water. a blue black colouration was formed by adding 2 – 3 drops of 5% ferricchloride solution which indicated the presence of tannins. flavonoids was determined in the samples by adding 2ml of petroleum ether to 0.5g of the plant extract and shaken to remove file:///c:/users/user/downloads/azojete143/www.azojete.com.ng erhenhi and lemy: an assessment of some of the poisonous plant species to animals found in delta state, nigeria. azojete, 15(3):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 728 the lipid layer. the residue was further dissolved in 20 cm3 of 80% ethanol and filtered. 5ml of 1% potassium hydroxide was added to 3cm3 of the filtrate in a test tube and colour change was observed. the presence of dark yellow colouration indicated the presence of flavonoids. alkaloid was determined by adding 2 -3 drops of dragendoff’s and mayer’s reagents to 10 cm3 of the aqueous extract in 2 separate test tubes. the presence of orange red precipitate/turbidity with dragendoff’s and white precipitates with mayer’s indicated the presence of alkaloids. cardiac glycoside was determined as follows. 5 cm3 of the aqueous extract was mixed with 2 cm3 of glacial acetic acid containing one drop of ferricchloride (fecl3) solution. this was followed by the addition of 1 cm3 concentrated sulphuric acid. the presence of brown ring at the interface indicated the presence of glycoside. test for saponins was carried out as follows. 0.5g of grounded plant material was poured into a test tube and 5 cm3 of water was added and shaken. saponin was indicated by persistent froth for about 15 min. 2.5 statistical analysis the results obtained from the different analysis were subjected to statistical analysis using microsoft office excel version 2007 to obtain mean values. the results were presented in simple statistical tables. 3. results and discussion 3.1 identification of poisonous plants nine (9) poisonous plant species to animals were investigated within local communities in delta state during the study. the plants include d. tripetala, c. nitida, d. arginata and c. melo, t. catappa, p. americana, m. esculenta, t. occidentalis and v. amygdalina. 3.2 identification of chemical constituents different phytochemical constituents were identified from the leaves, root and tuber of these plant species and presented in table 1. the study showed the presence of secondary metabolites such as alkaloid, anthocyanines, cardiac glycoside, flavonoid, glycoside, phenol, reducing sugar, saponin, saponin, tannin and terpenoid to be present at various levels in all the plants recorded. although, anthocyanines was absent in d. tripetala, c. nitida, d. marginata, c. melo, p. americana and t. catappa, glycoside was also absent in m. esculenta, t. occidentalis and v. amygdalina. similarly, phenol was absent in d. tripetala, c. nitida, d. and marginata, c. while reducing sugar was relatively absent in c. melo, p. americana, t. catappa, m. esculenta, t. occidentalis and v. amygdalina. the study also showed that terpenoid was absent in t. occidentalis while other phytochemicals were present in all plants at varying degrees (table 1). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):725-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 729 table 1: qualitative phytochemical constituents of poisonous plants to animals phytochemicals d. tri pe ta la c. ni tid a d. m ar gi na ta c. m elo p. am er ica na t. ca ta pp a m .e sc ul en ta t. oc cid en ta lis v. am yg da lin a alk aloid + + + + + + +++ + + anthocyanines + ++ ++ cardiac glycoside ++ + + + + ++ + +++ flavonoid + + + + + + +++ + ++ glycoside + + + + + + phenol + + + + + + reducing sugar + + saponin + + + ++ ++ + + ++ ++ steroid ++ + + + + + ++ + + tannin + + + + + + +++ + + terpenoid ++ + + + ++ + + + key: +: low, ++: moderate, +++: high, -: absent the chemical quantification revealed the presence of tannin, saponin, cyanogenic glycoside and hydrogen cyanide as the major cause of poisoning in the plants encountered. the result showed that c. nitida and d. tripetala showed the presence of tannin while n. laewis showed the presence of saponin as the cause of poisoning. cyanogenic glycoside was extracted from m. esculenta, v. amygdalina and t. occidenttalis roots. p. americana and t. catappa revealed the presence of hydrogen cyanide while c. melo showed the presence of tannin as the cause of poisoning (table 2). table 2: quantification of poisonous chemicals present in plants s/n plants tannin (%) saponin (%) cyanogenic glycoside (mg/l) hydrogen cyanide (mg/l) 1 cucumis melo 26.90 0.0 0.0 0.0 2 persea americana 0.0 0.0 0.0 0.76 3 terminalia catappa 0.0 0.0 0.0 0.75 4 cola nitida 27 0.0 0.0 0.0 5 newbouldialaewis 0.0 13 0.0 0.0 6 dennettia tripetala 22.95 0.0 0.0 0.0 7 manihot esculenta grantz. 0.0 0.0 3.24 0.0 8 telfairia occidentalis hook. f. 0.0 0.0 0.0 6.41 9 vernonia amyygdalina del. 0.0 0.0 1.11 0.0 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng erhenhi and lemy: an assessment of some of the poisonous plant species to animals found in delta state, nigeria. azojete, 15(3):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 730 3.3 discussion the result of the study revealed the presence of different phytochemicals in plants poisonous to animals in different parts of delta state. this includes tannin, saponin, flavonoid, steroid, terpenoid, cardiac glycoside, alkaloid, glycoside and reducing sugar in different concentration. similar phytochemical has previously been reported by several authors including auwal et al. (2012) and okwu (2004). the result showed that the phytochemical qualification varies from plant. phytochemical variation in plant has been reported to alter the consumption pattern of plants by herbivores (andrea et al., 2016). the study also reported hydrogen cyanide, a toxic substance to animal which occurs via exposure to cyanide ions (cn−) when dissolved in water (soto-blanco et al., 2008). however, the toxic effects of these plants to animals may be due to the presence of multiple phytochemicals in the plants (auwal et al., 2012). several factors are responsible for the toxic nature of plants to animals. the result of this study showed that c. melo posse’s toxic compounds which are responsible for its detrimental nature to animals. however, the presence of lectins in c. melo has been identified to be detrimental to numerous insect andpests of crop plants (raman et al., 2012). the majority of these plant lectins are present in seeds, roots, stems and leaves. these lectins act as chemical messengers that could bind to the sugars of cells in the gut and the blood cells, initiating an inflammatory response (de melo et al., 2011). at high intakes, lectins can seriously threaten the growth and health of consuming individuals (sze and tzi, 2011). toxicity of p. americana has been reported to be poisonous to different animals by eduardo et al. (2013). however, this plant has also been reported in this study to be poisonous to animals due to the presence of cyanogenic compounds. m. esculenta recorded to be poisonous in the study has previous been reported by cereda and mattos (1996) to be toxic to animals due to the presence cyanogenic glucosides such as linamarin and lotaustralinin cassava plant. toxicity can result from adverse cellular, biochemical, or macromolecular changes. examples are: cell replacement, such as fibrosis, damage to an enzyme system, disruption of protein synthesis, production of reactive chemicals in cells and dna damage (xinsheng and jose, 2012). some xenobiotics may also act indirectly by modification of an essential biochemical function, interference with nutrition and alteration of a physiological mechanism (cutler, 2010). 4. conclusion the present study reported phytochemical composition and quantification of selected plants with toxic effects on animals. the result showed that the phytochemical contents of the plants varied both in qualification and quantification. the presence of certain phytochemical content such as cyanogenic glycoside and hydrogen cyanide in the plants is of major concern as these substances are toxic and could be the cause of death to animals. there is need for evaluation of the effects of these substances on the organs and systems of animals in order to ascertain the actual site of toxicity of these substances. references andrea, eg., christopher, sj., matthew, lf., thomas, lp., chris, cn., joshua, pj., joseph, sw., thomas, rw., lora, ar., angela, ms., michael, dl., colin, rm., wilmer, s., luis, as., craig, dd., jim, sm., eric, jt., santiago, v., lee, ad. 2016. intraspecific phytochemical variation shapes community and population structure for specialist caterpillars. new phytologist 212(1):208-219. https://en.wikipedia.org/wiki/cyanide http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):725-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 731 assi, ma., hezmee, mnm., haron, aw., sabri, mym., rajion, ma. 2016. the detrimental effects of lead on human and animal health. veterinary world 9(6):660-671. auwal, sm., atiku, mk., wudil, am. and sule, ms. 2012. phytochemical composition and acute toxicity evaluation of aqueous root bark extract of securidaca longipedunculata (linn). bayero journal of pure and applied sciences, 5(2): 67– 72. birgit,p., amy, p. and leslie, w. 2006. toxic weeds and their impact on animals. california animal health and food safety laboratory system, university of california. p16. cereda, mp. and mattos, myc. 1996. laminarin – the toxic compound of cassava. journal of venomous animals and toxins 2(1):6-12. cutler, jc. 2010. toxicity. in: encyclopedia of earth.http://www.eoearth.org/article/toxicity. retrieved august 2011. de melo, cm., porto, cs., melo, jmr., mendes, cm., cavalcanti, cc. and coelho, lc. 2011. healing activity induced by cramoll 1,4 lectin in healthy and immune compromised mice. international journal of pharmacy 408(1-2):113-119. eduardo, pc., moises, mv., jose, mf. and socorro, vr. 2013. acute toxicity and genotoxic activity of avocado seed extract (persea americana mill., c.v. hass). the scientific world journal 13:1-4. federal republic of nigeria official gazette 2007. legal notice on publication of the details of the breakdown of the national and state provisional totals 2006 census. gupta, rc 2018. veterinary toxicology; basic and clinical principles; third edition. academic press. 1238p. gwaltney-brant sm. 2016. veterinary forensic toxicology. veterinary pathology 53(5):1067-1077. national human development report (2018). achieving human development in north east nigeria; towards an understanding of the humanitarian development – peace nexus. published by united nations development programme. 116p. okwu, de. 2004. phytochemicals and vitamin content of indigenous spices of south eastern nigeria. journal of sustainable agriculture and environment 6:30-34. okwu, de. 2005. phytochemicals, vitamins and mineral contents of two nigeria medicinal plants. international journal of molecular medicine and advance science 1(4): 375-381. osayande, pe., orhue, er., oneju, aa., oseghe, do., maidoh, fu. and irhemu, p. 2016. biophysical properties of selected areas of delta state and their suitability assessment for coconut, raphia and oil palms cultivation. journal of environment and earth science 6(10):32-38. pfister, ja., provenza, fd., panter, ke., stegelmeier, bl. and launchbaugh, kl.2002. risk management to reduce livestock losses from toxic plants. journal of range management 55:291300. puschner, b., woods, l. and peters, a. 2006. toxic weeds and their impact on animals. in: proceedings of the western alfalfa and forage conference, sponsored by the cooperative extension services, plant sciences department, university of california. 6p. raman, bv.,sravani, b., rekha, pp., lalitha, kvn. and rao, bn. 2012. effect of plant lectins on human blood group antigens with special focus on plant foods and juices. international journal of research in ayurveda and pharmacy 3(2):255-263. http://www.eoearth.org/article/toxicity file:///c:/users/user/downloads/azojete143/www.azojete.com.ng erhenhi and lemy: an assessment of some of the poisonous plant species to animals found in delta state, nigeria. azojete, 15(3):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aherhenhi@delsu.edu.ng 732 soto-blanco, b.,stegelmeier, b.l. and pfister, ja. 2008. comparative effects of prolonged administration of cyanide, thiocyanate and chokecherry (prunus virginiana) to goats. journal of applied toxicology 28 (3):356–63. sze, kl. and tzi, bng. 2011. lectins: production and practical applications. applied microbiology and biotechnology 89:45-55. united states department of agriculture 2011. plants poisonous to livestock in the western states. agricultural research service, agricultural information bulletin number 415. 120p. walelign, b. and mekuriaw, e. 2016. major toxic plants and their effect on livestock: a review. advances in life science and technology 45:1-12 woods lw, filigenzi ms, booth mc 2004. myocardial degeneration and gastrointestinal disturbance in three horses associated with ingestion of grass hay containing summer adonis (adonis aestivalis). veterinary pathology 41:215-220. xinsheng, g. and jose, em. 2012. molecular mechanisms underlying chemical liver injury. expert review in molecular medicine 3:14:4. https://www.ncbi.nlm.nih.gov/pubmed/?term=gu%20x%5bauthor%5d&cauthor=true&cauthor_uid=22306029 https://www.ncbi.nlm.nih.gov/pubmed/?term=manautou%20je%5bauthor%5d&cauthor=true&cauthor_uid=22306029 https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=22306029 https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&retmode=ref&cmd=prlinks&id=22306029 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):269-278 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 269 original research article development and performance evaluation of an okra slicer t. a. ishola* and l. adewole (department of agricultural and biosystems engineering, university of ilorin, ilorin, kwara state, nigeria) *corresponding author’s email address: istab@unilorin.edu.ng 1.0 introduction okra (abelmoschus esculentus l.), also known as lady’s fingers, is one of the most significant fruit vegetables grown throughout the tropics and warmer parts of the temperate climatic zone (sankar et al., 2008). it is a tall (2 m) annual tropical herb cultivated for its edible green seed pod (owolarafe et al., 2011). okra could be available fresh all year-round in the southern part of nigeria and from may to october in many other areas. okra has both domestic and industrial applications. the leave buds and flowers are edible. the pods, when cut, exude a mucilaginous juice that is used to thicken stews (gumbo), and have a flavour somewhat like a cross between asparagus and eggplant (ehler, 2010). okra is a rich source of many nutrients, including fibre, vitamin b6, vitamin c and folic acid. it has many medicinal applications such as stability of blood sugar, binding excess cholesterol, replenishing sodium in the body and as anti-oxidants among others (adeboye and oputa, 1996). when fresh okra fruits are harvested, the average moisture content is 11.42 % (wet basis) (owolarafe and shotonde, 2004). okra is utilized in both fresh and dried forms for soups/stew making and the seed can be used to fortify non-protein foods. also, okra in powdered form has the properties of an emulsifier and can be useful in making emulsified prepared food (douglas, 1982). in west africa, production of okra as fruit vegetable is estimated at 500,000 to 600,000 tonnes per year (burkil, 1997). okra farmers and marketers experience a lot of annual post-harvest losses caused by poor handling, inadequate storage facilities because of the high perishability article information abstract the traditional method of slicing okra with kitchen knife is labourious, time-consuming and also prone to finger injury. both traditional method and existing mechanized okra slicer result in damaged and unequal slices of okra which may hinder proper drying of the okra for preservation. an okra slicer was designed, constructed and evaluated. the main parts of the machine were cutting discs, guided removable tray, loading hopper, the transmission system and the supporting frame. in the evaluation of the machine with okra, the performance indices investigated were slicing efficiency, throughput capacity, mechanical damage index and slicing uniformity. the highest slicing efficiency and throughput capacity for okra were 99.88 % and 194.11 kg/h respectively. the least mechanical damage index value of 0.30 % was obtained at a cutting speed of 1200 rpm. the mean slicing uniformity was 93.87 %. the machine developed in this study was able to produce uniform slices of okra of about 3.4 mm thickness. hence, industrial production and shelf life of dried okra could be enhanced. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 march, 2018 revised 20 june, 2018 accepted 23 june, 2018 keywords: okra slicing uniformity and efficiency http://www.azojete.com.ng ishola and adewole: development and performance evaluation of an okra slicer. azojete,16(2):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 270 nature of fresh okra fruits. the traditional method of preservation in nigeria is to process the pods into a crispy dry product (òrúnlá). this involves slicing the fresh fruit with a sharp knife, sun-drying and storage in sacks till when needed for cooking and marketing. the traditional method of slicing okra is quite labourious, time consuming, results in drudgery and also prone to hazard of finger injury (aji et al., 2018). in the same vein, the existing motorized okra slicer employ the method of gravity in loading the okra to the slicing unit which result in damage, escape of okra and non-uniform slices of okra (owolarafe et al., 2012). although, this machine had a slicing efficiency of 85.7 % at a speed of 400 rpm, the conveyance of okra was by gravity which allowed the presentation of the okra to be longitudinal, lateral or in any other position to the slicing unit of the machine. in addition, the machine damaged some okra fruits by cutting them longitudinally as shown in figure 1 (owolarafe et al., 2012). the presentation of the okra to the slicing unit determines the quantity and type of sliced material to be obtained. therefore, it is imperative to have a machine that will slice the okra in an acceptable manner with a slicing capacity that is commensurate to the scale of production of the okra fruits required with minimal mechanical damage. hence, the objective of this work was to design and construct a slicing machine for okra that feeds the fruit laterally to the slicing unit. this would enhance high production of okra with minimal damage at uniform slices for preservation and storage. figure 1. sliced okra fruits from existing motorized okra slicer source: owolarafe et al. (2012) 2 materials and method 2.1 design considerations some of the factors that were considered in the design of the machine included material availability, capacity of the slicer, lateral presentation of okra for slicing, shear force required to cut okra, moisture content of freshly harvested okra fruits, physical properties of okra and slicing uniformity. experiments were carried out to determine some physical properties like length and diameter of okra fruits which were required for the design of an okra slicer. the ila-iroko variety of okra fruits was used in this study (owolarafe et al., 2012). the average length and diameter obtained for okra fruit were 56.40 mm and 26.20 mm respectively. the average moisture content was 13 % (wet basis). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 269-278. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 271 2.2 rotational force required to slice okra the required rotational force, fc , to drive the shaft carrying the cutting discs was given by (hall et al., 1983): fc = md 2 2πn 60 2 (1) where: m = mass of the cutting disc (kg), d = diameter of the cutting disc (m) and n = speed of the shaft (rpm). choosing m = 1.335 kg, d = 0.115 m (gauge 14 stainless steel) and n = 400 rpm (owolarafe et al., 2012), the calculated value of rotational force was 134.69 n. this calculated value is greater than the shear force of 68 n required to cut okra (daniela et al., 2012). therefore, the force of the cutting disc was adequate to slice the okra. 2.3 power required by the cutting discs according to (hall et al., 1983), the torsional moment, mt available on cutting disc is given by: mt = fc d 2 2 where all the symbols are as earlier defined. having fc = 134.69 n, d = 0.115 m, the computed value of torsional moment was 7.74 nm. therefore, the power required to turn the shaft (pd) was given by (hall et al., 1983): pd = 2πnmt 60 3 where: n = 400 rpm (owolarafe et al., 2012) and mt = 7.74 nm (as earlier calculated), the computed value of pd was 324.21 w 2.4 design of the cutting disc shaft the shaft of the cutting discs was exposed to bending moment and torsional stresses. from the bending moments calculation, the maximum bending moment mb obtained was 0.492 nm. according to (hall et al., 1983), the required shaft diameter could be obtained from the equation d3 = 16 πss kbmb 2 + ktmt 2 (4) where: mb = maximum bending moment (nm), mt = torsional moment (nm), ss = permissible shear stress (mpa), kb = combined shock and fatigue factor applied to bending moment, kt = combined shock and fatigue factor applied to torsional moment and d = required shaft diameter (m). for a rotating shaft with gradually applied load, the bending fatigue factor, kb = 1.5 and the torsional fatique factor, kt = 1, permissible shear stress, ss = 95 mpa (hall et al., 1983). having mb = 0.49 nm, mt = 7.74 nm, kb = 1.5, kt = 1 and ss = 95 mpa, the calculated value of diameter of the shaft was 7.47 mm. 2.5 description of the machine the isometric projection, orthographic projection and pictorial view of the constructed motorized okra slicer are shown in figures 2, 3 and 4 respectively. it comprises of a set of cutting discs which shear and cut the okra fruits that are brought in contact with them into slices. the other components of the machine are loading hopper, guided removable tray and transmission system. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola and adewole: development and performance evaluation of an okra slicer. azojete,16(2):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 272 2.5.1 loading hopper: this is hopper in which the okra fruits are poured and allowed to fall by gravity on the guided removable tray. the okra fruits are further adjusted by hand to ensure that they are all lying laterally in the guides of the tray and all the guides are filled up. the loaded tray is later moved to the slicing section of the machine. 2.5.2 guided removable tray: this is where the okra fruits are placed horizontally during slicing operation. the tray was demarcated into rows to hold the okra fruits such that okra fruits were conveyed laterally to the cutting discs so as to ensure uniform slices. 2.5.3 cutting discs: there were eight sharp plain-edged cutting discs of 115 mm diameter each. they were equally spaced at 3.5 mm interval along their shaft and each disc was 2 mm thick (gauge 14 stainless steel) so as to achieve okra slices of 3.4 mm thickness. they performed the actual slicing operation when rotated by an electric motor. 2.5.4 transmission system: this comprised of 2 hp electric motor, a speed reduction gear of ratio 1:3 and chain-sprocket and belt drives. this system was designed to move the tray of okra fruit through the cutting discs. 2.6 operation of the okra slicer the okra fruits are fed into the hopper. the okra fruits fall by gravity on the guided removable tray which is placed under it. the okra fruits are manually adjusted on the tray to ensure that they are positioned laterally with respect to the orientation of the slicing discs in order to enhance proper slicing. after the guided removable tray has been loaded and the okra fruits properly positioned, it is manually removed and placed on the carriage. the transmission system could move forward and backward in order to present itself for the placement and removal of the loaded guided removable tray within the cycle of operation of the machine. a loaded guided removable tray is placed on the carriage for conveyance to the cutting discs. when the machine is put on, the cutting discs start to rotate according the set speed and the guided removable tray moves the loaded tray through the cutting discs for the okra fruits to be sliced. after the okra fruits have been sliced, the tray is removed. the transmission system is actuated to move backward in order to enable another loaded guided removable tray to be placed on the carriage for conveyance to the cutting discs. the machine works on shearing and cutting principle and its operation is in batches. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 269-278. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 273 figure 2. isometric projection of the okra slicer figure 3. orthographic projection of the okra slicer cutting discs loading hopper guided removable tray electric motor file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola and adewole: development and performance evaluation of an okra slicer. azojete,16(2):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 274 figure 4. pictorial view of the constructed okra slicer 2.7 performance evaluation the designed and fabricated okra slicing machine was tested to evaluate its performance on the basis of slicing efficiency, throughput capacity, mechanical damage and slicing uniformity. the machine was tested at cutting disc speeds of 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm and 1200 rpm. the choice of this wide range of speed was due to the fact that a sharp cutting disc that is rotating at high speed is bound to make clean cut of the okra fruit. moreover, owolarafe et al. (2012) asserted that the okra slicer developed in their research had improved performance at a speed of 400 rpm. the okra at moisture content of 13 % (wb) used for the test were bought from ipata market, kwara state, nigeria. for each treatment, a sample of okra was arranged on the guided tray and placed on the carriage of the machine. the movement of the tray was timed in order to determine the slicing time using stopwatch. the output materials obtained from the machine was collected and separated into two groups, that is, undamaged sliced material and damaged sliced material. the mass of each category was measured by using cl series (model 201) digital electronic balance. each treatment was replicated six times. slicing efficiency the slicing efficiency of the machine was obtained by using equation (5) which was used by agbetoye and balogun (2009). se = ws −wd ws 100% (5) where: se = slicing efficiency (%), ws = weight of all slices of okra fruits (kg) and wd = weight of damaged slices of okra fruits (kg). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 269-278. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 275 throughput capacity the throughput capacity equation utilized by agbetoye and balogun (2009) was employed to determine the throughput capacity of the machine. tc = ws t (6) where: tc = throughput capacity (kg/h),ws =weight of all slices of okra (kg) and t= time of slicing operation (h) mechanical damage index the mechanical damage index of the machine was calculated by using the equation (7) as employed by agbetoye and balogun (2009) md = wd ws × 100 (7) where: md = mechanical damage index (%),ws =weight of all slices of okra (kg) and wd =weight of damaged slices of okra (kg) slicing uniformity for slicing uniformity determination, twenty five slices of undamaged sliced okra were randomly selected and each slice thickness was determined by vernier caliper. equation (8) was used by fayose (2007) to calculate the slicing uniformity q = 100 × 1 − σ x� (8) where: q = slicing uniformity (%), σ = standard deviation of measured slice thickness (mm) and x� =mean of the measured slice thickness (mm). however, the standard deviation was calculated by using the equation (9) given by freund and wilson (2003): σ = i=1 n x − x1 2� n − 1 (9) where: x = measured slice thickness (mm), x1 = designed slice thickness (mm), n = number of slice pieces taken and i = serial number of slice pieces (1, 2, 3,…, n). 3 results and discussion 3.1 effect of cutting disc on the slicing efficiency of the machine the effect of cutting disc speed on the slicing efficiency of the okra slicer is shown in figure 5. the slicing efficiency value of 99.88 % was highest at a cutting disc speed of 1200 rpm. the least value obtained was 92.23 %. the high values of slicing efficiency could be as result of the principle of operation of the machine. generally, the slicing efficiency increased with increase in cutting disc speed. this may be as a result of soft texture of the okra fruit. this observation agrees with the reports of agbetoye and balogun (2009) and owolarafe et al. (2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola and adewole: development and performance evaluation of an okra slicer. azojete,16(2):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 276 figure 5. effect of cutting disc speed on slicing efficiency of the okra slicer 3.2 effect of cutting disc speed on throughput capacity of the machine the effect of cutting disc speed on the throughput capacity for okra slicer is as shown in figure 6. the highest value of throughput capacity was obtained as 194.11 kg/h at a cutting disc speed of 1200 rpm. the lowest value observed was 82.33 kg/h. the throughput capacity increased with increase in cutting disc speed. this may be as a result of texture and fibre content of okra variety (ila-iroko) used in this study. also, the cutting disc was able to cut faster at higher speed. similar trend was reported by agbetoye and balogun (2009) and owolarafe et al. (2012) for the effect of speed on throughput capacity of a multi-crop slicing machine and okra slicer respectively. figure 6. effect of cutting disc speed on throughput capacity of the okra slicer 3.3 effect of cutting disc speed on mechanical damage index of the machine the effect of cutting disc speed on the mechanical damage index is shown in figure 7. the mechanical damage index value decreased from 16.05 % at 300 rpm to 0.30 % at 1200 rpm. this may be due to the fact that the machine was able to make neater cut on the okra at high speed. also, the trend observed may be due to the okra variety (ila-iroko) used in this study. this trend agrees with that reported by ogbobe et al., (2007), agbetoye and balogun (2009) and owolarafe et al. (2012). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 269-278. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 277 figure 7. effect of cutting disc speed on mechanical damage index of the okra slicer 3.4 slicing uniformity the mean thickness for okra was found to be 3.4 mm and standard deviation of 0.18. the average slicing uniformity for okra was also found to be 93.87 %. the value of slicing uniformity obtained is greater than those that were achieved by owolarafe et al. (2012) and ogbobe et al. (2007). this could be due to the fact that the mode of operation of the machine in this study allows for better slicing of the okra fruits. once the cutting discs are sharp, there is no escape for the fruits and they would be neatly cut. figure 8 depicts the sliced okra fruits products from the machine developed in this study. in comparison, the machine reported in this paper was able to achieve a slicing efficiency of 99.88 % whereas the machine reported by ogbobe et al., (2007), and owolarafe et al. (2012) had slicing efficiency in the range of 85 to 86.7 % respectively. likewise, the two earlier machines had throughput capacity ranging from 21 to 42.8 kg/h while the machine reported here had a throughput capacity of 194.11 kg/h. it should be noted that by the design of the guided removable tray, the throughput capacity of the machine could be increased by increasing the length of the tray. figure 8. sliced okra fruits from the okra slicer 4 conclusions an okra slicing machine was developed and tested. based on the results of the performance evaluation, the machine produced uniform slices with average thickness of 3.4 mm and standard deviation of 0.18. the highest slicing efficiency and throughput capacity for okra were 99.88 %, 194.11 kg/h respectively. the average slicing uniformity was 93.87 %. for okra, the least mechanical damage index of 0.30 % was obtained at a cutting speed of 1200 rpm. this machine could further enhance the scale of production and quality of dried okra. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola and adewole: development and performance evaluation of an okra slicer. azojete,16(2):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 278 references adeboye, oc. and oputa, co. 1996. effects of galex on growth and fruit nutrient composition of okra (abelmoschus esculentus). ife journal of agriculture, 18 (1 &2):1 9 agbetoye, las. and balogun, a. 2009. design and performance of a multi-crop slicing machine. proceedings of the 5th cigr section vi international symposium on food processing, monitoring technology in bioprocess and food quality management, potsdam, germany. august, 31 – september, 02, 2009. 5: 622 640 aji, is., vakaa jk., madu, mj., suleiman, zb. and yakda, sb. 2018. development of a small scale okro slicing machine, arid zone journal of engineering, technology and environment, 14(1): 54 – 60. burkil, hm. 1997. the useful plant of west tropical africa. 2nd edition. vol 4, royal botanic gardens, kew. united kingdom. pp. 969. daniela, fo., alicia, m., alicia, rc., rodolfo, hm. and sonia, zv. 2012. quality attributes of okra (abelmoschus esculentus l. moench) pods as affected by cultivar and fruit size. journal of food research, 1(4): 224-235. douglas, ml. 1982. food and food production encyclopedia. van nostrand reinhold company, new york. ehler, jt. 2010. okra history and facts. retrieved from: http://www.foodreference.com/html/artokra.html, (accessed on: 23 december, 2015). fayose, ft. 2007. development of a cutting machine for food materials. journal of agricultural engineering and technology (jaet), 15(1): 58 65. freund, rj. and wilson, wj. 2003. statistical methods. academic press, london, pp 103 -104. hall, as., hollowenko, ar. and laughlin, hg. 1983. schaum’s outline series of theory and problems of machine design. mcgraw-hill publishers incorporated, new york, pp 113–121. ogbobe, po., ugwuishiwu, bo., orishaghemi, co. and ani, ao. 2007. design, construction and evaluation of a motorized okra slicer. nigeria journal of technology, 26 (2): 42-49. owolarafe, ok., obayopo, so., amarachi, oa.. babatunde, o. and ologunro, oa. 2011. development and performance evaluation of an okra slicing machine. research journal of applied sciences, engineering and technology, 3(9): 914-922. owolarafe, ok., obayopo, so. and ogunsina, bs. 2012. development and performance evaluation of a motorized okra slicing machine. journal of agricultural engineering and technology (jaet), 20(1): 10 18. owolarafe, ok. and shotonde, ho. 2004. some physical properties of fresh okra fruit. journal of food engineering. 3: 299 – 304. sankar, b., abdul, j.c., manivannan, p., kishorekumar, a., somasundaram, r. and panneerselvam, r. 2008. relative efficacy of water use in five varieties of abelmoschus esculentus (l.) moench. under water-limited conditions colloids and surfaces. biointerfaces, 62 (1): 125-129. http://dx.doi.org/10.1016/j.colsurfb.2007.09.025 http://dx.doi.org/10.1016/j.colsurfb.2007.09.025 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):28-36 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 28 28 original research article evaluation of a low-cost greenhouse for controlled environment cultivation of sweet pepper m. o. omobowale (department of agricultural and environmental engineering faculty of technology, university of ibadan, ibadan, nigeria) * corresponding author’s email address: mo.omobowale@ui.edu.ng 1.0 introduction climate change as well as continuous increase in population has necessitated the need for highly productive agriculture (lutz, 2017). climate change is one of the most serious environmental and human threats undermining the achievement of agricultural production in almost every part of the world. it is a real threat to lives and livelihoods as well as to the environment (stephenson et al., 2010). if food security will be attained, technologies that minimize external threats to crops and increase crop production are needed. one major way of providing efficient agriculture while preserving the quality of the environment is through article information abstract sustainable agriculture is critical towards paving a way for year-round production and supply of food all year round. cultivation of fruits and vegetables are vital due to high demand and nutritional values it provides to consumers. the rising global population especially in developing countries require other alternatives for sustainable crop production. cultivation in controlled environments using functional and durable greenhouse structures presents an option. a low-cost greenhouse was designed and constructed in ibadan, nigeria using locally available materials was evaluated. afrormosia wood was used in constructing the frame while polyethylene of 2.5 mm thickness was used as sheathing material for the walls. the floor which covered an area of 24 m2 was made of porous concrete of batching mixture 1:4 (cement to gravel) while the wall was 4 m high. ventilation was passive with a vent area equal to 25% of total surface area; made up of 20% at the wall area and 5% as the roof vent. the roof was pitched at a 18° slope to allow easy drainage of rain water. sweet pepper (capsicum annuum, cabernet) seeds procured burpee seeds usa were cultivated with the aid of planting pots within the greenhouse in comparison with those planted in the open field for a duration of eight weeks. evaluation was based on crop growth and yield parameters correlated with solar radiation, temperature and relative humidity in the greenhouse and ambient environments, respectively using randomized complete block design. data were subjected to descriptive and correlation analysis. peak temperature and rh were 31.1°c and 91.1% respectively within the greenhouse in comparison with 29.7°c and 89.7% respectively outside. peak solar radiation was 413.4 w/m2 in the greenhouse compared to 690.3 w/m2 in the ambient. growth parameters showed that the crops in the greenhouse performed optimally when compared with plants in the open field with a yield of 18.1 t/ha in the greenhouse compared with no-yield recorded in the open field. utilization of greenhouses in crop cultivation can help to mitigate the problem of food shortage. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 february, 2019 revised 20 april, 2019 accepted 25 april, 2019 keywords: microclimate greenhouse temperature relative humidity sweet pepper. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 28-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 29 greenhouse cultivation. greenhouse allows for the manipulation of essential variables such as temperature and relative humidity to achieve optimal crop production. controlled environment agriculture (cea) is the alteration of the environmental conditions to achieve a desired conducive environment for crop and animal production. cultivation of crops in greenhouses can be independent of environmental conditions, thereby boosting the possibilities of multiple harvest as compared to the seasonal open field agriculture. controlled environment agriculture is a technology-based approach toward food production albright (1990) with the aim of providing a protected environment for crop growth while maintaining optimal growing conditions throughout all developmental stages. forms of controlled environment agriculture include hydroponics, aeroponics, aquaculture and aquaponics. the benefits of controlled environment are numerous and far reaching and include, high volume of local food production in urban and exurban environments on a year-round basis, optimal growth conditions that eliminate the need for chemical fertilizers and harmful pesticides, controlled nature of food production significantly reduces water use and protects water quality. generally, greenhouses are defined as structures used to control environmental conditions for different crop cultivations (mijinyawa and osiade, 2011). although, climatic conditions affect crop production in the open field, the effects are limited in a controlled environment facility because greenhouses are built to provide a conducive environment irrespective of climatic conditions (jones and harrison, 2004; gorjian et al., 2011). it has also been reported that the application of greenhouse technology is economical on the long run in planting different crops, both in small and large-scale production (cook and calvin, 2005). interestingly, within a greenhouse, structural, mechanical, nutritional, and micro-climatic conditions are optimized to achieve the desirable crop growth (connellan, 2002, shamshiri et al., 2018). geometry, dimensions, and roof characteristics; reduction of solar intensity using shades and vents; forced air circulation and evaporative cooling are manipulated to achieve optimal air temperature, relative humidity and illumination (ponjican et al., 2011). these factors are vital in achieving productive and sustainable crop cultivation in a greenhouse. ali et al. (2012) reported that the production of horticultural crop provides more job opportunities per hectare of production in comparison to cereal crop. a good perspective of increased employment opportunities can be observed from the gradual shift of cereal production to high value horticultural crops such as tomatoes in some parts of the world (rao et al., 2003, ibeawuchi et al., 2015). babatola (2004) highlighted some challenges facing the agricultural sector such as poor extension services, land tenure, limited planting materials, low technology application, and limited postharvest facility. crop cultivation in greenhouses is a viable option towards increasing crop production. modern and conventional greenhouses are expensive to set up. the development of greenhouses from locally available materials will be a welcome development. this paper provides details of the design, construction, and evaluation of a low-cost greenhouse for cultivation of sweet pepper. 2. methodology 2.1 design the design considerations were based on possible external and internal loads on the structure, materials of construction, durability, rigidity, and microclimatic conditions. the construction site is a swampy reclaimed soil with laterite. the site is water-logged in the rainy season with high file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omobowale: evaluation of a low-cost greenhouse for controlled environment cultivation of sweet pepper. azojete, 16(1):28-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 30 water-table. moreover, the unproductive nature of the area made the location a good ground for greenhouse evaluation. adequate natural ventilation was provided with a vent of about 25% of the wall area. afrormosia lumber (known locally as ayin wood) material was used in the construction of the greenhouse frame due to its durability, hardness, workability, and ready availability. the following parameters were utilized in the design of the greenhouse according to mijinyawa (2012), based on green grade moisture content of 40%; permissible bending stress parallel to grain (11.2 n/mm2), permissible shear stress (1.4 n/mm2), compression parallel to grain (9.0 n/mm2), modulus of elasticity, e (13,200 n/mm2) and density (650 kg/m3). all structural components which made up the frame (purlins, rafters, beams, and columns) were designed using standard procedures. wind load was calculated from the expression q = 0.0127 × v2 × k (where q = velocity pressure in n/m2, v = wind velocity in m/s and k is a constant relating to the height of the building in m, fao, 2011). some of the other design parameters adopted are given in table 1. table 1: design parameter and values of the greenhouse structure s/n parameters values 1 greenhouse dead-load, w 15.9 n/m 2 wind load, q 4.24 n/m2 3 polythene covering density (low range) 0.925 kg/cm3 4 polythene thickness covering 2 mm 5 slope angle of roof 18° 6 bending and allowable stress of purlin 0.56 n/mm2; 11.20 n/mm2 7 maximum bending moments for beam 43.1 nm; 8 greenhouse floor area 24 m2 9 total roof vent area 2.16 m2 10 length of greenhouse 6 m 2.2 construction the frame of the greenhouse was constructed using 100 by 100 mm wooden columns, installed 400mm into the foundation slab. the floor was constructed using concrete grade c20 (mixing ratio 1:3:5) as recommended by fao, (2011) and a black coloured plastic film was incorporated as the damp-proof course (dpc) level as in figure 1. the floor had a gentle slope of about 5° to allow efficient water drainage. a transparent plastic sheet (polyethylene) of 2 mm thickness was used as the covering material (figure 2). it was selected because it is cheap, readily available, has good light transmittance and easy to use. this was achieved through the provision of top and side vents across the length of the greenhouse. the side vents were 1 by 6m while the tope vents were 0.2 by 6m in dimension, to allow cool air to flow through the side vents driving warm air out through the roof vents. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 28-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 31 figure 1: the greenhouse floor at the dpc level figure 2: greenhouse covering the greenhouse 2.3 evaluation temperature and relative humidity profiles were monitored in the greenhouse after which an evaluation was carried out by cultivating sweet pepper (capsicum annuum, cabernet). the seeds were obtained from burpee seed company, usa and raised in the nursery for four weeks. the seedlings were thereafter transplanted from the nursery to the greenhouse on the 10th of september 2016 into 33 plastic pots with a volume of 10 liters each (figure 3). sandy-loam soil was obtained, and thoroughly mixed and foreign materials removed. the mixed soil was then filled into the plastic pots and watered to set before transplanting. nitrogen-phosphoruspotassium (npk) fertilizer (15:15:15) was applied on the soil; the first application was performed two weeks after transplanting while the second application was performed three weeks later. the transplanted seedlings were adequately watered and monitored for any development. the control experiment was set up in an open field beside the greenhouse and the pepper seedlings were transplanted and monitored. crop performance (plant height, number of leaves, leaf area index and yield) were measured and recorded. plant height was measured from the base of the soil to the collar of the uppermost leaf using a ruler. five plants per row were sampled for crop performance parameters on a weekly basis. these were also measured for the control experiment. the leaf area was traced out on graph paper to measure area. from this measurement, this surface area and leaf area index were estimated by the formula: leaf area index (lai) = sa la (1) where: la is the leaf area and sa is the soil surface area covered by the plant. temperature and relative humidity data loggers (lascar el-usb 2 model, lascar electronics, usa) were placed inside and outside the greenhouse to record both ambient and greenhouse conditions. the data loggers were set to read at every one-hour interval. a light meter (solar power meter sm-206) was also used to record the light intensity entering the greenhouse daily while a digital weighing scale (accuris instruments w3300 with a capacity of 10 kg, 1 decimal place) was used to measure the weights of the harvested pepper. data collected were subjected to correlation and descriptive statistics. 3. results and discussion 3.1 temperature and relative humidity trends ambient and greenhouse temperature trends during the two-month evaluation period are shown in figure 3. the greenhouse had a peak temperature of 31.1°c while that of the ambient file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omobowale: evaluation of a low-cost greenhouse for controlled environment cultivation of sweet pepper. azojete, 16(1):28-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 32 temperature was 29.7°c. expectedly, greenhouse temperatures were higher than that of the ambient as radiant energy from the sun heats up the structure and part of the heat is trapped within. the temperature ranged between 26.5 to 31.1°c in the greenhouse throughout the entire growing period. this is considered suitable for sweet pepper production, which is known to perform well within maximum air temperature up to 35°c (kittas et al., 2005). similarly, relative humidity (rh) data showed that the greenhouse had a peak rh of 91.1% while that of the ambient rh was 80.4% (figure 4). moreover, rh within the greenhouse was consistently higher than that of the ambient which can be attributed to the consistent application of water within the structure to meet the crop water requirements of the plants (omid and shafei, 2005). figure 3: mean daily temperature trends in the greenhouse and ambient environment figure 4: daily relative humidity trends in the greenhouse and ambient environment 3.2 solar radiation the peak solar radiation within the greenhouse was 413.4 w/m2 while that of the ambient was 690.3 w/m2. ambient solar radiation was consistently higher than that of the greenhouse is due to the direct radiation from the sun, unlike the greenhouse where part of the solar radiation is diffused as it passes through the covering material (polythene). the relatively low-cost covering material was however suitable as it allowed sufficient solar radiation needed for photosynthesis into the greenhouse (figure 5). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 28-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 33 figure 5: daily solar radiation trends in the greenhouse and ambient environment 3.3 crop performance sweet pepper planted in the greenhouse performed better throughout the period of evaluation compared to the open field crops. comparison between mean plant height, number of leaves and leaf area of crops in greenhouse and open field at the end of the evaluation were 200.0 ± 17.6 and 89.5 ± 18.3 mm, 30.7 ± 7.87 and 10.8 ± 2.58 and 28.0 ± 8.67 and 7.4 ± 2.12 mm2 respectively (figures 6-8). similar results were reported by priya et al. (2002) in sweet pepper. moreover, within the greenhouse, mean stem diameter, leaf girth, root depth and shoot height were 4.21 ± 0.57 mm, 61.7 ± 18.29 mm, 126.1 ± 37.14 mm and 182.0 ± 48.32 mm respectively (figure 9). a total mass of 1,874.5g of sweet pepper fruit was harvested from the greenhouse, equivalent to 18.1 t/ha when the soil surface area in the greenhouse is considered. typical yields of sweet pepper ranges between 10 to 30 t/ha (stoffella et al.,1995; alsadon et al., 2013; dagnoko et al., 2013). in contrast, the open field crops yielded no fruits in addition to the fact that the crops were stunted (figure 10). these results agree with the findings of papadopoulos and ormrod (1991). number of weeks after transplanting 2wat 3wat 4wat 5wat 6wat 7wat 8wat pl an t h eig ht (c m ) 0 5 10 15 20 25 greenhouse open field number of weeks after transplanting 1wat 2wat 3wat 4wat 5wat 6wat 7wat n o of l ea ve s 0 5 10 15 20 25 30 35 greenhouse open field figure 6: mean plant height under green house and open field cultivation figure 7: mean leaf count under green house and open field cultivation file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omobowale: evaluation of a low-cost greenhouse for controlled environment cultivation of sweet pepper. azojete, 16(1):28-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 34 figure 8: mean leaf area under green house and open field cultivation figure 9: crop parameters within the greenhouse figure 10: greenhouse and open field sweet pepper 7 weeks after transplanting 4. conclusion this study evaluated the performance of sweet pepper grown in a low-cost greenhouse in comparison with field growth conditions in an agriculturally unproductive soil. the greenhouse crops showed increased plant height, number of leaves and leaf area index, which translated into increased yield. observations confirmed that in the greenhouse, there is reliability of yield which shows the possibility of year-round production in an unproductive environment. the high performance observed in crops grown in the greenhouse is attributed to improved leaf physiology (i.e. increased number of stomata) and adequate photosynthesis. moreover, the micro-climate within the greenhouse was adequate for the crops to survive. however, due to the nature of the soil in the open field experimented, crop performance was extremely poor. this study recommends further work to evaluate performance using other crops across different seasons of the year with different water application regimes. performance under ventilated conditions should also be considered. advocacy to farmers living close to poor agricultural or degraded soils on the potentials of low-cost greenhouses should also be intensified. references albright, ld. 1990. environmental control for animals and plants. american society for agricultural engineers, st. joseph, michigan, pp. 453. ali, m., farooq, u. and shih, yy. 2002. vegetable research and development in the asean region: a guideline for setting priorities. in cg. kuo (ed). perspectives of asean cooperation in http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 28-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 35 vegetable research and development, shanhua. taiwan: asian vegetable research and development center, pp. 20-64. alsadon, a., wahb-allah, m., abdel-razzak, h. and ibrahim, a. 2013. effects of pruning systems on growth, fruit yield and quality traits of three greenhouse-grown bell pepper (capsicum annuum l.) cultivars. australian journal of crop science, 7(9): 1309-1316. babatola, j. 2005. export promotion of horticultural crops. nigerian journal of horticultural science, 9: 74-78. connellan, gj. 2002. selection of greenhouse design and technology options for high temperature regions. acta horticulturae 578: 113-117. doi: 10.17660/actahortic.2002.578.12. cook, r. and calvin, l. 2005. greenhouse tomatoes change the dynamics of the north american fresh tomato industry. united states department of agriculture washington, dc. economic research report no. err2, pp. 2-4. dagnoko, s., yaro-diarisso, n., sanogo, pn., adetula, o., dolo-nantoumé, a., gamby-touré, k., traoré-théra, a., katilé, s. and diallo-ba, d. 2013. overview of pepper (capsicum spp.) breeding in west africa. african journal of agricultural research, 8(13): 1108-1114. fao 2011. rural structures in the tropics: design and development. food and agricultural organization of the united nations, rome, pp. 481. gorjian, s., hashjin, tt. and ghobadian, b. 2011. solar powered greenhouses. proceedings of the 10th international conference on sustainable energy technologies, 4-7 september, instanbul, turkey, pp. 1-6. ibeawuchi, ii., okoli, na., alagbe, ra., ofor, mo., emma-okafor, lc., peter-onoh, ca. and obiefuna, jc. 2015. fruit and vegetable crop production in nigeria: the gains, challenges and the way forward. journal of biology, agriculture and healthcare, 5(2): 194-208. jones, am. and harrison, rm. 2004. the effects of meteorological factors on atmospheric bioaerosol concentrationsa review. science of the total environment, 326:151-180 rao, pp., birthal, ps., joshi, pk. and kar, d. 2004. agricultural diversification in india and role of urbanization. discussion paper no. 77 prepared for the markets, trade and institutions division of international food policy research institute, washington, dc., pp 59. kittas, c., karamanis, m. and katsoulas, n. 2005. air temperature regime in a forced ventilated greenhouse with rose crop. energy buildings, 37(8): 807-812. lutz, w. 2017. how population growth relates to climate change. proceedings of the national academy of sciences of the united states of america, washington dc., november 14, 114 (46): 12103-12105. mijinyawa, y. 2012. the design of farm structures. first edition. ibadan university press, publishing house, university of ibadan, ibadan, pp. 168. mijinyawa, y. and osiade, gi. 2011. the status of greenhouse utilization in oyo state, nigeria. journal of emerging trends in engineering and applied sciences, 2(4): 561-566. omid, m. and shafei, a. 2005. temperature and relative humidity changes inside greenhouse. international agrophysics, 19(2): 153-158 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omobowale: evaluation of a low-cost greenhouse for controlled environment cultivation of sweet pepper. azojete, 16(1):28-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 36 omobowale, mo. 2011. climate change adaptation strategy for sustainable food security and socio-economic development in africa: controlled environment agriculture through renewable energy as a viable option. africa-adapt climate change symposium, united nations conference centre, addis-ababa, 9-11 march, ethiopia, pp. 8-21. papadopoulos, ap. and ormrod, dp. 1991. plant spacing effects on growth and development of the greenhouse tomato. canadian journal of plant science, 71: 297-304. ponjican, o., bajkin, a., dimitrijevic, a., mileusnic, z. and miodragovic, r. 2011. the influence of soil mulching and greenhouse covering material on the temperature distribution in the lettuce production. proceedings of the 39th international symposium on agricultural engineering: actual tasks on agricultural engineering, 22-25 february, opatija, croatia, pp. 393401. shamshiri, rr., jones, jw., thorp, kr., ahmad, d., man, hc. and taheri, s. 2018. review of optimum temperature, humidity and vapour pressure deficit for microclimate evaluation and control in greenhouse cultivation of tomato. international agrophysics, 32: 287-302. stoffella, pj., locascio, sj., howe, tk., olson, sm., shuler, kd. and vavrina, cs. 1995. yield and fruit size stability differs among bell pepper cultivars. journal of the american society of horticultural science, 120 (2): 325-328. priya, w., vijayakumar, m., veeragavathatham, d., jeyakumar, p. and chezian, n. 2002. effect of seasons and growth environments on paprika (capsicum annum var. longum) growth and yield. south indian hortculture, 50(4-6): 463-471. kurpaska s. 2014. energy effects during using the glass with different properties in a heated greenhouse, technical sciences 17(4): 351–360 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):878-888 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 878 original research article health risks associated with consumption of vegetables grown using domestic wastewater in minna, niger state, nigeria p. a. adeoye1*, z. saidu1, a. i. kuti1, i. jibril1,2 and b. a. adabembe3 (1department of agricultural and bioresources engineering, federal university of technology, p.m.b. 65, minna, niger state, nigeria. 2niger state college of agriculture, p.m.b. 109, mokwa, niger state, nigeria. 3department of water resources management agrometeorology, federal university, oye ekiti, ekiti state,nigeria) * corresponding author’s email address: peter.adeoye@futminna.edu.ng 1.0 introduction a plant that is contaminated with high concentrations of heavy metals does not have visible changes in their appearance or yield but exceed animal and human tolerance or element consumption level. during the last twenty years, environmental problems have started to be a part of daily life in several countries. their impact is clearly on the manifest on the terrestrial and aquatic flora fauna and keeps on increasing (osma et al., 2012). knowledge of metal-plant interaction is essential for the safety of the environment and for reducing the risk of introduction of trace metals into the food chain. article information abstract most vegetables consumed in the cities of developing countries are grown using wastewater discharged through township drainage network. this paper, therefore, investigates the risk involved in the consumption of such vegetables. the human daily intake rate (dir) and health risk index (hri) of heavy metals were calculated using established formulae and the values of dir ranged from 0.10 mg/kg/day to 0.71 mg/kg/day in wastewater plots in dry season for adults and 0.10 mg/kg/day to 0.14 mg/kg/day for children. health risk index (hri) values ranges from 0.40 mg/kg/day to 0.75 mg/kg/day in wastewater plots for adults in dry season and 0.20 mg/kg/day to 0.95 mg/kg/day for children. in wet season wastewater plots, the hri ranges from 0.40 mg/kg/day to 0.95 mg/kg/day for children. the values of hazard index (hi) ranged between 1.00 mg/kg/day and 1.21 mg/kg/day for all the seasons. statistical analysis showed that there is a significant difference between the wet and dry season values for all the parameters assessed. finally, uptake of heavy metals from the soil by all the vegetable crops under investigation was established. therefore proper monitoring needs to be carried out to regulate consumption of vegetables produced from the experimental sites as continuous application of the industrial wastewater may lead to further accumulation of these heavy metals. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 december, 2018 revised 30 march, 2019 accepted 05 april, 2019 keywords: domestic wastewater health risk index heavy metals intake rate. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 878-888. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 879 the anthropogenic sources of environmental pollution by heavy metals include traffic emissions (vehicle exhaust particles, tire wear particles, weathered street surface particles, brake lining wear particles), industrial emissions (power plants, coal combustion, metallurgical industry, auto repair shops and chemical plants) domestic emissions, and weathering of building and pavement surfaces (ahaneku and sadiq, 2014). human activities in most cases have introduced potentially hazardous metals to the environment. human activities as a result of the industrial revolution, and urban development are promoting a significant threat to ecology and human well-being (mahmood and malik 2013; aljaboobi et al., 2014). contaminated air, soil, and water by human activities are associated with disease burden, and this could be reasons for the current shorter life expectancy in developing countries when compared with developed nations. heavy metal toxicity adversely disrupts growth and other physiological processes of the plant, explicitly leading to significant economic and ecological trauma. if heavy metals move too rapidly in a particular soil, they can pollute ground and surface water supplies while it has generally assumed that these metals retained in agricultural soils (bichi and bello, 2013). singh et al. (2012), assessed heavy metals accumulation and distribution pattern in different vegetable crops grown on heavy metal contaminated soil showed marked differences in metal accumulation, their uptake and distribution pattern. furthermore, from their studies, it was discovered that vegetable crop plants have a high ability to accumulate metals from the environment, which may pose risks to human health when consumed. despite all the glaring adverse effects domestic and industrial wastewater causes to human health when used for irrigation, the trend of using wastewater for irrigation is at increase as most people lack adequate knowledge of the health risk that is involved. this study therefore, seeks to investigate the heavy metals uptake and accumulation in some selected vegetable leaves, stems and roots in minna; as well as bringing forth useful recommendations for the farmers, the consumers and the policymakers. 2. materials and methods 2.1 description of the study area niger state is one of the north-central states in the guinea savannah zone of nigeria. it was at sometimes called the ‘food basket’ of the nation owing to the abundant potentials for all yearround farming. geographically, it is located on longitude 6° 00’ 00’’ e and latitude 10° 00’ 00’’ n as presented in figure 1. it is characterised by two distinct seasons; rainy and dry seasons. short grasses and scattered trees in its extreme north and dense forest towards the south are features of its vegetation with mean maximum and minimum temperatures of 37 °c and 20 °c respectively. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al: health risks associated with consumption of vegetables grown using domestic wastewater in minna, niger state, nigeria. azojete, 15(4):878-888 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 880 figure 1: map of niger state showing its boundary with other states of nigeria 2.2 experimental set-up a piece of land measuring 9m x 9m situated at dutsen kura along minna western by-pass in minna, niger state was selected as a plot area. wastewater from an urban drain (industrial/municipal) passing through keterin-gwari area was used as a source of irrigation water at the wastewater irrigation plot, while water from a closed well at dutsen-kuran gwari, down police secondary school avenue, was used for irrigation at control plot. the entire experimental is as presented in figure 2. figure 2: experimental plot design 2.3 vegetable samples collection from edible portion of different vegetables grown, 300g each were collected and washed with distilled water to remove soil particles, separated into three parts, chopped into small pieces using a knife and kept air-dried for approximately 70 hours at 105°c. these samples were roselle okro pepper jutemallow spinach okro roselle spinarch jutemallo pepper spinach roselle jutemallow okro okro jutemallo jutemallo spinach pepper roselle pepper spinach pepper okro roselle control plot http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 878-888. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 881 ground into a fine powder before use for heavy metals extractions by acid digestion. powdered samples (15g each) were placed in a silica crucible, and few drops of concentrated nitric acid were added. the dry-ashing process was carried out in a muffle furnace (swastik scientific co.mumbai, p.14, se.no 1021) by a stepwise increase of the temperature up to 550°c and then left to ash at this temperature for 6 hours. the ash was kept in desiccators and then rinsed with 3n hydrochloric acid. 2.4 sample digestion and heavy metal determination concentrations of heavy metals in the acidic solution were estimated using atomic absorption spectrophotometer (spectrometer ice 3000 aa 02134 dell, thermo scientific pvt. ltd., india). soil to plant metal transfer was carried out as transfer factor using equation 1: (1) where, is the concentration of heavy metals in plants and is the concentration of heavy metal in the soil (mahmood and malik, 2013). daily intake rate was determined as stated in equation 2. weightaverage akefood factormetal b d xcxcdim int (2) where, cmetal, cfactor, dfood intake and baverage weight represent the heavy metal concentrations in plants (mg kg-1), a conversion factor (0.085), daily intake of vegetables and average body weight (kg/person/day) respectively. health risk index and a hazard index of heavy metals were calculated by knowing the exposure levels of these metals on humans. 2.5 data analysis the heavy metals determined in the laboratory were analysed using descriptive statistics and one-way anova to determine the significance of the heavy metals in vegetables. 3. results and discussions 3.1 daily intake rate (dir), health risk index (hri) and hazard index (hi) at dry season the daily intake rate of metals for adults at wastewater plots ranges from 0.00 mg/kg/day to 0.11mg/kg/day for all the metals analysed. the highest element consumed by adults is iron with a value of 0.11mg/kg/day. the values of all metals are below the daily tolerable intake limits specified by (fao, 2013) as presented in table 1. for adults except for okra leaves, pepper leaves, spinach stem, and roselle stem with chromium values of 0.03 mg/kg/day, 0.03 mg/kg/day and 0.03 mg/kg/day respectively. daily intake for children at the wastewater plot also ranges from 0.00 mg/kg/day to 0.14 mg/kg/day for all the metals with iron having the highest value of 0.14 mg/kg/day. chromium and copper are present in some non-edible parts that are of no threat to the children. iron has the highest value which perhaps, might be due to the presence of iron in the soil at its original state. soil plant c c tf  file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al: health risks associated with consumption of vegetables grown using domestic wastewater in minna, niger state, nigeria. azojete, 15(4):878-888 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 882 table 1: upper tolerable daily intake limit for both adults and children heavy metals upper tolerable daily intake (mg/day) cr 0.0105 fe 45 cu 10 cd 0.0640 source: integrated risk information system fao (2013) the result also confirmed 0.03 mg/kg/day of iron in roselle leaves and 0.01mg/kg/day of copper. on the other hand, the concentration of the heavy metals in the vegetables grown on the control plots during the dry season is negligible for both adults and children, which is in line with cui et al. (2014). the result of the health risk index showed that, for the dry season at wastewater plots, the health risk index (hri) value for adult consumer ranges from 0.00 mg/kg/day to 0.16 mg/kg/day. chromium was 0.01mg/kg/day in okra leaves and 0.03 mg/kg/day in roselle stems. however, the values of 0.75 mg/kg/day of copper in okra leaves and 0.075 mg/kg/day in jute mallow leaves are of no threat to the adult’s consumer. hri values for children consumers of the edible parts of okra fruits was 0.00mg/kg/day, roselle leaves 0.06 mg/kg/day and spinach leaves 0.25 mg/kg/day. all values obtained are below the standard reference doses pegged by usepa as presented in table 2. table 2: oral reference doses rfdo(mg/kg/day) heavy metals rfdo(mg/kg/day) cr 1.5 fe 0.7 cu 0.04 cd 0.001 source: usepa (2013) the hazard index (hi) was computed by the summation of all metals investigated in accordance with wang et al. (2005), and mahmood and malik (2013). the results of dry season wastewater plots for adults and children are within the acceptable limit of 5, above which is hazardous for both consumers. the highest value of hi was found to be 0.092 mg/kg/day in okra leaves for adults and 1.21 mg/kg/day in okra leaves for children. figures 3, 4, 5 and 6 give clear pictorial views of the analysis of heavy metal concentration for all vegetables irrigated with wastewater. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 878-888. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 883 figure 3: dry season indices in adults for wastewater plots figure 4: dry season indices in children for wastewater plots figure 5: dry seasons indices in adults for clearwater plots (control plots) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al: health risks associated with consumption of vegetables grown using domestic wastewater in minna, niger state, nigeria. azojete, 15(4):878-888 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 884 figure 6: dry season indices in children for clearwater plots (control plots) 3.2 daily intake rate (dir), health risk index (hri) and hazard index (hi) during rainy season during the wet season, results were a little different even in the same wastewater plots. intake rate of 0.01mg/kg/day of chromium in the leaves of okra, 0.01mg/kg/day of copper and 0.13 mg/kg/day of iron was recorded, though was confirmed safe for children and adults as values are within the fao/usepa acceptable limit as marked by chanhan and chanhan (2014). on health risk index (hri), computation of result for both plots were done and compared with the oral reference doses rfdo (mg/kg/day). values obtained for all vegetables in all plots were negligible. hazard index (hi) according to the result obtained for vegetables grown on wastewater plots during the wet season had its highest value to be 0.45 mg/kg/day in roselle leaves for adult consumers and 0.14 mg/kg/day for children consumers. highest amounts of 0.07 mg/kg/day were recorded for okra leaves for adult consumers and 0.09 mg/kg/day for children consumers. for clear water (well water) or the control plots, the highest values were found to be 0.07 mg/kg/day in okra leaves for adults and 0.09 mg/kg/day in okra leaves for children consumers. these analyses are as presented in figures 7, 8, 9 and 10. from all results, it is clear that concentrations of heavy metals in vegetables grown on all plots during the wet season are negligible and therefore are safe for consumption for both adults and children. figure 7: wet season indices in adults for wastewater plots http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 878-888. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 885 figure 8: wet season indices in children for wastewater plots figure 9: wet seasons indices in adults for clearwater plots (control plots) figure 10: wet seasons indices in children for clearwater plots (control plots) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al: health risks associated with consumption of vegetables grown using domestic wastewater in minna, niger state, nigeria. azojete, 15(4):878-888 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 886 based on the levenes degree of significance, that is < 1 is not significance and 1 is significance the one-way anova test shows that concentrations of heavy metal are significant in some vegetables while some are not concerning season’s interactions. the differences in the concentration of heavy metals in plant parts may be due to their physiology and ability to take up or remove metals from the soil and or store the metals in their various tissues as reported by (aora et al., 2008; kalaskar, 2012 and akan et al., 2013). the analysis also indicated that the concentrations of fe, cu, cr and cd varies with the plant parts, though values are below the tolerable limit as contained in fao/who, 2007, 2010 and usepa, 2010 standards. the concentration of and iron, chromium and cupper are significantly difference in stems and leaves of okra while only iron and cupper concentrations are significant in the fruits. also, concentrations of cr, fe, and cu are significantly different in stems, roots and leaves of roselle with cd is not significant in any of the parts. in stems of spinach, only cr, fe, and cu concentrations are significant while cd is not. while in the leaves, fe and cd concentrations show significance. in the leaves and fruits of pepper, it’s only cd concentration that is not significant. the same applies to stems of jute mallow except for the leaves where concentrations of cr and cd are not significantly difference. these are as presented in table 3. table 3: mean of metals (mg/kg) in vegetables in dry season for wastewater plots vegetables cr fe cu cd okra fruits 0.50* 3.25** 2.75** 0.08* stems 7.07** 14.24** 25.24** 0.07* leaves 13.75** 227.74** 57.10** 0.10* roselle stems 82.50** 48.75** 24.06** 0.22* leaves 3.75** 97.06** 5.06** 0.24* fruits 5.1** 22.07** 4.00** 0.12* spinach stems 94.25** 52.74** 36.50** 0.03* leaves 0.50* 37.74** 0.10* 1.10** pepper leaves 111.75** 39.51** 18.75** 0.21* fruits 6.74** 28.25** 2.75** 0.10* jute/mallow stems 9.06** 211.10** 42.51** 0.31* leaves 0.10* 6.10** 6.07** 0.14* results are mean difference *not significant < 1 **significant within the columns at 99% confidence level. rainy season’s heavy metals accumulation in plant parts were the list compared to the dry season based on the anova test. this might be because excess rainwater or irrigation washes heavy metals and other elements present in the soil below the root zone of plants as also reported in (bichi and bello, 2013). table 4 is the anova result of heavy metals accumulation in parts of plants under study. in okra leaves, cu and fe concentrations are significantly difference, while cr, cu and fe concentrations are significantly difference in its stems and leaves. the concentrations of fe and cu in roselle leaves and stems are significantly difference, while and fe concentrations is significant in the fruits. in spinach stems, fe and cu concentrations are significantly difference, while only fe concentrations is significant in other parts. fe http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 878-888. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 887 concentration is confirmed to be significant in leaves and fruit of pepper. however, the concentrations of fe and cu are also found to be significantly difference in stems and leaves of jute mallow. table 4: mean of metals (mg/kg) in vegetables in wet season for wastewater plots vegetables crm fem cum cdm okra fruits 0.10* 3.07** 1.24** 0.08* stems 5.51** 10.25** 4.24** 0.02* leaves 11.10* 215.74* 26.75* 0.03* roselle stems 0.00* 35.75** 9.06** 0.00* leaves 0.00* 61.07** 1.50** 0.00* fruits 0.00* 22.02** 0.10** 0.00* spinach stems 0.00* 20.24** 5.50** 0.00* leaves 0.15* 4.51* 0.04* 0.00* pepper leaves 0.00* 8.75** 0.51** 0.00* fruits 0.00* 25.54** 0.50* 0.00* jutemallow stems 0.00* 47.40** 12.06** 0.00* leaves 0.04* 3.50** 4.74** 0.00* results are mean difference *not significant < 1**significant = 1. 4. conclusion the study investigated intake rate, health risk index and hazard index from consumption of vegetables irrigated with wastewater. the result showed that heavy metal concentrations in some of the vegetable tissues are within the tolerable range, most especially those raised during the wet season. the heavy metal concentration in vegetables grown (dry season) is also within the acceptable limit. however, it is advised that only those grown during wet season be consumed because of heavy metals build-up. references ahaneku, ie. and sadiq, bo. 2014. assessment of heavy metals in nigerian agricultural soils. journal of environmental studies, 23(4): 1098-1110. al-jaboobi, m., zouahir, a., mennane, z., tijane, m., el-housni, a., yachou, h. and bouksain, m. 2014. evaluation of heavy metals pollution in groundwater, soil and some vegetables irrigated with wastewater in skhirat region “morocco”. journal of material and environmental science, 5(3):961-966. bichi, mh. and bello, uf. 2013. heavy metals in soils used for irrigation of crops along tatsawarki in kano, nigeria. international journal of engineering research and development, 8(4): 01-07. cui, yj., zhu, yg., zhai, rh., chen, dy., huang, yz., qiu, y. and liang, jz. 2004. transfer of metals from soil to vegetables in an area near a smelter in nanning, china. journal of environmental international, 30: 785791. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al: health risks associated with consumption of vegetables grown using domestic wastewater in minna, niger state, nigeria. azojete, 15(4):878-888 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: peter.adeoye@futminna.edu.ng 888 chauhan, uk. and chauhan, g. 2014. risk assessment of heavy metal toxicity through contaminated vegetables from wastewater irrigated area of rewa (m.p). indian.international journal of advanced technology in engineering and science, 2: 44 – 58. mahmood, a. and malik, rn. 2013. human health risk assessment of heavy metals via consumption of contaminated vegetables collected from different irrigation sources in lahore, pakistan. arabian journal of chemistry, 4(6): 9199. osma, e., serin, m., leblebici, z. and aksoy, a. 2012. heavy metals accumulation in some vegetables and soil in istanbul. ekoloji journal. 21 (8): 1-8. singh, s., zacharias, m., kalpana, s. and mishra, s. 2012. heavy metals accumulation and distribution pattern in different vegetable crops, division of environmental sciences, indian agricultural research institute, new delhi. journal of environmental chemistry and ecotoxicology, 4(10): 170-177. wang, g., yusu, m., huichen, y., fan, lld. and fang, gs. 2005. transfer characteristics of cadmium and lead from soil to the edible parts of six vegetables species in south-eastern china. journal of environmental pollution, 144: 127-135. who/fao. 2013. guidelines for the safe use of wastewater and food stuff; vol. 2: no. 114, pp. 988 http://www.azojete.com.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 26-36 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng laboratory evaluation of free overfall equations for predictingwater profile overweir m. k. othman1, s. z. abubakar1, x. litrico2 and g. belaud3 abstract laboratory evaluation of three free overfall equations for predicting water profile over hydraulic structure – weir was conducted in irrigation laboratory of higher national college of agriculture of montpellier (ensam) , france. a broad-crested weir was constructed as a reduced physical model to simulate the gated-structure (begemann gate) for upstream water control in the main canal of hadejia valley irrigation project (hvip), northern nigeria. instrumentation in the ensam laboratory allows precise variation of channel flows with incremental changes of 5 l/s. three recently developed models in a progressive succession were used for comparison between measured and predicted data to establish degree of accuracy in the prediction of water profile passing over weir in open channel. results of the evaluation show that the three equations performed differently in predicting water profile over weir at the selected channel flows of 60 l/s, 30 l/s and 10 l/s respectively. these stream sizes were chosen because they were the maximum, medium and minimum for the canal capacity. although the stream size directly influenced the water profile as a result of internal pressure due to convergence of stream filaments between upper and lower laminar flow. longer velocity jumps were recorded at the higher stream size (60 l/s) of 35 cm from weir crest end while less than 25 cm distance was covered by the least stream size of 10 l/s. generally, based on the r2 values and percentage errors for the three models at all the three selected stream sizes, cavailhé model predicted the water profile with high degree of accuracy followed by that of davis and lastly the hager model. the same order was observed on ease of manipulation and user friendliness. the choice of water profile prediction model with high degree of accuracy is important in the design of hydraulic structures for water conveyance, diversion and measurements in irrigation canal network. 1. introduction in the design of water control and measurement structures, the concept of creating critical flow by inducing a reduction of specific energy through raising of channel bed or constricting the canal cross sectional area, thereby increasing the discharge per unit width, or combination of the two, are mostly adopted. this is done to make the discharge a single valued function of the up stream stage because it was found that when a structure is introduced into a sub-critical flow causing it to pass through the critical to the super critical, the stage of upstream is independent of the down stream stage (withers, 1974). this concept gives birth to the creation of critical-depth meters such as broad-crested weir, venturimeter, spillway and recently automatic control gates that have combination of broad-crested weir and gate structure. the hydraulic problems of the free overfall structures are concerned with characteristics of the control and dissipation of flow in downstream basin. ordinarily, flow over the structure is free discharging where air is admitted to the under side of the flow nappe to avoid the jet being depressed by reduced underneath pressure. dissipation of the flow in the downstream basin may be obtained by hydraulic jump, impact and turbulence induced in the basin where erosion and down stream flood may be the results. to address this issue, usdbr (1977) developed a relationship between drop distance y, unit discharge passing over the crest q and critical 1 national agricultural extension and research liaison services, ahmadu bello university, zaria (e-mail : mkothman@yahoo.co.uk) 2cemagref (centre national du machinisme agricole, du génie rural, des eaux et des forêts) montpellier, france (xavier.litrico.@montpellier.cemagref.fr) 3ensam (ecole nationale supérieur d’agronomie de montpellier), france mailto:mkothman@yahoo.co.uk mailto:xavier.litrico.@montpellier.cemagref.fr http://www.azojete.com.ng laboratory evaluation of free overfall equations for predicting water profile over weir 27depth hc. to reinforce this effort, several researchers attempted to determine the point of critical depth where a single measurement at established channel section might permit a direct computation of the discharge passing over the structure (rouse, 1936; hager, 1983; davis et al., 1999). part of this attempt was the development of mathematical equations to predict water flow profile falling over the hydraulic structures. among these equations were those of hager, davis and cavailhé. the three equations developed by these researchers could apply to both sub and super critical flows conditions. in using these equations, the designers may have difficulty of choosing the most efficient equation that can give a better prediction of the water profile at the same time links the water depth and discharge at each section of the overfall structure most accurately. it is pertinent to note that the overfall condition is of distinct importance in hydraulic and irrigation engineering for design and use of the structures to control or divert water in irrigation system. beside its close relation to broad crested weir, it forms the starting point in computations of the surface curve in non-uniform channel flow in which the discharge spill into an open reservoir at the downstream end. similarly, the equation of such condition is needed in the design of automatic control gates such as begemann and vlughter gates for determining the depth needed to be maintained at the upstream level. this paper presents the laboratory work and result of comparable accuracies of three selected equations in predicting the flow profile over the broad crested weir. the paper further highlighted the applicability of such principle in real-life situation where such weirs play dual functions of water diversion and upstream control/measurement structure as in the case of north main canal of hadejia valley irrigation project (othman et al., 2003). 2. background study of free overfall equations there is limited effort on hydraulic studies of free overfall structures adaptable to open canal irrigation system, the world over. however, few structures (weir, flumes, orifice, inverted siphon and gates) attracted researchers’ attention for more than seven decades across europe, america, asia and north africa. the work on hydraulics of free overfall structure was one of such studies which could be dated back to sixty years ago. the applicability of weir under wide range of field situations made it very attractive and a focus of research efforts especially where computer-based models are used to support the operation and management of canal irrigation. starting from the work of rouse (1936), the relationship between depth at the brink “he” and critical flow depth upstream “hc”, for a smooth rectangular horizontal channel, the ratio he/hc was obtained as 0.715. similarly, markland (1965), as reported by davis et al. (1999), used a relaxation method to integrate the potential flow equations and obtained solutions for the nappe and upstream profiles in a rectangular free overfall. strelkoff and moayeri (1970) used numerical integration and potential flow theory to compute free overfall conditions in rectangular, triangular and parabolic channel sections respectively. hager (1983) used an analytical approach to solve the conservation of energy equation (bernoulli equation), extended to take account of curvature effects, and applied it to rectangular free overfall conditions. marchi (1993) also solved the same equations analytically by expanding the stream function in a power series. with the exception of hager (1983) and marchi (1993), all the approaches are rigorous, requiring numerical solutions (davis et al., 1999). they all applied to critical and super-critical conditions and do not apply to sub-critical condition. davis et al. (1999) modified the method of hager (1983) and used parabola method which assumes two-dimensional flow (a prismatic rectangular channel with a confined nappe). it also assumed that a particle in a streamline in the nappe follows a free fall parabolic path, once the overfall structure is passed. that is, it accelerates downward in the vertical direction under the influence of gravity and possesses no acceleration in the horizontal direction. progressively, cavailhé (2001) further improved the work of davis et al. (1999) and came out azojete vol. 5 2007 28with a slightly different equation which predicts the water profile. the three equations of cavailhé, hager and davis were developed to predict water profile over hydraulic structure of weir in this study. 2.1 presentation of water surface profile equations the basic principles of free-overfall equations can be understood from figure 1 which illustrates a typical situation of water profile and dynamics of forces and other relevant parameters. figure 1: schematic diagram of free overfall water profile passing over hydraulic structure the three selected equations developed by cavailhé (2001), davis et al. (1999) and hager (1983) under evaluation were as follows: 2 cos2 1tan 3 2       x y xyy c c (1a) 2 cos2 tan          v xgxhy e (2a) 2 )1cos(2 )1tan(          vu xgxhey (3a) where yc = critical depth, the upstream depth above the weir it is given by cavailhé, (2001) as 3 1 2 2        a c gl qy (1b) q = discharge passing over the weir, m3/s g = acceleration due to gravity, m/s2 la= width of the canal, m laboratory evaluation of free overfall equations for predicting water profile over weir 29           l yc3 1 tan 1 refer to figure 1 l = length of the weir, m ho = yc 5 23 2 2 2   fr frh yh o ce (2b) where, fr = froude number 1 : angle = 2 2 2 1)(3 fr h he h hefr oo         180 (3b) 2 : angle = (20.555 5.686fr) 180  (2c) vu : flow velocity = )(2 heeg  e : energy at upstream = g voho 2 2  vo: average flow velocity of the discharge upstream vudav : flow velocity on the crest = )(2 heedavg  edav : upstream energy as modified by david = g vocho 2 2  c= fr 264.2 (davis et al., 1999). detailed procedures of determining these equations could be obtained from davis et al. (1999), hager (1983) and cavailhe (2001) respectively. however, figure 1 could assist in placing all the parameters that appear in the equations. figure 2: the experimental set-up . azojete vol. 5 2007 30 3. materials and methods a laboratory experiment was conducted to evaluate the three equations of water profile passing over crest of hydraulic structure as an overfall. the experiment took place at the irrigation laboratory of ecole nationale supérieur d’agronomie de montpellier (ensam,) montpellier, france in 2002. a regulator was installed at the upstream of the system, which supplies the canal with water for a desired discharge from 10 l/s up to maximum of 60l/s at interval of 5 l/s. the reference was taken at the upstream, 30 cm from the terminal end of the crest and the distance coincided with the thickness of the broad-crested weir used for the experiment. the broad-crested weir used for the experiment was constructed as a reduced model of the component of a gated-structure (begemann gate) for upstream water control in the north main canal (nmc) of hadejia valley irrigation project (hvip), nigeria. consequently, the dimensions of the weir were determined using the principle of dynamic similarity which implies the identity of all the dimensionless laws governing the model and prototype phenomena. thus, a comparison of froude numbers of the two structures (the one at hvip and the prototype model) at a critical depth with maximum canal capacity of nmc at hvip and the prototype model in the irrigation laboratory canal of ensam was done using the following relations (yalin, 1971): 32 2 3 2 2 hgb q gs bqfr  (4) 3222 hbgfrq  (4a) if h'=h (5) and b’=b (6) 32252' hbgfrq  (6a) where q’ discharge of the model, q discharge of the gated-structure in the field (hvip), b’ and h’ width and breath of the model while b and h are width and breath of gated-structure in the field. combining (4a) and (6a) yields (7a): 5 2 q 'q        (7a)  can be found by using the maximum discharge of the laboratory canal of 0.06 m3/s and that of the gate in the field (hvip) which was found from the design value to be 0.91 m3/s 337.0 91.0 06.0 5 2       (7b) h and b measured in the field were 93.5 cm and 112.8 cm, respectively and the height and width of 31.5 and 38 cm respectively were computed and used for the construction of the prototype model . small alloy rods installed into a plastic frame following the pattern of the water trajectory was used to measure the water profile passing over the structure for each of the desired discharge supplied from upstream (see figure 2). the water depth was taken from one-end of the crest length up to distance of 65 cm at interval of 5 cm for flow rates of 10 l/s to 60 l/s at interval of 5 l/s. the measurements were done with meter rule following the length of the alloy rod from its end to where it touches the water profile. the measurements were repeated four times at each point and the average was determined. thereafter, the three laboratory evaluation of free overfall equations for predicting water profile over weir 31 equations were used for the prediction of the profiles using the different discharges as used during the experiment. this was done using spreadsheet while substituting all the known parameters and then determining the profile depth at each point for the different discharges used. the profile predicted by each of the three equations was compared with the measured data using quantitative analysis. similarly, regression analysis and percentage error were conducted between the predicted and measured data for three selected flows in which r2 values were determined to measure the level of accuracy for each of the equations. the percentage error was computed using the equation ( dt-dp )/dt), where dt is measured depth and dp predicted depth. 4. result and discussion 4.1 measured depths of water profile table 1 shows the result of the surface water profile measurements for the different discharges supplied from 0 to 60 l/s respectively. the values in table 1 represent the profile of the upper nappe of the flowing water passing over crest with a shape of a trajectory of free overfall. this means that the flow accelerates downward in the vertical direction under the influence of gravity and no acceleration in the horizontal direction. as the acceleration in the horizontal direction is small and hence negligible, the thickness of the nappe could be determined using relationship given by rousse (1943). from the table and the graphs plotted, the results show that the influence of the upstream curvature started before the thickness of the crest, where there exist hydrostatic pressure condition which agrees with the reasoning of davis et al. (1999) that the curvature or downstream effects never reach upstream more than a distance equal to four times the upstream depth. table 1: average water profile measured depths (cm) at different points and flows passing over broad-crested weir discharge (l/s) in the upstream supplied from the source with sub critical flow distance (cm) 60 55 50 45 40 35 30 25 20 15 10 0 5 10 15 20 25 30 35 40 45 50 55 60 65 water depths from the bottom of the down stream bed (cm) 69 68,3 66,8 65,5 63,7 61,8 60,2 58,5 56,1 53,2 49,3 44,5 38,5 31,5 68,3 67,1 66,4 64,7 62,6 61,2 59,5 58 55,8 52,5 48,6 44,2 37,9 30 67,3 66,8 65,2 63,7 62 60,4 59 57,4 55 52 47,9 43 37,3 29,6 66,4 65,2 64,3 62,7 61,2 59,7 58,5 56,8 54,3 51,3 47,4 42,1 35,7 26,5 65,2 64,4 63,2 61,7 60 58,7 57,6 56,3 55,7 50,9 46,6 40,7 34,5 64,2 63,3 61,9 60,3 59 58 56,7 55,5 53,2 49,6 45,4 39,6 28,6 62,9 61,8 60,5 59,1 57,8 57 56,2 55 52,5 48,5 44,7 35,7 26,5 61,4 60,6 59,3 57,9 56,8 56,2 55,4 54,4 51,6 47,7 42,7 35,1 22,7 60,2 59,1 57,9 56,4 55,7 55,5 54,7 53,4 50,7 46,2 39,8 30,5 58,9 57,5 56 55,2 54,7 54,4 53,8 52,7 49 43,4 38,7 27,3 56,7 55,6 54,2 53,9 53,6 53,5 52,8 51,4 47,2 40,2 33 21,9 azojete vol. 5 2007 324.2 models comparison with experimental data figure3 shows the comparison of the data between the predicted values by the three models and measured values at channel flow of 60 l/s. from the figure, the cavailhé and hager models tend to obey the law where the acceleration in the horizontal direction is the lowest. on the other hand, davis model seem to obey the law with lesser precision indicative of lower slope. similarly, figures 4 and 5 show the comparison at 30 and 10 l/s flows respectively. the models predictions commence from where the nappe start. at this point, there is a complete aeration below and above the nappe, allowing the pressure to be atmospheric. under this condition hydrostatic pressure could be assumed to be zero. however, there is still exist considerable internal pressure due to convergence of the stream filaments between upper and lower surfaces of the flow. this internal pressure is dependent on the stream size, the higher the stream size, the higher the internal pressure and the higher the velocity of the jump. consequently, the shape of each channel flow is different as shown by the three figures. the slope for the curves at 60 l/s is lower as also shown in the figures, covering more than 35 cm horizontal distance from crest end. the slope increases for the curves at 30 l/s covering less than 30 cm horizontal distance from crest (figure 4) while the distance covered by 10 l/s was less than 25 cm from crest with the highest slope. again, from the models, the profile depth is dependent on the relationship between variable channel flow (flow velocity) and a constant geometrical form of the flow changes. therefore, the complete geometrical and dynamic similarities of any two different flows are hardly attainable as pointed out by rouse, (1936, 1943) and davis et al. (1999). thus, the points on the curves from the experimental data and those obtained from the models predictions could attest to this point (figures 3, 4 and 5). laboratory evaluation of free overfall equations for predicting water profile over weir 33 table 2: statistical comparisons of measured values with the three models at the maximum, minimum and medium flows (l/s) m = measured values, p = predicted values, %e = percentage error water profile depths (cm) in y-direction discharge of 60 l/s discharge of 30 l/s discharge of 10 l/s distance (xdirection) models cavailhe davis hager models cavailhe davis hager models cavailhe davis hager m p %e p %e p %e m p %e p %e p %e m p %e p %e p %e 0 5 10 15 20 25 30 35 60.2 58.5 56.1 53.2 49.3 44.5 38.5 31.5 64.1 63.1 60.9 57.6 53.0 47.3 40.4 32.2 6.5 7.9 8.6 8.2 7.6 6.3 4.8 2.3 59.7 59.4 58.4 56.8 54.5 51.6 48.1 43.9 0.8 1.5 4.1 6.8 10.6 16.0 24.9 39.4 59.7 59.1 57.4 54.4 50.3 45.1 38.6 31.0 0.8 1.1 2.3 2.3 2.1 1.3 0.3 1.5 56.2 55.0 52.5 48.5 44.7 35.7 26.5 58.9 57.6 54.3 49.2 43.2 33.3 22.6 4.8 4.6 3.5 1.5 5.5 6.6 14.4 56.1 55.6 54.1 51.5 47.9 43.3 37.7 0.1 1.1 3.0 6.2 7.2 21.4 42.4 56.1 55.1 52.4 47.7 41.2 32.9 22.7 0.1 0.3 0.2 1.6 7.7 7.9 14.4 52.8 51.4 47.2 40.2 33.0 21.9 54.3 51.9 45.6 35.4 21.3 0.0 0.0 0.1 0.4 0.5 53.0 51.9 48.7 43.4 36.0 0.0 0.0 0.1 0.4 0.5 53.0 51.0 45.2 35.6 22.1 0.0 0.0 0.0 0.1 10.3 r2values 0.9983 0.9962 0.9961 0.9981 0.9956 0.9957 0.9958 0.9948 0.9945 average % error 6.5 12.8 1.5 15.9 11.6 14.6 0.1 0.0 0.1 azojete vol. 5 2007 34 0 10 20 30 40 50 60 70 80 0 20 40 60 80 distance from 30 cm from crest end w at er d ep th fr om d ow ns tr ea m bo tt om (c m ) measured values cavailehé davis hager crest figure 3: graph of comparison between the three equations and measurement at 60 l/s figure 4: graph of comparison between the three equations and measurement at 30 l/s figure 5: graph of comparison between the three equations and measurement at 10 l/s laboratory evaluation of free overfall equations 35table 2 shows the statistical comparisons of the models predictions with the experimental data at the channel flows of 60 l/s, 30 l/s and 10 l/s respectively. from the table, the following can be deduced:  cavailhé model predict better than the other two models irrespective of the channel flows where r2 values of 0.9983, 0.9981 and 0.9958 were obtained at 60 l/s, 30 l/s and 10 l/s channel flows respectively. davis model follows in performance at 60 l/s and 10 l/s and performed least at 30 l/s while hager model shows the least prediction accuracy at 60 l/s and 10 l/s and performed better at 30 l/s.  the trend of percentage error recorded by the three models to predict water profile over weir has no consistent pattern. (table 2). the highest percentage errors were recorded by all the three models at 30 l/s channel flow while the least errors occurred at 10 l/s for all the three models. at highest channel flow (60 l/s), hager model had the least percentage of error (1.5) followed by cavailhé model (6.5) where davis model recorded 12.8 % error.  comparing the r2 values and percentage error for all the three models at the three selected channel flows, cavailhé model predict water profile with highest degree of accuracy followed by that of davis while hager model predict with least degree of accuracy. it is logical that the progressive improvement incorporated by cavailhé in davis work, who in turn, improved hager work are empirically justified in this study. 4. conclusion and recommendations the laboratory evaluation of the three free overfall models for predicting water profile over weir bring out the differentiation among the most recent models developed. the experimental set-up represent a real life situation where managers of irrigation schemes are confronted with decision on whether to use weirs as solely diversion structures or use them for dual functions of diversion and flow measurements as well as upstream control hydraulic structures. all the three models were found to predict fairly accurately the water profile depths flowing over broad crested-weir in an open channel. the choice among the three depends on the level of precision required for the type function the structure is intended to serve. the study would also guide in the choice of which model to use by irrigation engineers for design of water control and flow measurement hydraulic structures in canal network. similarly, the choice of which model can predict most efficiently is also useful in selection and in-corporation into a canal irrigation simulation packages. finally, the ease of manipulations of these models is also instructive of their accuracy in prediction and user friendliness. acknowledgement the first author is grateful to french embassy in nigeria for the award of scholarship to do this study in france. our thanks go to management of ensam in particular monsieur paul for his assistance in the laboratory work. azojete vol. 5 2007 36references cavailhé, m. (2001). modélisation d'une vanne amont constant de type begemann, mémoire de 3° cycle, cemagref, montpellier, france davis, c. a.; p.j. richard and g.s.e. brian (1999). estimating trajectory of free overfall nappe, journal of hydraulic engineering, asce jan.p. 97-82 hager, w. h. (1983). hydraulics of plane free overfall, j.hydr. div. asce 109(12) 16831697. marchi, e. (1993). on free-overfall. j. hydr. res., delft, the netherlands, 31(6) markland, e. 1965. calculation of flow at a free-overfall by relaxation method. proc. ice, london, p.31. othman, m.k.; x. litrico, j. p. baume, and s.z. abubakar, (2003). hydraulic modeling of begemann gate for effective water management system in hvip, paper presented in the 4th international conference of nigerian institute of agricultural engineers (niae) and 24th agm, held in damaturu, yobe state, nigeria rouse, h. (1936). discharge characteristics of the free overfall. civ.engrg., asce, 6(4) rouse, h. (1943). discussion to energy loss at the base of free overfall. trans. asce, 108 strelkoff, t. and m.s. moayeri (1970). pattern of potential flow in free overfall. j.hydr.div. asce, 96(4), 879-901 usdbr (1977). design of small dams. united states department of the interior bureau of reclamation, water resources technical publication. united state government printing office, washington withers, b. and s. vipond (1974). irrigation: design and practice. b. t. batsford ltd, london, uk yalin, m. s. (1971). theory of hydraulic models. the mcmillan press ltd, london, uk abstract 1. introduction figure 1: schematic diagram of free overfall water distance 4.2models comparison with experimental data models acknowledgement references arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):65-75 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 65 original research article response surface optimization of a plastic powder processing machine using desirability function approach c. n. nwogu1*, u. remy2, j. o. igbokwe2 and a. c. okoronkwo2 (*1department of mechanical engineering, michael okpara university of agriculture umudike, abia state nigeria. 2department of mechanical engineering, federal university of technology owerri, imo state nigeria) *corresponding author’s email address: checknolly@yahoo.com 1.0 introduction plastics are non-biodegradable, synthetic polymers derived primarily from petro-fossil feedstock (fossil fuels) and made-up of long chain hydrocarbons with additives and can be moulded into finished products (rosato, 2001). these polymers are broken in the presence of suitable catalyst, into monomers such as ethylene, propylene, vinyl, styrene and benzene. these monomers are then chemically polymerized into different categories of plastics. plastics are cheap, easy to manufacture, versatile, and unreceptive to water. hence, their applications are vast ranging from paper clips to aircrafts. they have already displaced many traditional materials, such as wood; stone; horn and bone; leather; paper; metal; glass; and ceramics, in most of their former uses (andrady and neal, 2009). plastics are generally categorized as thermoplastics and thermoset plastics. thermoplastics can be melted to form new products which if re-heated, the product can melt again to form yet another new product. some examples of thermoplastics include: ldpe, hdpe, pet, pvc, etc. thermoset plastics also melt when heated to form new products but once they solidify, they cannot be re-melted to form another product like thermoplastics. these include multilayer and article information abstract optimal performance and operational parameters of a plastic powder processing machine used for converting used pet bottles into powdered form was assessed in this study. the geometrical (operational) parameters investigated include: speed of hammermill shaft, number of blades on the hammermill, length of hammermill blade and intrinsic viscosity of the pet processed while grain size produced, throughput and conversion efficiency constitute the machine’s (performance) parameters. the interactions of these factors (operational parameters) and responses (performance parameters) were evaluated and estimated using a completely randomized box-behnken blocked design layout which comprises twenty seven (27) experimental runs. desirability function approach was the optimization technique applied. results revealed the optimal values of hammermill speed, number of blades, blade length and intrinsic viscosity as 1400 rpm, 4, 109.6 mm and 0.82798 respectively with responses of 89.71%, 1.9953 kg/min and 139.9998 for conversion efficiency, throughput and grain size respectively. these optimal operational parameters will make the machine economical to operate in terms of labour, time and energy requirement. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 22 march, 2019 revised 05 may, 2019 accepted 10 may, 2019 keywords: plastic powder optimization performance parameters response surface. http://www.azojete.com.ng nwogu et al: response surface optimization of a plastic powder processing machine using desirability function approach. azojete,16(1):65-75. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 66 laminated plastics, bakelite, polycarbonate, melamine, nylon etc. (luo et al., 2009). hence, all thermoplastics can be recycled. plastic recycling involves recollecting waste plastic materials and processing them to form new and useful products. a lot of plastics are manufactured daily, causing the world's annual consumption of plastic materials to increase from around 5 million tons in the 1950s to nearly 100 million tons today (plasticseurope, 2008; andrady, 2003). in nigeria municipal solid waste contains 78% by weight of plastic waste (abah, 2013). about eight million metric tonnes of plastic waste is poured into the ocean every year (hardesty and wilcox, 2015; jambeck et al., 2015). hence, recycling is a global effort to moderate plastic in the waterways since plastic is non-biodegradable. plastic recycling includes taking any type of plastic sorting it into different polymers, chipping it and then melting it down into pellets. after sorting, they are crushed into tiny pieces and then melted to form pellets which can be used to create items of any kind such as plastic bottles, bowls, chairs, tables, depending on the choice of the manufacturer and the type of plastic processed. however, since the discovery of 3d printing, there has been high demand for plastic in powdered form for easy manufacturing (3d printing) of components/parts. other advantages of plastic powder include: less storage space, easy/cheap transportation and possibility of plastic coating of materials. for this reason, the plastic powder processing machine was developed. according to nwogu et al. (2019), the machine is capable of crushing used plastics (especially pet bottles) into powdered form which is used as feedstock for 3d printing. determination of the optimal operational parameters of this machine will make its use economical in terms of labour, time and energy requirement. response surface methodology (rsm) is a set of statistical and mathematical technique which uses quantitative data from appropriate experimental designs to determine and simultaneously solve/analyze multi-variant models with the objective of finding the optimal settings of input factors or design variables that maximize or target some performance measures/quality characteristics or responses (myer and montgomery, 2002; buyske and trout, 2009). rsm is a critical technology in designing, formulating, developing, and analyzing new scientific studies and also efficient in the improvement of existing ones. thus, kathleen et al. (2004), wrote that rsm is a collection of statistical and mathematical techniques useful for developing and optimizing systems. optimal operational settings determined using rsm are always or nearly close to the optimal operating conditions of the true system (oehlert, 2000; nist/sematech, 2006). the main objective of this work is the optimization of a plastic powder processing machine using desirability function approach. this involves development of appropriate response surface model, as well as optimization of the fitted response equations. 2.0 materials and method 2.1 materials the plastic powder processing machine evaluated was developed by nwogu et al. (2019). the machine comprises of the following parts (figure 1): the frame, electric motor, melting pot, barrel, blower, tray, hammermill, crank mechanism and a temperature control circuit. http://www.ncbi.nlm.nih.gov/pmc/articles/pmc2873020/ http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 65-75. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 67 figure 1: isometric view of the machine (nwogu et al., 2019). materials/devices used in the optimization of the machine include: vernier calliper, measuring tape, pc, minitab software, sieve. two grades of pet bottles i.e. pet1 with intrinsic viscosity values ranging from 0.78-0.80 (used for water bottles) and pet2 with intrinsic viscosity values ranging from 0.80-0.85 (used for carbonated drinks bottles) were used for this evaluation. 2.2 method the determination of the optimal settings of the performance and operational parameters of the machine involves model selection, experimental design, data collection, model fitting, model validation and optimization. the empirical relationships between the performance and operational parameters of the machine were evaluated using a response surface design generated with minitab software. the design used is a completely randomized box-behnken blocked design comprising of twenty seven (27) experimental runs based on four factors: speed of the hammermill shaft, number of blades on the hammermill, length of hammermill blade and intrinsic viscosity (grade) of pet processed. the high, low and centre levels of the factors were determined from physical measurement and the limits are shown in table 1. table 1: limits of the machine operational parameters s/n factor description factor symbols factor values coded actual high (+1) low (-1) centre (0) 1 speed of hammermill shaft (rpm) x1 n2 2300 1400 1850 2 number of blades on the hammermill x2 n 8 3 5.5 3 length of hammermill blade (mm) x3 lb 115 95 105 4 intrinsic viscosity of pet processed x4 w 0.85 0.78 0.815 the machine was run with different grades of pet at different hammermill speeds while varying the length and number of blades on the hammermill. the performance of the machine at each factor combination was recorded. throughput and conversion efficiency for the different factor combinations were calculated from equations 1 and 2 respectively while grain size for each factor combination was obtained by passing the powder through sieves of different mesh sizes arranged vertically. the transformation formulae relating the coded and actual values of the factors are shown in equations 3-6. tp = m t (1) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwogu et al: response surface optimization of a plastic powder processing machine using desirability function approach. azojete,16(1):65-75. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 68 where: m = mass of the plastic powder produced, (kg) t = production time, (h) ƞc = quantity of powder produced kg quantity of pet processed kg × 100% (2) x1 = n2−1850 450 (3) x2 = n−5.5 2.5 (4) x3 = lb−105 10 (5) x4 = ω−0.815 0.035 (6) the completely randomized box-behnken blocked design layout used in this investigation is shown in table 2. table 2: design table for the response surface study of the developed machine design order coded factors responses std order run order pttype blocks x1 x2 x3 x4 grain size throughput conversion efficiency 6 1 2 1 0 0 1 -1 140.0 1.37 0.84 20 2 2 1 1 0 1 0 5.0 1.35 0.74 7 3 2 1 0 0 -1 1 180.0 1.56 0.79 19 4 2 1 -1 0 1 0 150.0 2.12 0.89 18 5 2 1 1 0 -1 0 10.0 1.24 0.65 26 6 0 1 0 0 0 0 75.0 1.67 0.81 24 7 2 1 0 1 0 1 114.0 2.31 0.80 15 8 2 1 0 -1 1 0 90.0 1.38 0.78 16 9 2 1 0 1 1 0 40.0 1.39 0.84 17 10 2 1 -1 0 -1 0 111.0 1.01 0.86 21 11 2 1 0 -1 0 -1 110.0 1.16 0.69 10 12 2 1 1 0 0 -1 60.0 0.92 0.64 9 13 2 1 -1 0 0 -1 120.0 1.85 0.93 3 14 2 1 -1 1 0 0 158.0 2.14 0.88 14 15 2 1 0 1 -1 0 30.0 1.51 0.75 8 16 2 1 0 0 1 1 50.0 1.56 0.83 23 17 2 1 0 -1 0 1 25.0 1.31 0.78 11 18 2 1 -1 0 0 1 170.0 2.86 0.91 27 19 0 1 0 0 0 0 75.0 1.67 0.81 25 20 0 1 0 0 0 0 75.0 1.67 0.82 1 21 2 1 -1 -1 0 0 200.0 1.40 0.85 5 22 2 1 0 0 -1 -1 15.0 1.16 0.69 12 23 2 1 1 0 0 1 10.0 1.07 0.65 22 24 2 1 0 1 0 -1 80.0 1.39 0.82 13 25 2 1 0 -1 -1 0 115.0 1.55 0.79 4 26 2 1 1 1 0 0 3.9 1.00 0.84 2 27 2 1 1 -1 0 0 25.0 0.92 0.73 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 65-75. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 69 the response surface design shown in table 2 was analyzed using minitab to estimate quadratic (response surface) models of the form (equation 7): y = β0 + i=1 k βixi� + i=1 k βiixii 2 + i<j k k−1 2 βijxixj� +∈� (7) where y represents each of the responses in their natural forms, x represents each of the factors in their coded forms, β represents the coefficient of each term of the models, k represents number of factors in the models, ϵ represents error in each estimate, i = 1,2,…,k and j>i. then analyses of variance, lack-of-fit test and residual analyses were conducted using minitab to check the adequacy of the estimated models to approximate the measured data well at 95% confidence interval. if fcal > ftab and p-val > 0.05, the models are adequate approximation of the measured data; if fcallof > ftablof and p-vallof > 0.05, the models have no significant lack-of-fit. also, if the residuals tend towards an ‘s’ shape along a straight line with minimum number of outliers in the normal probability plots the more the adequacy of the fitted models. also if the residuals are normally distributed along the mean lines of the residuals versus fitted value and residual versus observation order with little or no cluster, the models are adequate, and little or lack of skewness and outliers in the histogram shows that the models are adequate. finally coefficients of determination (r2 and adj – r2) and error standard deviation (s) were determined to check the goodness of fit of the models. the more r2 and adj – r2 approximate to 100% and the smaller the value of s and the better the models approximate the measured data well. 3.0 results and discussion the developed coded responses functions of the machine investigated are as follows (equations 8-10). sg = 82.85 − 66.26x1 − 11.59x2 + 1.17x3 + 2.00x4 + 29.7x2x4 − 63.8x3x4 (8) tp = 1.5015 − 0.4067x1 + 0.2350x4 (9) ηc = 0.79296 − 0.0892x1 + 0.0325x3 (10) these coded functions were converted into the following actual response functions of the machine from the transformation formulae shown in equations 3-6. sg = 148.69lb + 17330.72ω + 339.43 n ∗ ω − 0.147n2 − 281.28n − 182.29 lb ∗ ω − 13757 (11) tp = 6.71ω − 0.000904n2 − 2.299 (12) ηc = 0.00325lb − 0.000198n2 + 0.8180 (13) the standardized residual plots which include the normal probability plot, histogram, residual versus fitted value and residual versus observation order are shown in figures 2 to 4. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwogu et al: response surface optimization of a plastic powder processing machine using desirability function approach. azojete,16(1):65-75. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 70 50250-25-50 99 90 50 10 1 residual pe rc en t 16012080400 50 25 0 -25 -50 fitted value re si du al 40200-20-40 8 6 4 2 0 residual fr eq ue nc y 2624222018161412108642 50 25 0 -25 -50 observation order re si du al normal probability plot versus fits histogram versus order residual plots for grain size figure 2: residual plots for the machine’s grain size model 0.50.0-0.5-1.0 99 90 50 10 1 residual pe rc en t 2.001.751.501.251.00 0.5 0.0 -0.5 -1.0 fitted value re si du al 0.80.40.0-0.4-0.8 10.0 7.5 5.0 2.5 0.0 residual fr eq ue nc y 2624222018161412108642 0.5 0.0 -0.5 -1.0 observation order re si du al normal probability plot versus fits histogram versus order residual plots for throughput figure 3: residual plots for the machine’s throughput model http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 65-75. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 71 0.10.0-0.1 99 90 50 10 1 residual pe rc en t 0.900.850.800.750.70 0.1 0.0 -0.1 fitted value re si du al 0.100.050.00-0.05-0.10 10.0 7.5 5.0 2.5 0.0 residual fr eq ue nc y 2624222018161412108642 0.1 0.0 -0.1 observation order re si du al normal probability plot versus fits histogram versus order residual plots for conversion efficiency figure 4: residual plots for the machine’s conversion efficiency model according to buyske and trout (2009), figures 2 to 4 indicate that the developed models statistically fitted the machine’s responses adequately since: the residuals approximate or form ‘s’ shape along a straight line in all the three responses. the normal probability plots of the grain size, throughput and conversion efficiency of the developed machine has little or no outliers. the residuals are normally distributed along the mean lines of the residuals versus fitted values as well as residuals versus observation order with very minimal cluster in all the three responses. the developed models were used to predict values of grain size, throughput and conversion efficiency and these predicted values were compared with the actual values derived experimentally (table 3). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwogu et al: response surface optimization of a plastic powder processing machine using desirability function approach. azojete,16(1):65-75. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 72 table 3: determination of the prediction accuracy of the response models run order x1 x2 x3 x4 actual values predicted values percentage error sg tp ƞc sg tp ƞc sg tp ƞc 1 0 0 1 -1 140.0 1.37 0.84 145.85 1.32 0.83 -4.2 3.6 1.2 2 1 0 1 0 5.0 1.35 0.74 5.2 1.32 0.74 -4.0 2.2 0 3 0 0 -1 1 180.0 1.56 0.79 179.1 1.59 0.76 0.5 -1.9 3.8 4 -1 0 1 0 150.0 2.12 0.89 150.3 2.09 0.91 -0.2 1.4 -2.2 5 1 0 -1 0 10.0 1.24 0.65 10.2 1.20 0.67 -2.0 3.2 -3.1 6 0 0 0 0 75.0 1.67 0.81 76.1 1.62 0.79 -1.5 3.0 2.5 7 0 1 0 1 114.0 2.31 0.80 113 2.29 0.79 0.9 0.9 1.3 8 0 -1 1 0 90.0 1.38 0.78 91 1.40 0.80 -1.1 -1.4 -2.6 9 0 1 1 0 40.0 1.39 0.84 42 1.41 0.83 -5.0 -1.4 1.2 10 -1 0 -1 0 111.0 1.01 0.86 112 1.03 0.85 -0.9 -2.0 1.2 11 0 -1 0 -1 110.0 1.16 0.69 111 1.20 0.70 -0.9 -3.4 -1.4 12 1 0 0 -1 60.0 0.92 0.64 58 0.91 0.66 3.3 1.1 -3.1 13 -1 0 0 -1 120.0 1.85 0.93 121 1.82 0.90 -0.8 1.6 3.2 14 -1 1 0 0 158.0 2.14 0.88 153 2.12 0.88 3.2 0.9 0 15 0 1 -1 0 30.0 1.51 0.75 31 1.50 0.76 -3.3 0.7 -1.3 16 0 0 1 1 50.0 1.56 0.83 48 1.6 0.83 4.0 -2.6 0 17 0 -1 0 1 25.0 1.31 0.78 26 1.35 0.79 -4.0 -3.1 -1.3 18 -1 0 0 1 170.0 2.86 0.91 168 2.83 0.88 1.2 1.0 3.3 19 0 0 0 0 75.0 1.67 0.81 76.1 1.62 0.79 -1.5 3.0 2.5 20 0 0 0 0 75.0 1.67 0.82 77.1 1.61 0.79 -2.8 3.6 3.7 21 -1 -1 0 0 200.0 1.40 0.85 198 1.42 0.88 1.0 1.4 -3.5 22 0 0 -1 -1 15.0 1.16 0.69 15.2 1.19 0.71 -1.3 -2.6 -2.9 23 1 0 0 1 10.0 1.07 0.65 10.3 1.10 0.67 -3.0 -2.8 -3.1 24 0 1 0 -1 80.0 1.39 0.82 78 1.34 0.79 2.5 3.6 3.7 25 0 -1 -1 0 115.0 1.55 0.79 113 1.50 0.76 1.7 3.2 3.8 26 1 1 0 0 3.9 1.00 0.84 4.0 1.01 0.81 -2.6 -1.0 3.6 27 1 -1 0 0 25.0 0.92 0.73 25.8 0.94 0.70 -3.2 -2.2 4.1 results of the confirmatory tests for grain size, throughput and conversion efficiency are displayed in figures 5 to 7. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 65-75. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 73 figure 5: confirmatory test for grain size figure 6: confirmatory test for throughput figure 7: confirmatory test for conversion efficiency file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwogu et al: response surface optimization of a plastic powder processing machine using desirability function approach. azojete,16(1):65-75. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 74 figures 5 to 7 show very close relationship between predicted and actual values of the responses. hence, the model has very high prediction accuracy with less than 5% error in all the predicted values (table 3). this is in line with oehlert, (2000) and nist/sematech (2006) statements that ‘equations and optimal operational settings determined using rsm are always or nearly close to the optimal operating conditions of the true system’ these fitted functions were further used for optimization of the system. the optimization result is shown in figure 8. cur high low d: 0.9592 optimal predict d = 0.88651 targ: 0.930 conversi y = 0.8971 d = 0.99566 targ: 2.0 throughp y = 1.9953 d = 1.0000 targ: 140.0 grain si y = 139.9998 d: 0.9592 desirability composite -1.0 1.0 -1.0 1.0 -1.0 1.0 -1.0 1.0 no. of b blade le intrisicspeed [-1.0] [-0.8937] [0.4602] [0.3709] figure 8: optimization plot for the machine performance parameter models figure 8 shows the optimal setting of overall conversion efficiency, throughput and grain size to be approximately 89.71%, 1.9953 kg/min and 139.9998 respectively, with coded input variables at -1.0, -0.8937, 0.4602 and 0.3709. substituting these coded optimal values in the transformation equations give the approximate optimal values of speed, number of blades, blade length and intrinsic viscosity as 1400 rpm, 4, 109.6 mm and 0.82798 respectively. 4.0 conclusion a plastic powder processing machine capable of converting used pet bottles into powdered form was optimized.. response surface optimization of the developed machine showed the optimal setting of conversion efficiency, throughput and grain size as 89.71%, 1.9953 kg/min and 139.9998 respectively. hence, optimal values of hammermill speed, number of blades, blade length and intrinsic viscosity were determined as 1400 rpm, 4, 109.6 mm and 0.82798 for respectively. these optimal operational parameters will make the machine economical to operate in terms of labour, time and energy requirement as well as improve the machine’s output. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 65-75. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: checknolly@yahoo.com 75 references abah, ja. 2013. plastics everywhere-life wasting wastes. energy and environment resides in lagos, daily post nigeria, april 11. andrady, al. 2003. an environmental primer in plastics and the environment, hoboken, nj: wiley interscience. pp. 3–76. andrady, al. and neal, ma. 2009. applications and societal benefits of plastics. philosophical transactions of the royal society b: biological sciences, 364 (1526): 1977-1984. doi:10.1098/rstb.2008.0304. buyske, s. and trout, r. 2009. response surface methodology ii. http://www.stat.rutger.edu/buyske/591/lect06. accessed: 2009. pp. 57-68. hardesty, b. and wilcox, c. 2015. eight million tonnes of plastics are going into the ocean each year. academic rigour, journalistic flair. the conversation africa, inc. jambeck, j., geyer r., wilcox c., siegler t., perryman m., andrady a., narayan r. and lavender k. 2015. plastic waste inputs from land into the ocean. american association of the advancement of science (aaas), pp. 768-771. kathleen, mc., natalia, yk. and kamnwa, jr. 2004. response surface methodology. casos technical report. carnegie mellon university, pittsburgh, pa 15213. cmu-isri-04-136. http://www.casos.cs.cmu.edu. accessed: 2004. pp. 22-24. luo, x., ou, r., eberly, de., singhal, a., viratyaporn, w. and mather, pt. 2009. a thermoplastic/thermoset blend exhibiting thermal mending and reversible adhesion, national centre for biotechnology information, u.s. national library of medicine 8600 rockville pike, bethesda md, 20894 usa., 1(3): 612-620. myers, rh. and montgomery, dc. 2002. response surface methodology: process and product optimization using designed experiments. wiley-interscience publication, new york., pp. 800821 nist/sematech, 2006. engineering statistics e-handbook. www.iel.nist.gov/dv898/handbook. national institute of standards and technology, gaithersburg. md 20899. accessed: 2009. nwogu, c., uche, r., igbokwe, jo. and okoronkwo, ac. 2019. design and development of a plastic powder processing machine for recycling used polyethylene terephthalate. machine design, 11(2): 47-52. oehlert, gw. 2000. design and analysis of experiments, response surface methods and designs. john wiley and sons inc. new jersey. plasticseurope, 2008. the compelling facts about plastics 2008-an analysis of european plastics production, demand and recovery for 2008. association of plastics manufacturers, avenue e. van nieuwenhuyse 4/3 b-1160 brussels – belgium., pp. 1-23. rosato, dv. 2001. plastics engineering manufacturing and data book, vol. 1.. kluwer, academic publishers, 101 philip drive, norwell, massachusetts http://www.stat.rutger.edu/buyske/591/lect06 http://www.iel.nist.gov/dv898/handbook file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):355-364 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 355 original research article value management concept in construction projects delivery in kano state alhassan dahiru (department of quantity surveying, faculty of earth and environmental sciences, bayero university kano) *corresponding author’s e-mail address: adahiru.qs@buk.edu.ng article information submitted 19 august, 2018 revised 1 february, 2019 accepted 8 february, 2019 keywords: construction economics construction projects delivery construction professionals procurement administrators value management technique. abstract construction projects delivery play an important role in the economic development of any nation. nevertheless, review of project documents in nigeria and kano state in particular indicates that, the design of these projects is such that the whole life-value is not achieved. one of the suitable tools for the compensation of this drawback is the use of value management (vm) technique. this paper presents that the use of organized framework for the vm technique in the initial phase of a project generates good ideas that has the capacity to increase the project value. the objective of the study is to investigate the application of the vm in public construction projects, identify the constraint factors limiting its application, and suggest ways to expand its use in the built environment. questionnaire survey methodology, addressed to government ministries and agencies actively involved in construction and to project management consulting firms, was utilized. a total of 94 questionnaires responses were received from 7 ministries and agencies. another 13 responses were received from randomly selected consulting firms. the data was analyzed using spss 23 version. it was found that value management as a formal programme is not applied to the development of construction projects in kano state. lack of knowledge about the value management technique and its financial and technical benefits was found to be among the constraint factors of its application. furthermore, lack of government demand on vm, unfamiliarity with vm technique, and unavailability of experts to perform were determined to be the top constraint factors. therefore, it is recommended that the promotion of value management use can be achieved by creating awareness among the construction stakeholders, gaining top management support, providing training programmes, guideline, and financial incentives to procurement administrators © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction construction projects play a significant role in the economic development of every nation. in most developed and developing nations, these projects absorb large sums of the capital asset investment in the state budget, and the construction industry in nigeria is no exception (dahiru and bashir, 2017). from 1999 to 2017 thousands of billions of naira were invested exclusively in infrastructure projects development in kano state. regrettably, the survey conducted on these projects show that, in the design stage of the development, innovation is not considered. in nigeria, since remuneration of consultants in the design phase is based on the percentage of mailto:adahiru.qs@buk.edu.ng http://www.azojete.com.ng alhassan dahiru, value management concept in construction projects delivery in kano state. azojete, 15(2):355-364. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 356 implementation costs, consultants incline to increase these costs (leje et al., 2017). on the other hand, the owner tendency for faster operating of the project eliminates the possibility of innovation in the design stage. this leads to poor design and reduction of the project value. therefore, it is required to use a suitable tool in order to compensate this drawback. for this purpose, mesbah (2014) observed that use of the value management (vm) technique is one of the best tools designed to achieve the necessary functions of a project at the lowest resulting cost with optimum value for money. akram et al. (2011) defined the technique as a tool concerned about the relationship between function, value, quality and cost, with functional analysis as its principal components. vm is a systematic approach for analyzing the functional requirements of products or services to obtain the essential functions at the lowest total cost (rangelova and traykoval, 2014; musa et al., 2016). in fact, it aims to reduce overall project costs through identifying and eliminating unnecessary costs. in addition, the successful implementation of a vm practice can result in update of standards and policies, and quality improvement of products (green and liu, 2007). based on available technical literature on the global network of information, vm techniques have been able to make significant changes in the integrative management of complex and large projects as an effective instrument (spaulding, 2005; suhaimi, 2014; todorut and tselentis, 2015; musa et al., 2016). value management (vm) is a well-known and applied technique throughout the world. it is applied in construction as an efficient tool to achieve overall project success. todorut and tselentis (2015) emphasized that vm can be described as a systematic creative study performed on the project, aimed to achieve the project functions needed at the lowest possible cost without sacrificing quality, performance or reliability. the vm study can cover the architectural design of the project as well as the choice of its systems, materials and components (rangelova and traykoval, 2014). suhaimi (2014) pointed out that the benefits of vm are well recognized, making its application necessary in almost all construction projects. however, the concept of value management is relatively new in kano state but the extent of its awareness and application is investigated in this study. 1.1 statement of research problem the public procurement act (2007) emphasized the application of value for money standards and practices in the delivery of public construction projects for improving service delivery. the best way of improving service delivery in the construction industry is through value management practice (akram et al., 2011; oke and ogunsemi, 2011; hayatu, 2015). to improve service delivery through the application of value for money standards in the nigerian construction industry as contained in the public procurement act (ppa) 2007, there is the need to adopt value management as it is at the forefront for achieving and enhancing value for money (hayatu, 2015). however, value management has not been fully embraced in the nigerian construction industry (oke and ogunsemi, 2011; dahiru, 2018; bashir and dahiru, 2018). it is in view of this that the study was carried out to assess the level of personnel knowledge and reasons/or constraints for not applying value management with a view to achieve value for money in project delivery. bowen (2010) conducted a theoretical research and recognized that vm is suitable for application at the early state of project development. to maximize the benefits of vm, bashir and dahiru (2018) observed that government has the responsibility to enforce regulations on the vm application on public construction projects. however, the kano state government is yet to fully embrace value management techniques despite its advocacy. thus, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):355-364. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 357 there is the need to investigate the factors influencing the application of value management in kano state so as to provide an understanding as to why value management is yet to be fully embraced and also provide a guide on the necessary steps for its adoption in the construction industry. 2.0 methodology relevant literature was reviewed so as to discuss the development and application of value management. this was to provide an insight on the subject matter as well as the practice in the construction industry. the survey method used in this study was employed to reveal the opinion of architects, quantity surveyors and engineers regarding the constraint factors surrounding the application of value management technique in public construction project delivery. the data for the study was generated using a stratified sampling technique conducted with seven (7) government ministries and agencies heavily involved in the public construction projects in kano state. such ministries/or government agencies include: ministry of works and transport; ministry of land and housing development; ministry of education; ministry of local government; ministry of environment; ministry of health; and kano urban protection and development authority (knupda). on average, ten (10) respondents (architects, quantity surveyors and engineers) were surveyed from each ministry/or public agency. a total of 120 questionnaires were administered to the respondents of which 94 (78%) response rate were returned and ready for the analysis. similarly, 13 project management consulting firms were interviewed utilizing a similar questionnaire. the survey used the questionnaire to collect data from the two groups of respondents (public clients and project management consulting firms). the data inquired about the respondents’ knowledge of vm and its application and the possible constraints against vm future application. these were analyzed using spss 23 version to assess the factors constraining vm application. data on the importance of vm, its cost and expected savings as well as the suitable time for conducting vm study were obtained through interview method and assessed using tables with a view to seek the respondents’ opinions on its relevance in achieving value for money projects. 3.0 results and discussion twenty-five (25) responses were received from the project participants mainly architects, quantity surveyors, and engineers working at the state ministry for local governments; works, land and housing development, education, health, environment, and kano urban protection and development authority (knupda) as shown in table1. ten (10) of the respondents supported that vm is important for all construction projects regardless of the size. five (5) consider it important only for projects costing over 20 million naira. the remaining ten (10) respondents indicated that value management should be done on projects over n50 million (table 2). this shows that all respondents consider value management necessary for public construction projects over n20 million. these findings corroborate with the findings of todorut and tselentis (2015) that vm techniques is an effective instrument for the development of both complex and large projects that attract high capital outlay. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alhassan dahiru, value management concept in construction projects delivery in kano state. azojete, 15(2):355-364. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 358 table 1: participants drawn from various ministries participants’ ministries frequencies of responses by the respondents total architects q/surveyors engineers ministry of works 2 2 1 5 ministry of land & housing dev. 1 2 1 4 ministry for local government 1 1 1 3 ministry of education 1 2 1 4 ministry of health 1 1 1 3 ministry of environment 1 1 1 3 knupda 1 1 1 3 total responses 8 10 7 25 all of the respondents believed that a government regulation should enforce vm for public construction projects. however, only few thought that it should be enforced to all construction projects of all sizes. six others believed that value management should not be enforced for projects of less than n20 million. the remaining five said that vm should only be enforced on projects over n50 million, which concludes again that all respondents believe that value management should be enforced in public construction projects over n20 million. table 2: respondents’ perception regarding the vm application on project value project value in naira frequency of responses by the respondents total architects q/surveyors engineers less than 10million 0 0 0 0 10million 3 4 3 10 20million 2 2 1 5 50million 3 4 3 10 total responses 8 10 7 25 3.1 level of personal knowledge about value management only 12% of respondents worked in government agencies indicated that they know the value management concept very well, while 74% of the management consulting firms indicated the same claim as shown in table 3. the level of personal knowledge of vm among construction professionals working in public organizations is low in spite of the fact that most construction professionals worked in ministries and agencies indicated that they attended the vm workshops. however, construction professionals working in the management consultancy firms have adequate knowledge on value management as indicated on the same table 3. half of the management consultancy firms are medium sized firms employing between 6 -10 personnel and the other half are large firms employing more than 10 personnel. table 3 indicates that the concept of value management has recently been introduced in kano state and is still not well known to the state government construction professions. about 88% of these construction professionals working in government ministries and agencies who responded to the questionnaire knew little or nothing about value management. the value management concept is known to nigerian built environment professionals by seminars and workshops conducted by http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):355-364. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 359 the professional regulatory bodies such as niqs, qsrbn, coren, niob, corbon, nia, arcon, etc. the level of knowledge about vm concept among the consulting firms is 74% higher compared to the government offices. the large consulting offices knew more about vm as compared to the small ones. the result implies that formal value management education in various ministries and agencies in kano state is very limited. table 3: level of personnel knowledge of value management level of knowledge government agency (%) management consultancy firms (%) never heard of it 39 11 know little about it 49 15 know it very well 12 74 3.2 reasons for not applying value management majority of respondents (30%) involved in public construction projects works at government agencies indicated that they are not applying vm in their projects because the concept was never introduced to them. table 4 shows that 22% of respondents revealed that time given for project design is usually very short and thus limiting the application of vm. quite number of stakeholders (20%) did not understanding the benefits attached to vm application during the project design. unavailability of experts to apply vm concept into the project design (17%) has become a constraint factor influencing the application of vm concept. other respondents (11%) agreed that designs are usually done by best designers, so no need for vm as shown in table 4. table 4: reasons for not applying value management in government agencies reason for not applying vm public agencies response (%) the vm concept of is not introduced practically 30 lack of experts to apply vm concept in project design 17 time given for project design is usually very short 22 lack of understanding the benefits attached to vm application 20 designs are usually done by best designers, so no need for vm 11 vm concept is not worthwhile 00 table 5 indicates that 67% of the management-consulting firms indicated that they never conducted vm as they were never asked to perform such service by their clients for an additional fee. 12% of respondents claimed that the concept is not well known. additionally, 11 % of respondents indicated that vm is just relevant for construction project delivery which they do anyway. lack of experts to apply vm was agreed by the respondents (10%) as a constraint factor limiting its application. nobody claimed that value management is not good in achieving value for money. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alhassan dahiru, value management concept in construction projects delivery in kano state. azojete, 15(2):355-364. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 360 table 5: reasons for not applying vm in consulting firms reason for not applying vm professionals in ministries/agencies responses (%) vm is not adequately known by the majority of consultants 12 never been asked to conduct vm during the design process for additional fee 67 vm lacks experts to apply it 10 it is just relevant for construction project development which they do anyway 11 it is not good in achieving value for money 00 3.3 constraint factors limiting vm utilization the questionnaire survey has a list of twenty (20) constraint factors limiting vm utilization. respondents were asked to indicate their opinions on the degree of importance of each factor on a scale spanning from 'very important' to 'not important'. index values were calculated for each factor based on the degree of importance and the frequency of response as shown in table 6. the first constraint against value management application in public construction projects is that the concept is not well known and the unavailability of experts to apply it. lack of government regulations to support the vm application and the lack of top management support are influential factors limiting the application of vm. the management-consulting firms indicated that 'the lack of demand on vm' is the top constraint factor limiting its application. unfamiliarity with vm technique is the second constraint factor and the unavailability of experts to perform it is third factor. the two populations share common grounds in some respects. the following observations can be made: the main problem influencing the practice of value management lies with the government agencies. the top reason for this is lack of knowledge, even at top management levels in the government agencies (table 6). the government agencies lack expert staff to conduct the value management study on their projects. the management consultancy firms claim that they do not apply vm as the government agencies do not demand for it. this has support the view of oke and ogunsemi (2011), dahiru (2018), bashir and dahiru (2018) that value management has not been fully embraced in the nigerian construction industry. no government regulations to generally support vm studies and there are no provisions for financial incentives to use vm in the public construction projects. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):355-364. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 361 table 6: constraint factors limiting vm utilization constraints against vm application as indicated by professionals employed in ministries/agencies professions in ministries/agencies index constraints against vm application as indicated by consulting firms consulting firms index vm concept is not well known 98 vm concept is not well known 46 vm is not worthwhile 12 vm is not worthwhile 10 lack of experts to conduct vm study 76 lack of experts to conduct vm study 48 design is done by best designers so no need for vm 19 it is just good for construction project, 33 vm concept is complex in nature 26 vm concept is complex in nature 24 the concept is difficult to get started 36 the concept is difficult to get started 18 lack of support by the top management 86 never been asked to conduct vm in the 96 not ready to conduct vm at the design 52 not ready to conduct vm at the design 27 government regulations don't support it 83 the clients will not buy the concept 16 vm will not succeed in kano state 18 vm will not succeed in kano 25 3.4 importance of value management table 7 shows that majority of public owners (27%) indicated that vm is important and its application should be enforced on all projects. 26% of public clients indicated that the application should be enforced on projects above n20 million. while, 23% claim that, vm application is suitable for project above n50 million. furthermore, 12% agreed that vm is suitable for project above n100 million. the remaining 10% agreed that, it is suitable to be applied for project above n150 million. on the other hand, 11% of the consultancy firms claim that vm is suitable to be enforced on all projects. 21% of the respondents agreed that the concept is suitable for project above n20 million. majority of the respondents (26%) claim that vm is applicable for project above n50 million values. other 16% agreed to be suitable for project above n100 million values. the remaining 23% of the respondents indicate that vm is relevant for application of project above n150 million worth value as the results are presented on table 7. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alhassan dahiru, value management concept in construction projects delivery in kano state. azojete, 15(2):355-364. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 362 table 7: importance of vm for construction projects delivery construction project size vm importance responses from ministries/agencies vm enforcement responses from ministries/agencies vm enforcement responses from consulting firms all construction projects 27 22 11 projects > n20 million 26 32 21 projects > n50 million 23 21 26 projects > n100 million 12 11 16 projects > n150 million 10 13 23 vm is not important 02 01 03 3.5 cost of value management study and expected savings table 8 indicates that 31% of the public clients are ready to spend 5% of the savings generated on conducting vm studies. another 28% indicated readiness to spend 6 10%. additionally, 22% of the clients claim their readiness to pay 11-20% of the savings realized while conducting vm studies. the remaining 19% of the public clients agreed to spend over 20% of the savings. table 8: cost of vm study as indicated by public clients cost of vm (public clients who are prepared to pay to conduct vm) percent (%) 5% of the savings 31 6 10% of the savings 28 11 20% of the savings 22 over 20% of the savings 19 when asked about the expected savings vm can achieve as a percentage of the total project cost, the majority of public clients (37%) indicated that vm has expected savings of about 5% of total project cost (table 9). 35% of the clients revealed that expected savings of vm is about 10% of the total project cost. while 21% have the perception of saving from vm up to 15% of the total project cost (table 9). the result implies that when vm is appropriately utilized, it has the expected savings ranging from 5 – 15% of the total project cost. table 9: expected savings from vm study as indicated by public owners expected savings public owners’ response (%) i % of total project cost 4 2 5 % of total project cost 37 6 10% of total project cost 35 ii 15% of total project cost 21 over 15% of total project cost 3 3.6 suitable time for conducting vm study the findings in table 10 indicate that 76% of the public clients recognized that vm is suitable for application at the early state of project development. the perception of consulting firms (86%) on the application of vm at the early stage of project development is much higher than the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):355-364. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 363 public clients. 13% of public clients and 9% of consulting firms have agreed that vm can be applied up to the final design state of project development (table 10). the results concerning the suitable time for vm application can be summarized by the following: more than 70% of public clients and above 80% of consulting firms agreed that the most suitable time to conduct value management is during the early and final design phase of the project development. this is in conformity with the previous findings of bowen (2010) that, vm is suitable to be adopted at the design stage of project development. table 10: suitable time for vm application suitable time public clients response (%) consultancy firms response (%) during early stages 76 86 up to final design 13 09 after the design is awarded 11 05 4.0 conclusion the value management practice on construction projects delivery has been identified as the main challenges of the nigerian construction industry especially at the states level. several researches have been conducted at the national level to mitigate these challenges through different approaches and strategies and yet absolute resolutions have not been made. therefore, the study examined these challenges on construction projects delivery in kano state. regrettable, results of the findings revealed that value management application is very limited in the state especially among the relevant government employees. the most important reason for not applying value management in the state is due to the unfamiliarity of the concept among the public sector clients as well as local consulting firms. findings indicate that there are no incentives to the contractors or the consultants to adopt vm technique in public construction projects. moreover, government agencies lack expert staff to conduct the value management study on their projects. the management consultancy firms claim that they do not apply vm as the government agencies do not demand for it. no government regulations to generally support vm application and there are no provision for financial incentives to use vm in the public construction projects delivery in kano state. therefore, it is recommended that training programmes are essential for procurement administrators in the state. top management support is essential to introduce and operate a successful value management programme in government ministries and agencies. this will greatly help in improving the application of vm capable of improving projects value and reducing the high cost of construction projects in the state. references akram, s., minasowics, a., kostrzewa, b., mukherjee, a., nowak, p. 2011. value management in construction: common learning outcomes for european managers in construction. accessed on 22nd june, 2018, https://www.designingbuildings.co.uk/wiki/valuemanagement. bashir, am. and dahiru, a. 2018. implementation and utilization of value management practice in construction cost management practice in nigeria. a paper presented in: icec-paqs conference proceedings held at the international convention centre, sydney, australia. https://www.designingbuildings.co.uk/wiki/valuemanagement file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alhassan dahiru, value management concept in construction projects delivery in kano state. azojete, 15(2):355-364. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adahiru.qs@buk.edu.ng 364 bowen, p. 2010. the awareness and practice of value management by south african consulting engineer: preliminary survey findings. international journal of project management, 28(1): 285 – 295. dahiru, a. 2018. operational principles of due process bureau: walking the path of public procurement reforms in kano state. being a paper presented at the 3rd distinguished annual lecture organized by the niqs kano state chapter held at royal tropicana hotel, kano. 3: 34 – 52. dahiru, a. and bashir, am. 2017. investigating the barriers and benefits of value management practices in construction projects delivery in nigeria. proceedings of the 3rd annual research conference of the nigerian institute of quantity surveyors – recon3 held at zaranda hotel, bauch, nigeria. 3: 751 – 762. green, sd. and liu, am. 2007. theory and practice in value management. journal of construction management and economics, 25: 649 – 659. hayatu, ua. 2015. an assessment of the nigerian construction industry’s readiness to adopt value management process in effective project delivery. unpublished msc thesis, department of quantity surveying, faculty of environmental design, ahmadu bello university, zaria. leje, mi., kasimu, ma., kolawole, af. and jibrin, ia. 2017. value management practices in nigerian construction industry. proceedings of the 3rd annual research conference of the nigerian institute of quantity surveyors – recon3 held at zaranda hotel, bauch, nigeria, 3: 763 – 773. mesbah, m. 2014. value management for construction projects via an expert system framework. unpublished msc thesis, department of civil engineering, eastern mediterranean university, gazimagusa, north cyprus. musa, mm., pasquire, c. and hurst, a. 2016. where lean construction and value management meet. in proc. 24th annual conference of the international group for lean construction. boston, usa, 24: 103 – 125. oke, ae. and ogunsemi, dr. 2011. value management in the nigerian construction industry: militating factors and the perceived benefits. in: 2nd international conference on advances in engineering and technology (aet2011), entebbe, uganda, 2: 304 – 317. rangelova, f. and traykoval, m. 2014. value management in construction project. paper presented at the first scientific applied conference with international participation project management in construction. university of architecture, civil engineering and geodesy, japan.1: 213 – 224. spaulding, w. 2005. the use of function analysis as the basis of value management in the australian construction industry. journal of construction management and economics, 23(7): 723 – 731. suhaimi, ms. 2014. value management in design planning: a system based framework for multidisciplinary team involvement. unpublished phd in construction project management. queensland university of technology, uk. todorut, av. and tselentis, v. 2015. design the model for public value management. proceedings of the 9th international management conference: management and innovation for competitive advantage, november, bucharest, romania, 9: 416 – 428. http://www.azojete.com.ng original research article value management concept in construction projects kano state alhassan dahiru arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):223-241 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 223 original research article occurrence of similar periods in geomagnetic field variations and solar activity a. b. rabiu1*, r. b. abdulrahim2, o. a. garuba3, o. o. adekanmbi3, s. a. alabi3, l. l. ojurongbe3 and a. s. lawani3 1centre for atmospheric research, national space research and development agency, anyigba, nigeria 2centre for satellite technology development, national space research and development agency, abuja, nigeria 3network of space-earth environmentalists, abuja, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: periods solar activity geomagnetic field. abstract the periodicities associated with some geomagnetic field parameters under quiet and disturbed solar conditions have been examined using a set of data spanning through five years obtained courtesy of intermagnet network. hourly values of the horizontal component of the geomagnetic field simultaneously obtained at seven intermagnet stations were engaged in the study. the stations were well distributed across the latitudes, viz: bangui, 4.4 n; kourou, 5.1 n; alibag, 18.6 n; san juan18.1n; crozet, 46.4s; barrow,71.3n; scott base, 77.9s). solar quiet daily variation sq, superposed magnetic field spmf and solar disturbance daily variation sd in the horizontal magnetic field component were evaluated and studied for their spectral characteristics. the spectral analysis revealed the periods of 6 hours, 12 hours, 24 hours, 3 months, 6 months, 12 months and 16 months in the geomagnetic field variations. the observed periodicities were explained in terms of associated solar terrestrial processes. this clearly shows the influence of an extra terrestrial source (the sun) on terrestrial processes. sun is the undisputable driver of space weather © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the study of the ionosphere, and the region beyond it, has continued to attract attention due to its growing importance in several space-dependent technologies (rabiu et al., 2007a). for example, okoh et al. (2016) explained how ionospheric radio waves propagating through the ionosphere may experience frequency-dependent group delays as sources of error for the global navigation satellite system (gnss) and its dependent systems. the variability of ionospheric total electron content tec has a very good practical importance in communication systems, and navigation control application (ayorinde et al., 2016). variations in the ionosphere often manifest as variability in the earth ’ s magnetic field. the geomagnetic field pervades the region around the earth, extending to several times the radius of the earth. sun related activity plays an important role in producing several electric and magnetic processes, which in http://www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 224 turn affects the magnetic field of the earth. the impact this activity has on the magnetic field of the earth can be observed to follow a somewhat regular pattern. mursula and zieger (2000) studied the occurrence of mid-term quasi-periodicities “mtqp” in solar wind “sw” speed since 1964 and in geomagnetic activity since 1932 and found that the spectral structure in the mid-term period range is very similar in these two variables over the whole common time interval of nearly 40 years of direct sw measurements. prestes et al. (2006) observed that the 11-year solar cycle and the associated variability that it causes on the earth’s electromagnetical environment – the geospacehas been widely studied in the last decades. nevertheless, the long-term relation between the solar and geomagnetic activity is a topic of intense research and it is not well understood at present (gonzalez et al., 1990; gorney, 1990; cliver et al., 1996; stamper et al., 1999; echer et al., 2004). the time rate of occurrence of a phenomenon is an essential concept in the scientific world, hence, scientists and meteorologists observe phenomena in terms of time series, as this gives a clearer description and understanding of such phenomenon and provide us with information on its periodicity. the space researchers have been able to use and are still using this tool to unravel the complex variations both long-term and shortterm associated with the earth’s magnetic field. for example, researchers were able to deduce from time series observation a solar cycle of 11 years. this singular discovery has aided a better understanding of phenomenon and variations associated with the geomagnetic field. this present study employed the fast fourier transform to perform a spectral analysis on the hourly and monthly average time series of the solar quiet daily variation sq, disturbance daily variation sd, and superposed magnetic field, spmf of the horizontal component of earth’s geomagnetic field from 1996 through 2002. the primary objective is to identify the probable occurrence of solar activity related periods in the variations of the geomagnetic components. 2. methodology the data set consists of hourly values of horizontal component of the geomagnetic field intensity, h, for the years 1996 to 2002, obtained at four equatorial stations: bangui, kourou, alibag, and san juan sjg; one middle latitude station: crozet; two high latitude stations: barrow and scott base. table 1 presents the position coordinates of the stations. the data was obtained courtesy of the intermagnet network. intermagnet is a global network of observatories monitoring the earth’s magnetic field. hourly values of the horizontal component h of the geomagnetic field intensity on international quiet days iqds and disturbed days idds for the years 1996 to 2002 were utilized in this study. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 225 table 1: coordinates of the geomagnetic observatories s/n location station code geographical coordinates latitude (n) longitude (e) 1 bangui bng 4.4 18.5 2 kourou kou 5.1 307.3 3 alibag abg 18.6 72.9 4 san juan sjg 18.1 293.9 5 crozet czt -46.4 51.9 6 barrow brw 71.3 203.4 7 scott base sba -77.9 172.8 daily variation baseline values were obtained from the mean of the four hourly values, of the horizontal component h of the geomagnetic field intensity on a particular day, flanking the local midnightthat is 1h lt, 2h lt, 23h lt, 24h lt. the daily baseline value is subtracted from the daily hourly values, to obtain the hourly midnight departure values. the hourly midnight departures were further corrected for the non-cyclic variation after vestine (1967) and rabiu et al., (2007b). the hourly departure corrected for non cyclic variation gave the corrected solar daily variation. solar quiet daily variation, sq, was evaluated by estimating the solar daily variation as described above on international quiet days only. the monthly hourly means of the estimated values then gave the hourly sq. solar disturbed daily variation, sd, was obtained by estimating the monthly hourly means of the solar daily variation on international disturbed days. the difference between sd and sq of a particular month is the monthly disturbance daily variation and is defined as: sd = sd – sq (1) (mitra, 1947; rastogi, 2000) we defined the superposed magnetic field spmf as follows: spmft = sqt – mean (sqt) (2) where: spmft is the spmf value at t h; sqt is the hourly sq value at t h; mean (sqt) is the mean of the hourly sq values for each individual t h, for the five international quietest days of month. spmf is an improvement over the superposed field proposed by onwumechili (1997) and is a measure of ionospheric contributions to geomagnetic field variations. periodograms shown in figures 1 -7 are then obtained by the fast fourier transform fft technique using a matlab® based algorithm. figures 1 and 2 show the spectra of the hourly sq in horizontal intensity of the geomagnetic field as obtained for the years 1996 and 1999 respectively. figures 8, 9 and 10 present the spectra of the monthly averages of sq, sd and spmf respectively over the years 1996 – 2002 (84 months). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 226 figure 1: periodograms showing the periods associated with sq(h) hourly means for the year 1996 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 227 figure 2: periodograms showing the periods associated with sq(h) hourly means for the year 1997 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 228 figure 3: periodograms showing the periods associated with sq(h) hourly means for the year 1998 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 229 figure 4: periodograms showing the periods associated with sq(h) hourly means for the year 1999 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 230 figure 5: periodograms showing the periods associated with sq(h) hourly means for the year 2000 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 231 figure 6: periodograms showing the periods associated with sq(h) hourly means for the year 2001 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 232 figure 7: periodograms showing the periods associated with sq(h) hourly means for the year 2002 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 233 figure 8: periodograms showing the periods associated with sq(h) monthly means file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 234 figure 9: periodograms showing the periods associated with sd(h) monthly means http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 235 figure 10: periodograms showing the periods associated with spmf (h) monthly means table 1 presents the obtained periods through fft method of the hourly sq (h) for each of the years 1996 2002. table 2 shows the obtained periods of the monthly sq, sd and spmf series for the years 1996 – 2002. table 1: periods associated with the sq hourly means from 1996 through 2002 station lat. () period (hours) 1996 1997 1998 1999 2000 2001 2002 brw 71.32 8,12,24,42 6,8,12,24,36,48 12,18,24, 36 12,18,24,3 6,42,60,98 6,12,24,3 6 12,20, 24,36, 60 12,18,24 ,42, 60,98 abg** 18.64 6,8,12,36 8,12,24 8,12, 24 8,12,24 8,12,24,4 8 8,12,24 8,12,24, 48 kou 5.10 8,12,24 8,12,24 12,24,48 12,24 8,12,24 12,24 8,12,24 bng 4.44 8,12,24 8,12,24 8,12, 24 8,12,24 8,12,24 8,12,24 8,12,24 czt -45.43 6,8,12,24 6,8,12,24 6,12, 24,30 6,8,12,24 6,8,12, 20,24 6,8,12, 24 6,8,12,24 sba -77.85 12,24,36 12,18,24, 60 12,20,24, 36,48 12,24,60 12,18,24, 42,60 12,18, 24,36 12,24,48, 98 *data for sjg and not abg was used to evaluate hourly sq in 1996. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 236 table 2: periods associated with sq, sd and spmf monthly means (1996-2002) as depicted by the peaks in the periodograms of the horizontal intensity (h) station geog latitude () period (months) sq sd spmf brw 71.32 3,6,12,42 2,3,6,7,12,18 6,8,10,12,16,42 sjg 18.38 3,6,9,12 2,3,4,6,8,10,12,21 8,10,12,16 kou 5.10 6,12 2,3,6,8,10,12,21,42 6,8,10,12,30 bng 4.44 6 3,6,10,16 6,8,10,12 czt -45.43 6,12 3,6,9,12,21 6,10,12 sba -77.85 12 3,4,8,12,21,42 6,8,10,12 3. results and discussion 3.1. sq(h) hourly spectra table 1 presents clearly periods of 12-hour and 24-h as common to all the stations, irrespective of their latitudinal differences. the 24 h period signifies a 1-day periodicity in the observation which is reflected in the diurnal variation of sq, while the 12-h period corresponds to semidiurnal variation which may be due to lunar modulation as proposed by gouin (1962). this diurnal variation has been ascribed to the augmentation of the geomagnetic field by solar activity in daytime in consistency with the atmospheric dynamo theory of the geomagnetic variations (onwumechili and ezema, 1977). there are also additional periods (in hours) for the six stations as indicated in table 1. 3.2. monthly spectra of sq(h), sd(h) and spmf(h). from table 2, a 12-month period is noticed in each station except bng. this represents a 12-month periodicity which is consistent with those observed in the planetary sq variation and it indicates that sq(h) undergoes an annual modulation which is mostly as a result of a 12-month oscillation (arora et al., 1982). the non-prominence of the peak at the equatorial stations sjg and kou corroborates yacob ’s (1975) observation that the amplitude of the annual line does not show enhancement in the equatorial electrojet region. we also observe a 6-month periodicity which is common with those found in the planetary sq semi-annual variation (rabiu, 2001, 2004). while the 6-month and 12month are expected there are additional periods of 3 months and 42 months in brw and a period of 9 months in sjg. the 3and 6-months periodicity manifested in form of seasonal variation of the sq(h) which is solar controlled. the monthly spectra of sd(h), as listed in table 2, reveals the existence of a period of 6 months for all the six stations indicates a 6-month periodicity which is known to be associated with the semi-annual variation of geomagnetic activity (prestes et al., 2006). there is also a period of 12-month, which is pronounced in the high latitude region brw and sba; and the middle latitude station czt. as observed by yacob (1975), this also indicates that the amplitude of oscillation does not show enhancement in the electrojet region. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 237 the spmf spectra yielded a period at the 12-month line in all the stations which indicates a 12-month periodicity of the h component under superposed magnetic field (see the 5th column of table 2). there is also a peak at the 6-month line in all the six stations which signifies the 6-months periodicity associated with geomagnetic activity. the seasonal variability depicted by the observed 3-months periodicity in sq may be due to the ionospheric wind variations, atmospheric tidal forces, distant current systems such as current in the magnetosphere and the seasonal variation of the ionospheric electron current (rabiu, 2001). the 6-month period in sq, sd and spmf is obviously related to the semiannual variation of geomagnetic activity, which according to prestes et al. (2006), is characterized by a greater geoeffectiveness at equinoxes than at solstices (rabiu, 2001, 2004). this semiannual variation may be due to the annual and semi-annual changes that are observed in the earth’s heating and ionization during the yearly path around the sun (campbell, 1982). this semiannual effect in geomagnetic activity is explicable in terms of three possible mechanisms: russell–mcpherron effect (rm), the equinoctial hypothesis and the axial hypothesis (russell and mcpherron, 1973; clu´a de gonzalez et al., 1993). the rm effect is a projection effect that depends on the season. the interplanetary magnetic field in the heliocentric coordinate system has a component in the south direction in the solar magnetospheric coordinates, maximized in march and september equinoxes. in the equinoctial hypothesis, the geomagnetic activity is at its maximum when the angle between sun–earth line (solar wind flux direction) and the geomagnetic dipole is 901, and lower in other epochs. this effect reduces the efficiency of solar wind – magnetosphere coupling during solstices. in the axial hypothesis, the peaks in geomagnetic activity occur when earth is in higher heliolatitudes, where it is better aligned with any coronal mass ejection flux. clu´ a de gonzalez et al. (1993) have shown that the three effects are working together to produce the geomagnetic activity variation and they suggested that these mechanisms acting as modulators in the geomagnetic response for transient solar coronal mass ejections. cliver et al. (2000), on the other hand, suggests that the equinoctial hypothesis explains in a better way the semiannual fluctuations than rm and axial mechanism. they have estimated that equinoctial mechanism is responsible for around 65% of the seasonal modulation whereas rm and axial have between 15% and 20% each in the modulation. the annual periodicity (12-month periodicity) observed in the sq, sd and spmf is a reflection of the annual variation in geomagnetic activity. annual variation is also known in solar wind (sw) speed, temperature and density (bolton, 1990; paularena et al., 1995; szabo et al., 1996). szabo et al. (1996) showed that annual variation in solar wind speed is strongest around solar minima. zieger and mursula (1998) have observed a very similar annual variation in solar wind speed and geomagnetic activity during the whole period of direct solar wind observations including the four solar minima before 1998. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 238 16 months periodicity observed in spmf at brw (71.3 n) and sjg (18.38 n); and sd at bng (4.4 n), is quite similar to the 1.3 yrs periodicity observed by paularena et al. (1995) which occurred concurrently in solar wind speed and geomagnetic activity after 1987. szabo et al. (1995) discovered the 1.3-year variation in the imf north-south component. a strong, slightly longer periodicity of about 1.7 years ( 20.5 months) comparable with the 21-month periodicity found only in solar disturbance daily variation sd (see the 4th column of table 2) was also found in cosmic rays during solar cycle 21 (valdes-galicia et al., 1996). moreover, the 1.3-year periodicity has been observed in the variation of the solar rotation speed around the tachocline at the bottom of the solar convection layer (howe et al., 2000). this observation gives additional importance for mid-term periodicities by suggesting that they are related to the variation of the solar dynamo and the emergence of magnetic flux. valde’s galicia et al (2005) investigated the fluctuations in the total, open and closed solar magnetic flux (smf) for the period 1971–1999 and found periodicities around 1.3 and 1.7 yr in the smf with alternating importance during consecutive even and odd solar cycles. these fluctuations are directly related with variations present in cosmic rays, solar wind parameters and geomagnetic activity indexes. they asserted that it is through the magnetic flux that the solar dynamo influences several heliospheric phenomena. mursula and zieger (2000, 2001) and mursula et al. (2003) investigated the behaviour of the solar wind for several solar cycles and geomagnetic indices up to 15 solar cycles back in time. their findings report the existence of variations with periodicities of around 1.3 and 1.7 yr in the analysed parameters that alternate in consecutive solar cycles since 1930, with the former dominating in even cycles and the latter appearing during odd cycles. more recently, mursula and vilppola (2004) investigated the behaviour of periodic variations in the solar wind and the imf in the inner and outer heliosphere. they found that the 1.3 and 1.7-yr periodicities were present with different time behavior during solar cycles 21 and 22. more importantly the observed 1.3and 1.7yr periods in sq, sd and spmf are rooted in solar activity. 4.0. conclusion investigation of the spectra associated with the h component of the geomagnetic field under quiet solar condition sq, disturbed solar condition sd and superposed magnetic field spmf using the data set that consists of hourly horizontal component h of the geomagnetic field intensity obtained simultaneously for the period 1996 through 2002 from seven observatories being coordinated by the intermagnet network revealed the periods of 6 hours, 12 hours, 24 hours, 3 months, 6 months, 12 months and 16 months in the geomagnetic field components. these periods are associated with solar activities. this clearly shows the influence of an extra-terrestrial source (the sun) on terrestrial processes. sun is the undisputable driver of space weather. acknowledgements the authors wish to acknowledge the management of intermagnet network of observatories, especially the directors of the observatories at bangui, kourou, alibag, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 239 san juan, crozet, barrow, and scott base for making available the data used for this research. references arora, br., sastri, ns. and bhargava, bn. 1982. spectral characteristics of the geomagnetic field associated with equatorial electrojet and counter electrojet in the indian region. indian journal of radio and space physics, 11: 129-132. ayorinde, tt., rabiu, ab. and amory-mazaudier, c. 2016. inter-hourly variability of total electron content during the quiet condition over nigeria, within the equatorial ionization anomaly region. journal of atmospheric and solar-terrestrial physics, 145: 21–33. bolton, sj. 1990. one-year variations in the near-earth solar wind ion density and bulk flow velocity. geophysical research letter, 17: 37-40. cliver, ew., boriakoff, v. and bounar, kh. 1996. the 22-year cycle of geomagnetic and solar wind activity. journal of geophysical research ,101: 27091–27110. cliver, ew., kamide, y. and ling, ag. 2000. mountains versus valleys: semiannual variation of geomagnetic activity. journal of geophysical research, 105: 2413. clu ´ a de gonzalez, al., gonzalez, wd., dutra, slg. and tsurutani, bt. 1993. periodic variation in the geomagnetic activity: a study based on the ap index. journal of geophysical research, 98: 9215–9231. echer, e., gonzalez, wd., gonzalez, alc., prestes, a., vieira, lea., dal lago, a., guarnieri, fl. and schuch, nj. 2004. long-term correlation between solar and geomagnetic activity. journal of atmospheric and solar-terrestrial physics, 66: 1019–1025. gonzalez, wd., gonzalez, alc. and tsurutani, bt. 1990. dual peak cycle distribution of intense geomagnetic storms. planetary and space science, 38: 181–187. gorney, dj. 1990. solar cycle effects on the near-earth space environment. reviews of geophysics, 28: 315–336. howe, r., christensen-dalsgaard, j., hill, f., komm, rw., larsen, rm., schou, j., thompson, mj. and toomre, j. 2000. dynamic variations at the base of the solar convection zone. science, 287: 2456 2460. doi: 10.1126/science.287.5462.2456 mitra, sk. 1947. the upper atmosphere. the royal asiatic society of bengal, calcuta. mursula, k. and vilppola, j. 2004. fluctuations of the solar dynamo observed in the solar wind and interplanetary magnetic field at 1 au and in the outer heliosphere. solid physics, 221(2): 337-349, doi:10.1023/b:sola.0000035053.17913.26. mursula, k. and zieger, b. 2000. the 1.3-year variation in solar wind speed and geomagnetic activity. advances in space research, 25(9): 1939-1942. mursula, k. and zieger, b. 2001. long-term north-south asymmetry in solar wind speed inferred from geomagnetic activity: a new type of century-scale solar oscillation? geophysical research. letter, 28: 95-98. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu et al: occurrence of similar periods in geomagnetic field variations and solar activity. azojete, 15(sp.i2):223241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 240 mursula, k., zieger, b. and vilppola, jh. 2003. mid-term quasi-periodicities in geomagnetic activity during the last 15 solar cycles: connection to solar dynamo strength. solar physics, 212: 199-205. okeke, fn., onwumechili, ca. and rabiu, ab. 1998. day-to-day variability of geomagnetic hourly amplitudes at low latitudes. geophysical journal international, 134(2): 484-500. doi: 10.1046/ j.1365-246x.1998.00564. okoh, d., owolabi, o., ekechukwu, c., folarin, o., arhiwo, g., agbo, j., bolaji, s. and rabiu, ab. 2016. a regional gnss-vtec model over nigeria using networks: a novel approach. geodesy and geodynamics, 7: 19-31. onwumechili, ca. 1997. the equatorial electrojet. gordon and breach science publishers, netherlands, pp627. onwumechili, ca. and ezema, po. 1977. on course of the geomagnetic daily variation in low latitudes. journal of atmospheric and terrestrial physics, 39: 1079-1086. paularena, ki., szabo, a. and richardson, jd. 1995. coincident 1.3-year periodicities in the ap geomagnetic index and the solar wind. geophysical research letter, 22: 3001. prestes, a., rigozo, nr., echer, e., vieira, lea. 2006. spectral analysis of sunspot number and geomagnetic indices (1868-2001). journal of atmospheric and solar-terrestrial physics, 68: 182-190. rabiu, ab. 2001. seasonal variability of solar quiet at middle latitudes. ghana journal of science, 41: 15-22. rabiu, ab. 2004. semiannual variation of geomagnetic activity ak index and its response to solar activity. zuma journal of pure and applied sciences, 6 (1): 40-47. rabiu, ab., nagarajan, n. and saratchandra, k. 2007a. rising and decay rates of solar quiet daily variation and electrojet at equatorial region. online journal of earth sciences, 1 (2), 85-92. http://www.medwelljournals.com/fulltext/ojes/2007/85-92.pdf. rabiu, ab., mamukuyomi, ai. and joshua, eo. 2007b. variability of equatorial ionosphere inferred from geomagnetic field measurements. bulletin of the astronomical society of india, 35: 607 – 618. rastogi, rg. 2000. disturbance daily variation of electrojet current at indian longitude sector. journal of atmospheric and solar-terrestrial physics, 62: 695-700. russell, ct. and mcpherron, rl. 1973. semiannual variation of geomagnetic activity. journal of geophysical research, 78: 92–108. stamper, r., lockwood, m., wild, mn. and clark, tdg. 1999. solar causes of the longterm increase in geomagnetic activity. journal of geophysical research, 104(28): 325-342. szabo, a., lepping, rp. and king, jh. 1995. magnetic field observations of the 1.3-year solar wind oscillation. geophysical research letter, 22: 1845-1848. szabo, a., lepping, rp., king, jh., paularena, ki. and richardson, jd. 1996. twenty years of interplanetary magnetofluid variations with periods between 10 days and 3 years, in proceedings of solar wind 8, (winterhalter, d., gosling, j., habal, s., kurth, w and http://www.medwelljournals.com/fulltext/ojes/2007/85-92.pdf http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):223-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunderabiu2@gmail.com 241 neugebauer, m. eds). aip press, dana point,ca, usa, pp. 399. valde ´ s-galicia, jf., lara, a. and mendoza, b. 2005. the solar magnetic flux mid-term periodicities and the solar dynamo. journal of atmospheric and solar-terrestrial physics, 67: 1697–1701. valdes-galicia, jf., perez-enriquez, r. and otaola, ja. 1996. the cosmic-ray 1.68-year variation: a clue to understanding the nature of the solar cycle?, solid physics, 167: 409. vestine, e. 1947. the geomagnetic field, its description and analysis, carnegie institute, washington publ., p580. zieger, b. and mursula, k. 1998. annual variation in near-earth solar wind speed: evidence for persistent north-south asymmetry related to solar magnetic polarity. geophys. res. lett., 25: 841-844, 1998; correction of editorial errors in geophysical research letter, 25: 2653 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):211-221 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 211 original research article development of a motorized hydraulic press for sesame (sesamum indicum l.) oil expression t. a. ishola1*, a. n. efomah1, and a. gbabo2 (1department of agricultural and biosystems engineering, university of ilorin, ilorin, kwara state, nigeria 2department of agricultural and bioresources engineering, federal university of technology, minna, niger state, nigeria) *corresponding author’s email address: istab@unilorin.edu.ng 1.0 introduction sesame (sesamum indicum l.) otherwise known as beniseed is one of the major oil crops that contain approximately 50% oil and 25% protein (elleuch et al., 2007). it is an important crop for international trading with a production capacity of 2.6 million tonnes (mt) per year, 70% of which comes from india, china, myanmar and sudan (lee, 1995). the oil contains oleic acid (35.9 47.0%), linoleic acid (35.6 47.6%), palmitic acid (8.7 13.8%), stearic acid (2.1 6.4%), as well as arachidic acids (0.1 0.7%) (borchani et al., 2010). article information abstract sesame oil is edible and of high economic and medicinal potentials. however, its expression from the seeds is still largely done manually which is tedious and inefficient. the few imported mechanical oil presses are prone to incessant breakdown and costly. a motorized hydraulic press for sesame oil expression was designed, fabricated and tested. the major components of the machine include a hydraulic cylinder, hydraulic pump, two-way control valves, heater band with temperature controller, stopper plate, electric motor and the frame. paste of ground sesame seeds wrapped in a cheese cloth was forced against a stopper end plate on the expression barrel whose temperature is controlled in order to get the oil expressed out. the machine performance was evaluated using two levels of seed conditions (roasted (rs) and unroasted (urs)) at three levels of moisture contents (6, 9 and 12% wet basis) and four levels of temperature (70, 80, 90 and 100ºc). the performance indicators investigated included: throughput capacity, percentage oil yield, percentage expression efficiency and cake recovery efficiency. results of tests showed that the highest percentage oil yield of 33.3% was recorded when sesame seed was roasted, milled and pressed at a moisture content of 6% and expression temperature of 90ºc. also the highest expression efficiency was recorded as 69.4% when the seed was roasted, milled and pressed at a moisture content of 6% and temperature of 90ºc. the highest cake recovery was recorded as 74% when the sesame seed was milled without roasting at a moisture content of 12% and temperature of 70ºc. the oil press would assist in the growth of indigenous edible oil production industry. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 february, 2019 revised 28 august, 2019 accepted 05 september, 2019 keywords: sesame oil roasted unroasted and expression http://www.azojete.com.ng ishola et al: evelopment of a motorized hydraulic press for sesame (sesamum indicum l.) oil expression. azojete,16(1):211-221. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 212 the oil from the seed is renowned for its stability because it strongly resists oxidative rancidity even after long exposure to air (global agrisystems, 2010). the oil has some phyto-nutrients such as omega-6 fatty acids, flavonoid phenolic anti-oxidants, vitamins and dietary fiber with potent anti-cancer as well as health promoting properties (global agrisystems, 2010). after the extraction of oil, the cake is mostly used for livestock feed or manure. in nigeria, local methods are still used in extracting oil from sesame seeds. these local methods are usually slow, laborious and results in low oil yield. the local methods used include the plate press, ram press, mortar and pestle method etc. there are some imported screw presses which are usually quite expensive and prone to barrel clogging, wormshaft breakage, gear box malfunction, unavailable spare parts. with the increasing demand and economic values of sesame and its oil, these local extraction methods would not be able to meet up with the scale of production required. in order to enhance the hygienic, efficient and inexpensive extraction of sesame oil, a motorized hydraulic sesame oil press which would be adaptable to our local conditions was conceptualized. therefore, the objectives of this study were to design, construct and carry out performance evaluation of a motorized hydraulic press for sesame oil expression. this was expected to be more efficient and convenient than the local methods of extraction in terms of time consumption and the quantity and quality of oil obtained. 2. materials and methods 2.1 design considerations in carrying out the design work in the study, much effort was directed towards obtaining a system that would develop more than the minimum pressure required to extract the oil and still be dimensionally stable afterwards. that is none of the parts of the machine would fail after extracting the oil. physical and mechanical properties of the sesame seed were considered in order to arrive at a design concept for the machine. convenience of use was also considered. the machine expressed oil from paste of ground sesame seeds wrapped in a cheese cloth which compressed it against a stopper end plate of an expression barrel whose temperature was controlled in order to get the oil expressed out. the compression was achieved by movement of a press plate attached to the end of a hydraulic rod. the outward and inward movement of the hydraulic rod inside a hydraulic cylinder was actuated by hydraulic fluid from an electric motor powered hydraulic pump. various components of the oil press were designed and fabricated. all the components of the machine that were fabricated were obtained locally. the machine could be operated by one person and all the control levers are within his reach during operation. 2.2 design calculations 2.2.1 determination of the pressure acting on the expression barrel the expression barrel was considered as a thick hollow cylinder under pressure exerted by a rod moving inside a hydraulic cylinder. a preliminary test was carried out to determine the pressing force required to express oil completely from a 500g sample of ground sesame seed using the universal testing machine [utm] (model no: fs300ct). a test rig which had perforations at the base and the same bore area as the expression barrel of the machine was used. to determine the pressure required to express oil completely from the sample, the formula given by ramsdale (2006) was used: p = f a (1) where, f = force from the from utm machine = 160 kn , a = bore area of the test rig = 0.009 m2, p = pressure required to express oil completely was obtained to be 17.78 mpa. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 211-221. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 213 a press plate of diameter 100 mm travelling inside an expression barrel of internal diameter 106 mm was selected to facilitate easy movement within the expression barrel during operation. the length of the barrel was 600 mm but stroke length of the press plate inside it was 400 mm. 2.2.2 determination of the combined stresses on the expression barrel in order to obtain the combined stresses on the expression barrel, there was need to obtain the barrel thickness (t) which could withstand the internal pressure that it would be subjected to (khurmi and gupta, 2005). to calculate the thickness on the expression barrel pressure, the formula given by khurmi and gupta (2005) was used t = ri σt + p σt − p − 1 (2) where: p = operating pressure = 17.78 (earlier determined) mpa, ri = internal radius of barrel = 53 mm, σt = allowable tensile stress for mild steel barrel materials = 250 mpa, t = barrel thickness was calculated to be 8.11 mm. to calculate the hoop stress, longitudinal stress and radial stress, the formula given by ryder (1985) was used. hoop stress is given by the relation σh = pri t (3) where: p = maximum pressure applied on the barrel was 17.78 mpa, ri = internal radius of the barrel was 53 mm , t = thickness of the barrel was 8.109 mm and σh = hoop stress was calculated to be 116.209 mpa. longitudinal stress is given by the relation σl = σh 2 (4) where: σh = hoop stress = 116.209 mpa σl = longitudinal stress was calculated as 58.105 mpa. the radial stress (σr) is given by σr =− p (5) where: σr =− 17.78 mpa (as determined earlier) failure occurs in a member of materials subjected to combined stresses when one of the principal stresses reaches the failure value such as yield stress, (σ0 ) which ranges from 225 to 290 mpa for mild steel (ryder 1985). therefore, since none of the hoop stress, longitudinal stress or radial stress has a value that is up to the value of the yield stress, the expression barrel will not fail under any of these stresses. 2.2.3 determination of pump flow rate the hydraulic pump flow rate gives an index of the volumetric displacement of the hydraulic fluid per unit time. this index was needed in selecting a suitable hydraulic pump that will be capable of supplying the needed hydraulic fluid for the actuation of the hydraulic rod inside the hydraulic cylinder for the purpose of expressing the sesame oil out. the hydraulic cylinder selected for the purpose had inner bore diameter of 40 mm and the hydraulic rod stroke length was 400 mm. a period of 6 seconds was chosen for each round of oil expression based on experience from the utm machine. the pump flow rate was calculated using the formula given by nakayama and boucher (2000). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola et al: evelopment of a motorized hydraulic press for sesame (sesamum indicum l.) oil expression. azojete,16(1):211-221. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 214 q = 120 × a × s n × t (6) where: a = bore area of the hydraulic cylinder = 0.005 m2, s = stroke length of the hydraulic rod = 0.4 m, n = speed of the prime mover to run the pump = 1500 rpm and t = oil expression time 6 seconds, q = pump flow rate was calculated as 0.0000267 m3/s. 2.2.4 determination of the power required to run the hydraulic pump as earlier determined the pressure required to express the oil was found to be 17.78 mpa = 17780 kpa. also, the hydraulic pump flowrate was found to be 0.0000267 m3/s = 0.0267 l/s. hence, the power required to run the hydraulic pump was calculated by the formula given by khurmi and gupta (2005). pp = q × p 1000 (7) where: p = pressure required from the hydraulic pump was 17780 kpa. q = pump flow rate was 0.0267 l/s and pp = power required to run the hydraulic pump was calculated to be 0.475 kw. 2.3 component of the motorized hydraulic press the motorized hydraulic sesame oil press (figures 1) comprised of the following components as described below. 2.3.1 hopper the hopper (5) which was constructed using gauge “16” mild steel sheet is a truncated inverted cone in shape having an upper diameter of 300 mm, a protruded base diameter of 200 mm and a vertical height of 350 mm. these values were selected since the quantity of the ground paste of sesame was small. it is through the hopper that 500g of ground paste of sesame wrapped in cheese cloth is fed into the expression barrel. the base diameter of the hopper was selected to be wide enough to allow the passage of the 500g ground wrapped sesame paste. 2.3.2 oil expression unit this consisted of the oil expression barrel (6) that has internal diameter of 100 mm and a length of 600 mm. the thickness of the barrel was earlier determined as 8.11 mm. a 10 mm thick oil pressing plate (4) was connected to a connecting rod (3) that comes out of hydraulic cylinder (1) by actuation from a hydraulic pump. forward movement of the oil pressing plate leads to expression of oil. the expression barrel was surrounded with a 650w cylindrical heater band (7) for heating the sesame seed paste during expression. the temperature of the expression barrel was maintained at a set value by a temperature controller (12) (model no: ted-2001) which uses thermocouple and thermostat for this purpose. the expression barrel was cylindrical in shape but had 3 mm perforations on the stopper end plate (9) of the barrel for oil to flow out as such enhancing maximum oil extraction. the barrel was an 8.11 mm thick stainless steel cylinder capable of withstanding the internal pressure that is built up due to the pressing pressure. the stopper end plate at the end of the barrel was a 12mm thick plate which held the wrapped paste of sesame seed during expression. it is opened after the expression to discharge sesame seed cake left. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 211-221. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 215 2.3.3 sesame oil collector the sesame oil collector (10) was a rectangular shaped trough made from gauge “16” mild steel sheet and placed directly below the barrel in order to collect the extracted oil passing through the little perforations. it was inclined at an angle from the horizontal plane in order to enable the extracted oil flow freely into the collecting container. figure 1: exploded drawing of the hydraulic press for sesame oil file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola et al: evelopment of a motorized hydraulic press for sesame (sesamum indicum l.) oil expression. azojete,16(1):211-221. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 216 figure 2: orthographic projection of the hydraulic press for sesame oil 2.3.4 hydraulic control unit this comprised of the hydraulic tank (18), hydraulic pump (20), two-way hydraulic control valve (16) and hoses (11). the hydraulic tank was a cuboidal shaped box measuring 200 x 170 x 300mm made from thick plastic material which served as the reservoir to hold the hydraulic fluid. an upper opening was provided at the top of the tank through which the hydraulic fluid was poured into the tank. an outlet pipe of 20mm was connected at the bottom to serve as inlet to the pump. the hydraulic pump was a nachi vane pump (20 l/min at 58.61 bar). the twoway hydraulic control valve controlled flow of hydraulic fluid to the upper and lower chamber of the hydraulic cylinder. this valve was connected the hydraulic tank via the connecting pressure hoses. the hydraulic pump and control valve actuated forward movement of the connecting rod during pressing operation and backward movement after the pressing operation. a pressure relief valve was incorporated on the hydraulic circuit to forestall any accident. this whole unit was powered by a 2 hp electric motor which was connected to the hydraulic pump via a coupling. 2.4 mode of operation of the sesame oil press the fabricated hydraulic sesame oil press (figure 3) was operated as follow. after switching on the electric motor, the heater band and the temperature controller, the hydraulic pump and temperature controlling unit became operational. oven dried sesame seeds at specific moisture contents were ground using an attrition mill to form sesame paste. the sesame paste wrapped in a cheese cloth was fed into the extraction unit through the hopper. the operational heater band and the temperature controller ensured that the oil expression occurred at set http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 211-221. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 217 temperatures. the oil expression was achieved by movement of a oil pressing plate attached to the end of a connecting rod. the outward and inward movement of the connecting rod inside a hydraulic cylinder was actuated by hydraulic fluid from hydraulic pump which is powered by the electric motor. the stopper end plate at the end of the barrel held the wrapped paste of sesame seed during expression. it is opened after the expression to discharge sesame seed cake left. the expressed oil flew through the perforations at the end of the barrel and was collected via the oil collector. after oil expression and the discharge of the cake the oil press was ready for another cycle of expression. 500g of sesame seed paste wrapped in cheese cloth was pressed for 6 seconds in order to express the oil out. figure 3 : hydraulic sesame seed oil press 2.5 performance evaluation of hydraulic sesame oil press 2.5.1 test procedure a batch of 10 kg of sesame seed (ncri-98-60) was obtained from the national cereals research institute badeggi, bida, niger state. the sesame seeds were cleaned of impurities and oven dried at 105 ºc for 4 hours to achieve 6 % moisture content dry basis (mcdb). instant moisture meter (model-pm650) was used to ascertain the moisture content. the dried sesame seeds was divided into three. the first part was left at 6 % (mcdb). the second part was conditioned to be at 9 % (mcdb) by adding water. likewise, the third part was conditioned to be at 12 % (mcdb) by adding water. the quantity of water required to achieve the higher moisture contents was determined using the equation given by sacilik et al. (2003). q = wi mf −mi 100 − mf 8 where: q = quantity of water added (kg), wi = initial mass of sample (kg), mf = desired final moisture content (% db) and mi = initial moisture content (% db). each part was divided into two samples (sample a and sample b). all the sample a from each moisture content were roasted at 120 ºc for 15 minutes while all the sample b were left as unroasted sample. the samples were properly labelled and kept in desiccators according to their respective moisture conditions in order to maintain the needed moisture contents. hence, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola et al: evelopment of a motorized hydraulic press for sesame (sesamum indicum l.) oil expression. azojete,16(1):211-221. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 218 two seed conditions (roasted and unroasted) were maintained and placed in desiccators prior to pressing oil from the sesame seeds. the samples were ground and kneaded to form pastes following the method of makeri et al (2011). this was to enhance maximum oil extraction in the press during the expressing operation. the heater band was wrapped around the pressing barrel and connected to electronic temperature controller to ensure that the expressing occurred at temperatures of 70, 80, 90 and 100 ºc as given by (fao, 1986). the thermocouple probe of the temperature controller was attached to the pressing barrel which enables it to turn off the heater band when the set temperature is attained and off when the temperature falls below the set value. the oil was obtained by wrapping 500g of sesame seed paste in muslin (cloth) and placed in the hopper for onward passage into the barrel. by actuating the lever arm of the control valve, the connecting rod moved forward and with the expression temperature set as required, the oil pressing plate pressed the paste against the stopper end plate. this led to expression of oil from the perforations on the stopper end plate. the oil was collected via the oil collection trough. this expression continues until oil stop coming out of the perforations. the pressing time for each operation was also noted and recorded. the average time of each expression operation was observed to be 6 seconds. the performance evaluation of the sesame seed oil press was carried out by using 2x3x4 factorial experiment in a completely randomized design. the three factors that were considered in the factorial design were two levels each of seed conditions (s) (roasted and unroasted), three levels of moisture contents (m) (6, 9 and 12% wet basis) and four levels of temperature (t) (70, 80, 90 and 100 ºc). each treatment factor was done in three replicates. the data obtained for the performance indices from the performance evaluation of the sesame seed oil press was subjected to statistically analysis using analysis of variance (anova) to ascertain the significance of the each treatment factor considered. also, duncan’s multiple range test was used to check if the differences in mean values of the performance indices were significant. 2.5.2 performance indices the following parameters were used in carrying out the performance evaluation of the machine: 2.5.2.1 throughput capacity of machine �� : this is the ratio of the mass of pressed sesame paste to the total time taken to obtain the oil expressed in kg/h and is given as: cm = wg t (5) where: cm = throughput capacity of machine with respect to time (kg/h), wg= mass of sesame paste fed into the hopper (kg) and t = total time taken to press the sesame paste to obtain oil (h) 2.5.2.2 percentage oil yield: this is the ratio of the mass of sesame oil extracted to the mass of sesame paste fed into the hopper expressed in percentage and is given as: oy = wo wg × 100 (6) where: oy = percentage oil yield (%), w0 = mass of oil extracted (kg) and wg = mass of sesame paste fed into the hopper (kg) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 211-221. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 219 2.5.2.3 percentage extraction efficiency: this is the ratio of the mass of sesame oil extracted to the total oil content of the seeds expressed in percentage and is given as: ee = wo wc × 100 (7) where: ee = percentage extraction efficiency (%), wo = mass of oil extracted (kg) and wc = total oil content of the seed (kg) 2.5.2.4 cake recovery efficiency: this is the ratio of the mass of sesame cake obtained to the mass of sesame paste fed into the hopper expressed in percentage and is given as: cr = wd wg × 100 (8) where: cr = cake recovery efficiency (%), wd = mass of sesame cake obtained (kg) and wg = mass of sesame paste fed into the hopper (kg) quality of oil obtained the oil expressed from the roasted seeds was pale brown in colour while that obtained from the unroasted seeds was pale yellow in colour. there was no seeds particles in the oil. each experiment was replicated three times. 3 results and discussion 3.1 results the results generated from the calculated values of the average oil yield, extraction efficiency and cake recovery efficiency at the four levels of temperature, three levels of moisture content and two levels of seed conditions are summarized in table 1. 3.2 discussions from table 1, it could be seen that the highest oil yield was recorded when the seeds were roasted and milled prior to pressing giving an oil yield of 33.3 % at a moisture content of 6 % and extraction temperature of 90 ºc while for the milled sample that was pressed without roasting recorded the highest oil yield of 31.0 % at a moisture content of 6 % and extraction temperature of 90 ºc. similar result was reported by fasina and ajibola (1989) who noted that in conophur nut, there was increase in oil yield when the seeds were pre-heated prior to extraction. hamzat and clarke (1993) and okegbile et al. (2014) heated samples of groundnut at temperature of 65 °c for 45 minutes and temperature of 60 °c for 30 minutes respectively. it was observed that there was an increase in the oil yield of groundnut oil after extraction. roasting of oilseeds helps to boost oil yield because the oil cells are broken down, protein is coagulated in the seeds for easy separation of the proteinaceous fraction and oil viscosity is reduced which leads to easier flow of the oil (fasina and ajibola, 1989). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola et al: evelopment of a motorized hydraulic press for sesame (sesamum indicum l.) oil expression. azojete,16(1):211-221. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 220 table 1 : average performance indices of the sesame oil press the format of values in the table is mean value ± standard deviation it could also be seen from table 1, that the highest extraction efficiency of the machine was recorded when the sample was roasted and milled giving a value of 69.4 % at 90 ºc heating temperature and 6 % moisture level while the highest extraction efficiency recorded when the sample was milled and pressed without roasting was 64.6 % at 90 ºc heating temperature and 6 % moisture level. hamzat and clarke (1993) reported an increase in oil yield emanating from seed conditioning (roasting) also reported that when seeds are preheated, the extraction efficiency also increases. likwise, seed condition has a tremendous effect on the cake recovery efficiency as shown in table 1. the table shows that the highest cake recovery was recorded when the sesame seed was milled without roasting prior to pressing, giving a cake recovery efficiency of 74 % at a moisture content of 12 % and extraction temperature of 70 ºc while for the roasted, milled and pressed sample, the highest cake recovery efficiency was 72 % at a moisture content of 12 % and extraction temperature of 70 ºc. pressing sesame seed without first roasting will result to more cake and lesser oil. this is because roasting of oilseeds increases oil yield as the oil cells are broken down, protein is coagulated in the seeds for easy separation of the proteinaceous fraction and oil viscosity is reduced which leads to easier flow of the oil (fasina and ajibola, 1989). 4. conclusion a motorized hydraulic sesame oil press was designed, constructed and tested. based on the performance evaluation carried out on the oil press, the hydraulic press had a throughput capacity of 35 kg/h. the maximum oil yield and extraction efficiency of 33.3 % and 69.4 % respectively was achieved when the sesame seeds were roasted, ground and pressed at a heating temperature of 90 ºc and moisture content of 6 %. the maximum cake recovery of 74 % was achieved when the sesame seeds were not roasted and pressed at a heating temperature of 70 ºc and moisture content of 12 %. the developed sesame oil press would be found very moisture content (%) heating temperature (ºc) rs oil yield (%) urs oil yield (%) rs extraction efficiency (%) urs extraction efficiency (%) rs cake recovery (%) urs cake recovery (%) 6 9 12 70 80 90 100 70 80 90 100 70 80 90 100 30.0±0.0 32.3±1.5 33.3±0.6 32.7±0.6 29.0± 1.0 32.0±1.0 33.0±0.0 32.0±1.0 28.0± 1.0 30.0± 1.0 31.0±1.0 29.0± 1.0 28.3± 0.6 30.3±0.6 31.0±1.0 30.3±0.6 26.3±0.6 30.0±1.0 30.3±0.6 29.7±0.6 26.0±1.0 28.6±1.2 30.0±1.0 29.0±1.0 62.5±0.0 67.3±3.2 69.4±1.1 68.1±1.2 60.4±2.1 66.7±2.1 68.8±0.0 66.7±2.1 58.3±2.1 62.5±2.1 64.6±2.1 60.4±2.1 59.0±1.1 63.1±0.3 64.6±1.2 63.1±1.1 54.8±0.3 62.5±1.2 63.1±1.1 61.9±0.3 54.2±2.1 59.6±2.4 62.5±2.1 60.4±2.1 70.0±0.0 67.7±1.5 66.7±0.6 67.3±0.6 71.0±1.0 68.0±1.0 67.0±0.0 68.0±1.0 72.0±1.0 70.0±1.0 69.0±1.0 71.0±1.0 71.7±0.6 69.7±0.6 69.0±1.0 69.7±0.6 73.7±0.6 70.0±1.0 69.7±0.6 70.3±0.6 74.0±1.0 71.4±1.2 70.0±1.0 71.0±1.0 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 211-221. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: istab@unilorin.edu.ng 221 useful in the edible oil production industry. thus, increasing indigenous oil production and reducing edible oil importation. references borchani, c., besbes, s., blecker, ch. and attia, h. 2010. chemical characteristics and oxidative stability of sesame seed, sesame paste, and olive oils. journal of agriculture, science and technology, 12: 585-596. elleuch, m., besbes, s., roiseux, o., blecker, c. and attia, h. 2007. quality characteristics of sesame seeds and by-products. food chemistry, 103 (2): 641 – 650. food and agricultural organisation (fao). 1986. monthly bulletin statistics vol. 9 july /august, rome. fasina, oo. and ajibola, oo. 1989. mechanical expression of oil from conophor nuts (tetracarpidium conophonum). journal of agricultural engineering research, 44: 275 -287. global agrisystems. 2010. dehulled and roasted sesame seed oil processing unit. retrieved july 20, 2016 from http://www.mpstateagro.nic.in/ hamzat, ko. and clarke, b. 1993. prediction of oil yield from groundnuts using the concept of quasiequilibrium oil yield. journal of agriculture engineering research, 55(1): 79-87. khurmi, rs. and gupta, jk. 2005. machine design, 14th edition. s. chand and company ltd., ram nagar, new delhi110055. lee, j. 1995. varietal differences in sesame breeding, journal of agricultural science, 37(2): 169185. makeri, mu., bala, sm. and kassum, as. 2011. the effects of roasting temperatures on the rate of extraction and quality of locally-processed oil from two nigerian peanut (arachis hypogea l.) cultivars. african journal of food science, 5 (4): 194 – 199. nakayama, y. and boucher, rf. 2000. introduction to fluid mechanics. butterworth-heinemann publication. linacre house, jordan hill, oxford ox2 8dp. okegbile, oj., mohammed, a., hassan, ab. and obajulu, o. 2014. fabrication and testing of a combined roaster and oil expeller machine. american journal of engineering research, 3(4):230 – 235. ramsdale, r. 2006. reference tables: fluid power formulars . retrieved january 26, 2016 from http://www.engineershandbook.com/tables/fluidpowerformulas.html. ryder, gh. 1985. strength of materials. 3rd edition. macmillan publishers ltd, london http://www.mpstateagro.nic.in/ http://www.engineershandbook.com/tables/fluidpowerformulas.html file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):243-254 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 243 original research article computational model of artificial neural networks and its applications in data mining j. abah1*, e. s. alu2, a. e. chahari3 (1department of computer engineering, university of maiduguri, maiduguri, nigeria 2department of agricultural economics and extension, nasarawa state university, keffi, shabu-lafia campus, lafia, nigeria 3department of general studies education, school of general education, federal college of education, yola, nigeria) *corresponding author’s email address: abah@unimaid.edu.ng 1.0 introduction as long as knowledge is another name of power, many organizations give much importance to knowledge. when reaching this knowledge, they make use of the data in their databases. data is important since it enable them to learn from the past and to predict future trends and behaviours (larose, 2005). today, most of the organizations use the data collected in their databases when taking strategic decisions (singh and chauhan 2009). the process of using the data to reach this knowledge consists of two steps as to collecting the data and analysing the data. in the beginning, organizations are faced with difficulties when collecting the data so they have not enough data in order to make suitable analysis (kartalopoulos and stamatios, 1996). in the long run, with the rapid computerization, organizations are able to store huge amount of data easily. but at this time, they are faced with another problem when analysing and article information abstract data remain a very important ingredient required by any organization to make informed decision as it affects operations. companies have been collecting data from various sources over the decades bringing about a very large volume of data warehouse. unfortunately, most organizations build databases which are redundant and never used for any meaningful thing. while few companies use the data collected in their databases when taking strategic decisions others barely do same. however, for an organization to immensely derive benefits from the massive data warehouse, there is the need for an effective and efficient means of analysing the data with a view to extracting meaningful knowledge that is sufficient to achieve organizational goal. to achieve this, artificial neural network (ann) technique through the concept known as data mining is presented. the paper reviewed artificial neural network technique for data mining, examines the computational model behind this technique and analysed its use and application as a predicting or forecasting tool. results shows that ann’ has capability in data management, analysis and able to provide desirable knowledge for management decision making processes. it is therefore recommended that data mining tools like ann and others be applied to organization’s databases which hitherto have not been minned in order to provide management with intelligence for decision making. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 july, 2017 revised 15 october, 2019 accepted 04 april, 2020 keywords: artificial neural network databases data mining information organizations mailto:abah@unimaid.edu.ng1 http://www.azojete.com.ng abah et al: computational model of artificial neural networks and its applications in data mining. azojete,16(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 244 interpreting such large datasets. traditional methods like statistical techniques or data management tools are not sufficient anymore (berry and linoff, 2000). in order to manage this problem, the technique called data mining (dm) has been discovered to address this problem. according to singh and chauhan (2009) show that data mining is a useful and powerful technology that supports organizations to derive strategic information in their databases. it has been defined as: “the process of exploration and analysis by automatic or semi-automatic means of large quantities of data in order to discover meaningful patterns and rules” (berry and linoff, 1997; berry and linoff, 2000). the expression “meaningful patterns and rules” implies the followings; easily understood by humans, valid on new data, potentially useful and novel. validating a hypothesis that the user wants to prove can also be accepted as a meaningful patterns and rules (berry and linoff, 2000). in sum, it is essential to derive patterns and rules that help us to reach strategic and unimagined information in data mining. few organizations use the data collected in their databases when taking strategic decisions. this has made most organization’s databases redundant. the process of using accumulated data to reach knowledge consists of two steps; collecting the data and analyzing the data. the problem associated with the process of achieving these steps are first, most organizations are faced with difficulties when collecting the data so, they have not enough data in order to make suitable analysis and second, the technique of analysing the collected data in order to derive meaning or knowledge from it is often not sufficient and efficient to achieve the goal (cilimkoviv, 2015). in order to solve the stated problems, we explore ann as a data mining technique to bring to bear, it’s capability in data management and analysis and its ability to provide desirable knowledge for informed management decision making processes. hence, we present ann as a useful and powerful data mining technique that can support organizations to derive strategic information from their databases. the rest of this paper is organized as follows: section two provides details about ann; concept, models and topologies. section three provides experimental procedure of ann technique, section four gives the discussion of results and finally, section five gives the summary, conclusion and recommendation. 2. artificial neural networks an artificial neural network (ann), just called a "neural network" (nn), is a mathematical model or computational model based on biological neural networks (berry and linoff, 1997). in other words, ann is an emulation of biological neural system. it consists of an interconnected group of artificial neurons and processes information using a connectionist approach to computation. in most cases an ann is an adaptive system that changes its structure based on external or internal information that flows through the network during the learning phase (singh and chauhan, 2009; zurada, 1992). 2.1 concept of neural network neural networks are very sophisticated modeling techniques capable of modelling extremely complex functions. neural networks learn by example. the neural network user gathers representative data, and then invokes training algorithms to automatically learn the structure of the data. it is a model for classification and prediction (continuous value) of an outcome variable (beale and jackson, 1990). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 245 2.2 the basic artificial model the artificial neuron was developed in an effort to model the human neuron (kartalopoulos and stamatios, 1996; haykin and simon, 1994). inputs enter the neuron and are multiplied by their respective synaptic weights. they are then summed and processed by an activation function. examples of activations functions includes the logistic or sigmoid function (1). f(x) = 1/ (1+exp (-x)) (1) while the second is the gaussian function (2) f(x) = exp (-x2). (2) where the variable x represents the input vector in both equations. figure 1: artificial neural network model 2.3 neural network topologies feed forward neural network: the feedforward neural network was the first and arguably simplest type of artificial neural network devised (singh and chauhan, 2009). in this network, the information moves in only one direction, forward, from the input nodes, through the hidden nodes (if any) and to the output nodes. there are no cycles or loops in the network. the data processing can extend over multiple (layers of) units, but no feedback connections are present, that is, connections extending from outputs of units to inputs of units in the same layer or previous layers (zurada, 1992). recurrent network: recurrent neural networks that do contain feedback connections. contrary to feedforward networks, recurrent neural networks (rns) are models with bi-directional data flow. while a feedforward network propagates data linearly from input to output, rns also propagate data from later processing stages to earlier stages (singh and chauhan, 2009). 2.4 data mining data mining is a set of techniques and procedures that can be developed from various data sources such as data warehouses or relational databases (villanueva et al., 2018). flat files without formats are made from this predictive analysis using statistical study techniques to predict or anticipate statistical measures of certainty based on existing facts. data mining is seen as the evolution of information technology (jiawei and kamber, 2001), this is largely supported by the growth of the internet. data mining is a multidisciplinary field that allows relevant information to be obtained from large amounts of data at the confluence among other disciplines namely: artificial intelligence, statistics, databases and information science. figure 2 shows data mining taxonomy. f weighted suminput vector x output y activationfunction bias weight vector w  w0j w1j wnj x0 x1 xn file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abah et al: computational model of artificial neural networks and its applications in data mining. azojete,16(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 246 figure 2: data mining taxonomy (maimon and rokach, 2010) 2.4.1 phases of data mining task the data mining tasks are implemented with the goal of discovering patterns of relevant and interesting information in large volumes. this is done with the development of four phases according to villanueva et al. (2018), which are usually: filtering data; selection of variables; extracting knowledge and interpretation and evaluation. in general, all techniques have been proved in educational settings according to siemens and baker (2012), and different case studies have been developed to evaluate the performance of different techniques and to meet the main goals of data mining. 2.4.2 neural networks in data mining in more practical terms neural networks are non-linear statistical data modelling tools. they can be used to model complex relationships between inputs and outputs or to find patterns in data (singh and chauhan, 2009). using neural networks as a tool, data warehousing firms are harvesting information from datasets in the process known as data mining. the difference between these data warehouses and ordinary databases is that there is actual manipulation and cross-fertilization of the data helping users make more informed decisions. neural networks essentially comprise three pieces (zurada, 1992): the architecture or model; the learning algorithm; and the activation functions. neural networks are programmed or “trained” to store, recognize, and associatively retrieve patterns or database entries; to solve combinatorial optimization problems; to filter noise from measurement data; to control ill-defined problems; in summary, to estimate sampled functions when we do not know the form of the functions.” it is precisely these two abilities (pattern recognition and function estimation) which make artificial neural networks (ann) so prevalent a utility in data mining. according to villanueva, moreno and salinas (2018), the first known work on educational data mining titled "explaining student grades predicted by a neural network" (gedeon and turner, 1993). in this work, the researchers used neural networks were used to predict the final grades of students. later, in 1994, fausett and elwasif published "predicting performance from test http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 247 scores using back propagation and counter propagation" in which neural networks are used to predict the student’s performance (fausett and elwasif, 1994). "predicting and analyzing secondary education placement-test scores: a data mining approach" by şen, ucar and delen (2012) relied on neural networks and decision trees to predict outcomes of high school students in turkey. bayesian networks were used to work educational situations, the first of them is "predicting student's academic performance artificial using neural network: a case study of an engineering course" (oladokun et al., 2008) where the researchers explain how to predict the performance a candidate might have if it is accepted in some university courses. additionally, sundar (2013) in his work "a comparative study for predicting students academic performance using bayesian network classifiers" made a comparison of obtained results using bayesian networks in predicting student performance; likewise, bhise et al.,(2013) published "importance of data mining in higher education system" their work is based on clustering to help instructors improving student performance. today, educational and business information systems store large volume of data and its origin can come from different sources, different formats and different granularity levels (villanueva et al., 2018). the problems of business and educational data mining must be analyzed particularly due to their specific objective determines a singularity when it is solved by data mining techniques. for instance, in the domain of education, data mining for education is so important that in 2007 an international organization dedicated to researching this discipline was founded. such is the importance has prompted this research area that it is estimated that by the year 2022 all research related to education will involve analysis and data mining (baker and yacef, 2009). 2.5 feedforward neural network one of the simplest feedforward neural networks (ffnn), such as in figure 3, consists of three layers: an input layer, hidden layer and output layer. in each layer there are one or more processing elements (pes) (singh and chauhan, 2009). pes is meant to simulate the neurons in the brain and this is why they are often referred to as neurons or nodes. x1 xn figure 3: feedforward neural network a pe receives inputs from either the outside world. the simplified process for training a ffnn is as follows: 1. input data is presented to the network and propagated through the network until it reaches the output layer. this forward process produces a predicted output. pe pe pe file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abah et al: computational model of artificial neural networks and its applications in data mining. azojete,16(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 248 2. the predicted output is subtracted from the actual output and an error value for the networks is calculated. 3. the neural network then uses supervised learning, which in most cases is back propagation, to train the network. back propagation is a learning algorithm for adjusting the weights. it starts with the weights between the output layer pe’s and the last hidden layer pe’s and works backwards through the network. 4. once back propagation has finished, the forward process starts again, and this cycle is continued until the error between predicted and actual outputs is minimized. 2.6 artificial neuron using back propagation learning the mathematical formulae used for neural network in back propagation learning algorithm according to dhar et al. (1996) presented in figure 4, was used. figure 4: artificial neuron using back propagation learning figure 4 depicts a single artificial neuron and the actual computation that occurs in neural network in a single epoch through the data. 2.7 fitting a network to data the equations in figure 4 provides a good understanding on how neural network process data. however, for the purpose of clarity and understanding, we illustrate the actual computation that occurs in neural network in a single epoch through the data. typically, neural network performs exceptionally well with large dataset but for the purpose of this illustration a small dataset is used as shown in table 1. refer to figure 5 for the simulated neural network for the dataset provided in table 1. table 1: sample dataset observation milk score sugar score price 1 0.2 0.9 0.65 2 0.1 0.1 0.34 3 0.2 0.4 0.42 4 0.2 0.5 0.49 5 0.4 0.5 0.72 6 0.3 0.8 0.83 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 249 figure 5: simulated neural network considering the first observation: for the input at the input layer; milk = 0.2 and sugar = 0.9, the output of this layer is x1 = 0.2 and x2 = 0.9. hidden layer nodes take as input the output values from the input layer. the hidden layer in this example consists of 3 nodes. each of the nodes receives input from all the input nodes (figure 4). to compute the output of a hidden layer node, the weighted sum of the inputs is computed and then applies a certain function to it. 3. experimental procedure the procedure describes the steps involved in the computational process. first we describe the artificial neural network as follows; 3.1 the artificial neural network model let x1, x2,…, xp be the set of input values to a node, the weighted sum is computed thus; from the general algorithm λj + i=1 p wij xi� we have;    n i iijjin xwby 1 (3) where: b, wi,j,…,wnj are weights that are initially set randomly then adjusted as the network “learns”. the variable b, also known as the “bias” of node j, is a constant that controls the level of contribution of node j. the next step is to apply a function called transfer function (that is, linear function, exponential function and a logistics/sigmoidal function). in this paper, the sigmoid function in (1) is used for its practical value from the fact that it has a squashing effect on very small or very large value. output layerhidden layersinput layers milk sugar w15 w23 w24 w25 w14 w13 w36 w46 w56 b3 b4 b5 1 2 3 4 5 6 b6 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abah et al: computational model of artificial neural networks and its applications in data mining. azojete,16(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 250 node6 = node6 = using the logistic function then, the output of node j in the hidden layer is computed from the general formula:       n i xwbiijjj n i iijje xwbgoutput 1 11 1)( (4) as follows: g λj + i=1 p wij xi� = 1 1+ e− λj+ i=1 p wij xi� (5) where: wij is the weighted vector between i and j processing elements; xi is the input vector in i processing element; p is the processing element bj and λj are the bias in (4) and (5) respectively. 3.2 initializing the weights at this stage of the procedure, the values of bj and wij are typically initialize to small (but generally random) number in the range 0.00 ± 0.05. with this value range, we can then compute the outputs of node3, node4 and node5. suppose the following are the initial weights for; node 3 are bnw3=b3=-0.3, w13=0.05 and w23=0.01 node 4 are bnw4=b4= 0.2, w14=-0.01 and w24=0.03 node 5 are bnw5=b5=0.05, w15=0.02 and w25=-0.01 node 6 are bnw6=b6=-0.015, w36=0.01, w46=0.05 and w56=0.015 where: the input x1 and x2 are 0.2 and 0.9 respectively as seen in observation 1 in table 1. using the following values in (2), the output of node3, node4, node5 are computed as follows; the output from node3, node4 and node5 are fed into the output layer (node6) to compute the final output for the first observation in our sample data. 3.3 training the model after initializing the weights, the next step is to train the model. training the model means estimating the weights bj (bias node) and wij (link between nodes) that lead to the best predictive results. the process illustrated above for computing the neural network output for an node3 = = 0.4302 node4 = = 0.5560 = 0.5112 node5 = = 0.5062 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 251 observation is repeated for all the observations in the training set. for each observation, the model produces a prediction which is then compared with the actual response value. their difference is the error for the output node. this error obtained from the output node is use iteratively to update the estimated weights. in particular, the error for the output node is distributed across all the hidden nodes that led to it, so that each node is assigned “responsibility" for part of the error. each of these node-specific errors is then used for updating the weights. 3.4 back propagation of error back propagation is a process for using model errors to update weights (“learning”). as the name implies, errors are computed from the output layer back to the hidden layers. the error associated with output node is computed by the general formula; errj = nj (1-nj) (dj-nj) (6) the above equation is similar to the ordinary definition of an error (dj – nj) multiply by a correction factor. the weights are then updated as follows: ibjnew = bjold + lerrj (7) wijnew = wijold + lerrj (8) where: l is a learning rate or weight decay parameter, a constant ranging typically between 0 and 1, which controls the amount of change in weights from one iteration to the other. after the first iteration, the error associated with the output node is; err = 0.5062(1-0.5062) (0.65-0.5062) = 0.03594. hence the weight update for second iteration is computed as follows using l = 0.5 b3: -0.3 + 0.5 (0.03594) = -0.282 b4: 0.2 + 0.5 (0.03594) = 0.218 b5: 0.05 + 0.5 (0.03594) = 0.068 b6: -0.015 + 0.5 (0.03594) = 0.003 w13: 0.08 + 0.5 (0.03594) = 0.068 w23: 0.01 + 0.5 (0.03594) = 0.028 w14: -0.01 + 0.5 (0.03594) = 0.008 w24: 0.03 + 0.5 (0.03594) = 0.048 w15: 0.02 + 0.5 (0.03594) = 0.038 w25: -0.01 + 0.5 (0.03594) = 0.008 w36: 0.01 + 0.5 (0.03594) = 0.028 w46: 0.05 + 0.5 (0.03594) = 0.068 w56: 0.015 + 0.5 (0.03594) = 0.033 the adjusted weights are used on the second observation (i.e. x1=0.1 and x2=0.1) to computer the second output of the model. this process is repeated for the entire training data (in this case 6). hence one sweep through the data, is called an epoch, consisting of six (6) iterations. for the purpose of this simulation, the network is trained using 5 epochs so, there will be a total of 30 iterations. 4. results and discussion file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abah et al: computational model of artificial neural networks and its applications in data mining. azojete,16(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 252 table 2 reveal the computation result of the adjusted weights, hidden layers output and the final output for each epoch and the total sum of error associated with each epoch. table 2: output errors generated for each of the five (5) epochs from table 2, we observed that the total sum of error decreases after every epoch but after a while it begins to increase (for a large dataset). the point of minimum validation error is a good indicator of the best number of epoch for training and the weights at that stage are most likely to provide the best error rate in new data. however, it should be noted that the number of observations in this simulation is too small for estimating the 13 weights, hence the reason for the large error margin between the actual price and the predicted price (table 3). the negative margin signifies that the predicted value is more than the actual price. as the simulation runs from the sart epoch (epoch 1) to the final epoch (epoch 5), the predicted value seems to decrease hence, an increase in the margin. this is as a result of the learning process taking place from one epoch to the next. table 3 gives the predicted values on the sample dataset. the predicted values were obtained from the output values (output 6) of the last epoch (epoch 5). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 253 table 3: predicted values on a sample dataset 5. conclusion in this paper, we try to bring to the fore an overview of artificial neural networks (ann) as a prediction tool. it is an attempt to build machine that will mimic brain activities and be able to learn. ann usually learns by examples. basic ann is composed of three layers, input, output and hidden layer. each layer can have number of nodes and nodes from input layer are connected to the nodes from hidden layer. nodes from hidden layer are connected to the nodes from output layer. those connections represent weights between nodes. it further describes one of the most popular ann algorithms; the back propagation (bp) algorithm. the idea behind bp algorithm is quite simple; output of ann is evaluated against desired output. if results are not satisfactory, connection (weights) between layers are modified and the process is repeated again and again until error is small enough. simple bp example is demonstrated in this paper with ann architecture also covered. in conclusion, ann is able to perform classification and even discover new trends or patterns in data when supplied with enough samples. the dataset must be considerably large for ann to perform well. from the sample simulation, we were able to discover patterns or trend in the price of the given commodities (milk and sugar in this case). as the simulation iterates from one epoch to the next, the predicted value decreases to a given value before it increases again. the minimum value attained before it starts to inrease again point to the best prediction. similarly, the observed decrease in the margin between stated price and predicted value shows a pattern within the data which is not visible in the given dataset. this is an indication that in most cases neural networks perform better than the traditional statistical techniques. thus, neural networks are becoming very popular with data mining practitioners, particularly in medical research, finance and marketing. this is because they have proven their predictive power through comparison with other statistical techniques using real data sets (singh and chauhan, 2009). it is recommended therefore that organizations who want to make meaning from their huge data repository should apply ann models. this is not to say that ann are perfect but due to design problems neural systems need further research before they are widely accepted in industry. as software companies develop more sophisticated models with user-friendly interfaces, the attraction to artificial neural networks will continue to grow. references baker, rsj. and yacef, k. 2009. the state of educational data mining in 2009: a review and future visions. journal of educational data mining, 1(1): 3–17. s/no. x1 x2 price predicted values margin (price predicted value) 1 0.2 0.9 0.65 0.58 0.07 2 0.1 0.1 0.34 0.58 -0.24 3 0.2 0.4 0.42 0.57 -0.15 4 0.2 0.5 0.49 0.55 -0.06 5 0.4 0.5 0.72 0.55 0.17 6 0.3 0.8 0.83 0.56 0.27 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abah et al: computational model of artificial neural networks and its applications in data mining. azojete,16(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abah@unimaid.edu.ng 254 beale, r. and jackson, t. 1990. neural computing: an introduction. adam hilger, bristol, england., pp.1-14. berry, mja. and linoff, gs. 1997. data mining techniques. new york: wiley and sons., pp. 1-444. berry, mja. and linoff, gs. 2000. mastering data mining: the art and science of customer relationship management. new york: wiley., pp. 1-512. bhise, rb., thorat, ss. and supekar, ak. 2013. importance of data mining in higher education system. iosr journal of humanities and social science, 6(6): 18–21. dhar, v. and stein r., 1996. intelligent decision support methods: the science of knowledge work, prentice hall business publishing. upper saddle river, new jersey., pp. 11-94. fausett, l. and elwasif, w. 1994. predicting performance from test scores using back propagation and counter propagation. proceeding of 1994 ieee international conference on neural networks (icnn’94), 5: 3398–3402. gedeon, td. and turner, hs. 1993. explaining student grades predicted by a neural network. in proceeding of 1993 ieee international conference on neural networks (ijcnn-93-nagoya, japan), 1: 609–612. jiawei, h. and kamber, m. 2001. data mining: concepts and techniques. san francisco, ca, ltd: morgan kaufmann, pp. 377–385. larose, dt. 2005. discovering knowledge in data: an introduction to data mining. wileyinterscience., pp. 40-241. maimon, o. and rokach, l. 2010. data mining and knowledge discovery handbook 2nd ed. springer new york dordrecht heidelberg london, 1-37. cilimkoviv, m., 2015. neural network and back propagation algorithm, institute of technology blanchardstown, blanchardstown road north, dublin, ireland. 1-13. oladokun, vo., adebanjo, at. and charles, b. 2008. predicting student’s academic performance using artificial neural network: a case study of an engineering course. the pacific journal of science and technology, 9(1): 72–79. şen, b., uçar, e. and delen, d. 2012. predicting and analyzing secondary education placementtest scores: a data mining approach. expert systems with applications, 39: 9468–9476. siemens, g. and baker, rsjd. 2012. learning analytics and educational data mining: towards communication and collaboration. lak’12: proceedings of the acm 2nd international conference on learning analytics and knowledge, vancouver, bc, canada. 252-254. sundar, pp. 2013. a comparative study for predicting students academic performance using bayesian network classifiers. iosr journal of engineering, 3(2): 37–42. villanueva, a., moreno, lg. and salinas, mj. 2018. data mining techniques applied in educational environments: literature review. digital education review, 33: 235-255. singh, y. and chauhan, a.s., 2009. neural network in data mining. journal of theoretical and applied information technology, 5(6): 36-42. zurada, jm. 1992. introduction to artificial neural systems. west publishing co., st. paul, new york, united states. pp. 1-764 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):142-152 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 142 original research article characterization of blends of petrol and bioethanol synthesized from nigerian palm bunch j. o. igbokwe1, l. n. onuoha1*, m. o. i. nwafor1 and n. a. aviara2 (1department of mechanical engineering, federal university of technology owerri, imo state, nigeria 2department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, borno state, nigeria *corresponding author: freshlove2006@gmail.com article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: fuel properties bioethanol waste palm bunch (wpb) biofuel. abstract this study investigated fuel properties of pure petrol blended with bioethanol produced from nigerian waste palm bunch. the produced bioethanol was blended with pure petrol at volume percentage ratio of 0:100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40 and 100:0 to obtain e0, e10, e20, e30, e40, e50, e60 and e100 blend respectively. these were then characterized for fuel properties base on astm standard. the result confirmed that fuel properties of bioethanol produced from nigerian waste palm bunch met the international standard as established by astm for use in si engine. the blends improved the fuel properties of pure petrol. density of the blends increased as the percentage of bioethanol increases in the blends. octane number of pure petrol increased with increase in bioethanol in the blends. flash point of all the blends was below 15 oc making them susceptible to ignition and having the chance of flammability hazard. 10 % bioethanol increased the blend’s vapor pressure to a peak value of 53 kpa which declined with further increase of bioethanol percentage. the bioethanol increased viscosity of pure petrol. calorific value of pure petrol was decreased with increase in the bioethanol content. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction bioethanol is a biofuel made from biomass and primarily used in blends with petrol, for automotive, thermal and power generation, according to quality specifications set by the american society for testing and materials (astm), the environmental protection agency (epa), state regulatory agencies and their own producing company standards. engines run on fossil fuels are major contributors of various types of air polluting exhaust gasses such as particulate matter, carbon monoxide, oxides of nitrogen, sulfur, and other harmful compounds ashish and mohapatra, 2013). considering all these shortcomings of fossil fuels, there is need for an alternative fuels from biomass (cheng et al., 2007). biothanol has been widely encouraged as a substitute / improver for petrol to achieve emission reduction target of the kyoto protocol (1997). pure petrol blended with bioethanol is particularly promising since it is more readily incorporated into the existing fuel combustion system and burns cleaner (tan et al., 2014). however, producing biofuels from biomass crops has its own negative consequences such as food price hike; soil degradation and diversion of food land (ruth, 2008; koonin, 2006; anjan, 2013). according to regmi and mark, (2001), a 1 % increase in food prices causes an average of 0.75 % decline in food consumption in developing countries. in addition to reducing caloric http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):142-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 143 intake as food prices increase, low-income people also switch to less nutritious food (von braun, 2007; raneses et al., 1998). thus, to meet the energy demand without posing trait to human food chain, bio-waste is encouraged as feedstock for producing bioethanol (julian et al., 2011). the renewable feedstock is also abundant in nature (tan et al., 2014). focus is on utilizing preexploited agricultural land, and non food crops that are adaptive to current and foreseeable climatic conditions. this will lead to significant reduction of food price hike; soil degradation and diversion of food land. utilizing lignocellulosic agricultural wastes which constitute approximately 50 % of all land produced biomass such as waste palm bunch will result in transformation of waste to energy (thallada, 2011; siddegowda and venkatesh, 2013; siew et al., 2009). it is estimated that bioethanol produced from the world’s agri-waste and forest residues could replace 32 % of global petrol consumption (leland, 2005). a fuel blend of different fuels is a mixture with its own unique physical characteristics which depends on the miscibility of the components and their individual properties. these can as well be influenced by other factors like production process, feedstock type and environment. thus, fuel blends may have different effects on engine performance improving or reducing the performance (ashish and mohapatra, 2013; karl et al., 2005, chevron, 2004). in the light off the above, fuel properties of a fuel blend have to be ascertained before it is recommended for running a particular engine. this study was undertaken to investigate the fuel properties of the blend of pure petrol and bioethanol produced from nigerian waste palm bunch. 2.0 materials and methods 2.1 material procurement and preparation the bioethanol was produced from nigerian waste palm bunch collected from siat nigeria ltd, ubima, rivers state; by pretreatment, hydrolysis and fermentation (nuru et al., 2014, julian et al., 2011; lalit et al., 2011). the waste palm bunch was subjected to physical pretreatment, hydrolysis with 1.2 % dilute h2so4, at 160 oc for 30 min, fermentation for 72 h with s.scerevisea separated from palm wine, then distillation to obtain bioethanol fuel. 99.9 % pure petrol was obtained from nnpc port harcourt refining company limited, elesa-eleme, port harcourt rivers state. 2.2 fuel blends formulation and characterization elemental analysis of the produced bioethanol was carried out following the astm standard test procedures and compared to astm d4806 specification for denatured fuel bioethanol blend able with petrol for use as automotive si engine fuel. the elemental properties obtained include ash content, water content, acidity, ph and purity. the bioethanol content otherwise purity of the fuel was determined according to astm d 5501 in a gas chromatography. its ph was determined at room temperature using a ph meter according to astm d 6423. ash content was determined according to astm d482; 120 ml porcelain crucible was heated at 700 oc for 10 min. it was cooled to room temperature in a suitable container, and weighed as (w1). the sample of 5 g quantity (w2) was poured into the crucible, ignited and allowed to burn until only ash and carbon remains. the carbonaceous residue is reduced to ash by heating in a muffle furnace at 700 oc, cooled and weighed (w3). the average percentage ash was calculated with eqn (1). ash, % = w3 −w1 w2 x 100 (1) the acidity was determined according to astm d974, using potassium hydroxide (koh) as the titrant. the acid number was calculated by comparing to that of a blank as given in eqn (2). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng igbokwe, et al. characterization of blends of petrol and bioethanol synthesized from nigerian palm bunch. azojete, 15(1):142-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 144 acid number, mg of koh /g = a− b m x 56.1 w (2) where: a = koh solution required for titration of the sample ml, b = koh solution required for titration of the blank, ml, m = molarity of the koh solution, and w = sample used, g. water content of the bioethanol was determined based on astm d95. it was subjected to water content distillation using a dean and star distillation unit in figure 1. 100 ml of the bioethanol was mixed with 100 ml of aromatic mixture (80 % toluene and 20 % xylene) and subjected to heat for 2 h from boiling point. the trap solution was observed for separation and changes in the presence of methyl red dye. methyl red dye was used because it dissolves in pms but dissolves not in water. figure 1: water content distillation different blends of the bioethanol and pure petrol shown in figure 2 were then formulated and characterized for its fuel properties according to astm standard procedures for petrol, bioethanol, and petrol-oxygenated fuels. the blends were e0, e10, e20, e30, e40, e50, e60 and e100 formulated in 0:100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40 and 100:0 volume percentage of bioethanol/petrol respectively. e100 and e0 were the produced bioethanol and the obtained pure petrol respectively. figure 2: bioethanol-pure petrol fuel blends fuel properties determined includes density determined using the weight per volume method (tangka et al., 2011), viscosity in centipoise using capillary viscometers at a fixed temperature of 40 °c based on astm d 445, flash point using the pensky-martens closed cup tester (d 93), vapor pressure (vp) using an auto vapor pressure tester (d 4953), distillation profile or volatility using a batch atmospheric distillation apparatus (d 86), calorific values were determined by burning a known amount of bioethanol in a gallenkemp ballistic bomb calorimeter as described by abdullah et al., (2011). octane number (astm d 2699-86, d 2700-86) was determined using a portable cetane and octane meter, and a comparative fuel research engine (c48386 model) shown in figure 3. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):142-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 145 figure 3: comparative fuel research engine (c48386 model) the engine is of 1-stroke, 1-cylinder and operates on a fuel at a time. it consists of four carburetors, a detonation pick up, a dial indicator or micrometer, a detonator meter and a knock meter. two carburetors are for primary fuels blend (iso-octane and n-heptane) and two for sample fuel that need or need not temperature conditioning respectively before combustion. 1000 ml of the sample was poured into the carburetor to ensure that the fuel level is within 0.7 – 1.7 range in the carburetor sight glass. the detonation pick up threaded to the cylinder; has a sensor exposed to combustion chamber pressure and sends same to the detonation meter as voltage signal proportional to the rate of pressure change. the detonation meter being a signal conditioning equipment accepts, amplifies and then sends it to the knock meter. the knock meter, a 0 – 100 strip chart recorder displays the signal as knock intensity. the dial indicator displays the cylinder height with respect to the piston. the octane number was determined using the bracketing procedure (astm 2699); here, the knock meter reading was bracketed at constant compression ratio between knock meter readings for two reference fuels (i.e. 90 and 92 primary reference fuels), and the sample rating was calculated by interpolation. cylinder height was adjusted thereby varying the compression ratio, by a screw attached to each of the carburetors while reading was taken at knock meter display of ‘50’ to ensure a reliable result. this reading was then compared with the astm guide table for the corresponding octane number at the standard knock intensity for the specific fuel. drivability index (di) of the blends which is its quality of being drivable, of being easy or pleasant to drive. in other words, di of the blends give insight on how they response to the drivers demand and driving comfort. drivability index is based on the relationship between the distillation temperature of the fuel and the cold start and warming up parameters of the vehicle. lower values of di generally result in better cold-start and warm-up performance, but once good drivability is achieved, there is no benefit to lowering the di further. according to renewable fuels association (2010) and chevron (2009), di can be calculated using eqn (3). di (℃) = 1.5t10 + 3.0t50 + 1.0t90 + 1.33 ethanol % (3) where: t is distillation point temperature at 10 ml, 50 ml and 90 ml respectively. distillation was determined with 100 ml of each fuel samples distilled to observe its volatility. the distillation was performed according to astm d 86 in a batch atmospheric distillation apparatus hda 620 model (figure 4) at ambient pressure. systematic observations of temperature readings and volumes of condensate were made. the initial boiling point, ibp, end boiling point, ep and total distillate td were determined to plot their distillation profile curves presented in figure 1 under results and discussion. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng igbokwe, et al. characterization of blends of petrol and bioethanol synthesized from nigerian palm bunch. azojete, 15(1):142-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 146 figure 4: atmospheric distillation apparatus (hda 620 model) 3.0 results and discussion 3.1 characterization data elemental analysis obtained for the bioethanol is presented in table 1 while fuel properties of the blends are presented in table 2 and discussed below it with figure 3 – 7. table 1 satisfies astm d4806 requirement thereby confirming the produced bioethanol blend able with pure petrol. all petrol blend able with ethanol shall meet a minimum 50 % evaporated distillation temperature of 77°c (170°f) prior to blending with the ethanol (astm 4808). table 2 shows that the formulated blends fall within the qualities usable in si engine according to astm d4814 requirement, as they improved fuel properties of the pure petrol in the blends. table 1: elemental analysis of the produced bioethanol fuel parameters e100 astm range astm method purity % 97.68 d 5501 ash content % 0.03 0.05 d 482 h2o content (% vol) 0.42 1.0 (% vol) or 1.26 mass % d 95 acidity 5.05 mg/l 0.007 % mass or 56 mg/l (max) d 974 ph 6.61 6.5 – 9.0 d 6423 table 2: fuel properties of the formulated blends table 2 shows that densities of the sample fuels increased from 744.73 kg/m3 for pure petrol to 782.5 kg/m3 for e60 while the produced bioethanol e100 has 791.13 kg/m3 density making parameters sample fuel astm method e0 e10 e20 e30 e40 e50 e60 e100 density(kg/m3)@15 °c 744.73 747.65 752.7 759.93 768.89 777.64 782.5 791.13 d 4052 viscosity @ 40 °c (centipoise) 0.6097 0.6508 0.7132 0.9636 0.9951 1.3835 1.3592 1.6692 d 445 octane number 89.2 91.8 93.4 95 96.5 98.8 100 124 d2699 vp (kpa) 48.1 53.0 42.1 42.4 44.0 41.7 36.8 13.043 d 4953 flash pt, °c -69 -38 -27 -18 -13.2 -8.7 -4.8 12.8 d 93 calorific value (mj/kg) 43.62 41.81 40.22 38.54 37.03 35.36 33.73 29.16 d 240 drivability index (°c) 723.84 704.51 588.56 615.31 622.68 539.69 532.57 589.51 d 4814 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):142-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 147 6.23% increment. e100 has higher density than pure petrol and increased the density of its blends with pure petrol. as the percentage of bioethanol in the blend increased, the blend became denser. pure petrol density increased by 0.39 %, 1.1 %, 2.04 %, 3.24 %, 4.42 %, 5.07 % respectively with e10, e20, e30, e40, e50 and e60. density is the basic gauge of fuel adulteration, and is indirectly related to temperature. fuel density has the greatest impact on fuel capacity (donig, 2008). so, it is advice to ‘tank up’ vehicles in the morning and evening when fuel is denser with small volume, to get more value for money spent. since fuel is sold volumetrically, higher density promises greater potential energy. reported density of the produced bioethanol being 767 kg/m3 is less than 785 kg/m3 from potato waste by talal et al., (2010); 789 (kg/m3) from sugar cane-palmwine-raffia trunk by nwufor et al., (2014), and maize-raffia wine-palmwine by tangka et al., (2011). the kinematic viscosity of the bioethanol fuel at 40 °c is higher at 1.6692 centipoise compared to petrol which is 0.6097 centipoise (table 2). viscosity, a strong function of temperature affects fuel flow and amount atomized on pumping and injecting (viele et al., 2014). if fuel viscosity is high, the injection pump will be unable to supply sufficient fuel to fill the pumping chamber, causing poor atomization and a loss in power (van et al., 2004). lower viscosity causes smaller diameter of the droplets in the spray. below certain limits, low viscosity increases the leaks in the fuel system. adding bioethanol to petrol increased its viscosity with increase in bioethanol percentage in the blend. however, fear of poor atomization and leaks associated with high and low viscosity respectively is ruled out with lower bioethanol content. 1.6692 viscosity reported for the produced bioethanol in table (2) is higher than 1.1 reported by talal et al., (2012). the octane number of the fuels reported in table 2 was measured to be 124 for the product bioethanol which is higher than 89.2 for pure petrol with 39 % increment. the octane number of pure petrol increased continuously and linearly with percentage increase of bioethanol in the blends to 100 in e60. this could be because of higher oxygen content and octane number of the product bioethanol fuel resulting to a gradual shift from normal heptane (c7h16) to ideal isooctane (c8h18) of the blends. pure petrol having lower octane number and higher calorific value will burn faster than the bioethanol and its blends having lower calorific value and higher octane number. notwithstanding, octane number being a measure of the ignition quality of a fuel of which high octane number means more efficient ignition and consequently higher engine performance, proves that the presence of bioethanol in the blends will improve petrol engine performance as the octane number increased with increase in bioethanol in the blends. therefore, the fear of auto-ignition and knocking effect could be ruled out in the utilization of these blends. this suggests the product bioethanol as an effective agent for increasing the value of petrol octane number. octane number of 124 reported for e100 is higher than 108.6 and 114 but lower than 129 recorded by talal et al., (2010), nwufor et al., (2014) and tangka et al., (2011) respectively. as reported in table 2, vapor pressure of the product bioethanol is 13.043 kpa which is 72.9 % lower than 48.1 kpa for the petrol. vapor pressure is a measure of “front end” volatility, and a fuel with extremely high vapor pressure may cause problems with hot start ability, hot drivability and vapor lock protection (karl et al., 2005; chevron 2004). allowable rvp for petrol is 0.7 bar (70 kpa) in summer and 0.9 bar (90 kpa) in winter (at 37.8 oc) (rfa, 2002). 10 % bioethanol in pure petrol increased its rvp to a peak value of 53 kpa suggesting that it could reduce the risk file:///c:/users/user/downloads/azojete143/www.azojete.com.ng igbokwe, et al. characterization of blends of petrol and bioethanol synthesized from nigerian palm bunch. azojete, 15(1):142-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 148 for a flammable mixture forming than other blends. table 2 clearly shows that further increase in the bioethanol above 10 % declines the blend vapor pressure and the decrease is not linear. product bioethanol has fewer highly volatile components than pure petrol which suggest that it will have less emissions resulting from evaporation. however, when added to pure petrol, the vapor pressure of the blend was increased thereby increasing evaporative emissions. this could be because in its pure form, bioethanol molecules are polar and bond to each other via the hydroxyl (oh) groups. these forces of attraction prevent the molecules from leaving the liquid but in the presence of hydrocarbons, the bonding was weakened. it is expected that at a point addition of bioethanol will not further boost the vapor pressure. it can also be deduced that bioethanol contents higher than 40 % will increase the risk that vapor will form with pressures under the upper flammability limit. however, the blends ensure products of suitable volatility performance. vp of 13.043 kpa reported for e100 is higher than 9 and 9.5 but lower than 48 reported by tangka et al., (2011), nwufor et al., (2014) and talal et al., (2010), respectively. the observed flash point of produced bioethanol (table 2) is 12.8 °c while other blends has flash point below 10 °c. flash point indicates the lowest temperature at which the vapor overhead the sample is ignitable with the application of an ignition source under specified test conditions. it predicts the temperature at which the vapor pressure reaches the lower flammable limit. flammability limits is the maximum and minimum concentrations of combustible vapor in the air and the temperatures at which the vapor occurs, that will propagate a flame after sufficient ignition energy is provided (rfa, 2009, 2002). the result presented in table 2 shows that all the blends are susceptible to ignition and has the chance of flammability hazard. the flash point of the bioethanol is high compared to -69 °c for petrol, indicating that it is safer than petrol regarding its handling, transportation and storage. increase in bioethanol percentage continuously increased the flash point of pure petrol from -69 °c to -4.8 with 60 % bioethanol. thereby increasing its safety handling, transportation, storage and flammability limits. high flammability limits promotes safety handling of fuel (rfa, 2009, (ashish and deshmukh 2012). flash point of e100 which is 12.5 °c agrees with nwufor et al., (2014) and tangka et al., (2011) but talal et al., (2010) that reported 14 °c. calorific values of the pure and blended fuels are presented in table 2. calorific value or heat of combustion is a measure of the energy available from a fuel. knowledge of this value is essential when considering the thermal efficiency of equipment for producing either power or heat. the calorific value of the product bioethanol was found to be 29.16 mj/kg while that of pure petrol is 43.62 mj/kg on weight basis. for the product bioethanol (e100), calorific value is 31.73 % less than that of pure petrol. it is deduced from the table that the calorific value of the petrol blend steadily decreased as bioethanol content increased. it decreased to 33.73 mj/kg in e60. this means that the consumption of blends could be higher than petrol for a driving range (dhanapal et al., 2010; wallner et al., 2009). however, this can be partly offset by the higher octane number of the bioethanol. calorific value of 29.16 mj/kg reported for e100 is higher than that recorded by talal et al., (2010) and tangka et al., (2011) but within the same range as the 29.78 mj/kg from nwufor et al., (2014). the drivability index of pure petrol (table 2) was found to be 723.84 °c, and reduced with the presence of the bioethanol but not linearly. drivability index is a measure of the volatility characteristics of a fuel and high di is normally associated with low volatility (rfa, 2002; chevron, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):142-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 149 2009). pure petrol has the highest di compared to other fuel samples while e60 has the least with 532.57 °c proving that pure petrol is less volatile and e60 is most volatile. also, since low drivability is preferable in an engine, it means the bioethanol improved drivability and volatility of pure petrol and thus its cold start and warm up performance. high di causes poor fuel evaporation in cold start, leading to lean a/f ratio, unstable combustion, hc emission, piston and cylinder wear especially in carburetors (rfa, 2010; chevron, 2009). this is normally offset by automatic increase in injected fuel or choking in carburetor to achieve a rich mixture which results to more hc emission (rfa, 2010). therefore, engine need to be warmed up for at least 10 – 15 minutes to bring it to its normal operating condition (wallner, 2009). figure 1: effect of blends on distillation profile figure 1 presents the distillation profile of the sample fuels from their initial boiling point (ibp) to 90 % distillate. the distillation profile (volatility profile) for the produced bioethanol showed ibp of 79 °c, 99 °c at 90 %vol and ebp of 101 °c with total distillate of 97 % vol while petrol has ibp of 44 °c, 181 °c at 90 % vol and ebp of 205 °c with total distillate of 98 % vol. temperature of pure petrol when 10 % was distilled is 61 oc (i.e. t10), with respect to this temperature e10, e20, e30 and e50 decrease by 6.56 %, 3.28 %, 3.28 %, and 1.64 %, while e40 and e60 increased by 1.64 % and 6.56 % respectively. decrease of 3.74 %, 36.64 %, 30.84 %, 28.97 %, 28.97 % and 29.91 %, was observed with e10, e20, e30, e40, e50 and e60 respectively for t50 (107 °c), while decrease of 1.1 %, 1.66 %, 3.31 %, 3.87 %, 45.86 % and 56.69 %, respectively at t90 (181 °c). compared to pure petrol, the distillation curve for each blend was significantly depressed between t10 and t50 distillate. the curve depression could be attributed to the presence of the bioethanol in blends which increased its volatility. this may expect problem with cold starting and vapor lock. the resulting t10 is sufficiently low to allow enough fuel to evaporate and form a combustible mixture. t50 point associated with engine warm up; is sufficiently low to allow the engine to warm up and gain power quickly without stalling. t90 associated with the crankcase dilution and fuel economy; is not expected to be high. if t90 is too high, the larger fuel molecule will condensate on the cylinder liners and pass into the lubricating oil in the crankcase instead of burning; this will then be avoided with the blends. blending pure petrol with the bioethanol increased the volatility, decreases the 50 % distillation point t50, affects the driveability index and also improved its fuel quality. distillation profile of 79 101 °c reported for e100 is higher than 55 – 68 reported by nwufor et al., (2014). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng igbokwe, et al. characterization of blends of petrol and bioethanol synthesized from nigerian palm bunch. azojete, 15(1):142-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 150 though, the product fuel has lower density and consequent lower potential energy than pure petrol, its high viscosity which rules out poor atomization; and its high octane number which means more efficient ignition and consequent higher engine performance suggests it an effective compound for improving petrol fuel quality and recommends their blends for use in spark ignition engines. this means that engines optimized for bioethanol can be more energy efficient than engines that are currently optimized for petrol (wallner et al., 2009). the formulated blends fall within the qualities usable in si engine according to astm d4814 requirement, as it improved fuel properties of the pure petrol in the blends presented in table 2. 4.0 conclusion this study produced bioethanol from nigerian waste palm bunch by physical pretreatment, chemical hydrolysis and using a catalyst extracted from palm wine in the fermentation process. the produced bioethanol characterized according to astm standard was found to be blend able with pure petrol and the blends are usable in si engine. it can then be concluded that nigerian waste palm bunch can be treated to produce bioethanol, a reliable fuel to improve pure petrol fuel properties and engine performance, and thus can be a perfect replacement for lead compound used as an anti-knock agent. the project falls under the focus category of waste to energy as it addressed issues relating to conversion of waste which poses a disposal burden to energy. acknowledgement the authors would like to thank the chemical laboratory staff members of nigeria national petroleum corporation, port harcourt, rivers state; engr. james oko of jach petro analytical laboraory limited, port harcourt, rivers state; and emurigho tega anthony of federal polytechnic nekede, imo state, for their assistance. references abdullah, n., sulaiman, f. and gerhauser, h. 2011. characterization of oil palm empty fruit bunches for fuel application. journal of physical science, 22: 1–24. anjan, r. 2013. second-generation hydrocarbon fuels from oil palm by-products. journal of oil palm and the environment. 4: 22-28. ashish, s. and deshmukh, m. 2012. performance and emission characterization of si engine using lpg-ethanol blends: a review international journal of emerging technology and advanced engineering, 2(10): 1 – 7. ashish, m. and mohapatra, s. 2013. biomass-based gasifiers for internal combustion (ic) engines. indian academy of sciences, 38: 461– 476. astm d 4806-03, 2012. standard specification for denatured fuel ethanol for blending with gasolines for use as automotive spark-ignition engine fuel,” astm international, west conshohocken. cheng, c., hajar, h. and ku, s. 2007. production of bioethanol from oil palm empty fruit bunch. international conference symposium (icosm). university of malaysia pahang. http://umpir.ump.edu.my/7248/, 9 11th june, 69 72. http://umpir.ump.edu.my/7248/ http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):142-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 151 chevron 2009, 2004. motor gasoline technical review gasoline and driving. performance, and gasoline questions and answers oxygenated gasoline. chevron corporation publication, california, 1 124. dhanapal, b., periyasamy, g. and jayaraj, v. 2010. emission and combustion of si engine working under gasoline blended with ethanol oxygenated organic compound. american journal of environmental science, 6: 495 499. donig fermanian, 2008. petro-value. 2:1 – 45. julia´n, a. q., luis, e. r. and carlos, a. c., 2011. production of bioethanol from agro industrial residues as feedstocks. academic press, elsevier, usa. 1st jan., 251 – 285. karl, e., magnus, h., björn, r., mats, w. and roger, w. 2005. blending of ethanol in gasoline for spark ignition engines. study performed by stockholm university, atrax ab, autoemission kee consultant ab, and avl mtc motortestcenter ab, stoclholm, sweden, 1 – 133. www.avlmtc.com. koonin, s. 2006. getting serious about biofuels. science, 311: 401 435. kyoto protocol: http://unfccc.int/kyoto_protocol/items/2830.php. lalit, k., gaurav, ,c., majumderb, c. and sanjoy, g. 2011. utilization of hemicellulosic fraction of lignocellulosic biomaterial for bioethanol production. advances in applied science research, 2: 508-521. www.pelagiaresearchlibrary.com leland, m. v. 2005. a review of pervaporation for product recovery from biomass fermentation processes. journal of chemical technology and biotechnology. 80: 603 – 629. nwufo, o., nwaiwu, c., igbokwe, j. and nwafor o. 2014. production and 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talal, y., najafi, g. and david, b. 2010. theoretical and experimental investigation of si engine performance and exhaust emissions using ethanol-gasoline blended fuels. international conference on energy and environment (icee), 3:1 – 7. tan, k., lim, s., low, c. and chang, s. 2014. engine emission analysis and performance test with ethanol-gasoline blended fuel. european international journal of science technology, 3(7): 9 – 22. tangka, j., berinyuy, j., tekounegnin and okale, a. 2011. physico-chemical properties of bioethanol / gasoline blends and the qualitative effect of different blends on gasoline quality and engine performance. journal of petroleum technology and alternative fuels, 2: 35 44. thallada, b., balagurumurthy, b., rawel, s., desavath, vn., ajay, k. and hari, bg. 2011. thermochemical conversion of biomass to biofuels. council of scientific and industrial research (csir). academic press, elsevier, 3:51 77. van, g., shanks, b., prisszko, r., clements, d. and knothe, g. 2004. biodiesel analytical methods. national renewable energy laboratory. 1 – 100. viele, e., chukwuma, f. and uyigue, l. 2014. production and characterization of biodiesel from crude palm kernel oil and bioethanol using potash from ash of empty oil palm bunch residue as catalyst. international journal of application or innovation in engineering & management (ijaiem), 3(1): 355 – 363. von braun 2007. the world food situation: new driving force and required action. international food policy research institute, washington, 18: 1 – 27. wallner, t., miers, s. and mcconnell, s. 2009. a comparison of ethanol and butanol as oxygenates using a direct-injection, spark-ignition engine. journal of engineering for gas turbines and power, 3:131 137. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 777-791 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 777 original research article effects of soil properties and operational variables on the compactibility of a sandy loam soil d. audu1*, o. s. balogun2, f. a. adeniji3, and y. musa4 (1department of soil science, federal university of kashere, gombe state, nigeria 2department of water resources and environmental engineering, university of ilorin, ilorin, nigeria 3department of food, agriculture and bio-engineering, college of engineering technology, kwara state university, malete, nigeria 4department of agricultural education, federal college of education (technical), gombe, nigeria) * corresponding author’s email address: danladimsh@gmail.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: soil soil properties compaction compaction efforts empirical equation statistical significance abstract the evaluation of an empirical equation for the determination of degree of compaction of a sandy loam soil was carried out using seven soil physical properties and four compaction operational variables. the soil used was obtained from a borrow pit in gombe. five levels of compactive effort, e/a, using a drop-weight type compactor varying from 107.91 to 539.55 nm was used to compact each of seven pairs of embankment and slice thicknesses (z, z respectively) with z varying from 210 to 450 mm and z from 30 to 210 mm. the developed empirical equation, π1 = gπ2k in which π1 is the dimensionless degree of compaction and π2 is a dimensionless combination of the soil properties and the compaction operational variables, has a very high coefficient of determination, r2 varying from 98.8% to 98.9%. g and k are each polynomial functions of compactive effort per loading, el. that is, g = αgel2+βg el + λg and k=αkel2+βkel+ λk. the values of the respective α, β and λ are highly statistically significant at 99.95 confidence level. the “dependent” variables (g and k) are highly correlated at 99.95% confidence level of statistical significance with the “independent” variable (el). the multivariate expression of the degree of compaction obtained in this study shows that compaction depends, not only on cumulative compactive effort, e/a, but also on the compactive effort per loading (el), embankment and slice thicknesses (z and z respectively) as well as on easy-to-measure soil properties (i.e. soil texture, soil uniformity coefficient, antecedent soil moisture and antecedent bulk density). © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction appropriate response of an engineering soil to compaction is one of the most important qualities sought in civil and agricultural engineering construction activities such as those in building foundations for canals, railroad and highway works, earth embankments and dams, airport runways, sanitary landfills and excavation for structures and retaining walls (jack, 2007; davis, 2008). identification and measurement of the interactions of all relevant factors governing soil compaction still remain major challenges in geotechnics. this study seeks to address some of these challenges. the bulk density (ρbc) of a soil is a measure of soil’s response to compaction mailto:danladimsh@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):777-791. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 778 through rolling, ramming, free falling loads or by consolidation. the degree of compaction or compactibility of a soil cd is a function of compactive energy (e), the area (a) of the soil on which energy is exerted, soil moisture content (mc), density of water (ρw) in the soil, the mean soil particle size (φ50), thickness of the compaction slice (z), the coarseness of the soil (c/f), where c is coarse fraction of the soil and f is fine fraction, soil’s uniformity coefficient (uc = φ60/φ10), the soil particle density (ρs), its antecedent bulk density (ρbc), acceleration due to gravity (g), and the time (t) of contact between the compacting load and the soil being compacted. by definition cd is the ratio of the change in volume (δv = v1 – v2) where v1 is soil’s original volume and v2 is final soil volume after compaction to its original volume, v1. a universal function of the type: cd = f[(e/a), t, c/f, mc, ρw, z, φ50, uc, ρbc, ρs, g] (1) that simultaneously relates all the eleven independent variables believed to be influencing cd has not been successfully determined so far. the common practice has been to rely on casespecific model studies for a given project and apply the results to that project type only. that approach lacks the capacity for general application. the determination of the function “f” in equation 1 is the main problem that requires solution or solutions. the purpose of this study therefore is to evaluate the relationship between the degree of compaction and the easy-to-measure soil properties and compaction operational variables using a soil of given φ50, c/f and uc. equation 1, implicitly incorporating eleven independent variables, is a robust function, which has a potential for wide applicability in soil engineering works, such as the construction of canals, roads and earth dams, provided the constituent variables are known and measurable. compaction is the process of increasing the density of a soil by packing the particles closer together with a reduction in the volume of air within the soil. maximum compaction of a soil is achieved at the optimum moisture content of the soil (timothy et al., 2012). this is the water content at which a maximum dry unit weight is reached (craig, 1978; sutton, 1986). although this process involves the expulsion of air from the voids, the moisture content does not change significantly (bell, 1993). compaction results in increase in shear strength (duncan, 1990). the increase in soil density according to gray (2000) is as a result or consequence of compaction but not the goal. density is used as a target in engineering soil compaction specifications. the purpose of compaction is to change engineering properties of a soil in a desirable direction. optimally compacted materials display engineering properties that are substantially superior to the same materials in a loose state (watson and burnett, 1995; werkmeister, 2003; shestak et al., 2005). quality of compacted fill is influenced by inter-related factors such as soil type, thickness of compacting layer and the compactive effort. soil characteristics including grain size (φ50), gradation (uc) and clay or fine content (c/f), play an important role in soil behaviour under compaction. in coarse-grained soils, there exists an inter-granular contact and compaction processes brings about re-arrangement of soil particle positions. the way in which these particles are arranged within the soil mass and the distribution of particle sizes throughout, will ultimately determine the degree of compaction and hence the density, stability and the bearing capacity of the soil. therefore, the maximum compaction can be achieved by the best packing of well-graded soil where the fine grains fill the spaces between the large grains. however, surplus file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 779 of fines can be detrimental by preventing inter-granular contact between coarse particles (mosaddeghi et al., 2000; shaqour, 2004). effective compaction of earth materials can be achieved by applying the proper mechanical energy to a soil layer of suitably specified optimum thickness. an optimised compactive effort may be described as one that results in obtaining the compaction required from making the correct number of falls or passes, over a layer of optimum thickness. in a field, an optimum thickness, 200 to 300 mm is normally recommended (watson and burnett, 1995). the thickness of the compacting layer varies with grain size and compactive effort. generally, coarse-grained soils compact more readily than fine grained ones and hence the finer the particles the thinner the maximum layer to be compacted (shaqour, 2004; sch., 2005). 2. materials and methods 2.1 the study area gombe metropolis is located between latitude 10° 0' n and 10° 20' n and longitude 11°01' e and 11° 19' e and lies in the stretch of benue trough. it consists majorly two types of soils corresponding to the two geological formations from which they are derived; sandy soil found in the northwest underlain by keri keri formation and clayey soil which occurs to the south and southeast (mbaya, 2012). sandy loam soil could also be found in some parts of the metropolis, especially, in the north (audu, 2014). gombe metropolis has two distinct climates: the dry season which begun from november to march and the rainy season, from april to october with an average rainfall of 969.7 mm (yahaya, 2015). 2.2 description of the compaction device figure 1 shows the sketch of the compaction device that was constructed and used for this study. as depicted, it consists of the following components: (a) compactor and bearings; (b) mould; (c) removable plate; and (d) steel rod. figure 1: the compaction device http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):777-791. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 780 2.2.1 the compactor and bearings the compactor, cylindrical in shape, was constructed of concrete with cement, fines and coarse sand ratio of 1:2:4 by mixing 3.143 kg cement, 6.286 kg of fine sand and 12.571 kg of coarse sand with 2.2 litres of water and cured for 21 days, yielding 22 kg dry weight. the bearings were purchased. the cylindrical shaped compactor has a diameter of 305 mm and made 2 mm smaller than the diameter of the mould in order to allow its free in-and-out movement into the mould during compaction. the thickness of the compactor was 193 m with a circular hole at the centre to allow the steel rod to pass through and for the bearings to be situated inside as shown in figure 1. the bearings slide along the steel rod up and down during compaction. this helps to reduce friction that may occur between the steel rod and the compactor during compaction process. 2.2.2 the mould this is also cylindrical in shape, and was constructed with 2 mm thick sheet metal according to the shape of the compactor. its height was 500 mm and inner diameter was 307 mm, which was 2 mm larger than that of the compactor in order to allow free in-and-out movement of the compactor into it during the compaction process. it is built strong enough to withstand the pressure of the compacting force. 2.2.3 the removable plate this is of the same shape and diameter as the compactor and as the name implies, it is removable and constructed of the same material as the mould. it is placed at the base of the compactor to allow even distribution of compactive effort during the compaction process. it has a circular hole, 2 mm greater than the external diameter of the steel rod, at its centre, for the steel rod to pass through. 2.2.4 the steel rod this is a rigid, cylindrical structure placed vertically up at the bottom centre of the mould, passing through the drilled hole of the removable plate and the compactor, with an 85 mm thick (mahogany) wooden plate fixed at the base of the steel rod. the steel rod guides the compactor through the height of free fall during the compaction process. it was 1500 mm long. 2.3 compaction equipment the compaction facilities consist of the fabricated compaction device shown in figure 1 and moisture sprayer, sieves, pestle, scoop, knife, mixing pan, balances, drying oven, cans and polythene bags (mann, 2006). table 1 lists the specifications of the compaction equipment. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 781 table 1: specifications of the compaction equipment s/n definition/description quantity/value units 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. cross sectional area weight height of drop height of mould height of rod diameter of compactor thickness of compactor diameter of mould cement : fine sand : coarse sand water at 70% of the cement by wt. 0.07309 215.82 0.5 0.5 1.5 0.305 0.193 0.324 3.143 : 6.29 : 12.57 2.2 m2 n m m m m m m kg litres 2.4 soil sample preparation the soil used was obtained in federal college of education (technical), duku road, gombe, nigeria. it was air-dried, aggregates present in the sample were broken down gently, using pestle and mortar to maintain the natural size of the individual particles. soil particles larger than 76.2 mm are gravels and were discarded as the soil was characterized and classified geotechnically according to the system adopted by aashto standard no. m 145–91 (1995). the soil samples were then kept in polythene bags for compaction. 2.5 compaction procedure a soil sample of 3.55 kg, whose physical characteristics such as texture was determined according to braja (1986) was used to obtain uniformity coefficient and coefficient of curvature, particle density according to blake (1965), bulk density according to heed (1992), porosity by nyle and ray (1999) and moisture content by astm d 2216 (1998), was considered. the particle unit weight, bulk unit weight and unit weight of water were also calculated by multiplying the values of the particle density, bulk density and the moisture content by 9.81 m/s2. the soil sample was then taken and spread evenly over a flat surface of area, a = 0.07309 m2 in the mould, and its thickness, 30 mm was measured using a ruler placed vertically on the soil surface inside the mould. a compactor weight of 215.82 n was released from a height of 0.5 m, to drop one time on the soil layer; the new thickness was measured. another soil “slice” (2 loadings), of thickness 30 mm was spread evenly on the previous slice, a new pre-compacted thickness was determined. compactive effort was applied and a new compacted soil thickness was measured from which the new compaction was obtained. the above procedures were repeated until the desired “pavement” thickness of 210 mm was reached or slightly exceeded. the above procedures were repeated for 2, 3, 4 and 5 drops representing multiples of compacting energy per loading for the same soil thickness of 30 mm loaded in each case. the whole procedures were repeated for 60 mm, 90 mm and 120 mm, 150 mm, 180 mm and 210 mm soil thicknesses. from dimensional analysis, degree of compaction, π1=σδz/z and the governing variables, π2 = (ecφ50(c/f)uc) (aγbcz3se) for the 5 levels of compactive effort per loading was established. multiple regression analysis was used to analyse the data to estimate the connection between http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):777-791. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 782 corresponding author’s e-mail address: danladimsh@gmail.com degree of compaction, π1 and the governing variables, π2 and by how much. this provided an equation for the prediction and plotting of relationships. p-value and correlation coefficient were given to indicate the accuracy of the model. 3. results and discussions table 2 shows the results of the dry-sieving test which is used to obtain the grading curve (figure 2) by plotting % passing versus sieve opening. from the hydrometer analysis, silt and clay particles were found to be 8% and 19%, respectively. table 2: results of sieve analysis sieve opening (mm) soil weight retained (g) soil weight passing (g) percent retained (%) percent passing (%) 14 131.8 3868.2 3.295 96.705 5 267.3 3600.9 6.683 90.023 1.18 556.8 3044.1 13.920 76.103 0.3 2055.4 988.7 51.385 24.718 0.075 636.6 352.1 15.915 8.803 pan 349.6 0.0 0.0 0.0 from the grading curve (figure 2), φ10 = 0.11, φ30 = 0.34, φ50 = 0.49 and φ60 = 0.68, all φ values are in mm. from these data, uniformity coefficient uc = φ60/φ10 = 0.68/0.11 = 6.18 and the coefficient of curvature, cc = (φ30)2/(φ60φ10) = (0.342)/0.68 x 0.11 = 0.1156/0.0748 = 1.55. according to budhu (2004), a well graded soil is a soil with a uniformity coefficient (uc) greater than 6 and coefficient of curvature (cc) greater than 1 but less than 3. from the result of this analysis, the soil used was a well graded sandy loam soil and indicated that there was a wide spread of soil particle distribution of sand, silt and clay in the soil used, which is expected to compact well. figure 2: percentage soil particle size distribution table 3 below shows the physical properties of the soil used in the study. from the table, the energy deliverable per drop by the compactor of weight 215.82 n from a height of 0.5 m (i.e. 215.82 n x 0.5 m) was 107.91 n. the table also shows that the coarse to fine fraction ratio (c/f) https://www.statisticshowto.datasciencecentral.com/p-value/ https://www.statisticshowto.datasciencecentral.com/probability-and-statistics/correlation-coefficient-formula/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 783 was 2.7 and uniformity coefficient was 6.18; the unit weight of soil particle; bulk soil and water were 26045.55, 15882.5 and 9810 nm-3 respectively. in table 4 column 8, the quantity of soil used for the compaction test was 1505 kg. table 3: soil physical properties s/n item/notation definition/description quantity/values units 1. 2. 3. 4. 5. 6. 7. 8. 9. texture φ50 uc = φ60/φ10 c f c/f γbc γs γw sandy loam mean particle diameter uniformity coefficient coarse fraction fine fraction coarse:fine ratio initial antecedent unit weight particle unit weight unit weight of water 1505 0.49 6.18 73% 27% 2.7 15882.5 26045.55 9810 kg mm nm-3 nm-3 nm-3 3.1 processed compaction data table 4 shows the compaction test data for 7 levels of soil slice thicknesses, lst 1–7 and 5 levels of compactive effort per loading, lel 1–5. according to the table, one drop of the compactor released an energy, el of 107.91 nm per loading or 755.37 nm at the end of the 7th loading. thus, the cumulative compactive effort, ec, was 755.37 nm achieving a cumulative soil compaction σδz = 49.5 mm from z = 210 mm thick of uncompacted soil at 15882.5 nm3 unit weight to a “pavement” of thickness z′ = 160.5 mm at 19677.3 nm-3 unit weight. the last column shows the loading-by-loading computed degrees of compaction δz/zι varying from 18.33% to 5.31% for lst = 1 and loading ι = 1 to ι = 7. increasing values of el at multiples of 107.91 nm per loading carry similar information as described above. table 4: test data record “matrix” for 7 levels of soil slice thickness (lst) for the 1st level of compactive effort (el) per loading lel & el (1) 107.91 nm/loading lst z z ɩ ec zɩ δz m γbc se δz/zɩ x102 1 30 210 1 107.91 30.0 5.50 3.55 15882.5000 0.0469 18.3333 2 215.82 54.5 6.00 7.10 17485.3000 0.0557 11.0092 3 323.73 78.5 6.50 10.65 18209.2000 0.0608 8.2803 4 431.64 102.0 7.00 14.20 18685.2130 0.0648 6.8627 5 539.55 125.0 7.50 17.75 19058.8641 0.0682 6.0000 6 647.46 147.5 8.00 21.30 19381.9568 0.0715 5.4237 7 755.37 169.5 9.00 24.85 19677.3295 0.0748 5.3097 mc = 1.83% http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):777-791. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 784 corresponding author’s e-mail address: danladimsh@gmail.com 2 60 300 1 107.91 60.0 8.50 7.10 15882.4737 0.0989 14.1667 2 215.82 111.5 9.50 14.20 17093.2452 0.1123 8.5202 3 323.73 162.0 11.00 21.30 17647.1930 0.1197 6.7901 4 431.64 211.0 11.50 28.40 18065.3729 0.1260 5.4502 5 539.55 259.5 12.00 35.50 18361.2412 0.1308 4.6243 mc = 3.86% 3 90 450 1 107.91 90.0 12.00 10.65 15882.4737 0.0551 13.3333 2 215.82 168.0 13.50 21.30 17016.9361 0.0620 8.0357 3 323.73 244.5 14.50 31.95 17538.9280 0.0658 5.9305 4 431.64 320.0 15.00 42.60 17867.7829 0.0685 4.6875 5 539.55 395.0 16.00 53.25 18093.9573 0.0704 4.0506 mc = 2.15% 4 120 360 1 107.91 120.0 14.50 14.20 15882.4737 0.0794 12.0833 2 215.82 225.5 17.50 28.40 16903.7414 0.0883 7.7605 3 323.73 328.0 18.00 42.60 17431.9833 0.0937 5.4878 mc = 3.10% 5 150 450 1 107.91 150.0 16.50 17.75 15882.4737 0.1207 11.0000 2 215.82 284.0 17.00 35.50 16777.2609 0.1324 5.9859 3 323.73 417.5 18.00 53.25 17118.8339 0.1374 4.3114 mc = 4.71% 6 180 360 1 107.91 180.0 18.50 21.30 15882.4737 0.2132 10.2778 2 215.82 343.0 20.50 42.60 16669.6317 0.2311 5.9767 mc = 8.32% 7 210 420 1 107.91 210.0 19.00 24.85 15882.4737 0.1545 9.0476 2 215.82 403.0 22.00 49.70 16552.4539 0.1654 5.4591 mc= 6.03% se = ((γbc/γw)/(1-(γbc/γs))*mc, mc=gravimetric dry weight soil moisture content, γw, γs and γbc are as given in table 3. test data record matrix for 7 levels of soil slice thickness (lst) for the 2nd, 3rd, 4th and 5th levels of compactive effort (el) per loading convey the same trend of information with increasing relative magnitude of the coefficients in the polynomial function and power functions as the compactive effort increased. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 785 3.2 dimensionless degrees of compaction functions 3.2.1 the version of π1 versus π2 relationship table 5: input output data for computing π1 and π2 lel 1 2 3 4 5 lst el , nm 107.91 215.82 323.73 431.64 539.55 1 z = 30, z = 210 se 0.0469 0.0469 0.0469 0.0469 0.0469 ec 755.37 1510.74 2266.11 3021.48 3776.85 ʃδz 49.5 59 63.5 69 71.5 2 z = 60, z = 300 se 0.0989 0.0989 0.0989 0.0989 0.0989 ec 539.55 1079.1 1618.65 2158.2 2697.75 ʃδz 52.5 57.5 59.5 61.5 63.5 3 z = 90, z = 450 se 0.0551 0.0551 0.0551 0.0551 0.0551 ec 539.55 1079.1 1618.65 2158.2 2697.75 ʃδz 71 80 85.5 87 92 4 z = 120, z = 360 se 0.0794 0.0794 0.0794 0.0794 0.0794 ec 323.73 647.46 971.19 1294.92 1618.65 ʃδz 50 54 61 66 69.5 5 z = 150, z = 450 se 0.1207 0.1207 0.1207 0.1207 0.1207 ec 323.73 647.46 971.19 1294.92 1618.65 ʃδz 51.5 61.5 70 77 82 6 z = 180, z = 360 se 0.2132 0.2132 0.2132 0.2132 0.2132 ec 215.82 431.64 647.46 863.28 1079.1 ʃδz 39 46 51 54.5 56.5 7 z = 210, z = 420 se 0.1545 0.1545 0.1545 0.1545 0.1545 ec 215.82 431.64 647.46 863.28 1079.1 ʃδz 41 50.5 57.5 62.5 64.5 π1 = ʃδz/z; π2 = [ucφ50 (c/f)/(aγbc)](ec/(sez3)); where z=soil slice thickness, mm; z = total soil thickness in mm to be compacted; ec=cumulative compactive effort, nm. table 5, derived from table 4, contains the information required to compute the degree of compaction, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):777-791. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 786 corresponding author’s e-mail address: danladimsh@gmail.com π1=σδz/z (2) and the governing variables, π2 = (ecφ50(c/f)uc) (aγbcz3se) (3) for the 5 levels of compactive effort per loading. here, the cumulative compactive efforts, ec was used. the version of π1 versus π2 was discussed hereunder. from table 5, another table, table 6 was derived to determine the version of the multivariate soil compaction function. 3.2.2 function “weighted” by compactive effort per loading, el and its use each of the five pairs of columns in the main entries in table 6 showing π1 and π2 also has its own unique characteristics namely, its magnitude of compactive effort per loading, el in nm/loading. this is reflected in the “best fit” regression curves, also power curves of the type: π1 = gπ2k π2 = δz = g(ecφ50(c/f)uc)/(aγbcz3se)b (4) where: π1 and π2 are as defined in table 7, “g” is the coefficient and “k” the exponent which took different values as mel varied. as in section 3.2.3, g and k were regressed, but this time both on el from 107.91 to 539.55 nm/loading. figures 3 to 7 derived from table 6 show the coefficients “g”, exponents “k”, determination coefficients r2 varying from 0.925 to 0.985, averaging 0.955 and each with its own “g” and “k” as listed in table 7. table 6: the values of π1 (y) and π2 (x) for 7 levels of soil slice thickness (lst) and 5 levels of compactive effort per loading (lel) lel 1 2 3 4 5 mel = el 107.91 215.82 323.73 431.64 539.55 lst mst, mm π1x104 π2 π1x104 π2 π1x104 π2 π1x104 π2 π1x104 π2z z 1 30 210 2357 4201.466 2810 8402.932 3024 12604.400 3286 16805.860 3405 21007.330 2 60 300 1750 177.853 1917 355.705 1983 533.558 2050 711.410 2117 889.263 3 90 450 1578 94.613 1778 189.227 1900 283.840 1933 378.453 2044 473.066 4 120 360 1389 16.619 1500 33.237 1694 49.856 1833 66.475 1931 83.093 5 150 450 1144 5.597 1367 11.194 1556 16.791 1711 22.388 1822 27.985 6 180 360 1083 1.222 1278 2.445 1417 3.667 1514 4.890 1569 6.112 7 210 420 976 1.062 1202 2.124 1369 3.186 1488 4.249 1536 5.311 notations: π1 = σδz/z for c/f = 2.7, a = 0.07308895m2, uc = 6.18, φ50 = 0.49 mm, γbc = 15882.5 n, π2 = ec(c/f)φ50uc/(seγbcaz3) becomes π2 = ((c/f) φ50uc/aγbc)(ec/sez3)) = 7.043325 x 10-6(ec/sez3). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 787 figure 3: π1 vs π2 for 107.91 nm compactive effort figure 4: π1 vs π2 for 215.82 nm compactive effort figure 5: π1 vs π2 for 323.73 nm compactive effort figure 6: π1 vs π2 for 431.64 nm compactive effort figure 7: π1 vs π2 for 539.55 nm compactive effort table 7: power function π1 = g π2k, coefficient “g”, exponent “k” determination coefficient r2 and el for the el-governed variations s/n from figures 3 – 7 compactive effort per loading “g” “k” r2 el, nm 1. 2. 3. 4. 5. 1006 1104 1211 1276 1310 0.102 0.097 0.089 0.086 0.086 0.985 0.981 0.966 0.925 0.927 107.91 215.82 323.73 431.64 539.55 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):777-791. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 788 corresponding author’s e-mail address: danladimsh@gmail.com with the data derived from figures 3 to 7 and listed in table 7 above, both “g” and “k” were regressed on el as polynomial expressed in the following equations g = αg el2+βgel+λg (5) and shown in figure 8, and k = αk el2+βkel+λk (6) shown in figure 9 where: αg = -0.001, βg = 1.398, λg = 862.4, r2 = 0.996 for “g”; and αk = 9x10-8, βk = -1x10-4, λk = 0.112, r2 = 0.975 for “k”. within the limits of dependability of r2 from 0.975 to 0.996, equations (5) and (6) can be used to obtain best values for “g” and “k” for specified values of “el”. from that, π1 = σδz/z can be computed for specified values of the governing variables in π2. figure 8: coefficient “g” of π1 versus π2 against el figure 9: exponent “k” of π1 versus π2 against el 3.2.3 coefficient in the polynomials table 8 shows the respective values of α, β and λ for g and k. the correlation coefficient of y with x varied from 0.987 to 0.988 each indicating a high confidence level of statistical significance. table 8: the polynomial coefficients data matrix for calculating the coefficients and exponents of sandy loam soil degree of compaction equation: π1 = gπ2k function y = αx2+βx+λ correlation y x α β λ r t-test g k el el -0.001 9x10-8 1.398 -1x10-4 862.4 0.112 0.988 0.987 hs* hs * = highly significant at 99.95 confidence level. 3.3 comparison of the estimator with the measured values of degree of compaction table 9 shows the calculated values of the degree of compaction (π1)c (i) = gπ2k and its corresponding ratio with measured value (π1)m= σδz/z. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 789 table 9: comparison of estimated values with measured value of degree of compaction of sandy loam soil s/no variables validation test 1 2 1. 2. 3. measured π1 = σδz/z gπ2k ratio, %100[gπ2k/(σδz/z)] 0.2357 0.2167 97.79 0.2357 0.1745 97.98 from the above data, it is obvious that the function gπ2k estimated the degree of compaction of sandy loam soil accurately; g and k could be correlated significantly with el in this study. 4. conclusion the foregoing has described a study of compaction behaviour of a sandy loam soil. among many others, eleven quantifiable factors believed to be governing the compaction, σδv of the soil volume v have been identified and grouped to develop a multivariate compaction function using a “drop-weight” compactor designed and constructed for this study. from table 8, g and k can be computed for use in estimating the degree of compaction π1 = σδz/z = σδv/v for any combination of the eleven governing factors encapsulated in π2 as π1 = gπ2k. the other estimator aπ2b is weak. it needs more data from many other soils to characterize “a” and “b” more vigorously. two validation test results show that the procedure is durable for a large number and a wide range of operating variables with respect to sandy loam soil and “dropweight” compactor. the two estimators passed the t-test of statistical significance of correlation r of estimator with measured values of degree of sandy loam soil compaction. the usefulness of the procedure is that one does not need to carry out trial compaction tests to know the degree of compaction of sandy loam soil from a given borrow site before knowing its response to a given set of operating conditions, provided the easy-to-measure variables in π2 are known. references aashto 1995. standard no. m – 145 – 191 in soil engineering classification 2001. national soil survey hand book, 618. http://www.ohioagriculture.gov/pubs/curr/rules. accesed 2nd january, 1999. astm 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ohioagriculture.gov/pubs/curr/rules nyle, cb. and ray, rw. 1999. the nature and properties of soils. 12th edition. prentice hall. pp. 118-125. shaqour, fm. 2004. hydro-compaction of sand fills. university of jordan, amman. pp. 6-8 shestack, cj. and busse, md. 2005. compaction alters physical but not biological indices of soil health. soil science society of america journal, 69: 236-246. soil compaction handbook 2005. soil compaction-soil types, methods and compaction techniques. http://www.concrete-catalog.com/soil_compaction sowers, gf. 1960. introductory soil mechanics and foundations. geotechnical engineering. mcgraw-hill, new york, pp. 99. sutton, bhc. 1986. solving problems in soil mechanics. john wiley and sons, new york. pp. 234. http://www.dnr.state.oh.us/water http://www.forester.net/ecm_0209_optimizing http://en.wikipedia.org/w/index.php http://www.ce.washington.ed/geotech/courses/cee366/kramar/exercise http://www.concrete-catalog.com/soil_compaction http://www.dnr.state.oh.us/water file:///c:/users/user/downloads/azojete143/www.azojete.com.ng audu, et al: effects of soil properties and operational variables on the compactibility of a sandy loam soil. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: danladimsh@gmail.com 791 timothy, d., stark, f., hangseok, c., chulho, l. and brian, q. 2012. compacted soil linear interface strength importance. journal of geotechnical and environmental engineering, astm, 134(4): 544-550. yahaya, i. 2015. analysis of rainfall variability in north-eastern nigeria. m. sc. thesis, department of geography, bayero university, kano, pp.73. watson, i. and burnett, ad. 1995. hydrology and environmental approach. buchanam books, cambridge, pp.702. werkmeister, s. 2003. permanent deformation behaviour of unbound granular materials in pavement construction. m. sc. thesis in university of technology, dresden, germany, 10th february, 2013. pp.79 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):375-386 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 375 original research article microstructure and thermal analysis of brake pads developed from asbestos-free materials j. abutu1*, s. a. lawal2, r. a. lafia-araga3, m. b. ndaliman2 and m. a. oluleye4 1department of mechanical engineering, taraba state university, jalingo-nigeria 2 department of mechanical engineering, federal university of technology, minna-nigeria 3department of chemistry, federal university of technology, minna-nigeria 4department of mechanical engineering, faculty of engineering, ekiti state university, ado-ekiti *corresponding author’s email address: abutu.joseph@tsuniversity.edu.ng 1.0 introduction friction materials are heterogeneous substances composed of different constituents. each constituent element performs its own functions. these include improvement in frictional properties at low and high temperature, increase in strength, reduction in noise, prolonged life, rigidity and reduced porosity (natarajan et al., 2012). changes in the weight percentage or composition may lead to the alteration of the thermal, morphological, chemical, physical and mechanical properties of the developed brake pad materials (jang et al., 2004, mutlu et al., 2005, cho et al., 2005, zaharudin et al., 2011). early researchers have concluded that no simple relationship exist between properties of frictional materials (talib et al., 2012, tanaka et al., 1973). industrial brake pads are usually made up of large number of constituents such as fibres, metallic chips, solid lubricants, ceramic particles, minerals, and elastomers in a matrix material like phenolic resin. the use of antimony in brake pads was investigated by ole-von et al. (2005) and it was found that the use of antimony in brake pad should be suspended as it posed a human cancer risk due to considerable antimony concentrations in the material. the use of agricultural wastes is also rising as inexpensive and new materials in brake pads development, with environmental acceptability and commercial viability (bhaskar and vinay, 2013). cyras et al. (2001) reported that among the different kinds of agricultural products investigated, lignocellulose fillers such as coconut shells are most times seen as attractive article information abstract this study was conducted on developed asbestos-free brake pad using coconut shell and seashell as fillers. the use of hazardous reinforcement like asbestos fiber in friction materials is being avoided because of its carcinogenic effects. rule of mixture technique was utilized during sample formulation and a weight percent of 52% filler material, 5% friction modifier, 8% abrasive and 35% binder were utilized for production. a multi-response optimization technique (grey relational analysis) was used to obtain an optimal process parameter of moulding pressure (14 mpa), moulding temperature (140ºc), curing time (8 minutes) and heat treatment time (5 hours) for coconut shell-filled brake pad and moulding pressure (14 mpa), moulding temperature (160ºc), curing time (12 minutes) and heat treatment time (1 hour) for seashell-filled brake pad. thermal analysis of commercial and optimized samples shows that the commercial brake pads possesses a better thermal stability compared to the optimized formulated brake pad samples with the coconut shell-filled samples showing the least thermal resistance. also, microstructure analysis of the impact fractured surfaces of the commercial, seashell and coconut shell-filled brake pad was conducted using scanning electron microscope (sem). the results revealed that compare the commercial and seashell-filled samples, there were more uniform distribution of the resin in the coconut shell-filled composite leading to an improved bonding and closer interpacking distance between its constituent particles and the epoxy resin. it was also revealed that the commercial brake pad possessed a higher thermal stability as the components were not noticeably degraded at temperatures at which the coconut shell and the seashell filled brake pads showed appreciable degradation. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 feb., 2019 revised 07march, 2020 accepted 10march, 2020 keywords: brake pad; microstructure; thermogravimetric analysis; seashells; coconut shells. http://www.azojete.com.ng abutu et al: microstructure and thermal analysis of brake pads developed from asbestos-free materials. azojete,16(2):375-386. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 376 materials to be utilised as fillers due to its excellent properties. microstructure and thermal examination of newly developed formulations are required to assess their performance using microscopy and thermal stability testing with the aim of ascertaining that the developed brake pad meets the minimum requirements of its intended use (talib et al., 2012). in a related study, aigbodion et al. (2010) developed an asbestos-free brake pad using sugar cane bagasse as reinforcement and studied the microstructure and thermal resistance. the authors reported that there was more uniform distribution of the bagasse within the resin, as the particles size of the bagasse decreased. ikpambese et al. (2014) investigated the microstructure of worn surfaces of palm kernel fibre-reinforce pads. the result of the microstructural examination revealed that worn surfaces were characterized by abrasion wear, where the asperities were ploughed thereby exposing the white region of palm kernel fibres, thus increasing the smoothness of the friction materials. yawas et al. (2016) also used scanning electron microscope to study the distribution of periwinkle shell particle in phenolic resin using different sieve sizes. the results showed that the microstructures of samples revealed a homogeneous distribution as the sieve sizes decreased. similarly, ruzaidi et al. (2011) studied the microstructure of fractured surfaces of palm ash and pcb waste-containing friction material. overall observation shows the mixture of the brake pad materials were well dispersed even though there are some traces of pores due to the different particle size of each mixture. lawal et al. (2016) also studied the thermal degradation behaviour of rubber-scrap filled brake pad. the results indicate that the formulated sample degraded between 149.9 and 478.4 °c, with peak degradation at temperature 394.8 °c. in addition, the thermal decomposition of calcium carbonate (caco3) and seashells were studied by islam et al. (2013) and nurfatirah et al. (2015) respectively and the results showed that the decomposition pattern revealed two distinct phases. the first phase began with a minimum loss in weight while the second phase started at 580ºc and stopped at 815ºc. andrzej et al. (2010) studied the thermal stability of soft wood fiber, coconut shell and barley husk filled polypropylene composite and revealed that the total moisture content by fiber was removed before 150ºc while the decomposition temperature for coconut shell, barley husk and soft wood fiber were at 195°c, 235°c and 245ºc respectively. also, the thermal decomposition of calcium carbonate in cockle shell was also studied by mustakimah et al. (2012) using thermogravimetric analyzer and reported that as the temperatures increased from 700900°c, a quick change in weights of the samples occurred as the volatile material attempted to escape at the start of decomposition process. the thermal decomposition kinetics of epoxy resins in nitrogen-oxygen environment was also studied by chen et al. (1997) using a heating conditions of 20, 10, 5, and 2 k/min and revealed that under pure nitrogen atmosphere,only one peak temperature (459ºc) was found. also, yasmin and daniel (2004) studied the thermal stability of graphite/epoxy composite and revealed that a very high thermal stability was exhibited by pure graphite with only 1.6% of the entire weight of graphite lost at a temperature of 800ºc. the authors concluded that the inclusion of the graphite in composite production improved its thermal stability therefore, in this study, two material (seashells and coconut shells) combined separately with other additives (graphite and alumina) were used to develop pads using powder metallurgy technique employing statistical method such as grey relational analysis (gra) and response surface methodology experimental design. the morphology and thermal behaviour of the developed materials were also investigated with the aim of comparing the microstructure and thermal stability of the various constituents of the developed and commercial brake pad sample. 2. materials and methods 2.1 materials aluminium oxide (lot. no. 44100; cat. no. 34143) obtained from a commercial chemical shop in onitsha, anambra state, nigeria. this material was included to serve as an abrasive. graphite powder (friction modifier) was sourced from used 1.5 volt tiger head dry cell batteries. epoxy resin (epoblock, fip chemicals) was used together with a hardener (sikadur 42t; sika corporation u.s.a) and were obtained from a chemical store located in onitsha, anambra state, nigeria. coconut shells were obtained from a coconut trader in a sabon-tasha market in kaduna, nigeria while seashells (the shells of sea snails) were collected from a local http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 375-386. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 377 seafood vendor in lagos bar beach, lagos, nigeria. seashells and coconut shells (figure 1) were used as fillers. a. seashells b. coconut shells figure 1: fillers 2.2 methods 2.2.1 materials preparation as adopted by ikpambese et al. (2014) and abutu et al. (2018), the method involved in the preparation of the fillers (coconut shell and seashell) as well as graphite powder included washing of sourced materials, followed by cleaning with dried cloth and thereafter drying in an air circulating oven of 150ºc operating temperature. further preparation process involved crushing of the oven-dried filler materials with pestle and mortar as well as grinding using a grinder and finally sieving using a 10 µm. 2.2.2 formulation of brake pad in this study, rule of mixture (rom) was utilized in the formulation of the brake pads. this technique will help predict the brake pads properties and also provide information about the percentage composition of each constituent material in the developed brake pads. as suggested by ikpambese et al. (2014), sample formulation was based on 176g standard weight of commercial brake pad. eqns. 1 and 2 were utilized in the calculation of volume fraction (f) and theoretical densities (d) of the brake pads respectively (askeland, 1985).    j j i i i d p d p ffractionvolume (1) bbfmfmaafcomposite fdfdfdfdd  f (2) where: pj and pi is the weight percent of the total and individual constituent respectively, fi is the individual volume fraction. dj and di are densities of total and the individual constituents respectively. dcomposite is the theoretical densities of the seashell or coconut shell filled composite, df and ff are the density and volume fraction of the filler, da and fa are the density and volume fraction of the abrasive, dfm and ffm are the density and volume fraction of the friction modifier while db and fb are the density and volume fraction of the binder. 2.2.3 experimental design and grey relational analysis in this study, central composite design (ccd) via response surface methodology (rsm) and grey relational analysis (gra) was used to obtain optimal brake pad composite. this experimental design was built using minitab 17 software in accordance with standard rsm’s l27 (2)4 where mt (molding temperature), mp (molding pressure), ct (curing time) and htt (heat treatment time) were chosen as the process parameters. the data obtained from mechanical and tribological examination of samples produced using ccd experimental design were used to conduct grey relational analysis (gra) with the aim of obtaining optimal process parameters that will give the multi-response optimal performance in terms of its microstructure and thermal behaviour. grey relational grades (gr-grades) represent the average of grey relational coefficient (grc) of individual responses investigated. abutu et al. (2018) reported that grey relational coefficient can be calculated using eqn. 3. ij ijoj kk    max minmax),(    (i = 1, 2, . . . ,27 and j = 1, 2, . . . , 27) (3) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abutu et al: microstructure and thermal analysis of brake pads developed from asbestos-free materials. azojete,16(2):375-386. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 378 where: ɳ(k0j, kij ) is the grc between kij and k0j , ij = k0j –kij, min = min ( ij, i = 1, 2, . . . , m; j = 1, 2, . . . , n), ω is the distinguishing coefficient, ω ∈ [0, 1] and max = max ( ij, i = 1, 2, . . . 27; j = 1, 2, . . . ,27) ω was introduced in order to modify (compress or expand) the range of grc. yiyo et al. (2008) reported that, ω = 0.5, max= 1 and min= 0. 2.2.4 production of brake pad samples using optimized values production of optimized samples was carried out on a compression moulding machine (model; 0577-86365889, wenzhou zhiguang shoe-making machine co. ltd, china) using standard procedure specified by chemiplastica (2010) and abutu et al. (2019). 2.2.5 thermogravimetric analysis (tga) thermogravimetric analysis was conducted on between 10 to 20 mg samples on platinum pans using perkin elmer pyris tga 1, (usa), at a heating rate of 10.00°c/min from 50 to 950°c in nitrogen atmosphere at a flow rate of 20 ml/min. the weight change with temperature was analysed using the pyris software. peak degradation temperature (tp) was recorded as the temperature at which maximum degradation of the material occurred. this represents the peak of the derivative weight change with time. 2.2.6 microstructural analysis impact fractured surfaces of the optimized and commercial samples were observed using scanning electron microscope (tescan vegan iii xmu q150 te, usa), operating at an accelerating voltage of 10 kv after gold sputter coating at the characterisation laboratory of shehu musa ya’radua university, kastina, kastina state, nigeria. this result was achieved by clamping the specimen on the mechanical part of the microscope and using the adjustment knob to adjust the lens of microscope. immediately a clear image was observed at the specified magnification, the process was stopped, and the image captured on the computer connected to it with the aid of software was saved. 3. results and discussion 3.1 design matrix and grey relational analysis table 1 shows the process factor levels, while table 2 shows the experimental design matrix for rsm -ccd and the grgrades for seashell and coconut shell-filled brake pads obtained from gra. table 1: process factor levels factors level 1 level 2 level 3 level 4 level 5 htt (hr) 2.0 4.0 3 1 5 ct (min) 6.0 10.0 8 4 12 mt (ºc) 120 160 140 100 180 mp (mpa) 12 16 14 10 18 table 2: experimental matrix for rsm -ccd and gr-grades ru n experimental design gr-grade htt (hour) ct (minute) mt (ºc) mp (mpa) seashell-filled sample coconut shell-filled sample 1 2 6 120 12 0.4242 0.6346 2 2 6 120 16 0.4521 0.6031 3 2 6 160 12 0.5588 0.6731 4 2 6 160 16 0.4669 0.5305 5 2 10 120 12 0.4707 0.8122 6 2 10 120 16 0.4850 0.5197 7 2 10 160 12 0.7349 0.5588 8 2 10 160 16 0.4780 0.5739 9 4 6 120 12 0.5271 0.4421 10 4 6 120 16 0.5647 0.6392 11 4 6 160 12 0.5748 0.5592 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 375-386. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 379 12 4 6 160 16 0.6528 0.4211 13 4 10 120 12 0.4531 0.7152 14 4 10 120 16 0.5049 0.6085 15 4 10 160 12 0.7076 0.5979 16 4 10 160 16 0.8833 0.6630 17 3 8 140 10 0.5967 0.5481 18 3 8 140 18 0.3976 0.5689 19 3 8 100 14 0.6236 0.6209 20 3 8 180 14 0.4411 0.5622 21 3 4 140 14 0.5040 0.4482 22 3 12 140 14 0.6596 0.5577 23 1 8 140 14 0.8748 0.6360 24 5 8 140 14 0.6077 0.7403 25 3 8 140 14 0.5987 0.7193 26 3 8 140 14 0.6288 0.7375 27 3 8 140 14 0.6086 0.7355 the resulting process parameters factor effects for seashell and coconut shell-filled samples are shown in tables 3 and 4. the values in bold indicates the multi-response optimal level for each process parameters. the main effect plots obtained using table 3 and 4 are shown in figure 2 and 3. table 3: factor effects of process parameters (seashell-filled samples) factor level 1 level 2 level 3 level 4 level 5 htt 0.8748 0.5088 0.5621 0.6085 0.6077 ct 0.5040 0.5277 0.5975 0.5897 0.6596 mt 0.6236 0.4852 0.6085 0.6321 0.4411 mp 0.5967 0.5564 0.6163 0.5610 0.3976 table 4: factor effects of process parameters (coconut shell-filled samples) factor level 1 level 2 level 3 level 4 level 5 htt 0.636 0.6132 0.6109 0.580775 0.7403 ct 0.4482 0.5629 0.6521 0.63115 0.5577 mt 0.6209 0.6218 0.6324 0.572188 0.5622 mp 0.5481 0.6241 0.6397 0.569875 0.5689 figure 2: plots of factor effects (seashell-filled samples) figure 2: plots of factor effects (seashell-filled samples) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abutu et al: microstructure and thermal analysis of brake pads developed from asbestos-free materials. azojete,16(2):375-386. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 380 figure 3: plots of factor effects (coconut shell filled samples) from figure 2, it can be observed that the optimum values of seashell-filled brake pad can be obtained using 1 hour heat treatment time, 12 minutes curing time, 160 ºc moulding temperature and 14mpa moulding pressure while figure 3 shows that optimum values of coconut shell filled brake pad samples can be obtained using 5 hours heat treatment time, 8 minutes curing time, 140 ºc moulding temperature and 14 mpa moulding pressure. these results are in conformity with earlier work of dagwa and ibhadode (2006), who reported htt (2 hours), ct (8 minutes), mt (160ºc) and mp (16.74mpa) as optimal process parameter using palm kernel shells as filler material. 3.2 optimized samples during the production of the optimized samples, the optimal process parameters obtained using gra as shown in figure 2 and 3 were used while the composition of the samples formulated using rule of mixture (table 5) remained constant throughout the process. as suggested by abutu et al. (2018), preliminary preparation involved pouring 41.06 g (23.33 %) of the resin into a container followed by the addition of 20.54 g (11.67 %) of hardener (catalyst). the mixture of hardener and resin were stirred manually in a separate stainless steel bowl until homogenous mixture was observed while mixture of the weighed fillers (shells, friction modifier and abrasive) were also manually stirred in another separate stainless steel bowl. the entire mixture was afterward transferred into a fabricated mould of size 124 x 112 x 10 mm for compression moulding, using the optimized process parameters. the final products (figure 4) were subjected to further heat treatment using the optimal htt presented in figure 2 and 3 with the aid of a hot air oven (150°c). table 5: composition of optimized brake pad sample ingredient filler (coconut shell or seashell) binder (epoxy resin) binder (hardener) abrasive (alumina) friction modifier (graphite) percentage composition (%) 52 23.33 11.67 8 5 mass composition (g) 91.52 41.06 20.54 g 14.01 8.80 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 375-386. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 381 (a) coconut shell-filled samples (b) seashell-filled samples figure 4: heat treated optimized samples (a) seashell and (b) coconut shell filled brake pad samples 3.3 thermogravimetric analysis (tga) the results of tga and derivative thermogravimetric (dtg) analysis for commercial as well as coconut shell and seashell filled brake pads are presented in figures 5 and 6. data extracted from these thermograms are presented in table 6. the temperature range used in this experiment is below the degradation temperature for all the components of the commercial and the seashell brake pads. fig. 5: tga curves of coconut shell, seashell and commercial brake pad. fig. 6: dtg curves of coconut shell, seashell and commercial brake pad file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abutu et al: microstructure and thermal analysis of brake pads developed from asbestos-free materials. azojete,16(2):375-386. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 382 table 6: tga data for coconut, sea shell filled and commercial brake pads sample onset temperature, tonset 1 (°c) onset temperature, tonset 2 (°c) peak degradation temperature, tp1 (°c) peak degradation temperature, tp2 (°c) peak degradation temperature, tp3 (°c) coconut shell 308.6 none 350.5 475.7 sea shell 394.3 806.4 427.1 473.1 897.6 commercial 400.2 824.1 415.3 514.1 903.2 due to the fact that there is no concise data relating to the components of the commercial sample, the thermal degradation pattern of only the coconut and seashell filled samples will be discussed. however, a comparison was made with the commercial sample with respect to thermal stability. in addition, from the tga residue, the commercial samples were found to contain asbestos fibres. this may be responsible for the superior thermal properties of the commercial sample as indicated by the thermal degradation profile of the optimized coconut shell-filled, seashell-filled and commercial sample shown in the tga and the dtg curves in figure 5 and 6 respectively. similar degradation profile was observed for the coconut and the seashell brake pads, although the events occurred at different temperatures. an initial degradation is seen below 250°c. a close observation of this event revealed two overlapping events which occurred between 100 and 150°c. evaporation of moisture from the samples took place at this stage. also, another shoulder overlapping with this event up till 250°c could also be seen which may be attributed to the release of volatiles from the samples. this release of volatiles is more pronounced in the coconut shell than in the seashell samples and could be as a result of the extractives present in the coconut shell and the hardener used in the formulation. a small shoulder in the coconut-filled brake pad is also seen at about 350°c. this is attributed to the degradation of hemicelluloses in the coconut shell (chun et al., 2013a). hemicellulose has been reported to be the most thermally unstable component of a lignocellulosic material (chun et al., 2013b). from the coconut shell filled brake pad, it is evident that an overlap occurred in the thermal degradation of cellulose and lignin and the epoxy resin by the broad peak overlap between 350 and 400°c. this is in agreement with earlier works yasmin and daniel (2004) as well as chun et al. (2013a). while chun et al. (2013a) reported a degradation of the cellulose and lignin in coconut shell to have occurred between 350 and 400°c in coconut shell/polylactic acid eco-composites. also, yasmin and daniel (2004) investigated the mechanical and thermal properties of graphite platelet/epoxy composites and reported a thermal degradation of epoxy resin to have started at about 366°c and ended at 450°c in 5% graphite filled epoxy composites. it is worth mentioning that the optimized brake pad contains 5% graphite. in the optimized seashell filled brake pad, a clear degradation peak is seen at about 427°c. this peak occurred at a lower temperature in the commercial (412°c) and coconut shell filled brake pad (400°c). this indicates that the thermal degradation of the epoxy in the seashell composites occurred at a higher temperature than in the coconut shell filled brake pad. apart from the fact that the seashell is more thermally stable than the coconut shell, it is clear that incorporating seashell in an epoxy resin significantly improved its thermal stability. this is because seashell has been found to contain between 9599% by weight of calcium carbonate, caco3 (marin and luquet, 2004). hongwei et al. (2011) reported that incorporating nano calcium carbonate in epoxy improved the thermal stability of the resultant composites. the degradation of alumina in the brake pad is seen around 473.1°c in the seashell filled, 475.7°c in the coconut filled and 514.1 °c in the commercial brake pad samples. this is in line with the findings of schwentenwein and homa (2015) that investigated a new process for additive manufacturing of dense and strong ceramic objects and showed that the thermal degradation of alumina occurred between 400 and 500°c. contrarily, ramousse et al. (2001) reported that graphite in iron filled brake pads decomposed thermally between 688 and 850°c. while schwentenwein and homa (2015) examined the thermal decomposition of graphite in ceramic based composites, ramousse et al. (2001) reported the thermal behaviour of graphite in iron-filled brake pads. the differences in the materials used may have accounted for the different degradation temperatures reported. another degradation event could be seen at about 900°c, which is attributed to the decomposition of caco3 present in the seashell to cao. nurfatirah et al. (2015) reported that http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 375-386. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 383 at temperature of 815ºc, a rapid weight loss occurred in seashell as caco3 decomposes into cao. however, this event could not be captured completely as the temperature range of the experiment is below this degradation event. therefore, in this study, an environmentally friendly brake pad was produced with competitive thermal stability with the commercial brake pad. it is worth noting that these brake pads can be used in an automobile system whose braking temperature do not exceed 350°c for coconut shell-filled and 427°c seashell-filled brake pads. 3.2 microstructure analysis the microstructure of impact-fractured surfaces of commercial and optimized samples observed at magnification on a scanning electron microscope (sem) is shown in figure 7. commercial sample coconut shell filled sample c. seashell filled sample figure 7: microstructure of impact fractured surfaces of brake pad pamples at 1000x magnifications the microstructures of the fractured surfaces shown in figure 7 indicate the uniform distribution of various additives (seashell, coconut shell, graphite and alumina) in the friction materials. overall observation indicates that the particles of the brake pad samples show good dispersion even though there are more traces of micro-voids in seashell-filled than in the commercial and coconut shell-filled samples. these differences in the level of voids present on each sample may be due to the variation in filler materials and process parameters used during production. luka et al. (2016) studied the microstructure of a fiber/resin composite using sem and found that the amount of voids in the composite was dependent on the fibre/resin content and processing conditions which in turn affect its performance. also, it can be observed that all the fractured surfaces show basically brittle behaviour. surfaces presented in figure 7(a) shows the presence of asbestos fibres with patches of matrix adhering on the surfaces. in addition, figure 7(b) revealed that there was more uniform distribution of the fillers in the resin, leading to better bonding between the epoxy resin and the filler in the coconut shell filled brake pad when compared to constituents of the seashell-filled samples as shown in figure 7(c). abutu et al. (2019) had reported better mechanical properties exhibited by these coconut shell-filled brake pads. also, plate i(c) revealed an agglomeration of constituent particles as two particles were observed to be contacting each other with patches of resin adhering to the surfaces. these results are in agreement with the previous work of yawas et al. (2016), who studied the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abutu et al: microstructure and thermal analysis of brake pads developed from asbestos-free materials. azojete,16(2):375-386. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 384 microstructure of periwinkle shell filled brake pad and reported that the distribution of particles is influenced by good bonding properties of the binder and its constituent particles which in turn, lead to better interfacial interaction. 4. conclusion seashell and coconut shell were used as asbestos-free fillers to produce brake pads. the properties of formulated multi-response optimized friction materials were investigated by examining their thermal degradation behaviour and microstructure. the following conclusions can be drawn: from the grey relational analysis conducted, the seashell-filled brake pad should be produced using 14 mpa moulding pressure, mt of 160 ºc moulding temperature, 12 minutes curing time and 1 hour heat treatment time while coconut shell-filled brake pad should be produce using 14 mpa moulding pressure, mt of 140 ºc moulding temperature, 8 minutes curing time and 5 hours heat treatment time. the microstructure of the developed coconut shell-filled brake pads gave a more uniform distribution of the fillers leading to better bonding and closer inter-packing distance compared to seashell-filled and commercial brake pad. thermal analysis shows that the commercial and seashell filled brake pad show better overall thermal resistance compared to coconut shell filled brake pads. finally, the thermal degradation profile revealed that the developed coconut shell brake pad can be applied in an automobile whose braking temperature do not exceed 350°c, while the seashell-filled brake pad can be applied in an automobile system whose braking temperature do not exceed 427°c. overall, the commercial brake pad possessed a higher thermal stability as the components were not noticeably degraded at temperatures at which the coconut shell and the seashell filled brake pads showed appreciable degradation. acknowledgement the authors are thankful to the management of federal university of technology minnanigeria for the grant senate/futminna/2015/03, allocated to this research. conflict of interest: the authors declare that they have no conflict of interest in publishing this article. references abutu, j., lawal, sa., ndaliman, mb., lafia-araga, ra., adedipe, o. and choudhury ia. 2018. effects of process parameters on the properties of brake pad developed from seashell as reinforcement material using grey relational analysis. engineering science and technology, an international journal, 21: 787–797. abutu, j., lawal, sa., ndaliman, mb., lafia-araga, ra., adedipe, o. and choudhury, ia. 2019. production and characterization of brake pad developed from coconut shell reinforcement material using central composite design. sn applied sciences, 1:18. aigbodion, vs., agunsoye, jo., hassan, sb., asuke, f. and akadike, u. 2010. development of asbestos-free brake pad using bagasse: tribology in industry, 32(1): 12-18. andrzej, kb., abdullah, am. and jürgen, v. 2010. barley husk and coconut shell reinforced polypropylene composites: the effect of fibre physical, chemical and surface properties, composites science and technology, 70: 840–846. askeland, dr. 1985. the science and engineering of materials. massachusetts, pws publishers: u.s.a. bhaskar, j. and vinay, ks. 2013. physical and mechanical properties of coconut shell particles filled-epoxy composite. journal of materials and environmental science, 4(2): 227-232. chemiplastica 2010. thermoset processing manual compression molding, retrieved from, http://www.chemiplastica.com/pdf/compression-molding-guidelines.pdf, accessed on 5 august, 2015. http://www.chemiplastica.com/pdf/compression-molding-guidelines.pdf http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abutu.joseph@tsuniversity.edu.ng 386 ruzaidi, cm., mustafa, ab., shamsul, jb., alida, a. and kamarudin, h. 2011. morphology and wear properties of palm ash and pcb waste brake pad. international conference on asia agriculture and animal ipcbee held in singapore, 2-3 july 2011, proceedings pp. 145-149. schwentenwein, m. and homa, j. 2015. additive manufacturing of dense alumina ceramics. international journal of applied ceramic technology, 12(1): 1–7. talib, rj., mohmad, ss. and ramlan, k. 2012. selection of best formulation for semi-metallic brake friction materials development. katsuyoshi kondoh (ed), powder metallurgy, pp. 1-13, intech publisher, shanghai, china. tanaka, k., ueda, s. and noguchi, n. 1973. fundamental studies on the brake friction of resinbased friction materials. wear, 23(3): 349-365. yasmin, a. and daniel, im. 2004. mechanical and thermal properties of graphite platelet/epoxy composites. polymer, 45(24): 8211–8219. yawas, ds., aku, sy. and amaren, sg. 2016. morphology and properties of periwinkle shell asbestos-free brake pad. journal of king saud universityengineering sciences, 28(1): 103-109. yiyo, k., taho, y. and guan, wh. 2008. the use of a grey-based taguchi method for optimizing. multi-response simulation problems. engineering optimization, 40(6): 517–528. zaharudin, a.m., berhan, m.n., and talib, r.j. 2011. the effect of phenolic resin, rubber, calcium carbonate and graphite on tribological characteristic of semi-metallic brake. aip conference proceedings held in antalya, turkey, 12–15 may 2011, 1400: 274–279. http://dx.doi.org/10.1016/j.jksues.2013.11.002 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):337-350 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 337 original research article hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria b. a. ankidawa1*, j. m. ishaku2 and s. p. ahmadu2 (1department of agricultural and environmental engineering, school of engineering and engineering technology, modibbo adama university of technology, pmb 2076, yola, nigeria 2department of geology, school of physical sciences, modibbo adama university of technology, pmb 2076, yola, nigeria) *corresponding author’s email address: ankidawa03@yahoo.com 1.0 introduction gullies are widely spread in nigeria and it has adverse effect on agricultural productivity (okunlola et al., 2014; obiefuna et al., 2018). some effects of erosion include major changes to the patterns of overland flow causing sedimentation in watercourses and leading to increased rates of erosion where more subsoil material is exposed. sedimentation and increased flooding affecting fences, farms and public roadways. bank erosion problems. in the area of erosion, grove (1951) defined erosion as the progressive removal of surface sediment from the parent mass by wind and water and often followed by localized intense erosion producing gullies. based on the predominant erosion mechanism, onuoha and uma (1987) classified the active gully spots into three; the first group is composed of gully due to accelerated erosion which is called the classical gully erosion and the second group involved mass wasting, landslides, slumping and soil creep. floyd (1965) and egboka and nwankwo (1979) attributed the original and growth of complex gullies of the south eastern nigeria to the effect of agricultural and human activities. ishaku et al. (2002) noted that the loose nature of geologic materials, high permeability and shallow water table in the rainy season influenced the growth and development of gullies in lassa area of adamawa state. the rise in water table tends to reduce the effective stress of the materials and increase the hydrostatic pressure. it also reduces the shear strength of the article information abstract the research area is characterized by problems of gully erosion which have resulted in the destruction of roads and uprooting trees of economic importance. reduction in the area of arable and other agricultural land, which become divided into smaller parcels and leads to increased farming cost. hydrogeological and engineering investigations were conducted in zing and environs, taraba state of nigeria to characterize the rock materials that aid gully erosion in the area. the methods involve three (3) stages, reconnaissance survey, detailed field mapping and laboratory analysis. the area is underlain by porphyritic granite and biotite granite. the geologic structures include fractures, dykes, and veins which trend nnw to sse, nw-se and nne to ssw. the results of geotechnical parameters indicate that the plastic limit ranges between 0 to 24.2%, liquid limit ranges from 20.1% to 43.9%, plasticity index ranges between 11.2 to 19.7%. the coefficient of uniformity ranges between 4.2 and 11.5 while the coefficient of curvature ranged between 0.53 and 1.99. the optimum moisture content was from 8.3 to 9.8%, while maximum dry density is from 1.75 to 1.91mg/m³. the angle of internal friction was between 28° to 40°, while the cohesion is between 0 to 54kn/m². the statistical grain size methods gave hydraulic conductivity values ranging from 2.35 x 10-3m/s to 8.64 x 10-5m/s. the hydraulic head distribution map indicates that the gully sites are located in the discharge areas. the discharge areas are characterized by high hydrostatic pressure which decreases effective stress and in turn reduces the shear strength of materials, enhance, internal erosion in form of piping and cave ins in the discharge areas. from the results of the study, recommendations such as sand mining/excavation along the rivers should be avoided, ridging perpendicular to river bank are reduced, dumping of refuse on the river channels and floodplains should be discouraged and houses should not be constructed along the river banks. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2019 revised 02 february, 2020 accepted 08 february, 2020 keywords: hydro geological properties geotechnical properties gully erosion zing and environs nigeria mailto:ankidawa03@yahoo.com http://www.azojete.com.ng mailto:ankidawa03@yahoo.com ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 338 materials, enhanced internal erosion in form of piping and cave-ins in the discharge areas. obiefuna and simon (2010) carried out geological and geotechnical assessment of gully sites in jada area, northeastern nigeria. the geotechnical results of the soil samples indicate that the susceptibility of the materials to gully formation is due to its highly weathered nature and low silt/clay content of sites. the plasticity index is generally slightly low to medium, indicating that the soil has low to medium dry strength and hence can easily be crushed by fingers. therefore, it offers little resistance to gully erosion. compaction test results indicated that the maximum dry density values are generally low signifying that the soil is not compact but loose and thus susceptible to erosion. mbagwu and bazzofi (1998) worked on soil characteristics related to the resistance of breakdown of dry soil aggregation by water drops. soil samples collected from north central italy were analyzed in the laboratory. the result showed that soil properties determined the resistance of the soil aggregates to water drop impact, using the clay content which was the highest. muoghalu and ikegbunam (1997) studied “gully erosion in abagana, anambra state”, using the experimental analysis and horton’s calculation of slope length. the eroding force per unit area was calculated for various slopes at 17 locations. from the result derived, it was discovered that slopes between 2.3° and 7° were found in the lowland areas and it was in those areas that most of the gullies abounded at a general elevation of 122mm to 18m. ezechi (2000), in his work on the influence of runoff and lithology in the rate of gullies in the eastern nigeria, using the geological model, he reported that in certain areas of the south eastern region where lithologies are weak and the eroding energy of runoff maximum, the susceptibility of such areas to gully erosion was high. he urged that before any construction activity, the lithology of the area should be adequately examined. the research is aimed at determining the hydrogeological and engineering parameters of rock materials that aid in gully erosion in zing and environs. 2.0 the study area the study area lies between latitudes 8°36′ 00″ to 9° 00′00″n and longitudes 11° 43′00″ to 11° 47′ 00″e (figure 1) and covers an area of about 54km². the area is bounded to the east by mayo-belwa and to the north by jada local government area of adamawa state and to the west and south by yorro local government area of taraba state. the climate of the area is typically a tropical climate marked by two distinct seasons; dry and rainy seasons. the mean annual rainfall in the area ranges from 819-1761 mm (ray and yusuf, 2011). the rainfall starts from april and ends in october. the onset of the rains is april, with low amount but increases gradually reaching a maximum in august, and drops gradually with cessation in october. according to areola (1983), the study area is characterized by hydromorphic and ferruginous tropical soils which are highly influenced by local variation in altitude and human interference. the soil type is a mixture of loams and sands, and on the hilly terrain it is deep loamy found in between rocks (ray and yusuf, 2011). along the banks of streams and rivers are clay loam soils which support the growth of a variety of crops in the area. the area is located within the savannah grassland belt, particularly in the guinea savannah sub-region which is characterized by scattered, deciduous tall trees with broad leaves and tall grasses (ogidiolu, 2000). on relief configuration, the study area is categorized into two zones, highland/mountain range and lowlands. the highlands occupy the southern region stretching from west to south in chains of mountain (shebshi mountains), with elevation ranging from 1,800-2,400 meters above mean sea level (areola, 1983). he further stated that the lowland occupies about 60% of the region hosting most of the settlements in the region. http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 337-350. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 339 figure 1: map of the study area showing locations of gully sites and other infrastructures. 3.0 materials and methods 3.1 sample collection a total of eight soil samples were collected from eight different gully sites. the geometric dimensions (widths and depths) of the eight gully sites were measured using a graduated leveling staff and meter tape. the systematic geological mapping was carried out in the area, using global positioning system, compass clinometer, geological hammers and chisels, hand lens, contoured topographic map sheets, etc. the static water levels in wells were measured using a level indicator in some selected 27 hand-dug wells (figure 1). the elevation and coordinates of the area were determined using the global positioning system (gps). the static water level was subtracted from the elevation to obtain the hydraulic head values. these hydraulic head values were used to construct hydraulic head distribution map use of gis. 3.2 laboratory analysis 3.2.1 sieve/gradation analysis about 200g of prepared samples were washed and dried. the samples were sieved and the amount retained on each sieve were collected and weighed to determine the percentage of material passing each sieve size. the cumulative percentage retained and cumulative percentage passing were calculated. the coefficient of uniformity (cu) and coefficient of curvature (cc) were calculated using equations 1 and 2 to determine the grading of soil. for a material to be well graded it must fulfill one or all of the following: that cc is between 1.0 and 3.0; and or cu must be greater than 4.0 for gravels and greater than 6.0 for sands. otherwise it is poorly graded. d10 = grain size value at 10% passing, d30 = grain size value at 30% passing, d60 = grain size value at 60% passing has been used to calculate cc and cu (vukovic and soro,1992). cu = d60 d10 (1) cc = d30 2 d10 d60 (2) where: cu is coefficient of uniformity; cc is coefficient of curvature; d10 is grain size value at 10% passing; d30 is grain size value at 30% passing; d60 is grain size value at 60% passing file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 340 3.2.2 atterberg’s limit test a portion of the soil sample was dried and disaggregated in a mortar using a rubber pestle. the material was sieved using the no. 425 sieve. only the material passing the sieve was used for the test. the sieved sample was then soaked in distilled water to form a paste and then left over night, while reserving a portion of the dry sieve materials. measurement of atterberg limit test was carried out in the department of civil engineering, federal polytechnic, bauchi. 3.2.3 liquid limit test a portion of the paste was remoulded on a glass platen and placed in the liquid limit apparatus. it was grooved using a standard grooving tool. the handle of the cassagrande apparatus was then rotated which caused the blows to be jarred against the base plate and the groove got closed. the number of blows required to close the groove was recorded. a sample of material was then taken and its moisture content was determined gravimetrically. the above procedure was repeated four more times each time adding a little amount of the dry sample material to the paste in order to effect a change in the moisture content. the specimens collected were then placed into an oven for twenty-four hours; the moisture content was determined by measuring the weight. the result obtained was plotted on a graph and the best straight line was drawn between the points. the moisture content at twenty-five blows defines the liquid limits. 3.2.4 plastic limit the plastic limit has a similar procedure like the liquid limit test except for the absence of the liquid limit apparatus. the soil paste at different moisture content was rolled with the palm on a glass plate into threads. the threads were placed into containers like those in the liquid limit test and weighed, and then placed in an oven for twenty-four hours after which they were reweighed and the weight difference gives the plastic limit. the results of the two test when analyzed to give the plasticity index (p1) which is the numerical difference between the liquid limit (ll) and plastic limit (pi = ll – pl). 3.2.5 compaction test a sample of known weight of air dried soil was subdivided into three parts of approximately equal surface, and each was roughened in order to obtain a better bond between them. after compaction, the mould and its content were then weighed and the representative samples were taken and used in the determination of moisture content. the specimen was oven dried for twenty-four hours and the moisture content was obtained by determining the weight difference. this procedure was carried out three times on each sample. the result of the analyses was then used to determine the optimum moisture content and the corresponding maximum dry density. 3.2.6 shear strength/triaxial test triaxial test was used to determine the shear strength properties of soil samples. a test sampler of 50 mm in diameter with a height and length of between 2 and 3 m using the optimum moisture content obtained from compaction test was prepared. the sample was encased by a thin membrane and placed inside a plastic cylindrical chamber of 59 mm diameter and height of 3 m filled with water. eight soil samples were used for the test and each sample was subjected to a normal stress or confining pressure by compression of the fluid in the chamber. rock work software was used to plot the graph or normal stress to determine the angle of internal friction and cohesion. 3.3 statistical grain size analysis methods the hydraulic conductivities of the soil samples were determined using empirical equations as summarized by vukovic and soro (1992). as follows: several empirical methods from studies and presented a general formula: k = g v c. f n .de2 (3) where: k= hydraulic conductivity; g = acceleration due to gravity; v = kinematic viscosity; c = sorting coefficient; f(n) = porosity function, and de=effective grain diameter. the values of c, f (n) and de are dependent on the different methods used in the grain-size analysis. porosity can http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 337-350. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 341 be derived from the empirical relationship between porosity and the coefficient of grain uniformity (u) according to vukovic and soro (1992) as follows: n = 0.255 2 + 0.83u (4) where: u is the coefficient of grain uniformity and is given by: u = d60 d10 (5) where: d60 and d10 are the grain size diameter in (mm) for which 60 and 10% of the sample respectively are finer (odong, 2007). the empirical formulas which were formed on the same basis as represented in equation (1) vary with c, f (n) and de. the different empirical formulas employed in this study are presented below: 3.3.1 hazen method hazen formula was originally developed for determination of hydraulic conductivity of uniformly graded sand but is also useful for fine sand to gravel range, provided the sediment has a uniformity coefficient less than 5 and effective grain size between 0.1 and 3 mm(carrier, 2003).    2 10 4 26.0101106 dn v gk   (6) 3.3.2 kozeny-carman method the equation is one of the most widely accepted and used derivations of permeability as a function of the characteristics of the soil medium (odong, 2007). the equation however is not appropriate for soil with effective size above 3 mm or clayey soils (carrier, 2003). k = g v x 8.3 x 10−3 n3 1 − n 2 d10 2 (7) 3.3.3 breyer method the formula is often considered most useful for materials with heterogeneous distributions and poorly sorted grains with uniformity coefficient between 1 and 20, and effective grain size between 0.06 and 0.6 mm (cheng and chen, 2007). 2 10 4 560log106 d uv gk  (8) 3.3.4 slitcher method the formula is most applicable for grain size between 0.01 and 5 mm (carrier, 2003). 2 10 287.34101 dn v gk  (9) 3.3.5 terzaghi method terzaghi formula is most applicable for large-grain sand (cheng and chen 2007). k = g v . cr n−0.13 3 1−n 2 d10 2 (10) where the ct= sorting coefficient of average value 8.4x10-3 is used in this study. 3.3.6 usbr method the formula is most suitable for medium-grain sand with uniformity coefficient less than 5 (cheng and chen, 2007). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 342 2 10 3.0 20 4108.4 dd v gk   (11) 3.4 measurement of static water level and elevation measurement of static water level in wells was carried out using water level indicator while measurement of elevation was carried out using the gps. the static water level was subtracted from the elevation to obtain the hydraulic head values. these hydraulic values were used to construct hydraulic head distribution map employing the use of gis. 4.0 results and discussion 4.1 geology of the study area the porphyritic granite underlies more than half of the study area. they range from light to grey color and are coarse grained in texture (figure 2). the porphyries ranged from 1.6 to 4mm in size (figure 2). the biotite granite underlies the extreme northern corner of the study area around buban and kozonthchi (figure 3). from the geological mapping, it shows that the lithologic units in the study area are basically porphyritic granite which is the oldest rock. the older rock was intruded by biotite granite which is the younger rock. figure 2: outcrop of porphyritic granite at kojeng the geological structures observed in the study area are fractures, dykes, veins, micro faults and fault zones. fractures observed in the study area were trending nnwsse (figure 4). fine grained granite dyke was observed in the area which was weathered and dominantly trending nwse direction. a dyke is a discordant igneous rock or solidified magma cutting through the overlying sediments or body of a host rock vertically (figure 5) the veins observed in the study area are all quartz vein with a mean exposed length of 15.7 m with a mean thickness of 6cm (figure 6). veins are fractures filled with remobilized minerals such as, quartz feldspars or both. the soils in the area are the by-product of insitu weathering of the underlying rock. the geologic structures which represent deformational features enhance rock weathering by allowing flow of water to enhance chemical weathering. http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 337-350. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 343 figure 3: geological map of the study area figure 4: rose diagram of fractures figure 5: rose diagram of dykes file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 344 figure 6: rose diagram of veins 4.2 engineering assessment of the gully site table 1 shows that the results of the plastic limit ranges between 024.2%. according to clayton and juckes (1978), plastic limit <35% implies low plasticity, 35% to 50%= implies intermediate plasticity, and >50% signifies high plasticity. based on the above standard, the soil in the study area possesses low plasticity. the liquid limits ranged from 20.1 to 43.9%, this indicates low to intermediate plasticity. low liquid limit is attributed to low amount of fine fractions and indicate that the soil may change consistency with minimum change in water content. therefore, low liquid and plastic limit could result into loose, non-coherent soil which would slide upon getting in contact with water, or it will disintegrate under dry conditions. the plasticity index ranged s between 11.2%-19.7%. based on the above standard values, the plasticity index of soils in the study area is moderately plastic (table 2), this finding is similar to the result by obiefuna and adamu (2012). figure 7 show plots of optimum moisture content against soil properties of the study area. table 1: summary of laboratory results for soil from gully sites in the study area gully location kakulu gs1 danlanp a gs2 dosa gs3 anguwan fada gs4 anguwan nepa gs5 labimma ng 1 gs6 labimma ng 2 gs7 kojeng gs8 depth (m) 1.65 2.74 3.05 1.01 1.83 1.86 1.71 1.73 width (m) 0.3 1.58 1.06 0.39 0.37 1.39 1.04 1.22 natural moisture content (%) 26.78 32.01 19.96 20.99 22.66 18.87 43.18 41.53 plastic limit (%) 0 18.8 0 0 0 0 24.2 17.8 liquid limit (%) 27 30 20.4 20.6 23.1 20.1 43.9 36 plasticity index (%) 11.2 19.7 18.2 relative consistency cr -0.18 0.04 -0.3 coefficient of uniformity (cu) 11.5 8 6.67 9.05 10.87 6.67 4.2 11.5 coefficient of curvature (cc) 1.13 0.78 0.95 1.81 0.85 0.53 1.3 1.99 soil classification gravelly sand soil gravelly sand soil gravelly sand soil gravelly sand soil gravelly sand soil gravelly sand soil gravelly sand soil gravelly sand soil optimum moisture content (%) 9.4 9.2 9.8 9.3 9.5 8.3 9.6 8.3 mdd mg/m3 1.82 1.75 1.8 1.91 1.79 1.83 1.83 1.84 angle of friction ° 37 35 28 30 40 33 29 37 cohesion, c kn/m2 33 0 28 48 0 37 54 33 http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 337-350. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 345 table 2: the standard for plasticity index (burmister, 1997) plasticity index value remarks 0 non plastic 1 to 5 slightly plastic 5 to 10 low 10 to 20 moderately plastic 20 to 40 highly plastic >40 very highly plastic figure 7: plots of optimum moisture content against soil properties of the study area the sieve analysis results show that the coefficient of uniformity, cu ranges from 4.2 to 11.5 while the coefficient of curvature cc ranged between 0.53 to 1.99 (table 3). these materials file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 346 are highly susceptible to gully erosion. this agrees with obiefuna et al. (1999) and obiefuna et al. (2018) who concluded that high sand and low silt/clay content in the soil contribute to gully development. the compaction result shows that the optimum moisture content (omc) ranged from 8.3 to 9.8% while maximum dry density (mdd) was from 1.75 to 1.91mg/m³. these values are within the range classified as sandy clay by o’flaherty (1988). similar values were obtained by ishaku et al. (2002) also classified as low and that such soils are considered loose with little amount of clay as binding material. a low value of mdd indicates that the soil is not compacted but loose and has high void ratio and prone to short dispersion times (hudec et al., 2006). the triaxial shear test result shows that the angle of internal friction is between 28 to 40° while the cohesion is between 0 to 54 kpa. these values are low when compared with the values of cohesion of 65 kpa and 26° angle of friction classified as average by okunlola et al. (2014). this range makes it favorable for gully erosion to flourish. the results of hydraulic conductivity determined from the use of the different empirical formulas are presented in table 2. the average hydraulic conductivity values obtained using the six different statistical grain size methods ranges from 2.34 x10-3 m/s to 2.35 x10-4m/s which corresponds to the hydraulic conductivities of clean sand to gravel (freeze and cherry, 1979). among the statistical grain size methods, breyer gave the highest values followed by slitcher, kozeny-carman, terzaghi and hazen, and usbr have the least values. similar result was obtained by ankidawa et at. (2020), in otukpo and environs, benue state, nigeria. their result of hydraulic conductivity ranging from 2.01 x 10-4 m/s to 7.06 x 10-4 m/s indicating clean sand formation. table 3: soil particle size distribution and hydraulic conductivity values computed from the statistical grain size method locatio n of gully site lithol ogy d1 0 (m m) d2 0 (m m) d3 0 (m m) d5 0 (m m) d6 0 (m m) u n c c haz en m/s kozeny carman m/s bre yer m/s slitc her m/s terz aghi m/s us br m/s aver age m/s kakulu gs1 gravel ly sandsoil 0.0 2 0.0 39 0.0 72 0.1 9 0.2 3 1 1 . 5 2 . 6 9 1 . 1 5.9 6e5 2.22e-4 3.86 e-6 1.02 e-3 1.52 e-4 3.4 1e7 2.43 e-4 danlanp a gs2 gravel ly sandsoil 0.0 3 0.0 49 0.0 75 0.1 8 0.2 4 8 1 . 9 5 0 . 8 9.4 8e5 6.02e-4 9.51 e-6 7.93 e-4 2.54 e-4 5.7 7e7 2.92 e-4 dosa gs3 gravel ly sandsoil 0.0 39 0.0 62 0.0 98 0.2 0.2 6 6 . 6 7 1 . 6 7 1 1.3 5e4 1.29e-3 1.68 e-5 8.05 e-4 3.88 e-4 9.9 0e7 4.39 e-4 anguwa n fada gs4 gravel ly sandsoil 0.0 42 0.0 87 0.1 7 0.2 9 0.3 8 9 . 0 5 2 . 1 7 1 . 8 2.0 9e4 1.07e-3 1.81 e-5 2.21 e-3 5.45 e-4 2.1 6e7 6.75 e-4 anguwa n nepa gs5 gravel ly sandsoil 0.0 23 0.0 4 0.0 7 0.1 9 0.2 5 1 0 . 9 2 . 5 6 0 . 9 7.4 7e5 2.97e-4 5.18 e-6 1.14 e-3 1.91 e-4 3.6 1e7 2.85 e-4 labimm ang 1 gs6 gravel ly sandsoil 0.0 33 0.0 5 0.0 65 0.1 7 0.2 2 6 . 6 7 1 . 6 7 0 . 6 9.6 8e5 1.15e-3 1.20 e-2 5.77 e-4 2.78 e-4 6.0 0e7 2.35 e-3 labimm ang 2 gs7 gravel ly sandsoil 0.0 31 0.0 49 0.0 72 0.1 7 0.1 3 4 . 2 1 . 1 4 1 . 3 5.5 4e5 5.92e-6 1.17 e-5 1.45 e-4 3.00 e-4 5.7 7e7 8.64 e-5 kojeng gs8 gravel ly sandsoil 0.0 2 0.0 38 0.0 72 0.1 7 0.2 3 1 1 . 5 2 . 6 9 1 . 1 5.9 6e5 1.65e-4 3.86 e-6 1.02 e-3 1.52 e-4 3.2 e-7 2.34 e-4 average 9.8 1e5 6.00e-4 1.51 e-3 9.64 e-4 2.83 e-4 4.9 8e7 5.76 e-4 http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 337-350. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 347 4.3 hydraulic head distribution groundwater flow takes place from the south eastern and flows towards north southern part of the study area (figure 8) and it flows from the north western towards the northern and also flows from the south eastern toward the northern, it also flows towards the eastern and north western part of the study area to the northern. the recharge areas occur in the western parts of the study area around labimmang1, in the south east around nyali and in the north east around kozonthchi and also around kakulu. the discharge areas occur around dosa, zinna, danlanpa and kojeng of the study area. the hydraulic head distribution map indicates that the gully sites were located in the discharge areas. the discharge areas are characterized by high hydrostatic pressure. high hydrostatic pressure decreases effective stress and in turn reduces the shear strength of materials, and enhances internal erosion in form of piping and cave ins in the discharge areas. figure 8: hydraulic head distribution map showing ground water flow direction. 4.4 other factors contributing to gully erosion in the study area factors that were found contributing to gully erosion in the study include; dumping of refuse along stream channels (figure 9a) which results in the flooding and increase in runoff down the stream channel. this was more prominent in dosa area. sand mining/excavation (figure 9b) is a common practice along stream channels in the study area. they use it to make local blocks/ bricks for building purposes. this practice helps in the increment of stream channel and thus influencing gully development. soil tillage and building of domestic/farm structures were also observed as other contributory factors that encourage the development of gully erosion in the study area. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 348 figure 9: (a) refuse dump in dosa area, (b) sand excavation for making local bricks in kakulu area, (c) farm ridges placed perpendicular to s stream channel. 5.0 conclusion the geological investigation reveals that the area is underlain by porphyritic and biotite granite. the engineering parameters indicate loose, non-coherent soil which slide upon getting in contact with water or disintegrate under dry conditions. these materials are highly susceptible to gully erosion due to high permeability. the low maximum dry density indicates loose and high void ratio which is prone disintegration of the soil materials. the hydraulic conductivity values of the soil materials indicate permeability of silty sand to gravel which is an indication of high permeability. the gully sites are located in the discharge areas which were characterized by high hydrostatic pressure, low effective stress and in turn this reduces the shear strength of the materials and enhances internal erosion in form of piping and cave ins in the discharge areas. mitigation measures towards minimizing the menace of gully erosion in the study area should include regulated sand mining activities (especially sand mining/excavation) taking place along the rivers. improved farming practices that would check the development of gully erosion, regulated dumping of refuse on the river channels and flood plains, and appropriate positioning of domestic and farm structures away from erosion-prone zones. references ankidawa, ba., omepa, c., kabiru, mw. and dennis, yb. 2020. estimation of hydraulic conductivity using statistical grain-size analysis in otukpo and environs, benue state, north central nigeria. bayero journal of engineering and technology, 15(2): 8496. areola, o. 1983. soil and vegetation resources: geography of nigeria development, heinemann, ibadan, 102pp. http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 337-350. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 349 burmister, f. 1997. advanced soil mechanics (2ndedition) john wiley and sons new york, 471p. carrier, wd. 2003. goodbye hazen: hello. kozeny-carman. journal of geotechnical geoenvironmental engineering, 129(11): 1054p. cheng, c. and chen, x. 2007. evaluation of methods for determination of hydraulic properties in an aquifer-aquitard system hydrologically connected to a river. hydrogeology journal, 15: 669-678. clayton, cri. and jukes, aw. 1978. a one point penetrometer liquid limit test, geotechnique, 28, 469-472 coduto, d.p., 1999. geotechnical engineering: principles and practice. prentice hall inc. upper saddle river, new jersey, 07458. egboka, bc. and nwanko, gi. 1979. the hydro geological and geotechnical parameters as agent for gully-type erosion in the rainforest belt of nigeria. journal of african earth science, 3(4): 417-425. ezechi, j.f. 2000. the influence of runoff, lithology and water table on the dimensions and rates of gullying processes in eastern nigeria. international symposium on gully erosion under global change. catholic university of lerner, belgium, april 16-19, pp. 28-29. floyd, b. 1965.soil erosion and deterioration in eastern nigeria. nigerian geography journal, 8: 33-44. freeze, ra. and cherry ja. 1979. groundwater. prentice-hall inc., englewood cliffs nj, 604p. grove, at. 1951. land use and soil conservation in parts of onitsha and owerri provinces. geological survey of nigeria, 2: 25-28. hudec, p., simpson, f., akpokodje, e. and umenweke, m. 2006. proceedings of the eighth federal interagency sedimentation conference (8thfisc), april 2-6, 2006, reno, nv, usa, pp. 671-679. ishaku, jm., adekeye, jid. and negro, ss. 2002. hydrogeological and geotechnical characteristics of rock materials that aid gully erosion in lassa. water resources journal of nigerian association of hydrogeologists, 13: 50-54. mbagwu, jsc. and bazzofi, p. 1998. soil characteristics related to resistance of breakdown of dry soil aggregates by water-drops; soil and tillage research, 45: 133-145. muoghalu, ln. and ikegbunam, fi. 1997. gully erosion in some urbanizing communities of anambara state in nigeria. environmental review, 1(2): 1-14. o’flaherty, ca. 1988. highway engineering, vol. 2. edward arnold publishers, london. uk. obiefuna, gi. and adamu, j. 2012. geological and geotechnical assessment of selected gully sites in wuro bayare area ne nigeria. research journal of environmental and earth sciences, 4(3): 282-302. obiefuna, gi. and simon, ed. 2010. geological and geotechnical assessment of selected gully sites in jada area, ne nigeria. journal of environmental sciences and resource management, 2: 22-30. obiefuna, gi., agbo, co. and bawa, d. 2018. geological and geotechnical assessment of selected gully sites in lainde fulani area ne nigeria. journal of environmental science and resources management, 10(1): 1-39. obiefuna. gi., nur, a., bassey, ne. and baba. au. 1999.the geotechnical and geological assessment of gully site in yola area, ne nigeria. international journal of environmental hydrology, 7: 1-13. odong, j. 2007. evaluation of empirical formulae for determination of hydraulic conductivity based on grain-size analysis. journal of american science, 3(3): 54-60. ogidiolu. a. 2000.assessment of soil degradation under agricultural land uses in part of savannah region of nigeria. journal of environmental reviews, 3(1): 117 -129 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):337-350. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ankidawa03@yahoo.com 350 okunlola, ia., abdulfatai, ia., kolawole, ll. and amadi, an. 2014. geological and geotechnical investigation of gully erosion along river bosso, minna, north central nigeria. journal of geosciences and geomatics, 2(2): 50-56. onuoha, km. and uma, ko. 1987. groundwater fluxes and gully development in se nigeria. earth evolution science, 20: 25-30. ray, hh. and yusuf, mb. 2011. farmers’ perception and responses to soil erosion in zing local government area of taraba state, nigeria. ethiopian journal of environmental studies and management, 4(1): 9-18. vukovic, m. and soro, a. 1992. determination of hydraulic conductivity of porous media from grain-size composition. water resources publications, littleton, colorado http://www.azojete.com.ng mailto:ankidawa03@yahoo.com arid zone journal of engineering, technology and environment azojete, march, 2019. vol. 15(1):97-108 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 97 original research article a review of probabilistic approaches for available transfer capability calculation o. o. mohammed1,2*, m. w. mustafa1, a. o. otuoze2, s. salisu3, a. y. abdulrahman2, n. t. surajudeen-bakinde2 1school of electrical engineering, universiti teknologi malaysia, johor, johor bahru 2department of electrical and electronics engineering, university of ilorin, ilorin, kwara state, nigeria 3department of electrical engineering, ahmadu bello university, zaria, nigeria *corresponding author: mohammed.oo@unilorin.edu.ng, reacholaabdul@gmail.com article information submitted 12 january, 2019 revised 15 february, 2018 accepted 1 march, 2018 keywords: available transfer capability probabilistic load flow monte carlo simulation artificial intelligence abstract several deterministic approaches have been proposed in literature for available transfer capability (atc) computation. however, the gradual shift in power generation sources from fossil fuels to renewable energy sources has a remarkable influence on the atc evaluation. the deterministic approaches do not incorporate the uncertainties of the renewable energy sources efficiently, therefore, various probabilistic techniques have been proposed in literature. this article presents a review of the various probabilistic methods for atc computation. it provides the background, techniques and the features of atc. several contributions made by researchers, using probabilistic techniques for atc computation, have been highlighted in this paper. this review has shown that there is a need for improvement in the existing approaches in order to evaluate atc accurately. the improvement includes the development of a robust technique incorporating the system uncertainties and the uncertainties due to the renewable energy system as well as complete system dynamics in atc computation. in addition, evaluation of atc incorporating the transfer capability margins (trm and cbm) is necessary to avoid over-/under-estimation of atc value. this review will serve as a guide for the entrants in this research area © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the economic and effective system operations associated with power system restructuring have instigated electric power utilities globally to follow progressive transformation from vertical power system structure to a more efficient framework known as deregulated systems. the monopoly structure has given rise to ineffective economic turnout, technical degradation and administrative mismanagement in the sector resulting in customers' dissatisfaction. however, experiences have shown that an effective reformation scheme for the electricity sector is necessary for efficiency enhancement which will attract economic, sustainable, and reliable power supply (jamasb et al., 2014, sureban and ankaliki, 2017). therefore, the majority of the utilities are going through restructuring to control the ineffectiveness of the non-competitive market (kröger, 2008). this transformation has given rise to competition at the different level of utilities thereby regulating the existing monopolistic structure and encouraging nonmailto:reacholaabdul@gmail.com http://www.azojete.com.ng mohammed, et al: a review of probabilistic approaches for available transfer capability calculation azojete, 15(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 98 governmental participation in power system investment and control with guaranteed access to open access transmission network (christie et al., 2000). the operations of various utilities are included in the generation and distribution, and the decision about generation schedules and load dispatch is based on their contract agreement (lai, 2001). therefore, the power flow (pf) schemes in the deregulated environment are presumably different from the previous existing monopoly structure (lai, 2001). all stakeholders try to take advantage of cheaper derivation and broader profit differences; this consequently leads to transmission network congestion. the transmission congestion leads to the violation of voltage limits, voltage stability, and thermal limits, thereby threatening the system security. although the economic ways of transmission expansion have not been simulated (rodrigues and da silva, 2007), this is due to the antecedence constraints and economic challenges faced by the power sector in achieving the expansion. these constraints have forced transmission providers to operate the system network close to their limits. consequently, economic capacity indices have been employed to provide a quantitative measure for power transfer reliability assessment, among these indices is available transfer capability (atc). therefore, independent system operators (iso) are required to regularly update their atc on open access same-time information system (oasis), established by united state federal energy regulatory commission (ferc), for efficient system operation. hence, any scheduled power transfer either firm or non-firm transfer has to be within the atc of the interconnected systems. accurate evaluation of atc is very important to know the economic and technical feasibility of the available transmission system capability for security monitoring and efficient market operations. future upgrading of the transmission network can be predicted using system atc values (othman et al., 2009). the computation of atc should incorporate the following system limits; voltage limit, thermal limit, voltage stability limit, real and reactive power generation limit, and system uncertainties (rep, 1996), to avoid inaccuracies in atc evaluation. overestimation of atc has remarkable adverse effects on the system security (kundur et al., 2004) and underestimation of atc value results in ineffective utilization of the power system resources. for example, the major blackout in the north-eastern united states and ontario in august 2003 was a result of an overestimation of atc (jacobs). therefore, the results of atc inaccuracies can cause huge loss to the utilities. the information about the size of atc is vital to system utility and the planner as it depicts the general performance of the power system regarding efficiency and economic activities (sauer, 1997). essentially, atc is an index for measuring the transfer capability remaining in the physical transmission network over and above already committed uses, for future commercial activity (rep, 1996). the value of atc is obtained by considering various parameters associated with transfer capabilities such as total transfer capability (ttc), transmission reliability margin (trm), and capacity benefit margin (cbm). ttc is the summation of the transfer capability margins (trm and cbm), atc and the existing transmission commitments. trm is the network margin reserved for system uncertainties. cbm is the network margin reserved for the utilities to have access to external generation in case of emergency supply shortage (rep, 1996, dobson et al., 2001). the graphical representation of these terms is as shown in figure 1, the purple, blue and green dotted lines represent the ttc at different system limits as shown in the figure. the power transfer capability simulation is based on the equality and inequality constraints of load flow equations and the system limits (thermal, voltage and stability), respectively. ttc is obtained as the result of the simulation and it varies with the system limits. after then, atc value is obtained http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammed.oo@unilorin.edu.ng 99 by deducting other parameters (trm, existing transmission commitments and cbm) from the ttc obtained from the simulation. the atc can increase/decrease depending on the system operating conditions and the system limits. the purple line is the most restricted ttc value as shown in figure (min ttc) and hence, taken as the systems’ ttc (rep, 1996, khairuddin and alhammi, 2014, shin et al., 2007, mohammed et al., 2019b). figure 1: atc limitations and related parameters. mathematically, atc can be expressed as (rep, 1996): atc = ttc− trm− etc including cbm \* mergeformat (1) the quest for energy sustainability around the world has instigated a large integration of renewable energy sources in the modern power system network (mohammed et al ., 2019a). however, renewable energy sources are stochastic in nature, thereby, the evaluation of the network capacity can only be assessed probabilistically. despite the enormous deterministic approaches for atc computation, only a few probabilistic techniques exist. the objective of this paper is to present a review of the probabilistic atc determination methods. the probabilistic techniques include; numerical methods (e.g., monte carlo simulation (mcs)), analytical based techniques (e.g., using convolution technique with pdf of the system states) and approximate techniques (e.g., point estimation method) (chen et al., 2008). the various existing techniques are reviewed and the merits and demerits of each of the approaches are highlighted. probabilistic approaches for atc computation the deregulation in the electric power structure has started since 1996, and till present, many approaches have been suggested in the literature for accurate determination of atc. the calculation of atc is generally based on computer simulations, by simulating the interconnected transmission network operation for a postulated set of operating conditions. deterministic approaches are employed on a daily basis for the analysis and assessment of system planning and operation. it performs the steady-state simulation of power systems, i.e., specific values of the system generations and demands of a particular network configuration is used to compute pf and the system states (chen et al., 2008). however, the system uncertainties cannot be efficiently conveyed in the deterministic approaches. figure 2 summarizes the various probabilistic methods employed in literature to determine atc. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed, et al: a review of probabilistic approaches for available transfer capability calculation azojete, 15(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 100 figure 2: probabilistic approaches for atc computation the continuous increase in the percentage of renewable energy integration has created a great concern on the reliability of generation systems due to the stochastic nature of the power output from renewables especially the wind and solar energies. this has increased the uncertainties associated with power system operations (sharifzadeh et al., 2017). moreover, uncertainties in system loads due to costumers’ consumption patterns and weather variability, the outage of generators, and the change of network configurations also contribute to system uncertainties (chen et al., 2008). the traditional deterministic techniques determine the steadystate simulation of power systems, which indicate the snapshot of particular operating conditions of the network (shin et al., 2007). evidently, it is impractical to implement ideal load flow computations for every feasible and likely combination of generating unit outages and bus loads because of the eventuality of the extensive computational problem (shin et al., 2007, shin et al., 2003). to solve this limitation of the deterministic methods, probabilistic load flow techniques were proposed (rodrigues and da silva, 2007, shin et al., 2007, morales and perezruiz, 2007, zhang and lee, 2004, usaola, 2009, borkowska, 1974). probabilistic load flow is a principal tool used to provide essential information on power system planning, operation, and control (prusty and jena, 2016). it aimed at assessing node voltages, and network flow in responses to the system parameters’ uncertainties (aien et al., 2014). the uncertainty analysis of power system performance is crucial, and generally, the uncertainties in any engineering system study can be solved probabilistically (aien et al., 2016). probabilistic methods are not only accurate but also give more information such as the expected value and variance of atc. they can be broadly categorized into three methods (chen et al., 2008, gupta, 2016, le et al., 2017): numerical-based probabilistic techniques (e.g. mcs), analytical-based probabilistic techniques (e.g. using convolution technique with probability density function (pdf) of the system states) and approximate techniques (e.g. point estimation method). various artificial intelligence methods have been employed in literature for atc computation (jain et al., 2011, luo et al., 2000, jain et al., 2007, yi and yang, 2005, pandey et al., 2010) and remarkable progresses have been achieved due to the robustness, fastness, and the capability to solve complex nonlinear problems which are not feasible to be solved analytically (mohammed et al., 2019b). numerical based approach monte carlo simulation (mcs) method is usually adopted for the numerical based probabilistic method (chen et al., 2008). random number generation and random sampling are the two significant features of msc. generally, the probabilistic technique using mcs computes pf by using deterministic load flow for a large number of times with different combinations of nodal http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammed.oo@unilorin.edu.ng 101 power value at the inputs. it uses repeated distributions of nodal powers, network flows and losses (hojabri et al., 2010). the load flow computation is performed based on the samples of uncertain factors for many times and the statistical analysis is used to find the probability distribution of the reliability indices and the specified system states (li and zhang, 2009). therefore, the general non-linear load flow equations can be used for probabilistic analysis (chen et al., 2008). several probabilistic methods based on mcs have been employed in the literature for atc evaluation (sekita et al., 2008, da silva et al., 2004, rodrigues and da silva, 2007, gupta and kumar, 2016b, gupta and kumar, 2016a, shin et al., 2007). assessment of atc, ttc and power system reliability margins (trm and cbm) based on mcs considering system uncertainties was proposed in (sekita et al., 2008). the total benefit of the atc and cbm are compared based on the period of utilization. it was affirmed that the overall benefit strongly depends on the period of usage. however, in a deregulated environment the system security and the economic benefit are of paramount importance. atc serves as an economic index to measure the viability of the economic activity and should have a more significant benefit than the cbm whose value is a fixed amount and may not be utilized if there is no any loss of generation in the specified area. moreover, in this work lole is evaluated based on the largest demand in the areas, this may lead to underutilization of transmission equipment during the off-peak period because the space that could be used for atc has been reserved for cbm. an algorithm based on nonsequential mcs (da silva et al., 2004) to select system state and linear programming with dc pf model was employed to analyse and optimize each selected state. the probability density of the atc incorporating uncertainties from the unavailability of the system equipment was determined. the objective was to evaluate pdf associated with maximum power transfer from one area to another and to locate the best point in the system where additional generation and loads can be considered without jeopardising the existing system security and transactions. the chronological variation in atc due to uncertainties associated with hourly load fluctuations and equipment unavailability was assessed for a weekly study period (rodrigues and da silva, 2007) using the mcs method with sequential simulation. linear dc opf was used to evaluate the atc of each generated state. the results show that time-dependent uncertainties have a remarkable influence on the atc. a probabilistic assessment of atc incorporating wind power resources was used (gupta and kumar, 2016a, gupta and kumar, 2016b) while mcs and latin hypercube sampling were used to deal with the stochastic nature of the system load demand and wind resources (gupta and kumar, 2016a). the problem was formulated as an opf subject to the constraints of pf equations, voltage limits, line flow, generator active and reactive power limits. three different scenarios were assessed, in the first case, probabilistic nature of load was not considered, the second case incorporates the probabilistic nature of load using mcs and third case using lhs in place of mcs. the results indicate that the atc increases with wind power injection. incorporating the probabilistic nature of load reduces the values of atc using mcs, using lhs further reduced the atc values and gave better atc results due to an efficient approximation of normally distributed load compared with mcs. in (shin et al., 2007), ttc was determined using the cpf approach, trm and cbm are evaluated by probabilistic load flow (plf) and mcs respectively. the plf method converts the load flow problem from deterministic to the stochastic formulation using the gram-charlier series. the results from the stochastic approach define the range of pf analysis output quantities, i.e. bus voltage, real and reactive power, and line flows along with the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed, et al: a review of probabilistic approaches for available transfer capability calculation azojete, 15(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 102 related probabilities. evaluation of atc using a cubic-spline interpolation technique is proposed in (othman et al., 2005, busan et al., 2010). in this technique, the curves of voltage magnitude and pf variations are traced, and the atc was determined at the point where the pf or the voltage limits intersect the curves. contingency ranking and selection techniques are employed to select the critical lines that can influence the atc assessment. four incremental steps of power transfer were used, which was assumed to be sufficient to produce an accurate fitting of the curve, to avoid substantial computation time. sensitivity method was used to predict the maximum power transfer for the step four. the technique is faster than the repeated ac pf method. however, this technique will result in a substantial computation for large-scale power systems. the results obtained from other probabilistic methods using simplified load flow equations are usually compared with mcs results as a reference to check the accuracy of those methods. this is due to the ability of the mcs to use exact non-linear load flow equations (chen et al., 2008). however, considerable computation time is required as a result of a large number of load flow equations to be computed and also the number of system states to be sampled increases with the system size. different variance reduction methods (jirutitijaroen and singh, 2008) have been employed to reduce the time of computation (li and zhang, 2009). nevertheless, the enormous time of computations is still required to get accurate results, especially in bulk power systems. analytical approach convolution methods are the analytical methods commonly employed in the past to find the probability distributions of the desired variables (borkowska, 1974, allan et al., 1974, allan and al-shakarchi, 1977). the pdfs of the stochastic variables of the system states and line flows are determined using the convolution approach. however, the efficiency of the computation is very low; hence improvements have been made by using fast fourier transforms (allan and da silva, 1981, allan et al., 1981b) which leads to the development of numerical characteristics based methods such as moments and cumulants methods. the assumptions of these methods are: linearization of the non-linear load flow equations, the input power variables at different buses are independent or linearly correlated, load and generation follow a normal distribution and discrete distribution respectively, and network configurations and parameters are constant (chen et al., 2008, li and zhang, 2009). the details on the convolution methods for mixed continuous and discrete variables can be found in (allan et al., 1976, allan et al., 1981b, allan et al., 1981a). various analytical approaches have been employed in atc determination. an opf based atc model is formulated and extended blind number algorithm incorporating the various types of uncertainties was applied (gao et al., 2009) for the evaluation of the atc. the objective functions are to maximize the total active power of the source area and the total loads of the sink area as well as maximizing the active pf of the interconnecting lines. the algorithm was able to evaluate the approximate values of the interarea atc incorporating the uncertainties in the system load demand. however, the algorithm is impractical for large power systems, as it is computationally expensive. a probabilistic pf incorporating a correlated wind power model to evaluate the impact of high wind penetration in atc calculation was proposed in (fang et al., 2014). the proposed model compensates the imbalance caused by the wind variation using a set of conventional generators instead of using only slack bus through specific sharing factors. atc computation was converted to a linear programming problem via dc opf and sensitivity analysis approach. a stochastic algebraic methods (sam) is proposed in (stahlhut and heydt, 2007) to evaluate atc, the uncertainties due to bus loading and transmission element status are http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammed.oo@unilorin.edu.ng 103 incorporated as well as voltage and thermal limits. the approach adopted in calculating the atc is based on the concept of linear system behaviour, stationarity of statistics and uncorrelated bus load statistics. three different cases were considered and analysed. the first case used mcs incorporating the uncertainty due to bus loading; the second case employed sam with the same uncertainty while the third case includes both the bus loading and lines outages uncertainties using sam. the first case and the second case were compared, and the results show a similarity of 1% in mean and 12% in standard deviation. the algorithm is faster in comparison with mcs, the computation time for the mcs is 24 hours while the algorithm took 1 minute. analytical methods are computationally effective compared to numerical methods. however, the drawbacks of this method are the complicated mathematical computations involved and the degradation in the accuracy of the results due to linearization and assumptions. the assumptions are valid for a specific range of system operating conditions, as the network configuration changes, the results deviate from actual values. approximate approach accuracy and computational speed can be achieved by using approximate methods. first-order second-moment method (madrigal et al., 1998) and the point estimate method (su, 2005) are commonly employed in approximate methods. point estimate method is a combination of both analytical and numerical methods. it also makes use of numerical characteristics of input variables, similar to analytical methods. however, different techniques are employed to find the numerical features of the outputs without linearizing the load flow equations (li and zhang, 2009). the detailed formulation and procedure for analytical and approximate methods can be found in (li and zhang, 2009). a mathematical model of atc for hvdc-ac hybrid system was formulated (wei et al., 2013), and the sequential solution method was employed to solve the ac-dc pf. golden section is used to accelerate the pf convergence. several statistical indices were applied to evaluate the atc due to the uncertainties of the system. the hybrid algorithm of monte carlo and bootstrap was used to solve the statistical indices. a stochastic parallel algorithm was proposed (stahlhut et al., 2005) to evaluate atc. different statistical indices are applied to calculate atc, and they are calculated based on mcs and opf. the opf is used for pf solution. the results show that the proposed technique is faster, more effective and practical than conventional mcs. summary of the probabilistic approaches table 1 summarizes the efficacy of some of the important probabilistic approaches based on the system constraints and the uncertainties considered (hojabri et al., 2010). due to the limitation of the methodology employed in these approaches, the incorporation of all the constraints is not feasible. using table 1 to evaluate the performance of these approaches, it is evident that mcs is better than other methods because it incorporates more constraints and uncertainties than other techniques. in spite of the accuracy of these techniques, which is very crucial in the deregulated environment, they are rarely used for online applications because of the enormous computational time required especially for large power systems, and they are less accurate for relatively small power systems. therefore, probabilistic methods cannot completely replace the deterministic techniques in atc assessment due to some factors such as complex computations, substantial computation time which make probabilistic techniques unattractive in real-time applications. however, artificial intelligence can be modified to accommodate all the constraints and uncertainties in the face of large atc data (mohammed et al., 2019b). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed, et al: a review of probabilistic approaches for available transfer capability calculation azojete, 15(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 104 table 1: system uncertainties and limitations considered in some of the essential probabilistic approaches. uncertainties and constraints stochastic programming mcs cubic spline artificial intelligence v limit     thermal limit     pg limit     qg limit     pl limit     voltage stability limit     load variations     system components outages     comparison of the methods the comparison of the existing probabilistic approaches in terms of their advantages and disadvantages are highlighted in table 2. the accurate estimation of atc depends on the incorporation of the entire system dynamics, system’s parameter limits (voltage, thermal and stability) and system uncertainties in the approach employed which will eventually result in a considerable time of computation. however, fastness and simplicity rely on the use of linearized and simplified techniques. table 2: comparison of different methods with advantages and disadvantages. methods advantages disadvantages numerical method it incorporates system uncertainties, and accurate atc result can be obtained. remarkable computation time is required due to the enormous number of load flow equations to be calculated. analytical method it considers most system uncertainties, and it is computationally efficient compared with the numerical method. due to linearization and some assumptions in the mathematical formulation of the equations employed, the accuracy of the results is degraded. approximate method accurate atc results can be obtained without linearization of the load flow equations and the computational time is faster than the numerical method. they are seldom used for online application due to remarkable computation time required. artificial intelligent method fast and accurate to accurately evaluate atc, enormous atc data is required as input to these techniques, and this may eventually require remarkable computational resources. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammed.oo@unilorin.edu.ng 105 conclusion the review of the existing probabilistic approaches for atc determination has been presented in this paper. the three probabilistic techniques which include; numerical, analytical and approximate methods have been reviewed, evaluated and compared. each of the methods has its distinguishing attributes which have been highlighted in this paper. the merits and demerits of each approach have been emphasized. it is evident from the existing literature that much work has not been done on atc using probabilistic methods relative to deterministic approaches and most of the probabilistic methods do not incorporate the required system uncertainties and limits such as load uncertainties and state transition of system equipment (generator outages, tie-line outages, and transformer faults). of all the papers reviewed, only three papers (gupta and kumar, 2016b, gupta and kumar, 2016a, fang et al., 2014) incorporate wind energy resources in atc evaluation. therefore, more efforts are required in the consideration of renewable energy sources in the atc computation due to the global shifting from conventional sources of generating systems to renewable energies. hence, it can be concluded that a robust technique incorporating all system constraints, system uncertainties, and remarkable renewable energy sources in an online atc evaluation is essential for accurate assessment of atc in modern power systems. references aien, m., hajebrahimi, a. and fotuhi-firuzabad, m. 2016. a comprehensive review on uncertainty modeling techniques in power system studies. renewable and sustainable energy reviews, 57, 10771089. aien, m., rashidinejad, m. and fotuhi-firuzabad, m. 2014. on possibilistic and probabilistic uncertainty assessment of power flow problem: a review and a new approach. renewable and sustainable energy reviews, 37, 883-895. allan, r. and al-shakarchi, m. 1977. probabilistic techniques in ac load-flow analysis. proceedings of the institution of electrical engineers, 1977. iet, 154-160. allan, r., borkowska, b. and grigg, c. probabilistic analysis of power flows. proceedings of the institution of electrical engineers, 1974. iet, 1551-1556. allan, r. and da silva, al. 1981. 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sekita, k., yokoyama, a., verma, s. and nakachi, y. 2008. probabilistic evaluation method of available transfer capability considering reliability margins in transmission network. power system technology and ieee power india conference, 2008. powercon 2008. joint international conference on, 2008. ieee, 1-6. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed, et al: a review of probabilistic approaches for available transfer capability calculation azojete, 15(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 108 sharifzadeh, m., lubiano-walochik, h. and shah, n. 2017. integrated renewable electricity generation considering uncertainties: the uk roadmap to 50% power generation from wind and solar energies. renewable and sustainable energy reviews, 72, 385-398. shin, dj., kim, jo., kim, kh. and singh, c. 2007. probabilistic approach to available transfer capability calculation. electric power systems research, 77, 813-820. shin, dj., lee, hs. and kim, jo. 2003. quantifiction method of trm (transmission reliability margin) using probabilistic load flow. ifac proceedings volumes, 36, 679-684. stahlhut, j., heydt, g. and sheblé, ga. 2005. stochastic evaluation of available transfer capability. power engineering society general meeting, 2005. ieee, 2005. ieee, 3055-3061. stahlhut, jw. and heydt, gt. 2007. stochastic-algebraic calculation of available transfer capability. ieee transactions on power systems, 22, 616-623. su, cl. 2005. probabilistic load-flow computation using point estimate method. ieee transactions on power systems, 20, 1843-1851. sureban, ms. and ankaliki, sg. 2017. computation of available transfer capability in electrical transmission system-a review. i-manager's journal on power systems engineering, 5, 35. usaola, j. 2009. probabilistic load flow with wind production uncertainty using cumulants and cornish– fisher expansion. international journal of electrical power and energy systems, 31, 474-481. wei, j., li, g. and zhou, m. 2013. monte carlo simulation and bootstrap method based assessment of available transfer capability in ac–dc hybrid systems. international journal of electrical power and energy systems, 53, 231-236. yi, h. y. and yang, hc. 2005. multi-layer feedforward neural network-based atc estimator. power tech, 2005 ieee russia, 2005. ieee, 1-7. zhang, p. and lee, st. 2004. probabilistic load flow computation using the method of combined cumulants and gram-charlier expansion. ieee transactions on power systems, 19, 676-682. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):116-123 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 116 original research article temperature performance analysis of a photovoltaic module a. h. onyenweuwa centre for satellite technology development, abuja, nigeria article information submitted: 12/12/2018 revised: 26/12/2018 accepted: 18/03/2019 keywords: photovoltaic efficiency temperature voltage monocrystalline. abstract the electrical efficiency of photovoltaic (pv) cell is affected by significant increase of cell operating temperature. the efficiency and temperature performance variation on two mono-crystalline modules with and without an active cooling system have been studied. experimental investigation performed on both modules at different period of the day, under the same ambient temperature reveals that the module efficiency is affected by substantial changes in cell temperature. the module efficiency increases and decreases as temperature decreases and increases respectively. the minimum and maximum module temperatures recorded are 21°c and 102°c while the minimum and maximum module efficiencies are 15.27% and 9.80% respectively. the efficiency performance of the cooled module was high compared with the uncooled module and this indicates that the reduction in cell temperature due to active cooling process improved the efficiency of the module © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the current erratic electricity generation situation in nigeria presents an enormous challenge for the country to grow industrially and rank among the first twenty developed nations in the world. this therefore calls for a rethink in our energy resource mix. this issue is acerbated by the fact that the fossil fuel resources which are though abundant and exploited in the country since after independence are not only finite but also sourced through destructive processes. that is, the energy is obtained from sources that must be constantly destroyed, with a significant part of the results transformed into waste which is extremely aggressive both for our health and the equilibrium of the surrounding nature. nigeria is blessed with abundant renewable energy resources but the country has focused solely on the development of non-renewable energy. unfortunately, the fossil fuels have not provided the much-needed solution to the current energy crises as the total power generation capacity in nigeria over the years has been less than 5000 megawatts (akhator et al., 2019). the demand for electricity in nigeria is growing rapidly and supply can hardly keep pace with demand. economic and population growth are placing serious strain on the country’s energy infrastructure. electricity demand per person is expected to increase every year and this presents a new opportunity to invest in energy infrastructure. thus, there is a need to accelerate efforts towards the development of a new and renewable energy sources to meet future energy demand. renewable energy provides a continuous and http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):116-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 117 unlimited supply of energy. however, technical difficulties, the intermittent nature of some of the renewable energy resources, as well as other constraints still pose limits to their wider deployment. solar energy has been identified as the most promising of the renewable energy source as a result of its apparent potentials (oyedepo, 2012). this energy is converted to electrical energy using photovoltaic solar cell. however, previous research work on the performance analysis of the photovoltaic system revealed that the efficiency of the system is affected by the ambient temperature. the variation in daily average ambient temperature in nigeria over the year prompted the need to study the effect of temperature on the photovoltaic module output in our environment. according to (kumar et al., 2014), the efficiency improvement of the pv system is still one of the top priorities for many academic researches. also, (virtuani et al., 2010) and (abdulgafar et al., 2014) have shown that the efficiency and output of pv module voltage generation is inversely proportional to its temperature. (achara and adikankwu, 2017) investigation on cooled and uncooled module revealed that the voltage generation at low temperature is higher due to the orderliness in vibration of the silicon electrons. as the temperature increases, the vibration become more randomly and the net effect is lower voltage generation. however, research has also shown that improve in cell efficiency can be achieved by changing the ambient temperature variation around the photovoltaic module (siddiqui and bajpai, 2012). also, (adikankwu and ileberi, 2016) stated that cooling the module with an air-conditioning cooling system would improve the voltage output. an experimental result on solar module cooling using silicon oil also showed that the maximum power delivered by the module and hence efficiency increased (nikhil and premalatha, 2012). this is an indicator that the performance of the photovoltaic cell depends on its basic characteristic as well as the meteorological factor of the environment. this paper examines the ambient and module temperature pattern on the efficiency performance of cooled and uncooled monocrystalline module system at different period of the day pv module the performance of a solar module depends largely on its efficiency, and adequate knowledge of the ambient temperature and the cell temperature are vital in evaluating the module operational efficiency. research (abdulgafar et al., 2014; achara and adikankwu, 2017; siddiqui and bajpai, 2012; adikankwu and ileberi, 2016) have shown that temperature affects photovoltaic parameters such as open circuit voltage, short circuit current, maximum output power and fill factor. but the maximum influence of temperature is recorded in the open circuit voltage. this shows that open circuit voltage of a pv module is sensitive to cell temperature. the relationship between temperature and open circuit voltage is shown in equation (1) v oc = eg q − nkt q in i0max isc (1) where: eg equals the bang gap energy, i0max is the maximum reverses saturated current, k is boltzmann’s constant, t is the temperature, n is the ideality factor, q is electron charge and isc is short circuit current. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onyenweuwa, temperature performance analysis of a photovoltaic module. azojete, 15(sp.i2):116-123. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 118 for silicon cell, (dvoc /dt) is approximately equal to -2 mv/°c., this means that, the efficiency of the cell drops by about 0.4 % for increase of every one degree celsius. a silicon solar cell of 20% efficiency at 20°c will reduce to 16% at 30°c (katkar et al., 2009). according to (yixian et al., 2012), the pv module efficiency varies linearly with temperature as follows: ηpv = ηref 1 − β tcell − tref (2) where: the value for β is dependent on the material. for crystalline silicon, the value is taken to be 0.0045/°c. ηref is the pv efficiency of the solar cell at the reference temperature tref = 25°c, ηref = 15%. 2.0 methodology in this work, comparative studies of the cell temperature of an air-condition cooled and uncooled monocrystalline photovoltaic module have been carried out. the experiments were conducted outdoor under the same atmospheric condition to investigate the effect of ambient temperature, active cooling of module system and module temperature variation on the electrical performance of the module. the data sets which included ambient temperature, module temperatures and voltage, generated by the cooled and uncooled module for a period of 8 hours (0900 – 1700) were measured using the thermometer, thermostat and voltmeter respectively. these data were used to evaluate the module efficiency using equation 2. the experimental setup is given in figure 1 and 2. figure 1: cooled module figure 2: uncooled module 3.0 result and discussion the temperature and voltage data for the cooled and the uncooled system are presented in the figures (3 – 8). in each of the figures, the curves for ambient temperature, module temperature, voltage and efficiency are plotted against the time period of 0900 to 1700 for both cooled and uncooled module. the ambient temperature for a given time is the same for both cooled and uncooled module for any given day. also, a rise in ambient temperature caused the module temperature and voltage to increase and decrease respectively. however, a slight decrease in ambient temperature at any given period of the experiment causes a corresponding decrease in module temperature, and increase in the open circuit module voltage output. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):116-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 119 figure 3: cooled module temperature and voltage time profile for day one figure 4: uncooled module temperature and voltage time profile for day one these results; which presented the relationship between the temperature and voltage against different hours of the day, show that the morning (0900 – 1200) hours were characterized by increase ambient temperature and module temperature and then decrease solar module voltage generated. the noon period (1200 – 1400) hours was characterized by peak temperature generation and low voltage generation for both modules: the module’s temperature gets to maximum while the voltage reaches minimum. also, the evening (1400 – 1700) hours was characterized by decrease in the ambient and module temperature and increase in voltage generated by both modules. the increase and decrease in module temperature as a result of ambient temperature changes is a function of the solar insolation, which is less in the morning and evening periods and more at noon periods file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onyenweuwa, temperature performance analysis of a photovoltaic module. azojete, 15(sp.i2):116-123. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 120 figure 5: cooled module temperature and voltage time profile for day two figure 6: uncooled module temperature and voltage time profile for day two the rise in module temperature is more obvious in the uncooled module and correspondingly, the voltage generated by this module is low compare to the cooled module. this shows that temperature affects the module performance and reducing the module temperature by cooling improves the module output. the spikes vividly shown in figure 5, 6, 7 and 8 can be related and explained by the sun being temporarily overcast by cloud. figure 7: cooled module temperature and voltage time profile for day three http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):116-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 121 figure 8: uncooled module temperature and voltage time profile for day three figure 9: module daily temperature figure 10: module daily voltage figure 9 and figure 10 present respectively, the total daily temperature and voltage of cooled and uncooled modules for the three days period of experiment. based on the data analysis, the cooled module voltage performed better compare to the uncooled module voltage. this is due to the cooling of the module, which reduces the temperature and heat build-up on the module and then improve the module performance. the calculated module efficiencies with respect to temperature against time for day 1, day 2 and day 3 are shown in figure 11, 12 and 13. based on the analysis of the data, the periods of 1200 hours to 1450 hours are characterized by lowest module efficiency generation and this is due to increase in ambient and module temperature as a result of increase in solar activities within the period. the module efficiency decreases for the period of 0900 hours to 1200 hours and increases for the period of 1450 hours to 1700 hours. this increase and decrease of the module efficiency is a function of decrease and increase in the module temperature respectively. this show that the efficiency of the pv module depends largely on the temperature. however, in all the periods of the experiment, the efficiency performance of the cooled module was high compared with the uncooled module and this indicates that the reduction in cell temperature due to active cooling process improved the efficiency of the module. the results obtained in this study are consistent with other studies (abdulgafar et al., 2014; achara and adikankwu, 2017; dubey et al., 2013; and fesharaki et al., 2011). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onyenweuwa, temperature performance analysis of a photovoltaic module. azojete, 15(sp.i2):116-123. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 122 figure 11: module efficiency for day 1 figure 12: module efficiency for day 2 figure 13: module efficiency for day 3 4.0 conclusion the temperature performance of the photovoltaic module has been studied for various periods of the day. it has been found that the output of the module depends on the module temperature. increase in module temperature causes a decrease in module voltage and efficiency output and vice versa. also, the voltage and efficiency generated by the cooled module is higher compare to the uncooled module generation under the same environmental condition and this further show that the reduction in module temperature due to active cooling process improved the efficiency of the module. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):116-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: henryadiks@gmail.com 123 references abdulgafar, sa. omar, os. and yousif, km. 2014. improving the efficiency of polycrystalline solar panel via water immersion method. international journal of innovative research in science, engineering and technology, 3(1): 15-25. achara, n. and adikankwu, ho. 2017. temperature characterization of solar module voltage generation. international journal of science and research (ijsr), 6(6): 1077 – 1081. adikankwu, ho. and ileberi, gr. 2016. voltage outputs of air-condition cooled monocrystalline pv module. international journal of innovation research in science, engineering and technology, 5(9): 16466 – 16472. akhator, pe. obanor, ai. and sadjere, eg. 2019. electricity situation and potential development in nigeria using off-grid green energy solutions. journal of applied science and environmental management, 23(3): 527 – 537. dubey, s. sarvaiya, jn. and seshadri, b. 2013. temparture dependent photovoltaic (pv) efficiency and its effect on pv production in the world – a review. energy procedia, 33: 311-321. fesharaki, vj. dehghani, m. and fesharaki, jj. 2011. the effect of temperature on photovoltaic efficiency. the proceeding of the first international conference on emerging trends in energy conservation –etec tehran, iran, pp20-28. katkar, aa. shinde, nn. kohli gc., and gaikwad, sp. 2009. evaluation of industrial solar cell with respect to temperature. journal of association of radiographers of nigeria, (23): 16-22. kumar, mn. saini, hs. anjaneyulu, ksr. and singh, k. 2014. solar power analysis based on light intensity. international journal of engineering and science, 05: 01-05. nikhil, pg. and premalatha, m. 2012. performance enhancement of solar module by cooling: an experimental investigation. international journal of energy and environment, 3(1): 73-82. oyedepo, so. 2012. on energy for sustainable development in nigeria. renewable and sustainable energy reviews, 16: 2583 – 2598. siddiqui, r. and bajpai, u. 2012. deviation in the performance of solar module under climatic parameter as ambient temperature and wind velocity in composite climate. international journal of renewable energy research, 2(3): 486–490 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1067-1081 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1067 original research article investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality d. kwawuvi1, t. a. ewemoje2*, f. k. owofadeju3 and a. f. adesina4 (1pan african university, institute of life and earth sciences (including health and agriculture), university of ibadan, oyo state, nigeria 2agricultural and environmental engineering department, university of ibadan, oyo state, nigeria 3wood products engineering department, university of ibadan, oyo state, nigeria 4department of geography, obafemi awolowo university, ile ife, nigeria) * corresponding author’s email address: ta.ewemoje@mail.ui.edu.ng 1.0 introduction the reliance on groundwater is gradually increasing due to its perceived quality. however, with the increase in human population and the negligence exhibited towards waste management, groundwater is now susceptible to pollution from the increased wastewater generated due to increased human population. in developing countries especially, waste management has been reported to be an environmental and public health problems (akoteyon et al., 2011). in many developing countries like ghana, the most common method of waste disposal is through the land filling or open dumps. the dumping of solid waste in uncontrolled landfills can cause significant impacts on the environment and human health (dong et al., 2008). the pollutant that infiltrate from dumpsite has once been described as the worst threats to groundwater quality article information abstract this study investigated the possible groundwater quality threats from excessive removal of vegetation due to urban growth in an open dumpsite in waterloo, brong ahafo region, ghana. 15 water samples were collected from five (5) functional hand-dug wells at increasing distance from the dumpsite. the samples were assessed for some physico-chemical parameters. descriptive statistics were applied to investigate the quality of groundwater samples from the hand-dug wells. the groundwater was slightly acidic. total suspended solids (tss) and total coliform count were high for the groundwater samples but total dissolved solids (tds) were within the permissible limits of ghana ministry of water resources (gmwr) and who. analysed parameters such as ca2+, na+, cland cu conformed to the prescribed limits of gmwr and who for drinking water while pb was above the permissible limits of both. fe2+ conformed to the limit by gmwr but was above who. cd was above the permissible limit of gmwr but fell within that of who. urban growth effects investigated through the use of landsat images of 1986, 2000, 2006 and 2011 with the aid of arcgis 10.5 and envi 4.7 revealed that the study area, within these years, drastically reduced in forest cover due to the increase in built-up and has the tendency to cause contamination to groundwater in the area. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 07 may, 2018 revised 14 june, 2019 accepted 20 june, 2019 keywords: water quality land use land cover dumpsite sunyani built-up groundwater leachate. mailto:ta.ewemoje@mail.ui.edu.ng http://www.azojete.com.ng kwawuvi et al: investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality. azojete, 15(4):1067-1081. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1068 (mor et al., 2005). when waste is disposed at landfills, it undergoes series of physical, chemical and microbiological changes that results in the release of a toxic liquid known as leachate, which contains numerous organic and inorganic compounds. the leachate will continuously migrate through the soil strata, eventually contaminating the groundwater system if not prevented (kanmani and gandhimathi, 2013). the sunyani municipal in ghana has a main dumpsite where all wastes generated within the municipality are dumped. this municipal dumpsite is situated within 700m radius of several hand-dug wells that serve as a source of water for drinking and irrigation for the waterloo community. continued drinking of water from these wells may impair the health of the inhabitants because of its negative effects on the irrigated crops. exposure of waste dumpsites to storm water, results in the flow of liquid, salts, organic and inorganic compounds out of the dumpsite and predictably into surface or groundwater sources causing contamination (ewemoje et al., 2017). on this basis, it is necessary to understand the current and potential impacts on groundwater sources in sunyani municipality with a view to assessing the impacts of removal of vegetal cover in the area leading to increased built-up area and its attendant effects on groundwater quality and quantity within the municipality. 2.0 methodology 2.1 location of the study area sunyani is a city in the republic of ghana and is the capital of sunyani east municipal district and brong ahafo region (figure 1a). the sunyani municipal assembly covers a total land area of 506.7 km2. it lies approximately between latitudes 7.20°n and 7.05°n and longitudes 2.30°w and 2.10˚w (table 1). it is bordered on the north by sunyani west district; west by dormaa east district, south by asutifi district and east by tano north district. sunyani also lies within the middle belt of ghana between 750 (229 meters) to 1235 feet (376 meters) above sea level (googleearth.com). the city falls within the wet semi-equatorial climatic zone of ghana. the mean monthly temperature varies between 23°c and 33°c with the lowest temperature observed around august and the highest around march and april. the relative humidity is high, averaging between 75 and 80 % during the rainy seasons and below 70 % during the dry seasons of the year, creating an ideal climate for luxurious vegetative growth. the city experiences a bi-modal rainfall pattern with the main rainy season being between march and september and the minor between october and december (sunyani municipal assembly, 2014). figure 1b is a view of the sunyani municipal dumpsite and its features are shown in tables 2 and 3. table 1: sunyani dumpsite location data parameter location landfill longitude 2.320° w landfill latitude 7.290° n city/town sunyani administrative area sunyani municipal area source: (sunyani municipal assembly, 2014) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1067-1081. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1069 figure 1a: map of sunyani municipal figure 1b: a view of sunyani municipal dumpsite table 2: sunyani dumpsite physical data parameter description landfill type open dump landfill size – designed area 25 hectares designed capacity average waste depth about 1.5m waste types accepted msw, septage year filling began 1998 closure year source: (sunyani municipal assembly, 2014) source: (sunyani municipal assembly, 2014) 2.2 experimental design water samples from hand-dug wells located in waterloo community downstream of the dumpsite were collected and analysed. the sampling was undertaken between 18th and 20th january, 2018. purposive sampling method as reported by ewemoje et al. (2017) was employed to collect the groundwater samples from hand-dug wells (gw1, gw2, gw3, gw4 and gw5), out of 7 hand-dug wells (2 collapsed), which were within 700m radius from the dumpsite. a total of 15 water samples were collected from each of the hand-dug wells for analysis. the water samples were collected from the wells using drawing buckets tied with ropes. the groundwater samples were then collected in acid-washed polyethylene bottles of 1l capacity after rinsing with the sample. all samples were preserved in ice cooler to control effects of ambient temperatures on the sampled water to avoid deterioration of the samples. the gps table 3: site facilities and infrastructure data parameter description weighbridge none fencing none leachate collection none gas collection none treatment ponds none file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kwawuvi et al: investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality. azojete, 15(4):1067-1081. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1070 coordinates for each sampled hand-dug well and the dumpsite were recorded using gps garmin etrex10. a water sample location map was created from the collected gps coordinates using arcgis 10.5 (figure 2). figure 2: water sample location map 2.3 analytical procedures all the samples were taken to the civil engineering laboratory at kwame nkrumah university of science and technology for analyses. the ph was measured using the pc 300 waterproof handheld ph meter, total suspended solids (tss) using the gravimetric determination, total dissolved solids (tds) using the hach conductivity-tds meter. total coliform count was examined through the membrane filter technique using chromocult coliform agar. cadmium (cd), iron (fe2+), lead (pb) and copper (cu), were tested using the atomic absorption spectrophotometer (a.a.s) in the water samples (ackah, 2011). the sample aliquot was absorbed in nitric acid, diluted appropriately, then aspirated and the absorbance was then measured spectrometrically for each of the trace elements being tested. sodium (na+) and calcium (ca2+) were analysed using a sherwood model 420 flame photometer. chloride (cl-) was analysed using the argentometric method following protocols by the american public health organisation (1992). values obtained from these analyses were compared with the minimum standards set by the ghana ministry of water resources (gmwr) and world health organisation (who). descriptive statistics were used to describe the basic features of the data in the study. they provide simple summaries about the sample and the measures. together with simple graphics analysis, they form the basis of virtually every quantitative analysis of data. descriptive statistics simply describes what the data is, and what it shows (trochim, 2002). microsoft excel 2013 was used to compute the descriptive statistics from the replications of the analysis and the results presented in a table. 2.4 hydro-chemical data validity checks hydro-chemical data obtained from laboratory analysis in the study area were subjected to internal consistency tests. the concentration of the major anions and cations were compared to ensure that these concentrations were within ±5 of each other, using the charge balance error formula presented in equation (1) (hounslow, 1995). charge balance error = ∑cation−∑anion ∑cation+ ∑anion × 100% (1) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1067-1081. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1071 where: σcation is the sum of cations and σanion is the sum of anions. according to hounslow (1995), if the electrical balance calculated is less than 5%, then the analysis is assumed to be good and if it is greater than 5% the analysis is supposed to be poor or some missed constituent were not included in the calculation or the water is very acidic. the hydro-chemical data from the laboratory analysis of the water samples had charge balance error less than 5% and were permitted for further descriptive statistics. 2.5 land use/cover change analysis in the study area to examine how vegetal cover in the area has been replaced with built-up and its potential impact on the groundwater quality of waterloo, landsat 7 etm+ images of the area, for the years, 1986, 2000, 2006 and 2011 were obtained from the u.s geological survey archives. these images were processed to know whether changes that have occurred in the area are as a result of urban growth. the images were analysed using envi version 4.7, arcgis version 10.5 and ms excel 2013. data sets used for the study, their source and date of acquisition are shown in the table 4. table 4: landsat images used in the analysis of the study area landsat satellite wrs date of spatial spectral source sensor path/row acquisition resolution resolution 1 landsat 7 etm+ 195/055 20/11/1986 30m 8 bands glcf 2 landsat 7 etm+ 195/055 2/2/2000 30m 8 bands glcf 3 landsat 7 tm 195/055 5/5/2006 30m 8 bands glcf 4 landsat 7 tm 195/055 5/5/2011 30m 8 bands glcf 2.6 methods of image analysis 2.6.1 accuracy assessment for landsat images accuracy assessment is an integral step in analysing any land classification. accuracy assessment is the process by which the accuracy or correctness of an image classification is evaluated. it involves comparing the classified image to reference data that are assumed to be true (maus and golden, 1996). the assessment helps to determine whether or not the classified image is feasible depending on the acceptable level of error in the image. by selecting region of interests (rois) identified in the image and which are evenly distributed, the accuracy level of the map can be determined. equal number of pixels selected for the rois is not advisable as some classes may have larger number than others (thus, the larger the class, the more the pixels). 2.6.2 image pre-processing for analysing the change in the land cover, radiometric and geometric restorations are crucial in every remotely sensed data analysis. geometric restoration gives the accurate orientation of the satellite images, thus georeferencing the image. the acquired images had already been georeferenced from the world geodetic system (wgs 1984). they were re-projected to the coordinate system of the study area. that is, universal transverse mercator (utm zone 30 north, ghana) using envi version 4.7. radiometric restoration removes or suppresses the degree of spectral differences emanated from each detector causing distortion in the imagery. examples of such distortions are striping, scan line drop-out and atmospheric haze. the data-sets that were mostly affected by these distortions were the landsat 7 imageries for the years 2006 and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kwawuvi et al: investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality. azojete, 15(4):1067-1081. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1072 2011. landsat 7 tm developed a scan line corrector failure which made it impossible to have a correct image for the entire area [usgs, 2010]. the scan lines in the imagery were removed using the gap-fill method in envi version 4.7. 2.6.3 image enhancement this method deals with modifying or improving the quality of the image, making it more suitable to be perceived by the human eye. in order to improve the visibility of the images, a colour composite for the images were established using landsat etm+/tm bands 4, 3, 2, (near infrared, red and green) which were layer stacked for 1986, 2000, 2006 and 2011 images and created a false colour composite images in envi version 4.7 (figure 3). the false colour composite was selected because vegetation usually reflects an infrared colour, thus they appear in shades of red/dull red to pinkish smooth, built-up/urban areas in cyan blue, and soils vary from light brown and water appears very dark (desai, 2014). 2.6.4 change detection and analysis change detection measures the changes that have occurred in an area over a period of time. the study revealed the percentage cover change detected over the different years observed with regards to the landsat images analysed in arcgis 10.5 and envi 4.7. this was known by multiplying 30m×30m (i.e. 900 sq. meters /0.09 ha) to give the area of each raster cell in projection. for each class, the cell area was then multiplied with their respective cell count (table 5) and final values were then multiplied by 100 to give the percentage cover change for each year. 3.0 results and discussion the preliminary results of euclidean distance function performed in arcgis version 10.5 to determine the distance of each sampled hand-dug well from the dumpsite was given in table 5. table 5: sampled wells and their distance from dumpsite wells distance from dumpsite (m) gw1 300.37 gw2 460.15 gw3 471.34 gw4 490.72 gw5 664.63 3.1 change detection measure the percentage cover change detected over the different years observed with regards to the landsat images analysed in arcgis 10.5 and envi 4.7. this is illustrated in table 6 and figure 3 respectively. 3.2 physico-chemical characteristics of groundwater samples the groundwater samples are slightly acidic with ph ranging from 5.13-7.78 corresponding to a mean value of 6.19 ±0.924 (n = 5). the values of tss varied between 2-144 mg/l. the tds in the groundwater samples varied between 33.91-176.08 mg/l. total coliforms observed in the groundwater were very high with values between 143-300 cfu/100ml. iron (fe2+), calcium (ca2+) and sodium (na+) varied respectively between 0.179-0.466 mg/l with a mean value of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1067-1081. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1073 0.29±0.102 mg/l (n = 5), 2.4-37.68 mg/l with a mean value of 13.47±12.538 mg/l (n = 5) and between 5.214-11.448 mg/l with a mean value of 6.84±2.388 mg/l (n = 5). the proportion of chloride (cl-) present in the groundwater samples ranged between 18-46 mg/l with a mean value of 27.4±9.731 mg/l. the concentrations of cadmium (cd), lead (pb) and copper (cu) varied respectively between 0.005-0.023 mg/l (mean value of 0.01±0.006 mg/l; n = 5), 0.0230.038 mg/l (mean value of 0.03±0.005 mg/l; n = 5) and between 0.117-0.158 mg/l (mean value of 0.13 ±0.014 mg/l; n = 5) (table 7). table 6: land use land cover (lulc) cell counts lulc category 1986 2000 2006 2011 vegetation 738777 729101 34746 10717 built-up 785561 795237 1489592 1513621 figure 3: false colour composite of landsat images file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kwawuvi et al: investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality. azojete, 15(4):1067-1081. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1074 table 7: physico-chemical results of groundwater samples hand dug wells standard gmwr (2015) who (2014)parameters gw1 gw2 gw3 gw4 gw5 min max mean deviation ph 6.7 5.21 5.65 5.71 7.68 5.13 7.78 6.19 ±0.924 6.5-8.5 6.58.5 tss (mg/l) 15 45 7.33 92.67 3 2 144 32.60 ±41.862 0 0 tds (mg/l) 173.8 34.45 48.4 41.81 81.4 33.91 176.08 75.97 ±53.301 1000 600 tc cfu/100ml 250.67 290 287.33 147 238.67 143 300 242.73 ±56.533 0 0 fe2+ (mg/l) 0.18 0.29 0.46 0.3 0.21 0.179 0.466 0.29 ±0.102 0.3 0.01 ca2+ (mg/l) 35.27 2.67 4.01 8.01 17.37 2.4 37.68 13.47 ±12.538 200 200 na+ (mg/l) 11.34 5.42 6.69 5.44 5.3 5.214 11.448 6.84 ±2.388 200 200 cl(mg/l) 45.33 22.33 25.67 24 19.67 18 46 27.4 ±9.731 250 250 cd (mg/l) 0.005 0.012 0.014 0.021 0.015 0.005 0.023 0.01 ±0.006 0.003 0.01 pb (mg/l) 0.026 0.037 0.023 0.028 0.033 0.023 0.038 0.03 ±0.005 0.01 0.01 cu (mg/l) 0.12 0.15 0.13 0.12 0.11 0.117 0.158 0.13 ±0.014 2 0.4 tss: total suspended solids; tds: total dissolved solids; tc: total coliform count; gw: hand-dug wells; min: minimum; max: maximum; gmwr: ministry of water resources, ghana; who: world health organisation 3.3 accuracy assessment for landsat images the accuracy assessment was performed on the classified image using envi 4.7 version (figure 4). through the application of post classification analysis, a confusion matrix was done for the regions of interest (rois) (i.e. vegetation and built-up). confusion matrix composed of the kappa coefficient (k), overall accuracy, producer’s accuracy (errors of omission), user’s accuracy (errors of commission). overall accuracy is the total accuracy of the classified image. errors of omission occur when a pixel is left out of the category being evaluated. errors of commission result when a pixel is incorrectly included in the category being evaluated. kappa coefficient (k) gives a discrete multivariate technique used in accuracy assessment, thus k>0.80 gives a strong accuracy of the class assessed, 0.40 – 0.80 is average and < 0.40 is poor (tables 8 and 9). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1067-1081. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1075 figure 4: land use/cover map of sunyani (1986-2000; 2006-2011) source: (sunyani municipal assembly, 2014) table 8: summary of overall accuracy and kappa coefficient year classified image overall accuracy (%) overall kappa coefficient (k) 1986 landsat7 etm+ 99.98 0.999 2000 landsat7 etm+ 100 1 2006 landsat7 tm 100 1 2011 landsat7 tm 99.97 0.999 table 9: summary of user's and producer's accuracy vegetation built-up year user's accuracy (%) producer's accuracy (%) user's accuracy (%) producer's accuracy (%) 1986 100 99.98 99.96 100 2000 100 100 100 100 2006 100 100 100 100 2011 99.87 100 100 99.97 3.4. change detection results for landsat images (1986-2000, 2006-2011) the changes that have occurred in the area between the periods of 1986 to 2011 are shown in table 10. table 10: land use land cover distribution 1986 2000 2006 2011 lulc category area (ha.) area (%) area (ha.) area (%) area (ha.) area (%) area (ha.) area (%) vegetation 66489.93 48.47 65619.09 47.83 3127.14 2.28 964.53 0.7 built-up 70700.49 51.53 71571.33 52.17 134063.3 97.72 136225.9 99.3 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kwawuvi et al: investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality. azojete, 15(4):1067-1081. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1076 3.5 discussion 3.5.1 physico-chemical characteristics of groundwater the range of groundwater ph values reveals that the samples are slightly acidic. this could be attributed to discharge of acidic water into these sources from the dumpsite leachates, agricultural and domestic activities in the study area (brian, 2012; nyamekye, 2013). acidic water enhances the potential of dissolved rock minerals to release harmful trace metals into water making it toxic for human consumption (obeng, 2015). also, with acidic water, the growth and proliferation of microorganisms including coliforms tend to increase and this might affect the safety of the water for drinking purposes (mario et al., 2017). the hand-dug wells recorded a concentration of tss above the gmwr (2015) and who (2014) permissible limits of 0 mg/l for drinking water. poor management practices from activities such as construction and agriculture can strip vegetation and allow the quick influx of sediments into groundwater via overland flow (sharp, 2010). this could also be attributed to the likelihood of sediments entering the wells since they are open dug. tds values recorded for the groundwater samples were below the criteria set by both gmwr and who. however, the observed tds concentration may arise from the removal of grassland in the study area, which could have help to filter out sediments and associated nutrients (lee and isenhart, 2000). according to who (2006), there has not been any deleterious physiological reactions occurring in persons consuming drinking water that have tds values in excess of 1000mg/l. (kempster et al., 1997) reported that the consumption of water with a critical tds value of >1000 mg/l may result in some long term health problems due to excessive concentrations of dissolved particles in drinking water. the groundwater showed a concentration of total coliform above the prescribed limits of gmwr and who. this could be from the disposal of faecal matter by waste management companies in an area close to the dumpsite, domestic animal droppings as well as from the dumpsite which lies uphill of the wells. consumption of the groundwater can cause numerous cases of illness such as ear and eye discharges, skin rashes and gastrointestinal problems as revealed by recent study of chithra et al. (2015). the concentration of iron (fe2+) was found to conform to the permissible limit of gmwr but was above that of who for drinking water. the presence of fe2+ in the groundwater samples might be from the migration of leachates from the dumpsite into the wells as suggested by denutsui et al. (2012) and osei et al. (2011) from their study on abandoned waste disposal sites. also, the presence of iron in the groundwater could partly be from the windlass fixed on the wells which helps in drawing the water as well as infiltration from the heap of scrap metals gathered by scrap dealers as observed in the study area. it has been remarked by akinbile (2006) and shyamala et al. (2008) that the formation of blue baby syndrome in babies and goitre in adults are the results of consumption of water containing iron above the specified quantity. an essential element that is present in the human body is calcium. the concentration of ca2+ was within the permissible limits of gmwr and who. calcium ion (ca2+) can occur naturally in groundwater through the dissolution of carbonate minerals and the decomposition of sulphate, phosphate and silicate minerals (cabbina et al., 2012). the concentration of na+ in the groundwater was within the acceptable standard of gmwr and who. however, the presence of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1067-1081. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1077 sodium might be from releases from the dumpsite and domestic wastes. also, sodium is often naturally found in groundwater but can also result from sources such as road salt, water softeners, natural underground salt deposits, pollution from septic systems (who, 1979). the concentrations of clin the groundwater were within the acceptable limits of gmwr and who. high concentration of chloride in drinking water gives a salty taste and has a laxative effect on people not accustomed to it (ackah, 2011). the concentrations of cadmium in the groundwater samples were above the acceptable standards of gmwr but fell within who. the presence and high levels of cadmium observed may be attributed to the fact that the dumpsite receives paint pigment wastes, and the burning of cadmium-containing pvc plastics (dadzie, 2012). this makes the groundwater not suitable for drinking as its accumulation over a period of time can result in health problems. lead (pb) concentrations in the groundwater were far above the gmwr and who permissible limits. possible sources of lead contamination may be batteries, photographs, old lead-based paints and lead pipes disposed at the landfill, which are toxic to all forms of life (al-yaquot and hamoda, 2003). this result could be alarming to public health and for the environment because heavy metals such as lead is a carcinogenic substance and can adversely affect mental and neurological functions as well as altering metabolic processes in the human body system (adeyi and majolagbe, 2014). copper concentration in the groundwater samples were below the gmwr and who standards. the presence of copper in the groundwater samples, however, might be from migration of leachate from the dumpsite and domestic waste waters. leachate from a solid waste disposal site is generally found to contain trace metals like copper as suggested by a study of freeze and cherry (1979). 3.5.2 land use land cover changes in the study area a land use land cover change in the study area based on two classes (i.e. vegetation and builtup) is presented in figure 4. the expansion of cities is generally at the expense of destruction of forests and other natural ecosystems, thereby resulting in the increase in both air and water pollution (afdb, 2012). it was discovered from the classified landsat scenes that the year 1986 had a forest cover spanning a percentage area of 48.47% whilst 51.53% represented built-up areas. however, in the year 2000, it was revealed that the area of land with vegetation had reduced to 47.83% whereas the land area for built-up increased to 52.17%; in 2006, vegetal cover for the study area was revealed to be 2.28% with built-up covering an area of 97.72% and in the year 2011, vegetation was discovered to have further reduced to a percentage area of 0.7% whereas built-up further increased to cover a percentage area of 99.3% (table 10). the upsurge in population in the study area is contributing to the depletion of biodiversity resources. it has also led to congestion thereby driving it towards increased demand for land resources (sharma et al., 2012). this has adverse effects on both surface and groundwater resources because whatever happens on the land eventually ends in water bodies (randolph, 2012). as stated by forster and cherlet (2012), the removal of vegetation has a major influence on both groundwater quality and recharge rates. significant land-use change such as clearing of natural vegetation and forests, can have long lasting, and in some cases, irreversible impacts on aquifers; it can result in the mobilization of salt from sub-soil zone and a significant increase in recharge rate on flat grounds. the removal file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kwawuvi et al: investigating the possible threats from vegetal cover removal and open dumpsite to groundwater quality. azojete, 15(4):1067-1081. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1078 of vegetation in the area to cater for urban developments will also lead to increased imperviousness, which in turn induces more total runoff capacity. high percent impervious surface has been associated with increase in urban growth and a decrease in surrounding water quality because greater pollutant loads are transported to runoff flow channels (brabec and schulte, 2002). increase in impervious cover and runoff directly impact the transport of nonpoint source pollutants including disease-causing organisms from failing septic systems, nutrients, toxic contaminants, and sediment (hurd and civco, 2004; schueler, 1987). the transport of these highly potential pollutants through storm water runoff can in certain weather conditions degrade soil and percolate underlying layers thereby contributing to the degradation of groundwater quality (chithra et al., 2015). grasslands, in particular, help to filter out sediments and the associated nutrients (lee and isenhart, 2000), therefore provide an essential and unique way of improving water quality. hence this could render groundwater in the area susceptible to contamination. 4.0 conclusion the study reveals the case of waterloo community, where inhabitants primarily rely on groundwater within at least a 700m radius from a dumpsite, as a major environmental concern. the physico-chemical analysis from the study revealed that the groundwater samples are slightly acidic (ph = 5.13-7.78). tss (2-144 mg/l) and total coliform (143-300 counts/100ml) were above the acceptable limits of both gmwr and who while tds (33.91-176.08 mg/l) fell within the permissible limit of both gmwr and who. parameters such as ca2+, na+, cland cu with the mean values of 13.47±12.538 mg/l, 6.84±2.38 mg/l, 27.4±9.731 mg/l and 0.13±0.014 mg/l respectively were within the prescribed limits of both gmwr and who. other parameters such as pb, with the mean vale of 0.03±0.005 mg/l had a relatively high value that deviated from the acceptable limits of both gmwr and who; fe2+ with the mean value of 0.29±0.102 mg/l conformed to the limit by gmwr but was above the permissible limit set by who, and cd with the mean value of 0.01±0.006 mg/l, was also above permissible limit by gmwr but fell within the acceptable criteria by who. the groundwater in waterloo is therefore not recommendable for drinking. analysis of the forest cover in the study area through the aid of landsat images revealed that in the in the year 1986, the study area had 48.47% forest cover and built-up area of 51.53%; in the year 2000, percentage vegetal cover had reduced to 47.83% and built-up area increased to 52.17%; in the year 2006, percentage vegetal cover disturbingly reduced to 2.28% and built-up area increased to 97.72% and finally, in the year 2011, the study area had its percentage vegetal cover reduced to 0.7% with built-up area increasing to 99.3%. this extent of vegetation removal has the likelihood of inducing high runoffs and if pollutants within these runoffs are able to infiltrate the soil, they can have the potential to degrade groundwater quality in the area. this, therefore, is a major concern that requires necessary attention in waterloo. , acknowledgements: our sincere thanks to pan african university, and the waterloo community for the permission to carry out the study on the hand-dug wells. references ackah, m., agyemang, o., anim, ak., osei, j., bentil, no., kpattah, l., gyamfi, et. and hanson, jek. 2011. assessment of groundwater quality for drinking and irrigation: the case study of teimanhttp://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; 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vol. 15(4) 1067-1081. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ta.ewemoje@mail.ui.edu.ng 1081 obeng, m. 2015. assessment of groundwater quality in bogoso, a mining community in the western region of ghana. msc. thesis, kwame nkrumah university of science and technology, kumasi, ghana, p. 13. osei, j., osae, sk., fianko, jr., adomako, d., laar, c., anim, ak., ganyaglo, sy., nyarku, m. and nyarko, es. 2011. the impact of oblogo landfill site in accra-ghana on the surrounding environment. research journal of environmental and earth sciences, 3: 633-636. randolph, j. 2012. environmental land use planning and management; island press: washington, dc., usa. schueler, tr. 1987. controlling urban runoff–a practical manual for planning and designing urban best management practices; prepared for metropolitan washington water resources planning board. washington, dc, usa, pp. 240. sharma, l., pandey, pc. and nathawet, ms. 2012. assessment of land consumption rate with urban dynamics change using geospatial techniques. journal of land use science, 7: 135-148p. sharp, jm., jr. 2010. the impacts of urbanisation and groundwater systems and recharge. aquamundi, pp. 051-056, doi: 10.4409/am-004-10-0008. shyamala, r., shanti, m. and lalitha, p. 2008. physico-chemical analysis of borewell water samples of telun-gupalayam area in coimbatore district, tamilnadu, india. e-journal of chemistry, 5: 924–929. sunyani municipal assembly. 20114. report on draft 4-year medium term development plan (2014-2017), 2014. 21-25p. sunyani municipal assembly. 2012. district information. available online: http://sunyani. ghanadistricts. gov.gh /?arrow=dnf&_=30&r=10&rlv=climate accessed on 26 september 2017. trochim, wmk. 2002. research methods knowledge base. cornell university: cornell, usa, available online: http://trochim.human.cornell.edu/kb/index.htm (accessed on may, 26, 2018). usgs. 2010. united states geological survey: landsat missions. slc-off products: background. available online at: http://landsat.usgs.gov/products_slcoffbackground.php (accessed on august, 20, 2017). who regional office for europe. 1979. sodium, chlorides and conductivity in drinking water: euro reports and studies no. 2; who: denmark, copenhagen. who. 2006. guidelines for drinking water quality, 3rd ed.; who: geneva, switzerland. who. 2014. guidelines for drinking water quality. chemical fact sheets 12; who: geneva, switzerland. http://trochim.human.cornell.edu/kb/index.htm http://landsat.usgs.gov/products_slcoffbackground.php file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):124-145 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 124 original research article a feasibility study of mini-hydroelectric power plant for seasonal base load i. i. ozigis1, s. o. oodo2 and i. d. muhammad1 1department of mechanical engineering, university of abuja, nigeria. 2department of electrical engineering, university of abuja, nigeria. article information submitted: 12/12/2018 revised: 26/12/2018 accepted: 18/03/2019 keywords: base load electricity feasibility mini-hydropower. abstract this paper presents a feasibility study of a mini-hydroelectric power plant for seasonal base load at the main campus of university of abuja, along airport expressway, abuja, nigeria. the study was premised on the need to mitigate the insufficient electricity supply being experienced by the university. the use of backup diesel and petrol generating sets was noted to increased the overall operating costs of the university due to the need to purchase fuel, in addition to the associated maintenance cost. the presence of river wuye within the university brought to fore the need to explore the establishment of a hydropower plant as an alternative means of mininmizing the energy shortage. the methodology adopted included determination of the university electricity demand using clamp-on meter, determination of the river run-off via data obtained from nigerian meteorological agency (nimet), flow rate with the use of float and river geometry, while the head was obtained by global positioning system (gps). furthermore, the hydroelectric power potential, site layout for equipment installation and project cost were determined. the results indicated that the monthly lowest energy consumption (base load) at the university during the period of study was at 667 kw, while the highest (peak) load was 883 kw. river wuye assessment favoured conventional hydro power plant instead of hydro power plant technologies with out dam such as paddle wheel system as giri river flow was low and seasonal. river giri has run-off of 1,330 mm with the proposed dam estimated to have height and length of 10 m and 120 m, respectively. river wuye has a flow rate of 14.5 m3/s, maximum head of 10 m and hydropower potential of about 855 kw. the cost of the proposed hydro power plant ranged from 80.3-615.6 million naira (n) (equivalent to n93,960/kwn720,000/kw or $261/kw-$2000/kw).the range arose due to variation on cost of refurbished or new turbine-generator system and civil works. the electricity generation unit cost from the hydropower plant is expected to be n24.74-50.14/kwh. this feasibility work is significant as it will aid commencement of detailed project report (dpr) that will highlight detailed study of hydrology and geology, environmental impact assessment, flood control and weir structures for a hydropower plant on river wuye at 885 kw. in addition, when river wuye has low flow, wind and solar power plants could be deployed to provide the shortfall in electricity supply to the university © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 125 1.0 introduction electricity generation from flow of river is a clean and environmentally friendly renewable energy source. hydropower system relies on the kinetic and potential energies in flowing river (abebe, 2014). hydropower plant as a renewable energy system has continued to be a major contributor to the energy mix of nigeria (zarma, 2006). hydropower plant is currently the least expensive source of electric power and is much cleaner than power generated from fossil fuel. hydro power plant has remained a leading energy technology for isolated rural locations and is reliable; particularly for steady minimum electrical energy consumption in a period in a facility (base load). conventionally, the decision to establish a hydropower plant depends on an outcome of feasibility study. the economic evaluation of the hydro power by levelized cost of electricity (lcoe) will guide choice of unit energy cost for returns on the project and level of profitability between other alternative energy sources (fichtner, 2016). lcoe is useful to estimate future cost of electricity from a proposed hydropower plant. feasibility of hydropower also involves study of natural conditions such as topography, hydrology and energy potential that will aid commencement of detailed project report (dpr). detailed project report includes extensive study of hydrology, geotechnics, water quality, environmental impact assessment, flood control and weir structures, turbine-generator and power house, layouts among others. feasibility and detailed project reports are initial two stages, which are followed by tender and construction in development of a hydropower plant. hydropower plant technologies without dam and the conventional hydropower plant with dam are choices available in feasibility decisions. hydropower plant without dam includes paddle wheel hydropower plant that produces electric power out of flowing river (akinyemi and liu, 2015). the paddle wheel hydropower plant without dam, has easily rotatable pairs of paddle wheel by river flow and anchored in a river while water passes through the equipment. the kinetic energy of river rotates the paddle wheel with high torque at their axes. the rotating paddle will then drive a synchronous generator to produce electric power. another variant of a hydropower plant without dam is the turbulent hydropower plant. this technology involves the installation of a basin into which is lowered a generator. the river then flows through the associated canal into a turbine and produces energy as long as the river is flowing. the hydro power plants without dam needs floating platform and are useful in hill regions with rich water source (magureanu et al., 2011). conventional hydro power plants on the other hand require some levels of heads to establish a dam. the water in dam enters into turbine through a penstock or pipeline with valves to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 126 regulate flow (figure 1). water is returned to river at the down-stream of a turbine through a tail race with minimum wastage, after the energy had been extracted as it passes through the turbines. the generator transfers electricity to a step-up transformer for transmission to the area where the electricity is needed. the turning shaft of the turbine leads to the generation of electricity with regulated voltage and frequency (figures 1 and 2). figure 1: a schematic diagram of hydro power plant (johnson et al., 2012). figure 2: a schematic diagram of turbine-generator system (haugen, 2013). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 127 the first sets of hydropower plants in nigeria, were established in north central nigeria, on the sanga river system at ankwil i (1mw), ankwil ii (2 mw) and kurra (8mw) in 1929. nigeria has well established and fully operational hydropower plants at kainji (760 mw) commissioned in 1968; at jebba (570mw) commissioned in 1984; at shiroro (600mw) commissioned in 1990 and many others as reported by zarma (2006). sizes for small hydropower plants in various capacities such as small (l10 mw), mini-hydro (0.5 1mw), micro-hydro (50 to 500 kw) and pico-hydro (050 kw), are found across nigeria (adejumobi et al. 2013). available head between reservoir and tail race levels can be used to classify a hydropower into classes such as low head (h < 30 m), medium head (30 m < h <100 m ) or high head ( h >100) as stated by rao and parulekar (2004). nigerian landscapes, therefore, has great potential for more hydropower plants on account of her numerous rivers, to increase her electricity generation from hydro power plants into the national grid. the proposed location of weir on river wuye at giri is as shown in figure 3. proposed weir location on river wuye at giri figure 3: river wuye at giri, abuja, nigeria the study area is located within abuja, nigeria (figure 4). the main user of the proposed hydro power plant is the main campus of the university of abuja, located along airport-giri expressway, abuja. giri mean temperature ranges from 21oc to 34oc within the period of the study (nimet, 2016). river wuye is normally affected by the rainy, harmattan and dry seasons resulting in fluctuations occurring in its flow. seasonal rainfall prediction is useful in renewable energy studies particularly in the design of hydro, wind and solar power plants as reported by nimet (2016) and odeh (2014). river wuye traverses the university land at giri bounded by longitudes 7o09’54’’e and 7o10’38’’e and latitudes 8o59’13’’n and 8o59’49’’n. the river flows into river usuma, which is a tributary of river gurara (dikedi, 2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 128 figure 4: river wuye, giri, federal capital territory, abuja, nigeria (dikedi, 2012). nigerian meteorological agency (nimet, 2016), has several weather stations with rain gauges and mercury-in-glass type thermometers that measures rainfall and temperature, respectively. the records of both rainfall and temperature against time, are useful in the generation of river run-off, flow duration curves as well as storage capacity for dams (rajput, 2012). the nigerian rural electrification agency reported in an energy audit that 37 nigeria federal universities and 7 university teaching hospitals, use over 1,068 diesel electricity generating sets to provide electricity in their campuses (rea, 2018). the electricity supply from the national grid does not meet the needed energy for various activities in the university of abuja. this is compounded by load shedding, power outages and high costs of fuel and maintenance for backup electric generators, in addition to air and noise pollutions (ezema et al., 2016). the aim of this study is to develop feasibility study for the establishment of a hydropower plant on river wuye, at giri. the objectives are: the determination of the electricity demand of the university of abuja; estimation of river wuye run off and hydrology in giri, abuja; determine the characteristics of the hydro power plant (riverflow rate, head, capacity) and outline the plant layout as well as carry out the economic analysis of the hydro power plant 2 methodology 2.1 electricity demand of the university of abuja the estimated energy load was determined based on a walkthrough audit of the electrical supply to buildings using clamp-on meter of model 605 with accuracy of ± 2%, for example, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 129 17.63 ± 0.35a (aemc, 2012). the current in conductors were measured with clamp-on meter according to procedures described by aemc (2012). also, taken were records of installed electrical equipment and appliances ratings and the periods energized per day in all faculties/units, according to procedures reported by gul and patidar (2015) and delmastro et al. (2016). 2.2 river run-off and hydrology of giri, abuja the river run-off and hydrology provides insight into amount of water available and seasonality for prediction of energy generation at the potential site for hydropower plant. 2.2.1 river giri run-off estimation rainfall and temperature data for giri, abuja, were obtained from nigerian meteorological agency (nimet, 2016) and adopted for this work. river run-off was determined using equation (1) as follows (rajput, 2012): tfr 811.4 (1) where: r is the annual run-off in the area in mm, f is the annual rainfall (mm) and t is the mean monthly temperature (ok) 2.2.2 hydrology of giri area the characteristics of the river wuye discharge and storage capacity at the giri, for the proposed hydropower plant was evaluated by flow duration curve (fdc) according to the procedures outlined by rajput (2012) and karki (2014). the fdc to determine the storage capacity was carried out by ministry of water resources, abuja (fmwr, 2014) and was adopted for this work. 2.3 the characteristics of the proposed hydro power plant. the specifications of hydropower plant covered in this work were river flow rate and head of river wuye at giri, abuja as well as theoretical and available hydro power. 2.3.1 measurement of river flow rate the river flow rate was determined with the use of a half-filled plastic bottle with water as float with accuracy of readings at ± 5% (michaud and wierenga, 2005). tools such as a measuring tape, stakes, and a stop-watch were used. the river length was traversed by the researchers, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 130 during the period of study, with particular interest on the river bank, breadth and geometry to identify likely location for weir, upstream and downstream facilities an equal interval of distance were marked along the length and across the river profile. on the river speed measurement, intervals along the river length were taken for float travel. as the float were released on the river, stop-watch was used to record time for the float to travel from one location to other, within the interval. the river speed measurements were also repeated three times at three interval along the breadth of the river. the time it takes the float to travel on the river through a designated distance were recorded. on completion of the speed measurements at first interval, the process were repeated for several intervals established along the river. thereafter, mean of the river speed were calculated. the cross sectional area was taken between consolidated banks at three equal interval across the river. the depths occupied by the river during the period of study, were measured vertically across the breadth of the river at each interval along the river. the measurements of the mean river speed by the float and the river cross-sectional area were calculated as follows (nasir, 2014): t dcvr  (2) where: d is the distance between two stakes to demarcate a segment along the river (m) t is the time taken for the float to travel from stake 1 to stake 2 (s). c is the correction factor that ranges between 0.6 and 0.85, depending on the river course, bottom and bank. the cross-sectional area was given as (nasir, 2014): )....)( 2 ( 321 k hhhhbaa k  (3) where: a is the width at the top of the river (m), b is the width at the bottom of the river (m) h is the height measured on the stake (m), k is the number of stakes placed between the distance (interval) )....( 321 k hhhh k is average height (m) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 131 river flow rate was obtained as follows: ravq  (4) where: a is the cross-sectional area of the river (m2), vr is the river speed (m/s) 2.3.2 measurement of head along the river course for the hydro power plant hand held global positioning system (gps) was used to determine the head along the river course at measurement accuracy of 0.4 mm (nasir, 2014). the gross head was measured at a predetermined position on top of the stake. the gps model 12 garmin, was switched on when at location one, then page button was pressed to display positions after booting. the positions displayed includes northing, eastening and elevation at interval one, which were read and recorded. the gps was moved again to location two, location three up to the end and the process repeated to take readings and were recorded. thus, the elevations at equal distances formed a profile along the path of the river including proposed weir and turbine locations. the difference in elevation measured in meters from one interval to the other interval, were read and recorded as the height difference. the head (height dfference) at each stake were added together to determine the gross head. the gross head was evaluated using the following expression: 12 hhhg  (5) where: h2 is the height of the river surface level at the intake (m) and h1 is the height at the top of tail-race downstream (m) the net head was determined as follows: lgn hhh  (6) where: hl is the head losses along flow path. this was taken as 10% of the gross head from an average of 5 to 15%, depending on pipeline length, number of bends, valves and the velocity of flow (williams, 2003). hg is the gross head (m) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 132 2.3.3 available hydro power in river wuye at giri, abuja theoretical power available on the river wuye at giri was given as follows (rajput, 2012): gth gqhp  (7) where:  is the density of water (kg/m3), g is the acceleration due to gravity (m/s2) q is the flow rate of the river (m3/s) hg is the gross head (m) the overall efficiency for the hydropower plant was expressed as follows (rajput, 2012): o = 21   (8) where: o is the overall efficiency 1 is the efficiency of pipelines and intake in the upstream 2 is the efficiency of turbine-generator system the actual power capacity of the hydropower plant (rajput, 2012): goact gqhp  (9) where: o is the overall efficiency  is the density of water (kg/m3), g is the acceleration due to gravity (m/s2) q is the flow rate of the river (m3/s) hg is the gross head (m) 2.4 plant layout and economic analysis of the hydropower plant 2.4.1 layout for the hydro power plant plant layout aims to optimize the size of the hydro power plant to the unique natural conditions, technical and economic factors to efficiently exploit the available hydro power. the layout for the hydropower plant were made according to the procedure for diversion of scheme to exploit a higher head for a low head schemes as outlined by fichtner (2016). a walk-through survey of the proposed weir and turbine locations was carried out. consideration was given to http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 133 dimensions of turbine-generator systems and the electricity supply to the load centres (singal and saini, 2007). 2.4.2 project worth based on total cost and actual hydropower capacity the costs in this work were obtained from cost analysis for hydro power template provided by williams (2003), irena (2012) and fichtner (2016), which were converted into nigerian currency (naira). the costs were for small hydro power plant in africa as provided by unido (2010). the evaluation of power worth (pw) were calculated as follows: act c w p t p  (10) where: pw is the power worth in the hydropower plant (n/kw) tc is the total costs of the hydropower plant (n) pact is the actual power in the hydropower plant (kw) 2.4.3 economic analysis of the the hydropower plant the economic evaluation of the hydropower plant was based on levelized cost of electricity (lcoe). the data to the calculate the lcoe of hydro power plant were generated from this work while data for solar pv power plant were obtained from oodo et al. (2017). lcoe model utilizes net present value (npv) that incorporates capital (capex) and operating costs (opex) and were calculated with a discount rate (r) for the lifetime (eqn.11). the spreadsheet computation of lcoe was carried out according to procedures outlined by singal et al. (2010) and fichtner (2016):         t r e r opexcapex lifetimeovergenerationyelectricitofsum lifetimeovertsofsum npv npv lcoe tn t t ttn t gen t )1( )1( ( cos 1 1 cos (11) where: lcoe is the levelized cost of electricity (n/kwh)  is the summation of costs or electricity generation over life time n is the lifespan of the hydropower plant at 60 years r is the discount rate (%) t is the increment in years file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 134 et is electricity generation at t years (kwh per year) capext is the total capital or investment costs at t years (n per year t) opext is the total operating including maintenance costs at t years (n per year t). 3. results and discussion this section presents the results and discussion in both tabular and graphical forms for the hydro power plant at the main campus of the university. also included were river wuye run-off, head and flow rate at giri region as well as the hydropower plant capacity, the layout and the energy unit cost. 3.1. electricity demand of the university of abuja the main campus of the university is on a land space of over 11, 800 hectares. the presently occupied area was less than eight hectares having over 12 distinct building complexes with a centralized electricity supply meter. there were sub-meters at specific points of service, that record energy consumed at faculties/research buildings with energy intensive equipment as shown in table 1. the sub-meters were in two parts, one to record power into the buildings and the other measures demand from the equipment. the equipment was separated by their kilowatts particularly for electric motors, lightings, appliances and electronic devices. this division was similar to the work by menezes et al. (2014). laboratories, workshops, and hospital consumes large quantities of energy, often two to three times more than the faculties with offices and classrooms only as shown in table 1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 135 table 1. estimated electrical energy consumption in university of abuja as at august, 2015 s/n faculties/units motor pump heat. weld air con fridge freeze. comp. laptop copiers, printers lamp bulbs fan tv halog en total load kw 1-10 15 1-5 0.1-0.4 0.050-0.3 0.2-0.4 0.040-0.2 0.040-0.3 1.2-2 kw 1 agriculture/ farm 9 7 20 16 47 13 120 66 10 450 2 arts 2 37 19 67 17 156 81 8 450 3 health/clinic 6 6 46 31 60 21 170 97 13 900 4 education 2 38 32 72 19 178 82 12 450 5 management sciences 2 27 19 67 17 156 81 13 450 6 engineering /workshops 25 14 30 16 56 12 130 75 14 900 7 law 2 21 19 67 17 156 81 9 450 8 social sciences 2 23 16 64 23 172 56 8 450 9 sciences 4 3 30 17 59 17 173 63 11 450 10 veterinary medicine 2 6 26 31 60 21 89 67 13 450 11 post graduate 10 6 12 6 34 12 8 12 senate building 9 5 67 56 93 45 220 87 18 900 13 mini-hostels 3 78 79 320 289 22 900 14 main-hostels 3 67 121 350 312 25 1080 15 staff quarter 8 16 12 16 14 34 45 28 12 1440 16 mini campus (academic) 4050 17 water pump station/street 3 360 18 others 450 total 14580 the university of abuja average monthly peak and base loads, in 2015, were about 883 kw and 667 kw, respectively as shown in figure 5. these peak and base loads are from one energized 7.5 mva/33 kv/11 kv injection substation with over twenty distribution transformers of 11 kv/414 v at capacities of 1000 kva, 500 kva and 300 kva. the university had three 7.5 mva/33 kv/11 kv injection substations, which is sufficient to meet future demand, but will need additional distribution transformer substations. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 136 figure 5: average monthly load profile at university of abuja, 2015 3.2 river run-off and hydrology of giri, abuja. the data obtained from nimet weather stations were computed from january to december, 2015, as shown in table 2. the rainfall season spans from april to november, with 60% between months of july and september, yearly. hence, the excess river flows will be useful for storage in the proposed dam for the hydropower plant. in table 2, it was observed that giri area had an average mean temperature of 27.3oc while the rainfall was approximately 1,460 mm annually with river run-off of 1,330 mm in catchment area of over 30 km2. river wuye at giri will require little modification to the landscape and no resettlement as the river course is within the university and guided her master plan. the likely changes to the landscape and river flow regime will have little effects to the habitats and ecosystem in the life of the hydro power plant. table 2: rainfall and temperature prediction in giri, abuja (nimet, 2016). months jan feb mar apr may jun jul aug sep oct nov dec rainfall (mm) 0 0 20 60 140 220 260 300 300 140 20 0 temp (oc) 27.6 29.3 30.2 28.9 27.3 26.0 25.1 25.2 24.9 26.3 26.9 26.7 during the study, river wuye, was noticed to have annual pronounced wakes and eddies from may to october, caused by boulders on the bed along river course. this scenario is similar to report of some rivers classified as suitable for hydropower by abebe (2014). it is generally appreciated that bedrock on river course with consolidated banks enhances earth dam as http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 137 reported by rajput (2012). the proposed dam at giri, has aforementioned attributes. the specifications of proposed earth dam were estimated to have height of 10 m, maximum dam core height of 8.0 m, and dam lenth length of 120 m with accessories such as spillway for intake capacity of 4, 000 m3 (fmwr, 2014). the river when dammed for the hydropower plant, will generate electricity as well as provide water for the university. furthermore, the addition of a matching water treatment plant on the proposed dam of 4,000 m3 storage capacity, will have a flow rate that will exceed, 50 m3/h, previously obtained in the package treatment plant for the university staff quarters at giri, abuja, as reported by dikedi (2012). the water stored in the dam will be regulated to sustain the energy generation and to regulate flood. strong seasonal flow variations with strong peaks during rainy season will require reinforced construction works to protect dam structures and installations. apart from flooding that requires control, excessive sand affects turbine systems with resultant high wear rates and maintenance costs of the hydropower plant, hence periodic desilting of the dam will be necessary. thereafter, when the river flow is low, wind and solar power plants could be deployed fully to take over from the hydropower plant as base load (hussein et al., 2016). 3.3 the characteristics of the proposed hydropower plant. river wuye at giri does not dry completely even during dry season but it has minimum flow during the period of november to april yearly. the specifications of the hydropower plant on river wuye at giri, abuja, includes river cross-sectional area of 16.9 m2. the river speed of 0.86 m/s was an average taken during the year. based on the flow rate of 14.5 m3/s, gross head of 11 m, head losses of 1m, overall efficiency of 0.6, net head of 10 m, theoretical power of 1.4 mw and actual power of 855 kw obtained from the computation on river wuye at giri, abuja. a horizontal tabular turbine for the mini-hydro power plant at 855 kw, was selected. river wuye at giri has similar characteristics to some of the rivers in neighboring niger state, earlier reported by rufai et al. (2012). these rivers in niger state have flow rates that were found in the ranges of 13 m3/s to 18 m3/s except river swashi calculated to have a flow rate at 6 m3/s as reported by rufai et al. (2012). similarly, some of the dam heights range from 17100 m and the lengths range from 1002000 m as reported by rufai et al. (2012). there are several hydropower potentials in nigeria, with heads ranging from 1.5 to 72 m that are expected to power turbo or kaplan turbines as suggested in the work of adejumobi et al. (2013). in addition, there are some file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 138 small hydropower plants that have been completed in some locations in nigeria. these include two hydropower plants of 200 kw each in taraba state, two hydropower plants of 75 kw each at waya dam in bauchi state and a hydro power plant of 30 kw at ezioha-mboro dam, enugu state as reported by unido (2010). 3.4 plant layout and economic analysis of the hydro power plant the plant layout for the placement of components that constitute the hydropower plant on the river course, is shown in figure 6. the components of the hydropower plant are numbered from 1 to 14 on the drawing with their description in the attached legend. from figure 6, river wuye flows from suleja to giri, where the hydropower plant will be located and, then towards gwagwalada, on its journey to river usuma and onwards to river gurara in kaduna state. the layout depends on size of civil works, dimension of runner diameter of turbine and turbinegenerator system. the layout have effects on overall cost of the hydro power plant as stated by singal and saini (2007). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 139 figure 6: schematic layout of the proposed hydro power plant at giri, abuja, nigeria file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 140 the estimated cost for the hydropower plant of 855 kw was at n78.5 million as shown in table 3. the low cost for the hydropower plant at n93,960/kw ($261/kw at conversion rate of us$1= n360.00), arose due to the intended use of labour and materials for the construction. the local materials include laterite, clay, aggregates and boulders obtainable from the university land and source procurement from off-shore of a refurbished turbine-generator instead of a new turbine generator sets. similarly, unido (2010) reported that the cost of the hydro power plant per kw ranges from n93, 960.00 to n720, 000.00 ($261-$2000)/kw in some african countries. however, johnson et al. (2012) stated that some small hydropower plant total project costs can be up to $2,000/kw or more, depending on specific site characteristics. compared to johnson et al. (2012)’s work, with reasonable interpolations, the cost of the hydropower plant with a new set of turbine-generator and pipeline system could be up to n600 million ($1.7 million) for hydropower plant at 855 kw. in table 4, the estimate for the hydropower plant shows that the cost of equipment installation is half the equipment cost while earth dam and pipeline costs are equal to equipment cost. the cost estimates for some small hydropower plants reported by johnson et al. (2012), has similar trend. according to unido (2010), it should be appreciated that as power increases, the overall cost also increases due to extra cost as a result of the addition of electric poles, step-up and step-down transformers, transmission lines, particularly when distances are over 100 m. table 3: estimate of minimum costs of components and project worth of the hydro power plant s/n description (*unido, 2010) % of total cost (n) 1 project development, engineering, environmental, social, licenses, permits and legal costs 7.2 5,784,178.00 2 civil works(acess road, intake, weir, tailrace, pipelines, power house) 46.3 37,167,900.00 3 electro-mechanical equipment (turbine, governor, valves, generator, controllors, hydraulic structures) 31 24,904,098.00 4 other equipment and non-equipment (workshop, tools ) 1.3 1,044,365.00 5 grid connection (switchyard, transmission lines, transformers, and installation) 4.2 3,401, 679.00 sub-total (1-5) 72,302, 220.00 6 contingencies @10% of above sub-total 10 8,033,580.00 total project cost n80,335,800.00 project unit worth n93,960.00/kw levelized cost of unit energy are affected by discount rate as shown in figure 7. the computation of lcoe on spreadsheets used the assumptions on table 4. at the same discount http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 141 rate, the lcoe was higher for the solar pv power plant on account of high operating costs and lower capacity factor when compared to hydropower plant of similar name plate capacity as shown in figure 7. the lcoe for the hydro power plant ranges from n24.79 to n50.14/kwh while lcoe for solar pv power plant ranges from n70.74 to n118.58 kw/h, as against tarrif rate of n29.81/kwh by the abuja electricity distribution company, abuja, in november, 2017. according to unido (2010), electricity unit cost in east and southern africa is within the range of us cents 3.1 20/kwh (n11n72/kwh). however, in most countries, the hydro and solar power plant’s energy unit cost were generally in the range of us cents 5 10/kwh and us cents 40 60/kwh respectively, as separately reported by unido (2010) and sener and aytal, (2017). similarly, operating and maintenance costs of hydro and solar power plants were reported to be about $14.13/kw and $13.08/kw per annum, respectively, by irena (2012). table 4: assumptions for the economic analysis of the hydropower plant s/n hydro. model direct inputs value description and/or justification 1 capex: capital cost (n) 347,950,000.00 corbetti model 2 opex: operations cost (n/year) 22,555,000.00 6.5% of pfront investment per year 3 e: electricity production (kwh/year) 3,471,984.00 actual electricity generated based on nc, cf and hrs/year 4 r: discount rate (%) 10.00 discount rate approximated by wacc for business project 5 n: lifetime (years) 60.00 average lifetime of a small hydro power plant 6 tarrif rate (n/kwh) 29.81 abuja electricity distribution company, abuja, in november, 2017 hydro. model indirect inputs value description and or justification 7 nameplate capacity (kw) 855.00 corbetti model & basis of comparison 8 capacity factor (%) 47.00 average capacity factor of small hydro power plant in africa according to unido (2010) note average capital cost of small hydro power plant from unido (2010). millionnnntminimumtmaximumtcapital 95.347 2 )000,300,80000,600,615() 2 coscos(cos      file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 142 figure 7: effect of discount rate on lcoe in hydro power plant and solar pv power plant 4 conclusion from the investigations carried out on the feasibility of a mini-hydropower plant on river wuye at giri, for main campus of the university of abuja, the following conclusions were drawn: the electricity demand at the university of abuja, were determined to have base and peak loads of 667 kw and 883 kw, respectively, during the period of study.the run-off from rain records was 1330 mm, with the estimated dam height, maximum core height, dam length and reservoir at 10 m, 8 m, 120 m and 4,000 m3, respectively. based on the flow rate of 14.5 m3/s, maximum head of 10 m and the layout, a horizontal tabular turbine for the mini-hydro power plant at 855 kw, was selected.the cost of the hydro power plant ranges from n80.3 million to n615.6 million equivalent to n93,960/kwn720,000/kw or ($261/kw-$2000/kw), depending on refurbished or new turbine and generator system as well as the extent of associated civil works.the electricity energy unit cost for the hydropower plant was n24.74n50.14/kwh at maximum discount rate of 10%. acknowledgments part of the data used in this study was obtained during activities of the energy committee of the university of abuja, from 2014 to 2016. the authors also extend their gratitude to dr. a.a. esan and committee members for their individual contributions. dr. i.i ozigis and dr. s.o. oodo was part of the committee that carried out the field work. dr. s.o oodo, was the chairman, energy committee, university of abuja and has no objection to publish the manuscript in the journal. the three authors helped in writing, reading and approving the final manuscript. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 143 references abebe, n. 2014. feasibility study of small hydropower schemes in giba and worie sub basins of tekeze river, ethiopia journal of energy technologies and policy,4(8): 8-17. adejumobi, ia., adebisi, oi. and oyejide, sa. 2013. developing small hydropower potentials for rural electrification. international journal of research and reviews in applied sciences, 17(1): 105-110. aemc. 2012. aemc instruments, chauvin amoux, inc., 15 faraday drive, dover, nh 03820 usa, www.aemc.com :23-30. akinyemi, os. and liu, y. 2015. cfd modelling and simulation of a hydropower system in generating clean electricity from water flow. international journal of energy and environmental engineering, 6: 357-366. delmastro, s., mutani, g. and schranz, l. 2016. the evaluation of buildings energy consumption and the optimization of district heating networks: a gis-based model. international journal of energy and environmental engineering,7: 343-351. dikedi, pn. 2012. geo-electric probe for groundwater in giri, nigeria. global journal of science frontier research physics & space science, 12(2): 42-47. ezema, ic., olatuah, ao. and fagbenle, oi. 2016. evaluation of energy use in public housing in lagos, nigeria: prospects for renewable energy sources. international journal of renewable energy development, 5(1): 15-24. fichtner. 2016. hydro electric power, a guide for developers and investors. international finance corporation, world bank group, sarweystrasse 3, 70191 stuttgart, germany: 93-95. fmwrfederal ministry of water resources. 2014. giri hydropower plant committee report. federal ministry of water resources, abuja: 23-30. gul, ms. and patidar, s. 2015. understanding the energy consumption and occupancy of a multi-purpose academic building. energy and buildings, 87: 155–165. haugen, el. 2013. verification of simulation program for high head hydro power plant with air cushion. master of energy and environmental engineering, norwegian university of science and technology: 1-28. hussein, ak., walunj, aa. and kolsi, l. 2016. applications of nanotechnology to enhance the performance of the direct absorption solar collectors. journal of thermal engineering, 2(1): 529540. http://www.aemc.com file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis et al.: a feasibility study of mini-hydroelectric power plant for seasonal base load. azojete, 15(sp.i2):124-145. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@gmail.com 144 irena-international renewable energy agency. 2012. renewable energy technologies: cost analysis series, hydropower. irena working paper,1 issue 3/5: 1-31. johnson, k., hart, a., george, l.,young, n. and applegate, m. 2012. colorado small hydropower handbook. colorado energy office: 1-78. karki, p. 2014. a brief introduction to small hydropower, esmap-sar-eap renewable energy training program, world bank group, thailand: 21-23. magureanu, r., ambrosi, s., popa, b., ion, b., valeriu, d., viorel, b. and anatol, s. 2011. work package 5-common strategies to improve small hydropower implementation. handbook of innovative technologies to promote small hydropower: 28-70. menezes, ac., cripps, a., buswell, ra., wright, j. and bouchlaghem, d. 2014. estimating the energy consumption and power demand of small power equipment in office buildings. energy and buildings,75: 199–209. michaud, jp. and wierenga, m. 2005. estimating discharge and stream flows. ecology publication number 05-10-070, department of ecology, washington, us: 2-16. nasir, ba. 2014. design considerations of micro-hydro-electric power plant. energy procedia, 50: 19 – 29. nimet-nigeria meteorological agency. 2016. seasonal rainfall prediction. nigeria meteorological agency, abuja: 8, 15-23, 37-57. odeh, i. 2014. production economic feasibility of large scale photo voltaic water pumping application utilizing real field data for a case study in jordan. international journal of renewable energy development, 3(2): 107-117. oodo, os., ozigis, ii., ikpe, e. and garba, as. 2017. feasibility of a hybrid solar/wind/hydro power plants for the university of abuja. energy committee report, constituted by the vice chancellor, university of abuja, via memo: ua/r/com/44 dated 17th september, 2015: 4-13. rajput, rk. 2012. hydro-electric power plant, in: a text book of power plant engineering 4th edition, reprint, wiley and sons, new delhi: 524-639. rao, s. and parulekar, bb. 2004. energy technology: non-conventional, renewable and convectional, (3rd ed.), wiley and sons, new delhi: 965-993, 1052-1064. rea-rural electricification agency. 2018. nigerian electrification project, overview, the world bank report (pad2524), rural electrification agency: 10-16. rufai, ia., enagi, ii. and balami, aa. 2012. hydropower potential mapping of niger state. asian journal of natural and applied sciences, 1(1): 46-53. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):124-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 145 sener, b. and aytal, s. 2017. renewable energy potential of turkish coasts and a concept design of a near sea platform. journal of thermal engineering, 3(3): 1211-1220. singal, sk. and saini, rp. 2007. analytical approach for cost estimation of low head small hydro power schemes. international conference on small hydro power-hydro, sri lanka: 1-6. singal, sk., saini, rp. and raghuvanshi, cs. 2010. analysis for cost estimation of low head run-of river small hydro power schemes. journal of energy for sustainable development, http://franke.uchicago.edu/bigproblems/bpro29000-2015/team14-spreadsheet.xlsx, 14: 117126. unido-united nations industrial development organization. 2010. unido projects for the promotion of small hydropower for productive use. independent thermic review, united nations industrial development organization, vienna: 34-39. williams, r. 2003. a guide to understanding and constructing your own small hydro project. small hydro power handbook, email: rwilliams@wlake.com: 16-26. zarma, ih. 2006. hydro power resources in nigeria, energy commission of nigeria. being a country position paper presented at 2ndhydro power for today conference international centre on small hydro power (ic-shp), hangzhou, china: 1-17 http://franke.uchicago.edu/bigproblems/bpro29000-2015/team14-spreadsheet.xlsx mailto:rwilliams@wlake.com file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):802-812 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 802 original research article enhancement of selective mapping technique for peak-to-average power ratio reduction in ofdm using normalized hilbert matrix a. m. s. tekanyi, h. i. yarima*, and s. m. sani (department of electrical and computer engineering ahmadu bello university, zaria) * corresponding author’s email address: yarimahindu@yahoo.com article information submitted 10 december, 2017 revised 15 september, 2018 accepted 18 june, 2019 keywords: peak-to-average power ratio selective mapping normalization hilbert matrix abstract orthogonal frequency division multiplexing (ofdm) is good multicarrier transmission system used for broadband wireless communication systems owing to it is numerous benefits such as high bandwidth efficiency, high transmission rate, and robustness against multi path problem. however, one of the hitches of ofdm high peakto-average power ratio (papr) of the transmitted signal, which results in signal distortion and reduced power amplifier efficiency. selective mapping (slm) is attractive distortion less method for papr reduction. the performance of this technique in reducing the papr is largely affected by the magnitude of phase rotation vectors. it also requires to transmit the selected phase rotation vectors that produce the signal with the lowest papr to the receiver end for the recovery of the original data. in this paper, two normalization procedures in conjunction with the hilbert matrix are used to obtain phase rotation vectors for the slm technique to further reduce the papr value. the reduction of papr is desirable in order to have a better power efficiency of the amplifier. the simulation results demonstrated that the enhanced slm technique using normalized hilbert matrix achieved a better papr reduction compared to slm using hilbert matrix without normalization with 14.0%, and 14.0% percentage improvement. another benefit of this method is that the matrix can be generated at the receiver end to obtain the data signal, thus eliminating the transmission of side information with the original data. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction ofdm is a special type of multi-carrier digital multiplexing technique scheme deployed in numerous cutting-edge wireless standards. it has been employed for many broadcast standards, for instance in digital audio broadcasting (dab) and digital video broadcasting (dvb) standards. it is also used in wireless local area network (lan) standards such as wimax, 802.11n, and 802.11g. moreover, ofdm is also used in cellular telecommunication standard (mhatre and khot, 2015). the ofdm signals can be modulated and demodulated using inverse fast fourier transform (ifft) and fast fourier transform (fft) (sudha, 2015). however, the most famous obstacle of an ofdm system was that, it suffers high peak–to–average power ratio (papr). an mailto:amtekanyi@abu.edu.ng,*yarimahindu@yahoo.com, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 802-812. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 803 ofdm signal comprises of a large number of individual modulated subcarriers which can give birth to a huge papr when summed up constructively. when n signals aligned in phase, they yield a high instantaneous power that is n times the average power. large papr of the transmitted signals results in non– linear distortions of signals, clipping of signals, bit error rate (ber) performance degradation, energy leaking into adjacent channels, inter modulation effects on the subcarriers, as well as increased complexity of the analogue to digital and digital to analogue converters (girija, et al., 2014). therefore, it is useful to reduce the papr of ofdm systems. to combat the problem of high papr, various techniques or schemes have been suggested in literature. the reduction schemes can be categorized into distortion and distortion less schemes. clipping and filtering fall under distortion schemes. the distortion-based schemes minimized the papr of the ofdm symbol but at the expense of increasing clipping to the signal points in the subcarriers (raja et al., 2015). distortion schemes are considered to introduce bandwidth re-growth. they do not need any overhead side information to be sent to the receiver and they have low complexity compared to the distortion-less schemes, such as selective mapping (slm) and partial transmit sequence (pts). in this technique, modulated data is multiplied with phase rotation vectors then timedomain conversion takes place through ifft after that papr is calculated and finally, signal with minimum papr is selected for transmission. distortion-less schemes do not host bandwidth regrowth but they need transmitted overhead side information. zhong and wang, (2010) proposed the scheme with slm using randomness in phase sequence selection. this scheme obtained significant papr reduction performance with that of ordinary slm techniques. however, the work did not address the effect of large magnitude of phase rotation vectors on performance of slm in terms of papr reduction, which results in high power consumption by amplifier in ofdm system. palanivelan et al., (2011) employed circulant, hadamard, and hilbert matrices to obtain phase rotation vectors for the slm techniques. experimental results showed that hilbert matrix’s approach outperformed the other two matrices in terms of papr reduction. it is noteworthy that the researchers used the hilbert matrix without normalization, moreover, the problem of large magnitude of phase rotation vectors which affects the performance of slm, resulting in deterioration of power in ofmd transceiver was not considered. florence and kumari, (2013) reduced the papr by using hadamard slm technique in a multiple input multiple output (mimo) ofdm system. in this research work, the input sequence was convolved by a set of phase sequence and hadamard transform was applied to each of the sequence. ifft operation was then used to get the time domain signal. computer simulations were carried out using 64 subcarriers, 16-quadrature amplitude modulation (qam), and oversampling factor of l= 4. this method had lower computational complexity.. however, no normalization was done and therefore the effect of large magnitude of phase rotation vectors on performance of slm in term of papr reduction still existed. in the conventional slm, its performance in terms of papr reduction is largely affected by the magnitude of phase rotation vectors (prv) used to generate the candidates signals. large magnitude phase rotation vectors results in the escalation of amplitudes of signals when summed up coherently, thus leading to the exhibition of peak power. signals with peak power affect the power amplifier efficiency used in the ofdm transceiver. normalization schemes are file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tekanyi, et al: enhancement of selective mapping technique for peak-to-average power ratio reduction in ofdm using normalized hilbert matrix. azojete, 15(4):802-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 804 applied on rows of the hilbert matrix in order to reduce the magnitude of prv. data blocks are then multiply with prv in order to lower the amplitudes of generated signals before their summation at the transmitter and the process leads to further reduction of papr. 1.1 orthogonality in ofdm ofdm is a superior type of digital multiplexing technique which is mainly desirable for transmitting information over a harsh channel. diverse carriers are orthogonal against each other by completely standing alone against each other. two periodic signals are orthogonal if the integral of their multiplication over one complete cycle is equal to zero (gupta et al., 2013) and for continuous time signals, they are expressed mathematically as: 0 cos(2 ) cos(2 ) 0 t nft mft dt   (1) and, for discrete time signals, the expression of equation (1) becomes: 1 0 2 2cos cos 0 n k kn km dt n n                 (2) where: m is even integer value n is odd integer value n is number of sub carriers t is time for sub carrier to complete one cycle. f is frequency of sub carrier orthogonality in the context of an ofdm system can further be explained as a situation when two signals are precisely separated by an angle of ninety degrees both in frequency domain and time domain as shown in figure 1. figure1: two views of ofdm signal (abba, 2016). 1.2 papr of ofdm signal the papr of the transmitted signal x(m) can be express as the ratio of the peak instantaneous power of the signal to average power of the signal. mathematically, the papr of complex pass band signal xm is written (kwesi et al., 2015) as:   2 10 2 max 10log m m m x papr x e x      (3) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 802-812. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 805 where:  2max mx is the peak signal power.  2mxe is the average signal power. the peak value arises if the number of subcarriers escalates and the peak value is directly related to the amount of subcarriers of the ofdm system (kwesi et al.,2015). ofdm signal comprises of a number of independently modulated subcarriers, which can give rise to a high papr when summed up together. when n signals are aligned in the phase, they yield a high power that is n times the average power and a large papr of the transmitted signals leads to many problems highlighted in the last sentence of the first paragraph in the introduction section. 2. materials and methods 2.1 selected mapping (slm) in the slm technique first described by bauml et al., (1996), the input data sequences are multiplied by each of the phase rotation vectors to generate dissimilar candidates data blocks all representing the same information as the original data block. each of these candidates’ data blocks pass through ifft operation and then the one with the lowest papr is selected for transmission. a block diagram of the slm technique is shown in figure 2. each data block is multiplied by b number of different phase sequences, each of length n of subcarriers, resulting in b number of modified data blocks. 2.2. block diagram of slm figure 2: block diagram of slm technique (adegbite, et al., 2014). in the midst of the phase generated ofdm data blocks, the one with the minimum papr is chosen and transmitted. the scheme can handle any number of subcarriers, it minimizes papr without any signal distortion, support all modulation schemes, and papr minimization effect is better as the copy of block number u is increased. the setback of this scheme is that, it requires side information to be sent to the receiver (harne and zanjade, 2016) to enable the recovery of the original data. moreover, the performance of this technique is also largely affected by design type and design of phase rotation vectors used in the generation of candidates data blocks. one of the crucial aspects of the slm technique is the selection of right phase sequence which is random in the presence of phase sequence sets. for instance, in cheng et al., (2007), the shapiro rudin sequence created recursively by palanivelan et al., (2011) is the initial random sequence. this is also applied to the case of the phase sequence set explained by bauml, (1996) and many other researchers. in this enhanced slm technique used in this work, the rows of the normalized hilbert matrix are used as the phase rotation vectors for papr reduction. the hilbert matrix has file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tekanyi, et al: enhancement of selective mapping technique for peak-to-average power ratio reduction in ofdm using normalized hilbert matrix. azojete, 15(4):802-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 806 a unique definite structure and the receiver can easily generate the matrix for proper decoding of transmitted data. therefore, this enhanced slm does not require the transmission of side information to the receiver for decoding the transmitted data. 2.3 complementary cumulative distribution function of papr complementary cumulative distribution function (ccdf) is one of the top vital tool for signal analysis. it shows full analysis of peak signal power. it is a statistical technique that displays the duration of time a signal spends above any given power level. by using the plots of ccdf, one can detect the probability that a signal data block is larger than a given threshold. these ccdf plots can be further deployed to observe the papr characteristics of the signals used to compute the ccdf for a given data. mathematically, it can be expressed as (harne &zanjade, (2016) as: ccdf = pr (papr>papr (4) the ccdf plots can be simply simulated using matlab. 2.4 binary phase shift keying (bpsk) modulation scheme binary phase shift keying bpsk is a two phase modulation scheme, where the 0’s and 1’s in a binary message are represented by two different phase states in the carrier signal: θ = 00 for binary 1 and θ = 1800 for binary 0. in digital modulation techniques, a set of basis functions are chosen for a particular modulation scheme. generally, the basis functions are orthogonal to each other. basis functions can be derived using gram schmidt orthogonalization procedure. once the basis functions are chosen, any vector in the signal space can be represented as a linear combination of them. in bpsk, only one sinusoid is taken as the basis function. modulation is achieved by varying the phase of the sinusoid depending on the message bits. therefore, within a bit duration tb, the two different phase states of the carrier signal are represented as s1 t = ac cos 2πfc t , 0 ≤ t ≤ tb for binary 1 (5) s0 t = ac cos 2πfc t+π , 0 ≤ t ≤ tb for binary 0 (6) where: ac is the amplitude of the sinusoidal signal, fc is the carrier frequency (hz), t being the instantaneous time in seconds, tb is the bit period in seconds. the signal s0(t) stands for the carrier signal when information bit ak = 0 was transmitted and the signal s1(t) denotes the carrier signal when information bit ak = 1 was transmitted. 2.5 enhanced slm in this developed approach, two normalization procedures were applied on rows of hilbert matrix to obtain the phase rotation vectors used in enhancing the slm. the hilbert matrix was obtained from cauchy matrix of dimension, m × n with elements, aij derived from 1 ,and1 j ni m    in the expression of palanivelan et al., (2011) as: ji ij yx a   1 (7) where: ji yx  are elements of field f and 0 ji yx http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 802-812. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 807 hilbert matrix is computed from the cauchy matrix using the following: 1i jx y i j    (8) this gives a hilbert matrix with dimensions m = n = 8 as palanivelan et al., (2011): 1 1 1 1 1 1 11 2 3 4 5 6 7 8 1 1 1 1 1 1 1 1 2 3 4 5 6 7 8 9 1 1 1 1 1 1 1 1 3 4 5 6 7 8 9 10 1 1 1 1 1 1 1 1 4 5 6 7 8 9 10 11 1 1 1 1 1 1 1 1 5 6 7 8 9 10 11 12 1 1 1 1 1 1 1 1 6 7 8 9 10 11 12 13 1 1 1 1 1 1 1 1 7 8 9 10 11 12 13 14 1 1 1 1 1 1 1 1 8 9 10 11 12 13 14 15 a                                   (9) the normalization procedures of this matrix was carried out using the euclidean normalization (helm, 2004) and normalization using determinant of matrix order adelaide (2009) techniques. 2.6 normalization schemes. the following are the two normalization schemes the euclidean normalization (helm, 2004) find the square root of sum of the square of all elements in a row of a given matrix. let the answer you obtained in (i) to be c. divide each of the elements of that row by c. repeat steps i-iii above for the rest of the rows. 2 normalization by using determinant of a matrix. adelaide (2009) to normalize a matrix, divide each element by the determinant of the matrix a matrix is normalized when it is norm is equal to one. the matrix is normalized by dividing each of it is elements by it is norm. for example, a matrix x given in equation (10) . (williams, 2010) 2 1 2 x         (10) find the norm of the matrix ||x|| =√22 +12+22 = √4+1+4 =√9 = 3 then, the normalized matrix x is now 2 3 1 3 2 3 xx x                   (11) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tekanyi, et al: enhancement of selective mapping technique for peak-to-average power ratio reduction in ofdm using normalized hilbert matrix. azojete, 15(4):802-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 808 2.7 process procedures of slm technique step 1: the random data was generated. step 2: the generated data was modulated to produce sequence symbols using binary phase shift keying (bpsk). step 3: the sequence symbols were converted from series to parallel form and then they were divided into blocks of length n number of subcarriers. step 4: multiplying each ofdm data block was multiplied with different phase rotation vectors obtained from each row of normalized hilbert matrix. step 5: the new ofdm data blocks formed were transformed into time domain using ifft. step 6: complementary cumulative density function (ccdf) value of the papr of each of the block was computed and compared with the respective threshold values. step 7: the ofdm data block with the minimum papr was finally selected for transmission. 3. results and discussion extensive computer simulation using communication tool box inside matlab r2016a was carried out to assess the level of papr reduction of the proposed enhanced slm in ofdm communications system with number of subcarriers to be eight on bpsk modulated data signals. the normalized hilbert matrix from equation (11) was used for phase rotation vectors. the model simulation parameters were presented in table 1. table 1: model simulation parameters modulation bpsk no of subcarriers (m) 8 size of phase sequence 8 carrier frequency 10 mhz it is worthy to note that the choice of the parameters presented in table 1 were selected based on consultation of literature and since the work of palanivelan et al, (2011), that is slm using hilbert matrix without normalization was used to validate this research, parameters presented were adopted from their work, and varied based on the simulation and performance of the enhanced technique. hence, the value of these parameters can be varied depending on the simulation. the simulation results obtained using the model parameters highlighted in table.1 for the respective techniques as shown below with the performance of the enhanced slm highlighted in green and cyan, for two different normalization schemes used in this research work. slm with hilbert matrix highlighted in blue and the original ofdm signal with no slm highlighted in red. in the simulations, bpsk was adopted as the modulation scheme for the symbols(bpsk is considered to be more robust among all the modulation schemes due to difference of 180 degree between the constellation point. this makes the scheme to withstand severe amount of channel conditions or channel fading). the size of phase rotation vector for each simulation was equated to the number of subcarriers and the inputs symbol sequence is uniformly distributed among all the symbols. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 802-812. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 809 3.2 computing percentage improvement percentage improvement 100   cslm eslmcslm (12) cslm means conventional slm technique using hilbert matrix without normalization . eslm means enhanced slm technique using normalized hilbert matrix when euclidean normalization was used. figure 3 shows the ccdf result for the enhanced slm technique, slm with hilbert matrix, and original ofdm signal, to select the phase rotation vector for the papr reduction with the oversampling factor (l) of 4 and the number of subcarriers set at 8. l is oversampling factor, 4 gave better result than 2,while values above 4 took longer processing time. . figure 3: ccdf plot of papr using euclidean normalization. it can be deduced from figure 3 at ccdf of 10-2, the slm using hilbert matrix gave reduction of papr to 5.0db, while the enhanced slm technique using euclidean normalization led to reduction of papr to 4.3 db, which is 0.7db less than slm using hilbert matrix. this shows that the enhanced slm technique with normalized hilbert matrix yields a better result compared slm using hilbert matrix with 14.0% improvement. figure 4, shows the ccdf result for the enhanced slm technique when normalization using determinant of matrix order was used, slm with hilbert matrix, and the original signal, to select the phase rotation vector for the papr reduction with the oversampling factor (l) of 4 and the number of subcarriers set at 8. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tekanyi, et al: enhancement of selective mapping technique for peak-to-average power ratio reduction in ofdm using normalized hilbert matrix. azojete, 15(4):802-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 810 figure 4: ccdf plot of papr using normalization with determinant of matrix. it can be deduced from figure 4 that at ccdf of 10-2, the slm using hilbert matrix offers reduction of papr to 5.0db, while the enhanced slm technique using normalization with determinant of matrix offers reduction of papr to 4.29 db, which is 0.71db less than slm using hilbert matrix. this shows that the enhanced slm technique with normalized hilbert matrix yields a better result compared slm using hilbert matrix with 14.2% improvement. the enhanced slm with the two normalization procedures reduced the papr to 4.3db and 4.29db from 5.0db. the improvement occurred due to the fact that the normalization reduced the magnitude of the matrix, which could lead to minimum phase shift when the rows of the matrix are used as phase rotation vectors to generate candidates signals. due to this minimum phase shift, the amplitudes of sinusoidal subcarriers would not rise to peak level when these subcarriers are summed up constructively at the input of transmitter. this can lead to a lower peak-to-average power ratio reduction. from the simulation results, it is noteworthy observed that, papr reduction performance of the two normalization procedures are almost the same. this is as result of the fact that, the two normalization procedures did not change internal structure of the hilbert matrix, but rather reduced it is magnitude. amongst all possible ccdf values generated from the simulation results, ccdf of 10-2 was found to be the most suitable available lowest value to be used due to power and power processing issues. with this value, the eslm had a better papr reduction when compared to slm technique using hilbert matrix with percentage improvement of 14.0%, 14.2%, euclidean and determinant normalization scheme, respectively. 4. conclusions in this paper, enhancement of slm technique for further papr reduction in ofdm system using normalized hilbert matrix has been presented. phase rotation vectors are obtained by applying two different normalization schemes that is, using euclidean normalization (helm, 2004) and determinant of a matrix normalization. adelaide (2009) and)on hilbert matrix. the following are the conclusions: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 802-812. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 811 from simulation results, it was observed that the proposed method offers better papr result of 4.3db and 4.29db when compared to papr value 5.0db offered by hilbert matrix without normalization. the significant papr reduction achieved by the enhanced slm improved the power efficiency of amplifier more than conventional slm scheme. the closer the value of papr to zero or the lower the value of papr, the less power consumed during amplification process of the ofdm signals by amplifier side information need not be transmitted to the receiver to recover the original signal. this scheme can effectively be implemented in 4g and 5g wireless communications system. 5. acknowledgement gratitude and appreciation are to ahmadu bello university management, the lecturers of the department of communications engineering, and 9 mobile management for their support in my msc research work. references abba, m. 2016. performance evaluation of ofdm based wireless communication system, msc thesis, jodhpur national university. jodhpur, adegbite, sa., mcmeekin, sg. and stewart., bg. 2014. low-complexity data decoding using binary phase detection in slm-ofdm systems. electronics letters, 50(7), 560-562. adelaide, ak. 2009. how do i normalize a matrix. retrieved from http://mymathforum.com/linearalgebra/18218-how-do-i-normalize-matrix.html. 22/04/2017 bauml, rw., fischer, rfh. and huber, jb. 1996. reducing the peak-to-average power ratio of multicarrier modulation by selected mapping’, electron. letter, 32(22), 2056–2057. cheng, p., xiao, y., dan, l. and li, s. 2007. ‘improved slm for papr reduction in ofdm system. personal, indoor and mobile radio communications, 10(1109), 1–5. florence, g. and kumari, ur. 2013. reduction of papr using hadamard slm in sfbc mimoofdm system. international journal of engineering research and applications, 3(4), 1792-1795. girija, sp., srinivas, a., ramudu, k. and sneha, e. 2014. reduction of papr using modified slm technique-application to ofdm systems. international conference on recent advances in communication, vlsi & embedded systems, 75-78. gupta, k., kushawaha, m. and sharma, ap. 2013. papr reduction of ofdm using a new phase sequence in slm technique. international journal of advanced electrical and electronics engineering (ijaeee), 2(2), 4-9 harne, s and zanjade, a. 2016. papr reduction in ofdm system using phase sequence of riemann matrix. international advanced research journal in science, engi s. neering and technology, 3( i9), 56-60. helm. bl. 2004. introduction to numerical methods version one, workbook level 1(3), 1-5. irukulapati, b. and chakka, k. 2009. electronics letters 19th november 2009, 45(24) kwesi, md., wang, j. and sultan, k. 2015. slm technique with hadamard transform for papr reduction. international journal of computer networks and communications security, 3(12), 438–441. http://mymathforum.com/linearalgebra/18218-how-do-i-normalize-matrix.html file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tekanyi, et al: enhancement of selective mapping technique for peak-to-average power ratio reduction in ofdm using normalized hilbert matrix. azojete, 15(4):802-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yarimahindu@yahoo.com 812 mhatre, k. and khot, up. 2015. efficient selective mapping papr reduction technique. procedia computer science, 45, 620-627. palanivelan, m., anand, ds. and gunasekaran, m. 2011. matrix based low complexity papr reduction in ofdm systems. international journal of electronics and communication technology, 2(2), 158-162. raja, ms., hossain, i., jewel, kh. and aii, s. 2015. papr reduction of ofdm signal using sequential phase sequence slm based transceiver without side information. wireless and microwave technologies, 1(8), 34-42 sudha, v., anilkumar, b. and sriramkumar, d. 2015. low-complexity modified slm method for papr reduction in ofdm systems. paper presented at the proceedings of electronics and communication systems (icecs), 2015 2nd international conference. 1324-1328. wang, z. 2010. reduction papr of ofdm signals by combining slm with dct transform, paper presented at the proceedings of international journal of computer and network security, 888892. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):415-422 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 415 original research article thermal and mechanical properties of clay and drop-off of ceiba pentandra (kapok) plantwool mixture a. t. abdulrahim1*, s. abdulkareem2, s. a. abdulraheem1 and w. j. mohammed1 1department of mechanical engineering, university of maiduguri, p.m.b. 1069 maiduguri, nigeria 2department of mechanical engineering, university of ilorin, p.m.b. 1515, ilorin, nigeria *corresponding author’s email address: engrabdulrahimat@gmail.com, abdulrahimat@unimaid.edu.ng 1.0 introduction thermal insulations play a major role in the design and production of energy efficient process, devices and systems because of their ability to retard heat transfer by acting as barriers in the path of heat flow. the variety of insulation materials available are mostly those that are primarily made of fiberglass, mineral wool, polyethylene, form, or calcium silicate (cengel, 2007; holman, 2010). it is important to note that synthetic fiber composites are being replaced by environmentally friendly materials such as natural fiber because of their low weight, density, cost, renewable nature among others (ayugi, 2011). natural fiber low to zero toxin ratings, easy to reuse and dispose with significant health benefits have also been recognized as additional advantages (andy et al., 2011). drop-off of ceiba pentandra plant (kapok) wool have been reported in literature as a material for thermal insulation. studies carried out by abdulkareem et al. (2016) and abdulkareem et al. article information abstract this study is aimed at the investigation of the effects of the addition of clay to drop-off of ceiba pentandra (kapok) plant wool on the thermal and mechanical properties of the materials produced. because of the considerable increase in the use of insulations in many heat devices, process and systems, and dependence on imported insulations, the need to process natural fibre insulations to form rigid or semi-rigid material using appropriate and sustainable binding material cannot be over emphasized. for this study, kapok wool and clay mixture were investigated. five samples were prepared: sample a was 100% kapok wool while samples b, c, d, and e were mixture of kapok wool and clay in water with varying percentage of clay quantities (kapok to clay ratio; b 2:1, c 2:1.5, d 2:2.5, e 2:3.5). the samples were prepared into cylindrical shapes, compressed and dried. the thermal conductivity meter on armfield heat transfer equipment was used to find the thermal conductivity of each sample, while the thermal diffusivity and thermal resistivity of samples were determined using appropriate formula. universal testing machine (model: fs 50at) was used to determine the stress at yield and young modulus of elasticity for samples b, c, d, and e. results show that the density of sample increases with increase in clay content. thermal conductivities of the samples after the addition of clay ranges between 0.027 (w/mk) and 0.013 (w/mk). reversed was the case for thermal resistivity, the value of thermal resistivity first decreases with addition of clay content (sample b) and then started increasing with increased clay content in the samples, and the values range from 37.037 to 76.923mkw-1. thermal diffusivity of sample decreases from 1.2762 x10-3 m2/s to 0.2810 x10-3 m2/s with increasing clay content. results also show that the stress at yield of samples range from 0.012 n/mm2 to 0.022 n/mm2 while the young modulus of elasticity range from 0.113 n/mm2 to 0.222 n/mm2. kapok wool – clay combination of ratio 2:3.5 (sample e) have the highest value of thermal resistivity and lowest thermal diffusivity, though with high density, which suggests it to be the best among samples in the study for insulation purposes. the products are recommended for use as insulations of thermal storage for medium temperature applications. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 10 march, 2020 revised 22 may, 2020 accepted 27 may, 2020 keywords: kapok wool clay thermal conductivity thermal diffusivity modulus of elasticity mailto:engrabdulrahimat@gmail.com mailto:abdulrahimat@unimaid.edu.ng http://www.azojete.com.ng abdulrahim et al: thermal and mechanical properties of clay and drop-off of ceiba pentandra (kapok) plant wool mixture. azojete,16(2):415-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 416 (2015a,b) on the investigation of thermal insulation properties of biomass composites involving kapok wool, sugarcane bagasse, coconut fibre, luffa cylinderica and cellulose using molasses as binder revealed the potentials of composites from these biomass materials as insulation materials because of their high thermal resistivity and low thermal conductivity. ali and zeitoun (2012) have also investigated apple of sodom fibre (calotropis procera) as insulation material, and its potential as a good insulator has been established. because of the considerable increase in the use of insulations in many heat devices, process and systems, there is growing needs for the development of new and more effective as well as affordable insulation materials. the need for the use of locally available materials that will eliminate the problem of importation of insulators from other countries cannot be over emphasized. natural fibre insulations can be process to form rigid or semi-rigid rolls or loose insulation material for a variety of uses. clay could be a binding agent for processing natural fibre into a rigid or semi-rigid insulation materials because of its fine particle size and plastic nature as well as its refractory tendencies (lewis, 2013; ashby and jones, 1998). studies have shown the availability of clay in nigeria as well as its uses for pottery, mud building of local houses, refractories and glaze making (adams et al., 2018; adams et al., 2017; counts et al., 2000). to this effect, this study is aimed at the investigation of the effects of the addition of clay to drop-off of ceiba pentandra (kapok) plant wool on the thermal and mechanical properties of the insulation materials produced. 2 materials and methods 2.1 samples preparation the locally available insulating materials that have been considered in this study are kapok wool and clay. kapok pods were obtained at the university of maiduguri, maiduguri, nigeria from kapok trees. the kapok wool was removed from its pod (figure 1a) and hand picking of the kapok seed in the kapok wool was done and it was then brushed to remove other unwanted particles (figure 1b). the kapok wool comprise 64% cellulose, 13% lignin and 23% pentosane (kobayashi et al., 1977). figure 1: kapok wool source and processing: (a) kapok pod; (b) kapok wool, seed, exocarp and other unwanted particles clay was collected from a deposit in maiduguri, nigeria which was further dried and finally crushed down to smaller sizes. the clay was sieved by hand through a 500 µm sieve to remove coarse particles and foreign materials that might have been present in the clay. the chemical compositions of clay sample were determine using single beam spectrophotometer (with test kits, hot plate and furnace) at the department of geology, university of maiduguri, maiduguri, nigeria. samples were weighed using an electronic kitchen scale model: sf 400. five samples of the materials were prepared. sample a is 100% kapok wool while samples b, c, d, and e are mixture of kapok wool with clay mixed in water with varying percentage of clay quantities as shown in table 1. the samples were prepared into cylindrical shapes of thickness (t) in m and diameter (d) in m. the volume (v) is given by equation 1: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 415-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 417 trv 2 (1) where: 2 dr  table 2: composition of samples by mass s/no. sample kapok (g) clay (g) water (ml) 1. a 20 200 2. b 20 10 200 3. c 20 15 200 4. d 20 25 200 5. e 20 35 200 a 110mm diameter mould was used to mould the samples. sample a was achieved by adding 200ml of water to the 20g of kapok wool and vigorously mixing the contents until the kapok wool was soaked in the water. for samples b, c, d and e, 200ml of water was mixed with the corresponding mass of clay for each of the samples and them mixed with the kapok wool. the mixture was poured into the mould and compressed by a total load of 196 n. the samples were left for one day in the mould, then removed and sun dried for 2 days. the samples were oven dried for 9 hours at 105 oc before tests were carried out. this was done to eliminate moisture content if present in the samples. a total number of 5 samples were produced. the samples are as shown in figure 2. figure 2: dried samples of a, b, c, d, and e determination density of sample the density of the sample was obtained from equation 2 according to abbott (1980): volume massdensity  (2) thermal conductivity the thermal conductivity meter on armfield equipment (model: ht12) with heat transfer service unit (model: ht10xc) equipment were used to check the thermal conductivity of the materials. the probe consists of single heater wire and thermocouple. when constant electric power (energy) is given to the heater, the temperature of the wire will rise in exponential progression. temperature rising with time axis scaled in logarithm. the angle of this line increases if the sample has less thermal conductivity (tc) and decreases if it has higher tc. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: thermal and mechanical properties of clay and drop-off of ceiba pentandra (kapok) plant wool mixture. azojete,16(2):415-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 418 therefore, tc of a sample was determined from the angle of the rising temperature graphic line (armfield equipment model ht12 manual). thermal conductivity of sample, k [w/mk] is expressed as given in equation 3 as reported by tripathi et al. (2016), eeday et al. (2014) and rodriguez et al. (2011):  12 1 2 4 tt t tqin k          (3) where: q is generated heat per unit length of sample/time [w/m] t1 and t2 are measured time length [sec] t1 and t2 are temperatures at t1and t2 respectively [k] thermal resistivity the thermal resistivity of samples were calculated from equation 4 according to satta and steve (2008): thermal resistivity, k r 1  (4) thermal diffusivity the thermal diffusivity of samples were calculated using the expression given by incropera et al. (2007) as in equation 5: pc k   (5) where: thermal diffusivity, α (m2/s), ℓ is the density (kg/m3) of the material, cp is the specific heat capacity (j/gk). the plot of natural logarithm of change in temperature versus reciprocal of time ( in δt vs 1 t ) were drawn for the samples, and heat capacity of each sample was obtained from the intercept of the plots. compressive test the compressive stress test was determined by the use of universal testing machine (testometric type: dbbmtcl-5000kg; serial no. 38140; model: fs 50at) at the university of ilorin, ilorin, nigeria for samples b, c, d and e. on sample a, the study of effect of compression stress on the sample was not done since it is 100% kapok wool. for other samples (b, c, d, e), the samples were mounted one at a time and test speed of 2mm/minute was applied until samples failed after it has reached yield point. the stress at yield and young modulus of elasticity were then recorded. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 415-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 419 3 results and discussion table 2 show the chemical composition of kapok wool table 2: chemical compositions of the kapok wool and clay component chemical composition (%) clay kapok wool silica (sio2) 55.71 alumina (al2o3) 19.86 ferric oxide (fe2o3) 0.74 titanium oxide (tio2) lime (cao) 7.7 magnesium oxide (mgo) 1.68 potash (k2o) 7.23 soda (na2o) 0.52 manganese oxide (mno) 1.61 phosphorous pentaoxide (p2o5) 1.19 loi 2.8 98.57 carbon (c) 0.99 hydrogen (h) 0.41 nitrogen (n) 0.01 note: silica and alumina were determined by xrf while others by icp-oes. table 3 shows the results of the density, thermal conductivity, thermal diffusivity and thermal resistivity of the samples. table 3: density, thermal conductivity, thermal diffusivity and thermal resistivity of samples of kapok wool-clay mixture sample density,ρ (g/cm3) thermal conductivity (w/mk) thermal diffusivity (m2/s) thermal resistivity (mkw-1) a 0.067 0.0177 1.2762x10-3 56.497 b 0.125 0.027 1.1232 x10-3 37.037 c 0.240 0.026 0.7085 x10-3 38.462 d 0.275 0.021 0.5755 x10-3 47.619 e 0.700 0.013 0.2810 x10-3 76.923 from table 3, the density of sample increases with increase in clay proportion as reflected in samples b, c, d and e. sample a has the lowest density while sample e has the highest density. the addition of clay to kapok wool first caused a rise in thermal conductivity of the sample as shown in table 4 in the case of sample b, and with increase proportion of clay content, the thermal conductivity decreases as reflected in samples c, d and e. reversed were the case for thermal resistivity: the value of thermal resistivity first decreases with addition of clay content (sample b) and the started increasing with increase in clay content in the sample. this is an indication that samples c, d, and e have improved insulation properties proportion to increase clay contents. table 4 shows the results of the stress at yield and the modulus of elasticity at failure for the samples. table 4: stress at yield and modulus of elasticity of samples at failure s/no. sample stress at yield (n/mm2) young modulus of elasticity (n/mm2) 1. a 2. b 0.012 0.113 3. c 0.015 0.148 4. d 0.020 0.151 5. e 0.022 0.222 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: thermal and mechanical properties of clay and drop-off of ceiba pentandra (kapok) plant wool mixture. azojete,16(2):415-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 420 from table 4, it can be observed that both the stress at yield and the modulus of elasticity increase as the clay content in the sample increased. the chemical composition of the clay as presented in table 2 showed significant amounts of sio2 and al2o3 (55.71 and 19.86% respectively). the clay can be used as a binder with this level of silica and alumina contents, and it is plastic when moist but hard when fired (lewis, 2013). the results obtained revealed that the value of the thermal conductivities of the samples were found to first increase from 0.0177 w/mk to 0.027 w/mk with kapok wool to clay ratio 2:1 while the density increases from 0.067 to 0.125 g/cm3. the loose fibrous nature of kapok wool enhances its conductivity and with limited amount of clay added might brought about the increase since clays have plate-like molecules with charges on their surfaces (ashby and jones, 1998). more so at the low level the clay may just be serving as a binder and not as a reinforcement. similar report was made by ali and zeitoun (2012) when they asserted that lowdensity fibers (calotropis procera) with no resin (loose fibres) have a lower thermal conductivity than the ones made in a board form using phenol-formaldehyde resin. the addition of more clay to obtain a kapok wool to clay ratio 2:1.5 brought about a reduction in thermal conductivity to 0.026 w/mk while the density increases to 0.240 g/cm3. the solid clay particles might have been finely dispersed through air spaces within the kapok wool thereby preventing heat transfer by convection through the air in the void spaces as well serving as reinforcement. and subsequent increases in clay content (kapok wool to clay ratio 2:2.5) reduces the thermal conductivity while it increases sample density. reduction in thermal conductivity was also noted at kapok wool to clay ratio 2:3.5. this may be due to the evacuation of air in the space within the kapok wool due to increasing clay content which could have reduce the effective thermal conductivity of the system as supported by incropera et al. (2007) report. the stress at yield and the modulus of elasticity of the samples were found to increase with increasing clay content in sample. since clay also served as binder thereby binding the loose kapok wool together and improve its strength. results show that the stress at yield of samples range from 0.012 n/mm2 to 0.022 n/mm2 before failure while the young modulus of elasticity range from 0.113 n/mm2 to 0.222 n/mm2 before failure. the addition of clay in order to enhance the thermal properties showed on the average the decrease in thermal conductivity which is good because it indicated that the proposed materials produced are good insulators. samples with high thermal resistivity are desirable for insulation purposes. thermal diffusivity was found to decrease which is good because materials with high thermal diffusivity adjust rapidly to ambient temperature because heat is quickly connected. materials of high thermal diffusivity will respond quickly to changes in their thermal environment, while materials of small thermal diffusivity will response more sluggishly, taking longer to reach a new equilibrium condition (incropera et al., 2007). 4 conclusion this study investigated the effects of varying proportion of clay contents mixed with kapok wool on thermal and mechanical properties of materials produced. in this way, kapok wool which is loose in nature have been processed to form rigid or semi-rigid insulation materials. kapok wool – clay combination of ratio 2:3.5 (sample e) appear to have the highest value of thermal resistivity of 76.923 mkw-1 and lowest thermal diffusivity of 0.2810 x 10-3 m2/s, though with high density, which suggests it to be the best material among samples in the study for insulation purposes. while kapok wool – clay combination of ratio 2:1.5 (sample b) having thermal resistivity of 37.037 mkw-1 is the least in the group. the results obtained shows the possibility of having a combination of two different insulation materials (kapok wool and clay) to have desired thermal properties and strength. this study has established that the kapok woolclay mixture is a possible solution to meet insulation needs, and the insulators produced have a lower-cost of production and sustainable. the insulation materials produced can be use in thermal storage for medium temperature applications. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 415-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 421 acknowledgements the authors would like to acknowledge the tetfund through the ibr research grant no. tetfund/dess/unimaid/maiduguri/rp/vol.ii at university of maiduguri, maiduguri, nigeria for providing financial support for the study. the authors also appreciate mr. m. ndagi of the department of mechanical engineering, university of ilorin, nigeria for his assistance during the study. references abdulkareem, s., ogunmodede, s., aweda, jo., abdulrahim, at., ajiboye, tk., ahmed, ii. and adebisi, ja. 2016. investigation of the thermal insulation properties of biomass composites. international journal of technology, 6: 849-859. abdulkareem, s., olayemi, dj., abdulrahim, at., aweda, jo., and ajiboye, tk. 2015a. kapok wool, luffa cylinderica and cellulose as thermal insulation materials. a paper presented as poster presentation at the national engineering conference, exhibition and annual general meeting organized by the nigerian society of engineers(nse) held at akure, nigeria from 16th – 20th december, 2015. abdulkareem, s., ogunmodele, ss., aweda, jo., ajiboye, jk. and abdulrahim, at. 2015b. kapok, sugarcane bagasse and coconut fibres as thermal insulation composite. paper presented at the 3rd international conference of the u6 consortium on innovation trends in science and humanities for global development and social transformation held at university of ilorin, ilorin nigeria from 6th – 10th september, 2015. abbott, af. 1980. ordinary level physics. heinemann educational books, london, uk. adams, fd., joseph, mv. and shettima, b. 2017. geochemical investigation of clay minerals in marte, borno state, nigeria. arid zone journal of engineering, technology and environment, 13(5): 544-554. adams, fd., shettima, b., bukar, m. and joseph, mv. 2018. mineralogical and geochemical investigation of clays in some areas around southern part of yobe state, nigeria. research journal of science, 18(1): 23-31. aguyi, g. 2011. thermal properties of selected materials for thermal insulations in uganda. department of physics, makerere university. ali, me. and zeitoun, om. 2012. discovering and manufacturing a new natural insulating material extracted from a plant growing up in saudi arabia. journal of engineered fibres and fabrics, 7(4): 88-94. andy, s., pete, w., and daniel, b. 2011. natural fibre insulation to low-impact building materials. university of bath. available online at http://www.bre.co.uk/filelibrary/pdf/projects/low_impact_materials/ip18_11.pdf. accessed on july 13, 2013. ashby, mf. and jones, drh. 1998. engineering materials 2: an introduction to microstructures, processing and design. butterworth – heinemann, oxford, uk. cengel, ya. 2007. heat and mass transfer. a practical approach. 3rd edition, tata mcgrawhill publishing company limited, new delhi, india. counts, c., sadiq, yo. and baba, s. 2000. refractories and glaze making in northern nigeria. borno journal of geology, 2(2): 18-25. eeday, s., goteti, s. and anne, sp. 2014. experimental investigation of thermal properties of borassus flabellifer reinforced composites and effect of addition of fly ash. international journal of engineering trends and technology, 15(8): 379-382. holman, jp. 2010. heat transfer. 10th edition. mcgraw-hill, companies inc., new york, usa. incropera, fp., dewitt, dp., bergman, tl. and lavine, as. 2007. fundamentals of heat and mass transfer. six edition, john wiley and sons, inc., usa. http://www.bre.co.uk/filelibrary/pdf/projects/low_impact_materials/ip18_11.pdf file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: thermal and mechanical properties of clay and drop-off of ceiba pentandra (kapok) plant wool mixture. azojete,16(2):415-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng 422 kobayashi, y., matsuo, r. and nishiyama, m. 1977. method for adsorption of oils. japanese patent, 52,138,081, november, 17, 1977. lewis, a. 2013. worldweb international dictionary. worldweb software.com. rodriguez, nj., ya’nez-limon, m., gutierrez-miceli, fa., gomez-guzman, o., matadamasortiz, tp., lagunez-rivera, l. and vazquez feijoo, ja. 2011. assessment of cocoanut fibre insulation characteristics and its use to modulate temperatures in concrete slabs with the aid of finite element methodology. energy and building, 43(6): 1264-1272. satta, p. and steve, f. 2008. agricultural waste materials as thermal insulation for dwellings in thailand. plea-25th conference on passive and low energy architecture, university college dublin, ucd, dublin. tripathi, m., sahu, jn., ganesan, p. and jewaratnam, j. 2016. thermophysical characterization of oil palm shell (ops) and ops char synthesized by the microwave pyrolysis of ops. applied thermal engineering, 105: 605-612. http://www.azojete.com.ng cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 247-256 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s email: ajaotaiwooluwatoyin@gmail.com 247 original research article numerical analysis of two term model using newton’s method on drying kinetics of an improved cowpea (it 97k-56s-is) ajao, t. o.* and raji, a. o. department of agricultural and environmental engineering, faculty of technology, university of ibadan article information received: october, 2018 accepted: december, 2018 keywords: two term model newton raphson numerical solution drying kinetics it 97k-56s-is maturity date modelling nigeria abstract invention of computers has made numerical methods prevalent and widely accepted. different numerical methods exist but all aid in solving large numbers of tedious arithmetic calculations involving complex differential equations and so an analytical solution cannot be applicable, hence, computer simulations and numerical solution become functional. it 97k-56s-is, a high yielding, multiple disease resistant cowpea variety with maturity date of 60days was gotten from the international institute of tropical agriculture (iita). experiments were carried out on samples after harvesting at maturity in a convective dryer at drying temperature of 55, 65, 75 and 85ºc and drying kinetics was performed utilising the two term model. the model was numerically solved using newton raphson’s iterative method on account that it is a non linear equation, its fast convergence to the roots and requirement of a single guess. a well structured algorithm was written. the performance of the models was evaluated using the coefficient of determination (r^2) and root mean square error (rmse) showing the relationship between the experimental and predicted moisture ratios. the result shows that newton raphson’s method would be suitable for two-term model if used with a multiplication factor or constant. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction numerical methods are techniques by which mathematical problems are formulated so that they can be solved with arithmetic operations. although there are many kinds of numerical methods, they have one common characteristic which is that they invariably have large numbers of tedious arithmetic calculations. hence, with the development of fast, efficient digital computers, the role of numerical methods in engineering problem solving has increased dramatically in recent years (steven and raymond, 2010). the purpose of modelling is to allow engineers to select the most appropriate method of drying for a given product as well as to determine the most suitable conditions (aremu et al., 2013). the principle of modelling is based on having a set of mathematical http://www.azojete.com.ng ajao and raji: numerical analysis of two term model using newton’s method on drying kinetics of an improved cowpea (it 97k-56s-is). azojete, 14(sp.i4): 247-256. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: ajaotaiwooluwatoyin@gmail.com 248 equations which can satisfactorily explain the system. models are often used to study the variables involved in the process, predict drying kinetics of the product and to optimize the operating parameters and conditions (karathanos and belessiotis, 1999; raji and olanrewaju, 2015). they predict the drying times of several products and also generalize drying curves (meisami-asl et al., 200; raji and olanrewaju, 2015). a mathematical model can be broadly defined as a formulation or equation that expresses the essential features of a physical system or process in mathematical terms. differential equations can be used in describing nearly all systems undergoing change (steven and raymond, 2010). thin layer drying process of food products has been described by many mathematical models according to ojediran and raji (2010) and these include: cowpea (jianfang et al., 2013; raji and olanrewaju, 2015), green bean and onion (yaldiz and ertekin, 2001), millet (ojediran and raji), 2010), soybean (gely and santalla, 2000), grains (tagawa et al., 1996). high yielding, multiple disease resistant cowpea varieties with varying maturity periods as well as different seed colours, adapted to various nigerian agro-ecological zones have been developed in iita, in collaboration with several national research institutes and universities. several of these varieties have been released in nigeria and are promoted by the state agricultural development projects (adps), farmers’ groups and seed companies (boukar and ajeigbe, 2010). the most important factor in crop production is the choice of a good variety. varieties that have resistance to the prevailing biotic and abiotic stresses in the areas should be planted. maturity, growth pattern, market value, seed size, and seed colour should also be considered in variety selection (dpp, 2011). the demand for quality farm products increases, therefore, mechanical drying becomes more popular and acceptable as the advantages outweigh the disadvantages. matured cowpea can thus be harvested promptly and subjected to mechanical drying so as to reduce harvest moisture content to safe level for proper storage (yakubu et al., 2012). also, the error present in the solution of models is dependent on how the problem is solved. numerical methods are used when evaluating empirical information such as experimental data. such data, no matter how exact and regulated the experiment was conducted, will involve some degree of error. it would be a waste of time to employ exact analytical techniques in such a situation because the answer can never be more “correct” than the input data (swick, 2013). therefore, this work investigated the drying kinetics of an improved variety cowpea (it 97k-56s-is) at varying drying temperature using the application of numerical method for a complex uncommonly used model (two term model) thereby developing an efficient algorithm for finding its successive better approximations to the solutions of the complex model. http://www.azojete.com.ng 2.0 materials 2.1 sample preparation a high yielding cowpea, disease resistant, it 97k-56s-is with a maturity date of 60days was gotten from the international institute of tropical agriculture (iita). it was propagated by seeds during the period of a partially wet season on 5th of may, 2014 at the demonstration area, research farms unit, iita, ibadan, also as stated by raji and olanrewaju (2015) and raji and olanrewaju (2016). this was to ensure that the seeds tested were harvested at the period needed. for each drying experiment, two hundred (200) grams of the freshly harvested sample was used according to aremu and akintola (2014); tunde-akintunde and afon (2009); raji and olanrewaju (2015); raji and olanrewaju (2016). each experiment was replicated three times (aremu et al., 2013) and triplicate samples were spread out in thin layer and placed in the dryer. the drying temperature used for the experiment were 55, 65, 75, 85°c which are within the range of temperatures used by mario et al. (2003), mc watters et al. (1988) and wilton et al. (2008) for drying of cowpea. the drying process was monitored by weighing the samples every 10mins for the first one hour; then every 30mins for the next three hours and every 1hr for the next three hours till the end of drying according to ojediran and raji (2010) raji and olanrewaju (2015); raji and olanrewaju (2016). weighing continued until constant weights were obtained being the period that equilibrium with environment was assumed to have been reached and the test was terminated. moisture content determined at this point is the dynamic equilibrium moisture content. with the initial moisture already known, weight loss was used to calculate the moisture content using the equation used by ojediran and raji (2010) given as: �� � ������� ����� (1) where, mt is the moisture content (m.c.) at time t, (% w.b.), mi ,the initial m.c. (%w.b.), mi, the initial weight, (g) and wi is the weight loss at time, t (g). the moisture ratio (mr) of the samples during the thin layer drying experiments was calculated using equation 2.2 according to ojediran and raji (2010): �瀀 � ���� ����� (2) matured pods were harvested by hand at period of harvest of 60 days after planting (dap) in line with the recommendation of directorate plant production (dpp, 2011) and to avoid shattering of the pods. freshly harvested cowpea pods were then cleaned and sorted to remove foreign materials. the initial moisture content of the samples was determined using the drying method. samples of known weight (200g) were measured with the use of a top loading scout pro sensitive weighing scale and were placed in the cabinet tray dryer at 130°c for about 16 – 18 hours as required by asabe standards (asabe, 2003) as stated also by raji and olanrewaju (2015) and raji and olanrewaju (2016). ajao and raji: numerical analysis of two term model using newton’s method on drying kinetics of an improved cowpea (it 97k-56s-is). azojete, 14(sp.i4): 247-256. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: ajaotaiwooluwatoyin@gmail.com 250 3.0 method 3.1 iterative methods iterative methods can be used in solving equations by methods of successive approximations to the roots (variable or parameter that satisfy a single nonlinear equation). three methods of successive approximations include; newton-raphson’s formula, bisection method and an algebraic method. each successive approximation method relies on a reasonably good first estimate of the value of a root being made. one way of determining this is to sketch a graph of the function, say y=f(x), then determine the approximate values of roots from the points where the graph cuts the xaxis. another way is by using a functional notation method. this method uses the property that the value of the graph of f(x)=0. it changes sign for values of x just before and just after the value of a root (john, 2003). 3.2 reasons for the choice of newton raphson’s method newton raphson method was chosen for numerical solution of the two term model due to the following reasons: 1. it can be used for solving nonlinear equations. 2. it converges fast to the roots, if it converges. 3. it requires only one guess. 3.3 newton’s method the newton–raphson’s formula, often referred to as newton’s method, may be stated as follows: if �� is the approximate value of a real root of the equation � � � t , then a closer approximation to the root �� is given by: ��= ��+ �晦��� ��晦��� (3) the advantages of newton’s method over other methods of successive approximations is that it can be used for any type of mathematical equation (i.e. ones containing trigonometric, exponential, logarithmic, hyperbolic and algebraic functions), and it is usually easier to apply than other methods (john, 2003). 3.4 newton raphson’s iteration let �t be a good estimate of r and let r = �t + h. since the true root is r and h = r �t , the number, h, measures how far the estimate �t is from the truth. since h is ‘small,’ we can use the linear (tangent line) approximation to conclude that t � � � � �晦�� � ��t ≈ f (�t) + �f�晦xt� (4) http://www.azojete.com.ng therefore, unless fˈ (�t) is close to 0, h ≈ − �晦�t� ��晦�t� (5) it follows that, � = �t � � ≈ �t − �晦�t� ��晦�t� (6) then the new improved estimate of r is therefore given by; �� = �t+ �晦�t� ��晦�t� (7) the next estimate �� is obtained from �� in exactly the same way as �� was obtained from �t: �� = ��+ �晦��� ��晦��� (8) continuing in this way. if �� is the current estimate, then the next estimate ���� is given by: n+1is given by; ���� � ��+ �晦��� ��晦��� (9) 3.5 computer programming and algorithm computer programs are merely a set of instructions that direct the computer to perform a certain task. a well structured algorithm is easier to debug and test, resulting in programs that take a shorter time to develop, test, and update. structured programming is a set of rules that prescribe good style habits for the programmer. it is flexible enough to allow considerable creativity and personal expression. a key idea behind structured programming is that any numerical algorithm can be composed using the three fundamental control structures: sequence, selection, and repetition (steven and raymond, 2010). to keep this description generic, pseudocode was employed. 4 results and discussions 4.1 results the non linear model of the form (two term model): 0 1k t k ty e e    (10) solving the non linear regression model using newton raphson’s method, the parameters can be estimated using the non linear least square method, the sum of squares is given as: 0 1 2 ( ) ( ( ))i ik t k t if x y e e     (11) the partial derivatives with respect to the parameters `were found and also their second derivatives. recall from equation 8, the newton raphson formula is given as: 1 ( ) ( ) n n n n f xx x f x    this can be rewritten as: ajao and raji: numerical analysis of two term model using newton’s method on drying kinetics of an improved cowpea (it 97k-56s-is). azojete, 14(sp.i4): 247-256. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: ajaotaiwooluwatoyin@gmail.com 252 1 ( ) ( ) n n n n g yy y h y    (12) therefore, 0 11 ( ) ( ) n n n k t k tn n g yy e e h y       (13) 4.2 discussions 4.2.1 drying kinetics of an improved variety cowpea (it 97k-56s-is) the initial moisture content and equilibrium moisture content of (it 97k-56s-is) at period of harvest of 60dap and at drying temperatures of 55, 65, 75 and 85°c is presented in table 4.1 according to (raji and olanrewaju, 2015). the moisture ratio decreased exponentially with time and the time required to reaching equilibrium moisture content decreases with increasing temperature as illustrated in figure 4.1. this is a general trend reported for other food products e.g. mulberry, tomatoes, sweet pepper and peach slices. (doymaz, 2004; doymaz, 2007: vengaiah and pandey, 2007; kingsly et al., 2007, raji and olanrewaju, 2015). 4.2.2 model fitting the model constants and the coefficients for the two term model at period of harvest of 60dap and at 55, 65, 75 and 85°c is presented in table 4.2. the model fittings are illustrated as presented in figure 4.1a-d. 4.2.3 limitation of newton raphson’s method often times, the newton raphson’s method is very efficient but sometimes there are situations when it performs poorly especially in special case of multiple roots. there is tendency of the newton raphson technique to oscillate around a local maximum or minimum. such oscillations may persist, or as a near-zero slope is reached, whereupon the solution is sent far from the area of interest. obviously, a zero slope [f(x) = 0] is not suitable because it causes division by zero in the newton-raphson formula, it implies that the solution shoots off horizontally and never hits the x axis. therefore, there is no general convergence criterion for newton-raphson. its convergence depends on the nature of the function and on the accuracy of the initial guess. an initial guess sufficiently close to the root may be required (steven and raymond, 2010). 5 conclusions to select and apply the most appropriate method for a particular problem, it requires a good understanding of the characteristics of the method and of the problem being solved (craft, 2010). however, from the results gotten from this research it can be concluded that newton raphson’s method will be suitable for numerically solving twoterm model but due to its limitation a multiplying factor (constant) was applied. other numerical methods may also be applied. http://www.azojete.com.ng table 4.1 initial moisture content and equilibrium moisture content of (it 97k-56s-is) at period of harvest of 60dap and at 55, 65, 75, 85°c period of harvest initial m.c. (x100%d.b.) equilibrium m.c. (x100%d.b) 55°c 65°c 75°c 85°c 60 2.26 0.039 0.028 0.030 0.021 table 4.2 drying constants and coefficients of the models for it 97k-56s-is at period of harvest of 60dap multiplication factor constants and coefficients two term model 55°c 4.1354 a k b r 0.3050 0.6377 -0.0632 0.4128 r2 rmse 0.9423 0.0015 65°c 3.3847 a k b r -0.0716 0.7419 0.3670 0.9754 r2 rmse 0.9053 0.0025 75°c 3.5064 a k b r -0.0684 0.6513 0.3536 0.8861 r2 rmse 0.9839 0.0008 85°c 3.4130 a k b r 0.3617 0.7728 -0.0687 0.5356 r2 rmse 0.9946 0.0002 ajao and raji: numerical analysis of two term model using newton’s method on drying kinetics of an improved cowpea (it 97k-56s-is). azojete, 14(sp.i4): 247-256. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: ajaotaiwooluwatoyin@gmail.com 254 a b c d figure 4.1a: drying model fittings at period of harvest of 60dap at 55°c b: drying model fittings at period of harvest of 60dap at 65°c c: drying model fittings at period of harvest of 60dap at 75°c d: drying model fittings at period of harvest of 60dap at 55°c 6 acknowledgement special thanks to the international institute of tropical agriculture for the priviledge given to the authors to carry out this research in their institute. references aremu, a. k., adedokun a. j. and raji, a. o. 2013. ″effect of slice thickness and temperature on the drying kinetics of mango (mangifera indica), ijrras, 15(1): 41-50. aremu, a. k. and a. akintola. 2014. effects of some drying methods on nutritional characteristics of moringa (moringa oleifera) seeds. 2014 5th international conference on agriculture and animal science (icaas 2014) 2014. http://www.azojete.com.ng 255 boukar, ousmane and hakeem a. ajeigbe. 2010. improved agronomic practices for cowpea production and prospects for mechanized cultivation pp.1-10 in farmers’ guide to increased productivity of improved legume–cereal cropping systems in the savannas of nigeria iita, nigeria. directorate plant production, dpp. 2011. production guidelines for cowpeas, directorate agricultural information services, department of agriculture, forestry and fisheries, south africa. gely, m.c. and santalla m. 2000. effect of some physical and chemical properties of oilseeds on drying kinetics parameters. drying technology, 18(9), 2155-2166. jianfang, shi, wu huihuang, lou zheng, wu zhonghua, liu qing1. 2013. drying characteristics and model of cowpea in tunnel hot air dryer. vol. 29, no.11, 232, 2013, 6, transactions of the chinese society of agricultural engineering, jun. 2013. john bird, (2003). engineering mathematics, fourth edition, an imprint of elsevier science, isbn 0 7506 5776 6, copyright 2001, 2003. karathanos, v. t. and v. g. belessiotis. 1999. application of a thin layer equation to drying data fresh and semi-dried fruits. j. agric. eng. res., 74: 355-361. mario, eduardo range, moreira cavalcanti mata, maria elita martins duarte. 2003. drying simulation theory of the cowpea considering the grains shrinkage, revista. brasileira de produtos agroindustriais, campina grande, 5(2).179 185. mcwatters, k. h. m., chinnan, m. s., hung, y. c. and a. i. branch. 1988. the effect of predecortication drying temperature on cowpea paste characteristics and functionality in preparation of akara. cereal chemistry, 65(1), 1988. meisami-asl, e., shahin r., alireza k. and ahmad t. 2009. mathematical modeling of moisture content of apple slices (var. golab) during drying. pakistan journal of nutrition 8 (6): 804-809, 2009. issn 1680-5194. ojediran, j. o. and raji, a. o. 2010, ″thin layer drying of millet and effect of temperature on drying characteristics″ international food research journal, 17: 1095-1106. raji, a. o., and *t. o. olanrewaju. 2015. effect of period of harvest on drying characteristics of an improved variety cowpea (it 97k-56s-is). agric eng int: cigr journal, 17(4):291 305. raji, a. o. and *olanrewaju, t. o., (2016). moisture diffusivity and activation energy of an improved variety of cowpea as affected by period of harvest and drying conditions. journal of applied science, engineering and technology (2016) vol. 16(1), pp10-18. steven, c. chapra and raymond, p. canale. 2010. numerical methods for engineers, sixth edition ajao and raji: numerical analysis of two term model using newton’s method on drying kinetics of an improved cowpea (it 97k-56s-is). azojete, 14(sp.i4): 247-256. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: ajaotaiwooluwatoyin@gmail.com 256 swick, justin. 2013. an introduction to numerical methods. stem articles. http://www.crosscuttingconcepts.com/stem-articles/31-an-introduction-to-numericalmethods. created on wednesday, 10 april 2013 14:57. 2016 crosscutting concepts, llc. tagawa, a., kitamura, y. and murata, s. 1996. thin layer drying characteristics of adzuki beans. transactions of the asae 39(12): 605 609. tunde-akintunde, t. y. and a. a. afon (2009). “modelling of hot-air drying of pretreated cassava chips”. agricultural engineering international: the cigr ejournal. manuscript 1493 vol. august, 2009. wilton, p. da silva, mário, e. r. mata, m. c, cleiton, d. p. s. e silva, manoe a. guedes, antonio g. b. lima (2008); journal of biology, agriculture and healthcare, www.iiste.org, 2(2), 2012 . http://www.azojete.com.ng 1.0introduction 3.0 method 3.1 iterative methods arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):939-957 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 939 original research article project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria g. a. zarewa (department of quantity surveying, bayero university, kano, nigeria) * corresponding author’s email address: galzarewa.qs@buk.edu.ng 1.0 introduction involvement of many stakeholders with varying interests, power/influence and expectations in mips delivery has necessitated the need for the projects' managers to understand what enhances or militates against effective stakeholder management (esm) in the projects' delivery. a project's manager's ability to effectively manage stakeholders in a project's delivery plays a great role in ensuring achievement of the project's desired goals and objectives. this corroborated the views of some authors such as chinyio and omoloyaie (2015) who argued that esm sets a basis for deciding which stakeholders are to be involved in determining a project article information abstract many projects were known to have failed due to ineffective stakeholder management. this study investigated views of project managers (who participated in the delivery of multifarious infrastructure projects (mips) in north eastern and north western regions of nigeria) on barriers to effective stakeholder management (esm) in mips delivery in nigeria. the study was conducted with the aim of preventing or at least minimising the projects' failure rates due to ineffective stakeholder management. extensive literature review, questionnaire survey, and relative importance index (rii) analysis methods were used to conduct the study. barriers to esm in the projects' delivery were identified and ranked according to the project managers' perceptions on their respective levels of influence against esm. the study discovered that barriers with different levels of impact inhibit effective stakeholder management in mips delivery. client's uncooperative attitude; failure to identify potential conflict areas; uncooperative attitude of stakeholders; project manager's poor knowledge of stakeholder management/failure to understand stakeholders' needs and expectations; and failure to meet information requirements of all stakeholders were ranked as the first, second, third, fourth and fifth (in descending order) barriers to esm in mips delivery respectively. the study concluded that current approach to stakeholder management in mips needs to be improved considerably and accordingly recommends the development of an appropriate strategy for handling stakeholder management in the delivery of mips and other projects in nigeria. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 02 december, 2018 revised 04 may, 2019 accepted 10 may, 2019 keywords: barriers effective stakeholder management multifarious infrastructure projects project managers and stakeholders . http://www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 940 goals and measuring its success. chandrayan (2017) discovered that achievement of a project's desired goal depends upon the skill-set of project managers and their human management traits while bodepudi (2018) opined that managing people to ensure that project team members are meeting the deadlines and following the guidelines was the key element of project management. stakeholder management (sm) has been defined as “the systematic identification, analysis and planning of actions to communicate with and influence stakeholders” by project management institute (pmi, 2004). olander and landin, (2008) argued that the aim of stakeholder management in projects is to attain the desired and successful implementation of the project and avoid unnecessary conflicts and controversies with the project stakeholders. the foregoing statements imply that ineffective stakeholder management in a project delivery will affect the success of the project. chino and olomolaiye (2015) discovered that ineffective stakeholder management will reduce probability of successful project completion due to conflicts between stakeholders and result in dissatisfaction with project outcomes and adverse disruption to budget and schedule. another study by eskerod and jespen (2013) discovered that carrying out a project as planned was not a guarantee for success as the project may still fail if stakeholders are not sufficiently managed. ineffective stakeholder management has been identified as one of the main causes of projects' failure in nigeria. infrastructure concession regulatory commission (2012) attributed refusal of some motorists to pay road tolls, which affected the performance of lekki toll road concession project in lagos, to ineffective sm at the early phases of the project. ibrahim et al (2006), in their work, identified ineffective sm as risk associated with successful ppp projects in nigeria. the foregoing discourse clearly highlighted the need to identify factors that enhance or militate against esm in projects' delivery. eyiahbotwe1 et al (2015) suggested that it was imperative for appropriate stakeholders to identify factors militating against effective stakeholder management in the delivery of their projects. yang et al. (2009) discovered that there are significant barriers and challenges which militate against successful stakeholder management in construction projects' delivery. it has however been observed that despite identified negative impacts of ineffective sm on project success, not much efforts were made to identify and address factors militating against esm in project delivery particularly in developing countries like nigeria. eyiahbotwe1 et al. (2015) observed that while many studies have considered critical success factors (csfs) for stakeholder management, not much has been done on critical barrier factors (cbfs) to esm in developing countries. it is in view of the foregoing that this study investigated project managers' perceptions on barriers to esm and their respective levels of influence (ranking) on sm in mips' delivery with the aim of preventing or minimizing incidences of the projects' failure due to ineffective stakeholder management. finding from the study will give project managers an idea of which barriers to address/focus on in order to achieve esm in mips delivery. findings from this study can also help project managers to enhance their chances of managing their projects successfully. mip for the purpose of this study refers to one large infrastructure project comprising three different types of projects for example one large project comprising building, civil engineering http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 941 and services sub-project such as establishment of a large housing estate, hospital, industry and so on. the aim of the study was achieved through identification of factors pms considered to be barriers to esm in the delivery of mips in nigeria and assessing/ranking the level of influence of each of the identified barriers against esm in the projects' delivery. 2. literature review 2.1 multifarious infrastructure projects mips have been described differently by different institutions and scholars. fox and miller (2006) and bekker (2008) referred to them as mega-projects, macro-projects and/or super projects. the projects, which have significant impact on the socio-economic development of countries all over the world (bekker, 2008), are always in continuous demand due to increasing global population, aging infrastructure, increasing urbanisation and so forth. the projects usually attract huge investment in their procurement and involve numerous stakeholders often with conflicting interests in their delivery.mips comprise many sub-projects and involve many stakeholders such as the clients, consultants, contractors, sub-contractors, financial institutions, end users, government agencies, media, regulators such as the local and national authorities, local community groups, and other independent groups with special interests in their delivery. these stakeholders with varying stakes, influence and power; undertake different roles and responsibilities that could lead to the success or failure of the projects. the large number of stakeholders and/or role players and work packages involved in the delivery of mips makes their management more complex than those of small conventional projects. fox and miller (2006) were of the view that as a project increases in size, the challenges associated with managing relationships among its sub-projects grow more intricate. conflict between and among mips participants often occurs in the course of the projects' delivery due to divergent interests of the numerous participants and stakeholders involved in the delivery. fox and miller (2006) were of the opinion that potential for conflicts between and among project stakeholders depends largely on the project’s scope and environment. internal conflicts, conflicts in sponsor contractor relationship and conflicts over resources were identified by fox and miller (2006) as the three major conflicts likely to occur between and among mips' stakeholders in the course of the projects' delivery. the fact that each of these conflicts has the potential of impacting negatively on the projects' delivery, made it imperative for managers of the projects to handle issues associated with mips' stakeholders with utmost caution. the foregoing discourse clearly indicated that delivery of an mip involves significantly more stakeholders with multiple views and opinions than that of a conventional project thereby making the management of mips' stakeholders and the projects' delivery very challenging. 2.2 managing mip's stakeholders stakeholder management in mips' delivery is more complex than that in small conventional projects' delivery due to involvement of large number of stakeholders (with multiple stakes, views and opinions) in mips' delivery. it is therefore imperative for mips' project managers to adopt an effective strategy for managing these numerous stakeholders effectively with a view to achieving successful project delivery devoid of any rancour. attaining desired and successful file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 942 implementation of a project and avoiding unnecessary conflicts and controversies with project stakeholders had earlier been identified as a key aim of stakeholder management in projects by olander and landin (2008). project management institute (pmi) (2013a) has defined a project stakeholder as an individual, group, or organization that may affect, be affected by, or perceive itself to be affected by a decision, activity, or outcome of a project, program, or portfolio. although different kinds of stakeholders are involved in each particular project, stakeholders in construction projects such as mips can, according to chino and olomolaiye (2015), be classified into five main groups: clients, consultants, contractors, external public parties and external private parties. clients, consultants and contractors can be grouped together as internal stakeholders, while the remaining parties are considered external stakeholders. stakeholders can also be classified as primary or secondary. teye buertey (2016) reported that other works disagreed with the above conceptualisations and categorisations of stakeholders for uncertainty and suggested that a difference should be made between stakeholders, stake watchers and stake keepers. in terms of classification, stakeholders are those who have a tangible and real stake in a project. stake watchers, in turn, do not actually have a stake themselves but they guard the interests of actual stakeholders. examples of stake watchers are unions and community pressure groups. botchway (2001) postulated that stake keepers are autonomous regulators, such as governments, regulatory agencies and certification organizations, who have no stake but have influence and control. this study, while appreciating further explanation on stakeholder classification offered by the immediate foregoing argument, aligns itself with classification by chino and olomolaiye (2015). newcombe, (2003) postulated that construction projects such as mips have, by their nature, diverse stakeholders who play various roles and responsibilities in a project's delivery. these stakeholders who are from different disciplines, backgrounds, have different goals, interest, stake and influence which can affect or be affected by the project outcome. their interest, influence, power and perception about the project, among others, need to be managed effectively for a successful project delivery. meeting project stakeholders' satisfaction and needs has been identified as a measure of project success by project management institutes (2013). moreover, mok et al. (2013) discovered that mega construction projects such as mips require esm in their delivery due to the management challenges posed by involvement of numerous stakeholders in the delivery. sm is an essential part of project management process which entails processes and techniques employed to effectively manage relationships between project organisation and stakeholders with a view to enhancing positive and reducing negative impacts of stakeholder influence on project goals and objectives. sm requires systematic identification, analysis, planning actions, communication, and negotiation aimed at influencing these stakeholders (lock, 2007). the process could, if conducted properly, serves as an opportunity for achieving stakeholder satisfaction, which is a key to meeting client’s objectives, value, concern and success. an mip manager should, therefore, excel in organising, delegating, communicating, directing, and getting along with the project's stakeholders such as members of the project manager’s team, sponsors, government regulators, bankers, contractors, the media, and representatives of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 943 local interest groups. the pm should also adopt flexible and dynamic sm approach in order to deliver satisfactory outcomes to the stakeholders. a test for effective management of mips is the degree to which the projects’ objectives has been achieved in terms of quality, within budget, time and expected service delivery to relevant stakeholders’ satisfaction. the main steps involved in stakeholder management in construction projects include stakeholder identification, stakeholder analysis, stakeholder classification and formulating/adopting stakeholder management strategy. researchers have suggested several approaches to sm. lock (2007) recommended identification of stakeholders, gathering information about the stakeholders and analysing their influence as a systematic approach to sm. bourne and walker (2005) adopted stakeholder circle approach which involves identification of stakeholders, prioritisation, visualisation, engagement and monitoring effect of their involvement. chinyio and olomolaiye (2015) stated that stakeholder management can be carried out in many ways including evaluating needs and expectations of stakeholders in relation to main project goals. the foregoing statements implied that mips' managers should identify all stakeholders that are, in one way or the other, associated, with the delivery of their projects. it can also be deduced from the statements that it is important for every mip manager to understand the needs, expectations, power and influence of every stakeholder associated with the delivery of his/her project and manage them well in order to achieve successful delivery of the project. abdu lawan (2016) reported that some unidentified stakeholders protested against the execution of an mip because their needs and expectations were not taken into consideration when initiating the project. the protest led to suspension of works at the affected project's sites and affected its completion period. . the manager should also ensure that all stakeholders are appropriately communicated with, engaged and prioritised according to their influence on the success or otherwise of the project. limiting stakeholder engagement to only few stakeholders such as internal stakeholders, which used to occur in many circumstances, could derail a project. trb (2015) believed pm of complex projects such as mips must develop solutions to satisfy all stakeholders, including external stakeholders, who can affect the manager's ability to achieve the complex project’s objectives. whatever approach an mip manager adopts in managing a project's stakeholders, it is important to ensure that they (stakeholders) are effectively managed because effective management of stakeholders of a project is an important key to the project's success. findings of a study reported by chinyio and olomolaiye (2015) reinforced the foregoing statement by stating that ineffective stakeholder management reduces the probability of successful project completion due to conflicts between stakeholders, dissatisfaction with project outcomes and adverse disruption to budget and schedule. the importance of sm to successful project delivery highlighted above has made some scholars to investigate and discover factors that could influence sm in project delivery. yang et al., (2009) confirmed 15 critical success factors (csfs) for stakeholder management for developing countries while hammad, (2013) identified 23 csfs for the gaza strip construction industry. other studies by chinyio and akintoye, (2008); olander and landing, (2008); jepsen and eskerod, (2009); and li et al. (2011) have also identified and studied critical success factors (csfs) for stakeholder management in construction projects. critical success factors (csfs) for stakeholder file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 944 management have been described as activities, practices and considerations that can directly or indirectly ensure successful stakeholder management (eyiahbotwe1 et al. 2015). yang et al. (2009), in their work, discovered challenges associated with the processes of stakeholder management that are militating against effective stakeholder management (esm) in project delivery. a recent but yet to be published study on barriers to esm in mips delivery by this author has identified 39 barriers to esm in mips delivery in nigeria. it is therefore important for mips' managers to identify and understand these challenges and/or barriers with a view to achieving esm and successful delivery of their projects. 2.3 factors/barriers militating against effective stakeholder management in project delivery a review of extant literature on stakeholder management showed that many previous studies have identified challenges and factors militating against esm in project delivery. the challenges/factors were identified by studies conducted by authors such as abdu lawan (2016); chino and olomolaiye (2015); eyiahbotwe1 et al. (2015); molwus (2014); hammad, (2013); mok et al. (2013) and many others. an analysis of the challenges/factors resulted in the list of barriers contained in table 1. the table contains list of factors militating against esm in mips’ delivery obtained by the study from literature review. table 1 : factors militating against effective stakeholder management in mips' delivery in nigeria s/n barrier 1 incomplete stakeholder identification 2 late identification of stakeholders 3 failure to identify key stakeholders 4 failure to recognise and cooperate with adverse stakeholders 5 language barrier between stakeholders 6 cultural differences between stakeholders 7 uncooperative attitude of stakeholders 8 limited stakeholder engagement/involvement 9 lack of stakeholder engagement/involvement 10 stakeholders' incapacity to participate in discussions 11 involvement of numerous stakeholders 12 assignment of similar task to two stakeholders 13 failure to identify potential conflict areas 14 failure to assess levels of influence of various stakeholders 15 failure to understand stakeholders' needs and expectations 16 lack of constant communication with stakeholders 17 lack of open and ongoing communication process 18 issuance of the same information to all stakeholders 19 failure to meet information requirements of all stakeholders 20 issuance of incorrect information to stakeholders http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 945 21 lack of a person specifically assigned to handle sm 22 conflicts between stakeholders 23 lack of periodic stakeholder meetings 24 misunderstanding of roles by stakeholders 25 taking over roles from one stakeholder & assigning them to another 26 lack of continuity in sm process 27 project manager's poor knowledge of sm 28 absence of formal sm process 29 failure to understand relationship between and among stakeholders 30 lack of fairness and equity, for all stakeholders; 31 failure to engender trust with the stakeholders; 32 inhumane attitude in relating with stakeholders 33 imposition of leadership on stakeholders 34 nature and size of a project; 35 project location 36 interference in sm by client 37 client's uncooperative attitude 3. research methodology the study was conducted in three stages. the first stage involved extensive literature review from which the list of factors militating against effective stakeholder management in mips delivery in nigeria contained in table 1 was drawn. the identified factors were then carefully analysed and discussed with some mips’ project managers and other experts in order to identify major barriers to esm in mips’ delivery. a questionnaire survey was then conducted to evaluate the impact of each barrier against esm in mips' delivery on the basis of a 5-point likert scale where 1 represents very low impact, 2 represents low impact, 3 moderate impact, 4 high impact and 5 very high impact. the relative importance index (rii) for each factor was then calculated and ranked accordingly. this approach was used to rank causes of delay in construction projects and causes of delay for residential construction projects in indian context by abu hassan (2016) and megha and rajiv (2013) respectively. 3.1 survey design as mentioned earlier, a questionnaire survey approach was adopted for the purpose of data collection on the perceptions of the respondents on the level of impact of each of the 34 barriers against esm in the delivery of multifarious infrastructure projects (mips) in nigeria. the questionnaire is made up of three sections. the first section comprised introduction of the study and definitions of an mip, stakeholder and stakeholder management in the context of the study. the second section contained participants' information that was eventually used in categorising the participants into groups while the last section contained the respondents' perceptions on the barriers respective levels of impact against esm on the basis the 5 point likert scale described above. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 946 3.2 questionnaire administration the questionnaire was purposely administered to 25 experienced mips' project managers (pms) involved in and/or associated with the delivery of mips in the north eastern and north western regions of nigeria due to their knowledge in the study area and willingness to partake in the study. kumar (2011) argued that a researcher should only go to those people who in his/her opinion are likely to have the required information and willing to share it with the researcher while fellows and liu (2015) postulated that the real issue, after identifying data required for a study and sources of the data, is to determine which person is at an appropriate position to provide the data required for the study. the uncommon nature of mips also played significant role in deciding the number of respondents to be considered for the study because infrequent execution of mips in the regions covered by this study has limited the number of people to be considered as respondents for the study considerably. 3.3 ranking approach relative importance index (rii) was used to assess and rank each barrier to esm on the basis of respondents' scores collected from the survey. gunduz et al. (2014) used the relative importance index to rank factors that delayed turkish construction projects. it was also used by many other scholars such as somiah et al. (2015) who used it to conduct relative importance analysis of factors influencing unauthorized siting of residential buildings in the sekondi-takoradi metropolis of ghana. johnson and lebreton (2004) argued that rii ranking method best fits the purpose of a study of this nature which sets to find the contribution a particular variable makes to the prediction of a criterion variable both by itself and in combination with other predictor variables. the relative importance index (rii) used to assess and rank the pms' perceptions on each barrier to esm in the delivery of mips in nigeria was calculated using the following formula: rii = σw a*n (1) where: w = weight given to each attribute by the respondent (1 to 5). a = the highest weight (in this case is 5). n = total number of respondents rii value ranges from 0 to 1. the higher the rii value a barrier has, the higher its ranking and level of impact against esm. 4 results and discussions 4.1 results 4.1.1 outcome of analysis of and discussions on factors militating against esm in mips’ delivery the analysis and discussions resulted in the reduction of the 37 identified factors militating against esm in mips’ delivery to the 34 barriers to esm contained in table 2. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 947 table 2: barriers to esm in mips’ delivery s/n barrier 1 incomplete stakeholder identification 2 late identification of stakeholders 3 failure to identify key stakeholders 4 failure to recognise and cooperate with adverse stakeholders 5 language barrier between stakeholders 6 cultural differences between stakeholders 7 uncooperative attitude of stakeholders 8 limited stakeholder engagement/involvement 9 lack of stakeholder engagement/involvement 10 stakeholders' incapacity to participate in discussions 11 involvement of numerous stakeholders 12 failure to identify potential conflict areas 13 failure to assess levels of influence of various stakeholders 14 failure to understand stakeholders' needs and expectations 15 lack of constant communication with stakeholders 16 lack of open and ongoing communication process 17 issuance of the same information to all stakeholders 18 failure to meet information requirements of all stakeholders 19 issuance of incorrect information to stakeholders 20 lack of a person specifically assigned to handle sm 21 conflicts between stakeholders 22 lack of periodic stakeholder meetings 23 misunderstanding of roles by stakeholders 24 project manager's poor knowledge of sm 25 absence of formal sm process 26 failure to understand relationship between and among stakeholders 27 lack of fairness and equity, for all stakeholders; 28 failure to engender trust with the stakeholders; 29 inhumane attitude in relating with stakeholders 30 nature and size of a project; 31 project location 32 client's uncooperative attitude 4.1.2 received questionnaire response twenty five (25) questionnaires were distributed to pms who have actively participated in the delivery of mips in the north eastern and north western regions of nigeria. eighteen questionnaires (18) which represented 72% were returned and used for analysis. the returned questionnaires were considered adequate for the study because a comparative analysis on file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 948 response rate in academic studies by baruch (2014) discovered an average response rate of between 53 55.6%. another study by matthews (2007) recommended between 40 50% response rate while idrus and newman (2002) considered any questionnaire response in the range of 20% to 30% to be adequate for research in construction industry. 4.1.3 respondents' profile the respondents' profiles based on their professions, sectors of employment and years of experience are given in figures 1, 2 and 3. 4.1.3.1 respondents' profiles on the basis of their professions the professional callings of the respondents are shown in figure 1 figure 1: breakdown of respondents based on their professions the chart shows that quantity surveyors constituted 28% of the respondents while 22% were project managers by profession. builders also provided 22% of the responses whereas 17% of the respondents were architects by profession. responses provided by engineers contributed 11% of the responses. 4.1.3.2 respondents profile based on their sector of employment the respondents’ breakdown according to their respective sectors of employment is given in figure 2. figure 2: respondents profile on the basis of their sector of employment legend pm: project management qs: quantity surveying arch: architecture bldg: building eng: engineering http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 949 figure 2 above showed that the respondents were made up of 33% of the respondents were employed in the public sector and while 67% were employed in the private sector. 4.1.3.3 respondents profile based on their years of experience the respondents’ breakdown according to their years of experience is given in figure 3. figure 3: respondents' profile based on their years of experience figure 3 showed that respondents with 21 30 years working experience constituted 28% of the respondents while those with 11 20 years experience had 33% of respondents. respondents within the range of 5-10 years provided 17% of the responses while respondents within 31 41 years made up 22% of the respondents. 4.1.4 survey results and data analysis survey participants' perceptions (evaluations) on the impact of each barrier against esm in project delivery on the basis of a 5-point likert scale where 1 represents very low impact, 2 represents low impact, 3 moderate impact, 4 high impact and 5 very high impact were analysed using rii approach. the relative importance index (rii) value of each barrier was calculated using the formula given under ranking approach. the calculated rii values were then used to rank the barriers in descending order. the respondents' perceptions, rii values and ranking of each barrier against esm in mips' delivery are contained in table 3. the table contains list of barriers to esm, the respondents’ evaluations of their respective impacts, the barriers’ values and ranking. table 3: respondents' perceptions, rii values and ranking of barriers to esm in mips' delivery barrier n respondents evaluations rii rank 1 2 3 4 5 client's uncooperative attitude 18 0 0 0 5 13 0.9444 1 failure to identify potential conflict areas 18 0 0 1 9 8 0.8778 2 uncooperative attitude of stakeholders 18 0 1 1 7 9 0.8667 3 failure to identify key stakeholders 18 0 1 4 4 9 0.8333 4 failure to understand stakeholders' needs and expectations 18 0 0 4 7 7 0.8333 4 project manager's poor knowledge of sm 18 0 1 5 2 10 0.8333 4 failure to meet information requirements of all 18 0 2 7 6 3 0.8222 5 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 950 stakeholders conflicts between stakeholders 18 0 1 5 5 7 0.8000 6 lack of stakeholder engagement/involvement 18 1 0 4 7 6 0.7889 7 issuance of incorrect information to stakeholders 18 0 3 4 3 8 0.7778 8 lack of fairness and equity, for all stakeholders; 18 0 2 2 8 6 0.7778 8 inhumane attitude in relating with stakeholders 18 0 3 4 3 8 0.7778 8 limited stakeholder engagement/involvement 18 1 0 6 5 6 0.7667 9 misunderstanding of roles by stakeholders 18 0 0 7 7 4 0.7667 9 failure to engender trust with the stakeholders; 18 0 2 3 10 3 0.7667 9 failure to recognise adverse stakeholders 18 0 0 4 9 5 0.7556 10 taking over roles from one stakeholder & assigning them to another 18 0 6 4 6 2 0.7556 10 lack of open and ongoing communication process 18 0 1 5 10 2 0.7444 11 incomplete stakeholder identification 18 1 2 4 7 4 0.7222 12 lack of a person specifically assigned to handle sm 18 1 1 6 6 4 0.7222 12 late identification of stakeholders 18 1 1 5 9 2 0.7111 13 failure to assess levels of influence of various stakeholders 18 0 3 5 7 3 0.7111 13 failure to understand relationship between and among stakeholders 18 0 1 8 8 1 0.7000 14 lack of constant communication with stakeholders 18 0 0 10 8 0 0.6889 15 absence of formal sm process 18 0 3 6 7 2 0.6889 15 nature and size of a project; 18 1 3 6 4 4 0.6778 16 lack of periodic stakeholder meetings 18 0 3 9 5 1 0.6444 17 project location 18 4 3 2 6 3 0.6333 18 issuance of the same information to all stakeholders 18 2 5 4 3 4 0.6222 19 assignment of similar task to two stakeholders 18 1 4 5 5 3 0.6111 20 stakeholders' incapacity to participate in discussions 18 1 4 7 6 0 0.6000 21 cultural differences between stakeholders 18 3 4 4 5 2 0.5889 22 involvement of numerous stakeholders 18 3 3 5 6 1 0.5889 22 language barrier between stakeholders 18 4 3 5 5 1 0.5556 23 results of the study as contained in table 3 clearly indicated that pms have different perceptions on respective levels of impact of the various barriers to esm in mips’ delivery which resulted in different rii values and rankings for the barriers. it can also be clearly seen from the table that the rii values range between 0.5556 and 0.9444 while the barriers were ranked from first to twenty third positions. the table also clearly indicated that client's uncooperative attitude with an rii value of 0.9444 was ranked as the first barrier to esm in mips delivery in nigeria followed by failure to identify potential conflict areas with an rii value of 0.8778 and uncooperative attitude of stakeholders in the second and third positions respectively. language barrier between stakeholders with an rii value of 0.5556 was according to the table ranked as the twenty third and last barrier to esm in mips delivery. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 951 the result also showed that some barriers have the same rii values as a result of which they were ranked in the same positions. such barriers as shown on the included failure to identify key stakeholders, failure to understand stakeholders' needs and expectations and project manager's poor knowledge of sm with similar rii value of 0.8333 each of which was ranked as the fourth barrier. eighth and ninth positions were shown on the table to be occupied by three barriers while the tenth, thirteenth, fifteenth and twenty second positions were each shared by two barriers. 4.2 discussions findings from the study as presented in table 3 highlighted the pms perceptions on the level of impact of each barrier against esm in mips' delivery and implied that each of the barriers has different level of impact against esm in mips delivery. the rankings implied that esm cannot be achieved in the delivery of mips unless each barrier is given the attention it deserves based on its identified level of impact against esm in the projects' delivery. it further implied that successful delivery of an mip may not be achieved unless the barriers are adequately addressed because unexpected problems and uncertainty to a project can, according to karsen (2002), be caused by stakeholders, if stakeholder management is not adequately addressed in the project's delivery. the ranking of client's uncooperative attitude as the first barrier against esm in mips delivery by the study as shown in table 3 clearly underscored the importance of a client's attitude to ensuring esm and successful project delivery. a client, according to chinyio and omolaiye (2015), initiates a project, finances the project, determines its objectives and scope, specifies the functions the project's outcome should satisfy and largely determines its methods of implementation. the authors added that a client must be the starting point for understanding the priorities and interests of project stakeholders without which esm will not be possible. failure to identify potential conflict areas was, as shown in the table, ranked as the barrier with second highest level of threat to esm in mips delivery. the ranking, which represented the pms’ perceptions on the level of impact of the barrier, implied that the barrier may not allow stakeholders' managers to identify probable conflict areas in mip delivery, develop preventive measures and/or address the conflicts when they occur in order to achieve esm in mips delivery. stakeholder managers should therefore proactively identify all likely areas of conflicts and circumstances that may result in conflict between mip stakeholders and develop proactive measures to prevent the conflicts and/or addressing them when they eventually occur. the ranking of another barrier associated with failure to identify conflict areas, that is, conflicts between stakeholders as the sixth barrier was also shown in the table. this barrier has direct impact on esm and mip delivery because no meaningful achievement can be recorded in a conflict situation. conflict of authority between some role players of a large infrastructure project (lip) created serious management problem for the lip which contributed to the project's failure (zarewa et al., 2018).the likely impacts of these two barriers on esm have made authors such as jepsen and eskerod, (2009); yang et al. (2009) and chinyio and akintoye, (2008) to consider identifying and analysing possible conflicts and coalitions among stakeholders as well as effective resolution of conflicts among stakeholders as csfs for esm. the ranking of uncooperative attitude of stakeholders as the third barrier suggested that mips' stakeholders should strive to get the cooperation of all stakeholders associated with the delivery file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 952 of their project, if they wish to achieve esm and successful delivery of their projects. uncooperative attitude of some stakeholders can, according to chino and omolaiye (2015), make construction projects irrespective of their sizes to become embroiled in a process of controversy and conflict without warning. the ranking of failure to identify key stakeholders, failure to understand stakeholders' needs and expectations, and project manager's poor knowledge of sm in the same fourth position implied that respondents of the study perceived the three barriers to have the same level of impact in mips delivery. failure to identify key stakeholders will make esm difficult if not impossible because without identifying the stakeholders, the manager may not know their needs and expectations, power, perception, disposition towards the projects, constraints etc. and the approach to adopt in managing them. miller and oliver (2015) postulated that it is important to identify key stakeholders in order to understand how much power they have to either facilitate or hinder a project. the authors further argued that the identification will lead to their effective management and development of plans to ensure that they (key stakeholders) fulfill their functional position based on the project team’s identification of their position and influence in the stakeholder map. esm will also be difficult to achieve in a situation where a pm fails to understand stakeholders' needs and expectations because the manager's knowledge of what the stakeholders require and expect from the project will provide very useful information on how to manage them effectively. this can best be appreciated if the fact that stakeholders have different needs and expectations that may create clashes within the project is taken into consideration. it is therefore important for stakeholders to be managed according to their needs and expectations so that no stakeholders may feel left out. teye buertey et al. (2016) were of the views that project team must determine stakeholders' requirements and expectation and manage their influence in relation to their requirements in order to ensure esm and successful project delivery. project manager's poor knowledge of sm has direct relation with quality of sm in any project delivery because a project manager cannot effectively manage stakeholders without appropriate knowledge and skills. a study by eyiah-botwe1 et al. (2015) on the importance of a pm's appropriate knowledge to achieving esm identified pms’ poor knowledge as a major critical barrier factor to an effective sm. the authors further argued that a person cannot give what he/she does not have. failure to meet information requirements of all stakeholders ranked as the fifth barrier will make esm in mips delivery difficult to achieve because stakeholders cannot perform optimally without adequate, accurate and appropriate information. lack of appropriate, timely and correct information can make a project to become embroiled in a process of controversy and conflict without warning (chino and omolaiye 2015). another barrier closely related to the last one is issuance of incorrect information to stakeholders ranked as the eighth barrier against esm in mips delivery by the study. it will be extremely difficult to achieve esm in mips delivery on the basis of incorrect information because actions and/or decisions taken using such information may turn out to be wrong or fraught with mistakes. moreover, issuance of incorrect information may make stakeholders to suspect and/or mistrust any information issued to them and this will affect stakeholder management processes. stakeholders' perception of correctness or otherwise of information given to them has significant effect on sm. chinyio and omoloyaie (2015) argued that there is a serious prospect of failure in stakeholder management process if information given by those responsible for a project cannot be trusted by affected stakeholders. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 939-957. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 953 the ranking of lack of fairness and equity, for all stakeholder and inhumane attitude in relating with stakeholders as the eight barriers to esm in mips delivery did not come as a surprise because they are related. esm cannot be achieved if stakeholders are unfairly and inhumanly treated because these dual treatments can demoralise stakeholders and make them to work against achieving esm and successful project delivery. fairness and humane treatment of stakeholders can, on the other hand, motivate them to work at their best and contribute greatly towards esm and successful mip delivery. the two barriers can result in stakeholders' dissatisfaction, make the stakeholders unsupportive of a project and cause adverse relationship between stakeholders all of which will be inimical to esm and mips delivery. the importance of stakeholders' support, satisfaction, and healthy relationship between stakeholders to esm and successful project has been highlighted and emphasised by many authors. kelly (2015) argued that keeping stakeholders satisfied is vital for project success while charted body for the project profession (2014) discovered that investing effort in identifying and building stakeholder relationships can increase confidence across a project environment, minimise uncertainty, and enhance speed of problem solving and decision-making. three barriers, limited stakeholder engagement/involvement, misunderstanding of roles by stakeholders and failure to engender trust with the stakeholders were jointly ranked as the ninth barrier to esm in mips delivery. the ranking implied that the study respondents perceived them to have the same impact against esm in mips delivery. limited stakeholder engagement/involvement cannot ensure esm in mips delivery due to the fact limiting the stakeholder to engage with or involve in sm will not provide stakeholder managers with information to use in managing the excluded stakeholders' interests, needs, expectations, importance, power, influence, complaints, etc. full stakeholder engagement/involvement is regarded by many authors and researchers as a major success factor in construction projects. paul and ritchie (2012) opined that stakeholder engagement/involvement should be inclusive of all stakeholders that will affect or be affected by a project. teye buertey et al. (2016) argued that to ensure a successful project, the project team must identify and engage all stakeholders, determine their requirements and expectation and manage their influence in relation to their requirements. failure to engender trust with stakeholder will result in mistrust, suspicion and loss of confidence in project manager by stakeholders which will undoutbly impact sm in mips delivery. the level of trust stakeholder managers are able engender with their stakeholders will determine how the stakeholders will perceive the accuracy or otherwise of the information. chinyio and omoloyaie (2015) argued that a problem will arise once any given information is perceived to be inaccurate and any every effort to improve that information may face the risk of being met with suspicion by those stakeholders for whom the information is intended. failure to recognise adverse stakeholders and taking over roles from one stakeholder & assigning them to another shown to occupy tenth position in table 3 have the potential of hindering esm in mips. non recognition of adverse stakeholders will deprive stakeholders' managers the opportunity to assess their interests, power, influence, expectations and views on the project. cleland (1986) was of the views that failure to recognise or cooperate with adverse stakeholders may hinder esm and successful project outcome because some strong and vociferous adverse stakeholders can force their particular interest on a project manager at some time, perhaps at a time least convenient to the project. taking over roles from one stakeholder & assigning them to another has the potential of causing conflict between the affected file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zarewa: project managers' perceptions on barriers to effective stakeholder management (esm) in multifarious infrastructure projects (mips) delivery in nigeria. azojete, 15(4):939-957. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: galzarewa.qs@buk.edu.ng 954 stakeholders and hindering esm in mips delivery. an mip was discovered to experience serious conflict between in-house staff and consultants due to the taking over of the design and management of the mips' delivery from the in-house staff and assigning same to the consultants (abdu lawan, 2016). 5. conclusion this study investigated project managers' perception of barriers to effective stakeholder management in the delivery of multifarious infrastructure projects in nigeria. both the study and its timing were considered apt due to the recurring failure of the projects as a result of problems associated with sm. 34 barriers to esm in the projects' delivery in nigeria were identified, evaluated and ranked by the study. the findings indicated that barriers with different levels of impact inhibit esm in mips delivery and at times even lead to the projects' failure. the study recommends the development and effective implementation of stakeholder management strategy (sms) that will clearly spell out how to address both the barriers identified by this study and those yet to be identified. findings of the study will enable project managers and other stakeholders associated with the delivery of mips to understand barriers hindering esm in the projects delivery and develop strategies for overcoming the barriers. the study contributed to knowledge by increasing understanding of barriers to esm in mips delivery and their respective levels of impacts. it is however important to note that the study has some limitations that may affect generalisation of its findings. one of such limitations was the restriction of the study's respondents to project managers involved in the delivery of mips in north eastern and north western reasons of nigeria. findings of the study could, however, still be used to conduct another study to cover wider area using similar or different research method. references abdu lawan, gz. 2016. development of project 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the sekondi-takoradi metropolis of ghana. journal of building construction and planning research, 3: 117-126. http://dx.doi.org/10.4236/jbcpr.2015.33012 taylor, a. 2015. 5 steps to stakeholder engagement: strategic planning and management insights. https://www.smestrategy.net/blog/stakeholder-engagement-in-your-strategic-plan-pt112/11/2018. teye buertey, ji., amofa, d. and atsrim, f. 2016. stakeholder management on construction projects: a key indicator for project success. american journal of civil engineering, 4(4):117-126. watt, a. 2014. project management. http://open.bccampus.ca. www2.ensc.sfu.ca/~whitmore/courses/ensc305/.../project_management_watt.pdf 10/11/2018 yang, j., shen, gq., ho, m., drew, ds. and chan, ap. 2009. exploring critical success factors for stakeholder management in construction projects. journal of civil engineering and management, 15(4): 337-348. zarewa, ga., ibrahim, ad., ibrahim, ym. and adogbo, kj. 2018. governance impact assessment on large infrastructure project (lip) delivery. journal of engineering, project and production management, 8(1): 9-21 http://www.ucisa.ac.uk/publications/major_project_gov.aspx https://www.inxsoftware.com/.../tips-for-driving-effective-stakeholder-management https://www.smestrategy.net/blog/author/anthony-taylor http://www.sciencepublishinggroup.com/journal/index?journalid=229 http://www2.ensc.sfu.ca/%7ewhitmore/courses/ensc305/pdf%20files/project_management_watt.pdf file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):133-141 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 133 original research article evaluation of hy-8 modeling tool for hydraulic analysis of selected culverts along ilorin -jebba road, kwara state, nigeria a. g. adeogun1, m. a. akinpelu1, m. a. yusuf2 and r. a. animashaun2 (1department of civil engineering, kwara state university, p.m.b.1530, malete, kwara state, nigeria 2index engineering consults nigeria ltd, off pipeline road, ilorin, kwara state, nigeria *corresponding author: adeniyi.adeogun@kwasu.edu.ng article information submitted 29 march, 2018 revised 21 january, 2019 accepted 26 january, 2019 keywords: culvert crossing discharge hydraulic analysis hydrology roadway inlet control abstract in this study, selected culverts along ilorin – jebba road, kwara state were hydraulically analyzed using hy-8 modelling tool. hydrological analyses of the culverts were performed using rational method for the computation of design discharges. on site information such as tail water data such as channel type and bottom width, roadway data such as crest length and culvert data such as culvert material and span were collected from each of the culverts and were used in conjunction with estimated design discharge as input data for hy-8 modeling tool to facilitate the hydraulic analysis of the culverts. hydrological analysis showed that the highest design flow of 9.09 m3/s was obtained at culvert located at km 11+775 while the least design flow of 1.83 m3/s was obtained at culvert located at km 3+300. hydraulic analysis revealed that seven of the analyzed culverts have adequate capacity to convey the design flow while three culverts were found inadequate to convey the design flow and therefore, need to be resized. the outcome of this study will arouse the interest of engineers in the usage of the tool in sizing hydraulic culverts most especially in nigeria and other saharan african countries. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the provision for adequate drainage facilities is an integral part of roadway infrastructural design and cannot be overemphasized. the presence of excess water within the roadway adversely affects the engineering properties of the materials with which it was constructed. cut or fill failures, road surface erosion, and weakened subgrades followed by a mass failure are all products of inadequate or poorly designed roadway drainage system. culverts are typical drainage facilities used to convey water across urban and rural roadways. over the years, manual analysis of the hydrology and hydraulics of culverts have been in practice most especially in developing countries. this process is not only cumbersome and tedious, but also prone to error as the numbers of hydraulic culverts to be analyzed increase. several software programs such as hy-8 (fha,1996), thysys culvert (tsdh, 2007), culvert analysis program (cap) as documented by fulford, (1995), hec-ras (brunner, 2010), fishx-ing (bates, et al, 2003) and culvert master (bentley, 2003) have been developed to assist engineers in the design and analysis of culverts in a road project. while each of the developed programs for mailto:adeniyi.adeogun@kwasu.edu.ng http://www.azojete.com.ng adeogun, et al. evaluation of hy-8 modeling tool for hydraulic analysis of selected culverts along ilorin -jebba road, kwara state, nigeria. azojete, 15(1):133-141. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 134 culvert analysis has unique characteristics, they all provide automated solution to culvert analysis and design problem. out of all the available software packages for culvert analysis, hy-8 is the most widely used and distributed among users (rowley, 2016). one of the advantages of using hy-8 for culvert analysis is its ability to consider outlet-control situations and address issues relating to inlet control of culverts which significantly improves the output in terms of sizing of culverts. it is important to state that proper analysis of inlet control is critical when evaluating alternative material types such as corrugated metal, reinforced concrete, and smooth plastics. (peterson, 2019). therefore, this paper investigate the use and application of hy-8 tool for hydraulic analysis of selected culverts along ilorin jebba road in kwara state, nigeria 1.1 description of study area selected culverts for analysis are located along ilorin –jebba road in kwara state of nigeria (figure 1). the road is about 91.0 km long and takes off from ilorin on the ogbomoso-ilorin dualized road at about 1km from eyenkorin, ilorin. the host city is at latitude 4°30’05’s, longitude 8° 30’w and runs in a northern direction before terminating at jebba, km 90+906 at latitude 4° 40’n and longitude 9° 15’ 05”e. it has a varying width of 7.3m, 9m and 11m at different locations along the road alignment. the road is also characterised with washout shoulders on either side. the project road lies within the north central part of nigeria. the existing road is a two-lane single carriageway highway that links ilorin with jebba via ilorineast and moro local government area of kwara state. it is unarguably a vital route or link for transporters travelling to and from the federal capital territory and the north western and south eastern part of nigeria. the road consists of 74 culverts out of which 44 are box culverts while the remaining 30 are pipe culverts of different sizes. selected culverts are located between km 0+00 and km 15+00 and consist of 5 pipe and box culverts each making a total of 10 culverts in the study area. figure 2 shows pictorial view of some of the analyzed culverts located within the study area figure 1: map of nigeria showing the location of the study area http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):133-141. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 135 figure 2: some of the analyzed culverts located within the study area 2 materials and methods 2.1 selection and description of hy-8 software package hy-8 is a culvert hydraulic modeling tool developed by philip thompson and were provided to the federal highway administration (fhwa), usa for distribution in early 1980s. since the period the hydraulic model was developed, understanding of culvert hydraulics has increased significantly leading to development of more acceptable modeling techniques. various organization and government departments have adopted the usage of the model in designing and analyzing culverts along roadway. the package was selected for the study area because of its ease of use and efficiency as reported in some literatures (nwaogazie and agiho, 2019; fha, 2019) also, hy-8 tool has been recommended by the ministry of works and transport (nigeria) in volume iv, drainage design manual for culvert analysis which includes inlet control, outlet control and calculation of water profiles (fmw, 2013). some other deliverable of the software includes the estimation of tailwater downstream of the culvert based on the channel dimension and slope. the software also makes it possible to determine the flow regime and water surface profile in the culvert. 2.2 hydrological data and analysis hydrological data analysis of the drainage catchment was performed using the rational formula for the computation of design discharges for the cross culverts. the rational method (equation 1) has been widely used and formed the basis of most road drainage designs (raghunath, 2006). q = c∗i∗a 360 (1) where: q is the runoff (m3/s), c is the coefficient of runoff, i is the intensity of rainfall (mm/hr) and a is the area of water shed (km2). the rational method was applied to estimate the design discharge of each selected hydraulic culverts based on the assumptions as stated in the fmw (2013). also, the rainfall intensity (i) was estimated using the relationship developed by oyebande (1982) as written in equation 2. i = β+ y(1/ α) in mm/hr (2) where: i =rainfall intensity (mm/hr) , α and β are the scale and location parameters and are chosen from table 4.8 and 4.9 of the fmw (2013) for hydrological zone 2 where the study area belongs. y is a parameter obtained from relationship involving the return period or frequency of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeogun, et al. evaluation of hy-8 modeling tool for hydraulic analysis of selected culverts along ilorin -jebba road, kwara state, nigeria. azojete, 15(1):133-141. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 136 occurrence of rainfall in the zone as described in equation 3. coefficient used for each of the culvert locations was chosen based on the guidelines as stated in table 1 and 2 of highway design manual vol.vi. y = ln tr − 1 2tr − 1 24tr2 − 1 8tr3 (3) the catchment area of each of the analysed culverts was estimated using the digital elevation model (dem) of the study area and geographical information system (gis) tool in mapwindowgis software. the appropriate runoff coefficients for each culvert location were chosen from fmw (2013). the time of concentration, which is defined as the time required for runoff to travel by the longest available flow path to a particular location was estimated using the kerby’s formula as stated in equation 4. for the hydrological analysis of the culvert, a 50 year return period was adopted as recommended for lesser or minor culverts (table 4, federal ministry of work, drainage design manual, volume iv) tc = 0.604 rl/ s 0.467 (4) where: tc = time of concentration (hours), r = roughness coefficient, l = hydraulic length of catchment measured along flow path from the catchment boundary to the point of interest or where flow enters a defined watercourse, whichever is shorter (km) and s is the slope of the catchment (elevation difference divided by length of flow path) in m/m. 2.3 model input parameters the application of hy-8 tool for hydraulic analysis of culverts involved the collection of range of data which serve as input data before the running of model. these data defined the culvert barrels and the surrounding site condition at each of the analyzed crossing. a crossing is defined as the location where a channel crosses a road way, floodplain or another embankment. hy-8 allows for definition and modeling of up to six culverts at each crossing. data requirements include discharge data, tailwater data, roadway and culvert data. these data were collected using procedures as described nwaogazie and agiho (2019) and kang et al., (2009) using varieties of equipment such as gps garmin 600, total station, and measuring tape. the discharged data was obtained from the hydrological analysis of the watershed using the rational formula as described in fmw (2013). tailwater data which includes the channel type, slope and the channels invert elevation were all obtained on the field through observation and direct measurement. the tailwater data are used to define the water surface profile downstream of the channel crossing. information on the roadway data which include the crest length and crest elevation of the road and surface condition of the road (paved or gravel) were collected by measurement and direct observation at each of the culvert location. culvert data were acquired by measuring the span of the selected rectangular box culverts and diameter of the pipe culvert. also, the shape of the culverts were recorded and used as input file at the culvert data section. . 2.4 model run and analysis all the parameters necessary to define crossing and culvert information are done using the culvert data window (see figure 3). this is followed by the hydraulic analysis of the culvert including the balancing flow through multiple culverts and over the roadway. the analysis of the culverts involves the necessary hydraulic computation after which the overtopping table will be generated and displayed. at this stage, it is possible to view the water surface profiles as well as a customized table made up of any parameters computed during the analysis. in the case of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):133-141. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 137 overtopping of culverts after analysis, the culvert can be re-analyzed after increasing the size of the hydraulic culvert or by increasing the number of barrels until the design flow is fully accommodated. figure 3: typical culvert crossing data window in hy-8 modelling tool 3.0 results and discussion 3.1 validation of model results the results of the hydraulic analysis of selected culverts were checked against results obtained using manual calculations based on the inlet control principle for the sizing and checking the adequacy of the cross culverts. the outcome showed that the model results were adequate and in line with the manual calculation results. 3.2 hydrological analysis summary of the hydrological analysis of selected culverts are as presented in table 1. the table gives details of the chainages, existing culvert size, the estimated catchment area, computed design discharge (m3/s) on each of the analyzed culverts. from the table, it was found that the discharge of the culverts varied from the lowest value of 1.55 m3/s (culvert located at 10+375 km) to 9.09 m3/s for culvert located at km 11+775. also, the largest catchment area was obtained as 0.71 km2 for culvert located at km 11+775 km while the smallest catchment area was estimated as 0.12 km2 for culvert located at 13+375 km. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeogun, et al. evaluation of hy-8 modeling tool for hydraulic analysis of selected culverts along ilorin -jebba road, kwara state, nigeria. azojete, 15(1):133-141. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 138 table 1: summary of hydrological analysis of selected culverts using hy-8 modeling tool s/n chainages existing culvert size (m) culvert type catchment area (km2) intensity (mm/hr) design flow (m3/s) 1 1+400 2(0.9 ) pipe (double cell) 0.27 163.8 2.97 2 2+825 1.5x1.5 box (single cell) 0.28 188.77 3.11 3 3+300 2(0.9) pipe (double cell) 0.24 148.75 1.80 4 5+475 2(3.0x3.0) box (double cell) 0.32 158.16 3.40 5 7+500 3.0x3.0 box ( single cell) 0.30 158.16 2.39 6 9+125 0.9 pipe (single cell) 0.48 148.75 3.60 7 10+375 2(2.5x2.5) box (double cell) 0.36 153.62 1.55 8 11+775 2(2.5x2.5) box (double cell) 0.71 142.86 9.09 9 12+875 0.9 pipe (single cell) 0.18 188-78 4.44 10 13+375 0.9 pipe (single cell) 0.12 142.86 2.78 3.3 hydraulics analysis 3.3.1 hydraulic status of culverts the results of the hydraulics analysis of the culverts are as presented in table 2. the table contains details such as the sizes of existing and proposed culverts with their locations. also, the status column in the table provides information on adequacy or inadequacy of the analysed culvert to convey the design flow. those culverts found to be inadequate were further reanalysed by increasing the size of the existing culvert to accommodate the design flow. overall, three culverts were found to be inadequate as against seven culverts that have adequate capacity to accommodate the design flow. table 2: summary of hydraulics analysis of selected culverts using hy-8 modeling tool s/n location (chainage) (km) existing culvert size (m) status type of proposed culvert (m) 1 1+400 2(0.9) adequate 2(0.9) 2 2+825 1.5x1.5 adequate 1.5x1.5 3 3+300 2(0.9) adequate 2(0.9) 4 5+475 2(3.0x3.0) adequate 2(3.0x3.0) 5 7+500 3.0x3.0 adequate 3.0x3.0 6 9+125 0.9 not adequate 2(0.9) 7 10+375 2(2.5x2.5) adequate 2(2.5x2.5) 8 11+775 2(2.5x2.5) adequate 2(2.5x2.5) 9 12+875 0.9 not adequate 1.5x1.5 10 13+375 0.9 not adequate 2(0.9) 3.3.2 water surface profile of analyzed culverts hy-8 tool was used to plot the water profile using the direct step method in each direction and the sequent depth associated with each of the steps. if the sequent depth associated with the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):133-141. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 139 forward profile matches the depth along the backward profile through the culvert, a hydraulic jump occurs and the length of the jump is calculated from that location. once a profile is selected, the user may then plot and view the profile. figures 4-8 displayed the water surface profiles of the selected culverts. 323.0 323.5 324.0 324.5 325.0 325.5 326.0 326.5 90 100 110 120 130 140 crossing crossing 1, design discharge 2.97 cms culvert culvert 1, culvert discharge 2.97 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed 312.5 313.0 313.5 314.0 314.5 315.0 315.5 316.0 316.5 100 110 120 130 crossing crossing 2, design discharge 3.11 cms culvert culvert 1, culvert discharge 3.11 cms el ev at io n (m ) station (m) critical normal profile tailwater headwater streambed (a) (b) figure 4: water surface profile generated for culverts located at (a) km1+400 and (b) km 2+825 318.0 318.5 319.0 319.5 320.0 320.5 321.0 100 110 120 130 crossing crossing 3, design discharge 1.80 cms culvert culvert 1, culvert discharge 1.80 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed 302 303 304 305 306 307 100 110 120 130 crossing crossing 4, design discharge 3.40 cms culvert culvert 1, culvert discharge 3.40 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed hydraulic jump (c) (d) figure 5: water surface profile generated for culverts located at (c) km3+300 and (d) km 5+575 308.5 309.0 309.5 310.0 310.5 311.0 311.5 312.0 312.5 100 105 110 crossing crossing 5, design discharge 2.39 cms culvert culvert 1, culvert discharge 2.39 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed 315.0 315.5 316.0 316.5 317.0 317.5 318.0 318.5 319.0 90 100 110 120 130 140 150 crossing crossing 6, design discharge 3.60 cms culvert culvert 1, culvert discharge 3.60 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed (e) (f) figure 6: water surface profile generated for culverts located at (e) km 7+500 and (f) km 9+125 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeogun, et al. evaluation of hy-8 modeling tool for hydraulic analysis of selected culverts along ilorin -jebba road, kwara state, nigeria. azojete, 15(1):133-141. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 140 291.0 291.5 292.0 292.5 293.0 293.5 294.0 294.5 295.0 95 100 105 110 115 120 125 crossing crossing 7, design discharge 1.55 cms culvert culvert 1, culvert discharge 1.55 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed 301 302 303 304 305 306 90 100 110 120 130 140 crossing crossing 8, design discharge 9.09 cms culvert culvert 1, culvert discharge 9.09 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed (g) (h) figure 7: water surface profile for culverts located at (g) km10+375 and (h) km 11+775 316.5 317.0 317.5 318.0 318.5 319.0 319.5 100 110 120 130 crossing crossing 9, design discharge 4.44 cms culvert culvert 1, culvert discharge 4.44 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed 321.5 322.0 322.5 323.0 323.5 324.0 100 110 120 130 crossing crossing 10, design discharge 2.78 cms culvert culvert 1, culvert discharge 2.78 cms e le va tio n (m ) station (m) critical normal profile tailwater headwater streambed (i) (j) figure 8: water surface profile for culverts located at (i) km12+875 and (j) km 13+375 4.0 conclusion in this study, hydraulic analyses of selected culverts were carried out using hy-8 tool. prior to the analysis, appropriate design flows for each culvert was evaluated using rational method while other site data necessary for the modeling of the culverts were collected in-situ on site. based on the outcome of this study, the following can be concluded: the design flow of the selected culvert varied from the minimum values of 0.77m3/s for culvert located at to a maximum value of 1.55m3/s for culvert located at km three pipe culverts each of diameter 900mm were found to be inadequate to convey the estimated design flow. this is evident on their surface water profiles with a head water elevation which is above the roadway elevation. to prevent overtopping the road way, larger sizes have been recommended for the pipe culverts and redesigned. this study has confirmed the efficacy of hy-8 tool in its ability to size and resize culverts during the hydraulic design of road infrastructures and can also be used to address issues relating to inlets control of culverts. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):133-141. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 141 references bates, kb, barnard, k. heiner, b. klavas, jp. and powers. p. 2003. design of road culverts for fish passage. wash. dept. fish & wildlife, hab. and lands program env. eng division. brunner, gw. 2010. hec-ras, river analysis system hydraulic reference manual, u.s.army corps of engineer, hydrologic engineering centre (hec), davis, ca 95616-4687 bentley systems, 2003. – assessed on 02/12/2017, available at http://www.bentley.com/enus/products/culvertmaster/ fha 2018 (federal highway administration) culvert hydraulics, assessed on 23/04/2019, available at https://www.fhwa.dot.gov/engineering/hydraulics/software/hy8/index.cfm fha 1996 (federal highway administration) hy8 version 6.1 documentation background, assessed on 15/10/2018, available at: https://www.fhwa.dot.gov/engineering/hydraulics/software/hy8/ fulford, jm. 1995. user's guide to the culvert analysis program: u.s. geological survey openfile report 95-137, u.s. geological survey, reston, va 20192 fmw. 2013. federal ministry of works highway manual part 1: design volume iv: drainage design kang, ms., koo, jh., chun, ja., her, yg., park sw. and yoo, k. 2009. design of drainage culverts considering critical storm duration, biosystems engineering, issue (04) pp 425-434 nwaogazie, il. and agiho, gc. 2019. performance analysis of box and circular culverts using hy 8 software for aluu clan, port harcourt nigerian journal of technology (nijotech) vol. 38, no. 1, pp. 22 – 32 oyebande, l. 1982. deriving rainfall intensity-duration-frequency relationships and estimates for regions with inadequate data, hydrological sciences journal, vol.27 issue 3, pp353-367, doi: 10.1080/02626668209491115 : https://doi.org/10.1080/02626668209491115 peterson, m. 2019. culvert analysis using fhwa hy 8 software, american society of civil engineers (asce) course materials, available at https://www.asce.org/templates/conferencesevents-event-detail.aspx?id=9002 accessed on 30/04/2019 raghunath, hm. 2006. hydrology: principle, analysis and design, revised second edition, new age international publisher, new delhi, india rowley, bj. 2006. numerical modelling of culvert hydraulics: modernization of existing hy-8 software, m.sc thesis, department of civil and environmental engineering, college of engineering and technology, brigham young university, provo, utah pp 35-50 tsdh. 2017. us-manual for texas hydraulic systems (thysys) texas state department of highway and public transportation, available at accessed on 02/05/2019 https://library.ctr.utexas.edu/digitized/texasarchive/phase3/tx_ms1920_1977.pdf http://www.bentley.com/en-us/products/culvertmaster/ http://www.bentley.com/en-us/products/culvertmaster/ https://www.fhwa.dot.gov/engineering/hydraulics/software/hy8/index.cfm https://www.fhwa.dot.gov/engineering/hydraulics/software/hy8/ https://doi.org/10.1080/02626668209491115 https://www.asce.org/templates/conferences-events-event-detail.aspx?id=9002 https://www.asce.org/templates/conferences-events-event-detail.aspx?id=9002 https://library.ctr.utexas.edu/digitized/texasarchive/phase3/tx_ms1920_1977.pdf file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):226-236 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 226 original research article assessment of information technology adoption in project information exchange in nigerian construction industry y. u. datti1*, a. dahiru1 and o. olamilokun2 (1department of quantity surveying, faculty of earth and environmental sciences, bayero university kano, nigeria 2department of quantity surveying, faculty of environmental science, kaduna state university kaduna, nigeria) *corresponding author’s e-mail address: yudatti.qs@buk.edu.ng article information submitted 13 june, 2018 revised 25 january, 2019 accepted 13 june, 2019 keywords: construction project information exchange information technology information acquisition information dissemination. abstract information technology (it) has been applied by various industries with significant improvement in the practice and strategic standing of the industries. its successful application is evident in manufacturing, petroleum, banking, aerospace and military industries. however, despite this evidential benefit as a result of it adoption, delayed receipt of project information and/or loss of the project data/information are still prevalent in the nigerian construction industry. to reduce these inefficiencies in the data management of the industry, this study investigates the medium of project information exchange and examine the order of it adoption in the nigerian construction industry. a quantitative approach using questionnaire survey was employed. structured questionnaires were distributed among quantity surveyors in contracting, consulting and public sector. the resultant data was analyzed using descriptive statistical tool. the results revealed the dominance of the paper-based medium over the use of it tools in information acquisition and dissemination in the construction industry. about three-quarter of drawings, specifications and schedules were acquired through printed copy (paper based), and only about one-tenth of these information were acquired through email and disk/flash. while about four-fifth of the bills of quantities, claims and final account documents/information were being disseminated through the traditional paper-based printed copy, and less than one-tenth of these information are being disseminated through email and disk/flash. the order of it adoption and use in information acquisition in the nigerian construction industry was found to be paper based medium, then followed by online medium, email and others (mobile) came third and fourth respectively, while disk/flash and came fifth and sixth in ranking. furthermore, in contrast to the order of it adoption and use in information acquisition in the nigerian construction industry, paperbased and disk/flash medium came first and second in order of information dissemination. emails and online medium came 3rd and 4th in place, while fax and others (such as mobile phone), came 5th and 6th in adoption and use. thus, for construction professionals in developing countries to reap the benefit of it, it must go beyond the use of paper based medium to the use of it tools for the acquisition and dissemination of information in the industry. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. mailto:yudatti.qs@buk.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):226-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 227 1.0 introduction the world is undergoing profound and rapid changes due to the development of information super highway. the digital revolution in information and communication technologies (ict) has created a platform for a free flow of information, ideas and knowledge across the globe (shafique and mahmood, 2008). this development has provided the potential for bringing significant changes in the use of data, and information in the construction industry (datti, 2017). the main project participants in a typical construction project in nigeria are the client, his team of professional advisers (consultants), the main contractor, subcontractors and suppliers. the team of consultants is traditionally made up of architects, engineers and quantity surveyors. the consultants produce the documents/information (drawings, bills of quantities, specifications, equipment schedule) which at some point will be required by all the project participants during the project lifetime. project information exchange between the various project stakeholders has traditionally been based mainly on such paper documents as architectural and engineering drawings, specifications, bills of quantities and material schedules (luiten et al., 1998). duyshart (1997) noted much of this to involve duplication, continual translation and transcription from one medium or form to another, as well as the loss of information. thus the practice is far from being satisfactory, as about two thirds of construction problems are blamed on inadequate communication and exchange of information and data (cornick, 1990). the use of ict not only minimizes such problems but also helps to improve the process (oladapo, 2007; ferry et al., 1999). this explains the current paradigm shift being experienced in the construction industry from traditional paper-based to digitally based information exchange, which other industries such as aircraft manufacturing and banking have adopted and benefited from long ago (rivard et al., 2004). as more and more computers are connected through the internet to form the worldwide web, thus allowing firms located on different streets or in different cities, provinces, countries, or even continents to readily exchange information, the reach and benefits of ict to industries and organizations have indeed become global. smith (2003) asserted that the preparation of bills of quantities in the traditional paper based mode is tedious and time consuming and typically accounts for approximately 80% of the total time spent in preparing tenders, budgeting estimates and cost plans. removing much of the drudgery, albeit the traditional ‘bread and butter’, of the profession will provide practitioners with more time to focus on developing sophisticated cost management systems and a wider range of value added services (smith, 2003). microelectronics coupled with computing and telecommunications is revolutionizing the handling and storing of information. microelectronics has made it possible to store, retrieve, rearrange and disseminate large amounts of information almost instantly. a combination of computing and telecommunication has made it possible to communicate over great distances and with a large number of people (fryer, 1990). for instance a drawing can be revised on a computer in lagos and accurately reproduced on paper in kano, only second later. as information flows increasingly become electronic quantity surveying computing facilities, software and data bases will need to develop in a compatible manner. it is inevitable that documentation and data will be increasingly automated to the point where measurement and other technical processes will require minimal human intervention (smith, 2003). even where contract information is not presented to the contractor in electronic format, computer software has now made it possible to use scanning devices to allow the rapid transfer file:///c:/users/user/downloads/azojete143/www.azojete.com.ng datti, et al: assessment of information technology adoption in project information exchange in nigerian construction industry. azojete, 15(2):226-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 228 of information from bills of quantities, without the need for rekeying of information avoiding the tedium and possible errors in transformation that might occur (ashworth, 2002). the entire cost database systems of estimation are now stored on computer, so that outputs and current prices can easily and routinely be updated and then applied to the individual items in the bills of quantities allowing the estimator more time for analysis and evaluation of the project (ashworth, 2002). the widespread everyday use of plain paper facsimiles modems and e-mail has resulted in instantaneous’ communication that has never previously been possible or expected. it could be argued that this has resulted in compression of time scales and deadlines that are not necessarily always to the advantage of those charged with providing professional advice. at a basic level, the widespread use of common computer software, such as spreadsheets, has relieved much of the laborious and mundane nature of data manipulation in everyday situations, for example, the preparation and presentation of valuations (ferry, 1999). additionally, rivard et al. (2004) carried out studies on the use of it in the canadian construction industry and reported that many of them were at the cutting edge in their use of it for construction operation and processes. however, despite this evidential benefit as a result of it adoption, delayed receipt of project information and/or loss of the project data/information are still prevalent in the nigerian construction industry. for example, anigbogu and anunike (2014) and bamisile (2004) asserted that details of working drawings and many important specifications are frequently omitted, anigbogu and anunike (2014) revealed alarming rate of inconsistencies between contract drawings, bill of quantities and contract drawings and significant increase in incomplete information for construction purposes that reach an alarming rate of 73% in some instances. while ogunbayo (2013) showed that communication breakdown was the number one cause of conflict in the nigerian construction industry and suggested that the best tactics in reducing conflict is to improve communication channels. kululanga et al., (2001) identified four sources of conflict in construction which are errors, defects and omissions in contract documents, underestimating the real cost of the project in the beginning. however, it is against these negative practices that the study investigates the mechanism of project information exchange and examines the order of it adoption in the nigerian construction industry with a view to reducing inefficiencies in data management in the industry. 2.0 materials and methods this paper investigated the mechanism of project information and examine the order of it adoption in the nigerian construction industry. two methods seem adequate for this purpose: survey research and observation research. the survey research method was chosen for this study, been a much economical and convenient method of collecting data. it tends to be less time demanding upon its subsequent administration and provided more untied up time for use in other aspect of the research endeavours (kolo, 2005). the target population for the survey research was quantity surveyors in contracting, consulting and public sector organization. information about the respondents’ qualifications and experiences were generated and analyzed graphically. more importantly, data on the mode of acquisition of information and dissemination by the respondents were generated from the questionnaire. collecting information from the whole of the population would undoubtedly result in a true representation of the population but an attempt at such is prohibitively expensive and practically impossible within the confines of resource constraints. hence, the need to select appropriate sampling technique. de vaus (1991) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):226-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 229 identified two types of sampling method for a survey research: probability and non-probability samples. he advised that the probability samples are preferred "because they are more likely to produce representative samples and enable estimates of the sample's accuracy". hence, the choice of the probability sample type for the purpose of this study. 2.1 survey techniques/methods basically, data can be collected by observation, in-depth interview, content analysis, and/or through questionnaire amongst other known techniques. the questionnaire technique was found to be very suitable for the needs of this survey for been quick, allowing wide geographic coverage and allowing ample time for the respondents to check fact and give accurate answers (fellows and liu, 2008). additionally, denscombe (2010) asserted questionnaires to be economical, in the sense that they can supply a considerable amount of research data for a relatively low cost in terms of materials, money and time and relatively easy to arrange. of the three methods of administration identified by (de vaus 1991) viz: face-to-face, telephone and mail, the face-to-face method was adopted. this is due to the fact that the method allows quick dispatch, assurance of delivery and efficient response rate in terms of general and specialized samples. a total of 190 sets of questionnaires were distributed amongst various quantity surveying consulting firms in a random manner. an appreciable 70% were returned duly filled. these dully filled and returned sets were carefully sorted, presented and analysed using descriptive statistical tool. 3.0 results and discussion upon sorting and collating the questionnaires, they were studied to bring out likely patterns of the responses gathered. an appropriate tool for presenting such patterns is the chart. for the purpose of this research, two types of charts were used – the bar charts and the pie charts. presented below are the percentage distributions of the patterns of responses gathered during the field survey. 3.1 information about the respondents figure 1 above shows the level of educational attainment of the respondents. it indicates that majority of the respondents (38.10%) were ‘pgd holders’ while 28.70% of them had a first degree. added to their educational attainment, 38% of the respondents are ‘associate members’ of their respective professional bodies, with 19% of them being ‘fellows’ as shown on figure 2. thus, the aforementioned revelations suggest that the responses gathered were from a sample of qualified and experienced personal as further depicted in figure 3 which further affirm to the reliability of the data source and its confidence level. this implies that the results presented in the figure are reliable for the study considering the respondents’ qualifications and experiences obtained in the construction industry. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng datti, et al: assessment of information technology adoption in project information exchange in nigerian construction industry. azojete, 15(2):226-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 230 figure 1: respondents’ academic qualification figure 2: respondents professional attainment as much as 43% of the respondents did acquire over ‘16’ years of working experience with about 33% of them having between ‘5 to 10’ years as indicated in figure 3. in furtherance 5% of the respondents have experiences ranging between ‘11 to 15’ years, while only 19% of the respondents have less than 5years of experience. this indicates that responses were gathered from qualified and experienced personnel which further attest to the reliability of the result. figure 3: respondents working experience http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):226-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 231 figure 4 shows the respondents’ profiles by job environment. majority of the respondents worked in consulting organization. almost one-third of the respondents work in contracting organization job environment and about one-third work in public bodies (government, ministries, agencies and parastatals). thus, the aforementioned revelations suggest that the responses gathered were from a fairly balance sample of personnel across the job environment with the unique characteristics of each section fairly captured and true representation of the population reflected in the result. this is in line with the objectivity of the study as the opinions of the respondents across the various job environments have been captured and reflected in the result. figure 4: respondents current career/job environment figure 5 display means of acquiring information by the respondents. majority of the respondents acquired information through traditional paper-based (printed copy). about three-quarter of the drawings, specifications and schedules documents/information are being acquired through printed copy (paper based). while only about one-tenth of these information are acquired through email and disk/flash. the least acquired information through the traditional paper based copy are building cost indices, government regulations and tender price indices, with only onethird of these information being acquired through the printed copy form. this supports the findings of (oladapo, (2007 and oyediran and odusami, 2005) of the dominance of paper-based medium in project information exchange in nigeria. however, the reduction in paper-based operation in quantity surveying offices as reported by (rivard, 2004) has not been observed. it is interesting to notes that about half of the respondents that were asked about government regulations, building cost indices and tender prices do not respond to these questions. this lowresponse is partly due to non-availability of building cost and tender price indices information in the public domain of the nigerian construction industry, and also for the fact that government regulations on the industry is been carried out weakly with less information been provided, hence, the higher non-response rate by the respondents. this support the findings of (anigbogu and anunike, 2014) that regulatory framework is weak and that there are few existing national standards relating to building construction, many of which are not known (bamisile, 2004 and anny et al., 2015). though there were attempts by the nigerian institute of quantity surveyors to generate the databases for these indices, but till now, this has not come to fruition. acquisition of information through online medium by the respondents also put a strong show by coming second after the traditional paper-based medium as illustrated in figure 5. the top three data file:///c:/users/user/downloads/azojete143/www.azojete.com.ng datti, et al: assessment of information technology adoption in project information exchange in nigerian construction industry. azojete, 15(2):226-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 232 that are acquired through online medium are professional publications, 25%; standard/guides, 20% and manufacturer’s catalogue, 19%. as compared to drawings, specification and schedules which can be referred to as component part of the contract documents, there has been some significant growth of online medium for project information exchange for non-contract related information. for instance, the online medium adoption increased from one-tenth for acquiring drawings and other contract related documents to one-fifth for standard/guides and manufacturer’s catalogue and to a maximum adoption of one-quarter for professional publications. this might be due to the rising contention of the legality of contracts online or by email which makes legal responsibilities in an environment that the contract is not paper-based unclear (o’brien, 2000). despite wide availability and penetration of internet and email in the industry as reported by (datti, 2017; oyediran and odusami, 2005; deng, et al. 2001, rivard, 2000), their adoption in project exchange seems to be quite low. additionally, the significant increase in usage of online medium for non-contract related information such as professional publications, standard/guides and manufacturer’s catalogue might be due to the recognition of the potential improvements to be gained through the adoption of it tools in project information exchange as predicted by many among whom is oyediran and odusami (2005). buttressing the above point for non-contract related information, while email is not as prevalent as online medium, but its adoption is increasing from one document to another as illustrated in the figure 5. figure 5: mode of acquisition of information http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):226-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 233 additionally, disk/flash and fax comes 5th and 6th respectively in order of hierarchy of adoption for information acquisition by the respondents. thus, the above result illustrates the dominance of traditional means of information acquisition over the use of it tools and it also demonstrates the order of preference of each medium over the other in information acquisition in nigerian construction industry. this peculiar trend is depicted graphically in figure 6 in order of preference and adoption. figure 6: it ladder and trend in information acquisition in the nigerian construction industry 3.2 mode of dissemination of information the distribution of responses with respect to the mode of dissemination of information by qss is shown in figure 7. majority of the respondents disseminates information through printed copy (paper based). about four-fifth of the bills of quantities, claims and final account documents/information were being disseminated through the traditional paper-based printed copy. while less than one-tenth of these information are being disseminated through email and disk/flash. this might be due to the complicated nature of information exchange in the industry where amendment of drawings and bills are common which requires to be in hardcopy with signature affixed to it and acknowledgement of the receipt by the parties is expected to be in writing. hence, sending messages the in an electronic form cannot complete these endorsement procedures. the least disseminated information through the traditional paper based copy are feasibility reports and financial statements, with about half of these information being disseminated through the printed copy form. despite being the least information been disseminated through paper-based medium, more than half of these documents are being disseminated over the paper-based medium. this equally shows the dominance of traditional paper-based medium over the use of it tools, which support the findings of (oladapo, 2007). additionally, the dominance of paper-based medium in information dissemination seems to be slightly higher than dominance of paper-based medium in acquiring information. furthermore, in contrast to the response by the respondents on the second most preferred medium for information acquisition after the paper-based medium, the second most preferred medium for information dissemination is disk/flash. emails and online medium come 3rd and 4th in place in terms of usage in information dissemination. while, fax and others (such as mobile) comes 5th and 6th in preference as shown in figure 7. this go against the findings of oladapo (2007) and oyediran and odusami (2005) that reported widespread use of basic it tools for accounting, word processing, spreadsheets and e-mail. thus, the order of preference by the respondents for information dissemination in descending order can be graphically illustrated as follows: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng datti, et al: assessment of information technology adoption in project information exchange in nigerian construction industry. azojete, 15(2):226-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 234 figure 7: mode of information dissemination by the respondents figure 8 display the it ladder and trend in information dissemination in the nigerian construction industry. this can be seen in their preference for open, sophisticated and easily verifiable it tools after paper based medium in acquiring than in disseminating information. for instance, in acquiring information, online medium comes in higher preference order than emails, and email comes in higher preference order than others (mobiles) and it continues down to fax, which is in the lowest preference order. this might be due to the benefit that online and email medium provides effective information transfer (deng et al., 2001), so messages can not only reach the recipients more speedily and accurately, but also can be traceable on the event of dispute than flash and mobiles in the long run. however, in disseminating information the respondents show higher preference in the use of disk/flash which is less verifiable in the event of dispute, than email and online medium. additionally, the risk of data loss due to virus and other problems is high in disk/flash than with other mediums. figure 8: it ladder and trend in information dissemination in the nigerian construction industry 4.0 conclusion the study investigated the medium of project information exchange and examined the order of it adoptions in the nigerian construction industry. the results revealed the dominance of the paper-based medium over the use of it tools in information acquisition and dissemination in the construction sector. about three-quarter of drawings, specifications and schedules were printed copy onlineemail othersdisk/flash fax http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):226-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 235 acquired through printed copy (paper based), and only about one-tenth of these information were acquired through email and disk/flash. while about four-fifth of the bills of quantities, claims and final account documents/information were being disseminated through the traditional paper-based printed copy, and less than one-tenth of these information are being disseminated through email and disk/flash. the order of it adoption and use in information acquisition in the nigerian construction industry is paper based medium, then followed by online medium, email and others (mobile) came third and fourth respectively, while disk/flash and came fifth and sixth in ranking. furthermore, in contrast to the order of it adoption and use in information acquisition in the industry, paper-based and disk/flash medium come first and second in order of information dissemination. emails and online medium came 3rd and 4th in place in order of adoption in information dissemination. while fax and others (such as mobile phone), come 5th and 6th in adoption and use. finally, findings indicate that respondents in information acquisition show more diligence and sophistication in the use of the it tools. this can be seen in their preference for open, traceable and easily verifiable it tools in acquiring than in disseminating information. thus for construction professionals in developing countries to reap the benefit of it, it must go beyond the use of paper based medium to the use of it tools for the acquisition and dissemination of information in the industry. references anigbogu, na. and anunike, eb. 2014. standard of materials specifications, their implementation and enforcement on building construction projects in nigeria. atbu journal of environmental technology, (7)1: 33-44. anny, an., anthony, ci. and kehinde, om. 2015. critical issues in reforming the nigerian construction industry. british journal of applied science and technology, 5(3): 321-332. ashworth, a. 2002. precontract studies development economics, tendering and estimating. 2nd edition. blackwell publishing company ltd, oxford. bamisile, a. 2004 building production management. foresight press limited, lagos. cornick, t. 1990. quality management for building design. butterworth architecture management guides, london. datti, yu. 2017. appraisal of information technology requirements in quantity surveying firms in northern nigeria. arid zone journal of engineering, technology and environment (azojete), 13(3): 336-346. deng, zm., li, h., tam, cm., shen, qp., and love, ped. (2001) an application of the internetbased project management system. automation in construction, 10: 239–246. denscombe, m. 2010. the good research guide for small-scale social research projects, fourth edi. ed. mcgraw-hill education, new york, usa. de vaus, da. 1991. surveys in social research. 3rd edition. ucl press limited, london. duyshart, bh. 1997. the digital document. butterworth-heinemann, oxford. fellows, r. and liu, a. 2008. research methods for construction. 3rd edition. wiley, chichester. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng datti, et al: assessment of information technology adoption in project information exchange in nigerian construction industry. azojete, 15(2):226-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yudatti.qs@buk.edu.ng 236 ferry, dj., brandon, ps. and ferry jd. 1999. cost planning of buildings. 7th edition. blackwell publishing company, oxford. fryer, b. 1990. the practice of 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construction, 12: 20-33. oladapo, aa. 2006. impact of ict on professional practice in the nigerian construction industry. electronic journal on information systems in developing countries, 24: 1-19. oyediran, os. and odusami, kt. 2005. a study of computer usage by nigerian quantity surveyors. journal of information technology in construction, 10: 291-303. rivard, h. 2000. a survey on the impact of information technology in the canadian architecture, engineering and construction industry. journal of information technology in construction, 5: 3756. rivard, h., froese, t., waugh, lm., el-diraby, t., mora, r., torres, h., gill, sm. and o'reilly t. 2004. case studies on the use of information technology in the canadian construction industry. journal of information technology in construction, 9: 19-34. shafique, f. and mahmood, k. 2003. indicators of the emergency information society in pakistan. journal of information development, 24(1), 66-76. smith, p. 2003. trend in the australian quantity surveying 1995-2003. the australian journal of construction economics and building, 1(1): 1-15. http://www.azojete.com.ng original research article assessment of information technology adoption in p y. u. datti1*, a. dahiru1 and o. olamilokun2 arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 611-618 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 611 original research article impact of different fine aggregates on the compressive strength of hollow sandcrete blocks s. o. odeyemi1*, r. abdulwahab1, m. a. anifowose2 and r. j. ibrahim1 (1department of civil engineering, kwara state university, malete, nigeria. 2department of civil engineering, federal polytechnic, offa, nigeria.) * corresponding author’s email address: samson.odeyemi@kwasu.edu.ng article information submitted 13 september, 2018 revised 3 march, 2019 accepted 10 march, 2019 keywords: fine aggregates sandcrete block water absorption compressive strength abstract sandcrete blocks are walling materials that are made of fine aggregates and cement. though, sandcrete blocks are being used as building materials in many parts of nigeria, it has been discovered that many of the blocks produced do not conform to the minimum compressive strength requirement for such blocks. this study, therefore, examined the effect of using four (4) different fine aggregates (quarry dust, river sand, shocking sand and plastering sand) with binder to aggregate mix ratios of 1:6 and 1:4 on the compressive strength of sandcrete blocks. specific gravity and particle size distribution analyses were conducted on the fine aggregates to determine their properties while water absorption capacity and compressive strength tests were carried out on the hollow sandcrete blocks. five samples from each aggregate of size 450 mm x 225 mm x 225 mm were moulded and subjected to compressive strength tests. the water absorption capacity results revealed that shocking sand has the highest capacity to absorb water with a value of 8.69 %. river sand, with a value of 6.67 % has the lowest water absorption capacity. the 28th day compressive strength test results of 1.31 n/mm2, 1.10 n/mm2, 0.78 n/mm2 and 0.50 n/mm2 for the sandcrete blocks produced from quarry dust, river sand, shocking sand and plastering sand respectively, with mix ratio 1:6, did not meet the minimum requirement of 2.5 n/mm2 specified by nis 87:2007 for non-load bearing walls. however, with mix ratio of 1:4, the compressive strength of 2.52 n/mm2 and 2.50 n/mm2 for sandcrete blocks made with quarry dust and river sand respectively met this minimum requirement. it was concluded that only quarry dust and sharp sand at mix ratio 1:4 are suitable in the production of sandcrete blocks. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction sandcrete blocks are composite walling materials moulded into different shapes and sizes that are composed of fine aggregate in addition with cement and water (nis 87:2004, 2004). ewa and ukpata (2013) and oyekan and kamiyo (2011) described sandcrete hollow blocks as the most common masonry units in nigeria. nigeria industrial standard (nis 87:2000, 2000) reported that sandcrete blocks are formed either in solid or hollow rectangular shape. they are commonly found in 450 mm by 225 mm by 225 mm size for load bearing walls and 450 mm by 150 mm by 225 mm size for non-load bearing walls. material constituents, mix proportion, admixtures mailto:samson.odeyemi@kwasu.edu.ng http://www.azojete.com.ng odeyemi, et al: impact of different fine aggregates on the compressive strength of hollow sandcrete blocks. azojete, 15(3):611-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 612 presence, method of compaction and age of curing are significant factors that determine the mechanical properties of sandcrete blocks (oyetola and abdullahi, 2006; anosike and oyebade, 2012). the high cost of materials used in the production of sandcrete blocks has contributed to an increase in the cost of building construction. nair et al. (2006) posit that conventional building materials are beyond the reach of most of the world populace due to their poor affordability. however, the need for alternative materials for construction is very desirable for socio-economic development and materials that can complement cement at a cheaper rate will be of interest. though, sandcrete blocks are being used as building materials in many parts of nigeria, it has been shown (odeyemi et al., 2018) that many of the blocks produced do not conform with the minimum standard requirement for compressive strength value of 2.5 n/mm2 and 3.45 n/mm2 for non-load resisting wall and load resisting walls respectively as well as maximum specified 12 % water absorption recommended by nigeria industrial standard (nis 87:2000, 2000). the rate of building collapse in nigeria building and development industry has been on the rise due to the use of substandard materials (odeyemi et al., 2015). the durability of blocks depends on its quality, which in turn is greatly dependent on methods of production and properties of its constituents (abdulwahab and akinleye, 2016). therefore, this study was aimed at investigating the degree to which different fine aggregates influence the compressive strengths of sandcrete blocks. 2. materials and methods 2.1 materials dangote cement brands 42.5r, which conforms to nis 444-1:2003 (2003), clean water, fine aggregates (river sand, quarry dust, plastering sand, and shocking sand) were used to produce the sandcrete block specimens. the river sand, quarry dust, plastering sand, and shocking sand were purchased from danzaria block factory, ilorin in kwara state, nigeria. 2.2 methods particle size distribution of the fine aggregates (quarry dust, river sand, shocking sand and plastering sand) was conducted in accordance with bs 812-103.1:1985 (1989). the percentage of the particles passing from the sieves was plotted against the particle diameters. from the graphs, the values of d60 and d10 were obtained. equation (1) was adopted in calculating the uniformity coefficient (cu). cu = d60 d10 (1) where: cu is the uniformity coefficient, d60 is the diameter of particle corresponding to 60% finer on the cumulative particle-size distribution curve and d10 is the diameter of particle corresponding to 10% finer on the cumulative particle-size distribution curve. if coefficient of uniformity (cu) of soil < 4.0 then the soil is uniformly graded but if cu > 4.0 then soil is could be well graded, or gap graded (bowles, 1996; neville, 2011; shetty, 2008). specific gravity test was carried out on the aggregates in accordance with bs 1377-2 and aci education bulletin. equation (2) was used to calculate the specific gravity for each of the aggregates. sg = w2−w1 w4−w1 − w3−w2 (2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):611-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 613 where: sg is the specific gravity, w1 is the weight of empty bottle, w2 is the weight of aggregate and bottle, w3 is the weight of aggregate, bottle and distilled water, w4 is the weight of bottle and distilled water. the materials for the blocks were mixed manually using a shovel but vibrated mechanically using a sandcrete block moulding machine. a mix ratio of 1:6 (one portion of cement to six portions of sand) and 1:4 (one portion of cement to four portions of sand) was adopted respectively with water to cement ratio of 0.45, as specified by (nis 87:2000, 2000), for manufacturing of sandcrete blocks in nigeria and batching was done by weight. water absorption of a material is the ratio of the decrease in mass of that material to mass of its dry sample. it impacts on the bond between cement mortar and aggregates, the resistance of concrete to thawing and freezing, chemical stability and specific gravity (anosike and oyebade, 2012). the water absorption test carried out on the aggregates was done in accordance with (nis 87:2000, 2000). in determining the water absorption for the aggregates, the samples were cleansed, drained and placed in a wire basket before immersing in distilled water for 24 hours at a temperature of 25°c. when removed from the water, the aggregates were air dried, weighed and designated as ‘a’. afterwards, the aggregates were placed in an oven for 24 hours at a temperature of 105 °c. when removed from the oven, it was cooled, weighed and designated as ‘b’. the water absorption was calculated from equation 3. water absorption (%) = a−b b × 100 (3) the sandcrete blocks were cured for 7 and 28 days by immersion in water and taken in batches for compressive strength determination at age 7 and 28 days respectively. five blocks per case of observation were crushed at each maturing age and their crushing loads were recorded. the compressive strength test conducted on the sandcrete blocks was done in accordance with nigeria industrial standard (nis 87:2000, 2000). a manual compression testing machine with a maximum load capacity of 1,560 kn from the concrete laboratory of the department of civil engineering, university of ilorin, nigeria, was utilized for this test. the compressive strength of the sandcrete blocks in n/mm2 was obtained by dividing the recorded crushing loads by the effective area of the blocks. the average compressive strengths for blocks produced from the four (4) aggregates considered were plotted at 7 and 28 days of curing. a t-test statistical analysis was carried out to determine if there is a significant difference between the mean strength of the aggregates. a test of independence of the responses gotten was carried out using the following statement hypothesis: h0: the average compressive strengths are not significantly different from 2.5 n/mm2 h1: the average compressive strengths are significantly different from 2.5 n/mm2 significance level α: 0.05. the decision rule is ‘reject the null hypothesis h0 if the p-value is less than the significance (0.05).’ 3. results and discussion 3.1 sieve analysis test the results of the sieve analysis carried out on the four (4) types of aggregates are shown in figures 1-4, while the corresponding coefficient of uniformity are shown in table 1. the particle sizes of all the fine aggregates shown in figures 1-4 were between 1 mm and 0.10 mm which means they fell within the category of medium sand and fine sand (neville, 2011). from table 1, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng odeyemi, et al: impact of different fine aggregates on the compressive strength of hollow sandcrete blocks. azojete, 15(3):611-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 614 all the aggregates have their values of cu lower than 4.0. thus, they are all classified as being uniformly graded (bowles, 1996; neville, 2011; shetty, 2008). figure 1: particle size distribution of quarry dust figure 2: particle size distribution of river sand figure 3: particle size distribution of shocking sand http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):611-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 615 figure 4: particle size distribution of plastering sand table 1: uniformity coefficients for the samples s/no soil sample uniformity coefficient remark 1 quarry dust 1.5 uniformly graded 2 river sand 2.5 uniformly graded 3 shocking sand 3.3 uniformly graded 4 plastering sand 3.3 uniformly graded 3.2 specific gravity test the specific gravity of the fine aggregates (quarry dust, river sand, shocking sand and plastering sand) used in this study are shown in table 2. specific gravity for aggregates, specified by (aci education bulletin, 2007), ranged from 2.30 to 2.90. the results of the specific gravity of the quarry dust, river sand and shocking sand in table 2 are within the acceptable limits for aggregates, while that of plastering sand is below the limit specified by the standards. thus, quarry dust, river sand and shocking sand can be considered as suitable aggregates for sandcrete block production based on their specific gravity. table 2: specific gravity of fine aggregates fine aggregates specific gravity quarry dust 2.36 river sand 2.61 shocking sand 2.39 plastering sand 2.29 3.3 water absorption capacity test the result of the water absorption test carried out on the four (4) aggregates used in this study are shown in figure 5. the water absorption rate result reveals that shocking sand has the highest capacity to absorb water with a value of 8.69 %. however, river sand, with a value of 6.67 %, has the lowest water absorption capacity. this implies that blocks made from shocking sand file:///c:/users/user/downloads/azojete143/www.azojete.com.ng odeyemi, et al: impact of different fine aggregates on the compressive strength of hollow sandcrete blocks. azojete, 15(3):611-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 616 has a tendency of getting soaked earlier than blocks made from the other fine aggregates considered in the study. figure 5: water absorption capacity for the fine aggregates 3.4 compressive strength test the compressive test results obtained for the sandcrete blocks produced with the four (4) aggregates considered in this study are shown in figures 6 and 7 respectively. figure 6: average compressive strength for mix ratio 1:6 figure 7: average compressive strength for mix ratio 1:4 the results of the average compressive strength of sandcrete blocks with a mix ratio of 1:6 at 28th days of curing show that sandcrete blocks produced from quarry dust have the highest strength of 1.31 n/mm2 followed by that of river sand (1.10 n/mm2), shocking sand (0.50 n/mm2) and plaster sand (0.78 n/mm2). none of the strengths met the requirement of 2.5 n/mm2 specified by nigeria industrial standard (nis 87:2000, 2000). however, for mix ratio 1:4, the results showed that the compressive strength of sandcrete blocks made from quarry dust and river sand at 28 days met the requirement specified by nigeria industrial standard (nis 87:2000, 2000) of 2.5 n/mm2 for non-load bearing wall. a t-test statistical analysis was carried out on the results obtained for all the soil samples for both mix ratios 1:6 and 1:4 and the results are shown in tables 3 and 4. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):611-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 617 table 3: t-test for average compressive strength of sandcrete blocks produced with mix ratio 1:6 average compressive strength of sandcrete blocks produce with 1:6 t degree of freedom p-value quarry/stone dust -11.303 5 .000 river sand -20.431 5 .000 plastering sand -30.021 5 .000 shocking sand -29.336 5 .000 table 4: t-test for average compressive strength of sandcrete blocks produced with mix ratio 1:4 average compressive strength of sandcrete blocks produce with 1:4 t degree of freedom p-value quarry/stone dust .351 3 .749 river sand -.030 3 .978 plastering sand -14.189 3 .001 shocking sand -5.262 3 .013 from table 3, the p-values (0.000) for the sandcrete blocks produced from the 4 soil samples with mix ratio 1:6 are less than the significance value (0.05). thus, it is concluded that the average compressive strength of the sandcrete blocks are significantly different from 2.5 n/mm2. from table 4, the p-values for the sandcrete blocks produced with plastering and shocking sand (0.01 and 0.013) are less than significance value of 0.05, and the p-values for the sandcrete blocks produced with quarry dust and river sand (0.749 and 0.978) are greater than significance value of 0.05. thus, it is concluded that the average compressive strength is not significantly different from 2.5 n/mm2 for sandcrete blocks produced from quarry dust and river sand with mix ratio 1:4. 4. conclusion the following conclusion can be drawn from the study: the compressive strength of hollow sandcrete blocks is dependent on the type of fine aggregate and mix ratios used in its production. the coefficient of uniformity of the fine aggregates from particle size distribution shows that all the soils are uniformly graded. shocking sand has the highest capacity to absorb water with a value of 8.69 %. however, river sand, with a value of 6.67 %, has the lowest water absorption capacity. the 28th day compressive strength results of sandcrete blocks produced with mix ratio 1:6 does not meet the required strength of 2.5 n/mm2 for sandcrete blocks. however, with mix ratio 1:4 sandcrete blocks produced with quarry dust and river sand met this requirement. it is recommended that only quarry dust and sharp sand with mix ratios 1:4 are suitable for sandcrete block production. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng odeyemi, et al: impact of different fine aggregates on the compressive strength of hollow sandcrete blocks. azojete, 15(3):611-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 618 references abdulwahab, r. and akinleye, tm. 2016. the effects of production methods on the compressive strength of hollow sandcrete blocks. journal of materials and engineering structures, 3: 197–204. aci education bulletin, 2007. aggregates for concrete-materials for concrete construction. developed by committee e-701, american concrete institute, 38800 country club dr, farmington hills, michigan, united states. anosike, mn. and oyebade, aa. 2012. sandcrete blocks and quality management in nigeria building industry. journal of engineering, project, and production management, 2(1): 37–46. bowles, je. 1996. foundation analysis and design, the mcgraw-hill companies, inc., n.y. bs 1377:2. 1990, 1996. methods of test for soil for civil engineering purposes. british standards, bsi group headquarters 389 chiswick high road, london, w4 4al, uk, standards policy and strategy committee. bs 812-103.1:1985, 1989. methods for determination of particle size distribution-section 103.1 sieve tests.british standards, bsi group headquarters 389 chiswick high road, london, w4 4al, uk, standards policy and strategy committee. ewa, de. and ukpata, jo. 2013. investigation of the compressive strengths of commercial sandcrete blocks in calabar nigeria. international journal of engineering and technology, 3(4): 477–482. neville, am. 2011. properties of concrete. 5th ed., pearson education ltd, london. nair, dg., jagadish, ks. and fraaij, a. 2006. reactive pozzolanas from rice husk ash: an alternative to cement for rural housing. cement and concrete research, 36: 1062–1071. nis 444-1:2003, 2003. cement:pt. 1: composition, specifications and conformity criteria for common cements. nigerian industrial standard, standard organisation of nigeria, lagos, nigeria. nis 87:2000, 2000. standard for sandcrete blocks. nigerian industrial standard, standard organisation of nigeria, lagos, nigeria. nis 87:2004, 2004. standard for sandcrete blocks in nigeria.nigerian industrial standard, standard organisation of nigeria, lagos, nigeria. odeyemi, so., anifowose, ma., oyeleke, mo., adeyemi, ao. and bakare, s.b. 2015. effect of calcium chloride on the compressive strength of concrete produced from three brands of nigerian cement. american journal of civil engineering (ajce), 3(2–3): 1–5. odeyemi, so., akinpelu, ma., atoyebi, od. and orire, kj. 2018. quality assessment of sandcrete blocks produced in adeta, kwara state, nigeria. nigerian journal of technology (nijotech), 37(1): 53–59. oyekan, gl. and kamiyo, om. 2011. a study on the engineering properties of sandcrete blocks produced with rice husk ash blended cement. journal of engineering and technology research, 3(3): 88–98. oyetola, eb. and abdullahi, m. 2006. the use of rice husk ash in low-cost sandcrete block production. leonardo electronic journal of practices and technologies, 8: 58–70. shetty, ms. 2008. concrete technology theory and practice. s. chand and company ltd., newdelhi, india http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):48-57 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 48 original research article real-time detection of abandoned object using centroid difference method y. a. samaila1*, h. rabiu2 and i. mustapha1 (1deparment of electrical and electronics engineering, university of maiduguri, maiduguri, nigeria 2department of electrical engineering, bayero university, kano, nigeria) * corresponding author’s email address: yausamaila002@gmail.com 1.0 introduction an abandoned object is a stationary object that has not been in a scene before. to detect the abandoned objects, find the static regions in the scene and determine whether they correspond to abandoned or not. recently, several bomb explosions occurred in public areas. for instance, on 20th september 2015, at the ajilari area of maiduguri, nigeria, an abandoned polythene bag containing an explosive kept at a mosque entrance exploded, where several people were killed and many others sustained injury. the preventive action is imperative and wide scale deployment of surveillance systems are in demand. in spite of the sophisticated surveillance systems deployed in many places today, the problem still persists. such limitations are connected with human involvement in the systems. therefore, it is challenging for man to continuously monitor a scene round the clock, thus, the manual surveillance fails. semiautomatic surveillance using close circuit television (cctv) also seems ineffective due to the article information abstract an abandoned object is one that remains stationary for an extended period. such object might contain explosives and if left on purpose could cause death and injuries to people especially in crowded places. abandoned objects need to be detected on time to prevent what might endanger people’s lives and health. various methods have been developed to detect abandoned objects. the most reliable one is the vision-based method which automatically detects the abandoned object using image processing. the efficiency of the method was tested and evaluated on the customized datasets as well as the i-lids advanced video surveillance system database. the self -organizing background subtraction (sobs) method overrides other methods in terms of its detection accuracy and simplicity of implementation, but fails for dynamic background scenarios. this work presents a real time vision-based object detection method using the centroid difference to improve on the accuracy of the detection and to tackle challenges of dynamic background of the sobs method. matlab image processing toolbox was used to achieve this goal. the strategy is basically decomposed into two; foreground detection and stationary foreground object (sfo) detection. gaussian mixture model is used for detecting the presence of newly introduced object into a scene (foreground detection), while the blob tracking approach based on frame counting is used to determine whether the detected foreground object is static/ abandoned or not. the results show that the detection accuracy of 83% was obtained which outperform the sobs method with 67% accuracy. future research should focus on tracking the person that abandoned the object for onward prosecution. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 march, 2019 revised 27 september, 2019 accepted 03 october, 2019 keywords: stationary foreground object abandoned object gaussian mixture model self -organizing background subtraction centroid difference. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 48-57. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 49 fact that man cannot effectively monitor many scenes at a time without possible distraction. to ease this problem and improve scene monitoring systems, computer-based object detection and monitoring system is proposed. a computer-based surveillance system detects the left/abandoned object and activate alarm to alert security personnel act on it. several methods have been devised to detect foreground object. these include frame differencing, background subtraction, optical flow, single gaussian, gaussian mixture model (samaila et al., 2019). background subtraction identifies the presence of moving object by considering the difference between a fixed reference frame and a current frame (risha and chempak, 2016). the frame differencing method identifies the presence of moving object by considering the difference between two consecutive frames. frame differencing is subdivided into three parts. initial step is the selection of perfect reference or background. the second step is the arithmetic subtraction operation and the third step is the selection of a suitable threshold. reference image can be selected as a frame which is temporarily adjacent to an image from a dynamic sequence. this method lacks in obtaining the complete contour of the object (risha and chempak, 2016). this could arise due to suitable threshold selection that will be applied throughout the video frame, as each frame has its unique feature. a three (3) frame differencing is used to lessen this shortcoming (shaikh et al., 2014). interestingly, a hybrid approach coopting background subtraction and frame differencing detects moving object a lot effectively and precisely (alex and wahi, 2014). for scenes that are having dynamic background (tree branches, bushes, water surface or flags), a generalization based on a mixture of gaussians can be used to model such variations (changes cannot be modeled using one gaussian distribution per pixel). stauffer and grimson (1999) proposed a gaussian mixture model (gmm) method to deal with scenarios consisting dynamic backgrounds, illumination challenges, camouflage among others. tavakkoli, (2009) came up with a method that allows the background model to be a mixture of several gaussians (typically between 3 and 5). each pixel is labeled as foreground or background based on its probability. furthermore, for the stationary foreground object (sfo) detection; tracking of foreground and dual foreground comparison are some of the renowned methods. in the tracking of foreground method, blobs statistics such as object size/area, centroid position, were used in some studies by miguel and martinez (2008), bayona et al. (2009), utikari and uke (2014) and singh et al. (2009) to determine if an object is static or not. dual foreground comparison (dfc) strategy proposed by porikli et al. (2008) tried to identify the sfos by comparing two binary foreground masks at pixel level. these masks were obtained from two background models constructed with different learning rates. the models were constructed using multiple gaussians. the main objective of the research is to developed a database and as well use it in developing an algorithm for detecting abandoned object. 2. methodology the abandoned object detection method used in this work comprises of three stages. the block diagram representation of the abandoned object detection method is as shown in figure 1. figure 1: block diagram representation of the abandoned object detection method file:///c:/users/user/downloads/azojete143/www.azojete.com.ng samaila et al: real-time detection of abandoned object using centroid difference method. azojete,16(1):48-57. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 50 the custom database was developed in addition to the publicly available database to implement the technique. red, green blue (rgb) partitioned video frames were converted to gray scale for easier and faster processing. foreground detection: gaussian mixture method was used to detect foreground objects in the gray scale video frames. stationary foreground object (sfo) detection: centroid difference tracking method was used to track the stationary foreground object(s) across successive frames. figure 2 gives the flow chart of the gmm algorithm, from the design and the development of the database stage to the stationary object detection stage. figure 2: flow chart of the gmm algorithm 2.1. design and development of database two different databases were considered in this work. the advanced video surveillance system (avss) which is a publicly available database, contains objects (of interest) with confined shapes and sizes. the custom database takes care of the shortcomings of the avss database as it considers objects of different shapes and sizes. the properties of the abandoned object detection database is shown in table 1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 48-57. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 51 table 1: properties of the abandoned object detection database. sequence(s) no. of frames object of interest size (pixels) customized sequence 1(s1) 297 polythene bag 1390 customized sequence 2(s2) 660 big bag 1968 customized sequence 3(s3) 318 can 691 customized sequence 4(s4) 2071 big bag 2021 customized sequence 5(s5) 1676 small bag 1553 the video (database) shown in table 1 was partitioned into frames and converted from rgb to grayscale image in order to speed up the processing. background model was developed using gaussian mixture model in order to detect the foreground object. 2.2. the gaussian mixture model foreground detection for video scenes with dynamic background (tree branches, bushes, water surfaces or flags), a generalization based on a mixture of gaussians can be used to model such variations (changes cannot be modeled using one gaussian distribution per pixel). the use of a gaussian mixture model (gmm) was first introduced by stauffer and grimson (2000) to deal with dynamic background scenarios. this method allows the background model to be a mixture of several gaussians (typically between 3 and 5). each pixel is labeled as foreground or background based on its probability. a pixel-based method was presented which models each pixel (regarded as background) into a mixture of gaussians. the number of gaussians k is typically set from 3 to 5 (stauffer and grimson, 2000). in addition, each gaussian has its own weight to represent the portion of the data accounted for from corresponding distribution. the probability that a pixel regards a value x at a certain time t, xt is given as follows; p xt = j=1 k ω j,t ∗ ղ xt ,m j,t , j,t�� (1) where k is the number of gaussian distributions, ω j,t is the weight estimation of the jth gaussian in the mixture at time t, mj,t and σ j,t are the mean value and covariance matrix respectively, of the jth gaussian in the mixture at time t, and η is a gaussian pdf (probability density function) defined in (2); ղ xt. ,m,ʃ = 1 2π k 2 ʃ 1 2 exp − 1 2 xt −mt t ʃ−1 xt −mt (2) table 2 shows the modified gmm parameter values used which was originally adopted in another work (power and schoones, 2002). table 2: parameter values for the modified gmm symbol value related parameter k 5 25 frames/seconds a 0.005 x ε [0,255] t 0.7 ωinit 0.05 num training frames 50 @ 25fps x [0-255] file:///c:/users/user/downloads/azojete143/www.azojete.com.ng samaila et al: real-time detection of abandoned object using centroid difference method. azojete,16(1):48-57. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 52 where: k= number of gaussians t= minimum background ratio x=pixel value σinit=initial variance α= learning rate ῳinit= initial weight numtrainingframes= number of training frames the salient point of the gmm stage is given here. 1. the method terminates upon reaching convergence. the parameters are used to fit on the data point (each pixel is denoted as a data point). 2. upon fitting the gmm to the data, the component or surface (k) with the highest probability claims the pixel (that particular incoming pixel). 3. the process is repeated for all incoming pixel of the current frame as compared to the background model. the detected foreground object is used as an input to the next stage to determine whether it is stationary/abandoned or not. 2.3 stationary foreground object (sfo) detection using centroid difference tracking method the centroid is one of the easiest region properties used for determining whether a foreground object is stationary or otherwise. it comprises of two (2) axis-x and y. centroid r�=1a (r,c)εr r� , c�=1a (r,c)εr c� , (3) where r= row; c= column; r=region; a=area. note: for a foreground blob to be considered static, it has to satisfy two conditions; the centroid difference must be less than the set threshold [5 5]. the said difference should be maintained for at least 25 consecutive frames blob counting (tracking) across several frames is employed to track the stationary objects in the sequence. the tracking process is explained in section 2.4. 2.4. tracking of foreground using the centroid difference algorithm the basic steps are: the variables were declared and initialized counter(c)= 0, threshold (th)= [5, 5], no. of consecutive frames = 25 the centroid and area of blobs in each frame were obtained and stored in an array. the maximum area and its index as well as its corresponding centroid (maximum centroid) were determined for each frame. the maximum centroid entries were labeled as k1(x1, y1) for the 1st frame, k2(x2, y2) for the second, up to kn (xn, yn) for the last frame. if k1-k2<th, the condition is satisfied and c=c+1, then k1-k3. otherwise k2-k3. the condition in [5] was satisfied for at least 25 consecutive frames (1 second) that is up to k1k25 ,an abandoned object was declared at the coordinates of that frame. the coordinates were used to draw a bounding box around the declared static blob/object. the aspect ratio was used to distinguish static human from other static objects. aspect ratio=major axis length minor axis length which is> 2.0 for human. alarm was raised for static non-human objects http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 48-57. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 53 3. results and discussion 3.1 experimental results for foreground detection the grayscale images in table 1 were used for detecting the foreground objects. two detection strategies namely the gmm (proposed) and the self-organizing background subtraction (sobs) methods were considered. the sobs method has background which automatically organizes itself (yadav and jahagirdar, 2015). the gmm uses the first 50 frames to develop a background model. the grayscale of sequence 1(s1) for frame #50, frame #120 and frame #297 of sequence 1(s1) is shown in figure 3(a),3(b) and 3(c) respectively. since no new object was introduced, a zero foreground object was observed in frame #50. two foreground objects were detected in frame #120. figure 4(a), 4(b) and 4(c) shows the sobs foregrounds of frame #50, frame #120 and frame #297 of sequence 1(s1). the objects were large in figure 4(b) because they are closer to the camera. as the detected foreground objects go farther away from the camera position, the objects diminish in size . morphological opening operation with a square structural element of radius ‘10’ was carried out on the detected foreground objects to refine them so as to have a better and improved output devoid of noise. similarly, the gmm foregrounds of s1 for frame #50,frame #120 and frame #297 is shown in figure 5(a),5(b) and 5(c) respectively. figure 3: gray frames of s1: (a) frame #50 (b) frame #120 (c) frame #297 figure 4: sobs foregrounds of s1: (a) frame #50 (b)frame #120 (c) frame #297 figure 5: gmm foregrounds of s1(a) fg frame #50 (b)frame #120 (c)frame # 297 a comparison between the sobs method and the proposed gmm method in terms of detected foreground, show that the gmm as depicted in figure 5(c) gives a good detection of the foreground at the point of abandonment of the object of interest (polythene bag in this case) as compared to the sobs as portrayed in figure 4(c). in figure 5(c) the polythene bag is larger 1281 pixels’ as compared to figure 4(c) which is 681 pixels. the reason is that the gmm method overcomes variation in illumination and background challenges better than the sobs method. the larger object of interest in the detected foreground at the point of abandonment informed our decision for choosing the gmm in the detection of foreground. hence the larger the object the better the detection. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng samaila et al: real-time detection of abandoned object using centroid difference method. azojete,16(1):48-57. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 54 the results of the foreground detection stage were used to determine the sfo (abandoned object). 3.2 experimental results for stationary foreground detection (sfo) executing the centroid difference tracking algorithm on the detected foreground yielded some results. figures 6(a) shows the plot of maximum centroid y against maximum centroid x. there is an indication of abandoned object at points (409,350 and 409,351) of s1 denoted by an ellipse in figure 6(b) shows the abandoned objects detected at frame # 275 of s1. (b) figure 6:(a) plot of maximum centroid y against maximum centroid x (b) abandoned objects detected at frame # 275 of s1 figure 7(a) shows the plot of maximum centroid y against maximum centroid x, indicating abandoned object at points (126,151and 127,155) of s4denoted by an ellipse. figure 7(b) abandoned object detected at frame #800 of s4. (b) figure 7:(a) plot of maximum centroid y against maximum centroid x, (b) abandoned object detected at frame #800 of s4. figure 7(b) entails human having an aspect ratio of 2.3 denoted with green bounding box was distinguished from other objects (aspect ratio <2). the essence is to reduce or eliminate false detection, as static humans should not be declared as abandoned objects even if they are stationary. the larger the size of the blob (detected foreground object), the better the detection as shown in figures 4 and 5 for the sobs and gmm respectively. objects as small as a tea cup was detected by the proposed method which is not realizable in the sobs method. the proposed (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 48-57. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 55 method handles dynamic background (swaying trees and flowers) as it considered them as part of the background, thus minimizing wrong detection present in the reference method (sobs). the gmm method also overcomes the challenge of camouflage as the background and foreground objects in the custom database have similar appearance, which literally makes detection difficult in the other method. the proposed algorithm is equally unique from the sobs and other similar methods as it distinguishes human from other objects using the aspect ratio, as only non-human abandoned objects are declared abandoned. the system fails to detect multiple abandoned objects simultaneously, as it only detects one abandoned object at a time. it also fails for scenarios/sequences with low contrast, especially for sequences recorded at night. 3.3 performance metrics algorithm performance was assessed using the f1 weighted harmonic mean of ‘recall’ ‘precision ‘and ‘accuracy’. recall is the fraction of abandoned objects which were in fact abandoned. precision is the fraction of positive classifications which are correct. accuracy is the fraction of correctly classified objects over the number of objects classified. when presented with a sequence, each algorithm or system yields a number of entities (table 3) such as: (a) true detection/true positive (system alarms in response to a genuine alarm event) (b) false detection/false positive (system alarms without the presence of a genuine alarm event) (c) missed detection/false negative (genuine alarm events not resulting in a system alarm) (d) human detection (genuine non-alarm events that arises as a result of static human) the system performance of the two algorithms (sobs and gmm) were compared as depicted in table 3. table 3: performance comparison of the sobs and gmm methods sequence (s) true detection false detection missed detection human detection sobs gmm sobs gmm sobs gmm sobs gmm s1 1 1 0 0 0 0 0 0 s2 1 1 0 0 0 0 0 0 s3 0 1 0 0 1 0 0 0 s4 1 1 1 0 0 0 0 1 s5 1 1 1 0 1 1 0 1 total 4 5 2 0 2 1 0 2 key: a= true detection b=false detection c=missed detection d=human detection recall, r = a a+c precision, p = a a+b (4) recall, r sobs = 4 6 = 0.67 precision, psobs = 4 6 = 0.67 recall, r gmm = 5 6 = 0.83 precision, pgmm = 5 5 = 1 f1 = ∝+1 rp r+∝p . (5) where α is the ‘recall bias’; a weighting of recall relative to precision declared in each i-lids scenario definition. the weighting to be used for the i-lids avss is 35. the algorithm demonstrating the highest f1 score for each sequence will be deemed the better one. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng samaila et al: real-time detection of abandoned object using centroid difference method. azojete,16(1):48-57. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 56 thus, the f1 score for the two algorithms will be f1sobs = 35+ 1 0.67 ∗ 0.67 0.67 + 35 ∗ 0.67 ≈ 0.7 f1gmm = 35+ 1 0.83 ∗ 1 0.83 + 35 ∗ 1 ≈ 0.8 accuracy = true detection true detection + missed detection (6) accuracy sobs = 4 6 = 0.667 = 67% accuracy gmm = 5 6 = 0.833 = 83% table 3 showed that the fi score for the proposed method was the better option, since it has higher score (0.8) as compared to the sobs algorithm (0.7). the higher the fi score, the better the detection. the accuracy of abandoned object detection on gmm approach is 83%, whereas the sobs approach has 67% accuracy as shown from results of equation 6. 4. conclusion in this work, a vision-based abandoned object detection system that runs in real-time is presented. the system uses a custom database that was developed to take care of the shortcomings of the publicly available database which uses objects of confined shape and size. the proposed system (gmm) handles background challenges better than the sobs method and was able to detect object as small as a teacup. classification of abandoned objects into human (not declared abandoned) and non-human (declared abandoned) is achieved which was not presented in other existing methods. the experimental results show that the gmm outperforms the state-of-the-art sobs in terms of f1 score and detection accuracy. further research should focused on detecting multiple objects, tracking and identifying humans that carried and dropped the abandoned objects behind in the scene. references alex, ds. and wahi, a. 2014. background subtraction frame difference algorithm for moving object detection and extraction. journal of theoretical and applied information technology, 60(3): 623-628. bayona, a., miguel, jcs. and martinez, j. 2009. comparative evaluation of stationary foreground object detection algorithms based on background subtraction techniquesvideo processing and understanding lab. escuela politécnica superior, universidad autónoma de madrid, spain. advanced video and signal based surveillance, 25-30. miguel, jcs. and martinez, jm. 2008. robust unattended and stolen object detection by fusing simple algorithms. advanced video and signal based surveillance,. avss’08. ieee fifth international conference on, ieee, 18–25. porikli, f., ivanov, y. and haga, t. 2008. robust abandoned object detection using dual foregrounds. eurasip journal on advances in signal processing, 30: 1-11. power, pw. and schoones, ja. 2002. understanding background mixture models for foreground segmentation. proceedings on image and vision computing new zealand university of auckland, auckland, new zealand 26–28th november, 267-271. risha, k. and chempak, ka. 2016. a novel method of detecting moving object in video. international conference on emerging trends in engineering, science and technology (icetest 2015). procedia technology, 24:1055 – 1060. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 48-57. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yausamaila002@gmail.com 57 shaikh, sh., saeed, k. and chaki, n. 2014. moving object detection using background subtraction. springer briefs in computer science, 2-5. stauffer, c. and grimson, wel. 1999. adaptive background mixture models for real-time tracking’, in: computer vision and pattern recognition, 1999. ieee computer society conference, ieee, 2:246-252. stauffer, c. and grimson, wel. 2000. learning patterns of activity using real-time tracking, ieee transactions on pattern analysis and machine intelligence, 22(8): 747-757. tavakkoli, a. 2009. novelty detection: an approach to foreground detection in videos, university of nevada, reno usa, pp. 123-150. utikar, aa. and uke nj. 2014. abandoned object detection in educational institutes using video surveillance, international journal of advanced research in computer and communication engineering, 3(10): 8219-8222. singh, r., vishwakarma, s., agrawal, a. and tiwari, m. 2010. unusual activity detection for video surveillance, proceedings of the first international conference on intelligent interactive technologies and multimedia, acm, 297–305. samaila, ya., lawan, mb., tijjani, i., sarki, ma., gujja, mm. and tijjani, i. 2019. a review on foreground and stationary foreground object detection techniques. journal of multidisciplinary engineering science and technology, 6 (4): 9768-9775. yadav, p. and jahagirdar, a. 2015. a static object detection in image sequences by self organizing background subtraction. international research journal of engineering and technology, 2 (7): 72-76. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 111-120 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng ____________________ *corresponding author email: lawalbalo@yahoo.co.uk 111 original research article development of crop water production model in a rainfed tropical maize crop cultivation l. a. balogun*1, t. a. ewemoje2, m. a. aderemi3, a. r. nasirudeen1, d. lasisi1 and a. o. hammed4 (1department of agricultural and bio-environmental engineering, oyo state college of agriculture and technology, igboora; 2department of agricultural and environmental engineering, university of ibadan, ibadan. 3department of agricultural technology, federal college of forestry, ibadan. 4department of agricultural engineering, federal college of agriculture, ibadan.) article information received october, 2018 accepted december, 2018 keywords: rain-fed maize water yield secondary data regression nigeria abstract crop production, which is one of the sources of food for human and animal sustenance is a function of the availability of adequate quantity of water. the rainfall being seasonal is the main source of water for agricultural production in nigeria. maize production is majorly through rainfed agriculture in nigeria and the irregularity of which affect the yield. this research work was to develop crop-water production model in tropical rain fed maize crop cultivation using maize yield and rainfall data from oyo state. one of the major problems of food production in attempting to determine the relative future roles of irrigated and rain-fed agriculture is the lack of sufficient ground and accurate tool on a localized basis. hence, the essence of this research works. using correlation and full quadratic regression analysis, the effects of some rainfall indices (monthly and annual rainfall, raindays, and rainfall onset and rainfall cessation) on maize yield in oyo state were examined. the results of the correlation statistics showed that cessation has the strongest association (r= 0.284) with maize yield. the analysis also showed that early maize and late maize suffer moisture deficiency in march and november respectively while excessive rainfall of june/july and september also have implication for maize yield. it was also observed that the rainfall characteristics jointly contributed 96.7% in explaining the variations in the yield of maize per hectare. conclusively, a model was development for predicting maize yield in oyo state. the study also recommends the use of state own yield so as to harmonize with state rainfall data, application of appropriate moisture conservation management practices that ensured efficient use of water and use of drought resistance crop species with shorter growing periods as adaptive measures to the changing rainfall pattern within the study area. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserve 1.0 introduction crop production, which is one of the sources of food for human and animal sustenance is a function of the availability of adequate quantity of water. the water, natural is to be gotten directly from rainfall, but this source of water is also climatic dependent. this water is the main factor for any crop http://www.azojete.com.ng mailto:lawalbalo@yahoo.co.uk balogun, et al. development of crop water production model in a rainfed tropical maize crop cultivation. azojete, 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 112 production on which other factors may depend. the rainfall being seasonal is the main source of water for agricultural production in nigeria. this has restricted production of crop to only raining season during which the intensity of the events will still affect yield of crop production to some extent. in an interview with the director general of nimet, prof anthony anforom held on an nta program ”insight” in august, 2015, the director made it known that as the date, the production of crop in nigeria is limited to only rain-fed agriculture. that this has affected the crop production for the year, because of the late onset of rainfall and low rainfall as forecasted in the previous year. this, in general, limits the production of food in some areas that depended on rainfall for production and with limited amount of total rainfall per year. the vast potential of rain-fed agriculture needs to be unlocked through knowledge-based management of natural resources for increasing productivity and income to achieve food security in the developing world. soil and water management play a very critical role in increasing agricultural productivity in rain-fed areas in the fragile sat (semi-arid tropics) systems (wani et al., 2009). maize crop is one of the generally grown cereal crop in the world. maize, the main source of food in the tropical region, is grown in different varieties. the grains are rich in vitamins a, c and e, carbohydrates, and essential minerals, and contain 9% protein. they are also rich in dietary fiber and calories, which is a good source of energy (iita, 2015). crop production as stated earlier is limited to rainfall in some developing country and maize production is not an exception. maize production is majorly through rain-fed agriculture in nigeria and the irregularity of which affect the yield. international institute of tropical agriculture and other research institute scientists have developed high yielding, drought-resistant and disease-resistant varieties that are adaptable to sub-saharan africa's various agro-ecological zones but many of which have not been adopted by the local farmers. therefore this research work aimed at developing crop-water production model in tropical rain fed maize crop cultivation, with focus on rainfall dataset for oyo state between 1990 and 2013 periods and maize yield for the same period to determine rainfall indices for the years. one of the major problems of food production in attempting to determine the relative future roles of irrigated and rain-fed agriculture is the lack of sufficient ground and accurate tool on a localized basis. the variability and uncertainty of the climatic condition have drastic effect (low yield) on the crop production, the study of this variability and effect on the production will help for future planning to avert the effect of climatic change, hence the essence of this research work. (a) (b) fig 1. (a) photograph of maize plantation, and (b) harvested maize http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 113 2.0 material and methods 2.1 the location of the study area nigeria is located between latitudes 4° and 14°north of the equator and longitudes 3° and 14° east of greenwich meridian, and in west african region. the country is of area of 923768 sq kilometer, with tropical climatic condition and annual precipitation on the average ranging from 1800mm in the west to 4300mm in the east and 1300mm inland. the country experiences double rainfall maxima from march to july and september to october. ibadan city where nigeria meteorological agency (nimet) resides is located in coordinates of 7°23’47”n and 3°55’0” e and with mean total rainfall of 1420.06mm, falling in approximately 109 days and mean maximum temperature of 26.46°c (wikipedia, 2015). 2.2 sources of climatic and crop yield data in order to develop the crop-water production model for productivity of water for rain-fed maize crop, weather data comprising of rainfall indices like dates of onset and end of rainy season, annual amount, temperature, duration and rain days, and crop yield are needed. data on daily rainfall (from which monthly and annual values were derived) was collected over 24 years (19902013) from the official records of the meteorological centre of nimet, iseyin. the choice of this length of time is in line with the available data for the study, which is in accordance with numbers years for weather data in characterizing the climate of an area, as adopted by the world meteorological organization. the data used for this study were archival data on rainfall (in millimeters) and maize yield (in kilograms/hectare). the data on annual maize yield (kg) was collected from the official fao database for nigeria and for the same number of years 24 (1990 2013) 2.3 derivation of other parameters from the rainfall data collected, the following parameters were determined: date(s) of onset of the rainy season (in days); date(s) of end of the rainy season (in days); duration of the rainy season (in days);annual number of rain days (in days); and, annual rainfall amounts (in mm). there are several methods of computing onset, end and duration of the rains such as used by ilesanmi (1972) and benoit (1977). however, walter’s formulation as modified by olaniran (1983) was adopted in this study because of its high prediction reliability among other methods as used by ifabiyi and omoyosoye, (2011); emmanuel and fanan, (2013). the method was expressed as: (1) where: dm = the number of days in the month containing the date of onset/end; a = the accumulated total rainfall of the previous months; tm = the total rainfall for the month in which 51 mm or more is reached and 51 mm = the threshold of rainfall for both onset/end month. where such onset date was followed by dry spells of up to 14 days, the next rain day date that is not followed by such dry spells was chosen. for computing cessation or end dates, the formula was applied in reverse order by cumulating the total rainfall backwards from december. duration of the rainy season was derived by counting the number of rain days between the onset-date and the enddate of the rains in a given year. a rain day is a period of 24 hours (10:00 am 10:00 am local time) ../../../user/downloads/azojete143/www.azojete.com.ng balogun, et al. development of crop water production model in a rainfed tropical maize crop cultivation. azojete, 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 114 with at least 0.3 mm of recorded rainfall amount. annual rainfall total is the amount recorded for an entire year at a particular place (emmanuel and fannan, 2013). 2.4 suitability of study area for maize production the monthly water consumptive use of maize within its growing season as given by lema (1978) were compared with average monthly rainfall obtainable in the study area during the growing season to bring out the suitability of the study area for maize production. this is as shown in the table 1. table 1: monthly water consumptive use of maize within the growing season month 1st 2nd 3th 4th 5th total consumptive use (mm) 100 90 96 75 65 426 2.5 model formulation the study employed the mean, standard deviation and coefficient of variability in analyzing the variations in the study variables. partial correlation and multiple linear regression analysis were the statistical tools used to establish the relationship and effect of rainfall characteristics on maize yield. the regression model (as used by emmanuel and fannan, 2013) for the study was computed as: where: y = the value of the dependent variable (maize yield/ ha); b0= y intercept b1, b2, b3, b4, ··· bn= regression coefficients (each b represents the amount of change in y (maize yield/ha) for one unit of change in the corresponding x-value when the other x values are held constant; x1, x2, x3, x4, ··· xn= the independent variables (i.e. rainfall onset, cessation, duration, annual totals and annual number of rain days respectively); and e = the error of estimate or residuals of the regression. apart from the coefficients of the independent variables (rainfall characteristics), coefficient of multiple determinations (r2) was used to determine the percentage explanation achieved jointly by the rainfall characteristics. this method is preferred since it gives the best linear and unbiased estimates among other estimators. several authors to effectively study the impact of climate on crop yield (emmanuel and fannan, 2013) have used this. 3. results and discussion 3.1 variability in rainfall characteristics the descriptive statistics of the rainfall characteristics are shown in the tables below. table 2 shows the limit statistics of rainfall indices of the area of study and this indicates earliest onset of rainfall as 27th january 1997, latest onset of rainfall as 11th april 2007. mean onset of rainfall as 18th march http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 115 and earliest cessation of rainfall as 5th october 2001, while latest cessation of rainfall as 25th december 1999 and mean ceasation of rainfall as 28th october 1999. table 3 shows the limit statistics of other rainfall indices of the study area. table 3 shows minimum annual amount of rainfall, number of rain-days, annual duration of rainfall, and maize yield as 909 mm (in 2001), 78 days ( in 2006 ), 82 days ( in 2006) and 11181.31 hg/ha (in 1992) respectively. from table 3, the maximum annual amount of rainfall, number of rain-days, annual duration of rainfall, and maize yield as 1596.4 mm (in 1991), 119 days ( in 1993 ), 122 days ( in 1999) and 21961.28 hg/ha (in 2009) respectively. the mean annual amount of rainfall, number of rain-days, annual duration of rainfall, and maize yield as 1212.72 mm, 94 days, 99 days and 14612.25 hg/ha respectively. the result indicated that there was a delay in the dates of onset accompanied by early cessation dates of the rainy season, shortening duration of the growing season and number of rain days, consequently declining maize yield per hectare even though high rainfall amount was received. it was also be observed that the lowest rain-days was 78 days in 2006 and lowest annual rain-days ( 82 days) in the same year which might due to the late onset ( 12th march) and earlier cessation (25th october) of rainfall in the year. however, maize was not the lowest due to high rainfall (1169 mm) in the year. it can also be observed that 1992 recorded the lowest yield of maize per hectare (11181.30 hg/ha), probably due to the latest onset date (12th april), earliest cessation date (30th october), short duration (92 days), low number of rain-days (88 days) and annual rainfall amount (1047.5 mm) that occurred in the same year. the lowest annual amount of rainfall (909 mm) in 2001 and shorter annual duration (91 days) might be due to earliest cessation (5th october) of rainfall in the year. the highest amount of rain-days (119 days) and maximum annual duration (122 days) of rainfall and higher annual amount of rainfall (1447 mm) were recorded in 1993 which might be as result of latest cessation (25th december) in the same year but lower maize yield (11847.81 hg/ha). table 2. limit statistics of onset and cessation of rainfall at the study area indices mean earliest day year latest day year onset 79 27 1997 103 2007 date/days 18-mar 27-jan _ 11-apr _ ceasation 303 280 2001 361 1993 date/days 28-oct 5-oct _ 25-dec _ table 3. limit statistics of rainfall indices and maize yield at the study area indices mean minimum year maximum year annual amount 1212.72 909 2001 1596.4 1991 rain-days 94 78 2006 119 1993 annual duration 99 82 2006 122 1993/99 maize yield 14612.25 11181.31 1992 21961.28 2009 3.2 the coefficient of variability table 4 shows the descriptive statistics of rainfall indices and maize yield. the coefficient of variability of the rainfall characteristics shows that cessation dates of the rainy season has the highest coefficient of variability (56.1%), followed by dates of onset ( 29.11%), annual rainfall ../../../user/downloads/azojete143/www.azojete.com.ng balogun, et al. development of crop water production model in a rainfed tropical maize crop cultivation. azojete, 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 116 amount (13.82%), duration of the rainy season (12.77%) and the least variability of 12.12% was found in annual rain-days of the rainy season. table 4. descriptive statistics of rainfall indices and maize yield at the study area indices mean standard deviation coefficient of variance (%) sample variance maize yield(hg/ha) 15825.33 2730.03 17.25 7453088.84 onset(days) 79 23 29.11 539 cessation(days) 303 17 56.10 290 annual amount(mm) 1212.72 167.69 13.82 28116.81 rain-days(days) 94 12 12.77 142 annual duration(days) 99 12 12.12 140 on a general note however, the coefficient of variability of (17.25%) was recorded in maize yield per hectare (table 4). this result means that the annual rainfall durations were more reliable and predictable whereas the dates of cessation were more unreliable and unpredictable in the study area. the highest coefficient of variability of maize could be as a result of the joint effect of the variability in all the rainfall characteristics studied and other climatic and non-climatic factors not directly considered in this study. 3.3 suitability of the study area for maize production the analysis of maize consumptive water use is also presented in table 5. the mean rainfall amount obtainable in march according to table 5 is 52.0mm. this amount fell short of the 100 mm that is required at the first set of planting. thus, early maize plants in march may experience inadequate watering due to the nature of onset. table 5.mean monthly pattern of rainfall for oyo state (1990 – 2013) months rainfall(mm) jan 10 feb 18.2 mar 52 apr 106.3 may 150.8 jun 165.8 jul 152.8 aug 147.8 sep 198.9 oct 170.2 nov 21.5 dec 19.5 mean(x) 101.2 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 117 a critical period during the planting season of maize is the month of november; as the minimum required (65mm) looks almost impossible to be met. in november the obtainable rainfall is only 21.5mm. this indicates a need of irrigation for the period for the purpose of preventing drought to the planted crop. the total consumptive use of 426mm of rainfall for maize production can be met in oyo state as both rainfall obtainable for early maize and late maize were 627.7 mm and 710.7 mm respectively are more higher than the water consumption of maize production. however, it should be noted that the pattern of rainfall distribution is also relevant to the agronomy of any crop. table 6. monthly water consumptive use of maize within the growing season month 1st 2nd 3th 4th 5th total consumptive use (mm) 100 90 96 75 65 426 rainfall obtainable for early maize (mm) 52 (march) 106.3 (april) 150.8 (may) 165.8 (june) 152.8 (july) 627.7 rainfall obtainable for late maize (mm) 152.8 (july) 147.8 (august) 198.9 (september) 170.2 (october) 21.5 (november) 710.7 3.4 relationship between rainfall characteristics and maize yield the correlations between rainfall characteristics and maize yield shows that dates of onset (0.263) had weak (significant) positive correlation with maize yield; dates of cessation (-0.284), annual rainfall amounts (-0.241),and rain days (-0.174) had weak negative correlations with maize yield; while annual rain days (−0.088) had very weak negative correlations with maize yield (table 7). the dates of onset have greatest effect on the annual variation in yield. this implies that the area of study is prone to early onset of rainfall that has effect on the yield of early maize. annual rain-days have the lowest influence on maize yield. this reveals that only the rain days during production season has effect on the yield of maize significantly. table 7. correlation coefficients analysis of rainfall indices and maize yield at the study area chracteristics yield onset cessation rain-days annual amount annual rain-days (hg/ha) date date day mm day yield (hg/ha) 1 onset .263 1 cessation -.284 -.016 1 rain-days -.174 -.405 .481* 1 annual amount -.241 -.418 .408 .710** 1 annual rain-days -.088 -.287 .415 .975** .660** 1 *coefficient is significant at 0.10 confidence level (2-tailed), **coefficient is significant at 0.05 confidence level (2-tailed). 3.5 model for predicting maize yield 3.5.1 coefficient of prediction the model for predicting maize in relation with rainfall indices is presented in coefficients as shown in table 8. ../../../user/downloads/azojete143/www.azojete.com.ng balogun, et al. development of crop water production model in a rainfed tropical maize crop cultivation. azojete, 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 118 from the regression coefficients shown in table 8, the regression equation or predictor model of the study was stated thus: where; y = predicted yield of maize in the area. x1, x2, x3, x4, and x5 are onset date, cessation date, rain-days duration, annual amount and annual rain-days respectively. from this model, it can be inferred, that, given a unit change in any of the rainfall characteristics while holding others constant, the highest variation in yield of maize in the area will be accounted for, by rain days ( 19851.6 kg/ha), followed by interaction of rain days ( 859.51 kg/ha), interaction of annual rain days (756.40 kg/ha), annual amount (503.65kg/ha), cessation (356.20 kg/ha), interaction of cessation and annual rain days (258.64 kg/ha), interaction onset and rain days (167.61 kg/ha) and interaction annual amount and annual rain days (25.49kg/ha). also followed by interaction of onset and cessation (11.99 kg/ha), interaction of onset (0.469 kg/ha), interaction of onset and annual amount (0.07657 kg/ha), interaction of annual amount (-0.161 kg/ha),interaction of cessation and annual amount (-1.202 kg/ha), interaction of cessation (-7.256 kg/ha), interaction of annual rain days and annual amount ( -22.04 kg/ha), interaction of onset and annual rain days (155.42 kg/ha), interaction of cessation and rain days ( -221.88 kg/ha), interaction of rain days and annual rain days (-1613.6 kg/ha), onset (-4309.2 kg/ha), and the least change in yield will be from annual rain days (-35940.4 kg/ha). table 8. coefficient of prediction for full quadratic multiple regressions coefficient p value std error -95% 95% t stat vif b0 656575 0.308 536247 -1050000.761 2363150.624 1.224 b1 -4309.2 0.270 3196.2 -14481.1 5862.6 -1.348 29474.7 b2 356.20 0.918 3167.9 -9725.3 10437.7 0.112 13324.1 b3 19851.6 0.547 29320.2 -73458.5 113162 0.677 629446 b4 503.65 0.177 286.27 -407.38 1414.7 1.759 13607.9 b5 -35940.4 0.290 28040.0 -125176 53295.4 -1.282 558065 b6 0.469 0.933 5.153 -15.93 16.87 0.09104 1440.2 b7 11.99 0.481 14.94 -35.56 59.54 0.802 60003.0 b8 167.61 0.332 145.03 -293.95 629.17 1.156 466521 b9 0.07657 0.888 0.499 -1.511 1.664 0.154 1026.5 b10 -155.42 0.313 128.48 -564.29 253.45 -1.210 445507 b11 -7.256 0.399 7.399 -30.80 16.29 -0.981 29698.7 b12 -221.88 0.316 184.83 -810.09 366.34 -1.200 3888302.362 b13 -1.202 0.302 0.966 -4.277 1.873 -1.244 20737.7 b14 258.64 0.237 175.30 -299.26 816.54 1.475 3405930.095 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 119 b15 859.51 0.203 530.27 -828.03 2547.1 1.621 7949715.86 b16 25.49 0.126 12.11 -13.06 64.04 2.105 687535 b17 -1613.6 0.184 937.33 -4596.5 1369.4 -1.721 25375258.58 b18 -0.161 0.188 0.09466 -0.462 0.140 -1.699 9044.2 b19 -22.04 0.127 10.50 -55.45 11.36 -2.100 526325 b20 756.40 0.164 412.74 -557.12 2069.9 1.833 5132571.28 these showed that among the rainfall characteristics, number of rain days (x3) is the most valuable variable for the variation in maize yield in the study area indicating that the yield of maize increases as number of rain-days increases. this is followed by interaction of rain days (x12), meaning that there was higher yield of maize under years with high number of rain days than those with low rain days. the rain-days and annual amount over rainfall period has been the major determinant of maize yield in the area. the contributions of rain days and annual amount are followed by those of annual rain days, dates of cessation and date of onset but with insignificant coefficients. the coefficient of multiple determinations (r2) of 0.936 which was computed as 93.6% was observed. this means that 93.6% of the variations in the yield of maize per hectare for the past 25 years in the study area can be explained jointly by the variations in the five identified rainfall characteristics. the remaining 6.4% of the variations in the yield of maize can be attributed to other unexplained factors such as farming practices, soil properties, planting dates, weeds, fertilizer application seed varieties, pest and diseases, harvesting and other rainfall characteristics/climatic factors and technological involvement. 3.6 validation of the regression the figure 1 shows the scatter diagram of predicted yield and the original yield. the figure shows a good correlation between predicted yield and the yield, hence, the ability of the regression equation to predict yield, when all included rainfall indices are available. fig 1. scatter diagram of predicted yield versus yield 4.0 conclusions the study employed the mean, standard deviation and coefficient of variability in analyzing the variations in the study variables. partial correlation and multiple linear regression analysis were the statistical tools used to establish the relationship and effect of rainfall characteristics on maize yield. this study established high variability in rainfall characteristics, which indicates high variability in ../../../user/downloads/azojete143/www.azojete.com.ng balogun, et al. development of crop water production model in a rainfed tropical maize crop cultivation. azojete, 14(sp.i4):111-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 120 maize yield per hectare. additionally, the study showed the suitability of the area for maize production. the study shows that maize experiences moisture deficiency at the early stages (especially early maize) and at the last month of the growing season (late maize) in the study area. in the months of june, july and september rainfall is in excess of the total amount required and that there is relative response of variability in onset/cessation date to variability in rain days. this results in variability in amount of rainfall per rain period. the results also reveal that number of rain days and annual rainfall amount have the strongest influence on maize yield per hectare in the study area. conclusively, a predictive model was established for maize yield in the area. references benoit, p. 1977. “the start of the growing season in northern nigeria,” agricultural meteorology, vol. 18, no. 2, 1977, pp. 91-99. doi:10.1016/0002-1571(77)90042-5 emmanuel, ma. and fanan, u. 2013. effect of variability in rainfall characteristics on maize yield in gboko, nigeria, journal of environmental protection, 2013, 4, 881 887 http://dx.doi.org/10.4236/jep.2013.49103 published online september 2013 (http://www.scirp.org/journal/jep) fao. 2002. agriculture: towards 2015/30. technical interim report. (http://www.fao.org/es/esd/at2015/toce.htm). faostat. 2006. food and agriculture organization, rome, italy. fao, 2013. food and agricultural organization statistics database online. http//fao.org/faostatagateway/golobrowse/q/qc/e. retrieved on 24th december, 2013 ifabiyi, ip. and omoyosoye, o. 2011. rainfall characteristics and maize yield in kwara state, nigeria .indian journal of fundamental and applied life sciences issn: 2231 6345 (online) an online international journal available at http://www.cibtech.org/jls.htm 2011 vol. 1 (3) july-september, pp.60-65 iita 2015. maize http://www.iita.org/maize iken, je. and amusa, na. 2004. maize research and production in nigeria. african journal of biotechnology vol. 3 (6), pp. 302-307. available online at http://www.academicjournals.org/ajb. issn 1684–5315 © 2004 academic journals iita 2009. annual report on maize, www.iita.org/cms/details/maize-project-details.aspx. retrieved on 27th july 2015. ilesanmi, oo. 1972. “an empirical formulation of the onset, advance and retreat of rainfall in nigeria,” journal of tropical climatology, vol. 34, 1972, pp. 17-24. molden, d. (ed.) 2007. water for food, water for life: a comprehensive assessment of water management in agriculture. earthscan, london and international water management institute (iwmi), colombo, sri lanka, pp. 1–39. olaniran, oj. 1983. “the start and end of the growing season in the niger river basin development authority area of nigeria,” malaysian journal of tropical geography, vol. 9, 1983, pp. 49-58. van eijnathen lm. 1965. towards the improvement of maize in nigeria. ph.d. thesis. wageningen, the netherlands. wani, sp., sreedevi, tk., rockström, j. and ramakrishna, ys. 2009. rain fed agriculture past trends and future prospects. international crops research institute for the semi-arid tropics (icrisat) © cab international 2009 vol. 1 world rural observations 2012. 4(1) http://www.sciencepub.net/rural http://www.scirp.org/journal/jep http://www.fao.org/es/esd/at2015/toce http://www.iita.org/maize http://www.academicjournals.org/ajb http://www.iita.org/cms/details/maize-project-details.aspx http://www.sciencepub.net/rural http://www.azojete.com.ng article information 1.0introduction arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 702-713 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 702 original research article design, construction and performance evaluation of chicken defeathering machine m. abubakar, a. zakariyah and a. usman (department of agricultural and bioresources engineering, ahmadu bello university, zaria, nigeria) * corresponding author’s email address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: de-feathering scalding chicken feather release force frf cone abstract the demand for poultry meat world-wide has imposed great responsibility on poultry processing industry, and especially in defeathering operation which is usually achieved manually in nigeria. being a core stage of poultry processing, de-feathering when carried out manually attracts low production rate (the number of birds produced per hour), high time consumption and labour intensity. this study was focused on design, construction and performance evaluation of chicken de-feathering machine using locally available materials. the design was based on market weight of chicken. the selected materials used to fabricate the machine were trimmed tyre rubber, sheet metals, angle iron and shaft. the rubber cross section was 20 mm×20mm and were arranged both on the shaft length (50mm, 70mm, 90mm, 110mm, 130mm and150mm in length) and at the wall of the bottom cone (80mm length). the height of the machine was 1400mm and 500mm×500mm square area. the performance evaluation result showed that chicken variety had effect on the de-feathering efficiency, throughput capacity and energy consumption of the machine. scalding time and scalding temperature did not significantly affect throughput capacity and energy consumption but scalding temperature had significant effect on de-feathering efficiency. maximum mean throughput capacity of 1034 chickens per hour was obtained at 96 % de-feathering efficiency. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction poultry is a domesticated species of birds reared for production of eggs, meat, feathers. poultry is reared in great numbers with chicken being the most numerous. according to federal department of livestock and pest control service, no recent nationwide survey on commercial poultry exist, but expected annual production capacity was estimated as 96,981,001kg dressed broilers and 40,738,698kg dressed culled layers. poultry meat is popularly consumed among non-vegetarians world-wide due to its low fat and calorific content. the relatively increased preference for chicken over some other type of meat has generated keen interests in poultry farming and processing industry. likewise, with the growing world population livestock consumption rate may have to increase correspondingly to meet the effective protein requirement of the world (adetola et al., 2012). therefore, there is need for user-friendly, reliably and efficient poultry processing devices in order to meet up with ever increasing demand of poultry meat. there are numbers of important activities involved in the production of poultry mailto:basaleft@gmail.com mailto:zakariyahabdulbasit@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):702-713. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 703 meat (ready to cook-rtc meat) which contribute to the high cost of poultry meat in the market. slaughtering, de-feathering processes involving scalding and feather plucking, eviscerating, chilling, deboning, packaging and storage are the most important activities in poultry processing industry. scalding is process of soaking slaughtered chickens in hot water to softened the follicle around feathers prior to de-feathering operation. de-feathering process is identified as highly technical and time consuming among the various numbers of poultry processing activities when carried out manually (adetola et al., 2012). in nigeria, poultry processing is done manually, off-farm through local markets. de-feathering process is identified as highly technical and time consuming next to eviscerating process among the various numbers of poultry processing activities especially when carried out manually (dicken and shackelford, 1998). being a core stage of poultry processing, de-feathering when carried out manually attracts low production rate (the number of birds produced per hour), high time consumption and labour intensity. it can equally expose the workers to musculoskeletal disorder, cuts, skin rashes, dermatitis and avian influenza virus. level of human exposure to occupational risk and other health hazard resulting from intense manual operation is significant in scalding and de-feathering operations (adetola et al., 2012). jekayinfa (2007) assessed energy requirement of an automated de-feathering machine comprises an electric motor which drives a shaft supported by a bearing assembly and a belt system which drives the plucking head. the machine consists of a series of rotating plates held at an angle by a thrust plate at each end of the plate bearing. as the discs rotate, the chickens come together, drag in the feathers, grip them and pull them from the bird. adetola et al. (2012) investigated the mechanized scalding and de-feathering processes of both local and exotic birds, where effective and efficient defeathering was achieved on local chicken at a scalding temperature between 80oc – 85oc for 5min immersion duration, while that of exotic chicken took place between 65oc – 70oc for 3 min immersion duration. feather retention force (frf) of each categories of bird also varies significantly (adetola et al., 2012). in order to measure up with increasing demand for poultry meat, there is need for de-feathering machine in our local markets. also, to avoid accidents and infections from poultry carcasses which may occur during some of the processing operations, there is need for user-friendly, reliably and efficient poultry processing devices (ralph, 1980; scolt, 2000). though de-feathering machines exist in most developed countries, currently, they are not common among the local chicken processors. this is due the cost implication of the machines. adetola et al. (2012) reported that household de-feathering machine designed to handle less than 5 birds sold for between #83200 ($532.5) and #480000 ($3000), and that is quite expensive for an average nigerian. it is paramount to address the de-feathering problem associated with poultry processing industries. this calls for effective mechanization of the process which will support quality, safe, ergonomic and economic operation (adetola et al., 2012). the general objective of the study is to design, construct and evaluate the performance of a chicken de-feathering machine. 2. materials and methods 2.1 materials the materials used in the fabrication and performance evaluation of the chicken de-feathering machine include 1.5mm sheet metal, angle iron 50 mm × 50 mm, shaft of 25mm diameter and 1050 mm length, transmission belt of 1143 mm, a pulley size of 250mm, three bands shaft defeathering finger 20 mm × 20 mm cross section of 150 mm to 50 mm long, ball bearing 6305, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar, et al: design, constructionand performance evaluation of chicken de-feathering machine. azojete, 15(3):702-713. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 704 hitches and bolts and nuts. instrumentations used were stopwatch, thermometer and digital weighing balance. 2.2 methods the chicken de-feathering machine was designed and fabricated at the department of agricultural and bio-resources engineering, ahmadu bello university, zaria, nigeria. the procedures for the design, fabrication and performance evaluation including cost implication of the chicken de-feathering machine are as followed. 2.2.1 establishment of design parameters 2.2.1.1 survey method and physical properties of chicken questionnaires were administered at some selected abattoirs in zaria (sabon gari abattoir centre and samaru market abattoir) and kaduna (railway station market). the questionnaire was designed to determine the volume of chicken, scalding temperature, average scalding time, plucking time and cost of processing the chicken. feathers of various categories of poultry specifically layers, broilers, local chicken and guinea fowl were experimented by soaking respective feather in the hot water at specific temperature range of 65°c 70°c. this temperature was in accordance with scalding temperature obtained from conducted survey and scalding temperature used as operational parameter in chicken processing (adetola, et al., 2012). angle of repose of the wet feather of layers and broilers was determined. body parameters viz. neck length, back length, kneel length, wing length, breast width, thigh length and shank length, of eight (8) weeks old broilers at national animal production research institute, napri zaria, were obtained. 2.2.1.2 the feather plucking force the feather retention force of non-scalded local chicken was selected as 41.53n. because, higher force is required to de-feather local chicken under the same condition with exotic chickens. this is in accordance with the investigation into mechanized de-feathering process and optimal scalding temperature of exotic and local birds in southwestern nigeria (adetola et al., 2012). also dickens and shackelford (1987), the percentage reduction in feather retention force frf ranges from 18% to 81% after 2.5 min, 56oc scalding. design calculation in the course of this design, the following design consideration were observed. these are; power requirement, availability of raw materials, de-feathering speed, plucking force, weight of chicken, de-feathering capacity, quality of the material, cost of material and safety 2.2.2.1 selection of de-feathering rubber fingers rubber was used as the de-feathering finger because chicken is fleshy. based on available material, trimmed tractor tyre was used as de-feathering finger because of its hardness, rebound resilience, tear and tensile strength. the rubber finger is 20 mm by 20 mm in cross section. 2.2.2.2 determination of power required to pluck feather from the follicles the torque required to detach feather from follicles was calculated using the equation (1) due to kurmi and gupta (2006) and stated as follows: t = f × r (1) http://www.azojete.com.ng mailto:basaleft@gmail.com mailto:zakariyahabdulbasit@gmail.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):702-713. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 705 where: t = torque (knm), r = mean radius of de-feathering chamber (0.175m) f = total force on the shaft (n) total force required by the shaft = frf + wr + ws where: frf = feather retention force (plucking force) (n) wr = weight of rubber around the shaft (n) ws = weight of shaft (n) 2.2.2.3 feather retention force (frf) according to dickens and shackelfold (1987), frf can be estimated as follows �round���� = n�9d7)uou ��rdo � 9d7)uou ��rdo n�9d7)uou ��rdo × �� (2) where: unscalded force = 41.53n (adetola et al, 2012) % reduction = 80% (dickens and shackelfold, 1987) thus, the feather retention force frf is selected to be 10n. for ten chickens, frf is 100n. 2.2.2.4 power requirement according to kurmi and gupta (2006), the power required for de-feathering is expressed as; ���or � = ���㭀 �� (3) where: n = shaft speed (320 rpm), p = power requirement (w) the speed of 320 rpm was selected in accordance with an investigation of optimized operational parameters for a chicken slaughtering system in vietnam (nguyen et al., 2011). t = torque (34.77 nm) power p = 1165 w (1.56 hp) 2.2.2.5 pulley size determination the drive speed is the criteria for which the pulley sizes were based. single groove pulley was used on the de-feathering shaft and this pulley was driven by electric motor. kurmi and gupta (2006) expressed the ratio of pulley size as follows; n1d1 = n2d2 (4) where: n1 = speed of the motor (1400rpm) n2 = speed of de-feathering (320rpm) d1 = diameter of motor pulley (50mm) d2 = diameter of de-feathering pulley. shaft pulley of 250 mm pulley diameter was suitable. 2.2.2.6 determination of belt size the selection of belt sizes depends on the length thickness and properties of the materials from which the belt is made. the belt thickness and properties are based upon the power to be transmitted. kurmi and gupta (2006) stated the length of the belt as follows file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar, et al: design, constructionand performance evaluation of chicken de-feathering machine. azojete, 15(3):702-713. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 706 � = �ʹ� ��൅� �� u � ��u � �ʹ (5) where: l = effective belt length (mm) c = centre distance from driven to drive pulley (330 mm) d = diameter of de-feathering pulley (250 mm) d = outside diameter of motor pulley (50 mm) estimated length from motor to shaft of 1161mm and the belt length of 46 inches were selected. 2.2.2.7 determination of minimum shaft diameter for de-feathering the determination of the correct shaft diameter and length is such that it can transmit required power under the stated operating and loading conditions. it also involves material selections so that the stated conditions are economically and efficiently met. kurmi and gupta (2006) stated the equation for determining the minimum size of solid shaft having little or no axial loading as u� = �� �×t�7h ������� � ���㭀��� (6) where: d = diameter of shaft (mm) π = 3.142 τs = design stress of mild steel (56 × 106 n/m2) (kurmi and gupta, 2006) km & kt = combine shock and fatigue factor applied to bending and torsional moment respectively (kb = 2.0 & kt = 1.5) t = torsional moment (34.77 nm) mb = maximum bending moment (48.7 nm) the minimum shaft diameter was calculated as 21.6 mm. based on the available shaft size, 25mm shaft size was selected. 2.2.2.8 hopper design the hopper was made into frustum of cone, basically to occupy ten (10) chickens sequentially. the chickens were fed to the machine through the hopper, and had downward flow aided by gravity. the average volume 2 kg – 3 kg chicken was determined as approximately 1900 cm3. the hopper was; h = height of the cone (500 mm) d = large radius of the cone (500 mm) d = small radius of the cone (360 mm) 2.2.2.9 bottom cone dimensions the bottom cone aids the de-feathering and temporary storage of dressed chicken immediately after de-feathering. the bottom cone was constructed to occupy two chambers; the defeathering chamber and the dressed carcass chamber. the de-feathering chamber was made of arrangement of de-feathering rubbers around a vertical revolving shaft and at the wall of the cone. the de-feathering rubber fingers were 18 in number which formed 6 bands around the shaft, each band having 3 rubber fingers of equal length. the space between the rubber fingers along the longitudinal axis of the cone’s wall was selected based on back length (bl) of eightweek broiler at national animal production research institute, napri. the space between the http://www.azojete.com.ng mailto:basaleft@gmail.com mailto:zakariyahabdulbasit@gmail.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):702-713. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 707 revolving fingers and the wall of the cone was limited to 90mm which was selected in accordance with the breast width (bw) of the eight weeks broiler at napri. the space enables the easy and downward movement of the chickens, and sufficient rubbing through the successive contact of the fingers. therefore, the dimension of the de-feathering chamber was selected as; h = height of the cone (500 mm) d = large diameter of the cone (500 mm) d= small diameter of the cone (300 mm) 2.2.2.10 cross section for dressed chicken carcass the design was made for at least average of five chickens, therefore, volume of chickens = 5 × 1900 = 10000mm3 volume of chicken = π h � r� � r� � rr (7) (www.analyzemath.com) where: h = height of the cone (200 mm) r = large radius of the cone (150 mm) r = small radius of the cone (mm) π = 3.142 solving the quadratic equation, r = 100 mm, diameter of 200 mm. 2.3 construction procedure of the machine construction of chicken de-feathering machine was carried out at agricultural and bio-resources engineering department workshop, abu, zaria, nigeria. plate 1 and plate 2 show the fabricated and the orthographic views of the de–feathering machine. the various components of the machine are hopper, bottom cone, feather outlet, shaft, rubber fingers, pulley and belt system and electrical motor. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar, et al: design, constructionand performance evaluation of chicken de-feathering machine. azojete, 15(3):702-713. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 708 2.4 experimental setup the fabricated chicken de-feathering machine was evaluated at chiromawa poultry processing market, a registered market along zaria road, kano state. eighty chickens each for both local and exotic chicken were used in the evaluation. two level of chicken varieties (local and exotic chicken), two level of scalding time (3 minutes and 5 minutes) and two levels of scalding temperature (50°c and 60°c) were considered in a complete randomized design (crd). scalding equipment was adopted for the experiment. the chickens were voluntarily obtained from respective volunteers at the market, weighed, slaughtered, scalded and de-feathered by the machine. the results were subjected to analysis of variance anova test using statistical analysis software (sas) application. 2.5 operational and working principles the chicken is feed into the machine through the hopper, after which the chicken move to defeathering chamber where set of de-feathering rubber fingers were arranged to aid easy and effective de-feathering process. the de-feathering process is achieved when chicken revolved through the spaces between the adjacent wall fingers. in the same pass, the de-feathered chickens were finally deposited at dressed carcass chamber and eventually removed through the carcass outlet. the de-feathering machine works on the principle of impact, rubbing and collision. the revolving shaft exerts impact force on the chicken and subsequently creates rubbing action. this is in accordance with automated method of de-feathering reported by jekayinfa (2007) and investigation on optimum scalding temperature and de-feathering process by adetola et al. (2012). the degree of rubbing action depends on the area of contact of the rubber and roughness of the surface of the rubber. also, collision between the studded rubber at the wall of the cone and the chicken, indeed contribute significantly to the de-feathering processes. the impact, rubbing and collision lead to plucking of the feather. the machine was powered by 2 hp electric motor. plate 1. chicken de – feathering machine plate 2. orthographic views of de–feathering machine http://www.azojete.com.ng mailto:basaleft@gmail.com mailto:zakariyahabdulbasit@gmail.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):702-713. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 709 2.6 performance evaluation the performance evaluation was carried out at chiromawa along zaria road kano state, where eighty local and exotic chicken each were used. the chickens were manually slaughtered, and the blood duly drained for some minutes. then the slaughtered local chickens were scalded for 50 °c and 3 min scalding time (jekayinfa 2007). thermometer and stopwatch respectively were used to determine the scalding water temperature and time. subsequently, the chickens were weighed (w1), then introduced into the machine for de-feathering process as shown in plate 3. stopwatch was started as soon as the chickens were fed to the machine to determine the defeathering time. the chickens were removed from the machine after the de-feathering process and re-weigh to determine its weight after de-feathering (w2). remaining feathers were manually plucked and the weigh again to determine its final weight (w3). the procedure was repeated for exotic chickens. performance parameters such as de-feathering efficiency, defeathering time, throughput capacity and energy consumption were determined. 2.6.1 de-feathering efficiency this is the measure of amount of feather plucked by the machine. it is ratio of weight of plucked feather to the total weight of chicken’s feather (adejumo et al., 2013). it is express as follows �o = ����� ����� × ��� (9) where: w1 = initial weight of chicken before de-feathering (n) w2 = weight of the chicken after de-feathering (n) w3 = weight of the de-feathered chicken after manual removal of remaining feather (n) 2.6.2 de-feathering time, t this is the duration of de-feathering operation measured by a stopwatch in seconds. 2.6.3 throughput capacity, tc this is measure of numbers of chicken de-feathered in an hour. it is expressed as follows 㭀d = �u � ��r� (10) where: nd = number of chickens de-feathered t = de-feathering time (hour) plate 3: method of feeding scalded chicken to the machine. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar, et al: design, constructionand performance evaluation of chicken de-feathering machine. azojete, 15(3):702-713. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 710 2.6.4 energy consumption, ec this is the amount of electrical energy used for the de-feathering operation. it measured in kwh. �d = ���� × � ���� (11) where, ec= energy consumption (kwh) t = de-feathering time (sec). 3. results and discussion the design and construction of chicken de-feathering machine was completed and the dimensions of rubber finger of the machine, result of the performance evaluation and cost effectiveness are presented below. 3.1 dimension of de-feathering fingers table 1 shows the dimension of de-feathering fingers. rubber material was selected in order to avoid likely bruises that might be incurred during the operation. the rubber cross section of 20 mm × 20 mm was selected for considerable strength and flexibility to sustain the effect of load arising from the chickens which were fed by gravity. the rubbers around the shaft were selected as 150 mm, 130 mm, 110 mm, 90 mm, 70 mm, and 50 mm length. wall fingers were selected as 80mm length, and were arranged in four rubber fingers band at five equally spaced points along the length of shaft, making the total number of twenty (20) rubbers. the three band rubber fingers were constructed around the shaft mainly to increase the number of contacts with the chicken, thereby aiding the de-feathering of the machine. the distance between the adjacent rubbers around the shaft was selected as 50 mm. this prevents chickens from getting toward the shaft during operation. the distance between the adjacent rubbers at the wall of the cone enables optimum freedom for the chicken to flow downward. the flow is also influence by tapered arrangement of rubber fingers around the shaft. 3.2 de-feathering efficiency table 2 shows the mean de-feathering efficiency of the machine. exotic chicken recorded highest mean de-feathering efficiency of 96 % at 60 oc scalding temperature at both 3 minutes and 5 minutes scalding time. this was slightly higher than machine efficiency of 95 % recorded by adeyinka and olawale (2015). analysis of variance (anova) result showed that scalding temperature and chicken varieties were significant while scalding time was not significant on detable 1: dimension of de-feathering fingers de-feathering finger dimension (mm) distance between adjacent rubbers (mm)length cross section area (mm2) shaft finger 150 20×20 50 shaft finger 130 20×20 50 shaft finger 110 20×20 50 shaft finger 90 20×20 50 shaft finger 70 20×20 50 shaft finger 50 20×20 50 wall fingers 80 20×20 180 to 250 http://www.azojete.com.ng mailto:basaleft@gmail.com mailto:zakariyahabdulbasit@gmail.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):702-713. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 711 feathering efficiency. local chickens recorded least de-feathering efficiency of 93 % at 50 oc scalding temperature for both 3 minutes and 5 minutes scalding time. this may be attributed to the age of the chicken since exotics chickens are mostly under intensive care and matures early. table 2: mean de – feathering efficiency mean de-feathering efficiency (%) scalding temperature (°c) 50 60 scalding time (mins) 3 5 3 5 birds local 93 93 95 94 exotic 95 95 96 96 3.3 de-feathering time table 3 shows the mean de-feathering time of chicken de-feathering machine. exotic chickens recorded the least mean de-feathering time of 3.6 seconds at 60 °c scalding temperature and 5 minutes scalding time. while local chickens recorded highest de-feathering time of 4.47 seconds at 50 °c scalding temperature and 5 minutes scalding time. this may be attributed to ease in plucking the feather of exotic chicken since exotic chicken required lower feather retention force frf (adetola et al., 2012). table 3: mean de-feathering time mean de-feathering time (sec) scalding temperature (°c) 50 60 scalding time (mins) 3 5 3 5 birds local 4.33 4.47 4.4 4.13 exotic 3.59 3.63 3.74 3.6 3.4 throughput capacity table 4 shows the mean throughput capacity of the de-feathering machine. the exotic chickens recorded highest mean throughput capacity of 1034 chickens/hr at 60 °c scalding temperature and 5 minutes scalding time while local chickens recorded least mean throughput capacity of 825 chickens/hr at 50 °c scalding temperature and 5 min scalding time. analysis of variance anova result showed that chicken varieties were significant on throughput capacity while both scalding temperature and scalding time were not significant. table 4: mean throughput capacity (chickens/hr) mean throughput capacity (chickens/hr) scalding temperature (°c) 50 60 scalding time (mins) 3 5 3 5 birds local 875 825 879 904 exotic 1023 997 971 1034 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar, et al: design, constructionand performance evaluation of chicken de-feathering machine. azojete, 15(3):702-713. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 712 3.5 energy consumption table 5 shows the energy consumption of the machine. generally, the energy consumption of exotic chickens was lower than the local chicken. this may be attributed to early maturity of exotic chickens over local ones and succulent tendency of follicle of exotic chickens due to the chicken management practice. the highest and least energy consumption of 1.42 whr and 1.14 whr respectively were recorded. analysis of variance anova result showed that chicken varieties were significant while scalding temperature and scalding time were not significant on energy consumption. table 5: mean energy consumption mean energy consumption (whr) scalding temperature (°c) 50 60 scalding time (mins) 3 5 3 5 birds local 1.37 1.42 1.39 1.31 exotic 1.14 1.17 1.19 1.14 3.2.4 cost evaluation the machine costs an estimated sum of #52,080 which is less expensive as compared to other imported poultry processing equipment with the cost ranging from #83,200 ($532.5) and #480,000 ($3000) (adetola et al, 2012) which are quite expensive for average nigerians machine. 4. conclusion the design, construction and performance evaluation of the chicken de-feathering machine was completed. reliable data were attracted based on the scope of the project. the machine was fabricated from locally sourced materials, to ease interchangeability of parts. the rubber configuration around the wall of the cone and the shaft ensure appreciable degree of contact with the chicken, which guarantee efficiency of the machine. the performance evaluation showed that, using scalded chicken, the machine recorded minimum mean de-feathering time of 3.6 seconds and maximum mean de-feathering efficiency of 96%. the mean throughput capacity of 1034 chickens per hour was recorded. references adejumo, aod., adegbite, am., brai, s., oni, ov. and opadijo, oo. 2013. the effects of machine and poultry parameters on feather plucking. international journal of engineering research and applications, 3(6): 161 – 166. adetola, so., onawumi, as. and lucas, eb. 2012. investigation into mechanized de-feathering process and optimal scalding temperature of exotic and local birds in southwester nigeria. transnational journal of science and technology, 2(3): 87 – 96. adeyinka, aa. and olawale, jo. 2015. development and performance evaluation of chicken defeathering machine for small scale farmers. journal of advanced agricultural technologies, 2(1): 71 – 74. http://www.azojete.com.ng mailto:basaleft@gmail.com mailto:zakariyahabdulbasit@gmail.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):702-713. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: basaleft@gmail.com, zakariyahabdulbasit@gmail.com 713 dickens, ja. and shackelfold, ad. 1987. feather-releasing forces related to stunning, scaling time, and scalding temperature. poultry science, 67(7): 1069 – 1074. jekayinfa, so. 2007. energetic analysis of poultry processing operations, leonado journal of sciences, 10: 77 – 92. kurmi, rs. and gupta, jk. 2006. a textbook of machine design. 14th edition, schand, new delhi, 509 – 555. nguyen, vh., doan hm. and dang, ts. 2011. an investigation of optimized operational parameters for a chicken slaughtering system in vietnam, international transaction journal of engineering, management and applied sciences and technologies, l 2(4): 430. ralph, m. 1980. food processing technology. ellis horwood publ. cambridge, uk. scolt, mr. 2000. disinfection of poultry carcasses during scalding and immersion chilling www. knasecoinc.com accessed on july 10, 2012 www.analyzemath.com/geometry_calculators/surface-volume&-frustum.html. accessed on june 26, 2012 http://www.analyzemath.com/geometry_calculators/surface-volume&-frustum.html. accessed on june 26 http://www.analyzemath.com/geometry_calculators/surface-volume&-frustum.html. accessed on june 26 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):188-192 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 179 original research article ergonomic analysis of a developed wheelchair using creative algorithm f. i. ashiedu* and m. o. okwu (department of mechanical engineering, federal university of petroleum resources, effurun, warri, delta state, nigeria) *corresponding author’s email address: ashiedu.ifeanyi@fupre.edu.ng 1.0 introduction the recent developments of science and technology has drastically changed the way a normal person lives his/her life, modern technology has made it possible for the discovery of many functional area of life. for instance, transportation, business transactions and education has been made easy. technology has really made our lives better also made our lives easier, faster, better and more fun, but there are certain categories of people who have not been able to fully benefit from this development, on particular disabled people with limited mobility are still living a miserable life. rohit et al. (2013). this stem from their inability to access basic skill acquisition centres arising from the shortage of infrastructural facilities needful for accessibility and mobility article information abstract mobility aids are important for disabled and aged patients for transportation or replacement for walking especially in indoor and outdoor environments. to guaranty the effective and efficient use of these mobility aids devoid of any form of epidemiological conditions, the level of comfort and ease of use must be ascertained. in this research, a simple and affordable wheel chair designed in previous work was analyzed to support patients in terms of ease and comfort of use. the method adopted for this study was the use of creative algorithm. anthropometric measures were considered in the dimensioning of the wheel chair seat. it was necessary to test how ergonomically comfortable the wheelchair was in use by deploying an effective decision metrics tool known for dealing with complex decision-making process and may aid the decision maker to set priorities and make the best decision. by reducing complex decisions to a series of pair wise comparisons, and then synthesizing the results. our findings showed an average ergonomic rating of 0.62 which indicate a relatively high degree of comfort ability in the use of the wheelchair. the use of these wheelchairs would greatly improve the community of people who have lost some means of independent mobility thereby leading to an improvement in their self-esteem. this will enable them pursues their daily vocation and life goals. the wheel chair will also serve as a novel for medical facilities in hospitals and help facilitate movement of disabled patients in homes, schools, entrepreneurial centres and hospitals. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 29 march, 2019 revised 28 august, 2019 accepted 05 september, 2019 keywords: mobility anthropometry creative algorithm pair wise ahp. mailto:ashiedu.ifeanyi@fupre.edu.ng http://www.azojete.com.ng ashiedu and okwu: creative algorithm for effective analysis of a developed wheelchair. azojete,16(1):188-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 180 requirements. this turns most paraplegics into unemployable people, thereby they tend to end up as beggars along major road and markets places under awful circumstances reducing the quality of life of these set of people which invariably drops the nation gross domestic product (gdp) which is a critical economic index for measuring the strength of any nation (ashiedu and igboanugo, 2013). independent mobility is without doubt essential to individuals of any age as children without safe and independent mobility are denied beneficial learning opportunities, which places them at a disadvantage when compared with their peers. adults are also not left out as those who lack an independent means of locomotion are less self-sufficient, which can lead to a negative self-image and depression. a lack of independent mobility at any age, places additional obstacles in the pursuit of vocational and educational goals richard et al. (2004) a wheel chair aims to provide aid to those physically challenged and aged persons by providing them with some sort of mobility which would greatly improve their living. a wheelchair is a type of chair usually used by disabled people. it is moved either manually (by pushing the wheels with the hands, or pushed from behind with handles by somebody who is not sitting in the wheelchair) or by automated systems such as electric motors which can be controlled by the wheelchair user (the person sitting in the chair) or by somebody walking behind or beside the wheelchair if the wheelchair user needs help to move their wheelchair. wheelchairs are used by people for whom walking is difficult or impossible due to illness, injury, or disability. it comes in a wide variety of formats to meet the specific needs of their users. they may include specialized seating adoptions, individualized controls, and may be specific to activities, as seen with sports wheelchairs and beach wheelchairs. the most widely recognized distinction is between powered wheelchairs ("power chairs"), where propulsion is provided by batteries and electric motors, and manually propelled wheelchairs, where the propulsive force is provided either by the wheelchair user/occupant pushing the wheelchair by hand ("selfpropelled"), or by an attendant pushing from the rear. wheel chair as a support device can ease the lives of many disabled people, particularly those with severe impairments by increasing their range of mobility (nipanikar et al., 2013). this research centres on design, development and analysis of a wheelchair for disabled (physically challenged) individuals and aged people to help facilitate a large amount of independence for those who can neither walk nor operate a mechanical wheelchair alone as it requires great effort and help of other people. the first wheelchairs were self-powered, and worked by a patient turning the wheels of their chair manually (mohan et al., 2012), bellis, 2018) ). generally, wheel chair system find variety of applications which includes but not limited to; hospitals assisted homes and sports. wheel chairs can also be adopted during emergency situation like road accidents, fire accidents, air accidents, maternity emergency and physical disorders. 1.1 several works done on manual wheelchair nikhil et al. (2017) designed and fabricated a lever propelled wheelchair. the paper was of the opinion that many people who are disabled due to some injuries or other chronic diseases may not be able to wheel a conventional wheelchair. in their design they adopted a lever for transmitting the force to move the wheel chair instead of applying the force on the push rim. the wheelchair was designed in such a way that it requires less efforts and it is cheaper than the other advanced wheelchairs. pezzuti et al. (2006) suggested that during the last decades sport activities for disabled people are practiced by many athletes, both amateurs and professionals. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 188-192. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 181 they designed a chair with a self-adjustable cushion in order to give the possibility of playing safely. many factors were taken into account such as athletic performance, safety of player and opponents, comfort and reliability. in their article that employed the application of cadmultibody techniques to optimize the wheelchair for basketball. the target of their investigation was to give athletes the possibility of performing quick forward accelerations without rollover tendencies. ebrahimi et al. (2016) was of the opinion that biomechanical aspects of wheelchair design play an important role in physical activity and social participation of disabled individuals. in their article they reviewed key biomechanical features of wheeled mobility devices including propulsion methods, overuse injuries, assistive technologies, prevention of pressure ulcers, and tire and frame design. khaled (2016) proposed the design and development of a reconfigurable wheelchair for rehabilitation and self-assistance to fit the size of a seven years old child (average 35 kg weight). though the proposed prototype was developed to fit a child, it can be resized, after considering variations in weight and size, to fit an older adult. their design has a mechanism that enables the user to transform from sit-to-stand (sts) posture and vice versa. with the help of the developed wheelchair, the user would also be able to adjust the posture of his upper body using an adjustable back support. this configuration would allow the user to use the wheelchair as a mobility device as well as for rehabilitation purposes without the need of external support. the availability of sts and back adjustment mechanisms would allow the user to do regular exercising which would enhance blood circulation as sitting for long periods inflates lower limbs disability. the proposed configuration would help in enhancing the functional capabilities of end-users allowing for increased independence and ultimately quality of life. other interesting research done on electrical wheel chair to support movement of disabled people include cooper (1998); razak and shehab (2013); nida and riaz (2014); swapna et al. (2016); rakshith et al. (2017) and alexander et al. (2016). 2. materials and method 2.1 design process the seat was designed ergonomically, considering all the required anthropometric measurements. parameters considered along with their measures are as shown in table 1. table 1: anthropometric data (ashiedu & igboanugo, 2013) s/n parameters brief description dimensions (mm) 1 sitting height distance between the buttock and top of the head in sitting 936 2 popliteal height distance between the underside of the foot to the underside of the thigh at the knees in seating position 469 3 knee height (sitting) distance between the sole of the foot to the anterior surface of the thigh with the angle and knee each flexed to 90° 579 4 buttock to knee length distance between the buttock and knee 590 5 hand length distance between the wrist and the top of middle finger. 220 6 arm rest height distance between the underside of the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ashiedu and okwu: creative algorithm for effective analysis of a developed wheelchair. azojete,16(1):188-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 182 thigh to the underside of the arm 7 hip breath maximum horizontal distance across the hips in the sitting position 439 8 shoulder breath maximum horizontal breath across the shoulders, measured to the protrusions of the deltoid muscles. 480 9 elbow to wrist length distance between the elbow and wrist 10 angle of back inclination angle between the seat and back rest 110° 2.2 evaluation metrics the parameters that were taken into consideration in the design stage were also observed during analysis stage for evaluating the total performance indicators of the system. the metrics considered in the design and fabrication of a smart wheel chair includes: goal and objective, time efficiency, path navigation, precision, and strength/energy efficiency. the weighted value shows the order in which each metrics is important to the design. the weighted values of each metrics were obtained through a process known as analytical hierarchical process (ahp). figure 1 developed wheelchair 2.3 analytic hierarchy process (ahp) the analytic hierarchy process (ahp) is one of multi criteria decision making method that was originally developed by prof thomas saaty in 1980. it is known as an effective tool for dealing with complex decision making and may aid the decision maker to set priorities and make the best decisions. by reducing complex decisions to a series of pair wise comparisons, and then synthesizing the results, the ahp helps to capture both subjective and objective aspects of a decision. in addition, the ahp incorporates a useful technique for checking the consistency of the decision maker’s evaluations, thus reducing the bias in the decision-making process. the qualitative assessment of the ergonomic factor (er) is provided below. if er is between 0.10 – 0.29, then the wheelchair is very uncomfortable if er is between 0.30 – 0.49, then the wheelchair is slightest uncomfortable http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 188-192. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 183 if er is between 0.50 – 0.65, then the wheelchair is comfortable if er is between 0.66 – 0.78, then the wheelchair is slightest comfortable if er is between 0.80 – 1.00 , then the wheelchair is very comfortable the standard verbal judgement scale generally accepted for use in the ahp subjective and objective is presented in table 2. table 2: a pair wise comparison criteria s/n verbal judgement numeric value 1 extremely important 9 2 very important 7 3 moderately important 5 4 moderately less important 3 5 equally important 1 2.4 analytic hierarchy process (ahp) the analytic hierarchy process (ahp) is one of multi criteria decision making method that was originally developed by prof thomas saaty in 1980. it is known as an effective tool for dealing with complex decision making and may aid the decision maker to set priorities and make the best decision. by reducing complex decisions to a series of pair wise comparisons, and then synthesizing the results, the ahp helps to capture both subjective and objective aspects of a decision. in addition, the ahp incorporates a useful technique for checking the consistency of the decision maker’s evaluations, thus reducing the bias in the decision-making process. 2.5 ahp algorithm the ahp considers a set of evaluation criteria, and a set of alternative options among which the best decision is to be made. it is noteworthy that, since some of the criteria could be contrasting, it is not true in general that the best option is the one which optimizes each single criterion, rather the one which achieves the most suitable trade-off among the different criteria (saaty, 1980) . the ahp generates a weight for each evaluation criterion according to the decision maker’s pair wise comparisons of the criteria. the higher the weight, the more important the corresponding criterion. next, for a fixed criterion, the ahp assigns a score to each option according to the decision maker’s pair wise comparisons of the options based on that criterion. the higher the score, the better the performance of the option with respect to the considered criterion (saaty, 1980) . in this analysis, the weight gotten through the ahp process is used to develop the intelligence of the system. to obtain the weighted value of each metrics using the analytic hierarchy process the following steps were followed: develop a model for the decision: break down the decision into a hierarchy of goals and criteria; derive priorities (weights) for the criteria: the importance of criteria are compared pair wise with respect to the desired goal to derive their weights; check the consistency of judgments; that is, a review of the judgments is done in order to ensure a reasonable level of consistency in terms of proportionality and transitivity. the model architecture is shown in figure 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ashiedu and okwu: creative algorithm for effective analysis of a developed wheelchair. azojete,16(1):188-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 184 figure 2: block diagram of ahp model 2.5 deriving priorities (weights) for the criteria this step involves the derivation of the relative priorities (weight) for the criteria. it is referred to as relative because they are measured with respect to each other. the pair wise comparison criteria are presented in table 3 for ease of reference. table 3: a pair wise comparison criteria 2.6 ergonomic evaluation of the wheelchair ergonomics in this context is the process of designing the wheelchair so that it fits the people who use it. it is a branch of science that aims to learn about human abilities and limitations, and then apply this learning to improve people’s interaction with products systems and environment (dohrmann consulting, 2014) . in evaluating ergonomics and comfort, kapica and grbac, (1998) suggested that the basic principle of a comfortable seat is contained in the system where the sitting bones take the body weight off, while the feet are not loaded and the spine maintains its natural posture. construction of upholstery, shape and hardness of the sitting surface, degree of the seat and backrest deformity, etc. along with the product’s overall construction determine the sitting comfort and level of tiring (kapica & grbac, 1998) . the following objectives were considered in evaluating how ergonomically balanced the smart wheelchair developed in figures 1 and 2 include: back rest, seat, arm rest, leg rest. s/n verbal judgement numeric value 1 extremely important 9 2 very important 7 3 moderately important 5 4 moderately less important 3 5 equally important 1 goals criteria 2 criteria 3criteria 1 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 188-192. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 185 2.7 analytic hierarchy process analytic hierarchy process was employed is used to obtain the weighted value of each objective. table 3: a pair wise comparison criteria s/n verbal judgement numeric value 1 extremely important 5 2 very strongly more important 4 3 strongly more important 3 4 moderately less important 2 5 equally important 1 taking four (4) objectives stated above, we then have a 4 by 4 matrix. the diagonal elements of the matrix are always 1, we then proceed to fill the lower triangular matrix and upper triangular matrix. table 4: 4x4 criteria matrix back rest seat arm rest leg rest back rest 1 0.5 0.25 0.33 seat 2 1 0.2 0.5 arm rest 4 5 1 2 leg rest 3 2 0.5 1 sum 10 8.5 1.95 3.83 if bij is the element of row i and j of the matrix, the upper diagonal matrix is the reciprocal of the value filled in the lower triangular matrix. it’s given by the formula bij = 1 bij (2) 2.8 normalized matrix (bnorm) normalizing the matrix means to divide each element in every column by the sum of that column. this is given by the formula: bij = bij n=1 m bij� (3) table 5 shows the normalized criteria comparison matrix table 5: normalized criteria comparison matrix back rest seat arm rest leg rest back rest 0.1 0.06 0.13 0.09 seat 0.2 0.12 0.10 0.13 arm rest 0.4 0.59 0.51 0.52 leg rest 0.3 0.24 0.26 0.26 the criteria weight vector w (that is a m-dimensional column vector) is built by averaging the entries on each row of anorm. it is given by wj = i=1 m alk� m (4) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ashiedu and okwu: creative algorithm for effective analysis of a developed wheelchair. azojete,16(1):188-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 186 table 6: criteria weight matrix 2.9 checking for consistency the procedure in checking for consistency determine a weight sum vector, ws {ws} = [c] {w} (5) weight sum vector matrix obtained [0.38, 0.56, 2.09, 1.07]. to find the consistency vector, {consis} = {ws}{ 1 w } (6) consistency vector matrix average of the elements of {consis}, is denoted as λ λ = 4.03+4.05+4.14+4.07 4 = 4.07 (6) determine the consistency index, ci ci = (λ−n) (n−1) (7) where n is the number of criteria. ci = (4.07−4) (4−1) = 0.023 (8) determine the consistency ratio, cr cr = ci ri (9) if cr < 0.10, the rankings are consistent if cr ≥ 0.10, the comparisons should be recalculated. consistency index, ri (n=4) = 0.95, (saaty, 1980) cr = 0.023 0.95 = 0.024 (10) therefore, the ranking is consistent. three (3) persons were required to sit on the wheelchair for five (5) hours and were asked to rate the wheelchair based on their perceived level of comfort or distress. 2.10 mathematical model for evaluating ergonomic rating er = i=1 n wi� mi (11) where; er = ergonomic rating back rest 0.09 seat 0.14 arm rest 0.51 leg rest 0.26 4.03 4.05 4.14 4.07 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 188-192. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 187 mi = metrics wi = weight of the metrics i=1 n wi� mi ≤ 1 (12) qualitative assessment of the ergonomics factor (er) if er is between 0.10 – 0.29, then the wheelchair is very uncomfortable if er is between 0.30 – 0.49, then the wheelchair is slightest uncomfortable if er is between 0.50 – 0.65, then the wheelchair is comfortable if er is between 0.66 – 0.78, then the wheelchair is slightest comfortable if er is between 0.80 – 1.00, then the wheelchair is very comfortable table 7: verbal judgement scale s/n description numeric value 1 i feel completely relaxed 0.8-1.0 2 i feel quite comfortable 0.6-0.79 3 i feel uncomfortable 0.4-0.59 4 i feel restless 0.2-0.39 7 i feel pain 0.1-0.19 table 8: performance evaluation from equation (16) expanding equation 11 further, er = wbrmbr+wsms +warmar +wlgmlg (12) by further substitution, 1st er = 0.62, 2nd er =0.60 and 3rd er = 0.64. average er = 0.62 the ergonomic rating score for the overall system after evaluation is completed by three individuals gives a score of 0.62. this shows that the wheelchair is comfortable. 3.0 results and discussion the ergonomic rating of the developed smart wheel chair has been evaluated successfully using the ahp process. each criterion such as the back rest, arm rest, leg rest and hand rest were calculated, and the appropriate weight was assigned. the weight obtained was used for ergonomic assessment of the wheel chair using the mathematical model developed (eq. 1-12) and the information available in tables 1 to 7. the ahp process was applied to obtain the weight of each performance objectives such as the back rest, arm rest, leg rest and hand rest of the smart wheel. the pair wise comparison criteria are the verbal judgement and numerical values when comparing the performance objectives framework of the design. the four (4) performance objectives were compared which forms a 4x4 matrix as shown in table 4, their relative importance based on the pair wise comparison criteria were used to the level of comfort experienced. for example, if we consider arm rest very strongly more important than back rest, the arm rest-back rest comparison cell will contain a value of 4. mathematically, this means that s/n objective criteria 1st person 2nd person 3rd person 1 back rest 0.8 0.9 0.86 2 seat 0.95 0.8 0.8 3 arm rest 0.5 0.45 0.5 4 leg rest 0.62 0.7 0.76 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ashiedu and okwu: creative algorithm for effective analysis of a developed wheelchair. azojete,16(1):188-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashiedu.ifeanyi@fupre.edu.ng 188 the ratio of the importance of arm rest versus the importance of back rest is 4 (arm rest/back rest = 4). the opposite comparison, the importance of back rest relative to the importance of arm rest, will yield the reciprocal of this value (back rest/arm rest = 1/4) as shown in the back rest-arm rest cell in the comparison matrix. the importance of a criterion when compared with itself; for example, seat versus seat, and leg rest versus leg rest, or back rest versus back rest; the input value is 1 which corresponds to the intensity of equal importance in the scale of values. this is instinctively sound because the ratio of the importance of a given criterion with respect to the importance of itself will always be equal. the normalized matrix is then obtainedby adding the value in each column and dividing each cell by the total of the column. from this normalized matrix, the criteria weight is obtained by simply calculating the average value of each row. next the consistency is checked, when many pair wise comparisons are performed, some inconsistencies may typically arise. the process of checking consistency is shown in section 2.9. for example, considering three criteria such as seat, leg rest and arm rest respectively. if it is observed after evaluation that the first criterion is moderately less important than the second criterion, while the second criterion is strongly more important than the third criterion. an evident inconsistency arises if it was computed in error the decision maker evaluates by mistake that the third criterion is equally or more important than the first criterion. the ahp incorporates an effective technique for checking the consistency of the evaluations made by the decision maker when building each of the pair wise comparison matrices involved in the process. as presented in section 2.9, the procedure for checking the consistency of the results is to first determine the weight sum vector ws, this is clearly demonstrated in equations 5 and 6. the consistency ration of 0.024 obtained shows that the ranking is consistent. finally, the ergonomic rating of the wheelchair was calculated which showed that the developed smart wheel chair is quite comfortable. 4.0 conclusion the development of a wheelchair has been presented. the research was targeted to offer assistance to disabled and aged persons for easy routing about their various activities. the materials for the construction are local indigenous lightweight materials for the structural members of the supporting frame. the system is economical light efficient. the ahp model, an effective decision metrics technique for complex stochastic process was achieved by reducing complex decisions to a series of pair wise comparisons. the ergonomic rating of 62% showed that the developed wheelchair is quite comfortable for users.it would greatly improve the community of people who have lost some means of independent mobility thereby leading to an improvement in their self-esteem. thus, enabling them pursue their vocational and educational goals. in conclusion, creative algorithm like fuzzy logic and anfis can be adopted in subsequent research. references ahluwalia, ms. varghese, tn. nayan, patil, s. mayur, rs. and soheb, k. 2017. design and fabrication of sensors assisted solar powered wheelchair. international journal of engineering trends and technology (ijett),46(2): 71-74 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; 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engineering, technology & environment azojete december 2019. vol. 15(4):1026-1037 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1026 original research article web-based advanced traveller information system for minna metropolis, nigeria o. o. adeleke1*, s. idoko2, s. s. kolo2, a. r. anwar3, o. o. sijuwola1 and o. akinola1 (1department of civil engineering, university of ilorin, ilorin, nigeria 2department of civil engineering, federal university of technology, minna, nigeria 3department of civil engineering, kano university of science and technology, wudil, nigeria) * corresponding author’s email address: adeleke.oo@unilorin.edu.ng 1.0 introduction the dearth of detailed and explicit information on transportation routes and systems which are necessary to adequately prepare for any trip has almost all the times caused unnecessary delays, anxiety, added costs and even at times jeopardized the safety of travellers especially when using the transportation route or system for the very first time. the development and deployment of advanced traveller information system (atis) which is a category of intelligent transportation system (its) is used in contemporary societies to address this issue (adeleke et al., 2013, zhanga et al., 2011). atis refers to any system that acquires, analyses and presents information to assist surface transportation travellers in moving from a starting location (origin) to their desired destination (adeleke et al., 2013). an atis may operate using information supplied entirely within the vehicle (autonomous system) or it can use data supplied by traffic management systems. information such as location of incidents, weather and road conditions, optimal routes, recommended speed, lane restrictions are among those provided by the atis which help users in decision making (kristof et. al., 2005; zhanga et. al., 2011). this information is collected and disseminated using computer devices and telecommunication (us department of transportation (dot), 1998a). article information abstract advanced traveller information system (atis) is used to provide accurate, integrated and comprehensive travel and traffic information to road users. the information helps in both pre-trip and en-route decision making. this study developed a web-based atis for minna metropolis in nigeria. the information provided is from both primary and secondary sources. the developed atis provides information on route guidance, available intercity transport services and hotels in the metropolis. it also allows users to determine both weather and traffic flow conditions. a component of the system makes provision for electronic fare payment and booking of trips and hotel accommodation. the deployment of the atis is a source of static and dynamic information. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 january, 2019 revised 15 june, 2019 accepted 20 june, 2019 keywords: atis route guidance electronic fare payment weather condition traffic condition. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1026-1037. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1027 a review of existing atis deployments in some locations across the world include, the metropolitan transportation commission (mtc) 511 atis which is widely recognized as one of the leading atis in the united states. it is a one-stop, multimodal and trip planning regional traveller information resource. mtc’s 511 atis incorporates traveller information gathered from numerous sources, including the state department of transportation (dot), regional transit agencies, local transportation agencies, toll tag transponders and a private data provider. the utah department of transportation (udot) operates an atis website which contains traffic conditions map, a camera or dynamic message signs (dms) image, detailed text on high-priority events or incidents, weather forecast and links to other travel-related information and maps of other areas of the state. traffic conditions information can be shown graphically on the map or in text format while travel times can only be shown in text format. other atis sites which include london atis, taipei city ati system, munich atis also contain information on the various modes of travel which include underground rail, over-ground rail, buses, automobiles, bicycles, pedestrians, airplanes, river, tram, taxis and minicabs, and light railway system. other features on deployed atis include information on road networks, hospitals, government and private offices, stadia, tourist places, real-time parking information, trip scheduling (mid-ohio regional planning commission, 2009; supergeo technology, 2016; kumar et al., 2005; european commission, 2011; us dot, 1998b; minnesota dot, 2003). atis has been found to be of immense advantage in the transportation industry. the aim of the study therefore was to develop and deploy a web-based advanced traveller information system for minna, nigeria, a typical growing city in a developing economy in order to address the dearth of detailed travel information needed to facilitate the movement of travellers to, within and from the metropolis. the study had the specific objectives of improving travellers’ convenience and safety through the provision of needed travel and traffic condition information. 2. materials and methods 2.1 data collection primary and secondary data (hox and boeije, 2005) were used in the study. primary data was collected from two sampled public transportation companies that provide inter-city transport services and which in this study were identified simply as transport services a and transport services b. the transportation companies are among those that provide regular inter-city services in minna and are most widely used by travellers in the metropolis. they also have service networks that cover a sizeable number of states in nigeria. a data acquisition form was given to the transportation companies to fill. information obtained from the companies included: name of transportation company; addresses of parks in and outside minna; routes plied; transport fares; scheduled departure times and company’s transaction policy. primary data were also collected on four sampled hotels in the city. traffic surveys were carried out to determine the peak and off-peak periods at kpakungu and mobil intersections which were considered critical to the study as they are located in the central business districts of the metropolis with high traffic density. the information on the traffic condition was based on the traffic surveys data. the secondary data used were: 1. additional information obtained from the websites of i. the sampled public transportation companies (the information included transport routes, travel times and fares) ii. hotels (information obtained included room types and fares); 2. route maps, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeleke et al: web-based advanced traveller information system for minna metropolis, nigeria. azojete, 15(4):10261037. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1028 travel times and positional information as available on the google map and 3. weather condition (temperature, wind speed, cloud cover, atmospheric condition) as provided through the open weather map. 2.2 programming languages used for the website design programming languages and syntaxes used for the website design include: (i) hyper text mark up language (html5), (ii) cascading style sheet (css3), (iii) structural query language (mysql), (iv) java script, (v) php-hyper processor and (vi) ajax (asynchronous java script and xml). the utilization of the programming languages gave flexibility in the process of the design. the database schema is shown in figure 1 while figure 2 shows the flow chart. figure 1: database schema 2.3 system architecture the system architecture is shown in figure 3. the traveller interacts with the system using a mobile application or a computer which connects to the google map and weather map apis. the payment and booking modules allow the traveller to obtain information on transportation fare and hotel costs and to also make bookings and payments. 2.4 application programming interface an application programming interface (api) is a set of routines, protocols and tools for building software application. it is an already existing programme which is structured in such a way that would allow other programmers who may find it useful to easily engraft it into the application software or programme being designed (conrad et al., 2015). the apis used in the study include: google maps: the google maps api is used as the base for everything related to location and route maps on the website. it finds both the users’ instant location or queried location and also displays the maps and travel times of the respective routes as route guidance. open weather map: the open weather map api serves the purpose of weather detection and prediction. it states the weather condition in relation to elements such as temperature, wind speed, cloud cover and atmospheric humidity. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1026-1037. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1029 figure 2: flow chart obtain traffic report input departure time check traffic situation yes obtain distance & travel time global positioning system (gps) no input location process distance & travel time start location known? successful no yes print receipt p5 yes suitable? no book transp? yes no obtain fare booking file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeleke et al: web-based advanced traveller information system for minna metropolis, nigeria. azojete, 15(4):10261037. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1030 figure 2 cont’d: flow chart internet google map & weather apis atis website atis server payment/booking platform access point traveller interface updates traveller input traveller db figure 3: system architecture yes book hotel? no obtain hotel information booking successful? yes no print receipt stop p5 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1026-1037. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1031 3. results and discussion homepage the homepage of the developed website is shown in figure 4. route guidance this functionality provides users adequate route guidance from the point of origin to minna and further to any of the two campuses of the federal university of technology, minna (bosso and gidan-kwano campuses). the site is designed to help give drive directions to users who have knowledge of their startup locations and those that cannot identify their startup locations. if startup location is known, simply enter the name of the location in the space provided to answer the question “where are you coming from?". the name of the place entered can either be that of the state, local government, town or district. after entering the name, click on ‘get information’. the ‘get information’ button leads to a new page that displays a map with the drive directions to minna. to get drive directions to any of the campuses of the federal university of technology simply select the campus of interest from the upper right hand corner of the map area. the outcome is the route map depicted in figure 5. attached to each of the routes shown on the map is a text box that shows the distance between the entered startup location and the destination. the expected time of travel is also displayed. figure 4: screen print of website homepage file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeleke et al: web-based advanced traveller information system for minna metropolis, nigeria. azojete, 15(4):10261037. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1032 figure 5: screen print of drive directions from ilorin to f.u.t minna bosso campus (source: google map) the option of ‘finding your location’ is included to make provision for a user who either does not know or is not sure of his current location; this facility is however operational if the internet browser has a gps facility installed. a user simply finds his location by clicking on ‘find me’ in the homepage. this leads to a page showing both the name and the map of the user’s current location. trip booking this site provides users the platform through which booking can be made for a public transportation from any point of location through electronic means instead of going to the booking office of the transportation company. click on ‘transport’ to book a transport service. this leads to a page where it is required to select the name of the startup point (state) from the drop down menu as shown in figure 6. after selecting the state, click on ‘search’. this leads to the page shown in figure 7 which displays a list of all the transport companies in the database that go to minna from the selected state, the addresses of their parks, and the transportation fare. figure 6: screen print of ‘transport’ option distances and estimated times of travel between ilorin and f.u.t. minna, gidan-kwano campus using two alternative routes http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1026-1037. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1033 figure 7: screen print on a transport company that plies enugu to minna if none of the transport companies included in the database goes to minna from the selected ‘startup point’ it displays “no transport service available from this location”. click on “book now” to book the desired option. enter your name, phone number, next of kin phone number, date of trip. after the details, click on “proceed”, select automated teller machine (atm) card type and enter the atm details and click “pay”. this leads to a page where payment receipt will be displayed on the screen and payment receipt number will be sent as sms to the phone number provided. click on ‘print’ to print the receipt. trips can also be rescheduled. verification of weather condition the weather functionality provides information on the expected weather condition of the day in minna. the weather parameters provided include: i. temperature in degree celsius ii. humidity in percentage iii. wind speed in mph iv. time of sunrise and v. time of sunset. a screen shot for the weather condition is shown in figure 8. figure 8: screen print of a day’s weather reading in minna file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeleke et al: web-based advanced traveller information system for minna metropolis, nigeria. azojete, 15(4):10261037. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1034 hotel booking click on the “book a hotel” option to book a hotel. this leads to a page where the list of available hotels is displayed as shown in figure 9. click on the name of the hotel of choice for further details and take other needed steps to book. details to be entered by user include: name, check in and checkout dates, phone number and the number of adults. figure 9: screen print of ‘book a hotel’ page showing available hotels after entering the details, the user clicks on ‘proceed’ which leads to a new page where payment is made through electronic means online using atm details. the user will be required to select his card type, enter atm details in the appropriate spaces provided, and then click on “pay”. if the payment is successful, the receipt of payment is displayed on the screen. the user can then go ahead to print the receipt by clicking ‘print’ on the page. the receipt number is also sent to the provided phone number as sms. provision is also made for rescheduling of the hotel booking. traffic condition the website also presents to its users the traffic situation of minna at the expected time of arrival. the traffic information provided is however historic and not real-time. the traffic information is available on only the two most prominent intersections in minna (kpakungu and mobil intersections). the information on the traffic condition is obtained by clicking on ‘traffic information’ and the result is displayed on the screen. information displayed is on whether the roundabouts are expected to be congested (peak period) or not congested (off-peak period) at the time of arrival to minna. the admin panel the ‘admin panel’ is the section of the website that is reserved solely for the website administrator. the website administrator is granted access to the database of the website and can add or remove any information. access to this portion of the website is restricted with a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1026-1037. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1035 username and a password. the inventory of trip bookings is monitored by the administrator as shown in figure 10. the activities that the administrator performs are: view and/or print the list of hotel bookings done from the website alongside all the details of the bookings. view and/or print out the list of trip bookings done from the website alongside all the details of the bookings. add or remove a transportation company from the list of transportation companies ditto for hotels. figure 10: webpage screen print of trip bookings from the admin panel 4. flexibility and limitation of the system 1. information on route guidance (travel route map and travel time) between any two locations (other than ilorin and minna) can be obtained from the system’s website as presently designed by entering the appropriate locations information in the ‘where are you coming from’ box (the trip origin box) and the destination in the trip ‘destination’ box. similar enquiries and operations as done for minna can also be carried out for other cities by providing information on hotels, transportation services, traffic flow situations on the cities in the database of the developed atis. 2. re-routing that may be necessary as a result of unanticipated incidents en-route, such as traffic accidents, work zone is handled by the system. if a traveller is aware that a route has become impassable the user seeks for alternatives from a location before the incident scene or at the incident scene as the case may be, to the desired destination through the systems route guidance module. the traveller enters the location where he gets stuck as his new trip origin, then possible routes from this location to his destination will be displayed. 3. the traffic data as presently displayed on the website is static, however, in future; realtime traffic condition information can be incorporated into the developed system. this can be obtained by providing a link in the website to a traffic management centre that broadcasts real-time traffic information to the public or registered users. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeleke et al: web-based advanced traveller information system for minna metropolis, nigeria. azojete, 15(4):10261037. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1036 4. the database in the study is limited and would need more funding to capture more traveller’s needed information and services. 5. conclusion a website for advanced traveller information system (atis) has been developed in the study. the website provides route guidance for travellers to minna township. the website also provides static information on traffic condition at the two most prominent intersections in the town to the traveller based on the expected arrival time to minna. other information and services on the website include weather information on minna, available transportation services from major cities in nigeria to minna. trip and hotel bookings can also be carried out in the comfort of one’s room or from wherever using atm details directly on the website. the website deployment improved on travellers’ convenience, safety and economy. the database should be enlarged with more funding to capture more traveller’s needed information and services. the historic traffic condition data can also be improved on with real-time data as this will improve on the timeliness and accuracy of information provided. other means of relating traveller information other than the developed internet website; such as variable message sign (vms), highway advisory radio (har), interactive television, teletext, cable television should be explored and used to relay traveller information for the study area thereby increasing the information outlet options available to road users. acknowledgement the authors acknowledge the contributions of mr. o. t. adeleke in the production of some of the figures. references adeleke, oo., jimoh, ya. and akinpelu, ma. 2013. development of an advanced public transportation system for captive commuters on urban arterials in ilorin, nigeria. alexandria engineering journal, 52: 447 454. http://authors.elsevier.com/sd/article/s1110016813000355 conrad, e., misenar, s. and feldman, j. 2015. cissp study guide. 3rd ed. elsevier inc. usa. https://sciencedirect.com accessed on 14 june, 2019. european commission, 2011. its action plan – study ‘towards a european multi-modal journey planner’. european commission directorate-general mobility and transport, brussels, belgium. pp. 85 https://ec.europa.eu/transport/sites/transport/files/themes/its/studies/doc/2011_09multimodal-journey-planner.pdf accessed on 16 january, 2016. hox, jj. and boeije, hr. 2005. data collection, primary vs secondary. encyclopedia of social movement, 1: 594 – 599 http://www.joophox.net/publist/esm_dcol05.pdf accessed on 11 june, 2019 kristof, t., lowry, m. and rutherford, gs. 2005. assessing the benefits of traveler and transportation information systems. washington state transportation commission, department of transportation, olympia, washington and transportation northwest, university of washington, seattle, washington and in cooperation with the u. s department of https://sciencedirect.com https://ec.europa.eu/transport/sites/transport/files/themes/its/studies/doc/2011_09-multimodal-journey-planner.pdf https://ec.europa.eu/transport/sites/transport/files/themes/its/studies/doc/2011_09-multimodal-journey-planner.pdf http://www.joophox.net/publist/esm_dcol05.pdf http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1026-1037. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeleke.oo@unilorin.edu.ng 1037 transportation, federal highway administration, washington dc, usa. pp. 69. https://www.wsdot.wa.gov/research/reports/fullreports/597.1.pdf accessed on 12 march, 2016. kumar, p., singh, v. and reddy, d. 2005. advanced traveler information system for hyderabad city. ieee transactions on intelligent transportation systems, 6(1): 26-37. http://web.mit.edu/rama/public/papers/paper8.pdf accessed on 11 february, 2016. mid-ohio regional planning commission, 2009. advanced traveler information system study: final report. mid-ohio regional planning commission, ohio, usa. pp. 72. https://www.yumpu.com/en/document/view/45833709/advanced-traveler-information-systemstudy-mid-ohio-regionalaccessed on 11 june, 2019. minnesota department of transportation, 2003. commercial vehicle operation (cvo) advanced traveler information systems (atis) summary of national practice final report. minnesota department of transportation, office of freight and commercial vehicle operations, usa. pp. 65. http://www.dot.state.mn.us/ofrw/pdf/cvo%20atis%20final%20report_final.pdf accessed on 22 january, 2018. supergeo technology, 2016. taipei city advanced traveler information system web. supergeo technology inc., taipei , taiwan. pp. 2. http://www.supergeotek.com/inner/download/taipei%20city%20advanced%20travel er%20information%20system%20web-20100505141358.pdf accessed on 17 january, 2016. us department of transportation 1998a. intelligent transportation system field operation test cross-cutting study: advanced travelers information systems. department of transportation, federal highway administration washington d.c, usa. pp. 27. https://www.fhwa.dot.gov/publications/research/operations/its/jpo99038/fotatis.pdf accessed on 04 january, 2019. us department of transportation 1998b. developing traveler information systems using the national its architecture. intelligent transportation systems joint program office, washington d.c, usa. pp. 226. https://www.fhwa.dot.gov/publications/research/operations/its/98031/index.cfm accessed on 04 january, 2019. zhanga, j., liaoa, f., arentzea, t. and timmermansa, h. 2011. a multimodal transport network model for advanced traveler information systems. procedia social and behavioral sciences, 20: 313–322 https://www.wsdot.wa.gov/research/reports/fullreports/597.1.pdf http://web.mit.edu/rama/public/papers/paper8.pdf https://www.yumpu.com/en/document/view/45833709/advanced-traveler-information-system-study-mid-ohio-regionalhttps://www.yumpu.com/en/document/view/45833709/advanced-traveler-information-system-study-mid-ohio-regionalhttp://www.dot.state.mn.us/ofrw/pdf/cvo%20atis%20final%20report_final.pdf http://www.supergeotek.com/inner/download/taipei%20city%20advanced%20traveler%20information%20system%20web-20100505141358.pdf http://www.supergeotek.com/inner/download/taipei%20city%20advanced%20traveler%20information%20system%20web-20100505141358.pdf http://www.supergeotek.com/inner/download/taipei%20city%20advanced%20traveler%20information%20system%20web-20100505141358.pdf https://www.fhwa.dot.gov/publications/research/operations/its/jpo99038/fotatis.pdf https://www.fhwa.dot.gov/publications/research/operations/its/98031/index.cfm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 648-661 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 648 original research article assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process a. a. ahiakwo1*, k. j. simonyan2 and a. b. eke2 (1department of agricultural education, federal college of education (tech.) omoku, rivers state, nigeria 2department of agricultural and bio-resources engineering, michael okpara university of agriculture, umudike, nigeria) * corresponding author’s email address: a.ahiakwo@yahoo.com article information submitted 18 december, 2018 revised 6 march, 2019 accepted 10 march, 2019 keywords: sieving process traditional sieve musculoskeletal disorder dewatered cassava mash processors abstract this study was undertaken to assess the level of exposure of processors to work-related musculoskeletal disorder when using the locally developed traditional sieve in the sieving process. quick ergonomic checklist (qec) involving the researcher’s and the processors’ assessment using the risk assessment checklist, was used in this assessment and data was obtained from a sample of one hundred and eight (108) processors randomly selected from three senatorial districts of rivers state. thirty-six processors from each zone comprising of 14 males and 22 females, were selected., and assessed on the bases of their back, shoulder/arm, wrist/hand and neck posture and frequency of movement during traditional sieving process. the result of the assessment showed that the highest risk of discomfort occurred at the region of the wrist/hand, followed by back, shoulder/arm, and neck. the posture used in the sieving process exposed the processors, not only to the discomfort of pain but also put them at high risk of musculoskeletal disorder at indicated by a high level of percentage exposure of 66% qec rating. the result indicated a need for immediate attention and change to an improved method that will reduce the discomfort on the body parts assessed. identified parts. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction dewatered cassava mash (dcm) sieving process carried out to separate fine particles from the coarse using traditional method, whereby a processor sits in an awkward posture besides a traditional sieve made of raffia, load a lump of cassava mash, shatters it and then bends back and forth to shear the mash against the sieve with shearing and compressive force is considered to be labour intensive and hence consumes time and energy (agbetoye and oyedele, 2007; adetunji et al., 2013, abubakar et al., 2014, ahiakwo et al., 2015, abiodun et al., 2016). it takes two hours thirty minutes to sieve 60kg of dewatered cassava mash on a traditional sieve of dimension 600 x 700mm with 2.87mm average sieve aperture. on the average commercial cassava processors using traditional sieve spends 5 hours daily in the sieving operation (ahiakwo, 2018). mailto:a.ahiakwo@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 649 also, the cardiovascular response of the processors to the rigours of the sieving process is not static. , as research has shown that processors utilizing the traditional sieving process spend energy at the rate of 3.17 to 3.52kj/min (asiru et al., 2010; ahiakwo, 2018). this energy depletion over time together with the awkward posture incidental to this sieving process gives rise to work-related discomfort that may cause disorder in the processor’s musculoskeletal system. there is limited literature on the level to which processors are exposed to when using the traditional sieving process. however, there are methods that are designed to assess the exposure of workers to occupational discomfort. these methods include use of ergonomic questionnaire and postural evaluation method using: quick ergonomic checklist (qec), rapid upper limb assessment (rula), rapid entire body assessment (reba), ovako working posture assessment system (owpas), (alan 2005, joanne, 2007; sandiq et al., 2014, and mohsen et al., 2015). among these methods of exposure assessments, the quick ergonomic checklist (qec) offers an advantage of quickly assessing and evaluating the exposure of workers to the risks of workrelated musculoskeletal discomfort (wmsds) (anas et al., 2012). qec is centred on the practitioners’ requirement and investigation on major wmsd risk factors. qec has great level of usability and highly recommended observer reliability. field survey proves that qec is relevant for a wide variety of tasks. qec provides an appraisal of a workplace and design of equipment, which enhances redesign. qec helps to prevent many kinds of wmsds from developing and educates users about wmsd risks in their workplaces (samuel et al., 2016). qec uses observer’s and worker’s assessment checklist to investigate exposure to msd. the qec user (the observer) uses the “observer’s assessment” checklist, to carry out a risk evaluation for a particular task. at least one whole work process is observed before making the evaluation. the assessment can be carried out by direct observation or by using video footage. the worker being observed will have to complete the “worker’s assessment checklist,” (neville, et al., 2005). also, assessment of workers exposed to work-related musculoskeletal disorder (wmsd) has been done in other fields where energy, time consumption and awkward posture are involved, as it is in the traditional sieving process. simonson and rwamamara (2009), examined ergonomic exposures from the use of conventional and self-compacting concrete; oladele (2012) carried out study on discomfort levels in four working postures used during gari frying, anas et al. (2012) carried out ergonomic study of wmsd among the workers in typical indian saw mills, ismail and darshak, (2016) carried out anthropometric measurement for design of students’ furniture in india, samuel et al. (2016) carried out anthropometric studies for designing to fit gari-frying workers. these studies revealed the need to give attention to the levels to which workers are exposed to wmsd and make early adjustment where necessary for safety. a lot of musculoskeletal damages begin when worker starts feeling discomfort and if ignored, the risk factors responsible for the discomfort eventually leads to an upsurge in the severity of symptoms, and what began as mild discomfort would gradually become severe and will be experienced as aches and pains. more so, the pains and aches that signal some growing discomfort may eventually give rise to actual musculoskeletal damage, such as tenosynovitis, tendonitis, or serious nerve-compression injury like carpal tunnel syndrome (neville, 2005). considering that the traditional sieving process is labour intensive and consumes energy, it implies that processors using this method of sieving are exposed to work–related discomfort (asiru et al., 2010; ahiakwo et al., 2015, ahiakwo, 2018). it is important to determine this level of exposure to the risk factor, to enable a quick action to be taken on redesigning and educating file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahiakwo, et al: assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process. azojete, 15(3):648-661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 650 processors to change to a safer method of accomplishing this sieving task. redesigning besides reducing and where possible eliminating the risk factors will enhance high productivity in this unit operation. it is therefore the objective of this study to assess the level of exposure of processors to work-related musculoskeletal disorder when using the locally developed traditional sieve in the sieving process using quick ergonomic checklist (qec). 2. materials and method 2.1 material a quick ergonomic checklist was carried out to assess if processors using a locally developed traditional sieve constructed by the local craftsmen were exposed to wmsd as a result of the posture adopted during sieving process and the level of exposure. to do this, a sample of one hundred and eight subjects (108) randomly selected from the three senatorial districts of rivers state, 36 from each zone 14 males and 22 females were used. also used were the following materials: dewatered cassava mash (dcm), locally made traditional sieve receptacle wooden stool weighing scale and a mobile android phone the traditional sieve is usually square or rectangular in shape. it is made of cane, raffia palm or palm frond material. this is cut out into several pieces of flat rectangular flexible strip measuring about 0.5 x 60 cm, with thickness of about 1 mm. whereas 0.5 cm represent the width of a single sieve strip, 60 cm, which represent the length of the sieve can vary depending on the length of the sieve. these are weaved by the native specialist craftsmen in such a way that an aperture (square holes) of about 2 to 3 mm2 is revealed at alternate position throughout the sieve. the woven strip is secured over framework of thick material as shown figure 1 (ahiakwo et al., 2015) figure 1: a traditional sieve ready for sieving process 2.2 method before the assessment, the procedure was explained to each of the subjects involved. they got the following materials ready: the dewatered cassava mash (dcm), locally made traditional sieve, receptacle and wooden stool which were to be used for the sieving processing. three observers were trained to cover the three respective senatorial zones and were provided with a weighing scale and a mobile android phone. the weighing scale was for taking the weight of dcm sieved in a single task while the mobile android phone video/camera was used to capture processors posture and activities .sieving process (sandiq et al., 2014). the observers, observed processors in their traditional accustomed manner of carrying out the sieving task through one complete cycle with the traditional sieve. the processors were assessed on the basis http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 651 of their back posture, head/neck posture and wrist/hand deviation from neutral position during the sieving process, as shown in figure 2. the assessment was done by observation of the sieving process, measurement and noting how the back, head/neck and wrist/hand were bent away from the normal position and assigning values based on quick exposure checklist.they were also assessed on the basis of their back movement which was obtained by noting the number of times the processor moves back and forth during the sieving process, their shoulder/arm task position which was obtained by taking measurement of the sieving height and the seating height (figure 3) of the processor and their hand motion pattern which was obtained by noting the degree of frequency of hand motion during the sieving process and the number of times the hand swings forth and back as the dcm is moved across the traditional sieve (neville, 2005). figure 2: method of observer and processors’ assessment figure 3: a processor performing sieving task below waist height in the traditional posture on the other hand, the processors were assessed after filling the workers’ risk assessment checklist shown in tables 1 on the basis of maximum weight handled, average time on task, maximum force level exerted by one hand, visual demand, difficulty in keeping with the work and level of stress.the maximum weight (kg) handled was obtained by measurement with the weighing scale, the highest quantity of dcm lump a processor loads onto the sieve to carry out one complete sieving cycle. the average time on task was obtained by summing up the hours all the processors individually spent carrying out sieving task per day and dividing by the number of seating height task height waist height file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahiakwo, et al: assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process. azojete, 15(3):648-661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 652 processors (hr./day) while the maximum force exerted by one hand is the force required to overcome the resistance of the maximum weight of the dcm on the sieve in moving it across the sieve by one hand (kg). also the opinions of the processors were sought with respect to their visual demand, difficulty keeping with the work and level of stress during the sieving process. table 1: quick exposure checklist (qec) for work-related musculoskeletal risks assessment observer's assessment worker’s assessment back • what is the maximum weight handled in this task? a. when performing the task, is the back h1: light (5 kg or less) a1. almost neutral? h2: moderate (6 to 10 kg) a2. moderately flexed or twisted or side bent? h3: heavy (11 to 20 kg) a3. excessively flexed or twisted or side bent? h4: very heavy (more than 20kg) b select only one of the two following task option: • how much time on average do you spend per day doing this task? for sealed or standing stationary tasks. j1: less than 2 hours does the back remain in a static position most of j2: 2 to 4 hours the time? b1: no b2: yes j3: more than 4 hours for manual handling tasks only: is the movement of the back• when performing this task (single or double handed), what is the maximum force level exerted by one hand? b3: infrequent? (around 3 times per minute or less) k1: low (e.g., less than 1 kg) b4: frequent? (around 8 times per minute) k2: medium (e.g., 1 to 4 kg) b5: very frequent? (around 12 times per minute or more) k3: high (e.g., more than 4 kg) shoulder/arm .is the visual demand of this task • is the task performed l1 low (almost no need to view fine details)? c1: at or below waist height? l2 high (need to view some fine details c2: at about chest height? • do you have difficulty keeping up with this work? c3: at or above shoulder height? p1: never • is the shoulder/arm movement repeated p2: sometimes d1: infrequently? (some intermittent arm movement) p3: often d2: frequently? (regular arm movement with some • how stressful do you find this work? http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 653 source: winery ergonomic risk assessment (2012) in each of the cases, data and responses were obtained from the observers’ assessment and the processors’ assessment for analysis. from data obtained inferences were drawn and rated based on qec and scores assigned based on winery ergonomic risk assessment score sheet. data obtained by the observer, include data on back angle deviation (o) from normal and rated a1, a2 or a3 depending on degree of deviation, head/neck and data on hand/wrist angle deviation which was obtained by measuring degree of deviation from the processing picture (figure 3) was rated e1 or e2 depending on degree of deviation and inferences were drawn and rated based on qec and scores assigned based on winery ergonomic risk assessment score sheet (2012). pauses) d3: very frequently? (almost continuous arm movement q1: not at all stressful? wrist/hand q2: mildly stressful? • is the task performed q3: moderately stressful? e1: with almost a straight wrist? q4: very stressful? e2: with a deviated or bent wrist position? • is the task performed with similar repeated motion patterns f1: 10 times per minute or less? f2: 11 to 20 times per minute? f3: more than 20 times per minute? neck g. when performing the task, is head/neck bent g1: no g2: yes, occasionally g3: yes, continuously file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahiakwo, et al: assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process. azojete, 15(3):648-661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 654 table 2: ergonomic risk assessment score sheet source: winery ergonomic risk assessment (2012 back shoulder/arm wrist/hand neck back posture (a) & weight (h) a1 a2 a3 h1 2 4 6 h2 4 6 8 h3 6 8 10 h4 8 10 12 height (c) & weight(h) c1 c2 c3 h1 2 4 6 h2 4 6 8 h3 6 8 10 h4 8 10 12 repeated motion (f) & force(k) f1 f2 f3 k1 2 4 6 k2 4 6 8 k3 6 8 10 neck posture (g) & duration(j) g1 g2 g3 j1 2 4 6 j2 4 6 8 j3 6 8 10 back posture (a) & duration (j) a1 a2 a3 j1 2 4 6 j2 4 6 8 j3 6 8 10 height (c) & duration(j) c1 c2 c3 j1 2 4 6 j2 4 6 8 j3 6 8 10 repeated motion (f) & duration(j) f1 f2 f3 j1 2 4 6 j2 4 6 8 j3 6 8 10 visual demand (l) & duration (j) l1 l2 j1 2 4 j2 4 6 j3 6 8 duration (j) & weight (h) j1 j2 j3 h1 2 4 6 h2 4 6 8 h3 6 8 10 h4 8 10 12 duration (j) & weight (h) j1 j2 j3 h1 2 4 6 h2 4 6 8 h3 6 8 10 h4 8 10 12 duration (j) & force(k) j1 j2 j3 k1 2 4 6 k2 4 6 8 k3 6 8 10 work pace p1 p2 p3 1 4 9 frequency (b) & weight (h) b3 b4 b5 h1 2 4 6 h2 4 6 8 h3 6 8 10 h4 8 10 12 frequency(d) & weight (h) d1 d2 d3 h1 2 4 6 h2 4 6 8 h3 6 8 10 h4 8 10 12 wrist posture (e) & force(k) e1 e2 k1 2 4 k2 4 6 k3 6 8 stress q1 q2 q3 q 1 4 9 16 frequency (b) & duration(j) b3 b4 b5 j1 2 4 6 j2 4 6 8 j3 6 8 10 score 5:_________ frequency(d) & duration (j) d1 d2 d3 j1 2 4 6 j2 4 6 8 j3 6 8 10 score 5:_________ wrist posture (e) & duration(j) e1 e2 j1 2 4 j2 4 6 j3 6 8 score 5:_________ total score for back:______ total score for shoulder/arm:______ total score for wrist/hand:______ http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 655 scores were assigned by associating observer assessment and processors assessment. the back was assessed as a2 because on average, it was bent more that 20o but less than 60o whereas the maximum weight handled in this task was rated h1 because it fell in the range of light (table 1). this association attracted a score under a2h1 (table 2). the total association scores for back assessment was the summation of scores under a2h1, a2j3, j3h1, b3h1 and b3j3; the total association scores for shoulder/arm assessment was the summation of the scores under c1h1, c1j3, j3h1, d2h1 and d2j3 also the total association score for hand/wrist assessment was the summation of the scores under f3k2, f3j3, j3k2, e2k2 and e2j3 whereas the total association score for neck assessment was the summation of the scores under g3j3 and l1j3. the total actual exposure ( χ ) was the summation of the total scores under back, shoulder/arm, hand/wrist and head/neck with workplace and stress level assessment the resulting scores were presented in table of exposure score and analyzed based on ergonomic exposure equation expressed by neville (2005): �� � � ��뽘� � ���� (1) where: e = overall exposure x = actual total exposure score xmax = maximum possible total exposure (xmaxmh = 176%for manual handling neville, 2005) 3. results and discussion 3.1 observers’ assessment table 3 shows the measured back posture deviation from the normal position of 108 males and females processors who were observed performing sieving task using the locally developed traditional sieve. the average back posture deviation for the three senatorial zones is 37o. table 3: observer’s average assessment processors for the three zones male processors in zones female processors in zones parts assessed a b c mean sd a b c mean sd back posture (°) 35 37.9 27.9 34 5.14 45 38 28 37 8.54 back movement (no. of times) 3.2 4 3.4 3.5 0.42 3.95 4.18 3.5 3.88 0.35 shoulder arm task position (mm) 42 46 41 43 2.65 37 41.2 41.5 40 2.52 seating height (mm) 44 46 40.4 43 2.83 41 41.3 40.4 41 0.46 wrist hand deviation (°) 21.6 26 17.4 21 4.30 22 23 21 220 1 motion pattern per minute 62 57 61.8 60 2.83 62 57 61.8 60 2.83 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahiakwo, et al: assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process. azojete, 15(3):648-661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 656 the back movement of the processors as they carry out the sieving task was 4 times times per sieving cycle and rated b4.. the positions of the arm and the seating height while performing the sieving task were 40 mm and 41mm measured from the floor respectively indicating that the task was performed below waist height and rated c1. the average wrist hand deviation from normal was 22o and rated whereas the average movement of arm back and forth in a minute was 61 times. table 3 show also the measured back deviation from the normal position of men processors who were observed performing the sieving task using the locally developed sieve. the average deviation considering the three zones was 34o. the back movement of the processors’ as they carry out the sieving task was 3 to 4 times. the positions of the arm and the seating height while performing the sieving task were 43 and 43 measured from the floor respectively indicating that the task was performed below waist height. the wrist hand deviation from normal is 21o and the number of times the arm was moved back and forth in a minute was 60 times respectively (ahiakwo, 2018). 3.2 processors’ assessment table 4 shows the result of assessment of male and female processors carrying out sieving task with the locally developed traditional sieve. the average maximum weight handled was 2.1 ± 0.23kg , the average time spent per day on this task was 5 ± 0.40h and the maximum force exerted was 1.5 ± 0.10n table 4 : processors’ average assessment male processors in zones female processors in zones parts assessed a b c mean sd a b c mean sd max. weight handled (kg) 2.3 2.3 2.2 2.2 0.10 1.8 2.2 2.2 2.1 0.23 average time spent per day (hr.) 4.5 5.1 5.1 4.9 0.35 4.6 5.0 5.4 5.0 0.40 max force exerted (n) 1.9 1.3 1.6 1.6 0.30 1.5 1.4 1.6 1.5 0.10 table 4 also shows the result of assessment of 42 male processors carrying out sieving task with the locally developed traditional sieve. the average maximum weight handled, the average time spent per day on this task and the maximum force exerted were 2.2 ± 0.10kg, 4.9 ± 0.35h, and 1.6n ± 0.30, respectively. in the traditional sieving process, the maximum quantity of 2.2kg for a sieving cycle cannot easily be increased since it was limited by the sieve size. also the force exerted by the hand cannot be reduced in its reciprocation motion across the sieve. the fact that this quantity and the exerted force have to be repeated in each cycle of operation until the total quantity was exhausted in the awkward posture by the processor contributes to exposing the processor to an increase level of discomfort. it was also noted that the total time required to completely sieve a given quantity of dcm depended on the quantity of the dcm (maximum) that can be handled per unit cycle of sieving operation, the size of the sieve and its aperture as well as the frequency of the hand motion. if the quantity for a sieving cycle of operation, the sieve size and the aperture as well as the frequency of hand motion on the sieve were increased, sieving time per day on average would decrease below 4.9hours. obviously, these factors cannot be increased without increasing discomfort level of the processor. an alternative option to decreasing discomfort level of the processor would therefore be in the direction of developing an improved sieve that consider increasing the sieve aperture, sieve capacity and eliminating or http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 657 reducing the use of the hand. these provisions, while increasing the quantity considerably above 2.2kg and the throughput capacity, would reduce sieving time spent by farmers on average below the 4.9 h per day. 3.2.1 inferences on observers’ assessment the inferences drawn from observers’ assessment and processors’ assessment are expressed in tables 5 and 6 . table 5 shows the inferences from table 3 with respect to qec for observers’ assessment. table 5 : inferences on observers’ assessment and qec rating parts assessed observation inference rating back 1) back at370> 200 back is moderately bent a2 2) the back movements was around 3 times per minutes back movements is infrequent b3 3) task height ≈ seating height (40mm ≈ 41mm) task is performed at or below waist height c1 4) shoulder-arm moved about 61 times per minute shoulder arm movement is repeated frequently d2 wrist/hand 1) wrist is at 22°> 150 task is perform with bent wrist e2 2) task is repeated 61 times per minute task is performed with similar repeated motion more than 20 times per minute f3 head/neck 200> head/neck < 600 head and neck is bent continuously g3 from the table 5 , processors’ back deviation was > 20. the inference of this from quick exposure checklist (qec)was that the back was moderately bent and attracted a rating of a2. back movement was around 3 times, showing that the back movement was infrequent and rated b3. from the table also, the task was performed at a height approximate to the seating heightindicating from qec that the task was performed below waist height and rated c1. the shoulder arm movement was about 61 times per minute and the inference from qec was that the shoulder arm movement was repeated frequently and the rated d2. because the wrist deviation was > 15 the task was performed with a bent wrist. the sieving task was performed with similar repeated motion > 20 times per minutes, and rated f3. on the other hand head and neck were considered to be bent continuously at 200> head/neck < 600 rated g3. (neville, 2005, ahiakwo, 2018) the observation of the body parts namely back, shoulder arm, wrist and head neck and the inferences drawn indicated that these body parts were not in the normal position during the sieving process. it also showed that these body parts during sieving operation were stressed beyond comfort levels. the qec rating corresponding to the activity of these parts in the sieving process provided insight and means of interpreting the level to which the body parts were exposed to musculoskeletal discomfort. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahiakwo, et al: assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process. azojete, 15(3):648-661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 658 3.2.2 inference on processors assessment table 4 shows the inference from table 2 with respect to qec for workers’ assessment. table 4: inference on workers’ assessment and qec rating assessment assessment result inference qec rating maximum weight handled 2.1kg maximum weight handled is light (5kg or less) h1 average time spent on task per day 5hrs task is performed more than 4hrs j3 maximumforce level exerted by one hand 1.5n force exerted by one hand is medium (1 to 4kg) k2 visual demand low almost no need to view fine details l1 difficult keeping with task workers response sometimes p2 how stressful task is worker response mildly stressful g2 weight handled during the sieving process by the processor was considered light because it fell at the range of ≤ 5kg and rated h1. the inference drawn from the average time spent in the task was that the task was performed more than 4 hours with a rating of j3. force exerted by one hand was considered medium because it fell between 1 to 4kg and rated k2. the visual demand for the sieving task was low because there was almost no need to view fine details during the sieving process and was rated l1. the workers acknowledge sometimes having difficulty keeping up with the sieving task while using the locally made sieve and rated p2 from the qec. also, the workers acknowledge having mild stress while using the locally made sieve and attracted a rating of g2 (neville, 2005) 3.3 ergonomic exposure scores for traditional sieving method table 5 shows the interaction between the observer’s rating and the rating of workers’ assessment with resulting scores. table 5: exposure score – traditional sieving method back shoulder/arm wrist/hand neck work pace stress a2h1= 4 c1h1 = 2 f3k2 = 8 g3j3 =10 p2= 4 q2= 4 a2j3 = 8 c1j3 = 6 f3j3 = 10 l1j3 = 6 j3h1 = 6 j3h1 = 6 j3k2 = 8 b3h1= 2 d2h1= 4 e2k = 6 b3j3 = 6 d2j3 = 8 e2j3 = 8 total 26 26 40 16 4 4 from the ergonomic exposure score sheet and table 5, the total back exposure of the processors using the traditional sieve in terms of qec score was 26. the shoulder/arm exposure http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 659 was 26, the wrist/hand exposure scorewas 40 whereas the neck exposure score was 16. the scores indicated the level of exposure for the individual body parts involved in the sieving process. from the scores, it was seen that the back and shoulder/arm were highly involved and hence under stress during the sieving process. the score of 26 showed that these body parts as well as the neck were in abnormal position. on the other hand the highest score of 40 recorded under wrist/hand was an indication of the body part that suffered highest discomfort as it was subjected to continuous reciprocation during the sieving process. however, it was the combination of the exposures of the individual body parts’ discomfort that sumed up to the total exposure of the processors’ to work-related musculoskeletal discomfort (wmsd) while using the traditional sieve as shown in figure . figure 4 : exposure of processor performing manual dcm sieving task to wmsd from figure 4 , it was observed that the total exposure was the sum of the individual exposures. this resulted to overall percent exposure or total exposure “e” of 66% (neville, 2005).from table 6, the exposure of 66% indicated that the traditional sieving dewatered cassava mash sieving method requires to be changed soon to an improved method. table 6: preliminary action levels for the qec qec score (e) percentage total action equivalent ≤ 40% acceptable 41 – 50% investigate further 51 -70% investigate further and change soon >70% investigate and change immediately 4.0 conclusion cassava processors involved in dewatered cassava mash (dcm) sieving process using traditional method are exposed to work-related musculoskeletal discomfort (wmsd). the observer and processors’ assessment shown in the risk assessment exposure scores sheet revealed the level to which the processors’ body parts actively involved in the sieving process were exposure to wmsd. the wrist/hand was the most stressed with the highest score of 40 followed by back and shoulder/arm with exposure score of 26 respectively and head/neck with exposure score of 16 given an overall exposure level of 66% based on quick exposure checklist (qec) rating. when compared to the preliminary action levels for the qec, this method of processing dcm should be further investigated and change soon. processors therefore should be educated, to be aware that the sieving posture they adopted and with the sieve aperture currently used in traditional sieving process, exposes them not only to the discomfort of pain but also put them at high risk of musculoskeletal discomfort over a period of time and therefore need to change to an 4 4 116 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahiakwo, et al: assessment of workers’ level of exposure to work-related musculoskeletal discomfort in dewatered cassava mash sieving process. azojete, 15(3):648-661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 660 improved manual method that will consider adjusting the seating and the sieving task height such that the posture of the processors’ back and neck is close to normal and also adjusting the sieve aperture to a limit that will reduce the frequency of the processors’ hand motion. an alternative will be a motorized method that will factor in mechanisms such that during the sieving process, the involvement of the body parts that suffers discomfort during the sieving process are reduce or eliminated in consideration to ergonomic factor as soon as possible. references abiodun, lo., oladipo, no. and bamidele, bl. 2016. development of ncam reciprocating cassava mash sifter. international journal of basic and applied science, 5(3):10-13 abubakar m., olawale, jo., abdulkadir, bh. and dele, sj. 2014. the design of a pedal driven pulverizing and sieving machine for dewatered grated cassava. international journal of scientific and research publications, 4(4):45 49. adetunji, or., dario, ou., aiana, b. and sunland, as. 2013. development of an improved gari sifting machine. pacific journal of science and technology, 14(2): 67-75. agbetoye, las. and oyedele, oa. 2007. development of a dual powered gari sifter. journal of agricultural engineering and technology, 15(5): 126-130. ahiakwo, aa., isirimah, cb. and inimgba, dg. 2015. appraisal and projection of dewatered cassava mash sieving technology. net journal of agricultural science, 3(2): 5559. ahiakwo, aa. 2018. ergonomic intervention and sieve aperture effects on musculoskeletal discomfort in dewatered cassava mash sieving process. ph.d dissertation, department of agricultural and bio-resources engineering, michael okpara university of agriculture, umudike, pp. 39-41, 70 – 77. alan, h. 2005. handbook of human factors and ergonomics methods. crc press, new york, washington, d.c., pp. 5-9 anas, a., qutubuddin, sm., hebbal, ss. and kumar, ac. 2012. an ergonomic study of workrelated musculoskeletal disorders among the workers working in typical indian saw mills. international journal of engineering research and development, 3(9):38-45. asiru, wb., igbeka, jc. and olayanju, tma. 2010. energy expenditure in gari processing activities by nigerian women. journal of natural sciences, engineering and technology, 9(2):149-157. ismail, wt. and darshak, ad. 2016. anthropometric measurements for ergonomic design of students’ furniture in india. engineering science and technology, an international journal, 5(7): 206–217 joanne, c. 2007. the nordic musculoskeletal questionnaire, society of occupational medicine. london, 57(4): 300 -301available at http//www.10.1093/occmed/kqm036, accessed 4, july 2016. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):648-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: a.ahiakwo@yahoo.com 661 mohsen, z., sophie, b., rene, b. and yves, r. 2015. are there differences between various ergonomic risk evaluation methods? proceedings 19th triennial congress of the iea, melbourne, 9-14 august, 2015, pp 231 -238. neville, s., alan, h., karel, b., eduardo, s. and hal, h. 2005. quick exposure checklist (qec) for the assessment of workplace risks for work-related musculoskeletal disorders (wmsds). in: handbook of human factors and ergonomics methods. crc press new york, washington, d.c. pp 6 -11. oladele, pk. 2012. discomfort levels in four working postures in use during gari frying. icastor journal of engineering, 5(2): 103-110. samuel, tm., aremu, oo., salami, io., adetifa, bo. and onu, li. 2016. anthropometric studies for designing to fit gari-frying workers. agricultural engineering international: cigr journal, 18(1):180-191. sandiq, bw. and manish, kb. 2014. an ergonomics intervention in a transformer manufacturing industry to improve the productivity. journal of mechanical and civil engineering, 3(5): 52-57. simonson, p. and rwamamara, r. 2009. ergonomic exposures from the usage of conventional and self compacting concrete. proceedings for the 17th annual conference of the international group for lean construction safety, quality and environment, 2009, united states, pp 313-322 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):153-162 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 153 original research article a review of biofuels research in nigeria t. e. odetoye*, e. o. ajala and d. s. ogunniyi (department of chemical engineering, university of ilorin, pmb 1515, ilorin, nigeria) *corresponding author: todetoye@yahoo.com article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: biofuel research industry production nigeria abstract biofuels are attracting a lot of research attention as a source of renewable energy due to environmental benefits and prospects of energy security. the expectation of the global community is particularly high towards sub-saharan african countries like nigeria to meet the growing bioenergy needs by harnessing the abundant supply of biomass feedstock. however, lack of home-grown technology has been one of the major drawbacks of biofuel industrialization in nigeria. although a reasonable amount of biofuel research effort has been embarked on locally in nigeria, most of these research works have remained on the shelf instead of being translated into commercial production. this paper reviews some biofuel research work done on nigerian biomass. it recommends that funding the existing and new biofuel research work in nigeria and channeling research towards industrialization as important drivers towards biofuel production in nigeria. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the global challenge of climate change due to over-dependence on fossil fuel has necessitated the shift towards renewable fuel (irena, 2015). renewable energy has become the fastest growing source of energy globally and its share in the primary energy source has been projected to increase to 10% by the year 2035. moreover, the projected industrialization of africa is expected to further increase the global energy demands by 2035 (dudley, 2017). biofuels which are alternative fuels derived from biomass include gaseous, liquid or solid fuels like biogas, biobutanol, biodiesel, bioethanol, bio-oil that are produced from biological materials. biofuels can be used for generating power and heat (agbro and ogie, 2012). biomass can be defined as a material derived from recently living organisms which include plants, animals and their byproducts, e.g. manure, garden waste and crop residues (asfar, 2014). biomass has been regarded as one of the renewable energy source which has the potential of meeting the global energy targets (eia, 2013).the attending benefits of biofuels have been observed to go far beyond the clean burning nature of the product since biofuel’s renewable resource can help to create a market for farmers and reduce the amount of waste oil, fat and grease being dumped into landfills and sewers (idusuyi et al, 2012). according to research trend on biofuel feedstock and conversion technologies, biofuels are categorized as first, second and third generation biofuels. first-generation biofuels are produced mainly, from food sources such as sugar, starch, and vegetable oil while the second-generation mailto:todetoye@yahoo.com http://www.azojete.com.ng odetoye, et al. a review of biofuels research in nigeria. azojete, 15(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 154 are from dedicated bioenergy crops, non-food feedstock such as ligno-cellulosic biomass (agricultural and forestry feedstock) and other food processing biomass residues. third generation biofuels are produced mainly from aquatic feedstock such as algae (beetul, 2014; saladini et al., 2016). it is note-worthy that the food-fuel debate has favoured the preference for the second and third generation biofuel production (galadima, 2011) and the need for sustainable alternative biofuels had kept the interest of stakeholders and researchers in secondgeneration biofuels (saladini et al., 2016). nigeria has been regarded as one of the countries that have the potential to produce sufficient biofuel for both domestic use and export (elijah, 2010; abro and ogie, 2012) considering her agricultural land area of approximately 71,000,000 ha of which about 37.3% is arable land available for cultivation of biomass for biofuel (ben-iwo et al., 2016). however, the structure of the nigerian economy has been heavily dependent on fossil fuel which accounted for up to 95% of the country’s export earnings (chete et al., 2013), while the agricultural sector accounted for about 2% of the total export (kale, 2016). recently, nigeria faced an economic challenge as a result of over-dependence on crude petroleum for export earnings. whereas, production of biomass feedstock/biofuel, among other bio-based products, is a potential source of additional export earnings. there is need to develop existing biofuel research in nigeria into commercial production for domestic use and to attract foreign exchange for the nigerian economy. this work is aimed at reviewing the earlier works on biofuel production in nigeria and the prospects of commercialization of biofuel production in the country. 2.0 biofuel research in nigeria 2.1 potential feedstock potential crops for biofuel production as earmarked in the nigerian national petroleum corporation (nnpc) biofuel policy include sorghum, sugarcane, cassava and jatropha. while some food crops are currently been utilized as biofuel feedstock in the developed and emerging economies such as u.s., india and brazil, the food fuel debate has been a major consideration identified so as to avert food crisis in nigeria and the african continent in general. figure 1: bioenergy crop production in nigeria source: ben-iwo et al., 2016 figure 1 shows the percentage production of some nigerian food crops that are considered as feedstock for biofuel production that may pose food-fuel challenge in nigeria. first generation biofuel production which is usually based on the use of food crops as biofuel feedstock, has been criticized as non-suitable for nigeria, a developing country like (galadima et http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng al., 2011). other feedstock that have been reported as suitable for biodiesel production include soybean (us), rapeseed (europe), oil palm (south-east asia), jatropha and rice bran oil (india). biodiesels have also been produced from canola oil, waste restaurant oil, animal fat, rapeseed oil and palm oil. the potential biomass resources in nigeria include wood, charcoal, grasses and shrubs, agricultural residues, forestry residues, municipal biomass wastes, industrial biomass wastes and aquatic biomass (abro and ogie, 2012). agricultural residue, crop residue and agroindustrial by-products such as cocoa husk, coconut shell and husk, rice husks, oil seed cakes and oil palm empty fruit bunch have been investigated towards the production of biofuel. furthermore, cassava residue has been recognized as one of the major agricultural crop residues in nigeria with an estimated value of 29 metric tonnes per annum of residues generated. municipal solid wastes can also serve as potential feedstock for biogas production by anaerobic digestion with over 25 million tonnes of municipal solid wastes generated per annum in nigeria. the waste can be converted to wealth in biofuel production (agbro and ogie, 2012). many researchers have worked on generating biofuel from locally available nigerian biomass feedstock, ranging from agricultural residues to food and non-food biomasses. table 1 summarizes some recent biofuel research efforts in nigeria. table 1: some recent biofuel feedstock research efforts in nigeria palm kernel oil biodiesel was produced through transesterification by ethanol using naoh catalyst (alamu et al., 2008). the properties of the fuel produced were in good agreement with the american society for testing and materials (astm) standards. the fuel characteristics of the biodiesel produced demonstrated that the pko biodiesel produced can be used as fuel in diesel engines. umaru et al. (2014) reported the suitability of mango seed oil for biodiesel production. a biodiesel yield of over 80% wt was obtained at an optimal temperature of 60°c. the biodiesel produced was reported to be consistent with the threshold standard values quoted by astm and en for biodiesel and fossil diesel. coconut oil was also found suitable for biodiesel biofuel feedstock biofuel type method of production workers palm kernel oil biodiesel transesterification igbokwe nwafor,2014 mango seed oil biodiesel transesterification umaru et al., 2014 coconut oil biodiesel transesterification alamu et al., 2010 peanut oil biodiesel transesterification ajala et al., 2014 soy bean oil biodiesel transesterification fasogbon & asere, 2014 sugarcane bioethanol fermentation/ pilot plant misau et al., 2012 milk bush oil biodiesel transesterification oniya et al., 2016 jatropha oil biodiesel transesterification ameen et al, 2014 tobacco seed oil biodiesel transesterification motojesi et al, 2017 shea butter biodiesel transesterification/ processor ajala et al, 2015 parinari oil biodiesel transesterification catalyst aladetuyi et al, 2014 parinari residue bio-oil pyrolysis odetoye et al, 2014 parinari oil biodiesel transesterification pilot plant odetoye (ongoing) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng odetoye, et al. a review of biofuels research in nigeria. azojete, 15(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 156 production (alamu et al., 2010). a blend of the coconut oil biodiesel with petroleum diesel was reported to be suitable as alternative to diesel. table 2: physical property of some biodiesels from various feedstock physicochemical property peanut biodiesel soybean biodiesel sunflower biodiesel petroleum diesel palm biodiesel babassu biodiesel rapeseed biodiesel density at 40°c [kgl-1] 0.833 0.885 0.860 0.823 0.855 0.875 0.882 viscosity [40°c, mm2/s] 4.9 4.5 4.6 4.0 4.5 3.6 4.2 flash point [°c] 176 178 96 98.0 174.0 127 80 cloud point [°c] 5 1 18.0 16.0 pour point [°c] -7 15.0 16.0 cetane value 564 43 49 53 65 63 54 sulfur content [wt %] 0.10 0.04 carbon residue [wt %] 0.14 0.02 source: ajala et al., 2015 aladetuyi et al. (2014) have reported the utilization of cocoa pod ash (cpa) an agricultural residue which was used in place of koh as a conventional catalyst for bio-diesel production. the findings of the study suggested that the use of cocoa pod ash as catalyst led to higher yield of biodiesel both from palm kernel oil and oil recovered from spent bleaching earth. the physicochemical properties of the biodiesels produced was reported to fall within (astm) specifications for biodiesel. it was also reported that agricultural residues such as cpa could be utilized as alternatives to koh catalyst for biodiesel production (aladetuyi et al., 2014). olugbenga et al. (2013) ) also reported that a good biodiesel conversion of 94% yield was achieved when cocoa pod ash was used as catalyst for biodiesel production. in a recent study (odetoye et al., 2014), bio-oil was obtained from a non-conventional agricultural residues, parinari polyandra benth fruit shell (ppbfs). ppbfs was pyrolyzed via an intermediate pyrolysis process for the production of bio oil. the bio oils were obtained using a fixed bed reactor within a temperature range of 375–550°c.however, the ppbfs bio-oil needs to be upgraded before being used as a fuel substitute, particularly in engines as it consisted of various complex organic compounds such as acetic acid (odetoye et al, 2014). production of biodiesel from yellow oleander, theveta peruviana has been reported to have a high potential for use in production of environmentally friendly biodiesel (yarkasuwa et al., 2013). both ethanolysis and methanolysis of the oil were carried out with 50% of potassium hydroxide by weight of oil in ethanol and methanol respectively. the biodiesel was tested for biodegradability using e. coli. the percentage yield of the fatty acid ethyl esters and fatty acid methyl esters were 84.8% and 91.6% respectively. amos et al. (2015) also reported that parinari polyandra benth seed oil can be explored for biodiesel production. some bio-based catalysts (cocoa pod ash and rice husk ash (rha) were used to catalyze effectively the transesterification of parinari oil. although, the two bio-based http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng catalysts were effective, cpa gave a neater and better yield of biodiesel than rha. the biodiesels produced were reported as suitable for biodiesel production as properties compared favorably with astm specification for biodiesel standards. 2.2 industrialization of biofuel research in nigeria several attempts were reported on commercialization of biofuel research in nigeria. some of the works reported include that of akinbami et al. on the design of biogas plants at the usman danfodiyo university, nigeria. a 425 litres capacity biogas digester was found to be adequate for household cooking energy need in nigeria (akinbami et al., 2001). recent experimental efforts have been reported at the university of nigeria, nsukka and at the global network for environment and economic development research (gneeder) in ibadan, nigeria for developing appropriate technological innovations for harnessing existing potentials for producing biogas, particularly for household use. furthermore, there is domestication of biogas technology in nigeria (olugasa et al., 2014). the nigerian universities have taken up the challenge on biogas research by constructing biogas digesters and/ or pilot biogas plants at the university of ilorin, obafemi awolowo university, ladoke akintola university of technology, ogbomoso, ambrose ali university, nnamdi azikwe university, awka, uthman dan fodio university, ibrahim badamasi banbangida university, lapai, but to mention a few. the non-governmental organizaions are not left out in the development. most of these pilot biogas plants have been developed to use animal wastes as feedstocks (olugasa et al., 2014). the recent trend in biogas research is increasing the yield and enrichment to increase the biogas purity. the biomethane obtained can be converted to serve as source of electricity for household appliances (olugasa et al., 2014). government research institutions and industrialization of biofuel research in nigeria. one of the major roles of research institutions is to carry out research towards the development of the immediate community. however, presently, the researches on biofuel are not adequately co-ordinated. there is a need for significant centers of excellence for biofuel research as well as dedicated funding for biofuel research in the science, technology and innovations (sti) institutions. moreover, the government and policy makers have major roles to play in the commercialization of biofuel production in nigeria. the initial take off of the biofuel project in nigeria came with enthusiasm and strong political will with about 34 current and proposed biofuel plant projects as pioneer projects at planning phase, however with the passage of time the tempo was not sustained (elijah, 2010). the government sti policy and biofuel policy lack the political will for actualization of the policies. there is a need for the government to float / reactivate existing bioenergy parastatal to collate a database of biofuel research in nigeria. such government functionary should be responsible for driving the biofuel research incubation and commercialization. there is a need to review the biofuel and sti policy to reflect the devoid of first generation biofuel. opportunities of biofuel industrialization in nigeria the opportunities accruable to biofuel industrialization in nigeria mainly span across, economic, environmental and social dimensions (undesa, 2007). there are opportunities of rural file:///c:/users/user/downloads/azojete143/www.azojete.com.ng odetoye, et al. a review of biofuels research in nigeria. azojete, 15(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 158 development when biofuels are substantially produced in nigeria as more biofuel feedstock will be produced and thus lead to strengthening of the nigerian agro-economics. there will be provision of jobs for teeming youths and peasant farmers in the rural setting. rural-urban migration of the youths will also be minimized since agricultural sector will be enhanced and the rural youth will be involved in biofuel feedstock production. figure 2: criteria for sustainable production and use of liquid biofuel (undesa, 2007) in fact, industrialization of bioenergy production in nigeria can be a means of improving the economic status of farmers due to increased income realized from biofuel feedstock production. figure 2 shows the criteria for sustainable biofuel production. challenges of biofuel industrialization in nigeria the problems facing biofuel industrialization in nigeria are typical of those problems facing all forms of industrialization in nigeria. the problems ranged from lack of co-ordinated research work in biofuel leading to duplication of research efforts, inadequate funding of biofuel research, lack of home-grown technology, non-commercialization of biofuel research ideas to the relatively high cost of biofuel compared to fossil fuel. furthermore, the low-income people seem to be more dependent on traditional energy more than liquid biofuel as source of energy (akande and olorunfemi, 2009). recommendations the government has a paramount task in establishing industrial production of biofuel in nigeria. many of the existing research output on biofuel should be adopted and scaled up to commercial scale. this is to be co-ordinated by the appropriate dedicated and functional government http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng agencies and research outfits. the administration and monitoring of the biofuel policy should be taken out of the nnpc to encourage pragmatic attention for biofuel production. there is a need to review the existing nigerian biofuel policy to accommodate the research outputs on the utilization of some locally available biomass feedstock for sustainable biofuel production. the use of non-food feedstock should be promoted to reduce competition with food chain. there is also a need to ensure that the biofuel policy does not end up as mere paper work but consistently followed up through to implementation. much more, the academia should be funded and saddled with the responsibility of directing more effort into biofuel research and development which can translate the varieties of our tropical biomasses into biofuel feedstock. centers of excellences should be established in at least each political zone, fostering biofuel research consortium towards building a home grown technology for the nigerian biofuel industry. small-scale biodiesel production from the farms can also be encouraged by providing portable biodiesel processor which can be affordable to farmers in rural settlements. the production technologies of biodiesel are relatively not complex for the developing economy to adopt both at small-scale production and industrial scale. this is an advantage that can be utilized in nigeria and other african countries for biodiesel production. there should be pragmatic approach to implementing the biofuel policy. according to the biofuel policy, the roles of the biofuel energy commission were specified to include monitoring the supply and utilization of biofuels and biofuel blends in nigeria. furthermore, there is a need to review the 2007 biofuel policy to accommodate recent trends in biofuel development especially in the area of fourth generation biofuels as the 2007 policy was mainly based on third generation biofuel. the tax with-holding and tax holiday incentives will be a very encouraging support for the upcoming biofuel industries but there is need for research towards establishing non-edible biomass feedstock to avoid competition with food source. the agricultural system needs to be revitalized for both food and industrial crops and exports. there is a need for large scale growing of biomass feedstock both by peasant and large scale farmers to support the biofuel industry. the economic status of such peasant farmers will then be enhanced. for consistent supply of cheap feedstock for biofuel production, municipal solid wastes collection system should be restructured to encouraged separation of organic components from source so as to utilize them for biogas production. agricultural wastes should also be explored for industrial biofuel production. all existing biofuel research on nigerian biomass should be well-documented and well-archived in a database for easy documentation and retrieval of local biofuel information. also, centers of excellence for biofuel research should be established and more research should be directed towards establishing new and cheaper feedstock as energy crops and discovery of more economical methods of biofuel production. the improvement in production economy will include sourcing for potential feedstock with more biofuel yield, cheaper catalysts and cheaper source of energy inputs. the linkages between researchers, faculties of engineering and the industries should be strengthen and there should be synergy in the co-ordination of funding of research and research commercialization among national economic empowerment and development strategy (needs), tetfund, boi, small and medium industries development agency (smedan) manufacturers association of nigeria man federal ministry of agriculture and rural development. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng odetoye, et al. a review of biofuels research in nigeria. azojete, 15(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 160 4.0 conclusion this review work indicates that a reasonable number of indigenous biomass has been investigated and found suitable for biofuel production. however, these biomass are yet to be adopted as biofuel feedstock in nigeria. one of the major ways of actualizing the industrialization of biofuel production in nigeria is to adequately fund biofuel research, utilizing indigenous feedstock and home-grown technology. more research should be funded towards identifying more of the sustainable, non-food biofuel feedstock, pilot scale research and scaling up of the existing research outputs towards commercial scale. there is a need to engage in design and construction of portable scale biodiesel plants from cheap and locally available materials, plants which can be operated by sme’s. such move will position biofuel production in nigeria as a laudable step towards the revitalization of the agricultural sector which erstwhile had been neglected. considering the very high potential for biofuel production in nigeria, all hands should be on desk to ensure the effective commercialization of biofuel research, converting the existing research from bench scale to commercial scale. this will go a long way to enlist nigeria as an exporter of biofuel and improve the dwindling foreign reserve. production of feedstock for biofuel production will enhance the agricultural sector of the country which has been suffering a setback as a result of the over-dependence on petroleum. acknowledgement the contributions of the participants /discussants at the 6th regional conference of vicechancellors, deans of science, engineering and technology (covidset), 2015 towards enhancing this work are well appreciated. references agbro, eb. and ogie, na. 2012. a comprehensive review of biomass resources and biofuel production potential in nigeria, research journal in engineering and applied sciences 1(3): 149155. ajala, oe., aberuagba f., odetoye, te. and ajala, am. 2015. biodiesel: sustainable energy replacement for petroleum based diesel fuel a review, chembioeng reviews, 2(3): 145-156. akande, so. and olorunfemi, fb. 2009. research and development potentials in biofuel production in nigeria. african research review, 3 (3): 34-45. akinbami, jfk., ilori, mo., oyebisi, to., akinwuni, io. and adeoti o. 2001. biogas energy use in nigeria: current status, future prospects and policy implications. renewable,sustainable energy review. 5: 97-112. aladetuyi, a., olatunji, ga., ogunniyi, ds., odetoye, te. and oguntoye, so. 2014. production and characterization of biodiesel using palm kernel oil, fresh and recovered from spent bleaching earth and biofuel research journal, 1(4):134-138. alamu, oj., dehinbo, o. and sulaiman, am. 2010. production and testing of coconut oil biodiesel fuel and its blend, leonardo journal of sciences, 16: 95-104. amos, o., ogunniyi ds. and odetoye te. 2015. biodiesel production from parinari polyandra seed oil using bio-based catalyst, nigerian journal of technological development 13 (1): 26-30. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; 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e-issn 2545-5818, www.azojete.com.ng 162 olugbenga, ag., mohammed, a., and ajakaye, on. 2013. biodiesel production in nigeria using cocoa pod ash as a catalyst base, international journal of science and engineering investigations, 2(15): 114-117. oniya, oo., adebayo, ao. and ogunkunle, o. 2016. optimization of biodiesel production from milk bush (thevetia peruviana) oil using snail shell as catalyst, advances in multidisciplinary & scientific research 3 (1): 9-22, 2016. saladini, f., patrizi, n., pulselli, fm., marchettini n. and simone b. 2016. guidelines for energy evaluation of first, second and third generation biofuels. renewable and sustainable energy reviews, 66: 221–227. sekoia, pt. and yoro, ao. 2016. biofuel development initiatives in sub-saharan africa: opportunities and challenges, climate 4(33): 1-13. umaru m., mohammed ia., sadiq mm., aliyu am, suleiman b. and talabi, s. 2014. production and characterization of biodiesel from nigerian mango seed oil, proceedings of the world congress on engineering, london, u.k. undesa. 2007. small-scale production and use of liquid biofuels in sub-saharan africa: perspectives for sustainable development, background paper no. 2, a publication of united nations department of economic and social affairs, 31. yarkasuwa, ci., wilson d. and michael e. 2013. production of biodiesel from yellow oleander (thevetia peruviana) oil and its biodegradability, journal of the korean chemical society, 57( 3): 377-381. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4):20-36 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 20 original research article numerical and experimental studies on the cutting energy requirements of okra (abelmoschus esculentus l.) u. g. asonye1*, n. r. nwakuba2, s. n. asoegwu1 1*agricultural and bioresources engineering department, school of engineering and engineering technology, federal university of technology, owerri, nigeria. 2agricultural and bioresources engineering department, college of engineering and engineering technology, michael okpara university of agriculture, umudike, nigeria. *corresponding author’s e-mail address: u.asonye@yahoo.com article information received: october, 2018 accepted: december, 2018 keywords: modeling okra cutting energy dimensional analysis crop size nigeria abstract cutting energy requirements for vegetable crops is a prerequisite in the engineering design of appropriate cost effective cutting systems consuming minimum amount of energy while still providing high quality products. this study attempts the development of predictive equations describing the cutting energy for okra (abelmoschus esculentus l.). dimensional analysis based on the buckingham pi theorem was used to obtain the functional relationship between the cutting energy of the selected vegetable and the independent variables such as tool weight (w), height of tool drop (hd), tool edge thickness (t), cutting speed (v), crop size (s), crop moisture content (φ), crop contact area (a) and crop density (σ). the developed model was validated with experimental data. a high coefficient of determination of r2 value of 0.973 between the predicted and measured energy values showed that the method is good. hence the obtained predictive model is appropriate for determining the cutting energy requirements of okra up to 97%. © 2018 faculty of engineering, university of maiduguri, nigeria, all rights reserved. 1.0 introduction agricultural products often occur in sizes too large to be used, and therefore they need to be reduced and put into different sizes and shapes like cubes, thin slices or rings to facilitate further processing. cutting, which is a size reduction activity, is an energy consuming operation. however, the cutting energy requirements of vegetables have been estimated using different cutting systems and approaches (mcgorry et al., 2003, blahovec, 2007; mccarthy et al., 2007 and atkins, 2009) with the following objectives; to know the most efficient cutting conditions necessary for optimization of the cutting process; to determine the optimal energy required to cut and to achieve an overall efficient cutting operation. ciulica and rus 2011, elżbieta and agnieszka, 2012; and singh et al., 2016 have identified blade sharpness, slicing angle, contact area, depth of cut, cutting speed, and the engineering properties of vegetables such as crop variety, maturity stage, moisture content, mailto:u.asonye@yahoo.com http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 21 orthogonal dimensions and fiber orientation as some of the parameters affecting the energy requirements for cutting of vegetables. okra (abelmoschus esculentus l.) is a fruit vegetable of interest in this work. okra or lady’s finger, deriving its name from the ‘igbo’ word ‘툘 ko ro ’ (mcwhorter, 2000) is a widely cultivated vegetable crop in most parts of the world and one of the most popular vegetables in many west african markets and some other regions of the world (oyelade et al., 2003; andras et al., 2005; saifullah and rabbani, 2009). about 10% of the world’s annual okra production comes from west africa with nigeria as the leading producer (burkil, 1997). in south-western nigeria, the three known cultivars of okra are yaaya or kògbóyè, which has long slender pods; kúdìkán or ilá-òjò, which has short, sturdy pods and ilá-ìròkò which has long sturdy pods (farinde et al., 2007). okra is a multipurpose crop due to the various uses of the fresh leaves, buds, flowers, pods, stems and seeds. the benefits derivable from the okra fruit include nutritional benefits; a good source of minerals, vitamins, carbohydrate, protein and essential amino acids; (adeboye and oputa, 1996; adom et al.,1996; okra food, 2003; sobukola, 2009), medicinal benefits; detoxifies and aids digestion in human nutrition (makose and peter, 1990; owolarafe and shotonde, 2004) industrial benefits; valuable material for gum, paper glazing and quality soap making, contains glycans used in aqueous suspensions, an excellent source of iodine and raw material for flocculant used for removal of solid wastes from tannery effluent (owoeye et al., 1990; agarwal et al., 2003; falade and omojola, 2010) and economically it is a high income earner for vegetable farmers in producing countries (schippers, 2000). okra, like many other vegetables is highly perishable due to its relatively high moisture content, soft texture and high respiration rate. (atanda et al., 2011) and the traditional method of preserving fresh okra pods which involves spreading it in the air for few hours during cold weather only makes it preserve for just 3-4 days (schippers, 2000 and sobukola, 2009) after which, it becomes tough and unsuitable for use as a fresh vegetable. the unsold lots are processed by manually cutting into slices and sun-drying to preserve it, thereby extending its availability from one season to the other, improves the shelf life and also forestalling seasonal wastage. this manual cutting operation is a most laborious, time consuming one with the challenges of contamination of the product and injury to the hand. there have been efforts made by some researchers at developing equipment for handling the cutting operation (owolarafe et al., 2007, ogbobe et al., 2007). however, in spite of its many industrial, medicinal, economic and nutritional benefits, studies reveal that it is among the least studied vegetables, which portends a danger of gradual disappearance from our meal menu and eventual extinction unless urgent attention is given to it. also, it suffers a lot of postharvest losses due to inadequate post-harvest handling technologies which makes the crop scarce and expensive when it is not in season. hence cutting of okra as a postharvest handling operation will enhance further processing such as drying, packaging and preparation into several food forms. furthermore, extensive documentation on the properties of foods and food products exist, however data related to the cutting energy of different vegetables such as okra is scarce, even though such data is important in the design of cutters. this observation is affirmed by researchers like saravacos https://en.wikipedia.org/wiki/igbo_language http://www.ncbi.nlm.nih.gov/pmc/articles/pmc3614041/ http://www.ncbi.nlm.nih.gov/pmc/articles/pmc3614041/ http://www.ncbi.nlm.nih.gov/pmc/articles/pmc3614041/ http://www.ncbi.nlm.nih.gov/pmc/articles/pmc3614041/ http://www.ncbi.nlm.nih.gov/pmc/articles/pmc3614041/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 22 and kostaropoulos (2002) in their assessment that less work has been performed on energy involved for cutting of different food materials, and brown et al. (2005) who opined that limited published literatures on specific energy requirement in cutting of fruits and vegetables are available. also, mitcham et al. (1996) agreed that literature related to cutting of fruits and vegetables are limited, hence the need to intensify research activities in this post harvest area of cutting and determining the energy requirements for cutting vegetables such as the (ilá-ìròkò) variety of okra. 1.1 modeling agricultural processes modeling, simply defined is a representation in mathematical terms of the behavior of real devices and objects, or a system of postulates, data and inferences presented as a mathematical description of an entity or state of affairs. it could be descriptive, explanatory or predictive. in the prediction part, which can be envisaged as organized thinking of the possible, models are exercised to give information on a yet-to-be-conducted experiment. these predictions are then followed by observations that serve either to validate the model or to suggest reasons that the model is inadequate (dym and ivey, 1980; dym, 1994 and cha et al., 2000). various mathematical modeling techniques that are in use include: dimensional homogeneity and analysis, abstraction and scaling, conservation and balance principles and consequences of linearity. however, dimensional analysis has become a widely applicable and very powerful technique that is adopted in mathematical modeling. this is due to its simplicity in planning, presentation, and interpretation of experimental data, providing an organised way to plan and carry out experiments, and enables one to scale up results from model to prototype (bahrami et al., 2006). the dimensional analysis is a mathematical technique used in identifying the factors involved in a physical situation or phenomenon and forming a relationship between them. it offers a method for reducing complex physical problems to the simplest form prior to obtaining a quantitative answer (andrzej, 2015). although there are other methods of performing dimensional analysis, notably the indicial method, the method based on the buckingham pi theorems gives a well organized procedure for obtaining a solution. the buckingham pi theorem states that the number of dimensionless and independent quantities required to express a relationship among variables in any phenomenon is equal to the number of quantities involved minus the number of dimensions in which those quantities may be measured (fox and mcdonald, 1992). mathematically speaking, if there is a physically meaningful equation involving a certain number (n) of physical variables, then the original equation can be rewritten in terms of a set of p = n − k dimensionless parameters (π1, π2, ..., πp) constructed from the original variables (hart, 1995), (here k is the number of physical dimensions involved; which in this situation, (k = 3 i.e. mass, length and time). the application of mathematical models in different aspects of agricultural engineering including tillage operations (fielke, 1999), spraying machines (teske et al., 1991), crop handling machines (gorial and o’callaghan, 1991), harvesting (baruah and panesar, 2005a and b) and many versatile topics on post harvesting aspects have been successfully attempted such as; modeling flow rate of egusi-melon (colocynthis citrullus) through circular horizontal hopper orifice (asoegwu et al., 2010); modeling the grain cleaning process of a stationary sorghum thresher (simonyan et al., 2006) , modeling the drying process of a hybrid convective vegetable crop dryer (nwakuba, 2018) and http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 23 development of a model to describe infrared radiative and convective drying characteristics of onion slices for optimum management of operation parameters (jain and pathare, 2004). although a few research attempts have been made to model cutting processes like mathematical models and laboratory tests of impact cutting behaviour of forage crops, (mcrandal and mcnulty, 1978); performance modeling of the cutting process in sorghum harvesting (mohammed, 2002), mathematical modeling of laser based potato cutting and modeling yield efficiency of peeling (ferraz et al., 2007, somsen et al., 2004), much is left undone on modeling the energy requirement for cutting vegetables. some researchers used the dimensional analysis based on the buckingham’s pi theorem as veritable instrument in establishing a prediction equation of various systems which include the development of screw-conveyor performance models using dimensional analysis, (degrimencioglu and srivastava, 1996); a mathematical model for predicting output capacity of selected stationary grain threshers (ndirika, 2006); a mathematical model for predicting the cracking efficiency of vertical-shaft centrifugal palm nut cracker (ndukwu and asoegwu, 2011); and modeling flow rate of egusi-melon (colocynthis citrullus) through circular horizontal hopper orifice (asoegwu et al., 2010). the size reduction operation by cutting in most postharvest processes is a most laborious, time wasting and energy consuming task which deserves research attention. these studies are necessary in order to discover methods of efficiently improving the cutting process by maximizing the scarce energy, time and resources available and optimally enhancing the post harvest operations concerned. hence the need to undertake the present study which will establish a mathematical model using dimensional analysis based on the buckingham’s pi theorem to predict the cutting energy requirements for okra (abelmoschus esculentus l.). the mathematical model will become a design tool for machine designers in the development of energy saving and cost effective cutting systems that will provide good quality cut products. 2. materials and methods 2.1 theoretical development factors affecting the cutting energy requirements of vegetables obtained from literature include tool parameters like (materials of construction, sharpness, rigidity of cutting tools, knife speeds, etc.) and physical properties of the plant material like (crop variety, size, maturity stage, crop moisture content , crop density, fibre orientation, etc.) (nadulski, 2001; szot et al., 1987; atkins, 2009; blahovec, 2007; mccarthy et al., 2007; and mcgorry et al., 2003). in the development of the model, dimensional analysis based on the buckingham pi theorem was employed which is a technique used in identifying factors involved in a physical situation and forming a relationship among them. the buckingham pi theorem states that the number of dimensionless and independent quantities required to express a relationship among variables in any phenomenon is equal to the number of quantities involved minus the number of dimensions in which those quantities may be measured’(fox and mcdonald, 1992). i.e. if n = number of variables involved in a physical situation x = number of dimensions in which quantities may be expressed = (3), m, l, t m = mass; l = length; t = time file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 24 n =number of dimensionless groups as given in equation 1. hence, n = n x (1) however, due to the large number of variables influencing the energy of cut of the selected fruit vegetable, assumptions will be made in order to bring these large numbers to a reasonable and manageable number. (simonyan, et al., 2006). 2.2 assumptions made in model development i. variables that are design parameters which are measurable were considered. ii. variables that are functions of other variables were not considered e.g. volume which is a function of crop size. however, cutting speed which is a function of time was considered instead of time. iii. the fiber orientation, textural properties (inner hollow texture) and crop variety are considered negligible in the model development, since only the horizontal orientation of the okra fruit is considered. 2.3 development of the functional energy equation. these assumptions helped in reducing the number of variables involved to the underlisted as these were considered to have greater influence on the energy of cut of the selected vegetable (okra) and are measurable. the chosen variables are: tool weight (w), height of tool drop (hd), tool edge thickness (t), cutting speed (v), crop size(s), crop moisture content (φ), crop contact area (a) and crop density (σ). having identified the core variables influencing the energy required for cutting the selected vegetable, equation 2 represents the functional equation of the predictive model. i.e � � ������� ������φ�a�σ) (2) where e is the cutting energy of the okra crop (j) w = tool weight; hd = height of tool drop; t = tool edge thickness; v = cutting speed; s = crop size; φ = crop moisture content; a = crop contact area and σ = crop density. three primary dimensions m= mass, l= length, t= time were chosen in the description of the variables. from the buckingham pi theorem (fox and mcdonald, 1992) the total number of dimensionless groups to be formed is as given in equation 1 above. i.e � � � − � n = number of variables involve in the situation studied = 9 x = number of dimensions for describing these variables = 3 hence � � � � � � h п1, п2, п3, п4, п5, п6 hence six dimensionless groups were formed namely; п1, п2, п3, п4, п5 and п6. in determining the dimensionless groups, the following procedure was adopted (fox and mcdonald, 1992). the variables utilized in the establishment of the model equation for the cutting energy of the selected vegetable were expressed in terms of their dimensions as shown in table 1. http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 25 table 1. list of variables and their dimensions s/n variable symbol unit dimension 1 energy e kgm2s-2 ml2t-2 2 tool weight w kgms-2 mlt-2 3 height of tool drop hd m l 4 tool edge thickness t m l 5 cutting speed v ms-1 lt-1 6 crop size s m l 7 crop moisture content φ φ m0l0t0 8 crop contact area a m2 l2 9 crop density σ kgm-3 ml-3 the dimensional matrix of the variables is shown in table 2. this is needed to develop the indices of the involved variables. table 2. dimensional matrix of variables s/n variable symbol m l t 1 energy e 1 2 -2 2 tool weight w 1 1 -2 3 height of tool drop hd 0 1 0 4 tool edge thickness t 0 1 0 5 cutting speed v 0 1 -1 6 crop size s 0 1 0 7 crop moisture content φ 0 0 0 8 crop contact area a 0 2 0 9 crop density σ 1 -3 0 from the above matrix, φ is dimensionless and therefore excluded from the dimensionless terms determination and is to be added later (simonyan et al, 2006) while the other variables were combined to form the п groups. cutting speed (v), tool weight (w) and crop size (s) were selected as the major parameters (i.e. recurring set) because they contain all the primary dimensions involved in this problem and their combination does not form a dimensionless group. having selected w, v and s as the recurring set, the exponents a, b and c are attached to them respectively so that when their product ������ divide the remaining variables e, hd, t, σ and a, the dimensionless groups п1, п2, п3, п4 and п5 are obtained as given in equations 3 to 7 (ndirika, 2006; simoyan et al., 2006; asoegwu et al., 2010; ndukwu and asoegwu, 2011) .this is the basis of the buckingham pi theorem of dimensionless groups. п� = � ��vbsc (3) п� � �� ��vbsc (4) п� � � ��vbsc (5) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 26 п� � a ��vbsc (6) п� � σ ��vbsc (7) where a, b, and c are exponents needed to make the groups non-dimensional. the variables are substituted with their dimensions and the non-dimensional пs are replaced with m0l0t0 which is a dimensionless group. in order to obtain values for the exponents, the principle of dimensional homogeneity is used to equate the dimensions on each side of the equations of the п groups. equation 3 being expressed in terms of the dimensions on both sides becomes equations 8 ������ � ����−� ����−�)����−�)��� (8) crossmultiplying equation 8 gives equation 9. ������� ���−�)� ��−� ��� � ����−� (9) using dimensional homogeneity for m, l and t, the exponents a, b and c are got in equations 10, 11, 12 and 13. for m; ��u� � �� 0 + a = 1 a = 1 (10) for l; ��u�u�u� � �� 0+a+b+c = 2; from 3.10, a = 1 1+b+c =2 b+c = 2-1 =1 b+c = 1 (11) for t; ��−��−� � �−� -2a – b =-2 since a =1 -2(1) – b = -2 -b = -2+2 =0, b = 0 (12) from equation 11, b + c = 1, put b=0 0+c=1; c=1 (13) hence, a = 1, b = 0, c = 1; replacing the exponents with their values, п� becomes equation 14 п� = � ��v�s� = � �s (14) similarly, solving for the remaining п groups, we obtain equations 15 to 19. http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 27 п� = �� s (15) п� � � s (16) п� � a s� (17) п� � σv�s� � (18) пh = φ (19) combining these equations gives equation 20, whose components are dimensionless. i.e. � �s = f ( �� s � � s � a s� � σv �s� � � φ ) (20) combining the dimensionless terms to reduce it to a manageable level (shefii et al. 1996) by multiplication and/or division, we obtain equations 21 to 23 which are dimensionless. п�� = п� п� = � �s × s �� = � ��� (21) п�� = п3 п4 = t s × s2 a = ts a (22) п56 = п5 п6 = σv2s2 w × 1 φ = σv2s2 wφ (23) the new dimensionless functional relationship becomes equations 24 and 25. п�� = f (п�� , п�h) (24) e whd = f (ts a , σv�s� wφ ) (25) from equation 25, the equations for e are obtained as equations 26 and 27. e= whd ( ts a , σv�s� wφ ) (26) e = f (tswhd a � σv �s�hd φ ) (27) equation 27 gives the cutting energy e, with all the parameters in equation 2, as a function of two energy components tswhda and σv2s2hd φ which are represented as � and � in equation 28. e = f (���) (28) 2.4 experimental procedure green, mature and freshly harvested okra fruits (ilá-ìròkò variety) that were healthy and free from mechanical injuries were purchased from a local farmer in owerri west local government area of imo state, nigeria. they were thoroughly cleaned of all impurities and unwholesome fruits and thereafter sorted into four size ranges of 10 fruits each and some physical properties were obtained at an initial moisture content of 89.41± 0.4% (wb) (aoac, 2000). with an automated vegetable cutter, at a preset speed of 30mm/min, the cutter drops from a height of 20cm, cutting the sampleelectric motor file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 28 as it travels through it. the force-time relationship displayed on the monitor was used to calculate the cutting energy. plate 1.0 shows the experimental set-up of the cutting mechanism. plate 1.0: experimental set-up of the cutting mechanism the automated vegetable cutter consists of the hardware and software components. arduino controlled processors automatically and effectively measures, records and stores cutting variables and other basic parameters with minimum human supervision, thus making the entire cutting process automated. connecting to an electric power source switches on the cutter and a predetermined speed value is selected on the keypad. as the knife presses against the sample, the reactive force exerted on the load cell is amplified and measured. connecting to a computer using usb port the measured values are relayed and matlab intercepts the values and plots the resulting graph of force of cut against time travelled which is used in calculating the energy of cut. 2.5 determination of validation parameters in the determination of validation parameters, every other parameter was held constant while the crop size varied. the selected tool edge thickness (t) measured with a digital venier caliper (model 500-196, mitutoyo products, america) was 0.1cm. the weight (w) of the cutting tool determined with an electronic weighing balance (model gf-200, a & d company ltd, japan of an accuracy of ±0.01) was 23.1g. the cutting tool was dropped from a pre-determined height (h) of 20cm measured with a meter rule. the crop density (σ) determined by dividing the weight of the crop by the volume of water displaced when sample is placed inside a measuring cylinder was taken as 1.107g/cm3. the orthogonal dimensions of the sample were determined with the digital venier caliper (model 500196, mitutoyo products, america). the crop contact area (a) taken as 28.75cm2 was determined by multiplying the circumference at the point of cut (obtained by winding round with a tape and measuring out on the meter rule) with the major diameter of the crop sample. the moisture content cutter frame arduino processor cutting knife okra sample monitor display http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 29 of the crop sample determined with the method described in aoac (2000) was taken as 89.41± 0.4% (wb). 2.6 prediction energy equation the prediction energy equation was established by allowing �th � to vary at a time while keeping the other constant and observing the resulting changes in the function (shefii et al., 1996). this was achieved by plotting the experimental values of e against p = (����� a ) while keeping � constant. p = ( ����� a ) was evaluated by substituting the measured values for tool edge thickness (t), crop size(s), tool weight (w), height of tool drop (hd) and crop contact area (a) into �� also, e against � � � σv �s�hd φ ) was plotted while keeping p constant. values for � � � σv �s�hd φ ) were obtained by substituting the measured values for crop density (σ), cutting speed (v), crop size(s), height of tool drop (hd) and crop moisture content (φ). 3. results and discussion average values and standard deviation of the measured physical parameters of the okra fruits are shown in table 3. table 3. average values for physical properties of okra fruits at 89.41± 0.4% (w.b) s/n okra mass (g) diameter(mm) circumference (mm) area (mm2) 1 ok1 18.16±2.17 24.90±0.66 89.75±4.76 487.3±26.15 2 ok2 8.70±0.94 18.26±0.86 67.5±3.64 262.39±24.79 3 ok3 5.15±0.07 14.99±1.02 59.5±2.29 177.35±24.90 4 ok4 1.72±0.14 12.44±0.84 47.75±1.92 121.99±15.71 table 4 shows the experimental values of the cutting energy obtained with the automated vegetable cutter and the calculated values of the cutting energy obtained by substituting values of the cutting variables into the energy equations � � (����� a ) and q � � σv �s�hd φ ). note : crop size was varied while the other factors remained constant. table 4. experimental values (emeasured) and calculated values of cutting energy for okra fruits. s/n okra crop size (mm) (emeas)       a tswh p d          dhsvq 22 1 ok1 24.90±0.66 4.16 23.63 13.82 2 ok2 18.26±0.86 2.75 17.33 7.43 3 ok3 14.99±1.02 1.98 14.23 5.01 4 ok4 12.44±0.84 0.70 11.81 3.45 the plots of the cutting energy (emeasured) against ����� are shown in figures 1 and 2 with their linear equations and r2 values expressed in equations 29 and 30. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 30 figure 1. variation of cutting energy against � � tswhd a � keeping � � � σv �s�hd φ ) constant. figure 2. variation of cutting energy withq � (σv �s�hd φ )� keeping � � � tswhd a ) constant. e = 3.462p + 8.448 r� � ���h� (29) e = 3.026q + 0.170; r� � ����� (30) the plot of the p and q terms in figures 1 and 2 forms a plane surface in linear space and according to mohammed (2002), it implies that their combination favors summation or subtraction. therefore, the component equations formed by the subtraction and summation of equations 29 and 30 give equations 31 and 32 respectively. e = �� (��� ) �� (��� ) + k (31) e = �� (��� ) + �� (��� ) + k (32) it must be noted that; at f�, q was kept constant while p varied at f�, p was kept constant while � varied substituting equations 29 and 30 into equation 31 and performing some algebraic manipulations yields equation 33. http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 31 e = 3.462p – 3.026q + 8.278 (33) also, substituting equations 29 and 30 into equation 32 and performing some algebraic manipulations yields equation 34. e = 3.462p + 3.026q + 8.618 (34) a further manipulation as permitted under the rules of the burkingham pi theorem (shefii et al., 1996) is manipulating with a constant factor. hence, equations 33 and 34 were divided with a constant factor of 10 which yields the predicted model equations expressed in equations 35 and 36 respectively. dividing equations 33 and 34 with the constant factor of 10 yielded predicted values close to the actual ones. e = 0.3462p – 0.3026q + 0.8278 (35) e = 0.3462p + 0.3026q + 0.8618 (36) substituting the variables for p and � into equations 35 and 36 yield equations 37 and 38 respectively. e = 0.3462����� a – 0.3026σv �s��� φ + 0.8278 (37) e = 0.3462����� a + 0.3026σv �s��� φ + 0.8618 (38) however, the final predicted model equation will be either of the above two equations that gives the better statistical inference 3.1 model validation the mathematical model was validated using the data generated from the vegetable cutter. the model validation was done at four ranges of crop sizes (23-26mm, 17-20mm, 14-17mm and 1013mm) and a constant cutting speed of 30mm/min. the method of regression analysis as computed using microsoft excel environment was used to describe the relationships, plot the graphs and compute the coefficients of determination (r2). measured values of parameters were substituted into equations 37 and 38 to yield the predicted cutting energy values which were plotted against the experimental energy values on a regression curve in order to obtain the coefficients of determination as shown in figures 3 and 4 respectively. equations 39 and 40 express the relationship between the predicted cutting and experimental cutting energy with r2 values of 0.973 and 0.945 respectively. the high r2 values of 0.961, 0.921 and 0.973 obtained for the individual predictions equations and the equation for subtraction of component equations is an indication that the method adopted in the development of the mathematical models is acceptable and can be translated in the development of the other varieties of the okra fruit in particular and other vegetables in general. table 4 presents values of the predicted and experimental cutting energy and figure 3 presents the graphical relationship between the experimental and predicted cutting energy. equation 35 expresses the relationship between the predicted cutting and the experimental cutting energy with a very high correlation with r2 value of 0.973. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 32 figure 3. the graph of the relationship between experimental and predicted cutting energy (for subtraction of component energy equations) epred = 3.423 eexp – 12.59; r2 = 0.973 (39) where epred = predicted cutting energy eexp = experimental cutting energy figure 4. the graph of the relationship between experimental and predicted cutting energy. (for summation of component energy equations) epred = 0.447eexp – 1.584; r2 = 0.945 (40) from the statistical inference carried out, the predictive model equation derived from the subtraction of component energy equations gave a higher coefficient of determination (r2) value of 0.973, a lower mean difference of 1.983 between the predicted and experimental energy values and a lower standard error of 0.127 as compared to an r2 value of 0.945 obtained from the summation of component energy equations, a mean difference of 6.508 between the predicted and experimental energy values and a standard error of 0.199. hence, the predicted model equation which gives the better statistical inference of a higher r2 value of 0.973 and lower values of 1.983 and 0.127 for mean difference and standard error respectively is chosen as the predicted model equation for the cutting energy requirement for okra (abelmoschus esculentus l.) ‘ila-iroko’ variety and is given as equation 41. e = 0.3462����� a – 0.3026σv �s��� φ + 0.8278 (41) http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 33 4.0 conclusion a mathematical model for predicting the cutting energy of okra (abelmoschus esculentus l) was presented using dimensional analysis based on the buckingham’s п theorem. the model equation expressed as e = 0.3462����� a – 0.3026σv �s�hd φ + 0.8278 was validated with data from an automated vegetable cutter. results obtained showed a high coefficient of determination (r2 = 0.973), a low mean difference of 1.983 between the predicted and experimental energy values and a low standard error of 0.127. this is an indication that the method adopted in the development of the mathematical model is acceptable and can be translated in the development of predictive models for the other varieties of the okra fruit in particular and other vegetables in general. also, this expression will also help designers of the cutting equipment for okra (ilá-ìròkò) variety to avoid the rigors of experimentations and at the same time obtain efficient cutters. hence, the developed model could be used to predict the cutting energy for okra (ilá-ìròkò) variety up to 97%. references adeboye, oc. and oputa, co. 1996. effect of galex on growth and fruit nutrient composition of okra. ife journal of agriculture. 18 (12): 1-9. adom, kk., dzogbefia, vp., ellis, wo. and simpson, bk. 1996. solar drying of okraeffects of selected package materials on storage stability. food research international.29(7):589–593. agarwal, m., rajani, s., mishra, a. and rai, jsp. 2003. utilization of okra gum for treatment of tannery effluent. international journal of polymeric materials and polymeric biomaterials.52(11):1049– 1057. aoac, 2000. official methods of analysis. 17th edition. the association of official analytical chemists, gaithersburg, md, usa. 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[phd thesis.] department of agricultural and bio-resources engineering, federal university of technology, owerri. ogbobe, po., ugwuishiwu, bo., orishagbemi, co. and ani, ao. 2007. design, construction and evaluation of motorized okra slicer. nigerian journal of technology. 26(2):42-49. okra food. 2003. www.foodreference.com accessed on april 10, 2003. owoeye al., lauric, mc., allagheny, nn. and onyezili, fn. 1990. chemical and physical parameters affecting the viscosity of the mixed okra and tomato homogenate. journal of food and agricultural science. 53:283–286. owolarafe, ok., muritala, oa. and ogunsina, bs. 2007. development of an okra slicing device. journal of food science and technology. 44(4): 426-429. owolarafe, ok. and shotonde, ho. 2004. some physical properties of fresh okra fruit. journal of food engineering. 3:299-304. oyelade, oj., ade-omowaye, bio. and adeomi, vf. 2003. influence of variety on protein, fat contents and some physical characteristics of okra seeds. journal of food engineering. 57:111114. saifullah, m. and rabbani, mg. 2009. evaluation and characterization of okra (abelmoschus esculentus l.) genotypes. journal of agriculture. 7:91-98. saravacos, gd. and kostaropoulos, ae. 2002. hand book of food processing equipments. pp 138141. new york: kluwer academic / plenum publishers. schippers, rr. 2000. african indigenous vegetables. an overview of the cultivated species. chatham, uk: natural resources institute/acp-eu technical centre for agricultural and rural cooperation. pp 103-116. shefii, s., upadhyaya, sk. and garret, re. 1996. the importance of experimental design to the development of empirical prediction equations: a case study. transaction of american society of agricultural and bio-resources engineers. 39: 377–384. https://books.google.com/?id=czfufzi4zx4c&pg=pa77 https://books.google.com/?id=czfufzi4zx4c&pg=pa77 https://en.wikipedia.org/wiki/international_standard_book_number https://en.wikipedia.org/wiki/special:booksources/0-520-21999-6 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al: a mathematical model for predicting the cutting energy requirements of okra (abelmoschus esculentus l.), azojete, 14(sp.i4):20-36. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: u.asonye@yahoo.com 36 simonyan, kj., yilijep, yd. and mudiare, oj. 2006. modeling the grain cleaning process of a stationary sorghum thresher. agricultural engineering international: the cigr e-journal. 3: 1–16. singh, v., madhusweta, d. and susanta, k. 2016. effects of knife edge angle and speed on peak force and specific energy when cutting vegetables of diverse texture. international journal of food studies. 5: 22-38. sobukola, o. 2009. effect of pre-treatment on the drying characteristics and kinetics of okra (abelmoschus esculentus (l.) slices. internatonal journal of food engineering. 5(2):9. somsen, d., capelle, a. and tramper, j. 2004. manufacturing of par-fried french fries, part 2. modeling yield efficiency of peeling. journal of food engineering. 61(2):199-207. szot, b., ċsik, tk. and goáacki, k. 1987. badania zmiennoğci wáağciwoğci mechanicznych korzeni marchwi w zaleīnoğci od cech odmianowych, czynników agrotechnicznych i okresu przechowywania. zeszyty problemowe postċpów nauk rolniczych. 316: 227-246. teske, me., barry, jw. and ekbald, rb. 1991. preliminary sensitivity study of aerial application inputs for fscbg4.0. american society of agricultural engineers, paper no. 91 1052. st. josef, michigan. http://www.azojete.com.ng mailto:u.asonye@yahoo.com arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):309-320 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 309 original research article capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software p. t. adeke1*, a. etika2, a. a. atoo1 (1department of civil engineering, college of engineering, federal university of agriculture makurdi, nigeria 2institute for transport studies (its), university of leeds, united kingdom) *corresponding author’s email address: adeke.pt@outlook.com 1.0 introduction an efficient roundabout is essential in the distribution of traffic to various routes of a traffic network for smooth flow at its optimum services. the performance of roundabout is a function of its capacity, driver behaviour, delay, queue lengths, origin-destination (o-d) flow, fuel consumption and pollution emission (noise and small particles), vehicles and pedestrians characteristics, level-of-service (los), and gap acceptance among others. (akcelik, 2008; dixit, 2012; grossi, et al., 2012; akcelik, 2017a; yusuf et al., 2018). furthermore, the capacity and article information abstract following the recent public outcry over delays and long queues at the wurukum roundabout makurdi due to increase in travel demand at the road intersection, it is not certain if the performance of the roundabout is satisfactory based on engineering specifications and judgment. therefore, simulation of the 5-arm at-grade intersection was carried out using assessment of roundabout capacity and delay (arcady) and the signalised (and unsignalised) intersection design and research aid (sidra intersection) software. the geometric dimensions of the roundabout were measured and manual traffic counts were used to obtain average travel demand matric from the morning (8:30 – 9:30 am) and evening (4:30 – 5:30 pm) peak periods, and heavy vehicle proportion of origin-destination (o-d) flows on the roundabout. simulation models of the wurukum roundabout were built using arcady and sidra intersection software to measure its capacity and performance based on key parameters such as level of service (los), average geometric delay and queue length among others. though significant variations were observed among estimated performance indices, results obtained from the simulated models and statistical analysis (test of hypothesis using chi-square test) indicated that the roundabout operates at failed state classified as los f at its present condition. recommended strategies to improve the capacity and performance of the roundabout included any of the following; construction of a fly-over bridge connecting the northern and southern approaches as permitted by site physical features, signalisation of the roundabout with traffic signs, proper pavement markings and adjustment of its geometric features, or redesign and construction of road network within makurdi metropolis to divert and reduce traffic demand on the roundabout © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 june, 2019 revised 02 march, 2020 accepted 08 march, 2020 keywords: wurukum roundabout arcady sidra intersection lane utilisation degree of saturation level of service (los) http://www.azojete.com.ng adeke et al: capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software. azojete,16(2):309-320. issn 1596-2490; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 310 performance of roundabout is also affected by its geometric features, driver behaviour, visibility, traffic characteristics, frequency of priority reversal act, etc. (design manual for road and bridges dmrb, 2007; akcelik, 2008; findley et al., 2016: arcady, 2017). previous researches have examined roundabout capacity and performance level using several methodologies (highway capacity manual hcm, 2010; macioszek and akcelik, 2017; akcelik, 2017b). inefficient roundabout constitute congested traffic condition characterised by long queue lengths, high level of pollution, prolonged waiting time and consequently long travel times among others (akcelik et al., 1996; sheehan, 2010). these characteristics create unhealthy environment when it is saturated with pollutants, and also affects the social-economic wellbeing of commuters that are using the roundabout in terms of delays and abuse of value of travel time. essential geometric parameters used for roundabout analysis include; average effective flare length, conflict angle, inscribed circle diameter, entry width, approach half width and entry kerb radius (akçelik, 1997; dmrb, 2007; sidra intersection 8 user guide, 2018). the remedies of failed roundabout caused by high travel demand, o-d flow pattern or geometric dimensions include signalisation of the roundabout, conversion to grade separated intersection and adjustment of traffic network layout. advantages of signalised roundabout include improved capacity and a balanced or evenly shared delay on approaches (bernetti et al., 2003). the choice of converting an existing roundabout to a grade separated intersection or alteration of traffic network with the aim of decongesting a roundabout is usually capital intensive as it is relatively expensive and affects land use policies within the right-of-way. the wurukum roundabout is a 5-arm (including exit street) at-grade central intersection connecting cardinal parts of makurdi metropolis by roads. due to its central location in the metropolis, all traffic within the metropolis converge on the roundabout to link with other parts of the metropolis. it is not certain if the present performance status of wurukum roundabout is satisfactory or gives hope for acceptable performance in the near future. though unpublished, previous studies by the department of civil engineering, federal university of agriculture makurdi on the roundabout revealed that, traffic growth within makurdi has increased drastically in recent times (dce-uam, 2017), thereby affecting the performance of the roundabout. increased traffic volume is associated with congested traffic situation which generates negative transport externalities such as increased travel costs (fuel and delay), pollution, etc. (sheehan, 2010; gudmundsson et al., 2015). there are several simulation software used for examining the present performance of road intersections or for future performance predictions. these models include; assessment of roundabout capacity and delay (arcady), verkehr in städten – simulationsmodell (vissim) meaning traffic in cities simulation model in german, highway capacity manual (hcm), signalised (and unsignalised) intersection design and research aid (sidra) intersection software etc. (vaiana et al., 2012; akcelik, 2017a). 1.1 arcady model like other roundabout capacity simulation models, the arcady software is used for simulation of roundabouts to predict capacity and performance as well as accident risk. arcady is a software built in the united kingdom by transport and road research laboratory (trrl) currently referred to as transport research laboratory (trl) based on regression models built from empirical studies of roundabouts in the uk for roundabout simulation (brown, 1995; http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 309-320. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 311 akcelik, 1997; akcelik, 2017b). the software examines the relationship between roundabout arm capacities as a function of its geometric dimensions and circulating flow which hinder vehicle entry on the circulatory roadway. the arcady model estimates roundabout arm capacity as a function of circulating flow using the relationship given as equation 1; qe = fi − fiqc (1) where, qe is the entry capacity (pcu/h), qc is the circulating flow (pcu/h), fiandfi are constants representing intercept and slop respectively, which are estimated from geometric characteristics of the roundabout. capacity and performance analysis of roundabout using arcady software is based on approach or arm capacity (arcady, 2017). though arcady model was built after empirical examination of about 84 roundabouts in the uk within the period of 10 12 years based on uk’s unique roundabout characteristics and driver behaviours, it is not out of place for other countries to examine its suitability in capacity and performance assessment as well as accidents risk with or without further calibrations as the case may be, since the software has undergone modifications over the years to suit other countries traffic system like canada, usa, etc. (arcady, 2017). some researchers such as akcelik (2011, 2017b) and weber (2014), have criticised the suitability of arcady software for roundabout analysis in terms of capacity and performance prediction. some of the critiques include; lane-by-lane modelling concept, that arcady considers entering traffic to be evenly distributed on the circulatory carriageway irrespective of the demand flow with respect to lane configuration on both entry and circulatory carriageways; this affects capacity estimation of roundabouts with irregular lane configuration (akçelik, 2011; akçelik, 1997). its entry lane analysis model is based on simulation techniques rather than empirical studies hence generates unrealistic results (weber, 2014). arcady’s empirical capacity prediction is based on the geometry and circulating flow passing in front of an approach; it ignores other capacity mechanisms (weber, 2014; akçelik, 2011). the gap-acceptance theory and driver behaviour or traffic flow theorem are not considered by arcady; hence predictions are incorrect since in reality, there are several anomalies such as priority reversal which might halt circulating traffic to standstill (akçelik, 2011). finally, the calibration of arcady model is based on geometries considered in the lr942 study, hence results are prone to errors when used on other roundabouts (arcady, 2017). in spite of the above criticism, the adoption of arcady by this study is justified by the fact that, the geometry of roundabout and driving rules in the uk are akin those in nigeria (federal ministry of works, 2013). following the previous empirical studies, arcady software was found to use the average vehicle length of 5.75 m and specified average threshold values of 0.85 for volume/capacity ratio or degree of saturation beyond which the performance of an arm is classified as having los f, meaning it has failed. an average of 36 seconds delay and 20 veh. for queue lengths are used as acceptable thresholds for good performance. required geometric parameters for roundabout simulation using arcady software included; approach half and entry widths, average effective flare length, entry angle, entry kerb radius and inscribed cycle diameter. these parameters were measured on site using guidelines stated in the design manual for roads and bridges (dmrb) (2007) as shown in figure 1. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke et al: capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software. azojete,16(2):309-320. issn 1596-2490; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 312 figure 1: definition of roundabout features (dmrb, 2007) 1.2 sidra intersection model on the other hand, sidra is an acronym for signalised (and unsignalised) intersection design and research aid. sidra intersection is a simulation software first released in 1984 used for road intersection analysis and design. it is an advanced lane based and driver-path microanalytical tool used for capacity and performance analysis of stand-alone intersections and network of intersections, including modelling of separate movement classes of vehicles ranging from light vehicles, heavy vehicles, buses, bicycles, large trucks, light and rails/trams etc. the sidra intersection software analyses intersections using lane-based micro-analytical approach on stand-alone intersections or in a given road network considering different types of vehicles and dynamic human behaviour. its roundabout capacity model considers the effects of o-d pattern of flow, lane usage (utilisation) on multiple-lane approaches with heavy and unbalanced flows. the capacity and performance models of sidra intersection were calibrated using real-life and simulation data. the use of sidra software for intersection analysis http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 309-320. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 313 has been commendable over time. the software is capable of estimating intersection performance measures such as capacity, los, delay (geometric or operational), queue length and stops for vehicles and pedestrians, fuel consumption of all vehicles using the roundabout in terms of cost ($/km) and rate (l/100km), amount of emitted air pollutants from vehicles tail pipe such as carbon dioxide, hydrocarbon, carbon monoxide, nitrogen oxides in kg/hour, performance index estimated from the combined statistics of server variables, etc. the sidra intersection software within its framework provides operational alternatives of using the hcm models for estimating essential performance variables. according to the sidra intersection 8 user guide (2018), using its micro-analytical technique, the gap acceptance lane capacity in sidra intersection is estimated using equation 2; q = s.u 2 where, q is the capacity of a given lane (veh./h), s is its saturation flow rate expressed as 3600/tf (veh./h), where tf is defined as the follow-up headway (sec.), and u is the unblocked time ratio. the unblocked time ratio is the proportion of time when vehicles can depart from the queue of a specified lane. though researches on the suitability and improvement of the sidra software for intersection analysis and design stated long ago, works on its improvements are still ongoing (akcelik et al., 1998; akcelik, 2008). the software has gain wide acceptance around the world from transport infrastructural planners and development experts over the years in usa, europe, australia, south africa, new zealand, malaysia, singapore, latin america and arabian peninsula (sidra intersection 8 user guide, 2018). the aim of this study is to carry out a comparative study on capacity and performance assessment of the wurukum roundabout using arcady 9 and sidra intersection 8 software. specific objectives of the study included the assessment of the geometric features and travel demand pattern on the roundabout using guidelines specified in the acardy 9 and sidra intersection 8 user manuals, and simulating the capacity and performance of the roundabout using arcady and sidra intersection based on its present status. solutions to improve the roundabout’s performance if found inefficient were proposed. 2.0 materials and methods 2.1 the study area makurdi is the capital city of benue state in nigeria. it falls within the north-central geopolitical zone of nigeria. makurdi metropolis lies on the benue trough linking the north and southern parts of nigeria within latitudes 7°50’20’’n and n7°37’60’’n and longitudes 8°19’30’’e and e8°40’20’’e. the wurukum roundabout site is situated at 7° 43’ 56” n and 8° 32’ 21”e coordinates (google earth, 2017). according to the 2006 national population census (npc, 2006), makurdi metropolis has an estimated human population of 367,588 persons with a landmass of approximately 800 km2. the metropolis is separated by the river benue into makurdi-north and makurdi-south. the population of the metropolis is dominated by civil servants, business men and women, and students. the location of wurukum roundabout in the makurdi metropolis is as shown in figure 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke et al: capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software. azojete,16(2):309-320. issn 1596-2490; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 314 (a) extract map of makurdi metropolis (google earth, 2017) (b) layout of wurukum roundabout figure 2: layout of the wurukum roundabout road network in makurdi metropolis is aligned such that all major routes link to the central roundabout which receives and distributes influx and exit traffic respectively within the metropolis. the symmetrical nature of road network in makurdi metropolis made the study of traffic flow pattern simple since all major routes within the city are linked to a common central intersection called the wurukum roundabout. the roundabout connects traffic from the north (n), west (w), south (s) and east (e) approaches namely lafia road, iorchia ayu road, otukpo road and gboko road respectively. there is also an exit street named onitsha street between the north and east (ne) approaches. traffic streams within makurdi metropolis basically consist of private cars, motorcycles (okada), tricycles (keke napep), minibuses, taxicabs and trucks, meant to convey people, goods and services from one place to another. 2.2 data collection the geometric dimensions of wurukum roundabout were measured using steel measuring tape and protractors. essential parameters measured included; entry width (e), approach half width (v), average effective flare length (l’), entry angle (ϕ), entry kerb radius (r) and the inscribed circle diameter (d). a classified daily manual traffic count was carried out from 06:00 am to 06:00 pm to obtain average daily traffic (adt), and percentages of heavy vehicles based on o-d flows on the roundabout using writing materials for a period of two weeks with emphasis on morning (8:30 – 9:30 am) and evening (4:30 – 5:30 pm) peak periods. the average hourly traffic demand for morning and evening peak periods were obtained for all arms to generate average travel demand and percentage of heavy vehicles matrices based on passenger car unit per hour (pcu/h) of travel demand. 2.3 development of arcady model a simulation model of wurukum roundabout was built at the university of leeds, united kingdom using arcady software based on its geometric parameters and travel demand matrix, as well as the percentage proportion of heavy vehicles. the built arcady model was simulated to examine its performance. essential performance parameters targeted included; maximum average queue length, maximum delay, volume/capacity ratio and los which collectively defined performance of the roundabout in the context of arcady software. n http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 309-320. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 315 2.4 development of sidra intersection model development of the sidra intersection models involved the use of some input parameters characterising the site layout (same as for arcady model) and traffic behaviour and flow at the wurukum roundabout were specified under the movement definition, lane geometry, lane movement, travel demand and the vehicle movement data tabs. default settings for all exits lanes under the lane movements tab were ignored since the site was analysed as a standalone site and not a whole network. also, pedestrians’ behaviour at the roundabout were not considered. a simulation run of the configured system yielded detailed output results which described the performance of the roundabout. the diagnostic section of detailed output reports were used to check errors and troubleshoot during simulation iterations. 2.5 statistical analysis for fitness test the chi-squared test at 5% level of significance was used to test the performance similarity of both models with a null hypothesis of being equal to aid decision of the analysis. 3. results and discussion 3.1 site geometry and traffic flow rate the geometric dimensions and o-d flow rate matrix based on adjusted travel demand using peak hour factor (phf) on wurukum roundabout for year 2016 were as shown in tables 1 and 2 respectively. table 1: geometric dimensions of wurukum roundabout approaches no. of lanes v (m) e (m) l' (m) r (m) d (m) ϕ (0) s 1 5.50 8.80 29.20 38.10 50.00 17.00 e 2 7.80 13.90 21.00 17.65 50.00 13.00 n 2 6.20 12.90 20.10 10.85 50.00 15.00 w 2 8.80 12.10 24.50 33.64 50.00 24.00 nw 2 6.15 12.00 50.00 table 2: average o-d flow matrix (pcu/h) approaches s e n w nw total origin s 1223 337 425 24 2009 e 221 455 1110 103 1889 n 166 537 853 397 1953 w 722 1385 684 2791 total destination 1109 3145 1476 2388 524 8642 the n and s traffic volume travelled on undivided road corridors with relatively narrow lanes as shown in table 1. the average flare length which served as storage spot for waiting vehicles on all approaches ranged between 20 – 30 meters. table 2 shows that, average total travel demand on the roundabout within the study period was 8642 pcu/h, with the w corridor carrying relatively high volume of traffic followed by the n. approach e has the least volume of traffic lower than n approach. the percentage of heavy vehicle demand matrix on the wurukum roundabout was as shown in table 3, with s and n approaches having relatively high percentages of heavy vehicles. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke et al: capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software. azojete,16(2):309-320. issn 1596-2490; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 316 table 3: demand percentage of heavy vehicles approaches s e n w s 2.4 3.2 0.01 e 1.1 2.2 0.01 n 2.9 1.8 0.02 w 0 0.1 0.01 this proportion distribution is attributed to the haulage of oil and gas products as well as agricultural products from the southern to northern part and vice versa in nigeria. 3.2 simulation results the summary of simulation results for arcady 8 (ady) and sidra intersection 8 (sdi) software were as shown in table 4. table 4: summary of simulation results legs average delay (s) average queue (veh.) degree of saturation los junction delay (s) junction los ady sdi ady sdi ady sdi ady sdi ady sdi ady sdi s1 4861 1140.0 6.37 f 2511 1498 f f sa 9657 4861 1691 3267 3.53 6.37 f f e1* 123.1 75.8 1.08 f e2* 117.3 87.9 1.08 f ea* 5 120 3 87.9 0.74 1.08 a f n1 816.7 212.6 1.87 f n2 808.0 294.6 1.87 f na 164 812 89 294.6 1.10 1.87 f f w1 369.9 303.5 1.39 f w2 372.8 254.0 1.39 f wa 340 371 250 303.5 1.18 1.39 f f * subscripts 1, 2 and a define the inner lane, outer lane and maximum weighted average results respectively for the s, e, n and w approaches of the sidra intersection iterations. table 4 presents parameters used for performance examination based on outputs of arcady and sidra intersection software. arcady model presents average results for entire approach, while the sidra intersection software presents results for lane-by-lane analysis of each approach. both software yielded approximately similar results for lane degree of saturation, lane los, junction delay and junction los variables which described performance of the roundabout. using the average threshold values specified by the models, table 4 revealed that the performance parameters of the roundabout for approaches n, w and s showed poor performance using both models, which indicated a failed performance at los f. from the arcady model, the maximum average delay and queue length on approaches showed that performance of the s approach was relatively worse compared to the n and w approach lanes. the e approach performed relatively better compared to the n, w and s approach lanes. this was due to the degree of saturation of all lanes constituting the n, w and s approaches being greater than the weighted average threshold of 0.85 units defined by arcady model. though http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 309-320. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 317 the combined effects of lanes for the e approach had degree of saturation of 0.74 units which was less than the threshold, hence was the only approach performing within permissible los at present. based on analysis using the arcady model, though approach e performed at los a, the failure of approaches n, s, and w to attain fair los affected the performance of the entire roundabout leading to its failed status. therefore, based on these performance parameters, arcady software described the holistic performance of the roundabout at los f. on the other hand, results obtained from simulations using the sidra intersection software also showed some similarities to those obtained using arcady software, as shown in table 4. though the analysis carried out by the sidra intersection model were on a lane-by-lane bases, results presented in table 4 showed both the lane and approach performance estimated as the weighted averages of the lanes performance. this average is defined as the weighted averages of iteration runs for individual lane performance per approach (akcelik, 1996, 1997; sidra intersection 8 user guide, 2018). results obtained from the e approach indicated a relatively good performance which conformed to findings of the arcady models, though still classified as failed at los f by the sidra intersection models. these results indicate slight similarity with those of the arcady models which classified the e approach at los a since other performance parameters such as maximum average delay and queue length of the e approach showed relatively low magnitude as compared to the n, w and s approaches. based on these performance statuses, the sidra intersection software classified the wurukum intersection at los f which conforms to results of the arcady software. the test of hypothesis using chi square statistical test for similarity of results between the arcady and sidra intersection models at 5% level of significance and 3 degree of freedom with a null hypothesis of both being equal is as shown in table 5; table 5: statistical analysis – chi square test models chi square (χ2) values decision computed critical average delay (s) 5361.79 7.81 rejected average queue (veh.) 320.85 7.81 rejected degree of saturation (%) 1.72 7.81 accepted table 5 also shows significant variations in the magnitude of performance outputs estimated using the arcady and sidra intersection models. differences between the estimated average delay and average queue length per approach leading to rejection of the null hypotheses was attributed to the fact that, while sidra intersection model carried out laneby-lane analysis of the intersection which required detailed lane specifications such as flow distribution proportion, lane utilisation, etc. (sidra intersection 8 user guide, 2018), the arcady model carried out holistic analysis of the entire roundabout based on approach characteristics regardless of lane-by-lane properties to arrive at overall performance of the intersection (arcady, 2017). there was no significant difference in the estimated degree of saturation of both models leading to acceptance of the null hypothesis, hence the parameter confirm similarity in travel demand situation considered by both models (akçelik, 1996; 1997). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke et al: capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software. azojete,16(2):309-320. issn 1596-2490; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 318 4. conclusion a simulation and comparative analysis of the 5-arm at-grade wurukum roundabout situated in makurdi metropolis using arcady and sidra intersection software was carried out. the simulation results revealed that, there were statistically significant differences between estimated average delay and average queue lengths on approaching lanes by both models, leading to rejection of the null hypotheses. on the other hand, there was no significant difference between estimated degrees of saturation from both models, hence the null hypothesis was accepted. also, both models described the holistic performance of the roundabout at its present state as los f characterized by prolonged waiting times and long queue lengths on its approaches, especially the n, w and s approaches. in spite of variations in estimated outputs of the models which depended on different mathematical models used, results of the simulation analysis using the two software proved the failed status of the roundabout at los f. it was therefore concluded that, the wurukum roundabout has failed based on its performance tests using arcady and sidra intersection software, hence calls for reengineering for improved performance. the following recommendations were made; following the successes of using fly-over bridges to improve roundabout performance as stated in previous studies, this study therefore recommends the construction of a fly-over bridge connecting the n and s approaches of the roundabout to separate traffic streams and ease traffic flow as permitted by land use policy on the site. signalisation of the roundabout with road signs and proper pavement markings as well as alteration of geometrical features – expansion of weaving length on all legs and additional lane on the s approach will help increase its capacity and performance thereby eliminating high cost of compensation and major re-construction works on the site. alteration of the entire road network in makurdi metropolis to redirect and reduce traffic demand on the roundabout will reduce high traffic demand significantly, hence improve its performance. acknowledgement the authors acknowledge the supports rendered by balogun o. abdulmateen of the department of civil engineering, federal university of agriculture makurdi, while conducting the study; and the academic license of the sidra intersections software granted by rahmi akcelik of sidra intersections australia. references akçelik, r. 1996. intersection perforamcne measures for variable demand, working document wd to 96/036, arrb transport research ltd, vermont south, australia. akçelik, r. 1997. lane-by-lane modelling of unequal lane use and flares at roundabouts and signalised intersections: the sidra solution, arrb transport research ltd, australia traffic engineering + control, 38 (7/8): 388 399. akcelik, r. 2008. roundabouts in australia. akcelik and associates pty, ltd. greython victoria, australia. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 309-320. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 319 akçelik, r. 2011. roundabout model comparison table, akcelik and associates pty ltd p.o box 1075g, greythorn, vic 3104 australia. akcelik, r. 2017a. an assessment of the highway capacity manual edition 6 roundabout capacity model. paper presented at the 5th international roundabout conference, transport research board, green bay, wisconsin, usa. akcelik, r. 2017b. roundabout comparison table. akcelik and associates pty ltd, greythorn, australia. akcelik, r., christensen, b. and chung, e. 1998. a comparison of three delay models for signcontrolled intersections. 3rd international symposium on highway capacity, copenhagen, denmark, 22 – 27 june 1998, (1), edited by rysgaars, road directorate, ministry of transport, denmark, 35 – 56. akcelik, r., chung, e. and besley, m. 1996. performance of roundabout under heavy demand conditions. road and transport research, 5 (2): 36 – 50. arcady 9. 2017. assessment of roundabout capacity and delay, transport research laboratory (trl), united kingdom. bernetti, g., dall’acqua, m. and longo, g. 2003. unsignalised vs signalised roundabouts under critical traffic conditions: a quantitative comparison. association for european transport, london, united kingdom. brown, m. 1995. the design of roundabouts. transport research laboratory state –of-the-artreview, hmso, london, united kingdom. dce-uam, 2017. archives of the department of civil engineering, university of agriculture makurdi, nigeria. design manual for roads and bridges (dmrb) 2007. road geometry-junctions, geometric design of roundabouts, part 3, 6(2), td 16/07, london, united kingdom. dixit, vv. 2012. modelling origin-destination effects on roundabout operations and inflow control. journal of transportation engineering, 138 (8): 1016 – 1022. federal ministry of works 2013. highway manual part 1: design, volume 1: geometric design, federal republic of nigeria, abuja, nigeria. findley, dj., schroeder, bj., cunningham, cm. and brown, th. 2016. highway engineering; planning, design, and operations. the boulevard, langford lane, oxford, united kingdom. google earth, 2017. google earth, united states of america. accessed on 21th february, 2015, grossi, r., de riso di carpinone, v. and tocchetti, a. 2012. functional characteristics and safety of two-lane rural roads, siiv – 5th international congress – sustainability of road infrastructures, procedia – social and behavioural sciences 53, napoli, italy, october 2012, 921 – 932. gudmundsson, h., hall, rp., marsden, g. and zietsman, j. 2015. sustainable transportation. indicators, frameworks, and performance, management. springer texts in business and economics, london, united kingdom. hcm. 2010. highway capacity manual. transportation research board, national research council, washington dc. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke et al: capacity and performance assessment of wurukum roundabout in makurdi metropolis: a comparative study using arcady and sidra intersection software. azojete,16(2):309-320. issn 1596-2490; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 320 macioszek, e. and akcelik, r. 2017. a comparison of two roundabout capacity models. paper presented at the 5th international roundabout conference, transport research board, green bay, wisconsin, usa, 8 – 10 may 2017, 1 – 15. npc 2006. national population commission, federal republic of nigeria official gazette, 94, no. 24, abuja, nigeria. sheehan, md. 2010. congestion pricing in traffic control, transportation issues, policies and r&d series. new york: nova science publishers inc. sidra intersection 8, 2018. signalised (and unsignalised) intersection design and research aid (sidra intersection) software, user guide, akcelik and associates pty ltd p.o box 1075g, greythorn, vic 3104 australia. vaiana, r., gallelli, v. and luele, t. 2012. simulation of observed traffic condition on roundabouts by dedicated software, siiv – 5th international congress – sustainability of road infrastructures, procedia – social and behavioural sciences 53, napoli, italy, october 2012, 742 – 754. weber, p. 2014. introduction to roundabout analysis using arcady, toronto simcap user group technical event and ite toronto section social event, toronto. yusuf, it., abur, aa., ako, t. and bilewu, so. 2018. a quantitative analysis of rotary intersections in an urban metropolis, nigeria. malaysian journal of civil engineering, 30(2): 282 – 295. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):200-211 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 200 original research article design and experimental testing of a solar box cooker with paraffin wax as thermal energy storage using maiduguri weather condition m. b. maina*, s. shodiya and a.t. abdulrahim department of mechanical engineering university of maiduguri, p.m.b. 1069 maiduguri, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: solar box cooker phase change material energy off-sunshine. abstract the performance of paraffin wax as phase change material (pcm) for thermal energy storage (tes) was investigated using a solar box cooker (sbc) exposed to maiduguri weather condition. temperature and energy generated by sbc were experimentally established. the result shows tremendous improvement in energy storage compared to sbcs without tes in existence within maiduguri and environs. the measured temperature and energy generated by the pcm in the experiment were 118oc and 4164.5kj respectively, an adequate temperature and energy for cooking during off-sunshine hours and beyond. first figure of merit (f1) and second figure of merit (f2) were deduced to be 0.13 and 0.44 with overall sbc efficiency (ɳ) of 63% qualifying the sbc to grade a based on the bureau of indian standards (bis) © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction with the rapid development in civilization, man has increasingly become dependent on natural resources to satisfy his needs. cooking food is one of those indispensable processes that require natural resources in the form of fuels. solar cooking is fast becoming a preferred method of cooking food considering the potential of saving significant amounts of conventional fuel. the major factor that limits the solar energy for cooking application is that it is a cyclic time dependent energy source. therefore, solar systems require energy storage to provide energy during the night and overcast periods. in addition, one of the major requirements in using solar energy for cooking application is the development of a suitable cooking unit, which should be fast and energy efficient (elsebaii et al., 2011). over the last century, many studies have been performed on the development of various types of solar cookers and on the evaluation of the performance and economic aspects of solar cookers. there have also been several attempts to increase the performance and efficiency of cookers in non-tropical regions (oturanc et al. 2002). different types of solar cookers (box type, direct or concentrating type and indirect type) were modified and investigated by researchers (elsebaii et al., 2011). some researchers have investigated the performance of a solar cooker for possible use in different applications, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 201 with modifications in outer-inner reflectors (elsebaii, 1997); different insulating materials (mishra et al., 1984 and nahar, 2001), various booster mirrors (mirdha and dhariwal, 2008), absorber plate (amer, 2003 and harmim et al., 2010), a hybrid solar system (prasanna and umanand, 2011 and nahar, 1993) among several other modifications. recently, some studies have been performed concerning the use of phase change materials (pcms) integrated with solar cookers as thermal energy storage (tes). the use of a pcm results in shorter cooking times (sharma et al., 2005). it is concluded that, acetanilide is a promising pcm for cooking indoors with aluminum; but it exhibits some corrosion in contact with steel. however, magnesium nitrate hexahydrate is not stable during its thermal cycling due to the phase segregation problem; therefore, it is not recommended as a storage material inside solar cookers for cooking indoors (elsebaii et al., 2009). also, these pcm are rather expensive when high temperatures are concerned. in addition, sharma et al. (2002) found that paraffin wax showed reasonably good thermal stability in their melting temperature as well as variations in their latent heat of fusion. the ideal pcm to be used for latent heat storage system must meet the following requirements: highly sensitive heat capacity and heat of fusion, stable composition, high density and heat conductivity, chemical inert, non-toxic and non-inflammable, reasonable, and inexpensive (sharma et al., 2009). several attempts have been made to increase the performance and efficiency of solar cookers developed and tested in maiduguri and environs (ngala et al., 2015). solar cookers are expected to contribute considerably towards meeting the requirements of domestic cooking energy with 8-9 hours of sunshine hours in maiduguri and environs (maina et al., 2016). despite the enormous solar energy potential of maiduguri solar cookers are not widely used. available literature shows that no investigation dealing with pcm use in solar cooker has been carried out in the study area hence, this work intends to develop an experimental model of a solar box cooker with tes (paraffin wax) a phase change material using the weather conditions of maiduguri, this will also increase the reliability of the solar box cooker as it improves operational performance of the system to be used for off-peak periods. it is also an approach and or solution for bridging the gap between solar energy availability and demand, especially for cooking purposes in the study area (maiduguri). 2 materials and methods the design materials (parameters) considered included the energy requirements, daily average insolation, the thermal energy storage material (paraffin wax), ambient temperature and other thermo-physical properties of paraffin wax as highlighted in table 1. the experimental temperature measurement was performed in selected points using the t-type thermocouples of cu-ni (copper-nickel) with a temperature range of 185°c to 300°c. 2.1 design considerations the design parameters considered included the energy requirements, daily average insolation, and size of pcm container, ambient temperature and melting temperature of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina et al: design and experimental testing of a solar box cooker with paraffin wax as thermal energy storage using maiduguri weather condition. azojete, 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 202 the pcm. the experimental temperature measurement was performed in selected points. at the wall surfaces: convective and radiative heat transfer conditions were applied to all outer walls and to the feeding glass (receiver). heat flux to the wall was given by bird et al. (2001) in eqn. 1 as: (1) where: hf is the local heat transfer coefficient of air (w/m2k), tw is the wall surface temperature (k), tf is the local air (fluid) temperature (k) and, qrad is the radiative heat flux (w/m2). air, which consists of nitrogen, oxygen, a small amount of carbon dioxide and other gases, has been found not showing absorption band in those wavelength regions of importance to radiant heat transfer. the walls are insulated with saw dust. the heat loss which was calculated from the overall heat transfer coefficient that combines convection and conduction was estimated as being approximately. 13.0 w/m2k (birds et al., 2001). table 1: thermo-physical property of materials in use material ρ [kg/m3] cp [j/kgk] λ [w/mk] ε lhf(kj/kgk) plywood 850 1.250 0.150 0.8 mirror 1.19 6.7 aluminum 2700 896 229 glass 2700 840 0.76 0.94 air 0.7 1034 0.037 saw dust paraffin wax 0.900 0.2 189 source: mishra et al. (1984) 2.2 solar box cooker description the cooker for this study basically conforms to a box within a box with transparent double glazing and access door by the side as shown in figure 1. figure 1: a double glazed solar box cooker (sbc) with a booster mirror. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 203 the box unit consists of a double walled box. the inner and outer boxes were made of plywood. the dimensions of the outer box are were 100×90×50 cm and those of the inner box are were 88×78×35 cm. kundapur (2009) suggested that the depth of the inner box should not be more than 10-15 cm. the space between the two boxes was maintained at 6 cm and was filled with sawdust insulation obtained from local carpenters in maiduguri, borno state nigeria. the inner box was painted black for optimal heat absorption. the box geometry was designed and generated using ansys design modeler as shown in fig figures 2 and 3 respectively. figure . 2: 1nner box figure. 3: thermal energy storage tank experimental tests were conducted after constructing a physical model of the sbc as shown in fig figure 4 under various weather conditions to determine the viability of using paraffin wax as tes. to evaluate the performance of the solar box cooker in maiduguri the measured parameters include ambient temperature, solar irradiance, cooking chamber temperature, plate temperature, and pcm temperature. figure. 4: box unit with pcm tank before and after glazing 3.0 methods thermal performance tests were conducted under various weather conditions to determine the viability of using paraffin wax a phase change material (pcm) as tes, to evaluate the thermal performance of the solar box cooker in comparison with non-pcm box cooker used around maiduguri environs. the measured parameters include temperature, solar irradiance and the wind speed. the cooking power tests were done according to the bureau of indian standards, bis (2000) as one of the best standards for the evaluation of solar box cookers. all the measured parameters were recorded at intervals of ten minutes. according to funk (2000) the ten minutes is long enough time file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina et al: design and experimental testing of a solar box cooker with paraffin wax as thermal energy storage using maiduguri weather condition. azojete, 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 204 that the minor fluctuations in heat loss due to ambient temperature and wind variability are expected to be negligible. ten minutes is short enough time that the heat gain variability due to gradual sun angle changes may be considered constant during the interval. the t-type thermocouples of cu-ni (copper-nickel) with a temperature range of 185 °c to 300 °c were used to measure the temperature distribution inside the pcm storage unit, the temperature inside the cooking vessel, the absorber temperature and the ambient temperature. the sbc was operated under load and no-load situations to establish parameters for its evaluation. 3.1 thermal performance tests 3.1.1 stagnation test a number of tests without load were conducted on the cooker to determine its stagnation temperature and also to check the rise in temperature inside the cooker. the stagnation temperature, ambient temperature (ta) and absorber plate temperature (tp) were measured for different times of the day between 09:00 am and 4.00 pm during the operation of the cooker using type k, mineral insulated grounded junction, 1.6mm diameter thermocouple with elix digital thermometer (lx-6500) capable of reading temperature between -50°c and 350°c. thermo anemometer (prova instrument, avm 01) was used to measure wind speed (v) and solar radiation was measured using global radiation meter (grm 100). 3.1.2 full load test the loading test was carried out by boiling different volumes of water-filled in cylindrical pot covered with a lid and placed inside the cooker. the test was conducted for three days with 1.0 kg of water on the first day, 1.5 kg of water on the second day and 2.0 kg of water on the third day. each test was carried out on a relatively sunny day between 9:00 am and 4:00pm daily. the absorber plate temperature (tp), ambient temperature (ta), oven temperature (to), water temperature (tw), solar radiation (hs) and pcm temperature were measured using the instrumentation described in section 2.3.2 3.2 performance measurement the performance evaluation of the solar box cooker involved estimation of the following parameters: first figure of merit (f1), second figure of merit (f2) and cooker’s efficiency (ŋ). 3.2.1 first figure of merit the first figure of merit (f1) of a solar box cooker is defined as the ratio of optical efficiency (ŋo) and the overall heat loss coefficient (ul) as given by purohit, 2009. 1 0 1 u f   (2) experimentally, s asps h tt f  1 (3) where: tps,(°c) tas,(°c) and hs (w/m2) are stagnation plate temperature, average ambient http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 205 temperature and intensity of solar radiation, respectively. 3.2.2 second figure of merit the second figure of merit (f2) was evaluated under full load condition and can be represented by the expression given by mohod (2011) as follows:                              h tt f h tt fin a cmf f aw aw t ww 2 1 1 11 2 11 11 (4) where: f1 is first figure of merit (km2w-1), mw is the mass of water as load (kg), cw is the specific heat capacity of water (j/kg°c), ta is the average ambient temperature (°c), h is the average solar radiation incident on the aperture of the cooker (w/m2), tw1 is the initial water temperature (°c), tw2 is the final water temperature (°c), a is the aperture area (m2) and t is the time difference between tw1 and tw2 (s). 3.2.3 cooker efficiency the overall thermal efficiency of the solar box cooker was expressed mathematically by khalifa et al. (2005) and olwi (1993) and reported by el-sebaii (2005) as follows: tai tcm cav ww    (5) where: ŋu represents overall thermal efficiency of the solar cooker; mw, mass of water (kg); cw, specific heat of water (j/kg/°c); ∆t, the temperature difference between the maximum temperature of the cooking fluid and the ambient air temperature (°c); ac, the aperture area (m2) of the cooker; ∆t, time required to achieve the maximum temperature of the cooking fluid (s); iav, the average solar intensity (w/m2) during time interval δt. 3. results and discussion various test results as highlighted earlier are presented below graphically and discussed to draw inferences for or against” based on facts and figures established by the study. these include the stagnation test, the load test and the cooker efficiency test. 3.1 stagnation temperature tests figures 5 and 6 show the result of stagnation temperature tests under no load condition for wax tes solar box cooker. the figures reveal the variation in the solar radiation and its effects on ambient temperature, oven temperature and plate temperature. in figure 5 oven maximum temperature of 105°c and maximum ambient temperature of 36°c was recorded at 12:30 pm with corresponding insolation of 768 w/m2. figure 6 shows maximum plate temperature of 135.7°c was achieved at 12:30 pm while stagnating at 135.1°c between 10:45am to 1:30pm with corresponding average solar radiation of 770 w/m2. the pcm (wax) temperature was maintained despite drastic fall in solar radiation file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina et al: design and experimental testing of a solar box cooker with paraffin wax as thermal energy storage using maiduguri weather condition. azojete, 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 206 between the hours of 12; 45pm to 1; 30pm as shown in figure 7. the average ambient temperature for the test day was 35°c being cloudy with intermittent rainfall (7th-15th july 2018). first figure of merit (f1) was deduced based on eqn. 3 and was found to be 0.13 this figure qualifies the sbc as grade a cooker in accordance with the criteria set by bis. the result shows that heat loss from the absorber plate of the sbc was minimal and the absorber plate temperature increases irrespective of the fluctuations in solar radiation due to cloud cover, the findings are similar to the work of mohammed et al. (2013). figure 5: thermal performance curve in an sbc with wax as tes under no load condition in a test day showing ambient and oven temperature against corresponding solar radiation figure 6: thermal performance curve of plate temperature in sbc with wax as tes in a test day http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 207 figure 7: thermal performance curve of pcm (wax) temperature in sbc as tes in a test day 3.2 full load test the experiment was carried out during cloudy days of july (7th july 2018) in a rainy season from the morning through the evening hours (9:00am to 4:00pm) and the absorber ’ s surface temperature increased with a single reflector (booster mirror) at an appropriate focusing angle. the solar box cooker under full load condition was able to provide a hot environment adequate for cooking most food items and maintaining it hot/warm for long hours after completion of cooking as shown in figure 8. the highest oven temperature of 131°c was attained by the box cooker at 12:30 with corresponding insolation of 861 w/m2 and maximum plate temperature of 124.1°c with corresponding solar radiation of 876w/m2 at 12:15pm as shown in figure 9. plate temperature was maintained at 124°c from 11:45am to 12:45pm when most food items can be cooked at 75°c as reported by dormanski et al. (1995). maximum temperature of 108.1°c was attained by the pcm (wax) at 12:15 and 99°c by 4pm showing appreciable heat storage with declining solar radiation as shown in figure 10. the amount of energy stored by the pcm (wax) was determined to be 4167.5 kj, an amount much higher than that obtained by dormanski et al. (1995) and yuksel and avci (2010) showing that the cooker can also be used to get other food items cooked through the night at off sun-shine hours due to the heat storing capacity of the pcm under the prevailing weather conditions. figure 11 shows the thermal behavior of pot due to a multifaceted heat gain existing in the sbc with adequate insulation to extend energy conservation and usage. accordingly, the overall sbc efficiency with wax as pcm was found to be 51% using eqn. 5. however, higher efficiency may be achieved by modifying the thermal conductivity of wax and incorporation of solar tracking system, as demonstrated by yuksel and avci (2010). the maximum pot temperature during the water boiling test shown in fig. 11 was 98°c attained by 2:00pm with corresponding average insolation of 760 w/m2; f2 was deduced to be 0.44 using eqn. 4 above the minimum value of 0.4 set by bis for proper assessment of sbcs as grade a sbc in terms of efficiency. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina et al: design and experimental testing of a solar box cooker with paraffin wax as thermal energy storage using maiduguri weather condition. azojete, 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 208 figure 8: full load test with 1 kg of water in a sbc with wax as thermal energy storage showing ambient and oven temperatures against corresponding solar radiation in a test day figure 9: full load test in a sbc with wax as tes showing plate temperature behavior with corresponding solar radiation in a test day figure 10: full load test in a sbc showing pcm temperature behavior with corresponding solar radiation in a test day. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 209 figure 11: thermal curve of pot temperature in a sbc with wax as tes. 4.0 conclusion in this study, the geometry of box type solar cooker with single booster reflector was generated/ designed using ansys 19.0, constructed, and experimentally tested under the weather conditions of maiduguri. for the first time, the characteristics of wax as a pcm in solar box cooker were investigated within the study area. experiments were performed and the influence of different components was investigated from the experiments as shown in figures 5 to 11. from the experimental results of the designed solar cooker the following conclusions were drawn: the thermal efficiency of the solar cooker and the cooking times are found to depend strongly on the wax, the reflector, insulation, and solar intensity. wax can be used as a storage medium integrated with a solar box cooker using maiduguri weather conditions. wax as a pcm can be regarded as a high efficiency material due to the amount of energy stored (4167.5kj). it is obvious that the total solar radiation on cloudy days is lower than that of the clear days; the solar cooker receives also reflected radiation from only a single reflector hence there is a possibility that high temperatures can be achieved by changing the amount of wax and incorporation of solar tracking system for further optimization. it is also expected that an improvement in the cooker performance is possible with the choice of a storage unit, a pcm and the amount of radiation received from the sun looking at the present findings despite the intermittent solar radiation due to weather conditions during the test period. the use of thermal energy storage in solar cookers play a pivotal role in a sustainable energy management based on solar energy as well as for energy conservation. solar cooking has the potential to reduce fossil fuel use and the release of co2 to the environment file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina et al: design and experimental testing of a solar box cooker with paraffin wax as thermal energy storage using maiduguri weather condition. azojete, 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 210 references amer, eh. 2003, theoretical and experimental assessment of a double exposure solar cooker energy conversion and management, 44(16): 2651-2663. bird, rb., stewart, we. and lightfoot, en. 2001, transport phenomena, john wiley & sons, inc. (2nd ed.) new york. bureau of indian standards (bis) is 13429:2000. domanski, r., el-sabaii, aa. and jaworsky, m. 1995. cooking during off-sunshine hours using pcm as storage media. energy, 20(7): 607-616. el-sebaii, aa., al-heniti, s., al-agel, faa., al-ghamdi, f. and al-marzouki, kk. 2011. one thousand thermal cycles of magnesium chloride hexahydrate as a promising pcm for indoor solar cooking. energy conversion and management, 52(4): 1771-1777. el-sebaii, aa. 1997. thermal performance of a box-type solar cooker with outer-inner reflectors. energy, 22(10): 969-978. el-sebaii, aa., al-amir, s., al-marzouki, fm., faidah, as., al-ghamdi, aa. and al-heniti, s. 2009. fast thermal cycling of acetanilide and magnesium chloride hexahydrate for indoor solar cooking. energy conversion and management, 50(12): 3104–3111. funk, a. 2000. evaluating the international standard procedure for testing solar cookers and reporting performance. solar energy, 68(1): 1-7. harmim, a., merzouk, m. boukar m and. amar, m (2010), design and experimental testing of an innovative building-integrated box type solar cooker. solar energy, 98, 422433. khalifa, ama., taha, mma. and akyurt, m. 2005. solar cookers for outdoors and indoors energy, 10(7): 819–829. kundapur, a. and sudhir, cv. 2009. proposal for new world standard for testing solar cookers. journal of engineering science and technology, 4 (3): 272-281. maina, mb., ngala, gm. and abdulrahim, at. (2016). design, fabrication and performance evaluation of a solar brick oven. international journal of engineering research and technology, 5(1): 176-182. mirdha, us. and dhariwal, sr. (2008). design optimisation of solar cooker. renewable energy, 33(3): 530-544. mishra, rs., sabberwal, j. and prakash, sp. 1984, evaluation of solar cooker thermal performance using different insulating materials. international journal of energy research, 8 (4): 393-396. mohammed, il, ruma, uj. and abdulrahim, at. (2013). performance testing of a truncated pyramid solar thermal cooker. int. journal of engineering research and application, 3(4): 1174-1178. mohod, ag. and powar, ag. 2011. development and evaluation of multi reflector foldable type solar cooker. agricultural engineering international: the cigr journal. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):200-211. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad@unimaid.edu.ng 211 manuscript no. 1090. nahar, nm. 2001. development and testing of a double reflector hot box solar cooker with a transparent insulation material. renewable energy, 23(2): 167-179. nahar, nm. 1993. performance and testing of large-size solar water heater cum solar cooker. international journal of energy research, 17(1): 57-67. ngala, gm., maina, mb. and tela, mb. 2015. design and construction of a high concentration solar cooker. international journal of research in mechanical engineering, 3 (1): 01-07. oturanc, g., necdet, o. and gungor, a. 2002. performance analysis of a solar cooker in turkey. international journal of energy research, 26(2): 105-111. prasanna, ur. and umanand, l. 2011, modeling and design of a solar thermal system for hybrid cooking application. applied energy, 88(5): 1740-1755. purohit, i. and purohit, p.2009. instrumentation error analysis of a box-type solar cooker, energy conversion and management, 50(2): 365-375. sharma, a., buddhi, d. and sharma s. 2002, accelerated thermal cycle test of acetamide stearic acid and paraffin wax for solar thermal latent heat storage applications. energy conversion and management, 43 (14):1923-1930. sharma, a., chen, c., murty, v. and shukla, a. 2009. review on thermal energy storage with phase change materials and applications. renewable and sustainable energy reviews, 13(2): 318-345 sharma, s., buddhi, d., sawhney, r. and sharma, a. 2005. thermal performance of a solar cooker based on an evacuated tube solar collector with a pcm storage unit. solar energy, 78 (3): 416-426. yuksel, n. and avci, a. 2010, the use of solar energy on the cookers with latent heat storage (in turkish). proceedings, 8th national clean energy symposium, 2010 bursa, turkey, pp. 23-31 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):985-994 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 985 original research article evaluation of soil samples in abeokuta-south local government area of ogun state, southwestern nigeria a. a. bello* and a. t. oriaje (department of civil engineering, faculty of engineering, college of science, engineering and technology, osun state university, osogbo) * corresponding author’s email address: afeez.bello@uniosun.edu.ng 1.0 introduction the development of infrastructure cannot be made in an intelligent and satisfactory manner unless the designer has at least a reasonable and accurate conception of the physical properties and general behaviours of the soil involved. ogun state government is actively involved in the construction of new roads within the state and in abeokuta south local government area, majority of soil materials are not yet explored. rapid infrastructural development in terms of road construction, buildings and recreational centers are anticipated in the future within the studied area. this expectation calls for the knowledge of basic index and strength properties of the soils in question. ogunsanwo (1989) reported that these parameters influence in a great deal the performance of the highway pavement during service when in use. article information abstract this paper presents result of a laboratory investigation on soil samples from abeokuta south local government, southwestern nigeria. three comparative efforts namely standard proctor (sp), west african standard (was) and modified proctor (mp), were employed. the results obtained showed that the compaction characteristics and unconfined compressive strength of the soil samples were found to increase with comparative effort. the unconfined compressive strength (ucs) values increased with compactive effort and decreased with increase in degree of saturation of the soil samples. all the samples did not meet the minimum specified requirements except for a1, a6 and a8. upon stabilized with cement, samples a2 and a7 did not also meet the minimum cbr value of 180% as specified by the nigerian general specification for roads and bridgeworks (1997) or stabilized soil using standard proctor compactive effort at 4% cement content. however, all the soil samples met the requirement using was compactive effort at 4% cement content. the samples met the conventional ucs values of (1500-3000 kn/m2) for base course of lightly trafficked roads while only sample a4 compacted at 10% cement content using was compactive effort met the minimum (30006000 kn/m2) for base course of highly trafficked road. it is thus recommended that 4% cement should be used as an optimal content to stabilize the soils, if they are to be used as road construction materials. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 november, 2018 revised 19 may, 2019 accepted 25 may, 2019 keywords: compactive efforts unconfined compressive strength california bearing ratio stabilization. mailto:afeez.bello@uniosun.edu.ng http://www.azojete.com.ng bello and oriaje: evaluation of soil samples in abeokuta-south local government area of ogun state, southwestern nigeria. azojete, 15(4):985-994. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 986 the highway pavement consists basically of four elements, namely: subgrade, subbase, base and wearing or surface courses. the subgrade course is the most important of the structural elements because the ultimate traffic load is transmitted to it through the intermediate layers. hence, the durability of a highway pavement is a function of the bearing capacity and stability of the subgrade soil. on the other hand, mc knight (1993) defines soil as an infinitely varying mixture of weathered mineral particles, decaying organic matter, lying organisms and liquid solution. this definition illustrated how complex soil could be; therefore, because of the anisotropic and heterogeneity nature of soil it is difficult to conclude on the performance of soil without some laboratory investigations. various previous workers have stabilized natural soil both chemically and mechanically. adeyemi and abolurin (2000) also stated that cement stabilized samples exhibited the highest cured strength when compared with lime and some mixture of both. gadzama (2009) also established that 4% cement can be recommended as an optimal content to stabilize soil from parts of northern nigerian. portland cement is the most important hydraulic cement utilized extensively in various types of cement stabilization of lateritic soils. cement acts as a binder and provides the much desired hardening and strengthening properties. the addition of cement also increases compressive strength, the resistance of lateritic soils to freezing and thawing, wetting and drying. it also affects the particle size distribution of the soils by increasing the size of fine particles. in view of this, civil engineers must study the property of soil, such as grain size distribution, atterberg limit, strength, durability and ability to drain water (braja, 1999; bello et al., 2016; bello and olaore, 2017). this study is therefore aimed at investigating and evaluating the index and strength properties of the soils of abeokuta south local government, southwestern nigeria with the aim of making recommendations as to the suitability of the soil as construction materials. procedures for improving them if they are found deficient, as well as the types of structures that could be built on such with minimal foundation problems were outlined. 2 materials and method 2.1 sample collection the soil samples used for this study were obtained within abeokuta south local government area of ogun state, nigeria. the samples were collected via trial pitting at eight different locations which include itoko, olumo rock, oba ademola hospital, ijeun, st. pauls igbore, itoku and imo hill and these are represented as a1, a2, a3, a4, a5, a6, a7 and a8 respectively. 2.3 geology and description of the study area the geology in the western upland where abeokuta south local government is situated is underlain by rocks of the basement complex which forms a part of the african crystalline shield. the basement is composed predominantly of folded gneises, schists and quartzite of the precambrian age to which have been emplaced by charnockitic rocks from older granite by extrusion and replacement (morawo, 2008). abeokuta south local government of ogun state is bounded in the west by ayetoro, in the north by abeokuta north local government, in the east by sagamu local government and in the south by obafemi owode. two types of seasons are experienced in abeokuta south local government, they are the wet (rainy) and dry season. the wet season occurs between march and november with the heaviest rainfall experiences during http://www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 985-994. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 987 this period. the dry season occurs between november and february. during this period, the temperature is usually low. the dry season also brings about harmattan which is experienced between december and january; the harmattan is cold, dry, dusty and hazy. people of abeokuta south are also noted for adire (kampala) ties and dye and even having a big market for adire, which are itoku market and adire (kampala) international market situated in asero, abeokuta (morawo, 2008). 2.4 test methods eight trial pits of depth ranging from 0.6 – 1m were dug at various locations (table 1). the following laboratory tests such as particle size distribution, atterberg limits, specific gravity, natural moisture content, compaction and california bearing ratio. 2.4.1 natural moisture content the soil sample used for this test was sealed in an airtight bag at the point of collection from a trail pit, to retain the actual moisture of a soil in natural state. the mass of the moisture can and wet soil was recorded (m2) and placed in the oven and the mass of the moisture can and dry soil (m3) was reweighed after 24 hours. the mass of the moisture can is taken as m1. 2.4.2 sieve analysis (wet sieving) soil sample of approximately 1000g (1kg) was used for this test; it was soaked for 24 hours, washed and oven dried. the sieving was done by mechanical method using an automatic shaker, a set of sieves (bs sieve nos. 4, 8, 16, 30, 40, 50, 70, 120, 200) and a collecting pan. 2.4.3 atterberg limit liquid limit and plastic limits were done in line with recommendation of bs (1990) 2.4.4 specific gravity a 50ml pycnometer was used for the test and an air-dried soil sample passing through bs sieve no. 4 (4.75mm) was weighed to 20g (0.02kg); the mass of the pycnometer was recorded (m1), and the mass of the pycnometer and the soil sample (m2) was recorded separately, as well as the mass of the pycnometer and the soil sample and distilled water (m3), and also the mass of the pycnometer and distilled water (m4). density of water is taken to be 1000kg/m3 or 1g/cm3. 2.4.5 compaction (west african standard) a 4.5kg rammer and 1000cm3 (1 x 10-3m3) mould was used for this test. air-dried soil sample passing through an opening of 20mm was weighed to 3000g (3kg) and the sample was mixed at the initial stage with a suitable amount of water, about 5% of the total mass of soil sample, and later increased to 7%, 9%, 11% and 13% depending on the water retaining capacity of each sample. the compaction of the soil was done in 5 layers, using 10 evenly distributed blows and at a height of drop of 450mm (0.450m). the dry density of soil was then plotted against the moisture content and the maximum dry density (mdd) and optimum moisture content (omc) were determined at the highest peak of the graph. 2.4.6 california bearing ratio (cbr) a 4.5kg rammer and 2340cm3 (2.34 x 10-3m3) mould was used for this test. air-dried soil sample passing through an opening of 20mm was weighed to 5000g (5kg) and the sample was mixed with the optimum moisture content that was obtained from compaction test. the compaction of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng bello and oriaje: evaluation of soil samples in abeokuta-south local government area of ogun state, southwestern nigeria. azojete, 15(4):985-994. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 988 the soil was done in 5 layers, using 56 evenly distributed blows and at a height of drop of 450mm (0.450m). filter papers were placed at the top and bottom of the mould and it was then placed on a compression machine. the soil sample was thus subjected to an axial loading from the top as well as from the bottom and load deformation was recorded at an interval of 0.25mm penetration to 12.5mm. the cbr value was then determined at 2.5mm and 5.0mm using a standard force of 13.24kn and 19.96kn respectively. three compaction efforts were used, the standard proctor (sp), west african standard (was) and the modified proctor (mp) for the natural soil. the sp and was compaction efforts were considered for the stabilized soils. these laboratory tests were carried out in accordance with the procedures specified by the british standard institution (bs 1377, 1990; bs 1924, 1990) and federal republic of nigeria general specification (road and bridges) ii of 1997. the samples that were deem unfit for subgrade construction were stabilized with ordinary portland cement and thereafter compacted using sp and was. table 1: sample location and description sample location depth (m) constituent materials colour description no. a1 itoko 0.7 gravelly clay reddish brown a2 olumu rock 0.7 gravelly sand reddish brown a3 general post office 1.1 silty clay yellowish brown a4 oba ademola hospital 1.0 silty clay dark brown a5 ijeun 0.9 sandy clay yellowish brown a6 st. paul’s igbore 0.9 silty clay reddish brown a7 itokun 0.8 sandy clay reddish brown a8 imo hill 1.0 gravelly clay yellowish brown 3 results and discussion 3.1 natural moisture content the natural moisture content of the samples ranged between 4.8 and 9.9% (table 2). sample a3 has the highest moisture content because soil particle consist of highest fine grains that has the greatest affinity for water retention while sample a5 has the lowest moisture content because it consists of loosely packed soil particle which has low retention water capability. when comparing the natural moisture content with the optimum moisture content (omc) obtained from various compaction energy levels, it was observed that all the (omc) for modified proctor compactive efforts were either equal to or less than the maximum value obtained from the natural moisture content while for the west african standard, only sample a2 was found to be greater than the maximum value of the moisture content value. as for the standard proctor, all the omc of the samples are higher than the maximum value of the moisture content except for samples a8. from these foregoing, it can be suggested that if the samples were to be used as construction material, little or no extra moisture will be required to obtain the omc if west african standard and modified proctor compaction energy levels were to be used. 3.2 specific gravity the results of the specific gravity range from 2.6 to 2.66. samples a3 and a5 have the lowest values while sample a4 has the highest value which is dependent upon the minerals present in http://www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 985-994. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 989 the soil. the values fall within the range of specific gravity of solid of light coloured sand, which is mainly made up of quartz as predominant mineral (braja, 1998; bello, 2012). this was also found to fall within the range of 2.55 to 4.6 as recommended by maignien (1966) for lateritic soils (table 3). 3.3 particle size analysis the result of the particle size analysis is shown in figures. 1a and b. using the unified soil classification system, sample a4 has the highest value of 70.1% passing 0.075mm sieve size while sample a6 has the lowest value of 23.1% passing 0.075mm sieve size. out of all the samples, the percentage passing 0.075mm sieve size for samples a1, a6, and a8 are less than 35% which showed that these samples are effective subgrade materials for road and bridges (gadzama, 2009). according to aashto (1986) soil classification system samples a2, a3, a3 and a7 were classified as a – 4, samples a1, a8 were classified as a – 2 – 5, sample a6 was classified as a – 2 7 while samples a5 was classified as a 7 – 5 soils. table 2: summary of test results of soil samples property quantity range specific gravity, gs 2.60 – 2.66 natural moisture content, % 4.8 – 9.9 liquid limit, % 21.5 – 33.0 plastic limit, % 15.4 – 20.3 plasticity index, % 3.8 – 15.5 % passing bs sieve, 2mm 70.0 87.4 % passing bs sieve 0.425mm 38.6 – 76.4 % passing bs sieve, 0.075mm 23.1 – 70.1 maximum dry density (sp), mg/m3 1.89 – 2.07 maximum dry density (was), mg/m3 1.98 – 2.10 maximum dry density (mp), mg/m3 1.98 – 2.18 optimum moisture moisture (sp), % 8.90 – 12.50 optimum moisture contact (was), % 8.75 – 10.05 optimum moisture contact (mp), % 7.50 – 9.90 unconfined compressive strength (sp), kn/m2 88 248 unconfined compressive strength (was), kn/m2 152 240 unconfined compressive strength (mp), kn/m2 201910 california bearing ratio (sp), % 5.0 – 24.50 california bearing ratio (was), % 7.0 9.0 california bearing ratio (bsh), % 9.0 – 71.5 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng bello and oriaje: evaluation of soil samples in abeokuta-south local government area of ogun state, southwestern nigeria. azojete, 15(4):985-994. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 990 table 3: natural moisture content and specific gravity of sample sample no. a1 a2 a3 a4 a5 a6 a7 a8 n. m. c, % 8.2 7.9 9.9 9.2 4.8 9.6 9.5 8.8 gs 2.61 2.63 2.69 2.66 2.60 2.62 2.63 2.63 figure. 1a: particle size analysis for samples a1 a4 figure 1b: particle size analysis for samples a5 – a8 3.4 atterberg limits the results of atterberg limits revealed that the liquid limit values ranged between 21.5 and 33.0% with samples having the highest and lowest values respectively a8 and a6 which according to dillip and subhrajit (2002) is noncritical. plastic limit value for sample a7 was found http://www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 985-994. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 991 to be 15.40% while that of a3 was found to be 20.30% as the lowest and highest values respectively (table 4). the highest and the lowest plasticity indices were found to be 3.8% and 15.5% for a2 and a6 respectively which were classified as marginal by dillip and subhrajit and (2002). also, the soils have low swelling potential in accordance with ola (1980). table 4: aashto soil classification of the samples sample no. atterberg limit (%) % passing bs sieve (mm) classification ll pl pi 2 0.425 0.075 of soil a1 22.00 16.30 5.70 73.10 47.00 34.50 a – 2 – 5 (1) a2 22.50 18.70 3.80 84.30 73.00 69.00 a – 4 (0) a3 27.50 20.30 7.20 78.00 50.60 42.50 a – 4 (0) a4 24.00 17.00 7.00 87.40 76.10 70.10 a 4 (1) a5 27.50 16.00 11.50 85.20 71.20 65.90 a – 7 – 5 (4) a6 33.00 17.50 15.50 70.00 38.60 23.10 a – 2 – 7 (0) a7 24.00 15.40 8.60 87.20 76.40 67.30 a – 4 (3) a8 21.50 16.70 4.80 71.00 44.50 34.50 a – 2 – 5 (0) 4.5 compaction characteristics the maximum dry density ranged between 1.89 and 2.07 mg/m3 when standard proctor compaction energy was used it ranged between 1.98 and 2.10 mg/m3 when west african standard was used and ranged between 1.98 and 2.18 mg/m3 when modified proctor was used (table 5). in all, the maximum dry density increased with an increase in compaction effort, while the optimum moisture content decreases with increase in compaction efforts. this has been found to be true in all soils (braja, 1998; bello et al., 2015). table 5: compaction characteristics for soil samples sample no. sp was mp mdd(mg/m3) omc(%) mdd(mg/m3) omc(%) mdd(mg/m3) omc (%) a1 1.90 10.60 1.99 8.90 2.10 8.90 a2 1.89 12.60 1.98 10.05 1.98 9.90 a3 1.91 11.50 2.05 9.15 2.05 8.20 a4 2.05 10.33 2.03 9.40 2.15 9.80 a5 1.98 12.21 2.0 9.70 2.15 9.20 a6 1.97 11.15 2.05 9.30 2.10 8.00 a7 1.77 11.15 2.05 9.30 2.10 8.00 a8 2.07 8.90 2.10 8.75 2.18 7.50 3.6 california bearing ratio characteristics samples a1, a6 and a8 met the 15% minimum requirement to be used as a subgrade material using standard proctor in accordance with nigerian general specification for roads and bridgeworks of 1997 (table 6). no material met the requirement to be used as a subbase and base materials. when all compactive efforts were considered sample a8 has highest cbr values followed by a1 and a6. it was also observed that soils that had a higher liquid limit gave a lower file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng bello and oriaje: evaluation of soil samples in abeokuta-south local government area of ogun state, southwestern nigeria. azojete, 15(4):985-994. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 992 california bearing ratio value which was found to agree with gadzama (2009). this implies that soils of lower liquid limit have appreciable higher bearing capacity, hence should be used for subgrade soil in road construction. table 6: cbr and unconfined compressive strength of soil samples sample no. cbr (%) ucs (kn/m2) sp was mp sp was mp a1 19.20 25.3 63.50 200 580 870 a2 9.70 13.3 45.70 144 180 350 a3 9.2 12.7 28.50 120 440 550 a4 8.3 9.70 33.40 117 305 240 a5 5.0 7.0 9.0 88 152 210 a6 17.50 21.3 55.4 102 200 480 a7 7.5 11.5 25.9 195 490 770 a8 24.50 29.0 71.5 248 640 910 attempts were made to improve the strength properties of other soil samples that failed to meet the minimum requirement for subgrade materials with ordinary portland cement to stabilize the soils. the results are summarized in table 7. it was also observed that sample a2 and a7 did not meet the minimum cbr value of 180% as specified by the nigerian general specification for roads and bridgeworks (1997) or stabilized soil using standard proctor compactive effort at 4% cement content. however, all the soil samples met the requirement using was compactive effort at 4% cement content. table 7: california beaming ratio of cement stabilized soil sample no. cbr (%) cbr (%) standard proctor west african standard 2% 4% 6% 8% 10% 2% 4% 6% 8% 10% a2 98 170 220 249 298 115 197 213 270 340 a3 110 205 225 263 320 118 215 238 298 342 a4 125 227 280 325 408 140 269 302 394 470 a5 105 213 238 279 312 120 243 267 315 389 a7 90 172 210 270 315 110 236 259 302 357 3.8 unconfined compressive strength characteristics it was observed that (ucs) values increased with an increase in compaction energy. it was also observed that samples with lower optimum moisture content gave higher unconfined compressive strength and vice-versa which is in agreement with braja (1999). stabilized samples using the standard proctor and west african standard met the conventional ucs values of (1500-3000 kn/m2) for base course of lightly trafficked roads not only at 2% cement content but for all the ranges of stabilizers used (2-10%). only samples a4 using was compactive effort at 10% cement content met the conventional ucs values of (3000-6000 kn/m2) for base course of highly trafficked roads (table 8). http://www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 985-994. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 993 table 8: unconfined compressive strength of cement stabilized soil sample no. ucs (kn/m2) ucs (kn/m2) standard proctor west african standard 2% 4% 6% 8% 10% 2% 4% 6% 8% 10% a2 1550 1650 1650 1800 2000 1600 1800 1850 2000 2100 a3 1600 1700 1750 1950 2100 1650 1700 1750 2100 2000 a4 1580 1640 1800 2000 2200 1700 1900 2010 2800 3050 a5 1800 1850 1700 1850 2000 1600 1650 2000 2100 2300 a7 1700 1780 1700 1600 2000 1550 1800 1700 1950 2950 4. conclusion soil samples from abeokuta south local government area, southwestern nigeria have been investigated. the soil samples met the minimum values of liquid limit as specified by the nigeria general specification for roads and bridgeworks. samples a1, a6 and a8 met the minimum 15% requirements for subgrade material in accordance with the nigeria general specification for road and bridgework while the conventional cbr values of 80% minimum has not been met: but upon stabilizing with cement at 4% cement content using standard proctor, all the samples met the minimum cbr value of 180% with the exception of samples a2 and a7. when the samples were compacted using west african standard (was), all the samples met the requirement. the maximum dry density increases with compactive efforts while the optimum moisture content decreased with compactive effort for the samples. the unconfined compressive strength (ucs) values increased with compactive effort and decreased with increase in degree of saturation of the soil samples. on stabilizing the soil samples with cement, the samples met the conventional ucs values of (1500-3000 kn/m2) for base course of lightly trafficked roads while only sample a4 compacted at 10% cement content using was compactive effort met the minimum (3000 6000 kn/m2) for base course of highly trafficked road. references aashto 1986. standard specifications for transportation materials and methods of sampling and testing, american association for state highway and transportation officials, 14th ed. washington, d.c. adeyemi, go. and abolurin, sb. 2000. strength characteristics of a chemically stabilized lateritic soil from kilometer 4, ile-ife/sekona road, southwestern nigeria. journal of mining and geology, 36(1):113-119. bello, aa. 2012. geotechnical evaluation of reddish-brown tropical soil. journal of geotechnical and geological engineering, 30(2):481-498. bello, aa., ige, ja. and adebanjo, ua. 2015. flexible pavement assessment of selected highways in orolu local government south western nigeria. british journal of applied science and technology, 7(1):46-61. bello, aa., awogboro, os. and ajamagbiso, oa. 2016. flexible pavement assessment of selected roads in odo-otin local government, south western nigeria, journal of advances in technology and engineering research, 2(3):66-80. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng bello and oriaje: evaluation of soil samples in abeokuta-south local government area of ogun state, southwestern nigeria. azojete, 15(4):985-994. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afeez.bello@uniosun.edu.ng 994 bello, aa. and olaore, g. 2017. geotechnical properties of lateritic soils from ipetu-ijesa campus of osun state university. uniosun journal of sciences, 2(1):74-83. braja, md. 1998. principles of geotechnical engineering, fourth edition, pws, publishing company, boston. pp. 69. braja, md. 1999. principle of foundation engineering, fourth edition. pws publishing company, boston. pp. 62. bs1 1990. methods of testing soils for civil engineering purposes, british standards institution, bs 1377, london. bsi 1990. methods of testing for stabilized soils. british standards institution, bs 1924, london. dillip, kb. and subhrajit, d. 2002. gate – civil engineering. cyber tech. publications, new delhi. gadzama, ew. 2009. evaluation of soil sample from federal university of technology, yola state. nigeria journal of engineering, 15(2):80 – 88. maignien, r. 1966. review of research on laterites, unesco natural resources research iv. paris: 148 mc knight, tl. 1993. physical geography; a landscape appreciation. fourth edition, englewood cliff nj: prentice hall. morawo, sa. 2008. geotechnical properties of lateritic soil as highway pavement construction materials in abeokuta north local government of ogun state, b. tech. thesis, department of civil engineering, ladoke akintola university of technology ogbomoso. nigeria general specification 1997. bridges and road works. federal ministry of works and housing, headquarters, abuja, nigeria. vol. 11 ogunsanwo, o. (1989). “california bearing ratio and shear strength of compacted lateritic soils from south-western nigeria”. a quarterly journal of engineering geology, no 22, pp 317-328. ola, sa. 1980. mechanical properties of concretionary laterites from rain forest and savannah zones of nigeria. bulletin of international association of engineering geology, paris, 21 – 26 http://www.azojete.com.ng mailto:afeez.bello@uniosun.edu.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):867-877 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 867 original research article water quality analysis of some selected hand-dug wells in burutu community, delta state obiajulu peretomode (department of science laboratory technology, delta state university, abraka, p.m.b. 22, abraka, nigeria) * corresponding author’s email address: obipere@gmail.com 1.0 introduction water as a natural resource is very precious and vital to life, development and the environment. it can also serve as a means for poverty alleviation, lifting people out of degradation, while at the same time bringing prosperity to all (who, 2006). water is essential for agriculture, drinking, cooling, sanitation, a critical input in industry, for tourism and cultural purposes; and for its role in sustaining the earth’s ecosystem (mark et al., 2002). however, the demand for fresh water for drinking and other domestic use rises continuously as the world’s population grows. potable water is a fundamental need of man to sustain life. it serves as a lubricant, regulates the body temperature and provides the basis for the body fluids and metabolism (schafera et al., 2009). drinking water should be suitable not only for human consumption but also for washing/bathing and household food preparation. it is a well-known fact that when water is polluted, its normal functioning and properties are affected (trivedi et al., 2010). continual article information abstract this study investigated the bacteriological and physico-chemical properties of water in selected hand-dug wells in burutu community, delta state and compared it with world health organisation (who) standard. water samples from wells in twelve different locations were selected and subjected to filtration prior to chemical analysis. the methods of analyses were determined according to the procedure in apha. results obtained show that some of the parameters analyzed were within who (2006) guidelines for drinking while others exceeded the threshold. in relation to bacteriological contamination, the result revealed that all the sampled wells were contaminated with total and faecal coliform organisms as they exceeded who standard. the sampled wells had a mean of total coliform 175.16155.73mpn from twelve samples with a range of 67 to 576 mpn. samples across the wells varied in the range of 67, 86.00, 70 mpn for (ambar), 110, 360, 294 mpn for (chicoco), 112, 111, 114mpn for (low beach) and 102, 576 and 100 mpn for (okorodudu) quarters respectively. it also shows that none of the wells are of quality in terms of portability for drinking. however, they can be used for other domestic activities like washing of clothes and bathing. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 december, 2018 revised 30 march, 2019 accepted 05 april, 2019 keywords: water quality consumption burutu community bacteriology. http://www.azojete.com.ng obiajulu: water quality analysis of some selected hand-dug wells in burutu community, delta state. azojete, 15(4):867-877. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 868 improvement in the quality of water for purposes of drinking, domestic consumption, personal hygiene and certain medical situations is among the top challenges of the world. waterborne diseases are the cause of death and suffering of millions of people, especially, children in developing countries (schafera et al., 2009). according to the world bank, only 39% of people that live in cities have improved water source (yusuf, 2007). this situation has not improved significantly over the past decade. given such a grim situation, residents are left with no other choice but to seek other sources of freshwater from rainfall, the lagoon and groundwater (by digging wells). the niger delta region of nigeria among any other region in the world faces huge challenges with multiple issues that adversely affect public health such as oil spillage and gas flaring. one major challenge in the region is the ability for both the rural and urban areas to access clean water supply. estimates suggest that nearly 10 million people in the niger delta region of nigeria lack safe drinking water and at least 3 in every 8 deaths per year are attributed to waterborne diseases, with over 68 percent of the niger delta region covered by water. not only is their poor access to readily accessible drinking water, but even when water is available in these small towns and villages, there are risks of contamination due to several factors. water quality testing is not performed as often as is necessary, and lack of education among the people utilizing the water source leads them to believe that as long as they are getting water from the creeks, it is safe. it is against the background of the above that this study aims to determine the physicochemical parameters, analyse and compare these parameters to who maximum acceptable limits, and ascertain the quality and potability of hand-dug wells in burutu community. 2.0 materials and methods 2.1 the study area burutu island is an ancient town. it is also the headquarter of burutu local government area, delta state nigeria as shown in the delta state map below (fig.1). it is closely bordering the atlantic ocean which falls within the beach ridges on-shore geomorphic sub-environment of the niger delta and lies between latitude 5° 21' 11.81''n and longitude 5° 30' 29.74''e with an elevation of 13m above the sea level (administrative regions in nigeria, 2019). the area is characterized by strong wave and tidal action, which further compact the sediments. the estimated population of burutu island in 2006 national census was 98,354. the population of the island is on the increase as a result of mass influx of people into the area. the rapid growth in population is largely due to the expansion of the oil and allied industries, the local government council secretariat and delta state school of marine technology that was established in april 2011. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 867-877. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 869 figure 1: map of delta state showing the study location (delta state government, 2007). 2.2 water sampling water samples from the selected dug-out wells were collected from twelve locations categorized into four major quarters: ambar, chicoco, low beach, okorodudu that makes up burutu island. a total of twelve dug-out wells were sampled. in order to obtain accurate results, proper sampling procedures were adopted to eliminate or minimise potential contamination of the samples. sample containers were soaked in nitric acid (nho3) overnight and washed with distilled water, rinsed with deionised water and dried in a drying cabinet. sample containers were clearly labelled to enhance record keeping. an analysis was done approximately 72hrs after sampling. 2.3 analyses for physico-chemical parameters the samples were analyzed for major physical and chemical water quality parameters namely ph, total dissolved solid (tds), total suspended solids (tss), total hardness (th), chlorides, sulphate, nitrates, magnesium, calcium, manganese, copper, zinc, iron and lead. samples were subjected to filtration prior to chemical analysis. the methods of analyses were determined according to the procedure in apha. the ph of the water samples was obtained ph meter (model phs-25, rex instrument factory shanghai). electrical conductivity of the water samples was measured using the battery operated conductivity bridge (model mc-1 markv electronic switchgear). total dissolved solid was determined according to the procedure and protocols outlined in apha (1998). whatman filter paper and 250ml conical flask was oven dry at 50oc for 3 hours, cool in a dessicator and weighed. 100ml was filtered exactly through the filter paper into the conical flask. the water evaporated to dryness on a hot plate and the filter paper was dried in the oven set at 50°c until a constant weight was obtained for each. the weight of the filter paper and flask were recorded separately. the difference between the weights obtained from burutu file:///c:/users/user/downloads/azojete143/www.azojete.com.ng obiajulu: water quality analysis of some selected hand-dug wells in burutu community, delta state. azojete, 15(4):867-877. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 870 the total solids and total dissolved solids for each sample gave the value of the total suspended solids content in mg/l of the sample. the colour of the samples was determined using a nessleriser. standard disc nsa was also used for comparison. the value of colour was read directly in hazen units on the platinum-cobalt scale. nitrate was determined by the colorimetric methods using phenoldisulphonic acid as described in apha, (1998). 50ml of samples was put in a porcelain dish and evaporated at 1080c in a gallenkamp water bath. the dry residue was then dissolved by adding 2ml of phenoldisulphonic acid, followed by 20ml of distilled water and 7ml of concentrated ammonia solution until a maximum yellow colour developed. the absorbance was then read at a wavelength of 410nm using the milton roy spectronic 21d spectrophotometer. chloride was determined by mohr’s method as described in apha, (1998). this method employs silver nitrate as titrant and potassium chromate as the end point indicator. the chloride ion present in the samples is precipitated as white sliver chloride. firstly, a reddish-brown colour comparison blank was prepared by adding 1ml potassium chromate and then 0.2ml 0.02m silver nitrate solution to 100ml distilled water in a clean conical flask. it was shaken gently and left to stand. 100ml of sample was put into a conical flask with the aid of a pipette followed by 1.0ml of potassium chromate indicator and titrated, with constant stirring, with 0.02m silver nitrate to the colour of the comparison blank. the value of chloride ion concentration was obtained by equation (1). cl (mgl-1) = (1) where: a = ml silver nitrate used for titrating sample b = 0.2ml silver nitrate used for titrating blank m = morality of silver nitrate 2.4 measurement of sulphate in water this was determined by the turbidimetric method as described in apha, (1998). this method involves a mixture of sodium chloride-hydrochloric acid (dissolve 60g nacl in water add 5ml concentrated hcl), barium chloride, glycerol-ethanol solutions. 100ml of sample was measured into a 250ml conical flask, followed by 5ml conditioning reagent and mixed in a stirring apparatus while 20ml of nacl-hcl solution, 20ml glycerol-ethanol, and 0.3g of barium chloride was added and stirred for 2 minutes. the mixture was immediately poured into absorption cell and measure using the absorbance at 420nm after 3 minutes. the reading from the spectrophotometer was compared with the blank. 2.5 total hardness twenty-five (25) ml of the well-mixed water sample was measured into a conical flask. two (2) ml of buffer solution and a pinch of eriochrome black were added. when the sample turned into http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 867-877. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 871 wine red in color, magnesium and calcium was present. the solution was titrated against 0.01 m edta until the wine red color turned to blue. a blank titration was also carried using distilled water as recommended by apha (1998). calculation: total hardness = (2) where; a = volume of edta consumed for sample (ml), b = volume of edta consumed for blank (ml) and c is the volume of the water sample (ml). 2.6 total coliform bacteria total coliform and faecal coliform were enumerated by multiple tube fermentation tests as described by apha (1998). coliform count was obtained using the three tube assay of the most probable number (mpn) technique. presumptive coliform test was carried out using macconkey broth (oxoid). the first set of the five tubes had sterile 10ml double strength broth and the second and third sets had 10ml single strength broth. all the tubes contained durham tube before sterilization. the three sets of the tubes received 10ml, 1ml and 0.1ml of water samples using sterile pipettes. they were carefully labeled and incubated at 37ºc for 24-48 hours for estimation of total coliform. acid production was determined by colour change in the broth from reddish purple to yellow and gas production was checked for by entrapment of gas in the durham tube. the mpn was then determined from the mpn table for the three set of tube. 3.0 results and discussion table 1 presents the physico-chemical and bacteriological analysis of water samples collected from residential hand hug wells in burutu community, delta state. results of physical-chemical and bacteriological analyses (mean ± standard deviation, minimum, median, maximum values) are indicated in table 2. the results show that the colour of water samples collected were found to range from 5.0-15 pt/co with a mean and standard deviation value 7.53.371 pt/co. the lowest value of 5 was observed in wells 1, 2, 3, 4, 7, 9 and 12 pt/co, while the highest value 15 pt/co was observed in well 11 of okorodudu quarter (table 1). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng obiajulu: water quality analysis of some selected hand-dug wells in burutu community, delta state. azojete, 15(4):867-877. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 872 table 1: physicochemical and bacteriological parameters of hand dug wells parameters ambar burutu chicoco low beach okorodudu well 1 well 2 well 3 well 4 well 5 well 6 well 7 well 8 well 9 well 10 well 11 well 12 colour 5 5 5 5 10 10 5 10 5 10 15 5 ph 5.83 5.10 4.80 5.16 5.66 5.69 4.52 4.45 4.43 5.68 5.8 5.73 ec (µs) 200 150 460 500 490 670 230 400 250 670 270 170 tds (mg/l) 130 100.00 300.00 330 320 420 140 260 160 420 180 80 tss (mg/l) 1.05 1.05 1.05 1.05 12.60 12.85 1.25 14.50 0.00 16.50 15.05 1.05 th (mg/l) 46.97 14.40 113.19 86.24 45.43 61.60 23.87 61.60 56.21 83.16 96.25 16.17 chloride (mg/l) 29 7.0 48 76 87 87 44 52 34 171 73 10 sulphate (mg/l) 20 6 40 150 25 30 40 200 40 200 20 21 nitrate (mg/l) 2.02 0.50 2.53 5.05 6.10 6.50 2.10 2.80 2.06 12.20 4.85 0.85 mg (mg/l) 8.45 4.94 46.05 16.65 14.85 12.95 5.25 11.25 12.85 20.85 18.16 6.25 ca (mg/l) 36.47 8.64 85.95 68.85 28.95 46.70 17.66 48.64 39.06 59.86 76.84 8.96 manganese (mg/l) 0.082 0.000 0.210 0.205 0.213 0.478 0.000 0.000 0.000 0.050 0.135 0.010 cu (mg/l) 0.137 0.080 0.285 0.048 0.041 0.053 0.015 0.025 0.069 0.000 0.013 0.000 zn (mg/l) 0.342 3.190 3.285 5.120 0.000 6.680 1.025 1.127 5.589 0.000 0.024 0.000 fe (mg/l) 0.420 0.837 0.865 0.900 0.874 0.921 0.163 0.245 0.311 0.343 1.799 0.068 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 867-877. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 873 table 2: mean values of physico-chemical and bacteriological parameters of hand dug wells parameters n minimum maximum mean std. deviation who colour (pt/co) 12 5.0 15 7.5 3.371 15 ph 12 4.43 5.83 5.24 0.563 6.5-8.5 ec (µs) 12 150 670 371.66 186.24 1000 tds (mg/l) 12 80 420 236.66 120.78 500 tss (mg/l) 12 0.0 16.50 6.50 6.96 400 th (mg/l) 12 14.40 113.19 59.83 31.70 na chloride (mg/l) 12 7.0 171.0 59.83 44.32 250 sulphate (mg/l) 12 6 200 66 72.51 250 nitrate (mg/l) 12 0.5 12.2 3.96 3.25 10 mg (mg/l) 12 4.94 46.05 14.87 11.08 0.20 ca (mg/l) 12 8.64 85.95 43.88 25.61 75 manganese (mg/l) 12 0.0 0.478 0.12 0.144 na cu (mg/l) 12 0.0 0.285 0.06 0.07 na zn (mg/l) 12 0.0 6.68 2.19 2.47 5.0 fe (mg/l) 12 0.068 1.799 0.65 0.48 0.3 pb (mg/l) 12 0.0 0.0 0.00 0.00 0.01 tc count (cfu/100ml) 12 67 576 175.16 155.73 0 tf coliform (cfu/100ml) 12 18 282 58.42 76.33 0 tb count (cfu/100ml) 12 169 1218 436.41 106.68 0 the ph of all the sampled wells had a ph lower than who (2006) guideline for drinking water. ambar, chicoco, low beach and okorodudu are situated along and/or close to akewa group of company, npa, burutu local government industrial plant house and delta state school of marine technology industrial workshop, hence the lower mean ph values can be attributed to industrial emission. one major attribute resulting to low ph is that the community is situated in an island that is surrounded by the ocean; hence salt water from the creek may have altered the acid-base equilibrium of the surrounding water table. out of all the well water sources sampled, samples from ambar, chicoco, low beach and okorodudu quarters showed light and dark brown colour with a range of 5 to 15 (pt/co) across the wells. the source of the samples was open well where water table was 8 ft deep. the surrounding possible contamination sources found were decayed plants since burutu was land filled (dredging). thus the colour of the sample may be due to suspended minerals and dead organic matter. in this study, electrical conductivity (ec) value in samples from ambar quarter ranged from 150 to 460 μs/cm across the wells, 490 – 670 μs/cm in samples from chicoco quarter, 230 to 400 μs/cm for low beach quarter and 170 – 670 μs/cm in well samples from okorodudu. however, the high mean conductivity of samples from chicoco quarter can be adduced to high amount of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng obiajulu: water quality analysis of some selected hand-dug wells in burutu community, delta state. azojete, 15(4):867-877. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 874 dissolved ions resulting from industrial activities in that area. the electrical conductivity values were within the standards for drinking water quality (who, 2006). the tds values of sampled wells across the quarters varied in the range of 80 to 420 mg/l, the lowest being observed in well sample number 10, while the highest was in well samples number 6 and 10. this range is similar to the one obtained by nnaji and omotugba (2014). the most remarkable observation of this study was the alarmingly high level of total dissolved solids (tds) in well samples number 6 and 10. samples from okorodudu quarter wells were collected from domestic tube wells and metal drums having age of 5-10 years and water table of 8 ft. the surrounding sewage line and gutter were located at about 15-22 ft away. on overall basis, it is evident that the underground strata contain high concentration of easily soluble salts, which may be the main cause of high tds value across the quarter’s well water samples. however, the level of tds recorded in the samples is an indicator of potential concern and warrant further investigation. the tss values of water from ambar, chicoco, low beach and okorodudu varied in the range of 1.05 mg/l, 1.05– 12.85, 0.00 – 14.50 and 1.05 to 16.50 mg/l respectively. the relatively high tss mean for samples from okorodudu quarter indicates high concentration of bacteria, nutrients and metals in the water. the mean values of tss recorded for samples from okorodudu quarter were much higher than that of ambar and low beach samples. also, the high tss values recorded across the sampled wells except sample number 9 indicates bad taste, high water hardness and could also result in laxative effect. the relative high levels of tss in well water are not acceptable due to the resulting taste. water with very low concentrations of solids is also unacceptable to consumers because of its insipid taste, often resulting to corrosion of water supply systems (srinivasa and venkateswarlu,1999). the total hardness values of the samples were found in the range of 14.40 to 113.19 mg/l. samples from ambar, chicoco, low beach and okorodudu quarters varied in the range of 14.40 to 113.19, 45.43 to 86.24, 23.87 to 61.60 and 16.17 to 96.25 mg/l respectively. the relatively high mean of total hardness recorded for samples from ambar quarter may be due to run-off that carried dissolved calcium and magnesium ions into the wells as some of them are not properly protected with concrete. the means of total hardness across the sampled wells may be due to dissolution of ions by rainwater percolation in the soil. the ions may have originated from runoffs that infiltrated into the soil causing leaching. the values of total hardness recorded from the samples also indicated that burutu land is rich in calcareous and carbonaceous minerals. these results clearly revealed that total hardness value of the sampled wells is above the threshold of who standards and could be harmful to the local inhabitants. the concentration of chloride across the samples varied in the range of 7.0 for well sample number 2 to 171 mg/l for sample number 11. clcontent values varied from 7.0 to 48 mg/l in ambar quarter, 76 to 87 mg/l in chicoco, 34 to 52 mg/l in low beach and 10 to 171 mg/l in okorodudu quarter respectively. this relative mean value of chloride recorded may be attributed to seawater intrusion. the high values of chloride in the water samples may be due to the aquifer which is prone to seawater in the coastal area. thus, the high value of chloride of the sampled well water can increase the electrical conductivity of the water and also increases its corrosivity. however, the results indicate that chloride content in the water sources were within the acceptable limit of 250 mg/l (who, 2006). mean values of 20, 6 and 40 mg/l for ambar, 150, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 859-866. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 875 25 and 30 mg/l for chicoco, 40, 200 and 40 mg/l for low beach and 200, 20 and 21 mg/l for okorodudu were recorded for the sampled wells respectively. although, samples from well numbers 8 and 10 had the highest values; these values are lower than the 250 mg/l of who (2006) permissible standard for drinking water quality. the relative high values of sulphate recorded in some of the wells could be traced to the geology of the soil. the values recorded for well samples number 8 and 10, suggests a likely characteristic taste of somewhat bitter. based on the results, sulphate level is not likely to cause health hazard. the result revealed that the lowest nitrate value was recorded in well sample 2 (0.50 mg/l) and the highest value of 12.20 mg/l in surface well sample 10. the nitrate values of the different sampled wells in ambar quarter were found to be below the permissible limit of who (2006) for drinking water. the values of nitrate obtained in samples from chicoco quarter varied between 5.05 to 6.50 mg/l which was also below the drinking water standard of who (2006) but higher than values obtained from ambar quarters. the higher nitrate values recorded for these samples may be a reflection of the organic material loads that settled at the bottom of the wells. mg values in all the sampled wells varied in the range of 11.08 to 14.87mg/l, the lowest being observed in well sample 2 and highest in well sample 10. mg values of water from ambar, chicoco, low beach and okorodudu quarters varied in the range of 8.45, 4.94, 46.05, 16.65, 14.85, 12.95, 5.25, 11.25, 12.85, 20.85, 18.16 and 6.25 mg/l respectively. these values were found to be within the 150 mg/l who (2006) guideline for drinking water. the relative mean values of magnesium recorded across the samples may be due to seawater intrusion since the water table is very high, dissolved minerals and run-offs contaminated with magnesium. the values of magnesium recorded may also be attributed to the geological locations of the area. the concentration of calcium ranges from 8.64 to 85.95 mg/l for ambar sampled wells, 28.95 to 68.85 mg/l for chicoco sampled wells, 17.66 to 48.64 mg/l for low beach sampled wells and 8.96 to 76.84 mg/l for okorodudu sampled wells respectively. the relatively high values of calcium recorded across the samples except well number 2 and 12 may be attributed to the various construction materials, such as cement, brick lime and concrete sued for the well as well as the geological conditions of the area. also, the values recorded may be attributed to seawater intrusion and run-offs containing dissolved minerals. however, these values were within the who (2006) guideline for drinking water. the average zinc concentration in seawater is 0.6 – 5 ppb. zinc concentration in the analysed water samples were 0.342, 3.190 and 3.285 mg/l for samples 1 to 3 (ambar), 5.120, 0.000 and 6.680 mg/l for samples 4 to 6 (chicoco), 1.025, 0.000 and 6.680 mg/l for samples 7 to 9 (low beach) and 0.000, 0.024 and 0.000 mg/l for samples 10 to 12 (okorodudu) quarters respectively. some of these values were within 5.0 mg/l acceptable limit of who (2006) except well samples number 4, 6 and 9 which had mean value that exceeded the standard. the relatively high values of zinc recorded in some of the sampled wells may be attributed to point and non-point sources of pollution. the variations in zinc values across the sampled wells maybe adduced to poor environmental hygiene. the observed mean fe concentrations were in the order of well 1<well 2<well 3 (ambar quarter), well 5<well 4<well 6 (chicoco quarter), well 7<well 8<well 9 (low beach quarter) and well file:///c:/users/user/downloads/azojete143/www.azojete.com.ng obiajulu: water quality analysis of some selected hand-dug wells in burutu community, delta state. azojete, 15(4):867-877. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 876 12<well 10<well 11 (okorodudu quarter) respectively. samples from ambar quarter had mean fe concentrations that were above the who (2006) standard value of 0.3 mg/l while the mean values for samples from chicoco quarter still exceeded the standard. in addition, the mean values for samples from low beach and okorodudu quarters exceeded the standard guideline except well samples number 7 and 12 which was within the standard. the high iron concentrations recorded in majority of the sampled wells suggest dissolved iron by rainwater from soil particles into the ground water. the relatively high iron concentration values may also be adduced to run-offs that carried sediments containing iron particles. the high concentration of iron recorded in the samples is validated by the level of ph and total hardness of the water samples recorded. samples across the four quarters had mean iron concentrations that were above the acceptable level except well sample 7 and 12. in comparison of the sampled wells in terms of lead variations is shown in table 2. the values of lead recorded were below detectable limit of who (2006) standard for drinking water. the bacteriological results showed that all the sampled wells were contaminated with total and faecal coliform organisms because they exceeded who standard of 10mpn/100ml and 0mpn/100ml respectively. the sampled wells had a mean of total coliform 175.16155.73mpn from twelve samples with a range of 67 to 576 mpn. samples across the wells varied in the range of 67, 86.00, 70 mpn for (ambar), 110, 360, 294 mpn for (chicoco), 112, 111, 114 mpn for (low beach) and 102, 576 and 100 mpn for (okorodudu) quarters respectively. this indicates that bacteriologically, none of the sampled wells are fit for drinking. this result corroborates the finding of olobaniyi and efe (2007) that the mpn coliform index per 100ml of water samples collected from selected areas in the oil producing region of nigeria had 23 to 45 mpn/100ml. conclusion from the results, some of the parameters analysed were within who (2006) guideline for drinking while others exceeded the threshold. in relation to bacteriological contamination, the result revealed that all the sampled wells were contaminated with total and faecal coliform organisms as they exceeded who standard of 10mpn/100ml and 0mpn/100ml respectively. it also shows that none of the wells are of quality in terms of portability for drinking. however, they can be used for other domestic activities like washing of clothes and bathing. references administrative regions in nigeria, 2019. https://latitude.to/map/ng/nigeria/cities/burutu accessed on 10 september, 2019 american public health association (apha), 1998. standard methods for the examination of water and wastewate. 20th edn. washington, d.c: pp. 1134. delta state government. 2007. map of delta state. retrieved june, 2014. www.delta.state.gov.ng accessed on october, 2019 mark, wr., ximing, c. and sarah, ac. 2002. world water and food to 2025: dealing with scarcity. international food policy research institute, nw, washington, dc, usa. 317pp. https://latitude.to/map/ng/nigeria/cities/burutu http://www.delta.state.gov.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 859-866. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 877 nnaji, jc. and omotugba, s. 2014. physicochemical quality of drinking water in new bussa, niger state, nigeria. international research journal of pure and applied chemistry, 4(4): 437446. olobaniyi, sb. and efe, i. 2007. comparative assessment of rainwater and groundwater quality in an oil producing area of nigeria: environmental and health implications. journal of environmental health research, 6(2):1-7. schafera, ai., rossitera, hma., owusub, pa., richardsc, bs. and awuah, e. 2009. physicochemical water quality in ghana: prospects for water supply technology implementation. desalination, 248: 193–203. srinivasa, ei. and venkateswarlu, ay. 1999. impact of domestic sewage on fresh water body. journal of environmental biology, 29(3): 303-308. trivedi, p., bajpai, a. and thareja, s. 2010. comparative study of seasonal variation in physicochemical characteristics in drinking water quality of kanpur, india with reference to 200 mld filtration plant and ground water. nature and science, 8(4): 11-17. world health organization (who), 2006. guidelines for drinking-water quality. first addendum to 3rd ed. 1, recommendation. geneva, who (world health organization), pp. 595. yusuf, ka. 2007. evaluation of groundwater quality characteristics in lagos-city. journal of applied sciences, 7:1780-1784 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 37-40 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 37 original research article chemical composition of millet-based infant formula supplemented with treated bambaranut flour. t. u. nwabueze1, s. james2, j. c. anuonye2 and k. kachiro2 1department of food science and technology, michael okpara university of agriculture, umudike, nigeria 2department of food science and technology, federal university of technology, minna, nigeria article information received october, 2018 accepted december, 2018 keywords: millet bambara groundnut fermentation sprouting infant chemical chemical properties nigeria abstract fermentation and sprouting have been shown to increase nutrient bioavailability and modify the functional properties of foods. application of these methods in the preparation of infant foods and complementing cereals with legumes will address nutrient density and viscosity problems associated with infant foods. infant foods were formulated from blends of treated bambaranut and pearl millet and chemical composition of the samples were studied. millet and bambaranut were soaked separately in water and allowed to ferment for 48 hr at room temperature. while for sprouting, millet and bambaranut were soaked for 12 and 24 hr, respectively, at room temperature, and soaked seeds were separately sprouted for 48 hr. after fermentation and sprouting, the seeds were oven-dried and then milled into a flour of 0.6 mm size. the flours were formulated to six (a, b, c, d, e, and f) complementary diets. the results show that blending treated bambaranut with pearl millet significantly increased the protein, fibre, fat and ash content from 14.46, 0.68, 6.21 and 3.32% to 19.35, 1.21, 8.01 and 5.35% respectively; while, the moisture and carbohydrate contents were significantly reduced. in the same vein, blending treated bambaranut with pearl millet significantly increased all the amino acids composition of the blends. however, blending treated bambaranut with pearl millet increased the trypsin, hydrogen cyanide, oxalate and phytate contents; though, the values fall within the safe consumption limit. hence, this study revealed that, blending treated bambaranut with pearl millet is beneficial in increasing the nutrient density of infant food. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1. introduction infant formula or complementary foods are foods other than breast milk usually in liquid, semisolid or solid form introduced to infants to provide appropriate nutrients. in nigeria and most especially west african countries, the common first weaning food is pap, locally called akamu in the southeast nigeria, ogi in the south-west nigeria or koko in northern nigeria. it is made from cereals such as maize, millet or sorghum. these traditional weaning foods are starchy and characterized to be low in nutritive value (low protein and low energy density), high bulk density and high viscosity. traditional food processing methods such as sprouting and fermentation have been reported to increase bioavailability of nutrients, predigest macro molecules, reduce antinutrients and reduce gruel viscosity (james et al., 2018). in essence, these processes make the foods simpler to digest and http://www.azojete.com.ng nwabueze, et al: chemical composition of millet-based infant formula supplemented with treated bambaranut flour. azojete, 14(sp.i4): 37-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 38 the nutrients easier to assimilate. since heat is not required in the two processes, there is considerable retention of enzymes, vitamins and other nutrients that are usually destroyed by high temperature processing. therefore, there is the need to augment the protein content with cheap and local protein source (bambaranut) and to assess the positive benefits of sprouting and fermentation on the chemical quality of the infant formula. 2. materials and methods 2.1 sources of raw material bambara nut and pearl millet were purchased from kure ultra-modern market, niger state, nigeria. 2.2 material preparation 2.2.1 fermentation of pearl millet and bambaranut bambara nut and millet were fermented as described by james et al. (2018) with slight modification. the two raw materials were cleaned manually, washed in clean water after which they were soaked separately in cold water in a ratio of 1:3 weight by volume (w/v) and allowed to ferment for 48 hr at room temperature (28 ± 2°c). fermented millet and bambara nut were thoroughly washed in clean water and oven-dried separately at 60°c for 12 and 24 hr, respectively, and then hammer milled into a fine flour of 0.6 mm size. the flours were packaged differently in coded high-density polythene bags for further analysis. 2.2.2 preparation of sprouted pearl millet and bambaranut methods described by okafor et al. (2014) and james et al. (2018) were used to sprout millet and bambara nut with slight modifications. millet and bambara nut were sorted, washed, and soaked in clean water for 12 and 24 hr, respectively, at room temperature (28 ± 2°c) with change in soaking water at 4 hr interval to prevent fermentation. soaked seeds were separately spread on jute bag and covered with the same and allowed to sprout for 48 hr with sprinkling of water at 3 hr intervals. after sprouting period, the seeds were evenly spread on oven trays and dried at 60°c for 12 and 20 hr, respectively, and then hammer milled into a flour of 0.6 mm size and packaged differently in high-density polyethylene for further analysis. 2.3 product formulation the samples for this study were formulated, thus 100% sprouted millet flour, 100% fermented millet flour, 95% sprouted millet flour and 5% sprouted bambara nut flour, 95% fermented millet flour and 5% fermented bambara nut flour, 95% sprouted millet flour and 5% fermented bambara nut flour, and 95% fermented millet flour and 5% sprouted bambara nut flour, representing samples a, b, c, d, e, and f, respectively. amino acid profile, antinutrients and proximate composition were determined using standard methods. 3. results and discussion the results of this study show that samples a (100% spouted millet) and b (100% fermented millet) had significantly high moisture contents, 9.93 and 9.91%, respectively; while, different blends showed significantly low moisture content. blending treated bambaranut flour with millet significantly increased the protein content from 14.46% to 19.35%. sample f (95% fermented millet and 5% sprouted bambaranut flour) had significantly (p<0.05) high fibre (1.21%), fat (8.01%) and ash http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 37-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 39 (5.35%) contents; while, sample a (100% sprouted millet) had the lowest values: 0.68%, 6.21% and 3.32% respectively. this implies that blending treated millet and bambaranut flours at different ratios used in this study enhanced the fibre, fat and ash contents. samples a (100% spouted millet) and b (100% fermented millet) had significantly high carbohydrate contents, 65.43 and 63.58% respectively. however, blending significantly reduced the carbohydrate content with sample f (53.29%) having the lowest value. samples e (95% sprouted millet and 5% fermented bambara nut) and f (95% fermented millet and 5% sprouted bambara nut) had significantly (p<0.05) high histidine, isoleucine, leucine, lysine, methionine, phenyl alanine, threonine, tryptophan and valine. this implies, blending and treatment significantly increased the amino acid contents of samples. however, samples a and b showed significantly low values. in antinutrients, samples a (100% sprouted millet) and b (100% fermented millet) had significantly (p<0.05) low trypsin, hydrogen cyanide, oxalate and phytate contents; while, samples e and f showed significantly high values. this implies that addition of treated bambaranut flour to millet increased the antinutrients content of blended samples. in tannin content, samples a and b had significantly (p<0.05) high values 0.74 and 0.71% respectively; while blended samples showed significantly low values. 4. conclusion sprouting, fermentation and blending ratios used in this study significantly increased the nutritional quality of the formula and these would improve digestibility and bioavailability of nutrients. inclusion of treated bambaranut flour in the blend increased a number of antinutrients content, however, the values fall within the tolerable limits by humans. 5. acknowlegment the authors are grateful to federal university of technology, minna, nigeria; michael okpara university of agriculture umudike, nigeria and adamawa state university mubi, nigeria for their support. ../../../user/downloads/azojete143/www.azojete.com.ng nwabueze, et al: chemical composition of millet-based infant formula supplemented with treated bambaranut flour. azojete, 14(sp.i4): 37-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 40 table 1. chemical composition of the formulated infant formula parameter (%) a b c d e f moisture 9.93a ± 0.01 9.91a ± 0.01 9.86b ± 0.01 9.80c ± 0.00 9.79c ± 0.01 9.78c ± 0.01 protein 14.46f ± 0.01 15.12e ± 0.00 16.44d ±0.00 17.20c ± 0.00 18.42b ± 0.00 19.35a ± 0.01 fibre 0. 68f ± 0.01 0.75e ± 0.01 0.84d ± 0.01 0.94c ± 0.00 1.00b ± 0.00 1.21a ± 0.00 fat 6.21f ± 0.00 7.11e ± 0.00 7.45d ± 0.00 7.81c ± 0.01 7.91b ± 0.01 8.01a ± 0.01 ash 3.32f ± 0.06 3.51e ± 0.01 3.86d ± 0.00 4.22c ± 0.00 5.04b ± 0.01 5.35a ± 0.01 carbohydrate 65.43a ±0.05 63.58b ± 0.04 61.53c ± 0.03 59.35d ± 0.01 57.84e ± 0.03 53.29f ± 0.04 histidine 1.12f ±0.00 1.63e ± 0.00 1.85d ± 0.00 1.89c ± 0.00 2.04b ± 0.00 2.11a ± 0.00 isoleucine 1.76f ± 0.00 1.81e ± 0.01 2.06d ± 0.01 2.51c ± 0.00 2.77b ± 0.00 2.84a ± 0.01 leucine 5.11e ± 0.01 5.34d ± 0.00 5.52cd ± 0.00 5.62bc ± 0.00 5.84a ± 0.00 5.74ab ± 0.14 lysine 2.72f ± 0.00 2.94e ± 0.00 3.23d ± 0.01 3.46c ± 0.01 3.82b ± 0.00 3.94a ± 0.00 methionine 1.24f ± 0.00 1.56e ± 0.00 1.81d ± 0.01 1.94c ± 0.01 1.98b ± 0.00 2.42a ± 0.00 phenyl alanine 2.45f ± 0.05 2.51e ± 0.00 2.78d ± 0.00 2.83c ± 0.00 2.94b ± 0.01 3.01a ± 0.00 threonine 1.84f ± 0.00 1.92e ± 0.00 2.28d ± 0.01 2.47c ± 0.00 2.61b ± 0.00 2.84a ± 0.00 tryptophan 4.71f ± 0.00 4.87e ± 0.00 5.05d ± 0.01 5.33c ± 0.01 5.63b ± 0.01 5.74a ± 0.01 valine 1.72f ± 0.00 1.94e ± 0.01 2.27d ± 0.01 2.64c ± 0.00 2.75b ± 0.00 2.84a ± 0.00 trypsin 0.28f ± 0.00 0.33e ± 0.01 0.39d ± 0.01 0.52c ± 0.01 0.62b ± 0.01 0.73a ± 0.00 tannins 0.74a ± 0.01 0.71a ± 0.00 0.66b ±0.00 0.54d ± 0.01 0.50e ± 0.00 0.59c ± 0.01 hydrogen cyanide 0.29f ± 0.01 0.36e ± 0.01 0.43d ± 0.01 0.56c ± 0.00 0.62b ± 0.01 0.74a ± 0.01 oxalate 0.14f ± 0.00 0.22e ± 0.00 0.30d ± 0.00 0.38c ± 0.00 0.47b ± 0.00 0.53a ± 0.01 phytate 0.97f ± 0.01 1.22e ± 0.01 1.88d ± 0.00 2.11c ± 0.00 2.74b ± 0.01 3.04a ± 0.00 mean ± sd of triple determinations. values followed by different subscript on a row are significantly different from each other (p < .05). a = 100% sprouted millet; b = 100% fermented millet; c = 95% sprouted millet and 5% sprouted bambara nut; d = 95% fermented millet and 5% fermented bambara nut; e = 95% sprouted millet and 5% fermented bambara nut; f = 95% fermented millet and 5% sprouted bambara nut. 6. references aoac. 2005. association of official analytical chemists. in: official methods of analysis, 18th edn. (edited by w. horwitz and g.w. latimer jr.). gaithersburg, md, usa. james, s., akosu, ng., yakubu, cm., ibrahim, ab., nwokocha, l., james, ya., audu, y. and omeiza, myz. 2017. effect of addition of processed bambara nut on the functional and sensory acceptability of millet-based infant formula. food science and nutrition, https://doi.org/10.1002/fsn3.618. okafor, jn., jane, c., ani, c., and gabriel, io. 2014. effect of processing methods on qualities of bambara groundnut (voandzeia subtterranea (l) thouars) flours and the acceptability in extruded snacks. american journal of food technology, 9, 1557–4571. http://www.azojete.com.ng article information 1.introduction 2. materials and methods 2.1sources of raw material 3. results and discussion 4. conclusion 5. acknowlegment arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):321-336 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 321 original research article investigation of small hydropower potential of river oshin in kwara state, north central, nigeria a. s. oladeji1,2, m. f. akorede2, a. a. mohammed1, a. g. adeogun3, and a.w. salami1 (1national centre for hydropower research and development university of ilorin, ilorin, nigeria 2advanced power and green energy research group, department of electrical and electronics engineering, university of ilorin, ilorin, nigeria. 3kwara state university, malete, nigeria) *corresponding author’s email address: akinsun3k@yahoo.co.uk 1.0 introduction presently, electrical energy demand in nigeria is being met largely with conventional sources of energy such as oil, gas and coal which lead to emission of greenhouse gases into the atmosphere. this results in negative effect of climate change. the world is going green, therefore there is need for assessing and harnessing all the renewable energy sources. but, as the electrical energy demand increases on yearly basis, the conventional sources decreases. consequently, several countries have focused on renewable energy sources, like hydropower, article information abstract this paper presents the investigation of hydropower potential of river oshin via babaloma in ifelodun local government area of kwara state, north central, nigeria. the inhabitants of the study area which is a cluster of three off-grid rural communities: sangotayo, budo umoru and idi isin lack access to electrical energy despite the huge potential for renewable energy resources most especially, the hydropower potential. water velocity of the river was measured using flow probe fp211 model. the measured water velocity was converted to discharge using relationship between the channel geometry and velocity. relationship between measured discharge and water level was used to develop rating equation for the river. net head was estimated using digital elevation model (dem) embedded in arcgis (arcmap 10.3) software. the results revealed that the average water level and discharge were high in the month of may through november with discharges varying between 3.48 to 11.90 m3/s while water levels ranged between 0.79 to 1.84 m. the relationship between the water level and discharge revealed a correlation coefficient of 0.99 with positive upward trend. the design flow of 4.63 m3/s was determined from the flow duration curve (fdc) while the net head was estimated as 7.62 m. the hydropower potential of the river at the subbasin 9 was estimated as 363.36 kw which is in the range of mini hydropower plants (mhp). annual energy generation from the river is estimated as 2624482.08kwh. the estimated hydropower potential can satisfy the present and future electricity needs of the inhabitants of the cluster of the three rural communities under consideration. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2019 revised 02 february, 2020 accepted 08 february, 2020 keywords: flow duration curve hydropower potential river oshin budo umoru http://www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 322 wind and tidal (agiralioglu et al., 2017). renewable energy sources such as hydropower, wind, solar and biomass are important technology options for reducing greenhouse gas emissions and local air pollutants associated with the burning of fossil fuels. hydropower is currently the dominant renewable energy source accounting for 18% of the world total electricity supply (zhou et al., 2015). hydropower is also technically mature and economically competitive. moreover, hydropower plants can help balancing electricity supply and demand. therefore, improving the efficiency of thermal power plants and reducing the impacts of variability in other renewable energy resources (zhou et al., 2015). increasing the amount of renewable energy for electricity generation (res-e) is a major target within the european union as well as global scale (haas et al., 2011). nigeria has been facing serious electrical power shortage due to inadequate power generation, lack of strong political will to develop power system infrastructure, unstable government policies in power sector reform, corruption, in-efficiency in electrical power generation, transmission and distribution among others. according to the nigerian energy policy report of 2003, it is estimated that the population connected to the national grid system is short of power supply over 60% of time. the estimated long-term power demand of nigeria was put at 25gw for the year 2010 to sustain industrial growth (okanefe and owolabi, 2001). the power holding company of nigeria (phcn) has an installed capacity of 6 gw, but the actual available output is less than 2.5 gw out of which thermal plants provides 61%, while hydropower generation is about 31% of the power generation (okpanefe and owolabi, 2002). according to bilewu et al., (2011), the total estimated hydropower potential of nigeria is 11 gw. this implies that less than 20% of the hydropower potential of the country has been harnessed (bilewu et al., 2011). smallscale hydropower is a good and reliable form of sustainable energy supply in rural areas (reichl and hack, 2017). it generally has no artificial storage and relies solely on the river flow to generate electricity (rees et al., 2004). the definition of a small hydro project differs from one country to another, but a generating capacity not exceeding 10 mw is generally accepted as the upper limit of what can be defined as a small hydro plant in nigeria (sambo, 2005; bilewu et al., 2011; shobayo et al., 2014). from economic perspective, the cost of developing a small hydropower generating system is considerably low as compare a large hydropower generating systems which usually require the construction of a large dam that usually gulp larger percentage of the overall project cost (basnyat, 2006; bha, 2005; shobayo et al., 2014). likewise, most small hydropower plants does not require dam construction (without significant water storage facility) hence, the negative environmental impacts such as, ecological disruption; flooding and social conflicts associated with large scale hydro projects are drastically reduced (bha, 2005; shobayo et al., 2014). small hydropower plants have emerged as a source of renewable energy, which can be easily developed, inexpensive and harmless to the environment. the accurate estimation of discharge is an essential component of hydropower design and constructions for energy generation capacity estimation as well as environment protection on ungauged river basins (tuna, 2013). in nigeria, streamflow measurements are carried out by government through river basin development authority (rbda) and state water boards, which established gauging stations on rivers within their catchment areas and streamflow data can be obtained from them. however, in the past fifteen years it was reported that there was no been streamflow measurements along major rivers in nigeria due to lack of funding (adedokun et al., 2013). this is quite worrisome as http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 323 availability and reliability of hydro-meteorological data are very critical to hydropower potential assessment of rivers globally (kling et al., 2016). in a related research, khan and zaidi (2015) determined the hydropower potential of kunhar river in pakistan using geospatial data and techniques. satellite data used in the study included aster digital elevation model (dem). streamflow data was obtained from regional hydrologic gauges. remote sensing (rs) and geographical information systems (gis) tools were used for processing the satellite images, delineation of watershed, stream network and identification of potential sites for hydropower projects. emeribe et al. (2016) assessed hydropower potentials of some rivers in edo state, nigeria for small-scale development. four rivers namely: ovia, ikpoba edion and orlie were investigated. discharge measurement was carried out for 12 calendar months (january to december, 2013) using velocity-area method while gross hydropower potential (ghp) was determined using model developed by united nations industrial development organization (unido). results revealed that ovia river recorded the highest power yield of 61.619 mw due to its high flow rate, making it suitable for a medium hydropower scheme. abebe (2014) carried out feasibility study of small hydropower schemes in giba and worie subbasins of tekeze river in ethiopia. discharge for ungauged hydropower potential sites was estimated using the runoff coefficient method. topographical map and digital elevation model (dem) of the study area were used for analyzing watershed delineation, river networks, location of the potential sites and gauging stations. the viability of the hydropower potential sites was analysed using retscreen software. results revealed that five locations namely: meskila-1, meskila-2, meskila-3, genfel-1, genfel-2 and suluh were feasible with total power of 3591kw. in a similar vein, prajapati(2015) studied the hydropower potential of the run of river in karnali basin in nepal using gis and hydrological modeling system (hms). dem was used to estimate the elevation of upstream and downstream ends of the reaches and daily discharges of the reaches were derived from precipitation data using hms model with nash efficiency ranging from 61.7 to 82.02 %. results showed that design discharge corresponding to 40th percentile flow had total hydropower potential of 14150.80 mw. gumindoga et al. (2016) estimated runoff from ungauged catchments for reservoir water balance in the lower middle zambezi basin in zambia. this study applied a rainfall-runoff hydrologic engineering centre-hydraulic modelling system (hec-hms) model with gis techniques to estimate both gauged and ungauged runoff contribution to the water balance of cahora bassa reservoir. the rivers considered in the study were the zambezi, kafue, luangwa, chongwe, musengezi and manyame. dem hydro-processing technique was used to determine the spatial extent of the ungauged area. a hydrological model, hechms, was used to simulate runoff from the catchments. results revealed that the catchment contributed about 12% of the total estimated inflows into the reservoir. okorafor et al. (2013) evaluated the hydropower potential of otamiri river in imo state, nigeria for electric power generation. the study involved the estimation of maximum design floods for the watershed using the gumbels probability distribution method for various return periods (tr) with the development of unit hydrograph, storm hydrograph, runoff hydrograph and flood duration curve for the catchment area of the river. soil conservation service (scs) method and other empirical formulas were used to determine peak flow (qp), lag time (tl), time of concentration (tc) and rainfall intensity (ic). the available flow for power generation, the head of the river was estimated from records provided by the anambra-imo river basin development file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 324 authority (rbda) and flow duration analyses were carried out. the results indicated that flows of 50, 75 and 100% chance of occurring had the following 34.5, 11.3 and 1.5 mw power generation respectively. kling et al. (2016) assessed the regional hydropower potential of rivers in west africa. the study covered more than 500,000 river reaches. the theoretical hydropower potential was computed from channel slope and mean annual discharge simulated by a water balance model. the model was calibrated with observed discharge at 410 gauges using precipitation and potential evapotranspiration data as inputs. the results showed that the west africa regions are classified to have hydropower potentials varying between < 1mw to > 30 mw. most of the hydropower projects especially small hydropower projects are constructed on ungauged river and consequently hydrologists have for a long time applied streamflow estimation methods to simulate streamflow (kasamba et al., 2015). the power potential of flowing river is a function of the discharge (q), the specific weight of water and the difference in head (h) between intake point and turbine (kasamba et al., 2015). in summary from the literature reviews, it can be concluded that assessment of hydropower of rivers is very vital to design and development of hydropower scheme. it is a common knowledge that the output of small hydropower plants changes with the hydrological cycle of a river (bha, 2005; natural resources, 2004). hence, a reliable assessment of available small hydro resource cannot be accomplished without a prior assessment of the hydraulic turbine’s response to the annual variability of river flow (shobayo et al., 2014). it is this assessment that will determine the available of electrical energy at any hydro site. the study area is a cluster of three communities which are located closed to one another but are not connected to the national grid. river oshin flows along the communities with high hydropower potential before finally discharged into the river niger. the objective of this study is to investigate the small hydropower potential of the river oshin in kwara state, north central, nigeria. the small hydropower potential of the river if assessed and harnessed will solve the power challenges of the area. 2. materials and methods 2.1 characteristics of study area the study area is located in ifelodun local government area of kwara state, nigeria and comprises of three (3) rural communities namely: sangotayo, budo umoru and idi isin. the study area is a complete off-grid location. the features of each of the rural community are shown in table 1. the primary source of energy is fuel wood for cooking and secondary source is kerosene for lighting and security in all the three rural communities. the significant commercial activity in these communities is agriculture which involves crop production and animal husbandry. the main crops grown are corn, millet, yam, beans and cassava. the study area is rich in hydro, solar and wind renewable resources. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 325 table 1. features of the study area. features sangotayo budo umoru idi isin number of houses 14 63 9 number of shops 3 4 number of primary schools 1 shared primary school 1 shared primary school 1 shared primary school number of mosque 1 3 number of church 2 number of households 70 158 45 map of nigeria showing the case study river is presented in figure 1. the dem of the river oshin was geo-processed in arcgis tool (arcmap 10.3). the entire river course was delineated into 11 sub-basins as shown in figure 1. ila orangun, osun state, nigeria jebba lake, nigeria sub-basin under consideratio n figure 1: map of nigeria showing the case study river catchment the river has its source from ila, orangun, osun state and flows into jebba lake. the direction of flow of the river from ila orangun to jebba lake is presented in figure 1. the total area of the river course and total stream length was estimated as 2121.86 km2 and 225.77 km respectively. the sub basin that is located near the rural off-grid communities (sub basin where forebay and powerhouse will be located) is sub basin 9. this sub-basin also has a reasonable drop of 28 m and stream length of 13481.00 m with area of 141. 95 m2 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 326 2.2 measurements of stream discharge river oshin is an ungauged perennial river. in order to determine its hydropower potential, a hydrological gauge station was installed along a uniform reach of the river to measure the daily water level for a period of one year. a hydrological gauge reader was engaged for a period of one hydrological year to measure daily water level of the river. the flow velocity of the river was measured using flow probe model fp211. the flow probe model fp211 operates using the principle of water current as a distance which one length of water covered in one second. the velocity of water was measured by dipping the flow probe into the river at the various sections of the river channel and readings were taken until the end of the channel. the measure flow velocity at the various section of the river was converted to river discharge using the relationship between the flow velocity and channel cross-sectional as shown in equation (1) (wali, 2013). fdc of the river was plotted using the measured discharge data and the corresponding return period estimated using the equation (2) (booker and snelder, 2012). (oregon state university, 2005; rajput, 2008; shobayo et al., 2014). avq  (1) where: a is sectional area (m2),v is flow velocity (m/s) and q is discharge (m3/s). %100 1  n rp (2) where: p is the percent of time during which specified discharges were equaled or exceeded in a given period (%), r is the rank of observed data and n is total observation. the discharges were arranged from maximum to minimum and ranked from r = 1 to n (castellarin et al., 2004; castellarin; 2014). 2.3 measurement of head head is defined as the loss of elevation by the river over its stretch between the water surface at the proposed intake and the river level at the point where the water entered the proposed turbine location (shobayo et al., 2014; bha 2005; esha, 2004). contours were generated from 30 m x 30 m dem of the case study area obtained from united state geological survey (usgs) online database. the contours were used to determine the possible location of turbine and forebay. the gross head was estimated using topographical map of the study area, as the vertical distance between the proposed forbay and turbine location. the actual head available for the turning of the turbine is called net head. the difference between the gross head and losses gives net head as presented in the equation (3). all the losses were estimated using the equations (4), (6), (7) and (8). the input parameters used in computing the head losses are presented in table 2 (ratnayake and pitawala, 2014). the expression for estimating frictional losses (hf) is presented in equation (4) (wali, 2013). the net head is always less than the gross head due to losses suffered when moving the water into and away from the turbine through water carriage arrangements.  obtrfgn hhhhhh  (3) where: hn is net head (m), hg is gross head (m), hf is a frictional loss (m), htr is a trash rack loss (m), hb is loss due to bend (m) and ho is outlet loss (m). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 327 333.5 2229.10 d qnlh f   (4) where: l (m) is length of penstock, d (m) is pipe diameter, n is the manning coefficient for different type of pipes and q (m3/s) is discharge. the pipe diameter was estimated using equation (5) (wali, 2013). yh lqnd g 1875.022 1003.10  (5) where: n is manning roughness coefficient for commercial pipes, q is discharge (m3/s), l is the length of the penstock, hg is the gross head, y is the percent loss of the total gross head due to friction. raynal et al., (2013) formulated htr as shown in equation (6). the expressions for estimating hb, ho, velocity in tube (v) and entrance velocity (vo) are presented in equations (7) to (10) (raynal et al., 2013). sin 2 23/4             g v b tkh o tr (6) where: k is the factor describing the shape of the rack, t is the bar thickness (mm), b is the width between the bars (mm), vo is the entrance velocity (m/s), g is gravitational acceleration (m/s2),  is the angle between the grid and the horizontal reference. g vkh bb 2 2  (7) where: bh is losses due to bend, bk is loss coefficients due to bends. g vho 2 2  (8) 2 4 d qv   (9) )sin( 1 )(1 1     s q bt t k vo (10) s = total grid area table 2. input parameters for estimating head losses. parameters unit value remarks l m 158 using topography map of the area  (o) 60 gh m 8 using topography map of the area t mm 12 b mm 70 s m2 5 k 0.8 assuming an automatic cleaner is used for the trash rack file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 328 2.4 determination of hydropower and energy potential the mathematical expression used for estimating the hydropower potential of the river is presented in equation (11) (emeribe et al., 2016; cyr et al., 2011; raghunath, 2008) while, the annual energy output of the river ( anhe ) was calculated using equation (12) (cyr et al., 2011). ngqhp  (11) where p is power (w),  is overall efficiency (%),  is density of water (kg/m3), g is acceleration due to gravity is 9.81m/s2, q is discharge (m3/s), h is effective head (m)    8760 1t tanh pe (12) where tp is power demand at time t (w),  is overall efficiency (%),  is density of water (kg/m3), g is acceleration due to gravity is 9.81m/s2, q is discharge (m3/s), nh is net head (m). 2.5 capacity factor capacity factor (cf) is defined as the fraction of total energy supplied from a facility over a period of time, divided by the highest energy that could have been delivered if the facility was used at its maximum capacity over the entire period (jaramillo et al., 2004). the annual capacity factor was calculated using equation (13) (adejumobi and shobayo, 2015). the expression for estimating highest energy ( rne ) is shown in equation (14) (adejumobi and shobayo, 2015). rn anh e ecf  (13) tnpe hrrn  (14) where: rne is the highest energy that could have been delivered if the facility was used at its maximum capacity over period t , rp is the rated capacity of a single hydro plant unit, hn is the number of hydro plant units, t is the required annual operating period of time in hours which is equal to 8760 hours, that is the product of number of days in a year with number of hours in a day. 2.6 relationship between the water level and discharge the relationship between the water level and discharge for the study area was evaluated so as to validate the discharge data using the correlation coefficient ( r ) presented in equation (15) (giri and singh, 2014). one way analysis of variance (anova) in statistical package for social sciences (spss) version 16.0 was also used to examine statistical significant difference between discharge and water level at 0.05 level in order to check for variation in the data used. http://scialert.net/asci/author.php?author=aradhana&last=giri http://scialert.net/asci/author.php?author=n.b.&last=singh http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 329 22                               didiwiwi didiwiwi yyyy yyyy r (15) where: wiy is the observed water level, diy is observed discharge , wiy  is mean of observed water level,  diy is mean observed discharge,n is total number of observations 3. results and discussion 3.1 river water level and discharge the measured water level and corresponding discharge statistics of the river are presented in tables 3 and 4 respectively. statistics of the water level and discharge indicated that both hydrological parameters of the river vary with each other. average water level and discharge were high in the month of may through november with discharges varying between 3.48 to 11.90 m3/s while water levels ranging between 0.79 to 1.84 m. this is due to high streamflow common during raining season. the least water level and discharge of 0.14 m and 0.22 m3/s respectively were observed in april and this may be due to the peak of dry season experienced at that period of the year. maximum water level and discharge of 2.08 m and 14.3 m3/s respectively were noticed in september, this is as a result of high intensity of rainfall in the month. table 3. monthly water level statistics of the river (m). jan feb mar apr may jun jul aug sep oct nov dec mean 0.42 0.23 0.19 0.18 0.79 1.03 0.96 1.6 1.84 1.75 1.08 0.618 min 0.29 0.21 0.17 0.14 0.3 0.88 0.78 0.78 1.6 1.6 0.84 0.28 max 0.5 0.27 0.2 0.3 1.4 1.48 1.04 2.06 2.08 1.88 1.54 0.84 std 0.07 0.01 0.01 0.05 0.36 0.16 0.08 0.49 0.17 0.08 0.26 0.172 table 4. monthly discharge statistics of the river (m3/s). jan feb mar apr may jun jul aug sep oct nov dec mean 1.25 0.48 0.37 0.33 3.48 4.91 4.36 9.87 11.9 11 5.32 2.278 min 0.69 0.42 0.3 0.22 0.73 3.8 3.16 3.16 9.55 9.55 3.54 0.652 max 1.59 0.62 0.39 0.73 7.77 8.47 4.92 14.1 14.3 12.2 9 3.54 std 0.29 0.04 0.03 0.15 2.29 1.22 0.52 4.33 1.73 0.81 1.98 0.9 also, the relationship between the water level and discharge revealed a very strong relationship with correlation coefficient of 0.99. the discharge of the river is highly dependent on the water level. seasonal variation of water level with highest water level in september and least water level in april is presented in figure 2. also, the runoff hydrograph for the river which shows the variation in hourly discharge for one year is presented in figure 3. the variation of water level and discharge for the river shown in figures 2 and 3 indicated that discharge increases with file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 330 increase in water level. high discharge and water level were observed in the months of may through november while lower values noticed in january through april. this indicated that the river actually flowed throughout the year; this is an indication that the river can used for hydropower generation, domestic water supply and mini irrigation projects. these corroborate the results presented in tables 2 and 3. the seasonal variations in the water level and discharge of the river are associated with the rainfall and groundwater contribution within the river catchment based on the available measured data and information received from the people living in the communities around the river catchment (adedokun et al., 2013). likewise, high electrical energy potential was observed in the months of may through november while lower values noticed in january through april based on the measured hydrological data of the study area (salami et al., 2015). anova result for comparison between water level and discharge measured shown in table 5. it was observed from the anova results that increase in water level results in corresponding increase in discharge. at 5% significant level, p-value was 0.00, this implies that variation is significantly difference. this means that increasing in the water level statistically result in much increase in discharge. figure 3. hourly variation of discharge in the river for one year (january to december, 2017) figure 2. seasonal variation of water level in theriver. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 331 table 5. anova result for comparison between water level and discharge. sum of squares df mean square f p-value between groups 134.86536 105 1.28443 3.8e+32 0.00 within groups 8.7236e-31 259 3.4e-33 total 134.86536 364 scattered plot of discharge against water level shown in figure 5 revealed that there is a perfect linear relationship between them with the determination coefficient (r2) of 0.98. therefore, the generated linear equation for the variables can be used to predict the future discharge for the river. relationship between discharge and water level in figure 5 revealed that at lower value of water level there is corresponding lower value of discharge. this is depicted in the linear equation presented in the figure 5 with higher gradient value and low intercept. this is similar to the results presented in (sefe, 1996). rating curve generated for the river presented in figure 6 also indicated that there is perfect relationship between the water level and discharge with r2 value of 0.99. daily flow duration curve for the oshin river at budo umoru kwara state shown in figure 7 revealed that discharge of 0.224 m3/s will be available throughout the year. also discharge of 3.670 m3/s will be available for 50 % of time. this implies that discharge of 3.670 m3/s will be available in the river for a period of a year (bilewu et al., 2011). figure 5. scattered plot of discharge against water level file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 332 3.2 estimation of energy potential of the river hourly energy variation for the river for one year (january to december, 2017) shown in figure 8 revealed that change in the river discharge has a corresponding effect on the quantity of energy generated from the river. annual energy generation from the river is estimated as 2,624,482.08kwh. also, the annual capacity factor was estimated as 0.83. this is typically due to variation in water level and discharge (availability of water). since, the discharge is not constant throughout the year, the capacity factor will always be less than 1 (100%). high energy generation were observed in the months of may through november while lower values noticed in january through april as shown in figure 8, this is in with (salami et al., 2011). figure 6. rating curve generated for the river figure 7. daily flow duration curve for river oshin at budo umoru kwara state http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 333 the net head was estimated as 7.62 m. design flow was estimated as 4.63 m3/s from the fdc. the hydropower potential of the river at the sub-basin 9 is estimated as 363.36 kw which falls in the range of mini hydropower plants (mhp) (emeribe et al., 2016). the estimated power can be deployed to satisfy the present and future electricity needs of the nearby rural dwellers. 4. conclusion this paper presented the assessment of hydropower potential of river oshin via budo umoru and environs in north central nigeria. the results of this work have shown that there is reasonable small hydropower potential of 363.36 kw at the selected sub-basin along the river. the estimated hydropower potential of the river at the selected sub-basin is in the range of mini hydropower plants (mhp). annual energy generation from the river is estimated as 2624482.08kwh and the annual capacity factor was found to be 0.83. the potential at this location can satisfy the present and future electricity demand of the inhabitants the cluster of the three rural communities if it is properly and economically harnessed. acknowledgements the authors wish to thank the management of the national centre for hydropower research and development (nachred), university of ilorin, ilorin nigeria for providing funding and enabling environment in the course of this study. we also appreciate the cooperation of the budo umoru community for giving necessary supports while the hydrological gauge was installed at the location. references abebe, n. 2014. feasibility study of small hydropower schemes in giba and worie subbasins of tekeze river. ethiopia journal of energy technologies and policy, 4(8): 8-17. adedokun, g., oladosu, ja. and ajiboye. tk 2013. small hydropower potential capacity estimation for provision of rural electricity in nigeria. acta technica corviniensis, bulletin of engineering, hunedoara romania, 4(2): 117-120. adejumobi, ia. and shobayo. di. 2015. optimal selection of hydraulic turbines for small hydro electric power generation: a case study of opeki river, south western nigeria. nigerian journal of technology, 34(3): 530-537. figure 8. hourly variation of energy in the river for one year (january to december,2017) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 334 agiralioglu, ne., andic, g., cigizoglu, hk., coskun, hg., yilmaz, l., alganci, u. and toprak, zf. 2017. practical methods for the estimation of hydroelectric power potential of poorly gauged basins. sigma journal of engineering and natural science, 35(2): 347-358. basnyat, d. 2006. fundamentals of small hydro power technologies, financing cogeneration and small-hydro projects in the sugar and tea industry in east and southern africa training, nairobi, kenya. adb finesse training course on renewable energy and energy efficiency for poverty reduction, pp. 5-36. bha, 2005. british hydropower association, "a guide to united kingdom mini–hydro developments", version 1.2, london, united kingdom. available on line at: http://www.britishhydro.org/useful20%information/a20% . accessed online on 23rd january, 2018 bilewu, so., salami, aw., sule, bf., adeleke, oo., usman, a. and jimoh, mo. 2011. retrofitting asa water supply dam for hydroelectric power generation. a technical report number 6, submitted to national centre for hydropower research and development, university of ilorin, ilorin, nigeria. pp. 1-75 booker, dj. and snelder, th. 2012. comparing methods for estimating flow duration curves at ungauged sites. journal of hydrology, 4(3): 78-94. castellarin, a. 2014. regional prediction of flow-duration curves using a three-dimensional kriging. journal of hydrology, 513: 179-191. castellarin, a., galeati, g., brandimarte, l., montanari, a. and brath. a. 2004. regional flowduration curves: reliability for ungauged basins. advances in water resources, 27: 953-965. cyr, jf., landry, m. and gagnon. y. 2011. on the large scale assessment of small hydroelectric potential: application to the province of new brunswick (canada). world renewable energy congress, 8th -13th may, 2011, linoping, sweden, 55: pp. 1472-1479. dashora, i. 2015. hydrological investigations and analysis for hydropower projects. ph.d. thesis, alternate hydro energy centre, indian institute of technology roorkee, india. pp. 1-250. emeribe, cn., ogbomida, et., fasipe, oa., biose, o., aganmwonyi, i., isiekwe, m. and fasipe, ip. 2016. hydrological assessments of some rivers in edo state, nigeria for small-scale hydropower development. nigerian journal of technology, 35(3): 656-668. esha2004.european small hydropower association, "guide on how to develop a small hydropower plant", esha, brussels, belgium,. available on line at: http://www.esha.be/fileadmin/esha_files/documents/publications/guides/guide_shp/guide_s hp_en. pdf. accessed online on 23rd june, 2018. giri, a. and singh. nb. 2014. comparison of artificial neural network algorithm for water quality prediction of river ganga. environmental research journal, 8(2): 55-63. gumindoga, w., makurira, h., phiri, m. and nhapi. i. 2016. estimating runoff from ungauged catchments for reservoir water balance in the lower middle zambezi basin. water and sanitation association, 42(4): 641-649. haas, r., panzer, c., resch, g., ragwitz, m., reece, g. and held, a. 2011. a historical review of promotion strategies for electricity from renewable energy sources in eu countries. renewable and sustainable energy reviews, 15:1003-1034. jaramillo, oa., borja, ma. and huacuz, jm. 2004. using hydropower to complement wind energy: a hybrid system to provide firm power. renewable energy, 29: 1887-1909. http://www.british-hydro.org/useful20%25information/a20%25 http://www.british-hydro.org/useful20%25information/a20%25 http://scialert.net/asci/author.php?author=aradhana&last=giri http://scialert.net/asci/author.php?author=n.b.&last=singh http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 321-336. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 335 kasamba, c., ndomba, pm., kucel, sb. and uamusse, mm. 2015. analysis of flow estimation methods for small hydropower schemes in bua river. energy and power engineering, 7: 55-62. khan, m. and zaidi, az. 2015. run-of-river hydropower potential of kunhar river, pakistan. pakistan journal of meteorology, 12(23): 25-32. kling, h., stanzel, p. and fuchs, m. 2016. regional assessment of the hydropower potential of rivers in west africa. energy procedia, 97: 286 -293. natural resources, 2004. small hydro project analysis chapter, retscreen engineering and cases textbook, published by natural resources canada. ottawa, canada, catalogue no. m39 – 38/2003e. okorafor, oo., okereke, naa. and egwuonwu, cc. 2013. evaluation of the hydropower potential of otamiri river for electric power generation. research journal of applied sciences, engineering and technology, 6(24): 4541-4547. okpanefe, pe. and owolabi, s. 2002. small hydropower in nigeria. a tcdc training workshop in small hydropower programme. hangzhou, china, pp. 1-24. oregon state university, 2005. “analysis techniques: flow duration tutorial”, in stream flow evaluations for watershed restoration planning and design. available on line at:http://streamflow.engr.oregonstate.edu/analysis/flow/flow_duration_tutorial.pdf. springer, london, (accessed on 14th march, 2018). pp. 1-85. prajapati, rn. 2015. delineation of run of river hydropower potential of karnali basin-nepal using gis and hec-hms. european journal of advances in engineering and technology, 2(1): 50-54. raghunath, hm. 2008. hydrology principle, analysis and design, a revised second edition, new age international limited publishers, new delhi, india. pp. 1-463. rajput, rk. 2008. a textbook of power plant engineering. laxmi publications limited, new delhi, india. ratnayake, as. and pitawala, a. 2014. prediction of ungauged river basin for hydropower potential and flood risk mitigation: a case study at gin river, sri lanka. interdisciplinary environmental review, 15(4): 203-214. raynal, s., courret, d., chatellier, l., larinier, m. and david, l. 2013. an experimental study on fish friendly trash racks. journal of hydraulic research, 51(1): 56-66. rees, g., gustard, a. and kansakar, sr. 2004. development and testing of a flow estimation model for nepal. journal of hydrology and meteorology, 1(1): 16-23. reichl, f. and hack, j. 2017. derivation of flow duration curves to estimate hydropower generation potential in data-scarce regions. water, 9(2): 1-15. salami, a.w., mohammed, a.a., adeyemo, j.a. and olanlokun o.k. 2015. modeling of reservoir inflow for hydropower dams using artificial neural network. nigerian journal of technology, 34(1): 28-36. sambo, s. a. 2005. renewable energy for rural development: the nigerian perspective, isesco science and technology vision, volume 1, isesco islamic educational, scientific and cultural organization, rabat, kingdom of morocco, pp. 12-22. http://streamflow.engr.oregonstate.edu/analysis/flow/flow_duration_tutorial.pdf file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladeji et al: investigation of small hydropower potential of river oshin in kwara state, north central, nigeria. azojete,16(2):321-336. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akinsun3k@yahoo.co.uk 336 sefe, ftk. 1996. a study of the stage-discharge relationship of the okavaiigo river at mohembo, botwana. hydrological science, 41(1): 97-116. shobayo, di., adejumobi, ia., awokola, os., and akinwale, at. 2014. an assessment of the small hydro potential of opeki river, southwestern nigeria. science journal of energy engineering, 6(3): 25-31. tuna, mc. 2013. feasibility assessment of hydroelectric power plant in ungauged: a case study. arabian journal of science and engineering, 38: 1359-1367. wali, u.g. 2013. estimating hydropower potential of an ungauged stream. international journal of emerging technology and advanced engineering, 3(11): 592-600. zhou, y., hejazi, m., smith, s., edmonds, j., li. h., clarke, l., calvina, k. and thomson a. 2015. a comprehensive view of global potential for hydro-generated electricity. energy environmental science, 8: 2622-2633 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):85-91 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 85 original research article kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung as inoculum n. h. abdulhakeem and a. a. lawal (1department of agricultural technology, federal college of horticulture dadin-kowa, gombe state, nigeria. 2department of agricultural and environmental resources engineering, university of maiduguri, borno state nigeria) *corresponding author’s email address: hnuruddeen15@gmail.com 1.0 introduction as the world population increases, so also the demand for fossil-based fuels. this demand is further aggravated by urbanization and its attendant effects on energy demand as well as uncertainty in fuel supply and prices in the global market (bentley, 2002; cavallo, 2003). nigeria loses an estimated five billion (usd) annually to poor environmental management practices from environmental pollution, waste mismanagement and improper agricultural waste handling (melford, 2003). the resulting output of poor environment management practices leads to pollution of air, water and environment. exposure to these pollutants pose great threat to human health, economic development and environmental safety. due to these challenges, researchers have tried to find alternative use of these slaughterhouse wastes that includes horns, bones, paunch manure, spent-water to transform them into a sustainable and renewable energy source (ezeoha and idike, 2007; monch-tegeder et al., 2013; ojolo et al., 2007). article information abstract anaerobic co-digestion offers a prospective medium for transforming organic solid wastes into fuel, thereby providing an extra source of energy. this study investigates the kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung as inoculum for biogas production. anaerobic assay setup was in 3 digesters of 4 replicates with a total of 12 replicate batch digesters under mesophilic temperature range (30-35°c) for a retention time of 30 days. cumulative biogas production for all digesters were measured and fitted to some selected models. the modified gompertz equation was tested for its fitness. the kinetic parameters viz., biogas yield potential (p), maximum biogas production rate (rm) and the duration of lag phase (λ) were recorded for each case as the digester with 0g sugarcane peels (control) produced maximum biogas of (83.14 (ml/g vs)) and the kinetic parameters p, rm and λ were 89.0018 ml (g vs-1), 4.7089 ml (g vs d)-1, 0.8734 days respectively. it was observed that biogas production potential was inversely proportional to the substrate concentration of sugarcane peels in the digesters, the highest concentration of sugarcane peels (1.8g sp) recorded the lowest quantity of biogas with 37.9075 ml/g vs, 1.4547 g vs-1, 1.0891 days. therefore, sugarcane peels should be co-digested with other substrates. the experimental kinetic data in-line with the gompertz model, modified gompertz model equation. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 september, 2019 revised 06 december, 2019 accepted 08 january, 2020 keywords: anaerobic digestion paunch manure sugarcane peels inoculum modified gompertz equation. mailto:hnuruddeen15@gmail.com http://www.azojete.com.ng mailto:hnuruddeen15@gmail.com abdulhakeem and lawal: kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung as inoculum. azojete,16(1):85-91. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 86 some researchers argued that, the biogas production potential of paunch manure without codigestion results in lower biogas yields due to its composition and opined that, paunch manure be co-digested with other substrates during the production process (ezeoha and idike, 2007; melford, 2003; monch-tegeder et al., 2013). anaerobic co-digestion is a systematic means of having more than one substrate in a formation to form a unit for producing biogas with the aim of improving the biogas yield potential (jagadish et al., 2012), also as an alternative way of converting these wastes to energy, which is cost-effective where the end products could be used as organic manure for agricultural purposes (bentley, 2002; cavallo, 2003). sugarcane peels (sp) are waste products of sugarcane (suaccherum species) as a result of human consumption of raw sugarcane or as waste product in jaggery production. sugarcane is one of the major crops cultivated in northern region of nigeria popularly known as “rake” and the peels as “bawon rake” in the local dialect. it is noteworthy that because sp waste products are not properly utilized, it would be a good idea to assessed its potentials as alternative source of energy. therefore, this study intends to investigate the kinetics of producing biomethane from slaughterhouse paunch manure (pm) codigested with sugarcane peels at different mixture ratios for anaerobic digestion using cow dung as inoculum. 2.0 materials and methods 2.1 substrate sources and characteristics fresh samples of paunch manure, sugarcane peels and inoculum were obtained sealed to avoid moisture depletion from kasuwan shanu, mairi ward and university of maiduguri animal farm in borno state. the samples were sun dried for 48 hours to remove excess moisture before analysis on ash content, moisture content, total solids, volatile solids and ph. anaerobic assay set up three sets of 473 ml capacity bottles were used as digesters and labelled as a, b and c with each letter having 4 replicates of 3g of paunch manure (pm), 0, 0.6, 1.2 and 1.8g of sugarcane peels (sp) to obtain digesters with 0%, 20%, 40% and 60% co-digestion with total of 12 digester replicates. preparation of fermentation slurries the pm and sp used in this experiment were pulverized into about 2mm size then sun dried for 48 hours. a moisture free pm and sp were used to prepare the fermentation slurries into 0%, 20%, 40% and 60% co-digestion, 100 ml of water was added to each digester with 1 ml of stock solution and 50 ml of inoculum. a blank assay for inoculum (control) was used to measure the inoculum activity in 3 replicates as in srinidhi et al. (2012). the digesters were set up in control temperature range of 30-35o c then allowed to undergo anaerobic digestion for a retention time of 30 days’ mesophilic temperature range. the gas collection was done using liquid displacement method over a 24-hour interval to measure cumulative biogas production (jagadish et al., 2012). analytical methods solid analysis: total solids (ts) and volatile solids (vs) analysis were performed for pm and sp according to standard methods (sluiter et al., 2008; lay et al., 1998). http://www.azojete.com.ng mailto:hnuruddeen15@gmail.com arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 85-91. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 87 modified gompertz model the kinetic data obtained from the study were checked using modified gompertz model for fitness. the equation gives the cumulative biogas production from the digesters with assumption that the gas produced is a function of bacterial growth (jagadish et al., 2012; luengo and alvarez, 1988; atlas, 2008). m = p ∗ exp { − exp rm∗e p λ − t + 1 } (1) y = a exp − exp b − ct (2) where: m = cumulative biogas production, l/g(vs) at any time t p = biogas yield potential, l/g (vs) rm = maximum biogas production rate, l/ (g vs d) λ = duration of lag phase, d (days) t = time at which cumulative biogas production m is calculated, d y = biogas production accumulation (l kg-1) at time t t = time (day) over the digestion period. a = biogas production potential (l kg-1) c = constant (d-1), b= constant (no unit) the parameters p, rm and λ were estimated for each of the digesters using microsoft excel software. these parameters were determined for best fit. 3.0 results and discussions 3.1 physic-chemical properties of paunch manure and sugarcane peels table 1 showed the physic-chemical properties of pm and sp. the results showed that, pm appeared to have the same ts as sp with 80 %. the vs of sp was 88.14 % because of its organic matter contents which was higher than that of pm with 67.78 %. the ash content for pm was 14.95 % higher than sp with 12.42 %, this is because pm contains more nonorganic nutrients as compared to sugarcane peels which is in line with ojolo et al., (2007). the ph values were lower than 6.5 which inhibit the formation of acetic, lactic and propionic acids which becomes toxic for methane forming bacteria and are essential for acetogenesis and methanogenesis. the optimum ph for biogas production was between 7 and 8 similar to the findings of budiyono et al., (2013), who investigated the effect of ph on food wastes and on buffalo manure. moisture content shows the percentage of liquids to solids constituents of the materials, higher liquid contents aids in increased biogas production through increased contact between microorganisms and organic matter as observed by alnakeeb et al., (2017), pm and sp had 6.39% and 4.17% solids and 93.61%, 95.83% liquids. table 1: the physic-chemical properties of paunch manure and sugarcane peels materials total solids (%) volatile solids (%) moisture content (%) ph ash content (%) pm 80 67.78 6.39 7.4 14.95 sp 80 88.14 4.17 7.4 12.42 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:hnuruddeen15@gmail.com abdulhakeem and lawal: kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung as inoculum. azojete,16(1):85-91. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 88 3.2 simulation of biogas production accumulation figure 1 shows the biogas accumulation of pm co-digested with sp, control over a thirty-days retention time. it was observed that the digesters (control, sp 0.6g, sp 1.2g sp 1.8g) had 83.14 ml/g, 49.83 ml/g, 46.45 ml/g, and 30.89 ml/g respectively. this shows that as the concentration of sp is increased in the co-digestion process with pm the production accumulation decreases. figure 1: the biogas production accumulation of pm cd 0.6 g sp, 1.2 g sp and 1.8 g sp figure 2 shows the plot of gompertz model equation for the digesters; control, pm co-digested with 0.6g, 1.2g, and 1.8g sp. from the graph it is clear that the experimental data fits well with the gompertz model equation and the values for r2 were 0.98, 0.95, 0.99 and 0.99 for the control, 0.6g sp, 1.2g sp and 1.8g sp respectively. figure 2: shows the plot of gompetz model equation for control, pm cd with 0.6g, 1.2g and 1.8g sp observations made from table 2 shows that the cumulative biogas production from each digester was tested for fitness with the modified gompertz model equation, the equation described the cumulative biogas production with the time of digestion through biogas yield potential (p), maximum biogas production rate(rm) and duration of lag phase (λ). the parameters obtained shows that the digesters control and pm cd with 1.8 g sp had the shorter lag period of 0.873588 days and 1.089084 days respectively while pm cd with 1.2 g sp has the highest lag period of 4.168447 days followed by pm co-digested with 0.6g sp with 4.021884 days. control has the maximum biogas production rate of 4.708995383 ml/ g vs then 0.6g sp with 3.070026891 ml/ g vs, 1.2g sp was 2.251043986 ml/ g vs and 1.8g sp with 1.4546893 ml/ http://www.azojete.com.ng mailto:hnuruddeen15@gmail.com arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 85-91. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 89 g vs. the maximum biogas produced at the end of the digestion period was highest for control which as 89.00184625 ml/ g vs. this could be because paunch manure is rich in nutrients and contains adequate amount of carbon, oxygen, hydrogen, nitrogen, phosphorus, potassium, calcium, magnesium and a number of trace elements which are very essential elements for the growth of anaerobic bacterium as in kanwass and kalia, (1992). it also could have optimized syntrophic (cross feeding) interaction between acetogenes and methanogens which is the most critical step in the biomethanation process as reported by schink and stams, (2005). furthermore, the digesters; control, pm co-digested with 0.6g, 1.2g and 1.8g sp produced 83.14 ml/ g vs, 49.83 ml/g vs, 46.45 ml/g vs, 30.89 ml/ g vs respectively. figure 3 shows the experimental kinetic data fits well with the modified gompertz equation. table 2: shows the summary of the results obtained from the modified gompertz model equation to check the performance of the digesters. digesters biogas yield (ml/ g vs) modified gompertz parameters (model) r2 p, (ml/g vs) rm (ml/g vs d) λ, d control 83.138 89.0018 4.7089 0.8734 0.91 0.6 g sp 49.834 54.6859 3.0700 4.02198 0.98 1.2 g sp 46.446 60.5884 2.2510 4.1684 0.72 1.8 g sp 30.889 37.9075 1.4547 1.0891 0.68 figure 3: shows the plot of modified gopertz.model equation for the digesters control,pm cd with 0.6g , 1.2g and 1.8g sp. 4.0 conclusions the conclusions drawn from this study were: sugarcane peels had higher volatile solids when compared to paunch manure indicating a higher biogas potential. it was observed that, the digester(control) produced the highest biogas with better production rate as compared to when co-digested with varying substrate concentrations of sp. higher substrate concentration of sp was found to be very poor when co-digested with pm as the digester with 1.8g sp recorded the lowest biogas production over 30 days’ retention period. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:hnuruddeen15@gmail.com abdulhakeem and lawal: kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung as inoculum. azojete,16(1):85-91. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 90 sp should be co-digested with other organic wastes to investigate further alternatives to its biogas potentials. the simulation results indicated that the first order exponential rise, gompertz and modified gompertz model equations best predicted the cumulative biogas produced as a function of retention time. references alnakeeb, a., khudayer, n. ausama, a. 2017. anaerobic digestion of tomato wastes from groceries leftovers: effect of moisture content. international journal of current engineering and technology, 7(4): 1468-1470. atlas, l. 2008. inhibitory effect of heavy metals on methane -producing anaerobic granular sludge. journal of hazard and meterology, 162:1551-1556. bentley, rw. 2002. global oil and gas depletion: an overview. energy policy, 30:189-205. budiyono, si. and sumardiono, s. 2013. biogas production from bioethanol waste: the effect of ph and urea addition to biogas production rate. waste technology, 1(1): 1-5. cavallo, aj. 2003. predicting the peak in world oil production. natural resource research, 11:187-195. ezeoha, sl. and idike, fi. 2007. biogas production potentials of cattle paunch manure. journal of agric engineering technology (jaet), 15: 25-31. jagadish, ph., malourdu, ar., desai, pl. and mahadeva, sm. 2012. kinetics of anaerobic digestion of water hyacinth using poultry litter as inoculum. international journal of environmental science and development, 3(2): 94-98. kanwass, ss. and kalia, ka. 1992. anaerobic fermentation of sheep droppings for biogas production. world journal of microbiology and biotechnology, 9: 174-175. lay, jj., li, yy. and noike, t. 1998. mathematical model for methane production from landfill bioreactor. journal of environmental engineering, 124(8): 730-736. luengo, pl. and alvarez, mj. 1988. influence of temperature, buffer, composition and straw particle length on the anaerobic digestion of wheat straw-pig manure mixtures. resources conservation and recycling, 1: 27-37. melford, i. 2003. wasteis the developing world ready? science in africa. http://234next.com/csp/cms/sites/next/home experts syas nigeria must reduce waste generation. monch-tegeder, m., andreas, l., hans, o. and thomas, j. 2013. investigation of the methane potential of horse manure. agricultural engineering international: cigr journal, 15(2): 161-172. ojolo, s., oke, sa., animasahun, k. and adesuyi, bk. 2007. utilization of poultry, cow and kitchen wastes for biogas production: a comparative analysis. iranian journal of environmental health science and engineering, 4(4): 223-228. schink, a. and stams, m. 2005. syntropism among prokaryotes. in dworkin m.(ed). in: the prokaryotes: an evolving electronic resource for microbiological community. new york: springer inc. http://www.azojete.com.ng mailto:hnuruddeen15@gmail.com arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 85-91. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 91 sluiter, a., hames, b., hayman, d., payne, c., rulic, r., scalrlata, c. and sluiter, j. 2008. determination of total solids in biomass and total dissolved solids in liquid process samples laboratory analytical procedure (lap), batelle: national renewable energy laboratory. srinidhi, a., adiga, rr., shankar, bb., jagadish ph. and geetha, rc. 2012. kinetics of anaerobic digestion of water hyacinth, poultry litter, cow manure and primary sludge: a comparative study. singapore, iacsit press, 73-78. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:hnuruddeen15@gmail.com arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):146-159 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 146 original research article exploiting iot and lorawan technologies for effective livestock monitoring in nigeria u. s. abdullahi*, m. nyabam, k. orisekeh, s. umar, b. sani, e. david and a. a. umoru center for satellite technology development, national space research and development agency, abuja article information submitted: 12/12/2018 revised: 26/12/2018 accepted: 18/03/2019 keywords: iot lorawan agriculture cloud data analytics cellular network satellite. abstract with global population predicted to rise continuously (from 7.2 billion to between 9~10 billion people by the year 2050), the world would need to produce almost twice the amount of food as it does today to sustain such human needs. this coupled with recent environmental/climatic changes and urbanization would continue to place enormous burden on the available land, water and energy resources required for both crop and animal farming which is even more critical for developing regions, such as sub-saharan africa due to arid lands, poverty, extreme hunger and endemic diseases. hence, there is an urgent need for more effective, intensification and industrialization of the region’s agricultural sector to improve food supply. internet-of-things (iot) is a new and attractive family of technologies capable of modernizing africa’s agricultural sector in line with best practices to improve productivity and minimize cost with reduced energy consumption. this paper intends to kick-start discussions around iot-based solutions in livestock farming in nigeria, with a view to addressing issues of cattle rustling as well as improved livestock health-care and better herd management through real-time monitoring. the proposed solution leverages lorawan (long-range wireless access network) technology, whereby very low-power sensors with extremely long-range are attached to the cattle, and communicate with a gateway for linking to the cloud/satellite network to the internet for data processing and analytics. such a system is also ideal for rural/remote areas where there is limited or no cellular network and internet coverage, which is where most nigerian farms/ranches may be located. the paper sheds some light on some real-life use cases, benefits and challenges of deploying such smart systems and provides some recommendations/action points for all relevant stake-holders towards a sustainable implementation in nigerian agricultural sector © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction animal production has been a major source of wealth and employment for numerous people in nigeria and africa at large. with growing population figures across the continent, animal production is sure to play a key role in not just ensuring food sufficiency, but also help with accompanying manure for crop production as well as job creation (nrc, 2015). however, increasing land-use pressure and fast depleting agro-hydro-ecological potential due to climatic changes, urbanization and exploding population is seriously threatening the progress of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 147 livestock farming in sub-saharan africa, as evidenced by recent herdsman-farmer clashes across nigeria over land-use for example. to cope with these harsh realities, livestock farming must undergo a modernization process in the african continent, whereby production is maximized, cost minimized, and resources efficiently utilized. technology, through internet-of-things (iot) can help catalyze this modernization in ways traditional and conservative methods can dare not (nrc, 2015); (malvade et al., 2016); (mohammed et al., 2017). the internet of things (iot), sometimes referred to as the internet of objects (ezechina, 2017) or the internet of everything (cisco connect, 2015), is predicted to have a huge impact on our everyday lives as illustrated in figure 1. today, the internet plays a significant role in communication, government, science, education and humanity (mohammed et al., 2017; ezechina et al., 2015). it has become clear that the internet of things will revolutionize the way we live and relate with objects in our environment (meraevents, 2018). figure 1: iot impact on all (mohammed et al., 2017) iot is an intelligent connectivity of physical devices driving massive gains in efficiency, business, growth and quality of life (cisco connect, 2015). with the use of iot, objects are capable of communicating with themselves, making decisions and developing intelligent behaviour based on an aggregate of data supplied by other devices or other services (ezechina et al., 2015); what the internet of things need, 2014). the iot network consists of interconnected devices, which can transfer data efficiently without human interference. it involves different building blocks of sensors, network components and other external devices (malvade et al., 2016). the concept of iot has found application in various areas such as smart cities, smart farming, smart health, smart buildings, manufacturing, transportation, energy and utility, to mention but a few (mohammed et al., 2017). by 2020, it is estimated that about 50 billion things will be connected electronically by the internet (cisco connect, 2015; gubbia et al., 2013). figure 2 depicts the growth of things connected to the internet from 1988 to forecast 2020. iot is set to provide the technology for smart actions for machines to be able to communicate with another with vast streams of information (kejriwal et al., 2016). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al: exploiting iot and lorawan technologies for effective livestock monitoring in nigeria. azojete, 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 148 figure 2: likely growth in iot (mohammed et al., 2017) 1.1 livestock farming in sub-saharan africa: livestock farming constitutes a key component of the agricultural economy, especially in developing nations – food, manure, savings mechanism, contribution to gdp and so much more. it represents a critical socio-cultural aspect for millions of rural farmers for whom animal ownership directly relates to financial security, social standing as well as guaranteed food security in africa. however, sub-saharan africa contributes among the lowest in animal production globally as shown in figure 3. ensuring greater productivity in the livestock sector depends on sustainable development efforts that provide farmers and pastoralists with access to technology, training, and resources. figure 3: global livestock productivity (fao, 2018) the aim of this paper is to present the application and benefits of iot in agriculture, specifically livestock monitoring, and kick-start discussions around development of feasible models for implementation in nigeria. some lessons learned from other existing models are presented as well as recommendations going forward considering the unique nigerian environment. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 149 the rest of the paper is structured as follows: section 2 highlights some related works on use of iot for livestock farming, while section 3 presents the architectural model proposed in this paper. section 4 discusses major benefits of such systems and also enumerates some challenges for practical implementation in nigeria. in section 5, some key recommendations are provided and the paper is finally concluded in section 6. 2. related studies 2.1 internet of things in livestock monitoring the world’s population is estimated to be about 9.7 billion in 2050 (mohammed et al., 2017; elijah et al., 2016). this places a high demand on livestock farming. there is a need for the agricultural industry to rely on technology and innovation to bring about better yields with the most efficient use of limited resources (linklabs, 2016). as a result, the growth in technological advancements in farming has become more popular and significant in today’s world (xiaohui et al., 2014). solutions have been proposed to meet such agricultural challenges of the future today. one of such solutions is the use of internet of things (iot) in the farming of livestock (elijah et al., 2016; xiaohui , 2014). the application of iot in livestock monitoring is about empowering the livestock owners with the tools and devices that seamlessly integrate product and knowledge services to enhance efficiency, productivity in the global market, save time and cost with reduced human presence (elijah et al., 2016; linklabs, 2016). the farmer can monitor the entire condition without their physical presence. the use of iot in livestock farming is a field of precision agriculture that uses analytic measurements to optimize farming decisions. with iot sensors attached to cattle, farmers can easily locate livestock in the field, know their health state, determine when they are ready for reproduction and monitor milking frequency through the use of a smartphone or a computer. for instance, the identification of cow estrus which is critical to milk yields. normally, a farmer needs to spend 20–30 min each time, four to five times a day in the stables to check if a cow is in heat, which is a sign of estrus. however, over 60% of estrus cases happen at night when the farmer is asleep (anderson, 2016). another example is the monitoring of cattle lameness that has a large impact on a cow’s performance in terms of yield, fertility, and longevity (van metre, 2005). in general, the iot paradigm can help livestock farming or ranching to improve the productivity of water, energy, food, and other resources use, while maintaining the well-being of animals. it also helps farmers to make lists, prepare reports, sort cows by category, and track each animal’s overall lifetime (anderson, 2016; van metre, 2005). 2.2 brief insight on lora and lorawan technology lora (short of long range) is a long-range, low-data rate, low power wireless technology platform developed by semtech corporation, which utilizes unlicensed radio spectrum in the industrial, scientific, and medical radio band (ism band), and is fast becoming the de facto technology for internet of things (iot) networks. lora aims to eliminate repeaters, reduce device cost, increase battery lifetime on devices, improve network capacity, and support a large file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al: exploiting iot and lorawan technologies for effective livestock monitoring in nigeria. azojete, 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 150 number of devices. lora range is extensive, capable of reaching 2-5 km in urban areas and 1520 km in rural areas. the lorawan open specification is a low power, wide area networking (lpwan) protocol based on lora technology. it is designed to wirelessly connect battery-operated things to the internet in regional, national or global networks. the specification defines the device-to-infrastructure of lora physical layer parameters and the lorawan protocol, and provides seamless interoperability between devices worldwide. 2.3 features of lora technology lorawan strikes a balance between cellular and wifi networks which either require high bandwidth or high power, or limited range as shown in figure 4 below. in essence, lora technology offers features, which enable flexibility of operation on ushering in new, unique use cases in smart cities, smart homes and buildings, smart agriculture, smart metering, and smart supply chain and logistics. figure 4: lorawan as a technology gap-filler (semtech, 2017) in december 2018, the lora alliance announced that it had exceeded 100 lorawan operators globally, significantly expanding coverage making it easier to deploy iot solutions worldwide, as shown in figure 5. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 151 figure 5: worldwide lorawan coverage showing coverage areas in yellow (source: lora alliance, 2018) figure 6: key features of lorawan (source: semtech, 2017) 2.4 proposed system model an iot-based solution relying on the lora technology is proposed in this paper, whereby livestock (cattle in this case), are equipped with devices that contain built-in gps nodes, temperature sensors and other important sensors, which communicate with one or more gateways installed around a ranch for reception and transmission of information (semtech, 2017; swedberg, 2018). location updates, cattle body temperature readings etc. are sent from file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al: exploiting iot and lorawan technologies for effective livestock monitoring in nigeria. azojete, 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 152 the attached devices to the gateways, and the data forwarded to cloud-based software for processing/data analytics (braemac, 2015; semtech, 2017). meaningful information is then transmitted to farmers/ranch managers on a pc or any mobile device on the location of cattle, body temperature status reports to predict reproductive patterns, and/or illnesses for promptaction (semtech, 2017, swedberg, 2018). this is exactly what occurs the in scenario presented in figure 7 below shows the typical set-up for such solution. figure 7: proposed iot-based cattle monitoring solution as shown in figure 7, the system relies on the lora technology, which is a specifically suited for iot-enabled devices due to very lower power requirements and extremely long range. sensors are relatively inexpensive with batteries able to last at least 2 years (semtech, 2017). the proposed system could work independently as shown in figure 7, or could be connected to a cellular or satellite network as shown in figures 8 and 9 respectively. the proposed solution allows farmers/ranch managers to easily monitor their cattle using an app on mobile device, or from a pc. it is also possible to detect anomalies in herd behaviour when some cows remain isolated/stationary for long, check for ideal fertility periods (studies show that cows could have as little as only 8 h a month when they are in fertility (reese, 2018) using temperature readings, and mitigate cattle rustling with location updates. farmers/managers could also set-up geo-fencing to receive alerts when cattle approach a prohibitive zone without actually installing physical fences over long fields. the device is expected to be indigenously designed and be highly ruggedized, solar-powered with water-proof casing (swedberg, 2018). in the case of figure 8 where cellular network coverage is available, the data is relayed from the lorawan gateway to a nearby base transceiver station (bts) where now relies on cellular network to reach the end-users directly, or after further processing in the internet/cloud-based software. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 153 figure 8: proposed iot-based cattle monitoring solution with cellular network lastly, another scenario is presented in figure 9, where there is no cellular network and satellite link is used to improve coverage to the end-users, especially useful in remote areas, and where this is a critical need to connect vast farmlands (with livestock) to a central office for processing and subsequent dissemination of important information to rural farmers/groups of farmers across large geographical areas. this helps provide important information to curtail endemic livestock diseases promptly, provide key immunization/vaccination information, security information and so much more. figure 9: proposed iot-based cattle monitoring solution with satellite network file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al: exploiting iot and lorawan technologies for effective livestock monitoring in nigeria. azojete, 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 154 3.0 advantages and potential limitations of proposed solution sections 3.1 and 3.2 provide some likely benefits and potential obstacles to uptake of the proposed livestock monitoring system relying on iot and lorawan technologies. 3.1 benefits of proposed solution 3.1.1 improved feeding feeding habits of the cattle can be monitored from their behavior such as grazing and sleeping. knowing how often these happen will enable the farmers make adjustments towards the feeding requirements to prevent over feeding or wastage of food. farmers can now use iot to know when to purchase more feeds (dawsey, 2017). maximize milking iot devices can be useful to farmers that have cows that require milking several times a day. it can also track the milking speed of each cow, the amount and the quality of milk the cow produces, the steps taken by each cow, how much each cow eats in a given day. the data obtained can assist the farmer in knowing the cow that is able to produce more milk and make dietary changes where necessary (cognizant reports, 2014; dawsey, 2017). monitoring health iot solutions make it possible for farmers to monitor livestock health. using iot, blood pressure, heart rate, respiratory rate, digestion, temperature and other vitals can be monitored allowing the farmer to be alerted at the first sign of illness prompting quicker corrective measures to reduce losses. (cognizant reports, 2014; dawsey, 2017). improved livestock tracking the iot platform makes tracking of cattle easier by providing advanced level of information to pin-point the location of a cattle spread over multiple acres. the farmer can locate ill cattle, or one that is in heat such that it can be separated and proper treatment can be carried out. in addition, livestock tracking can help in maximizing pastureland by establishing optimized grazing patterns (bhayani, 2016; dawsey, 2017). lower operational cost with the use of sensors and connectivity, the farming business can benefit from better asset utilization. this reduces human error, the consumption of resources and minimizes cost (cognizant reports, 2014; c2m plasma business intelligence, 2016). efficient processes iot offers efficiency in the process such that the farmers or the ranch owners have real-time data and operational insight thereby accelerating the decision making process (bhayani, 2016, c2m plasma business intelligence, 2016). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 155 increased production iot provides a platform for optimized livestock farming by offering accurate planning and monitoring which directly affects production rates (c2m plasma business intelligence, 2016). improved quality of production analysis from data received such as the results from quality of treatment can teach the farmers to make adjustments to improve the quality of production (cognizant reports, 2014, c2m plasma business intelligence, 2016). remote monitoring commercial and local farmers can monitor a numerous field from different locations across the globe from the internet. real-time decisions can be made from anywhere in the world. (bhayani, 2016, c2m plasma business intelligence, 2016). potential obstacles to the proposed solution 3.2.1 power supply these mobile devices require a self –sufficient energy source to remain smart. the future is to look into low power processors and communication units for embedded systems that can function with significant low energy (mohammed et al., 2017). 3.2.2 cost this is one barrier to the adoption of iot especially in emerging markets. the cost of some of the sensors can be capital intensive to not just the small scale farmers but also the large ones as well (agricultural machine to machine (agri-m2m). 2015; mohammed et al., 2017). limited knowledge limited or no knowledge of iot is a significant barrier to the growth of this technology. developers and service providers need to understand the use of this technology, know when and how to apply this technology in various business and operational cases. the absence of this, will make the benefits of iot unclear to the end-user thereby losing interest in what the service has to offer. to add, the end –user may lack the know-how on setting up, maintaining and using the application. for the developed world, this might not prove to be an issue, however, for the developing world this is a challenge because the users might not be familiar with the basic technology (agricultural machine to machine (agri-m2m). 2015). network coverage about 85% of the world’s population is covered by mobile network. however, this coverage is heavily focused on the urban and sub-urban areas leaving the rural settlement, places where agricultural practices are dominant, underserved (agricultural machine to machine (agri-m2m). 2015; mohammed et al., 2017). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al: exploiting iot and lorawan technologies for effective livestock monitoring in nigeria. azojete, 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 156 reliability of equipment due to operational environments such as continuous exposure to vapours from chemicals, heat, cold, dust as well as moisture, of some of these devices, the use of iot in livestock farming imposes demands on existing technology. owing to this, equipment with special requirements and resistance to these working environments will have to be used for better functionality (agricultural machine to machine (agri-m2m). 2015; mohammed et al., 2017). security there is a need to protect certain services from having access to the things on the iot platform. a breach in security will result in compromising the confidentiality, authenticity, integrity and other requirements that are important on the platform. also, there is a need for protection of the information from these smart devices from competitors (mohammed et al., 2017; semtech, 2017). software complexity a more extensive software infrastructure will be needed on the network and background servers in order to manage the smart objects and provide services for them (mohammed et al., 2017). low wages in emerging markets for livestock farmers this poses to be a challenge because the value added per agricultural employee in developed worlds are much higher than that of developing worlds. in the developing world, labour is relatively cheap and where agriculture is the only source of employment available, it will be difficult to invest in iot (mohammed et al., 2017, semtech, 2017). data volume and interpretation due to the amount of data collected on central networks, this will require many operating mechanisms and new technologies that will aid in storing, processing and managing information. the interpretation of this high volume of data poses to be a challenge when the data is not harmonized with other networks. the data generated will need to have a generalized conclusion that will be incorporated into the system to prevent contradicting solutions or scenarios in solving challenges on the iot network (agricultural machine to machine (agri-m2m). 2015; mohammed et al., 2017). 4.0 conclusion this paper has attempted to provide a starting point for practical implementation of iot-based solutions for livestock monitoring in nigeria with a view to improving productivity and efficiency to guarantee food security, address cattle rustling and enhance well-being of livestock. bearing in mind the unique nature of rural areas in nigeria whereby mobile coverage and associated internet connectivity may be unavailable or sparse at best, this paper proposes the use of the new lora technology which is becoming the candidate technology for iot-enabled devices with low-power requirements and very long-range. such lora-based sensors are attached to cattle and communicate to gateways in ranches/farms, sending location updates, body temperature readings, and other vital information such as pressure, humidity etc. depending on the different sensors included in the system. this enables farmers/ranch managers and other relevant stakehttp://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 157 holders to pro-actively take measures to combat animal theft, spread of diseases and maximize cattle productivity by exploiting the best reproductive window via heating data derived over time. 5.0 recommendations it is important to educate the end-users regardless of them being individual farmers, cooperative societies, or agro-businesses as well as those on the value chain on the benefits and application of iot. in addition, stakeholders might take up the role of setting up and maintaining the systems and provide analysis. then, the farmer can make informed decisions based on the physical technology and the analysis of data handled by an application. this puts the farmer in the position of following some few simple instructions on the best course of action (agricultural machine to machine (agri-m2m). 2015). the school curriculum, especially at primary and secondary school level, should be reviewed to include key modules on agro-technology and agro-economics to help re-orient the minds of young nigerians towards commercial and efficient agricultural practices. pro-active government policies should be created aimed at facilitating technology use in agricultural sector, ensuring that all stake holders across the eco-system are carried along right from inception to actual implementation. encouraging the use of cooperative societies and other social groups to facilitate collective agricultural practices and help subsidize costs of technology, raw materials and logistics for local farmers. for practical implementation of such wireless-based systems in livestock farming, lower frequency spectrum (<1ghz) can be used rather than high frequency spectrum for rural areas. lower frequencies offer extended coverage at a lower cost as fewer base stations are required (mohammed et al., 2017). network providers and mobile software developers can also play a key role in creating and maintaining bespoke agro-apps and services which would lead to an increase in connectivity, market share, new value added services as well as improved revenue base (mohammed et al., 2017). references agri-m2m, 2015. a platform to expansion availability in london. agricultural machine to machine,https://www.gsmaintelligence.com/research/?file=9186f77efc0a47fe7f127d79d789c64c&do wnload accessed on 15 june, 2018. anderson, m. 2016. saving the world with the internet of cows. https://blog.equinic.com/blog/2016/03/01/saving-the-world-with-the-internet-of-cows/ accessed on 12 april, 2018. bhayani, m., patel, m. and bhatt, c. 2016. internet of things: in a way of a smart world availability in anand, india. https://www.gsmaintelligence.com/research/?file=9186f77efc0a47fe7f127d79d789c64c&download https://www.gsmaintelligence.com/research/?file=9186f77efc0a47fe7f127d79d789c64c&download https://blog.equinic.com/blog/2016/03/01/saving-the-world-with-the-internet-of-cows/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al: exploiting iot and lorawan technologies for effective livestock monitoring in nigeria. azojete, 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 158 https://www.researchgate.net/publication/303809222_internet_of_things_iot_in_a_way_of_smart_wo rld accessed in 31 march, 2018. braemac. 2015. cattle traxx incorporates ruggedized iot sensors, lorawan mesh network, geofencing and cloud based analytics to improve livestock monitoring availability in california. http://www.braemacca.com/en/news/item/iot-and-lorawan-modernize-livestock-monitoring accessed on 20 april, 2018. cisco connect. 2015. the internet of things vertical solutions availability in dubai. https://www.cisco.com/web/offer/emear/38586/images/presentations/p11.pdf accessed on 7 april, 2018. cognizant reports, 2014. reaping the benefits of internet of things available in new jersey. https://www.cognizant.com/insightswhitepapers/reaping-the-benefits-of-the-internet-of things.pdf accessed on 22 june, 2018. c2m plasma business intelligence, 2016. 10 benefits of a smart agriculture solution availability in texas. https://www.c2m.net/blog/10-benefits-of-a-smart-agriculture-solution.aspx accessed in 13 april, 2018. dawsey, p. 2017. using iot to increase efficiency, productivity for livestock. availability in ohio. https://www.precisionag.com/systems-management/using-iot-to-increase-efficiency-productivityfor-livestock/ accessed on 12 april, 2017. ejilah, o., thalek, a., igbafe, o., chee, yl. and nour, h. 2016. an overview of internet of things (iot) and data analytics in agriculture: benefits and challenges. ieee internet of things journal, 5(5): 37583773. ezechina, ma., okwara, kk. and ugboaja, cau. 2015. the internet of things (iot): a scalable approach to connecting everything. the international journal of engineering and science, 4(1): 9-12. fao, 2018. global livestock environmental assessment model (gleam) availability in italy. food and agriculture organization of the united nations, rome. http://www.fao.org/gleam/results/en/ accessed on 12 april, 2018. gubbia, j., rajkumar b., slaven m. and marimuthu, p. 2013. internet of things (iot): a vision, architectural elements, and future directions. future generation computer systems, 29: 1645-1660. kejriwal, s. and mahajan, s. 2016. how iot technology aims to add value for real estate companies. deloitte insights. https://dupress.deloitte.com/dup-us-en/focus/internet-of-things/iot-commercialreal-estate-intelligent-building-systems.html accessed in 2016. lora alliance, 2019. https://lora-alliance.org/in-the-news/lora-alliance-passes-100-lorawantmnetwork-operator-milestone-coverage-100-countries. accessed 11th january 2019. linklabs. 2016. an in-depth look at iot in agriculture and smart farming solutions availability in annapolis. https://www.link-labs.com/blog/iot-agriculture accessed in 6 june, 2018. meraevents, 2018. workshop on internet of things using raspberrypie,hyderabad, india. http://www.meraevents.com/event/iot-workshop accessed on 20 february, 2018. mohammed, zka. and ahmed, esa. 2017. internet of things application challenges and related future technologies. word scientific news, 67(2): 126-148. nrc, 2015. national research council. critical role of animal science research in food security and sustainability. the national academies press. washington dc., pp. 19-20. https://www.researchgate.net/publication/303809222_internet_of_things_iot_in_a_way_of_smart_world https://www.researchgate.net/publication/303809222_internet_of_things_iot_in_a_way_of_smart_world http://www.braemacca.com/en/news/item/iot-and-lorawan-modernize-livestock-monitoring https://www.cisco.com/web/offer/emear/38586/images/presentations/p11.pdf https://www.cognizant.com/insightswhitepapers/reaping-the-benefits-of-the-internet-of-things.pdf https://www.c2m.net/blog/10-benefits-of-a-smart-agriculture-solution.aspx https://www.precisionag.com/systems-management/using-iot-to-increase-efficiency-productivity-for-livestock/ https://www.precisionag.com/systems-management/using-iot-to-increase-efficiency-productivity-for-livestock/ http://www.fao.org/gleam/results/en/ https://dupress.deloitte.com/dup-us-en/focus/internet-of-things/iot-commercial-real-estate-intelligent-building-systems.html%20accessed%20in%202016 https://dupress.deloitte.com/dup-us-en/focus/internet-of-things/iot-commercial-real-estate-intelligent-building-systems.html%20accessed%20in%202016 https://lora-alliance.org/in-the-news/lora-alliance-passes-100-lorawantm-network-operator-milestone-coverage-100-countries https://lora-alliance.org/in-the-news/lora-alliance-passes-100-lorawantm-network-operator-milestone-coverage-100-countries https://www.link-labs.com/blog/iot-agriculture http://www.meraevents.com/event/iot-workshop http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):146-159. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 159 reese, h. 2018. iot for cows: 4 ways farmers are collecting and analyzing data for cattle. techrepublic. https://www.techrepublic.com/article/iot-for-cows-4-ways-farmers-are-collecting-and-analyzingdata-from-cattle/ accessed on 3 june, 2018. semtech, 2017. cattle tracking availability in california. semtech smart agriculture. available on https://www.semtech.com/uploads/technology/lora/appbriefs/semtech_agr_cattletracking_appbrie f-final.pdf accessed on 30 april, 2018. swedberg, c. 2018. cattle ranching gain for iot-based intelligence. rfid availability in hauppauge accessed the 15 may, 2018. van metre, dc., wenz, j. and garry, f. 2005. lameness in cattle: rules of thumb. proceeding of the american association of bovinc practitioners, 38: 40-43. xiaohui, w., and nannan, l., 2014. the application of internet of things in agricultural means of production supply chain management, journal of chemical and pharmaceutical research, 6(7): 23042310 https://www.techrepublic.com/article/iot-for-cows-4-ways-farmers-are-collecting-and-analyzing-data-from-cattle/ https://www.techrepublic.com/article/iot-for-cows-4-ways-farmers-are-collecting-and-analyzing-data-from-cattle/ https://www.semtech.com/uploads/technology/lora/appbriefs/semtech_agr_cattlet file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 733-749 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 733 original research article review of agricultural waste utilization as improvement additives for residual tropical soils k. ishola1*, o. a. olawuyi1, a. a. bello1, r. k. etim2, p. yohanna3 and j. e. sani4 (1department of civil engineering, osun state university, osogbo, osun state, nigeria. 2department of civil engineering, akwa ibom state university, ikot akpadent, nigeria. 3department of civil engineering, university of jos, plateau state, nigeria 4department of civil engineering, nigeria defense academy, kaduna, nigeria.) * corresponding author’s email address: isholakzm@gmail.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: agricultural waste soil improvement rice husk ash palm oil fuel ash corn cob ash abstract the development of a nation partially depends on sustainable materials obtained from agricultural products. increased agricultural products could increase the amount of waste generated yearly. this paper presents a review on the use of agricultural waste with pozzolanic properties (rice husk ash, locust bean waste ash, palm oil fuel ash, banana leaf ash, bagasse ash, coconut shell ash, bamboo leaf ash, corn cob ash, cassava peel ash and palm kernel shell ash) in various geotechnical engineering applications. interestingly, these wastes were subjected to various laboratory tests such as (particle size distribution, compaction, atterberg, unconfined compressive strength (ucs) and california bearing ratio (cbr)) to assess their effectiveness in soil improvement. in all these, the percentages of the materials required for soil improvement were discussed. the reports from various researchers have shown that agricultural waste having pozzolanic properties improves the engineering properties of soil. for instance, palm oil fuel ash (pofa) is mostly used as an admixture in concrete as reported elsewhere. few studies have been carried out on the use of banana leaf ash and palm oil fuel ash as soil improvement materials. it is recommended that further researches should focus on the possibility of using other agricultural waste from cocoyam, yam peel, maize trunk, cashew and guava that have limited reporting researches for use as soil improvement materials. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction several studies have shown the importance of agricultural waste products as an alternative to conventional material for soil improvement (olonode, 2010; oluremi et al., 2012; ako and yusuf, 2016, ishola et al., 2019). the residues generated from the growing and processing of raw agricultural materials such as fruits, vegetables, meat, poultry, dairy products, and crops are regarded as agricultural wastes. the report of obi et al. (2016) sheds light on the waste obtained from the food processing industry especially that of maize where it was indicated that 20% is good for canning and remaining 80% counted as waste. the significant increase in http://www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 734 agricultural wastes globally was due to intensifying farming systems, high demand in the food industry and increase in housing areas that lead to the clearance of plantation area (daud et al., 2016). the increases in global population lead to a high rate of agricultural products which in turn increases the waste produce yearly (agamu, 2009). interestingly, wastes from agricultural product like locust bean, rice husk, palm oil, banana tree, sugarcane, bamboo tree and palm kernel have widely been used to improve the geotechnical properties of tropical soils ( lateritic and black cotton soils) among others that are deficient for engineering application in their natural form (bello et al., 2015; sadiq et al., 2015). a report shows that about 998 million tonnes of agricultural waste are generated every year (agamu, 2009). these rates prompted researchers to focus more on how the materials can be converted for use as a material for soil improvement in construction. lateritic soils are generally used in many developing countries like nigeria for the construction of sub-base and base courses in both flexible and rigid pavements. in most of these regions, the dominant soil material available is lateritic soil. additionally, it is readily available and found in abundance and are cost-effective (alhassan and mustapha, 2015). naturally, lateritic soil has a low bearing capacity and low strength due to high clay content. it has been reported that lateritic soil with large clay materials would not have guaranteed strength and stability under loading in the presence of moisture (bello et al., 2015). typical laterite soils are generally rich in iron and aluminum formed in tropical areas. most laterites are rusty-red because of the presence of iron oxides (osinubi et al., 2009). they are formed by intensive and long-lasting weathering of the underlying parent rock. tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. the initial products of weathering are essentially kaolinite rocks called saprolites (nnochiri and aderinlewo, 2016). researchers have worked extensively on the geotechnical and engineering properties of lateritic soils in all geopolitical zones of nigeria and other part of the country (adewoye et al., 2004; agbede and osuolale, 2005; bello, 2007; bello et al., 2007; bello and adegoke, 2010; owoseni et al., 2014 and lekha, 2015). black cotton soil is tropical black clay having a colour characteristic of dark grey to black with high clay content and usually expansive in nature and contains over 50 % of montmorillonite which is the principal clay mineral (rajakumar and meenambal, 2015). these soils dominated semi–arid regions of tropical/ temperate zones and mostly found anywhere in the world, especially where the annual evaporation exceeds the precipitation (rajakumar and meenambal, 2015). tropical black clays possess shrink-swell characteristics and cause damages (settlement) to structural pavement resting on such soils. however, this happened as a result of variation in moisture content that is not evenly distributed (osinubi et al., 2010; akinmade, 2016). generally, deposits of black cotton soil in the field show a general pattern of cracks during the dry season of the year. the cracks measured about 70 mm wide and over 1m deep have been observed and may extend up to 3m or more in case of high deposits (rajakumar and meenambal, 2015). black cotton soil usually loses its strength properties to the wet and dry characteristic which have effect in its hardness. the presence of montmorillonite and illite in the black cotton soil has made it exhibit very low bearing capacity, low permeability, and high volume change. however, in their natural state, these properties make them unsuitable for construction of embankment, highway, building or any other load bearing structure (das, 1998). these types of soil group form found in the north eastern part of nigeria and exhibit large volume changes with respect to the variation of seasonal moisture content (eberemu et al., 2012). they usually pose challenges to http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 735 civil engineering works because of their swelling and shrinkage characteristics and call for a need to improve such soils prior to their applications for load bearing structures. in order to make deficient soils suitable for use as a construction material, it presents properties needed to be improved. such soils required the laboratory test such as permeability, unconfined compressive strength, and california bearing ratio, to assess their suitability for various engineering applications such as embankment, concrete and road construction (george and oriola, 2010; ochepo, 2014; eberemu, 2013; eberemu 2015; george et al., 2013; sadiq et al., 2015; amu et al., 2011; bello et al., 2015). generally, the improvement of deficient soils could either be by modification or stabilization or both. in the modification process, a modifier such as cement and lime are added to soil to change (improve) its index and friction properties. while soil stabilization enhanced the strength and durability characteristic of the soil. however, they become totally suitable for construction beyond their original classification. over time, cement and lime have been the two main materials used for stabilizing soils. neville (2000) reported that the cost of these materials has rapidly increased due to the sharp increase in the cost of energy since the 1970s. current trend in research works of geotechnical engineering and construction materials has focused more on the search for cheap and locally available materials such as agricultural wastes (rice husk ash(rha), locust bean ash (lba), palm oil fuel ash (pofa), banana leaf ash (bla), sugar cane bagasse ash (scba), bamboo leaves ash (bla), cassava peel ash (cpa), corn cob ash (cca) and palm kernel shell ash (psa)) as stabilizing agents for the purpose of full or partially replacement of traditional stabilizers. agricultural waste has become a focus of researchers, because of the enhanced pozzolanic capabilities of such waste when oxidized by burning. thus, this review work evaluated the possibility of utilizing agricultural wastes in the improvement of residual tropical soils as suggested by several authors and pointed at the agricultural products that have limited reports in the literature. 2.0 literature review 2.1 saw dust ash sawdust ash is obtained as a byproduct of burning of sawdust from a timber shed. the sawdust is first air-dried and burnt under atmospheric condition within a temperature range of 550 – 650°c measured with a thermocouple. the ash obtained from the sawdust is allowed to pass through the no. 200 sieve (75 µm aperture) to meet the requirement of astm c618-78 (2013) thompson (2012) evaluated the effects of saw dust ash (sda) on the geotechnical properties of soil obtained from two locations (a and b) in southwestern nigeria. laboratory test was carried out on the two samples and samples mixed with up to 10% sda content with respect to consistency limits, specific gravity, compaction, california bearing ratio, unconfined compressive strength and shear strength. the results show that saw dust ash has improved the geotechnical properties of the soil samples: maximum dry density increased from 1403 to1456 kg/m3 and 1730 to 1785 kg/m3, optimum moisture content increased from 23.6 to 28.2% and 26.2 to 29.2%, unconfined compressive strength increased from 101.4 to 142.14 and 211.11 to 154.97, shear strength increased from 50.92 to 71.07 kn/m2 and 77.49 to 105.99 kn/m2 for samples a and b, respectively. based on the laboratory test results, he concluded that saw dust ash is therefore found to be an effective stabilizer for lateritic soils. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 736 yohanna et al. (2016) performed a reliability assessment of black cotton soil stabilized with sawdust ash admixtures for use in road construction. treatment with up to 8% sawdust ash significantly improved the index properties, compaction and strength characteristics of the natural black cotton soil studied. reliability estimates of strength characteristics (california bearing ratio, cbr and unconfined compressive strength, ucs) results with variable factors produced safety index values that are less than 1.0 and unacceptable. the results recorded indicate that black cotton soil compacted with reducing british standard light ( rbsl) energy cannot be used as a road pavement material, but for low load bearing structures such as road shoulders and pedestrian walkways. however, saw dust ash (sda) can be beneficially used as an admixture in road construction when a higher compactive effort is used. mannir et al. (2016) studied the effect of sawdust ash mixtures on compacted black cotton soil as road construction material. the result shows that the liquid limit, plastic limit, and linear shrinkage decreased, while the plasticity index increased with sda content. also, optimum moisture content (omc) increased to a maximum value of 30% while maximum dry density decreased to a minimum value of 0.86mg/m3 at 10% sda content. peak unsoaked california bearing ratio (cbr) value of 4% was recorded at 2% sda content. on the other hand, peak 7 days unconfined compressive strength (ucs) value of 90kn/m2 was recorded at 8% sda content. the results recorded indicate that black cotton soil compacted with rbsl energy cannot be used as a road pavement material, but for low load bearing structures such as road shoulders. oluremi et al. (2007) evaluated the plasticity characteristics and cation-exchange capacity (cec) of lateritic soil treated with up to 10% of iron ore tailing (iot) and waste wood ash (wwa) using laboratory tests and regression analysis. their results showed an initial increase in the cationexchange capacity up to 8% iot content and 2% wwa content. however, the plasticity characteristics (liquid limit and plastic limit) initially increased with higher iot content and then decreased up to 2% wwa content and thereafter increased up to 10% wwa content. the plasticity index decreased up to 8% for iot and 6% for wwa and thereafter increased with additional iot and wwa contents, respectively. the regression analysis showed a close relationship between the experimental values and the predicted values for both iot and wwa treated lateritic soil. the conclusion was made on the treated soil that an optimal blend of 8% iot and 6% wwa contents with lateritic soil improved the consistency indices for use as a subgrade material in lightly trafficked roads. 2.2 rice husk ash rice husk is an agricultural waste obtained from milling of rice/ rice mill factories and contains pozzolanic material (yoobanpot and jamsawang, 2014). rice mill factories create a waste product called raw husk which is used as heating fuel in rice mill processing and produces the rha as a byproduct from the burnt raw husk. in a year, about 10 tons of rice husk is usually produced globally (bello et al., 2014). oyetola and abdullahi (2006) reported that in nigeria, about 2.0 million tons of rice is produced annually, especially in niger state where about 96,600 tons of rice grains are produced, however, this rate of production shows that high quantities of rice are being consumed, which in turn increase the quantity of rice husk produce annually. generally, rice husk ash has been reported to be a pozzolanic material with about 67-70 % (silica), 4.9 % (aluminum) and 0.95% (iron oxides) (oyetola and abdullahi, 2006). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 737 bello et al. (2014) investigated the influence of four compactive efforts namely reduced british standard light (rbsl), british standard light (bsl), west african standard (was) and british standard heavy (bsh) on the engineering properties of lateritic soil stabilized with rice husk ash (rha) derived from osun state university main campus, osogbo, osun state, southwestern nigeria. the results of laboratory tests conducted showed a reduction in maximum dry density (mdd) values for rbsl, bsl, was, bsh compaction energies, when natural soil was treated with 6%, 8%, 10% and 12% rha respectively, however, increase in optimum moisture content (omc) was recorded for rbsl, bsl, was, bsh at 4 %, 6 % and 8 % rha respectively. they reported an improvement in california bearing ratio (cbr) of soaked samples from 2.5, 8 and 11% for bsl, was and bsh to 10, 18 and 30% at 4 -8% rha content. finally, the bsl that yielded cbr value of 10% at 6% rha treatment of soil was recommended for use as subgrade of lightly trafficked roads and bsh that yielded cbr value of 30% at 4 % rha stabilization of soil was being recommended for subbase construction (bello et al., 2014). yoobanpot and jamsawang (2014) investigated the compressive strength characteristics of soft soil improvement using rha as a partial replacement of cement at various curing times of 3, 7, 14 and 28 days. in their results, 30% of rha produced the soil strength of 424, 722, 915 and 1,126 kpa at 3, 7, 14 and 28 days curing respectively. they concluded that the increase in strength of the stabilized soil was relative to the formation of major reaction products such as calcium silicate hydrate. choobbasti et al. (2010) conducted a laboratory test to determine the influence of adding rha on the amount and quickness of soil and lime reaction. they reported that the combination of soil with 4% lime gives the maximum amount of cohesion and internal friction angle parameters which is similar to the situation of using 3% and 5% rha. however, the addition of rha to the combination of soil with 4% lime caused an increase in the dilation parameter but shows a decreasing rate in the combination of soil with 6% lime. the addition of lime and rha to the soil causes a decrease in the deformability of soil samples and gives more brittle materials. moreover, this action causes an increase in shear strength. the maximum shear strength of soil with lime combination occurs at 5% rha for 28 days of soil samples. chao-lung et al. (2011) carried out a laboratory test to investigate the effect of marble dust on the strength and durability of an expansive soil stabilized with an optimum percentage of rice husk ash (rha). their report showed that the optimum percentage of rha used was 10% based on unconfined compressive strength (ucs) tests. however, compaction tests, ucs tests, soaked cbr tests, swelling pressure tests, and durability tests were conducted on these samples after 7 days of curing. finally, the result of ucs and soaked cbr of rha stabilized expansive soil showed an increase of up to 20% addition of marble dust. 2.3 locust bean waste ash (lbwa) the locust bean waste is a material obtained from locust bean fibrous after the husk has been removed. locust bean tree is common in the environment, especially in nigeria. the tree grows to about 15 m in height with dark, evergreen, pinnate leaves. an estimated value of about 200,000 tons of locust bean seeds is reported gathered each year in nigeria (osinubi et al., 2016). this comprises of husk, powder, and the seed which is commonly used to produce local seasoning for food. however, the husk is known to be waste among the three components which when burnt in an open place, produces ash called locust bean waste ash (lbwa). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 738 nwadiogbu and salahudeen (2014) reported that lbwa is a pozzolanic material that is capable of reacting with lime in the presence of water at ordinary temperature to produce a cementitious compound. samaila and srividhya (2015) reported the results of laboratory tests conducted to evaluate the characteristics of two weak soils (sample 1 and sample 2) stabilized with up to 8% and 6% lbwa content respectively. the preliminary test produced results for the two soil samples and showed that sample 1 and sample 2 that classified as cl and ch soil respectively have 75% and 100% free swell index, 43.6% and 53.2% liquid limits; 19.6% and 18.12% plasticity index; 72% and 68% fine content. they reported the results of other properties such as maximum dry densities, optimum moisture contents and unconfined compressive strength (ucs) for the two soil samples (sample 1 and 2) and are given as (1.74 g/cm3 and 1.67 g/cm3), (17.5% and 18%) and (1.5 kg/cm2 and 2.1 kg/cm2) respectively for the two soil samples. however, result of the stabilized samples showed that the ucs improved by 45% when soil sample 1 was treated with 8% lbwa, while the improvement of 102% was obtained when soil sample 2 was treated with 6% lbwa content for the same 7 days curing. their report indicated that the properties of weak soils improved when stabilized with lbwa. nwadiogbu and salahudeen (2014) carried out a laboratory test on the lateritic soil to evaluate the potential of lime on modified lateritic soil using locust bean waste ash as an admixture. the lateritic soil used was treated with up to 4% lime content and 8% lbwa content by weight of the dry soil sample in the sieve analysis performed, an increase in the particle sizes was observed with an increase in lime/lbwa content. however, an improvement in the atterberg limits was also observed as the maximum dry density (mdd) for british standard light (bsl) compaction increased to a peak value at 4% lbwa for all lime contents, while the west african standard (was) compaction, have the mdd trend that followed continuous decrease. as per british standard heavy (bsh) compaction, no consistent trend was observed. their report showed that corresponding optimum moisture content (omc) values for all the three compactive efforts generally increased steadily. generally, cohesion decreased while the corresponding angles of internal friction increased with increase in lime/lbwa content. adama et al. (2013) evaluated the effect of locust bean pod ash on the compaction characteristics of weak subgrade soils. their studies made use of soils obtained from old borrow pits along minna-kataeregi-bida road in northern nigeria and analyzed for the main index properties and compaction. the experimental results revealed that locust bean pod ash reduced the maximum dry density from 1.68-1.62, 1.33-1.304 and 1.62-1.50 g/cm3 respectively for all the lateritic soil samples obtained while it increased the optimum moisture content from 10.4 -11.5, 18.0 -19.5 and 12.03-18.50% respectively thus, improving the compaction properties. considering compaction characteristics and economy, 6-10 % weight of stabilizer to the soils was considered as the required optimum values for satisfactory accomplishment of the stabilization of the weak soil as road sub-base. akinmade et al. (2016) conducted a study on the evaluation of strength characteristics of tropical black clay treated with locust bean waste ash up to 15 % of lbwa to assess its soil improvement potential. the natural and treated soil samples used for the study were subjected to index and compaction test using three energy levels (british standard light, bsl, west african standard, was or ‘intermediate’ and british standard heavy, bsh), shear strength (unconfined compressive strength, ucs), california bearing ratio, cbr and durability tests. it was reported that maximum http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 739 dry density (mdd) and optimum moisture content (omc) decreased and increased, respectively. however, regardless of the compactive effort and curing period, strength and durability properties increased with higher lbwa content.in checking for durability results, it was observed that optimal 12.5% lbwa treatment of black cotton soil obtained from bsl energy level cannot satisfy criteria for its use in road construction. namadi and yamusa (2013) carried out a laboratory test to investigate the influence of locust bean waste ash (lbwa) on cation exchange and plasticity characteristics of ordinary portland cement (opc) modified lateritic soil. in the preliminary tests carried out on the natural soil and soil-cement mixtures up to 4% opc admixed with 8% lbwa content by weight of the dry soil showed an improvement in the plasticity characteristics of the soil, reflected in the decrease in liquid limit, increase in plastic limit and decrease in plasticity index with increase a cement and lbwa content .following the results obtained, they concluded that modification with cement and lbwa blend significantly improved the plasticity characteristics through cation exchange of the lateritic soil. 2.4 palm oil fuel ash (pofa) palm oil fuel ash (pofa) is a product of palm oil residue obtained from palm oil mills, when burnt into ashes it contained a large amount of silica in its chemical composition, which may be used as a cement replacement like rice-husk ash and sawdust (ikpong and okpala 1992; elinwa and mahmood 2002; tangchirapat et al., 2009). however, the use of pofa as a pozzolanic material to replace conventional stabilizing materials (cement, lime etc) is known to few researchers and pofa not more than 10% by weight of a binder has been recommended by tay (1990). pofa exhibited some pozzolanic properties and could be used as a partial replacement for cement (safiuddin et al., 2011; tangchirapat et al., 2009). pourakbar et al. (2015) investigated the possible uses of palm oil fuel ash (pofa) on clayey soil. the laboratory tests (proctor compaction, atterberg limit and unconfined compression strength) were carried out on stabilized and unstabilized soil and results obtained were then compared with samples treated with cement. scanning electron microscopy with x-ray microanalysis was conducted on untreated and treated soil to show their strength properties. from their findings it was revealed that pofa/cement mixture treatments result significantly reduce the soil plasticity index (pi), decrease the optimum moisture content and increased the maximum dry density across selected binder dosages. however, using pofa alone to stabilize clayey soil resulted in a slight increase in the ucs of the specimens until the 28 days of curing, whereas combining pofa with cement results in a sharp increase in the ucs of the samples in the same curing time. tangchirapat et al. (2009) conducted a research study on utilizing palm oil fuel ash (pofa) as a pozzolanic material for replacing portland cement. the pofa was grounded to replace cement 40% by weight of the binder and the effects of pofa fineness on the set times, compressive strength, and expansion of mortars exposed to a 5% mgso4 solution was investigated. it was found that the use of pofa to replace portland cement caused an increase in water demand and setting time. up to 10% replacement of portland cement with pofa increased the compressive strength of the mortar. however, the ground pofa was a good pozzolanic material and can be used to increase both the compressive strength and the sulfate resistance of mortar. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 740 2.5 banana leaf ash (bla) banana is known as a plant that produces fruit and possesses the largest herbaceous flowering plant that consists of fruit, flower, and leaves. banana is produced in 135 countries and among the highest producer in the year 2017 were indian and china, which approximated to about 38 % of the total world population (faostat, 2017). this rate showed the wide application and high consumption level of banana in the country, especially in nigeria. banana leaf is large, flexible, and waterproof and often used as ecologically friendly disposable food containers or as "plates" in south asia and several southeast asian countries. emeka and aderinlewo (2016) investigated the geotechnical properties of lateritic soil stabilized with banana leaf ash. they carried out preliminary soil tests (natural moisture content, specific gravity, and atterberg limit) on the natural soil sample collected from the federal university of technology, akure (futa), nigeria and engineering tests such as compaction, california bearing ratio, and unconfined compressive strength tests were also performed on the lateritic soil at their natural and stabilized states up to 10% banana leaf ash content by weight of the dry soil. result of the strength tests showed that the banana leaf ash enhanced the strength of the lateritic soil. the unsoaked cbr and unconfined compressive strength values improved at 4% banana leaf ash. however, they concluded that banana leaf ash satisfactorily acted as cheap stabilizing agents for subgrade purposes. 2.6 bagasse ash (ba) bagasse is the fibrous residue obtained from sugar cane after the extraction of sugar juice at sugar cane mills (osinubi and stephen, 2005). bagasse ash is the residue obtained from the incineration of bagasse in sugar producing factories. the ash has been reported to be a good pozzolanic material (osinubi and alhassan, 2008., osinubi and mustapha 2008) with possession of silica and alumina contents of up to 77. 29% and 10.95% respectively for ash obtained from bagasse burnt at 700°c temperature. osinubi et al. (2009) investigated the geotechnical properties of the deficient lateritic soil up to 12% bagasse ash by dry weight of the soil sample. soil samples were subjected to particle size analysis, compaction, unconfined compressive strength (ucs), california bearing ratio (cbr) and durability tests. the energy level employed for compactions test was british standard light (bsl) producing results that showed changes in moisture-density relationships resulting in lower maximum dry densities (mdd), higher optimum moisture contents (omc), reduction in fine fractions with higher bagasse ash content in the soil – stabilizer mixtures. results of ucs and cbr values were given as 836 kn/m2 and 16%, respectively at 2% bagasse ash treatment of lateritic soil. they concluded that since these values were below 1,700 kn/m2 and 80% for ucs and cbr, respectively, recommended for adequate cement stabilization. it implies that bagasse ash cannot be used as a ‘standalone’ stabilizer but should be employed in admixture stabilization. salahudeen and ochepo (2015) carried out laboratory tests on lateritic soil to evaluate the effect of bagasse ash (ba) on the california bearing ratio of lateritic soil. the tests were performed on natural and bagasse ash treated soil. in the study, treated specimens were prepared by mixing the soil with bagasse ash in steps of 0, 2, 4, 6 and 8% by dry weight of soil. results of their investigation showed that the specific gravity of the soil samples decreased from 2.61 for the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 741 natural soil to 2.48 at 8% bagasse ash content. however, by dry weight of the soil sample the liquid and plastic limits increased from 36.32 to 38.0 and 21.30%, to 21.54 % respectively at 2% bagasse ash content. the maximum dry density (mdd) of the soil increased from 1.48 mg/m3 for the natural soil to a peak value of 1.49 mg/m3 at 8% bagasse ash content with the corresponding increase in optimum moisture content (omc) from 18.5% for the natural soil to 19.0% at 4% bagasse ash content. result obtained for unsoaked california bearing ratio for the lateritic soil treated with 4% ba content and above met the minimum cbr value of 30% specified by (bs 1990) for material suitable for use as base course material when determined at mdd and omc. however, the highest cbr value of 62% recorded at 8% ba content failed to meet the 80% cbr value recommended by the nigerian general specification (1997) for cement stabilization. bagasse ash improved the cbr value of lateritic soil when compacted at optimum moisture content. ochepo et al. (2015) evaluated the effect of bagasse ash on the california bearing ratio of contaminated lateritic soil. in their study, the treated specimen was mixed with bagasse ash up to 8% by dry weight of the soil sample and contaminated with used oil up to 6% by dry weight of the soil sample. result of investigations showed that the specific gravity of the soil sample decreased from 2.61 for the natural lateritic soil to 2.48 at 8% bagasse ash content and a similar trend was reported for 6% oil / 0% bagasse ash and 6% oil/8% as decreased to 2.16 and 2.11 respectively. other test results such as liquid limit and plastic limit increased from 36.32 and 21.30 % respectively to peak values of 38.0% and 21.54 % at 2% bagasse ash content for all oil contents. the mdd of the soil increased from 1.48 mg/m3 to 1.49 mg/m3 at 8% bagasse ash content for all oil contents. omc values increased from 18.5% for the natural soil to 19.0% at 2% bagasse ash content. result of unsoaked cbr obtained at 4% ba content and above met the minimum cbr value of 30% specified by bs 1990 for materials suitable for use as base course material when determined at mdd and omc. however, higher cbr value of 62% recorded at 8% ba content failed to meet 80% cbr value recommended by the nigeria general specification (1997) for cement stabilization. oil contamination caused reduction in the strength andcbr value of lateritic soil. 2.7 coconut shell husk ash (csha) coconut shell husk can be regarded as an agricultural waste that is widely available in larger quantities in tropical countries of the world (obi et al., 2016) and it is used in nigeria and some other part of the country as a source of fuel for the boilers (obi et al., 2016). onyelowe (2016) studied the effect of coconut shell husk ash (csha) and palm kernel shell husk ash (pksha) on the axial load and compaction behavior of pozzolan stabilized lateritic soil. the admixtures (csha and pksha) used in the study, were applied in proportions by weight of soil sample as 0, 2, 4, 6, 8 and 10 %. results showed that the two admixtures increased optimum moisture content and decrease the maximum dry density of soil. the triaxial test examination conducted on the stabilized soil showed that the value of unit weight and dry unit weight decreased at addition of different percentages of csha and pksha but that of pksha reduced drastically than that of csha. however, the unconfined compression strength (ucs) increased with respect to the curing days and also increased at different percentages of csha and pksha. natural ucs value was given to be 6.43 kn/m2, 8.65 kn/m2 and 14.80 kn/m2 for 0, 7 and 14 days respectively and later improved to 10.79 kn/m2, 31.82 kn/m2 and 40.00 kn/m2 respectively when stabilized with up to 10% csha content. however, 11.38 kn/m2, 33.43 kn/m2 and 41.64 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 742 kn/m2 was recorded for an improvement at 10% pksha for 0, 7 and 14 days respectively. with the improvement of the strength properties of the weak soil studied by using csha and pksha, he then recommended for use as admixtures for the improvement of the geotechnical properties of weak engineering soil. 2.8 bamboo leaf ash (bla) bamboo grows abundantly in most of tropical countries and found naturally as a composite material. the possession of cellulose fibers embedded in a lignin matrix makes bamboo considered a composite material (amu and babajide, 2011). some researchers has identified various species of bamboo to be 1,200 globally (wang and shen, 1987). bamboo chips were used to record history in ancient china and have been used as a building material over the history of mankind (amu and babajide, 2011). it has also been used widely for household products and extended to industrial applications due to advances in processing technology and increased market demand. massive plantations of bamboo provide an increasingly important source of raw material for the pulp and paper industry in china (hammett et al., 2001). amu and adetuberu (2010) conducted a research study on the characteristics of lateritic soil stabilized with bamboo leaf ash (bla) in highway construction. preliminary and geotechnical property tests (compaction, california bearing ratio (cbr), and triaxial) were performed on the three soil samples at step concentration of 0, 2, 4, 6, 8 and 10% bamboo leaf ash (bla) by dry weight of soil sample. the results showed that the addition of bla improved the strengths of the samples. however, reduction in optimum moisture contents was recorded for the three soil samples (a, b and c) classified as a-2-7(2), a-2-4(1) and a-2-5(3) soil respectively at 8, 4 and 6% bla, respectively, while mdd increased for the samples (a, b and c) at 8, 2 and 4% bla respectively. the unsoaked cbr values and shear strength values increased for sample a and b, and it was concluded that bamboo leaf ash had a good potential for stabilizing lateritic soils in highway construction. umoh and adesola (2015) investigated the characteristics of bamboo leaf ash blended cement paste and mortar. in their test results, the physical properties of pastes were determined and compared with the requirements stipulated by relevant standards. an increase in compressive strength was recorded for the mortar cubes with an increase in curing age. they reported that the mix with 15% bamboo leaf ash favourably satisfied the standard mix at 28 days. therefore, it was recommended that 15% bla could replace cement for adequate production of masonry mortar. 2.9 corn cob ash (cca) corn cob is an agricultural waste product obtained from maize or corn. zhang et al. (2013) reported that an estimated weight of about 160180 kg corncobs generated from every 1 ton of corn produced. however, most of the corncobs generated worldwide are discarded as waste (zhang et al., 2010). the disposal of this enormous waste constituted pollution to the environment. thus, many researchers have considered recycling it for various applications. akinwumi and aidomojie (2015) investigated the effect of corncob ash (cca) on the geotechnical properties of lateritic soil stabilized with portland cement. preliminary tests (specific gravity, consistency limits, compaction, california bearing ratio (cbr) and permeability) were http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 743 carried out on natural soil and stabilized soil with up to 12 % corn cob ash. results obtained from the test showed that the addition of cca to the lateritic soil reduced its plasticity, swell potential and permeability; and increased its strength. it improved the geotechnical properties of the soil for pavement layer material application. raheem et al. (2010) investigated the effects of plasticizer on the properties of corn cob ash (cca) cement concrete. their study was aimed at the workability and compressive strength of cca cement where the end results showed an improvement in the workability of corn cob ash cement concrete. the cca cement concrete incorporated with accelerator achieved greater strength at early ages, plasticizer achieved very high strength at both young and old ages; and water retards the strength at old age. olafusi and olutoge (2012) made a study to determine the strength properties of corn cob ash concrete, enhancement of the reduction of corn cob wastes and reduction in the cost of concrete. they carried out various tests on concrete cubes of size 150 × 150 × 150 mm³ and concrete cylinders of size 100 x 200mm with different percentages by volume of cca to portland cement and their physical and mechanical properties were determined. result of mechanical properties tests on the compressive strength showed that 10% of the cca in replacement for cement was quite satisfactory with no compromise in compressive strength requirements for concrete mix ratios 1:2:4 at 7days. in addition, the test results also showed that the use of cca as a partial replacement for cement in concrete, particularly in plain concrete works and non-load bearing structures will enhance the waste to wealth initiative. hence, cca could be used as a partial replacement for cement in high strength concrete. 2.10 cassava peel ash (cpa) cassava peels is an agricultural waste obtained from cassava processing, either for domestic consumption or industrial uses and constituted up to 20-35% of the weight of tuber, especially in the case of hand peeling. in nigeria, about 6.8 million tonnes of cassava peel are produced yearly which estimated to be 20% of the total population (bello et al., 2015). the disposal of cassava peels indiscriminately constitutes a nuisance to the environment due to improper management and lack of appropriate technology to recycle them. olatokunbo et al. (2018) investigated the effect of cassava peel ash as a replacement for cement at 5, 10, 15, 20 and 25%. the cassava peel used was calcinated at 700oc temperature to obtain ash and test results showed that addition of 10 and 15% cpa gave stable compressive strength. the improvement reported was attributed to the cassava peel ash that contained all the main chemical constituents of cement in lower percentage compared with opc which showed that it can serve as a suitable replacement if the right percentage is used.its durability and sulphuric acid resistance improved considerably at 10% replacement of cement with cassava peel ash. bello et al. (2015) carried out studies to assess the impact of cassava peels ash (cpa) on the stabilization of lateritic soil deposit found within osogbo local government area in osun state, nigeria. the preliminary and geotechnical property tests (compaction, california bearing ratio (cbr), and unconfined compression test) were performed on three samples, l1, l2, and l3 classified as cl, sc and cl soil respectively for identification and classification purposes. the natural soil used was improved at step concentrations of 2, 4, 6, 8 and 10% cassava peels ash (cpa) by dry weight of soil. results obtained showed that addition of cpa improved the strengths of the samples as optimum moisture contents (omc) reduced to 14.58, 18.40 and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 744 16.0% at 6, 4 and 6% cpa for samples l1, l2 and l3 respectively while maximum dry density (mdd) increased to 1470, 1410 and 1440 kg/m3 at 10, 4 and 2% cpa for samples l1, l2, and l3 respectively. the unsoaked cbr values increased for the three soil samples at 8 and 10% cpa content and the shear strengths of samples (l1, l2, and l3) also increased up to 10 % cpa content. the studies concluded that the cpa has a good potential for stabilizing lateritic soil. 2.11 palm kernel shell husk ash(pksha) onyelowe (2016) evaluated the effect of coconut shell husk ash (csha) and palm kernel shell husk ash (pksha) on the axial load and compaction behaviour of pozzolan stabilized lateritic soil. in his study, he made use of lateritic soil collected from oboro in delta state, coconut shell husk ash and palm kernel shell husk ash were applied in step concentration by dry weight of soil sample as 2, 4, 6, 8 and 10% respectively. an increase in optimum moisture content and a decrease in maximum dry density were recorded for the addition of the varied proportions of csha and pksha. however, the triaxial test results showed that the value of unit weight and dry unit weight of the test decreased at different percentages of csha and pksha while ucs results also show improvement for treated soil at 10 % csha and pksha. 3.0 conclusion this study showed the resurgence of interest in the use of alternative naturally occurring materials to the conventional additives (cement, bitumen and lime) for soil development. agricultural wastes such as (rice husk ash, locust bean waste ash, palm oil fuel ash, banana leaf ash, bagasse ash, coconut shell ash, bamboo leave ash, corn cob ash, cassava peel ash, and palm kernel shell husk ash) have been found useful in concrete, geotechnics and highway engineering applications. engineering properties such as atterberg, strength, durability, and gradation to soil particles could be modified and improved upon by simple use of these materials as additives. however, there is little information regarding the use of banana leave ash and palm oil fuel ash as soil improvement materials. furthermore, further study is required for the use of palm oil fuel ash to understand its property and potential as a soil improvement material. in addition, waste sourced from cocoyam, yam, maize trunk, cashew, and guava have limited reports and is recommended to check for their properties and use as hydraulic conductivity material in stabilizing problematic soil. references alhassan, m. and mustapha, a. 2007. effect of rice husk ash on cement stabilized laterite, leonard electronic journal practical technology 6(11):47-58 andrew, y. yinusa, a. and stephen s. 2013. effect of locust bean pod ash on compaction characteristics of weak sub grade soils. international journal of engineering science invention 2(1):25-30 alhassan, m. and mustapha, a. 2015. improvement of deficient soils in nigeria using bagasse ash. international journal of environmental, chemical, ecological, geological and geophysical engineering 9(10):12341243 ako, t. and yusuf, i. 2016. effect of palm kernel shell ash on compaction characteristics of a lateritic soil websjournal of science and engineering application, 5(1):449-45 https://images.search.yahoo.com/yhs/search;_ylt=awrcmrdxr5fcms4afvepxqt.;_ylu=x3odmtbymjb0ag5zbgnvbg8dymyxbhbvcwmxbhz0awqdbhnlywnzyw--?p=leonard+electronic+journal+practical+technology%2c+6%2811%29%3a47-58.&fr=yhs-trp-001&hspart=trp&hsimp=yhs-001 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 745 amu, o. and adetuberu, a. 2010. characteristics of bamboo leaf ash stabilization on lateritic soil in highway construction. international journal of engineering and technology 2(4):212-219 amu, o. and babajide, s. 2011. effects of bamboo leaf ash on lime stabilized lateritic soil for highway construction. research journal of applied sciences, engineering, and technology, 3(4):278–283. amu, o., ogunniyi, s. and oladeji, o. 2011.geotechnical properties of lateritic soil stabilized with sugarcane straw ash, american journal of scientific and industrial research, 2(2):323-331. astm c618-78 2013. standard specification for determination of compacting factor. bristish institution london agamuthu, p. 2009. challenges and opportunities in agro-waste management: an asian perspective inaugural meeting of first regional 3r forum in asia 11 -12 nov., tokyo, japan. akinwumi, i. and aidomojie, o. 2015. effect of corncob ash on the geotechnical properties of lateritic soil stabilized with portland cement. international journal of geomatics and geosciences, 5(3):375-392. bello, a., ige, ja. and ayodele, h. 2015. stabilization of lateritic soil with cassava peels ash, british journal of applied science and technology, 7(6):642–650. bello, aa., olufemi, a. and tajudeen, o. 2014. influence of compactive efforts on lateritic soil stabilized with rice husk ash, international journal of applied engineering research, 9(21):96399653 bello, a., ige, j. and tajudeen, s. 2007. geotechnical characterization of lateritic soils in parts of ejigbo local government area, southwestern nigeria. lautech journal of engineering and technology, 4(2): 34-38. bello, a. 2007. geotechnical evaluation of some lateritic soils as foundation materials in ogbomoso north local government area southwestern nigeria. science focus, 12(2): 7075. bello, a. and c. adegoke. 2010. evaluation of geotechnical properties of ilesha east southwest nigeria’s lateritic soil. pacific journal of science and technology. 11(2): 617-624. chao-lung, h., anh-tuan, b. and chun-tsun, c. 2011. effect of rice husk ash on the strength and durability characteristics of concrete. construction and building materials, 25(9): 3768–3772. choobbasti, aj., ghodrat, h., vahdatirad, mj., firouzian, s., barari, a., torabi, m. and bagherian, a. 2010. influence of using rice husk ash in soil stabilization method with lime journal of earth science, 4(4): 471480. daud, n., norsyahariati, n., jalil, a., nisa, f., sadiq, m. a. and azmi, g. 2016. influence of agricultural properties of soil wastes on shear, matec web of conferences 47. 10.1051/matecconf 2016 00/47318. das, m. 1998 . principles of geotechnical engineering, 4th edition. pws publishing division of international thomas publishing, ny.. emeka, s. and olufikayo, o. 2016. geotechnical properties of lateritic soil stabilized with banana leaves ash. fuoye journal of engineering and technology, 1(1): 116119 eberemu, a. 2015. compressibility characteristics of compacted lateritic soil treated with bagasse ash, jordan journal of civil engineering, 9(2): 214 – 228. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ishola, et al: review of agricultural waste utilization as improvement additives for residual tropical soils. azojete, 15(3):733-749. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 746 eberemu, a. amadi, a. and edeh, j. 2013. diffusion of municipal waste contaminants in compacted lateritic soil treated with bagasse ash. environmental earth science, 70(2): 789-797. eberemu, o, amadi, a. and lawal, m. 2012. the geotechnical properties of black cotton soil treated with glass cullet. nigeria journal of engineering, 2: 23-30. ghassan, k., mouin, a. and panagiotis, g. 2013. natural pozzolan as a partial substitute for cement in concrete. journal open construction and building technology, 7: 33-42. george, m. and oriola, f. 2010. groundnut shell ash stabilization of black cotton soil groundnut shell ash stabilization of black cotton soil. electronic journal of geotechnical engineering, 15: 415-428. ishola, k., olawuyi, oa., bello, aa. and yohanna, p. 2019. effect of plantain peel ash on the strength properties of tropical red soil. nigerian research journal of engineering and environmental sciences, 4(1): 447-459 lekha, b., goutham, s. and shankar, a. 2015. evaluation of lateritic soil stabilized with arecanut coir for low volume pavements. transportation geotechnics, 2: 20–29. moses, g., oriola, f. and afolayan, j. 2013.the impact of compactive effort on the long term hydraulic conductivity of compacted foundry sand treated with bagasse ash and permeated withmunicipal solid waste landfill leachate. frontiers in geotechnical engineering, 2(1): 7-15. mannir, i., yohanna, p. and osinubi, k. 2016. evaluation of compacted black cotton soil – sawdust ash mixtures as road construction material. nigerian journal of material science and engineering, 7(2): 65-72. namadi, m. and yamusa, b. 2013. influence of locust bean waste ash on cation exchange and plasticity characteristics. cement modified lateritic soil,1(2):58–63. nnochiri, e. and aderinlewo, o. 2016. geotechnical properties of lateritic soil stabilized with the ashes of oil palm fronds, civil engineering journal 4(2): 1–9. nwadiogbu, p. salahudeen, a. 2014. potential of lime on modified lateritic soil using locust bean waste ash as admixture. journal of mechanical and civil engineering 11(1): 69–73. neville, a. 2000. properties of concrete, 4th edition. pearson education asia ltd, malaysia. obi, f., ugwuishiwu, b. and nwakaire, j. 2016 agricultural waste concept, generation, utilization and management, nigerian journal of technology, 35(4): 957–964. ochepo. j. 2014. stabilization of laterite soil using reclaimed asphalt pavement and sugarcane bagasse ash for pavement construction. journal of engineering research, 2(4): 1-14. ochepo, j., salahudeen, ab. and sadeeq, ja. 2015. assessment of bagasse ash effect on the california bearing ratio of used oil contaminated lateritic soils. nigerian journal of technology, 34(2): 223–231. olatokunbo, o., anthony, e., rotimi, o. and solomon, o. 2018. assessment of strength properties of cassava peel ash-concrete. international journal of civil engineering and technology, 9(1): 965–974. olonode, k. 2010. prospect of agro-by-products as pozzolans in concrete for low-cost housing delivery in nigeria. proceedings of the international conference of the obafemi awolowo university, faculty of technology, 1:217 – 221. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; 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vol. 15(3):733-749. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: isholakzm@gmail.com 749 zhang, c., geng, z., cai, m., zhang, j., liu, x., xin, h. and ma, j. 2013. microstructure regulation of superactivated carbon from biomass source corncob with enhanced hydrogen uptake. international journal of hydrogen energy, 38: 9243-9250. kwon, e., kelly, jw. and marco, jc., 2009. an investigation into the sngas production from municipal solid waste (msw) under various pressures and co2 concentration atmospheres, 17th annual north waste -to -energy conference, chantilly, virginia, usa, proceedings , pp. 231236. osemeahon, sa. and dimas, bj. 2014. development of urea formaldehyde and polystyrene waste as copolymer binder for emulsion paint formulation. academic journal, 6(3): 75 -88. poletto, m. 2016. polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties. revista materia, 21(3): 552-559. ricky, g., oscar, l. and yusef, s. 2010. an investigation into polystyrene recycling at ubc. dawn mills apsc 262. the university of british columbia. pp. 1-18. voulgardis, ev., passialis, cn. and philippou, jl. 2003. experimental results of reclaimed polystyrene utilisation in wood products. in: proceedings of 8th international conference on environmental science and technology lemnos island greece 8-10 september, 2003 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):25-39 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 25 original research article comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models o. a. adetayo1* and b. i. o. dahunsi2 1 department of civil engineering, federal university oye ekiti, nigeria 2 department of civil engineering, university of ibadan, ibadan, nigeria *corresponding author: oluwaseun.adetayo@fuoye.edu.ng, tayo.seun4real@gmail.com article information submitted 02 september, 2018 revised 19 february, 2019 accepted 23 february, 2019 keywords: nigerian wood empirical models charring rate australian standard eurocode model white’s model abstract the rate at which timber chars varies between species and predominately dependent on density and moisture content. this study involved determination of charring performance of nigerian wood species used for constructional purposes and comparing their charring rate with selected existing models. six out of ten identified wood species commonly used for constructional purposes: terminalia superba (black afara), milicia excels (iroko), nauclea diderrichii (opepe), khaya ivorensis (mahogany), mansonia altissima (mansonia), tectona grandis (teak) were selected for the study. the densities of the woods were determined at moisture contents (mc) of 9.0, 12.0, and 15.0%. selected samples from each species, were exposed to fire at temperature ranges of 20° to 230°c for 30 min; 230° to 300°c for 30 min; 20° to 300°c for 60 min. the charring rate results based on 15% moisture content for all 0 30 min, 30 60 min and 0 60 min, being the ones having the lowest correlation values at each of the fire exposure time were analysed using anova at α0.05 and compared with selected models; australian standard as 1720.4 relation, eurocode en recommendation and white's model. at 0-30 min fire exposure (20 to 230°c), and 15% mc, the experimental charring rate results showed significant regression relations at r2 = 0.9961, 0.8586, and 0.9523 for eurocode en recommendation, australian standard as 1720.4 relation, and white's model respectively. at 0-60 min fire exposure (20 to 300°c), and 15% mc, the results of experimental charring rate also showed significant regression relations at r2 = 0.9925, 0.8926, and 0.9701 for eurocode en recommendation, australian standard as 1720.4 relation, and white's model respectively. afara at 15.0% mc, and 20° to 300°c temperature, had the highest mean charring rates of 0.68 ± 0.02mm/min, while opepe had the lowest charring rates of 0.47 ± 0.02 mm/min at the same mc level and temperature. the experimental test results indicated that density was a major predictor of the charring rate of constructional timber. opepe specie, having the highest density exhibited the lowest charring rate and is recommended to ensure the safety and comfort of occupants in case of fire outbreak. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. mailto:oluwaseun.adetayo@fuoye.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 26 1.0 introduction steel and concrete members (bednarek, 1996) under fire have been extensively investigated in the last five decades. however, far fewer investigations have been carried out on timber structures (bednarek, et al., 2002). the keyword for timber's behaviour in fire is predictability, although it burns, it occurs at a predictable speed known as the charring rate (adetayo and dahunsi, 2018). the charring rate effect on wood makes it have superior fire performance over other structural alternatives; as wood members are exposed to fire, an insulating char layer is formed that protects the core of the section. under practical conditions of use, wood products always contain percentage of moisture, in the incipient of fire development, heating of potential fuel is taking place. ignition is the start of flaming combustion, marking the transition to the growth period. in the growth period, the temperature of wood rise to a point when the moisture starts to evaporate (janssens, 2002), most fires spread slowly at first on combustible wooden surfaces, then more rapidly as the fire grows, providing radiant feedback from flames and hot gases to other fuel items (buchanan, 2001). when large timber members are exposed to a severe fire, the surface of the wood reaches its burning point at about 300℃ (bednarek, 2008), the wood initially ignites and burns rapidly. the burnt wood becomes a layer of char which loses all strength but insulates the solid wood below and thus prevents excessive temperature rise in the core. inside the wood below the char layer, the moisture in the wood continues to evaporate. some of this moisture travels out to the burning face, but some travels into the wood, resulting in an increase in moisture content of the heated wood a few centimeters below the char (fredlund, 1993, white and schaffer, 1981). the initial charring rate decreases to a slower steady rate which continues throughout the fire exposure. the charring rate is more or less constant and depends on the density and moisture content of wood and heat exposure (purkiss, 1996). the layer of the char shrinks, making it thinner than the original wood, causing fissures which facilitate the passage of combustible gases to the surface (drysade, 1998). the charring rate layer does not usually burn because there is insufficient oxygen in the flames at the surface of the char layer for oxidation to occur. studies have shown that many factors are involved in wood charring, among them are density and wood moisture content, heat flux and oxygen concentration of the surrounding air, physic-chemical effects, including diffusion of condensable vapors inward, internal convection outward, kinetics of pyrolysis, and energetic of pyrolysis (shafizadeh, 1984). of all these factors, density has a significant effect on the rate of charring (adetayo and dahunsi, 2017). the rate of mass loss is proportional to density; lower density allows more rapid heat penetration and provides greater surface area per unit weight which allow more heat influx in the wood. in terms of charring rate, (white, 1988), showed that it is inversely proportional to density. hence, although the rate of mass loss increases with density, the rate at which the char develops is lower. the rate of charring is little affected by the severity of the fire, so for an hour's exposure, the depletions are 40 mm for most structural timbers and 30 mm for the denser hardwoods (en, 2004). this enables the fire resistance of simple timber elements to be calculated. the predictive method is published in en 1995-1-2. it assumes that the charring rate of timber made of solid or glued-laminated hardwood decreases linearly with density, with a limit of 0.5 mm/min for density file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 27 larger than 450 kg/m3. for softwood species the standard provides a mean value of 0.7 mm/min for density larger than 290 kg/m3. the australian standard as 1720.4 timber structures: fireresistance of structural timber, confirmed that large cross-section is able to carry load during a fire event as the char occurs on the outside of the element and the effective cross section of the timber is only slowly reduced, the insulating qualities of timber mean that although the temperature at the char layer may be 300℃, the temperature of the inner wood is considerably lower. the remaining uncharred cross sectional area of large wood member remains at low temperature and can continue to carry a load. in the development of an empirical model for charring rate, white (1988) tested eight structural hardwood species and used analytical methods to predict the endurance of the structural wood members in a fire based on the reduction of the cross section of the member due to charring of the wood. fires in buildings have always been a threat to human safety. that threat increases as larger numbers of people live and work in larger buildings throughout the world (buchanan, 2001). hence, the issue of fire safety has taken preeminence in the design and construction of timber structures. in nigeria, limited information is available on the charring rate of hardwood species, and a good knowledge of the fire performance of wooden members is necessary to provide data for the rate of depletion of wooden members exposed to fire. depletion rate is necessary to provide an environment with an acceptable low probability of loss of life or properties due to fire. this research is aimed to identify timber species used for constructional functions in nigeria, evaluating their charring behaviour, comparing with the results derived from these models: white's model, australian standard as 1720.4 relation, and eurocode en recommendation. 2. materials and methods 2.1 selection of samples the selected six structural wood species out of ten recommended frequently used species were gotten from timber markets ibadan, abeokuta oyo, lagos and oshogbo towns of south western nigeria. samples were taken from the heartwood region of the individual timber because of its lesser moisture contents as compared to the sapwood region (timber manual data file, 2004). the six species were: afara (terminalia superba) iroko (milicia excelsa) mahogany (khaya ivorensis) mansonia (mansonia altissima) opepe (nauclea diderrichii) teak (tectona grandis) focus of the experimental test was on structural members used in beam, column and building roofs. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 28 2.2 experimental methods wood samples were tested inside electrical-fired furnace having temperature range capacity up to 1500°c, at the department of foundry, federal institute of industrial research (fiiro), oshodi, lagos, nigeria. fifty-four samples cut into rectangular blocks; nine from each species and each of them having the dimension of 150mm x 150mm x 510mm (figure 1) were tested at the moisture contents of 9%, 12%, and 15% and furnace exposure period of 0 – 30 min, 30 – 60 min, and 0 – 60 min. the specimens were held horizontally and subjected to the heat flux perpendicular to the wood grain according to both eurocode en recommendation and australian standard as 1720.4. traditionally and in the procedure, it would be assumed that the charring front reaches when its temperature indicates 300℃ (bednarek, 2008), assuming that ignition starts at this point. samples were obtained for each wood species at varying moisture contents of 9%, 12%, and 15%. the moisture content of the samples were obtained as the ratio of the mass of removable water to the dry mass of wood samples. the dry mass is obtained by oven drying at 103 ± 2 °c for 24 hours as per astm d143-94. at the time of test, the following data were recorded for the specimen properties: species ring orientation specimen dimensions specimen weight moisture content (percent) specimen density the selected specimen of the wood species were gotten from timber markets at various locations in south western region of nigeria as mentioned earlier, the specimen dimensioned were taken and their corresponding weight with the aid of weighing balance were recorded. specimen density were calculated by dividing the mass of the sample with their corresponding volume, and their moisture contents were obtained as the ratio of the mass of removable water to the dry mass of wood samples. they were positioned horizontally and perpendicular to the ring orientation in the electric furnace. figure 1: measured specimen for the fire test on display file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 29 the specimen, was enclosed in the furnace to carry out fire exposure test as shown in figure 2. the electric furnace was powered, the initial temperature of the electric furnace when switched on was 20°c (white, 2002). at the time of burner ignition, the following functions were done as simultaneously as possible. automatic temperature recorder was started stop watches started furnace temperature controller started. the automatic temperature recorder was used autonomously to monitor and gather temperature data from the furnace in addition to the furnace temperature controller. the stop watch was used to monitor the time intervals of the fire exposure test. figure 2: specimen burning inside furnace specimens were exposed to fire in three batches. the first batch went for the time of 0-30 min, the second batch for 30 60 min and the last batch was for full 0 – 60 min. the first test for exposure period of 0 – 30 min was stopped at exactly when the stop watch reached 30 min, temperature reading was 20°c to 230°c. specimens exposed during the second period of 0 – 30 min were subjected to higher temperature from 230°c to 600° c. the third test for exposure period 0 – 60 min, furnace temperature ranges between 20°c to 300°c. when testing was completed, the charred wood was scrapped away from the samples and char depth was measured (figure 3). the charred specimens were also cut in half to obtain the thickness of the charred slab and the char layer. for each specimen three sets of data were produced according to the time of exposure. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 30 figure 3: charred wood after 1-hour fire exposure 2.2 charring rate models the charring rate (mm/min) results were determined for the three moisture contents level of 9.0%, 12.0%, and 15.0% using linear formula, (en, 2004). β = dchar t (1) β = charring rate (mm/min) dchar = thickness of char layer or char depth (mm) t = time of fire exposure (min) the results of the experimental charring rate were calculated and tabulated for each fire exposure time at moisture contents of 9.0%, 12.0%, and 15.0%. experimental charring rate results were compared with the values predicted by three selected models. the australian standard (1990) expresses the notional charring rate β (mm/min) as a function of wood density: β = 0.4 + 280 ρ ² (2) where: ρ is the wood density at 12% moisture content (kg/m3). in the development of charring models, eurocode 5 (en, 2004) recommendation has a simple constant charring rate relationship as follows: dchar = βοt (3) dchar = charring depth mm βο = charring rate (mm/min), usually between (0.5 to 0.8) mm/min t = time in min. in determining the remaining effective residual section for structural purposes, both standards en and as 1720.4 (2006), calculate an effective charred depth by adding a constant thickness of 7.5mm to the calculated value in order to take into account the heat-affected zone. that is, the effective depth of charring (in mm) is given by file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 31 dc = β t + 7.5 (4) dc = calculated effective depth of charring in millimetres (mm) β = notional charring rate in millimetres per minute (mm/min) as calculated t = time of exposure to heating regime specified in as 1720.4 (min) the effective residual cross section was obtained by subtracting the calculated effective depth of charring from all fire exposed surfaces of the timber member. white (2002), established an empirical model for the charring rate based on four tests on hardwood species with extensive sets of specimens. species were hard maple (acer sp.), yellowpoplar (liriodendron tulipera), red oak (quercus sp.) and basswood (tilia sp.). the following non-linear relation was proposed: t = mxc1.23 (5) the linearization of eqn(5) through logarithmic transformation yields eqn (6) as follows: ln t = ln m+ 1.23 ln xc (6) t = the time of exposure (min), xc = charred depth from original fire-exposed surface (mm), m = reciprocal char rate (min/mm) the reciprocal char rate was given by white (2002) as m =− 0.147 + 0.000564ρ + 0.012u + 0.532fc (7) where: ρ = oven-dry density (kg/m³) u = moisture content (percent), and fc = char contraction factor, defined as the thickness of the char layer at the end of the fire exposure divided by the original thickness of the wood layer that has charred ( tran and white, 1992). an expression for the char contraction factor for hardwood species was obtained as follows; fc = 0.529 − 0.00036d + 0.002ρ (8) d = depth of char (preservative) penetration (mm) (3 for low to 36 for highly treatable species). 3. results and discussion the effect density of each wood species were glaring on the results of the calculated charring rates, it showed that wood species with low density wood exhibited high charring rate and viceversa. the mean charring rate results for specimens exposed for 0 to 30 minutes fire interval, temperature ranged of 20° to 230°c are illustrated in tables 1 to 3. afara of 9, 12 and 15% mc had the highest charring rates of 0.84±0.02 mm/min, 0.82±0.02 mm/min and 0.82±0.02 mm/min respectively, while opepe had the lowest charring rates of 0.48±0.02 mm/min, 0.48±0.02 mm/min and 0.47±0.03 mm/min respectively at the three mc levels. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 32 table 1: charring rate of samples at 9% mc (0-30) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 444 25.20 0.84 0.02 0.80 0.86 iroko 532 19.30 0.64 0.02 0.62 0.66 mahogany 439 19.70 0.66 0.02 0.64 0.69 mansonia 566 19.40 0.65 0.02 0.63 0.67 opepe 630 14.30 0.48 0.02 0.45 0.50 teak 505 19.50 0.65 0.02 0.62 0.67 table 2: charring rate of samples at 12% mc (0-30) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 444 24.60 0.82 0.02 0.79 0.85 iroko 544 19.60 0.65 0.02 0.63 0.68 mahogany 451 19.50 0.65 0.02 0.63 0.67 mansonia 580 18.70 0.62 0.03 0.58 0.65 opepe 686 14.40 0.48 0.05 0.44 0.55 teak 569 19.40 0.65 0.02 0.63 0.68 table 3: charring rate of samples at 15% mc (0-30) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 469 24.80 0.82 0.02 0.79 0.85 iroko 614 19.50 0.65 0.02 0.62 0.68 mahogany 521 21.30 0.71 0.03 0.68 0.74 mansonia 591 18.90 0.63 0.02 0.60 0.66 opepe 752 14.10 0.47 0.03 0.45 0.51 teak 657 19.40 0.65 0.02 0.62 0.68 specimens exposed for the second period of fire of 30 minutes, 230° c to 600° c temperature experienced more intense heating, and as expected, charred at a greater rate. tables 4 to 6 showed the results of specimens exposed to fire at the mc levels. both iroko and teak species had the lowest charring rates of 0.71±0.02 mm/min at 9% mc and 0.69±0.02 mm/min at 12% mc respectively. at 15% mc, iroko exhibited the lowest (0.67±0.02 mm/min) while afara exhibited the highest (0.88±0.05 mm/min) charring rates. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 33 table 4: charring rate of samples at 9% mc 30 minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 444 28.20 0.94 0.02 0.91 0.96 iroko 532 21.30 0.71 0.03 0.67 0.74 mahogany 439 24.60 0.82 0.03 0.80 0.86 mansonia 566 26.70 0.89 0.05 0.83 0.94 opepe 630 24.30 0.81 0.02 0.78 0.84 teak 505 21.30 0.71 0.03 0.67 0.74 table 5: charring rate of samples at 12% mc (30) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 444 27.90 0.93 0.02 0.91 0.95 iroko 544 20.70 0.69 0.02 0.66 0.72 mahogany 451 24.60 0.82 0.01 0.80 0.84 mansonia 580 25.50 0.85 0.01 0.84 0.86 opepe 686 23.70 0.79 0.03 0.77 0.84 teak 569 20.70 0.69 0.02 0.66 0.72 table 6: charring rate of samples at 15% mc 30 minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 469 26.40 0.88 0.05 0.80 0.94 iroko 614 20.10 0.67 0.03 0.63 0.71 mahogany 521 23.70 0.79 0.03 0.76 0.83 mansonia 591 24.60 0.82 0.03 0.80 0.86 opepe 752 23.40 0.78 0.03 0.75 0.82 teak 657 20.70 0.69 0.02 0.67 0.71 the results of fire exposure test for specimens that were exposed for 0 to 60 minutes time interval, temperature ranged of 20° c to 300° c are shown in tables 7 to 9. as the exposure time increased (0 – 60 minutes), the charring rate gradually increasing. afara having the lowest density of 444 kg/m3 at both 9% and 12% mc among the species exhibited the highest charring rate of 0.74±0.02 mm/min. opepe species of 9.0, 12.0 and 15.0% mc had the lowest charring rates of 0.47±0.03 mm/min, 0.48±0.05 mm/min and 0.47±0.03 mm/min respectively. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 34 table 7: charring rate of samples at 9% mc (0-60) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 444 44.50 0.74 0.02 0.71 0.77 iroko 532 33.40 0.56 0.01 0.55 0.58 mahogany 439 35.70 0.59 0.02 0.57 0.62 mansonia 566 33.20 0.55 0.02 0.53 0.59 opepe 630 28.30 0.47 0.03 0.44 0.50 teak 505 29.40 0.49 0.03 0.46 0.54 table 8: charring rate of samples at 12% mc (0-60) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 444 44.50 0.74 0.02 0.71 0.76 iroko 544 32.30 0.54 0.02 0.51 0.56 mahogany 451 33.70 0.56 0.01 0.55 0.58 mansonia 580 32.80 0.55 0.02 0.53 0.58 opepe 686 28.60 0.48 0.05 0.44 0.55 teak 569 29.20 0.49 0.02 0.47 0.52 table 9: charring rate of samples at 15% mc (0-60) minutes fire exposure species mean density (kg/m3) mean char depth (mm) mean actual charring rate (mm/min) standard deviation minimum (mm/min) maximum (mm/min) afara 469 40.80 0.68 0.02 0.65 0.71 iroko 614 30.20 0.50 0.02 0.48 0.52 mahogany 521 33.90 0.56 0.03 0.54 0.60 mansonia 591 33.70 0.56 0.02 0.53 0.59 opepe 752 28.40 0.47 0.03 0.45 0.51 teak 657 29.20 0.49 0.02 0.46 0.52 3.1 comparisons of experimental charring rate results and selected models the results of the experimental charring rates based on 15.0% mc, having lowest correlation values at each of the fire exposure time interval were compared with the selected models as shown in table 10 to 12. from table 10 and figure 4, at fire exposure interval of 0-30 minutes, temperature ranged 20°c to 230° c, the results of experimental charring rate were similar to eurocode en model, and close to both australian relation and white’s model file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 35 table 10: comparisons of experimental charring model with the selected charring models result for 15% mc (0 – 30) minutes fire exposure 20°c to 230°c temperature experimental results (mm/min) calculation models result (mm/min) species density (kg/m3) char depth (mm) charring rate (mm/min) standard deviation australian standard model (mm/min) β=0.4+[280/ρ]2 eurocode5 model(mm/ min) dchar= β0 t white’s model (min/mm1.23) t =m xc1.23 afara 469 24.80 0.82 0.02 0.76 0.83 0.58 iroko 614 19.50 0.65 0.03 0.61 0.65 0.77 mahogany 521 21.30 0.71 0.02 0.69 0.70 0.70 mansonia 591 18.90 0.63 0.03 0.62 0.63 0.81 opepe 752 14.10 0.47 0.02 0.54 0.47 1.16 teak 657 19.40 0.65 0.02 0.58 0.64 0.78 figure 4: comparison of experimental charring model with the result of selected charring models for 15% mc (0-30 minutes) fire exposure temperature at 20°c to 230°c. at fire exposure of 30 minutes interval, temperature ranged 230°c to 600° c, the results of experimental charring rate were similar to both eurocode en model and white’s model, but far from the results of australian standard relation as shown in table 11 and figure 5. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 36 table 11: comparisons of experimental charring model with the selected charring models result for 15% mc 30 minutes fire exposure 230°c to 600°c temperature experimental results (mm/min) calculation models result (mm/min) species density (kg/m3) char depth (mm) charring rate (mm/min) standard deviation australian standard model (mm/min) β=0.4+[280/ρ]2 eurocode5 model (mm/min) dchar= β0 t white’s model (min/mm1.23) t =m xc1.23 afara 469 26.40 0.88 0.02 0.76 0.89 0.54 iroko 614 20.10 0.67 0.02 0.61 0.67 0.75 mahogany 521 23.70 0.79 0.02 0.69 0.79 0.61 mansonia 591 24.60 0.82 0.02 0.62 0.81 0.58 opepe 752 23.40 0.78 0.02 0.54 0.77 0.62 teak 657 20.70 0.69 0.02 0.58 0.69 0.72 figure 5: comparison of experimental charring model with the result of selected charring models for 15% mc (30 minutes) fire exposure temperature at 230°c to 600°c. at fire exposure interval of 0-60 minutes, temperature ranged of 20° c to 300° c. the experimental charring rates results were close to the three selected models results as shown at both table 12 and figure 6. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 37 table 12: comparisons of experimental charring model with the selected charring models result for 15% mc (0 – 60) minutes fire exposure 20°c to 300°c temperature experimental results (mm/min) calculation models result (mm/min) species density (kg/m3) char depth (mm) charring rate (mm/min) standard deviation australian standard model (mm/min) β=0.4+[280/ρ]2 eurocode5 model (mm/min) dchar= β0 t white’s model (min/mm1.23) t =m xc1.23 afara 469 614 521 591 752 657 40.80 0.68 0.02 0.76 0.68 0.63 iroko 30.20 0.50 0.02 0.61 0.49 0.91 mahogany 33.90 0.56 0.03 0.69 0.57 0.78 mansonia 33.70 0.56 0.03 0.62 0.56 0.79 opepe 28.40 0.47 0.02 0.54 0.47 0.98 teak 29.20 0.49 0.02 0.58 0.48 0.95 figure 6: comparison of experimental charring model with the result of selected charring models for 15% mc (0-60 minutes) fire exposure temperature at 20°c to 300°c. 4.0 conclusion the charring rates behaviour of, constructional wood species has been studied through literature review, laboratory experiments and calculations. from the experimental results of the fire exposure test, it can be concluded that density and moisture content are of great importance properties of wood, as the moisture content increases, the wood density also increases, wood with higher density exhibited higher resistance to fire. the experimental charring rate results http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 38 were similar to the two of the three selected models of eurocode 5 and white’s mode and close to the results obtained by australian standard model. heavy wood or similar members under sever fire exposure, but not absolute extreme conditions will char at similar rates to those found in fire-resistance electric furnace tests, with charring rates roughly 0.5 to 0.8 mm/min. the research showed that the charring rate of wood species was optimum at 12 percent moisture content with opepe species which had the highest density exhibited the lowest charring rate of 0.48 mm/min. based on the results obtained in this study, the following recommendations are made: (1) the charring rate of timber presented in this study were limited to only six timber species. there is the need to consider the charring rates of other timber species. (2) determination of the charring rate for different wood species with varying dimensions and check their variations and similarities. (3) systematic research on how various material properties and external factors influence the charring rate of structural wood. references adetayo, oa. and dahunsi, bio. 2017. variation of density and compressive strength before and after charring of some selected constructional timber species of southern nigeria. fuoye journal of engineering and technology, 2(2): pp. 43 – 46. adetayo, oa. and dahunsi, bio. 2018. charring rate characteristics of some selected southern nigeria structural wood species based on their fire resistance. acta technica corviniensis, bulletin of engineering tome xi, 3: pp. 91 96. astm d 143-94. 2006. standard methods of testing small clear specimen of timber. american society for testing and materials, usa. as1720.4; 1990. timber structures part 4: fire resistance of structural timber members. north sydney, australia: standard australia. as 1720.4; 2006. timber structures fire resistance for structural adequacy of timber members. north sydney, australia: standard australia. bednarek, z. 2008. influence of strength reduction of timber in fire on structural resistance. the main school of fire service journal 5. pp. 26. bednarek, z. 1996. determination of the temperature of uncovered steel constructions using numerical methods statyba, 4(8): pp. 6-10. bednarek, z., kaliszuk-wietecka, a. and wiśniewski, т. 2002. research on the influence of fire protection impregnation carried out by the vacuum and pressure method on wood dynamic strength –building review (przegląd budowlany), 10: pp. 12−14. buchanan, ah. 2001. structural design for fire safety. john wiley and sons, ltd, west sussex, u.k. pp. 421. drysdale, dd. 1998. an introduction to fire dynamics, 2nd edition. john wiley & sons ltd., chichester, uk pp. 447. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adetayo and dahunsi: comparison of experimental charring rate of some selected constructional wood species from south western nigeria with selected charring models. azojete, 15(1):25-39. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 39 en 1995-1-2: 2004 eurocode 5: design of timber structures. part 1-2: general rulesstructural fire design. european pre-standard. fredlund, b. 1993. modelling of heat and mass transfer in wood structures during fire. fire safety journal, 20: pp. 39 – 69. janssens, ml. 2002. modelling of thermal degradation of structural wood members exposed to fire international journal of fire and material, 28: pp. 2 4. purkiss, ja. 1996. fire safety engineering design of structures. oxford: butterworth heinemann, pp. 342. timber manual data file, 2004. timber species and properties. national association of forest industries. revised edition. pp. 2-18. shafizadeh, f. 1984. “the chemistry of pyrolysis and combustion”, in the chemistry of solid wood. america chemical society, washington d.c. ed. r.m. rowell, pp. 489 – 529. tran, hc. and white, rh. 1992. burning rate of solid wood measured in a heat release calorimeter. fire and materials, vol. 16: pp. 197 – 206. white, rh. and schaffer, el. 1981. transient moisture gradient in fire exposed wood slab. wood and fiber, 13: pp. 17 38. white, rh. 1988. charring rates of different wood species. phd dissertation, university of wisconsin, madison (wi). white, rh. 2002. analytical methods for determining fire resistance of timber members, in sfpe handbook of fire protection engineering, society of fire protection engineers. 3rd edition, vol.4. pp. 257 – 27 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):25-39. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 40 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):375-384 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 375 original research article shear wall provision influence on medium rise multi-storey framed building in maiduguri a. m. alkali*, l. o. onundi, and k. mohammed (department of civil and water resources engineering, university of maiduguri, maiduguri, borno state, nigeria) *corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng article information submitted 29 march, 2018 revised 5 february, 2019 accepted 10 may, 2019 keywords: shear-walls frame network aerodynamic loading multi-storey buildings abstract this study compares the aerodynamic behaviour of medium rise multistorey frame structures with and without shear walls using the local wind gust of maiduguri (47m/s) as primary data. the wind assessment was carried out in accordance with recommendations of british standard and other relevant specifications. analysis of the structural system was carried out using extended three-dimensional analysis of building system (etabs) software; where the forces, maximum floor drifts and stresses are obtained and compared. the result shows that, the displacement fora 15 storey building with shear wall was 91.44% less than same without shear walls while with increasing storey height, the differences reduce; for example, the displacement for 20 storey building with shear wall showed 81.5% lesser than same building without shear wall. this signifies that building with shear wall resist aerodynamic load more efficiently principally due to the influences of the rigidity and strategic locations of the shear wall in the building. the shear walls are usually effective in stabilizing displacements on medium rise multi-storey buildings subjected to lateral forces from wind, seismic and explosive to satisfy serviceability criteria of h/500 stipulated by most conventional standard.. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction wind is a phenomenon of great complexity because of the many flow situations arising from the interaction of wind with structures and the shear drag with the ground roughness. the significance of turbulence is that dynamic loading on a structure depends largely on the size of eddies generated along the height. the gustiness is strong at the lower levels of the atmosphere due to shear drag with features such as hills, grasses, trees and buildings. the average wind speed over a period of time in the order of 10minutes or more tends to increase with height, while the gustiness tends to decrease with height (haritos et al., 2007). structural gustiness decreases with height but vibration increases; therefore, gustiness and vibration are inversely proportional with respect to height (mendis, et al., 2007). multi-story buildings shear walls are often incorporated at strategic locations to ensure adequate stiffness to resist lateral forces induced by wind or earthquakes. the walls may be placed in the form of elevator cores, enclosed stairways, shear boxes or facade walls. such systems may be constructed in steel or concrete and may be either solid or perforated (couple http://www.azojete.com.ng alkali, et al: shear wall provision influence on medium rise multi-storey framed building in maiduguri. azojete, 15(2):375-384. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 376 shear walls). normally, shear walls are designed to resist lateral forces while the frame is assumed to carry vertical loads. columns, of course, also resist lateral forces, their contribution depending on their stiffness relative to the shear walls (houssam, 1997). shear walls provide full resistance to horizontal loadings. they are usually continuous from the top floor down to the base where they are rigidly fixed to form vertical cantilevers. there high in plane stiffness and strength make them well suited for bracing building up to about 35 stories, while simultaneously carrying gravity loading (smith and coull 1991). the types of forces resisted by shear walls are two; these are shear and uplift forces. shear forces are generated in fixed buildings by motions resulting from ground movement and by external forces like wind. this action creates shear forces throughout the height of the wall between the top and bottom shear wall connections. uplift forces however exist on shear walls because the horizontal forces are applied to the top of the wall. these uplift forces try to lift up one end of the wall and push the other end down. in some cases, the uplift force is large enough to overturn the wall over. appropriate anticipation of wind effects is an important aspect of successful multi-storey building design. by providing shear wall in some frames, the top deflection was reduced to permissible deflection. additionally, both bending moment and shear force in some frames are significantly reduced with the provision of shear wall (anshuman et al., 2011). lateral displacement and inter-story drift was studied on a square symmetric structure with walls at the centre and by the edges, and found that the presence of shear wall can affect the seismic behaviour of frame structure to a large extent this is true, because the shear wall increases the strength and stiffness of the structure the shear wall increases the strength and stiffness of the structure (shahjad et al., 2013). similar study was conducted by rasikan and rajendra (2013) that showed the displacements of multi-storey buildings with shear walls were 20% and 15% less than that without shear walls for 15 and 20 stories respectively but with the use of staad pro software. this shows the effectiveness of shear wall system is more economical for multi-story height (chnadurkar et al, 2013 and shahzad and umesh, 2013). from the foregoing, it is seen that shear wall systems are one of the most commonly used lateral-load resisting systems, which have very high in-plane stiffness and strength, which can be used to simultaneously resist large horizontal loads and support gravity loads, making them quite advantageous in many structural engineering applications. hence, this study compares the behavior of medium rise building (with and without shear wall) subjected to local prevailing wind gust in maiduguri. since, when the buildings are tall, deflection is major problem as well as beam and column sizes that are quite heavy, with lot of reinforcement congestion at the joints and they are difficult to place and vibrate concrete at those places. the study objective is how viable a typical maiduguri wind gust influence a medium rise building using extended threedimensional analysis of building system (etabs). 2.0 methodology 2.1 building model and wind load estimation the buildings were assumed to be situated on a relatively flat terrain in an open area in maiduguri, borno state of nigeria where they are exposed to winds gusting from all directions. the local prevailing wind speed of maiduguri, category ii, 100 year mean recurrent intervals is 47m/s (onundi, 2010). the research studied two different model (15 and 20 storey medium rise http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 377 buildings) with and without shear walls shown in figures (1 and 2) respectively and in addition, compared their sway characteristics when subjected to aerodynamic loadings using etabs software packages. the horizontal load and forces generated by the local aerodynamic loading were in accordance with bs6399-2(2004) and literature recommendation (onundi, 2010). the modelled reinforced concrete multi-storey buildings were 16m wide 60m long with a 45m for the 15 storey and 60m for the 20 storey heights respectively. the horizontal loads were resisted by eight (8) frames consisting of 8m two bays rigid frames interspaced at 3m centres and three (3) shear walls also positioned at 30m centres along the length of the building (figures 1 and 2) respectively. equations (1-4) bs6399-2 (2004) were used for the estimation of the equivalent wind loads (i.e. the external pressure total effect on the building for given axis). figure 1: structural layout of the model without shear walls figure 2: plan of the building structural model with shear walls (all dimension are in mm) 16 00 0 10@6000 = 60 000 80 00 80 00 x y (all dimension are in mm) 16 00 0 10@6000 = 60 000 80 00 80 00 x y file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alkali, et al: shear wall provision influence on medium rise multi-storey framed building in maiduguri. azojete, 15(2):375-384. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 378 2.2 wind load estimation the procedure for the estimation of the characteristic wind load on the building was carried out in accordance with the specification of the bs6399-2 (2004) which is the code of practice for wind load. the code offers two alternative methods for determining the loads that the structure must with stand. for all structures where the wind loading can be represented by equivalent static loads, the wind loading can be obtained either by the standard or the directional method respectively. the standard method uses a simplified procedure to obtain a standard effective wind speed, which is used with standard pressure coefficient to determine the wind loads for orthogonal design cases. whereas the directional method derives wind speeds and pressure coefficient for each wind direction, either orthogonal or oblique. in both methods, the dynamic wind pressures qs is calculated according to clause 2.1.2of the code (bs6399-2 2004). for buildings that are at most slightly dynamic, (i.e. cr< 0.25 and h <300 m, as is this case of study), the dynamic wind pressure according to (bs6399-2 2004) is given by: qs = 0.163 ve2n/m2 (1) ve = vs x sb (2) vs = vb x sq x sdx ssx sp (3) where: ve= effective wind speed, vs = the site wind speed, vb = the basic wind speed, sa = the altitude factor, sd = the direction factor, ss = the seasonal factor, sp = the probability factor and sb = the terrain factor, cr=dynamic augmentation factor the internal and external pressures that are applied to the structure are calculated from the generic expression of clause 2.1.3.2 (bs6399-2 2004). p = qscpca x a= 0.85qsca cp,wind + cp,lee 1 + cr x a 4 where: p = either the internal or external applied pressure (kn/m2), cpi= the internal net pressure coefficient or cp, wind=wind ward, cpe= the external net pressure coefficient or cp, lee-lee ward, ca= the size effect factor for either internal or external pressures, cr= dynamic augmentations factor and a=site exposure type, a= area of the building exposed to wind 2.3 analytical example (analysis procedure) the etabs three dimensional models of 15 and 20 storey buildings without shear wall (figures1) and with three shear walls (figure 2) were evaluated using preliminary geometrical dimension and properties of the structures table 1. table 1: geometrical dimensions and properties of the structures geometrical properties 15 storey 20 storey number of storey of the building model fifteen (g+14) fifteen (g+19) shear wall thickness 150 mm 150 mm grade of concrete and steel c25/30 and fyk 415 c25/30 and fyk 415 size of beam 300 x 500 mm 300 x 600 mm size of column 300 x 600 mm 350 x 600 mm slab thickness 150mm 150mm location maiduguri maiduguri http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 379 2.4 design assumptions dead load (dl) and live load (ll) complied with the requirements of bs 6399-part 1 (1996) and bs 8110-part 1(1997); whereas, the wind load calculation was as per bs 6399-part 2 (2004) respectively. loads live load 3 kn/m2 floor finishing 1 kn/m2 wind load and coefficients wind speed 47m/s terrain category 2 structure class b risk coefficient(k1) 1 topography(k3) 1 material properties the materials and their general properties are: materials properties material type concrete c25/30 unit weight 24.993kn/m3 mass per unit volume 2548.538 kg/m3 modulus of elasticity 31000 mpa shear modulus 12916.67 mpa poisson's ratio 0.2 coefficient of thermal expansion 0.00001 1/c 2.5 load combinations load combination and the distribution of those loads on various components of the structure like frame network (beams, columns, slabs) and shear walls are of critical primary importance to the design of structures. these are obtained by multiplying the characteristic loads by appropriate partial factors of safety, (bs 2.4.1.3). for example, if a structure is subjected to dead load (dl) and live load (ll) only, the design will need only one loading combination, namely 1.4dl+ 1.6 ll. however, in addition to the dead and live loads, if the structure is subjected to wind (wl) and/or earthquake (el) loads, and considering that these loads are subject to reversals actions; the following load combinations for ultimate limit state might have to be considered (bs 2.4.3): 1.4 dl 1.4 dl + 1.6 ll (bs 2.4.3) 1.0 dl ± 1.4 wl 1.4 dl ± 1.4 wl for wind load 1.2 dl + 1.2 ll ± 1.2 wl (bs 2.4.3) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alkali, et al: shear wall provision influence on medium rise multi-storey framed building in maiduguri. azojete, 15(2):375-384. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 380 2.6 etabs analysis the 3d medium rise building models were modelled and analysed as equivalent static method (clause 1.6, bs 6399-2) using etabs 2013 software. parameters such as storey maximum/average displacement, maximum shear force, axial force and maximum bending moment were calculated for the building models (building with shear walls and without shear walls, figure 3). a) building without shear walls (b) building with shear walls figures 3: typical etabs model of the multi-storey buildingswith and without shear walls 2.7 assessment of human perception criteria the human perception criterion is the evaluation given to the possible intensity of pulsation or sensation occupants are likely to feel when the multi-storey building is subjected to aerodynamic or seismic loadings. the perception criteria were therefore assessed by using the worst conditions of the coefficient for the characteristic mode of vibration as indicated by the equations (onundi, 2011). displacement y, velocity v, acceleration a, limit and human comport assessment hca for the buildings were given by equations (5, 6, 7 and 8) respectively: y = a × sin ωt (5) v = 0.101937 ωa cos (ωt) (6) a = − 0.010391 (ω2 a) cos (ωt) (7) hca =− 0.0105923 ω2a cos(wt) (8) where, y = the maximum horizontal displacements in mm, a = amplitude in mm,ω = frequency in rad/sec, t = the period for vibration for the building in sec, g = acceleration due to gravity m/s2 and hca = human comport assessment milli-g. 3.0 results and discussion this study analysed3d models for the displacements for the buildings along major axes for structural elements of 15 and 20 storey reinforced concrete multi-story buildings subjected to the influence of prevailing wind speed for maiduguri environment assessed with the recommendations of bs 6399 using the etabs 2013 software. the parameters considered as http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 381 critical were the maximum and average displacements, storey forces and moments, maximum base moments, support reactions and the variation of the displacements along the model heights. hence, the computed medium rise buildings’ displacement for both prevailing conditions are presented in figure 4. from figures 4(a and b) and table 2, were observed that the maximum top drifts or displacements of the 45m, 15 storey building without shear walls was 107.7mm which is 19.67% higher than the permissible serviceability limit state h/500 recommended by bs 8110 (1997), whereas, when compared with the result of the same building with three shear walls, only 7.7mm was recorded which is 91.44% less. similarly, the maximum top drifts or displacements of the 60m, 20 storey building without shear walls was 146.3mmwhich is 21.92% higher than the permissible serviceability limit state h/500 recommended by bs 8110 (1997) and (abdur rahman, 2012), whereas, when compared with the result of the same building with three shear walls, only 22.1mm was recorded which is 81.58% less which is obviously due to the influence of the lateral resistance offered by the shear walls and strategic location of the walls. these results are in consistent with the studies conducted by file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alkali, et al: shear wall provision influence on medium rise multi-storey framed building in maiduguri. azojete, 15(2):375-384. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 382 (rasikan and rajendran 2013) and (anshuman et al., 2011) on comparative study on building with and without shear wall, and location of shear wall in building respectively. table 2: models displacements and limiting values building model top storey displacements without shear walls (mm) top storey displacement with shear walls (mm) recommended limit %differences 15 storeys 107.7 7.7 90 91.44 20 storeys 146.3 22.1 120 81.5 the evaluation of human perception criterion at the top of 15 and 20 storey buildings without and with shear walls are presented in tables 3 and 4 respectively. table 3: 15 storey modal frequencies, periods, acceleration, human perception limits multi-storey period frequency circular frequency eigenvalue displacement amplitude velocity acceleration milli-g sec cyc/sec rad/sec rad²/sec² mm mm mm/sec mm/sec2 without shear walls 3.48 0.288 1.81 3.28 107.70 984.12 181.80 33.58 34.23 with shear walls 3.37 0.297 1.86 3.47 7.70 70.37 13.37 2.54 2.59 table 4 : 20-storey modal frequencies, periods, acceleration, human perception limits case periods frequencies circular frequencies eigenvalue displacement amplitude velocity acceleration milli-g sec cyc/sec rad/sec rad²/sec² mm mm mm/sec mm/sec2 without shear walls 3.622 0.276 1.7345 3.0086 146.300 1336.949 236.386 41.795 42.607 with shear walls 3.703 0.27 1.6967 2.8789 22.100 201.942 34.927 6.041 6.159 tables 3.0 and 4.0gives the acceleration and human perceptions criteria limits values, and this shows that the acceptable limit of 3% (30 milli-g) was exceeded of gravity for office buildings without shear walls and that was obviously due inadequacy of the frame alone to provide the necessary lateral resistance. this indicates the necessity of conducting detailed dynamic evaluation for wind tunnel as shown in literature (taranath, 2010). however, the buildings with shear walls have satisfied these recommended limits. generally, more stringent requirements are suggested for residential and hotel buildings, which would have continuous occupancy in comparison to office buildings usually occupied only part of the time and whose occupants have the option of leaving the building before there is windstorm. 4.0 conclusion in designing medium rise multi-storey buildings it is necessary not only to aim at, acquiring strength, safety and durability, but also to consider the necessity to provide adequate rigidity and serviceability criteria (comfort for occupants) due to excitation caused by the influence of lateral loadings as shear walls are often incorporated at strategic locations to ensure adequate stiffness to resist lateral forces induced by wind. therefore, it can be concluded that: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 383 bending moments and shear forces were increased at the base (i.e. ground level) in moment frames after providing shear walls in 15 and 20 storey buildings respectively. it also inferred that, because of the rigidity; shear walls and the moment frames play important roles with respect to displacement at top floor of the buildings subjected to pulsating wind gust. the limiting displacement (i.e. top drift) of h/500 is satisfactory taking into consideration the simultaneous frame and foundation rotation condition. the rigidity and stability are vital and of significant importance to arresting the throbbing influences of wind load excitation mechanism in design of tall building. the human perception criterion limit is also within the permissible value of 30 milli-g when shear walls were provided in the buildings. the limiting drift in the range of h/500 is satisfactory but more stringent value is recommended to take in to account super-structure /foundation rotation condition, which will help in achieving a better evaluation of deflection and other forms of dynamic loading. occupancy perception criterion level or motion of the building when subjected to the dynamic wind pulsation should be kept as low as 2% 3% of gravity. wind tunnel analysis method is recommended for better understanding of the dynamic behaviour of structure’s vibration and other serviceability criteria. references anshuman, s. dipendu, b. and bhavin, r. 2011. solution of shear wall location in multi-storey building, international journal of civil and structural engineering, 2(2): 493-506. alfa, r. and rajendran, mg. 2013. wind behavior of buildings with and without shear wall. international journal of engineering research and applications, 3(2): 480-485. bs. 8110. 1977.structural use of concrete (b.s 8110-part 1, 1997).code of practice for design and construction, part 1 building, british standard institution and civil engineering sector board, united kingdom. b.s. 6399. 2004. loadings for buildings (b.s. 6399 part 2, 2004). code of practice for wind loads on building british standard and civil engineering sector board, united kingdom. smith, bs. and coull, a. 1991.tall building structures analysis and design. a wiley's interscience publication, new york. chandurkar, pp. and pajgade, ps. 2013.seismic analysis of rcc building with and without shear wall. international journal of modern engineering research, 3(3): 1805-1810. houssam, at. 1997. the effect of foundation flexibility on the interaction between shear walls and frames. engineering structures, 19(12): 1036-1042. mendis, p., no, t., haritos, n., hira, a., samali, b. and cheung, j. 2007. wind loading on tall buildings, electronic journal structural engineering, special issue: loading on structures.1-14 onundi, lo. 2010. the impact of climate change on sustainable infrastructural development –a case study of the appropriate wind speed and other measures required for design of tall structures in nigeria. proceedings the 19thengineering assembly of the council for regulation of engineering in nigeria (coren) abuja, nigeria, 2010,19(1):146 – 166. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alkali, et al: shear wall provision influence on medium rise multi-storey framed building in maiduguri. azojete, 15(2):375-384. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbamalkali@unimaid.edu.ng 384 onundi, lo. 2012.dynamic analysis of wind resistant designs of multi-storey braced steel shear wall. phd thesis, civil engineering, abubakar tafawa balewa university, bauchi. onundi, lo., matawal, ds. and elinwa, au. 2010. the influence of euler critical load on the method of initial parameters for the dynamic analysis of a multi-storey building subjected to aerodynamic forces. continental journal of engineering science, 5:113-118. onundi, lo., elinwa, au., matawal, ds. and oumarou, mb. 2010. vibration analysis of high-rise buildings with narrow rectangular plane configuration using method of initial parameters. continental journal of engineering sciences, 5: 1-13. shahzad, js. and umesh, nk. 2013. effect of change in shear wall location on story drift of multistory building subjected to lateral loads. international journal of innovative research in science, 2 (9): 4241-4249. taranath, bs.2010. structural analysis and design of tall buildings. mcgraw-hill company. new york http://www.azojete.com.ng original research article shear wall provision influence on medium rise mult a. m. alkali*, l. o. onundi, and k. mohammed arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):100-108 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 100 original research article cloud-based iot monitoring system for poultry farming in nigeria a. s. gbadamosi (department of electrical and electronics engineering, federal university of technology, minna) *corresponding author’s email address: g_safiu.its@futminna.edu.ng 1.0 introduction nigeria is becoming sufficient in poultry meat due to government policies. recently, poultry farming is one of the fast paying and a very attractive job in nigeria with a net annual worth of 250 billion naira (pagani et al., 2008). poultry chicken provides nutritious food rich in high animal protein, low cholesterol and fat, and a lower amount of energy than any other kinds of poultries. however, several environmental factors limit the growth and mass production of these chickens. these factors may cause extremely high loss of birds before they reach maturity if not properly managed. environmental factors such as temperature, humidity, carbon iv oxide (co2) concentration and ammonia concentration (wu et al., 2011) determines the health condition of poultry birds. these environmental factors could be altered by installing a device that monitors the changes in these parameters. traditional methods employed in managing these parameters involves close observation using trial and error method and may increase human efforts and time. these methods may not be effective when compared with the proposed method. the introduction of internet of things (iot) has brought real-time surveillance, information analysis as regards to health conditions of the birds, remote device control, and decision and policy article information abstract the monitoring of environmental parameters of poultry farm using iot applications is no longer a new research area in the field of engineering. however, the cost of implementing most of the reviewed research work seams unaffordable to rural farmers in nigeria. this could limit the adoption and usage of such devices. in this paper, we present a costeffective cloud-based iot monitoring system for poultry farming. the system uses two vital weather parameterstemperature and humidity. the methodology adopted, employed the use of dht11 sensor (a temperature and humidity sensor) to note every change in temperature and humidity data of the farm environment. the sensed data were extracted, sampled and processed by the microcontroller before transmitting the data to a remote cloud server through the wifi module. the cloud server (thingspeak) received the sensed data, analysed the data and plot the data graphically. the plotted graph is viewed from a computer or any smart devices. the result indicates that temperature and humidity values range between 33-38°c and 3133mmhg respectively. furthermore, the results show that the device is efficient in monitoring the two environmental parameters. therefore, the efficiency of the system will no doubt provide much quicker and accurate information about change in temperature and humidity data of farm environment. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 september, 2019 revised 02 december, 2019 accepted 04 january, 2020 keywords: cloud server dht11 sensor microcontroller internet of things (iot) thingspeak. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 100-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 101 support for poultry farmers (bhavanam, 2018) which improves the efficiency and reduce labour intensity. in this paper, a cloud-based iot monitoring system for poultry farming which can generate realtime environmental-based information on maximum and minimum temperature and humidity of poultry farm to a remote server daily was proposed. the system is internet-oriented, costeffective due to the available online remote server and has a remote sensor for collection of data which can be viewed on the cloud. the optimum driving factors of this system is that it is noise-free, cloud-based analytic and offers iot-based data collection. the system analyzes samples data in every five (5) seconds. the device, of course, has little or no impact on the daily activities of the chicken and can be installed in any poultry farm to monitor environmental parameters. several research works have been done on iot-based monitoring. however, li et al. (2015) implemented a remote monitoring system for the henhouse environment based on iot technology using a mysql server. the system was designed to record all the parameters such as temperature, humidity and ammonia concentration of the henhouse. the records of all the parameters were uploaded on the mysql database. the accuracy of this system was compensated and corrected using a data loss recovery strategy software to recover data missing during transmission. the deployment of wireless sensor and mobile phone in monitoring and controlling the environmental parameters of poultry was proposed by sneha et al. (2016). the research employed all the environmental parameter sensors including the mq135 sensor module for monitoring air pollution level within the poultry farm. the results of all sensed parameters were sent to the mobile phone through the computer system using the internet. the limitation of this research is in the event of network failure or limited coverage area of the network as regards to the location of the user. the automation of poultry feeding using iot was also implemented (rupali and mahale, 2016). the implementation of this research has greatly reduced the effort of going back and forth to check if the food is enough for the birds. the use of a raspberry-pi approach to building a cost-effective monitoring device was proposed by ibrahim et al. (2015) who used a coded python programming language on a single-board of raspberry-pi to control and monitor the environmental conditions of the poultry farm. the information from the sensors was uploaded directly to the internet where it can be viewed and accessed any-where and any-time. the system can also be used to detect earthquakes through an assembled seismic sensor. the monitoring of water, food level and environmental parameters of a poultry farm were also investigated (bai et al., 2006). the system notifies the poultry manager about the internal condition of the farm through the use of wireless sensor and gprs network (jindarat and wuttidittachotti, 2015). the system can also be adopted for controlling and monitoring of humidity in agricultural, science and engineering fields (palle et al., 2016). the adoption of cc3200-based cloud iot for measuring humidity and temperature was proposed by ms. minal goswami (2017). cc3200 is the first simple-link wifi internet-on-chip launch-pad developed by texas instruments for measuring humidity and temperature graphically. the result of the measurements was sent to the cloud server for onward analysis. the research work of goud and sudharson (2015) elaborated more advanced technique of using sms to query the system using wireless sensor and mobile network. the system can be used to automatically monitor and control the environmental parameters of the poultry. one particular feature of the system is that it only receives a command from a registered mobile number. the best industrial practice was adopted in measuring all the parameters with emphasis on the welfare of the birds (corkery et al., 2013). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):100-108. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 102 the reviewed work above has no doubt brought advancement in technology. however, the cost of implementation of all these reviewed works might not be economically viable. most especially, in the rural areas of developing countries like nigeria where social amenities like electricity, good roads and water are not available. therefore, a cloud-based iot monitoring system for poultry farming was proposed. the system has less protocol in programming and employed the services of a cloud-based server ‘thingspeak’ for ease of data computation and analysis. this would reduce the cost of implementation and real-time access to information on the health conditions of the poultry birds on the farm. 2.0 materials and methods the implementation of the system was based on the general knowledge of iot applications which involve five (5) sections namely; sensing unit, microcontroller unit (mcu) embedded with wifi, the display unit, the cloud services (thingspeak database) and the power unit as shown in figure 1. each of the specified sections were embedded together to form a functional modular system. the cloud-based iot monitoring system was set up and powered using a 3-5.5v battery bank on a school farm located in tunga area of minna. the sensing unit comprising of humidity and ntc temperature modular component (dht11) powered-on and allow to initialized to undergo the unstable stage. the sensor was then calibrated with an accurate humidity calibration. the calibration coefficients were stored in the otp memory as a program used by the sensor’s internal signal detecting process to set the data single-bus to a high voltage level. this establishes a communication platform between the mcu and the sensor component (dht11) which takes about 20-40µs. the sensor senses the temperature and humidity of the poultry farm, and sends the information to the mcu for further processing. the mcu processes the sent information and transmits it to the wi-fi module through the universal synchronous receiver/transmitter (usart) for onward transmission to the database on the cloud using specific communication protocols. the mcu used, is an atmega 328p programmable iot-oriented application component, initially configured to interface with the sensing unit, wi-fi module and the display unit. temperature& humidity sensor display unit sensing unit microcontroller unit cloud services power unit figure 1 schematic diagram of cloud-based iot monitoring system http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 100-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 103 the cloud database received the data collected from the mcu, analyzed it and plot the data graphically in real-time. the database uses api to stock and recalls data from things using hypertext transfer protocol (http) over the internet (the mathworks, 2018). the document is a plain text-file with special markup tags that uses a web browser to interpret and displays information on the device screen. the webpage of the database can be implemented by logging-on to the website (the mathworks, 2018) as illustrated in figure 2, 3, 4 and 5. the cloud services employed for the research is thingspeak. the selection of thingspeak was based on the cost-effectiveness, open-source access of the database, analysis and data computation of the sensed data and easy implementation for visual monitoring of the poultry from any remote location. figure 3 login into the account created [the mathworks, i. (2018)] figure 2 creating an account in thingspeak [the mathworks, i. (2018)] file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):100-108. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 104 the display unit displays the sensor reading on a 16 x 2 liquid crystal display (lcd). the configuration of the display unit involves interfacing with the mcu in a four (4) bit modes as well as with the power supply as illustrated in figure 6. the power supply was connected to the vdd of the lcd and grounded through the vee pin. the vee pin was used to vary the contrast of the lcd screen. pins of lcd namely, rs, en, d4, d5, d6 and d7 are all connected to arduino digital pin 14, 15, 16, 17, 18 and 19 respectively which ensures the lcd output the sensor readings as displayed in figure 10. the entire circuit diagram was designed using proteus 8 professional. figure 4 creating of channel [the mathworks, i. (2018)] http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 100-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 105 the dc power supply was a source from the usb lithium battery pack with 2800mah. the choice of the power source was due to the portability and reliability characteristics of the battery bank. the sample diagram of the power supply is illustrated in figure 7. 3.0 results and discussion the results from the prototype system were obtained after successful connection of various components of the proposed cloud-based iot monitoring system to the network. the manager or the user can log-on to the designed webpage (www.thingspeak.com) with the created username and password to view the plot in the variation of both humidity and temperature as shown in figures 8 and 9 respectively. the information was also displayed on the display unit (lcd) as depicted in figure 10. figure 6 circuit diagram of cloud-based iot monitoring system figure 7 12v/5v dc (usb) rechargeable 2800mah lithiumion battery pack figure 8 plot of humidity variations file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):100-108. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 106 the plot in figure 8 shows the fluctuations in the value of humidity within the farm environment. the data were plotted within an interval of 5s which is an indication that the sensed data are sampled, collated and transmitted in every 5s. the value of the humidity varies from 3133mmhg as indicated in figure 8. it was also observed that; as the humidity increases from 31 32mmhg, the temperature of the poultry farm remains largely constant within the value of 33°c of the said value range of humidity. the fluctuations in the value of the temperature were also observed within the same interval of 5s time. the value of 38°c was recorded as observed in figure 9 as the highest temperature value. the straight-line graph observed within the first 5s in both figure 8 and figure 9 was due to the failure in power. the complete prototype of the proposed system is displayed in figure 10. the results above were view on a thingspeak webpage in real-time. the proposed system has been able to measure and analyze the humidity and temperature of a sample poultry farm. this proves the reliability and efficiency of our system in monitoring temperature and humidity parameter within any poultry farm in nigeria. 4.0 conclusion humidity and temperature are one of the important variables for the proper performance of any poultry farm. therefore, the monitoring of these parameters is of utmost importance. the research “cloud-based iot monitoring system for poultry farming” has been achieved. the figure 10 prototype of the described system figure 9 plot of temperature variations http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 100-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 107 research work has brought in a more cost-effective system for monitoring the condition of poultry birds on the farm. the system is cost-effective because it uses an already installed online remote server that can analyze and compute data graphically aside from the reduced cost implication associated with managing poultry farm. the results obtained from the system indicate that temperature and humidity have the value between 33-38°c and 31-33mmhg respectively. it can also be deduced from figures 8 and 9 that, the temperature remains constant with a value of 33°c for a value range of 31 – 32 mmhg of the measured humidity. therefore, if the temperature and humidity of the poultry farm are maintained and monitored with the aid of the system, it will enhance the quality and quantity of chicken produced. thus, guaranteed the health of the poultry birds which could reduce the cost, time and intensive labour spent on the farm. references bai, hw., teng, gh., ma, l., yuan, zd. and li, cy. 2006. layer healthy breeding management information system based on internet. transactions of the canadian society of agricultural engineers, 22: 171-173. bhavanam, dsn. 2018. iot in poultry and farming. university college of engineering and technology acharya nagarjuna university. available at:https://www.aphrdi.ap.gov.in/documents/trainings@aphrdi/2018/4april/digitalworld/iot in poultry & farming.pdf. accessed on 19th june 2019. corkery, g., ward, s., kenny, c. and hemmingway, p. 2013. monitoring environmental parameters in poultry production facilities. in computer aided process engineering-cape forum. institute for process and particle engineering, graz university of technology, austria. goud, ks. and sudharson, a. 2015. internet based smart poultry farm. indian journal of science and technology, 8(19): 1-5. ibrahim, m., elgamri, a., babiker, s. and mohamed, a. 2015. internet of things based smart environmental monitoring using the raspberry-pi computer. in fifth ieee international conference on digital information processing and communications (icdipc), pp. 159-164. jindarat, s. and wuttidittachotti, p. 2015. smart farm monitoring using raspberry pi and arduino. in ieee international conference on computer, communications, and control technology (i4ct)., pp. 284–288. li, h., wang, h., yin, w., li, y., qian, y. and hu, f. 2015. development of a remote monitoring system for henhouse environment based on iot technology. future internet, 7(3): 329-341. ms. minal goswami, kb. 2017. iot based smart greenhouse and poultry farn environment monitoring and controlling using lamp server and mobile application. international journal of advance research and innovative ideas in education (ijariie), 03(2): 4114–4125. available at: https://pdfs.semanticscholar.org/efef/b03cc72a54d052b09d4e1279cd6ac6ebf19a.pdf. pagani, p., abimiku, y. and emeka-okolie, w. 2008. assessment of the nigerian poultry market chain to improve biosecurity. fao (nigeria, consultative mission on poultry) study, food and agricultural organization, rome, pp. 1–65. palle, d., kommu, a. and kanchi, rr. 2016. design and development of cc3200-based cloud iot for measuring humidity and temperature. in ieee international conference on electrical, electronics, and optimization techniques (iceeot)., pp. 3116–3120. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):100-108. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: g_safiu.its@futminna.edu.ng 108 rupali, b. mahale, dsss. 2016. smart poultry farm: an integrated solution using wsn and gprs based network. international journal of advanced research in computer engineering and technology, 5(6): 1984–1988. available at: http://ijarcet.org/wp-content/uploads/ijarcet-vol5-issue-6-1984-1988.pdf. sneha, m., raghavendra, tn. and kumar, dhp. 2016. internet based smart poultry farm using labview. international research journal of engineering and technology, 03: 107–111. available at: https://businessdocbox.com/green_solutions/75183040-internet-based-smart-poultry-farmusing-labview.html. the mathworks, i. 2018. thingspeak documentation. available at: https://www.mathworks com/help/thingspeak/. accessed on 17th june, 2019. wu, jf., zhan, k., li, jy., liu, w., chen, gy., zhu, yc. and tang, y. 2011. effect of environment parameters of semi-enclosed layer house on production performance and egg quality of primiparity laying hen in winter. china poultry, 33: 16-20. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1). 54-60 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng. 54 development of a small scale okro slicing machine i. s. aji*, j. k. vakaa, m. j. madu, z. b. suleiman and s. b. yakda department of mechanical engineering, faculty of engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email: suleimanaji@yahoo.com; tel.: +2348037862071 abstract the technique of slicing okro using kitchen knife often exposes users to the danger of knife cut and the output of the technique has been found to be low due to the drudgery involved in the process. it was in recognition of the need to reduce drudgery, injury and associated rigors to the user and to enhance quality, hygiene and efficiency in okro processing that the research of developing a suitable okro slicing machine was initiated. a simple motorized device was developed for slicing okra using locally available materials which include: bearings, shaft, pulleys, electric motor, cutting blade, rail, bolts and nuts. the slicing mechanism was based on the high shear stress that is generated when a blade edge is brought into contact with fibrous material causing the blade to move in rotary motion and to the direction of the applied force. after coupling and testing the machine, results obtained showed that it takes 3 seconds to slice one okro using machine while in the case of manual slicing, it takes 8.22 seconds. the device has a slicing efficiency of 66.67%. the machine has shown to enhance processing of okra in small scale industry application. the machine therefore is of great importance to the industries within the country and beyond where preservation of okro in sliced and dried form is important. keywords: okro, slicer, slicing efficiency, machine 1. introduction okro also known as hibiscus esculents is very important to man and animal which cannot be overemphasized. okro is a vegetable grown on commercial and house hold consumption scale during wet and dry seasons. okro is a widely cultivated vegetable and can be found in almost every market in africa. its most reliable part is the tender and non-fibrous which is usually eaten as a fried or cooked vegetable. okro pod has so many nutritive values which includes minerals, vitamins, carbohydrates, protein and contain sizable amount of essential amino acid (adeboye and oputa, 1996; okro food, 2003). slicing is a cutting process for size reduction of fruits and vegetables. it involves pushing or forcing a thin sharp knife to shear through the materials intended to be sliced (owolarafe et al. 2007). there are different types of slicing machines designed and constructed for different purposes. this includes bread slicing machine. it works on the principle of gravity loaf in-feed system and the up-and-down reciprocating motion of the blade frame that carries 22 parallel cutting blades spaced at a regular interval of 14.5mm apart. it is driven by a 2 horsepower electric motor via v-belt. considering the results of the performance test, it was observed that the machine will serve the purpose of slicing operation at reduced vibration, reduced cost and clean slicing environment with optimum efficiency as very smooth slices were obtained (kolawole et al. 2016). aji et al. (2013) developed an electrically operated cassava slicing machine. the machine is portable and easy to operate which can be adapted to medium scale industries. others include development of plantain slicers, yam slicers, meat slicers, tomatoes slicers and many others. all these slicers work with the different principle of cutting using blades of different types. a manually operated device for slicing okro was developed by owolarafe et al. (2007) based on this mechanism has been adopted as a unit of an integrated system for okro processing by rural women in south-western nigeria because it reduced the drudgery associated with manual slicing. mailto:suleimanaji@yahoo.com http://www.azojete.com.ng aji et al.: development of a small scale okro slicing machine; azojete, 14(1):54-60. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 55 kitchen knife is the most common tool used for slicing okro but it is also associated with a lot of rigors to the users and farmers. this paper therefore presents the development of a suitable small scale okro slicing machine in other to ease the work of okro farmers and to save them from the danger of knife cut. 2. design analysis the frame is designed to carry all the machine components such as the electric motor, shaft, feeder and receiver. length of frame �겘ჵ � ���楲楲 breadth of frame �tჵ � ���楲楲 height of frame � ჵ � �͵�楲楲 since the frame shape is rectangular in shape, the area (a) of the frame is given by � � 겘ჵ � tჵ (1) � ��� � ���� � ��p��楲� according to the relations provided by khurmi and gupta (2005), speed of rotation is given by: �p �� � �� �p (2) where: n1 = speed of electric motor �ph�� �t楲� �� � speed of shaft (?), �p � diameter of the driving pulley ���楲楲� �� � diameter of the driven pulley �p��楲楲 using equation (2), �� � ����t楲 the length of the belt was determined from the relation; 겘� � �h� � �p��� � � �p��� � hh (3) where: �p � diameter of the driver pulley, �� � diameter of the driven pulley, h � distance from center to center between the driving and driven pulley ����楲楲� using equation (3), 겘� � 1479.57mm velocity of moving belt: � � ��� �� (4) � � h�㈮ 楲șஈ power driven mechanism: �p � � � �h (5) where: t = maximum tension in the tight side of the belt, tc = centrifugal tension t1 = tension in the tight side of the belt. � � � � � (6) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):54-60 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 56 where: � = maximum tension in the tight side of the belt, � = stress in the tight side of the belt, � � area of the belt �p�h 楲楲� � � ����� �� � ��䁨��� �p � ����p�� the power transmitted (p) was determined from the relation; � � �p � �� � (7) where: �p � tension in the tight side of the belt, �� � tension in the slack side of the belt � � power transmitted, � � velocity of the belt in meters per second. � � �䁨��p� shaft design: 楲 � �� (8) m = mass of the shaft, ρ = density of the shaft, v = volume of the shaft, mass of shaft is calculated as 0.381kg however, volume of shaft � � � � 겘 (9) where: a = cross sectional area and l = length of the shaft (100 mm) � � �� h (10) volume calculated to be h�㈮㈮� � p��� 楲͵ 2.1 slicing unit (cutting blade) the slicer is the basic part that does the slicing/cutting. it is made up of the transmission shaft, cutting blade and the power driven mechanism. area of cutting blade � p䁨�楲楲 � ͵�楲楲 the blade is rectangular in shade and placed horizontally on the shaft. there are four blades on the shaft. 2.2 feeder (hopper) the feeder is where the okro pods are first collected before it is discharged into the slicing unit for further processing. the feeder is designed to take an average of five (5) average okro sizes per entry. 3. materials and method the material used for the different component in this design involves the following considerations: cost and availability of the material, strength, ductility, corrosion resistance, ease of fabrication. the best selection of materials could be made after considering factors such as spectrum of material properties, ease of fabrication, its durability and alterability with frequency of use, corrosion resistance an economic-cost advantage (olagoke, 2002). the table below describes the selection of appropriate components based on some suitable reasons. table 1: selection of components http://www.azojete.com.ng aji et al.: development of a small scale okro slicing machine; azojete, 14(1):54-60. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 57 component/ construction process used transmission shaft to gears and gear trains to provide speed and torque conversions from a rotating power source to another device. pulley in order to transmit power from one rotating shaft to another. belt used as a source of motion to transmit power efficiently or to track relative movement. bearing used to enable rotational or linear movement while reducing friction. frame the construction started with the main frame; the mild steel angle iron was bought from the market and welded together after considering all the necessary dimensions. cutting blade used for slicing the okro. electric motor used to produce linear or rotary force (torque) and used to converts electrical energy into mechanical energy. 3.1 assembly and principle of operation  the construction started with the main frame.  the mild steel angle iron was welded together after considering all the necessary dimensions.  the bearings were fixed into the bearing housing of the top edge of the frame side into which the shaft was inserted.  this was followed by the mounting of the pulleys on the shaft that transmits the motion from electric motor to shaft by the use of belt.  the cutting blade and the bearings were placed on the rail in order to obtain the rotary motion as a result of connecting the shaft, and the feeder is fitted to the receiver on the frame which is joined by bolts and nuts. this machine is driven by 1hp electric motor which is the main source of power. it works on the principle of rotary motion of the blades. torque is generated on the shaft which gives the rotary motion on the pulley and transmitted by a v-belt. the rotating blade then slices the loaded okro by shear and cutting force. sliced okro is collected through the receiver fitted on the frame beneath the hopper. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):54-60 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 58 fig. 1: assembly drawing of the machine fig. 2: shows the wire frame of the machine plate 1: small scale okro slicing machine. http://www.azojete.com.ng aji et al.: development of a small scale okro slicing machine; azojete, 14(1):54-60. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 59 4. results and discussions 4.1 efficiency of the machine to obtain the efficiency of the machine: mass of unsliced okro 楲p � ��㈮ �t mass of sliced okro (楲� � ��� �t �ㄠㄠ㈮�㈮൭ㄼ�㹂 � � 楲� 楲p � p��⺁ (11) � �����⺁ okro used for the purpose of this experiment has an average of 80mm length, 30mm diameter and 10mm thickness. table 2: results of load testing specimen (䁨� � ͵� � p�楲楲 of okro) sample number of okro time (sec) average sample result of slicing operation using machine a1 1 3.28 1 b1 1 2.95 2.992sec c1 1 3.62 d1 1 2.16 e1 1 2.95 sample result of slicing operation using machine a2 4 5.05 b2 4 6.02 4.556sec 2 c2 4 2.49 d2 4 6.23 e2 4 2.99 sample results of slicing operation manually a3 1 9.18 3 b3 1 8.23 8.22sec c3 1 8.00 d3 1 7.90 e3 1 7.80 from table 2, the time taken to slice one okro at a time for sample a1 to e1 is within the range of 2.16 seconds to 3.62 seconds respectively. the average time taken to slice one okro is 2.99 seconds. approximately 3 seconds was used to slice one okro, this shows greater efficiency of the machine for use in okro slicing units semi-industrial use. furthermore, the machine can slice up to 5 okro at a time, this can help increase the total quantity of okro to be processed. the time taken to complete the operation for sample a2 to e2 is within the time frame of 2.496 seconds to 6.23 seconds respectively. the average time taken to slice four (4) okro is 4.55 seconds, which is an indication of utilizing little time to process the okro using the slicing machine. similarly, result in table 2 show that the use of knife to slice one pod of okro at a time is within the range of 7.80 seconds to 9.18 seconds. the average time taken to slice one okro manually is 8.22 seconds. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):54-60 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 60 manual processing shows less efficiency in processing okro for small scale industries, this is in addition to the problem of hygiene which can be a factor in manual processing. comparing the test results of a1 to e1 and a3 to e3, it can be seen that the average time taken to slice or process okro using machine and knife is very far apart. the advantage of using the slicing machine cannot therefore be overemphasized. the economy in processing large quantity and the fatigue that comes in when the process is undertaken manually is obvious. 5. conclusion an okro slicing device has been developed using locally available materials as an improvement on existing manually operated devices. the machine designed and constructed is used to ease the work of processing okro thereby enhancing quality, hygiene and efficiency of okro processing in small scale industries. the average time taken to slice the okro using the machine is 3 seconds which is faster compared to manual process which is 8.22 seconds. the device is a step further in okro processing in nigeria and other places in sub-saharan african region where preservation of okro in sliced and dried form is important. references adeboye, oc. and oputa, co. 1996. effect of galex on growth and fruit nutrient composition of okra. ife journal of agriculture, 18 (1/2): 1-9. aji, is., james e., ejovwoke, a. and mshelia, da. 2013. development of an electrically operated cassava slicing machine, arid zone journal of engineering, technology and environment, 9: 90 – 95. khurmi, rs. and gupta, jk. 2008. a text book of machine design. eurasia publishing house (pvt.) ltd, ram nagar, new delhi-110 055 kolawole, ao., kehinde, at., dare, aa and afolabi, tm. 2016. bread-slicing machine. agricultural engineering international: the cigr journal, 18(2): 209-218, open access at http://www.cigrjournal.org. owolarafe, ok, muritala, oa. and ogunsina, bs. 2007. development of an okro slicing device. journal of food science and technology, 44(4): 426-429. olagoke, sa. 2002. properties of materials, 2nd edition, sao multi ventures, dugbe ibadan, nigeria. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):58-64 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 58 original research article performance studies of natural rubber�organomodified kaolin vulcanizates developed for tire sidewall applications c. o. mgbemena1 and c. e. mgbemena2 (1department of mechanical engineering, federal university of petroleum resources, effurun, delta state, nigeria 2department of industrial and production engineering, nnamdi azikiwe university, awka, anambra state, nigeria) * corresponding author’s email address: mgbemena�ogonna@fupre�edu�ng 1.0 introduction rubber clay nanocomposites �rcns� have emerged as novel advanced materials, attracting the interests of the academia and industry (bhowmick et al., 2010)� one of the unique features of rcns is the exceptional improvement in their physical ��� mechanical properties, such as barrier properties �impermeability to gases�, thermal stability, storage modulus, tensile properties, wear resistance and flame resistance at low filler concentrations� in a pioneering study, it was shown that the mechanical properties of nr with 10 phr of organo�montmorillonite are comparable to one containing 40 phr of carbon black (arroyo et al., 2003). a review of related publications on rcns shows that apart from natural rubber �nr�, various synthetic rubbers have been used along with clays such as montmorillonites, bentonites, saponite, fluorohectorites with and without organomodifiers which are mostly petrochemicalbased and are quite expensive� studies on the use of nano kaolin for vulcanised rubber article information abstract this study aims at evaluating the performance of natural rubber/organomodified kaolin vulcanizates to ascertain its suitability for tire sidewall applications. the cure characteristics, filler dispersion, tensile and tear properties and de�mattia flex fatigue characteristics of natural rubber �nr� �attra with 2�10 phr of rubber seed oil �rso�, and tea seed oil �tso� modified kaolin developed specifically for tire sidewall applications were assessed. the nr compounds containing rso and tso modified kaolin showed lower optimum cure time �t90 at 150°c� as against that containing the same dosage of unmodified kaolin� the results show significant increases in tensile modulus, tensile strength and tear strength for the nr vulcanizates containing the organomodified kaolins, compared to vulcanizates containing unmodified kaolin� �ro �taa�ara �宱tta宽 �xto宱宽ad宱qrl 宱q ���� showed better resistance to crack initiation and flex fatigue failure� the sem and afm micrographs of the vulcanizates containing organomodified kaolins also showed an excellent uniform dispersion of the filler particles in the nr matrix� �　૒ �૒�宨�宱� �i宱per૒i ��� �p宱宨�p� �宨ii૒���૒p �૒૒i �e� ��ie�e૒i �p��er �宨�opredp宱૒� p宱 �ꮜ�　� �　�⹉� p �　��宱 ��宱e�宨� o宨�૒ 宱e�૒� 　e޷　 �p䁙e�宨� 宱��ၾ宨૒� i૒宱宱૒� 宱૒p� �宱�૒r޷宱　� ૒䁙o૒��૒r宱 �૒�e�宱pro૒ 宱� o�po� ere宱ep宱e�r pri ��૒䁙 �p宱e޷宨૒ i૒　p�e�宨�⹉ �　૒�૒ erieop宱૒ 宱　p宱 宱　૒ �p宱宨�p� �宨ii૒���૒p �૒૒i �e� ��ie�e૒i �p��er �宨�opredp宱૒� p�૒ ��૒�૒��૒i �p宱૒�ep�� ��� 宱e�૒ �ei૒⹉p�� p���eop宱e�r�. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 october, 2018 revised 01 november, 2019 accepted 05 november, 2019 keywords: natural rubber organomodified kaolin nanocomposites. mailto:mgbemena.ogonna@fupre.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 58-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 59 nanocomposites are limited (dai, 1999; liu et al., 2008; mgbemena et al., 2016; puşcă et al., 2010; sookyung et al., 2014; yahaya et al., 2009). for large scale industrial applications, it is imperative that rcn compositions be tailored to meet the required technical specifications� the selection of low cost renewable natural resources such as kaolin and organomodifiers such as rso and tso for rcns could be an ideal proposition� earlier studies have shown that derivatives of rso and tso could be used as organo�modifiers for kaolin to function as �reinforcing nano�fillers� for natural rubber at very low dosages (mgbemena et al., 2013; sukumar and menon, 2008; yahaya et al., 2009)� recent findings also support the above observations (mgbemena et al., 2016). the purpose of this study is to evaluate the properties of natural rubber/organomodified kaolin nanocomposites to determine its suitability for vehicle tire sidewall applications. 2� materials and method kaolin �grade bck� was obtained from m�s� english indian clays ltd�, thiruvananthapuram� tso was obtained from nigeria� rso, nr �grade rss5� and rubber chemicals were obtained from local suppliers� the organomodified kaolins were prepared by modification of kaolin with sodium salts of the oils �rso & tso� and hydrazine hydrate according to (ihueze and mgbemena, 2016, mgbemena et al., 2013, mgbemena et al., 2016 and yahaya et al., 2009). rubber mixes, as shown in table 1 were prepared by mixing on an open, two�roll mixing mill at room temperature of 25℃� table 1� composition of mixes mix code� ingredient �phr� urk2 unmodified kaolin 2 urk6 unmodified kaolin 6 urk10 unmodified kaolin 10 mrk2 rso modified kaolin 2 mrk6 rso modified kaolin 6 mrk10 rso modified kaolin 10 mtk2 tso modified kaolin 2 mtk6 tso modified kaolin 6 mtk10 tso modified kaolin 10 � base mix� nr 100, zno 5, stearic acid 2, sulfur 2, mercapto benzothiazole 2 2�1 characterizations of the materials the cure characteristics at 150°c of the mixes were tested with an oscillating disk rheometer �odr� [mv-odr brand; micro-vision enterprises, india] according to astm d 5289 � 1979� the essential data deduced from the rheographs are as follows� the minimum torque �ml�, maximum torque �mh�, scorch time �ts2�, optimum cure time �t90� and cure rate index �cri�� the tensile properties of the vulcanizates were according to is: 3400 (part 1) � 1977. the resistance to flex cracking of the vulcanizates was measured on a goodrich flexometer according to is: 3400 (part 7) � 1985 and is: 3400 (part 8) � 1983. the tear strength of the vulcanizates was measured with a universal testing machine �hounsfield h5 ks; united kingdom� according to standard astm � d624�86� the fracture surfaces of the vulcanizates were file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mgbemena and mgbemena: performance studies of natural rubber�organomodified kaolin vulcanizates developed for tire sidewall applications. azojete,16(1):58-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 60 observed under a scanning electron microscope �sem model �jsm 5600lv; jeol, usa� after sputter coating with gold� 3d images of the failure surfaces of the vulcanizates were obtained using an atomic force microscope �afm model � nt�mdt, russia� using the tapping mode probe� 3� results and discussion 3�1 cure characteristics and scanning electron microscopy table 2 shows the results on the cure characteristics of the rubber compounds at 150°c, as obtained from odr� table 2� cure characteristics at 150°c of nr compounds containing unmodified and organomodified kaolin mix code scorch time, ts2 �s� optimum cure time, t90 �s� minimum torque ����om� maximum torque ����om� ��� � ��� � ����om� cr= 100 �90���2 (min) urk2 113 274 0�58 4�71 4�13 37�17 urk6 99 273 0�51 5�16 4�65 34�48 urk10 93 255 0�80 5�51 4�71 37�04 mrk2 82 222 0�60 5�20 4�60 42�92 mrk6 86 205 0�71 5�56 4�85 46�51 mrk10 78 222 1�07 5�58 4�51 41�67 mtk2 91 250 0�65 5�19 4�54 37�74 mtk6 84 234 0�87 5�65 4�78 40�00 mtk10 63 216 0�84 6�80 5�96 38�46 the observed reduction in scorch time and optimum cure time of the mixes as above is similar to that reported by liu et al. (2008). liu et al. (2008) has reported that the smaller value of minimum torque �ml� is related to slightly large size of kaolinite flakes and weaker interactions between kaolinite particles. thus, the higher values of ml for the mixes containing rso modified kaolin and tso modified kaolin could be an indication of smaller sizes of kaolinite flakes and more interaction between them, as evidenced by sem images of vulcanizates containing nr�unmodified kaolin at 10 phr in figure 1; nr/rso modified kaolin in figure 2 and nr/tso modified kaolin in figure 3� however, the increases in cure rate index �cri�, maximum torque �mh� and delta torque ���� of the mixes containing rso and tso modified kaolins as against that of the unmodified kaolin indicate an overall increase in the ultimate state of cure and crosslinking efficiency in presence of the organomodified kaolins� a previous report also shows a higher cure rate and state of cure for nr containing rso modified kaolin (sukumar and menon, 2008)� http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 58-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 61 figure 1� sem micrograph for nr/unmodified kaolin (10 phr) figure 2� sem micrograph for nr/rso modified kaolin (10 phr) figure 3� sem micrograph for nr/tso-modified kaolin (10phr) 3�2 mechanical properties the result on the mechanical properties of the vulcanizates is given in table 3. the crack initiation and failure frequencies in the de mattia flex�crack test are almost similar for all the vulcanizates, except that the vulcanizates containing 2�6 phr of tso modified kaolin show some improvements over that containing the same dosage of unmodified kaolin� it shows that in all the vulcanizates there is a steady increase in the tensile modulus with the increase in dosage of filler from 2 to 10 phr� however, the values for the vulcanizates containing rso modified kaolin and tso modified kaolin are higher than that containing the same dosage of unmodified kaolin� a higher degree of intercalation in the morphological structure resulted in higher tensile file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mgbemena and mgbemena: performance studies of natural rubber�organomodified kaolin vulcanizates developed for tire sidewall applications. azojete,16(1):58-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 62 strength and other mechanical properties; this was particularly the case of rso-modified kaolin/nr composites at 10 phr filler loading where there was an increase in tensile strength which is attributed to the increase in interfacial area of kaolin platelets and good interaction between the kaolin platelets as clearly seen in the sem and afm morphologies of rso-modified kaolin at 10 phr and a magnification of 10000x. poor filler dispersion lowers the tensile strength of the material. the surface chemistry of the layered silicates in a polymer matrix plays a crucial role in composites formation. electrostatic forces present in the silicate layers could complicate the filler dispersion in the polymer matrix. the incompatibility between the hydrophilic silicates and the hydrophobic polymer results in strong inter-particle forces and agglomeration as indicated at 10 phr pristine kaolin filler loading. table 3� mechanical properties of nr vulcanizates containing unmodified and organomodified kaolins sample code tensile modulus m�300� �mpa� tensile strength �mpa� elongation at break ��� de mattia flex tear strength �kn�m� crack initiation �cycles� failure �cycles� urk2 1�42 13�1 696 71884 373451 12�78 urk6 1�64 12 628 69488 206057 27�48 urk10 2�00 12�7 712 75016 298065 26�79 mrk2 1�9 11�7 658 62116 194867 16�20 mrk6 2�19 15�8 649 52116 225380 24�73 mrk10 2�35 15�8 625 63126 290584 18�46 mtk2 1�17 11�1 815 74629 272480 22�20 mtk6 2�01 16�2 687 73542 256491 24�79 mtk10 2�73 20�7 648 74172 288283 29�29 3�3 the atomic force microscopy �afm� the results obtained from the tensile tests and sem revealed that the following selected composites have high tensile strength: nr/unmodified kaolin composites at 10phr, nr/rubber seed oil modified kaolin composites at10phr and nr/tea seed oil modified kaolin composites at 6phr. these three composite samples were further analyzed by afm using the tapping mode probe. the afm 3d images of nr vulcanizates are shown in figures 4�6 respectively� figure 4� 3d image of nr vulcanizate containing unmodified kaolin (urk10) figure 5� 3d image of nr vulcanizate containing rso modified kaolin (mrk10) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 58-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 63 figure 6� 3d image of nr vulcanizate containing tso modified kaolin (mtk 6) the 3d images for the unmodified kaolin filled nr composite as indicated in figure 4 clearly show filler agglomeration within the nr matrix. in figure 5 the 3d image in nr/rso-modified kaolin composites further revealed a good dispersion of the fillers on the rubber matrix as indicated by the white colored peaks while in figure 6 the level of dispersion of stso-modified kaolin is an indication that the fillers were well intercalated on the nr matrix. 4� conclusion the organomodified kaolins were prepared by modification of kaolin with derivatives of rubber seed oil �rso� and tea seed oil �tso�� natural rubber �nr� compositions containing 2�10 phr of the modified kaolins showed higher cure rate and state of cure, compared to that containing the same dosage of unmodified kaolin� the vulcanizates containing the organomodified kaolins showed an increase in tensile modulus, tensile strength, tear strength and resistance to fatigue failure� morphological analysis of the vulcanizates using sem and afm showed a more uniform distribution of smaller kaolinite particles in the nr matrix, upon organomodification with rso and tso� �　૒ �૒�宨�宱� �i宱per૒i ��� 宱　૒ ��宱e�宨� o宨�૒ 宱e�૒�� �p䁙e�宨� 宱��ၾ宨૒� pri 宱૒p� �宱�૒r޷宱　� �� 宱　૒ �宨�opredp宱૒� �宨�宱　૒� �૒�૒p�૒i 宱　p宱 ������ ��ie�e૒i �宨�opredp宱૒� p宱 �ꮜ�　� ⹉p� ��宨ri 宱� i૒ 宱　૒ i૒�宱 �p宱૒�ep� ��� 宱e�૒ �ei૒⹉p��� ⹉e宱　 宱　૒ �p�宨૒� �i宱per૒i p� �q⹉�qg��� ��� 宱　૒ 宱૒p� �宱�૒r޷宱　� �⹉䁒ꮜi�� ��� 宱　૒ �p䁙e�宨� 宱��ၾ宨૒ pri ���� ��� 宱　૒ optimum cure time, t90 as indicated in tables 2 and 3. this observation is in tandem with an earlier study on mechanical properties of industrial tire rubber compounds which posited that nr compounds with higher torques and shorter cure times are better sidewall materials (bijarimi, zulkafli, and beg, 2010). acknowledgements the authors would like to thank dst, new delhi and cics, chennai for the award of rtfdcs fellowship one of the authors under which programme this work was carried out� our sincere thanks to niist, thiruvananthapuram for providing the necessary facilities and to the technical consultancy division, rubber research institute of india, kottayam for the measurements of cure characteristics, mechanical properties and resistance to fatigue failure� references arroyo, m., lópez-manchado, ma. and herrero, b. 2003. organo-montmorillonite as substitute of carbon black in natural rubber compounds. polymer, 44: 2447–2453. bhowmick, ak., bhattacharya, m., mitra, s., kumar, kd., maji, pk., choudhury, a., george, jj. and basak, gc. 2010. morphology–property relationship in rubber-based nanocomposites: some recent developments. in: pp.1–83. available from: http://link.springer.com/10.1007/12_2010_95 [accessed on 11 october 2018]. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mgbemena and mgbemena: performance studies of natural rubber�organomodified kaolin vulcanizates developed for tire sidewall applications. azojete,16(1):58-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mgbemena.ogonna@fupre.edu.ng 64 bijarimi, m., zulkafli, h. and beg, mdh. 2010. mechanical properties of industrial tyre rubber compounds. journal of applied sciences, 10(13):1345–1348. dai, j. 1999. surface modification of clays and clay–rubber composite. applied clay science [online], 15(1–2):51–65. ihueze, cc. and mgbemena, co. 2016. computational modelling of a p195/55 r16 85h radial tire developed from natural rubber/ tea seed oil (camellia sinensis) modified kaolin vulcanizates. journal of presidency university, 3(2):1–10. liu, q., zhang, y. and xu, h. 2008. properties of vulcanized rubber nanocomposites filled with nanokaolin and precipitated silica. applied clay science, 42(1–2):232–237. mgbemena, co., ibekwe, no., sukumar, r. and menon, arr. 2013. characterization of kaolin intercalates of oleochemicals derived from rubber seed (hevea brasiliensis) and tea seed (camelia sinensis) oils. journal of king saud university science, 25(2):149–155. mgbemena, co., ihueze, cc. and menon, arr. 2016. performance characteristics and analysis of tailored natural rubber/organo-kaolin composites. international journal of plastics technology , 20(1):11–27. puşcă, a., bobancu, ş. and duţă, a. 2010. mechanical properties of rubber-an overview. bulletin of the transilvania university of braşov, 3(52):107–114. sookyung, u., thaijaroen, w. and nakason, c. 2014. influence of modifying organoclay on the properties of natural rubber/organoclay nanocomposites. journal of composite materials, 48(16):1959–1970. sukumar, r. and menon, arr. 2008. organomodified kaolin as a reinforcing filler for natural rubber. journal of applied polymer science, 107(6): 3476–3483. yahaya, le., adebowale, ko. and menon, arr. 2009. mechanical properties of organomodified kaolin/natural rubber vulcanizates. applied clay science, 46(3):283–288. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):342-354 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 342 original research article investigation of the mechanical and microstructural properties of welded api x70 pipeline steel t. m. ike, o. adedipe, s. a. lawal*, m. s. abolarin and o. a. olugboji department of mechanical engineering, federal university of technology, minna, nigeria *corresponding author’s e-mail address: lawalsunday@futminna.edu.ng article information submitted 23 june, 2018 revised 25 november, 2018 accepted 5 january, 2018 keywords: base metal sea water ambient air welded joint haz abstract the mechanical properties of pipelines particularly those in marine environments are influenced by corrosion activity of seawater throughout their service lives. the degree to which these properties are influenced in seawater compared to those exposed to air needs to be better understood. in this study, the chemical composition of api x70 pipeline steel plate, microstructure and mechanical properties of the welded joints of same steel plates exposed to ambient air and seawater respectively were investigated. it was found that the base metal consisted of manganese (0.51wt% mn), low carbon content (0.051 wt% c) and small quantities of alloying elements such as vanadium (0.021wt% v), molybdenum (0.118 wt% mo), chromium (0.240 wt% cr), copper (0.002 wt% cu), and a carbon equivalent (ce iiw) of 0.38. scanning electron microscope (sem) showed that the microstructure of base metal sample has large grains formed in packets which have certain crystallographic orientation but contain submicron grains arranged in a chaotic interlocking manner. the tensile tests performed using a united type universal testing machine confirmed that the yield strength of the base metal was 573.045mpa which conforms to api standard for x70 steel pipe. the manual metal arc (mma) welding technique was applied to produce the welded joints. for the welded joints exposed to ambient air at room temperature, the yield strength was 680.624mpa while the compressive strength was 1500.2mpa, and the impact energy at -10°c was 112.68j. air tests referred to tests conducted in the laboratory at room temperature. for the welded joints exposed to seawater for 12 weeks, the yield strength was 609.154mpa while the compressive strength was 1219.34mpa, and the impact energy at -10°c was 61.48j. the above results for air and seawater exposures were used to determine the environmental reduction factors of the two environments. hardness tests conducted using vickers hardness tester revealed variations in hardness across the base metal, the haz and the weld, with the weld having the highest average vicker’s hardness value (223.8hv) followed by the base metal (217.3hv) and the haz had the least (214.5hv) © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in various service environments, pipelines used for the transport of natural resources including oil and gas present an enormous challenge as the failure of the pipeline is always associated with serious environmental damage and heavy losses (hopkins, 2007). most often, the failure mailto:lawalsunday@futminna.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):342-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 343 starts at welded joints that join different elements of pipeline steel (nanninga et al., 2010). the pipeline industry has shown an increasing demand for pipeline steel that can transport diverse and higher quantities of petroleum products at higher operating pressures across hostile (marine) environments and this has led to the use of higher strength steel grades (fabian et al., 2010). current pipeline materials in the world market are often regulated according the american petroleum institute’s (api) standard 5l. the main design considerations outlined in api-5l are based on alloy chemistry and tensile strength. the chemical compositions of the x-grade steels are such that there are maximum limits on c, mn, s, p in combination with dispersoid-forming elements such as niobium and vanadium (omale et al., 2017). the variations in strength (for example, between x70 and x80) do not result primarily from variations in alloy composition, but from variations in the processing route of the steel (omale et al., 2017). tm processing allows the yield strength of the pipe steels to be tailored through combinations of grain refinement, precipitation hardening (micro-alloying) and phase formation (cheng and xue, 2011). the risk associated with pipeline in terms of safety of people, damage to the environment and loss of income has been a major concern to pipeline integrity managers. there have been a number of studies conducted by researchers on causes of oil pipeline failures in the oil and gas industry. nakano et al. (1993) examined the corrosion fatigue crack propagation behavior of welded carbon steels and demonstrated that crack propagation rates can be higher in hardened weld area microstructures than the parent material. omale et al. (2017) studied the microstructure and mechanical properties of welds in pipeline steel and discovered that hardness was highest in the weld bead, a bit lower in the base metal and lowest in the heat affected zone. in this study, higher density of voids was observed at the top of the weld bead than in the middle. it was also demonstrated that large grains and dislocation density in heat affected zone is related to the high susceptibility of the steel weld to failure under tensile load. aliu (2012) investigated the mechanical and microstructural properties of welded joint of nigerian national petroleum corporation pipelines and observed that the pipeline was made of high strength low alloy (hsla-a105) steel. at the end of the investigations, it was concluded that inadequate mechanical tests and lack of micro structural examination of the welded joints before installations were possible sources of pipeline failures. omale et al. (2017) studied the evolution of microstructure, texture and mechanical properties of api x70 pipeline steel after different thermomechanical treatments using a combination of x-ray diffraction and electron backscatter diffraction (ebsd). the investigations revealed that different microstructure consisting of polygonal ferrite, bainite, coarse and fine acicular ferrite grains was obtained with a centre line segregation traversing through and parallel to the rolling direction. ebsd investigations confirmed that both dynamic recovery and partial recrystallization occurred during hot rolling requiring further annealing for a more homogenous equiaxied grain structure. it was also observed that after accelerated cooling, the fast cooling rate and low temperature interruption allows the formation of more bainite which in turn increased the tensile strength of the steel. leonardo et al. (2014) investigated the microstructure and mechanical properties of two api steels for iron ore pipelines. a chemical analysis of x70 steel was performed by means of a thermoarl optical emission spectrometer and the microstructure was observed by a jeol scanning electron microscope (sem). the chemical composition of the x70 steel used for the experimental investigation in leonardo et al. (2014) is shown in table 1. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ike, et al: investigation of the mechanical and microstructural properties of welded api x70 pipeline steel. azojete, 15(2):342-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 344 table 1: chemical composition of api-5l x70 steel (wt%) c si s p mn ni cr cu al ti nb v 0.109 0.239 0.004 0.023 1.536 0.011 0.024 0.011 0.026 0.016 0.045 0.045 source: leonardo et al. (2014) the tensile, impact and hardness tests revealed yield strength of 586mpa, tensile ultimate strength of 640mpa, a total elongation of 38%, rockwell hardness a, hra 65, and charpy impact absorbed energy of 184j (leonardo et al. 2014). however, in this study, the mechanical properties of welds exposed to ambient air and welds exposed to seawater were investigated as a means of estimating the environmental reduction factors. in this paper, mechanical tests were conducted on samples that are extracted from api x70 pipeline steel. results are presented for tests conducted in air at room temperature and are compared with results obtained from samples that are exposed to seawater, in order to have a better understanding of the influence of time dependent activity of corrosion on mechanical properties of steel. 2.0 materials and methods 2.1 materials api x70 pipeline steel plates of thickness 20.8mm with equal width and length of 304.8mm was used as the base metal or test specimen. this material was obtained from the engineering laboratory of the pipe construction company belonging to scc nig ltd at ushafa, bwari, abuja fct-nigeria. the seawater used for testing was obtained from lagos lagoon. 2.2 methods the first task carried out in order to prepare the steel plate for welding was the removal of all the impurities such as rust and oxide by cleaning the edges using iron brush. a butt joint was prepared by using cutting technique and a double v joint preparation was adopted to make for easier welding with less metal weld and less distortion. the manual metal arc (mma) welding technique, in flat welding positions (1g), was applied to fill the joints. a sketch of the typical joint prepared before the welding is as shown in figure 1. figure 1: diagram of weld joint prepared before welding specimen plates where: t (plate thickness) = 20.8mm, a (root opening) = 4mm, b (land thickness) = 2.4mm and c (groove angle) = 60° welding joints were produced using manual metal arc (mma) welding technique. this method was the recommended and established method used by the operators of the scc abuja test c http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):342-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 345 facility. to ensure conformity to the american society for testing and materials (astm) d114 on standard composition of seawater, the seawater was tested and analysed at the chemistry lab in river basin office, minna, niger state. a total of ten (10) tensile test specimens with welded joints were prepared, five of them were immersed into seawater, while the remaining five were exposed to ambient air. ambient air refers to the normal laboratory condition. for the compressive tests using the universal testing machine located in scc abuja, ten (10) test specimens with welded joint were also prepared; five of the specimens were immersed into the seawater, while the other five were exposed to ambient air. hardness test was also conducted using the vickers hardness tester located in scc abuja. the tests were conducted in accordance with the specifications in api 5l standard. hardness test was conducted on specimen containing sections of the base metal, heat affected zone (haz) and weld. it was ensured that the specimen was extracted in a way to encompass the weld, base material and the haz of the plate. in order to reveal the location of the haz, a slice extracted from the weld area was etched by applying 2 % nital solution. the toughness of the welds was investigated at scc abuja using the charpy method and based on the specifications in iso 148 standard. ten (10) charpy test specimens with welded joints were also prepared and likewise, five of the specimens were immersed into seawater while the rest were exposed to ambient air. the duration for the immersion into seawater for all test specimens was 12 weeks after which tensile, compressive and charpy tests were conducted. the choice of the immersion time was based on the investigators decision bearing in mind that the phenomenon of corrosion will be revealed regardless of the soaking or immersion period. at this juncture, it should be mentioned that corrosion damage is time dependent. it should therefore be expected that in simulated corrosive environment used during experimental investigation, the effect on corrosion will be revealed regardless of soaking time. microstructural examination and analysis of fracture surfaces of the samples were carried out using the scanning electron microscope (sem) located at spectral research and laboratory kaduna, while spectroscopic analysis was carried out at oshogbo machine tools. figures 1 to 4 show the pictures of test specimens used while figures 5-8 are the corresponding schematic representations. figure 1: tensile test specimen file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ike, et al: investigation of the mechanical and microstructural properties of welded api x70 pipeline steel. azojete, 15(2):342-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 346 figure 2: compressive test specimen figure 3: charpy test specimen figure 4: hardness test specimen weld figure 5: schematic of the tensile test specimen with welded joint 5 0 5 0 . 8 1 5 0 .8 20.8r 25 40 .018 rd td http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):342-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 347 weld 20mm =60mm 20mm figure 6: schematic of the compressive test specimen with welded joint figure 7: schematic for charpy-v notch specimen pm(middle left ) haz(top left 3) haz(top left 2) haz(top left 1) pm(top left ) pm(bottom left ) haz(bottom left 1) haz(bottom left 2) haz(bottom left 3) weld(bottom 1) haz(middle left 3) haz(middle left 2) haz(middle left 1) haz(top right 1) haz(top right 2) haz(top right 3) pm(top right) pm(middle right ) pm(bottom right ) haz(bottom right 3) haz(bottom right 2) haz(bottom right 1) haz(middle right 1) haz(middle right 2) haz(middle right 3) weld(bottom 2) weld(bottom 3) weld(top 1) weld(top 2) weld(top 3) weld(middle 1) weld(middle 2) weld(middle 3) figure 8: schematic of hardness test specimen showing the various points of indentation 3. results and discussions the following sections present the results of microstructure, chemical properties of the steel that was used for investigation as well as the results and discussions of the mechanical tests such as tensile, compressive toughness and hardness tests. 3.1 microstructure of base metal the micrograph obtained from base material through sem is shown in figure 9 where large grain sizes can be observed, and this depicts ductility. basically, ductility is caused by the slip phenomenon of crystals and slip lines are confined to the grain boundaries. the finer the grain file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ike, et al: investigation of the mechanical and microstructural properties of welded api x70 pipeline steel. azojete, 15(2):342-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 348 sizes may be related to the lesser ductility. however, in case of larger grains, larger amounts of slip could occur thus, giving better ductility (morris, 2013). figure 9: microstructure of base metal in air (1,500x) 3.2 chemical composition of base metal spectroscopic analysis involves the dispersion of an object's light into its component colors (i.e. energies). by performing this dissection and analysis of an object's light, one can infer the physical properties of that object (such as temperature, mass, luminosity and composition). table 2 contains the chemical composition and ce of the base metal after the spectroscopic analysis was conducted. table 2: chemical composition of sample base metal elements %c %si %mn %cr %mo %ni %v %cu %al ce (iiw) base metal 0.051 0.210 1.510 0.240 0.118 0.071 0.021 <0.002 0.048 0.38 3.3 seawater analysis the laboratory analysis of the seawater put the ph level at 7.8 and showed that the percentage composition of the seawater as: sodium chloride (nacl) was 58%, magnesium chloride (mgcl2) was 26%, sodium sulfate naso4 was approximately 10%. other salts present in small amounts include calcium chloride (2.4%), potassium chloride (1.3%), sodium bicarbonate (0.5%), and sodium fluoride (0.007%). the values are in agreement with the astm d1141 standard for the preparation of substitute seawater. 3.5 tensile strength five tensile test results for welded joints exposed to air and seawater respectively were recorded and plotted as shown on figure 10. it was observed that the tensile strength of the welds reduced after exposure to seawater environment for 12 weeks. the average tensile strength of the samples that were exposed to seawater was found to be 609.154 mpa, while for those exposed to air was 680.624 mpa. the percentage reduction in tensile strength was found to be 10.5%, which implies that the corrosive activity of the seawater would be revealed irrespective of the exposure time as mentioned previously. however, it must be mentioned that investigation of mechanical properties of the unwelded samples is beyond the scope of this paper. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):342-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 349 figure 10: tensile strength for tensile test specimens with weld joints 3.6 compressive figure 11 shows that the compressive strength of all five compressive test samples with welded joint were reduced after immersion into seawater environment for 12 weeks. the average compressive strength of the samples exposed to seawater was 1209.34 mpa, while those exposed to air was found to be 280.68 mpa. the percentage reduction in compressive strength was determined to be 18.7%, which implies that the effect of soaking time was significant in compressive test samples than in samples used for tensile tests. figure 11: compressive strength for compressive test specimens with weld joints 3.7 hardness the hardness test results are shown on table 3 while figure 12 depicted the hardness profile across the weld top surface. from table 3 the weld has a higher average hardness value of 223.8 hv compare to haz which has an average value of 214.5 hv as well as the parent metal with an average value of 217.3 hv. these results obtained are in agreement with the work done by omale et al. (2017). the variations in the hardness across the weld may be attributed to several factors such as residual stresses developed just after welding. from the microstructural point of view, the high hardness in the weld may be attributed to the fine grain size, and the interlocking file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ike, et al: investigation of the mechanical and microstructural properties of welded api x70 pipeline steel. azojete, 15(2):342-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 350 nature of the ferrite grains (loureiro, 2002). one of the factors contributing to lower hardness in the haz is high heat input below its melting point and hence retention of heat in this region. the lower hardness in the haz might be explained by the intense grain growth in this region resulting from high heat input below its melting point (kacar and kökemli, 2005) table 3: vickers’s hardness values s/n part hv s/n part hv 1 pm top left 217 18 haz top right 3 230 2 pm top right 220 19 haz middle right 1 224 3 pm middle right 221 20 haz middle right 2 220 4 pm middle left 219 21 haz middle right 3 229 5 pm bottom left 214 22 haz middle left 1 229 6 pm bottom right 213 23 haz middle left 2 199 7 haz top left 1 218 24 haz middle left 3 208 8 haz top left 2 206 25 haz bottom left 1 217 9 haz top left 3 219 26 haz bottom left 2 204 10 haz top right 1 220 27 haz bottom left 3 205 11 haz top right 2 205 28 haz bottom right 1 234 12 haz bottom right 2 200 29 weld middle 2 224 13 haz bottom right 3 195 30 weld middle 3 232 14 weld top 1 218 31 weld bottom 1 231 15 weld top 2 202 32 weld bottom 2 238 16 weld top 3 213 33 weld bottom 3 232 17 weld middle 1 224 figure 12: hardness profile as a function distance from the center of weld bead http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):342-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 351 3.8 charpy the test results are shown in table 4 and represented in figure 13, it can be observed that the impact energy of the weld samples exposed to air is higher than the impact energy of the weld samples exposed to sea water at all the temperatures used. the lower impact energy observed for weld samples exposed to seawater was due to the corrosive environment which affected the microstructure of the weld. the test results also confirm the work done by nakano et al, (1993), concerning corrosion fatigue crack propagation behaviour of tmcp steels. table 4: charpy impact test result type of experiment energy (j) at impact at -10°c energy (j) at impact at 0°c energy (j) at impact at 10°c test sample exposed to ambient air 112.68 150.7 240.8 test sample exposed to seawater 61.48 80.3 150.7 figure 13: fracture energy (j) and temperature (°c) 3.9 fracture surfaces of charpy test specimen figures 14(a-b) show sem images of the fracture surfaces of x70 steel charpy test specimens with welded joints. the fracture surface morphology of the specimen without exposure to corrosive environment was 100% ductile with numerous fine dimples in the fracture surface which is considered a sign of ductile fracture as shown in figure 14a. moreover, a considerable amount of necking was observed during deformation. after exposure to seawater for three months the fracture surface was still predominantly ductile and shows evidence of dimples. this specimen also shows some necking during deformation as shown in figure 14b. it means that if the specimen were exposed for a longer time, it would eventually show the characteristics of completely brittle failure. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ike, et al: investigation of the mechanical and microstructural properties of welded api x70 pipeline steel. azojete, 15(2):342-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 352 figure 14a: sem images of the fracture surfaces of weld charpy test specimen figure 14b: sem images of the fracture surfaces of weld charpy test specimen exposed to seawater for 12 weeks. 4.0 conclusions based on the characterization of structure carried out with sem, spectroscopic analysis, and investigation of mechanical properties through destructive testing experiments, the following conclusions may be drawn. 1. large grain sizes were observed in the microstructure of the sample api x70 steel plate and that implied that the steel was ductile since large grains give room for large amounts of slip to occur thus giving better ductility. the api x70 steel base metal composed of manganese (0.51wt% mn), iron (97.73 wt% fe), in combination with very low carbon content (0.051 wt% c) and minor additions of alloying elements such as vanadium (0.021wt% v), molybdenum (0.118 wt% mo), chromium (0.240 wt% cr), copper (0.002 wt% cu), and a carbon equivalent (ce iiw) of 0.38. the api x70 is therefore classified as low carbon steel with alloying elements (mn, v, cr, si, ni, mo and cu) that help in the strengthening of the ferrite 2. the average tensile strengths for welded joints exposed to air and seawater for 12 weeks were 680.624mpa and 609.154mpa respectively while the average compressive strengths for welded joints exposed to air and seawater for 12 weeks were 1500.02mpa and 150.75mpa respectively. at the temperature of zero degrees celsius and same exposure period, the charpy impact energy absorbed by welded joint exposed to air was 150.7j while that absorbed by welded joints exposed to seawater was 80.3j. necking dimples necking dimples http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):342-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 353 3. the hardness profile of welded joints showed variations in hardness across the base metal, haz and weld metal whereby the weld metal had the highest value of hardness (223.8hv) followed by the base metal (217.3hv) and the haz had the least (214.5hv). 4. the mechanical properties of the welds are compromised by exposure to corrosive environment such as seawater as observed in the results obtained from tensile, compressive, and charpy test experiments. the results showed 10.5% reduction in the tensile strength, 18.7% reduction in compressive strength and at least 37% decrease in impact energy absorbed by the welds after exposure to seawater for 12 weeks. references aliu, s. 2012. investigation of mechanical and microstructural properties of welded joint of nigerian national petroleum corporation pipelines. m. eng. thesis, federal university of technology minna, nigeria. cheng, yf. and xue, hb. 2011. characterization of inclusion of x80 pipeline steel and its correlation with hydrogen-induced cracking. corrosion science, 53(4): 1201-1208. fabian, g., heike, m., florian, g. and elke m. 2010. super-high strength steel. 2nd international conference on super-high strength steel, peschiera del garda, italy, 17th to 20th october 2010, (www.tib.eu) hopkins, p. 2007. pipeline stream, past, present, and future’ from the 5th asian pacific iiw international congress. sydney, australia. kacar, r, and kökemli, k 2005. effect of controlled atmosphere on the mig -mag arc weldment properties. materials & design, 26(6): 508-516. leonardo bg., luiz cc., rodrigo vb. and soares, lh. 2014. microstructure and mechanical properties of two api steels for iron ore pipelines. journal of universidade federal de ouropreto, mg, brazil, 17: 1516 – 1639. loureiro , aj. 2002. effect of heat input on plastic deformation of undermatched welds. journal of materials processing technology. 128(1): 240-249. morris, jw. jr. 2013. the influence of grain size on the mechanical properties of steel. department of materials science and engineering, university of california, berkeley and center for advanced materials, lawrence berkeley laboratory, berkeley, ca 94720. nakano, y., matsumoto, s., watanabe, o. and hatomura, t. 1993. corrosion fatigue crack propagation behaviour of tmcp steel. offshore mechanics and arctic engineering, pipeline technology, 5: 215-223. nanninga, n., slifa, a., levy, l. and hite, c. 2010. a review of fatigue crack growth for pipeline steel exposed to hydrogen” journal of reserve national institution standard technology, 115 (6): 437-452. omale ji., oheri, eg., tiamiyu, aa., eskandari, m. and szpunar, ja. 2017. microstructure, texture evolution and mechanical properties of x70 pipeline steel after different thermo mechanical treatments. material science and engineering, 703: 497 – 485. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ike, et al: investigation of the mechanical and microstructural properties of welded api x70 pipeline steel. azojete, 15(2):342-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lawalsunday@futminna.edu.ng 354 nomenclature: haz heat affected zone api american petroleum institute iiw international institute of welding astm american standards for testing materials aws american welding society sem scanning electron microscope ebsd electron back scattered diffraction dwtt drop weight tear test tem transmission electron microscope saw submerged arc welding mma manual metal arc welding tmcp thermo mechanically controlled processing hv vickers hardness number ce carbon equivalent od outside diameter bm base metal fz fusion zone n newton x70 graded steel specification wt weight oc degree celsius α alfa particle γ gamma particle µm micrometer mpa mega pascal kg/l kilogram per litre g/l gram per litre n/mm2 newton per millimeter square http://www.azojete.com.ng original research article investigation of the mechanical and microstructura t. m. ike, o. adedipe, s. a. lawal*, m. s. abolar arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):461-469 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 461 original research article performance and economic analysis of kainji hydropower plant in nigeria i. k. okakwu1*, a. s. alayande2 and o. e. olabode3 (1department of electrical and electronics engineering, university of benin, benin city, nigeria 2department of electrical and electronics engineering, university of lagos, akoka-yaba, nigeria 3department of electronic & electrical engineering, ladoke akintola university of technology, ogbomoso, nigeria) *corresponding author’s e-mail address: igokakwu@yahoo.com article information submitted 29 march, 2018 revised 20 april, 2019 accepted 23 april, 2019 keywords: kainji hydropower station capacity factor outage cost plant use factor performance abstract in this study, performance and economic evaluation of kainji hydropower station in nigeria from 2008 to 2017 was carried out. data including total energy generated (mwh), station service consumption (mwh), total energy sent out to the grid (mwh), average inflow rate (m3/s) and average gross operating head (m) were obtained from the efficiency department of the hydropower station from the year 2008 to 2017. mathematical models were used based on some key parameters which include: capacity factor, plant use factor, availability, power generated and economic cost of outages and operations. the result reveals that the average power generated within the period under review was 363.53mw, with a maximum of 476.95mw in 2010 and 292.44mw in 2014 as against the installed capacity of 760mw. the capacity factor of the plant was between 11.04% (2014) and 40.51% (2008) as against industry best practice of between 50% to 80%. the plant use factor ranged between 38.48% in 2014 to 62.76% in 2010 as against acceptable value of 95% and above, while the plant availability hovers between 28.69% in 2015 and 91.26% in 2009 as against the recommended standard of 99.99%. the study further reveals that the revenue loss due to system downtime was ₦169,134,293,297. this revenue loss is about 66.82% of the revenue generated which is by no means a huge amount. the above values call for the need of a total overhaul of the generating plant in order to salvage the terrible state of these plants. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in the nigerian scenario of today, access to reliable and stable power supply has become a major source of concern for both urban and rural dwellers (franco et al., 2017). this epileptic power supply in nigeria has hindered both economic and industrial development. enhancing the power generation capacity of the country has been the topmost priority of successive governments since 1999, even to the extent of declaring a state of emergency in the power sector in 2007 (gbadamosi et al., 2015). in spite of all these rhetorics, the power generation is still very far from the country’s energy demand (sambo, 2008). this huge shortfall in energy supply is marginally being addressed with an inefficient and comparatively expensive means like using gasoline and diesel generating sets (obodeh and isaac, 2011). electricity production in http://www.azojete.com.ng okakwu, et al: performance and economic analysis of kainji hydropower plant in nigeria. azojete, 15(2):461-469. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 462 nigeria entails two major methods, namely hydro and thermal, these two methods are meant to complement each other in time of difficulties (akorede et al., 2017). the hydropower is cheaper to run than the thermal and is expected to perform optimally during favorable season, while the thermal performs better at the other season when the water in the dams run down (liao et al., 2015). successive government policies in nigeria are geared towards building more thermal generating stations due to inadequate generation, without considering exploiting the hydropower potential source of the country, which is the oldest source of electric energy in commercial quantity (osakwe, 2017), or even considering revamping the existing generating plant which are in a declining state. the performance analysis of olorunsogo thermal power plant using data covering 2013-2017 was done by (okoye et al., 2017). the study showed that the performance of the plant fell short of international standard. also, (adegboyega and famoriji, 2013) did a performance study on edgeba gas turbine power plant. the outcome of their study is also not too far-fetched from other results obtained from previous studies. the performance evaluation of egbin thermal power plant for a period from 2000-2010 was studied by (adegboyega and odeyemi, 2011). their result also reveals a short fall in performance of the plant. performance analysis of some selected gas turbine plants which include afam power plant, ughelli power plant and aes power plant was again reviewed (oyedepo et al., 2015). their result revealed that the starting reliability of the plants are low compared to international standard. evaluating the outage cost due to system downtime of egbin thermal power station was also investigated by (emovon et al., 2011). in this study, performance and economic evaluation of kainji hydropower station, which is the first hydropower station with the highest installed capacity in nigeria is presented. 1.1 overview of kainji hydropower station kainji hydropower station is the oldest hydropower plant in nigeria. figure 1 shows the side view of the hydropower dam. kainji dam is a dam across the niger river in niger state of northern nigeria (madu, 2018). construction of the dam was carried out by an italian civil engineering company in 1964 and was completed in 1968. the cost of the dam was estimated at $209 million, with one-quarter of this amount used to resettle the displaced people by the construction of the dam (madu, 2018).the dam was designed to have a generating capacity of 960mw, however, only 8 of its 12 turbines have been installed, making the installed capacity to 760mw (ajeigbe et al., 2013). figure 1: side view of kainji hydropower dam (adegboyega and famoriji, 2013) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):461-469. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 463 2.0 materials and methods 2.1 data collection data for this study were obtained from the power station logbook and inventory records. data collected include installed capacity of plant, total energy generated (mwh), station service consumption (mwh), total energy sent to the grid (mwh), average inflow rate (m3/s) and average gross operating head (m) for the period between 2008-2017. based on the data obtained, the plant installed capacity was found to be 760 mw, the total energy generated in mwh depreciated appreciably from 2008 to 2014, thereafter it appreciated significantly from 2016 to 2017; several factors could be held responsible for this significant improvement in power generated between 2016 and 2017, prominent factors among others could be as a result of well planned maintenance of equipment, replacement of ageing parts and management decision. the station service consumption showed a slight difference in the amount of energy consumed within the reviewed years. also, similar trend was observed with amount of energy sent as compared to the amount of energy generated. a cursory look at the average inflow rate of water showed that the flow rate undulated within the reviewed years while the average gross operating head was observed to exhibit fairly constant values from 2008 to 2017. table 1: data obtained for energy profile of kainji hydropower plant year installed capacity of plant (mw) total energy generated (mwh) station service consumption (mwh) total energy sent out to grid (mwh) ave. inflow rate (m3/s) ave. gross operating head (m) 2008 760 2,695,223 6,334 2,688,889 1,238 33.84 2009 760 2,505,663 6,819 2,498,844 1,182 31.80 2010 760 2,300,991 4,960 2,296,031 1,451 39.42 2011 760 1,769,060 6,144 1,762,916 1,118 34.46 2012 760 1,391,853 6,473 1,385,380 1,326 32.96 2013 760 935,868 5,602 930,266 1,256 34.48 2014 760 735,062 4,268 730,794 1,021 34.35 2015 760 1,602,378 6,511 1,595,867 1,233 34.55 2016 760 2,425,464 5,887 2,419,577 1,405 34.68 2017 760 2,697,307 6,235 2,691,072 1,376 source: (kainji power station logbook and inventory records, 2017) 2.2 plant performance indices in order to access the performance of the power station, some performance indices equations were used as follows: capacity factor (cf): the cf of a plant is a measure of the usage of the generating plant. the plant’s cf was determined using equation (1) (adegboyega and famoriji, 2013). cf = energy generated in a given period installed capacity of plant×number of hours in the given period × 100% (1) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okakwu, et al: performance and economic analysis of kainji hydropower plant in nigeria. azojete, 15(2):461-469. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 464 plant use factor (puf): this is the ratio of the total energy generated during a given period to the product of plant rated capacity and number of operating hours of plant during a given period. the puf was determined using equation (2) (adegboyega and famoriji, 2013). puf = total energy generated (mwh) plant rated capacity×number of operating hours × 100% (2) availability (a): availability is the probability that a power plant will be available as required or that it will be in a state of operational effectiveness within a given period. availability is very important in achieving high performance. the availability of a plant was determined using equation (3). a = operating hour expected running hours × 100% (3) outage cost: this is the amount lost as revenue due to system downtime. system outages could be either forced outage or planned outages which are both inevitable. the cost of outage was determined using equation (4) (emovon et al., 2011). if; pf = annual power generated (mw) installed capacity of plant (mw) (4) td = expected operating hour − actual operating hour (5) actual operating hours = total energy generated (mwh) annual power generated (mw) (6) the annual expected operating hour was assumed to be 8760 hours, then the annual power outage was obtained by combining equations (4), (5) and (6); cc = pg × td × pf × uc (7) where: cc=annual power outage cost, pg=annual power generation (mw), pf =annual power factor of plant and uc=unit cost of energy (kwh). for the purpose of this study, uc value is given as ₦27.2/kwh (as at 2017) from power holding company of nigeria (phcn). 3.0 results and discussion the economic and performance of kainji hydro power station was investigated using capacitor factor, plant use factor, plant availability, annual power outage cost and generated revenue as performance metrics. applying equations (1) to (7) to analyze the data obtained, the results obtained for each of the performance metric employed was presented in table 2 yearly. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):461-469. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 465 table 2: summary of performance and economic analysis year power generation (mw) capacity factor (%) plant use factor (%) availability (%) annual power outage cost (₦) generated revenue (₦) 2008 349.33 40.48 45.96 88.07 4,562,500,791 33,696,822,324 2009 313.42 37.64 41.24 91.26 2,691,397,548 28,106,741,625 2010 476.95 34.56 62.76 55.07 32,041,336,936 39,277,351,672 2011 321.25 26.57 42.27 62.86 12,015,976,168 20,339,622,318 2012 364.43 20.91 47.95 43.60 23,484,867,938 18,153,791,442 2013 361.11 14.06 47.52 29.58 28,788,348,048 12,095,246,932 2014 292.44 11.04 38.48 28.69 19,119,257,034 7,693,424,572 2015 355.22 24.07 46.74 51.49 19,188,786,322 20,371,328,251 2016 406.30 36.43 53.46 68.15 16,485,232,823 5,269,028,002 2017 394.81 40.51 51.95 77.99 10,756,589,689 38,113,315,577 the plant full load installed capacity is 760mw, however, table 2 showed that the generated power for the period under review ranges from 292.44mw to 476.95mw. a graphical illustration depicting how the generated power varies the selected years under review was as shown in figure 2. this indicates a significant gap between installed capacity and actual power generated per year, which may be due to ageing equipment, seasonal variation in the volume of water coupled with poor maintenance culture. also, for the period under review, this short fall in generation ranges from 61.5% to 37.2%, which is against acceptable values of from 5% to 10% (obodeh and isaac, 2011). figure 2: power generation from 2008-2017 the plant cf ranged from 11.04% to 40.51% for the period under review as shown in figure 3. this is as against industrial best practice of from 50% to 80% (oyedepo et al., 2015). low value of cf is an indication of low energy generation and by economic implication, the accrued revenue will be appreciably less than operational cost. notable among other factors that can be held accountable for low value of cf is recurrent plant failure; frequent plant failure most often caused under-utilization of the plant for major part of the year (ekeh, 2008). it needs to be reiterated that high cf is beneficial and desirable for economic operation of the power plant and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okakwu, et al: performance and economic analysis of kainji hydropower plant in nigeria. azojete, 15(2):461-469. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 466 to sustain high cf value, scheduled routine maintenance should be encouraged, this will in no doubt reduce if not eliminate the occurrence of recurrent plant failure. consequently, the above trend will be drastically improved (akinbulire et al., 2007). figure 3: capacity factor from 2008-2017 presented in figure 4 is the plot of puf values obtained against the reviewed years, it was observed that puf ranges between 38.48% in 2014 to 62.76% in 2010, these values are comparatively lower as measured to the international standard of over 95% for hydropower station (oyedepo et al., 2015). puf indicates how the plant is well managed in terms of downtime. the ranges of the puf for the period under review shows huge downtime which can be attributed to excessive plant failures most often caused by poor maintenance culture (oyedepo et al., 2015). figure 4: plant use factor from 2008-2017 figure 5 shows the plant availability for the period under review (2008-2017). it was found that the plant availability ranges from 28.69% in 2015 to 91.26% in 2009. these values of availabilities are against the recommended standard of 99.99% (oyedepo et al., 2015). the poor plant availability is as a result of huge downtime which can be significantly improved upon by proper routine maintenance and personnel training on technical know-how knowledge (chris et al., 2017). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):461-469. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 467 figure 5: availability of plant from 2008-2017 figure 6 shows the plant revenue loss and revenue generated from 2008-2017. the result revealed for the period under review, the total revenue generated was ₦253,116,672,716, while the total revenue loss due to system downtime was ₦169,134,293,297. the revenue loss is about 66.82% of revenue generated which is by no means a huge amount. the management of the power station should embark on routine preventive maintenance in order to mitigate this huge revenue loss to get good returns on their investment. figure 6: cost analysis of plant furthermore, the study revealed that for the period under review, the plant cost of outage due to system downtime was ₦169,134,293,297, which is about 66.82% of revenue generated. the analysis carried out showed that the value obtained for the all the performance metrics revealed the deplorable state of the power station and as a matter of concern, the economic operation of the power station is far behind the standard. this is by no means a small value and an eye opener for the authorities concerned to do more by investing in the power plant in order to get good return on investment. 4.0 conclusion in this study, performance and economic analysis of kainji hydropower station has been investigated with specific emphasis on some key parameter indices which includes: capacity factor, plant use factor, availability and economic (cost of outages and revenue generated) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okakwu, et al: performance and economic analysis of kainji hydropower plant in nigeria. azojete, 15(2):461-469. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 468 value of plant. the study revealed that for the period under review, the capacity factor ranges from 11.04% (2014) to 40.51% (2017) as against the acceptable value of 50%-80%. the plant use factor also ranges from 38.48% (2014) to 62.76% (2010) as against accepted value of 95% and above. again, the availability of the plant ranges from 28.69% (2014) to 91.26% (2009), also against international best practices of 99.99%. the above evaluated parameters for the plant are low compared to international best practice standard. these could be attributed to a number of reasons that may include poor maintenance culture, ageing equipment, lack of personnel training, lack of spare parts among others. this study therefore recommends that routine maintenance should be given priority, in addition staff training, particular on hands-on experience should be embraced routinely and most importantly, the ageing-equipment should be replaced according to the standard specification. if these suggestions are taken into consideration, system downtime, hazard to equipment and personnel will be drastically reduced, and plant’s operational efficiency will be sustained. references adegboyega, ga. and famoriji, jo. 2013. performance analysis of central gas turbine power station, edgeba, delta state, nigeria. international journal of science and research, 2(3): 511-517. adegboyega, ga. and odeyemi, ko. 2011. performance analysis of thermal power station: case study of egbin power station nigeria. international journal of electronic and electrical engineering, 4(2): 281-289. akinbulire, to., awosope, coa., and oluseyi, po. 2007. solving the technical problems facing electrical energy development in nigeria, 3rd annual conference research and fair of the university of lagos, nigeria; pp. 175–181 akorede, mf., ibrahim, o., amuda, sa., otuoze, ao. and olufeagba, j. 2017. current status and outlook of renewable energy development in nigeria. nigerian journal of technology, 36(1):196-212. ajeigbe, oa., adeleke, ad., ibraheem, tb., olasusi, ka. and essien, ev., 2013. energy management as a way out of nigeria’s energy poverty. international journal of scientific and engineering research, 4(3): 1-5. chris, c., satish, d., mahesh, c., and deuel, e. 2017. making maintenance smarter: predictive maintenance and the digital supply network. available at: https://www2.deloitte.com/insights/us/en/focus/industry-4-0/using-predictive-technologies-forasset-maintenance.html, accessed on tuesday, june 11, 2019. ekeh, jc. 2008. positioning the power sector for electricity sufficiency in nigeria to meet up with vision 2020, 20th public lecture series, covenant university, ota, nigeria. emovon, i., kareem, b. and adeyeri mk. 2011. performance evaluation of egbin thermal power station, nigeria. proceedings of the world congress on engineering and computer science, 2: 15. franco, a., shaker, m., kalubi, d. and hostettler, s. 2017. a review of sustainable energy access and technologies for healthcare facilities in the global south. sustainable technologies and assessment, 22: 92-105. https://www2.deloitte.com/insights/us/en/focus/industry-4-0/using-predictive-technologies-for-asset-maintenance.html https://www2.deloitte.com/insights/us/en/focus/industry-4-0/using-predictive-technologies-for-asset-maintenance.html http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):461-469. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: igokakwu@yahoo.com 469 gbadamosi, sl., adedayo, oo. and nnaa, l. 2015. evaluation of operational efficiency of shiroro hydroelectric plant in nigeria. international journal of science and engineering investigations, 4(42): 14-20. liao, s., cheng, c., wang, j. and feng, z. 2015. a hybrid search algorithm for midterm optimal scheduling of thermal power plant. mathematical problems in engineering, 17(4): 1250–1257 madu, ke. 2018. prospects of improved power efficiency and operational performance of kainjidam, nigeria. international journal of innovation and sustainability, 2: 4149. obodeh, o. and isaac fo. 2011. performance analysis for sapele thermal power station: case study of nigeria. journal of emerging trends in engineering and applied sciences, 2(1): 166-171. okoye, cu., adeniji, oa. and sunmonu, ao. 2017. a study and performance evaluation of olorunsogo thermal power plant in nigeria. international journal of engineering sciences and research technology, 6(12): 151-158. osakwe, pn. 2017. unlocking the potential of the power sector for industrialization and poverty alleviation in nigeria. united nations conference on trade and development research, 6: 1-18. oyedepo, so., fagbenle, ro. and adefila, ss. 2015. assessment of performance indices of selected gas turbine power plants in nigeria. energy science and engineering, 3(3): 239-256. sambo, as. 2008. matching electricity supply with demand in nigeria. international association for energy economics, 4: 32-36 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng original research article performance and economic analysis of kainji hydrop arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):85-93 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 85 the zeta potential in crude extracts of some hibiscus plants for water treatment a. n. jones department of civil and water resources engineering, faculty of engineering, university of maiduguri, maiduguri, nigeria. corresponding author’s e-mail address: alfred_ndahi@yahoo.com abstract the aim of this study was to investigate the coagulation mechanism and turbidity removal potential of some members of the hibiscus family namely; okra crude extract (oce), sabdariffa crude extract (sce) and kenaf crude extract (kce) in treating both river water and synthetic kaolin water samples. experiments were conducted in a series of batch tests using standard jar test apparatus and a zeta sizer nano particle analyser. the results show that while the coagulation mechanism of the extract in treating synthetic kaolin water was likely due to charge neutralisation and bridging action, in the river water it was by adsorption and bridging effect caused by raw water constituents. in addition, turbidity removal performance in synthetic kaolin water sample was 94, 88 and 85% using oce, sce and kce respectively. similarly, the efficiency of oce, sce and kce in treating river water was observed to be excellent, achieving 98, 96 and 83% respectively. overall, the coagulation mechanism and residual turbidity in water treated using hibiscus seed extracts could be a feasible alternative to the conventional chemical to provide rural people with clean water in developing countries. keywords: coagulation mechanism; zeta potential; protein; crude extract; water treatment 1. introduction coagulation and flocculation are considered to be the principle behind the treatment of both water and wastewater in most conventional plant. coagulation is simply the process of destabilizing the particles by introducing metal salts to chemically change the stability of the particles in solution, such that the charge maintaining their stability is overcome by a simple charge neutralization action where the aggregate are smaller and dense (gregory, 2005). coagulation mechanism is measured by the rate of destabilization of the particles. the process is achieved through destabilization and precipitation mechanisms, such as surface charge modification, double layer compression, adsorption and particle bridging (duan and gregory, 2003, gregory, 2009). flocculation on the other hand is a slow mixing process (i.e. orthokinetic aggregation) used after the particles are coagulated. flocculation process brings together (bridging) the destabilized smaller, micro-flocs resulting from coagulation into contact with one another to form larger macro-flocs (klimpel and hogg, 1986). flocculation step is crucial and is measured by the rate of collision efficiency between particles which do not settle and are thus difficult to remove by sedimentation. in water treatment, floc formation depends on the collision efficiency (α) between the particles (gregory, 2005) where the intensity of mixing is reduced as the water proceeds through this process to achieve optimum performance. it is noteworthy that coagulation and flocculation processes are dependent on the zeta potential of the solution, which is the potential difference between the external thin surface layer of ionized particle and that of the surrounded oppositely charged ions from the liquid. in a simpler term, it is a measure of surface charge on particles in suspension. it indicates the behaviour of particles in a system and is widely related to the stability of the suspended mailto:alfred_ndahi@yahoo.com jones: the zeta potential in crude extracts of some hibiscus plants for water treatment. azojete 14(1):85-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 86 materials under given set of water characteristics. thus, any zeta potential near zero reveals the minimal electrical repulsive force and so increases the tendency of capture (gregory, 2005). all particles in water are invariably negatively charged (dentel, 1991, sharp, 2005). however, changes in general water characteristics and environment effects which generate process compliance issues, have resulted to increased application of charge measurement in the water industry. most natural colloids in water exhibit a negative zeta potential of between – 5 and − 40 mv (sharp, 2005). zeta potential is a property of an electrically charged interface which is measurable and is determine from any of following methods; electrophoresis, electro-osmosis, stream potential and sedimentation (branko, 1992, delgado et al., 2005). on the other hand, the state of a charged surface is characterized by spatial distribution of ions around the particle whereas the zeta potential is the characteristic of the charged surface. therefore, both zeta potential and charge are obtain from the same measurement (ionic measurement) using the same methods (delgado et al., 2005). it is noteworthy that the use of anionic compounds to flocculate negatively charged particle is debatable. however, in contradicting the theory of double layer compression when dealing with anionic coagulant, la mer (1966) used potato starch which is an anionic compound to flocculate kaolin particles in water. similarly, diaz et al. (1999), zhang et al. (2006) and miller et al. (2008) flocculated kaolin water with an anionic compound extracted from cactus latifaria and cactus opuntia and observe a turbidity removal performance of ˃ 90%. la mer (1966) argued that the anionic compound hydrolysed in solution where the cooh group replaces the amino groups and increases the adsorption effect of the anion at higher dosage. under high dosage, the adsorption ability increases and outweighs the electrostatic repulsions between the coagulant and the particle which later transformed to bridging action. thus, it is not out of place to say an anionic extract could flocculate negatively charged particles in water through adsorption and bridging action, and not by charge neutralization because of electrostatic repulsion between the coagulating compounds and the negatively charged particles. therefore, the aim of this study was to identify the zeta potential of the three crude hibiscus seeds, viz, okra, sabdariffa and kenaf and evaluates their mechanism of coagulation in drinking water treatment. 2. materials and methods all the three hibiscus seed (okra, sabdariffa and kenaf) samples were obtained from marama in hawul local government area of borno state-nigeria. the seeds were harvested from mature plants and the seed kernels were manually removed from the seedpod/capsules, followed by washing with tap water in civil engineering laboratory (at the university of birmingham, uk) to eliminate any surface contamination. the seed was ground into a fine powder for 2 minutes using a tema laboratory disc mill. the ground seed powders were then sieved in a set of sieves arranged in descending order. the powders retained in the 212 µm and 300 µm sieve sizes were combined, and thoroughly mixed and used in the preparation of the suspension. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):85-93. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 87 2.1 preparation and extraction of the coagulants the crude seed extract (cses) were prepared from the ground seed powders following (jones and bridgeman, 2016a) where 1.0 m nacl solutions were added to the seed powder to make 2% (w/v) suspension. the suspension was vigorously stirred using a magnetic stirrer for 15 minutes at room temperature (19±2°c). the suspension was then centrifuged at 4000 rpm for 10minutes using a heraeus megafuge16 (thermo scientific, germany). the suspension was decanted and the residual solids were dried in an oven at 50°c overnight. the weight of the dried solid material was measured to ascertain the amount of seed powder used in making the suspension. the decanted suspension was then filtered through whatman no. 42 and was then used as coagulant in a series of jar test experiments. 2.2 lipid extraction the combined seed powders were defatted using high-grade hexane in a soxhlet extractor. 20 grams of the ground powder was extracted in the extraction thimble of the apparatus. for efficient extraction, two litres of solvent volume (high-grade hexane) was heated to 60 °c. the process was run continually for 8 hours with each complete cycle taking between 2 to 3 minutes. the residue from the extraction thimble was dried overnight at room temperature (19±2°c), the dried residue was then ground into a fine powder using pestle and mortar. the ground oil-free powder was then employed in the subsequent protein purification process. 2.3 protein purification protein purification was conducted according to jones and bridgeman, (2016b) and jones (2017) where a 1 ml hitrap q hp anionic ion exchange column, (ge healthcare, sweden) was used for the purification of the proteins of interest. 2.4 collection of water sample river water samples were collected in bourn brook river adjacent university of birmingham train station in a set of one-litre (1 l) sterilised plastic containers. a total of sixty (60) representative samples (twelve sets each i.e. 12 l) from 5 location across the river were collected for the experiments. the collected water (60 l) was emptied in a single sterilised plastic bucket and the low-turbid water allowed to settle naturally before conducting any test. water samples were kept in a refrigerator at 4 °c and the tests conducted within 4 hours of collection to avoid sample deterioration. 2.5 jar test experiments jar tests were carried out using a conventional apparatus (phipps and bird, 7790-900b, usa) in triplicate, comprising six 1l beakers following (jones and bridgeman, 2016a) to evaluate the optimum coagulant dose for the determination of zeta potential in water. zeta potential was measured using zetasizer nano zsp (malvern instrument, uk). instrument temperature was kept constant at 25°c throughout the test runs. an average of 10 measurements was made for each sample and the measured data automatically logged onto a computer and the zeta potential measurement recorded. a mean value of 7 measurements was calculated using the zetasizer software. jones: the zeta potential in crude extracts of some hibiscus plants for water treatment. azojete 14(1):85-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 88 the zeta potential measurement was undertaken on the raw water sample and on the treated water samples after 1hr sedimentation in a series of jar test experiments to determine the coagulation mechanism and performance of the samples. measurements were conducted with ±2% accuracy over the entire measurement cycle. 3. results 3.1 coagulation mechanism of the extracts in synthetic kaolin water the results on the surface charge potential and turbidity reduction by oce, sce and kce on a synthetic water with a turbidity of 55 ntu are presented in figure 1. the results show that the kaolin water has an initial zeta potential of −15.5 mv, indicating that kaolin particles are negatively charged (katayon et al., 2004, miller et al., 2008). during the coagulation process, a 20 mg/l dose of oce was used to achieve a residual turbidity of less than 3.5 ntu, corresponding to 94% removal efficiency while the zeta potential of oce (ozp) treated water increased from −15.5 to −4.39 mv likely due to adsorption. the significant increase in zeta potential of the water after treatment could be due to the effect of some tap water constituents. in addition, the surface charge potential of oce was −8.3 mv as shown in table 1. incidentally, the zeta potential of oce also increased substantially from −8.3 to −4.39 mv in the clarified water. earlier work by ndabigengesere et al. (1995) reported the zeta potential of moringa oleifera (mo) stock solution to be mv and suggested that mo consists of cationic proteins. the amount of protein used for coagulation was 2.036 mg from the 20 mg/l dose, indicating that 17.964 mg of the extract are contaminants compounds in the seed that may affect its coagulation ability. further coagulant dose addition was also investigated in order to understand the effect of increasing the anionic charge in the treatment process. the addition of more dose from 40 to 100 mg/l resulted in increased turbidity due to re-stabilisation and at the same time, the zeta potential decreased further from −4.39 mv at an optimum dose to −6.6 mv at 40 mg/l, followed by a linear reduction to −8.06 mv at 100 mg/l dose. the coagulation mechanism of sce in treating synthetic water was investigated. optimum performance was achieved with 60 mg/l dose which yielded a reduction of 88% from 55 ntu to less than 7 ntu. at the optimum dose, the zeta potential of sce (szp) treated water increased from −15.5 to −6.31 mv. table 5.4 also shows the surface charge potential of sce as a coagulant to be −6.4 mv, higher than that of oce, which was −8.3 mv. coagulant dose above 60 mg/l resulted in an increase in residual turbidity. for example, at a 100 mg/l dose, the residual turbidity was 10.82 ntu, representing 80% reduction and the zeta potential also decrease from −6.31 mv with 60 mg/l dose to −9.44 mv at 100 mg/l due to charge reversal. the coagulation mechanism presented by sce was typical of charge neutralisation. the amount of protein used for coagulation was 5.058 mg while the remaining 54.492 mg used in the 60 mg/l dose extract are contaminants. the application of kce as a coagulant was also evaluated and its coagulation mechanism determined after treating 55 ntu water. the surface charge potential of kce was found to be −8.3 mv similar to that of oce (table 1). various doses of kce sample was added to the synthetic water and the residual turbidity decreases continually until the maximum dose of 100 mg/l. turbidity removal performance was 85%, with 100 mg/l as the optimum dose. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):85-93. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 89 however, the work presented here observed that kce behaved differently to oce or sce, and the zeta potential response was quite the opposite of coagulation mechanism of ok and sb seeds. in kce, residual turbidity decreased continually as coagulant dose increased which resulted in an increase in zeta potential until the maximum dose of 100 mg/l was reached. the zeta potential of kce (kzp) final water increased from −15.5 to −6.67 mv at the end of the treatment. figure 1: coagulation mechanism of oce, sce and kce in 55 ntu synthetic water. the degree of charge neutralisation action was different requiring more dose to destabilise the kaolin particles. the amount of protein used for coagulation in the kce treated water was 6.31 mg from the 100 mg/l dose whereas the remaining 93.69 mg in the extract was contaminants added into the treatment process. table 1: surface charge potential of crude, purified and contaminants in hibiscus seeds. samples ok sb ke zeta potential of purified seeds −10.1 −11.4 −8.1 zeta potential of crude seed extracts −8.3 −6.4 −8.3 zeta potential of contaminants −10.3 −14.1 −5.1 while oce and sce required doses of 20 and 60 mg/l respectively, the kce sample used the maximum dose of 100 mg/l to destabilise the kaolin particles in the raw water to achieve turbidity reduction. 3.2 coagulation mechanism of the extracts in river water to understand further the coagulation mechanisms of the extracts in water treatment. oce, sce and kce were applied to treat river water with similar range of doses used in treating the synthetic water. figure 2 shows the performance of varying doses of oce, sce and kce in river water with a turbidity of 19 ntu and zeta potential of −12.3 mv. -20 -10 0 10 20 30 40 50 60 0 20 40 60 80 100 ze ta p o te n ti al ( m v ) r es id u al t u rb id it y (n tu ) coagulant dose (mg/l) residual turbidity in oce water zeta potential of oce water residual turbidity in sce water zeta potential of sce water residual turbidity in kce water zeta potential of kce water jones: the zeta potential in crude extracts of some hibiscus plants for water treatment. azojete 14(1):85-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 90 the results show a maximum turbidity removal of 98% was achieved with 40 mg/l dose of oce, and the zeta potential remained largely unaffected at −12.6 mv. the addition of more coagulant dose eventually led to overdosing leading to re-stabilisation. the zeta potential in the water marginally increased from −12.3 to −11.7 mv, with 100 mg/l dose. overall, there was a relative change in zeta potential and the optimum dose did not correspond to the highest zeta potential value in the water due to background effect (zeta potential) from nom in river water. under this condition, the coagulation mechanism was by adsorption and bridging action. meanwhile, when a 40 mg/l dose of either sce or kce was used, turbidity reductions were 96 and 83%, from 19 ntu to less than 0.68 and 3.25 ntu respectively. at the optimum coagulant dose, the zeta potentials value increased marginally in sce to −11.4 mv while −10.6 mv was found in kce treated water. again, the coagulation mechanism is unlikely to be by charge neutralisation, but due to adsorption and bridging action. however, river water treated with these extracts presents two common features; firstly, the optimum coagulant dose that achieved the minimum residual turbidity was 40 mg/l, and secondly, at 20 mg/l dose, the zeta potential in the treated water remained unaltered at −12.4 mv from −12.3 mv across all the samples. this is clearly due to the background impact of zeta potential from other river water constituents (noms) in the system. figure 2: coagulation mechanism of oce, sce and kce in 19 ntu river water. in addition, re-stabilisation was also observed after the addition of more coagulant dose in the water and the zeta potential increased accordingly. for instance, at 80 mg/l dose, the zeta potential of the final water was between −10.3 mv and −11.0 mv for all the extracts. at 100 mg/l dose, the final zeta potential value was reduced from −10.3 mv to −11.7 mv in oce treated water. -15 -10 -5 0 5 10 15 20 25 0 20 40 60 80 100 ze ta p o te n ti al ( m v ) r es id u al t u rb id it y (n tu ) coagulant dose (mg/l) residual turbidity in oce water zeta potential of oce water residual turbidity in sce water zeta potential of sce water residual turbidity in kce water zeta potential of kce water arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):85-93. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 91 the water sample which had been treated with 100 mg/l of sce had an overall zeta potential reduction from −10.7 mv to −11.0 mv while that of kce increases from −11.0 mv to −10.1 mv. again, measurement of the zeta potential of the treated water with 60 and 80 mg/l doses reveals a zeta potential of −11.0 mv with kce as a coagulant. there was no consistency in the coagulation mechanism by the extracts in river water treatment. while the coagulation mechanism by the extracts was not consistent in river water, the overall removal of turbidity was considerably higher in river water than in the synthetic water. however, there were situations where the zeta potential of the treated water increased, but such an increase was not substantial enough to adjudge the coagulation mechanism to be due charge neutralisation action. 4. discussion measurements of zeta potential before and after treatment in kaolin water using the three extracts show a significant increase in zeta potential in the treated water. even though the coagulants are anionic, and kaolin particles are negatively charged as demonstrated by katayon et al. (2004), the coagulation mechanism requires further investigation, because it unlikely by charge neutralisation. most notably, during adsorption, kaolin particle can formed hydroxylated surfaces in water (sharp, 2005). for optimum flocculation performance, zeta potential should be near zero (kleimann et al., 2005, bolto and gregory, 2007, morfesis et al., 2009). in all these cases, the zeta potential operating window of the extracts was −6.67 <ζ<−4.39 mv, with minimal turbidity in the treated water. the difference in the zeta potential operating window was due to the coagulation mechanism by the natural extract, which was by adsorption and bridging while in the uk river water with multi-charged ions, metal coagulants are used, the effect of surface charge on the particles may be quite different. the zeta potential of the river water presented in this work is within the range reported by (sharp, 2005). the coagulation mechanism in river water was different due to background effect of nom in the raw water. a similar observation was reported by mpofu et al. (2003) who investigated anionic polyacrylamide acrylate copolymer in kaolin water. these findings suggest that the mechanism exhibited by hibiscus extracts is unlikely to be via charge neutralisation, but rather by adsorption due to the positioning of the surface shear plane. river water may consist of variably charged ions and various nom from different sources which may affect the coagulation mechanism. many studies have shown that the presence of bivalent ions such as magnesium and calcium can also enhance flocculation activity (tripathi et al., 1976, choy et al., 2015). it is noteworthy that turbidity removal was higher in river water than synthetic water due to background effect of raw water constituents such as bivalent ions of calcium and magnesium. 5. conclusion and recommendation zeta potential measurement played an important role to achieve the desired goal of water treatment. in this study, although all the samples are anionic, yet their mode of action were majorly by charge neutralisation, adsorption and bridging. the impact of the extract base on surface charge potential was clearly seen in treating both synthetic and river water. river water constituent impacted positively in the overall treatment process where turbidity removal was found to be significantly higher than that of synthetic water. jones: the zeta potential in crude extracts of some hibiscus plants for water treatment. azojete 14(1):85-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 92 however, optimising the coagulation stage/unit by adopting zeta potential measurement would provide a more robust performance in water treatment. references bolto, b. and gregory, j. 2007. organic polyelectrolytes in water treatment. water research, 41: 2301-24. branko, sd., suzana, kf. 1992. measurement and application of zeta potential. rudarskogeolosko-naftni zbornik, 4, 147-151. choy, sy., prasad, kmn., wu, ty. and ramanan, rn. 2015. a review on common vegetables and legumes as promising plant-based natural coagulants in water clarification. international journal of environmental science and technology, 12: 367-390. doi 10.1007/s13762-013-0446-2. delgado, av., gonzález-caballero, f., hunter, rj., koopal, lk. and lyklema, j. 2005. measurement and interpretation of electrokinetic phenomena (iupac technical report). pure and applied chemistry, 77 (10): 1753–1805. dentel, sk. 1991. coagulant control in water treatment. critical reviews in environmental science and technology, 21: 41-135. diaz, a., rincon, n., escorihuela, a., fernandez, n., chacin, e. and forster, cf. 1999. a preliminary evaluation of turbidity removal by natural coagulants indigenous to venezuela. process biochemistry, 35: 391-395. duan, j. and gregory, j. 2003. coagulation by hydrolysing metal salts. advances in colloid and interface science, 100: 475-502. gregory, j. 2005. particles in water: properties and processes, crc press, taylor and francis group. iwa publishing, london, pp 1-179. gregory, j. 2009. monitoring particle aggregation processes. advance colloid interface science, 147-148: 109-123. jones, an. 2017. investigating the bacterial inactivation potential of purified okra (hibiscus esculentus) seed proteins in water purification. arid zone journal of engineering, technology and environment, 13: 6-14. jones, an. and bridgeman, j. 2016a. an assessment of the use of native and denatured forms of okra seed proteins as coagulants in drinking water treatment. journal of water and health, 14: 768-779. jones, an. and bridgeman, j. 2016b. investigating the characteristic strength of flocs formed from crude and purified hibiscus extracts in water treatment. water research, 103: 21-29. katayon, s., megat mohd noor, mj., asma, m., thamer, am., liew abdullah, ag., idris, a., suleyman, am., aminuddin, mb. and khor, bc. 2004. effects of storage duration and temperature ofmoringa oleifera stock solution on its performance in coagulation. international journal of engineering and technology, 1: 146-151. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):85-93. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 93 kleimann, j., gehin-delval, c., auweter, h. and borkovec, m. 2005. super-stoichiometric charge neutralization in particle-polyelectrolyte systems. langmuir, 21: 3688-3698. klimpel, r. and hogg, r. 1986. effects of flocculation conditions on agglomerate structure. journal of colloid and interface science, 113: 121-131. la mer, vk. 1966. filtration of colloidal dispersions flocculated by anionic and cationic polyelectrolytes. discussions of the faraday society, 42: 248-254. miller, sm., fugate, ej., craver, vo., smith, ja. and zimmerman, jb. 2008. toward understanding the efficacy and mechanism of opuntia spp. as a natural coagulant for potential application in water treatment. environmental science and technology, 42: 42744279. morfesis, a., jacobson, am., frollini, r., helgeson, m., billica, j. and gertig, kr. 2009. role of zeta potential in the optimization of water treatment facility operations. industrial engineering and chemical research, 48: 2305–2308. mpofu, p., addai-mensah, j. and ralston, j. 2003. investigation of the effect of polymer structure type on flocculation, rheology and dewatering behaviour of kaolinite dispersions. international journal of mineral processing, 71: 247-268. ndabigengesere, a., narasiah, ks. and talbot, b. g. 1995. active agents and mechanism of coagulation of turbid waters using moringa oleifera. water research, 29: 703-710. sharp, e. 2005. natural organic matter coagulation. phd thesis, unpublished. cranfield university, cranfield water science institute, united kingdom, pp 361. tripathi, p., chaudhuri, n. and bokil, s. 1976. nirmali seed a naturally occurring coagulant. indian j. environ. health, 18 (4): 113-121. zhang, j., zhang, f., luo, y. and yang, h. 2006. a preliminary study on cactus as coagulant in water treatment. process biochemistry, 41: 730-733. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng technology options for public safety and disaster relief networks n. faruk 1* , n. t. surajudeen-bakinde 2 , a. a. ayeni 3 , o. w. bello 4 , o.a. fadipe-joseph 5 and o. kolade 6 1,3 department of telecommunication science, university of ilorin, ilorin, nigeria 2 department of electrical and electronics engineering, university of ilorin, ilorin, nigeria 4 department of information and communication science, university of ilorin, ilorin, nigeria 5 department of mathematics, university of ilorin, ilorin, nigeria 6 monitoring & evaluation depat, gis/mis/qa division, national planning commission, abuja, nigeria *corresponding author‟s email address: faruk.n@unilorin.edu.ng abstract the rise in global cases of emergencies as a result of man-made and natural disaster necessitates the need for a robust and reliable means of communication networks. the partial or complete, disruption of telecommunications infrastructure as a result of disaster has caused delays in emergency response and disaster relief efforts, leading to loss of lives and damage to properties. although, modern telecommunications networks have reliability and resiliency to physical damage, however, the risks associated with communications failures remain a major issue as the severity of the damages may depend on the underlying technologies and architecture used. it is however important to also note that each technology option available for public safety network has its own unique characteristics. some of these options are widely deployed for commercial purposes in nigeria, while others are still in the developmental stages. this paper therefore outlines some of the existing, new and affordable technological options, available today that can be deployed for public safety and disaster telecommunications networks in nigeria. furthermore, the paper recommends that the national broadband network plan needs to be aligned to the current commercial deployments of the 4g long term evolution (lte) wireless services, this is to ensure that the pace is maintained with the changes in the technology and leveraging cost efficiencies for the public safety networks. keywords: public safety; disaster; telecommunication; technology options 1. introduction public safety networks (psns) are essentially wireless communications networks used by emergency services organizations. it is basically providing 24-hour communication facilities in response to natural and man-made disasters, such as medical emergencies, threats to public order and a host of other life-threatening situations (arthur, 2012). this is conventionally expressed as a governmental responsibility of each country. the primary objective of the public safety is prevention and protection of the public from threats or disasters. public safety (ps) organizations such as national emergency management agency (nema) in nigeria, federal road safety corps (frsc), law enforcement agencies (i.e., police and the military), fire departments and emergency medical services (ems) are crucial in disaster preparedness and recovery. the critical role played by the ems is assisting in the response to emergency events. the first responders are typically the law enforcement agencies such as the police, and then other responders are the fire-fighters, and emergency medical personnel (ambulance). therefore, the ability of the first responders to communicate effectively in an emergency situation would determine the safety level. the public safety of nigerians especially those in the north-eastern part of the country becomes a very big issue with the frequent attacks from a sect called boko haram. it became so alarming when the base stations of mobile service providers were destroyed mailto:faruk.n@unilorin.edu.ng nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 2 and people in this part of the country became incommunicado. it equally made it impossible for agencies to communicate with each other and the people in the communities could not relay any forehand information of an intended attack to the necessary security agencies. in nigeria, different public safety agencies like nema and frsc do not have a common means of communication, with a few deployments of mobile land system, and so it is the public mobile service that had been attacked that these agencies rely on to communicate with each other, especially during an emergency situation. globally, there are several cases in which the communication infrastructures are damaged such include: the indian ocean tsunami of december 2004 (townsend and moss, 2005), new york city, september 11 terrorist attack (ncta, 2004), the 1995 kobe, japan, earthquake (kobe, 2017), the 1989 loma prieta earthquake (barnum, 1994), the kocaeli-golcuk earthquake of august 17, 1999 (george p. c, 2017) and many others. in all these situations, telecommunication infrastructures were physically damaged or disruption of supporting infrastructure such as transportation and electricity grid. high traffic volumes of users causing congestions also contribute in the same way of disrupting the telecommunication service. whether partial or complete, disruption of telecommunications infrastructure as a result of disaster causes delays and errors in emergency response and disaster relief efforts, leading to loss of lives and damage to properties, which are all preventable with the help of first responders (townsend and moss, 2005). although, modern telecommunication networks have reliability and resiliency to physical damage, however, the risks associated with communication failure remain a major issue due to dependence upon these tools in emergency operations (mitchell and townsend, 2004). in recent years, nigeria has seen an improvement in the commercial communications infrastructure, and also increased in subscribers and teledensity from 2.2 million and 1.89 to 149 million and 108.1 from 2002 to first quarter of 2016 respectively (ncc, 2016). although the capabilities of the commercial communication systems have greatly improved, the same cannot be said for the communication systems used by most public safety and disaster relief agencies. based on information available to the authors indicate that our public safety and disaster relief agencies utilize cellular mobile phones for emergency communication and responding to disaster cases like motor accidents, bomb blast, floods, gas explosions and etc. due to the shortcomings of the traditional cellular systems, today‟s public safety communications systems in nigeria are prone to network congestion, interoperability problems, which make it very difficult for first responders from different agencies and locations to communicate and coordinate. this also, undermines the inter-agency communications. in sept 2012, the nigerian government, through the ministry of communication technologies, released the 2013-2018 national broadband plan (nbp) (nbp, 2012), which maps out strategies and recommendations for improving access across the country. the nbp plan had identified the role of broadband in public safety and emergency response. although, government proposes to establish emergency call centres (ecc) in all the 36 states of the federation and the fct with a arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 3 three-digit emergency code number, known as e112 with the promise that when people dial 112 the call goes to the nearest ecc. however, in the nbp, there were no provisions and clear-cut strategy for creating a public safety broadband infrastructure in the country. most likely, this added service (i.e. ecc) may rely on the underlying commercial mobile cellular infrastructures. in order to provide reliable public safety network infrastructure, there is the need to consider available options. it is however important to note the geographical location and local terrain of environment which are the major issues to be considered when deploying telecommunication infrastructure to provide access. each option has its own unique approach to serving the public and has its own advantages and shortcomings. some of these options are widely deployed for commercial purposes in nigeria, while others are still in the developmental stages. this paper therefore, outlines some of the existing, new and affordable technological options, available today that can be deployed for public safety and disaster telecommunications networks in nigeria. 2 disaster management cycle disaster can be defined at different levels of household; community; district; state; national and international, as an unforeseen event that occurs suddenly which is highly overwhelming. depending on the level of occurrence of the disaster, calamities such as economic and social, serious illness and even death could be experienced. examples of disaster that can be encountered are displacement of people as a result of conflict, earthquake leading to buildings collapse, livelihood destruction, fire outbreak, flood and even epidemic (abdallah and burnham, 2008). most recent of man-made disaster are the use of bombs and other means to attack, kidnap, and kill large number of people. disaster management cycle includes: warning phase, response phase, preparedness phase, reconstruction/rehabilitation phase and prevention/mitigation phase. figure 1 provides a conceptual diagram of disaster management cycle. a warning phase usually precedes a disaster, which is subsequently followed by a response which can only be substantiated with the level of preparedness in place. during the emergency phase, efforts are made to bring succor to the affected and this transforms into the reconstruction or rehabilitation phase. to prevent same type of disaster from reoccurring, experiences of the previous occurrences are used for mitigation and to be very ready in case of reoccurrence. figure 1 presents the four main different stages encountered in case of a disaster. even though, the phases are in a cycle showing occurrence in sequence, but some may occur at the same time. the consequences of disaster most times go beyond the reconstruction phase, which is not shown in the block diagram. in a situation where there are insufficient resources to take care of the reconstruction and mitigation, then another disaster might occur (abdallah and burnham, 2008). nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 4 figure 1: disaster management cycle 3. public safety networks 3.1 roles of the public safety organizations public safety (ps) organizations are very important in preparing for disaster, ensuring recovery and helping in taking care of emergency events like disasters that are catastrophic. law enforcement, fire-fighters, emergency medical personnel, and others are those usually found in an emergency scene. non-governmental and military organizations, volunteer groups and other local and national organizations are those found when the disaster is a large one. the schematics block diagram of the main functions of ps is given in figure 2 (baldini et al, 2013). figure 2: provides the schematics of the main functions of public safety arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 5 police, fire-fighters, border guards, coastal guards, medical associations and non-governmental organizations (ngos) are functional as described in figure 2, at local, national and regional levels. the relationships between organizations and functions are highly dependent on the concerned country‟s legislation (baldini et al, 2013). fragmented networks and obsolete wireless technologies limit the first responders. the use of nationwide public safety wireless broadband network that are cheap to acquire will make access to advanced, cutting edge technologies and applications available to the public safety agencies to ensure improved emergency response capabilities. in any case, all arms of government and the private sectors must cooperate for transition from traditional land mobile radio (lmr) communications to broadband to be effective and operational (homeland security, 2011). 3.2 areas of applications of psdn ps networks have diverse areas of applications (baldini et al, 2013), which include: verification of biometric data, whereby potential criminals have their features like fingerprints checked during patrol by the ps officer. remote monitoring and video surveillance done wirelessly where a fixed or mobile sensor records and distributes data in video streaming format to enable the ps responders and command and control centers share files is also an application. the use of camera to take pictures of plate numbers of vehicles and the images are transmitted to the headquarters where verification is done is a description of another application called automatic number plate recognition. documents scan used during patrolling or border security operations; database checks, in this case, data are obtained from the headquarters to assist the ps officers in automatic vehicle or officer location operation.the ps officers have a gnss (e.g., gps) position localizer on the terminals. the decision management team makes use of the positions transmitted from time to time to the headquarters. this application is especially found very useful when there is fire outbreak or earthquake and people are trapped. remote emergency medical service in which video and data are transmitted is also found to help the medical personnel to work with the team on the field in case there is an emergency patient. figure 3 provides areas of application of ps networks and respective data rates requirements (drq). nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 6 figure 3: areas of application of ps networks 3.3 special features of psdrn backup in the transmitters and power supplies with very rugged handheld devices, protection against being brought down by hoodlums are required by highly dependable public safety systems. sufficient capacity for unusual periods must be available on public safety communication systems, especially when emergencies occur that a lot of first responders are needed. in most cases, the public safety systems have unused capacity because they carry less traffic, especially the mission-critical ones. spectral efficiency would be increased and possible cost reduction would be experienced if sharing of resources is allowed (peha, 2007). voice, data connectivity, text messaging, push-to-talk and security services are the basic services for ps communication systems (baldini et al, 2013). 4. technology options for psdrn 4.1 land mobile systems for psdrn i. paging systems paging systems are generally single-band (frequency), simplex radio system which is able to display messages received as numeric messages or announces it as voice messages. simplex pagers which are also commonly known as “one way pagers” can only receive messages, although, two-way pagers can receive and acknowledge, moreover, they can also originate messages using an internal transmitter (pager, 2016). common wireless paging systems include wireless smoke detectors, push buttons calls, ambulating patient help pager, infrared room locator, wireless pull cord station etc. figure 4 shows a typical synchronizing paging system. the major shortcoming of this type of technology is that it operates in a half duplex mode with single frequency this therefore, limits its capacity. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 7 figure 4: synchronous paging system (pager, 2016) the deployment of paging systems was achieved at different frequency bands, i.e. the vhf (very high frequency), uhf (ultra high frequency), and fm (medium frequency). there were many standards set for the operation of the system but the popular ones being the british post office standard, called pocsag (post office code standardization advisory group), and motorola‟s flex system (kathy and hart, 2003). ii. two-way simplex radio systems unlike the pagers, two-way radio systems operate on half duplex mode and can both transmit and receive but not at the same time. two-way radios can be implemented as ad-hoc network as in the case of walkie-talkies or with base stations. figure 5 shows a two-way radio system. one advantage of this system is that it can operate both in vhf and uhf bands, except the 220 mhz band. very long distance communication can be achieved with high power and high transmitter in the case of base station. however, one major problem is that the system has very low antenna heights, and this limits the communication range to usually few miles in flat terrain (kathy and hart, 2003). however, this limitation is associated to only handheld and mobile radio systems. although, repeated transmissions from one mobile to another could alleviate this problem and this gives rise to the development and deployment of mobile relay or repeaters. nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 8 (a) (b) figure 5: two-way radio system (a) repeater operation (walki-talkie) and (b) using base station (infotrunk, 2016) power and coverage limitations of the handheld and mobile two-way system can be enhanced using two-way relay systems. this is commonly referred to as mobile repeaters as shown in figure 6. in this case, the repeater uses the two frequencies, one in uplink (input) and the other downlink (output). the primary function of the repeater is to function as an amplified relay station, whereby, low-power base stations signals from low-level mobile, and handheld could be received, amplified and re-transmitted on another frequency. the output frequency is different from the inputs. usually, these types of repeaters are installed on the highest points within the coverage areas such as in high buildings and mountain tops where the elevation allows signal to travel far and thus, achieving maximum coverage and penetration. the coverage distance could be above 60 miles in radius. the repeater stations transmit with very high-power 600 to 3,500 watts erp (kathy and hart, 2003), depending on the need and this can cover a large area. figure 6: two-way repeater stations (wiki, 2016a) another problem that could arise with using this type of system is shadowing due to the movement of the mobile radios, within mountainous terrain or in urban areas where tall buildings and other shadowing objects could block the transmission. in these areas, the radio signal from the handheld system may not be detected by the repeater site considering the fact that the arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 9 handheld radios, transmit with very low output power, typically, of range between 0.5 to 3 watts erp (kathy and hart, 2003). however, satellite receiving sites could be deployed in the areas where there could be potential low-power radios. the satellite would receive the low signal and transmit via telephone line or microwave radio transmission to a signal comparator at a central site. the satellite in this case, would serve as backhaul. this scheme is illustrated in figure 7. figure 7: satellite and mobile relay system (kathy and hart, 2003). in some situations, small vehicular repeaters or mobile repeater could be used. iii. trunked radio systems one of the biggest challenges with the repeater system is scalability. for example, in developed countries like the usa, many of their communities use separate repeaters for the first responders (i.e. police department, the fire department and the likes). moreover, other non life threatening services such as the administrative and road maintenance departments also make use of these repeaters. due to the system of allocation, each unit is assigned a dedicated channel, in a situation when a department such as police is using two repeaters for its operation and another department‟s repeater is available, the police department may not be able to use it as it may cause interference. this raises the issue of scalability. the trunk radio system was proposed by research community to mitigate these problems. the trunk system consists of computercontrolled two-way radio system that allows sharing of few radio frequency channels among a large group of users (solid signals, 2015). this allows flexibility in the spectrum usage as it allows a pool of channels be shared to many different groups of users which is in contrast to the conventional two-way radio system where a dedicated channel (frequency) for each individual group of users. figure 8 provides simple illustration of trunk radio system. nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 10 figure 8: trunk radio systems (solid signals, 2015) two main types of tetra network architectures were defined by (mikuli and modlic, 2008), the conventional systems that use centralized switching and management infrastructure as illustrated in figure 8 and recent systems with distributed network architecture. the centralized tetra system is the most widely deployed as more than hundred of base stations can be deployed with single central network switching. this makes the call set-up times to be short and possibility of quality of service control. however, the distributed architecture is commonly referred to as tetra over ip networks, have also been implemented but with few number of base stations at about 50 base stations (mikuli and modlic, 2008). this raises scalability issue. however, it is possible to scale-up the number of bts but there is a risk of performance degradation. in order to achieve tradeoff, a hybrid system could be implemented based on a centralized ip based system. tetra could also be integrated with wireless lan (wlan) technologies (salkintzis, 2006) to provide more enhanced service delivery, such as broadband data connectivity, voice transmission delays, improved voice quality and simultaneous reception of many group calls since wlan is based on ip multicast and voip technologies. table 1 provides comparison of tetra with other different public safety technologies. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 11 table 1: comparison of different public safety technologies t ec h n o lo g ie s f re q u en cy b a n d s p ec tr u m c a rr ie r b a n d w id th a n d d o w n li n k d a ta r a te s c o v er a g e m o b il it y s u p p o rt s ec u ri ty a n d q o s s u p p o rt c o m m en ts project 25 50 mhz 150 mhz 170 mhz 220 mhz 410 mhz 500 mhz 750 mhz 800 mhz licensed 25/12.5 khz and 9.6 kb/s wide area yes yes low data rates, the puh-to-chirp latencies is quite low tetra voice + data 390 mhz 420 mhz 450 mhz 900 mhz licensed 25 khz and up to 28 kb/s wide area yes yes low data rates, the puh-to-chirp latencies is quite low tetra enhanced data service 390 mhz 420 mhz 450 mhz 900 mhz licensed 50/100/15 0 khz 473 kb/s wide area yes yes applications that use large bandwidth and multimedia messaging are well supported. also image transfer has high resolution tetra advanced packet service 390 mhz 420 mhz 450 mhz 900 mhz licensed 200 khz and 473 kb/s wide area yes yes applications that use large bandwidth and multimedia messaging are well supported. also image transfer has high resolution tia-902 upper 750 mhz licensed 50/100/15 0 khz 690 kb/s wide area yes yes applications that use large bandwidth and multimedia messaging are well supported. also image transfer has high resolution cellular 400 mhz 450 mhz 700 mhz 800/900 mhz 850 mhz 900 mhz 1800 mhz 1900 mhz 2100 mhz license/ unlicensed flexible bandwidt h for some technolo gies details in table 2. wide area yes yes global compatibility and a large number of users can be taken care of. coverage is limited. total network failure when hit by major disaster. wlan (ieee802.11a) 5 ghz unlicensed 6 – 54 mb/s wide area yes yes cheap alternative for access to the internet for disaster network. it offers less rf interference. coverage, interference and line of sight requirements in hilly or heavily foliated terrain could be major challenging factors. nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 12 4.2 wireless cellular system cellular technology was originally designed for mobile services, such as communication from moving vehicles. in developing countries like nigeria, wireless cellular communication systems provide primary access to telephone services through portable handsets. this has to be because of the inefficiency and near-collapse of wireline technology. figure 9 shows a typical architecture of mobile cellular system, it consists of base transceiver stations each covering a geographical area call cell. each cell or base station is connected to the mobile telephone switching center via backhaul network. the backhaul technology could be wired such as fiber and adsl or wireless such as microwave, satellite or the emerging television white spaces (tvws). cells range can vary from 10 meters (femto cells) up to 35 kilometers (macro cells) and above. the macro cells are deployed outdoor and are able to provide 2g, 3g and 4g services in range of kilometers and are backhauled via fiber optics and/or microwave (faruk et al., 2016). this is typically suitable for public safety communications as it covers wide area with minimal number of sites. the major challenge is the power consumption. mostly, developing countries do have shortage in power generation and transmission and such macro base stations consumes between 1.7.kw-5 kw depending on the type of the sites (faruk et al., 2012). most of the commercial operators rely on diesel generators to power-up the sites. this type of solution may be unsustainable for public safety deployments. the good news, nigeria is a temperate region with abundance of solar energy, therefore, sustainable solar energy solution is very feasible and this has been proposed by (faruk et al., 2012a) or a hybrid or solar and any other renewable solution such as wind power. these systems are found to be very reliable compared to diesel alone ((faruk et al., 2012c). two common cellular technologies that have become the toast of nigeria are the global system for mobile communications (gsm) and code division multiple access (cdma). in the us and canada, gsm operation is on 850 mhz and/or 1900 mhz. in nigeria, gsm uses the time division multiple access (tdma) technique to multiplex up to 8 calls per channel in the 900 mhz and/or 1800 mhz spectrum bands. cdma is a 3g network which uses direct sequence spread spectrum, ds-ss, and communication system to support voice and data communication. the two popular cdma standards are the wcdma and several variants of cdma2000 (adediran et al., 2016). the frequency bands used by 3g networks include the following: 25002690 mhz, 1710-1885 mhz and 806-960 mhz. more advanced technologies such as the 4g lte are at early stage of deployment. however, table 2 provides comparison of different cellular technologies. some of the advantages of cellular system are: o global compatibility and very large number of subscribers can be accommodated. o due to large chunk of available bandwidth, cell capacity can easily be increased to accommodate more users or traffic demand. o adaptive power control and interference management systems o reliability is very high even under the worst environmental conditions. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 13 figure 9: cellular telephone system: chapal (2010) cellular mobile phones i.e. the gsm systems have been used for over a decade for public safety communication in nigeria and this has been the sole, dominant technology option. however, due to the favourable propagation characteristics of cdma 450, wider coverage could be provided and it has lower overall capital and operational expenditure when compared with other access technologies such as the hspda, wcdma and gsm. also, it is expected that cdma 450 will provide less penetration loss through buildings when compared with others (adediran et al., (2015). more enhanced technologies such as the lte systems are evolving; these technologies provide more flexibility and data capacity than the already deployed 3g and 3.5g systems. in addition, lte systems have an inbuilt public safety features, the performance of lte in terms of capacity, reliability and security is enough to fulfill the strict requirements of the public safety users (simić, 2012). nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 14 table 2: comparison of different cellular technologies. technologies cdma2000 gsm/gprs /egprs umts/hsdp a lte 802.16x 5g technologies frequency bands 450 mhz 850 mhz 900 mhz 1800 mhz 1900 mhz 1900 mhz 2100 mhz 400 mhz 700 mhz 800/900 mhz 10 – 66 ghz los 28 ghz expected frequency reuse 1/1 4/12 on first carrier; 1/3, 1/1 on others 1/1 1/1 1/1, 1/3 spectrum licensed licensed licensed licensed licensed and unlicensed licensed and unlicensed carrier bandwidth 1.25 mhz 200 khz 5 mhz 1.4 mhz up to 20 mhz scalable (1.25 –20 mhz) 800 mhz coverage wide area wide area wide area wide area wide area wide area qos yes (with 1xrtt and evdo rev yes yes qos class identity (qci) yes yes data rate 3.1 mbps downlink, 1.8 mbps uplink 114 kb/s/473 kb/s 14.4 mb/s downlink, 384 kb/s uplink 300 mb/s downlink, 75 mb/s uplink 30 mb/s (in 10 mhz fdd) 35.46 gb/s mobility support yes yes yes yes developmen t of 802.16e is considered in its planning. yes multiplexing frequency division multiplex frequency division multiplex frequency or time division multiplex frequency and time division multiplex frequency or time division multiplex multiplexing millimeter-wave comments ip based multimedia subsystem (ims) signalling framework make information readily available and also make access to state of the art applications easy for the ps officers. lack of peerto-peer communicat ion ip based multimedia subsystem (ims) signalling framework make information readily available and also make access to state of the art applications easy for the ps officers. main advantage is in the simplicity of its ip system architecture. the main disadvantage is the lack of peer-to-peer communicati on and very high cost lack of peerto-peer communicati on expected advantages higher number of simultaneously connected devices, higher syste spectral efficiency, lower battery consumption, lower outage probability (better coverage), ower latencies, lower infrastructure deployment costs, higher versatility and scalability, or higher reliability of communication arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 15 some of the major problems of using terrestrial cellular network are the limit of the cellular coverage and failure of the network in the event of major disaster. in the event of disaster happening outside the coverage radius of the cells, it will be practically impossible for the mobile to communicate with the network. therefore, it is expected that during major emergency operations, such as natural or man-made disasters, both the commercial and dedicated terrestrial networks will fail to provide the necessary support due to destruction of the network infrastructure. in other to mitigate this problem, casoni et al., (2015) proposed a cellular system with integrated satellite backhaul for both infrastructure-based and infrastructure-less scenarios. the paper provided field operators and people in distress with easy access and guarantee quality of service when the underlying terrestrial infrastructures are lacking or failed. this features helps to expand coverage, capacity and network resilience when compared to the conventional systems. figure 10 shows lte system with integrated satellite backhaul. figure 10: lte system with integrated satellite backhaul (casoni et al., 2015) in figure 10, lte was considered to be the access technology, while, the satellite is used as the backhaul linking the lte base stations and the internet. in the architecture, a mobile emergency operations-control center (meoc) acts as the access technology and this provides first responders (frs) with a lte incident area network (ian), thus representing a deployable (and mobile) lte repeater station for field operators (casoni et al., 2015). the satellite link serves as the backhaul medium between the meoc and the emergency operations-control center (eoc), which is non-mobile and represents the operations headquarters of the public safety authorities (casoni et al., 2015). in this architecture, frs, meoc and eoc will be able to communicate irrespective of the geographical locations. 4.3 wireless lan (wlan) and (wman) technologies wireless lan (wlan) technology was designed to provide high speed wireless connection in a local area. wlan supports two architectures, namely: the infrastructure-based, also known as centralized system, which is based on a central controller called access point, and decentralized or ad-hoc architecture which does not require any infrastructure to be in place. wlan have been deployed widely in individual homes and businesses. most of the government agencies, nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 16 universities in nigeria and internet cafes today utilize the wifi technology for internet services. this service could be extended to voice by employing the use of software, such as skype, to communicate. figure 11 shows a typical wireless local area network. figure 11: wireless local area network (wlan, 2014) wi-fi is one of the wlan technologies belonging to the general family of ieee 802.11 standards. some of the strengths of wlan are: it is a relatively cheap alternative for access to the internet for disaster network and no spectrum licensing is required as it operates in the unlicensed ism band. however, coverage, interference and string line of sight requirements particularly in hilly or heavily foliated terrain could be major challenging factors. wireless metropolitan area network (wman) technology is based on broadband wireless access (kuran and tugcu, 2007). there are two major standards for wman technology, namely, ieee 802.16 (wimax) and ieee 802.20 (mobile-fi). however, ieee 802.16 wimax is the global most acceptable standard which aims to provide broadband internet service in urban, suburban and rural areas. the ieee 802.16 standard (ghosh et al, 2005) supports two architectures, namely, last mile access and mesh network architectures. in last mile access architecture, the base station (bs) controls the transmission to/from the subscriber stations (sss), which is similar to the cellular architecture. in mesh network architecture (i.e. ieee 802.16j), the sss can relay traffic from other sss to the bs in a multi-hop fashion. as earlier started, the wlan could be integrated with the tetra system to provide more enhanced service delivery during disaster operation. figure 12 gives a typical deployment scenarios of wman. figure 12: an example of wimax providing internet access source: (frank et al, 2013) arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 17 ieee 802.16 with single carrier air interface operates in the 10 66 ghz band with los communication. ieee 802.16a with ofdm/tdma air interface operates in the 2 11 ghz band with non los communication. there is also ieee 802.16e which supports broadband wireless access for high mobility. contrary to wlan, wman technologies could theoretically extend the range up to 50 km with a single tower. in terms of cost, data rates, flexibility and user mobility, wman could be a very good candidate for psdn. although, the initial cost of deployment, site installation and maintenance could be issues to worry about since the network will be deployed for public service. the network still operate on unlicensed spectrum, therefore, problems of interference could manifest if the network is deployed in urban centers where the usage of wlan technologies is high. 4.4 emerging technologies for psdn lte device-to-device (d2d) communication and ecall are two dominant emerging technologies for future public safety and disaster relief network. (i) lte device-to-device (d2d) communication d2d communication enables direct communication between nearby mobiles as illustrated in figure 13. it does this by enabling mobile devices to discover the presence of other devices in their vicinity and to communicate with them directly, with minimal involvement from the network (brydon, 2014). fodor et al., (2014) proposed d2d communications as an underlay to long term evolution (lte) networks as a means of harvesting the proximity, reuse, and hop gains. figure 13: d2d communication (brydon, 2014) d2d is expected to facilitate the interoperability between public safety communication networks and other commercial networks. the 3gpp solution for d2d is termed proximity services (prose) and has two main components (brydon, 2014), as shown in figure 12. nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 18  d2d discovery: this enables a mobile device to use the lte radio interface to discover the presence of other mobile capable devices in its vicinity.  d2d communication: the d2d mobile devices use the lte radio interface to communicate directly with each other, without routing the traffic through the lte network. some of the benefits that could be derived in d2d communications is that the spectrum utilization and efficiency will be greatly improved, network throughput with energy saving could be achieved. d2d standardization is currently under research and one of the major challenge of this type of system is defining the under laying architecture for the network. for example, in figure 13, it can be seen that difficulties may arise for the devices to communicate in an event of failure in the cellular network therefore, the risks to the long-standing cellular architecture, which is centered around the base station (bs). similarly, it is still not clear on how to share spectrum resources between cellular and d2d communications. another shortcoming of d2d is the communication range since the mobile stations are having limited uplink transmit power, the communication range could be an issue. however, it was shown in babun et al, (2015) that coverage could be improved in d2d multi-hop communications with underlying cellular networks. (ii) ecall for public safety ecall (öörni, 2014) is a european in-vehicle emergency call system, the aim is to deploy a wireless device or sensors in all vehicles that will automatically dial emergency number in the event of a serious road accident such as head-on-collision. these devices are expected to be mandatory in new vehicle models type-approved in the eu after october 2015 (öörni, 2014). in the future, deployment of a public safety answering point (psap) infrastructure capable of receiving and processing ecalls will become mandatory for eu member states (öörni, 2015). an overview of the standards of ecall is given in figure. 14. figure 14: overview of standards of pan-european ecall (öörni, 2015) arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):1-25. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 19 4.5 deployment case studies currently, there is no global dedicated psdrn infrastructure. however, countries from various regions deployed and implemented different technologies for public safety communications. in africa, mostly amateur radios (i.e. land mobile systems) are often used for emergency communication when landline phones, mobile phones and other conventional communications fail or are congested. however other regions like the europe and the united states of america have a psdr infrastructure. table 3 provide summary of the regional psdrn deployment case studies. 5.0 conclusions the need to have a robust and reliable means of communication in the event of an emergency, such as fire outbreak, natural and artificial disasters, medical emergencies, threats to public order such as boko haram has been established. all the existing and emerging technological options with their pros and cons are given. this work enumerated all the available options to ensure that viable psdrn are implemented for safety of lives and properties of the populace. land mobile systems have been found to be the dominant technology deployed globally for public safety communication. aside limited capacity, detecting the signal from mobile radios when on motion particularly in hilly or mountainous terrain or in urban areas having numerous tall buildings would be difficult by the repeater site due to low transmit power of the mobile. tetra systems allow greater flexibility in radio usage and provide more capacity. cellular mobile phones i.e. the gsm systems have been used for over a decade for public safety communication in nigeria and this has been the sole, dominant technology option. it is noted that this technology may not be a good candidate for this type of service, moreover, in the event of disaster, the network infrastructure could be physically damaged and high volume of traffic will certainly cause network congestion. in addition, support delivery service such as transportation and fuel may almost be impossible to attain. however, the lte system has inbuilt public safety features, the performance of lte in terms of capacity, reliability and security is enough to fulfill the strict requirements of the public safety users. furthermore, the lte can be integrated with satellite backhaul for both infrastructure-based and infrastructure-less scenarios. the nationwide public safety wireless broadband network needs to be closely aligned to commercial deployments of long term evolution (lte) wireless services to keep pace with changes in technology and leverage cost efficiencies. nasir, et al., technology options for public safety and disaster relief networks. azojete 14(1):1-25. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 20 table 3: case studies publications countries/ regions technologies deployed comments (wia, 2015) australia amateur radio landline and mobile phones amateur radio deployed for emergencies when landlines and mobile phones fail or are congested (tredger, 2015) africa unified communications amateur radio trunking with lte broadband, there is also video surveillance, and video conferencing among others make use of computer aided dispatch system are available officials and emergency services providers will find this technology very useful to take care of data that are in very large quantities and incidents can be given quick response that is required. the officials are also equipped with ways to help the victims even after the incidence to help them settle back to normal life. (camilla et. al., 2015) europe terrestrial trunked radio tetra (trans european trunked radio) and later terrestrial trunked radio/lte  group calls (wide area fast call set-up).  direct mode operation (dmo) allowing communications between radio terminals independent of the network.  high level voice encryption to meet the security needs of public safety organisations.  priority call (an emergency call facility that gets through even if the system is busy).  full duplex voice for pabx and pstn telephony interconnection. (baldini,et. al. 2015) france tetrapol a fixed network infrastructure is considered here. (ryan and jon, 2013) usa lte/the mobile emergency alert system (m-eas)/raytheon/ motorola‟s premiere one ps agencies are given the rare opportunity to utilize the public safety networks such that users could roam into commercial networks with ease. m-eas is provided for many users at the same time as it relies on digital broadcasting and not on wireless networks. the mobile digital broadcasting is for the provision of media alerts. one force mobile application was launched in 2012, for first responders to use when they are outside the coverage of land mobile radio (lmr) and they are found to be reliable and secure and at the same time provide real time communication. computer aided dispatch, records management system are used by first responders to access and share information, as well as from local, state and federal databases. (premkumar and raj, 2014) china a self-powered wireless communication platform (spwc)/self powered micro wireless ballooned network in spwc, unmanned aerial vehicles (uav) are deployed in lap as opposed to high platform since the high altitude platform need the satellite to host the networks which significantly increases the cost. it provides high rate at very low latency and these connections can be used by almost any application that uses ip communication. lte is basically divided into two parts: the evolved umts terrestrial radio access network (e-utran). it has multiple wireless balloon access nodes, fixed access point and end devices (mobile pc and ip telephones). during disasters, the wireless balloon nodes connect with each other in the sky to form large ad-hoc networks which are used for emergency communications. the nodes are powered by a solar panel power supply unit or by a power battery for emergency or vehicle on the ground via a very thin wire arid zone journal of engineering, technology and environment, march, 2018; 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[accessed on 08/05/17]. http://www.upc-cablecom.biz/en/produkte/business-internet/wlan-hotspot.htm%20visited%2006/11/2014 http://www.upc-cablecom.biz/en/produkte/business-internet/wlan-hotspot.htm%20visited%2006/11/2014 http://www.wia.org.au/members/emcom/about/ https://en.wikipedia.org/wiki/lte_(telecommunication) arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):278-291 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 278 original research article combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design s. a. abdulrahman*, a. t. abdulrahim and a. m. el-jummah (department of mechanical engineering, faculty of engineering, university of maiduguri, maiduguri, nigeria) *corresponding author’s e-mail address: kadiri0802@yahoo.com article information submitted 18 november, 2018 revised 8 march, 2019 accepted 16 march, 2019 keywords: biomass downdraft gasifier gasification modeling abstract thermochemical conversion of biomass in a gasifier for the production of syngas provides the enabling technology for efficient biomass resource utilization. gasification is a complex process involving the interactions of numerous parameters, hence cfd tool is usually utilized to numerically optimize the design and operation of the gasifier reactor for improved performance. the gasification of multiple biomass usually requires a complex set of facilities for experimental set up in order to determine the optimum operating conditions for maximum gas yield. when this is not available, it can pose a bottle-neck to process development and optimization. in this study, the gambit and fluent were used to model and simulate the gasifier reactor with emphasis on the combustion and gasification (reduction) zones in order to maximize the thermal output of the combustor by an optimization of biomass fuel types. model validation was achieved by showing a close agreement between numerical and experimental results within the same configuration, particularly to show the effect of temperature on the gasification of fixed bed downdraft gasifier. the fraction of initial moisture content, air flow rate, temperature of the pyrolysis zone, and chemical composition of the biomass were the required input data for the model to predict the gasification temperature. computations were carried out for rice husk, saw dust and corn cobs as gasifier fuels, whereby air was used as the oxidizing agent. the porosity and oxidizer velocity were varied between 0.1 – 0.5 and 5 – 15 m/s respectively. the predicted results compared with experimental data showed good agreement. the simulated temperature gradient also indicated that rich fuel combustion zone was greater for rice husk corn cobs, an indication that improved gasification and pyrolysis were present. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the utilization of biomass for energy is usually via the thermochemical conversion process from which the desired product may be gaseous, liquid and solid fuel respectively. previous researches (abdulrahman et al., 2016, sharma and sheth, 2016, rahul gupta et al., 2017, zainal et al., 2001) aimed at the optimization of the gasification process have in addition to the experimental investigations conducted, also made significant efforts from numerical approach, whereby numerical models were developed using computational fluid dynamics (cfd) codes such as ansys fluent and ansys cfx software. simulation results from the numerical mailto:kadiri0802@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 279 approach can help to optimize the system design and operation, in addition to understanding the dynamic process inside the reactor. wang (2008) asserted that the entire thermochemical process has strong influence on the pyrolysis rate irrespective of the type of biomass or mechanism used. recent modelling effort focused on the thermo-chemical equilibrium gasification model that described the application of one biomass fuel alone (sharma and sheth, 2016,), while attempt has also been made for the investigation of multiple fuels (begum et al., 2013). zainal et al. (2001) studied an equilibrium model based on equilibrium constants to simulate the gasification process in a downdraft gasifier and reported that the residence time of the reactants can be considered to be high enough to reach chemical equilibrium. vaezi et al. (2008) conducted the simulation for the gasification analysis of 55 different biomass materials. the study which was aimed at the optimization of the biomass gasification operation produced a chart based on the predicted results that can be used to estimate the fuel characteristics value and ultimately the selection of a desired biomass material. moreover, mohan raj and srividhya (2013) conducted a performance analysis using a cfd simulation tool on a 20kw thermal gasifier plant which used wood chips as fuels, they varied the porosity at 0.525 – 0.439 and oxidizer velocity at 3 – 13m/s and found that there was more amount of unburned fuel at velocities 11m/s and 13m/s. they also reported that less amount of unburnt fuel and combustion stability were present at higher temperature when velocities was 4 m/s and 5 m/s. muilenburg et al. (2011) investigated the cfd modeling of the combustion zone of downdraft gasifier by varying the bulk density, inlet velocity of oxidizer and fuel types. furthermore, their report compared between wood chips and corn and observed that a fuel with packing density that correlate to porosity of 0.5 produced good results. using both experimental and numerical method, sharma and sheth (2016) investigated the performance of a downdraft gasifier by varying the operating parameters such as moisture content, steam to biomass ratio and equivalent ratio via the equilibrium model approach to predict the composition of the producer gas and calorific value. rahul and gupta (2017) studied the performance analysis of a 10 kwe biomass downdraft gasifier facility, in which a simple and economic technique was also developed to calculate the composition of the producer gas. the simulation was done through the specie transportation model with volumetric and particle surface reaction for the calculation of gas temperature and mass fractions. however, the reviewed literatures did not indicate the effect of biomass mixtures on the corresponding gasification temperatures. the objectives of this study were to understand the effects of multiple fuel injections in the reduction zone of the gasifier on temperature profile. the mathematical model of the downdraft gasification was developed on the development of the gasifier combustion zone that used saw dust, rice husk and corn cobs as fuels by varying process parameters of oxidizer velocities and particle packed densities for the mentioned feedstock. this study applied cfd tool which numerically optimize the fixed bed (fb) downdraft biomass gasifier developed by abubakar (2013) for the gasification of rice husks. 2.0 cfd methodology 2.1 description of the gasifier model figure 1 shows the downdraft gasifier facility developed by abubakar (2013) for the experimental investigation of the performance of biomass gasifier that used rice husk and saw dust as fuel. the gasifier facility is available at the engineering teaching workshop, university of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahman, et al: combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design. azojete, 15(2):278-291. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 280 maiduguri. the dimension of the gasifier is shown in table 1. this model was considered in this study. figure 1: downdraft gasifier facility developed by abubakar (2013) table 1: dimension of the gasifier s.n. parts of gasifier dimensions (cm) 1 outer shell diameter 30 2 inner shell diameter 20 3 height of gasifier 101 4 thickness of shell 10 5 insulation diameter 30 6 air nozzle diameter 3 7 length of air nozzle 8 8 gas outlet diameter 6 2.3 model setup a two-dimensional (2d) model of the fb downdraft gasifier shown in figure 2 was modeled using gambit 2.2 and exported to fluent 6.2 solver for further analysis. the 2d representation of the gasifier reactor focuses on the combustion zone and was completed with meshes of 8000 elements. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 281 figure 2: a 2-d meshed model of the gasifier. 2.4 model formulation the equilibrium model (sharma and sheth, 2016) assumes that all reactions are in thermodynamic equilibrium, such that the residence time allow pyrolysis product to burns out completely and achieve equilibrium in the reduction zone. the general assumptions also include: steady state flow i.e. zero dimensional no-slip condition on wall surfaces, and the gasifier chamber is perfectly insulated dry air enters the chamber (relative humidity is zero), with 21% oxygen and 79% nitrogen by mass. all carbon in solids are completely converted to syngas and all syngas exited the gasifier chamber 2.4.1 governing equations the process fundamental governing equations which describe cfd models for the thermochemical process of fluid flow, heat and mass transfer and chemical reactions are the conservation law of mass, momentum, and energy as presented in equations (1) – (3) (eljummah et al., 2015): ∂ρ ∂t + ∂ρ ∂xi ρ vi = 0 (1) ∂ ∂t ρ vi + ∂ ∂xi ρ vi vj = − ∂ρi ∂xi + 1 re ∂ ∂xj τij (2) ∂ ∂t ρh + ∂ ∂xk ρhvk = ∂ ∂xk [ μ σ ∂h ∂xk + μ α=i n 1 scα − 1 σ h0� ∂γα ∂xk ] (3) where the following notations were used: , is density in kg/m3 v, is velocity of fluid flow across the control boundary in m/s re, is reynolds number h, is the enthalpy in kj/kg file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahman, et al: combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design. azojete, 15(2):278-291. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 282 , is the dynamic viscosity in kg m-1 s-1 , is the stefan–boltzmann constant and subscripts, i, k, are the number of control volumes j, is the reaction number , n initial and final particle mass respectively selecting non-premixed combustion as the solver in fluent, while also applying the species transport phenomena, eddy dissipation and turbulent model as k-epsilon (sharma and sheth, 2016), the simulation was done for progressive change in the flow models by solving the conservation of mass, momentum and energy equations shown in equations (1-3). the chemical formula for biomass material takes the form chxoy , whereby subscript x and y represents coefficients of the chemical species at molecular level of the biomass material. the global gasification reactions for biomass can be written as follows (muilenburg et al., 2011): chxoynz +wh2o+ sh2o + m(o2 + 3.76n2) = x1h2 + x2co+ x3co2 + x4h2o + x5ch4 +3.76m n2 (4) where, the subscripts x, y, and z represents the number of atoms of hydrogen, oxygen, and nitrogen per one atom of carbon in the feedstock respectively, while w and m are the amounts of water and air, per one kmol of feedstock respectively. all inputs in equation 4 are prescribed according to the operating conditions and the feedstock composition given by the proximate and ultimate analysis as shown in table 2 and table 3. table 2: parameters for boundary and operating conditions boundary and operating conditions specification air inlet temperature (k) 300 fuel inlet temperature (k) 300 equivalence ratio 0.4 mass flow rate (kg/s) 0.25 – 1 oxidizer velocity (m/s) 0.1 – 0.5 moisture content (%) 8.5 – 12.5 porosity 0.1 – 0.5 gasifying agent air gasification pressure 1 atm http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 283 table 3: ultimate and proximate analysis for feedstock used for this study source: abdulrahman et al. (2016) 2.4.2 boundary types the boundary types as defined are oxidizer inlet, wall and pressure outlet. the air inlet was defined as velocity inlets, velocity inlet boundary conditions are used to define velocity and scalar properties of the flow at inlet boundary whereby mass flow rate, temperature of the mixture, mass fractions of all species in wood volatiles, turbulent intensity and hydraulic diameter are specified respectively. table 2 gives the boundary conditions as used in the simulation process. additional boundary conditions specified as well as material specification are shown in table 4 and table 5. table 4: additional boundary types zones name id type fluid 1 fluid centre 2 symmetry outlet 3 pressure-outlet throat 4 walls nozzle 5 velocity-inlet outer-wall 6 wall fuel-hopper 7 wall default-interior 9 interior fuel types (solid) rice husk sawdust corn cobs ultimate analysis carbon wt % 48.84 52.0 49.3 hydrogen wt % 7.24 6.07 5.7 oxygen wt % 42.84 41.5 44.6 nitrogen wt % 0.87 0. 28 0.4 sulphur wt % 0.18 0 0 proximate analysis volatile matter wt % 68.8 80.7 77.8 fixed carbon wt % 13.5 8.6 15.6 ash wt % 10.1 2.7 0.8 moisture content (dry basis) wt % 7.6 7.8 5.8 hhv (dry basis) mj/kmol 150.73 470.45 170.67 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahman, et al: combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design. azojete, 15(2):278-291. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 284 table 5: material specification for fuel (solid) used; rice husks, sawdust and corn cobs property units methods values (s) density kg/m3 constant 700 cp (specific heat) j/kg-k constant 2310 thermal conductivity w/m-k constant 0.17299999 while outlet surfaces were defined as pressure outlet boundary. when backflow occurs, specifications at the pressure outlet boundary becomes necessary and is suitable for both compressible and incompressible flows as was also observed by vaezi et al., (2008). the outside surfaces were defined as wall boundary, no-slip condition was imposed on the surface giving that it is stationary, hence velocity is zero. for adiabatic case, the heat flux on the wall was also set to zero. walls with constant temperature were assigned specified value. the reaction in the combustion zone of the gasifier determines the temperatures of the reactions in the other zones of the reactor. 2.5 experimental testing in order to evaluate the performance of the gasifier, selected mixture ratios that are made up of rice husks and sawdust were batched fed and gasified using the test facility. the mixtures ratios were in accordance with the specification given by abubakar (2013). table 6 shows the test data comprising of the biomass mixture ratios weight of biomass (kg) used and time spent (s) for respective gasification experimentation and the corresponding gasification temperature. table 6: measured test temperatures ratio of biomass feed qty of feed (kg) gasification temp (°c) time of stable flame (min) 0:6 6 1100 15.5 6:0 6 768 27.3 6:1 7 800 35.3 6:2 8 810 36 6:3 9 880 46.5 6:4 10 890 63 6:5 11 950 95.7 source: abdulrahman et al. (2016) table 6 reveals that varying the quantity of feed in the gasifier across the mixed ratios, the maximum capacity of the gasifier was 11 kg. feed left after gasification are within the range of 0 3.5 kg and feed consumed (burnt) which is also a fractions of the total quantities of feed used are within the range 5 8.2 kg. time of stable flame in minutes was also reported for the entire experiment as between 15.5 – 95.7. the effect of feed mixture at 6:2 ratio shows that the quantity of feed consumed during gasification suddenly decreases when compared with the other test samples, it also records mild increase in the duration of gas flow when compared with 6:1 mixture. considering that 6:1 mixture is the only case at which this mild change was observed, the addition of sawdust obviously has no further influence on the entire gasification test. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 285 the gasification temperature ranges between 950 1100 °c for the entire gasifier tests, this is in agreement with the values from literature on the gasification temperature of rice husk and saw dust (abubakar, 2013 and begum, et al., 2013). this is satisfactorily, considering that the duration of gas flow is increased proportional to the quantity of fuel used and not the mixture ratio as found from the test (abubakar, 2013). 2.6 comparison of the experimental and cfd predicted temperatures for rice husk and sawdust gasification. figure 3 presents the relationship between measured temperatures reported by abdulrahman et al. (2016) with the cfd prediction. the range of values for predicted gasification temperatures for rice husks and saw dust mixtures is 927 – 1125 °c. maximum gasification temperature for the fuel mixtures is 1398 k (1125 °c) and this is close to the value measured experimentally, 1373 k (1100 °c) which confirms the adequacy of the cfd application. figure 3: experimental and computational results for rice husk and sawdust the relationship between experimental and predicted gasification temperatures was also evaluated by means of statistical approach as presented in figure 4. the analysis indicate good agreement between the experimental and simulated results with r2 value greater than 0.93. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahman, et al: combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design. azojete, 15(2):278-291. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 286 figure 4: experimental and cfd predicted results validation 2.6 model validation in order to validate the model, measured data reported by abdulrahman et al., (2016) were used. maintaining the same operating parameters as applied experimentally for the simulated results while also using rice husk and sawdust as feedstock, the predictions showed reasonable agreement which were statistically tested to have r2 value greater than 0.93 as shown in figure 4. the comparison between numerical and experimental results are shown in figure 5. figure 5: graphical comparison between numerical and experimental results from figure 5, maximum reactor temperature reached for rice husk sawdust mixtures after cfd analysis is 1398 k (1125 °c), this is close to the value measured experimentally (1100 °c). furthermore, the range of values of predicted temperatures is 927 – 1125 °c. considering that the predicted temperatures were higher than measured values is an indication that biomass fuel had adequate residence time in the reactor to actualize complete gasification as earlier observed by muilenburg, et al. (2011). this indicates that computations of the other two fuels mixtures (i.e. rice husks corn cobs and saw dust corn cobs) could give reasonable and acceptable data that are expected to optimize gasifier design. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 287 3.0 results and discussion figures 6 9 shows the contours of temperature gradients with variations in porosity, fuel types and velocity magnitude as well as the effects on fuel types are discussed as follows. 3.1 influence of porosity variations on temperature the temperature gradient due to the variation in porosity for rice husk and sawdust mixture is shown in figure 6. the first two contour plots (figure 6a and 6b) of 0.1 and 0.25 porosities respectively shows that the gasification reaction is progressing. considering that the reaction progresses from the combustion zone moving down to the lower part of the reactor for both plots, yet maximum temperature can be seen to be much higher (1100 k) in figure 6b and relatively lower for 6a (400 k). furthermore, figure 6a appears to have an even control of temperature distribution at the region where temperature measured approximately 335 k. however, porosity of 0.25 has a more even distribution of temperatures throughout the porous zone as shown in 6(b). at porosity of 0.5, maximum temperature of 1375 k was observed at the region where oxidizer and fuel combined as shown in figure 6c this is an indication that biomass gasification of fuels (such as saw dust) with porosity of 0.5 has been fully achieved. furthermore, temperature ranges between 13051400k in this region. however, comparing figure 6c with the first two cases shows that the majority of its post-mixture temperatures are greater than 700 k which indicates that a more even distribution of higher temperatures would be present since there appears an even mixture of fuel to oxidizer. the higher temperatures present also increases the chance for gasification and pyrolysis to occur in this zone and indicate that they would occur at a faster rate. figure 6: contours of temperature gradient with variations in porosity 3.2 influence of fuel types on temperature biomass investigated also include mixture of rice husk and corn cobs, sawdust and corn cobs, which are all component of the study area. the porosity was kept at 0.25 and the oxidizer inlet velocity was set to 1.5 m/s while fuel mass flow rate was 1 kg/s. the ranges of temperature observed for the three fuel types indicated that: rice husk has 450 – 2300 k, sawdust, 350 – 800 k and corn cobs, 480 – 1100 k as shown in figures 7a, b and c respectively. the temperature range for sawdust being the least low of the three fuels was attributed to the influence of moisture content of fuel material as was also reported for the experimental investigation of this study. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahman, et al: combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design. azojete, 15(2):278-291. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 288 figure 7c (corn cobs) shows a temperature gradient in which the central portion of the reactor refusing to light up, this may be attributed to corn cobs packing density which was mildly achieved at a porosity of 0.25 hence the air-fuel reaction and was progressing slowly. however, the hottest region can be found along the wall and towards the pressure outlet for both rice husk (930k) and corn cobs (1100k), although only a smaller region of the gasification zone of the reactor was covered in the case of corn cobs. the high temperature zone is always located in the vicinity of the fuel and oxygen blend. an improved temperature gradient of the reactor gasification zones was observed for rice husks (figure 7a), which is in agreement with the result reported for the experimental investigation by abdulrahman et al. (2016). figure 7: contours of temperature with variations in fuel types figure 8 shows the variations in temperature with fuel mixtures. the mixture of rice husk – corn cobs as fuel produced temperature range of 300 – 1100 k (figure 8a). while temperature range obtained for sawdust – corn cobs fuel mixtures is 300 1080 k as shown in figure 8b. usually, the porosity and moisture content of the fuels play a vital role in the distribution of heat in the reactor as observed in both cases. in addition, low temperature at the locality of exhaust gas outlet can be attributed to the reaction temperature distribution as observed in figure 8a as compared with figure 8b since in the latter it appears that hot wall impact is responsible for the internal conduction and chemical reaction of the reacting species, hence there is even temperature distribution in the reactor at the areas which serves as the oxidation and reduction zones where all the biomass fuel are burnt. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 289 figure 8: contours of temperature with variations in fuel mixtures 3.3 influence of oxidizer velocity on temperature figure 9 demonstrates that the oxidizer velocity makes a great deal of difference in the combustion of the biomass mixtures. at an oxidizer velocity of 1 m/s, the temperature gradient creates a bubble rising from the lower left corner up and to the right. temperature ranges from 300 400 k as shown in figure 9a and maximum temperature was observed near the right fuel inlet and moving against the left towards the pressure outlet. in figure 9b, an oxidizer velocity of 5.0 m/s was set and it is observed that most of the fuel in the particle zone is burn off and the temperature gradient was also observed to have gradually risen up to the oxidizer inlet. the maximum temperature exists at the bottom wall and on the entire left side at 550 k while the arc of temperature around the combustion zone has a temperature of around 450 k. at oxidizer velocity of 15 m/s, the temperature profile is much different as shown in figure 9c. the gradient also increases quickly to the maximum temperature of 1100 k from 300 k which also stretches from oxidizer inlet along the left wall to the pressure outlet and considerable region of this temperature gradient lie between the ranges 300 – 1100 k. however, of all the three cases analyzed, case 2 with 5m/s oxidizer inlet velocity gave smaller area of unburned fuel within the combustion and gasification zones, this development was considered to be the best operating parameter since greater part of the gasifier combustor was covered and larger fraction of the fuel is burnt for maximum yield. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahman, et al: combustion modeling of a fixed bed downdraft biomass gasifier using computational fluid dynamics design. azojete, 15(2):278-291. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 290 figure 9: contours of temperature gradients with variations in velocity magnitude 4.0 conclusion the study has successfully applied a cfd tool to numerically optimize fixed bed downdraft gasifier. the performance of the fixed bed downdraft gasifier in terms of the gasification temperature was obtained. it was observed that changing the porosity of the bed material in the particle packing zones (combustion and gasification zones) indicated that a fuel with a packing density that correlates to a porosity of 0.25 would be the best. this porosity produced an even temperature gradient to allow for a larger and more thorough combustion and gasification zone. the study further revealed that, at 5 m/s velocity inlet biomass material (especially rice husk and rice husk – corn cobs mixtures) gave smaller area of unburned fuel with smaller combustion and gasification zones. the overall analysis of the three fuels computed showed that the corn cobs have large portions of the combustion and gasification zones and is within a temperature range of 300 – 1100 k, which is within the acceptable temperatures for gasification and pyrolysis to occur as earlier reported by abdulrahman et al. (2016). considering that both corn cobs and sawdust was used in this model, sawdust as biomass fuel appears to have a lower temperature gradient with a larger probability of gasification. using cfd as a design tool, mathematical and numerical methods were used to analyzed the gasification process of downdraft biomass gasifier with multiple fuels, the predicted results ensured the optimization of the biomass gasifier operating parameters with improved gasifier temperature. references abdulrahman, sa., abubakar, ab. and el-jummah, am. 2016. performance evaluation of downdraft gasifier fueled using rice husk and saw dust. faculty of engineering seminar series, university of maiduguri, 7: 72 – 77. abubakar, ab. 2013. performance evaluation of downdraft gasifier using rice husk and sawdust additives. m eng. thesis, energy and environmental studies, university of maiduguri, maiduguri. december, 2013. 215p. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):278-291. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kadiri0802@yahoo.com 291 el-jummah, am., mukhtar ua. and adam mk. 2015. computational fluid dynamic procedures for grid generation and solution induced cooling applied to gas turbine hot walls. university of maiduguri, annals of borno, 20: 1-17. mohan, r. and srividhya, pk. 2013. cfd simulation of 20 kw downdraft gasifier. international journal of current engineering and technology, 3(1): 209-214 muilenburg, m., shi, y. and ratner a. 2011. computational modeling of the combustion and gasification zones in a downdraft gasifier. asme 2011 international mechanical engineering congress and exposition, american society of mechanical engineers. denver, colorado. usa. november 11 -17, 4: 151-158. gupta, r., jain, p. and vyas, s. 2017. cfd modeling and simulation of 10kwe biomass downdraft gasifier. international journal of current engineering and technology, 7:(4) 1446-1447. sharma s. and sheth, pn. 2016. air–steam biomass gasification: experiments, modeling and simulation. energy conversion and management, 110: 307–318. vaezi, m., passandideh-fard, m., moghiman, m., and charmchi, m. 2008. modeling biomass gasification: a new approach to utilize renewable sources of energy. proceedings of imece2008 68707, asme international mechanical engineering congress and exposition, boston, massachusetts, usa. october 31 november 6, 2008. 1-9. wang, y. and yan, l. 2008. review cfd studies on biomass thermochemical conversion. international journal of molecular sciences, 9: 1108-1130. zainal, za., ali, r., lean, ch. and seetharamu, kn. 2001. prediction of performance of a downdraft gasifier using equilibrium modeling for different biomass materials. energy conversion and management, 42: 1499-1515. sharmina, bs., rasul, mg., akbar, d. and ramzan, n. 2013. performance analysis of an integrated fixed bed gasifier model for different biomass feedstocks. energies, 6: 6508-6524. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng original research article combustion modeling of a fixed bed downdraft bioma s. a. abdulrahman*, a. t. abdulrahim and a. m. el arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):395-406 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 395 original research article adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis) a. o. okewale* and a. t. adebayo (department of chemical engineering, federal university of petroleum resources, effurun, delta state, nigeria, p. m. b., 1221.) *corresponding author’s email address: okewale.akindele@fupre.edu.ng 1.0 introduction corrosion is a natural occurrence which results in the deterioration of metals by chemical attack or reaction with its environment. corrosion is inevitable for metals, therefore its control and management are more practicable than complete elimination. inhibitors are often added in industrial processes to secure metal dissolution from acid solutions. the known hazardous effects of most synthetic organic inhibitors and the need to develop cheap, nontoxic and ecofriendly processes have now made researchers to focus on the use of natural products. the performance of an organic inhibitor is related to the chemical structure and physicochemical properties of the compound like functional groups, electron density at the donor atom, p-orbital character, and the electronic structure of the molecule. the inhibition could be due to adsorption of the molecules or its ions on anodic and/or cathodic sites, increase in cathodic and/or anodic over voltage, and the formation of a protective barrier film (rani and basu, 2012). organic inhibitors generally have heteroatoms; o, n, and s are found to have higher basicity and electron density and thus act as corrosion inhibitors. the heteroatoms are the active centre for the process of adsorption on the metal surface. the use of organic compounds containing oxygen, sulphur, and especially nitrogen to reduce corrosion attack on steel has been studied. the previous research work carried out on most organic inhibitors showed that organic inhibitors are adsorbed on the surface of metal by displacing water molecules on the surface and forming a compact barrier. availability of non-bonded (lone pair) and p-electrons in inhibitor molecules facilitate electron transfer from the inhibitor to the metal. a coordinate covalent bond involving transfer of electrons from inhibitor to the metal surface may be formed (evans, 1976; rani and basu, 2012). in a bid to have less expensive, environmentally friendly, readily available and less toxic inhibitors, researchers have used various plant materials as corrosion inhibitors. pumpkin (telfairia occidentalis) is a tropical vine grown in nigeria and other west african region for its leaf and edible seeds. the phyto-chemical composition of the leaf, root, pod and stem were investigated (ogbonnaya and uadia, 2016). akwukwaegbu et al. (2016) investigated the phytochemical composition of the pumpkin pod, it was found out that it contains tannins, saponins, alkaloids, and flavonoids. this present study investigated the use of pumpkin pod extract as an inhibitor, its mechanism of adsorption, and adsorption isotherms. article information abstract in this study, the inhibition effect of ethanolic extract of pumpkin pod (telfairia occidentalis) on the corrosion of carbon steel in acidic medium was investigated using weight loss method at 308k 348k. the energy of activation, adsorption and thermodynamics parameters such as enthalpy, entropy, and gibb's free energy were evaluated from the results of temperature studies. the activation enthalpy of corrosion process increases from 28.782kj/mol to 62.678kj/mol. as the temperature increased, the inhibition efficiency decreased. the adsorption of pumpkin pod extract on carbon steel was found to best fit langmuir, and freundlich adsorption isotherms. the activation energy of adsorption and gibb’s free energy values indicated an endothermic and strong spontaneous adsorption of the pumpkin pod extract on the surface of carbon steel respectively. scan electron microscope (sem) analyses showed that pumpkin pods (telfairia occidentalis) extract protected the surface of the metal from corrosion by forming a protective layer on the metal surface. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2019 revised 19 feb., 2020 accepted 23 feb, 2020 keywords: pumpkin pod carbon steel thermodynamics activation adsorption mailto:okewale.akindele@fupre.edu.ng http://www.azojete.com.ng okewale and adebayon: adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis). azojete,16(2):395-406. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 396 2. materials and methods 2.1 materials pumpkin pods (telfairia occidentalis) were obtained from agbarho community in effurun, delta state, nigeria. carbon steel was procured from accredited iron sheet dealer in effurun and machined in mechanical workshop at federal university of petroleum resources, delta state. hanna model ph – 211 (ph meter), genlab oven model mino/75/f (oven), weighing balance of model (bh – 600), and beakers, were employed for this corrosion study. hydrochloric acid, acetone, and ethanol solutions used were of analytical grades (sigma aldrich). distilled water was procured from the department of chemical engineering laboratory, federal university of petroleum resources, effurun delta, state, nigeria for both sample preparation and solutions. 2.2 methods 2.2.1 pre-treatment of sample and sample characterization pumpkin pods were thoroughly washed thereafter sun dried and pulverized into powdery form with the aid of laboratory blender. it was then sieved with a sieve of 0.143µm mesh. the sample was later stored in a desiccator prior to use. 2.2.2 fourier transform infrared spectroscopy (ftir) pumpkin pods (telfairia occidentalis) 0.143μm particle size was observed with ftir spectroscopy (buck scientific model 530) with the range 500 4000 cm-1 (wavelength). the background material used in the analysis is potassium bromate (kbr). 2.2.3 x – ray fluorescence analysis (x – rf) the elemental compositions of the carbon steel used was observed with x – supreme 800, oxford instrument. the metal was machined to flat shape of 20 – 50 mm diameter. sample cup was cleaned and filter fixed in it shape thereafter the metal sample was placed in the cup to cover the filter and ensure a thickness of 3mm at the bottom. the instrument was switched on, the elemental composition method was selected, and the sample identity was then level in the position selected with reading accepted. the instrument was rotated to the position of the sample in the tray at x – ray position after the start button was pressed while the intensity of radiation was now converted to the weight percentage. 2.2.4 extraction of pumpkin pods (telfairia occidentalis) extract 50 g of the dried pumpkin pods (telfairia occidentalis) powder was transferred into a 500 ml soxhlet extractor and 500 ml of 70% ethanol reflux continuously for 3 hours at 78 ºc. the set-up was placed on a heating mantle and the pumpkin pods (telfairia occidentalis) extract was extracted exhaustively by heating the solution. the extract was obtained after recovering ethanol in a rotary evaporator (model r-210) at 40 ºc. 2.3 weight loss measurement the gravimetric or weight loss method was used. the carbon steel was mechanically polished with silicon carbide abrasive paper, degreased with ethanol, washed in distilled water and dried in acetone. each carbon steel coupon was sized 40 mm × 20 mm × 2 mm. before polishing, a hole of 0.1 cm was drilled on each coupon. the coupon was suspended with the aid of a nylon thread in a 100 ml beaker with 100ml of 1.5m hcl at different inhibitor concentrations. the mechanism of inhibition and thermodynamic parameters were studied at 308, 318, 328, 338, and 348 k temperature at contact time of 7 hours. each of the carbon steel metal coupon after the corrosion process was dipped in both distilled water and ethanol solutions. this was scrubbed to remove any remaining residual inhibitor concentration and hcl. thereafter, the coupon was then washed thoroughly with washing liquor, rinsed with distilled water and later dried in acetone before been reweighed. 2.4 determination of weight loss the weight loss of the carbon steel coupon was determined using equation 1 below: weight loss, (g) = w – wi (1) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 395-406. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 397 where: w is the initial weight of the mild steel coupon, wi is the weight of the carbon steel coupon after corrosion study. 2.5 determination of inhibitor efficiency the efficiency of corrosion inhibition was obtained using equation 2 e % = wb −wc wb × 100 (2) where: wb is the loss in weight in uninhibited medium (blank), and wc is the loss in weight in inhibited medium. 2.6 corrosion rate determination the expression for measurement of corrosion rate (c.r) in millimeters penetration per year (mm/yr) was used to measure the rate of corrosion rate for the specimens, which was expressed in equation 3 (callister, 1997). c. r. = 87.6w atρ (3) where: w is corrosion weight loss of carbon steel (mg), a is the total surface area of the specimen in (cm2), t is the exposure time in hours (h), and ρ is the density of the specimen (g/cm3). 2.7 determination of activation energy the activation energy parameter of the corrosion inhibition process on carbon steel surface was gotten using equation (4) below log cr = log a ea 2.303rt (4) where: cr is the rate of corrosion, ea is the apparent activation energy, r is the universal gas constant, t is the absolute temperature, and a is the frequency factor. 2.8 determination of thermodynamic parameters the thermodynamic parameters such as enthalpy, and entropy of carbon steel corrosion inhibition in acidic medium was calculated using equation (5) while the gibb’s free energy was calculated using equation (6). the transition state theory equation given by equation 5 was used (mouheddin et al. 2018; ogoke et al. 2009). log cr t = log r nh + ∆so 2.303r − ∆ho 2.303rt (5) where: h is the planck's constant (6.626176 × 10-34 js), n is the avogadro's number, (6.022×1023 mol-1), r is the universal gas constant (8.314 j/kmol) and t is the temperature of the medium. the gibb’s free energy of adsorption (δg°ads) which can characterize the interaction of adsorbed molecules and metal surface δg°ads = rt ln (55.5 x kads) (6) where: kads is the adsorption equilibrium constant, r is the gas constant (8.314 j/mol.k), t is the absolute temperature in kelvin and the value 55.5 is the concentration of water in solution expressed in mol/l.. 2.9 adsorption isotherms four different adsorption isotherms were tested so as to have an understanding on the interface between the inhibitor and carbon steel surface. the isotherms tested were langmuir, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okewale and adebayon: adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis). azojete,16(2):395-406. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 398 freundlich, temkin, and el awady adsorption isotherms. the linear regression coefficient of determination (r2) was used to determine the model that fitted best to the experimental values. 2.9.1 langmuir isotherm langmuir relationship is represented by equation (7) c ɵ = 1 k + c (7) where: k is the equilibrium constant of adsorption (m-1) which was employed to obtain the gibb’s free energy, c is the inhibitor concentration ppm, and ɵ is the degree of surface coverage (rajendran et al. 2000; nnanna et al. 2014). 2.9.2 freundlich isotherm the fitting of non – ideal system can be done sometimes by fitting the experimental data to freundlich adsorption isotherm as seen in figure 6 (yaro and khadom, 2008). this is expressed in equation 8: θ = kcn (8) equation 8 can be re – written lnθ = lnk + nlnc (9) where: ɵ is the degree of surface coverage, c is the inhibitor concentration, in ppm, k is the adsorption constant which is a measure of adsorption capacity, (l/g), and n is the positive constant called the freundlich exponent which talks about the intensity of adsorption process on the carbon steel surface. 2.9.3 temkin isotherm this is expressed in equation (10) while the linear form of equation (10) is given by equation (11) ɵ = 1 f ln (kadsc) (10) equation 10 can be re written as ɵ = 1 f lnc + 1 f lnk (11) where: ɵ is a linear function of ln c (nnanna et al. 2010), k is the equilibrium constant of adsorption, (l/g), c is the inhibitor concentration, (g/l), and f is a coefficient of inhomogeneity connected with the range of inhomogeneity c by equation 12. f = c/rt (12) 2.9.4 el-awady isotherm this model is also referred to as the kinetic/thermodynamic model and is written as follows; log ɵ 1− ɵ = logk + ylog c (13) where: y represents the number of inhibitor molecules occupying one active site of the metal surface, ɵ is the degree of surface coverage, c is the inhibitor concentration, ppm. y can be related to the binding constant, b, according to equation (14). b = k1/y (14) when 1/y>1, each inhibitor molecule is believed to occupying more than one active site on the metal surface and vice – versa (fouda and ellithy, 2009). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 395-406. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 399 3. results and discussion 3.1 characterization of carbon steel and pumpkin pods (telfairia occidentalis) extract table 1 shows the result of the x – ray fluorescence of the carbon steel used. table 1: result of the x – rf analysis on carbon steel elements concentration (mg/kg) magnesium 81.865 aluminium 685.113 silicon 281.657 sulphur 164.989 chlorine 363.401 calcium 113.130 titanium 161.193 chromium 191.483 manganese 733.821 iron 173710.764 cobalt 132.529 lead 26.057 bromine 47.343 ftir analysis of pumpkin pod (telfairia occidentalis) extract the ftir spectrum of pumpkin pods (telfairia occidentalis) extract is shown in figure 1. at broad band of 3324 cm-1 corresponds to an alcoholic –oh stretching group. the peak at 2974 cm-1 can be assigned to alcoholic c-h group. 1639 cm-1wavelength indicates an aromatic (c=c) stretching while the value of 1728 cm-1 suggest (c=o) stretching frequency. aromatic rings due to aromatic skeletal vibrations is noticed at 1508 cm-1 and 1421cm-1 can be assigned to aromatic rings due to aromatic skeletal vibrations. the broad band of 1329 cm-1 seen in the spectrograph is due to bending vibrations of oh group while 1209 cm-1 is due to guaicynl ring in conjunction with c-o stretching group. the presence of aromatic, and carbonyl groups in the extract suggest that it can be used as an inhibitor. figure 1: ftir spectra of pumpkin pod extract 3.2 effect of temperature figure 2 shows inhibition efficiency against temperature at 7 h immersion time. the results show that with increase in temperature the percentage of inhibition efficiency for the inhibitor at different concentration decreases, a trend that supports physical adsorption mechanism. this can be explained that the protective films of the inhibitor are formed on the surface of the carbon steel are less stable at higher temperature. it can be due to desorption of some file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okewale and adebayon: adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis). azojete,16(2):395-406. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 400 adsorbed molecules from the surface of the carbon steel at higher temperature thereby leading to the greater area of carbon steel been exposed to attack from the acidic environment. the results obtained in this work is similar to that reported by abd el-hameed, (2011). figure 2: effect of temperature on inhibition efficiency of pumpkin pod extract 3.3 thermodynamic activation parameters of the corrosion process arrhenius equation represented by equation (4) was used to calculate the activation energy ea in the presence and absence of cocoa leaf extract inhibitor. the arrhenius plot of log cr against reciprocal of absolute temperature (1/t) is shown in figure 3 which gives a straight-line graph with slope equal to -ea/2.303r and the intercept equal to log a. hence, the activation energy (ea) and the pre-exponential factors (a) were calculated and tabulated in table 2. these activation energy values were found to range from 58.75 kj/mol 65.511 kj/mol. the value obtained for pumpkin pods (telfairia occidentalis) inhibitor used was higher than that of the blank, indicating that the corrosion of carbon steel is retarded by the presence of pumpkin pods (telfairia occidentalis) extract in hcl. it can also be observed that the activation energy value obtained is lower than the threshold value of 80 kj/mol that is required for chemical adsorption mechanism. it can be suggested that the inhibitor adsorption mechanism on the carbon steel surface is physisorption. higher values of ea in the presence of inhibitor is a good indication that the extract increases the energy barrier for the corrosion process. this process occurs because the pumpkin pod extract (inhibitor) forms a passive layer on the surface of the carbon steel, thereby making the solubility of iron (fe) to be reduced (yetri et al., 2015). similar results were reported in findings of eddy et al. (2009). figure 3: plot of log corrosion rate against the inverse of absolute temperature thermodynamic properties such as enthalpy (∆h°) and entropy of activation (∆s°) are studied so as to determine the mechanism of adsorption process involved in the corrosion process. in other to calculate the thermodynamic parameters like enthalpy (∆hads), and entropy (∆sads) of corrosion process in the presence and absence of pumpkin pods (telfairia occidentalis) extract in acidic environment. the plot of log (cr/t) against 1/t is seen to be linear in figure 4 from which (∆hº) and (∆sº) values were deduced from the slopes and intercept of the graph respectively and listed in table 2. the enthalpy of activation (δhads) and the entropy of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 395-406. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 401 activation (δsads) were calculated, alongside their linear regression coefficient which is indicated in table 3. the large positive values of δhads and the negative value of δsads indicate that the adsorption of pumpkin pods (telfairia occidentalis) extract on the surface of carbon steel is endothermic in nature. it is also noted that the values of activation energy (ea) are larger than the corresponding values of (δhads) which indicate that the corrosion process might have involved a gaseous reaction, like the evolution of hydrogen reaction, associated with a decrease in the total reaction volume (andreani, 2016). also, the average difference in the value of the (ea − ∆hads) is 2.72 kj/mol which is approximately equal to the value of rt (2.73 kj/mol) at the average temperature (328 k) used in the study. this result is in agreement with known perfect gas equation which suggest that the corrosion process is a unimolecular reaction. the result obtained shows that the inhibitor acted equally on eads, and δhads. the result of this work corroborate the findings of zarrouk et al. (2011). figure 4: showing the plot of log cr/t against the inverse of absolute temperature table 2: activation energy, enthalpy and entropy of corrosion inhibition using pumpkin pods (telfairia occidentalis) on carbon steel. inhibitor concentration (ppm) ea (kj/mol) ∆hº (kj/mol) ea ∆hº ∆sº (j/mol k) 50 65.399 62.678 2.721 19.966 100 59.856 57.135 2.721 38.284 150 63.685 60.965 2.72 28.025 200 65.512 62.793 2.72 23.66 250 59.088 56.034 3.054 46.069 blank 31.503 28.782 2.721 113.786 large and negative values of entropies show that the activated complex in the rate determining step represents an association rather than a dissociation step, meaning that a decrease in disordering takes place on going from reactants to the activated complex (dahmani, et al., 2010). table 4 depicts adsorption thermodynamic parameters of the pumpkin pods (telfairia occidentalis). the negative value of (δg°ads) ensures stability, strong and spontaneous adsorption of the pumpkin pods (telfairia occidentalis) on the metal surface, which explains its high corrosion inhibition efficiency of absorbed layer on the metal surface for the adsorption process. it can be seen that there was a decrease in the absolute value of free energy (δg°ads) with rise in temperature which implied a physical adsorption mechanism. generally, the values of (δgads) up to -20 kj/mol are associated with the electrostatic interaction between the charged molecules and charged metal (physisorption), while those negative values higher than 40 kj/mol involve sharing or transfer of electrons from the inhibitor to the metal surface to form a co-ordinate type of bond (chemisorption). the calculated value of (δg°ads) was found to be negatively less than 40 kj/mol. in general, the adsorption may be enhanced by the presence of hetero atoms like n / o / s atoms with lone pair of electrons, in the inhibitor molecules that makes it adsorbed electrostatically on the metal surface forming insoluble stable films and thus decreasing metal dissolution. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okewale and adebayon: adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis). azojete,16(2):395-406. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 402 3. 4 adsorption isotherm for langmuir isotherm a plot of c/ɵ against c as depicted in figure 5 gave a reciprocal of intercept as the adsorption constant. figure 5: langmuir isotherm for adsorption of inhibitor on carbon steel surface freundlich isotherm as seen in figure 6 is a plot of log ɵ against log c which gave a straight line. figure 6: freundlich isotherm for adsorption of inhibitor on carbon steel surface temkin isotherm is depicted in figure 7 which showed a plot of ɵ against lnc that gave a straight line which is an indication that temkin isotherm model is followed. figure 7: temkin isotherm for adsorption of inhibitor on carbon steel surface el – awady isotherm is a plot of log (ɵ/1-ɵ) against log c which is shown in figure 8. it can be used to determine the associated parameters such as the reciprocal of y which is used to describe the number of active sites on the surface occupied by one molecule of the inhibitor on the surface of steel metal. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 395-406. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 403 figure 8: el awady isotherm for adsorption of inhibitor on carbon steel surface table 3: langmuir adsorption isotherms parameters temperature (k) kads (l/g) r2 ∆g (kjmol-1) 308 0.1025 0.9991 -4.452 318 0.1119 0.9995 -4.828 328 0.0875 0.9989 -4.309 338 0.015 0.9543 0.515 348 0.011 0.9977 1.428 table 4: freundlich adsorption isotherm parameters temperature (k) kads (l/g) r2 ∆g (kjmol-1) 308 0.6494 0.8825 -9.179 318 0.6286 0.9287 -9.391 328 0.5776 0.9394 -9.455 338 0.1281 0.9484 -5.512 348 0.0649 0.9739 -3.708 table 5: temkin adsorption isotherm parameters temperature (k) kads (l/g) r2 ∆g (kjmol-1) 308 4.13 0.8792 -13.916 318 3.942 0.9271 -14.045 328 3.506 0.9331 -14.373 338 2.349 0.9117 -13.686 348 2.526 0.9918 -14.301 table 6 el awady adsorption isotherm parameters temperature (k) kads (l/g) r2 ∆g (kjmol-1) 308 0.682 0.8583 -9.305 318 0.803 0.9201 -10.039 328 0.855 0.9193 -10.525 338 6.35e-11 0.5831 54.695 348 0.0237 0.9903 -0.793 tables 3 – 6 shows the various parameters of adsorption isotherms studied. the adsorption equilibrium constant (kads) value was seen to decrease with increase in temperature, this indicates that, the inhibitor is easily adsorbed on the carbon steel surface at lower temperature. but when the temperature was higher, the adsorbed inhibitor tended to desorb from the carbon steel surface. the result obtained in this work is similar to that reported by manimegalai and manjula (2015). langmuir adsorption isotherm indicated that the ppe extract contains organic compounds having polar atom or groups which are adsorbed on the metal surface and may interact by mutual repulsion or attraction (subhashini, 2004; sivaraju and kannan, 2010). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okewale and adebayon: adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis). azojete,16(2):395-406. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 404 3.5 surface morphology analysis scanning electron microscope (sem) images were taken in order to study the surface morphology of carbon steel in absence and presence of pumpkin pods (telfairia occidentalis inhibitor. figure 9a revealed that in the presence of pumpkin pods (telfairia occidentalis) inhibitor in 1.5m hcl solution while figure 9b showed the carbon steel without inhibitor. figure 9a is the carbon steel metal in 250ppm of pumpkin pods (telfairia occidentalis) after 120 hr. it showed a surface with fibre –like protective layer as a result of the pumpkin pods (telfairia occidentalis) extract deposition on the metal surface. figure 9b shape is that typical to pitting corrosion (andreani, et al., 2016). comparison of both figure 9a and 9b showed that the pits had disappear and carbon steel surface is almost free from corrosion in hcl due to the formation of an adsorbed film (protective layer) of pumpkin pods (telfairia occidentalis) on the carbon steel surface. (a) (b) figure 9a: sem of carbon steel with inhibitor figure 9b: sem of carbon steel without inhibitor conclusion pumpkin pod (telfairia occidentalis) was extracted and characterized using ftir spectroscopy and was subsequently used as a corrosion inhibitor on carbon steel metal. weight loss method was employed in corrosion study. adsorption and thermodynamics studies were carried out to estimate the mode of adsorption mechanism for the inhibitor molecules on the carbon steel surface. the inhibition efficiency increases with increase in the inhibitor concentration but decreases with rise in temperature while corrosion rate decreased as inhibitor concentration is increased. the corrosion inhibition performance of pumpkin pods (telfairia occidentalis) extract was found to depend on temperature and its concentration. the inhibition by pumpkin pod extract occurred through physisorption as evidenced in increase of the activation energy for the inhibited medium which was higher than the one without an inhibitor (blank). the activation enthalpy increases from 28.782kj/mol to 62.678kj/mol. the positive values of the enthalpy signified an endothermic adsorption process. the activation entropy (∆so) values in the absence and presence of inhibitor were all negative which implied that the activated complex in the rate determining step represents association rather than a dissociation step. this indicates that during the adsorption process, an increase in the degree of disorderliness occur. experimental data fitted well to langmuir, and freundlich isotherms in comparison to both temkin and el – awady isotherms. the adsorption process is strong, feasible, and spontaneous with the negative value of free energy (∆go ads) obtained. acknowledgements the authors would like to thank the department of chemical engineering, federal university of petroleum resources effurun, delta state nigeria, for providing the facility to carry out the experimental work. thanks also goes to mr. akpeji honesty of department of chemistry, federal university of petroleum resources, effurun, for his technical assistance. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 395-406. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 405 references. abdel-hameed, rs. 2011. aminolysis of polyethylene terephthalate waste as corrosion inhibitor for carbon steel in hcl corrosive medium, advances in applied science research, 2(3): 483-499. akwukwaegbu, pi., peters, de. and wegwu, mo. 2016. proximate analysis and phytochemical screening of fluted pumpkin (telfairia occidentalis) pod, american journal of food, nutrition and health, 1(1): 1 – 6. andreani, s., znini, m., paolini, l., majidi, j., hammouti, b., costa1, j. and muselli, a. 2016. study of corrosion inhibition for mild steel in hydrochloric acid solution by limbarda crithmoides (l.) essential oil of corsica, journal of material and environmental sciences, 7(1): 187-195. callister, wd. 1997. material science and engineering, 4th edition, john wiley and sons inc., new york, usa. dahmani, m., et-touhami, a., al-deyab, ss., hammouti, b. and bouyanzer, a. 2010. corrosion inhibition of c38 steel in 1 m hcl: a comparative study of black pepper extract and its isolated piperine, international journal of electrochemical sciences, 5: 1060 – 1069. eddy, no., ekwumemgbo, pa. and mamza, ap. 2009. ethanol extract of terminalia catappa as green inhibitor for the corrosion of carbon steel in acidic medium, green chemistry letters and reviews, 2: 223-231. evans, ur. 1976. the corrosion and oxidation of metals, hodder arnold, london. fouda, as. and ellithy, as. 2009. inhibition effect of 4 – phenyl thiazole derivatives on corrosion of 304l stainless steel in hcl solution. corrosion science, 51: 868 – 875. manimegalai, s. and manjula, p. 2015. thermodynamic and adsorption studies for corrosion inhibition of mild steel in aqueous media by sargasam swartzii(brown algae). journal of material and environmental science, 6(6): 1629 – 1637. mouheddin, ta., umoren, sa. ime, bo. and shaikh, aa. 2018. isoxazolidine derivatives as corrosion inhibitors for low carbon steel in hcl solution: experimental, theoretical and effect of ki studies. royal society of chemistry, 8: 1764 – 1776. nnanna, la., onwuagba, bn., mejeha, im. and okeoma, kb. 2010. inhibition effects of some plant extracts on the acid corrosion of aluminium alloy. african journal of pure and applied chemistry, 4(1): 011 – 016. nnanna, la., uchendu, ko., nwosu, fo., ihekoronye, u. and eti, ep. 2014. gmelina arborea bark extracts as a corrosion inhibitor for mild steel in an acidic environment. international journal of materials and chemistry, 4(2): 34 – 39. ogbonnaya, ea. and uadia, po. 2016. phytochemical screening and acute toxicity evaluation of telfairia occidentalis aqueous extracts on rats. pakistan journal of pharmaceutical science, 29(3): 913 – 917. ogoke, ec., odoemelam, sa., ita, bi. and eddy, no. 2009. adsorption and inhibitive properties of clarithromycin for the corrosion of zinc in 0.01 to 0.05m h2so4, port. electrochim. acta. 27: 713 – 724. rajendran, s., joany, mr., apparao, bv. and palaniswamy, n. 2000. synergistic effect of calcium gluconate and zn2 on the inhibition of corrosion of mild steel in neutral aqueous environment. transactions of the society for advancement of electrochemical science and technology, 35(3, 4):113. rani, bea. and basu, bbj. 2012. green inhibitors for corrosion protection of metals and alloys: an overview. international journal of corrosion, v.2012, art. 380217: 1 – 15, doi:10.1155/2012/380217. sivaraju, m. and kannan, k. 2010 inhibitive properties of plant extract (acalypha indical.) on mild steel corrosion in 1n phosphoric acid, international journal of chemical technological research, 2(2): 1243-1253. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okewale and adebayon: adsorption and thermodynamics studies of corrosion inhibition on carbon steel using pumpkin pod extract (telfairia occidentalis). azojete,16(2):395-406. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okewale.akindele@fupre.edu.ng 406 subhashini, s. 2004. corrosion inhibition study of mild steel in acid media by extracts of some leguminous seeds as eco-friendly inhibitors, journal of camel practical resources, 11(1): 27 – 34. yaro, as. and khadom, aa. 2008. evaluation of the performance of some chemical inhibitors on corrosion inhibition of copper in acid media. journal of engineering, 2(14): 2350 – 2362. yetri, y., emriadi, e., jamarun, n. and gunawarman, g. 2015. corrosion inhibitor of mild steel by polar extract of theobroma cacao peels in hydrochloric acid solution. asian journal of chemistry, 27(3): 875 – 881. zarrouk, a., hammouti b., zarrok, h., al-deyab, ss. and messali, a. 2011. temperature effect, activation energies and thermodynamic adsorption studies of l-cysteine methyl ester hydrochloride as copper corrosion inhibitor in nitric acid 2m. international journal of electrochemical science, 6: 6261 – 6274 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):363-374 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 363 original research article characterization of soils in east andwest zones of kano river irrigation project, nigeria d. mohammed1, m. m. maina,2 i. audu3, i .y. tudun wada4* n. k. nasiru5 and abhishek raj6 (1department of agricultural and bio-environmental engineering, kaduna polytechnic, kaduna, nigeria 2department of agricultural and environmental engineering, bayero university, kano, nigeria 3department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria 4advance space technology laboratory, bayero university, kano, nigeria 5national space research and development, bayero university, kano, nigeria 6department of forestry, faculty of agriculture & veterinary sciences, mewar university, rajasthan, india) *corresponding author’s email address: wadata4all@yahoo.com 1.0 introduction the most efficient method of ensuring sufficient food supply to support life is sustaining soil and environmental qualities. management of tropical soils is important in addressing challenges of food security, soil degradation, environmental quality and the issue of the global carbon cycle (chimdi et al., 2012). the knowledge of particle-size distribution or texture is a determining for many agricultural factors such as choice of crops, irrigation methods, management of soil and fertilizer application. it is very important in the management of agricultural soils for optimum crop production. plants’ growth is influenced by the size of the soil particle because they control the availability of nutrient and root growth. three types of grains control soil texture, these are sand, silt and clay (chakraborty and biswaranjan, 2015). soil usually contain some amount of clay which influences its management and productivity (newman, 1984). the amount of clay in soil is very important as the structure of soil depends very much on clay (dixon, 1991). article information abstract the relationship between clay composition and on organic matter content, saturated hydraulic conductivity, bulk density and location of soils in a different part of the kano river irrigation project (krip) was studied by taking soil samples from forty (40) sectors. sampling was done from the depth of 0-45 cm with soil auger, digger, a wooden plank and core samplers. particles size analysis has shown that the percentage of clay varies from the range of 22.12% to 5.4% as observed in raje and butalawa respectively. the texture in most of the sectors was dominated by sandy loam. the organic matter (om) content is typical of agricultural topsoil as all the sectors have organic matter within the range of 1–6%. spearman correlation coefficient of 0.452 indicates that the relationship between % clay and bulk density was more of a non-linear relationship than linear. the pearson correlation coefficient of 0.876 between % clay content of the soil in all the sectors and saturated hydraulic conductivity represents a strong negative relationship between the variables, as % clay content increases, the strength of sat. hydraulic conductivity tends to decrease. the % clay has no relationship with location of sectors based on the correlation analysis. the pearson and spearman coefficients between % clay content and % om were 0.407 and 0.473 respectively and this represent a positive relationship between the variables. it was recommended that organic matter content, saturated hydraulic conductivity and bulk density can be used as one of the determinant variables in the development of a model aimed at predicting the % clay of soils in krip. application of organic manure and fertilizer to improve soil productivity and buffering capacity was also recommended due to low organic matter content. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 feb., 2019 revised 07 march, 2020 accepted 10 march, 2020 keywords: clay organic matter content correlation soil properties kano river irrigation project mailto:wadata4all@yahoo.com http://www.azojete.com.ng mailto:wadata4all@yahoo.com mohammed et al: characterization of soils in east and west zones of kano river irrigation project, nigeria. azojete,16(2):363-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 364 the term clay refers to the soil separate consisting of particles less than 0.002mm in equivalent diameter. it influences many of the chemical and physical properties that make the soil a useful medium for plants’ growth (dixon, 1991). the cations exchange capacity (cec) of clays is among their most important properties in retaining plant nutrient because the selectivity of cations influences soils as a medium for plant growth and disposal of wastes e.g., radioactive and toxic metal ions (dixon, 1991). under any environmental condition, plant growth and production are controlled by soil structure resulting from reactions involving clay. soil with low clay content such as sand and silt exhibit a narrow range over which physical properties can change and such soils may have low fertility and therefore, unfavorable for plant growth (page, 1952). soils with little clay have a simple structure compared to the one that has a higher amount with a more complex structure. clay contributes to the formation of soil structure by undergoing seasonal shrinking and swelling (dixon, 1991). compared to other soils separates, clay often have a large predominantly negatively charged large surface area that retains nutrients against leaching and buffers the soil against extreme change in ph. when clay degrades, it is a source of plant nutrients (newman et al., 1984). soil organic matter tends to increase as the clay content increases. under similar climate conditions, the organic matter content in heavy textured soils like clayey is two to four times that of lighttextured soil like sandy soil (bot and benites, 2005). presence of clay in soil particularly with small amounts of organic matter has a great effect on soil properties. sodium adsorption ratio and exchangeable sodium percentage relationship (sar-esp) vary with soil type due to differences in clay minerals content and consequently soil texture (ezlit et al., 2010). this paper is aimed at identifying variables that can be a determinant in the development of the proposed regression model for predicting the percentage of clay from saturated hydraulic conductivity, bulk density, organic matter content and location. coordinates of each irrigation sector were used for the location. the research will also study the relationship of clay as it exists in soil not as a soil separate with the aforementioned properties in the kano river irrigation project (krip). the knowledge of this relationship is important due to the influence of these properties on soil condition that favours the growth of crops. the findings will be applied in the management of soil both under rain-fed and irrigated conditions. 2. material and methods 2.1 study area the study was conducted in kano river irrigation project located between latitudes 11°32`n and 11°51`n and longitudes 8°20`e and 8°40`e within the sudan savannah zone of northern nigeria (figure1). rainfall is usually between july and september with maximum amounts of 214.0 mm. average annual rainfall ranges from 635 to 889 mm, about 60% of which falls in july and august and varies considerably from year to year (maina et al, 2012). the geology of the area consists of older granites and younger meta sediments of precambrian to lower paleozoic age. the soils are mostly moderately deep to deep and well-drained with sandy loam texture at the surface and sandy clay loam textured subsoil (jibrin et al., 2008). http://www.azojete.com.ng mailto:wadata4all@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 363-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 365 figure 1: map showing the location of the study area. source: advance space technology laboratory, buk, 2019 the krip with a total area of 62,000 ha was planned to be implemented in two phases; the kano river irrigation project phases i and ii. the main source of water for irrigation is the tiga dam which was constructed across river kano between 1970 and 1974 and has a capacity of 1.968 billion m3, a length of 6km and a height of 48 m (mohammed et al., 2015). 2.2 collection of soil samples soil samples were collected from forty (40) sectors in the study area for the measurement of soil properties. the collection was done with soil auger, digger, a wooden plank and core samplers. the auger was driven to a depth of 0-45 cm (active rooting depth for the crop grown in the study area). the collected samples were placed in a properly labeled polythene bags. the choice of the sampling points in a sector was done making sure that representative samples were collected. the coordinates of all the sampling points were taken using garmin 78 gps. the samples were taken to the laboratory for analysis. laboratory analysis grain size analysis was performed in the laboratory by the bouyoucos hydrometer method (gee and dr, 2002). the percentage of sand, silt and clay particles in the samples were determined using eqns. 1 through 4 (zakari et al, 2014):   100% 1  ws chrcsi (1) 2% 100c h rc w s   (2)  % % %s i s i c c   (3)  % 1 0 0 %s s i c   (4) where: si = silt, c = clay, s = sand, chr1 = first corrected hydrometer reading and chr2 = second corrected hydrometer reading, ws= weight of sample. bulk density was determined by the use of the core sampler method (grossman and reinsch, 2002). the saturated hydraulic conductivity (ksat) was measured using the constant-head permeameter method (klute and dirksen, 1986). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:wadata4all@yahoo.com mohammed et al: characterization of soils in east and west zones of kano river irrigation project, nigeria. azojete,16(2):363-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 366 2.4 statistical analysis kriging which involved spatial interpolation was used to estimate values at unknown points of the sectors based on the values at sampling points. this is based on the fact that the result of the measured areas of the sectors in the krip close to points where samples were not taken have the most influence. krige map of the parameters are presented in figures (2.0, 3.0 and 4.0). pearson correlation and spearman coefficients were also used to determine the correlation between the variables viz-a-viz percentage clay content, saturated hydraulic conductivity, bulk density percentage organic matter content and location. 3. results and discussion the result of the percentage of clay, saturated hydraulic conductivity (ksat), and organic matter content as well as soil texture was presented in table 1. the data was used to study the influence of clay composition on these related properties of soil. the texture in most of the sectors of the krip is dominated by sandy loam. jibrin et al. (2008) reported moderately deep and well-drained soil with sandy loam texture at the surface and sandy clay loam textured in the subsoil as recorded in cirin and other sectors. the percentage of clay varies from the range of 22.12% to 5.4% as observed in raje and butalawa respectively. soil having more clays and organic matter percentage composition could exhibit higher buffering capacity which is associated with greater cation exchange capacity (goswami et al., 2012). figure 2 shows the distribution of organic matter in krip. the mean value ranges from 0.9561.83%. goswani et al. 2012 reported that organic matter composition in tropical soil is often less than 1% compared to a range of 5 10% in the temperate regions. the lowest organic matter content of 0.1% was observed at danbaki sector located in bunkure local government (table 1). variations were observed in the organic matter contents of the soils studied and this was largely attributed to the management and the environmental condition they are subjected to. these might be the reason for the difference in organic matter composition among the sectors. most of the productive agricultural soils have organic matter content ranging between 3-6% (bot and benites, 2005). the organic matter content of agricultural topsoil is usually in the range of 1–6% (sare, 2012).the percentage composition of organic matter in some of the sectors is outside this range as seen in figure 2. table 1: some physical parameters in the krip s/n . sector latitude longitud e %clay sat. h. c. mm/s b.densit y g/cm3 % o. m texture 1 makwaro 11.79361 8.42555 13.76 37.09 1.48 0.93 sandy loam 2 samawa 11.72648 8.41517 14.12 40.1 1.49 0.75 sandy loam 3 maura 11.71181 8.41544 5.76 86.15 1.44 0.89 loamy sand 4 yadakwari 11.75556 8.43 16.12 19.85 1.42 2.3 loam 5 karfi 11.82691 8.49362 13.04 48.18 1.48 0.62 sandy loam 6 yakasai 11.80896 8.48967 6.12 91.26 1.44 0.72 loamy sand 7 fako 11.80427 8.4489 7.76 72.48 1.45 1.13 loamy sand 8 majabo 11.80896 8.48967 6.12 96.48 1.44 1.17 loamy sand 9 kadawa 11.65653 8.42211 13.76 38.08 1.48 1.17 sandy loam 10 agalawa 11.66929 8.41747 14.12 0.56 1.4 2.71 silt loam 11 raje 11.67514 8.41458 22.12 12.94 1.43 0.86 loam 12 bangaza 11.62383 8.4228 9.76 39.37 1.44 1.06 loam 13 yantomo 11.62702 8.4181 11.76 50.82 1.48 1.06 sandy loam 14 waire 11.62011 8.42201 12.12 33.66 1.45 1.48 loam 15 gayere 11.6088 8.4401 10.12 42.15 1.45 2.13 sandy loam 16 dorayi 11.60343 8.45695 15.76 30.06 1.49 1.13 sandy loam 17 butalawa 11.80043 8.43136 5.4 85.05 1.43 0.96 sandy loam 18 gore north 11.7838 8.41911 9.76 54.28 1.46 1.34 sandy loam http://www.azojete.com.ng mailto:wadata4all@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 363-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 367 in western canal, nine sectors which include karfi, yakasai, butalawa, raje, azore, makwaro, maura, samawa and kosawa were found to have a value of less than 1 %. sectors with the composition of organic matter below 1% in eastern canal are turba, danbala, bunkure east and bunkure west (table 1.). these imply the soils in such sectors are likely to have the low buffering capacity, low fertility and low microbial activities as well as low moisture retention(overstreet and dejong-huges, 1992). the difference might be due to variation in texture, mineral composition and topography which influences organic matter accumulation through drainage. organic matter could easily be lost from fine-textured soils whereas soil reach in clay minerals such as montmorillonite that favours accumulation of organic matter become aggregated (goswami et al., 2012). these might be the reason for the variation in texture of the soils in the krip as reflected in table 1. this study stresses the need for the application of manure and fertilizers to improve the productivity of soil in the krip. 19 gore south 11.77794 8.41166 17.76 24.83 1.49 2.37 sandy loam 20 rakauna 11.77254 8.41522 17.76 23.19 1.48 1.37 sandy loam 21 azore 11.75889 8.40485 9.76 51.12 1.46 0.65 sandy loam 22 makwaro t. 11.76028 8.41473 12.12 44.32 1.47 1.44 sandy loam 23 agolas 11.76083 8.76083 21.76 14.88 1.47 2.3 loam 24 kosawa 11.77075 8.45932 13.76 44.27 1.5 0.82 sandy loam 25 dalili 11.78264 8.42941 19.76 18.01 1.47 1.85 sandy loam 26 kuruma 11.65692 8.54608 13.4 31.58 1.45 2.75 loam 27 turba 11.67368 8.5572 5.76 73.85 1.44 0.75 sandy loam 28 danbaki 11.6786 8.57298 12.12 33.66 1.45 0.1 loam 29 lautaye 11.68669 8.57095 13.76 40.1 1.49 1.85 sandy loam 30 bunkure east 11.70087 8.54927 9.4 56.48 1.45 0.86 sandy loam 31 bunkure west 11.70425 8.53818 5.76 73.85 1.44 0.62 sandy loam 32 danbala 11.72052 8.52496 9.76 69.45 1.47 0.79 loamy sand 33 unguwar rimi 11.7253 8.52774 11.76 40.61 1.46 1.1 sandy loam 34 korawa 11.70209 8.53122 13.76 32.3 1.46 2.26 sandy loam 35 barnawa 11.59692 8.46341 11.4 43.52 1.46 1.68 sandy loam 36 shiye 11.62968 8.48921 9.76 49.57 1.46 1.48 sandy loam 37 kode 11.6458 8.50751 13.76 26.97 1.44 2.33 loam 38 cirin 11.64561 8.52347 23.64 13.36 1.53 1.34 sandy clay loam 39 gafan 11.67092 8.41915 17.2 22.41 1.46 1.82 loam 40 kore 11.71632 8.42597 13.76 28.69 1.45 1.48 loam file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:wadata4all@yahoo.com mohammed et al: characterization of soils in east and west zones of kano river irrigation project, nigeria. azojete,16(2):363-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 368 figure 2.: map showing distribution of organic matter in clayey soils, the ideal soil bulk density that favors plant growth ranges from 1.47 and 1.10 g/cm3 (arshad et al., 1996). this is because it is an indicator of soil compaction. it also indicates the suitability for root growth and soil permeability and is very important for the soil-plantatmosphere system (katherine and andrew, 2019). it is generally desirable to have soil with a bulk density <1.5 g/cm3 for optimum movement of air and water through the soil (hunt and gilkes, 1992). bulk density above thresholds indicate impaired function or soil’s ability for structural support, water and solute movement, and soil aeration. however, the prevalent texture in the krip is sandy loam and in almost all the sectors, the value observed is below this range as seen in figure 3. therefore, soils in all the sectors are well aerated and will facilitate the movement of water through them. http://www.azojete.com.ng mailto:wadata4all@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 363-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 369 figure 3.: map showing distribution of bulk density the bulk density of the clay is usually low in contrast to the coarse grain soils like sand which has larger values, but fewer, pore spaces. in clay soils with good soil structure, there is a greater amount of pore space because the particles are very small, and many small pore spaces in between. the difference in soils bulk densities usually alters their saturated hydraulic conductivity. saturated hydraulic conductivity is a measure of soil’s ability to transmit water under saturation conditions. it is an essential parameter as it affects several processes such as infiltration rate, runoff, groundwater recharge, and nutrient transport in soil. the magnitude of saturated hydraulic conductivity is a function of texture among other factors, and is very essential in cultural and management practices, such as irrigation scheduling, drainage, flood protection, and control of erosion (garcía-gutiérrez,et al, 2018). variation of texture and bulk density in the krip might be the reason for the high range of ksat in the sectors as seen in figure 4. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:wadata4all@yahoo.com mohammed et al: characterization of soils in east and west zones of kano river irrigation project, nigeria. azojete,16(2):363-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 370 figure 4. distribution of hydraulic conductivity in krip 4. correlation analysis the pearson correlation coefficient between location (latitude and longitudes) and % clay content as presented in table 2 is -0.107 and represents a week negative relationship between the variables. the p-value of 0.511 for latitude as seen in table 3 and figure 5 indicates insignificant correlation as the value is higher than the significant level of 0.05. table 2: correlation coefficients of the variables with location % clay saturated hydraulic conductivity (mm) bulk density (g/cm3) % organic matter (r) rho (r) rho (r) rho (r) rho latitude -0.107 -0.1 0.322 0.283 0.025 0.055 -0.202 -0.255 longitude 0.072 -02 0.018 0.152 0.08 -0.052 0.077 -0.048 % clay -0.876 0.442 0.452 0.407 0.473 r = pearson correlation coefficient rho =spearman correlation coefficient a similar relationship was observed between latitude and saturated hydraulic conductivity, latitude and bulk density, latitude and percentage of organic matter content. the same trend of week and insignificant relationship between longitude and saturated. hydraulic conductivity, bulk density, %organic matter were also observed as presented in figure 6. http://www.azojete.com.ng mailto:wadata4all@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 363-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 371 252015105 1007550250 11.80 11.75 11.70 11.65 11.60 1.521.481.441.40 11.80 11.75 11.70 11.65 11.60 3210 %clay la tit ud e sat. hydraulic conductivity (mm bulk density (g/cm3) % o. m scatterplot of latitude vs %clay, sat. hydraul, bulk density, % o. m figure 5: scatter plot of latitude vs % clay, saturated hydraulic conductivity, bulk density and % organic matter this implies that the clay composition in all the sectors has no relationship with the location of the sector in the krip. correlation analysis has also shown that the bulk density, organic matter content and saturated hydraulic conductivity of soils in all the sectors have no relationship with the location of the sectors in the scheme. table 3: strength (p-value) of the correlation coefficient % clay saturated hydraulic conductivity (mm) bulk density (g/cm3) % organic matter (r) rho (r) rho (r) rho (r) rho latitude 0.511 0.539 0.043 0.076 0.879 0.735 0.212 0.113 longitude 0.658 0.217 0.91 0.348 0.624 0.749 0.636 0.769 % clay 0.000 0.004 0.003 0.009 0.002 r = pearson correlation coefficient, rho =spearman correlation coefficient however, the results show that there is a linear relationship between % clay content and saturated hydraulic conductivity, latitude and bulk density, latitude and % organic matter. the pearson correlation coefficient between % clay content of the soil in all the sectors and saturated hydraulic conductivity as seen in table 2 is -0.876 and represents a strong negative relationship between the variables. this is evidenced in figure 3. the p-value of 0.000 as shown in table 3 is less than the significant level of 0.05 and that indicates significant correlation, i.e. as % clay content increases, the strength of saturated hydraulic conductivity tends to decrease. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:wadata4all@yahoo.com mohammed et al: characterization of soils in east and west zones of kano river irrigation project, nigeria. azojete,16(2):363-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 372 252015105 1007550250 8.8 8.7 8.6 8.5 8.4 1.521.481.441.40 8.8 8.7 8.6 8.5 8.4 3210 %clay lo ng itu de sat. hydraulic conductivity (mm bulk density (g/cm3) % o. m scatterplot of longitude vs %clay, sat. hydraul, bulk density, % o. m figure 6: scatter plot of longitude vs clay, saturated hydraulic coductivity, bulk density and % organic matter the pearson correlation coefficient between % clay content of the soil in all the sectors and bulk density is 0.452 and represents a medium positive linear relationship between the variables. however, the spearman correlation coefficient of 0.452 which is slightly higher than the value of the pearson coefficient indicates that the relationship is more of a non-linear relationship than linear. the p-values for both pearson and spearman coefficients (0.04 and 0.03 respectively) are less than the significant level of 0.05. this indicates that the correlation is significant. as percentage clay content increases, the bulk density tends to increase. the pearson and spearman coefficients between percentage clay content and percentage o.m content are 0.407 and 0.473 respectively. this represents a positive relationship between the variables as seen in figure 7. based on the magnitude of the coefficient, it may be deduced that the relationship is more of non-linear. the p-values (0.009 and 0.002) of these coefficients, are also less than the significant level of 0.05. hence, the correlation is significant. the reason for the increase might be due to the presence of sand particles more than the silt in the soils as higher percentage of sand was observed compared to other soil separates. 1007550250 1.521.481.441.40 25 20 15 10 5 3210 25 20 15 10 5 sat. hydraulic conductivity (mm % cla y bulk density (g/cm3) % o. m scatterplot of %clay vs sat. hydraulic c, bulk density (g/, % o. m fig. 7: scatter plot of clay vs sat. hydraulic, bulk density and % o.m http://www.azojete.com.ng mailto:wadata4all@yahoo.com arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 363-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 373 based on the above analysis, it is only % clay content of the soil that has a relationship with the other variables and hence organic matter content, saturated hydraulic conductivity and bulk density can be used as one of the determinant variables in a model aimed at predicting the percentage clay in soils. 5. conclusions the influence of clay composition on organic matter content, saturated hydraulic conductivity and bulk density of soils in a different part of the krip was studied. the percentage clay varied from the range of 22.12 to 5.4% as observed in raje and butalawa respectively. the texture in most of the sectors is dominated by sandy loam. the organic matter content is typical of agricultural topsoil as all the sectors have an organic matter within the range of 1–6%. however, there is a need for the application of organic manure and fertilizer to improve soil productivity and buffering capacity as the organic matter of all the sectors is below the range of 3-6% for productive soils. the variation of texture and bulk density in the krip might be the reason for the high range of ksat in the sectors. the pearson correlation coefficient between percentage clay and bulk density is 0.452 and represents a medium positive linear relationship between the variables. however, the spearman correlation coefficient of 0.452 indicates that the relationship is more of a non-linear relationship than linear. the pearson correlation coefficient (0.876) between percentage clay content of the soil in all the sectors and saturated hydraulic conductivity represents a strong negative relationship between the variables that is to say as the percentage clay content increases, the strength of saturated hydraulic conductivity tends to decrease. the percentage clay has no relationship which location of sectors based correlation analysis. the pearson and spearman coefficients between percentage clay content and percentage organic matter are 0.407 and 0.473 respectively and this represents a positive relationship between the variables. therefore, organic matter, saturated hydraulic conductivity and bulk density can be used as one of the determinant variables in a model aimed at predicting the percentage clay of soils in krip. references arshad, ma., lowery, b. and grossman, b. 1996. physical tests for monitoring soil quality. in: doran, j.w., jones, a.j., editors. methods for assessing soil quality. madison, wi. p 123-41. bot, a. and benites, j. 2005. the importance of soil organic matter: key to drought resistant soil and sustained food production. food and agriculture organization. soils bulletin 80, rome, 94pp. chakraborty, k. and biswaranjan, m. 2015. importance of soil texture in sustenance of agriculture : a study in burdwan-i importance of soil texture in sustenance of agriculture, burdwan, west bengal. eastern geographer, 21(1): 475-482. chimdi, a., gebrekidan, h., kibret, k., and tadesse, a. 2012. status of selectedphysicochemical properties of soils under different land use systems of western oromia, ethiopia. journal of biodiversity. and environmental science, 2(3): 57–71. dixon, jb.1991. roles of clays in soils. applied clay science, 5(5-6): 489-503. ezlit, yd., smith, rj. and raine, sr. 2010. a review of salinity and sodicity in irrigation. cooperative research centre for futures, irrigation matters series no. 02/10 garcía-gutiérrez, c., pachepsky, y. and ángel martín, m. 2018. technical note: saturatedhydraulic conductivity and textural heterogeneity of soils. hydrology and earth system sciences, 22(7): 3923–3932. gee, gw. and dr, d. 2002. particle size analysis. in: methods of soil analysis, part 4, physical methods (dane, jh. and topp, gc. (eds.)). asa and sssa, madison, wi., pp: 255-293. grossman, rb. and reinsch, tg. 2002. bulk density and linear extensibility. in: methods of soil analysis. part 4. physical methods (dane, jh. and topp, gc. (eds.)). asa and sssa, madison, wi, pp: 201-228. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:wadata4all@yahoo.com mohammed et al: characterization of soils in east and west zones of kano river irrigation project, nigeria. azojete,16(2):363-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wadata4all@yahoo.com 374 hunt, n. and gilkes, r 1992. farm monitoring handbook. the university of western australia: nedlands, wa. jibrin, jm., abubakar, sz. and suleiman, a. 2008. soil fertility status of the kano river irrigation project area in the sudan savanna of nigeria. journal of applied sciences, 8(4): 692–696. katherine, b. and wherrett, a. 2019. fact shhet bulk density-measurement. downloaded from www.soilquality.org.au on 20th december, 2019. klute, a. and dirksen, c. 1986. hydraulic conductivity and diffusivity. in: methods of soil analysis part 1. physical and mineralogical methods (klute, a. (ed.)). asa and sssa, madison, wi., pp: 687-734. maina, mm., amin, msm., aimrun, w. and asha, ts. 2012. evaluation of different et calculation methods : a case study in kano state , nigeria. philipine agricultural scientist, 95(4): 378–382. mohammed, d., hassan, ai. and amina, a. 2015. variabilty of irrigation water quality in kano river irrigation project. journal of research in national development, 12(2): 337–343. newman acd. 1984. the significance of clay in agriculture and soil. philosophical transaction of royal society of london. series a, mathematical and physical science, 311(15): 375-389. overstreet, lf. and dejong-huges, j. 1992. the importance of soil organic matter in cropping systems of the northern great plains. university of minnesota bulletin, 20: 1–13. page, jb. 1952. role of physical properties of clays in soil science. clays and clay minerals, 1: 167–176. sare 2012: why soil organic matter is so important. http://www.sare.org 29th october, 2019. http://www.azojete.com.ng mailto:wadata4all@yahoo.com arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):124-132 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 124 original research article effect of different riser heights on sprinkler irrigation performance under constant operating pressure i. a. kuti1, t. a. ewemoje2, b. a. adabembe3, j. j. musa1, s. c. nwosu1 (1department of agricultural and bioresources engineering, federal university of technology, minna, nigeria 2 department of agricultural and environmental engineering, university of ibadan, ibadan, nigeria 3 department of water resources management and agro meteorology, federal university oye -ekiti, nigeria) *corresponding author: abykuti6@futminna.edu.ng article information submitted 15 april 2018 revised 15 september 2018 accepted 19 september 2018 keywords: riser height operating pressure coefficient of uniformity (cu) distribution of uniformity (du) sprinkler irrigation abstract the study assessed the effect of different riser heights on the sprinkler irrigation performance to cater for the cultivation of taller crops and reduce water losses. a layout of 144 m2 was designed according to the length of mainline and lateral lines, and 36 catch cans were positioned in a grid of 2 m apart. the water caught in cans were subjected to one-way anova using the tukey method in minitab 17 environment. the risers 4m, 3m and 2m, were significantly different because the means without any letter in common and concluded that some of the riser height have the different mean value of water caught in the catch cans. the results showed that as the riser height increased the mean application rate decreased. also, the coefficient of uniformity (%) for riser height 2 m and 3 m were rated excellent. the distribution of uniformity (%) for 2 m and 3 m were rated excellent and fair. the study concluded that riser heights 2 m and 3 m had the optimum cu and du at 1.6 bar (operating pressure) reduce water losses. the study suggested that sprinkler irrigation should be carried out in gidan kwano campus between 5:06 pm and 11:35 am. also, wind direction should be established before the installation of sprinkler irrigation. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction irrigation is viewed as the application of water to the soil to supply moisture for plant development and crop production (yahaya, 2002). the need for irrigation arises when the frequency and amount of rainfall are insufficient to replenish the water required by the crop. in more arid regions, drought periods last longer in a year, and the seasonal rainfall is unable to meet crop needs during their growth period (onwualu et al., 2006). irrigation systems are classified as surface, sub-surface, sprinkler and drip irrigation (onwualu et al., 2006). sprinkler irrigation method is a pressurised irrigation system that consumes water from a different source and sprays it to the cultivated ground or earth as in the shape of rain using an enclosed system and under pressure (nakayama and bucks, 2012). sprinkler irrigation is an adaptable means of supplying crops with common and uniform application of water over a broad range of topography and ground conditions (nakayama and bucks, 2012; fanadzo et al., 2010; evans and sadler, 2008). water distribution application in a sprinkler system is rich and more coherent than surface irrigation system (yazar et al., 1999). a riser is one of the essential elements of a solid set mailto:abykuti6@futminna.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):124-132. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 125 sprinkler system that influence the performance indicators of the coefficient of uniformity (cu) and distribution uniformity (du) under specified environmental conditions. the cu has either a positive or negative effect on crop production (okasha and pibars, 2016). in summation, the weak cu and du reduce the efficiency of sprinkler irrigation system. water losses in sprinkler irrigation system occur due to evaporation and wind movement. thus, there is a need to improve the functioning of the sprinkler irrigation system to bring down the cost of irrigation and water losses (okasha and pibars, 2016). various surveys have indicated that the two common methods of determining sprinkler water uniformity are the coefficient of uniformity (cu) and distribution uniformity (du). cu is the average deviation of the catch compared to the depth of the catch can, while du compares the driest quarter of the field to the rest (kara, 2008). magagula (2013) reported that a catch-can test is a safe method of assessing the efficiencies of the existing sprinkler irrigation system. bishaw and olumana (2015) said that increase in riser heights between 2.5 m and 4.0 m lead to increase in sprinkler water uniformity and riser height 4 m produced optimum cu and du at low wind speed. in view of this, the study aims at assessing the effect of different riser heights on the sprinkler irrigation performance to cater for taller crops and reduce water losses. 2 materials and methods 2.1 study area the study area is located within the federal university of technology, minna, gidan kwano, minna, nigeria. it lies on latitude 9°32'04.1 n and longitude 6°26'53 e. the study was carried out on the land adjacent to the department of agricultural and bio-resources engineering laboratory of the university. gidan kwano has two seasons namely rainy and dry. the annual maximum and minimum rainfall in the area is 1086 mm and 1309 mm, respectively, which occurs in may and ends in october. the yearly maximum and minimum temperature in the area is 37 °c and 19.3 °c respectively (galadima, 2014). 2.2 materials and equipment 2.2.1 water pump the water pump moves water by pressure or suction from the reservoir to field, and its specification was presented in table 1. table 1:water pump specifications item description water pump model wp20x type df1 connection diameter 50 mm delivered volume 600 l/min total head 26 m power speed 3600 rpm 2.2.2 sprinkler irrigation system the sprinkler irrigation system has a main line of 6 m long with 50 mm diameter. two lateral lines have 25 mm diameter with 3 m long each. it has different riser heights such as 1.5 m, 2 m, 3 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuti, et al. effect of different riser heights on sprinkler irrigation performance under constant operating pressure azojete, 15(1):124-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 126 m, and 4 m with 2.5 mm diameter. sprinkler irrigation system conveys water from the reservoir through the main and lateral line to the nozzle which sprays the water in the form of rain to the field. 2.2.3 sprinkler heads the sprinkler head sprays the water in the form of raindrops to the area. the specifications, characteristics and manufacturers details of the pressure, spraying radius, nozzle diameter and discharge of the four sprinkler heads were shown in table 2. table 2: sprinkler head manufacturers’ specifications specification comments/remarks pressure 0.5 – 4.0 bar spraying radius 3.0 – 16.5 m nozzle diameter 5.0+2.5 mm (7.5 mm) flux/ discharge 6.8-32.4 l/min size ¾ inches operation capacity 360º full circle coverage model rc130 zinc/brass 2.2.4 catch cans the diameter, height and volume of the catch cans were 84 mm, 130 mm and one litre respectively. 2.2.5 water hose and siphon tube siphon tube sucks water from the tank to the pump impeller. water hose conveys water from the pump to the mainline. the hose connected at the other end of the impeller to the main line which was held firmly by a clip to prevent leakages. 2.2.5 tape a 50 m tape was used to measure the layout and the spacing of the catch cans. 2.2.6 volumetric cylinder the cylinder was used to measure the water caught in the catch cans. it has a capacity of 500 cm3. 2.2.7 marking pegs pegs were used to map out the area and grid system. 2.2.8 stopwatch a stopwatch was used to measure the time it takes the sprinkler head to fill the container. 2.2.9 pipe wrenches pipe wrenches was used to screw in the laterals into the main line and the risers into the laterals. 2.2.9 cup anemometer cup anemometer was used to measure wind speed and direction. 2.2.9 portable thermo-hygrometer portable thermo-hygrometer was used to measure the temperature and humidity of the area http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):124-132. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 127 2.3 methods 2.3.1 experimental description and design layout field evaluation was carried out at agricultural and bio-resources department, federal university of technology, minna. the field had an area of 144 m2 (12 m by 12 m). the vegetation of the field was cleared in line with osie (2009) and mapped out with pegs to form a grid as shown in figure 1. sprinkler compositions used were different riser height (such as 1.5 m, 2.0 m, 3.0 m and 4.0 m), pump, siphon tube, rubber hose, 36 catch cans, four sprinkler nozzles (model rc130), one main line (6 m in distance and 50 mm in diameter) and two laterals (6 m in length and 25 mm in diameter). the water pump has two impeller hoses which included a siphon tube and a rubber hose. the rubber hose was attached or connected to the mainline while the siphon tube was attached water tank as shown in figure 1. these components assembled such that the laterals were spaced 3 m apart on the main line. in summation, the catch cans were spaced 2 m apart along the grid. the 36 catch cans estimated according to the area of the field figure 1: experimental view of sprinkler set up, the arrangement of catch cans on the grid and design layout 2.3.2 operation of sprinkler system performance the operating pressure of the water pump adjusted via a pressure gauge and pitot tube. the pitot tube was held at 3 mm from the nozzle head and recorded with the operating pressure. in the trial test, the operating pressure and flow rate were adequately controlled in this experiment. the speed and direction of the wind are measured every 15 minutes at height 2m with cup anemometer. at the end of the trial, the amount of water accrued in each catch cans was measured with cylinders (ml), and the procedures were repeated for each sprinkler nozzle as described by kara et al. (2008). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuti, et al. effect of different riser heights on sprinkler irrigation performance under constant operating pressure azojete, 15(1):124-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 128 2.4 calculation of basic parameters 2.4.1 evaporation and wind drift losses in sprinkler irrigation, water losses came from the nozzle to the irrigated areas due to the wind in the form of water drift and direct evaporation from the nozzle to the soil (molle et al., 2012). because of this, it is essential to determine evaporation and wind drift losses as described by bishaw and olumana (2015). e =[1.98 (d)−0.72 + 0.22 (es – ea)0.63 + 3.6 x 10−4(h)1.16 + 0.14 (u)0.7]4.2 (1) where: e = evaporation and wind drift, per cent d = nozzle diameter, m h = riser height, m u = wind velocity, m/s = vapor pressure deficit, kpa vapour pressure deficit is a predominant factor that affects evaporation from the sprinkler sprays. it is important to determine the vapour pressure deficit affecting the evaporation of the water from the nozzle (bavi et al., 2009). the vapour pressure deficit was determined as follows: es – ea = 0.61 exp [17.27 � �+237.3 ] (1 − rh) (2) where, t = air temperature, °c rh = relative humidity, fraction. the evaporation and drift losses were determined for different riser height as recommended by smajstrla and zazueta (1994). (3) where, e = evaporation and drift losses, % d = nozzle diameter, m h = riser height, m u = wind velocity, m hr-1 rh = relative humidity, % t= air temperature, °c http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):124-132. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 129 2.4.2 christiansen’s coefficient of uniformity (cu) the coefficient of uniformity (cu) was determined as follows: cu % = 100(1 − the standard deviation of the water in the catch can mean of water in the catch can ) (4) 2.4.3 distribution uniformity (du) the distribution uniformity (du) was calculated as follows: du % = 100 × ( an average low quarter of water in the catch can the average total of water in the catch can ) (5) 2.4.4 mean application rate (mar) the mean application rate (mar) was determined as follows: i = q sm × sl × 100 (6) i= mean application rate is (m hr-1) q = sprinkler discharge (m3 hr-1), sl = sprinkler spacing (m), sm = lateral spacing (m). 2.5 data analysis the quantity of water measured in each riser were subjected to one-way anova with multiple comparisons in minitab 17 environment. the amounts of water caught in the cans were used to compute the coefficient of uniformity, distribution uniformity and mean application rate of the sprinkler irrigation system. the results are presented in tables and charts. 3. results and discussion 3.1 determination of the volume of water caught in the catch cans the evaporation and wind drift losses range between 5.22% to 10.2% which was in line with the work of okasha and pibars (2016). the amount of water determined in each riser was shown in table 3. in a riser 1.5, the amount of water computed in the catch-can equal 799 ml. also, the amount of water estimated in riser 2 was 632 ml. the amount of water calculated at riser 3m was 745 ml. the riser 4m has a total amount of 874 ml. the mean application rate for each riser 1.5, 2, 3 and 4 was 8.56 mm hr-1, 7.76 mm hr-1, 7.56 mm hr-1 and 6.76 mm hr-1 respectively as shown in table 3. the study revealed that as the riser height increases the mean application rate decreases because the evaporation and drift losses also increase as indicated in table 3. this study agrees with the work of bishaw and olumana (2015). the riser heights 4.0 m, 3.0 m and 1.5 m have the highest depth of water, whereas 2.0 m has the lowest volume of water caught in the catch cans as shown in table 3. the practical implication is that more water was well distributed on the land at riser height 2 m while risers 4.0 m, 3.0 m and 1.5 m were not. thus, riser (2 m) generates less runoff. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuti, et al. effect of different riser heights on sprinkler irrigation performance under constant operating pressure azojete, 15(1):124-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 130 table 3: determination of the volume of water caught in the cans under constant operating pressure date time riser height (m) total volume of water in the cans (ml) evaporation and drift losses (%) wind direction mean application rate (mm hr-1) 29/72016 5:06 pm 1.5 799 5.22 nw 8.56 30/7/2106 9:32 am 2 632 5.7 ne 7.76 30/7/2106 10:27 am 3 745 8.21 ne 7.56 30/7/2106 11:23 am 4 874 10.2 se 6.76 3.2 effect of riser height on water caught in the catch cans under constant operating pressure the analysis of variance for the water determined in the catch cans was shown in table 1. the factor riser 1.5m, 2m, 3m and 4m do bring significant information to the model since the computed p-value is less than alpha (0.05). the risers 2 and 3 were significantly different because their means do not have any letter in common (table 1), and concluded that the riser height has the different mean value of water caught in the catch cans. besides, the tukey pairwise comparisons show that riser heights 1.5 m, 2 m, 3 m and 4 m have different water trapped in the catch cans because the means that do not share a letter are significantly different. tukey simultaneous tests for differences of means for water caught were shown in table 3. the difference in level between riser height 4 m and 2 m have a higher effect on the water found in the catch-can be followed by the riser 2m and 1.5m, 4m and 3m and 3m and 2m since their pvalues were 0.000, 0.001, 0.016 and 0.046 respectively. thus, the risers have a different effect on the volume of water caught. table 1: analysis of variance source df adj ss adj ms f-value p-value riser 3 863.9 287.97 11.28 0.000 error 140 3575.4 25.54 total 143 4439.3 table 2: tukey pairwise comparison risers mean grouping 4 24.28 a 1.5 22.19 ab 3 20.694 b 2 17.556 c means that do not share a letter are significantly different http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):124-132. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 131 table 3: tukey simultaneous tests for differences of means (volume of water) difference in level difference of means se of difference 95% ci t-value adjusted pvalue 2.0 1.5 -4.64 1.19 (-7.74, -1.54) -3.89 0.001 3.0 1.5 -1.50 1.19 (-4.60, 1.60) -1.26 0.590 4.0 1.5 2.08 1.19 (-1.02, 5.18) 1.75 0.303 3.0 2.0 3.14 1.19 ( 0.04, 6.24) 2.64 0.046 4.0 2.0 6.72 1.19 ( 3.62, 9.82) 5.64 0.000 4.0 – 3.0 3.58 1.19 ( 0.48, 6.68) 3.01 0.016 3.3 determination of coefficient of uniformity (cu) and distribution uniformity (du) under different riser heights at constant operating pressure (1.6 bars) the uniformity coefficient and the distribution coefficient of the sprinkler irrigation system were shown in table 4. at riser height 1.5 m, the coefficient of uniformity (cu) and distribution uniformity (du) were 70% and 61% respectively. the cu and du values at 2 m riser height were 89% and 85% respectively. at riser 3.0 m, cu and du values were 85% and 78% respectively. the cu and du at 4 m riser height were 72% and 70 respectively. this study found out that the riser height 2.0 m had the highest cu (89%) and du (85%) values. also, the riser height of 1.5 m had the lowest cu (70%) and du (61%) values. cu for riser height 4.0 m and 1.5 m were classified unsatisfactory while the cu for riser height 2 m and 3 m were rated good (little et al., 1993). also, the du for 2 m and 3 m were rated excellent and fair while the du for 1.5 m and 4 m were rated poor (bloomer, 2006). the study revealed that riser heights 2 m and 3 m have optimum cu and du. table 4: coefficient of uniformity and distribution of uniformity of different risers riser height (m) cu (%) du (%) 1.5 70 61 2 89 85 3 85 78 4 72 70 4 conclusion the effect of different riser heights on the performance of sprinkler irrigation at constant operating pressure was assessed to provide water for the cultivation of high crops and reduce water wastage. the study revealed that as the riser height increases the mean application rate decreases. the riser heights 2 and 3 m were significantly different because their means do not have any letter in common, and concluded that some of the riser height have the different mean value of water found in the catch-can. this study reveals that as the wind direction changes the volume of water trapped in catch cans also increases which in turn cause weak cu. the study concluded that riser heights 2m and 3m have the highest cu and du at 1.6 bars and these riser heights can provide water for taller crop and reduce water losses on the field. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuti, et al. effect of different riser heights on sprinkler irrigation performance under constant operating pressure azojete, 15(1):124-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 132 references bavi, a., kashkuli, ha., boroomand, s., naseri, a. and albaji, m. 2009. evaporation losses from sprinkler irrigation systems under various operating conditions. journal of applied sciences, 9(3), 597-600. bishaw, d., and olumana, m. 2015. evaluating the effect of operating pressure and riser height on irrigation water application under different wind conditions in ethiopia. asia pacific journal of energy and environment, 2(1): 41-48. bloomer dj. 2006. irrigation evaluation code of practice. hastings, new zealand: bloomer associates ltd. evans, rg., and sadler, ej. 2008. methods and technologies to improve the efficiency of water use. water resources research, 44, 1-15. fanadzo, m., chiduza, c., mnkeni, pns., van der stoep, i., and stevens, j. 2010. crop production management practices as a cause for low water productivity at zanyokwe irrigation scheme. water south african, 36 (1): 27-36. galadima, im. 2014. an analysis of growth trends in gidan kwano and its impact on agriculture. project submitted to federal university of technology minna, pp 9. little, ge., dj. hills, br. and hanson. 1993. uniformity in pressurized irrigation systems depends on design, installation. california agriculture, 47: 18-21. magagula, c. 2013. technical efficiency of sprinkler irrigation in swaziland: a case study of the lusip phase 1 in lubovane area. m. sc. thesis submitted to the university of zimbabwe, pp. 1-15. molle, b., tomas, s., hendawi, m. and granier, j. 2012. evaporation and wind drift losses during sprinkler irrigation influenced by droplet size distribution: irrigation and drainage, 61(2), pp.240250. nakayama, fs., and bucks, da. 2012. trickle irrigation for crop production: design, operation and management. tokyo: elsevier science, pp 10. onwualu, ap., akubuo, co., and ahaneku, ie. 2006. fundamentals of engineering for agriculture. lagos: immaculate ltd., pp. 259-262. okasha, em. and pibars, sk. 2016. investigation of riser height and operating pressure on sprinkler irrigation performance under different wind condition. international journal of chemtech research, 9(7): 292-299. smajstrla, ag., and zazueta, fs. 1994. evaporation loss during sprinkler irrigation. university of florida cooperative extension service, institute of food and agriculture sciences, edis, pp. 1-8. yahaya, mk. 2002. development and challenges of bakolori irrigation project in sokoto state, nigeria. nordic journal of african studies, 11 (3): 411-430. yazar, a., howell, ta., dusek, da., and copeland, ks. 1999. evaluation of crop water stress index for lepa irrigated corn. irrigation science, 18(4): 171-180 kara, t., ekmekci, e. and apan, m. 2008. determining the uniformity coefficient and water distribution characteristics of some sprinklers. pakistan journal of biological sciences, 11(2), 214219. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3):488-509 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 488 original research article analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review o. h. aliyu (department of building, faculty of environmental sciences, the federal university birnin kebbi, p.m.b. 1157, birnin kebbi, nigeria) * corresponding author’s email address: ohunene.hafsa@fubk.edu.ng article information submitted 14 september, 2018 revised 16 march, 2019 accepted 18 march, 2019 keywords: homogenization heterogeneous material representative volume element (rve) effective properties volume averages computational homogenization abstract this paper reviews the analytical, numerical as well as the computational homogenization multiscale modelling schemes for determining the effective material properties for heterogeneous medium at the macroscopic level. it also looked at the limitations of the analytical homogenization techniques in simulating the effective non linear heterogeneous material behaviours (for example the rapid localization of damage and so on) as well as the advancements of the computational techniques in addressing these limitations. in addition, the possible future trends for the computational technique such as the development of a fully coupled micro-macro computational scheme were also discussed. it was concluded that although, the analytical technique was quite popular and straight forward, its inability to capture rapid localization of damage limited its application and that numerical and computational schemes were able to address these limitations as they relied on the establishment of constitutive relations for the macroscopic problems in a numerical form through which the macroscopic problems were constructed and solved in a nested manner. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction most engineering materials (steel, concrete, polymer-blends, functional materials and so on) are inherently heterogeneous in nature (figure 1) when viewed at a particular scale and are mostly referred to as composites (nguyen et al., 2012; matous et al., 2017). figure 1: natural random heterogeneous material adapted from torquato (2013). mailto:ohunene.hafsa@fubk.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 489 studies (llorca et al., 2007; kouznetsova et al., 2012) have shown that, the macroscopic behaviour of these composite materials are linked to their mechanical behaviour as well as the details of their microstructure (that is volume fraction, spatial distribution of the different phases and inter-phases, their morphological properties, sizes and shapes et cetera). these microstructural material details tend to evolve by undergoing phase transformations under the application of thermo-mechanical loadings as well as advanced forming operations; thus, making it essential to understand the relationship between the microstructure properties and the macroscopic material behaviour (also known as the micro-macro structure property relation). it is hoped that by taking advantage of this micro-macro structure-property relationship, it should be possible to manipulate the material microstructure so as to influence the macroscopic mechanical behaviour of the composite material to obtain desired results. for example, “improved strength and toughness, high stiffness and high damping, improved thermal conductivity and electrical permittivity, improved permeability” et cetera (kanoute et al., 2009); consequently, improving the materials performance in special industrial applications from an engineering perspective, provides an economic alternative to the designing of new materials with desirable macroscopic characteristics (nguyen et al., 2012; llorca et al., 2007). establishing this micro-macro structure-property relation has been a major challenge in computational micromechanics as well as material science as it is not feasible to carry out an upfront experimental measurement where all the micro-structural characteristics are explicitly considered. it is the need to provide an efficient modelling strategy, to better understand the relationship between material micro-structure and macroscopic properties (that is the micromacro structure property relation) leading to the determination of the general macroscopic homogenised constant value for the heterogeneous material, that has lead to the development of the multiscale models. this is because for the analysis of composite materials, it is the effective or homogenised material property that is used as opposed to the properties of the separate components that make up the material (kanoute et al., 2009; nguyen et al., 2012). multiscale modelling, is therefore, an area of study which involves resolving problems which have significant characteristics at multiple scales of resolution. it usually entails modelling from the smallest scale of the material to a much larger scale (for example, from nanoscale that is quantum level to the macroscale that is continuum level as shown in figure 2) this is usually achieved through the use of various models at the different scales of resolution which are then coupled either analytically, numerically or computationally (engquist et al., 2007; weinan and jianfeng, 2011). figure 2: illustration of the multi-scale modeling hierarchy adapted from weinan and jianfeng (2011). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 490 figure 3: a seamless integration of models of the different length scales into one coherent multiscale modelling frame work. adapted from icams webpage ruhr university germany although, most engineering problems are solved at the macroscopic scale, the results obtained from such analysis are not sufficiently precise while the direct micro-scale modelling of engineering problems are not cost effective and offer too much information; hence the need for multiscale modelling (weinan and jianfeng, 2011; kanoute et al., 2009). the driving force behind carrying out multiscale modelling is to achieve a balance between accuracy and efficiency by coupling together both the microscopic and macroscopic models; thus, providing an accurate predictive tool which is considered crucial in engineering and material science (engquist et al., 2007). this paper reviews the advancements in multiscale modelling of composite material (such as steel, concrete, polymer-blends, and so on) which are used for various industrial applications to determine their macroscopic material properties such as stress and stain fields in addition to their macroscopic material behaviour such as their energy absorption at high strain rates, cracking, creep, et cetera by using the various homogenization methods (nguyen et al., 2012; aliyu, 2019). 2. homogenisation techniques as previously mentioned, the significance of modelling across multiple-scales is that the predictions obtained from such modelling techniques are more precise and accurate (weinan and jianfeng, 2011). the conventional multi-scale modelling of composites is either carried out within the framework of homogenisation methods or the concurrent method depending on whether the scales are distinctively separated or coupled (nguyen et al., 2012). the fundamental aim of homogenisation techniques is to determine the effective properties for heterogeneous materials from the mechanical behaviour of the materials constituents’ microstructure; thus, providing a means for replacing the heterogeneous material with a homogenous one. for many decades now, quite a number of micromechanical modelling techniques dealing with heterogeneous materials have been developed (kanoute et al., 2009). the micromechanical modelling technique to be adopted in achieving a homogenised constant material value for a heterogeneous or composite material falls into one of three main categories. in the first category, schemes employed used high resolutions at certain sections of the domain where fine (microscopic) scale detail of the microstructure morphology (i.e. at cracked tips, and interfaces) needs to be determined. for the second category, the schemes rely on the description of the http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 491 macrostructure from the analysis of the underlying fine (microscopic) scale problem while the third category uses schemes which allows for some sections of the domain to be completely resolved at the fine microscopic scale and the other sections resolved by using the effective macroscopic response (nemat-nasser and hori 1999; sluis et al., 2000; kouznetsova et al., 2012; torquatom, 2013; matous et al., 2017). schemes under the above three categories will be discussed in the following sections analytical/mathematical homogenisation, numerical homogenisation as well as computational homogenisation. 2.1 analytical/mathematical homogenisation initial research on homogenization techniques can be attributed to the works of voigt (1889) and reuss (1929). they were both able to develop models which gave rough estimates of the upper and lower bound values of the effective moduli of heterogeneous materials. both models only took into account the volume fraction. this limited its application as the influence of other characteristic properties of the microstructure was not taken into consideration. 2.1.1 general procedure as the principle objective of homogenization is to describe the effective properties of the composite material from the mechanical behaviour of the materials constituents’ microstructure as shown in figure 4. figure 4: schematic representation of homogenization of material (temizer and zohid 2006; cited in nyguyen et al. 2012). the bridging of length scales is necessary and this is carried out by volume averaging and is denominated homogenization (llorca et al., 2007). ∈� = 1 ω ω ∈� (x)dω and σ� = 1 ω ω σ� (x)dω (1) where: ω is the microscopic sample; �(�) microscopic stress; �(�) microscopic strain; position vector; (�� )macroscopic strain and (��)macroscopic stress. while the expression which gives the denominated localization is given by: ∈ (x) = a(x):∈� and σ(x) = b(x):σ� (2) where: �(�) and �(�) are the stain and stress concentration tensors. the increasing complexity of the microscopic mechanical behaviour and geometries hinders the underlying objective of the above technique. hence, the simplifications of the above file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 492 assumptions are necessary which leads to a number of homogenization models with the most significant simplification being the “mean-field approach which approximates the strain and stress fields by phase-wise constant fields” �� and �� given in equation 3. ϵi = ai :ϵ� and σi = bi :σ� (3) where: �� � strain concentration tensor for the phase i �� stress concentration tensor for the phase i (llorca et al., 2007) in adopting this principle, eshelby (1957), came up with an effective medium approximation in obtaining the overall effective properties of the heterogeneous medium where the microstructure is composed of a matrix and a spherical or ellipsoidal inclusion. he also noted that the strain field within the inclusion was constant. so that for a linear constitutive equation: σi = li:εi; (4)l = i n fili:� ai (5) i = i n fi� ai = i n fi� bi (6) ϵi = aidil:ϵ� (7) where aidil = i + si:lm�1: li � lm �1 (8) the elastic stiffness tensor of the effective material can then be evaluated from equations (1), (6) and (8) as: l = lm + fi li � lm :aidil (9) where: ��stiffness tensor for the matrix ��elastic stiffness tensor for the inclusion �effective elastic stiffness tensor nnumber of phases i-identity tensor ��eshelby’s tensor for the inclusion. ����� strain concentration tensor for the dilute condition ���dilute �� volume fraction this eshelby effective medium approximation was further extended by hill (1965) along the lines of this mean field approximations, kr�� ner (1958) came up with a self consistent approach for obtaining the effective material property for a matrix and spherical or ellipsoidal inclusions in the elastic regime. the main idea behind this approach is that for a composite composed of scattered particles, it is possible to assume that the composite is composed of a particle of one phase embedded in an effective medium. in his work, the strain concentration tensor aisc was obtained from the eshelby dilute solution in eqn. (8) above by replacing the matrix elastic constant (lm) in eqn. (8) with those of the effective medium ( ) to give the resulting expression in equation (10) ���� = � + ��:���: �� � � �� (1�) the effective material property (�) was then be evaluated by substituting eqns. (10) in (5) to obtain eqn. (11). http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 493 l = i n fili:� i + si:l�1: li � l �1 (11) this self consistent approach was further extended to non-linear cases in the studies carried out by hill (1965), hutchinson (1976) and bereviller (1979). the effective properties of the heterogeneous medium in an elastic regime can also be evaluated using the variation principles. employing this technique gives an upper and a lower bound value for the effective property. the simplest works on this variation principle were those of voigit and ruess (hill, 1963). in their models the strain energy density function (x, ) and the complementary energy density function (x, ) were expressed in terms of a homogenous phase potential as: ω(x,ε) = r=1 n χ(r)(x) ω(r)(ε)� (12) u(x,σ) = r=1 n χ(r)(x) u(r)(σ)� (13) where: ω(r)(ε) and u(r)(σ) – are the homogeneous phase potentials and χ(r)(x)=1 if x � ω(㌠) or zero. firstly, the effective strain and complementary potentials (w� (ε�) andu�(σ�)) for the heterogeneous medium is achieved by averaging their minimum potential energies given as: w� (ε�) = min ω(x,ε) (14) �(x)∈k u�(σ�) = min u(x,σ) (15) �(x)∈s (kanoute et al., 2009) where: ��(��) – average minimum complimentary potential (�� ) average of the actual strain field � ��(��) -average minimum complimentary strain (��) average of the actual strain field � while the strain energy and complementary density functions as given in the mccauley brackets (that is equation (14) and (15)) gives the volume averages in the domain ω .; �� and �� are the average strain and stress fields while k is the set of kinematically admissible strains and s is the set of statically admissible stresses. the effective strain and stress potential for the elastic heterogeneous medium at the macroscale is therefore given by the voigt and ruess model as shown in eqns. (18) and (19): file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 494 (a) voigt model w� (ε�) = 1 2 ε� : l�: ε� (16) l� = r=1 n c(r) l(r) (17)� to arrive at the above expressions, voigt assumed that the strain field within the heterogeneous medium was constant. u�(σ�) = 1 2 σ� : m� : σ� (18) (b) ruess model l��1 �1 = r=1 n c(r) (l(r))�1 (19)� the assumption in ruess model is that a uniform stress was applied to the polycrystals with resulting comparable stresses in the constituent crystallite. where: lis the effective elastic tensor mcompliance tensor the volume fraction for the phase r �(㌠) the elasticity tensor for the phase r hill (1952), noted that because of the assumptions of a constant strain field in eqn. (14) and a constant stress field in eqn. (15), voigt model gives an upper bound estimate as shown in eqn. (16) while ruess model gives a lower bound estimate as shown in eqn. (17) w� (ε�) < 1 2 ε� : l�: ε� (2�) u�(σ�) ≤ 1 2 σ� : m� : σ� (21) in adopting the variation principle, voigt and ruess have only taken into account the volume fraction of each phase (one-point limit) which limited the application of their model as the influence of other characteristic properties of the microstructure on the effective properties of the heterogeneous medium have not been taken into consideration. hashin and shtrikman (1962a, 1962b and 1963), also employed the variation principles but took into account the polarization fields and were able to derive much tighter bounds for the effective properties of heterogeneous materials (two-point bounds) in comparison to that obtained from the voigt and ruess model (one-point limit). k1 + v2 1 k2 � k1 + 3 1� v2 3k1 + 4μ1 ≤ k∗ ≤ k2 + 1� v2 1 k1 � k2 + 3v2 3k2 + 4μ2 (22) μ1 + v2 1 μ2 � μ1 + 6 1 � v2 (k1 + 2μ1) 5μ1(3k1 + 4μ1) ≤ μ∗ ≤ μ2 + 1� v2 1 μ1 � μ2 + 6v2(k2 + 2μ2) 5μ2(3k2 + 4μ2) (23) where: �1,�1– bulk moduli in the first phase of the microstructure �2,�2– shear moduli in the second phase of the microstructure �2 – volume fraction in the second phase (konoute et al., 2009) http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 495 this technique was later expanded by torquato (2001) by including the details of the phase arrangement in his model (three-point bounds). the variation technique was further extended to non-linear cases in the work carried out by talbot and willis 1985 and willis 1986. further advancement in variation principles has lead to the ponte castaneda (1991, 1992) and talbot and willis (1992) variation principles in estimating the effective properties of non-linear composites (such as, the rapid localization of damage, energy absorption at high strain rates that is large plastic deformations and so on) as well as the suquet variation principles for power law composites. as an improvement on voigt upper bound estimate of the effective macroscopic properties for rigid plastic material, olson (1994) came up with his own variation principles for perfectly plastic composites. lately, homogenization schemes employed in the analysis of elasto-plastic composite materials has been reviewed by scholars such as: ponte castaneda and suquet (1998) as well as chaboche et al. (2005). in their opinion the schemes can be categorised into two groups, namely, those based on the use of secant stiffness tensor and those based on the use of tangent stiffness tensor. schemes based on the secant formulations dealt with plastic deformations within the frame work of non-linear elasticity, where the effective secant stiffness tensor is used to assess the relationship between the stress and strains at the elasto-plastic stages. this approach is best adopted when the composite material is subjected to monotonic and proportional loading (llorca et al., 2007). the elasto-plastic tangent modulus approach for evaluating the mechanical response of composites was presented by hill (1965) where he linearized the local constitutive equation by bringing it back in an incremental form: �(�) = �(�):�(�) (24) where: l is the tangent modulus (konoute et al., 2009). the initial models based on this approach gave very stiff predictions of the flow stress. the source of the inaccuracy was attributed to the anisotropic characteristic of the tangent stiffness tensor. more accurate predictions of the flow stress were obtained by adopting an isotropic estimation of the tangent operator (chaboche et al., 2005). another homogenizational approach is the mathematical asymptotic homogenization theory which employs an asymptotic expansion of the displacement and stress fields based on a ratio of the length scales ( � ). this technique gives both the effective overall properties such as the effective stiffness as well as the local stress and strain values (kouznetsova et al., 2012). 2.2 numerical homogenization schemes in computational micromechanics, the macroscopic or effective behaviour of composites is obtained through the solution of the boundary value problem (bvp) for a representative volume element (rve) of the microstructure by using numerical techniques. within this frame work, it is possible to obtain the local values of the field variable which facilitates the accurate simulation of crack nucleation and growth of damage as well as the localization of strains leading to damage which is a major advantage of the technique over analytical homogenizational schemes (llorca et al., 2007; zohdi and wriggers 2005). 2.2.1 numerical simulation schemes the current advancements in computing power and simulation tools, facilitating the solution of boundary value problems (bvp) of representative volume element (rve) of composites or file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 496 heterogeneous materials, of a size statistically sufficient enough to represent the microstructure without introducing undesired or non-existent properties is a welcome development in the computational micromechanics community. these numerical strategies (fast fourier transform algorithms, boundary element method as well as the finite element method fem) adopted in the solution of bvp are not only computationally efficient but also facilitates the solution of problems involving complex geometries. although the fem is the most preferred in the micromechanics community because of its mesh generation capabilities as well as its ability to implement complex constitutive equations; it tends to produce large models when simulating micro fields in regions with large strain gradient (llorca et al., 2007). the voronoi cell finite element method (vcfem) was introduced as an innovation to the fem in solving non-linear problems in composite materials. this technique is designed to simulate the behaviour of the composite material microstructure having different morphologies. in order to capture the variation in morphology, the finite element discretization was obtained by using voronoi tessellations where every voronoi cell contains an inclusion embedded in the matrix representing the basic hybrid finite element (moorthy and ghosh 1994; llorca et al., 2007). this formulation lowers the cost of computation in determining the micro fields in heterogeneous materials as the hybrid finite element reduces the number of degrees of freedom (d.o.f) in the analysis (moorthy and ghosh 1996, 2000). a three-dimensional vcfem (figure 5) for analysing composite material with randomly distributed composites was developed by ghosh and moorth (2004). figure 5: a two-dimensional voronoi cell finite-element mesh and detail of one voronoi finite element adapted from llorca et al. (2007) this technique was further extended by li and ghosh (2006). they came up with the extended voronoi cell finite element method (x-vcfem) used to model interfacial debonding in heterogeneous materials. in computational micromechanics, the use of efficient simulation tools (that is the domain decomposition method, iterative solvers such as: the conjugate gradient method) capable of solving bvp for rve is key as most micromechanics simulations require very large models with complex non-linear behaviour (zohdi and wriggers, 2005). the numerical homogenization discussed, gives emphasis on multiscale techniques based on coupled homogenization techniques and numerical analysis of the rve for both periodic and non periodic (random) microstructure morphological compositions as shown in figure 4. http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 497 figure 6: schematic representation of periodic and non periodic rve from nguyen et al. (2012). 2.2.2 asymptotic homogenization one such multiscale modelling technique is the coupling of asymptotic homogenization and finite elements. in this method the mathematical asymptotic concept is adopted in solving multiple scale problems by coupling finite element problems across length scales. this homogenization technique adopts an asymptotic expansion of the displacement and stress field on natural scale parameters see eqn. (25) (kanoute et al., 2009; nguyen et al., 2012). as such, it is important to distinguish both length scales, as the ratio of the length scales � � describes the small parameter ( �㇀ඟ� �◠ � � = � (25) where: r and r are the position vectors on the macro and microscale respectively (figure 6). u r,r = r � = u� r + �u1 r,r + o2 (26) eqn. (26) gives the asymptotic expansion of the displacement field where: �� � – macroscopic displacement field �1 �,㌠ – periodic first order fluctuations or perturbations due to the microstructure referred to as fast and slow variables respectively. � a small positive number linking the length scales at the macro and micro level udisplacement field figure 7: schematic strategy for the multi-scale simulation based on the finite element method and asymptotic homogenization adapted from llorca et al. (2007) this asymptotic expansion is regarded as an approximate solution of the boundary value problem (bvp) especially when � is reasonably small. the stress field is given as: ϵ r,r = grad� ���� s u = gradsu + 1 � gradsu = gradsu� + gradsu1 + � gradsu�1 (27) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 498 while the asymptotic expansion of the stress field assuming a linear elastic behaviour is given in eqn. (28) as: σ r,r = l :ϵ r,r = l :grad� ���� s u = σ1 r,r + �σ2 r,r + … (28) the homogenized stiffness tensor l� according to llorca et al. (2007) is computed from mean strain value ��−1 as: σ� = 1 ω ωσ 1� dω = 1 ω ω l : i + ∂χ r ∂r dω� :gradsu� = l� :gradsu� (29) although, this technique can be used for composites with either a local periodic microstructure (that is microstructure having different morphologies) or global periodicity (that is having repetitive cell units) as shown in figure 7, it is however, mostly restricted to simple microscopic geometries at very small strains ( ) as well as simple material models (mostly at small strains) where the macroscopic fields are virtually stable at the microscopic length scale. figure 8: a representation of a microstructure (a) with local periodicity and (b) with global periodicity from kouznetsova et al. cited in galvanetto and aliabadi (2010) this homogenizational approach offers not only the effective material properties, but also gives information on the local micro fields (llorca et al., 2007; kanoute et al., 2009; kouznetsova et al., 2001). 2.2.3 mesh superposition method this multiscale technique was introduced by fish (1992), where he superimposed an additional mesh on the macroscopic (or global) mesh especially in the regions of high stress and strain gradients with the aim of obtaining detailed information on the heterogeneous material microstructure at critical regions (crack tips, interfaces et cetera).the less critical benign regions of the heterogeneous materials, were modelled using coupled finite element method with asymptotic homogenization technique. in summary, numerical homogenization is used in the field having benign deformations while concurrent method is used in the critical regions of high stress and strain gradients where there is a substantial variation in the macroscopic field as shown in figure 9 (nguyen et al., 2012). the grading arrangement of the displacement field (u) in figure 9 is of a hierarchical nature as the displacement field has been separated into global and local regions respectively that is (30) (31) ul � displacement field in the local mesh with respect to the global mesh http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 499 . figure 9: schematic representation of the mesh superposition method from llorca et al. (2007). this hierarchical nature of the displacement field facilitates the modelling of the exact behaviour of the heterogeneous material microstructure in areas of high strain gradient. to ensure homogenous displacement compatibility at the boundary points between the local and global meshes, the local displacement field must equal zero (that is ul = � at ∂ω) while stiffness matrix ( �gl ) that links the displacement degrees of freedom of the global and local meshes are obtained from a system of equilibrium equations as given in eqn. (32) kg kgl kgl kl ug ul = f � (32) which can be arrived at by deriving the navier equations from the overall displacement field given in eqn. (30) where: kg and kl – stiffness matrix obtained from local and global meshes kgl stiffness matrix that combines the displacement d.o.f of the global and local meshes f nodal force vector 2.2.4 embedded cell method for this technique the model adopted describes the characteristics of the microstructure in detail at critical core regions which are then embedded within a homogenous medium. the finite element mesh of the core region is much finer than the embedding medium hence; it is capable of capturing fast variations in field which ensues as a result of damage. the mesh of the embedding medium is coarse, it is able to relay the macroscopic far field to the core region by implementing displacement continuity which links the core and the embedding region (llorca et al., 2007; nguyen et al., 2012). this technique has proven to be quite invaluable in accurately simulating the fracture process in localized regions. the technique as shown in figure 10 was adopted gonzalez and llorca (2006), in simulating fracture behaviour in fibre reinforced composites. they were able to accurately show from the multiscale computational model the main deformation and failure micromechanism. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 500 figure 10: schematic representation of the embedded cell method from llorca et al. (2007). 2.3 modern multiscale modelling as stated earlier the essence of multi-scale modelling is to take advantage of simplicity and efficiency that exists by coupling both microscopic and macroscopic models. it can therefore be stated that the task of multiscale modelling is to devise a coupled macroscopic-microscopic computational method which is not only efficient but also capable of giving the required information with the desired accuracy as opposed to solving the full microscopic model (weinan and jianfeng, 2011). while the traditional multiscale solvers as given in table 1 are general purpose microslovers which give solution of the microscale model (that is it focuses on just on scale), the modern multiscale method also listed in table 1 gives macroscopic behaviour from data obtained from the microstructure either sequentially or concurrently at a cost much less than the general microsolvers such that: cost of multiscale method cost of microscale slover on the full domain ≪ 1 (33) table 1: classical and modern multiscale technique traditional multiscale methods new multiscale techniques multigrid method carparrinello method domain decomposition method quasi-continuum method wavelet-based methods optimal prediction adaptive mesh refinement heterogeneous multiscale method fast multipole method gap-tooth scheme conjugate gradient method adaptive mode refinement adapted from weinan et al. (2007). the objective of multiscale modelling, is striking a balance between accuracy and feasibility hence, the focus here will be on the heterogeneous multiscale method (hmm) with a close methodology to the computational homogenization method used in computational mechanics (matous et al., 2017). the idea behind this technique is to work out the incomplete macroscopic model by obtaining the required data from the microstructural model. there are two major components to the heterogenous multiscale methodology namely: the overall macroscopic scheme for approximating the macroscopic variable u u = qu (34) also known as the compression operator, where: http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 501 uis the local averages of the microscopic variables (�) over the macro cells the scheme for evaluating the missing macroscopic data from the microscopic model u the overall macroscopic scheme for approximating the missing macroscopic data (for example the stiffness matrix, transition rates and so on) from the microscopic model is achieved by solving the micro models locally subject to the following constraint: q�u = u (35) where: -is an estimate of and in the present state of the macrostructure the above two processes (1 and 2) as well as the macro state variable u are linked to each other by the compression (u) as well as the reconstruction (r) operators given in eqns. (36) and (37) in that order; having the property known as the gradient operator given in equation (38). u = qu (36) ru = u (37) in summary, the heterogeneous multiscale methodology, essentially entails reconstructing the micro state from u then evolving the micro state using the microscopic model subject to certain constraint ( ) to evaluate the missing data from u. this way the coupling between both the macro and micro models is done in such a way that the constraints for setting up the micro models are obtained from the macro models while the micro model in turn, provides the much needed constitutive data for the macro model (weinan and jianfeng, 2011;weinan et al., 2007; weinan et al., 2003 ). 2.3.1 computational homogenization the last few decades have seen the development of an alternative multiscale method for micromacro coupling adopted in the homogenization of complex heterogeneous materials know as the computational homogenizational technique also called global-local analysis or finite element analysis in a more particular form (kouznetsova et al., 2012). with computational homogenization the details of the macroscale models are computed on-the-fly from the microscale models as simulations are ongoing (weinan and jianfeng, 2011). this characteristic nature of the computational homogenizational method makes it suitable in obtaining the effective mechanical behaviour of materials with evolving microstructural geometries, phase transformation as well as nonlinear mechanical problems (large deformations, initiation and propagation of cracks, dislocation mechanics and defects, creep and stress relaxation) (matous et al., 2017). in this method, materials are generally examined using characteristic volume (that is rv�◠) as shown in figure 11. figure 11: a two dimensional representative volume element from kouznetsova et al. (2001). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 502 while the homogenization process relies on the principles of separation of scales where the molecular length scale is smaller than microscopic length scale of the rve which in turn is much smaller than the typical size of the macroscopic sample that is as shown in figure 12 . the information obtained from this length scales are volumetrically averaged in a hierarchical order( that is ) to obtain the homogenous macroscopic properties such as stiffness tensor, the gradient tensor (fm) , the stress tensor (pm) and so on (kouznetsova et al., 2012); geers et al., 2010; matous et al., 2017). figure 12: length scales relevant for the separation of scales principles adapted from matous et al. (2017). 2.3.2 basic theory of micro-macro modelling in computational homogenization, the macroscopic or effective behaviour of composites is obtained by the following basic procedures listed below and schematically shown in figure 13. firstly, define the rve and the local constitutive equations to obtain input variables. next carry out a construction of boundary conditions for the rv from the above input variables as well as the solution of the boundary value problem (bvp) for the (rv ) of the composite using numerical techniques. this is also known as down scaling or macro-to-micro transition. the internal fields (output variables) obtained from the solution of the bvp of the rv are then volumetrically averaged (or homogenized) using averaging theorems (i.e. coupling between micro and macro levels) to obtain the regularized or effective material properties used in the macroscopic analysis at component level. this is also known as up scaling or micro-to-macro transition (kouznetsova et al., 2001; grytz and mechke 2007; nguyen et al., 2012; petracca et al., 2016). this regularization process is therefore referred to as “homogenization” (zohdi and wriggers 2008). an advantage of this computational homogenization over other homogenizational schemes is that the microscopic constitutive behaviour is defined as the simulations are ongoing thus, making it suitable for predicting the mechanical behaviour of composites with complex microstructure as well as adequately accounting for microstructure evolution under complex loading (feyel and chaboche 2000; kouznetsova et al., 2001; ozedmir et al., 2008; weinan and jianfeng, 2011; weinan et al., 2007; nguyen et al., 2012). figure 13: a schematic representation of the computational homogenizational scheme adapted from kouznetsova et al., cited in galvanetto and aliabadi (2010). http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 503 in the computational homogenizational scheme shown, is the gradient tensor for any point on the macro solid which is used to set up the boundary condition imposed on the rve boundary (figures 11 and 12) with a microscopic domain of size . a solution of the bvp for the rve should give the macroscopic stress tensor which is achieved by the volume averaging of the microstructural stresses over the rve (kouznetsova et al., cited in galvanetto and aliabadi 2010). implementing the above process in a finite element frame work gives the finite element method for computational homogenization which has been used in twodimensional problems. the results from two-dimensional scheme showed the importance of fibre/matrix interface strength on the macroscopic behaviour (damage and failure phases) of the composite materials (feyel 1999; kouznetsova et al., 2001). this scheme has been further extended to treat three dimensional problems by facilitating large deformations and rotations making it appropriate for dynamic problems on a finer scale. it can also be used on homogenous materials (on a finer-scale) with various shapes of rve (wiechert and wall 2010). 2.3.3 averaging theorems based on the principles of separation of scales, the rve is much smaller than the characteristic macroscopic sample that is therefore; the internal body forces at the macroscale are generally overlooked so that the static equilibrium state of the rve is mathematically expressed as: ∇m. σm = � in ωm (39) (kouznetsova et al., cited in galvanetto and aliabadi 2010) where: – gradient operator – microscopic stresses 2.3.3.1 deformation averaging theorem as the actual coupling of the micro-macro kinematic quantities are based on averaging theorems (kouznetsova et al., cited in galvanetto and aliabadi 2010), the deformation gradient tensor at any point on the macroscopic solid (figure 13) is given by volume averages of the microstructural deformation gradient tensor. fm = 1 vo vo fm� dvo = 1 vo γo x n� dγo (4�) the above expression for was obtained after transforming the integral of the un-deformed volume of the rve to a surface integral using the divergent theorem (kouznetsova et al., cited in galvanetto and aliabadi 2010). where: ��macroscopic deformation gradient tensor �� microscopic deformation gradient tensor ��– reference domain � for every �x in the domain � – un-deformed position x deformed position (kouznetsova et al., cited in galvanetto and aliabadi 2010). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 504 2.3.3.2 energy averaging theorem generally referred to as the hill-mandel macro-homogeneity principle, ascertains that the macroscopic volume averages on the rve (given by the expression in eqn. (41) which is expressed in terms of work conjugate set as given in eqn. (41) can also be stated in terms of rve surface quantities given in eqn. (42). 1 �� �� ��: ��� �� ��� = ��: ��� � (41) δwom = 1 vo vo pm: δfmc� dvo = 1 vo γo p.� δxdγo (42) where: �� is the first piola – kirchhoff stress tensor (grytz and mechke 2007; kouznetsova et al., cited in galvanetto and aliabadi 2010). 2.3.4 representative volume elements (rv�� ) the rve is the smallest material volume statistically representative of the microstructure of the heterogeneous material or the smallest volume of the heterogeneous material that exactly replicates the macroscopic behaviour (drugan and willis 1996; llorca et al., 2007; kouznetsova et al., cited in galvanetto and aliabadi 2010). accurate simulations in continuum micromechanics rely on simulating the behaviour of the rve of the heterogeneous material. with traditional computational homogenizational models, different rv�◠ have been used at various points on the microstructure to ensure accuracy (llorca et al., 2007). based on the model introduced by grytz and meschike (2007) shown in figure 14 it is possible to use the same rve at all points on the microstructure. figure 14 schematic representation of the micro-macro computational homogenization of finite deformation in curvilinear coordinates adapted from grytz and mechke (2007). similarly, the computational schemes addressed so far are applicable in the standard cartesian coordinates (that is one physical space), but with this development, the scheme can be applied to address problems formulated in curvilinear coordinates in the three-dimensional euclidean space both at the macro and micro levels. grytz and mechke 2007, employed this technique in the multiscale analysis of a spherical shell subjected to internal pressure shown in figure 15 where the homogenization of the 3d microstructure was carried out numerically at the macro level. similarly, only two rves were considered all through the shell thickness. http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 505 figure 15: spherical shell subjected to internal pressure-undeformed and deformed configurations of the macro-structure and the underlying micro-structure with the distribution of the cauchy stresses ��11 adapted from grytz and mechke (2007). from their study, they came to the conclusion that simplification of recommended computational scheme for problems formulated in curvilinear coordinates (such as the use of the same rve and so on), greatly simplified the solution of the multiscale problem when assessed against the traditional approaches using only a single physical space for both micro and macro scales thus demonstrating the efficiency of the proposed scheme over the traditional schemes particularly for problems in 3d euclidean space. from this study, the efficient application of computational homogenization in different physical space at different scales was demonstrated (grytz and mechke 2007). 3. conclusion from the review of the existing mathematical, numerical and computational homogenizational scheme for composite materials, it has been shown that: prior to the development of digital computers as well as the corresponding development in simulation tools (that is the fast fourier transform, the boundary element method and more recently the finite element method) as a means of analysing multi-scale models, the analytical/mathematical homogenization technique was considered the main workhorse to simulate the macroscopic mechanical behaviour of multi-phase heterogeneous material from the behaviour of the representative volume element (rve) of the microstructure of the material. the straight forwardness of the fundamental assumptions of the technique made it quite popular. despite its popularity (in computing internal stress in multiphase materials during deformation) the inability of the method to capture rapid localization of damage has limited the application of the method in computing mechanical behaviour of material where progressive damage is involved. although, the method describes quite accurately the effective macroscopic properties of the heterogeneous material in the elastic system it is not as effective in the nonlinear regime which has been the major drawback for this technique. with the current technological developments in simulating technologies the above limitation of the mathematical homogenization schemes in simulating the effective non linear heterogeneous material behaviour were addressed by adopting computational homogenizational schemes which rely on established constitutive relations for the macroscopic problems in a numerical form through which the macroscopic problems are constructed and solved in a nested manner. it can therefore be seen that: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 506 the homogenization schemes in general, have proven to be an invaluable tool for obtaining heterogeneous macroscopic material properties from the mechanical properties of the material microstructure. the accuracy of the analytical schemes is limited to elastic systems which are mostly applicable for accurately modelling microstructures with simple geometrical features. a limitation which has largely been attributed to the simplifications adopted in the analytical homogenisation models preventing it from capturing rapid localization of strains, nucleation, growth of damage as well as complex loading paths which causes phase transformation . computational homogenization on the other hand, has been able to give accurate predictions of the macroscopic material behaviour in non-linear systems. it allows the pragmatic assumption of local periodicity in the material microstructure which further improves on the accuracy of the results obtained. the major drawback of this technique is that the completely coupled micro-macro technique is quite expensive to simulate computationally. this has however been compensated for by adopting numerical strategies where the benign fields are modelled using coupled homogenization and finite elements and then carrying out detailed micro-macro analysis in the core regions (crack tips, interfaces) where it is essential to obtain a detailed information of the stress and strain fields at the core regions since it is the information from these regions that govern failure mechanisms. 4. future trends a major hindrance of the computational homogenizational scheme is in the development of a fully coupled micro-macro technique. a development of a fully coupled scheme is highly needed in order to be able to validate computational homogenizational multiscale models against experimental results without have any discrepancies at relatively low cost. furthermore, the application of this computational homogenizational scheme in designing as well as enhancing existing engineering materials by manipulating the microstructure is still lacking and needs more study. a significant improvement in this area will be highly invaluable in applications of engineering material for particular industrial applications. for example, the designing of novel lightweight materials such as: magnesium alloys, aluminium alloys, amorphous polymers etcetera which are energy efficient and aid in facilitating the reduction of greenhouse gas emissions from buildings, transportation and industrial sector. references aliyu, o. 2019. design recommendations for steel beams to prevent brittle fracture. nigerian journal of technologycal development, 16(2): 78-84. chaboche, jl., kanoute, p. and roos, a. 2005. on the capabilities of mean-field approaches for the description of plasticity in metal matrix composites. international journal of plasticity, 22: 1879-1898. drugan, wj., and willis, jr. 1996. a micromechanics-based non local constitutive equation and estimates of representative volume element size for elastic composites. journal of mechanics and physics of solids, 44(44): 457-524. http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 507 engquist, ew., lix, ren, w., vanden-eijnden, e. 2007. heterogenous multiscale methods: a review. community of computational. physics, 21: 367-450. eshelby, j. 1957. the determination of the elastic field of an ellipsoidal inclusion and related problems. proceecings of the royal society of london series a :a241 -3967doi: 10. 1098/rspa.1957.0133 feyel, f. 1999. multiscale elastoviscoplastic analysis of composite structures. compuational materials science, 16(1-4): 344-354. feyel, f. and chaboche, jl. 2000. multiscale approch for modelling the elastoviscoplastic behaviour of long fiber sic/ti composite materials. computer methods in applied mechanics and engineering, 183(3-4): 309-330. fish, j. 1992. the s-version of the finite element method. computers and structures, 43(3): 539547. galvanetto, u. and aliabadi, mh. 2010. multiscale modelling in solid mechanics. 3: 1-42 imperial college press 57 covent garden london. geers, mgd., kouznetsova, vg., and brekelmans, wam., 2010. muliti-scale compuational homogenization: trends and challenges. journal of compuational and applied mathematics, 234(7): 2175-2182. gonzalez, c. and llorca, j. 2006. multiscale modelling of fracture in fiber reinforced compostites. acta mater, 54: 4171-4181. ghosh, s. and moorthy, s. 1994. elastic-plastic analysis of arbitrary heterogenous materials with the voronoi cell finite element method. computer methods in applied mechanics and engineering 121: 373-401 ghosh, s. and moorthy, s. 2004. three dimensional voronoi cell finite element model for microstructures with ellopsoidal heterogeneities. computatonal. mechanics, 34: 510-531. grytz, r. and meschke, g. 2007. consistent micro-macro transition at larte objective strains in curvilinear connective coordinates. international journal for numerical methods in engingineering,doi: 10.1002/nme.2105 hashin, z. and shtrikman, s. 1962. a variational approach ot the theory of elastic behaviour of ploycrystalls. journal of mechanics and physics solids, 10: 335-345. hashin, z. and shtrikman, s. 1962. on some variational principles in anisotropic and homogeneous elasticity. journal of mechanics and physics solids, 10: 335-342. hashin, z. and shtrikman, s. 1963. a variational approach ot the theory of elastic behaviour of mulitphase materials. journal of mechanics and physics solids, 11: 127-140. hill, r. 1965. a self-consitent mechanics of compoiste materials. journal of mechanics and physics solids, 13: 213-222. hill, r. 1963. elastic properties of reinforced sloids: some theoretical principles. journal of mechanics and physics solids, 13: 213-222. hill, r. 1963. the elastic behahiour of crystalline aggregate. proceecings of the royal society of london series a, 65: 349-354. hutchinson, j. 1963. bonds and self-consistent estimates for creep and polycrystalline materials. proceecings of the royal society of london series a 348: 101-127. kanoute, p., boso, pd., chaboche, jl., schreller, ba. 2009. multiscale methods for composites: a review. arch comput methods eng, 16: 31-75. doi 20.1007/s11831-008-9028-8 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng ohunene hafsa aliyu: analytical, numerical and computational multiscale modelling techniques for heterogenous materials: a review. azojete, 15(3):488-509. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 508 kouznetsova, v., brekelmans. wam., and baaijens, fpt. 2001. an approach to micro-macro modelling of heterogeneous materials. compuatational mechanics, 27(1): 37-48. kröner, e. 1958. berechnung der elastischen konstanten desvielkristalls aus den konstanten des einkristalls. z phys, 504-5 li, s. and ghosh, s. 2006. extended voronoi cell finite element model for mulitple cohesive crack propagation in brittle materials. international journal for numerical method in engineering, 65(7): 1028-1067. llorca, j., gonzalez, c., and segurado, j. 2007. finite element and homogenization modelling of materials in: gou xiao z. (ed.) multiscale materials modelling.cambridge england: woodhead publishing and maney publishing, 121-144 matous, k., geere, mgo., kouznetsova, vg., gillman, a. 2017. a review of predictive nonlinear theories of multiscale modelling of heterogenous materials. journal of computational physics, 330: 192-220. moorthy, s. and ghosh, s. 1996. a model for analysis of arbitrary composite and poros microstructure with voronoi cell finite element. international journal for numerical method in engineering, 39: 2363-2398 moorthy, s. and ghosh, s. 2000. adaptivity and converganc in the voronoi cell finite element model for analyzing heterogeneous materials. computer method in applied mechanics and engieering, 185(7): 37-74. nemat-nasser, s. and hori, m. 1999. micromechanics: overall properties of heterogeneous material. 2nd edition elsevier amsterdam – lausanne – new york – oxford – shannon – singapore tokyo nguyen, vp., stroven, m. sluys, lj., 2012. mulitiscale continuous and discontinuous modelling of heterogeneous mateials: a review on recent developments. journal of multiscale modelling, 4 (3): 1-42 imperial college press doi: 10.1142/s1756973711000509 . olson, t. 1994. improvements on a taylors upper bound for rigid-plastic composites. material science engineering, a175: 15-19. ozdemir, i., brekelmans, wam., and geers, mgo. 2008. computational homogenization for heat conduction in heterogeneous solids. international journal of numerical methods in engineering, 73: 185-204. ponte casta eda, p. 1996. exact second-order estimates for the effective mechanical properties of non linear composite materials. journal of mechanics and physics solids, 44: 827-862. petracca, m., pela. luca, rossi, riccardo, oller. s., camata, s., spacone, e. 2016. regularization of first order computational homogenization for multiscale analysis of masonry structures. springer 2 (57): 257-276. ponte castan eda, p. 1997. non linear composite materials: e⒐ective constitutive behaviour and microstructure evolution䇅 in: suquet, p. (ed) continuum micromechanics cism courses and lectures. 337: 188-195 ed. new york: spinger. ponte castenda, p. and suquet, p. 1998. nonlinear composites. advanced applied mechanics, 34: 171-301. reuss, a. 1929. berechnung del fliessgrenze von mis-chkristallen auf grund der plastizitätbedingung für einkristalle. z angew math mech, 9: 49-58. suquet, p. 1993. overall potential and external surfaces of power law or ideally plastic composite. journal of mechanics and physics solids, 41: 981-1002. http://www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):488-509. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 509 talbot, drs. and willis, jr. 1985. variational principles of inhomogeneous non-linear media. journal of applied math, 35: 39-54. talbot, drs. and willis, jr. 1992. some explicit bounds for the overall behaviour of nonlinear composites. international journal for structures, 29: 1981-1987. torquato, s. 2001. random heterogenous materials.new york: springer torquato, s. 2013. random heterogenous materials.new york: springer: 5. van der sluis, o., schreurs, pjg., brekelemans, wam., and meijer, heh. 2000. overall behaviour of heterogenous elastoviscoplastic materials: effect of microstructural modelling. mechanics of materials, 32(8): 449-462. voigt, w. 1889. über die beziehung zwischen den beiden elastizitätskonstanten isotroper körper. wied ann, 38: 573–587. weinan, e., engquist, b., li, x., ren, w., and vanden-eijnden, e. 2007. heterogeneous multiscale methods:a review. community of computational physics, 2: 367-450. weinan, e. and jianfeng, l. 2011. 䇅mulitiscale modelling䇅. scholarpedia, 6(10), pp. 11527. wiechert, l. and wall, w.a. 2010. a nested dynamic multi-scale approach for 3d problems accounting for micro-scale multi-physics. computer methods in applied mechanics and engineering, 199(21-22): 1342-1351. willis, j. 1986. variational estimates for the overall response of an inhomogeneous nonlinear dielectric in: ericksen j.l. et al (eds) 䇅homogeneous and effective moduli of materials and media. new york: springer. zohdi, t.i. and wriggers, p. 2005.introduction to compuational micromechanics. 1st edition berlin berlin–verlag berling heidelberg: springer : springer. zohdi, t.i. and wriggers, p. 2008.introduction to compuational micromechanics. p 2 2nd edition, berlin–verlag berling heidelberg: springe file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):174-189 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 174 original research article a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) g. u. asonye, s. n. asoegwu, j. n. maduako, and c. n. madubuike agricultural and bioresources engineering department, school of engineering and engineering technology, federal university of technology, owerri, nigeria. *corresponding author: u.asonye@yahoo.com article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: modeling cocoyam (colocasia esculenta) cutting energy dimensional analysis crop size abstract information on the optimum energy requirements for cutting vegetables is useful in order to estimate the amount of energy needed to cut given products with known physical characteristics. this will aid engineers and product designers in the development of appropriate cost effective cutting systems consuming minimum amount of energy while still providing high quality cut products. in this study, predictive equations were developed for describing the cutting energy of cocoyam (colocasia esculenta) cormels. dimensional analysis based on the buckingham pi theorem was used to obtain the functional relationship between the cutting energy of the selected vegetable and the independent variables such as tool weight (w), height of tool drop (hd), tool edge thickness (t), cutting speed (v), crop size(s), crop moisture content (φ), crop contact area (a) and crop density (σ). the developed model was validated with experimental data and a high coefficient of determination of r2 = 0.982 between the predicted and measured values was established. the obtained predictive model proved appropriate for determining the cutting energy required for cocoyam cormels up to 98%. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction agricultural products often occur in sizes too large to be used, and therefore they need to be reduced and put into different sizes and shapes like cubes, thin slices or rings to facilitate further processing. cutting, which is a size reduction activity, is an energy consuming operation. however, the cutting energy requirements of vegetables have been estimated using different cutting systems and approaches with the following objectives: to know the most efficient cutting conditions necessary for optimization of the cutting process; and to determine the optimal energy required to cut and to achieve an overall efficient cutting operation. blade sharpness, slicing angle, contact area, depth of cut, cutting speed, and the engineering properties of vegetables such as crop variety, maturity stage, moisture content, average diameter, orthogonal dimensions and fibre orientation have been identified as some of the parameters affecting the energy requirements for cutting of vegetables (ciulica and rus 2011; elżbieta and agnieszka, 2012 and singh et al., 2016). cocoyam (colocasia esculenta) is the root vegetable of interest in this study. it is a member of araceae family and in the group of monocotyledons, constituting of one of the six most mailto:yabiodun@unilag.edu.ng mailto:yabiodun@unilag.edu.ng mailto:u.asonye@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):174-189. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 175 important root and tuber crops worldwide (edet and nsukka, 2000). cocoyam is an aroid because it is grown mainly for its edible cormels and some of the varieties include; tannia (xanthosoma sagittifolium), taro (colocasia esculenta) eddo (colocasia antiquorum), tarul, arum, alocasia macrorrhizos and alocasia odora (ekanem and osuji, 2006). nigeria is the largest producer of cocoyam in the world with an annual production of 3.450 million metric tonnes in 2012, representing 72.2 %, 57.7 % and 45.9 % of total production in west africa, africa and the world, respectively (faostat, 2012). cocoyam is said to be a giant crop, because its cormels, leaves, stalks and inflorescence are all utilized for human consumption (chukwu et al., 2008). it has been found to have nutritional, medicinal and industrial benefits; reported to be more suitable for several food products, especially as food for potentially allergic infants, and persons with gastro-intestinal disorders (opara, 2002; ekwe et al., 2009; eleazu et al., 2013). the cocoyam cormels could be processed into many products including poi (fresh or fermented paste, canned, and canned-acidified), flour, cereal base, beverage powders, chips, sun-dried slices, grits, drum-dried flakes, a binding agent in tablet manufacture and a source of industrial starches. (onayemi and nwigwe, 1987; iwuoha and kalu, 2000; subhadhirasakul et al., 2001; lawal, 2004; lewu et al., 2009 and owuamanam et al., 2010) however, in spite of its many industrial, medicinal and nutritional benefits, studies reveal that it is an under-exploited and insufficiently studied crop (nguyen and nguyen, 1987; goenaga and heperly, 1990; giacometti and león, 1994; watanabe, 2002) which portends a danger of gradual disappearance from our meal time table and eventual extinction unless urgent attention is given to it. also, it suffers a lot of postharvest losses due to inadequate post-harvest handling technologies which makes the crop scarce and expensive when it is not in season. hence in postharvest processes such as drying, frying, grinding, pelleting, packaging, transportation and storage of cocoyam cormels, size reduction by cutting is a necessary operation that equally increases the surface area of the processed cormel. furthermore, extensive documentation on the properties of foods and food products exist, however data related to the cutting energy of different vegetables is scarce, even though such data is important in the design of cutters. this observation is affirmed by researchers like saravacos and kostaropoulos (2002) who noted that less work has been performed on energy involved in the cutting of different food materials, and brown et al. (2005) who opined that limited published literatures on specific energy requirement in cutting of fruits and vegetables are available. also, mitcham et al. (1996) agreed that literature related to cutting of fruits and vegetables are limited. 1.1 modeling agricultural processes modeling, simply defined is a representation in mathematical terms of the behavior of real devices and objects, or a system of postulates, data and inferences presented as a mathematical description of an entity or state of affairs (dym and ivey, 1980). it could be descriptive, explanatory or predictive. in the prediction part, which can be envisaged as organized thinking of the possible, models are exercised to give information on a yet-to-be-conducted experiment. these predictions are then followed by observations that serve either to validate the model or to suggest reasons that the model is inadequate (dym, 1994 and cha et al., 2000). various mathematical modeling techniques that are in use include: dimensional homogeneity and analysis, abstraction and scaling, conservation and balance principles and consequences of linearity. https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4444859/ https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4444859/ https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4444859/ https://www.ncbi.nlm.nih.gov/pmc/articles/pmc4444859/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al. a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) azojete, 15(1):174-189. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 176 however, dimensional analysis has become a widely applicable and very powerful technique that is adopted in mathematical modeling. this is due to its simplicity in planning, presentation, and interpretation of experimental data, providing an organized way to plan and carry out experiments, and enables one to scale up results from model to prototype (bahrami et al., 2006; maheedhara and diwakar, 2014). the dimensional analysis is a mathematical technique used in identifying the factors involved in a physical situation or phenomenon and forming a relationship between them. it offers a method for reducing complex physical problems to the simplest form prior to obtaining a quantitative answer (andrzej, 2015). although there are other methods of performing dimensional analysis, notably the indicial method, the method based on the buckingham pi theorems gives a well-organized procedure for obtaining a solution. the buckingham pi theorem states that the number of dimensionless and independent quantities required to express a relationship among variables in any phenomenon is equal to the number of quantities involved minus the number of dimensions in which those quantities may be measured (fox and mcdonald, 1992). mathematically speaking, if there is a physically meaningful equation involving a certain number (n) of physical variables, then the original equation can be rewritten in terms of a set of p = n − k dimensionless parameters (π1, π2, ..., πp) constructed from the original variables (hart, 1995), (here k is the number of physical dimensions involved; which in this situation, (k = 3 namely mass, length and time). the application of mathematical models in different aspects of agricultural engineering including tillage operations (fielke, 1999), spraying machines (teske et al., 1991), crop handling machines (gorial and o’callaghan, 1991), harvesting (baruah and panesar, 2005a and b) and many versatile topics on post harvesting aspects have been successfully attempted such as; modeling flow rate of egusi-melon (colocynthis citrullus) through circular horizontal hopper orifice (asoegwu et al., 2010); modeling the grain cleaning process of a stationary sorghum thresher (simonyan et al., 2006) and development of a model to describe infrared radiative and convective drying characteristics of onion slices for optimum management of operation parameters (jain and pathare, 2004). although a few research attempts have been made to model cutting processes like mathematical models and laboratory tests of impact cutting behavior of forage crops, (mcrandal and mcnulty, 1978); performance modeling of the cutting process in sorghum harvesting (mohammed, 2002), mathematical modeling of laser based potato cutting and modeling yield efficiency of peeling (somsen et al., 2004, ferraz et al., 2007), much is left undone on modeling the energy requirement for cutting vegetables. some researchers used the dimensional analysis based on the buckingham’s pi theorem as veritable instrument in establishing a prediction equation of various systems which include the development of screw-conveyor performance models using dimensional analysis, (degrimencioglu and srivastava, 1996); a mathematical model for predicting output capacity of selected stationary grain threshers (ndirika, 2006); a mathematical model for predicting the cracking efficiency of vertical-shaft centrifugal palm nut cracker (ndukwu and asoegwu, 2011); and modeling flow rate of egusi-melon (colocynthis citrullus) through circular horizontal hopper orifice (asoegwu et al., 2010). the size reduction operation by cutting in most postharvest processes is a most laborious, time wasting and energy consuming task which deserves research attention. these studies are necessary in order to discover methods of efficiently improving the cutting process by maximizing the scarce energy, time and resources available and optimally enhancing the posthttp://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):174-189. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 177 harvest operations concerned. hence the need to undertake the present study which will establish a mathematical model using dimensional analysis based on the buckingham’s pi theorem to predict the cutting energy requirement for cocoyam (colocasia esculenta) cormels. the mathematical model will become a design tool for machine designers in the development of energy saving and cost effective cutting systems that will provide good quality cut products. 2.0 materials and methods 2.1 theoretical development factors affecting the cutting energy of vegetables obtained from literature include tool parameters like (sharpness, rigidity of cutting tools and knife speeds) and physical properties of the plant material like (crop variety, size, maturity stage, crop moisture content, crop density, fiber orientation) (szot et al., 1987; nadulski, 2001; mcgorry et al., 2003; blahovec, 2007; mccarthy et al., 2007 and atkins, 2009). in the development of the model, dimensional analysis was employed which is a technique used in identifying factors involved in a physical situation and forming a relationship among them. however dimensional analysis based on the buckingham pi theorem which states that the number of dimensionless and independent quantities required to express a relationship among variables in any phenomenon is equal to the number of quantities involved minus the number of dimensions in which those quantities may be measured (fox and mcdonald, 1992) was adopted. if n = number of variables involved in a physical situation x = number of dimensions in which quantities may be expressed = (3), m, l, t n = number of dimensionless groups as given in eqn (1). hence, n = n − x (1) however, due to the large number of variables influencing the energy of cut of the selected root vegetable, assumptions will be made in order to bring these large numbers to a reasonable and manageable number. (simonyan et al., 2006). 2.2 assumptions made in model development variables that are design parameters which are measurable were considered. variables that are functions of other variables were not considered e.g. volume which is a function of crop size. however, cutting speed which is a function of time was considered instead of time. the fiber orientation, textural properties and crop variety are considered negligible in the model development. 2.3 development of the functional energy equation these assumptions helped in reducing the number of variables involved to the under listed as these were considered to have greater influence on the energy of cut of the selected vegetable and are measurable. the chosen variables were: tool weight (w), height of tool drop (hd), tool edge thickness (t), cutting speed (v), crop size(s), crop moisture content (φ), crop contact area (a) and crop density (σ). having identified the core variables influencing the energy required for cutting the selected vegetable, eqn 2 represents the functional equation of the predictive model. e = f (w, hd, t, v, s, φ, a, σ) (2) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al. a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) azojete, 15(1):174-189. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 178 where e = cutting energy (j), w = tool weight (kg), hd = height of tool drop (m), t = tool edge thickness (m), v = cutting speed (m/s), s = crop size (m), φ = crop moisture content (%), a = crop contact area (m2) and σ = crop density (kg/m3). three primary dimensions m= mass, l= length, t= time were chosen in the description of the variables. from the buckingham pi theorem (fox and mcdonald, 1992) the total number of dimensionless groups to be formed is as given in eqn 1 above. for n = n − x and n = number of variables involve in the situation studied = 9 x = number of dimensions for describing these variables = 3 then, n = 9 − 3 = 6 six dimensionless groups were formed namely; 1 , 2 , 3 , 4 , 5 and 6 . in determining the dimensionless groups, the following procedure was adopted (fox and mcdonald, 1992). the variables utilized in the establishment of the model equation for the cutting energy of the selected vegetable were expressed in terms of their dimensions as shown in table 1. table 1: list of variables and their dimensions s/n variable symbol unit dimension 1 energy e kgm2s-2 ml2t-2 2 tool weight w kgms-2 mlt-2 3 height of tool drop hd m l 4 tool edge thickness t m l 5 cutting speed v ms-1 lt-1 6 crop size s m l 7 crop moisture content φ φ m0l0t0 8 crop contact area a m2 l2 9 crop density σ kgm-3 ml-3 the dimensional matrix of the variables is shown in table 2. this is needed to develop the indices of the involved variables. table 2: dimensional matrix of variables s/n variable symbol m l t 1 energy e 1 2 -2 2 tool weight w 1 1 -2 3 height of tool drop hd 0 1 0 4 tool edge thickness t 0 1 0 5 cutting speed v 0 1 -1 6 crop size s 0 1 0 7 crop moisture content φ 0 0 0 8 crop contact area a 0 2 0 9 crop density σ 1 -3 0 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):174-189. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 179 from table 2, it was seen that φ is dimensionless and therefore excluded from the dimensionless terms determination and is to be added later (simonyan et al., 2006) while the other variables were combined to form the п groups. cutting speed (v), tool weight (w) and crop size (s) were selected as the major parameters (i.e. recurring set) because they contained all the primary dimensions involved in this problem and their combination does not form a dimensionless group. having selected w, v and s as the recurring set, the exponents a, b and c are attached to them respectively so that when their product wavbsc divide the remaining variables e, hd, t, a and σ, the dimensionless groups п1, п2, п3, п4 and п5 are obtained as given in eqns 3 to 7 (ndirika, 2006; simoyan et al., 2006; asoegwu et al., 2010; ndukwu and asoegwu, 2011) .this is the basis of the buckingham pi theorem of dimensionless groups. п1 = e wavbsc (3) п2 = hd wavbsc (4) п3 = t wavbsc (5) п4 = a wavbsc (6) п5 = σ wavbsc (7) where a, b, and c are exponents needed to make the groups non-dimensional. the variables are substituted with their dimensions and the non-dimensional пs are replaced with m0l0t0 which is a dimensionless group. in order to obtain values for the exponents, the principle of dimensional homogeneity is used to equate the dimensions on each side of the equations of the п groups. eqn 3 being expressed in terms of the dimensions on both sides becomes eqn 8 m0l0t0 = ml2t−2 (mlt−2)a(lt−1)blc (8) crossmultiplying eqn 8 gives eqn 9. m0l0t0( mlt−2)a lt−1 blc = ml2t−2 (9) using dimensional homogeneity for m, l and t, the exponents a, b and c are got in eqns 10, 11, 12 and 13. for m; m0+a = m1 0 + a = 1 a = 1 (10) for l; l0+a+b+c = l2 0+a+b+c = 2; from eqn 10, a = 1 1+b+c =2 b+c = 2-1 =1 b+c = 1 (11) for t; t0−2a−b = t−2 -2a – b =-2 since a =1 -2(1) – b = -2 -b = -2+2 =0, b = 0 (12) from eqn 11, b + c = 1, put b=0 0+c=1; c=1 (13) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al. a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) azojete, 15(1):174-189. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 180 hence, a = 1, b = 0, c = 1; replacing the exponents with their values, п1 becomes eqn 14 п1 = e w1v0s1 = e ws (14) similarly, solving for the remaining п groups, we obtain eqns 15 to 19. п2 = hd s (15) п3 = t s (16) п4 = a s2 (17) п5 = σv2s2 w (18) п6 = φ (19) combining these equations gives eqn 20, whose components are dimensionless. i.e. e ws = f ( hd s , t s , a s2 , σv 2s2 w , φ ) (20) combining the dimensionless terms to reduce it to a manageable level (shefii et al. 1996) by multiplication and/or division, we obtain eqns 21 to 23 which are dimensionless. п12 = п1 п2 = e ws × s hd = e whd (21) п34 = п3 п4 = t s × s2 a = ts a (22) п56 = п5 п6 = σv2s2 w × 1 φ = σv2s2 wφ (23) the new dimensionless functional relationship becomes eqns 24 and 25. п12 = f (п34 , п56) (24) e whd = f ( ts a , σv2s2 wφ ) (25) from eqn 25, the equations for e are obtained as eqns 26 and 27. e = whd ( ts a , σv2s2 wφ ) (26) e = f (tswhd a , σv 2s2hd φ ) (27) eqn 27 gives the cutting energy e, with all the parameters in eqn 2, as a function of two energy components tswhd a and σv2s2hd φ which are represented as p and q, respectively in eqn 28. eqns 29 and 30 give the energy components represented by p and q. e = f (p,q) (28) where p = tswhd a (29) q = σv2s2hd φ (30) 2.4 experimental procedure fifty cocoyam cormels (colocasia esculenta spp) bought from the eke-onunwa market at owerri, imo state, nigeria were thoroughly cleaned of all impurities and unwholesome cormels, thereafter sorted into four size ranges of 10 corms each and some physical properties obtained at an initial moisture content of 71.8±0.16% (wb)(aoac, 2000). the measured physical properties of the selected cocoyam cormels were; mass (kg) determined with an electronic weighing balance (model gf-200, a & d company ltd, japan of an accuracy of ±0.01); the circumference at the point of cut (obtained by winding round with a tape and measuring out on the meter rule); the area (mm2) was determined by tracing out on a graph sheet and summing http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):174-189. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 181 up the number of squares; the orthogonal dimensions (major, intermediate and minor diameters) were determined with a digital venier caliper (model 500-196, mitutoyo products, america), these were used to calculate the equivalent diameter of the cocoyam samples. with an automated vegetable cutter, at a preset speed of 40mm/min, the cutter drops from a height of 30cm, cutting the sample as it travels through it. the slope of the force-distance relationship displayed on the monitor was used to calculate the cutting energy. figure 1.0 shows the experimental set-up of the cutting mechanism. figure 1.0: experimental set-up of the cutting mechanism the automated vegetable cutter consists of the hardware and software components. arduino controlled processors automatically and effectively measures, records and stores cutting variables and other basic parameters with minimum human supervision, thus making the entire cutting process automated. connecting to an electric power source switches on the cutter and a predetermined speed value is selected on the keypad. as the knife presses against the sample, the reactive force exerted on the load cell is amplified and measured. connecting to a computer using usb port the measured values are relayed and matlab intercepts the values and plots the resulting graph of force of cut against distance travelled which is used in calculating the energy of cut. 2.5 model input parameters and validation in the determination of validation parameters, every other parameter was held constant while the crop size varied. the selected tool edge thickness (t) measured with a digital venier caliper (model 500-196, mitutoyo products, america) was 0.2cm. the weight (w) of the cutting tool determined with an electronic weighing balance (model gf-200, a & d company ltd, japan of an accuracy of ±0.01) was 300g. the cutting tool was dropped from a pre-determined height (h) of 30cm measured with a meter rule. the crop density (σ) determined by dividing the weight of the crop by the volume of water displaced when sample is placed inside a measuring cylinder was taken as 1.35g/cm3. the orthogonal dimensions of the sample were determined with the digital venier caliper (model 500-196, mitutoyo products, america). the crop contact area (a) taken as 28.75cm2 was determined by multiplying the circumference at the point of cut (obtained by winding round with a tape and measuring out on the meter rule) with the major electric motor cutter frame arduino processor cutting knife cocoyam sample monitor display file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al. a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) azojete, 15(1):174-189. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 182 diameter of the crop sample. the moisture content of the crop sample determined with the method described in aoac (2000) was taken as 71.8 %(wb). 2.6 prediction energy equation the predicted cutting energy equation was established by allowing one of the energy components p( tswhd a ) or q( σv 2s2hd φ ) to vary at a time while keeping the other one constant and observing the resulting changes in the function (shefii et al., 1996). this was achieved by plotting the experimental values of e against p = ( tswhd a ) while keeping q constant. p = ( tswhd a ) was evaluated by substituting the measured values (as listed out in section 2.5) for tool edge thickness (t), crop size(s), tool weight (w), height of tool drop (hd) and crop contact area (a) into p. also, e against q = ( σv 2s2hd φ ) was plotted while keeping p constant. values for q = ( σv 2s2hd φ ) were obtained by substituting the measured values (as listed out in section 2.5) for crop density (σ), cutting speed (v), crop size(s), height of tool drop (hd) and crop moisture content (φ) into the equation. in evaluating the energy values for p and q, the crop size was varied while the other factors remained constant (simonyan et al., 2006; shefii et al., 1996). the obtained values for the predicted cutting energy were plotted against the measured (experimental) values on regression curves using the statistical package, microsoft excel 2007 and the coefficient of determination (r2) and root mean square error (rmse) values obtained. the validity or suitability (goodness of fit) of the models developed for the cutting energy requirement of the selected crop was tested by comparison with experimental data. values obtained for the root mean square error (rmse) and the coefficient of determination (r2) were indicators of the suitability of the developed models. 3.0 results and discussion average values and standard deviations of the measured physical parameters of the cocoyam cormels (as described under the experimental procedure) are shown in table 3. table 3: average values for physical properties of cocoyam cormels at 71.8± 0.16% (w.b) s/n corms mass (g) diameter (mm) circumference (mm) area (mm2) 1 c1 300±6.29 60.50±0.22 205.2±1.44 2874.75±32.89 2 c2 140±1.30 48.31± 0.62 165.7±1.02 1833.01±40.11 3 c3 100±4.53 36.20±0.60 120.5±0.84 1029.22±25.16 4 c4 70±1.24 22.15± 0.48 79.8±0.35 385.33±10.28 from the results displayed in table 3, it can be observed that the measured physical properties (in terms of mass, equivalent diameter, circumference and area) of the cocoyam samples sorted from the largest (c1) to the smallest (c4) based on measurement decreased in the measured values from c1 to c4. this is indicative of the significant effect of size on the physical characteristics of agricultural products, which is expected to influence the energy required for cutting the products. table 4 shows the experimental values of the cutting energy obtained with the automated vegetable cutter and the predictive values of the cutting energy obtained by substituting values of the cutting variables into the energy equations p = (tswhd a ) and q = ( σv 2s2hd φ ). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):174-189. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 183 table 4: experimental values (emeas) and calculated values (p, q) of cutting energy for cocoyam cormels. s/n corms crop size (mm) (emeas)       a tswh p d          dhsv q 22 1 c1 60.50±0.22 192.21 378.8 110.2 2 c2 48.31± 0.62 170.73 302.4 70.2 3 c3 36.20±0.60 129.25 226.65 39.4 4 c4 22.15± 0.48 75.22 138.99 14.8 cutting energy results as observed from table 4 show the reduction in both the experimental values (emeas) and the predictive values (p, q) obtained as the cormel sizes reduced. the results obtained showed the significant effect of crop size on the cutting energy requirement for cocoyam cormels as the highest energy observed was for c1 which is the largest range of crop sizes tested and the lowest energy obtained was for the least range of crop sizes tested i.e c4 (over 60% reduction in the cutting energy values from highest size range to lowest size range). furthermore, while c1 is 63.4% bigger in size than c4, the cutting energy components, emeas, p and q for c1 were found to be 60.9%, 63.3% and 86.6% higher than for c4. this goes to authenticate the effect of crop size on the cutting energy requirement of the crop being studied. the plots of the cutting energy (emeas) against p and q are shown in figures 1 and 2 with their linear equations and r2 values expressed in eqns 31 and 32. figure 1: variation of cutting energy against p = tswhd a , keeping q = ( σv 2s2hd φ ) constant. figure 2: variation of cutting energy with q =(σv 2s2hd φ ), keeping p = ( tswhd a ) constant. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al. a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) azojete, 15(1):174-189. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 184 e = 1.973p – 17.96; r2 = 0.977 (31) e = 0.764q – 49.83; r2 = 0.916 (32) the plot of the p and q terms in figures 1 and 2 forms a plane surface in linear space and according to mohammed (2002), it implies that their combination favors summation or subtraction. therefore, the component equations formed by the subtraction and summation of eqns 31 and 32 give eqns 33 and 34 respectively. e = f1 (p,q ) f2 (p,q ) + k (33) e = f1 (p,q ) + f2 (p,q ) + k (34) it must be noted that; at f1, q was kept constant while p varied at f2, p was kept constant while q varied substituting eqns 31 and 32 into eqn 33 and performing some algebraic manipulations yields eqn 35. e = 1.973p – 0.764q + 31.87 (35) also, substituting eqns 31 and 32 into eqn 34 and performing some algebraic manipulations yields eqn 36. e = 1.973p + 0.764q 67.79 (36) a further manipulation as permitted under the rules of the burkingham pi theorem (shefii et al., 1996) is manipulating with a constant factor. hence, eqns 35 and 36 are divided with a constant factor of 3 which yields the predicted model equations expressed in eqns 37 and 38 respectively. dividing eqns 35 and 36 with the constant factor of 3 yielded predicted values close to the actual ones. e = 0.658p – 0.255q +10.62 (37) e = 0.658p + 0.255q 22.60 (38) substituting the variables for p and q into equations 37 and 38 yield equations 39 and 40 respectively. e = 0.658tswhd a – 0.255σv 2s2hd φ +10.62 (39) e = 0.658tswhd a + 0.255σv 2s2hd φ 22.60 (40) however, the final predicted model equation will be either of the above two equations that gives the better statistical inference. 3.1 model validation the mathematical model was validated using the data generated from the vegetable cutter. the model validation was done at four ranges of crop sizes (20-23mm, 35-38mm, 45-49mm and 6063mm) and a constant cutting speed of 40mm/min. the method of regression analysis as computed using microsoft excel environment was used to describe the relationships, plot the graphs and compute the coefficients of determination (r2). measured values of parameters were substituted into eqns 39 and 40 to yield the predicted cutting energy values which were plotted against the experimental energy values on a regression curve in order to obtain the coefficients of determination (r2) and the root mean square error (rmse). eqns 41 and 42 express the relationship between the predicted cutting and experimental cutting energy with r2 values of 0.982 and 0.970, respectively. however, eqn 41 which gives the higher r2 value of 0.982 with a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):174-189. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 185 rmse of 0.97 between the experimented and predicted cutting energy values which is less than 1% of the average value of the experimental cutting energy is taken as the predicted model equation for the cutting energy of cocoyam cormels. figures 3 and 4 presents the regression curves between the predicted and experimental cutting energy respectively with their linear equations and r2 values given in equations 41 and 42 respectively. figure 3: relationship between experimental and predicted cutting energy (for subtraction of component energy equations) epred= 1.100 eexp + 11.74; r2 = 0.982 (41) where epred= predicted cutting energy, eexp = experimental cutting energy figure 4: relationship between experimental and predicted cutting energy. (for summation of component energy equations) epred = 0.650 eexp + 34.75; r2 = 0.970 (42) where epred= predicted cutting energy, eexp = experimental cutting energy from the results of the correlation graphs, the coefficient of determination obtained when component equations were subtracted was r2 = 0.982 with a rmse of 0.97 between the experimental and predicted cutting energy which is less than 1% of the average value of the experimental cutting energy. also the coefficient of determination obtained when component equations were summed was r2 = 0.970 with a rmse of 1.06 between the experimental and predicted cutting energy which is more than 1% of the average value of the experimental cutting energy. however, a higher coefficient of determination of r2 = 0.982 and a lower rmse of 0.97 were obtained with subtraction of the component energy equations as compared to coefficient file:///c:/users/user/downloads/azojete143/www.azojete.com.ng asonye, et al. a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) azojete, 15(1):174-189. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 186 of determination (r2 = 0.970) and rmse of 1.06 obtained by the summation of the component energy equations. hence, the prediction model equation for the cutting energy requirement for cocoyam (colocasia esculenta) cormels will be the equation which gives a higher value of coefficient of determination of r2 = 0.982 and a lower value of rmse = 0.97 expressed as eqn 43. 0.658tswhd a – 0.255σv 2s2hd φ +10.62 (43) where: w = tool weight (kg), hd = height of tool drop (m), t = tool edge thickness (m), v = cutting speed (m/s), s = crop size (m), φ = crop moisture content (%), a = crop contact area (m2) and σ = crop density (kg/m3). 4.0 conclusion a mathematical model for predicting the cutting energy of cocoyam (colocasia esculenta) cormels was presented using dimensional analysis based on the buckingham’s п theorem. the model equation expressed as e = 0.658tswhd a – 0.255σv 2s2hd φ +10.62 was validated with data from an automated vegetable cutter. results obtained showed a high coefficient of determination (r2 = 0.982) and a low root mean square error (rmse) of 0.97 which implies that the model is good. therefore, the developed model could be used to predict the cutting energy of cocoyam cormels up to 98%. references andrzej, f. 2015. basic principles and theorems of dimensional analysis and the theory of model similarity of physical phenomena, technical transactions in civil engineering (2b). cracow university of technology. pp. 242-272. aoac, 2000. official methods of analysis. 17th edition. the association of official analytical chemists, gaithersburg, md, usa. 6: 200-220. asoegwu, sn., agbetoye, las. and ogunlowo, as. 2010. modeling flow rate of egusimelon (colocynthis citrullus) through circular horizontal hopper orifice. advances in science and technology, 4(1): 35-44. atkins, t. 2009. the science and engineering of cutting: the mechanics and process of the separating, scratching and puncturing biomaterials metals and non-metals, pp. 283-284. uk butterworth, heinemann elsevier. bahrami, m., yovanovich, mm. and culham, jr. 2006. pressure drop of fully developed laminar flow in rough microtypes. journal of fluid engineering. transaction of the american society of mechanical engineers, 128: 632-637. baruah, dc. and panesar, bs. 2005b. energy requirement model for combine harvester, part 2: integration of component models. biosystems engineering, 90 (2): 161-171. baruah, dc. and panesar, bs. 2005a. energy requirement model for combine harvester, part 1: development. biosystems engineering, 90 (1): 9 25. blahovec, j. 2007. role of water content in food and product texture. international agrophysics, 21(3): 209-215. brown, t., james, sj. and purnell, gl. 2005. cutting force in foods: experimental measurements. journal of food engineering, 70 (2): 165-170. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; 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environment azojete, june, 2019. vol. 15(2):406-417 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 406 original research article prediction of bus travel time on urban routes without designated bus stops in makurdi town, benue state, nigeria p. t. adeke1*, o. j. inalegwu2 and k. jirgba3 (1,2department of civil engineering, college of engineering, federal university of agriculture makurdi, benue state, nigeria. 3department of civil engineering, faculty of engineering and technology, university of ilorin, ilorin, kwara state, nigeria) *corresponding author’s e-mail address: adeke.pt@outlook.com article information submitted 14 september, 2018 revised 17 february, 2019 accepted 19 february, 2019 keywords: makurdi town bus services bus travel time multiple linear regression model ann model abstract the lack of information on bus travel time in makurdi town to enable trip makers plan for journeys is seen as a challenge in recent times. this study developed a multiple linear regression model for predicting bus travel time along bus routes in makurdi town. specifically, the study assessed bus travel time on routes without designated bus stops, examined geometric features of bus routes, assessed bus dwell time and travel speeds in a heterogeneous traffic stream on routes in makurdi town. it developed and validated a model for the bus travel time. field survey focused on the major bus routes in makurdi town which included; high level roundabout to school of remedial studies junction (hl-srs), high level roundabout to federal medical centre junction (hl–fmc), wurukum roundabout to coca cola complex (wccc) and wurukum roundabout to welfare quarters junction (w–wq). independent parameters examined on the sites for model development included; bus route length, bus travel speed, average dwell time at random stops for pick-up and alighting of passengers, bus headway, the total number of cross and tee intersections along the bus route, volume of motorcycles, private cars and trucks in the traffic stream, while the dependent variable was bus travel time. based on the built model, 15 minutes approximately was established as the average bus travel time for all bus routes in makurdi town assuming all other variables have zero magnitude. goodness of fit test of the model yielded significant value for coefficient of determination (r2 = 0.952) and the use of artificial neural network (ann) method for validating the model also confirmed it accuracy at 93% approximately. it was therefore concluded that, bus travel time on major routes in makurdi town could be accurately estimated using the built multiple linear regression model provided all essential input parameters of the model are used. the establishment of designated bus stops along bus routes within makurdi town to minimise bus dwell frequency and for accurate estimation of bus travel time, as well as erection of travel information bill boards along bus routes stating average bus travel time to inform commuters that have high value of travel time were recommended. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. mailto:adeke.pt@outlook.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):406-417. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 407 1.0 introduction one of the essential parameters used for measuring the level of liveability of cities is the effectiveness of their public transport systems which mostly focuses on bus services (cullinane, 2002; ceder, 2007; gurmu, 2010; ibarra-rojas et al., 2015; gudmundsson et al., 2015). public transport services in most urban areas of developing countries like makurdi town of benue state employ the use of mini buses. these buses are usually owned and operated by nongovernmental organisations or private individuals who gain profit from the business of providing public transport services. bus services for public transport has been in use from time immemorial especially in developed countries (cullinane, 2002; zheng, 2011). the capacity of mini buses ranges between 10 – 14 persons, unlike standard bus services in modern cities in europe, usa, canada, etc. that use coaches whose capacities range between 20 – 60 persons. in most cities of developing countries, the minibuses usually shuttle along routes to pick-up and alight passengers at non-designated stops that are rather convenient to the passengers as they alert drivers whenever they wish to alight. these buses operate in an interrupted and heterogeneous traffic stream characterised by mixed traffic flow and pedestrian interferences (crossing at non designated spots). this disorderly and continues stop-and-move movement of mini-buses along routes in search of passengers, boarding and alighting has significant impact on the smooth flow of traffic, hence affects travel time significantly (izadpanah, 2010; ibarra-rojas et al., 2015). also, while commuters hope to arrive at their destinations quickly, bus travel time is basically influenced by time used for walking from/to the bus stops, waiting time at the stop, in-vehicle travel time, and mode transfer period, etc. these processes are associated with traffic congestion and affects the certainty of travel time estimation which makes its prediction more complicated (ibarra-rojas et al., 2015). in such a mixed traffic situation with a lot of complications, it is more meaningful to attempt a short term bus travel time prediction which falls within the range of 0 to 60 minutes so as to minimise the impact of variability among estimated variables (izadpanah, 2010; gurmu, 2010). in line with previous researches, it has been observed that all essential parameters employ for estimation of (bus) travel time exhibit stochastic properties with high degree of uncertainty (jeong, 2004; ramezani and geroliminis, 2012), which therefore requires sophisticated method of analysis. the importance of travel time in assessing road network performance by transport planners and engineers for efficient operation management and for developing travellers’ information system for commuters cannot be overemphasised. this is because most travellers’ are keen about trip planning and wish to optimise or minimise waiting time due to their high value of travel time (schiller et al., 2010; zheng, 2011; zaki et al., 2013; mannini et al., 2015; gudmundsson et al., 2015). according to bonsall et al. (2005), the act of modelling behaviour of transport systems using realistic assumptions is very essential, “it is better to use values that are realistic-butunsafe than values that are safe-but-unrealistic”. like many other prediction models, researchers have stated that accurate prediction of bus travel time is very difficult, especially in a system where public transport system is not given priority (liu, 2010), only average value could be easily estimated since most factors affecting the estimation of travel time are stochastic in nature (ramezani and geroliminis, 2012; bharti et al., 2017). these factors include weather condition, time of the day, driver behaviour, traffic volume, vehicle characteristics, etc. (izadpanah, 2010; liu and sinha, 2007). technically, major factors that can influence bus travel time include; intersection delays due to queues and traffic control operations, delay caused by turning vehicles, on-street parking of vehicles, crossing pedestrians and cyclists, etc. (zheng, 2011; liu et al., 1999). others include travel distance, number of stops, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke, et al: prediction of bus travel time on urban routes without designated bus stops in makurdi town, benue state, nigeria. azojete, 15(2):406-417. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 408 dwell times, number of boarding passengers and alighting passengers and weather description (gurmu and fan, 2014). though a difficult task to achieve, technologies used for data collection in developed countries for the purpose of travel time prediction have improved accuracy of estimations. morden devices used for data collection include; probe vehicles, loop detectors, digital cameras, automatic number plate recognition (anpr) camera, bluetooth scanners, speed sensors (coifman, 2000; zheng, 2011; bharti et al., 2017). there are several bus travel time prediction models developed by previous researchers. analytical techniques such as probability theorem (bharti et al., 2017), regression models (you and kim, 2000; wu et. al., 2004; bharti et al., 2017), artificial intelligence techniques (gurmu, 2010; gurmu and fan, 2014; bharti et al., 2017; zaki et al., 2013; kumar et al., 2017), etc. have been used in the past. the degree of accuracy of these models depends on the level of variability of input parameters and the reliability of the analytical technique used (izadpanah, 2010; gurmu, 2010; kumar et al. 2017). zaki et al. (2013) combined the neural network (nn) and the kalman filter techniques to form a hybrid methodological algorithm for estimating arrival time at bus stops using global positioning system (gps) data and historic travel speed data, the study yielded satisfactory results. bharti et al. (2017) considered traffic volume and car percentage composition in traffic stream as independent variables for travel time estimation modelling. the authors recommended the use of artificial intelligence method such as the artificial neural networks (ann) and the use of stochastic response surface methods (srsm) since they yielded relatively accurate results compared to the multiple linear regression model. though, the multiple linear regression model dose not predict bus travel time accurately as stated by other researches (gurmu and fan, 2014; bharti et al., 2017), its approach is capable of measuring the degree of sensitivity of all the input variables used for predicting the bus travel time (gurmu and fan, 2014). it is not certain if the transferability of calibrated and validated bus travel time prediction models built by previous researchers for other locations will suite cities like makurdi town, benue state of nigeria. major challenges of bus services in cities of developing countries like makurdi town include poor services characterised by disorderly and uncertain/non-organised operations on routes without designated bus stops (zheng, 2011). it therefore becomes a challenge for concerned persons or organisation to develop local models that actually suits the unique properties of developing societies. some of the peculiar properties that may weaken the strength of other existing models for use in developed cities include the use of bus rapid transport (brt), bus assigned lanes, designated bus stops, bus time table, etc. efficient public transport system in cities is important because it improves their liveability and boost economic and social growth of the cities (gurmu, 2010). because there is no previous research work which attempted to predict bus travel time on routes without designated bus stops in a heterogeneous traffic stream associated with several uncertainties in estimating model input parameters, in this part of the world, this study is relevant and justified. the study aims at developing a multiple linear regression model for predicting bus travel time on urban roads without designated bus stops based on bus services in makurdi town and, then validate the model using ann technique. objectives of the study include; to assess bus travel time on routes without designated bus stops, to examine geometric features of roadways, to assess bus dwell time and travel speeds in a heterogeneous traffic stream on routes in makurdi town, to validate the built model and examine sensitivity of all input variables. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):406-417. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 409 2. literature review 2.1 multiple linear regression model the multiple linear regression model is a mathematical function that defines the relationship between independent (input) and the dependent (output) variables that explain the behaviour of a system (rohatgi and saleh, 2001; soong, 2004). development of multiple linear regression model usually employs statistical tools such as; statistical product for service solution (spss), r programming, microsoft excel, etc. which are capable of defining the relationship between the independent and dependent variables in form of a function. the strength of the function is usually examined using it coefficient of determination (also known as r square – r2) value which ranges from 0 – 1, with 0 defining a weak relationship and 1 showing a stronger relationship between variables (rohatgi and saleh, 2001). another relevant model performance indicator is the measure of sensitivity of input variables using their respective p-values. the p-value tests the null hypothesis that coefficient of a variable is equal to zero, meaning the variable has no effect on the model; such that a low p-value (< 0.05) indicates that the null hypothesis should be rejected, that is, the variable is likely to be meaningful to the model. multiple linear regression models are generally expressed as mathematical function in the form shown in equation 1; y = β0 + β1x1 + β2x2 + β3x3 + . . . + βnxn (1) where, y is the dependent variable, xi and βi for i = 1, 2, . . n denote the independent variables or input parameters and their respective coefficients, β0 is the constant value which defines the average behaviour of the system when the magnitude of all other variables is zero. n represents the total number of input variables used in the model. the use of multiple linear regression model for property or performance prediction of engineering systems has been in use over a long period of time (ramakrishna et al., 2006; gurmu and fan, 2014). the model best suites systems that exhibits deterministic behaviour rather than those that are stochastic in nature, since stochastic systems exhibit behaviours that are nonlinear or uncertain and difficult to predict (zheng 2011). 2.2 artificial neural network (ann) models the ann method is an artificial intelligence (ai) technique used for analysing systems (munakata, 2008; russell and norvig, 2010). the application of ann models in predicting bus travel time has gained acceptance decades ago (balaubramanian and rao, 2015; amita et al., 2015). it is an iterative simulation process which has gained wide acceptance in predicting system behaviour due to its ability to handle system complexities of nonlinearity and challenges of missing or incomplete dataset, inaccurate data, etc. the network consists of numerous layers of parallel processing neurons. hidden layers exist between input and output layers. neurons in one or more hidden layers are connected to the neurons of the neighbouring layers by weighted factor that is adjustable during model training process. ann model could adopt a sigmoid performance function which is probabilistic in nature having multilayer processing framework capable of accepting multiple inputs to produce the desired outputs. running an ann model is an iterative and a trial-and-error process which requires specifying the number of layers which are usually more than one (gurmu and fan, 2014). the training process requires a feed forwardbackward propagation algorithm, specification of the maximum number of training epochs and number of iterations which describes the number of times a batch of data passes through the algorithm for forward and backward propagations. from the process, mean square errors and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke, et al: prediction of bus travel time on urban routes without designated bus stops in makurdi town, benue state, nigeria. azojete, 15(2):406-417. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 410 biases of estimations are usually computed using the model function specified. figure 1 is an architectural presentation of a typical ann model. figure 1: the architecture of an ann model (amita et al., 2015) the ann method is usually implemented using software that are capable of simulating the probabilistic behaviour of the systems such as the ann tool found in matlab (zheng, 2011; matlab, 2018). the ann tool in matlab is used to simulate systems based on the ann model. it requires input parameters, targeted output values, then validate results to a certain degree of accuracy. it is therefore relevant to employ such technique in this study for model validation to check for variations caused by the probabilistic nature of some input variables such as dwell time, bus headway, traffic composition, etc. as they influence the regression model significantly (gurmu and fan, 2014; amita et al., 2015). 3. materials and methods 3.1 description of study area this study was carried out in makurdi town, benue state of nigeria. makurdi town is an urban area known to be the capital city of benue state, nigeria. the city located on latitude 7° 43’ 56” and longitude 8° 32’ 21” (google earth, 2018) has an estimated human population of over 367,588 persons with a land mass of approximately 800 km2 (npc, 2006). traffic streams in makurdi town are described as being heterogeneous since they comprise private cars, mini buses, heavy goods vehicles (hgv) and light goods vehicles (lgv), motorcycles, tricycles and pedestrians. though mini-buses are the major mode for mass transit in makurdi town, the design and construction of roadways in the town does not provide special road facilities such as bus lane for the mini-buses therefore, the buses travel and share lanes with other traffic components. this is described as a mixed traffic stream since it comprises different modes including pedestrians. traffic flow in makurdi town is generally characterised by interruptions http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):406-417. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 411 from differed sources such as pedestrian crossing, the stop-and-move pattern of mini-buses that have no designated stopping spots (bus stops) along the routes, operations of intersection, etc. town shuttle mini-buses operating within the city travel along the arterials conveying commuters along the routes. the routes in makurdi town considered by this study as presented in figure 2 included; the high level roundabout – school of remedial studies junction (hl srs), high level roundabout – federal medical centre junction (hl – fmc), wurukum roundabout – coca cola complex (w ccc) and wurukum roundabout – welfare quarters (w – wq). figure 2: sampled routes on an extract map of makurdi town (google earth, 2018) 3.2 data collection trained traffic enumerators carried out the field survey. the road network in makurdi town was divided into routes namely; hl srs, hl – fmc, w – ccc and w – wq. the movement of minibuses used for public transport services in makurdi town within the traffic streams was examined from 07:00 am to 05:00pm daily. the geometric characteristics of bus routes such as; route length, average lane width and number of lanes in both directions. other essential model parameters and methods of measurements were as following; traffic volume in one direction (veh/h) this was measured using manual traffic count technique. the composition volume of motorcycles, private cars and trucks in the traffic stream were estimated. materials used were basically record sheets, stop watch and writing instruments. bus travel speed (km/h) – it was estimated using the plate number matching methods. this involved identifying the bus plate number from its journey origin, then total travel speed was estimated using time lapse during the journey period, and the route length measured using a meter counter wheel. average bus headway (s) – it is the average time lapse between the passage of a sampled lead bus and the following bus measured from bomber-to-bomber using a defined reference spot marked on the road pavement as buses pass over along the routes. w-cc hl-srs hl-fmc w wq file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke, et al: prediction of bus travel time on urban routes without designated bus stops in makurdi town, benue state, nigeria. azojete, 15(2):406-417. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 412 average dwell time (s) – this is the time lapse between stops for pick-up of passengers and start-up movement of buses. it was measure by an enumerator who travelled along with the bus from its origin to the destination. bus travel time in minutes (min) – this is the time required for a mini-bus to travel from its origin to the terminal point of the journey or destination of the trip. number of intersection (unit) – these were counted by the enumerator who travelled along with the bus. types of intersection identified included; roundabouts, cross-intersection and tintersections. total distance travel (m) – this is the distance between the origin and destination of the journey measured along the travel route using the meter counter wheel. for a given road segment, it was measured in meters (m). 3.3 data analysis a multiple linear regression model for estimating short term bus travel time along routes without designated bus stops was developed using spss. the process involved creation of a spreadsheet in microsoft excel for the raw data which comprised the independent and dependent variables. the excel file was then imported into spss for statistical analysis to build the regression model. results of the analysis revealed the data characteristics which was used to check for accuracy of the built model. the built model was first validated using goodness of fit test based on the measured (on field) and predicted (using model) bus travel times. it was further validated using ann tool simulated in matlab. the simulation process involved series of iterations at several times to arrive at a better fit for the network model testing, validation, training and estimation of the overall coefficient of determination of variables. the validation process aimed at comparing outputs of the multiple linear regression model and those of the ann model using, coefficient of determination value for best fit. 4.0 results and discussion table 1 shows the geometric characteristics of bus routes in makurdi town as considered by this study. table 1: geometric characteristics of minibus routes in makurdi town name of bus route carriageway share (dual/single) number of lanes in one direction avg. lane width (m) route length (m) number of intersections roundabouts cross tee hl – srs 70%/30% 2 3.60 6420 1 3 2 hl – fmc 80%/20% 2 3.47 4000 1 1 3 w – ccc 100%/0% 2 3.70 5000 0 3 4 w wq 0%/100% 1 3.50 4000 0 1 5 table 1 revealed that, only few bus routes in makurdi town have dual and single carriageway along the entire route length. some routes have alternating type of carriageway for dual and single. only major cross and tee intersections connecting the highways and arterials were counted. intersections connecting minor streets supplying less than 50 veh/h were ignored. only traffic flow in the direction of movement of sampled mini-buses with corresponding geometric features were considered. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):406-417. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 413 4.1 model development this study employed the multiple linear regression and ann methods of modelling for the prediction of bus travel time along routes in makurdi town. 4.1.1 the multiple linear regression model a multiple linear regression model for estimating short term bus travel time on routes within makurdi town was developed using spss software, the summary of results from the statistical analysis were as shown in table 2. table 2: summary of statistical results of the multiple linear regression model model unstandardized coefficient t-statistic p-value 95% confidence interval for βi βi std. error lower bound upper bound constant 14.962 1.604 9.328 0.000 11.757 18.167 js -0.024 0.002 -13.292 0.000 -0.027 -0.020 rl 0.002 0.000 8.281 0.000 0.002 0.003 tm 0.001 0.002 0.744 0.460 -0.002 0.005 tpc -0.006 0.003 -1.959 0.055 -0.013 0.000 tt -0.029 0.019 -1.531 0.131 -0.066 0.009 adt 0.008 0.006 1.363 0.178 -0.004 0.020 cj 0.507 0.256 1.978 0.052 -0.005 1.018 bh -2.374 2.305 -1.030 0.307 -6.980 2.232 r2 = 0.954 adjusted r2 = 0.949 table 2 revealed that journey speed, composition of private cars and trucks in a traffic stream and bus time headway affects bus travel time negatively, in other words, the variables are inversely proportional to bus travel time. this implies that the higher the magnitude of these aforementioned variables the lesser the bus travel time. on the other hand, the higher the magnitude of route length, composition of motorcycle and tricycles in the traffic stream, average dwell time and number of cross-junctions along the route the higher the bus travel time. these results agreed with findings of gurmu and fan (2014). this model indicates that, the estimated average bus travel time along routes in makurdi town without considering the impacts of other variables is approximate 15 minutes (constant). table 2 also shows the statistical strength of the built multiple linear regression model. though the coefficient of determination obtained from the analysis (adj. r2 = 0.949) showed a strong relationship in estimating output using the input variables considered by the study, only pvalues for the journey speed and route length variables showed a stronger relationship (having value of 0.00) between the input and output variables in the model. the p-values for traffic composition of private cars and number of crossed intersections along the route showed a slight (> 0.05) variation which indicates it significant strength in determining short term bus travel time using this model. other independent variables such as the composition of motorcycle and trucks in the traffic stream, average dwell time and average bus headway showed less importance in file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke, et al: prediction of bus travel time on urban routes without designated bus stops in makurdi town, benue state, nigeria. azojete, 15(2):406-417. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 414 estimating bus travel time using this model, which agreed with findings of previous researchers (gurmu and fan, 2014). therefore, the developed mathematical model for predicting short term bus travel time is as shown in equation 1; tt = 14.962 − 0.024js + 0.002rl + 0.001tm − 0.006tpc − 0.029tt + 0.008adt + 0.507cj 2.374bh (2) where: tt is the estimated bus travel time measured in minutes, js is journey speed of the bus measured in meter per minute, rl is the bus route length measured in meters, tm is the volume of motorcycles in the traffic stream measured in units per hour, tpc is the volume of private cars in the traffic stream measured in vehicles per hour, tt is the volume of trucks in the traffic stream measured in vehicles per hour, adt is the average dwell time measured in seconds. some variables such as the number of roundabout along routes,, number of tee intersections along routes and the composition of motorcycles in traffic stream as obtained from the field work were ignored by the statistical tool (spss) used for the analysis which indicated their irrelevance to a great extent in predicting bus travel time using the built model. 4.1.2 model validation statistical test for goodness of fit using the actual and estimated dataset was carried out using the plot shown in figure 3. the coefficient of determination obtained from the plot was 0.95 which indicated that, the model discribes up to 95% of the vaiables considered in the study which shows a statistically good fit. figure 3: model validation using statistical method an intelligent approach was also employed to further examined the fitness of the built model since p-values of some variables considered by the model such as the composition of motorcycle and trucks in the traffic stream, average bus dwell time and bus headway did not show statistically satisfactory relationship between the input and output variables of the model (p–value > 0.05). this involved developing an ann model using the matlab tool to further check for accuracy of the built multiple linear regression model. 4.2 the ann model a matlab tool based on the nntool command was used for this study. the tool used for simulating the ann models is capable of estimating weighted mean values, mean square errors http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):406-417. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 415 and biases from the input variables. model validation using the ann approach implemented in matlab yielded results as shown in figure 4. figure 4: model validation using ann model figure 4 showed fitness of the built model in defining the relationship between the input and output variables considered by the study. the training, validation and testing of the model using 1000 iterations for a sigmoidal function gave satisfactory output measured at levels 100%, 93% and 98% respectively. the entire performance of the model is measured at 99% approximately, which showed a strong relationship between variables. thus, using this model, all performance indicators of the model showed satisfactory results. 5.0 conclusion this study developed a multiple linear regression model for predicting bus travel time using spss software. input variables required by the model included; bus route length, bus travel speed, average dwell time at random stops for pick-up and alighting of passengers, bus headway, volume of motorcycles in the traffic stream, volume of private cars in the traffic stream, volume of trucks in the traffic stream and the total number of cross intersections along the route. based on the built model, an average bus travel time of 15 minutes approximately was established as bus travel time for all bus routes in makurdi town (assuming all other variables have zero magnitude). goodness of fit test in statistics and ann model were used to confirm the accuracy of the built model for predicting short team bus travel time on bus routes within makurdi town, in benue state. it was therefore concluded that, bus travel time on major routes in makurdi town could be accurately estimated using the built multiple linear regression model file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeke, et al: prediction of bus travel time on urban routes without designated bus stops in makurdi town, benue state, nigeria. azojete, 15(2):406-417. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeke.pt@outlook.com 416 provided all essential input parameters required by the model were available. the following recommendations were therefore made; establishment of designated bus stops along bus routes within makurdi town was recommended to minimise bus dwell frequency and for more accurate estimation of travel time in line with the design and development of modern cities. travel information bill boards should be erected at strategic locations along bus routes in makurdi town stating their average bus travel time to help enlighten commuters that have high value of travel time. references amita, j., singh, js. and kumar, gp. 2015. prediction of bus travel time using artificial neural networks. international journal for traffic and transport engineering, 5(4): 410 424. balaubramanian, p. and rao, kr. 2015. an adaptive long-term bus arrival time prediction model with cyclic variations. journal of public transportation, 18(1): 1 -18. bharti, ak., sekhar, cr. and chandra, s. 2017. modelling travel time of car with varying demand on an urban midblock section. journal of intelligent transport systems, 22(2): 99 – 105. bonsall, p., liu, r. and young, w. 2005. modelling safety-related driving behaviour impact of parameter values. elsevier, transport research part a, 39: 425 – 444. ceder, a. 2007. public transit planning and operation theory, modelling and practice, elsevier, london. coifman, b. 2000. estimating travel times and vehicle trajectories on freeways using dual loop detectors. transportation research part a: policy and practice, 36(4): 351 364. cullinane, s. 2002. the relationship between car ownership and public transport provision: a case study of hong kong. transport policy, 9: 29 – 39. google earth. 2018. google earths inc. gudmundsson, h., hall, rp., marsden, g. and zietsman, j. 2015. sustainable transportation. indicators, frameworks and performance management. printer texts in business and economics, london. gurmu, zk. 2010. a dynamic prediction of travel time for transit vehicles in brazil using gps data. msc. dissertation, department of civil engineering and management, university of twente, the netherlands. gurmu, zk. and fan, w. 2014. artificial neural network travel time prediction model for buses using only gps data, journal of public transport, 17(2): 45 – 65. ibarra-rojas, oj., delgado, f., giesen, r. and munoz, jc. 2015. planning, operation and control of bus transport systems: a literature review. transport research part b, 77: 38 – 75. izadpanah, p. 2010. freeway travel time prediction using data from mobile probes. phd thesis, department of civil engineering, university of waterloo, waterloo, ontario, canada. jeong, rh. 2004. the prediction of bus arrival time using automatic vehicle location systems data. ph.d. thesis at texas a&m university, texas. kumar, ba., jairam, r., arkatkar ss. and vanajakshi, l. 2017. real time bus travel time prediction using k-nn classifier. transport letters, the international journal of transport research, 7: 1 – 11. liu, r. 2010. traffic simulation with dracula. in: barcelo, j. ed. fundamentals of traffic simulation, international series in operations research and management science. springer new york. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; 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maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 534 original research article effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed n. a. aviara1*, s. ekaso jr.1 and o. u. nwanja2 (1department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, borno state, nigeria 2department of agricultural technology, akanu ibiam federal polytechnic, unwana-afikpo, ebonyi state, nigeria) * corresponding author’s email address: nddyaviara@yahoo.com article information submitted 23 november, 2018 revised 20 march, 2019 accepted 25 march, 2019 keywords: afzelia africana physical properties angle of repose static and kinetic coefficients of friction coefficient of restitution specific heat abstract some engineering properties of afzelia africana, namely axial dimensions, one thousand seed mass, surface area, particle density, bulk density, porosity, angle of repose, static and kinetic coefficients of friction, coefficient of restitution and specific heat were determined as a function of moisture content in the moisture range of 6.1 – 32.3% (d.b). results showed that in the above moisture range, major, intermediate and minor axial dimensions of the seed increased from 25.4 – 26.2mm, 13.2 – 13.95mm and 10.2 – 11.2mm, respectively. one thousand seed mass, surface area, particle density, porosity, angle of repose, static coefficient of friction, kinetic coefficient of friction and specific heat capacity of the seeds all increased with increase in moisture content. seed bulk density decreased with increase in moisture content and coefficient of restitution decreased as drop height and moisture content increased. the relationship existing between the engineering properties and seed moisture content, established using regression analysis showed high coefficient of determination. these properties would be useful in the design of afzelia africana seed handling, storage and processing equipment. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction afzelia africana also known as african mahogany (figure 1) is an economically valuable and drought resistant leguminous tree crop with its species widely distributed in the continent of africa. it is found from senegal in west africa to the sudan, uganda and tanzania in the east. it is occasionally grown in other tropical countries as ornamental tree. its uses range from foods to pharmaceuticals. in west africa, the edible seed is used in soup making as thickening agent. the seed flour is used as a substitute for wheat flour in biscuits and doughnuts. afzelia africana seeds (figure 2) have been reported to contain 24% protein, 4.29% crude fibre, 3.43% ash and 21% lipid (matouk et al., 2004), indicating good nutritional value. the seeds help in softening bulky stool and have been associated with protection against colon and rectal cancer. hydro gel is also found in the afzelia africana seed and it is called afzelia gum -a non starch polysaccharidewhich is useful in the food and pharmaceutical industries (builders et al., 2009). mailto:nddyaviara@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 535 with these numerous uses the popularity of this important seed has been limited because of lack of proper handling equipment to project its commercial value. figure 1: afzelia africana tree figure 2: afzelia africana seeds in west africa and nigeria in particular, this important seed is subjected to such different processing operations as soaking, roasting, parboiling, de-hulling, grinding and drying, prior to utilization or storage. the present manual techniques of carrying out these operations are not only labour intensive and time consuming, but also tasky with low output in terms of quantity and quality of product. therefore, there is the need to develop improved methods of handling processing and storing the seeds using suitable machines and equipment. the development of such machines and equipment require knowledge of the engineering properties of the seed. the performance and adjustment of such machines are also dependent on the moisture content of the produce (aviara et al., 1999), therefore, the effect of moisture content on engineering properties of afzelia africana seed is an important consideration in the design of its handling and processing equipment. no work however, appears to have been carried out of the engineering properties of afzelia africana seed and their relationship with seed moisture content. the objective of this study was to determine some engineering properties of afzelia africana seed and investigate their relationship with moisture content. the properties include axial dimensions, one thousand seed mass, surface area, particle density, bulk density, porosity, angle of repose, static and kinetic coefficients of friction, coefficient of restitution and specific heat. relevant literature was studied in order to select the appropriate method of determining each of the above properties. the selection of a method was based on simplicity, accuracy of results and wide acceptability. 2. materials and methods the bulk quantity of afzelia africana seeds used in this study were purchased from onueke in ebonyi state, and supplied by a marketer in monday market, maiduguri, nigeria. the seeds were taken to the laboratory and cleaned manually to remove all foreign materials and damaged seeds. the market stable storage moisture of the seeds was determined by oven drying triplicate samples at 105°c for 6 hours (aviara et al., 1999). the bulk seed was divided into 5 batches and conditioned by soaking in water for 12, 36, 58 and 84 hours including the market stable storage to obtain samples at five moisture levels for the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 536 experiments. after conditioning, the seeds were poured separately into polyethylene bags and sealed before being kept in a curing room for the three days to make the moisture distribute uniformly throughout the grains. after the grains reached uniform moisture contents, the bags were placed in desiccators and stored at room temperature. to determine the amount of moisture content of seeds in the differently conditioned lots, samples were collected and weighed using an electronic balance and placed in an oven set at 105°c with weight loss monitored on hourly basis until three consecutive weighing gave identical values of mass. the moisture content was calculated from the relation used by aviara (2005 b). ��ࠀ� � ��−�� �� � ��� (1) where: mw.b = wet basis moisture content (%), wi = initial weight (g) and wf = final weight (g) it was converted to dry basis moisture content by using the relation: ��� � �ࠀ� �tࠀ�� � ��� (2) where: md.b = dry basis moisture content (%). the axial dimensions of the seed, namely: the length (l), width (b), and thickness (t) were measured using the method of ndukwu (2009). the dimensions of 100 randomly selected seeds at different moisture contents were measured using a venier calliper of 0.01mm accuracy in order to determine the seed size. the average values of length, width and thickness of the seeds at each moisture content were recorded. the geometric mean diameter was determined by applying the length, width and thickness of the seeds to equation (3) (joshi et al., 1993) dp = (lwt)1/3 (3) where: dp = geometric mean diameter (mm), l= length (mm), w= width (mm) and t= thickness (mm) arithmetic mean diameterwas determined by using equation (4) (mohsenin, 1986). am = ����� � (4) where: am = arithmetic mean diameter. (mm) the aspect ratio was determined using equation (5): ra = � � (5) where: ra = aspect ratio, w= width (mm) and l= length (mm) the surface area of the seed was measured using the method of ndukwu (2009). this involved carefully wrapping the seeds completely with a foil paper and cutting of the edges. the paper was then unwrapped and placed on a graph sheet. the outline covered by the foil paper on the graph sheet was traced with a pencil and the surface area of the seeds was determined by http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 537 method of counting the squares. this was carried out at each moisture level using 30 seeds. the average surface area of the seeds at various moisture contents was then obtained. the one thousand seed weight was determined using the method of taimirat, (2011). it involved counting 1000 seeds and pouring them dockage free into a bucket of known weight.the seeds and bucket was weighed using an electronic balance of approximately 0.001g reading accuracy. the mass of the bucket was subtracted from the mass of the 1000 seeds plus bucket and the mass of the 1000 seeds at each moisture content was recorded. the true density of afzelia africana seeds was determined using the standard liquid displacement method as reported by aviara et al. (1999).the samples were coated with epoxy resin around the ring, weighed individually on an electronic balance and tied with a thread before immersing them individually into a 25ml cylinder containing water to a known level. the volume of water displaced in the cylinder was noted and taken in order to obtain the volume of the seed. 30 trials were carried out at each moisture level. true density was then calculated from the obtained values using the formula: ρt = � ��−�� (6) where: ρt = true density (kgm-3), m = mass of individual seed (kg), vi = initial volume of water in the cylinder (m3) and vf = final volume of water in the cylinder after submergence of seed (m3). the bulk density was determined using the aoac (1980) method. samples were poured from a height of 15cm into a 500ml cylinder of known mass. the cylinder containing samples was weighed on abalance and weight of the seeds was obtained by subtracting the mass of the cylinder from the final mass of seeds and cylinder, while the volume of the cylinder was taken as the volume occupied by the seeds. bulk density was then determined using the expression: ρb = (ms / vs) (7) where: ρb = bulk density (kg/m3), ms = mass of seeds alone (kg) and vs = volume of seeds (m3) the porosity of afzelia africana seeds were determined using the formula (mohsenin, 1986) � � � t ρb ρt � ��� (8) where: � = porosity (%), ρb = bulk density (kg/m3) and ρt = true density (kg/m3) in determining the angle of repose, the cylindrical pipe method reported by zewdu and solomon (2007) was used. a topless and bottomless cylinder placed on a flat surface was filled with seeds at specified moisture content and slowly raised until it completely gets lifted off from the seeds leaving them to pile in form of a cone. the diameter and height of the cone were measured using a venier calliper and used to calculate the angle of repose. the formula (equation 9) given by zewdu and solomon (2007) was applied to determine the angle of repose. � � tan−� h � (9) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 538 where: � = angle of repose in degrees, h = height of piled seeds (mm) and r = radius of base of cone formed by seeds (mm) static coefficient of friction of the seeds on different structural surfaces (steel sheet, wood, hessian bag and glass)was determined using the inclined plane method as described by dutta et al. (1988) and suthar and das (1996). this involved the placing of an open-ended box (50mm × 100mm × 100mm) on an adjustable tilting surface which was formed with structural surface. the box was filled with seeds at specified moisture content and the structural surface with the box and its content on top was gradually raised using a screw device until the box started to slide down and the corresponding tilting angle, α was recorded. the value of static coefficient of friction was calculated using equation (10) due to mahapatra et al. (2002). (10) where: � = static coefficient of friction and α = tilting angle for the kinetic coefficient of friction, the open-ended box was used as described by aviara et al., (2000). in this method, the box was placed on a horizontal surface. the box was filled with seeds and connected by means of a string, parallel to the surface and passed over a pulley to a pan hanging down from it. weights were placed in the pan subsequently until the box and its content moved uniformly when given a gentle push. the kinetic coefficient of friction of the seeds on a given structural surface was determined using equation (11). four different surfaces were used for each moisture level of the seeds namely and these were plywood, fibre glass, hessian bag material and steel sheet. � � �t ��� �� ��香 (11) where: � = kinetic coefficient of friction, wp = weight of pan (g), wi = weight placed in pan to move the box (g), wb = weight of box (g) and ws = weight of sample (g). coefficient of restitution of the seeds was determined using the method described by kumar (1995). the nuts were dropped from a height of 50, 90, 120, and 150 cm on four structural surfaces namely: wood, galvanised steel sheet, hessian bag and fibre glass. a graduated scale was kept at the background and the maximum height of rebound was recorded using a video camera. this was replicated three times at each moisture content level for seed fall on both axial and longitudinal orientation. the coefficient of restitution was calculated using equation (12) as given by aviara et al. (2010): ��� � h � (12) where: c.r is the coefficient of restitution, h = height of rebound (cm) and h = height of drop (cm). coefficient of restitution on each surface for different drop heights was regressed against moisture content. the specific heat of the seeds was determined using a copper calorimeter placed inside a flask by method of mixtures as described by ogunjimi et al., (2002). a sample of known weight and temperature was poured into calorimeters containing water of known weight and temperature. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 539 the final temperature was noted and the specific heat of the sample was calculated using equation (13): cs = �t�tࠀ�ࠀ�� �t−ࠀ� �香 �t−�香 (13) where: cc = specific heat of calorimeter (j/kgk), cs = specific heat of sample (j/kgk), cw = specific heat of water (j/kgk), mc = mass of calorimeter (kg), ms = mass of sample (kg), te = equilibrium temperature of seed (k), ts = initial temperature of sample (k) and tw = initial temperature of water (k). the experiments were replicated thrice at each moisture content except in cases otherwise stated and the average values of the properties were recorded. the relationship existing between the properties and seed moisture content as well as the coefficient of determination of the equation used to express the relationship were determined using regression procedure. the variation of the engineering properties with moisture content was also expressed graphically. 3. results and discussion 3.1 seed moisture content the initial moisture content of afzelia africana seeds was found to be 6.1% (d.b). the four other moisture levels obtained after conditioning the seeds were 7.9, 12.8, 25.4 and 32.3% (d.b), respectively. the investigations were carried out at the above moisture levels to determine the effect of moisture content on the physical, frictional and thermal properties of afzelia africana seeds. 3.2 axial dimensions the variation of the afzelia africana seed size measured at different moisture content levels is presented in figure 3. figure 3: effect of moisture content on the axial dimensions of afzelia africana seed the figure shows that the three axial dimensions increased with increase in moisture content in the moisture range of 6.1 – 32.3% d.b. major axis increased from 25.4 – 26.2mm, the intermediate axis increased from 13.2 – 13.95mm and the minor axis from10.2 – 11.2mm. the arithmetic and geometric mean axial dimensions also increased with increase in moisture content. the arithmetic mean had higher values than the geometric mean axial dimensions of the seeds. the aspect ratio which is the ratio of the intermediate axis to the major axis also file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 540 increased with increase in moisture content. the increase in axial dimensions indicates that upon increase in moisture contents, the seeds expand in length, width and thickness thereby increasing their average dimensions. the relationship between moisture content and the axial dimensions of the seeds was found to be linear with the following equations: a = 0.26m + 9.92 (14) b = 0.205m + 25.095 (15) c = 0.19m + 13 (16) am = 0.214m + 16.022 (17) dp = 0.237m + 14.373 (18) ra = 0.0032m + 0.5181 (19) with values of coefficient of determination r2 = 0.9298, 0.9941, 0.981, 0.9745, 0.9454 and 0.9063 respectively. where: a = major axis (mm), b = intermediate axis (mm), c = minor axis (mm), am = arithmetic mean dimension (mm), dp = geometric mean dimension (mm), ra = aspect ratio and m = moisture content (%, db). similar results of increase are reported by tavakkoli et al., (2009) for the soybean grains and almahasneh and rababah, (2007) for green wheat. the results of the axial dimensions can be used in sizing, mechanical separation and grading of afzelia africana seeds from similar sized materials such as stones. irtwange and igbeka (2002) and aviara et al., (2005b) observed similar trend of arithmetic and geometric mean dimensions for african yam bean and sheanut respectively. 3.3 one thousand seed weight the variation of one thousand seed weight of afzelia africana with moisture content is presented in figure 4. figure 4: the effect of moisture content on the one thousand seed weight of afzelia africana seed figure 4 shows that one thousand seed weight increased from 2.4 – 2.8kg in the moisture range of 6.1 – 32.3% d.b. this positive trend of one thousand seed weight with moisture content was due to increase in weight gained by the presence of more water thereby producing a heavier seed. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 541 the relationship between moisture content and mass of one thousand seeds was seen to be linear and can be expressed with the following equation: w1000 = 0.101m + 2.287 (20) with value of coefficient of determination r2 = 0.9697, where w1000 is the one thousand seed weight (kg). similar trend was reported by irtwange and igbeka, (2002) for african yam bean, kaleemullah and gunasekar, (2002) for arecanut, aviara et al., (2005b) for sheanut, isik, (2007) for round red lentil grain and simoyan et al., (2007) for samaru sorghum. this result on seed mass can be applied practically in the design of equipment for cleaning, separation, conveying and elevating unit operations. it can also be used to estimate the overall bulk weight of afzelia africana seeds during bulk handling. 3.4 particle density the effect of moisture content on particle density of afzelia africana seeds is presented in figure 5. figure 5: effect of moisture content on the particle density of afzelia africana seed the figure shows that particle density increased from 1190 – 1446kg/m3 as the moisture content increases from 6.1 – 32.3% d.b. the increase in particle density of afzelia africana seeds with increase in moisture content may be due to the higher rate of increase in mass of the individual seeds than its volume as the moisture content increased. the relationship existing between particle density and moisture content was found to be linear and can be represented by the regression equation: ρt= 65.2m + 1109.6 (21) with correlation coefficient of r2 = 0.9622, where: ρt = particle density (kg/m3). baumler et al., (2006) and coskuner and karababa (2007) reported polynomial relationship between particle density and moisture content for safflower and coriander seeds respectively. an increase in particle density had also been reported by perez-alegria et al., (2001) for parchment coffee bean, ozarslan, (2002) for cotton seed, aviara et al., (2005 a) for balanites aegyptiaca nuts, aviara et al., (2005 b) for sheanut and isik (2007) for round red lentil grain. the particle density of agricultural products have been reported to play significant importance in the design of silos and storage bins, maturity and quality evaluation of products which are essential to grain file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 542 marketing (irtwange and igbeka, 2002) and also could prove useful in the separation and transport of the seeds by hydrodynamic means (omobuwajo et al., 2003). 3.5 bulk density the effect of moisture content on the bulk density of afzelia africana seeds is shown in figure 6. figure 6: effect of moisture content on the bulk density of afzelia africana seed bulk density was found to decrease from 670 – 626kg/m3 as the moisture content increased from 6.1 – 32.2% (d.b). it was seen that as the moisture content increased, the size of the seeds increased resulting in less mass and amount of seeds occupying equal bulk volume. therefore, the decrease in bulk density of the seeds resulted from increase in size with moisture content. also, the resistance of the seeds to consolidation may have increased with moisture content as a result of increase in internal pressure. the relationship existing between moisture content and bulk density was observed to be a power law relationship and it’s further represented by the equation: ρb = 665.78m -0.041 (22) with the coefficient of determination r2 = 0.9379, where: ρb = bulk density (kg/m3). carman (1996), gupta and das (1998), and visvanathan et al., (1996) found the bulk density of lentil seeds, sunflower seeds and neem nuts, respectively, to decrease as the seed moisture content increases. bulk density is applied practically in the calculation of thermal properties in heat transfer problems, in determining reynold’s number of materials and in predicting pressures in storage structures as well as chemical composition. 3.6 porosity the porosity of afzelia africana seeds calculated from relevant experimental data in the moisture range of 6.1 – 32.2% (d.b) increased from 43.7 – 56.6%. the effect of moisture on porosity is presented in figure 7. figure 7: effect of moisture content on the porosity of afzelia africana seed http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 543 the increase in porosity may bedue to decrease in compaction and increase in void spaces within the grain mass as bulk density decreased, invariably increasing the porosity of the seed in bulk. this may be expected because the larger the size of an object, the more loosely packed it becomes. the relationship existing between moisture content was found to be linear and can be represented with the equation: ԑ = 3.46m + 39.58 (23) with coefficient of determination r2 = 0.9809, where: ԑ = porosity (%). the dependence of porosity on true and bulk densities are definitely different for each seed or grain with increasing moisture content. a decrease in porosity with moisture content was reported by irtwange and igbeka (2002) for african yam bean. chowdhury et al., (2001) and konak et al., (2002) reported a linear increase in porosity with increase in moisture content for gram and chick pea seed. baryeh (2002) and coskuner and karababa (2007) reported a polynomial relationship between porosity and moisture content for millet seeds and coriander seeds. these results indicate that porosity of seeds of different crops could respond differently in manner, which could be dependent on their morphological characteristics. 3.7 surface area the effect of moisture content on the surface area of afzelia africana seeds is presented in figure 8. figure 8: effect of moisture content on the surface area of afzelia africana seed the surface area of afzelia africana seeds increased from 8.3 – 8.52cm2 in the moisture range of 6.1 – 32.3% (d.b). the increase in surface area is mainly due to the increase in the linear dimensions with increase in moisture content thereby resulting in increased volume causing the seeds to occupy a larger area. the relationship found between moisture content and surface area of the seeds was logarithmic and can be expressed using the equation: sa = 0.1248ln (m) + 8.0841 (24) with the coefficient of determination r2 = 0.9913, where: sa = surface area (cm2).the trend of increasing surface area with moisture content have been reported by fatholahzadeh et al. (2008) for apricot kernel from 282.35 – 297.24mm2, and isik (2007) for soybean grains from 118.756 – 197.654 mm2. aviara et al. (2014) reported the seed surface area of brachystegia eurycoma seeds file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 544 to increase from 7.67 – 8.48cm2. also, tavakoli et al. (2009) reported the surface area for barley grains to increase linearly from 56.66 – 71.09mm2. 3.8 angle of repose the variation of angle of repose with moisture content is shown in figure 9. figure 9: effect of moisture content on angle of repose of afzelia africana seed from the figure, it was observed that the angle of repose increased from 27.7 – 34° as the moisture content increased from 6.1 – 32.3% (d.b). it was also observed that at higher moisture content within the above range, seeds tend to stick together resulting in better stability and less flowability, which must have resulted in increases in the value of θ. the relationship between moisture content and the angle of repose of the seeds was found to be linear with the equation: θ = 0.2437m + 26.042 (25) with the coefficient of determination r2 = 0.9966, where: θ = angle of repose (°). a linear relationship between angle of repose and moisture content was also observed for cumin seed and coriander seed (singh and goswani, 1996; yalcin and ersan, 2007). however, a logarithmic relationship was observed for okra seed and sheanut (sahoo and srivastava, 2002; aviara et al., 2005) respectively. this property is used in the design of discharging equipment for particulate solids. 3.9 static coefficient of friction the static coefficient of friction obtained experimentally on four structural surfaces against moisture content in the range of 6.1 – 32.3% (d.b) is presented in figure 10. figure 10: effect of moisture content on the static coefficient of friction of afzelia africana seed http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 545 it was seen that the static coefficient of friction of afzelia africana seeds initially decreased with increase in moisture content for wood and hessian bag but later increased at higher moisture content of the experimental range, while it completely increased on galvanised steel sheet and fibre glass. the static coefficient of friction varied according to the surface. it could be said that at higher moisture content, the seeds became rough thereby increasing friction characteristics. the static coefficient of friction was maximum on hessian bag (0.528 – 0.595), followed by wood (0.485 – 0.581), galvanised steel sheet (0.385 – 0.507) and was minimum on fibre glass (0.325 – 0.456). the relationship existing between moisture content and the static coefficient of friction of afzelia africana seeds for different structural surfaces were found to be linear and can be expressed with the following equations: μhb = 0.019m + 0.4962 (26) μw = 0.0264m + 0.4428 (27) μgs = 0.0298m + 0.3652 (28) μfg = 0.0341m + 0.2873 (29) with values of coefficient of determination r2 = 0.8907, 0.9033, 0.9691, and 0.9904 respectively. where: μhb = static coefficient of friction on hessian bag, μw = static coefficient of friction on wood, μgs = static coefficient of friction on galvanised steel sheet, μfg = static coefficient of friction on fibre glass. singh and goswani (1996), milani et al., (2007) and kheiralipour et al., (2008) reported linearly increasing trends on the static coefficient of friction for cumin seed, cucurbit seed and wheat respectively. this property is very useful in the product movements during processing. in the design of silos, bins and other storage facilities for the seed, the vertical load on the walls of the structure or equipment is determined by the friction coefficient. 3.10 kinetic coefficient of friction the kinetic coefficient of friction obtained experimentally on four structural surfaces against moisture content in the range of 6.132.3% (d.b) is presented in figure 11 figure 11: effect of moisture content on the kinetic coefficient of friction of afzelia africana seed the figure shows that the kinetic coefficient of friction increased with increase in moisture content and well varied with structural surface.the highest friction coefficient was recorded on hessian bag (0.536 – 0.63), followed by fibre glass (0.42 – 0.563) and galvanised steel sheet file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 546 (0.321 – 0.509), while the least was recorded for wood (0.321 – 0.482). this could be due to the surface characteristics of the seeds with increasing moisture content. the relationship existing between moisture content and the kinetic coefficient of friction of afzelia africana seeds for different structural surfaces were found to be linear and can be expressed with the following equations: μhb = 0.0254m + 0.4948 (30) μw = 0.0409m + 0.2815 (31) μgs = 0.0506m + 0.255 (32) μfg = 0.0389m + 0.3711 (33) with values of coefficient of determination r2 = 0.8848, 0.9932, 0.9702, and 0.9713 respectively. where: μhb = kinetic coefficient of friction on hessian bag, μw = kinetic coefficient of friction on wood, μgs = kinetic coefficient of friction on galvanised steel sheet, μfg = kinetic coefficient of friction on fibre glass. carman (1996), ebubekir et al. (2004) and sessiza et al. (2007) reported linear increase of kinetic coefficient of friction for lentil seed, fenugreek seeds and capper fruit seeds, respectively. kinetic coefficient of friction is needed before the power requirements for continued flow of granular or unconsolidated materials can be estimated. 3.11 coefficient of restitution the variation of the coefficient of restitution of afzelia africana seeds with moisture levels in the range 6.1 – 32.3% (d.b), drop heights between 50 – 150cm and different structural surfaces namely hessian bag, wood, fibre glass and galvanised steel sheet are presented in figures 12 – 15. figure 12: effect of moisture content on the coefficient of restitution of afzelia africana seed from a drop height of 50cm figure 13: effect of moisture content on the coefficient of restitution of afzelia africana seeds from a drop height of 90cm http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 547 figure 14: effect of moisture content on the coefficient of restitution of afzelia africana seeds from a drop height of 120cm figure 15: efect of moisture content on the coefficient of restitution of afzelia africana seeds from a drop height of 150cm coefficient of restitution decreased with increase in drop height and also decreased with increase in moisture content and exhibited a linear relationship with moisture content on all the surfaces. the decrease in the coefficient of restitution appeared to be almost entirely as a result of increased impact velocity at increased drop heights. the non-spherical seed’s impact on a point increased the local stress in the material, thus causing reduction in coefficient of restitution. the relationship between coefficient of restitution and moisture content on all surfaces at various heights can be expressed using linear equations of the form: c.r = xm + y (34) where: c.r = coefficient of restitution, x and y are constants and m = moisture content (%). the constants in equation (34) obtained for the seeds on different structural surfaces and drop heights with the coefficients of determination are presented in table 1. it was also observed that coefficient of restitution depends not only on the impact velocity but also on the seed composition and structural surface roughness as the highest coefficient of restitution was observed on wood, followed by galvanised steel sheet, fibre glass and least on file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 548 hessian bag at all drop heights. aviara et al. (2010) and locurto et al. (1997) reported decrease in the coefficient of restitution with increase in moisture content and drop height for mucuna flagellipes and soy bean respectively. decrease in coefficient of restitution was also reported by jayan and kumar (2004) for maize and red gram and by ozturk et al. (2010) for chickpea and lentil seeds. table1: values of the constants in equation (34) expressing the coefficient of restitution of afzelia africana seeds as a function of moisture content at different drop heights on different structural surfaces structural surfaces drop heights (cm) constants r2 x y hessian bag 50 -0.0025 0.186 0.908 90 -0.0011 0.1415 0.7593 120 -0.0008 -0.134 0.8469 150 -0.0005 -0.1226 0.7304 fibre glass 50 -0.0017 0.2681 0.9959 90 -0.0015 0.2174 0.8217 120 -0.0014 0.2129 0.9765 150 -0.0013 0.2027 0.9264 galvanised steel sheet 50 -0.0016 0.3424 0.965 90 -0.0009 0.2628 0.9674 120 -0.0008 0.2508 0.9767 150 -0.0007 0.2374 0.8438 wood 50 -0.0014 0.3943 0.7457 90 -0.0011 0.3085 0.9284 120 -0.0009 0.2898 0.91 150 -0.0006 0.2712 0.8887 3.12 specific heat the variation of specific heat of afzelia africana seeds with moisture content in the range of 6.1 – 32.3% (d.b) is presented in figure 16. figure 16: effect of moisture content on the specific heat capacity of afzelia africana seeds http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 549 it was observed that the specific heat of afzelia africana seeds increased linearly with increase in moisture content from 2080.3 – 5488.2j/kgk. the relationship between moisture content and the specific heat capacity of the seeds can be further expressed using the linear equation: cs = 133.03m + 1215.2 (35) with the value for the coefficient of determination r2 = 0.997, where: cs = specific heat capacity of the seeds (j/kgk) and m = moisture content (%, db). desphande and bal (1999), aviara and haque (2001) and aviara et al., (2008) reported a similar trend of linear increase in specific heat for cumin seeds, sheanut kernel and guna seeds and kernel, respectively. knowledge of the specific heat of seeds as well as the effect of moisture content and temperature on it value is essential for the design of thermal processing systems, as varying moisture content and temperature could form some of the process conditions. the thermal properties of the seed are also essential in the development of processes and equipment needed in drying and storage. 4.0 conclusion this study investigated the moisture dependence of some engineering properties of afzelia africana seeds (axial dimensions, arithmetic mean diameter, geometric mean diameter, aspect ratio, one thousand seed weight, surface area, particle density, bulk density, porosity, angle of repose, static and kinetic coefficient of friction, coefficient of restitution and specific heat)in the moisture range of 6.1 – 32.3% d.b. the outcome of the study revealed that the major, intermediate and minor axial dimensions, the arithmetic and geometric mean diameters as well as the aspect ratio of afzelia africana seed increased linearly with moisture content. one thousand seed weight, particle density, porosity and angle of repose also increased linearly as the moisture content increased. surface area of the seed increased logarithmically with increase in moisture content, while bulk density decrease at a trend that had power relationship with increase in moisture content. static coefficient of friction increased linearly with moisture content and varied with structural surfaces with the highest values being on hessian bag, followed by wood, steel and the least on glass. kinetic coefficient of friction also increased linearly with moisture content and its highest values were on hessian bag, followed by glass, galvanised steel sheet and the least was on wood. coefficient of restitution decreased with increase in drop height as well as increase in moisture content and varied with surface. specific heat of the seeds increased linearly with moisture content and ranged from 2080.3 – 5488.2j/kgk. references atlantus, e. and yaldiz, m. 2007. effect of moisture content on some physical properties of faba bean grain. journal of food engineering, 78:174-183. amin, mn., hossani, ma. and roy, kc. 2004. effects of moisture content on some physical properties of lentil seeds. journal of food engineering, 65(1): 83-87. aoac, (1980). official methods of analysis (13th ed.). washington, dc: association of official analytical chemists. aviara, na., haque, ma. and ogunjimi, lao. 2008. thermal properties of guna seed. international agrophysics, 22:291-297. aviara, na., haque, ma. and izge, ia. 2000. physical and frictional properties of sheanut. agro science, 2(1):19-34. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al:. effect of moisture content on some engineering properties of african mahogany (afzelia africana) seed. azojete, 15(3):534-553. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 550 aviara, na. and haque, ma. 2001. moisture dependence of thermal properties of sheanut kernel. journal of food engineering, 47(2):109-113. aviara, na. and haque, ma. 2000. moisture dependence of densities, coefficient of friction and angle of repose of guna seed and kernel. journal of engineering application, 2:44-53. aviara, na., ajibola, oo. and oni, sa. 2003. effect of moisture content and temperature on the specific heat of soybean tgx 1440-ie. proceedings of the 4th international conference of the nigeria institution of agricultural engineers, 25:183-193. aviara, na., gwandzang, mi. and haque, ma. 1999. physical properties of guna seeds. journal of agricultural engineering research, 73:105-111. aviara, na. and haque, ma. 2002. processing and storage of guna crop in the north east arid region of nigeria. agricultural mechanization in asia, africa and latin america, 33:49-54. aviara, na., onuh, oa. and ehiabhi, se. 2010. phyisical properties of mucuna flagellipes nuts. gsb seed science and biotechnology, 4(1): 59-68. aviara, na., oluwole, fa. and haque, ma. 2005. effect of moisture content onsome physical properties of sheanut (butyrosperm paradoxum). international agrophysics, 19:193-198. aydin, c., ogut, h. and konak, m. 2002. some physical properties of turkish mahaleb. biosystems engineering, 82(2):231-234. barbosa-canovas, gv., juliano, p. and palag, m. 2004. engineering property of foods, in food engineering (ed. gustavo v. barbosa-canovas). in encyclopaedia of the support systems (eolss), developed under the auspices of the unesco, eollas publishers, oxford, uk, (http://www.eolass.net). baryeh, ea. 2002. physical properties of millet. journal of food engineering, 51:39-46. brenan, jpm. 1967. leguminosae, subfamily caesalpnoideae in: milne-redhead, e. and polhill, rm. 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 552 milani, e., seyed, m., razavi, a., koocheki, a., nikzadeti, v., vahedi, n., moeinfard, m., and gholanhosseinpour, a. 2007. moisture dependent physical properties of curcubit seeds. international agrophysics, 21:157-168. moshenin, nn. 1986. physical properties of plant and animal materials. gordon and breach press. new york. ndukwu, mc. 2009. determination of selected physical properties of brachystegia eurycoma seeds. journal of agricultural engineering research, 55:165-169. nimkar, pm. and chattopadhyay, pk. 2001. some physical properties of green gram. journal of agricultural engineering resources, 80(2):183-189. ogunjimi, lao., aviara, na. and aregbesola, oa. 2002. some engineering properties of locust bean seed. journal of food engineering, 55:95-99. oje, k. 1994. moisture dependence of some physical properties of cowpea. ife journal of technology, 4:23-27. oje, k. and ugbor, ec. 1991. some physical properties of oil bean seed. journal of agricultural engineering research, 50:305-313. power, pp. 2006. effects of moisture content on the engineering properties (physical) of moringa africana seeds. b.eng. university of maiduguri, maiduguri, nigeria. sacande, m. 2007. afzelia africana. seed leaflet, (118). millennium bank seed project. forest and landscape denmark. 2 pp. sacilik, k., ozturk, r. and keskin, r. 2002. some physical properties of thrump seed. biosystems engineering, 86(2):191-198. sahoo, pk. and srivastava, ap. 2002. physical properties of okra seed. biosystems engineering, 83(4):441-448. selvi, kc., pinar, y. and yesilobglu, e. 2006. some physical properties of linseed.biosystems engineering, 95(4):607-612. sessiz, a., esgici, r. and kizli, s. 2007. moisture dependent physical properties of caper (capparis spp.) fruit. journal of food engineering, 79(4):1426-1431. shepherd, h. and bhardwaj, rk. 1986. thermal properties of pigeon pea. cereal foods world, 31:466-470. simonyan, kj., el-okene, am. and yiljep, yd. 2007. some physical properties of samaru sorghum 17.agricultural engineering international:the cigr e-journal, manuscript fp07 008. vol. ix. simonyan, kj., yijep, yd., oyatoyan, ob. and bawa, gs. 2009. effects of moisture content on some physical properties of lablabpurpureus (l.) seeds. agricultural engineering international: the cigr ejournal, manuscript 1279. vol. xi., july 2009. singh, kk. and goswami, tk. 1999. thermal properties of cumin seed. journal of food engineering, 54(4):181-187. singh, kk. and goswami, tk. 1996. physical properties of cumin seed. journal of agricultural engineering research, 64:93-98. suthar, sh. and das, sk. 1996. some physical properties of karinga seed. journal of agricultural engineering research, 54:219-229. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):534-553. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 553 tabatabaeefar, a. 2003. moisture dependent physical properties of wheat. international agrophysics, 17:207-211. timbers, ge. 1975. properties of rapeseed: thermal conductivity and specific heat. canadian agricultural engineering, 17:81-84. tunde-akintunde, ty. and akintunde, bo. 2007. effect of moisture content and variety on selected physical properties of beniseed.agricultural engineering international: the cigr ejournal, manuscript fp 07 021. vol. ix. yalcin, c. and ersan, k. 2007. physical properties of coriander seeds. journal of food engineering, 80(2):408-416. zewdu, a. and solomon, w. 2008. moisture dependent physical properties of grass pea (lathyrus sativus l.) seeds. agricultural engineering international. the cigr ejournal. manuscript fp 06 027. vol.x file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):67-76 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 67 original research article model design, simulation and control of a robotic arm using pic 16f877a microcontroller a. b. buji, y. p. mshelia, a. g. ibrahim and m. a. sarki department of electrical and electronics engineering, university of maiduguri, maiduguri, nigeria *corresponding author: babuji@unimaid.edu.ng article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: microcontroller programmable integrated circuit servo motor pulse width modulation robotic abstract this paper focuses on model design, simulation and control of a five degree of freedom (dof) robotic arm using servo motors. the robotic arm is controlled by a pic 16f877a microcontroller and its main function is to generate pulse width modulation (pwm) signals which are applied to the servo motors for achieving the desired rotation angle. a pwm signal could have different effects on various servo motors depending on their specifications. thus, it is important to apply the exact pwm signals to achieve the rotation angle desired. the main advantage of controlling the servo motors with pwm signals is that they can be programmed to have an initial position and to rotate with an exact degree with respect to the requirements. a general formula is derived for finding the pulse width required to achieve the desired rotation in each servo motor. the main advantage of this formula is that it can be used for any servo motor with different specification. simulation results presented showed that for pwm signal (p) a difference of 0.45 µ s to 1.45µs and angle rotation difference of 0.04º to 0.11º were obtained. the results obtained from the derived equation is found to have 98% accuracy compared to the simulation results. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction robot is an automatically controlled material handling unit that is widely used in the manufacturing industry. it is generally used for high volume production and better quality. the word 'robot' first appeared in 1921 in the czech playwright karel capek's play "rossum's universal robots'. the word is linked to czech words robota (meaning work) and robotnik (meaning slave) (rao et al., 2001) international organization for standardization (iso) defines a robot as an automatically controlled, reprogrammable, multipurpose, manipulative machine with several reprogrammable axes, which is either fixed in place or mobile for use in industrial automation application. robots are indispensable in many manufacturing industries. the reason is that the cost per hour to operate a robot is a fraction of the cost of human labor needed to perform the same function. more than this, once programmed, robots repeatedly perform functions with a high accuracy that surpasses that of the most experienced human operator. however, human operators are far more versatile. humans can switch job tasks easily. robots are built and programmed to be job specific but as robots evolve, they will become more versatile, emulating the human capacity and ability to switch job tasks easily (ishak s.h., 2011). the robots play important roles in our lives and are able to perform the tasks which cannot be done by humans in terms of speed, accuracy and difficulty. (lin et al,2011) stated that robots can be employed to imitate human behaviors and then apply these behaviors to the skills that allow the robot to achieve a certain task. robotics is applied in different forms and fields to simulate human behavior and motions (nikku s., 2011), and this fact allows the workers to have more free time to spend on skilled professions including the programming, maintenance and operation of the robots which are essential (robotics, 2017). in this paper, servo motors are used for robotic arm joint actuators and are controlled by using pwm signals generated by the pic 16f877a microcontroller. mikro c pro is used to program the microcontroller and control switches are used to command pic microcontroller which is connected to robotic arm. robotic arm movement can be done by moving to the left or right. the robotic arm will be controlled via the controller and it will be able to grab, pick up, move and place objects according to their weights and shape in different places. the manipulator design is mostly expected to pick up cubes and the geometric shapes like a box. this robotic arm operates using 5 servo motors thus it has 5 degree of freedom. 2. materials and methods 2.1 design of robotic arm the robotic arm design involves mathematical modeling of the kinematics, structure design, electronic design and software design (nones, 2003). inverse kinematics is used for the kinematic modeling analysis algorithm and plastic sheets are recommended for the structure design. 2.1.1 mathematical model of the kinematics mailto:babuji@unimaid.edu.ng http://www.azojete.com.ng buji et al: model design, simulation and control of a robotic arm using pic 16f877a microcontroller. azojete, 15(1):67-76. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 68 robot arm kinematics deals with the analytical study of geometry motion of robot arm from fixed reference of co-ordinate system as a function of time without regard to movements that cause the motion. articulated 5-dof robotic arm is designed by direct and inverse kinematic analysis methods (patil and lakshminarayan, 2012). 2.1.2 direct kinematic analysis direct kinematics usually refers to home position of geometric link parameters. it is used to find the position and orientation of end effector with respect to the base with the help of denavit-hartenberg algorithm used to obtain modeling equations (patil. and lakshminarayan, 2012). this method is not discussed in this paper. 2.1.3 inverse kinematics analysis inverse kinematics usually refers to position and orientation of end effector. it helps to find joint variables to achieve correct position of source location part. in order to control the position and orientation of end effector of a robotic arm to reach its object, the inverse kinematic solution is more important. in this paper, inverse kinematics problem is solved by geometric approach method (patil. and lakshminarayan, 2012).. this method provides more insight to solving simple manipulators with rotary joints. the robotic arm has a total of five axes. three major axes which correspond to the base, shoulder and elbow are needed to move the arm to the desired spot and two minor axes which correspond to the gripper pitch and gripper spin. the design has six rotary joints. although we consider the number of joints as five because two joints that move the shoulder, rotate in the same direction with the same speed. therefore, they are counted as one joint. figure 1.0 shows the precise link coordinate diagram of axes and joints (seki et al, 2012). figure 1. link coordinates of axes and joints of the proposed robot design. the parameters and kinematic equations of the robotic arm can be written as follows; l0 to l5 – six unit frames 5 – gripper length 1to 5 – joint variables ( = ) – gripper spin 1 – height of shoulder from base x0 to x5 – motion of base, shoulder elbow, gripper pitch and spin in x direction y0 to y5 – motion of base, shoulder elbow, gripper pitch and spin in y direction z0 to z5 – motion of base, shoulder elbow, gripper pitch and spin in z direction 1,2, … ,5 – rotary joints 2, 3, 4 – link lengths base: 1= 1 (1) where: θ1= tan−1 y0 x0 and [−2 ≤ θ1≤ 2 ] for full clockwise and counter clockwise rotation. shoulder: xshoulder = (x1)2 + (y1)2 (2) zshoulder = z1 − d1 (3) yshoulder = xshoulder − d2 (4) h = (xshoulder)2 + (zshoulder)2 (5) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):67-76. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 69 θ2 = tan−1 zshoulder xshoulder − cos−1 ll 2+ lu 2−h2 2llluh and [π 6 ≤ θ2 ≤ 2π 3 ] for: (ll=lower link, lu= upper link, ℎ = height of shoulder from base) for the rotation from 30° to 120°. elbow: θ3 = cos−1 (ll)2+ lu2 − h2 2llluh (6) where [ 7π 6 ≤ θ3 ≤ π 3 ] , for the rotation from 60o to 120o. gripper pitch: θ4 =− θ2 − θ3 (7) where: [− π 4 ≤ θ4 ≤ π 4 ], for the rotation from − 45o to 45o. gripper spin: θ5 = cos−1 ll 2+ (lu)2−h2 2llluh (8) where: [− π 4 ≤ θ5 ≤ π 4 ], for the rotation from − 45o to 45o. a model design of the robotic arm structure according to the schematic and kinematic presentation was carried out using auto cad design software. the model design is shown in figure 2. figure 2: model design of robotic structure as carried out using auto cad electrical circuit design the electrical circuit of a static robotic arm consists mainly of the joint actuators (rc servo motors), the controller (this is achieved by pic 16f877a microcontroller) and the power supply. a block diagram of the robotic circuit is shown in figure 3. figure 3: block diagram of robotic circuit 2.3.1 servo motors servo refers to an error sensing feedback control which is used to correct the performance of a system. servo or radio controlled servo motors are dc motors equipped with a servo mechanism for precise control of angular position. the rc servo motors usually have a rotation limit from 90° to 180°. servo motor is a geared dc motor with positional feedback that allows rotor to be positioned accurately (ibrahim, 2006). internally, a servo consists of dc motor, potentiometer and control circuit as shown in figure 4. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng buji et al: model design, simulation and control of a robotic arm using pic 16f877a microcontroller. azojete, 15(1):67-76. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 70 figure 4: servo motor and its components the control circuitry compares an angular position, determined by a control signal, to the current position of the motor shaft as shown in figure 5. the motor shaft’s angular position is often determined by a potentiometer, which is rotated by the motor shaft. a potentiometer is a three terminal resistor, whose center connection has variable resistance, usually controlled by a slider or dial. the potentiometer acts as a variable voltage divider. the voltage from the center connection of the potentiometer represents the angular position the motor shaft is in. the built-in controller generates an internal signal from the voltage controlled by the potentiometer, compares it to the control signal, and then provides power to the dc motor to rotate the shaft in the appropriate direction to match the two. figure 5: signal flow diagram of the control circuitry of a servo motor 2.3.2 pic 16f877a microcontroller pic 16f877a microcontroller has 40 pins and is a popular microcontroller capable of doing complex tasks. this microcontroller has 8192 × 14 flash program memory which consists of 368 bytes of ram and 256 bytes of non-volatile eeprom memory. 33 pins are dedicated for input/output pins and 8 multiplexed analog/digital converters with 10 bits resolution. this microcontroller also has specifications such as pwm generator, 3 timers, analog capture and comparator circuit, universal synchronous receiver transmitter (usart), internal and external interrupt capabilities. the operating voltage for the microcontroller is 2.0v to 5.56v dc and operates at an external oscillator frequency in the range of 0hz to 20hz. figure 6 and 7 shows the pin configuration of the pic 16f877a microcontroller and the pins which are used for pwm generation are marked (ibrahim, 2006). pic 16f877a was chosen for this design because it size of 368 bytes and additional 256 bytes of non-volatile eeprom. it also has high clock speed of up to 4mhz, and it is cheap. figure 6: pic 16f877a microcontroller http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):67-76. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 71 figure 7: pic 16f877a pin configuration software design there are variety of programming languages and compilers such as assembly, basic, pascal, c and c++. in this paper, mikro c pro for pic compiler (c language) is used to generate hex files for programming the microcontroller. when the hex code is ready, it can be written on the eprom of the microcontroller. implementation each servo motor was operated manually with two buttons for rotation and automatically controlled with two buttons and each input control button causes the microcontroller to generate the necessary pwm signal and send it to the corresponding servo motor, all these are shown in the figure below. the servo motor which was responsible for the rotation of the base (s1) was connected to port d.0 of the microcontroller. two servos which are responsible for the motion of the shoulder (s2 and s3) were connected to port d.1 of the microcontroller. the servo motor responsible for the rotation of the elbow (s4) was connected to port d.2 of the microcontroller. the servo motor for the gripper pitch (s5) is connected to port d.3 of the microcontroller. the corresponding servo motor for the gripper spin (s6) was connected to the port d.4 and the gripper servo (s7) was connected to port d.5 which was responsible for opening and closing the end-effector. figure 8: schematic diagram of user controlled robotic arm circuit simulation results proteus simulation software was used to design a virtual circuit containing pic 16f877a microcontroller and the servo motors used to design the robotic arm (tower-pro sg-90 and futaba s3003). this was done to simulate and analyze the results on the effects of pulse width modulation (pwm) signals on the servo motors for adequate and optimum control as shown in figure 9. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng buji et al: model design, simulation and control of a robotic arm using pic 16f877a microcontroller. azojete, 15(1):67-76. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 72 figure 9: virtual implementation of robotic circuit in proteus. since there are two types of servos with different specifications in the robotic arm design, the results obtained from the simulation on proteus differ in terms of pulse width, angle and the general servo motor behavior. the simulation considers the rotation angle with respect to the generated pulses with the pulse width ranges from 600µs to 2400µs for futaba s3003 and from 400µs to 2400µs for towerpro sg-90 servo. 4.0 simulation and calculation results for tower-pro sg-90 table 1: simulation and calculation results for tower pro sg-90 servo motor table 2: simulation and calculation results for futaba s3003 servo motors simulation result in progression simulation results in random results obtained from derived equation pwm (μs) angle (°) pwm (μs) angle(°) pwm (μs ) from angle angle( °) from pwm 800 -53.9 450 -85.4 451.11 -85.50 810 -53.0 570 -74.6 571.11 -74.70 820 -52.1 675 -65.2 675.55 -65.25 830 -51.2 891 -45.7 892.22 -45.81 840 -50.3 1287 -10.1 1287.77 +10.17 850 -49.4 1576 +15.9 1576.66 +15.84 860 -48.5 2070 +60.4 2071.11 +60.30 870 -47.6 2222 +74.1 2223.33 +73.98 simulation result in progression simulation results in random results obtained from derived equation pwm (μs) angle (°) pwm (μs) angle (°) pwm( μs ) from angle angle( °) from pwm 800 -69.9 600 -89.9 601 -90.0 810 -68.9 653 -84.6 654 -84.7 820 -67.9 675 -82.4 676 -82.5 830 -66.9 891 -60.8 892 -60.9 840 -65.9 1287 -21.2 1288 +21.3 850 -64.9 1576 +7.70 1577 +07.6 860 -63.9 2070 +57.1 2071 +57.0 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):67-76. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 73 observations from table 4.1, the comparison between calculated and simulation results for sg-90 servo shows that: for pwm signal (p) a difference of 0.45μs to 1.45μs was presented. for rotation angle (θ) of the servo motor a difference of 0.04° to 0.11° was presented. from table 4.2, the comparison between calculated and simulation results for s3003 shows that: for pwm signal (p) a difference of 1μs was presented. for rotation angle (θ) of the servo motor a difference of 0.1° was presented. as seen in the table 4.1 and 4.2, both servos have a stable response to their pwm signals. thus, rotation angle of the servo motors increases proportionally to increase of the pwm signals. by considering the accuracy and comparisons of the equation results and simulation results, a general formula for any servo can be derived to find the required pwm input signal. px = θ+ ε 2 ε pm − po − po for: − 90 < θ <+ 90 where: px is the pulse width signal required, θ is the angle required, ε is the maximum rotation angle range of servo. pm is the maximum pulse width required by servo motor, pois the minimum pulse width required by servo motor. conclusion in this paper, the procedure of designing and simulating an articulated robotic arm using a microcontroller and servo motors with the help of pwm was shown. the effect of pulses on the servo motors using software simulation were shown and discussed. a general formula which facilitates the design and motion control of the robotic arm has also been proposed. the accuracy of the proposed formula can be obtained as almost 98%, this means that the rotation of the servo can possibly have 2% error comparing to the expectations. references http://www.robotics.org/content-detail.cfm/industrial-robotics-featuredarticles/how-robots-willaffect-future generations/content_id/834 ibrahim, d. 2006. “30 projects using pic basic and pic basic pro”, uk: mpg books ishak, sh. 2011. design of robotic arm controller using matlab, malaysia. lin, ih., liu, cy. and chen, lc. 2011 "evaluation of human-robot arm movement imitation", proceedings of 8th asian control conference (ascc), pp.287-292. nikku, s. 2011. “introduction to robotics”, usa: john wiley & sons. nones, ya. 2003. “heterogeneous modeling & design of a robot arm control system”, illinois tech robotics (itr), pp.1-6. rao, pn., ahmad, a., omar, ar. and ayub, ma. 2001. design and fabrication of a robotic arm for material handling,malaysia. seki, k., yokoi, h. and iwasaki, m. 2012. “experimental evaluations of friction behavior in microdisplacement region positioning for servo motor with air bearings” proceeding of ieee international conference on advanced intelligent mechatronics, pp.731-736. patil, s. and lakshminarayan, s. 2012. “position control of pick and place robotic arm”, eie 2nd international conference on computers, energy, networking, robotics and telecom lao. 2008. thermal properties of guna seed. international agrophysics, 22: 291-297. 870 -64.3 2222 +72.3 2223 +72.2 http://www.robotics.org/content-detail.cfm/industrial-robotics-featuredarticles/how-robots-will-affect-future%20generations/content_id/834 http://www.robotics.org/content-detail.cfm/industrial-robotics-featuredarticles/how-robots-will-affect-future%20generations/content_id/834 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng buji et al: model design, simulation and control of a robotic arm using pic 16f877a microcontroller. azojete, 15(1):67-76. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 74 bamgboye, ai. and adejumo, oi. 2010. thermal properties of roselle seeds. international agrophysics, 24: 85-87. cansee, s., watyotha, c., thivavarnvongs, t., uriyapongson, j. and varith, j. 2008. effect of temperature and concentration on thermal properties of cassava starch solutions. songklanakarin journal of science and technology, 30(3): 405 411. donsi, g., ferrari, g and nigro, r. 1996. experimental determination of thermal conductivity of apple and potato at different moisture contents. journal of food engineering, 30: 263-268. enwere, jn. 1998. foods of plant origin. afro-orbis publications, nsukka, nigeria. 64-124. njie, dn., rumsey, tr. and singh, rp. 1998. thermal properties of cassava, yam and plantain. journal of food engineering, 37(1): 63-76. odebunmi, eo., oluwaniyi, oo., sanda, am. and kolade, bo. 2007. nutritional compositions of selected tubers and root crops used in nigerian food preparations. international journal of chemistry, 17(1): 37-43. odeku, oa., awe, oo., popoola, b., odeniyi, ma. and itiola, oa. 2005. compression and mechanical properties of tablet formulations containing corn, sweet potato, and cocoyam starches as binders. pharmaceutical technology, 29(4): 82-90. onwuka, no. and eneh, oc. 1998. the potentials of cocoyam (colocasia) in stout beer brewing. journal of science and technology, 4: 78-80. onyeka, j. 2014. status of cocoyam (colocasia esculenta and xanthosoma spp) in west and central africa: production, household importance and the threat from leaf blight, lima (peru). cgiar program on roots, tubers and bananas (rtb). www.rtb.cgiar.org singh, kk. and goswami, tk. 2000. thermal properties of cumin seed. journal of food engineering, 45:181-187. taiwo, ka., akanbi, ct. and ajibola, oo. 1996 thermal properties of ground and hydrated cowpea. journal of food engineering 29: 249-256 yang, w., sokhansanj, s., tang, j. and winter, p. 2002. determination of thermal conductivity, specific heat and thermal diffusivity of borage seeds. biosystems engineering, 82(2): 169–176. zhu, s., ramaswamy, hs., marcotte, m., chen, c., shao, y. and le bail, a. 2007. evaluation of thermal properties of food materials at high pressures using a dual-needle line-heat-source method. journal of food science, 72: 49–56. http://www.rtb.cgiar.org http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):212-222 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 212 original research article development of adaptive sensing algorithm for minimizing energy and bandwidth consumption in cooperative spectrum sensing technology j. f. opadiji1*, s. a. olatunji1 and t. o. fajemilehin2 1department of computer engineering, university of ilorin, ilorin, nigeria 2department of electrical and electronics engineering, university of ilorin, ilorin, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: cognitive radio cooperative spectrum sensing energy and bandwidth consumption. abstract optimized consumption of energy and bandwidth is crucial for efficient utilization of the limited electromagnetic spectrum for telecommunication purposes. cognitive radio is one of the dynamic spectrum management applications with numerous benefits related to the management of available spectrum. but it has the challenge of high energy and bandwidth usage when the cooperative scheme of spectrum sensing is applied for accurate sensing. in this paper, an adaptive spectrum sensing algorithm was developed to minimize energy and bandwidth consumption in cognitive radio spectrum sensing while ensuring accurate spectrum sensing. the adaptive algorithm was developed based on the signal-to-noise ratio conditions of the channel. results reveal that the energy and bandwidth usage by the cooperative spectrum sensing can be significantly reduced without negatively affecting the performance and detection of the cognitive radio in varying noisy conditions © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the electromagnetic radio spectrum is a limited treasured resource which exists naturally. utilizing it efficiently for wireless communication has become a huge challenge due to the growth and advancement of wireless systems, services and devices in recent years (goldsmith, 2005; kakalou et al., 2018; riya et al., 2018). this growth has increased the energy and bandwidth requirement of these devices and services to ensure optimum connectivity (gupta, verma and dubey, 2016; wang et al., 2018). moreover, the conventional spectrum allocation policy does not permit full utilization of the radio spectrum. a dynamic rather than static usage of the spectrum must be encouraged to increase the availability of frequency spectrum (lee et al., 2012; sahu et al., 2018). this would aid channel capacity expansion since cell occupancy varies with traffic load. cognitive radio which applies the concept of dynamic spectrum access is utilized to exploit the spectrum holes in order to ensure more efficient spectrum utilization (riya et al., 2018). cognitive radios are aware of their surroundings and bandwidth availability and are able to dynamically tune the spectrum usage based on location, nearby radios, time of day and other factors (goldsmith, 2005). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 213 transmitter detection techniques (otherwise called single user detection techniques) especially the energy detection technique suffer severely from fading and path loss effects (lee et al., 2012).this makes it unreliable in low signal to noise ratio conditions(sahu et al., 2018). it therefore necessitates the inclusion of more cognitive radios to improve on the sensitivity and accuracy of report (zou, 2010). this process of including more cognitive radios to improve detection accuracy can be referred to as cooperative spectrum sensing. the cooperative sensing technique was developed to boost the quality of service (qos) of the network and to improve on the results obtained from single user detection techniques. but it has a major challenge of consuming additional energy and bandwidth thereby increasing communication overhead (sobron et al., 2015; kakalou et al., 2018). there is therefore a need for a more efficient and adaptive sensing algorithm that can reduce the overall energy and bandwidth consumption of the cooperative sensing technique to the barest minimum without a negative toll on the performance of the cognitive radio system which is the aim of this study. the objectives worked on to achieve this aim include: simulating and studying the detection performance of the single user and cooperative sensing using an improved energy detection algorithm under varying signal to noise ratios, evaluating the effect of change in probability of false alarm on detection and then making the cooperative sensing adaptive based on the snr threshold set. this study is limited to cooperative spectrum scheme of cognitive radios with focus on energy and bandwidth optimization for improved performance of cognitive radio systems. 2.0 related studies dynamic spectrum management (dsm) design when initially proposed had mainly been focused on maximization of data rates (tsiaflakisa et al., 2007). however, reducing the total power had become a main target as it power consumption has been identified as a significant contributor to global warming (santhanam and keller, 2018). traditional dsm design was also extended towards a much wider power-efficient scope and how to tackle the corresponding optimization problems. the technique developed helped to save about 50% power alongside improved data rate performance. some research efforts have also been made to the energy efficiency of spectrum sensing sharing while ensuring simplicity and robustness using a multi-rate asynchronous subnyquist sampling system (sun, 2011). further improvements were made to the algorithms employed in dsm. the coordination of power was decentralized in order to make it more distributed to minimize cost and complexity was a major focus of the research effort (rognsvåg, 2008). the results showed admirable improvement in the capacity of the system as compared to static spectrum management (ssm). some other researchers proposed a sensing method which chose between single energy sensing and cooperative energy according to the received signal's signal to noise ratio (snr) from file:///c:/users/user/downloads/azojete143/www.azojete.com.ng opadiji et al: development of adaptive sensing algorithm for minimizing energy and bandwidth consumption in cooperative spectrum sensing technology. azojete, 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 214 the primary user (pu). the simulation using conventional energy detection technique produced results which showed that the adaptive spectrum sensing produced efficiency and improvement in cognitive radio systems (lee et al., 2012). some adaptive systems have also been developed such as the adaptive random access technique (lee, 2015). in this technique, a heuristic approach was utilized to improve the sensing data collection. some other adaptive systems have been developed which focused on detection sensitivity, not on the energy and bandwidth consumption (sobron et al., 2015; gupta et al., 2016)). one of these adaptive systems employed an adaptive threshold for each cognitive radio (cr) in cooperative spectrum sensing scheme based on the neyman pearson theorem (huber and strassen, 1973; yan and blum, 2001). most of these systems which produced better performances for the cooperative spectrum sensing, but was placed more computational demand on the system (rauniyar and shin, 2018). another study utilized a dynamic threshold for detection but used matched filters which require prior information of the pu signals with more complexity (salahdine et al., 2016). a recent survey of sensing algorithms for cognitive radio networks (kakalou et al., 2018) revealed that the majority of the sensing algorithms employed in research are energy based sensing algorithms due to the low implementation complexity and the fact that they do not require prior information of the pu signals. however, there is still a need for adaptively aimed reducing energy and bandwidth consumption specifically when cooperative spectrum sensing is utilized. this is the need which this paper addresses. it proposes a method to minimize the energy and bandwidth consumption at the fusion point during cooperative sensing while making consideration for low snr conditions. 3.0 methods 3.1 proposed adaptive spectrum sensing the adaptive spectrum sensing algorithm is proposed to solve the problem of increased energy and bandwidth consumption by the multiple cognitive radios in cooperative spectrum sensing. the algorithm is meant to be adaptive based on the secondary user's snr status. if the secondary user has sufficient snr to detect reliably, single user sensing is employed. otherwise, cooperative sensing is utilized. this is done using a supervised mode of learning to ensure that the communication overhead is reduced considerably. each of the cognitive radios employed in the adaptive sensing algorithm utilizes the improved energy detection technique introduced by (lopez-benitez and casadevall, 2012). this ensures higher sensitivity in the single user and cooperative sensing algorithms compared to the conventional sensing schemes. the adaptive spectrum sensing works with two hypotheses: h1 (signal plus noise hypothesis) and h0 (noise only hypothesis) to indicate the presence and absence of the primary user respectively. if an h1 cell is being tested, the probability density function (pdf) of the received signal (y) of a specific cr user can be expressed (as used in lee et http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 215 al., 2012) as: fyf y h1 = 1 2πmσf 2 e (y−s�f i )2 2 (1) where s�f = i=1 m s�f i� (2) s�f i = mean value of the transmitted signal from the ith cr user. sc� = mean magnitude value of primary user’s transmitted signal. m� = total number of cognitive radios σf2 = standard deviation of primary user’s transmitted signal. fyf = probability density function (pdf) of the received signal (y) and if an h0 cell is being tested, then the pdf of received signal (y) can be expressed as: fyf y h0 = 1 2πmσf 2 e −y2 2 (3) after each cr user determines whether there is the primary user or not, the results are retransmitted to the fusion center over wireless channel. then, the fusion center makes the final decision by combining the received signals from m cr users. when the h1 and h0 cells are being tested, the pdfs of the combined result yf (k) at the fusion center are expressed in line with lee et al.(2012)in equation (1) and in equation (4) as follows: fyf y h0 = 1 2πmσf 2 e −y2 2 (4) the detection probability for a given value of the decision threshold is defined as the probability of the event that the output decision variable corresponding to the h1 cell exceeds the decision threshold, which can be obtained as: pd = γ ∞ fyf y h1� dy (5) pd = γ ∞ 1 2πmσf 2 e (y−s�f i )2 2� dy (6) where pd represents the detection probability of the h1cell. let z = y−s�f mσ2 f (7) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng opadiji et al: development of adaptive sensing algorithm for minimizing energy and bandwidth consumption in cooperative spectrum sensing technology. azojete, 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 216 then the detection probability can be expressed as: pd = γ−s�f mσ2f ∞ − 1 2π e z2 2 dz� (8) pd = q γ−s�f mσ2 f (9) where: q (.) denotes q function. since the transmitted signal of primary user is random signal, the improved energy detection technique is utilized. various techniques such as equal gain combining (egc), maximum ration combining (mrc), selective combining (sc) and many more could be used to combine the signal from multiple antennas. in egc, each signal branch weighted the same factor irrespective of the signal amplitude. egc is simpler to implement than mrc and channel amplitude estimation is unnecessary. in this work each local sensing result is combining employing egc due to the advantage of using the same factor in combining for each cognitive radio. 3.2 algorithm for adaptive cooperative spectrum sensing an improved energy detection (ied) algorithm (lopez-benitez and casadevall, 2012; olatunji et al., 2019) is utilized for each of the cognitive radios in the cooperative sensing scheme. the adaptive mechanism is then implemented based on the snr status of the channel. the algorithm for this mechanism is presented as a flowchart in figure 1. it should be noted that the procedure for the simulation of the ied is similar to the conventional energy detection (ced), except that an additional check of the immediate past sensing event ti−1 yi−1 asides just the immediate signal energy check and the check for the average energy of the former sensing episodes ti avg ti is included. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 217 figure 1: flowchart for adaptive spectrum sensing the approach suggested to achieve this has been discussed earlier which entails making the number of cognitive radios employed for sensing adaptive based on the signal to noise ratio (snr). therefore, when the snr is poor, several cognitive radios are utilized to ensure accurate sensing, else just one cognitive radio is utilized for sensing the simulation was first done with one cognitive radio using the ied procedure to observe the performance under varying snr conditions. the number is then increased to two and then five and later ten to observe the performance of cooperative sensing using ied scheme under varying snr conditions. 3.3 simulation 3.3.1 simulating the received signal the simulations were carried out using matlab version r2017a. receiver operations characteristics (roc) analysis was used to study the performance of the energy detector in the simulations as a trade-off between the probability of detection (pd) and the probability of false alarm (pfa). chi-square distribution was used to analyse the output which was assumed as gaussian distribution for large samples. for a sampling episode, one hundred samples were simulated. the sample energy was varied from 2.07x108 to 2.005x108 dbm. signal to noise ratio (snr) values were varied from -15db to 15db with the pfa initially set to 5%. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng opadiji et al: development of adaptive sensing algorithm for minimizing energy and bandwidth consumption in cooperative spectrum sensing technology. azojete, 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 218 3.3.2 simulating cooperative spectrum sensing ten cognitive radios were simulated for the cooperative sensing. each cognitive radio is simulated to operate with the ied algorithm explained earlier in section 3.2. the simulation parameters are given in table 1. table 1: simulation parameters parameter value snr variation pfa no. of cognitive radios operating frequency of pu observation time variance of the noise (σ2n) variance of the received signal (σ2s) operating power -15db – 15db 0.05 10 1 x 109 hz 1 x 10-4 1 x 10-12 (σ2n x 10-1)2 40 mw 4.0 results and discussion. 4.1 performance of the cooperative ied under varying snr conditions the result presented in figure 2 shows the performance of the ied scheme when only one cognitive radio is employed in sensing. the scenario represents a very noisy environment where the noise level has been raised. yet it is still observed from the result that detections begin from about 13.6db and increases rapidly to maximum detection probability within a range of about 1db. this reveals the sensitivity of the ied scheme. 13 13.2 13.4 13.6 13.8 14 14.2 14.4 14.6 14.8 15 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 snr (db) p ro b a b ili ty o f d e te c ti o n ( p d ) figure 2: spectrum sensing using ied scheme with a single cr performance improves as the number of cognitive radios used in sensing is increased to ten as seen in figure 3. the result compares the performance of cooperative sensing with single user sensing working with the ied algorithm. the result validates the fact that multiple sensors give a more accurate result since the individual reports of each of the cognitive radios are collated before the final decision is taken. hence, cooperative sensing done with a greater number of cognitive radios had truer detections than those with a smaller number of cognitive radios. this therefore means that some of the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 219 detections observed between 13.6db and 14.5db could have been false alarms. this is confirmed from the result using ten cognitive radios where the true detections began at 14.5db. this therefore implies that the higher the number of cognitive radios employed in sensing, the better and more accurate the detection result. 13 13.5 14 14.5 15 15.5 16 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 snr (db) p ro ba bi lit y of d et ec tio n (p d) crs=1 crs=2 crs=5 crs=10 figure 3: performance of cooperative sensing using ied scheme it should also be noted that these performance simulations were performed with the probability of false alarm (pfa) fixed at 5%. varying the pfa was also explored and outcome is presented in section 4.2. 4.2 effect of change in probability of false alarm (pfa) on detection the result presented in figure 4 reveals the effect of changing the probability of false alarm. 14.5 15 15.5 16 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 snr (db) pr ob ab ilit y of d et ec tio n (p d) pfa=1% pfa=5% pfa=10% figure 4: cooperative sensing using ied scheme at various pfa file:///c:/users/user/downloads/azojete143/www.azojete.com.ng opadiji et al: development of adaptive sensing algorithm for minimizing energy and bandwidth consumption in cooperative spectrum sensing technology. azojete, 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 220 the result shows detections starting from 14.6db when the probability of false alarm is set to 1% which is about the same point where detections begin when it is set to 5%. but detections did not commence until about 14.8db when the probability of false alarm is increased to 10%. it is also observed that detections when pfa is 1% rise higher and at a faster pace than the higher values of pfa which is expected and logical. this reveals that the higher the probability of false alarm, the lower the detection probability. performance of the cognitive radios using the adaptive algorithm the result in figure 4 reveals that the detection using a single cognitive radio commences slightly before the cooperative spectrum sensing. this is expected, owing to the fact that a single sensor detection possesses less computations and may also be infiltrated with missed detections and false alarms. but the same detection was obtained for both schemes at about 15.5db. therefore, the adaptive cooperative spectrum sensing is activated when the snr is poor (<15db). when the snr improves, a single cognitive radio was used. this gave accurate detections as shown in figure 5. 14 14.2 14.4 14.6 14.8 15 15.2 15.4 15.6 15.8 16 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 snr (db) p ro b a b ili ty o f d e te c ti o n ( p d ) figure 5: adaptive cooperative sensing using single and multiple crs figure 6: comparison of percentage energy and bandwidth consumption for http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 221 4.3 conventional and adaptive cooperative sensing the outcome was compared to a conventional cooperative spectrum sensing system and a reduction of 31% in energy and bandwidth consumption was recorded. this is presented in figure 6. 5.0 conclusion the adaptive cooperative spectrum sensing developed using supervised learning helped set a threshold which is adaptive to the noise level. at this threshold, both cooperative and uncooperative spectrum sensing perform efficiently. the adaptive scheme activated the single sensing technique when the snr condition was above this threshold. when the channel snr conditions was equal to or lower than this threshold, cooperative sensing was activated. this cut the energy and bandwidth requirement by about 31%. the results imply considerable conservation of resources for further needs in the network. only in poor snr scenarios would full cooperative sensing be employed. this adaptive technique employed ied algorithm for the individual cognitive radios in the cooperative sensing scheme which ensured accurate spectrum sensing sensitivity. the adaptive cooperative spectrum technique developed proved to be energy and bandwidth efficient after testing. future work would explore evaluating this adaptive scheme in other forms of fading channels such as rayleigh and nakagami with varying signal conditions. the outcome of this present research suggests, that the developed adaptive cooperative technique will be effective in such channels as well. references goldsmith, a. 2005. wireless communication. cambridge university press, uk, pp. 1 27 gupta, m., verma, g. and dubey, rk. 2016. cooperative spectrum sensing for cognitive radio based on adaptive threshold. proceedings 2nd international conference on computational intelligence and communication technology, (cict 2016), ghaziabad, india, 12-13 feb., 2016,. ieee, pp. 444–448. doi: 10.1109/cict.2016.94. huber, pj. and strassen, v. 1973. minimax tests and the neyman-pearson lemma for capacities on jstor. the annals of statistics, 1(2): pp. 251–263. kakalou, i., papadopoulou, d., xifilidis, t., psannis, k.e., siakavara, k., ishibashi, y. 2018. a survey on spectrum sensing algorithms for cognitive radio networks. proceedings 7th international conference on modern circuits and systems technologies, (mocast 2018) thessaloniki, greece, may 7-9, 2018. ieee, 1(3), pp. 1 – 4. doi: 10.1109/mocast.2018.8376562. lee, dj. 2015. adaptive random access for cooperative spectrum sensing in cognitive radio networks. ieee transactions on wireless communications. ieee, 14(2): 831–840. doi: 10.1109/twc.2014.2360857. lee, sm., kim, yh. and kim, j. 2012. adaptive spectrum sensing algorithm for cognitive radio system. information science and industrial applications: proceedings international conference, isi, cebu, phillipines, may 29-31, 2012: 34-45. lopez-benitez, m. and casadevall, f. 2012. improved energy detection spectrum sensing file:///c:/users/user/downloads/azojete143/www.azojete.com.ng opadiji et al: development of adaptive sensing algorithm for minimizing energy and bandwidth consumption in cooperative spectrum sensing technology. azojete, 15(sp.i2):212-222. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jopadiji@unilorin.edu.ng 222 for cognitive radio. iet communications, 6(8): 785–796. doi: 10.1049/iet-com.2010.0571. olatunji, sa., fajemilehin, to. and opadiji, jf. 2019. reduction of computational time for cooperative sensing using reinforcement learning algorithm. african journal of computing and ict, 12(2): 90 108. rauniyar, a. and shin, sy. 2018. cooperative spectrum sensing based on adaptive activation of energy and preamble detector for cognitive radio networks, apsipa transactions on signal and information processing, 7: 1–7. doi: 10.1017/atsip.2018.5. riya, p., pamoli, n. and soumyasree, b. 2018. design of spectrum sensing system ’ , lecture notes in electrical engineering, 44(2): 537–544. doi: 10.1007/978-981-10-47626_51. rognsvåg, jv. 2008. autonomous algorithms for dynamic spectrum management in dsl systems, 59. institutt for elektronikk og telekommunikasjon. available at: https://brage.bibsys.no/xmlui/handle/11250/2369157. sahu, ak., singh, a. and nandakumar, s. 2018. improved adaptive cooperative spectrum sensing in cognitive radio networks ’ , proceedings 2nd international conference on electronics, materials engineering and nano-technology, (iementech. 2018) 4-5 may 2018, kolkata, india. ieee, pp. 1–5. doi: 10.1109/iementech.2018.8465199. salahdine, f., ghazi, he., kaabouch, n., fihri, wf. 2016. matched filter detection with dynamic threshold for cognitive radio networks. wireless networks and mobile communications (wincom), 2015 international conference on, ieee, oct 2015, 2015-1023, france. ff10.1109/wincom.2015.7381345ff. ffhal-01371162. santhanam, a. and keller, c. 2018. the role of data centers in advancing green it: a literature review. journal of soft computing and decision support systems, 5(1): 9–26. sobron, i., diniz, psr., martins, wa., velez, m. 2015. energy detection technique for adaptive spectrum sensing. ieee transactions on communications, 63(3): 617–627. doi: 10.1109/tcomm.2015.2394436. sun, h. 2011. compressed collaborative spectrum sensing in cognitive radio network. engineering thesis and dissertation collection, edinburgh research archive, university of edinburg. tsiaflakisa, p. yi, y., chiang, m., moonen, m. 2007. dynamic spectrum management for green dsl. available at: www.dslforum.org (citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.488.1537&rep=rep1&type=pdf) wang, c., song, t., wu, j., miao, l., hu, j. 2018. energy-efficient cooperative spectrum sensing for hybrid spectrum sharing cognitive radio networks. ieee wireless communications and networking conference, wcnc. ieee, 2018-april, pp. 1 – 6. doi: 10.1109/wcnc.2018.8377191. yan, q. and blum, rs. 2001. distributed signal detection under the neyman-pearson criterion. ieee transactions on information theory, 47(4): 1368 – 1377. doi: 10.1109/18.923720. https://www.era.lib.ed.ac.uk/handle/1842/3520 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.488.1537&rep=rep1&type=pdf http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1061-1066 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: bakura@unimaid.edu.ng 1061 original research article comparative analysis of received gsm signal strength network in university of maiduguri, borno state, nigeria a. o. adegoke*, m. u. m. bakura, i. mustapha and i. m. sani (department of electrical and electronics engineering, faculty of engineering, university of maiduguri, borno state, nigeria) * corresponding author’s email address: bakura@unimaid.edu.ng 1.0 introduction from time immemorial, information and communication have fashioned the basis of human existence. people want to communicate with their family and friends and to be communicated. this desire has been a driving force, inspiring people to continuously seek for a new and effective means of dissemination of information to one another on real time basis irrespective of distance. the development in technology ushered in this desire with advent of the first generation cellular telephone systems that enable people to communicate with one another irrespective of time and place. this first generation cellular telephone system, which was analog system, was launched in 1960s before digital communication became prevalent (hillebrand, 2001, popoola et al., 2009, codebreaker, 2011). the penetration of telecommunications has been found to have a significant positive impact on growth. mobile penetration in particular, being easier and cheaper to supply than fixed telephony, can be expected to play a crucial role in the economic growth of africa and other developing countries (sridhar, 2004). article information abstract gsm network in nigeria in recent times has been epileptic due to drop in signal strength, which causes customer dissatisfaction with the quality of service delivery by network operators. university of maiduguri has experience low signal quality in recent years due to frequent dropped calls, poor network interconnectivity, echoes and network congestion, therefore this work presents a detail analysis of the received gsm signal strength in university of maiduguri. an android application program known as network cell info lite was used for the measurement of signal strength for three different network in the university at random sampling points. the three network considered are: network a, network b and network c, in three different locations; academic area, student hostel and staff quarters within the university. the data collected were analyzed using spss statistical tool. the mean value of the signal strength received using the software application shows that network a with hspa -91.91db and gprs -73.59db is the best network in the academic area, network b with hspa 87.27db and gprs -73.43db has the best network quality in the staff quarters and network c with hspa -88.73db and gprs -69.85db is the best network in the student hostel, results above shows that the quality of signal strength depends on location within the university. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 07 may, 2018 revised 14 june, 2019 accepted 20 june, 2019 keywords: global system for mobile communication (gsm) general packet radio service (gprs) high speed packet access (hspa) enhanced data gsm evolution edge base trans receiver station (bst). mailto:bkumar52@hotmail.com http://www.azojete.com.ng adegoke et al: comparative analysis of received gsm signal strength network in university of maiduguri, borno state, nigeria. azojete, 15(4):1061-1066. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bakura@unimaid.edu.ng 1062 cellular phones have become an indispensable part of our everyday life. we continuously make use of them in voice calls, sending short message services (sms), sending e-mails, in ecommerce, e-banking, e-learning and watching movies. these cellular phones operate through cellular networks, which are responsible for generating and distributing of radio signals that are used by cellular phones over wide geographic areas (emeruwa, 2015). wireless mobile communication system has grown from the first generation (1g) of analogue system, through the second generation (2g) of digital system to the ever maturing third generation (3g) high speed multiple service system, the fourth generation (4g) long term evolution (lte) standard and has transformed the ease of communication (yong, 2006). however, the widespread use of mobile communications has heightened consumer demand for better quality service. thus, network operators the world over, face the challenges of improving the quality of service (qos) while increasing capacity and rolling out new services. the rollout of global system for mobile communication (gsm) services across nigeria has positively altered the socioeconomic landscape of the country and has brought huge revenues to the operators as well as the government through tax and license fees( popoola et al., 2009). gsm network in nigeria is currently faced with the challenges of customers’ dissatisfaction in the quality of service offered by the existing network operators due to frequent dropped calls, poor network interconnectivity, echoes and network congestion encountered (ogbutezie et al., 2013). similarly, the citizenries have benefited immensely from the services, not only as a means of communication but it has also provided job opportunities for thousands of people in the country. the objective of this study was therefore to determine the signal strength of three gsm service provides at different locations in the university of maiduguri. 2. materials and method 2.1 measurement equipment the measurement equipment used for this study are: techno y6 mobile phone network cell info lite subscriber identification module (sim) spss statistical software 2.2 method the study was divided into two phases. the first phase involved measurement of signal strength while the second phase was statistical data analysis base on phase one. an android software (network cell info lite) installed on a techno y6 mobile android phone was used to monitor the signal strength for the three leading mobile operators of gsm (network a, network b and network c). the signal strength generated for each of the mobile operators can easily be displayed. it is also important to note that the signal strength for each of the mobile network was recorded daily for a period of 60 days. three (3) locations which are the academic area (complex), university staff quarters and student hostel area respectively were observed. in each of the location, the signal strength (hspa and gprs) for each of the three leading gsm network were monitored at the same time http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1061-1066. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bakura@unimaid.edu.ng 1063 using the same mobile phone in the morning within the hours of 7am – 8am, in the afternoon 1pm – 2pm and in the night 7pm – 8pm with a distance of at least 100m given from the location measured the previous day. this was done from 3rd march, 2017 to 1st may, 2017. these signal values were then analyzed using spss to calculate the mean value of the signal strength of the networks, after which comparison of the signal strength for the various networks was done and line graphs were also used to compare and determine the network with the best signal strength within the university environment. 3. results and discussion table 1 shows average daily hpsa and gprs signal strength for the three networks. the results indicate that in academic area, network b has the highest signal strength for hspa with 86.21db followed by network c and network a with -89.58db and -91.91db respectively, while network c has the highest gprs network with -66.25db followed by network b and network a with -72.68db and -73.59db respectively. in the student hostel, network b has the highest signal strength with -80.97db followed by network a and glo with -87.15db and -88.73db respectively, while network b also has the highest gprs network with -67.84db followed by network a and network c with -68.52db and 69.85db respectively. in the staff quarters, network c has the highest signal strength with -83.65db followed by network a and network b with -86.75db and -87.27db respectively, and network c also has the highest gprs network with -67.51db followed by network b and network c with -73.43db and 73.53db respectively. table 1: average daily hspa and gprs signal for the three locations from (march to may) s/no location signal strength (db) network a network b network c hspa gprs hspa gprs hspa gprs 1 academic area -91.91 -73.59 -86.21 -72.68 -89.58 -66.25 2 student hostel -87.15 -68.52 -80.97 -67.84 -88.73 -69.85 3 staff quarters -86.75 -73.53 -87.27 73.43 -83.65 -67.51 mat lab simulation software is used to graphically compare the signal strengths of the three networks. figures 1 to 6 show the signal strengths (db) for both hspa and gprs signals of the three leading mobile networks, in the academic area, student hostel and staff quarters area of the university of maiduguri. figures 1 and 2 shows that network b has the best hspa signal and network c with the best gprs signal in the academic area. figure 3 and 4 shows that network b has the best hspa and gprs signal in the student hostel. figures 5 and 6 shows that network c has the best hspa and gprs signal in the staff quarters area of the university of maiduguri. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adegoke et al: comparative analysis of received gsm signal strength network in university of maiduguri, borno state, nigeria. azojete, 15(4):1061-1066. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bakura@unimaid.edu.ng 1064 figure 1: comparison of hspa signal strength for the three networks in academic area figure 2: gprs signal strength (db) against time (days) for the three networks in academic area figure 3: hspa signal strength (db) against time (days) for the three networks in student hostel http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1061-1066. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bakura@unimaid.edu.ng 1065 figure 4: gprs signal strength (db) against time (days) for the three networks in student hostel figure 5: hspa signal strength (db) against time (days) for the three networks in staff quarters figure 6: gprs signal strength (db) against time (days) for network a, network b and network c in staff quarters file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adegoke et al: comparative analysis of received gsm signal strength network in university of maiduguri, borno state, nigeria. azojete, 15(4):1061-1066. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bakura@unimaid.edu.ng 1066 4. conclusion in this study, signal strengths of three major gsm networks in nigeria were collected, analyzed and compared. the study revealed that signal strength from the three networks in university of maiduguri varies with locations and time. it is observed from the three network under consideration network a with hspa -91.91db and gprs -73.59db is the best network in the academic area, network b with hspa -87.27db and gprs -73.43db has the best network quality in the staff quarters and network c with hspa -88.73db and gprs -69.85db is the best network in the student hostel, results above shows that the quality of signal strength depends on location within the university. in choosing a network, the signal strength should be considered seriously since the quality of signal provided by a network is a function of the signal strength of that network. references emeruwa, c. 2015. comparative analysis of signal strength of some cellular networks in umauahia eastern nigeria. journal of electronics and communication engineering research, 2 (3): 122-133. famoriji, jo. and olasoji, yo. 2013. radio frequency propagation mechanisms and empirical models for hilly areas. canadian journal on electrical and electronics engineering, 4(2): 6570. helen, b. and fried h. 2001. gsm and umts: the creation of global mobile communications. john wiley and sons, pp. 590. karsten, nohl. 2011. why your phone is insecure by design forbes.com.http://www.forbes. com/sites/andygreenberg /2011/08/12/codebreakerkar mir, g., jun – ichi, t. and tetsuro, i. 2013. radio wave propagation through vegetation, wave propagation theories and application, retrieved january 16, 2013, from http:creativecommons.org/licenses/by/3.0. 155-175 ogbulezie, jc., onu, mu., ushibe, jo. and ushibe, be. 2013. propagation models for gsm 900 and 1800 mhz for port harcourt and enugu, nigeria. network and communication technologies, 2(2): 1-10. popoola, jj., megbowon, io. and adeloye, vsa. 2009. performance evaluation and improvement on quality of service of global system for mobile communications in nigeria. journal of information technology impact, 9: 91-106. sridhar, v. 2004. telecommunications infrastructure and economic growth: evidence from developing countries. journal of applied econometrics and international development, 7(2):91116 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):21-34 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 21 original research article applications of space technology for accelerated infrastructures development for rural areas development in nigeria s. o. onuh, s. y. aiyeola*, c. t. tofade and l. o. adesina centre for satellite technology development, national space research and development agency, obasanjo space centre, opposite pyakassa junction, airport road, abuja, fct, nigeria article information submitted: 03/01/2019 revised: 17/02/2019 accepted: 03/04/2019 abstract rural to urban migration still persists in nigeria despite government’s claim of rural development programs. this situation if not checked portends negative signal for the already overpopulated urban areas, particularly in areas of food security, sanitation, housing, crimes, etc. the development of rural areas is measured by the availability of infrastructures and economic opportunities that are available to the people. these infrastructures include: transportation infrastructure, educational infrastructure, healthcare infrastructure, energy infrastructure, water supply/sanitation infrastructure, information and communication technology (ict) infrastructure and so on. rural areas in nigeria urgently require accelerated infrastructure development to alleviate poverty. when this is done rapid growth is ensured and poverty is drastically reduced. the world today has become increasingly reliant on information and communication technologies (ict) and with it comes the need for societies and communities to stay connected and be integrated into the global information super highway. space technology today has also become an integral part of global information infrastructure, connecting people across the world and serving communications needs of governments, businesses and individuals. for nigeria to be technologically developed, the “digital divide” (that is the imbalance between urban and rural dwellers in which the rural dwellers have far lesser access to the same quality of knowledge), information, and education resources that are more readily available to urban areas because of the absence of required communication infrastructure need to be removed. the digital divide brings a virtual, but real impediment to the advancement of the society and individuals in remote rural settlements. this paper seeks to discuss the applications of space technology for accelerated rural infrastructures development in rural areas in nigeria © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction it is believed that the development and growth of the society inhabited by human depend to a large extent on the functionality, availability and sustainability of infrastructural facilities. a key parameter for measuring economic development is the sufficiency of infrastructure possessed by a nation. infrastructure means services that are accessible to the inhabitants of a society which http://www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 22 makes life worth living. generally, the term infrastructure refers to the physical structures installation and manpower established by a country to facilitate industrial, agriculture, maintenance of security, commercial production, and rendering of social services to a community. these include communication facilities, transportation infrastructure, utility supply (such as water and electricity), housing, education, and health care infrastructure (ezekwe, 1992). figure 1 depicts the infrastructures needed to make life meaningful for rural dwellers in nigeria. figure 1: types of infrastructure each of the infrastructures in figure 1 comprises many other sub-units. transport infrastructure for example comprises roads, ports, airport and railways, while education infrastructure includes structure required for managing schools, schools can be primary, secondary, and tertiary. also included in education infrastructure are facilities such as libraries, laboratories and the teachers. facilities needed for the production and distribution of electricity such as dams, substations, transmission and distribution lines make up power infrastructure. trained personnel, hospitals with necessary equipment, regulatory agencies, community health facilities and rescue teams make up the healthcare infrastructure. other infrastructures also have their components. infrastructure is the cornerstone of civilization. as the society and economic organizations become complex, the relevance of infrastructure grows (chidi and izuwah, 2017). despite nigeria’s economic success in the last decade, strong economic growth wasn’t followed by the required infrastructure investments and the country’s infrastructure stock is becoming inadequate to support its huge population and level of economic activities. 1.1 the needs for infrastructure in rural areas the success of agricultural and manufacturing activities is determined by infrastructure (world bank, 2015). the use of information and communication technologies extends the reach of education, promote growth, and advance cultural and social services. they also improve the delivery of health and other services. infrastructure helps in regional economic integration. the economic growth and success of us, south korea, singapore, and taiwan can be attributed to investments in social infrastructure such as transportation system, health, education and health. energy transport healthcare information water supply education communication infrastructure http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 23 investments in sanitation, water, housing, transport, and energy, and improve lives and reduce poverty availability of infrastructure ensures growth and development regular power supply or electricity is crucial for production units of any economy and it augments the production of goods and services a well-developed transport networks reduces the cost of bringing raw materials and farm produce from rural areas to other parts of a country countries with better infrastructure attract more foreign investments 1.1.1 transportation infrastructure transportation allows products, its use, and consumption to occur at different locations. it has been observed that transportation plays key roles in the economic, political, and social development of any country by providing means through which different parts of the country are brought together. this ensures the rural areas are not isolated from other parts of the country (aderamo and magaji, 2010). the absence of good transportation infrastructure in rural areas has led to low productivity, low standard of living, and low income for rural dwellers. it is evident that this situation would result to high level of poverty. good transportation system is known as enhancer of rapid marketing and industrialization in rural areas. this will enhance improved productivity through increase in export of processed goods from the small and medium companies. figure 2 depicts an example of transport infrastructure. figure 2: example of transportation infrastructure (chidi k. c. izuwah, snr. 2017) 1.1.2 healthcare infrastructure healthcare infrastructure can be understood in quantitative and qualitative terms as the quality of care and accessibility to healthcare facilities available in a country. healthcare infrastructure is judged by the quality of technological, physical and human resources available at a given time. physical part of it refers to the buildings and other fixed structures such as good access roads, pipes borne water, electricity and so on which are within the healthcare environments. the technology aspect has to do with the equipment that are used in hospitals (erinosho, 2006). the technology also includes consumables and computer equipment, while the human resource comprises the health professionals including the pharmacists, midwives, nurses, doctors, accountants, laboratory technologists and other sundry workers. healthcare delivery in any file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 24 country is anchored on all these components put together and they determine the healthcare infrastructure of a country (ademiluyi et al., 2009). healthcare infrastructure and human resources are depicted in figure 3 (thet khin, 2012). figure 3: healthcare infrastructure (thet khin, 2012). 1.1.3. information and communication technology (ict) infrastructure the world today is regarded as a global village and telecommunication plays key roles. it is an important infrastructure for social and economic development; and a major catalyst for information and knowledge that can create development opportunities for rural communities and helps to improve the living conditions of the rural poor. poverty is a problem in nigeria and the mostly affected are the rural dwellers. information communication technology (ict) is very crucial in reducing poverty. mobile telephone is an integral part of information communication technology and it has become ubiquitous and it is also an important medium of information dissemination of our time (ogunsola et al., 2015). ict has brought so many benefits to different aspects of human endeavor. development finds ict as the pivot around which it revolves. it makes available to the rural populace, up-to-date information on activities such as market locations, prices of goods at different markets, agricultural practices, and food processing techniques. ict is a tool for income growth and enhanced productivity and it invariably leads to poverty reduction (onwuemele, 2011). 1.1.3.1. ict for rural area development the use of ict in rural areas is often hampered by inadequate or non-existent infrastructure. however, if they are deployed, they can improve many aspects of rural life, providing people with better networking opportunities and facilitating access to outside expertise. ict also enables rural populations to open up new markets and gain access to digital services, such as credit insurance or crop failure insurance, or consult the latest weather report, making their agricultural activities both more productive and more secure. moreover, ict offers solutions for overcoming problematic access to educational and health services in rural areas. however, right from the outset, special care needs to be taken to ensure that proposed solutions are tailored to local conditions, for rural areas are often characterized by a lack of experience in the use of ict or existing services are not suited to the local language or specific cultural situation (onwuemele, 2011). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 25 1.1.3.2. ict for social security ict enable security systems to provide targeted assistance specifically tailored to the respective situation, providing decentralized, and therefore faster, access to data, and facilitating data transfers and analysis. thus, they not only increase the range of social services, but also create transparency and curb corruption. 1.1.3.3. application of ict in health sector e-health and telemedicine solutions offer numerous possibilities for improving medical care, even in rural areas. examples include experts who offer their know-how and carry out analyses remotely. however, in the health sector, more than any other, the necessary skills are vital, as they are the only way of gaining acceptance for and properly implementing new solutions (onwuemele, 2011). 1.1.3.4. ict for sustainable infrastructure icts can significantly help to make infrastructure more sustainable. for example, they can provide numerous ways of handling resources more responsibly in future and reducing damage to the environment, for instance through the use of intelligent electricity grids or more environmentally compatible production processes. smart cities use millions of sensors and all kinds of communication channels to manage traffic flows efficiently and thus reduce greenhouse gas emissions. icts are also indispensable for water management, being used to develop weather forecasting models, gather data on water resources and plan, administer and secure access to supplies to meet users’ needs. these kinds of infrastructure require special attention because they need to be fully secure to prevent any unauthorized access or manipulation by outside agents. at the same time, they must protect the data of anyone whose motion profiles are used to operate and improve systems. furthermore, sufficient capability must be made available for the monitoring and operation of such infrastructure (onwuemele, 2011). 1.1.4. educational infrastructure education is said to entail activities which promote learning, and it can be described as the process of providing necessary knowledge which is used as a tool for assisting and guiding human beings towards achieving desired life and self-rewarding life and also for the good of the society (idialu and idialu, 2012). unfortunately, one of the challenges facing education in nigeria today is the death or lack of infrastructure due to insufficient/poor funding. the country is faced with educational system that is bedeviled by some challenges which greatly impact on the outcome of its products. one of such challenges is inadequate funding which has effect on infrastructural development (omagu, 2016). the absence of quality infrastructure in our schools lowers the quality of education. yearly budgetary allocation to the sector may be grossly inadequate and it covers the primary, secondary, monotechnics, colleges of education, universities and polytechnics. it also caters for other aspects of the education regulating bodies such as the national universities commission (nuc), the universal basic education (ube), and national board for technical education (nbte) (odiba, 2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 26 1.1.4.1. effects of insufficient funding on infrastructural development in education sector in nigeria budgetary allocation for education is the amount of money set aside for its development (ijaiye and lawal, 2000). the main sources of revenue generation to fund education are derived from profits from exports and imports, taxes and duties on petroleum, and the centrally collected value added tax (vat). the derived revenue from these sources is inadequate to cater for education and other sectors of the economy. insufficient funding has been a major challenge for the education sector since independence. in fact, the yearly budgetary allocation and funding for educational institutions in nigeria falls far below the recommended 26% by unesco. this budgetary inadequacy has led the poor state of infrastructural facilities and teaching materials available in our schools. poor funding of the sector has also resulted into graduating poorly educated teachers and graduates, deteriorating facilities, battered classroom floors, leaking roofs, and window glasses replaced with wire gauze. this has resulted in poor state of infrastructural facilities and materials for teaching and learning. it has also resulted into an army of poorly educated school teachers and graduates in varied disciplines, deteriorating facilities, antiquated equipment, cracked walls, leaking roofs and windows with wire gauze in place of glasses (omagu, 2016). figure 4 shows an example of poor facilities in schools in nigeria (kolawole, y, 2018). figure 4: example of poor facilities in schools (kolawole, 2018) source: https://infoguidenigeria.com/problems-education-nigeria/ 2. space technology as an infrastructure for rural area development in nigeria over the past five decades, space technology has been regarded as either the dream and future of mankind or an endeavor of the cold war space race. neither of these views is relevant today. the essential role space serves today is that it is a critical infrastructure for the world. space is no longer the “big boys club”. today, about 60 countries own and operate at least one satellite, and almost everyone benefits from the services these satellites render. space technology has become an indispensable infrastructure on which everyone relies. space technology has the capabilities to provide information vital for the environment, education, food security, public health, water resource management, human rights, disaster relief and nuclear security. services derived from this technology not only improve the efficiency and effectiveness of many terrestrial activities but also provide much of the information and understanding needed to prevent and mitigate a variety of risks (kazuto, 2012). https://infoguidenigeria.com/problems-education-nigeria/ http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 27 space-based technologies are embraced in developing countries and some of the applications are rooted in education. this was not so in the past, as the technologies were considered ancillary tools for only wealthy nations. space technology includes the spacecraft otherwise known as satellite, space stations, other supporting infrastructure, equipment, and procedures. the development of space technology can play significant roles in the development of rural areas in nigeria (kazuto, 2012). the objective of this section is to elucidate the use of space technology as a vital infrastructure to develop and improve the life of rural inhabitants as it applies to tele-education, telemedicine and telecommunication. 2.1. space technology for tele-education in 1980 the u.s. agency for international development (aid) initiated the rural satellite program (rsp) to explore the potential of telecommunications as a means of extending scarce expert resources and expanding educational opportunities to remote and rural areas (shaw, 2005). there is no doubt that the world today has become increasingly dependent on information and communication technologies (ict) and with it comes the need for societies and communities to stay connected and be integrated into the global information super highway. communication satellites today have become an integral part of global information infrastructure, connecting people across the world and serving communications needs of individuals, businesses and governments. distance learning is a very useful and promising application of satellite-based technology. with this, high-quality educational institutes can share their resources with their counterparts that are underserved and this can be used to train the trainers. the train the trainer programme via space technology is to ensure that teachers in the remote/rural areas have access to the tools, curricula and the necessary assistance they need. tele-education concept is shown in figure 5 (onuh et al., 2019). the figure depicts the links from satellite, the teaching end, class rooms 1 and 2. the edusat is an example of satellites used for tele-education. it is a satellite owned by indian and it was launched to exclusively serve the educational sector in india. the tele-education network makes it possible for data to be transferred from the teaching end to remote classrooms. the data transferred include lecture notes, presentation materials, exercises, courseware, and other component needed to make learning effective (onuh et al., 2019). while some satellite applications that have been used to advance access to and quality of education in some countries are shown in table 1, which indicates all the educational activities that can be achieved through space technology such as examinations, communicating with teachers, accessing digital library resources, communication with pair learners, group work, receiving materials and sending assignments. from the table the possible ways of how space technology can help in achieving all these possibilities. for instance, examination can be conducted via internet access, one-and two-way interactive connectivity, and vsat network, while receiving of materials can be realized through internet access, one-and two-way interactivity, vsat network, and data broadcast. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 28 figure 5: tele-education concept (onuh et al., 2019) table 1: application of satellite in education educational activity internet access interactive television one-and twoway interactivity vsat network data broadcast broadcast examinations x x x communicating with teachers x x x x accessing digital library resources x x x communicating with pair learners x x x x group work x x x x receiving materials x x x x x sending assignments x x x 2.1.1. compositions of tele-education network the edusat, a satellite owned by india is an example of satellites used for tele-education. the satellite was launched to exclusively serve the educational sector in india. the tele-education network makes it possible for data to be transferred from the teaching end to remote classrooms. the data transferred include lecture notes, presentation materials, exercises, courseware, and other component needed to make learning effective (mamta and manoj, 2009). tele-education network comprises the following: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 29 satellite the satellite is the spacecraft launched for educational purposes. the satellite is used to provide virtual classroom concept to provide education to children and adults in rural and remote areas. this concept is also employed to offer quality higher education to students in areas without access to good technical institutes, and adult learning programs and training modules for teachers. the satellite could be equipped with c, ku, ka and other frequency-band transponders. teaching end the teaching end consists of an earth station and a small studio. in the studio, recorded and live lectures can be found and it is linked to the uplink earth station. the lectures, which are audio signals and visual images are transmitted to the spacecraft (satellite). the satellite beams the transmitted signal back to the earth spanning a large geographical area. the presentation pc, digital camera and dvd player are all attached to a switcher which is used to select the signal of interest among those from the presentation pc, digital camera and dvd player. the pc used by the presenter has a digital monitor that is used as a “white board”. the teacher can use digital pen to draw pictures and write texts on the white board and whatever the teacher writes at his end can be transmitted to the students end. a microphone is directly attached to server. the mixed output that is, the audio and video is sent to the modem through server. the modem then converts the digital inputs to analog and sends it to antenna using high quality cables. remote classrooms in the classrooms live lectures are received. we have two types of classrooms-non-interactive and interactive. at the location of the classrooms, receiving antennas are installed. the antenna installed at the non-interactive classroom has receive-only capability and the students can only interact with the resource person via a telephone line, internet and mobile phones. in the case of interactive classroom, the students can interact with the resource person at the teaching end using voice link via the satellite using an audio return channel (onuh et al., 2019). the use of satellite for tele-education is also illustrated using figure 6. figure 6: tele-education network (sohanvir and suresh, 2010) space-based learning programmes are cost-effective and independent of ground-based infrastructure. this technology is used to improve access to education everywhere in the world thereby bridging the gap between the sparsely and densely populated areas. this technology file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 30 has recorded tremendous success in some countries and it is still being embraced throughout the world. the following are some of the successes recorded (kazuto, 2012-2014): case study 1: brazilian education case study 2: china-using television for education case study 3: virtual university for africa case study 4: education in india called educat 2.2. space technology for telemedicine telemedicine is referred to as the delivery of healthcare services by healthcare professionals employing information and communication technologies for the transfer and exchange of relevant information required for prevention, diagnosis, and treatment of injuries and diseases, and for continually educating healthcare providers (carlo et al., 2016). innovative healthcare technology and delivery methods are required for the provision of high-quality healthcare for low density population areas. space technology provides such solution. space technologies have had tremendous impact in human health. space resources, such as gis and communication satellites make it possible to deliver remotely healthcare services to rural areas (kazuto s, 2015). telemedicine provided by satellites in space, scientific research, geographical information systems (gis), and space spin-offs are providing new ways to improve human health in rural areas. telemedicine is the use of two-way telecommunications technology, multimedia and computer networks that is used to enhance and deliver healthcare. space technology makes it possible for medical researches to be conducted. the microgravity environment available in space is an example of excellent laboratory. in space, microbes and cells behave differently, hence monitoring reaction and processes in space in the absence of gravity variable has the advantage of giving a better understanding of infectious diseases. rural areas lack adequate number of experienced doctors. space-based telemedicine can remove the healthcare divide between rural and urban dwellers (jabir, et al, 2009). connecting rural hospitals to the world medical centres requires the provision of high speed internet connection very small aperture terminal (vsat), fibre optics and so on to rural hospitals. the very small aperture terminal link may have the following hardware specifications: indoor unit: comprises of ip based satellite modem, and a personal computer outdoor units: comprises of radio frequency (rf) transmitter and a satellite dish antenna of required diameter depending on the operating frequency band and other hardware. there are two possible configurations for the vsat connection: a. point-to-point connection in this configuration, the vsat provides network connection between the server and the client computer and static ip addresses are assigned to the server and client computers. this configuration is depicted in figure 7: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 31 figure 7. point to point connection using vsat (onuh et al., 2019) b. point-to-multipoint connection in the point-to-multipoint configuration, the vsat provides internet connection for the pc with public ip address. this configuration has the advantage of connecting to any consultation hospital or specialist which are connected to the internet figure 8 is used to depict this configuration: figure 8: point to multipoint connection using vsat (onuh spencer ojogba et al, 2019) 2.3. space technology for telecommunication information sharing is one of the ways people interact. this is peculiar to both the rural and urban dwellers. information sharing is done using personal computers, mobile phones and other electronic communication devices. space-based technologies enables communication to be extended to rural area with the use of communications satellites, which makes global telecommunications possible by relaying signals in form of audio, video, and data to and from one or more locations. space-based technologies can reduce the cost of ground-based infrastructure requirements and even offer cost effective options for service delivery. for instance, installation of a large number of signal transmitting and relaying towers to broadcast file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 32 television programmes to distant locations may not be necessary when space-based communication is used. to achieve this, one satellite dish could be installed in a rural area to pick up the broadcast signal received from a satellite (un, 2012). example of communications using space-based technology is depicted in figure 9. communication is an important component and a driving force for rural development. it is used for bringing the much needed social and behavioral changes among the vulnerable rural society. communication via satellite is able to simultaneously reach a huge population, spread over long distances (nair, 2009). mobile market in recent time has experience huge growth across the globe. however, mobile service providers are finding it difficult to extend their services to rural areas due to the absence of infrastructure in these areas. while it is inefficient and impractical to terrestrially extend mobile services, the use of small cells and space technology offers cost-effective and quick solution to connect rural areas to mobile networks. mobile market has grown to the extent that subscription in cities are actually tapering off. mobile subscription in those areas is often more than 100% meaning that we have more subscriptions than people. but there is an aspect which remains untapped in the global mobile service market: the nearly two billion potential subscribers in rural areas, who are not within the coverage of the mobile network (gilat, 2015). we can bridge this gap by employing satellite technology to extend mobile services to rural areas. figure 9. space-based communication using mobile devices (un, 2012). 3. conclusions while this paper has focused primarily on infrastructural development, the need for infrastructures in rural areas in nigeria, the use of space technology as a critical infrastructure for these areas, the nigerian government too, has a role to play. it is observed that most of the firms in nigeria prefer the urban to rural area due to the presence of the required critical infrastructure and because the technical personnel and critical infrastructures for manufacturing and technological development are lacking in the rural areas. these infrastructures, even when available in the rural areas are not adequately maintained. there is an urgent need for the government to aggressively address this ugly situation. adequate infrastructure in rural areas will attract investors to those areas and rapid development will take place. furthermore, the inhabitants will be gainfully employed. to tackle the challenge of infrastructural deficit in nigeria, local, state and federal governments should prioritize funding of infrastructure by setting aside http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 33 substantial amount in their annual budgets for the provision, upgrading and maintenance of existing ones. government at all levels should promote private sector provision of services. private sector financing can be promoted by the government ensuring that: (i) a friendly legal environment is established which may include clearly assigned property rights, a framework for management of contracts, including means of recourse, (ii) removal of barriers/obstacles to market entry, and elimination of distortive grants for those services and goods and services capable of being financed by the private sector, and (iii) removal of physical and financial obstacles to private sector development, such as improving access to affordable credit, and improved access to basic facilities. references ademiluyi, ia. and aluko-arowolo, so. 2009. infrastructural distribution of healthcare services in nigeria: an overview. journal of geography and regional planning, 2(5): 104-110. aderamo, aj. and magaji, sa. 2010. rural transportation and the distribution of public facilities in nigeria: a case of edu local government area in kwara state. journal of human ecology, 29(3): 171-179. carlo, c., gabriele, p. and giuseppe, p. 2016. telemedicine for developing countries. applied clinical informatics, 7(4): 1-26. chidi, kc. and izuwah, s. 2017. infrastructure development as a panacea to national growth, being a paper presented by the ag. dg of icrc at the fellows investiture of the institute of directors nigeria, 1-114. erinosho, oa. 2006. health sociology for universities colleges and health related institutions. bulwark consult, abuja, ezekwe, g. 1992. engineering infrastructure: the missing link. first distinguished lecture in engineering and technology, university of lagos, lagos. gilat, 2015. extending mobile networks into rural areas via satellites. gilat satellite networks ltd, pp.1-13. idialu, ju. and idialu, e. e. 2012. entity, ownership, educational subsidies and funding of nigerian tertiary institutions. current research journal of social sciences, 4(1): 56-61. ijaiye, ma. and lawal, wa. 2000. education sector financing and government spending in nigeria: an investigation, ilorin. journal of business and social science, 11: 3-11. jabir, sa., osama, ah. and amer, n. 2009. design of telemedicine systems for rural and urban areas in iraq. asian research publishing network (arpn) journal of engineering and applied sciences, 4(2): 64-72. kolawole, y. 2018. fifteen problems of education in nigeria and possible solutions: available at: https://infoguidenigeria.com/problems-education-nigeria/ kazuto, s. 2015. bringing space down to earth: global agenda councils. a community of the world economic forum iii, 1-52. kazuto, sc. 2012. global agenda council on space security. global agenda councils. a community of the world economic forum i, 1-44. mamta, g. and manoj, k. 2009. edusat-e-learning through satellite-reaching the unreached. international journal of recent trends in engineering, 1: 1-3. https://infoguidenigeria.com/problems-education-nigeria/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuh, et al, applications of space technology for accelerated infrastructures development for rural areas development in nigeria.azojete, 15(sp.i2):21-34. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aiyeolasikiru@gmail.com 34 nair, gm. 2009. space technology applications for rural development in india. eighth bharat ratna rajiv gandhi memorial lecture, new delhi, india, 1-9. odiba, i. 2012. strategic planning as a tool for managing nigeria’s tertiary education for national. international journal of economic development research and investment, 3: 118-123. ogunsola, go., salman, kk. and popoola, oa. 2015. effect of telecommunication on poverty status of rural households in nigeria. global journal of human-social science: economics, 15(3): 1-9. omagu, fe. 2016. infrastructural development in nigeria: a panacea for transforming educational sector for sustainable national development. international journal of capacity building in education management (ijcbem), 3(1): 13-19. onuh, so., aiyeola, sy., tofade, ct. and adesina, lo. 2019. space technology, an essential infrastructure for rural area development. american journal of environmental and resource economics, 4(3): 25-31. onwuemele, a. 2011. impact of mobile phones on rural livelihoods assets in rural nigeria, a case study of ovia north east local government area. global journal of human-social science: economics, 9(2): 1-14. shaw, wd. 2005. distance education via satellite: a case study of the indonesian distance education satellite system. online journal of space communication, january, article 8. sohanvir, c. and suresh g. 2010. on using satellite-based networks for capacity building and education for all: a case study of rajiv gandhi project for edusat-supported elementary education. educational research and reviews, 5 (4):158-168. thet khin, pe. 2012, health infrastructure, an opening speech at 2012. world tb day commemoration ceremony, 1-29. united nations office of outer space affairs (unoosa), 2012. benefits of space: agriculture. available at: www.unoosa.org/oosa/en/benefits-of-space/agriculture.html http://www.unoosa.org/oosa/en/benefits-of-space/agriculture.html http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):919-928 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 919 original research article performance evaluation of tracking and non-tracking pv systems in scotland, uk f. m. kajiama1*, g.m. ngala1, m. abdulkadir2 and w. g. fruh3 (1department of mechanical engineering, university of maiduguri, p. m. b. 1069, maiduguri, nigeria 2department of electrical and electronics engineering, university of maiduguri, p. m. b. 1069, maiduguri, nigeria 3school of engineering and physical sciences heriot-watt university scotland uk) * corresponding author’s email address: timakaj@yahoo.com 1.0 introduction solar energy is an important component of renewable energy resources. edinburgh is a location that has variation in sunshine hours with high latitude; hence to capture solar radiation in the application of solar photovoltaic (pv) technology it is necessary to apply a technology that optimizes the solar resources in the location. solar tracking system is a suitable option that could be used in capturing both direct (beam) and diffuse radiation. this will enhance performance at low cost. a solar tracking system is a device which direct solar panels or modules toward the sun. these devices change their orientation throughout the day to follow the suns path to maximize energy capture. the work under study will be achieved by modelling the resource data (monthly and daily irradiation record) for higher power output during winter months, with the use of the tilt-angle solar pv tracker (solar power world, 2013). solar tracking increases the energy received by the photovoltaic modules which in turn increases the annual and daily power output, but its application will be more expensive and more complex than fixed mount. the solar tracking system will be cost effective in cases where there is sufficient output power throughout the year. the tracking system can be defined as a device which manoeuvres with respect to the movement of the sun. the device can decrease article information abstract solar energy is an important component of renewable energy resources. solar tracking system is a suitable option that could be used in capturing both direct (beam) and diffuse radiation. to investigate the performance of tracking and non-tracking pv systems, solar angles were estimated based on solar geometry and combined with global and direct radiation measurement covering a year. results showed that using horizontal fixed panels or tracking the sun about single axis was worst to boost the energy collection of the panels, while tracking the sun about two axes or using fixed but optimally tilted panels was found to be better and efficient. with an annual electricity of 67.3 and 66.3 kwh/h respectively and an improvement of 3.65 and 2.12%. this implies that fixed tilted panel will be suitable to be employed in the region with lower irradiance as edinburgh. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 october, 2018 revised 15 june, 2019 accepted 19 june, 2019 keywords: non-tracking panels tracked panels global radiation direct radiation. http://www.azojete.com.ng kajiama et al: performance evaluation of tracking and non-tracking pv systems in scotland, uk. azojete, 15(4):919928. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 920 the angle of incidence of the radiation beam on its surface by rotating on its axis which in turn increases the direct radiation acting on its surface. solar tracking device can be classified according to its rotation as a single axis or two (dual) axis tracking. single axis tracking device follows the direction of the sun either across east to west in the sky or up and down while two axis tracking device follows the sun from east to west and it tilts the modules with respect to movement of the sun. (solar power world,2013). both devices are being investigated in this study, they are said to operate with electrical/thermal power gain of about 20-40% higher than fixed panel (ryan, 2010). there is not any trading importance for both direct and diffuse radiation, because edinburgh lies in higher latitude it’s always cloudy and rainy. standard photovoltaic are used in this study because they are not expensive, and simple to use. they have the added advantage of using both component of irradiation that is diffuse and direct radiation. when tracking is introduced it decreases incident angle to the direct radiation and increases energy production. photovoltaic modules received maximum radiation when the sun strikes on it at right angle. when tilted to the sun, the collection of energy by the module becomes lower, and therefore optimal installation of fixed or single-axis devices depends on latitude of the site. the collected energy not only depends on the panel’s angle to the sun, which depends on latitude, day of year and time of day, but also on local weather conditions, clouds. it is therefore important to use local radiation information to assess the expected amount of energy collected in a year (duffie and beckman,2013). areas with higher radiation data tend to have 30% increase with single axis tracking while 20% increase was observed in areas with lower radiation data when compared to fixed photovoltaic module. shadow geometry in azimuth tracking was used in his photovoltaic plant design (lorenzo et al, 2002). percentage increase in mean surface irradiance due to tracking for 18 temperate sites was reported (nann, 1990) and 34% average increase in irradiance resulted by using single axis instead of fixed panels with mean irradiance of 29 to 37% while 39% increase in average with two axis tracking is capable of increasing the mean irradiance from 33 to 42% than fixed panel. therefore, transferring from single to dual will result to irradiance mean increase of about 3 to 7%. the main purpose of this study is to model and simulate the behaviour, define and compare the performance of a horizontally fixed photovoltaic panel, a single-axis tracking pv panel and a twoaxis tracking pv panel system. it also intends to evaluate the performance of tracking and non-tracking pv systems in scotland choosing edinburgh as the location based on hourly global horizontal radiation data. the outcome would enable renewable energy planners to determine which of the solar technologies is most suitable to be implemented in edinburgh. successful installation of such a renewable technology would assist in meeting the growing energy demands of the country and in the reduction of environmental problems associated with the use of fossil fuel such as green house gases (ghg) whilst promoting the use of renewable energy. in order to reduce the electricity cost generated, a configuration of three tracking modes namely seasonal, one axis n-s tracking and diurnal tracking are incorporated into the system. more than 120%of electrical energy was achieved by fixed panels with an azimuth tracking in damascus, syria (al-mohamad, 2004). another theoretical analysis (chang, 2009b) on gain of isna (inclined south north single axis) based on extra-terrestrial radiation for different latitudes http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 919-928. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 921 and period of time for areas having latitude lower than 65 with tracking panels showed the ratio of collectible annual radiation than fixed panel to be approximately 1.5, this is said to increase gradually for latitudes with a higher value of about 1.8 in arctic zone. in taiwan, (chang, 2009c) discovered a 3.1% increase in annual energy capture for a month by using tilted angle photovoltaic panel over the single axis tracking. horizontal east west axis tracking panels were said to be lower than that of inclined south north single axis (isna) tracking panel when radiation was collected annually (chang, 2009b). applying single axis tracking system to fixed panels (chang, 2009a) observed that using single axis tracking in taiwan for assessing photovoltaic performance; an improvement of 19% was achieved. chang (2009c) also predicted that single axis tracking with an optimized inclination rotational axis is said to experience about 50% higher irradiance than fixed panel but at latitude lower than 65°. identical panels in germany were tested side by side and higher energy of about 118% and 130% was obtained with one axis azimuth tracking and dual axis tracking panels, respectively, than fixed slope panels (helwa et al., 2000). for some days, with north south tracking system showed a gain of 30 to 45% higher in power output than fixed photovoltaic module. in the same period 50% gain in solar energy was found by orienting horizontal module to two axes tracking in a cloudy day (kelly et al., 2009). a study carried out by lubitz (2011) shows that tilting an azimuth tracker between two and twelve times per year manually produces better gain in irradiation than fixed, south facing panel. lubitz (2011) also found that at optimum tilt angle, converting due south fixed panels with azimuth single axis tracking will yield higher gain. an investigation on optical performance of inclined south north single axis tracking photovoltaic modules, estimated mathematically the annual collectible radiation on fixed and tracked modules and found out a tracking system is more efficient than fixed panel (li et al., 2010). 2. material and methods 2.1 solar angles in order to be able to track the pv panel one must know the exact direction of the sun ray. this can be obtained by sun path: the equatorial or global system and the azimuthal or local system. azimuthal system makes use of altitude (α) and azimuth angle )as shown in figure 1, while equatorial system uses declination (δ) and hour angle (w) as shown in figure 2. figure1: sun position in the sky is typically given as an azimuth and altitude angle. (solar position,1994-2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al: performance evaluation of tracking and non-tracking pv systems in scotland, uk. azojete, 15(4):919928. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 922 figure 2: solar angles ( ), declination (δ), hour angle ( ), altitude (α), azimuth ( ), and zenith (z). the formulas below where source from (duffie and beckman, 2013) the azimuth angle, , can be expressed as; ( ) = cos-1(sin α * sin φ – sin δ/cos α * cos φ) (1) the altitude or (elevation) angle, α can also be expressed as; α= sin-1 (sin δsin θ+ cos δ cos θcos (hra)) and α = 90-θ (2) the equatorial system has the following expression; declination :( duffie and beckman, 2013) δ = 23.45◦ sin 360◦ (n – 80) /36 (3) hour angle; w: = 15◦ (12 – t) (4) the constant angles defining the orientation and location of the tilted plane: ϒ, solar azimuthally angle. solar azimuth angle ( ) is defined as the horizontal angle which is measured from south in the northern hemisphere to the horizontal projection of the sun rays (duffie and beckman, 2004). n is the time of year δ, declination (δ) angle is the angle between the line joining the sun and the earth and its projection on the equatorial plane. declination angle is zero at the venal (20/21 march) and autumnal (22/23 september) positions. w, hour angle w is the angle between the meridians passing through the sun and the meridian of the site. hour angle is zero at solar noon and increases toward the east. (markvart, 1996). φ, latitude φ is defined as the number of degrees north or south of the equator. or the angle made by the radial line joining the location to the centre of the earth with the projection of the line on the equatorial plane, rotating axis of the earth intersect the surface of the earth at 90° latitude (north pole) and −90° latitude (south pole). each location on the earth surface can be found by intersection of longitude and latitude angle. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 919-928. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 923 solar altitude angle refers to how high in the sky the sun is. it is described in terms of solar zenith angle which is the vertical angle between the sun rays and a line perpendicular to the horizontal plane through the point (θz = 90 α).equation (3) and (4) are used in equatorial system, whereas (1) and (2) are used in azimuthal system. an important formula which indicates the hour angle, at which the sun rises and set, was depending on the latitude and season (agee et al., 2007); wsr, ss =+ or – cos-1(−tan φ tan δ). (5) in most renewable energy projects, it is very important to know how long it will take for the investment to pay for itself. this is why payback period will be calculated. with the following advantages: a longer payback period indicates capital is tied up. focus on early payback can enhance liquidity. investment risk can be assessed through payback method. payback period = installation cost savings cost−maintenance cost 2.2 methodology the methodology developed to complete the project is based on the following: latitude, longitude, time zone, local time (hours and year). the location was used for the computation of solar angles at different hours of the day for each month. the hourly global radiation and the daily ‘synoptic’ direct and global radiation for edinburgh for the year 20102011 were obtained from the united kingdom met. office through the british atmospheric data centre (midas, 2012) and is expressed in kwh/m2. for fixed horizontal photovoltaic panel the tilt angle is zero. incidence angle θwas calculated using the equation below. cos θ = sin α (6). where: θ= incidence angle α = elevation angle an excel spreadsheet was used to calculate incidence angles for varying elevation angles. for tilted surfaces facing south the angle of incidence was calculated using the equation below: cos θ = sin α cos β – cos α sin β cos a (7) where: α = elevation angle (degrees) β = tilt or slope (degrees), = azimuth angle (degrees). an excel spreadsheet was used to calculate incidence angles for varying elevation angles of tilted surfaces facing south. from synoptic radiation, the daily direct radiation and daily global radiation for each month at a specific date of the year was deduced respectively. the ratio of the direct to the global radiation is shown in figure 3. this shows that the direct radiation is only a few percent of the global radiation in the summer but was much higher in some winter months, typically around 20% between november and february, with an unusually sunny december in edinburgh. to split hourly global into direct radiation and diffuse radiation at different hours of the day for each month the following equations were used to calculate direct radiation and diffuse radiation respectively. direct = global radiation * ratio diffuse = global radiation *(1-ratio) (8) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al: performance evaluation of tracking and non-tracking pv systems in scotland, uk. azojete, 15(4):919928. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 924 global radiation was obtained from met office data. knowledge of view factor is important in estimating the solar radiation incident on the surface of a collector. and view factor was calculated for fixed horizontal pv system using the formula below. view factor = cos (incidence angle) (9) view factor for tilted surfaces was calculated using the formula below view factor = cos (incidence angle) (10) the radiation captured by the collector or received radiation was calculated using the equation below; received radiation = view factor * direct radiation diffuse radiation. performance curve was determined from the generic example in twidell and weir (pg., 222 i-v characteristic). this is because pv modules create a flow of current that’s described as direct current (dc) because the electrons move in just one direction. as sunlight strikes the pv cells, the electrons move off the cells and through a load (any piece of electrical equipment) before heading back to the cells, all while staying in a straight line. the power was calculated using the equation below, as p = iv (11) where: i=current (ampere) and v=voltage (volt). a straight-line graph was obtained with a slope of 0.068 0.0004 3. result and discussions 3.1 fixed horizontal panel as the view factor for fixed horizontal panel is shown in figure 3. the view factor for two-axis tracking is always equal to one; both single axis and fixed panel has a view factor of cosine of incidence angle, summer month (may to sept. 2012) has a higher view factor than winter month (nov. to jan. 2012) as seen in the graph, with the resulting electricity generated as shown in figure 4 figure 3: view factor for fixed horizontal panel http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 919-928. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 925 figure 4: daily electricity generated from fixed horizontal panel (kwh) 3.2 view factor for other panels optimum tilt pv panels makes almost identical in summer and winter month but single horizontal axis tracking panel did not achieved that whereas two axes tracking always has a view factor of one as shown in figure 5. figure 5: graph of view factor from the five systems 3.3 electricity production results obtained by simulation in this work are shown in tables 1 and 2. it is seen that two axis sun tracking system generate 54.03% more electricity than the fixed tilt, single axis tracking and horizontal fixed pv panel, with a clear weather ht = 7.95 kwh/m2 day in july 24, 2011 which is much higher than single axis tracking and horizontal fixed pv panel which generates about the same amount of electricity annually. the simulation result shows that the highest daily electricity generated from horizontal fixed pv panel is 53.612% on july 24, 2011, with a total daily received radiation ht = 7.88412 kwh/m2 (warmest month with an average temperature of over 20 °c ) and 31.2423% on may 21,2011, with total daily received radiation ht = 4.59445 kwh/m2 (partly cloudy). in general, the power generation of horizontal fixed pv panel usually increases much more on clear weather. but in some partly cloudy days, the increase in power generation will still be obvious which may be due to the variation of diffuse radiation from ground, sky or cloud. the monthly result also shows that the increase in power generation from the system is around 16.61972 kwh and 9.685111 kwh respectively which is from a period of july and may with an annual output of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al: performance evaluation of tracking and non-tracking pv systems in scotland, uk. azojete, 15(4):919928. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 926 64.94633 kwh/h. which can represent the typical summer weather in edinburgh but also there are many daily performance in august, september and june which also represent the weather in summer. with respect to single axis tracking the simulation results indicates that the electricity generated will be higher or larger in areas with abundant solar energy resource (that is high ht). then the present daily generated power result (51.3849%) which was made in edinburgh with low solar energy resource with an annual output of 65.01102 kwh. 3.65% improvement was also obtained by two axis sun tracking system and an improvement of 2.12% from fixed tilt pv panel table 1: annual electricity generation for the five systems system horizont al fixed panel fixed tilted panel horizontal single axis tracking vertical single axis tracking two axis tracking annual electricity 64.9 66.3 65.0 63.2 67.3 table 2: monthly daily electricity for five pv systems, kwh. month horizontal fixed fixed tilted horizontal single axis vertical single axis tracking two axis tracking jan 2.55 2.76 2.62 2.51 2.83 feb 1.44 1.59 1.53 1.32 1.66 mar 7.17 7.28 7.26 6.98 7.36 apr 7.28 7.34 7.37 7.16 7.43 may 9.68 9.70 9.76 9.51 9.79 jun 5.73 5.75 5.64 5.49 5.81 jul 16.61 16.63 15.92 16.36 16.74 aug 5.99 6.06 6.07 5.75 6.13 sep 4.12 4.22 4.25 4.00 4.32 oct 2.70 2.86 2.78 2.62 2.93 nov 1.47 1.67 1.54 1.37 1.75 dec 0.15 0.40 0.22 0.17 0.49 3.4 cost benefit analysis / pay back periods for the systems the following price per kw was assumed for nontracking system calculations. installation cost of non-tracking is (£500.00 per 1kw of 1 m2 area) (pv panel guide, 2011). cost of maintenance £30.00 per year. savings £77.00 per year calculated from percentage improvement (using an electricity price of 13.95p per kwh) using the formula below; therefore; payback period = 10 years assumptions; the following price per kw was assumed for tracking system calculations installation cost for tracking is (£4,000 per 1kw of 1 m2 area) of 1 m2 area (energy saving trust, 2012, eco experts, 2007). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 919-928. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 927 cost of maintenance £50.00 per year. savings £78.00 per year it is also calculated from the improvement using same electricity price as the non-tracking system. payback period = 14 years 2 4. conclusions these results indicated that two axis sun tracking was an effective technique to boost the radiation collected by solar panel which always points the panel directly to the sun. the only difference in performance of the photovoltaic system in summer and winter is the module temperature which is said to be lower in winter. the result shows that single axis sun tracking will not be of important to the location (edinburgh). the present simulation result shows that tracking pv panel will only be useful in areas with high solar energy resource and the cost is much more expensive as compared to conventional pv panel. it is concluded that fixed tilted panel will be suitable to the people in edinburgh because two axis tracking manoeuvres with respect to the movement of the sun, horizontal fixed panel can’t capture enough energy therefore, fixed tilt will be the best for the location (edinburgh) according to my simulation result. as shown in figure 4 and 5 respectively. references agee, jt., obok-opok, a. and lazzer, md. 2007. solar tracker technologies: market trends and field applications. advanced material research, 19: 339-344. al-mohamad, a. 2004. efficiency improvements of photovoltaic panels using a suntracking system. applied energy, 79: 345-354. british atmospheric data centre. 2012. global radiation observation. met officemidas land surface station data, edinburgh http://badc.nerc.ac.uk/data/ukmo-midas. (accessed 20thjune, 2012). chang, tp. 2009a. performance study on the east-west oriented single-axis tracked panel. energy, 34 (10): 1530-1538. chang, tp. 2009b. the gain of single axis tracked panel according to extra-terrestrial radiation. applied energy, 86: 1074-1079. chang, tp. 2009c. output energy of a photovoltaic module mounted on a single axis tracking system. applied energy, 86: 2071-2078. duffie, ja., and beckman, wa. 2004. solar engineering of thermal processes. 3rd ed. john wiley and sons canada, pp. 56-63. duffie, ja. and beckman, wa. 2013. solar engineering of thermal processes. 4th ed. john wiley and sons canada, pp. 38-40. energysavingtrust. 2012. costs, savings and maintenance. [online] available at: http://www.energysavingtrust.org.uk [ accessed 9, august 2012]. helwa, n., bahgat, a. and el shafee, a. 2000. maximum collectible solar energy by different tracking systems. energy sources, 22: 2334. http://badc.nerc.ac.uk/data/ukmo-midas http://www.energysavingtrust.org.uk file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al: performance evaluation of tracking and non-tracking pv systems in scotland, uk. azojete, 15(4):919928. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 928 kelly, n., gibson, a. and thomas, l. 2009. improved photovoltaic energy output for cloudy conditions with a solar tracking system. solar energy, 83: 2092-2102. li, z., liu, x. and tang, r. 2010. optical performance of inclined south-north single –axis tracked solar panels. energy, 35: 2511-2516. lorenzo, e., perez, m., ezpeleta, a. and acedo, j. 2002. design of tracking photovoltaic systems with a single vertical axis progress in photovoltaics. research and applications, 10(8): 533-543. lubitz, wd. 2011. effect of manual tilt adjustments on incident irradiance on fixed and tracking solar panels. applied energy, 88: 17101719. markvart, t. 1996. solar electricity. 2ndedition.john wiley and sons inc. new york: pp170-178. nann, s. 1990. potentials for tracking photovoltaic systems and v-troughs in moderate climates. solar energy, 45(6): 385-393. mayfield, r. 2010. photovoltaic design and installation for dummies. wiley publishing inc. canada: pp36-78. the pv panel guide. 2011. costs of pv solar panel installation. [online] available at: http://www.pvpanelguide.co.uk [ accessed 9 august 2012]. the eco experts. 2007. solar tracker cost, dual axis and single axis. [online] available at:<http://www.theecoexperts.co.uk> [accessed 20 august 2012] http://www.pvpanelguide.co.uk http://www.theecoexperts.co.uk http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):304-313 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 304 original research article effects of pid controller on performance of dish antenna position control for distributed mobile telemedicine nodes a. t. ajiboye*, a. r. ajayi and s. l. ayinla (department of computer engineering, university of ilorin, ilorin, nigeria) *corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng, atajiboye@yahoo.co.uk article information submitted 10 june, 2018 revised 25 may, 2019 accepted 10 june, 2019 keywords: mobile telemedicine node nigcomsat-1r pid controller time delay position control abstract introduction of telemedicine into developing nation’s healthcare delivery scheme could be a solution to a number of challenges facing the scheme including acute shortage of medical personnel. because of distribution and mobility nature of the system combined with nigeria’s large land mass, the resulting propagation delay will be large which may lead to system poor quality of performance or instability if the system is not compensated. this study aimed at assessing the effects of introducing proportional-integral-derivative (pid) controller into the control of the position of dish antenna mounted on distributed mobile telemedicine nodes within nigeria when the link is via nigcomsat-1r. the system closed loop composite transfer function was obtained and subjected to unit step forcing function which then yielded time domain parameters. there was reduction in the value of system time domain parameters obtained for pid controller compensated system compared to uncompensated system. based on the value of the system time domain parameters obtained from the simulation, introduction of pid controller into this system has improved the system response significantly. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction telemedicine is the provision of healthcare delivery and sharing of medical knowledge over a distance using information and communication technology (ict) (kakkar et al., 2017; saravanan and sudhakar, 2017; anyaegbunam, 2014). it is one of the pilot projects of nigcomsat-1 to improve remote diagnosis and to deliver cost effective and qualitative healthcare in nigeria (anyaegbunam, 2014). the major objective of mobile telemedicine is to improve the quality and timeliness of healthcare delivery offered during the golden window of treatment opportunity immediately following injury, and to provide better information to health personnel just before physical presence of the patient at the health centre (cullen et al., 1999). integration of information and communication technology into healthcare delivery is making it more affordable and available even in rural areas without sacrificing the quality of delivery as obtainable in urban cities (ibiyemi and ajiboye, 2012a). investing in the development of telemedicine technology if properly managed can serve as a way to alleviate the effects of acute shortage of medical personnel and low level of healthcare delivery in developing countries in mailto:ajiboye.at@unilorin.edu.ng mailto:atajiboye@yahoo.co.uk http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):304-313. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 305 general and nigeria in particular. the medical information sent or received by the telemedicine nodes are usually through the dish antenna at the node. the quality of performance of any satellite tracking mobile dish antenna depends majorly on how effective the antenna position can be controlled. many methods and approaches for dish antenna position control have been reported in the literature. in (waghmare et al., 2017; maske et al., 2017; chahar et al., 2016) satellite dish positioning system was designed to track geostationary satellite; the design was implemented using microcontroller. although the system can be remotely controlled but there was limitation imposed by the distance the signal from the remote controller can cover as the transmission was by infrared signal. many control system fundamentals like the plant model, controller algorithm were not considered because the control methodology employed was bang-bang control. similar satellite dish position control system was designed by (shubham et al., 2017), but in this case the reference position which has already been stored was sent remotely to the microcontroller via infrared signal. the interpretation of the sent position allows the system to locate the satellite of interest whose position has been sent. the system can only be used for a predetermined satellite and the distance covered by the remote control signal was limited as infrared signal was used. a microcontroller-based dish antenna positioning system was developed by (rahane et al., 2018), in this system the reference input was dedicated to satellite identification. since a given satellite which has been specified by its unique identity through the reference input was the target, any small out of sight from this satellite amount to an error which serve as input to the controller. the controller power the dc motor that rotate the satellite and the motor continue to rotate the dish until when the targeted satellite was tracked. this system operates on the strength of the radiated signal from the satellite not satellite position, therefore weather condition can have serious effects on the performance. a microcontroller-based dish antenna position control system was developed in (amritha et al., 2017), the information about the satellite to be tracked was sent using an android phone, and then decoded by raspberry pi before being sent to the microcontroller as reference input. based on this information the controller sends control signal to the servomotor to dictate the direction of rotation of the dish antenna and when the desired antenna position was reached the controller stops the motor and the dish tracks the satellite in question. it has enormous time delay which is capable of degrading the system quality of performance or even in the worst case scenario destabilises the system. microcontroller-based automatic antenna position control system whose operation was solely dependent on the strength of the signal received `from the targeted satellite was developed by (choudhary et al., 2014). when the signal from the targeted satellite was received by the antenna it passes through a monostable circuit and the output of the monostable gives a logic 1 if the signal was higher than a particular threshold and logic 0 if lower. the logic output serves as reference input to the microcontroller which initiates the rotation of the antenna by powering the driving motor when the logic was at level 1 and stop the rotation when the logic was at level 0. the angular position of the antenna with respect to a given reference was also sensed, processed by the microcontroller and displayed. the results from laboratory simulation using infrared signal shows that the system was feasible for real live implementation when the signal transmission distance was improved and the control can be carried out in two plane instead of the present one plane. antenna azimuth angle control system using microcontrollerbased rate corrected method was developed and implemented by (mullaa and vasambekarb, 2017). in this system, the speed of the antenna driven motor (stepper motor) was controlled by file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng ajiboye, et al: effects of pid controller on performance of dish antenna position control for distrbuted mobile telemedicine nodes. azojete, 15(2):304-313. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 306 the output of the microcontroller. therefore, for fast positioning, high rotational speed and acceleration are required. the speed of the motor depends on the delay in the step sequence which was calculated using the speed rate corrected method. the results obtained from the laboratory tests shows improvement in the system response speed. aloo et al (2016) designed a hybrid of pid and lqr controller for dc servomotor-based antenna positioning system. the results of system performance evaluation carried out via simulation using matlab shows that the classical pid controller compensated system has lower rise time but higher overshoot and settling time compared with the hybrid pid-lqr controller compensated system. a pid controller designed using ziegler-nichols method and a separate controller designed using quadratic optimal regulator (qor) approach by (ahmad et al., 2011) were tested via simulation on a modelled servomotor actuated parabolic dish antenna to control the antenna position. the system closed loop step response without controller; with the pid controller and with qor controller was simulated respectively using matlab 7.1. the results show improvement in system performance when controller was incorporated with qor controller compensated system having the best response. ahmed et al., (2014) designed a quadratic optima regulator (qor) and incorporated it into the position control system of parabolic antenna dish, the response of the system with and without controller to unit step input were simulated using matlab, the value of the system time domain performance parameters obtained reveal that the response of the compensated system was superior to that of uncompensated system. a proportional-integral position controller for a parabolic satellite antenna used in tracking the precise location of a moving ship was designed by (kim et al.,2013); the controller was designed for both the antenna azimuth and elevation. as the ship pitch, roll and yaw varies, gyro sensor was incorporated to monitor these variables and the controller sees the gyro sensor output as disturbances and handled as such. the reference input was the predetermined signal strength from the satellite that links the antenna to the ship position monitoring room. the time domain performance parameters obtained from the system step response indicate the effectiveness of the system. classical and discrete pid controller was designed by (yadav and sharma, 2016) for controlling of elevation position of a giant meter wave radio telescope. the performance of this designed controller was evaluated from system step response; the result shows that the discrete pid controller has superior performance. in this study, the link between the base station which is the system controller and the distributed mobile node of dish antenna which is the plant is via nigerian’s communication satellite (nigcomsat-1r) which is located in itu region1 at 42.5° east, therefore the transmitted signal will encounter propagation delay which is a function of the distance between the base station and the distributed nodes. considering the nigeria’s large land mass of about 923,677 sq km and mobility nature of the distributed nodes, the propagation delay will be large and variable which led to system poor quality of performance or instability in the worst case if no controller is introduced (ajiboye, 2012, ibiyemi and ajiboye, 2012a). the aim of this study is to assess the effects of introducing pid controller into the control of the position of satellite dish mounted on distributed mobile telemedicine nodes within nigeria when the link is via nigcomsat-1r. pid controller algorithm was proposed for the control and command in this study because of its structural simplicity, easy to tune and industrial popularity (farhan, 2013; farhan et al., 2017). more than 90% of all control loops are pid, therefore, pid is the first solution that should be http://www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):304-313. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 307 tried when feedback is to be used (åström and hägglund, 2001). in other to achieve the aim of this study, the delay was modelled and simulated to get the propagation delay transfer function. the closed loop composite transfer function was determined from the controller, delay and plant transfer functions. the system closed loop transfer function was subjected to unity step forcing function to obtain the system time-domain performance parameters. 2.0 determination of time delay range the geographical coordinates of nigeria are between longitude 2°43.207'e and 14°54.685'e and latitude 4°17.825'n and 13°52.837'n. the base station is at university of ilorin which is located at 4°40.500'e, 8°29.100'n and the dish mounted telemedicine nodes are distributed all over nigeria as shown in figure 1. the location and geographical coordinates of points a, b, c and d presented in figure 1 are as follows: point a is located at niger republic and its coordinate is 2°43.207'e, 13°52.837'n; point b is located at lake chad and its coordinate is 14°54.685'e, 13°52.837'n; point c is located at gulf of guinea and its coordinate is 2°43.207'e, 4°17.825'n and finally point d is located at cameroon and its coordinate is 14°54.685'e, 4°17.825'n. the subsatellite point for nigcomsat-1r satellite is at 42.5°e, 0°. figure 1: nigeria geographical map showing distribution of telemedicine nodes (ibiyemi and ajiboye, 2012a) the parameters needed for the determination of time delay are the distance between the base station and mobile telemedicine nodes and the signal speed. the equation for the determination of the distance between any two points on the earth surface via any geostationary satellite is as given in equation (1) (ibiyemi and ajiboye, 2012a; ibiyemi and ajiboye, 2012b; ibiyemi and ajiboye, 2012c). dsr = d2 + r2 − 2drcos αsn cos ∆sn − ∆s + d2 + r2 − 2drcos αrn cos ∆rn − ∆s (1) where: dsr= distance between the source and the receiving node, r = radius of the earth in km, d = sum of the radius of the earth and satellite altitude in km, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng ajiboye, et al: effects of pid controller on performance of dish antenna position control for distrbuted mobile telemedicine nodes. azojete, 15(2):304-313. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 308 ∆s = angle of longitude of the subsatellite point in degrees, αsn = latitude of the sending node location on the earth surface in degrees, αrn = latitude of the receiving node location on the earth surface in degrees, ∆sn = angle of longitude of the sending node location on the earth surface in degrees and ∆rn = angle of longitude of the receiving node location on the earth surface in degrees. therefore, the model equation for the time delay encountered in sending signal between these two points was obtained by dividing the distance by the signal speed and is as shown in equation (2). t = dsr v (2) where: t = time delay in seconds and v = signal speed in m/s 3.0 determination of system transfer function the plant transfer function was determined from the dish structure and jack actuator dynamics model. the determination of the dish dynamics was based on the moment of inertia of the dish structure (satellite dish and buc/lnb), spring constant, and damping coefficient. these parameters were determined by experiment because their value cannot be read off the plant at the node (ibiyemi and ajiboye, 2012b). due to the same reason the actuator jack dynamics was also empirically determined. the system can be represented by the block diagram of figure 2. figure 2: block diagram of the composite system from figure 2, the transfer functions for the uncompensated and compensated systems are as shown in equations (3) and (4) respectively. θa s θr s = gp s gd1 s 1+gp s gd1 s gd2 s (3) where: θa s = dish actual position in degree, θr s = dish reference position in degree, gd1 s = forward path time-delay transfer function, gp s = plant transfer function and ��(s) gp(s)gd1(s)gc(s) ��(s) θm(s) gd2(s) + http://www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):304-313. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 309 gd2 s = feedback time delay transfer function. θa s θr s = gc s gp s gd1 s 1+gc s gp s gd1 s gd2 s (4) where: gc s = pid controller transfer function. the plant transfer function is made up of the transfer function of the dish structure, and actuator jack and is as expressed in equation (5): gp s = 3.76 s4+67.56s3+62.36s2+150.52s (5) the transfer function for the forward and feedback path time delay is as expressed in equation (6). gd1 s = e− t1s gd2 s = e− t2s (6) where: t1 = feed forward delay from base station to the node in seconds and t2 = feedback delay from the node to base station in seconds. assuming that t1= t2 = t, then from equation (6) gd1 s = gd2 s = gd s = e−ts or gd s = e−ts (7) transfer function for pid controller is as expressed in equation (8) gc s = kds2+kps+ki s (8) where: kp = proportional gain, ki = integral gain and kd = derivative gain. substituting equations (5) and (7) in equation (3) gives the uncompensated system closed loop transfer function of equation (9). θa s θr s = 3.76e−ts s5+67.56s4+62.36s3+150.52s2+3.76e−2ts (9) substituting equations (5), (7) and (8) in equation (4) result to the pid compensated system closed loop transfer function of equation (10). θa s θr s = 3.76 kds2+kps+ki e−t1s s5+67.56s4+62.36s3+150.52s2+3.76 kds2+kps+ki e−(t1+t2)s (10) the effects of pid controller on the system was evaluated by comparing the time domain performance parameters that is the rise time, time to peak overshoot, percentage overshoot, settling time and steady state error for the uncompensated system with that of pid controller file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng ajiboye, et al: effects of pid controller on performance of dish antenna position control for distrbuted mobile telemedicine nodes. azojete, 15(2):304-313. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 310 compensated system when the system is subjected to a unit step function. the performance parameters for the uncompensated system form the basis for the determination of the effects of the pid controller on the system. 4.0 simulation and analysis using equation (2) and assuming the signal speed to be the speed of light (30×109 m/s.), the simulation of the time delay was carried out in matlab r2015a environment and the system time delay simulation graph is as shown in figure 3. the maximum and minimum time delay was determined to be 0.2502 second and 0.2469 second respectively and these occurred at point a and point d as shown on the graph of figure 3. points a and d are in niger republic (2°43.207’e, 13°52.837'n) and cameroon (14°54.685’e, 4°17.825’n) respectively. figure 3: system time delay simulation graph also using equations (9) and (10), simulation experiment was carried out in matlab r2015a environment to assess the effects of incorporating pid controller into the system. the pid controller parameter values obtained by (ajiboye et al., 2013) for optimisation of system settling time for mobile satellite dish position control within nigeria ( kp =20, ki =4 and kd =0) was adopted for the simulation because these controller gain values were determined for similar system with the same dynamics and architecture within nigeria terrain. also the maximum obtainable time delay (0.2502 second) being the worst case was used for the simulation. for easy of comparison, the closed loop step responses for the uncompensated and pid controller compensated systems were presented on the same axis as shown in figure 4. figure 4: step response for uncompensated and pid compensated systems http://www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):304-313. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 311 the time domain performance parameters obtained from the system step response of figure 4 are as presented in table 1. table 1: system time domain performance parameters as can be seen in table 1, the system rise time was 86.5 seconds before the introduction of pid controller into the system but changed to 1.34 seconds when pid controller was introduced. this shows an improvement on system rise time as a result of incorporating pid controller into the system. the time to peak overshoot was 300 seconds when the system was without pid controller and reduced to 3.94 seconds when pid controller was introduced which is also an improvement as far as time to peak overshoot is concerned. the percentage overshoot was 0% when the system was without pid controller but it changed to 50.5 as a result of pid controller introduction into the system, this shows that the performance of compensated system has degraded compared with that of the uncompensated system that has overshoot of 0%. the settling time for the uncompensated system was 155 seconds as against the 21.3 seconds for pid compensated system which is an indication of improvement in compensated system performance with respect to settling time. the steady state error for system without pid controller and system with pid controller was 0 at 300 seconds and 0 at 30 seconds respectively which shows an improvement in the performance of the system with pid controller from steady state error point of view. it can also be deduced from the simulation results of table 1 that system with pid controller has both better transient and steady states response because of the lower value of system time domain parameters. the only time domain parameter that look abnormal for system with pid controller is the percentage overshoot which is 50% against the 0% for the uncompensated system. this will have no negative effect on the overall performance of the pid controller compensated system since this system would have settled down before the uncompensated system even rise as can be seen from the system step response of figure 4 and the values of system rise and settling time in table 1. 5.0 conclusion the propagation time delay between any sending and receiving nodes via any geostationary satellite was modeled. using this model the minimum and maximum time delay incurred in sending data between university of ilorin and any location within nigeria via nigcosat-1r was determined. the effects of introducing pid controller into the system were assessed based on time domain performance parameters using matlab as simulation tool. the obtained results from the system step response simulation experiments shows remarkable improvement in the system condition rise time (seconds) time to peak overshoot (seconds) percentage overshoot (%) settling time (seconds) steady state error system without pid controller 86.5 300 0 155 0 at 300 seconds system with pid controller 1.34 3.94 50.5 21.3 0 at 30 seconds file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng ajiboye, et al: effects of pid controller on performance of dish antenna position control for distrbuted mobile telemedicine nodes. azojete, 15(2):304-313. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 312 performance of the pid compensated system over the uncompensated system in the area of rise time, time to peak overshoot and settling time. references ahmad, m., jiya, jd., anene, ec. and haruna, ys. 2011. position control of parabolic dish antenna using feedback, zeigler-nichols and quadratic optimal regulator methods. continental j. engineering sciences, 6: 7-13. ahmed, m., mamman, hb., anene, ec. and balami, it. 2014. parabolic antenna control. international journal of engineering research & technology (ijert), 3: 759-761. ajiboye, at. 2012. development of automatic position controller for mobile satellite dish network within nigeria. phd thesis, university of ilorin, ilorin, nigeria. ajiboye, at., ibiyemi, ts. and falade, ja. 2013. optimisation of settling time for pid position control in mobile satellite dish network within nigeria. journal of telecommunications, 20 (5): 22-26. aloo, la., kihato, pk. and kamau, si. 2016. dc servomotor-based antenna positioning control system design using hybrid pid-lqr controller. european international journal of science and technology, 5: 17-31. amritha, mas., divyasree, mv., jesna, p., kavyasree, sm. and keerthana, v. 2017. microcontroller based wireless 3d position control for antenna. international journal of science and research (ijsr), 6: 924-927. anyaegbunam, fnc. 2014. on national e-healthcare delivery through nigcomsat-1. international journal of engineering research & technology, 3: 2270-2276. åström, kj. and hägglund, t. 2001. the future of pid control. control engineering practice, 9: 1163-1175. chahar, m., chandak, m., malav, m., sardiwal, m. and imran, m. 2016. satellite dish positioning control by dc motor using ir remote control. international journal of electrical engineering and technology (ijeet), 7: 9-18. choudhary, sd., rai, p., kumar, a. and alam, i. 2014. microcontroller based wireless automatic antenna positioning system. international journal of electronics, electrical and computational system, 3: 12-26. cullen, js., gagliano, dm., gaasch, wr., gunawardane, rdp., hu, pf., lamonte, mp., mackenzie, cf. and xiao, y. 1999. mobile telemedicine testbed. systems and information technology review journal, spring/summer, 1-16. farhan, as. 2013. new efficient model-based pid design method. european scientific journal, esj, 9: 181-199. farhan, as., mohamed, mk. and usama, hi. 2017. proposed simple and efficient control algorithm design approach. international journal of applied engineering research, 12: 20442053. http://www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):304-313. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ajiboye.at@unilorin.edu.ng 313 ibiyemi, ts. and ajiboye, at. 2012a. automatic tracking of nigcomsat-1r satellite by dish network mounted on mobile tele-medicine vehicles. international journal of engineering research and technology, 1(4): 1-4. ibiyemi, ts. and ajiboye, at. 2012b. on pid controller design for mobile node network with variable delays. international journal of science and advanced technology, 2: 176-180. ibiyemi, ts. and ajiboye, at. 2012c. robust pid control of mobile satellite dish network within nigeria. international journal of computer applications, 41(21): 32-36. kakkar, a., naushad, s. and khatri, sk. 2017. telemedicine and ehr integrated approach for an effective e-governance healthcare framework. international journal of medical research and health sciences, 6: 108-114. kim, m., kim, j. and yang, o. 2013. precise attitude control system design for the tracking of parabolic satellite antenna. international journal of smart home, 7: 275-290. maske, sa., vishwasrao, sa., sanjay, sa. and krushnat, mn. 2017. dish positioning by using ir remote. international research journal of engineering and technology (irjet), 4: 266-269. mullaa, aa. and vasambekarb, pn. 2017. speed rate corrected antenna azimuth axis positioning system. international journal of electronics engineering research, 9: 151-158. rahane, sd., mhaske, sa. and shingate, sr. 2018. design of advanced antenna positioning system. international journal of research in advent technology, 6: 251-253. saravanan, s. and sudhakar, p. 2017. telemedicine technology using internet communication. international journal of pure and applied mathematics, 115(6): 147-156 115, 147-156. shubham, p., sankalp, pt., tanmay, w. and nandanwar, vs. 2017. satellite dish positioning control by geared motor using rf module. international journal of advanced research in science, engineering and technology, 4: 3388-3393. waghmare, s., pathak, p., meshram, p., pawar, v. 2017. satellite dish positioning system. international journal for innovative research in science and technology (ijirst), 4: 50-54. yadav, s. and sharma, v. 2016. modelling and simulation of elevation position control of a giant meter wave radio telescope (gmrt) in matlab using pid and discrete pid controllers. international journal of innovative research in electrical, electronics, instrumentation and control engineering, 7: 165-168. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ajiboye.at@unilorin.edu.ng cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 62-73 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng *corresponding author’s email: funkeeze@gmail.com 62 original research article moisture sorption characteristics of dehydrated in-shell african walnut (tetracarpidium conophorum) o. o. ezekiel*1, t. o. olurin2 and a. o. akomolafe1 1department of food technology, university of ibadan, ibadan, nigeria; 2department of food science and nutrition, college of natural and applied science, bells university of technology, ota, nigeria article information received: october, 2018 accepted: december, 2018 keywords: african walnut drying sorption isotherm sorption models equilibrium moisture content nonlinear regression abstract moisture sorption isotherms are useful thermodynamic tools for determining water interactions within food systems and providing information that can assist in optimizing food processing operations such as drying, mixing, packaging and storage, as well as to maximize retention of quality parameters such as colour, aroma, texture, and nutrient. moisture sorption isotherm characteristics of african walnut were evaluated at three different temperatures (28, 33 and 38°c) and relative humidity range of 11.20 97.00 % using gravimetric method; five mathematical models (gab, bet, peleg, smith and ferro fontan) were fitted into the experimental data. sorption isotherms of the dehydrated walnut gave type ii (s-shaped) isotherms according to bet classification. temperature had significant effect on the equilibrium moisture content (emc). a nonlinear regression analysis method was used to evaluate the constants of sorption models. the models were evaluated statistically by calculating coefficient of determination (r2), the mean relative percentage error (p) and the reduced chi-square (λ2). the bet model gave the best fit for the obtained data among the tested models with r2 value of 0.9892. calculated monolayer moisture (mo) content from bet ranged from 5.018 to 7.922% db for adsorption and 9.842 to 10.143% db for desorption respectively. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction african walnuts (tretracarpidium conophorum) can be described as rounded, stone fruits of the walnut tree with single seed. the fruit of the walnut is enclosed in a hull which is green, leathery, and fleshy. after harvest, this hull is usually removed to reveal the wrinkly walnut shell that encloses the kernel, and the shell is then removed to obtain the kernel (atungulu et al., 2013). primarily, walnut plant is cultivated in nigeria for the nuts, which is traditionally eaten after boiling (akpuaka and nwankwor, 2000; ndie et al., 2010). biochemically, walnut is composed of polyunsaturated fatty acids, especially linoleic and oleic acid, it is also high in protein content (savage et al., 2001), which makes it of significant economic value and medicinal importance for human health; due to these facts, there has been an increasing interest in its consumption and utilisation. some of the other beneficial components it contains include plant protein (for example, arginine, leucine), carbohydrates (for example, dietary fibre), http://www.azojete.com.ng mailto:funkeeze@gmail.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 63 vitamins (for example, vitamin a and e), pectic substances, minerals (magnesium, potassium, phosphorus, sulphur, copper and iron), plant sterols and phytochemicals (savage et al., 2001; colaric et al., 2006; ogunmoyole et al., 2011). although african walnuts have high socio-economic potentials, the product is still under-utilised in nigeria, especially at industrial level. this can mainly be attributed to the fact that there is lack of storage facilities for the walnut market which has been hampering the production on a full scale and exploration of its inherent potentials (ekwe and ihemeje, 2013). thus, in order to overcome the challenge of spoilage and inconsistent seasonal availability, there is need for development and provision of appropriate storage facilities for the african walnut (babalola, 2011) as well as appropriate preservation methods. deterioration of food occurs during handling or due to mechanical, physical, chemical or microbial damage (rahman, 1999; mujumdar, 2004); microbial growth depends on the storage conditions and the moisture level in the product. among the commonly employed methods for preserving food such as freezing, vacuum packing, canning, preserving in syrup, food irradiation, addition of preservatives, the most popular is dehydration (jangam et al., 2010). 1.1 research justification dehydration which removes water from food materials will result in its stability and as well reduce storage and transportation cost. to a great extent, most dried foods quality depends upon their physical, chemical and microbiological stability, which is mainly a consequence of the relationship between the equilibrium moisture content (emc) of the food material, and its correspondence water activity (aw) or relative humidity at a given temperature (guilan et al., 2007). moisture sorption isotherms (msi) is the terminology usually used to express the relationship between equilibrium moisture content and equilibrium relative humidity (erh) or water activity of materials being studied. it is worthy of note to know that this relationship is complex and unique for each product due to different interactions which may be colligative, capillary or surface effects between the water and the solid components of the product at different moisture contents. according to al-mahasneh et al., 2011, msi are useful thermodynamic tools for determining water interactions within food systems and providing information that can assist in optimizing food processing operations such as drying, mixing, packaging and storage, as well as to maximize retention of quality parameters such as colour, aroma, texture, and nutrient. several authors (johnson and brennan, 2000; chowdhury et al., 2005; akanbi et al., 2006; samapundo et al., 2007; oyelade et al., 2008) have reported some of the importance of knowing the sorption characteristics of products as being essential in respect to storage stability and food product acceptability, drying process modelling, design and optimization of drying equipment, aeration, calculation of moisture changes which may occur during storage and for selecting appropriate packaging materials for dehydrated products. isosteric heat of sorption, often referred to as differential heat of sorption, is used as an indicator of the state of water adsorbed by the solid particles (fasina et al., 1997; togrul and arslan, 2007). water sorption properties of foods can be predicted using water sorption isotherm equations. guilan et al., 2007 noted that many empirical and semi-empirical equations describing the sorption characteristics of foods have been proposed in the literature; these equations are suitable for some food products only, or for selected ranges of aw, and part of these equations clearly show the effect ../../../user/downloads/azojete143/www.azojete.com.ng ezekiel et al: moisture sorption characteristics of dehydrated in-shell african walnut (tetracarpidium conophorum), azojete, 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 64 of temperature on sorption isotherms. according to togrul and arslan (2007), among the models which were reviewed, 23 common equations for fitting sorption isotherms to different food materials were reported, some of the models took into consideration the effect of temperature; these include modified chung-pfost (chung and pfost, 1967), modified henderson (henderson, 1952), modified halsey (halsey, 1948) and modified oswin (oswin, 1946) models. brunauer– emmett–teller (bet) and guggenheim–anderson–de boer (gab) equations were reported to be the most popular food isotherm equations (cadden, 1988; togrul and arslan, 2007). while the sorption characteristics of other exotic walnut of the juglandaceae family (juglans regia, microcarpa, hindsii cultivars) have been studied extensively, there is dearth of information on the sorption characteristics of african walnut (tetracarpidium conophorum) specie available in nigeria and other neighbouring african countries. the study of sorption isotherm properties of african walnut will provide information that can be used directly to know the storability, solve process design problems (e.g. dryer design and operations), predict energy requirements and determine its proper storage conditions (ekwe and ihemeje, 2013). 1.3 objectives this study therefore experimentally determined the sorption characteristics of dehydrated in-shell african walnut kernels at three different temperatures of 28, 33, and 38 °c, evaluated the suitability of five moisture isotherm model equations and investigated the nature of the moisture sorption hysteresis. 2.0 materials and methods 2.1 materials raw unshelled walnuts were obtained from ogbese market, ondo state, nigeria. all other reagents used were of analytical grade. 2.1.1 sample treatment the bulk quantity of walnuts was cleaned and divided into two portions. one portion of the walnuts used for adsorption isotherm was dried in an air-draught oven at 120 °c for 10 hours to obtain a moisture content of about of 4 % (dry basis). the other portion used for desorption process was first dampened by placing in known amount of water so as to allow them pick up moisture for 4 days this enabled the moisture content to be raised to a stable and uniform level. 2.2 methods 2.2.1. experimental sorption isotherm water sorption isotherms (adsorption and desorption) were determined by gravimetric method which involved exposure of samples to different salts (licl, ch3cook, mgcl2.6h2o, k2co3, mg (no3)2.6h2o, nabr, srcl2.6h2o, nacl, (nh4)2so4, bacl2.2h2o) at aw of 0.112 to 0.970 as shown in table 1. the salts were employed as saturated solutions to give constant water activity environment. the samples were placed on perforated lid in different desiccators containing the salts. after which the desiccators were placed in a temperature-controlled chamber at different temperatures of 28, 33 and 38°c covering the main range of possible storage condition (to investigate the effect of different temperatures). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 65 samples were weighed consistently daily until a constant weight was achieved. moisture content was determined by aoac vacuum oven method (aoac, 1990) at 60°c. an analytical balance (model) with a sensitivity of 0.1mg was used to measure water uptake. this procedure was performed in triplicate. table 1: amount of water and salt used to prepare the different saturated salts and expected water activity no. name salt (g) distilled water (g) aw (30oc) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. licl ch3cook mgcl2.6h2o k2co3 mg(no3)2.6h2o nabr srcl2.6h2o nacl (nh4)2so4 bacl2.2h2o k2so4 112 126 300 300 225 300 300 300 300 375 20 63 79 100 135 34 120 75 90 120 105 100 0.112 0.226 0.327 0.431 0.528 0.577 0.708 0.752 0.800 0.903 0.970 2.2.2 determination of moisture content moisture content was determined by gravimetric method (aoac, 2000). five gram (5g) of the sample was pre-weighed (w1) in a petri dish and placed in an oven at 105 °c for 3 hour. the sample was removed from the oven, cooled in a desiccator, and re-weighed. it was taken back to oven for another 1 hour, cooled and weighed, this was repeated until a constant weight was achieved and recorded as (w2). all analyses were carried out in triplicates. moisture percentage was calculated as shown in equation 1: (1) 2.2.3 data analysis: mathematical modelling of moisture sorption isotherm five mathematical equations namely; gab, bet, peleg, smith and ferro fontan were used for describing desorption and adsorption isotherms of in-shell walnut in the range of temperature 28, 33 and 380c. the expressions and the parameters of the five models used to fit the data are presented in table 2. the goodness of fit of the data to the equations was evaluated by the criteria of correlation coefficient (r2), the mean relative percentage error (p) and the reduced chi-square (x2) presented as in equations 2, 3 and 4 respectively. the higher the r2 value and the lower the x2 and p values, the better is the goodness of the fit.                              n i iipre n i iprei n i n i iipreiprei mmmm mmmm r 1 2 exp,, 2 1 ,exp, 1 1 exp,,,exp, 2 (2) ../../../user/downloads/azojete143/www.azojete.com.ng ezekiel et al: moisture sorption characteristics of dehydrated in-shell african walnut (tetracarpidium conophorum), azojete, 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 66     n i i iprei m mm n p 1 exp, ,exp,100 (3) (4) where, mexp,i = ith experimentally observed equilibrium moisture content, mpre,i = ith predicted equilibrium moisture content, n = number of observations and n = number of constants (kaya and kahyaoglu, 2007). where a, b, c and d are parameters of the equations, t is temperature (oc), xe is equilibrium moisture content (kg/kg d.b.), and aw is the water activity (kaya and kahyaoglu, 2007). table 2: mathematical models used to describe moisture adsorption and desorption isotherm behaviours of the dehydrated african walnut model name equilibrium moisture content model equation smith  we abax  1ln gab ferro-fontan                        r w e a x 1 ln11   peleg bet 3.0 results and discussions 3.1 moisture sorption isotherms of dehydrated walnut: effect of temperature on sorption isotherms the isotherms shown in figures 1 and 2 were obtained by plotting the corresponding mean emc of three replicates against aw at each temperature for adsorption and desorption processes respectively. the effect of temperature on the moisture sorption isotherm reveals that there was an initial increase in the equilibrium moisture content as temperature increased to 33°c and then the equilibrium moisture content decreased as temperature further increased to 38°c at constant aw (0.226 – 0.800), but there was decrease in the equilibrium moisture content with increasing temperature, at a constant aw (0.903 – 0.970); the decrease in emc with increasing temperature signifies that the product became less hygroscopic with increasing temperature which means it can absorb more moisture at lower temperatures than at higher temperatures at constant relative humidity environment (ariahu et al., 2006). according to ronald et al., (2005), this can be explained by the change in the excess enthalpy of water binding, dissociation of water, or increase in solubility of solute in water as temperature increases. also, this trend may be due to a reduction in the total number of active sites for water binding as a result of physical and/or chemical changes in the product induced by temperature (mazza and lemaguer, 1980; moreira et al., 2008; saad et al., 2014). the effect of temperature on the sorption isotherm is of great importance (falade and awoyele, 2005), this is due to the fact that foods are exposed to a range of temperatures during storage and processing, and also aw changes with temperature. temperature affects the mobility of the water molecules and the dynamic equilibrium between the vapour and adsorbed phases (al-muhtaseb et al., 2004). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 67 figure 1: effect of temperature on the adsorption isotherm of dehydrated african walnut figure 2: effect of temperature on the desorption isotherm of dehydrated african walnut the monolayer moisture content (mo) for each temperature, calculated using the bet and gab models, is presented in table 3. in general, the mo value calculated using the bet model was lower than that calculated using the gab equation this is in agreement with the reports of other researchers (erbas et al., 2005; mcminn et al., 2007; lee and lee, 2008). for adsorption, mo decreased as temperature increased while it decreased for desorption isotherm. the behaviour of mo decreasing with increase in temperature been ascribed to a reduction in the number of active sites due to physical and chemical changes induced by temperature (moreira et al., 2008). the mo is the minimum moisture content covering hydrophilic sites on the material surface, and it is a necessary data for achieving storage with minimum quality loss for long time. furthermore, at this condition, the rates of spoilage reactions, except for oxidation of unsaturated fats, are minimal. therefore, at a given temperature, the safest aw level is that corresponding to mo or lower (moreira et al., 2008) table 3: estimated parameters and fitting criteria of the models applied to experimental sorption data of dehydrated african walnut model names constants adsorption desorption 28°c 33°c 38°c 28°c 33°c 38°c smith a 9.3806 9.4023 9.6824 15.1562 14.5851 11.8149 b -8.1272 -9.5799 -10.5799 -11.3994 -12.6404 -17.7076 r2 0.9992 0.8758 0.8758 0.7906 0.8929 0.9499 p 0.0000 0.0211 1.164e-10 1.707e-15 0.0000 8.574e-10 x2 1.69e-17 1.34e-02 4.00e-19 8.08e-29 0.00e+00 1.25e-17 bet c -6.02e+00 -8.93e+00 -9.02e+00 -1.13e+01 -1.12e+01 -1.62e+01 mo 5.018 5.856 7.922 10.143 9.913 9.842 r2 0.9027 0.9392 0.9892 0.987 0.9771 0.9771 p -2.36e-08 0.0008222 0.0001921 0.0027622 1.63e-12 1.63e-12 x2 8.79e-14 1.90e-09 8e-05 3e-05 8.13e-14 8.13e-14 gab c -3.79e-07 -2.38e-07 -2.38e-07 -8.35e-07 -1.12e-07 -1.12e-07 k 0.8219 0.73913 0.73913 0.7688 0.1622 0.1622 mo 8.642 9.2241 14.8728 20.3271 17.9138 17.9138 r2 0.943 0.869 0.962 0.922 0.9731 0.9731 p -8.36e-10 3.59e-08 4.921e-08 1.67e-15 1.13e-15 1.13e-15 x2 1.53e-13 0.001 1e-05 8.01e-23 3.03e-23 3.03e-23 ferro-fontan α 4.4426 5.3367 6.0169 11.0965 7.03742 4.1174 ../../../user/downloads/azojete143/www.azojete.com.ng ezekiel et al: moisture sorption characteristics of dehydrated in-shell african walnut (tetracarpidium conophorum), azojete, 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 68 y 2.5528 2.7230 2.9101 4.8628 5.0022 7.9389 r 0.216736 0.2451 0.2699 6.05e-02 9.58e-02 9.87e-02 r2 0.8375 0.8892 0.8892 0.9856 0.9697 0.9812 p 3.36e-10 0.05979 1.192e-06 -0.003498 0.0098708 0.0330662 x2 1.17e-03 1.07e-01 2.81e-01 3.39e-04 1.83e-03 1.86e-02 peleg k1 3.9892 6.9166 7.6596 8.1121 7.62 6.18 k2 10.84 11.89 13.901 12.3797 14.8789 16.1923 n1 1.8529 2.50449 2.82829 2.4099 2.2645 2.2917 n2 0.00079 0.00085 0.00091 0.00081 0.00099 0.0010 r2 0.9003 0.8540 0.8540 0.9895 0.9616 0.9715 p -8.36e-05 0.0214 0.0369261 0.0008715 0.0277175 0.0277175 x2 0.0000 0.0137 0.0000 0.0000 0.0144 0.0144 3.2 modeling of sorption isotherms table 3 showed the result of the nonlinear regression analysis of adsorption and desorption isotherms of in-shell walnut obtained at 28°c, 33°c, and 38°c. the values of constants of the five models, that is, gab, bet, smith, ferro-fontan, peleg, fitted to the desorption and adsorption data along with their standard error (p), the correlation coefficient (r2), and the reduced chi-square (x2) for the studied temperatures are given. examination of the results revealed that some of the models are acceptable for predicting the emc. in considering the models with lowest standard error and the highest coefficient of correlation, the bet gave the best fitting for adsorption at 33°c and 38°c and smith model was best fit at 28°c, while peleg models gave the best fitting of desorption isotherms at 28°c, bet gave the best fitting at 33°c and ferro fontan gave the best fitting at 38°c. the r2 of the models that fit the isotherms ranged from 0.903 to 0.999. lomauro et al., (1985) pointed out that when percentage average relative deviation is less than 5, the fit is considered to be excellent. it is well-known that the fit becomes better as the coefficient of determination ‘r2’ approaches 1. also, the smaller the standard errors of models the better is the fit. considering all these three criteria for the isotherms of the walnut at the three temperatures, the sorption data were in good agreement with gab and other tested models. however, bet model seems to be excellent to represent the experimental sorption data. comparison of the experimental and predicted isotherms for dehydrated walnut over the range of temperature and aw commonly encountered in the tropics in food storage structures are shown in figures 3-5 for the adsorption isotherms and figures 6-8 for the desorption isotherms. 3.3 moisture sorption hysteresis of dehydrated african walnuts the experimental adsorption and desorption isotherms (change in emc with aw) obtained at 28, 33, and 38°c for african walnut are shown in figures 9, 10, and 11. the emc at each aw represents the mean value of three replications. the temperature chosen is suggestive of average ambient temperature at which most food products are stored in tropics. the results indicated that the adsorption isotherms of the dehydrated walnut exhibit about type ii curve. the adsorption isotherms at the temperatures lay below their desorption counterparts and both enclosed hysteresis loop. hysteresis has been related to the nature and state of the components in a food, reflecting their potential for structural and conformational rearrangements (yan et al. 2008). the sorption http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 69 isotherms have the sigmoidal-shaped profile according to the bet classification. these curves are typical of plant products as reported by kouhila et al., (2002), ait-mohammed et al., (2004) and idlimam et al., (2008). hysteresis between adsorption and desorption existed over almost the entire range of water activity at 28°c. similar behaviour of adsorption and desorption isotherms was observed for 33°c and 38°c. the hysteresis effect was more pronounced at lower temperatures in which water content on the desorption isotherm is higher than that on the adsorption side at the same water activity, this is one of the reasons for difference in moisture content between the two closures. figure 3: comparison of experimental and gab predictive adsorption isotherms of dehydrated african walnut at 28°c figure 4: comparison of experimental and gab predictive adsorption isotherms of dehydrated african walnut at 33°c figure 5: comparison of experimental and gab predictive adsorption isotherms of dehydrated african walnut at 38°c figure 6: comparison of experimental and gab predictive desorption isotherms of dehydrated african walnut at 28°c figure 7: comparison of experimental and gab predictive desorption isotherms of dehydrated african walnut at 33°c figure 8: comparison of experimental and gab predictive desorption isotherms of dehydrated african walnut at 38°c ../../../user/downloads/azojete143/www.azojete.com.ng ezekiel et al: moisture sorption characteristics of dehydrated in-shell african walnut (tetracarpidium conophorum), azojete, 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 70 figure 9: adsorption and desorption isotherm of dehydrated african walnut at 28oc figure 10: adsorption and desorption isotherm of dehydrated african walnut at 33oc figure 11: adsorption and desorption isotherm of dehydrated african walnut at 38oc points is that, during drying (desorption), some solutes may supersaturate below their crystallization water activity and thus hold more water as aw is lowered (barbosa-carnovas et al., 2007; saad et al., 2014). . the swelling of polymeric materials during moisture adsorption can also lead to hysteresis (raji and adeniran, 2011). iglesias and chirife (1976) recognized that it is not possible to give a single explanation of the hysteresis phenomena in foods due to food being a complex biological material. the figures revealed that the equilibrium moisture content increased with water activity at constant temperature. this may be due to the fact that vapor pressure of water present in foods increases with that of surroundings (shivhare et al., 2004). in the first segment (with low water activity) of the s-shaped sorption isotherm curves, walnut kernels sorbed relatively lower amounts of moisture. however, larger amount of moisture was absorbed at higher aw. similar behaviour has been reported by other authors for different foods (sanni et al., 1997; lee and lee, 2008). two bending regions are noted, one around 0.1 to 0.3 and another at 0.5 to 0.6. the isotherm is therefore divided into three zones. according to aguilera and stanley (1999), in zone i (aw between 0.05 and 0.2) minimal water is contained in the product, and the water molecules present are tightly bound to active sites (e.g., polar groups in molecules) mainly by hydrogen bonding. in zone ii (aw between 0.2 and 0.5) the water is more loosely bound, initially as multilayer above the monolayer; later, as moisture content increases, this water successively fills micro-pores and macro-pores in the system. in this region, chemical and biochemical reactions requiring solvent water start to take place because of the increased mobility of solutes. in zone iii (aw between 0.6 and 0.9), excess water is http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 62-73. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 71 present in macro-capillaries, exhibiting nearly all the properties of bulk water. microbial growth becomes a major deteriorative reaction in this region (saad et al., 2014). according to vanden berg and bruin (1981), a general sigmoid sorption isotherm can be divided into three different parts; ranges i (aw 0–0.22), ii (aw 0.22–0.73) and iii (aw 0.73–1.0). in ranges ii and iii, water molecules penetrate newly created pores of the already swollen structure and are mechanically entrapped in the void spaces. therefore, water uptake particularly at higher aw would be markedly influenced by the stability of the micro-porous structure. 4.0 conclusions moisture sorption isotherms were determined for dehydrated african walnut at three different temperatures of 28, 33 and 38°c. there was a significant effect of temperature on the equilibrium moisture content (emc) in the range of temperatures studied. the emcs were found to decrease with increasing temperature at constant aw; they were also found to increase with increasing aw at constant temperature. the isotherms obtained are sigmoidal in shape and showed evident effect of hysteresis. in general, bet model provided a better fit to the experimental data than other tested models, thus it was found to be the most appropriate equation for representing the sorption isotherms. mo increased with temperature for adsorption, while it decreased with increasing temperature for desorption. references ait-mohammed, l., kouhila, m., jamali, a., lahsasni, s. and mahrouz, m. 2004 “experimental study of adsorption-desorption isotherms of bitter orange leaves,” in proceeding of the 14th international drying symposium, sao paulo, brazil. pp. 1404–1410. akanbi, ct., adeyemi, rs. and ojo, a., 2006. drying characteristics and sorption isotherm of tomato slices. journal of food engineering 73, 157–163. akpuaka, mu. and nwankwor, e. 2000. extraction, analysis and utilization of a drying-oil from tetracarpidium conophorum. bioresources technology 73: 195-196. al-mahasneh, ma., bani-amer, mm. and rababah. 2011. modeling moisture sorption isotherms in roasted green wheat using least square regression and neural-fuzzy techniques. food bioproducts processing doi:10.1016/j.fbp.2011.02.007 al-muhtaseb, ah., mcminn, wam. and magee, tra. 2004. water sorption isotherms of starch powders. part 1: mathematical description of experimental data. journal of food engineering 61: 297–307. aoac 1990. official methods of analysis, 15th edition. association of official analytical chemists, arlington, va. aoac 2000. official methods of analysis, 17th edition. association of official analytical chemists, washington. ariahu, cc., kaze, sa. and achem, cd. 2006. moisture sorption characteristics of tropical fresh water crayfish (procambarus clarkia). journal of food engineering 75: 355–363. atungulu, he., wang, t., fu r., wang, x., khir, r. and pan, z. 2013. infrared pre-drying and drydehulling of walnuts for improved processing efficiency and product quality. american society of agricultural and biological engineers 29(6): 961-971 babalola, fd. 2011. marketing of african walnut [tetracarpidium conophorum mull. 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intermediate moisture content banana. journal of food engineering, 86: 342–348. ../../../user/downloads/azojete143/www.azojete.com.ng article information 1.0introduction 2.0materials and methods 3.0results and discussions arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 692-701 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 692 original research article prediction modeling of 28-day concrete compressive strength using artificial neutral network o.a.u. uche1 , m.t. abdulwahab2*, a. suleiman3 and y. ismail4 (1,4department of civil engineering, bayero university kano, kano, nigeria 2department of civil engineering, kebbi state university of science and technology, kebbi, nigeria 3department of civil engineering, abubakar tafawa balewa university, bauchi, nigeria) * corresponding author’s email address: amtaytechnology@yahoo.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: prediction compressive strength concrete artificial neural network abstract compressive strength of concrete at the age of 28 days is an important parameter for the design of concrete structures and waiting for that length of time to obtain the value can be tasky. this study developed an alternative approach using artificial neutral network (ann) to estimate or predict the compressive strength of concrete at 28th day from early age results. in the study concrete cubes of mix ratio 1:2:4 were cast with different water-cement ratios (0.4, 0.5, 0.6 and 0.65) and their seventh (7th) and twenty-eighth (28th) day strength were measured in the laboratory. in all, 400 cubes of 150 x 150 x 150mm of 200 sets were subjected to compressive strength test using avery denison universal testing machine of 2000 kn load capacity at a constant load application of 15kn/s. ann model was then developed using the time series tool of ann in matlab 7.12.0 (r2011a) applying back propagation algorithm. out of the 200 sets of results, 110 sets (55%) were used for the training of the network while 30 sets (15%) were used to validate and 60 sets (30%) to test the network. the result of the crushing test shows that the higher the compressive strength at seventh (7th) day the higher it will be at twenty-eighth (28th) day. the result of the ann model shows a good correlation between the seventh (7th) day compressive strength and the twenty-eighth (28th) day compressive strength with training and validation correlation coefficients of 0.99751 and 0.99736 respectively. it was also found that the ann model ��u � 쳌䁐�䀀㌳㌳�� � ͷ䁐䀀ͷⷸ� is quite efficient in determining the twenty-eighth (28th) day compressive strength of concreteas the predicted strength values match very well with those obtained experimentally with a correlation coefficient of 0.99675. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction concrete is one of the most widely used building materials in the world because of its versatile application, satisfying performance in strength requirements and its ability to be moulded into a variety of shapes and sizes (kayode and ilessama, 2015). it is a synthetic construction material made by mixing of cement, fine aggregates, coarse aggregate and water in the correct proportion, and each of these components contribute to the strength of the concrete as reported by gambhir (2004). the fine aggregates fill up the voids formed by the coarse mailto:amtaytechnology@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):692-701. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 693 aggregates; and cement fills up the voids of the fine aggregates as the lesser the voids the more the strength of concrete (mehta and monteiro, 2006). the strength of concrete comprises mainly of the compressive, split tensile and flexural. in the construction industry, strength is a primary criterion in selecting concrete for a particular application. concrete used for construction gains a significant component of its strength during the initial 3 to 4 weeks, but continues to do so over a long period of time after pouring (chopra et al., 2015). the characteristic strength of concrete is defined as the compressive strength of a sample that has been cured for 28 days. the use of concrete for mass concreting in huge civil projects like bridges, dams, power plants, are usually performed in several layers and the concrete strength of each layer must be achieved. therefore, one has to wait for 28 days to achieve a 28-day strength for each layer of the concrete. this is time consuming and costly to perform as days will be needed to obtain the 28-day strength for � layers. however, to hasten the construction progress we must be able to predict the concrete strength based upon the early strength data. therefore, rapid and reliable prediction for the strength of concrete would be of great significance. the prediction of concrete strength and behaviour, therefore, has been an active area of research and a considerable number of studies have been carried out in it (bamiyo et al., 2016; zain and abd, 2009; zelic et al., 2004; akkurt et al., 2004; hwang et al., 2004; kheder et al., 2003; zain et al., 2002). it is well recognized that the prediction of concrete strength is important in the modernized concrete construction and engineering judgment (dias and pooliyadda, 2001). thus, for the sake of saving time, decreasing the cost of production of concrete and wastage of materials, the help of artificial neural network (ann) is taken to develop models, so that the knowledge extracted from these models, can be utilized to predict the strength of concrete. the artificial neural network (ann) is a form of artificial intelligence (ai) that attempts to mimic, in a very simplistic way, the human cognition capability to solve engineering problems that have defied solution using conventional computational techniques (flood, 2008). a typical structure of ann consists of a number of processing elements (pes), or nodes, that are usually arranged in layers: an input layer, an output layer and one or more hidden layers as shown in figure 1. the ann modelling philosophy is similar to a number of conventional statistical models in the sense that both are attempting to capture the relationship between a historical set of model inputs and corresponding outputs (shain et al., 2001). figure 1: typical structure of ann (chopra et al., 2015) unlike conventional problem solving algorithms that are basically based upon statistical analysis by which many linear and nonlinear regression equations have been constructed to model such a prediction problem (monjurul and ahsanul, 2011), artificial neural network can be trained to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng uche, et al: prediction modeling of 28-day concrete compressive strength using artificial neutral network. azojete, 15(3):692-701. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 694 perform a particular task. this is done by presenting the system with a representative set of examples describing the problem, namely pairs of input and output samples. the ann will then extrapolate the mapping between input and output data. after training, the ann can be used to recognize data that is similar to any of the examples shown during the training phase (rafiq, 2001). the ann can even recognize incomplete or noisy data and also have the ability to selforganize, therefore enabling segmentation or coarse coding of data. this is an important feature that is often used for prediction, diagnosis or control purposes. in general, ann have the ability to simulate the behaviour of systems with limited modelling effort and provide speedy and reasonably accurate solutions in complex uncertainties and subjective situations. thus, this study aims at investigating the feasibility of predicting the 28th day compressive strength of concrete with the aid of ann using its strength obtained at the 7th day. 2. materials and methods the materials used for this study were sourced within kano state, nigeria and the experimental procedures to arrive at the desired results were carefully followed. also, the specification and quality of the test materials were kept same throughout the test 2.1. materials the binder used in this study was ordinary portland cement (opc), 3x brand manufactured by dangote cement nigeria plc. the cement was of grade 42.5 with a specific gravity of 3.14 as determined in accordance with bs 812 (1985). naturally occurring clean sand, free of adulteration, obtained from river challawa in kano state was used as the fine aggregates. the specific gravity of the fine aggregate was found to be 2.6 and it was then classified as zone-ii after conducting sieve analysis in accordance to bs 882 (1992). crushed granite stones of 20mm nominal diameter with aggregates crushing value of 22% and specific gravity of 2.7 were used as the coarse aggregates. it was obtained from a standard quarry site of abduljalil hajaig and sons ltd in kano state. the water used for mixing and curing was portable tap water from the civil engineering laboratory of bayero university kano and satisfied astm c1602-12 specification of water for use in concrete mixtures. artificial neural network toolbox in matlab (r2011a) package was used in developing the network architecture for the predictions in this study. the input variables for the proposed neural network consisted of water cement ratio (w/c), cement content, fine aggregate content, coarse aggregate content and 7th day compressive strength, while the output variable was the 28thday compressive strength. 2.2. method a grade 25 concrete was produced using water/cement ratio of 0.4, 0.5, 0.6 and 0.65 as shown in table 1. fifty (50) concrete cubes were cast for each mix proportion using 150mm x 150mm x 150mm metal moulds. a total of 200 sets of concrete cubes were cast, de-moulded after 24hours and then immersed in water for curing ages of 7 and 28 days respectively. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):692-701. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 695 table 1: concrete mix proportion cement (kg/m3) fine aggregate (kg/m3) coarse aggregate (kg/m3) water (kg/m3) water cement ratio (w/c) 360.4 720.8 1441.7 144.2 0.4 348.8 697.6 1395.2 174.4 0.5 337.6 675.2 1350.4 202.6 0.6 332.2 664.5 1329.0 216.0 0.65 2.2.1 compressive strength the compressive strengths of the cubes were carried out using the mix proportions in table 1. mixing was done manually and cast in steel cube molds of 150mm and cured in water for 7 and 28 days. a total of 400 cubes amounting to 200 sets were tested at the end of each curing regime. the samples were crushed in accordance with bs en12390-3 (2009) using the avery denison compressive testing machine of 2000 kn load capacity at constant loading rate of 15kn/s and the average loading rate taken. the compressive strength was taken as the maximum compressive load the cube can carry per unit areas and was calculated as follows: a fstrengthecompressiv  (1) 2.2.2 network development, training, validation and testing ann tool box in matlab (r2011a) was used in developing the network architecture. input data in the form of 6-column matrix containing the input parameters: water content (kg/m3), cement content (kg/m3), fine aggregates (kg/m3), coarse aggregates (kg/m3) and 7th day compressive strength (n/mm2) were fed into the workspace. these automatically made the input neurons in the input layer to be six (6). the training algorithm adopted for the study in the feed forward network is the levenberg – macquardt’s and after several random trials, the number of neurons in the hidden layer for optimal convergence was found to be three (3). since the output parameter is one (1) (28th day compressive strength), the number of neurons in the output layer was one (1). the final network architecture for the study and the workflow showing the step-bystep ann development processes are as shown in figures 2 and 3 respectively. figure 2: final artificial neural network architecture file:///c:/users/user/downloads/azojete143/www.azojete.com.ng uche, et al: prediction modeling of 28-day concrete compressive strength using artificial neutral network. azojete, 15(3):692-701. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 696 figure 3: flow chart for the artificial neural network development the imported data were randomized automatically by the system and divided into three (3); 55% for training, 15% for validation and 30% for testing. thus, among the 200 data sets for this study, 110 randomly collected data were used in the training stage to construct the ann model, 30 for validation and the remaining 60 data set were used in testing the network to estimate the model performance. the network was trained and retrained until it understood the relationship between the input variables and the 28th day compressive strength (output variable). back-propagation, as one of the most well-known training algorithms for the multilayer perception (mlp), which is a gradient descent technique that minimizes the error for a particular training pattern in which it adjusts the weights by small amount at a time, was used. however, it was recommended by el-chabib and nehdi (2005) that a sigmoid function be employed as transfer function for the hidden layers because it was non-linear, differentiable, continuous, and it varies monotonically between 0 and 1 (log-sigmoid) or -1 and 1 (tan-sigmoid). momentum rate and learning rate values were determined and the model was trained through iterations. the trained model was tested with the input values and the results found were close to experiment results. the values of parameters used in this study were as follows: number of input layer units = 6 number of hidden layers = 3 number of output layer unit = 1 learning cycle = 24 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):692-701. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 697 3. results and discussion this section presents the results of the laboratory tests for concrete cubes strengths in order to form the database of sets of data for use in the artificial neural network modelling. it also describes the findings on the suitability of ann in the prediction of 28th day concrete compressive strength. 3.1 compressive strength of concrete cubes the prepared samples of 150mm by 150mm by 150mm with four different water cement ratios (0.4, 0.5, 0.6, 0.65) were tested at 7th and 28th days using compression machine and their strength results were obtained as shown in table 2. table 2: results of compressive strength at various concrete mix constituent concrete mix constituent (kg/m3) compressive strength (n/mm2) w/c ratio cement coarse aggregate fine aggregate 7th day 28th day 0.4 360.4 1441.7 720.8 24.9 38.0 0.5 348.8 1395.2 697.6 20.1 30.5 0.6 337.6 1350.6 675.2 16.0 23.7 0.65 332.2 1329.0 664.5 14.3 22.1 figure 4: compressive strength at various water-cement ratio figure 4 shows the relationship between compressive strength (n/mm2) at 7th and 28th day with water-cement ratio, this shows an inverse relationship, where the compressive strength decreased with increase in water-cement ratio, hence the compressive strength increased with increase in cement content and decreased with increase in water content. also from table 2 it can be deduce that the compressive strength decreased with decrease in fine and coarse aggregate content, hence a direct relationship exist between compressive strength and aggregates content. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng uche, et al: prediction modeling of 28-day concrete compressive strength using artificial neutral network. azojete, 15(3):692-701. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 698 figure 5: relationship between 7th and 28th day compressive strength figure 5 shows an approximately linear relationship between the 7th day and the 28th day concrete strength, with the 28th day increasing with increase in the 7thday strength. the relationship between the 28thday and 7thday concrete strength is defined by equation (2). (2) where: f28 = 28th day compressive strength (n/mm2) f7 = 7th day compressive strength (n/mm2) table 3: comparison between experimental and mathematical model strengths at 28th day experimental result (n/mm2) f�u � 쳌䁐�䀀㌳㌳f� � ͷ䁐䀀ͷⷸ� 38 38.52 30.5 31.15 23.7 24.86 22.1 22.25 the comparison between the experimental 28th day strength and the 28th day strength obtained using the mathematical model as in equation (2) is presented in table 3. it was observed that the model result is slightly higher than the experimental results. 3.2 outcomes of the ann the results of the network testing after training and validation shows that the predicted 28th day compressive strength of concrete are very close to those measured in the laboratory. this is an indication that the network has learned the relationship between the input and the output values during the training. the comparison between the measured and predicted compressive strength at 28th day are shown in figures 6 and 7. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):692-701. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 699 figure 6: relationship between measured and predicted 28th day compressive strength figure 7: comparison between measured and predicted 28th day compressive strength in general, the r value for the training data set was larger than that for the testing set, that is, the neural network made better prediction for the training data sets than the testing data set. the combination of transfer function composed of tan-sigmoid and linear function gives a good result. figure 8 shows the relationship between output targets and predicted values obtained through the training and testing process. the model shows very good correlation for both the training (r = 0.99751), validation (r = 0.99736) and testing data (r = 0.99482) and the general correlation of r = 0.99675. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng uche, et al: prediction modeling of 28-day concrete compressive strength using artificial neutral network. azojete, 15(3):692-701. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 700 figure 8: correlation between measured and ann predicted result 4. conclusion from the study, the following conclusion and observations were drawn. the 28thday compressive strength was found to be directly proportional to 7th day compressive strength. it has been demonstrated in this study that the ann model ��u � 쳌䁐�䀀㌳㌳�� � ͷ䁐䀀ͷⷸ� was quite efficient in determining the 28th day compressive strength of concrete asit was found that the measured compressive strength and predicted strength are very close with a correlation of 0.99675. mathematical model results are slightly higher than the experimentally results. references akkurt, s., tayfur, g. and can, s. 2004. fuzzy logic model for the prediction of cement compressive strength. cement concrete research, vol. 34, no. 8, pp. 1429 – 1433. astm c1602-12. standard specification for mixing water used in the productionhydraulic cement concrete, astm international, west conshohocken, pa, 2012, www.astm.org bamiyo, s.p., uche, o.a.u. and abdulwahab, m.t. 2016. load deflection behaviour of two-way rc slab using artificial neural network approach. proceedings of the 2nd national engineering conferenceon bridging the gap between academia and industry in nigeria, bayero university kano, pp. 144 – 149, isbn: 978-978-8203-24-7. http://www.astm.org http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):692-701. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 701 bs en 12390-3 2009. testing hardened concrete—part 3: compressive strength of test specimens. management centre, brussels. chopra, p., sharma, r.k. and kumar m. 2015. artificial neural networks for the prediction of compressive strength of concrete. international journal of engineering and applied sciences (ijeas), vol. 13, issue 3, pp. 187 – 204. dias, w. p. s. and pooliyadda, s. p. 2001.neural networks for predicting properties of concretes with admixtures. construction and building materials, vol. 15, pp. 371379. el-chabib, h. and nehdi, m. 2005. neural network modelling of properties of cement-based materials demystified. advances in cement research, vol. 17, no. 3, pp. 91 – 102. flood, i. 2008. towards the next generation of artificial neural networks for civil engineering. advanced engineering informatics, vol. 22, no. 1, pp. 4 – 14. gambhir, m. l. 2004. concrete technology, tata mcgraw – hill publishing company limited, new delhi, pp. 352 448 hwang, k., noguchi, t. and tomosawa, f. 2004. prediction model compressive strength development of fly-ash concrete. cement concrete research, vol. 34, no. 12, pp. 2269 – 2276. kayode, o. and ilesanmi, o. 2015.self-compacting concrete: strength evaluation of corn cob ash in a blended portland cement. american scientific research journal for engineering, technology, and sciences vol. 13, no. 1, pp. 123-13. kheder, g.f., al-gabban, a.m. and abid, s.m. 2003. mathematical model for the prediction of cement compressive strength at the ages of 7 and 28 days within 24hours. materials and structure, vol. 36, no. 10, pp. 693 – 701. mehta, p.k. and monteiro, p.j.m. 2006. “concrete, microstructure, properties and materials”. 3rd edition, mcgraw-hill, usa. monjurul, h.m. and ahsanul, k. 2011. prediction of compressive strength of concrete from early age test result. proceedings of 4th annual paper meet and 1st civil engineering congress, dhaka, bangladesh, pp. 1 – 7. rafiq, m.y., bugmann, i. and easterbrook, d.j. 2001. neural network design for engineering applications. computers and structures, vol. 79, pp.1541 – 152. shain, m.a., mark, b.j. and holger, r.m. 2001. artificial neural network-based settlement prediction formula for shallow foundations on granular soils.school of civil and environmental engineering, the university of adelaide. zain, m.f.m. and abd, s.m. 2009. multiple regressions model for compressive strength prediction of high performance concrete. journal of applied sciences, vol. 9, no. 1, pp. 155 – 160. zain, m.f.m., mahmud, h.b., ilham, a. and faizal, m. 2002. prediction of splitting tensile strength of high-performance concrete. cement concrete research, vol. 32, no. 8, pp. 1251 – 1258. zelic, j., rusic, d. and krstulovic, r. 2004. a mathematical model for prediction of compressive strength in cement-silica fume blends. cement concrete research, vol. 34, no. 12, pp. 2319 – 2328 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):77-96 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 77 original research article transmission expansion programme for electric network reinforcement p. o. oluseyi*, t. o. ajekigbe and t. j. akintunde (department of electrical and electronics engineering, university of lagos, akoka, lagos, nigeria) *corresponding author: poluseyi@unilag.edu.ng; drpeteroluseyi@gmail.com article information submitted 29 march, 2018 revised 05 september, 2018 accepted 10 september, 2018 keywords: electricity transmission expansion power grid evolutionary algorithm voltage collapse power flow abstract due to the increase in electricity demand, transmission sector has become overstressed since it can only be built at vast cost. in many developing economies, the network is highly susceptible to outages, collapse as well as partial or total failures, since the existing transmission capacity limit is often closely approached. to overcome this challenge better transmission expansion needs to be considered. this paper identified the implementation of transmission expansion with a number of creative approaches for overcoming network collapse in poor economy. the study deployed the application of improved strength pareto evolution algorithm (spea-2) optimization approach for solving the transmission expansion problem based on a simple power flow model. this model was deployed for running the nigeria31-bus system; to serve as the benchmark hence the standard ieee 30bus system was also considered. using the traditional approach, the results obtained from the power flow analysis revealed that there are four major buses that recorded very high severity of violation. these were jos, kaduna, kano and birnin-kebbi buses. in furtherance to this, additional effort was made to establish these findings by adapting the contingency analysis tests which provided more information on the earlier results so as to establish that these buses made the adjoining transmission lines connecting them to be identified as weak. thus this serves as the contributory factor to the violation experienced by the entire the power network. for a more creative vivid display of the results; the powerworld software was engaged for the analysis of the existing nigeria-31 bus system while the violated buses that require more energy flow were provided with double circuit. this, thus, resulted in improved power outflow and inflow to the buses which led to the reduction of losses in the network. in conclusion, this study established that the transmission line connecting the geographical northern and southern parts of nigeria dissipated quantifiably large value of losses which is mainly due to the nature and length of the line linking the source of electricity supply to a number of the load centres in the farther part of the country. hence, it is suggested that the transmission expansion programme should be adopted for the improvement of power flow quantity which will, on the long run, reduce the power loss suffer by the existing network. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. mailto:poluseyi@unilag.edu.ng mailto:drpeteroluseyi@gmail.com http://www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 78 1.0 introduction electric power transmission is the long-distance transfer of electrical energy from where it was generated to where it is consumed. electricity is successively delivered to consumers through the distribution networks. the transmission grid is therefore the basic infrastructure that permits large physical power flow in a power system operation. therefore, transmission expansion programme (tep), which decides which new lines will enable the system to satisfy future loads with the required degree of reliability is one of the main strategic decisions in power systems operation (levi and calovic, 1993). the problem of inadequate power supply can be tackled by generation upgrade and/or expansion. this means that more generating units are added to the existing power plants or new power plants are built at new locations in a nation’s power grid. further generation always results in increased power flow on transmission lines connecting the grid. if the present transmission network is not capable of transferring this added generation, then an improvement or expansion of the transmission system is needed (levi and calovic, 1993). in respect of nigeria, the electric power system is continually undergoing metamorphosis due to steady increase in installation/commission of new power generating projects with little no improvement in the power grid. so, in most cases, the system fails to maintain its stability when there is a sudden outage of one of its components. this always affects the power quality delivered by the system. in a typical power system, the supply of electricity to load centres is as a result of the system operation that involves three stages namely: : the generated power at the generating stations which is thus transferred to the distribution centres through the high voltage transmission network. at the distribution station, the electrical power is derated to a lower voltage level to serve low voltage consumers. due to the rising electricity consumption and expected renewable energy integration, transmission network expansion planning is required to help provide alternative paths for power transfer from power plants to load centres during emergencies. for improved power delivery in the nation; this expansion programme needs to be incorporated to the existing power system operation. fundamentally, the transmission network expansion planning is defined as the problem technical approach for determining the optimal location of new transmission lines within an existing grid in order to enhance power transfer. this helps in complementing the grid rehabilitation exercise for fast-tracking power sector recovery to ensure that the growing national electricity demand is met at the lowest economic cost. this is better achieved through mathematical modelling that is based on the optimization approach. there are different forms of optimization techniques which have been lately adopted in solving the transmission expansion planning. this includes but not limited to the following, namely: linear programming (levi and calovic, 1993), bendersde composition (pereira, et al. 1985), branch and bound (haffner, et al. 2001), genetic algorithm (jingdong and guoqing, 1997), simulated annealing (romero, et al. 1996), etc. the purpose of the transmission expansion planning problem programme is to propose the least economic cost transmission expansion strategy while fulfilling all the operation and security constraints of the power system operation. for the purpose of developing an effective transmission expansion network; the optimal decision on the location of the proposed new transmission lines is best obtained by modelling the system with the help of robust mathematically designed optimization technique. this procedure would involve the dynamic determination of the best combination of the conflicting goals/objectives desired for http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 79 optimization in the presence of a number of trade-offs for the purpose of identifying the optimal location of the proposed new lines through adequate modelling, development and evaluation of the existing transmission network parameters. 2. materials and methods the materials for the analysis of transmission expansion programme were variously ranging from the data gathered from the transmission company of nigeria (tcn) on the nigeria-31 bus system as well as the data of the ieee-30 bus test case as obtained from the e-laboratory webpage of the department of electrical and computer engineering of the university of washington. so also, the deployment of the power flow features of the powerworld software for pictorial display of load flow analysis, and the use of the matlab software for the mathematical analysis. 2.1 implementation of the improved strength pareto evolution algorithm (spea-2) with a solid inspiration from other forms of the evolutionary algorithm, two researchers zitzler and thiele (1999) developed the spea as a multi-objective optimization solution approach (zitzler and thiele, 1999). few years later, this method was later improved to provide a better approach known as the improved spea (normally referred to as spea 2) approach (zitzler, et al. 2002). the later tries to overcome the weaknesses of the later. some of the weaknesses in the spea are that the fitness assignment scheme doesn’t individuals that it dominates and dominated by, so also no strict guidance of the search process and the boundary solutions are highly threatened that there is high degree of failure to account for them in the final evaluation of best solutions. fortunately, all the aforementioned setback are addressed in the spea-2. in other words, the spea-2 uses a regular population and an archive (external set). starting with an initial population and an empty archive the following steps are performed per iteration: first, all non-dominated population members are copied to the archive; in which case any dominated individuals or duplicates (regarding the objective values) are removed from the archive during this updated operation. however if the size of the updated archive exceeds a predefined limit, further archive members are deleted by a clustering technique which preserves the characteristics of the non-dominated front. afterwards, fitness values are assigned to both archive and population members with the help of the following steps: each individual i in the archive is assigned a strength value ( )s i , which at the same time represents its fitness value ( )f i . ( )s i are the numbers of population members (i.e. j) that are dominated by or equal to individuals in the archive (i.e. i ) with respect to the objective values, divided by the population size plus ‘1’. the fitness ( )f j of an individual ‘j’ in the population is calculated by summing the strength values ( )s i of all archive members ‘ i ’ that dominate or are equal to ‘j’; and adding ‘1’ at the end. the next step represents the mating selection phase where individuals from the union of population and archive are selected by means of binary tournaments. it should be noted that fitness is to be minimized here, hence each individual in the archive has a higher chance to be selected than any other population member. finally, after recombination and mutation the old population is replaced by the resulting offspring population. to avoid the situation whereby the individuals dominated by the same archive members have identical fitness values, thus as stated file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 80 earlier on; the beauty of the spea-2 is that for each individual; both dominating and dominated solutions are taken into account. in detail, each individual ‘’ in the archive tp and the population tp is assigned a strength value ( )s i , representing the number of solutions it dominates; thus as earlier stated, the spea-2 algorithm helps in the following ways, namely: the number of individuals contained in the archive is constant over a period of time of operation, and the truncation method prevents boundary solutions being removed. during the process of environmental selection, the first step is to copy all non-dominated individuals, i.e., those which have fitness lower than unity from archive and population size to the archive of the next generation. the following should be noted in developing this algorithm (abido, 2006): input: n (population size), n (archive size), t (maximum number of generations), output: a (nondominated set). to facilitate this procedure in the work herein presented; thus the algorithm is executed in a step-by-step approach as follows: step 1 initialization: generate an initial population tp and create the empty archive (external set) 0p = ( ); .set t = 0. step 2 fitness assignment: calculate fitness value of individual tp step 3 environmental selection: copy all non-dominated individuals in tp to 1tp . if size of 1tp exceeds n then reduce 1tp by means of the truncation operator, otherwise if size of 1tp is less than n then fill 1tp with dominated individual in tp and tp . step 4 termination: if t >t or another stopping criterion is satisfied then add set a to the set of decision vectors represented by the non-dominated individuals. step 5 mating selection: perform binary tournament selection with replacement on tp >1 in order to fill the mating pool. step 6 variation: apply recombination and mutation operators to the mating pool and set 1tp to the resulting population. increment generation counter (t =t + 1) and go to step 2. in this research; the improved strength pareto evolution algorithm (spea-2) as a multiple objective function technique, as introduced above, is implemented. it should be noted that this approach involves solving a multi-criteria decision making complex problem moderated with the help of relevant trade-offs. in this study, the decision making involves the following objective functions namely: power loss, relevant cost (comprising reactive power support and fuel cost) and capital investment cost. this can thus the power loss and cost can be modelled as shown in equation (1) and equation (2): http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 81 for the power loss,    , lossf x z min p (1) so also for the cost of fuel and reactive support;  min cost = )( max gi s gi sminc (2) equation (2) is simplified as the combination of reactive power support and fuel cost as depicted in equation (3) i.e. )()()( maxmaxmaxmax gi p gigigi q gigi s gi pcqcsminc  (3) equations (1) and (2) are subjected to inequality constraints as shown in equations (4) and (5), i.e.: maxmin, iii vvv  (4) max,max, gigigi qqq  (5) in the case of the investment in new transmission line; then equation (6) was adopted; thus the capital investment cost (i.e. in):      n k kgkkgkkikik r cpbpazdfcrin 1 21)1( (6) while the general line impedance equation is given in equation (7); ikikik jxrz  (7) where rik:=resistance of the line to be expanded xik:=reactance of the line to be expanded dik:=distance between adjacent buses of the transmission lines of interest. fc:=capital cost of building a transmission line per km($/km) to calculate the capital investment cost or value, in, the simple interest formular for determining the rate paid on invested principal value is obtained in equation (8) r:=interest rate, pt inr )(100  (8) t:= number of time periods p:= principal amount of money to be invested in:= capital investment cost or value , ,k k ka b c := constant coefficient of generators thus pgk as the active power generation of the k generating units subjected to active power balance constraint is obtained as in equation (9); dii k gk ppp i   (9) where :dip active power demand at bus, i :ip net active power injection at bus i :gkp net active power flowing out of various buses into bus i  :ik  total number of buses transmitting power into bus i file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 82 2.2 power flow model the adopted modelling approach is the establishment of nonlinear relationship among the critical system parameters such as the bus power injection; as shown in equation (10), the branch power flow is as displayed in equation (11). so also, the bus voltages are as presented in equation (12) and the voltage angles which is as expressed in equation (13). so also the expression for line admittance is as shown in equation (14). . from the foregoing therefore; the power flow model which supplies information on the electrical performance of the lines with respect to the actual power flow in the various lines is thus presented as depicted in equation (15). this thus provides the needed information about the line loading capacity is as introduced in equations (16) and (17).. in developing power flow equations, it should noted that the balanced 3-phase system operation is assumed; hence per-phase analysis is utilized to obtain the relevant equations. digii sss  (10) )sincos( 1 * 1 ** ikikikikk n k ik n k ikiiii jbgvvvyvivs     (11) ikj iikii evvv   (12) kiik   (13) ikikik jbgy  (14)  ikikikikk n k ii jbgvvs  sinsin 1   (15)  ikikikikk n k ii bgvvp  sinsin 1   (16)  ikikikikk n k ii bgvvq  sinsin 1   (17) where n:=total number of buses in the system pi and qi:=specified active and reactive demand at load bus i gik:= element of line conductance bij:= element of line susceptance θij:= phase angle between sending end voltage and receiving end voltage iv := bus voltage at bus i; jv := bus voltage at bus j; contingency analysis the term contingencies are defined as potentially harmful disturbances that occur during the steady state operation of a power system. load flow constitutes the most important study in a power system for planning, operation and expansion. the purpose of load flow study is to compute operating conditions of the power system under steady state. these operating conditions are normally voltage magnitudes and phase angles at different buses, line flows (mw http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 83 and mvar), real and reactive power supplied by the generators and power loss (ezechukwu, 2013). the contingency analysis is becoming an essential task for power system planning and operation. thus the power system security analysis forms an integral part of modern energy management system. in other words, the power system security, as a term, is used for expressing the power systems ability to meet its load without unduly stressing its apparatus or allowing variables to stray from prescribed range under the apparatus or allowing variables to stray from prescribed range under certain pre-specified credible contingencies. hence in order to predict the effect of outages; the contingency analysis approach is widely embraced. this is predictably achieved by appealing to the contingency ranking protocol. this is best developed by determining, in descending order, the contingency ranking line severity index. this is the measurement of the effect of contingency event on the power system. the evaluation of the contingency effect is thus obtained in the off-line mode suing the earlier developed power flow model (as expressed in equations 10 to 14). the violation of the line active power index is expressed as equation 15:    n i i i p p p 1 max  (15) where pi := active power flow in line i pimax:= maximum active power flow in line i so also the violation voltage violation is obtained as in equation (16);             1 1 minmax )(2mn i ii ioi v vv vv  (16) where n-m-1:= total number of load buses m:= number of pv buses n:= total number of load buses vi:= voltage at bus i vio:= nominal voltage at bus, i (i.e. 1p.u.) vimin:= minimum voltage limit (95% of vio) vimax:= maximum voltage limit (105% of vio) it should be noted that this analysis is very apt in determining the state of robustness of a transmission network. in other words, the higher the value of severity indices (in equations (15) and equation (16)), the more the threats of the possibility of potential collapse of the system. thus the value obtained has measurable tendency for predicting the necessity for the importunity of the transmission expansion programme. 3. results and discussion from the foregoing methodology; a set of numerical results is then obtained by implementing the powerworld software and matlab software. thus, table 1 shows the results obtained from the power flow analysis using the newton raphson load flow iteration method. this is then applied to the nigeria-31 bus system by using the bus and line data gathered from the transmission company of nigeria. thus it presents the voltage profile of the nigeria-31 bus system in which the generation buses within the network are seven in number with one of them file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 84 serving as the slack bus for the network. to further appreciate the foregoing; the appropriate equations derived in the preceding sections were then applied on the electrical loading capacity of the various lines. further investigation was also performed on the nigeria-31 bus system to evaluate the single line contingency test. the summary of the contingency analysis was showcased in the succeeding graphs and tables. whereby the voltage profile is as presented in table 1, this vividly shows at a glance the lines and buses that need attention of the network planners. from table 1, it is clearly evident that a number of buses violated the %5 boundary set for the operation of power system; such buses are bus number: 2, 10, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25 and 28. it must be noted that at the verge of violation is found bus number: 5. in the case of table 2; for the nigeria-31 bus system, the lines that are highly threatened due to the line losses is arranged in the order severity are lines: 9-11, 29-12, 8-15, 10-15 and 18-12. table 1: voltage profile of the nigeria-31 bus system loading and generation of network including bus voltage and angle bus no v (pu) angle injection generation load (degree) mw mvar mw mvar mw mvar 1 1.020 0.000 825.461 332.244 825.461 332.244 0.000 0.000 2 0.990 -2.956 200.000 -43.876 200.000 -43.876 0.000 0.000 3 1.000 -2.382 300.000 11.300 300.000 11.300 0.000 0.000 4 1.000 -8.914 250.000 138.405 250.000 138.405 0.000 0.000 5 1.030 7.076 490.000 -52.650 490.000 -52.650 0.000 0.000 6 1.040 7.387 350.000 -27.038 350.000 -27.038 0.000 0.000 7 1.030 9.587 450.000 -35.419 450.000 -35.419 0.000 0.000 8 0.995 -5.036 -156.000 -79.900 0.000 0.000 156.000 79.900 9 1.040 4.645 -8.600 -5.600 0.000 0.000 8.600 5.600 10 0.982 -5.693 -429.900 -258.400 0.000 0.000 429.900 258.400 11 1.016 -0.557 -201.000 -136.700 0.000 0.000 201.000 136.700 12 1.034 -1.170 -166.200 -97.800 0.000 0.000 166.200 97.800 13 1.063 -6.450 -58.400 -28.400 0.000 0.000 58.400 28.400 14 0.978 -11.259 -144.700 -88.400 0.000 0.000 144.700 88.400 15 0.973 -10.828 -115.200 -42.000 0.000 0.000 115.200 42.000 16 0.996 -4.827 -82.100 -44.500 0.000 0.000 82.100 44.500 17 0.958 -12.711 -112.600 -50.000 0.000 0.000 112.600 50.000 18 0.994 -8.084 -184.900 -60.000 0.000 0.000 184.900 60.000 19 1.075 -10.670 -102.900 -17.500 0.000 0.000 102.900 17.500 20 1.021 2.030 -60.300 -70.000 0.000 0.000 60.300 70.000 21 1.006 -6.017 -26.800 -10.500 0.000 0.000 26.800 10.500 22 0.978 -6.133 -292.000 -114.900 0.000 0.000 292.000 114.900 23 0.998 -3.220 -193.500 -101.200 0.000 0.000 193.500 101.200 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 85 24 0.993 -4.123 -139.400 -61.000 0.000 0.000 139.400 61.000 25 1.000 -3.005 -109.700 -64.200 0.000 0.000 109.700 64.200 26 0.996 -4.356 0.000 0.000 0.000 0.000 0.000 0.000 27 0.999 -4.675 -64.300 -44.200 0.000 0.000 64.300 44.200 28 0.981 -10.991 -119.300 -65.700 0.000 0.000 119.300 65.700 29 1.041 2.785 -61.500 -10.300 0.000 0.000 61.500 10.300 30 1.045 4.892 0.000 0.000 0.000 0.000 0.000 0.000 31 1.040 4.932 0.000 0.000 0.000 0.000 0.000 0.000 in the case of table 2; for the nigeria-31 bus system, the lines that are highly threatened due to the line losses is arranged in the order severity are lines: 9-11, 29-12, 8-15, 10-15 and 18-12. table 2: line flow and line loss of the nigeria-31 bus transmission line from bus to bus p (mw) q (mvar) from bus to bus p (mw) q (mvar) line loss (mw) (mvar) 25 1 -825.940 -242.193 1 25 825.940 291.920 0.000 49.727 26 2 -200.000 35.026 2 26 200.000 -30.002 0.000 5.024 27 3 -300.000 -15.482 3 27 300.000 27.581 0.000 12.099 28 4 -250.000 -129.449 4 28 250.000 141.171 0.000 11.722 29 5 -490.000 86.333 5 29 490.000 -48.893 0.000 37.440 30 6 -350.000 30.718 6 30 350.000 -15.387 0.000 15.331 31 7 -450.000 63.900 7 31 450.000 -26.891 0.000 37.009 10 8 -31.213 -54.646 8 10 31.445 56.397 0.232 1.751 11 8 109.331 14.496 8 11 -108.156 -5.665 1.175 8.831 8 15 245.872 32.086 15 8 -242.515 -6.816 3.357 25.270 21 8 -26.800 22.002 8 21 26.892 -21.313 0.092 0.689 8 26 -155.680 4.482 26 8 155.889 -2.663 0.209 1.819 8 27 -196.404 59.991 27 8 197.633 -59.109 1.229 0.882 9 11 633.489 129.221 11 9 -625.505 -69.260 7.984 59.961 9 29 95.623 -17.475 29 9 -95.202 20.634 0.421 3.159 30 9 289.242 6.360 9 30 -288.018 -5.137 1.224 1.223 31 9 450.000 -61.006 9 31 -449.694 63.263 0.306 2.257 11 10 105.643 40.585 10 11 -104.185 -29.618 1.458 10.967 10 22 292.377 112.165 22 10 -292.000 -109.378 0.377 2.787 24 10 68.176 30.731 10 24 -67.865 -28.390 0.311 2.341 10 25 -519.014 -77.597 25 10 522.604 104.548 3.590 26.951 11 24 209.531 67.682 24 11 -207.576 -52.983 1.955 14.699 12 13 164.637 -65.939 13 12 -162.356 83.129 2.281 17.190 18 12 -184.900 -22.413 12 18 188.078 46.318 3.178 23.905 29 12 523.702 4.711 12 29 -518.916 31.226 4.786 35.937 13 19 103.956 -25.158 19 13 -102.900 33.097 1.056 7.939 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 86 15 14 14.140 -14.523 14 15 -14.113 14.722 0.027 0.199 14 28 -130.587 -70.858 28 14 130.700 71.711 0.113 0.853 15 17 113.175 39.805 17 15 -112.600 -35.475 0.575 4.330 26 16 44.111 -5.689 16 26 -44.061 6.061 0.050 0.372 27 16 38.067 36.211 16 27 -38.039 -35.998 0.028 0.213 20 30 -60.300 -16.630 30 20 60.758 20.079 0.458 3.449 25 23 193.636 97.753 23 25 -193.500 -96.744 0.136 1.009 3.1 pareto space according to table 3 as regards the implementation of the improved strength pareto evolutionary algorithm (spea-2), it can be seen that the adopted number of generation (i.e. the previous generation from which the next parent for current generation are chosen) was 200 while the size of archive (externally stored pareto solution) was 50 and the population size was 250. whenever this is implemented; it resulted in the convergence to a pareto front as will be displayed in a number of scenarios that would later be presented in this study. table 3: improved strength pareto evolution algorithm parameters generation 200 archive set 50 population size 250 3.2 optimal solution as stated earlier, there is need in decision making to consider trade-offs due to conflicting goals that must be optimized in the application of the optimization theory. in the case of this research work, the three parameters of interest are namely; the line index, power losses and capital investment cost needed for the expansion of the network; in order to alleviate the challenges of outages that are necessitated by weak links as presented in the violated lines. in order to have a better understanding of this, using the spea-2 the nigeria-31 bus system is compared with a standard benchmark as represented by ieee-30 bus system. thus, the outcome of this led to the results displayed in figures 1 and 2 in which the power loss was compared with the power generation cost for both bus systems. from the available details in both diagrams; the results of the ieee-30 bus is quite optimal in outlook while that of the nigeria-31 bus system is highly violated hence there is need for capital-intensive investment; i.e. using the transmission expansion as a formidable option; to ensure that the power loss is reduced drastically so as to be more competitive to the ieee-30 bus system. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 87 figure 1: nigeria 31-bus pareto front for power loss against power generation cost figure 2: ieee 30-bus pareto front for power loss against power generation cost 3.3 transmission expansion philosophy with reference to previous discussion, from the output of the earlier considered graphs; it’s very essential to consider the power loss against investment cost. this would provide information on the extent to which the transmission network needs to be upgraded to avoid incessant outages (which is currently very prevalent). thus, since a number of lines has been discovered as the weakest link in the energy flow chain of the nigeria-31 bus system hence there is need to reinforce the network to overcome the influence of voltage collapse through the threats emanating from these identified buses on the network. in this vein, figure 3 shows the investment cost as compared with the power loss. thus if this investment well managed at critical buses then the network will experience a better power flow. in line with the multi-objective solution philosophy of transmission expansion programme, thus the nigeria-31 bus system was subjected to a three-objective function. with the help of the spea-2; this results in the generation of the results that displayed in figure 4. this thus corroborates the propensity of the well-planned transmission expansion programme as a last resort of the current energy crisisthat is bedeviling the nigeria electricity industry. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 88 figure 3: pareto front for power loss against investment cost figure 4: pareto front for investment cost, line index and power loss 3.4 results of the contingency analysis of the nigeria-31 bus network to achieve the contingency analysis, the lines or generators were carefully chosen and then remove from service for the purpose of subjecting the network to contingency test. in this case only one line is taken out of service in each scenario as shown in table 5. thus, from the foregoing, this shows that when the generators were subjected to contingency test, with one of the generators shutdown, it gave rise to cascaded violation of the network. it can be seen from this table that when contingency analysis was performed on the network; the buses that the buses that suffered major violation were: the buses located at jos (i.e. bus 14), gombe (i.e. bus 17), birnin kebbi (i.e. bus 28) and kaduna (i.e. bus 29). obviously, this is due to a number of factors among which are the distance and source of power generation to these buses. so also lack of transmission line reinforcement using the power conditioners (such as the bank of reactors, shunt power electronics devices) at the identified buses are all contributory indices http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 89 to the violation suffered by the lines during this contingency test. however, with the introduction of the new generation at geregu and ajaokuta, it is expected that it will relieve the buses in the network around this section of the transmission network. table 4: single transmission line contingency test contigency considered skip processed solved violations line from 11 (benin) to 2 (deltaps) c1 no yes yes 4 line from 2 (deltaps) to 21 (aladja) c1 no yes yes 4 line from 15 (onitsha) to 3 (okpai) c1 no yes yes 5 line from 11 (benin) to 4 (sapele) c1 no yes yes 4 line from 4 (sapele) to 21 (aladja) c1 no yes yes 4 line from 26 (alaoji) to 5 (afam) c1 no yes yes 4 line from 10 (oshogbo) to 6 (jebba) c1 no yes yes 4 line from 27 (jebbats) to 6 (jebba) c1 no yes no unsolved line from 7 (kainji) to 27 (jebbats) c1 no yes yes 4 line from 7 (kainji) to 27 (jebbats) c2 no yes yes 4 line from 7 (kainji) to 28 (b. kebbi) c1 no yes yes 3 line from 27 (jebbats) to 8 (shiroro) c1 no yes no unsolved line from 8 (shiroro) to 30 (shirorots) c1 no yes no unsolved line from 9 (geregu) to 24 (ajaokuta) c1 no yes yes 4 line from 10 (oshogbo) to 11 (benin) c1 no yes yes 4 line from 10 (oshogbo) to 12 (ikeja-west) c1 no yes yes 4 line from 13 (ayede) to 10 (oshogbo) c1 no yes yes 4 line from 12 (ikeja-west) to 11 (benin) c1 no yes yes 4 line from 11 (benin) to 15 (onitsha) c1 no yes yes 4 line from 11 (benin) to 24 (ajaokuta) c1 no yes yes 4 line from 13 (ayede) to 12 (ikeja-west) c1 no yes yes 4 line from 16 (akangba) to 12 (ikeja-west) c1 no yes yes 5 line from 32 (egbints) to 12 (ikeja-west) c1 no yes no unsolved line from 14 (jos) to 17 (gombe) c1 no yes yes 2 line from 29 (kaduna) to 14 (jos) c1 no yes yes 4 line from 15 (onitsha) to 25 (n. haven) c1 no yes yes 4 line from 15 (onitsha) to 26 (alaoji) c1 no yes yes 4 line from 30 (shiroro ts) to 18 (abuja) c1 no yes yes 5 line from 29 (kaduna) to 22 (kano) no yes no unsolved line from 23 (aja) to 32 (egbints) c1 no yes yes 4 line from 23 (aja) to 32 (egbints) c2 no yes yes 4 line from 30 (shirorots) to 29 (kaduna) c1 no yes yes 4 line from 30 (shirorots) to 29 (kaduna) c2 no yes yes 4 line from 31 (egbinps) to 32 (egbints) c1 no yes no unsolved file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 90 table 5: summary of contingency analysis contigency considered buses violated line from 11 (benin) to 2 (deltaps) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 2 (deltaps) to 21 (aladja) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 15 (onitsha) to 3 (okpai) c1 jos (14), gombe (17), b. kebbi (28), kaduna (29) and n. haven (25) line from 11 (benin) to 4 (sapele) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 4 (sapele) to 21 (aladja) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 26 (alaoji) to 5 (afam) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 10 (oshogbo) to 6 (jebba) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 7 (kainji) to 27 (jebba ts) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 7 (kainji) to 27 (jebbats) c2 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 7 (kainji) to 28 (b. kebbi) c1 jos (14), gombe (17) and kaduna (29) line from 9 (geregu) to 24 (ajaokuta) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 10 (oshogbo) to 11 (benin) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 10 (oshogbo) to 12 (ikeja-west) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 13 (ayede) to 10 (oshogbo) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 12 (ikeja-west) to 11 (benin) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 11 (benin) to 15 (onitsha) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 11 (benin) to 24 (ajaokuta) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 13 (ayede) to 12 (ikeja-west) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 16 (akangba) to 12 (ikeja-west) c1 jos (14), gombe (17), b. kebbi (28), kaduna (29) and oshogbo (10) line from 14 (jos) to 17 (gombe) c1 kano (22) and b. kebbi (28) line from 29 (kaduna) to 14 (jos) c1 abuja (18), kano (22) b. kebbi (28) and kaduna (29) line from 15 (onitsha) to 26 (alaoji) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 15 (onitsha) to 26 (alaoji) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 30 (shiroro ts) to 18 (abuja) c1 jos (14), gombe (17), b. kebbi (28), kaduna (29) and shirorots (30) line from 23 (aja) to 32 (egbints) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 23 (aja) to 32 (egbints) c2 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 30 (shirorots) to 29 (kaduna) c1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) line from 30 (shirorots) to 29 (kaduna) c2 jos (14), gombe (17), b. kebbi (28) and kaduna (29) generator 2 (deltaps) u1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) generator 3 (okpai) u1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) generator 4 (sapele) u1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) generator 5 (afam) u1 jos (14), gombe (17), b. kebbi (28) and kaduna (29) 3.5 power flow analysis with powerworld software furthermore, the same network data were subjected to the implementation of the the powerworld software to display the pictorial situation of the existing transmission network in the nigeria-31 bus system so as to identify the area of improvement needed for the healthy http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 91 operation of the network. the investigation is as displayed in figure 5 whereby the existing power network of the nigeria-31 bus system data were deployed for giving information on the existing state of the nigeria’s transmission network. just as earlier declared by the traditional analysis approach that identified a number of buses are the weak links in the nigeria’s transmission network, the pictorial software further displays vividly the precarious state of power system operation in the nigeria-31 bus system. this results further validate the earlier pronounced findings which identified the most violated buses as those situated at kaduna, gombe, jos and birnin kebbi. in anticipation of the solution, as a correction step, extra single line was introduced between kanji bus and birnin-kebbi transmission bus while another line was introduced shiroro and abuja buses as well as an extra line along kaduna to jos bus; this leads to immense improvement in the power flow in the network, especially with regard to the identified weak buses, the power flow in them increased considerably as shown in figure 6. thus it can be summarized that the existing nigeria’s transmission network needs the assistance of the double line as introduced in figure 6. this is expected to bring about great improvement in the voltage profile which has a direct and constructive influence on the reliability of electricity supply within the nigeria-31 bus system. figure 5: existing nigeria-31-bus network file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 92 figure 6: improved nigeria-31-bus transmission network 4. conclusion this study addressed the transmission system expansion planning using an optimization approach known as the improved strength pareto evolution algorithm (spea-2) while also using the contingency analysis to isolate the most threatened lines and buses in the nigeria’s transmission network. it was discovered that four major buses were violated which were located at jos, kaduna, kano and birnin-kebbi respectively. suggestively, it was also observed during this research work that transmission lines linking the geographical northern and southern parts of nigeria experienced more power losses than any others. this is believed to be due to the length of transmission lines which remained uncompensated by neither traditional bank of reactors nor the modern power electronics devices. . further to this, it was observed that when contingency test was applied to the same network; the kano, birnin-kebbi, kaduna and gombe buses had the highest number of violation when transmission line were opened as well as while one of the generators was shutdown. this thus suggests that, with the addition of double circuit on each transmission line connected to the weak buses in the nigeria-31 bus system, thus the violation was drastically reduced. furthermore, with the implementation of the improved strength pareto evolution http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 93 algorithm (spea-2); it was possible to determine the optimal and best solution in terms of line index function, investment cost analysis and the power loss protocol. thus the transmission expansion philosophy has shown a great potential for overcoming the identified congestion created by the weak transmission lines in the various locations. . appendix figure 7: one line diagram of the nigerian transmission network table 6: generator data of nigerian 330 kv grid system bus no pg (mw) qg (mvar) qmax (mvar) qmin (mvar) base mva vg (p.u.) 1 830.23 0 450 -255 100 1.00 2 200 0 450 -250 100 0.99 3 300 0 450 -250 100 1.00 4 250 0 450 -250 100 1.00 5 490 0 450 -250 100 1.03 6 350 0 450 -250 100 1.04 7 450 0 450 -250 100 1.03 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 94 table 7: line data of nigerian 330 kv grid system from bus to bus r (p.u.) x (p.u.) 0.5b (p.u.) 25 1 0 0.00648 0 26 2 0 0.01204 0 27 3 0 0.01333 0 28 4 0 0.01422 0 29 5 0 0.01638 0 30 6 0 0.01351 0 31 7 0 0.01932 0 10 8 0.0055 0.04139 0.9425 11 8 0.00987 0.07419 0.41575 8 15 0.00538 0.0405 0.2269 21 8 0.00766 0.05764 0.323 8 26 0.0003098 0.00739 0.16565 8 27 0. 00287 0.02158 0.1209 9 11 0.00206 0.01547 0.78 9 29 0.0048 0.03606 0.80825 30 9 0.00159 0.01197 0.2683 31 9 0.00016 0.00118 0.0265 11 10 0.01163 0.0875 0.49025 10 22 0.00036 0.00266 0.0595 24 10 0.00538 0.0405 0.227 10 25 0.00122 0.00916 0.2054 11 24 0.00412 0.03098 0.1736 12 13 0.00774 0.05832 0.3263 18 12 0.00904 0.06799 0.38095 29 12 0.00189 0.01419 0.318 13 19 0.01042 0.07833 0.4398 15 14 0.00605 0.04552 0.25505 14 28 0.00049 0.00369 0.0828 15 17 0.00377 0.02838 0.159 26 16 0.00248 0.01862 0.10435 27 16 0.00102 0.00769 0.043065 20 30 0.01218 0.09163 0.51345 25 23 0.00028 0.00207 0.0464 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):77-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 95 table 8: bus data of nigerian 330 kv grid system bus no type pd (mw) qd (mvar) base kv vmax (p.u.) vmin (p.u.) 1 1 0 0 16 1.1 0.9 2 2 0 0 16 1.1 0.9 3 2 0 0 16 1.1 0.9 4 2 0 0 16 1.1 0.9 5 2 0 0 16 1.1 0.9 6 2 0 0 16 1.1 0.9 7 2 0 0 16 1.1 0.9 8 0 156.8 79.9 330 1.1 0.9 9 0 8.6 5.6 330 1.1 0.9 10 0 429.9 58.4 330 1.1 0.9 11 0 201 136.7 330 1.1 0.9 12 0 166.2 97.8 330 1.1 0.9 13 0 58.4 28.4 330 1.1 0.9 14 0 144.7 88.4 330 1.1 0.9 15 0 155.2 42 330 1.1 0.9 16 0 82.1 44.5 330 1.1 0.9 17 0 112.6 50 330 1.1 0.9 18 0 184.9 60 330 1.1 0.9 19 0 102.9 17.5 330 1.1 0.9 20 0 60.3 70 330 1.1 0.9 21 0 26.8 10.5 330 1.1 0.9 22 0 292 114.9 330 1.1 0.9 23 0 193.5 101.2 330 1.1 0.9 24 0 139.4 61 330 1.1 0.9 25 0 109.7 64.2 330 1.1 0.9 26 0 0 0 330 1.1 0.9 27 0 64.3 44.2 330 1.1 0.9 28 0 119.3 65.7 330 1.1 0.9 29 0 61.5 10.3 330 1.1 0.9 30 0 0 0 330 1.1 0.9 31 0 0 0 330 1.1 0.9 acknowledgment the authors wish to appreciate the department of electrical and electronics engineering of university of lagos, nigeria for the provision of software and the privilege embark on this study. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al. transmission expansion programme for electric network reinforcement. azojete, 15(1):77-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 96 references abido, ma. 2006. multiobjective evolutionary algorithms for electric power dispatch. ieee transactions on evolutionary computation, 10(3), 315-329. ezechukwu, oa. 2013. expansion planning of nigeria south east electrical power transmission network. the international journal of engineering and science, 2(9), 97-107. gupta, br. 2008. power system analysis and design. new delhi: s. chand limited, india. . haffner, s., monticelli, a., garcia, a. and romero, r. 2001. specialized branch-and-bound algorithm for transmission network expansion planning. ieee proceedings generation, transmission and distribution, 148(5), 482-488. jingdong, x. and guoqing, t. 1997. the application of genetic algorithms in the multi objective transmission network planning. 4th international conference on advances in power system control, operation and management apscom-97. institution of engineering and technology (iet), hong kong. pp. 338-441. levi, v. and calovic, m. 1993. linear-programming-based decomposition method for optimal planning of transmission network investments. iee proceedings cgeneration, transmission and distribution, 140(6), 516-522. pereira, mv., pinto, lm., cunha, sh. and oliviera, gc. 1985. a decomposition approach to automated generation/transmission expansion planning. ieee transactions on power apparatus and systems, 104(11), 3074-3083. romero, r., gallego, ra. and monticelli, a. 1996. transmission system expansion planning by simulated annealing. ieee transactions on power systems, 11(1), 364-369. zitzler, e., laumanns, m. and thiele, l. 2002. spea2: improving the strength pareto evolutionary algorithm for multiobjective optimization. in: giannakoglou, kc. (eds.) proceedings of the eurogen2001 conference, barcelona, spain, cimne, pp. 95–100. zitzler, t. and thiele, l. 1999. multiobjective evolutionary algorithms: a comparative case study and the strength pareto approach. ieee transactions on evolutionary computation, 3(4), 257271. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):179-187 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 179 original research article performance analysis of horizontal axis wind turbine using variable blade pitch control mechanism m. shuwa*, g. m. ngala and a. m. eljummah (department of mechanical engineering, university of maiduguri, maiduguri, nigeria) *corresponding author’s email address: shuwa07201@gmail.com 1.0 introduction wind is a form free-flowing green energy caused by the uneven heating of the atmosphere by the sun. wind possesses kinetic energy which can be captured and converted into other useful means especially electrical energy through the use of wind turbines (ngo and natowitz, 2009) . horizontal axis wind turbine (hawt) is the most common type of wind turbines used for extracting kinetic energy from wind because of its low cut-in wind speed, easy furling and relatively high power coefficient. it is a type of wind turbine that has wind flowing along the axis of rotation of its rotor (daminia and petal, 2013) . in capturing part of the kinetic energy (ke) in the wind and convert same to other forms of useful energy (electricity), the hawt is subjected to stochastic high wind speed phenomena. this is disastrous to the wind turbine causing generator burnout, rotor and tower failure (shuwa et al. 2016). while power is being captured from the wind by the hawt, it is desired that the wind turbine be design to a wind speed that will not exceeds it critical limit and develop a control system that article information abstract this work investigates the performance of a horizontal axis wind turbine (hawt) with variable blade pitch control mechanism. the control mechanism is a simple mechanical watt governor design, which was developed to regulate the blade pitch angle of the hawt depending on wind speed magnitude. the hawt model with the control mechanism was tested for performance in a wind tunnel. response of the control mechanism in terms of blade pitch angle, rotor speed and generator power output were analyzed based on regulated predetermined wind speeds. the result shows a gradual increase in rotor speed and a proportional increase in generator power output between cut-in wind speed of 2.5m/s and rated wind speed of 6 m/s. these parameters were kept constant at 100 rpm and 50 watts as observed due to the steady response of the control mechanism. the steadiness lasted up to a cut-out wind speed of 9 m/s. the control mechanism subsequently shutdown the turbine at the cut-out wind speed to protect the turbine against wind speeds higher than 9 m/s. the performance test predicts that the variable blade pitch control mechanism was able to regulate and bring about the require control of hawt model. the mechanism allows the turbine to only operate between 2.5 and 9 m/s at blade pitch angle between 82 and 90 degrees from the axis of wind flow and change in governor height between 0 to 8 mm. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 23 august, 2018 revised 29 july, 2019 accepted 08 august, 2019 keywords: hawt blade pitch control wind speed rotor speed generator power output. mailto:shuwa07201@gmail.com http://www.azojete.com.ng shuwa et al: performance analysis of horizontal axis wind turbine using variable blade pitch control mechanism. azojete,16(1):179-187. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 180 will make it operate within a safe wind speed range. this is in order to avoid unforeseeable damages to the machine structure and highly fluctuating power output under high wind speeds (soriano et al, 2013) . the aerodynamic forces on the rotor can be controlled to limit the speed of the hawt by employing blade pitch control mechanisms as shown in figure 1. it involves the use of centrifugal force to regulate and control the blade pitch angle depending on wind speed magnitude (chen et al, 2014). figure 1: the hawt with a simple mechanical blade pitch control mechanism the blade pitch control mechanism could be the active pitch control (apc) or passive or stall pitch control (ppc or spc). in the active pitch control the rotor blades turn around their longitudinal axis to the pitch by a speed controlled system that is usually computer type. even though this type of control provide good pitch control, but its equipment are too expensive to afford. hence the need for an alternative type of control system especially in small hawt as used in low wind speed region. while the passive or stall pitch control (ppc or spc) the blade does not rotate around its longitudinal axis, rather the blade is designed to naturally create a stall and lower rotational speed of the rotor. this requires structurally strong towers and that the blade is precise in its design and this is an additional expense on the total cost of the turbine (maheswari and tamilvendhan, 2012). the principle of a simple mechanical watt governor is applied in order to regulate the blade pitch angle of the hawt which depends on the magnitude of the wind speed the turbine is subjected to. a watt governor (typically centrifugal governor) is a device that will be used to measure and regulates the speed of a machine (rana et al, 2012) . date back to 17th century; watt governors have been used to regulate the distance and pressure between millstones in windmills. although, the early steam engines employed a purely reciprocating motion and were used for pumping water, an application that could tolerate variations in the working speed of machines (navathale et al, 2017) . presently, the watt governor type is used to control the rotor speed of a three blades hawt model, the blades was designed and developed by shuwa et al (2016). the aim of this work is carry out a performance analysis of a horizontal axis wind turbine using variable blade pitch control mechanism. response of the control mechanism measured in terms of blade pitch angle, rotor speed and generator power output with respect to change in wind speed, these parameters are analysis to determine if the desired hawt control is achieved. 2.0 methodology a horizontal axis wind turbine blade geometry developed by shuwa et al (2016) was scaled down to 1:10 based on the principle of dimensional analysis and similitude and used in this http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 179-187. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 181 work. a watt governor was used to regulate the blade pitch angle of the hawt model depending on wind speed magnitude. the model was tested for performance in a wind tunnel at the department of mechanical engineering, university of maiduguri. response of the control mechanism was determined at regulated predetermined wind speeds in terms of rotor speed, blade pitch angle and generator power output. cut-in, rated and cut-out wind speeds of the hawt model were also established. 2.1 the hawt blade the blade geometry developed by shuwa et al (2016) for a micro hawt was modified and used for the hawt model analysis in this work. the modified blade parameters and its specification are shown in table 1. table 1 modified hawt blade parameters and its specifications parameter specification scaled down specification chord length (c), m 0.26 0.024 blade span (l), m 1.5 0.15 rotor diameter (d), m 3 0.3 number of blades (n) 3 3 swept area (a), m2 7.55 0.755 tip speed ratio (�� ) 5 5 angle of attack (θ), degrees 8 8 wind relative angle (�), degrees 48 48 reynolds number 3 ×106 3 × 106 solidity ratio (�) 0.08 0.08 2.2 operational principle of the hawt blade pitch control mechanism the hawt blade pitch control mechanism is a simple mechanical control system that works on the principle of centrifugal governor also known as watt governor. a centrifugal governor is based on the balancing of centrifugal force on the rotating balls by an equal and opposite radial force. it consists of three balls of equal weights, which are attached to the arms called linkages as shown in figure 2. figure 2: centrifugal governor on the hawt rotor shaft the balls revolve with the rotor depending on wind speed magnitude. the upper ends of the arms are pivoted to the blade shaft in the hub, so that the balls may pull outward or inward as they revolve about the rotor axis. the arms connect the sliding and fixed flange or sleeve. the fixed flange is keyed to the rotor shaft and the sliding flange moves to and fro against a spring according to the speed of the rotor. the movement of the sliding flange determines the change in governor height (∆h) of the control system. the balls pull out due centrifugal force when the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuwa et al: performance analysis of horizontal axis wind turbine using variable blade pitch control mechanism. azojete,16(1):179-187. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 182 rotor speed increases due increase in wind speed. when this occurs the balls move the sliding flange against the spring (governor height) to reduce the blade pitch angle (wind to blade angle of attack) which reduces the speed of the rotor. the balls (weights) push inwards due to the spring action when wind speed decreases. this increases the blade pitch angle and reduces the angle of attach to maintain safe rotor speed. the travel of the sliding flange is limited by the maximum compression limit of the coil spring and as wind speed exceed critical limits the sliding flange luck up to short down the turbine. 2.3 design of the blade pitch angle control mechanism the hawt control system is a mechanical control process designed based on a nonlinear closed-loop (feedback) control action govern by a second order nonlinear differential equation given by equation 1. fac = m d2h dv2 + bc dh dv + ksh (1) the applied centrifugal force (fac) is generated by the fly masses (m) due to the rotational speed of the rotor (ωr) as a result of increase in wind speed (v). the applied centrifugal force generate a displacement (h) against an opposing force due spring elasticity with a spring constant (ks ). the speed of the rotor which is the input signal to the control system determines the change in the displacement of the sliding flange which regulates the blade pitch angle. change in displacement of the sliding flange or sleeve ((∆h)) from its rest or initial (minimum) position to its maximum position due the applied centrifugal force was obtained using equation 2. the minimum and maximum displacement of the sliding flange also indicates limits of the control system. ∆h = bb1 ∙ cos ∆θ (2) where: bb1 is the maximum travel of the slider flange in mm and is equal to the radius of the blade pitch circle bk, while α the blade pitch angle and θ is the blade angle of attack as in figure 2 given by equation 3 and ∆h is the sleeve travel from point b to b1. θ = tan−1 20v πnr (3) v is the wind speed, n is the speed of the rotor and r is the radius of the rotor. figure 3: section of the blade pitch angle control mechanism as the sliding flange travel increases from point b to b1 due to increase in wind speed so will the blade pitch angle, thus reducing the blade angle of attack. the change in blade pitch angle α due change in wind speed is determined from equation 4. ∆α = ∆(90 − θ) (4) the slider flange travel due to generated centrifugal force is against a spring. the spring used on the control system was a coiled compression spring. the function of the spring was to restores back the blade to its original angle of attack gradually as the wind speed decreases. the spring constant (ks) determines the ability of the spring to store and release back the stored http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 179-187. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 183 energy as the magnitude of the applied centrifugal force decreases. the spring constant (ks ) is determined from equation 5. ks = gd4 8nsd3 (5) where: g is the spring’s material modulus of elasticity, ds is the spring coil diameter, ds is the wire diameter, ns is the number of spring active turns and c is the spring index given by ds ds . moreover, determined experimentally in a wind tunnel test is the response of the control system in terms of rotor speed, blade pitch angle and generator power output based regulated predetermined wind speed. determined also are cut-in, rated and cut-out wind speed of hawt model with transient and steady response of the control mechanism under the changing wind speed. 2.4 experiment performed on the developed hawt in a wind tunnel the horizontal axis wind turbine (hawt) model developed with the scale down blade and the blade pitch control mechanism was tested in a wind tunnel (figure 4). the wind turbine was subjected to variable wind speeds profile generated in the tunnel (from 1 to 10 m/s). performance of the turbine in terms of rotor speed, blade pitch angle and generator power output speed were examined under a wind tunnel predetermined different wind speed conditions. detail of the wind tunnel in terms of size and capacity alongside the types of instrument used are in table 2. figure 4: the hawt model in an experimental wind tunnel assembly file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuwa et al: performance analysis of horizontal axis wind turbine using variable blade pitch control mechanism. azojete,16(1):179-187. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 184 table 2: descriptive parts of the wind tunnel and its associated instrument s/no. name of instrument make model 1 wind tunnel type um-me open ends type 2 wind tunnel size 600 × 600 × 3000 mm 3 wind tunnel motor drive atlas mt atlas 0054 4.4 kw 2900 rpm wt fan drive 4 wind tunnel drive control easy drive cvr 106 regulates wt air flow/velocity 5 multimeter fluke rms 117 true rms voltage 6 hot wire anemometer ctlutron yk yk-2004 ah air velocity, temperature 7 optical tachometer compact c. cp no 003201 revolution over time 3.0 results and discussion performance analysis of the hawt model with the blade pitch control mechanism developed based on the design parameters in table 3. table 3: design parameters of the hawt model and blade pitch control mechanism parameter value tower height (th), mm 200 rotor radius (r), mm 300 blade angle of attack (θ), ° blade chord length (c), mm drag force (fd), n coefficient of drag (cd), 8 25 0.023 0.0125 lift force (fl), n coefficient of lift (cl) reynolds number solidity ratio (�) power coefficient (cp) turbine theoretical efficiency (�) % ultimate wind speed (vulti.) extractable power from the wind (p), watts 0.19 1.007 3x106 0.08 0.189 32 9 27.22 change in governor height (∆h), mm 0 to 8 mass of the centrifugal weight (m), kg 0.09 deflection of the governor spring (δ), mm 4.32 spring rate (k), n/mm 0.232 figure 5 shows the response of the blade pitch control mechanism in terms of blade pitch angle and rotor speed with respect to wind speed range between 0 to 10 m/s at intervals of 0.5 m/s. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 179-187. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 185 figure 5: response of the control mechanism in terms of blade pitch angle and rotor speed the blade pitch angle and rotor speed indicate that, below cut-in wind speed of 2.5 m/s the system is in rest position. this result shows that from 0 to 2.5 m/s the blade pitch angle (82°) and rotor speed (0 rpm) remain constant, thus indicating that the turbine is at rest. the transient response of the control mechanism in terms of wind speed is between 2.5 m/s (cut-in wind speed) and 6 m/s (rated wind speed). the control mechanism stabilizes the blade pitch angle and rotor speed above wind speeds of 6 m/s and shutdown the turbine as wind speed reaches 9 m/s. chan and shiah (2016) revealed that an effective control mechanism shall be able regulate the blade pitch angle based on their rotational speed at the rotor and wind speed magnitude. similarly, the current test results showed that the control mechanism increases the blade pitch angle as rotor speed increases with increase in wind speed. moreover, change in governor height (∆h) from 0 to 8 mm of the blades pitch control mechanism due to increase in rotor speed, the mechanism gradually rotates the blade about a pivot increasing the blade pitch angle and decreasing angle of attack of the blade airfoil to the wind steam. maheswari and tamilvendhan (2012) in their work showed that it is not always possible, to obtain rated conditions for a wind turbine. therefore, it becomes necessary to control the wind turbine in order to increase energy production and realize a long lifetime. the control should be such that it can instantly convert the energy in the wind between, the rated wind speed (cut-in and cutout) in proportion to speed of the rotor. generator power output depends on rotational speed of the rotor between cut-in and rated wind speed of the turbine as in figure 6. due to response of the control mechanism, rotor speed and generator power output were kept constant at 100 rpm and 50 watts respectively up to cut-out or ultimate wind speed of 8.9 m/s. at 9 m/s there exists a subsequent shutdown of the turbine by the control mechanism. the turbine starts up again with drop in wind speed. here, the response indicates that the control mechanism was effective. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuwa et al: performance analysis of horizontal axis wind turbine using variable blade pitch control mechanism. azojete,16(1):179-187. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 186 figure 6: generator responses to increase in wind and rotor speeds according to maheswari and tamilvendhan (2012) and soriano et al (2013) a control can only be effective if it can respond quickly and effectively for any changes in the wind speeds, so as to keep the turbine operation within its safe rated range. the result in figure 6 shows that the control system only allows the turbine to operate between 2.5 m/s and 9 m/s cut-in and cut-out wind speeds respectively. 4. conclusion in conclusion the result shows that 2.5 m/s was the cut-in wind speed of the hawt model and at 3 m/s rotor speed has reached 35 rpm with generator power output of 15 watts. the hawt blade pitch control mechanism has propitiously controlled the turbine to steadiness between rated wind speed of 6 m/s and cut-out wind speed of 9 m/s. rotor speed and generator power output between these wind speeds are steady at 100 rpm and 50 watts respectively. the cutout wind speed of the turbine has been established to be 9 m/s at a change in governor height of 8 mm, at this wind speed the control mechanism shutdown the turbine to protect it from wind speed above 9 m/s considered high for this model design. this has been achieved because of the ability of the control mechanism to gradually change the blade pitch angle from 82 to 90 degrees deflecting the blade from the wind in other to control the turbine rotor speed. however, cut-out wind speed could be increased in further designs of prototype models for better performance under real environmental conditions. reference chen, y. and shiah, yc. 2016. expeiment on the performance of small horizontal axis wind turbine with passive pitch contro by disk pulley. energies journal, 9(10): 353-366. chen, y. tsca y. huang, c. li m. and hsiao, f. 2014. the design and analysis of passive pitch control for horizontal axis wind turbine. elsevier ltd, 6(1): 683-686. daminia, s. and petal, h. 2013. performance prediction of horizontal axis wind turbine blade. international journal of innovative research in science, engineering and technology, 2(5): 14011406. maheswari, ru. and tamilvendhan, j. 2012. analysis of modelling of active stall controlled and active pitch controlled variable speed wind turbines. international journal of modern engineering research (ijmer), 2: 2662-2667. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 179-187. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 187 navathale, tj., paralkar, aa. and ghorade, vs. 2017. design and analysis of centrifugal governor: a review. international research journal of engineering and technology (irjet), 4(1): 1058-1062. ngo, c. and natowitz, j. 2009. resources, alternatives and the environment. new jersey, usa: john wiley and sons inc., pp. 342-389. rajakumar, s. and ravindran, d. 2010. computational fluid dynamics of wind turbine blade at various angle of attack and low reynolds number. international journal of engineering science and technology, 2(11): 11-17. rana, rs., purohit, r. and singh, a. 2012. design and stress analysis of watt and porter governor. international journal of scientific and research publications, 2(6): 1-6. shuwa, m., ngala, mg. and maina, m. 2016. development and performance test of a micro horizontal axis wind turbine blade. international journal of engineering research and applications, 6(2): 11-17. soriano, la., yu, w. and rubio, j. 2013. modeling and control of wind turbine. wind energy, 10(1): 1155-1168. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 72 the cooling systems and weather statistics of maiduguri and yola nigeria j. a. olorunmaiye 1* and o. o. awolola 2 1 department of mechanical engineering, university of ilorin, p.m.b. 1515, ilorin, kwara state, nigeria 2 department of mechanical engineering, the federal polytechnic, ilaro, p.m.b. 50, ilaro, ogun state, nigeria *corresponding author’s email address: adeolorunmaiye@gmail.com, lekanoba@yahoo.com tel.: +234-8036000053, +234-8027955316 abstract bin data for dry bulb temperature, relative humidity and two-dimensional bin for dry bulb temperature relative humidity were compiled using a fifteen-year hourly dry bulb temperature and relative humidity data for maiduguri and yola. the data were collected from nigerian meteorological agency (nimet), oshodi, lagos. the bins sizes of 1°cand 5% were used for dry bulb temperature and relative humidity respectively. the number of hours in each month in which dry bulb temperature ≥ 32.2°c and relative humidity ≤ 50% during which appreciable evaporative cooling can occur and when dry bulb temperature/relative humidity pair was in the comfort zone were determined. the modal bin for dry bulb temperature (tdb) and relative humidity (rh) are 25 26°cand 15-20% for maiduguri and 25-26°cand 90-95% for yola. april and march are the months that appreciable evaporative cooling usually occurs in the chosen locations and evaporative coolers could be applied during the months of march up to may. but from july to september the evaporative coolers perform poorly in both locations. during the months of october to february, low monthly costs of running the refrigerators and air conditioners significantly different from other months of the year, were indicated by the results. key words: bin data, dry bulb temperature, relative humidity, evaporative cooling, comfort zone, refrigerators and air conditioners 1. introduction the world is experiencing increase in ambient temperature which resulted from several human activities that releases greenhouse gases in to the atmosphere. this experience termed global warming has caused increase in energy and water consumption and equally badly affects human wellbeing (karl and easterling, 1999). human comfort in the work place is a challenge in temperate zone especially in summer, hence there is need to cool occupied spaces. on the other hand in tropical countries like nigeria, cooling is necessary almost all year round, especially in hot and humid weather conditions. besides human discomfort and loss of concentration at work, extreme heat affects health and productivity. it is difficult to dissipate heat when dry bulb temperature is extremely high especially if the relative humidity is also high (harris, 1983). ambient temperature is a factor to be considered when performance of certain types of equipment used in cooling systems is an issue. there is a reduction of heat rejection of an air cooled condenser of vapour compression refrigeration system when the dry bulb temperature of the environment increases (olorunmaiye and ariyo, 1998). 1.1 review of previous investigation on global warming a number of studies have been carried out on the effect of global warming on energy utilized by cooling systems. olorunmaiye et al. (2012) investigated the effect of change in ambient mailto:adeolorunmaiye@gmail.com mailto:lekanoba@yahoo.com arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 73 temperature on energy consumption of refrigerators by operating the refrigerator at three ambient temperature conditions and they found that energy consumption by refrigerator increases with increase in ambient temperature of the space where the refrigerator is operated. saidur et al. (2005) found that among the three independent variables affecting power required for operating the refrigerator-freezer (ambient temperature, load in the refrigerator-freezer and the number of times the door was opened per hour), ambient temperature had the greatest effect. a report by the energy commission of california said that with increase in ambient temperature, higher energy utilization was anticipated. (xu et al., 2009). other studies have been done on weather statistics of some locations in nigeria by earlier researchers which included maiduguri and yola. shoboyejo and shonubi (1974) used 1951-1965 meteorological data to compute the outside design condition of air conditioning systems for some locations in nigeria among which were maiduguri and yola in which they obtained the outside design condition of dry bulb and wet bulb temperatures for 1%, 2½%, and 5% confidence values for the four warmest months assuming gaussian probability distributions. olorunmaiye and awolola (2015) used 1995-2009 meteorological data of 18 locations which included maiduguri and yola to compute 1%, 2½%, and 5% confidence values for dry and wet bulb temperatures. the values they obtained for both dry-bulb and wet-bulb temperatures were higher than corresponding values obtained by shoboyejo and shonubi (1974) for both maiduguri and yola. statistical analysis of 1995-2009 dry bulb temperature and relative humidity data for ilorin, was done and it was reported (olorunmaiye and awolola, 2015) that there is increase in the values got when compared with those obtained by olorunmaiye and ariyo (1998) which were based on 1978-1992 dry bulb temperature and relative humidity data for ilorin. the above results show that nigeria is not excluded from the scourge of global warming and climate change. wet bulb temperature is an important parameter which affects the performance of evaporative cooling systems such as earthen pots, evaporative coolers used as refrigerators (olorunmaiye, 1995) and evaporative coolers used in dry arid areas for air conditioning (harris, 1983). high degree of evaporative cooling can be experienced when the system is in an environment in which high dry bulb temperature (≥32.2°c) and low relative humidity (≤50%) occur concurrently. the concept of effective temperature has been developed from the research of the american society of heating, refrigeration and air conditioning engineers (ashrae) relating temperature, humidity and air movement to human comfort. effective temperature lines on wet bulb temperature versus dry bulb axes are lines joining different combination of dry bulb temperature and relative humidity which give the same feeling of comfort to a high percentage of people equally clothed and equally active, for a given air velocity (0.0762-0.1270 m/s for the comfort chart for still air) (harris, 1983). the comfort zone in the chart is between effective temperatures of 17.2°c and 23.9°c. the dry bulb temperature and the relative humidity of the four corners of the comfort zone are: 18.3°c/70%, 25.7°c/70%, 19.8°c/30%, and 29.1°c/30%. maiduguri is located on latitude 11.85 ° n and longitude 13.08 ° e with an altitude of 345m above sea level, maiduguri falls within the semi-arid zone of west africa geographically and it experiences little rainfall and more of dry season (abdulrahim et al, 2012). yola is the capital of adamawa state, nigeria. the town is situated at an altitude of 186m. the geographical olorunmaiye and awolola. the cooling systems and weather statistics of maiduguri and yola – nigeria. azojete 14(1):72-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 74 coordinates are 09°14'n and 12°28'e. yola is located on the benue river and it has a mean temperature of 28.3°c (alexander, 2015) the aim of the work reported in this paper is to carry out statistical analysis on 15-year data of hourly dry bub temperature and relative humidity of both maiduguri and yola in the north east geo-political zone of nigeria, by compiling the bin data for dry bulb temperature, relative humidity and two dimensional dry bulb temperature/ relative humidity. the proportion of the hours in the year when the weather is within the comfort zone and the amount of time a high level of evaporative cooling could be experienced will equally be estimated. 2. materials and methods fifteen year hourly dry bulb temperature and relative humidity data for maiduguri (1995-2009) and for yola (1994-2008) were obtained from nigerian meteorological services (nimet), oshodi, lagos. the data were keyed into the computer using microsoft office excel 1997-2003 version. from the meteorological data, the bin data for both dry bulb temperature and relative humidity were compiled. microsoft excel codes were written to do the compilation of both dry bulb temperature and relative humidity bins for both locations while visual basic codes were written to compile twodimensional dry bulb temperature/relative humidity bin for the two locations. the bins width of 1 degree celsius for dry bulb temperature and 5 percent for relative humidity were employed. 3. results and discussion (i) diurnal variation of the monthly average weather conditions figures 1 and 3 show the diurnal variation of the monthly average hourly dry bulb temperature for january to december for maiduguri and yola respectively. the diurnal variation of the monthly average hourly relative humidity for january to december for maiduguri and yola are shown in figures 2 and 4. the hours of the day in the abscissae of the sets of graphs are greenwich mean time (gmt) since gmt was used as the time base for the data collected from nigerian meteorological agency (nimet). figures 1 through 4 show that, for any month, as the average values of hourly dry bulb temperature increases there is corresponding decrease in the average values of hourly relative humidity. thus there is negative cross correlation coefficients of dry bulb temperature and relative humidity for all the months. the variations of relative humidity shown in figures 2 and 4 are caused majorly by diurnal changes in dry bulb temperature. as air warms up, the moisture it can carry per unit mass increases and its relative humidity is lowest in the afternoon around 15.00 greenwich mean time (gmt) at the highest dry bulb temperature and conversely relative humidity is highest at 6.00 gmt at the lowest dry bulb temperature, this was equally reported by olorunmaiye and ariyo (1998) in respect of ilorin weather conditions based on 1978-1992 data. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 75 figure 1: diurnal variation of monthly-average hourly dry bulb temperature formaiduguri figure 2: diurnal variation of monthly-average hourly relative humidity for maiduguri 10.0 15.0 20.0 25.0 30.0 35.0 40.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 1st quarter jan feb mar 21.0 24.0 27.0 30.0 33.0 36.0 39.0 42.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 2nd quarter apr may jun 20.0 22.0 24.0 26.0 28.0 30.0 32.0 34.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 3rd quarter jul aug sep 10.0 15.0 20.0 25.0 30.0 35.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 4th quarter oct nov dec 0 10 20 30 40 50 60 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 1st quarter jan feb mar 0 20 40 60 80 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 2nd quarter apr may jun 40 50 60 70 80 90 100 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 3rd quarter jul aug sep 0 20 40 60 80 100 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 4th quarter oct nov dec olorunmaiye and awolola. the cooling systems and weather statistics of maiduguri and yola – nigeria. azojete 14(1):72-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 76 figure 3: diurnal variation of monthly-average hourly dry bulb temperature for yola figure 4: diurnal variation of monthly-average hourly relative humidity for yola 10.0 15.0 20.0 25.0 30.0 35.0 40.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 1st quarter jan feb mar 20.0 25.0 30.0 35.0 40.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 2nd quarter apr may jun 20.0 22.0 24.0 26.0 28.0 30.0 32.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 3rd quarter jul aug sep 10.0 15.0 20.0 25.0 30.0 35.0 40.0 0 4 8 12 16 20 24 te m p e ra tu re (° c ) time of the day (hrs) 4th quarter oct nov dec 0 10 20 30 40 50 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 1st quarter jan feb mar 0 20 40 60 80 100 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 2nd quarter apr may jun 60 70 80 90 100 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 3rd quarter jul aug sep 0 20 40 60 80 100 0 4 8 12 16 20 24 r e la ti ve h u m id it y (% ) time of the day (hrs) 4th quarter oct nov dec arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 77 (ii) weather, bin data and cooling systems the bin data compiled for ambient temperature and relative humidity are shown in figures 5 and 6, respectively, for both locations. figure 5: comparison of maiduguri and yola dry bulb temperatures bins figure 6: comparison of maiduguri and yola relative humidity bins from figure 5 the minimum dry bulb temperature for maiduguri is in 6-7°c bin at an average of 0.07 hours per year in january during harmattan season, and minimum temperature for yola -50 50 150 250 350 450 550 650 750 0 -5 5 -1 0 1 0 -1 5 1 5 -2 0 2 0 -2 5 2 5 -3 0 3 0 -3 5 3 5 -4 0 4 0 -4 5 4 5 -5 0 5 0 -5 5 5 5 -6 0 6 0 -6 5 6 5 -7 0 7 0 -7 5 7 5 -8 0 8 0 -8 5 8 5 -9 0 9 0 -9 5 9 5 -1 0 0 1 0 0 -1 0 5 n u m b e r o f h o u rs relative humidity bin maiduguri yola -50 50 150 250 350 450 550 650 750 6 -7 8 -9 1 0 -1 1 1 2 -1 3 1 4 -1 5 1 6 -1 7 1 8 -1 9 2 0 -2 1 2 2 -2 3 2 4 -2 5 2 6 -2 7 2 8 -2 9 3 0 -3 1 3 2 -3 3 3 4 -3 5 3 6 -3 7 3 8 -3 9 4 0 -4 1 4 2 -4 3 4 4 -4 5 4 6 -4 7 4 8 -4 9 n u m b e r o f h o u rs dry bulb temperature bin maiduguri yola olorunmaiye and awolola. the cooling systems and weather statistics of maiduguri and yola – nigeria. azojete 14(1):72-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 78 occurred in 12-13°c bin for an average of 0.07 hours in november. the maximum dry bulb temperature occurs in 48-49°c bin for an average of 0.07 hours per year and 44-45°c bin for an average of 0.57 hours per year, for maiduguri and yola respectively. the modal temperature for the two locations occurred in 25-26°c bin. the minimum and maximum temperatures are two extremes which fortunately occur for few hours per year, otherwise this would have posed a great challenge for human comfort. the charts in figure 6 for relative humidity bins for maiduguri and yola show that 15-20% rh bin and 90-95% rh bin are the modes for maiduguri and yola with 725.02 hours and 675.41 hours respectively. the charts show that most of the time when maiduguri was dry yola was relatively humid. the ambient air condition will be outside comfort zone about 2930 hours in yola when compared to 1725 hours in maiduguri and there is need for dehumidification to achieve comfort most of the time in yola. tables 1 and 2 show respectively the two-dimensional dry bulb temperature/relative humidity bin data of maiduguri and yola. the number in each cell is the average number of hours in a year that dry bulb temperature and relative humidity combination are in the bin. the twodimensional dry bulb temperature/ relative humidity bin data show the coincidence and distribution of dry bulb temperature and relative humidity. this bin data is useful for accurate estimation of building cooling loads. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 79 table 1: two dimensional dry bulb temperature/relative humidity bin data for maiduguri rh 0-5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60 60-65 65-70 70-75 75-80 80-85 85-90 90-95 95-100 100-105 temp 6-7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 7-8 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.07 0.47 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8-9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.27 0.73 0.40 0.33 0.14 0.00 0.00 0.00 0.00 0.00 0.00 9-10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.20 0.87 1.20 0.80 0.33 0.40 0.33 0.00 0.00 0.00 0.00 0.00 0.00 10-11 0.00 0.00 0.00 0.00 0.00 0.07 0.20 0.40 1.33 2.67 3.73 2.87 1.13 1.13 0.60 0.40 0.00 0.00 0.00 0.00 0.00 11-12 0.00 0.00 0.00 0.13 0.07 0.13 0.07 0.93 3.40 6.47 8.13 4.07 2.27 1.53 0.07 0.13 0.00 0.07 0.00 0.00 0.00 12-13 0.07 0.00 0.00 0.00 0.20 0.33 1.80 3.60 8.53 10.87 11.00 6.40 4.67 1.66 0.33 0.07 0.07 0.00 0.00 0.00 0.00 13-14 0.00 0.00 0.00 0.00 0.47 0.93 2.67 8.27 12.80 15.73 12.60 10.87 4.47 1.13 0.46 0.07 0.00 0.00 0.00 0.00 0.00 14-15 0.00 0.00 0.00 0.13 0.73 1.80 6.60 14.00 21.00 21.13 14.13 11.33 3.67 1.40 0.40 0.20 0.00 0.07 0.00 0.07 0.00 15-16 0.00 0.00 0.00 0.13 1.27 4.27 11.80 19.46 23.26 23.33 16.73 10.80 3.33 1.07 0.20 0.13 0.00 0.00 0.00 0.00 0.00 16-17 0.00 0.00 0.07 0.40 2.60 9.26 19.06 22.66 25.06 25.80 21.53 9.20 3.87 0.93 0.60 0.00 0.00 0.00 0.00 0.00 0.00 17-18 0.00 0.00 0.20 1.27 4.47 12.40 25.71 25.86 23.53 22.00 15.27 8.13 2.67 1.40 0.47 0.00 0.07 0.00 0.00 0.00 0.00 18-19 0.00 0.00 0.07 1.79 9.40 19.00 30.19 30.20 28.26 20.20 14.73 5.33 3.80 1.27 0.87 0.47 0.40 0.40 0.07 0.00 0.00 19-20 0.00 0.13 0.27 3.53 12.40 24.33 31.80 31.26 23.86 17.60 11.20 6.67 3.33 1.40 1.34 0.93 0.67 0.20 0.07 0.00 0.00 20-21 0.07 0.07 1.00 6.80 22.33 35.79 34.79 31.33 24.47 16.67 11.87 7.42 5.02 3.22 2.01 1.34 2.71 1.64 2.39 6.28 0.93 21-22 0.00 0.07 2.00 9.86 25.53 35.66 33.20 26.26 17.73 13.93 9.37 4.24 5.44 3.98 3.94 3.34 4.99 7.73 15.22 26.81 3.09 22-23 0.00 0.33 2.20 14.93 35.72 41.40 36.20 23.53 19.07 12.38 7.03 7.39 6.84 6.79 5.66 8.57 14.16 21.69 46.36 52.61 5.37 23-24 0.07 0.53 4.27 21.33 38.39 47.33 33.26 21.33 12.93 10.17 7.58 6.44 6.74 8.64 10.88 17.38 30.84 51.96 88.81 42.68 1.27 24-25 0.20 0.20 6.13 28.86 47.06 44.73 33.00 17.67 12.61 8.88 7.54 7.86 8.11 11.93 17.65 36.07 62.02 87.72 88.83 26.77 0.98 25-26 0.27 0.40 12.13 34.33 48.13 42.60 27.87 16.27 9.94 6.69 6.49 8.08 13.50 19.17 37.81 58.22 82.14 73.36 48.58 14.60 0.68 26-27 0.20 1.34 15.47 42.06 44.73 35.86 24.34 13.80 8.87 7.61 7.90 12.29 23.87 36.33 54.05 65.33 74.71 40.08 19.19 8.63 0.40 27-28 0.07 1.93 22.46 48.66 47.13 31.67 21.40 11.53 8.07 8.50 14.07 25.50 41.29 49.67 69.99 60.64 38.96 17.02 10.43 6.19 0.34 28-29 0.20 3.53 29.06 53.39 43.27 31.33 17.34 9.87 10.16 15.52 25.05 38.58 55.55 58.96 58.86 38.36 16.83 10.82 8.60 3.84 0.54 29-30 0.27 6.80 35.59 55.13 38.73 22.01 16.73 10.41 12.49 18.71 37.37 51.25 56.36 59.81 41.49 16.46 9.65 6.60 5.66 1.78 0.34 30-31 0.60 11.46 49.12 59.60 37.73 21.47 16.15 12.01 14.79 32.19 43.65 49.18 62.33 49.59 17.78 6.07 5.45 3.15 3.55 2.34 0.55 31-32 0.27 13.20 47.19 51.33 30.13 18.15 11.74 12.22 21.04 37.14 44.27 53.53 54.79 23.33 8.43 4.89 3.52 2.60 2.10 2.29 0.28 32-33 0.60 16.93 51.06 45.73 28.67 15.20 10.40 14.29 31.01 38.77 43.68 46.06 28.52 10.23 4.91 2.92 2.00 2.13 1.59 1.03 0.21 33-34 1.07 21.33 55.19 47.80 26.20 11.94 11.68 19.80 36.99 39.67 37.72 26.05 10.75 5.08 3.73 1.69 1.49 1.16 1.92 0.97 0.21 34-35 0.67 22.46 48.93 41.87 24.67 11.21 15.84 30.37 35.48 31.14 21.35 10.60 5.47 2.65 1.42 0.68 1.23 0.68 0.62 0.75 0.28 35-36 0.40 27.26 49.80 35.53 22.80 13.87 24.29 33.43 31.79 17.47 9.82 5.03 2.39 1.61 0.60 0.75 1.10 0.41 0.35 0.27 0.14 36-37 0.26 29.93 45.13 31.60 17.27 13.75 31.85 35.57 17.99 6.12 3.04 1.74 1.02 1.42 0.61 0.20 0.21 0.20 0.27 0.33 0.00 37-38 1.26 27.73 34.93 21.87 14.88 18.91 29.78 18.63 5.98 2.42 1.27 1.27 0.40 0.47 0.46 0.07 0.07 0.20 0.00 0.07 0.07 38-39 1.27 34.06 30.67 17.27 14.15 22.86 21.68 7.23 1.67 1.27 0.67 0.27 0.53 0.07 0.07 0.19 0.00 0.00 0.00 0.00 0.07 39-40 1.33 32.60 25.00 12.34 20.03 21.93 12.03 3.14 1.40 0.93 0.47 0.13 0.00 0.13 0.20 0.07 0.00 0.00 0.00 0.07 0.00 40-41 1.53 30.60 28.07 14.54 18.15 12.35 4.61 1.07 0.13 0.13 0.07 0.13 0.00 0.13 0.07 0.00 0.00 0.00 0.07 0.00 0.00 41-42 1.66 24.40 18.40 13.61 12.41 5.20 2.53 0.60 0.20 0.27 0.07 0.07 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 42-43 0.27 13.74 10.40 8.07 4.80 2.40 0.53 0.00 0.13 0.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 43-44 0.07 5.93 3.61 1.07 0.93 0.33 0.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 44-45 0.07 1.47 0.73 0.07 0.26 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 45-46 0.00 0.00 0.13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 46-47 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 47-48 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 48-49 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 olorunmaiye and awolola. the cooling systems and weather statistics of maiduguri and yola – nigeria. azojete 14(1):72-84. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 80 table 2: two dimensional dry bulb temperature/relative humidity bin data for yola rh 0-5 5-10 1015 1520 2025 2530 3035 3540 4045 4550 5055 5560 60-65 65-70 70-75 75-80 80-85 85-90 90-95 95100 100105 temp 12-13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 13-14 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.20 0.07 0.40 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 14-15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.27 0.13 1.13 0.47 0.53 0.20 0.07 0.00 0.00 0.07 0.00 0.00 15-16 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.33 0.40 1.13 3.20 3.00 2.47 1.40 1.00 0.80 0.67 0.13 0.00 0.00 0.00 16-17 0.00 0.00 0.00 0.00 0.00 0.07 0.20 0.87 1.53 3.27 5.73 6.67 6.67 4.47 4.47 2.53 1.27 0.60 0.00 0.00 0.00 17-18 0.00 0.00 0.00 0.00 0.00 0.33 0.73 2.13 4.13 8.00 7.87 8.40 9.20 6.73 7.40 5.07 3.20 1.00 0.40 0.07 0.00 18-19 0.00 0.00 0.00 0.00 0.13 0.93 2.20 4.67 7.67 13.73 14.80 10.73 11.40 12.20 9.13 6.27 5.00 2.33 0.33 0.00 0.00 19-20 0.00 0.00 0.00 0.07 0.33 1.73 5.47 11.80 12.47 15.93 16.40 15.40 15.07 10.93 8.33 7.13 4.20 2.07 1.13 0.13 0.00 20-21 0.00 0.00 0.07 0.47 1.40 5.47 10.60 11.07 20.40 18.13 13.67 14.07 16.67 12.07 9.33 6.20 5.47 3.13 1.87 1.69 0.54 21-22 0.00 0.00 0.07 0.80 3.07 10.80 16.86 19.33 19.60 20.33 17.40 14.87 13.80 12.80 8.20 5.47 5.67 6.01 6.52 18.63 6.82 22-23 0.00 0.00 0.00 1.20 5.87 14.47 20.40 20.40 30.47 13.80 17.67 15.80 12.20 8.80 8.73 7.13 10.42 11.13 37.21 85.44 16.15 23-24 0.00 0.00 0.07 1.47 6.13 18.29 23.74 27.87 21.80 19.21 14.87 14.87 9.73 7.94 6.67 11.61 17.34 40.49 117.64 122.44 10.73 24-25 0.00 0.07 0.41 2.67 8.26 21.29 31.87 25.10 22.63 14.87 14.23 10.53 9.60 9.09 9.41 14.25 39.84 105.74 202.35 115.19 4.21 25-26 0.07 0.00 0.40 3.00 13.73 30.07 29.36 31.27 19.44 16.76 10.87 9.74 9.87 10.16 12.26 27.85 104.63 174.62 184.49 52.36 2.20 26-27 0.00 0.13 0.40 4.61 17.89 29.90 38.08 25.86 16.62 14.92 9.57 9.50 9.25 15.70 32.16 63.82 163.63 139.42 84.83 17.65 1.20 27-28 0.00 0.00 0.67 7.47 21.38 34.50 33.72 25.43 14.75 10.31 9.99 9.26 14.84 23.66 63.36 104.04 141.72 73.85 21.66 6.27 0.80 28-29 0.00 0.07 1.41 10.81 28.49 36.52 36.16 19.67 15.02 11.33 8.61 12.14 29.75 47.39 106.81 116.34 67.19 30.05 7.42 3.08 0.60 29-30 0.00 0.22 2.50 13.62 34.14 34.75 29.40 22.71 13.45 9.43 12.45 27.76 42.90 96.34 124.45 78.89 24.59 6.97 2.93 2.20 0.40 30-31 0.00 0.00 3.81 20.06 40.88 38.67 27.21 18.53 11.42 11.63 19.44 41.32 69.94 139.50 79.97 26.62 7.48 3.88 2.27 1.87 0.47 31-32 0.00 0.07 6.87 30.63 39.25 37.17 28.33 14.94 9.89 16.10 29.78 52.31 109.04 107.14 31.70 7.95 3.20 1.47 2.40 1.00 0.60 32-33 0.00 0.27 8.74 31.49 45.13 37.15 24.81 12.35 11.54 20.14 35.24 70.92 95.63 37.01 9.23 3.76 1.80 1.33 1.15 0.87 0.40 33-34 0.00 0.61 11.78 38.92 46.48 31.23 20.86 14.04 16.59 29.40 53.48 62.01 36.86 12.30 2.53 1.00 1.14 0.47 0.47 0.27 0.27 34-35 0.00 0.75 14.58 39.12 42.49 32.35 20.17 18.40 23.80 39.07 46.72 26.04 6.77 2.28 0.74 0.74 0.74 0.49 0.28 0.21 0.07 35-36 0.00 1.28 18.98 38.52 39.11 26.57 17.10 16.61 27.74 41.32 22.56 5.69 1.21 0.33 0.13 0.21 0.56 0.15 0.14 0.00 0.00 36-37 0.00 1.29 18.59 33.55 33.66 19.71 17.55 24.33 31.02 27.82 4.86 0.48 0.28 0.20 0.22 0.22 0.56 0.35 0.07 0.00 0.00 37-38 0.00 1.99 19.70 32.44 22.07 15.53 16.93 26.16 31.60 10.51 0.55 0.00 0.13 0.21 0.47 0.49 0.20 0.07 0.00 0.00 0.00 38-39 0.00 2.45 24.60 24.46 16.29 12.74 20.88 28.17 14.86 2.56 0.56 0.20 0.07 0.42 0.50 0.20 0.00 0.07 0.07 0.00 0.00 39-40 0.07 3.68 22.37 21.17 16.71 16.05 22.16 16.83 4.00 0.21 0.07 0.07 0.28 0.35 0.07 0.07 0.07 0.00 0.00 0.00 0.00 40-41 0.00 4.27 19.49 17.43 15.30 17.98 13.54 4.69 0.27 0.07 0.21 0.00 0.07 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 41-42 0.00 4.17 11.10 10.84 11.01 7.56 4.61 1.49 0.40 0.13 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 42-43 0.00 1.66 8.46 5.36 4.99 2.77 0.36 0.07 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 43-44 0.00 0.28 0.36 1.77 0.99 0.36 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 44-45 0.00 0.00 0.07 0.49 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 81 (iii) evaporative cooling when a place has dry bulb temperature equal to or higher than 32.2°c with coincident relative humidity of less than 50%, there will be appreciable evaporative cooling. the number of hours in each month for both locations in which a high level of evaporative cooling could occur (dry bulb temperature ≥ 32.2°c with relative humidity ≤ 50%) are shown in figure 7. from tables 1 and 2, the number of hours for tdb and rh within these ranges for both maiduguri and yola are shown inside the lower rectangles and the total number of hours are1978.34 and 1686.68 hours respectively for maiduguri and yola. these figures compare well with results obtained from the addition of monthly average number of hours for maiduguri and yola in figure 7. figure 7: number of hours in which a high degree of evaporative cooling can take place figure 8: number of hours in which the weather is within the comfort zone 0 50 100 150 200 250 300 350 400 450 1 2 3 4 5 6 7 8 9 10 11 12 n u m b e r o f h o u rs month of the year maiduguri yola 0 50 100 150 200 250 300 350 400 1 2 3 4 5 6 7 8 9 10 11 12 n u m b e r o f h o u rs month of the year maiduguri yola olorunmaiye and awolola. the cooling systems and weather statistics of maiduguri and yola – nigeria. azojete 14(1):72-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 82 figure 9: number of hours in which the dry bulb temperature is less than 25°c (iv) comfort zone and ventilation the average number of hours in the year in which the weather condition lies within the comfort zone is the addition of the hours bounded by the upper rectangles in tables 1 and 2 and the totals are 1498.04 and 1449.03 hours for maiduguri and yola respectively. the monthly number of hours of this is shown figure 8 for both locations which added up to be 1498.05 and 1448.48 hours for maiduguri and yola respectively. the small differences (1498.05 – 1498.04) and (1448.48 – 1449.03) are due to computational errors. october, november and december are the three months having highest number of hours per month in the comfort zone for maiduguri. while the four months with highest number of hours per month in the comfort zone for yola are november, december, january and february; these months are in the hammattan season for yola. in maiduguri, august and september have the lowest number of hours in the comfort zone. while the lowest number of hours in the comfort zone for yola occur in august to october. when weather is within the comfort zone, only ventilation is needed for human comfort which could be achieved by natural breeze or fans driven by electric motor. air conditioning systems will be expected to work for the highest number of hours and thus consume highest amount of energy per month in the months of august and september for maiduguri and yola respectively, since they have the lowest number of hours in the comfort zone. on the other hand, the cooling units are expected to work for minimum number of hours for december and january in maiduguri and october and november in yola, leading to minimal energy consumption. figure 9 shows the number of hours in each month in which dry bulb temperature is less than 25°c for both cities. since the indoor design dry-bulb temperature for comfort air conditioning systems is 24°c, the hours having dry-bulb less than 25°c are the hours in which it is not necessary to put on an air conditioner. 0 50 100 150 200 250 300 350 400 450 500 1 2 3 4 5 6 7 8 9 10 11 12 n u m b e r o f h o u rs month of the year maiduguri yola arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):72-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 83 the transmission heat gain resulting from temperature difference between the outside air and the air in the space being cooled and air change heat gain due to door opening and infiltration are important components of the cooling load of a cooling system. the numbers of hours when the ambient temperature is above 25°c can be used as an indicator of the magnitude of these heat gains. from figure 9, the refrigerator can be expected to consume minimum energy per months in the months of december and january at both maiduguri and yolaand maximum energy in may and april at maiduguri and yola respectively. 4. conclusions dry-bulb temperature and relative humidity data for maiduguri and yola have been analysed to produce one dimensional bin data for both variables and also tdb/rh two-dimensional bin data. there are higher numbers of hours in the comfort zone in december and january for yola while the best period for comfort is november for maiduguri; the two lowest number of hours for comfort zone occur in august and september for the two locations. evaporative coolers will work best at both maiduguri and yola from march to may. the poorest performance of evaporative cooler will occur from july to september. from october to february, the monthly cost of running refrigerators and air conditioners will be lowest compared to other months of the year since these are months having low rh and also low tdb. acknowledgement the authors acknowledge with appreciation the provision of the weather data by nigerian meteorological agency, (nimet), oshodi, lagos, nigeria. references abdulrahim, at., mshelia,rb., stephen, og., kyauta, et. 2012. heat stress as a measure of human level of comfort in a semiarid zone, maiduguri, nigeria. world journal of engineering and pure and applied sciences; 2(3): 107-111. alexander, cb. 2015. statistical 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for air conditioning systems in nigeria. technical transactions of the nigerian society of engineers, 49(2): 54-66 olorunmaiye, ja., awolola, oo. and opadiji, jf. 2012. experimental investigation of the effect of change in ambient air temperature on power consumption of domestic refrigerator. nigerian journal of technological development 9(2): 96-105 saidur, r., chew, wc. and masjuki, hh. 2005. development and validation of refrigeratorfreezers energy consumption model with the aid of rsm, journal of energy and environment, 4:11-19. soboyejo, abo. and shonubi, fa. 1974. evaluation of outside design conditions for airconditioning system design in nigeria, the nigeria engineer, 9(1): 5-11 xu, p., huang, y., miller, n., and schlegel, n., 2009. california energy commission report, effect of global climate change on building energy consumption and its implication on building energy codes and policy in california. arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):55-66 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 55 original research article comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design a. t. layeni1, a. i. olanrewaju1, c. n. nwaokocha*1, m. a. waheed2, s. o. giwa1, s. i. kuye2, and k. a. adedeji3 1department of mechanical engineering, college of engineering and environmental studies, olabisi onabanjo university, ibogun campus, nigeria. 2department of mechanical engineering, federal university of agriculture, abeokuta, nigeria. 3department of mechanical engineering, lagos state university, epe, nigeria. *corresponding author: collinsnwaokocha@gmail.com, yomilayeni@oouagoiwoye.edu.ng article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: thermal comfort indoor climate hvac system variable refrigerant flow (vrf) multi-split system abstract the design and comparative engineering economic analysis of two airconditioning (ac) systems, mini-split and variable refrigerant flow (vrf), for the new engineering complex building, at the college of engineering and environmental studies, ibogun campus of olabisi onabanjo university, under the same indoor and outdoor conditions for a one-year period was carried out using carrier hourly analysis (cha) program software for determining cooling load estimation, and the net present worth approach for calculating the economic analysis of both systems’ design. the cooling load estimation was done using the american society of heating, refrigeration and air-conditioning engineers (ashrae) transfer function method rooted within the carrier software. the total cooling load for the building was found to be 239,243 w. equipment used in analysis was selected from the toshiba selection catalogues (mini split system), while that for the vrf system was selected using toshiba simulation software. the annual energy cost analysis of both systems revealed that the vrf system require more energy to run annually than the mini split system. however, the analysis was carried out without considering the part load potential energy savings of the vrf system. results further indicated from the net present worth analysis carried out, the mini split system, in terms of net present value of both systems, is more favoured. on the bases of the engineering economic analysis carried out on the two systems, the overall net present value for the vrf system was about n78 million, while that of the mini-split system was about n47 million. these results show that the vrf system had a higher cost implication than the mini-split system. therefore, in terms of cost, the mini-split system was found to be a more viable option being an older and more established technology to the vrf system. in terms of design, the mini-split system, with equal number of indoor and outdoor units, is generally a system with more component units than the vrf system, with less outdoor units to indoor units, was expected to be more complicated and complex in design. however, control and operation flexibilities favour the mini-split system to the vrf system. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. mailto:collinsnwaokocha@gmail.com mailto:yomilayeni@oouagoiwoye.edu.ng http://www.azojete.com.ng layeni, et al.: comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design. azojete, 15(1):55-66 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 56 1.0 introduction the air conditioning systems are a subset of the heating, ventilation and air conditioning systems, popularly known as h-v-a-c systems. design and selection of air-conditioning systems in the contemporary framework involves lots of factors that are put into consideration for various applications. generally, when designing and selecting viable heating, ventilating, and air-conditioning (hvac) systems designers aim to come up with the most efficient hvac systems which will be appreciated from the architectural perspective, energy consumption angle, installation aspect, indoor air quality, thermal comfort and majorly from the aspect of economics and cost implication. research literatures are in abundance on the comparison of performance characteristics of different types of air-conditioning systems (aynur et al., 2008a, aynur et al., 2008b, kim et al., 2016 and zhou et al., 2017). aynur et al. (2008a, 2008b) noted in their studies that variable refrigerant flow (vrf) air conditioners are noted for high energy saving potentials and are expected to save more energy than other conventional air conditioning systems. similarly, in the studies of zhou et al. (2017), using the generic dynamic building energy simulation package energy plus, developed a new vrf module and investigated the energy usage of the vrf system. a comparative analyses of the energy consumption of the vrf system with that of two other conventional air-conditioning systems, namely, variable air volume (vav) system as well as fan-coil plus fresh air (fpfa) system were carried out. simulation results showed that the energy-saving potentials of the vrf system were expected to achieve 22.2% and 11.7%, compared with the vav system and the fpfa system, respectively. the present study focuses on establishing a comparative analysis between a variable refrigerant flow air conditioning system (which is similar to a multi split air conditioning system) and a mini split air conditioning system from the perspective of both design as well as economics. brar (2012), developed a new methodology for the evaluation, comparison, ranking and optimum selection of air conditioning systems from different design options. the proposed methodology is based on multi attribute decision making (madm) approach (brar, 2012). relevant features, which describe the whole air conditioning system, were identified exhaustively for the madm approach. popovici and hudişteanu (2015) carried out investigation of the performance of the heating, ventilation and air conditioning system at “vasile alecsandri” national theatre of jassy, romania, for varying external conditions. a 2d simulation model of the building was used to carryout performance analysis with ansys fluent software. the performance of the hvac system during winter and summer seasons were simulated and analysed for the situation when the entire theatre hall was occupied. their results revealed and established that the hvac system provided adequate conditions for both studied seasons. barot (2014) reiterated that the main objectives of the hvac system design are that of providing thermal comfort, good indoor quality and energy conservation. however, some special hvac projects may not be necessarily energy-efficient in daily operations due to their operations requirements, specific design and control of the hvac the system. the design and equipment selection of the hvac system for a commercial building (with required cooling capacity of 376 tr) was studied. the results of the study of barot (2014) revealed efficient air conditioning methods (water cooled screw chiller, air cooled screw chiller, conventional split ac units and air cooled vrf system) for the design of hvac systems with minimum energy consumption and equipment selection based on operating and life cycle cost analysis. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):55-66. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: collinsnwaokocha@gmail.com, yomilayeni@oouagoiwoye.edu.ng 57 1.1 statement of problem/ purpose of study buildings have a characteristic exterior air temperature, known as the balance point temperature, at which the building in use would be able to maintain thermal comfort without the need for a heating or cooling system. at the balance point temperature (strongly influenced by internal loads, solar influence and envelope design) building heat gains and losses are in equilibrium so that a suitable interior temperature be maintained naturally. however, when the outside air temperature drops below the balance point temperature, heat losses through the building envelope will increase, and interior air temperature will drop unless heat is added to the building to compensate for the heat losses from the building, which is accomplished by a space (or building) heating system. likewise, when the outside air temperature exceeds the balance point temperature, heat gain through the building envelope will upset thermal equilibrium and cause the interior air temperature to rise. a system that removes such excess heat is called a cooling/air conditioning system. due to an increase in the outdoor temperature as well as consistent indoor temperatures above the balance point temperature, a system needs to be designed that will effectively offset the heat gains into the spaces in the oou college of engineering complex building, while saving energy in the process. moreover, to maintain a proper indoor air quality, contaminants which include radon, moulds, allergens, carbon monoxide (co), volatile organic compounds (voc), legionella, asbestos fibres, co2, among others, need to be diluted by proper ventilation methods, which also needs to be energy efficient. hence, this study aims to design an energy efficient and environmentally friendly air conditioning and ventilation system for the complex building. and to achieve these purposes, two air conditioning systems are compared, which are the vrf and mini split air conditioning systems. the objectives of the study are: carryout a site survey and determination of the various environmental parameters. carryout space audit and determination of cooling loads of the various zones of the building complex. design analysis of a vrf and mini split system for the building complex. engineering economic analysis of the vrf and mini split systems. 2. methodology 2.1 site survey and environmental parameters the study building is the olusegun obasanjo engineering complex (figure 1) in ibogun campus, olabisi onabanjo university ogun state, nigeria on longitude 3.4728610oe and latitude 6.7003410on at about 39 meters above sea level, 50.2% 94% relative humidity, and a dry season design temperature of 35oc and a rainy season design temperature of 21oc. the engineering complex consists of three departmental buildings, which are identical but vary with respect to orientation. each building has 2 lecture halls, 2 laboratories, 1 seminar hall and 13 offices as shown in figure 1. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng layeni, et al.: comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design. azojete, 15(1):55-66 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 58 figure 1. the building plan the environmental data collected for the site are co2, particulate matters [pm2.5/ pm10) at different time of the day categorised into morning and afternoon, which helps to determine the number and spread of particulate matters and concentration of co2 present in study area. the design for ventilation and indoor air quality of the building complex depends on these information. the collected data was analysed to derive the minimum, maximum and average values of each parameter collected. 2.2 space audit/ cooling load estimation the air conditioning load was estimated to provide the basis for selecting the most suitable air conditioning equipment for offsetting the estimated load. the load estimate took into consideration the ‘heat gains’ into the space from outdoors on a design day as well as the heat being generated within the space. in this context, design day is referred to: a day on which the dry band wet bulb temperatures are peaking simultaneously resulting in high relative humidity. a day on which there is little or no haze in the air to reduce solar heat gains. a day on which all the internal loads are at their peak. for the study, a computer simulation software (carrier hourly analysis program) was used for estimating the weather data for a period of one year. after which, the design day was gotten and was used as basis for the cooling load estimation. 2.3 comparative analysis of the two alternate systems 2.3.1 variable refrigerant flow (vrf) system vrf systems are improved versions of multi-split systems (figure 2), allowing more indoor units to be connected to an outdoor unit, with extra features such as simultaneous heating and cooling and heat recovery. the outdoor unit contains one or more variable speed compressors, condenser, accumulator, receiver, expansion device and controls. the outdoor unit is connected via a single flow and return refrigerant pipe-work system to a number of indoor units containing http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):55-66. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: collinsnwaokocha@gmail.com, yomilayeni@oouagoiwoye.edu.ng 59 a fan, evaporator, expansion device and controls. a vrf system contains at least two indoor units (a system can extend to 64 indoor units) and one outdoor unit and a central controller. all the indoor and outdoor units are connected via an electronic system controlled by software-based systems within the outdoor unit. the indoor units are controlled either individually or in zones. [goetzler (2007)]. figure 2. vrf system [source: amarnath and blatt, (2008)] 2.3.2 mini split air-conditioning system a mini split air conditioning system (figure 3) comprises of an outdoor condensing unit containing a constant speed compressor, a condenser, a receiver, a fan, and controls linked via a liquid and gas refrigerant pipe-work to the indoor unit containing the fan, the cooling coil, the thermostatic expansion valve and controls. figure 3. mini split system [source: brar, (2012)] 2.3.3 design analysis both the vrf and mini split air conditioning systems are direct expansion systems, therefore the procedure for the design analysis of the two systems followed the same trend. the procedures for accomplishing the design analysis of the two systems includes: building survey: architectural drawings and field sketches [oou, (2006)] were taken for the building survey and the following physical aspects were considered: building orientation, compass points, nearby permanent structures, reflective surfaces, use of spaces, physical dimensions of the spaces, construction materials (for walls, windows, roof, doors & partitions), surrounding conditions, occupancy levels and activities, lighting, appliances and thermal storage. location of equipment and services: air conditioning load estimate: the air conditioning load was estimated to provide the basis for selecting the most suitable air conditioning equipment for offsetting the estimated load. carrier file:///c:/users/user/downloads/azojete143/www.azojete.com.ng layeni, et al.: comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design. azojete, 15(1):55-66 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 60 hourly analysis program [carrier (2011)] was used for estimating the air conditioning loads for the various spaces in the building. the software (hourly analysis program for detailed cooling load calculation) utilises the ashrae transfer function method (tfm) of cooling load calculation for estimating the heat gains from walls and roofs, windows, doors, floors, lighting, equipment, people and infiltration sources [ashrae (1992), ansi/ashrae (2004)]. figure 4. vrf system divisions: ground floor (a and b), and first floor (c) figure 5. mini-split system divisions: ground floor (a and b), and first floor (c) with the transfer function method applied in the study to determine the cooling load of the building complex, a general mathematical model, which defines load as a function of heat gain and time was determined for each heat gain component in the rooms. this relationship was then used to calculate loads for each hour in the rooms. the mathematical model used expresses the room transfer function [hap (2016)] equation (1) as: qo = v0 q0 + v1 q1 + v2 q2 w1q1 w2 q2 (1) in this equation: q0 represents a load. the subscripts refer to specific points in time. subscript 0 is the current hour, 1 is the previous hour and 2 is two hours previous. q represents a heat gain. the subscripts 0, 1 and 2 have the same meaning as for loads. v0, v1, v2, w1 and w2 are transfer function coefficients. values of these coefficients vary for each type of heat gain and room due to the different heat transfer processes involved in converting each kind of heat gain into a load. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):55-66. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: collinsnwaokocha@gmail.com, yomilayeni@oouagoiwoye.edu.ng 61 the room transfer function equation relates the load for the current hour (qo) as a function of the heat gain for the current and preceding two hours, plus the loads for the preceding two hours. because loads for the preceding two hours are themselves dependent on a series of heat gains for prior hours, the present hour's load is very dependent on the effects of heat gains from many preceding hours. detailed simulations resulted in generation of both sensible and latent loads for each of the spaces, which were further used for the selection of the appropriate hvac equipment, for the two alternate systems. catalogues were used for selecting the equipment for the mini split air conditioning system, while toshiba smms-shrm selection module was used for selecting the equipment for the vrf air conditioning system. detailed layout of both systems indicated that the vrf system required only four outdoor units to provide thermal comfort for the spaces served by the individual indoor units (figure 4), while the mini-split system requires as much outdoor units as the number of indoor units to provide thermal comfort for each of the spaces as shown in figure 5. 2.4 engineering economic analysis (eea) to select the economically sound option between the vrf and the mini-split systems designed for the building, an engineering economic analysis was carried out using the net present worth analysis for both systems [brar, (2012)]. in the eea, the following costs were taken into consideration and converted into the net present worth values for proper comparisons; first cost: this refers to the cost of purchasing the equipment and installing the systems i.e. all the units and piping networks. annual maintenance cost: this refers to the cost necessary to maintain the systems on an annual basis. annual energy cost: this refers to the electrical energy cost necessary to run the airconditioning systems on an annual basis. this was based on 9 hours of equipment usage on a daily basis, and 5 days on a weekly basis. the total kwhr of energy usage for both systems were computed using the electrical energy capacities of the a/c equipment selected. the net present worth values of the various future cost components was computed as a function of the future cost, the interest rate, number of years and the annual cost, equations (2) and (3) [newnan et. al., (2004)]. an interest rate of 12% based on cbn 10-year average inflation rate [cbn (2018)] was used for the computation. p = f (p/f, i%, n) = p = f(1 + i)-n (2) & p = a (p/a, i%, n) = a 1+i n−1 i 1+i n (3) where, p = present worth of estimated future cost f = estimated future cost i% = interest rate n = number of years a = estimated annual cost file:///c:/users/user/downloads/azojete143/www.azojete.com.ng layeni, et al.: comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design. azojete, 15(1):55-66 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 62 3. results and discussion environmental conditions the environmental conditions as revealed in table 1 show that the particulate matter pm 10 and co2 are within the ashrae standards. this implies that no critical ventilation and air filtration systems are required in the design of the air conditioning system for the building complex. table 1. average values of the environmental conditions of the study area morning afternoon maximum minimum maximum minimum ashrae standard pm10 µg/m3 35 20 33 14 50 co2 (ppm) 840 730 1000 701 350 – 1,000 cooling load estimation table 2. sensible and latent cooling loads for various zones zone zone load sensible latent (w) (w) f001 (dean’s office) 6996 1480 f002 (conference room) 10021 2617 f003 (office) 3151 789 f004 (office) 4779 1330 f005 (secretary’s office) 3127 847 f006 (office) 3322 762 f007 (hod’s office) 5559 1620 f008 (lab) 14379 4972 f009 (lab) 15484 5642 g001 (lab) 14699 2787 g002 (lab) 21235 4178 g003(lab tech) 5042 672 g004 (office) 4148 636 g005 (office) 4571 606 g006 (lr) 15791 3234 g007 (lr) 14063 2874 g008 (lr) 14767 3451 g009 (lr) 15422 3574 g10 (ddt) 6765 1290 g11 (office) 2092 449 g12 (office) 2057 449 g13 (office) 2092 449 g14 (office) 1754 451 g15 (office) 2317 451 total cooling load (w) 193,633 45,610 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):55-66. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: collinsnwaokocha@gmail.com, yomilayeni@oouagoiwoye.edu.ng 63 based on the design analysis carried out, the total design cooling load for the building complex was 239.2 kw, with 193.6 kw as sensible heat and 45.6 kw as latent heat as shown in table 2. the design layouts (figures 4 and 5) indicate that the vrf system requires only four outdoor condensing units to serve all the indoor air conditioning units in the building. this system hence aesthetically improves the look of the building which is a major architectural consideration, while the mini-split system requires a single space for each of the outdoor units which definitely requires an angle iron bracket or a condensing unit shelter for each of the outdoor units which becomes an extra consideration by the structural engineer and definitely comes with a cost implication. the mini-split system, which requires more components and invariably higher initial cost, has gains in annual maintenance cost (n1.6 million) in comparison with the vrf system’s annual maintenance cost (n4 million ) as shown in table 3. however, due to the newness of the vrf system, the initial cost is higher than that of the mini-split as also noted by william, (2007), which will reduce in time as the technology becomes widely used. in terms of flexibility in operations and control the mini-split is found to be more flexible and cost saving in operation as many units can be switched off at a time without each unit affecting other units, this is in agreement with the report of str partners and cs2 design group (2013).while for the vrf system in which an outdoor unit controls two or more indoor units, if one or more of the indoor unit is switched off and only one indoor unit is in operation, the outdoor unit continue to operate. and in the event the outdoor unit becomes faulty, all the indoor units attached to it will become inoperative. table 3. a breakdown of the various cost components as used for analysis of both systems cost vrf system mini split system first cost n29.5 million n22 million annual maintenance cost n4 million n1.6 million annual energy cost n2.5 million n2 million total cost n36 million n25.6 million table 4. a breakdown of the various cost components converted to net present worth cost vrf system mini split system first cost n29.5 million n22 million annual maintenance cost converted to the net present worth n30 million n11 million annual energy cost converted to the net present worth n17.5 million n13 million net present worth n77 million n46 million based on the engineering economic analysis carried out on the two systems, the overall net present value for the vrf system is n77 million , while that of the mini-split system is n46 million as shown in you started your methodology with systems analysis and began your results and discussion with costs. this is unacceptable and unpublishable. you must reorganize and revise your paper appropriately. table 4. this result shows that the vrf system has a higher cost implication than the mini-split system. hence, in terms of cost, the mini-split system is a more viable option. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng layeni, et al.: comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design. azojete, 15(1):55-66 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 64 however, it should be noted that a number of parameters were left out of consideration during the analysis. of utmost importance is the annual energy estimation of the vrf system at part load operation which requires a detailed simulation of the electrical energy consumption with respect to the cooling load at different points in time. this simulation would have resulted in a lesser value for the electrical energy consumption as compared to the actually estimated value. from figure 6, it is observed that the initial cost of the two systems are close. however, using a 15% of initial cost as annual maintenance cost builds up the maintenance cost of the vrf system over the period of time used for the analysis. the difference in the initial cost of the two systems is due largely to the newness of the vrf into the market. with time the vrf system is bound to cost less than the mini-split system as demand for the product increases. figure 6. comparative cost analysis of vrf and mini-split systems. also as noted, the analysis of cost is based on full-load, where all the units are working at maximum capacity. however, under part-load conditions the gains of the vrf systems will be obvious. gains such as the lower energy consumption of the outdoor unit under part-load conditions, which may bring the energy cost of the vrf system lower than that of the mini-split since most of the energy demand of the vrf is for the outdoor unit. this is due to the presence of multiple compressor and variable speed compressor that enable good part load performance permitting capacity modulation to serve 7% to 100% of the cooling or heating loads. furthermore, the efficiency of the systems were not considered in the analysis, which will affect the performance and the energy cost over the duration of usage. the hvac systems operation’s daily time period has between 30% and 70% of the system working on maximum capacity where the vrf system efficiency is high. another energy gain of the vrf system has to do with its abilities to provide good zone control, saving energy and cost by not conditioning zones that are unoccupied and also providing capability to condition single zones off hours at a reasonable cost. 4. conclusion the set objective of the research, which was to design an energy efficient, cost effective and environmentally friendly air-conditioning and ventilation system for the engineering complex building at the college of engineering and environmental studies, ibogun campus, olabisi onabanjo university, was achieved. environmental data taken at the initiation of the study showed that the average value of the ambient co2 was within the internationally acceptable standard, and thus not critical ventilation system required. the total cooling load estimation of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):55-66. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: collinsnwaokocha@gmail.com, yomilayeni@oouagoiwoye.edu.ng 65 the building complex was 193.6 and 45.6 kw for sensible and latent cooling loads respectively. technical and performance characteristics indicated that the variable refrigerant flow system is a better air-conditioning option, with fewer components and a centralised system, than the minisplit air-conditioning system with many more components and a decentralised control system. however, the economic analysis carried out favoured the mini-split air-conditioning system with a net present worth of n46 million over of the vrf system with a net present worth of n77 million. to come up with a more detailed engineering economic analysis of both systems, a further research would be necessary for the estimation of the actual energy consumption of both systems as this would result in a more concise figure for the systems since energy cost is a major consideration during the actual running of the systems. references ashrae 1992 ‘fundamentals’ handbook. american society of heating, refrigerating and airconditioning engineers, inc. 791 tullie circle, ne, atlanta, ga 30329-2305 ansi/ashrae 2004. ashrae standard 62.1. ventilation for acceptable indoor air quality. american society of heating, refrigerating and air-conditioning engineers, inc. 791 tullie circle, ne, atlanta, ga 30329-2305. 1 – 13. issn 1041-2336. amarnath ammi and blatt morton, 2008. variable refrigerant flow: an emerging air conditioner and heat pump technology. 2008 american council for an energy-efficient economy (aceee) summer study on energy efficiency in buildings aynur, t.n., hwang, y., and radermacher, r. 2008a. simulation evaluation of the ventilation effect on the performance of a vrv system in cooling mode—part i, simulation evaluation. journal of hvac&r research, volume 14(4): 615-630. aynur, tn., hwang, y., and radermacher, r. 2008b. simulation evaluation of the ventilation effect on the performance of a vrv system in cooling mode—part ii, simulation evaluation. journal of hvac&r research, volume 14(5): 783-795. barot, jm. 2014. comparative analysis of hvac system based on life cycle cost analysis. int. journal of engineering research and applications. vol. 4, issue 7(1): 171-174. www.ijera.com brar, js. 2012. study, modelling, analysis, evaluation, selection and performance improvement of air conditioning system. m.eng. thesis, department of mechanical engineering, thapar university, patiala-147004, india. carrier software systems 2011. new features in the carrier hourly analysis program v4.51. carrier corporation syracuse, new york rev may 13, 2011. 10th edition. 1 – 8. copyright © 2011 carrier corporation cbn (central bank nigeria). inflation rates (percent). https://www.cbn.gov.ng/rates/inflrates.asp?yea (sited march 2018) goetzler, william. 2007. variable refrigerant flow systems. ashrae journal, april 2007. 24-31. hap 2016. carrier hourly analysis program quick reference guide. carrier corporation syracuse, new york rev may 13, 2011. 1 – 8. http://www.ijera.com file:///c:/users/user/downloads/azojete143/www.azojete.com.ng layeni, et al.: comparative engineering economic analysis of a variable refrigerant flow and mini-split air conditioning system design. azojete, 15(1):55-66 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 66 kim, w., jeon, sw. and kim, y. 2016. model-based multi-objective optimal control of a vrf (variable refrigerant flow) combined system with doas (dedicated outdoor air system) using genetic algorithm under heating conditions. energy, 107: 196 – 204. newnan dg., eschenbach, tg. and lavelle, jp. 2004. engineering economic analysis, 9th edition. oxford university press, new york. 1-627 oou, physical planning unit, 2006. architectural design for tetfund sponsored olusegun obansanjo engineering complex building, located at the college of engineering & technology, ibogun campus, olabisi onabanjo university ago-iwoye popovici, cg. and hudişteanu, sv. 2015. comparative analysis of hvac system functionality in “vasile alecsandri” national theatre of jassy. buletinul institutului politehnic din iaşi publicat de universitatea tehnică „gheorghe asachi” din iaşi tomul lxi (lxv), fasc. 2, 2015 secţia construcţii. arhitectură. romania. 43 – 51. str partners, llc, cs2 design group, llc, 2013. project report: air conditioning study for 8 elementary schools, oak park, il 60302. board of education of oak park elementary school district 97 970 w. madison street oak park, il 60302. november 14, 2013. str project number: 1 3159 zhou, yp., wu, jy., wang, rz. and shiochi, s. 2007. energy simulation in the variable refrigerant flow air-conditioning system under cooling conditions. energy and buildings, 39(2): 212 – 220. //doi.org/10.1016/j.enbuild.2006.06.005. http://doi.org/10.1016/j.enbuild.2006.06.005 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):889-897 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 889 original research article effect of period and storage conditions on essential oil yield and composition of eucalyptus citriodora leaves k. mu’azu1*, a. ganiyu1, a. s. alkali1, a. u. ahmed1, s. m. jibia2, m. shehu1, and i. u. adamu1 (1department of pilot plants and fabrication, national research institute for chemical technology, zaria, nigeria 2department of scientific and industrial research, national research institute for chemical technology, zaria, nigeria) * corresponding author’s email address: kabirumuazu@yahoo.co.uk 1.0 introduction essential oils are volatile, natural base products, which are found in spices, aromatic and medicinal plants. the extraction of essential oils is well known from old ages when pure essential oil and crude extract of essential oil bearing plants, herbs and grasses were in use for various medicinal and fragrances, flavors, preservatives and insect repellants purposes (weiss, 1997; panda, 2000). eucalyptus plant is mainly grown in tropical and sub-tropical regions because of its resistance to many pest and adaptability to various climatic conditions. the plant has up to 700 species and can grow as high as 40 m tall in an altitude of 600m. the yield of eucalyptus oils from leaves depends on the species and varies from 0.10 to 9.0 % on dry weight basis. oil content also article information abstract fresh eucalyptus citriodora leaves were harvested and kept under shade and sun for a period of four weeks. the effect of storage conditions and period of storage on the oil yield, oil composition and extraction pattern of the oil were investigated. it was observed that for the leave kept under sun there was significant decrease in the oil yield from 0.38% in the 1st week to 0.11% in the 4th week. however, for leaves kept under shade the oil yield slightly decreased from about 0.40% in the 1st week to 0.36% in the 4th week. the results further revealed that the storage condition and period of storage had no effect on the extraction pattern of the oil with about 72% of the oil extracted within 40 minutes of extraction time after induction period of 24 minutes. two mathematical model equations were developed for the prediction of oil yield as a function of storage time for both conditions. the models predicted that for leaves stored in the shade and sun the expected oil yield would be 34.5% and 1% respectively. physiochemical analysis of the oils revealed that the properties of the oil were not affected by both the period and condition of storage except the colour which changed from pale yellow to light brown. these results imply that the leaves should best be kept under shade before production in order to preserve its oil content and physiochemical properties. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 22 november, 2018 revised 12 september, 2019 accepted 19 september, 2019 keywords: eucalyptus citriodora leaves essential oil shade storage sun storage and oil yield. mailto:kabirumuazu@yahoo.co.uk http://www.azojete.com.ng mu’azu, et al: effect of period and storage conditions on essential oil yield and composition of eucalyptus citriodora leaves. azojete, 15(4):889-897 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 890 fluctuates with season. for instance, e. citriodora leaves collected in pakistan in april-may contained 0.9% oil than 1.3% in december (rafique and chaudhary, 1996). in terms of toxicity, eucalyptus oils have been categorized as gras (generally classified as safe) by the united states environmental protection agency (us epa) due to the high ld 50 of their major components for rats (batish et al., 2008). the physiochemical properties of essential oil are primarily responsible for its biological activities (barbosa et al., 2016; vuong et al., 2015). some of these activities include antimicrobial (saleem et al., 2016; mekonnen et al., 2016; luis et al., 2016; said et al., 2016), herbicidal (tomaz et al., 2014), anticancer (vuong et al., 2015), and insecticidal activities (karemu et al., 2013; bossou et al., , 2015). many research works have been published on different factors affecting eucalyptus oils yields: tree age (andrade and gones, 2000), leaf age (goguadza, et al, 1986; silvestre et al, 1997), altitude (manian and gopalakrishinan, 1995), season (rafique and chaudhary, 1996), harvest time (doran et al, 1995) and fertilizer application (maffeis, et al, 2000). however, scanty information is available on effect of storage of eucalyptus citriodora leaves under different conditions on the oil yield and its physiochemical properties. the objective is to provide detail information on the best period and condition of which the leaves should be stored so as to preserve the oil yield and its physiochemical properties. it will also serve as an important resource to the commercial producers in the essential oil industry regarding the best period and condition of leave storage. 2. materials and methods 2.1 material sourcing and preparation fresh eucalyptus citriodora leaves were obtained from national research institute for chemical technology (narict) plantation in zaria, nigeria. the leaves were removed from its stalk and freed from any foreign materials presence. 20kg of the leaves were weighed into 8 places (portions) for eight batches operation and kept four (4) portions under shade (figure 1). the remaining four (4) portions were kept in the sun (figure 2). 2.2 extraction of essential oil the pilot plant for the extraction process is shown in figure 3. the plant consists of cylindrical tank still, condenser, steam generation and cooling water units. 20 litres of water was charged into the boiler section (steam generation unit) of the tank still which is located at the bottom figure 1: eucalyptus citriodora leaves kept under shade figure 2: eucalyptus citriodora leaves kept under the sun http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 889-897. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 891 and occupies 1/5 of the tank height. the boiler section is separated from the oil extraction chamber by a stainless steel weir mesh. the extraction was first carried out using fresh leave as control before using stored leaves. 20 kg of the fresh leave was then charged into the tank still from the top and tight properly to avoid steam leakage. the gas burner located at the bottom of the tank still was then ignited and timed immediately. the burner fueltoair ratio was adjusted until blue flame was obtained implying steady energy supply. figure 3: essential oil extraction pilot plant the steam produced from the boiler passed across the packed bed of leaves and extracted the oil which was conveyed to the condenser. the cooling water entered the condenser from the overhead high density polyvinyl chloride (pvc) tank by action of gravity at the rate of 1 litre per minute. the flow of steam-oil mixture in the condenser and cooling water was counter current for effectiveness. the condensate (essential oil + warm water mixture) was collected in a transparent glass separating flask at various time intervals and separated. the volume of oil (see figure 4) and corresponding warm water collected at various times were measured and recorded. sodium sulphate was then added to the oil and allowed to stay overnight followed by filtration to remove any traces of moisture and suspended impurities. figure 4: essential oil extracted file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: effect of period and storage conditions on essential oil yield and composition of eucalyptus citriodora leaves. azojete, 15(4):889-897 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 892 after 1st week of storage, same extraction procedure mentioned above was repeated using leaves kept under sun (sun) and shade (shd) separately. in each case, the cumulative oil collected, extraction time, steam requirement and energy consumption were recorded. the same procedure was repeated for 2nd, 3rd and 4th week of storage for both sun and shade storage. the percentage yield of the extracted oil was calculated using equation (1). oil yield % = weight of oil weight of leaves x 100 (1) 2.3 determination of physiochemical properties of the oil the physiochemical properties of the extracted essential oil such as refractive index, specific gravity, solubility in ethanol and ester value were determined according to the methods described elsewhere (galadima, 2004 and unido, 1983) 3. results and discussion 3.1 effect of extraction time on oil volume the effect of extraction time on the quantity of essential oil extracted from eucalyptus citiriodora leave kept under both shade and sun are presented in figures 5 and 6 respectively. in figure 5, it can be seen that throughout the storage period (1-4 weeks), the volume of the oil extracted increases with increase in extraction time until it reached extraction time of 20 minutes after the induction period before declining. the induction period is the time between ignition of the burner and the first drop of the steam plus oil mixture collected. this period is generally dependent on the energy supply, volume of the water in the boiler and loading density of the leaves and was found to be about 24 minutes. figure 5: extraction pattern of essential oil as a function of time for leaves dried under shade figure 6: extraction pattern of essential oil as a function of time for leaves dried under sun http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 889-897. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 893 however, similar pattern of extraction was observed for leaves dried under sun (figure 6) with maximum oil extracted within 20 minutes before declining. it was also observed that about 72% of the oil was extracted within 40 minutes for dried leaves in the shade and 45% of the oil also in 40 minutes for the leaves dried in the sun. this implies that there was significant reduction in the oil extracted from the leaves dried in the sun when compared with the leaves under shade and fresh leaves (67%) as reported by other researchers (mu’azu, et al., 2009). it also evident from these graphs (figures 5 and 6) that storage of the leaves under both conditions (sun and shade) had no effect on extraction pattern of the oil but rather the oil yield. 3.2 effect of storage period and condition on oil yield it was observed that during storage of the leaves under both sun and shade there was significant reduction in the weight from 20 kg of fresh leave to 8 kg for storage under shade and 7kg under sun in the 4th week as shown in table 1. table 1: effect of storage period on eucalyptus leave storage period (week) weight (kg) sun shade 0 20 20 1 12 14 2 9 10 3 8 9 4 7 8 this reduction in leave weight is primarily due to evaporation of both moisture and oil from the leaves and is more pronounced on the leaves kept under sun which also increases with time of storage in both cases. the effect of storage time (weeks) and condition (shade and sun) on oil yield were studied as shown in figure 7. as can be seen from figure 7, there was slight significant changes in the oil from 1st week of storage (0.40%) through the 4th week (0.36%) for the leaves kept under shade. this implies that the reduction in leaves’ weights as shown in table 1 were basically due to evaporation of the moisture not the oil. figure 7: effect of storage period and condition on oil yield in the case of leaves kept in the sun also shown in figure 7, significant reductions in the oil yield were observed from 0.38% in the 1st week to 0.11% in the 4th week. this also implies that file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: effect of period and storage conditions on essential oil yield and composition of eucalyptus citriodora leaves. azojete, 15(4):889-897 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 894 storage of the leaves in the sun reduces both oil and the moisture significantly. it also evident that in the 1st week of storage the oil yield remained relatively constant in both cases (0.380.40%) in spite reduction in the leave weight. this explains the fact that the reduction in the weight was due to evaporation of the moisture not the oil and was being held as unbound moisture or free moisture while the oil is bound moisture held within the leave’s matrix (mu’azu et al., 2009) comparison of the oil yield obtained from sun and shade storage in the 4th week with the oil yield from the fresh leaves, the results revealed reduction in oil yield by 70.3% for sun and 10% for shade indicating that storage under the shade preserve more oil than sun. it is worth mentioning that the oil yield obtained from this plant species (0.579%) is far lower than the yield obtained from same plant species (1-1.2%) grown in india as reported elsewhere (manika et al., 2012). the difference could be due time of harvesting, maturity, tree age, leaf age and fertilizer application (maffeis, et al., 2000) figure 8: linearization of effect of storage period and condition on oil yield linearization of figure 7 resulted in figure 8 and two model equations for prediction of oil yield as a function of time of storage of the leaves for shade and sun as shown in equations (2) and (3) respectively. y =− 0.013x + 0.41 (2) y =− 0.089x + 0.455 (3) in the above equations, y represents oil yield and x storage period. for instance, if x=5 in equation (2), then y= -0.031(5) + 0.41 = 0.345 or 34.5%. similarly, for x=5 in equation (3), then y= -0.089(5) + 0.455 =0.01 or 1%. in other words, when the leaves are kept under both shade and sun for a period of 5 weeks, the expected oil yield would be 34.5% and 1% respectively. 3.3 physiochemical properties of the essential oil the physiochemical properties of the extracted essential oil presented in table 2 and 3 for both sun and shade storage shows a very good correlation with the literature values as well as the oil extracted from the fresh leaves. these results clearly indicate that the properties of the oil were not significantly affected by the time of storage (1-4 weeks) considered in this study and storage condition (sun and shade). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 889-897. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 895 table 2: effect of storage period on physiochemical properties of the oil stored in the sun parameter storage period (week) fresh 1 2 3 4 literature value colour pale yellow light brown light brown light brown light brown pale yellow appearance liquid liquid liquid liquid liquid liquid odour aromatic aromatic aromatic aromatic aromatic aromatic taste spicy spicy spicy spicy spicy spicy refractive index @25°c 1.4520 1.4519 1.4535 1.4565 1.4539 1.45111.4570 specific gravity@25°c 0.88 0.91 0.89 0.94 0.92 0.89-0.93 solubility (in 70% ethanol) 1:3 1:4 1:5 1:4 1:3 1:3-1:5 ester value 15 17 16 16 14 12-60 table 3: effect of storage period on physiochemical properties of the oil stored in the shade parameter storage period (week) fresh 1 2 3 4 literature value colour pale yellow light brown light brown light brown light brown pale yellow appearance liquid liquid liquid liquid liquid liquid odour aromatic aromatic aromatic aromatic aromatic aromatic taste spicy spicy spicy spicy spicy spicy refractive index @25°c 1.4525 1.4529 1.4553 1.4555 1.4540 1.45111.4570 specific gravity@25°c 0.90 0.92 0.88 0.93 0.91 0.89-0.93 solubility (in 70% ethanol) 1:4 1:3 1:4 1:5 1:3 1:3-1:5 ester value 14 15 16 13 15 12-60 4. conclusions the following conclusions were made from this study. 1. the pattern of oil extraction was not affected by both the storage period and condition. 2. storage of the leaves under shade slightly decreased the oil yield as compared with sun storage which significantly decreased the oil yield by about 25% on weekly basis. 3. the best condition to store the leaves is under shade to preserve the oil. 4. model equations were developed for the prediction of oil yield as a function of time of storage for both sun and shade file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: effect of period and storage conditions on essential oil yield and composition of eucalyptus citriodora leaves. azojete, 15(4):889-897 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 896 5. the physiochemical properties of the oil do not significantly change with both the condition and storage period. acknowledgements the authors express their sincere appreciation to the director-general/ceo of national research institute for chemical technology (narict), zaria for his moral and financial supports towards this project. the friendly corporation and support by members of staff of pilot plants & fabrication technology, narict, zaria is also highly appreciated. references andrade, am. and gomes, sds. 2000. influence of some non-genetic factors on the essential oil content of leaves of eucalyptus citriodora hook. floresta e ambiente, 7: 181-189. barbosa, lca., filomeno, ca. and teixeira, rr. 2016. chemical variability and biological activities of eucalyptus spp. essential oils. molecules, 21: 1671. batish, dr., singh, hp., kohli, rk. and kaur, s. 2008. eucalyptus essential oil as a natural pesticide. forest ecological management, 256: 2166–2174. bossou, ad., ahoussi, e., ruysbergh, e., adams, a., smagghe, g., de kimpe, n., avlessi, f., sohounhloue, dck. and mangelinckx, s. 2015. characterization of volatile compounds from three cymbopogon species and eucalyptus citriodora from benin and their insecticidal activities against tribolium castaneum. industrial crops and products, 76: 306–317. doran, jc., caruhapattana, b., namsavat, s. and brophy, jj. 1995. effect of harvest time on the leaf and essential oil yield of eucalyptus camaldulensis. journal of essential oil research 7: 627632. galadima, ms. 2004. design and fabrication of a pilot plant for steam distillation of essential oil. unpublished m.sc. thesis, department of chemical engineering, ahmadu bello university, zaria, nigeria. pp. 4-6. karemu, ck., ndung’u, mw. and githua, m. 2013. repellent effects of eos from selected eucalyptus species and their major constituents against sitophilus zeamais (coleoptera: curculionidae). international journal of tropical insect science, 33: 188–194. luis, a., duarte, a., gominho, j., domingues, f. and duarte, ap. 2016. chemical compo-sition, antioxidant, antibacterial and anti-quorumsensing activities of eucalyptus globulus and eucalyptus radiata essential oils. industrial crops and products, 79: 274–282. maffeis, ar., silveira, rl. and brito, jo. 2000. macronutrients and boron deficiencies reflexes on plant growth, production and essential oil in eucalyptus citriodora. scientia forestalis, 57: 87-98. manika, n., priyanka, m., narendra, k., chanotiya, cs. and bagchi, gd. 2012. effect of season on yield and composition of the essential oil of eucalyptus citriodora hook. leaf grown in subtropical conditions of north india. journal of medicinal plants research, 6(14): 2875-2879. available online at http://www.academicjournals.org/jmpr manian, k. and gopalakrishnan, s. 1995. physiological basis for ecological preference of eucalyptus globules labill. (bluegum). ii. growth and oil production. indian forester, 121: 300305. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 889-897. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 897 mekonnen, a., yitayew, b., tesema, a. and taddese, s. 2016. in vitro antimicrobial activity of essential oil of thymus schimperi,matricaria chamomilla,eucalyptus globulus, and rosmarinus officinalis. international journal of microbiology, 8. http://dx.doi.org/10.1155/2016/9545693. article id 9545693. mu’azu, k., okonkwo, em. and abdullahi, m. 2009. economic analysis of production of essential oil using steam distillation technology. nigerian journal of basic and applied sciences, 17(2): 218-222. available online at http://www.ajol.info/browse-journals. panda, h. 2003. essential oils handbook, national institute of industrial research, delhi. rafique, m. and chaudhary, fm. 1996. seasonal variations in the composition of essential oil of eucalyptus citriodora of pakistan. pakistan journal of scientific and industrial research, 39: 83-84. said, zbos., haddadi-guemghar, h., boulekbache-makhlouf, l., rigou, p., remini, h. and khoudja, nk. 2016. essential oils composition, antibacterial and antioxidant ac-tivities of hydrodistillated extract of eucaplyptus globulus fruits. industrial crops and products, 89: 167– 175. silvestre, aj., cavaleiro, js., delmond, b., filliatre, c. and bourgeois, g. 1997. analysis of the variation of the essential oil composition of eucalyptus globulus labill. from portugal using multivariate statistical analysis. industrial crops and products 6: 23-27. tomaz, ma., costa, av., rodrigues, wn., pinheiro, pf., parreira, la., rinaldo, d. and queiroz, vt. 2014. chemical composition and allelopathic activity of the eucalyptus essential oil. bioscience journal, 30: 475–483. unido, 1983. practical manual on essential oils industry (unido, vienna, austria) pp. 3-5. vuong, qv., chalmers, ac., bhuyan, dj., bowyer, mc. and scarlett, cj. 2015. botanical, phytochemical, and anti-cancer properties of the eucalyptus species. chemical biodiversity, 12: 907–924. weiss, ea. 1997. essential oil crops, cab international, usa http://www.ajol.info/browse-journals file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1038-1048 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1038 original research article shortest route: a mobile application for route optimization using digital map o. e. oduwole1, o. s. asaolu1* and m. s. osigbemeh2 (1department of systems engineering, university of lagos, nigeria. 2department of electronics and computer engineering, ae federal university ndufe-alike ikwo, nigeria) * corresponding author’s email address: asaolu@yahoo.com 1.0 introduction optimization involves finding an alternative with the most cost-effective or highest achievable performance under given constraints, by maximizing desired factors and minimizing undesired ones (ibidapo-obe and asaolu, 2006). thus “route optimization” is planning destination(s) along a start-end combination with cost-effective or utmost achievable performance within known constraints. it involves maximizing manpower and customer satisfaction whilst minimizing inconveniences, time, resources and fatigue (korel et al., 2018). one of the most important factors in the success of a central business region in recent times is cost reduction (manpower, logistics, time, resources.). this study provides a solution to an aspect of route optimization in a metropolis via a mobile application. this approach was considered because in recent times, people usually access information on the internet via mobile devices. the shortestroute mobile application is created using mapping technology to solve the travelling salesman problem (tsp) of finding the shortest route between multiple destinations while visiting each destination only once and returning to the initial destination, by using the nearest article information abstract businesses that have embarked on using digital maps have been able to increase employee productivity, communicate visually; reduce cost of logistics, planning, resources by more than half of its initial cost. many industries that have benefitted from this technology include online markets, delivery companies, agriculture, real estate, engineering, media, energy and utilities, insurance, architecture. seeing this need especially in nigeria where cost of logistics is high, resources are wasted in the process and productive time is also wasted leading to fatigue and low outcome; there is therefore the need for route optimization for businesses in nigeria. tsp (travelling salesman problem) nearest neighbour algorithm is used to solve the problem of route optimization on google map. this study developed a mobile application in java, html and google sdks, to find shortest route between various numbers of locations enumerated on digital maps on a smart device. the application was implemented successfully on the android operating system for mobile devices. anyone can download it from the google play store, install and freely use. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 september, 2018 revised 30 june, 2019 accepted 05 july, 2019 keywords: route optimization google maps mobile application android shortestroute. mailto:asaolu@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1038-1048. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1039 neighbour algorithm. in using this mobile application, users can easily find the shortest route with unlimited number of destinations, re-order the desired destinations, select any starting point (address) and save the list of re-ordered addresses for future use. in order to plan an effective route, important factors to be considered are convenience, time and an optimized route; ultimately saving money, resources and energy. for instance, a route of 9 addresses can be sequenced in 362,880 ways using permutations which can become stressful to enumerate and consider. it is time consuming to identify the optimal result by brute-force search. these problems emerge in real-life problems like a postman that needs to reach 50 different destinations to deliver letters or an online market dispatch rider who needs to deliver goods to about 20 different customers within a region. imagine trying to plan a route for this number of destinations. tedious! this mobile app solves such problem in seconds with options useful to the user. with the trend in technology, it is observed that businesses need to stay competitive (brown et al., 2012) by reducing cost (in terms of time and deployed resources). those that have embarked on using digital maps have been able to increase employee productivity, communicate visually; reduce cost of logistics, planning and resources by more than half of its initial cost. industries that have benefitted from this technology include online markets, delivery companies, agriculture, real estate, engineering, media, energy and utilities, insurance and architecture amongst others. 1.1 route optimization routing optimization problems on networks consist of finding paths (simple paths, closed paths, tours, or walks) between nodes of the networks in an efficient way. these problems and their solutions have proved to be essential ingredients for addressing many real-world decisions in applications as diverse as logistics, transportation, computer networking, internet routing, to name a few. in many of these routing applications, especially those imposing deadlines on when to visit nodes, the presence of uncertainty in the networks (such as presence or not of some of the nodes) is a critical issue to consider explicitly if one hopes to provide solutions of practical values to the end users. the deterministic version of many routing optimization problems (such as shortest path problems, traveling salesman problems, vehicle routing problems) have been studied extensively over many decades. due to the recognized practical importance of incorporating uncertainty, the uncertain versions of routing problems have also attracted increasing attention. researchers have established distinct selection criteria. one intuitive and well-discussed way is to select a route with the largest probability of arriving on time (bertsimas, 1992; bertsimas and sim, 2003; bertsimas and sim, 2004; agra et al., 2012). for logistics and distribution companies, the rising cost of fuel means that they need to become efficient in the way they plan their transportation routes and schedules. the traditional methods of route planning do not address real time events that affect businesses every day. to accommodate customers short-notice requirements, route availability, and vehicle issues, route planning has to be able to respond quickly to any event to ensure the lowest cost of transportation. the basis for route optimization is the use of models to describe the transport network that needs to be planned. when building a model, the scope of the overall network should be well defined; ensuring that cogent information is considered, such as regulations and typical highway problems. the model has a number of components such as products, vehicles, and personnel. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oduwole et al: shortest route: a mobile application for route optimization using digital map. azojete, 15(4):10381048. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1040 mobile gisglobal information system the mobile gis is emerging at the intersection of the evolution of mobility with the development of geo-informatics, it represents the user demand and ambition to exploit the geographic knowledge in decision support everywhere and anytime (vu et al., 2019). ubiquitous network analysis is a major requirement for many people moving with mobile devices, they need to comprehend their nearby location and manage their trips and movement. this aspiration is facing many challenges in online navigation from the accurate position to the geo data and up to algorithms and solutions for route problems. the visualization of the geospatial data is the main concern of the mobile user. through it, the user can build his/her mental image about the space around. the mobile cartography is related to the display of geographic information on the screen of mobile device. it has distinct differences from digital cartography, first the screen size and resolution are much smaller, second, it targets only single user in mobility, third, it is not connected to a plotter or printer for hardcopy output, fourth, the user current location is the fundamental feature at the centre of the display, and finally it displays minimal amount of features. the main objective of mobile cartography is to make the user aware of his/her location, direction, and important features around, and this is for the real-time display of geographic information. the other applications of mobile cartography are the enquiry of existing geographic data and performing proximity and network analysis for the required destinations, such as the optimal path from origin to destination. the mobile cartography presents to the user the required geospatial information in the required time and adopts the geospatial data to fit the mobile device requirements at information level. the mobile device has limited hardware resources and most notably small screen with low resolution, which has effect on cartographic representation (reichenbacher, 2001). the statistical maps are hard to be displayed on a mobile device, same as for cartograms maps related to dense analysis of geospatial data. the dot thematic maps are essential in mobile cartography in order to represent the locations important to a mobile user. the mobile user expects from the mobile gis to display on its screen the position and direction of the user, the location of specific features and how to navigate from one place to another (rajagopal et al., 2014). tsptravel salesman problem the traveling salesman problem (tsp) is one of the most intensively studied problems in optimization (claus, 1984; kara and derya, 2015). loosely speaking, given a set of locations on a map, the problem consists of finding a tour that goes through each city exactly once and ends in the same point it started with. there has been much research done on finding efficient heuristics to get provably optimal and close to optimal solutions to tsp problems (ha et al., 2018). in this study, the nearest neighbour algorithm is used to implement the mobile application. the nearest neighbour algorithm is easy to implement and executes quickly, but it can sometimes miss shorter routes which are easily noticed with human insight, due to its "greedy" nature. as a general guide, if the last few stages of the tour are comparable in length to the first stages, then the tour is reasonable; if they are much greater, then it is likely that there are much better tours. another check is to use an algorithm such as the lower bound algorithm to estimate if this tour is good enough. minimum travel cost approach for travelling salesman problem tsp is a prototype of hard combinatorial optimization problem where the possible solutions are (n-1)! and is considered np-hard and np-complete. the prevalent algorithms to solve tsp are heuristic algorithms which do not necessarily guarantee the minimum cost (eleiche, 2015). the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1038-1048. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1041 standard technique for obtaining lower bounds on the tsp problem is to use a relaxation that is easier to solve than the original problem such as the cutting-plane algorithm through linear programming initiated by dantzig, fulkerson and johnson in 1954, but still unable to solve large instances (averbakh and lebedev, 2004). minimum travel cost a full graph of n nodes (with number of edges n*(n -1) having edges of equal cost c, the tour cost is n*c and there are (n-1)! tours satisfying this cost. for asymmetric graphs, where cij ≠ cji, the tsp states that there are (n-1)! tours visiting all nodes (each node once) and returning to the origin, but the required is the tour of least cost. this can be achieved by visiting each node through its least travel cost. the least travel cost for each node is the sum of the cost of incident edge with minimum cost and cost of outgoing edge with minimum cost. outgoingincidenti ccc minmin  (1) where: ci is the least travel cost of node i, cincident is the edge cost from node k to node i, and coutgoing is the edge cost from node i to node j. in ideal situations, (though rare), the aggregation of the sequence of minimum travel cost (nodes: k, i, j) for each node will be the tour with least cost. the minimum travel cost unifies the directions of paths for the minimum travel cost of each node thus minimizing the tsp total cost. android based mobile application development in the advancing world of technology mobile applications are evolving at a fast pace to give users a unique personal experience. google released android which is an open-source mobile phone operating system with linux-based platform. it consists of the operating system, middleware, and user interface and application software. android is a new, next-gen mobile operating system that runs on the linux kernel. android mobile application development is based on java language codes, as it allows developers to write codes in the java language. these codes can control mobile devices via google-enabled java libraries provided in the google android sdk. aside the standard java virtual machine (jvm), google has created a custom vm called dalvik which is responsible for converting and executing java byte code on androids. as developers, we only need call the relevant application programming interface (apis) to develop applications on the android platform as we build product the interface via layered approach. as at early 2015, 48.61% of mobile devices are operating on android os, 11.04% on ios, 14% on windows and 26.34% use other operating systems (android, 2015). this gave a clear distinction on the platform to create the mobile application apart from the reality that android application courses are easier to access, create cheaper platforms for learning, an open marketplace and simple to inculcate for a mobile application beginner (brahler , 2010). 2. methodology programming, testing and deployment tasks were accomplished to build the mobile app by: app development using os with eclipse ide, jdk (java se development kit) ide and xml (extensible mark-up language) called google map api for the access to digital maps using java programming language invoked gps (global positioning system) on mobiles for navigation to find the current location of user file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oduwole et al: shortest route: a mobile application for route optimization using digital map. azojete, 15(4):10381048. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1042 created a test website using html (hypertext mark-up-language), jquery (javascript query) and javascript that gives full instruction on how to use, navigate and download the shortest route mobile application (www.shortestroute-app.com) created required certificate and version for publishing on the google play developer console uploaded product on the google play developer console for beta and alpha testing final live upload to the google play store for user download and installation. uploaded product on the google play developer console for beta and alpha testing final live upload to the google play store for user download and installation. figure 1 shows some stages of the shortestroute mobile application development as described in steps i to iv above. for the nearest neighbour implementation so solve the tsp, the algorithm is depicted in the flowchart of figure 2. the sequence of the visited vertices is the output of the algorithm. google maps provides directions, interactive maps, and satellite/aerial imagery of many countries. google maps is the only site surveyed that readily allows users to search by keyword for points of interest, and its mapping service allows users to refine searches interactively. the figure 1: shortestroute development chart http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1038-1048. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1043 api uses images from the popular google earth application to provide optional satellite views of locations around the globe. this is also the best site for viewing international online maps because it does not require complete address information. 57% of all digital maps use the google maps api (reichehenbacher t. 2003). using the google map application programming interface is a skill any programmer could learn by consulting the accompanying google documentation, numerous online support groups and tutorial sites. with the google map api, we were able to create a map layout. since smart mobile devices already come with a gps tracker, our android mobile application provides users ability to view current location, unlimited numbers of location on the map, get the route pattern, order the route and save the route via their android os mobile devices. it is important to evaluate the features of the mobile application and the development of the application. there were a wide range of compatibility and design requirements from the google play developer console to publish the shortestroute mobile application. however, before publishing on play store, the mobile application was tested for functionality and compatibility for all android os devices from version 3.0. currently, most android mobile devices run on version 4.4 or later. the shortestroute mobile application was tested on 23 different mobile devices from different products that include htc, nokia, tecno, sony, huawei, infinix, samsung and gsmart. a rigorous test on different android os versions ranging from 3.0 (honeycomb) to 5.1 (lollipop) was carried out before embarking on google play developer console for publishing. we tested the built app to ensure successful implementation of basic features such gps tracking, map loading and zooming, time and distance indicators, ability to save or delete locations. several functionality evaluations were carried out to develop a flexible mobile app for users with notifications guiding the user. when the app is about to launch, the following conditions are considered. if internet connectivity is on and gps is on, it would automatically find the user’s current location and automatically becomes the “starting point” of the journey. if internet connectivity is on and gps is off, it would show a dialogue box asking if you need gps on. if yes, immediately points to settings where gps/location is activated. if no, the mobile app continues with the world map display. once the first address is entered, it takes it as the “starting point”. if internet connectivity is off and gps is on, a dialogue box is opened to ask if user wants to turn it on internet connectivity. if yes, it immediately points to settings where internet connectivity is activated and shows a notification that mobile app should be reopened if it has been activated. if no, a notification explaining that the mobile app cannot work without internet access will come up. if internet connectivity is off and gps is off, the process for turning on internet connectivity and gps above will initiate. if map connectivity is not showing, then the mobile device needs to install or update google play services on the mobile device. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oduwole et al: shortest route: a mobile application for route optimization using digital map. azojete, 15(4):10381048. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1044 figure 3 shows the app interface while figure 4 illustrate the framework for the mobile app operations. figure 3. the interface of the shortestroute mobile app figure 4. shortestroute framework architecture google maps is used for displaying locations/addresses, showing the user’s current location and route directions of the user’s listed addresses (hu, 2012; hu and dai, 2013). the google earth engine is used as the webserver to get information for location points’ addresses. the mobile app runs on google play services and internet connectivity. a temporary, responsive test http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1038-1048. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1045 website (www.shortestroute-app.com) was created with dreamweaver ide, html and javascript query! to give users easy access to information on the navigation and step-by-step guide for shortestroute mobile application usage. the responsive website also gives access to easy download of the mobile application from google play store. this was to provide an optimal viewing experience, easy reading and navigation with a minimum of resizing, panning, and scrolling across a wide range of devices (from desktop computer monitors to mobile phones). google play, which was originally referred to by google as “android market,” is google's official store and portal for android apps, games and other content for android-powered phone or tablet, just as apple has its app store. shortestroute mobile app is successfully uploaded to the google play store for downloads after going through the beta and alpha test phases. anyone could visit www.play.google.com and search for shortestroute. it automatically opens the download page shown in figure 5 below. figure 5. shortestroute view on google play store via smartphone 3. results and discussion typical screnshots of the startup are provide in fugures 6 and 7. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oduwole et al: shortest route: a mobile application for route optimization using digital map. azojete, 15(4):10381048. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1046 figure 6. shortestroute mobile app showing the gps dialogue box figure 7. shortestroute mobile app when gps is on, automatically points to user’s current location for the 20 sample runs performed with locations in lagos metropolis, the product generated feasible paths which are optimal in all cases. shortestroute mobile application was found easy to use; appropriate notifications were generated to notify user on every step to take while using the app. all the possible uncertainties in the use of the mobile application were covered. however, the application can also be easily updated to accommodate new features and developments that include real-time traffic update data. shortestroute integrated the combination of existing innovational technologies for its implementation. some of these technologies include an android mobile app, google maps, gps tracker, a responsive website and the google app engine as webserver for feeding information to the mobile app. shortestroute mobile app users includes street travelers, tour guides, delivery service providers, tourists, professional drivers and logistics planners. the app solves the problem of routing for individuals or firms and help improve productivity and efficiency. a shortestroute mobile app user saves time, resources, energy and cost of transportation by easily entering address on the mobile app and getting the best route pattern for his journey. the mobile application with its user friendly interface will enable developed countries include traffic updates with real time data to get best route with time. the following improvements could be considered in future research: currently, the app gives best route with respect to total distance and not expected duration of travel because it does not incorporate traffic updates that could give the best time. real-time data on traffic updates can be integrated into this application. shortestroute mobile app is currently not capable of showing the walk routes and bus routes to users. this can be integrated from the google app engine webservers to allow walk routes and bus routes in the route optimization method. shortestroute mobile app does not give information for different modes of transportation. this feature can be integrated in future research. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1038-1048. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asaolu@yahoo.com 1047 google streetview can be integrated showing the street view of locations entered. shortestroute mobile app can be implemented on other mobile os platform to allow users on other mobile os platforms such as apple ios or microsoft windows get the benefits of the app. voice mapping to give directions during navigation to multiple destinations and message texting to automatically receive sms (short message service) on routes planned and other features used. 4.0 conclusion shortestroute mobile app was successfully developed, tested and deployed to the google play store for android devices. adopting it cuts logistics planning cost thereby increasing business performance, productivity, growing delivery volumes and customer satisfaction in businesses. shortest shortestroute can be used by individuals, tourists, campaign managers, band tour managers, businesses that run transport systems as in schools, street travelers, professional drivers, delivery service providers, mail dispatch services in making informed decisions about different locations to visit. it is cost effective, for all it only requires is an android mobile device and internet connectivity. this route optimization mobile app has proven to be useful to users who have currently installed the app and are using it to run and plan routes frequently, as evident in their online review comments. business owners should adapt its use for better performance in their businesses. the shortestroute can be extended to manage schedules, and appointments for users. reports could be generated on transport logistics performance using key performance indicators. references agra, a., christiansen, m, figueiredo, r, hvattum, lm., poss, m. and requejo, c. 2012. layered formulation for the robust vehicle routing problem with time windows. computers and operations research, 40(3):856 866. android 2015. understanding android. android is for everyone, available at https://www.android.com/everyone/facts/ last accessed on 12/07/2017 averbakh, i. and lebedev, v. 2004. interval data minmax regret network optimization problems. discrete applied mathematics, 138: 289 – 301. bertsimas, d. 1992. a vehicle routing problem with 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1311–1322. vu, hl., bolingbroke, d., wai ng, kt. and fallah, b. 2019. assessment of waste characteristics and their impact on gis vehicle collection route optimization using ann waste forecasts. waste management, 88:118-130 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3):519-534 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 519 original research article prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition s.o. jekayinfa1, a.o. adebayo1*, m. a. sulaiman2 and v.o. ayoola1 (1department of agricultural engineering, ladoke akintola university of technology, ogbomoso, oyo state, nigeria 2department of agricultural and mechanical engineering, olabisi onabanjo university, ago iwoye, ogun state, nigeria) * corresponding author’s email address: aoadebayo57@lautech.edu.ng article information submitted 29 march, 2018 revised 3 february, 2019 accepted 16 february, 2019 keywords: density viscosity biodiesel fame composition regression analysis prediction abstract viscosity and density are important properties that qualify biodiesel fuel to serve as an alternative fuel because all other properties directly or indirectly depend on them. the processes involved in determining the viscosity and density of biodiesel are relatively simple and costly and there are discrepancies in the results obtained due to the differences in the oil composition of the feed-stocks used as against the reported cause of experimental errors. this work aimed at theoretically determining and developing relationship between the density and viscosity of different feed-stocks and the fatty acid methyl ester composition at different temperatures. in the study, density and viscosity data of biodiesel fuels and the composition of fame were collected from literatures. a linear regression analysis was carried out for density and viscosity on the average values of viscosity and density data obtained at different temperatures range (10˚c-40˚c) of fame composition. equations relating density and viscosity with the percentage composition by weight of fame of biodiesel fuel were developed. predicted mean values for kinematic viscosity and density were respectively between 4.31 5.64 mm2/s and 861.67 – 885.66 kg/m3. the developed equations were able to predict with up to 97.1% accuracy for viscosity and 98.5% accuracy for density. the developed equations could effectively predict the quality of biodiesel (viscosity and density) from various feedstocks based on fame compositions. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction developing countries are often faced with added impasses about environmental protection owing to their heavy reliance on biomass and fossil fuel. biomass is gaining more ground and becoming more important because of rampant fuel scarcity, emissions of dangerous pollutants and increase in the prices of fossil fuels (sensoz et al., 2000). global warming, the destruction of the ozone layer and acid rain are as a result of economic growth and heavy consumption of natural resources (thakur, 2006). as a result of the soaring prices of oil coupled with its environmental impact worldwide, there is an increasing use of “green” fuels globally. most countries these days are taking advantage of crops and even their residues for http://www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 520 biofuels production. in the us and brazil, for example, maize and sugarcane serve as the main feedstocks for the production of ethanol, while kernel seed and rapeseed are respectively used for biodiesel production in malaysia and europe (srinivasa et al., 2010). biodiesel has also been produced from nigerian palm kernel, milk bush and sandbox kernel oil (alamu, et al., 2007a, 2007b, 2007c, 2008, 2009, jekayinfa, 2018, oniya et al., 2016 and ogunkunle et al., 2017). rudolf diesel researched into the use of vegetable oils as fuel for diesel engines (lang et al., 2001). it was also established that biodiesel can be obtained from feedstocks like animal fats, and oils from other organisms such as cyanobacteria, micro algae and is produced from triglyceride transesterification which serves as the major constituent of vegetable oils or animal fats in the presence of an alcohol (jazie etal., 2013). apart from the fact that biodiesel has lower carbon monoxide emissions and low viscosity, it is also non-toxic, simple to use and essentially free of sulphur (alcantara et al., 2000). biodiesel, though very advantageous, has got some limitations as well especially when using it (nolte, 2007). biodiesel produces relatively high no2 levels at combustion level due to the high oxygen content in it. this can however be minimized below that of the fossil fuel levels simply by adjusting the timing of the engine. a catalytic converter can as well be used (manohar et al., 2010). researchers have attempted to determine the best biodiesel composition that would result into enhancement of combustion process as well as the quantity of various fatty acid that can be employed in predicting both the physical and performance properties of biodiesel (bamgboye and hassen, 2008). viscosity as one of the fuel properties is used as an indicator to ascertain the following; the ease of starting the engine, effectiveness and completeness of the ester conversion process, the quality of spray, the penetration of the injected jet and the quality of the fuel-air mixture combustion is greatly affected by viscosity but reduces considerably with increase in unsaturation (alptekin and canakci, 2008). density is another property which is greatly influenced by temperature. it also has the capacity to affect fuel performance. fuel properties such as heating value, cetane number, and viscosity are connected to density (barabas and todorut, 2011). the quality of atomization and combustion is affected by density as well (barabas and todorut, 2011). molecular properties had influence on the density and viscosity (kinematic) of biodiesel. as chain length increases, density decreases slightly but larger alkyl esters are all solids at room temperature. it can be affirmed that the level of un-saturation plays a significant role in the determination of density of a given fatty acid methyl esters sample (alptekin, and canakci, 2008). also, temperature is one of the key factors that have influence on the density of the liquid as large change in the density at higher temperatures affect the atomization and combustion processes of the engine(knotheet al., (2005),tate et al., (2006)and knothe and steidley, 2005) carried out investigations on the varying effects of temperature on density of methyl soyate, rapeseed methyl ester and ethyl ester of fish oil and found out that with an increase in temperature, the density decreases linearly and at 300oc the density was as low as 0.5 gcm-3. geller and goodrum (2004) opined that the longer the fatty acid chains, the more saturated the molecules and this would automatically result into higher viscosity. however, viscosity is lowered drastically when the saturation is less. there is a vast variation in the values of http://www.azojete.com.ng ademola adebayo remove jekayinfa, 2018 arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):519-534. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 521 viscosity and density (tesfa et al., 2010). tables 1 and 2 present the value of viscosity and density of the selected feedstocks respectively as obtained from past studies. density and viscosity of biodiesel obtained from soybean oil ranged from 882.80 to 900 kgm-3 and 3.5-9.31 cst respectively (mariceli et al., 2012, omotola, 2011). for palm-oil derived biodiesel the density and viscosity ranged from 857.80 to 900 kgm-3 and 3.70-4.61 cst respectively (leung et al.,2010). also, density and viscosity values obtained for waste cooking oil methyl ester ranged from 879.55 to 889.90 kgm-3 and 5.21 to 6.00 cst respectively (tesfa et al., 2010, leung et al., 2010). the density and viscosity values vary from one feed input to another. this is dependent on the chemical composition of the fuel. it also has effect on the nox emissions. it has also been observed that there is always a less significant variation in density and viscosity at different temperatures for feedstock of the same type of oil (mccormick et al., 2001). density and viscosity fall among properties that can be easily measured though a bit costly. ballantine et al., (1997) and josse et al., (2001), noted that these properties can be measured using a thickness shear mode (tsm) resonator or a guided shear horizontal surface acoustic wave (sh-saw) device. the shortcoming that the tsm systems have are their sensitivity and selectivity to only newtonian liquids, sh-saw devices are much more sensitive and selective than their counterparts such as thickness shear mode (tsm), shear horizontal acoustic plate mode (sh-apm) and flexural plate wave (fpw). another method of measuring the viscosity is to use a miniaturized thermal conductivity sensor made from molybdenum or another metal and literature reveals that it measures liquids displaying nonnewtonian properties. (kuntner et al., 2005). in order to theoretically determine the density and the kinematics viscosity of fame and to establish the findings of researchers that have worked on this subject whether their results conform to the limits set out by the standardization organization, there is a need to develop models that can be used to predict the density and kinematic viscosity of some known parameters. since the composition of fame has been established to have great influence on its viscosity and density at varying temperature, models can be developed relating viscosity and density to fame composition. yuan model (yuan et al., 2009) with parameters specific for fames was used in the work of mesquita et al., (2011). also, yuan model as revised by pratas (pratas et al., 2010) and do carmo et al., (2012) were used to predict biodiesel viscosity. in correlating pure fame and biodiesel densities, the tait equation of state (eos) was used (dymond and malhotra,1988, pratas et al., 2011, schedemann et al., 2013 and aparicio et al., 2007). pratas et al., (2011) applied the cpa eos to correlate pure fame density, and the calculated pure component parameters were applied to predict the density of methyl biodiesels with deviations ranging from 0.79% to 2.5%. schedemann et al., (2013) in his own turn made use of the vtpr method to predict density data of methyl linoleate and biodiesel as submitted in the findings of prieto et al., (2015). in developing the present model, the composition of fatty acid in percentage of ester in pure form together with the mixtures of esters (biodiesel) and their experimental density and viscosity were considered (bamgboye and hassen 2008). this study aimed at developing regression equations which can be used to predict the density and viscosity of biodiesel based on the fame chain compositions and authenticating the applicability of the established equations for predicting the density and viscosity based on the fame composition of the feedstock oils used for biodiesel production. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 522 table 1: reported values of viscosity of different biodiesel feedstock (mm2/s) at varying temperature (10-40°c) *sunme: sunflower methyl esters; come: corn oil methyl ester; sme: soybean methyl ester; cme: canola seed methyl ester; pome: palm oil methyl esters; rme: rapeseed methyl ester; csome: cotton seed oil methyl ester; wcme: waste cooking oil methyl ester; osme: olive seed oil methyl ester **the number in the parenthesis represent the different authors from which the viscosities were sourced from literatures for this study: 1. barabás & todoruţ, (2010); 2. chuepeng & komintarachat, (2010); 3. zahan and kano (2018).; 4. singh and singh (2010), 5. leung et al., (2010), 6. auwal et al., (2011), 7. tesfa et al., (2010), 8. maricelida et al., (2012). 9. omotola (2011). temp.°c sunme* come sme cme pome rme csome wcme osme 10.00 9.92 [8]** 9.54 [8] 9.31[8] 15.00 20.00 7.44[8] 7.69[8] 28.00 30.00 5.58[8] 40.00 4.03 [1] 4.63[11] 4.57[8] 4.9[5] 4.51[9] 4.38-4.90[3] 4.18-4.52[1] 4.89 [7] 3.39 [5] 4.32[8] 3.39-4.36[3] 4.44[8] 4.10[6] 4.08 [5,9] 4.08-4.42[3] 4.344.84[1] 4.68[8] 3.70 [1] 4.42 [5] 4.42-4.76[3] 5.7[4] 4.2[4] 4.83-5.65[1] 4.48[2] 5.48[7] 4.3-5.83[5] 4.59-5.83[3] 4.07 [5] 4.0-4.96[3] 5.78-6.00[1] 5.81[5,9] 5.21[7] 4.70 [1] http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):519-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 523 table 2: reported values of density of different biodiesel feedstock (kg/m3) at varying temperature (10-40ºc) temp.°c sunme come sme cme pome rme csome wcme osme 10.00 887.60[8] 885.86[8] 886.33[8] 886.43[4] 15.00 882.70[9] 880[10] 882.90[9,10] 880-890[10] 882.20[8] 884[1] 885[9,10] 882.80[8] 888[5] 860900[10], 867[5] 864.4870[1] 883.7 [2] 880.2[1] 880-888[10] 875[10] 884.1[3] 874.0[9] 897[6] 881.50[1] 15.60 20.00 883.41[8] 25.00 26.00 30.00 32.00 34.00 36.00 38.00 40.00 874.96[8] 879.65[7] 874.51[8] 879.35[7] 864.4[3] 879.55[7] 920[1] *sunme: sunflower methyl esters; come: corn oil methyl ester; sme: soybean methyl ester; cme: canola seed methyl ester; pome: palm oil methyl esters; rme: rapeseed methyl ester; csome: cotton seed oil methyl ester; wcme: waste cooking oil methyl ester; osme: olive seed oil methyl ester **the number in the parenthesis represent the different authors from which the densities were sourced from literatures for this study: 1. barabás & todoruţ, (2010); 2. chuepeng&komintarachat, (2010); 3. prieto et al, 2015; 4. fan et al., (2009), 5. nolte (2007) 6. zahan and kano (2018)., 7. tesfaet al., (2010), 8.maricelida et al., (2012). 9. omotola (2011), 10. leung et al., (2010) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 524 2. materials and methods 2.1 fuel data selection the viscosity and density of the biodiesel (fame esters) were gotten from different reports submitted to fuel standards by various testing laboratories (european standard en 14214, astm d 6751) as shown in tables 3 – 6. average values of the data collected for the percentage composition of the fatty acids in the diverse feedstocks of pure methyl esters were utilized in this study. 2.2 regression analysis a seven by eight matrix was formed with density and viscosity as the dependent variable respectively and pure fame composition as the independent variables as shown in tables 3 and 4. the linear regression equation conceptualized can be presented as follows; = ……… 1 and, ………..2 where, , and b, is the viscosity in , a, b, c, d, e, f, g, h are constants to be determined in the regression analysis; …… are % compositions of fame. table 3: reported average values of density for pure methyl esters of different fatty acids (kg/m3) at temperature 40°c fatty acid methyl esters density ρ kg/m3 references laurate 853.90a, (barabás and todoruţ, 2011)a, myristate 852.20a (barabás and todoruţ, 2011)a palmitate 850.80a, 852b (barabás and todoruţ, 2011)a, (lapuertaet al., 2010)b palmitoleate 853.80a, 875b (barabás and todoruţ, 2011)a, (lapuertaet al., 2010)b stearate 849.80a, 850b (barabás and todoruţ, 2011)a, (lapuertaet al., 2010)b oleate 859.50a, 874b (barabás and todoruţ, 2011)a, (lapuertaet al., 2010)b linoleate 871.50a, 889b (barabás and todoruţ, 2011)a, (lapuertaet al., 2010)b linolenate 887.00a, 895b (barabás and todoruţ, 2011)a, (lapuertaet al., 2010)b http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):519-534. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 525 table 4: reported average values of density for pure methyl esters of different fatty acids (kg/m3) at temperature (15˚c)a (15.5ºc)b fatty acid methyl esters density ρ kg/m3 references laurate 873.70a (barabás and todoruţ, 2011)a myristate not determineda, (barabás and todoruţ, 2011)a palmitate not determineda, 867b (barabás and todoruţ, 2011)a (janarthananet al.,1996)b palmitoleate 872.80a (barabás and todoruţ, 2011)a stearate not determineda, (barabás and todoruţ, 2011)a, oleate 877.70a, (barabás and todoruţ, 2011)a, linoleate 889.90a, (barabás and todoruţ, 2011)a, linolenate 905.70a (barabás and todoruţ, 2011)a table 5: reported average values of kinematic viscosity for pure methyl esters of different fatty acids (mm2/s) at temperature 40˚c fatty acid methyl esters viscosity (mm2/s) references laurate 2.4331a, 2.43c (barabás and todoruţ, 2011)a, (knothe,2005)c myristate 3.3381a, 3.23c, (barabás and todoruţ, 2011)a, (knothe,2005)c palmitate 4.4136a, 4.38c, (barabás and todoruţ, 2011)a, (knothe,2005)c, palmitoleate 3.0642a, 3.67d (barabás and todoruţ, 2011)a, (moser, 2009)d stearate 5.8675a , 5.51c (barabás and todoruţ, 2011)a,(knothe,2005)c oleate 4.5728a, 4.51c (barabás and todoruţ, 2011)a, (knothe,2005)c linoleate 3.7028a, 3.65c (barabás and todoruţ,2011)a, (knothe,2005)c linolenate 3.2980a, 3.14c, (barabás and todoruţ, 2011)a, (knothe,2005)c file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 526 table 6: reported average % composition of fatty acids in different feedstocks at 40°c feedstock lauric myristic palmitic stearic palmitoleic oleic linoleic linolenic sme 0a, 0.08e 0.06a, 0b,d, 0.12e 10.64a 13.9d,11.4e, 12b 3.88a, 2.1d, 3b, 4.14e 0.14a, 0.3d, 0b, 0.16e 32.38a, 23.2d, 23b, 23.47e 46.36a, 56.2d, 55b,53.46e 5.53a, 4.3d, 6b, 6.64e sunme 0a, 0.01a, 0b,d 0.04e 6.48a, 6.2d,12b, 6.26e 4.25a, 3b, 2.95d, 3.93e 0a, 0.1d, 0b, 0.06e 18.97a,17.35d, 17b, 20.77e 69.07a,73.45d, 74b, 67.75e 0.26a, 0d,b, 0.15e csme 0.02a 0.32a, 0d, 0.72e 22.05a, 28.35d, 25.93e 2.17a,0.95d, 1.74e 0.13a, 0.36e 16.13a, 13d, 15.98e 55.72a, 57.7d, 55.12e 0.25a,0d, 0.16e pome 0a, 0.37e 0a, 1c, 1.13e 11.1a, 42.6d,41c 42.39e 4.22a, 4.4d, 3b,4.20e 0a,0.3d, 0c, 0.17e 47.23a, 40.5d, 45c,40.91e 32.14a,10.1d,9c, 9.97e 0.68a,0.2d,1c, 0.29e rme 0a 0.02a,0d, 0.04e 4.06a,3.25d,4.07e 1.2a,0.95d, 1.55e 0.04a, 0.23e 63.12a,64.05d, 62.24e 21.28a,22.15d, 20.61e 8.63a,8.1d, 8.72e wcme 1.98a,0.20e 0a,0.67e 15.65a, 15.69e 3.10a,6.14e 0.31a, 0.73e 29.57a, 42.84e 41.53a, 29.36e 1.04a,2.03e osme 0a, 0a 11.60a, 3.10a, 0.9a, 74.98a, 7.80a, 0.60a bamboye and hassen (2008), b. bagbyet al.,(1987), c. ziaziet al.,(1996), d. singh and singh, (2010), e. giakoumis, (2013) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):519-534. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 527 3. results and discussion table 5 presents the reported average values of kinematic viscosity for pure methyl esters of different fatty acids (mm2/s) at temperature 40˚c while table6 presents the reported average % composition of fatty acids in different feedstocks at 40˚c. substituting the values of m, a – h in eq. (1) and (2) respectively for the coefficients obtained during regression analysis for each of the feedstocks whose reported data were used,the new equations are presented in tables 7 and 8 for viscosity and density respectively. equations (1) to (7) show the relationship between fatty acid composition and viscosity of feedstocks. from equations (1) to (7), it was observed that coefficient of determination (r2) of viscosity for sme was 0.775, which indicated that the viscosity of sme can be predicted with 77.5% accuracy. the coefficients of determination (r2) of viscosity of other feedstocks include sunme (r2=0.734), pome (r2=0.609), cme (r2=0.971), rme (r2=0.097), wcme (r2=0.804) and osme (r2=0.959). the above results indicated that fatty acid compositions of methyl esters of different feedstocks are a major predictor of viscosity of biodiesel produced from them and the quality of biodiesel produced is positively influenced by saturated and long fatty acids. also, shorter and more unsaturated chains always increase the viscosity and flow characteristics at low temperatures (desirable characteristics of fuels). similarly, table 8shows that the coefficient of determination (r2) of density for sme was 0.737, which indicated that the viscosity of sme can be predicted with 73.7% accuracy. the coefficients of determination (r2) of density of other feedstocks include sunme (r2=0.524), pome (r2=0.837), cme (r2=0.985), rme (r2=0.0115), wcme (r2=0.982) and osme (r2=0.835). this implies that the density of a methyl ester depends on its molecular weight (saturated and unsaturated), free fatty acid content, water content, and temperature and indicates that fatty acid compositions of methyl esters of different feedstocks are a major predictor of density of biodiesel produced from them. these results agree with the findings of knothe (2005), who claimed that an appropriate ratio between saturated and unsaturated fatty acids should be maintained in order to obtain a biodiesel with appropriate quality characteristics. )775.0( 34.0448.045.024.555.167.01.1115.25161.44)( 2 87654321   r xxxxxxxxsmeb (1) )734.0( 49.4904.833.100.009.660.100.00.057.638)( 2 87654321   r xxxxxxxxsunmeb (2) )609.0( 67.077.036.148.091.114.113.012.055.124)( 2 87654321   r xxxxxxxxpomeb (3) )971.0( 40.405.293.017.00.018.009.3295.123.125)( 2 87654321   r xxxxxxxxcmeb (4) )097.0( 757.010.00.052.00.00.092.00..0897.0)( 2 87654321   r xxxxxxxxrmeb (5) )804.0( 68.1873.4773.290.072.188.110.00..060.3024)( 2 87654321   r xxxxxxxxwcmeb (6) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 528 )959.0( 05.6965.2495.057.1110.189.045.972.4975.17)( 2 87654321   r xxxxxxxxosmeb (7) the regression model equations indicating the relationship between fatty acid composition and density of feedstocks are given in equations (8) to (14) )737.0( 02.931.1163.1044.7205.3914.1172.22911.531760.2060)( 2 87654321   r xxxxxxxxsmep (8) )524.0( 585.2698.5593.60.052.0199.50.00.061.386)( 2 87654321   r xxxxxxxxsunmep (9) )837.0( 93.7166.725.213.9781.3384.669.2194.2115.1464)( 2 87654321   r xxxxxxxxpomep 10) )985.0( 25.194.112.002.353.1736.058.231.949.988)( 2 87654321   r xxxxxxxxcmep (11) )115.0( 31.811.168.10.00.00..087.60.025.945)( 2 87654321   r xxxxxxxxrmep (12) )982.0( 14.002.8968.810.010.8514.1350.00.022.2247)( 2 87654321   r xxxxxxxxwcmep (13) )835.0( 26.138964.1320.2060.20997.1526.297.18279.3423.302)( 2 87654321   r xxxxxxxxosmep (14) where x1…….x8 are percentage (%) composition of fame b= is the viscosity in p= is the density in kg/m3 the equations developed (equations 1 to 14) were used to predict the viscosity and density of different biodiesels consisting of different fame compositions. the predicted values were plotted against the measured values for both the viscosity and density (figures 1 and 2). the viscosity and density of biodiesel predicted were comparable to the standard values (astm d6751). hence, it could be concluded that the viscosity and density of biodiesel can be predicted based on fame compositions. the equation developed was applied to other studies previously carried out by different researchers. the results gave an indication of variation of the density and viscosity based on the % composition of fame. however, the average range of reported values for density and viscosity of different types of biodiesel as shown in tables 1 and 2 differs considerably. table 6 projects average fame compositions of different feedstock for biodiesel fuel as extracted from related past works. the mean viscosity of sme, sunme, pome, cme, rme, wcme, and osme at varying temperatures (10°c to 40°c) were determined and plotted (figure1). the means of sme, sunme, pome, cme, rme, wcme and osme were found to be 5.026, 5.514, 4.319, 5.488, 5.266, and 5.64 and 4.894 respectively. the kinematic viscosity at up to 40°c for the selected biodiesel samples were between 4.319091-5.64cst which thus satisfies the recommended http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):519-534. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 529 limits by astmd6751 ranges are 1.9—6.0 cst for a fatty acid methyl ester. in the same vein, the observed mean density ranged from 871.2009 to 885.6582kg/m3 while the predicted mean density also ranged from 861.673 to 885.6582 kg/m3 for the selected feedstocks. cme reported highest density (885.6582kg/m3) while osme reported lowest mean density (871.2009 kg/m3) and is within the ranges (860.0—900.0) recommended for fatty acid methyl esters (fame) en: 14214, 2008. key: blue bars =observed value while orange bars=predicted values figure 1: observed and predicted mean values for the selected feedstocks viscosity key: blue bars =observed value while orange bars=predicted values figure 2: observed and predicted mean values for the selected feedstocks density 4.0 conclusions the following conclusions were drawn: the study has established the regression equations relating viscosity and fame compositions for the selected feedstocks (sme, sunme, pome, cme, rme, wcme and osme). similar equations were also developed for viscosity and fame compositions. the equations developed to predict based on the fame composition and were able to predict with up to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 530 97.1% accuracy for viscosity and 98.5% accuracy for density. the developed equation can effectively predict the quality of biodiesel (viscosity and density) from various feedstocks based on fame composition. the predicted mean values for kinematic viscosity and density were respectively 4.31 5.64 mm2/s and 861.673– 885.6582kg/m3. references alamu, oj., waheed, ma. and jekayinfa, so. 2007a. laboratory preparation of nigerian palm kernel oil biodiesel: influence of transesterification duration on yield. agricultural engineering international: the cigr e – journal.manuscript ee 07 0018 vol. ix. alamu, oj., waheed, ma. and jekayinfa, so. 2007b. biodiesel production from nigerian palm kernel oil: effect of koh concentration on yield. journal of energy for sustainable development, 11(3):77-82. alamu, oj., waheed, ma. and jekayinfa, so. 2007c. alkali-catalysed laboratory production and testing of biodiesel fuel from nigerian palm kernel oil. agricultural engineering international: the cigr e – journal.manuscript ee 07 009 vol. ix. alamu, oj., waheed, ma. and jekayinfa, so. 2008. effect of ethanol-palm kernel oil ratio on alkali-catalyzed biodiesel yield. fuel,87(8-9): 1529-1533. alamu, oj., waheed, ma. and jekayinfa, so. 2009. determination of optimum temperature for the laboratory preparation of biodiesel from nigerian palm kernel oil. energy sources part a, 31(13): 1105-1114. alcantara, r., amores, j., canoira, l., fidalgo, e., franco, mj. and navarro, a. 2000. catalytic production of biodiesel from soybean oil, used frying oil and tallow, biomass bioenergy, 18 (6): 515-527. alptekin, e. andcanakci, m. 2008. determination of the density and the viscosities of biodieseldiesel fuel blends. renewable energy, 33, (12), 2623−2630. aparicio, c, guignon, b, rodriguez-anton, lm. sanz, pd. 2007. determination of rapeseed methyl ester oil volumetric properties in high pressure (0.1 to 350 mpa). journal of thermal analysis calorimetry, 89(1): 13–19. american society for testing and materials (astm). 2003. d6751 standard specification for biodiesel fuel (b100) blend stock for distillate fuels. astm international, 100 bar harbor drive, west conshohocken pa, usa.. auwal a., oseke, g. and abdulhamid, h. 2011. biodiesel production from waste soybean oil. der chemicasinica, 2011, 2(2): 286-289. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; 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vol. 15(3):519-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 533 nolte, m. 2007: commercial biodiesel production in south africa: a preliminary economic feasibility study. thesis, chemical engineering department, university of stellenbosch, south africa, pp. 139. ogunkunle, o., oniya, oo. and adebayo, ao. 2017. optimization of solvent extraction of oil from sandbox kernels (huracrepitans l.) by a response surface method. energy and policy research, 4(1):36-43. omotola, ob. 2011. optimisation of biodiesel production via different catalytic and process systems.ph.d thesis, department of chemistry, university of the western cape, pp.246. oniya, oo., adebayo, ao. andogunkunle, o. 2016.optimization of biodiesel production from milk bush (thevetia peruviana) oil using snail shell as catalyst. advances in multidisciplinary and scientific research, 3(1): 1-9. pratas, mj, freitas, s, oliveira, mb, monteiro, sc, lima, as, coutinho, jap. 2011. densities and viscosities of minority fatty acid methyl and ethyl esters present in biodiesel. journal of chemical and engineering data, 56(5): 2175–2180. pratas, mj., freitas, s., oliveira, mb., monteiro, sc., lima, as. and coutinho, jap. 2010. densities and viscosities of fatty acid methyl and ethyl esters. journal of chemical and engineering data, 55(9):3983-3990. pratas, mj, oliveira, mb, pastoriza-gallego, mj, queimada, aj, pineiro, mm, coutinho, jap. 2011. high-pressure biodiesel density: experimental measurements, correlation, and cubic-plusassociation equation of state (cpa eos) modeling. energy fuels, 25:3806–3814. schedemann, a, wallek, t, zeymer, m, maly, m. and gmehling, j.2013. measurement and correlation of biodiesel densities at pressures up to 130 mpa. fuel, 107:483–92. sensoz, s., angin, d, yorgun, s. 2000. influence of particle size on the pyrolysis of rapeseed (brassica napus l.): fuel properties of bio-oil. biomass bioenergy, 19: 271–279. singh, sp, singh, d. 2010. biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: a review. renewable and sustainable energy review, 14(1):200–216. srinivasarp., reddy, bvs., blümmel, m., subbarao, gv., chandraraj, k., sanjana reddy, p. and parthasarathy rao, p. 2010.sweet sorghum as a biofuel feedstock: can there be food-feed-fuel tradeoffs? available at http://www.wgcrop.icidonline.org/sweet%20sorghumdec 09. accessed on 12thfebruary, 2018. tate, re., watts, kc. allen, caw. and wilkie, ki. 2006. the viscosities of three biodiesel fuels at temperatures up to 300 °c. fuel, 85:1010-1015. http://www.wgcrop.icidonline.org/sweet%20sorghumdec http://www.wgcrop.icidonline.org/sweet%20sorghum_dec09 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jekayinfa, et al: prediction of density and viscosity of biodiesel fuel from fatty acid methyl ester (fame) composition. azojete, 15(3):519-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aoadebayo57@lautech.edu.ng 534 tesfa, b., mishra, r., gu, f. and powles, n. 2010. prediction modelfor density and viscosity of bio diesel and their effects on fuel supply system in ci engines.renewable energy, 35 (12):2752­276 0. thakur, is. 2006. environmental biotechnology. basic concept and applications. new delhi; ik international pvt ltd. p. 486. yuan, w., hansen, ac., zhang, q. 2009. predicting the temperature dependent viscosity of biodiesel fuels. fuel, 88:1120-1126. zahan, ka. and kano, m. 2018. biodiesel production from palm oil, its by-products, and mill effluent: a review. energies, 11:2132 zaizi, ds., hamdan, k., dzulkefly, ka., faujan, bha. and laili.cr. 1996. malaysian red palm oil in a surfactant association structure. journal of the american oil chemists’ society, 73(1):153-155 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):92-99 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 92 original research article rollover stability models for three-wheeled vehicle design s. j. ojolo, o. o. ajayi and g. a. asuelinmen* (department of mechanical engineering, university of lagos, lagos, nigeria) *corresponding author’s email address: asuegeo@gmail.com 1.0 introduction the tricycle, called trike or three-wheeler, is a three-wheeled vehicle (twv). in african and asian countries, they are used mainly for commercial purposes (gawade et al., 2004) as shown in figure 1. figure 1: three-wheeled vehicle (twv) the vehicle is safer when compared with commercial motorcycle, and cheaper and able to manoeuvre through heavy traffic in urban environments when compared with four-wheeled vehicles. it is fuel efficient and generates about 33% of green gases per rider when compared with cars and jeeps as a result of weight difference (goodarzi et al., 2015). all this have accentuated its usage. however, there are some safety problems associated with the usage of these twvs. they are more accident prone when compared to four wheeled vehicles. the stakeholders of threearticle information abstract the current commercial three-wheeled vehicles (twvs) in the market are rollover unstable, with adverse effects on life and property. this places limitation on their speed and usage, even though they are fuel efficient, cheap and generate about 33% of green gases per rider when compared with four-wheeled vehicles.this work derived mathematical models for the analysis of the stability of the three-wheeled vehicle (twv). based on these models, the test method for rollover stability was adopted. rollover test was carried out on a twv on nigerian road. the results showed that the vehicle is unstable with respect to rollover stability. the test procedure if adopted and legislated upon, would significantly enhance safety of life and property of the population. moreover, the speed and usage of the vehicle for both private and commercial purposes will be enhanced. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 september, 2019 revised 06 december, 2019 accepted 08 january, 2020 keywords: three-wheeled vehicle rollover stability safety of life and properties test method. mailto:asuegeo@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 92-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 93 wheeled vehicles attested to it that the vehicle can tip-over when negotiating a bend, even though their maximum speed is about 60km/h. this places some limitations on their usage. the development of the twv was based on the old scooter motorcycles without much stability considerations. the upright sitting positions of occupants result in high centre of gravity (mukherjee et al., 2007). considering also that the vehicle is narrow and cannot lean inwards when negotiating a bend to counter the effect of centrifugal force, there are bound to be instability problems (berote et al., 2008; dardaine et al., 2008). consequently, there are challenges posed by the twv especially in the area of safety of life and property, due to this instability. however, huston et al. (1982) and valkenburgh et al. (1982) asserted that it is possible to engineer a twv that can be safe as the four-wheeled ones. therefore, the aim of this study is to generate mathematical models and to investigate the rollover stability of twv, in order to enhance safety of life and property on the roads. 2. materials and methods 2.1 rollover stability model under static condition figure 2 shows the static model for twv on a banked road for the determination of rollover stability factor and height of centre of gravity h. where θ is the angle of inclination of the vehicle to the horizontal plane. the basic assumptions of the model are: load distribution is symmetrical about xaxis when on horizontal plane and the effect of depression of tyre due to load transfer is negligible. figure 2: three-wheeled vehicle on a banked road the governing equations are derived by vertical and horizontal resolution of forces about the plane of motion: fri + ff + fro = mg sin θ (1) rri + rf + rro = mgcos θ (2) ff = l2 wb mgsin θ (3) rf = l2 wb mgcos θ (4) fri + fro = l1 wb mgsinθ (5) rri + rro = l1 wb mgcos θ (6) wherewb is wheelbase andwt is the wheel-track taking moment about centre of gravity: h(fri + ff + fro) = wt 2 (rri − rro) (7) substituting equation (1) and (6) in (7) to eliminate rro: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):92-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 94 h(mg sinθ) = wt 2 (rri − ( − rri + l1 wb mgcos θ ) (8) rearranging equation (8): rri = l1 2wb mgcosθ + h wt mgsinθ (9) similarly, substituting equation (1) and (6) in (7) to eliminate rri: h(mg sin θ) = wt 2 ( − rro + ( − rro + l1 wb mgcos θ ) (10) rearranging equation (23): rro = l1 2wb mgcos θ − h wt mgsinθ (11) if the vehicle does not slide or is blocked from sliding as θ is increased, at limit of rollover, rro will become zero, therefore equation (11) becomes: l1 2wb mgcosθ = h wt mgsin θ (12) or: l1 2wb cos θ = h wt sin θ (13) therefore, the static stability factor (ssf) for the three wheeled vehicle is defined as: tanθ = l1 wb wt 2h (14) the equation is basically the same as that of huston et al., (1982) only that a different methodology of derivation was adopted. rearranging equation (14), where h is height of centre of gravity of the vehicle: h = l1 wb x wte 2tanθ (15) equation (15) can be used to determine the height of centre of gravity h for a twv, using rollover angle, since other parametric values can be accessed or determined. 2.2 rollover stability model under dynamic condition figure 3 shows the model of three wheeled vehicles moving in circle of radius r. the basic assumptions of the model are: that the vehicle is moving in horizontal plane with constant tangential velocity v, the effect of aerodynamic drag force is not significant, load distribution is symmetrical about x-axis and the effect of depression of tyre due to load transfer is negligible. mathematical models were developed from the model to determine dynamic behaviour of twv as it affects the rollover stability, using force and torque equations. figure 3: rollover dynamic stability model http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 92-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 95 the centrifugal force acting at the centre of gravity (c.g) of the vehicle in the direction of y-axis is balanced by lateral frictional resistance from the three wheels (fri + ff + fro ) if there is no slide, while the rear wheels reactions due to the weight of the vehicle is given as l1 wb (mg). therefore, the force equations are: mv2 r = fri + ff + fro (16) rro + rri = l1 wb (mg) (17) taking moment about centre line a-o (along x-axis) to eliminate rf the equation becomes: mv2 r h = wt 2 (rro−rri) (18) substituting equation (17) in (18): mv2 r h = wt 2 l1 wb mg− rriwt (19) at the limit of rollover stability the reaction at inner wheel will be zero (rri = 0), therefore: mv2 r h = wt 2 l1 wb mg (20) where v is now the critical or rollover velocity (vr) and a is the centrifugal acceleration vr 2 r = a = wt 2h l1 wb g (21) rearranging equation (6): a g = wt 2h l1 wb (22) equation (22), which is dimensionless, is the dynamic stability factor. the equation is basically the same as that: static stability factor for twv as seen in equation (14); and valkenburgh et al., (1982), except for the methodology of derivation. the lateral friction coefficient (µ) is in the opposite direction to dynamic stability factor. if the dynamic stability factor is less than the lateral friction coefficient, such that: a g = wt 2h l1 wb < µ (23) then vehicle will rollover since the lateral friction force will stop the vehicle from sliding, which is not what is desirable in vehicle design. it is easier to handle sliding challenges under emergency situation than rollover (huston, et al., 1982). if however, the dynamic stability factor is greater than the lateral friction coefficient, then the vehicle will slide before rollover based on equation (24), which is the desirable option in vehicle design. a g = wt 2h l1 wb > μ (24) the rollover velocity (vr) is defined in equation (25) based on equation (21): vr = (wt h l1 wb gr) 1 2 (25) the other dynamic reactions that may be incorporated into the basic equation (22) are: dynamic reactions due to acceleration and deceleration (huston, et al., 1982) aerodynamic reactions due file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):92-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 96 to drag force (sachdeva and kamiyo, 2015; rajamani, 2012); gyroscopic couple and coriolis force. these reactions put together will change the value of l1 to l1a . since other factors are constant, the final equation becomes: a g = wt 2h l1a wb (26) 2.3 test method for rollover stability determination of twv there are various test methods for rollover stability. the following are some of the standard methods for vehicle testing: the tilting test, constant cycle test, slowly increasing steer (sis), nhtsa (national highway traffic safety administration’s) j-turn and road edge recovery (per). for the purpose of testing the vehicle for stability, tilting test method is adopted based on equations (14) and (15). moreover, it is less involving and easy to implement in a developing country. 0.8 is taken as minimum rollover stability factor or 39° minimum tilting angles (mukherjee et al., 2007). briscoe garage unilag service centre was used for the test with fairly flat horizontal surface. items used for the test were: twv, long jack, protractor with attached pendulum, camera and engineering tape. the vehicle was placed on the floor of the garage with attached protractor and a pendulum at the back of vehicle. the vehicle was jacked up from left or right until it reached the rollover point as shown in the figure 4. all necessary readings were taken. other values that involved loads were obtained through analysis (swearingen, 1962) , since it will be very involving to obtain standard human weights with average centre of gravity. dimensions taken from the vehicles were: wheelbase, wheel-track, horizontal distance from the ground centre of front axle driver back support, horizontal distance from the ground centre of front axle to the passenger back support, vertical distance from the to the top of driver seat and vertical distance from the ground to the top of passenger seat. for the purpose of this work, 72kg average weight for an adult was adopted based on the random survey that was carried out at ogun state property and investment cooperation (opic) estate agbara, nigeria for one hundred adults. shown in figure 4 is the picture of the vehicle during the tilting test. figure 4: tilting of twv to rollover angle http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 92-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 97 3. results and discussion 3.1 rollover tilting test results the rollover dynamic stability factor determination was based on angle of tilt, which is tan θ (equation 14). table 1 shows the values of rollover angles that were obtained through the tilting test that was carried out at briscoe garage unilag service centre with the centre gravity of humans taken into consideration (swearingen, 1962) for a twv on nigerian roads. table 1: rollover stability report item occupants rollover angle actual rollover angle minimum standard variance a b compliant (c) / non-compliant (nc) a b c d e 1 0 390 390 00 c 2 1 = driver 340 390 -50 nc 3 2 = driver + 1 passenger 340 390 -50 nc 4 3 = driver + 2 passengers 300 390 -90 nc 5 4 = driver + 3 passengers 280 390 -110 nc figure 5 shows the twv rollover stability simulations. figure 5: rollover stability angle versus occupants from table 1 and figure 5, it can be deduced that the vehicle itself without any occupant is rollover stable. with the driver alone, the vehicle became unstable. the reason is quite obvious. the weight of the driver shifted more load to the front wheel than the rear. this reduced the value of l1 and also increased the overall height of c.g. since centre c.g. of vehicle is lower than that of the driver. the two factors combined together brought down the value of rollover stability below the minimum required based on equation (14). the result is in line with that of literature (mukherjee et al., 2007; karanam et al., 2012). however, with the first passenger at rear seat, more loads were transferred to the rear wheels than the front wheel because of the position of c. g. of the vehicle (karanam et al., 2012). one would have expected rollover stability to increase but the height of c. g. of the passenger nullified the effect of increase in stability. moreover, with more passengers, the effect of the height of c. g. of passengers took over since file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ojolo et al: rollover stability models for three-wheeled vehicle design. azojete,16(1):92-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 98 there were no more backward movements. this made the vehicle to become more and more rollover unstable. therefore, the non-compliance of the vehicle, in terms of rollover stability is mainly due to the high c. g. of occupants. it can be deduced from the variances that the vehicle itself is rollover stable and it will suffer rollover instability with one occupant and above. from equations (14) and (22) it can be seen that the factors that affect rollover stability are: wheel-track (wt), horizontal distance from centre of front wheel to the c. g. of vehicle (l1 ), height of c. g. (h) and wheelbase (wb). deceleration will transfer more load to the front wheel thereby increasing rollover instability and should be taken into account in vehicle design stability. outward cambering of rear wheels will increase rollover stability since wheel-tract is increased (ihueze and ebisike, 2018). in case of the redesign of the vehicle, the effect cambering of the wheels should be taken into consideration, including suspension, and roll resistance. there are other factors such as steering compliance, gyroscopic couple due to road bumps, coriolis force due to curvilinear motion, etc. that could impact negatively on lateral stability. all these factors should be taken into consideration in a major modification of the vehicle at the initial stage of its design to be rollover stability compliant based on equation (26), so that newer models of the vehicle will be rollover stable. 4. conclusions this study came up with mathematical models and tilting test method for the determination of the rollover stability of twvs and for the design and regulation of the vehicle in developing countries, in order to enhance safety of life and property. the test method was used in the determination of the rollover stability of one of the commonest twv on the nigerian road. the vehicle was found to be rollover unstable with one occupant and above. however, this instability could be minimised on the current twv by increase in the wheel-track of the vehicle relatively to wheelbase and lowering seat heights of the occupants. the ultimate solution lies in redesigning of the vehicle to take care of the problem. the twst currently being used by developing countries is not too safe in terms of rollover stability due basically to the high centre of gravity of occupants. therefore, the following recommendations are made to ensure its rollover stability: that the rollover stability factor should not be less than 0.8 which amounts to 390 rollover angle, taken into consideration all the loadings through redesign and modifications. developing countries should at least adopt the tilting method of vehicle testing for the design, regulation and importation of twv. references berote, j., ivan pa., darling, j., edge, k. and plummer, a. 2008. the dynamics of a three-wheeled narrow-track tilting vehicle. fisita world automotive congress 2008, the future of automobiles and mobility, munich, germany, 14–19 september 2008, f2008-sc-032., pp. 1 – 9. dardaine, j., rodier, l. and venaille, v. 2008. preliminary study of a three-wheel tandem powered by a pen fuel cell. fisita world automotive congress 2008, the future of automobiles and mobility, munich, germany, 14–19 september 2008, f2008-sc-039., pp. 1 – 5. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 92-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asuegeo@gmail.com 99 gawade, tr., mukherjee, s. and mohan, d. 2005. six-degree-of-freedom three-wheeled-vehicle model validation. in: proceedings of the instituttion of mechanical engineers , part d: journal of automotive engineering, 219(4): 487-498. goodarzi, a., soltani, a., shojaeefard, mh. and khajepour, a. 2015. an integrated vehicle dynamic control strategy for three-wheeled vehicles. in: proceedings of the instituttion of mechanical engineers, part k: journal of muiti-body dynamics, 229(3): 225-244. huston, jc., graves, bj. and johnson, db. 1982. three wheeeeled vehicle dynamics. society of automotive engineers, 820139, 45-55. ihueze, cc. and ebisike, ps. 2018. dynamic analysis of instability in three-wheeler automobile vehicle. archives of current research international, 13(3): 1-10. karanam, vm., chatterjee, a. and ghosal, a. 2012. procedural aspects of modelling the dynamics of a three wheeled vehicle using adams-car. india institute of science, bangalore [online]. available at: http://epints.iisc.ernet.in/40423/ (accessed: november 2019)., pp. 1 – 22. mukherjee, s., mohan, d. and gawade, tr. 2007. three-wheeled scotter taxi: a safety analysis. sadhand journal, 32: 459-478. rajamani, r. 2012. vehicle dynamics and control. new york: springer science + business media., pp. 89. sachdeva, rc. and kamiyo, o. 2015. fundamentals of engineering heat and mass transfer. new delhi: new age international publishers., pp. 291-292. swearingen, jj. 1962. determination of centre of gravity of man. oklahoma: federal aviation agency., pp. 11-12. valkenburgh, pg., klein, rh. and kanianthra, j. 1982. three-wheel passenger vehicle stability and handling. society of automotive engineers, 820140, 59-81 http://epints.iisc.ernet.in/40423 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):859-866 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 859 original research article physico-chemical properties of yellow oleander (thevetia peruviana) and their effects on the qualities of biodiesel a.r. nasirudeen1, d. lasisi1, l.a. balogun1, a.j. eebo1, f.o. ogunsola1, a.j. adesope1, s.o. ogundare1 and f.a. ola2 ( 1department of agricultural and bio-environmental engineering, oyo state college of agriculture and technology, igboora, nigeria 2department of agricultural engineering, ladoke akintola university of technology, oyo state, nigeria) * corresponding author’s email address: jibolarufai@gmail.com 1.0 introduction due to rapid population growth and economic development, the worldwide energy demand is constantly increasing. the energy demand is fulfilled mainly from the conventional energy resources like coal, petroleum and natural gas. but, the petroleum reserves concentrated in certain regions of the world are fast depleting day by day and at the current usage rate, these sources will soon be exhausted (barua et al., 2014; basumatary, 2013; khan et al., 2009; vyas et al., 2010).the search for alternative sources of fuel to supplement or replace fossil fuels so as to cater for their increasing demands, uncertain availability and to reduce the related pollution problems of their combustion, has drawn our attention towards fuels of biological origin (encinar et al., 1999), which provide regenerable feedstocks. the most common fuel being article information abstract this study investigated the effects of physico-chemical properties of yellow oleander (thevetia peruviana) on quality of biodiesel. the seeds were processed and extraction of oil was carried out using solvent extraction method. biodiesel was produced from the extracted oil using trans esterification process. physical and chemical properties of thevetia peruviana biodiesel were determined using the astm standard test procedures. results showed that the biodiesel contained little sulphur (3.0 mg/kg) and exhibited a high cetane number of 55 that exceeded the standard limit of 47 and 51 prescribed for en 14214 and en 590 respectively, which is a good indication of fuel’s ignition and combustion quality. kinematic viscosity of the biodiesel at 40°c was 4.81 mm2/s, which was within the range specified by en 14214. the density at 15°c was found to be 0.89g/cm3 which was well within the range specified by en 14214. 0.16 mg/g of acid level was obtained for the bio-diesel, which conformed to the standard set by calorific value of the biodiesel produced from yellow oleander seed oil was obtained as 40.42 kj/g which indicated good fuel properties such as density, ignition quality, viscosity, cetane number, heating value and flash point. carbon residue of the biodiesel was 0.14 mass %. quality of the biodiesel produced conform to biodiesel and petroleum diesel standards of en14214 and en590 respectively. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 december, 2018 revised 30 march, 2019 accepted 05 april, 2019 keywords: biodiesel thevetia peruviana energy physical chemical properties. http://www.azojete.com.ng nasirudeenet al: physico-chemical properties of yellow oleander (thevetia peruviana) and their effects on the qualities of biodiesel. azojete, 15(4):859-866. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 860 developed and used at present is the biodiesel, which is fatty acid methyl esters (fames) of seed oils and fats. biodiesel has been chosen as one of the interesting alternative fuels and has been receiving a lot of attention throughout the world as it is a renewable, biodegradable, non-toxic and environment-friendly fuel (basumatary and deka, 2012; basumatary, 2013; basumatary et al., 2013). biodiesel, an alternative and renewable fuel for diesel engines, consists of mono-alkyl esters of long chain fatty acids, more commonly methyl esters and is typically made from nontoxic, biological resources such as edible and non-edible vegetable oils, animal fats, waste cooking oils and oil from algae by transesterification with methanol (basumatary and deka, 2012; basumatary, 2013; basumatary et al., 2013; takase et al., 2014). biodiesel produces lower emissions, possesses high flash point, better lubrication and high cetane number and has very close physical and chemical characteristics to those of conventional diesel fuel allowing its use either on its own (pure biodiesel, b100) or mixed with petroleum based diesel fuel (preferred ratio 5– 20%, b5–b20) with very few technical adjustments or no modification (basumatary, 2013; basumatary et al., 2014; biswas et al., 2010; fazal et al., 2011). a myriad of edible and non-edible oils could be used as bio-diesel feed stocks, but traditionally, biodiesel has been produced from edible oils due to their low free fatty acids. however, their use has elevated some issues such as food versus fuel and many other problems that have negatively affected their economic viability. therefore, exploration of non-edible oils may significantly reduce the cost of biodiesel especially in poor countries which can barely afford the high cost of edible oils. one of these non-edible feed stocks is theveta peruviana (yellow oleander) oil (basumatary, 2013). yellow oleander commonly known as milk bush, shown in figure 1, is an evergreen, dicotyledonous shrub which is believed to have originated from the forest of tropical america, precisely from central america, but has naturalized in the tropical and subtropical regions of the world ((olaoye, 2000).)it is abundantly available in nigeria, where it is mainly grown as an ornamental plant. the seed of the plant contains about 60% oil and the defatted seed cake is about 37% protein (olaoye, 2000). figure 1: thevetia peruviana fruit the importance of thevetia peruviana has revolved around the clinical, toxicological and pharmacological aspects. probably this is the reason for limited research on oil and protein of thevetia that would have promoted its industrial and domestic potentials. though literature is available on thevetia plant and its soil characteristics (ibiyemi et al., 2002), a few studies are http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 859-866. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 861 available on its physicochemical properties. therefore, this study aims at investigating the effect of physical and chemical properties of thevetia peruviana on quality of biodiesel produced from its oil. 2. materials and methods 2.1 collection and preparation of thevetia peruviana seeds the ripe and matured thevetia peruviana was harvested and collected from thevetia peruviana plants in iseyin metropolis, iseyin local government area of oyo state, nigeria. the succulent green outermost layer of the fresh fruits was removed manually using a knife to peel off the outer layer from the seed and the seeds separated from the peels manually. the peeled seeds were then decorticated manually using a stone to impact force on the seed in order to open the seed shell and free the seed kernels from its compartments. the mixture of the contents was winnowed to separate the seed kernels from the empty shells. the cleaned seed kernels collected were then sun dried for about 7 days in order to reduce its moisture content to about 10-11% wet basis required for oil bearing seed processing. the dried seed kernels were pound in a mortar and pestle into paste (cake) in order to weaken or rupture the kernel walls to facilitate oil extraction using solvent extraction method. the grind seed kernel paste was then packed in a plastic container for further processing. for oil extraction, 250 g of thevetia peruviana paste was placed on the cotton wool inside the thimble and 300 ml of n-hexane was poured into the round bottom flask and processed. the heating chamber was switched on and set to the predetermined heating temperature and the heating process allowed for the required predetermine heating time. the vapour condensed and accumulated in the thimble and gets siphoned into the distillation flask. after the heating process, the thimble was carefully removed to collect the mixture of both n-hexane and oil extracted. the mixture collected was then separated using rotary evaporating device. the procedure was repeated up to 14 more times with the same quantities of thevetia peruviana paste and n-hexane to obtain enough oil quantity for the biodiesel production. the n-hexane removed was stored and reused for subsequent extraction operation, while the oil collected was stored for biodiesel production. oil yield was determined using equation (1). %oil yield = weight of oil obtained (g) weight of sample (g) × 100 (1) 2.2 conversion of extracted oil to biodiesel free fatty acid of the oil was firstly determined in order to use the value in biodiesel production using trans-esterification method. methanol and sodium hydroxide were mixed inside the conical flask at a ratio of 1:10, that is 1% of methoxide to 10% of oil and the sodium hydroxide was allowed to completely dissolve in the methanol and heated to 40oc on the hot plate. one litre of the oil extracted was taken into flat bottom flask and heated to the 50oc temperature on the hot plate. the warmed methoxide was poured into the oil slowly, heated and stirred vigorously using magnetic stirrer for the required time and temperature. the mixture was poured into the container and allowed to cool to 40ºc temperature (canakci and gerpen, 2001). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nasirudeenet al: physico-chemical properties of yellow oleander (thevetia peruviana) and their effects on the qualities of biodiesel. azojete, 15(4):859-866. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 862 2.3 biodiesel separation, washing and drying processes the mixture obtained after the transesterification process was transferred into a separating funnel which was mounted on a retort stand to separate biodiesel from glycerol. the lower layer (glycerol and soap) was collected from the bottom of the separating funnel. after the separation, the mono methyl ester (biodiesels) separated still contain traces of sodium hydroxide, methanol, and glycerol. this was established by seeing traces of foams and other particles in the biodiesel indicating that it was not 100 % pure. warm water was then used to wash the biodiesel to remove any excess glycerol and soap that remain in the funnel. this was done by mixing the hot water with the biodiesel several times and then separating the water from the biodiesel until the clear water was seen below the biodiesel in the separating funnel. then, the biodiesel was dried by placing it on a hot plate where excess water was removed at 110oc. the quantity of biodiesel collected was measured and recorded. the procedures were repeated by varying the required molar ratio of thevetia peruviana oil to methanol (12:1, 10:1 and 8:1); heating time (55, 60 and 65 minutes) and heating temperatures (55, 60 and 65 °c) (canakci and gerpen, 2001). 2.4 physicochemical properties of thevetia peruviana oil and biodiesel the physical and chemical properties of thevetia peruviana oil and biodiesel were determined using the astm standard test procedures. the fuel properties of biodiesel such as ignition quality, viscosity, cetane number, heating value, flash point and carbon residue were compared with commercially available diesel. moisture determination, ffa content, density, ignition quality, viscosity, cetane number, heating value, flash point, carbon residue of biodiesel were determined in the laboratory and compared with both biodiesel and petroleum diesel standards. 2.4.1 moisture determination of seed kernel about 2 g of the thevetia peruviana seed kernel was weighed into a previously weighed crucible. the crucible plus sample was then transferred into oven set at 100°c to dry to a constant weight for 24 hours, the crucible plus sample were removed from the oven and transferred into desiccators to cool for 10 minutes and weighed. the moisture content (d.b.) was evaluated from equation (2). % moisture content (d.b.) = w₂−w₃ w₃−w₁ x 100 (2) where: w1=weight of empty crucible, (g) w2 =weight of sample plus crucible before drying, (g) w3 =weight of crucible plus oven dried sample, (g) 2.4.2 flame test of oil the nature of the flame of burning oil sample was determined by heating the oil in a stainless saucer, and placing a clean white ceramic plate above the oil sample and the ceramic plate was removed after a period of about 10mins and the presence of soothe was observed using astm standard d93. 2.4.3 ph of the oil ph of the thevetia peruviana oil was determined using soil and water analyzer using astm standard d6751. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 859-866. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 863 2.4.4 ash content of oil about 2.0 g of the thevetia peruviana oil was weighed into a porcelain crucible. it was then transferred into a muffle furnace set at 550ºc and was left 4 hours for it to turn to white ash. the crucible and content were then cooled in the air to about 100°c, then at room temperature in desiccators and was weighed using astm standard d6751. 2.4.5 density of biodiesel density of the biodiesel was determined using a density bottle at 25oc. this was determined by weighing the sample and comparing it with its volume. the ratio of the mass of the fuel to its volume was then determined by equation (3) using astm standard d93. ρ= m v (3) where: ρ= density (kg/m3) m = mass of the sample (kg) v = volume of the sample (m3). 2.4.6 ignition quality of biodiesel the cetane number (cn) of the fuel is one such important parameter which is responsible for the delay period. ignition quality tester was used to determine the cetane number using astm standard d445. 2.4.7 viscosity of biodiesel sample dispersed with concentration ranging from 0.4 to 2.0% (w/v) are prepared with distilled water at room temperature. the dispersion was hydrated for 2 h at room temperature under continuous stirring (monostir magnetic stirrer). the viscosity of the hydrated dispersion was measured at 25°c using the nv sensor of the haake – rotovisco viscometer (haake – rotovisco gmbh germany) using astm standard d445. 2.4.8 the congealing temperature of oil sample the congealing temperature was determined by putting 10ml of the oil sample in a 100ml beaker and inserting a laboratory thermometer into the oil and putting it in a freezer. the oil was closely monitored as the oil sample starts getting jelly, and the temperature at which gelation took place within the oil was also noted. 2.4.9 flash-point of biodiesel flash point measures the lowest temperature at which application of the test flame causes the vapor above the sample to ignite. it is used to assess the overall flammability hazard of a material. specifically, flash point is used in safety regulations to define "flammable" and "combustible" materials. it can be determined using pensky-martens closed cup tester. higher values indicate materials that are less likely to ignite accidentally. d 975 requires a minimum of 52°c. the biodiesels would be considered significantly safer with temperatures between 128°c and 167°c using astm standard d93. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nasirudeenet al: physico-chemical properties of yellow oleander (thevetia peruviana) and their effects on the qualities of biodiesel. azojete, 15(4):859-866. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 864 2.4.10 calorific value of biodiesel the calorific value measures the available energy in a fuel and a critical property of fuel intended for use in weight-limited vehicles. this was determined using bomb calorimeter using astm standard d445. 3. results and discussion 3.1 physicochemical properties of yellow oleander oil and biodiesel the analysis of the physicochemical properties of the yellow oleander oil extracted is as presented in table 1. the table shows that the oil extracted from yellow oleander kernel was found to be suitable for biodiesel production as its free fatty acid value was found to be 1.21 mg koh/g. oil yield was found to be 62.44% which is within the range reported for the seed. iodine value of thevetia peruviana oil (68.2 g i2 /100 g) was also far below the maximum limit of 120 prescribed in en 14214. the acid value of thevetia peruviana was found to be 0.16 mg of koh/g. ph value was found to be 6.8 neutral which means the oil is save for biodiesel production as stated by adebayo et al. (2011). the oil was congealed at 4c and was also frozen. table 1: some physicochemical properties of yellow oleander oil properties unit yellow oleander oil free fatty acid mg koh/g 1.21 iodine value i2/100g 68.2 acid value mg/g 0.16 moisture content wt % 1.86 oil yield wt % 62.44 specific gravity 0-89 congealing temperature c 4.0 freezing temperature c 1.0 ph value 6.8 table 2 shows the analysis of the physicochemical properties of the biodiesel produced from the thevetia peruviana oil extracted.the biodiesel contain little sulphur and has exhibited a higher cetane number of 55 that exceeds the minimum limits of 47 and 51 prescribed in en 14214 and en 590 respectively, which is a good indication of fuel’s ignition and combustion quality. the kinematic viscosity of the biodiesel at 40°c was 4.81mm2/s. this is within the range specified by en 14214. the density at 15°c was found to be 0.89g/cm3 which is well within the range specified by en 14214. it is prescribed in astm d6751 and en 14214 that the maximum limit of acid value for biodiesel should not exceed 0.50 mg of koh/g. the european standard en 14213 for use of biodiesel as heating oil prescribes a minimum heat of combustion of 35.0 kj/g. the calorific value of the biodiesel obtained was 40.42kj/g. biodiesel with petroleum diesel standards from yellow oleander seed oil was found to be 40.42 kj/g indicating good fuel properties. the carbon residue of the biodiesel was 0.14 mass%. the results also conform to the one gotten by (adebayo et al., 2011). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 859-866. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 865 table 2: comparison of physicochemical properties of yellow oleander properties unit biodiesel standard petroleum diesel yellow oleander biodiesel specification en 14214 en 590 ns density 15 °c (g/cm3) 0.86 0.90 0.82 0.845 0.89 viscosity (@ 40°c) mm2/s 3.5 5.0 2.0 4.5 4.81 flash point °c 120 min 55 min 142 sulphur mg/kg 10 max 350 max 3.0 carbon residue % mass 0.3 max 0.3 max 0.14 cetane number calorific value biodiesel yield kj/g 51 min 35 51 min 55 40.42 83.17 4. conclusion this study has shown that biodiesel produced from thevetia peruviana oil is a potential replacement for fossil diesel while the production and effective usage of biodiesel will help to reduce the cost of protecting the atmosphere from the hazards in using fossil diesel and hence will boost the economy of the country. the quality of the biodiesel produced conformed to standards set for biodiesel standard en14214 and petroleum diesel standard en590. references adebayo, gb., ameen, om. and abass, lt. 2011. physico-chemical properties of biodiesel produced from jatropha curcas oil and fossil diesel. journal of microbiology and biotechnology research, 13: 12 16. barua, p., dutta, k., basumatary, s., deka, dc., deka, dc. 2014. seed oils from non-conventional sources in north-east india: potential feedstock for production of biodiesel. natural product research, 28(8), 577–580. basumatary, s. 2013. non-conventional seed oils as potential feedstocks for future biodiesel industries: a brief review, res. j. chem. sci., 3(5), 99–103. basumatary, s. 2013. transesterification with heterogeneous catalyst in production of biodiesel: a review, j. chem. pharm. res., 5(1), 1–7. basumatary, s. 2013.non-edible oils of assam as potential feedstocks for biodiesel production: a review, j. chem. bio. phy. sci., 3(1), 551–558. basumatary, s. 2013. pithecellobium monadelphum kosterm: a non-edible feedstock for biodiesel production, der chemica sinica, 4(3), 150–155. basumatary, s. 2013. heterogeneous catalyst derived from natural resources for biodiesel production: a review, res. j. chem. sci., 3(6), 95–101. basumatary, s., barua, p., deka, dc. 2013. identification of chemical composition of biodiesel from tabernaemontana divaricata seed oil, j. chem. pharm. res., 5(1), 172–179. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nasirudeenet al: physico-chemical properties of yellow oleander (thevetia peruviana) and their effects on the qualities of biodiesel. azojete, 15(4):859-866. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibolarufai@gmail.com 866 basumatary, s., barua, p., deka, dc. 2014. gmelina arborea and tabernaemontanadivaricata seed oils as non-edible feedstocks for biodiesel production, int. j. chem. tech. res., 6(2),1440– 1445. basumatary, s., deka, dc. 2012. identification of fatty acid methyl esters in biodiesel from pithecellobium monadelphum seed oil, der chemica sinica, 3(6), 1384–1393. basumatary, s., deka, d.c., 2012. composition of biodiesel fromgmelina arborea seed oil, adv. appl. sci. res., 3(5), 2745–2753. biswas, pk., pohit, s., kumar, r. 2010. biodiesel from jatropha: can india meet the 20% blending target? energy policy, 38: 1477–1484. canakci , m. and jv. gerpen, 2001. biodiesel production from oils and fats with high free fatty acids. transactions of the asae, 44(6): 1429-1436. encinar, jm., gonzalez jf., sabio e., and ramiro mj. 1999. preparation and properties of biodiesel from cyanaracardunculus l.oil. ind.eng.chem.res.,38(8),2927-2931. fazal, ma., haseeb, asma., masjuki, hh. 2011. biodiesel feasibility study: an evaluation of material compatibility; performance; emission and engine durability, renew. sustain. energ. rev., 15, 1314–1324. ibiyemi, sa., akinremi, oo. and bako, ss., 2002. variation in oil composition of thevetia peruviana juss fruit seeds. j appl. sci. environ management 6 (2): 61-65. khan, sa., hussain, mz., prasad, s., banerjee, uc. 2009. prospects of biodiesel production from microalgae in india, renew. sustain. energ. rev., 13, 2361–2372. marchenko, ap. and semenov, vg., 2001. alternative biofuel from rape oil derivative. chem. technol. fuels oils, 37(3), 183-185. olaoye, jo. 2000. some physical properties of castor oil relevant to design of processing equipment, journal of agricultural engineering research, 77: 113 – 118. oyeyemi, sm., okeniyi, so. and olaniyan, io. 2007. the effect of physical soil properties on the prospect of castor seed production. journal of engineering and applied sciences, 2(1): 86-89. takase, m., feng, w., wang, w., gu, x., zhu, y., li, t., yang, l., wu, x. 2014. silybum marianum oil as a new potential non-edible feedstock for biodiesel: a comparison of its production using conventional and ultrasonic assisted method, fuel process. technol., 123, 19–26. vyas, ap., verma, jl., subrahmanyam, n. (2010). a review on fame production processes, fuel, 89, 1–9. wu, jh. shi, s., xue, y., kakuda, d., wang, y., jiang, x., ye, y.and li, j. 2011, essential oil extracted from peach (prunus persica) kernel and its physicochemical and antioxidant properties, lwt food science and technology, 44: 2032-2039. weibel, ro. 1948. the castor oil plant in the united states. economy botany 2(3): 273-283. accessed from jstor. weimer, hj. and altes, fwk 1989. small scale processing oil fruits and oil seeds eschborn, germany: gate/gtz zarnowski, ry. 2004. expedient soxhlet extraction of resorcinolic lipids from wheat grains. journal of food composition and analysis, 17: 649–663 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):898-910 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 898 original research article design and implementation of a computer-based power management system o. omenogor* and a. l. imoize (department of electrical and electronics engineering, university of lagos, akoka lagos, nigeria) * corresponding author’s email address: ogeomenogor@gmail.com 1.0 introduction our contemporary world is undergoing technological revolution which has prompted engineers to move with the recent trends in technology in order to meet with the current standards and specifications. toward this end, efforts have been put in place to set up systems that enhance effective power supply management in order to minimize the up-scaling cost of generation, article information abstract power supply is of great importance and interrupting it may impact negatively on our daily activities. with the application of power management systems, the vulnerability of energy is effectively managed, thereby ensuring a smooth flow of energy requirements for domestic and industrial operations. this also reconciles efficiency, safety, economic, health and environmental conditions. therefore, this paper presents the design, construction and implementation of a computer-based power management system for household applications. it enables the user to transfer management of power supply to appliances in the house to a real time monitoring, switching and control system. this is achieved by programming an atmega 328 microcontroller, which coordinates the overall activities of the system from a central control unit through an esp8266 module. this wireless fidelity (wi-fi) module is where internally processed result is being sent to the central control unit. system design shows that the interoperability of the power management system is hinged upon a wi-fi as the signals are sent as packets in ascii format from the point harnessed by the gui software. the design was tested for performance and results show that when the power up icon is clicked on the personal computer, the bulb glows and when the power down button is clicked, the bulb goes off. also, the measured and actual current of the transformer used in the design, justifies the efficiency of the power management system. the system design was seen to be more scalable and flexible when compared with existing home automation systems, and the hardware interface module can be handled by one server when there is wi-fi coverage. in conclusion, it is seen that power can be effectively managed from the personal computer, thereby reducing the overall power consumption in the facility. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 december, 2018 revised 18 march, 2019 accepted 20 march, 2019 keywords: power management system wireless fidelity (wi-fi) atmega 328 esp8266 module computer technology. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 898-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 899 transmission, distribution and supply. power supply is indispensable in our daily activities, and its absence or inordinate interruption could result in a catastrophic process leading to systems collapse. the unstable energy costs, and the prevailing increase in environmental awareness and more severe legislations are some factors influencing the global drive for enhanced energy management. therefore, power management system (pms) is envisioned as the candidate technology to curb frequent fluctuations and prevalent disturbances in the operations of a typical power system, often resulting in total blackouts. the deployment of a suitable pms could potentially enhance operational safety, regulate the cost of energy, and mitigates both health and environmental impacts. the objective of the proposed home automation system is to assist handicapped and aged people in controlling home appliances without any encumbrances, provide more safety control on the switches with low voltage methods of activation, user friendly interface and ease of operation. 1.1 related work home automation system was presented as multiple agent systems (mas). basically, home automation includes appliances and devices at home that are managed and maintained for home management (conte et al., 2003). similarly, a system in which task are performed by the appliances via the use of speech thereby establishing remote communication was presented (potamitis et al., 2003). the method was targeted at the performance of real-life operations at home by physically challenged people where the speech is used as a medium for controlling appliances. in order to take suitable approach by speech recognition, the scheme of voice separation was adopted. the use of short message service (sms) in automating devices and global system for mobile technologies was reported (pan, 2003; malik et al., 2009). in another study, an automation system for homes in which a wireless internet-based connectivity was adopted for multifunctional devices was recommended (alkar et al., 2005). it was observed that factors such as power failure and range pose a challenge despite the fact that flexible web-based solution at low cost were achieved. in addition, the design and implementation of an sms based control monitoring systems (stanescu et al., 2006), has three modules comprising of processing unit which is the microcontroller, sensing unit for monitoring the complex applications, and a communication module that uses cell phone via serial port rs232 or gprs modem. consequently, problems arising from home automation system implementation ranges from lack of solidity, affinity issue, and acceptability among the aged and physically challenged people was investigated (delgado et al., 2006), thereby devising possible solutions through various network technologies. furthermore, a general packet radio service (gprs) was created, the status of alerts and home appliances are controlled and monitored by wireless sensor network which uses the medium of instant messaging to keep occupants abreast of possible dangers (she jin et al., 2008). monitoring remotely via mobile phone in which spoken commands are used was proposed (malik, 2009). after generating the spoken words, it is sent in form of sms to the microcontroller and control system which takes decision on a dedicated task. the remote control of appliances and supplying security when the end user is absent was reported (jawarkar, 2008). the system is based on sms and applies wireless technology to restructure the standard of living thereby leading to the flexibility and cost effectiveness of the system. more so, gsm technology is adopted by the system thus, providing global access to the system for security and automated file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omenogor and imoize: design and implementation of a computer-based power management system. azojete, 15(4):898-910 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 900 control of appliances. this in turn presents a better result to the challenges encountered daily by homeowners. more so, a real-time electricity consumption data is provided to residents via a virtual or physical in-home monitor (so called “energy dashboard”). the energy consumed at home is ardently managed using the data provided (grunwald, 2009; barnes et al., 2017). basically, research on energy monitoring till date has placed emphasis on the preoperative design and workflow in comparison with post-design monitoring. key energy monitoring systems have been proposed which introduces a real time power monitoring tool for designing feasible buildings which perform adequately through optimization of the hvac system (brychta, 2017). in another study, a comprehensive work describing how home appliance can be managed using mobile phone was designed (ahmad et al., 2011). to manage the appliance, a command in form of sms is sent by the user from his/her mobile phone to a computer connected to the appliance. upon reception of the message, the command is sent by the computer to the microcontroller for controlling the appliance adequately. here, distance is not a barrier as people can use this system to work in their homes from a very far distance. also, a prototype power management system was designed and developed for homes which will enhance energy behavior for achieving energy consumption efficiency. the home power management system developed under test produced outputs which exhibit good correlation with the input supply (apeh, 2013). conclusively, this paper seeks to establish a suitable design principle, construct a functional power management system (pms), develop a desktop app with communication capabilities for pms and control. 2.0 materials and method 2.1 materials to achieve the design of this system, many components were assembled. each component has a unique function different from the others and highly dependent on others. it is difficult to get a single component that can achieve the design on its own and no component function is trivial. components used include: atmega328 microcontroller, transistors: c1815, tip 120, resistors: 200ω, 2.2kω, relay: 30a rated, electrical connectors, copper clad, etchant, soldering lead, drilling machine, correction ink, esp8266, ic socket, transformer and capacitors. 2.1.1 esp8266: the esp8266 wi-fi module is a self-contained system on chip (soc) with integrated transmission control protocol/internet protocol (tcp/ip) stack that can give any microcontroller access to wi-fi network. the esp8266 is capable of either hosting an application or offloading all wi-fi networking functions from another application processor (imoize et al., 2019). each esp8266 module comes pre-programmed with an attention (at) command set firmware. it can simply be hooked up to arduino device and get about as much wi-fi-ability as a wi-fi shield offers. the esp8266 module is an extremely cost-effective board with a huge, and ever-growing open source community support. block diagram description of the esp8266 is as shown in figure 1 (adetona et al., 2018a). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 898-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 901 antenna figure 1: description of the esp8266 module 2.1.2 microcontroller: the microcontroller is the central processing unit which coordinates every process that occurs in the system ranging from data processing to arithmetic and logical processes while being able to transmit and receive signals through its universal asynchronous receiver/transmitter (uart). a uart is the channel with which programming that controls a computer's interface to its attached serial devices. atmega 328 microcontroller, a 28-pin wide dip (dual-in-line) package chip was used. this chip was selected because it is robust and the dip package interfaces for prototyping. this same microcontroller is available in a surface mount package. 2.2 method parameters ranging from functionality, economical value and accessibility were important factors that were put into consideration during the design of this work computer-based power management system. the design is achieved through process automation with the aid of computer program which is based on .net microsoft software, which gives an edge for a centralized control while utility is monitored in real time. the interoperability communication parameter is wireless fidelity (wi-fi) based while every access point communicates with the central control unit. this approach has the edge of real time utility tracking while cost can be pre-estimated based on prior utility timeline range. 2.2.1 circuit design the circuit design is clearly illustrated in figure 2 and each box plays an important role in ensuring wireless communication is achieved between the power management system and the personal computer. i) power supply: a direct current source that powers the microcontroller and other chips and actuators being a regulated full bridge rectified 5 volts supply. ii) microcontroller: the central processor of the powerline transmission architecture with which pulse width modulated data of a defined frequency is relayed from a transmission point to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omenogor and imoize: design and implementation of a computer-based power management system. azojete, 15(4):898-910 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 902 subscription end points in a coordinated sequence. hence, the analysis of adc (analog to digital conversion) and io (input/output) signals which are being transmitted to the appropriate quarters through logical addressing protocols can be encrypted against adulteration via the microcontroller. iii) wi-fi module: this enables efficient wireless transmission of data from the computer system and other close ranged devices in the absence of lan cable to the powerline architecture. iv) subscribers’ microcontroller unit: by virtue of the pulse width modulation of signals at defined frequency, the signals are captured at different endpoints by this designated microcontroller units. v) restricted lines: on the basis of transmission of signals through powerline basically through active electric lines cables, utmost precaution approach is essential, only a chosen line is designated and other lines are referred to as restricted. vi) normal lines: this the chosen line of communication through which pulse width modulated signals at designated frequency are sent from one end to subscription points. vii) transducers: these are component parts with which signals received are relayed into human logical perspective through controls. figure 2: block diagram of the power management system the rectifier circuit peak inverse voltage (piv) can be defined as the maximum voltage across the rectifying diode in the reverse direction. for the full wave rectifier employed in this design, the piv rating of the diode should be at least 1.5 to 3 times the peak voltage . for this design, 1.5 was used as the multiplier factor as given in equation (1). (1) central power control unit admin panel wi-fi module microcontroller wi-fi modem power supply subscriber’s microcontroller unit transducers restricted line normal line http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 898-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 903 to get the output voltage, equations (2) and (3) are applied. (2) (3) where is the average or dc output voltage, is the peak value of half wave, is the root mean square value of output voltage vdc = 2 × 31.82 π = 20.25v recall, = the current rating of the rectifier unit can be mathematically calculated using equation (4). (4) = since the maximum secondary current is 998ma, a full wave bridge was used. therefore, in5399 diodes were used in accomplishing the design. 2.3 operation of the computer-based power management system the primary aim of the system is automation and control of power system. the control is actualized through a microcontroller, which coordinates the overall activities of the system ranging from detection of power availability to interoperability communication from central control unit through a wi-fi module (esp8266) with which internal operation process results are being sent across to the central control unit (adetona et al., 2018b). the central processing unit of the system is based on microcontroller which by default operates on dc (direct current). this is actualized by rectification of alternating current (ac) with bridge rectification layout of diodes to achieve a full wave rectification which is filtered through 1000μf to ostracize ripples off the supply. a 9-0-9 transformer was utilized to step down the voltage signal for effective operation in relation to the voltage regulator supply (7805). the terminals of the transformer are being factored as a result of voltage drop in the mains which has great effect on the supplied induced current at the secondary side of the transformer. the voltage regulator ensures that the voltage supplied to the microcontroller does not exceed 5v in order to avoid the system being affected. to further filter noise, a 0.1μf capacitor is introduced between vcc and the ground terminal of the voltage regulator. in order to ascertain that the abrupt reset of the microcontroller does not file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omenogor and imoize: design and implementation of a computer-based power management system. azojete, 15(4):898-910 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 904 occur, a limiting resistor is introduced between the master clear (mclr) and the positive terminal of the voltage supply. in order to actualize the interoperability access of the system, a wi-fi module is used which communicates via uart protocol. the wi-fi module is capable of being an access point (ap) while it can also access wi-fi stations dependent on its operability configuration prior to being mounted on the main board. this configuration is based on at commands thereby getting a unique service set identifier (ssid), internet protocol (ip), operability mode, channel configuration etc. the baud rate with respect to magnitude of data being processed is set to 115,200 bits per second. for access and control of the system, information is being transmitted in an extensible markup language (xml) format which can be processed by a browser and other interfaces while designated systems like phones and computer systems can send commands and get feedbacks from the system. the executable window operating system software is written to control and obtain feedbacks from the system device. in order to actualize this, a c# application is written using micro visual studio factoring graphical user interface (gui) in place for ease of access and operation. the communication is based on either the device being on the same network with the system or the system connects to the device via designated static ip of the power management system. 2.4 system implementation 2.4.1 circuit board printing proteus isis was used in the implementation of the design. a concrete implementation procedure is presented as shown in table 1. the 3d aerial view in figure 3 and the gerber view in figure 4 shows the component placement and the pcb routing, respectively. figure 3: 3d aerial view http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 898-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 905 figure 4: gerber view during this design, a toner printer was used in printing the routed circuit on a glossy paper where the copper prints were properly traced to effectively connect the circuit components obtained after careful design and calculations were completed. the resistance of the resistors, the capacitance of the capacitors, and the workability of all the other discreet components were verified before they were all used in the design. the complete circuit was first simulated with proteus by lab center electronics, found to be working satisfactorily, before the actual components were assembled on a bread board. it was only after the testing of the project has been done and its workability verified that the components were then transferred to a vero board and soldered carefully. the resistors, capacitor, the integrated circuit and diodes were first placed on the board, before the bigger components like the relay and voltage regulator were placed and soldered carefully. finally, the transformer was mounted and tested for functionality. table 1: implementation procedure for the power management system a schematic design this is the process of presenting the circuitry in a graphical way which can be simulated prior to the real-life implementation thereby being able to ascertain that the design will conform to the design intention using proteus isis professional. b component placement this is the immediate process after the transition to the gerber design phase of which if prior simulation is made facilitates easy navigation of routing thereby making auto routing, process actualized taking anticipated size of design into consideration. c routing this is the process involved in tracking the path of component connections geared towards establishing current flow from one point to another file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omenogor and imoize: design and implementation of a computer-based power management system. azojete, 15(4):898-910 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 906 d board edging this facilitates logical design and resource efficiency through designation of design boundaries. e board registry this is the process involved in transferring design from printed format to the onboard physical output actualized through heat transfer with the aid of laundry iron which aids to ascertain effective contact between tonner printed glossy paper and the copper clad. f etching this is the process involved in being able to actualize the track on the printed circuit board through chemical reaction between the copper on the clad and a ferric chloride solution thereby iron displaces the copper from the surface of the clad. thus, leaving the toner-plated regions. g drilling and component mounting based on the design convention being of throughhole conformity, the holes are drilled while components are fixed. h soldering this is the process of establishing connection between individual components and the board with the aid of soldering lead so as to allow the free flow of current. i continuity testing this is aimed at being able to ascertain that there is no discontinuity in connection in relation to the processes undergone in the course of implementation of the device with the aid of a digital multi-meter j code burning in order to actualize computer simulated environment, the code which was written in c++ is converted into hexadecimals which in turn is being embedded into the microcontroller for real life behavioral automations. 3.0 results and discussion the software designed was installed on the system with windows 7 operating system. this brings about a wireless connectivity between the microcontroller, esp8266 and the application. when the system activated by plugging to the source of power supply, the clicking of the power up icon on the app makes the bulb to come up and clicking the power down button, makes the bulb to go off. this in turn helps in managing the load in the building as illustrated in figures 5 and 6. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 898-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 907 figure 5: when power up icon is clicked figure 6: when power down icon is clicked for the purpose of this design, a 7w energy saving bulb was used as shown in figures 5 and 6. this bulb represents the electrical appliance in the house. when the power up icon is clicked, the bulb is ignited and when the power down icon is clicked, the bulb goes off. this is illustrated in the interface shown in figure 7. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omenogor and imoize: design and implementation of a computer-based power management system. azojete, 15(4):898-910 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 908 figure 7: interface of the system designed for power management to further expand the results, the transformer voltages and current were measured as shown in tables 2 4. table 2: actual and measured voltages of the transformer transformer voltages (v) actual voltage (v) measured voltage (v) primary voltage (vp) 230 215 secondary voltage (vs) 15 13 table 3: actual and measured current of the transformer transformer current (i) actual current (ma) measured current (ma) primary current (ip) 16.67 16 secondary current (is) 1000 990 table 4: comparison of measured and actual power power actual power (w) measured power (w) input power (pi) 15.33 14.19 output power (po) 15 11.7 4.0 conclusion a computer-based power management system was designed and implemented in a home. this design shows that load can actually be managed and controlled using application software, thereby making life more convenient and comfortable. the computer-based smart home application seamlessly interacts with the wi-fi module esp8266, which functions as an access point. users could control and monitor home power supply using this computer application. a more economical way to implement the smart home power system is provided by an arduino microcontroller. this system can be used for effective wireless communication by integrating all the devices in wireless mode. with the deployment of this system, wastage of electricity is greatly reduced. this system could be very useful to the aged and disabled people because it is user friendly, and it can be used as an alternative to existing switches in homes that often produce sparks which can result in fire accidents. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 898-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ogeomenogor@gmail.com 909 references adetona, s., ahemba, l., and imoize, al. 2018a. design and implementation of a low-cost experimental testbed for wireless sensor networks. nigerian journal of technology, 27(1):226232. adetona, so., ahemba, l. and imoize, al. 2018b. a cluster head assisted routing (char) scheme for improved energy load balancing in wireless sensor networks. journal of engineering and technology, 9(2). available: https://journal.utem.edu.my/index.php/jet/article/view/4808 ahmad, bi., yakubu, f., bagiwa, ma. and abdullahi, ui. 2011 remote home management: an alternative for working at home while away. world of computer science and information technology journal (wcsit), 1(4):144-147. alkar, az. and buhur, u. 2005 an internet based wireless home automation system for multifunctional devices. ieee consumer electronics, 51(4): 1169-1174. apeh, st. and mokogwu cn. 2013 development of pms. nigeria journal of technological research, 8(2): 30-34. barnes, v., collins, t.k. and mills, g.a., 2017, august. design and implementation of home energy and power management and control system. in 2017 ieee 60th international midwest symposium on circuits and systems (mwscas), 6-9 aug. 2017, boston, ma, usa, 241-244, doi: 10.1109/mwscas.2017.8052905 brychta, m., dubisch, f., stift, f. and palensky, p. 2017. queen-a novel design flow and decision support tool for sustainable buildings. iecon 201036th annual conference on ieee industrial electronics society, 7-10 nov. 2010, glendale, az, usa: 2448-2453. conte, g. and scaradozzi, d. 2003. viewing home automation systems as multiple agents’ systems. http.//www.robosiri.it/robocup_2003/robocupsitosiri/articles/pdf/conte.pdf (accessed on 30th november, 2018). delgado, ar., picking, r. and grout, v. 2006 remote-controlled home automation systems with different network technologies. in proceedings of the 6th international network conference (inc 2006), university of plymouth, united kingdom, 357-366. espressif system 2016. esp8266ex datasheet version 4.3. retrieved from: http://bbs.espressif.com on 30th november, 2018. grunwald, m. 2009. wasting our watts: we don‘t need new drilling or new power plants, we need to get efficient. time magazine, 173 (1): 32-36. imoize, al., oyedare, t., ezekafor, cg. and shetty, s. 2019. deployment of an energy efficient routing protocol for wireless sensor networks operating in a resource constrained environment, transactions on networks and communications, 7(1):34-50. jawarkar, np., ahmed, v., ladhake, sa. and thakare, rd. 2008. micro-controller based remote monitoring using mobile through spoken commands. journal of networks, 3(2): 58-63. malik, shk., aihab, k. and erum, s. 2009 sms based wireless home appliance control system (hacs) for automating appliances and security. issues in informing science and information technology, 6: 887-894. https://doi.org/10.1109/mwscas.2017.8052905 http://bbs.espressif.com file:///c:/users/user/downloads/azojete143/www.azojete.com.ng omenogor and imoize: design and implementation of a computer-based power management system. azojete, 15(4):898-910 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 910 pan, jy., lee, wt. and huang nf. 2003. providing multicast short message services over selfrouting mobile cellular backbone network. ieee transactions on vehicular technology, 52(1):240-253. potamitis, i., georgila, k., fakotakis, n., and kokkinakis, g. 2003. an integrated system for smarthome control of appliances based on remote speech interaction. eurospeech 2003, 8th european conference on speech communication and technology, 1-4 september 2003, geneva, switzerland, 2197-2200. she-jin, j., jin, j., wang, y., zhao, k. and hu, j. 2008. development of remote-controlled home automation system with wireless sensor network, embedded computing, 2008. sec '08. fifth ieee international symposium, 6-8 october 2008, beijing, china, 169-173. stanescu, d., ciubotaru-petrescu, b., chiciudean, d., cioarga, r. 2006. wireless solutions for telemetry in civil equipment and infrastructure monitoring. in: 3rd romanian-hungarian joint symposium on applied computational intelligence (saci) (2006). may 25-26, 2006, timisoara, romania, retrieved from http://www.bmf.hu/conferences/saci2006/ciubotaru.pdf http://www.bmf.hu/conferences/saci2006/ciubotaru.pdf http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):231-241 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 231 original research article optimizing energy utilization in unequally spaced linear array for smart antenna t. o. fajemilehin1*, j. f. opadiji2 and s. a. olatunji2 (1department of electrical and electronics engineering, university of ilorin, ilorin, nigeria 2department of computer engineering, university of ilorin, ilorin, nigeria) *corresponding author’s email address: fajemilehin.to@unilorin.edu.ng 1.0 introduction antenna arrays are widely used in wireless communications. an antenna with higher directivity and lower side lobe level (sll) is usually preferred. in an antenna radiation pattern, nulls are directed towards interfering signals while the main beam is pointed towards signals-of-interest. a single element antenna has limited performance. thus, antenna arrays are used to achieve low side lobes, narrower beamwidth, gain and higher directivity (balanis, 2016). an antenna array consists of radiating elements of an antenna connected electrically and geometrically. the radiation pattern of an antenna array is formed by the contribution of the pattern of each element. several variables could be used to determine the general radiation pattern of an antenna array. these include the geometrical configuration of the array, the relative displacement between elements, excitation amplitude of individual elements, excitation phase of individual elements, and relative pattern of the individual elements (lakshmi and raju, 2011). in the wireless communication systems, the purpose of using array antennas is to separate the desired signal from unwanted interferences. article information abstract radiation in the form of unwanted patterns, energy wastage and reduction is caused by high side lobe levels in a radiation pattern. this, in turn, affects the overall performance of the antenna. the purpose of this work is to improve the performance of a smart antenna by optimizing the radiation pattern using the genetic algorithm. optimal antenna parameters that would minimize side lobe level were obtained using genetic algorithm. simulations were carried out to determine the impact of the increase in inter-element spacing on array factor and beamwidth using the optimal antenna parameters. the optimal arrangement of inter-element spacing and number of elements in unequally spaced antenna elements were then considered. the array factor model for a uniform linear array of elements was used to obtain the optimum weights that would give the desired radiation pattern with reduced side lobe level. results for the unequally spaced linear arrays revealed that non-tapered arrangement among all the possible configurations gave the best improvement in the side lobe level. the outcome of this improvement is an optimized radiation pattern which is expected to aid the reduction of radiated power wasted in the side lobes of linear arrays in antenna systems. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 january, 2019 revised 12 june, 2019 accepted 20 june, 2019 keywords: array factor genetic algorithm side lobe level unequally spaced linear arrays mailto:jopadiji@unilorin.edu.ng http://www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng fajemilehin et al: optimizing energy utilization in unequally spaced linear array for smart antenna. azojete,16(2):231-241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 232 it is usually desired in the antenna arrays that the height of side lobes be kept low to optimize energy utilized. but the level of the side lobes in a normal radiation pattern is usually high thereby causing unwanted radiation in undesired patterns, energy wastage and reduction in the overall performance of the antenna. lower side lobe antenna arrays are becoming increasingly important. it is, therefore, necessary to discover faster and more reliable methods at arriving at the optimum solution to support the development of high-performance components in electronic communication systems, particularly those in complex environments. this motivates the simulation of the antenna radiation pattern carried out in this research work using unequally spaced linear array elements to optimize the performance of smart antennas. the research aims to improve the performance of an unequally spaced linear array antenna by optimizing the energy utilized in the radiation pattern. the following are the specific objectives that helped achieve this aim: determining the optimal inter-element spacing, arrangements and the number of elements in an unequally spaced linear antenna array. the scope is limited to unequally spaced linear arrays in antenna systems and particularly focused on the reduction of radiated power wasted in the side lobes. review of literature on arrays sanchez, covarrubias-rosales and panduro, (2009) used legendre functions for the optimization of linear and planar arrays. this produced some reduction in the side lobe level, half-power beam width as well as a better directivity for non-uniform linear and planar arrays than in the uniform ones. kumar and branner, (1999) used a simple inversion algorithm to determine the inter-element spacing in linear arrays. the work revealed some improvement in unequally spaced linear array compared to an equally spaced array with the same number of elements. in abdullah et al. (2012), a combination of method of moments (mom) and genetic algorithm (ga) was used for linear antenna arrays to obtain a maximum side lobe level reduction. side lobe level reduction was achieved with a reduced number of antenna elements while keeping the main lobe beamwidth intact. maharimi et al. (2012) showed the effect of spacing and number of elements on gain and halfpower beamwidth (hpbw). the study showed an increase in the h pbw and the number of side lobes as the inter-element spacing increased while the gain remained the same. however, there was an increase in gain with an increasing number of elements. further work was done on the unequal spacing technique to reduce the side lobe level and the number of elements of a linear antenna array. the paper showed that an unequally spaced antenna with a lower number of elements produced better side lobe level, same half-power beamwidth and similar antenna gain when compared with an equally spaced antenna with little more elements than it. some years after, mahmoud (2016) synthesized unequally-spaced linear array using modified central force optimization (cfo). the modification of the cfo algorithm was based on the concept of combining the social thinking value of particle swarm optimization with the original cfo search pattern and some time-varying acceleration coefficients. the outcome produced minimal side lobe levels but the computational complexity of the algorithm compared to other optimization techniques was not reviewed. gangwar, singh and singh (2017) considered computational efficiency of a new approach for the synthesis of a uniformly excited unequally spaced linear antenna. an inertia-weight particle swarm optimization technique was utilized. numerical analyses were carried out on 16and 32element linear arrays and results revealed outstanding results. the results showed that simpler methods to accomplish optimized results can still be further achieved. liu et al. (2017) http://www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 231-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 233 proceeded with improvement by utilizing a virtual active element pattern (aep) expansion method for the synthesis of the unequally spaced array. fast fourier transform was utilized for iterative processing which led to the development of a novel iterative synthesis method. you et al. (2017) utilized another method of synthesizing unequally spaced linear arrays using convex optimization. the excitation vector and auxiliary weighting vector are alternately selected as optimization variables in the study. the results also contributed to improvements in beamforming and side lobe level reduction. sudhakar and ravindranadh (2017) focused on obtaining the desired shaped beam array by using woodward synthesis technique. this was accomplished by acquiring the required amplitude distribution that would produce the desired beam shapes. this worked well for larger arrays, but there were deviations from the desired shape for small arrays. simultaneous adaptive processing was also carried out at multiple frequencies using one type of antenna array by salama et al. (2017) and salama (2019). the antenna used, consisting of a dissimilar antenna with nonuniformly spaced elements which were deployed above an imperfect ground plane. the outcome of these was an effective design which was robust to interferers from multiple directions and frequencies, which could be non-coherent. however, the focus of these studies was not on energy optimization. li et al. (2018) made the effort of simulating patch antenna arrays by ansys hfss software for the design of a 15.5 �� linear array. genetic algorithm was also used but for one specific form of configuration. another study by singh and salgotra (2018) utilized an enhanced version of firefly algorithm to provide a better solution at a fast rate. partial element equivalent circuit (peec) approach was employed by moreno et al. ( 2019) using a new nature-inspired cheetah metaheuristic. miranda et al. (2018) utilized pso algorithms for the antenna pattern synthesis, while singh and salgotra (2018) used the flower pollination algorithm. all these algorithms contributed to the optimal design of antennas with non-uniform spacing between the array elements. however, only specific configurations were used. while acknowledging all the contributions made, the current paper builds on these research efforts by exploring various configurations for the unequally spaced linear array to optimize energy consumption through the reduction of sidelobe level. 2.0 methods linear arrays consist of radiating elements spaced in a straight line. the radiation pattern of the array is a weighted sum of radiating elements’ patterns and its directivity is achieved by changing the weight coefficients that are calculated using an adaptive algorithm. the unequally spaced symmetrical arrangement can be classified into space-tapered (st) arrays and nontapered (nt) arrays (tan et al., 2010). the inter-element spacing increases from the centre of the array towards the end for the space-tapered arrangement (figure 1). however, the interelement spacing decreases from the centre of the array towards the end for non-tapered arrangement (figure 2) (maharimi et al., 2012). figure 1: symmetric unequal spacing arrangement file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng fajemilehin et al: optimizing energy utilization in unequally spaced linear array for smart antenna. azojete,16(2):231-241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 234 figure 2: asymmetric unequal spacing arrangement the array factor for a uniform linear array of n elements with an inter-element spacing d is given by eqn. 1 (balanis, 2016): af θ = n=1 n inej n−1 kd cosθ =� n=1 n in� ej(n−1)φ (1) where: in is the excitation of the element n. k is the wave number. d is the spacing between the elements. letting: z = x + jy = ejφ = ej(kd cos θ) (2) expanding and rearranging (1) gives eqn. 3 af θ = n=1 n anzn−1� (3) the goal of the optimization process is to achieve a reduced side lobe level of the radiation pattern and a narrow main beamwidth. hence, the problem formulated is aimed at obtaining the optimum weights that give a radiation pattern with reduced side lobe level (sll) (balanis, 2016). this objective is achieved by eqn. 4(balanis, 2016) minsll = 20 log abs(afi) j=1 n abs(afj)� (4) where: afi = contribution of element i to array factor af(θ) subject to: anzn−1 ≤ zn−1∀ 1 ≤ n ≤ n 0.5λ ≤ d ≤ λ θ ≤ 90° an ≥ 0 ∀ 1 ≤ n ≤ n 2.1 simulation of methods a linear array of antennas with unequal inter-element spacing and n elements in the array was considered. a specific signal-to-noise ratio (snr) of 20db is used and the noise is gaussian and independent from one antenna to the next. the distances for an unequal spaced linear array of an antenna with n-element are non-uniform in the arrangement. the configurations were arranged using the symmetrical and asymmetrical arrangement. these configurations were simulated using matlab. optimization toolbox with ga-genetic algorithm solver in matlab was used in the experiments for all the possible types of unequal inter-element spacing arrangements. the effects of different unequal inter-element spacing on the side lobe level and beamwidth were investigated. genetic algorithm (ga) is a biologically inspired optimization method using the principle of evolution. the use of ga started in the 1970s in holland. however, it became widely known after goldberg’s research (grajeda, 2011; laseetha and sukanesh, 2011). ga comprises a set of individuals called population. these individuals are called chromosomes and each individual is represented by binary strings of 0s and 1s. each individual is a point and possible solution in the solution space. the next generation is selected based on a fitness function which gives higher http://www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 231-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 235 -80 -60 -40 -20 0 20 40 60 80 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 x: 10.27 y: -25.82 aoa (deg) a f (d b ) values for fitter chromosomes. afterwards, two random pairs are taken for reproduction. in reproduction, crossover and mutation take place to give better offspring from the parent generation. genetic algorithm helps solve non-linear multivariable problems. genetic algorithm was used to obtain optimal weights for each antenna element using symmetric and asymmetric spacing for the different number of elements and a small increase in inter-element spacing (lambda). using ga helped to get the best combination of inter elements which would give rise to a lower array factor thereby producing a much lower level in the side lobes. 3.0 results and discussion having obtained the optimal inter-element distances which indicated an interval of about 0.04λ, the arrangement of these distances was then put into consideration. the number of elements considered for this work was 18 and 20 elements. ga is used to optimize the weights obtainable for each antenna element. the results, which are shown in figures 3-8 show the array factor versus the angle of arrival of the signal for the various spacing arrangements, are presented in the following subsections. 3.1 asymmetric element arrangement this arrangement is as explained earlier where the inter elements spacing are arranged in ascending or descending order. the simulation was carried out with the simulation parameters earlier highlighted as well as the optimal array factor, weights and optimal inter-element spacing obtained through genetic algorithm. the radiation pattern using the asymmetric arrangement for 18 and 20 elements is as shown in figure 3 and figure 4 respectively. figure 3: radiation pattern for 18 elements using the asymmetric arrangement file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng fajemilehin et al: optimizing energy utilization in unequally spaced linear array for smart antenna. azojete,16(2):231-241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 236 -80 -60 -40 -20 0 20 40 60 80 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 x: 10.27 y: -23.92 aoa (deg) a f (d b ) figure 4: radiation pattern for 20 elements using the asymmetric arrangement the results shown in figures 3 and 4 are the radiation patterns obtained for 18 and 20 elements respectively using asymmetric spacing arrangement. it can be observed from the results that the side lobe level was about 25.8db which is not as low as the results obtained when experiments were conducted with equally spaced antenna elements. the side lobes for the asymmetric spacing were also not as well spread when compared to the pattern obtained with equally spaced antenna elements. this arrangement is therefore not recommended. 3.2 space-tapered element arrangement space-tapered is a symmetric arrangement where the unequal distances spread out from the centre. simulations for this arrangement was done using similar parameters as in the asymmetric arrangement based on optimum array factor, weights and inter-element spacing obtained after the use of genetic algorithm the results obtained especially for the 18 and 20 elements were different from the asymmetric results as clearly seen and presented as shown in figures 5 and 6 respectively. http://www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 231-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 237 -80 -60 -40 -20 0 20 40 60 80 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 x: -22.96 y: -32.5 aoa (deg) a f (d b ) -80 -60 -40 -20 0 20 40 60 80 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 x: 7.403 y: -33.79 aoa (deg) a f (d b ) figure 5: radiation pattern for 18 elements using the spacetapered arrangement figure 6: radiation pattern for 20 elements using the space-tapered arrangement the results presented in figures 5 and 6 depict the observations made when the inter-element spacing was arranged in space-tapered order for 18 and 20 elements respectively. it is noted that the side lobe level reduced significantly beyond the level where the equally spaced antenna elements reached. this value (-33.79db) indicated a significant improvement compared to the value obtained when equal inter-element spacing was used. the beamwidth also reduced to about 12° which was lower than that of equally spaced antennas. another significant file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng fajemilehin et al: optimizing energy utilization in unequally spaced linear array for smart antenna. azojete,16(2):231-241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 238 -80 -60 -40 -20 0 20 40 60 80 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 x: 10.27 y: -35.6 aoa (deg) a f (d b ) -80 -60 -40 -20 0 20 40 60 80 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 x: 9.695 y: -34.77 aoa (deg) a f (d b ) observation made was the fact the side lobes were well laid out contrary to the irregular layout observed when the asymmetric arrangement was utilized. 3.3 non-tapered element arrangement this is another form of symmetric arrangement where the inter-element spacing decreases outwards from the centre. the parameters used in this simulation were similar to that used to produce the results in figures 3-6 except for the arrangement pattern. the significant changes occurred when the elements were increased to 18 elements. the results presented, therefore, are for 18 and 20 elements. this form of arrangement gave significant results as shown in figures 7 and 8 respectively. figure 7: radiation pattern for 18 elements using the non-tapered arrangement figure 8: radiation pattern for 20 elements using the non-tapered arrangement http://www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 231-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 239 16 16.5 17 17.5 18 18.5 19 19.5 20 -36 -34 -32 -30 -28 -26 -24 -22 number of elements si de lo be l ev el (d b) space-tapered(st) non-tapered(nt) assymetric(as) the results shown in figures 7 and 8 showed better improvements in the side lobe level as well as the beamwidth. the side lobe level was further reduced to -35.6db while the beamwidth obtained was 13.26°. the non-tapered arrangement, therefore, gave the best result in terms of side lobe level while the space-tapered gave the best result in terms of beamwidth. the three inter-element spacing arrangements used were then compared in terms of their side lobe level and beamwidth. this was done to have a clearer of the results. the results of the comparison obtained are presented in figures 9 and 10 respectively. figure 9: comparison of arrangement on side lobe level 16 16.5 17 17.5 18 18.5 19 19.5 20 10 12 14 16 18 20 22 number of elements f ir s tn u ll b e a m w id th ( d e g ) space-tapered(st) non-tapered(nt) assymetric(as) figure 10: comparison of arrangement on beamwidth figure 9 shows the comparison of side lobe level versus the number of elements for the spacetapered, non-tapered, and asymmetric element arrangements. the non-tapered arrangement gave the best result while the asymmetric gave the worst side lobe level. figure 10 presents the comparison of beamwidth versus the number of elements for the spacetapered, non-tapered, and asymmetric element arrangements. the space-tapered arrangement gave the best result of the three arrangements while the asymmetric arrangement gave the worst beamwidth value. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng fajemilehin et al: optimizing energy utilization in unequally spaced linear array for smart antenna. azojete,16(2):231-241. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 240 4.0 conclusion the research aimed to improve the performance of an unequally spaced linear array antenna by optimizing the energy utilized in the radiation pattern. this was achieved using ga with consideration for several configurations. the technique used was to first obtain weights which would produce optimum output for 18 to 20 elements. the best combination of inter-element distances which would give a much lower level in the side lobes was then searched for using ga. the optimum interval obtained was 0.04λ. the arrangement of these distances was then explored to identify the most effective configuration which reduces the side lobes optimally without compromising the performance of the antennae. this was a major contribution of this paper as most research in unequally spaced linear array did not consider several other configurations. the space-tapered arrangement in this study gave a better beamwidth compared to other configurations. the non-tapered configuration gave the best result with an improvement in the sidelobe level (sll) of approx. 3.5db for 20 elements. this improvement is significant compared to results obtained with the equally spaced linear array. it reveals that with a smaller number of antenna elements using non-uniform inter-element spacing, energy wasted through the side lobes can be significantly reduced. references abdullah, hh., khamis, s., hussein, ah., attiya, am. and nasr, m. 2012. side lobe level reduction of linear antenna arrays using a hybrid approach based on mom/ga algorithms. proceedings progress in electromagnetics research symposium, (piers) kuala lumpur, malaysia, march 27–30, 2012. pp. 1328-1332. balanis, ca. 2016. antenna theory : analysis and design. john wiley & sons, inc., new york. gangwar, vs., singh, ak. and singh, sp. 2017. an effective approach for the synthesis of unequally spaced antenna array by estimating optimum elements density on the aperture. ieee antennas and wireless propagation letters, 16: 2278–2282. grajeda, vz. 2011. bio-inspired optimization algorithms for smart antennas. university of edinburgh. kumar, bp. and branner, gr. 1999. design of unequally spaced arrays for performance improvement. ieee transactions on antennas and propagation, 47(3): 511–523. laseetha, tsj. and sukanesh, r. 2011. synthesis of linear antenna array using genetic algorithm to maximize sidelobe level reduction. international journal of computer applications, 20(7): 2733. li, y., hong, w., li, m. and lu, g. 2018. unequally spaced linear antenna arrays synthesis based on genetic algorithm., proceedings 2018 ieee international workshop on antenna technology (iwat) nanjing, china, march 5–7, 2018. pp. 1–4. liu, y., huang, x., xu, kd., song, z., yang, s. and liu, qh. 2017. pattern synthesis of unequally spaced linear arrays including mutual coupling using iterative fft via virtual active element pattern expansion. ieee transactions on antennas and propagation, 65(8): 3950–3958. maharimi, sf., jamlos, mf., malek, mfa. and neoh, sc. 2012. impact of number elements on array factor in linear arrays antenna. proceedings ieee 8th international colloquium on signal processing and its applications melaka, malaysia, march 23–25, 2012. pp. 296–299. http://www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 231-241. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fajemilehin.to@@unilorin.edu.ng 241 mahmoud, kr. 2016. synthesis of unequally-spaced linear array using modified central force optimisation algorithm., iet microwaves, antennas & propagation, 10(10):1011–1021. miranda, av., ashwin, p. and gangwar, vs. 2018. optimization of unequally spaced linear antenna array by employing pso technique. proceedings 2018 ieee second international conference on advances in electronics, computers and communications (icaecc) bangalore, india, february 9-10, 2018. pp. 1–4. moreno, sr., klein, ce., mariani, vc., coelho, lds., alotto, p., torchio, r., bauernfeind, t. and baumgartner, p. 2019. non-uniformly spaced linear antenna array design by means of peec approach applying cheetah optimization algorithm, international journal of applied electromagnetics and mechanics. 60(s1): s15–s24. salama, d., abdallah, mn., sarkar, tk. and salazar-palma, m. 2017. smart non-uniform antenna arrays deployed above an imperfect ground lane at multiple frequencies. proceedings 2017 ieee-aps topical conference on antennas and propagation in wireless communications (apwc) verona, italy, september 11-15, 2017. pp. 292–295. salama, d., sarkar, tk., abdallah, mn., yang, x. and salazar-palma, m. 2019 adaptive processing at multiple frequencies using the same antenna array consisting of dissimilar nonuniformly spaced elements over an imperfectly conducting ground. ieee transactions on antennas and propagation, 67(1): 622–625. sanchez, j., covarrubias-rosales, dh. and panduro, ma. 2009. a synthesis of unequally spaced antenna arrays using legendre functions. progress in electromagnetics research, 7: 57–69. singh, u. and salgotra, r. 2018. synthesis of linear antenna array using flower pollination algorithm., neural computing and applications, 29(2): 435–445. sudhakar, a. and ravindranadh, j. 2017. realization of desired shaped beam array of helical antennas. proceedings 2017 ieee progress in electromagnetics research symposium spring (piers) st petersburg, russia, may 22–25, 2017. pp. 3326–3329. tan, mnm., rahman, ta., rahim, ska., ali, mt. and jamlos, mf.. 2010. elements reduction using unequal spacing technique for linear array antenna. proceedings progress in electromagnetics research symposium cambridge, usa july 5-8, 2010. pp 558-562 you, p., liu, y., chen, sl., da, k., li, w. and liu, qh. 2017. synthesis of unequally spaced linear antenna arrays with minimum element spacing constraint by alternating convex optimization. ieee antennas and wireless propagation letters, 16: 3126–3130. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:jopadiji@unilorin.edu.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1004-1012 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1004 original research article cotton seed bio-based metal working fluid for sustainable machining operation s. i. hassan1, s. a. lawal2, k. o. adeyemi3* and a. a. adamu4 (1national agency for science and engineering infrastructure abuja, nigeria; 2department of mechanical engineering, federal university of technology, minna, nigeria; 3department of mechanical engineering, university of abuja, nigeria; 4department of mechanical engineering, bayero university, kano, nigeria) * corresponding author’s email address: kafayat.adeyemi@uniabuja.edu.ng 1.0 introduction according to lawal et al. (2011) cutting fluids have been used extensively in metal cutting operations for the last 200 years. in the beginning, cutting fluids consisted of simple oils applied with brushes to lubricate and cool the machine tool. occasionally, lard/animal fat or whale oils were added to improve the oil's lubricity. as cutting operations became more severe, cutting fluid formulations became more complex. today’s cutting fluids are special blends of chemical additives, lubricants and water formulated to meet the performance demands of the metal article information abstract this work investigated the viability of cottonseed oil as bio-based oil as a contribution to meeting the challenges of developing green industrial materials that are environmentally friendly and sustainable alternatives for use as metal cutting fluid, as many of the conventional metal working fluids were established to be harmful and hazardous both to the environment and health of the operator. the tests revealed that the metal working fluid properties of cottonseed oil were: ph-value, 4.37; viscosity, 33.85 mm2/s at 40 ºc, and 7.89 mm2/s at 100 ºc; density, 0.911 g/cm3; and a flash point of 263 ºc. this result shows that some of these properties compare favourably with those of the conventional mineral oil. it was concluded that at the lower temperature of 40°c the oil is still viscous enough and therefore is suitable for lower temperature operation such as low speed cutting, smaller depth of cut etc., while at a higher temperature of 100°c, the oil becomes less viscous and is thus not viable for higher temperature machining operations such as high-speed cutting operation and larger depths of cut; the density shows that cottonseed oil has high lubricity; the oil is acidic in nature and therefore would require addition of anticorrosive agents to function as a metal working fluid; and that the flash point of the oil is higher than that of the conventional mineral metal working fluid and so can be adjudged to be a very good candidate for the production of bio-based metal working fluid. the analysis indicated that the cottonseed oil, if significantly improved with the use of additives and chemically modified seeds, can be one of the potential candidates to substitute the conventional mineral oil in machining industry. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 october, 2018 revised 15 june, 2019 accepted 20 june, 2019 keywords: cottonseed oil metal working fluids machining process and anticorrosion agents. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1004-1012. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1005 working industry. however, the most essential transformation going on in the energy sector globally and in nigeria today is the use of renewable energy, largely because they are environmentally friendly with minimal impact, improved energy security, lower maintenance cost and high purity among others. with the growing rate of industrialization, conventional metal working fluids, that is, petroleum and synthetic oil, are extensively used in machining industries. with pressure from environmental protection agencies and global eco-friendly partners, the development in bio-based sustainable cutting fluid began to gain global acceptance due to the aforementioned benefits of renewable energy source. cutting fluids play a significant role in machining operations and impact shop productivity, (iowa waste reduction centre, iwrc, 2003). its importance includes, lubrication, temperature control, and chip removal. however, the metal working fluid possesses a great threat to the health and safety of the operator and the environment. the situation has been further deteriorated by the development of petroleum and synthetic, chemically based cutting fluid in the machining industry. it has been reported by the occupational safety and health administration (osha) that the conventional metal working fluid has given rise to about sixty-three health related problems, chief among which are skin infection, allergy, acute respiratory disorders etc. one of the devastating effects of the metal working fluid on the environment is its discharge which causes oxygen depletion, and nutrients reduction in the soil due to its non-biodegradable nature (vishnu et al., 2013). there is, as talib and rahim (2015) noted, therefore, a need to develop environment friendly metal working fluids as an alternative to the use of the conventional lubricants. previously, bio-based oils have been used in wide applications such as automotive lubricant, biofuel, hydraulic oil, grease and metalworking fluids. bio-based oils from soybean, rapeseed, sunflower, palm oil and coconut have been extensively studied for lubricant applications. erhan et al. (2006) studied the lubricant properties of soybean while erhan and asadauskas (2000) worked on lubricant base stocks from high oleic sunflower oil. problems associated with the use of bio-based oils are low temperature and lack of oxidative stability; these can however, be improved through chemical modification and mix with additives. similarly, shashidhara and jayaram (2010) showed that soybean, sunflower and rapeseed oil have the potential to be used as metal working fluids. the authors concluded that oil performances can be improved by additive mixtures, chemical modification of crude oil and genetic modification of the oil seed. this is supported by wu et al. (2000) whose work revealed that the modified rapeseed oil provides better lubrication properties by reducing friction and extreme pressure ability than the crude oil. khan et al. (2009) reported that bio-based oil has been used as metal working fluids for various material and machining conditions. they concluded that metal working fluids from palm oil, coconut and sunflower have greater lubricating properties and showed similar performance with mineral oil in terms of cutting force, cutting temperature, surface finish and tool wear. the work by khan et al. (2009) on the effects of minimum quality lubricants using bio-based oil also studied the turning performance of low alloy steel aisi 9310 as compared to completely dry and wet machining in terms of chip-tool interface temperature, chip formation mode, tool wear and surface roughness using uncoated carbide tool. the process parameters were cutting velocity (223, 246, 348 and 483 m/min) feed rate (0.10, 0.13, 0.16 and 0.18 mm/rev) and depth of cut (1.0 mm). the study showed that, with increase in cutting velocity and feed rate, average chip-tool interface temperature increased, even under minimum quality lubrication (mql) condition, due to increase in energy input and the roles of variation of process parameters. gradual growths of average principal flank were observed under all the environments. the surface roughness deteriorated drastically under wet machining compared to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan et al: cotton seed bio-based metal working fluid for sustainable machining operation. azojete, 15(4):10041012. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1006 dry, which might possibly be attributed to electrochemical interaction between tool and workpiece. mql appeared to be effective in reducing surface roughness. ojolo et al. (2008) performed an experiment to determine the effect of some straight bio based oils (groundnut oil, coconut oil, palm kernel oil and shear butter oil) on cutting force during cylindrical turning of three materials (mild steel, copper and aluminum) using tungsten carbide tool. the variables of cutting speed, feed rate and depth of cut were employed during the turning process. the spindle speeds of 250, 330, 450 and 550 rpm were investigated at a constant feed of 0.15 mm/rev and 2 mm depth of cut for each of the workpieces. they concluded that the bio oils were suitable for metal working fluids and that the effects of vegetable oils on cutting force depend on material. talib and. rahim (2015) evaluated the performance of chemically modified jatropha oil-based trimethylolpropane ester from crude jatropha oil as bio-based metal working fluids. the modified jatropha oil was developed by transesterification process with different molar ratios of jatropha methyl ester to trimethylolpropane. the modified jatropha oils were then tested on viscosity, density and tribology. the results of their work showed that the lubricant viscosity gave a significant effect on the machining performance, that is, as the lubricant viscosity decreases, the cutting force and maximum cutting temperature increased; that even though crude jatropha oil has better tribology properties, it was not recommended as a lubricant for machining processes due to the lack of oxidation and thermal stability; and that modified jatropha oil recorded comparable performances in terms of lubricant properties and machining performance. they concluded further that modified jatropha oil improves the coefficient of friction compared to synthetic ester; that the machining performance of modified jatropha oil was only slightly different from that of the synthetic ester; and that modified jatropha oil would be able to substitute synthetic ester as a sustainable metal working fluid in machining operations. this study investigated the idea of developing a cutting fluid from cottonseed oil. although there are a large number of vegetable oil-based cutting fluids available in the market, the question of availability of the product is a vital issue associated with other sources of the fluid. base material such as cotton which is commercially available in nigeria can be looked into for the production of sustainable metal working fluid. the specific objective is to measure and analse some of the metal working properties of cotton seed oil, such as the ph-value, viscosity, density and flash point. 2. methodology the method followed in carrying out this study involved a comprehensive review of literature related to the development of metal working fluids for both conventional and bio-based, and that enabled the materials for the extraction and performance test to be appropriately selected. the tests for the physicochemical properties were carried out at the ajaokuta iron and steel rolling complex. the flash point, and viscosity tests were carried out according to astm d92 and astm d445 standards, respectively. this was followed by the performance analysis. 2.1 materials 2.1.1 apparatus and equipment the materials and equipment used for the determination of various parameters in this research work are listed in the table 1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1004-1012. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1007 table 1: list of equipment s/n test equipment/material 1 determination of ph value laboratory ph meter, distilled water, buffer solution of ph 4.0 and 9.0, sample of oil, and beaker of 50ml. 2 determination of viscosity glass viscosity, oven or bath, thermometer, and stop watch. 3 determination of flash point open crucible, sand bath, thermometer and open cup. 4 determination of density hydrometer measuring cylinder of 100ml. 2.1.2 equipment components description this section explains the various component and accessories of the equipment used in the characterization of the cottonseed oil, obtained directly from national research institute for chemicals technology (narict), zaria. viscosity apparatus: in line with the procedures set out in sibata (2017) the viscosity apparatus consists of u-tube viscometer, which is made up of calibrated glass capillary; it has viscometer ladders which enable the viscometer to be suspended in the viscometer bath, while the viscometer bath is made up of any transparent liquid (water, in this case) and temperature range of 15°c to100°c which is to be maintained via heater and thermostat attached to the set up. it equally consists of thermometer used for measuring the temperatures and stop watch used to calculate the time of fall for the fluid in the viscometer. hydrometer cylinder: hydrometer: the hydrometer cylinder is made from glass which is graduated in unit of density. it is a clear glass having a size of about 100ml. the hydrometer was also used by santos et al. (2017) and ademoh et al. (2016). ph value apparatus: the ph value apparatus consists of a laboratory ph meter used for the measurement of the ph value, buffer solution of ph 4.0 and 9.0 and a standard glass beaker of 50ml capacity (buck et al. 2002, iwrc, 2003, and brinksmeier, 2015) flash point apparatus: the flash point apparatus consists of cleveland open cup which is made up of brass material or any other non-rusting material (metal) of equal conductivity, it also consists of a heating plate which has a hole surrounded by an area of plane depreciation and sheet of hard asbestos covering the metal plate except the depreciation. the apparatus also consists of a test flame applicator used in applying flame with an operating device mounted to permit automatic duplication of the sweep of the test flame and it also consist of a thermometer having a temperature range of 6°c and 300°c used in measuring the temperature (gorbett and kennedy, (2004). 2.2 method the parameters with which the base cotton seed oil is identified were determined for the oil extracted by the national research institute for chemicals technology (narict), zaria, using the following methods: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan et al: cotton seed bio-based metal working fluid for sustainable machining operation. azojete, 15(4):10041012. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1008 2.2.1 ph value determination the secondary standard (buck et al. 2012) of ph determination was used. this procedure for measuring ph is an electronic method using a combination of glass electrode with a reference potential provided by standard calomel electrode. before sample measurement the ph meter was standardized with two buffer solutions of different ph value (4.0and 9.0) to serve as check for proper instrument. the electrode was then rinsed with distilled water after the standardization or calibration. the oil sample was poured 2/3 full into the 50 ml beaker, an electrode was dipped inside the oil in the beaker and a direct reading corresponding to the ph value of the sample under test was taken. 2.2.2 determination of viscosity the essence of the method lies in measuring the time it takes a given volume of the test liquid to flow out of a container by gravity as described in sibata (2017) the viscometer was filled with the cotton oil via tube one until the meniscus of the oil became level at the lines marked m3 and m4 on the viscometer bulb labeled a. rubber hoses were then attached to tube 2 and 3 and a rubber bulb to tube 3; the viscometer was placed vertically in the liquid oven to the level of thermometric liquid (that is, until the viscometer bulb labelled c was fully submerged). the viscometer was kept at the test temperature (40°c) for 10 to 15 min, and with tube 2 closed, the liquid was sucked to above the mark m1 to about the center of bulb c using the rubber bulb. the cock connected with tube 3 was kept closed. the cock of tube 3 was closed and the clamp on tube 2 was released. the time taken for the liquid to flow from the upper marked line m1 to the lower marked line m2 on bulb labelled b was then measured. when doing this it was ensured that there were no air bubbles in the capillary tube. the outflow time was measured at least 3 times. the above procedure was repeated using a constant temperature of 100°c for determination of viscosity at 100°c the kinematic viscosity of the test oil (v) in mm²/sec is calculated from: v = ct (1) where: v = viscosity (mm²/sec) c = viscometer calibration constant (mm²/sec²) t = average outflow time of test oil in the viscometer (sec) 2.2.3 determination of density the same method as used by santos et al. (2017) and ademoh et al. (2016) was used in determining the density of the oil. the oil under test was poured to about 4/5 full of the measuring cylinder. to avoid contamination with dirt or other liquids the hydrometer was cleaned, and then dipped into the oil inside the measuring cylinder so that the hydrometer was lifted to a mark corresponding to the specific gravity of the oil. the density of the oil was than obtained by multiplying its specific gravity by the density of water of 0.997 g/cm3 at the room temperature of 27°c (annamalai and puri, 2002). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1004-1012. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1009 2.2.4 determination of flash point in open crucible before the test was conducted, the crucible was washed with a solvent; it was then heated and cooled down to room temperature. using the method described by negm et al. (2014) the crucible was positioned in the sand bath so that between its bottom and the cup there was a layer of sand of between 5 and 8mm thickness. it was ensured that the level of sand was about 12 mm away from the edge of the crucible. the thermometer was fixed to stand vertically so that the mercury ball was equidistant between the crucible and the oil level. a sample of the dehydrated and room temperature cooled oil was poured in the crucible. in the case of oil having flash point of up to 210 °c its level would be 12 mm away from crucible edge and 18 mm in the case of that having a flash pint of over 210 °c. care was taken to avoid splashing of the oil on the inner crucible above the oil level. the instrument was placed in a dark draught free place where the flash can be seen very well. the sand bath was then heated at the rate 10°c/min. 40° before the anticipated flash point, and then reduced to 40°c/min .10 °c before the anticipated flash point the flame of the igniter was slowly passed along the crucible edge at distance of 10-14mm from the test oil surface parallel to it. the flame length would be 3-4mm the time of the operation 2-3sec. the procedure was repeated at every 2°c. the temperature at which the first blue appears over part or entire surface of the test oil was taken for its flash point. the average of these temperatures was calculated and taken as the flash point of the oil. 3. result and discussion table 2 shows some of the physiochemical parameters of cottonseed oil (cso) obtained at the laboratory unit of ajaokuta steel complex, and that of the commercial mineral metal working fluid (cmmwf) obtained from the literature. table 2: physiochemical properties of the cso and that of cmmwf parameter cso cmmwf viscosity: at 40oc: at 100oc: 33.846 mm²/sec 7.893 mm²/sec 29 mm²/sec density 0.911 g/cm3 0.906 g/cm3 ph 4.37 flash point 263 °c 173 °c as seen from table 2, the physiochemical properties of the bio based cutting fluid from cotton seed (cso) is compared with that of conventional mineral based cutting fluid (cmmwf). viscosity: the values of viscosity for cso as shown in table 2 are 33.846mm²/sec at 40 °c and 7.893 mm²/sec at 100℃. the viscosity tests were carried out at two different temperatures, that is, lower temperature at 40°c and higher at 100 °c, in accordance to astm d 445 2006 standard (negm et al. 2014) to ascertain the viscous nature of the fluid during operation at both low and high temperatures. the result shows that at lower temperature of 40°c the oil is still viscous which implies that the oil is suitable for lower temperature operation such as low speed cutting, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan et al: cotton seed bio-based metal working fluid for sustainable machining operation. azojete, 15(4):10041012. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1010 smaller depth of cut etc., while at a higher temperature of 100°c, the oil becomes less viscous with kinematic viscosity of 7.893 mm²/sec. which, because it is much less than that of the cmmwf (as given in table 2), is an indication that the oil is not viable for higher temperature machining operations such as high speed cutting operation and larger depth of cut., (www.scientific.net). density: from table 2 the value of density of cso is 0.911g/cm; this is a strong parameter in the characterization of the cutting fluid, as an oil with high density reduces surface roughness of the working tool, (www.scientific.net); the result obviously shows that cso have high lubricity and is in conformity with the result presented by (lawal et al. 2011). ph: it can be seen from table 2 that the ph value of the cso is 4.37. the ph is the term used to express the intensity of the acidic or alkaline content of solution. from the ph scale, any value below 7 is acidic and above 7 is alkaline while 7 is neutral. the ph-value of the cso shows that the oil is acidic in nature and is prone to corrode the work piece and hence there would be need to add anticorrosive agents like sodium nitrite, lead naphthenate and sodium sulphonate. flash point: the value of flash point of cso oil as contained in table 2 is 263 0c. the flash point of oil is a point at which the vapours of petroleum product heated under certain condition form with the surrounding air, a mixture capable of flashing when flame is brought close to it. the value is higher than the corresponding value cmmwf as seen from table 2. this is an indication that the cmmwf does not contain high volatile and flammable material. (iwrc, 2003). 4. conclusion the performance evaluation of cotton seed oil (cso) was carried out and the results obtained were compared with that of the cmmwf and the following conclusions were drawn. the cso can be considered in low temperature machining operations such as low speed cutting operations, due to the viscous nature of the oil at such temperature. the lubricant viscosity gave a significant effect on the machining performance. as the lubricant viscosity decreases, the cutting force and maximum cutting temperature increases. the cottonseed oil extracted by using screw press cannot be wholly used as cutting fluid material because of its acidic contents (ph value of 4.37), but certain anti corrosive additives such as sodium nitrite, lead naphthenate and sodium sulphonate could be added which can prevent rust from forming on metallic parts. considering its higher value of flash point (263 °c), the cso can be adjudged to be a suitable candidate for the production of bio-based metal working fluid. based on the result of the test obtained for the density of the cso (0.911 g/cm3), it can be concluded that the cottonseed oil is suitable as vegetable cutting fluid. conclusively cotton seed oil was found to be a promising alternative for mineral based oils due to its environmentally friendly characteristics. its excellent biodegradability and nontoxic characteristics along with other technical suitability makes it a promising alternative in metal cutting industries based on the result obtained in this research, the following recommendations were made. further research may be carried out on some of the physiochemical properties of the oil such as iodine value, thermal stability to ascertain the full performance of the oil as cutting fluid; http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1004-1012. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1011 it is also recommended that the oil be subjected to further testing in machining shop to ascertain its performance under wider application; and additives such as corrosion inhibitors rust inhibitors, anti-wear agent viscosity improver etc., could be added to increase the quality of the oil reference ademoh, na., didam, jh. and garba, dk. 2016. investigation of neem seed oil as an alternative metal cutting fluid. american journal of mechanical engineering, 4(5): 191-199. annamalai, k. and puri, ik. 2002. advanced thermodynamics engineering. crc press llc, new york. 1 – 801. brinksmeier, e., meyera, d., huesmann-cordes, ag. and herrmann, c. 2015. metalworking fluids—mechanisms and performance. cirp annals manufacturing technology, 64: 605–628. buck, rp., rondinini, s., covington, ak., baucke, fgk, camões, mf., milton, mjt, mussini, t., naumann, r., pratt, kw., spitzer, p. and wilson, gs. 2002. measurement of ph. definition, standards, and procedures. international union of pure and applied chemistry, pure and applied chemistry, 74(11): 2169–2200. erhan, sz., sharma, bk. and perez, jm. 2006. oxidation and low temperature stability of vegetable oil-based lubricants. industrial crops and products, 24(3):292–299. erhan, sz. and asadauskas, s. 2000. lubricant basestocks from vegetable oils. industrial crops and products, 11(2–3): 277–282. gorbett, ge. and kennedy, pm. 2004. a phenomenon in flash point testing for fire safety evaluation. interflam 2004, fire science and engineering conference, edinburgh, scotland. july 5-7, 2004; 1 11. iowa waste reduction centre, iwrc 2003. cutting fluid management for small machining operation: a practical pollution prevention guide, 3rd edition, university of northern iowa. khan, mma., mithu, mah. and dhar, nr. 2009. effects of minimum quantity lubrication on turning aisi 9310 alloy steel using vegetable oil-based cutting fluid. journal of material processing technology, 20(9): 5573–5583. lawal, sa., choudhury, ia. and nukman, y. 2011. application of vegetable oil-based metalworking fluids in machining ferrous metalsa review. international. journal of machine tools and manufacture, 52(1): 1–12. negm, na., kandile, ng., abd el salam, am. and mansour, sa. 2014. performance evaluation of cutting fluids additives developed from recycling of polyethylene terephthalate. iosr journal of applied chemistry, 7(5. 1): 69-79. ojolo, sj., amuda, moh., ogunmola, oy. and ononiwu, cu. 2008. experimental determination of the effect of some straight biological oils on cutting force during cylindrical turning. revista matéria, 13: 650–663. santos, e., camargo, ap., azevedo de faria, e., ferreira de oliveira junior, fa., alves, sm. and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan et al: cotton seed bio-based metal working fluid for sustainable machining operation. azojete, 15(4):10041012. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kafayat.adeyemi@uniabuja.edu.ng 1012 neto, el. 2017. the lubricity analysis of cutting fluid emulsions. materials research, 20(2): 644650. shashidhara, ym. and jayaram, sr. 2010. vegetable oils as a potential cutting fluid-an evolution. tribology international, 43(5–6):1073–1081. sibata 2017. viscosity measurement series – constant-temperature baths for viscometers: glass viscometers (as per jis k 2283 3000). sibata scientific technology, ltd., japan. talib, n. and rahim, ea. 2015. performance evaluation of chemically modified crude jatropha oil as a bio-based metalworking fluids for machining process, 12th global conference on sustainable manufacturing. 22nd – 24th september, 2014, universiti teknologi, malaysia. procedia cirp, 26:346 – 350 vishnu, p., anbuudayasankar, sp., ashokkumar, a. and sharan, a. 2013. development of bio based semi-synthetic metal working fluid from industrial wastewater. international conference on design and manufacturing, july 18, 2013 – july 20, 2013, iiitdm kancheepuram, chennai, india procedia engineering 64: 1436 – 1444. wu, x., zhang, x., yang, s., chen, h. and wang, d., 2000. the study of epoxidized rapeseed oil used as a potential biodegradable lubricant. journal of the american oil chemists’ society, 77(5): 561–563 http://www.utm.my/ http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 8-19 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 8 original research article modelling of tractor fuel consumption for harrowing operation in a sandy loam soil o. a. oyelade1* and k. c. oni2 1*farm power and machinery department, national centre for agricultural mechanization (ncam), ilorin, kwara state, nigeria. 2agricultural and biosystems engineering department, university of ilorin, ilorin, kwara state, nigeria. article information received october, 2018 accepted december, 2018 keywords: fuel harrowing evaluation prediction tractor consumption abstract in the study of agricultural machinery management, fuel consumption is considered as a very important factor that plays a significant role in the selection and management of tractors and equipment. in nigeria, there are no tractor fuel consumption models developed for harrowing operation. considering the importance of harrowing operation to tillage practice in nigerian agriculture, it became necessary to embark on the study on the modelling of tractor fuel consumption in litres per hectare (l/ha) during harrowing operation in a sandy loam soil using available information gathered from the national centre for agricultural mechanization (ncam) tractor test reports. a multiple linear regression method was used to develop the model. a 10-repeated 10-fold cross-validation method was used to validate the model. the study revealed that the model developed for harrowing operation had a r2-value of 0.477 showing tractor power rating as the only operation parameter contributing to the model developed. cross-validation revealed that the harrowing operation model had a test error value of 0.986 l/ha. the study also identified other contributing factors to tractor fuel consumption during harrowing operation in a sandy loam soil. the model developed for tractor fuel consumption during harrowing operation in a sandy loam soil is recommended for use in budgeting for diesel consumption. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction tillage of soil is considered to be one of the biggest farm operations (al-suhaibani and ghaly, 2010). it is also a conventional farming system involving the use of the tractors which results in high energy costs. the sustainability of such a system requires a well-controlled resource management leading to a significant reduction in crop production costs derived from savings in fuel consumption (serrano et al., 2009). agricultural machinery has become increasingly important in carrying out farm work. the application of machines to agricultural production has been one of the outstanding developments in agriculture. machinery contributes a major capital input cost in most farm businesses. in agriculture, the tractor remains a very important machine due to its ability to provide mechanical power to farm implements both on and off the farm. the choice of a tractor based on field performance can be very challenging due to limited information with regards to performance on the field. according to sirelkatim, et al. (2001), land preparation is one of the most energy demanding operations in agriculture, it involves soil cutting, turning and pulverizing and thus demands high energy, hence there is need to optimize tractor performance http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 9 in order to utilize the available energy. this energy utilization depends on many factors such as soil type and condition, operating depth and speed, and hitch geometry. the use of models for budgeting of tractor fuel consumption has been of great use to farmers in developed nations. most studies on model development for tractor fuel consumption centres mainly on ploughing operation which is the first tillage operation carried out on the soil. harrowing operation has been considered as a very important tillage operation that needs to be carried out during land preparation in nigerian agriculture. considering the importance of harrowing operation to tillage practice in nigerian agriculture, there is a need to develop a simple model equation for predicting tractor fuel consumption in litres per hectare (l/ha) during harrowing operation. the study is aimed at developing a statistical model for predicting tractor fuel consumption during harrowing operation in a sandy loam soil. 2.0 materials and methods 2.1 experimental procedure the study involves the use of information gathered from the national centre for agricultural mechanization (ncam) tractor test reports on 41 agricultural tractors compiled by oyelade (2016) which were tested during harrowing operation on a sandy loam soil. each tractor was tested on an area of 0.25 hectare (25 m x 100 m) in a randomized complete block design (rcbd). the implement used for the trials was tractor mounted off-set disc harrow. parameters measured during harrowing operation include speed of operation, fuel consumption, field capacity, field efficiency, wheel slip, duration of operation, draught force, the width of cut, depth of cut, soil cone index, soil moisture content, and soil bulk density. the three soil properties, namely, soil cone index, soil moisture content and soil bulk density were all measured at depths 0 – 7 cm, 7 – 14 cm and 14 – 21 cm. the resulting average values of these three soil properties were part of the data collated. all the parameters of the tractor-implement performance were measured and recorded in line with the recommendations of rnam test codes and procedures for farm machinery technical series (1983). out of the 41 tractor test data, 37 tractor test data termed model development data-set was used to generate multiple regression for use in future predictions of tractor fuel consumption in litres per hectare during harrowing operation on a sandy loam soil. the remaining four tractor test data termed model validating data-set were used to validate the model developed. 2.2 description of the study area the study was carried out at the national centre for agricultural mechanization (ncam), ilorin, kwara state which is located at 370 m above sea level in the southern guinea savanna ecological zone of nigeria by longitude 4o 30′ e and latitude 8o 26′ n. the various test locations where these tractors were tested fall under the sandy loam soil textural class with the following fractions: sand 56.79% to 69.92%, silt 15.33% to 28.64% and clay 6.44% to 18.33%. the soil in the various test locations of the study area were classified as alfisols (soil survey staff, 1975) under the usda soil order. 2.3 particle size analysis particle size analysis was carried out using the hydrometer method described by gee and or (2002). sodium hexametaphosphate (calgon) was used as the dispersant. the textural class of the soil was determined using the usda textural triangle. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyelade and oni. modelling of tractor fuel consumption for harrowing operation in a sandy loam soil. azojete, 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 10 2.4 test parameters 2.4.1 speed of operation the speed of operation was determined by placing two poles 20 m a part in-between the longest distance of the test plot. on the opposite side of the test plot, two poles were placed in a similar position 20 m apart. the speed of operation for each tractor evaluated during harrowing operation was mathematically expressed as:        1 206.3 t vs (1) where, vs = speed of operation (km/h) t1 = time taken to cover 20 m (sec) 2.4.2 depth and width of cut the depth and width of cut during field operation were measured using a steel rule and measuring tape, respectively. 2.4.3 draught of the implement the draught of implement was measured using the trace tractor technique described by oyelade (2016). 2.4.4 theoretical field capacity theoretical field capacity measured in ha/h was expressed mathematically as:   t 3600 a eg (2) where, g = theoretical field capacity (ha/h), e = area of field (ha) ta = actual time taken in doing the main tillage work (sec) 2.4.5 effective field capacity effective field capacity measured in ha/h was expressed mathematically as: t t ex )3600( 5  (3) where, x5 = effective field capacity (ha/h) e = area of field (ha) tt = total time taken in completing the whole tillage operation (sec) 2.4.6 field efficiency field efficiency, according to asae (2000), is the ratio of effective field capacity to theoretical field capacity, expressed in percent. it was expressed mathematically as: %100 g 5 xxh  (4) where, h = field efficiency (%) x5 = effective field capacity (ha/h) g = theoretical field capacity (ha/h) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 11 2.4.7 fuel consumption the fuel required for each tillage operation was determined by filling the tank to full capacity before and after the test. amount of refueling after each test is the fuel consumption for the test. the filling of fuel tank before the operation and then refilling after completing the operation in determining the amount of fuel consumed during operation is a common method used in the field for determining tractor fuel consumption in litres per hectare. this same method was as reported by (ajav and adewoyin, 2011; ikpo and ifem, 2005; kudabo and gbadamosi, 2012; meshack-hart, 1997; sirelkatim et al., 2001; udo and akubuo, 2004) in determining tractor fuel consumption in litres per hectare. fuel consumption measured in either l/ha or l/h was expressed mathematically as: e ji  (5) ixk 5x (6) where, i = fuel consumption (l/ha) j = volume of fuel consumed (l) e = area of field (ha) k = fuel consumption (l/h) x5 = effective field capacity (ha/h) 2.4.8 travel reduction (wheel slip) in determining the wheel slip (travel reduction), a mark was made on the tractor drive wheel with coloured tapes. this was used to measure the distance covered by the tractor drive wheel at every 10 revolutions under no load and the same revolution with a load on the same surface. the travel reduction (wheel slip) measured in % was expressed mathematically as: %100 m m m 2 12 l (7) where, l = travel reduction (wheel slip) (%) m2 = distance covered at every 10 revs of the wheel at no-load condition (m) m1 = distance covered at every 10 revs of the wheel at load condition (m) 2.4.9 tractive efficiency tractive efficiency measured in % is the ratio of drawbar power to wheel power and was expressed mathematically according to (macmillan, 2002) as: %100 w p t q d q (8) where, qt = tractive efficiency (%) dp = drawbar power (kw) qw = wheel power (kw), power losses in the transmission from engine to the wheels of, say 10% is assumed, it can be written as: %100 9.0    e p t q d q (9) where, qe = engine power (kw) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyelade and oni. modelling of tractor fuel consumption for harrowing operation in a sandy loam soil. azojete, 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 12 2.4.10 duration of operation the duration of operation measured in h/ha which is the time spent in completing the whole operation was mathematically expressed as: 5 9 1 x x  (10) where, x9 = duration of operation (h/ha) x5 = effective field capacity (ha/h) 2.5 soil parameters 2.5.1 soil bulk density soil bulk density (ρb ) is a measure of the mass of soil per unit volume and is usually reported on an oven-dry basis. the soil bulk density was determined by the core method described by anwanane (2014). the core samples were oven dried at a temperature of 1050c to a constant weight. ρb = ms vt (11) where, ρb = soil bulk density (g/cm3) ms = mass of dry soil (g) vt = total volume of soil (cm3) 2.5.2 soil moisture klenin et al. (1985) defined soil moisture content as the amount of liquid, usually water that is present in the soil. it is expressed as a percentage of the mass of water in the soil to the mass of the dried soil (for dry weight classification). the soil moisture content (in dry basis) measured in %, can be expressed mathematically as: %100 s w c w w m (12) where, mc = soil moisture content (%) ws = mass of oven dried soil (g) ww = mass of water present in soil (g) 2.5.3 soil cone index the soil cone index (ci) is the soil resistance to penetration and was measured using a cone penetrometer. 2.6 statistical tool 2.6.1 regression analysis multiple linear regression method which is a form of regression analysis was used for establishing the relationship that existed between fuel consumption (the model response variable) and other factors (or predictors of fuel consumption) identified to be factors influencing tractor fuel consumption in litres per hectare during harrowing operation. multiple regression is when there is one dependent variable but more than one independent variables. in this study, tractor fuel consumption in litres per hectare was the dependent variable while other factors identified as factors influencing tractor fuel consumption in litres per hectare stands as the independent variables. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 13 in developing this model, the following hypotheses were drawn: test of hypothesis about full regression model of harrowing operation hypothesis 1: [test of significance about all regression parameters] null hypothesis h0 : the model does not fits the data/ the model is not adequate alternative hypothesis h0 :the model fits the data/ the model is adequate mathematically, null hypothesis h0 : βj = 0 [none of the predictors contributes significantly to the model] alternative hypothesis h0 : :βj = 0 for at least one j [at least one of the predictors contributes significantly to the model] tests statistic: fratio = msregression mserror [global f-test] decision rule: reject thenull hypothesis in favour of the alternative hypothesis at 0.05 significance level if p − value < 0.05, otherwise do not reject the null hypothesis. hypothesis 2: [test of significance about individual regression coefficient] null hypothesis h0 : βj = 0 [predictor xj is not statistically significant in the model given that others are included in the model] alternative hypothesis h0 : : βj ≠ 0 [predictor xj is statistically significant in the model given that others are included in the model] tests statistic: tvalue = βj cjjσ2 [individual t-test] jjc diagonal element of the covariance matrix corresponding to j 2 variance of j this same tests statistic was also used by james et al. (2013) decision rule: reject the null hypothesis in favour of the alternative hypothesis at 0.05 significance level if p − value < 0.05, otherwise do not reject the null hypothesis. 2.7 developing models without an intercept term models with intercept term are common to all models built round multiple linear regression models. in this study, the assumption was whether a tractor could consume some amount of fuel before commencement of harrowing operation if such variable as air (ambient) temperature could constitute measurable parameters. the study was therefore governed by building models without intercept term because it is the most appropriate model type that fits this study based on the cylinder method of measuring fuel consumption. 2.8 model validation the model validation method adopted for this study is the cross validation method. this validation method is an extremely flexible and powerful technique and widely used approach in validation work for estimating prediction error. the measure of error for cross-validation is the mean square error (mse) for a quantitative response. the 10-fold cross-validation is commonly used. according to bouckaert (2003), 10-fold cross-validation remains the most widely used validation procedure. 3.0 results and discussion 3.1 model development and validation one model with p-value < 0.05 was statistically developed for harrowing operation on a sandy loam soil. details of the pair-wise correlation analysis showing the result of the correlation strength of the developed model for harrowing operation is presented in table 1. results file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyelade and oni. modelling of tractor fuel consumption for harrowing operation in a sandy loam soil. azojete, 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 14 obtained for parameter estimates and analysis of variance (anova) for the model developed for harrowing operation are presented in tables 2 and 3, respectively. table 1. pair-wise correlation result of fuel predictive values of model 2 with observed fuel values during harrowing operation * = significant at 5% level when r-value ≥ 0.338788 table 2. table of parameter estimates for model 2 of harrowing operation *significant at 5% level table 3. anova table for model 2 of harrowing operation source of variation degree of freedom sum of squares means squares f-value p-value tractor power rating 1 234.430 234.430 151.6806 4.503e-11 * width of cut 1 6.257 6.257 4.0487 0.05721 depth of cut 1 3.660 3.660 2.3684 0.13875 draught force 1 4.110 4.110 2.6594 0.11785 effective field capacity 1 3.300 3.300 2.1349 0.15879 tractive efficiency 1 11.101 11.101 7.1828 0.01401 * field efficiency 1 4.096 4.096 2.6499 0.11847 wheel slip 1 1.576 1.576 1.0200 0.32401 duration of operation 1 0.086 0.086 0.0556 0.81594 speed of operation 1 11.162 11.162 7.2223 0.01379 * average soil moisture content 1 0.750 0.750 0.4851 0.49378 average soil bulk density 1 2.365 2.365 1.5301 0.22975 average soil cone index 1 0.020 0.020 0.0131 0.90999 residuals 21 32.457 1.546 *significant at 5% level model developed observed model 2 of harrowing operation 0.690468* p-value of model model multiple r-square value model adjusted r-square value coefficients estimates std. error t value p-value 1.519e-07 0.4767 0.1778 tractor power rating 0.055996 0.059842 0.936 0.3601 width of cut -0.050569 0.029628 -1.707 0.102 depth of cut 0.059737 0.062936 0.949 0.3533 draught force -0.698953 0.954827 -0.732 0.4722 effective field capacity 10.673913 8.512772 1.254 0.2237 tractive efficiency 0.250983 0.190038 1.321 0.2008 field efficiency -0.031328 0.059421 -0.527 0.6036 wheel slip -0.060759 0.054501 -1.115 0.2775 duration of operation 5.464993 3.336067 1.638 0.1163 speed of operation -1.523374 0.598055 -2.547 0.0188 * average soil moisture content -0.085734 0.115415 -0.743 0.4658 average soil bulk density 2.768087 2.346524 1.180 0.2513 average soil cone index 0.003298 0.028825 0.114 0.9100 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 15 model 2 of harrowing operation with p-value < 0.05 recorded a r-squared value of 0.4767. the model explains 48% of the proportion of variance in the mean squared errors of tractor fuel consumption for harrowing operation with only speed of operation showing statistical significance with a p-value of 0.0188 in the model. in terms of marginal (individual) significance of the predictor variables, results in table 4 reveal that we reject the null hypothesis about only tractor power rating, tractive efficiency and speed of operation with corresponding p-values of 4.503e-11, 0.01401 and 0.01379, respectively. this means that each of these variables is statistically significant in the model provided others are included in the model. it also implies that they cannot be removed from the model. the equation used for expressing model 2 of harrowing operation as contained in table 2 was given as: the equation used for expressing model 2 of harrowing operation as contained in table 2 was given as: �� = 0.055996x1 − 0.050569 x2 + 0.059737x3 − 0.698953x4 + 10.673913x5 + 0.250983x6 − 0.031328x7 − 0.060759x8 + 5.464993x9 − 1.523374x10 − 0.085734x11 + 2.768087x12 + 0.003298x13 where, y� = tractor fuel consumption (l/ha), x1 = tractor power rating (hp), x2 = width of cut (cm), x3 = depth of cut (cm), x4 = draught force (kn), x5 = effective field capacity (ha/h), x6 = tractive efficiency (%), x7 = field efficiency (%), x8 = wheel slip (%), x9 = duration of operation (h/ha), x10 = speed of operation (km/h), x11 = average soil moisture content (%), x12 = average soil bulk density (g/cm3) and x13 = average soil cone index (n/cm2). the model equation generated for model 2 of harrowing operation was used for predicting tractor fuel consumption using the 37 model development dataset. results obtained from the fuel prediction values of model 2 of harrowing operation is presented in table 4. the values for both observed and predicted tractor fuel consumption of model 2 of harrowing operation as shown in table 4 were correlated together and gave a correlation coefficient of 0.690468 as shown in table 1. according to the rule of thumb as provided in http://www.westgard.com/lesson42.html for evaluating correlation coefficient, noted that size of r with correlation values between 0.50 and 0.69 are said to be moderate. it indicates that tractor fuel consumption predictions of model 2 of harrowing operation is moderately correlated with the observed tractor fuel consumption values obtained during harrowing operation on a sandy loam soil. figure 1 shows the graph plot of observed and predicted tractor fuel consumption using model 2 of harrowing operation. (13) http://www.westgard.com/lesson42.htm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyelade and oni. modelling of tractor fuel consumption for harrowing operation in a sandy loam soil. azojete, 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 16 table 4. results of predicted tractor fuel consumption values during harrowing operation on a sandy loam soil using model 2 of harrowing operation figure 1. the plot of observed and predicted tractor fuel consumption using model 2 of harrowing operation tractor observations observed fuel values (l/ha) predicted fuel values (l/ha) residuals (l/ha) 1 3.28 2.711058 0.568942 2 4.12 3.783405 0.336595 3 5.47 4.624426 0.845574 4 1.44 1.972107 -0.53211 5 4.76 3.74173 1.01827 6 5.26 3.453034 1.806966 7 3.2 3.192731 0.007269 8 0.9 2.68324 -1.78324 9 3.8 2.452152 1.347848 10 3.53 4.300108 -0.77011 11 3 2.040149 0.959851 12 0.85 1.749665 -0.89966 13 3.92 3.35114 0.56886 14 0.92 1.557942 -0.63794 15 2.32 2.938795 -0.6188 16 2.24 1.525242 0.714758 17 1.84 2.549917 -0.70992 18 0.8 1.956347 -1.15635 20 1.68 2.904075 -1.22407 21 1.04 1.58534 -0.54534 22 0.9 1.847902 -0.9479 24 3.4 2.173657 1.226343 25 3 2.561103 0.438897 26 4 3.364288 0.635712 27 1.6 3.417445 -1.81745 28 1.9 2.857485 -0.95749 29 2.8 3.153878 -0.35388 30 2.1 1.820463 0.279537 32 2.88 1.907434 0.972566 33 2 2.748966 -0.74897 34 4.53 5.363732 -0.83373 35 4 2.156639 1.843361 36 1.2 1.338286 -0.13829 37 4.13 3.083001 1.046999 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 17 3.2 model predictors for harrowing operation the results of the parameter estimates and analysis of variance (anova) for the only model developed for harrowing operation on a sandy loam soil as shown in tables 2 and 3, respectively, have revealed that the only developed model for harrowing operation contains some important predictors found to be significant at 5% level. these predictors include tractor power rating, tractive efficiency and speed of operation. these three set of predictors are harrowing operation parameters affecting tractor fuel consumption in litres per hectare during harrowing operation on a sandy loam soil. among these three factors affecting tractor fuel consumption during harrowing operation on a sandy loam soil, only tractor power rating contributed highly to the model developed. therefore, tractor power rating, strongly determine tractor fuel consumption in litres per hectare during harrowing operation on a sandy loam soil. 3.3 model validation for harrowing operation model result of 10-repeated 10-fold cross-validation method as presented in table 5 was used for validating the model developed for harrowing operation on a sandy loam soil. it can be deduced from table 5, that model 2 of harrowing operation recorded a root mean square error of 0.98643 l/ha serving as the model’s test error value using the four model validating datasets presented in table 6. table 5. results of 10-repeated 10-fold cross-validation for model 2 of harrowing operation replicate no. mse value 1. 0.967218 2. 1.023916 3. 0.967739 4. 0.967430 5. 0.967155 6. 0.967337 7. 0.967429 8. 0.967726 9. 0.967282 10. 0.967218 average mse (l2ha-2) 0.973045 average rmse (lha-1) 0.98643 key: mse – mean square error rmse – root mean square error note that each replicate contains the average mean square error value of 10-fold crossvalidation table 6. results of fuel predictive and residual values of model 2 of harrowing operation used for model validation data observed fuel values (l/ha) predicted fuel values (l/ha) residual (l/ha) 4.00 3.384845 0.61516 1.60 3.1639 -1.5639 2.60 1.671801 0.9282 1.42 0.802705 0.6173 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyelade and oni. modelling of tractor fuel consumption for harrowing operation in a sandy loam soil. azojete, 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 18 4.0 conclusion a study was carried out to develop a model for future prediction of tractor fuel consumption during harrowing operation in a sandy loam soil using information gathered from ncam tractor test reports. from the outcome of this study, it can be concluded that: one effective model with p-value < 0.05 was developed for harrowing operation. model 2 of harrowing operation developed for future prediction of tractor fuel consumption in litres per hectare during harrowing operation on a sandy loam soil recorded a coefficient of multiple determination (r-squared) value of 0.4767. harrowing operation parameters such as tractor power rating, the speed of operation and tractive efficiency were found to be statistically significant at 5% level in model 2 of harrowing operation with only tractor power rating contributing highly to the model developed. the model for harrowing operation based on cross-validation result had a test error of 0.98643 l/ha. acknowledgement we want to thank members of ncam tractor testing team for the tremendous work they have been doing over the years in the testing of agricultural tractors imported into the country for use in nigerian agriculture. reference ajav, ea. and adewoyin, ao. 2011. the effects of ploughing depth and speed on the fuel consumption of some commonly used farm tractors in selected states of south western nigeria. proceedings of the nigerian institution of agricultural engineers (niae), 32: 114 – 122. al-suhaibani, sa. and ghaly, ae. 2010. effect of plowing depth of tillage and forward speed on the performance of a medium size chisel plough operating in a sandy soil. american journal of agricultural and biological engineers, 5(3):247 – 255. anwanane, nb. 2014. modeling of soil water retention characteristics (swrcs) from basic properties on a typical alfisols in unilorin teaching and research farm. unpublished m.sc. report of the department of agronomy, university of ilorin, ilorin, nigeria. asae standards. 2000. uniform terminology for agricultural machinery management. asae s495 dec99. pp. 342. bouckaert, rr. 2003. choosing between two learning algorithms based on calibrated tests. in proceedings of 20th international conference on machine learning. pp. 51 – 58. gee, gw. and or, d. 2002. “particle size analysis,” in: dane, j. h., toop, g. c. (eds.), methods of soil analysis part 4, sssa. book series no.5. soil sci. society of am., madison, wi, usa pp. 255-293.http://www.westgard.com/lesson42.html. accessed 02/12/2015. ikpo, c. and ifem, jlc. 2005. fuel consumption of tractors – steyr 768 & 8075 during tillage operations in makurdi, benue state. proceedings of the nigerian institution of agricultural engineers, 27: 60 – 63. james, g., witten, d. hastie, t. and tibshirani, r. 2013. an introduction to statistical learning with r application. springer texts in statistics 103, doi 10.1007/978-1-4614-7138-7_1, © springer science + business media, new york. http://www.westgard.com/lesson42.html http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 8-19. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yemibamigbedjdoyelade@gmail.com 19 klenin, ni., popov, if. and sakun, va. 1985. agricultural machines: theory of operation, computation of controlling parameters and condition of operation. america publication. new delhi. pp 15 – 18; 54 – 58. kudabo, ea. and gbadamosi, l. 2012. effects of forward speed on the performance of a disc plough. journal of science and multidisciplinary research, 4: 25 – 32. macmillan, rh. 2002. the mechanics of tractor-implement performance: theory and worked examples. a textbook for students and engineers. printed from: http://www.eprints.unimelb.edu.au. meshack-hart, et. 1997. selection of tractors for tillage operations in rivers/bayelsa state of nigeria. proceedings of the nigerian society of agricultural engineers (nsae), 19: 28 – 32. oyelade, oa. 2016. modelling of tractor fuel consumption for tillage operations in a sandy loam soil. unpublished ph.d. report of the department of agricultural and biosystems engineering, university of ilorin, ilorin, nigeria. rnam. 1983. regional network for agricultural machinery test codes and procedures for farm machinery. technical series no. 12. general guidelines in the use of test codes. serrano, jm., peca, jo., silva, jr. and luis, m. 2009. the effect of liquid ballast and tyre inflation pressure on tractor performance. biosystems engineering 102(1):51-62. sirelkatim, ka., alhashem, ha. and saeed, mo. 2001. the effect of some operating parameters on field performance of a 2wd tractor. scientific journal of king faisal university (basic and applied science), 2 (1): 153 – 166. soil survey staff. 1975. soil taxonomy, a basic system of soil classification for making and interpreting soils. handbook no. 436, usda, us government printing office, washington dc. udo, dc. and akubuo, co. 2004. fuel consumption in tillage operation for sandy loam soil. proceedings of the nigerian institution of agricultural engineers (niae), 26: 74 – 83. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):293-308 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 293 original research article performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors i. ajunwa*, d. s. yawas, d. m. kulla, m. b. abdullahi, i. u. ibrahim and m. iorpenda jnr. (department of mechanical engineering, ahmadu bello university, zaria) *corresponding author’s email address: unclezick@yahoo.com; unclezicko@gmail.com 1.0 introduction in the nations of world with less improved facilities, agricultural products are being wasted year in year out due to lack of proper handling. bhardwaj et al. (2017) and chan et al. (2015) reported that a significant percentage of agricultural losses are related to improper and/or untimely drying of foodstuffs such as cereal grains, pulses, tubers, meat, and fish among others. estimate of the wastages of this agricultural produce is cited by toğrul and pehlivan (2004) to be of order of 40% emphasizing that under very adverse conditions, it can be as high as 80%. the use of article information abstract the need of food preservation cannot be over-emphasised. crops need to be processed and preserved in times of their abundance to ensure for life and specie sustainability in times of scarcity. flat plate collectors (fpcs) are often made fixed and the positions of reflectors used on them are not normally specified; in this paper, a report of an experimental test of an indirect solar dryer whose fpc is operated manually in a single axis to track the sun is presented. to avoid incurring extra cost on the existing design, the fpc was rather made to be operated manually instead of the automation process. using the engineering equation solver (ees) and the trnsys 16 softwares, the angular positions of reflectors placed east and west on the fpc were simulated for the first quarter months of the year of the experiment – this included the month of the test. this is to ascertain the best positions for the reflectors in other to achieve maximum insolation. for the month of the test, march, the angular positions of the reflectors placed east and west of the fpc were found to be 40° and 80° respectively relative to the horizontal plane. the performance of the solar dryer in terms of the percentage moisture loss, drying rate, collector efficiency and drying efficiency was evaluated when the fpc was fixed and when it was made to track the sun and the results obtained there from were compared. in comparison, it was found that the dryer tested by manually tracking the sun increased the total percentage moisture loss by 5.11%; the total drying rate by 2.10×10-5 kg/s; the average collector efficiency by 3.92% and the overall drying efficiency by 2.0% as compare to when the fpc was fixed, i.e. not tracking the sun. the indirect solar dryer with the ability to manually track the sun in a single axis using the meteorological conditions of zaria, nigeria was therefore found to have increased the performance of the system dryer as compare to when tracking of the sun was not done. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 may, 2019 revised 16 january, 2020 accepted 01 february, 2020 keywords: indirect solar dryer flat plat collector manually tracking angular positions mailto:unclezick@yahoo.com mailto:unclezicko@gmail.com http://www.azojete.com.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 294 dryers was suggested to serve as a solution to post-harvest wastages and contribute to the availability of food in developing countries (toğrul and pehlivan, 2004). in order to reduce postharvest losses and enable farmers increase the quality of their products, weiss and buchinger (2002) also suggested that the use of locally manufactured low cost solar dryers could reduce postharvest losses. one major component needed by a solar dryer is the flat plate collector (fpc). the fpc or solar collector plate serve the purpose of heating up the ambient air before it is passed into use (ajunwa et al., 2018); that is to say it helps in harnessing the solar insolation and raising its temperature above the ambient before it is passed into the drying chamber. the intensity of solar radiation falling on a fpc can be improved upon by use of reflective mirrors as reported by maiti et al. (2011) and shahat et al. (2016). the flat plate collector can be made to track the sun. tracking of the sun was is reported to avails extra energy for use. for instance, in their report, kancevica et al. (2012) emphasized that “the task of the tracking system is to rotate and orientate the equipment of the solar energy collector so that the collector’s surface is placed perpendicular to the solar rays all day long to receive maximum solar energy”. thus the primary benefit of a tracking system is to collect solar energy for the longest period of the day. solar tracking, thus, ensures that the maximum amount of sunlight strikes the collectors throughout the day. it has also been estimated that the use of a tracking system, over a fixed system, can increase the power output by 30 60% (mayank, 2014). tracking can be achieved manually or by automation. apart from adding to the initial cost of the system, mayank (2014) reported that the automated trackers have the disadvantages of additional cost due to regular repair and maintenance. to avoid the aforementioned problems and yet have optimum tracking effect, the manual tracking system was rather reported in this paper. going round the world, a lot of solar dryers have been developed and tested for different applications. these include the works of shanmugam and natarajan (2007) that built and tested an indirect forced convection with desiccant integrated solar dryer. the useful temperature rise of about 10 ºc was achieved with mirror, which reduced the drying time by 2 hours and 4 hours for green peas and pineapple, respectively. the drying efficiency of the system varied between 43% and 55% and the pick-up efficiency between 20% and 60%. ajao and adedeji (2008) assessed the drying rates of vegetables, tubers and grain crops. they considered four tropical crops in the passive type solar dryer. their report showed that high drying rate at an average dryer efficiency of 18% was recorded for yam at an average value of 9.0 g/hr while the lowest of 1.6 g/hr was recorded for pepper. bolaji and olalusi (2008) designed and constructed a simple solar dryer consisting of a black painted, aluminum heat absorber plate mounted on a well-seasoned wood. they placed a foam material having thermal conductivity of .043w/mk in the space between the inner and outer box. they found from their test that the drying rate and collector efficiency for the drying of yam chips to be respectively 0.62 kg/hr and 57.5%. they concluded by stressing that the results of their experiment demonstrated a considerably high drying rate of their device for food products and could be useful in preserving food products at safe moisture levels. mohanraj and chandrasekar (2009) developed an indirect forced convection solar dryer for drying chilies and incorporated it with sensible heat storage material. their test revealed that http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 293-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 295 the chili was dried from an initial moisture content of 72.8% to a final moisture content of about 9.2% at the bottom tray and about 9.7% (wet basis) on the top tray. with the inclusion of the heat storage material (gravel), they reported an increase in the drying time by about 4 hours per day. the estimated thermal efficiency of solar dryer was about 21% and specific moisture extraction rate was about 0.87 kg/kwh as they concluded. maiti et al. (2011) designed and developed an indirect, natural convection batch-type solar dryer which they fit on the solar collector with north-south reflectors. they reported that with the help of the reflectors, the solar collection efficiency with no load was enhanced from 40.0 to 58.5%. they dried a popular indian wafer, ‘papad’, with desired moisture content of 12%, wet basis, which was achieved within 5 hours with their dryer. amedorme et al., (2013) designed and constructed a simple and inexpensive forced convection indirect solar dryer for drying moringa leaves. they dried a batch of moringa leaves, 2 kg by mass, with an initial moisture content of 80% wet basis from which 1.556 kg of water was needed to be removed to have it dried to a desired moisture content of 10% wet basis. eke and arinze (2011) developed a direct mode natural convection mud type solar dryer used for drying maize. the moisture content was reduced from 29 to12% on wet basis from the conducted test. the dryer in comparison, achieved 55% saving in drying time against the open sun drying. the drying efficiencies for the dryer and the open sun drying systems were respectively reported to be 45.6% and 22.7%. adelaja and babatope (2013) developed and evaluated a thermal and drying analysis on a natural convection indirect type of solar dryer which they tested by drying plantain fillets. the collection efficiency and system efficiency were respectively found to be 46.4 and 78.73% from their test. the collector also had moisture removal efficiency of 77.5% achieved in 20 hours. paul and singh (2013) designed and developed a forced convection mirror booster based solar dryer for drying red chilli (capsicum annum) in madhya pradesh, india. the test showed a reduction in drying time of chillies to be nearly 83% in comparison to open sun drying. the average time required to dry 1.5 kg chillies from moisture content of 89.09% to 4.36% on wet basis was reported to be 16 hours. rajagopal et al. (2014) developed an indirect forced convection solar dryer incorporated with evacuated tube collector used for drying of copra. for the test, there was a reduction from 52.3 to 8% of the moisture content of copra. it was observed also that the drying time in forced convection mode was less than the natural convection mode. chan et al. (2015) designed and constructed a recirculation type of solar dryer for drying rough rice. in the testing of the dryer, the experiment was performed under two different loads. in the first case, with load 104 kg, the moisture content was reduced from 28.4% to 14.3% in 5 hours at a drying air temperature of 50 °c, the efficiency here was 23.6%. while in the second drying process, with a load of 200 kg, the moisture content was reduced from 27.3% to 14.6% within 8 hours, with 35.7% efficiency under drying air temperature of 47 °c. fudholi et al. (2016) carried out a novel design of solar dryer for salted catfish in perlis, malaysia. in the experimentation, 200 kg of salted catfish divided equally were placed on 8 trays with the drying temperature fixed at 50 °c. the moisture content was reduced from 73% (wb) to 30% file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 296 (wb) within 18 hours. 6.3 kg/h and 0.385 kg/kwh were respectively obtained as the moisture extraction rate and specific moisture extraction rate. jadhav et al. (2017) presented the design, construction and performance of a mixed-mode solar dryer. results obtained from the test of the dryer showed that the temperatures inside the dryer and that of the collector were much higher than the ambient temperature during most hours of the day-light. the temperature rise inside the drying cabinet was up to 74% for about three hours immediately after 12.00 noon. bhardwaj et al. (2017) carried out an experimental investigation of an indirect solar dryer integrated with phase change material for drying valeriana jatamansi in himachal pradesh (india). the test for the system showed that, the moisture content of rhizomes reduced from 89% to 9% in 5 days as compared to heat pump drying and shade drying, which respectively took 8 days and 14 days. the drying time using phase change material reduced by 37.50% and 64.29% when compared to heat pump drying and shade drying, respectively. abubakar et al. (2018) developed and tested a mixed-mode solar dryers for crop drying with and without thermal storage materials. it was observed that the average drying rates, collector efficiencies, and drying efficiencies of the solar crop dryers with and without thermal storage for june and august 2016 test period were 2.71× 10−5 kg/s and 2.35 ×10−5 kg/s, 67.25% and 40.10 %, 28.75 % and 24.20% respectively. for the experimental results, the efficiency of the dryer with the storage materials is enhanced by about 13 % due to the thermal storage used. umar et al. (2018) designed and manufactured a solar dryer at fadis agricultural research center workshop of oromia. for no load test, the collector raised the ambient temperature of air of 20°c to 41°c to a warm air of 28°c to 64°c between the morning and midday. onion sliced at 3 mm thickness were loaded at a rate of 4 kg/m2 and dried in the dryer from an initial moisture content of 87.10% (w.b) to 9.1% (w.b) in 10 hours. for the works reviewed, there are no attempts by the researchers in trying to maximise the solar radiation available by day by tracking the sun with the fpc that has reflectors positioned east and west at optimised (simulated) angular positions. shahat et al. (2016) studied the effect of four drying methods such as natural sun drying and electric hot air drying method and compared with solar drying with or without reflective mirrors on grapes and apricot fruits. the results obtained indicated that, drying rate of tested samples using solar drying with reflective mirrors and electric hot air drying methods were faster than those without reflective mirrors and natural sun drying. they also reported that a useful temperature rise of about 10 ºc was achieved with the mirrors. lingayat et al. (2016) designed and developed an indirect type solar dryer to dry agricultural products. the experimental test of the dryer showed that moisture content of banana was reduced from initial value of 356% (db) to final moisture content of 16.3292%, 19.4736%, 21.1592%, 31.1582%, and 42.3748% (db) for tray 1, tray 2, tray 3, tray 4, and open sun drying respectively. the average thermal efficiency of the collector was found to be 31.50% and that of drying chamber was 22.38%. musembi et al. (2016) designed and fabricated an indirect natural convection updraft solar dryer suit for mid-latitude applications. the dryer was experimented by drying sliced apples of 2.5 mm thickness spread over the drying trays. for the experiment, 886.64 g of fresh apple with 86% moisture content were dried to a moisture content of 8.12 % (wet basis) within 9 hours 20 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 293-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 297 minutes at an average irradiance of 534.45 w/m2. the overall dryer efficiency was found to be 17.89%. puello-mendez et al. (2017) constructed and tested a plastic roof solar dryer for drying cocoa beans. the test showed that the dryer was able to dry cocoa beans from 58 to 7 % in 6 days. while the greenhouse drying took only 4 days and produced better quality cocoa beans, protected from direct solar radiation, environmental pollution and animal contact. khan et al. (2018) developed and carried out a study on an innovative solar sustained maize dryer along with screw conveyor for unloading the grain and central air perforated duct (throughout aeration chamber length). the dryer was evaluated using 758 kg of freshly harvested maize at moisture content of 24% (wet basis). it was found to have a drying time of 27 hours in drying the whole maize from a moisture content of 24% to 13%. deshmukh et al. (2018) evaluated the performance of pop can solar dryer which worked as indirect type passive mode without thermal energy storage for the drying of products. all experimentations were carried at amravati maharashtra india. they reported that the use of pop-corn solar dryer reduced the drying time significantly and essentially provided a better product quality compared with conventional drying method. this paper presents a system of solar dryer that is able to track the sun manually. the manual tracking system was rather chosen (instead of the automated system) to minimize the cost of production and that of regular repair and maintenance mayank (2014) and yet have optimum tracking effect. 2. materials and methods 2.1 description of the dryer system the system is made up of the flat plate collector, the drying chamber and the biomass combustion chamber as shown in figure 1. figure 1: schematic diagram of the dryer system file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 298 2.1.1 the flat plate collector (fpc) this avails the platform where the solar energy is harvested for drying. its parts include: a. absorber plate: this was made of aluminum sheet metal painted black and of length 797 mm, width 531 mm and thickness 0.08 mm. b. glazing or glass cover: this was made of the transparent glass; dimensioned to the length of 797 mm, width 531 mm and thickness 4 mm. c. reflectors: two back silvered glasses each with dimensions 797 mm x 265.5 mm were used on both sides of the fpc to serve as reflectors and cover to the fpc. 2.1.2 drying chamber this chamber holds the product which is being dried. it is made up of the following parts: a. dryer’s body: the body of the dryer was made of plywood of thickness 10 mm with 753 mm x 531 mm dimensions. b. trays: this was made using the wire mesh with dimensions of 753 mm x 531 mm. c. chimney: a mild steel of 2 mm thickness, diameter 53.1 mm and height 407 mm shaped into a cylindrically form was used to make the chimney. this paper presents only the parts and results of the solar dryer (excluding the biomass chamber). 2.2 working-principle-of-the dryer-system the fpc which is tilted at 20° to the horizontal ajunwa et al. (2018) was opened at one end for inlet air and the other end linked to the drying chamber. the fpc energized by the sun’s rays entering through the glazing cover, heats up the fpc by converting high frequency, low wavelength radiations from the sun into low frequency, high wavelength radiations (greenhouse). this energy is boosted by the inner surface of the collector made of aluminum sheet painted black and the reflector mirrors; the trapped energy then heats up the air inside the fpc, creating an updraft of the heated air into the dryer where it is circulates removing water from the product being dried and finally expelled through the chimney. this whole process underwent a repetition until the crop being dried was dried to the desired moisture content. 2.3 trnsys/ees system model for optimum reflector angle trnsys (transient system simulation) and ees (engineering equation solver) were used to model and simulate the best positions of the east and west mirrors placed on the fpc for optimum absorption. average daily/hourly radiation over a time period was generated from the typical meteorological year (tmy) weather data of (the location of the experiment) zaria, nigeria (latitude 11.2 °n and longitude 7.8 °e) using solar radiation and weather data processor of trnsys software. this simulation was performed in 2018; tmy however details the collation of selected weather data for a number of years over a specific location. the ees was linked to the trnsys through the type66a. the equations governing the reflection of solar radiation from the reflectors kumar et al. (1995) and transmittance – absorptance product were modelled in ees and linked to the trnsys model as shown in figure 2. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 293-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 299 figure 2: the trnsys/ees model of the system for the reflectors positions optimization. the type tmy-2 weather data component evaluates the radiation values together with the angles associated with directions. the output was sent to the ees reflector model where the angle of incidence of reflected solar beam on the collector, and the exchange and shading factors of the reflectors were processed and returned to the trnsys environment. the transmittance – absorptance product was processed for the direct and reflected components of radiation and the output sent to the equations component which finally computes the absorbed solar radiation. the result was integrated by the type24 quantity integrator. this integrates the absorbed energy over a period of time indicated in the control card. the result is finally displayed in the type 25c printer component. 2.4 manual tracking motion of the flat plate collector (fpc) this involves manually reorienting the fpc such that the sun shines directly onto it. the fpc is adjusted by 15° for every 1 hour movement of the sun. two discs, one affixed with a bearing at the middle and welded to the tip of the collector plate beneath it and the other with a rod at the middle and welded to the collector frame were made to mesh together with a clearance for easy east to west (and vice versa) movement. these discs were bored at the edges with 24, 15° 5 mm holes apart to help in the hourly manual repositioning of the collector plate using nut and bolt, with a hole that makes the collector plate stay horizontally upward by 12.00 noon (serving as the reference point). the fpc is positioned three steps, 45°, from its horizontal position facing eastward (this is its default state by 9.00 am). during the period of drying, 9.00 am to 5.00 pm, the fpc is tilted a step, 15°, for every one hour movement of the sun toward the west and finally repositioned to its default state after the day’s drying; waiting for the commencement of the next day’s drying process. the pictorial views of the collector facing the sun at noon time, before noon time and after noon time are shown in figure 3. 2.5 experimentation-of-the-system 2.5.1 instrumentation of the system dryer the sl-100 solarimeter: this measures the combined direct and diffuse solar radiation of the sun and was used to measure the solar radiation on the glazing surface of the collector. thermocouple wire and digital thermometer: the ambient air temperatures, collector outlet air temperature and the drying chamber temperature were all measured using copper/constantan file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 300 thermocouple wires and a digital kane-may 340 thermocouple device that measures temperature either in celsius or fahrenheit. the digital camry weighing scale: this was used to measure the weight loss of the tomato slices. the el-3 aero vane digital anemometer: this was used to measure the wind speed of the surrounding ambient air. 2.5.2 testing of-the-dryer the ashrae/ansi 93-2003 standard test procedure, which requires that during a collector test, the operating collector to be exposed to solar radiation and the fluid inlet and outlet temperatures, the fluid flow rate, radiation on the collector, ambient temperature and the wind speed be measured and recorded as recommended by duffie et al. (2013) was followed. the testing of the dryer was carried out in march, 2018 in the department of mechanical engineering, ahmadu bello university, zaria, nigeria (latitude 11° 7’ 48’’ and longitude 07° 41’). the moisture removal and thermal analysis which are the basic standard procedures for evaluating solar dryer performances as recommended by leon et al. (2002) were also used in evaluating the dryer. the main aim of the experimental setup (as shown in figure 3) was to determine the performance of the solar dryer at hourly motion of the sun by monitoring the drying rate of 6 kg tomato sample placed in the drying chamber. figure 3: pictorial (real) views of the fpc (a) facing the sun at noon time (b) facing east before noon time (c) facing west after noon time. the drying procedure involved exposing the solar dryer to solar radiation and loaded with 2.0 kg of tomato slices of about average thickness of 5-10 mm on each of the three trays. in order to maximize insolation centration on the fpc, in this work, reflective mirrors were used on the east and west sides of the fpc at optimized angles of the first quarter months of the year which included the month of the test (march). energized air (boosted by the black painted aluminum plate and reflector mirrors) from the fpc was siphoned into the drying chamber where it was circulated thereby transferring energy to the sliced fruits and abstracting moisture from it and finally expelled through the chimney. this whole process underwent a repetition until the fruits were dried to the desired moisture content. at an hourly interval, the ambient air temperature, temperatures of the air exiting from the collector, and that of trays 1, 2 and 3, and the hourly a cb http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 293-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 301 weight loss for each of the trays were recorded. the corresponding wind speed and solar radiation were also recorded. the drying started at 9.00 am and ended at 5.00 pm. 2.5.3 evaluation of the dryer the following parameters were evaluated using the equations as: a. percentage moisture content, wbm on wet basis was calculated from eqn.1 (zaman and bala, 1989): mwb = ww −wd ww × 100% (1) where; ww = weight of wet product, (kg), wd= weight of dried product, (kg) b. average drying rate, mdr was calculated from eqn. 2 (tonui et al., 2014): mdr = mw td (2) where; mw = mass of water evaporated from the product, (kg),td = drying time, (hr). c. solar collector efficiency, ηc was calculated from eqn. 3 (forson et al., 2007): ηc = m� acp(to − ta) acit (3) where;it = total solar radiation (w/m2), ta = ambient air temperature (℃), to = temperature of outgoing air from the collector (°c), m� a = mass flow rate of air (kg/s). d. dryer efficiency, ηdwas calculated from eqn. 4. (forson et al., 2007): ηd = mwlv itact (4) where; mw= mass of water evaporated, (kg),lv = latent heat of vaporization of water, t = drying time, (hours), ac= collector area, (m2). 3.0 results and discussion 3.1 simulation of the reflectors positions placed west and east of the fpc using the trnsys 16 software application, simulated energy contribution of each of the reflectors placed on the east and the west (qre and qrw) of the fpc was determined and plotted as a function of the reflector tilt angle is as shown in figures 4. – 5. figure 4: solar energy absorbed with reflector rw for the first quarter months (january to march) of the year. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 302 figure 5: solar energy absorbed with reflector re for the first quarter months (january to march) of the year. the optimum reflector angle for maximum enhancement is the value at the highest point of the curve for each month. figure 4 shows the solar energy absorbed with reflector placed to the west of the flat plate collector (fpc), rw, for the first quarter months of the year (january to march); which include the month of the experiment, march. figure 4 shows that, for optimum insolation absorption for the month of january, the reflector if placed on the west of the fpc should be inclined at 80° absorb 1019 kj/hr/m2, and at 80° to absorb 5572 kj/hr/m2 for the month of february and at 80° to absorb 6222 kj/hr/m2 for the month of march. after each of these angles of inclination however, there is a decrease in the amount of energy that can be absorbed by the reflectors. since the experiment here was carried out in march, for maximum absorption, the reflector on the west of the fpc was positioned at 80° to absorb 6222 kj/hr/m2 of energy. figure 5. shows the solar energy absorbed with reflector placed to the east of the flat plate collector (fpc), rw, for the first quarter months of the year (january to march). this was done to include the month of the experiment, march. the figure also shows that, for optimum energy absorption for the month of january, the reflector if placed on the east of the fpc should be inclined at 45°to absorb 808 kj/hr/m2, and at 40° to absorb 774 kj/hr/m2 for the month of february and at 40° to absorb 991 kj/hr/m2 for the month of march. after each of these angle of inclination, there was however a declination in the amount of energy absorbed by the reflectors. for maximum absorption, the reflector on the east of the fpc was positioned at 40° to absorb 991 kj/hr/m2 by march (month of test) for zaria metropolis. 3.2 fixed and tracking (manual) modes of the fpc figures 6 through 9 shows the line graphs for moisture content (%), drying rate (kg/s), collector efficiency (%) and drying efficiency (%) of the dryer for the experimental results for fixed and tracking (manual) modes of the fpc. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 293-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 303 fig. 6.: variation of moisture content, mc (%) with time taken (hours) for drying for fixed and manual tracking modes of the fpc. fig. 7: variation of drying rate (kg/s) with time taken (hours) for drying for fixed and manual tracking modes of the fpc. fig. 8: variation of collector efficiency (%) with time taken (hours) for drying for fixed and manual tracking modes of the fpc. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 304 fig 9: variation of drying efficiency (%) with time taken (hours) for drying for fixed and manual tracking modes of the fpc. figure 6 shows the variation of percentage moisture loss (moisture content, mc) for the experimental values for fixed and manual tracking modes of the collector plate. from figure 6 it can be observed that except for the period of 12.00 to 1.00 pm when the fixed mode of the collector plate recorded a higher value of 0.7% more than the tracking mode (both collectors being directly overhead at this time of the day); throughout the period of drying, the tracking mode system maintained a higher percentage moisture loss. while an average hourly moisture content of 4.00% was recorded for the fixed mode system, 4.64% was recorded for the tracking mode system. for the entire 8 hours drying period, 31.99% moisture content was recorded for the fixed mode while 37.10% was recorded for the manual tracking mode system with the manual tracking system performing better by 5.11%. the tracking mode system is observed to record higher values of moisture content both in the mornings and evenings of drying; this could be because of the tilting of the collector plate to harvest both the morning and the evening energies. it is observed in this work that there was a decrease in moisture (i.e. increase in percentage moisture loss) of the food product with time as also reported by paul and singh (2013), amedorme et al. (2013) and musembi et al. (2016). figure 7 shows the graph variation of drying rate for the experimental values for fixed and manual tracking modes of the collector plate. from figure 7., it can be observed that, except for the period of 12.00 to 1.00 pm when the fixed mode of the collector plate recorded a higher hourly value; throughout the period of drying, the tracking mode system maintained a higher hourly drying rate. an average hourly drying rate of 2.19×10-5 kg/s was recorded for the tracking mode system, while 1.92×10-5 kg/s was recorded for the fixed mode system. for the entire drying period, 1.54 ×10-4 kg/s drying rate was recorded for the fixed mode while 1.75 ×10-4 kg/s was recorded for the manual tracking mode system with the manual tracking system performing better by 2.10 ×10-5 kg/s. bolaji and olalusi (2008) reported a drying rate of 0.62 kg/hr (1.72×10−4 kg/s) in their designed and constructed simple solar dryer. the manual tracking mode system in this work which recorded an average drying rate of 1.75×10−4 kg/s showed a slight improvement over what is obtained by bolaji and olalusi. the results of the drying rate obtained for both the fixed and the manual tracking systems reveal a higher performance as when compare with that reported by ajao and adedeji, (2008) who obtained an average drying rate of (9.0 g/hr) 2.50×10−6 kg/s. this shows good functionality of this dryer in terms moisture extraction rate of the product being dried. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 293-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 305 figure 8. shows the graph of variation of collector efficiency for the experimental values for the test of the dryer for fixed and manual tracking modes of the collector plate. the tracking mode system is observed to record higher values both in the morning and evening of the drying, due to the harvest of the morning and evening radiation by tilting the collector plate. except for 1.00 pm, when the fixed mode system recorded a higher value of efficiency. while an average collector efficiency of 69.09% was recorded for the tracking mode system, 65.17% was recorded for the fixed mode system throughout the period of drying. while maiti et al. (2011) recorded a collector efficiency of 40.0% which was enhanced to 58.5% by the use of north-south reflectors, lingayat et al. (2016) reported an average thermal efficiency of their collector to be 31.50%; the efficiency obtained in this work shows an improvement over that reported by both maiti et al. (2011) and lingayat et al. (2016). moreover, the result here also shows an improvement of 18.77% for the fixed system and 22.69% for the manual system over that reported by adelaja et al. (2013) who reported a collector efficiency of 46.4% in their work. figure 9. shows the graph of variation of drying efficiency for the experimental values for the test of the dryer for fixed and manual tracking modes of the collector plate. from the figure (9.), it can be seen that from 10.00 am to 12.00 pm, the tracking mode recorded an average hourly drying efficiency value of 2.49% higher than the fixed mode system. by 1.00 am however, the fixed mode system recorded a drying efficiency value of 4.50% higher than the tracking mode system. between the hours of 2.00 and 3.00 pm, both modes (tracking and fixed) recorded approximately equal values. after 3.00 pm, between the hours of 4.00 and 5.00 pm, the tracking mode recorded an hourly average value of 6.19% higher than the fixed mode system. in as much as drying efficiency takes into consideration the weights of the products being dried, it also faces consistency in its graphical (values) representations since it also partly depends on solar insolation and air speed rate which varies periodically. for the entire drying period, 21.33% drying efficiency was recorded for the fixed mode system while 23.27% was recorded for the manual tracking mode system with the manual tracking system performing better by an approximate value of 2.0%. mohanraj and chandrasekar, (2009) and ajao and adedeji, (2008) respectively reported drying efficiencies of 21% and 18% in their various works; in this work, while the fixed mode system recorded an approximate same drying efficiency with that reported by mohanraj and chandrasekar, the manual tracking mode system showed an improvement of 2.27% over that reported by mohanraj and chandrasekar and an improvement of 5.27% over that reported by ajao and adedeji, (2008). the overall dryer efficiency (of 17.89%) reported also by musembi et al. (2016) showed that the dryer efficiency obtained in this work have an improvement over theirs for both the fixed and the manual tracking systems which yielded 21.33% and 23.27% respectively. the use of reflectors and the tracking system employed could have led to the dryer in this work performing better. 4. conclusion the performance of an indirect solar dryer with the ability to manually track the sun in a single axis was successfully carried out at the ahmadu bello university, zaria using the meteorological conditions of zaria, nigeria. the angular positions of the west and east mirrors placed on a flat plate collector was successfully determined for the first quarter months of the year(january to march) which include the month of the test, march. the angular positions of the west and east reflectors on the fpc were respectively found to be 80° and 45° for the month of january, 80° and 40° for the month of february; and 80° and 40° for the month of march, the month of the test. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ajunwa et al: performance improvement of an indirect solar dryer with single axis manual tracking system and angular simulation of the flat plate collector reflectors. azojete,16(2):293-308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 306 the test of the dryer carried out by tracking the sun increased its performance as compared to when drying was done without tracking. the dryer tested by manually tracking the sun increased the total percentage moisture loss by 5.11%; the total drying rate by 2.10x10-5 kg/s; the average collector efficiency by 3.92% and the overall drying efficiency by 2.0% as compare to when tracking of the sun was not done. acknowledgment the contributions of the members of technical staff of the welding and fabrication section of the department of mechanical engineering, ahmadu bello university, zaria, and the moral and financial assistance of members of my family are hereby acknowledged. references abubakar, s., umaru, s., kaisan, mu., umar, ua., ashok, b. and nanthagopal, k. 2018. development and performance comparison of mixed-mode solar crop dryers with and without thermal storage. renewable energy, 128: 285-298. adelaja, ao. and babatope, bi. 2013. analysis and testing of a natural convection solar dryer for the tropics. journal of energy, volume 2013, article id 479894:8. ajao, kr. and adedeji, a.a. 2008. assessing the drying rates of some crops in solar dryer. journal of research information in civil engineering, 5(1):1-12. ajunwa, i., yawas, ds., kulla, dm., iorpenda, mj., edet, aa. and abdullahi, mb. 2018. parametric optimisation of tilt angle, back and edge heat losses of a solar flat plate collector using matlab. national engineering conference proceedings, 14th-17th, nov., faculty of engineering, ahmadu bello university, zaria, nigeria, pp.449 – 453. amedorme, sk., apodi, j. and agbezudor, k. 2013. design and construction of forced convection indirect solar dryer for drying moringa leaves. scholars journal of engineering and technology, 1(3): 91-97. bhardwaj, ak., chauhan, r., kumar, r., sethi, m. and rana, a. 2017. experimental investigation of an indirect solar dryer integrated with phase change material for drying valerianajatamansi (medicinal herb). case studies in thermal engineering, 10: 302-314. bolaji, bo. and olalusi, ap. 2008. performance evaluation of a mixed-mode solar dryer. technical report, au journal of technology, 11(4):225-231. chan, y., dyah, n. and abdullah, k. 2015. performance of a recirculation type integrated collector drying chamber (icdc) solar dryer. energy procedia, 68: 53-59. deshmukh, sj., sardar, ad. and ingole, ss. 2018. performance and evaluation of pop can solar dryer for batch products. american journal of renewable and sustainable energy, 4(1): 1-7. duffie, ja. and beckman, wa. 2013. solar engineering of thermal processes, fourth edition, new york: wiley and sons.eke, ab. and arinze, ea. 2011. natural convection mud type solar dryers for rural farmers. nigerian journal of technological development, 8(2): 92-108. forson, fk., nazha, ma. and rajakaruna, h. 2007. modelling and experimental studies on a mixed-mode natural convection solar crop-dryer. solar energy, 81(3): 346-357. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 308 shanmugam, v. and natarajan, e. 2007. experimental study of regenerative desiccant integrated solar dryer with and without reflective mirror. applied thermal engineering, 27(8-9): 1543-1551. toğrul, i̇.t. and pehlivan, d. 2004. modelling of thin layer drying kinetics of some fruits under open-air sun drying process. journal of food engineering, 65(3): 413-425. tonui, ks., mutai, ebk., mutuli, da., mbuge, do. and too, kv. 2014. design and evaluation of solar grain dryer with a back-up heater. research journal of applied sciences, engineering and technology, 7(15): 3036-3043. umar, a., abera, s. and befikadu, d. 2018. design development and performance evaluation of solar dryer for drying onion used as powder in food. international journal of sciences basic and applied research, 38(1): 231-243. weiss, w. and buchinger, j. 2002. solar drying–austrian development cooperation. aee intec, arbeitsgemeinschft erneuerbare energie-institute for sustainable technologies. gleisdorf, feldgasse 19, astria, 110. zaman, ma. and bala, bk. 1989. thin layer solar drying of rough rice. solar energy, 42(2): 167171 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 86-94 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 86 original research article recent advances in solar drying of agricultural produce in nigeria: nspri experience *a. r. ade1., f. f. olayemi1., a. o. adebiyi1., o. m. zubair1., o. a. adeiza1. and k. c. achime2 1post harvest engineering research department, nigerian stored products research institute, km 3 asa-dam road, ilorin, nigeria. 2research outreach department, nigerian stored products research institute, km 3 asa-dam road, ilorin, nigeria. article information received october, 2018 accepted december, 2018 keywords: solar tent dryers green house film drip acrylic temperature relative humidity abstract agricultural products are dried to enhance storage stability, in order to reduce post harvest losses, minimize packaging requirement and reduce transport weight. crop drying through the sun is the most common practice in the country due to its no energy cost but often result in poor quality, unhygienic and contaminated products. this has been a major threat to food safety. energy consumption and quality of dried products are critical parameters in the selection of drying process. an optimum drying system for the preparation of quality dehydrated products is supposed to be cost effective with less drying time and damage to the product. to reduce the energy utilization and operational cost as well to further produce high quality safe products, new trends in solar drying system were developed by the nigerian stored products research institute (nspri) in order to proffer solutions to the threat in food safety as well as farmers and processors quest for drying with minimal energy cost. the technologies include mobile solar tent dryers, green house solar tent dryers and parabolic solar tent dryers. these entire dryers have great scope for the production of quality dried products and powders. these advancements have taken the advantage of material selection, design calculations to improve on the technology in order to achieve quality output in terms of environmental parameters and product quality. the advancement has also taken care of times of low solar irradiance especially during the rainy season which is highly humid. the temperature range obtained from the mobile, green house and parabolic solar dryers are 20 – 59.5°c, 21.5 68°c, and 25-78°c respectively while their respective average relative humidity are 71.64%, 60.21%, 49.77%. the ambient temperature range and relative humidity are 20 – 42.5°c and 74.88%. experimental studies on the performance of the varied solar tent dryers were conducted using chilli pepper, yam, meat, fish, vegetables and plantain have been carried out the beef meat, chilli pepper and telefeiria occidentalis vegetable were dried in the mobile solar tent dryer, greenhouse solar dryer and parabolic solar dryer. the beef of 71.243% initial moisture content was dried to 12.15%, 12.01% and 10.09% in the aforementioned respective dryers within a period of 5 days. also the chilli pepper of 89.40% initial moisture content was dried to 12%, 11.3% and 9.3% moisture content respectively in the dryers within a period of 8 days; while the telefairia occidentalis vegetable of 11.0% initial moisture content was dried within a period of 5 hours to 6.0%, 5.5% and 4.0% moisture content © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: snoyeengr@gmail.com 87 1.0 introduction the preservation of foods by drying is without doubt the oldest method practised and it remains most commonly used method worldwide (mujumdar and sakamon, 2012). drying, which affects the physical parameters food products, by removal of water causes weight reduction and increased storability (robert et al,. 2014). while grains and pulses are the most important, in term of tonnage, the range of products dried is wide and includes meats, fish, fruits, vegetables, spices, and nuts. the conventional drying system to preserve fruits, vegetables, grains, fish, meat, wood and other agricultural products is sun drying which is a free and renewable source of energy. but, for large-scale production, there are various known limitations of sun drying as damage to the crops by animals, birds and rodents, degradation in quality due to direct exposure to solar radiation, dew or rain, contamination by dirt, dust or debris. also this system is labourand time intensive, as crops have to be covered at night during bad weather, and have to be protected from attack by domestic animals. there is also a chance of insect infestation and growth of micro-organisms due to non-uniform drying. the advancement of sun drying is solar drying systems whereby products are dried in a closed system in which inside temperature is higher (rajkumar, 2007; kumar and shrivastava, 2017). major advantage includes protection against flies, pests, rain or dust. several significant attempts have been made in recent years to harness solar energy for drying mainly to preserve agricultural products and get the benefit from the energy provided by the sun. sun drying of crops is the most widespread method of food preservation in nigeria because of solar irradiance being very high for most of the year. due to no energy cost, it is more beneficial to the small scale farmers who can’t afford the electricity or other fuel for drying. if it is necessary to dry product in the night or during bad weather, an additional bio-fuelled heater can be used for heat supply. the high temperature dryers used in industrialized countries were found to be economically viable, in developing countries only on large agro sectors and generally it is not affordable by small and medium entrepreneurs because of high cost and process variability (ibrahim et al, 2009). therefore, the introduction of low cost and locally manufactured solar dryers provides a promising alternative to reduce the grand postharvest losses. the opportunity to produce high quality marketable products appears to be a chance to improve the economic status of the farmers. taking into account the low income of the rural population in developing countries, the relatively high initial investment for solar dryers still remains a barrier to a wide application (chapman et. al., 2006). however, if it is manufactured by locally available material such as wood, glass etc., it will be economically affordable for the farmers. amongst all, with the submission of kumar and shrivastava, (2017), the objective of a solar dryer is to provide ample amount of heat more than ambient heat under given humidity. this heat increases the vapour pressure of the moisture confined within the product and decreases the relative humidity of the drying air as to increase the moisture carrying capacity of the air. 2.0 description of solar dryers 2.1 mobile solar tent dryer (mstd) a mobile greenhouse solar tent dryer (mstd) of 8ft x 4ft is made of polyurethane insulators. this material makes up the walls and floor of the solar tent dryer. it is comprised of a drying platform made of steel with 6 drying trays. the inner surfaces are painted black to increase the rate of heat absorption while the top frames were made of ½ inch galvanised hollow pipes to form arcs which serve as a support for the transparent sheet/film. the top of the mstd is installed with a pneumatic extractor fan which absorbs the moisture from the products being dried (plate 1). all https://www.omicsonline.org/open-access/effect-of-different-drying-method-on-volatile-flavor-compounds-of-lactarius-deliciosus-2157-7110-1000615.php?aid=78374 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ade, et al: recent advances in solar drying of agricultural produce in nigeria: nspri experience. azojete, 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 88 the parts of the mstd are dismountable for easy carriage from one location to the other and better erected in an east-west direction for effective solar radiation. plate 1: nspri’s mobile solar tent dryer 2.2 greenhouse solar dryer the greenhouse dryer was designed to combines the function of the solar collector with a greenhouse system. the roof and wall of this dryer can be made of transparent materials such as glass, fibre glass, uv stabilized plastic or polycarbonate sheets. the transparent materials are fixed on a steel frame support or wooden roofs with bolts and nuts and sealed to prevent humid air or rain water leaking into the chamber other than those introduced from the inlet opening. the surface of the floor is painted black in order to increase absorption rate. inlet and exhaust fans are placed at proper position within the structure to guarantee even distribution of the drying air. nspri has developed a natural convection greenhouse dryer with dimension (12 x10)ft2 and dwarf wall of 3.3ft high (plate 2). the drying chamber consists of two parallel rows of 4 drying platforms made up of 24 trays with an effective drying space of 112ft2. the construction materials were greenhouse film, wooden supports, a manual extractor fan, wooden drying racks with galvanised mesh as trays, a black surface painted with food grade enamel paint. this dryers were erected in east-west longitudinal and north south width direction for efficiency. the floor of the solar dryer is made of concrete floor sandwiched with a polyurethane material to serve as an insulation to prevent heat sink and painted with black food grade enamel paint. the drying chamber is made of 24 trays and a wind power extractor fan to remove moisture out of the drying chamber, 6 vents to induce required air flow in the system, a black surface to absorb heat energy, and a greenhouse film to trap solar radiation. air is drawn through the dryer by natural convection or sometimes by a fan. it is heated as it passes through the collector and then partially cooled as it catches moisture from the material. the green house film which is the transparent material is laid on the wooden roof. the inclined transparent roof allows solar radiation over the product. vents with shutters at the outer length sides of the building regulated the air inlet while a pneumatic extractor fan is place at the centre of the ridge of the roof to extract moisture from the products being dried. as this heated air rises and flows up the hurricane to the outside of the dryer, fresh replenishing air is drawn in through the vents for the drying process to continue. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: snoyeengr@gmail.com 89 figure. 2: the nspri’s greenhouse solar tent dryer 2.3 parabolic greenhouse solar dryer (pgsd) nspri has developed a parabolic greenhouse solar tent dryer. the pgsd is a 26ft x18ft with an effective drying area of 22ft x14ft as depicted in (plate 3). the frame supports are made of steel which had been shaped into a parabola of height 7.5ft. it has 2 drying racks made of steel which comprise of 56 trays with an effective drying space of 224ft2. the floor of the pgsd is a concrete floor sandwiched with polyurethane to avoid heat sink. the concrete floor is tiled with glazed black tile which was painted with food grade black enamel paint. the transparent material is made of a 2mm thick acrylic material with the trademark name perspex. the perspex sheet were laid on the parabolic frame support and fixed with bolts and nuts. the pgsd is installed with 2 blowers powered by 100amperes solar battery which is being charged by 2 units of 180w solar panels. these blowers serve as a dehumidifier which will enhance the drying process during the rainy season. the top of the pgsd is also installed with 2 units of pneumatic extractor fans of diameter 18’’ to aspirate the moisture being driven out by the hot air from the products undergoing drying process. plate. 3: nspri’s parabolic greenhouse solar tent dryer 3.0 evaluation of the solar dryers 3.1 evaluation of the solar dryers at no-load test the solar dryers were evaluated at a no load test. the dryers were installed with data loggers to record the temperature and relative humidity of the solar dryers and the ambient conditions and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ade, et al: recent advances in solar drying of agricultural produce in nigeria: nspri experience. azojete, 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 90 comparisons of their environmental conditions were defined as shown in figure 1, 2, 3, 4 and table 1. 3.2 evaluation of the solar dryers loaded with agricultural products the following products telefaria occidentalis, meat and chilli pepper were dried using the solar dryers. the samples of products were sorted, cleaned and weighed. the initial moisture content of the products were also determined using the oven dried method as prescribed by asabe 2007 prior to drying in the solar dryers. the vegetables were sorted, washed, drained and shredded with knives into thickness of 10mm. its moisture content were determined using the oven method and products were weighed and put in dryers simultaneously to dry appropriately. also weighed portions were kept in the open sun as control. weights of the vegetables were monitored periodically. the beef meat was procure and cleaned to remove fat deposits. meat was thinly filleted into 2mm. the moisture content was determined using the oven method. meat was weighed, spread on trays in all the solar dryers and also in the open sun as control. weights were monitored periodically. the chilli pepper were procured, sorted, cleaned, and blanched at a temperature of 80°c. moisture contents of pepper was determined using the asabe 2007 standard, weighed and spread on trays in the solar dryers and also in the open sun simultaneously as control. the final moisture contents of the products and the duration of the drying from the different solar dryers are depicted in table 2. 4.0 results figure. 1: the no load test of the environmental conditions of the mobile solar tent dryer for duration of 5 days. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: snoyeengr@gmail.com 91 figure. 2; the chart of the no load test of the environmental conditions of the greenhouse solar tent dryer for duration of 5 days figure. 3: the no load test of the environmental conditions of the parabolic solar dryer for duration of 5 days figure. 4: chart of environmental conditions of the ambient file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ade, et al: recent advances in solar drying of agricultural produce in nigeria: nspri experience. azojete, 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 92 table 1: f-test of the environmental conditions of all the solar dryers in nspri dryers temperature oc humidity % dew point oc mobile tent 33.28±12.61b 70.15±30.68c 24.24±2.48b greenhouse solar tent 35.72±13.67b 60.48±25.44 b 24.26±3.32b parabolic 40.5±15.15c 48.49±23.25a 23.96±2.17b ambient control 28.39±5.06a 63.85±26.87d 23.17±0.78a f-value 31.354 44.244 8.502 sig. value 0.000 0.000 0.000 environmental conditions (columns) with the same alphabet are the same while those with different alphabet are different at pvalue=0.05 ho: there is significance difference in the environmental conditions h1: there is no significance difference in the environmental conditions table 2: moisture contents of different products dried in the solar dryers moisture contents of products products fresh products % parabola % greenhouse dryer % mobile solar dryer % control % drying duration beef (meat) 71.243 10.09 12.01 12.15 71.243 5 days chilli pepper 89.4 9.3 11.7 12 27.67 8 days telefairia occidentalis vegetable 11 4 5.5 6 6.3 5 hours 4.0 discussion the different solar dryers developed by the nigerian stored products research institute have proven to have better environmental conditions in terms of temperature and relative humidity for drying of agricultural produce. the no load test carried out on the mstd depicted a minimum temperature of 20.4°c and a maximum temperature of 59.5°c with an average of 32.49 ± 12.10°c. the relative humidity recorded a mean relative humidity of 71.64 ± 29.65%. the graphical illustration depicted in figure 2 for the greenhouse solar dryer shows that the temperature range is 21.5-68°c and a mean relative humidity of 60.21% while the figure 3 for the parabolic greenhouse solar dryer has a temperature range of 25.0 -78°c. it has an average temperature of 39.4±14.24°c. the relative humidity had a minimum of 14.5% and a maximum of 83.5% and mean value of 49.77 ± 22.64%. the ambient environmental conditions as illustrated graphically in figure 4 has an average temperature of 28.56 ± 5.15°c while it has a minimum and a maximum temperature of 20°c and 42.5°c respectively. it has an average relative humidity of 74.88 ±17.94%. the statistical analysis to compare the environmental conditions in the different solar dryers which are implied in table 1 above indicates that in terms of temperature, there is no difference in the mobile solar tent and greenhouse solar tent while a significant difference exists between http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: snoyeengr@gmail.com 93 the temperature obtained in the parabolic solar dryer and other solar dryers. also there is a significant difference in the relative humidity observed in all the dryers as indicated in table 1. the parabolic solar dryer has the highest temperature followed by solar tent but the least is control followed by mobile. also the parabolic solar dryer has the least relative humidity while the mobile solar tent has the highest humidity followed by control. these environmental conditions exhibited by the parabolic solar dryer makes it highly effective for high moisture crops. in the advances, the average relative humidity in the greenhouse parabolic solar dyer is 48.49%. this indicates that the products that will be obtained in the parabolic solar dryer can be considered safe from a microbiological point of view since they are characterized by a low water activity (aw), and usually no growth occurs below water activity of about 0.62 (sagar and kumar, 2010). the table 2 which indicate the moisture contents and the drying duration of the agricultural products (beef meat, chilli pepper, and telefairia occidentalis vegetable) showed that products dried well in all the solar dryers. the beef meat, chilli pepper and telefeiria occidentalis vegetable were dried in the mobile solar tent dryer, greenhouse solar dryer and parabolic solar dryer. the beef of 71.243% initial moisture content was dried to 12.15%, 12.01% and 10.09% in the aforementioned respective dryers within a period of 5 days. also the chilli pepper of 89.40% initial moisture content was dried to 12%, 11.3% and 9.3% moisture content respectively in the dryers within a period of 8 days; while the telefairia occidentalis vegetable of 11.0% initial moisture content was dried within a period of 5 hours to 6.0%, 5.5% and 4.0% moisture content. among solar dryers, the parabolic solar dryer attained a lower moisture content followed by those in the green house dryers, that of the mobile solar dryers and the control which were placed under direct sun. this implies that the parabolic solar dryer has the best and optimal performance as compared with the other solar dryers. it is therefore imperative to know that the choice of materials used in the parabolic solar dryers have given it an advancement over the two other solar dryers. 5.0 conclusion various model of solar dryers developed by nspri was found to have better performance in comparison to the conventional open air system practice. the choice of the different construction materials for the solar tent dryers developed by nspri has played a very major role in the achievement of the optimal environmental condition gotten in the dryers. it has also further enhanced the advances in the development of solar dryers. these advances, which has gotten to the height of the parabolic greenhouse solar dryer, although expensive but with a higher life span has made it possible to be able to carry out drying process even in the humid season of the year; thereby taking care of the shortcomings of the low solar irradiance. references asabe standards 2007. d245.6. moisture relationships of plant based agricultural materials and their products. st. joseph mich; asabe kumar, a. and shrivastava, v. 2017. historical trends and recent developments in solar greenhouse dryer operated under active mode: a review. indian journal of science and technology, vol 10(33), 10.17485. mujumdar, as. and devahastin, s. 2012. fundamental principles of drying. department of mechanical engineering national university of singapore ay 2011/2012 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ade, et al: recent advances in solar drying of agricultural produce in nigeria: nspri experience. azojete, 14(sp.i4):86-94. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 94 banout j. havlik j., kulik m., kloucek p. and lojka b. 2010. effect of solar drying on the composition of essential oil of sacha culantro (eryngium foetidum l) grown in the peruvian amazon. j food process eng 33: 83-103. boughali, s., benmoussa, h., bouchekima, b., mennouche, d. and bouguettaia, h. 2009. crop drying by indirect active hybrid solar electrical dryer in the eastern algerian septentrional sahara. solar energ 83: 2223-2232. chapman, k., twishsri, w., marsh a, naka, p. and ngangoranatigarn, p. 2006. robusta coffee drying alternatives in south thailand international. ibrahim, m, sopian, k, daud, wrw, alghoul, ma. 2009. an experimental analysis of solar-assisted chemical heat pump dryer. int j lowcarbon technol 4: 78-83. jayaraman p. and gupta, d. 1995. handbook of industrial drying. marcel decker inc, new york. olayemi ff. and akinnusi o. 1991. development of low cost dryer for humid area of nigeria. annual report of nigerian stored products research institute. rajkumar, p. 2007. drying kinetics of tomato slices in vacuum assisted solar and open sun drying methods. drying technology 25: 1345-1357. robert, d., stephanie, c., stephanie j., and buddhi l. 2014, food processing: principles and applications, second edition. edited by john wiley & sons, ltd. published by john wiley & sons, ltd. sagar, vr., suresh kumar, p. 2010. recent advances in drying and dehydration of fruits and vegetables: a review. journal food sci. technol. 47(1):15–26. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 586-597 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 586 original research article stabilization of laterite soil with eggshell powder and sodium silicate used as fill material in road construction j. a. oke*1 and m. k. olowoyo2 (1, 2department of civil & environmental engineering, university of lagos, akoka, lagos state, nigeria) * corresponding author’s email address: idaraobong2013@gmail.com article information submitted 7 april, 2018 revised 12 june, 2019 accepted 22 june, 2019 keywords: eggshell powder sodium silicate stabilization laterite soil california bearing ratio unconfined compressive strength abstract the investigation carried out in this paper was to evaluate the effect of eggshell powder and sodium silicate as stabilizers to laterite soil used as fill material for the purpose of constructing light traffic pavement. the laterite soil used in this study was collected from ikorodu north local government area in lagos state, nigeria and treated with eggshell powder (esp) and sodium silicate (ss) blend in stepped concentrations of 3% esp + 2% ss, 6% esp + 4% ss, 9% esp + 6% ss, 12% esp + 8% ss and 15% esp + 10% ss by dry weight of the soil. results from the tests carried out showed a general improvement on the engineering properties of the laterite treated with esp and ss blend. optimum california bearing ratio (cbr) tests results for un-soaked and soaked samples were recorded as 51% and 22% at 12% esp + 8%ss content. peak unconfined compressive strength (ucs) values of 355 kn/m2 and 570 kn/m2 were recorded at 7and 28-days curing periods respectively at an optimum blend of 12% esp + 8%ss content. from the results obtained in this research, an optimum blend of 12% esp and 8% ss using the west african standard (was) compactive effort can be used to stabilize laterite soil material for use as fill material for the construction of light traffic roads. an advantage of applying the esp is the decrease in the deleterious environmental impact of eggshell waste. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction according to hainin et al. (2011) a low volume road is a road that is said to have a low average daily traffic (adt). they also stated that it could also be referred to a road with a cumulative number of equivalent standard axel load (esal) traversing over the design life of the roads. roads in the rural areas and within some estates are mostly classified as low volume or low traffic roads. it is therefore important to know how much the subgrade and fill soil can support the volume of traffic expected without any failure on or within the pavement structure. in geotechnical engineering, deficient soils are soils, which do not meet certain requirement for their intended geotechnical use. the intended use could either be for road construction (as in this case), embankment construction, construction of liners for leachate containment etc. in nigeria and other tropical regions of the world, the dominant soil material available for the construction of subgrade, fill, sub-base and base courses for both flexible and rigid pavements is the laterite soil however; the natural properties of these soils need to be improved so as to meet http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):586-597. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 587 engineering specifications for the required engineering purpose. figure (1) shows the map the of laterite-abundant zones in nigeria. figure 1: map showing laterite abundant zones. one of the major methods of soil improvement according to alayaki (2012) is through a process known as stabilization. he went further to show that the process of soil stabilization involves improving the engineering properties of deficient soils so as to meet engineering requirements for construction purposes. another research (gofar and kassim, 2007) also showed that stabilization as a method of soil improvement is usually carried out to increase the strength of the pavement layers in order to provide a suitable platform for the intending traffic this practice of stabilization is widely used in road construction with the aim of increasing its strength by making it less compressible, permeable and porous, which results in higher bearing capacity, and decreased volumetric change (osinubi and mustapha, 2009). sherwood, (1995) reported that stabilization could be carried out with additives such as, cement, lime and fly ash. these additives known as the conventional stabilizers have been used in stabilizing weak soils on road construction in order to provide a firm base or sub-base for all types of paved areas as well as improve foundation conditions. other researchers; nalbantoglu, (2004), osinubi et al. (2007), mahto and duggal (2015) also confirmed the usefulness of some other additive such as fly ash, rbi grade 81, bagasse ash as stabilizers which can also be used to improve the strength of deficient soils. they all reported that when these additives were added to expansive clay soils, the plasticity index, amount of the clay size particles, as well as their swell potentials reduced. however, the over dependence on the utilization of these industrially manufactured conventional soil stabilizers or additives (cement, lime etc.); have continually kept the cost of construction of stabilized road high (musa and mohammed, 2015). this hitherto, have continued to deter the underdeveloped and poor nations of the world from providing accessible roads to their rural dwellers who constitute the higher percentage of their population who are mostly agriculturally dependent (alhassan and mustapha, 2007) and so, the improvement in the strength and durability of laterites with locally sourced materials that are readily available has become imperative as a result of the high cost involved in the construction of roads for which file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oke and olowoyo: stabilization of laterite soil with eggshell powder and sodium silicate used as fill material in road construction. azojete, 15(3):586-597. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 588 cheaper means of building them are essential (neville, 2000; odula, 2010). this has resulted some researches into using stabilizers that can be sourced locally at a very low-cost using sugarcane straw ash (amu et al. 2011, ogunribido, 2012), rice husk ash (alhassan and mustapha, 2007), bamboo leaf ash (amu and adetuberu, 2010) and oil palm empty fruit bunch ash (oke and osinubi 2019). in addition to the high cost involved in the construction of roads, indiscriminate dumping of wastes has led to environmental issues and so, this has in addition prompted these researches on the use of local materials as alternatives to the conventional additives as construction materials. these local materials can be classified as either agricultural or industrial wastes (amu et al, 2011). different types of soils may be suitable for use in the construction of an embankment or fill for the purpose of a road construction, ranging from granular soils (sand and gravel), which are more preferred, to the more finely sized soils (silt and clay), which usually lack the required engineering properties hence a need for stabilization. in nigeria, laterite soils, which contain silts and clays, are usually used as fill material on road projects and so its stabilization is necessary. regardless of the type(s) of soil(s) to be used as fill material, the material should be well graded, capable of adequate compaction, be within a proper range of moisture to optimize compaction, and be free of unsuitable or deleterious materials, such as grasses, tree roots, branches, stumps, sludge, waste etc. this study was aimed at stabilizing laterite soil used as fill material with eggshell powder and sodium silicate for the purpose of constructing light traffic roads. location and geology of the study area the laterite used in this study was obtained from borrow pits along itokin road, adamo, ikorodu north local government area in lagos state, nigeria. the borrow site lies within the coordinates of latitude 6° 39' 0"n and longitude 3° 35' 0"e. 2.0 materials and methods 2.1. materials 2.1.1. soil the laterite soil used in this study (figure 2a) was obtained from a borrow pit along itokin road, adamo, ikorodu north local government area in lagos state, nigeria. the soil was obtained using the disturbed sampling method from an average depth of about 1.5-2.5m below existing ground level to avoid organic topsoil. 2.1.2. eggshell the eggshells were obtained as waste from bakeries, restaurants and individual homes. for ease of pulverising, they were further dried naturally and thereafter, pulverised and sieved through 0.075mm bs sieve (figure 2b). the powder obtained was then stored in airtight buckets to prevent hydration or other form of contamination. 2.1.3. sodium silicate a new liquid stabilizing agent, with a commercial brand name of “tx-85” had been introduced in the construction industry for improving the strength and reliability of soils for construction of building and road. this liquid stabilizer was obtained from chemical dealers in lagos state. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):586-597. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 589 (a) (b) figure 2: (a) laterite soil sample. (b) eggshell powder 2.2. methods 2.2.1. index properties index properties (atterberg limits, sieve analysis, specific gravity) tests were carried out in accordance with the procedures outlined in bs 1377 (1990) on the natural laterite. for atterberg limits, air-dried samples were crushed and sieved through the no. 40 sieve (0.425mm) and mixed with different eggshell powder (esp) and sodium silicate (ss) content to establish the effect of the stabilizers on the atterberg limits. deionized water was also used in all samples to avoid any distraction or contamination by chemicals. 2.2.2. compaction to simulate the variation in compactive effort that may be expected from field operations, the west africa standard compaction was carried out to study the moisture-density relationship of compacted laterite and laterite – esp+ss blend. air-dried laterite samples passed through bs no. 4 sieve were mixed with 3% esp + 2% ss, 6% esp + 4% ss, 9% esp + 6% ss, 12% esp + 8% ss and 15% esp + 10% ss by dry weight of soil. 8% of water by dry weight of soil was used for the first compaction. five (5) layers of the treated laterite was placed into the mould, with each layer receiving 10 blows uniformly distributed with a 4.5kg hammer dropped from a height of 450mm and the resulting dry unit weight was measured. the procedure was repeated subsequently with a stepped increment of 2% of water to establish a relationship between the dry unit weight and the water content of the natural and treated soil mixtures. 2.2.3. strength tests california bearing ratio (cbr) the laterite soil was mixed with esp and ss in their respective blends (3% esp + 2% ss, 6% esp + 4% ss, 9% esp + 6% ss, 12% esp + 8% ss and 15% esp + 10% ss), compacted and tested. for un-soaked samples, they were tested immediately after compaction. for the soaked samples, after compaction, they were soaked for 48 hours. after 48 hours, they samples were removed from the water tank and allowed to sit for 15 minutes before testing. unconfined compressive strength (ucs) for the unconfined compressive strength (ucs) test, the samples were mixed with the esp and ss additives (3% esp + 2% ss, 6% esp + 4% ss, 9% esp + 6% ss, 12% esp + 8% ss and 15% esp + 10% ss), compacted and left to cure for 7, 14 and 28 days respectively. all strength tests were carried out in accordance with bs 1377 (1990) part 4, bs 1924 (1990) and federal ministry of works and housings, fmw&h (1997). 3.0 results and discussion table1 shows the properties of the natural laterite used in the study while tables 2 and 3 show the chemical composition of the additives and the laterite soil respectively. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oke and olowoyo: stabilization of laterite soil with eggshell powder and sodium silicate used as fill material in road construction. azojete, 15(3):586-597. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 590 table 1: properties of natural soil s/no properties results 1 colour reddish brown 2 percentage passing sieve no 200 52.3 3 liquid limit (%) 46.15 4 plastic limit (%) 17.6 5 plasticity index (%) 28.55 6 linear shrinkage (%) 8.59 7 sesquioxide ratio 1.26 8 specific gravity 2.61 9 aashto classification [gi] a-7-6 [12] 10 unified soil classification system cl (clay of intermediate plasticity) 11 maximum dry density (mg/m3) 1.656 12 optimum moisture content (%) 14.15 13 california bearing ratio: 48 hours soaked (%) 11.55 14 california bearing ratio: un-soaked (%) 22.3 15 unconfined compressive strength (kn/m2) at 28 days 45 the eggshell powder as shown in table 2 has a high calcium oxide content of about 52%. this oxide component has contributed to the strength gain exhibited in the treated samples (bello et al. 2015). table 3 shows the oxides present in the natural soil. the sesquioxide ratio: sio2/(fe2o3+al2o3) as calculated from the table gives a value of 1.26. this value implies that the soil used for the study is a true laterite (joachin and kandiah, 1941) table 2: chemical compositions for eggshell powder and sodium silicate table 3: chemical composition of laterite soil component (%) sio2 fe2o3 al2o3 mgo na2o k2o cao so3 laterite soil 43.92 0.025 34.89 0.039 0.045 0.16 1.42 0.00 components (%) sio2 fe2o3 al2o3 mgo cao k2o na2o eggshell powder 0.001 0.034 0.002 0.58 52.4 0.002 0.004 sodium silicate 26.59 0.001 0.002 0.002 0.004 0.003 28.24 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):586-597. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 591 3.1. index properties 3.1.1. grain size distribution figure (3) shows the grain size distribution of the natural laterite used in the study. the soil was classified to be a-7-6 (12) soil using the aashto classification system. from the graph, it is observed that the percentage retained on sieve no 200 was 47.3% and percentage passing was 52.3% in the soil. this was then used for hydrometer test to determine the silt content as shown in the graph in fig. (3). figure 3: grain size distribution curve. 3.1.2. atterberg limits (liquid limit: ll, plastic limit: pl, and plasticity index: pi) figure (4) shows as a variation of atterberg limits with varying esp + ss content used to mix the soil to get a homogeneous paste. a similar trend was observed for the atterberg limit test results i.e. ll, pl and pi. there was a sharp drop observed in ll, pl and pi with an initial addition of 3% esp + ss. thereafter, further increase in the esp and ss content resulted in an increase in ll, pl and pi at a decreasing manner. this may be due to the fact that the quantity of esp was not initially sufficient to endothermicaly combine with ss. this inconsistency of results can be attributed to the differences in stabilizing mechanisms of the two additives, i.e. the eggshell powder causes flocculation due to lime content (calcium oxide) while sodium silicate did the opposite by making montmorillonite particles repel one another. this finding is in agreement with the research carried out by muthu and tamilarasa (2014). the ll of 29% and pi of 10% meets with the requirement specified in the federal ministry of works & housing (1997) for fill material which is given as ll: 0-45% and pi: 0-20%. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oke and olowoyo: stabilization of laterite soil with eggshell powder and sodium silicate used as fill material in road construction. azojete, 15(3):586-597. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 592 figure 4: variation of atterberg limits with the varying esp + ss content 3.2. compaction characteristics 3.2.1. optimum moisture content (omc) figure (5) shows a variation of omc with varying esp and ss additives. the compaction result showed that there was an increase in the optimum moisture content (omc) with higher esp and ss content up from 14.15% for the natural soil to a maximum value of 21.2% at 15 % esp and 10 % ss combination. this could be attributed to the increase in fines content due to the inclusion of esp which has a larger surface area that required more water to react or complete its hydration reaction, thus this stepped up the rate of hydration reaction which rapidly continued to use up the water in the system as reported by osinubi (1999) and musa (2008). these trends are also in agreement with established trend for stabilization of laterite with cement and lime, (ola, 1983a), south chicago clay with lime-kiln dust (daita et. al, 2005), laterite with rice husk ash (alhassan, 2008) and laterite with bamboo leaf ash (amu and adetuberu, 2010). also, research findings reported by osinubi (1999), osinubi et al. (2007) and oke and osinubi (2019) explains that the increase in omc with increasing amount of treatment is as a result of an increasing desire for water commensurate with the higher amount of the additives because more water was required for the disassociation of admixtures with ca2+ and ohions to supply more ca2+ for the cation exchange reaction. another reason could be due to the increasing surface area caused by the higher amounts of additives that require more water for the lubrication of the entire matrix. figure 5: variation of omc with varying esp and ss additives http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):586-597. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 593 3.2.2. maximum dry density (mdd) the variation of maximum dry density (mdd) with varying content of esp and ss is shown in figure (6). the mdd in this case decreased from 1.66 mg/m3 for the natural soil to 1.57 mg/m3 at 10% ss and 15% esp content. this explanation is considered to hold true for esp given that k2o and cao contents of the esp that add up to 52.4% could combine with any naturally occuring cao in the lateritic soil to initiate cation exchange, flocculation and agglomeration of the soil, in a manner similar to the effect of lime stabilization (alao, 1983; daita et al, 2005). the decrease in dry densities may also be due to the flocculated and agglomerated clay particles occupying larger spaces leading to corresponding decrease in dry densities. this trend is in agreement with lees et al. (1982). osinubi et al. (2000) also connects this to the initial simultaneous flocculation and agglomeration of clay particles caused by cation exchange as well as the additives occupying the voids within the soil matrix. ola (1983) also showed that the process led to an increase in air voids and thereby giving rise to a decrease in dry density. figure 6: variation of mdd with varying esp and ss additives 3.3. strength characteristics 3.3.1. california bearing ratio the variation of cbr value with varying esp and ss content under the soaked and un-soaked conditions are shown in figure (7). un-soaked condition the variation of value with esp and ss content under the un-soaked condition shows that cbr values increased from 22.3% for the natural soil to an optimum value of 51.8% at 12% esp + 8%ss combination and then decreased to 40.72% at a maximum combination of 15% esp + 10%ss. this increase in the cbr could be as a result of the presence of adequate amounts of calcium required for the formation of calcium silicate hydrate (csh) and calcium aluminate hydrate (cah), which are the major compounds responsible for strength gain (bello et al. 2015). the fmw&h (1997) recommends a cbr value of 180 % to be attained in the laboratory for cement-stabilized material to be constructed by the mix-in-place method. usually, a minimum cbr value of 80 % is required for base specification and 20-30 % for sub-base specification and a minimum of 10% for fill material specification both when compacted at optimum moisture content and 100 % west african standard (gidigasu and dogbey, 1980) and (gidigasu, 1982). in accordance with the specification, the minimum un-soaked requirement of 10% cbr for fill and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oke and olowoyo: stabilization of laterite soil with eggshell powder and sodium silicate used as fill material in road construction. azojete, 15(3):586-597. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 594 minimum un-soaked requirement of 30% for sub-base construction was achieved. a value of 51.8% at an optimum blend of 12% esp + 8%ss was obtained. this value of 51.8% meets with requirements stated above which makes the optimally treated laterite soil material suitable as a fill material when compacted with the was energy. soaked condition the variation of cbr value (48 hours soaked conditions) for natural and esp/ss-stabilized laterite using the was compactive efforts shows that there was a gradual increase of cbr values from 11.55% for the natural soil to peak value of 21.8% at the optimum 12% esp + 8%ss combination and then a decrease to 13.5% at a maximum combination of 15% esp + 10%ss. the lower values recorded in comparison to the un-soaked cbr values were due to ingress of water into the specimen, which led to a reduction in strength. relating with the required specifications for subgrade and fill construction materials, which should have a value of 10%, it meets with the specification. figure 7: variation of cbr values with varying esp and ss content 3.3.2. unconfined compressive strength figure 7 shows the variation of ucs value with varying esp and ss content. the unconfined compressive strength (ucs) results indicated that the unconfined compressive strength of the soil after curing for 7, 14 and 28 days with the increasing proportions of esp + ss, increased gradually with the days of curing and the peak values for each combination was recorded at 28 days of curing. the optimum strength achieved was recorded as 570 kn/m2 obtained from a combination of 12% esp + 8%ss at 28 days of curing. however, it was observed from the result that a further increase in the esp + ss combination to 15% esp + 10% ss rather showed a decrease in strength. these result as reported by osinubi et al. (2007) and oke and osinubi (2019) can be attributed to the progressive increase in the amount of calcium oxide as a result of the gradual increase in the amount of eggshell powder added to the mixtures, thus increasing the cementitious compounds formed for increased strength properties. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):586-597. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 595 figure 8: variation of ucs value with varying esp and ss content 4.0 conclusion and recommendations from the results obtained in this research, using an optimum blend of 12% esp and 8% ss, soaked and un-soaked cbr values of 22% and 51% were obtained and these values meet with the 10% requirements for fill material stabilization for light traffic pavement. it can therefore be concluded that an optimum combination of 12% esp and 8% ss, can be used to stabilize laterite soil material for the construction of the fill layer of light traffic roads. the optimum blend is also recommended as an additive or stabilizer to the subgrade layer of light traffic roads during rehabilitation works. references alayaki, fm. 2012. water absorption properties of lateritic soil in road pavement: a case study ife-ilesha highway, south western nigeria. international journal of emerging technology and advanced engineering, 2(11): 51-57. alao, da. 1983. geology and engineering properties of laterites from ilorin, nigeria. engineering geology journal, 19: 111 – 118. alhassan, m. and mustapha, am. 2007. effect of rice husk ash on cement stabilized laterite. leonardo electronic journal of practices and technologies, 6(11): 47 – 58. alhassan, m. 2008. potentials of rice husk ash for soil stabilization. a.u. journal of technology, 11(4): 246-250 amu, oo. and adetuberu, aa. 2010. characteristics of bamboo leaf ash stabilization on lateritic soil in highway construction. international journal of engineering and technology, 2(4): 212219. amu, oo., ogunniyi, sa. and oladeji, oo. 2011. geotechnical properties of laterite stabilized with sugarcane straw ash. american journal of scientific and industrial research, 2(2): 323-331. bello, aa., ige, ja. and ayodele, h. 2015. stabilization of lateritic soil with cassava peel ash. british journal of applied science and technology, 7(6): 642-650. bs 1377. 1990. methods of testing soil for civil engineering purposes. british standards institute, london. bs 1924. 1990. methods of tests for stabilized soils. british standards institute, london. daita, kr., drnevich, vp. and kim, d. 2005. family of compaction curves for chemically modified soils. publication fhwa/in/jtrp-2005/07. joint transportation research program, indot and purdue university, west lafayette, indiana, us. degirmenci, n., federal ministry of works and housings. 1997. roads and bridges. in: nigerian general specification, abuja, nigeria, 13–25. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oke and olowoyo: stabilization of laterite soil with eggshell powder and sodium silicate used as fill material in road construction. azojete, 15(3):586-597. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 596 gidigasu, md. and dogbey, jlk. 1980. geotechnical characterization of laterized decomposed rocks for pavement construction in dry sub-humid environment. 6th south east asian conference on soil engineering, taipei, 1: 493-506. gidigasu, md. 1982. importance of material selection, construction control and field performance studies in developing acceptance specification for laterite paving gravels. solos e rochas. 3: 1-12 gofar, n. and kassim, ka. 2007. introduction to geotechnical engineering, part 2. prentice-hall inc., singapore. hainin, mr., ismail, cr. and yaacob, y. 2011. highway engineering. universiti teknologi malaysia, malaysia. joachin, awr. and kandiah, s. 1941. the composition of some local laterites, soil concretions and clays. tropical agriculturist. 96: 67-75 lees, g., addelkader, mo. and hamdani, sk. 1982. sodium chloride as additive in lime-soil stabilization. journal institute of highway engineers.,29(11): 8-16 mahto, b. and duggal, ak. 2015. improvement of subgrade by rbi grade 81 and pond ash. international research journal of engineering and technology, 2(5): 1010-1020 musa, a. and mohammed m. 2015. improvement of deficient soils in nigeria using bagasse ash: a review. international journal of geological and environmental engineering. 9(10): 1234-1243 musa, a. 2008. potential of rice husk ash for soil stabilization. assumption university journal of technology 11(4): 246-250. muthu, km. and tamilarasan, vs. 2014. effect of eggshell powder in the index and engineering properties of soil. international journal of engineering trends and technology. 11: 319-321 nalbantoglu, z. 2004. effectiveness of class c fly ash as an expansive soil stabilizer. construction and building materials, 18(6): 377-381. neville, am. 2000. properties of concrete, 4th edition. pearson education asia ltd, malaysia. oduola, r. 2010. studies on a cement kiln dust (ckd)-stabilized low-strength soil for road pavement construction in eastern nigeria. in proceedings of the green streets and highways conference asce, 449-460 ogunribido, tht. 2012. potentials of sugar cane straw ash for lateritic soil stabilization in road construction. international journal of scientific emerging technology. 3(5): 102-106 oke, ja. and osinubi, kj. 2019. oil palm empty fruit bunch ash as a sustainable stabilizer for laterite subbase of highway pavements. iop conference series: materials science and engineering. 640(1): 1-11 ola, sa. 1983. the geotechnical properties of black cotton soils of north eastern nigeria. in s. a. ola (ed) tropical soil of nigeria in engineering practice. balkama, rotterdam, pp160-178. ola, sa. 1983a. tropical soils in engineering practice. balkema publishers, rotterdam, netherlands. osinubi, kj. 1999. evaluation of admixture stabilization of nigerian black cotton soil. nigerian society of engineers technical transactions, 34(3): 88-96. osinubi, kj. 2000. treatment of laterite with anionic bitumen emulsion and cement: a comparative study. ife journal of technology. 9(1): 139-145. osinubi, kj., bafyau, v. and eberemu, a. o. 2009. bagasse ash stabilization of lateritic soil. proceeding of the first international conference on environmental research, technology and policy ertep 2007” under the auspices of international society of environmental geotechnology, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):586-597. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idaraobong2013@gmail.com 597 accra, ghana, 16-19 july, category e: state-of-the-art technologies for environmental performance and protection, pp. 1-7. osinubi, kj. and mustapha, am. 2009. optimal use of bagasse ash on cement stabilized laterite.’ submitted to the nigerian society of engineers technical transaction. 44(1): 1-16 sherwood, pt. 1995. soil stabilization with cement and lime. her majesty’s stationery office, london. 14-55 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):14-20 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 14 original research article application of firefly optimization algorithm to the design and characterization of helmholtz coils for magnetic field sensor calibration u. a. sadiq, o. w. oluyombo, s. o. onuh 1centre for satellite technology development, national space research and development agency, obasanjo space centre, airport road, abuja 2engineering and space system department, national space research and development agency, obasanjo space centre, airport road, abuja 3director centre for satellite technology development, national space research and development agency, obasanjo space centre, airport road, abuja article information submitted: 11/12/2018 revised: 12/01/2019 accepted: 04/06/2019 abstract this paper presents the application of firefly optimization algorithm (foa) to the design and characterization of helmholtz coils to create homogenous magnetic field needed for calibrating magnetic field sensors and used for other experiments. magnetometer is used to monitor and record the earth’s magnetic field data at the geomagnetic observatory. earth’s magnetic field data from ground-based magnetometer observatories are important for studying geomagnetic storm. the absence of earth’s magnetic field data observatories results in a complex mysterious phenomenon of geomagnetic storm and remains as unexplained one. fluxgate magnetometer is contributing to the ongoing extensive research work dedicated to the explanation of some of the complex phenomena related to geomagnetic storm and solar terrestrial system. in order to examine magnetic field sensing of a fluxgate sensor, a large area with uniform magnetic field is required. the advantage of having a large area is to allow easy access of the sensor during magnetic field measurements. a laboratory design and characterization of high quality helmholtz coils is a better choice when helmholtz coil with larger areas that are available in the market are very expensive © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction helmholtz coil is a parallel pair of two similar circular or square shaped coils, spaced one radius apart with coils wound in series such that the current passes in the same direction in each coil (abbott, 2015; alao et al., 2018). helmholtz coils are used for earth’s magnetic field nullification, magnetic field sensors calibration and other experiments where a controllable amount of uniform magnetic field is required (abbott, 2015). the basic principle of helmholtz coils is that the coils produces uniform magnetic field at the center (abbott, 2015; daron et al., 2015) of the coils, which is equivalent to the radius of the coil. this arrangement of coil was invented by german physicist, hermann von helmholtz, over a century ago (bhatt et al., 2010). the intensity of magnetic field is directly proportional to the number of turns, radius of the coil and the excitation current through the coils (abbott, 2015). according to the definition of helmholtz coil, there are some uncertainties even if the mean radius of the coils is equals to the separation http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):14-20. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqumar2001@googlemail.com 15 distance between the coils (yang et al., 2018). an ideal helmholtz coil with ampere-turn (ni) can be realized with the number of layers, number of turns per layer, coil excitation current and radius of the coil (yang et al., 2018). biot-savart law is employed for the magnetic field calculation, while the coil turns of each helmholtz coil are concentric rings as shown in figure 1. thus, the magnetic field strength at the center of helmholtz coils due to current-carrying element is as follows (bhatt et al., 2010): b = n . μ0.ic r . 4 5 3 2 (1) where: r is the radius of each turn of a coil, ic is the coil current, and μ0 is the permeability of air. when calculating the diameter of wire for the design of helmholtz coils, the power supply for driving the coils must be taken into consideration as this provides the current needed to generate the required magnetic field (bhatt et al., 2010; yang et al., 2018). the schematic describing the configuration of helmholtz coils is shown in figure 1. figure 1: the schematic diagram of helmholtz coils (bhatt et al, 2010) as shown in figure 1, each helmholtz coil produces equal amount of magnetic field parallel to the axis of the coils (bhatt et al., 2010), while the two coils produce uniform magnetic field, which is accomplished by a controllable amount of excitation current (abbott, 2015). the uniform field within the coils is due to the summation of fields parallel to the axis and the difference of vertical component fields (abbott, 2015; yang et al., 2018). helmholtz coil design is simple and there are many commercially available designs for all kinds of applications (yang et al., 2018). in order to examine the magnetic field sensing of a fluxgate sensor, a large area with uniform magnetic field is required (butta et al., 2010). helmholtz coils with large area will allow easy access of the sensor during measurements (butta et al., 2010; alao et al., 2018). a laboratory design and characterization of helmholtz coils is of great advantage when large area helmholtz coil is desired and the commercial helmholtz coils are very expensive (alao et al., 2018). moreover, in order to calibrate magnetic field sensors, a high magnetic field with low rise in temperature and power consumption are required. when total power consumption and magnetic field of the helmholtz coils are the objectives function, helmholtz coils design needs to satisfy the design limits and geometric constraints. in order to find the optimal performance of helmholtz coils in this study, a systematic design approach is employed, where the modified multi-objective firefly optimization algorithm (foa) is used to simultaneously obtain the parameters and predicts the magnetic field inside the helmholtz coils. such a multi-objective optimization approach is powerful in dealing with design problems in electro-magnetic with a file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sadiq et al.: application of firefly optimization algorithm to the design and characterization of helmholtz coils for magnetic field sensor calibration. azojete, 15(sp.i2):14-20. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 16 large number of design variables and multiple objectives under complex nonlinear constraints (yang, 2013). 2.0 methodology in order to implement the design of helmholtz coils, the foa was written in matlab environment and the results were obtained by running the developed program on a 1.50 ghz intel® core™ duo cpu windows 7 ultimate 32-bit personal computer (alao et al., 2018). in this study, the primary aim of the helmholtz coils design was to create uniform magnetic field in the test area. the characterization was carried out by using a matlab program for plotting the magnetic field inside the helmholtz coils. 2.1 helmholtz coils design approach using foa the aim of systematic design approach applied to helmholtz coils design in this study is to simultaneously find the optimal number of coil turns per layer, number of coil layers, wire size, coil radius, and the excitation current requires for creating uniform magnetic field at the center of the helmholtz coils. this is achieved by using helmholtz coils equation to modify firefly optimization algorithm. the algorithm starts by placing the fireflies in random locations. the location of a firefly corresponds to the values of the parameters (number of coil turns per layer, number of coil layers, wire size, coil radius, and the excitation current) for the objective function (magnetic field) to be solved. initialize the number of fireflies, n, biggest attraction β0, absorption coefficient of light intensity γ, step size factor α, and maximum number of iterations or generations tmax. initialize the positions of fireflies randomly, namely initializing design variables of the helmholtz coils parameters (number of coil turns per layer, number of coil layers, wire size, coil radius, and the excitation current), the values of objective function (magnetic field) of fireflies are set as their maximum brightness of fluorescence i0. calculate relative brightness and attractiveness of fireflies, which belong to the population. the direction of movement depends on the relative brightness of fireflies. here (yang, 2013): i = i0 × e−γrij (2) β = β0 × e−γrij (3) where: i0 is the maximum fluorescence brightness of the firefly, namely the fluorescence brightness itself (r = 0), which depends on the value of the objective function. β0 is the maximum attractiveness, namely the attractiveness of the light source (r = 0). γ is the absorption coefficient of the light intensity. the fluorescence will gradually weaken according to the increasing distance and the absorption of media. the absorption coefficient of light intensity is set to reflect this feature. rij is the spatial distance between firefly i and j. update the spatial positions of fireflies. random perturbations are injected to the firefly with the best position. the updated equation is: xi = xi + β × xj − xi + α × rand − 0.5 (4) where xi, xj represent the spatial positions of firefly i and j, respectively. α is the step size factor. rand is random factor distributed uniformly in [0,1]. recalculate the brightness of fireflies according to the updated positions. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):14-20. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqumar2001@googlemail.com 17 return to step 3 until the search precision is met or the maximum number of generations is achieved. the optimization of helmholtz coils design problem is formulated as non-linear programming problem, expressing the objective function and constraint function in terms of the specified independent variable. 2.2 design variables in the design optimization of helmholtz coils in this study, if large number of variables is selected, the problem will become complicated. the following quantities are chosen as helmholtz coils design variables for optimization. number of turns per layer (x1) number of coil layers in the winding (x2) wire diameter (x3), mm radius of coil winding (x4), m coil excitation current (x5), a the problem can be stated in mathematical terms as follows: x = x1, x2, … x5 = number of turns per layer number of layers wire diameter coil radius coil current t (5) where x1, x2, x3, x4, and x5 are the set of independent design variables with their lower and upper bounds as xmin and xmax. the design variables are presented in table 1. table 1: helmholtz coils design variables and ranges variables range unit number of turns per layer 8 – 60 number of layers 6 – 65 wire diameter 0.135 – 1.5 mm coil radius 0.01 – 0.35 m coil current 5 – 250 ma 2.3 constraints g(x) is the set of constraints imposed on the design to make it feasible and practically acceptable, the constraints that have been used in this study are: total number of winding turns total magnetic field the geometric constraints and operating limits are represented in equation (6) and the geometry constraints and operating limits are shown in table 2. g x ≤ 0 ⇔ total winding turns total magnetic field (6) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sadiq et al.: application of firefly optimization algorithm to the design and characterization of helmholtz coils for magnetic field sensor calibration. azojete, 15(sp.i2):14-20. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 18 table 2: helmholtz coils design constraints constraints range unit total winding turns ≤ 1600 magnetic field ≤ 750 μt the objective function optimization problem is to optimize the magnetic field. in the computation of f(x) and g(x) as well as calculating the optimal performance of the helmholtz coils, the optimization design problem of the helmholtz coils is formulated by defining the magnetic field at the center of the helmholtz coils as the objective function: maximize b z = μ0 .ic . r2 2 . z + r 2 2 + r2 − 3 2 + z − r 2 2 + r2 −3/2 (7) 3.0 results and discussion to verify the effectiveness of the proposed foa for optimizing the helmholtz coils design problem, the optimization procedure starts with the design variables. in the design optimization problem, five independent variables are chosen, such as number of coil turns per layer, number of coil layers, wire size, coil radius, and the excitation current during the iteration. the modified foa was written in matlab environment and the results were obtained by running the developed program on a 1.50 ghz intel® core™ duo cpu windows 7 ultimate 32-bit personal computer. equation (7) is used in the firefly optimization algorithm to calculate the optimum magnetic field inside the helmholtz coils and to find the coils parameters. the algorithm predicts the total number of windings needed to produce a magnetic field of 356.1µt. the number of windings is a function of the radius of the raw coil form. the results obtained by the proposed foa method are presented in figure 2. figure 2: optimization results obtained from matlam program http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):14-20. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqumar2001@googlemail.com 19 as shown in figure 2, magnetic field of 356.1µt will be generated with an excitation current of 68.30 ma by each of the helmholtz coils when wound with 23 turns per layer and 22 layers of coil. as obtained from the modified foa result, each coil had a diameter of 8.9 cm with 506 turns each of copper wire and copper wire size of 0.62 mm diameter. table 3 shows the optimal design variables for the proposed helmholtz coils design. table 3: foa results for the helmholtz coils simulations. input variables output variable helmholtz coils coil turns per layer number of layers wire diameter (mm) coil radius (mm) coil current (ma) magnetic field (μt) foa design 23 22 0.62 89.23 68.30 356.1 as shown in table 3, the width of each coil is 14.26 mm while the height of each coil is 13.64 mm. moreove, the mean radius of each coil is 96.05mm with inner radius of 89.23 mm and outer radius of 102.87 mm, respectively. the designed ampere-turn is ni = 68.3 ma * 506, where number of layers is 22 and number of turns per layer is 23. in order to characterize the designed helmholtz coils, these parameters were put in matlab-program. magnetic field plot arising from the contributions of the modified foa designed coils is shown in figure 3. -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 coils axial distance [m] m ag ne tic f ie ld [m t] figure 3: magnetic field as a function of distance obtained from foa design. from this plot, good agreement between the predicted and simulated magnetic fields can be found in the helmholtz coils. it is observed that the total magnetic field at the center point of the helmholtz coils is eventually the vector summation of the two coil winding pairs. the field distribution is homogenous, especially at the center of the coils where the axial distance is equivalent to the radius of the coil. beyond this distance, the field uniformity tends to be deteriorated. this result indicates that one can increase the axial distance to improve the field uniformity by increasing the coil radius. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sadiq et al.: application of firefly optimization algorithm to the design and characterization of helmholtz coils for magnetic field sensor calibration. azojete, 15(sp.i2):14-20. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 20 moreover, the magnetic field in the negative axis on the graph represents the contribution of the left coil while the magnetic field in the positive axis on the graph represents the contribution of the right coil. the magnetic field inside the helmholtz coils is homogenous within 0.08 m axial distance. this is close to the 0.089 m coil radius predicted by firefly algorithm. therefore, any deviation from the optimum coil configuration would cause the graph to be in different form. 4.0 conclusion the optimization algorithm and matlab program have enabled the predictions of the helmholtz coils design parameters and the visualization of the magnetic field coverage inside the chosen design. this is done by using equation (7) to modify the firefly optimization algorithm and also using matlab program to plot equation (7) as a function of distance along the axial length of the helmholtz coils. it is observed that there is 10% difference between the radius of the coil and the magnetic field coverage along the axial distance of the helmholtz coils (figure 3). this validates the helmholtz coils principle; the separation distance between the helmholtz coils equals the radius of each coil. this therefore shows the effectiveness of firefly optimization algorithm for helmholtz coils design. references abbott, jj. 2015. parametric design of tri-axial nested helmholtz coils. review of scientific instruments, 86:1-10. alao, oj., metu, mo., amibor, ip., ibe, cc. and oluyombo, ow. 2018. firefly optimization design and simulation of a single-axis helmholtz coils for spacecraft components testing. international journal of engineering and applied sciences (ijeas), 5(11): 12-16. bhatt, v., rautela, rs., sharma1, p., tiwari, dc. and khushu, s. 2010. design and development of helmholtz coil for hyperpolarized mri. proceedings of the comsol conference, 1-6. butta, m., ripka, p., infante, g., badini-confalonieri, ga. and vázquez, m. 2010. magnetic microwires with field induced helical anisotropy for coil-less fluxgate. ieee transactions on magnetics, 46(7): 2562-2565. crosser, ms., scott, s., clark, a. and wilt, pm. 2010. on the magnetic field near the center of helmholtz coils. the review of scientific instruments, 81(8): 1-8. daron, bb., jonathan, e. and madsen, mj. 2015. magnetic field mapping. wabash journal of physics (wjp), 4(3): 1-13. sasada, i. and nakashima, y. 2006. planar coil system consisting of three coil pairs for producing a uniform magnetic field. journal of applied physics, 99: 08d904: 1-3. yang, j., wang, y., pan, j. and wang, y. 2018. parametric tuning of the helmholtz coil and its optimal designs with thick winding pairs. american institute of physics (aip) advances, 8 (8): 1-8 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 762-776 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 762 original research article computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer s. k. oyeniyi1*, o. s. olatunbosun1, a. k. aremu1, n. a. aviara2, and i. j. iyilade3 (1*department of agricultural and environmental engineering, faculty of technology, university of ibadan, ibadan, nigeria. 2department of agricultural and environmental resources engineering, faculty of engineering, university of maiduguri, maiduguri, borno state, nigeria 3department of agricultural and bio environmental engineering, the oke-ogun polytechnic, saki, oyo state, nigeria) * corresponding author’s email address: oyeniyisk@gmail.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: drying thermal analysis energy exergy cfd simulation abstract this paper presents a simulation of the drying process of okra (abelmoschus esculentus) in a center shaft (cs) rotary tray cabinet dryer using three drying temperatures (50, 60 and 70 °c). ansys 14.5 workbench was used to simulate the dryer model in 2d (2 dimensional). the detail of the cfd simulation was utilized to investigate the energy and exergy of the dryer. the ansys design modeler was used to model the 2d representation of the dryer and the meshing was done using ansys icem. ansys fluent cfd solver was then used to calculate the alternative using the normal turbulence-realizable k-epsilon model in a steady-state system with improved wall temperature treatment. the simulation outcome was used in calculating the dryer's exergy and energy analysis based on the thermal efficiency. it was noted that the simulated temperature from the experiment is greater than that of the experiment. the results indicated that the experimental energy utilization (eu), energy utilization ratio (eur) and energy efficiency increased from 14.1 to 57.93 j/s, 0.15 to 0.20 and 18.89 to 33.98 percent, while the simulated energy utilization ratio increased from 23.91 to 57.68 j/s, 0.19 to 0.20 and 26.21 to 33.40 percent, respectively, and as the drying air temperature increased from 50 °c to 70 °c. experimental exergy inflow, outflow, exergy loss and exergy efficiency increased from 4.01 j/s to 6.98 j/s, 1.83 j/s to 1.9 j/s, 3.18 j/s to 5.07 j/s and 21 to 27%, while simulated air temperatures increased from 5.01 j/s to 7.49 j/s, 1.33 j/s to 2.20 j/s, 3.66 j/s to 5.29 j/s and 27 to 29% respectively with respect to the drying air temperature range (50–70 °c). model equations were derived from the plotted graphs to express the energy and exergy parameters as a function of drying temperature. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 763 1.0 introduction drying is an industrial preservation method widely used in which water activity of food is decreased to minimize biochemical reactions of degradation. in order to improve the control of this unit operation, it is important to use accurate models to simulate the drying operation most especially the air flow and temperature distribution in the dryer as this is responsible for the uneven drying of the products which is one of the most reoccurring situation in a static convective dryers. odewole and oyeniyi, (2016) reported that drying is one of the most important processes in food processing and preservation. it is also defined generally as the removal of moisture from a material to a predetermined level by different authors (mujumdar, 2007; kumar et al., 2012; aviara, et al., 2014 and odewole and olaniyan, 2015). the use of computer programmes to predict the behaviours of drying process especially the thermal profile of drying air in the drying chamber has been advanced recently due to the advances in the development of computer software like computational fluid dynamics software that has the great capacity in evaluating the drying parameters with high efficiency which gives high impact to the cost of energy being used during the operation. amanlou and zomorodian, (2010) wrote that evaluating drying experimentally is costly but computational work using computer programs and models are more important to use due to lower cost and acceptable accuracy with minimum error. it has been adjudged that computational fluid dynamics (cfd) software reduces a lot of trial and error on experimental work because of its ability to give detailed account of the stringent parameters that cannot be observed analytically since it is capable of presenting visualized results. the advancement in the trust of cfd simulation has been enhanced by the improvement in computer codes in solving partial differential equations (pde) equations many dryer types have been reported to be in existence and several works have been done to improve their efficiencies but in terms of dryer simulation there are few reports on centre shaft (cs) rotary tray cabinet dryer in order to predict the thermal profile of the dryer system and the thermal analysis of the energy and exergy accounting of the dryer. data obtained from the cfd analysis were used to achieve this objective. 1.2 thermodynamics analysis the significance of thermodynamic principles is very important in performing the energy and exergy analyzes of the drying procedures. reason being that the fundamental rules of thermodynamics (i.e. first and second laws) govern the accounting of the analyzes. the first law is the foundation of the heat-balance technique of assessment frequently used in the performance analysis of the engineering system and the second law includes the reversibility or irreversibility of procedures and is a very significant element in the assessment of the energy system's exergy technique (i.e. the quality of the energy available in the scheme). dincer and sahin (2004) wrote that thermodynamic analyzes, especially exergy analyzes, seemed to be an important instrument for designing, analyzing and optimizing thermal systems. ozegerner and ozegernar (2006) wrote that the available and unavailable forms consist of energy from the thermodynamic point of view. work performed by a system is obtained from the available energy while the unavailable form of energy remains unexploited. whereas exergy refers to the accessible type of energy of the system that is convertible to full helpful job and strikes a balance with its setting from its initial state (coskun et al., 2009; hou et al., 2007). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 764 1.3 energy and exergy analysis the energy quality available for the drying method has been referred to as exergy, which is clarified by the second thermodynamic legislation (chemmala and dinesh, 2014). measuring these parameters has put cfd in a pinnacle in such a manner that it has been used in various ways to forecast fluid flow behavior and also to analyze the multiphysics governing such a complicated scenario. exergy is said to be the highest quantity of work obtainable from a stream of matter when some matter is carried to a state of thermodynamic equilibrium with the prevalent element of the natural environment through reversible processes and is a measure of the ability of a stream to cause change as a result of not being entirely stable in relation to the reference setting (dincer, 2002; pandey et al., 2012; prommas et al., 2010). the thermodynamic analysis-energy and exergy of a thermal system is very essential to technicians in order to optimize system efficiency, minimize losses, decrease operating and capital investment expenses, and improve heat system productivity (riviere et al., 2009). the optimal thermodynamic efficiency of a system is the proportion of helpful job to the quantity of energy provided to the system. drying process and dryer design have been advanced in a variety of ways based on the requirements for high-quality dried products, but the energy used during the drying process, especially for cabinet dryers, has not been spelt out in terms of the energy and exergy analyzes that were the focus of this present study. a number of research on this cogent element in dryer design have been performed on solar dryers, but few on this form of dryer. the aim of this research is therefore to conduct energy and exergy analyzes of the cabinet dryer using the information obtained during the cfd simulation and to input three inlet velocities in order to assess the impact of air velocity on the effectiveness of the csrtc dryer. 2.0 materials and methods 2.1 description of the csrtc dryer the dryer used for the drying procedure is shown in figure 1. it is basically split into three parts, the heat producing portion, the heat exchanger, and the drying chamber. the heat producing segment consists of a blower (axial cross flow fan) and a 1.8 kw red hot heating element. here, the blower vanes turns the flow centrifugally outwards through the blades to the pipes in the heat exchanger conveying the hot air to the drying chamber. the incorporation of the pipes is to control direct heating of the products being dried in the drying chamber. the third segment is the drying chamber separated into three compartments with a center rotating shaft that assists the uniformity of warm air in the drying chamber. three trays were stacked vertically here. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 765 figure 1: schematic diagram and part list of the csrtc tray dryer. 2.1 cfd simulation setup the 2-dimensional assessment of the flow pattern in the dryer was performed in ansys fluent solver as follows: the dryer's geometry was modeled in ansys design modeler to portray the dryer in 2-dimensions ; mesh analysis was performed in ansys icem. ansys fluent cfd solver was used because it is the easiest solution to analyze cfd simulation. (murathathunyaluk, et al., 2015). the fluid flow within the dryer was defined by using the commercial cfd code ansys fluent to solve iteratively using a 2d solver with a steady state condition, mass conservation, momentum equations and energy equations. the code utilizes a pressure-based solver for velocity-pressure coupling using the simple technique. the relaxation variables were 0.3 for stress, 0.7 for momentum, 1 for density, 1 for body strength and 0.8 for turbulent kinetic energy. gauss seidel's smoother form was used in sophisticated solution control. the velocity and temperature fields were discretized with a second order upwind system, while the pressure field was discretized with a presto (pressure discretization schemes) scheme. the convergence criteria for continuity and momentum equations residuals were 10-4 and 10-6 for standard model power and radiation equations with improved wall temperature therapy. the initialization of all the boundary conditions was done in order for the software to solve the numerical equations. the amount of iterations and the reporting rates were set at 600 and 10, respectively, in which the outcome converged at the 470th iteration. the airflow distribution and heat transfer inside the cabinet tray dryer were then plotted with contour lines to better represent the flow patterns. for the exergy assessment, the inlet and outlet temperatures calculated from the ansys fluent solver were used. in this research, a thorough thermodynamic inquiry is performed through energy and exergy analyzes to evaluate the performance of a center shaft rotary tray cabinet tray dryer during the drying phase of okra and to study how its working conditions and effectiveness can be further enhanced by varying the drying air temperature. some of the data used in the calculations were taken from computer-generated results during the cfd simulation conducted with ansys fluent 14.5 by varying the drying air temperature in order to converse materials and energy needed to run the experiments in replicates. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 766 figure 2: discretization of the 2d model of the csrtc dryer 2.2 energy usage by the dryer the following equations (1-3) govern the detailed account of the drying air behavior and the energy change with respect to the components in the dryer. it was presumed that the stream is steadystate with regard to the first thermodynamics law. the three equations describing navier-stokes equations are as follows (dincer, 2002): the conservation of mass for dry air m� hi� = m� ho� (1) the conservation of mass for humidity is given by: m� hi +m� hi� = m� ho� (2) the conservation of energy q� −w� = m� o h0 + vo2 2� − m� i hi + vi2 2� (3) where m� i and m� o are the mass flow rate at the inlet and outlet respectively (kg/s) q is heat energy inflow (kj/s), w is rate of mechanical work output in (j/s), hi and ho are the enthalpies of air at the dryer inlet and outlet temperature (j/kg) vi and vo are air velocities at dryer inlet and outlet respectively (m/s) since there is no resultant motion in the drying process, the momentum components vo2 2 and vi2 2 were eliminated and the equation is reduced to (4) q� = m� oh0� − m� ihi� (4) considering the mass flow rate of the air to be uniform (i.e. m� a = m� i = m� o ), equation (4) is reduced to q� = m� a h0 − hi (5) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 767 2.3 thermodynamic parameters wet air is considered a one-phase homogeneous system with only two components governed by the ideal gas law for fluid mixtures. 2.3.1 relative humidity it is defined as the ratio between the partial vapour pressure of water in the mixture at a given temperature (pv,t), and the saturated vapour pressure at the same temperature (psat,t): ∅ = pv@t psat@t × 100% (6) ∅ is the relative humidity (%), pv@t vapour pressure at time, t (pa) and psat@t saturated vapour pressure at time, t (pa) 2.3.2 specific humidity this is defined as the water vapour mass per drying air unit mass w = mv ma = 0.622 pv@t p − pv@t (7) w is the specific humidity (kg/kg dry air), mv mass of vapour (kg/s), ma mass of air (kg/s), pv@t vapour pressure at temperature, t (pa) and p is the total pressure (pa) 2.3.3 enthalpy (of the drying air) hda = cpdatda +whsat@t (8) hda is the enthalpy of the drying air (kj/kg), cpda is the specific heat of drying air (kj/kg.k), tda is the drying air temperature (k), w is the specific humidity (kg/kg dry air) and hsat@t is the enthalpy of the saturated vapour (kj/kg). figure 3: the mass-energy model for the drying experiment in respect to the components where: w = specific humidity (kg/kg dry air) t = air temperature (k) ∅ = relative humidity (%) h = enthalpy of air (kj/kg) fi and fo are the air conditions at the fan inlet and outlet file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 768 hi and ho are the air conditions at the inlet and outlet of the heater hei and heo are the air conditions at the inlet and outlet of the heat exchanger dci and dco are the air conditions at the inlet and outlet of the drying chamber qeva = thermal power obtained from evaporation (kj/s) qloss = thermal power loss (kj/s) 2.3.4 determination of fan outlet conditions q� −w� f = m� da hfo − hfi + vfo2 − vfi2 2 × 1000� (9) q� = 0 since there is no heat transfer and also since we are considering only the outlet conditions, vfi = 0 thus: hfo = w� f − vfo2 2 × 1000 1 m� da + hfi (10) where: hfi and hfo are the enthalpies of air at the inlet and outlet of the fan (kj/kg) vfi and vfo are the air velocities at the inlet and outlet of the fan (m/s) w� f is the power of the fan (kj/s) m� da is the mass flow rate of dry air (kg/s) 2.3.5 determination of heater inlet and outlet conditions qusable = m� dacpda thi − tho (11) 2.3.6 determination of energy utilization (eu) eu (energy utilization) was determined by applying the first law of thermodynamics as expressed by equation (5) and transformed in equation (12) eu = m� a h0 − hi (12) 2.3.7 determination of energy utilization ratio (eur) the energy usage ratio during the drying process was found from the equation given by (akpinar, 2004) eurdc = m� a hdci @ t − hdco@ t m� a hdci @ t − ha∞ (13) where: eurdc = the energy usage ratio for the drying chamber mda = mass of dry air hdci @ t = enthalpy of air at the inlet of the drying chamber at temperature, t (kj/kg) hdco @ t = enthalpy of air at the outlet of the drying chamber at temperature, t (kj/kg) ha∞ = enthalpy of air at ambient temperature, t (kj/kg) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 769 2.3.8 energy efficiency this was evaluated as the ratio of the energy used and the input energy ηe = ei − eo ei = m� a hdci @ t − hdco @ t m� ahdci @ t × 100% (14) where ηe is the energy efficiency in %, ei and eo are the input and output energy respectively in kj/s 2.4 exergy analysis the helpful notion of exergy in the assessment of thermal systems is implemented by the second law of thermodynamics which is a measure of the energy quality in the thermal system. total exergy of in stream, outflow and drying chamber losses were estimated in the scope of the second law assessment of thermodynamics. the fundamental method for chamber exergy assessment is to determine the exergy values at steady-state points and the reason for the process's exergy variation. the exergy values are calculated using the features of the working medium from the energy equilibrium of the first law. for this purpose, the mathematical formulations used to perform the exergy balance are as shown below as shown by (ahern, 1980). exergy = u− u∞� � �� � i − t∞ s − s∞� � ��� �� ii + p∞ j v − v∞ � � ��� �� iii + v2 2gj� iv + z − z∞ g gcj� � ��� �� v + ec μc − μ∞ nc + eiaifi 3t4 − t∞4 − 4t∞t3 +…� � �������������� ������������� vi (15) i – internal energy ii – entropy iii – work iv – momentum v – gravity vi – chemical radiation emission u specific internal energy, (kj/kg) t temperature, (k) s specific entropy, (kj/kg k) p pressure, (kpa) j joule constant v specific volume, (m3/s) v velocity, (m/s) g gravitational acceleration, m/s2 z altitude coordinate, (m) gc constant in newton's law h enthalpy, (kj/kg) μc – kinematic viscosity(m2/s) n number of species file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 770 the subscript indicates the terms of reference. only some of the conditions shown in equation 15 are used in the exergy analyzes of many structures, but not all. since exergy is energy accessible from any source, it can be created using materials ' electrical present flow, magnetic fields, and diffusion flow. one popular simplification is to replace enthalpy with internal energy and pv conditions relevant to steady-flow systems. equation 15 is often used under circumstances where the terms of gravity and momentum are ignored. in addition, the stress changes in the scheme are also overlooked because of v ≅ v∞, the general exergy equation is being derived from the above equation as follows: ex� = m� dacpda t− t∞ − t∞ in t t∞ (16) the inlet and outlet exergies were determined according to the drying chamber inlet and outlet temperatures. exdci = cpda tdci − ta − ta ln tdci ta (17) exdco = cpda tdco − ta − ta ln tdco ta (18) where: exdci and exdco are the exergy at the inlet and outlet of the drying chamber respectively (kj/s) 2.4.1 exergy efficiency akbulut and durmus, (2010) explained exergy efficiency as the ratio of the exergy use in the drying of the product exergy to energy inflow from the drying chamber. midilli and kukuk, (2003) gave the general form of the exergetic efficiency as follows: exloss = exdci − exdco (19) ηex = exdco exdci (20) where: exdci and exdco are the exergy at the drying chamber inlet and outlet respectively cpa is the specific heat of the air tdci and tdco are the temperature at the air inlet and outlet of the drying chamber respectively ta is the temperature of the environment ηex is the exergy loss 2.4.2 exergetic improvement potential the equation given by hammond and stapleton, (2001) was used to determine the exergetic improvement potential of the drying process. this is expressed as: ip� = 1− ηex exi� − ex0� (21) 3.0 results and discussions energy utilization (eu) was varied with the drying air temperature during the simulation process of okra (abelmoschus esculentus) drying and the relationship is presented in table 1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com table 1: temperature and enthalpies of air obtained from the cfd simulation drying temp. (°c) tdci@t tdco@t hdci@t hdci@t energy utilization energy utilization ratio energetic efficiency exp sim exp sim exp sim exp sim exp sim exp sim exp sim 50.00 322.38 328.56 294.82 301.00 152.34 186.12 123.56 137.33 14.10 23.91 0.15 0.19 18.89 26.21 55.00 328.04 331.51 299.04 302.51 219.00 218.96 150.73 159.21 33.45 29.28 0.21 0.19 31.17 27.29 60.00 332.06 332.45 303.64 304.03 259.67 251.79 187.93 181.08 35.15 34.65 0.18 0.18 27.63 28.08 65.00 337.35 337.15 306.73 306.53 304.11 302.60 208.43 207.89 46.88 46.41 0.19 0.19 31.46 31.30 70.00 339.27 341.85 306.44 309.02 347.89 352.41 229.66 234.70 57.93 57.68 0.20 0.20 33.98 33.40 3.1 energy utilization it can be said that the energy utilization increased from 14.10 to 57.93 j/s for the experimental data while 23.91 to 57.68 j/s for the simulation as the temperature of the drying air increased from 50 to 70°c this trend is in good agreement with aviara et al. (2014) in the drying of cassava starches that energy utilization increased from 1.93 to 5.51 j/s with varied drying air temperature of 40 to 60 °c. similar have been recorded by erbay and icier (2011) on the drying of olive leaves in a tray dryer and motevali and minaei (2012) on the drying of sour pomegranate arils in a microwave dryer. also, odewole and oyeniyi (2016) in the drying of green bell pepper in a convective cabinet tray dryer that energy utilization increased with increase in the drying temperature from 50 to 60 °c. the current research shows that the relationship that exist between eu (energy utilization) and drying air temperature is polynomial of the third order and can be represented by the following equation: eusim =− 0.0003t3 + 0.1106t2 − 8.0345t + 189.97, r2 = 0.9966 (22) euexp = 0.0113t3 − 2.0547t2 + 125.47t − 2535.8, r2 = 0.9804 (23) where, eu is the energy utilization, t is the dry air temperature and r² is the coefficient of determination. 3.2 energy efficiency the energy efficiency of okra (abelmoschus esculentus) drying in a center shaft rotary tray cabinet (csrtc) dryer increased from 18.87 to 33.98 percent for the experiment and from 26.21 to 33.40 for the simulation as the drying air temperature increased from 50 ° c to 70 ° c. the energy efficiency of okra drying in a cabinet dryer was discovered to have a third-order connection with drying air temperature and this connection was expressed with the following equation: ηesim =− 0.0006t3 + 0.1126t2 − 7.108t + 169.52, r2 = 0.9845 (24) ηeexp = 0.0097t3 + 1.7763t2 + 108.44t − 2171.6, r2 = 0.8954 (25) where, ηesim is the simulated energy efficiency, ηeexp is the experimental energy efficiency t is the dry air temperature and r2 is the coefficient of determination. 3.3 energy utilization ratio it can be deduced from table 1 that the energy utilization ratio increased from 0.15 to 0.20 for the experimental data while the simulated eur increased from 0.19 to 0.20 as the drying air temperature increased from 50 to 70 ° c this trend is advantageous because the energy used is minimal. current study demonstrates that the connection between eur (power usage ratio) and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 772 drying air temperature is third-order polynomial and can be represented by the following equation: eursim =− 4 × 10−6t3 + 0.0009t2 − 0.0597t + 1.4767, r2 = 0.9127 (26) eurexp = 6 × 10−5t3 − 0.0104t2 + 0.6265t − 12.359, r2 = 0.7161 (27) 3.4 variation of exergy inflow, exergy outflow and exergy loss with drying air temperature figure 4 below demonstrates the variety of exergy inflow, exergy outflow and exergy loss with drying air temperature in okra processing (abelmoschus esculentus). experimental exergy inflow, outflow and losses decreased from 4.01 to 6.98, 0.83 to 1.90 and 3.18 to 5.07 j / s respectively as the drying air temperature rose (50-70 ° c), while simulated exergy inflow, outflow and losses increased from 5.01 to 7.49, 1.35 to 2.20 and 3.66 to 5.29 respectively. this outcome gave a nice representation of the drying method since the drying method used energy. in addition, the quality of the energy used which was characterized as exergy improved with the drying temperature; this means that the drying temperature also improved the energy quality required for the drying procedure. aviara, et al. (2014) reported similar results in drying cassava starch using 40 to 60 ° c air temperature. akpinar et al. (2005) also noted the same trend in drying coroba slice in a convective type dryer connection between exergy inflow, outflow and exergy loss in drying air. colak et al. (2008) observed that the loss of exergy increased with an rise in temperature when drying mint leaves using a heat pump dryer. figure 4: effect of drying temperature on the exergy inflow, outflow and loss. the connections between exergy inflow, outflow and exergy loss and drying air temperature were discovered to be second-order polynomial. the connection is demonstrated in the following equations: exin_sim = 0.0044t2 − 0.4046t + 14.379, r2 = 0.985 (28) exin_exp = − 0.0023t2 + 0.4262t − 11.609, r2 = 0.9927 (29) exout_sim = 0.0011t2 − 0.092t + 3.1587, r2 = 0.9987 (30) exout_exp = − 0.0024t2 + 0.3505t − 10.645, r2 = 0.9778 (31) exloss_sim = 0.0033t2 − 0.3126t + 11.32, r2 = 0.9715 (32) exloss_exp = 0.0002t2 + 0.0757t − 0.9636, r2 = 0.9885 (33) where, exin_exp, exout_exp and exloss_exp are the experimental exergy inflow, outflow and exergy loss respectively, exin_sim, exout_sim and exloss_sim are the simulated exergy inflow, outflow and exergy loss respectively t is the dry air temperature and r² is the coefficient of determination. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 3.5 variation of exergy inflow, exergy outflow and exergy loss with energy utilization figure 5 shows that exergy inflow, outflow and losses varied with energy usage in a way comparable to their drying air temperature variability. each of them improved with enhanced energy usage and had a linear connection with energy usage. the relationships with the following equations were articulated: exin_sim = 0.0572eu+ 3.9113, r2 = 0.9214 (34) exin_exp = 0.072eu+ 2.9278, r2 = 0.9479 (35) exout_sim = 0.0374eu+ 2.9322, r2 = 0.9126 (36) exout_exp = 0.0449eu+ 2.4503, r2 = 0.9718 (37) exloss_sim = 0.0198eu+ 0.9792, r2 = 0.9221 (38) exloss_exp = 0.027eu+ 0.4775, r2 = 0.856 (39) where, eu is the energy utilization figure 5: effect of energy utilization (eu) on the exergy inflow, outflow and loss. 3.6 relationship between the exergetic efficiency with drying temperature figure 6 demonstrates differences in the center shaft rotary tray cabinet dryer's exertion effectiveness with drying air temperature. exergetic efficiency increased from 0.21 to increased drying air temperature (50–70 ° c). similar results were reported on the drying of cassava starches (aviara et al., 2014), eggplant slices (akpinar et al., 2005), green olive (colak and hepbasli, 2007), mint leaves (colak et al., 2008), jackfruit leather (chowdhury et al., 2011) and sour pomegranate arils (motevali and minaei, 2012). with regard to the temperature range used, the exergetic effectiveness differs inversely with the conduct of the energy efficiency. the connections between experimental exergetic effectiveness and drying air temperature were discovered to be second-class polynomial while third-class polynomial was discovered for simulated exergetic effectiveness. the connection is demonstrated in the following equations: ηex_sim = − 1 × 10−5t3 + 0.0021t2 − 0.1187t + 2.5125, r2 = 0.9333 (40) ηex_exp = 0.0024t2 − 0.2409t + 8.7156, r2 = 0.9498 (41) where, ηex_sim , ηex_exp are the simulated and experimental exergetic efficiency, t is the dry air temperature and r² is the coefficient of determination file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 774 figure 6: variation of exergetic efficiency with drying temperature 3.7 exergetic improvement potential figure 7 shows the impact of drying air temperature on the enhancement potential of drying okra (abelmoschus esculentus) in a center shaft rotary tray cabinet dryer. the figure shows that the potential for exertional enhancement increased with an rise in drying air temperature, which is in excellent agreement with the results obtained from the drying of cassava starches. aviara et al., (2014). erbay and icier, (2011) and aghbashlo et al., (2013) reported similar trend on the drying of olive leaves and fish oil encapsulation, respectively. the relationship existing between improvement potential and drying air temperature was depicted by the following equation: ipsim = 0.0024t2 − 0.2409t + 8.7156, r2 = 0.9498 (42) ipexp = 0.0015t2 − 0.1241t + 5.0283, r2 = 0.9646 (43) where: ipsim and ipexp are the simulated and experimental improvement potential in j/s respectively, t is drying air temperature in °c and r² is coefficient of determination. figure 7: variation of exergetic improvement potential with drying temperature. 4.0 conclusion computational fluid dynamics simulation using ansys 14.5 fluent cfd solver was used to explore the energy and exergy analysis of a center shaft rotary tray cabinet dryer. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):762-776. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com the relationship between the energy utilization (eu) and the drying air temperature is a polynomial with third order. second-order polynomial can best be used to define the trend between the energy utilization ratio and the drying air temperature. drying air temperature is directly proportional to exergy inflow, exergy outflow and exergy loss since an increase in the drying air temperature brings about increase in the exergy analysis. the energy utilization has the same trend with the drying air temperature when varied with the exergy inflow, exergy outflow and exergy loss. references aghbashlo, m., mobli, h., rafiee, s., and madadlou, a. (2013). a review on exergy analysis of drying processes and systems. renewable and sustainable energy reviews, 22, 1-22. ahern, j.e. (1980). the exergy method of energy systems analysis, john wiley, new york, 1980. akbulut, a. and durmuş a. (2010). energy and exergy analyses of thin layer drying of mulberry in a forced solar dryer. energy, 35:1754–1763 akpinar, e.k., midilli, a, and bicer, y. (2005). energy and exergy of potato drying process via cyclone type dryer. energy convers. manag. 2005;46:2530-2552. akpinar, e.k. (2005). energy and exergy analyses of drying of eggplant slices in a cyclone type dryer. j. mech. sci. technol. 2005;19(2):692-703. akpinar, e.k. (2004). exergy and exergy analyses of drying red pepper slices in a convective type dryer. int. j. of heat and mass transfer, 31 (8), pp. 1165-1176, 2004. amanlou, y. and zomorodian, a., (2010). applying cfd for designing a new fruit cabinet dryer, journal of food engineering, 101, 8-15. ansys, inc. ansys fluent user’s guide, southpointe 275 technology drive canonsburge pa 15317; usa, 2010. aviara, n.a., onuoha, l.n., falola, o.e. and igbeka, j.c. (2014). energy and exergy analyses of native cassava starch drying in a tray dryer. energy http://dx.doi.org/10.1016/j.energy.2014.06.087 elsevier celma, a.r., and cuadros, f. (2009). energy and exergy analyses of omw solar drying process. renew energy 2009;34:660–6. chemmala, f. and dinesh, l.r. (2014). exergy analysis of solar energy applications and renewable energy systems international conference on advanced trends in engineering and technology-2014 (forschung) chowdhury, m.m.i., bala, b.k., and haque, m.a. (2011). energy and exergy analysis of the solar drying of jackfruit leather. biosyst eng 2011;110:222-229. colak, n. and hepbasli, a. (2007). performance analysis of drying of green olive in a tray dryer. j food eng. 2007;80(4):1188-1193. colak, n., kuzgunkaya, e. and hepbasli, a. (2008). exergetic assessment of drying mint leaves in a heat pump dryer. j food process eng. 2008;31:281-298. coskun, c., bayraktar, m., oktay, z. and dincer, i. (2009). energy and exergy analyses of an industrial wood chips drying process’, int. j. low-carbon tech., vol. 4, pp. 224-229 dincer, i. (2002). on energetic, exergetic and environmental aspects of drying systems”, int. j. energy res., vol. 26, no.8, pp. 717–727.2002 http://dx.doi.org/10.1016/j.energy.2014.06.087 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyeniyi , et al: computational fluid dynamics (cfd) analyses of energy and exergy in thin layer drying of okra (abelmoschus esculentus) slices using centre shaft rotary tray cabinet (csrtc) dryer. azojete, 15(3):762-776. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyeniyisk@gmail.com 776 dincer, i. and sahin, a.z. (2004). a new model for thermodynamic analysis of a drying process”, international journal of heat and mass transfer, vol. 47, no. 4, pp. 645–652.2004 erbay, z. and icier, f. (2011). energy and exergy analysis on drying of olive leaves (olea europaca l.) in tray drier. j food process eng 2011;34:2105-2123. hammond, g.p. and stapleton, a.j. 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(2007). handbook of industrial drying fourth edition crc press taylor and francis group london new york, 2007 murathathunyaluk, s., srisakwattana n., saksawad t., and bumrungthaichaichan, e. (2015). development of rotating tray dryer and study of the hot air flow pattern with computational fluid dynamics, chemical engineering transactions, 43, 1669-1674 doi: 10.3303/cet1543279 odewole, m.m. and olaniyan, a.m. (2015). empirical modeling of drying rate and qualities of red bell pepper. lap lambert academic publishing. odewole, m.m. and oyeniyi, s.k. (2016). analyses of energy parameters in convective drying of osmo-pretreated green bell pepper in a cabinet dryer. proceedings of the 5th international specialized scientific and practical conference september 14, 2016 kyiv, ukraine. pg. 13-15 ozegerner, l. and ozegerner, o. (2006). energy analysis of industrial pasta drying processes’, int. j. of energy research, vol. 30, № 15. pp 1323-1335 prommas, r., rattanadecho, p., and cholaseuk, d. (2010). energy and exergy analyses in drying process of porous media using hot air. international communications in heat and mass transfer, 37:372–378 riviere, a., khalil, b.a. and berthou, m. (2009). an energy efficiency assessment, tool base on process energy and exergy analysis method’, paper presented at the proceedings of the european council for energy efficient economy (eceee) summer study. panel 5, june 9-10, stockholm, sweden http://www.ache.org.rs/ciceq http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):395-405 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 395 original research article modification and performance evaluation of active solar dryer for high moisture tomato crop k. mu’azu1*, a. mahmood2, b. inuwa2, i. g. sadiq2 and m. u. shitu3 (1department of pilot plants and fabrication technology, national research institute for chemical technology, zaria, nigeria 2department of industrial and environmental pollution, national research institute for chemical technology, zaria, nigeria 3department of petrochemical and allied technology, national research institute for chemical technology, zaria, nigeria.) *corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk article information submitted 14 september, 2018 revised 17 february, 2019 accepted 19 february, 2019 keywords: modified dryer unmodified dryer drying rate drying time moisture content abstract in this study, two active solar cabinet dryers with capacity each to dry 10 kg of fresh vegetable were fabricated. the drying cabinet of the first dryer was fabricated using plywood and is refer to as unmodified dryer (um) while the second dryer with white transparent glass and is refer to as modified dryer (md). the performances of the two dryers in terms of total drying time, final moisture content obtained and preservation of nutritive values of the dried vegetable were investigated using tomato as sample. ten kilogram of the sample were sliced to about 1cm and neatly arranged in the drying chamber for the drying process in a period of two days (8am-6pm). the results revealed that there was a reduction in total drying time of 2.5 hours, from 18 hours in um to 15.5hours in md which corresponds to reduction in moisture content (wet basis) from initial value of 92% to final moisture content of 1213.3%. the results further revealed that maximum drying rate of 6.9 kg/h was observed for um dryer and 9.4 kg/h for md both obtained within 8 hours of drying time. the average temperature recorded in the md was found more than the um by about 13°c at 3.00pm. the efficiency of the md in terms of reduction in total drying time was 13.89% higher than the um. proximate analysis result shows the composition of the dried tomato in the um to be protein, 0.76%; lipids, 1.00%; vitamin e, 0.0083%; moisture content, 13.3%; ash, 0.60% and crude fiber, 1.80%. however, the composition of dried tomato in md were protein, 0.69%; lipids, 0.90%; vitamin e, 0.0080%; moisture content, 12%; ash, 0.58% and crude fiber, 1.78%. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction vegetable crops are grown in many parts of the world contributing significantly to income security and the nutritive diet (30-50% iron and vitamin a) of many households. global production of fruits and vegetables tripled from 396 million mt in 1961 to 1.34 billion mt in 2003 (usda, 2007). in spite these promising figures, hardly two percent of the produce is processed and 40-50 % is being wasted due to lack of processing and preservation infrastructure. mailto:kabirumuazu@yahoo.co.uk http://www.azojete.com.ng mu’azu, et al: modification and performance evaluation of active solar dryer for high moisture tomato crop. azojete, 15(2):395-405. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 396 the situation is worse for farmers in the rural areas and requires urgent attention. most of the harvested vegetables and fruits are susceptible to deterioration due to poor preservation. the moisture content in the agricultural produce contributes greatly to the deterioration of vegetables and fruits. therefore if the agricultural produce is to be stored for longer length of time, it is necessary to reduce its moisture level to certain well-defined limit. this will prevent the production of undesirable chemical compositional changes in the produce by bacteria, mould and enzyme which will spoil the vegetables and fruits (bolaji et al., 2011). tomato (lycopersicon esculentum mill.) fruit is one of the most popular, as well as important, commodities in the world. over 20 million metric tons of tomato is produced each year on a world basis. the united states, italy, spain, and the united arab emirate are the leading producers of this crop. in the united states alone, it ranks second only to potatoes in production among vegetable crops and contributes approximately 400million dollars to the economy. nigeria is ranked 16th on the global tomato production scale, accounting to 10.79% of africa’s and 1.2% of total world production (weingberger and lumpkin, 2007). solar drying is a process of using solar energy to heat air so as to achieve drying of agricultural products (ajay et al., 2009). solar air heaters are simple devices usually employed to heat air by utilizing solar energy and in many applications requiring low grade to moderate temperatures below 80oc such as in crop drying and space heating (bukola and ayoola, 2008). the application of passive solar dryers for drying agricultural products in the tropics has often been hampered because crops mature during the peak of the rainy season when frequent downpours and overcast skies are the norm. this often slows down drying, causes rewetting during periods of downpours even in some cases where forced convection is used for the drying. the final dried product takes longer time to dry and does not have an attractive appearance because of moisture pick up during drying resulting in mould growth (berinyuy et al., 2012). many researchers have studied drying pattern of vegetables using unmodified (um) type of active solar dryer and reported various drying times, rate of drying and final moisture contents obtained; bello et al (2013); joel et al (2013); ibrahim, (2005) and wankhade et al (2013); investigated drying characteristics of okra using hot air dryers. mu’azu et al (2012) studied drying pattern of tomato, kabiru et al (2016) investigated drying characteristics of moringa leaves while akintunde and afolabi (2009); hussan and tabassum (2015), studied that of red pepper and onion respectively. however, drying characteristics of high moisture vegetables using this type of modified dryer system appears not to be available in the literature. therefore, the main purpose of this study is to evaluate the performance of the md in terms of total drying time, final moisture content and preservation of some active nutrients present in the dried sample and compare with the um. in evaluating this dryer, tomato was used as experimental sample primarily because of its high moisture content of about 92% (wet basis). 2.0 materials and methods 2.1 materials 2.1.1 description of the unmodified dryer the schematic diagram of the dryer with dimensions in centimeter is shown in figure 1. the unmodified cabinet solar dryer (um) consists mainly of solar collector, drying cabinet, and moisture extracting fan. the cabinet was constructed using plywood and covered with aluminum sheet to protect it from rain. inside the cabinet at mid position 5 perforated trays were placed. an opening was provided at the top of the cabinet to suck the moist air inside the dryer with the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):395-405. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 397 help of 0.5 hp suction fan. the power rating of the air suction fan was calculated from equation (1) as given by youcef–ali et al (2001). ml ta m pv p    (1) where: va is the volumetric flow rate of air (m3/hr) and is defined as the ratio of mass flow rate of air/density of air, ∆pt is the total pressure drop in the system (pa), ηl is the fan efficiency factor (%) and ηm is the motor efficiency factor (%). based on the power rating the photovoltaic (pv) solar cell was selected. figure 1: schematic diagram of fabricated solar vegetable dryer 2.1.2 description of the modified dryer the existing dryer (um) described above in figure 1 was modified (md) by replacing all the side walls of the drying chamber constructed using plywood with white transparent glass. the dimensions of the dryer remained unchanged as well as the number of trays and position of the moist air extracting fan. the choice of white transparent glass as replacement to plywood was based on the fact that glass has higher thermal conductivity (1.05 w/m k) than wood (0.13 w/m k). this means that glass material will allow more heat to pass to the vegetable to be dried than plywood. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: modification and performance evaluation of active solar dryer for high moisture tomato crop. azojete, 15(2):395-405. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 398 2.1.3 solar collector (air heater) the solar collector was constructed from wooden box having gross dimensions of 148cm long, 50cm wide and 30 cm deep. the area of the solar collector was determined using equation (2) sodha et al. (1987). acφƞ = et (2) where: et= total useful heat received by the drying air (j), φ = total global solar radiation on horizontal surface during dry season (w/m2) and η = 30 to 50% (collector efficiency). in this work, η = 44%. the optimum angle of tilt of the solar collector was equal to the latitude of the location and the minimum angle should be 15°. the total useful heat needed q in joules to transfer to the drying air was also estimated using equation (3) as given by youcef–ali et al. (2001) and where mw is the mass of water evaporated in kg; and hfg is the latent heat of vaporization of h20 in j/kg, q can be calculated using equation 3. q = mw × hfg (3) the side walls and bottom were constructed using two layers of plywood (3 mm thick). low density foam of 0.04m thick was inserted in the space between the two layers of the plywood. the absorber plate was formed from a corrugated iron sheets which is a good conductor of heat. it was painted with matt black paint in order to absorb the maximum amount of solar radiation. the solar collector was covered with one layer of a clear glass, 3 mm thick to reduce the reflection of radiation and heat losses by convection (mu’azu et al., 2012). the solar collector was attached to the drying chamber by an air duct. the solar collector was oriented to face south direction and tilted to an optimum tilt angle of 15° at noon (figure 1). 2.1.4 drying chamber the side walls and bottom of the drying chamber were constructed from plywood (3 mm thick) and covered with aluminum sheet to protect it from rain. the shelves were made from aluminum mesh and arranged horizontally as shown in figure 1. the chamber door was located at the back side and constructed using the same material as the walls with dimensions of 60cm long, 35cm width and 35cm breadth. drying air enters the chamber after leaving the solar collector through the bottom of the dryer connected with an air duct and passes through the trays from the bottom (ajay et al., 2009). 2.1.5 drying air conditions the conditions of the drying air used in this work were determined by the method described by mohammed et al (2010) and presented in table 1. table 1: drying air conditions used in this study parameter value location zaria, nigeria (lat. 11°11’n) relative humidity, % 19 mass flow rate of air, kg/s 0.039 incidence solar radiation, mj/m2/day 20 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):395-405. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 399 2.1.6 material source and preparation fresh tomato (lycopersicon esculentum), were obtained from galma farm, zaria, along jos road, nigeria. the tomato was sliced to approximate sizes of 1cm to increase the surface area exposed to drying air. 2.2 methods 2.2.1 drying procedure the experiment was performed in the month of april when the fabrications of the dryers were completed. each experiment started at 8:00 am and continued till 6:00 pm for two days. at the initial stage, digital thermometer was inserted in each of the dryers to monitor variation of temperature with time inside the drying cabinet. to determine moisture loss on the drying samples during experiments, 10 kg of the sliced tomato were weighed and neatly arranged in the drying cabinet with maximum of 2 kg per tray. samples were taken out of the solar dryer and weighed at various time intervals, ranging from 30 minutes at the beginning of the drying process to 1hr during the last stage. the drying process was stopped when no further changes in the masses of drying tomato were observed. the mass of the tomato samples were determined with the help of a digital electronic weighing balance having an accuracy of 1% and the moisture content (wet basis) in each case was calculated using equation (4). mw = (mi −mdt /mi] x 100 (4) where: mw is the moisture content in percentage; mi is the initial weight of the tomato in kg and mdt is the weight of the tomato at any time during the drying process in kg. the partially dried tomato in the first day was collected in a polyethylene bag and air tight to avoid moisture absorption at night. these partially dried tomatoes were again spread in the dryer in the following day and the drying process continued until no further changes in their masses were observed. mu’azu et al (2012) reported that the rate of drying at any given time in the dryer can be estimated using equation (5). similarly, both atmospheric and dryer temperatures were monitored and recorded at 30 minutes interval (wankhade et al., 2012). rd = (mp −md) td (5) where: rd is the drying rate in kg/h; mp is the weight of the tomato in kg; md weight of the tomato at any given time in kg; td is the drying time (h) at which md is obtained during the drying process. the total drying time is the difference between initial drying time and final drying time to achieve the equilibrium moisture content. 2.2.2 proximate analysis the proximate analysis which include ash content, lipids content, total protein, water content, and crude fiber content of both fresh and dried tomato in the md and um were evaluated according to the standard established methods described by joel et al. (2013). lipids were determined by soxhlet extraction of a sample of 10g, with hexane as solvent. the initial water content of the tomato was estimated after drying of 10 g of sample at 103°c in an oven to a file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: modification and performance evaluation of active solar dryer for high moisture tomato crop. azojete, 15(2):395-405. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 400 constant weight. the estimation of vitamin e content was performed according to jedlicka et al. (2005). 3.0 results and discussion 3.1 variation of temperature in the dryer figure 2 and 3 depicts variation of temperature in both modified and unmodified dryer for the first and second day of drying process respectively. as seen in figure 2, the unmodified dryer attained a maximum temperature of 49°c at about 3:00 pm while the modified dryer attained its maximum temperature of 58°c at 2.00pm. this means that the modification provides temperature rise of about 9°c (58°c-49°c) which resulted in increase in moisture removal from the tomato and consequently reduction in the drying time. figure 2: variation of temperature inside and outside the dryer as a function of time in the first day however, maximum ambient temperature of 35°c was recorded also at 2.00pm and minimum of 29°c at 9:00 a.m. this difference between air temperatures of the surrounding and cabinet solar dryer (modified and unmodified) is responsible for buoyancy effect which causes air flow as reported by bolaji et al (2011); james and peter (2012); el-sebali and shalaby (2011) and adelaja and babatope (2013). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):395-405. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 401 figure 3: variation of temperature inside and outside the dryer as a function of time in the second day in the modified dryer, maximum of 56°c was recorded at 2.00pm and then declined while for unmodified dyer maximum temperature of 49°c was attained at 3.00pm. it can also be seen (figure 2) that as surrounding temperature increases the temperature inside the cabinet solar dryer also increased and vice versa. these changes in temperature were due to the continuous rotation of the earth along its axis with maximum solar incidence of about 20mj/m2 per day obtained during peak time between 1-3pm as reported by mu’azu et al. (2012). however, similar pattern of temperature variation was also observed in the second day of the drying process (figure 3) with maximum temperatures of 56.7°c and 49.5°c recorded at 3pm for both modified and unmodified dryer respectively. 3.2 variation of moisture content with drying time the curves in figure 4 depict the changes in moisture content of the drying tomato with time in both um and md. at the initial stage, the tomato had moisture content of 92% (wet basis) and decreased over time until a final moisture content of 13.3 % was achieved within total drying time of 18 hours for um and 12% (wb) for md in 15.5 hours for md. therefore, modification of the drying cabinet significantly reduced the drying time by 2.5 hours (18-15.5 hours) due to a quicker moisture removal from the tomato. figure 4: variation of moisture content with time in the dryer file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: modification and performance evaluation of active solar dryer for high moisture tomato crop. azojete, 15(2):395-405. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 402 the final moisture content of 12 and 13.3% (wb) achieved in this study were relatively higher than 5.7% (wb) obtained by mu’azu et al. (2012) but in agreement with the result obtained by adewale et al (2018). this could be attributed to the high relative humidity (19%) of the drying air used in this study. significant reduction in moisture content was observed between 0-10 hours in um and 0-8 hours in md before declining to insignificant values. the rapid removal of moisture at the initial stage (0-10 hours) was due to evaporation of free moisture (unbound) from the outer surface layer and gradually progressed to internal moisture (bound). this internal moisture migrates from the inner layers to the surface and subsequently evaporated (monhanraj et al., 2009). it was also observed in figure 4 that there was insignificant reduction in moisture between 4.00-6.00pm in the first day and 9.00-11.00am in the second day and was attributed to low insolation during these periods. 3.3 variation of drying rate with time the rate of moisture removal from the tomato as a function of drying time is shown in figure 5. it is evident from figure 5 that at the initial stage of drying process (0-3 hours), the rate of moisture removal was insignificant in both md and um which corresponds to 9.00-11.00am of the drying time. this was due to the low insolation and higher relative humidity during these periods. however, beyond 4 hours of drying time, significant moisture removal was observed reaching a maximum value of 9.4kg/h at corresponding time of 8 hours for md and 6.9kg/h for um also within the same drying time. this means that an increase in moisture removal of 2.5kg (9.4kg/h – 6.9kg/h) was recorded in the md. these higher drying times in both dryers were attributed due to the following two reasons; 1. attainment of peak insolation rate of about 20mj/day which occurred between 12 noon to 3.00pm depending on the latitude, 2. the moisture removed during these drying times were mostly free moisture or unbound moisture held within the porous structure of the tomato fiber and its removal is usually governed by mass transfer process (mu’azu et al., 2012). figure 5: rate of drying as a function of time the decline in the rate of drying was observed after 8 hours for both md and um and continued until insignificant values were observed in 15.5 hours for md and 18 hours for um. at these http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):395-405. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 403 times, the final moisture content achieved were 12% (wb) in um and 13.3 % (wb) in md implying that no further drying could take place under this drying air conditions used (mu’azu et al., 2012). it is also important to note in figure 5 that the rate of moisture removal from md was generally faster than the um which resulted in reduction of total drying time. 3.4 proximate chemical composition comparative analysis of nutritional values of fresh and dried tomato in both um and md is presented in table 2 and the fresh tomato was served as control. the values obtained for dried tomato in md were slightly lower than those obtained in um and fresh sample. table 2: proximate analysis of both fresh and dried tomato in um and md parameter fresh dried (um) dried (md) proteins, % 0.78 0.76 0.69 lipids, % 1.10 1.00 0.90 vitamins e, % 0.089 0.083 0.080 moisture, % 92 13.3 12 ash, % 0.60 0.60 0.58 crude fiber, % 1.86 1.80 1.78 the high moisture contents obtained was due to high relative humidity of the drying air compared to 8.67% (wb) obtained by opadotun et al. (2016). there was good correlation on the nutritional values in both dryers with slight differences which could be largely attributed to the direct effect of uv light on the tomato during drying in md. generally, both dryers have proved to be effective in terms of preservation of these active ingredients and also agreed closely with the work conducted by other researchers (joel, et al., 2013; navalea et al., 2015). 4.0 conclusions this study showed that the temperatures in the md were generally higher than in the um with maximum temperature of 58°c recorded in md and 49°c in um at about 3 pm. the total drying time to achieved final moisture content of 12-13.3% (wb) had reduced due to modification from 18 hours to 15.5 hours representing reduction of 13.89% or 2.5 hours. proximate analysis of some active nutrients in the dried tomato in both dryers showed good correlation when compared with the fresh tomato. this study will be useful in exploiting the concept of this modified dryer by farmers in drying vegetables instead of the traditional active solar dryer due its numerous advantages especially reduction in drying time. references adelaja, ao. and babatope, bi. 2013. analysis and testing of a natural convection solar dryer for the tropics. journal of energy, 4(1): 1-8. http://dx.doi.org/10.1155/2013/479894 adewale, o., jumoke, i. and ifeoluwa, a. 2018. influence of drying temperature and storage period on the quality of cherry and plum tomato powder. food science and nutrition, 6:11461153. https://doi.org/10.1002/fsn3.658 http://dx.doi.org/10.1155/2013/479894 https://doi.org/10.1002/fsn3.658 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu, et al: modification and performance evaluation of active solar dryer for high moisture tomato crop. azojete, 15(2):395-405. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 404 ajay, c., orsunil, ks. and deepak, dp. 2009. design of solar dryer with turbo ventilator and fireplace. www.solarfood.org/solarfood. akintunde, tt. and afolabi, tj. 2009. drying of chili pepper (capsicum frutscens). journal of food process engineering, 33(4): 649-660. bello, mo., olabanjo, io., abdulhammed, m. and okunade, to. 2013. characterization of domestic onion wastes and bulb (allenion cepa l): fatty acids and metal contents. international food research journal, 20(5): 2153-2158. berinyuy, je., tangka, jk. and weka-fotso, gm. 2012. enhancing natural convection solar drying of high moisture vegetable with heat storage. agricultural engineering institute: cigr journal, 14(1): 141-148. bolaji, bo., olayanju tma. and falade to. 2011. performance evolution of a solar wind ventilated cabinet dryer. the west indian journal of engineering, 33(1): 12-18. bukola, ob. and ayoola, po. 2008. performance evaluation of a mixed-mode solar dryer. american journal of food technology, 11(4): 225-231. el-sebali, aa. and shalaby, sm. 2011. solar drying of agricultural products: a review. renewable and sustainable energy reviews, 16: 37-43. hussan, ab. and tabassum, y. 2015. antimicrobial, phytochemical, ethno-botanical and proximate analysis of allium cepa l. journal of advanced botany and zoology, 3(1): 1-4. ibrahim, d. 2005. drying characteristics and kinetics of okra. journal of food engineering, 69(3): 275-279. james, s. and peter, s. 2012. performance evaluation of an enhanced fruit solar dryer using concentrating panels. energy for sustainable development, 16: 224-230. jedlicka, a. and klimes, j. 2005. determination of water and fat-soluble vitamins in different matrices using high-performance liquid chromatography. chemical processing, 59 (3): 202-222. joel, bk., cisse-camara, m., absalom, am., georges, gt., daniel, es. and etienne tv. 2013. comparative study of proximate chemical composition of two varieties of okra dried by two methods: sun and electric drying. american journal of bioscience, 1(4): 74-79. kabiru, m., mahmood, a., bashir, i., shittu, mu., musa, ak. and zakariyya, a. 2016. design, development and performance evaluation of active solar dryer for drying moringa leave under controlled conditions. proceeding of 6th annual international conference of the renewable & alternative energy society of nigeria (raeson). mohammed, ma., gamea, gr. and keshek, mh. 2010. drying characteristics of okra by different solar dryers. journal of agricultural engineering, 27(1): 294-312. mu’azu, k., bugaje, im. and mohammed, ia. 2012. performance evaluation of forced airconvection vegetable drying system. journal of basic applied science research, 2(3): 2562-2568. monhanraj, m. and chandrasekar, p. 2009. performance of a forced convection solar dryer with gravel as heat storage material for chilli drying. journal of engineering science and technology, 4: 305-314. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):395-405. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 405 navalea, sr., harpaleb, vm. and mohitec, kc. 2015. comparative study of open sun and cabinet solar drying for fenugreek leaves. international journal of renewable energy technology research, 4(2): 1-9. opadotun, oo., adekeye, sa., ojukwu, eo. and adewumi, aa. 2016. comparative analysis of nutritional values of tomatoes subjected to different drying conditions. international journal of basic and applied sciences, 5(1): 6-9. sodha, ms., bansal, nk., kumar, a., bansal, pk. and malik, ma. 1987. solar crop drying. vol. i and ii. cpr press, boca raton, florida, usa. usda. 2007. the us and world situation: fresh and processed tomatoes. usda foreign agricultural services horticultural and tropical products division. wankhade, pk., sapkal, rs. and sapkal, vs. 2012. drying characteristics of okra slices using different drying methods by comparative evaluation. proceedings of the world congress on engineering and computer science, vol.ii, san francisco, usa. wankhade, pk., sapkal, rs. and sapkal, vs. 2013. drying characteristics of okra slices on drying in hot air dryer. proceeding engineering, 51: 371-374. weingberger k. and lumpkin, ta. 2007. diversification into horticulture and poverty reduction: a research agenda, 35(8):1464-1480. youcef -ali, s., messaoudi, h., desmons, jy., aene, a. and le ray, m. 2001. determination of the average coefficient internal moisture transfer during the drying of a thin bed of potato slices. journal of food engineering, 48 (2): 95-101 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng original research article modification and performance evaluation of active k. mu’azu1*, a. mahmood2, b. inuwa2, i. g. sadiq2 arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):823-836 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 823 original research article crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria m. d. zakari1, i. audu2, h. e. igbadun3, n. m. nasidi1, a. ibrahim1 and a. shitu1* (1department of agricultural and environmental engineering, bayero university, kano, nigeria 2department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria 3department of agricultural and bioresource engineering, ahmadu bello university, zaria, nigeria) * corresponding author’s email address: ashitu.age@buk.edu.ng 1.0 introduction tomato (lycopersicon esculentum) is an essential and popular vegetable crop grown in nigeria. tomato is grown almost throughout the country, though the most important areas lie in the northern and south-western regions. in the southern parts of the country, the crop is grown in small holdings under rain-fed conditions while it is grown extensively under irrigation in the northern parts of the country (olorunaiye, 2009). tomato yields of between 18 and 52 tonnes/ha have been reported for northern savannah regions (quim, 1980) and between 12 and 24 article information submitted 5 september, 2016 revised 5 october, 2018 accepted 9 october, 2018 keywords: deficit irrigation mulching crop coefficient (kc) mulch practices abstract this work determined the effects of deficit irrigation and mulching practices on crop coefficient (kc) of tomato in the kano river irrigation project (krip) kadawa, kano, nigeria. experiments comprised of four levels of water application depths (40, 60, 80, and 100% of weekly reference evapotranspiration) and four levels of mulching (no-mulch (nm), rice-straw-mulch (rsm), wood-shaving-mulch (wsm) and white-polyethylene-mulch (wpm)) was conducted to examine changes in kc value. the mean kc values (early, developmental, mid and late stages) of fully irrigated treatments were 0.70, 0.81, 1.07 and 0.78; 0.64, 0.76, 0.99 and 0.71; 0.60, 0.73, 0.94 and 0.69; and 0.53, 0.66, 0.86 and 0.62 for nm, rsm, wsm and wpm respectively while that of deficit irrigation ranged from 0.17 to 1.13 across the treatments, noting that the highest kc was observed under nm treatments. statistical analysis reveals that the effect of various levels of irrigation and mulching practices on kc of tomato was highly significant at p＜ 0.05 level of significance with a high mean value of 1.13 obtained at i100 and nm respectively. it was concluded to encourage tomato farmers in krip to adopt the use of their rice straw for mulching cum deficit irrigation (20%) towards conserving irrigation water for sustainability. also, results obtained from this study can be used as a guide to farmers in irrigating tomato crop and to engineers in the design of irrigation systems. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. http://www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 824 tonnes/ha for southern rainforest areas of the country (oyinlola and akintoye, 2004). much lower yields are obtained in local farms because of the use of low yields varieties, diseases and pests problems and inadequate cultural management as well as reliance on rain-fed production and residual soil (olorunaiye, 2009). thus, improved management and planning of the water resources are needed to ensure proper use and distribution of the water among competing water users. achieving greater efficiency of water use will be a primary challenge for the near future and will include the employment of techniques and practices that deliver a more accurate supply of water to crops (geerts and raes, 2009). hence, deficit irrigation practice is aimed at minimizing water applied to the crop to maximize crop yield per water applied (faloye and alatise, 2015). a preliminary study (oral interview physical and observation) indicates the problems of waterlogging, off-farm water overflow, and the increasing rise of the water table in the study area while areas downstream of the schemes rarely received water. moreover, majority of the farmers in the study area applies irrigation water base on their personal experiences. towards establishing best irrigation water management practice in krip, knowledge of the amount of water required for growing the crops is essential. the crop coefficient (kc) remains a useful parameter in determining the amount of water the crop requires. however, the kc values of the majority of the crops grown in nigeria and particularly in krip have not been determined for the area. farmers and researchers mostly rely on published literature which are mainly determined elsewhere. therefore, this work attempted to determine the kc values of uc 82b tomato variety in the study area, also investigates the effect of mulching and deficit irrigation practices on the kc values. 2. materials and methods 2.1 climate and location the study was conducted at the irrigation research station, kadawa, situated in the kano river irrigation project i (krip) under hadejia jamare river basin development authority (hjrbda), kano state, nigeria. the study area is located between latitudes 11°32`n and 11°51`n and longitudes 8°20`e and 8°40`e within the sudan savannah zone of northern nigeria (jibril et al., 2008). it has a planned gross irrigable area of 22,000 ha comprising of two main canals called the west branch and east canals as phase i and phase ii respectively. the area being tropical has a wet-and-dry type climate with relatively broad and rapid changes in temperature and humidity. the mean daily maximum and minimum temperatures were 31°c and 21°c, respectively. rainfall was concentrated between july and september with maximum and minimum of 214.0 and 132.7 mm, respectively as reported by maina et al. (2012) and the rainfall preceded by violent sand storms and the average annual rainfall was 884.4 mm, 60% of which falls in july and august. 2.2 field/laboratory work 2.2.1 soil moisture content determination soil samples were collected randomly at upstream, midstream, and downstream of the experimental site using core sampler. the soil moisture content was determined gravimetrically following the methods described by michael and ojha (2005) using equation 1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 100 t w w w wm (1) where: mw = wet basis moisture content in % ww = weight of water in g wt = total weight of the soil in g 2.2.2 bulk density determination soil bulk density obtained following the core sampler method as reported by (grossman and reinsch, 2002), using equation 2. s b c mp v  (2) where: ρb is the soil bulk density in g/cm3, ms is the mass of oven-dried soil, in g, and vc is the volume of the core cutter in cm3. 2.2.3 depth of root zone determination the depth of the root zone for the tomato crop was obtained from (erzd, 2014), as reported vegetables are generally shallow-rooted, which ranges between 50 – 60 cm (fao, 2013). 2.3 experimental treatments a total area of 1,500 m2 land was used in this study. the fieldwork was conducted using tomato crop of uc 82b variety at krip, kadawa, kano state, nigeria, and the seeds were purchased from the state ministry of agriculture. the field experiments consisted of 16 treatments. the treatments comprised four levels of irrigation (water application depths) and four levels of mulch practices, thus constituting a 24 factorial experiment. the four levels of irrigation were water application depths of 100, 80, 60, and 40% of weekly reference evapotranspiration (wret), while the four levels of mulch practice consisted of no mulch (nm); straw milled (rsm), wood shaving (wsm) and white polyethylene mulch (wpm) as mulch materials. the 16 treatments were replicated three times, making 48 treatments in total (igbadun and oiganji, 2012). the experimental treatments were assigned to plots in a randomized complete block design (rcbd), with the blocks lying across the general field slope (see figure 1a, b, and c). a distance of approximately 3.5 m separated the blocks while the basins in each block were separated by a distance of approximately 1 m which minimizes lateral movement of water from one basin to another. 2.4 agronomic operations a land area of 60 m × 25 m was harrowed and prepared into leveled basins of 2.5 m × 2.5 m. the field was cleared by weeding grown weeds and then irrigated before transplanting. tomato (uc 82b variety) seedlings were transplanted. the tomato seedlings were raised in the nursery and transplanted three (3) weeks after planting (fao, 2013). the transplanting was done in a row at plant spacing of 30 cm between plant and 30cm between rows and the plant's population per plot was approximately 80 tomatoes, and consequently, 3,840 tomato stands for the entire fortyeight (48) experimental plots. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 826 fertilizer (di-ammonium phosphate fertilizer (npk 15:15:15) was applied two weeks after transplanting and weeded, as recommended by fao (2013). the mulch materials, except white polyethylene materials, were placed two weeks after transplanted tomatoes were well established. the white polyethylene materials placed on the same day of transplanting. because it will be difficult and may distort the smooth growth of the tomato after the establishment of the tomato plants, the white polyethylene materials were cut into 6.25 m2 size and placed over the entire basin on the day of transplanting, precisely before transplanting in order not to distort the smooth growth of the tomato plants. in additions, planting of tomato was carried out by the plant spacing, and the tomato seedlings passed through the holes. the average weights of rice straw and wood-shaving mulch spread in each of the plots with assigned treatments of rice straw and wood-shaving were 1.2 kg and 2.25kg, respectively. weeding was carried out three times before harvesting on plots with mulch and without mulch treatments, while no weeding was carried out on plots with white polyethylene mulch material after transplanting. figures 1a, b, and c show the operational field setup from plot layout up to the overall setup of the experiment. systemic insecticide (cypermathrin) was applied at the rate of 65 kg/ha every week at the early flowering stage. the duration or interval was reduced to the 3-day interval during mid to maturity stages; this was to minimize damage to occur to the crop fruits from disease and pests. figure 1. (a) field setup before water measurement installation (b) water conveyance pvc pipes before installation (c) ariel view of the mulch treatment plots. (c) (a) (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 827 2.5 irrigation water application basin irrigation method was adopted because it is the most dominant practice by the farmers around the study area. water is released from a secondary canal into a tertiary ditch that conveyed the water to the field ditches via a siphon and eventually served the basins. a 75 mm diameter pvc tube of length approximately 2 m was installed in each basin to admit water into the basins. the pvc tubes were installed through the embankment of each basin with one end in the field ditch and the other end in the basin. the tubes were installed to give a free orifice flow into the basins. stage gauges were placed at the water inlet of each basin to measure the depth of water over each tube as water enters the basin. pvc corks were placed at the entrance such that when the corks were removed, water flowed into the basins. when the desired depth of water was applied, the pvc corks use to stop the water flow into the plot. the flow rates into each basin were determined and related to the time of application. the time required to apply the depth of water was monitored using a stopwatch. the flowrate for each basin was calculated using equation 3. kghdkghaavkq       2 2 2 2  (nally, 2013) (3) where: q = water flow rate in the basin, m3/s, a = area of the orifice in m2, v = velocity of the liquid in m/s, k = 0.82 constant for the shape of tube used (nally, 2013), g = acceleration due to gravity in m/s2 = 9.81 m/s2, h = head across the orifice in m, d = diameter of the orifice in m. moreover, the amount of water applied (equation 4,5, and 6) at every irrigation event (weekly interval) was observed throughout the crop growing season and was based on the reference evapotranspiration amount for that week of irrigation and the experimental treatment, and this is in accordance with (igbadun and oiganji, 2012). but it should be noted that; wretavolume (m3) (4) where: a= area of plot = 2.5 x 2.5mm =6.25 mm2 and wret= weekly reference evapotranspiration (mm/week) also, tqvolume (m3) (5) q volumet  (6) where: t = time duration for irrigation (s) (allen et al., 2011). 2.6 soil moisture measurement the soil moisture status of the experimental field was monitored throughout the crop growing season using an in-situ soil moisture meter. the soil moisture meter was used to monitor the soil moisture at 0 20, 20 40, 40 60 and 60 80 cm depths respectively, this is by igbadun and oiganji (2012). soil moisture measurements were carried out twice a week, at two days after irrigation and on the seventh day (just before the next irrigation), because the soil most have attained its field capacity at two days after irrigation while on the seventh day, the soil has reached its wilting file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 828 point. with an assumption that most soil would attain field capacity two days after irrigation (igbadun and oiganji, 2012). 2.7 determination of reference evapotranspiration (eto) reference evapotranspiration (eto) of the site was computed using the fao-penman-monteith method incorporated in the cropwat model (fao, 1977). the weather data for the calculation of eto were obtained from national horticultural research institute, bagauda; irrigation research station-institute for agricultural research, ahmadu bello university, kadawa and nigeria meteorological station (nimet) situated in aminu kano international airport, kano. daily maximum and minimum temperatures, relative humidity, wind speed at 2 m height, sunshine hours, and rainfall data were used. fao-penman monteith explicit equation incorporated in the cropwat model used in the estimation of eto as given in equation 7 (fao, 1977).      2 2 34.01 273 900408.0 u eeu t gr et qsn o        (7) where: eto = reference evapotranspiration (mm/day); rn = net radiation at the crop surface (mj/m2/day); g=soil heat flux density (mj/m2/day); t=average temperature at 2m height (°c); u2=wind speed measured at 2m height (kpa); δ=slope of vapour pressure curve (kpa/°c), γ =psychometric constant (kpa/°c), 900 = coefficient for the reference crop (kj-1 kg k/day);  qs ee  = vapour pressure deficit for measurements at 2m height (kpa); 0.34=wind coefficient for the reference crop and 0.408 = value for λ-1 (reciprocal of the latent heat flux required to vaporize one unit of water). 2.8 crop water requirement (etc) the crop water use between successive moisture measurements were estimated using the soil moisture depletion method (igbadun and oiganji, 2012), with the expression given in equation 8.   t damcmc cwu n i isiii    1 21 (8) where: cwu is average daily crop consumptive use between successive soil moisture sampling periods (mm/day); mc1i is soil moisture content (g/g) at the time of first sampling (2 days after irrigation) in the ith soil layer; mc2i is soil moisture content (g/g) at the time of second sampling (7 days after irrigation) in the ith layer; asi is bulk density (g/cm3) of the ith layer; di is thickness of ith layer (mm); ‘n’ is a number of soil layers sampled in the root zone depth d, and ‘t’ is the number of days between successive soil moisture content sampling. the weekly consumptive use was obtained as the product of the daily crop consumptive use between successive soil moisture content sampling and the number of days in the week while the seasonal crop water use is the summation of the weekly cwu. the consumptive crop use of the treatments irrigated at 100% wret (with or without mulch), was regarded as actual http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 829 consumptive use while the cwu of the deficit irrigated treatments (i80, i60, and i40) was regarded as deficit consumptive use (cwudeficit), (igbadun and oiganji, 2012) 2.9 determination of crop coefficient (kc) the kc (crop coefficient is also known as crop evaporation rate) of tomato crop for both full and deficit irrigation were measured on the field by igbadun and oiganji (2012) using equation 9a, and b; oet cwukc  (9a) o deficit deficit et cwu kc  (9b) where: kc = crop coefficient, oet =reference evapotranspiration 2.10. statistical analysis results shown are expressed as mean ± standard deviation. analysis of variance (anova) was used to test the significance of the results, and the differences were considered statistically significant when p ＜0.05. 3.0 results and discussion 3.1 meteorological data of the site meteorological data averaged between 2002 and 2012 is presented in table 1. the average relative humidity in march was found to be 31%, which was the lowest. this might be attributed to the peak dry season while the highest (84%) was recorded in august. the reason may be due to the peak wet season. the average minimum and maximum temperatures are 16.9°c and 39.8°c, respectively while the minimum wind speed (113 km/day) was observed in september and the maximum wind speed (477 km/day) in march. the eto obtained are 7.12, 8.83, 10.48, and 8.86 mm/day for january, february, march, and april respectively. table 1: meteorological data averaged between 2002 and 2012 (nhri, 2013). month minimum temperature (°c) maximum temperature (°c) relative humidity (%) wind speed (km/day) sunshine hours eto (mm/day) january 16.9 28.7 42 474 9.1 7.12 february 17.1 34.5 38 460 9.6 8.83 march 21.1 37.4 31 477 9.1 10.48 april 24.1 39.8 52 424 8.3 8.86 3.2 daily crop water use the soil of the site was found to have an average bulk density of 1.3 g/cm3 and the average moisture content of 25.12%. further, the daily crop water use ranged from1.67 to 11.41 mm/day file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 830 across the treatments, as shown in table 2. a comparison of the daily crop water use on the bases of irrigation treatment indicated that daily crop water use decreased with increase in deficit irrigation. the average peak crop water use of the plants given full irrigation (i100) was 7.99 mm/day. the average peak crop water use of the deficit-irrigated plant (that is, i80 (20% deficit), i60 (40% deficit), and i40 (60% deficit)) were 7.66, 5.21 and 3.51 mm/day respectively. all the peak values were obtained in the no-mulch treated plants of the experiment, and this may be because the plots are directly exposed to the atmosphere, unlike the other plots treated with mulch materials. the decrease in daily crop water use due to deficit irrigation ranged from about 20 to 40% of moisture content with the highest values in the range occurring at i40 (60% deficit) treatments. the mode of decrease in crop water use as a result of deficit irrigation was expected since the amount of water available in the soil for plant uptake reduces with deficit irrigation (igbadun and oiganji, 2012). however, it was observed that applying water at 80% (20% deficit) of eto reduces peak crop water use of the tomato crop by about 10%. additionally, if water was applied at 40% (60% deficit) of eto, the peak consumptive use of the tomato crop will be reduced by about 56% (igbadun, 2012). a comparison of the daily crop water use as influenced by mulching showed that the daily cwu of the no mulch (nm) treated plants ranged from 2.45 to 11.41 mm/day across irrigation regimes, while the average daily cwu of the mulched plants ranged from 1.67 to 10.8 mm/day across irrigation regimes. the trend of daily cwu was carefully studied, and this revealed that the daily crop water use was more pronounced in the developmental and fruit formation stages of the growth, most especially in the nm treated plants. it was observed that among the mulched treatments; the rice straw mulch (rsm) treatments were found to be higher than other mulched treatments and consequently, wood shaving mulch (wsm) followed and lastly by white polyethylene mulch (wpm). the average peak crop water use in nm treated plants was noticed to be higher than in rsm-treated plants by 7.3 60% across the treatment, with higher value in the range occurring at higher irrigation deficit. the average peak crop water use of rsm-treated plants was also found to be higher than the other mulch treatment by 13.4 to 65.5%. the higher cwu in the nm treated plants compared to the mulched treatments at the establishment to maturity-harvest growth stages can be attributed to the influence of direct surface evaporation since the soil cover was exposed to the atmosphere (igbadun and oiganji, 2012). 3.3 crop coefficients under full irrigation conditions table 3 shows the crop coefficient values for tomato crop. the kc of the fully irrigated plants ranged from 0.70 to 1.15, 0.64 to 1.08, 0.59 to 1.04, and 0.53 to 0.96 for the nm, rsm, wsm, and wpm treatments, respectively. the least values of kc in the ranges above were found at the establishment stage of the season (which is taken as the kcinitial) while the highest values (peak kc) were recorded at fruit formation stage (which is taken as the kcmid). moreover, the mean kc values for the four growth stages of the no-mulch treated plants: establishment, developmental, fruit formation, and maturity to harvest stages (which can also be classified as initial, develop, midseason and late-season) were obtained to be 0.70, 0.81, 1.07 and 0.78, respectively. the mean kc values for the four growth stages of the rsm treated plants were 0.64, 0.76, 0.99, and 0.71 for the initial, develop, midseason, and late season, respectively. the mean kc values for http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 831 the four growth stages of the wsm and wpm treatments were 0.60, 0.73, 0.94 and 0.69, and 0.53, 0.66, 0.86 and 0.62, respectively. the mean kc values of midseason were a bit lower; this may be because there was very harsh weather condition in march to april (peak of the dry season) of the experimental season. although, some researchers have recorded variability in kc values over the years for basal and tomato crops (shrestha and shukla, 2014; amayreh and al-abed, 2005). the kc values obtained in this study were in agreement with those reported by (fao, 2013). the kc values of 0.6, 1.15 and 0.7 – 0.9 for initial, midseason and late season respectively for the tomato crop, only the kc values of midseason that is lower than that reported by fao, (2013), this might be due to the reason as mentioned earlier. despite the variation in the midseason kc values obtained from the field compared to that reported by fao, (2013), the results showed a reasonable degree of acceptance which is an indication of an established trend in the study area. it is important to note that kc is affected by all the factors that influence soil water condition, among others are meteorological factors, soil characteristics and agronomic techniques that affect crop growth (doorenbos and pruitt, 1977; lazzara and rana, 2010; stanghellini et al., 1990). hence, kc values reported in the literature for the same crop may vary slightly or significantly if their growing conditions differ. 3.4 crop coefficient values under deficit irrigation conditions table 3 presents the crop coefficient values under deficit irrigation (kcdeficit) conditions for different management practices. as can be seen, crop coefficients were affected significantly by irrigation deficits. the values decrease with increase in deficit irrigation. a comparison of kc fully irrigated treatments (kcfit) and kcdeficit showed that the mean values of kc were higher than kcdeficit by about 4, 25 and 51% for i80, i60, and i40 treatments, respectively. the peak kc (fully irrigated treatments) values of the respective mulch management conditions were found to be higher than the peak kcdeficit values. as previously reported that under deficit irrigation, peak crop coefficient values may be decrease drastically (ayana, 2011). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 832 table 2: average daily crop water use of the tomato crop treatment growth stage establishment development fruit formation maturity-harvest days after transplanting 2 – 9 10 – 16 17 – 23 24 – 30 31 – 37 38 – 44 45 – 51 52 – 58 59 – 65 66 – 72 73 – 79 80 – 86 87 – 93 94 100 i100 5.45 5.73 6.96 7.39 7.48 7.61 11.01 10.80 11.41 10.49 7.09 7.25 6.60 6.54 nm i80 5.10 5.31 6.46 6.90 7.05 7.39 10.50 10.38 11.01 10.29 6.95 7.03 6.40 6.47 i60 3.86 4.02 5.01 5.41 5.47 5.87 5.59 5.64 5.97 5.41 5.46 5.47 4.90 4.90 i40 2.45 2.61 3.41 3.64 3.61 3.72 4.92 3.72 3.92 3.53 3.64 3.53 3.17 3.29 i100 4.98 5.26 6.55 6.99 7.08 7.18 9.76 10.16 10.80 9.67 6.46 6.76 6.05 5.99 rsm i80 4.77 5.05 6.41 6.93 6.79 6.98 9.24 9.85 10.49 9.36 6.34 6.62 5.99 5.84 i60 3.71 3.87 5.02 5.44 5.33 5.49 4.89 5.30 5.52 4.90 4.85 5.14 4.57 4.57 i40 2.43 2.62 3.30 3.59 3.55 3.58 3.13 3.49 3.60 3.29 3.26 3.29 2.94 3.07 i100 4.69 4.90 6.20 6.66 6.79 6.91 9.24 9.65 10.40 9.27 6.19 6.49 5.84 5.77 wsm i80 4.55 4.61 6.00 6.37 6.38 6.77 8.93 8.82 10.19 8.85 6.13 6.30 5.70 5.63 i60 3.52 3.64 4.69 4.99 5.06 5.30 4.79 4.72 5.42 4.80 4.85 4.69 4.39 4.45 i40 2.34 2.46 3.19 3.31 3.44 3.54 3.22 3.01 3.61 3.27 3.22 3.15 2.79 2.83 i100 4.10 4.39 5.64 6.09 6.15 6.35 8.53 8.84 9.58 8.34 5.63 5.93 5.22 5.14 wpm i80 3.89 4.33 5.35 5.80 5.86 6.07 8.43 8.65 9.38 8.03 5.57 5.65 5.14 5.07 i60 3.05 3.40 4.23 4.53 4.52 4.63 4.45 4.63 5.03 4.35 4.34 4.41 4.00 4.00 i40 2.06 2.30 2.83 1.69 1.67 1.73 2.94 3.15 3.27 2.95 2.87 2.95 2.71 2.71 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 833 table 3: crop coefficients for the tomato crop treatments growth stage establishment development fruit formation maturity-harvest days after transplanting 2 – 9 10 – 16 17 – 23 24 – 30 31 – 37 38 – 44 45 – 51 52 – 58 59 – 65 66 – 72 73 – 79 80 – 86 87 – 93 94 100 kc of nm treatment i100 0.71 0.70 0.86 0.76 0.87 0.74 1.02 0.95 1.15 1.15 0.75 0.78 0.67 0.89 kc deficit of nm treatments nm i80 0.67 0.64 0.80 0.71 0.82 0.72 0.97 0.91 1.11 1.13 0.74 0.76 0.65 0.88 i60 0.50 0.49 0.62 0.55 0.64 0.57 0.52 0.50 0.60 0.59 0.58 0.59 0.50 0.67 i40 0.32 0.32 0.42 0.37 0.42 0.36 0.46 0.33 0.39 0.39 0.39 0.38 0.32 0.45 kc of rsm treatment i100 0.65 0.64 0.81 0.72 0.82 0.70 0.90 0.89 1.08 1.06 0.69 0.73 0.62 0.82 kc deficit of rsm treatments rsm i80 0.62 0.61 0.79 0.71 0.79 0.68 0.86 0.87 1.05 1.03 0.67 0.72 0.61 0.80 i60 0.48 0.47 0.62 0.56 0.62 0.54 0.45 0.47 0.55 0.54 0.52 0.56 0.47 0.62 i40 0.32 0.32 0.41 0.37 0.41 0.35 0.29 0.31 0.36 0.36 0.35 0.36 0.30 0.42 kc of wsm treatment i100 0.61 0.59 0.77 0.68 0.79 0.67 0.86 0.85 1.04 1.02 0.66 0.70 0.60 0.79 kc deficit of wsm treatments wsm i80 0.59 0.56 0.74 0.65 0.74 0.66 0.83 0.77 1.02 0.97 0.65 0.68 0.58 0.77 i60 0.46 0.44 0.58 0.51 0.59 0.52 0.44 0.41 0.54 0.53 0.52 0.51 0.45 0.61 i40 0.31 0.30 0.40 0.34 0.40 0.35 0.30 0.26 0.36 0.36 0.34 0.34 0.29 0.39 kc of wpm treatment i100 0.54 0.53 0.70 0.62 0.71 0.62 0.79 0.78 0.96 0.92 0.60 0.64 0.53 0.70 kc deficit of wpm treatments wpm i80 0.51 0.52 0.66 0.59 0.68 0.59 0.78 0.76 0.94 0.88 0.59 0.61 0.53 0.69 i60 0.40 0.41 0.52 0.46 0.53 0.45 0.41 0.41 0.50 0.48 0.46 0.48 0.41 0.54 i40 0.27 0.28 0.35 0.17 0.19 0.17 0.27 0.28 0.33 0.32 0.31 0.32 0.28 0.37 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 834 the mean kcdeficit values of the no-mulch treated plants for four growth stages of the crop: establishment, developmental, fruit formation, and maturity to harvest stages were also found to be 0.65, 0.76, 1.03 and 0.76; 0.50, 0.60, 0.55 and 0.59; and 0.32, 0.39, 0.39 and 0.39, for i80, i60 and i40 respectively. similarly, the mean kcdeficit values of the rice straw mulched plants were also found to be 0.62, 0.74, 0.95 and 0.70; 0.48, 0.58, 0.50 and 0.54; and 0.32, 0.38, 0.33 and 0.36, for i80, i60 and i40 respectively. furthermore, the mean kcdeficit values at the four stages for the wood shaving and white polythene mulch treated were 0.58, 0.70, 0.90 and 0.67; 0.45, 0.55, 0.48 and 0.52; and 0.30, 0.37, 0.32 and 0.34, and 0.52, 0.63, 0.84 and 0.61; 0.41, 0.49, 0.45 and 0.47; and 0.27, 0.18, 0.30 and 0.32, for i80, i60 and i40, respectively. it was observed that there were variations among the mean kcdeficit values of mulched and no-mulch plants. the present study supported the fact that mulching has a great influence on crop coefficient under deficit irrigation (chakraborty et al., 2008; mirani et al., 2011). 4. conclusion crop coefficient, kc of tomato crop under deficit irrigation, and mulch practice were obtained in this study. the kc values of fully irrigated treatments ranged from 0.53 to 1.15, while that of deficit irrigation ranged from 0.17 to 1.13 across the treatments. this means that deficit irrigation and mulching practices of tomato crop affects kc. the result also shows that both deficit irrigation and mulching practices irrespective of the depth of irrigation level have an effect on kc of tomato grown in the study area. based on our findings, we concluded that; tomato producers in krip, kadawa kano, should adopt the use of rice straw mulch as a way of water conservation which is readily available in the study area with irrigation level of 80% wret. the results obtained from the study can also be used as a guide by farmers in irrigating tomato crop and as well as researchers for further research and design of irrigation systems. references allen, rg., pereira, ls., howell, ta. and jensen, me. 2011. evapotranspiration information reporting: i. factors governing measurement accuracy. agricultural water management, 98(6):899–920. amayreh, j. and al-abed, an. 2005. developing crop coefficients for field-grown tomato (lycopersicom esculentum m.) under drip irrigation with black plastic mulch. agricultural water management, 73: 247–254. ayana, m. 2011. deficit irrigation practices as alternative means of improving water use efficiencies in irrigated agriculture   : case study of maize crop at arba minch. african journal of agricultural research, 6(2):226–235. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 835 chakraborty, d., nagarajan, s., aggarwal, p., gupta, vk., tomar, rk., garg, rn., kalra, n. 2008. effect of mulching on soil and plant water status, and the growth and yield of wheat (triticum aestivum l.) in a semi-arid environment. agricultural water management, 95(12):1323–1334. doorenbos, j., pruitt wo. 1977. guideline for prediction of crop water requirement. irrigation and drainage paper no.24. fao, rome. italy. p. 144. erzd. 2014. effective root zone depth. south jersey rc& d council, inc. http://www.sjrcd.org/ag/effective_root_zone.htm faloye, ot., and alatise, mo. 2015. effect of varying water applications on evapotranspiration and yield of cowpea under sprinkler irrigation system. international journal of agriculture and crop sciences., 8(3):307–319. fao. 1977. guidelines for predicting crop water requirements by j. doorenbos & w.o. pruitt. fao irrigation and drainage paper no. 24. rome. fao. 2013. water development and management crop water information tomato, food and agriculture organization (fao), rome. geerts, s. and raes, d. 2009. deficit irrigation as an on-farm strategy to maximize crop water productivity in dry areas. agricultural water management, 96(9):1275–1284. grossman, rb. and reinsch, tg. 2002. bulk density and linear extensibility. in: methods of soil analysis. part 4. physical methods, dane, j.h. and g.c. topp (eds.). asa and sssa, madison, wi, pp: 201-228. igbadun, he. 2012. estimation of crop water use of rain-fed maize and groundnut using mini-lysimeters. pacific journal of science and technology, 13(1):527–535. igbadun, he. and oiganji, e. 2012. crop coefficients and yield response factors for onion (allium cepa . l ) under deficit irrigation and mulch practices in samaru , nigeria. african journal of agricultural research, 7(36):5137–5152. jibril, jm., abubakar, sz. and suleiman, s. 2008. soil fertility status of the kano river irrigation project area in the sudan savanna of nigeria. journal of applied sciences, 8(4):692–696. lazzara, p., and rana, g. 2010. the crop coefficient (k c) values of the major crops grown under mediterranean climate. agricultural water management, 1–28. http://www.sjrcd.org/ag/effective_root_zone.htm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng zakari et al: crop coefficient of tomato under deficit irrigation and mulch practices at kano river irrigation project, nigeria. azojete, 15(4):823-836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ashitu.age@buk.edu.ng 836 maina, mm., amin, msm. and aimrun, w. and sani, i. 2012. soil salinity assessment of kadawa irrigation of the kano river irrigation project (krip). journal of food agriculture and environment 10(3):1028-1034 michael, am. and ojha,tp. 2005. principle of agricultural engineering. volume ii. jain brothers publication, new delhi, india. mirani, aa., dahri, zh., kalwar, sa., soomro, kb., and ali, z. 2011. investigating water productivity and economic efficiency of wheat-crop under different sowing methods. science,technology & development, 30(3):41–52. nally, mc. 2013. approximate flow through an orifice. the mc nally institute book division, dade city, florida. retrieved from: http://www.mcnallyinstitute.com/13html/13-12.htm nhri. 2013. meteorological data. national horticultural research institute, bagauda, kano-nigeria. shrestha, nk. and shukla, s. 2014. basal crop coefficients for vine and erect crops with plastic mulch in a sub-tropical region. agricultural water management, 143:29–37. olorunaiye, es. 2009. evaluation of selected crop–yield water use models for tomato (lycopersicon esculentum) under moisture stress conditions. agricultural engineering, faculty of engineering, ahmadu bello university, zaria, nigeria. an msc. thesis. oyinlola, ey. and akintoye, s. 2004. response of irrigated tomato to boron fertilizer. nigeria journal of soil sc. 5:53 – 61. quim, jg. 1980. a review of tomato cultivarstrials in the northern states of nigeria samaru miscellaneous paper 84. stanghellini, c., bosma, ah., gabriels, pcj. and werkhoven, c. 1990. the water consumption of agricultural crops: how crop coefficient are affected by crop geometry and microclimate. acta hortic., 278:509–516. http://www.mcnallyinstitute.com/13-html/13-12.htm http://www.mcnallyinstitute.com/13-html/13-12.htm http://www.azojete.com.ng references allen, rg., pereira, ls., howell, ta. and jensen, arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):1-17 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 1 original research article preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse f.a. aderibigbe1*, a. l. adejumo2, i. a. mohammed1, s. i. mustapha1 and e. o. akinkahunsi1 (1department of chemical engineering, university of ilorin, ilorin, nigeria 2department of pure and applied chemistry, osun state university, osogbo, nigeria) * corresponding author’s email address: aderibigbe.fa@unilorin.edu.ng 1.0 introduction the yeast saccharomyces cerevisiae is one of the most abundantly used yeasts in industry (snoek, 2007), and the most utilized microorganism for the biosynthesis of ethanol due to its several advantages such as high fermentation efficiency, rapid growth, effective sugar use, osmotolerance, thermotolerance, and more (reis et al., 2013). from economic point of view, lignocellulosic ethanol production using s. cerevisiae has been considered a viable route to commercialize the second-generation biofuel (ask, 2013). the cost of bioethanol production would be reduced further if s. cerevisiae is prepared also from lignocellulosic biomass. sugarcane bagasse is an abundant lignocellulosic biomass and residue from industrial and agricultural processing (jabasingh and nachiyar, 2012). it is mainly used in the manufacture of pulp and paper products, building materials, fuel and cellulosic ethanol (jabasingh and nachiyar, 2012). fermentation as an important industrial process of using microorganisms for several applications is affected by factors such as the concentration of microorganisms, cells, cellular components, enzymes, ph, and temperature (yusuf, 1999; rao, 2005). it is a suitable means of producing s. cerevisiae from lignocellulosic biomasses by either simultaneous hydrolysis and fermentation (ssf), or separate hydrolysis and fermentation (shf). both the ssf and shf have been widely studied. article information abstract in this study, the pretreatment by milling, dilute-acid hydrolysis of sugarcane bagasse, and subsequent fermentation of its glucose product was performed to investigate the effects of process conditions on the production of saccharomyces cerevisiae. the hydrolysis was carried out using hcl at three substrate concentrations of 20, 25, and 30% (w/v) of bagasse to distilled water. hydrolysis parameters (time, acid concentration, and temperature) were varied for each case of substrate concentration in full factorial experiments, and an optimum glucose yield of 1.907 g/l was obtained with the 20% (w/v) substrate concentration, at conditions of 10 min time, 0.5 m acid concentration, and 80°c temperature. thereafter, fermentation experiment was performed with s. cerevisiae in the product of hydrolysis. an optimum ca. 207 yeast number of colonies (yield: 20, 700, 000 cfu/ml) was achieved in 40 h, and the growth of s. cerevisiae was governed by the kinetic equation, ln xt = 8.4338 + 0.2943t. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 november, 2018 revised 13 july, 2019 accepted 08 august, 2019 keywords: saccharomyces cerevisiae sugarcane bagasse acid hydrolysis fermentation. http://www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 2 however, it has been difficult to identify one best method to hydrolyze lignocellulosic material into its building blocks, especially that this is affected by the source of the lignocellulose material and its geographic location (kumar et al., 2010; tomás-pejó et al., 2011; binod et al., 2011; stephen, mabee and saddler, 2013). generally, the hydrolysis methods have been extensively studied using pretreatment, chemical hydrolysis, enzymatic hydrolysis, or combinations thereof, with varying results (olsson and hahn-hägerdal, 1993; galbe and zacchi, 2012). pretreatment can affect the yields of sugar obtained during hydrolysis, and the techniques range from physical, physicochemical, chemical, and biological pretreatments (rosalin and amit, 2007). the present study has adopted physical pretreatment by mechanical milling, followed by dilute acid hydrolysis under moderate heating of 80 – 97°c since acid hydrolysis is able to penetrate lignin without pretreatment of biomass, hence breaking down the cellulose and hemicellulose polymers into individual sugar molecules (galbe and zacchi, 2002). sulphuric and hydrochloric acids in concentrated or dilute forms are the most studied for hydrolysis of lignocellulosic biomass (lenihan et al., 2010). again, dilute acid hydrolysis is preferred because equipment corrosion is lessened and less amount of acid is utilized, except that the high processing temperatures for achieving high cellulose conversion would need to be reduced. the task of identifying the optimum conditions of dilute acid hydrolysis, and efficient sugar utilization during fermentation are optimization problems to be addressed (you et al., 2017). nonetheless, this study investigated the effects of acid concentration, temperature, and time on the acid hydrolysis of milled sugarcane bagasse at different substrate concentrations in order to obtain the conditions of optimum glucose yield for use in preparation of s. cerevisiae by fermentation. hydrolysis experiment was systematically carried out in a full factorial design of experiment. 2. materials and methods 2.1 equipment, materials and chemicals a 14-liter locally fabricated bioreactor with a working volume of 10.5 liters was used. its suitability for metabolites synthesis has been investigated previously (aransiola, 2016), by converting corn cob into bioethanol. it has a temperature controller, and the agitator speed varied from 200 to 250 rpm. an air compressor supplied air to the vessel, while a flow meter measured the air flow rate. other apparatuses and materials used for the study include a water bath, weighing balance, whatman filter papers, test tubes, conical flask, beaker, glass stirrer, petri dish, sugarcane bagasse, glucose analysis kit (cypress diagnostics), colony counter, drop pipette, and sieve. also used for the study were analytical grade sodium hydroxide, ammonium sulphate, potassium hydrogen phosphate, magnesium sulphate heptahydrate, distilled water, yeast extract agar, cell biomass, concentrated ethanol, and hcl. 2.2 pretreatment of sugarcane bagasse the sugarcane bagasse used for this study was obtained in ilorin, nigeria. it was air-dried, milled and screened to select the fraction of particles in the sub-150 μm size range. a sieve analysis was carried out on a sieve shaker equipped with sieves of pore diameters of 150 μm, 75 μm, 48 μm, and 38 μm, respectively. the stainless steel sieves were stacked with the sieve size increasing from top to bottom (38 μm, 48 μm, 75 μm, and 150 μm). about 75 g of the milled sugarcane bagasse was placed into the top sieve. the sieves were shaken until no more particles http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 3 passed through. all the prepared samples were stored at room temperature in sealed polythene bags. 2.3 acid hydrolysis of sugarcane bagasse acid hydrolysis of the bagasse particles was performed using hcl and water bath as heat source. three sets of substrates with concentration of 20, 25, and 30% (w/v) were prepared by the addition of 20, 25, and 30 g of bagasse particles to 100 ml distilled water respectively. in order to optimize the hydrolysis process, for each case of substrate concentration, the effects of hydrolysis time (10 – 60 min), temperature (80 – 97°c), and acid concentration (0.1 – 0.5 m) were investigated by varying these parameters in 23 factorial experiment (8 runs) as presented in table 1. table 1: levels of factors used in the factorial experimental design of acid hydrolysis parameter time (min) acid concentration (m) temperature (°c) upper level 60 0.5 97 lower level 10 0.1 80 each substrate sample previously prepared in 100 ml of distilled water was added to 100 ml of acid (0.1/0.5 m), maintaining (1:1 v/v) of acid to distilled water. it was then heated in water bath at set temperature (80/97°c) for the required time (10/60 min). at the completion of hydrolysis duration, the mixture was taken out of the water bath and then filtered. the filtrates (hydrolysate) were immediately kept in the refrigerator for analysis of glucose concentration. 2.3.1 glucose estimation glucose analysis was carried out using glucose analysis kit with wavelength of 505 nm, temperature 37 °c or 15 – 25 °c critical temperature, and the instrument was adjusted to zero with distilled water. the standard was prepared by measuring 10 µl of glucose standard and 1ml of working reagent into a test tube. also, 10 µl each of the 8 samples of hydrolysate obtained from factorial experimental runs and 1 ml of working reagent were measured into a different test tube, the mixture was shaken and incubated for 15 – 20 min at room temperature and the absorbance for each was taken using a uv spectrophotometer. absorbance recorded for each sample was used for the calculation of the glucose concentration using appropriate equations provided with the kit. the absorbance of the standard was observed to be 0.175. 2.4 fermentation experiment 2.4.1 pre-culture medium the saccharomyces cerevisiae (baker’s yeast) was provided by the department of microbiology of university of ilorin, and it was maintained on agar at room temperature. afterward, 200 ml of distilled water was measured into a conical flask, followed by the addition of 4.6 g of yeast extract agar, and stirred until a homogenous mixture was obtained. the solution was then autoclaved at 121°c and 15 psi for 15 min. after autoclaving the solution, it was poured into a petri dish and then allowed to cool. cells of s. cerevisiae were transferred into the petri dish aseptically in a sterile condition and incubated at 30°c for 6 h. 2.4.2 sterilization of fermenter the bioreactor (fermenter) was sterilized using concentrated ethanol and using sterile distilled water at 90°c. fermentation media was prepared by measuring 1 l of the hydrolysate into a file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 4 conical flask, followed by the addition of 4 g of yeast extract, 2 g of ammonium sulphate, 2 g of potassium hydrogen phosphate, 0.75 g of magnesium sulphate heptahydrate, and the ph was adjusted to 5.5 using naoh. 2.4.3 sterilization of the fermentation medium the fermentation media was autoclaved at 121°c, 15 psi for 15 min to maintain sterile condition. 2.4.4 fermentation proper the yeast (biomass) was aseptically added into the sterile culture of glucose obtained at highest yield conditions. this was added to the fermenter with the agitation rate set at 160 rpm. the reactor temperature was set to 34°c and samples were withdrawn at a 4-hour interval for 48 h. air was supplied to the reactor at a safe working pressure. analysis was carried out on the sample immediately to determine the yield of s. cerevisiae. 2.4.5 yeast estimation plate count was carried out to determine the yeast biomass produced in each run. five (5) test tubes were filled with 9 ml of distilled water each, as they were all sterilized in an autoclave at 121°c, 15 psi for 15 min. these were all labeled 1 to 9. then, 1 ml of the sample was measured into the first test tube using a drop pipette and was shaken; 1 ml was measured from the first test tube and added to the second test tube and so on until the desired dilution factor is reached (i.e. for the dilution factor of 10-5 it was stopped at test tube 5). then, 1 ml was measured from the desired dilution level into the petri dish and the prepared yeast extract agar that has been allowed to cool was poured into the petri dish aseptically to avoid contamination. it was covered, taped with a paper tape and kept aside for 24 – 48 h after which the organisms were counted using colony counter. the essence of the dilution is to avoid overcrowding of the organism on the plate and to ensure proper counting of the organisms. 3. results and discussion 3.1 particle size distribution of milled bagasse the particle size distribution (psd) of the milled bagasse as obtained after screening with the sub 150 μm sieves (150 μm, 75 μm, 48 μm, and 38 μm sieves) is shown in figure 1. the psd as presented is indicative of bagasse composed of 9.6% wt particles in the sub 38 μm size range, 13.7% wt in the 38 48 μm size range, 22.8% wt in the 48 75 μm size range, 17.6% wt in the 75 150 μm size range, and 36.3% wt above the 150 μm size. figure 1: particle size distribution of milled sugarcane bagasse in sieve pore diameters of 150μm, 75 μm, 48 μm, and 38 μm. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 5 previous studies on enzymatic hydrolysis of lignocellulosic biomass have shown that smaller particle sizes of the substrate resulted in lower crystallinity index, higher specific surface area, cellulose adsorption, cellulose adsorption per specific surface area, and larger average pore size (li et al., 2016). that study also revealed a strong dependence of glucose yield on the crystallinity index and average pore size of sugarcane bagasse. smaller particle sizes are desirable for high yield of glucose during enzymatic hydrolysis. however, acid hydrolysis could show contrary results to enzymatic hydrolysis since acids are able to penetrate the lignin without pretreatment. thus, the effect of particle size was not considered in the present study. the bagasse biomass after milling exhibited particle size distribution dominated by particles above 48 μm size range. 3.2 acid hydrolysis 3.2.1 acid hydrolysis with 20% (w/v) substrate concentration presented in table 2 is the factorial experimental design matrix for the acid hydrolysis with 20% (w/v) substrate concentration, and glucose yield as the response. table 2: experimental design matrix for acid hydrolysis with 20% (w/v) substrate concentration run time (min) acid conc. (m) temperature (°c) glucose yield (g/l) 1 60.00 0.10 80.00 1.406 2 60.00 0.50 80.00 1.321 3 10.00 0.50 97.00 1.583 4 60.00 0.50 97.00 1.068 5 10.00 0.10 97.00 1.096 6 60.00 0.10 97.00 1.532 7 10.00 0.10 80.00 1.017 8 10.00 0.50 80.00 1.907 using the 20% (w/v) substrate concentration, the results of glucose yield in table 2 shows that the highest yield of 1.907 g/l was obtained under acid hydrolysis conditions of 10 min hydrolysis duration, 0.50 m acid concentration, and 80°c temperature (run 8). the varying yields of glucose under different conditions also indicate that the hydrolysis parameters have influences on the process. effects of these parameters on the glucose yield were investigated, and results are presented in figures 2 to 4 for the hydrolysis temperature, acid concentration, and time respectively. figure 2: effect of hydrolysis temperature on glucose yields at different acid conc. in (a) 10 min., and (b) 60 min. (a) (b) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 6 as presented in figure 2(a) and (b), the effect of hydrolysis temperature on the yield of glucose is dependent on acid concentration. regardless of duration of hydrolysis (10 or 60 min), higher temperature favored glucose yield at 0.1 m acid concentration (figure 2a). but, the reverse is the case with 0.5 m acid concentration where the glucose yield decreased with increase in temperature irrespective of hydrolysis duration (figure 2b). this observation could be due to a combined effect of temperature and acid concentration on the yield of glucose. however, this supports the claim that hydrolysis with dilute acids requires high processing temperatures for achieving high cellulose conversions, and thus lower temperatures favor the hydrolysis with more concentrated acids. in figure 3, the influence of acid concentration on the yield of glucose is dependent on hydrolysis time. when 10 min hydrolysis time was employed (figure 3a), an increase in acid concentration from 0.1 to 0.5 m caused the glucose yield to increase regardless of temperature (80 or 97°c). but, with 60 min hydrolysis time (figure 3b) at either temperature of 80 or 97°c, an increase in acid concentration from 0.1 to 0.5 m caused the glucose yield to decrease. this indicates an interactive effect of acid concentration and duration of hydrolysis. figure 3: effect of hydrolysis acid concentration on glucose yields at different temperatures in (a) 10 min., and (b) 60 min. again in figure 4, the effect of hydrolysis time on the yield of glucose is also not independent of acid concentration. the more dilute acid of 0.1 m concentration was influenced positively by increase in hydrolysis time yielding more glucose at 60 min, regardless of temperature employed (figure 4a). when 0.5 m acid concentration was used, the glucose yield was favored by shorter hydrolysis time and lower hydrolysis temperature (figure 4b). figure 4: effect of hydrolysis time on glucose yields at different temperatures and (a) 0.1 m, (b) 0.5 m acid concentrations. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 7 generally, the interactive effects of the hydrolysis parameters may not be disconnected with the molecular adsorption and liquid-solid mass transfer mechanisms that occur during the hydrolysis. it seems that when concentrated acids are used, longer hydrolysis time and higher temperatures encourage quick adsorptive mass transport of products on the surface of the lignocellulosic substrate which blocks the pores available for mass transfer. in this case, shorter hydrolysis time and mild temperatures are desirable to allow the hydrolysis to proceed further. because such obstructions may not occur with the more dilute acids, the conversion process is able to proceed at higher temperatures and for longer duration of hydrolysis. using the glucose yield results presented in table 2, a statistical analysis of variance (anova) was carried out on the data, with result presented as in table 3. table 3: anova table for acid hydrolysis with 20% (w/v) substrate concentration source ss df ms f value p – value (prob > f) model 0.65 6 0.11 1577.31 0.0193 x1 0.009554 1 0.009554 138.23 0.0540 x2 0.085 1 0.085 1235.14 0.0181 x3 0.017 1 0.017 252.24 0.0400 x1x2 0.46 1 0.46 6711.45 0.0078 x1x3 0.001695 1 0.001695 24.53 0.1268 x2x3 0.076 1 0.076 1102.27 0.0192 residual error 0.00006912 1 0.00006912 corrected total 0.65 7 x1 = time (min.), x2 = acid conc. (m), and x3 = temp. (°c) ss: sum of squares, df: degree of freedom, ms: mean square the anova results in table 3 indicate the model f-value is 1577.31, which implies that the model is significant, and there is only a 1.93% chance that it could occur due to noise. the r2 value of 0.9999, and the difference between the adjusted r2 (0.9993) and the predicted r2 (0.9932) shows that the model is reliable. also, using the p-value (< 0.05) criteria, the model terms with significant effects are the main effects from acid concentration (p-value = 0.0181) and temperature (p-value = 0.0400), and the interactive effects of (time and acid concentration, p-value = 0.0078), and (acid concentration and temperature, p-value = 0.0192). among all the model terms, the combined effect of time and acid concentration has the most significant effect on glucose yield. a linear regression model equation (1) was fitted to represent the parametric effects of the acid hydrolysis process variables on the yield of glucose: y = 1.37 − 0.035x1 + 0.10x2 − 0.047x3 − 0.24x1x2 + 0.015x1x3 − 0.098x2x3 (1) where y is the yield of glucose (g/l), and x1, x2 and x3 are the coded values of time, acid concentration and temperature respectively. based on the model equation (1), the graph of ‘predicted’ against ‘actual’ for glucose yield as presented in figure 5 indicates a good correlation between the predicted and the actual values, and hence the model can be used to predict other hydrolysis process conditions. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 8 figure 5: predicted vs. actual values for glucose yield in the acid hydrolysis with 20% substrate concentration. with the experiment on 20% substrate concentration, numerical optimization was performed which gave optimal glucose yield of 1.907 g/l (corresponding to experimental run 8) at hydrolysis conditions of 10 min time, 0.5 m acid concentration, and 80oc temperature with a resulting desirability of 0.999, out of a total number of 35 solutions. 3.2.2 acid hydrolysis with 25% (w/v) substrate concentration the factorial experimental design matrix for the acid hydrolysis with 25% (w/v) substrate concentration with glucose yield as the response is presented in table 4. table 4: experimental design matrix for acid hydrolysis with 25% (w/v) substrate concentration run time (min) acid conc. (m) temperature (°c) glucose yield (g/l) 1 60.00 0.10 80.00 1.42857 2 60.00 0.50 80.00 1.29143 3 10.00 0.50 97.00 1.61143 4 60.00 0.50 97.00 1.28000 5 10.00 0.10 97.00 1.35429 6 60.00 0.10 97.00 1.66286 7 10.00 0.10 80.00 1.05714 8 10.00 0.50 80.00 1.57143 with 25% (w/v) substrate concentration, the results of glucose yield in table 4 shows that the highest yield of 1.66286 g/l was obtained under conditions of 60 min hydrolysis time, 0.10 m acid concentration, and 97°c temperature (run 6). the effects of hydrolysis parameters on the glucose yield were also investigated and results are presented as shown in figures 6 to 8. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 9 figure 6: effect of hydrolysis temperature on glucose yields at different acid conc. in (a) 10 min., and (b) 60 min. figure 6 shows that at the substrate concentration of 25% (w/v) and employing 0.1 m acid concentration, the effect of hydrolysis temperature on glucose yields presented a similar trend as observed with 20% (w/v) substrate concentration: higher temperature favored glucose yield irrespective of hydrolysis time. but, when the 0.5 m higher concentration of acid was used, the effect of hydrolysis temperature depended on hydrolysis time: higher temperature favored glucose yield at 10 min, while it caused the glucose yield to decrease at 60 min. more so, the changes in hydrolysis temperature had no significant effect on glucose yields at 0.5 m acid concentration. again with 0.5 m concentration, the molecular mass transfer could have affected the hydrolysis process by reaching equilibrium at the early time; longer time only decreased the conversion to glucose or affected selectivity by forming undesired products. however, figures 7 and 8 showing the effects of acid concentration and hydrolysis time present similar relationship between the process variables and yield of glucose as observed with 20% (w/v) substrate concentration. figure 7: effect of hydrolysis acid concentration on glucose yields at different temperatures in (a) 10 min., and (b) 60 min. in figure (7a), when 10 min hydrolysis time was employed, higher concentration of acid caused the glucose yield to increase regardless of temperature employed (80 or 97°c). with 60 min hydrolysis time (figure 7b) lower acid concentration favored the yield of glucose at either temperature of 80 or 97°c. again, this shows that the effect of acid concentration is dependent on duration of hydrolysis. further, the change in substrate concentration of 20 to 25% (w/v) did (a) (b) (a) (b) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 10 not influence the effect of hydrolysis time on the yield of glucose (figure 8): hydrolysis time affected the glucose yield in a way that depended on acid concentration. figure 8: effect of hydrolysis time on glucose yields at different temperatures and (a) 0.1 m, (b) 0.5 m acid concentrations. in figure 8, when 0.1 m acid concentration was used, longer duration of hydrolysis of 60 min yielded more glucose regardless of temperature employed (figure 8a). but, with 0.5 m acid concentration, the glucose yield was favored by shorter hydrolysis time and lower hydrolysis temperature (figure 8b). table 5 shows the result of anova performed on table 4 experimental results of glucose yield for 25% (w/v) substrate concentration. table 5: anova table for acid hydrolysis with 25% (w/v) substrate concentration source ss df ms f value p – value (prob > f) model 0.29 6 0.048 2954.33 0.0141 x1 0.0005878 1 0.0005878 36.00 0.1051 x2 0.007902 1 0.007902 484.00 0.0289 x3 0.039 1 0.039 2401.00 0.0130 x1x2 0.21 1 0.21 12769.00 0.0056 x1x3 0.001633 1 0.001633 100.00 0.0635 x2x3 0.032 1 0.032 1936.00 0.0145 residual error 0.00001633 1 0.00001633 corrected total 0.29 7 x1 = time (min.), x2 = acid conc. (m), and x3 = temp. (°c) ss: sum of squares, df: degree of freedom, ms: mean square the anova results in table 5 indicating the model f-value of 2954.33 and p – value of 0.0141 imply that the model is significant and there is only a 1.41% chance that it could occur due to noise. the model is shown to be reliable based on r2 value of 0.9999, and the close agreement between the adjusted r2 (0.9996) and the predicted r2 (0.9964). using the p-value (< 0.05) criteria, the model terms with significant effects are the acid concentration (p-value = 0.0289), temperature (p-value = 0.0130), and the interactive effects of time and acid concentration (pvalue = 0.0056), and acid concentration and temperature (p-value = 0.0145). the combined effect of time and acid concentration has the most significant effect on glucose yield. (a) (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 11 a linear regression model equation (2) was fitted to represent the parametric effects of the acid hydrolysis process variables on the yield of glucose (y): y = 1.41 + 0.008571x1 + 0.031x2 + 0.070x3 − 0.16x1x2 − 0.014x1x3 − 0.063x2x3 (2) based on the model equation (2), the graph of ‘predicted’ against ‘actual’ for glucose yield as presented in figure 9 also indicates a good correlation between the predicted and the actual values. figure 9: predicted vs. actual values for glucose yield in the acid hydrolysis with 25% substrate concentration. with the experiment on 25% substrate concentration, numerical optimization produced an optimal glucose yield of 1.663 g/l at 60 min hydrolysis time, 0.1 m acid concentration, and 97oc hydrolysis temperature (corresponding to run 6), having a desirability of 0.999. 3.2.3 acid hydrolysis with 30 % (w/v) substrate concentration table 6 shows the factorial experimental design matrix for the acid hydrolysis with 30% (w/v) substrate concentration, using glucose yield as the response. table 6: experimental design matrix for acid hydrolysis with 30% (w/v) substrate concentration run time (min) acid conc. (m) temperature (°c) glucose yield (g/l) 1 60.00 0.10 80.00 1.37714 2 60.00 0.50 80.00 1.21714 3 10.00 0.50 97.00 1.44000 4 60.00 0.50 97.00 1.27429 5 10.00 0.10 97.00 1.23429 6 60.00 0.10 97.00 1.61714 7 10.00 0.10 80.00 1.01714 8 10.00 0.50 80.00 1.40000 for the experiment results with 30% (w/v) substrate concentration as presented in table 6, the highest yield of 1.61714 g/l was obtained under conditions of 60 min hydrolysis time, 0.10 m acid concentration, and 97°c temperature (run 6). the effects of the three hydrolysis parameters on the yield of glucose are discussed using figures 10 to 12. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 12 in figure 10, an increase in hydrolysis temperature (80 – 97°c) favored glucose yield at all conditions of hydrolysis time and acid concentration. figure 10: effect of hydrolysis temperature on glucose yields at different acid conc. in (a) 10 min., and (b) 60 min. by careful look at figure 10, and following the observations made in sections 3.2.1 (figure 2) and 3.2.2 (figure 6) on the effects of hydrolysis temperature using experimental results with 20 and 25% (w/v) substrate concentrations, it can be inferred that substrate concentrations play an important role in the hydrolysis especially at higher acid concentrations. particularly using 0.5 m acid concentration and substrate concentration of: (a) 20% (w/v), glucose yield decreased with increase in temperature irrespective of hydrolysis time of 10 or 60 min; (b) 25% (w/v), the effect of hydrolysis temperature depended on hydrolysis time where higher temperature favored glucose yield at 10 min and decreased the glucose yield at 60 min; (c) 30% (w/v), glucose yield increased with increase in temperature irrespective of hydrolysis time of 10 or 60 min. there was a gradual migration from negative to positive effect of hydrolysis temperature on glucose yield as substrate concentration increased from 20 to 30% (w/v). generally, in these three cases the variation in hydrolysis temperature from 80 to 97°c caused insignificant changes in the glucose yield. using 30% (w/v) substrate concentration in the hydrolysis experiment, the trends of effects of acid concentration and hydrolysis time on yield of glucose as presented in figures 11 and 12 are similar to the observations made with experimental results of 20 and 25% (w/v) substrate concentrations. the change in substrate concentration from 20 to 30% (w/v) did not influence the effect of acid concentration or hydrolysis time on the yield of glucose. figure 11: effect of hydrolysis acid concentration on glucose yields at different temperatures in (a) 10 min., and (b) 60 min. (a) (b) (a) (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 13 in figure 11a, when 10 min hydrolysis time was employed, increase in acid concentration favored glucose yield regardless of temperature employed (80 or 97°c) but with 60 min hydrolysis time (figure 11b) decrease in acid concentration favored the yield of glucose at either temperature of 80 or 97°c. based on the graph presented in figure 12, hydrolysis time affected the glucose yield in a way that depended on acid concentration. figure 12: effect of hydrolysis time on glucose yields at different temperatures and (a) 0.1 m, (b) 0.5 m acid concentrations. in figure 12, when 0.1 m acid concentration was used, longer duration of hydrolysis of 60 min yielded more glucose regardless of temperature employed (figure 12a). but, with 0.5 m acid concentration, the glucose yield was favored by shorter hydrolysis time and higher hydrolysis temperature (figure 12b). presented in table 7 is the result of anova performed on table 6 experimental yields of glucose for 30% (w/v) substrate concentration. table 7: anova table for acid hydrolysis with 30% (w/v) substrate concentration source ss df ms f value p – value (prob > f) model 0.22 6 0.037 9149.00 0.0080 x1 0.019 1 0.019 4761.00 0.0092 x2 0.0009184 1 0.0009184 225.00 0.0424 x3 0.038 1 0.038 9409.00 0.0066 x1x2 0.15 1 0.15 36481.00 0.0033 x1x3 0.0002 1 0.0002 49.00 0.0903 x2x3 0.016 1 0.016 3969.00 0.0101 residual error 0.000004082 1 0.000004082 corrected total 0.22 7 x1 = time (min.), x2 = acid conc. (m), and x3 = temp. (°c) ss: sum of squares, df: degree of freedom, ms: mean square the anova results in table 7 indicating model f-value of 9149.00 and p – value of 0.0080, implies that the model is significant and there is only a 0.80% chance that it could occur due to noise. in addition, the r2 value of 0.9999 and the close agreement between the adjusted r2 (0.9996) and the predicted r2 (0.9964) show that the model is reliable. by the p-value (< 0.05) criteria, all model terms have significant effects except the interactive effects of time and temperature (p-value = 0.0903). the combined effect of time and acid concentration (x1x2) has (a) (b) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 14 the most significant effect on glucose yield. a regression model equation for the experimental results, following anova, can be represented as given in equation (3): y = 1.32 + 0.049x1 + 0.011x2 + 0.069x3 − 0.14x1x2 + 0.005x1x3 − 0.045x2x3 (3) the graph of ‘predicted’ against ‘actual’ for glucose yield using 30% (w/v) substrate concentration is presented in figure 13 indicating a good correlation between the predicted and the actual values. figure 13: predicted vs. actual values for glucose yield in the acid hydrolysis with 30% substrate concentration. an optimal glucose yield of 1.617 g/l was obtained at 60 min hydrolysis time, 0.1 m acid concentration, and temperature of 97°c (corresponding to experimental run 6). 3.3 fermentation in s. cerevisiae following the fermentation in s. cerevisiae, of the glucose product obtained at highest-yield condition of hydrolysis (20% substrate conc., 0.5 m acid conc., 80°c temp., and 10 min) and estimation of s. cerevisiae by the plate count method, results of the 4-hourly observation up to 48 h is presented in table 8. table 8: experimental result of the analysis of yeast (s. cerevisiae) biomass production run time (hours) dilution factor vol. of h2o plate (ml) no. of colonies counted no. of colonies counted ave. no. of colonies counted yield (cfu/ml) 1 0 10-2 1 42 50 46 4600 2 4 10-4 1 165 163 164 1640000 3 8 10-5 1 37 37 37 3700000 4 12 10-5 1 59 61 60 6000000 5 16 10-5 1 79 85 82 8200000 6 20 10-5 1 91 91 91 9100000 7 24 10-5 1 108 112 110 11000000 8 28 10-5 1 145 135 140 14000000 9 32 10-5 1 176 164 170 17000000 10 36 10-5 1 194 202 198 19800000 11 40 10-5 1 209 205 207 20700000 12 44 10-5 1 200 194 197 19700000 13 48 10-5 1 195 189 192 19200000 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 15 table 8 shows that optimum yield of 20, 700, 000 cfu/ml was attained in 40 hrs. beyond this period, the number of s. cerevisiae counted reduced with further time. figure 14 shows an image of the s. cerevisiae taken under a compound light microscope at x40 magnification. the organism as presented on yeast extract agar plate shows a flat and smooth morphology which is moist, dull, and has creamy color. figure 14: colonies of s. cerevisiae as observed under a compound light microscope 3.4 kinetics of growth figure 15 shows a growth curve which was obtained to investigate the rate of production of s. cerevisiae in the fermentation experiment. again, the growth curve indicate that there was a steady increase with time in the average number of colonies counted until the maximum was observed at 40 hr. afterwards, there was a decline in the rate of s. cerevisiae growth. figure 15: variation of the concentration of s. cerevisiae with time the kinetic equation for the growth of s. cerevisiae can be represented by the general equation (4): ln xt = ln x0 + μt (4) where xt is the concentration/yield of s. cerevisiae at time t, x0 is the concentration at time zero (0), and µ is the specific growth rate represented by the slope in the straight line graph of ln xt against time t (figure 16). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderibigbe et al: preparation of yeast (saccharomyces cerevisiae) biomass from sugarcane bagasse. azojete, 16(1):117. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 16 figure 16: plot of ln xt against t as presented in figure 16, the plot gave a slope µ of 0.2943 hour –1, and ln xt at time t of zero is found at ln x0 = 8.4338. thus, the kinetic equation for s. cerevisiae growth becomes ln xt = 8.4338 + 0.2943t, with r2 value of 0.671. 4. conclusion particles of sugarcane bagasse prepared into three different concentrations of 20, 25, and 30% (w/v) were hydrolyzed with hcl under various conditions of time (10 – 60 min), acid concentration (0.1 – 0.5 m) and temperature (80 – 97°c). using anova, the interactive effect of hydrolysis time and acid concentration showed the most significant influence on glucose yield. it was clear from the acid hydrolysis that the role of acid concentration in achieving high conversion into glucose is dependent on hydrolysis duration and temperature; high acid concentrations require low temperature and minimum time, while low acid concentrations require high temperature and maximum time. also, substrate concentration tends to determine how acid concentration of 0.5 m particularly affected the yield of glucose. an optimum glucose yield of 1.907 g/l was attained by employing 20% (w/v) substrate concentration at hydrolysis conditions of 10 min, 0.5 m acid concentration and 80°c temperature. fermentation of the glucose obtained was able to produce an optimum yeast (s. cerevisiae) biomass of 20, 700, 000 cfu/ml within 40 h. a kinetic equation for the growth was obtained as ln xt = 8.4338 + 0.2943t, having a correlation coefficient, r2 value of 0.671. acknowledgements the authors wish to acknowledge the department of chemical engineering, university of ilorin, nigeria for permission to use laboratory equipment. references aransiola, mm. 2016. development of a bioreactor for metabolites synthesis: case study with bioethanol production from corn cob. b.eng. thesis, university of ilorin, ilorin. ask, m. 2013. towards more robust saccharomyces cerevisiae strains for lignocellulosic bioethanol production: lessons from process concepts and physiological investigations. phd thesis, chalmers university of technology, gothenburg, sweden. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 1-17. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aderibigbe.fa@unilorin.edu.ng 17 binod, p., janu, ku., sindhu, r. and pandey, a. 2011. hydrolysis of lignocellulosic biomass for bioethanol production. in pandey, a., larroche, c. and ricke, sc. (eds), biofuels: alternative feedstocks and conversion processes, pp. 229-250, elsevier inc., usa. galbe, m. and zacchi, g. 2002. a review of the production of ethanol from softwood. applied microbiology and biotechnology, 59(6): 618-628. galbe, m. and zacchi, g. 2012. pre-treatment: the key of efficient utilization of lignocellulosic materials. biomass bioenergy, 46: 70–78. jabasingh, sa. and nachiyar, cv. 2012. optimization of cellulase synthesis by rsm and evaluation of ethanol production from enzymatically hydrolyzed sugarcane bagasse using saccharomyces cerevisiae. journal of scientific and industrial research, 71: 353–359. kumar, l., chandra, r., chung, pa. and saddler, j. 2010. can the same steam pretreated conditions be used for most softwoods to achieve good enzymatic hydrolysis and sugar yields? bioresource technology, 101: 7827–7833. lenihan, p., orozco, a., o’neil, e., ahmad, mnm., rooney, dw. and walker, gm. 2010. dilute acid hydrolysis of lignocellulosic biomass. chemical engineering journal, 156(2): 395–403. li, j., zhou, p., lv, x., xiao, w., gong, y., lin, j. and liu, z. 2016. sugarcane bagasse hydrolysis: use of sugarcane bagasse with different particle sizes to determine the relationship between physical properties and enzymatic hydrolysis. bioresources, 11(2): 4745–4757. olsson, l. and hahn-hägerdal, b. 1993. fermentative performance of bacteria and yeast in lignocellulose hydrolysates. process biochemistry, 28: 249–257. rao, dg. 2005. introduction to biochemical engineering. 1st ed., pp. 97-100; 341-342. tata mcgraw-hill education, ny, usa. reis, vr., bassi, apg., silva, jcg. and ceccato-antonini, sr. 2013. characteristics of saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation. brazilian journal of microbiology, 44(4): 1121-1131. rosalin, p. and amit, n. 2007. production of ethanol from bagasse. national institute of technology, rourkela, india. snoek, isi. 2007. identification and regulation of genes involved in anaerobic growth of saccharomyces cerevisiae. phd thesis, leiden university, leiden, netherlands. stephen, jd., mabee, we. and saddler, jn. 2013. lignocellulosic ethanol production from woody biomass: the impact of facility siting on competitiveness. energy policy, 59: 329–340. tomás-pejó, e., alvira, p., ballesteros, m. and negro, mj. 2011. chapter 7 pre-treatment technologies for lignocellulose-to-bioethanol conversion. in pandey, a., larroche, c., ricke, sc., dussap, c. and gnansounou, e. (eds), biofuels: alternative feedstocks and conversion processes, pp. 149-176, elsevier inc., usa. you, y., li, p., lei, f., xing, y. and jiang, j. 2017. enhancement of ethanol production from green liquor–ethanol‑pretreated sugarcane bagasse by glucose–xylose cofermentation at high solid loadings with mixed saccharomyces cerevisiae strains. biotechnology for biofuels, 10: 92. yusuf, c. 1999. encyclopedia of food microbiology. in robinson, rk., batt, ca. and patel, pd. (eds), fermentation (industrial): basic considerations, pp. 663–674, academic press, london file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):255-268 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 255 original research article design and construction of an arduino based solar power parameter-measuring system with data logger oladimeji i.1*, adediji y. b.1, akintola j. b.1, m. a. afolayan1, o. ogunbiyi2, ibrahim s. m.3, olayinka s. z.1 (1department of electrical and electronics engineering, university of ilorin, nigeria 2department of electrical and computer engineering, kwara state university, nigeria 3department of electrical engineering, kano university of science & technology wudil, nigeria) *corresponding author’s email address: reacholaibrahim@gmail.com 1.0 introduction the rising costs of fossil fuels, global warming, and severe weather conditions have compelled many nations to look into alternative sources of energy to reduce reliance on fossil-based fuels. the solar energy is one of the most promising renewable sources of energy currently being used globally for meeting rising demands of electric power (kannan and vakeesan, 2016; kabir et al., 2018). solar energy is considered as fastest growing renewable energy source for electricity generation after the wind energy (adib et al., 2015). it involves conversion of solar energy into electric and/or heat energies. the sunlight is collected either directly by using photovoltaics cells or indirectly using concentrated solar energy (singh, 2013). the solar photovoltaic (pv) energy system directly converts the sun photons energy to electricity through the solar cells. solar cells are made from light sensitive semiconductors that use photon energy to dislodge electrons to drive an electric current. the two broad classifications of photovoltaic modules are the mono-crystalline and poly-crystalline. polycrystalline solar cells are formed from multiple silicon crystals while mono-crystalline solar article information abstract accurate monitoring and measurement of solar photovoltaic panel parameters are important for solar power plant analysis to evaluate the performance and predict the future energy generation. there are always challenges of getting such data readily available due to huge amount of money to be spent on state of the art equipment or the purchase of reliable satellite weather data. this study aimed at the development of a cost-effective parameter-measuring system for a solar photovoltaic panel using arduino microprocessor board. the systems measure five parameters, including voltage, current, light intensity, temperature, and pressure. the hardware circuit was designed to link different sensors with the arduino board and the measured data were in turn were documented into a computer for further analysis. the accuracy of the constructed device was ascertained by comparing the measured parameters with that of conventional standard measuring instruments which shows good agreement. the measured parameters show that the output energy generation from solar photovoltaic panel largely depends on the solar irradiance and temperature. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 february, 2020 revised 10 april, 2020 accepted 20 april, 2020 keywords: solar photovoltaic measurement system light intensity temperature pressure voltage current mailto:reacholaibrahim@gmail.com http://www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 256 cells are made from a single silicon crystal and they usually have higher efficiency (yamaguchi, 2003). the output of power generated from a solar cell largely depends on weather conditions most especially the solar irradiance and air temperature (osueke et al., 2013; ibrahim et al., 2015). the recent development in energy sector have shown that solar-energy market is one of the most rapidly expanding renewable energy markets in the world (adib et al., 2015). presently there is significant increasing in demands for remote monitoring and control equipment for solar-energy applications. the advancement in the solar cell technology has led to the development of a more efficient, flexible and lighter pv cells named smart solar cells (luque and hegedus, 2011; battersby, 2019). solar manufacturing company now embeds electronics such as power optimizers, micro dc-todc converters, and condition monitoring devices in the solar pv modules. the monitoring and measurement of solar pv parameters and site condition has some importance in evaluating the performance of existing solar installations, advanced system monitoring and the prediction of future generation (diagne et al., 2013; shamim et al., 2015; verbois et al., 2018; ghasempour et al., 2019). they also aid in decision making, product development, system maintenance, and many other applications. a solar pv energy system requires reliable means of data acquisition of all the electrical and meteorological data for condition monitoring, and evaluation of the system performance. acquiring such data has been capital intensive when state of the art equipment is to be installed at the site and there is a concern of reliability over the use of satellite data in place of site data. this study involves the development of low-cost arduino-based solar photovoltaic parametermeasuring system with data logger. the developed system successfully measures the solar photovoltaic parameters such as incident light intensity, voltage, current, and temperature. 2. materials and methods in this work, an arduino-based solar parameter-measuring system was designed and constructed using arduino uno and multiple sensors. the system was found to be capable of measuring different solar pv parameters including the voltage, current, real time temperature, real time atmospheric pressure, and light intensity. the measured parameters were simultaneously logged into a personal computer (pc) for future analysis or references. figure 1 shows the block diagram of an arduino based solar pv parameter-measuring system having sensors interfaced between the solar panel and arduino board. the system comprised of both hardware circuit design and software programming for interfacing solar with the arduino board. the hardware development involves the design of electronic components for the sensors interface between the solar panel to the arduino uno. the hardware unit comprised of the voltage sensor, current sensor, light dependent resistor (ldr) sensor, pressure-temperature sensor and the arduino uno. the acquired data from sensors are analogue, thus the conversion to digital equivalent was performed within the arduino uno analogue-to-digital converter module programmed in clanguage. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 255-268. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 257 figure 1: solar pv parameter-measuring system 2.1 system components 2.2.1 solar panel a solar photovoltaic panel converts sunlight (photons) into electrical energy through the influence of the photovoltaic effect. the photovoltaic modules constitute the photovoltaic array of a photovoltaic system that generates and supplies electric energy from solar energy in commercial quantities for community uses. the common types of photovoltaic modules are mono-crystalline, poly-crystalline, and thin film photovoltaic modules. in this study, a 12v, 20w solar panel composed of mono-crystal solar cell with an efficiency of 17% was selected. the manufacturer’s technical specifications of the 12v solar panel is presented in table 1 (bluesolar datasheet). table 1: manufacturer’s description of the mono-crystalline solar panel name: bluesolar series 4a solar panel dimensions (mm): 440 × 350 x 25mm net weight (kg): 1.9 nominal power (pmpp-w): 20 max-power voltage (pmpp-v): 18.5 max-power current (impp-a): 1.09 open-circuit voltage (voc-v): 22.6 short-circuit current (ioc-a): 1.19 2.2.2 arduino microcontroller arduino is an open-source, prototyping platform that is widely used in digital world owing to simplicity and ease of configuration. the arduino uno r3 used in this project is a microcontroller board based on the atmega328. the microcontroller is shown in figure 2, it has 16 mhz crystal oscillator, 14 digital input/output pins of which 6 can be used as pwm outputs. it has 6 analog inputs, a usb connection function as power source and communication channel, a power jack, an icsp header, and a reset button. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 258 figure 2: arduino uno r3 microprocessor 2.2.3 light dependent resistor (ldr) the light dependent resistor (ldr) is a light-controlled variable resistor. its resistance depends on the light impinging on it. the resistance offered by the ldr is inversely proportional to light strength. light dependent resistors are useful especially in light/dark sensor circuits application. the symbol is shown in figure 3, they usually have high resistance up to 1mω, but when they are illuminated with light, the resistance drops drastically. figure 3: light dependent resistor in this work, the ldr sensor is used to monitor the light intensity incidence on the solar pv.the change in resistance can easily be measured by converting the resistance into voltage equivalent. the input of the ldr is connected to a 5v supply and in series with a 10kω resistor. the middle point is used as output connected to the arduino board. when light falls on the ldr, the resistance of ldr decreases and the analog voltage changes. this voltage is applied to the analog input of the arduino which is converted to digital equivalent corresponding to light intensity. for measuring the light intensity in degree lux, the ldr voltage (vldr) is converted using equation (1) (ashishi, 2018). 1023 5 ldrvlight intensity   (1) 2.2.4 temperature and pressure sensor the temperature and barometric pressure were measured using bmp180 temperature-pressure sensor. the bmp180 sensor is an environmental sensor for different weather sensing and can be used with both i2c (inter-integrated circuit) and spi (serial peripheral interface) communication protocol. this precision sensor from bosch company is a popular low-cost precision sensing solution for measuring barometric pressure with ±1 hpa absolute accuracy, and at temperature ±1.0°c accuracy. figure 4 show the bmp180 sensor with the connection pins for interface with the arduino board. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 255-268. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 259 figure 4: bmp 180 temperature-pressure sensor 2.2.5 voltage sensor module the voltage sensor as shown in figure 5 is used to measure the voltage of the solar panel. the voltage module analog interface can detect input voltage up to 5v and a voltage greater than 5v will not be detected. the solar pv voltage was measured employing a voltage divider. the voltage sensor interface circuit comprised of two series resistors r1 and r2 obtained as 30kω and 7.5kω and resistance factor (rf) obtained from equation (3) is responsible for converting the voltage back to the original solar panel value to be displayed on the pc. the measured solar panel output voltage is given by eqn (2) (ravi 2018). figure 5: voltage sensor module voltage devider analogue value ×reference voltage resis measured volta tance factor ge (rf) = (2) 1 1 2 1023 ( ) rf r r r   (3) 2.2.6 current sensor (acs712) the acs712 20a rating current sensor shown in figure 6 was selected for measuring the current flowing into the system. the sensing terminal of the current module can measure load current on medium voltage system up to 230v ac mains while output sensed voltage is isolated from measuring part. in this application, the sensor was operated with 5v supply voltage and outputs analog voltage is proportional to current measurement on the sensing terminals. the microcontroller adc converts the analogue value to digital current equivalent for displayed or file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 260 storage in data logger. the measured solar panel current is given by equation (4) and the power is computed from equation (5) (ravi 2018). figure 6: current sensor module (analogue value×analogue factor)-acoffsetcurrent measurement sensitivity  (4) where: analogue factor=5/1023, acoffset=2500ma, and sensitivity=100mv/a the power per square meter measurement for the solar panel was obtained using the relationship in equation (5) voltage currentpower area   watts/m2 (5) 2.2 software programming this section presents the programming of the arduino board and highlights the software relevance in the system operation. some of the sensors such as temperature and ldr sensor output are in analog format which the conversion to digital equivalent was done using the analog-to-digital converter (adc) module of the microcontroller. the arduino uno was programmed using the codeblocks arduino ide (integrated development environment) which is an open -source customized software for arduino development. the microcontroller was interfaced to the pc with using universal serial bus (usb) cable. the arduino board adc monitors the analogue input voltage changes and converts it to a binary number between 0 to 1023 bit. in between, analog read(pin no )returns a number between 0 and 1023 proportional to the amount of voltage being applied to the pin. the flow chart in figure7 shows the analogue to digital conversion process and how the measured data were display on lcd screen and log to the pc. https://www.arduino.cc/en/reference/analogread http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 255-268. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 261 display data on pc close serial port end start open serial port start reading analog input converting to equivalent temperature and lux figure 7: arduino adc conversion the data logging of the measurement data was done using an add-on called plx-daq (parallax data acquisition). the plx-daq is an open access program used to establish communication between microsoft excel on a windows computer and any device that support serial port protocol. the plxdaq user interface is shown in figure 8. it was originally written to allow communication between arduino board and microsoft excel. figure 8. plxdaq user interface 2.3 system simulation after designing the sensor interface circuit for the solar pv parameter measuring system, a simulation was carried out in proteus isis to optimize the circuit parameters prior to practical construction of the designed system. each component was picked by selecting the proteus schematic capture and component mode from the library’s toolbar. the complete circuit file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 262 schematic is presented in figure 9 showing all essential components placed in the workspace before the circuit was wired up. figure 9: simulated solar pv parameter measuring system the voltage sensor measures the voltage generated by the solar panel in volts and sends the analog input to the microcontroller. the current sensor measures the current drawn by the load in ampere and sends the analog input to the microcontroller. also, the bmp180 sensor senses the pressure (pa) and air temperature (°c) but provides the values directly in digital output. this is done by interfacing the output of the bmp180 to the analog input of the microcontroller. the ldr sensor was used to measure the light intensity in lux. these sensors output parameters provide the input value to the arduino and the output is displayed on the lcd screen. the arduino uno adc module was programmed to convert the analog input from the sensors to digital output equivalent for display via lcd screen and logged in the plxdaq data acquisition. the lcd screen displays output of the voltage, current, temperature, pressure, and light intensity values. 2.4 circuit construction and testing the designed circuit parameters were first simulated on proteus isis software which was in turn was used to select components for the construction of the arduino-based solar pv parameter-measuring system. the system construction encompasses mounting and soldering of the circuit elements on the breadboard. the hardware construction involves the coupling of physical part of the system which is made up of circuit units and interface between the voltage sensor unit, current sensor unit, temperature and pressure sensor unit, light intensity sensor unit and the arduino microcontroller unit. the constructional stage of the system is presented in figure 10 showing the assemblage of the components parts on the breadboard. the second stage involves programming of the arduino in c-language which provides central control for the system operation. the program used for the system testing on the proteus isis software was downloaded to the board to complete the circuit construction. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 255-268. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 263 fig. 10: constructed solar pv parameter-measuring system after the circuit construction, the measuring system was tested with a mono-crystalline 20w solar panel and 10w dc bulb as load. the test was conducted outdoor for few days and the values of the voltage, current, light intensity, temperature and pressure were all logged into a computer. to confirm the accuracy of the constructed measuring device, a comparative measurement was also taken by using standard multimeter (aneng an8002) for current and voltage measurement and also the temperature measurement using the multimeter since it has thermocouple probe. the constructed measurement values and that of the standard instrument shows good similarity. the field experimental setup is shown in figure 11 together with the pc for data logging. the testing was conducted on the 19th, 20th, 21st of june 2019 at university of ilorin, faculty of engineering and technology. the readings were taken from 7:00am to 6:00pm daily for each of the testing days. figure 11: field testing of measuring system the solar pv panel was placed in horizontal positions throughout the three days test period in which the readings were logged to pc. it was well positioned to ensure that the solar panel was not affected by shading and surface was kept clean at all times to avoid errors in the readings. the results for voltage, current, light intensity, temperate and pressure were presented. the results were recorded on the 19th, 20th and 21st of june, 2019 between 7:00am to 6:00pm daily. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 264 3.0 results and discussion 3.1 voltage and light intensity measurement the results of voltage and light intensity against the hours of the day for the solar pv panel are presented in figures 12, 13 and 14, respectively. the highest voltage for 19th of june, 2019 was 17.44v at 3.00pm with light intensity of 1014.5lux and the lowest voltage was 9.21v at 7.00am with light intensity of 990.5lux. the highest voltage for 20th of june, 2019 was 13.79v at 12.00 noon with light intensity 1010.25lux and the lowest voltage was 9.28v at 7.00am with light intensity 1000lux. the highest voltage for 21st of june,2019 was 18.54v at 12.00pm with light intensity 1016lux and the lowest voltage was 10.16v at 7.00am with light intensity of 1000.5lux. as observed from the graphs, there is direct relationship between the light intensity and the solar panel output voltage. figure 12: graph of voltage and light intensity against time for day 1. figure 13: graph of voltage and light intensity against time for day 2. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 255-268. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 265 figure 14: graph of voltage and light intensity against time for day 3. figure 15 presented a comparison of light intensity for the three days, from the bar chart shows that highest light intensity of 1016lux was recorded at 12.00 pm on the 21st of june while the lowest light intensity was 960.75 lux at 10am on the 19th of june 2019. figure 15: graph of light intensity against time 3.2 temperature and pressure measurement the three days result of the ambient temperature and pressure around the solar pv panel are presented in figures 16, 17 and 18. the highest pressure and temperature recorded for 19th of june, 2019 were 976.09pa and 32.71°c respectively at 3.00pm and the lowest pressure and temperature were 971.35 pa and 23.89°c at 7.00am. the highest pressure and temperature for 20th of june, 2019 were 976.96pa, 30.91°c respectively at 1.00pm and lowest pressure and temperature were 971.37 pa and 24.19°c at 6.00pm. the highest pressure and temperature for 21st of june, 2019 were 975.97pa, 33.41°c at11.00am. the lowest recorded pressure and temperature for the day were 971.35 pa and 23.9°c t at 7am. it can be seen from the pressuretemperature graphs that the air pressure is directly proportional to the air temperature. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 266 figure 16: pressure and temperature against time day 1 figure 17: pressure and temperature against time day 2 figure 18: pressure and temperature against time for day 3 3.3 solar pv panel output power the result of the power generated by the solar panel is shown in figure 19. the result pattern shows that the output power depends directly on the solar panel voltage, light intensity and the temperature. the solar panel highest power of 7.5w was recorded on the 21st of june when the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 255-268. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 267 day was brightest with moderately low temperature of 33.31°c at 11.00pm while the lowest power was 0.48w at 7.00am on the 19th of june 2019. fig. 19: solar panel output power against time. 4.0 conclusion an arduino based solar power parameter-measuring system has been designed and constructed using the optimized simulated parameter from proteus isis. this device was then used to acquire solar pv current, voltage, power, temperature, pressure and light intensity. the system can measure data from solar panel that can be used to evaluate the performance of solar energy generated for future energy generation prediction. based on the measurement data, it was observed that the solar pv energy generation directly depends on the solar irradiance, temperature and air pressure. references adib, r., murdock, h., appavou, f., brown, a., epp, b., leidreiter, a., lins, c., murdock, h., musolino, e. and petrichenko, k. 2015. renewables 2015 global status report. ren21 secretariat, paris, france: 162. ashish a, 2018. using an ldr sensor with arduino. available online at https://maker.pro/arduino/projects/using-an-ldr-sensor-with-arduino. battersby, s., 2019. news feature: the solar cell of the future. proceedings of the national academy of sciences, usa, 116:7-10. bluesolar-monocrystalline-panels-datasheet. available at https://cdn.shopify.com/s/files/1/0017/8847/7489/files/victron-bluesolar-monocrystallinepanels-datasheet.pdf?1506 diagne, m., david, m., lauret, p., boland, j. and schmutz, n. 2013. review of solar irradiance forecasting methods and a proposition for small-scale insular grids. renewable and sustainable energy reviews, 27:65-76. ghasempour, r., nazari, ma., ebrahimi, m., ahmadi, mh. and hadiyanto, h. 2019. multi-criteria decision making (mcdm) approach for selecting solar plants site and technology: a review. international journal of renewable energy development, 8(1): 15-25. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al: design and construction of an arduino based solar power parameter-measuring system with data logger. azojete,16(2):255-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaibrahim@gmail.com 268 ibrahim, o., yahaya, nz., saad, n. and umar, mw. 2015. matlab/simulink model of solar pv array with perturb and observe mppt for maximising pv array efficiency. 2015 ieee conference on energy conversion (cencon), johor bahru malaysia, 2015: 254-258. kabir, e., kumar, p., kumar, s., adelodun, aa. and kim, kh. 2018. solar energy: potential and future prospects. renewable and sustainable energy reviews, 82:894-900. kannan, n. and vakeesan, d. 2016. solar energy for future world:-a review. renewable and sustainable energy reviews, 62: 1092-1105. luque, a. and hegedus, s. 2011. handbook of photovoltaic science and engineering. john wiley & sons, : 1-38, new york city, united states. osueke, c., uzendu, p. and ogbonna, i. 2013. study and evaluation of solar energy variation in nigeria. international journal of emerging technology and advanced engineering, 3: 501-505. ravi, 2018. interfacing acs712 current sensor with arduino – measure current with arduino: available online at https://www.electronicshub.org/interfacing-acs712-current-sensor-witharduino/ ravi, 2018. interfacing voltage sensor with arduino – measure up to 25v using arduino. available online at https://www.electronicshub.org/interfacing-voltage-sensor-with-arduino/ shamim, m., remesan, r., bray, m. and han, d. 2015. an improved technique for global solar radiation estimation using numerical weather prediction. journal of atmospheric and solarterrestrial physics, 129: 13-22. singh, gk. 2013. solar power generation by pv (photovoltaic) technology: a review. energy, 53: 1-13. verbois, h., huva, r., rusydi, a. and walsh, w. 2018. solar irradiance forecasting in the tropics using numerical weather prediction and statistical learning. solar energy, 162: 265-277. yamaguchi, m., 2003. iii–v compound multi-junction solar cells: present and future. solar energy materials and solar cells, 75:261-269. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):387-394 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 387 original research article evaluating the potential of microorganisms in bioremediation of lead polluted soil e. atikpo1*, and n. i. ihimekpen2 (1department of civil and environmental engineering, faculty of engineering, delta state university, oleh campus, pmb 1, abraka, delta state, nigeria. 2department of civil engineering, faculty of engineering, university of benin, pmb 1154, benin city, nigeria.) *corresponding author’s email address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 1.0 introduction human activities like mining, agriculture and manufacturing have kept the environment at a high risk of pollution through heavy metals (gupta et al., 2016; kure et al., 2018). heavy metals have been reported to be very injurious to plants and animals (vijaya et al., 2010; girma, 2015). metals are important for the performances of living organisms, but at concentrations above the required; they could be very injurious to lives (musa et al., 2017). lead (pb) is classified among hazardous metals negatively affecting soil quality, crops yields; and public health (gupta et al., 2016; upadhyay et al., 2017). at concentration above the threshold (100 mg/kg) in soils (chiroma et al., 2014), it can be injurious to plants; it can limit plant growth as a result of hampered photosynthetic activities, nutrients, and performances of necessary enzymes (kabatapendias, 2010; namatian et al., 2013). metals are capable of bioaccumulation in food chain and in this manner; their effects on lives and associated risk are wider (tak et al., 2013). effects of lead include mental retardation, anemia, renal dysfunction, palsy, reproductive systems disorder (athar and vohora, 2006). the removal of metals from the environment requires effective and affordable techniques that are better than the physical and chemical techniques with associated devastating post remediation toxicity, unwanted sludge, very high cost, and under performance at very low concentration (ayangbenro and babalola, 2017). these disadvantages of physical and chemical techniques of remediation are the reasons for a push for further remediation alternatives, which include bioremediation that involves the use of organism for the removal of contaminants from the environment. the capacities of organisms to effect bioremediation is tied to some vital factors (suitable ph, temperature, and moisture) which promote their metabolism and growth (verma and jaiswal, 2016). beside the use of organisms that are genetically engineered, the use of indigenous micro organisms is efficient for bioremediation (gupta et al., 2016). human activities during mining in amita agricultural forest in ebonyi state of nigeria has contaminated the forest soils (ezeh and chukwu, 2011) and some crops (tubers and vegetable) article information abstract this study evaluated and compared the abilities of indigenous bacillus sp. and micrococcus sp. for treating lead polluted soil. the organisms were inoculated into the contaminated soil samples prepared with the optimum values of screened determinant factors and experimented on 8, 16, 24, 32, 40, 48, and 56 days respectively for lead ion residual concentration using atomic absorption spectrophotometer. bacillus sp. showed greater remediation strength than micrococcus sp. the results show that bacillus sp. attenuated the pb initial concentration from 150.74 mg/kg to control level in 40 days while micrococcus sp. achieved that in 48 days. the 56th day residual concentrations and removal efficiencies were 81.43 mg/kg and 46% for bacillus sp., and 86.91 mg/kg and 42.34% for micrococcus sp. the removal rate was higher for bacillus sp. (0.0715 d-1) than for micrococcus sp. (-0.0744d-1); and the remediation process was transport controlled. this information will be useful for remediation programs; and it will serve as a reference material for future research. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 feb., 2020 revised 24 may, 2020 accepted 30 may, 2020 keywords: lead soils contamination bioremediation removal kinetics mailto:eguasbridge@gmail.com mailto:eatikpo@delsu.edu.ng http://www.azojete.com.ng atikpo and ihimekpen: evaluating the potential of microorganisms in bioremediation of lead polluted soil. azojete,16(2):387-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 388 (onyedika and nwosu, 2008) with some heavy metals including lead. these soils need effective and affordable remediation for their restoration for meaningful agricultural practice. microorganisms (fungi, bacteria and algae) are known to be effective for removing heavy metals from water and soils (kure et al., 2018). dixit et al. (2015) documented that microbes like pseudomonas, escherichia, bacillus, yeasts and enterobacter are useful for the removal of heavy metals from soils and water. this study focused on determining the potential application of indigenous bacillus sp. and micrococcus sp. acquired from amita forest soils for tackling the pb pollution through the process of bioremediation for safe food and commercial supply purpose. the work also examined the processes controlling the bioremediation through rate-limiting steps established by some kinetics models. 2.0 materials and methods 2.1 materials and reagents the materials and reagents used in this study include: 1. soil samples collected from amita forest, ebonyi state in nigeria; 2. maccartney bottles; 3. oxidase reagent; 4. incubator; 5. kovac’s reagent; 6. cotton wool; 7. whatman filter papers; 8. sodium hydroxide; 9. measuring cylinder; 10. atomic absorption spectrophotometer; 11. perchloric acid; 12. wire loops; 13. refrigerator; 14. inoculating needles; 15. perchloric acid; 16. pipettes; 17.sulphuric acid; 18. crystal violent; 19. hot plate; 20. methylene blue; 21. lugo’s iodine; 22. autoclave; 23. ethanol; 24. hydrogen peroxide; 25. petri dishes; 26. hydrochloric acid; 27. beakers; 28. safranin; 29. microscope; 30. nitric acid; and 31. conical flasks. 2.2 nutrients preparation to prepare the nutrients needed for isolation of organisms and biostimulation of the organisms for effective bioremediation, 15g of peptone water powder; 28 g of nutrient ager; 65 g of triple sugar iron agar; 24 g of simon citrate agar; and 52 g of powered macconkey agar were dissolved in 1000 cm3 each of water for 10 minutes according to cheesebrough (2000) and manufacturer’s manual. the formulated solutions were autoclaved at 10342.14 n/m2 for 15 minutes at 121 ºc and cooled to 45 ºc for use. 2.3 acquisition of microorganisms at a microbiology laboratory of delta state university in abraka, delta state of nigeria, bacteriological evaluation of the collected soil sample was conducted. the soil was serial diluted by dissolving 1g of the soil in 10 ml of distilled water. one (1) ml of the resultant solution was diluted with 9 ml of distilled water and the resultant solution was serial diluted from step 10-1 to 10-5. using the pure plate method, 0.1ml from 10-1, 10-3 and 10-5 serial delusion was measured into several petrri-dishes and cover with nutrient and macconkey agars respectively (baron et al., 1994); and incubated at 37 ºc for 24 h. developed colonies of the organisms were sub-cultured and recognized using the techniques in (holt, 1994; cheesebrough, 2000). 2.4 selection of optimal factors bioremediation is very effective when carried out with optimum values of determinant factors (murthy et al., 2012; atikpo and michael, 2018). this makes it imperative to select the optimum values of these determinant (ph, temperature, stirring frequency, mass of organisms and nutrient dosage) experimentally (atikpo, 2016; atikpo and ezugwu, 2017). the experiments were conducted by adopting the method in (atikpo and micheal, 2018). five grams of soil samples were measured to have 39 pairs of 5g of the soil. from the 39 pairs of 5g of soil samples, 8 pairs were conditioned with nutrient dosage of 4, 5, 6, 7, 8, 9, 10 and 11ml; nine pairs were conditioned with 1, 2, 3, 4, 5, 6, 7, 8 and 9g of organisms’ masses; seven pairs were conditioned with 10, 15, 20, 25, 30, 35 and 40 oc of temperature; eight pairs were conditioned with 4, 5, 6, 7, 8, 9, 10 and 11 of ph; and seven pairs were conditioned with 0, 1, 2, 3, 4, 5 and 6 per week (pw) of stirring frequency. one out of each pair was for inoculation with bacillus sp. while the second one out of each pair was for inoculation with micrococcus sp. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 387-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 389 these pairs of soil samples were inoculated with respective 24hr old bacillus sp. and micrococcus sp. that were isolated and sub-cultured and identified with the methods in (baron et al., 1994; holt, 1994; cheesebrough, 2000). adopting the least residual pb ion content of soil as the criteria for identifying the optimum values of ph, temperature, stirring frequency, mass of organisms and nutrient dosage, their optimum values were then determined and recorded by evaluating the residual lead (pb) ion content of the pairs of soil samples with atomic absorption spectrophotometer (gbc sensaa model no. a6358) on the 24th day. 2.5 remediation studies the bioremediation studies were conducted following the method reported by (atikpo and micheal, 2018). the optimum masses selected for the organisms were inoculated in 5g each of soil sample in 50ml beaker and conditioned with the selected optimum values of ph, temperature, stirring frequency, mass of organisms and nutrient dosage. the remediation abilities of the organisms were determined at time 8, 16, 24 and 32, 40, 48 and 56 days by analyzing the residual pb ion in the soils using atomic absorption spectrophotometer (gbc sensaa model no. a6358) after separating the organisms from the sample with a centrifuge. the pb ion removed with time; pb ion removed at equilibrium; and the ionic removal efficiencies were determined using equations (1), (2) and (3) respectively (badmus et al., 2007). qt = co−ct m .v (1) qe = co−ce m .v (2) efficiency = co−cf co .100 (3) where: qt (mg/kg) is pb ion removed with time t; qe (mg/kg) is pb ion removed at equilibrium; co (mg/kg) is the initial lead ion brought in contact with the organisms; cf (mg/kg) is the final pb ion; v(m3) is the volume of soil used; and m (g) is the optimum mass of organism. difference in the organisms’ removal proficiencies was evaluated with microsoft excel 2016 at (p < 0.05); and the rates of pb ion removal by organisms were assessed with pseudo-first order kinetics model (owamah, 2014; atikpo, 2016). 2.6 removal kinetics this study was conducted to deduce the rate-limiting steps (chen and wang, 2007; atikpo, 2016) useful for establishing process controlling the bio-removal of the metal ion from the soil (atikpo, 2016); and for establishing the rate of the ion removal by the bio-sorbents (owamah, 2014). the kinetics were evaluated by fitting the elovich, pseudo-first order, intra-particle diffusion, and pseudo-second order models with the batched experimental data using equations (4), (5), (6) and (7) (chien and clayton, 1980; mckay and poots, 1980; ho et al., 2000;); and the models’ coefficient of determination, r2 was engaged in determining the rate-limiting steps.  t t q dt dq   exp (4)  te t qqk dt dq  (5) xtkq t  2 1 2 (6)  2 1 te t qqk dt dq  (7) where: qt in mg/kg is the ion removal capacity with time t in days; k is pseudo first order model rate constant per day (d-1); qe in mg/kg is equilibrium ionic removal capacity; k1 is pseudo second order model rate constant in kg. mg-1d-1;  in mg/kg is elovich model initial ion removal rate;  in mg/kg is elovich model ion desorption rate constant; and k2 is intra-particle diffusion model rate constant. 3.0 results and discussion 3.1 organisms and bioremediation optimum factors file:///c:/users/user/downloads/azojete143/www.azojete.com.ng atikpo and ihimekpen: evaluating the potential of microorganisms in bioremediation of lead polluted soil. azojete,16(2):387-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 390 the developed and sub-cultured colony (3.2 x 102 cfu/ml) of microorganisms was found to contain bacillus sp. and micrococcus sp. through various microbiology analyses. figure 1 shows the influences of ph values and the corresponding residual pb concentration. ph is very sensitive to bioremediation process. it affects negatives charges on organisms’ cells and physiochemistry of metals (lopez et al., 2000; samarth et al., 2012). the organisms were influenced differently by the ph. the optimum values were 6 for micrococcus sp., and 8 for bacillus sp. the residual concentrations at these values were 83.91 mg/kg for bacillus sp. and 103.81 mg/kg for micrococcus sp. figure 1: performance of organisms under varied ph values the performances of these organisms observed under varied temperature values of 10, 15, 20, 25, 30, 35 and 40 ºc were evaluated. the organisms performed differently under these temperatures. figure 2 showed a common optimum temperature value of 30 ºc for the organism; but their removal potential differs markedly. bacillus sp. was more sensitive to temperature change than micrococcus sp. this was evident from the residual concentrations of 85.47 mg/kg and 119.11 mg/kg relative to their performances. the optimum value is important because temperature influences remediation process (ajaykumar et al., 2009; murthy et al., 2012). the influence of 4, 5, 6, 7, 8, 9, 10 and11ml of nutrients dosage; 2, 3, 4, 5, 6, 7, 8 and 9 g of organisms and 0, 1, 2, 3, 4, 5 and 6 (pw) of stirring frequencies were studied. the observed optimum values of these factors were 8ml for bacillus sp. and 9 ml for micrococcus sp.; 5 g for bacillus sp. and 4 g for micrococcus sp.; and 6 pw for the organisms. figure 2: performances of organisms under varied temperature values http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 387-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 391 3.2 bioremediation the bioremediation abilities of the organisms were experimented using the batched techniques in (lin and lin, 2005; atikpo and michael, 2018) for 8, 16, 24, 32, 40, 48 and 56 days. their abilities to bring the concentration of pb from 150.74 mg/kg to below the maximum allowable concentration value of 100 mg/kg set for agricultural soils by standards in (chiroma et al., 2014) were assessed. the difference between 150.74 mg/kg and 100 mg/kg showed that the forest soil was unhealthy and needed remediation. figure 3: comparative removal by the organisms figure 3 shows the organisms to be effectively useful for treating the lead contaminated soil. they are capable of reducing the concentration from 150.74 mg/kg to below 100 mg/kg at different rates and times. removal by bacillus sp. was more rapid than removal by micrococcus sp. bacillus sp. attenuated the pb concentration to control level in 40 days while micrococcus sp. did in 48 days. the respective residual concentrations and efficiencies on the initial safe concentration dates were 96.78 mg/kg and 35.80% for bacillus sp., 93.45 mg/kg and 38.01% for micrococcus sp. these safe concentration values were barely below the maximum allowable concentration. the 56th day residual concentrations and removal efficiencies were 81.43 mg/kg and 45.99% for bacillus sp., 86.91 mg/kg and 42.34% for micrococcus sp. two-ways anova at (p < 0.05) conducted with microsoft excel, 2016 revealed the possibility of greater sorption by a consortium of the organisms because there was a significance difference between the organisms’ sorption capacities. the anova also revealed a possibility of relevant performances with time intervals shorter than the one adopted in this study. this was evident from the significant difference in sorption with experimental times adopted. from descriptive statistics, the mean residual ion is 109.18 mg/kg for bacillus sp., and 113.82 mg/kg for micrococcus sp. the maximum residual ion (maxri), minimum residual ion (minri), and ion removed (ir56) on 56 day are shown in table 1. table 1. descriptive parameters organism minri (mg/kg) mari (mg/kg) ir56 (mg/kg) micrococcus sp. 86.91 144.53 63.83 bacillus sp. 81.43 140.57 69.31 3.3 kinetics of removal deducible rate-limiting steps from kinetics models (chen and wang, 2007; atikpo, 2016) are useful for establishing whether biosorption process is reaction or transport controlled (atikpo, 2016). kinetics models are useful for establishing the rate of ions removal (owamah, 2014). kinetics models: elovich, pseudo first order, pseudo second order, and intraparticle diffusion were fitted with the experimental data to deduce the rate-limiting steps. the relationships of ln(qe-qt) and t; t/qt and t; qt and ln(t); and qt and t1/2 from the linear version of models in equations (4), (5), (6), and (7) respectively were plotted as shown in file:///c:/users/user/downloads/azojete143/www.azojete.com.ng atikpo and ihimekpen: evaluating the potential of microorganisms in bioremediation of lead polluted soil. azojete,16(2):387-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 392 figures 4, 5, 6 and 7 reflecting the regression models and r2. the high values of models’ r2 indicated that the experimental data were describable by the fitted kinetics models. the order of models fit was the fit for micrococcus sp. before the fit for bacillus sp. using pseudo-first and second order, intraparticle diffusion; and bacillus sp. before micrococcus sp. using elovich model. the removal rate of pseudo first order was higher for bacillus sp. (-0.0715 d-1) than for micrococcus sp. (-0.0744d-1). figure 4: fit of pseudo first order model figure 5: fit of pseudo second order model figure 6: fit of elovich model figure 7: fit of intraparticle diffusion model the laboratory data fitted well with tested kinetics models. the r2 values comparisons in table 2 displayed the intraparticle diffusion model as the best for describing the removals by the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 387-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 393 organisms, micrococcus sp. with r2 of 0.992 and bacillus sp. with r2 of 0.982. therefore, the diffusion process was the rate-limiting step for the removals by these organisms (chen and wang, 2007) and the processes were transport controlled (atikpo, 2016). table 2. kinetic parameters for the fitted kinetic models organism kinetic models and their parameters pseudo first order pseudo second order elovich intraparticle diffusion k (d-1) r2 k1 (kg.mg-1.d-1) r2 α (mg.kg-1) r2 k2 (mg/kg.d1/2) r2 micrococcus sp. -0.0744 0.8262 0.0088 0.950 0.0054 0.950 0.0133 0.992 bacillus sp. -0.0715 0.8123 0.0079 0.844 0.0058 0.957 0.0134 0.982 conclusion this study is on bioremediation of lead contaminated soil in amita forest in ebonyi state of nigeria using indigenous and biostimulated bacillus sp. and micrococcus sp. the organisms were effective for treating the lead contaminated soil. bacillus sp. showed greater remediation potential than the micrococcus sp.; removal rate of (-0.0715 d-1) for bacillus sp. was higher than (-0.0744d-1) for removal with micrococcus sp.; and the remediation processes was transport controlled. this study furnishes relevant insight that will be helpful for soil cleaning programs and further research. references ajaykumar, av., nalf, ad. and hilal, n. 2009. study of various parameters in the biosorption of heavy metals on sludge. world applied sciences journal, 5: 32-40. athar, m. and vohora, sb. 2006. heavy metals and environmental, new age international (p) limited publishers, 4835/24, ansari road, daryaganji, new delhi-110002. atikpo, e. 2016. spatial distribution and attenuation of heavy metals pollution in amaonye ishiagu forest soils. a phd thesis submitted to the department of civil engineering, university of benin, benin city, nigeria. atikpo, e. and ezugwu, mo. 2017. preferential removal of lead, cadmium and zinc from contaminated agricultural soil by bacillus subtilis. journal of nigerian association mathematical physics, 41: 339-346. atikpo, e. and michael, a. 2018. performance evaluation of six microorganisms ultilized for the treatment of lead contaminated agricultural soil. journal of applied science and environmental management, 22(7):1105-1109. ayangbenro, as. and babalola, oo. 2017. a new strategy for heavy metal polluted environments: a review of microbial biosorbents. international journal of environmental research and public health, 14: 94. badmus, mao., audu, tok. and anyata, bu. 2007. removal of lead ion from industrial wastewaters by activated carbon prepared from periwinkle shells (typanotonusfuscatus). turkish journal environmental engineering and science, 31: 251-263. baron, ej., peterson, lr. and finegold, sm. 1994. bailey and scotts diagnostic microbiology, 9th edition. mosby, baltimore. chiroma, tm., ebewele, ro. and hymore, fk. 2014. comparative assessment of heavy metal levels in soil, vegetables and urban grey waste water used for irrigation in yola and kano. international refereed journal of engineering and science, 3(2):01-09. dixit, r., malaviya, d., pandiyan, k., singh, ub., sahu a., shukla, r., singh, bp., rai, jp., sharma, pk. and lade, h. 2015. bioremediation of heavy metals from soil and aquatic environment: an overview of principles and criteria of fundamental processes. sustainability, 7:2189-2212. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng atikpo and ihimekpen: evaluating the potential of microorganisms in bioremediation of lead polluted soil. azojete,16(2):387-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eguasbridge@gmail.com; eatikpo@delsu.edu.ng 394 ezeh, hn. and chukwu, e. 2011. small scale mining and heavy metals pollution of agricultural soils: the case of ishiagu mining district, south eastern nigeria. journal of geology and mining research, 3(4):87-104. girma, g. 2015. microbial bioremediation of some heavy metals in soils: an updated review. indian journal of scientific research, 6(1): 147. gupta, a., joia, j., sood, a., sood, r., sidhu, c. and kaur, g. 2016. microbes as potential tool for remediation of heavy metals: a review. journal of microbial and biochemical technology, 8:364-372. ho, ys., johnwase, da. and forster, cf. 2000. study of the sorption of divalent metal ions onto peat. adsorption science technology, 18:639-650. holt, j.c. (ed) 1994. the shorter bergeys manual of determinative bacteriology, eight edition, williams and willkins company, baltimore. kure, jt., gana, m., emmanuel, a., isah, rm. and ukubuiwe, cc. 2018. bacteria associated with heavy metal remediation: a review. international journal of applied biological research, 9(1): 134 148. lin, c. and lin h. 2005. remediation of soil contaminated with the heavy metal (cd2+). journal of hazardous materials, 122 (1-2):7-15. lopez, a., lazaro, n., priego, jm. and marques, am. 2000. effect of ph on the biosorption of nickel and other heavy metals by pseudomonas fluorescens 4f39. journal of industrial microbiology and biotechnology, 24:146-151. mckay, g. and poots, vj. 1980. kinrtics and diffussion processes in colour removal from effluent using wood as an adsorbent. journal of chemical technology, biotechnology, 30:279-292. murthy, s., bali, g. and sarangi sk. 2012. biosorption of lead by bacillus cereus isolated from industrial effluents. british biotechnology journal, 2(2):73-84. musa, jj., mustapha, hi., bala, jd. ibrahim, yy., akos, mp., daniel, es., oguche, fm. and kuti, ia. 2017. heavy metals in agricultural soils in nigeria: a review. arid zone journal of engineering, technology and environment, 13(5):593-603. nematian, ma. and kazemeini, f. 2013. accumulation of pb, zn, c and fe in plants and hyperaccumulator choice in galali iron mine area, iran. international journal of agriculture and crop sciences, 5:426-432. onyedika, go. and nwosu, gu. 2008. lead, zinc and cadmium in root crops from mineralized galena-sphalerite mining areas and environment. pakistan journal of nutrition, 7(3):418-420. owamah, hi. 2014. biosorptive removal of pb (ii) and cu (ii) from wastewater using activated carbon from cassava peels. journal of material cycle and waste management, 16(2):347-358. samarth, dp., chandekar, cj. and bhadekar 2012.biosorption of heavy metals from aqueous solution using bacillus licheniformis. international journal of pure and applied sciences and technology, 10(2):12-19. tak, hi., ahmad, f. and babalola oo. 2013. advances in the application of plant growth-promoting rhizobacteria in phytoremediation of heavy metals. in whitacre, d.m. (eds), reviews of environmental contamination and toxicology, 223:3–52. upadhyay, n., vishwakarma, k., singh, j., mishra, m., kumar, v., rani, r., mishra, rk., chauhan, dk., tripathi, dk. and sharma, s. 2017. tolerance and reduction of chromium (vi) by bacillus sp. mnu16 isolated from contaminated coal mining soil. frontiers in plant science, 8:778. verma, jp. and jaiswal, dk. 2016. book review: advances in biodegradation and bioremediation of industrial waste. frontiers in microbiology, 6:1555. vijaya, cb., kiran, k., and nagendrappa, g. 2010. assessment of heavy metals in water samples of certain locations situated around tumkur, karnataka, india. coden ecjhao e-journal of chemistry, 7(2): 349-352. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):435-448 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 435 original research article a review of optimization approach to power flow tracing in a deregulated power system m. a. tijani1*, g. a. adepoju2, k. a. hamzat3 and m. a. sanusi1 (1department of electrical and electronics engineering, federal polytechnic, ede. 2department of electronic and electrical engineering, ladoke akintola university of technology, ogbomoso. 3department of electrical and electronics engineering, osun state college of technology, esa-oke) *corresponding author’s e-mail address: muhammedtijani@gmail.com article information submitted 29 march, 2018 revised 20 april, 2019 accepted 23 april, 2019 keywords: power flow tracing optimization deterministic method stochastic method hybrid method abstract power flow tracing (pft) is known to be the best method in the allocation of charges to users of transmission systems, generators and loads, in a deregulated environment. the optimization approach to pft produced better results than other methods because it considers the physical power flow results and electrical constraints of the system. a brief review of the optimal power flow concept, pft techniques, and the deterministic and non-deterministic optimization methods applied to pft are presented. the paper also highlighted the future trends of hybrid optimization approach to pft. it is recommended that more research work should be directed on the hybrid optimization methods to solve pft problems. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the mechanism that helps to trace the contributions or share of each user in the power flow of a particular line or in the demand power of a particular load is known as power flow tracing (pft) (morsali and sheikholeslami, 2011; vinothkumar and arul, 2013). pft results in a comprehensive view of usage allocation problems in power systems which is an important tool in transmission cost and losses allocations (khan and agnihotri, 2014). conventional wisdom believes it is not possible to trace the flow of power from individual generators to individual loads in transmission networks (al-rajhi and bialek, 2002). however, under various assumptions and approximations, which include ignoring linear characteristics of generators and the operating constraints of generators and transmission constraints, several tracing schemes have been proposed (azami et al, 2012; islam et al, 2013; khan and agnihotri, 2013). tracing generators’ shares accurately is difficult due to the nonlinear nature of power flow (mustapha et al, 2010). traditionally, some techniques such as postage stamp method, mw-mile methodology and contract path method have been implemented for generators and loads tracing in the deregulated power systems. postage stamp method allocates charges and losses proportionally to load and generators based on the active generation and load consumptions of mailto:muhammedtijani@gmail.com http://www.azojete.com.ng tijani, et al: a review of optimization approach to power flow tracing in a deregulated power system. azojete, 15(2):435-448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 436 the generator and loads respectively. contract path methodology only choses a specific continuous path between generation and load for wheeling transaction, this selection is not based on load flow studies and it cannot clearly identify the facilities that are actually involved in the transaction. the mw-mile method based its charges on the measure of transmission capacity that is used in the transaction (narayana, 2017; naresh et al, 2010). these methods were found to be inefficient because users of transmission systems were not differentiated by the extent of use of the transmission facilities (mishra et al., 2010). the methods did not consider physical power flow results and electrical constraints such as power directions and losses. the uses of power flow tracing methods have solved the problems of transmission usage allocation in a transmission system (lim et al, 2006). pft is the method of determining the extent of use of a power system network by both generations and loads. it makes it possible to decompose power flows and losses in a transmission line into generator and load constituent commodities (abhyankar et al, 2005). optimization approach to power flow tracing problem is the most efficient method because it provides fairness in allocation of charges, flows and losses to generators and loads with simple problem formulations (mustapha et al, 2011; khan and agnihotri, 2013). optimization methods are classified into three broad categories: the deterministic, the nondeterministic and the hybrid methods. this paper presents a review of these optimization methods that have been applied to solve the power flow tracing problems in deregulated power systems. the objective is to bring researchers up to date and suggest directions for future research works. power flow tracing techniques the typical power-pool operators are faced with the challenge of how to allocate transmission usage and what should be the criteria for charging other utilities. utilities in general consider locational signals, consistency, simplicity, accuracy and predictability, but, it is extremely difficult to accommodate all these considerations in a complex phenomenon like pft (chengaiah and jyoshna, 2013). pft techniques are mainly classified into the following (khan and agnihotri, 2013). proportional sharing principle (psp) graph theory circuit theory (z-bus tracing) optimization approach game theory relative electrical distance equilateral bilateral exchange the main differences of these methods lie with the way to treat losses, reactive power, loop flows and the arithmetic. the psp satisfies kirchhoff’s current law and assumes that the network node is a perfect ‘mixer’ of incoming flows. in this respect, the principle is fair as it treats all incoming and outgoing flows in the same way (bialek, 1997; su and liaw, 2007). this approach allocates usage to each transmission system user based on the extent of use of the system. this is determined as a function of magnitude, path and distance travelled by transacted power (khan and agnihotri, 2013). directed graphs are used in the graph theory method. the vertices of the graphs are system buses and the edges of the graphs are lines and transformers. the direction of each edge is the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):435-448. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 437 direction of power flow. the directed graphs of active power may be different from that of reactive power flow in edge directions (wu et al, 2000). graph theory is quite mature and suitable to tackle network topology related issues such as counter flows (lim et al, 2006). circuit theory method trace the power flow based on the converged alternating current power flow solution. the method uses the transmission network structures, the equivalent-current-injections and load equivalence admittances where all the electrical circuit theories are satisfied (lin et al, 2006). the method allocates line losses according to the true contributions where counter flows can be fairly treated (meng and jeyasurya, 2009). optimization techniques came about since the contributions of generators satisfy simultaneously different objectives such as the real power balance flow at each line, generator real power outputs and real power balance at each node of the system. optimization method offers accuracy in determining the generators contribution (vlachogiannis and lee, 2005). inaccurate assumptions have been made in all other previous methods, ignoring various characteristics of the generators and operating constraints of transmission lines, which have resulted in the reduction of their acceptability, accuracy and flexibility in complex and large systems (hasanpour et al, 2010). game theory provides a concept that is used when assessing the interactions of different agents in competitive markets and in the solution of conflicts that arise in that direction, such as those of electricity markets (zolezzi and rudnick, 2002). the concept of relative electrical distance (red) is based on the relative locations of load points with respect to the generator points in open access (thukaram and vyjayanthi, 2009). red overcomes the limitations of other methods because it considers network configuration which is independent of the location of the slack bus (thukaram and vyjayanthi, 2008). equivalent bilateral exchange (ebe) works on the linearized model of power system (silva and cuervo, 2008). the principle calculates agent’s use of network using a simple direct current load flow model (silva et al, 2005). ebe principle is characterised by independence from slack bus. satisfaction of kirchhoff’s laws, counter flow acceptance or rejection, location dependent rates and low temporal volatility of transmission use rates and allocation of non-zero charges to all network users (galiana et al, 2003). optimal power flow concept optimization is the process through which the best possible values of decision variables are obtained under a given set of constraints and in accordance with a selected optimization objective function (shrivastava and siddiqui, 2014). optimal power flow (opf) concept was first introduced in 1960s to solve economic dispatch problems in power systems. the concept was developed using voltage and power flow as optimization constraints (nazaran and selvi, 2014). opf optimizes specific objective function such as generation cost and total power loss by controlling power flow within an electrical network subject to a number of constraints due to system control and operational factors (frank et al, 2012; low, 2014). optimal power flow (opf) is used to efficiently allocate power in the electrical network, under various operation constraints on voltages, power flows, thermal dissipation and bus powers. due to the nonlinearity of the power flow equations, opf problems are generally non-convex which make them hard to solve, in other words, there can be no general, efficient algorithm for solving the opf (bukhsh et al, 2013). opf, like power flow analysis (pfa), determines the voltage, current and power injections in an electrical power system that is operating in its steady state. the difference between opf and pfa is that opf can have multiple solutions because it performs multiple power flow iterations (frank file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tijani, et al: a review of optimization approach to power flow tracing in a deregulated power system. azojete, 15(2):435-448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 438 et al, 2012). opf problem is generally expressed as a nonlinear, non-convex, large scale static optimization problem with both continuous and discrete variables (capitanescue et al, 2007; frank et al, 2012). different opf formulations have been developed to address specific instances of the problem using varying assumptions and selecting different objective functions, control and system constraints. energy market calculations, transmission switching, distribution network configuration, capacitor placement, expansion planning, vulnerability analysis and power system restoration are some of the subsets of power system optimization problems that include a set of power flow equations in the constraints and are all classified as a form of opf but given different names (frank et al, 2012). variables are required to represent electrical states of the system in opf formulations. the types of variables commonly used in the formulations of opf are state control variables. state variables are continuous and mostly include bus voltage magnitude, bus voltage angle and real and reactive power injections at each bus. control variables may be continuous or discrete and typically include a subset of state variables as well as variables representing control device settings such as transformer tap ratios (soliman and muntary, 2012; frank et al 2012). the general structure of opf formulations is represented using the following standard form (capitanescue et al, 2007; frank et al, 2012): min f u, x (1) subject to: g u, x = 0 (2) h u, x ≤ 0 (3) where; f(u, x) = objective function of the system’s optimization goal g(u, x) = system equality constraints h(u, x) = system inequality constraints the opf objectives commonly used are the minimization of generation costs, with or without consideration of system losses, and minimization of system total loss. other objectives include maximization of power quality and minimization of capital costs during system planning. in nearly all these cases, the objectives are functions of the system’s real and reactive power generations (frank et al, 2012). opf constraints are categorized into equality and inequality constraints. equality constraints, g(u, x), include the power flow equations and any other balance constraints. the inequality constraints, h(u, x), include the minimum and maximum limits on control and state variable such as bus voltage and line current magnitudes (lavaei and low, 2012; rao et al, 2014). classifications of optimal power flow problem solutions the first work on opf was carried out by carpentier in 1962 (lavaei et al, 2011). the increasing need for opf to solve today’s deregulated industry and the unresolved problems of the vertically integrated industry gave way to extensive studies in literatures (momoh et al, 1997; lavaei et al, 2011). evolutions of the opf since inception and their applications have been reported in literatures (pandya and joshi, 2008; amarnath and ramana, 2008; frank et al, 2012; frank et al, 2013). numerous algorithms have been proposed, developed and applied to the highly nonlinear, nonconvex large scale opf problems in power system. the algorithms are classified as deterministic http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):435-448. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 439 and non-deterministic methods (frank et al., 2012; khamees et al, 2016). deterministic methods are classical or conventional methods based on mathematical programming approach (narayana, 2017). excellent progress has been made in the deterministic methods but the methods still have the disadvantages of, among others, differentiability and linearization requirements, getting stuck at local optimum, poor convergence, weak handling of qualitative constraints, becomes too slow for large number of variables and can only find single optimized solution in a single simulation run. the deterministic methods applied also have the limitations of that include not been able to model discrete power system variables and requirements of enormous computational efforts which tend to fail as the problem increases. the non-deterministic methods, on the other hand, have the advantages of handling various qualitative constraints, find multiple optimal solutions in a single simulation run, solves multiobjective optimization problems and finds global optimum solution. the deterministic methods include the following (pandya and joshi, 2008; amarnath and ramana, 2008; lavaei and low, 2011; frank et al, 2012; frank et al, 2013): gradient method newton’s method quadratic programming method linear programming method nonlinear programming method nonlinear programming method interior point method in linear programming (lp) method, objective function as well as constraints with nonnegative variables are involved and their linearization is required which possess extra burden. gradient method uses the first order derivative vector (i.e. gradient) of the objective function of a nonlinear optimization to determine improvement in the direction for the solution in the iterate steps. gradient method has the advantage of being reliable, easy implementation, and guaranteed convergence but are slow compared to higher order methods (narayana, 2017). quadratic programming (qp) has its objective function being quadratic while the constraints are linear. qp is a special form of nonlinear programming. newton method is a second order method for an unconstrained optimization based on the application of second-order taylor series expansion about the present candidate solution (bansal, 2005). optimization problems involving nonlinear objective and/or constraints are referred to as nonlinear programming (nlp). nlp captures power system accurately, however, it involves much theoretical and computational challenges. interior point method (ipm) solves both linear and nonlinear optimization problems which constraint the search to the feasible interior region by introducing barrier terms to the objective function. ipm is the most successful deterministic optimization method (frank et al, 2012; frank et al, 2013; narayana, 2017). the non-deterministic methods are the intelligent methods which have been developed to overcome the weak global search capabilities of the traditional methods. the following are some intelligent methods used in solving opf problems (pandya and joshi, 2008; amarnath and ramana, 2008; frank et al, 2013): genetic algorithm (ga) particle swarm optimization (pso) artificial neural network (ann) evolutionary algorithms (ea) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tijani, et al: a review of optimization approach to power flow tracing in a deregulated power system. azojete, 15(2):435-448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 440 chaos optimization algorithm coa) ant colony optimization (aco) genetic algorithm (ga) is an evolutionary search algorithm which use the mechanics of natural generations. it operates on encoded binary string where each string represents a chromosome that completely describes one candidate solution to the problem (bansal, 2005). particle swarm optimization (pso) is a population based non-deterministic method based on naturally arising processes in socially organised colonies such as bird flocks and fish schools. the method exploits individual’s population to explore promising regions within the search space (bansal, 2005). artificial neural network (ann) is a computational tool based on biological neural network operations. its principle of operation is based on the principle of parallel processing analogous to the operation of human brain. ann is fast and can deal with stochastic variations of the scheduled operating point given increasing data (bansal, 2005). evolutionary algorithm (ea) include a numerous technique based on the principles of biological evolution which requires maintenance of a pool to mimic individual’s evolution inside a population. eas are efficient for problems evolving over time and solved repeatedly. chaos is a common nonlinear phenomenon whose action is a complex action similar to randomness (lu et al, 2006). coa is population based optimization method which uses chaotic maps based on ergodicity, stochastic properties and regularity of chaos. this method does not escape from local minima, unlike some optimization methods, by accepting some bad solutions according to certain probability (mohammad and roghiyeh, 2015). ant colony optimization was proposed in 1992 (rahmat and musirin, 2013). the method was inspired by the foraging behaviour of ants in their search for food. ants frequently explore the areas surrounding their nests in a random manner when searching for food and when an ant finds a source of food, it evaluates the quantity and quality of the foods and deposits pheromone in their paths (galal et al, 2013). two or more different optimization techniques can be combined into one algorithm to form hybrid method. hybrid method is the combination of two or more different techniques or two or more high strength algorithms. the aim is to use the advantages of one method to overcome the disadvantages of the other methods or taking the advantages of their high performance characteristics which lead to powerful algorithms (frank et al, 2012). hybrid algorithms have produced the best results for many practical and academic optimization problems because of the exploitations of benefits of hybrid synergies (blum et al, 2011). hybrid methods are more robust and converge more quickly to optimal solutions than their individual components operating alone. hybrid optimization techniques started gaining popularity in the last two decades in their applications to various opf problems. hybrid optimization algorithms can be formed in three different ways (blum et al, 2011): deterministic methods combined non-deterministic methods combined deterministic and non-deterministic methods combined interior point method (ipm) which is a deterministic method has been combined with newton’s method and line search which are also deterministic methods to form a hybrid optimization method by han et al, (2009). the ipm was used in the computation of direction of descent for the objective function while the newton’s method and the line search technique were used to solve various auxiliary problems. the hybrid algorithm was found to converge to a karush-kuhnhttp://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):435-448. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 441 tucker point of the opf and it maintained feasibility in each iteration. the algorithm was evaluated using several test systems and the results were promising. hybrid pso algorithm incorporating chaos was proposed as an effective and efficient optimization algorithm for numerical functions. the two separate optimization methods are both non-deterministic methods combined to form a hybrid. exploration process was performed by the pso while the exploitation process was performed by chaotic local search. the hybrid algorithm was found to have superior search quality, efficient and robust on initial conditions. it was much faster than the heuristic methods individually (liu et al, 2005; wang and lin, 2016). a non-deterministic-deterministic hybrid optimization method was developed by shengsong et al, (2002) which combined a chaos optimization algorithm and linear ipm. in this work, coa performed the global search while ipm was used for local search. the algorithm was reported to produce a more robust convergence and determined a global optimum solution compared to either algorithm separately. power flow tracing optimization problem formulation pft problems are framed as optimization problems with objective function, equality constraints and inequality constraints. the power generated by a generator is equal to the sum of the total power contributed to loads and the total loss due to that generator (chellam and kilyani, 2014). mathematically, the unified optimal tracing problem is expressed as follows: ),(min yxf (4) subject to: adx = bd (5) auy = bu (6)    lggk k ili i k ninkpxpy ,...,2,1,,...,2,10  (7)      tt x 1,...,1,10,...,0,0  (8)    ty 0....,0.0 (9) where; x = solution vector to generation tracing y = solution vector to load tracing ad = equality constraints matrices corresponding to generation tracing au = equality constraints matrices corresponding to load tracing bd =right-hand-side of equality constraints for generation tracing bu = right-hand-side of equality constraints for load tracing ng = total number of generators nl = total number of loads pli = real power at bus i pgk = real power injection by generator k xi k = real power fraction of generator k contributions towards load i yi k = real power fraction of load i contributed by generation k file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tijani, et al: a review of optimization approach to power flow tracing in a deregulated power system. azojete, 15(2):435-448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 442 (4) is the objective function derived from the power-balance equation. equation (5) and (6) represent the equality constraints for both generation and load tracing formulations. equations (7) to (9) are the inequality constraints. power flow tracing optimization deterministic optimization methods the most famous optimization approach to pft foundation was first proposed by abhyankar et al, (2005a). the paper was devoted to constraint modelling of the approach. a multi-commodity network optimization approach was used for optimal tracing of power flows to introduce a linear constrained problem known as optimal tracing problem. the formulation of the optimization problem required flow specification constraints, source and sink specification constraint and conservation of commodity flow constraints which were all modelled as equality constraints. the result was the formulation of a unified generic model for optimal pft which can be solved with and objective function to achieve fairness in transmission costs, usage or loss allocations. the optimization formulation resulted in a sparse linear programing problem. the advantage of the linear constrained optimization is that all of the degree of freedom in tracing are retained and exploited. this work forms the basis for almost all the research works as all other works only applied the theories to solve different tracing problems. only objective functions were required to be formulated while the framework provides the constraints modelling. different deterministic optimization methods have been used to solve the linear programing problems and the solutions have been applied to various power system problems. general arithmetic modelling system (gams) software was used to solve the programing problem and used to allocate loss and its cost between system loads by amoli and jadid (2008). the power flow optimization approach in this work was based on the work of abhyankar et al., (2005a). in this work, proportional tracing and optimal real power tracing methods were used for allocation of loss and its cost considering congestion in the transmission lines. power flow tracing analysis was carried out using the ieee 14 bus standard system. the result was compared with the proportional tracing method, a non-optimization method, and it was concluded that optimization method was a better method than the proportional tracing method. abhyankar et al, (2005b) proposed a tracing compliant modified postage stamp loss allocation method. this was based on their established previous work that formulated the power flow tracing as a linear constraint optimization problem. the method computes a traceable solution that minimises deviation from the postage stamp allocation of losses. the paper considered the load allocation of three different methods which are optimal tracing method, postage stamp method and network usage method by proportional tracing. a specific case of indian power system was used. the conclusion was that the tracing compliant postage optimization method achieved fairness to all users of the network. this same method was applied in the allocation of transmission fixed cost determination of the indian power system and results showed it is better than the postage stamp method (abhyankar et al., 2006). the optimization approach to power flow tracing was used in tackling circular flows which terminates the graph theoretic approach when directed graph of power flow is cyclic. this paper tackled the problem of circular flow using the optimal power flow tracing approach developed by abhyankar et al, (2005a). it was shown that optimization method converged to a solution even in the presence of circular flows due to the constraint modelling in the optimization method (abhyankar et al,2006). a min-max algorithm which equalises allocations within constrained space and reaching equilibrium where it cannot be achieved in other methods was http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):435-448. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 443 used to achieve fairness in fixed cost allocations. the method corresponded to solving a sequence of sparse linear programing problems for real power tracing (abhyankar et al, 2007; rao et al, 2010). non-deterministic optimization methods various non-deterministic optimization methods have also been applied to power flow tracing problems. a genetic algorithm for the determination of generator contribution to transmission systems was used by mustapha and sulaiman (2010) and naresh et al, (2010). by treating voltage contribution as an optimization problem, the transmission usage allocation problem was traced by tracing the voltage contribution for the individual generator at each bus. in these papers, genetic algorithm (ga) is used to rework the power flow tracing using the approach of the traditional tracing. the genetic algorithm (ga) was used to compute an optimized result of voltage contribution to allocate power flow and loss in the power system. the formulation of pft equations were based on the formation of branch impedance matrix and adjacency matrix in the mw-km and mva-km methods. transmission cost allocation using ga was compared with the traditional mva-km tracing method. it was shown that ga performed better than other methods; ga distributed the power flow effectively and minimises the net system transmission costs and losses. evolutionary programing and evolutionary algorithms were employed for the generator and load tracing in deregulated the power system (hamid et al, 2011a; hamid et al, 2011b). the power flow tracing equations were solved using the evolutionary programming approaches were the optimal power flow tracing equation developed by abhyankar et al., (2005) which are equations (4) – (9) above. the results of the stochastic optimization method were recorded to be better alternatives to traditional tracing methods due to problems of matrix inversion which can lead to an indefinite and undefined solution in the conventional problem. it was concluded that artificial intelligence based tracing solutions are fair and non-discriminatory with tolerable computation time and simplicity in computation. flower pollination algorithm (fpa) for real power generation tracing in a deregulated system was carried out by kerta at al, (2015). the formulations were based on the objectives and constraints developed by abhyankar et al, (2005a). fpa gave satisfactory results compared to traditional methods. the method is free from matrix inversion and independent of matrix singularity. it has fast computational time and is simple. basha and anitha (2016) used the firefly algorithm (ffa) for power flow tracing based congestion management in a deregulated electricity market. non-deterministic optimization methods have the major disadvantage of premature convergence and been trapped at the local minimum. hybrid optimization methods many hybrid optimization methods have been employed in power flow tracing. vlachogianis and lee (2005) used the vector evaluation particle swarm optimization (vepso) algorithm for the determination of generators contribution to a transmission system. power flow tracing was formulated as a multi-objective optimization problem that combined the nonlinear characteristics of power system which include thermal limits of transmission lines and prohibited operating zones of generators. the multi-objective function has three objectives which are equal total contribution of generators to each transmission line; satisfactory real power balance between all generators contributions and the local generation and demand at each node; total contribution of a generator injected into the transmission system must be equal to the generator real power output minus local demand. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tijani, et al: a review of optimization approach to power flow tracing in a deregulated power system. azojete, 15(2):435-448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: muhammedtijani@gmail.com 444 genetic algorithm (ga) was incorporated into least square support vector machine (ls-svm) has been used to determine the shares of generators to loads and lines mustafa et al, 2011). a circuit theory based superposition method was adopted in this work as a tracing, validating and testing process. the ga is used to find the optimal values of hyper-parameters of ls-svm which adopts a supervised learning approach to train the ls-svm model. the result showed the advantage of ga-svm in better computational time. blended crossover continuous ant colony optimization (bx-caco) with simple and easy formulation steps has been used for load tracing (hamid et al, 2012a; hamid et al, 2012b; hamid and musirin, 2014). a hybrid mean calculated during solution update process is introduced in the aco and crossover operation of ga was adopted. the formulations were based on the objectives and constraints developed by abhyankar et al, (2005a). the method produced a wide variety of solution to prevent premature convergence problem in the original aco. mutation operation of ga was also introduced into particle swarm optimization (pso) to solve power flow tracing problem (chellam and kalyani, 2014) to prevent pre-mature convergence in pso. conclusion power flow tracing is an important power system analysis in this era of power system deregulation. pft provides the best way of addressing loss and cost allocation problems. this paper has briefly reviewed the best method of pft. this work showed all the methods applied to power flow tracing problems which are deterministic, non-deterministic and hybrid methods. the hybrid methods combined the advantages of both the deterministic and stochastic methods to form the best optimization method. it was observed that so much works has been carried out using deterministic, non-deterministic and hybrid methods to solve pft problems. it was also observed that no known work has been reportedly published to solve pft problem using hybrid deterministic-non-deterministic optimization method. research works are therefore encouraged to explore the advantages of a hybrid optimization approach to pft especially methods that will combine deterministic and non-deterministic optimization approaches. references abhyankar, ar., soman, sa. and khaparde, sa. 2005a. real power tracing: an optimization approach. international journal of emerging electric power systems, 3(2): 1 – 30. abhyankar, ar., soman, sa. and khaparde, sa. 2005b. new paradigm of tracing algorithm: application to fair loss allocation in indian system. proceedings of the international conference on future power system, amsterdam, netherland, 16 – 18 november, 2005: 1 – 30. abhyankar, ar., soman, sa. and khaparde, sa. 2006. optimization approach to real power tracing: an application to transmission fixed cost allocation. ieee transactions on power systems, 21(3): 1350 – 1361. abhyankar, ar., soman, sa. and khaparde, sa. 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(2016): 1 – 10. wu, ff., ni, y. and wei, p. 2000. power transfer allocation for open access using graph theory – fundamentals and applications in systems without loopflow. ieee transactions on power systems, 15(3): 923 – 929. zolezzi, jm. and rudnick, h. 2002. transmission cost allocation by cooperative game and coalition formation. ieee transactions on power systems, 17(4): 1008-1015 http://www.azojete.com.ng original research article a review of optimization approach to power flow tr arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):17-24 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 17 original research article moisture-dependent thermal properties of cocoyam cormels b. o. oyefeso¹* and a. o. raji (1department of agricultural and environmental engineering, university of ibadan, ibadan, nigeria.) *corresponding author: oyefesobabatunde@gmail.com article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: cocoyam cormels thermal conductivity thermal diffusivity specific heat moisture content abstract cocoyam (xanthosoma sagittifolium) has served as a cheap carbohydrate source for many people in the developing countries with prospects in the production of animal feed, lager beer, and its starch as binding agent in drug formulation. drying is an important unit operation in cocoyam processing and there appears to be lack of information on the thermal properties which are significant in designing heat treatment systems such as dryers for the cormels. this study therefore, investigated some thermal properties of x. sagittifolium cormels as affected by moisture content. thermal properties namely thermal conductivity, diffusivity and specific heat of whiteand pink-fleshed cocoyam cormels were investigated at moisture contents within the ranges of 130 to 395% and 85 to 200% (dry basis), respectively. the selected thermal properties of the cormels were determined with the aid of a thermal properties analyser which has a dual needle probe and uses transient line heat source method. thermal conductivity, diffusivity and specific heat were within the ranges of 0.454 to 0.562 wm-1k-1, 1.62×10-7 to 2.32×10-7 m2s-1, 1.836to 4.029 kjkg-1k-1, respectively for white-fleshed cocoyam and 0.489 to 0.601 wm-1k-1, 1.79×10-7 to 2.65×10-7 m2s-1, 1.615 to 2.991 kjkg-1k-1, respectively for pink-fleshed cormels. analysis of variance showed that there were significant differences between the measured properties at different moisture content levels. regression models were established between the investigated thermal properties and moisture content. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction cocoyam, xanthosoma sagittifolium, is cultivated for various applications. it ranks third in importance after cassava and yam although it is superior to them in terms of the nutritional value (onyeka, 2014). the cormel has a lot of potentials which include its utilization for production of lager beer (onwuka and eneh, 1998)), as binding agents in paracetamol tablet formulation (odeku et al., 2005) and as carbohydrate source of juvenile african catfish (aderolu et al., 2009). itis also used traditionally as soup thickeners (enwere, 1998). it is processed before consumption and used essentially in the same way as yam (odebunmi et al., 2007). it undergoes several heat treatment processes such as boiling (cooking), drying, frying, smoking and refrigeration to produce its various end products such as chips, flakes, flour and fufu. the knowledge of its thermal properties, such as thermal conductivity, thermal diffusivity and specific heat, is necessary in designing heat treatment systems for processing of the cormels; mailto:oyefesobabatunde@gmail.com http://www.azojete.com.ng oyefeso and raji: moisture-dependent thermal properties of cocoyam cormels. azojete, 15(1):17-24. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 18 to foster a sound understanding of the behaviour of the crop when exposed to heat treatments such as cooling, drying, freezing, frying and smoking (yang et al., 2002); in modelling of heat transfer and temperature distribution during processing (zhu et al., 2007); in the simulation of heat treatment processes involved in the conversion of cocoyam cormels into cocoyam flour which is one of its important final products. thermal conductivity, thermal diffusivity and specific heat have been determined for cassava root, yam tuber and plantain fruit (njie et al., 1998), cumin seed (singh and goswami, 2000), shea nut kernel (aviara and haque, 2001), borage seeds (yang et al., 2002), berberis fruit (aghbashlo et al., 2008), guna seed (aviara et al., 2008), roselle seeds (bamgboye and adejumo, 2010) and doum palm fruit (aremu and fadele, 2010). however, there appears to be scarcity of information on the thermal properties of cocoyam. the objectives of this study include the determination of thermal conductivity, thermal diffusivity and specific heat of whiteand pink-fleshed cocoyam (xanthosoma sagittifolium (l.) schott) cormels and the investigation of the effect of moisture content on the selected thermal properties. 2. materials and methods fresh whiteand pink-fleshed cormels were obtained from ogunmakin market near ibadan city, ogunmakin town, ogun state, south western nigeria. fresh agricultural products are usually brought in large quantities to the market from neighbouring farms. the cormels were cleaned, peeled manually and cut into the cylindrical shape of 22 mm diameter and 33 mm height with the aid of a cylindrical borer for uniformity and reduce the probable effect of variation in shape and size. the dimensions of the samples were similar to that of a standard verification block provided with the equipment used in determining the thermal properties. the initial average moisture content of the cocoyam cormels was determined by the air oven method as described by aghbashlo et al. (2008). this involved keeping cocoyam sample of known weight in an oven maintained at a temperature of 105±2°c until the differences between three consecutive weights were within 0.05g. the quantities of moisture removed from the samples were obtained and the moisture contents obtained according to equations 1 and 2. mcwb = mw mwp × 100 (1) mcdb = mcwb 100−mcwb × 100 (2) where: mcdb = % moisture content (dry basis) mcwb = % moisture content (wet basis) mw = mass of moisture removed from the cormel (kg) mdp = mass of fresh cocoyam cormel (kg) the thermal properties of white-fleshed cocoyam cormels were investigated at 130, 180, 250, 320 and 395% average moisture content levels (db) and pink-fleshed cocoyam cormels at 85, 105, 125, 150 and 200% average moisture content levels (db). the desired moisture contents were obtained by conditioning the samples as described by olaniyan and oje (2002). selected thermal properties of the cocoyam cormels namely thermal conductivity, thermal diffusivity and specific heat, were determined with the aid of kd2 pro thermal properties analyser (decagon devices inc., usa) which has a dual needle probe and uses the transient line heat source method in its operation. one of the needles has a heater while the second one has a temperature sensor. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):17-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 19 the dual needles (30mm long, 1.3 mm in diameter and spaced at 6mm apart) were inserted into the cocoyam sample. pilot holes were made near the centre of the sample to ensure that the needles have correct spacing. the needles were allowed to equilibrate to the surrounding before beginning a reading and good thermal contact was ensured between the sensors and the cocoyam sample by fitting the sample tightly into the hole to ensure accurate measurements. after inserting the needles into the cocoyam sample, both the needles and sample were allowed to attain temperature equilibrium before starting the measurements. current was passed through the needle with a heater and the heat was applied for a minute and 30 seconds were allowed for temperature equilibration before heating starts. sixty temperature readings were taken at 15 seconds intervals. analysis of the probe temperature was used to determine the thermal conductivity of the cocoyam samples (njie et al., 1998) while the volumetric specific heat was obtained from an algorithm developed based on relationships established between thermal conductivity and specific heat. thermal diffusivity was determined according to equation 3. the measured thermal conductivity, diffusivity and specific heat were read directly from the menu display and properly documented for further analysis. the measurements were taken by allowing 15 minutes interval between readings to allow the temperatures to re-equilibrate. all the measurements were carried out in triplicates and the average values were recorded. the experimental set up for thermal properties measurement was as presented in figure 1. μ = k ρcp (3) where: μ = thermal diffusivity m2s−1 k = thermal conductivity wm−1k−1 ρ = density of cormel (kgm−3) cp = specific heat (kjkg−1k−1) analysis of variance (anova) was carried out to determine the effect of moisture content on the measured thermal properties. figure 1: experimental set up for thermal properties measurement menu display needle probe dual needle probe cocoyam sample file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyefeso and raji: moisture-dependent thermal properties of cocoyam cormels. azojete, 15(1):17-24. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 20 3. results and discussion the thermal conductivity, specific heat and thermal diffusivity of the whiteand pink-fleshed cocoyam cormels are as presented in figures 2 to 4. figure 2: thermal conductivity of cocoyam cormels figure 3: specific heat of cocoyam cormels http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):17-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 21 figure 4: thermal diffusivity of cocoyam cormels thermal conductivities of white-f and pink-fleshed cocoyam cormels increased with increasing moisture content (figure 2). a similar trend has been reported for potato (donsi et al., 1996) and cassava root and yam tuber (njie et al., 1998).the thermal conductivity of the white-fleshed cormels were within the ranges of 0.454 to 0.562 wm-1k-1 while that of the pink-fleshed cormels were within the ranges of 0.489 to 0.601 wm-1k-1 for the range of moisture content considered. the relationships between the thermal conductivity of the cormels and moisture content could be represented by equations 4 and 5. white: k = 0.0003m + 0.4762 (r² = 0.886) (4) pink: k = -1e-06m2 + 0.0009m + 0.395 (r² = 0.923) (5) the increase in thermal conductivity with increasing moisture content could be attributed to the high thermal conductivity of water in the cormel which made it possible for heat energy to be easily conducted through its tissues. this implies that low heat energy input will be required to uniformly distribute heat (as in drying) through the cocoyam cormels at high moisture content (taiwo et al., 1996; cansee et al., 2008). similar trends were observed for shea nut kernel (aviara and haque, 2001) and borage seeds (yang et al., 2002). the relationships between specific heat and thermal diffusivity of white-f and pink-fleshed cocoyam cormels and moisture content could be represented by equations 6 to 9. pink: cp = 3e-06m3 0.0015m2 + 0.1977m 5.999 (r² = 0.771) (6) white: cp = 2e-07m3 0.0002m2 + 0.0432m 0.4359 (r² = 0.670) (7) white: µ = -3e-06m3 + 0.0013m2 0.1806m + 9.7461 (r² = 0.943) (8) pink: µ = -1.35e-07m3 + 1.02e-04m2 2.23e-02m + 3.32e+00 (r² = 0.953) (9) the relationships were non-linear and sinusoidal in nature since the specific heat and thermal diffusivity increased and decreased within the range of moisture content considered for both varieties. this sinusoidal variation in specific heat and thermal diffusivity of the white-fleshed and pink-fleshed cocoyam could be attributed to the non-homogeneous nature of the cormel as a bio-material and structural arrangement of its tissues (aremu and fadele, 2010). similar sinusoidal trend was observed for the thermal diffusivity of doum palm fruit (aremu and fadele, 2010) while a linear decreasing trend was observed for whole guna seed and kernel (aviara et al., file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyefeso and raji: moisture-dependent thermal properties of cocoyam cormels. azojete, 15(1):17-24. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 22 2008). taiwo et al., (1996) observed an increase in specific heat of ground and hydrated cowpea up to a point followed by a decrease with subsequent increase in moisture content while only a linear decreasing trend was observed for roselle seed (bamgboye and adejumo, 2010).the specific heat and thermal diffusivity of the white-fleshed cormels were found to be within the ranges of 1.836 to 4.029 kjkg-1k-1 and 1.62  10-7 to 2.32  10-7m2s-1, respectively while those of the pink-fleshed cormels were within the ranges of 1.615 to 2.991 kjkg-1k-1 and 1.79  10-7 to 2.65 10-7m2s-1, respectively. the thermal conductivity and specific heat of the cormels compared well with the range of values obtained for other agricultural materials such as doum palm fruit, berberis fruit, plantain, cassava root and yam tuber (aremu and fadele, 2010; aghbashlo et al., 2008; njie et al., 1998). the anova results of the effect of moisture content on the selected thermal properties are as presented in tables 1 and 2. the statistical analysis showed that the effect of variation in moisture content was significant (p<0.05) on all the measured thermal properties. this clearly indicated that the response of the cocoyam cormels as biological materials to heat treatments is dependent on the amount of moisture present in the cormels. this could serve as a guide in determining the amount of energy required to properly condition cocoyam cormels at a given moisture content during heat treatments and in storage. therefore, knowledge of thermal properties investigated with respect to moisture content is applicable in the optimization of thermal processing systems and serve as an essential guide in the design of heat treatment equipment such as a dryer for cocoyam cormels. table 1: effect of moisture content on thermal properties of white-fleshed cocoyam cormels source model sum of squares degree of freedom (df) mean square fvalue level of significance thermal conductivity regression 0.002 1 0.002 10.014 0.051 residual 0.001 3 0.000 total 0.002 4 thermal diffusivity regression 0.000 1 0.000 6.360 0.086 residual 0.000 3 0.000 total 0.000 4 specific heat regression 0.173 1 0.173 0.829 0.430 residual 0.627 3 0.209 total 0.800 4 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):17-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 23 table 2: effect of moisture content on thermal properties of pink-fleshed cocoyam cormels source model sum of squares degree of freedom (df) mean square fvalue level of significance thermal conductivity regression 0.000 1 0.000 7.737 0.069 residual 0.000 3 0.000 total 0.001 4 thermal diffusivity regression 0.000 1 0.000 1.551 0.301 residual 0.000 3 0.000 total 0.000 4 specific heat regression 0.317 1 0.317 5.910 0.093 residual 0.161 3 0.054 total 0.478 4 4. conclusions thermal properties of whiteand pink-fleshed cocoyam (x. sagittifolium) cormels were examined in the study. the results showed that: thermal conductivity of the cormels increased with increasing moisture content and the values were within the ranges of 0.454 to 0.562 wm-1k-1 and 0.489 to 0.601 wm-1k-1, for whiteand pink-fleshed cormels respectively; thermal diffusivity of white-f and pink-fleshed cormels were within the ranges of 1.62×10-7 to 2.32×10-7 m2s-1 and 1.79×10-7 to 2.65×10-7 m2s-1, respectively; specific heat of white-f and pink-fleshed cormels were within the ranges of1.836 to 4.029 kjkg1k-1 and 1.615 to 2.991 kjkg-1k-1, respectively; all the investigated properties were dependent on the level of moisture present in the cormel. data on the thermal properties investigated with respect to variation in moisture content is applicable in the optimization of thermal processing systems and as an essential guide in the design of heat treatment equipment for cocoyam cormels. references aderolu, az. 2009. processed cocoyam tuber as carbohydrate source in the diet of juvenile african catfish (clarias gariepinus). european journal of scientific research, 35(3): 453-460. aghbashlo, m., kianmehr, mh., hassan-beygi, sr. 2008. specific heat and thermal conductivity of berberis fruit (berberis vulgaris). american journal of agricultural and biological sciences, 3(1): 330-336. aremu, ak. and fadele, ok. 2010. moisture dependent thermal properties of doum palm fruit (hyphaene thebaica). journal of emerging trends in engineering and applied sciences (jeteas), 1(2): 199-204. aviara, na. and haque, ma. 2001. moisture dependence of thermal properties of sheanut kernel. journal of food engineering, 47: 109-113. aviara, na., haque, ma. and ogunjimi, lao. 2008. thermal properties of guna seed. international agrophysics, 22: 291-297. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyefeso and raji: moisture-dependent thermal properties of cocoyam cormels. azojete, 15(1):17-24. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 24 bamgboye, ai. and adejumo, oi. 2010. thermal properties of roselle seeds. international agrophysics, 24: 85-87. cansee, s., watyotha, c., thivavarnvongs, t., uriyapongson, j. and varith, j. 2008. effect of temperature and concentration on thermal properties of cassava starch solutions. songklanakarin journal of science and technology, 30(3): 405 411. donsi, g., ferrari, g and nigro, r. 1996. experimental determination of thermal conductivity of apple and potato at different moisture contents. journal of food engineering, 30: 263-268. enwere, jn. 1998. foods of plant origin. afro-orbis publications, nsukka, nigeria. 64-124. njie, dn., rumsey, tr. and singh, rp. 1998. thermal properties of cassava, yam and plantain. journal of food engineering, 37(1): 63-76. odebunmi, eo., oluwaniyi, oo., sanda, am. and kolade, bo. 2007. nutritional compositions of selected tubers and root crops used in nigerian food preparations. international journal of chemistry, 17(1): 37-43. odeku, oa., awe, oo., popoola, b., odeniyi, ma. and itiola, oa. 2005. compression and mechanical properties of tablet formulations containing corn, sweet potato, and cocoyam starches as binders. pharmaceutical technology, 29(4): 82-90. onwuka, no. and eneh, oc. 1998. the potentials of cocoyam (colocasia) in stout beer brewing. journal of science and technology, 4: 78-80. onyeka, j. 2014. status of cocoyam (colocasia esculenta and xanthosoma spp) in west and central africa: production, household importance and the threat from leaf blight, lima (peru). cgiar program on roots, tubers and bananas (rtb). www.rtb.cgiar.org singh, kk. and goswami, tk. 2000. thermal properties of cumin seed. journal of food engineering, 45:181-187. taiwo, ka., akanbi, ct. and ajibola,oo. 1996 thermal properties of ground and hydrated cowpea. journal of food engineering 29: 249-256 yang, w., sokhansanj, s., tang, j. and winter, p. 2002. determination of thermal conductivity, specific heat and thermal diffusivity of borage seeds. biosystems engineering, 82(2): 169–176. zhu, s., ramaswamy, hs., marcotte, m., chen, c., shao, y. and le bail, a. 2007. evaluation of thermal properties of food materials at high pressures using a dual-needle line-heat-source method. journal of food science, 72: 49–56. http://www.rtb.cgiar.org http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):351-362 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 352 original research article geological setting and solid mineral potentials of southern borno, northeastern nigeria s. baba, b. shettima and h.i. kamale* (department of geology, faculty of science, university of maiduguri, p.m.b 1069 borno state nigeria) *corresponding author’s email address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 1.0 introduction the southern part of borno state is located within longitudes 11º 40' 00"e and 14º 20' 00"e and latitudes 10º 15' 00"n and 10º20' 05"n in northeastern nigeria. it politically comprises of 8 local governments areas of askira-uba, biu, chibok, damboa, gwoza, hawul, kwaya-kusar and shani (figure 1). geographically, the area falls within the sudan savannah characterized by short shrubs and few scattered trees, with short wet-season (june-september) and long dry season (october-may). topographically it is characterized by rugged terrain provided by the mandara (pulka-gwoza-chibok) mountains and the biu plateau (figure 2). the geology of southern borno is typified by vast occurrence of precambrian basement complex rocks in its eastern region, whereas the western flank of the area is underlain by the tertiary-quaternary basaltic rock of the biu plateau. sedimentary rock of albian-tertiary age underlies the extreme western region and locally associated with volcanic intrusions. a number of solid mineral resources, particularly industrial/non-metallic types (examples are feldspars, quartz, clays, dimension stones) and gem quality stones have been identified in the area. good quality feldspar with high triclinicity (δ) value (baba et al., 1991) has been mined from liga pegmatites in gwoza area since 1985 for ceramic production while gem-quality stones, including tourmaline, garnet and topaz have also been identified and mined from gunda area of biu plateau in the 1990s (baba, 2005). this work intends to re-evaluate the geological setting of the area with the aim of further differentiating the rock types in more detail as well and their structural framework and their implications in possible mineralization processes. it also intends to re-examine the solid mineral resources potentials of the different rock types in the area with the aim of harnessing the exploration targets for possible exploitation. article information abstract this research work has principally succeeded in updating the geological map of southern borno and brought out zeolite as one of the prominent solid minerals to work on. the field mapping of the area constituting of askira uba, bayo, biu, chibok, damboa, gwoza, hawul, kwaya kusar, and shani local government areas indicate the occurrence of basement and sedimentary rocks. the crystalline rocks comprises of migmatites, gneisses, granites and basaltic rocks, dominantly occurring in gwoza, askira uba, chibok, biu and hawul, whereas the sedimentary formations cover kwaya kusar, shani, bayo and damboa with outcrops of cretaceous-quaternary sediments comprising bima formation, gongila formation, fika shales, gombe sandstone, kerri kerri formation and chad formation. mineralogical evaluation of the basement complex rocks indicate the occurrences of feldspars, quartz, micas and ornamental stones, with the basalts chiefly hosting zeolite and quality gemstones (aquamarine, corundum, amethyst, tourmaline and topaz). the zeolites are typical of chabazite variety mostly developing from feldspathoid associated with mafic igneous/basic volcanic rocks. the cretaceous-quaternary sediments present quality clays, kaolinite, diatomite, trona and bentonite industrial minerals. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14oct., 2019 revised 07march, 2020 accepted 10march, 2020 keywords: zeolite gemstones solid minerals southern borno nigeria mailto:ishakukamale@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 351-362. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 353 figure 1: political map of southern borno figure 2: topographic map of southern borno file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):351-362. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 354 2. materials and methods 2.1 geological mapping the southern part of borno was mapped on a scale of 1:50,000 using topographic map as base map. a total area of about 24,150 km2 was covered using traverse compass mapping technique. representative rock samples were chipped, described on the spot as hand specimen. samples were then labelled, the locations noted and plotted on the base map with the aid of the gps which gives exact coordinates of sample points in terms of latitudes and longitudes. the megascopic features and characteristic field relationships of the formations, structural elements as well as possible mode of occurrence of the various rocks and formations in the areas were measured, described and recorded. 2.2 thin section preparation rock and mineral samples collected from the field were taken to petrology and mineralogy laboratory of geology department, university of maiduguri and were thin sectioned following the procedure outline by kerr (1977) which involves cutting a thin slice from the rock samples using cutting machines. the slices were polished with abrasive powder until a required thickness of 0.03mm was attained. the polished surfaces of the slices were then mounted on the glass slides using araldite. the glass slides with the mounts were placed on the hot plate and heated for 10 minutes. the samples were removed from the hot plate and allowed to cool. the slides were once more polished to standard thickness of 0.03mm using abrasive powder of various grades on glass laps. canada balsam drops were smeared on the glass slides while on the hot plate and very thin glass covers were placed on the finished polished surfaces in which gentle pressure were applied to remove trapped air bubbles as well as excess canada balsam. the slides were allowed to cool, hardened while the overflow of the balsam was washed off using organic solvent. the slides were then properly labelled and subjected to petrographic studies using petrological polarizing microscope. 3. results and discussion 3.1 geological setting field mapping reveals that southern borno is underlain by basement complex rocks, cretaceous sediments and tertiary-quaternary volcanics (figure 3). figure 3: geological map of southern borno (inset-map of nigeria showing the location map) 3.1.1 the basement complex rocks: the basement complex rocks constitute about 60% and outcrop dominantly in the eastern part of the study area particularly in pulka, gwoza, hambagda, limankara and chibok areas. the basement complex rocks are precambrian in age the evolution of which has been attributed to four major orogenic episodes in nigeria (baba, 2005); the liberian (2800±200 ma), the eburnean (2000±200 ma), the kibaran (1100±200 ma) and the pan-african (600±150 ma). the whole of africa was affected by the liberian and eburnean episodes but the kibaran and http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 351-362. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 355 pan-african are not pronounced in some areas on the continent. in nigeria, the kibaran activity, which was largely sedimentation and volcanism with subsequent metamorphism producing lowgrade, n-s trending, gold bearing metasedimentary schist belts, was restricted to the western half of the country west of longitude 8o e (baba, 2005). the pan-african orogeny engulfed the whole of nigeria making it fall fully within the pan-african mobile belt. rocks resulting from the liberian and eburnean episodes are represented by migmatite-gneiss complex (mgc). these rocks are generally low-lying, highly deformed, petrologically confusing and structurally gost-looking units. in southern borno the mgc outcrops at the margins of the prominent mandara mountains in pulka-gwoza areas as well as hambagda apparently enveloping the mountain range. the pan-african orogeny on the other hand is the most extensive and widespread episode in africa which has largely obliterated the footprints of the older episodes. it resulted in the emplacement of large volume of granitic plutons which are now generally referred to as “older granites” to distinguish it from the high-level jurassic granites of central nigeria which is called “younger granites” (falconer, 1911). recently however, the term “pan-african granitoids” is preferred by modern nigerian geologists. the pan-african granitoids in southern borno vary in texture but are mineralogically similar except a few subordinate basic variants. the dominant variants include coarse porphyritic biotite granites (pink-feldspar and white-feldspar sub-variants), coarse grained granite, medium grained granites and fine grained granites with subordinate but genetically important pegmatites, aplites and dolerites. fracturing and felsic veins (including the aplite) chacterize the closure of the pan-african activity in nigeria (islam et al.,1989). the cretaceous sediments the sediments in southern borno are part of the cretaceous-recent sediments in the nigerian sector of the chad basin. general sequence of the sediments include; bima formation, gongila formation, fika shales, gombe sandstones, kerri-kerri formation and chad formation (fig. 3). the aptian-albian bima sandstone, encompasses the northern, western and extreme south western parts of the area, a continental formation represents the oldest sedimentary succession in the entire northeast, which rests directly and unconformably on the precambrian crystalline basement rocks and consists of three siliclastic members: the lower bima (b1), middle bima (b2), and upper bima (b3) (carter et al., 1963; guiraud, 1990, 1991)). the formation generally consists of massively bedded, sparsely fossiliferous, poorly sorted, mediumcoarse grained arenaceous feldspathic sandstone. it is mainly composed of sandstones, although the occurrence of shale intercalations has been reported (carter et al., 1963, avbovbo et al., 1986). the lithology is diverse, indicating accumulation under widely varying conditions, including fluviatile, deltaic and lacustrine depositional environments (carter et al., 1963; allix, 1983; guiraud, 1990). the lower bima sandstone is the oldest unit and was interpreted as a proto-rift and syn-rift succession (guiraud, 1990), which is a thick continental deposits being the infillings of semiisolated grabens, with a variable thickness ranging from 0 to greater than 1500m. the sediments consist of poorly sorted, angular arkoses, granulestones, pebbles and boulder conglomerates. fresh fragments of acidic rocks are common. red to mottled colours are characteristic suggesting pedo-genetic features, and intercalations of volcanic rocks indicate contemporaneous volcanic activity (popoff, 1988). the thickness of the middle bima sandstone ranges from 100-150m, consisting of gravelly to coarse-grained feldspathic sandstone dominated by large-scale trough and tabular cross bedding and clays. palaeosols may occur at the top of this unit. guiraud (1990, 1991.) reported fossil wood to which late albian age was assigned. the upper bima sandstone is fairly homogeneous and relatively mature fine to coarse-grained sandstone with pebbly beds and rare bands of calcareous sandstones characterized by tabular cross-bedding. convulate bedding and overturned cross-bedding are common. its thickness ranges from 500-1500m. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):351-362. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 356 the gongila formation with outcrops restricted to the western half of the study area, overlies the bima sandstone which was deposited in shallow paralic environment hence regarded as transitional between the underlying continental bima and full marine fika shale above. it consists of basal limestone and interbeds of shale and sandstone giving a thickness of 1500m (hamza et al., 2002). the limestone is rich in ammonites and mollusc, these assemblages indicates early turonian age (carter et al., 1963). the fika shale with occurrences in western part of the study area around balbaya (fig. 3) conformably overlies the gongila formation and it consists of a sequence of blue-black, gypsiferous and ammonite-rich shales with occasional thin limestone beds. it has a thickness of 1190m (hamza et al., 2002). fish, ostracod and reptile remains have been reported which supports turonian-santonian age (carter et al., 1963; kachroo et al., 2000). the gombe sandstone comformably overlies the fika shale with occurrences in the northern portion of the study area notably around damboa and balagala areas. it consists of sandstones, siltstones, mudstones and ironstones. it has amaximum thickness of 310m and it is of maastritchian age (zaborski et al., 1997). the kerri-kerri formation was observed to occupy the northern part of the study area, a purely continental deposit, comprises of grits and sandstones having well-developed crossbedding structures suggesting deltaic environment. it is distinctly characterized by reddish and often capped by oolitic lateritic horizon. based on field and palynological studies, a paleocene age was assigned to it with thickness of 320m (dike, 1993). the chad formation outcrops in the extreme northern part of the mapped area and is made up of blue-grey, fine to coarse-grained sand, with intercalation of sandy clay, clay, grits, gravel and diatomite. it is lacustrine and fluviatile in origin. based on some vertebrates’ jaw bones and diatoms the formation is pliocene-pleistocene in age (barber and jones, 1960). 3.1.3 the volcanics there are two areas of volcanic occurrence in southern borno, the biu plateau and the kirawaareas.biu area was subjected to two volcanic eruptions, the pliocene (5-3 ma) and the quaternary (< 1.4 ma) (grant and freeth, 1972). these eruptions are represented by two compositionally similar but structurally different volcanic rocks, the “biu type basalts and the miringa-type basalts” together forming the spectacular biu-plateau. biu plateau is the largest area of volcanic rocks in nigeria covering an area of about 500 km2 (carter et al., 1963) with an average elevation of 700m. the biu basalts belong to the early eruption and from field evidence, it is believed to have resulted from fissure (gentle) eruption now represented by extensive massive lava flows covering the entire southern part of the plateau. the later eruption (miringa-type) is associated with violent eruption (vent-type) as evident by the occurrence of pyroclastic materials such as volcanic bombs, pumice, welded tuff etc. around volcanic cones. the two ages of pliocene and quaternary given by grant and freeth (1972) were further collaborated by the mineralogical work of islam (1986) where the olivine phenocrysts in the biu-type basalts were found to be usually altered, commonly to iddingsite, while those in the miringa-types were relatively fresh. the biu-type basalts areessentially “alkali olivine basalts” while the miringa-type are mainly “basanites”. kirawa volcanics are also tertiary in age and form part of the cameroon-line in the northeastern part of the study area. they are compositionally acidic as opposed to the basic nature of the biu-plateau volcanic. okeke (1991) identified two variants of kirawa volcanic as “commendites” and pentellerites”. the pentellerites are homogenous rhyolitic lavas while the commendites are tufaceous. from petrological point of view the commendites are younger as field evidence has shown them to contain xenoliths of the pentellerites. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 351-362. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 357 3.2 petrography as stated above, southern borno is underlain by precambrian basement complex rocks, cretaceous sediments and tertiary-quaternary volcanics. because of the preliminary nature of this report, only the detail petrography of the basalts is presented. generally, the basalts consist of plagioclase feldspars, augite, olivines, nepheline, zeolite and opaque minerals. the plagioclases occur both as phenocrysts and as groundmass. the phenocrysts are colourless and subhedral in form with low relief and weak birefringence. they shows white to gray interference colour of first order and exhibit a combined albite and carlsbad twinning (figure 4) though some crystals show only albite twinning (figure 5). the crystals have perfect cleavage in two directions perpendicular to one another. augite occurs as pale green crystals having prismatic form of short dimensions. it has high relief and strong birefringence with pale green to greenish interference colour of the second order. it shows perfect cleavages in two directions normal to one another. olivine occurs as large phenocrysts, yellowish in colour and euhedral in form. some crystals occur both as subhedral and anhedral with high relief and strong birefringence. it shows pale blue to deep blue upper second order interfence colours. it is characterized by numerous irregular but characteristic y-shaped fractures (figure 6) and exhibits parallel extinction with evidence of alteration in most crystals. the nepheline is turbid white coloured and short prismatic form. it has perfect cleavage in two directions with low relief and weak birefringence which exhibits grey of first order interference colour. it shows symmetrical extinction and occurs as small phenocrysts with rows of inclusions in some crystals while some constitute the groundmass. zeolite occurs as colourless and tabular in form having imperfect cleavages in two directions. relief is low and birefringence is weak and shows gray to white first order interference colours (figure 7). the mineral appears to fill empty cavities in the rock indicating that it is secondary material and the variety is recognized as chabazite variety. pyroxenes occur dominantly in the groundmass where, at places, they cluster together forming a unique concentration (figure 8). figure 4: photomicrograph of basalt showing phenocryst of plagioclase feldspar exhiting both carlsbad and albite twinning plg file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):351-362. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 358 figure 5: photomicrograph of basalt showing plagioclase phenocryst in groundmass of olivine, augite, plagioclase and nepheline figure 6: photomicrograph of basalt showing phenocryst of olivine plg olv http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 351-362. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 359 figure 7: photomicrograph of zeolite filling empty cavity of basalt figure 8: photomicrograph of basalt showing pyroxene concentration (prx conc.) in a groundmass of olivine, augite and plagioclase 3.3 mineralization the various geological components of southern borno are individually characterized by different types of solid mineral potentials. the basement complex rocks are known to harbour some industrial minerals such as feldspars, clays and ornamental stones among others. the zeo prx conc. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):351-362. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 360 cretaceous sediments on the other hand also host good quality clays, kaolin, diatomite, trona and bentonite. the tertiary-quaternary basalts host good quality gemstones and clays. because of the preliminary nature of this work only zeolite, occurring in the biu-plateau basalts has been treated petrographically. 3.3.1 zeolite zeolite is a group of hydrated aluminosilicate minerals consisting of over forty (40) varieties. all are of framework silicates (figure 9a) containing open cavities capable of holding loosely bonded large cations and water. they are complex tektosilicates containing 3d network of sio4and alo4 tetrahedra linked to form channels, cages, rings or loops (figure 9b). because of these channels and cages in their structures cations and water molecules pass in and out of them without disruption. a b figure 9: structures of zeolite, a: framework silicates and b: 3d network of sio4and alo4 tetrahedra linked to form channels each oxygen ion is shared by two si4+. some number of si4+ may be replaced by al3+ and the charge deficiency is balanced by the introduction of n+, k+ or ca2+. the open cavities are responsible for the low density of zeolite. the general formula is: (na+, k+, 1/2ca2+)xz [(sialx)o2(x+y]z.nh2o (1) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 351-362. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 361 occurrence of zeolites in southern borno has been found to be within the basalts of the biu plateau. the zeolite occurs in two generations. the first generation appear as primary constituent in the basalts and in some instances predate the late eruptions (figure 10) where the basalt is seen to cross-cut the zeolite. the second generation of the zeolite is secondary in nature where it is seen to fill vesicles and cavities within the basalts (figure 7), probably formed by late hydrothermal processes. physical and petrographic analysis of the zeolite shows that the variety is whitish in hand specimen with hardness of approximately 4 and specific gravity of about 2. in thin section the variety is colourless in plane polarized light and rhombohedron in form. birefringence is high with grey to white interference colours and often zoned (figure 7). these physical and optical properties suggest that the zeolite in the biu basalts is chabazite (caal2si4o12.6h2o) variety which is the most common and useful type. other natural zeolite varieties include natrolite, laumonite, stilbite and sodalite. the biu zeolite variety (chabazite) is closely related to feldspathoid associated with mafic igneous rocks/ basic volcanic rocks. zeolites are industrial minerals used as drying agents, catalysts and washing materials. figure 10: photomicrograph of basalt showing zeolite being crosscut by groundmass of basalt 4.0 conclusion the landscape of the southern part of borno state is characterized by basement complex rocks and sedimentary covers. the crystalline basement is prominent around gwoza, askira uba, chibok and biu which are differentiated into migmatites, gneisses, granites and basalt rocks. the sedimentary units dominate kwaya kusar, bayo, shani and damboa with occurrences of bima formation, gongila formation, fika shales, gombe sandstone and chad formation. the basement complex rocks host feldspar, quartz, mica mineralization and ornamental stones. the basaltic rocks are composed of zeolite mineralization and gemstones comprising of aquamarine, corundum, amethysts, tourmaline and topaz. the cretaceous-quaternary sedimentary rocks are rich in quality clays, kaolinite, diatomites, trona and bentonite industrial minerals. references abaa, si. and najime, t. 2006. mineralization in precambrian rocks, central nigeria.implication for oban-obudu-mandara-gwoza complex of eastern nigeria. global journal of geological sciences, 4 (2): 121-128. zeo bst file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ankidawa et al: hydrogeological and engineering investigations of gully sites in zing and environs, northeastern nigeria. azojete,16(2):351-362. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ishakukamale@gmail.com; hikamale@unimaid.edu.ng 362 allix, p. 1983. environments mesozoiques de la paritcnord-orientale du fosse de la benue (nigeria), stratigraphic, sedimentologic, evolution geodynamique. travaux laboratoire science terre st. jerome marseille bulletin, 21: 1-200. avbovbo, aa., ayoola, eo. and osahan, ga. 1986. depositional and structural styles in the chad basin of north-eastern nigeria. aapg bulletin, 70: 1787-1798. baba, s., islam, mr., el-nafaty, jm., and amate, mk. 1991. exploration and evaluation of industrial minerals and rocks in the northern part of mandara hills n.e, nigeria. journal of mining and geology, 27 (2): 11-14. baba, s., emofurieta, wo. and el-nafaty, jm. 1995. petrochemistry of liga hill, gwoza area, n.e nigeria. borno journal of geology, 1(1): 35-58. baba, s. 2005. geology and solid mineral potentials of crystalline rocks in borno state, ne nigeria. university of maiduguri. occasional publication. faculty of science seminar series, 2: 11-19. baba, s., abaa, si. and dada, ss. 2006. preliminary petrogenetic study of some rocks from gwoza area, ne, nigeria. global journal of geological science, 4(2): 147-156. baba, s. 2011. some geochemical considerations in the petrogenesis of madagali granitoids, ne, nigeria. global journal 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obiosio, eo. 2002. foraminiferal assemblage and palaeoenvironment of the fika shale, bornu basin, northeastern nigeria. journal of mining and geology, 38 (1): 49-55. islam, mr. 1986. the petrological study of biu plateau basalts, borno state, nigeria. annals of borno, 3: 215-226. kachroo, rk., ali, ij. and kurah, al. 2000. records of some ostracods from gongilaformation ne nigeria. kerr, pf. 1977. optical mineralogy. fourth edition, mcgraw hill inc., new york: 492p okeke, pi. 1991. petrology of kirawa volcanic and geochronology of some gwoza rocks. journal of mining and geology, 37: 77-84. popoff, m. 1988. du gondwana a’l’ atlantique, sud: connexions du fosse’ de la benoue avec les basins du nord-estbresilienjusqu’al’ ouvature du golfe de guinean cretaceinfeneur. journal of african earth sciences, 7: 409-431. zaborski, p., ugodulunwa, f., idonigie, a., nnabo, p. and ibe, k. 1997. stratigraphy and structure of the cretaceous gongola basin, northeastern nigeria. bulletin of center of research and exploration production, elf-aquitaine, 21: 153-185 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):929-938 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 929 original research article symmetric and asymmetric based encryption model for mobile commerce o. c. abikoye, a. h. dokoro* and a. abdullahi (department of computer science, university of ilorin, ilorin, nigeria) * corresponding author’s email address: harunadokoro@gmail.com 1.0 introduction information security has become a serious issue due to the tremendous development in information technology (nath, et al, 2015). nowadays, it is a real challenge to exchange confidential information (such as credit/debit card details, account information) between two end points without facing the threat of the information being intercepted while on transit (nath et al, 2015). to achieve high degree of confidentiality, sensitive information needs to be encoded into a format that can only be decoded by the authorized parties so that it would be rendered meaningless to the would-be interceptor (nath et al., 2015). in order for the article information abstract secure information exchange in a mobile commerce environment has become a difficult task due to the involvement of sensitive financial information and the tremendous development in information technology in recent years. this poses a great threat while conducting transaction in a mobile commerce environment. cryptography has been employed to eliminate this using symmetric and asymmetric cryptography. however, in symmetric cryptography, secret key distribution can create a performance bottleneck, while asymmetric ciphers consume significant computational resources. this paper proposed symmetric and asymmetric based encryption model so as to achieve robust security and faster processing speed, by employing advanced encryption standard (aes) as symmetric algorithm and rivestshamir-adleman (rsa) as asymmetric algorithm. in this model, rsa was used to encrypt aes secret key in order to secure the exchange of the key, while the rest of the sensitive data was encrypted using aes. the proposed model was implemented using java programming language. performance evaluation of the proposed model was carried out in terms of encryption/decryption time and the results show that the proposed model takes a little longer time than the rsa algorithm. this is as a result of the aes key encryption being introduced into the model. it is therefore recommended that the model be implemented in mobile commerce applications as an added layer of security in order to strengthen the applications against numerous security threats due to the robust security and faster processing speed provided by the proposed model. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 22 november, 2018 revised 01 may, 2019 accepted 10 may, 2019 keywords: cryptography encryption symmetric and asymmetric aes and rsa model security mobile commerce. mailto:harunadokoro@gmail.com http://www.azojete.com.ng abikoye et al: symmetric and asymmetric based encryption model for mobile commerce. azojete, 15(4):929-938. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 930 authorized parties to read the encrypted or cipher text, they must have access to a secret key or password with which only the message or information can be decrypted. two forms of encryption algorithms exist; symmetric and asymmetric. symmetric uses a single key for both encryption and decryption of data while asymmetric uses key pair, public and private key for encryption and decryption respectively (choudhary and som, 2016). according to kalaiselvi and anand (2016), combination of symmetric and asymmetric key cryptographic algorithms such as advanced encryption standard (aes) and rivest-shamiradleman (rsa) is one of the possible proactive solutions for securing sensitive information. 1.1 review of the aes algorithm advance encryption standard (aes) being symmetric cryptographic algorithm developed by vincent rijmen and joan daeman was established as the specification for encrypting electronic data by the united states (us) national institute of standards and technology (nist) in the year 2001. aes is a block cipher with a block size of 128 bit and allows for three different key lengths; 128 bits, 192 bits and 256 bits. the key length determines the number of encryption rounds to be performed ritambhara et al. (2017). table1 below summarizes the relationship between the key lengths and the encryption rounds of the aes algorithm. table 1: relationship between key lengths and encryption rounds of aes aes version key length (bits) encryption rounds aes-128 128 10 aes-192 192 12 aes-256 256 14 the aes algorithm consists of four invertible transformations; subbytes, shiftrows mixcolumns, and addroundkey as seen from figure 1. these transformations are performed in all the encryption rounds, except the final round where the mixcolumns transformation is omitted in order to make the encryption and decryption scheme symmetric. the subbytes transformation replaces each byte of the state by a byte indexed by row (first 4bits of the state byte) and column (second 4-bits of the state byte) of a 16x16 substitution table (s-box) with special mathematical properties. the shiftrows move the rows of the state by shifting the bytes in each row by a certain offset so as to ensure that columns are not encrypted independently. the mix column is a matrix operation composed of multiplication and addition of the entries, treated as coefficients of polynomial of order x7. during the add round key operation, 16-byte sub-key derived from the main key using rijndael’s key schedule is added to the 16-byte state by combining each byte of the round key with the corresponding byte in the state using bitwise exclusive or (xor) operation ritambhara et al (2017). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 929-938. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 931 figure 1: description of aes algorithm (source: ritambhara et al, 2017) review of the rsa algorithm rivest-shamir-adleman (rsa) is the most commonly used asymmetric key cryptographic algorithm that was developed by three scientists; ron rivest, adi shamir, and leonard adleman in the year 1997 (christof & jan, 2010). rsa can be used for ensuring both confidentiality (encryption) and authentication (digital signatures) of a message (christof & jan, 2010). in this study, rsa was used to eliminate the difficulty of symmetric key distribution of the aes algorithm. the rsa implementation process is described as follows: two random secret primes p, q are selected such that the modulo n = p ∗ q. phi of n (ϕ n ) is then calculated using the relation ϕ n = p− 1 ∗ q − 1 . an integer e is randomly selected such that 1 < e < ϕ n and gcd e, ϕ n = 1. according to congruence equation, ed mod ϕ n ≡ 1 , the decryption key d is then obtained such that the key pairs (e, n) is used for encryption, and (d, n) is used for decryption. to encrypt a message m, the sender uses the public key (e, n), such that, cipher text c = me(mod n). to decrypt the cipher text c, the receiver uses the private key (d, n) such that, m = cd mod n . note that, p, q, d, and ϕ n must remain secret to the owner of the key pairs. the encryption or public key (e, n), as the name suggest should be made available to anyone that wants to communicate with the recipient. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abikoye et al: symmetric and asymmetric based encryption model for mobile commerce. azojete, 15(4):929-938. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 932 the security of the rsa algorithm lies on the factorisation of a big prime number, at least 1024 bits which prove to be a problem till today because it requires very long processing time and huge computational power. this is referred to as the factorisation problem. to achieve a reasonable level of security, at least 1024-bits key lengths is recommended. mobile commerce mobile e-commerce (m-commerce) is a term used to describes online sales transactions that use wireless electronic hand-held devices such as, smart phones and tablets (lu and lei, 2017). these wireless devices interact with computer networks that have the ability to conduct online merchandise purchases. it is referred to as next-generation e-commerce (rouse, 2017). the industries affected by m-commerce include: financial services such as mobile banking. brokerage services in which stock trading can be conducted using handheld device. telecommunications, in which service such as bill payment and account reviews can all be conducted using handheld device service/retail, as consumers are given the ability to place and pay for orders on-the-fly it has been noted that, m-commerce has incomparable superiorities when compared to traditional e-commerce. however, it has brought forward higher request for a robust security (jianping, 2011). related work kumar, et al (2017) proposed the hybridization of symmetric and asymmetric encryption techniques to ensure confidentiality, integrity, and authentication of digital medical images. the researchers employed the use of rsa and aes cryptographic algorithms to guarantee authentication and confidentiality of the image. encryption keys are generated using rsa algorithm. once the keys are generated, aes algorithm is used to encrypt the image using the key generated. while least significant bit (lsb) method is used to embed the encrypted image into the cover image. baihaqi and briliyant (2017) worked on an e-learning system that implements both encryption and digital signature as security services to prevent data theft and modification. the design uses rsa 2048-bit for digital signature in order to verify the authenticity of information sent, while aes 128-bit encryption was proposed to ensure data confidentiality. rsa was not used to eliminate the difficulty of aes key distribution, it was only used to authenticate users of the system. sadikin and wisnu (2016) presents an implementation of rsa-1048 and aes-256 with digital signature for securing health record application. the system is used in two schemes; verification and protection schemes. rsa-1048 and sha-256 are used for digital signatures for the purpose of verifying the authenticity of users of the system. while the electronic health record is then protected using the aes-256 cryptographic algorithm. liang, ye, et al (2016) proposed a hybrid cryptographic consisting of improved rsa and aes. user’s files are encrypted using aes algorithm, while rsa algorithm encrypts the aes secret key. the encrypted file is uploaded to the cloud storage system. when users need to retrieve their http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 929-938. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 933 file, they will need to first download the encrypted file from the cloud storage system, use the rsa algorithm to decrypt the aes secret key in order to obtain the plaintext key of the aes algorithm. the aes algorithm is then used to decrypt the ciphertext data to get the original file. mahalle and shahade (2014) presented a hybrid (rsa-1024 and aes-128) algorithm for securing data in cloud environment. when a user tries to upload a file, four different keys wil be generated; rsa public key-n, rsa public key-e, rsa private key-d, and aes secret key. rsa private key-d, and aes secret key are known only to the user. the file is then encrypted using both rsa and aes algorithms with rsa-public key-e and aes secret key before it is stored into the database corresponding to the user’s account. later when the user wants to access the stored file, the user has to specify the filename to download, and then provide the aes secret key and rsa private key-d which will be used to decrpyt the downloaded encrypted file. this approach is proved to be time consuming due to the double encryption involved. this is not ideal for most systems. khanezaei and mohd (2014) introduced a framework based on rsa and aes encryption algorithms that can be used for cloud computing. the researchers argued that, to secure cloud storage services, combination of encryption algorithms such as rsa and aes is one of the possible solutions. the framework consists of three entities: sender, receiver, and cloud storage service (css). to send a file, the sender request from the cloud system its public key and the cloud system will respond by sending the public key together with the generated file id. the sender then encrypts the file using rsa with the public key and sends it to the cloud server. to receive a file, the receiver sends a request for a particular file to the cloud system and the cloud system encrypt the file using aes algorithm and sends it to the receiver. the receiver again sends his public key to the cloud system, the cloud system then encrypts the secret key (the key used to encrypt the requested file) and sends it to the receiver. the receiver then uses his own private key to decrypts the encrypted secret key received, and later uses this decrypted secret key to decrypt the file. nevertheless, the double encryption and decryption processes for each files can cause system overhead. the proposed model the proposed model combines aes and rsa algorithms to ensure secure secret key establishment as well as confidentiality in exchanging sensitive data. the model is divided into two phases. phase one deals with the secret key establishment, while phase two deals with the secure exchange of information. 3.1 phase one phase one of the model deals with the symmetric or secret key establishment, that is, ensuring the secure exchange of the generated aes secret key between the sender and the receiver. secure key establishment can be achieved through the following operations: the sender (client) generates aes secret key whose length is either 128, 192, or 256 bits. the receiver (server) generates rsa key pairs; public and private keys. the sender requests the receiver’s public key. the receiver then sends his/her public key to the sender. the sender encrypts the aes secret key using the receiver’s public key and sends it to the receiver. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abikoye et al: symmetric and asymmetric based encryption model for mobile commerce. azojete, 15(4):929-938. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 934 lastly, the receiver decrypts the encrypted aes secret key using his/her private key to obtain the plain aes secret key. the secret key is now established between the sender and the receiver, data can now be encrypted with the secret key and exchanged between the two end points using the aes algorithm. phase two the second phase of the model, also known as the secure message exchange phase, involves the use of the aes algorithm to carry out the rest of the communication between the communicating points after the secret key has been established. for encryption, the plain message and the plain aes secret key (whose ciphered version was sent to the recipient in phase one) serves as input to the aes algorithm. the output from the aes algorithm, which is the cipher message is then sent to the recipient. upon the receipt of the cipher message, the recipient uses the decrypted version of the aes secret key received in phase one to decrypt the message using the aes algorithm. the communication continues until all the data is sent. the operations are summarized as follows: sender uses the aes secret key to encrypts the plain message using aes algorithm. the encrypted message (cipher message) is then sent to the receiver. the receiver uses the decrypted version of the aes secret key received in phase one to decrypt the cipher message using aes algorithm. figure 2 depicts the proposed model which combines symmetric (aes) and asymmetric (rsa) encryption algorithms. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 929-938. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 935 figure 2: model for combined aes and rsa 3.3 system implementation the proposed model was implemented in java. java was chosen because of its platform independent feature; this means that a single program can runs on different platforms. netbeans 8.2 was used as the integrated development environment (ide) to implement the system. 3.4 encryption window using the encryption window, client first generates the rsa keys by providing the rsa key length (in bit) and click on generate rsa keys button. the aes version is then selected and the aes secret key is entered in the space provided. the aes secret key entered is then encrypted using rsa algorithm, utilizing the generated rsa public key pair to obtain the ciphered aes secret key. the user then entered the plain text in the space provided and click on the encrypt button to encrypt the plain text using the aes algorithm. figure 3 shows the implemented encryption window of the proposed model. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abikoye et al: symmetric and asymmetric based encryption model for mobile commerce. azojete, 15(4):929-938. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 936 figure 3: encryption window of the proposed model 3.5 decryption window to decrypt a given cipher text, the user has to first get the rsa encrypted aes secret key by clicking on the get aes secret key (cipher) button. the encrypted aes secret key is then decrypted using rsa algorithm to reveal the plain aes secret key, by utilizing the private key component of the previously generated rsa keys. lastly, the cipher text is decrypted using the aes algorithm with the decrypted aes secret key. figure 4 shows the implemented decryption window of the proposed model. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 929-938. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 937 figure 4: decryption window of the proposed model 4. results and discussion the proposed model was evaluated against the aes and rsa algorithms in terms of encryption and decryption time. the results are obtained by encrypting 1024 bytes of data using the three algorithms; aes, rsa, and the proposed model. the results are presented in table 2. table 2: performance evaluation of aes, rsa and the proposed model algorithm key length (bit) encryption time (ms) decryption time (ms) aes 256 0.613186 0.626901 rsa 2048 1.533471 1.594019 proposed model 2048 1.856794 1.906412 from table 2, it can be seen that the encryption and decryption time for the proposed model is less than that of aes and rsa combined, even though the model is a combination of aes and rsa. moreover, the model eliminates the major problem of symmetric key algorithms by ensuring secure secret key establishment. the 5. conclusion a model which combines symmetric and asymmetric cryptographic algorithms using aes and rsa was presented. the model was represented as two phase processes, with phase one deals with secret key establishment, while phase two deals with secure information exchange. the proposed model which suggest secure way of aes secret key establishment was implemented in java. performance evaluation was carried out in terms of encryption/decryption time. the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abikoye et al: symmetric and asymmetric based encryption model for mobile commerce. azojete, 15(4):929-938. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: harunadokoro@gmail.com 938 evaluation results show that the encryption/decryption time for the proposed model is less than that of the aes and rsa combined but it is a little longer than that of the rsa algorithm, this is as a result of aes key encryption being introduced. moreover, the model can be implemented as an added layer of security in order to ensure confidentiality while exchanging sensitive financial and personal information in a mobile commerce environment. references baihaqi, a. and briliyant, oc. 2017. implementation of rsa 2048-bit and aes 128-bit for secure e-learning web-based application. lambok, indonesia, ieee. choudhary, r. and som, s. 2016. encryption technique using dynamic table and block division process on binary field. noida, india, ieee, pp. 353-358. christof, p. and jan, p. 2010. understanding cryptography: a textbook for students and practitioners. berlin, germany: springer-verlag berlin heidelberg. jianping, w. 2011. the analysis and optimization on m-commerce secure payment model. qingdao, china, ieee, pp. 41-44. kalaiselvi, k. and anand, k. 2016. enhanced aes cryptosystem by using genetic algorithm and neural network in s-box. bangalore, india, ieee, pp. 1-6. khanezaei, n. and mohd, zh. 2014. a framework based on rsa and aes encryption algorithms for cloud computing services. kuala lumpur, malaysia, ieee, pp. 58-62. kumar, sbj., nair, a. and raj, rvk. 2017. hybridization of rsa and aes algorithms for authentication and confidentiality of medical images. chennai, india, ieee, pp. 1057-1060. liang, c., ye, n., malekian, r. and wang, r. 2016. the hybrid encryption algorithm of lightweight data in cloud storage. bangi, malaysia, ieee, pp. 160-166. lu, t. and lei, x. 2007. study on security framework in e-commerce. shanghai, china, iinstitute of electrical and electronic engineers (ieee), pp. 3541-3544. mahalle, vs. and shahade, ak. 2014. enhancing the data security in cloud by implementing hybrid (rsa & aes) encryption algorithm. amravati, india, ieee, pp. 146-149. nath, a., madhumita, s., supriya, m. and kanij, fa. 2015. bit level encryption algorithm – implementation of bit-wise operations and randomized bit-wise columnar transposition method. jabalpur, india, ieee, pp. 1057-1063. ritambhara, gupta, a. and jaiswal, m. 2017. an enhanced aes algorithm using cascading method on 400 bits key size used in enhancing the safety of next generation internet of things (iot). greater noida, india, ieee, pp. 422-427. rouse, m. 2017. m-commerce (mobile commerce). [online] available at: http://searchmobilecomputing.techtarget.com/definition/m-commerce sadikin, ma. and wisnu, rwm. 2016. implementation of rsa 2048-bit and aes-256-bit with digital signature for secure electronic health recprd application. lombok, indonesia, ieee, pp. 387-392. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 628-637 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 628 original research article evaluation of geotechnical and structural performance of cementstabilized soil with saw dust ash (sda) c. a. fapohunda1*, o. o. amu1 and o. f. babarinde2 (1department of civil engineering, federal university, oye-ekiti, nigeria. 2department of civil engineering, obafemi awolowo university, ile-ife, nigeria) * corresponding author’s email address: christopher.fapohunda@fuoye.edu.ng article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: cement lateritic soil saw dust ash (sda) soil stabilization strength abstract availability of good soils for the construction of civil engineering works is pivotal to the development and progress of any nation. where good soils are lacking, it is necessary to make the soil fit through soil improvement methods. this study investigates the geotechnical performance of soil stabilized with the blend of cement and saw dust ash (sda). the blend consists of 9% cement by weight and up to 10% of sda at interval of 2%. the tests conducted on both stabilized and unstabilized soils samples at three different locations, identified as a, b, and c were: particle size distribution, natural moisture content, atterberg’s limits, compaction, california bearing ratio (cbr) and unconfined compression strength (ucs). the results showed decrease in plasticity index from high to medium, increase in cbr values: 4 – 10% for sample a, 2 – 12% for sample b and 5 – 8% for sample c, and increase in unconfined compression strength values: 45.23 – 65.88 kn/m2 for sample a, 34.01 – 59.18 kn/m2 for b and 41.80 – 63.94 kn/m2 for c. the results of this investigation showed that improvement of soil for construction purpose can be achieved when sda is applied as a stabilizer in a cement-stabilized soil, up to 6% by weight of cement. specifically, improved shear stress demonstrated up to 6% replacement is an indication of fitness for application of such soil in the design of footing, especially for columns, where shear stresses usually control the footing thickness. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction no civil engineering construction is possible with a foundation on weak soil, neither can any civil engineering structure exist for long without being founded on soil with adequate strength and settlement characteristics. thus, the importance of good soil cannot be overemphasized for enduring civil engineering infrastructures. there are instances however, when an engineer has no alternative than to work with soils of inadequate bearing capacity. in such instance, he can avail himself of any of the available soil improvement methods such as stabilization, aimed at altering the soil properties for improved engineering performance. according to ola (2013), soil stabilization is an improvement technique in which the resistance of the soil to various types of deformations and forces are increased. this may be achieved through compaction, preloading, drainage, densification, grouting, use of geotextiles and application of chemical admixtures (boyles, 1998). the chemical stabilization of soil, the subject of this paper, involves the use of lime, cement, fly ash, bituminous materials, and or combination of two or more of these (boyles, mailto:christopher.fapohunda@fuoye.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):628-637. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 629 1998, ola, 2013) to make it good for founding civil engineering structures. the use of cement as soil stabilizer has been found to considerably improve the bearing capacity of the soil (boyles, 1998). the optimum dosage of cement ranges between 2 and 12% (ola, 2013; anthanasopoulou, 2016), depending on the type of soil. it is believed that when cement is added to a soil, the liquid limit, plastic limit and the potential for volume change of soils are usually reduced, while there is an increase in the shrinkage and shear strength behaviors (anthanasopoulou, 2016).the reduced plasticity has been attributed to the partial or complete destruction or even the alteration of any clay minerals. increased compressive and tensile strength of the cement treated soil is provided by strength-forming cementitious reactions (primary and secondary) in the soilcement matrix in the presence of the soil pore water. the diand tricalcium silicates (c2s and c3s), tri-calcium aluminate (c3a) and tetracalcium aluminoferrite (c4af) in the cement, with water formed the c-s-h gel that is responsible for strength development. but using cement as stabilizer is expensive, thereby necessitating the need to research into finding a suitable but cheap, available and accessible replacement, especially from anthropogenic wastes. one of the wastes examined in this investigation as a possible stabilizer, is saw dust ash (sda). saw dust ash (sda) is produced, when saw dust, which is a waste material from the saw mill industry, is burnt into ashes. due to lack of efficient disposal systems, saw dust waste presently constitutes environmental problems. fapohunda et al. (2018) did a comprehensive review on sda and other wood products, highlighting their properties and application potentials for construction purposes in built environment. particularly, the review showed that the sum of sio2 + al2o3 + fe2o3 of sda in the review was above 50%, indicating a cementitious pozzolanic traits of classes c and n, and thus, a potential material for cement replacement. but the review, despite its extensiveness, contains very little literature on the use of sda as a soil stabilizing agent. few literature (amu et al., 2011, butt et al., 2016), however showed that when sda is used in conjunction with lime in soil stabilization, improved geotechnical properties resulted. however, no researcher has looked into the possibility of using sda with cement as a soil stabilizer. the present study investigates some geotechnical properties of lateritic soil stabilized with a blend of cement-sda. lateritic soil occurs in all wet tropical regions of east, west and central africa, indonesia, thailand, brazil and various island such as hawaii and cuba (figure1). figure 1: distribution of lateritic soil (source: thagesen, 1996) according to boyles (1998), lateritic soil is characterized by high porosity and relative incompressibility. some of the effects of these include, poor compaction due to high moisture file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda, et al: evaluation of geotechnical and structural performance of cement-stabilized soil with saw dust ash (sda). azojete, 15(3):628-637. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 630 content, sensitivity to fluctuations in moisture, where strength may be significantly reduced with a slight increase in water content, low bearing capacity and low strength (bello et al., 2015). it is thus imperative for researchers to come out with improvement strategy for lateritic soils where it is available. its abundance in nigeria, is the justification for its choice, in an attempt to investigate and evaluate its geotechnical fitness for constructional purpose with cement-sda blends as stabilizing agent. in attempts to improve its properties to make it suitable and fit for use as a material on which to found civil engineering foundations, researchers have carried out stabilization of lateritic soil with different of materials. for example, amu et al. (2011) worked with lime; bello et al. (2015) with cassava peel ash; nnochiri and aderinlewo (2016) with banana leaf ash; todingrara et al. (2017) with lime and cement; aderinola and nnochiri (2017) with terrasil solution; and nnochiri et al. (2017) with palm kernel shell ash. thus, the aim of this work is to evaluate the geotechnical performance of lateritic soil stabilized with cement-sda blend. in carrying out the investigation, the percent of cement was at a constant value of 9% by weight of the lateritic soil. the sda was varied from 0 to 10% at increment of 2% by weight of cement. 2. materials and methods 2.1 materials the materials used for this investigation were, laterite, sda, ordinary portland cement (opc), and water. the lateritic soils used for the investigation was obtained from three different locations within the new market clearing area of tonkere gate of obafemi awolowo university, ile-ife. the sampling area was so selected so that the results of this investigation will be representative of lateritic soil found in the field. the samples were labelled as sample a, b and c for the purpose of identification. the sawdust that was used in this investigation was obtained from sawmills along ondo road in ile-ife. the saw dust was then air-dried so as to aid better combustion and was subsequently burnt using open burning system using the method suggested by oyekan and kamiyo (2011). the ash that was obtained from the combustion process was then sieved through 212μm sieve aperture, collected and stored in air-tight container. for this work, ordinary portland cement (opc), classified as grade 42.5 and meeting the requirements of bs 12 (1996) and nis 441 (2014) was used. clean and potable water was used for this investigation. 2.2 methods in order to determine the index properties of the samples, preliminary investigations were carried out to obtain the followings: the moisture content, specific gravity, particle size distribution, atterberg limits, and the density. the moisture content was determined in accordance to astm d 2216 (1996). specific gravity bottle was used to determine the specific gravity of the soil samples. the particle size distribution of the soil samples was obtained by carrying out mechanical sieve analysis. the atterberg limits consisting of the liquid limit and plastic limit were carried out using atterberg limits apparatus as per bs (1990). geotechnical tests such as compaction test, california bearing ratio and unconfined compression tests were conducted on samples with cement only (at 9%), that is, 0% sda and subsequently on cementsda blends. for the compaction test, the standard proctor compaction test was used. this test was carried out both on untreated and treated soil sample so that the effect of the additive could be measured as per bs: 1377-4 (1990). unsoaked soil samples was used for cbr test in accordance to (ngs, 1997). the unconfined compression test was performed in accordance to bs 1377 (1990) the proportion sda in the mix was varied from 0 – 10% at interval of 2%. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):628-637. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 631 3. results and discussion 3.1 index properties the properties of samples a, b and c are presented in table 1. it can be seen that sample b has the highest moisture content of 10.12% while sample a has the lowest of 6.23%. lambe and whiteman (1979) stated that the moisture content of a soil depends on the void ratio of the soil, thus these values are indicative of the void spaces present in each soil sample. it can therefore be inferred from this statement that sample b has the largest void ratio out of the three samples. table 1: summary of lateritic soils index properties soil property sample a sample b sample c percentage passing bs no 200 sieve (%) 57.60 48.00 54.00 natural moisture content 6.23% 10.12% 7.15% specific gravity 2.684 2.267 2.318 liquid limit (%) 48 34 42.7 plastic limit (%) 23.01 13.18 21.03 plasticity index (%) 24.99 20.82 21.67 gi 25 6 9 uscs classification cl cl cl aashto classification a-7-6 a-6 a-7-6 maximum dry density kg/m3 1689.60 1566.80 1649.90 optimum moisture content (%) 13.00 16.83 17.24 california bearing ratio (%) 3 2 4 compressive strength (kpa) 72.576 45.484 54.432 the specific gravity (sg) of the samples is in the range of 2.27 – 2.68. when viewed against the observation of das (2006) that the sg of sand, silt, clay, clay/silty-clay, halloysite and organic soils are respectively in the range 2.63 – 2.67, 2.65 – 2.7, 2.67 – 2.90, 2.0 – 2.55, and less than 2.0, it is obvious that none of the lateritic soil samples is organic. the fact that sg of the samples are very close suggests the same degree of laterization (ola, 2013). based on the uscs classification system, it is shown from table 1 that all the three soils samples belonged to the lean clay (cl) group implying that they are silts and clays with liquid limit 50% or less. inorganic clays of low to medium plasticity, gravely clays, sandy clays, silty clays and lean clays are all considered to belong to cl group. though the association of american state highway transport official (aashto) classification system puts the soil samples as a-7-6 (25), a-6 (6) and a-7-6 (9), it is obvious that in real sense, it agrees with unified soil classification system (uscs) in that both classes are characterized as containing materials such as silty or clayey with more than 35% passing the 75μm sieve. this type of soil is not good as foundation material because of susceptibility to compressibility. this conclusion can also be deduced from the values of the atterberg limits. from table 1, it is obvious that the samples are of intermediate plasticity as the liquid limit fell between 35 and 50% (areola, 1982). however, high values of plasticity index (pi), above 20%, is an indication of potential geotechnical problems if the lateritic soil is to be used as foundation materials (ola, 2013), necessitating the need for improvement efforts through stabilization. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda, et al: evaluation of geotechnical and structural performance of cement-stabilized soil with saw dust ash (sda). azojete, 15(3):628-637. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 632 3.2 geotechnical properties the results of geotechnical properties of the samples after stabilization with cement-sda blends, keeping the cement content at 9% but varying the sda content from 0-10% at incremental rate of 2% are presented in figure 1 and tables 2 – 4. from figure 1, the plasticity index, (which is the range of water content between liquid and plastic limits within which the soil behaves as plastic material), of the samples decreased with increase in sda addition and then starts to increase again. the lowest values for samples a and c occurred at 6% of sda while that of sample b occurred at 4% of sda. the progressive decrease in the values of the plasticity index is an indication of geotechnical improvement of the soil using sda as stabilizing agent, until 6% sda for samples a and b, as well as 4% sda for sample b. the decrease could be attributed to the probable stoppage of pozzolanic activities of sda, due to exhaustion of pore water in the soil (neville, 2011, white et al., 2015, anthanasopoulou, 2016). however, the highest numerical values of the pi obtained from all the stabilized lateritic soil samples was 14.51% for sample a at 4% of sda replacement. thus, the plasticity index of all samples fell between 10 and 20%, indicating medium plasticity (bowles, 1998). figure 1: effect of sda on the plasticity of the lateritic soil the unstabilized lateritic soil samples have pis of between 20.82 and 24.99 indicating high plasticity. the plasticity of soil was classified as follows: 0 as non-plastic, 1-5 as slightly plastic, 5 – 10 as low plasticity, 10 – 20 as medium plasticity, 20 – 40 as high plasticity and greater than 40 as very high plasticity (das, 2006). the results of this investigation clearly demonstrate improvement in the lateritic soil from high plasticity to medium plasticity when stabilized with cement-sda blends. the results of the optimum moisture contents (omc) and maximum dry density (mdd) are presented in table 2. moisture content is an indication of compacting effort required to achieve full compaction of soil samples (das, 2006 and ola, 2013). from table 2, it can be observed that omc values obtained do not affect the mdd of the soil samples. the nature of the variation of the mdd with omc for all samples displayed a striking resemblance to that of sand (bowles, 1998), though the samples were found to tend towards silt-clay as earlier explained. the absence of marked increase in the mdd in the samples, according to das (2006), are due to capillary tension in the pore water, which resists the tendency of soil particles to move and be densely packed. it is possible that the pozzolanic action of sda turned the lateritic samples found to be silty-clay, into sand particles. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):628-637. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 633 table 2: summary of compaction results for the stabilized soil samples sample sda (%) optimum moisture content (omm) (%) maximum dry density mdd (kg/m3) a 0 14.65 1825.00 2 16.63 1729.90 4 20.38 1715.90 6 19.00 1744.00 8 18.00 1758.00 10 19.50 1760.00 b 0 17.20 1694.00 2 17.40 1672.00 4 17.80 1696.00 6 20.10 1692.00 8 19.60 1686.00 10 19.80 1688.00 c 0 17.55 1774.00 2 17.60 1776.00 4 18.00 1682.00 6 19.40 1696.00 8 20.40 1704.00 10 20.00 1692.00 the results of the unsoaked cbr tests for the stabilized lateritic soil samples are shown in table 3. from table 3, it can be seen that the unsoaked cbr value of the cement-sda mix at 0, 2, 4, 6, 8 and 10% sda contents for sample a are 3, 5, 11, 11, 6 and 8% respectively; for sample b: 3, 8, 10, 12, 7 and 5% respectively while for sample c, 4, 4, 6, 9, 7 and 6% respectively. all these values demonstrate a general increasing trend up to 6% for all the samples before decline in values set in. this demonstrates that application of sda to stabilized lateritic soil incorporating cement, up to 6% will bring improvement in the properties of the soil. the observed increase in the cbr values was attributed to secondary cementitious materials resulting from the strength forming c-s-h gel product of pozzolanic reaction of sda in the presence of water. the observed decrease after 6% replacement value could be due to consumption of pore water that is needed to sustain the hydration process (alp et al., 2009; falade et al. 2014). however, from table 3, it is obvious that addition of sda generally has a beneficial effect on the cement-stabilized lateritic soil and practically produces optimal improvement at 6% replacement value. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda, et al: evaluation of geotechnical and structural performance of cement-stabilized soil with saw dust ash (sda). azojete, 15(3):628-637. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 634 table 3: summary of unsoaked cbr results for the soil samples sample sda (%) cbr top (%) cbr bottom (%) a 0 3 4 2 5 6 4 11 9 6 11 10 8 6 6 10 8 8 b 0 3 2 2 8 9 4 10 11 6 12 12 8 7 7 10 5 6 c 0 4 5 2 4 5 4 6 5 6 9 8 8 7 7 10 6 6 the results of the unconfined compression strength (ucs) conducted on the unstabilized and stabilized lateritic soil is shown in table 4. unconfined compression strength test is the main test recommended for the determination of the required amount of additive to be used in stabilization of the soils (butt et al., 2016). as a general convention, for a given type of stabilization, the higher the compressive strength, the better is the quality of the stabilized material. it can thus be seen in table 4 that strength of stabilized samples increased up to 4% of sda for samples a and b, but up to 6% of sda for sample c. for all the samples, a pattern of progressive increase is followed by progressive decrease with increase in sda. the unconfined compression strength of the cement-sda mix at 0, 2, 4, 6, 8 and 10% sda contents for sample a were 90.458kn/m2, 111.565kn/m2, 131.768kn/m2, 83.251kn/m2, 95.498kn/m2 and 110.525kn/m2 respectively; for sample b 68.027kn/m2, 80.398kn/m2, 118.367kn/m2, 113.369kn/m2, 37.829kn/m2 and 31.295kn/m2; for sample c 82.355kn/m2, 114.610kn/m2, 127.871kn/m2, 135.456kn/m2, 106.416kn/m2 and 77.760kn/m2. the values of the unconfined compressive strength are also indication of the level of consistency of clayey soil (ola, 2013). it has previously been shown from the observed index properties that the lateritic soil used in the work is clayey. according to das (2006), consistency of a clayey soil can be determined as follows: 0–25 kn/m2 indicates very soft, 25–50 kn/m2 is soft, 50–100 kn/m2 is medium soft, 100– 200 kn/m2 is stiff 200–400 kn/m2 is very stiff and greater than 400 kn/m2 indicates hard clay. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):628-637. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 635 table 4: summary of ucs results for the soil samples sample sda (%) normal stress σ (kn/m2) shear stress (kn/m2) a 0 90.458 45.229 2 111.565 55.783 4 131.768 65.884 6 83.251 41.626 8 95.498 47.749 10 110.525 55.263 b 0 68.027 34.014 2 80.398 40.199 4 118.367 59.184 6 113.369 56.685 8 37.829 18.915 10 31.295 15.648 c 0 82.355 41.178 2 114.610 57.305 4 127.871 63.936 6 135.456 67.728 8 106.416 53.208 10 77.760 38.880 from the study addition of sda to cement-stabilized lateritic soil changes the consistency from very soft to soft at the optimal levels of replacement, which is 4% for samples a and b; and 6% for sample c. the maximum values of compressive strength were at 4% sda for samples a and b, but at 6% for sample c. thus at these values, the use of sda will enhance geotechnical properties of the soil and subsequently promote its use in construction. 4. conclusion from the analysis of the results of investigations carried out on the lateritic soil stabilized with cement-sda blends, the following conclusions were drawn: the lateritic soil investigated was clayey materials according to both unified soil classification system (uscs) and the american association of state highways and transportation officials (aashto) soil classification systems. it was rated as fair to poor subgrade and foundation material, thus needing improvement for civil engineering application. addition of saw dust ash (sda)s to cement-stabilized lateritic soil, at the levels considered, resulted in reduction of plasticity index with optimum values for all samples recorded at 6%. addition of aw dust ash (sda) increased the cbr values of cement-stabilized lateritic soil, but a replacement with sda up to 6% resulted in optimum performance. addition of saw dust ash (sda) of up to 6% to cement stabilized lateritic soil increased the unconfined compression strength (ucs) of the samples. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda, et al: evaluation of geotechnical and structural performance of cement-stabilized soil with saw dust ash (sda). azojete, 15(3):628-637. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 636 the results of this investigation showed that improvement of soil for construction purpose can be achieved when sda is applied as a stabilizer in a cement-stabilized soil, up to 6% by weight of cement. when this is juxtaposed against the background of the fact that sda is an unavoidable waste, and as such, constitutes environmental menace, using it as stabilizer is an efficient and innovative wastes disposal and environmental management system and strategy. furthermore, soil stabilization with cement has been found not to be economical. therefore, using sda, which is cheaper than cement will results in drastic reduction in cost when applied for stabilization purpose. references aderinola, os. and nnochiri, es. 2017. stabilizing lateritic soil using terrasil solution. ssp journal of civil engineering, 12(1): 19 – 28. alp, i., deveci, h., süngün, yh., yilmaz, ao. kesimal, k. and yilmaz, e. 2009. pozzolanic characteristics of a natural raw material for use in blended cements. iranian journal of science & technology, transaction b, engineering, 33(4): 291-300. amu, oo., adedipe, aa. and oguntona, ot. 2011. modification of strength properties of limestabilized laterites with sawdust ash. journal of applied science and technology (jast), 16:38 – 44. amu, oo., bamisaye, of. and komolafe, ia. 2011. the suitability and lime stabilization requirement of some lateritic soil samples as pavement. int. j. pure appl. sci. technol. 2 (1): 29– 46. anthanasopoulou, a. 2016. the role of curing period on the engineering characteristics of a cement-stabilized soil. romanian journal of transport infrastructure, 5(1):38 – 52. areola, o. 1982. soils. in: nigeria in maps, r. m, barbour, editor hodder and stoughton, london, uk. astm d 2216, 1996. standard test method for laboratory determination of water (moisture) content of soil, rock, and soil-aggregate mixtures. american society for testing of materials, farmington, usa. bello, aa., ige, ja. and ayodele, h. 2015. stabilization of lateritic soil with cassava peels ash. british journal of applied science & technology, 7(6): 642-650 bowles, je. 1998. foundation analysis and design. mcgraw hill international book company, london. bs 1377, 1990. methods of test for soils for civil engineeringproperties. british standard institution: london bs 1924, 1990. methods of test for stabilized soils. british standards institutions, london. bs 12, 1996. specification for portland cement. british standard institution, london. butt, wa., gupta, k. and jha, jn. 2016. strength behaviour of clayey soil stabilized with saw dust ash. international journal of geo-engineering, 7(18): 2 – 9. das, bm. 2006. principles of geotechnical engineering. nelson, canada. falade, f., ikponmwosa, e and fapohunda, c. (2014). flexural performance of foam concrete containing pulverised bone as partial replacement of cement. maejo int. j. sci. technol. 8(1): 2031 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):628-637. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 637 fapohunda, c., akinbile, b. and oyelade, a. 2018. a review of the properties, structural characteristics and application potentials of concrete containing wood waste as partial replacement of one of its constituent material.ybl journal of built environment,6(1): 63 – 85. neville, am. 2011. properties of concrete. pearson international, london, uk. nigeria general specification. bridges and road works. federal ministry of works and housing, headquarters, abuja, nigeria. 1997;11. (revised) nis 444-1, 2014. cement – part i: composition and conformity criteria for common cements. standard organization of nigeria, abuja. nnochiri, se. and aderinlewo, oo. 2016. geotechnical properties of lateritic soil stabilized with banana leaves ash. fuoye journal of engineering and technology, 1(1):116 – 119. nnochiri, es., ogundipe, om. and oluwatuyi, o. (2017. effects of palm kernel shell ash on limestabilized lateritic soil. slovak journal of civil engineering, 25(3): 1 – 7. ola, sa. 2013. essentials of geotechnical engineering. university of ibadan press, ibadan. oyekan, g. l. & kamiyo, o. m. 2011. a study on the engineering properties of sandcrete blocks produced with rice husk ash bended cement. journal of engineering and technology research, 3(3): 88-98. thagesen, b. 1996. tropical rocks and soils. in: thagesen b. eds. highway trafficengineering in developing countries, 1st edition, e & f.n spon, london. todingrara, yt., tjaronge, mw., harianto, ti. and ramli, m. 2017. performance of laterite soil stabilized with lime and cement as a road foundation. international journal of applied engineering research, 12(14): 4699-4707 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3):573-585 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 573 original research article a review of tv white space technology and its deployments in africa i. mustapha1, mala u.m. bakura1, d. mustapha2 and m. abbagana1 (1department of electrical and electronics engineering, university of maiduguri, nigeria 2department of computer engineering, university of maiduguri, nigeria) * corresponding author’s email address: mustib@unimaid.edu.ng article information submitted 12 september, 2018 revised 10 may, 2019 accepted 15 june, 2019 keywords: tv white space cognitive radio dynamic spectrum access wireless communication internet access abstract the emergence of bandwidth-driven applications in the current wireless communication environment is driving a paradigm shift from the conventional fixed spectrum assignment policy to intelligent and dynamic spectrum access. practical demands for efficient spectrum utilization have continued to drive the development of tv white space technology to provide affordable and reliable wireless connectivity. it is envisaged that transition from analogue transmission to digital terrestrial television (dtt) creates more spectrum opportunity for tv white space access and regulatory agencies of many countries had begun to explore this opportunity to address spectrum scarcity. to convey the evolutionary trends in the development of tv white space technology, this paper presents a comprehensive review on the contemporary approaches to tv white space technology and practical deployments of pilot projects in africa. the paper outlines the activities in tv white space technology, which include regulations and standardization, commercial trials, research challenges, open issues and future research directions. furthermore, it also provides an overview of the current industrial trends in tv white space technology which demonstrates that cognitive radio as an enabling technology for tv white space technology. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction wireless communication is steadily migrating from traditional voice-based services to application-based services as demonstrated by the number of people who use smartphones with numerous underlying applications. the emergence of bandwidth-driven applications in the current wireless communication environment is driving a paradigm shift from the current fixed spectrum assignment policy to dynamic spectrum access, which prompts the need to re-analyze spectrum assignment. generally, radio spectrum bands are divided into fixed number of different frequency channels in which segments of the radio spectrum bands are allocated for different wireless communication services as shown in figure 1 (mustapha, 2016). mailto:mustib@unimaid.edu.ng http://www.azojete.com.ng mustapha, et al.: a review of tv white space technology and its deployments in africa. azojete, 15(3):573-585. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 574 figure 1: schematic representation of division of radio spectrum and radio ranges (mustapha, 2016). studies on spectrum usage carried out in many countries including malaysia (elshafie et al., 2014), spain (lopez-benitez et al., 2009), (islam et al., 2008), germany (wellens et al., 2007), new zeeland (chiang et al., 2007) , united kingdom (chiang et al., 2007) and usa (patil et al., 2011) at different locations show that large portion of licensed radio spectrum bands especially the tv spectrum bands have not been efficiently utilized. the utilization of licensed radio spectrum bands varies from 15% to 85% of the spectrum which indicates significant disparities in the usage of the radio spectrum bands. it can be deduced that the conventional policy of allocating spectrum bands to licensed users regardless of temporal and geographical variations has inadvertently contributed to the spectrum scarcity and hence necessitates the need for dynamic spectrum access. consequently, the federal communications commission (fcc) proposed rules that allow unlicensed user to opportunistically access the unused portions of spectrum bands, also called white spaces or spectrum holes. the guidelines permit secondary users (sus) to transmit on tv white spaces frequencies without interfering with the incumbent tv transmitters and wireless microphones transmissions. tv white space (tvws) is the unused spectrum in the very high frequency (vhf) band and ultra-high frequency (uhf) bands that have the potential to bridge the digital divide effectively by delivering affordable and reliable communication services (elshafie et al., 2014). research efforts toward the utilization of tvws technology for internet access indicate that african continent has better opportunities for such technique compared to europe. this is due to low internet penetration rate across the african continent and availability of abundant unused tv broadcasting spectrum particularly in the rural areas where fewer spectrum users exist. therefore, tvws technology could be used to provide affordable and reliable internet access to african countries. the few tvws trials implemented in some african countries have demonstrated that tvws and other dynamic spectrum access technologies could play a vital role in providing reliable and affordable internet connectivity to both the isolated rural and urban areas in africa (mustapha et al., 2016). the main challenge in deploying wireless internet services and other wireless services is the high cost of license spectrum bands and cost of deployment of equipment which in turn increase the end user costs. it is evident that the use of tvws technology can drastically reduce the cost of internet access and improve internet penetration rate in africa. recently, there is intensive effort toward standardization, prototyping and commercialization of tv white space devices (mustapha, 2016). this paper presents a comprehensive review on the contemporary approaches to tv white space technology and practical deployments of pilot projects in africa. the paper outlines the activities http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):573-585. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 575 in tvws technology, which include regulations and standardization, commercial trials, research challenges, open issues and future research directions. furthermore, it also provides an overview of the current industrial trends in tvws technology. the remainder of the paper is organized as follows: section 2 discusses the general introduction to tv white space and its availability. section 3 presents tv white space trials and pilot projects in africa and highlights the potentials of tv white space technology in africa. section 4 suggests potential research opportunities and challenges for the application of tv white space technology. 2. review of tv white spaces technology cognitive radio (cr) is an enabling technology for efficient utilization of spectrum holes which is frequently referred to as white spaces. it allocates unoccupied licensed spectrum bands to unlicensed users frequently referred to as secondary users (sus) in an agile manner without causing harmful interference to the licensed or primary users’ (pus) transmission. the concept of cognitive radio has several meanings in broad perspectives. it was first coined as an intelligent radio that sense its surroundings for operational electromagnetic and dynamically change its behaviours to optimize user experience (mitola, 2000). therefore, the cognitive radio cycle involves spectrum sensing, spectrum decision, spectrum sharing, and spectrum hand off. dynamic spectrum access (dsa) is a key enabling technique for exploitation of spectrum holes in temporal and space domains to address both future and current spectrum scarcity in wireless networks (mustapha et al., 2016) and (salami et al., 2011). spectrum sharing among wireless systems can occur horizontally (spectrum underlay) and vertically (spectrum overlay), as depicted in figure 2 and figure 3, respectively (akyildiz et al., 2006).in the underlay spectrum sharing technique, all wireless nodes have equal access to the available spectrum resources. unlicensed users are constrained to transmit at a very low transmission power below noise floor of the licensee such that accumulated interferences of the unlicensed users is below tolerable interference threshold. typical example of this approach is ultra-wide band (uwb) technology in which unlicensed users spread their transmit power over a wide range of frequency bands such that accumulated interferences do not exceed the threshold (akyildiz et al., 2006). this approach is suitable for short range, high data rate communication with a low transmission power. the overlay model approach prioritizes spectrum architecture for spectrum-sharing scheme. it is based on temporal and spatial spectrum holes or white spaces opportunities in which unlicensed users can dynamically access unused licensed spectrum bands without degrading licensed users’ performance. furthermore, unlicensed users can transmit at higher transmission power as long as licensed users protection from interference is guarantee (akyildiz et al., 2006a). figure 2: spectrum underlay dynamic spectrum scheme figure 3: spectrum overlay dynamic spectrum scheme (mustapha, 2016) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mustapha, et al.: a review of tv white space technology and its deployments in africa. azojete, 15(3):573-585. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 576 2.1 availability of tv white space spectrum spectrum hole or white space is the frequency band in which a secondary user accesses communications channel without interfering with any primary user. tv white space is the portion of the spectrum in very high frequency (vhf) band between 30 –300 mhz and ultra-high frequency (uhf) band between 470 960 mhz that are not utilized by primary users (broadcast television stations) in specific time and location (adediran et al., 2014). regulatory agencies such as fcc, ncc and nbc prohibit the use of unlicensed devices in frequency bands allocated to tv stations, except for devices such as wireless microphones, remote control and medical telemetry devices (elshafie et al., 2014). in nigeria, the current tv broadcasting services mainly operate on analogue transmission in the vhf spectrum band between 174 – 230 mhz and uhf spectrum band between 470 and 960 mhz band except for the tv stations that migrated to digital broadcasting platform (adediran et al., 2014). it is envisaged that transition from analogue transmission to digital terrestrial television (dtt) creates more spectrum opportunity for tv white space access and regulatory agencies of many countries had begun to explore this opportunity to address spectrum scarcity(van de beek et al., 2012). therefore, it is evident that after completion of digital switchover (dso) process, a portion of tv analogue channels would become entirely vacant due to transition to higher spectrum efficiency digital tv (dtv). although, some of the vacant bands such as the imt bands for mobile use may be reallocated by the regulators to other services, a quite number of the tv channels may be unused in each geographic area. although, spectrum utilization and tvws availability measurements have not fully been conductor in nigeria, the results from many countries indicate the availability of tvws (patil et al., 2011) and (elshafie et al., 2014). 2.2 tv white space spectrum sensing spectrum sensing is the fundamental function of cognitive radio to detect the presence or absence of primary users (pus) in a licensed spectrum band (mustapha et al., 2015). its main goal is to identify and access spectrum holes without compromising pus’ transmission. generally, spectrum sensing can be classified into two main classes viz transmitter detection and receiver detection. the main goal for transmitter detection method is to find out if the primary user is utilizing tv spectrum band, while receiver detection tries to find out if there are primary receivers in the area even when primary transmitter is utilizing spectrum. the receiver detection is practically very complex. therefore, most of research focused on transmitter detection method where detecting white space is based on target signals received. this method can be classified into blind detection, feature detection and noise dependent detection. the detection methods suitable for tvws are enumerated in table 1 (elshafie et al., 2014, mustapha, 2016). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):573-585. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 577 table 1: tvws detection techniques technique features drawbacks energy detector(nekovee, 2009, tandra and sahai, 2008, yucek and arslan, 2009) compares signal samples received over an observation interval with a threshold to detect white space. optimum non-coherent technique and the most commonly used suitable for detecting analog tv and wireless microphone signals. exhibits low performance compare to other sophisticated techniques. inability to distinguish licensed user’s signals from other interference signals such as noise. cyclic prefix and autocorrelation compares energy of cyclic prefix sequence of each signal segments with a threshold and uses autocorrelation function of dvb-t signals to detect white space. coherent technique that able to distinguish target signals from other interference signals such as noise. suitable for detecting dvb-t signals. exhibits relatively good performance under high correlated signals. it exhibits moderate computational and implementation complexities. cyclostationary feature(chen et al., 2007) exploits cyclic autocorrelation function of the received signals by correlating the received signals with a known tv signal to detect white space. coherent technique that can distinguish different transmission signals, e.g weak signal at a very low snr, noise with pus’ signals suitable for detecting both atsc and dvb-t signals. implementation complexity is high. susceptible to synchronization error and requires prior knowledge of pu signal features to demodulate the signal. pilot based uses pilot subcarriers of the received signals to set threshold for detecting white space, channel estimation and synchronization at the receiver. it is immune to noise uncertainty since position of the pilot can be accurately determined. achieves better sensing performance with short sensing time. suitable for detecting both atsc require a prior knowledge about the target signals sensing unit may be practically large. implementation complexity is relatively high. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mustapha, et al.: a review of tv white space technology and its deployments in africa. azojete, 15(3):573-585. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 578 2.3 tv white space device a tv white space device needs to sense the tv bands and successfully detect vacant channels that are not used by the incumbent users. generally, the licensed incumbent users that operate within the tv bands comprise of analog television system such as national television system committee (ntsc), digital television system such as television systems committee atsc and dvb-t and wireless microphones. tv signals are known to exhibit a high autocorrelation function (acf), low zero crossing points, periodicity and a high degree of signal differencing function which make them relatively easy to characterize and analyze. to protect the licensed incumbent systems (atsc, ntsc and wireless microphone) from tv white space devices, the fcc has defined the power levels at which a tv white space device can sense the spectrum for detection of incumbent signals. the specified power levels are below the noise floor of a receiver measured in a 6 mhz tv channel which make sensing of the signals very challenging. there is quite a few techniques that can be used to detect the presence of the three incumbent signals in the tv bands (elshafie et al., 2014, saeed and shellhammer, 2011). features of tv white space devices that can be used for detection of these incumbent signals are illustrated in table2. table 2: features of tv white space devices incumbent signal features of tv white space sensing devices atsc the device must search for atsc pilot at both nominal pilot frequency and alternate pilot frequency. also processes the averaged power spectra density (psd) obtained from a sequence of quiet times and determines the average of the individual psds from the individual quiet times to obtain average thermal noise. the device indicates presence of atsc signal in the channel if the test statistic exceeds a threshold. ntsc the device must search for the ntsc luminance carrier in frequency segments centered on each of the multiple frequencies and uses power in the luminance carrier to detect the presence of the ntsc signal in the channel. the device determines the ntsc test statistic which is the maximum of the values of the psd in frequency segments divided by the noise floor. wireless microphone the device must be able distinguish between carrier frequency location of a wireless microphone signal and pure noise to reliably detect the presence of wireless microphone signals. sensing device for wireless microphone signals must employ a classification procedure to expurgate narrow-band interference. 2.4 wireless standards for tvws generally, coexistence between incumbent users and other unlicensed users have been extensively discussed in wireless communication communities and several standards have been proposed. for example, ieee 802.22 wireless regional area network (wran) standard provides rules that permit unlicensed users to access unused tv spectrum bands or white spaces within the television bands between 5 mhz and 862 mhz (saeed and shellhammer, 2011). even though, the standard is designed for rural broadband, it does not attract many manufacturers http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):573-585. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 579 due to its implementation complexity. similarly, ieee 802.11af standard which is simpler and easier to implement, suffers significant drawbacks due to its wifi parentage. other standards and task groups on coexistence of other technology in tv white space (tvws) include ieee 802.15.2 wireless personal area network (wpan), ieee 802.16h wireless metropolitan area network (wman), ieee 802.19.1 and ieee 802.22/11af tvws standards (saeed and shellhammer, 2011). in addition to the ieee-based tvws standards, the european computer manufacturers association (ecma) has inaugurated and deployed the ecma-392 standard as a platform for portable devices that operate on tvws. ecma 392 and ieee 802.22 are different in many fronts. the ieee 802.22 draft standard focuses mainly on high-power fixed access devices, portable and rural applications, while the ecma 392 standard targets portable devices and targets in-home, in building and neighbourhood-area applications (wang et al., 2010). other wireless standards include weightless standard which was originally designed for tvws based machine to machine (m2m) communication but was later adopted for broadband communication when the demand for tvws in rural broadband applications became more apparent. td-lte standard is another tv white spaces standard developed by huawei primarily for backhaul and femto cells coordination in mobile communication (saeed and shellhammer, 2011). 3.0 the potentials of tv white spaces technology in africa africa is the second-largest continent, after asia in terms of size and population. the continent comprises of 58 countries and regions with a population size of over one billion. the trend in digital divide is becoming more pronounced in the african continent with majority of the countries experiencing low internet penetration rate (kennedy, et al., 2015). for instance, while almost 75% of people in africa do not have access to internet, only 21% of europeans are offline as depicted in figure 4 (facts, 2016). furthermore, itu report in 2016 indicates that internet penetration at the household level is estimated at 15.4% in africa compared with 84% in europe as shown in figure 5. a similar pattern is reported in the case of internet penetration rate in which african continent has less than 22% as compare to europe with about 85% as depicted in figure 6 (facts, 2016). naturally such a trend is expected because over 65% of the population reside in the rural areas with limited basic internet infrastructure and high cost of internet access, which makes wireless services largely unaffordable to many people. this means that high proportion of people would be denied of full participation in the digital revolution to access online learning materials, interact with friends through social media, effectively utilize online government services and gain knowledge through numerous internet resources. figure 4: internet usage across the globe (facts, 2016) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mustapha, et al.: a review of tv white space technology and its deployments in africa. azojete, 15(3):573-585. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 580 figure 5: percentage of households with internet access. figure 6: internet penetration rate (facts, 2016) the potential application of tv white spaces is essentially boundless, it can be used for a wide variety of services and technologies and it possess several important properties that make it highly attractive for wireless communications services such as campus broadband services, wide area wireless internet, home and enterprise wireless networking and smart city networks (adediran et al., 2014). in addition, it can be used by mobile system operators as an alternative carrier backbone to reduce network congestion during peak periods. the demand for new services and higher peak bit rates and system capacities can only be achieved by heterogeneous wireless platforms, for which tvws is an excellent candidate (gbenga, 2014). tvws technology can be cost-effective and valuable contributor to the wireless ecosystem supporting broadband services to un-served and underserved rural and urban areas in the african continent. it is currently being exploited by many large consumer electronics companies and internet/software companies including google and microsoft. tvws technology provides excellent radio propagation characteristics compared to other technologies that are using higher frequencies because it operates on the lower frequency bands which are less affected by haze, snow, rain and other natural disturbances. it is an ideal technology that has the potential to bridge the digital divide and significantly improve the economics of deploying wireless broadband in underserved communities (roberts et al., 2015). 3.1 tvws spectrum trials and pilot projects in africa in recent years, significant efforts have been made by several regulatory bodies in different african countries to implement the necessary infrastructure for the utilization of tvws technology. google and microsoft are the main driving companies that promote dynamic re-use of unused tv spectrum to provide reliable and affordable internet access to africans. they are the sponsors of many trials in africa with google mainly in south africa and microsoft in kenya. (mureu et al., 2016) there are also independent efforts going on in malawi and some other few african countries toward implementation of tvws trials. tvws is attracting considerable attention as a key part of the regulatory toolbox in many african countries. many regulators clearly saw the potential and were working to integrate tvws into their strategic planning. although manufacturers of tvws equipment are gradually coming on board, tvws equipment has yet to achieve its full mass market potential. equally the standards for tvws are still evolving and it is up to african governments, regulators, and entrepreneurs to decide whether to seize the opportunity or not. the following represent the most notable attempts toward the realization of tvws in africa (lysko et al., 2014), . http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):573-585. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 581 3.1.1 tvws trial in nigeria the estimated internet users in 2016 was 47.9% of the population and the internet penetration rate is 8.3% which is very low compared to south africa that recorded 25.3% internet penetration (facts, 2016). this is because large percentage of nigerian populace are residing in rural areas with no access to basic communication services coupled with low demand for communication which increases the cost of providing communication services. therefore, providing low cost communication services through tvws for such a large community is definitely an important step for societal development (gbenga, 2014). however, there is no any official tvws deployments or trials in either the urban or rural areas in nigeria to the best of our knowledge. it is important to note that at the moment, only wavetek has secured the west african distribution rights for carlson wireless to implement tvws trial in nigeria and university of ilorin has already engaged it services to provide campus wi-fi and tvws connectivity across the entire campus and satellite hostels in off campus. the project is expected to cover neighboring villages and provide high speed internet services. the project will be the first largest tv white space based campus wide wi-fi in africa (opawoye et al., 2015). 3.1.2 tvws in south africa with the support of the independent communication authority of south africa (icasa), google worked jointly with the wireless access providers association (wapa), the e-schools network, and carlson wireless to carry out the necessary spectrum measurements to provide the necessary evidence of viability of the project. the trial project was adopted in ten schools in the cape town to provide a broadband internet service at a speed of 4 mbps using vacant uhf spectrum (lysko et al., 2014). similarly, microsoft 4afrika initiative implemented tvws project in limpopo that provides low-cost wireless connectivity to five schools. the project is the result of active collaboration between microsoft, the university of limpopo, the network builder, multi source and the council for scientific and industrial research and was funded by the government (masonta et al., 2015). 3.1.3 tvws in ghana with the support of the ghana national communications authority (nca), microsoft and spectralink announced the creation of a commercial tvws pilot in ghana in may 2014. the pilot project is part of microsoft’s 4afrika initiative and its main objective was to provide low cost and affordable wireless network connectivity to students and staff at universities in koforidua. the networks use tvws technology with other wireless technologies to connect the entire campus and hostels to provide fast broadband internet access. this level of connectivity was substantial benefit to both students and staff at the universities (roberts et al., 2015), (louis et al., 2016). 3.1.4 tvws in kenya tvws pilot project in kenya was supported by the kenya’s ministry of information and communications, indigo telecom ltd., and adaptrum, microsoft launched its first pilot project in february 2013 to provide affordable wireless access to underserved places near nanyuki and kalema towns in mawingu. the areas are connected using tvws include the burguret dispensary (healthcare clinic), the male primary school, the male secondary school, gakawa secondary school and laikipia district community library. this pilot project utilizes tvws and base stations that are powered by solar energy to deliver broadband internet access to enhance education, improve healthcare and preserve the environment (opawoye et al., 2015), (mureu et al., 2016). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mustapha, et al.: a review of tv white space technology and its deployments in africa. azojete, 15(3):573-585. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 582 3.1.5 tvws in tanzania in collaboration with the tanzania commission for science and technology (costech) and the local isp uhuru one, microsoft 4afrika initiative implemented a pilot tvws trial project. the project enhances connection facilities and provides reliable and affordable internet access to students in dares salaam, tanzania (chavez et al., 2016). 3.1.6 tvws in malawi the university of malawi and malawi communications regulatory authority (mcra) in collaboration with the international centre for theoretical physics in trieste (ictpt)implemented a tvws pilot project in september 2013 (chavez et al., 2016). they first developed a very lowcost spectrum analyser based on open hardware to carry out a spectrum survey to determine the viability of the project. the project provides affordable and reliable connectivity to several hospitals, tertiary institutions, schools, an airport and a research facility in the city of zomba, in southern malawi (atimati et al., 2016). 3.1.7 tvws in botswana a tvws pilot project was launched in march 2015 by the botswana innovation hub in collaboration with microsoft and other agencies. the project which is known as project kgolagano provides internet connectivity and specialised telemedicine services to local hospitals and clinics. it enables access to specialised medicine in other locations around the world, where hospitals and clinics in rural areas send high-resolution patient photographs back to major cities for a more accurate diagnosis and care. the project was made possible under an authorisation from the botswana communications regulatory authority (bocra) to transmit using tv white spaces. it is also operating with the support of the botswana ministry of health and the ministry of infrastructure, science and technology (roberts et al., 2015). tvws deployments in africa would mainly depend on the availability of vacant tv spectrum bands within the region. although tvws spectrum usage and availability have been investigated in many countries (elshafie et al., 2014), (lopez-benitez et al., 2009), (islam et al., 2008), (wellens et al., 2007), (valenta et al., chiang et al., 2007), (patil et al., 2011), such investigations have not been fully conducted in most african countries. therefore, it is extremely important to investigate the potentials of tvws in africa and develop modelling tools that can quantify the availability of tvws spectrum for cognitive access. it is evident that tvws technology is still evolving and performance improvements can be expected. 4.0 potential challenges and research topics although tvws technology has existed for some time and many standards to be employed in tvws communications has been proposed, numerous significant problems and issues toward the practical realization of this technology remain unexplored. many countries have either completed tvws measurements or are on the verge of identifying tv white spaces in their frequency domains. the challenging issues and research areas that need to be explored are not peculiar to african countries rather general issues to tvws technology. tvws is envisioned to be inhabited by heterogeneous networks, each acting selfishly. thus, there is a need to develop autonomous coexistence etiquette capable of guaranteeing optimal qos to end-users. interference is expected to mar the qos of tvws networks. the selection of the appropriate interference estimation model is therefore critical and an important research http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):573-585. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 583 topic. similarly, handoff and spectrum mobility issues for a cognitive radio in respect of tvws technology is an important research topic. when a mobile node is moving out of the coverage area of one provider, the best handover mechanism and information exchange to be used by different operators need to be investigated. in addition, high-precision tvws spectrum sensing is an important research topic. this is because utilization of tv bands through dynamic spectrum access is largely rely on the ability of the tvws devices to optimally sense the spectrum bands and successfully detect tvws. this requires tvws device to detect weak signals (-114 dbm for 6 mhz us channels and −120 dbm for 8 mhz uk channels) much lower than thermal noise which is quite challenging (xing, et al., 2013). a tvws device is expected to be capable of dynamically changing their operating spectrum through software define radio paradigm to access the best available spectrum. this requires adaptive and flexible reconfigurable hardware and software design to accommodate several performance factors such as received power, frequency range, antenna gain, transmitter frequency band and modulation. it is envisaged that tvws device that employs mimo technology can significantly enhance receiver sensitivity and other key wireless communications parameters such as transmit power and coverage. some of the open issue that needs to be exploited in the application of mimo technology to tvws devices include optimal use of mimo antenna and estimation and control of aggregate interference from multiple cognitive radio equipment (mustapha, 2016). 4.0 conclusions in this paper, tvws technology is shown to be a reliable and affordable wireless communications resource capable of mitigating the current spectrum crunch in the wireless system technology. the technology has the potential to improve the economics of deploying wireless communications services in underserved communities in both isolated rural and urban areas in africa. we have demonstrated the great potentials for leveraging tvws technology to provide reliable and affordable wireless communication services in africa where abundant unused tv broadcasting spectrum exist. the overview of the current industrial trends in wireless communications indicate that tvws technology is evolving from merely theoretical approach to a practical realization as demonstrated by few tvws trials implemented in some african countries. we have also highlighted the intensive efforts toward standardization and commercialization of tv white space devices. references adediran, ya., kolade, o., faruk, n., surajudeen-bakinde, n., ayeni, aa. and bello, ow. 2014. tv white space in nigeria in uhf band: geo-spatial approach. 6th ieee international conference held on adaptive science and technology (icast), 22-24 august 2018, accra, ghana. akyildiz, if., lee, wy., vuran, mc. and mohanty, dj. 2006. next generation and dynamic spectrum access and cognitive radio wireless networks: a survey. computer networks, 50: 2127-2159. atimati, e., ezema, l., ezeh, g., iwuchukwu, u. and agubor, ca. 2016. survey on the availability of tv white spaces in eastern nigeria (fut owerri, as case study). international journal of scientific and engineering research, 6(12): 609-614. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mustapha, et al.: a review of tv white space technology and its deployments in africa. azojete, 15(3):573-585. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 584 chavez, a., littman-quinn, r., ndlovu, k. and kovarik, cl. 2016. using tv white space spectrum to practise telemedicine: a promising technology to enhance broadband internet connectivity within healthcare facilities in rural regions of developing countries. journal of telemedicine and telecare, 22: 260-263. chen, hs., gao, w. and daut, dg. 2007. spectrum sensing using cyclostationary properties and application to ieee 802.22 wran. ieee global telecommunications conference, 26-30 november, 2007, washington, dc, usa, pp. 3133-3138. chiang, ri., rowe, gb. and sowerby, kw. 2007. a quantitative analysis of spectral occupancy measurements for cognitive radio. 2007 ieee 65th vehicular technology conference-vtc2007spring apr 22-25, 2007, dublin, ireland, pp. 3016-3020. elshafie, h., fisal, n., abbas, m., hassan, wa., mohamad, h., ramli, n., jayavalan, s. and zubair, s. 2014. a survey of cognitive radio and tv white spaces in malaysia. transactions on emerging telecommunications technologies, 26(6): 975-991. gbenga-ilori, ao. and sanusi, oi. 2014. maximizing tv white space in nigeria using an optimized sfn and k-sfn network design. international journal of science, environment and technology, 3(4): 1489-1501. itu, ict. 2016. facts and figures 2016. https://scholar.google.com/scholar?hl=en&as_sdt=0%2c5&q=itu%2c+ict.+2016.+facts+and+ figures&btng= islam, mh., koh, cl., oh, sw., qing, x., lai, yy., wang, c., liang, yc., toh, be., chin, f. and tan, gl. 2008. spectrum survey in singapore: occupancy measurements and analyses. 3rd international conference on cognitive radio oriented wireless networks and communications (crowncom 2008), may 15, 2008, singapore, pp. 1-7. kennedy, r., george, k., vitalice, o. and okello-odongo, w. 2015. tv white spaces in africa: trials and role in improving broadband access in africa. africon 2015 september, 14: 1-5. lopez-benitez, m., umbert, a. and casadevall, f. 2009. evaluation of spectrum occupancy in spain for cognitive radio applications. vtc spring 2009. ieee 69th vehicular technology conference, april 26, 2009, pp. 1-5. louis, dk., hanson, i. and masonta, mt. 2016. tv white space usage in education: an overview of gtuc tv white space network in accra, ghana. 2016 ieee ist-africa week conference, 11 may, 2016, pp. 1-11. lysko, aa., masonta, mt., mofolo, m r., mfupe, l., montsi, l., johnson, dl., mekuria, f., ngwenya, d. w., ntlatlapa, ns. and hart, a. 2014. first large tv white spaces trial in south africa: a brief overview. 2014 6th international congress on ultra modern telecommunications and control systems and workshops (icumt), october 6-8, 2014, st. petersburg, pp. 407-414. masonta, mt., ramoroka, tm. and lysko, aa. 2015. using tv white spaces and e-learning in south african rural schools. 2015 ieee ist-africa conference, 06 08 may 2015, lilongwe, malawi, pp. 1-12. mitola, j. 2000. cognitive radio: an integrated agent architecture for software defined radio. ph.d. dissertation, kth royal institute of technology, stock-holm, sweden, pp. 115-179. mureu, ew., kihato, pk. and langat, pk. 2016. the potential of tvws technology in the provision of broadband internet in kenya. proceedings of sustainable research and innovation conference 27 july, 2016, kenya, pp. 318-322. mustapha, i., ali, bm., rasid, mfa., sali, a. and mohamad, h. 2015. a weighted hard combination scheme for cooperative spectrum sensing in cognitive radio sensor networks. 2015 ieee 12th https://scholar.google.com/scholar?hl=en&as_sdt=0%2c5&q=itu%2c+ict.+2016.+facts+and+figures&btng= https://scholar.google.com/scholar?hl=en&as_sdt=0%2c5&q=itu%2c+ict.+2016.+facts+and+figures&btng= http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):573-585. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mustib@unimaid.edu.ng 585 malaysia international conference on communications (micc), 23-25 nov. 2015, kuching, sarawak, pp. 12-17. mustapha, i. 2016. a reinforcement learning-based energy-efficient spectrum-aware clustering algorithm for cognitive radio wireless sensor network. ph.d. dissertation, universiti putra malaysia, selangor, malaysia, pp. 78-112. mustapha, i., ali, bm., sali, a., rasid, m. and mohamad, h. 2016. an energy efficient reinforcement learning based cooperative channel sensing for cognitive radio sensor networks. pervasive and mobile computing, 35: 165-184. nekovee, m. 2009. a survey of cognitive radio access to tv white spaces. international conference on ultra modern telecommunications and workshops, icumt'09, october 12, 2009., petersburg, russia, pp. 1-6. opawoye, i., faruk, n., bello, o. and ayeni, a. 2015. recent trends on tv white space deployments in africa. nigerian journal of technology, 34: 556-563. patil, k., prasad, r. and skouby, k. 2011. a survey of worldwide spectrum occupancy measurement campaigns for cognitive radio. 2011 international conference on devices and communications (icdecom), mesra, february 24, 2011 pp. 1-5. roberts, s., garnett, p. and chandra, r. 2015. connecting africa using the tv white spaces: from research to real world deployments. local and metropolitan area networks (lanman), 2015 ieee international workshop on local and metropolitan area networks, pp. 1-6. ieee, 2015. saeed, ra. and shellhammer, sj. 2011. tv white space spectrum technologies: regulations, standards, and applications, crc press, boca raton, fl, usa, pp. 283-302. salami, g., durowoju, o., attar, a., holland, o., tafazolli, r. and aghvami, h. 2011. a comparison between the centralized and distributed approaches for spectrum management. ieee communications surveys and tutorials, 13(2): 274-290. tandra, r. and sahai, a. 2008. snr walls for signal detection. selected topics in signal processing, ieee journal of selected topics in signal processing, 2(1): 4-17. valenta, v., marsalek, r., baudoin, g., villegas, m., suarez, m. and robert, f. 2010. survey on spectrum utilization in europe: measurements, analyses and observations. 2010 proceedings of the fifth international conference on cognitive radio oriented wireless networks and communications, cannes, june, 2010, pp. 1-5. van de beek, j., riihijarvi, j., achtzehn, a. and mahonen, p. 2012. tv white space in europe. ieee transactions on mobile computing, 11(2): 178-188. wellens, m., wu, j. and mahonen, p. 2007. evaluation of spectrum occupancy in indoor and outdoor scenario in the context of cognitive radio. cognitive radio oriented wireless networks and communications (crowncom), orlando, florida, usa, 1-3august, 2007, pp. 420427. xing, x., jing, t., cheng, w., huo, y. and cheng, x. (2013). spectrum prediction in cognitive radio networks. ieee wireless communications, 20(2): 90-96. yucek, t. and arslan, h. 2009. a survey of spectrum sensing algorithms for cognitive radio applications. ieee communications surveys and tutorials, 11(1): 116-130. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3):560-572 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 560 original research article development of hydropower turbines powered by dam overflow o. o. oyebode1* and j. o. olaoye2 (1department of food, agricultural and biological engineering, kwara state university, malete, kwara state, nigeria 2department of agricultural and biosystems engineering, university of ilorin, ilorin, kwara state, nigeria) * corresponding author’s email address: oyebodeoyetayo@yahoo.com article information submitted 27 july, 2018 revised 28 february, 2019 accepted 7 march, 2019 keywords: power generation hydropower pelton wheel turbine cross flow turbine abstract the epileptic power supply in most rural areas in nigeria and its attendant negative impact on the economy of the nation, agricultural productivity and huge rural emigration, is a serious source of concern. this necessitated the development of two hydro-power turbines powered by the overflow (which was rather considered a waste) from university of ilorin (unilorin) dam. a portion of the overflow was channeled into a polyvinyl chloride (pvc) pipe and the flow rate was calculated to be 0.017m3/sec using the bucket method. the change in elevation between the overflow and the point of usage was reported to be 4m. the flow (q) and head (h) were typical values for many streams and rivers in different rural areas of nigeria, hence its suitability and adoption for this study. two turbines viz: pelton wheel (pw) and cross flow (cf) were developed and tested. the pw generated a speed of 538.4rpm and a torque of 46.2knm at off load condition while the cf generated a speed of 330.1rpm and a torque of 39.07knm at the same condition. during loading – when the alternator had been connected to the turbine the pw turbine speed and torque became 392.0rpm and 36.5knm respectively, while that of the cf became 197.7rpm and 25.0knm respectively. a belt and pulley mechanism was used to deliver the rotational speed to the alternator and this increased the alternator speed from the pw and cf turbines to 1768.6rpm and 879.24rpm respectively. the speed from the pw was enough to power the alternator as the alternator only requires 1500rpm to function optimally. the pw was thus adjudged the most suitable for use. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the use of renewable energy is not new and its impact on world’s energy economy is significant. the six renewable sources of energy used most often include hydropower, solar energy, biomass, wind energy, geothermal and tidal wave or ocean energy. hydropower is however the most often used of the renewable energy sources that generate electricity. it is one of the oldest sources of energy and was used thousands of years ago to turn paddle wheels for purposes such as grinding grain and water lifting. hydropower plants use the motion of water from sources such as the ocean, rivers and waterfalls to move vane-like blades in a turbine which turns a shaft connected to a generator. the generator has a powerful electromagnet (a rotor) which is turned inside a coil of copper bars (a starter). this produces an electromotive force or the process of exciting electrons to jump from atom to atom. when electrons flow along a wire or any other conductor, jumping from atom to atom, they create an electric current or a flow of electricity. mailto:oyebodeoyetayo@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):560-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 561 the estimated long-term power demand of nigeria was 25gw for the year 2010 to sustain industrial growth (okpanefe and owolabi, 2001). according to ezennaya et al. (2014), this demand is said to be expected to increase geometrically to about 88gw by the year 2020. considering the current installed capacity of less than 10gw, out of which less than 4gw is the actual reliable output, there is an acute energy deficit in the country. now, thermal plants provide 61%, while hydropower generation is about 31% (olivia, 2008). although the overall potential of hydropower generation of nigeria was estimated to be in excess of 11gw, less than 3gw has been harnessed (zarma, 2006; aliyu and elegba, 1990). utilizing the abundant hydro power resources could be a way of reducing the huge energy deficit nigeria is currently facing. the first hydropower supply station in nigeria is at kainji on the river niger for which the installed capacity is 836mw with provisions for expansion to 1156 mw. a second hydropower station on the niger is located at jebba with an installed capacity of 540 mw. an estimate (aliyu and elegba, 1990) for rivers kaduna, benue and cross river (at shiroro, makurdi and ikom, respectively) put their total capacity at about 4,650 mw. estimates for the rivers on the mambila plateau are put at 2,330mw. the foregoing assessment is for large hydro schemes which have predominantly been the class of schemes in use prior to the oil crisis of 1973. since that time, however, many developed and developing countries have opted for small scale hydropower with appreciable savings made over the otherwise alternative of crude oil. it should be noted that hydropower plants that supply electrical energy between the range of 15kw to 15mw are minihydro while those supplying below 15kw are normally referred to as micro-hydro plants (sambo and taylor, 1990). indeed, small scale (both micro and mini) hydropower systems possess so many advantages over large hydro systems, and these include ease of setting up, low maintenance requirement, less skilled operators required, and the problems of topography is minimal. in effect, small hydropower systems can be set up in all parts of the country so that the potential energy in the large network of rivers can be tapped and converted to electrical energy. in this way the nation's rural electrification projects can be greatly enhanced. hydropower has been regarded as the ideal fuel for electricity generation because, unlike the non-renewable fuels used to generate electricity, it is almost free, there are no waste products, and hydropower does not pollute the water or the air. however, it is criticized because it does change the environment by affecting natural habitats and large hydropower schemes have been seen as a weapon of mass destruction in case of failure or attack during war (eia, 2004). development of micro hydropower from the overflow from unilorin dam could be easily adapted for use in most rural areas because it has a flow (q) and head (h) that most small rivers and streams in most rural areas can produce all-year-round. small rivers and streams exist within many rural areas in nigeria, and most of them maintain a minimum flow all year round (aliyu and elegba, 1990). these streams and rivers can be used to develop hydroelectric energy for rural agriculture. studies by aliyu and elegba (1990) further confirmed the great potential of small hydropower to improve on the energy deficits experienced in rural households in nigeria. the objectives of this research were to assess the hydropower potential of the overflow from unilorin dam, design, fabricate and test small hydro turbines for generation of electric power from the dam overflow. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com oyebode and olaoye, development of hydropower turbines powered by dam overflow. azojete, 15(3):560-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 562 2. materials and method 2.1 description of the machine the machine was made up of the turbine (cross flow or pelton wheel), nozzle, chamber, alternator, pulley, bearing, shaft, adjuster, cover, frame. figures 1 and 2 show the component parts of the cross flow and pelton wheel turbines respectively. figure 1: the cross flow turbine figure 2: the pelton wheel turbine 2.2. design criteria figure 3 shows the pictorial view of the university of ilorin (unilorin) dam. the dam was commissioned in 2007 primarily for water supply. it is located on the oyun river. the dam is a zoned earth-fill embankment with an ogee-shaped concrete spillway. the intake for water supply and the low lift pumping station are located on the wing wall. to decide on the hydropower potential of the dam, it is important to begin with an evaluation of the available water resource of the river. the energy potential of the scheme is directly proportional to the flow and head. to fairly select the most appropriate hydraulic equipment and estimate the dam’s hydropower potential, the water resource analysis must take into consideration the water to meet the primary responsibility of the dam. considering this, only the water from the spill way was available for use. figure 3: pictorial view of the overflow from unilorin dam 2.2.1 hydraulic head (h) in hydroelectric projects, calculations are based on the available hydraulic head which is a measurement of the difference in elevation between the water source and the turbine. according to a technical report on unilorin dam, the head was 4m. http://www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):560-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 563 2.2.2 flow rate (q) a portion of the overflow was channeled into a pvc pipe. to measure the amount of water available through the pipe, (known as the flow rate), the outlet valve attached to the end of the pipe was opened, and the amount that flowed out in 10 seconds was collected in a large bucket. once the experimental time had elapsed, the content of the bucket was measured by pouring it into a measuring cup. 2.2.3 available hydro power from the channeled overflow the theoretically available hydropower from the overflow from unilorin dam was calculated using equation (1). p = ρghqη 1000 (1) where; p is power in (kw), q is flowrate in (m3s-1), g is acceleration due to gravity which was taken as 9.8m/s2, ρ is density of water in (kg/m3) and η was the efficiency (since the power calculated is theoretical, it was taken as 100%) 2.2.4 choice of generator three main factors were used in choosing a generator for the project, namely cost, rate of rotation and available power. specialty electric generators of the scale needed for this project, though available, are far too expensive to be considered and were rejected based on their price. the chosen generator (alternator) was a second hand 12v diesel engine alternator. no other information was available, but a survey of similar brands revealed that the alternators were rated 650w and run between 1000 and 1500 rpm. since these parameters satisfy the factors considered for selection, and the test performance was satisfactory, it was selected for the project. 2.3. design of the hydropower turbine (pelton wheel) the design of the ideal pelton wheel was divided into three segments, namely calculation of ideal water jet width; calculation of the ideal diameter of the wheel and calculation of the dimensions of the runners. in the first two cases, the calculations were based on the initial characteristics, while the shape and dimensions of the runners were determined primarily by the calculated width of the water jet. 2.3.1 ideal width of the water jet the width of the water jet used is an important factor that will help to establish the physical shape of the pelton wheel runners. the width of the water jet determines the flow speed of the fluid impacting the runners and is based on the available hydraulic head. the following calculations were used to design the water jet width. *note that all calculations and assumptions used to generate the shape and dimensions of the pelton wheel were all based on those found in mhpg (1991) series. 2.3.1.1 absolute velocity of the water jet (c1) this was calculated using equation (2). (kc ranges from 0.96 to 0.98) assuming worst case, 0.96 was used. c1 = kc(2gh) 1 2 (2) where; c1 is the absolute velocity of the water jet and kc is nozzle coefficient file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com oyebode and olaoye, development of hydropower turbines powered by dam overflow. azojete, 15(3):560-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 564 2.3.1.2 optimal jet diameter (d) the optimal jet diameter was calculated using equation 3 d = 4q πc1 1 2 (3) 2.3.1.3 the ideal diameter of the pelton wheel the ideal diameter or pitch circle diameter is the width of a circle calculated from the point of impact of the water jet. the water jet impacts the runners towards the back of the scoops, so the real diameter or outside diameter will be slightly larger. the pitch circle diameter along with the width of the water jet will determine the speed of rotation and the torque on the wheel. the reason for this is that the jet width determines the speed at which the water strikes the wheel, while the larger the wheel, the larger the moment arm, but the slower its rotation. based on the chosen generator and the expected load, the pitch circle diameter will be designed to produce a minimum of 1500 rpms. (1: 5 belt transmission was used to obtain the needed 1500 rpm, thus, the required turbine speed was 300rpm). 2.3.1.4 optimal peripheral velocity (u1) this was calculated using equation (4) (ku ranges from 0.45 to 0.49) assuming worst case, 0.45 was used. u1 = ku(2gh) 1 2 (4) where ku is the coefficient after impact 2.3.1.5 pitch circle diameter (d) the pitch circle diameter was calculated using equation (5). no which is the rotational speed was taken to be 1500 rpm and transmission ratio: i which is the ratio of turbine to generator turns is taken to be 1:5). d = 60u1×i πn0 (5) 2.3.1.6 the physical dimensions of the runners the dimensions of the runners were calculated based on the width of the water jet. the following formulas were used based on mhpg (1991) standards. bucket width: b (mm): the bucket width was calculated using equation (6). b = 3.2 d (6) bucket height: h (mm): the bucket height was calculated using equation (7). h = 2.7 d (7) cavity length: h1 (mm): the cavity length was calculated using equation (8). h1 = 0.35 d (8) length to impact point h2 (mm): the length to impact point was calculated from equation (9). h2 = 1.5 d (9) bucket depth t (mm): the bucket depth was calculated from equation (10). t = 0.9 d (10) cavity width a (mm): the cavity width was calculated from equation (11). a = 1.2 d (11) offset of bucket k (mm): the offset of bucket was calculated from equation (12). k = 0.17 d (12) http://www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):560-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 565 a typical bucket showing all the calculated geometries above is shown in figure 4. figure 4: ideal dimensions of a pelton wheel. source: mhpg (1991) series 2.4 design of cross flow turbine 2.4.1 selection of the outside diameter (d1) according to renewables first (2009), the size of the outside diameter of cross flow turbines is dependent on available hydraulic head and it normally ranges from 100mm to 500mm in 50mm or 100mm steps. for very high heads (above 10m), diameters below 200mm could be used while 300mm diameter is used for heads between 2m to 5m. diameters between 400 to 500mm are used for very low head sites below 2.5m (muhammad and saeed, 2014). therefore, the rotor diameter (d1) is taken to be 300mm since the hydraulic head in this research was 4 meters. 2.4.2 other dimensions most of the construction dimensions of the crossflow turbine can be established using the outside diameter (d1) and the relationships are given by muhammad and saeed (2014). a) inner diameter (d2) the inner diameter was calculated from equation (13). d2 = 0.66d1 (13) (b) the radius of the blade (rb). the radius of the blade was calculated from equation (14). rb = 0.326 x d1 2 (14) (c) the spacing of the blades (t) was calculated from equation (16) s1 = k × d1 where k = 0.09 (15) and t = s1 sinβ1 where β1 = 30 t = k x d1 sinβ1 (16) (d) position of blades. the leading edge of the blade should be at 30 degrees to the tangent at the point of contact. the trailing edge of the blade is radial, i.e., all the trailing edges point directly to the center. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com oyebode and olaoye, development of hydropower turbines powered by dam overflow. azojete, 15(3):560-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 566 (e) position of the water jet. the water jet angle to the blade should be 16 degrees with respect to the tangent at the point of contact. a cross-section of a cross flow turbine showing all the calculated geometries above is shown in figure 5. figure 5: critical geometry of the cross-flow turbine. source: www.lightmypump.com 2.5 fabrication the fabrication of the machine involved material selection, marking out, cutting, welding of components, sand casting of the pelting wheel cups, assembling of component parts, finishing and painting. the materials used are stainless steel pipes and plates (for parts in direct contact with water), galvanized steel pipes and plates (for frames and other parts) while aluminum cast was used for molding the pelton wheel cups because of ease of forming and its relative water resistance ability. all the important views of the hydro-generator were drawn with autocad 2019. 2.6 testing of the turbines the turbines were tested by opening the control valve on the outlet pipe and left until the operation of the turbines become stable. the speed and the torque were measured using a tachometer which also doubles as a torque meter. the nob of the tachometer was placed at the punched center of the turbine and alternator shaft and the readings were recorded. the tachometer used was a contact type manufactured by fisons with model number taf – 420 – k. the output voltage was measured using a multimeter connected to the output terminals of the alternator. it was manufactured by fison with model number dt9205m. ten readings were taken each over a period of 30 minutes and the averages were found. the results were plotted on a graph using microsoft excel 2016 for a comparison between the two turbines 3. results and discussion 3.1 design results table 1 shows a summary of the hydraulic properties of the dam used and calculated geometry of the pelton wheel while table 2 shows a summary of the calculated geometry of the cross flow geometry. http://www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):560-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 567 table 1: summary table for hydraulic properties of the dam and the pelton wheel geometry. s/n parameter dimension 1. hydraulic head (hn) 4.0m 2. flow rate (q) 1.7 x 10-2 m3s-1 3. available power 667 watts 4. rotational speed (rpm) 1500 rpm 5. absolute velocity of water jet (c1) 8.50 m/s 6. optimal jet diameter (d) 51mm 7. optimal peripheral velocity 4.0m/s 8. pitch circle diameter (d) 0.26m 9. bucket width (b) 163.2mm 10. bucket height (h) 137.7mm 11. cavity length (h1) 17.5mm 12. length to impact point (h2) 76.5mm 13. bucket depth (t) 45.9mm 14. cavity width (a) 61.2mm 15. offset of bucket (k) 8.7mm table 2: summary table for the cross flow geometry s/n parameter dimension 1. rotor diameter (d1) 300mm 2. position of water jet 16 degrees 3. position of blades 30 degrees 4. inner diameter (d2) 198mm 5. radius of blade (rb) 50mm 6. spacing of blade (t) 28mm 3.2 machine fabrication figures 6 and 7 show the isometric view of the cross flow and pelton wheel turbines respectively which reveals the position of the alternator, the pulley attached to the turbine and the intermediate pulley which was fabricated for speed increment. figure 8 is the exploded view of the cross flow turbine which reveals the two adjusters, the nozzle inclined at an angle as well as the turbine assembled in the casing. figures 9 and 10 depict the orthographic views of the cross flow and pelton wheel turbines respectively which show the front, plan and end views of the machines. figures 11 and 12 show the pictorial views of the pelton wheel turbine and the cross flow turbine respectively. table 3 is the bill of engineering measurement and evaluation (beme) as at year 2014, which contains the quantity, description/specification and cost of component parts. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com oyebode and olaoye, development of hydropower turbines powered by dam overflow. azojete, 15(3):560-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 568 figure 6: isometric view of the cross flow turbine. figure 7: isometric view of the pelton wheel turbine. figure 8: exploded view of the cross flow turbine. http://www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):560-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 569 figure 9: orthographic view of the cross flow turbine. figure 10: orthographic view of the pelton wheel turbine. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com oyebode and olaoye, development of hydropower turbines powered by dam overflow. azojete, 15(3):560-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 570 figure 11: pictorial view of the pelton wheel turbine figure 12: pictorial view of the cross flow turbine table 3: bill of engineering measurement and evaluation (beme) (2014) s/n item description/specification quantity unit price ₦ amount ₦ 1. pulley 300mm 2 4000 8000 2. pulley 50mm 1 2000 2000 3. flat bearing 25mm self aligning 4 1000 4000 4. shaft 25mm 2 800 1600 5. belts c type 3 300 900 6. angle iron 2 by 2 (mild steel) 1.5 4000 6000 7. mild steel plate (2 by 4) 4mm gauge length 1 1000 1000 8. flange 150mm 2 1500 3000 9. pelton wheel cup pattern 1 8000 8000 10 pelton wheel cup 16 1000 16,000 11 stainless steel plate (4 by 4) 2mm gauge length 1 12,000 12,000 12 cross flow turbine 1 6000 6000 13 nozzle 100mm by 50mm 1 2000 2000 14 electrode stainless 24 100 2400 15 electrode mild steel 4 dozens 100 400 16 transportation 5000 17 workmanship 30,000 total 108,300 18 plumbing work 30,300 sub total 138,600 over head @ 10% 13,860 grand total 152,460 http://www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):560-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 571 3.3. machine testing and performance for the cross flow turbine, a maximum turbine speed of 538.4 rpm and turbine torque of 46.2 knm was achieved in off load condition, while at on-load condition, a maximum turbine speed of 392 rpm, turbine torque of 36.5 knm, alternator speed of 1768.6m rpm. similarly, a maximum turbine speed of 330.1 rpm and turbine torque of 39.1 knm was achieved in off-load condition, while at on-load condition, a maximum turbine speed of 197.7 rpm, turbine torque of 25 knm, alternator speed of 879.24 rpm. generally, for all the measured outputs, the pelton wheel turbine recorded higher values than the cross flow turbine as shown in figure 13. this is in contrast to the findings of dunavent and erwin, (1998); gass, (1998); staubli, et. al., (2001); atthanayake, (2009) which concluded that pelton wheel is not efficient at low heads and also, robert and robert, (2002); donners, et. al., (2002) reported that the most efficient turbine for low head is the crossflow turbine. this could be due to some design modifications in the pelton wheel used, such as the cup size, cup shape, groove inclusion and number of cups amidst others. to corroborate this assumption, tilahun et.al. 2017 reported that changing the length, depth, angular position (jet bucket interaction), and number of the buckets while keeping all other parameters constant could improve maximum efficiency and reduce production cost. figure 13: comparing the mean output from the two turbines * turbine speed (rpm) turbine torque (nm) alternator speed (rpm) 4. conclusion two turbines were designed, constructed and evaluated. the turbines were designed for use at the unilorin dam which has a net head of 4m, flow of 0.017m3 and a theoretical hydro energy of 668w. the two turbines were tested, and the result showed that the pelton wheel turbine gave the highest alternator speed of 1768.6rpm which exceeded the required 1500rpm needed for optimally running the alternator. this improved performance of the pelton wheel could be due to some design modifications in the pelton wheel used, such as the cup size, cup shape, groove inclusion and number of cups amidst others. the rotary motion generated also has sufficient torque that could make it adaptable for powering small farm machines like threshers, winnower, press, etc. since, the overflow from the dam was sufficient for powering the turbines, other flowing streams and rivers with similar head and flow rate could as well be able to power the developed turbines. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com oyebode and olaoye, development of hydropower turbines powered by dam overflow. azojete, 15(3):560-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodeoyetayo@yahoo.com 572 references aliyu, uo. and elegba, sb. 1990. prospects for small hydropower development for rural applications in nigeria. nigerian journal of renewable energy, 1: 74-86. donners, k., waelkens, m. and deckers, j. 2002. water mills in the area of sagalassos! a disappearing ancient technology-a natolian studies, 52: 1-17 dunavent, jc. and erwin, jr. 1998. investigation of repeated series of turbine blade profiles in cascade. national advisory committee for aeronautics, washinton, naca. tn3802. eia.2004. energy information administration, energy info card, october 2004. ezennaya, os., isaac, oe., okolie, uo. and ezeanyim, oic. 2014. analysis of nigeria’s national electricity demand forecast (2013-2030). international journal of scientific and technology research, 3(3): 333-340. gass, me., 1998. modernization and performance improvement of vertical pelton turbines, hydropower and dams, 2: 1-5 mhpg series, 1991. harnessing water power on a small scale; micro pelton turbines, skat, swiss center for appropriate technology, switzerland, 9: 9-26. muhammad, ak. and saeed, b. 2014. design and analysis of cross flow turbine for micro hydro power application using sewage water. applied sciences, engineering and technology 8(7): 821828 okpanefe, pe. and owolabi, s. 2001. small hydropower in nigeria. tcdc training workshop on small hydropower programme, ministry of power and steel, abuja, pp. 2-4. olivia, p. 2008. international electric consulting limited, nigeria: electric power sector report. renewables first (r.f.) 2009. development of cross flow turbines for very low heads. skat, swiss centre for appropriate technology, switzerland, pp. 107-113. robert, a. and robert h. 2002. the tangential impulse water wheels in california gold mining. conference proceedings, national association of mining history organization held in california, usa on 3rd march 2002, pp. 65-68. sambo, as. 2009. the place of renewable energy in the nigerian energy sector. presented at the world future council workshop on renewable energy policies, addis ababa, ethiopia, 10th october 2009. pp. 1-6. staubli, t., bissel, c. and leduc, j., 2001. jet quality and pelton efficiency, hci publications, 2nd edition, kansas city, usa. pp. 103-114 . tilahun, n., abraham, e. and edessa, d., 2017. design, modeling, and cfd analysis of a micro hydro peltonturbine runner: for the case of selected site in ethiopia. international journal of rotating machinery, 2017(1): 1-17, https://doi.org/10.1155/2017/3030217 zarma, hi. 2006. hydropower resources in nigeria. country paper presented at 2nd hydropower for today conference, international centre on hydropower, hangzhou, china. 22-25 april 2006, pp. 1-17. https://doi.org/10.1155/2017/3030217 http://www.azojete.com.ng mailto:oyebodeoyetayo@yahoo.com arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 714-724 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 714 original research article effect of moisture content variation on thermo-physical properties of brown variety tigernut (cyperus esculentus) d. d. usman1*, e. o. adanu2, b. g. jahun1 and k. ibrahim1 (1department of agricultural and bioresource engineering, abubakar tafawa balewa university, p. m. b. 0248 bauchi, nigeria. 2department of agriculture, federal college of education (technical), gombe, nigeria) * corresponding author’s email address: ddusman@atbu.edu.ng article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: tigernut thermal conductivity thermal diffusivity brown variety thermophysical properties abstract knowledge of thermophysical properties is essential to the food processing industries. the properties are useful in modeling of thermal behavior of seeds during processing operations such as frying, baking, boiling fermentation and drying. to this end, the thermo physical properties (bulk density, porosity, surface area, thermal conductivity, thermal diffusivity and specific heat capacity) of brown variety tigernut (cyperus esculentus) were investigated as a function of moisture content. in this study, thermal conductivity and specific heat capacity were determined by transient state heat transfer (line heat source) and mixture methods respectively, whereas, thermal diffusivity, bulk density, porosity and surface area were determined using formula methods. the evaluation was conducted at 5 moisture levels (20, 25, 30, 35 and 40% w.b) with 5 replications. the thermal conductivity and diffusivity increased from 0.03wm-1k-1 to 0.13wm-1k-1 and from 7.24 x 10-7m2s-1 to 11.06 x 10-7m2s-1 as the moisture content increased from 20 to 40% respectively. the specific heat increased from 10.55 jkg-1k-1 to 18.75 jkg-1k-1, while the bulk density and surface area showed an increase from 421.40 kg/m3 to 639.80 kg/m3 and from 197.26 mm2 to 413.21 mm2 as moisture content increased. however, porosity decreased in value from 61.84 to 32.33% with an increase in moisture. moisture content variation was statistically significant (p<0.05) on all properties. the obtained results will find use in the selection of suitable methods for processing of tigernut products, in a quality assessment of optimal modes of technological processes, and in the development of modern processing and handling equipment. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction knowledge of thermo-physical properties is of primary importance to the food industry. this information is required to make proper design of food processing equipment such as tanks, pumps, pipes, chillers and evaporators (de moura et al., 1998). the thermal conductivity of materials can be influenced by a number of factors such as the moisture content of the material, porosity and fiber orientation of the material (mohsenin, 1990; stroshine and hamann, 1994). several researchers including rahman (1993) and yang, et al. (2002) have emphasized the need for thermal properties of foods in general and seafood in particular. thermal properties are http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):714-724. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 715 useful in modeling thermal behavior of seeds during thermal processing operations such as drying, boiling, baking and frying (alagusundaram et al., 1991; yang et al., 2002). the primary thermal properties of food and agricultural products are specific heat capacity, thermal conductivity and thermal diffusivity. specific heat is the property needed in the estimation of the amount of energy required to change the temperature of a product, while thermal conductivity and thermal diffusivity are involved in the determination of the rate of heat transfer for efficient process and equipment design. (aviara et al., 2003). knowledge of thermo-physical properties is a basic condition for describing material’s behavior during food processing. there is, however, dearth of information on the thermo-physical properties of tiger-nut which has limited its utilization in the food industry in nigeria. tiger-nut (cyperus esculentus var. sativus), an emergent grasslike plant (figure 1) belonging to the sedge family, is a cosmopolitan perennial crop of the same genus as the papyrus plant commonly found in seasonally flooded wetlands (vilmorin, 2010). it is widely distributed in the temperate zones within south europe as its probable origin, and has become naturalized in ghana, nigeria and sierra leone (anorn, 1992). tigernut (figure 2) is one of the earliest domesticated crops and found abundantly in nigeria as either fresh, semi-dried or dried form in local markets and consumed as snacks in its uncooked form. tiger nuts are grossly underutilized due in part to paucity of information on their nutritional potential (rita, 2009). tigernut grows mainly in the middle belt and northern regions of nigeria. it is known in nigeria as‘ayaya in hausa, ‘imumu’ in yoruba and ‘akiausa’ in igbo, and three varieties (black, brown and yellow) are cultivated (osagie and eka, 1998). among these, only two varieties, yellow and brown are readily available in the market. the yellow variety is preferred over others because of its inherent properties like its large size, attractive colour and fleshier nature. the yellow variety also yields more milk, contains lower fat, higher protein and less anti-nutritional factors especially polyphenols (okafor et al., 2003; belewu and abodunrin, 2005; ebringa, 2007). the tubers contain up to 30% of non-drying oil which is used in cooking, soap making, component of beauty product, medicinally as enemas and oral medications (shaker et al., 2009; muhammad et al., 2011). figure 1: tigernut plant figure 2: tigernut tuber file:///c:/users/user/downloads/azojete143/www.azojete.com.ng usman, et al: effect of moisture content variation on thermo-physical properties of brown variety tigernut (cyperus esculentus). azojete, 15(3):714-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 716 the selected thermo-physical properties (specific heat capacity, thermal conductivity, thermal diffusivity, bulk density, porosity and surface area) for this present study are important in many problems associated with the design of machines and the analysis of the behavior of the product during agricultural process operations such as handling, planting, harvesting, threshing, cleaning, sorting and drying. solutions to problems in these processes involve knowledge of these engineering properties (irtwange, 2000; varnamkhasti et al., 2008; tavakoli et al., 2009). temperature and moisture present the most important parameters having clear relation to the character of physical, chemical and physiological processes in biological agricultural materials. physical processes, above all heat and moisture transport, affect the intensity of physiological processes, nominally of breath, germination, microorganisms progress and many others and in consequence determine the final quality of food sources. the understanding of the thermal properties of food and their responses to process conditions is necessary not only because they affect physical treatment received during processing but also because they are the commonest indicators of other properties and qualities. hence, the main objective of this study is to determine the effect of moisture content variation on the thermo-physical properties of brown variety tiger-nut. 2. material and methods 2.1 sample preparation the brown variety of tigernut used for this study was obtained at a local market in bauchi, bauchi state, nigeria. the tubers were cleaned manually to remove all foreign matters such as dirt, stones, immature and broken seeds. the initial moisture content of the samples was determined by oven drying method at 103 ºc for 48 h, as used by sacilik et al. (2003). selected samples were moistened with a calculated quantity of distilled water and conditioned to raise their moisture content to the desired different levels. equation (1) was used to calculate the quantity of distilled water used according to coskun et al. (2006). q = wi (mi−mf) 100−mf (1) where: q = mass of added water (kg), wi is the initial mass of the sample (kg), mi is the initial moisture content of the sample (%,) and mf is the final moisture content of the sample (%,). five levels of moisture contents were used for the brown variety, 20, 25, 30, 35 and 40% (w.b), which were achieved by oven drying at 72 °c (recording mc at every 15 min interval). the samples were then stored in airtight polythene and kept at 5 °c in a refrigerator for a week to achieve uniform moisture distribution within them. 2.2 determination of bulk density bulk density is the ratio of the mass of a sample of seed to total volume (shafiee et al., 2009). bulk density for all the samples were determined by filling an empty 300 ml beaker with tigernut seeds and weighing it. the weight of the seeds was obtained by deducting the weight of the empty beaker from the weight of the seed-filled beaker. to achieve uniformity in bulk density, the beaker was tapped 10 times for the seeds to consolidate in the beaker (ahmadi et al., 2009). the beaker was filled with seeds dropped from a 15 cm height and a sharp–edged, flat metal file was used to remove excess seeds to level the surface at the top of the graduated beaker (nalbandi et al., 2010). bulk density was calculated using equation (2). ρb = m/v (2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):714-724. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 717 where, ρb, bulk density, (kg/m3), m, mass of sample bulk, (kg) and v, volume occupied by seed bulk, (m3).this was replicated five times and the mean calculated for each sample. 2.3 determination of porosity the porosity (ε) values were calculated from the values of true density and bulk density using the relationship in equation (3) as reported by bup et al. (2013). porosity (ε) = (1 �� �� ) x 100 (3) where ρb, bulk density (kg m-3), ρt, true or particle density (kg m-3) 2.4 determination of surface area the surface area (sa) was determined by analogy using equations (4) and (5) as reported by balami et al. (2014). sa = ���� ��−� (4) d = (b c) 0.5 (5) where, a, major diameter (mm), b, intermediate diameter (mm), c, minor diameter, (mm) and d, geometric mean diameter, mm) 2.5 determination of specific heat capacity the method of mixtures has been the most common technique reported in the literature for measuring the specific heat of agricultural and food materials (singh and goswani, 2000; nouri jangi et al., 2011). for the determination of specific heat in this study, the method of mixtures was used. sample of brown variety tiger nut of known mass, temperature and moisture content was dropped into a copper calorimeter containing water of known mass and temperature. the calorimeter was well insulated so as to prevent heat loss to the room in which the experiment was performed. the mixture was stirred continuously using a glass rod stirrer. the equilibrium (final) temperature was noted and the specific heat determined using equation (6) as used by aviara and haque (2001). �䓨 = �e�er�i�i �ti− t݁r�� � ms � tertr −t䓨� (6) where: cc, cs and cw are the specific heats of calorimeter, sample and water, respectively (j kg-1 k-1), mc, ms and mw are the masses of calorimeter, sample and water (kg), respectively, r is the rate of temperature fall of the mixture after equilibrium (k s-1), te is the equilibrium temperature of the sample and water mixture (k), ts, and tw are the initial temperatures of sample and water, respectively (k), and t is the time taken for the sample and water mixture to come to equilibrium (s). the term tr accounts for the heat of hydration and heat exchange with the surroundings. 2.6 determination of thermal conductivity the thermal conductivity of the seeds was determined at five different moisture levels, using the transient line heat source method assembled in a thermal conductivity probe. the probe was passed through the center of the seed and a fall in temperature occurred. a fall in temperature continued until a constant temperature was obtained. a rise in temperature occurred after a file:///c:/users/user/downloads/azojete143/www.azojete.com.ng usman, et al: effect of moisture content variation on thermo-physical properties of brown variety tigernut (cyperus esculentus). azojete, 15(3):714-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 718 constant temperature period and at this point, the time was taken against the temperature. the thermal conductivity was calculated from equations (7) and (8) as reported by sadiku and bamgboye (2014): k = ��� (�2−�0)/ (�1−�0)/4� (t2−t1) (7) � q = �2� (8) where: k, thermal conductivity of sample (w/m°c), q, power dissipation by heater wire (w/m), t1, time since probe heater was energized (s), t2, time since probe heater was energized (s), t0, time correction factor (s), t1, temperature of probe thermocouple at time t1 (°c) and t2, temperature of probe thermocouple at time t2 (°c), i, electric current in a and r, electric resistance (ohm/m). 2.7 determination of thermal diffusivity the thermal diffusivity was calculated using experimental values of specific heat, thermal conductivity and bulk density using equation (9) as reported by vijay (2013). ∝ = �/�e� (9) where: α is the thermal diffusivity (m2 s-2), k is the thermal conductivity (wm-1°c-1), ρ is the bulk density (kg/m3) and cp is the specific heat (kjkg-1 °c-1) 2.8 statistical analysis the data generated were analyzed using the analysis of variance (anova) to determine which treatment effect was significant or not and tukey’s studentized range (p < 0.05) was used to determine significant difference between means using statistical analysis system (sas9.2) 2010. 3.0 results and discussion 3.1 results the values of physical and thermal properties of tigernut at varying moisture the mean values and standard deviations of bulk density, porosity, surface area, specific heat, thermal conductivity and thermal diffusivity variation with moisture content of brown variety tigernut is shown in table 1. it is observed that values of the properties increases as moisture increases for the properties with the exception of porosity, which decreases as moisture increases. table 1: thermophysical values at varying moisture content of brown variety tigernut property unit moisture content (%) 20 25 30 35 40 bulk density kg/m3 421.4d±2.61 475.2c±0.45 564.8b±1.10 620a±0.71 639.8a±1.1 0 porosity % 61.84h±3.16 52.27g±2.46 48.52f±1.83 33.47e±2.3 9 32.33e±1.2 2 surface area mm2 197.26l±28.68 211.07k±10.73 221.93k±26.9 8 298.21j±27. 24 413.21i±34. 07 specific heat capacity kjkg-1 °c-1 10.55o±0.18 12.37o±0.15 14.39n±0.17 15.92n±0.6 1 18.75m±0.4 5 thermal conductivity wm-1°c-1 0.032e±0.00 0.056d±0.00 0.081c±0.00 0.106b±0.0 0 0.133a±0.0 0 thermal diffusivity x10-8 m2 s-2 7.24g±0.13 9.45f±0.43 9.94f±0.34 10.59f±0.48 11.06f±0.36 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):714-724. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 719 values in the same row followed by different letters are significantly different (p<0.05). table 2 is the analysis of variance on the variation of moisture on the physical and thermal of brown variety tigernut. table 2: anova on variation of moisture content on thermal properties of brown tigernut source df ss ms fvalue pr > f properties (bv) 5 6020489.673 1204097.935 9922.34** < .0001 replication 4 349.557 87.389 0.72ns 0.5799 moisture content (mc) 4 93925.097 23481.274 193.5** < .0001 properties* mc 20 247091.85 12354.592 101.81** < .0001 **highly significant, ns = not significant 3.2 discussion 3.2.1 effect of moisture content on bulk density table 1 presents the variation of bulk density with moisture content for brown variety tigernut. the bulk density of brown variety tigernut increased linearly from 421.4 to 639.8 kgm-3 as moisture content increased from 20 to 40% as presented in table 2.the increase in the bulk density was due to increase in the mass of tigernut with a gain in moisture which was higher than the volumetric expansion of the bulk (pradhar et al., 2008). the effect of seed moisture content on bulk density was statistically significant (p<0.05). similar increasing bulk density with variation in moisture content was reported by baryeh and mangope (2002) for qp – 38 variety pigeon pea, kingsley et al., (2006) for dried pomegranate seeds, nikoobin et al. (2009) for chickpea seeds and oyerinde and olalusi (2013) for two varieties of tigernut. 3.2.2 effect of moisture content on porosity porosity of materials usually is dependent on the bulk as well as the true densities (oyerinde and olalusi, 2013). the porosity of the brown variety tigernut decreased from 61.84 to 32.33% as moisture content varied from 20 to 40%. similar trend was reported by oyerinde and olalusi (2013) for two variety tiger-nut. this decrease may be due to the changes in the mass and density value of the tiger-nut as it absorbed water. higher porosity at low moisture content indicates that high number of tigernut tubers can be stored at lower moisture content than at high moisture content due to an increase in the cohesion of the cell structure of the tigernut as moisture increases (abano and amoah, 2011). table 2 presents the variation of porosity with moisture content for the brown variety, and the effect of moisture on porosity was statistically significant (p< 0.05) except between 25 and 35%moisture content. 3.2.3 effect of moisture content on surface area the effect of moisture content on the surface area of the tigernut is presented in table 2. the surface area increased linearly from 197.26 to 413.21 mm2 as the moisture content varied from 20 to 40%. the values for surface area were statistically significant (p < 0.05) from 30 to 40%, however, a reverse trend was reported for black variety tigernut by abano and amoah (2011). hence, the results may be due to the different shape assumption of the tuber and this suggests that it’s advisable to store the tubers at lower moisture content when the surface area is lowest for the tuber to present less surface area for moisture absorption during storage (abano and amoah, 2011). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng usman, et al: effect of moisture content variation on thermo-physical properties of brown variety tigernut (cyperus esculentus). azojete, 15(3):714-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 720 3.2.4 effect of moisture content on specific heat capacity specific heat capacity is needed in estimating the amount of heat energy required to change the temperature of material by 1°c (sadiku and bamgboye, 2014). the specific heat capacity of brown variety tigernut increased from 10.55 to 18.75 kjkg-1 °c-1 as moisture content increased from 20 to 40% and the result (table 2) was not statistically significant (p > 0.05). similar trend was reported for parkia seeds (sadiku and bamgboye, 2014) which indicated an increase from 2.74 to 4.38 kjkg-1 °c-1 for a moisture increase of 5.9 to 28.2%. the increasing trend in specific heat capacity with moisture content correlates with work done by other researchers on cumin seeds (singh and goswani, 2000), lentil seeds (tang, et, al., 1991), potato (wang and breman, 1993) and pistachio nuts (razavi and taghizadeh, 2007), all of which shows similar trend with brown variety tigernut. the increased specific heat capacity with moisture is due to high specific heat of water compound to dry material (sadiku and bamgboye, 2014). 3.2.5 effect of moisture content on thermal conductivity thermal conductivity is the possibility of transmitting heat within seeds in bulk. hence, the thermal conductivity of brown variety tigernut increased from 0.032 to 0.133 wm-1°c-1 as moisture increased from 20 to 40%, this indicates that heat transmission within the tigernut is less when dried and more if wet (sadiku and bamgboye, 2014). the increase in thermal conductivity as moisture increased was because the increased moisture, increased the bulk thermal conductivity as moisture has higher thermal conductivity than that of air (vijay, 2013). similar results were reported for borage seed by yang et al. (2002), soya bean pod by mohsen et al. (2013), coriander seed (vijay, 2013) and three varieties of melon (isa et al., 2014). the result for thermal conductivity of brown variety tigernut is in agreement with the findings of sadiku and bamgboye (2014) for parkia seeds. the effect of moisture content on the thermal conductivity of tigernut was presented in table 1, though the moisture effect was not statistically significant (p > 0.05). the relationship between thermal conductivity and moisture content of tigernut was linear (as shown in table 1). 3.2.6 effect of moisture content on thermal diffusivity the variation of thermal diffusivity with moisture content is presented in table 2. thermal diffusivity of tigernut increased from 7.24 x 10-8 m2 s-2 to 11.06 x 10-8 m2 s-2 as the moisture content increased from 20 to 40%. the increase in thermal diffusivity at different moisture content may be due to the fact that the value of bulk density decreased at these moisture levels (singh and goswani, 2000). bamgboye and adejumo (2010) also reported similar results for roselle seeds. the results for the thermal diffusivity of brown variety tigernut is in agreement with the findings of aviara and haque (2001), that thermal diffusivity of sheanut kernel increased with moisture content, but disagreed with the findings of subramanian and viswanathan (2003), for minor millet grain and flour, singh and goswani (2000), for cumin seeds and aremu and fedele (2010), whose obtained values for doum palm fruits showed an inverse relationship with moisture content. this ascending and descending trend of relationship between moisture content and thermal diffusivity is because the magnitude of thermal diffusivity depend on the combined effect of thermal conductivity, bulk density and specific heat capacity (yang et al., 2002). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):714-724. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 721 3.2.7 analysis of variance (anova) analysis of variance (anova) was conducted to ascertain the significant effect of moisture content variation on the thermophysical properties (specific heat capacity, thermal conductivity, thermal diffusivity, bulk density, porosity and surface area) of brown variety tigernut as shown in table 2. the results of the anova showed that there were highly significant differences (f = 9922.34, p = 0.0001 < 0.05) among the values obtained for the properties of brown variety tigernut. this indicates that the values of the properties were highly influenced by moisture content. the effect of replication from the anova was not significant (f = 0.72, p = 0.599 > 0.05), this may be due to minimized error in the performance of the experiment in the laboratory. the variation in moisture content was highly significant (f = 193.5, p = 0.0001 < 0.05), this means as moisture increased, the values of thermophysical properties either increased or decreased. however, the interaction between the properties and moisture content indicate a highly significant difference (f = 101.81, p = 0.0001 < 0.05). the interaction effect shows that the relationship between tigernut properties and moisture content depends on the amount or variation of the moisture content. 4. conclusion thermophysical properties of brown variety tigernut (cyperus esculentus) were determined for the typical ranges of moisture content. the results showed the significant variations in thermophysical properties values with changing moisture content. all the properties increased as the moisture level increased, with the exception of porosity, which reduced as moisture increased. the bulk density and surface area increased from 421.40 kg/m3 to 639.80 kg/m3 and from 197.26 mm2 to 413.21 mm2 as moisture content increased. however, porosity decreased from 61.84 to 32.33% with an increase in moisture. the specific heat increased from 10.55 jkg-1k-1 to 18.75 jkg-1k-1, while the thermal conductivity and diffusivity increased from 0.03 wm-1k-1 to 0.13 wm-1k-1 and from 7.24 x 10-7m2s-1 to 11.06 x 10-7m2s-1 as the moisture content increased from 20 to 40% respectively. references abano, ee. and amoah kk. 2011. effect of moisture content on the physical properties of tiger nut (cyperus esculentus). asian j. agric res 5: 56-66. ahmadi, h., fathollahzadeh, h. and mobli, h. 2009. post-harvest physical and mechanical properties of apricot fruits, pits and kernels (c.v. sonnati salmas) cultivated in iran. pakistan journal of nutrition, 8: 264-268. alagusundaram, k., jayas, ds., muir, we. and white, ndg. 1991. thermal conductivity of bulk barley, lentils and peas. transactions of the asae, 34(4): 1784-1788. anon, a. 1992. cyperules. in: the new encyclopedia britannica, macropaedia chicago. vol. 3 (15th edn), p. 185. aremu ak. and fadele ok. 2010. moisture dependent thermal properties of doum palm fruit. journal of emerging trends in engineering and applied sciences (jeteas), i (2), 199-204. aviara na. and haque ma. 2001. moisture dependence of thermal properties of sheanut kernel. journal of food engineering, 47, 109-113. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng usman, et al: effect of moisture content variation on thermo-physical properties of brown variety tigernut (cyperus esculentus). azojete, 15(3):714-724. issn 1596-2490; 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddusman@atbu.edu.ng 724 varnamkhasti, mg., mobli, h., jafari, a., keyhani, ar., soltanabadi, mh., rafiee, s. and kheiralipour, k. 2008. some physical properties of rough rice (oryza sativa l.) grain. journal of cereal science, 47(3), 496-501. vilmorin, a. 2010. the vegetable garden. ten speed press 0 isbn 0-89815-041-8. vijay singh sharanagat. 2013. determination of thermal properties of coriander seeds and its volatile oil (coriandrum sativum). international journal of engineering research and applications. vol. 3, issue 2, pp.1767-1773. wang, n., and brennan, jg. 1993. the influence of moisture content and temperature on the specific heat of potato measured by differential scanning calorimetry (dsc). journal of food engineering, 19(3): 303-310. yang, w., sokhansanj, s., tang, j. and winter p. 2002. determination of thermal conductivity, specific heat and thermal diffusivity of borage seeds. biosystem engineering., 82, 169-176 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):147-163 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 147 original research article modification of thermal hydraulic transient models for the miniature neutron source reactor n. abubakar1, 2*, i. garba1, and m. t. jimoh1 1department of mechanical engineering, bayero university, kano, nigeria 2centre for energy research and training, ahmadu bello university, zaria, nigeria) *corresponding author’s email address: nabubakar@abu.edu.ng 1.0 introduction analysis of transient behaviour of research reactors is significantly relevant in the determination of the safety limits and margins imposed by fuel and clad melting temperatures as well as boiling temperature of the coolant (anglart, 2011; abubakar and yahaya, 2012). miniature neutron source reactor (mnsr) is a tank-in-pool reactor. the core of the reactor is immersed in the tank (reactor vessel) which is immersed in a large pool of water as shown schematically in figure 1. it uses uranium-aluminum alloy as fuel with an in-core inventory of about 1kg of 90.2% enriched uranium, thick metallic beryllium surrounding the core as reflector and light water as coolant and moderator. mnsr has a nominal power of approximately 30 kw. the heat generated by the fuel is being removed by natural convection heat transfer process from the core to the pool. under normal reactor operating conditions, it is expected that the rate of heat generation in the fuel will be the same as the rate of heat removal by the coolant. the reactor small core is designed to be compact, safe, and to maintain a stable neutron flux for neutron activation analysis which is the principal utilization of the reactor. it is also used for production of short-lived radioisotopes and for education and training (yongchun et al., 1992). article information abstract a modified miniature neutron source reactor (mnsr) model dealing with transient thermal hydraulic problem is presented. the model based on lumped parameter method is adopted in this work to numerically solve a system of coupled algebraic and differential equations governing heat transfer in mnsr, using matlab solver for variable order method in stiff differential equations and differential-algebraic equations, coupled with maple soft. the simulated results obtained from the model were generally in agreement when compared with reactor operation data recorded from 0 to 270 minutes during experiments. radiating energy of fuel and clad and heat transferred at the gap or clearance were taken in to account. fuel and clad temperatures as well as various temperatures at different sections of the reactor were predicted with the model, in addition to the effect of the installed chiller on the reactor coolant. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 september, 2019 revised 18 december, 2019 accepted 04 january, 2020 keywords: chiller coolant pool natural convection thermal hydraulic mnsr model. mailto:nabubakar@abu.edu.ng http://www.azojete.com.ng mailto:nabubakar@abu.edu.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 148 the previous simplified mnsr thermal hydraulics models described (zhang, 1993; albarhoum and mohammed, 2009; yamoah et al., 2011) did not include the fuel heat transfer process model from the fuel pellet to the clad involving expression for estimating the fuel temperature, but instead assumed an approximate value of 1°c difference between the fuel and clad temperatures and therefore neglect the difference and assume same temperature at any point and time for both fuel and clad. in addition, they did not account for the eventuality of existence of a very small non uniform space or gap between the fuel and clad (quian, 1990). these models were over simplified as this study shows that the difference in temperature could not necessarily be as assumed previously. zang, 1993 model could not take into account the eventuality of cooling some parts of the tank vessel) or the pool of the reactor by cooling coil or chiller. albarhum and mohammed (2009), and yamoah et al. (2011) models considered the effect of the cooling coil in the pool and the upper section of the reactor vessel, while all the previous models could not account for the gap resistance and fuel temperature estimation. it was assumed that at any power level attained during transients, the temperature at the fuel and cladding regions will be the same (quian, 1990; yamoah, et al., 2011) neglecting the thermal resistance expected between the pellet and the clad. because the clad is a tube in which the fuel pellet is inserted, as a result there exist a small non-uniform gap which should be accounted for. even though mnsr fuel rods are very small, it is true that that there exists a minute empty gap in the tube (saha et al., 2013). with the conversion of mnsr fuel for heu to leu, the fuel-clad gap may be wider due inclusion of an inert gas in the gap to take care of the apparent expansion of leu during operation; hence the need for this work to achieve sufficiently precise outputs. the previous models were modified using the configuration of the nigeria mnsr (nirr-1) whose nominal power is 31 kw (dim et al., 2012) and applies to structurally similar reactors, taking in to cognisance that some features in the structural design of the reactor and behavior of the power rise up time to its operational level may differ from one mnsr to another. the modification is also dependent on the reactor structure as such takes no account of reactivity insertions. radiating energies from the fuel, gap and clad are also taken into account and calculated. this work specifically considers the gap clearance which exist between the fuel pellet to predict the true representation of the fuel and clad temperatures separately and this modifies the previous mnsr models that assumed and lumped the fuel and clad temperatures as approximately the same. this paper modifies the previous mnsr thermal hydraulic models to provide a more accurate predictive tool which is necessary and important for obtaining information to ensure the safety of the reactor when making modifications (iaea, 2001). matlab software was employed to model and simulate the mnsr natural convection coolant flow which depends on the coolant density difference due to temperature changes and pressure drop in the core which depends on the fuel elements grids in the core structure. parameters studied are fuel and clad temperatures, coolant average temperatures at the core inlet, core outlet, core (bulk) and pool, and the coolant upward flow velocity in the reactor core. the model was validated by comparing with the experimental data and used to simulate and study other reactor parameters at nominal reactor power such as fuel temperature and effect of the cooling coil installed around the vessel in the reactor pool. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 149 figure 1: vertical cross-section of mnsr assembly 2. materials and methods to develop the generic mnsr thermal hydraulic model for the natural convection, the practical and theoretical data available including structural information were obtained. some required data were generated through experiments using nirr-1, and by estimations and assumptions. these data were used to develop the systems of mathematical expressions that form the model. the expressions were coupled together and solved numerically using matlab to simulate and validate the model behaviour. during the validation process, comparison of results was carried out between the simulated results and the data obtained through experiments. 2.1 reactor core coolant flow pattern in mnsr the flow pattern for the mnsr shown schematically in figure 2 depicts the natural (circulation) convection of the coolant within the core area in the vessel. the process is established with the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 150 generation of heat by fission occurring within the fuel elements in the core. the coolant moves up along the cladded walls of the fuel elements through the channels in the core and leaves it through the apertures surrounding the grids of the fuel elements to the outlet orifice, after which the coolant mixes with the water in the upper part of the vessel. cold coolant from the bottom replaces the hot one leaving the core by siphoning effect causing the coolant in the down-comer (side of beryllium annulus) to move downwards at a maintained temperature and enters the reactor core at the inlet orifice (wuqin, 1997). figure 2: sketch of natural circulation coolant flow pattern in mnsr 2.2 fuel element model the mnsr fuel element is depicted in figure 3 with dimensions in mm. the labels are described as: 1. top end plug (al alloy); 2. gap between fuel meat and clad; 3. clad (al alloy); 4. fuel pellet (u-al alloy); 5. lower end plug (al alloy). the core of mnsr contains 350 fuel elements lattices or positions, and some of few positions are filled with dummy fuel elements. the number of dummies differ from one mnsr to another. nirr-1 core has 347 fueled elements and 3 dummies which are distributed evenly in the core. the model in figure 4 shows the structure of the fuel element with the gap in-between the pellet and clad where rc is the clad radius from the fuel centre line, rf is the fuel pellet radius, and d is the gap width. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 151 figure 3: mnsr fuel element diagram figure 4: mnsr fuel element model heat is transferred through the fuel pellet to its surface with the gap by conduction, then through the gap to the inner surface of the clad by radiation since the gap does not contain any fluid, then pass through the clad to the outer clad surface by conduction and then to the coolant by convection and radiation at the clad surface. in a simplified lumped parameter formulation (kazeminejad, 2008), for cylindrical fuel elements immersed in a coolant given the assumptions that there is azimuthally uniform fuel to clad conductance; there is no azimuthal variation of fuel heat generation; there is uniform clad to coolant heat transfer; and no axial heat flow along the fuel element. eq. (1) and (2) are the partial differential equations for the diffusion of heat within each fuel element in the reactor core region in time domain were reduced to eq. (3) and (4) are the required boundary conditions. for fuel region; cpfρf ∂tf ∂t r, t = 1 r ∂ ∂r kfmr ∂tf ∂r r, t + qv(r, t) (1) and for the cladding region, it is expressed in the form; cpcρc ∂tc ∂t r, t = 1 r ∂ ∂r kcr ∂tc ∂r r, t (2) the required boundary conditions may be reduced to eq. (3) and (4); kc ∂tc ∂r r, t r = rc = h (tc − tf) (3) kfmr ∂tf ∂r r, t t = tfm = kc ∂tc ∂r r, t r = rfm (4) where: cpf is heat capacity for the fuel element, cpc is heat capacity for the cladding, kfm is thermal conductivity of fuel meat, kc is thermal conductivity of cladding, tc is clad surface temperature, tf is fuel pellet surface temperature, qv is the volumetric heat generation rate, rf is the fuel pellet radius, rc is the clad radius, and tf and tc are the fuel and clad average temperatures respectively. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 152 2.3 modified thermal hydraulic model considering the heat transfer process in the reactor fuel element from the fuel pellet through the gap to the clad based on the afore mentioned assumptions and average temperatures of the fuel and clad, eq. (1) and (2) with the conditions in eq. (3) and (4) can be simplified to yield 1st order ordinary differential equations (5) and (6). cf dtf dt = q1 af − tf−tc rf −qrg (5) cc dtc dt = (tf− tc) rf − tc−tb rc − qrc (6) where; cf = πrf 2cpfρf (7) cc = 2πrc(rc − rf)cpcρc (8) rf = 1 4πkf (9) rc = 1 2πrch (10) qrg = σ εf εc εf+εc−εfεc tf 4−tc4 (tf−tc) (11) qrc = σac tc4 − tb 4 (12) h = k dh n(gr pr)m (13) where: cf is the thermal capacity of fuel pellet (w/mk), cc is the thermal capacity of clad (j/mk), rf and rc are the resistances between fuel pellet and gap, and between clad and coolant respectively (mk/w), h is the heat transfer coefficient for natural convection in fuel rod bundles (w/m2k), q1 is the reactor power (w), af is the average cross section of the fuel (m2), ac is the clad surface cross-section, εf and εc are the fuel and clad surfaces emissivity, qrg is the rate of heat transferred at gap by radiation (w), qrc is the rate of heat transferred from clad surface by radiation (w), σ = 5.67 × 10−8w/m2k4 (stefan-boltzmann constant), k is the thermal conductivity of the coolant (light water), dh is the hydraulic diameter or equivalent length (m), and gr and pr are grashof’s and prandtle’s numbers respectively. the constants n and m for mnsr have been determined (zhang, 1993, wuqin, 1997) where; n = 0.68, m = 1/4, for gr. pr < 6 × 106 (laminar flow) n = 0.174, m = 1/3, for gr. pr ≥ 6 × 106 (turbulent flow) (14) the heat transfer and exchange in the core, from the fuel element clad to the core coolant and the pool is obtained by conservation of momentum and energy balance based on the average flow velocities and temperatures in the various regions and heat is supposed to transfer only radially. the lumped parameter method is most suitable for this type of transients. for mnsr diagram presented in figure 5 and having a coolant flow pattern as depicted in figure 6, the reactor is segmented in to regions as follows: r1 is the fuel elements region in core, r2 is the reflector, r3 is the reactor vessel region above the core, r4 is the bottom reflector region, r5 is the reflector shim (tray) region, r6 is the down-comer region between the side reflector and vessel wall where the downward movement of the coolant occurs due buoyancy in the circulation process and r7 is the reactor pool. the governing equations of heat transfer process as shown in figure 6 for the entire reactor system can be written as follows: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 153 hcpbρb dtb dt = ac af hc tc − tb − cpbubρb t2 − t1 − q2 (15) 2(h + h1) ρb dub dt = gh ρ1 − ρb + gh1 ρ1 − ρ2 − ∆p (16) m1cp dt1 dt = adccpudcρ3 t3 − t1 + q2 − q2b − q3 (17) t2 = 2tb − t1 (18) m3cp dt3 dt = afcpubρb t2 − t1 − adccpρbudc t3 − t1 − q4 −q6 (19) m4cp dt4 dt = q2b − q5 (20) m5cp dt5 dt = q5 − q35 − q9 (21) m6cp dt6 dt = q3 − q34 − q35 −q8 (22) m7cp dt7 dt = q4 + q34 − q7 (23) where: h (m) is the reactor core height, h1 (m) is the coolant height above the core, cp is the average specific heat of coolant (j/kg k), ρ is the coolant average densities (kg/m3), u is coolant averages velocity (m/s), g is the acceleration due to gravity (m/s2), t denotes average temperatures (°c) depending on regions, δp is the pressure drop across the core, a is the cross sectional area, m is coolant mass (kg) and q denotes heat transfers (w/m2k) defined by eq. (29) to (35). the subscripts c refers to clad; b refers to bulk coolant in the core; dc refers to down comer; and the numbers refer to the various positions shown in figure 6. δp is defined by eq. (24) with the friction factor given in eq. (25) as a function of the reynold’s number (re) which is also defined in eq. (26) and µ is the coolant average viscosity (ns/m2). the frictional drag coefficient (ξ) for flow in the coolant channel is in the form given in eq. (27) which considers the core grid plate (albarhoum and mohammed, 2009) with ‘a’ denoting a geometric factor with average value of 0.45, and d1 and d2 denoting the equivalent diameter of the coolant sub-channels below and above the grid plate respectively. eq. (28) expresses the coolant flow velocity at the down comer. ∆p = fh 2dh + ξ 2 ρbub 2 (24) f = 64 re (25) re = ρbubdh μb (26) ξ = a 1 − d2 d1 2 (27) udc = ρ2ubac adcρ1 (28) in figure 6, q1 is the reactor power, q2 is the rate of heat transferred from the coolant in the reactor core to the annulus beryllium reflector by convection through the reflector by conduction to the coolant in the middle of the vessel by convection, q3 is the rate of heat transferred from the middle of the vessel to the middle of the pool, q4 is the rate of heat transferred from the upper part of the vessel to the upper part of the pool, q5 refers to the rate of heat transferred from the lower part of the vessel to the lower part of the pool, q2b is the rate of heat transferred from the upper part to the middle of the vessel, q34 is the rate of heat file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 154 transferred from the upper part to the middle of the pool and q35 is the rate of heat transferred from the middle part to the lower of the pool. q6 is the rate of heat transferred to the chiller which absorbs heat through the coiled pipe wound at the upper part of the reactor vessel in the pool, q7 is the rate of heat transferred from the upper part of the pool to the pool wall, q8 is the rate of heat transferred from the middle of the pool to the pool wall and q9 is the rate of heat transferred from the lower part of the pool to the pool wall. q6 is described as the chiller (cooling coil) power in (w). q2= a2h2 tb − t2 (29) q3= a6h6 t1 − t6 (30) q4= a7h7 t3 − t7 (31) q5= a5h5 t4 − t5 (32) q2b= a2bh2b t3 − t1 (33) q34= a34h34 t6 − t7 (34) q35= a35h35 t6 − t5 (35) the time for linear power rise from zero to the selected value termed as reactor power establishment time (rpet) of nirr-1 is not less than 300 seconds and is estimated experimentally in this work. eq. (36) described the function that relate rising reactor power (rp) and rpet. q1 t = rp rpet t,for t 0 ≤ t ≤ rpet and q1 t = rp, for t ≥ rpet (36) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 155 reactor core figure 5: mnsr diagram file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 156 coolant flow directions heat transfer directions figure 6: mnsr thermal hydraulic model for natural convection the lumped perimeter model formulated in this review constitutes the solution of the transient thermal hydraulic heat transfer problem of the mnsr. in this model, transient behaviour of the reactor is observed by the variations of eleven essential parameters involved; namely: tf, tc, tb, t1, t2, t3, t4, t5, t6, t7, and ub. where t3, t4, t5 and t6 denote the temperatures at the various r5 r4 r1 q1 q4 q2b q5 q3 q9 q2 q8 q7 q6 vessel (tank) pool q35 r7 q34 t6 t1 t5 t4 t2 tb r2 r6 t7 t3 r3 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 157 regions as shown in the figure 6, t7 denotes the average pool temperature, while ub is denotes the coolant flow velocity. the system of equations from eq. (5) to (35) were coupled together and solved numerically using matlab solver for variable order method in stiff differential equations and differential-algebraic equations (shampine, et al., 1999, endre, 2014), coupled with maplesoft software. 3. results and discussion nirr-1 was nominally operated at 31 kw for about six hours without chiller which gives the data recorded in table 1. the reactor power begun to decline at about four and half hours of operation and the reactor was then shutdown. the operation of the reactor was also carried out with the chiller being operated as recorded in table 2 and the reactor was shut down just before the reactor begun to decline. the core average temperature tb presented in the tables referred to the coolant bulk temperature in the core and is computed using eq. (18). the chiller installed capacity for nirr-1 is 4000 kcal/hr. which is equivalent to about 5000 w. from the experimental data, the rpet necessary for the power to reach its steady operational level was measured to be about 300s from the reactor startup. the core inlet and outlet as well as the pool temperatures were measured using the monitoring and control systems. there is limited instrumentation available to measure other important parameters. these parameters can only be estimated by simulation. table 1: reactor core thermal hydraulics parameters recorded during operation at 31 kw without chiller time (s) inlet temperature, t1 (oc) outlet temperature, t2 (oc) core average temperature, tb (oc) pool temperature, t7 (oc) 0 23.00 23.40 23.20 25.50 720 24.30 41.60 32.95 25.50 1440 26.70 47.00 36.85 25.50 2160 29.70 49.50 39.60 25.70 2880 31.80 48.00 39.90 26.00 3600 32.90 52.30 42.60 26.10 4320 33.80 52.80 43.30 26.30 5040 34.40 53.60 44.00 26.60 5760 34.00 54.20 44.10 26.60 6480 34.30 54.70 44.50 26.80 7200 35.90 54.30 45.10 27.00 7920 36.20 55.20 45.70 27.30 8640 36.30 55.40 45.85 27.40 9360 36.70 55.70 46.20 27.50 10080 36.00 55.80 45.90 27.80 10800 36.50 56.00 46.25 28.10 11520 36.50 56.20 46.35 28.20 12240 36.70 55.10 45.90 28.40 12960 36.70 56.80 46.75 28.50 13680 36.80 56.60 46.70 28.80 14400 36.70 56.50 46.60 28.90 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 158 15120 37.50 57.00 47.25 29.20 15840 37.40 56.90 47.15 29.20 16560 37.40 57.00 47.20 29.40 17280 36.00 56.80 46.40 29.40 18000 33.90 36.70 35.30 29.70 18720 31.40 33.80 32.60 29.70 19440 29.70 32.00 30.85 29.80 20160 28.90 30.80 29.85 30.00 20520 28.40 30.60 29.50 30.00 table 2: reactor core thermal hydraulics parameters recorded during operation at 31 kw with chiller time (s) inlet temperature, t1 (oc) outlet temperature, t2 (oc) core average temperature, tb (oc) pool temperature, t7 (oc) 0 24.40 26.63 25.51 25.70 300 24.81 45.18 34.99 25.71 1200 27.10 47.31 37.20 25.71 2400 30.44 50.19 40.31 25.71 3600 32.74 52.32 42.53 25.73 4800 34.48 53.80 44.14 26.33 6000 35.38 53.90 44.64 26.34 7200 35.37 54.95 45.16 26.39 8400 36.10 55.40 45.75 26.52 9600 36.69 55.96 46.32 26.71 10800 36.60 55.80 46.20 26.76 12000 36.26 56.08 46.17 26.88 13200 37.30 56.80 47.05 27.07 14400 36.90 55.50 46.20 27.32 15600 37.10 57.20 47.15 27.60 16800 37.90 57.20 47.55 28.27 the system of equations formulated in describing the model used in this work was solved to produce the simulated time behaviour of the reactor parameters. t1, t2, tb, t7, tf, tc and ub are the most important thermal hydraulic parameters of interest in the mnsr (dim et al., 2012). the simulation outputs produced were tested by comparing the results to the experimental data to validate the model. in figures 7, 8, 9 and 10, the inlet, outlet, bulk (core average) and pool temperatures from table 1 are compared with the simulation outputs for t1, t2, tb, and t7 respectively. these were computed at the instance when q6, q7, q8 and q9 are equal to zero. this means that the chiller power was zero, thus, there was no heat exchange between the coolant and cooling coil. therefore, the heat transferred from the core was only sunk in the pool. figure 11 illustrates the simulated behaviours for tf and tc at 31 kw without applying the chiller. at reactor startup, tf and tc had the same initial condition and begun to separate at about 40 oc in few seconds (figure 11) and maintained a maximum difference in-between of about 3 oc. this difference aroused from the tiny gap (clearance) between fuel pellets and clad which http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 159 accumulates gases like xenon which could produce some resistance to heat transfer during operation. ub was raised from in initial value (table 3) to a maximum of about 0.012 m/s after few seconds from the reactor startup and was maintained until the reactor was shut down. the transient behaviours in figures 7 and 11 has exhibited identical pattern by falling at about 4 hours 30 minutes in both experimental and simulated results. the fall in temperatures observed during operation can be largely attributed to the rising temperature effect which slows down the fission reaction in the fuel (doppler effect). this makes the reactor power to also fall (albarhoum and mohammed, 2009, anglart, 2011, abubakar and yahaya, 2012). the rpet was also observed to be 300s from reactor start-up to the pre-set value of 31 kw during the simulations. it can be noticed in figures 7, 8, 9 and 10 that good agreement is achieved between the model predictions and the experimental results. the sharp fall of the temperatures in the experimental data as plotted against the simulation outputs were due to the deliberate reactor shutdown. it can be observed that both experimental and simulated t1 begun to decline at the same time in figure 7. the behaviour exhibited by the model follows the same trends as plotted with the experimental data up to the maximum time of about 16,700s (5 hrs.) known for steady stable mnsr operation. in figures 7, 8, 9 and 10, the average difference or error between recorded data and simulated result is 3%. based on the aforementioned agreements between the experimental and simulation outputs, the model was used to simulate tf, tc, ub and the influence of the chiller at different power levels. the influence of varying the chiller (cooling coil) power q6, on various temperatures in the reactor was analysed at different cooling coil powers. the position of the cooling coil is shown in figure 5 and its rate of heat transfer is represented by q6 in figure 6. table 2 shows the record obtained when the chiller was operated during reactor operation. the results recorded showed no significant difference in values with or without chiller except in the pool average temperature which was noticed to have reduced by about 1oc. table 3 shows the variation of reactor transient thermal hydraulic parameters at various chiller powers. it is noticed that the installation of cooling coil of the chiller system at the at the upper part of the reactor pool (present position) would have no advantage on the core cooling. table 3: computed thermal hydraulic parameters at different chiller powers (this work) parameter minimum (initial) values at 0.0 s maximum average values computed at (270 minutes) 16200 s maximum average values when the chiller cooling coil is position at the core area at (270 minutes) 16200 s tf (oc) 24.57 65.68 65.62 65.56 65.44 65.22 63.90 tc (oc) 24.57 63.22 63.16 63.09 62.97 62.76 60.87 tb (oc) 23.20 47.64 47.56 47.49 47.34 47.05 45.55 t1 (oc) 23.00 36.84 36.79 36.75 36.66 36.48 34.24 t2 (oc) 23.40 58.44 58.33 58.23 58.02 57.62 56.86 t7 (oc) 24.57 29.20 25.67 25.66 25.63 25.58 25.72 ub (m/s) 0.0100 0.0118 0.0118 0.0118 0.0118 0.0118 0.01178 chiller power, q6 (kw) 0.0 30 60 120 240 installed power (5 kw) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 160 comparing tables 1 and 2, when the chiller was operated at the installed capacity of 5000 w, only the pool temperature was slightly affected by reduction at a magnitude of about 2 oc. table 3 gives the summary of the simulation outputs computed by adjusting the chiller power from 0 to 240 kw at 30 kw interval. an insignificant decrease was noticed at all maximum values of the reactor thermal hydraulic parameters with increase in the chiller power, except for the pool temperature which notably shows a reduction from 29.20 oc to 25.67 oc at 30 kw (a difference of about 4oc). if increase in the chiller power (up to about four times the reactor power) is compared with the decrease in the maximum temperature values recorded, the effect of the cooling coil is relatively insignificant. when the cooling coil position was changed to the core area r6 in figure 6 and equating q6 to the install chiller power of 5 kw, a significant change was observed by reduction in tf, tc, tb, t1 and t2 at a magnitude of about 2 oc. the core coolant flow velocity was not affected by the change in the chiller power. it remains constant when it reached its maximum value of 0.0118 m/s in all the cases shown in table 3. the simulation outputs reassured that there would not be efficient heat transfer in the core. therefore, if efficient core cooling is required in the mnsr core, the present position of the cooling coil has to be considerably changed to a position below the current one closer to the core region r6. figure 7: inlet temperature (t1) variation http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 161 figure 8: outlet temperature (t2) variation figure 9: bulk (core average) temperature (tb) variation 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 x 10 4 25 26 27 28 29 30 31 time (s) p oo l t em pe ra tu re (c ) simulated experimental file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar et al: modification of thermal hydraulic transient models for the miniature neutron source reactor. azojete,16(1):147-163. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 162 figure 10: pool temperature (t7) variation figure 11: fuel (tf) and clad (tc) average temperatures variation 4. conclusion a model based on lumped parameter method is presented to predict the thermal hydraulic behaviour of the mnsr and validated using nirr-1 facility configuration. the model is capable of predicting flow velocity and the fuel and clad temperatures. it can be used of to simulate the reactor operation with or without operating the cooling coil and can also predict the reactor behaviour by changing the position of the cooling coil. both transients and beginning of steady state conditions can be predicted. the fuel and clad temperatures exhibited the same pattern as expected but begun to differ in transient until the difference rieaches a steady maximum of about 3 oc. this is at the instance of the gaseous accumulation in fuel tube during operation as a result of the fission reaction. xenon gas was considered as the major gas produced from fission during transients. when the cooling coil was repositioned to the core area at installed capacity of 5 kw, the computation shows a significant improvement with temperatures ’ decrease in magnitude of about 2oc. thus, the chiller would be more effective if installed at the middle section of the pool. in the present work, the model is used to predict variations in eleven reactor parameters and to study the effect of cooling the reactor from the pool upper section by the installed chiller at different powers. this study finds experimentally and by simulation at different chiller power, that the effect of cooling the reactor at the pool upper section is insignificant in the reactor core. and whenever the reactor fuel is changed in the future as intended, only the fuel parameters are required to be changed in the model. references abubakar, n. and yahaya, db. 2012. an overview of thermal hydraulic behaviour of the first nigeria nuclear research reactor (nirr-1) manifesting to its inherent safety. journal of engineering and technology, 7(1-2): 29-33. albarhoum, m. and mohammed, s. 2009. a thermal-hydraulic code (thyd) for the miniature neutron source reactor thermal-hydraulic transients. progress in nuclear energy, 51: 470-473. anglart, h. 2011. nuclear reactor dynamics and stability; compendium [program] kth research reactor project. stockholm: royal institute of technology. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 147-163. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nabubakar@abu.edu.ng 163 dim, l., usman, k., balogun, g., mallam, s., ewa, i., funtua, i., yusuf, i., mati, a. and ogunleye, p. 2012. nigeria research reactor 1 safety analysis report. zaria: centre for energy research and training cert. international atomic energy agency, iaea. 2001. reactor simulator development. technical document tecdoc-1203. vienna: iaea. endre, s. 2014. numerical solution of ordinary differential equations. mathematical institute. oxford: university press. kazeminejad, h. 2008. thermal-hydraulic modelling of flow inversion in a research reactor. annal of nuclear energy, 35: 1813-1819. saha, p., aksan, n., andersen, j., yan, j., simoneau, p., leung, l., bertrand, f., aoto, k. and kamide, h. 2013. issues and future direction of thermal hydraulics research and development in nuclear power reactors. nuclear engineering and design, 264: 3-23. shampine, lf., reichelt, mw. and kierzenka, ja. 1999. solving index-1 daes in matlab and simulink. siam review, 41: 538–552. yamoah, s., akaho, ehk., nyarko, bjb., asamoah, m., ampong, ag. and amponsah-abu, eo. 2011. analysis of thermal-hydraulic transients for the miniature neutron source reactor (mnsr) in ghana. research journal of applied sciences, engineering and technology, 3(8): 737-745. quian, s. 1990. design of fuel elements for low power research reactors. iaea workshop on low power research reactors. beijing: china institute of atomic energy. wuqin, z. 1997. dynamic characteristics of the miniature neutron source reactor. technical document. beijing: china institute of atomic energy. yongchun, g., jijin, g., huabai, t. and yuewen, y. 1992. miniature neutron source reactor general descriptions, mnsr-dc-1. technical document. beijing: china institute of atomic energy. zhang, y. 1993. the whole simulated heat transfer experiment and calculations. mnsr training materials. beijing: china institute of atomic energy file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 41-50 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng *corresponding author’s e-mail address: vicabode95@gmail.com 41 original research article some engineering properties of breadfruit seed varieties relevant to handling v. a. abodenyi1, t. k. kaankuka2 and s. v. irtwange3 1department of agricultural and bio-environmental engineering, the federal polytechnic, bauchi 2,3department of agricultural and environmental engineering, university of agriculture, makurdi article information received: october, 2018 accepted: december, 2018 keywords: breadfruits seed terminal velocity drag coefficient percentage porosity abstract determination of some engineering properties of two varieties of breadfruit seeds (var. africana and var. inversa) was carried out. the initial moisture content was 6.85% and later adjusted by rewetting to 14.85%, 21.85% and 28.85% (wb). the following engineering properties, true density, bulk density, percentage porosity, specific heat capacity, terminal velocity and drag coefficient were determined. thermal property (specific heat capacity) of the seed was determined using the calorimeter method. the aerodynamic properties (terminal velocity and drag coefficient) were also determined by using an air column made of a vertical wind tunnel in conjunction with a voltage regulator to vary the wind speed and a digital anemometer to determine the air speed. data obtained were statistically analyzed using minitab statistical software. the following results were obtained. the true density of var. africana decreased from 1033.68 kg/m3 to 842.81 kg/m3 which amounted to 18.5% decrease, while for var. inversa it decreased from 948.38 kg/m3 to 911.89 kg/m3 amounting to 3.85% decrease as the moisture content increased from 6.85 to 28.85%. the bulk density was observed to increase linearly as the moisture content increased. it increased from 361.239 to 408.723 kg/m3 for var. africana and 317.55 to 387.638 kg/m3 for var. inversa. the porosity of var. africana ranges from 65.06% to 51.6% while for var. inversa it ranges from 66.5% to 57.2%. the terminal velocity increased from 5.5 to 8.0 m/s for var. africana and 3.89 to 6.8 m/s for var. inversa respectively as the moisture content increased from 6.85 to 28.85 %. © 2018 faculty of engineering, university of maiduguri, nigeria, all rights reserved 1. introduction the breadfruit seed is the mature ovule of treculia africana, it is light brown in colour, roughly oval and spherical in shape. the seeds are contained in a pulp mass inside the fruit. when the fruits are harvested they are stored to ferment for 3-4 days, then mashed and the seeds freed by washing the solubilized pulp off the seeds in a basket with running water, and later sun dried. the dried seeds are available in the market in the undehulled state (omobuwajo et al., 1999). when dehulled the seeds may be cooked and eaten as the main dish like rice or roasted and eaten as a snack in the same way as peanut. it could also be cooked with fresh corn into porridge. the seed is used in these food forms in several parts of west africa and especially southeastern nigeria (akande, 1998). it is used in preparing pudding, as a thickener in traditional soups and in manufacture of food products such as flour for bread, beverages and weaning food for children (onyekwelu and fayose, 2007). engineering properties of breadfruit seed are essential for the design of equipment for handling, separation, and conveying, drying, storing, aeration and processing. bulk density, true density and porosity can be useful in sizing grain hoppers and storage facilities; they can affect http://www.azojete.com.ng abodenyi, et al: some engineering properties of breadfruit seed varieties relevant to handling, azojete, 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 42 the rate of heat and mass transfer of moisture during aeration and drying processes. rajabipour et al. (2006) reported that drag coefficient and terminal velocity of material are important parameters in aerodynamic and hydrodynamic behaviour which depends on acceleration due to gravity and fluid flow. these properties help in the design of equipment for separation and handling. knowledge of specific heat capacity is important in engineering design calculations involving thermal processing of agricultural products (mortaza et al., 2008). temperature and moisture content greatly influence the specific heat capacity of agricultural materials due to the relatively high specific heat of water. the aim of this research work was to investigate some engineering properties of two varieties of breadfruit seed var. africana and var. inversa relevant to bulk handling. these properties include densities, porosity, aerodynamic and thermal properties as influenced by moisture content. regression models were also generated with respect to moisture content. 2 materials and methods 2.1 moisture content determination and adjustment standard procedures stated for ungrounded grain and seed in the asae s352.2 (2003) was adopted in order to obtain the different moisture content. electric oven (gallenkamp oven 300 plus series), carrying cans, and electronic weighing balance (wensar pgb series) with accuracy of 0.01 g were used to determine moisture content of the two varieties of breadfruit seed. the moisture content was calculated using equation 1 (abodenyi, et al., 2015) m.c w.b = mb−ma mb−mc × 100% (1) where; mc(wb)= moisture content (wet basis) mb = the weight of moisture can plus sample weight before oven-drying (gm) ma = the weight of moisture can plus sample weight after oven-drying (gm) mc = weight of moisture can (gm) the desired moisture content were obtained by determining the required amount of water, m, as calculated from equation 2 (davies and zibokere, 2011), m = ws m2− m1 100−m2 (2) where, ws = weight of sample (kg) m = weight of distilled water that was added (kg) m1 = initial moisture content (%) of breadfruit seed m2 = desired moisture content (%) of breadfruit seed the samples were adjusted from 6.85% to 14.85%, 21.85% and 28.85% w.b. 2.2 determination of true density of breadfruit seeds the seed volume and true density ρt as a function of moisture content was determined by water displacement method (adejumo et al., 2007, davies and zibokere, 2011). one hundred seeds of known average weight were dropped into a container filled with water. the net volumetric water displacement by the seed were noted and recorded. the experiment was repeated five times. the true density of breadfruit seed was then evaluated using the expression as given by equation 3; ρt = m v (3) where, �� = true density (kg/m3) m = mass of the sample (kg) and v = volume (m3) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 43 2.3 determination of bulk density and percentage porosity the bulk density (ρb ) in kg/m3 is the ratio of the mass sample of thes breadfruit seeds to its volume. equation 4 was used to determine the bulk density using a container of 300 mm height and 200 mm diameter. the container was filled with the sample from a height of about 150 mm, (karababa, 2006). the electronic balance was used to weigh the samples: ρ b = mρ2 − mρ1 v (4) where, mρ2 = mass of cylinder plus seeds (g) mρ1 = mass of empty cylinder (g) v = volume of the cylinder (cm3) the porosity (ε) of the bulk seed was computed from the values of the true density (ρt) and bulk density (ρb) of the seeds by using equation 5; � = ρt − ρb ρt × 100 (5) 3.1 determination of aerodynamic properties 3.1.1 determination of terminal velocity the terminal velocity of the breadfruit seed was determined by using an air column as used by adedeji (2012). it is made of vertical wind tunnel of diameter 44.28 mm and height of 600 mm. a voltage regulator and a digital anemometer (model am4812) were used to determine the air speed. each sample of the two varieties at the required moisture of 6.85, 14.85, 21.85 and 28.85% were dropped into the air stream from the top of the air column and the air velocity adjusted until the seed, is suspended in the air stream. the respective velocity (m/s) near the location of the seed suspension was measured with the help of the digital anemometer having accuracy of ± 0.1 m/s. the experiment was replicated five times and the readings recorded. 3.1.2 determination of drag coefficient the drag coefficient was calculated from equation 6 (mohsenin, 1986) �t = 2�� �� �� �� (6) where, cd = the drag coefficient m = weight of the seed at terminal velocity (g) g = acceleration due to gravity (m/s2) aρ = area of the particle (m2) ρ a = density of air (kg/m3) vt = terminal velocity of the particle (m/s) 3.2 determination of specific heat capacity the specific heat capacities of the two varieties of the seed were determined by the method of mixture as described by oje and ugbor (1991) and ogunjimi et al., (2001). hot water of known weight and temperature was poured into an adiabatic drop calorimeter containing twentyfive seeds of each variety at a time. the initial temperature of the seeds was taken. the mixture was stirred with a copper stirrer until equilibrium was reached; the final temperature of the mixture was recorded. specific heat capacity was computed from equation 7. the experiment was replicated five times for each of the variety at the required moisture content. ��= �� �� ��t− ��� �� ��t− ��� (7) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abodenyi, et al: some engineering properties of breadfruit seed varieties relevant to handling, azojete, 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 44 where, cs = specific heat capacity of the seed (j/kg/oc) cw = specific heat capacity of water (j/kg/oc) mw = mass of water (g) ms = mass of the seed (g) twi = initial water temperature (oc) twf = final water temperature (oc) tsi = initial temperature of seed (oc) 4 experimental design and statistical analysis the experimental design was a 2×4 rcbd (randomized complete block design) with replications. two varieties of breadfruit seed (var. africana and var. inversa) were used at four different moisture content levels of 6.85, 14.85, 21.85 and 28.85 % and each parameter determined was replicated five times. 5 results and discussion 5.1.1 true and bulk densities the result of the effect of moisture variation on true density is presented in table 1. the true density of var. africana decreased from 1033.68 kg/m3 to 842.81 kg/m3 which amounted to 18.5% decrease, while for var. inverse it decreased from 948.38 kg/m3 to 911.89 kg/m3 amounting to 3.85% decrease as the moisture content increased from 6.85 to 28.88%. the regression equations, 8 and 9 indicates a negative linear correlation which is to say that as the moisture content increased the true density decreased. taheri et al., (2012) observed the same result for hemp seed, and bagherpour et al (2010) also found true density to decrease with increase in moisture content from 1330 to 1194 kg/m3 and moisture content from 8 to 20% wb. ρta = -10.25mc + 1140 r2 = 0.856 (8) ρtin = -2.055mc + 979.8 r2 = 0.812 (9) this result revealed that the relative increase in the weight of breadfruit seed due to moisture absorption is lower than the corresponding volumetric increase. this finding agrees with tunde-akintunde and akintunde (2007) for beniseed and davies and zibokere (2011) for three varieties of cowpea, and solanki et al (2011) for neem fruit and seed. the anova (table 2) result indicated that the moisture content had significant effect on true density at p≤0.05 probability. also the interaction effect between moisture content and variety was significant. the bulk density was observed to increase linearly as the moisture content increased. it increased from 361.239 to 408.723 kg/m3 for var. africana and 317.55 to 387.638 kg/m3 for var. inversa. the increase in bulk density for neem seed indicated increase in mass owing to moisture in the seed. this result agrees with the result of solanki et al. (2011) on neem fruit and seed, adedeji (2012) on neem seed and kernel and dursun and dursun (2005) caper seed. the anova of the effect of moisture content on bulk density of breadfruit varieties indicates that the effect was significant at p≤0.05 probability and also significant for the interactive effect of moisture content and variety. the coefficient of determination r2 obtained from the regression models gave values of 0.983 for var. africana and 0.996 for var. inversa on the effect of moisture content on bulk density of the two breadfruit seed varieties. β ρa = 2.122mc + 349.0 r2 = 0.983 (10) β ρin = 3.196mc + 293.9 r2 = 0.996 (11) asoegwu et al, (2011) found the r2 value for african breadfruit seed to be 0.984. the mean separation between the varieties and moisture content is presented in table 1. there is a significant difference between all the moisture content levels for both varieties which tallies http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 45 with the anova result in table 2. bulk density and true density are useful in the design of hoppers and storage facilities. 5.1.2 porosity of breadfruit varieties figure 3 shows the effect of moisture content on percentage porosity of var. africana and var. inversa. increase in moisture content decreased the porosity of the seeds. the porosity of var. africana ranges from 65.06% to 51.6% while for var. inversa it ranges from 66.5% to 57.2%. this shows that a pack of var. inversa is more porous than var. africana. this property is required in the aeration process in agricultural material handling; from this result var. inversa might dry faster than var. africana during air drying process. this result agrees with aydin et al. (2002), for turkish marhleb, irtwange and igbeka (2002b) for two african yam bean accessions tss 137 and tss 138 and alonge and adegbalugbe (2005) for groundnut. the result in table 1 and the anova (table 2) indicate that there is a significant difference between all the moisture content levels for both varieties at p≤0.05 alpha level. regression equations 12 and 13 shows that the coefficient of determination are significant for the two varieties at p≤0.05. εa = 0.676mc + 70.74 r2 = 0.912 (12) εin = 0.418mc + 70.14 r2 = 0.945 (13) the coefficient of determination (r2) tended towards unity (1) indicates that the interaction of the independent variable has a very strong effect on the dependent variable. 5.2 effect of moisture content on thermal properties of breadfruit seed varieties 5.2.1 specific heat capacity of breadfruit seed varieties the influence of moisture variation on specific heat capacity of var. africana and var. inversa is presented in figure 4. increase in moisture content resulted to increase in specific heat capacity of the two varieties. var. africana increased from 2869.70 j/kg/oc to 3909.63 j/kg/oc while, var. inversa increased from 2811.35 to 3777.30 j/kg/oc as the moisture increased from 6.85 to 28.85%. the mean effect of moisture content on breadfruit varieties is shown in table 1. regression analysis from equations 14 and 15 showed that there is a linear relationship between var. inversa and the moisture content while var. africana had a polynomial relationship as evident in figure 4. ca = 2.663mc2 + 141.9mc + 2026 r2 = 0.999 (14) cin = 47.67mc + 2500 r2 = 0.929 (15) the r2 value for var. africana is higher than that for var. inversa, so the model for the var. africana is recommended. the increase in specific heat capacity of breadfruit varieties is in agreement with findings of some previous researchers. the specific heat of hard red spring wheat was found to increase linearly from 1054 to 2521 j/kg/°c with moisture content in the range of 10 to 23 % db by muir and viranvanichai (1992) and mirzaee et al. (2008) for apricot fruit. the specific heat of shea nut kernel as a function of moisture content was determined by aviara and haque (2001). they found that the specific heat increase linearly from 1792 to 3172 j//kg/°c as moisture was increased from 3.32% to 20.7% (db). this property can be used to determine the amount of heat required in the processing of the seed. it can also be used to design equipment and facilities for drying, preservation and processing of breadfruit seed, for making industrial products such as beverages, snacks pastas, flours, and cosmetics and in the pharmaceuticals, the knowledge of the specific heat capacity is important. the anova (table 2) showed that moisture content has a significant effect on the specific heat capacity of breadfruit seed. but there was no significant effect on the interaction between moisture and variety at 0.05 probability level. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abodenyi, et al: some engineering properties of breadfruit seed varieties relevant to handling, azojete, 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 46 5.3 effect of moisture content on the aerodynamic properties of breadfruit seed varieties 5.3.1 terminal velocity of breadfruit seed varieties the mean effect of moisture content on terminal velocity is shown in table 1. as moisture content increased from 6.85 to 28.85% (wb) the terminal velocity also increased from 5.5 to 8.0 m/s for var. africana and 3.89 to 6.8 m/s for var. inversa respectively. the result is in agreement with the report of simonyan et al. (2008), gursoy and guzel (2010) and adedeji (2012). the increase in terminal velocity with increase in moisture content can be attributed to the increase in the weight of an individual breadfruit seed per unit frontal area presented to the air stream. the regression equations and correlation between the moisture content and terminal velocity are shown in equations 16 and 17 and figure 5. vta = 0.120mc + 4.668 r2 = 0.970 (16) vtin = 0.132mc +2.989 r2 = 0.999 (17) the terminal velocity for var. africana was found to be higher than that of var. inversa. this is a good parameter for effective separation. the anova indicates that the effect of moisture content on the breadfruit variety is significant at 0.05 level of probability, but not significant for interaction effect of variety and moisture content. this result indicates that in the design of a cleaning chamber for breadfruit seed decorticator the terminal velocity should not be more than 8.0 m/s but higher than 3.89 m/s. terminal velocity has practical application in calculating volume of air stream for seed and chaff separation, such as fan and sieve arrangement of the thresher. 5.3.2 drag coefficient of breadfruit seed varieties from table 1 it was observed that as the moisture content increased the drag coefficient for var. africana reduced from 0.01 to 0.0029, for var. inversa it reduced from 0.005 to 0.0018. drag coefficient is resistance of a seed in a flow environment. this property is required in the design of cleaning and sorting machine. the result obtained agrees with mccormick (1989) findings that less drag coefficient of an object the higher the moisture content. the anova shows that there is no significant effect at p ≤ 0.05 for the two varieties. the regression analysis indicates a polynomial correlation as shown in figure 6 and equations 18 and 19 cda = 0.005mc2 – 0.003mc + 0.014 r2 = 0.999 (18) cdin = 0.006mc2 – 0.002mc + 0.007 r2 = 0.981 (19) conclusion 1. the bulk density increased from 361.239 kg/m3 to 408.723 kg/m3 as the moisture content increased from 6.85% to 28.85 % wb for var. africana, and from and 317.55 to 387.64 kg/m3 for var. inversa 2. the following properties for var. africana decreased with increase in moisture; true density and porosity; ranging from 1033.68 kg/m3 to 842.81 kg/m3 and 65.06 to 51.58% respectively. while for var. inversa the decrease ranged from 948.38 to 911.89 kg/m3 for true density and 66.51% to 54.24 % for porosity. 3. the specific heat capacity was found to increase from 2869.70 to 3909.63 j/kg/oc for var. africana while for var. inversa it increased from 2811.35 to 3777.30 j /kg/ oc as the moisture content increased from 6.85 to 28 85%. 4. the terminal velocity for var. africana and var. inversa increased from 5.50 to 8.0 m/s and 3.89 to 6.8 m/s, respectively as moisture content increased from 6.85 to 28.85% 5. the drag coefficient was observed to decrease with increase in moisture content for var. africana from 0.010 to 0.0029, while for var. inversa it deceased from 0.005 to 0.0018 for moisture range of 6.85 to 28.85 %. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 47 table 1: mean separation for some engineering properties of breadfruit seed varieties using lsd at 0.05 variety mc (%) true density (kg/m3) bulk density (kg/m3) porosit y (%) terminal velocity (m/s) drag coefficient specific heat capacity(j/kg/ oc) africana 6.85 14.85 21.85 28.85 1033.68a 1047.71b 863.38c 842.81d 361.24a 383.9b 395.82c 408.72d 65.06a 63.31b 54.06c 51.58d 5.50a 6.30b 7.75c 8.01d 0.010a 0.0059a 0.0038a 0.0029a 2869.70a 3560.13b 3842.32c 3909.63c lsd 0.05 13.554 2.1673 0.6009 0.2192 0.0582 348.08 inversa 6.85 14.85 21.85 28.85 948.38a 962.13b 948.34c 911.89d 317.55a 339.30b 362.85c 387.64d 66.51a 64.80b 61.82c 54.24d 3.89a 4.96b 5.90c 6.80d 0.005a 0.0035a 0.0020a 0.0018a 2811.35a 3142.60b 3720.74c 3777.30c lsd 0.05 13.554 2.1673 0.6009 0.2192 0.0582 348.08 means having the same letter in the same column are not means having the same letter in the same column are not statistically different from each other at p ≤ 0.05. table 2: summary of anova results for some engineering properties of two breadfruit seed varieties parameters sources of variations df f p true density variety m.c interaction 1 3 3 1.18 90.75 51.54 0.286ns 0.000* 0.000* bulk density variety m.c interaction 1 3 3 1137.14 544.64 32.20 0.000* 0.000* 0.000* porosity variety m.c interaction 1 3 3 186.45 320.08 24.91 0.000* 0.000* 0.000* terminal vel. drag coefficient variety m.c interaction variety m.c interaction 1 3 3 1 3 3 180.65 127.51 1.13 160.42 119.26 3.14 0.000* 0.000* 0.354 ns 0.068ns 0.070ns 0.069ns specific heat capacity variety m.c interaction 1 3 3 1.15 7.45 0.22 0.292 ns 0.001* 0.880 ns *= significant at p ≤ 0.05, ns = not significant at p ≤ 0.05 figure 1: effect of moisture content on true density of var.africana and var. inversa file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abodenyi, et al: some engineering properties of breadfruit seed varieties relevant to handling, azojete, 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 48 figure 2: effect of moisture content on bulk density of breadfruit seed varieties figure 3: effect of moisture content on porosity of breadfruit seed varieties figure 4: effect of moisture content on specific heat capacity of breadfruit seed varieties figure 5: effect of moisture content on terminal velocity of breadfruit seed varieties http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 49 figure 6: effect of moisture content on drag coefficient of var. africana and var. inversa references abodenyi, va., obetta, se and kaankuka tp. 2015. an assessment of the of moisture content on the physical and economical properties of breadfruit seed ( artocarpus altillis). journal of engineering research and technology (jert) 5(2) :13 – 25 adedeji, ma. 2012. the selected engineering properties of neem seed. m.sc project, agricultural engineering departmentment, obafemi awolowo university ileife.pp 147. adejumo, oi., alfa, aa and mohammed, a. 2007. physical properties of kano white variety of bambara groundnut. nigerian academic forum, 12(1): 68 – 77. akande, ea. 1998. adaptation of a rice mill for dehulling african breadfruit (treculia africana ) seeds. agricultural engineering department unpublished m.sc thesis, university of ibadan, ibadan nigeria. 3-17 alonge, af. and adegbalugbe, ta. 2005. some physical properties of groundnut. journal of agricultural engineering and technology (jaet) vol.13: 34-41 asae s352.2. 2003. moisture measurement – unground grain and seeds. american society of agricultural engineers. mi 49085-9659, usa. 6-89 asoegwu, sn, iroakazi, gu., agbetoye, as. and ogunlowo, as. 2011. effects of moisture content on the frictional properties of african breadfruit seeds. proceedings of the 11th international conference and 32nd annual general meeting of niae ilorin, oct. 17th – 20th, 2011. 32: 639 – 653 aviara, na. and haque, ma. 2001. moisture dependence of thermal properties of shea nut kernel. journal of food engineering, 47: 109-113 aydin, c. and ozcan, m. 2002. some phsico-mechanical properties of terebinth fruits. j. food eng., 53: 97-101 bagherpour, h. minaei, s. and khoshtaghaza, mh. 2009. selected physico –mechanical properties of lentil seeds international agro physics, 24: 81 – 84 davies, rm. and zibokere, ds. 2011. effects of moisture content on some physical and mechanical properties of three varieties of cowpea (vina unguiculta (l) walp). agricuitural engineering international:cigr journal 13(1): 241-250 dursun, e. and dursun, j. 2005. some physical properties of caper seed biosystem engineering. 92, 237 – 245. gursoy, s. and guzel, e. 2010. determination of physical properties of some agricultural grains. res. journal of applied science, engineering and technology 2(5): 492 – 498. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abodenyi, et al: some engineering properties of breadfruit seed varieties relevant to handling, azojete, 14(sp.i4): 41-50. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 50 irtwange, sv. and igbeka, jc. 2002b. some physical properties of two african yam bean (sphenostylis stenocarpa) accessions and their interactions with moisture content. journal of applied engineering in agriculture of the asae 18(5); 567 – 576. karababa, e. 2006. physical properties of popcorn kernel. journal of food engineering 72: 100 – 107 mccormick, b. 1989. aerodynamics and flight mechanics john wisly and sons inc. new york pp. 24 mirzaee, e., rafiee, s., keyhani, ar., emam djom–eh z. and kheuralipour, k. 2008. mass modeling of two varieties of apricot (prunus armenaica l) with some physical characteristics. plant omics 1 (1); 37-43. mohsenin, nn. 1986. physical properties of plant and animal materials (2nd ed). gordon and breach science publishers, new york, pp 151 -152. mortaza, a., kianmehr, mh., and hassan-baygi, sr. 2008. specific heat and thermal conductivity of berberis fruit (berberis vulgaris). american journal of agricultural and biological sciences 3(1): 330 – 336. muir, we. and viranvanichai, a. 1992. specific heat of wheat, journal of agricultural engineering research; 17: 338-342. ogunjimi lao., aviara na. and aregbesola oa. 2001. some engineering properties of locust bean seed. journal of food engineering, 55: 95 – 99. oje, k. and ugbor, ec. 1991. some physical properties of oil bean seed. journal of agricultural research 50: 305 – 31. omobuwajo, to. akande ea. and sann. la. 1999. selected physical, mechanical and aerodynamics properties of african breadfruit (treculia africana) seeds. journal of food engineering 40: 241-244. onyekwelu, jc. and fayose, oj. 2007. effect of storage methods on the germination and proximate composition of treculia africana seeds. conference on international agricultural research for development. university of kessel – witzenhauesen and university of gottingen, october 9 -11, 2007. rajabipour, a., tabatabaefar, a. and farahani, m. 2006. effect of moisture on terminal velocity of wheat varieties. international journal of agriculture and biology 8 (1): 10-13. selders, a. w. (2011). material handling in agriculture. cooperative extension service west virgins university and us department of agricultural cooperative. 322-350 simonyan, kj., el-okene, am and yijep, yo. 2008. determination of some mechanical properties of bambara nuts (vigine substerraneal york) relevant to shelling proceedings of 8th int. conference and 29th agm of niae. 29: 367 -371. solanki, rc., naik, sn., sarivastava. ap. and santosh, s. 2011. physical and mechanical properties of neem fruit and seed relevant to depulping and decoration. journal of agricultural engineering, 48 (3): 52 – 57 taheri-garavand, a., nasari, a. and alharbzahadi, st. 2012. physical and mechanical properties of hemp seed. international agro physics 26, 211 – 215. tunde-akintunde, ty. and akintunde, bo. 2007. effect of moisture content and variety on selected properties of beniseed; agricultural engineering international; cigr journal 9; 1-13 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):46-56 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 46 original research article on-orbit results of photoelectron current measurement system in low earth orbit on horyu-iv satellite e. ewang1,2, o. ogah2, h. suleiman4, g. agbaje2, d. faizullin3, k. toyoda1 and m. cho1 1laboratory of spacecraft environment interaction engineering (la seine), kyushu institute of technology, kitakyushu, japan 2african regional centre for space science and technology education in english (arcsste-e), o.a.u. campus ile-ife, nigeria 3space dynamics laboratory, kyushu institute of technology, kitakyushu, japan 4centre for satellite technology development (cstd), nasrda, abuja, nigeria article information submitted: 02/11/2018 revised: 25/02/2019 accepted: 18/03/2019 keywords: on-orbit, result, photoelectron current, horyu-iv satellite and materials. abstract on-orbit photoelectron current experiment is one of the missions carried out with the less resource available from a horyu-iv satellite, for measuring the current from metallic and insulator surfaces from air mass zero (amo) spectrum. this is with the view to determined photoelectron potential of materials widely used in spacecraft in space. horyu-iv also known as arc event generator and investigator satellite (aegis) is among horyu satellite series of kyushu institute of technology, which was launched on february 17, 2016 as a piggy-back on-board h-iia rocket. the measurement system consists of current-voltage amplifier circuits for au, kapton and black kapton samples with varying gains and other discrete components. we present the analysis of the telemetry data obtained after the launch; validate the effectiveness of the design and verification processes. the results show that the current measured from black kapton sample surface had 1.80 na and 2.70 na, corresponds to 69.1ᵒ and 75.1ᵒ minimum and maximum elevation angles respectively. this paper described the on-orbit result of pec and its verification through ground tests © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction on-orbit photoelectron current measurement is very significant in the estimation of photoelectrons emission influence on spacecraft charging and therefore discharge phenomenon. this could provide basic information in predicting photoelectron potential on spacecraft and the electric properties of various materials irradiated by sunlight. through this, most suitable materials could be selected during the spacecraft design phase. spacecraft operating in the sunlight cannot avoid one side exposing to the sun while the other side is in shadow, so it has to face the problem of surface charging caused by photoemission phenomenon (jiang et al., 2015). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 47 the photoelectron current as a consequence of photoelectric effect can cause spacecraft exposed to sunlight to develop a positive charge. this can be a major problem, as other parts of the spacecraft in shadow develop a negative charge from nearby plasma, and the imbalance can discharge through delicate electrical components (lai, 2011). spacecraft surface charging can lead to arcing and a loss of electrical power generation capability of solar panel or even loss of a satellite (mundari et al., 2011). spacecraft charging is a serious issue for safety of spacecraft operation. therefore, thorough investigation of spacecraft charging at an early stage of satellite design is desirable to prevent the fatal anomaly in orbit. charging properties, such as secondary electron yield, photoelectron emission yield and conductivity of spacecraft surface materials are the important parameters to predict charging in orbit (ewang, 2017). in order to overcome these anomalies, a voltage-current amplifier circuit was developed to measure photoelectron current in the orbit using the facility of horyu-iv satellite. horyu-iv is a 30cm cubic satellite with an approximate mass of 10kg. horyu-iv carries a high voltage photovoltaic solar array capable of generating a voltage up to 350v. its main mission is to acquire an arc current waveform by an onboard oscilloscope and capture its image by a camera triggered by the oscilloscope (cho et al., 2016). in addition, pec mission is one of the scientific experiments carried out by this satellite, located on its – z panel. the satellite was successfully launched to an orbit of 575km altitude and 31ᵒ inclination on february 17, 2016 by h-iia rocket as a piggyback satellite with astro-h (hitomi) satellite. all experimental testing was performed at the laboratory of spacecraft environment interaction engineering (laseine) in kyushu institute of technology, kitakyushu, japan. 
 this paper presents on-orbit results of the photoelectron current measurement system on-board horyu iv satellite. 2. photoelectron emission current definition the electron emission by photon as a fundamental particle of light, is massless and has no electric charge, whereby free electrons are emitted. the current produced due to this process is called photoelectron current (jph). this is expressed in eqn. (1), while eqn. (2) expresses the current from the sample surfaces. eqn. (3) is the photo fluence; define as the ratio solar intensity per energy of the photon from sun light. 2 1 λ λ jph = q x f(λ)xy(λ)dλ  (1)    2 1 λ sample e λ i = q ×s× f λ ×y λ dλ (2) f(λ) = ir/w (3) 2.1 on-orbit photoelectron current this is defined as emitting electrons from the sunlit surface of a spacecraft (muranaka et al., 2009). these photoelectrons are created when photons strike the spacecraft surface and impart enough energy to induce electrons emission from the spacecraft surface. typical photoelectron energy is about a few electron-volts. the number of photoelectrons produced and their energies are largely dependent on spacecraft material properties and designs (jose,2003). as a result of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ewang, et al, on-orbit results of photoelectron current measurement system in low earth orbit on horyu-iv satellite. azojete, 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 48 electrons emission due to photons strike, a current is produced, namely the photoelectron current, jph. 2.2. principle of photoelectron current on-orbit measurement figure 1 shows the schematic of principle of on-orbit pec measurement mission. this is based on the photoelectric effect whereby when the sun sensor measurements, provided by the aods through adc in serial peripheral interface (spi) mode, shows that the incident sunlight on the -z panel of the satellite is within the threshold of 16.5ᵒ. then the big apple microcontroller subsystem of horyu-iv closes the +24 v switch to bias the pec grid electrode. the sun sensor allow energy carried in a photon from the sun light (uv), transmitted to an electron in the surface of gold, kapton(r) polyimide and black kapton (r) samples on pec subsystem and mission starts. (ewang 2017). fig. 1 schematic of principle of on-orbit pec measurement, (ewang 2017) the electron absorbs the photon’s energy and dislodged from the surface of these materials. this thereby, creates a small electric current. the pec measurement system, comprises of current-voltage amplifier circuit is used for the amplification of this current. at the end of the mission, the microcontroller in big apple board receives data from pec system, which are then written to its flash memory. the obc reads the pec data through flash memory prior to data transmission through uhf yagi antenna to the ground station. (ewang et al., 2017). 3. materials and methods 3.1 the circuitry of photoelectron current system figure 2 shows the schematic of pec circuit board. this is made of a current-voltage amplifier circuit that consist of two amplifiers; the lmc6001 ultra-low input operational and mcp6032sn operational amplifiers, with the capacitors, resistors, and others discrete components. this circuit was designed to have three sub-circuits mounted on a single board for measurement of each sample (gold, kapton(r) polyimide and black kapton (r)) output current. each material sample has its own dedicated circuit with gains of 1g, 3g and 1g, respectively. the circuit was designed with easily applicable graphical layout editor (eagle) software and the components http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 49 were located on the printed circuit board (pcb) as defined in the circuit diagram and then soldered. the circuit has an electrical power system (eps) connected to supply ±5v to dcdc converter which converts to ±5volts and +24volts levels. the ±5v is used to switch on the pec circuit and +24v for generating of the required voltage for grid electrode. this +24v grid electrode is useful in the process of emitting the photoelectron current from the sample surfaces. the lmc6001is connected in the circuit to amplified the photoelectron current measured at the sample surface. this is connected to the input (cin) and feedback (cf) capacitors to maintained the required voltage level. the input current (iin) is use to move the current from sample surface along the circuit over r1. a pull up resistor, 9.1 k in the circuit ensures that the signal was at a valid logic level. at point v1 the produced voltage was negative. the mcp6032sn connected to it amplifiers the voltage, converts it to a positive value that could be read by microcontroller circuit of big apple subsystem of horyu iv. the big apple serves as a memory via the pic device on the big apple board for storage of pec data. interfaced between pec subsystem with the electrical power system (eps), altitude orbit and determination system (aods) and on-board computer (obc). at vout, the waveform is obtained over the oscilloscope via ad converter; the data collected and analyzed using eqns. (4) – (6), to obtained an equivalent input current for each sample. (ewang, 2017). v = -iinr1 (4) vout = r4r1iin/r3 (5) iin = vout/r1 (6) fig. 2 schematic circuit of pec board 3.2. pec measurement system figure 3 depicts the schematic diagram of on-orbit pec measurement system onboard horyuiv satellite. the system comprises of the voltage-current amplifier printed circuit board (pcb), samples, +24 volts’ grid electrode, holes and analog to digital converter (adc). the pec pcb consists of a rectangular pcb with a length of 133mm and width of 27mm. the pcb is made of three dedicated circuit for each sample, mounted on one board. each of this circuit is file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ewang, et al, on-orbit results of photoelectron current measurement system in low earth orbit on horyu-iv satellite. azojete, 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 50 identified with 1gώ, 3gώ and 1gώ for gold, kapton ® and black kapton samples respectively. the three samples are placed on the pcb front side and electronic components on the back side. (ewang et al., 2017). dedicated holes for each sample were made on the insulator substrates and in the satellite structure. this is to allow photons strikes onto the different sample surfaces. the area of each hole is based on the sample type. for the au sample, there is one hole of 15mm diameter over the sample, whereas for kapton® and black kapton®, there are two holes of 15mm diameter over the sample to increase the sample area exposed to photons strikes and increase chances to generate and measure photoelectron current for these two samples. fig. 3 schematic of pec measurement system the biased mesh grid electrode at +24v with the same dimensions as the pcb is placed between the samples and the satellite panel. this grid was placed in between insulator substrates to prevent plasma sheath effect. these substrates protect the pcb from the effect of +24 v of grid electrode that could have interfere with the proper functioning of the circuit. and also prevent the heat effects to the electronic component on this board. the analog to digital converter (adc) connected to the pec circuit converts output signals to an equivalent digital number that is stored in the memory device, the big apple subsystem via the peripheral interface controller (pic). 4. experimentals 4.1 ground test experiment experiments were performed to confirm the operation, verify the performance of the pec system and to validate its accuracy. the experiments used a low earth orbit plasma chamber of dimension of diameter 1.0 m x length 1.2 m, pressure of1x 10-4 pa, temperature of 1.0 ev and pumping speed of 300 i/s. located at the laboratory for spacecraft environment interaction engineering (laseine) of kyushu of kyushu institute of technology. the plasma was generated by electron cyclotron resonance (ecr) at 3.5 5 ghz. the xenon (xe) gas was fed at a flow rate of 0.40 sccm controlled by a flow-meter. during the experiments, the gas pressure inside the chamber was maintained at 2.0x10-2 pa. the chamber was evacuated by a rotary pump backed by turbo molecular pump connected in series that confirmed the ultimate vacuum level of 7.5x10-3 pa. this chamber generates plasma density of 1011 ~1012 m-3(ewang 2017) figure 4 shows the schematic diagram of pec experimental set up in the leo chamber. this consist of the pec measurement system, ozone light (gl-6z: model), oscilloscope (tbs1104), http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 51 voltage regulator (psw-80-13-5 gw, instek), isolation transformer, langmuir probe, cylindrical cup, plasma source and dc source (battery). fig. 4 schematic diagram of pec experiment in leo chamber the pec system in an aluminum box of dimensions 178 cm x 178 cm x 71 cm shielded by kapton tape to prevent effect of plasma, has one input and output sources. the input consists of + 5 volts, 5 volt and ground connected from the dc (battery) source. the output has au, kapton (r) polyimide and black kapton samples source connected to the oscilloscope. the + 24 volts’ line connected to voltage regulator to provides the required biased voltage to pull out more electron from samples surfaces. (ewang et al., 2017). all the electronic components were connected to a common ground and in series with the isolation transformer to suppress the effect ac noise. the box was placed 15 cm from the uv source. the cylindrical cup was to regulate the plasma density by changing its position in the chamber. and the langmuir probe was to measure the plasma parameters in the chamber. the output waveform was observed over the oscilloscope; the data collected and analyzed. 4.2 in-orbit experiment the mission success criterion is in-orbit photoelectron current measurement from the metallic and insulator surfaces from amo spectrum. horyu-iv was launched aboard hii-a f30 at 17:45, february 17, 2016 (jst) from tanegashima space centre. the satellite was inserted into an orbit of 575km altitude and 31° inclination. after the launched, pec mission on-orbit experiments have been successfully performed from amo spectrum; june 20, and july 08, 2016. the result of the experiment performed on june 20, 2016 has been published (ewang et al., 2017). figure 5 shows the schematic diagram of pec interface connections with others subsystem of horyu iv satellite. the sequence of operation was such that when the pec signal was turned on from kyutech ground station, the obc writes a command to the big apple flash memory. the microcontroller in the big apple board reads this command and closes a 5 v switch, provided by (eps) power system. if the –z panel sun sensor measurements, provided by aods through adc using serial peripheral interface connections, show that the incident sunlight measurement is at the acceptable threshold of 16.5° from the perpendicular to the surface. big apple microcontroller closes the +24v switch to bias the pec grid electrode. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ewang, et al, on-orbit results of photoelectron current measurement system in low earth orbit on horyu-iv satellite. azojete, 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 52 this sun-sensor has square field of view (fov) with half angle of 16.5 degree. the pec mission starts. after the mission ends, big apple microcontroller receives data from pec system. data received from pec system are written to big apple flash memory. obc reads the pec data through big apple flash memory. pec data are transmitted through uhf antenna to kyutech’s ground station. (ewang, 2017). fig. 5 schematic diagram of pec system interfaces (ewang. 2017) 5. results and discussion 5.1 ground result figures 6(a) – (c) show the output current time profile for gold, kapton polyimide (r) and black kapton (r) samples. these show that the pec circuit was turned on at -0.5 second, +24 volts turned on at 0 second and mission was performed for 0.6 seconds. table 1 shows the measured maximum current values under uv only and plasma and uv for each sample. the increase in current between the two signals is due to the plasma ions and electrons charge effect on the surface of these materials. (a) (b) (c) fig. 6 samples current profile. a) gold; b) kapton®; c) black kapton ® for ground data http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 53 table 1 measured current values for each sample 5.2. on-orbit results of pec mission figure 8 shows the pec on-orbit result of july 08, 2016.the data were obtained on the orbit relative to the earth at (28.6016 ᵒ e, 115.7390 ᵒn) in china and (26.9462ᵒ e, 129.1254 ᵒ n) in philippine sea respectively. figure 7 shows the sun sensor signal to pec mission of the data obtained. when the incident sunlight on the -z panel of the satellite was at the threshold of 16.5 degree. level1indicates when the signal was turned on at 249 seconds and level 2, turned off at 293 seconds. fig. 7 sun sensor signal to pec mission figure 8 (a)-(c) shows the current time profile for on-orbit current measured on the surface of the three samples. this shows that the pec current was turned on at o second, when obc writes a command to the big apple flash memory. the microcontroller in the big apple board reads this command and closes a 5 v switch, provided by (eps) power system. when the sun sensors measurements, provided by the aods through adc in serial peripheral interface (spi) mode, shows that the incident sunlight on the -z panel of the satellite was within the threshold of 16.5ᵒ, then the big apple microcontroller closed the +24 v switch, biased the pec grid electrode for 2 seconds and mission starts. the gold and kapton ® polyimide current values went on saturation for 37.7 seconds. the black kapton (r) maintained a stable increased in the current values from 1.80 na at 33.8 seconds to maximum value of 2.70 na at 71.5 seconds. the big apple subsystem of horyu iv, recorded these data for 37.7 seconds after that ellipse (ec) at value of 3.13 na. this shows that the current values were stable at 2.60 na for 4 seconds between 34.1–35.7 seconds, with respect to minimum angle of elevation of 69.1ᵒ. then changes up to 2.70 na with respecct to maximum angle of elevation of 75.1ᵒ. these elevations were provided by the sun sensor via aods subsystem of horyu iv. this means that pec can be measured from black kapton sample surface on horyu iv satellite at minimum and maximum elevation angles 69.1ᵒ and 75.1ᵒ respectively. sample uv only (na) max. plasma and uv (na) gold 1.88 2.89 kapton polyimide ® 0.47 0.76 black kapton ® 0.88 2.60 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ewang, et al, on-orbit results of photoelectron current measurement system in low earth orbit on horyu-iv satellite. azojete, 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 54 after 71.5s, there was no incident of sunlight, due to an exit sun from the threshold of the sunsensor, then showing value of 3.13 na. table 2 indicates the on-orbit measured current with corresponding elevations with respect to time. this means that the on-orbit minimum and maximum current values of 1.80 and 2.70 nano-amperes was measured, this corresponds to minimum and maximum elevation angles of 69.1 and 75.1 degrees with respect to time of 33.8s and 71.5s respectively. photoelectron current emitted from a surface is directly proportional to the light intensity (leijtens et al., 2008) and the proportionality constant depends on the surface material of the object (milton et al., 1996). thus, at maximum elevation angle, more photoelectron current is emitted. the incident angle is measured from the perpendicular to the surface to the sunlight vector. the elevation angle is measured from the parallel to the surface to the sunlight vector. figure 9 illustrates the sensor with characteristic of a square field of view with half angle 16.5ᵒ. with: d1 = d2 = 16.5ᵒ; d3 = 21.2ᵒ, maximum incident angle. pec mission is on when the incident angle is less than sensor field of view (16.5ᵒ). this 16.5ᵒ corresponds to the period the incident sunlight on the surface of material was within the acceptable threshold from 33.8s 75.1 s. table 2: on-orbit current with respect to time (a) (b) (c) fig. 8: samples current profile. a) gold; b) kapton®; c) black kapton® for on-orbit dat fig. 9: sensor field of view time, s incident angle (ᵒ) elevation angle (ᵒ) orbit current (na) 33.8 20.9 69.1 1.80 71.5 14.9 75.1 2.70 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 55 in this study, photoelectron current for black kapton ® polyimide was measured in orbit. previously, photoelectron current density in orbit was determine for black kapton® polyimide sample (ewang et al., 2017). looking at these results, it is observing that the photoelectron current measured is within the range as in (ewang et al., 2017). thus, serves as a confirmation to this study. 6. conclusion on-orbit result of photoelectron current measurement system in low earth orbit (leo) on horyu-iv satellite was implemented. this was with a view of measuring photoelectron on-orbit from the sample surfaces. pec measurement system demonstrated its capability to measure photoelectron current in the order of nano-ampere in leo using a biased grid electrode. photoelectron current was successful measured on orbit from black kapton sample surface at 1.80 na and 2.70 na with minimum and maximum angles of elevations of 69.1ᵒ and 75.1ᵒ respectively. thus, indicates that at higher elevation angle with higher intensity from the sun light, there was more photoelectron current from the sample surface. this indicates that the +24 volts’ grid biased electrode was working both on ground and in space. acknowledgments the author would like to appreciate all members of horyu iv team for their support in this research. also extends his thanks to amateur radio operators, who helped in the satellite operation. this research is supported by jsps kakenhi grant 25220915s. references cho m., fukuda h. 2016. flight results of new technology onboard a lean satellite horyu-iv, ieee region 10 annual international conference, proceedings/tencon, singapore, p.3439 – 3442, 2017.02 , doi:10.1109/tencon.2016.7848693. ewang, e., akira, m., arifur, k., kazuhiro, t. and mengu, c. 2017. photoelectron current measurement in low earth orbit using a lean satellite, horyu-iv, international review of aerospace engineering, 10(3): 12-23. ewang, e. 2017. photoelectron current measurement on nana-satellite in low earth orbit, phd thesis, laboratory of spacecraft environment interaction engineering, kyushu institute of technology, kitakyushu, japan. lai, s. 2011. fundamentals of spacecraft charging spacecraft interactions with space plasma (illustrated ed), princeton university press, new jersey, u.s.pp.1-6 isbn 878-0-691-12947-1. leijtens, j. 2008. sun sensor miniaturization where is the end, in proceedings of ieee sensors, lecce, italy, 26–29 october 2008; 2: 1348–1351. mundari, n., arifur, k., masaru, c., teppei, o., hirokazu, m., minoru, i. kazuhiro, t. and mengu, c. 2011. effect of atomic oxygen exposure on surface resistivity change of spacecraft insulator material. transactions of the japan society for aeronautical and space sciences (jsass), aerospace techology, japan, 9: 1-8. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ewang, et al, on-orbit results of photoelectron current measurement system in low earth orbit on horyu-iv satellite. azojete, 15(sp.i2):46-56. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ewang_arcsste@yahoo.com 56 milton, cp. and jenifer lk. 1996. using the sun analog sensor (sas) data to investigate solar array yoke motion on the goes-8 and -9 spacecraft proceeding, usa, spie 1996, 2812: 753-763. muranaka, t., ueda, h., usui, h. and shinohara, i. 2009. numerical evaluation of electric field sciences observation in the magnetospheric plasma. aerospace research central (arc), florida, 8 of 29: 5142. jose, t. 2003. spacecraft charging at geosynchronous altitudes current balance and critical temperature in a non-maxwelian plasma. msc thesis, department of the air force, air university, ohio. jiang, w., akira, m., arifur, k., minoru, i., kazuhiro, t., mengu, c. and xiaoquan, z. 2015. effects of space environmental exposure on photoemission yield of polyimide. ieee transactions on dielectrics and electrical insulation, 22 (2): 1204 – 1212 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1082-1091 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1082 original research article internet of things (iot) cloud based model for low cost demand side management infrastructure o. k. oyetola1*, a. a. okubanjo1, a. a. okandeji2, o. o. olaluwoye1, p. o. alao,1 and s. n. ukagu3 (1department of electrical and electronics engineering, olabisi onabanjo university, ago-iwoye, ogun state, nigeria. 2department of electrical and electronics engineering, university of lagos, akoka, lagos state, nigeria 3department of electrical and electronics engineering, igbinedion university, okada, edo state, nigeria ) * corresponding author’s email address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1.0 introduction electricity as a form of energy is inevitable for human survival. as human activities increase and new technologies evolve, the importance of electricity cannot be over emphasized. the standard of living and per capital income of any nation largely depends on the availability and consumption of electricity (oyedepo, 2012). as energy consumption is steadily increasing, there is a continuous demand to optimally increase the generation capacity. increasing generation capacity often requires complex processes and control, with costly fuel and sophisticated equipment. this invariably leads to high tariff and billing system as well as an increase in greenhouse gas emission effects. however, despite the significance attached to electricity, it is estimated that approximately 45% of the electricity generated in nigeria is wasted or it cannot be accounted for. this is due to energy theft, unavailability of proper energy management policy, public illiteracy on the importance of electricity, and the need for efficient utilization of available energy (omole et al., 2016). nigeria’s electricity demand is growing faster than the country’s population. the electricity per capita of nigeria, which is 137.2 kwh per capita, is one of the lowest in the world. article information abstract this paper presents a model for low cost demand side management infrastructure using cloud-based technology and internet of things to facilitate the implementation of smart grid in nigeria. the electricity market has experienced a rapid increase in demand attributed to unprecedented growth in human population, urbanization, and industrialization. accordingly, utilities are faced with the challenge of meeting daily energy demand. research has shown that 45% of electricity generated are wasted or cannot be accounted for. energy management is thus a major issue affecting the power sector of nigeria. efficient utilization of energy is therefore crucial for sustainable development both from an economic and ecological perspective. the proposed smart, low cost and iot-enabled power distribution board can be adopted and implemented as part of energy conservation measures to reduce energy demand in domestic building and mitigate the energy crisis in the country. with the iot based smart board energy management, users can get personalized recommendation of actions for energy conservation and load shifting, and have control over the energy use and the billing system. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 march, 2019 revised 17 july, 2019 accepted 20 july, 2019 keywords: smart grid demand side management cloud computing internet of thing. mailto:okubanjo.ayodeji@oouagoiwoye.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1082-1091. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1083 lighting constitutes about 18% of the total power generated as compared to 8 – 10% in developed countries (adelakun et al., 2014). this can be attributed to lack of investment, combined with an asset life of 0250 or more years’ transformers, transmission and distribution networks and inability to use energy conservative policy measures to transform the power sector in nigeria. to mitigate the problem of energy wastage and poor utilization of electricity, a proper demand side management (dsm) infrastructure must be implemented by utilities especially for commercial/residential users. it offers the promise of cutting costs for commercial customers, saving money for households, help utilities operate more efficiently, reduce frequent energy instability, save overhead cost of building backup plants, and to reduce emission of greenhouse gases(cheng et al., 2016: marinakis, 2018; patel et al., 2016). dsm is a firstgeneration of smart grid technology and crucial to overall performance of smart grid systems(eseosa et al., 2014). installing smart grid technology in the nigerian power sector has been identified to be full of myriad of challenges, one of which is dilapidation of existing infrastructures whose replacement and upgrade to meet 21st century energy demand is capital intensive (vincent and yusuf, 2014). with these known challenges, realizing full potential of smart grid technology could take several years in nigeria. however, internet of things (iot) and cloud technology can be employed to reduce the cost of installing grid technology to leverage dsm for domestic and commercial customers (botta et al., 2015: nazir, 2012). iot can be described as a system comprising many distinguishable components that are able to communicate through the internet, either amongst themselves or with end-user or other entities in the network (vadimir and mirjana, 2015). thus, iot is a system of interrelated computing devices, mechanical and digital machines provided with unique identifiers and the ability to transfer data over a network without requiring human-to-human or human-tocomputer interaction. iot therefore helps us to gain knowledge of the world around us. the utilities can benefit from different methodologies to manage the demanded energy by the users using iot-enabled power distribution board (pdb) that can be accessed, monitored and controlled remotely. they may utilize demand response (dr) or direct load control (dlc) methodologies and send a signal to the customers in order to force them to reduce their energy consumption or schedule their consumption to another time when there is more supply. conversely, the utilities may use an incentive-based methodology where they offer cheaper electricity rate for the time when there is more supply. this methodology is typically referred to as time-of-use (tou) rate policy which is becoming common in many utilities. the concept of smart, low cost and iot-enabled power distribution board (slcdb) is relatively a new technology in the power sector. intuitively, pdb is an electrical equipment which consist of necessary electrical components for connecting, controlling and protecting electric circuit in a building or premises. (a. delhi corporation, 2018). slcdb facilitates real-time access to consumer power profile and energy demand for proper management and supply. in addition, slcdb leads to making home automation and appliances smart, as dlc is possible remotely. also, customers demand policy can be implemented and amended easily through the cloud. considering the aforementioned challenges and possibilities, this paper presents a model for low cost dsm infrastructure using cloud based technology and iot to facilitate implementation of smart grid in nigeria and sub-sahara africa. the architecture includes the use of arduino mega 2560 as a microcontroller, relay module, current and voltage sensors and internet technologies. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyetola et al: iinternet of things (iot) cloud based model for low cost demand side management infrastructure. azojete, 15(4):1082-1091. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1084 2. materials and methods the proposed model for implementing dsm is to install slcdb at the demand side for seamless control and monitoring of customer’s energy profile. as shown in figure 1, each customer is connected to the cloud via slcdb, designed to adjust electricity consumption based on existing policies enrolled by customers. basically, this method effectively balances the electricity demand and supply chain without totally removing customers (especially residential) completely from the grid even when they are willing to adjust their demand during peak period. in our proposed model, the design of slcdb is key to the performance of the system and as we focused on cost, convenience of installation and maintenance was also considered. in addition, slcdb was developed to take control instructions over the cloud either from utilities or consumers. figure 1: proposed model architecture slcdb is incorporated with different electrical and electronic devices connected in modules, with some algorithms running on the programming framework. furthermore, this programming framework is equipped with an interface for connecting and controlling equipment, appliances and some other sensor devices. it also contains network interface for transmission and collection of data to execute some actions remotely via an internet protocol (ip) network address. figure 2 shows a block diagram that illustrates the concept of this project. as shown in figure 2, the project comprises of the regulated power supply, the arduino mega board 2560 powered by dc supply, the relay module powered by 5v power supply, ethernet module (ethernet shield w5100) which is mounted on the arduino board and digital display (blue lcd 1602). hence, current sensors are connected to the relay module and to the home appliances. slcdb serves as iot sensor node, it detects the amount of power used in real time and send it over to the cloud. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1082-1091. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1085 figure 2: block diagram of slcdb figure 3 shows the schematic diagram of the slcdb model implemented in a smart home. it is connected in such a way that the model monitors the energy profile, and ensure that no energy is wasted by remotely alerting the users on the status of the appliances through the cloud. the users can then remotely switch off the redundant appliances or utilities. furthermore, the proposed model has a core advantage of shifting the electricity consumption to low cost time tariffs and save energy. figure 3: slcdb breadboard view file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyetola et al: iinternet of things (iot) cloud based model for low cost demand side management infrastructure. azojete, 15(4):1082-1091. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1086 more so, the web server emulator and the control interface of the slcdb are programmed with hthl5 programing language to activate the web server and the arduino, and also link up other components in the slcdb. figure 4 shows the detailed information of the programming and networking part of the system from the web client with a static ip address of 192.168.1.102, to the network containing the internet gateway and the wireless lan, and to the smart, iotenabled power distribution board that has the wed server emulator and the control interface in it. the codes snippet developed for the web server emulator and the control interface for the slcdb model are as follows: figure 4: programming framework for slcdb web-server emulator client=server.available(); if (client) { boolean currentlineisblank = true; string http_req = string(100); int switchrelaynumber = -1; while (client.connected()) { delay(7); if(client.available()){ char c = client.read(); http_req.concat(c); if (c == '\n' && currentlineisblank) { if (http_req.indexof("?relay") > 0) { int startindex =http_req.indexof('?'); int endindex = http_req.indexof('='); switchrelaynumber = (http_req.substring(startindex + 6, endindex)).toint(); int changestate = low; startindex = http_req.indexof("switch+"); endindex = http_req.indexof (" http/1.1"); if ((http_req.substring(startindex + 7, endindex)) == "off") { changestate = high; http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1082-1091. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1087 } switchrelaystate(switchrelaynumber, changestate); } // send a standard http response header printouthtlmcode(); } if (serial.available()) { // read the most recent string inputstring = serial.readstringuntil('\n'); string msg = getstringat(inputstring, ':', 0); if (msg == "switch") { msg = getstringat(inputstring,':', 1); int relaynumber = (msg).toint(); msg = getstringat(inputstring, ':', 2); int state = (msg).toint(); switchrelaystate(relaynumber, state); } else if (msg == "read") { msg = getstringat(inputstring, ':',1); int relaynumber = (msg).toint(); serial.println("sensorcurrent[" + string(relaynumber) + "] = " + string(sensorcurrent[relaynumber], 5)); } } control interface slcdb if (serial.available()) { // read the most recent string inputstring = serial.readstringuntil('\n'); string msg = getstringat(inputstring, ':', 0); if (msg == "switch") { msg = getstringat(inputstring,':', 1); int relaynumber = (msg).toint(); msg = getstringat(inputstring, ':', 2); int state = (msg).toint(); switchrelaystate(relaynumber, state); } else if (msg == "read") { msg = getstringat(inputstring, ':',1); int relaynumber = (msg).toint(); serial.println("sensorcurrent[" + string(relaynumber) + "] = " + string(sensorcurrent[relaynumber], 5)); } } file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyetola et al: iinternet of things (iot) cloud based model for low cost demand side management infrastructure. azojete, 15(4):1082-1091. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1088 4. results and discussion 4.1 phases and implementation this is the phase that involves the construction and testing of the smart, low cost and iotenabled power distribution board. figure 2 above shows how the various components in the smart board interact with each other. the stage is sub dived into phase 1, 2 and 3. 4.1.1 phase 1 the smart, low cost and iot-enabled power distribution board, slcbd was initially assembled and tested on the breadboard as shown in figure 3 using a 9v battery as the power source. the slcbd was further placed on a dc load with acs712 current sensor connected in series and which was later connected to the arduino to obtain the reading. the voltage sensor units consisting of a voltage transformer and 2 resistors of 10k ohms and 100k ohms were also tested. 4.1.2 phase 2 at the second stage, the relay was tested separately when placed on home appliances as a load. the developed smart board consists of 16 on/off relays as shown in figure 5. in this phase, the 16 relays can be controlled remotely whenever demand arises. 4.1.3 phase 3 after obtaining the current reading, the w5100 ethernet module connection to the arduino was implemented and activated to establish communication over the internet via a wi-fi module. in the ethernet module, to establish a connection, the model is connected to a router with the use of rj-45 as shown in figure 6, and the router uses dynamic host configuration protocol to dynamically assign an ip address for the system. a static ip address of 192.168.1.102 is dynamically assigned to the system, and this serves as a gateway to sign-in to the system and control the 16-relays. also, the user access module was developed in this stage to grant access to the user for proper monitoring and controlling of the energy usage through switching on/off relays remotely. additionally, this phase also contains automated control units that coordinates the automatic switching of the load connected to the smart, low cost and iotenabled power distribution board. a relay module is integrated into the smart board for the switching purpose, and the arduino mega2560 oversees the switching of the relay. hence, the users switch off the devices that are not in use through on/off relay to optimize energy cost and save energy. the developed smart, low cost and iot-enabled power distribution board is shown in figure 5 and it is connected over the network through rj45 and a router as shown in figure 6. figure 5: developed smart, low cost and iot-enabled power distribution board http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1082-1091. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1089 figure 6: rj45 and a router figure 7: slcbd graphical user interface the data obtained from the smart, low cost and iot-enabled power distribution board are sent to the cloud which can be exploited in the future as big data, data mining, data storage and database management. invariably, the data sent to the cloud can be later retrieved by the user to monitor the energy consumption profile and control the home appliances remotely in order to reduce outrageous electricity charges. however, data sent and received from the cloud always experience a delay, so the transit time of each data sent to the cloud is evaluated and recorded as shown in table 1. table 1: cloud computing data size and its transit time data size (mb) transit time ((ms) 10 47.93 20 95.86 40 191.73 60 287.6 80 383.47 100 479.34 120 575.21 140 690.82 160 766.95 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyetola et al: iinternet of things (iot) cloud based model for low cost demand side management infrastructure. azojete, 15(4):1082-1091. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1090 it can be deduced from table 1 that the transit time depends on the data size. figure 8 shows the pictorial view of the transit time, and the corresponding data size. from figure 8, it is observed that the transit time increases with the data size. figure 8: graph of transit time against data size for cloud computing 5. conclusion iot technology can contribute significantly to energy saving by monitoring and supporting the behavioral change of energy consumption pattern in a smart home. the proposed smart, low cost and iot-enabled power distribution board facilitates the awareness of energy end-users on how much energy is consumed monthly or yearly i.e., it provides an intelligent energy consumption information and also informs the energy users on the contribution they have made to the energy sector. by means of smart, low cost and iot-enabled power distribution board developed, users are able to monitor the load profile and develop energy consumption habit so as to save energy bill by optimally reducing the energy consumption at the peak of demand hour, when the home appliances are not in used. with this iot based smart board energy management, the user can get personalized recommendation of actions for energy conservation and load shifting, and also have control over the energy used and the billing system. the proposed smart, low cost and iot-enabled power distribution board can be adopted and implemented as part of energy conservation measures to reduce energy demand in domestic building and mitigate the energy crisis in the country reference adelakun, aa., adeyinka, a., abdulkareem, aa. and olowoleni, jo. 2014. automatic control and monitoring of electrical energy consumption using pir sensor module. international journal of scientific and engineering research, 5(5):493–496. botta, a., donato, w., donato, w. and de persico, v. 2015. integration of cloud computing and internet of things:a survey. future generation computer systems, 56(3):1-56 https://doi.org/10.1016/j.future.2015.09.021. cheng, c., peng, j., liao, w. and chang, c. 2016. relationship between building hot water usage and energy and carbon reduction. building services engineering research and technology, 37(6): 682–693. https://doi.org/10.1177/0143624416644483 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1082-1091. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okubanjo.ayodeji@oouagoiwoye.edu.ng 1091 eseosa, o., harcourt, p. and harcourt, p. 2014. improving energy consumption using demand side management system. international journal of science and advanced technology (issn 2221-8386), 4(10): 39–50. marinakis, v. and doukas, h. 2018. an advanced iot-based system for intelligent energy management in buildings. sensors, 18(2): 610-616. nazir, mohsin. 2012. cloud computing: overview and current research challenges. iosr journal of computer engineering, 8(2): 14-22. 10.9790/0661/0811422. omole, os. akpobasah, d. and atayero, aa. 2016. development of a smart , low-cost and iotenabled system for energy management. in 3rd international conference on african development issues (cu-icadi) 150(1): 401–406. https://doi.org/10.13140/rg.2.1.3234.2643 oyedepo, so. 2012. energy and sustainable development in nigeria : the way forward. energy, sustainability and society, 15(2): 1–17. patel, p., patel, m., panchal, v. and nirmal, v. 2016. home automation using internet of things. imperial journal of interdisciplinary research, 3(5): 648–651. vincent, en. and yusuf, sd. 2014. integrating renewable energy and smart grid technology into the nigerian electricity grid system. smart grid and renewable energy, 05(9): 220–238. https://doi.org/10.4236/sgre.2014.59021 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):253-262 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 253 original research article design of rf power amplifier for adual-purpose communication satellite s. umar, s. onuh, e. david* and l. adesina centre for satellite technology development (nasrda), abuja, nigeria article information submitted: 14 october, 2018 revised: 01 november, 2018 accepted: 18 march, 2019 keywords: rf amplifiers communication satellite drain efficiency power mosfets. abstract this paper focuses on the design of rf power amplifiers for a dualpurpose communication satellite. the rapid growth in the use of power amplifiers for satellite communication is been documented. one of the major part of a high frequency communication system is the power amplifiers which amplifiers signals above 3ghz, into a frequency in the order of millions of cycles. the design of a radio frequency power amplifier is the most obvious solution to overcoming the battery lifetime limitation in the satellite communication system. this paper focuses on the design of a radio frequency amplifier with a technique to improve the drain efficiency of the class-f amplifier. this technique uses two passive networks; one of them is in series with the shunt capacitor cs and the other in series with the mosfet transistor’s source terminal. the technique shows a significant improvement in the drain efficiency, which increases from 62% to 90%. this results to the demand for compact, low cost, and low power rf amplifiers. thus, the design consideration was implemented, recorded, tested and met design specification © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction a dual purpose communication satellite can be used as navigation satellite and gps. this creates a communication channel between a source transmitter and a receiver at different locations on earth. dual purpose communications satellites find useful application for internet, television, telephone and military. the rf power amplifiers (pa) are used in a wide variety of applications including wireless communication, tv transmissions, radar, and rf heating. the basic techniques for rf power amplification can use classes as a, b, c, d, e, and f, for frequencies ranging from vlf (very low frequency) through microwave frequencies. rf output power can range from a few mw to mw, depending on application (more and yadav 2016). the introduction of solid-state rf power devices brought the use of lower voltages, higher currents, and relatively low load resistances (li et al., 1984). the most important parameters that define an rf power amplifier are: output power, gain, linearity, stability, dc supply voltage, efficiency and ruggedness. choosing the bias points of an rf power amplifier can determine the level of performance ultimately possible with that pa. by comparing pa bias approaches, can evaluate the tradeoffs for output, power, efficiency, linearity, or other parameters for different applications. (bin and xingang 2014) https://en.wikipedia.org/wiki/communication_channel https://en.wikipedia.org/wiki/transmitter https://en.wikipedia.org/wiki/radio_receiver http://www.azojete.com.ng umar, et al: design of rf power amplifier for adual-purpose communication satellite. azojete, 15(sp.i2):253-262 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 254 1.1 literature review traditionally, pas are categorized into different classes according to their historical precedence. different pa classes can be divided into two major groups: linear and nonlinear pas. class a, ab, b and c pa are some of the well-known linear pas, which are distinguished primarily by their bias condition. the power class of the amplification determines the type of bias applied to an rf power transistor. linear pas have the advantage of high linearity that is important for variable envelope modulation schemes (example4-qpsk) (kazimierzet al., 2001). however, linear amplifiers suffer from poor maximum power efficiency which limits their applications in low power devices. in practice, an efficiency of only below 20% can be achieved in those systems. in contrast, non-linear pas (also known as switched mode pas) can achieve better efficiency. as suggested by its name, non-linear pas have poor linearity performance. nevertheless, it is still acceptable for constant envelope modulation schemes (example fsk). to overcome the problem of linearity to adapt to variable envelope systems, many linearization techniques have been proposed for non-linear amplifiers (kazimierz et al., 2001). therefore, due their high efficiency and the development of linearization techniques, non-linear pas have received more attention over linear topologies in mobile communication in the last decade. class e and f are the most common classes of non-linear pas. in comparison, table 1 shows the classes of pa and its comparison, class e pa requires fast switching driver signal while class f pas does not require such. moreover, because of relatively large switch stresses to active devices, (tan et al., 2012) class e amplifiers do not scale gracefully with the trend toward lower-power technology with lower breakdown voltage. for these reasons, (yadav, 2016) class-f pa has drawn more attention for its easier implementation and better integration with sub-micron cmos technology. table 1: pa class comparison class operation mode angle of conduction (%) drain efficiency (%) a current source 100% 50% b current source 50% 78.5% ab current source 50%-100% 50%-78.5% c current source <50% 100% d switch mode 50% 100% e switch mode 50% 100% f switch mode 50% 100% the first cmos rf power amplifier which delivered the hundreds of mw power reported in 1997, implemented on the single ended configuration with 0.8 µm cmos technology, the power amplifier was able to give 62% drain efficiency of (824~ 849) mhz using the supply voltage of 2.5v. the first ghz range differential power amplifier was reported in 1998, implemented using 0.35 µm cmos technology. in 2001, 130 nm cmos technology came into notice, the main goals for the further improvement in the pa are as follows: (more and yadav 2016). high linearity to satisfy higher-order modulation scheme. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):253-262. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 255 greater average output power level broader operating bandwidth low consumption of radio network energy reduces the environmental impact. 2.0 methodology figure 1 shows the block diagram of the dual purpose amplifier. the figure was the foundation for the detailed design of the dual purpose amplifier. figure 1: block diagram of an rf power amplifier figure 2 is the slave circuit diagram for the dual-purpose amplifier. the circuit was design using resistor r20 value of 10/5w. this resistor and inductor l1 help in frequency modulation however; resistor r21 to r25 must use a uniform value of 10k in order to deliver maximum efficiency. the deliverable power of the pa lies on the numbers of nchannel and p-channel mosfet. the implication of this is that increasing the numbers of mosfet will automatically increase the efficiency. the values c10 and c12 was also consider as they are very significant in signal filtering process. the value of l1 (inductor was considerably chosen). in order to determine the failure rate of the dual purpose amplifier a reliability test was carried out using parts country analysis. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng umar, et al: design of rf power amplifier for adual-purpose communication satellite. azojete, 15(sp.i2):253-262 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 256 figure 2: slave circuit diagram for the dual-purpose amplifier 2.1 determination of input/output matching load line the input matching configuration, including the bias circuit, has an important impact on the operation of the rf power amplifiers. this is because the input match will show different optima for maximum gain, best linearity, and highest efficiency. optimization of the efficiency may involve substantial reduction in power gain. correct handling of harmonics is a necessary feature on the input and the output match. device used well below its cutoff frequency may require specific harmonic terminating circuit elements on the input. the performance of the output matching circuit is critical for a power amplifier. in pa impedance control the amount of power delivered to the output is critical for maximum performance. this is in addition to the amount of gain and noise. this explains why matching network is critical for maximum performance. as aspect that is sometimes overlooked is the power dissipation design in the output matching circuit. this power is lost in the capacitors, inductors, and other loss elements that are part of the matching network. this "dissipation loss" degrades the pa's efficiency and output power capability. different implementations of the output match results in different losses. it is worthy of note that there are still significant design tradeoffs to be made between bandwidth and dissipation loss. for a pa, the loss of the output match is always a concern because of the large power levels involved. a capacitor's quality factor is inversely proportional to its capacitance (c). to minimize the dissipation loss of the output match, it is therefore necessary to design the output match with the lowest possible value of c. the tradeoff is between bandwidth and dissipation loss. different capacitor technologies give different losses when used in http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):253-262. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 257 output matching circuits. one way of understanding the loss mechanisms of an output match is to simulate the match with loss-less components, then introduce loss into one component at a time. mismatch loss[db] = 10*log (1-γ2) (1) where reflection coefficient γ = (vswr−1) (vswr+1) (2) vswr is the voltage standing wave ratio, which is the measure of how efficiently radiofrequency power is transmitted from a power source, through a transmission line, into a load. because the dissipation loss does not depend on the source impedance it is possible to use s21 to find the correct dissipation loss in a circuit simulation. the procedure involves using the complex conjugate of the simulated load line as the source impedance. running at a low efficiency not only reduces talk time in a portable device, but it also creates significant problems with heating and reliability. the load line is set based on the needed power amplifier output power and available supply voltage. rl = vmax imax (3) where rl is the impedance load. matching for maximum gain occurs when the amplifier is unconditional stable and load impedance is equal to the complex conjugate of the same source impedance (conjugate matching). complex conjugate simply refers to complex impedance having the same real part with an opposite reactance. figure 3 shows the input and output matching diagram. e.g. if the source impedance is zs=r+jx, then its complex conjugate would be zs*=r-jx figure 3: input and output matching if matched: zin= zo, γs = s11*, and zout = zo, γl = s22* matching for maximum output power occurs when optimum load impedance (rl) is equal to source impedance (rgen). in order to obtain maximum output power, typically the power amplifier is not conjugate matched. instead, the load is designed such that the amplifier has the correct voltage and current to deliver the required power. if operation is at the optimal power added efficiency point, optimal-power tuning produces about 1 db to 3 db of higher power. gain is reduced (for small pin) typically by a slightly smaller amount. the transistor ’ s input and output impedances will also decrease with an increase in frequency, which further complicates the design of a pa’s matching networks, especially since these impedances can be as low as 0.5 ω . thus, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng umar, et al: design of rf power amplifier for adual-purpose communication satellite. azojete, 15(sp.i2):253-262 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 258 when matching a discrete driver stage to its pa with maximum efficiency, we would normally want to implement a direct match from the true output impedance of the driver to the true input impedance of the pa, instead of first forming a 50-ω match at the output of the driver, and then another 50ω match for the input of the power amplifier, as this would needlessly transform the impedances from low to high, and then back from high to low. by selecting a transistor with a high collector voltage requirement, output impedance can be increased over a transistor that operates at lower values of collector voltage. 3.0 results and discussion from figure 2, the input signal of the slave circuit for the power amplifier is processed and filter through the slave circuit and then passed to the amplification stage, the amplification is done with the aid of p-channel and n-channel mosfet. in the circuit diagram p+ and pis the input power supply from the rectified dc source and the ground terminal. however, two fuses fu1 and fu2 were connected to the input terminal of the slave circuit to protect the circuit from over voltage surge. the design was analyzed and simulated using ltspice electronic software as shown below. figure 4 shows that there is a rise in voltage (gain) with time, this means that at every instant of time the power amplifier experiences an increase in voltage, and however an increase in voltage is an increase in gain. this is in agreement with the result of a study on comparative study of audio amplifiers (vimal raj et al., 2017). figure 4: simulation of voltage gain with time 3.1 reliability calculation of this model using parts country analysis table 2 shows the component used in calculating the failure rate of the system, the total failure rate of the device is 1.057854 x 10-6per hour. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):253-262. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 259 table 2: estimation of failure rate in the circuit component/part no of similar parts �g (x10-6) total failure rate (x10-6) per hour power transistors fet 8 0.014 0.112 low power transistor 2 0.0560 0.112 npn & pnp transistors 4 0.00015 0.0006 zener diode 2 0.0110 0.022 resistor, o.1 watt 19 0.0115 0.2185 resistor, film 5 0.0323 0.1615 capacitor, electrolytic 6 0.0540 0.324 ceramic capacitor 5 0.0035 0.0175 inductor, fixed 2 0.000032 0.000064 (general purpose) diode 9 0.0036 0.0324 switching 1 0.00094 0.00094 rf coaxial 1 0.00045 0.00045 hand solder 43 0.0013 0.0559 σ = 1.057854 λeqpt = i=1 n niλgiπqi� (4) where: eqpt = total equipment failure rate (failure per 106 hours), gi = generic failure rate for the i-the generic part (failures per 106 hours, qi = quality factor for the i-the generic part, ni = quality of i-the generic part, n = number of different generic part categories in the equipment. figure 5 shows the power mosfet (amplification drivers circuit diagram) this circuit uses e-mosfet shown in figure 6, which must have vgs greater than the threshold value (vgs (th)) so that zero bias cannot be used. from equation (5) vg can be determined. this method of e-mosfet bias is equivalent to collector – feedback bias in transistor figure 6(i) shows the drain-feedback bias circuit for n-channel f-mosfet. this is in agreement with an earlier work on cmos based current feedback op-amp with improved bandwidth (akshay2015). a high resistance rg is connected between the drain and the gate. since the gate resistance is super high, no current will flow in the gate circuit (i.e. ig = 0). therefore, there will be no voltage drop across rg. since there is no voltage drop across rg, the gate will be at the same potential as the drain. this fact is illustrated in the dc equivalent circuit of drain-feedback bias as in figure 6(ii) vd = vg and vdg = vgs (5) where; vd = drain voltage vg = gate voltage vdg = voltage along drain and gate terminal vgs = voltage along gate and source file:///c:/users/user/downloads/azojete143/www.azojete.com.ng umar, et al: design of rf power amplifier for adual-purpose communication satellite. azojete, 15(sp.i2):253-262 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 260 figure 5: power mosfet (amplification drivers) figure 6: feedback bias transistor the value of drain-source voltage vds for the drain-feedback circuit is vds = vdd idrd (6) since vds = vgs , vgs = vdd – idrd since in this circuit vds = vgs , id = id(on) therefore, the q-point of the circuit stands determined. from the calculation, the rf power amplifier for the proposed dual purpose communication satellite was successfully designed and developed as shown in figure 8. .the circuit diagram was then printed on a pcb as shown in the layout in figure 9. a prototype of the dual purpose amplifier was then assembled and integrated as shown in figure 10. the prototype was tested at the centre for satellite technology development, abuja. the tests include reliability test and calculation for this design. the results are in agreement with the finding of a study on the comparative study of audio amplifiers (vimal raj et al., 2017). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):253-262. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 261 figure 8: complete circuit diagram of an rf power amplifier figure 9: pcb design layout figure 10: finished prototype rf power amplifiers for the proposed dual purpose communication satellite file:///c:/users/user/downloads/azojete143/www.azojete.com.ng umar, et al: design of rf power amplifier for adual-purpose communication satellite. azojete, 15(sp.i2):253-262 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edet.david@cstd.nasrda.gov.ng 262 4.0 conclusion in this paper, some recent developments of class-f power amplifiers are presented, especially on their integration with deep sub-micron cmos technology. this result is a significant step in the design of a dual purpose amplifier for communication satellite in order to achieve low cost and efficient power amplifier. in addition, many issues are still needed to be resolved before the goal of system-on-a-chip can be realized. nevertheless, the rapid growing demand of mobile communication devices will be a good catalyst for the development of rf power amplifiers and a real soc solution will hit the market very soon in the future. references akshay, d., 2015. cmos based current feedback op-amp with improved bandwidth. american journal of engineering research (ajer) volume-4, issue-10, pp-86-91 bin, w and xingang, w., 2014. overview of commercially available analog/rf simulation engines and design environment in solid-state and integrated circuit technology (icsict), 2014 12th ieee international conference on, vol., no., pp.1-4, 28-31 oct. kazimierz, s., paul, w., and susan, p., 2001. ultra-wide band radio: the emergence of an important new technology, ieee vehicular technology conference, vol.2, pp. 1169-1172, may 2001 li, pw., chin, mj., gray pr., and castello, r. 1984. a ratio-independent algorithmic analog-to-digital conversion technique. ieee j.solid-state circuits, vol. sc-19, pp. 828– 836 more, p and yadav aa 2016. a survey on rf power amplifier designing with cmos technology. international journal of computer applications (0975 – 8887) national conference on advances in computing, communication and networking (accnet – 2016) tan, j., chun-huat, h, and yong, l. 2012. design of efficient class-e power amplifiers for short distance communications. circuits and systems. i: regular papers, ieee transactions on 59.10 (2012): 2210-2220. vimal raj, v., aravindan, s., agnishwar, j., harith, m., manivannan, rb., 2017. g comparative study of audio amplifiers. iosr journal of electronics and communication engineering (iosr-jece) e-issn: 2278-2834,pissn: 2278-8735.volume 12, issue 1, ver. i (jan.-feb. 2017), pp 32-36 yadav, aa., 2016. a survey on rf power amplifier designing with cmos technology. international journal of computer applications (0975 – 8887) national conference on advances in computing, communication and networking (accnet – 2016) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 41 utilization of ceramicware waste as complementary aggregate in hollowmasonry unit production a. a. ajayi-banji1*, d. a. jenyo1, m. a. adegbile1, t. d. akpenpuun1, j. bello1, a. o. ajimo2 and s. sujitha3 1agricultural and biosystems engineering department, faculty of engineering and technology, university of ilorin, ilorin, kwara state, nigeria 2civil engineering department, school of civil and natural resources engineering, yaba college of technology, jibowu, lagos state, nigeria 3civil engineering and environmental engineering department, college of engineering, north dakota state university, fargo, north dakota, usa *corresponding author’s e-mail address: ajayibanjiademola@gmail.com abstract continuous increase in ceramic ware waste from construction and demolition waste without good management practice has resulted in elevated volume of this waste category. however, utilization of this waste in masonry unit production could be a plausible option to solve this menace, particularly, in its ability to enhance masonry unit compressive strength. in this study, ceramic ware waste was utilized for hollow masonry unit production and three different natural fine aggregate to ceramic aggregate mix ratios of 100:0, 90:10, 80:20 and 70:30 were examined. furthermore, the cement to total aggregate mix ratio considered was 1:7. sequel to the process of aggregates mixing, casting, and subsequently demoulding, the masonry units were cured for 28 days prior to inspection for compressive test parameters. results indicated that masonry unit with natural sand to ceramic waste mix ratio of 80:20 has the highest crushing strength at peak, yield and break point which were 60.903kn, 60.493kn and 53.863kn respectively. the compressive stress at peak and break were 6.57mpa and 6.50mpa in that order and young’s modulus was 0.262gpa. statistically, there were no significant differences at 95% confidence interval between the aggregate mix masonry units when the compressive strength indices were evaluated. ceramics ware waste from demolition and construction waste is a suitable co-aggregate in hollow masonry unit production. keywords: construction and demolition waste, ceramic ware waste, reuse, hollow masonry unit, compressive strength, natural fine aggregate 1. introduction construction and demolition wastes generation are on the increase due to growth in dilapidated structures, aged structures and those threatened and affected by natural disasters, and it constitutes the largest fraction globally (zimbili et al., 2014). usually, wastes emanate from neighbourhood where simple structures are demolished and replaced with new and gigantic ones like stories and skyscrapers that can accommodate the growing population demand. replacement of old and dilapidated buildings with aesthetically improved ones has equally contributed to the generation. other salient factors contributive to the waste generation are fire incident and wars (ali and moon, 2007). natural disasters such as earthquake, hurricane and flood are equally inclusive in the list (icsu, 2008, mühr et al., 2017). hence, the waste will continue to grow in volume and pose threat to the environment except pragmatic steps are employed for its judicious utilization. composition of construction and demolition wastes are ceramics ware, metal, wood, concrete, stone, related aggregates, glass, plastic, asphalt, plaster, rubbish, paper and others. mailto:ajayibanjiademola@gmail.com http://www.azojete.com.ng ajayi-banji, et al.: utilization of ceramic ware waste as complementary aggregate in hollow masonry unit production. azojete 14(1):41-53. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 42 among this composition, ceramic ware wastes contribute the greatest stony fraction to the waste stream; about 72% of the fraction (zimbili et al., 2014). the ware wastes are innate materials with high earth minerals subjected to dehydration, with regulated heating of about 1200°c (medina et al., 2012). the wastes are often landfilled though this common disposal option is neither economical nor environment friendly. recently, the non-biological wastes have found unique applications in our society beyond disposal. one important use is as storage bank for nuclear wastes (devanathan et al., 2011). another prominent application of ceramic waste ware was as binding agent in concrete production due to the pozzolanic property (kenna and archbold, 2014). other uses are as fine and coarse aggregates for construction and fillers (amitkumar et al., 2013). production of masonry unit is another feasible area of application. masonry units are used in places like malaysia as noise barrier (herni et al., 2015). they are employed globally in construction industries due to the fire resistance ability, good heat insulating properties and chemical resistance compared with wood and steel (cigr, 1999). although, the low tensile strengths when compared with steel and wood have been the primary challenge of using this construction material especially for load bearing functions. hence, this study intends to investigate the effect of ceramic ware waste as a partial substitution for natural sand aggregates in hollow masonry production and equally inspect the quality in terms of compressive strength. other substances that have been utilized in masonry unit production are rice husk (chukwudedelu et al., 2015) and coconut fiber and shell (ganiron et al., 2017). masonry unit in nigeria is either in the hollow or solid form. this is the major construction material for all kinds of buildings in nigeria as compared with some part of the western world where emphasis is placed on wood. for the purpose of this study, the scale of hollow block considered to nigerian industrial standard (nis) 87 (2001) was 1: 3. 2. materials and methods natural fine aggregate was collected from the stream bed channeled through oke-odo, ilorin in kwara state in nigeria. visible biological materials were sifted with 2 mm diameter plastic sieve from the natural sand to ensure the aggregate was free from organic materials. natural fine aggregate particle size considered in this study was ≤ 0.3 mm. standard methods were employed to determine the natural fine aggregate composition, properties and sand type. ceramic aggregate was obtained from white single fired sanitary ware haphazardly discarded in dumpsites within ilorin metropolis, kwara state, nigeria (figure 1). the sanitary ware was crushed into 0.075 mm particle sizes using 2hp hammer milling machine after collection, cleaning and manual size reduction with sledgehammer (figure 2). structural characterization of both natural sand and ceramic samples were inspected using a jeol jsm-6490lv scanning electron microscope (sem). ceramic and natural sand aggregate proportions were varied into three mix ratios, other than the control. the mix ratios include 100 percent natural sand without ceramic waste (m0), 90 percent natural sand with 10 percent ceramic waste (m10), 80 percent natural sand with 20 percent http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 43 ceramic waste (m20) and 70 percent natural sand with 30 percent ceramic waste (m30). physical properties of the co-ballasts such as specific gravity, moisture content, bulk density and porosity were inspected using standard methods. ordinary portland cement (dangote trade name), potable water, and aggregates were batched by weight and mixed thoroughly to ensure homogeneity in the ratio 1:7 before pouring into the 150 × 75 × 75 mm (inner dimensions) mild steel formwork. water to cement ratio was 0.5. the choice of these ratios was based on recommendation from literatures (afolayan et al., 2017; artêmio et al., 2012; prakash et al., 2013). this formwork dimension was 1:3 of the nigerian industrial standard sandcrete endorsed by the nigerian industrial standard (nis) 87 (2001). the formwork was filled and compacted manually to avoid air spaces within the poured mixture that may reduce strength of masonry unit. freshly formed hollow masonry units were carefully demoulded on approximately 300 × 120 mm plain pallets to avoid cracks (figure 3). the fresh masonry units were stored temporarily in a well-ventilated shed. the blocks were cured by submerging in potable water for 28 days (figure 4). kaosol (2010) recommended this curing age in a study on water treatment sludge reuse for hollow concrete block production. cured masonry units were carefully removed after each curing period, stacked to dry and stored in a wellventilated shed. blocks produced from each mix ratios were duplicated. each block was labelled based on aggregate mix using oil-based paint applied with a soft brush. densities of the masonry units were investigated using standard methods. compressive strength indices were also inspected using testometric (m500) universal testing machine at a test speed of 5 mm/min (figure 5). 3. results and discussion aggregate composition natural fine aggregate obtained from oke-odo contained 91.5 % sand, 2.0 % silt and 6.5 % clay. the clay content was less than 7 %, though this was expected to improve the binding process in the hollow block due to the pozzolanic property. specific gravity of the aggregate was in line with amitkumar et al., (2013) documentation in a study on ceramic waste powder as replacement for cement in concrete production. organic carbon and organic matter resident in the soil were less than 2.0 % each (table 1). this is an indication of soil type suitability for construction purpose, as most organic materials decompose with time, creating pore within dried structures. porosity of ceramic aggregate was over 200 % of the fine aggregate, though the bulk density was less by approximately 900 % (table 1). http://www.azojete.com.ng ajayi-banji, et al.: utilization of ceramic ware waste as complementary aggregate in hollow masonry unit production. azojete 14(1):41-53. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 44 figure 1: ceramic ware waste collected from dumpsite figure 2: granulated ceramic ware waste figure 3: freshly moulded hollow block figure 4: hollow masonry unit under curing figure 5: masonry unit under compressive test properties of aggregate table 1: physical properties of natural sand and ceramic aggregates properties natural sand ceramic particle size (mm) ≤ 0.30 0.075 porosity (%) 8.16 20.95 specific gravity 2.87 2.88 bulk density (g/cm3) 1.64 0.18 moisture content db (%) organic carbon (%) organic matter (%) 1.83 1.10 1.90 2.21 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 45 3.1 density the least density after moulding and before crushing was observed for m0 and m30 respectively (table 2). density after moulding increased between 1.47 – 5.08 % for the entire masonry unit category. reduction in density prior to crushing could be because of handling. decrease in weight could also be attributed to the curing process that ensures the complete hydration of the masonry unit and water loss. solely natural sand aggregate block had the least density. this is an indication that hydration process influences the density of ceramic-based masonry unit than purely natural sand block. furthermore, these densities were within the range for type a hollow sandcrete block (nis, 2001). the densities after moulding was higher than the values obtained for concrete hollow block with the inclusion of coconut fiber cum shell and commercial concrete hollow block documented by ganiron et. al., (2017). table 2:mean masonry unit density block density after moulding (kg/m3) density before crushing (kg/m3) m0 1635.5 1422.2 m10 1718.5 1214.8 m20 m30 1718.5 1659.3 1333.3 1185.2 3.2 scanning electron microscopy pore spaces were noticed in the ceramic ware waste morphological structure while natural sand had rough and crystal–like surface at 50µm and 500 magnification (figures 6 & 7). the pore and rough surface will possibly enhance adhesion of the mix. figure 6: natural sand figure 7: ceramics ware waste http://www.azojete.com.ng ajayi-banji, et al.: utilization of ceramic ware waste as complementary aggregate in hollow masonry unit production. azojete 14(1):41-53. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 46 3.3 compressive strength test results show that energies and forces required to crush the modified aggregates masonry units at 5 mm/min speed were greater than the pure natural sand aggregate hollow blocks (m0) by 57.5 – 467.45 % and 17.7 54.1 % in that order irrespective of the mix ratios considered (table 3). this suggests that hollow masonry unit produced from ceramic-sand aggregates might have higher compressive strength and possibly be a better product than solely natural sand aggregate blocks. the three levels of energies (peak, yield and break) increased with ceramic aggregate increase. similar trend was observed for the compressive force exerted to crush the blocks except for hollow blocks with 30% ceramic aggregate (m30). block produced with mix ratio of 20 % ceramic to 80 % natural sand aggregate required the highest crushing force (60.903kn) as shown in table 3. there was no significant difference among the three ceramic-sand masonry units (m10, m20 and m30) with respect to energies and forces (p > 0.05). the crushing force was higher than the value documented by maroliya (2012) despite the mix ratios of 1:3:6 used in the study. this was also greater than the values reported for commercialized concrete hollow blocks reported by ganiron et. al., (2017). however, it is very close to the force required to crush commercialized hollow bock concrete with the addition of fiber and coconut shell. other possible reason for the difference was the block dimension. crushing energies in this study were greater than values observed by chukwudedelu et. al., (2015). the author obtained crushing energy between 7.55 and 12.80 nm in a study on hollow and dense block production from mixture of rice husk and slaked lime. biological material introduced by the author seems to be the major constituent that might have affected the crushing energy. however, higher energy required in this study to crush the ceramic-sand aggregate blocks shows that ceramic aggregate is a better option than rice husk in terms of strength in hollow masonry unit production, though rice husk block evidently has light weight advantage. table 3: average force and energy values for compressive test class compressive force (kn) energy (nm) peak yield break peak yield break m0 30.435 27.755 27.469 30.42 19.89 41.70 m10 51.449 43.643 39.123 74.77 46.80 88.41 m20 m30 60.903 56.999 60.493 45.730 53.863 54.400 94.08 172.62 69.42 44.06 124.08 186.13 there was no significant difference among the three ceramic-sand masonry units (m10, m20 and m30) with respect to stresses and strains (p > 0.05). stress result followed the same trend with density. the stress at peak, yield and break for the ceramic-sand aggregate blocks were greater than that of natural sand aggregate blocks by 19.3 56.2 %. the greatest yield stress increment based on mix ratio occurred at m20 about 56.2 %. stress at peak for this mix ratio was the highest produced. masonry units with aggregate mix of m20 has highest stress value (6.57 mpa) and lowest strain value (3.72 %). this confirms that m20 masonry unit was stronger and therefore more suitable for construction than other mix ratio and particularly pure natural sand http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 47 masonry unit. the stresses obtained (compressive strength) were lower than the values obtained by barbosa and hanai (2009) in a study on strength and deformation of hollow block with dimension 140 x 390 x 190 mm. however, it was greater than the values obtained for pure concrete hollow block and concrete hollow block with the addition of coconut fiber and shell (ganiron et al., 2017). difference in block size was the obvious explanation for the disparity. despite this, the compressive strength for the ceramic masonry units met the british and nigerian standard (3.5 mpa and 3.45 mpa respectively). it equally met the a(3.5) and a(4.5) hollow load bearing unit specified for indian standard (2005). table 4: average stress and strain values for compressive test class stress (mpa) strain (%) peak yield break peak yield break m0 3.10 2.85 2.83 5.22 4.59 5.83 m10 5.30 4.70 4.14 5.54 3.79 5.90 m20 m30 6.57 5.81 6.50 4.66 5.86 5.45 4.07 7.70 3.72 3.98 5.06 8.05 young’s modulus value was highest with masonry unit produced from 80 % natural sand and 20 % ceramics aggregate mix ratio (0.262gpa). this almost doubled the value for pure natural sand aggregate blocks. this stated elastic modulus is the only value in table 5 greater than the one reported by ganiron et al., (2017) for concrete hollow block with coconut and fiber inclusion. though with respect to deflection from these masonry unit category, the least deflection was observed for m20 (table 5). the high young’s modulus value indicates the suitability of m20 masonry unit compared with the other block categories in this study. there was no significant difference among the three ceramic-sand masonry units (m10, m20 and m30) with respect to deflection (p > 0.05). deflection during compression test was highest for m10 at break, 10 % ceramicsand aggregate mix ratio (table 5). table 5: average deflection and young’s modulus values for compressive test class deflection (mm) young’s modulus (gpa) peak yield break m0 3.65 3.21 4.08 0.139 m10 3.88 3.04 4.13 0.147 m20 m30 2.85 4.43 2.62 2.79 3.54 5.63 0.262 0.213 3.4 stress-strain pattern the three stress strain curves in figures 8 10 followed the same trend. hemant et al., (2007), reported these overall non-linear shaped stress-strain curves. non-linearity in the blocks were more obvious and pronounced when ultimate failure loads were reached (figures 8 – 10). http://www.azojete.com.ng ajayi-banji, et al.: utilization of ceramic ware waste as complementary aggregate in hollow masonry unit production. azojete 14(1):41-53. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 48 these curves trend seem to be specific for hollow masonry units, as prism masonry units had linear stress strain curve (prakash et al., 2013). therefore, stress-strain pattern is subjective to the type of masonry unit under consideration. block produced with mix ratio of 20 % ceramic to 80 % fine aggregate had the best stress-strain curve pattern. figure 8: stress strain curve for hollow block with10% ceramic ware waste hollow block figure 9: stress strain curve for hollow block with 20% ceramic ware waste hollow block m10 sample a m10 sample b m20 sample a m20 sample b http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 49 figure 10: stress strain curve for hollow block with 30% ceramic ware waste hollow block 3.5 intra-relationship between mix ratio and compressive test output masonry unit with 30% ceramic waste mix ratio was exempted from the intra-relationship between mix ratio and compressive test output. this was due to inconsistent pattern observed as compared with other mix ratios. graphs for m10 were equally not presented. strong nexus exits between the various natural sand-ceramic mix ratio and the compressive test outputs such as compressive force and energy required to crush masonry units. the correlation coefficients (r2) were more than 0.95. this is an indication that crushing energy and force values under this mix ratio conditions can be predicted. on the contrary, relationships for the other compressive test parameters such as compressive strength, strain, deflection and young’s modulus investigated in this study were inconsistent and mostly below 0.81 (figures 11-16). figure 11: aggregate mix ratio and compressive force nexus m30 sample a m30 sample b http://www.azojete.com.ng ajayi-banji, et al.: utilization of ceramic ware waste as complementary aggregate in hollow masonry unit production. azojete 14(1):41-53. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 50 figure 12: aggregate mix ratio and energy applied nexus figure 13: aggregate mix ratio and compressive stress nexus figure 14: aggregate mix ratio and strain nexus http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 51 figure 15: aggregate mix ratio and deflection nexus figure 16: aggregate mix ratio and young’s modulus nexus 4. conclusion quest for strength in masonry units in order to meet present day demands in construction has fostered the utilization of various materials, especially solid waste introduction into aggregate mix. this study considered the 10, 20 and 30 % fractional replacement of natural sand aggregate with single fired sanitary ware waste. hollow masonry units from ceramics and fine aggregates have more suitable compressive strength than pure natural sand ballast blocks. however, m30 did not follow the same trend as other modified hollow blocks from the compressive strength indices investigated. block from 80:20 percent ceramic to fine aggregates mix ratio was the best under the study, the compressive strength ranges from 5.86 6.57 mpa and as such suitable for load bearing structures. stress-strain curves followed overall non-linear pattern. there was no significant difference among the three ceramic-natural sand mix ratios utilized in this study, however m20 masonry unit has the highest potential of being utilized than other grades considered in this study. modification of aggregate composition in masonry unit production with ceramic ware waste enhanced masonry unit quality and this will reduce environmental nuisance resulting from poor management practices of construction and demolition waste. ceramic wares from demolition and construction wastes are feasible co-ballast in hollow masonry unit construction. http://www.azojete.com.ng ajayi-banji, et al.: utilization of ceramic ware waste as complementary aggregate in hollow masonry unit production. azojete 14(1):41-53. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 52 references afolayan, jo., ijimdia, st. and oriola, fop. 2017. effect of water-cement ratio on the compressive strength of sandcrete block blended with sawdust ash. international journal of development research, 7(9):14923-14928. ali, mm. and moon, ks. 2007. structural developments in tall buildings: current trends and future prospects. architectural science review, 50(3): 205 – 223. amitkumar, dr., indrajt, np. and jayeshkumar, p. 2013. ceramic waste: effective replacement of cement for establishing sustainable concrete. international journal of engineering trends and technology, 4(6): 2324 – 2328. artêmio, f. jr., machado, cj., lima, oa. and p. jr., luiz roberto 2012. a mix design methodology for concrete block units. developing the future masonry. fifteenth international brick and block masonry conferenceflorianópolis, brazil. barbosa, cs. and hanai, jb. 2009. strength and deformability of hollow concrete blocks: correlation of block and cylindrical sample test results. ibracon structures and materials journal, 2(1): 85 – 99. british standard 3921 (1969) specification for bricks and blocks of fired brick earth clay or shale chukwudebelu, ja., igwe cc., and madukas, ei. 2015. prospects of using whole rice husk for the production of dense and hollow bricks. african journal of environmental science and technology, 9(5): 493 – 501. cigr handbook of agricultural engineering (1999) animal production and aquacultural engineering, volume ii. edited by cigr–the international commission of agricultural engineering. devanathan, r., gao, f. and sun, x. 2011. challenges in modelling the degradations of ceramic waste forms, united states department of energy, united states, pp. 1 – 4. ganiron, tu., ucol-ganiron, n. and ganiron, ut. 2017. recycling of waste coconut shells as substitute for aggregate in mix proportion of concrete hollow blocks. world science news, 77(2): 107 – 123. hemant, bk., durgesh, cr. and sudhir, kj. 2007. stress-strain characteristics of clay brick masonry under uniaxial compression. journal of materials in civil engineering, 728 – 739. herni, h., ramdzani, a. abang, aa. and mohd, jm. 2015. effectiveness of existing noise barriers: comparison between vegetation. concrete hollow block, and panel concrete, procedia environmental sciences, 30: 217-221. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):41-53. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 53 indian standard 2005. concrete masonry units — specification part 1. hollow and solid concrete blocks.is 2185. international council for science regional office for asia and the pacific, icsu, (2008) science plan on hazards and disasters: earthquakes, floods and landslides, 1 – 37. kaosol t. 2010. reuse water treatment sludge foe hollow concrete block manufacture. energy research journal, 1(2): 131 – 134. kenna f. and archbold, p. 2014. ceramic waste sludge as a partial cement replacement. civil engineering research in ireland, queens university belfast, pp. 1-6. medina c., sanchez de rojas, mi. and frias, r. 2012. reuse of sanitary ceramic waste as coarse aggregate in eco-efficient concretes. cement and concrete composites, 34: 48 – 54. mühr, b., daniell, j., kron, a., jahanbazi, m., bartsch, m., raskob, w., wisotzky, c., barta, t., kunz, m., wandel, j., becker, f., latt, c. and mohr, s. 2017. center for disaster management and risk reduction technology, cedim forensic disaster analysis group (fda) hurricane/ tropical storm harvey information as of 29 august 2017 – report no. 1, karisruhe institute of technology, pp. 1-16. nigerian industrial standard (nis) 87 2001. standard for sandcrete blocks. standards organisation of nigeria. prakash, tm., naresh, k. and karisiddappa, bg. 2013. strength and elastic properties of aerated concrete block masonry. international journal of civil and structural engineering, 2(1): 63-76. zimbili, o., salim, w. and ndambuki, m. 2014. a review on the usage of ceramic wastes in concrete production. international journal of civil, environmental, structural, construction and architectural engineering, 8(1): 91 – 94. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 74-85 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng *corresponding author email: babsina@oauife.edu.ng 74 original research article sensory, textural and cooking quality of instant noodles produced from musa spp wheat composite flours w. a. adebayo1, b. s. ogunsina2* and k. a. taiwo1 1dept. of food science and technology, obafemi awolowo university, ile ife, nigeria. 2dept. of agricultural and environmental engineering, obafemi awolowo university, ile ife, nigeria. article information received: october, 2018 accepted: december, 2018 keywords: instant noddles musa spp cooking quality characteristic abstract enormous post-harvest losses (35 60%) associated with banana and plantain products in nigeria and other producing countries in the tropics culminate in great losses for farmers. in nigeria, unripe plantain is normally processed into flour with limited consumption only as reconstituted dough in local food systems. previous studies established that nigerians have acquired taste for noodles and it is widely consumed across all strata of the economic divide. information regarding the production of instant noodles from musa spp. is rarely found in literature; hence in this study the quality characteristics of instant noodles produced from musa spp – wheat composite flours was investigated. musa spp – wheat composite flours in the ratios 0:100; 5:95; 10:90; 15:85; 20:80 and 25:75 were processed into instant noodles. the proximate composition, sensory, textural and cooking quality of the instant noodles were determined following standard procedures. the results showed a corresponding increase in the crude fat, ash and fibre contents of instant noodles as the percentage substitution with musa spp flour in the instant noodle formulation increased. significant differences (p<0.05) were observed in the taste, colour, flavor, texture and overall acceptability of the products. it was observed that cooking time and cooking loss decreased from 4.38 – 3.40 min and 7.61 – 5.51% as percentage substitution increased, respectively; whereas cooking gain, moisture and fat uptake increased as substitution level increased. the force–deformation curve of musa spp wheat instant noodle obeyed the hooke’s law showing a decrease in the strength characteristics of noodles as percentage substitution with musa spp flour increased. the production of instant noodles from banana and plantain offers means of promoting and extending its utilization, thereby boosting the income obtainable from its production. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction instant noodle has increasingly become an important food item globally, with annual production of 101,420 million packs in 2012, and a steady increase of 3% annually since 2010 (world instant noodle association, 2013). most instant noodles are made of wheat as the base material, thus instant noodle consumption led to dependency on massive importation of wheat in non-wheat producing countries nigeria inclusive. apart from high cost of wheat importation, excessive consumption of wheat has been associated with allergy, asthma, autoimmune response, or gluten sensitivity (rosell et al., 2013) in some parts of the world. several works have been done on gluten-free noodle using different types of flour, although rice flour (inglett et al., 2005; yadav et al., 2011; heo et al., 2013) seems to be the best replacement for its small http://www.azojete.com.ng mailto:babsina@oauife.edu.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 75 granule sizes to benefit noodle textural characteristics. some other raw materials for glutenfree noodle include sorghum (liu et al., 2012), and corn starch (yuan et al., 2008; yousif et al., 2012) or corn flour (padalino et al., 2013). lately, sweet potato starch (silva et al., 2013), pseudo-cereal such as amaranth flour in combination with cassava starch (fiorda et al., 2013) have also been used for the making of gluten-free pasta. the absence of gluten in non-wheat noodle composition often adversely affects noodle quality; hence non-gluten noodle requires treatment to improve its textural quality. several techniques commonly used for starch textural improvement are annealing, hydrothermal treatment (hormdok and noomhorm, 2007), gelatinization (yousif et al., 2012) and fermentation (yuan et al., 2008). in addition, the use of hydrocolloids such as carboxymethylcellulose (choy et al., 2012), konjac glucomannan (zhou et al., 2013), β-glucan (inglett et al., 2005; heo et al., 2013a), transglutaminase (gan et al., 2009; kim et al., 2014), and acetylated starch (choy et al., 2012) have also been reported. however, in this work, the sensory, textural and cooking quality of instant noodles produced from musa spp and wheat flours is investigated with the view to providing baseline information on the production of instant noodles from musa spp fruits. 2.0 materials source of material: freshly harvested bunches of musa spp fruits (plate 1) were obtained from obafemi awolowo university teaching and research farm, ile-ife. the extent of maturity was based on the stage one colour classification documented (ahenkora et al., 1997 and dadzie and orchard, 1997). other materials such as white wheat flour (dangote brand), iodized table salt (dangote brand), potato starch, guar gum, potassium carbonate (food grade), sodium carbonate (food grade) and sodium tripolyphosphate (sttp, food grade) were bought from a local market in ile-ife, osun state. the chemicals used for analysis were of analytical grade. preparation of musa spp flour: about 10 kg of freshly harvested debunched musa spp fruits were immersed in a plastic bowl containing potable water on individual variety basis for 5 min. the fruits were removed from the bowl and peeled with the aid of a stainless kitchen knife. the pulp was sliced into cylindrical discs with thickness of about 5 mm and dipped in citric acid (cit) (1% w/v) for 1 min to prevent enzymatic browning reaction (adeyemi and oladigi, 2009). accumulation of moisture on the sliced surface as a result of the pretreatment was drained with a cheese cloth before samples were transferred to dryer set at 70 °c (adeniji et al., 2010). the citric acid treated musa spp fruit slices were dried in a convective air-oven at +70°c (±1°c) air velocity of 2.2 m/s (adeyemi and oladigi, 2009; adeniji et al., 2010). prior to loading of the fruit slices, the dryer was run for 30 min to reach drying air temperature conditions. the sliced fruits were dried in thin layer for 48 h to constant weight at which the chips were considered to have attained its equilibrium moisture content. the chips were milled using laboratory milling machine (sieve size 500 µm aperture) and stored in an air tight bottle until the time of use. figure 1 shows the flow chart for the production of pretreated musa spp flour samples. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adebayo, et al: sensory, textural and cooking quality of instant noodles produced from musa spp wheat composite flours, azojete, 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 76 plate 1: a freshly harvested matured plantain (agbagba) musa spp fruits blend formulation of musa spp-wheat composite flour: the processed musa spp flour was blended with wheat flour at 0, 5, 10, 15 20 and 25% replacement (arshad et al., 2010) using a kenwood food processor (model 49074, kenwood ltd, hants, uk) operated at full speed for 10 mins. the blends were stored in high density polyethylene bags (0.77 mm thick) prior to use. figure 1: a flow chart showing production of musa spp flours source: adeniji et al. (2010) musa spp wheat instant noodle production: a laboratory model rotating single screw extruder was used to produce extrudate. the barrel diameter and length-diameter (l/d) ratio were 37 mm and 27:1, respectively with screw configuration standardized for processing flourbased products. the screw profile comprises self-wiping elements to improve mixing and apply shear to the material being extruded, while restricting flow and building up pressure. the exit diameter of the circular die is 1 mm. the extrusion of musa spp-wheat flour composite dough was conducted at barrel temperature, 100 °c and screw speed, 85 rpm. the formulations and flow chart for the instant noodle production are shown in table 1 and figure 2, respectively; while plate 2 shows samples of the instant noodles. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 77 3.0 methods proximate analysis: the proximate composition of instant noodles samples was determined according to aoac (2002) method. the parameters investigated are: moisture content, crude protein, crude fat, ash, crude fibre and carbohydrate. all reagents used are of analytical grade (bdh chemicals, poole, uk). determination of optimum cooking time: the optimum cooking time was determined following the method of widjaya et al. (2008). about 10 g of instant noodle was boiled in 1000 ml of boiling water and after each minute of cooking for the first 2 min, noddle was removed and squeezed between clear glass slides. this procedure was then repeated by removing the noodles every 15 s until the white core becomes unnoticeable. therefore, the time taken for the white core to disappear when the noodle strand was boiled in the distilled water is taken as the optimum cooking time. determination of cooking weight and cooking loss: cooking weight and cooking loss were determined by methods of oh et al. (1985) and aacc international (2000) approved method 66 – 50, respectively. ten grams (10 g) of instant noodle was cooked in 300 ml of distilled water in a beaker to their optimum cooking time, rinsed with distilled water, drained and left to cool for 5 min at room temperature. the noodles were weighed and % increase in weight was obtained by gravimetry. residual water was removed by drying in the oven at 100 °c until there was no trace of water in the beaker. the samples were cooled and weighed table 1: formulation of instant noodle from musa spp-wheat composite flour formulations ingredients 0%nod 5%nod 10%nod 15%nod 20%nod 25%nod wheat flour, g 100 95 90 85 80 75 musa spp flour, g 0 5 10 15 20 25 water, ml 34 34 34 34 34 34 salt, g 1.6 1.6 1.6 1.6 1.6 1.6 potato starch, g 12 12 12 12 12 12 guar gum, g 0.2 0.2 0.2 0.2 0.2 0.2 potassium carbonate, g 0.12 0.12 0.12 0.12 0.12 0.12 sodium carbonate, g 0.8 0.8 0.8 0.8 0.8 0.8 sttp, g 0.1 0.1 0.1 0.1 0.1 0.1 0%nod (control) =100% wheat flour; 5%nod = 95% wheat+ 5% musa spp flour; 10%nod = 90% wheat+ 10% musa spp flour; 15%nod = 85% wheat+ 15% musa spp flour; 20%nod = 80% wheat+ 20% musa spp flour and 25%nod = 75% wheat+ 25% musa spp flour (hou et al., 1997) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adebayo, et al: sensory, textural and cooking quality of instant noodles produced from musa spp wheat composite flours, azojete, 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 78 figure 2: a schematic diagram showing production of fried instant noodle plate 2: fried instant noodles produced from musa spp-wheat flours (a)100% wheat flour instant noodle; (b) 5% musa spp flour + 95% wheat flour instant noodle; (c) 10% musa spp flour + 90% wheat flour instant noodle; (d) 15% musa spp flour + 85% wheat flour instant noodle; (e) 20% musa spp flour + 80% wheat flour instant noodle; (f) 25% musa spp flour + 75% wheat flour instant noodle again. the percentage weight loss during cooking was obtained by gravimetric method. values reported are average of five replications. 100   d dc w w ww c (1) where: cw = cooking weight (%); wc = weight of cooked instant noodle, g and wd = weight of dried instant noodle, g. 100 d l l w wc (2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 79 where: cl = cooking loss, %; wl = weight of loss solid, g determination of crude fat: ground instant noodle (3 g) was subjected to soxhlet extraction with n-hexane for about 6 h. the was desolventized by flash evaporation and further drying in a hot-air oven at 100 °c for 30 min. to remove residual organic solvent and moisture. the oil was allowed to cool in a dessicator and weighed. the quantity of oil obtained was expressed as percentage of the original sample weight used. 100%  sample oil w w cf (3) where: cf = crude fat content ,%; woil = weight of extracted oil, g; wsample = weight of sample, g sensory evaluation of produced instant noodle: a semi-trained twenty-six panelist was used from the department of agricultural and environmental engineering of obafemi awolowo university, ile-ife, south-western nigeria (mcwatter et al., 2008). criteria for selection are that panelists are 18 and above years of age; regular consumers of noodles; and not allergic to any food. the panelists filled a consent form approved by the university institutional review board and received instructions on how to use the sensory booth signal lights to communicate with the server. they were instructed to evaluate appearance and colour first and taste each sample afterwards to evaluate flavour, texture and overall liking. a rating scale of l – 7 points (1 = dislike very much; 7 = like very much) was used (mcwatter et al., 2008). the formulated products were evaluated 3 h after production. water and unsalted crackers were provided to panelists to cleanse their palates between samples and covered expectoration cups if they did not wish to swallow the samples. samples were identified with 3 digit code numbers and presented in a random sequence. panelists were also asked if they would buy the product if it were commercially available and how much they would be willing to pay (lower, same, or higher price) compared with similar commercial products. they were also asked to comment freely on the samples. evaluation was conducted in a climate-controlled sensory evaluation laboratory equipped with individual partitioned booths without special lighting determination of textural quality: compression test was conducted using a universal testing machine (instron electromechanical testing systems, model 3369, 50 kn, instron corporation, usa) at centre for energy research development, obafemi awolowo university, ile ife. the samples were discreetly loaded at the rate of 10 mm/min. the test results and graphs were automatically generated. the data obtained included compressive load at yield, compressive strain at yield, compressive stress at yield and energy at yield. the experiment was replicated fifteen times. 4.0 results and discussion the proximate composition values of musa spp-wheat instant noodle were expressed on dry basis (table 2). the carbohydrate content of the musa spp-wheat instant noodle samples ranged from 73.67 – 76.32 % with samples 25%nod and 0%nod having the minimum and maximum values, respectively. there is significant difference (p< 0.05) in the carbohydrate content of all the noodle samples, with all the instant noodle samples being of high calorie values. the carbohydrate content of musa spp-wheat instant noodle compared favourably with 64.6 – 79.1%; 70.3973.80% and 68.30% reported for cassava instant noodle (sanni et al., 2004), sweet potato-wheat instant noodle (taneya et al., 2014) and corn-tapioca-wheat instant noodle file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adebayo, et al: sensory, textural and cooking quality of instant noodles produced from musa spp wheat composite flours, azojete, 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 80 (pakhare et al., 2016). the crude protein content values of musa spp-wheat instant noodle samples ranged from 9.46 to 11.86% with samples 25%nod and 0%nod having minimum and maximum values, respectively, indicating significant differences at p<0.05. this implies that substitution of wheat flour with musa spp flour reduced the crude protein content of the instant noodles. the crude protein values compared favourably with 5.8 – 12.4% and 11.66 – 12.51% reported for cassava-wheat instant noodle (sanni et al., 2004) and sweet potato-wheat instant noodles (taneya et al., 2014), but lower than 14.29% and 14.9% reported by pakhare et al. (2016) for defatted rice bran-soybean-wheat noodle, respectively. the crude fat, crude fibre and ash values of musa spp-wheat instant noodles ranged from 10.35 – 14.74%; 0.40 – 0.88% and 1.09 – 1.17%, respectively. increased addition of musa spp flour as replacement for wheat in instant noodle production affected the crude fat, fibre and ash contents of the products significantly (p< 0.05). the improved crude fat content may be as a result of the absorption of fat during frying. the crude fat results compared favourably with 11.1 – 18.4% documented by sanni et al. (2004) for cassava-wheat instant noodle but higher compared with 5.3 – 6.25% and 4.98% documented by taneya et al. (2014) for sweet potato-wheat instant noodle and pakhare et al. (2016) for corntapioca-wheat instant noodle. in addition, the crude fiber results compared favourably with 0.2 0.8% and 0.54 – 0.58% documented by sanni et al. (2004) for cassava-wheat instant noodle and taneya et al. (2014) for sweet potato-wheat instant noodle, respectively; although, pakhare et al. (2016) reported a higher crude fibre value (4.02) for corn-tapioca-wheat instant noodle. the ash content also compared favourably with 0.6 – 1.2% and 1.54% documented by sanni et al. (2004) for cassava-wheat instant noodle and pakhare et al. (2016) for corn-tapioca-wheat instant noodle but lower compared with 2.212.44% documented by taneya et al. (2014) for sweet potato-wheat instant noodle. table 2: proximate composition of musa spp-wheat instant noodle sample moisture content, d.b (%) crude fat (%) crude fibre (%) ash (%) crude protein (%) carbohydrate (%) 0%nod 3.72a±0.32 10.35f±0.27 0.40f±0.02 1.09c±0.01 11.86a±0.02 76.30a± 0.25 5%nod 3.78a±0.41 10.79e±0.24 0.44e±0.02 1.09c±0.01 11.37b±0.12 76.32a±0.14 10%nod 3.88a±0.38 11.13d±0.10 0.55d±0.01 1.12b±0.01 10.81c±0.03 76.20a±0.50 15%nod 3.95a±0.26 12.82c±0.06 0.70c±0.02 1.13b±0.01 10.43d±0.01 74.92b±0.10 20%nod 4.02a±0.35 13.97b±0.07 0.83b±0.02 1.15a±0.00 9.96e±0.08 74.08c±0.14 25%nod 4.05a±0.29 14.74a±0.05 0.88a±0.01 1.17a±0.01 9.46f±0.05 73.67c±0.09 values are mean ± standard deviation of triplicate. values followed by the same letter in the same column are not significantly different (p< 0.05), 0%nod = 100% wheat flour instant noodle; 5%nod = 5% musa spp flour + 95% wheat flour instant noodle; 10%nod = 10% musa spp flour + 90% wheat flour instant noodle; 15%nod = 15% musa spp flour + 85% wheat flour instant noodle; 20%nod = 20% musa spp flour + 80% wheat flour instant noodle; 25%nod = 25% musa spp flour + 75% wheat flour instant noodle cooking properties: the cooking time ranged from 3.40 – 4.38 min for the instant noodle samples with sample 25%nod and 0%nod having minimum and maximum values, respectively (table 3). the values showed that as percentage of substitution of glutten-rich (wheat) flour with non-gluten (musa spp) flour, there is reduction in cooking time of the instant http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 81 noodle. this may be attributed to discontinuity within the gluten matrix, which resulted in weak dough properties (manthey et al., 2004; omeire et al., 2015). there is significant difference (p< 0.05) in the instant noodles cooking time at all levels of substitution. the cooking time values of musa spp-wheat instant noodle compared favourably with 3.11 – 4.77 min for breadfruitkonjac-pumpkin-wheat instant noodle; 4.5 – 8.29 min for plantain-wheat instant noodle and 4.3 – 5.41 min for corn-tapioca-wheat instant noodles (purwandari et al., 2014; ojure and quadri, 2012; pato et al., 2016) but lower than 5.6 – 6.6 min reported by ritika et al. (2016) for malted and fermented cowpea-wheat instant noodle; 7.33 – 8.67 min for sago starch-wheat instant noodle (purwani et al., 2006); 7.30 min for defatted rice bran-soywheat instant noodle (pakhare et al., 2016) and 7.16 – 9.36 min reported for raw jackfruit-wheat instant noodle (kumari and divakar, 2017). the cooking gain values ranged from 168.11 – 183.55% with samples 25%nod and 0%nod having the minimum and maximum values, respectively. there is significant difference (p<0.05) among the instant noodles’ cooking gain. the results obtained compared favourably with 120.7 – 160.3% reported by ritika et al. (2016) for malted-fermented cowpea-wheat instant noodle but lower than 252 – 379% and 287 – 362% reported by purwani et al. (2006) for sago starch-wheat instant noodle and foo et al. (2011) for soy protein isolate-wheat instant noodle respectively. cooking loss values ranged from 5.51 – 7.65 with samples 0%nod and 20%nod having lowest and highest values, respectively. the optimum solution (cooking loss of 7.03%) is found at barrel temperature of 100 °c and 85 rpm conveying shaft speed. the cooking loss results obtained compared favourably with 6.39 – 10.40% reported by ojure and quadri (2012) for cassava-wheat instant noodle but higher than 0.93 – 1.63% and 2.01 – 6.19% reported by ritika et al. (2016) for malted-fermented cowpea-wheat instant noodle and purwani et al. (2006) for sago starchwheat instant noodle, respectively. purwandari et al. (2014) reported that cooking loss of instant noodles from blends of breadfruit, konjac, pumpkin and wheat flours, ranged from 12.45 – 17.04%. these results are in the agreement with the study of martinez et al. (2007) who reported that partial or complete substitution of durum wheat semolina with fibre material can result in negative changes to pasta quality, including increased cooking loss. the high cooking loss recorded by musa spp-wheat instant noodle as substitution increases could be due to a weakening of the protein network by the presence of musa spp (non-gluten protein) flour which allows more solids to be leached out from the noodles into the cooking water (yu and ngadi, 2004; wu et al., 2006). the moisture uptake ranged from 9.79 – 12.01% with samples 0%nod and 25%nod having minimum and maximum values, respectively. the fat uptake values ranged from 9.37 – 12.82% with samples 0%nod and 25%nod having lowest and highest values, respectively. table 3: cooking properties of musa spp-wheat instant noodle sample cooking time, min cooking gain, % cooking loss, % moisture uptake, % fat uptake, % 0%nod 4.38±0.01 183.55±2.11 5.51±0.01 9.79±0.55 9.37±0.32 5%nod 4.17±0.01 173.78±1.78 6.31±0.01 10.27±0.81 9.94±0.51 10%nod 4.06±0.02 173.68±1.83 6.31±0.01 10.7±1.09 10.01±0.23 15%nod 4.09±0.01 173.45±1.21 7.19±0.02 11.16±0.95 11.17±0.64 20%nod 3.48±0.01 169.68±1.56 7.65±0.02 11.59±0.27 12.47±1.02 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adebayo, et al: sensory, textural and cooking quality of instant noodles produced from musa spp wheat composite flours, azojete, 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 82 25%nod 3.40±0.01 168.11±1.97 7.61±0.01 12.01±1.02 12.82±1.17 values are mean ± standard deviation of triplicate analysis, values followed by the same letter in the same column are not significantly different (p < 0.05), 0%nod =100% wheat flour instant noodle; 5%nod= 5% musa spp flour + 95% wheat flour instant noodle; 10%nod = 10% musa spp flour + 90% wheat flour instant noodle; 15%nod = 15% musa spp flour + 85% wheat flour instant noodle; 20%nod = 20% musa spp flour + 80% wheat flour instant noodle; 25%nod = 25% musa spp flour + 75% wheat flour instant noodle sensory evaluation the values of sensory attributes of musa spp-wheat instant noodle are presented in table 4. overall acceptability of the instant noodle products ranged from 1.15 – 5.96% with products 0%nod and 25%nod having minimum and maximum values, respectively on a 7-point hedonic scale. there is decline in overall acceptability of the instant noodle from like moderately to dislike very much as percentage of substitution of wheat flour was increased in the formulation. the products 5%nod and 10%nod were slightly liked by the panelists but further decline in wheat flour percentage proportion in the formulation beyond 10% (w/w) led to dislike of the products by the panelists. the taste, colour and texture values of the musa sppwheat instant noodles ranged from 2.42 – 6.15%, 1.19 – 6.15% and 3.77 – 6.23%, respectively. the taste values showed that as the proportion of wheat substitution increased, the panelists’ assessment of taste changed from being like moderately to dislike moderately. the panelists liked the taste of the instant noodle as the proportion of wheat flour replacement is not beyond 10% (w/w). another important organoleptic property in instant noodle is colour because it influences purchasing decisions of its consumers. the panelists assessed the colour of the product 0%nod as like moderately but as the inclusion of musa spp flour into the instant noodle formulation increased, the panelists’ assessment of the instant noodle changed to dislike very much. this showed that the colour of musa spp-wheat instant noodle was not acceptable to the panelists. the instant noodle flavour was liked moderately by the panelists till 10% (w/w) substitution of wheat flour with musa spp flour. further increase in percentage proportion of musa spp flour in the formulation made the panelists to dislike very much the instant noodle flavour. table 4: sensory evaluation score of musa spp-wheat composite flour instant noodle products taste colour flavor texture overall acceptability 0%nod 6.15a±0.77 6.15a±0.72 5.58a±0.49 6.23a±0.69 5.96a±0.71 5%nod 5.73b±0.59 2.38b±0.49 5.15b±0.53 5.42b±0.68 4.69b±0.77 10%nod 5.31c±0.67 2.42b±0.49 5.42ab±0.68 5.27b±0.81 4.39b±0.49 15%nod 4.23d±0.57 1.62c±0.48 3.50c±0.50 3.96c±0.71 2.08c±0.73 20%nod 3.19e±0.62 1.50c±0.50 3.39c±0.49 3.62c±0.56 1.58d±0.49 25%nod 2.42f±0.49 1.19d±0.39 1.73d±0.59 3.77c±0.42 1.15e±0.36 values are mean ± standard deviation of triplicate, values followed by the same letter in the same column are not significantly different (p< 0.05), 0%nod = 100% wheat flour instant noodle; 5%nod = 5% musa spp flour + 95% wheat flour instant noodle; 10%nod = 10% musa spp flour + 90% wheat flour instant noodle; 15%nod = 15% musa spp flour + 85% wheat flour instant noodle; 20%nod = 20% musa spp flour + 80% wheat flour instant noodle; 25%nod = 25% musa spp flour + 75% wheat flour instant noodle mechanical properties of musa spp-wheat instant noodle the force – deformation characteristics exhibited by musa spp-wheat instant noodles at different levels of substitution under compressive loading is presented in figure 2. for all levels http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 83 of substitution, the deformation of musa spp-wheat uncooked instant noodle increased with an increase in compressive force. deformation decreased after rupture occurred in the samples and the compressive at this point was denoted as the bio-yield point or load at break (gupta and das, 2000). the force beyond the bio-yield point represented the force required to crush the instant noodle after rupture had occurred (poulsen, 1978; gupta and das, 2000). as the levels of substitution increased, there was a fall in force – deformation characteristics curves of musa spp-wheat instant noodles. the fall in force – deformation characteristics curves of the instant noodle correlate well with its yield stress of musa spp-wheat dough. the fall in force – deformation curves of musa sppwheat instant noodle may be attributed to the weakening of the protein network by the presence of musa spp (non-gluten protein) flour (yu and ngadi, 2004; wu et al., 2006). the texture parameters obtained from the force – deformation curves of musa spp-wheat instant noodles thereafter investigated were bio-yield point or load at break, energy at break, tensile stress at break and maximum tensile stress. figure 3 showed the texture parameters of musa spp-wheat instant noodle. the bio-yield point or load at break ranged from 0.747 – 4.21 n. the values showed that as percentage of substitution increased, there was reduction in load at break due to the weakening of the protein network by the presence of musa spp (non-gluten protein) flour (yu and ngadi, 2004; wu et al., 2006). the load at break is an indication of how the instant noodle strands resist breakdown (seib et al., 2000). it also gives an indication on how the noodles bind together during cooking reflecting the cooking tolerance and quality (bhattacharya et al., 1999). the energy at break of the instant noodle values ranged from 0.00054 0.0068 j. the values followed similar trend as bio-yied point values. it showed that as percentage of substitution increased, there was reduction in energy at break of musa spp-wheat instant noodle. the values showed that as percentage of substitution increased, less energy would be required by the noodle strands to resist breakdown. this is as a result of weakening of protein network by the presence of musa spp flour in the instant noodle (seib et al., 2000). the energy at maximum tensile stress values ranged from 0.02 – 1.3 j. the values also followed energy at break pattern showing that increase in percentage of substitution reduced the energy at maximum tensile stress of the instant noodles. the tensile stress at break of the instant noodle values ranged from 0.130 – 1.81 mpa. the values also followed a similar pattern with bio-yield points and energy at break. the values showed that as percentage of substitution increased, there was corresponding decrease in tensile stress of the noodles. the tensile stress of the instant noodle correlated well with cooking loss of the noodle. the result obtained compared favourably with 0.113 – 0.158 mpa reported by chen et al. (2002) for sweet potato-wheat noodles. figure 2: the force-deformation curve of uncooked musa spp-wheat instant noodles figure 3: mechanical properties of uncooked musa spp-wheat instant noodle file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adebayo, et al: sensory, textural and cooking quality of instant noodles produced from musa spp wheat composite flours, azojete, 14(sp.i4): 74-85. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 84 5.0 conclusions the proximate and cooking properties of musa spp-wheat instant noodle decreased as percentage of substitution with musa spp flour increased. all the sensory attributes of musa spp-wheat instant noodle were assessed above average except colour. colour being one of the major factor for consumers’ choice affect panelists’ acceptability of the instant noodle. the optimum percentage of substitution in musa spp-wheat instant noodle is 10% as further increase in substitution affected panelist acceptability. the production of a 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mlj., biswas, mmh. and shams-ud-din, m. 2014. the studies on the preparation of instant noodle from wheat flour supplementing with sweet potato flour. journal of bangladesh agriculture university, 12(1): 135 – 142. world instant noodle association. 2013. expanding market. instantnoodles.org/noodles/expanding-market.html. accessed on 11/03/2018. wu, j., aluko, re. and corke, h. 2006. partial least-squares regression study of the effects of wheat flour composition, protein and starch quality characteristics on oil content of steamed and fried instant noodles. journal of cereal science, 44: 117 – 126. yadav, bs., yadav, rb. and kumar, m. 2011. suitability of pigeoan pea and rice starches and their blends for noodle making. lwt-food science and technology, 44: 1415 1421. yousif, ei., gadallah, mge. and sorour, am. 2012. physico-chemical and rheological properties of modified corn starches and its effect on noodle quality. annals of agricultural science, 57 (1): 19-27. yu, lj. and ngadi, mo. 2004. textural and other quality properties of instant fried noodles as affected by some ingredients. cereal chemistry, 81(6): 772-776. yuan, ml., lu, zh., cheng, yq. and li, lt. 2008. effects of spontaneous fermentation on the physical properties of corn starch and rheological characteristics of corn starch noodle. journal of food engineering, 85: 12-17. http://dx.doi.org/10.1016/j.jcs.2013.10.001 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):237-247 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 237 original research article effect of moisture content and grain variety on frictional properties and specific heat capacity of acha (fonio) grains u. a. kawuyo*, n. a. aviara and d. c. okolo (department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria) *corresponding author’s e-mail address: kawuyo2011@gmail.com article information submitted 20 december, 2018 revised 11 february, 2019 accepted 14 may, 2019 keywords: acha moisture content coefficient of friction specific heat capacity abstract there are many varieties of acha, but the most prominent two are white acha (digitaria exilis) and brown acha (digitaria iburua). this study was undertaken to determine the static coefficient of friction, kinetic coefficient of friction and specific heat of the grains as influenced by moisture content. the moisture levels considered were 5, 11, 23 and 28% db for the white variety and 5, 9, 21 and 30% db. the study revealed that increase in moisture content resulted to increase in the value of the properties considered for both varieties, with the white acha showing the highest values. static coefficient of friction increased linearly with moisture content and had maximum values of 0.49 0.62 for the brown variety and 0.52-0.66 for the white variety all on steel sheet, while the minimum values for both varieties were on glass surface. kinetic coefficient of friction increased linearly with moisture content and the highest value was obtained on hessian bag material (0.62-0.66) with the least being on steel sheet (0.58-0.64) for the two acha grain varieties. the study further revealed that, specific heat capacity of acha grains increased with increase in moisture content from 2.93 – 11.29 kj/kgk (5 – 28% db) for the white variety and from 2.33 – 13.88 kj/kgk (5 – 30% db) for brown variety. this study concludes that variety and changes in moisture content significantly affected the determined properties of acha. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction acha is a cereal crop of west african origin belonging to the family graminaea (gibon and pain 1985), it is a great grain available, inexpensive, gluten free, easy to cook and super nutritious. the plant is an important crop in southern mali, western burkina faso, eastern senegal, northern guinea, north-eastern nigeria, and southern niger (harlan, 1993; jideani, 1999; chukwu and abdul-kadir, 2008). there are many varieties of acha, but the most prominent two are brown acha (digitaria iburua) and white acha (digitaria exilis) as shown in figures 1 and 2. in nigeria, chukwu and abdul-kadir (2008) reported that, the white acha is grown more widely. mailto:kawuyo2011@gmail.com http://www.azojete.com.ng kawuyo, et al: effect of moisture content and grain variety on frictional properties and specific heat capacity of acha (fonio) grains. azojete, 15(2):237-247. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 238 figure 1: brown acha grains (digitaria iburua) figure 2: white acha grains (digitaria exilis) acha contains at least 85 % dry matter, of which about 10 % is starch (morales payan et al., 2002), 5 % is mineral and 7% is crude protein (temple and bassa, 1991). the protein of acha is higher compared to that of other grains (chukwu and abdul-kadir, 2008), and is reputed to contain almost twice as much methionine as egg protein does (temple and bassa, 1991). in gross nutritional composition, acha differs little from wheat. in white acha (d. exilis) sample, the husked grain contained 8 % protein and 1 % fat. in a sample of brown acha (d. iburua), a protein content of 11.8 % was recorded. thus, acha has important potential not only as survival food but as a complement for standard diets. acha is also known as one of the best diets for diabetic patients (dury et al., 2006). philip and itodo (2006) highlighted the traditional tools and manual techniques currently used in west africa for acha cultivation, harvesting and post harvest process operations such as threshing, winnowing, hulling and de-stoning. the authors noted the tedium and drudgery associated with the manual methods, and opined that acha production had to be stimulated by initiating research activities to address its mechanization constraints. inspite of its nutritional and economic importance, not much scientific data are available on the engineering (frictional and thermal) properties of acha for the design of equipment for its harvesting and processing operations. literatute has shown that the physical and mechanical properties of many cereals have extensively been investigated. these include the study of fathollahzadeh et al., (2008) who listed among others, gram, hazel nuts, okra seed and chick pea seed. nwakonobi and onwualu (2009) conducted a study on the effect of moisture content and types of structural surfaces on coefficient of friction of millet and sorghum. they reported that the coefficient of friction for the grains increased linearly with increase in moisture content. it was reported by adesola and theresa (2012) that, mechanization of acha processing has been limited by dearth of data on engineering properties to aid design of equiptment for its post harvest operation. due to lack of knowledge of the interplay between its properties and these factors, design and fabrication of machine for acha have been fortuitous. it was reported by davies and el-okene (2009) that designing the seed processing without considering engineering specifications may yield poor results. some problems associated with the processing of acha (digitaria exilis and digitaria iburua) that has limited its proper production and utilization are seen in harvesting, de-hulling, winnowing, threshing, de-stoning and processing in general. therefore, this study was aimed to investigate the effect of moisture content and grain variety on some engineering properties of two acha varieties. these include static and kinetic coefficient of friction on different structural surfaces and specific heat at different moisture contents. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):237-247. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 239 2. materials and methods 2.1 sample procurement and preparation the acha grains used for this study was un-de-hulled white and brown acha varieties (digitania exilis and digitania iburua) respectively. the bulk quantity of white and brown coloured acha grains was obtained from the wadata market, makurdi, benue state, nigeria. asae standards s.352.2 (asae, 1998) for moisture content of seed determination was used to determine the storage moisture content of the acha grains. this method involved oven drying of sample at 105o for 8 hours with weight loss monitored to give an idea of the time at which the weight began to remain constant. this was carried out in three replicates and the average value recorded. the bulk of the grain mass of each variety was divided into four lots. the first lot was left at the market moisture content, while the remaining lots were conditioned by adding an amount of water to obtained the desire moisture content levels. the amount of water added to the samples was obtained using the equation of solomon and zewdu (2009): q = ws mf−mi 100−mf (1) where: q = quantity of water to be added, g mi = initial moisture content, % mf = final moisture content, % ws = weight of samples, g. 2.2 moisture content determination to investigate the physical properties of acha as affected by moisture content and grain varieties, the samples conditioned to different moisture levels were weighed with an electronic weighing balance (0.001 g accuracy) and oven dried at 105°c with weight loss noted on hourly basis. the samples were found to have a constant mass after oven drying for 5 hours. the moisture content was calculated from the relation used by aviara et al., (2005) on sheanut as: mw.b = wi−wf wi × 100 (2) where: mwb = moisture content (%) wi = initial weight (g) wf = final weight (g) this was converted to dry basis moisture content by using the equation: md.b = mw.b 1−mw.b × 100 (3) where: mdb = dry basis moisture content (%) 2.3 determination of static coefficient of friction the static coefficient of friction was evaluated on four different surfaces namely: plywood, hessian bag material, fiberglass and steel. the inclined plane method was used as described by dutta et al., (1998). this involved placing of an open-ended box of dimensions (50mm×100mm×100mm) on an adjustable tilting surface which was formed with structural surface. the box was then filled with grains and its content on top of the structural surface was gradually raised using a screw device until the box started to slide down and the corresponding tilting angle α was recorded. the value of static coefficient friction was calculated using koocheki et al., (2007) formula. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kawuyo, et al: effect of moisture content and grain variety on frictional properties and specific heat capacity of acha (fonio) grains. azojete, 15(2):237-247. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 240 μ = tanα (4) where: μ = static coefficient of friction, and α = tilting angle 2.4 determination of kinetic coefficient of friction in determining the kinetic coefficient of friction, the open-ended box used in determining the static coefficient of friction was placed on a horizontal surface. the four surfaces used in the determination of the kinematic coefficient of friction were plywood, fibreglass, hessian bag material and steel. the fibre box was filled with grains. it was connected by means of a string, parallel to the surface and passed over a pulley to a pan hanging from it. weights were placed in the pan until the box and its content moved uniformly when given a gentle push. the kinetic coefficient of friction of the product on a given structural surface was determined using the relationship: μ = wp+wi wb+ws (5) where: μ = kinetic coefficient of friction. wp = weight of pan (kg) wi = weight placed in pan (kg) wb = weight of box (kg) ws = weight of sample (kg) 2.5 determination of specific heat the specific heat of the grains was determined using a copper calorimeter placed inside a flask by the method of mixture as described by ogunjimi et al., (2002). a sample of known weight and temperature was poured into the calorimeters containing water of known weight and temperature. the mixture was stirred with a copper stirrer until equilibrium was attained. the final temperature was noted and the specific heat of the sample was calculated using the equation: cs = mccc+mwcw tw− te ms te− ts (6) where: cc = specific heat of calorimeter (j/kgk) cs = specific heat of sample (j/kgk) cw = specific heat of water (j/kg/k) mc = mass of calorimeter (kg) ms = mass of sample (kg) mw = mass of water (kg) te = equilibrium temperature of mixture (k) ts = temperature of ample (k) tw = temperature of water (k) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):237-247. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 241 3. results and discussion 3.1 grain moisture content the initial moisture content of white and brown acha (digitaria exilis and digitaria iburua) grains was found to be 5 and 5% d.b respectively. the three other moisture levels obtained after conditioning the grains were 11, 23 and 28% for the white variety and 9, 21 and 30% for the brown variety. the investigations were carried out at the four different moisture levels above for each variety to determine the effect of moisture content on the frictional and thermal properties of acha varieties. these are static coefficient of friction, kinetic coefficient of friction and specific heat of the seeds. 3.2 static coefficient of friction the static coefficients of friction obtained experimentally on four structural surfaces against moisture content are presented in figures 2a and 2b. it showed, that, the static coefficient of friction of the two varieties of acha grains increased linearly with increase in their respective moisture content ranges. the highest value was obtained when using steel and followed by hessian bag, wood and glass respectively for both varieties of acha considered in this study. figure 2a: the effect of moisture content on the static coefficient of friction of white acha grains figure 2b: the effect of moisture content on the static coefficient of friction of brown acha grains file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kawuyo, et al: effect of moisture content and grain variety on frictional properties and specific heat capacity of acha (fonio) grains. azojete, 15(2):237-247. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 242 the static coefficient of friction varied according to the surface used. it could be said that at higher moisture content, the seeds became rough thereby increasing friction characteristics and the structural surface roughness also had decisive influence. the static coefficient of friction was maximum on steel (0.52 0.66) and (0.49 0.62), followed by hessian bag (0.40 0.65) and (0.35 0.58), wood (0.37 0.49) and (0.37 0.47) and was minimum on fibre glass (0.24 0.50) and (0.19 0.41) for the white and brown varieties respectively. the relationship existing between moisture content and the static coefficient of friction of acha grains for different structural surfaces was found to be linear and expressed in equation form as: μs = x1m + y1 (7) where: μs = static coefficient of friction x1 and y1 are constants. m = moisture content (%) singh and goswani (1996) and milani et al., (2007) reported linearly increasing trends on the static coefficient of friction for cumin seed, cucurbit seed and wheat respectively. this property is very useful in the product movements during processing. in the design of silos, bins and other storage containers for the seed, the vertical load on the walls of the structure or equipment is determined by the friction coefficient. 3.3 kinetic coefficient of friction the kinetic coefficients of friction obtained experimentally on four structural surfaces against moisture content are presented in figures 3a and 3b. this shows that the kinetic coefficient increased with increase in moisture content. it also varies with structural surface used in the study.the highest friction was recorded on hessian bag (0.62 0.66) and (0.58 0.64), followed by wood (0.37 0.52) and (0.41 0.49) and galvanised steel sheet (0.32 0.54) and (0.34 0.53), while the least was recorded for glass (0.29 0.57) and (0.25 0.49) for the white and brown varieties respectively. this could be due to the surface characteristics of the seeds with increasing moisture content. it was also seen that for the white variety, the kinetic coefficient of friction on glass was initially lower than that of wood and steel but as the moisture content increased it rose higher than that of wood and steel. figure 3a: the effect of moisture content on the kinetic coefficient of friction of white acha grains http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):237-247. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 243 figure 3b: the effect of moisture content on the kinetic coefficient of friction of brown acha grains the relationship existing between moisture content and the kinetic coefficient of friction of the two varieties of acha grains on different structural surfaces was found to be linear as expressed in the equation: μk = x2m + y2 (8) where: μk = kinetic coefficient of friction x2 and y2 are constants m = moisture content (%). carman (1996) reported a linear increase of friction for lentil seed. it was also reported by sessiz et al., (2007) that a linear relationship was obtained when moisture content was studied against kinematic coefficient of friction for capper fruit seeds. the kinetic coefficient of friction is needed before the power requirements for continued flow of granular or uncosolidated materials can be estimated. 3.4 specific heat the variation of specific heat of two varieties of acha grains at four moisture levels are presented in figures 4a and 4b. it was observed that the specific heat of acha increased linearly with increases in moisture content from 2.33 13.88 kj/kgk as the moisture content increased from 5 30% for the brown variety and from 2.93 11.29 kj/kgk in the moisture range of 5 28% for the white variety. the relationship between moisture content and the specific heat capacity of the seeds was found to be: csw = 0.30m + 1065.1 (9) csb = 0.41m + 861.94 (10) with the value for the coefficients of determination, r2 = 0.7408 and 0.7718 for white and brown acha respectively. where: cs = specific heat capacity of the seeds (kj/kgk) m = moisture content (%). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kawuyo, et al: effect of moisture content and grain variety on frictional properties and specific heat capacity of acha (fonio) grains. azojete, 15(2):237-247. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 244 figure 4a: the effect of moisture content on the specific heat capacity of white acha figure 4b: the effect of moisture content on the specific heat capacity of brown acha aviara and haque (2000) reported a similar trend of linear increase for guna seeds. the increasing trend in specific heat with moisture content correlated with works done by many other reseachers on different agricultural crops. hsu et al., (1991) reported linear variation of specific heat with moisture content for pistachios. isa et al., (2014) studied the thermal properties of some selected species of egusi melon in moisture range of 5.79 41.80% and reported that, specific heat increased linearly from 1.39 to 3.42 kj/kg°c for colocynthis citrulius variety. knowledge of the specific heat of seeds as well as the effect of moisture content and temperature on it is essential for the design of thermal processing systems, as varying moisture content and temperature could form some of the process conditions. the thermal properties of the seed are also essential in the development of processes and equipment needed in drying and storage. the values of constants obtained using equations 7 and 8 against different surfaces for each variety of acha is presented in tables 1 and 2. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):237-247. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 245 table 1: values of the constants for the static coefficient of friction on different structural surfaces varieties of acha structural surfaces constants r2 x1 y1 white wood 0.043 0.33 0.9362 hessian bag 0.081 0.335 0.9742 steel sheet 0.054 0.46 0.8526 fibre glass 0.084 0.1309 0.9 brown wood 0.0033 0.362 0.8157 hessian bag 0.007 0.3787 0.6507 steel sheet 0.0039 0.5212 0.4983 fibre glass 0.007 0.2108 0.7169 table 2: values of the constants for kinetic coefficient of friction of acha grains on different structural surfaces varieties of acha structural surfaces constants r2 x2 y2 white wood 0.049 0.335 0.9471 hessian bag 0.014 0.61 0.8909 steel sheet 0.067 0.245 0.8811 fibre glass 0.085 0.215 0.9198 brown wood 0.0029 0.3974 0.9586 hessian bag 0.0022 0.5612 0.7871 steel sheet 0.0066 0.3035 0.8142 fibre glass 0.0091 0.2263 0.9648 4. conclusions the moisture dependence of some physical properties of d. exilis and d. iburua grains in the moisture range of 5 to 28% and 5 to 30% respectively on the frictional and thermal properties was determined. the study revealed that, the static coefficient of friction of the grains increased with increase in moisture content and varied on structural surface used. the highest value was recorded in hessian bag (0.4 – 0.65), followed by galvanized steel sheet (0.52 – 0.65), wood (0.37 – 0.49) and the least on fiber glass (0.24 – 0.5) for the white variety and for the brown variety the highest was found when using galvanized steel sheet (0.49 – 0.62), followed by hessian bag (0.35 – 0.58), wood (0.37 – 0.47) and the least on fiber glass (0.19 – 0.41). the kinetic coefficient of acha grains increased with increase in moisture content and varied on structural surfaces. it was seen that for hessian bag the kinetic coefficient of friction increased from 0.62 – 0.66 and 0.58 – 0.64, 0.37 – 0.52 and 0.41 – 0.49 on wood, 0.29 – 0.57 and 0.25 – 0.49 on fiber glass, 0.32 – 0.54 and 0.34 – 0.53 on galvanized steel sheet for the white and brown varieties respectively. the specific heat capacity of acha grains increased with increase in moisture content from 2.93 – 11.29 kj/kgk in the moisture range of 5 – 28% d.b for the white variety and from 2.33 – 13.88 kj/kgk in the moisture range of 5 – 30% d.b for brown variety. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kawuyo, et al: effect of moisture content and grain variety on frictional properties and specific heat capacity of acha (fonio) grains. azojete, 15(2):237-247. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 246 references adesola, as. and theresa, kp. 2012. physical properties of acha as affected by moisture content. agricultural engineering international: cigr journal, 14(4): 231 237. asae 1998. moisture measurement unground seeds s352.2. american society of agricultural engineers, 2950 niles road, st. joseph mi 49085-9659' michigan, usa. aviara, na. and haque, ma. 2007. physical properties of guna seeds relevant in bulk 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(1988). thermal properties of gram. journal of agricultural engineering research, 39: 269 275. fathollahzadeh, h., mobli, h., beheshti, b., jafari a. and borghei, am. 2008. effects of moisture content on some physical properties of apricot kernel (cv. sonnati salmas). agricultural engineering international: the cigr ejournal. manuscript fp 08 008. vol. x. gibon, d. and pain, a. 1985. crops of the dryer regions of the tropics. longman group, uk ltd. harlan, jr. 1993. genetic resources in africa. in: new crops. (j. janick and je. simon, eds), wiley, new york. p. 65. hsu, mh., mannapperuma, jd. and singh, rp. 1991. physical and thermal properties of pistachios. journal of agricultural engineering research, 49: 311321. isa, j., oladele, so. and akinlade, es. 2014. the effect of moisture content on thermal properties of some selected species of egusi melon (colocynthis citrillus l.). international. journal of engineering and advanced engineering, 4 (4): 580 586. jideani, ia. 1999. traditional and possible technological uses of digitaria exilis (acha) and digitaria iburua (iburua): a review. plant foods human nutrition, 54 (4):363-374. koocheki, a., razavi, sma., milani, e., moghadam, tm., abedini, m., alamatiyan, s. and izadkhah, s. 2007. physical properties of watermelon seed as a function of moisture content and variety. international agrophysics, 21: 349 359. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):237-247. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kawuyo2011@gmail.com 247 milani, e., seyed, m., razavi, a., koocheki, a., nikzadeh, v., vahedi, n., moeinfard, m. and gholamhosseinpour, a. 2007. moisture dependent physical properties of cucurbit seeds. international agrophysics, 21: 157-168. morales-payán, jp., ortiz, jr., cicero, j. and taveras, f. 2002. digitaria exilis as a crop in the dominican republic. in supplement to: trends in new crops and new uses. (j. janick and a. whipkey, eds.). ashs press, alexandria, va. p.s1-s3. nwakonobi, tu. and onwualu, pa. 2009. effect of moisture content and types of structural surfaces on coefficient of friction of two nigerian food grains. agricultural engineering international: the cigr ejournal., volume xi. ogunjimi, lao., aviara, na. and aregbesola, oa. 2002. some physical engineering properties of locust bean seed. journal of food engineering, 55, 95-99. philip, t k. and itodo, in. 2006. acha (digitalia spp.) a “rediscovered” indigenous crop of west africa. agricultural engineering international: the cigr ejournal. invited overview no 23. vol. viii. sessiz, a., esgici, r., and kizil, s. 2007. moisture dependent physical properties of caper (capparis ssp.) fruit. journa of food engineering, 79: 1426 1431. singh, kk. and goswani, tk. 1996. physical properties of cumin seed. journal of agricultural engineering research, 64: 93-98. solomon, wk. and zewdu, ad. 2009. moisture dependent physical properties of niger (guiconia abyssinicacass.) seed. industrial crops and products, 29:165-170. temple, vj. and bassa, jd. 1991. proximate chemical composition of acha (digitaria exilis) grains. journal of the science of food and agriculture, 56: 561-564. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):973-984 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 973 original research article strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria o. j. oyebode (department of civil and environmental engineering, college of engineering, afe babalola university, ado-ekiti, ekiti state, nigeria) * corresponding author’s email address: oyebodedare@yahoo.com 1.0 introduction sustainable use of the resources such as soil and groundwater and protection and conservation of their quality are key issues of developing countries and an enormous challenge for engineers and researchers on planet earth. water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds. water pollution affects plants and organisms living in these bodies of water. in almost all cases article information abstract soil pollution and groundwater contamination are rampant in urban and rural areas of various developing countries including nigeria. the quality of groundwater is a vivacious concern for human beings since it is directly associated with the human welfare and it is needed to conserve water resources. this paper x-rays strategic approach for controlling soil and groundwater contamination to enhance the efficiency of civil and environmental engineering design through recent trends and practice which will play a vital role in handling environmental pollution. strategic approach highlighted involves the formulation and implementation of the major goals and initiatives based on consideration of resources and an assessment of the internal and external environments in which the organization competes. one or more of these approaches are often combined for more cost-effective treatment. the field studies for assessment of contamination comprised of detailed hydro-geological investigations which include geophysical investigations, borehole drilling, development of monitoring wells, followed by collection and analysis of existing field samples (dumpsite, subsurface soil and groundwater) are very critical for efficient handling of environmental pollution. it has been concluded that basic necessities for a healthy environment and public health include clean air, safe and sufficient water safe and adequate food, safe and peaceful settlements, stable global environment in order to achieve excellent public health without soil pollution and groundwater contamination. strategic approaches to remediation of contaminated soils include isolation, bioremediation, immobilization, toxicity reduction, physical separation and extraction. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 november, 2018 revised 05 may, 2019 accepted 10 may, 2019 keywords: bioremediation contamination environmental pollution groundwater hydro-geological investigations mailto:oyebodedare@yahoo.com http://www.azojete.com.ng oyebode: strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria. azojete, 15(4):973-984. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 974 the effect is damaging not only to individual species and populations, but also to the natural biological communities. strategic management involves the formulation and implementation of the major goals and initiatives taken by a company's top management on behalf of owners, based on consideration of resources and an assessment of the internal and external environments in which the organization competes. water is a natural resource that is necessary for sustenance of life, ecological systems and a key resource to social and economic development (ipma, 2013). water is vital for sustainable socio-economic development as a strategic primary input playing a pivotal role in poverty alleviation through enhancing food security, domestic hygienic security, hydropower, industrial development, mining, navigation, and the environment for sustenance of ecosystems (oyebode, 2019). the stress on our water environment as a result of increased industrialization, which aids urbanization, is becoming very high thus reducing the availability of clean water. polluted water is of great concern to the aquatic organism, plants, humans, and climate and indeed alters the ecosystem. the preservation of our water environment, which is embedded in sustainable development, must be well driven by all sectors (inyinbor and adebesin , 2018). 1.1 basic definitions according to marcella and donna (2017), environmental health comprises those aspects of human health, including quality of life, that are determined by physical, biological, social, and psychosocial factors in the environment. it also refers to the theory and practice of assessing, correcting, controlling, and preventing those factors in the environment that can potentially affect adversely the health of present and future generations. “soil pollution” means the introduction into soil of substances, biological organisms or forms of energy that alter soil quality, impact the normal use of the soil or endanger public health and the living environment. groundwater pollution means the introduction into groundwater of substances, biological organisms or forms of energy that alter soil quality, impact the normal use of the soil or endangers public health and the living environment. soil pollution monitoring standards” means the determined pollutant concentrations at which soil pollution monitoring is required for the purpose of preventing soil pollution. groundwater pollution monitoring standards means the determined pollutant concentrations at which groundwater pollution monitoring is required for the purpose of preventing groundwater pollution. soil pollution control standards means determined soil pollution control limits to prevent and control the worsening of soil pollution. groundwater pollution control standards” means determined groundwater pollutant limits to prevent and control the worsening of groundwater pollution. soil pollution remediation goals" means the limit on pollutants set according to the purpose of soil pollution remediation. 1.2 water pollution and soil contamination is not only in nigeria the issue of concern in this paper is not peculiar to nigeria alone. larger percentage of cities in china suffers from some degree of water pollution, and nearly 500 million people lack access to safe drinking water. in addition to the acute problems of water pollution in developing countries, industrialized countries, continue to struggle with pollution problems as well. in the most recent national report on water quality in the usa, 45 % of assessed stream km, 47 % of assessed lake ha, and 32 % of assessed bay and estuarine square km were classified as polluted. water is http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 973-984. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 975 typically referred to as polluted when it is impaired by anthropogenic contaminants and either does not support a human use, such as drinking water. natural phenomena such as volcanoes, algae blooms, storms and earthquakes also cause major changes in water quality and the ecological status of water. climate change issues must be addressed in all ramifications for effective integrated water resources management. civil engineers put global changes into consideration in all construction, research, community development and consultancy work in order to achieve effective integrated water resources management (oyebode, 2018). figure 1 indicates raw sewage and industrial waste flows across in a typical nigerian community. figure 1: raw sewage and industrial waste flows in a community in nigeria 1.3 aim and objectives of this study the aim of this study is to obtain strategic approach for controlling soil and groundwater contamination in nigeria. the objectives include protection of water resources in order to prevent environmental hazards, water stress, and other health related issues. the largest environmental challenge that nigeria is facing today is water scarcity. health protection is primary reason for environmental control in the whole world. other reasons are protection of water resources, conservation of fishing zones, development of recreational areas. figure 2 shows a typical anthropogenic water turnover cycle. figure 2: anthropogenic water turnover cycle (oyebode, 2018) ../../user/downloads/azojete143/www.azojete.com.ng oyebode: strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria. azojete, 15(4):973-984. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 976 2. literature review water pollution is a major global problem which requires ongoing evaluation and revision of water resource policy at all levels (international level down to individual aquifers and wells). soil and groundwater pollution not only impact the normal use of the land but also may endanger nationals’ health as well as the surrounding living environment. for this reason, apart from impairing the value of real estate on individual polluted land, pollution may result in external effects and affect the price of surrounding real estate. a good knowledge of the remediation effect of pollution sites will contribute to assessing the feasibility, proper scale, and schedule of the remediation plan, for the purpose of more effectively allocating financial resources. in addition, the benefit analysis of pollution remediation plans can be taken as private sectors’ investment incentive so as to encourage them to actively devote themselves to remediation and cooperate with local government’s macro long-term urban redevelopment, which will contribute to the sustainable development of cities and resources. current water use already exceeds renewable supply. many methods have been suggested to increase the sources of water supply; and one of these alternative sources is rainwater harvesting (rwh). (sridhar and coker, 2001). flowing surface water bodies have the natural capacities to purify themselves from the pollutions that come into them from external sources (garg, 2006; longe omole, 2008). many of the community ’s streams are highly polluted and disease-causing. rainwater was thus a viable option considered in the design of a water supply scheme for the community (coker, 1999). environmental law is a collective term describing the network of statutes, regulations and customary laws addressing the effects and human activity on the natural environment. the need for environmental laws in the country is as a result of the inappropriate use of the environment with regards to the ecosystem (oyebode, 2018). currently, the above two water-pollution impacts are added to the vast other forecasted general effects of global warming, there's abundance of motivation to advocate action on global warming as element of an extensive approach to address water pollution. lately, the world bank and united nations agencies issued a series of publications to promote the development of water policy and strategy in developing nations. serous guide lines were seriously gathered to be followed. it is strongly recommended – in these documents – to ensure that the development of national water policy and strategy to be performed by the concerned developing country itself with an uninterrupted assistance from the international agencies among the process. in fact, there are some conservative critics to this international policy in terms of the current and future understanding of water policy and strategy (vajpeyi 1998). 2.1 environmental and economic effect by pesticides use pesticide use raises a few environmental concerns. over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, including non-target species, air, water and soil. pesticide drift occurs when pesticides suspended in the air as particles are carried http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 973-984. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 977 by wind to other areas, potentially contaminating them. pesticides are one of the causes of water pollution, and some pesticides are persistent organic pollutants and contribute to soil contamination. in addition, pesticide use reduces biodiversity, reduces nitrogen fixation, contributes to pollinator decline, destroys habitat (especially for birds), and threatens endangered species. pests can develop a resistance to the pesticide (pesticide resistance), necessitating a new pesticide. in most cases, treatment of the solid component of the waste was confined to dumping, followed by land application (sangodoyin, 1992). 2.2 causes of groundwater pollution it is essential to highlight some causes of pollution. causes of groundwater pollution include: increased urban waste water impact of industrial sectors soil contamination surface water pollution lack of groundwater protection legislations and standards lack of groundwater protection awareness 3. strategic approach the method adopted is strategic approach through reconnaissance survey and stakeholders’ consultation. one of the strategic approaches is to strengthen the prevention and control of groundwater pollution from soil in every sector and in all ramifications as indicated in figure 3. figure 3: strengthen the prevention and control of groundwater pollution from soil another approach is to conduct groundwater pollution remediation in a holistic and planned way as indicated in figure 4. ../../user/downloads/azojete143/www.azojete.com.ng oyebode: strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria. azojete, 15(4):973-984. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 978 figure 4: conduct groundwater pollution remediation in a planned way also, we need to establish groundwater environmental monitoring, management, control and supervision system. areas prone to petroleum hydrocarbon attack need special attention. development of appropriate legislation to protect public health is very imminent. figure 5 indicates ten essential services for pollution control. figure 5: based on ten essential services for pollution control (nphps, 2014) water pollution can be controlled by treatment of water before leaving in water bodies, restoration of polluted water bodies, river training, water monitoring, effective action plan by government and copious stakeholders (oyebode, 2018). no successful remediation of the site can be done until this periodic release of the petroleum hydrocarbon product is stopped. oil skimmer was used in the skimming off the pure phase hydrocarbon from the monitoring wells within the pilot test area (ola, et al. 2017). the oil skimming technology was adopted to remove hydrocarbon contamination from groundwater without the pumping of groundwater with the contaminant in baruwa lagos state as indicated in figure 6. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 973-984. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 979 figure 6: the map of baruwa-lagos: case study of contaminated site in nigeria (oyebode, 2018). 4.0 strategic handling of soil pollution soil pollution is defined as a phenomenon characterized by the loss of structural and biological properties by the soil layers as a result of numerous human and natural factors, such as wind, deforestation, chemical use, among others, etc. soil can become contaminated in many ways. chemicals, like herbicides and pesticides, are major polluters; oil dumps, landfills, and industrial wastes can also wreak havoc. pollution may be defined as an undesirable change in the physical, chemical and biological characteristics of air, water and soil which affect human life, lives of other useful living plants and animals, industrial progress, living conditions and cultural assets. a pollutant is something which adversely interferes with health, comfort, property or environment of the people. soil contamination or soil pollution is caused by the presence of human-made chemicals or other alteration in the natural soil environment. this type of contamination typically arises from the failure caused by corrosion of underground storage tanks (including piping used to transmit the contents), application of pesticides, oil and fuel dumping, disposal of coal ash, leaching of wastes from landfills or direct discharge of industrial wastes to the soil (mohammed et al, 2013). water resource management is very essentials for handling development of water bodies for future, protection of available water bodies from pollution, over exploitation and for prevention of dispute. high gross domestic product (gdp) per capita, sustainable water resource management, high average incomes, well developed infrastructure, low unemployment, low levels of crime and corruption are crucial parameters for national development. (oyebode, 2018) 4.1 result from niger delta contamination there is a lot of surface water pollution and soil contamination in the study area as indicated in figure 7. ../../user/downloads/azojete143/www.azojete.com.ng oyebode: strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria. azojete, 15(4):973-984. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 980 figure 7: surface water pollution and soil contamination in niger delta area (oyebode, 2019) soil pollution is caused by the presence of chemicals or other alteration in the natural soil environment. resulting in a change of the soil quality is likely to affect the normal use of the soil or endangering public health and the living environment. soil is upper layer of earth crust, contains organic matter and other minerals. dumping of wastes, garbage, rubbish like glass, plastics, metallic cans, papers, cloth rags, containers causes soil pollution. other causes include discharge of industrial wastes, fly ash from thermal power plants, sewage sludge and radioactive wastes, fertilizers and pesticides on soils. effects are reduction of soil productivity, adverse effect on soil flora and fauna, sludge contains worms, bacteria and pathogens that are detrimental to public health, radioactive wastes enter food chain, untreated products and wastewater before discharge. the application of sewage sludge can either stimulate soil microbial activity, due to an increase in available carbon and nutrients, or inhibit activity, due to the presence of heavy metals and other pollutants (baath, 1989). role of an individual in pollution prevention includes thinking globally and act locally, use ecofriendly products, use rechargeable batteries, no to excess pesticides, chemicals, paints, solvents, use of less or only required quantity of resource, planting of trees (local species) and application of 3 r’sreduce, reuse, recycle (oyebode, 2018). table 2 highlighted screening standards for assessing the contamination levels while figure 7 gives the pollutant source. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 973-984. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 981 table 2: screening standards for assessing the contamination levels (compounds relevant to the studies) from figure 7 and as shown by oyebode (2018) on pollutant source pathways, the following could be identified. arsenic poisoning high levels of arsenic above the permissible levels of 50 parts per billion (ppb) are found in the alluvial plains of ganges covering six districts of west bengal. arsenic contamination of drinking water causes a disease called arsenics, for which there is no effective treatment. arsenic contamination is by far the biggest mass poisoning case in the world putting 20 million people from west bengal and bangladesh at risk though some other estimates put the figure at 36 million people. a lot of cost of emission controls is needed in areas of high pollution. the law of diminishing return is applicable to the relationship of pollutant emissions and cost of emission controls as shown in figure 8. figure 8: the law of diminishing return ../../user/downloads/azojete143/www.azojete.com.ng oyebode: strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria. azojete, 15(4):973-984. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 982 5. conclusions it has been established that groundwater environmental monitoring, management, control and supervision system is essential for pollution abatement and contamination reduction. prevention and control of groundwater pollution from soil in every sector need to be strengthened. no successful remediation of the site can be done until this periodic release of the petroleum hydrocarbon product is stopped. it has been concluded that strategic approach for controlling soil and groundwater contamination in nigeria is very critical for environmental sustainability. strategic approaches to remediation of contaminated soils include isolation, bioremediation, immobilization, toxicity reduction, physical separation and extraction. peaceful settlements, stable global environment and clean air are essential in the achievement of excellent public health without soil pollution and groundwater contamination. general approaches to remediation of contaminated soils include isolation, immobilization, toxicity reduction, physical separation and extraction. one or more of these approaches are often combined for more costeffective treatment. a few of the available technologies have been demonstrated in full-scale applications and are presently commercially available. necessities for a healthy environment and public health include clean air, safe and sufficient water safe and adequate food, safe and peaceful settlements, stable global environment in order to achieve excellent public health without soil pollution and groundwater contamination. there is a desire and concern for the protection and management of groundwater quality. water quality analysis of groundwater contains determination of its physical, chemical and organic characteristics, from that its suitability for drinking, irrigational, industrial and different purposes. environmental health, safety and security awareness and development of necessary legal framework can avert groundwater pollution in nigeria. recommendations the following recommendations were made for effective and helpful impact on the environment: nigerian society of engineers and other engineering professional bodies must be assisted by governments, organization, stakeholders and every sector for revitalization of nigerian environment. holistic preventive measures of water pollution and soil contamination by government, private companies, engineers, environmental experts and individuals is very essential.. it is recommended that the contaminated wells should be immediately sealed so as to prevent use of water from these wells for any purpose by the populace. measures to prevent water pollution are to conserve and protect water quality in terms of its use reduction and disposal, wastewater treatment, technical changes and recycling. practice of waste to wealth and health needs to be encouraged. strengthening of groundwater monitoring and management systems should be adopted in all ramifications. it is essential to establish groundwater pollution risk prevention system. scientific sustainable remediation measures need to be developed, adopted for effective overall environmental monitoring and management. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 973-984. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 983 oil industries need to embrace spatial techniques for effective monitoring of pipeline, environmental impact assessment facility index mapping, spill contingencies planning and environmental data-base management to avoid groundwater contamination and to achieve social equity, economic sustainability and environmental sustainability. government, water development agencies, environmental health scientists, engineers and researchers must ensure that there is proper funding as well as right procedures in the planning and execution of water resource management contracts. strategic approach such as sensitization of the public on the impact of soil and groundwater contamination on the public health in the community should be adopted. special consideration for pollution and contamination amelioration by engineers and other experts in construction fields are essentials. supervision, assistance and approval of soil, sediment and groundwater pollution prevention, monitoring and remediation work by special municipality, county or city competent authorities are crucial for public health and reduction of pollution. drafting, deliberation and interpretation of soil, sediment and groundwater pollution remediation laws and regulations are very crucial substantial capacity building for groundwater projects is essential for environmental monitoring and supervision is required in nigeria, references baath e. 1989. effects of heavy metals in soil on microbial processes and populations. water, air, and soil pollution, 47(3-4): 335–379. coker, ao. 1999. the design of water supply scheme for akufo village, oyo state of nigeria, nigerian journal of science, 33 (3): 229-235. garg, sk. 2006. sewage disposal and air pollution engineering. environmental engineering, vol. ll, 18th ed., khanna publishers, new delhi, pp. 228-278. inyinbor, aa. and adebesin, bo. 2018. water pollution: effects, prevention, and climatic impact, water challenges of an urbanizing world, matjaž glavan, intechopen, doi: 10.5772/intechopen.72018. available from: https://www.intechopen.com/books/waterchallenges-of-an-urbanizing-world/water-pollution-effects-prevention-and-climatic-impact. international project management association (ipma). 2013. organisational competence baseline – the standard for moving organisations forward (ocb). switzerland, zurich: international project management association (ipma). marcella, rt. and donna, sb. 2017. the concept of exposure in environmental health for nursing. journal of advanced nursing, 73(6): 1315–1330. national public health performance standards (nphps) 2014 (https://www.cdc.gov/publichealthgateway/publichealthservices/essentialhealthservices.html ola, sa., fadugba, og. and ojuri, oo. 2015. comparison of effectiveness of two remediating agents on hydrocarbon contaminated soil/ groundwater in the laboratory. environment and natural resources research, 5(1): 1. https://www.ncbi.nlm.nih.gov/pmc/articles/pmc5423851/ https://www.ncbi.nlm.nih.gov/pmc/articles/pmc5423851/ https://www.cdc.gov/publichealthgateway/publichealthservices/essentialhealthservices.html ../../user/downloads/azojete143/www.azojete.com.ng oyebode: strategic approach for controlling soil and groundwater contamination in urban and rural areas of nigeria. azojete, 15(4):973-984. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyebodedare@yahoo.com 984 oyebode, oj. 2018a. impact of environmental laws and regulations on nigerian environment. world journal of research and review, 7(3): 9-14. oyebode, oj. 2018b. integrated water resources management and adaptation to global changes: a critical issue of special concern to civil engineers. nigerian institution of water engineers – 2nd national conference "climate change and water resources in nigeria – processes, impacts and adaptations" abeokuta, october 15th – 17th 2018. oyebode, oj. 2019. water resource management and environmental sustainability in the niger delta states. a paper presented during 2019 conference on sustainable construction for national development organized by the department of civil engineering, university of ibadan held at nlng conference hall, faculty of technology, university of ibadan, ibadan between 10th and 12th july, 2019. sangodoyin, ay. 1992. environmental study on surface and groundwater pollutants from abattoir effluents. journal of bioresource technology, 41(3): 193-200. sridhar, mkc., coker, ao. and adegbuyi, sa. 2001. rainwater harvesting in nigeria: prospects and problems. proceedings of the 10th international rainwater catchment systems conference, september 10-14, mannheim, germany, 122. 2001.vajpeyi d. 1998. water resource management, library of congress cataloging-in-publication data, usa p107 – 122) [online] available from: http://www.google.com/books?hl=en&lr= [accessed on 25 december 2009] https://www.sciencedirect.com/science/journal/09608524/41/3 http://www.google.com/books?hl=en&lr= http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 792-801 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 792 original research article drag reduction with polymer mixtures in pipes of different diameters m. m. gimba1., l. c. edomwonyi-otu,1,2*., n. yusuf,3 and a. abubakar1 (1department chemical engineering, ahmadu bello university, zaria, nigeria 2department of chemical and petroleum engineering, delta state university, abraka, nigeria 3department of chemical and petroleum engineering, bayero university, kano, nigeria) * corresponding author’s email address: uceclce@ucl.ac.uk article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: drag reduction polymers polymer-polymer mixture pipe diameter oil-water flow abstract transporting crude oil and other fluid in pipelines of different sizes over long distances in process industries require high amount of energy which results to high cost of installing pumping stations and maintenance. addition in part per million (ppm) of high molecular weight polymeric solution reduce such cost. the effect of pipe diameter, oil input volume fraction and flow rate (superficial velocity) on drag reduction (dr) in horizontal oil-waterflows was investigated in unplasticised polyvinylchloride (upvc) horizontal pipe with two different pipe diameters (0.012 and 0.02 m ids). the two liquids used were diesel oil (ρ = 832 kg/m3, µ = 1.66 cp) and water (ρ = 1,000 kg/m3, µ = 0.89 cp) as test fluids at ambient conditions (25°c, 1 atm). partially hydrolyzed polyacrylamide (hpam; magnafloc 1011), polyethylene oxide (peo) and aloe vera mucilage (avm) separately, as well as mixture of hpam-avm and peo-avm at different oil input volume fraction (δo; 0,0.25, 0.5, 0.75 and 1) and flow rate (q; 0.65, 1.28, 1.90 and 2.46 m3/hr) were used. the master solution of 2,000 ppm, 2,000 ppm and 20,000 ppm for hpam, peo and avm respectively and their respective mixtures were used to achieve the required concentrations. mercury u-tube manometer was used to measure the pressure drop. dr of 62%, 65%, 54% for hpam, peo and avm; 69 and 71% for hpam-avm and peo-avm respectively at mixing ratio of 3:1 and 1:19 in 0.012 m id. also, dr of 58%, 62%, 43% for hpam, peo and avm; 67% and 68% for hpam-avm and peo-avm respectively in 0.02 m id were obtained at the same condition. the pressure drops observed in the smaller pipe (0.012 m id) was higher than that of the larger pipe diameter (0.02 m id). from the experimental results, dr decreased with increase in the pipe diameter at the same conditions. this result implies that, dr in oil-water pipeline flow is a function of oil input volume fraction, superficial velocity and pipe diameter © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the turbulent pipeline transportation of two immiscible liquids (oil-water) is always encountered in chemical and petroleum industries, which requires large amount of energy because of the pressure drop experience. turbulent structures (eddies) of different sizes are formed during the turbulent liquids pipeline flow, which increase the pressure drop and dissipate pumping energy (yusuf et al., 2013; abdulbari et al., 2014; edomwonyi-otu and angeli, 2014, 2019). the large decrease in pressure drop by addition of small amount of polymers in parts per million (ppm) is referred to as percentage drag reduction (dr) (sellin et al., 1982; bewarsdorff and gyr, 1995; gimba et al., 2018). one of the first industrial applications of dr was the trans-alaska pipeline mailto:uceclce@ucl.ac.uk http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):792-801. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 793 system (1300 km, 1.2 m id) in 1979, where 10 ppm of oil-soluble polymer was used to increase the flow rate. drag reduction of 50 % was achieved, which eliminated the need of installing additional two pumping stations to boost the throughput from 1.45 to 2.1 million barrel per day. other application includes marine and biomedical system, crude oil pipeline transportation over a long distances, irrigation, floodwater disposal and sewage, drilling of oil from reservoir, firefighting, extraction, filtration, heat and mass transfer application (marmy et al., 2012; gimba et al., 2017). it is also now being suggested for transportation of drinking water because of its harmless properties (edomwonyi-otu and adelakun, 2018). the parameters responsible for pressure drop in oil-water pipeline flow include pipe diameter, superficial velocities (mixture velocities), volume fraction of each phase (oil and water), density, and viscosity of the fluids at constant pressure and temperature (abubakar, et al., 2015). the effect of pipe diameter on drag reduction in pipeline flow using drag reducing polymers (drp) was studied by many researchers (lescarboura et al., 1971; virk, 1975; interthal and wilski, 1985; ahmad et al., 2009; karami and mowla, 2012; yusuf et al., 2013; abubakar et al., 2015a; edomwonyi-otu et al., 2016). abubakar et al., (2015b) studied the drag reduction on oil-water flow in relatively large pipe diameter with polymer concentration of 40 ppm and pipe diameter of 0.0747 m id. mixture velocities ranging from 0.1 – 1.6 m/s and 0.05 – 0.9 oil input volume fractions were used. they compared their results with that of abubakar et al., (2015a), where they used pipe diameter of 0.306 m id at the same conditions. maximum dr of 51% in 0.0747 m id and 64% in 0.0306 m id at oil input volume fraction of 0.05 and mixture velocity of 1.6 m/s were achieved by (abubakar et al., 2015b). they (abubakar et al., 2015b)also concluded that, dr increased with decrease in pipe diameter. karami and mowla (2012) also studied dr of three drag reducing polymers in two galvanized iron pipes of 0.0254 and 0.0127 m ids at the same conditions. they also reported that the drag reduction decreased with increase in pipe diameter for all drp used. ahmad et al., (2009) investigated the effect of okra mucilage on dr in different size of pipes (0.015 and 0.025 m id) in turbulent water flow. they observed that, dr increased (50 – 71%) with decrease in the pipe diameter (0.025 – 0.015 m ids) at the same conditions. they suggested that, decreasing the pipe diameter means increasing velocity inside the pipe, which results to high degree of turbulence. the high velocity observed in the smaller pipe brings good interaction between the additive and the turbulent structure (eddies), which subsequently brings about the drag reduction effectiveness. this agreed with the work of karami and mowla (2012). interthal and wilski (1985) were among the first to publish the effect of drag reducing polymers and pipe diameter on dr. they (interthal and wilski, 1985) also reported that dr increased (66 – 80%) with increase in pipe diameter (0.003 – 0.014 m id) and then fall to 76% at the highest pipe diameter (0.03 m id), showing lack consistency in their results. lescarboura et al., (1971) investigated dr in crude oil (single phase) pipeline flow with 8 and 32-inch id and length of 28 and 32 miles, using polymer concentration of 300, 600 and 1000 ppm respectively. they achieved dr of 16, 21 and 25% (8-inch id) and 16, 16.2 and 16.9% (32-inch id) at the same conditions. they concluded that dr decreased with increase in pipe diameter and decrease in velocity. despite the available works done in open literature, the influence of pipe diameter on drag reduction is still scanty. more data were needed to develop models for the accurate prediction of drag reduction in horizontal oil-water pipeline flow than is currently available. hence, the motivation of this work is to provide more data on the study of the effect of pipe diameter on file:///c:/users/user/downloads/azojete143/www.azojete.com.ng gimba et al: drag reduction with polymer mixtures in pipes of different diameters. azojete, 15(3):792-801. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 794 drag reduction in horizontal oil-water flow system using aloe vera mucilage (avm), polyethylene oxide (peo) and hydrolyzed polyacrylamide (hpam) as well as their mixture (hpam-avm and peo-avm). 2. experimental set-up 2.1 description of the flow facility the schematic diagram of the experimental set-up is shown in figure 1. the flow facility is divided into: the handling section, pumping or regulating section and test section. the handling section consists of three tanks where the fluids are stored: the oil, water and separator tanks have capacity of 200, 200 and 220 liters respectively. the separator tank allows settling under gravity where water is drain through the bottom opening and the oil is recycled. in the regulating or pumping section, 0.012 and 0.02 m id unplasticised polyvinylchloride (upvc) pipes are each connected to water and oil tanks. the centrifugal pumps (model jet 102m/n.31227) with maximum flow rate of 65 l/min each were used to circulate the test fluids into the test section. the globe valves were used to regulate the flow rates which were measured with variable area flow meters (lzm-20j; ±5% accuracy), separate for each fluid. the water flow meter has maximum flow rate of 100 liters per minute (lpm). the flow meter was calibrated before the commencement of experiments. the injection port for the polymer master solution is located by the side of the water pipeline before the y-junction. the new era-programmable peristaltic pump (model ne-9000; ±2% accuracy) was used to inject the polymer master solution into the water phase. the test section was made up of straight acrylic pipe of 0.012 and 0.02 m id and 140 times the diameter of the pipe (140d) long from the y-junction to the second pressure port. the pressure taps were created by making small holes at the bottom of the acrylic pipe walls at the distance of 140d which provides fully developed flow in the test section. figure 1: schematics of experimental set-up of flow facility 2.2 polymer preparation the polymers used are partially hydrolysed polyacrylamide, hpam (magnafloc 1011) manufacture by basf chemicals 10 × 106 g/mol, polyethylene oxide (peo) manufacture by sigma-aldrich with average molecular weight of 8 × 106 g/mol, and aloe vera mucilage (avm) extracted from aloe vera plant. all the polymers are water soluble and were used without further purification. the polymers solutions were prepared individually first, before the polymer mixture http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):792-801. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 795 solutions were prepared. a master solution of 2,000 ppm of each of the synthetic polymer was prepared as follows. 10 g of each of the polymer powder was measured using weighing balance (kerro, blc 3002) and gently spread over 5 liters of water surface and stirred for 3 hours with a mechanical stirrer (gilverson, l28) at a very low speed (to avoid degradation of the polymer) for the mixture to be completely homogenized. the stirred solution was left for 12 hours to ensure complete dissolution of the polymer particles and removal of trapped gas bubbles to form the master solution (gimba et al., 2018;edomwonyi-otu and angeli, 2014, 2019). aloe vera leaves were harvested from a garden and washed thoroughly with tap water. the leaves were then cut vertically on both sides and soaked in tap water for 10 minutes, to remove the aloin within them. the leaves were then peeled and the aloe vera mucilage (avm) was extracted by scraping and sieving the gel from the aloe leaves (gimba et al., 2017). aloe vera leaf contains about 98% water while the remaining 2 % is the avm (bozzi et al., 2007; davis, 1997). master solution of avm was prepared with 20,000 ppm. for the polymer mixture preparation, the total concentration (tc) of 30 ppm and 400 ppm for the mixture (hpam-avm and peo-avm) were because one of the polymers in the mixture gave maximum dr at that concentration (reddy and singh, 1985). 250 milliliters of 20,000 ppm of avm master solution was measured and diluted with 10,000 milliliters of water to achieve 500 ppm.1500 ppm of the synthetic polymers (hpam and peo) was mixed with 500 ppm of avm and stirred for 3 hours and the stirred solution was left for 12 hours to form a master solution of 2000 ppm for the polymer mixtures (reddy and singh, 1985; malhotra et al., 1988). it was injected into the water phase at specific flow rate to achieve the required concentration in the water flow line. 2.3 experimental procedure the flow meters and injection pump were tested before running the experiments to ensure accurate delivery of the required amounts of oil and water into the test section, and the polymer master solution into the water phase. the experiment was carried out in horizontal pipe diameter of 12 mm id and length of 140 times the diameter of each of the pipe at ambient conditions (25 °c, 1 atm). the u-tube manometer (pyrex) was used for the pressure drop measurement. each experimental run was repeated three times and the average of the pressure drop measured before and after the addition of the dras. hpam, peo, avm, hpam-avm and peo-avm were tested at different oil input volume fraction (δo) and superficial velocity (us). the total concentration (tc) of 30 ppm and 400 ppm for hpam, peo, aloe vera mucilage (avm) as well as their mixtures at flow rate of 30 l/min was tested.the optimal polymer concentration (30 ppm for hpam and peo and 400 ppm for avm) and 30 l/min were obtained from our preliminary single phase water experiments (gimba et al., 2017 and 2018). the optimal concentration was selected to be the total concentration (tc) of the polymer mixture (reddy and singh, 1985). the mixing ratio of 3:1 and 1:19 were used. the superficial velocities investigated range from 0 m/s to 1.68 m/s for 0.020 m and 0 m/s to 4.67 m/s for 0.012 m id. they superficial velocity and the oil input volume fraction (δo) was calculated from the equations 1 4. the pressure drop was recorded and used for calculation of drag reduction as defined by equation 5; u = q a (1) usw = qw a (2a) uso = qo a (2b) δo = qo qo+ qw × 100% (3) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng gimba et al: drag reduction with polymer mixtures in pipes of different diameters. azojete, 15(3):792-801. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 796 δw+ δo = 1 (4) dr = ∆pwo − ∆pw ∆pwo × 100% (5) where; � is the average velocity of the fluid in a pipe (m/s),�th and �th are the superficial velocities of water and oil (m/s). � is the cross-sectional area of the pipe (m), �h and �h are the flow rate of water and oil (m3/s) and δw and δo are the input volume fraction of water and oil. ∆��� and ∆�� is pressure drop of the fluid without and with dras (n/m2). table 1: fluid properties density of water, �h at 25°c 1000 kg/m3 density of diesel oil, �h at 25°c 832 kg/m3 viscosity of water, �h at 25°c 8.9 × 10−4 ns/m2 viscosity of oil, �h at 25°c 1.664 × 10−3 ns/m2 3.0 results and discussion only average values of the pressure drop obtained from three measurements were used in the calculation of percentage drag reduction as well as the viscosity readings. the dr calculated using equation (1) was presented graphically against oil input volume fraction and pipe diameter (figures 2 to 8). 3.1 effect of oil input volume fraction, superficial velocity and pipe diameter the dr of three polymers (hpam, peo and avm) was studied in oil-water flow (multiphase flow; mpf) at different oil input volume fractions (δo; 0, 0.25, 0.50, 0.75 and 1), superficial velocities (0, 1.17, 2.33, 3.50 and 4.67 m/s) and pipe diameters (0.012 and 0.02 m id). figures 2 4 show that, dr decreased with increase in the oil volume fraction (25 75%) due to decrease in the superficial velocity of the water phase because the drp used were only soluble in the water phase. the decreased in superficial velocity of the water phase decreased the turbulent intensity of the water phase, this results to a decrease in drp turbulent eddies interaction and increase the pressure drop. the pressure drop increase (dr decreased) since the superficial velocity of the water phase inside the pipe was not enough to stretch the polymer molecules due to the increase in superficial velocity of the oil phase. this was in agreement with previous reports (virk, 1975; yusuf et al., 2013; abubakar et al., 2014b; abubakar et al., 2015b; edomwonyi-otu et al., 2015). in addition, it was observed that at the same conditions, dr increased (58% to 62%; 62% to 65% and 43% to 54% for hpam, peo and avm respectively) with decrease in the pipe diameter (0.02 – 0.012 m ids). the velocity inside the pipe increased as the pipe diameter was reduced, resulting to a high pressure drop in the smaller pipe diameter, which increased in the degree of turbulence. the high degree of turbulence in the smaller pipe brings about formation of many smaller eddies in the water phase due to collisions of larger eddied. the drp easily overcome smaller eddies due to lower amount of energy require by the smaller eddies than the larger once. this corroborate with the findings of virk, (1975); interthal and wilski, (1985); ahmad et al., (2009); karami and mowla, (2012). at lower flow rate, the effect of pipe diameter is clearly http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):792-801. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 797 noticeable than at higher flow rate where dr values for 0.012 and 0.02 m are closed to each other. figure 2: effect of oil input volume fraction on drag reduction at different flow rate and pipe diameter (0.012 and 0.02 m id) in oil-water flow for hpam. figure 3: effect of oil input volume fraction on drag reduction at different flow rate and pipe diameter (0.012 and 0.02 m id) in oil-water flow for peo. figure 4: effect of oil input volume fraction on drag reduction at different flow rate and pipe diameter (0.012 and 0.02 m id) in oil-water flow for avm. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng gimba et al: drag reduction with polymer mixtures in pipes of different diameters. azojete, 15(3):792-801. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 798 3.2 effect of oil input volume fraction, superficial velocity and pipe diameter the percentage dr of two polymer mixtures (hpam-avm and peo-avm) was studied in oilwater flow at different oil input volume fractions (0, 0.25, 0.50, 0.75 and 1), superficial velocities (0, 1.17, 2.33, 3.50 and 4.67 m/s) and pipe diameters (0.012 and 0.02 m id). figures 5 8 show that, dr decreased with increase in the pipe diameter (from 0.02 – 0.012 m ids) at same conditions. even though dr decreased due to the increase in oil input volume fraction, the effect of pipe diameter is clearly noticeable at lower flow rate than at higher flow rate. this corroborate with the previous findings (virk, 1975; interthal and wilski, 1985; ahmad et al., 2009; karami and mowla, 2012). synergism in dr observed for both pipe diameters (0.012 and 0.02 m id) in the water phase may be due to the interaction among the polymer molecules, which influence the extension of the molecules. it may also be attributed to the increase in the polymer coil dimension and their rigidity. this was in agreement with the work of edomwonyi-otu et al. (2016); dingilian and ruckenstein (1974); reddy and singh (1985); malhotra et al., (1988); gustavo and soares (2016) who reported a decrease in drag reduction with increased pipe diameter. figure 5: dr against oil input volume fraction at different flow rate (superficial velocity) and pipe diameter (0.012 and 0.02 m id) in oil-water flow for hpam-avm at total concentration of 30 ppm. figure 6: dr against oil input volume fraction at different flow rate (superficial velocity) and pipe diameter (0.012 and 0.02 m id) in oil-water flow for peo-avm at total concentration of 30 ppm. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):792-801. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 799 figure 7:dr against oil input volume fraction at different flow rate (superficial velocity) and pipe diameter (0.012 and 0.02 m id) in oil-water flow for hpam-avm at total concentration of 400 ppm. figure 8: dr against oil input volume fraction at different flow rate (superficial velocity) and pipe diameter (0.012 and 0.02 m id) in oil-water flow for peo-avm at total concentration of 400 ppm. 4.0 conclusion the effect of pipe diameter, oil input volume fraction and superficial velocity on drag reduction in oil-water flow has been studied. from the results obtained, it can be concluded that: dr decreased with an increase in pipe diameter and decrease in the superficial velocity of the water phase. dr is a function of oil input volume fraction, superficial velocity and pipe diameter. combining hpam and peo onto avm enhanced effectiveness of drag reduction of the avm. acknowledgements the authors would like to thank the department of chemical engineering, ahmadu bello university zaria and the members of the multiphase flow and separation systems research group of the department, for their moral and technical support. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng gimba et al: drag reduction with polymer mixtures in pipes of different diameters. azojete, 15(3):792-801. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 800 references abdurrahman, hn., shabirin, a., and hayder, aa. 2014. bio-polymers for improving liquid flow in pipelines-a review and future opportunities. journal of industrial and engineering chemistry, 20: 1157-1170. abubakar, a., al-wahaibi, t., al-wahaibi, y., al-hashmi, ar., and al-ajmi, a. 2014b. roles of drag reducing polymers in singleand multi-phase flows. chemical engineering research and design. elsevier b.v, 92(11): 2153-2181. abubakar, a., al-wahaibi, t., al-wahaibi, y., al-hashmi, ar., al-ajmi, a. and eshrati, m. 2015a. performance of a drag reducing polymer in horizontal and downward inclined oil-water flow. chemical engineering research and design, 1–28. abubakar, a., al-wahaibi, t., al-wahaibi, y., al-hashmi, ar., al-ajmi, a, and eshrati, m. 2015b. drag reduction with in polymer oil-water flow in relatively large pipe diameter . chemical engineering research and design, 1–28. ahmad, ma., bari, ah. and yunus, rm. 2009. studying the effect of addition of okra-natural mucilage as drag reducing agent in different size of pipes in turbulent water flowing system. national conference on postgraduate research (ncon-pgr). pp: 128-133. bewersdoff, h. and gyr, a. 1995. drag reduction of turbulent flows by adittives. fluid mechanics and its applications, 2: 101-153. bozzi, a., perrin, c.and austin, s. 2007. quality and authenticity of commercial aloe vera gel power. food chemistry, 103: 22-30. davis, rh. 1997. aloe vera-a scientific, approach. vantage press inc., new-york, usa, pp: 290306. dingilian, g. and ruckenstein, e. 1974. positive and negative deviations from additivity in drag reduction of binary dilute polymer solutions. alche journal, 20(6): 1222–1224. edomwonyi-otu, lc. and angeli, p. 2014. effects of polymer addition on pressure drop and interfacial waves in horizontal oil-water flows by. petroleum technology develoment journal, 2: 41–48. edomwonyi-otu, lc., chinaud, m. and angeli, p. 2015. effect of drag reducing polymer on horizontal liquid-liquid flows. experimental thermal and fluid science, 1–27. edomwonyi-otu, lc. and angeli, p. 2019. separated oil-water flows with drag reducing polymers. experimental thermal and fluid science, 102: 467–478 edomwonyi-otu, lc., simeoni, m., angeli, p. and campolo, m. 2016. synergistic effect of drag reducing agents in pipes of different diameters. nigerian journal of engieering, 22: 1-5. edomwonyi-otu, lc.and adelakun, do. 2018. effect of heavy molecular weight polymer on quality of drinking water. materials today communications. elsevier publication. 15: 337-343. edomwonyi-otu, lc., chinaud, m. and angeli, p. 2014. dag reduction in stratified oil-water flows. spejournal-onepetro2014-c2-bhrpublishers. gimba, mm., edomwonyi-otu, lc., abubakar, a. and yusuf, n. 2017. synergistic effect of natural and synthetic polymers as drag reducing agents in single phase water flow. nigerian journal of materials science and engineering (njmse), 7:16-21. gimba, mm., edomwonyi-otu, lc., abubakar, a. and yusuf, n. 2018. synergistic effect of polymer-polymer mixtures as drag reducing agents in turbulent water flows. research journal of engineering and environmental sciences (rjees), 3(2): 560-570. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):792-801. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 801 gustavo, a. and soares, ej. 2016. effect of combined polymers on the loss of efficiency caused by mechanical degradation in drag reducing flows through straight tubes. rheologica acta, 55(7): 559–569. interthal, w. and wilski, h. 1985. drag reduction experiments with very large pipes. collid and polymer science, 263: 217-229. karami, hr. andmowla, d. 2012. investigation of the effects of various parameters on pressure drop reduction in crude oil pipeline by drag reducing agents. journal of non-newtonian fluid mechanics, 177-178: 37-45. lescarboura, ja., culter, jd. and wahi, ha. 1971. drag reduction with a polymeric additive in crude oil pipelines. spe journal, 11(3): 229-235. malhotra, jp., chaturvedi, pn. and singh, rp. 1988. drag reduction by polymer-polymer mixtures. journal of applied polymer science, 36: 837–858. marmy, rms., hayder, ab. and rosli, my. 2012. improving the flow in pipelines by cocos nucifera fiber waste. international journal of physical science, 7(26): 4073–4080. reddy, gv. and singh, rp. 1985. drag reduction effectiveness and shear stability of polymerpolymer and polymer-fibre mixtures in recirculatory turbulent flow of water. rheologica acta, 24: 296–311. sellin, rhj., hoyt, jw. and scrivener, o. 1982. the effect of drag-reducing additives on fluid flows and their industrial applications part 1: basic aspects. journal of hydraulic research, 20(1): 29–68. virk, ps. 1975. drag reduction fundamentals. alche journal, 21(4): 625–656. yusuf, n., al-wahaibi, t., al-wahaibi, y., al-ajmi, a., al-hashmi, ar., olawale, as., mohammed, ia. 2013. experimental investigation on the performance of drag reducing polymers through two pipe diameters in horizontal oil–water flows. experimental thermal and fluid science, 50: 139149. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):163-173 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 163 original research article mechanical properties of rice husk ash cement mass concrete mixed with discrete steel fibres y.o. abiodun1* and o.o. sijuwola2 1department of civil and environmental engineering, university of lagos, nigeria 2department of civil engineering, university of ilorin, nigeria *corresponding author: yabiodun@unilag.edu.ng article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: rice husk ash discrete steel fibre compressive strength flexural strength tensile strength abstract the potential use of supplementary cementitious materials in concrete for improving concrete properties has been a growing concern in recent years. this is due to the environmental and health hazards associated with the increase in the use of cement in concrete as a result of infrastructural development all over the world. the effective strengthening of the concrete matrix by reinforcements helps to prevent brittleness that occurs in plain concrete. this study investigated the mechanical properties of randomly distributed discrete steel fibers in rice husk ash-cement matrix and its effect on the strength and performance of concrete. rice husk was burnt at a controlled temperature of 600°c for 4 hours in an electric furnace to get the rice husk ash. prescribed mix ratio of 1:2:4 and water-cement ratio of 0.5 were used in all the mixes of rice husk ash cement mass concrete mixed with discrete steel fibres. the parameters varied were rice husk ash content at 0%, 10%, 15%, 20%, and 25% and discrete steel fiber dosage of 0.5kg and 1kg.the mechanical properties of the rice husk ash cement mass concrete mixed with discrete steel fibres were studied through compressive strength test, split tensile test and flexural test. results obtained show that the rha-cement mass concrete mixed with discrete steel fibres reached maximum compressive strength at an optimum value of 10% rha and 1kg of discrete steel fibres. the highest values for split tensile and flexural strengths were obtained at 10% rha replacement. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction concrete is well known as a heterogeneous mix of cement, water, fine and coarse aggregates. globally, it is the backbone for the development of infrastructure, including buildings, industrial structures, bridges and highways. the contribution of portland cement production worldwide to greenhouse gas emission is estimated to be about 1.35 billion tonne annually or about 7% of the total greenhouse gas emissions to the earth’s atmosphere. to reduce the greenhouse effect, some mineral admixtures have been studied as partial replacements for cement in plain and reinforced concrete (malhotra, 2002). mailto:yabiodun@unilag.edu.ng mailto:yabiodun@unilag.edu.ng http://www.azojete.com.ng abiodun and sijuwola. mechanical properties of rice husk ash cement mass concrete mixed with discrete steel fibres. azojete, 15(1):163-173. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 164 in recent years, rice husk ash (rha) has been used as ordinary portland cement replacement material in concrete industries. rha is the ash produced from husk fibre of rice burning. it is found to have high pozzolans material and it can not only be used as a partial cement replacement but also can increase the compressive strength and durability of concrete (fernandez, 2007). fibre reinforced concrete (frc) is concrete containing fibrous material which increases its structural integrity. it may also be defined as a composite material mixed with portland cement, aggregate, and incorporating discrete discontinuous fibre. without the fibre, the concrete has is relatively strong in compression but weak in tension and brittle. the weakness in tension can be overcome by the use of conventional steel reinforcement and to some extent by the inclusion of a sufficient volume of certain fibres (lofgren, 2005). the reason for adding such fibres to concrete is that plain, unreinforced concrete is a brittle material, with a low tensile strength and a low strain capacity. the role of randomly distributed discontinuous fibres is to bridge across the cracks that develop and provide some post-cracking “ductility”. if the fibres are sufficiently strong and sufficiently bonded to material, this permit the frc to carry significant stresses over a relatively large strain capacity in the post cracking stage (zhang et al, 2005). della, et al. (2002) have shown that rha burnt under controlled conditions produces high levels of reactive silica particles in amorphous state (up to 95%). the increased reactivity of rha is mainly caused by the high content of non-crystalline silica and in general reactivity is also favoured by the increased fineness of rha. isaiah, et al. (2003) have demonstrated that residual rha is produced with a lower quality because of its high carbon content, which led to an increase in water demand and produces a darker color of mortar and concrete. however, residual rha has a better filling effect compared to pozzolanic material. chao-lung, et al. (2011) and raoul, et al. (2003) investigated the effect of rice husk ash content as partial replacement of cement on compressive strength and volume stability for different mixes and test results showed that up to 40% replacement by rice husk could be made without affecting the compressive strength when compared to the control concrete. the aim of this study was to investigate the mechanical properties of rice husk ash – cement mass concrete, mixed with discrete steel fibres using an indigenous species of rice; olomo-nla/ oryza glaberrima from kaduna state, nigeria. specifically, this involves the: determination of chemical composition of the rice husk ash obtained from the study specie determination of mechanical properties of the rice husk ash cement mass concrete mixed with discrete steel fibres through compressive strength test, flexural test and split tensile test determination of the optimum percentage replacement of rice husk ash in the rice husk ash cement mass concrete mixed with discrete steel fibres investigation of effect of discrete steel fibres in the rice husk ash – cement mass concrete 2.0 materials and methodology 2.1 materials the rice husk used in this study was sampled from katsina state, nigeria and the local name of the specie is olomo nla/soro. 100kg of rice husk was burnt at a controlled temperature of 600°c/4 hours in an electric furnace at federal institute of industrial research oshodi (fiiro), lagos, nigeria. about 25kg of rice husk ash was generated after burning. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):163-173. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 165 hooked end steel fibres of diameter 0.9 mm and length 30 mm was used for this study. the fibre was imported from china. from the manufacturer’s data, the range of ultimate tensile strength on tension test is above 1100 n/mm2 for diameters ranging from 0.45 1mm. the density of steel fibre is 7850 kg/m3. granite of sizes between 12mm and 19mm was used in this study and it was sourced from bm mining and quarrying limited located along abiola way, abeokuta, ogun state, nigeria. river sand from olorunsogo village, ifo local government area, ogun state, nigeria was used. the particles passed through a 9.5mm sieve. dangote portland cement was used in this study. the quality of the portland composite cement was approved by sirim (certified to ms 522-1:2007) and bs en 197-1:2000, cem ii/b-l 32.5n/42.5r. the cement was stored away from air moisture in the workshop to ensure the material was in good condition during the experimental period. master rheobuild 850 admixture produced by master builders, inc., was used. according to manufacturer’s data and specifications, it is a high range; water-reducing super plasticizer. it is normally dispensed depending on the desired plasticizing or water reducing effect at a rate of 0.2-2.0ltr/100kg of cement or 0.23–2.34% cwt. in this study, 0.03% of the weight of water was replaced with rheobuild850. 2.2 methodology 2.2.1 sieve analysis on aggregates a sieve analysis (or gradation test) was used to assess the particle size distribution of both the granite (coarse aggregate) and sand (fine aggregate). column of sieves with wire mesh cloth (screen) were arranged and a representative weighed sample of each aggregate was poured into the top sieve which has the largest screen openings. each lower sieve in the column has smaller openings than the one above. at the base is a round pan, called the receiver. the column of sieves was placed in mechanical shaker for about 10mins. the material on each sieve was weighed and the weight was divided by the total weight to give percentage retained on each sieve. 2.2.2 experimental design rice husk ash was used to partially replace cement at 0%, 10%, 15%, 20% and 25% by weight of binder content and steel fibre replacement levels of 0.5 and 1.0% volume fraction. mix ratio 1:2:4 and water-cement ratio of 0.5 were adopted all through the study. nine mixes were prepared and fiftyfour (54) beams of size of 150 mm x 150 mm x 550 mm were cast in accordance to bs en 12390-5:2000 (methods for making test beams from fresh concrete). these beams were tested, using the flexural testing machine with a capacity of 100 kn operating at a rate of 1.5 mm/min to study the flexural tensile properties of the hardened concrete using a third-point loading arrangement. specimens were water-cured for 28 and 56 days. figures 1 and 2 show the cast beam specimens and the set-up of the specimen for flexural strength test https://en.wikipedia.org/wiki/particle_size_distribution file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abiodun and sijuwola. mechanical properties of rice husk ash cement mass concrete mixed with discrete steel fibres. azojete, 15(1):163-173. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 166 figure 1: cast beam specimens figure 2: set-up for flexural strength test the split tensile test was carried out in accordance to bs en 12390-6:2000 on a digital compression testing machine with a capacity of 200 kn and loading rate of 2 kn/sec. the load was applied by the machine platens through two plywood strips (25 mm wide, 3.2 mm thick). the cured cylinders were tested as shown in figure 3 with their horizontal axes between the platens until failure occurred. the strips allowed even load distribution by conforming to small irregularities on the specimen surface. the splitting tensile strength is given by: σ = 2p πld (1) where p is the maximum load, d is the cylinder diameter, and l is the cylinder length. fifty-four (54) cylinders of size 150mm × 300mm were cast. specimens were water-cured for 28 and 56 days. figure 3: testing of specimen for split tensile strength figure 4: compressive strength test set-up for the compressive strength test was carried out in accordance to bs en 12390-3:2002. eightyone (81) cubes of size 150mm × 150mm ×150mm were cast. the specimens were de-moulded after 24 hours and cured under water in a curing tank for 3, 14 and 28 days. the cured specimens were taken to the electronic testing machine as shown in figure 4 where load was applied and increased until failure. the machine automatically stops when failure occurs, and then displays the load and the compressive strength was evaluated. the compressive strength of each sample was determined as follows; compressive strength (n/mm²) = crushing load / area of cube http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):163-173. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 167 three cubes at each percentage rha replacement and fibre content were tested to determine the compressive strength. 3.0 results and discussions 3.1 results of sieve analysis tables 1-4 show the sieve analysis of coarse aggregate, fine aggregate and rice husk ash while figure 5 shows the graphical representation of the sieve analysis data from tables 1 and 2. table 1: sieve analysis for coarse aggregate test sieves weight retained (g) percentage retained (%) cumulative percentage retained (%) percentage passing (%) 25 µ − 19 µ 726.2 13.30 13.30 86.70 14 µ 1,544.8 28.29 41.59 58.41 12.7 µ 458.4 8.39 49.98 50.02 10 mm 1,242.8 22.76 72.74 27.26 5 mm 1,268.1 23.22 95.96 4.04 2.36 mm 73.8 1.35 97.30 2.70 dust 147.2 2.70 100.00 0.00 table 2: sieve analysis for fine aggregate test sieves weight retained (g) percentage retained (%) cumulative passing retained (%) percentage passing (%) 10mm 8.6 0.25 0.25 99.75 5mm 20.1 0.58 0.83 99.17 2.36mm 91.7 2.64 3.47 96.53 1.18mm 538.4 15.52 18.99 81.01 600µ 1,249.1 36.00 54.99 45.01 300µ 1,173.6 33.82 88.81 11.19 150µ 307.5 8.86 97.67 2.33 75µ 1.1 0.03 97.70 2.30 dust 79.7 2.30 100 0 table 3: aggregates coefficients sand granite d10 0.279 6.749 d30 0.461 10.325 d60 0.775 14.211 cu 2.78 2.11 cc 0.98 1.11 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abiodun and sijuwola. mechanical properties of rice husk ash cement mass concrete mixed with discrete steel fibres. azojete, 15(1):163-173. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 168 figure 5: particle size distribution curves for sand and granite using the equations below, the coefficient of uniformity (cu) and the coefficient of curvature (cc) were obtained from figure 2 and the results shown in table 3. cu = d60 d10 (2) cc = d30∗d30 d10∗d60 (3) the fine and coarse aggregates had uniformity coefficients (cu) of 2.78 and 2.11 respectively while they had a coefficient of curvature (cc) of 0.98 and 1.11 respectively. according to unified soil classification, the fine aggregates could be classified as well graded medium to coarse sand while the coarse aggregates could be classified as well graded fine to medium granite. 3.2 chemical composition of rha table 4: comparison between the chemical composition (%) of ordinary portland cement (opc) and rice husk ash (rha) s/n name of compounds ordinary portland cement (%) rice husk ash (%) 1 silica, (sio2) 18.34 59.5 2 sodium oxide (na2o) 0.55 3.0 3 potassium oxide (k2o) 0.48 12.6 4 calcium oxide (cao) 63.97 7.3 5 magnesium oxide (mgo) 2.16 2.2 6 aluminium oxide (al2o3) 4.73 2.1 7 ferric oxide (fe2o3) 3.58 8.8 8 9 sulphate (so32-) manganese oxide (mno) 1.67 2.0 10 insoluble residue (ir) 20.02 2.5 11 loss on ignition (l.o.i) 1.11 12 fibres 0.002 it was observed that cumulative percentage of sio2, al2o3 and fe2o3 in composition of rice husk ash is 70.4%. this value falls within the range recommended for class n pozzolan and it is an indication of high reactivity of the rha sample tested for in this study (astm c618-92a 1994). the percentage of cao present in cement was higher than that of rha. this portrays the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):163-173. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 169 cementing power of cement over rha which is a pozzolan; a siliceous or siliceous and aluminous material, which in itself possesses little or no cementing property, but will in a finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties (malhotra and mehta, 1996) 3.3 effect of rha-steel fibre matrix on the setting times of cement table 5: setting time values (mins) with percentage replacement of rice husk ash percentage replacement initial setting time (mins) final setting time (mins) control 166 268 10 176 279 15 182 283 20 188 290 25 196 297 the results indicated that the addition of steel fibres considerably increases the initial and final setting time of cement based pastes. the rice husk ash particles in the pastes act as agents to suppress nucleation and prompt decelerated hydration mechanism. the deceleration of the setting time of cement pastes could have been caused by the decreasing volume of hydration compounds as well as the reduction of distances between individual particles as a result of the presence of steel fibres in the matric. the relationship between the setting time and percentage of replacement of rha-steel fibre matrix is shown in figure 6 figure 6: effect of rha-steel fibre on setting times (initial and final) of cement paste 3.4 workability test table 6: slump values and degree of workability % percentage replacement slump value (mm) control (0% rha) 33 10% rha+fibre 58 15% rha+fibre 70 20% rha+fibre 79 25% rha+fibre 85 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abiodun and sijuwola. mechanical properties of rice husk ash cement mass concrete mixed with discrete steel fibres. azojete, 15(1):163-173. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 170 the workability of the fresh concrete, as determined by the slump test in accordance with bs en 12350-2:2009 for all the mix proportions with constant percentages of cement replaced with rice husk ash is presented in table 6. it was observed that the workability reduced at 10% cement replacement with rice husk ash. this indicates a dehydrating effect of rice husk ash. 3.5 compressive strength test table 7: average compressive strength (n/mm2) curing ages 3 days 14 days 28 days steel fibres (kg) 0.5 1.0 0.5 1.0 0.5 1.0 0% (control) 14.96 20.81 23.25 10% 23.9 25.5 27.9 29.8 32.2 34.7 15% 17.8 19.1 18.5 20.2 23.3 23.9 20% 16.5 16.7 17.3 18.9 19.3 19.9 25% 14.5 15.0 15.3 16.5 17.3 18.0 in the case of plain concrete mixes, the addition of steel fibres showed a marginal increase of the compressive properties. a marginal increase in compressive properties was caused by the effect of the fine to coarse aggregate ratio. it can also be noted that the maximum strength gain of the rice husk ash-cement matrix was achieved at the 10% replacement with rha, at 28 days. further increase after 10% replacement showed a gradual reduction in strength of 27.64% and 31.12% at 15% replacement for 0.5kg and 1.0kg of steel fibres respectively. it can be also noted that the increased addition of steel fibres in rice husk ash substituted concretes exhibited a slight increase in compressive strength value. the effect of steel fibre addition on the compressive properties is known to be a marginal improvement because compressive failure of concrete involves fracture in which case the tensile failure of the fibres is not realized. it can be deduced from the experimental results that a homogeneous presence of fibres in the matrix does not actively contribute to stress redistribution in compressive failure mode and thereby neither the matrix nor the aggregate failure is delayed. the results suggest that the addition of rice husk ash at a level of 10% and steel fibres of up to 1kg at 28 days curing age gave remarkable improvement of compressive strength as shown in figure 7. figure 7: 28-day average compressive strength at percentage replacement levels http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):163-173. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 171 3.6 flexural strength test table 8: average flexural strength (n/mm2) curing ages 28 days 56 days steel fibres (kg) 0.5 1.0 0.5 1.0 0% (control) 12.30 13.6 10% 12.52 13.31 13.81 14.0 15% 8.92 10.59 9.34 11.3 20% 7.15 9.25 8.75 10.2 25% 6.78 8.72 7.82 9.56 a comparison of the flexural strength properties evaluated for the various concrete mixtures is given in table 8 above. it can be observed from the experimental trends shown in the results that, in the case of plain concrete the improvement in flexural strength were noticeable at later ages. in the case of 10% rice husk ash substituted concretes containing a steel fibre dosage of 1kg (vf), the highest flexural strength was recorded at 56 days. this resulted in an increase of flexural strength compared to plain concrete. also, an increase in rha percentage beyond 10% yielded no further increase in flexural strength, even with the addition of steel fibres as shown in figure 8. figure 8: flexural strength at various replacement levels this result is similar to what was obtained by sandesh et al. (2004), where the inclusion of steel fibers showed more significant effects on flexural tensile strength at 0.25% to 1.0% volume fractions and an increase in fibre content resulted in an increase in flexural strength. the test results show clearly that steel fibre addition gives better enhancement of flexural properties up to 10% rha and randomly distributed discrete steel fibres helps to control cracks. 3.7 split tensile test table 9: average split tensile strength (n/mm2) curing ages 28 days 56 days steel fibres (kg) 0.5 1.0 0.5 1.0 0% (control) 1.78 1.92 10% 1.88 1.98 1.96 2.05 15% 1.61 1.70 1.64 1.75 20% 1.57 1.64 1.61 1.71 25% 1.48 1.56 1.50 1.65 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abiodun and sijuwola. mechanical properties of rice husk ash cement mass concrete mixed with discrete steel fibres. azojete, 15(1):163-173. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 172 the split tensile values of the various concrete mixtures are compared in figure 8 above. it can be noted that the maximum value of split tensile strength for rice husk ash substituted concrete was observed at 10% replacement, with 1kg (vf) of steel fibres as shown in figure 9. as the percentage replacement increases, there was a gradual reduction in split tensile value; however, increase of the steel fibre dosage suitably improved the strength properties. the increased addition of steel fibres showed reasonable improvement of the split tensile strength because of the bridging action of the fibres realized under tension. on the other hand, increased percentage replacement of rice husk ash did not show an appreciable increase in strength, because of probable reduction of the microstructural densification. the results shows that the effect of steel fibre addition is better realized when bridging stress developed during indirect tension. figure 9: average split tensile strength at various replacement levels this result is also in accordance with sandesh et al. (2004) where for 12.5% rha and 0.25% steel fibres, the split tensile strength was 2.76n/mm2 and for 12.5% rha and 0.5% steel fibres, the split tensile strength was 2.83 n/mm2. steel fibers in the concrete increase the splitting tensile strength and the highest volume fraction of fibers gives the maximum increase of strength. 4.0 conclusions concrete mix with 10% replacement level of rha gave maximum compressive strength, flexural strength and split tensile strength. the increase was insignificant at a higher substitution level (15%) because of decreased reactivity. the rate of strength gains in rice husk ash substituted concretes was appreciable for various curing ages because of the more effective pozzolanic reaction, the pore filling effect and the fineness of the rice husk ash particles. the results demonstrated that a higher substitution of rice husk ash showed a gradual reduction in split tensile value; however, increase of the steel fibre dosage suitably improved the strength properties. the increased addition of steel fibres showed reasonable improvement of the split tensile strength because of the bridging action of the fibres realized under tension. on the other hand, increased rice husk ash substitution did not show an appreciable increase in strength, because of probable reduction of the microstructural densification. the test results demonstrate that the effect of steel fibre addition is better realized when bridging stress developed during indirect tension. 28 days 56 days http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):163-173. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 173 references american society for testing materials (astm), astm c618-92a, standard specification for fly ash and raw calcined natural pozzolan for use as mineral admixture in portland cement concrete. astm designation c618-92a-1994. west conshohocken, pa: astm, 1994 british standard code of practice 2009. bs 12350 part 2. testing fresh concrete sampling. british standards institution. london, uk british standard code of practice 2000. bs 12390 part 5. testing hardened concrete: flexural strength of test specimens. british standards institution. london, uk british standard code of practice 2000. bs 12390 part 6..testing hardened concrete: tensile splitting strength of test specimens. british standards institution. london, uk british standard code of practice 2009. bs 12390 part 3. testing hardened concrete: compressive strength of test specimens. british standards institution, london.uk chao-lung, h., anh-tuan, bl. and chun-tsun, c. 2011. effect of rice husk ash on the strength and durability characteristics of concrete. construction and building materials, 25(3): 3768-3772 della, vp., kuhn, i. and hotza, d. 2002. rice husk ash as an alternate source for active silica production. mater lett, 57(4): 818-821 fernandez, h. 2007. partial replacement of sand with fly ash. international conference on fly ash utilization and disposal in india by cbip. january 20-22, 2007. 45-54 isaiah, gc., gastaldini, alg. and moraes, r. 2003. physical and pozzolanic action of mineral additions on the mechanical strength of high performance concrete. cement concrete composite, 25(1): 69-76 malhotra, vm. and mehta, pk. 1996. pozzolanic and cementitious materials. gordon and breach publishers, philadelphia malhotra, vm. 2000. role of supplementary cementing materials in reducing greenhouse gas emissions, in concrete technology for a sustainable development in the 21st century, o.e. gjorv and k. sakai, eds., e&fn spon, london raoul, j., rendell, f., tamba, s. and cisse, ik. 2003. properties of cement rice husk mixture, construction and building materials 17, 239-243 löfgren, i. 2005. fibre-reinforced concrete for industrial construction – a fracture mechanics approach to material testing and structural analysis. ph.d. thesis, department of civil and environmental engineering, chalmers university of technology, göteborg, pp. 1-162 sandesh, dd., pravin, vd., satish, dk. and deotale, rs. 2004. experimental study on strength of concrete by artificial fibres with rice husk ash. international journal of engineering research and applications, 1(3): 571-581 zhang, l. and mindess, s. 2005. the compressive toughness of high strength fibre reinforced concrete. construction materials symposium, vancouver, columbia, canada, august 22-24, 2005. cdrom. vancouver, canada: university of british columbia file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):329-341 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 329 original research article properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder i. o. hassan1, o. w. bolaji2* and j. o. adedapo3 1department of building. federal university of technology, minna, niger state, nigeria 2department of agricultural and bio-environmental engineering technology, federal college of forestry mechanization afaka, kaduna state, nigeria 3department of horticulture and landscape technology, federal college of forestry mechanization afaka, kaduna state, nigeria *corresponding author’s e-mail address: owbolaji@yahoo.com article information submitted 8 may, 2018 revised 31 july, 2018 accepted 5 august, 2018 keywords: binder calcium carbide waste mortar self compacting sorghum husk ash abstract the quest for the development of alternative and more sustainable construction material stemmed out from the current global concern on issues relating to global warming and green house effect. in recent time, research direction has shifted towards the use of agro-industrial waste as complete replacement of ordinary portland cement. in this study the effects of the blends of sorghum husk ash (sha) and calcium carbide waste (ccw) on the fresh properties of self compacting mortar was investigated where various tests were carried out which included physical and chemical properties of the constituents materials, flow cone test for paste, mini v-funnel flow time and mortar flow spread test for determination of saturation dosage of hrwr for self compacting mortar made with sorghum husk ash and calcium carbide waste as binder, were carried out. then developments in the compressive strength of the hardened mortar were determined at 3, 7, 14, 28, 56 and 90 days. the study revealed that sha sample have high silicon dioxide (sio2 (84%) while ccw is majorly calcium oxide (cao(66%).the optimum saturation dosage of high range water reducer (hrwr) determined from flow cone test and mini-v-funnel was 3.5%. the 70/30 (sha/ccw) shows the highest mortar flow spread of 290 mm compared to the control (295mm).the agro-industrial binder exhibited good binding properties at a slow hydration rate. analysis of the compressive strength results show that 70/30 (sha/ccw) proportion has the highest value of 14.08 n/mm2 at 90 days. self compacting mortar made with sha/ccw combinations as binder can be adopted for use in masonry work as it conforms to type n of astm c270 mortar © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction building components are fabricated by concrete been placed into formwork and then compacted, according to (le et al., 2012), sprayed concrete and self compacting concrete (scc) are two other construction strategies methods which could be used to eradicate the compaction process. in 1986 research programme on scc and sprayed concrete commended at one of the institution in asia (topcu and bilr, 2009). due to its enhanced quality, productivity and working mailto:owbolaji@yahoo.com http://www.azojete.com.ng hassan, et al: properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder. azojete, 15(2):329-341. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 330 condition, scc gives more leverage in the construction process. generally, scc has great powder form and a reduced granite volume ratio than conventional concrete which in turn ensures scc filling rate, passing rate and segregation impedance (liu, 2011). largest manufactured product (concrete) depends majorly on portland cement for strength and other desired properties (mehta and monteiro, 2014). the manufacturing process of this portland cement is observed to have contributed up to 5% of global co2 emission resulting from clinkers production which involves heating calcium carbonate (caco3) at temperature of above 900 °c which result into lime (cao) and carbon dioxide (co2) (rubenstein, 2012). the quick lime according to (neville, 2011), is further made to react with materials that have silica (sio2), alumina (al2o3) and iron (fe2o3) at temperature of about 1450 °c.the combination is allowed to cool, grinded to powdered form and mixed with 5% gypsum content. the major strength determinant in portland cement (pc) which is a combination of cao, sio2, al2o3 and fe2o3 is sio2 in combination of cao, which form ca(oh)2 (hydrated lime) including water, which is the final stage for strength development (neville, 2011). climate change which has been attributed to global warming caused due to the emission of greenhouse gases resulting from human and industrial activities has prompted research and development on alternative binder to replace portland cement (nca, 2014). past findings on the quest for alternative binders concentrated on making used of natural pozzolan such as volcanic ash (hassan, 2006) or ashes from agricultural waste such as corn cob ash (cca) (raheem, 2006) amongst others as partial pc replacement in concrete and mortar. attempt to completely replace cement in concrete brought about studies into geo-polymer concretes which simply involves alkali activation of pozzolanic materials with the use of chemical based hydroxide (naoh) at an elevated temperature (turner and collins, 2013) other studies on total replacement of cement with pozzolans includes combination with alternative cao which is the source calcium carbide waste (ccw) in the works of makaratatet et al. (2010) combining fly ash (fa) and ccw sourced within nigeria and reportedly observed hydration reaction with a 28 days strength of 11n/mm2 without any treatment on the ccw. pozzolans are silicate based materials that react with calcium hydroxide generated by hydrating cement to form additional cementitious materials. incinerated ashes from agro wastes at a regulated temperature have being found to be pozzolanic with major components been amorphous silica which combines with lime in a moisture form to give cementitious properties (neville, 2011). portland cement according to (mehta and monteiro, (2014) react using tri calcium silicate (c3s) with water (h20) to give calcium silicate-hydrate and calcium hydroxide which is a pozzzolans cement reaction. the pozzolanic reaction is basically lime consuming and does not necessarily require presence of cement but an active source of lime; hence the thought for alternative source of lime to enhance pozzolanic reaction with an agricultural waste ash as silica source sorghum husk ash (sha) is of great importance in the present day study. sha is ash gotten from open air burning of the husk and sorghum or guinea corn being popular which serve as major staple food in the country nigeria. calcium carbide waste (ccw) is reported to be 70-80% http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):329-341. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 331 calcium hydroxide (ca(oh)2) with the impurities in it, listed as lead, copper, iron, manganese, nickel and zinc (chukwudebelu et al., 2013). the quest by nigerian government towards food security and sustainability, with maize and other cereals grains like millet and sorghum being the central focus and northern nigeria known as a major contributor to sorghum and cereals production is a pointer that the husk of these crops will always be available. the usage of this agricultural and industrial waste material in mortar and concrete production should be seen as action taken in the right direction. the sustainability of these materials to guarantee total portland cement (pc) replacement promises to offer great contribution towards improving knowledge in concrete technology and development of nigeria as a nation. the aim of this research is to determine the performance of self compacting mortar made with sorghum husk ash and calcium carbide waste as binder. the specific objectives are as follows; to examine the chemical properties of sorghum husk ash and calcium carbide waste. determination of degree of hydration of sorghum husk ash and calcium carbide waste as binder. to assess the features of fresh self compacting mortar made with sorghum husk ash and calcium carbide waste as binder. to assess the strength property of the self compacting mortar made with sorghum husk ash and calcium carbide waste as alternative binder. 2.0 materials and methods 2.1 materials the materials used for the research are sorghum husk ash (sha), calcium carbide waste (ccw), portland cement (pc-cem1 42.5n). the fine aggregate (fa), masterglenium ace 456 high range water reducer (hrwr) and portable water available at the building laboratory of the federal university of technology, minna (futminna) was used for the mixing and curing. 2.1.1 portland cement the pc used was cem1 42.5n from obajana factory of dangote cement company which served as the binder for the control of self compacting mortar (scm) mix. 2.1.2 sorghum husk ash (sha) the sorghum husk ash was collected from a local guinea corn mill at tundun fulani near bosso area in minna, niger state, nigeria. the husk were collected and burnt in an open air with a locally fabricated incinerator available in the building department of federal university of technology minna, niger state, nigeria. the ash was collected and ground to finer particles then sieved with a 75µm sieve (bs en 196-6:2016). the particles passing were used as the sha for the experiments. 2.1.3 calcium carbide waste (ccw) the calcium carbide waste was gotten in slurry form as a by-product of acetylene gas production and was packed from the dumping area of a local automobile welder’s (panel beater’s) workshop around minna environs. ccw was sun-dried for approximately 4 days and later oven-dried at 105°c for 24 hrs before it was ground in a local mill at gidankwano village of minna and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan, et al: properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder. azojete, 15(2):329-341. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 332 sieved with 75μm sieve (bs en 196-6:2016). then the particle passing was used as the ccw samples for the experiments. 2.1.4 fine aggregate the fine aggregate retained within 1.18 mm and 75µm (simulated reference sand) sieved out from the available natural sand obtained from bosso local government area, minna, niger state, nigeria in accordance with bs en 196-1 (2016) reference sand prescription for strength test on cement was used for the experiments. 2.1.5 tap water portable tap water available at the building laboratory of federal university of technology minna, niger state, nigeria was used for mixing and curing. water was ensured clean and free from contaminations harmful to the setting of mortar. the water is also free from impurities that would affect the hydration mechanism of the cementitious components within the mix (neville, 2011). 2.1.6 superplasticiser (master glenium ace 456) the choice of superplasticiser (masterglenium ace456) is because of its ability to hasten the concrete or mortar hydration by uncovering an expanded surface of the bond grain to respond with water. thus it is conceivable to acquire prior advancement of the warmth of hydration a quick improvement of the hydration item and as a result, higher quality at the early age. masterglenium ace456 meet the requirement type a, e&f of bs.en 934-2 (2009) and astm c494 (2013). 2.2 physical analysis of the constituents materials particle size distribution (psd) of the available natural sand was analyzed using the dry-sieve approach in -line with the bs en 196-1 (2016) for proper classification of the available natural sand. the reference sand required for mortar production in strength determination test specified in the standard bs en 196-1 (2016) was then extracted using an arrangement of sieve size 1.18 mm to 75 µm. the particles passing the 1.18 mm sieve but retained on the 75 µm sieve was used for the mortar mixture for the strength test. the 1.18 mm sieve was adopted as the upper limit value for the simulated reference sand instead of the 1.6 mm sieve specified by bs en 196-1 (2016). table 3.1 shows the particle size distribution of fine aggregate used. additional physical properties determined for all the materials used for this experiment are the bulk density in line with astm c128 (2015) and fineness test conducted on pc and varied combination of sha/ccw via-wet-sieving method as prescribed by bs en 196-6 (2016) using a 45 µm sieve available in the laboratory. 2.3 chemical analysis of cementitious materials (pc, sha and ccw) 20g of each samples of pc,sha and ccw which was sieved by 75 µm was package and then taken to ewekoro work department of lafarge cement using xrf analyser fitted with digital display system for data acquisition to analysed the respective chemical compositions and x-ray fluorescence analysis for determination of oxides composition of pc, sha and ccw sample. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):329-341. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 333 2.4 fresh properties of self compacting mortar made with sha and ccw. hassan,(2015) procedure was adopted in an attempt to establish an optimum paste and mortar volume that will satisfy certain flow time in which the method considered a fixed water binding ratio of 0.4 and superplasticiser dosages ranging from 1.5%, 1.75%, 2.00%, 2.25%, 2.50%, 2.75%, 3.00%, 3.25%, 3.50% and 3.75%. 2.4.1 filling ability of the paste. the filling ability in respect to the flow time was evaluated by a flow cone which is in line with (astm c939, 2010). the flow cone was levelled with the prepared sample according to the method considered a fixed water binding ratio of 0.4 and superplasticiser dosages ranging from 1.5%, 1.75%, 2.00%, 2.25%, 2.50%, 2.75%, 3.00%, 3.25%, 3.50% and 3.75%. then the discharge tube was closed using a rubber stopper. the paste measured up to the calibration mark in the flow cone, the rubber stopper was then removed to allow the paste to flow out of the cone simultaneously, a stop watch was used to record the flow time of the paste. the discharge paste was collected using a container and subsequently released into the mixer pan for further mixing with additional masterglenium ace456. numerous additional dosages of masterglenium ace456 were added to the paste and the flow time was determined for each increment. figure 2.1: set up for filling ability (flow cone test). 2.4.2: flow ability of mortar (mini v-funnel test). the flow ability of the mortar was tested using the mini v-funnel test, this measure the time it takes for the mortar to flow through the funnel, which enabled the determination of the mortar viscosity. the test apparatus was assembled firmly in the ground, the wall of the funnel was lubricated to allow for easy flow of mortar. the trap stopper closed and the funnel filled to the brim, after a delay of 5s, the stopper opened and the time taken for mortar to flow from the funnel to the time it takes to sight the light was recorded. this time interval is referred to as vfunnel flow time (akram et al., 2009).the v-funnel apparatus is shown in figure 2.2. figure 2.2: set up for flow ability of mortar (mini-v-funnel). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan, et al: properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder. azojete, 15(2):329-341. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 334 figure 2.3: mortar flow mould 2.4.3: filling ability of mortar (flow mould test). the flow mould test was conducted to investigate the filling ability of the mortar at various dosage of masterglenium ace456. a standard flow mould which attunes to astm c 231/c 231m (2010) was locally fabricated and used to evaluate the filling ability with respect to the mortar flow spread. the flow mould used was shown in the figure 2.3. the mould was placed over a leveled plexiglas plate. then the mould was raised vertically without any disturbance after it has been filled with mortar sample and the mortar was allowed to flow over the plexiglas plate. the average diameter of the mortar spread was the flow spread. 2.5: determination of degree of hydration of the binders. determinations of degree of hydration of the binders were carried out using 50mm mortar cubes. production of the mortar samples involved weighing out the appropriate constituents materials and making sure that the sha and ccw were properly mixed before measured quantity of simulated sand was injected. then the sand and the binders were mixed properly before the weighed mixing water already added with hrwr mixed continuing until a uniform mix was attained before casting into 50 mm cubes mould. the control mortar a sample, on the other hand was mixed as described above. then the samples were left covered with jute bags and cured by water sprinkling until 3 days before de-moulding and water curing by immersion until testing age. the step taken in achieving the determination of degree of hydration highlighted below adopted similar procedures reported in (olawuyi, 2016). the mortar cubes were cast and crushed at different curing ages (3, 7, 14 and 28 days) immediately after de-moulding. the crushed sample of the mortar cubes was then milled properly by iron mortar and pestle and kept in an air tight polythene bag to stop further hydration. a known weight of the vacuum dried sample about 20g from the particle passing 75µm standard sieve. 20g of the vacuum dried sample was oven dried for 24hours at 105°c and then weighed to determine the mass of the evaporated water. this sample was then placed in the furnace set to 900°c at one hour time after the furnace temperature reads 900°c, the furnace was switched off and allowed to cool and the sample weighed. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):329-341. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 335 all calculations were then based on ignited weight basis to give the following equation. hence, the percentage of non – evaporable water (wn%) is calculated by using the following formula: wn% = 100 x (dried weight of paste − ignited weight of paste) (ignited weigth of paste − loss on ignition of cement) (1) the degree of hydration (α) is then: α = 100 x wn 0.23 (2) 2.6: compressive strength the test was done with the digital universal testing machine (dutm). the strength is the most important factor which determines the overall quality of masonry unit. the strength test was carried out on three specimens for each of the mortar mix corresponding to 3, 7, 14, 28, 56 and 90days for compressive strength test which is in line with the procedure of astm c39/39m, (2012). 3.0: results and discussion 3.1: particle size distribution of fine aggregate. table 3.1: particle size distribution of fine aggregate sieve opening (mm) cen reference sand (%) simulated reference sand (%) 2.00 0 0 1.60 7 ± 5 0 1.00 33 ± 5 3 0.50 67 ± 5 16 0.16 87 ± 5 92 0.08 99 ± 1 99 table 3.1 however presents psd of the cen reference sand for determination of strength of cement as compared to the simulated reference sand used. it was observed that the simulated reference sand was in-line with three (3) of the six (6) range requirements of the cen reference sand as prescribed in bs en 196-1 (2016). the strength of the mortar samples from pc used in this study serves purely as a reference to which the strength of the alternative agro-industrial waste binder was compared. table 3.2: bulk density of constituent materials (kg/m3) material bulk density(kg/m3) pc 3150 sha 3320 ccw 2290 sand 2580 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan, et al: properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder. azojete, 15(2):329-341. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 336 table 3.2 presents the bulk density for materials and the valves obtained corresponded to what was reported by (neville, 2011) on bulk density of pc for mortar production. table 3.3: fineness of the binders binder pc sha ccw wt. of binder before sieving (g) 250 250 250 wt .of binder residue after sieving (g) 10 12 14 fineness (%) 4 4.8 5.6 table 3.3 present the average result on fineness of the binder. the table reveals that the fineness of the binder used in this study are 4, 4.8 and 5.6% for pc, sha and ccw respectively of the percentage retained. the fineness value of the binders conforms to astm c786 (2016) of 10% maximum of the retained. table 3.4: result of xrf analysis for oxides composition of cementitious material sa m pl es lo i sio 2 al 2o 3 fe 2o 3 ca o m go so 3 na 2o k 2 o tio 2 p 2 o 5 m no 3 cr 2o 3 ar sr sio 2 +a l 2o 3 + fe 2o 3 sha 5.6 83.0 2.9 2.7 1.3 0.8 0.0 0.2 2.8 0.2 0.5 0.0 0.0 1.1 14.7 88.6 ccw 26.4 3.6 1.6 1.3 65.8 0.2 0.0 0.1 1.0 1.0 0.1 0.0 0.0 1.2 1.2 6.5 pc 0.0 21.5 5.2 1.2 64.0 2.9 4.5 0.6 0.0 0.1 0.2 0.0 0.0 4.5 3.4 27.8 table 3.4 shows the oxides composition of the various cementitious materials obtained through xrf conducted at larfarge cement in ewekoro. the sha sample is major in silica and sio2 of 83%. the table indicated the agro waste as class n pozzolan with total sio2 +al2o3+ fe2o3 above 70%, so3 below 4% and loss on ignition (loi) of less than 10%. the ccw was detected to contain 66% cao, a similar value to the cao content (64%) of the pc sample. the ccw was however noted to be of lower in sio2 and al2o3 when compared to the pc sample. 3.3 the fresh properties of self compacting mortar. hassan,(2015) procedure was adopted in an attempt to establish an optimum paste and mortar volume that will satisfy certain flow time in which the method considered a fixed water binding ratio of 0.4 and superplasticiser dosages ranging from 1.5%, 1.75%, 2.00%, 2.25%, 2.50%, 2.75%, 3.00%, 3.25%,3.50% and 3.75%. the result of filling ability of paste, flow ability of mortar and filling ability of mortar made from varied combinations of sha/ccw (70:30) was gotten from the tables below. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):329-341. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 337 table 3.5: flow cone test for paste (70:30) pn sha % ccw % w/b ratio sha (kg) ccw (kg) h2o hrwr ft (sec) 70/30 a 70 30 0.40 282.14 121.18 161.56 1.50 15:30 70/30 b 70 30 0.40 282.14 121.18 161.56 1.75 13:34 70/30 c 70 30 0.40 282.14 121.18 161.56 2.00 11:26 70/30 d 70 30 0.40 282.14 121.18 161.56 2.25 8:40 70/30 e 70 30 0.40 282.14 121.18 161.56 2.50 7:13 70/30 f 70 30 0.40 282.14 121.18 161.56 2.75 6:01 70/30 g 70 30 0.40 282.14 121.18 161.56 3.00 4:03 70/30 h 70 30 0.40 282.14 121.18 161.56 3.25 2:22 70/30 i 70 30 0.40 282.14 121.18 161.56 3.50 1:08 70/30 j 70 30 0.40 282.14 121.18 161.56 3.75 1:06 result of the flowing ability of binder paste which involves determining the time of flow of the proportion of binder (70:30%) sha : ccw paste at an incremental dosage of hrwr from 1.5 to 3.75% by weight of binder. ten (10) batches of pastes were tested for flowing ability. table 3.5 show the filling ability of series of binder pastes with respect to the flow time at various dosage of hrwr. as can be seen, the filling ability increases as the flow time of the paste decrease. also the decrease in the flow time is as a result of increase in the dosage of hrwr. it is particularly due to the reduction in the plastic viscosity of the binder paste. this occurs because of the liquefying ability of the hrwr. lastly it was observed that at greater than 3.25% the flow time of the binder paste becomes relatively close, this shows that if the hrwr dosage increase beyond 3.5% saturation dosage or point is attained, any addition of hrwr dosage will not have noticeable effect on the flow time of the respective binder paste. table 3.6: mini v – funnel reading for mortar (70/30) pn sha % ccw % wb ratio fa (kg) sha (kg) ccw (kg) h2o % hrwr % ft (sec) 70/30 a 70 30 0.40 826.2 282.14 121.18 161.56 1.50 10:42 70/30 b 70 30 0.40 826.2 282.14 121.18 161.56 1.75 9:22 70/30 c 70 30 0.40 826.2 282.14 121.18 161.56 2.00 8:36 70/30 d 70 30 0.40 826.2 282.14 121.18 161.56 2.25 5:32 70/30 e 70 30 0.40 826.2 282.14 121.18 161.56 2.50 4:52 70/30 f 70 30 0.40 826.2 282.14 121.18 161.56 2.75 3:01 70/30 g 70 30 0.40 826.2 282.14 121.18 161.56 3.00 2:19 70/30 h 70 30 0.40 826.2 282.14 121.18 161.56 3.25 0:47 70/30 i 70 30 0.40 826.2 282.14 121.18 161.56 3.50 0:37 70/30 j 70 30 0.40 826.2 282.14 121.18 161.56 3.75 0:35 result of the flowing ability of mortar which involves determining the time of flow of the proportion of binder (70:30%) sha : ccw mortar at an incremental dosage of hrwr from 1.5 to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan, et al: properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder. azojete, 15(2):329-341. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 338 3.75% by weight of binder. ten (10) batches of mortar were tested for flowing ability. table 3.6 shows the flowing ability of series of mortar with respect to the flow time at various dosage of hrwr. as can be seen, flowing ability increases as the flow time of the mortar decreases. also the decrease in the flow time is as a result of increase in the dosage of hrwr. it is particularly due to the reduction in the plastic viscosity of the binder paste. this occurs because of the liquefying ability of the hrwr. lastly it was observed that at greater than 3.25% the flow time of the binder paste becomes relatively close, this shows that if the hrwr dosage increase beyond 3.5% saturation dosage or point is attained, any addition of hrwr dosage will not have noticeable effect on the flow time of the respective mortar. table 3.7: flowing ability of mortar-flow mould test mortar nomenclature fine aggregate (kg). water(kg) saturation dosage (%) w/b ratio flow spread (mm) pc (control) 826.2 161.06 3.5 0.40 295 sha/ccw(70/30) 826.2 161.06 3.5 0.40 290 sha/ccw(60/40) 826.2 161.06 3.5 0.40 285 sha/ccw(50/50) 826.2 161.06 3.5 0.40 280 sha/ccw(40/60) 826.2 161.06 3.5 0.40 275 sha/ccw(30/70) 826.2 161.06 3.5 0.40 265. the result of flow mould test presented in table 3.7 shows the flow spread characteristic exhibited by different group of mortar formulated as shown in table 3.7. the flowing ability was discussed in terms of how mortar spread, and from the results obtained the spread varied between 265-295 mm for the different mortar which was in accord with 260 mm specified by efnarc (2002). thus the saturation dosage of the corresponding mixtures was found to be sufficient. therefore the importance of the flow spread results of mortar has shown that the flow pattern of mortar is greatly affected by hrwr dosage and powder content of the binder. the end means of this research helps in sufficient proportioning of high range water reducer (hrwr) for production of scm. figure 3.1: degree of hydration of hardened sha/ccw mortar http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):329-341. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 339 3.4 degree of hydration the degree of hydration presented in figure 3.1 shows the trend of hydration rate of binder combination with their respective ages. the graph shows that 70/30 of sha/ccw has the highest degree of hydration value of 52.7% as compared to pc at 28 days curing ages. also the hydration process proofed to improve as the curing ages advanced likewise the binders are expected to show good long term age strength development. figure 3.2: average compressive strength of scm the compressive strength test presented in figure 3.2 was determined over a period of 90 days. a rise in compressive strength was observed until the end of the 90 days for all scm and this is as a result of enhancement in the hydration process. the compressive strength at the first 28 days was in the range of 5.29-6.52 n/mm2 and at age of 90 days it ranges from 7.34-14.08 n/mm2. sha/ccw (70/30) by proportion shows a higher compressive strength (14.08 n/mm2) comparing with the work of egwuda (2018). the compressive strength value was 7.56n/mm2 for 28 days which is about 36% of pc strength and for 90 days (8.03n/mm2) about 37% of pc strength. more so, a direct proportional relationship between the curing ages and the strength because there is slow hydration process due to the presence of sha and ccw which is triggered the pozzolanic reaction at later ages. also it was observed that the samples bind effectively with the fine aggregates after de-moulding at the third day after casting and the mortar made from agro based binders did not dissolve all through the curing ages (by total immersion in water). 4.0 conclusion the chemical analysis shows sha as class n pozzolans with total sio2 +al2o3+ fe2o3 above 70% according to astm c618-05 (2017) while ccw was observed to contain 66% calcium oxide a similar value to the calcium oxide content (64%) of the pc sample. the fineness of the constituent’s materials conforms to bs en 1097-6 (2013). the highest compressive strength of scm made with sha/ccw was gotten at 90 days of sha/ccw (70/30) proportion with the value of 14.08 n/mm2 which is in line with type n of astm c270 mortar. the optimum saturation dosage of 3.5% was obtained from flow cone test for paste and mini-v-funnel test for mortar. the sha/ccw (70/30) shows the highest mortar flow rate of 290mm compared to the control (pc) 295mm. the alternative binder from agro waste (sha) in combination with industrial waste (ccw) has a good binding property. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hassan, et al: properties of self-compacting mortar made with sorghum husk ash and calcium carbide waste as binder. azojete, 15(2):329-341. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owbolaji@yahoo.com 340 references akram, t., memon, sa. and obaid, h. 2009. production of low-cost concrete using bagasse ash. construction and building materials, 23: 703-712. astmc128. 2015. standard test method for relating density (specific gravity) and absorption of fine aggregate. annual book of astm standard, 04(02), 9. philadephia, usa: american society for testing and materials. astmc231/c231m. 2010. standard test method for air content of freshly mixed concrete by the pressure method, annual book of astm standards, 04(02),10. philadelphia, usa: american society for testing and materials. astmc494/c494m. 2013. standard specification for chemical admixtures for concrete, annual book of astm standards, 04(02), 10. philadelphia, usa: american society for testing and materials. astmc618 2017. standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete astm international, west conshohocken, pa, 2017. astmc786/c786m-10. 2016. standard test method for fineness of hydraulic cement and raw materials astm international, west conshohocken, pa, 2016. astmc39/c39m 2012.standard test method for compressive strength of cylindrical concrete specimens, annual book of astm standards, 04(02) 7. philadelphia, usa: american society for testing and materials. astmc939. 2010. standard test method for flow of grout for preplaced-aggregate concrete (flow cone method), annual book of astm standards, 04(02) 3. philadelphia, usa: american society for testing and materials. british standard institution, 2013. tests for mechanical and physical properties of aggregates. determination of particle density and water absorption, bs en 1097-6, london, british standard institution (bsi). british standard institution, 2016. method of testing cement. part 1: determination of strength (bs en 196-1:2016), london, british standard institution. british standard institution, 2009. admixtures for concrete, mortar and grout. concrete admixtures: definitions, requirements, conformity, marking and labelling, (bs en 9342:2009) london, british standard institution. chukwudebelu, ja., ige, cc., taiwo, oe. and tojola, ob. 2013. recovery of pure slake lime from carbide sludge: case study of lagos state, nigeria, african journal of environmental science and technology, 7(6): 490-495. egwuda, ci. 2018. development of alternative binder for mortar using sorghum husk ash and calcium carbide waste. unpublished mtech thesis, federal university of technology, minna. efnarc. 2002. specification and guidelines for self compacting concrete. surrey, uk. hassan, io. 2015. self-consolidating high performance palm oil fuel ash and pulverized burnt clay blended concrete. phd thesis, universiti teknologi, malaysia, pp. 389. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; 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a comparison between geopolymer and opc cement concrete. construction and building materials, 43:125-130. united states national climate assessment. 2014. climate change impacts in the united states. a publication of us global research program, accessed online on 6th february, 2017. http://nca2014.globalchange.gov/downloads. http://blogs.ei.columbia.edu/2012/05/09/emissions-from-the-cement-industry http://nca2014.globalchange.gov/downloads file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 678-691 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 678 original research article seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria f. o. nwosu1*, o. d. olayinka1 and c. o. akoshile2 (1department of industrial chemistry, university of ilorin, p.m.b 1515 ilorin, nigeria 2department of physics, university of ilorin, p.m.b. 1515 ilorin, nigeria) * corresponding author’s email address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: insoluble dust soluble dust ash volatile matter wet season dry season abstract the enormous vehicular activities on the commercial motor parks of university of ilorin, nigeria called for concern as a result of noticeable level of particulate matter in the atmosphere of the area. this study was carried out to indicate the seasonal variation in the rate of dust fall at three motor parks in the permanent site of the university campus by using the single bucket sampling method. the study was carried out for five months each of wet and dry season periods. the sampling sites were first motor park (pk1), new motor park (pk2) and clinic area (cl). gravimetric method was used to quantify the soluble, insoluble, volatile matter and ash content of the dust. volatile matter and ash were the component of insoluble dust and the highest rate of insoluble dust deposition was observed in january (2043.12 ± 41.4 and 284.1 ± 35.5 mg/m2/day) for pk2 and cl and in november (1282.7 ± 64.9 mg/m2/day) for pk1 when their respective traffic density (1509.5 ±72.1, 29.8 ± 1.2 and 1000.8 ± 48.3 vehicles per hour) was highest. the highest (32713.0 ± 1290.1 mg/m2/day) and lowest (70.6 ± 6.9 mg/m2/day) rate of soluble dust deposition in the study were observed at pk1 for september and february respectively which was suspected to be due to increase and decrease in the amount of rain fall. the pearson correlation showed that increases in traffic density were correlated with increases in the rate of insoluble dust fall at various sites and the relationship was in the stronger order of pk2 > pk1 > cl. the motor parks ambient air was highly contaminated with soluble dust in the wet season and insoluble dust in the dry season their being values are more than the recommended 133 mg/m2/day. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction air pollutants can either be particles, liquids or gaseous in nature. pollutants may come from natural sources or caused by human activities (anthropogenic) such as use of motor vehicles, domestic activities, industry and other economic activities (jimoda, 2012). particulate matter is used to describe contaminant particles like dust found in the air (yahi et al., 2014; nwosu et al., 2016). there could be environmental degradation and hazard on the health status of human and animal due to presence of particulate matter in the air (kamble, 2015). particulate matter in the form of dust is usually in the size range from about 1 to 10μm in diameter, and they settle slowly mailto:f.o.nwosu@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 679 under the influence of gravity (espinosa et al., 2001). the ones greater than 10μm that settle to surfaces from the air are the main component of dust fall (sami et al., 2006; alahmr et al., 2012) and are too heavy to remain suspended in the air for any period of time. the potential environmental impacts of dust fall were described by piechota et al. (2002) to include surface and groundwater quality deterioration, soil contamination, toxicity to soil and water its toxicity to humans, air pollution and changes in hydrologic characteristics of the soils cannot be over emphasized. a number of medical conditions can be traced to the impact of dust, and the effects of fine wind-borne particles on human health (garrison et al., 2003, polizzi et al., 2007, alahmr et al., 2012). the most health-damaging dust particles are those lesser in size with a diameter less than 10 microns (10µ ≤ pm). humans mostly at risk are elderly and children with symptoms of asthma, heart or cardiovascular disease as stated by kamble (2015). the presence of dust in the ambient air is very noticeable in the areas where there are more vehicular activities and the composition varies in complex mixture of soluble and insoluble forms of organic and inorganic substances suspended in the air (polizzi et al., 2007). the enormous vehicular activities on the commercial motor parks of university of ilorin, nigeria called for concern as a result of noticeable level of particulate matter in the atmosphere of the area due to continuous increase of students and other users of the parks. therefore, the objective of this study is to assess the seasonal variations and traffic effect on the rate of soluble, insoluble, volatile matter, ash and total dust fall at three different parks in the permanent site of the university of ilorn. 2. materials and method 2.1 study area the dust samples were collected at three different motor parks within the permanent site of university of ilorin, kwara state, nigeria. there were two parking locations for commercial vehicles within the campus of the permanent site of university of ilorin between 2016 and 2017 during the period of this study. the first motor park is located behind lagos boys’ hostels of the school, another park; the new park is by the sky chicken restaurant in the permanent site of the university campus. the clinic area of the university is about 150 m away from the location of the new park and is a parking lot for the clinic staff and their visitors. figure 1 shows the sampling point locations. it should be noted that none of the parks was paved during the period of the study. figure 1: google map of university of ilorin (permanent site) showing the park locations the nomenclature of sampling points and description of geographical coordinates are given in table 1. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwosu and olayinka: seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 680 table 1: description of sampling points and their geographical location. sampling points location point coordinates pk1 first motor park 8°47’94.2’’n 4°67’06.9’’e pk2 new motor park 8°48’13.8’’n 4°66’84.0’’e cl clinic area 8°48’27.5’’n 4°66’90.3’’e 2.2 material preparation all the sampling buckets were usually washed thoroughly with soap and water, followed by dilute nitric acid and then deionised water before drying properly. also, all the sampling apparatus were cleansed by subjecting them to acid wash and then rinse with distilled water before use. analytical grade stock solutions were used for the preparation of samples and standards. 2.3 sampling method the dust fall (bulk type) was sampled using the method of open bucket system according to is 5182 (2006) and astm (2010) standard procedures. this involved the use of a cylindrical sampling bucket with height (h), radius (r) and surface area (a) of 0.342 m, 0.138 m and 0.05983 m2 respectively as employed by. annegarn and scorgie, (2002); moja and mnisi, (2013); kamble, (2015) and nwosu et al., (2016) in their various studies. the 20 l bucket was filled with a known 5 l of distilled water, opened and exposed on a rigid stand to trap the dust fall sample. the rigid stand of 2 m long comprised of a ring supported by four stabilizing bars above the base plate to prevent the sample from contamination by perching birds. the openings of the buckets were covered with insect net so as to only collect dust of smaller size which is most hazardous to health. although there was rapid evaporation due to exposure of sampling bucket, the 5 l distilled water in the bucket was sufficient to remain and trap dust sample during each sampling period. also, it usually do not overflow due to rainfall during sampling period. figure 2 shows one of the rigid stands with bucket used for the sampling. the stands were buried into the earth to a depth of about 0.5 m according to some criteria laid by astm d 5111 standards (astm, 1996) such as locating the sampler towards the predominant wind direction and considering the distance from obstacles that could interfere in sampling. the sampling buckets were exposed at the various sites for a month and the sampling buckets were replaced with new ones of the same dimensions following the same process. the study was carried out for a total of ten months to include five months of rainy season period (september and october, 2016; april to june, 2017) and five months of dry season period (november and december 2016, january to march, 2017). figure 2: one of the sampling stands at the first park http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 681 2.4 traffic density the estimation of the traffic density was conducted by counting the number of vehicles that went in and out of the park during the periods of heavy traffic, usually about 3h in the morning and 3h in the afternoon. the average of morning and afternoon counts was the traffic count for a day. two different daily counts were obtained during the sampling period of each month throughout the study. the average of the daily counts was used to determine the traffic density for each month (number of vehicles per hour) according to adekola and oloruntoba (2000). 2.5 determination of insoluble particle fall out rate a dried pre-weighed ashless filter paper number 42 was placed in the filter unit according to is 5182 (part 1) (2006). the bucket content was then carefully poured through the filtration set up to obtain a filtrate and residue. the residue, an insoluble component of the dust fall, was weighed after drying in an oven at 105°c for 2 hrs. the rate of insoluble dust fall was estimated in duplicate following the method stated by is 5182 (part 1) (2006) and norela et al. (2009) based on number of days and the surface area of the bucket, calculated as in equation (1): where: cidf = concentration of insoluble dust fall (mg/m2/day), mf = weight of loaded filter (mg), mb = weight of blank filter (mg), a = surface area of the bucket (m2), t = sample duration (days). 2.6 determination of total soluble particle fall out rate a known volume of filtrate (soluble matter) obtained from 2.3 was concentrated in a preweighed evaporating dish and dried in an oven at 105°c for 2h as stated by latif and rozali (1999). it was cooled in a desiccator before being weighed. the rate of soluble dust fall was calculated as given in the equation (2): css (mg/m2 )/day = �� −�� �� �2 at ………….(2) where: css = concentration of soluble solids, m3 = weight of evaporating dish without the soluble matter (mg), m4 = weight of soluble matter with the weight of the evaporating dish (mg), v1 = volume of filtrate (all the water in the sampling bucket) (ml), v2 = volume of filtrate used for analysis (30 ml), a = bucket surface area (m2), t = sampling period (days). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwosu and olayinka: seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 682 2.7 determination of total dust particle fall out rate total dust particle was computed in duplicate by the addition of concentration of the insoluble and soluble dust fall together according to the aqmm (2016) and is 5182 (part 1) (2006) as shown in equation (3): tdf (mg/m2/day) = cidf +css ………… (3) where: tdf = total dust fall rate (mg/m2/day), cidf = concentration of insoluble dust fall (mg/m2/day), css = concentration of soluble solids (mg/m2/day). 2.8 determination of ash particle fall out rate a known mass of the homogenised dried insoluble matter from 2.3 above was collected into an ashless filter paper. this was then put in a pre-weighed porcelain crucible. the porcelain crucible was placed in a muffle furnace and fired at 550 ºc for 4 h. the sample was cooled to constant weight. the amount of ash was determined in duplicate using the equation (4) due to norela et al. (2009): ashrate mg/m2/day = (mfa − mco) at ………….(�) where: mfa = weight of porcelain crucible with ash after incineration (mg), mco = weight of porcelain crucible only (mg), a= surface area of the sampling bucket (m2), t= sampling period (days). 2.9 determination of volatile particle fall out rate this was estimated in duplicate using equation (5) due to al-harbi (2015) and kamble (2015). vm (mg/m2/day) = cidf – ash rate …………….(5) where: vm =volatile matter, cidf = rate of insoluble pm in mg/m2/day 2.10 meteorological data meteorology data of rain fall, wind speed, humidity and temperature were obtained from the atmospheric research laboratory, physics department, university of ilorin, ilorin, nigeria. this department have the appropriate instruments that measured the various meterological factors. 3.0 results and discussion 3.1 traffic density table 2 shows the average rate of various dust depositions with traffic density at the three sites. the highest traffic density at pk1 was 1000.8 ± 48.3 vehicles per hour in november while the least traffic density at pk1 was 3.0 ± 0.5 vehicles per hour in april. the highest traffic density at pk2 was in january (1509.5 ± 72.1 vehicles per hour) while the least (43 ± 3.3 vehicles per hour) was in september. the traffic density at cl was highest (29.8 ± 1.2 vehicles per hour) in january while lowest (16.5 ± 0.7) in september. the least value of traffic density in this study was observed in april (3 ± 0.5 vehicles per hour) at pk1 during the period of inter-semester break http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 683 and when it was not really active as motor park. though, the school resumed in october, it seemed most students and staff resumed fully to school or more visitors entered into the school campus in january. this accounted for the highest traffic density in this study to be in january (1509.5 ± 72.1 vehicles per hour) at pk2. also pk2 was the most active park during this january period. nwosu et al. (2016) reported a similar observation on a motor park in the same university. table 2: average and standard deviation of soluble, insoluble, ash, volatile and total dust fall in mg/m2/day with traffic density (number of vehicles per hour) (n = 2). month sample insoluble soluble ash volatile matter total dust fall traffic density sep pk1 340.8 ± 3 32713.03 ± 1290 94.4 ± 1.4 246.1 ± 4.3 33053.5 ± 1287 305 ± 22.6 pk2 208.9 ± 0 27579.6 ± 732 82.7 ± 1.2 126.2 ± 1.2 27788.5 ± 732 43 ± 3.3 cl 154.6 ± 5.9 19706.2 ± 442 116.3 ± 3.9 38.3 ± 2.0 19860.8 ± 448 16.5 ± 0.7 oct pk1 355.1 ± 5.9 18094.8± 928 124.4 ± 14.6 230 ± 8.7 18094.8 ± 928 387.8± 22.4 pk2 305.4 ± 6.5 17012.1 ± 666 136.1 ± 17.03 169 ± 23.5 17317.5 ± 672 51.2 ±2.1 cl 213.1 ± 5.9 13780.4 ± 826 170.1 ± 15.5 43 ± 9.6 13993.5 ± 8 18.3 ±0.9 nov pk1 1282.7 ± 64.9 4671.5 ± 454 690.1± 16.8 592.6 ± 48.1 5954.2 ± 389 1000.8 ± 48.3 pk2 630.9 ± 17.7 1848.5 ± 102 503.7 ± 66.4 127.2 ± 48.7 2479.4 ± 120 58.5 ±3.1 cl 238.6 ± 29.5 1314.4 ± 199 179.4 ± 29.4 58.8 ± 0.3 1552.5 ± 228 25.7 ± 1.9 dec pk1 129.5 ± 5.9 2372.3 ± 466 40.9 ± 4.6 88.7 ± 1.3 2501.8 ± 460 3.5 ± 0.7 pk2 2013.9 ± 118.2 891.1 ± 31.2 431.02 ± 27.2 1582.8 ± 91 2905 ± 87 1428.7 ± 388 cl 309.2 ± 11.8 727.7 ± 26.6 227.7 ± 16.3 81.5 ± 4.5 1036.84 ± 14.8 25.8 ± 2.6 jan pk1 259.0 ± 11.8 825.9 ± 33.2 213.5 ± 11.7 45.5 ± 0.1 1085 ± 21.4 5.3 ± 0.9 pk2 2043.1 ± 41.1 1247.3 ± 39.5 1865.8 ± 30.4 177.3 ± 11 3290.4 ±1.9 1509.5 ±72.1 cl 284.1 ± 35.5 983.5 ± 12.1 266.2 ± 34.5 17.9 ± 0.9 1267.6 ± 47.6 29.8 ± 1.2 feb pk1 254.9 ±29.5 70.6 ± 6.9 179.8 ±21.1 75.0 ± 8.5 325.5 ± 22.7 4.3 ± 0.9 pk2 1654.6 ±23.6 134.9 ±15.6 363.3 ±10.3 1291.2 ± 13.4 1789.1 ± 8 1506 ±144.2 cl 267.4 ±11.8 281.5 ± 25.7 192.3 ± 9.9 75.1 ± 1.9 548.9 ± 13.8 29.7 ± 2.8 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwosu and olayinka: seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 684 mar pk1 208.9 ± 11.8 297.5 ± 41.4 88.6 ± 2.4 120.3 ± 14.2 506.4 ± 29.5 3.8 ± 0.2 pk2 1261.8 ± 11.8 500.6 ± 15.3 554.6 ± 1 707.2 ± 10.8 1762.4 ± 3.5 930 ± 59.4 cl 263.2 ± 5.9 446.4 ± 10.8 115.8 ± 0.12 147.4 ± 5.79 709.6 ± 4.92 21.8 ± 1.2 apr pk1 254.9 ± 5.9 502.6 ± 1.4 76.4 ± 4.8 178.5 ± 10.7 757.5 ± 4.6 3 ± 0.5 pk2 292.5 ± 11.8 886.0 ± 64.6 104.7 ± 1.5 187.8 ± 13.3 1178.5 ± 52.8 528 ± 169.7 cl 288.3 ± 5.9 690.4 ± 9.7 170.1 ± 0.6 118.2 ± 6.5 978.7 ± 3.8 17 ± 1.9 may pk1 167.1 ± 11.8 4129.4 ±382 60.5 ± 8.2 106.6 ± 3.6 4296.5 ± 370.2 3.7 ± 0.9 pk2 259.0 ± 11.7 2541.6 ±10.0 239.7 ± 16.4 19.3 ± 4.6 2800.6 ± 21.9 1164 ± 67.9 cl 228.1 ± 3.6 2219.2 ±208 189.3 ± 0.3 38.8 ± 3.8 2447.3± 211.9 26.3 ± 0.9 jun pk1 271.6 ± 17.7 3416.3 ± 364 68.0 ± 8.9 203.5 ± 8.9 3687.8 ± 381 992 ± 18.4 pk2 196.4 ± 17.7 3326.1 ± 174 37.4 ± 0.9 158.9 ± 16.9 3522.5 ± 156.7 1057.5 ± 31.8 cl 346.8 ± 17.7 3813.5 ± 299 154.8 ± 21.3 191.9 ± 3.6 4160.3 ± 281 24.5 ± 0.7 (±) standard deviation 3.2 insoluble, soluble dust and traffic density the lowest insoluble dust was observed at pk1 in the month of december (129.5 ± 5.9 mg/m2/day) which could be due to low traffic density (3.5 ± 0.7 vehicles per hour) observed at this park during the month as shown in table 2. the highest (2043.12 ± 41.4 mg/m2/day) insoluble dust was observed at pk2 for the month of january which may be attributed to the highest traffic density (1509.5 ±72.1 vehicles per hour) observed at the park in that month. the highest insoluble dust was observed in january (2043.12 ± 41.4 and 284.1 ± 35.5 mg/m2/day) for pk2 and cl respectively; pk1 in november (1282.7 ± 64.9 mg/m2/day) when their respective traffic density (1509.5 ±72.1, 29.8 ± 1.2 and 1000.8 ± 48.3 vehicles per hour) was highest. the same observation was reported by khan et al., (2002), khan et al. (2013), norela et al. (2009), malokootia et al. (2013), tyagi et al., (2014) and nwosu et al., (2016) in their separate studies. that is, the rate of insoluble dust deposition increased as the traffic density increased. this means that movement of vehicles and passengers are key factors in the generation of insoluble dust. the soluble dust had no regular pattern of relationship with the traffic density. thus, some other factors may be responsible for its deposition. 3.3 ash matter, volatile matter and traffic density generally, the highest (1865.8 ± 30.4 mg/m2/day) ash matter was observed at pk2 for january and the lowest (40.9 ± 4.6 mg/m2/day) was obtained at pk1 for december as given in table 2. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 685 the traffic density was highest (1509.5 ±72.1 vehicles per hour) at pk2 in the month of january. also, pk1 which had the lowest ash in december had a very low traffic density (3.5 ± 0.7 1 vehicles per hour). thus, it seemed that the major cause of the ash component is dependent on the traffic activities. during the period of this study, the highest (1582.8 ± 91 mg/m2/day) volatile matter was observed at pk2 for december which was not the month of its highest traffic density. volatile matter was lowest (17.9 ± 0.9 mg/m2/day) for january at cl when it had its highest traffic density as 29.8 ± 1.2 vehicles per hour. this seemed that volatile matter did not necessarily depend on the traffic density. that is, vehicular activities were likely not the major cause of volatile matter but probably the combustion of oil, refuse and tiny decaying leaves shed from the trees around the areas of study (kamble, 2015). 3.4 dust fall at various sampling points as can be seen from table 2, the soluble dust generally decreased monthly from september to february and increased from march to may at all the sampling points such that the highest (32713.0 ± 1290.1 mg/m2/day) and lowest (70.6 ± 6.9mg/m2/day) soluble dust in the study were observed at pk1 for september and february respectively. the decrease in the soluble dust must be due to decrease in the amount of rain fall from september to february while the increase must be due to increase in rain fall and precipitation from march to may. this was in line with the findings of norela et al. (2009) and kamble (2015) who said that the soluble dust was always more than the insoluble dust in the wet season. therefore, the major cause of the soluble dust may be components of aerosols which are usually washed down from the atmosphere in larger quantity by rain during wet seasons. on the other hand, the insoluble dust increased from september to january and decreased from february to may for pk2 and cl. at pk1, the insoluble dust increased from september to november before the park became inactive in december. the increase in the insoluble dust was likely due to decrease in the amount of rain fall from september to january. al-harb (2015) reported that insoluble dust increases as the rain fall decreases. this is because when there is no heavy rain fall to wet the ground and wash away the top soil, the traffic activities would be able to lift more dust into the atmosphere. 3.5 seasonal comparison of the three sampling points and other studies the average rate of parameters of each season was obtained by taking the average of monthly concentrations for each season. table 3 presents seasonal comparison of average insoluble, soluble, volatile, ash and total dust fall. 3.5.1 wet season the results in table 3 for wet season shows that rate of soluble dust was highest (11771.2mg/m2/day) at pk1 followed by pk2 (10269.1mg/m2/day) and then cl (8041.9mg/m2/day). there was probably high amount of soluble particles in the suspended particulate that was washed down by rain fall at pk1 than pk2 and cl. the observed amount for the rate of soluble dust in the present study at all the sampling sites during the wet season period was higher than observed by norela et al. (2009) (216.11 mg/m2/day) and alahmr et al. (2012) (78.41 mg/m2/day). this may be because the study of norela was at a residential area and that of alahmr et al. (2012) was at a semi-urban area both of which have less amount of soluble aerosol or suspended particulate matter washed down by the rain fall or the rain falls were not heavy enough to wash down the suspended matter. the insoluble dust at all sampling points were very close in the wet season with pk1 having the highest (277.9mg/m2/day), followed by file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwosu and olayinka: seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 686 pk2 (252.4 mg/m2/day) and then cl (246.2 mg/m2/day). the insoluble dust at all the sampling points in this present study during the period of wet season were more than that of norela et al. (2009) (37.83 mg/m2/day) and alahmr et al. (2012) (53.08 mg/m2/day). this may be attributed to the two studies conducted in areas of less traffic densities and low generation of dust. table 3: seasonal comparison of average insoluble, soluble, ash, volatile and total dust fall (mg/m2/day) in this study and previous studies (*) not available the total dust fall at pk1 was highest (12049.1 mg/m2/day) followed by pk2 (10521.5 mg/m2/day) and then cl (8288.1 mg/m2/day) according to table 3. that means the rate of dust deposition at pk1 was higher than pk2 and cl in the wet season period. the observed amounts of total dust study research site area season traffic density soluble insoluble volatile matter ash total dust fall doe, 2005 this study,pk1 motor park wet season 338.3 hr-1 11771.2 277.9 193.1 84.7 12049.1 133 dry season 203.5 hr-1 1647.6 427 184.4 242.6 2074.6 this study,pk2 motor park wet season 568.7 hr-1 10269.1 252.4 132.3 144.4 10521.5 hot season 1086.5 hr-1 924.5 1520.8 543.2 974 2445.3 this study,cl motor park wet season 20.5 hr-1 8041.9 246.2 85.3 167.6 8288.1 dry season 26.6 hr-1 750.7 272.4 76.1 196.3 1023.1 nwosu et al., (2016) unilorin motor park dry season 300 day-1 * 1122.2 * * * kwasu motor park dry season 103.2 day-1 * 627.7 * * * unibadan motor park dry season 273.4 day-1 * 316.3 * * * alahmret al., (2012) semiurban area (kajang and bangi, malaysia) wet season * 78.41 53.08 * * 131.50 norela et al., (2009) residential area (negeri malaysia) wet season * 216.11 37.83 * 106.96 253.95 al-harbi, 2015 urban area, (shuwaikh, kuwait) dry season * * * * 944.23 * http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 687 fall in this study at all the sampling stations were higher than observed by norela et al. (2009) (253.95 mg/m2/day) and alahmr et al. (2012) (131.50 mg/m2/day). this may be because the study of norela was at a residential area and that of alahmr was at a semi-urban area, both of which may have lesser amount of settling dust. the volatile matter component was highest (193.1mg/m2/day) at pk1 followed by pk2 (132.3 mg/m2/day) and then cl (85.2mg/m2/day) in the wet season. volatile was higher than ash in the months of the wet season while low in the months of the dry season for pk1. it was probably because pk1 had been a motor park quite a time before this study. rainfalls could have washed down suspended matter generated as a result of combustion of oil, refuse and tiny decaying leaves shed from the trees around the area. the volatile matter was higher than ash in the months of the wet season for pk1. the ash matter in the wet season as presented in table 6 shows highest value (167.5mg/m2/day) at cl followed by pk2 (144.4 mg/m2/day) and pk1 (84.7mg/m2/day). this high value at cl could mean that the top sandy soil at cl was rich in soil mineral than in pk1 and pk2 areas in the wet season period. the top soil could be blown up by rainy season wind to become settling dust. all the values obtained for ash in this study during wet season period were higher than (106.96mg/m2/day) obtained by norela et al, (2009). 3.5.2 dry season table 3 also presents the results obtained in the dry season period. soluble component was highest (1647.6 mg/m2/day) at pk1 followed by pk2 (924.4mg/m2/day) and then cl (750.7mg/m2/day). the highest value at pk1 could be as a result of deposition of soluble particles lifted from the ground. the insoluble component was highest (1520.8mg/m2/day) at pk2 followed by pk1 (427mg/m2/day) and then cl (272.4mg/m2/day) in the dry season as presented on table 3. this must have resulted from their respective obtained traffic density (1086.5, 203.5, 26.6 vehicles per hour) in the season. the insoluble dust obtained for pk2 in the dry season of this present study was more (1743.3mg/m2/day) than that obtained by nwosu et al. (2016) (1122.2 mg/m2/day) at a motor park in the same university environment. the higher average traffic density (1086.5 vehicles per hour) observed for dry season at pk2 during this present study compared to that of nwosu et al. (2016) (300, 103.2 and 273.4 vehicles per day) in the same dry season must have contributed to the increase in the insoluble dust. total dust fall at pk2 was the highest (2445.3mg/m2/day) followed by pk1 (2074.5mg/m2/day) and then cl (1023.1 mg/m2/day) in the dry season. the high traffic density (1086.5 hr-1) and hauling movement of people on the dry unpaved area of land at pk2 must have greatly contributed to this high value. volatile matter component was highest at pk2 (543.2 mg/m2/day) followed by pk1 (184.4 mg/m2/day) and then cl (76.1mg/m2/day) in the dry season as shown in table 3. the soil around pk2 could contain more of volatile dust than other sites in this study. it might be because it was formerly a grass land before it was recently adopted as a motor park. therefore, it was easier for traffic activities and hauling movement of people to have contributed to lifting of soil reach in organic matter in the area. the ash matter component presented on table 6 was highest (974 mg/m2/day) at pk2 followed by pk1 (242.5mg/m2/day) and cl (196.3mg/m2/day) in the dry season. that is the insoluble dust collected at pk2 during the dry season contains more of ash than cl which has the highest in the rainy season. also, ash component at pk2 in the dry season was more than that obtained (944.23 mg/m2/day) by al-harbi 2015 in an urban area of his study. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwosu and olayinka: seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 688 3.5.3 comparison between dry and wet seasons figures 4-6 show the seasonal comparison of dust fall and components at all sampling sites. it was observed that at all the sampling points in this study; the total dust in the wet season period was more than that in the dry season period which could be attributed to the washing down of more suspended particulate matter in the rainy season than dry season. according to alahmr et al. (2012), wet deposition is the main process which brings down particles from the air. soluble component obtained during the wet season period was found to be more than that of the dry season period. that is, rain fall do contribute to the washing of the atmosphere thereby depositing aerosol and other particulate matter most of which are probably dissolved in water. chate and pranesha (2004) reported that heavy rain could capture aerosol particles and wash it down from the atmosphere. the insoluble matter was lower in the wet season period than in the dry at all the sampling points. glavas et al. (2008) and al-harbi (2015) reported that heavy rain fall causes wetting of the ground and wearing away of the top soil which cause reduction in insoluble matter during wet season. that is, insoluble dust increases from wet season period to the dry season period. figure 4: seasonal comparison of total dust fall and components at pk1 (tdf = total dust fall, sol = soluble dust, ins = insoluble dust, vol = volatile matter and ash) figure 5: seasonal comparison of total dust fall and components at pk2 (tdf = total dust fall, sol = soluble dust, ins = insoluble dust, vol = volatile matter and ash) this is according to the findings of kamble (2015) and ifeanyi et al. (2016) that reported dust fall increases during the dry season because of low humidity conditions which enables easy lifting of dry soil by hauling movement and traffic activities. volatile matter was lower in wet season http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 689 period than in the dry season period at pk2, while the opposite was the case at pk1 and cl. rainfalls could have washed down suspended matter generated as a result of combustion of oil, refuse and tiny decaying leaves shed from the trees around the pk1 and cl. kamble (2015) also observed that increase in volatile matter may be from combustion of oil, coal or refuse. ash matter was also lower in wet season period than in dry season period at all the sampling points. the observation suggested that the surface dust found around all the sampling points may be rich in minerals which have been blown into the container by traffic and wind activities. figure 6: seasonal comparison of total dust fall and components at cl (tdf = total dust fall, sol = soluble dust, ins = insoluble dust, vol = volatile matter and ash) 3.6 influence of meteorological parameters on dust fall level table 4: meteorological data parameter wet period dry period temperature (ºc) 28.02 ± 2.18 31.51 ± 1.67 relative humidity (%) 59.57 ± 11.07 44.02 ± 8.49 rainfall (mm) 0.73 ± 1.02 0 wind speed (km/h) 2.04 ± 0.69 1.76 ± 0.7 table 5: pearson correlation sig (2-tailed) for comparison of dust fall, traffic density and rainfall pearson correlation coefficient (r) sites insoluble/traffic density insoluble/rainfall soluble/traffic density soluble/rainfall pk1 0.687 -0.018 0.178 0.988 pk2 0.707 -0.432 -0.641 0.991 cl 0.557 -0.757 -0.633 0.978 correlation is significant at the 0.05 level the meteorological data supported the discussion so far. there was a lower average temperature (28.02 ºc), higher relative humidity (59.57 %) average higher rainfall (0.73 mm) and an average higher wind speed (2.04 km/h) in wet season than their dry season corresponding value as shown in the table 4. the lower temperature and higher humidity favour the binding of aerosol particles in the atmosphere while the higher rainfall contribute in increasing the washing down of these aerosol particles which are majorly soluble in water in rainy season. although the wind speed was lower in the dry season, the increase in the level of insoluble dust must have been caused by the hauling movement and traffic activities in the studied sites. also, increase in file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nwosu and olayinka: seasonal variation in rates of dust fall at motor parks of university of ilorin, ilorin, nigeria. azojete, 15(3):678-691. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com, fonwosu@unilorin.edu.ng 690 temperature, decrease in relative humidity, and decrease in rainfall activities favour the lifting of soil particles into the collecting containers (mkoma et al. (2010), kamble (2015) and ifeanyi et al. (2016). 3.7 pearson correlation a pearson product-moment correlation coefficient was computed to assess the relationship between the levels of insoluble and soluble dust generated with traffic density and rainfalls at various sites. the closer the coefficient (r) to 1, the stronger the relationship while the closer it is to 0, the weaker the relationship. the results are shown in the table 5. there was a positive correlation for monthly data of insoluble/traffic density at various sites such that increases in traffic density were correlated with increases in the level of insoluble dust at various sites. the relationship was strongest at pk2 (r = 0.707), followed by pk1 (r = 0.687) and the cl (r = 0.557). however, there was a negative correlation for monthly data of insoluble/rainfall at various sites. that is, as either of them increases, the other decreases. the monthly level of soluble dust showed a weak positive correlation (0.178) with traffic density at pk1 while it was negative at pk2 (r = -0.641) and cl (r = -0.633). also, level of soluble dust showed a very strong correlation with amount of rainfall at all sites, pk1 (r = 0.988), pk2 (r = 0.991) and cl (r = 0.978). this also suggests that increases in the amount of rainfall correlated with increases in the level of soluble dust fall. 4.0 conclusion this study had observed that the highest total dust fall and soluble dust fall were obtained in the month of september while that of insoluble dust was in the month of january for pk2 and cl while in november for pk1. also, the rate of soluble dust and total dust deposition decreases from wet season to dry season while that of insoluble dust and ash deposition increases from the wet season to dry season. these variations were observed to be majorly as a result of traffic density and were supported with meteorological data. the observed total dust fall in dry and wet seasons at various sites is more than the recommended 133 mg/m2/day of malaysian department of environment. it was also above the south african permissible limit (600 – 1200 mg/m2/day) for dust in heavy commercial and industrial area (sans 1929, 2005). therefore, the motor parks ambient air was highly contaminated with soluble dust in the wet season and insoluble dust in the dry season. it is therefore advisable for the university community and other appropriate authority that have unpaved motor parks all over the nation to take necessary control measurements such as proper paving or regular wetting of the park. references adekola, fa. and oloruntoba, k.2000. seasonal variation in heavy metals distribution in the roadside soils and vegetation in ilorin city and its environs, nigeria. bioscience research communications, 1(2): 1-8. ahmad, n. 1975. air pollution survey of the peshawar university area. pakistan journal science, 27:149–152. aqmm, 2016. national environmental engineering research institute, 1978. air quality monitoring manual. nagpur, india, pp. 3-21. accessed online (16/07/2017). alahmr, fo., murnira, o., nurul, ba., azhar, a. and mohd, tl. 2012. composition of dust fall around semi-urban areas in malaysia. aerosol and air quality research, 12:629-642. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):678-691. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: f.o.nwosu@gmail.com , fonwosu@unilorin.edu.ng 691 al-harbi, m. 2015. characteristics and composition of the falling dust in urban environment. international journal of environmental science and technology. 12:641-652 annegarn, hj. and scorgie, y.2002. air quality – chemistry and physics of the atmosphere. msc course work notes, university of the witwatersrand. astm, 1996. standard guide for choosing locations and sampling methods to monitor atmospheric deposition at non – urban locations. astm international, west conshohocken. pp.48-64. astm, 2010. standard test method for collection and measurement of dust fall (settleable particulate matter). pp. 1739-98, astm international, west conshohocken. beg, maa., yousufzai, ahk. and mehmood, sn. 1987. air pollution in karachi. pakistan journal of science and resources. 30: 60-66. cattle, sr., mctainsh, gh. and wagner, s. 2002. aeolian dust contribution to soil of the namoi valley, northern nsw, australia. catena, 47: 245-264. chate, dm. and pranesha, ts. 2004. field studies of scavenging of aerosols by rain events. journal of aerosol science, 35:695–706. espinosa, ajf., rodriguez, mt., delaroza, fjb. and sanchez, jcj. 2001. size distribution of metals in urban aerosols in seville (spain). atmospheric environment 35:2595-2601. garrison, vh., shinn, ea., foreman, wt., griffin, dw., holmes, cw., kellogg, ca., majewski, ms.,richardson, ll., ritchie, kb. and smith, gw. 2003. african and asian dust: from desert soils to coral reefs. bioscience, 53: 469-480. glavas, sd., nikolakis, p., ambatzoglou, d. and mihalopoulos, n. 2008. factors affecting the seasonal variation of mass and ionic composition of pm2.5 at a central mediterranean coastal site. atmospheric environment, 42: 5365–5373. ifeanyi, fo., gilbert, ua. and godson, ra. 2016. review of particulate matter and elemental composition of aerosols at selected locations in nigeria from 1985-2015. journal of health and pollution, 6(10):1-18. is 5182. 2006. indian standard, methods for measurement of air pollution. part 1dust fall (first revision), ics 13.040.30. bureau of indian standards, manak bhavan, 9 bahadur shah zafar marg, new delhi. pp. 1-8. iupac, 1990. glossary of atmospheric chemistry terms. international union of pure and applied chemistry, applied chemistry division, commission on atmospheric chemistry. pure and applied chemistry 62(11):2167-2219. jimoda, la. 2012. effects of particulate matter on human health, ecosystem, climate and materials: a review. working and living environmental protection, 9(1): 27–44. kamble, rk. 2015. dust fall rate and its composition in chandrapur industrial cluster, central india. international journal of environment, 4(3); 96-110 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):109-123 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 109 original research article vegetable plants with water treatment potential: a review alfred n. jones (department of civil and water resources engineering, faculty of engineering, university of maiduguri, p.m.b 1069, maiduguri, nigeria *corresponding author: alfred_ndahi@yahoo.com article information submitted 28 march, 2018 revised 15 december, 2018 accepted 19 december, 2018 keywords: natural extracts water treatment coagulation seed protein abstract chemical coagulants and flocculants have been used for decades in water treatment. however, because of cost issues associated with the entailment of importation importing of these chemicals, developing countries were left with no other option than to rely on contaminated water for their domestic consumptions. in view of this, some communities used their ingenuity and successfully employed natural plant and animal products to purify their water supply. in many instances, these products were found to achieve comparable water quality results to that of the conventional chemicals. the aim of this study was to evaluate some of the different plant genera that have been tested in water treatment. their advantages and setbacks are highlighted. most notably, some of these natural extracts performed double functions as a coagulant and as disinfectant. conversely, several research works have pointed out that the main drawback of using natural extract in water treatment is the addition of organic compounds in the treated water which makes it unfit for human consumption due to change in taste, color, and odor. this drawback was, however, overcome in some studies where the materials were purified to obtain only the coagulant compounds. therefore, the use of natural extracts in drinking water treatment would bring relief to many inhabitants in developing countries in terms of access to clean drinking water. additionally, the study recommends further investigation into disinfecting the treated water with chlorine to assess their disinfectant by-products (dbps) formation. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the growing concern about clean water supply in developing countries has triggered innovative research to find potential alternatives to chemicals used in conventional water treatment (jahn, 1986; diaz et al. 1999; zhang et al. 2006). water treatment in any part of the world seeks to provide the population with clean and safe drinking water, devoid of pathogens (hyung and kim, 2009). access to safe drinking water improves productivity, health and wealth (un, 2016). however, this life sustaining commodity is inaccessible in many communities across the globe. to tackle this challenge, the world health organisation (who) formulated a programme to alleviate drinking water supply problems worldwide through the millennium development goals (mdgs), which stipulated the halving of the population without access to clean drinking water by the year 2015 (who, 2000). to date, over 663 million inhabitants in developing countries, most of who live in rural areas still lack access to safe and improved drinking water (jmp, 2013, who, mailto:alfred_ndahi@yahoo.com http://www.azojete.com.ng alfred n. jones, vegetable plants with water treatment potential: a review. azojete, 15(1):109-123. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 110 2015). furthermore, the major problems associated with poor access to clean water are exacerbated by economic deprivation and social incapacitation of many of the affected countries, rendering them unable to afford conventional methods of water treatment. in the year 2015, 91% of the world population, approximately 6.6 billion used improved drinking water compared with 82% in 2000 (un, 2016). however, despite the progress made in water supply in all region of the world, coverage was low in sub-saharan africa and oceania (un, 2016). moreover, not all improved drinking water were properly managed and treated to make it clean because at least 1.8 billion people were exposed to drinking water contaminated with faecal bacteria (un, 2016). in order to sustain the current effort on water supply, the united nation came up with 17 goals, tagged sustainable development goals (sdg) to sustain and build upon the progress made by the mdgs by the year 2030. one of the key aspects of the sdg is the implementation of the integrated water resource management (iwrm) following the mdg goal 6 to half the population without clean drinking water by 2015 (un, 2016). the 2030 sdg agenda (for goal 6) recognizes the importance of clean drinking water in bringing development in other areas such as health, education and poverty reduction (un, 2016). additionally, the sdg is to address the water management cycle holistically with more countries facing the challenge of being below the 25% threshold, which is the first stages of water stress (un, 2016). to effectively manage the water crises, there is a need for innovative point-of-use (pou) water treatment in developing countries (ghebremichael, et al. 2006). pou is the most cost-effective and straightforward water treatment technology adopted in ancient civilization by employing natural extracts (bodlund et al. 2014). the use of natural extracts of plant origin in water treatment dates back to over 4000 years (kansal and kumari, 2014) and as far back as to sanskrit writings where certain natural derivatives were used in water treatment. it is also on record in the old testament and roman archives that the use of natural extracts dates back to 77 ad (dorea, 2006). naturally-occurring materials consist of both animal and plant-based resources. for instance, roasted seed powders of maize (zea-mays) and nirmali were used to treat water by peruvian soldiers as well as in some indian communities (kansal and kumari, 2014). in sudan, rural women used moringa oleifera (mo) seed extract to treat their drinking water supply (jahn and dirar, 1979, jahn, 1986). therefore, the aim of this paper was to review some of the natural plant extracts that have been investigated for their viability in addressing the problem of access to clean water supply in developing countries. this review is based on the application of natural plant-based materials in water treatment. the main reason for excluding animal-based materials is, however, based on their applicability, since they are unlikely to be used for mass production due to limited availability. 2. coagulation and flocculation mechanisms coagulation and flocculation are considered to be the principle behind the treatment of both water and wastewater in most conventional plants (gregory, 2005). coagulation is simply the process of destabilizing the particles by introducing metal salts to chemically change the colloidal particles, such that the charge maintaining their stability in the water is overcome by charge neutralization where the aggregate are smaller and becomes bigger by agglomeration and are denser (gregory, 2005). coagulation mechanism is measured by the rate of destabilization of the colloidal particles in water. the coagulation process is the first step in a conventional water treatment which is achieved through destabilization and precipitation mechanisms, such as surface charge modification, double-layer compression, absorption and particle bridging (duan and gregory, 2003, gregory, 2009). flocculation, on the other hand, is a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):109-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 111 slow mixing process (i.e. orthokinetic aggregation) used after the particles are coagulated. flocculation process brings together (bridging) the destabilized smaller, micro-flocs resulting from coagulation into contact with one another to form larger macro-flocs (klimpel and hogg, 1986). flocculation step is crucial and is measured by the rate of collision efficiency between particles which do not settle and are thus difficult to remove by sedimentation. floc formation depends on the collision efficiency (α) between the particles (gregory, 2005) where the intensity of mixing is reduced to achieve optimum performance. the five (5) natural extracts reviewed in this study used in water treatment are as follows: 2.1 moringa oleifera (mo) seeds mo is a tropical plant species which belongs to the family known as moringaceae. mo is referred to as a multipurpose or multifunctional plant because most of its parts have been found to be very useful, for instance, it is used in folk medicine and as a primary source of food (fuglie, 2001). the leaves, stem, roots, shell, seed oil and protein are used in a variety of applications such as a vegetable in soup, cure of diabetes and lowering of blood pressure in patients, cooking oil and in the preparation of morning coffee. as such, it is often referred to as being a 'miracle tree' (fuglie, 2001). mo contains high mineral and protein content and is recommended to be used to fight malnutrition in developing countries (ghebremichael, 2004). it is resistant to drought and is found in abundance in most regions of africa and asia. it is thought of being native to asian countries and africa and grows within one year of planting. many people have used mo leaves as a source of vegetable in asia and africa because of its nutritional values (morton, 1991). mo seed oil has been used as machine lubricant and in the cosmetic industry (ghebremichael, 2004). figure 1 shows some seed of mo figure 1 shows some seeds, leaves and stem of moringa oleifera the plant is the most studied natural material in water treatment to date (jahn, 1986). jahn and dirar (1979) conducted the first study using mo water extract in sudan as was being prepared by the people for the removal of turbidity from the nile river. significant turbidity removal was reported compared to that obtain with ash which was also used in many villages in sudan. in addition, having seen the potential of mo as a coagulant in water treatment, jahn (1986) further studied the quality of water produced using mo water extract. the study observed a change in taste and colour of the water treated using the extract and also noted an odour is emanating from the water after 48-hour post treatment. to address the issue of deterioration in water quality, jahn (1986) recommended that water treated using mo extract to be consumed within 24 hour treatment. following these studies, ndabigengesere et al. (1995) characterized the active coagulant compound in mo seed using different techniques such as lyophilisation, dialysis, ultrafiltration, chemical precipitation and electrophoresis. interestingly, it was observed that the active agents in mo extract are proteins with a molecular weight of 13kda and isoelectric point (iep) of 10 and 11 (ghebremichael et al. 2005). furthermore, the result of zeta potential measurement of mo extract suspension showed that it is a cationic polyelectrolyte with surface charge of (+6 mv) and its coagulation mechanism was file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alfred n. jones, vegetable plants with water treatment potential: a review. azojete, 15(1):109-123. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 112 reported to be by adsorption and charge neutralization (ndabigengesere et al. 1995). in contrast, okuda et al. (1999), okuda et al. (2001a) and okuda et al. (2001b) improved the extraction process using nacl concentration and purified the seeds by dialysis, de-lipidation and ion exchange. overall, the studies showed improved coagulation performance of mo using the salt extract to water extract (in terms of turbidity removal), and the coagulation mechanism was said to be neither by double-layer compression, interparticle bridging nor by charge neutralization but by enmeshment of particles (okuda et al. 2001a). okuda et al. (2001b) also argued that protein analysis by lowry and bio-rad methods after dialysis showed negative results and the polysaccharide concentration analysis also showed zero concentration. similarly, it was clear that there was no more lipid after the extraction step. thus, it is arguable that mo salt extract is neither a protein, polysaccharide nor lipid, but a polyelectrolyte having single molecular weight (mw) band as small as three kilo dalton (3kda). conversely, gassenschmidt et al. (1995) identified the mw of the purified mo protein in ion exchange column (iec) as also consisting of dimeric mw bands of 6.5 and 14 kda with isoelectric point (iep) of 11 whereas ghebremichael et al. (2005) found the mw of the purified mo protein on a cationic exchanger to be less than 6.5 kda with iep greater than 9.6. the slight variation in the protein band with mw around 6.5 kda and iep of (10 and 11, and ˃9.6) may be due to the different processing methods adopted to obtain mo protein. interestingly, ali et al. (2010) used a high-performance liquid chromatography method to identify the bioactive mw of the coagulant protein in mo seed. the result showed that mo protein has mw between 1 and 6.5kda. although, many studies (jahn 1986; ndabigengesere et al 1995; ghebremichael et al. 2006) have accepted that the active agent in mo is a natural cationic protein showing charge neutralization as the main coagulation mechanism, except that of okuda et al. (2001b) who revealed that the coagulating compound is not a cationic protein but a polyelectrolyte. thus, the results reported by okuda et al. (2001b) should be considered because there might be a coagulating agent in mo with such property. an assessment of the quality of treated water by ndabigengesere and narasiah (1998a) using both dry shelled and non-shelled mo in a jar test experiment showed that the concentration of organic load in treated water increased significantly at higher dosage with no change in water ph, alkalinity and conductivity in treated water with small sludge volume production. these results were considered to be an advantage compared with the application of aluminium sulphate (as) in water treatment. it is noteworthy that all the purified protein reported showed high coagulation performance in a jar test experiments compared with the crude samples under different laboratory conditions due to increased adsorption (okuda et al., 2001b, ghebremichael et al., 2005, ghebremichael et al., 2006, sanchez-martin et al., 2010, ali et al., 2010). the studies also indicated that the issue of organic nutrients addition in treated water was eliminated and showing dissolved organic carbon (doc) removal in water and the ph remained unaffected. similarly, both muyibi et al. (2002) and pritchard et al. (2009) used mo seed obtain from nigeria and malawi in treating turbidity in pond water in kano-nigeria and in a shallow well in malawi which achieved between 92−99% turbidity removals. the findings from these studies showed no significant variation in mo extracts performance in respective to region. muyibi and evison (1995a) and muyibi and evison (1995b) optimized physical parameters in kaolin water and also investigated the softening potential of hardness in waters using mo extracted with de-ionise (di) in synthetic water spiked with calcium chloride, naturally hard surface water and groundwater in newcastle upon tyne. the results observed higher coagulant dose demand in high turbidity water with increased rapid and slow mix velocity gradient and http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):109-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 113 time compared with optimization of low turbidity water. similarly, in the case of hard water, it was observed that calcium hardness softened faster with an increased in mo dosage while ph showed no effect on hardness removal. in addition, a reduction of over 27% in alkalinity of the groundwater was observed, thus presenting another advantage in using mo over as as a coagulant. in synthetic wastewater treatment, ndabigengesere and narasiah (1998b) showed excellent removal of lead from contaminated synthetic water using shelled and unshelled mo extracts due to the formation of natural organic matter (nom) complexes with lead. the performance of the stored mo extracts and raw seed in low medium and high turbidity water (50, 100-200 and 200-300 ntu) were assessed by katayon et al. (2004) who stored mo extract suspension at room temperature of 3 and 28 °c for 1, 3, 5 and 7 days and katayon et al. (2006) who again stored the raw seeds at 3 and 28 °c for between 3 and 5 months respectively. maximum turbidity removal of 92.3% was observed in 300 ntu compared with between 73-86% in the (50-100 ntu) water using sample which had been stored for one day while maximum performance of 14 and 3% was recorded with crude extract stored for 5 and 7 days respectively. in addition, performance decreased with storage where seeds which had been stored for 1 month out performed those stored for up to 5 months in high turbidity water. interestingly, the efficiency of mo seed was found to be independent of temperature condition. aside its turbidity removal potential, madsen et al. (1987) investigated the traditional method of water purification in sudanese village at 30 °c using mo extract to remove turbidity, faecal coliform and other enteric bacteria. a turbidity reduction of between 80-99% was observed with a 1-4 log removal of bacteria. after 24-h post treatment, a regrowth of secondary bacteria such as salmonella typhimurium, shigellasonnei and e-coli were witnessed whereas vibrio cholerae, streptococcus faecalis and clostridium perfringens remain totally inhibited. later, ndabigengesere and narasiah (1998b) investigated the efficacy of shelled and non-shelled mo seed, and as in treating two samples each from municipal and industrial waste water from magog canada. both shelled, non-shelled and as application resulted in considerable reduction in total coliform count from 35000 to 3000 for total coliform and 21000 to 1800 for faecal coliform per 100 ml. however, after resuspension of the sludge, a regrowth of both total and faecal coliform was witnessed, suggesting that the microorganisms were not inactivated but lived in the sludge. hence, the claim that mo extract could inactivate pathogen in water by some authors is not in agreement with this study. conversely, ghebremichael et al. (2005) reported an antimicrobial activity of 1.1-4 log removal of e-coli (d31 and k12) and b. thuringiensis (bt7, bt75) and p. aeruginosawhen purified mo protein was obtain on an iec. furthermore, some studies have shown that the coagulation compound in mo extract is a water-soluble protein capable of removing total coliform and e-coli in natural pond water (anwar et al., 2007, pritchard et al., 2010). recently, da conceicao et al. (2015) used mo di water extract to obtain a result that was compliant with brazilian drinking water standards in fluoride-polluted groundwater. the importance of mo was further demonstrated by petersen et al. (2016) who showed the potential of mo extract to successfully eliminate cryptosporidium parvum oocysts in waste water intended for irrigation farming. as reported in the preceding sections, the main setback of using mo extracts is the continuous increase organic compounds into the treated water (okuda et al., 2001b, ghebremichael et al., 2006, marobhe et al., 2007) leading to a change in colour, taste and odour. following this setback, purification of crude mo seed to address this change yielded positive results where only the coagulant mo protein was obtained (ghebremichael et al., 2006, ali et al., 2010, sanchezfile:///c:/users/user/downloads/azojete143/www.azojete.com.ng alfred n. jones, vegetable plants with water treatment potential: a review. azojete, 15(1):109-123. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 114 martin et al., 2010). interestingly, the two-step purification of mo proteins using 0.3 and 0.6 m nacl concentrations significantly reduced residual doc in treated water (sanchez-martin et al., 2010). this is advantageous because any issue related to disinfection by-product (dbp) formation would have been taken care of if the final water is recommended to be disinfected using chlorine. in contrast, there are limited studies on the application of mo extract in waste water treatment and sludge dewatering ability. assessment of possible dbp formation should be done to understand if mo could release natural organic compounds that could exacerbate this challenge. 2.2 cactus mucilage cactus is an indigenous plant grown in many arid and semiarid regions of the world (sáenz et al., 2004) and is a member of cactaceae family as shown in figure 2 with many species in central america (shilpaa et al., 2012). the opuntia species is well-known as a primary source of mucilage substances similar to that of okra (ok) (sáenz et al., 2004, miller et al., 2008). the mucilage contains compounds such as l-rhamnose, d-galactose, l-arabinose, d-galactose and some other compounds such as galacturonic acid (sáenz et al., 2004, yin, 2010). cactus is also medicinal and has been used in the treatment of several ailments by native herbalists (yin, 2010). figure 2 a cactus pad prickly pear type used as coagulant. (source: alamy stock photo site) because of the presence of water-soluble mucilage in cactus latifaria pad, diaz et al. (1999) prepared 5% w/v suspension in water which was initially extracted with methanol to remove the polar substances in the cactus pad. the jar test results conducted on 20−200 ntu synthetic water show that in all the turbid water tested, between 10–20 mg/l dose was the optimum to achieve residual turbidity of less than 10 ntu. furthermore, diaz et al. (1999) compared and observed the performance of cactus latifaria in water treatment with that of as and mo to be similar although the required dose of as was higher, yet turbidity removal efficiency was the same. in addition, the methanol-treated solid from cactus latifaria was tested for coagulation which did not show any difference with the non-treated solids, thus indicating the use of solvent to remove polar substances could only incur additional cost and offer no advantage in terms of performance. cactus latifaria contain about 11.6% protein (diaz et al., 1999). furthermore, zhang et al. (2006) used water extract of cactus opuntia species in a jar test experiment to test for turbidity, alkalinity and effect of change in ph of the water on its performance. turbidity removal was 94% in 200 ntu water using an optimum dose of 50 mg/l higher than that reported by (diaz et al., 1999). however, at optimum ph (ph at which maximum turbidity removal was achieved) of 10, zhang et al. (2006) demonstrated low performance of cactus opuntia in 10°c than in 35°c water although the difference was not much. the effect of turbidity removal on alkalinity in water treated with cactus opuntia also showed increase in turbidity removal resulted in increased final water alkalinity and zhang et al. (2006) suggested that the presence of some ions in the sample affected the coagulation process. however, this study indicated that the performance of cactus opuntia species was similar to that of as and mo extract in water treatment (zhang et al., 2006) but the impact of ions in the sample need a serious evaluation. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):109-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 115 further study was conducted by miller et al. (2008) using cactus opuntia species in kaolin suspension at ph of 10. turbidity removal was reported to be 98% in 162−200 ntu water ranges (miller et al., 2008). although opuntia spp.is ananionic compound with iso-electric point (iep) of 2, the coagulation mechanism is mainly by adsorption and bridging as observed from the microscopic image of flocs formed and zeta potential measurement (miller et al., 2008). furthermore, these studies indicated that the mucilaginous substance obtained from cactus (opuntia and latifaria) is a strong water treatment candidate (diaz et al., 1999, miller et al., 2008, yin, 2010, zhang et al., 2006). the presence of galacturonic acid and protein in the cactus pad was found to be responsible for the coagulation process which achieved significant turbidity removal in water (diaz et al., 1999, miller et al., 2008). in the tropics, cactus plant could be a useful alternative to the traditional coagulant currently in use. shilpaa et al. (2012) also evaluated the potential of powder opuntia ficus indica in a jar test experiment using synthetic water. at 20 mg/l, cactus opuntia mucilage reduced the turbidity from 500 to 1.3 ntu, approximately 99.8% reduction. in waste water treatment, nharingo et al. (2015) revealed that cactus fiscus indica water extract contains a bio-flocculent capable which removed 100 % of pb and 85.74 % of zinc (zn) in a waste water sample. in addition, cactus extract achieved 84.16 % removal of cd and 93.02 % of copper (cu) in zimbabwean river (nharingo et al., 2015). overall, all the studies indicated the water treatment potential of cactus plant species at smaller coagulant dosage compared with as and other natural coagulants. investigation of its toxic effect has not been conducted as it is not a primary source of food. thus its application in drinking water needs to be carefully evaluated. also, there has not been any detailed study regarding the effect of natural organic matter (nom) addition and the application of its purified form in water treatment processes, this also needs further evaluation. 2.3 nirmali extract the plant nirmali (strychnos potatorum), linn, is a plant belonging to the loganiaceae family as shown in figure 3 (jayaram et al., 2009). nirmali seed extract is used extensively in folk medicine in many parts of india and sri lanka (jayaram et al., 2009). literature has shown that the first ground seed powder was investigated as water treatment coagulant by sen and bulusu (1962) who attributed the removal of turbidity due to the presence of an anionic polyelectrolytes and protein. figure 3 some seeds of nirmali used in water treatment (source: alamy stock photo site) similarly, tripathi et al. (1976) observed that the coagulation potential of nirmali seed extract was due to the presence of carbohydrates and alkaloids having a −cooh− group with free oh− which significantly improved its turbidity removal performance. adinolfi et al. (1994) also investigated the combination of polysaccharide and galactan extracts from the ground powder of nirmali seed to achieve a turbidity removal of 80% in synthetic kaolin water. in addition, raghuwanshi et al. (2002) conducted some analysis on 20 agro-based coagulants and observed that with 3 mg/l dose of nirmali seed extract as a coagulant aid in combination with as, the dosage of as was reduced from 45 mg/l to 25 mg/l, achieving residual turbidity of less than 0.2 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alfred n. jones, vegetable plants with water treatment potential: a review. azojete, 15(1):109-123. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 116 ntu. the volume of sludge produced after the experiment was found to be 40% lower compared with the volume of sludge produced using as as a primary coagulant. similarly, sowmeyan et al. (2011) had shown that 80% of the turbidity in 32 ntu water was removed using nirmali seed extract. it is clear from these results that nirmali seed possesses some water treatment potential even though the number of studies conducted so far is limited to turbidity removal and sludge volume production. however, further study was conducted by jayaram et al. (2009) who evaluated the use of the nirmali seed powder for the removal of heavy metal waste water using a batch mode adsorption experiments at varying ph and contact time. the study observed that the removal of pb was highly affected by ph, contact time, biomass dose and metal concentration and its adsorption ability was 16.4 mg/g. the fourier transform infrared (ftir) spectroscopy analysis showed the adsorption process of the extract was due to the presence of many functional groups (jayaram et al., 2009). it is noteworthy that at present there is little information with regard to nom addition and the effect of oh groups along galactomannan and that of galactan chains which were said to ultimately lead to abundant adsorption sites for interparticle bridging (yin, 2010) using nirmali extract. 2.4 common bean seed common bean belongs to the genus and species of (phaseolus vulgaris) figure 4. it is a good source of protein and carbohydrate and highly consumed in latin american and african countries (de almeida costa et al., 2006). the protein contents in raw and freeze-dried cooked common bean sample was reported to be between 20.9 and 22.1% whereas the carbohydrate component is 54.3 and 59.9% respectively (de almeida costa et al., 2006). figure 4 some seeds of common bean used as coagulant in water treatment. (source: alamy stock photo site) similarly, sciban et al. (2006) had shown that the protein content in common bean seed is between 20 and 30% while gunaratna et al. (2007) and marobhe et al. (2007) identified the protein compounds to be cationic after purification on a cationic iec, which is capable of removing turbidity in water. common bean extract have low sugar contents, phenolic and phytic acid and the iep was obtained by measuring the zeta potential at varying ph and the point with zero zeta potential (i.e. ph 3.61) regarded as its iep (kukić et al., 2011). an important analysis by sds-page was conducted by montoya et al. (2008) on the coagulant protein from common bean to identify its mw. the mw was then identified as being a dimeric protein with mw of approximately 20 and 50 kda. in contrast, morales‐de león et al. (2007) observed in a separate sds-page analysis that the iep is 4.5 and two mw proteins present in common bean are 26 and 49 kda. it is notable, however, that both the iep and mw of common bean seed are different from that of mo seed and may likely present some unique activities. however, similar assessment was made on the concentration of protein in common bean seed by antov et al. (2010) who observed an equivalent concentration of 0.51 mg/ml in the seed, and this support http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):109-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 117 the fact that common bean is a popular food amongst the brazilian population for a long time (de almeida costa et al., 2006). the presence of high protein contents in common bean has resulted in innovative researches into the coagulation potential of its extract because several studies using natural extracts indicated protein as a coagulant compound (ndabigengesere et al., 1995, ghebremichael et al., 2006, bodlund et al., 2014). common been has been investigated for its suitability in water treatment by sciban et al. (2005) who reported higher turbidity removal of the extract at ph above 10 and in low turbidity water of 18 ntu. however, this result is not in agreement with previous studies who observed poor performance of natural extracts in low turbidity water (ndabigengesere et al., 1995; katayon et al., 2006). this is a useful property that gives it a unique advantage over other extracts. however, considering the impact of nom in treated water, sciban et al. (2006) and antov et al. (2010) performed partial purification of the protein using ammonium sulphate, desalting, dialysis and ion exchange (iex) and elution with sodium chloride (nacl) solution. the results showed a good turbidity removal efficiency of 72.3% in 35 ntu water which was 22 times higher than the performance of the crude di water extract at a dose of 0.73 mg/l. similarly, the purified sample produced organic matter concentration of 0.35 compared with 5.9 mg of crude extract treated water from 2.3 mg/l. this finding agrees with the results obtained by some authors who using mo extracts (gassenschmidt et al., 1995, ghebremichael et al., 2005, sanchez-martin et al., 2012) who observed greater adsorption ability and reduced nom in treated water. additionally, the purification of common bean did not require lipid extraction because it does not have lipid which is advantageous. the challenge of possible floc formation being inhibited through surface coating as indicated with other extracts is also eliminated in common bean (ali et al., 2010). sciban et al. (2006) further observed that, precipitation and desalting by dialysis of the samples eluted with 0.5, 1.0, 1.5 and 2.0 m nacl solutions presented different coagulation mechanisms. such observation suggests that there may be different protein in the various fractions with varying coagulation potential. identification and characterisation of these proteins would give a clearer understanding of fraction with higher activity. with an average of 50 grams of the extract, 20 l of turbid water was treated, achieving 90% turbidity removal. however, coagulant protein from common bean obtained by ultrafiltration of the crudes extract produced lower turbidity removal of 49% compared with 51% achieved with the crude sample (antov et al., 2012). in terms of extraction time, kukić et al. (2011) reported that 10 min is sufficient to extract coagulant protein from common bean compared with 3hrs using a magnetic stirrer which would save time used in processing the extract. beside the coagulation ability of the common bean species, the antimicrobial compounds in the seed has been reported elsewhere (amarowicz et al., 2008). tannin extracted from common bean was compared with a conventional drug, streptomycin in bacterial inhibition. the minimum inhibitory concentration (mic) of bacteria with tannin were 125 µg/ml for listeria monocytogenes, salmonella typhimurium and lactobacillus plantarum while streptomycin achieved only 31.3 and 7.8 µg/ml mic for salmonella typhimurium and lactobacillus plantarum respectively (amarowicz et al., 2008). 2.5 luffa cylindrica extract luffa cylindrica is a member of (cucurbitaceouse) family which is in abundance in many tropical countries figure 5, such as asia, africa and the united state (partap et al., 2012). it is spongy and commonly called sponge gourd, mainly used by local people in washing their body and cleaning of cooking utensils. luffa cylindrical has a cellulose structure which is negatively charged when in file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alfred n. jones, vegetable plants with water treatment potential: a review. azojete, 15(1):109-123. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 118 contact with water (shahidi et al., 2015a). the immature fruit is eaten raw as it contains compounds such as lavonoids and ribosome-inactivation protein (rip) used in traditional medicine (anbukarasi and kalaiselvam, 2015). figure 5 a bunch of luffa cylindrica used in water treatment. (source: alamy stock photo site) similarly, bhattarai (1989) has reported that one of the most used natural extract among nepal population is the seed of luffa cylindrical. in addition, the importance of luffa cylindrical has been reported in a study by ruiz-marín et al. (2009) who investigated the removal of nutrients and organic matter in a bioreactor supported with luffa cylindrical fibre. the results showed that luffa cylindrical improved biofilm development as a support material. it recorded a significant removal of biochemical oxygen demand of 92.5% compared with 80% obtained with pvc as a support material (ruiz-marín et al., 2009). the study further observed that, in the final effluent the mean ammonia nitrogen concentration was 17 mg/l for luffa cylindrical and 19 mg/l for pvc support respectively (ruiz-marín et al., 2009). though, the study of luffa cylindrical is new, one of the first known optimization study using a jar test apparatus was conducted by sowmeyan et al. (2011) on different natural extracts including luffa cylindrical and as as primary coagulants. while several authors followed through aqueous extracting processes by washing using tap water, sowmeyan et al. (2011) used formaldehyde for the washing of the seeds. the reason for using this chemical instead of water is because it is efficient in the washing and cleaning of dust and debris on any substance. interestingly, luffa cylindrical achieved maximum turbidity and hardness removal of approximately 86 and 40% respectively. however, a reaction between the extract and chloride in water causes a reduction of up to 7.6% in chloride concentration at optimum dose of 8g/l of the extract (sowmeyan et al., 2011). thus, the application of luffa cylindrica in water treatment may pose some challenges if chlorine is used as disinfectant because it will consume the available residual chlorine in the treated water. additionally, as with the other natural coagulants, luffa cylindrical also achieved 60% removal of total dissolved solid (tds) in water treatment (sowmeyan et al., 2011). furthermore, the anionic nature of luffa cylindrical made it an active extract for the removal of cationic metals in waste water (anbukarasi and kalaiselvam, 2015) in the form of luffa fibre. anbukarasi and kalaiselvam (2015) investigated the water adsorption potential of composite particle fibre and showed a significant performance than the non-treated sample which can be used in damp site. in a very important test in water purification, shahidi et al. (2015b) performed some batch adsorption tests using luffa cylindrica fibre as a natural adsorbent for the removal of cadmium (cd) (ii). the results indicated that a high possibility of using luffa for the removal of cd (ii) in water with adsorption capacity of 6.7 mg/g. however, cadmium removal was observed to be highly dependent on solution ph, dosage and cd (ii) concentration. because of the presence of antioxidants such as saponin, rip, phenolic compounds etc. direct application of luffa cylindrical extracts against e-coli and many other bacteria is reported elsewhere (oyetayo et al., 2007). shaheed et al. (2009) evaluated the potential of luffa cylindrica http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):109-123. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 119 fruit and seed between 40 and 333g/l as a disinfectant against total and faecal coliform in water treatment using a contact time from 15-180 min. the results showed that the inhibition of the two indicator organisms was variable and dose dependent with a maximum performance of 86% at 180 min for faecal bacteria. although the overall results revealed some disinfection ability in luffa plant, the performance did not achieve the who standard for drinking water quality. similarly, the limited results conducted using the extract as a coagulant is not sufficient to judge its potential in water treatment which requires more studies. 3. conclusion coagulation and flocculation are the first step in conventional water treatment. it is a major unit operation which is straightforward with regard to potable water production. several natural extracts as reviewed contain coagulating compounds that could compete effectively with the inorganic ones. they have potential to be used as either primary coagulants or as coagulant aids in water treatment. in most cases, destabilisation of the colloidal particles in water was achieved or induced through charge neutralisation and bridging action resulting in low sludge volume. interestingly, while many studies have been conducted to assess their turbidity and bacterial removal efficiency, production/processing of such products in commercial quantity are yet to commence. however, it is noteworthy that apart from mo, most of those plants presented have limited information although they have been tested in water treatment in one form or the other. some of the few natural plant-based extracts that have been used in water treatment are at this moment presented: however, it is noteworthy that most research work used a batch test in a series of jar tester to evaluates their coagulation and flocculation performance. additionally, there is still the need to conduct some studies especially with regards to disinfection by-product (dbp) formation precursor. possibility of its industrial application should also be encouraged further in order to provide local communities in developing countries with cheaper access to potable water supply. it is also important to characterise natural extract to properly understand the main agents responsible for coagulation by different naturallyoccurring extracts. references adinolfi, m., corsaro, mm., lanzetta, r., parrilli, m., folkard, g., grant, w. and sutherland, j. 1994. composition of the coagulant polysaccharide fraction from strychnos potatorum seeds. carbohydrate research, 263: 103-110. ali, en., muyibi, sa., salleh, hm., alam, mz. and salleh, mrm. 2010. production of natural coagulant from moringa oleifera seed for application in treatment of low turbidity water. journal of water resource and protection, 2: 259-266. amarowicz, r., dykes, ga. and pegg, rb. 2008. antibacterial activity of tannin from phaseolus vulgaris, fagoypyrum esculentum, corylus avellana and juglans 79: 217-219. anbukarasi, k. and kalaiselvam, s. 2015. study of effect of fibre volume and dimension on mechanical, thermal, and water absorption behaviour of luffa reinforced epoxy composites. materials and design (1980-2015), 66, part a: 321-330. antov, mg., ciban, mb. and petrovic, nj. 2010. proteins from common bean (phaseolus vulgaris) seed as a natural coagulant for potential application in water turbidity removal. bioresource technology, 101: 2167-2172. antov, mg., ciban, mb. and prodanovic, jm. 2012. evaluation of the efficiency of natural coagulant obtained by ultrafiltration of common bean seed extract in water turbidity removal. ecological engineering, 49: 48-52. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng alfred n. jones, vegetable plants with water treatment potential: a review. azojete, 15(1):109-123. issn 1596-2490; 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they can be overridden so easily and are not useful inside structures. one method of overcoming the above problem is the use of feature based navigation system. nature has so much perfected this that copying nature is one of the best approaches available to scientist. in this study, desert ant (cataglyphis fortis) was imitated. a simple infra-red based active beacons and robot mounted rotating receiver based on tsop31138 infra-red sensor was implemented using new three objects triangulation algorithm (total) in its firmware for the robot pose. the designed robot with the triangulation algorithm was able to compute its pose such that on a grid of 6 m x 6 m, it can home to its base with a maximum error of 14.8 mm. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction ants are an interesting class of organisms, because of the manner in which they carry out tasks, withstanding heat, and the homing skills they possess during foraging. the desert ants (cataglyphis sp.) in particular, navigate long distances, find food, communicate and avoid predators. they care for their family in similar manner as any mammal. when finding a new home, ants take advice from their more experienced brethren who had memorized alternative hive locations. ants integrate many types of information for navigation, these are: the number of steps, direction of travel, wind, land type, angles of the sun, visual memories of landmarks and smells (lieff, 2015). individual ants use diverse information in different situations and can learn entirely new ways to navigate (lieff, 2015). pathwayz (2017) reported that regardless of whether an organism is travelling a shorter distance or extremely long distances, in order to find its way back it must have some method http://www.azojete.com.ng oyegbade et al: a step towards autonomous, biomimetic, non-gps based navigation methodology. azojete, 15(4):813-822. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 814 of navigation. these methods of navigation include; visual cues and landmarks, magnetic fields, solar navigation, star navigation and chemical navigation. the sahara desert ants refer to any of several species of ant in the genus cataglyphis that dwell in the sahara desert, particularly c. fortis and c. bicolor. the navigational capabilities of these ants have been the subject of scientific investigations (wehner, 2003; sahara, 2016). these ants travel over 200m in zigzag patterns while foraging, and when they get their food, they return to their hole in approximately a straight line from the point of pick of meal to the nest. the nest entrance is usually an inconspicuous 5mm hole in the desert floor. the ant does not retrace the zig-zagging path of its outward journey; even if a scent-trail is possible, such a route would be a waste of time and an increased risk. instead, it runs in a straight line directly back to its nest-hole. it is amazing that the 0.1 mg brain housed in the head of a 10 mg ant accomplishes such feats of navigation. biomimetic systems are greatly desired because natural systems are highly optimized and efficient (afolayan, 2012), such as the desert ant (cataglyphis sp.). biologically inspired robots imitate some characteristics of life such as mobility, vision, flying, and navigational methodology. the challenge of developing biomimetic systems is the requirement of a deep understanding of the operation of the living systems being copied (csn, 2011). in this study, it is the navigational skill of cataglyphis sp. we intend to copy. the ability of a robot to localize or recognize its location, navigate or move about its environment, are critical building blocks in creating truly autonomous robots. there has been significant progress in this aspect of autonomy, particularly indoors robots as reported by thrun et al. (1999), fox et al. (1999), menon et al. (2007) and marder–eppstein et al. (2010). in like manner, field robots in the form of autonomous cars (on streets and highways) are also being researched into intensively (montemerlo et al., 2008 and thrun, 2011). in recent years, significant advances have been made in robotics, artificial intelligence and other fields allowing for the making sophisticated biomimetic systems (bar-cohen and breazeal, 2003). scientists often perform reverse engineering biological specimens in other to copy them either their form or function or both. this present study is aimed at carrying out static test (triangulation test) on a triangulation algorithm we developed for the robot. this is the very first step in developing a mobile robot that will use landmark (in this scenario, omni-directional active infra-red beacons) for its autonomous navigation and homing mechanisms. the triangulation algorithm is based on the new three objects triangulation algorithm by pierlot and droogenbroeck (2014). 2.0 methodology the approach used in this study involved the selection of a biological model, specifically c. fortis, imitating it functionally (that is not its physical form) and finally building a wheel robot that can roam about and home back to base on the methodology used by the biological model. 2.1 selection of biological model the desert ant (cataglyphis fortis) was selected for the study. the skills demonstrated during foraging and homecoming (homing) by the ant were demonstrated in the various navigational mechanisms it employs. in this study the landmark based homing methodology was approximated by using omni-directional active infra-red beacons as the fixed landmark. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 813-822. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 815 2.2 imitation level and strategy the desert ant uses the orientation of the various landmark features in its surrounding during homecoming to locate the hole to its nest on the ground. we plan to use active infra-red beacons and sensors for imitating the landmark and its detection augmented with ultrasonic sensors for obstacle detection and avoidance. together, they will give the robot pose (position and orientation) at any instance. 2.3 the robot design the robot (figure 1) is a four-wheeled device designed to imitate one of the desert ant navigational capabilities – feature based navigation. on it is mounted with two ultrasonic sensors, a rotating infrared receiver sensor, a motor driver and control circuit comprising of atmel atmega328p-pu microcontroller and the other basic elements. the motor driver circuitry is based an l298n dual h-bridge motor controller; it allows the robot to move forward, backward, left-forward, right-forward, left-backward and right-backward. it allows for the braking or slowing down of the robot as well. the top mounted servomotor serves the purpose of rotating the infrared receiver sensor. the ultrasonic sensor is mounted at the front for object detection using timed reflected echo. echo coming back after 4000ms implies there is no object in front of the robot. the microcontroller (atmega328p-pu) controls the servomotor, the ir receiver sensor and the ultrasonic sensor as well as the drive motors. the active beacons (figure 2) are a group of three (3) infra red led transmitters mounted radially outwards so as to transmit omni-directionally. they are referred to as being active because the signals they send out are coded and each beacon is managed by a built in microcontroller. these codes are detectable by the rotating infra red receiver sensor mounted on the robot as it moves about. the robot is powered by four (4) icr18650 2000-mah 3.7-v li-ion rechargeable dry cells. figure 1: the line drawing of the proof of concept robot. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyegbade et al: a step towards autonomous, biomimetic, non-gps based navigation methodology. azojete, 15(4):813-822. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 816 a b c figure 2: the beacon with 8 infra-red led round about its periphery. (a) isometric view (b) top view (c) the transmission pattern of the beacon, each is at 180o angle. 2.4 control algorithm the control algorithm for the navigation of the robot presented in this study is based on the three objects triangulation algorithm (total) shown in figure 3 as a flowchart. this algorithm satisfies biological plausibility defined by vardy and moller (2005) as the likelihood of an algorithm existing in biological model. furthermore, it is required that the algorithm be constrained to share some set of properties known to exist in the model animal in its implementation. the navigation algorithm we have built into the robot use simple landmarks and memorize their locations relative to its own pose. this information is noted at the beginning of operation and it is then used to find its track back when it desire to do so just like the desert ant does. 3 experimental verification of the built-in algorithm the test for the triangulation algorithm of the robot at different coordinates was carried out by placing the robot and the beacons on known coordinates within the 6m x 6m experimental grid area. the robot was switched on and connected to a computer (hp 250 g3 notebook) via a usb port so as to record the robot computed triangulation output (from its firmware). the computation of its coordinates was based on the information obtained from the infrared sensor and the active beacons and using the new three objects triangulation algorithm built into its firmware. the experimental setup is shown in figure 4. the test was carried out three times, whereby, for each fixed and known beacon position, the robot was placed at ten different positions and was allowed to search for the positions of each of the beacons and thereafter compute its position relative to those of the beacons. using figures 5 and 6; for the first experiment, beacon1 was placed at (0, 0), beacon2 was placed at (1, 0) and beacon3 was placed at (0, 1). the coordinates are given in metres. also, for the second experiment, beacon1 was placed at (0, 0), beacon2 was placed at (1.5, 0) and beacon3 was placed at (0, 1.5) and lastly, for the third experiment, beacon1 was placed at (0, 0), beacon2 was placed at (2.0, 0) and beacon3 was placed at (2.0, 0), with the coordinates all given in metres. as the robot positions were statically altered, the actual coordinate (randomly selected) was recorded and the robot infra-red led 108o the beacon pattern http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 813-822. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 817 estimate of its own coordinates computed using the triangulation algorithm. furthermore, the distance to the goal (gda) (in straight line) was measured and also computed (gdc) with the algorithm. figure 4: experimental setup for the test on triangulation with a fixed beacon coordinates and different robot position. this figure is for experiment 1beacons coordinates while the robot position is at (0.5, 0.5) coordinates. the robot is tethered to the computer performing the recordings file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyegbade et al: a step towards autonomous, biomimetic, non-gps based navigation methodology. azojete, 15(4):813-822. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 818 4. results and discussion the goal coordinates are the reference coordinates, fixed at (x=6, y= 6) in meters. the robot actual coordinate and its computed coordinate’s results for the three experiments are presented in tables 1 to 3. plots of absolute deviation from the goals for the three experiments are shown in figures 7, 8 and 9. they all appear to be random. we could only attribute these random variations to be due to the components (especially the infra-red sensor) warming up in order to accommodate the changes in the ambient temperature. they were actually not compensated for in our design. we expect a steady variation, not sharp and unpredictable one. experiment 3 (figure 9) has the least varying response which corroborates our idea since the infra-red sensors were already very warm by the time the 3rd experiment was being conducted. however, the absolute variation of the goal computed from the actual goal is encouraging as the worst case is 0.015 m (ignoring the outlier in the first experiments). it means the robot will miss its target by maximum of 0.015 m (15mm) if homing from the corner of the 6 m x 6 m grid. this result is an improvement when compared to gps based systems whose precision is in the order of 3-5m (ping-ya, 2000; andrew, 2017). however, on a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 813-822. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 819 relative scale, there is need for a lot of improvement; a low orbit gps system has 1:300,000 best error value to orbit height (1500km) ratio whereas, our system has 1:400 error to target (6m ahead) ratio. the limitation is obviously in the triangulation sensing device used – ie the infrared sensor and the rotary scanner minimum angular resolution. table 1: experiment 1: the robot pose; actual and measured coordinates repeat actual coordinate(m) computed coordinate(m) distance to goal(m) actual calculated xa ya xc yc gda gdc 1 0.34 0.34 0.336 0.300 8.0328 8.0353 2 0.74 0.46 0.739 0.457 7.6393 7.6420 3 0.58 0.73 0.571 0.737 7.5597 7.5617 4 0.54 0.65 0.542 0.650 7.6442 7.6426 5 0.34 0.93 0.334 0.938 7.5987 7.5983 6 0.79 0.95 0.799 0.950 7.2558 7.2491 7 0.22 1.25 0.231 1.252 7.4814 7.4716 8 0.64 1.70 0.701 1.722 6.8717 6.8104 9 1.50 1.25 1.530 1.212 6.5468 6.5505 10 0.10 1.11 0.123 1.131 7.6630 7.6321 table 2: experiment 2: the robot pose; actual and measured coordinates. repeat actual coordinate (m) computed coordinate(m) distance to goal(m) actual calculated xa ya xc yc gda gdc 1 0.30 0.42 0.306 0.417 7.9766 7.9748 2 0.79 0.95 0.789 0.959 7.2558 7.2503 3 1.55 0.94 1.545 0.980 6.7384 6.7120 4 1.83 1.83 1.821 1.821 5.8973 5.9098 5 0.40 2.22 0.411 2.228 6.7564 6.7426 6 1.35 0.30 1.356 0.301 7.3561 7.3513 7 0.99 1.03 1.000 1.031 7.0570 7.0492 8 1.00 1.37 1.004 1.374 6.8145 6.8089 9 1.15 0.95 1.150 0.964 7.0018 6.9922 10 1.64 2.24 1.632 2.213 5.7574 5.7815 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyegbade et al: a step towards autonomous, biomimetic, non-gps based navigation methodology. azojete, 15(4):813-822. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 820 table 3: experiment 3: the robot pose; actual and measured coordinates repeat actual coordinate(m) computed coordinate(m) distance to goal(m) actual calculated xa ya xc yc gda gdc 1 1.00 0.58 0.998 0.577 7.3740 7.3773 2 1.49 1.25 1.479 1.261 6.5500 6.5497 3 0.48 1.32 0.478 1.319 7.2369 7.2389 4 1.38 1.65 1.377 1.669 6.3456 6.3350 5 1.84 1.53 1.837 1.543 6.1063 6.0988 6 0.87 1.56 0.863 1.561 6.7846 6.7888 7 0.74 2.05 0.726 2.044 6.5780 6.5928 8 0.75 1.35 0.749 1.346 7.0132 7.0162 9 1.35 1.60 1.317 1.619 6.4018 6.4126 10 0.27 1.86 0.264 1.865 7.0691 7.0710 figure 7: absolute deviations of the coordinates computed by the robot (experiment 1) figure 8: absolute deviations of the coordinates computed by the robot (experiment 2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 813-822. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 821 figure 9: absolute deviations of the coordinates computed by the robot (experiment 3) 5. conclusion in this paper, a preliminary work on a robot based on desert ants (cataglyphis fortis) was reported. the built-in triangulation algorithm known as the new three-object triangulation algorithm was found to be simple and require less computation, with ability to aid the robot to home in with a maximum error of 14.8 mm (or 15mm approximately). the limiting factors observed is due to the infra-red sensors (tsop31138) used, itneeds warming up before stabilizing so as to get a repeated reading. however, the transmitter led mounted on the beacons had no problem. 6. recommendations this study being a preliminary work, we are recommending the use of fast acting infra red sensors or any alternative directional sensing system with high signal to noise rejection ratio. also, a mobile platform should be used perhaps with a long range sensors like laser based tentacles for open terrain experiments. references afolayan, m.o. 2012. design and development of a biologically inspired hyper-redundant robot joint mechanism. phd thesis, ahmadu bello university, zaria. andrew b. 2017. global navigation satellite system fundamentals and recent advances in receiver design. available onlineat:https://www.ieee.li/pdf/viewgraphs/gnss_fundamentals.pdf bar-cohen, y. and breazeal, c. 2003. biologically inspired intelligent robotics. smart structures and materials 2003: electroactive polymer actuators and devices (eapad) in proceedings of the spie smart structures and material conference, san diego, ca., vol. 5051(2003). doi:10.1117/12.484379. pp 14-20. csn, 2011. convergent science network of biomimetic and biohybrid systems.http://csnetwork.eu/conf2012/conference. accessed 7.35pm 24, november 2011 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyegbade et al: a step towards autonomous, biomimetic, non-gps based navigation methodology. azojete, 15(4):813-822. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tunde_afolayan@yahoo.com 822 fox, d., burgard, w., dellaert, f. and thrun, s. 1999. monte carlo localization: efficient position estimation for mobile robots. in proceedings of sixteenth national conference on artificial intelligence (aaai’99).pp 343-349. lieff, j. 2015. ant intelligence update. searching for the mind. http://jonlieffmd.com/blog/antintelligence-pdate on. accessed: march 22, 2016. marder-eppstein, e., berger, e., foote, t., gerkey, b. and konolige, k. 2010. the officemarathon: robust navigation in an indoor office environment. proceeding of ieee international conference on robotics and automation (icra)., pp 300-307. menon, c., broschart, m. and lan, n. 2007. biomimetics and robotics for space applications: challenges and emerging technologies. proceedings ieee international conference on robotics and automation (icra) workshop on biomimetic robotics., 19-27. montemerlo, m., becker, j., bhat, s., dahlkamp, h., dolgov, d., ettinger, s., haehnel, d. hilden, t., hoffman, g., huhnke, b., johnston, d., klumpp, s., langer, d., levandowski, a., levinson, j., marcil, j., orenstein, d., paefgen, j., penny, i., petrovskaya, a., pfueger, m., stanek, g., stavens, d., vogt, a. and thrun, s. 2008. junior: the stanford entry in the urban challenge. journal of field robotics, 25(9): 569-597. pathwayz., 2017. methods of navigation.animals.https://www.pathwayz.org/tree/plain/methods+of+navigation. accessed on july 11, 2017 pierlot, v. and van droogenbroeck, m. 2014. a new three object triangulation algorithm formobile robot positioning. robotics, ieee transactions 30(3), 566-577. ping-ya k. 2000. gps-based precision approach and landing navigation emphasis on inertial and pseudolite augmentationand differential ionosphere effect. a phd dissertation at stanford university. sahara desert ant. 2016. encyclopaedia britannica.http://www.britannica.com/animal/saharadesert-ant. accessed on march 23, 2016 at 15:33 thrun, s. 2011. google’s driverless car. http://ted.com/talks /sebastian_ thrun_google_s_ driverless_car.html. accessed on april 25, 2016”. thrun, s., bennewitz, m., burgard, w., cremers, a., dellaert, f., fox, d., hahnel, d.,rosenberg, c., roy, n., schulte, j. and schulz, d. 1999. minerva: a second generation mobile tour-guide robot. proceedings ieee international conference on robotics and automation (icra)., 35-44. vardy, a. and moller, r. 2005. biologically plausible visual homing methods based on optical flow techniques. connection science, 17(1-2): 47-89. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):847-858 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 847 original research article a new formula for groundwater recharge estimation in yola, nigeria a. b. umaru1*, s. lukman2, i. a. oke3, and b. g. umara4 (*1department of agricultural and environmental engineering, modibbo adama university of technology, yola nigeria 2 civil engineering department, university of hafr al-batin, hafr al-batin, saudi arabia 3department of civil engineering, obafemi awolowo university, ile-ife, nigeria 4department of agricultural and environmental resources engineering, university of maiduguri, nigeria) * corresponding author’s email address: ababayi234@yahoo.com 1.0 introduction moisture of soil and soil – water are important ingredients in fertility of the soil and food security. groundwater recharge includes the drive of water from the unsaturated zone into the saturated region of the soil below the water table. the water runs together with the associated article information abstract in this paper,relationship between rainfall and groundwater recharge estimation was evaluated. a standard numerical formula that relates rainfall to groundwater recharge estimation was proposed with the aim of providing error-free groundwater estimate from rainfall. rainfalls measured in a selected location in yola, nigeria and standard formula were used to fix the constants (a,b and c) in the new numerical formula using microsoft excel solver. the constants were used to establish new numerical formula. the new numerical formula was used to estimate groundwater recharge from the rainfall. the accuracy of the new numerical formula was evaluated statistically using analysis of variance (anova), relative error; the degree of accuracy, numerical reliability, model of selection criterion (msc) and akaike information criterion (aic) and compared with the previous formulae in use for field groundwater recharge estimation with uttar pradesh (up) as the reference value of groundwater recharge. the study revealed that groundwater recharge estimated using the formula   814.0019.1621.0  prgr was similar to groundwater recharge estimated using standard formulae (up, modified chaturvedi, kumar and seethapathi and rao). in all cases there were significant differences between the groundwater recharge estimated using all the formulae. the new formula provided the lowest relative error of 0.887%, the highest msc of 4.911; the degree of accuracy of 99.113 % and the lowest aic of 436.306. the accuracy of the formulae was in the order of new formula greater than chaturvedi formula greater than kumar and seethapathi formula greater than rao formula. it was concluded that modelling of groundwater recharge using the numerical formula is a promising tool for estimating groundwater recharge with minimum error in water resources management. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 april, 2018 revised 01 september, 2018 accepted 05 september, 2018 keywords: groundwater recharge soil –moisture numerical solution microsoft excel solver statistical methods. mailto:ababayi234@yahoo.com http://www.azojete.com.ng umaru, et al: a new formula for groundwater recharge estimation in yola, nigeria. azojete, 15(4):847-858. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 848 flow pattern away from the water table within the saturated region (freeze and cherry, 1979; yeh et al., 2008). groundwater recharge occurs at a point when water containing dissolved minerals flows beyond the groundwater level and infiltrates into the saturated zone. groundwater recharge is a tremendously important water component of the hydrological cycle in nature. modifications in groundwater storage comprise various recharge and discharge progressions. most important recharge sources are rainfall, recharge from rivers, recharge from ponds, recharge from irrigation fields. the crucial discharge processes are evapotranspiration, pumping, baseflow to rivers. there are several factors that can affect the existence and discrepancy of groundwater level in a region. the major and significant factors include topography, lithology, geological structures, depth of weathering, the extent of fractures, the primary and secondary porosity of the soil, slope and drainage patterns of the region, landform and land cover, environmental factors and climate (mukherjee 1996; jaiswal et al., 2003). it is well known and established that ground water recharge estimation methods are numerous. it has been documented that none of these methods will give the same groundwater recharge rates when used for the same area. the use of these groundwater recharge eastimate methods are limited to particular environments (humid or arid), and the availability of data for evaluation (adams et al., 2004). the groundwater recharge methods and models in the determination of the groundwater recharge are characterized into three groups (physical model, calculated from the base flow, chemical model, measurement of water-soluble substances and numerical model, using numerical method). the numerical approaches include the computer programs such as help, rora, pulse, part, hy sep and wells water-table fluctuations (risser et al., 2008; seyed et al., 2013). chandra (1979) reported that the methods and techniques that are prevalently applied to estimate the natural groundwater recharge are soil water balance, zero flux plane; one-dimensional soil-water flow model, inverse modeling technique, ground water level fluctuation, hybrid water fluctuation, ground water balance method; isotope and solute profile techniques. kumar (2000) grouped the methods and the techniques of estimation of groundwater recharge into four groups as empirical methods; groundwater resource estimation; groundwater balance approach and soil moisture data based methods (seyed et al., 2013; islam et al., 2014). the empirical methods are the following equations modified chaturvedi, kumar and seethapathi, up and rao formulae. chaturvedi (1973) derived an empirical equation which expresses recharge as a function of annual precipitation as follows ((ala-aho et al., 2015; oke et al., 2017; natarajan et al., 2018)):   4.0150.2  prr (1) where: rr is the net recharge due to precipitation during the year (inches), and p is the annual precipitation(inches). the chaturvedi formula was restructured and modified by further work at the u.p. irrigation research institute, roorkee and the modified chaturvedi (up) form of the formula is as follows (oke et al., 2017):   5.01435.1  prr (2) kumar and seethapathi (2002) established an empirical relationship between groundwater recharge and the corresponding values of rainfall in the monsoon season using the non-linear regression equation of (oke et al., 2017): http://www.azojete.com.ng mailto:ababayi234@yahoo.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 847-858. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 849   76.028.1563.0  mrm pr (3) where: rrm is the groundwater recharge from rainfall in monsoon season (inch), and pm is the mean rainfall in monsoon season (inch). rao derived an empirical relationship to determine the groundwater recharge in limited climatological homogeneous areas as follows (ala-aho et al., 2015; oke et al., 2017; natarajan et al., 2018):  xrkrr  (4) where rr is the recharge (mm); k is constant; r is the precipitation(mm), and x is the number of point rainfall. the following boundary empirical equations were applied to different parts of karnataka as follows: rr = 0.20 (p 400); for regions with annual normalrainfall (p) between 400 and 600 mm; rr = 0.25 (p 400); for zones with p between 600 and 1000 mm rr = 0.35 (p 600); for regions with p above 2000mm, (ala-aho et al., 2015; oke et al., 2017; natarajan et al., 2018). islam et al. (2014) gave an empirical relationship between recharge and the corresponding values of rainfall. the relationship is as follows (oke et al., 2017):   56.051.2785.0  prr (5) several other studies conducted on groundwater recharge estimate include ichwana and summono (2013), kung et al. (2013), rana et al. (2014), adeleke et al. (2015), islam et al. (2015), sabri et al. (2015), and oke et al. (2015; 2016). estimating recharge in nigeria has been a difficult issue due to many factors which comprise the paucity of data, non-availability of mathematical and numerical formulae applicable in the country. literature (ala-aho et al., 2015; oke et al., 2017; natarajan et al., 2018) stressed the prominence of groundwater recharge in the national development and economics. these discoveries show that there is the need to develop a numerical formula for groundwater estimate in nigeria. the key objective of this study, therefore was to develop a numerical formula for groundwater estimation that will be applicable in nigeria, and evaluate its accuracy and applicability using relative error; total error; degree of accuracy, numerical reliability, model of selection criterion (msc) and akaike information criterion (aic). 2.0 materials and methods a non-linear regression formula that represents generalization of the simple formulae that relate rainfall to groundwater recharge estimate (depth) was proposed as follows (oke et al., 2017):   cgr bpar  (6) where; rgr is the groundwater estimate (depth, mm); a, b and c are the constants for the model and p is the depth of rainfall (mm). the formula was proposed and selected based on the simplicity, nature of the soil, soil cover, infiltration rate, previous studies from literature (ala-aho et al., 2015; oke et al., 2017; natarajan et al., 2018) and a minimum number of fixed parameters to be determined. monthly rainfall data between 1931 and 2010 for yola, nigeria was obtained from literature (akintola, 1986) and upper benue river basin development authority (ubrbda) meteorological station and used. the rainfall data (annual and monthly) were analysed statistical using analysis of variance (anova) and used to calculate the recharge from rainfall using file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ababayi234@yahoo.com umaru, et al: a new formula for groundwater recharge estimation in yola, nigeria. azojete, 15(4):847-858. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 850 standard empirical formulae (equations 1 to 5). the constants in the proposed new numerical formula (a, b and c) were determined using microsoft excel solver and groundwater estimated from rainfall. microsoft excel solver was selected based on availability (at no additional cost) and accuracy in numerical solutions. the new formula was used to estimate groundwater recharge from the rainfall in yola, nigeria. relationship between groundwater recharge and year was established. the accuracy of the developed formula was evaluated using analysis of variance (anova), relative error; a model of selection (msc) and akaike information criterion (aic) and compared with selected formulae in use (rao, islam et al, 2014, chaturvedi and modified chaturvedi formulae). although, chaturvedi and the kumar and seethapathi formulae were developed using the imperial unit, the groundwater recharge estimated was converted to system international (si) unit to ensure consistency in the units of measurement(ala-aho et al., 2015; oke et al., 2017; natarajan et al., 2018). analysis of variance was conducted using microsoft excel package. procedures employed in the computations of model parameters using microsoft excel solver are as follows (oke et al., 2017): microsoft excel solver was added in on the toolbar of microsoft excel; target (limit, 0, equation (7)) value of the iteration was set for the software based on square of difference as   2 1 1 0 cn n t t t t r a p b              (7) changing cells of the iterations were selected, number of iterations, degree of accuracy and maximum time for the iteration were set for the software to meet the target; and the iteration started through microsoft excel solver as presented in figure 1. the model of selection criterion (msc) is interpreted as the proportion of expected groundwater recharge variation that can be explained by the obtained groundwater recharge. the higher the value of msc indicates a higher accuracy, validity and the good fitness of the method. msc can be computed using equation (8) as follows (oke, 2007):     n p yy yy msc n i caliobsi n i obsobsi 2ln 2 1 2 1         (8) where: yobsi is the groundwater recharge estimated using up formula; obsy is the average groundwater recharge estimated using up formula; p is the total number of fixed constants to be estimated in the equation; n is the total number of groundwater recharge estimated, and ycali is the groundwater recharge estimated using new formula. the aic was derived from the information criterion of akaike (1976). it allows a direct comparison among models with a different number of parameters. the aic presents the information on a given set of parameter estimates by relating the coefficient of determination to the number of parameters. the aic and relative errors (rerr) were determined using eqns 9 and 10 respectively as follows: http://www.azojete.com.ng mailto:ababayi234@yahoo.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 847-858. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 851   pyynaic n i caliobsi 2ln 2 1             (9) n y yy rerr n i obsi caliobsi          1 100 (%) (10) 3.0 results and discussion results from this study are discussed in the following categories: rainfall and statistical evaluation, the new formula, estimated groundwater recharges and performance evaluation of the developed formula. 3.1 rainfall figure 2a presents monthly and annual rainfall of the location. from the figure the monthly rainfall varied with the month as well as the year, which indicated that rainfall season in yola starts from april and ends in the month of october every year. although there were fluctuations in the amount of rainfall, the range for the month remains valid. table 1 shows summary of analysis of variance (anova) for the monthly and annual rainfalls. the table revealed that there was a significant difference between the annual rainfall at 95 % confidence level (f76, 836 = 1.099, p = 0.271). the table also revealed that there was no significant difference between the pattern of the monthly rainfall for the selected period and location (f11, 836 = 233.562, p = 3.9 x 10 -246). open microsoft excel check under data at the tool bar if solver is available no yes at the toolbar click microsoft logo, open excel option and select add in. ok set the target ($l$53), operation (minimization or value of zero) and changing cell($k$2: $k$6) at solver dialogue set the number of iterations and time. click on solver to solve target reached end (record the values) yes no figure 1: procedure for using microsoft excel solver in the computation of the constants file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ababayi234@yahoo.com umaru, et al: a new formula for groundwater recharge estimation in yola, nigeria. azojete, 15(4):847-858. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 852 3.2 the new formula the proposed numerical formula is as presented in equation (11). the values of the parameters were a = 0.621; b =1.019 and c = 0.814. the value indicates that the new numerical equation for estimating groundwater recharge can be expressed as follows:   0.8140.621 1.019grr p  (11) this result shows that the new formula is similar to previous numerical formulae in literature such as oke et al. (2016), asani et al. (2019). in previous studies, oke et al. (2017), the numerical formula for groundwater recharge for abeokuta, nigeria is as presented in equation (12) with the value of the parameters as a = 1.673; b = 7.219 and c = 0. 672. these constants in the formulae indicated that the numerical equation for estimating groundwater recharge in abeokuta can be written as follows:    672.0219.7673.1  prgr (12) oke et al. (2016) documented that relationship between rainfall and groundwater recharge in abeokuta and ikeja, nigeria can be expressed as follows: 0.15 102.8grr p  (13) 0.320 258grr p  (14) from oke et al. (2016) correlation coefficients (r2) for abeokuta [equation (13)] and ikeja [equation (14)] are 0.180 and 0.393 respectively, which indicates that these relationships are weak and needs to be improve upon. lukman et al. (2018) developed relationship between rainfall and groundwater recharge in sokoto, nigeria as 0.5006.814( 355.722)grr p  (15) these results revealed that no numerical model is the same in values and in magnitude of the constants. figure 2b presents relationship between groundwater recharge and period (year). from the figure this relationship is weak, which indicated that there was no strong relationship between year and groundwater recharge. http://www.azojete.com.ng mailto:ababayi234@yahoo.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 847-858. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 853 figure 2a: rainfall data for yola, nigeria over a period of 77 years figure 2b: relationship between groundwater recharge and period file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ababayi234@yahoo.com umaru, et al: a new formula for groundwater recharge estimation in yola, nigeria. azojete, 15(4):847-858. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 854 figure 3: estimated groundwater recharge using various numerical formulae 3.2.1 estimated groundwater recharges figure 3 presents the statistical summary of groundwater recharges estimated using the new numerical formula and formulae that are in use for all the locations. the figure revealed that groundwater recharge estimated using the islam et al. (2014) formula had the lowest minimum and the mean in all the cases, while groundwater estimated using the kumar and seethapathi's formula had the highest maximum and the mean in all the cases. the implication is that accuracies of these two formulae are lower than other formulae. the figure also revealed that the lowest standard deviation came from chaturvedi formula in all the case, while the highest standard deviation came from rao formula. the result from standard deviation indicates that variation in the groundwater recharge estimated was higher in rao formula than any other formula. the highest median of computed groundwater recharge came from rao formula, and the lowest median of computed groundwater recharge came from islam et al. (2014) formula. source of variation sum of squares degree of freedom mean sum of square fvalue p-value years 179140.2 76 2357.108 1.098801 0.270962 months 5511304 11 501027.6 233.5615 3.9 x 10 -246 error 1793356 836 2145.163 total 7483800 923 table 1: anova of the rainfall data in yola over a period of 77 years http://www.azojete.com.ng mailto:ababayi234@yahoo.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 847-858. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 855 these results and observed in term of median of computed groundwater recharge indicates that rao formula gave a higher value of groundwater recharge computed than other standard formulae used in the computation of computed groundwater recharge, while islam et al. (2014) gave the lowest groundwater recharge computed. the implication is that in design and computation of infiltration from rainfall in water budget selection of these two formulae should be done with caution. results from computed groundwater recharges revealed that there are three empirical formulae exhibit some similarities and closeness in term of computed groundwater recharge. the three empirical formulae are the new formula, modified chaturvedi and chaturvedi formulae. the figure also showed that the estimated groundwater recharges varied with the location as well as the empirical formulae used. this result indicates that accuracy of these formulae is not the same. table 2 presented result of analysis of variance of computed groundwater recharge. analysis of variance of this computed groundwater recharges revealed that there was a significant difference between the estimated groundwater recharges within the formulae and within the year (table 2) at 99 % confidence level. the f – values range from 14.59 to 106.06 and pvalue ranges between 1.49 x 10-66 and 1.29 x 10-54. this result of anova indicated that is a significant factor in the magnitude of groundwater recharge computation 3.2.2 performance evaluation of the new formula table 3 presented the performance evaluation of the standard formulae and the new formula. the table revealed that groundwater recharge computed using islam et al. (2014) formula provided the lowest msc and accuracy, as well as the highest aic and errors (relative error, total and root square errors). from the table, it was revealed that the highest msc and accuracy; lowest errors (total, relative and root square) and aic were from the new formula. modified chaturvedi and chaturvedi were the next accurate formulae after the new formula, which indicated that the new formula is among accurate formulae. the table also revealed that there was a slight reduction in the accuracy of these two formulae with reference to the new formula. this slight reduction in accuracy may be attributed to the development of the two formulae (modified chaturvedi and chaturvedi) as an imperial unit’s formulae and conversion of the unit from imperial unit to system international unit(si). the table revealed that there were three empirical formulae that exhibit some similarities and closeness in respect of computed groundwater recharge. the three empirical formulae are the new formula, modified chaturvedi and up formulae. the table showed the values of msc were as negative for three standard formulae (kumar and seethapathi formula, rao formula and islam et al. formula), which indicated that utilization of these three formulae with negative msc in the groundwater recharge computation should be at the lowest level. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ababayi234@yahoo.com umaru, et al: a new formula for groundwater recharge estimation in yola, nigeria. azojete, 15(4):847-858. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 856 conclusion it can be concluded that the new formula and other two empirical formulae are more accurate than other standard formulae used in this study. there was a significant difference in the computed groundwater recharges. performance evaluation of the formulae revealed that care should be taken in the use of islam et al, rao kumar and seethapathi formulae in the computation of groundwater recharge based on the value of msc, aic and their accuracies. the new formula is among the best for groundwater recharge estimate based on msc, aic and relative error references adams, s., rian, t. and yongxin, x. 2004. groundwater recharge assessment of the basement aquifers of central namaqualand. report to the water research commission. south africa. wrc report no. 1093/1/04. adeleke, oo., makinde, v., ayobami, oe., oluwaseun, fd., akintayo, oo. and taiwo, ja. 2015. estimation of groundwater recharges using empirical formulae in odeda local government area, ogun state, nigeria. challenges, 6: 271-281. akaike, h. 1976. an information criterion (aic), mathematical science, 14:1-5. chandra, s. 1979. groundwater studies project. final report, school of hydrology, university of roorkee . pp. 356 numerical model chaturvedi kumar rao islam et al., (2014) relative error (%) 0.887 6.82 8.80 36.31 59.34 total error 267.305 8789.63 34009.90 287532.10 661215.22 root square error 3.47 114.15 441.69 3734.18 8587.21 aic 436.306 705.26 809.45 973.82 1037.94 msc 4.911 1.42 0.07 -2.07 -2.90 accuracy 99.113 93.185 91.198 63.686 40.662 table 2: anova of the estimated groundwater recharges (yola) source of variation sum of squares degree of freedom mean sum of square fvalue p-value years 418215.2 76 5502.832 14.58899 1.49 x 10 -66 methods 152478.9 4 38119.72 101.0622 1.29 x 10 -54 error 114666 304 377.1908 total 685360.1 384 table 3: results of statistical evaluations of the models http://www.azojete.com.ng mailto:ababayi234@yahoo.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 847-858. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 857 asani, ma., lukman, s. and oke, ia. 2019. application of software in soil and groundwater recharge estimation in ilorin, nigeria. applications of image processing and soft computing systems in agriculture edited by navid r. published by igl global, new york. pp 184 205 chaturvedi, rs. 1973. a note on the investigation of ground water resources in western districts of uttar pradesh. in annual report. u.p. irrigation research institute, roorkee, pp. 86-122. freeze, ra and cherry, ja. 1979. groundwater. prentice-hall inc., englewood cliffs, pp. 168. ichwana, zn. and sumono, jl. 2013. ‘determining groundwater recharge from stream flow with seasonal recession method. aceh. international journal of science and technology, 2:8–16. islam, mr., anupam, c., kazi, m., islam, m. and ziaur, r. 2014. development of rainfall recharge model for natural groundwater recharge estimation in godagari upazila of rajshahi district, bangladesh. american journal of civil engineering, 2(2): 48-52. islam, s., ram, ks. and roohul, ak. 2015. methods of estimating ground water recharge. international journal of engineering associates, 5 (2): 6 – 13. jaiswal, rk. mukherjee, s., krishnamurthy, j. and saxena, r. 2003. role of remote sensing and gis techniques for generation of groundwater prospect zones towards rural development—an approach. international journal of remote sensing, 24: 993–1008. kumar, cp. 2000. groundwater assessment methodology. 21: national institute of hydrology, roorkee, pp. 345. kumar, cp. and seethapathi, pv. 2002. assessment of natural ground water recharge in upper ganga canal command area. journal of applied hydrology, 15(4): 13-20. kung, wj., yeh, hf., lin, hi., chen, wp. and lee, ch. 2013. an approach to evaluate groundwater recharge from streamflow and groundwater records. geosciences journal, 17(3): 353–362. oke , mo., martins, o., salako, fk. and idowu, oa. 2016. estimation of groundwater recharge in the lower-ogun river basin using two independent methods. nigerian journal of hydrological sciences, 4: 181 – 200. oke, ia. 2007. reliability and statistical assessment of methods for pipe network analysis. environmental engineering and sciences, 24(10): 1481-1489. oke, ia., lukman, s. and ismail, a. 2017. development and performance evaluation of a new numerical model for groundwater recharge estimation. nigeria journal of engineering, 23(2): 56 -65. oke, mo., martins, o., idowu, oa. and aiyelokun, o. 2015. comparative analysis of groundwater recharge estimation value obtained using empirical methods in ogun and oshun river basins. ife journal of science, 17(1): 5364. rana c. and ray, rk 2014. assessment of ground water resources: a review of international practices. government. of india ministry of water resources central ground water board. faridabad. pp. 354 risser, dw., gburek, wj. and folmar, gj. 2008. comparison of recharge estimates at a small watershed in east-central pennsylvania, usa. hydrogeology journal, 17(2): 287-298. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ababayi234@yahoo.com umaru, et al: a new formula for groundwater recharge estimation in yola, nigeria. azojete, 15(4):847-858. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ababayi234@yahoo.com 858 sabri, b., lahbassi, o. and mehdi, k. 2015. combination of two evolutionary methods for groundwater recharges estimation in semi-arid regions, north eastern algeria. international. journal of. water, 9(3): 286297 seyed, r., saghravani, iy., sa’ar, im. and seyed, fs. 2013. estimating groundwater recharge using empirical method: a case study in the tropical zone. sains malaysiana, 42(5): 553–560 yeh, hy., cheng-haw, l., kuo-chin, h. and po-hsun, c. 2009. gis for the assessment of the groundwater recharge potential zone. environmental geology, 58:185–195. ala-aho, p., rossi, pm. and kløve, b. 2015. estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using scots pine inventories. hydrology. earth system. science., 19, 1961–1976 natarajan p., kottiswaran, sv., balasubramanian a. and palanikumaran b. 2018. groundwater recharge estimation using comparison of methods in sirumugai area of coimbatore, tamil nadu, india. international journal of current microbiology and applied science, 7(6): 1433-1440 http://www.azojete.com.ng mailto:ababayi234@yahoo.com arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 750-761 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 750 original research article simulation of prototype active agricultural solar dryer with slit-type transpired solar collector a. kuhe 1*, j. s. ibrahim1, l. t. tuluen1 and s. a. akanji2 (1department of mechanical engineering, university of agriculture, makurdi, nigeria 2department of mechanical engineering, federal polytechnic, mubi, nigeria) * corresponding author’s email address: moseskuhe74@gmail.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: validation results solar drying system experimental rig typical meteorological year moisture content abstract this paper presents a functional and easy method for simulation of thin bed drying of maize in an active solar dryer with slit-type transpired collector using trnsys software. thin layer solar drying model written in trnsys equation blocks in combination with existing components in the software library were used to build a solar mixed mode dryer system in trnsys environment for simulation. experimental data for thin-bed solar dryer drying of maize obtained at different air mass flow rates of 0.026, 0.033, 0.034, 0.035 and 0.038 kg/sec, respectively, were used for model verification. there was good agreement between simulation results and experimental dryer temperatures for thin-bed solar dryer drying of maize with root mean square error (rmse) and nashsutcliffe efficiency coefficient (nse) of 0.95, 0.57, 0.65, 1.15, 1.32 and 0.92, 0.93, 0.92, 0.85, 0.89 respectively for the air mass flowrates investigated. the results further confirmed that trnsys software can be a useful tool in the design and optimization of solar dryer systems. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction drying of agricultural produce is a task that must be done due to the large amount of harvested agricultural produce which is impossible to consume immediately. drying process is one of the most important components of postharvest handling of maize, therefore, a properly designed and operated dryer is an important feature of the maize value chain. drying is defined as dual process of heat transfer to the product from the heating source and mass transfer of moisture from the interior of the product to its surface and from the surface to the surrounding air (ekechukwu and norton, 1999). drying is the removal of moisture from the agricultural produce to prevent deterioration within a period of time regarded as the safe storage period for the purpose of preservation and to prevent the growth of micro-organisms such as enzymes, bacteria, yeast and moulds (maame, 2014). the objective of the dryer is to supply the produce with more heat than is available under ambient conditions, increasing sufficiently the vapor pressure of the moisture held within the crop, thus enhancing moisture migration from within the crop and decreasing significantly the relative humidity of the drying air, thus increasing its moisture carrying capability and ensuring a sufficiently low equilibrium moisture content. in solar drying, solar energy is used as either the sole source of the required heat or as a supplemental source, and the air flow can be generated by either forced or natural convection. the heating http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):750-761. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 751 procedure could involve the passage of the pre-heated air through the product, by directly exposing the product to solar radiation or a combination of both. the major requirement is the transfer of heat to the moist produce by convection and conduction from surrounding air mass at temperatures above that of the produce, or by radiation mainly from the sun and to a little extent from surrounding surfaces, or conduction from heated surfaces in conduct with the produce (soteris, 2004). the sun is the primary source of solar energy. the energy coming off the sun, called solar energy reaches us in the form of electromagnetic waves after experiencing considerable interactions with the atmosphere (supranto et al., 2011). the radiant energy emitted or reflected by the constituents of the atmosphere forms the atmospheric radiation. the sun, which is 1.50 x 1011 m away, is a sphere of intensely hot gaseous matter with a diameter of 1.39 x109 m. the solar energy strikes our planet within 8 min 20 seconds after leaving the giant furnace. it has an effective black body temperature of 5762 k. in the central region, the temperature is much higher and it is estimated at 8 x 106 to 40 x 106 k. the sun’s total output is 3.8 x 1020 mw which is equal to 63 mw/m2 of the sun’s surface. solar energy radiates outwards from sun in all directions. out of the total solar radiation emitted, the earth only intercepts a very small fraction of 1.7 x 1014 kw (duffie and beckman, 2013). it is estimated that 30minutes of solar radiation falling on earth is equal to the world energy demand for one year (soteris, 2004). every day the sun delivers 4.176x106 kwh. muneer (2004) noted that one hour of solar energy that falls on earth is equivalent to one year world fuel consumption. harnessing of solar energy can reduce fossil fuel consumption and reduce the co2 and co emissions from heat engines. traditional open sun drying has been the most popular method of drying agricultural produce since the stone age to present age because it is simple and cheap. sun drying for preservation of agricultural produce is as old as the creation of the world (osman and ertekyn, 2001). however, traditional open sun drying, which is regarded as direct sun drying, utilized widely by the rural farmers, has some disadvantages, such as requirement for large space, long drying time, crop damage by the hostile weather, contamination of grain from foreign materials, high crop losses as a result of inadequate drying, fungal attacks, insects, birds and rodents encroachment. due to the problems of open sun drying, indirect solar energy cabinet dryers appear increasingly to be attractive as the best solution for the drying of agricultural produce. indirect solar drying technology is becoming a better option to replace direct traditional open sun drying of agricultural produce because it is clean, hygienic and sanitary conditions to national and international standards (samaneh et al., 2011). when comparing the direct traditional open solar dryers with indirect solar cabinet dryers, the later saves time, occupies less area, improves product quality and hygiene, makes the process more efficient and protects the environment (bala and woods, 1994). many researchers have designed, fabricated, tested and evaluated different types of solar dryers with different types of solar air heaters such as flat plate, parabolic and transpired. most of the designers evaluated dryer with flat plate because of its simplicity, others improved it by using transpired plate with slit-like perforations. this study improved the transpired plate with slit-like perforations by reducing the depth of perforations and increases the effective area of heat transfer which in turn increases the rate of collisions of molecules, increase the temperature, gives strong jet impingement and better heat transfer. lixin et al. (2014) validated glazed and unglazed transpired collector, the results show that the exit air temperature of glazed transpired collector (gtc) is higher than that of unglazed transpired collector (utc) for a crosswind velocity file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuhe, et al: simulation of prototype active agricultural solar dryer with slit-type transpired solar collector. azojete, 15(3):750-761. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 752 exceeding 3.0 m/s with solar radiation of 400 w/m2, ambient temperature of -10°c and suction velocity of 0.01 m/s. bojia et al. (2014) validated glazed transpired solar collector with slit-like perforations, the simulated and experimental results were in good agreement with average deviation of 2.25 %. wenke et al. (2017) validated the dynamic photovoltaic thermal collector (pvt) – solar air heater with fins (sah) model under variable boundary condition and its performance was compared with an equivalent steady state model, the results show that the steady state model could overestimate the thermal energy gains of pvt – sah system by 35 %. zomorodian and zamanian (2012) evaluated the effect of porosity and thickness on absorber performance of collector and the results show that the thermal efficiency of collector was increased as the porosity and the thickness increased. samenah et al. (2011) compared the predicted and experimental data of temperature, humidity and moisture content on each tray of an indirect solar cabinet dryer, the simulated and experimental results agreed with each other. kumar et al. (2009) discovered that the thermal efficiency of transpired solar collectors using jet impingement is found to be higher than other types of collector by about 10 – 20%. xianli et al. (2016) discovered that gtc with slit-like perforated absorber plate maximize the effective heat transfer area of the absorber plate than utc, thereby increase the thermal performance. in transpired absorber plate, the quality of the heat transfer coefficient and thermal efficiency were improved through effective strengthening of air that passes through the collector absorber when solar radiant heat and the heat between air and absorber were absorbed (zomorodian and zamanian, 2012). trnsys energy modeling software is a powerful tool for designing, analyzing, and developing renewable energy systems (aghbashlo et al., 2015). this energy simulation software has been deployed substantially and suitably for the study of solar thermal processes, building models and many other renewable energy technologies. the extreme flexibility of this software provides a suitable opportunity to simulate the performance of transient, ill-defined, and unforeseeable energy systems such as solar drying systems (aghbashlo et al., 2015). there is very little information available in literature on simulation of maize solar drying using a mixed mode dryer with a transpired slit-type absorber air heater. the main objective of this paper is to develop a trnsys simulation model for forced convection maize solar drying using a mixed mode dryer integrated with a transpired absorber air heater, and then validate the model using experimental drying data for five mass flow rates; 0.026, 0.033, 0.034, 0.035 and 0.038 kg/sec. the proposed method can be used for visualizing the dryer system and prediction of the solar dryer environment under different operating conditions. 2. materials and methods 2.1 description of the dryer the experimental set up as illustrated by figures 1 and 2, was designed and fabricated to dry food crops and vegetables in department of mechanical engineering, university of agriculture, makurdi, nigeria. the solar drying experiments were carried out during the month of june 2017. each test started at 09:00 am and continued till 15:00 pm. the drying of maize was done in experimental field-type solar dryer made up of a 0.746 kw variable speed centrifugal fan, air heater, a drying chamber, a vent and the base structure. the variable speed centrifugal fan was used to blow air into the glazed transpired solar air heater through a square duct (50 mm × 50 mm) insulated with polystyrene insulating materials. the air-heater, through which the drying air is heated as it flows through the perforated absorber plate during solar drying mode, consists of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):750-761. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 753 a 0.5 mm thick absorber (1500 mm × 600 mm) with 518 slit-like perforations (37 rows by 14 columns) on a 0.5 mm aluminum sheet. the top surface of the aluminum absorber (1500 mm by 600 mm) is coated with black paint to maximize absorption of incident solar radiation. ambient air is drawn into the plenum between the back plate and absorber plate; it passes through the slit-like perforated absorber plate into the plenum between the glass cover and absorber plate to the drying chamber. the sides and back plate of the air heater are made from wood particle board. the wood particle board is a poor thermal conductor, thereby serving as heat insulators for the air heater. the transparent top of the collector is a 1500 mm × 600 mm by 240 mm clear glass, to provide heating through the greenhouse effect. the drying chamber in which the maize to be dried has a dimension of 600 mm by 600 mm by 20 mm consisting of three trays and a rectangular frustum top made of 40 mm iron sheet with the side facing the sun coated in black for additional heating and a vent (figure 3), through which the moist air is vented out. it houses three removable extended galvanized iron-mesh trays, arranged vertically in line on guides that are spaced 300 mm apart. the side walls are made up of wood particle board. there is a door that provides access to the chamber for loading, and unloading the maize grains. figure 1: complete assembly of the experimental rig file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuhe, et al: simulation of prototype active agricultural solar dryer with slit-type transpired solar collector. azojete, 15(3):750-761. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 754 figure 2: 1 fan, 2 blower fan housing, 3 fan regulator casing, 4 fan regulator, 5 solarimeter, 6 transpired absorber plate 7 thermocouple, 8 thermocouple probe, 9 trays, 10. drying cabinet, 11 vent, 12 air flow probe,13. air flow meter, 14 stair case, 15 probe hanger, 16 frame, 17 glass cover, 18 absorber plate hanger, 19 insulated lining, 20 solar box collector 2.2 validation of the model in order to validate the model of the presented drying system using trnsys software, experimental data from a prototype mixed mode solar maize dryer integrated with a transpired absorber air heater (akanji, 2019). detailed information on the experimental solar mixed mode solar maize drying system integrated with a transpired absorber air heater, its design and data collection was presented by akanji (2019). data on solar drying of maize at different mass flowrates of 0.026, 0.033, 0.034, 0.035 and 0.038 kg/sec were used for model validation. the experiments were conducted in june, 2017, in makurdi, nigeria. the root mean square error (rmse) and nash-sutcliffe efficiency coefficient (nse) was used to determine the level of deviation of the predicted result from the actual result. the root mean square error (rmse) measures the quality of fit between the actual data and predicted model (julien et al, 2013). the root mean square error (rmse) of the model prediction with respect to the estimated variable x model is defined as the square root of the mean squared error (neil, 2010) rmse = �霨೭ � ����h������������ � (1) where: xexp = experimental values xsim = simulated values the lower the mean absolute error or bias percentage value, the better the performance of the model (neil, 2010). the nash-sutcliffe efficiency coefficient (nse) is used to access the predictive power of hydrological models (morasi et al., 2007). it is an indicator of the model’s ability to predict about http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):750-761. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 755 the 1:1 line between the observed (experimental) and predicted (modeled or simulated) values. nash-sutcliffe efficiency coefficient (nse) is defined as; nse = ೭ � �霨೭ � ����hf������f���� �霨೭ � �����f������f���� (2) nash-sutcliffe efficiency coefficient (nse) can be used to quantitatively describe the accuracy of model outputs other than discharge. this method can be used to describe the predictive accuracy of other models as long as there is observed (experimental) data to compare with the model (simulated) results (morasi et al., 2007). nash-sutcliffe efficiency coefficient (nse) can range from �� to 1. an efficiency coefficient values equal to 1 (e=1) indicate a perfect fit between observed (experimental) and predicted (simulated) values. an efficiency coefficient of zero (e=0) indicates that the model predictions are accurate as mean of the observed data, whereas an efficiency coefficient less than zero (e<0) occurs when the observed mean is better predictor than the model (ibrahim, 2015). 2.2 trnsys model the mixed mode solar maize dryer integrated with a transpired absorber air heater was developed using a transient systems simulation (trnsys16.0) software, which is a quasi-steadystate computer simulation and analysis program. trnsys contains a standard library including various subsystem components currently used in thermal and electrical energy systems, as well as components to apply input variables of local weather data or other arbitrary time-dependent forcing functions and desired outputs of simulation results. all components have been programmed in fortran language (klein et al., 2007). a known output of a given component can be applied as input to itself or to any number of other components according to the actual structure of a system to accomplish a specified task. these components can be selected and interlinked in any optional manner to establish a system’s model (aghbashlo et al., 2015). the general structure of the solar drying system model for the five mass flow rates with two drying chamber trays in the trnsys environment is shown in figure 2. figure 2: structure of transpired solar drying system schematic model in trnsys 3. results and discussion tables 1, 3, 5, 7 and 9 show the experimental and simulated results for temperature of trays obtained from rig and trnsys 16 software (type 109 tmy2 included in the solar weather data processor) for different days. tables 2, 4, 6, 8 ad 10 show the validation of simulated results with experimental results of average drying temperature for all trays for different days using rmse and nse statistical tools. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuhe, et al: simulation of prototype active agricultural solar dryer with slit-type transpired solar collector. azojete, 15(3):750-761. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 756 table 1: experimental and simulated results for temperature of trays obtained (0.026 kg/s) time (hrs) tt1.sim (°c) tt1.expt (°c) tt2.sim (°c) tt2.expt (°c) t3.sim (°c) t3.expt (°c) 10.00 3.49e+01 36.9 2.95e+01 30.4 2.42e+01 25.9 11.00 3.67e+01 37.7 3.14e+01 32.5 2.61e+01 27.8 12.00 3.94e+01 38.9 3.41e+01 34.9 2.88e+01 29.0 13.00 4.22e+01 42.3 3.69e+01 36.7 3.16e+01 30.4 14.00 4.32e+01 43.5 3.79e+01 38.6 3.26e+01 32.9 15.00 4.32e+01 42.2 3.79e+01 37.8 3.27e+01 31.8 table 2: validation of simulated and experimental results of average drying temperature for all trays using rmse and nse (0.026 kg/s) time tlsim tlexpt (tlsim tlexpt) (tlsim -tlexpt)^2 (tlexpt-tlexpt_ave)^2 10 3.49e+01 36.9 -2.0000 4.0000 11.2225 11 3.67e+01 37.7 -1.0000 1.0000 6.5025 12 3.94e+01 38.9 0.5000 0.2500 1.8225 13 4.22e+01 42.3 -0.1000 0.0100 4.2025 14 4.32e+01 43.5 -0.3000 0.0900 10.5625 15 4.32e+01 42.2 1.0000 1.0000 3.8025 total 2.40e+02 241.5 6.3500 38.1150 ave 3.99e+01 40.25 rsme 1.0583 nse 0.8334 table 3: experimental and simulated results for temperature of trays (0.033 kg/s) time (hrs) tt1.sim (°c) tt1.expt (°c) tt2.sim (°c) tt2.expt (°c) t3.sim (°c) t3.expt (°c) 10.00 3.49e+01 35.7 2.96e+01 30.5 2.43e+01 25.0 11.00 3.62e+01 37.7 3.09e+01 30.3 2.56e+01 27.5 12.00 3.76e+01 38.2 3.23e+01 31.8 2.70e+01 27.7 13.00 3.87e+01 38.9 3.34e+01 32.9 2.81e+01 28.2 14.00 3.98e+01 40.8 3.45e+01 34.2 2.92e+01 30.6 15.00 4.07e+01 41.2 3.54e+01 34.9 3.01e+01 29.9 table 4: validation of simulated and experimental results of average drying temperature for all trays using rmse and nse (0.033 kg/s) time tlsim tlexpt (tlsim tlexpt) (tlsim -tlexpt)^2 (tlexpt-tlexpt_ave)^2 10 3.49e+01 35.7 -0.7754 0.6012 9.3025 11 3.62e+01 37.7 -1.4554 2.1181 1.1025 12 3.76e+01 38.2 -0.6087 0.3706 0.3025 13 3.87e+01 38.9 -0.1787 0.0319 0.0225 14 3.98e+01 40.8 -1.0172 1.0347 4.2025 15 4.07e+01 41.2 -0.4986 0.2486 6.0025 total 2.28e+02 232.5 4.4051 20.9350 ave 3.80e+01 38.75 rsme 0.7342 nse 0.7896 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):750-761. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 757 table 5: experimental and simulated results for temperature of trays (0.34 kg/s) time (hrs) tti.sim (°c) tt1.expt (°c) tt2.sim (°c) tt2.expt (°c) texit.sim (°c) texit.expt (°c) 10.00 3.94e+01 38.9 3.40e+01 34.1 2.87e+01 30.8 11.00 4.18e+01 42.3 3.65e+01 36.6 3.12e+01 31.2 12.00 4.42e+01 43.0 3.89e+01 40.2 3.36e+01 34.6 13.00 4.63e+01 46.7 4.11e+01 41.1 3.58e+01 35.5 14.00 4.81e+01 46.6 4.28e+01 42.9 3.75e+01 38.3 15.00 4.65e+01 45.1 4.12e+01 42.0 3.60e+01 36.8 table 6: validation of simulated and experimental results of average drying temperature for all trays using rmse and nse (0.034 kg/s). time tlsim tlexpt (tlsim tlexpt) (tlsim -tlexpt)^2 (tlexpt-tlexpt_ave)^2 10 3.94e+01 38.9 0.4541 0.2062 23.6844 11 4.18e+01 42.3 -0.4527 0.2050 2.1511 12 4.42e+01 43 1.2224 1.4942 0.5878 13 4.63e+01 46.7 -0.3515 0.1236 8.6044 14 4.81e+01 46.6 1.4700 2.1610 8.0278 15 4.65e+01 45.1 1.4164 2.0063 1.7778 total 2.66e+02 262.6 6.1962 44.8333 ave 4.44e+01 43.76667 rsme 1.0327 nse 0.8618 table 7: experimental and simulated results for temperature of trays (0.035 kg/s) time (hrs) tti.sim (°c) tt1.expt (°c) tt2.sim (°c) tt2.expt (°c) t3.sim (°c) t3.expt (°c) 10.00 3.90e+01 38.1 3.37e+01 33.8 2.84e+01 29.6 11.00 4.11e+01 39.2 3.58e+01 35.9 3.05e+01 30.9 12.00 4.29e+01 41.9 3.76e+01 38.4 3.23e+01 32.0 13.00 4.48e+01 45.1 3.95e+01 42.2 3.42e+01 32.2 14.00 4.66e+01 44.9 4.13e+01 41.8 3.60e+01 35.1 15.00 4.50e+01 44.3 3.97e+01 40.3 3.45e+01 35.9 table 8: validation of simulated and experimental results of average drying temperature for all trays using rmse and nse (0.035 kg/s) time tlsim tlexpt (tlsim tlexpt) (tlsim -tlexpt)^2 (tlexpt-tlexpt_ave)^2 10 3.90e+01 38.1 0.9189 0.8444 17.2225 11 4.11e+01 39.2 1.9262 3.7104 9.3025 12 4.29e+01 41.9 0.9682 0.9375 0.1225 13 4.48e+01 45.1 -0.2855 0.0815 8.1225 14 4.66e+01 44.9 1.6943 2.8708 7.0225 15 4.50e+01 44.3 0.7193 0.5173 4.2025 total 2.59e+02 253.5 8.9619 45.9950 ave 4.32e+01 42.25 rsme 1.4937 nse 0.8052 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuhe, et al: simulation of prototype active agricultural solar dryer with slit-type transpired solar collector. azojete, 15(3):750-761. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 758 table 9: experimental and simulated results for temperature of trays (0.036 kg/s) time (hrs) tt1.sim (°c) tt1.expt (°c) tt2.sim (°c) tt2.expt (°c) t3.sim (°c) t3.expt (°c) 10.00 3.93e+01 38.3 3.40e+01 32.6 2.87e+01 29.2 11.00 4.26e+01 41.5 3.73e+01 37.0 3.20e+01 33.5 12 .00 4.57e+01 44.5 4.04e+01 41.8 3.51e+01 36.2 13.00 4.88e+01 47.4 4.35e+01 44.2 3.82e+01 37.9 14.00 4.77e+01 48.3 4.24e+01 42.7 3.71e+01 36.3 15.00 4.37e+01 43.9 3.84e+01 37.6 3.31e+01 34.3 table 10: validation of simulated and experimental results of average drying temperature for all trays using rmse and nse (0.036 kg/s) time tlsim tlexpt (tlsim tlexpt) (tlsim -tlexpt)^2 (tlexpt-tlexpt_ave)^2 10 3.93e+01 38.3 1.0171 1.0345 32.3003 11 4.26e+01 41.5 1.1259 1.2677 6.1669 12 4.57e+01 44.5 1.1956 1.4294 0.2669 13 4.88e+01 47.4 1.4190 2.0136 11.6736 14 4.77e+01 48.3 -0.6361 0.4047 18.6336 15 4.37e+01 43.9 -0.2278 0.0519 0.0069 total 4.46e+01 263.9 6.2018 69.0483 ave 4.46e+01 43.98333 rsme 1.0336 nse 0.9102 figures 3, 4, 5, 6 and 7 show the comparison of hourly average drying temperature for all trays recorded experimentally with the simulated values from trnsys 16 software for different days plotted in matlab 2009b. the results of rmse and nse for mass flow rates; 0.026, 0.033, 0.034, 0.035 and 0.038 kg/sec. are 1.06, 0.73, 1.03, 1.49, 1.03 and 0.83, 0.79, 0.86, 0.81, 0.91 respectively. the simulated data acceptably agreed with experimental data for both inlet drying air and outlet moist air. 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 34 35 36 37 38 39 40 41 42 43 44 time (hrs) te m pe ra tu re (d eg re e c el ci us ) expt sim figure 3: comparison of experimental and simulatedhourly average drying temperature for all trays recorded with the predicted values (0.026 kg/s) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):750-761. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 759 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 37 38 39 40 41 42 43 44 time (hrs) te m pe ra tu re (d eg re e c el ci us ) expt sim figure 4: comparison of experimental and simulatedhourly average drying temperature for all trays recorded with the predicted values (0.033 kg/s) 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 36 37 38 39 40 41 42 43 44 45 time (hrs) te m pe ra tu re (d eg re e c el ci us ) expt sim figure 5: comparison of experimental and simulated hourly average drying temperature for all trays recorded with the predicted values (0.034 kg/s) 10 10.5 11 11.5 12 12.5 13 13.5 14 33 34 35 36 37 38 39 40 41 42 43 time (hrs) te m pe ra tu re (d eg re e c el ci us ) expt sim figure 6: comparison of experimental and simulated hourly average drying temperature for all trays recorded with the predicted values (0.035 kg/s) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kuhe, et al: simulation of prototype active agricultural solar dryer with slit-type transpired solar collector. azojete, 15(3):750-761. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 760 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 32 34 36 38 40 42 44 46 time (hrs) te m pe ra tu re (d eg re e c el ci us ) expt sim figure 7: comparison of experimental and simulated hourly average drying temperature for all trays recorded with the predicted values (0.036 kg/s) the rmse values imply that the error between the mean of the experimental drying chamber temperature are 1.06, 0.73, 1.03, 1.49 and 1.03 for five different days. the nse values of 0.83, 0.79, 0.86, 0.81 and 0.91 indicate a good quality of fit between the experimental data and predicted data from the model. therefore, good model predictive powers as the nse values are positive and approaches 1. the simulated data fittingly tracked the experimental drying air temperature. the digression between experimental and trnsys solar radiation data could have a significant role in the difference between experimental and simulated drying air temperatures (aghbashlo et al., 2014) 5. conclusion a trnsys model was developed for simulation of dryer conditions in thin layer drying of maize by integrating a mathematical model of a mixed mode solar dryer with transpired slit-type absorber for air heating. the validated trnsys model can be used to simulate conditions of solar-drying systems in different locations predict system condition under different operating conditions. the advantage of applying this approach is that the solar dryer operation can be visualized and tinkered as much as possible without actual construction and test running in the preliminary design phase. this will eliminate a huge cost at the design and optimization phase. references aghbashlo, m., müller, j., mobli, h., madadlou, a. and rafie, s. 2014. modeling and simulation of deep-bed solar greenhouse drying of chamomile flowers. drying technology, 33(6): 684–695. akanji, sa. 2019. development and performance evaluation of an active solar drying system for preservation of agricultural produce. phd thesis, university of agriculture, makurdi, nigeria., pp. 268. bala, bk. and woods, jl. 1994. simulation of the indirect natural convection solar drying of rough rice. journal of solar energy, 53: 259-266. bojia, li., shijun, y., tianzhen, y., huan, z., xianli, li. and chao, li. 2014. mathematical modelling and experimental verification of vacuum glazed transpired solar collector with slit-like perforations. journal of renewable energy, 69: 43-49. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):750-761. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moseskuhe74@gmail.com 761 duffie, ja. and beckman, wa. 2013. solar engineering of thermal processes. fourth edition. john wiley and sons inc., hoboken, new jersey, united states of america., pp. 862. ekechukwu, ov. and norton, b. 1999. review of solar energy drying systems iii: low temperature air heating solar collectors for crop drying applications. journal of energy conversion and management, 40(6): 657-667. ibrahim, mh. 2015. design and modeling of tomato solar dryer. m.sc thesis submitted to ahmadu bello university, zaria, nigeria, pp. 112. julien, ga., emmanuel, l., clement, a., rufin, oa. and brice, as. 2013. modelling solar energy transfer through roof material in africa sub-saharan regions. journal of renewable energy, 34(7): 632-645. klein, sa, beckman, wa., mitchell, jw., duffie, ja., duffie, na., freeman, tl., mitchell, jc., braun, je., evans, bl., kummer, jp., urban, re., fiksel, a., thomton, jw., blair, nj., williams, pm., bradley, de., mcdowell, tp., kummert, m. and arias, da. 2012. a transient simulation program. solar energy laboratory, madison university of wisconsin, usa., pp. 1124. kalogirou, sa. 2004. solar thermal collectors and applications. journal of progress in energy and combustion science, 30(3): 231-295. kumar, a., bhagoria, jl. and sarviya, rm. 2009. heat transfer and friction correlations for artificially roughened solar air heater duct with discrete w – shaped ribs. journal of energy conversion management, 50: 2107 – 2117. lixin, g., hua, b. and shufeng, m. 2014. potential application of glazed transpired collectors to space heating in cold climates. journal of energy conversion and management, 77: 690-699. maame, td. 2014. development of a parabolic solar dryer for efficient solar energy use in the rural areas in ghana. m.sc thesis submitted to the department of mechanical engineering, kwame nkrumah university of science and technology, ghana., pp. 58. muneer, t. 2004. solar radiation and daylight models. butterworth – heinemann. oxford, united kingdom., pp. 392. neil, js. 2010. encyclopedia of research design. sage publishing, london, united kingdom., pp. 1736. sami, s., rahimi, a. and etesami, n. 2011. dynamic modeling and a parametric study of an indirect solar cabinet dryer. drying technology, 29: 825–835. supranto, mh., ruslan, m., yahya, my., sulaiman, ma., ghoul, az. and sopian, k. 2009. some design aspects of the assisted solar drying system with double-passed finned solar collectors. proceedings of the 3rd world scientific and engineering academy and society (wseas) international conference on renewable energy sources. canary island, spain, july 1-3, 2009., pp. 326-330. wenke, f., georgios, k., zhenjun, m. and paul, c. 2017. development of a dynamic model for a hybrid photovoltaic thermal collector – solar air heater with fins. journal of renewable energy, 101: 816-834. xianli, l., chao, l. and bojia, l. 2016. net heat gain assessment on a glazed transpired solar air collector with slit-like perforations. applied thermal engineering, 99: 1-10. yaldyz, o. and ertekyn, c. 2001. thin layer solar drying of some vegetables. drying technology, 19(3&4): 583-597. zomorodian, a. and zamanian, m. 2012. designing and evaluating an innovative solar air collector with transpired absorber and cover. renewable energy, 20(1): 1-5 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):172-186 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 172 original research article experimental validation of a best-fit model for predicting radio wave propagation through vegetation a. l. imoize*, e. m. otuokere, s. o. ajose and a. o. adegbenro department of electrical and electronics engineering, faculty of engineering, university of lagos, akoka-lagos, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: radiowave propagation measured pathloss vegetation environment ground reflection cost 235 model multi-scattering attenuation foliage-induced loss. abstract in this study, a model for predicting radio wave propagation through vegetation at 900 and 1800mhz is proposed. an integrated model comprising of ground and foliage induced effects is evaluated with respect to experimental data obtained through drive test in and around a vegetation environment, using test mobile system (tems) investigation tools. measured path loss was compared against predictions made by four empirical vegetation models. results indicate that the european cooperation in science and technology (cost) 235 model gives the best prediction and compare favourably with measured path loss in areas where vegetation is dominant. although, this model showed the most accurate prediction of foliage loss in the investigated area, there is a need to modify it for enhanced signal prediction. the modified model was found to predict the measured path loss with root mean square errors (rmses) of 6.98db and 10.00db at 900 and 1800mhz, respectively. overall, findings revealed that these rmses are within the acceptable range of up to 15.00db, for quality signal prediction in related environments © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the importance of vegetation in maintaining the stability of the ecosystem and conserving the ozone layer from further depletion cannot be overemphasized. however, when vegetation, such as a thick forest is located along the path of a radio signal, network performance is usually affected by strong multi-scattering attenuation, diffraction and absorption of propagating electromagnetic waves, and this imposes excess signal attenuation in addition to loss due to free space propagation (koh, et al., 1999; usman and adefalu, 2010; ndzi, et al., 2012). since actual vegetation environments are too complex to accurately describe, empirical models have been developed using results of experimental data obtained through drive test at various frequency bands for such environments. in the rain forest zone of nigeria, a vast part of the land is predominantly covered with dense vegetation, and radio wave attenuation would occur due to the presence of heavy foliage (rahman et al., 2013). in addition, busy highways for road travels are constructed through vegetation environments where travelers often experience poor quality of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 173 service, frequent call drops, and poor inter-connectivity (mishra, 2007; ajose and imoize, 2013). al salameh (2019) reported a recent study that is quite close to the results reported in this paper. the author presents a novel propagation model, which find a very useful application in the evaluation of fading characteristics of wireless communication signals in a forest environment. the model takes into account among other features, the rainfall and snowfall effects, and makes it easy to derive or estimate pathloss at varying frequencies in the vhf/uhf bands, which are currently in use by cognitive radios. in the study, the author modeled the vegetative environment such that it comprises of five distinct material layers; scrubs, soil, trunk of trees, small plants under the trees, foliage of trees, and free space, and the least square algorithm was adopted for the optimization of the model parameters. in order to validate the model, the author compared its performance characteristics with measured data taken in the jordanian environment, and the model was found to be in good agreement with real world measurement results. different from our work, this study did not consider the case where ground and foliage induced effects are included in the model for application in areas where vegetation is evergreen. propagation models are derived from experimental data for different areas under welldefined environmental conditions, and they are not globally applied to all environments due to varying terrain features from one environment to another (chebil, et al., 2013; ayekomilogbon, et al., 2013). in order to effectively apply models designed for a particular environment to another environment, the parameters of a well-established model could be fine-tuned to suit the environment of interest (adegoke and siddle, 2012; ndzi, et al., 2012; ibhaze et al., 2017). therefore, this study presents a model for predicting radio wave propagation through vegetation at 900 and 1800mhz in south western nigeria. field measurements were taken from selected base stations located in and around a vegetation terrain in the neighborhood of lagos and ondo states, nigeria, using test mobile system (tems) investigation tools and a global positioning system (gps) for accurate mobile location tracking. propagation measurements with forest depth included were compared against predictions made by the weissberger's modified exponential decay model (weissberger, 1982), radio-communication sector of international telecommunication union (itu-r) vegetation model (meng et al., 2009; ccir, 1986; itu, 2012), cost 235 model (hall, 1996), fitted itu-r (fitu-r) model (alnuaimi and stephens, 1998), each model combined with the plane earth (pe) model (li et al., 1999a). in order to determine the model, which best predicts the path loss of measured data in the investigated environment, the root mean square error (rmse) was applied, and a modification of the best-fit model is proposed. in practice, foliage medium can greatly influence the quality of the received signal, especially when the receiver is located in a dense forest area (al-nuaimi and stephens 1998; meng et al., 2009; meng et al., 2010). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 174 as the number of mobile users increases, network operators need to increase system capacity and this requires the location of transmission antennas at heights relatively higher than the surrounding trees and buildings (de jong and herben, 2004). notably, limited knowledge of pathloss modeling could pose great difficulties in implementing theoretical models, though these models can predict signal attenuation with reasonable accuracy. the empirical foliage loss models, which are derived from specific measurements data, rarely apply to all environments because of complex terrain features varying from one environment to another (rappaport, 2002; saunders and aragón-zavala, 2007; mishra, 2007; joshi, 2012; chebil et al., 2013; ayekomilogbon et al., 2013). therefore, the need for an appropriate model for predicting path loss especially for busy highways crossing dense vegetation terrain at 900 and 1800mhz becomes imperative. 1.1 problem statement there is currently a huge demand for propagation models for planning radio networks in forested environments, since it is quite difficult to avoid vegetation for most wireless outdoor channels, especially for military communications. however, radio wave propagation through dense foliage is unavoidably demanding and highly expensive due to the random characteristics of the channel. unfortunately, the behaviour of radio signals propagating through tropical vegetation has not been given adequate treatment in the available literature. different from existing reports (tharek and zahri, 1992; cavalcante et al., 1999; koh et al., 1999; blaunstein et al., 2003; meng et al., 2009; meng et al., 2010; al salameh, 2019), this paper focuses on characterizing a typical vegetation terrain, especially as it applies to a dense vegetation environment, with a view to determining the best fit propagation model for the environment. the specific objectives are to investigate the behaviour of radio waves in the vegetation environment via measurements campaign, compare measured pathloss with well-known empirical propagation models, select the best-fit empirical model, and demonstrate a modification of the best fit model for quality signal prediction in related vegetation environments. 1.2 types of propagation models propagation models are used mainly for network planning, more specifically for carrying out feasibility studies and during initial wireless network deployment (ajose and imoize, 2013). in addition, these models are key to performing interference studies and management of available radio resources, as mobile network deployment proceeds (sarkar et al., 2003). these models are broadly classified into three categories namely; deterministic, empirical and statistical models. 1.2.1 deterministic models these models utilize maxwell ’s equations alongside with reflection and diffraction laws. these models use detailed information from the environment to give near precise prediction of the desired radio signal. however, these models require very rigorous mathematical operations and they are often applied to simplified environments (joshi, 2012). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 175 1.2.2 empirical models unlike the deterministic models, the empirical models make use of a set of equations obtained from measurements campaign. the accuracy of these models is dependent on the location, frequency bands, range, and clutter characteristics of the environment (milanović et al., 2010). 1.2.3 statistical models these models rely on probability analysis by finding the probability density function as a function of various parameters. these models utilize measured and mean losses for different types of radio links, and are generally used for cellular network planning, estimating the coverage of mobile radio links, and planning for broadcast coverage (milanović et al., 2010). 1.3 propagation models used for comparison 1.3.1 free space propagation ideally, there is no obstacle in the path of radio wave propagation in free space. this implies a direct line of sight between the transmitter and the receiver, and this is very difficult to achieve in real life scenario. rappaport (2002) and saunders and aragónzavala (2007) give the free space propagation loss as in eq. (1). ��摨���� � ���� � ���th�� � � ���th���t� (1) where f = frequency (mhz) and d = distance (km) 1.3.2 weissberger’s modified exponential decay (med) model the modified exponential decay model as proposed by weissberger (1982) is given in eq. (2). �� �� � ����t������t ����� �� � �t� � ���� ����t������t � � �t � ��� (2) where lw = weissberger predicted loss; f = frequency in ghz; �t= depth of the trees in meters. 1.3.3 early international telecommunication union (itu) model the early itu model proposed by the international telecommunication union (itu) mainly for foliage attenuation (ccir, 1986; itu, 2012) is given in eq. (3). ���� �� � ����t����t ��� (3) where ���� (db) = early itu predicted loss, f = frequency in ghz and �t= depth of the trees in meters. 1.3.4 international telecommunication union radio (itu-r) model al-nuaimi and stephens (1998) presented a modified version of the itu-r model to cater for both in-leaf and out-of-leaf cases at 11.2ghz. raheemah et al., (2016) reported a further modification to the parametric equation for the itu-r model as given in eq. (4). ������ �� � ����t������� (4) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 176 1.3.5 cost 235 model the cost 235 model (cost 235, 1996) is a proceed of the cost project involving extensive field measurements in the millimeter wave frequencies. the measurements were carried out when the trees are in-leaf and out-of-leaf (phaiboon and seesaiprai, 2012). the model can be applied to frequencies between 200mhz to 95ghz. the parametric equations for this model are given in eq. (5). ��론摨� �� � ����t������� tݑ� � tt� ��݂t ����t�����݈����� �݊ � ��݂t (5) 1.3.6 fitted itu-r (fitu-r) model the foliage induced path loss can be represented by eq. (6). � �� � t�t��� (6) where a, f and d are variables of fitted values derived from field measurements. the three parameters a, b and c can be obtained using empirical methods, depending on the type of foliage, where b and c are the two parameters that show the frequency and distance dependence of the foliage induced excess loss in the specified model. alnuaimi and stephens (1998) earlier performed an optimization of these three parameters using the least square error fit for several sets of measured data to derive the fitted itu-r (fitu-r) model, and in a similar fashion, meng et al., (2009) extended the application of this model with validity at 11.2ghz to 20ghz as given eq. (7). ������� �� � ����t��������݈ tݑ� � tt� ��݂t ���݈t���݈����� �݊ � ��݂t (7) 1.3.7 plane earth model as compared to the through-vegetation loss models proposed by (tharek and zahri, 1992; cavalcante, et al., 1999; meng, et al., 2009) for radio wave propagation in forests, other propagating components such as ground reflected waves and lateral waves etc., are desirable as reported in (li, et al., 1999b; wang and sarabandi, 2007; michael, 2013). when the radio wave propagates near the ground, the plane earth (pe) model can better describe the path loss. the plane earth model includes the effect of ground reflection and it is modeled as given in eq. (8). ��� �� � ���th�� � � ���th�� �� � ���th������ (8) where d is the distance between the isotropic transmit and receive antennas in meters; �� and �� are transmit and receive antenna heights in meters, respectively. 1.4 pathloss and root mean square error 1.4.1 pathloss of measured data the path loss of measured data ������� is given by (rappaport, 2002; saunders and aragón-zavala, 2007; mishra, 2007) in eq. (9). measured path loss was obtained by substituting the computed values of the effective isotropically radiated power ����� ����� and the values of �� ��� into eq. (9). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 177 ������� � ����� � ������� (9) where ����� = effective isotropic radiated power (dbm) and ��= mean power received in dbm. the effective isotropic received power eirpt (dbm) is given in eq. (10). ����� � ���摨 � ���摨 � ��摨 � ��� � �t� � ��� (10) ���摨 = transmitter power (dbm), ���摨 = transmitter antenna gain (dbi), ��摨 = receiver antenna gain (dbi), ��� = feeder cable and connector loss (db), �t� = antenna body loss (db), ��� = combiner and filter loss (db). ���摨 � ��� ���th���� � ����� ���摨 � ����� � ��� � ����� � �������� ��摨 � ����� ��� � ���� �t� � ���� ��� � ����� substituting these values into eq. (9) gives; ����� � �� � ����� – � – � – ��� � ������� 1.4.2 root mean square error in order to determine the performances of the propagation models, the root mean square error (rmse) between the measured path loss and the predicted path loss was calculated using eq. (11). this error describes how good the propagation model matches the experimental data, and values of rmses closer to zero show a better fit (ajose and imoize, 2013; ibhaze et al., 2017; imoize et al., 2019). ��摨� � ��� � ��� � ���� � � � (11) where ������ = measured path loss (db), ������ = predicted path loss (db) and k = 20 (number of measured data points). 2.0 materials and method 2.1 investigated environments the typical vegetation environment where the measurements were carried out is located in the suburb of epe (geographical coordinates are latitude 6 ° 35' 0" north, and longitude 3° 59' 0" east) in lagos state and ore axis (geographical coordinates are 6° 43' 0" north, 4 ° 53' 0" east) of ondo state, and these areas are located in the southwest zone of nigeria. the terrain is a tropical region characterized by non-uniformly distributed trees of average height roughly 12m. a tarred road crosses the forest layer thereby creating a discontinuity of the vegetation and provides a mixed path environment as shown in figure 1. here, in-leaf vegetation is assumed since the environment of study is in the tropics and the forest is evergreen (de jong and herben, 2004). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 178 figure 1: a pictorial view of a drive section of the investigated environment showing a road crossing a natural vegetation 2.2 methodology this study adopted experimental approach, loss due to the presence of vegetation was obtained using test mobile system (tems) investigation tools installed on a personal computer, and the global positioning system (gps) receiver was used for accurate location tracking. the operating frequency is set from the computer and other readings such as transmitter-receiver distance, received signal level, and locations are viewed from the personal computer (imoize et al., 2019). measured data was compared with existing empirical models at 900 and 1800mhz, two frequency bands used by mobile operators in nigeria. the radio path was monitored at distances of 100m interval up to 2km from the fixed transmitter, and the comparison between the integrated model and the measured foliage loss was done using matlab, following the method reported in (ajose and imoize, 2013; imoize and oseni, 2019). 2.3 measurements procedure the experimental setup for the measurements campaign is presented in a companion report (imoize et al., 2019). further details of the equipment and measurements specifications are available in recent reports (imoize and adegbite, 2018; imoize and dosunmu, 2018; imoize and ogunfuwa, 2019). the test locations were concentrated mainly within a maximum propagation distance of 2 km from each base station, starting from a reference distance (do) of 100 m. over 2000 readings were recorded at 200 measurement locations from the base stations. each location measurement is an average of ten different readings taken at an interval of 60 seconds of various parameters including the received signal power in dbm. this was repeated for each of the ten base stations (bts1 bts10) with various heights of approximately 30-45m. field measurements were taken in the year 2017 and 2018, and measured data were taken at a mobile receiver height maintained close to 1.5 m. finally, measured data was extracted and analyzed in matlab, following the method in earlier reports (wang and sarabandi, 2007;meng et al., 2010; imoize and oseni, 2019). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 179 3.0 results and discussion 3.1 results the mean power received (dbm) from the vegetation environment for bts1 to bts10 at 900 and 1800mhz are as shown in figures 2 and 3, respectively. in addition, measured path loss was obtained by substituting the computed values of ����� ����� and the values of �� ��� into eq. (9). measured path loss at 900 and 1800mhz are as shown in figure 4. furthermore, the computed results showing the variations of predicted path loss with measured path loss plus additional ground reflection at 900 and 1800mhz are as shown in figures 5 and 6, respectively. in order to obtain the rmses between the measured and predicted pathloss, eqn. (11) is applied to the predicted models with and without the plane earth (pe) loss for the frequency bands, and the rmses obtained are as shown in table 1. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 -140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 distance between tx and rx (km) m e a n p o w e r r e c e iv e d (d b m ) mean power received (dbm) at 900mhz bts 1 bts 2 bts 3 bts 4 bts 5 bts 6 bts 7 bts 8 bts 9 bts 10 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 -140 -120 -100 -80 -60 -40 -20 distance between tx and rx (km) m e a n p o w e r r e c e iv e d (d b m ) mean power received (dbm) at 1800mhz bts1 bts2 bts3 bts4 bts5 bts6 bts7 bts8 bts9 bts10 figure 2: mean power received from bts1 to bts10 at 900mhz figure 3: mean power received from bts1 to bts10 at 1800mhz 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 100 110 120 130 140 150 160 170 180 190 distance between tx and rx (km) p a th l o s s (d b ) measured path loss (db) at 900 and 1800mhz pathloss at 900mhz pathloss at 1800mhz 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 50 100 150 200 250 distance between tx and rx (km) p r o p a g a ti o n p a th l o s s (d b ) measured and predicted pathloss at 900mhz measurement fsl pe wsbpe iturpe fiturpe cost235pe figure 4: measured path loss at 900mhz and 1800mhz figure 5: comparison of measured and predicted path loss at 900mhz file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 180 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 50 100 150 200 250 300 distance between tx and rx (km) p r o p a g a ti o n p a th l o s s (d b ) measured and predicted pathloss at 1800mhz measurement fsl pe wsbpe iturpe fiturpe cost235pe figure 6: comparison of measured and predicted path loss at 1800mhz table 1: root mean square errors for predicted models with and without integrated plane earth model at 900 and 1800mhz. root mean square error (rmse) in db path loss model 900mhz 1800mhz free space 66.96 60.83 weissberger wsb 81.19 66.50 wsbpe 17.11 30.72 itu-r 60.49 43.99 itu-rpe 34.54 57.88 fitu-r 125.77 116.21 fitu-rpe 42.44 33.25 cost235 69.25 69.88 cost235pe 15.20 15.89 3.1.1 modification of cost 235pe model from table 1, it is seen that the cost235pe model predicted the measured loss due to foliage with the greatest accuracy. however, the cost235pe model predicted the path loss with rmses of 15.20db at 900mhz and 15.89db at 1800mhz, which are relatively higher than the specified range of up to 15db (parson, 1992; blaunstein et al., 2003). therefore, there is a need for the modification of the cost235pe model for improved signal prediction. the modification of cost235pe is fundamental to this study since its initial development followed propagation measurements carried out in a different environment. the modification is achieved by subtracting the rmses obtained in table 1 from the calculated values for the cost235pe. the modified cost235pe denoted by cost235modifed is given in eqns. 12 and 13 for 900 and 1800mhz, respectively. the measured path loss, cost235pe model and the cost235modifed at 900 and 1800mhz are as shown in figs. 7 and 8. �론摨�����t��t��� � �론摨������ � ����� at 900mhz (12) �론摨�����t��t��� � �론摨������ � ����݈ at 1800mhz (13) where http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 181 �론摨������ �� � ��론摨���� �� � ������� (14) ��론摨�������� � �����t�����݈����� �݊ � ��݂t (15) ������� � ���th����� � ���th������ � ���th������ (16) at 900 and 1800mhz, we have eq. (17) and (18), respectively. �론摨�����t��t��� � ����� ����� � ���th�� � � � �݈�� (17) �론摨�����t��t��� � ����� ����� � ���th�� � � ����݈ (18) where d =0.1, 0.2… 2.0 km 3.1.2 validation of the modified model the root mean square error (rmse) was used to compute the error between the measured and the predicted path loss (imoize et al., 2019). this is obtained by applying eq. 11 to the calculated values of the measured and predicted path loss. the rmses between the measured and predicted path loss based on the cost235pe and the modified cost235pe models are as shown in table 2. from table 2, it is observed that the rmses for the cost235modifed are lower compared with the rmses for the cost235pe. here, lower values of rmses for the cost235modifed indicate improvements in the signal prediction capability of the model (ajose and imoize, 2013). for clarity, a comparison of the measured, predicted, and the modified pathloss models for the two frequency bands is as shown in figures 7 and 8, respectively, and it is seen that the modified models show better agreement with measured pathloss when compared with the original predicted model at the operating frequencies. table 2: rmses for cost235pe and cost235modifed root mean square errors (rmses) in db model 900mhz 1800mhz cost235pe 15.20 15.89 cost235modifed 6.98 10.0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 60 80 100 120 140 160 180 200 220 distance between tx and rx (km) p r o p a g a ti o n p a th l o s s (d b ) modification of cost 235 model at 900mhz measurement cost 235 modified cost 235 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 60 80 100 120 140 160 180 200 220 distance between tx and rx (km) p r o p a g a ti o n p a th l o s s (d b ) modification of cost235 model at 1800mhz measurement cost 235 model modified cost 235 model figure 7: measured path loss, cost235pe model and cost235modified model at 900mhz figure 8: measured path loss, cost235pe model and cost235modified model at 1800mhz file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 182 3.2 discussion of results as shown in figures 2 and 3, it is observed that the mean received signal level decreases with an increase in the transmitter to receiver distance. this is in agreement with practical design of antennas revealing poor reception as the mobile receiver is farther away from the fixed transmitter (rappaport, 2002). as seen in figure 4, the pathloss increases as the propagation distance between the transmitter and receiver increases. this is in line with the results reported in related works (li et al., 1999a; li et al., 1999b; wang and sarabandi, 2007; al salameh, 2019). the measured pathloss at 900 and 1800mhz show a relatively close agreement from 1.2 to 1.6km, and the widest departure is seen at 0.1 and 0.4km from the transmitter. this explains the fact that pathloss varies with the frequency of transmission of radio waves from the transmitter to the receiver. as shown in figures 5 and 6, the predicted pathloss and the measured pathloss show an increase in pathloss as the antenna separation distance increases. however, some models were seen to overestimate or over-predict the measured pathloss. as presented in table 1, the predicted models without the additional plane earth loss tend to overshoot the pathloss of measured data with very high rmses at both frequencies. however, when the plane earth loss was introduced to the actual empirical model, the rmses reduce appreciably. overall, the cost 235 model with plane earth loss (cost235pe) was observed to be the most accurate. propagation measurements at 900 and 1800mhz have been compared using some wellknown vegetation models, and taking into consideration both the foliage induced losses and the loss due to ground reflection. the comparison showed that the integration of the plane earth model into the empirical vegetation models significantly reduces the rmses and improves how the propagation model matches the measured pathloss. in addition, the wsbpe, itu-rpe and fitu-rpe models show high values of rmses at 900mhz with 17.11db, 34.54db and 42.44db, respectively. similarly, these models show rmses of 30.72db, 57.88db and 33.25db, respectively, at 1800mhz. the cost235pe model with ground reflection showed the best performance at the 900 and 1800mhz frequency bands with rmses of 15.20db and 15.89db, respectively. therefore, the cost235pe model was selected as the best among the contenders, for better signal prediction at the tested frequency bands. however, rmses of 15.20db and 15.89db comparatively overshoot the accepted range of up to 15db, thus the need to modify the cost235pe model for improved performance. furthermore, table 2 shows the rmses for the predicted and the modified cost 235 model with additional plane earth loss. the rmse is seen to reduce sharply from 15.20db for the cost235pe model to 6.98db for the cost235modified model at 900mhz, and fall appreciably from 15.89db for the cost235pe model to 10.0db for the cost235modified model at 1800mhz as illustrated in figures 7 and 8. as seen in figure 7, the modified cost 235 model is in close agreement with the measured data at 900mhz, except at 0.1km where there is an obvious variation of about 22db. also, the existing cost 235 appears to align closely with the measured pathloss up to around 0.4km from the transmitter. after 0.4km from the transmitting station, the modified cost 235 shows http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 183 appreciable agreement with measurements results up to 2km, except at 1.2km, where a little deviation is observed. as depicted in figure 8, there is a sharp deviation of the modified cost 235 from the measured data at 0.1km. however, this trend decreases gradually till 0.8km, but the cost 235 shows better agreement with the measured data at 0.1km, and afterwards, deviates sharply with the most deviation observed at 2km. this implies that the modified model has shown better prediction of foliage loss due to dominant vegetation in the investigated environment. 4.0 conclusion this study has presented a model for predicting radio waves propagation through vegetation at 900 and 1800mhz. the performances of four empirical models were analyzed with respect to experimental data obtained through drive test, using tems investigation tools, and the most accurate model for the investigated environment was determined, using the root mean square error. for improved signal prediction, this model was fine-tuned, and the modified model was found to predict the measured path loss with greater accuracy at the operating frequency bands. finally, the evolved model showed characteristics, which bear direct relevance to radio waves propagation through foliage, and could give very useful information to enhance accurate design of link budget for related environments. further work would focus on improving on the prediction accuracy of the wsbpe, itu-rpe and the fitu-rpe models. acknowledgement the authors thank the university of lagos and huawei technologies limited for support during measurements campaign. references adegoke, as. and siddle, d. 2012. investigation into vegetation effects on propagating radio waves. in proceedings of the conference on applied radio systems research and smart wireless communications for postgraduates and early stage researchers (arsr-swicom'12), manchester, united kingdom, may 2012: 1-4. ajose, so. and imoize, al. 2013. propagation measurements and modelling at 1800 mhz in lagos nigeria. international journal of wireless and mobile computing, 6(2): 165-174. al-nuaimi, mo. and stephens, rbl. 1998. measurements and prediction model optimisation for signal attenuation in vegetation media at centimetre wave frequencies. iee proceedingsmicrowaves, antennas and propagation, 145(3): 201-206. al salameh, msh. 2019. an optimized five-layer model with rainfall effects for wireless propagation in forests. in: kumar a. and mozar s. (eds.). international conference on communications and cyber physical engineering (iccce). lecture notes in electrical engineering, springer, singapore, 500: 115-123. ayekomilogbon, ot., famoriji, jo. and olasoji, yo. 2013. evaluation and modeling of uhf radio wave propagation in a forested environment. international journal of engineering and innovative technology, 2(12): 101-106. blaunstein, n., censor, d., katz, d., freedman, a. and matityahu, i. 2003. radio propagation in rural residential areas with vegetation. progress in electromagnetics research, pier 40: 131-153. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 184 cavalcante, g.p., sanches, m.a. and oliveira, r.a. 1999. mobile radio propagation along mixed paths in forest environment. in ieee international microwave and optoelectronics conference, 1999. sbmo/ieee mtt-s, aps and leos-imoc'99, 1: 320-324. chebil, j., lawas, a.k. and islam, m.d. 2013. comparison between measured and predicted path loss for mobile communication in malaysia. world applied sciences journal, 21: 123-128. hall, m. 1996. radio wave propagation effects on next-generation fixed-services terrestrial telecommunication systems. european cooperation in science and technology (cost), technical report, information and communication (ict) cost action, 235. de jong, yl. and herben, mh. 2004. a tree-scattering model for improved propagation prediction in urban microcells. ieee transactions on vehicular technology, 53(2): 503-513. ibhaze, ae., imoize, al., ajose, so., john, sn., ndujiuba, cu. and idachaba, fe. 2017. an empirical propagation model for path loss prediction at 2100mhz in a dense urban environment. indian journal of science and technology, 10(5): 1-9. imoize, al. and adegbite, od. 2018. measurements-based performance analysis of a 4g lte network in and around shopping malls and campus environments in lagos nigeria. arid zone journal of engineering, technology and environment, 14(2): 208-225. imoize, al., ibhaze, ae., nwosu, po. and ajose, so. 2019. determination of best-fit propagation models for pathloss prediction of a 4g lte network in suburban and urban areas of lagos, nigeria, west indian journal of engineering, 41(2): 13-21. imoize, al. and dosunmu, ai. 2018. path loss characterization of long term evolution network for lagos, nigeria, jordan journal of electrical engineering, 4(2): 114-128. imoize, al. and ogunfuwa, te. 2019. propagation measurements of a 4g lte network in lagoon environment. nigerian journal of technological development, 16(1): 1-9. imoize, al. and oseni, ai. 2019. investigation and pathloss modeling of fourth generation long term evolution network along major highways in lagos nigeria. ife journal of science, 21(1): 39-60. international radio consultative committee (ccir), 1986. influences of terrain irregularities and vegetation on troposphere propagation, ccir report 235-236, geneva, switzerland. international telecommunication union (itu), 2012. attenuation in vegetation, itu-r recommendation 833-7, geneva, switzerland. joshi, s. 2012. outdoor propagation models a literature review. international journal on computer science and engineering, 4(2): 281-291. koh, jh., li, lw., kooi, ps., yeo, ts. and leong, ms. 1999. dominant lateral waves in the canopy layer of a four‐layered forest. radio science, 34(3): 681-691. li, lw., koh, jh., yeo, ts., leong, ms. and kooi, ps. 1999a. analysis of radiowave propagation in a four-layered anisotropic forest environment. ieee transactions on geoscience and remote sensing, 37(4): 1967-1979. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 185 li, lw., yeo, ts., kooi, ps., leong, ms. and koh, jh. 1999b. analysis of electromagnetic wave propagation in forest environment along multiple paths. progress in electromagnetics research, 23: 137-164. meng, ys., lee, yh. and ng, bc. 2009. empirical near ground path loss modeling in a forest at vhf and uhf bands. ieee transactions on antennas and propagation, 57(5): 1461-1468. meng, ys., lee, yh. and ng, bc. 2010. path loss modeling for near-ground vhf radio-wave propagation through forests with tree-canopy reflection effect. progress in electromagnetics research, 12: 131-141. michael, ao. 2013. further investigation into vhf radio wave propagation loss over long forest channel. international journal of advanced research in electrical, electronics and instrumentation engineering, 2(1); 705-710. milanović, j., rimac-drlje, s. and majerski, i. 2010. radio wave propagation mechanisms and empirical models for fixed wireless access systems. tehnički vjesnik, 17(1): 43-53. mishra, ar. 2007. advanced cellular network planning and optimisation: 2g/2.5 g/3g... evolution to 4g. john wiley & sons, england. ndzi, d., kamarudin, l., mohammad, e., zakaria, a., ahmad, r., fareq, m., shakaff, a. and jafaar, m. 2012. vegetation attenuation measurements and modeling in plantations for wireless sensor network planning. progress in electromagnetics research b, 36: 283-301. parson, j. d. 1992. mobile radio propagation channel, wiley, west sussex, england. phaiboon, s. and seesaiprai, s. 2012. path loss through pine forest around beach for wireless sea-wave energy sensor network. in advanced materials research, trans tech publications, 433: 3954-3958. raheemah, a., sabri, n., salim, ms., ehkan, p. and ahmad, rb. 2016. new empirical path loss model for wireless sensor networks in mango greenhouses. computers and electronics in agriculture, 127: 553-560. rahman, nza., tan, kg., omer, a., rahman, ta. and reza, aw. 2013. radio propagation studies at 5.8 ghz for point-to-multipoint applications incorporating vegetation effect. wireless personal communications, 72(1): 709-728. rappaport, ts. 2002. wireless communication: principles and practice, 2nd edition, prentice hall, upper saddle river, nj, usa. sarkar, tk., ji, z., kim, k., medouri, a. and salazar-palma, m. 2003. a survey of various propagation models for mobile communication. ieee antennas and propagation magazine, 45(3): 51-82. saunders, s. and aragón-zavala, a. 2007. antennas and propagation for wireless communication systems. 2nd edition, john wiley & sons, england. tharek, ar. and zahri, y. 1992. radio wave propagation studies through tropical vegetation in malaysia at vhf. in proceedings of the international symposium on antennas and propagation, japan institute of electronics, information and communication engineers, 34: 897-897. usman, ba. and adefalu, ll. 2010. nigerian forestry, wildlife and protected areas: status report. biodiversity, 11(3-4): 54-62. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng imoize, et al: experimental validation of a best-fit model for predicting radio wave propagation through vegetation. azojete, 15(sp.i2):172-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimoize@unilag.edu.ng 186 wang, f. and sarabandi, k. 2007. a physics-based statistical model for wave propagation through foliage. ieee transactions on antennas and propagation, 55(3): 958-968. weissberger, ma. 1982. an initial critical summary of models for predicting the attenuation of radio waves by trees. esd-tr-81-101, electromagnetic compatibility analysis center, annapolis, maryland usa, final report 833-7 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):1-16 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 1 original research article gps anti-jamming technique using smart antenna systems g.c. akobundu1, and a.o. gbenga-ilori2* (1 nigerian airspace management agency, lagos, nigeria 2 department of electrical and electronics engineering, university of lagos, lagos, nigeria) *corresponding author’s e-mail address: gbengailori@unilag.edu.ng article information submitted 11 april, 2018 revised 26 july, 2018 accepted 30 july, 2018 keywords: array antennas cma doa esprit lms music beamforming abstract this paper presents a global positioning system (gps) anti-jamming technique using a smart antenna system. in anti-jamming systems, adaptive array antennas are used to estimate the direction of signals arriving at the antenna and spatially filter the desired signal from the unwanted signals by adaptively controlling the direction of the maximum radiated beam. in this study, the uniform linear array was used for the smart antenna configuration. the work compared the performance of non-blind adaptive algorithms with blind algorithms for adaptive beamforming. non-blind adaptive algorithm using least mean square (lms) algorithm and blind algorithm using constant modulus algorithm (cma) was studied and implemented for adaptive beamforming while estimation of signal parameters via rotational invariance technique (esprit) and multiple signal classification (music) algorithms were implemented for the direction of arrival (doa) estimation. the effect of varying the number of elements in the antenna array and the required spacing between them was also investigated. results of comparison carried out using numerical analysis showed that both algorithms performed well for the doa estimation, with music algorithm producing a better direction of arrival spectrum with little or no minor peaks. for the beamforming, both lms and cma produced maximum radiation in the direction of the desired signal. lms placed deeper nulls in the directions of interference with faster convergence and fewer errors as compared with cma that presented errors and was able to suppress the interference to a minimal extent. it was also shown that as the number of elements in the array increases, a more directive beam and doa spectrum is produced. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the global positioning system (gps) offers satellite navigation services that are widely used in aviation and military applications. the accuracy of received gps signal and jamming prevention issues are of utmost importance in designing gps systems due to its areas of critical applications. it is important to design gps systems with efficient anti-jamming capabilities so as to protect the accuracy of received data. gps is particularly vulnerable to jamming because the receivers are extremely sensitive in order to receive the extremely weak signals from orbiting satellites (esmaeilkhah and lavasani, 2018; lang et al., 2017; mukhopadhyay et al., 2007). when the jamming signals and the desired signal share the same frequency, the conventional filtering techniques become inefficient in eliminating jammers. this has led to the study of file:///c:/users/i3/downloads/gbengailori@unilag.edu.ng http://www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 2 various anti-jamming techniques using adaptive antenna system with direction-of-arrival (doa) estimation and adaptive beamforming algorithms. these smart antenna systems are made up of an array of antenna elements with digital signal processors (dsp) to implement the adaptive signal processing. the objective is to estimate the direction of arrival of all impinging signals and adjust the antenna weights to ideally steer the maximum radiation of the antenna pattern toward the desired signal and to place nulls toward the interfering signals. therefore, adaptive antenna systems combine multiple antenna elements with a signal processing capability to optimize its radiation and reception pattern automatically in response to the signal environment (joshi and dhande, 2014). in a smart antenna system, the optimum weights of each antenna elements are iteratively determined using algorithms based upon different criteria to give a maximum gain in the direction of the source signal and placing the null in the direction of the interference signal (shivapanchakshari and aravinda, 2017; shahab et al., 2017). these algorithms can be categorized into two classes depending on whether a training signal is used or not. one class of these algorithms is the non-blind adaptive algorithm in which a training signal is used to adjust the array weight vector (joshi and dhande, 2014; ali et al., 2011). another technique is to use blind adaptive algorithms that do not require a training signal (rao and sarma, 2014; elkassimi et al., 2017; udawat et al., 2011). a lot of work has been done on the implementation of anti-jamming systems using non-blind adaptive beamforming algorithms. joshi and dhande (2014) used least mean square (lms) algorithm for adaptive beamforming. they evaluated the effect of the lms algorithm on its beamforming capability using normalized array factor and the convergence of its mean square error (mse). the effect of varying the number of antenna elements and the distance between array elements on the array factor and mse was also evaluated. ali et al. (2011) authors worked on adaptive beamforming algorithms for anti-jamming. they studied and compared the performance of three beamforming algorithms; lms, optimized-lms and recursive least square (rls) algorithms and concluded that rls algorithm had the best performance as it provided deeper nulls in the direction of the signal not of interest (snoi) and faster convergence. a few others considered blind adaptive algorithms. rao and sarma (2014) analyzed and compared the beamforming capabilities of lms, normalized lms, constant modulus algorithm (cma), and rls for smart antenna application using three different antenna array geometries; linear, circular and planar geometries. extensive comparison was done using these algorithms and geometries. they also compared the beamforming of lms and nlms algorithms using different inter-element spacing and number of elements in the array and concluded that as the number of elements increased, the algorithms converged faster. though an extensive analysis was done for various beamforming algorithms, implementation of complete beamforming system involving direction of arrival estimation was not considered. elkassimi et al. (2017) proposed the use of algorithm based on zero-forcing (zf) and minimum mean square error (mmse) methods for blind channel equalization. they compared performance of this algorithm with other adaptive filter algorithms like cma, fractional space cma (fscma) and sign kurtosis maximization adaptive algorithm (skmaa). udawat et al. (2011), the convergence characteristics of blind beam-forming algorithm known as least square constant modulus algorithm (lscma) were analyzed. the algorithm was used with smart antenna systems (sas) for improving the performance of a wireless communication system by optimizing the radiation pattern according to the signal environment. kundu and ghosh (2008) demonstrated http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 3 an implementation of real-time adaptive beamforming for code division multiple access 2000 (cdma2000) reverse link using digital signal processing technique. simulation was performed for uniform linear array (ula) of several elements and they found that algorithm computation time and accuracy of beam pattern direction were proportional to the number of antenna elements. doa estimation is also a key research area in adaptive array antenna systems. beulah and vigneshwani (2014), focused on the design of a smart antenna system based on multiple signal classification (music) doa estimation algorithm, and adaptive beamforming using lms. array pattern synthesis was achieved using the dolph-chebyshev method which is popularly used for obtaining the weights and current excitation for uniformly spaced linear arrays steered to broadside. this method produced array pattern with side lobes of equal magnitude and made use of a class of polynomials called chebyshev polynomials. mukhopadhyay et al., (2007) proposed a new simple doa estimation method based on the mechanical rotation of an array plane by small angles. in this method, the frequencies of the signals impinging on the array must be known. by taking the ratio of these frequencies before and after rotation of the array plane and comparing with ratio of the cosine function of the angle of arrival (aoa) before and after rotation, a simple trigonometric equation was obtained for doa estimation. simulations showed that the estimated doas and frequencies matched with actual values. the authors also showed that adaptive beamforming using lms algorithm can be used to constructively receive signal with multipath interference. very few papers addressed anti-jamming techniques for gps receivers. in zhang and amin (2012), authors proposed a novel array-based anti-jamming gps receiver that enables effective jammer suppression with negligible phase distortion. they pointed out that one of the major problems with existing blind anti-jamming array signal processing technique is that they introduce errors in the carrier phase, and developed a technique that achieves gps signal phase continuity by using accurate estimation of phase rotated steering vector of the gps signal. in chi (2016), the authors proposed an anti-jamming measurement method based on antenna array. this method uses array antenna to estimate the direction of arrival of jamming signal through music algorithm. the adaptive nulling algorithm based on the linear constrained minimum variance algorithm is used to eliminate the jamming signals and hold the navigation signal. according to the above papers, non-blind adaptive algorithms require prior information like the reference signal and direction of arrival (doa) of the signal and may not be suitable for gps systems. in this paper, the performance of non-blind adaptive algorithm using lms algorithm and blind algorithm using cma algorithm is studied and implemented for adaptive beamforming while the estimation of signal parameters via rotational invariance technique (esprit) and music algorithms have been implemented for doa estimation purposes. the purpose is to compare these known techniques and determine the most suitable for an antijamming system in gps receivers. 2. materials and methods 2.1. gps signal generation gps signal generation is achieved by modulating a carrier frequency with pseudorandom noise (prn) codes. the precision code (p-code) and coarse acquisition (c/a) code are used for gps and two carrier frequencies which are the l1 that contains both codes and the l2 carrier that is modulated with only the p-code exist. this paper focused on the l1 signal generation. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 4 figure 1: block diagram of gps l1 signal generation (saab, 2012) figure 1 shows the functional block diagram describing the gps signal generation. the system is driven by a 10.23mhz clock signal producing a pure sine wave. multiplying this clock frequency by 154 gives the l1 carrier frequency (1.57542 ghz). the clock frequency is stabilized to 1.023mhz, which is the chipping rate of the c/a code and applied as the clock signal for c/a code generation. the p-code is generated at the clock frequency. after code generation, the codes are combined with the navigation data with a data rate of 50bps through modulo-2 adders. this is accomplished through an xor operation. the results of the modulo-2 addition of the c/a code and the navigation data with the modulo2 addition of the p-code and the navigational data are supplied to the bpsk modulators (borre et al., 2012). the system uses two modulators to achieve an in-phase and quadrature modulation of the codes, therefore the output of the modulators is two components of the l1 signal with a 90° phase shift between them. the outputs from the two modulators are then summed together to form the resulting l1 signal. 2.2 interference signals generation the interference signals used in the simulation was generated using a random process. an excerpt is given below showing the process and the matlab code used. from the extract, random numbers were generated for the number of interfering signals, isize. these random numbers were used to form a matrix of the same size as the gps signal, data. this is for easy addition and other matrix operation. the generated signal is assigned a steering vector and combined with the gps signal using an awgn channel to form the received signal. %% generate interferer signal idata = []; for i=1:isize id = randn(1, length(data)); idata = [idata; id]; end http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 5 2.3 gps receiver system implementation the functional block diagram of the system implementation is shown in figure 2. it shows that the system locates the desired signal using the direction-of-arrival (doa) algorithm, and continuously tracks it by adaptively adjusting the weights of the elements. figure 2: the functional block diagram of the system implementation (moghaddam et al., 2011) by using a cost function, the adaptive algorithm computes the appropriate weights that result in an optimum radiation pattern. the next subsections will consider in details the steps needed to implement the algorithms used in the functional blocks. 2.3.1 doa estimation using music music algorithm is one of the angles of arrival (aoa) estimation method used in this paper. it is a subspace-based method and relies on the following properties; the space spanned by the correlation matrix eigenvectors may be partitioned into two subspaces; the signal subspace and the noise subspace. the noise subspace is spanned by the eigenvectors associated with smaller eigenvalues of the correlation matrix, and the signal subspace is spanned by the eigenvectors associated with the large eigenvalues of the matrix the steering vectors corresponding to the directional sources are orthogonal to the noise subspace. therefore the product of the array steering vector and the noise subspace is null (zero) for a particular angle of arrival (aoa). the process has been extensively studied in previous literature (kintz and gupta, 2016; sit et al., 2012; huang et al., 2005) and is summarized in the algorithm described in algorithm 1. algorithm 1: music algorithm input: received gps signal and interference signals. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 6 output: direction of arrival (doa) of the signals. procedure: 1. collect input samples x tk , k = 1,2,⋯,k and estimate the input covariance matrix; rxx ≈ 1 k k=1 k x tk xh tk = 1 k xxh ,� where k is the number of snapshots. 2. perform eigen decomposition on rxx. rxxv = vλ, where λ = diag{λ1, λ2,⋯,λn} , and λ1 ≥ λ2 ≥ … ≥ λn are the eigenvalues and v contains all the corresponding eigenvectors of rxx. 3. sort the eigenvalues of rxx. for n number of antenna elements and m number of signals, the n− m eigenvalues of rxx correspond to the smallest eigenvalues. λ1 ≥ λ2 ≥ … ≥ λm ≥ λm+1 ≥ ⋯ ≥ λn. 4. form a matrix vn containing the eigenvectors corresponding to the smallest eigenvalues of rxx to obtain the noise subspace. vn = [qm+1,⋯,qn], where qi, for all i = m + 1, m+ 2,⋯,n , are the eigenvectors corresponding to the smallest eigenvalue λmin. 5. compute the music spectrum as; pmusic θ = 1 ah θ vnvnha(θ) where a(θ) is the steering vector corresponding to the doa. 6. find the � largest peaks of the music spectrum, ��ܷ�ܵ�(�), to obtain doa estimates. 2.3.2 doa estimation using esprit the steps to implement esprit algorithm which has been extensively studied in previous literature (pradhan and bera, 2015; qian et al., 2014; gao and gershman, 2005) is summarized in algorithm 2. algorithm 2: esprit algorithm input: correlation matrix of the received signal at the array. output: direction of arrival (doa) of the signals. procedure: 1. estimate the array correlation matrices ryy and rzz from the data samples from two identical sub arrays. perform eigen decomposition and find their eigenvalues and eigenvectors. for example, the eigen decomposition of ryy gives; ryy = vλv, where λ = diag{λ1, λ2, ⋯,λn} and v = {q1, q2,⋯,qn} are the eigenvalues and eigenvectors of ryy. 2. form two matrices uy and uz with their columns being the m eigenvectors associated with the largest eigenvalues of each correlation matrix. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 7 for a ula, this is achieved by first forming a n ×m matrix u which its columns are the m eigenvectors associated with the largest eigenvalues of the estimated array correlation matrix rxx of the full array of n elements. then select the first l < n rows of u to form uy and the last of its l rows to form uz. 3. form a 2m × 2m matrix c and perform its eigen decomposition; c = uyh uzh uy uz , c = vcλvch , where λ = diag{λ1, λ2,⋯,λ2m} with λ1 ≥ λ2 ≥ … ≥ λ2m are the eigenvalues of c while vc contains the eigenvectors corresponding to the eigenvalues. 4. partition vc into four matrices of dimension m×m as follows; vc = v11 v12 v21 v22 5. calculate the eigenvalues λm, m = 1,⋯⋯,m, of the matrix −v11v22 −1. 6. estimate the angle of arrival θm using; θm = sin−1 arg(λm) 2π∆0 , m = 1,2, ……, m ____________________________________________________________________________ 3. beamforming methods 3.1 beamforming using lms one of the adaptive algorithms that will be used to optimize the weights of the array elements for adaptive beamforming is the lms algorithm. figure 2 shows the output of the system y(n)and it is given by; y n = wh n x n . (1) the error between the desired signal d(n) and system output y(n) is given as; e n = d n − y n . (2) the lms weight update equation is given by; w n+ 1 = w n + μ − ∇�j n , (3) where μ is the step size parameter which controls the speed of convergence and lies between 0 and 1.∇�j(n) denotes the instantaneous estimate of the gradient which is given as; ∇� � � = �� ��� = �� ��0 �� ��1 � �� ��� . (4) the gradient estimate can simply be obtained by taking the error value for a single input pattern, squaring it and differentiating with respect to weight w. ∇�j n = ∂e2 n ∂w n = ∂e2 n ∂e n ∙ ∂e n ∂w n , (5) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 8 = 2e n ∙ ∂ d n −wh n x n ∂w n (6) since e n = d n −wh(n)x(n), ∴ ∇�j n = − 2e n x n . (7) putting equation (7) into equation (3), the weight update equation is given by; w n+ 1 = w n + 2μx n e∗ n . (8) therefore, the lms algorithm can be described by the three equations as given below; y n =wh(n)x(n) e n =d n −y(n) w n+1 =w n +2μx n e∗(n) (9) the logical flowchart for its implementation is shown in figure 3. 3.2 beamforming using cma constant modulus algorithm is another method used in this study to adjust the weights of the array elements to an optimal value for adaptive beamforming. cm algorithm implementation is similar to lms but differs in its error signal computation since it is a blind method and does not require any reference signal for its operation. the flowchart for its implementation is shown in figure 4. the cost function to be minimized is given as; j w = e w n hx n − 1 2 = e y(n) − 1 2 . (10) taking the gradient of the above cost function yields; ∇j w = ∂j(w) ∂w = e ∂ ∂w y n − 1 2 , (11) and if u = y n − 1 , then ∇j w = e ∂u2 ∂w = e ∂u2 ∂u ∙ ∂u ∂w (12) = e 2u ∙ ∂(y(n)y ∗(n)) 1 2 ∂w = e 2u ∙ ∂(w n hx(n)x n hw(n)) 1 2 ∂w (13) if w n hx n x n hw n = v, then ∇j w = e 2u ∙ ∂v 1 2 ∂w = e 2u ∙ ∂v 1 2 ∂v ∙ ∂v ∂w (14) = e 2u ∙ v −1 2 2 ∙ x n x n hw(n) = e 2( y n − 1) ∙ y n x(n) 2|y(n)| (15) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 9 figure 3: flowchart of lms algorithm figure 4: flowchart of cm algorithm implementation. implementation. removing the expectation parameter gives the instantaneous gradient value as; ∇j w = y n − y n y n x n (16) equation (16) can then be used to replace the gradient term in the traditional lms weight update algorithm of equation(3) to yield; w n+ 1 = w n − μx n y n − y n y n (17) this is similar to lms but with update error, e, expressed as; e n = y n − y n y n (18) therefore the cma can be described by the three equations set given below; y n = wh(n)x(n e n = y n − y(n) |y(n)| w n+ 1 = w n − μx n e∗(n) (19) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 10 4. results and discussions in this paper, for the simulation, it is assumed that the desired gps signal impinging on a uniform linear array of eight elements arrives at an angle of 0° and will be estimated using the doa algorithms. in addition, there are two interference signals arriving at angles of 50° and − 60°. both lms and cma are used for beamforming. table1 gives a complete list of parameters used for the simulation and their respective values. table 1: simulation parameters parameter value desired signal angle 0° interference signal angles 50° and − 60° signal to noise ratio (snr) 25db lms step-size parameter 0.005 cma step-size parameter 0.00005 number of array elements 8 inter-element spacing 0.5λ figure 5 shows the music and esprit spectrum of the estimated angles of arrival of both the desired and interference signals. from the figures, it can be seen that both doa algorithms gave an accurate estimate of the directions of arrival. since both doa algorithms were able to estimate the correct angles of arrival, only one of the algorithms was used for other results as they produced a similar response. the plots of figure 6 show the radiation pattern and amplitude response of the array output in the simulations. from the plots, it can be seen that both beamforming algorithms used were able to give maximum radiation in the direction of the desired gps signal ( 0° ). in terms of placing nulls in the directions of interference, lms algorithm had the best response by placing deeper nulls in these directions (50° and − 60°) whereas cm algorithm had a shallow null at 50° and couldn’t place a null at − 60° though a minor side lobe was formed. this is because cma is less stable and presented some errors during implementation and as shown in subsequent results. the figure shows that the algorithms achieved the goal of the system by placing maximum radiation in the direction of the desired signal. the plots of figure 6 shows the radiation pattern and amplitude response of the array output in the simulations. from the plots, it can be seen that both beamforming algorithms used were able to give maximum radiation in the direction of desired gps signal (0° ). in terms of placing nulls in the directions of interference, lms algorithm had the best response by placing deeper nulls in these directions (50° and − 60° ) whereas cm algorithm had a shallow null at 50° and couldn’t place a null at − 60° though a minor side lobe was formed. this is because cma is less stable and presented some errors during implementation and as shown in subsequent results. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 11 the figure shows that the algorithms achieved the goal of the system by placing maximum radiation in the direction of the desired signal. -100 -50 0 50 100 150 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 angle |p ( )| -100 -50 0 50 100 150 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 angle |p ( )| (a) (b) figure 5: (a) music spectrum of estimated angles of arrival of the signals (b) equivalent esprit spectrum. (a) (b) figure 6: (a) radiation pattern of the system after beamforming (b) polar representation figure 7 depicts the mean square error (mse) plot or convergence plot for the cma and lms algorithm respectively. it was observed that the lms algorithm converged to a near-zero value before 100 iterations whereas implementing the system with cma presented lots of errors. it was also observed that the cma attempted to converge at some point, but due to the discrete nature of the desired signal as shown later, erroneous results were obtained while tracking of the amplitude levels is done. figure 8 shows the acquisition and tracking curve of the system. it can be seen that the system is excellent in tracking the reference signal when the lms algorithm is implemented and there is no delay in the output of the system to align perfectly with the reference signal. on the other hand, it was difficult for the output of the system to track and align to the reference signal when the cm algorithm is implemented. finally, a phase comparison of the system output and the reference signal as shown in figure 9 indicates that there is no much difference between the two when either of the algorithms is used. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 12 0 100 200 300 400 500 600 700 800 0 0.5 1 1.5 simulation iteration m ea n sq ua re e rr or mean square error convergence curve lms cma 0 100 200 300 400 500 600 700 800 0 1 2 3 4 5 6 m ag ni tu de samples magnitude comparison of reference and output lms cma ref figure 7: mse convergence of both figure 8: tracking and acquisition lms and cm algorithm curve of the system 0 100 200 300 400 500 600 700 800 -300 -250 -200 -150 -100 -50 0 ph as e( ra d) samples phase comparison of reference and output lms cma ref figure 9: phase comparison of the system output and the reference signal 4.1 effect of array elements spacing on beamforming for this part of the simulation, it is assumed that the desired signal impinges on the ula of eight elements at an angle of 10° , and also a single interference signal arrives at angle 40°. figure 10 shows the effect of the antenna array elements separation distance on the radiation pattern. it shows that the inter-element spacing is an important factor to be considered in the design of an antenna array system. figure 10 (a) shows that when the inter-element spacing is greater than λ 2, especially when it is greater than or equal to a wavelength (λ), grating lobes appear (at − 55° from the plot) which degrades system performance. grating lobes are unintended maximum radiation in other directions other than the desired direction and occur when array element separation is too large. therefore, to avoid this, the element separation should not be equal to multiples of a wavelength (d ≠ nλ, n = 1, 2, 3, ⋯). furthermore, figure 10 (b) shows that when elements are spaced closely (typically less than λ 2), mutual coupling effect occurs. this is a situation whereby the radiation characteristics of an excited array element are influenced by the presence of the others. this usually causes the maximum and nulls of the radiation pattern to shift thereby causing the doa and beamforming algorithms to produce inaccurate results. therefore, in other to produce the desired radiation pattern, the elements have to be far enough to avoid mutual coupling, and the spacing should not be too large to avoid grating lobes. for all practical applications, a spacing of λ 2 is recommended. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 13 (a) (b) figure 10: effect of inter-element spacing on beamforming (a) d = λ, (b) d = λ 8 4.2.2 effect of the number of array elements on beamforming in this performance study, the step size of both the lms and cm algorithms were adjusted to 0.00005 and 0.000005 respectively to ensure the system produced a good response. the angle of arrival of the desired signal was maintained at 10°, and that of the interference at 40°. from figure 11 and also comparing with figure 6 where the number of elementsn is eight, it is observed that as the number of elements in the array increases, the directivity of the array radiated output increases with multiple side lobes of narrow beamwidth and low power levels. this shows that a more directive radiation can be achieved by increasing the number of array elements. in figure 12, the number of elementsn is varied between 8, 20 and 50, and it was observed that as the number of elements in the array increases, estimated doa spectral beamwidth becomes narrower, the directivity of the array is enhanced meaning that its ability to distinguish spatial signals is improved. therefore an accurate doa estimation can be achieved by increasing the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 14 number of array elements, however, this can increase the data processing and computational requirements of the system and thereby negatively affecting the system speed. (a) (b) figure 11: effect of number of elements n on beam pattern (a) n = 20, (b) n = 50 figure 12: effect of number of elements n on doa estimation using music spectrum http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):1-16. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 15 5. conclusion this paper focused on the implementation of an anti-jamming system using doa estimation and adaptive beamforming algorithms for gps application. music and esprit doa estimation algorithms, as well as lms and cma adaptive beamforming algorithms, were considered in this study. matlab was used to develop these algorithms and to model the desired (gps) and interference signals. simulation results presented showed that for the doa estimation, both algorithms are high-resolution algorithms as seen by the accuracy of the estimated direction of arrival although music algorithm produced a better direction of arrival spectrum with little or no minor peaks. also for the beamforming, both lms and cma produced maximum radiation in the direction of the desired signal. lms placed deeper nulls in the directions of interference with faster convergence and fewer errors as compared with cma, which presented errors and was able to suppress the interference to an extent. it was also shown that as the number of elements in the array increases, a more directive beam and doa spectrum is produced. in conclusion, the results show that smart antenna system is viable and very instrumental in the development of anti-jamming systems. references ali, rl., ali, a., khan, sa. and malik, sa., 2011. adaptive beamforming algorithms for antijamming. international journal of signal processing, image processing and pattern recognition, 4(1): pp.95-106. beulah, re. and vigneshwari, na., 2014. design and simulation of smart antenna array using adaptive beam forming method. ijesit, vol. 3, issue 6: pp. 434-441. borre, k., akos, dm., bertelsen, n., rinder, p. and jensen, sh., 2007. a software-defined gps and galileo receiver: a single-frequency approach. springer science & business media. elkassimi, s., safi, s. and manaut, b., 2017. blind channel equalization by adaptive filter algorithms. universal journal of applied mathematics, 5(3): pp.45-52. esmaeilkhah, a. and lavasani, n., 2018. jamming efficacy of variable altitude gps jammer against airborne gps receiver, theoretical study and parametric simulation. advanced electromagnetics, 7(1): pp.57-64. gao, f. and gershman, ab., 2005. a generalized esprit approach to direction-of-arrival estimation. ieee signal processing letters, 12(3): pp.254-257. huang, l., wu, s. and zhang, l., 2005, january. a novel music algorithm for direction-of-arrival estimation without the estimate of covariance matrix and its eigen decomposition. in vehicular technology conference, 2005. vtc 2005-spring. 2005 ieee, vol. 1: pp. 16-19. joshi, r. and dhande, ak., 2014. adaptive beamforming using lms algorithm. international journal of research in engineering and technology, 3: pp. 589-593. kintz, al. and gupta, i.j., 2016. a modified music algorithm for direction of arrival estimation in the presence of antenna array manifold mismatch. ieee transactions on antennas and propagation, 64(11): pp. 4836-4847. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akobundu and gbenga-ilori: gps anti-jamming technique using smart antenna systems azojete, 15(1):1-16. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 16 kundu, a. and ghosh, s., 2008, january. development of smart antenna array signal processing algorithm for anti-jam gps receiver. in progress in electromagnetics research symposium (piers 2008), pp. 1-7. lang, r., xiao, h., li, z. and yu, l., 2017. an anti-jamming method for satellite navigation system based on multi-objective optimization technique. plos one, 12(7), p.e0180893. moghaddam, ss., akbari, f. and vakili, vt., 2011. a novel array geometry to improve doa estimation of narrowband sources at the angles close to the array endfire. in electrical engineering (icee), 2011 19th iranian conference on icee, vol. 63: p. 04015. mukhopadhyay, m., sarkar, bk. and chakraborty, a., 2007. augmentation of anti-jam gps system using smart antenna with a simple doa estimation algorithm. progress in electromagnetics research, 67: pp. 231-249. qian, c., huang, l. and so, hc., 2014. computationally efficient esprit algorithm for directionof-arrival estimation based on nyström method. signal processing, 94: pp. 74-80. pradhan, d. and bera, r., 2015. direction of arrival estimation via esprit algorithm for smart antenna system. international journal of computer applications, 118(6). rao, ap. and sarma, nvsn., 2014. adaptive beamforming algorithms for smart antenna systems. methods, 4(8): pp.10-11. saab, m, 2012. antijamming on gps receivers. final project, dept. of electricity and electronics telecom. eng., lebanese university. shahab, sn., zainun, ar., ali, ha., hojabri, m. and noordin, nh., 2017. mvdr algorithm based linear antenna array performance assessment for adaptive beamforming application. journal of engineering science and technology. shivapanchakshari, tg. and aravinda, hs., 2017. review of research techniques to improve system performance of smart antenna. open journal of antennas and propagation, 5(02): p. 83. sit, yl., sturm, c., baier, j. and zwick, t., 2012, may. direction of arrival estimation using the music algorithm for a mimo ofdm radar. in radar conference (radar), 2012 ieee, pp. 02260229. udawat, a., sharma, pc. and katiyal, s., 2011. lscma blind adaptive algorithm with comparison of optimization capabilities for smart antenna systems. international journal of engineering and technology, 3(5): p. 518. zhang, yd. and amin, mg., 2012. anti-jamming gps receiver with reduced phase distortions. ieee signal processing letters, 19(10): pp. 635-638. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):76-84 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 76 original research article optimization of fin geometry for condensation on integral fin tubes h. a. dandajeh* and y. s. sanusi (department of mechanical engineering, ahmadu bello university, zaria, nigeria) *corresponding author’s email address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 1.0 introduction extended surfaces (fins) are mostly applicable in condensation such as those in refrigeration and air conditioning. upon their usage, enhanced heat transfer and provision of additional drainage systems may be obtained due to surface tension effects (fitzgerald, 2011). surface tension greatly affect heat transfer due to capillary retention of condensate between fins (chen and lin, 2009). these fins can be rectangular, triangular or trapezoidal in nature. enhancement ratio of the fin tubes is generally defined as ratio of the heat-transfer coefficient of the enhanced tube (based on the pinor fin-root diameter) to that of a plain tube with diameter equal to the root diameter of the enhanced tube provided the vapour-side temperature difference is the same (ali and briggs, 2013). figure 1 shows a schematic diagram of an idealised fin-tube geometry. figure 1: schematic diagram of idealized rectangular fin-tube (ali and briggs, 2013) article information abstract this paper reports an optimization aimed at verifying the accuracy of a semi-empirical condensation heat transfer model in calculating the enhancement ratio of a rectangularfinned tube. three condensing fluids (ethylene glycol, refrigerant-r113 and steam) and three tube materials (copper, brass and bronze) were used to evaluate the response of the model at different fluid properties. optimum tube geometries (diameter, fin thickness, height and spacing) were calculated and later compared with those geometries of a real condenser. the verification was achieved by comparing the condensation results of the model based on numerical calculations using excel spread sheet with an established experimental data from the measurements of condensation heat transfer. the optimization results showed that the model accurately predicted the observed trends in the experimental data for the condensing fluids of steam, r113 and ethylene glycol. condensation of refrigerant-r113 on copper tube material was found to be the best predicted model. calculated optimum fin spacing for steam as a condensing fluid corresponded reasonably to those of a real condenser. optimum fin spacing increased with increased surface tension. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 may, 2019 revised 01 november, 2019 accepted 05 november, 2019 keywords: heat transfer condensation fin-geometry fin-tubes optimization. mailto:hadandajeh@abu.edu.ng mailto:hadandajeh@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 76-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 77 enhancement ratio varies with the shapes and sizes of the various fin geometries as well as nature of the condensate fluids and materials with which the fin tube is made. effect of pin fin rotational angle on the enhancement ratio as a function of vapour velocity has recently been reported (haseeb, 2020). research into the effects of the interdependence of these factors on the enhancement ratio has received substantial attention for the past few decades. for example, honda et al. (1983) reported the highest enhancement ratio of 10.2 for refrigerant-r113. honda et al. reported that low surface tension refrigerant-r113 resulted in reduced condensate flooding. wanniarachchi et al. (1985) reported enhancement ratio of slightly over 4 while condensing steam. briggs et al. (1992) reported enhancement ratio of 4.7 for ethylene glycol. ethylene glycol was reported to have ratio of surface tension to density ratio between the extremes of water and other refrigerants. briggs et al. (1995) systematically studied the effect of condensing r-113 and steam on a rectangular fin tube made up of brass, bronze and copper. fin thickness and fin height were also varied. briggs et al. (1995) found that the enhancement ratio while condensing r-113 varied strongly with fin height and thickness and; weakly dependent on the thermal conductivity of the tube materials. enhancement ratio for condensing steam appeared to have lesser effect on the fin height and thickness, but strongly dependent on the thermal conductivity. more recently, jan et al. (2017) experimentally investigated the enhancement of condensation of heat transfer rate of the air-steam mixture on a passive condenser using annular fins. jan et al. reported that the condensation heat transfer was enhanced by a factor of 1.54 when the area for the heat transfer increased by 84%. this paper is aimed at verifying the accuracy of a semi-empirical model by rose (1994) in calculating the enhancement ratio of a rectangularfinned tube. the methods employed in calculating the enhancement ratio is described as follows. 2. methodology 2.1 model equations the enhancement ratio (ε) of the rose (1994) model is given by eqn.1. three condensing fluids (ethylene glycol, refrigerant-r113 and steam) and tube materials (copper, brass and bronze) were used to evaluate the response of the model at different fluid properties. details of the model are summarized in eqns. (1), (2), (3), (4), (6) and (8). the verification was achieved by comparing the results of the model based on calculations from excel spread sheet with an established experimental data from briggs (2012) obtained from the measurements of condensation heat transfer. optimum tube geometries (diameter, fin thickness, height and spacing) were calculated and compared with those in manufacturing a real condenser. the model was implemented on an excel spread sheet using relevant fluid properties shown in table 1. tube geometry parameters from the experimental data base of briggs (2012) obtained from the queen mary university of london, united kingdom was used to calculate the enhancement ratio for all the condensing fluids (ethylene glycol, r113 and steam) and on all the different tube materials (copper, brass and bronze). the definition of each parameter and numerical values of constants are shown on the nomenclature page. piece-wise calculations of the enhancement ratio in eqn.1 and all other subsidiary model equations from eqn.2 to eqn.8 were computed on an excel spreadsheet. the input parameters with their respective si units were strictly employed. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng dandajeh and sanusi: optimization of fin geometry for condensation on integral fin tubes. azojete,16(1):76-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 78 table 1: properties of condensing fluid (briggs, 2012 and ees nasa equations, 2019) s /no condensing fluids temperature (°c) density (kg /m3) surface tension (kg /s2) 1 ethylene glycol 197 970 0.03268 2 r113 48 1510 0.01642 3 steam 100 970 0.0588 ε = do d 3/4 t 0.281 + btipσdo t3ρ�g 1/4 + ϕf π 1− ff cos β do2−d2 2hv 1/4d3/4 0.791 + bflankσhv h3ρ�g 1/4 + b1 1 − fs s ξ(ϕf) 3 + bintσd s3ρ�g 1/4 /0.728(b + t) (1) although eqn. (1) is a model for trapezoidal fins, adequate care has been taken during the computation to use the requirements for rectangular fins only. the fin-tip half angle (β) in eqn.1 differentiates the model for different fin geometry (β=0) for rectangular fin geometry. ϕf, ff ,fs , hv and ξ ϕ in the model are further defined in the following equations: ϕf = cos−1 4σ ρgbdo − 1 for b < 2h (2) where ϕf is the retention or flooding angle of the retained condensate from the top of the fin ff and fs are the fractions of the fin flank and inter-fin tube surface “blanked" by condensate "wedge” respectively. according to masuda and rose (1987), ff and fs are respectively given by eqns. (3) and (4) for a rectangular fin. fs = 2σ ρgdh . tan(ϕf/2) ϕf (3) fs = 4σ ρgds . tan(ϕf/2) ϕf (4) according to rose (1994), the mean vertical height of the fins (hv) is given by eqn. (5) and eqn. (6). however, only eqn. (6) corresponds to the condition of ϕf for all the data points during computation on an excel spreadsheet. hv = ϕf sin (ϕf) h for ϕf≤ π 2 (5) hv = ϕf 2− sin (ϕf) h for π 2 < ϕf ≤π (6) active area enhancement ξ(ϕf) as defined by masuda and rose (1987) for a rectangular fin is given by eqn. (7). ξ ϕf = unblanked area of finned tube area of smooth tube = rrbϕf 1− ft +(ro2− rr2)ϕf 1− ff + πrot πrr b+t (7) where: rrbϕf 1 − ft = area of a fin top; (ro2 − rr2)ϕf 1 − ff = area of unblanked part of fin flank and πrot = area of unblanked part of inter-fin tube surface rose (1994) calculated the active area enhancement as a function of flooding angle based on nusselt (1916) theory and is given by eqn. (8). ξ ϕ = 0.874 + 0.1991 × 10−2ϕ – 0.2642 × 10−2ϕ2 + 0.5530 × 10−2 ϕ3– 0.1363 × 10−2 ϕ4a (8) the standard deviation for a sample of data between the calculated and experimental values is given by eqn. (9) as reported by freedman et al. (1998). standard deviation (std. dev.) = i=1 n εc− εe 2� n−1 (9) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 76-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 79 where: n= total number of data points. however, three (3) standard deviations were calculated to reflect the effect of removing some data points due to their inconsistencies with the model. they are as shown below: std. dev. 1 = i=1 148 εc− εe 2� 148−1 = 0.573 for the entire 148 data points std. dev. 2 = i=1 146 εc− εe 2� 146−1 = 0.553 for 146 data points (2 data points where the fin tip half angle is not zero removed) std. dev. 3 = i=1 139 εc− εe 2� 139−1 = 0.549 for 139 data points (9 data points that could not predict the model removed). 3.0 results and discussion 3.1 verification of the model with experimental data figure 2 shows a graph of calculated enhancement ratio ( εc ) from the model against the experimental enhancement ratio (εe ) for the three condensing fluids (steam, r113 and ethylene glycol) in the three tube materials (bronze, brass and copper). the εe was adopted from briggs (2000), while εc was calculated from the model. the line of best fit in fig.2 has an equation of y = 0.9817x from the origin. the other two lines showed the deviation of +25% and -25% from the line of best fit. figure 2: calculated and experimental enhancement ratios of different working fluids and tube materials it can be seen from figure 2 that most of the data points for the condensation of refrigerantr113 in copper tube material fall within the standard deviations of ±25% of the line of best fit, and therefore predicted the model best. similar observations could be seen on the condensation of r113 in brass and bronze and the condensation of ethylene glycol in copper. condensation of steam in copper was partly predicted by the model, because some of the data points fall outside the ±25% standard deviations. however, condensation of steam in brass and bronze did not to predict the model well, since none of the data point fall within the ±25% standard deviations. it is noteworthy that condensation of r113 in copper did not only predict the model correctly, but also provided the highest calculated and experimental enhancement ratios. generally, the model predicts the observed trend in the data for condensation of steam, r113 and ethylene glycol. the calculated enhancement ratio response varies in the same file:///c:/users/user/downloads/azojete143/www.azojete.com.ng dandajeh and sanusi: optimization of fin geometry for condensation on integral fin tubes. azojete,16(1):76-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 80 manner for all the fluids. therefore, the trend on the enhancement ratio is found to be dependent on the fluid properties. generally, the model can be said to be in good agreement with the experimental data. this is evident from figure 1 where most of the data points were having standard deviations of ±25% to the line of best fit on the graph. although an assumption of zero flooding angles was made for seven data points for which the component ( 4σ ρgbdo − 1) from eqn. 2 is greater than unity. nevertheless, the model reasonably predicted these points to a high degree of accuracy. this indeed is a fair approximation, since, the seven points were assumed to be completely flooded within the inter-fin spaces at zero vapor velocity (fitzgerald, 2011). two data points designate points where the fin tip half angle is not zero (i.e., β = 4.50 and β = 50), which is obviously not true for rectangular fins. hence, the reason for the discrepancy of the points with the rest of the data. it can be seen clearly from the 3 values of the standard deviations calculated from eqn. 9 that, std. dev. 2 seemed to be more reasonable, since it excludes the 2 points on which the model is not valid and includes the fair approximation for the 7 data points. furthermore, it is quite justifiable to remove some data points from the data-base since the model could not provide reasonable predictions. the two data points where the fin tip half angle is not zero were therefore removed. the assumption that the model is rectangular does not work for these points. due to differences in the prediction of condensation for steam on brass and bronze tube materials, briggs and rose, (1994) modified the model to include conduction in the rectangular fins. the subsequent section discuss how the change in the fluid and tube materials influence the enhancement ratio. 3.2 influence of condensing the same fluid on different tube materials 3.2.1 condensation of steam on copper, brass and bronze figure 3 shows the response of experimental enhancement ratio ( εe ) against the calculated enhancement ratio (εc ) for steam condensing on copper, brass and bronze. a fair response for steam condensing on copper tube material was observed from figure 3. however, the prediction of condensation of steam on brass and bronze tubes was totally inconsistent with the model. good prediction of the model by condensing steam on copper tube materials is believed to be due to high thermal conductivity of copper. on the other hand, condensing steam on brass and bronze tubes is inconsistent with the model primarily due to temperature fall for large αh2 tkw explained by briggs, (2012) and differences in surface tension of steam on brass and bronze (rose, 2004). figure 3: calculated and experimental enhancement ratios for condensation of steam on copper, brass and bronze tubes. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 76-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 81 3.2.2 variation of enhancement ratio with fin geometry three fin geometry were considered (spacing, height and thickness) and the response of the calculated enhancement ratio was determined at a fixed fin root diameter (d = 12.7 mm) while also keeping two out of the three fin geometries constants. figure 4 show variations of the calculated enhancement ratio ( εc ) with fin spacing (s) (h =1.6mm and t = 0.5mm). it can be observed from the figure 4 that the calculated enhancement ratio ( εc ) decreases with increasing fin spacing for steam, r113 and ethylene glycol. figure 5 presents variations of enhancement ratio (εc) with fin thickness (t) (h = 0.9 mm and t = 1 mm). it can be seen from the graph that the calculated enhancement ratio also decreases with increasing fin thickness. figure 6 shows the relationship between εc and fin height (h) (s = 1mm and t = 0.5 mm). it can be deduced from figure 6 that εc increases with increasing fin height for all the condensing fluids. wanniarachchi et al. (1985) also observed similar trend of increased enhancement ratio with increased fin height. figure 4: variation of calculated enhancement ratio with fin spacing (s) figure 5: variations of calculated enhancement ratio with fin thickness figure 6: variations of calculated enhancement ratio with fin height (h) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng dandajeh and sanusi: optimization of fin geometry for condensation on integral fin tubes. azojete,16(1):76-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 82 these variations have been associated with surface tension effects and capillary retention of the condensate (briggs, 2012). pravin, (2011) listed surface of the condensing fluids (σ), density (ρ) and surface tension to density ration (σ / ρ) as the basic factors that could affect the trend of the model. these parameters are all included in the model which help to predict the trends reasonably well. this observation could be underpinned using earlier models such as those of beatty and katz, (1948) and rudy and webb, (1981) in rose, (1994). these two models neglected the effects of surface tension and thus, suffer limitations of interpretations and under-predictions (briggs, 2012). 3.2.3 influence of tube geometries on the model performance tube geometries from the data base were optimized for condensation of steam and refrigereant-r113 while making the following parameters constants (maximum fin root diameter d = 19.1 mm, fin thickness t ≥ 0.5 mm and rectangular fins θ = 0). results for the optimum tube geometries are presented in figures. 4, 5 and 6. the results are then compared with that of a commercial real condenser shown table 2. it can be seen from table. 2 that optimum fin spacing for steam is 1.5mm which is within the specified range of 12 mm for a commercial condenser obtained from briggs, (2012) while the optimum fin spacing for r113 is 0.5mm which is out of the range and therefore, not highly recommended. however, these correspond with values obtained by patten, (1988) using the same diameter. optimum fin height and thickness for both steam and r113 are 2mm and 0.5mm respectively. table. 2: comparison of calculated optimum tube geometries with commercial tube geometry for practical tube manufacture of a real condenser (briggs, 2012) tube geometry parameters calculated optimum tube geometries for condensing fluids at d = 19.1mm values from the commercial tube geometries for condensing fluids steam refrigerants steam refrigerants fin spacing, s (mm) 1.5 0.5 1 2 1 – 2 fin thickness, t (mm) 0.5 0.5 fin height, h (mm) 2 2 1 0.2 – 0.4 fin root diameter, d (mm) 19.1 12.7 fin tip diameter, do (mm) 23.1 16.7 4. conclusion the accuracy of a semi-empirical model of rose (1994) has been verified and the following conclusions could be deduced: the model clearly predicted an observed trend in the experimental data for most of the condensing fluids (steam, r113 and ethylene glycol) on brass, bronze and copper. condensation of refrigerantr113 on copper tube predicted the model with the best results while condensation of steam in brass and bronze were poorly predicted by the model. standard deviations between the calculated and experimental enhancement ratio data was found to be 0.553 calculated enhancement ratio appeared to increase with fin height but decreased with increasing fin thickness and fin spacing regardless of the condensing fluid and the tube material. calculated optimum fin spacing for steam corresponded reasonably to those of a real condenser and the optimum fin spacing increased with surface tension increase. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 76-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 83 acknowledgement the first author wishes to gratefully acknowledge the petroleum technology development fund (ptdf) for sponsoring his post graduate studies at queen mary university of london, united kingdom. references ali, hm. and briggs, a. 2013. condensation heat transfer on pin-fin tubes: effect of thermal conductivity and pin height. applied thermal engineering, 60, (1-2): 465-471. briggs, a., wen, xl. and rose, jw. 1992. accurate heat-transfer measurements for condensation on horizontal integral-fin tubes. transaction on american society of mechanical engineers (asme) journal of heat transfer,114:719-726. briggs, a. and rose, jw. 1994. effect of fin efficiency on a model for condensation heat transfer on a horizontal integral fin tube. international journal of heat and mass transfer, 37: 457-463. briggs. a., huang, x. and rose, jw. 1995. an experimental investigation of condensation on integral fin tubes: effect of fin thickness, height and thermal conductivity. american society of mechanical engineers (asme) national heat transfer division conference, 308: 2129. briggs, a. 2012. condensation, denm031. condensation heat transfer project tutorial. advanced fluid mechanics and heat transfer modules. school of engineering and material science, queen mary university of london. chen, ck. and lin, yt. 2009. forced-convection film condensation on a horizontal cylinder with wavy surface structure. heat and mass transfer, 45(6):775–782. nasa. 2019. engineering equation solver, national aeronautics and space administration. ideal gas and condensed specie data. available at: http://fchart.com/ees/eeshelp/fluid_property_information.htm. accessed on 28th october, 2019. fitzgerald, cl. 2011. forced convection condensation heat transfer on horizontal integralfin tubes including effects of liquid retention. phd thesis, school of engineering and material science, queen mary, university of london, united kingdom. freedman, d., pisani, r. and purves, r.1998. statistics. 3rd ed. new york. norton and company ltd, united states of america. haseeb, ur., hafiz, ma., sajjad, a. and mansoor, ab. 2020. experimental investigation of condensate retention on horizontal pin fin tube with varying pin angle. case studies in thermal engineering, 17:1-15 honda, h., nozu, s. and mitsumori, k.1983. augmentation of condensation on finned tubes by attaching a porous drainage plate. proceeding of asme-jsme thermal engineering joint conference, 3:289295. jang, yj., choi, dj., kim. s., hyun, mt. and lee, yg. 2017. enhancement of condensation heat transfer rate of the air-steam mixture on a passive condenser system using annular fins. energetics, 10:1771 1777. masuda, h. and rose, jw.1987. static configuration of liquid films on horizontal tubes with low radial fins: implications for condensation heat transfer. proceedings of the royal society a: mathematical, physical and engineering sciences, 410:125–139. http://fchart.com/ees/eeshelp/fluid_property_information.htm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng dandajeh and sanusi: optimization of fin geometry for condensation on integral fin tubes. azojete,16(1):76-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hadandajeh@abu.edu.ng; hadandajeh@yahoo.com 84 petten, v.1988. film wise condensation of low integral tubes of different diameter. m.sc. thesis, mechanical engineering, submitted to naval post graduate school, monterey, california, united states of america. pravin, pr. 2011. enhancement of condensation heat transfer over horizontal integral fintube: a review study. journal of engineering research and studies. 2(2): 76 -81. rose, jw.1994. an approximate equation for the vapour-side heat transfer condensation on low-finned tubes. international journal of heat and mass transfer, 37(5): 865 -875 rose, jw. 2004. surface tension effects and enhancement of condensation heat transfer. chemical engineering research and design, 82: 419–429. wanniarachchi, as., marto, pj. and rose, jw.1985. film condensation of steam on horizontal finned tubes: effect of fin spacing, thickness and height, multiphase flow and heat transfer. american society of mechanical engineers (asme), national heat transfer division, 47: 93-99 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):449-460 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 449 original research article development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion a. b. hassan1*, a. musa1, a. babawuya2 and i. yahuza3 (1department of mechanical engineering, federal university of technology, p.m.b. 65, minna, niger state, nigeria. 2department of mechanical engineering, federal university of technology, p.m.b. 65, minna, niger state, nigeria. 3department of automotive engineering, abubakar tafawa balewa university, bauchi, bauchi state, nigeria) *corresponding author’s e-mail address: abhassan@futminna.edu.ng article information submitted 29 march, 2018 revised 20 april, 2019 accepted 23 april, 2019 keywords: airbag tyre burst vehicle laboratory abstract the incessant rate of traffic accident as a result of tyre burst on our roads from the motor vehicle necessitated the development of this airbag to cushion the effect of tyre burst. the development of this laboratory airbag model is such that the airbag is incorporated into the rim (i.e. on the rim, inside the tyre). this allows the vehicle balance for some time until the driver is able to maneuver and park the vehicle safely. the frame of the airbag model was made of 0.5 mm ply wood cut into six (6) pieces and to form the box. a hole was drilled at the front to give space for motor to be used as a prime mover. the shaft produced from a 30 mm diameter mild steel rod was machined on a lathe machine to 25 mm diameter and cut to length of 10 mm. the calculated resultant stress upon impact was 83.96 mpa. the contact area and airbag thickness was 0.258 m2 and 2.8 mm, respectively. a mini inflator was selected and actuated with the aid of an infrared sensor; it took less than six (6) seconds to actuate the shape airbag. the laboratory model was powered by a dc source and tyre burst signals were transmitted wirelessly through a control system. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction nearly 1.3 million people die in road crashes each year, on the average 3,287 deaths are recorded a day (anand, 2000). nigeria is one of the worst hit countries with a human population of about 167 million, a high level of vehicular population estimated at over 7.6 million, a total road length of about 194,000 km (vitus, 2014). nigeria has suffered losses due to fatal car accidents. its population density varies in rural and urban areas at about 51.7% and 48.3%, respectively and translates to a population – road ratio of 860 persons per square kilometer, indicating intense traffic pressure on the available road network, (tyremarket, 2016). undoubtedly, this immense pressure contributes to the high road traffic accidents in the country (vitus, 2014). vitus (2014) categorized the causes of fatal car accidents in nigeria into human, mechanical, and environmental factors. the human factor accounts for up to 90% of accidents, while the mechanical and environmental factors contribute to the other 10%. human factors include visual acuteness, driver fatigue, poor knowledge of road signs and regulations, illiteracy, health problems, excessive speeding, drug abuse, and over-confidence while at the steering wheel. among the mechanical factors that lead mailto:abhassan@futminna.edu.ng http://www.azojete.com.ng hassan, et al: development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion. azojete, 15(2):449-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 450 to fatal car accidents are poor vehicle maintenance, tyre bursts, poor lights, non-roadworthiness of vehicles, and broken-down vehicles on the road without adequate warning. the environmental factors include heavy rainfall, harmattan winds, reflection, heavy wind, pot holes, and un-tarred roads. these factors have independently or collectively contributed to the high rate of fatal road accidents in nigeria. over-speeding and tyre burst are frequently being reported as the most common causes of road accidents around the country (maureen, 2016). a survey by the federal road safety corps (frsc) shows that tyre-related crashes have been responsible for the destruction of 5,288 vehicles between 2011 and 2015. a total of 224 road traffic crashes due to tyre burst have been recorded between the 1st of january and 15th may in the year 2016, (maureen, 2016). in the present-day nigeria, a road accident ranks the second to boko haram as the source of violent death. about 11,363 head accidents were recorded in 2016 of which 4,796 deaths were recorded, 40% of these fatal accidents were due to tyre burst, (maureen, 2016). these tyre bursts cannot be controlled in nigeria with the use of new and nonexpired tyres because the states of the roads are accident prone. for this reason, it has become imperative to develop airbag mechanism as a means of reducing the effect of tyre burst. torus shape airbag is therefore adapted in this study, because it has the same shape as a vehicle tyre; with the device consisting of shaft, motor, mini inflator, transmitter and receiver. 2. literature review the airbags are spreading in use with several now being fitted to each vehicle-for driver, passenger, thorax, knee side and side curtain airbagsand it is expected that in europe alone approaching 100 million modules will be required gülsah, (2008). rishikesh, (2014), designed an airbag system for 2-wheeler vehicle system. the design made use of airbag (leather material with grip technology), chemical cylinders for releasing the air or gas, sensors (angle sensor and crash sensor), fitting cage, angle measurement instrument (angle indicator) and battery used (bike battery). a maximum of 50 milliseconds were recorded for the airbag to be deployed through the explosion of nitrogen gas. yi-jen mon, (2013), developed a test platform for airbag controller design so as to obtain a crash data for design. the test platform was implemented using recurrent fuzzy neural network (rfnn) algorithm. the airbag ignition was verified for good effectiveness. an average of 29 ms was recorded with his taste platform. 3. materials and method 3.1 materials the materials used in this study and their specifications are presented in table 1 table 1: materials used for the development of airbag. s/n material specification 1 casing 12.5 m plywood 2 plexiglas: light weight used to hold receiver 2 mm thick 3 airbag torus shape 4 inflator model ap 101 5 power switch two way 6 hose ∅30 mm× 150 mm http://www.azojete.com.ng mailto:abhassan@futminna.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):449-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 451 3.2 method the process followed in the development of the airbag model are presented as follows:. 3.2.1 design considerations according to khurmi and gupta (2008), the design considerations are characteristics that influence the design of the elements on the entire system, therefore, the design considerations that are important to this design are: strength of the airbag: the ability to withstand the internal stress and impact upon tyre burst. inflation time (in seconds): the inflator will be required to pump air into the airbag in< 5 ms. fatigue resistances: the resistance to fatigue load due to tyre roll. shape: an airbag to cushion the effect of tyre burst must be able to roll like tyre. airbag pressure is assumed to be distributed uniformly. 3.2.2 working principles the sensor is connected to the controller and the controller is connected to the transmitter. as a result, when the distance to the ground is shortened the controller sends a message to the radio transmitter. on the other hand, the radio receives the message and activates the relays which operate the inflator. a torus tube was used as an airbag (as shown in figure 1). because a torus like airbag can easily be fitted into wheel tire assembly. an ultrasonic (uts) proximity sensor was used to monitor the position of the tyre while in active position that is fully inflated and if there is a tyre burst, the uts will activate the mini tyre inflator which in turn pumps air into the torus like airbag. the inflator, the sensors and other electronic components are beef powered by a 12v battery. the uts installed on the transmitter located around the tyre send a signal to the receiver. the detail cad drawings are show in figure 2 and 3. figure 1: schematic diagram of airbag mechanism inflator receivertransmitter dc motor torus shape airbag control board battery shaft file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:abhassan@futminna.edu.ng hassan, et al: development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion. azojete, 15(2):449-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 452 figure 2: isometric drawing airbag mechanism. figure 3: orthographic projection of airbag mechanism plan front view side view http://www.azojete.com.ng mailto:abhassan@futminna.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):449-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 453 3.3.3 design requirements the weight of a toyota camry (2012 model) with four passengers were used as the design weight for the airbag about the weight is about 144.959kg according to miller-wilson, (2017), while the average adult weight (wa) is 81.64kg halls (2017). therefore, the total design weight, wd were computed using equation 1; wd = wc + 4wa × 9.81 (1) therefore, the weight of the vehicle on one tire is given by: ww = wd 4 (2) from the equation 2, the design load is ww = 5kn, and a nylon fabric rubber material can withstand an impact load of up to 11.9kn miller-wilson, (2017). 3.3.4 determination of airbag internal pressure required to sustain the weight of the car the airbag governing equations as presented by anand (2000) is used and presented in equation 3. �1 �2 = v1 v2 γ = e2 e1 γ (3) where: γ = cp cv cp = heat capacity at constant pressure cv = heat capacity at constant volume. v = volume also e = e ρo then the airbag internal pressure pi is given by pi = γ − 1 ρe (4) and the airbag internal energy depends on the gas entering and leaving the airbag. (see equation 5) ein = cp mintin +mouttout − pv (5) 3.3.4 determination of stresses acting on the torus airbag the hoop stress is the force exerted circumferentially (perpendicular both to the axis and to the radius of the object). in the directions on every particle in the cylinder wall david, (2000) stated that the hoop stress of a torus shaped object can be obtained using equation 6 σrit = ri 2pi−ro 2po ro 2−ri 2 ∓ ri 2ro 2(pi−po) ro 2−ri 2 r2 (6) where: σrradial stress σttangential stress σi – internal radius σo −external radius r – radius file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:abhassan@futminna.edu.ng hassan, et al: development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion. azojete, 15(2):449-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 454 3.3.5 device shaft design the shaft is subject to bending load from the weight of the airbag tube, and twist load from the motor, therefore equation 7 is used for the shaft design (kost, 2014). τe = m2 +t2 (7) where: te is the equivalent twisting moment, m is bending moment and t is the twisting moment. figure 2: the shaft with a pointed load. the bending moment is obtained using equation 8 m = w× l = m.g.l (8) where: wload on shaft (n). l shaft length (220 mm, constrained by space.). m mass of air in the airbag (0.0299kg) g 9.81 m/s2 the torque or twisting moment was obtained using equation 9 τ = 60p 2πn (khurmi and gupta, 2008) (9) a 12v motor was used for this design with 50 rpm and 350 w power rating. 3.3.5 the power supply the power supply for the dc motor, the drives the airbag is 12v, 7ah battery. this was used instead of the car battery to save cost. however, in the car, the car battery is the kind of battery needed. another 9v battery was used to power the transmitter which is regulated to 5v via a regulator 7805. this regulator converts 9v to 5v. the essence of having a 5v supply is to ensure the powering of the controller which is usually not more than 5v any attempt to do that will damage the chip. the current supply by the battery to the motor were determined from equation 10; v = ir (10) where: v = voltage (v) i = current (a) r = resistance (ω) w l http://www.azojete.com.ng mailto:abhassan@futminna.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):449-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 455 3.3.6 rating of battery capacities of battery are rated in terms of output ampere-hour. figure 3, presets the powered circuit while, equation 11 represents the battery power required. power = vi (11) watt hour = voltage (v) × current (a) × time (hour) a12v, 7ah lead acid battery is selected. figure 3: circuit diagram of the power. 3.3.7 proximity sensor the sensor used is an infrared barrier detector. the sensor was bought in an open market in minna, niger state of nigeria, as a module. it consists of three pins vcc, ground and output. the module which has an infrared transmitter and receiver can sense distance. when the distance is at a particular level, the output goes high. figure 4: pictorial view of the sensor. controller: the controller used is pic16f628a. the reason for the selection of the chip is because it is small in size so it will ensure compactness. the 5v system has a serial port which is connected to the radio transmitter at the transmitter unit to send message which is a string “aaax”. at the receiver, the controller receives this message among other radio messages in the air, however it is programmed to discard every other message except this particular one sent by the transmitter. the circuit diagram of the controller is shown below in figure 5. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:abhassan@futminna.edu.ng hassan, et al: development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion. azojete, 15(2):449-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 456 figure 5: circuit diagram of controller unit. 3.3.8 transmitter/receiver unit the module in figure 6 were used to transmit the signal from the proximity sensor to the control board, which in turns actuate the inflator. this is made up of radio module 433 mhz the radio module has the ability to send message for a distance of 25 meters. it has three pins vcc which is connected to 5v, ground pin and data line. for efficiency it is important for the module to have an antenna (cai and duan, 2015). this unit is made up of 433 mhz radio receiver. the receiver receives many messages from the air. the four pin device has vcc, ground, and two data lines. figure 6: the pictorial view of rftx and rx. 3.3.9 relay unit the relay unit for which the circuit is shown in figure 7 were used to control (ie switching on/off ) the inflator. this is achieved via the use of electromagnetic switch as shown in figure 7. the relay cannot operate on its own since the controller cannot supply all the current it needs. therefore, a transistor is used as a driver. figure 7: circuit of transistor the transistor used is a1015 biased with a 1k ohms resistor. this is used to drive a relay. http://www.azojete.com.ng mailto:abhassan@futminna.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):449-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 457 3.3.10 test procedure the model airbag mechanism in figure 7 were tested with a lead acid battery (with 12v 7.2ah) connected via terminals switch. the system was switch on as the time was working that is simulating vehicle movement. a object placed in front of the sensor signifying a tyre burst, this activate the transmitter and receiver led circuit which in turn inflate the airbag. the time, airbag pressure and volume were recorded. 4. results and discussion 4.1 design analysis results the design analysis was carried out to satisfy the design consideration earlier mentioned. that is to establish minimum safe dimensions and to ensure its functionality. the mechanical design results obtained from equations 1 – 13 are presented in table 2. table 2: mechanical design result s/no item value obtained 1 design load 5kn 2 tyre contact area 0.0258 m2 3 stress upon impact 195.93 mpa 4 airbag strain energy 73.8j. 5 airbag internal pressure (max) 0.369 mpa (53.33psi) 6 airbag max radial/stress 52.16 mpa 7 airbag max tangential stress 65.52 mpa 8 resultant stress/airbag 83.96 mpa 9 airbag min thickness 2.8 mm according to anand, (2000), nylon fabric rubber has a yield stress of 450 mpa and can take up to 11,000kn. the resultant stress calculated for the airbag is less than the yield stress of the airbag materials, the thickness of the airbag material is close to what has been used in the works of anand (2000) and bells (2016). the results of stress analysis of the torus airbag are shown in figure 8 and 9 this shows that the maximum stress the nylon fabric rubber is been subjected to is less than its yield stress. figure 8: airbag resultant stress file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:abhassan@futminna.edu.ng hassan, et al: development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion. azojete, 15(2):449-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 458 figure 9: airbag radial (σr) and tangential (σt) stress 4.2 test results after the design and fabrication, the laboratory model of the torus airbag system was tested and the result obtained are shown in table 3. the pressure in the airbag and its corresponding weight was recorded as shown over time in seconds. table 3: experimental data recorded of pressure in the airbag and its corresponding weight. figure 10: experimental data on time (s) against pressure (mpa) time(s) pressure mpa volume (m³) gram 0 120.3 407111.9 4.912334 3 121.6 422037.1 5.092426 5 123.1 439699 5.30554 7 125.6 470200.7 5.673583 9 127.8 498163.6 6.010991 10 129.5 520503.3 6.280548 12 131.1 542120.8 6.541392 15 134 582790.6 7.032126 20 137.1 628429.6 7.58282 http://www.azojete.com.ng mailto:abhassan@futminna.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):449-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 459 figure 11: experimental data on time(s) against volume (m3) figure 10 shows the results of the test conducted as recorded in table 3. these were plotted in figure 10 and 11. it was observed that during the test it took about 6 seconds for this airbag pressure to reach 45 mpa required to sustain the impact from the crash. note: the capacity of the mini inflator use is small in size as compared with what is required in real life situation. according to bells (2016), the response time and inflating time is always less than 1.6 milliseconds. 5. conclusion the laboratory test model for this mechanism were developed. the design analysis of the model components was carried out. also a control system was built for the mechanism. a transmitter and receiver module was to authenticate control of mini inflator. the dimension obtained from design analysis was used in the fabrication of the airbag mechanism. after fabrication a performance test was conducted. it was found that the mini inflator used was able to pump the torus airbag up to 45 mpa in less than six (6) seconds. the design load obtained is 5 kn, with a tyre contact area of 0.0258 m2 and stress upon impact determined references anand, n. 2000. dynamic testing of airbag fabric permeability and extensibility for depowered airbags. retrieved from https://ttu-ir.tdl.org/ttuir/bitstream/handle/2346/10246/31295013710842.pdf?sequence=1. bells, m. 2016. "the history of airbags". about.comnew york times company. retrieved 16 march 2017. cai, y., zang, m., and duan, e. 2015. modeling and simulation of vehicle responses to tire blowout. tire science and technology, 43(3): 242-258. david, f. 2000. metallurgical failures in fossil fired boilers. 2nd edition. usa. john wiley and sons, new york. halls, sb. 2017. feeling fine chart. retrieved from http://halls.md/average-weight-men/ 19 march, 2017 khurmi, rs. and gupta, jk. 2008. a textbook of machine design (multicolour edition), new delhi, eurasis publishing house, india. https://ttu-ir.tdl.org/ttu-ir/bitstream/handle/2346/10246/31295013710842.pdf?sequence=1 https://ttu-ir.tdl.org/ttu-ir/bitstream/handle/2346/10246/31295013710842.pdf?sequence=1 http://inventors.about.com/od/astartinventions/a/air_bags.htm http://halls.md/average-weight-men/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:abhassan@futminna.edu.ng hassan, et al: development of a laboratory airbag model to cushion the effect of vehicle tyre burst while in motion. azojete, 15(2):449-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abhassan@futminna.edu.ng 460 kost, f. 2014. basic principles of vehicle dynamics. in: reif k. (eds) fundamentals of automotive and engine technology. bosch professional automotive information. springer vieweg, wiesbaden. retrieved from https://link.springer.com/chapter/10.1007%2f978-3-658-039721_10#citeas maureen, o. 2016. curbing tyre-related accidents on nigerian roads. http://www.dailytrust.com.ng/news/feature/curbing-tyre-related-accidents-on-nigerianroads/150811.html#f7tqrw3m5qvavzy6.99 miller-wilson, k. 2017. list of car weights. retrieved from http://cars.lovetoknow.com /list_of_car_weights. 18 march, 2017 vitus, nu. 2014. trends and patterns of fatal road accidents in nigeria. institut français de recherche en afrique. http://www.nigeriawatch.org/media/html/ wp6vitusv6final.pdf xiaoguang, y. 2011. finite element analysis and experimental investigation of tyre characteristics for developing strain-based intelligent tyre system, (doctorate thesis). university of birmingham. retrieved from http://etheses.bham.ac.uk/3072/1/yang11phd.pdf https://link.springer.com/chapter/10.1007%2f978-3-658-03972-1_10 https://link.springer.com/chapter/10.1007%2f978-3-658-03972-1_10 http://www.dailytrust.com.ng/news/feature/curbing-tyre-related-accidents-on-nigerian-roads/150811.html http://www.dailytrust.com.ng/news/feature/curbing-tyre-related-accidents-on-nigerian-roads/150811.html https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahukewj8topmjjzsahvduhqkhzfkbqiqfggbmaa&url=http%3a%2f%2fwww.ifra-nigeria.org%2f&usg=afqjcneqlfp9fsi629qndpcci_xadcrsug https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahukewj8topmjjzsahvduhqkhzfkbqiqfggbmaa&url=http%3a%2f%2fwww.ifra-nigeria.org%2f&usg=afqjcneqlfp9fsi629qndpcci_xadcrsug http://www.nigeriawatch.org/media/html/%20wp6vitusv6final.pdf http://etheses.bham.ac.uk/3072/1/yang11phd.pdf http://www.azojete.com.ng mailto:abhassan@futminna.edu.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):242-254 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 242 original research article development of a modified east-west interface for distributed control plane network e. a. adedokun* and a. adekale department of computer engineering, ahmadu bello university, zaria, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: software-defined networks distributed control plane east-west interface high availability multi-domain inter-controller communication. abstract the east-west interface is important in achieving communication in a distributed control plane network such as a wide area network (wan); to enable scalability and distribution of the control plane. in this paper, a modified communication interface for distributed control plane (mcidc) was developed to ensure communication in wans. the mcidc interface allows the synchronization of different modules in the controller to enable consistent high availability and efficient communication among controllers in the east-west interface needed for software defined network (sdn) to scale in a wan environment. the modified-cidc (mcidc) is developed based on the communication interface for distributed control plane (cidc) and implemented on top of floodlight controller using the isyncservice module. the performance of the mcidc and cidc was compared using captured transmission control protocol (tcp) packets, tcp errors and inter-controller communication overload (ico). the results indicated that for claranet_2; mcidc showed a better performance in minimizing number of captured tcp packets, tcp errors and ico by 26.55%, 17.89%, and 19.35% respectively when compared with cidc, while for claranet_3; 15.82%, 21.60% and 29.25% for captured tcp packets, tcp errors and ico respectively, when compared with cidc. this shows that the mcidc ensures communication by transmitting the necessary required packets (information) among controllers with reduced tcp errors and fewer overloads © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):242-254. issn 15962490; e-issn 2545-5818; www.azojete.com.ng 243 1.0 introduction traditional networks (networks that require manual configuration) are faced with many challenging concerns (chen et al., 2015) such as: implementing high-level policies in network, manually configuring each network device using low-level configuration and meeting up with the dynamic nature of today’s applications. software defined network (sdn) is a new networking paradigm that addresses the limitations of traditional networks by simplifying network management, enable innovation and evolution of networks (kreutz et al., 2015). sdn concept involves separating the control function from networking devices to a single point of control. the sdn architecture decouples the network control in the control plane and the forwarding functions in the data plane enabling the abstraction of the network for applications and network services. it transfers the intelligence from the traditional network devices to a centralized control plane and enables network programmability. sdn architecture is vertically split into three functional layers (or planes) (jarraya et al., 2014): infrastructure layer (data plane), control layer and application layer. the sdn controller in the control plane interacts with these functional layers through the northbound application programming interface (api), southbound api and east/westbound api. this apis enable communication across the sdn architecture, making the architecture dynamic, manageable, cost-effective and adaptable (rao et al., 2016). sdn was initially designed for testing new protocols in campus networks, but thereafter several works have shown that this concept is suitable for several types of networks such as data centers, wireless networks, and wide area network (wan) (benamrane et al., 2017). the benefits of sdn can be achieved in multi-domain networks such as wan by distributing the sdn control plane. the distributed control plane addresses the single point of failure (spof) problem; which makes sdn architecture highly vulnerable to attacks (kreutz et al., 2013). it also addresses the challenges of scalability and performance. the distributed control plane involves the use of multiple controllers and this is divided into: logically centralized and logically distributed control planes (blial et al., 2016). large networks such as wan with complex infrastructure and protocols use the logically distributed control plane. the logically distributed control plane does not need extensive synchronization between controllers for global network view. it enables each controller to manage its own domain and distribute necessary data to other controllers (benamrane et al., 2017). this control plane can be designed vertically (hierarchical) or horizontally (flat). communication between the multiple controllers in the distributed control plane is of primary importance (benamrane et al., 2017). this communication addresses scalability and ensures that requirements of sdn in wan such as global knowledge, real-time monitoring, decision making, policy updating and fined-grained control (liu and lil, 2015) are achieved. the communication between the controllers at the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adedokun and adekale: development of a modified east-west interface for distributed control plane network. azojete, 15(sp.i2):242-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 244 control plane is handled by the east-west api (or interface). to identify and provide common compatibility and interoperability between different controllers, it is necessary to have a standard east/westbound interface (kreutz et al., 2015). there is no standard for the east-west interface (jarraya et al., 2014). in this paper; a modified east-west interface based on the communication interface for distributed control plane (cidc) by (benamrane et al., 2017), was developed. the mcidc provides high availability using the floodlight isyncservice, enabling consistent and efficient communication in the east west interface. 1. literature review in addressing the challenges faced by the physically centralized sdn control plane architecture such as spof, scalability and limited processing capacity, the distributed control plane architecture is used. this architecture consists of the logically centralized and logically distributed approaches (benamrane et al., 2017). in the logically centralized approach, the controllers collaborate to manage the network and have the same view of the network using the same shared database. in the logically distributed approach, each domain is managed by its controller and can share only some useful information with the other controllers to achieve some services such as the topology view. most of the distributed control plane architectures in literature with a logically centralized approach such as onix, hyperflow, elasticon and onos, currently cannot manage inter-domain flows between sdn domains (wibowo and gregory, 2016). to achieve a scalable control plane in large distributed multi-domain networks (such as wan), the logically distributed control plane architectures are proposed. some literatures suggest that the east-west interface communication is very important in achieving scalability in multiple controllers such as software defined networking interface sdni (yin et al., 2012) and east-west bridge ew bridge (lin et al., 2013). the east-west interface is the communication channel that exists solely for distributed sdn controllers (oktian et al., 2017); providing inter-domain communications. however, there is no standard for the east-west interface. lin et al. (2013) designed a high-performance mechanism called east-west bridge (ew bridge), for heterogeneous sdn domains to exchange network view in multidomain network. the ew bridge is enabled in the controllers/network operating systems (noses) for each sdn domain by adding network virtualization, ew bridge and link layer discovery protocol (lldp) extension to guarantee communication between controllers. messages are delivered for update by the publish/subscribe system and each database stores the entire topology locally. ew bridge focuses on enterprise, datacenter and intra-domain networks. inter-domain networks are not considered. phemius et al. (2014) proposed an extensible distributed sdn control plane (disco) for wan and overlay networks. the disco controller is composed of intra-domain http://www.azojete.com.ng mailto:wale@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):242-254. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 245 and inter-domain. the intra-domain monitors the network and manages flow prioritization, while the inter-domain manages communication with other disco controllers. an extended database in each controller is used to store network topology information from both domains. the inter-domain enables the exchange of aggregated network-wide information using messenger and agents. the messenger is implemented using the advanced message queuing protocol (amqp). the messenger module builds channels between neighboring controllers while each agent publishes and consumes message through the messenger. disco uses four main agents (connectivity, monitoring, reachability and reservation) to support network-wide functionalities and ensure consistency. benamrane et al. (2017) implemented communication interface for distributed control plane (cidc) was implemented for inter-controller communication using a logically distributed architecture. the cidc interface was implemented in a wan, and used by each controller in the network to synchronize its stats and services with neighboring controllers; for inter-controller communication. the role of each controller in the network was customized with three communication modes: notification, service and full. the cidc interface shares necessary data among controllers based on the desired communication mode. 3. materials and methods 3.1 materials the mcidc was implemented on top of floodlight controller. the mcidc modules and isyncservice were developed in java. the experimental emulation was carried out on a 64-bit windows 8 operating system, intel core i5 cpu3.20ghz with 8gb ram. 3.2 description of mcidc mcidc followed the concept of the cidc interface by benamrane et al. (2017). the mcidc considered the logically distributed control plane architecture with multiple controllers. the mcidc interface is composed of four essential modules: consumer, producer, dataupdater and datacollector. the modules are connected and communicate with the core elements of the controller. each controller plays the role of a consumer for external events (events outside its network) and producer for local events (events within its network). the mcidc uses the netty framework to reduce resource consumption. the interface uses the notification (the producer notifies all remote controllers when changes occur in its domain) and full (the producer shares all events and services) communication modes. the mcidc uses an event-driven paradigm (actions are made by events). the controller is active, when new events such as packet-in are received. events are determined by event listeners and observers in the controller. figure 1 shows the flowchart of mcidc. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adedokun and adekale: development of a modified east-west interface for distributed control plane network. azojete, 15(sp.i2):242-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 246 figure 1: flowchart of mcidc 3.3 mcidc operation the mcidc used the isyncservice to synchronize updates between controller’s state by providing access to updates published by all other modules in the controller in an efficient manner. the controller starts up initializing the default modules and states such as forwarding and topology manager. the producer starts by reading the configuration to recognize the ip addresses of the neighboring controllers. the producer uses the isyncservice and initializes connection with the consumers, and joins each consumer that respond to a list of connections. state information such as topology and link discovery are shared using isyncservice. the channels are configured and ready for any new events from the data-collector. when changes occur (new events are detected), the data-collector sends network status to all connected consumers to notify remote controllers that a local status has changed and to synchronize data between controllers. the data-updater receives external data from the consumer and updates the system. 3.4 testbed and setup the network environment was emulated on three virtual machines (vms), where each vm represents a wan domain. the vms are emulated using ubuntu 16.04 lts. the vms emulate the claranet network topology in figure 2, obtained from the internet zoo topology, using mininet. the vms are emulated using graphical network simulator 3 (gns3), and each vm contains the local network composed by open virtual switch (vswitch), to which one virtual host is attached, and an sdn controller. the controllers form a full mesh on connecting with one another. with each controller managing one domain, the link between switches and hosts is set to 1 gbps for the bandwidth and 30 ms for the one-way delay (benamrane et al, 2017). http://www.azojete.com.ng mailto:wale@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):242-254. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 247 figure 2: claranet network topology (benamrane et al. 2017) 3.5 experimental description the vms are powered “on” from the gns3 interface, starting all three vms. each vm represents a wan domain. each domain controller is launched. the network topology in each domain is started using mininet. openflow 1.3 is used as the southbound protocol. after the successful establishment of openflow connections between the nodes (hosts and switches) and the controllers, then new traffic is injected into the network using the iperf tool, for a default time of 10 seconds. this is achieved by simulating a scenario where switches must request their controller for new events processing, by fixing one of the emulated hosts as a server and the remaining hosts as clients. new flow from the client passes through the switch, sending a packet-in message to its controller. the controller installs forwarding rule in the switch flow table. these operations result in network changes, causing the controller to synchronize with its neighboring controllers (benamrane et al. 2017). wireshark analyzer was used for network analysis, the experimental description was carried out on cidc and mcidc using notification mode. the experiment was carried out on different claranet network topology size as shown in table 1. table 1: network topology topology pseudo-name domain nodes per domain nodes claranet claranet_2 2 15 30 claranet claranet_3 3 15 45 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adedokun and adekale: development of a modified east-west interface for distributed control plane network. azojete, 15(sp.i2):242-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 248 3.6 performance metrics synchronization metrics such as tcp packets captured, tcp errors and intercontroller communication overload (ico) that could affect response time and controller performance in a distributed architecture are considered as performance metrics. the performance metrics are obtained from the wireshark analyzer. these performance metrics are used to evaluate the necessary data to synchronize information. i. tcp errors these are the tcp errors during conversations between client and server. these errors include: out-of order, dup ack, lost segment, fast retransmission, windows update and so on. ii. captured tcp packets this is the tcp packets captured using wireshark analyzer, between clients and server. the tcp packets represents the necessary information transmitted across different controller domains. iii. inter-controller communication overload (ico) this is the total rate of bidirectional traffic (kbit/s) exchanged between controllers, during transmission. 4. results and discussion in this section; simulation results for the claranet network topology are provided. for each metric, we obtained results for the cidc and mcidc, using the notification mode. claranet topology with different sizes was used to test, and compare the performance of cidc and mcidc. 4.1 captured tcp packets figure 3: captured tcp packets against tcp errors for cidc claranet_2 http://www.azojete.com.ng mailto:wale@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):242-254. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 249 figure 4: captured tcp packets against tcp errors for cidc claranet_3 figure 5: captured tcp packets against tcp errors for mcidc claranet_2 figure 6: captured tcp packets against tcp errors for mcidc claranet_3 it was observed from figure 3 to 6 that the number of packets increases from claranet_2 to claranet_3; showing that the number of packets is related to the number of nodes, the more connected nodes in the topology, the more packets are exchanged. it is also observed that the captured tcp packets increases as the tcp errors generated increases from claranet_2 to claranet_3 in both cidc and mcidc. comparing cidc (figure 3 and 4) and mcidc (figure 5 and 6); the number of captured tcp packets in mcidc is less than that of cidc with a percentage decrease of 26.55% and 15.82% for claranet_2 and claranet_3 respectively. this decrease file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adedokun and adekale: development of a modified east-west interface for distributed control plane network. azojete, 15(sp.i2):242-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 250 indicates that the isyncservice in mcidc requires less packet exchange for communication. 4.2 inter-controller communication overload (ico) figure 7: ico against tcp errors for cidc claranet_2 figure 8: ico against tcp errors for cidc claranet_3 figure 9: ico against tcp errors for mcidc claranet_2 http://www.azojete.com.ng mailto:wale@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):242-254. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 251 figure 10: ico against tcp errors for mcidc claranet_3 4.3 the ico as shown in figure 7 to 10 indicates that as the number of tcp errors generated increases, the ico decreases for both claranet topologies in cidc and mcidc. this decrease is due to the congestion of the tcp window pipe; making it difficult for exchange of information (traffic) between controllers. the ico in mcidc (figure 9 and 10) is less than that of cidc (figure 7 and 8), with a percentage decrease of 19.35% and 29.25% for claranet_2 and claranet_3 respectively. mcidc generates less ico during multi-domain communication across the wan. 4.4 tcp errors the tcp errors as shown in figure 3 to 10 shows that as the tcp errors generated increases; the captured tcp packets increases while the ico decreases for both cidc and mcidc. the tcp errors in mcidc is less than cidc with a percentage decrease of 17.89% and 21.60% for claranet_2 and claranet_3 respectively. this shows that mcidc enables sharing of necessary data among controllers with less generated errors; providing efficient network communication. 5. conclusion the east-west interface is very important in large sdn networks or sdn based multidomain networks with multiple controllers (such as wan). the main purpose of east –west interface is to synchronize states for high availability, by enabling communication between groups or federations of controllers; this is achieved through monitoring /notification capabilities and exchange of data between controllers. the mcidc is a modified east-west interface developed for wan, achieving high availability across multiple controllers in the control plane, for efficient communication. the mcidc improves on the cidc in the experiments, showing that the mcidc establish high availability with decrease in captured tcp packets and ico as compared to cidc. this will improve communication, policy updating and decision making in multi-domain networks (wan). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adedokun and adekale: development of a modified east-west interface for distributed control plane network. azojete, 15(sp.i2):242-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: wale@abu.edu.ng 252 acknowledgment we would like to thank nigeria liquified natural gas limited (nlng) for provision of computers and a laboratory to carry out this study. references benamrane, f. and benaini, r. 2017. an east-west interface for distributed sdn control plane: implementation and evaluation. computers and electrical engineering, 57: 162-175. blial, o., ben mamoun, m. and benaini, r. 2016. an overview on sdn architectures with multiple controllers. journal of computer networks and communications, article id 9396525: 8. chen, j., zheng, x. and rong, c. 2015. survey on software-defined networking. in: qiang w., zheng x., hsu ch. (eds) cloud computing and big data. cloudcom-asia 2015. lecture notes in computer science, springer. cham, n.y. jarraya, y., madi, t. and debbabi, m. 2014. a survey and a layered taxonomy of software-defined networking. ieee communications surveys and tutorials, 16(4):1955-1980. kreutz, d., ramos, f. and verissimo, p. 2013. towards secure and dependable software-defined networks. in proceedings of the second acm sigcomm workshop on hot topics in software defined networking, hong kong, china august 12 16, 103(1): 14-76. kreutz, d., ramos, f. m., verissimo, p. e., rothenberg, c. e., azodolmolky, s. and uhlig, s. 2015. software-defined networking: a comprehensive survey. arxiv preprint arxiv:1406.0440. lin, p., bi, j. and wang, y. 2013. east-west bridge for sdn network peering. in: su j., zhao b., sun z., wang x., wang f., xu k. (eds) frontiers in internet technologies. communications in computer and information science, 401: 170 -181. springer, berlin. liu, s. and li, b. 2015. on scaling software-defined networking in wide-area networks. tsinghua science and technology, 20(3): 221-232. oktian, y., lee, s., lee, h. and lam, j. 2017. distributed sdn controller system: a survey on design choice. computer networks, 121: 100 – 111. phemius, k., bouet, m. and leguay, j. 2014. disco: distributed multi-domain sdn controllers. in 2014 network operations and management symposium (noms) ieee: pp.1–4. rao, a., auti, s., koul, a. and sabnis, g. 2016. high availability and load balancing in sdn controllers. international journal trend research and development, 3 (2): 310314. wibowo, f. and gregory, m. 2016. software defined networking properties in multidomain networks. in 2016 26th international telecommunication networks and applications conference (itnac), new zealand: pp. 95-100. ieee http://www.azojete.com.ng mailto:wale@abu.edu.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 101-110 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng __________________ *corresponding authors e-mail: peter.adeoye@futminna.edu.ng 101 original research article assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria p. a. adeoye,1* z. saidu,1 a. i. kuti,2 j. ibrahim and b. a. adabembe3 1department of agricultural and bioresources engineering, federal university of technology, p.m.b. 65, minna, niger state, nigeria. 2college of agriculture, p.m.b. 109, mokwa, niger state, nigeria. 2department of water resources management agrometeorology, federal university, oye ekiti, ekiti state, nigeria article information received october, 2018 accepted december, 2018 keywords: waste water heavy metals uptake health risk index daily intake rate hazard index abstract consumption of vegetable crops grown on soil irrigated with industrial wastewater has been the order of the day in most urban towns and cities of nigeria, despite reports of its serious health impact. this study assessed the possibility of uptake of heavy metals by crops grown on soil receiving industrial wastewater during rainy and dry seasons. the crops investigated are spinach, cayenne pepper, jute mallow, roselle and lady’s fingers okra. the initial composition of the wastewater was analyzed to contain 0.89 mg/l of chromium, 0.74 mg/l of cadmium, 1.04 mg/l of copper and 2.81 mg/l of iron. control water used for this experiment contain no trace of any of these heavy metals. the experimental soil was also analyzed and contained 0.10 mg/kg of chromium, 0.06 mg/kg of iron before irrigation in dry season. after irrigation at the wastewater plots, the heavy metal concentrations in soil had increased to 6.24 mg/kg of chromium and 7.50 mg/kg of iron. in wet season, the concentrations of heavy metals in the soil were 0.00 mg/kg of chromium and 2.32 mg/kg of iron before irrigation. after irrigation in wet season, the concentrations increased to 6.01 mg/kg of iron. mean difference of heavy metal concentrations were significantly high in vegetables in dry season, with values ranging from 0.03 mg/kg to 211mg/kg in wastewater plots, 0.20 mg/kg to 215 mg/kg in wet seasons wastewater plots, 0.00 mg/kg to 157 mg/kg in dry season. it is however recommended that consumption of vegetables irrigated with domestic/industrial wastewater be strongly discouraged because of its serious health implications. © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1. introduction irrigation is the application of water to soil for the purpose of supplying moisture essential for plant growth (egharevba, 2009). irrigation depends basically on the availability of water and water rights. irrigation leads to accumulation of heavy metals in the soil if wastewater and sewage water are use (queirolo et al., 2000). using wastewater to irrigate agricultural land is one of the ways to reuse the http://www.azojete.com.ng adeoye, et al. assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria. azojete, 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 102 wastewater from urban and industrial areas (zegi, 2018). heavy metals implicated as a result of sewage water includes cu, cd, zn, pb, ni, cr, in food items. even at low concentrations of heavy metals in sewage effluents, long term uses of sewage often result in built up of these metals in the soil and consequently taken up by plants. other sources of heavy metals in the soils include industrial and domestic effluents in addition to agricultural applications of fertilizer and pesticides (singh et al. 2009; kalaskar, 2012). the reuse of domestic and industrial waste water for plant growth is one of the options during water scarcity, and remains the common sources of water for irrigation of vegetables in most urban towns and cities of nigeria. it contains an appreciable quantity of plant requirement though are a chief contributor to metal load in irrigated land from wastewater (rattan et al., 2005; mahmood and malik, 2013). this leads to environmental pollution which brings food safety issues and potential health risks due to the accumulation of heavy metals in agricultural soil and plants. it also possesses potential barriers for international trading of food stuff (cui et al., 2004). most crops irrigated with wastewater are vegetables. vegetables accumulate heavy metals existing in the environment in their edible and non-edible parts. intake of vegetables that is contaminated is an important path of heavy metal toxicity to humans (wang et al., 2005; rattan et al., 2005 and osma et al., 2012). a plant that is contaminated with high concentrations of heavy metals does not have visible changes in their appearance or yield but exceed animal and human tolerance. during the last twenty years, environmental problems have started to be a part of daily life in several countries. their impact is clearly on the manifest on the terrestrial and aquatic flora fauna, and keeps on increasing (osma et al., 2012). knowledge of metal-plant interaction is important for the safety of the environment and for reducing risk of introduction of trace metals into the food chain. the anthropogenic sources of environmental pollution by heavy metals include traffic emissions (vehicle exhaust particles, tire wear particles, weathered street surface particles, brake lining wear particles), industrial emissions (power plants, coal combustion, metallurgical industry, auto repair shops, chemical plants, etc.), domestic emissions, and weathering of building and pavement surfaces (rattan et al., 2005). human activities in most cases have introduced potentially hazardous metals to the environment. this is as a result of the industrial revolution and urban development promoting a major threat to ecology and human well-being (mahmood and malik 2013). contaminated air, soil, and water by human activities are associated with disease burden and this could be reasons for the current shorter life expectancy in developing countries when compared with developed nations. heavy metal toxicity adversely disrupts growth and other physiological processes of plant, specifically leading to great economic and ecological trauma. if heavy metals move too rapidly in a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 103 particular soil, they can pollute ground and surface water supplies while it has generally been assumed that these metals are retained in agricultural soils (bichi and bello, 2013). despite all the glaring negative effects domestic and industrial wastewater causes to human health when used for irrigation, the trend of using wastewater for irrigation is at increase as most people lack adequate knowledge of the health risk that is involved. this paper therefore seek to investigate the heavy metals uptake and accumulation in some selected vegetables leaves, stems and roots in minna; as well as bringing forth useful recommendations for the farmers, the consumers and the policy makers. 2. materials and methods: 2.1 background and description of the study area niger state is one of the north-central states in the guinea savannah zone of nigeria. it is at sometimes called the food basket of the nation owing to the abundant potentials for all year round farming. geographically, it is located on longitude 6o 00’ 00’’ e and latitude 10o 00’ 00’’ n as presented in figure 1. it is characterized by two distinct seasons; rainy and dry seasons. short grasses and scattered trees in its extreme north and dense forest towards the south are features of its vegetation with mean maximum and minimum temperatures of 37 oc and 20 oc respectively. fig. 1: map of niger state showing its boundary with other states of nigeria 2.2 experimental set-up/arrangements a piece of land measuring 9m x 9m situated at dutsen kura along minna western by-pass in minna, niger state was selected as a plot area. wastewater from an urban drain (industrial/municipal) passing through keterin-gwari area was used as source of irrigation water at the wastewater irrigation plot, while water from a closed well at dutsen-kuran gwari, down police secondary school avenue was used for irrigation at control plot. the entire experimental set-up is as presented in figure 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al. assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria. azojete, 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 104 2.3 soil and water samples collection and analysis samples of water used for irrigation were collected in plastic bottles washed with detergent and distilled water and finally rinsed with the samples were stored at 4oc before taken to the chemistry laboratory of sheda science and technology complex (shestco) abuja, nigeria. soil samples from the selected plots were collected by digging a hole of 15 cm and a representative samples were made by the cone and quarter method after removing unwanted debris. the collected soil samples were then dried in an oven and then sieved, store in a labeled polyethylene bags. fig. 2: experimental plot design 2.4 vegetable samples collection three hundred grams of edible portion of different vegetables grown at the study area were collected and washed with distilled water to remove soil particles, separated into three parts, chopped into small pieces using a knife and kept air-dried for approximately 70 hours at 105oc. these samples were grinded into fine powder before use for heavy metals extractions by acid digestion. powdered samples (15g each) were placed in a silica crucible and few drops of concentrated nitric acid were added. dry-ashing process was carried out in a muffle furnace (swastik scientific co.mumbai, p.14, se.no 1021) by stepwise increase of the temperature up to 550°c and then left to ash at this temperature for 6 hours. the ash was kept in desiccators and then rinsed with 3n hydrochloric acid. 2.5 sample digestion and heavy metal determination concentrations of heavy metals in the acidic solution were estimated using atomic absorption spectrophotometer (spectrometer ice 3000 aa 02134 dell, thermo scientific pvt. ltd., india). soil to plant metal transfer was carried out as transfer factor using equation 1: �t = ��⽰ସ愀ю���th⽰ (1) where, ��⽰ସ愀ю is the concentration of heavy metals in plants and ��th⽰ is the concentration of heavy metal in the soil (mahmood and malik, 2013). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 105 health risk index of heavy metals was calculated by knowing the exposure levels of these metals on humans. the statistical package used for analyzing the collected data was spss software 22.0, 2006 version. one way anova was used for evaluating the significant difference between heavy metal concentrations in vegetables cultivated on the plots in dry and wet seasons. 3. result and discussions 3.1 result of heavy metal concentration in irrigation water the concentration of heavy metals in the wastewater samples used for irrigation were higher than their concentration in well water used for irrigation at the control plots, cadmium (cd) and chromium (cr) higher above standard as mentioned in who/fao (2007) and usepa (2010). however, the iron (fe) and copper (cu) concentrations are within the permissible level set by who/fao (2007). the results are as presented in tables 1 and 2. table 1: results of wastewater heavy metal analysis samples heavy metal composition (mg/l) cr cd mn cu fe 1 0.19 0.04 0.71 0.04 2.81 2 0.19 0.04 0.71 0.04 2.81 3 0.19 0.04 0.71 0.04 2.81 table 2: results of well water heavy metal analysis samples heavy metal composition (mg/l) cr cd mn cu fe 1 0 0 0.02 0 0 2 0 0 0.02 0 0 3 0 0 0.02 0 3.2 heavy metals concentrations in the soil concentrations of heavy metals in the soil before and after irrigation are as presented in tables 3 and 4. wastewater and well water plots (control plots) in dry season show higher concentrations of iron in both plots while wet season show less sign of heavy metal concentration. however the concentration was even less on the control plots as indicated in table 5. it could be deduced that the availability of these metals in the soil at its original state might have contributed to the uptake of some of these metals before the wastewater application. table 3: mean of metals (mg/kg) in dry season for soil samples at wastewater plots sample crm fem cum cdm before irrigation 26.10* 730.06** 0.26* 0.00* after irrigation 76.24* 777.50** 0.00* 0.02* results are mean difference *not significant < 1** significant = 1. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al. assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria. azojete, 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 106 table 4: mean of metals (mg/kg) in wet season for soil samples at wastewater plots sample fem crm cum cdm before irrigation 557.32 0.00* 0.00* 0.00* after irrigation 496.01 0.00* 0.00* 0.00* results are mean difference *not significant < 1 **significant = 1. 3.3 heavy metals concentrations in vegetables parts the anova test shows that concentrations of heavy metals are significant while some are not with respect to season’s interactions. the availability of heavy metals in plant parts may be due to the ability of the plant parts to store metals in their tissues, which is in line with the works of chauhan and chauhan (2014). table 5: mean of metals (mg/kg) in dry season for soil samples at well water plots (control plots) sample crm fem cum cdm before irrigation 25.10* 730.24* 0.26* 0.00* after irrigation 20.10* 71.240.26* 0.00* 0.00* the differences in the concentration of heavy metals in plant parts may also be due to their physiology and ability of the individual plants to take up, remove and store the metals in their various parts. this result also conforms to the results obtained by arora et al., (2008), kalaskar, (2012) and akan et al., (2013) who had a similar work and found out those different concentrations in vegetables grown using different sources of water. the concentration of heavy metals like fe, cu, cr and cd varies with the plant parts, but all are below the tolerable limit as stated by fao/who, (2010) and usepa, (2010) standards. rainy season’s accumulations were the list compared to the dry season analyzed. this might be due to the rain water that washes the heavy metals in the soil and wastewater below the root zone. okra leaves, pepper leaves and fruits irrigated with wastewater are seen to have accumulated higher concentrations of metals investigated. this is also in line with the works of bichi and bello (2013) in kano, nigeria and singh et al., (2010) in india which confirmed that vegetables have different accumulation capacity. 3.4 transfer factor of metals transfer factors of metals in vegetables grown using industrial/municipal wastewater is the ratio of concentration in plant tissues to the concentration of pollutant in the soil. as shown in figures 3 – 6, transfer factors of metals from soil to plant were found to be higher in dry season at wastewater plots with the values greater than 1, indicating that bioaccumulation has taken place while the values less than 1 indicates that bioaccumulation has not taken place (akpofure, 2012). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 107 fig 3: transfer factor (tf) of metals (mg/kg) in dry season for wastewater plots fig 4: transfer factor of metals (mg/kg) in wet season for wastewater plots fig 5: transfer factor of metals (mg/kg) in dry season for well water plots (control plots) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al. assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria. azojete, 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 108 fig 6: transfer factors of metals (mg/kg) in wet season for well water plots (control plots). chromium was found to be highly transferred with values that ranges from 0.01mg/kg to 1.47mg/kg with non-edible parts having the highest except for roselle fruits that has a value of 0.07mg/kg. iron was found to be present in all the vegetable parts analyzed with a range of 0.01mg/kg – 0.27mg/kg. the transfer value of copper and cadmium were negligible, and could be due to the inability of the crops to absorb the element in dry season due to the soil ph. in comparing the transfer factors of the studied elements in vegetables parts, the transfer factor for leaves was higher than the other parts signifying that bioaccumulation will occur first in leaves before other parts. this outcome is in accordance with that of akpofure (2012). from the wastewater plots in which irrigation was supplementary during the wet season, iron were found to have higher transfer factor with a value that ranges from 0.01mg/kg to 0.43 mg/kg with leaves of okra been the highest; however, the transfer factors of chromium, copper and cadmium were negligible. consequently in dry season iron has the highest transfer factor in the control plots with a value that ranges from 0.00 mg/kg to 2.21mg/kg, while chromium, copper and cadmium were also negligible. this might be due to the important of iron in chlorophyll of vegetables. result also showed that iron has the highest transferred factor with a range of 0.02 mg/kg to 1.63 mg/kg in the leaves of okra in the well water plot during the rainy season, while copper, chromium and cadmium were negligible. plots of transfer factors are as shown in figures 3, 4, 5 and 6 in the appendix pages. on metal toxicity in all the seasons for all the plots considered, wet seasons and dry season well water plots (control plots) were found to be the safest. 4. conclusions the assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria was successfully carried out during the 2016/2017 wet and dry seasons. concentrations of heavy metals were found to increase after the application of the domestic/industrial wastewater for irrigation on the plots. uptake of heavy of heavy metals like iron, chromium and cadmium by vegetables was also identified, most especially on the leaves of the plant. this is an indication that the population who consume such vegetables might have health http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 109 related problems since such metals are harmful to human season. it is however recommended that in as much as vegetables are very vital to human health, the growing processes must be done with qualitative and quantitative water. references ahaneku, ie. and sadiq, bo. 2014. assessment of heavy metals in nigerian agricultural soils. journal of environmental studies, 23(4): pp 1098-1100. akpofure, rr. 2012. uptake of heavy metals by okro (hibiscus esculentus) grown on abandoned dump sites in effurun, nigeria. journal of emerging trends in engineering and applied sciences (jeteas) vol. 3(4): pp 640-644. arora, m. kiran, b. rani, s. kaur, ab. and mittal, n. 2008. heavy metal accumulation in vegetables irrigated with wastewater from different sources. journal of food chemistry, (111) pp 811-815. al-jaboobi, m. zouahir, a. mennane, z. tijane, m. el-housni, a. yachou, h. and bouksain, m. 2014. evaluation of heavy metals pollution in groundwater, soil and some vegetables irrigated with wastewater in skhirat region “morocco”. journal of material and environmental science. 5(3): pp 961-966. akan, jc. kolo, bg. yikala, bs and ogungbuaja,vo. 2013. determination of some heavy metals in vegetable samples from biu local government area, borno state, north eastern nigeria. international journal of environmental monitoring and analysis. 1(2): pp 40 46. bichi, mh. and bello, uf. 2013. heavy metals in soils used for irrigation of crops along tatsawarki in kano, nigeria. international journal of engineering research and development. 8(4): pp 01-07. cui, yj., zhu, yg., zhai, rh. chen, dy., huang,yz., qiu, y. and liang, jz. 2004. transfer of metals from soil to vegetables in an area near a smelter in nanning, china. journal of environmental international. 30: pp 785791. chauhan, uk. and chauhan, g. 2014. risk assessment of heavy metal toxicity through contaminated vegetables from wastewater irrigated area of rewa (m.p.), india. international journal of advanced technology in engineering and science. vol. 2. pp 44-460. egharevba, na. 2009. irrigation and drainage engineering, principles, design and practices. second edition. jos university press. isbn: 978-166-847-4. pp 8-26. kalaskar, mm. 2012. quantitative analysis of heavy metals from vegetables of amba nalain amravati district. der pharma chemical. journal of scholars research library. 4(6): pp 23732377. mahmood, a. and malik, rn. 2013. human health risk assessment of heavy metals via consumption of contaminated vegetables collected from different irrigation sources in lahore, pakistan. arabian journal of chemistry. pp 9199. osma, e. serin, m. leblebici, z. and aksoy, a. 2012. heavy metals accumulation in some vegetables and soil in istanbul. ekoloji journal. 21(82): pp 1-8. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeoye, et al. assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial wastewater in minna, nigeria. azojete, 14(sp.i4):101-110. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 110 queirolo, f. stegen, s. restovic, m. paz, m. ostapczuk, p. schwuger, mj. and munoz, l. 2000. total arsenic, lead, and cadmium levels in vegetables cultivated at the andrean villages of northern chile. the science of total environment. 255: pp 75-84. rattan, rk. datta, sp. chonkar, pk. suribabu, k. and singh, ak. 2005. long-term impact of irrigation with sewage effluents on heavy metal content in soils, crops and groundwater. a case study. journal of agriculture ecosystem and environment. 109: pp 310-322. singh, a. sharma, rk. agrawai, m. and marshall, fm. 2009. risk assessment of heavy metal toxicity through contaminated vegetables from wastewater irrigated area of varanasi, india. journal of international society for tropical ecology. 1(25): pp375-387. usepa. 2010. risk-based concentration table, united state environmental protection agency, washington dc. who/fao. 2007. joint fao/who food standard programme codex alimentary commission, 13th session. wang, g. yusu, m. huichen, y. fan, lld. and fang, gs. 2005. transfer characteristics of cadmium and lead from soil to the edible parts of six vegetables species in south-eastern china. journal of environmental pollution. 144: pp127-135. zegi, u. 2018. assessment of heavy metals uptake by vegetables cultivated on soil receiving industrial/ municipal wastewater in minna, niger state. nigeria. a thesis, submitted to postgraduate school, federal university of technology minna. in partial fulfillment of the requirement for the award of master degree in soil and water engineering. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1049-1060 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mtjimoh.mec@buk.edu.ng 1049 original research article development of a pseudo-closed loop solar collector sun tracking system with optimized set-point paths for flat plate payload m. t. jimoh* and a. b. aliyu (department of mechanical engineering, bayero university, kano, nigeria) * corresponding author’s email address: mtjimoh.mec@buk.edu.ng 1.0 introduction conventional energy sources like oil and coal still constitute more than 80% of the global energy mix (iea, 2018). yet apart from being finite, the conventional energy sources pollute and warm the environment. according to a report by (nasa, 2018), about 97% of actively publishing climate scientists agree that the earth’s climate is warming due to human activities, especially the use of fossil fuels. these reasons have given impetus to the exploration and use of nonconventional, clean, and renewable energy sources such as solar energy and wind energy. solar energy is the direct utilization of the sun’s radiant energy. a major component of all solar energy applications is the payload the part that absorbs the solar energy directly and converts it to a useful form, or transmits it to another media. in helioelectrical applications, the payload is the solar photo-voltaic panel, and it is a solar collector in helio-thermal applications. solar collectors absorb solar energy and convert it into heat which is then transferred to a stream of liquid or gas. to get the most from solar payloads, they must be pointed to the directions that capture the most solar energy. in general, results show that solar tracking can increase the yearly energy capture by up to 40% compared to the case in which the payload is fixed (bari, 2000, lee et al., 2009, mohd et al., 2001). solar tracking can be manual or automatic. in automatic solar tracking, the payload tracks the sun at all times with very little human intervention (that is the angle of incidence of the sun with respect to the receiving surface of the payload equal to zero at specified times). in the strict sense, there are two categories: open loop tracking and closed loop tracking. between these two categories, there can be another – a pseudo closed loop solar tracking. all these are explained as follows. article information abstract this paper provides the theoretical framework for the development of a pseudo-closed loop solar tracking system incorporating a microcontroller for a flat payload, where the outputs of the system (the slope and the azimuth angles of the payload) are observed and the set-points for the system are to be optimally computed by the microcontroller. it also presents, from literature, the equations and models solar angles and incident angles for the development of the optimum set point path for the tracking, and gives the outline of the signal flow plan, as well as the corresponding flowchart, for the tracking system’s components interaction. the concept would provide a cheaper and simpler alternative to dual axis solar tracking incorporating solar sensors. the models presented here are adaptable to any geographical location in nigeria and globally. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 january, 2019 revised 07 july, 2019 accepted 07 july, 2019 keywords: solar collector solar tracking closed-loop tracking open-loop tracking angle of incidence. http://www.azojete.com.ng jimoh and aliyu: development of a pseudo-closed loop solar collector sun tracking system with optimized set-point paths for flat plate payload. azojete, 15(4):1049-1060. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1050 1.1 open loop solar tracking in open-loop tracking, data of the desired payload’s altitude and surface azimuth angles at specified times are computed based on some sun-earth geometry or models, or solar irradiation algorithms. the data is fed into, or computed by, an appropriately coded microcontroller which, using information from a real time clock sends signal to an actuating mechanism to manipulate the altitude and surface azimuth angles of the payload appropriately. figure 1 gives a schematic of a general open-loop solar tracking. it can be seen from the figure that an open-loop solar tracking system only manipulates the altitude and/or surface azimuth angles of the payload, it does not observe the actual payload’s incidence angle using any form of sensor or feedback mechanism, so it cannot correct for any errors in the actual incidence angle. for this reason, it is poor in disturbances rejection. models and algorithms for computing the desired paths for open-loop solar tracking systems exist in literature. some of these modes and algorithms require basic input parameters such as date, time (local standard time (lst), time zone (tz)), longitude, latitude and surface azimuth rotation of a location. the very complex and precise algorithms are contained in blanco-muriel et al. (2001), michalsky (1988), grena (2008), meeus (1998) and reda and andreas (2004). actual development or design and construction of open loop solar trackers using a form of the formulas and algorithms already mentioned have also been reported. among them is al-naima and yaghobian (1990), who designed and constructed a dual axis sun tracker in which the controller is a microprocessor. abdallah and nijmeh (2004) used plc controllers in the dual sun tracker they developed. 1.2 closed loop solar tracking closed-loop tracking systems are based on feedback control principles. in these systems, the payload’s incident angle is sensed indirectly through a system of light detecting or measuring devices such as light detecting resistors (ldr), pyrheliometer and four quadrant photo detectors. using feedback mechanisms, the error signal from the sensed incident angles are sent to a controller, which carries the necessary control action and send to the actuator. a form of closedloop tracking system (with provision for alternate set point input) is shown in figure 2. because of the light sensor and controllers required in their operations, closed loop solar tracking systems are generally more complicated and expensive than the open-loop solar tracking systems. transducer controller actuatordesired altitude/ azimuth angle 1 ldr 1 actual altitude/ azimuth angle payload comparator ldr 2 incidence angle equivalent sensors/ transducers +2-+ sensors/ transducers comparator figure 2: schematic of closed loop solar tracking real time clock actuator payload actual altitude/ azimuth angle micro controlleroptimum altitude/ azimuth angle data figure 1: schematic of open loop solar tracking http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1049-1060. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1051 different types of closed loop solar tracking systems have been developed. kalogirou (1996), barsoum (2011) and aiuchi et al. (2004) employed light-dependent resistors (ldrs) in their oneaxis closed loop solar tracking systems. jiang and cao (2003) used an emulated sunflower based on a spherical four-quadrant photoelectric sensor for sensing the incident angle of their solar tracking systems. roth et al. (2004) and georgiev et al. (2004) designed and constructed a sun tracking system in which a pyrheliometer was used to measure the direct solar radiation, a fourquadrant photo detector to sense the sun’s position. xinhonz et al. (2007) and alata et al. (2005) used fuzzy logic algorithms in their controllers. the objective of this paper is to develop a tracking system that is a bridge between the open loop system and closed loop system described above. such developed tracking system is termed pseudo-closed loop solar tracking system and the process is presented in the following section. 2.0 materials and methods the main material for this research is a computing facility with matlab® software. the methods include conceptualising the pseudo-closed loop solar tracking system, presenting and simulating the solar energy equations required for developing the optimum set points for the pseudo tracking system, and developing the procedure required for implementing the pseudo closed loop solar tracking system. 2.1. the pseudo-closed loop solar tracker concept the proposed pseudo-closed loop solar tracker will have all the features of an open loop system but would also incorporate a feedback system to observe the altitude and surface azimuth angles of the payload. it is a pseudo-closed loop tracker in the sense that the feedback would not observe the actual incidence angle of the sun. the development of the concept of the tracker, and its components, as well as the development of the equations to be used for obtaining its optimum set-points, and its signal flow plan, are presented in the following subsections. figure 3 is a schematic of the pseudo-closed loop solar tracker. compared to a closed loop system of the type shown in figure 2, the pseudo-closed loop system would use a smaller number of sensors/transducers, and would avoid the use of controllers like pid, fuzzy logic and the like, that may introduce additional complications in design and implementation. it has as its major components a microcontroller, a real time clock, angular position sensors and actuators. the microcontroller uses signal from the real time clock to determine which value from the optimum altitude and azimuth data set to be used as error signal for the actuator at specified time interval. the optimum dataset may be supplied externally, as indicated in figure 3, or the codes for generating it may be stored in the microcontroller and the optimum dataset computed real time clock actuator payload altitude angle micro controlleroptimum altitude and azimuth angles data sensor/ transducer figure 3: schematic of pseudo-closed loop solar tracking system file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jimoh and aliyu: development of a pseudo-closed loop solar collector sun tracking system with optimized set-point paths for flat plate payload. azojete, 15(4):1049-1060. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1052 this concept does not correct for any errors in the actual incidence angles: this will depend on the accuracy of the algorithm used to obtain the optimum set point paths, and the system setup and calibration during installation. in addition, having optimized set-point calculation incorporated in a pseudo-closed loop system is an avenue to experiment on the correctness of existing solar angle models and algorithms. 2.2 developing the optimum set point path for the pseudo-closed loop solar tracker the main aim of solar tracking is always to try and keep the angle of incidence of solar radiation on a payload at or close to zero . optimum set point path is about being able to specify the degree of vertical and/or horizontal rotation of the payload necessary to make the angle equal to zero at specified times. for this a form of solar geometry formulas or algorithms for estimating the angle of incidence and the position of the sun, is required. for many solar energy applications, tracking accuracy of between 0.1° and 0.25° is sufficient given that the diameter of the solar disk subtends an angle of 0.52° (at aphelion, when the sun is farthest) to 0.54° (at perihelion, when the sun is closest) in the sky (myer, 2013) . for these situations, solar tracking equations or algorithms used need not be overly complex. the basic equations for estimating the angle of incidence as contained in duffie and beckman (1991), tiwari (2002), myer (2013), and some solar energy books as described in this section will suffice for those situations. 2.2.1 angle of incidence (��) for a flat payload, the angle of incidence (θi ) is the angle between the beam radiation and the normal to the surface of the payload (duffie and bechman, 1991). this angle is a function of three sun-earth angles the latitude angle (ϕ) , the declination angle (δ) , the hour angle (ω) , and two other angles which define the placement of the payload on a surface – its slope angle (β) and its surface azimuth angle (γ ). the geometrical relationships between these angles are shown in figure 4. the angle of incidence is defined by its cosine (duffie and beckman, 1991) as: cosθi = sinδsinϕcosβ + cosδcosϕcosβcosω + cosδsinϕsinβcosγcosω + cosδsinβsinγsinω − sinδcosϕsinβcosγ (1) the latitude angle, together with the longitude angle, uniquely defines a location on the earth’s surface. the declination angle and the hour angle are defined as follows: a) declination angle (δ) the declination angle is the angle between the equatorial plane and a line joining the centres of the sun and the earth, and this angle gives rise to variation in the length of the day (sunshine hours) throughout the year. the equation for calculating the declination angle for a non-leap year is given (duffie and beckman, 1991) as: δ = 23.45sin 360 365.25 284 + n (2) where n is the number that represents the day of the year, for example, n = 32 on the 1st of february. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1049-1060. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1053 � figure 4: relationship between azimuth, zenith, altitude and incidence angles b) the hour angle (ω) the hour angle is the angle of the sun from solar noon. for solar radiation calculations, the solar time is used instead of the local standard time. when the solar time (st) for the location in hours is known, the hour angle can be calculated from (tiwari, 2002): ω = 15 st − 12 (3) while the local standard time ( lst ) is always known, the solar time ( st ) for a location is obtained from calculation as (iqbal, 1983): st = lst − 4 ψst −ψa + et (4) where, ψst = the standard longitude (time zone), in degrees, for the location. ψa = the actual longitude angle (in degrees) for the location. lst = the local standard time (in hours) and et is the equation of time in hours given as (spencer, 1971): et = 229.2 60 0.000075 + 0.001868cosb− 0.032077sinb − 0.014615cos2b− 0.04089sin2b (5) where b is defined as: b = 360(n − 1)/365 (6) 2.2.2 the position of the sun the position of the sun with respect to a location on the earth’s surface can be defined using the altitude angle ( α ), the zenith angle ( θz ) as well as the solar azimuth angle ( γs ). the relationships between these angles are defined as follows: a) altitude angle and zenith angle the zenith angle is the angle between the sun’s ray and the perpendicular line to a horizontal plane at the location (figure 7). the altitude angle (α ) is the complement of the zenith angle. the altitude angle (and the zenith angle) can be calculated from the expression (myer, 2013): sinα = cosθz = sinδsinϕ + cosδcosωcosϕ (7) b) the solar azimuth angle (γs) in the northern hemisphere, the solar azimuth angle is the angle between the projection on a horizontal plane, of a line between the sun and a point (say p), and the line due south (figure 4). in the southern hemisphere, it is defined as the angle between the projection and the line due north. by convention, the azimuth angle is taken as negative east of south and positive west of south for northern hemisphere (it is taken as negative east of north and positive west of north file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jimoh and aliyu: development of a pseudo-closed loop solar collector sun tracking system with optimized set-point paths for flat plate payload. azojete, 15(4):1049-1060. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1054 for southern hemisphere). this means that γs is negative in the morning, and positive in the afternoon, and therefore, the sign of γs should match that of the hour angle ω . the solar azimuth angle can be calculated from the expression (myer, 2013): cosγs = (sinαsinϕ − sinδ)/ cosδcosϕ (8a) or cosγs = (cosδsinϕcosω − sinδcosϕ)/cosα = (cosδsinϕcosω − sinδcosϕ)/sinθz (8b) taking the inverse cosine to obtain γs in equation (8) will not always come with the correct sign. so, it must be ensured that γs takes the sign of the hour angle ω as explained before. if δ > 0 , the sun can be north of the east-west line. in addition to the angles mentioned in the above equations, it is important to know when it is sunrise or sunset, and calculate its accompanying angles, so that the actuator may be instructed about periods of idleness or activity. for this the following angles and hours are defined. c) hour angle at sunrise (ωsr) and sunset (ωss) at sunrise, the zenith angle is 90o (altitude angle equals to 0o) on a horizontal plane, and this information is used in equation 7 to obtain the expression for the hour angles at sunrise and sunset. thus sunrise (or sunset) hour angle can be calculated from (tiwari, 2002): ωs = cos−1 − tanϕtanδ (9) the sunrise (or sunset) angle can also be evaluated using the following equations (myer, 2013): cosωs = cosθz − sinδsinϕ cosδcosϕ (10) sinωs =− cosαsinγ cosδ (11) the hour angles at sunrise ( ωsr ) and sunset ( ωss ) are the same numerically (i.e. ωsr = ωsr = ωs ), however the sunrise hour angle is negative and the sunset hour angle is positive. d) number of daylight hours (n) the total angle between sunrise and sunset, in degrees is thus equal to 2ωs. this angle between sunrise and sunset (2ωs ) can be used to find the number of daylight hours (n) for a particular day by using the expression (tiwari, 2002): n = 2ωs 15 (12) there are always 4380 hours of daylight per year (non-leap year) everywhere on the globe. when − tanδtanϕ ≥ 1, there is no sunrise (i.e. 24 hours of darkness). this implies that ωsr = 0. also the solar times at sunrise and sunset for this condition are both equal to 12. when − tanδtanϕ ≤− 1 , there is no sunset (i.e. 24 hours of daylight). this implies that ωsr =− 180 and ωss = 180. the solar times at sunrise and sunset for this condition are respectively equal to 0 and 24. 2.2.3 optimum set point path for solar tracking. equation (1) shows that in order to make a flat payload track the sun, only its surface orientation ( β ) and surface azimuth angle ( γ ) are open to adjustments. the others (the latitude, the declination and the hour angles) are automatically determined from knowledge of the location http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1049-1060. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1055 and the date and time. therefore, the cosine of the angle of incidence may be expressed as a function of two variables by re-writing equation (1) as: cosθi = c1cosβ + c2sinβcosγ + c3sinβsinγ (13) where c1 = sinδsinϕ + cosδcosϕcosω c2 = cosδsinϕcosω − sinδcosϕ c3 = cosδsinω from equation (13), the pair of the values of β and γ which makes the cosine of the angle of incidence equal to unity, or the angle of incidence equal to zero, at any location and for specified date and time, is that which makes the payload perfectly tracks the sun at that time. so, sun tracking is about finding the optimum values of this pair at desired times. equation (13) can further be reduced to one of a function of a single variable if, at any location and for specified date and time, the payload is oriented such that its surface azimuth angle (γ) is numerically equal to the solar azimuth angle ( γs ), as can be seen from figures 4 and 5. so equation (13) may be re-written for case the of perfectly tracked sun as: c6cosβ + c7sinβ − 1 = 0 (14) where c6 = sinδsinϕ + cosδcosϕcosω c7 = cosδsinϕcosωcosγs + cosδsinωsinγs − sinδcosϕcosγs with reference to figure 3, a microcontroller in a pseudo closed loop control can be coded to calculate the desired inclination angle ( β ) and azimuth angle ( γ ) a location at regular time intervals in a day, or even as once in a day, once in a month or once a year calculation. then this optimum data set would be sent to the actuator for the desired altitude and azimuth alignment. the feedback path in the figure (with its sensors or transducers) is optional, just to provide either historical data and/or to provide information about the correctness of the control system. optimum value of β for known γs , at any location and period, can be evaluated from equation (14) by closed-domain method for solving nonlinear equations such as bisection method or false position method. the matlab® software has a function fminbnd for solving single variable closed-domain problems. using matlab® software, the codes for evaluating equation (13), and all the associated equations from equations 1 to 12, are implemented and the trends of the angle of incidence for a range of surface orientation (β) and surface azimuth angle (γ), for kano, nigeria (11.9683 °n, 8.4261 °e) at 14:27 hour on 19-oct-2018, as an example, computed. 2.2.4 development of the signal flow plan for the pseudo-closed loop solar tracking system a signal flow plan, which describes an option of calculating the optimum angles for sun tracking as once a day, was developed. a flowchart for implementing such code for a microcontroller was also developed. the option of once a day calculation was preferred over periodic calculations within a day to reduce the computational load on the microcontroller. it was also preferred to the other options (once a month or year calculations) for data storage issues. the proposed pseudo-closed loop solar tracking system would operate by having its set-points (optimum azimuth and slope angle) being automatically adjusted. the development of the signal flow plan for the system is such that it should be fully operational for all days of the year, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jimoh and aliyu: development of a pseudo-closed loop solar collector sun tracking system with optimized set-point paths for flat plate payload. azojete, 15(4):1049-1060. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1056 if it is powered on. the complete signal flow chart is given in figure 5, and the steps in the signal flow plan are outlined as follows: power on read current date make � = 0� � = 0 as set points calculate sunrise and sunset times delay by ���u read current time no current time within sunrise and sunset? yes calculate optimum � and � for times of the day send optimum data to internal storage read current time end of day? yes no check for equality between current time and stored times calculate off-service delay times ���u delay by ���� calculate end-of-day delay time ���� delay by 30 secs read current time no equality found? yes make current � and � as set points delay by 2 mins figure 5: flow chart for the pseudo-closed loop sun tracking system set � = 0� � = 0 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1049-1060. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1057 at power on, the system reads the latitude and longitude data for the location. it then makes the set-points for the system (azimuth and slope angles) equal to zero. the system then reads the current date from the attached real time clock the system then calculates the sunrise and sunset times for the day, using equations 2,3 and 9. the system then reads the current time the system then checks if the current time is within sunrise and sunset times calculated in step 3. if the current time is not within sunrise and sunset times, the system calculates the necessary delay time tdos based on the current time and the sunrise and sunset values calculated. the system is then delayed by tdos, then returns to step 3 to attempt another date reading. if the current time is within sunrise and sunset times, the system calculates the optimum azimuth and slope angles for specified time intervals (say every 4 minutes) between sunrise and sunset. it uses equations 2-6, 8, 14 the system sends the optimum set-point data to the internal storage of the microcontroller. the system reads the current time again (to compensate for any time lapse since the first reading) the system checks if the end of day has been reached (i.e. if current time is beyond the sunset time value already calculated. if it is end of day, the system calculates the necessary delay time tded based on the current time and the sunset values calculated. the system is then delayed by tded , then returns to step 3 to attempt another date reading. if it is not end of day, the system searches for a match between the current time and the stored times in the optimum data table of the microcontroller. if equality is not found in step 11, the system delays by 30 seconds and return to step 8 to read the current time. if equality is found, the system sets the corresponding slope and azimuth data that is a match for the data (in step 11) as the set point for the system. the system delays by 2 minutes (assuming the optimum times were calculated at 4-minute intervals) before returning to step 9. 3. results and discussions as an example, the plots of the trends of the incident angles (θi ) for various azimuth angles (γ) and inclination angles (β) are plotted as shown in figure 6 for kano, nigeria (11.9683 °n, 8.4261 °e) at 14:27 hour on 19-oct-2018. while figure 6(a) shows the 3-d plot, figure 6b shows its contour plot. the contour plot (with the colour bar at the right) shows that at this time, the optimum pair of β and γ lie in the darkest part of the plot (the dark blue region is the region of lowest angle of incidence), which evaluates to between 22° to 55° for β and 30° to 75° for γ. while figure 6 shows the different combinations of azimuth angles (γ) and inclination angles (β) to give possible incident angles (θi ) at an instant (a given time), figure 7 shows the plots of optimum pairs of β and γ for a day. for the date specified for kano, nigeria on 19-oct-2018, the optimum pair of β and γ that will make a flat payload track the sun from sunrise to sunset are given in the figure. the solar time is shown on the horizontal axis while the azimuth and inclination angles are shown on the vertical axes. for example, the figure shows that the optimum pair of β and γ at 10.00 solar time on this date is about 55° for β and -40° for γ (the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jimoh and aliyu: development of a pseudo-closed loop solar collector sun tracking system with optimized set-point paths for flat plate payload. azojete, 15(4):1049-1060. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address:mtjimoh.mec@buk.edu.ng 1058 points where β and γ curves intersect the 10.00 solar time line). likewise on this date, the optimum pair of β and γ at 12.00 solar time is about 0o for β and 35° for γ, and at 14.00 solar time, the optimum pair is about 45° for β and 40° for γ. 4.0 conclusions a concept of pseudo-closed loop solar tracking system for a flat payload, where the set-points for the system are optimally computed by a microcontroller, and the outputs of the system (the slope and the azimuth angles of the payload) observed, has been proposed. the models for the development of the optimum set point path for the tracking system for use within a microcontroller are also presented. example of using the models to calculate optimum payload orientation angle and azimuth angle for a given day was presented. the outline of the signal flow plan for the tracking system’s component interaction, and the corresponding flowchart, were also developed and presented. the pseudo-closed loop solar tracking system offers a viable and cheaper alternative to a full closed loop solar tracking system. figure 6: 3-d plot (a) and contour plot (b) of angles of incidence for ranges of inclination angle (β ) and azimuth angle (γ ) for kano, nigeria (11.9683 °n, 8.4261 °e) at 14:27 hour on 19-oct2018 figure 7: plots of optimum pairs of inclination angle (β) and azimuth angle (γ) from sunrise to sunset for kano, nigeria (11.9683 °n, 8.4261 °e) on 19-oct-2018 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; 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[online]. available at: https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/dc/_2007/t3c.pd f [accessed 2019] https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/dc/_2007/t3c.pdf https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/dc/_2007/t3c.pdf http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):164-178 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 164 original research article prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study m. n. bello* and m. a. musa (department of chemical engineering, university of maiduguri, maiduguri, borno state, nigeria) *corresponding author’s email address: mnasirbello@gmail.com article information abstract natural gas compressibility factor plays important roles in pipeline design, reserve estimation and gas metering. the aim of this study is to presents the most accurate and reliable method of computing gas compressibility factor in a single-phase gas reservoir at various reservoir pressures. in this study, the gas compositions and the specific gravity of the respective gas compounds were retrieved from literatures. this specific gravity determine the pseudo critical and the pseudo reduced properties (temperature and pressure) of the respective gas compounds being studied. the predicted methods studied are papay correlation, hall-yarborough equation of state (eos), viral eos, beggs and brill and dranchuk-abu-kassem correlation. the methods are expressed as functions of the pseudo-reduced temperature and pressure, thereby predicting the compressibility factor of the predicted methods. the accuracy and the performance of the methods were tested by comparing the results obtained from the methods studied with experimental z-factor values obtained from the literatures. the experimental z-factor values were set as standard for the predicted methods studied. six (6) statistical parameters and various charts (line and column charts) were used to attest the effectiveness and the precision of the methods. the statistical tools are average absolute error (aae), average absolute relative error (aare), root mean square error (rmse), residual sum of square (rss), mean square error (mse) and coefficient of determination (r2). the results of the study shows that, the papay correlation has the highest coefficient of regression, r2= 92%, rated as the most accurate, reliable and best method. the hallyarborough equation of state has r2 of 86%. the viral equation of state has r2 of 83%. the beggs and brill correlation has r2 of 42%. the dranchuk-abu-kassem correlation has r2 of 10.5%. the beggs and brills correlation method is not suitable for application, if the pseudoreduced pressure is less than 0.92. the dranchuk-abu-kassem correlation is only applicable, if the pseudo-reduced properties are within the range of 0.2<ppr<15, 1.0<tpr<3.0. the hall-yarborough equation of state cannot be used if the pseudo-reduced temperature is less than one. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 december, 2019 revised 13 july, 2019 accepted 28 july, 2020 keywords: compressibility factor pseudo-critical temperature and pressure pseudo-reduced temperature and pressure equation of state correlation statistical tools single phase reservoir. mailto:mnasirbello@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 165 1.0 introduction natural gas plays an important role in the global energy resources transition to a cleaner, affordable, and safer energy utilization (world energy resource, 2016). this causes the gas demand to increase globally by 1.7% to 3468.6bcm (billion cubic meter) in 2015 which was an improvement over the 2014 consumption rates. the consumption rate decreased significantly in the last decade, 2.3% average observed from 2005 to 2015 (bp statistical review of world energy, 2017). natural gas is widely used as sources of energy in power sector, transportation sector, building and industry. these sectors largely increased the consumption of natural gas by 87.3% from the 3507bcm (billion cubic meter) global consumption rate (bp statistical review of world energy, 2016). the power sector is the highest consumer of the energy resources which is responsible for the continued increase in demand for natural gas (bp statistical review of world energy, 2016). in 2013, the power sector represents 40.3% (1414 billion cubic meter) of the total utilization of the gas (bp statistical review of world energy, 2016). natural gas is the essential component of energy that powered the world and is the most important of all sources of energy, (speight, 2007). natural gas is environmental friendly compared to other fossil fuels (speight, 2007). it availability, affordability and environmental friendly makes the world energy demand to shift natural gas. nigeria is renowned for its vast gas reserve which was estimated to be 202 trillion cubic feet (5.475 trillion cubic meter) of proved gas reserved in 2019, ranking 1st and 8th position in the africa and the world respectively. the production of natural gas in nigeria increases from about 6bcfpd (billion cubic feet per day) in 2012 to about 10bcfpd (billion cubic feet per day) (avuru, 2013). in 2019, the production increased to 44.48bcm (billion cubic meter). the domestic consumption of gas rises from 1bcf/d (billion cubic feet per day) in 2012 to 3bcf/d (billion cubic feet per day) in 2020 with power sector being the largest consumer of the energy resources (avuru, 2013). nigeria is the largest exporters of natural gas via liquefied natural gas (lng) in the world (world energy resources, 2016). however, the production of natural gas in nigeria is low compared to its vast natural gas proved reserve. if this abundant gas resources could be harnessed for some years in nigeria just as crude oil exploitation, it will go a long in diversifying nigeria’s economy by increasing its source of revenue to 15bilions us dollars (obuba et al., 2013). natural gas compressibility factor is essential for the determination of gas physical properties such as gas density, viscosity, gas formation volume factor, gas expansion factor, and specific gravity of gas. these properties are necessary for the analyses and design of natural gas production and processing system (guo and ghalambor, 2012). hence, the need natural gas compressibility factor become imperative in the exploitation of natural gas reserves. compressibility factor account for the deviation of real gas from ideal gas law (ahmed, 2001). at low pressure most gases behave as an ideal. the gas tends to compress more than ideal at moderate pressure for temperature close to its critical values. however, the gas tends to compress less than the ideal gas at high pressure (ikoku, 1992). to correct for the deviation of the gases from ideal behavior, a correction factor called the gas deviation factor is incorporated to the ideal gas law (equation 1) and shown in equation 2 (ahmed, 2001). pv=nrt (ideal gas law) (1) pv=znrt (real gas law) (2) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 166 where: z is compressibility factor is defined as the ratio of the actual volume of n-moles of gas at t and p to the ideal volume of n-moles at the same temperature and pressure and is a dimensionless parameter, (mohammed et al., 2016). z= vactual videal (3) compressibility factor plays a vital role in the oil and gas industry for the estimation of gas reserve, predict future gas production, gas metering, design of gas pipeline and production turbine (elsharkawy and elkamel, 2001). sources of the compressibility factor are experimental method, zfactor correlation of standing and katz chart, empirical correlations (direct calculation of compressibility factor) and the corresponding state principle. 1.1 experimentation experimental technique is one of the most accurate and reliable methods of predicting the compressibility factor of natural gas. this method is too expensive and is time consuming in estimating the gas compressibility factor (ikoku, 1992). also, the pvt data are not always available. therefore, it is difficult to measure the compressibility factor experimentally for all composition of gas at any temperature and pressure (obuba et al., 2013). 1.2 z-factor correlation of standing and katz chart this is one of the most widely used correlation method that is accepted in the oil and gas industry (ikoku, 1992). it involves the use of chart in estimating the z-factor value. in order to make effective use of the chart, the knowledge of pseudo-critical pressure and temperature, gas specific gravity or gas composition is necessary to determine the pseudo-reduced temperature and pressure. these pseudo-reduced properties determined the compressibility factor in the chart (ikoku, 1992). this method is widely and suitably used for computing the compressibility factor of sweet natural gas with small amount of impurities (co2 or h2s) and/or natural gas which has been corrected. however, when there is significant amount of impurities in the natural gas system, the standing and katz chart is not recommended because it will not give accurate predictions of the z-factor values. 1.3 direct calculation of z-factors (empirical correlations methods) since the standing and katz chart was developed based on the natural gas system that has small amount of impurities. the advent of computer calls for the demand to search for a convenient method of predicting the gas compressibility factor rather than feeding in the entire chart from which the z-factor value can be obtained from the lookup in the table (ikoku, 1992). these include: hallyarborough eos, dranchuk-abu-kassem, dranchuk-purvis-robinson. 1.3.1 hall-yarborough equation of state this equation is developed based on the sterling-carnahan equation of state (ahmed, 2001). unlike the standing and katz chart this method predicts the compressibility factor of natural irrespective of the amount of impurities in the gas composition, (mohammed et al., 2016). however, the method cannot be used if the pseudo reduce temperature is less than one. 1.3.2 dranchuk-abu-kassem correlation method this method uses eleven constant variable which generate the analytical expression. this expression is used to determine the reduced density was developed and expressed in terms of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 167 the pseudo reduced temperature and pressure. hence, it determined the compressibility factor of the natural gas (ahmed, 2001). this correlation method is applicable within the range of 0.2<ppr<15, 1.0<tpr<3.0. 1.3.3 dranchuk-purvis-robinson correlation method this method is a modification of the dranchuk-abu-kassem correlation methods. the correlation was developed based on the benedict-webb-rubin equation of state and it uses seven constant variables (ahmed, 2001). the correlation method is applicable within the range of 0.2<ppr<3.0, 1.05<tpr<3.0. 1.3.4 begg and brill (bb) this is an explicit equation of state expressed as functions of the pseudo-reduced temperature and pressure which predict the compressibility factor of natural gas (begg, 1973). the method is not suitable for used if the pseudo-reduced pressure is less than 0.92. 1.3.5 papay correlation method papay proposed a simplify expression of compressibility factor as functions of pseudo-reduced temperature and pressure. this method is more accurate and reliable for predicting the gas compressibility factor (baghmolaei et al., 2015). 1.4 corresponding state principle this is a powerful correlation tool, it state that the physical and thermodynamic properties such as viscosity, density and vapor pressure which depend on the intermolecular forces are related to the critical properties in a universal way. the disadvantage of this concept is that it is valid partially for real fluid only (campbell, 1992). 1.5 third parameter equation of state the thermodynamic and physical properties can be expressed as functions of their reduced properties according to the corresponding state principle property = f(pr, tr) (4) the above concept is not valid entirely. therefore, in order to improve the accuracy and validity of the equation of state, a third parameter called the pitzer may be included to the above corresponding state principle. property = f(pr, tr, pitzer) (5) the pitzer is capale of characterizing the behavior of fluid (campbell, 1992). for non-polar or slightly polar gases, the pitzer correlation provides a reliable result of zfactor. the simplest form of the third parameter equation of state is the viral equation of state. the equation of state is valid for low to moderate pressures. determination of the gas composition through measurement is very important because complex mixtures of hydrocarbon which contained small amount of inorganic compound form the constituent of the natural gas (guo and ghalambor, 2012). knowing the gas composition will make it possible to determine the gas properties using the correlations (guo and ghalambor, 2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 168 correlation method of predicting the gas compressibility factors are much easier and faster than the equation of state. this study intend to carry out a comparative study on various methods of predicting gas compressibility factor, thereafter evaluate the best method in terms of accuracy and reliability in the prediction of the compressibility factor. 2. materials and methods seven (7) compositions of natural gas in the reservoir under study were retrieved from the literatures for the analysis. the specific gravity of the respective gas composition was used to compute the gas pseudo-critical properties such as pseudo critical temperature and the pseudo-critical pressure according to equations 6 and 7. tpc=168 +325γg-12.5 γ2g (6) ppc=677-15.0γg-37.5 γ2g (7) where: γg = specific gravity of the gas. the pseudo-reduced temperature and the pseudo-reduced pressure as functions of the pseudocritical temperature and pressure were calculated using equations 8 and 9. tpr= t tpc (8) ppr= p ppc (9) where: t and p are reservoir temperature (°c, k) and pressure (pa, bar) expressed in s. i unit respectively. for a single phase reservoir, the temperature, t =149.072°c (422.222k) and the reservoir pressures are 25.511*106 pa (255.11 bar), 23.442*106 pa (234.42 bar), 21.374*106 pa (213.74 bar) and 19.305*106 pa (193.05 bar). the predicted methods under this study are expressed as functions of the pseudo-reduced temperature and pseudo-reduced pressure (tpr, and ppr) as shown in equation 8 and 9 above. the prediction methods considered in this study are papay correlation, hall-yarborough eos, viral eos, beggs and brill correlation and the dranchuk-abu-kassem correlation method. 2.1 papay correlation method papay proposed z-factor expression as a function of the pseudo-reduced temperature and pressure as shown in equation 10. z = 1 − 3.53ppr 100.9813tpr + 0.274p2pr 100.815tpr (10) substituting the values of tpr, and ppr equations 8 and 9 into equation 10 gives the values of zfactors of the gas compositions studied. 2.2 hallyarborough equation of state the generalized form of the hall-yarborough equation of state is expressed as functions of the pseudo-reduced temperature and pseudo-reduced pressure as shown in equation 11. z= 0.06125pprt y exp − 1.2(1 − t)2 (11) where: ppr = pseudo-reduced pressure. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 169 t= reciprocal of the pseudo-reduced temperature= tpc t and y = reduced density terms and is expressed as: f(y) = -0.06125ppr te-1.2(1-t) 2 + y +y2 +y3−y4 (1−y)3 − (14.76t − 9.76t2 + 4.58t3)y2 (90.7t-242.2 t2 + 42.2t3)y 2.18+2.82t = 0 (12) this can also be written as f(y) =x1 + y +y2 +y3−y4 (1−y)3 − x2 y2(x3)y x4 = 0 (13) where: x1= -0.6125pprtexp[-1.2(1-t)2] (13a) x2= (14.76t-9.76t2+4.58t3) (13b) x3= (90.7t-242.2t2+42.4t3) (13c) x4= (2.18+2.82t). (13d) the values of ppr obtained in equation 9 and the reciprocal of the tpr, in equation 8 were substituted in equations 13a-13d to give the values of x1, x2, x3, and x4. the calculated values of x1, x2, x3, and x4 were substituted into equation 13. the unknown parameter (y), is the reduced density term which is computed using newton raphson iteration approach in microsoft excel software. initial guess value of y is made until the function f(y) in equation 13 converges to zero and the corresponding value of y at which the convergence occur is the accurate value of the reduced density (y). this value is substituted into equation 11 to give the values of the compressibility factor of the various gas compositions. this correlation method has high degree of confidence level with little error low encountered in this study. 2.3 viral equation of state the generalized expression of viral coefficient correlation is as shown in equation 14, below. z = 1 + bp rt + bpc rtc pr tr (14) bpc rtc = bo + biω (15) where: bo = 0.0830.422 t1.6r and bi = 0.1390.172 t4.2r the z-factor can further be expressed as: z = 1 + bo pr tr + ωbi pr tr (16) substituting the values of ω, bo, bi into equation 16, gives the values of the zfactors of the gas compositions. this correlation method has moderately high degree of confidence level with little error encountered in this study. 2.4 beggs and brill correlation this correlation expressed the z-factor in terms of the pseudo-reduced and temperature and pressure as shown below. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 170 z = a + (ia) exp (-b) + cpdpr (17) where: a = 1.39(tpr-0.92)0.5 – 0.36tpr-0.101 b = (0.620.23tpr)ppr + 0.066 tpr−0.86 − 0.037 p2pr + 0.32 109 tpr−1 p6pr c = 0.1320.32log (tpr) d = 10 0.3106−0.49tpr +0.182t2pr substituting the values of a, b. c and d into equation 17 gives the values of the z-factor of the respective gas compositions. the correlation method has fairly low degree of confidence level and moderately high error encountered in this study. 2.5 dranchuk-abu-kassem correlation method this correlation presents an analytical expression for calculating the reduced density terms as shown below. f(ρr) = (r1) ρrr2ρr +(r3) ρr2-(r4) ρr5 +(r5)(1+a11 ρr2)exp[-a11 ρr2] +1=0 (18) where: ri, r2, r3, r4 and r5 are expressed in terms of the pseudo-reduced temperature and pressure as below. r1= a1 + a2 tpr + a3 t3pr + ar t4pr + at t5pr (18a) r2= 0.27ppr tpr (18b) r3= a6 + a7 tpr + a8 t2pr (18c) r4=a9 a7 tpr + a8 t2pr (18d) r5= a10 t3pr (18e) the constant are a1 = 0.3262 a2 = -1.0700 a3 = -0.5339 a4 = 0.01569 a5 = -0.05165 a6 = 0.5475 a7 = -0.7361 a8 = 0.1884a9 = 0.1056 a10 = 0.6134 a11 = 0.7210 (ahmed, 2001). the values of r1 to r5 were obtained by substituting the constant terms, a1 to a11 and the values of the pseudo-reduced temperature and pressure into equations 18a-18e. the calculated values of r1 to r5 and the values of a11 were substituted into equation 18. the reduced density (ρr) term is the unknown variable which is computed using newton raphson iteration in microsoft excel environment. a value of (ρr) is guess until the function f(ρr) converges to zero. the value of ρr at which the function f(ρr) converges, is its right value. this value is substituted into equation 14 to give the values of the compressibility factor of the various gas compositions. z = 0.27ppr ρrtpr (19). this correlation method has low degree of confidence level and significant errors were encountered. in this study, six (6) statistical tools were used to evaluate the effectiveness and the accuracy of the predicted methods. the tools are average absolute error (aae), average absolute relative error (aare), root mean square error (rmse), residual sum of square (rss), mean square error (mse) and coefficient of determination (r-square). low values of aae (%), aare (%), rmse, rss, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 171 and mse give high coefficient of determination (r-square). this implies better agreement between the predicted methods and the experimental methods which entails the best method. 3. results and discussion tables 1 to 4 present the results obtained from the methods studied at a reservoir temperature of 149.072°c (422.222°k) and reservoir pressures of 25.511  106 pa (255.11 bar), 23.442  106 pa (234.42 bar), 21.374 106 pa (213.74 bar) and 19.305 106 pa (193.05 bar). the methods are papay (pp) correlation, hall-yarborough (hy) equation of state, viral equation of state, beggs and brill (bb), and dranchuk-abu-kassem correlations (da) method. the accuracy and performances of the methods could be ascertained by comparing the results obtained from the methods with experimental compressibility factor values. because, the experimental zfactor prediction method is very accurate and reliable method. therefore, it was set as standard or reference for validating the accuracy and performances of the compressibility factor prediction methods studied in this work. the tables clearly show the effect of molecular weight of the gases compositions on the pseudo-reduced properties (temperature and pressure). for hydrocarbon gases such as nc1-nc4, the molecular weight of the gases compound increases as the pseudoreduced pressure increases but the pseudoreduced temperature decreases. this causes the compressibility factor values to shift close to the standard leading to better agreement between the predicted method studied and the standard method. this is also the same for non-hydrocarbon gases such as nitrogen gas (n2) and carbon monoxide gas (co). however, for non-hydrocarbon gases, the compressibility factor values are highly deviated from the standard method leading to inadequate agreement between the predicted method studied and the standard method. this is because, the pseudo-reduced properties are expressed as are functions of reservoir pressures and temperatures and the z-factor methods studied are also expressed as functions of the pseudo-reduced properties. these properties along with the reservoir conditions have effect on the compressibility factor. furthermore, reservoir conditions such as temperature, pressure and compositions are the main factors responsible for the deviation of gases from ideal condition to real. at low temperature and pressure, all gases behave as ideal obeying the ideal gas laws. however, as the temperature and pressure increases, gases intend to deviate from ideal behavior to real. this is clearly shown in tables 14, where at a high reservoir pressure of 25.511  106 pa (255.11 bar), the compressibility factor values obtained from the methods studied deviated highly from the standard method leading to inaccurate prediction of deficiency z-factor. hence, significant error and least coefficient of determination occurred in the methods. while at a low reservoir pressure of 19.305  106 pa (193.05 bar), the z-factor values of the methods studied showed a slight deviation from the standard method. therefore, least error and high coefficient of determination occurred leading better prediction of z-factor values. 3.1 statistical analysis tables 5 to 8 show the results of six different statistical parameters which were used to evaluate the effectiveness and the accuracy of the various methods studied in this work. the tables clearly show that papay correlation has the highest coefficient of regression (r-square) and the least values errors such as of aae (%), aare (%), rmse, rss, and mse. hence, it is the most accurate method in this work. the accuracy of the methods are arranged in descending order of magnitude ranging from the best performed to the least performed methods, these includes file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 172 papay correlations, hall-yarborough eos, viral eos, begg and brill and dranchuk-abu-kassem method correlation. the dranchuk-abu-kassem method correlation is the least performed correlation because it has the least coefficient of regression (r-square) and the highest values of errors such as aae (%), aare (%), rmse, rss, and mse in this work. the summary of the performance of the methods studied is shown in table 9. 3.2 graphical analysis figures 1 to 2 present the line and column chart which show the comparison of the various methods with the experimental values of z-factor. it can be seen from the figures that the values of z-factor predicted by papay correlation agreed closely to the standard method (experimental method). this is because it has the highest coefficient of regression and the least values of error. this is preceded in descending by the following methods such as hallyarborough, viral, and beggs and brill, and dranchuk-abu-kassem methods in descending order of nearness of predicted values to that of the experimental method. the dranchuk-abukassem methods is highly deviated from the standard method because it has the least coefficient of regression and the significant error is encountered in the method. figures 3 to 6 show the pictorial representation of the statistical analysis which present the errors encountered in the prediction methods studied. table 1: comparison of experimental and predicted z-factor methods at 149.072oc and 25.511  106 pa (255.11 bar). gas comp m wt tpr ppr z-exp. z-pp z-hy z-viral z-bb z-da c1 16.043 2.875 5.456 1.002 1.008 1.053 1.012 0.064 1.197 c2 30.07 2.693 5.460 0.769 1.008 1.044 1.020 0.835 1.211 c3 44.097 2.306 5.481 0.785 1.003 1.018 0.982 1.010 1.243 ic4 58.124 2.190 5.492 0.898 0.998 1.003 0.968 0.992 1.254 nc4 58.124 2.150 5.497 0.872 0.995 1.004 0.962 0.983 1.258 n2 28.016 1.797 5.565 1.107 0.952 0.946 0.760 0.895 1.298 co 44.01 1.786 5.568 1.109 0.949 0.946 0.842 0.892 1.300 table 2: comparison of experimental and predicted z-factor methods at 149.072°c and 23.442 106 pa (234.42 bar) gas comp. m wt tpr ppr z-exp. z-pp z-hy z-viral z-bb z-da c1 16.043 2.875 5.013 1.001 1.004 1.046 1.011 0.248 1.182 c2 30.07 2.693 5.017 0.776 1.004 1.038 1.018 0.861 1.194 c3 44.097 2.306 5.036 0.786 0.994 1.010 0.984 1.004 1.225 ic4 58.124 2.190 5.047 0.899 0.988 0.997 0.970 0.985 1.236 nc4 58.124 2.150 5.051 0.883 0.985 0.993 0.966 0.977 1.240 n2 28.016 1.797 5.114 1.104 0.934 0.932 0.779 0.886 1.280 co 44.01 1.786 5.117 1.106 0.931 0.930 0.855 0.883 1.281 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 173 table 3: comparison of experimental and predicted z-factor at 149.072°c and 21.374  106 pa (213.74 bar) gas comp. m wt tpr ppr z-exp. z-pp z-hy z-viral z-bb z-da c1 16.043 2.875 4.571 0.9990 1.0015 1.0376 1.0104 0.4077 1.166 c2 30.07 2.693 4.575 0.7830 0.9997 1.0297 1.0168 0.8841 1.178 c3 44.097 2.306 4.592 0.7890 0.9875 1.0015 0.9851 0.9980 1.207 ic4 58.124 2.190 4.601 0.9030 0.9797 0.9886 0.9731 0.9804 1.218 nc4 58.124 2.150 4.605 0.8890 0.9762 0.9834 0.9686 0.9723 1.222 n2 28.016 1.797 4.662 1.0870 0.9201 0.9191 0.7988 0.8794 1.262 co 44.01 1.786 4.665 1.0930 0.9172 0.9165 0.8674 0.8760 1.263 table 4: comparison of experimental and predicted z-factor at 149.072°c and 19.305  106 pa (193.05 bar). table 5: error analysis of the predicted methods at 25.511 106 pa (255.11 bar) eos/correlations aae (%) aare (%) rmse rss mse r-sq. hall-yarborough 16.004 18.091 0.175 0.214 0.031 0.810 papay 14.291 16.150 0.160 0.179 0.026 0.869 viral 16.004 18.916 0.209 0.307 0.044 0.800 beggs and brill 26.601 27.527 0.387 1.047 0.150 0.253 dranchuk-abu-k 31.715 36.252 0.336 0.792 0.113 0.100 table 6: error analysis of the predicted methods at 23.442 106 pa (234.42 bar) eos/correlations aae (%) aare (%) rmse rss mse r-sq. hall-yarborough 15.536 17.847 0.170 0.203 0.029 0.830 papay 13.922 15.997 0.157 0.173 0.025 0.899 viral 16.864 18.573 0.199 0.278 0.040 0.828 beggs and brill 23.966 25.318 0.324 0.736 0.105 0.328 dranchuk-abu-k 29.738 34.299 0.317 0.702 0.100 0.105 gas comp m wt tpr ppr z-exp. z-pp z-hy z-viral z-bb z-da c1 16.043 2.875 4.129 1.0004 0.999 1.030 1.009 0.546 1.151 c2 30.07 2.693 4.132 0.8230 0.997 1.022 1.015 0.905 1.161 c3 44.097 2.306 4.148 0.8510 0.982 0.994 0.987 0.993 1.190 ic4 58.124 2.190 4.156 0.9400 0.973 0.981 0.976 0.977 1.200 nc4 58.124 2.150 4.160 0.9250 0.970 0.976 0.972 0.969 1.204 n2 28.016 1.797 4.211 1.0700 0.910 0.910 0.818 0.876 1.244 co 44.01 1.786 4.214 1.0900 0.907 0.907 0.880 0.873 1.245 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 174 table 7: error analysis of the predicted methods at 21.374 106 pa (213.74 bar) eos/correlations aae (%) aare (%) rmse rss mse r-sq. hall-yarborough 14.603 14.688 0.162 0.183 0.026 0.837 papay 13.203 16.285 0.151 0.159 0.023 0.910 viral 15.781 17.102 0.185 0.238 0.034 0.830 beggs and brill 21.238 22.211 0.269 0.507 0.072 0.419 dranchuk-abu-k 28.171 32.003 0.299 0.628 0.090 0.102 table 8: error analysis of the predicted methods at 19.305 106 pa (193.05 bar) eos/correlations aae (%) aare (%) rmse rss mse r-sq. hall-yarborough 11.543 12.243 0.133 0.125 0.018 0.866 papay 10.382 10.959 0.125 0.109 0.016 0.917 viral 12.577 13.111 0.154 0.166 0.024 0.803 beggs and brill 16.727 16.981 0.214 0.322 0.046 0.418 dranchuk-abu-k 24.218 26.319 0.254 0.452 0.065 0.073 table 9: summary of the assessments of the predicted methods at various pressures studied predicted methods 25.511 106 pa (255.11 bar) 23.442 106 pa (234.42 bar) 21.374 106 pa (213.74 bar) 19.305 106 pa (193.05 bar). average hall-yarborough 2 2 2 2 2 papay 1 1 1 1 1 viral 3 3 3 3 3 beggs and brill 4 4 4 4 4 dranchuk-abu-k 5 5 5 5 5 figure 1: comparison of the predicted method and the experimental method http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 175 figure 2: comparison of predicted method with experimental method figure 3: summary of error in the predicted methods at 25.511  106 pa file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 176 figure 4: summary of error in the predicted methods at 23.442 106 pa figure 5: summary of error in the predicted methods at 21.374*106 pa figure 6: summary of error in the predicted methods at 19.305*106 pa http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 164-178. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address:mnasirbello@gmail.com 177 4. conclusion the important of compressibility factor can never be over emphasize as it plays vital a roles in the exploitation of natural gas. therefore, accurate and reliable prediction of compressibility factor as well as selection of the best method is necessary. this study assessed the effectiveness and accuracy of some selected compressibility factor prediction method in a single-phase gas reservoir at a particular reservoir temperature and various reservoir pressures. the methods studied were based on empirical correlation and equation of state (eos). the following findings were drawn from this study. empirical correlation methods are easier and suitable for application than the equation of state (eos) method because the equation of state methods considered in this work are cumbersome and time consuming which may easily lead to error during computation. the z-factor predicted methods studied in this work are suitable and effective only for application within the range of the reservoir pressures prescribe for this study. this is due to the fact that the accuracy and performance of the various methods studied in this work increase as the reservoir pressures decrease. the accuracy of the methods studied is rated using statistical tools which analyzed the effectiveness of the methods. if the coefficient of regression is high and least error is encountered in the method, then the method will give better performance. in this case, papay correlation method gives the highest coefficient of regression with least error encountered in the method and hence, is the most accurate and reliable method. dranchuk-abu-kassem methods gives the least performance in this work because it has the lowest coefficient of regression with highest values of errors. therefore, the dranchuk-abu-kassem methods is not suitable for application in this reservoir, it need further modification. while the other methods are suitable for application in this reservoir. however, these methods may not be reliable and suitable in reservoirs with complex fluid compositions where polar and non-polar gases are predominantly occur in the reservoir. reference ahmed, t. 2001. reservoir engineering handbook (2nd edition). london, gulf professional publishing. pp.29-59. avuru, oa. 2013. outlook for energy: a view to 2030. seplat petroleum development company limited lagos, nigeria. baghmolaei, mm., azin, r., osfouri, s., baghmolaei, rm. and zarei, z. 2015. prediction of gas compressibility factor using intelligent models. natural gas industry b, 2: 283-294. beggs, dh. and brill, jp. 1973. a study of two phase flow in inclined pipes. journal of petroleum technology, 25(5): 607-617. bp. 2016. statistical review of world energy, 2016. retrieved from https://www.bp.com>energyeconomics.05/07/2018 bp. 2017. statistical review of world energy, 2017. retrieved from https://www.bp.com>energyeconomics.05/07/2018 cambell, jm. 1992. gas conditioning and processing. cambell petroleum series. norman, oklahoma, vol. 1, pp. 47-49. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:mnasirbello@gmail.com bello and musa: prediction of natural gas compressibility factor in a single-phase gas reservoir: a comparative study. azojete,16(1):164-178. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mnasirbello@gmail.com 178 elsharkawy, am. and elkamel, a. 2001. the accuracy of prediction of compressibility factor for sour natural gases. journal of petroleum science and technology, 19(5&6): 711-731. guo, b. and ghalambor, a. 2012. natural gas engineering handbook (2nd edition). gulf publishing company, houston, texas., pp.13-20. ikoku, cu. 1992. natural gas production engineering. malabar, florida, krieger publishing company., pp.39-45. mohammed, ea., saleh, ra. and mrehel, an. 2016. evaluation of correlation for libyan natural gas compressibility factor. zawia university bulletin, 1(18): 74-101. obuba, j., ikiesnkimana, ss. and ekeke, ic. 2013. natural gas compressibility factor correlation evaluation for niger delta gas fields. journal of electrical and electronic engineering, 6(4): 1-10. speight, jg. 2007. natural gas: a basic handbook. gulf publishing company, houston, texas., pp.16-26. world energy resources 2016. natural gas. retrieved from https://www.worldenergy.org/publication/2016.05/07/2018 https://www.worldenergy.org/publication/2016.05/07/2018 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):137-146 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 137 original research article effects of crushed and powdered brick particles on lightweight papercrete m. u. tangbo* and m. ibrahim (department of building, federal university birnin kebbi) *corresponding author’s email address: usman.tangbo@fubk.edu.ng 1.0 introduction several factors are pushing the demand for alternative materials to substitute or supplement concrete. one of such is the need for low-cost construction materials. secondly, as sustainability has come forth as the most dangerous environmental issue at present, the movement is now towards the utilization of materials that aid ecological sustainability. moriconi (2007) traced the current construction practice as unsustainable remarking that it goes to wasteful use of cement and mineral resources which are restricted. as an example, aggregate which constitutes the biggest ingredient of concrete is being quickly consumed as it is estimated that close to eleven billion tonnes of aggregate is used annually (smith, 2009). of this amount, roughly eight billion tonnes of aggregate comprising sand, gravel and crushed rock is used in concrete (mehta, 2001; naik and moriconi, 2005). also, moriconi (2007) showed that in summation to the enormous amounts of crushed rock, sand and drinking water consumed, two billion tonnes of portland cement is also consumed, which is not an environmentally-friendly material considering that it article information abstract this paper studied a light weight paper and mortar composite called papercrete which was produced using brick particles as aggregate and as pozzolan. papercrete samples were produced with crushed brick particles to completely substitute sand as fine aggregate and labelled sample bap. another set of samples were produced using crushed brick particles as aggregate and powdered brick particles as pozzolan to partially replace 10% of the cement content. these were labelled sample bcp. additional samples labelled sample sp were produced with sand as aggregate and with no cement replacement to serve as controls. initially, an x-ray diffraction analysis was performed on powdered brick particles to assess their chemical composition in line with astm 618. a total of 135 test samples were cast and tested for density, water absorption, compressive strength and tensile strength at 14 and 28 days. similarly, samples were subjected to thermal conductivity and fire reaction tests. the results show an increase in density, compressive and tensile strength of samples bap and bcp over sample sp. additionally, all samples recorded low thermal conduction and a good reaction to fire as none of the samples ignited when subjected to fire. however, all samples had high water absorption values. it was concluded that using crushed and powdered brick particles to produce papercrete increases its density and strength and can be used as aggregate and pozzolan in producing papercrete. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 september, 2019 revised 18 december, 2019 accepted 04 january, 2020 keywords: compressive strength papercrete crushed bricks pozzolana insulation concrete. mailto:usman.tangbo@fubk.edu.ng http://www.azojete.com.ng tangbo and ibrahim: effects of crushed and powdered brick particles on lightweight papercrete. azojete,16(1):137146. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 138 uses up a great deal of energy during manufacture and releases greenhouse gases (ghg) which contributes to global warming. one key effort towards ensuring sustainability is the usage of reused materials in concrete and concrete based systems. lately, there has been much interest in a concrete based system called papercrete. papercrete is produced by mixing recycled paper, portland cement and sand (chung et al., 2015; lyons, 2007; mohammed, 2009 and titzman, 2006). when these materials are mixed and cured, they raise a material like concrete. the benefit of this material is multi-fold. first, it provides an environmentally favourable and fertile means of throwing out wastepaper which makes a significant component of environmental waste. the bureau of international recycling (bir) in 2012 estimate that over 400 million tons of paper is created and consumed annually with only around 50% recovered. in nigeria, the food and agriculture organization (fao) (2012) estimate that 19,000 tons of paper and paperboard was produced and a further 570,000 tons imported with only 8000 tonnes recovered. even before the advent of papercrete, other recycled materials have been widely applied to supplement or substitute some ingredients in concrete based systems. one such endeavour is the usage of waste brick. waste bricks are byproducts of brickmaking and construction demolishing which are crushed to appropriate sizes for use as pozzolan or as aggregates. as aggregates, cbb is mostly used to replace coarse aggregate. when applied as fine aggregate, it significantly increases the water taken in a mix (bektas, 2007). however, khatib (2005) reported comparable strength properties with concrete containing normal fine aggregate when cbb was used as fine aggregate, hence suggesting the feasibility of using cbb as fine aggregate. being a comparatively new material, most studies on papercrete have focused on measuring its properties. sangrutsamee et al. (2012) examined the properties of papercrete containing different paper types and content and obtained compressive strength as high as 6.14n/mm2 and thermal conductivity as low as 0.28910w/mk. titzman (2006) studied a papercrete-concrete composite with acceptable results for compressive strength (143.6psi-0.99n/mm2), tensile strength (28.3psi-0.19n/mm2), thermal conductivity (0.10w/mk); while samples subjected to flammability test did not inflame. primarily, papercrete is produced by shuffling in mortar with paper fibres. this investigation on the other hand assessed the viability of utilizing other materials as constituents in papercrete by producing papercrete using cbb as fine aggregate. 1.1 papercrete papercrete also called fibrous concrete or fibercrete is a generic term applied to identify a mixture of cement, sand, paper and water (chung et al., 2015; mohammed, 2009 and titzman, 2006). papercrete is primarily made by mixing shredded paper with cement, sand and water to make a paper-mache slurry that can be cast into block units and also used as mortar in binding the blocks (lyons, 2007). when papercrete dries, the resulting fabric is gray in colour and is highly water-absorbent (titzman, 2006). nevertheless, due to its light weight, it has good insulating properties and the cement content significantly increases its resistance to fire (lyons, 2007). each of the ingredients in papercrete contributes a different property in the admixture. the cement is responsible for the strength of the material as it binds other ingredients together (kokkinos, 2010). sand adds thermal mass, makes the mix stronger and less water absorbent (kokkinos, 2010). the fibres on the other hand, are responsible for low density, low strength and low thermal conductivity (sangrutsamee et al., 2012). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 137-146. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 139 surveys on the utilization of wastepaper–mortar composites indicate varying strengths of papercrete. in the study by sangrutsamee et al. (2012), compressive strength of over 6n/mm2 was achieved by varying the pulp content. mohammed (2009) obtained a 28-day compressive and flexural strength of 5.56n/mm2 and 1.43n/mm2 respectively at a papercrete density of 650kg/mb. papercrete also has sound insulation properties. kokkinos (2010) reported that papercrete has a low thermal conductivity coefficient and high thermal diffusivity which means even though papercrete changes temperature quickly, it does not transfer much heat. this has been noted by other researchers. studies by masjuki et al. (2008) obtained a thermal conductivity k, for papercrete of 0.85w/mk. sangrutsamee et al. (2012) carried out a study to assess the thermal conductivity of papercrete containing different paper types and varying pulp content, and obtained values ranging between 0.2890 and 0.6250w/mk. titzman (2006) obtained thermal conductivity as low as 0.10 w/mk. papercrete however absorbs water easily, behaving like a sponge when exposed to water (titzman, 2006). also, in a study of suganya (2012), water absorption values as high as 74% were obtained. 1.2 crushed brick as concrete ingredient recycled clay bricks are waste materials obtained either from building demolitions or discarded products that do not adapt to standard during manufacture (bektas, 2007). these materials are crushed to smaller sizes to get the shape of material involved (0.075mm-50mm for aggregate or ground to powder fineness for pozzolan) (bektas, 2007). crushed brick is mainly used as coarse aggregate in construction. bektas (2007) attributed the averseness to its use as fine aggregate to the increased water demand when used as fine aggregate. according to schultz and hendricks (1992), using waste brick as aggregate helps to get rid of the large amount of masonry rubble generated and serves to meet aggregate demand for novel building. in addition, khalaf and devenny (2004) reported that crushed brick tends to increase tensile and flexural strength when used as aggregate as a result of improved bonding between brick aggregate and cement paste. the same view is held by khatib (2005) who reported that when broken brick or concrete is used as aggregate, cementation continues beyond 28 days hence the rate of strength development is higher when fine crushed concrete or crushed brick is used. raw clay in itself, has no pozzolanic property. however, when clay is fired during the brick making process, it acquires the possibility to undergo a pozzolanic reaction with lime in the presence of water (roger, 2011). when excited to temperatures between 600-950°c, the structure of clay minerals undergoes an alteration that allows them to react with calcium hydroxide. when calcined, the loss of water in clay causes the collapse of the crystalline structure of alumino-silicates, leaving alumina and silica in an unstructured (amorphous) state. it is in this unstructured state that silica and alumina have the potential to combine with and reduce calcium hydroxide. this is, however, not possible in clays that are mixed with high quantities of very crystalline minerals like quartz and feldspar (pinheiro et al., 2010). also, if calcination temperature exceeds certain limit, the disordered silica and alumina will recrystallize and form other unchanging composites like mullite (a3s2) that will not react with lime. 2. materials and methods binder: dangote portland cement obtained from local dealers in zaria and conforming to bs 12 (1996) was used. river sand was also obtained from local dealers in zaria. the sieves used were 4.75mm, 2.36mm, 1.18mm, 600µm, 300µm, 150µm and conformed to bs 410 (1986). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tangbo and ibrahim: effects of crushed and powdered brick particles on lightweight papercrete. azojete,16(1):137146. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 140 cbb: waste bricks were obtained from a local dealer in pz zaria and were manually crushed to smaller sizes. the bricks were also screened using a 5mm sieve in order to get rid of large particles and to obtain particles within the fine aggregate limit (4.75mm to 600µm) pozzolans (75µm and below). grading of the crushed burnt brick was carried out based on the result of the sieve analysis conducted i.e. the percentage by weight of particles retained on each sieve in the sieve analysis of the river sand was used to grade the crushed brick. this was done in order to enable comparison between samples containing crushed brick with samples containing river sand. paper sludge: the preparation of the paper sludge involves soaking the paper in water and then grinding. newspapers were soaked in water until they were indulgent enough to mash. the soaked newspapers were then ground until the desired consistency was obtained. the ground paper was left in slurry form until it is needed. before usage, water was drained from the ground paper thus leaving it in a saturated surface dry (ssd) condition. this was done in order to apply the same measure of water for all the mixes. casting of samples: the experiment started with the determination of the quantity of water to ensure a workable mix. a mix ratio of 1:1:3 as suggested by lyons (2007) was employed with varying quantities of water. the trials established that 2.5g of water per 1g of ground paper at saturated surface dry condition was suitable. three samples ‘sp’, ‘bap’ and ‘bcp’ were prepared. sample sp contained cement, sand as fine aggregate and paper. sample bap contained cement, cbb as fine aggregate and paper. sample bcp contained cement, cbb as fine aggregate, cbb replacing 10% of cement and paper. the moulds used were 72mm x 72mm x 72mm cube moulds for density, water absorption, compression, and thermal conductivity tests. cylinder moulds 100mm x 200mm (astm c42, 1990; bs 1881-120, 1983) were used for tensile test and 250mm x 90mm x 25mm rectangular moulds (bs en 11925-2, 2010) were used for fire reaction test. three samples each were produced per batch for the compressive strength, tensile strength and water absorption tests. a sample per batch was used for the thermal conductivity test. six samples per batch were used for the reaction to fire test. a total of 135 specimens were cast. the samples for strength tests were also used to assess the density of the materials. curing: as papercrete is highly water absorbent and takes a significant time to dry, the samples were cured for 7 days by covering with polythene sheets and then, allowed to get air-dried. density test: the density of the papercrete samples was determined in accordance with bs en 12390-7 (2009). the samples for each mix were weighed and their volume determined in accordance with section 5.5.5 of the standard. water absorption test: this was determined by total immersion in accordance with astm c642 (1997). the oven dry mass (a) and saturated mass (b) after immersion in water was determined for all the samples. the oven dry mass was determined by weighing the samples and drying in an oven at a temperature of 100°c for 24 hr. the saturated mass was determined by immersing the samples in water until they achieved a constant mass. this took up to 48 hours. the absorption percentage was then calculated using the eqn (1) due to astm c642 (1997): absorption after immersion (%) = ��� � � �tt (1) strength tests: the compression test was conducted in accordance with bs en 12390-3 (2009). the cubes were placed, trowelled face sideways, in the testing machine and loaded. the loading http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 137-146. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 141 was stopped once the sample became fractured. the tensile strength was also determined using the same compression machine as in the compression test. thermal conductivity test: the test was carried out at the laboratory of the department of chemical engineering, kaduna polytechnic. the parameters for determining the thermal conductivity were measured using the standard method for thermal conductivity described by ashraful (2005). a free and forced heat transfer apparatus was used. the apparatus consists of a controller and a hot plate. the power supply is set from the controller. the temperature of the hot plate was then recorded after the readings reached a steady state. the temperature at two points on a sample was then recorded. the thermal conductivity was then computed using fourier’s law as stated by incropera and dewitt (2002) and presented in eqn (2): q = � � �� �� � (2) where: q = heat transfer (w); k = thermal conductivity (w/mk); a = area of the specimen (m2); δt = difference in temperature (k) between two sections (of area a) at a distance l (m); l = distance between two sections (of area a) at which temperature is taken. fire reaction test: the reaction of papercrete to fire was assessed using single flame ignitability (sfi test) in accordance with bs en 11925-2 (2010). the samples were fixed in a horizontal position and a filter paper placed underneath the sample. flame was placed on the edge and surface of three samples each per mix for 30 seconds. the time to ignition and the time until the flames spread up and reach 150mm above the flame application point are recorded. also, the ignition or otherwise of the filter paper was noted. 3. results and discussion 3.1 chemical analysis of cbb table 1 presents the composition of major oxides in powdered brick while table 2 presents the composition of oxides in the cbb used in relation to the requirements for class n pozzolana. table 2 shows that the sum of silica, alumina and iron oxide in cbb exceeds the 70% minimum recommended by astm c618. the sulphur trioxide (so3) content was also less than the maximum 4% required by the standard. also, the analysis revealed no traces of magnesia (mgo) while the sum of minor oxides was less than 5%. hence based on the oxide composition the cbb used in the study has the potential to undergo pozzolanic reaction. table 1: chemical composition of cbb and pumice concentration, % compound al2o3 sio2 fe2o3 cao so3 mgo na2o k2o cbb 16.10 65.20 10.66 1.69 0.12 � � 2.80 table 2: chemical requirements of class n pozzolana s/no. properties recommendation for class n pozzolana cbb 1 silica (sio2) + alumina (al2o3) + iron oxide (fe2o3) 70 (min %) 91.96% 2 sulphur trioxide (so3) 4 (max %) 0.12 3 magnesia (mgo) + � 4 free alkali e.g. na2o, k2o 5 (max %) 2.80 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tangbo and ibrahim: effects of crushed and powdered brick particles on lightweight papercrete. azojete,16(1):137146. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 142 3.2 bulk density and water absorption figure 1 presents the density of the papercrete samples at 14 and 28 days. samples bap and bcp containing brick particles had higher densities than the control sample, sp at both ages. this increase in density could be as a result of the pozzolanic effect of very fine cbb particles which reduce the amount of caoh2 thus improving densification. also, joy (2005) pointed that regardless of the reactivity of pozzolanic particles, if very fine, it will be able to fit into cement grains thus resulting in more efficient paste packing. this lowers the mean capillary size and reduces bleeding and hence results in a denser microstructure (joy, 2005). even with the increase in density of samples bap and bcp over sample sp, papercrete containing crushed and powdered brick still meets the requirement of astm c332 (1999) which requires the density of lightweight concrete to be lower than 1440 kg/m3. figure 2 indicates that all samples are highly water absorbent. this could be due to the high content of paper (60%) used in the mixes just like titzman (2006) acknowledged that unless special treatments are applied to papercrete, it behaves like a sponge soaking in water. sangrutsamee et al. (2012) also obtained water absorption values as high as 58% using different types of recycled paper at varying contents. 3.3 strength of papercrete the results of the compressive and tensile strength tests are also presented in figure 3. at 14 days, samples bap and bcp containing brick particles gained 9% in strength over the control sample, sp. at 28 days, sample bap containing crushed brick particles as fines gained 3% in strength over the sample sp. in an earlier study by khatib (2005), strength results similar to the control mixture containing normal fine aggregate were obtained using crushed brick as fine aggregate to produce concrete. sample bcp containing crushed and powdered brick particles gained 39% increase in strength over sample sp and 36% over sample bap. this significant increase in strength could be attributed to the pozzolanic action of the powdered brick particles as rogers (2011), indicated that burnt brick if fine enough will undergo pozzolanic reaction when combined with lime in the presence of water. lin et al. (2010) pointed that pozzolans reduce calcium hydroxide caoh2 from the hydrating cement paste resulting in additional cement gel thus improving strength. additionally, the compressive strength of all the samples fall within the range 0.7 n/mm2 – 7.0 n/mm2 required by astm c332 (1992). results of the tensile strength test in figure 4 were in tandem with those of the compressive strength with samples bap and bcp containing crushed and powdered brick particles recording similar or higher values than the control at both ages. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 137-146. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 143 3.4 thermal properties figure 5 presents the thermal conductivity of the papercrete samples. sample bap (0.641 w/mk) containing crushed brick particles recorded a lower thermal conductivity than the control (0.657w/mk). however, sample bcp (0.663w/mk) containing crushed and powdered brick particles increased in thermal conductivity over the control. these differences in thermal conductivity could be attributed to variations in porosity and density of the samples. however, the values obtained by all the samples were more than the maximum 0.43 w/mk prescribed in astm c332 (1999). still, the thermal conductivity of the samples are very low when compared to other materials such as concrete (1.25w/mk). also, in an earlier study, sangrutsamee et al. (2012) assessed the thermal conductivity of papercrete containing different paper types and obtained values ranging from 0.289w/mk to 0.625 w/mk for different mixes of papercrete. just as with the thermal conductivity test, all the samples reacted well upon impingement with flame. none of the samples ignited upon application of flame as there were no flaming droplets nor ignition of the filter papers used in the test. 4. conclusion this study assessed the effect of using crushed and powdered brick particles as aggregate and as pozzolan in producing papercrete. an initial xrd analysis on powdered brick particles reveal the presence of major oxides – silica (sio2), alumina (al2o3) and iron oxide (fe2o3) above the minimum recommended in astm 618 thus signifying its suitability as a pozzolan. density and strength tests show an increase for samples containing crushed brick particles over ordinary papercrete and even greater increases in samples containing both crushed and powdered brick particles. in addition, all samples met the density and strength requirements for lightweight insulation concrete outlined in astm c332 (1999). the thermal conductivity values of the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tangbo and ibrahim: effects of crushed and powdered brick particles on lightweight papercrete. azojete,16(1):137146. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 144 samples were above the limit recommended by the standard but significantly low when compared to other widely used materials like concrete and steel. furthermore, all the samples responded well to the fire reaction test as there was no ignition in any of the samples. conversely, all the samples were highly water absorbent. overall, brick particles increase the density and strength of papercrete with no significant adverse effect on water absorption, thermal conductivity and fire reaction. references american society for testing and materials astm c 42. 1999. standard test method for obtaining and testing drilled cores and sawed beams of concrete. 100 barr harbor drive, west conshohocken, pa 19428-2959, united states. american society for testing and materials astm c 642. 1997. standard test method for density, absorption and voids in hardened concrete. 100 barr harbor drive, west conshohocken, pa 19428-2959, united states. american society for testing and materials astm c 332. 1999. standard specification for lightweight aggregates for insulating concrete. 100 barr harbor drive, west conshohocken, pa 19428-2959, united states. american society for testing and materials astm c 642. 1997. standard test method for density, absorption and voids in hardened concrete. 100 barr harbor drive, west conshohocken, pa 19428-2959, united states. ashraful, m. 2005. thermal properties of paving materials. msc. thesis, arizona state university, tempe, arizona, usa. bektas, f. 2007. use of ground clay brick as a supplementary cementitious material in concrete-hydration characteristics, mechanical properties and asr durability. phd dissertation, iowa state university, ames, iowa, usa. bir 2012. paper. retrieved from http://www.bir.org/industry/paper (accessed 27 january 2013). bs standard bs en 11925-2. 2010. reaction to fire tests: ignitability of products subjected to direct impingement of flame, single flame source test. bsi, linfordwood, milton keynes mk14 6le, u.k. bs standard bs en 12390-3. 2000. testing hardened concrete: compressive strength of test specimens. bsi, linfordwood, milton keynes mk14 6le, u.k. bs standard bs en 12390-7. 2000. testing hardened concrete: density of hardened concrete. bsi, linfordwood, milton keynes mk14 6le, u.k. bs standard bs 12. 1996. portland cement. bsi, linfordwood, milton keynes mk14 6le, u.k. bs standard bs 410-1. 2000. test sieves: technical requirements and testing. test sieves of metal wire cloth. bsi, linfordwood, milton keynes mk14 6le, u.k. bs standard bs 812-103.1. 1985. methods for determination of particle size distribution. bsi, linfordwood, milton keynes mk14 6le, u.k. bs standard bs 1881-120. 1983. testing concrete: method for determination of compressive strength of concrete cores. bsi, linfordwood, milton keynes mk14 6le, u.k. http://www.bir.org/industry/paper http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 137-146. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 145 chung, jh., kim, bh., choi, hk. and choi, ck. 2015. development of papercrete due to paper mixing ratio. proceedings of the international conference on sustainable building, department of architectural engineering, hanyang university, seoul, korea, 317-318. fao 2012. fao production yearbook. retrieved from http://www.faostat.fao.org (accessed 14 january 2013). incropera, fp. and dewitt, dp. 2002. fundamentals of heat and mass transfer. new york: john wiley and sons, pp. 104-107. joy, mj. 2005. evaluation of metakaolin for use as supplementary cementitious materials. msc thesis, georgia institute of technology, atlanta, georgia, usa. khalaf, fm. and de venny, as. 2004. recycling of demolished masonry rubble as coarse aggregate in concrete: review. journal of materials and civil engineering, 16(4): 331-340. khatib, jm. 2005. properties of concrete incorporating fine recycled aggregate. cement and concrete research, 35(4): 763-769. kokkinos, m. 2010. precast papercrete facade panels. msc thesis, technische universiteit delft. lin, l., wu, h., shie, j., hwang, c. and cheng, a. 2010. recycling waste brick from construction and demolition of buildings as pozzolanic materials. waste management and research, 28(7): 653-659. lyons, a. 2007. materials for architects and builders. oxford: elsevier, pp. 336-337. masjuki, sa, mohammed, bs. and al-mattameh, hma. 2008. hybrid composite wall system by using local waste: panel of cement bonded wood infilled with papercrete. proceedings of the international conference of construction and building technology (iccbt), 22(4): 239-250. mehta, pk. 2001. reducing the environmental impact of concrete. concrete international, 23(10): 61-66. mohammed, bs. 2009. papercrete as infill materials for composite wall system. european journal of scientific research, 34(4): 455-462. moriconi, g. 2007. recyclable materials in concrete technology: sustainability and durability. in: rudolp n. kraus, t., arun, r. n., peter, c., sadeghi, p. (eds). proceeding international conference on sustainable construction materials and technologies, 11-13 june 2007 coventry, special papers proceedings, pub. uw milwaukee cbu, pp. 1-12. naik, tr. and moriconi, g. 2005. environmental-friendly durable concrete made with recycled materials for sustainable concrete construction. international symposium on sustainable development of cement, concrete and concrete structures. october 5-7, toronto, ontario, pp. 277-298. pinheiro, is., montenegro, lc. and gumieri, ag. 2010. pozzolanic activity of recycled ceramic bricks. coventry university and the university of wisconsin milwaukee centre for by-products utilization, second international conference on sustainable construction materials and technologies. june 28 – june 30 2010, universita politecnica delle marche, ancona, italy, pp. 1-9. rogers, sb. 2011. evaluation and testing of brick dust as a pozzolanic additive to lime mortars for architectural conservation. msc thesis, university of pennsylvania, philadelphia, usa. http://www.faostat.fao.org file:///c:/users/user/downloads/azojete143/www.azojete.com.ng tangbo and ibrahim: effects of crushed and powdered brick particles on lightweight papercrete. azojete,16(1):137146. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: usman.tangbo@fubk.edu.ng 146 sangrutsamee, v., srichandr, p. and poolthong, n. 2012. re-pulped wastepaper-based composite building materials with low thermal conductivity. journal of asian architecture and building engineering, 11(1): 147-151. schulz, rr. and hendricks, f. 1992. recycling of masonry rubble. in: tc hansen (editor) recycling of demolished concrete and masonry. the international union of testing and research laboratories for materials and structures (rilem) report of technical committee 37drc demolition and reuse of concrete, chapman and hall: london, uk. smith, jt. 2009. recycled concrete aggregate – a viable aggregate source for concrete pavements. phd thesis, university of waterloo, waterloo, canada. suganya, s. 2012. lightweight bricks made up of wastepaper. international journal of computing and organization trends, 2(2): 29-40. titzman, lc. 2006. analysis of low-cost building material for the mixalco process. msc thesis, texas a & m university, college station, texas, usa http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):423-434 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 423 original research article basic constitutive equations in elasto-plasticity – a review o. h. aliyu (department of building, faculty of environmental sciences: the federal university birnin kebbi, p.m.b. 1157, birnin kebbi, nigeria) *corresponding author’s email address: ohunene.hafsa@fubk.edu.ng 1.0 introduction constitutive equations tend to characterize and establish the macroscopic behaviour of materials when loaded. they are ideally mathematical equations that substantially approximate the physical observations of real materials responses over limited range of parameters for example, temperature and deformations. real materials, generally behave in a complex manner under various parameters (of temperature and deformation) as such separate equations of elasticity, viscosity, visco-elasticity, visco-plasticity as well as plasticity are used to describe the different observed material responses (marlvern 1969; stein 1993). here we will be looking at the elastoplastic constitutive equations for materials such as metals, concrete, soils and so on which exhibit elastic-plastic material behaviour. these materials are classified as either rate-independent or rate-dependent (belytschko et al., 2014) with their constitutive equations grouped into infinitesimal and finite elastoplasticity. the finite elastoplasticity constitutive equations are further classified as either hyperelastic-base plasticity or hypoelastic-base plasticity; this has been widely studied by hashiguchi, (2017) and hashiguchi, (2019). these elasto-plastic models are however based on a combination of the following plasticity theories namely: decomposition of the strain increments into elastic and plastic parts; yield functions which control the inception and continuation of plastic straining; flow principles of plasticity which governs plastic flow; as well as evolution equations (grassl and jirasek, 2006; marlvern 1969; belytschko et al., 2014). 2.0 constitutive equations for rate-independent and rate-dependent elasticplastic material behaviour when the stress-strain curve of a material is independent of its rate of deformation, such a material is said to be rate independent; else it is rate dependent. the stress-strain responses of rate-independent and rate-dependent materials in one dimension are illustrated in figure 1. article information abstract the present paper reviews the constitutive equations of engineering materials in the elasto-plastic regime. here the plastic flow rules, strain rate, yield function, overstress function as well as evolution equations for the internal parameters are discussed. similarly, the implementation of the elasto-viscoplastic constitutive model in a standard finite element code is also discussed and it has been concluded that an appropriate choice of material model is key in accurately simulating the behaviour of an engineering material to applied loading. it is also recommended that the appropriateness of the selected constitutive response is crucial for mimicking precise the material behaviour. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 05 may, 2020 revised 21 may, 2020 accepted 24 may, 2020 keywords: elasto-plasticity finite strain rate-of-deformation rate independent rate dependent figure 1: engineering stress-strain curve a) rate-independent b) rate-dependent adapted from belytschko et al. 2014. mailto:ohunene.hafsa@fubk.edu.ng http://www.azojete.com.ng aliyu: basic constitutive equations in elasto-plasticity – a review. azojete,16(2):423-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 424 in the following sections, the basic frame work for the rate-independent and rate-dependent elastoplastic constitutive equations are described concisely. 2.1 rate-independent plasticity rate-independent plasticity constitutive equations are grouped under the infinitesimal elastoplasticity such as: a. here the infinitesimal strains �� in equation (1) are additively decomposed into elastic and plastic parts. ��� � ���� � ���� ��� hence, in terms of strain rates it is expressed as shown in equation (2): �� � ��� � ��� �t� b. the stress rate is related by the elastic modulus to the strain rate as given in equation (3): �� � ���� � ���� � ���� ��� here the elastic strain (���) is calculated by subtracting the plastic strain from the effective strain that is: (��� � ��� � ����) while the stress is calculated by substituting the elastic strain into the hyperelastic equation as given in equation (4). �� � ���� �t� where: � � is the elastic (young’s) modulus (figure 2). c. the plastic strain rate is given by the plastic flow rule as expressed in equation (5): ��� � ��� �ψ �� � ��� � ��� � � � � � ��� ψ �/ σ /� ��� d. the evolution equation for the back stress (� also known as the kinematic hardening variable) is given as in equation (6): �� � t��� ��� e. the yield condition (�) with isotropic and kinematic hardening is expressed as given in equation (7) : � �/� � �/ � ������ � h �t� f. the loading and unloading condition is expressed as in equation (8): �� � h� � � h� ��� � h ��� where: �� � h � is the condition for plastic loading �� � h � is the condition for elastic loading � � is the internal variable called the back stress ��� � is the effective plastic strain rate �� � is the effective plastic strain t � is the kinematic hardening variable ��� � is the plastic strain rate http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 423-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 425 ψ� is the plastic flow potential for plastic flow to occur the yield condition � � h must be met. g. the tangent modulus (����) during the plastic loading is given as: ���� � �� � �t � � �d� t� �t� where: � � is the plastic switch parameter having a value of 1 for plastic loading and zero for purely elastic loading or unloading. d� is the plastic modulus. ���� � is the elastic-plastic tangent modulus, (belytschko et al., 2014; hashiguchi and ueno, 2017; hashiguchi 2019). figure 2: stress-strain curve for a typical elastic–plastic material adapted from belytschko et al. (2014) 2.2 rate-dependent plasticity for rate-dependant materials: a. the plastic response depends on the rate of loading which can be described by an over stress model given as: ��� � ������� � � �� ��h� where: � � is the overstress � � is the viscosity ��� is the effective plastic strain ��� � is called the effective plastic strain rate and it is equivalent to the plastic rate parameter (�� �. b. the plastic flow rule and the evolution equation is given by: �� � ������t�� t� � ��� ���� c. the above plastic deformation in rate-dependant materials occur when the yield condition giving in equation (12) � �/� � �/ � ������ � h ��t� is met or exceeded. (belytschko et al., 2014; hashiguchi and ueno, 2017; hashiguchi 2019). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng aliyu: basic constitutive equations in elasto-plasticity – a review. azojete,16(2):423-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 426 d. the evolution equation is given by belytschko et al. (2014) as: �� � t��� ���⹉ �σ� � ���� 3 elasto-viscoplastic constitutive model for the above rate dependent model in equation 10, the plastic deformation (that is the viscoplastic deformation which is unrecoverable) is described by an overstress model (hashiguchi 2014). in this section, the original overstress model called the bingham model is modified so that it is applicable for use in loading rates ranging from quasi-static to impact loads. 3.1 elasto-viscoplastic constitutive equations generally, constitutive equation adopted in describing rate dependence at a stress level below yield is called the viscoelastic constitutive equation also known as the maxwell model. here, the strain rate ε� is additively decomposed into the elastic and viscous strain rates. �� � ��� � ��� ��t� the above viscoelastic constitutive equation is applicable with rate dependent deformation at stress below the yield stress (hashiguchi, 2014). on the other hand, when the stress level is at yield stress (figure 2) to describe the plastic deformation, the prandtl elasto plastic constitutive models are used where the strain rate is additively composed of the elastic and plastic parts. �� � ��� �t� � � �� ��� � ��� �t� � � �� ���� with rate dependent models where the stress is above the yield stress (figure 3) the model that describes plastic deformation is called the elasto-viscoplastic model; here the strain rate ε� is given by: �� � ��� � ���� �t� � � �� (16) the above original overstress model in equation (16); called the bingham model was first proposed by bingham (1922) and subsequently extended by prager (1961) for von mises metal and later generalised by perzyna, (1963) for all materials expressed as given in equation (17): � � �� � ��� ��t� (hashiguchi, 2014; fincato and tsutsumi, 2019). where: the strain rate � is additively decomposed into the elastic strain rates �� and viscoplastic strain rates ��� with the viscoplastic strain rate expressed as given in equation (18): ��� � � μ� f�σ� f�h� � � n n ���� μ� � viscoplastic coefficient d� is the hardening variable http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 423-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 427 figure 3: rate dependent deformation of solids adapted from hashiguchi, (2014) the deformation ��� as in equation (17) above is expressed as: � � ���� �� � � μ� f�σ� f�h� � � n n ��t� �� � �� � � � μ� f�σ� f�h� � � n e�n �th� (hashiguchi, 2014; hashiguchi and ueno 2017) equations 14-20 above give a brief history of the advancement in the rate dependent viscoplastic constitutive models. with infinitesimal rates of deformation, where �� � h and � � h� the yield condition f�σ� � f�h� (hashiguchi, 2014; hashiguchi and ueno, 2017) is satisfied that is: f�σ� f�h� � � � h �t�� equation (21) gives the elastoplastic response in a quasi-static deformation (figure 4). figure 4: response past over stress model adapted from hashiguchi, (2014) for infinite rate of deformations here �� � t and � � t equation (20) above becomes �� � ���� h �tt� suggesting the material behaves elastically under extreme loading which is not realistic. implying that equation 19 and 20 as it is, are not applicable for use in low speeds (high period) impact loading. for use with such loading conditions, equation (19) is modified as follows: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng aliyu: basic constitutive equations in elasto-plasticity – a review. azojete,16(2):423-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 428 � � �� � ���� � � ���� �� � � μ� r � � nn �t�� where: r � f��� f�h� �tt� so that when � � ��; r > 1 equation (23) is better able to model the exact material behaviour under low speeds (high period) impact loading by restricting the dynamic ratio as shown in figure 5 to a limiting value of ��� � �� (hashiguchi, 2014; fincato and tsutsumi, 2019). where: ris the dynamic loading ratio ��is the limiting dynamic loading ratio figure 5: stress-strain cure predicted by the modified overstress model adapted from hashiguchi, (2014) 4 hypoelastic-based plasticity the constitutive models here relate the rates of stress to the rate-of-deformation. they are appropriate when the elastic strains (ε�e ) are small in comparison to the plastic deformations �ε�p� (belytschko et al., 2014; hashiguchi 2019). here the use of cauchy (true) stress mainly results in constitutive equations with non-symmetric tangent modulus. using the kirchhoff stress on the other hand, leads to constitutive equations with symmetric tangent modulus. 4.1 hypoelastic-plastic constitutive equations (based on the cauchy stress formulations) a. here the rate-of-deformation tensor ��� is additively decomposed into elastic and plastic parts. d � d� � d� �t�� b. the (jaumann) cauchy stress rate is related by the constant elastic moduli (��뼘 �� ) to the elastic part of the rate-of-deformation expressed as: �∇� � ��뼘 ���d� � ��뼘 ���d � d�� �t�� http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 423-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 429 although, the elastic response is hypo-elastic, the work done in a closed cycle of deformation does not vanish hence cannot be expressed precisely (belytschko et al., 2014; kim, 2015; hashiguchi, 2017; hashiguchi, 2018). c. the plastic strain rate is given by the plastic flow rule as: d� � ��� ���t�� t� � ��� ���t� �tt� where: �� �is the plastic rate parameter d. the yield condition (�) expressed as in equations (28) is required to be isotropic: ����t� � h �t�� e. the loading and unloading condition is expressed as given in equations (29): �� � h� � � h� ��� � h �tt� f. the relationship between the (jaumann) cauchy stress rate and the total rate-ofdeformation tensor for plastic loading is expressed as: �∇� � ����� ��h� so that with elastic loading or unloading, ��� � ��뼘 �� where: ��� � is the continuum elasto-plastic tangent modulus which is a fourth order tensor (belytschko et al., 2014; kim, 2015). in formulating the above constitutive equations in terms kirchhoff stress ��� (which is also called the weighted cauchy stress expressed as � � t� ) that is using the kirchhoff stress in the plastic flow equation, will result in a symmetric tangent moduli (belytschko et al., 2014). the above hypoelasticbased plasticity constitutive equations have been expressed under the limitations of the infinitesimal elastic deformations (hashiguchi 2017; hashiguchi 2019). 4.2 hyperelastic-plastic constitutive equations hyperelastic constitutive equations are designed to eliminate some of the restrictions on the hypoelastic equations such as the isotropy of its elastic moduli as well as its yield function (belytschko et al., 2014). here: a. the deformation gradient (f = �� �� ) is decomposed multiplicatively into elastic �� and plastic �� parts as in equation 31. � � �� � �� ���� b. the stress is evaluated by means of hyperelastic potential in terms of the elastic strain and expressed as: ��� � ��뼘 �� ���� � ��t� c. for plastic flow, the plastic flow rule which determines the plastic flow rate ���� � is given as: ��� � �� �� ��� �� � ���� ����t�� ���� file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng aliyu: basic constitutive equations in elasto-plasticity – a review. azojete,16(2):423-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 430 here the internal variable is defined in the intermediate domain �ω�� as shown in figure 5. d. the yield condition in terms of the effective second piola-kirchhoff stress ���� is expressed as: �� ����t�� � h ��t� e. the rate of evolution of internal variables given in equation 35 can be derived from the hardening (softening) law as: t�� � �� ������t�� ���� f. while the effective second piola-kirchhoff stress rate is given as in equation 36. ��� � ��뼘 �� ���� � ��뼘 �� ���� � ���� ���� where: ��� � is the plastic part of the spatial velocity gradient. ��뼘 �� is the anisotropic elasticity tensor ��� and ��� are the elastic and plastic parts of the rate of deformation. �� � is the plastic flow direction �� � is the plastic moduli � � position vectors in the current configuration �� position vectors in the reference configuration (see figure 6 below) (belytschko et al., 2014; hashiguchi 2017; hashiguchi 2019). for large deformations, it will no longer be viable to additively decompose the strains into elastic and plastic parts, rather the deformation gradient (�) is multiplicatively decomposed into elastic and plastic parts (kim, 2018). this multiplicative decomposition of the deformation gradient into elastic and plastic components as given in equation (31) sets up the configuration as shown in figure 6 (belytschko et al., 2014). this configuration shows the mapping of the point x in the reference domain �ωh� to �� in the intermediate domain �ω�� by the plastic part of the deformation gradient ��. it also shows the mapping of �� in the intermediate domain �ω�� to x in the current domain (ω) by the elastic part (��) of the deformation gradient (belytschko et al., 2014; kim, 2015). the formulation of the above constitutive equations is done on the virtual configuration as shown in figure 6. 4.3 structural model the rate dependent elasto-viscoplastic material model has been used in the transient finite element analysis of a steel beam (ub ���xt�hxtt with a thickness of �h.�mm ) subject to http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 423-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 431 impact loading tested by aliyu, 2019. this is because mild steels are generally strain rate sensitive with its stress strain relationship highly dependent on the rate of loading. the mild steel beam was subjected to impact loads at both the mid span and quarter span respectively where the loading was applied incrementally. according to aliyu, 2019 loading of this nature tends to generate strain rates in the range of �ht /sec. hence, the material model specification adopted from the ansys material library used in the transient nonlinear finite element analysis of the beam to determine the plastic deformation capacity is as given below in the material model parameter section. 4.4 material model parameters for this particular finite element (fe) simulation, the ansys nonlinear finite element code adapted for rough nonlinear elasto-plasticity problems was used; with the following material model specification: non-linear > inelastic > rate dependent > visco-plasticity > isotropic hardening plasticity > mises plasticity > bilinear isotropic this was to ensure that the beam is properly modelled in both the elastic and the plastic range. the end condition of the beam was fixed. the mesh discretion was done using the beam4 3-d finite element (figure 7) which has two nodes per element and six degrees of freedom per node. this particular element had tension, compression, torsion and bending capabilities as well as special features of stress stiffening and large deformation capabilities. figure 7: details of the beam 4 3d geometry adapted from the ansys material library figure 8 shows the idealized elasto-plastic relationship assumed in aliyu, 2019; the values of the material properties adopted were: modulus of elasticity 2.1 x �h�� � �t ; passion ratio 0.3; yield stress 4.10 x �h� � �t tangent modulus of elasticity 0 (aliyu, 2019) et et fy file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng aliyu: basic constitutive equations in elasto-plasticity – a review. azojete,16(2):423-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 432 where: �� = tangent modulus �� = elastic modulus for the adopted idealized elasto-plastic stress strain curve in figure 8, the initial behaviour was assumed elastic until yield stress fy was reached after which the plastic phase was assumed to have begun. the results from the nonlinear transient finite element simulation using the above elasto-viscoplastic material model showed good agreement with the results obtained from the analytical model. figures 9 and 10 compares the resulting displacements (from both the simulation and analytical model) of the steel beam after being struck at mid-spans and quarterspans respectively by varying impactors from height ranges of 15m, 20m, and 25m respectively. the resulting displacements obtained from the mid span appeared to match exactly both the allowable and actual deflections predicted from the analytical calculations as given in aliyu, (2019) which was arrived at by using the energy momentum balance technique suggested by mughal et al. (1994). however, a very minor variation was observed with the actual quarter span deflections. figure 9: a plot of actual versus allowable displacement considering the effects of other loads for mid span deflection adapted from aliyu, (2019) figure 10: a graph of actual versus allowable displacement considering the effects of other loads for quarter span deflection adapted from aliyu, (2019) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 423-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 433 5 conclusion it can be concluded that, the choice of a suitable constitutive material model is considered key in any analysis simulation in order to properly model the exact material behaviour under loading conditions. this recommendation has been verified in the study carried out by aliyu, 2019 where the rate dependent elasto-viscoplastic material model was selected from the material library of the ansys standard finite element code as the appropriate model for use in the deformation regime where the mild steel beam behaves ductile for low speed (high period) loading and becomes brittle for high speed (low periods) loading. the model predicted with reasonable accuracy the behaviour of mild steel beams under impact loading when compared to comparable results from an analytical model reported by aliyu, 2019. an improvement in the simulation results for the quarter span deflection may be achieved by using higher order finite elements such as solid 186 which is an eight noded finite element with six degrees of freedom per node. this particular element, supports plasticity, hyperelasticity, creep, stress stiffening, large deflection, and has large strain capabilities. the use of this higher order finite element may result in an increased simulation time and cost. generally, the elastoplastic constitutive equations discussed can be used in modelling the behaviour of geomaterials (such as: soils, concrete and so on) where permanent/irreversible strains are developed upon unloading. similarly, the stress strain relationships discussed in the text, postulates that plastic strain rate develops when stress approaches yield surface. hence, models developed from this principle can be used to describe rate-independent/dependent elasto-plastic deformations of materials under monotonic/cyclic loading and proportional/non-proportional loading. furthermore, elasto-plastic constitutive equations can also be employed in describing friction between solids; formulating damage and plastic models used in fracture and damage analysis of composite material subject to dynamic loadings. the above applications of elasto-plastic constitutive equations are however, not exhaustive but only to mention a few. 6 future trends elasto plastic constitutive equations in formulating damage and plastic models for simulating the behaviour of geomaterial have also been proposed in literature but this is still a long standing challenge as more studies are required particularly in understanding the influence of combined damage and plasticity on analysing failure patterns in these material under monotonic/cyclic loading and proportional/non-proportional loading. improvement in this area would be highly invaluable in automobile, aerospace industries and so on. glossary � � elastic (young’s) modulus (pa or kpa� � � plastic switch parameter with a value of 1(� � �) corresponding to plastic loading ` and (� � h) corresponding to pure elastic loading � � back stress 1pa ���� � slope of a line tangent to the stress-stain cure at a point of interest it is expressed as a percentage of the young’s modulus e d� plastic modulus ����� � � overstress which is the stress above the yield surface which describes viscoplastic ` ` deformation � � viscosity with s.i unit of pascal-second (pa s) �� � super imposed dot denotes the time derivative of the backstress file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:ohunene.hafsa@fubk.edu.ng aliyu: basic constitutive equations in elasto-plasticity – a review. azojete,16(2):423-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ohunene.hafsa@fubk.edu.ng 434 ��� � effective plastic strain rate t � kinematic hardening parameter σ� � difference between the stress on the yield surface and the backstress �� directional vector ��� �viscoplastic rate μ� � viscoplastic coefficient f�σ� � yield condition ��� �� � elastic plastic parts of the deformation gradient � � �� � �� � � kirchhoff stress tensor � �cauchy stress tensor ��� � effective second piola-kirchhoff stress rate ��� � effective green strain rate �� � internal variable references aliyu, o. 2019. design recommendations for steel beams to prevent brittle fracture. nigerian journal of technologycal development, 16(2): 78-84. belytschko, t. liu, wk. moran, b. and elkhoday, ki. 2014. nonlinear finite element for continuua and structures. second edition ed. west sussex united kingdom: john wiley and sons. fincato, r. and tsutsumi, s. 2018. coupled damage viscoplasiticity model for metals under cyclic loading conditions. elsevler procedia structual integrity, 18: 75-85. grassl , p. and jirasek, m. 2006. damage plastic model for concrete failure. international journal of solids and structures , 43:. 7166-7196. hashiguchi, k. and veno, m. 2017. elastoplastic constitutive equation of metals under cyclic loading. international journal of engineering science , :86-112. hashiguchi, k. 2014. elastoplasticity theory. 2nd edition ed. hannover germany: springer. hashiguchi, k. 2017. basic constitutive equations in multiplicative hyperelastic-based plasticity. the japan society of mechanicl engineers , 3. hashiguchi, k. 2019. multiplicative hyperelasticity based plasticity for finite elastoplastic deformations/sliding: a comprehensive review. archives of computational methods engineering, 26: 597-637. malvern, le. 1996. introduction to the mechanic of a continous medium. united states of america: prentice-hall, inc. mughal, ma. smith, sj. and roberts, ac. 1994. design guide for structures subject to impulse and impactive loads. ppg report no. sxb-ic-096565; nda report n0. pwr/92/161 bechtel guide n0. c-2.45 kim, nh. p. 2015. introduction to nonlinear finite elements analysis. springer, new york. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):57-74 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 57 original research article socio-economic benefits of microgravity research e. m. afolayan1*, f. a. oluwafemi1, e. o. jeff-agboola2, t. oluwasegun2, j.o. ayankale3 1space life sciences unit, national space research and development agency (nasrda), airport road, abuja, nigeria. 2department of biological sciences, joseph ayo babalola university, ikeji arakeji, osun state, nigeria. 3ground segment, centre for satellite technology development (cstd), nasrda, abuja, nigeria. article information submitted: 15/10/2018 revised: 24/11/2018 accepted: 25/03/2019 keywords: microgravity research socio-economic life-sciences . abstract microgravity researches are conducted in low gravity environments. these low gravity environments can be achieved in a number of ways including parabolic aircraft flights, sounding rockets, drop towers, clinostat. gravity dominates everything on earth, from the way life has developed to the way materials interact. the reduction of gravity causes significant changes in the chosen sample which could be cells, plants, micro-organisms and small samples from material sciences. the changes that occur as a result of the effect of microgravity have led to discoveries that have been found to be of socio-economic benefits. socio-economic benefits involve benefits in wealth, health, economic, environment. sustainable development in an economy includes economic growth, environmental protection and social equality. space technology applications such as in microgravity stimulate economic growth and improve the quality of life of people, in this way, it is beneficial to mankind. overall, products manufactured in microgravity environments have key properties usually surpassing the best terrestrial counterparts. commercially, these products have attractive features that facilitate marketing. this review considers the various benefits of microgravity research in life-sciences such as in microbiology, pharmacy, and medicine. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction microgravity literally means very little gravity. scientists do not use the term microgravity to accurately represent millionth of 1g, as 1g is the earth’s gravity. the microgravity environment, expressed by the symbol µg, is defined as an environment where some of the effects of gravity are reduced compared to what is experienced at earth’s surface. microgravity is generally referred to as a state of weightlessness (figure 1). gravity at the earth’s surface is referred to as a one-gravity (1g) environment. http://www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 58 figure 1: in microgravity, astronaut suni williams could easily move this equipment that weighs more than 700 pounds on earth. image source – credits: national aeronautics and space administration (nasa) (2012). sir isaac newton (1642-1727) described gravity as a force that governs motion throughout the universe, not just on earth. it is the attraction between all masses in the universe. the body is accustomed to a one-gravity (1g) environment and feels different if that gravitational force is changed (nasa, 1997). a gravity-related phenomenon is either directly affected by reduced gravity or becomes significant as the gravity level is reduced (national research council, 2000). in general, the focus of microgravity research and applications are in the study and assessment of these biological, physical, and chemical phenomenology and related issues (jeanne and john, 2015). conducting experiments in a microgravity environment has the potential for discoveries that can both improve life on earth and advance the understanding of space (jeanne and john, 2015). actual microgravity environment can be provided for short duration by generating free fall conditions close to the earth’s surface with sounding rockets and airplanes in parabolic flight and drop facilities (clement and slenzka, 2006). orbiting spacecraft provide the best laboratories for long periods of microgravity research. scientists also use drop towers (figure 2), aircraft, and rockets to achieve short periods. an important advantage of having longer periods of time available is that scientists have the ability to do research like it is done on earth. experiments can be performed multiple times with different parameters (oluwafemi et al., 2018a). thus, scientific researchers will be able to gather comprehensive data. the space laboratories such as the international space station (iss) (figure 3), is such that platform (oluwafemi et al., 2018a). the space station provides a microgravity environment for researchers to conduct multidisciplinary investigations, for educators to inspire next generation scientists and engineers, and to serve as a stepping stone to future exploration that was not possible just some years ago. the space station has the potential to improve and change lives on earth with each investigation and technology test that takes place in orbit. with collaboration from the original international partnerships to the insights of inventors and integrators of the research and technology on the ground, there can be anticipation of continued space station benefits for humanity (nasa, 2013). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 59 these all led to the development of several alternative ground-based instruments for simulation of microgravity or elimination of gravity. clinostat is one of such instruments. types of clinostat include the two-dimensional (2d) (figure 4) and three-dimensional (3d) clinostat. to perform experiments using 2d clinostat, possible samples are plants, cells, micro-organisms, fungi and small samples from material sciences, but it cannot accommodate averagely more than 500g of sample. depending on the sample chosen, there are many factors such as the humidity, temperature and light that need to be maintained at a specific range, while on the clinostat, rotation speed, rotational axis angle and rotation direction depends on the discretion of the experimenter (oluwafemi et al., 2018a). figure 2: the drop tower in bremen, germany. image source – credit: european space agency esa (1998). figure 3: the international space station (iss). image source – credit: nasa television (https://www.nasa.gov/mission_pages/station/ main/index.html) figure 4: 2d clinostat. image source – credit: microgravity simulation laboratory, engineering and space systems department (ess), national space research and development agency (nasrda), abuja, nigeria. oluwafemi (2018a). since spaceflight microgravity experiments are unusual and expensive, this therefore restrict the number of research scientists in this area. therefore, the use of the microgravity simulations equipment such as clinostat and drop tower has enhanced microgravity research on earth; as before the advent of the microgravity simulators, spaceflight microgravity experiments are unusual and expensive, this therefore restricted the number of research scientists in this area (oluwafemi, 2018a). several researches ranging from physical to life sciences have being conducted under both real and simulated microgravity researches. for example, the principle behind the use of the clinostat as a microgravity simulations equipment is that the centrifugal and the centripetal forces are made equal (united nations, 2013). most of the plants grown on the clinostats usually have better growth rates than those grown under normal earth gravity file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 60 (oluwafemi et al., 2018b). this is usually determined by measurement of the root lengths of both samples using imagej software to analyze the pictures of the plants’ seeds taken per time (united nations, 2013). the data generated can add to the analytical knowledge of the effect of simulated microgravity on the plants experimented upon on earth which will help for future space experiments and missions on such plants. since clinostat rotation majorly affects plants growth positively (oluwafemi et al., 2018b), this will help to increase the productivity in sectors like agriculture for example by isolating the gene for growth from the microgravity simulations sample and inserting them into the wild type of such plant (oluwafemi et al., 2018b). therefore, the focus of this review work is on the benefits of microgravity research in the life sciences. the benefits of microgravity research in the following fields are discussed: biology, microbiology, agriculture, pharmacy and medicine. 2. why research in microgravity? gravity can be a disrupting factor for scientists, because it may distort the underlying physical processes they attempt to study. it is fundamental for scientists to create microgravity conditions in order to better observe and control phenomena and processes that are normally masked by the effects of gravity, and to perform experiments that would be impossible on the earth's surface (mark, 2017). the reduction of gravity causes significant changes on the chosen samples during experiments. these samples could be plants, cells, micro-organisms and nanoparticles. the changes that occur as a result of the effect of microgravity have led to discoveries that have been found to be of socio-economic benefits. conducting experiments in a microgravity environment has the potential for discoveries that can both improve life on earth and advance the understanding of space (oluwafemi, 2017). from integrated circuits, to silicon solar cells and memory foam, the benefits of previous ventures into space have transformed the way we live and operate as humans. the promises of this new generation of space exploration are equally vast, offering us the potential for an array of possibilities from the design of more efficient therapies and better vaccines, to creating stronger and more conductive materials, to developing new plant varieties that are better adapted to extreme conditions. the opportunity for advances offers an infinite horizon of possibilities that does not just lead to new products, but to entirely new categories that can fundamentally change the way we live (jeanne and john, 2015). some selected examples of research where microgravity as a tool is relevant for applicationoriented and industrial research, in a wide range from physical to life sciences under crystal growth are (esa, 1998): crystal growth of electronic and photonic materials from the melting or the vapour phase allows to understand the influence of gravity on the crystal growth process and produce benchmark samples which improve the quality and homogeneity of crystals of compounds. this application is found in the high sensitivity x-ray detectors for medical diagnostics (esa, 1998). another example is the crystal growth of biological macromolecules that allows to monitor and control the process in order to grow high quality crystals suitable for http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 61 detailed structure determination which identify the drug inhibiting an active molecule. this application is found in the fast drug design on the basis of the detailed structure of the target molecule (esa, 1998). the microgravity environment of space makes it an excellent biological laboratory (kazuto, 2015). in microgravity environment, scientists conduct experiments that are impossible to perform on earth, as this environment can serve as biological scaffold (nasa, 2008). cells, microbes, plants, samples from material science down to macromolecules behave differently in space. monitoring reactions and processes in the absence of the gravity variable which can mask subtle observations can lead to a better understanding of infectious diseases and the human immune response to them. the effect of microgravity on protein crystallization cannot also be overemphasized in the making of new drugs, since protein structure is key in therapeutics (esa, 1998). this is because protein structure (primary, secondary, tertiary or quaternary) cannot change under normal earth gravity, but under microgravity, it can inter-convert to another. new drugs can then be produced as a result of this change in structure of the protein. structural information gained from protein crystals can provide a better understanding of the role of a given protein in the body’s immune system. (esa, 1998). scientists have been studying the effects of microgravity on astronauts in orbit for some time. an example is research on bone and muscle mass while in space (kazuto, 2015). this has yielded valuable data that can help the diagnosis and treatment of patients suffering from muscle wasting diseases and bone density conditions such as osteoporosis. the iss is where the best scientists on and off earth are performing these experiments. life in the microgravity environment of space brings many changes to the human body. the loss of bone and muscle mass, change in cardiac performance, variation in behavior, and body-wide alterations initiated by a changing nervous system are some of the most apparent and potentially detrimental effects of microgravity. changes to bone are particularly noticeable because they affect an astronaut's ability to move and walk upon return to earth's gravity. some of the processes and functions of bones change after the astronaut has lived in microgravity for several days. in space, the amount of weight that bones must support is reduced to almost zero. at the same time, many bones that aid in movement are no longer subjected to the same stresses that they are subjected to on earth. over time, calcium normally stored in the bones is broken down and released into the bloodstream. the high amount of calcium found in astronaut's blood during spaceflight (much higher than on earth) reflects the decrease in bone density, or bone mass. this drop-in density, known as disuse osteoporosis, leaves bone weak and less able to support the body's weight and movement upon return to earth, putting the astronaut at a higher risk of fracture. the exact mechanism that causes the loss of calcium in microgravity is unknown (shelley and brian, 2009). many scientists believe that microgravity somehow causes bone to break down at a much faster rate than it is built up. however, the exact trigger for this rate change has not been found. multiple lines of research, including hormone level, diet, and exercise, are being done in order to determine exactly what causes, and may control or prevent osteoporosis during space flight. just file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 62 as astronauts eat a careful diet and get plenty of special exercise in space to prevent disuse osteoporosis, steps can be taken to prevent osteoporosis on earth (shelley and brian, 2009). a balanced diet rich in calcium and vitamin d, exercise, a lifestyle free of smoking and alcohol, bone density testing, and medication all prevent or alleviate osteoporosis (shelley and brian, 2009). astronauts are not the only ones who must worry about bone loss. one and a half million canadians suffer from osteoporosis, a disease that causes bones to lose density and strength. one in four women and one in eight men over the age of 50 have osteoporosis. solving the problem of bone loss in space will also help to prevent and cure the disease on earth (canadian space agency, 2006). therefore, actual and "simulated" spaceflights, with investigations conducted at whole body and cellular levels, are needed to elucidate pathogeny of bone loss in space, to develop effective countermeasures, and to study recovery processes of bone changes after return to earth (zerath, 1998). 3. socio economy in microgravity research prosperity encompasses every good thing of life. it involves wealth, riches, sound-health, affluence, well-being, plenty, ease, luxury, having-speed, fortune, peace, joy, success etc. hence, economic prosperity in this context means having a sustainable and developed economy. sustainable development in an economy includes economic growth, environmental protection and social equality. space technology applications such as in microgravity stimulates economic growth and improves the quality of life of people; therefore, it increases economic prosperity and reduces poverty. in this way, it is beneficial to mankind (oluwafemi, 2018b). space technology has contributed immensely in the drastic transformation of space-faring nations socially, industrially and economically. most developed and some developing nations like the usa, russian, uk, canada, china are well known to be space-pioneering nations. space technology through its spin offs and by-products has made an impact in every aspect of life, from the economic and industrial development to the mini technologies used for terrestrial applications. space technology has helped in the improvement of information and communications technology, infrastructure, agriculture, education, all these being the basic factors for a sustainable development (oluwafemi, 2018b). space technology application in economic growth is through these means: new jobs, new markets, increased efficiency, improved competitiveness etc. it also includes through: activities directly related to space products and services (satellites, launch vehicles, ground systems); new capabilities, businesses, products and services derived from space technologies (i.e. spinoffs from the space program); productivity enhancements and quality of life improvements, such as from improved health, enriched baby food and other medical advancing spinoffs (oluwafemi, 2018b). overall products manufactured in microgravity environments have key properties usually surpassing the best terrestrial counterparts. commercially, these products have attractive features that facilitate marketing (nasa, 1997). these does not just lead to new products but to entirely new categories that can fundamentally change the way we live. as most of the plants grown under microgravity environment usually have better growth rates than those grown under normal earth gravity (oluwafemi et al., 2018b). this can help to increase the productivity in the agriculture sector by isolating the gene for growth from the microgravity http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 63 sample and inserting them into the wild type of such plant (oluwafemi et al., 2018b). this makes this microgravity product better than the terrestrial counterpart. nasa’s budget related to microgravity research and development exceed $350 million per year between 2016 and 2017 (nasa, 2017). in 2013, with $314 billion in commercial revenue and government spending, an average annual growth rate between 5% and nearly 8% was recorded (nasa, 2017). this makes the space sector one of the fastest growing sectors in the world. 4. patents resulting from microgravity research more than 818 patents have been granted from 1981 to 2012 as related to the subject of microgravity as seen in figure 5. the use of patents as an indicator of value creation signifies economic potential (jessica, 2012). patents are government authority or license conferring a right or title for a set period, especially the sole right to exclude others from making, using, or selling an invention. the use of patents as an indicator of value creation signifies economic potential. in addition to granted patents in microgravity, additional 580 microgravity applications have filed with the u.s. patent and trademark office during the last decade. from microgravity technologies, there is a prediction of a 21st century revolution in microbiotics that will dramatically change the approach to human health care and food production" (jessica, 2012). developments based on microgravity investigations and exploration creates compelling competition between agencies, scientists and engineers. this includes both research and technology developments, as seen in both cooperative and parallel projects that may lead to benefits for humanity. "the fields of molecular and cellular biotechnology have already demonstrated the competitive advantages of microgravity environments" (jessica, 2012). the top seven patent categories include the following: biotechnologies (36%), instrumentation/analytical (13%), materials (12%), aerospace components (12%), and systems in the areas of thermal, measurement, and human health (4% each) (jessica, 2012). figure 5: this chart shows the upward trend of microgravity-related patents over 30 years, as related to the international space station (iss). image source credit: jessica (2012). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 64 5. benefits of microgravity research in life sciences life sciences comprise the fields of science that involve the scientific study of living organisms, such as micro-organisms, plants, animals, and human beings, as well as related considerations like bioethics. while biology remains the center-piece of the life sciences, technological advances in molecular biology and biotechnology have led to a burgeoning of specializations and new, often interdisciplinary fields. life sciences are helpful in improving the quality and standard of life. it has applications in health, agriculture, medicine, pharmaceutical industry, food science industry (valenti, 2014). influence of gravity on living organisms cannot be under-estimated. gravity is a fundamental force that has a marked influence on all life on earth. life scientists and biomedical researchers exploit the space environment and in particular the near-weightlessness in order to answer fundamental questions in basic biology relating to humans, plants and animals. various investigations on the response of microgravity on lungs, brain, nervous system, bones and muscles have already been performed. experiments in microgravity are needed to observe and to determine the influence of gravity on the processing and amplification of signals involved in the gravity sensing and response of cells, cell aggregates and tissue or whole organisms. any advance in the understanding of these fundamental aspects is important for the future of medical science (esa, 1998). so many experiments in space life sciences has been carried out for example by the space life science of national aeronautics and space administration (nasa). some of them are: nasa researchers are learning new things about the human brain by studying how astronauts regain their balance; flames form tiny almost-invisible balls that might reveal the secrets of combustion here on earth; taking small columns of sand into space, and returning with valuable lessons for earthquake engineers, farmers and physicists (nasa, 2003). 5.1 benefits of microgravity research in microbiology micro-organisms are living microbes that cannot be seen without an aid of a microscope. they could be unicellular, multicellular, or cellular for example viruses, bacterial cells, bacterial and fungal spores, and lichens. microbiology encompasses numerous sub-disciplines including virology, mycology, parasitology, and bacteriology. micro-organisms form biofilm which are mainly antibiotics resistant, this makes them to play essential roles. space microbiology is the study of microorganism in outer space. micro-organisms behave differently under microgravity. spaceflight microbes are great potential for novel therapeutics and vaccine. the responses of microorganisms to selected factors of space (microgravity, galactic cosmic radiation, solar ultraviolent radiation, and space vacuum) were determined in space and laboratory simulation experiments. in general, microorganisms tend to thrive in the space flight environment in terms of enhanced growth parameters and a demonstrated ability to proliferate in the presence of normally inhibitory levels of antibiotics (horneck et al., 2010). however, there are some microbes that are beneficial to human health too. for instance, specimens of fungi were found to produce new compounds that could be used for medical purposes. due to the stress of microgravity, fungi could produce new substances that might be used in cancer http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 65 treatment. note that, these microorganisms under normal earth gravity will not produce such compounds. 5.1.1 secondary metabolite production basic research shows that space flight is generally conducive to bacterial growth, it has also been hypothesized that secondary metabolite production of commercial interest might likewise be enhanced. in the first of a series of experiments aimed at characterizing this response, (lam et al., 1998) showed that monorden production by the fungus humicola fuscoatra was increased when it was cultured on two different solid agar media in space. interestingly, the increase was attributed to microgravity environment as fungal biomasses were not significantly different between the flight and ground cultures. a follow-up spaceflight experiment similarly showed specific productivity of actinomycin d by streptomyces plicatus in suspension to be increased as well (lam et al., 2002). in a related endeavor, brown et al., 2002 found that e. coli not only reached higher cell concentrations in space (and on clinostat) but also did so without consuming more glucose, suggesting that a more efficient nutrient utilization process accompanied the gains in growth with cost effectiveness. these promising studies culminated in an experiment conducted using an automated fed-batch reactor placed onboard the iss, which corroborated the findings that actinomycin d production by streptomyces plicatus increased during the first 2 weeks of the mission (beniot et al., 2006). additional ground-based research aimed at evaluating secondary metabolite production has been conducted using the rwv bioreactor microgravity simulation technique (fang et al., 2000) examined the effect of simulated microgravity on production of rapamycin by streptomyces hygroscopicus. interestingly, a proportionally greater quantity of rapamycin was extracellularly localized in the simulated microgravity environment, both with and without beads, than under normal gravity conditions (fang et al., 2000, gao et al., 2001, guadarrama et al., 2005). 5.1.2 vaccine development a series of commercially sponsored vaccine development experiments has been performed based on altered microbial virulence in spaceflight. these opportunities, now being carried out aboard the iss, are part of the national lab pathfinder (nlp) missions. the goal of the nlp projects is to develop a vaccine against diarrhea-causing strains of salmonella, for which no vaccine is currently available. the study is conducted by launching salmonella enterica and caenorhabditis elegans worms in isolated containment, after which they are serially mixed, grown, and fixed in flight. these promising pilot studies suggest potential beneficial commercial applications of enhanced antibiotic production efficiency and novel vaccine development from microbial space research; however, conclusive results from this research are not yet available (tara, 2019). 5.1.3 microbial virulence and drug resistance in space beyond the outcomes described above indicating that bacteria generally tend to fare well in space in terms of reduced lag phase, increased population growth, and potentially enhanced secondary metabolite production, other experiments further suggest that the effectiveness of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 66 antibiotics against microorganisms may be reduced and microbial virulence may be increased (nickerson et al., 2004). leys et al. (2004) reported that significantly greater concentrations of various antibiotics were needed to inhibit in vitro bacterial growth in space. two somewhat competing hypotheses can be posed to address this observed outcome. either bacterial resistance is increased in space or overall drug efficacy and/or uptake rate is reduced. microbial virulence and drug resistance in space can also plausibly result in visible growth occurring in space (or in a simulated space environment). 5.2 space farming and benefits of microgravity research in agriculture (crop) space farming refers to the cultivation of crops for food and other materials in space or on offearth celestial objects – equivalent to agriculture on earth (jessika, 2019). figure 6 shows a concept of a device for growing plant in space. supply of food to space stations and proposed interplanetary spaceships is staggeringly expensive. furthermore, the impracticality of resupplying interplanetary missions makes the prospect of growing food inflight appealing. the existence of a space farm would aid the creation of a sustainable environment, as plants can be used to recycle wastewater, generate oxygen (10m² of crops produces 25% of the daily requirements of 1 person, or about 180-210grams of oxygen, continuously purify the air and recycle faeces on the space station or spaceship. this essentially allows the space farm to turn the spaceship into an artificial ecosystem with a hydrological cycle and nutrient recycling. it can therefore be said that plants can assist the life support system since they can be used to purify water and recycle carbon dioxide into oxygen. when grown on a large-enough scale, plants therefore hugely impact how spacecraft and colonies are designed (mike, 2017). figure 6: showing device for growing plants in space. image source – credit: jay (2015). back here on earth, the impact of space farming will expand our knowledge of agriculture. there are several spin-offs from iss research and technology. monitoring of crop growth for disease and fertility differences are usually done on space farming and earth crop farming. farmers are now using cameras aboard the iss to come up with new and more efficient ways of maintaining their crops. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 67 researchers hope to transfer what they learn about growing food in the inhospitable climate of space to equally challenging and hostile climates on earth. they are collecting detailed information about how plants grow and hope this information will help as land becomes scarcer and less fertile. goals include higher quality crops, higher crop yields and better controlled agricultural systems and greenhouses (mike, 2017). space farming has led to some other surprising and useful applications on earth. one is a special device called bio-kes which converts ethylene into co2 and water using ultraviolet light. ethylene causes plants to ripen and eventually spoil. a device like bio-kes, used in food storage units and display cases, could help increase the shelf life of produce, flowers and other perishable items on earth (andrew, 2003). another area which could have unexpected consequences involves the study of plants' cell walls. through space farming, scientists may discover how to control and regulate how sturdy a plant will grow. some plants might benefit from this research in regards to better weather durability. in addition, trees with less-sturdy cell walls would grow faster and be easier and cheaper to process into paper. these genetically-modified trees could help slow deforestation by becoming reliable, quick-growing resources for paper production (mike, 2017). however, nations engaged in space are actively assessing, both qualitatively and quantitatively, the productivity, effectiveness, and return on investment (roi) of these endeavors, given the intense competition for resources and funding for alternate pursuits. with the high costs associated with a space program and the limited resources available, a growing number of states are recognizing the need to identify and provide value back to their societies in order to justify spending on space. india, for example, has found a number of ways to articulate the benefit to their people of improved space capabilities including affordable launch and expanding satellite networks that yield terrestrial benefit through increasing crop yields by providing farmers with greater environmental data, or by mitigating the loses from severe weather from better warning systems (jeff, 2016). 5.3 benefits of microgravity research in pharmacy space-based pharmaceutical research introduces an opportunity to improve the understanding of how bioprocesses occur by removing the ever-present influence of gravity from a cell and its surrounding environment. this unique research environment opens new horizons for exploring unconventional bioprocessing techniques, perhaps initially for gaining knowledge to be applied in terrestrial production facilities but also for future visions of space-based products with sufficient value added to warrant commercially viable, on-orbit production (kazuto, 2015). biological macromolecules such as proteins, enzymes and viruses play a key role in the complex machinery of life. they possess active sites which make them bind or interact with other molecules in a very specific manner that determines their biological function. they intervene in the regulation, reproduction and maintenance mechanisms of living organisms, and they can be the cause of diseases and disorders. pharmaceutical drugs are molecules that inhibit the active sites of macromolecules and, in principle, are intended to affect only the targeted macromolecule. the vast majority of current drugs are the result of systematic testing, first at molecular level, then at a clinical level (esa, 1998). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 68 this extensive process significantly increases the cost of the product. with a detailed knowledge of the 3d structure of a macromolecule, biochemists can restrict the range of drugs to be tested. furthermore, with a rational drug design approach, one may attempt to synthesize a drug targeted exclusively on a specific macromolecule. that means a drug will perfectly bind to the macromolecule and inhibit its biological function while remaining inert viz-a-viz other macromolecules (esa, 1998). the 3d structure of the macromolecule can be discovered through the analysis of crystals by xray diffraction: the diffraction pattern maps the structure of the molecules in the crystal. high quality crystals lead to fast determination of accurate structure which leads to faster identification of drug. controlled crystallization requires a multi parameter approach. gravitydependent parameters that may affect crystallizations include sedimentation, convection and consequently nutrient transport rate and wall contacts (kazuto, 2015). research efforts in laboratories aim to control the conditions in order to favor the nucleation of a small number of crystals and, subsequently, steady growth to large sizes and crystallographic perfection. crystals of photosystem grown in space had a 10 to 20 times larger volume than those grown on the ground and allowed the refinement of the structure from 4 å to 3.4 å. space crystals of collagenase diffracted with a higher intensity compared with their ground counterparts, and allowed a further refinement of the structure. under otherwise identical conditions in space, fewer but larger thaumatin crystals were obtained with a measurably higher internal order (esa, 1998). comparable improvements in crystallization under microgravity have been reported in the scientific literature for about 20% of the macromolecules tested. it is likely that the growth of many crystals could be conducted more successfully in space. current efforts toward understanding and controlling the various mechanisms involved in the overall process should continue, and a well-defined and documented experiment in microgravity will also help to learn to control and optimize conditions, leading to better crystals. it will also permit the prediction of which molecules of interest to the pharmaceutical industry will benefit from crystallization in space conditions (binot et al., 1998). in figure 7, the image is from a research on the iss. it has been said that in microgravity, crystals grow more slowly, but the molecules have time to more perfectly align on the surface of the crystal which returns much better research data (julie, 2015). the other benefits of microgravity research and application in pharmacy are: it allows for longer shelf life of drugs, gives better delivery routes of drugs and allows for better packaging of drugs. cells grown in microgravity replicate and grow into complex structures, unlike the way cells grow on earth (nasa, 2008). pure, precisely ordered protein crystals of sufficient size and uniformity for x-ray analysis are in demand by the pharmaceutical industry as tools for research. structural information gained from protein crystals can provide a better understanding of the role of a given protein in the body’s immune system. protein crystal research ultimately aid in the development of more effective drugs and life-saving treatments for many diseases. microgravity http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 69 environment allows for the production of high-quality crystals. protein crystals produced in space are larger and more precisely ordered than those produced on earth. these improvements are important to scientists who analyze a crystal’s 3-dimensional structure-the key to understanding a protein’s activity and possibly develop new and more effective drugs (nasa, 2008). figure 7: in microgravity, crystals grow more slowly, but the molecules have time to more perfectly align on the surface of the crystal. image source – credits: brian dunbar, national aeronautics and space administration (nasa), (2016). 5.5 benefits of microgravity research in medicine millions of people suffer organ or tissue loss from diseases and accidents every year. yet transplantation of tissues and organs is severely limited by the availability of donors. growing tissue samples outside the body is one of the major goals of current medical research, and the microgravity environment has great potential for advancing this research. experiments in bioreactors are performed to study how cells multiply and interact to form skin, bone and organs, and these cells and tissue culturing techniques also aids the study of cancer cells and tumour formation (kevin et al., 2018). knowledge gained in microgravity on the regulation of cell growth and differentiation will also help improve the cultivation of sensitive and highly differentiated cell strains like those needed to obtain artificial organs. studies of cells’ ability to migrate in reduced gravity may produce new insights into the factors that allow cancer to spread. when combined with biomedical research on earth, these investigations could contribute to the development of new ways to prevent and treat related diseases (esa, 1998). simulating microgravity conditions on earth could increase the preservation time of blood cells both for therapeutic and research applications. to achieve this goal, one must first understand how microgravity acts on the cell metabolism and then create these conditions in blood banks. the use of stored blood cells is of importance in the treatment of bleeding or the pathological deficiency of certain cell types. platelets and red blood cells must be stored ready to use in blood banks. improving the preservation conditions would preserve the functional state of the cells and therefore guarantee the efficiency of the treatment while at the same time reducing the treatment costs (esa, 1998). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 70 5.4 benefit of microgravity to medical instrumentation monitoring the health and body function of astronauts and related investigations have led to a variety of new insights into the influence of space environment on human beings. dedicated instruments were developed for medical diagnostics and validated in space, and are now used on earth. an example is the fluid shift in the human body caused by the absence of hydrostatic pressure observed under microgravity conditions. a dedicated instrument using ultrasound has been developed to measure fluid accumulation in human tissues resulting from such fluid shift. analogous forms of edema occur preferentially in the facial tissue for kidney disease for example, whereas cardiac patients show edema in the lower part of the body. in this way swellings in the forehead or the tibia can serve as diagnostic or prognostic hints and be controlled by the new ultrasound instrument (christian, 2016). for the measurement of inner eye pressure in space (figure 8), a device which the user can operate without help, has been developed that determines the increase due to microgravity. this ‘self-tonometer’ can also be used to control the increase of the intra-ocular pressure on earth. the instrument registers the pressure by total reflection of an infrared beam and is now in the market for regular self-control and diagnostic of patients with risk of glaucoma, one of the most frequent reasons for early blindness. the development of a non-invasive detection instrument to observe eye movements in all three dimensions by video-oculography is another example. the reaction of the eye to light stimulation can be registered continuously and has been used to investigate the coordination of information on orientation obtained by the eye and by the gravity-sensing organ in the inner ear. this method has been successfully tested on space missions, and can be used in the detection of disturbances in the vestibular, neurological or oculomotor domains. this diagnostic instrument is now commercially available for terrestrial use (christian, 2016; binot et al., 1998). figure 8: oculography being used to measure the pressure of the eye on the iss. image source – credit: christian (2016). 6. conclusion microgravity researches have the ability to widen our understanding of various challenges that have been faced in life sciences which can in turn generate revenue for nations. some emerging and aspiring space-faring nations have developed assessment schemes to measure the value of their investments in space and have generally identified positive returns by considering the broader economic implications of space activities. it is generally easier to make the case for http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 71 space program spending that generates and delivers sustainable value. from this review, haven known the socio-economic benefits of microgravity research, it will be good to intensify effort into it especially in life sciences because of its ability to give novel therapeutics. the iss, the drop tower and the 2d clinostat are some of the available platforms for microgravity research. the 2d clinostat is a facility that is very much available for experimental purposes at the microgravity simulation laboratory, engineering and space systems (ess) department, national space research and development agency (nasrda), abuja, nigeria. this equipment is one of the scarce equipment for microgravity research around the globe and especially in africa. the concept for a controlled environment for planting in space where there is reduced gravity could be made as spin-offs of space technologies which could lead to other surprising and useful applications on earth. research under microgravity using all the various means described are paramount to pursue and to have a sustained economy, as the space sector is one of the fastest growing sectors in the world. to impede or accelerate progress towards achieving this potential is funding, not just funding but consistent funding, especially to develop robust university programs; as the decisions made on the approach to funding the exploration, exploitation and development of the resources required for microgravity research will determine the speed of progress. aside funding, awareness of the benefits of microgravity research, especially in life sciences should be created. references andrew, mt. 2003. the commercial space age conquering space through commerce. author house, n.y., pp. 374. binot, r., kufner, e., minster, o., routier, d., sprenger, hj. and walter, hu. 1998. microgravity: a tool for industrial research. european space agency (esa) publication division, isbn: 92-9092605-8. brian, d. 2016. a lab aloft (international space station research), national aeronautics and space administration. https://blogs.nasa.gov/iss_science_blog/author?bdunbar/ accessed on 9 october, 2017. brown, rb., klaus, d. and todd, p. 2002. effects of space flight, clinorotation, and centrifugation on the substrate utilization efficiency of e. coli. microgravity science and technology, 13:24–29. canadian space agency. 2006. what happens to bones in space. http://www.asccsa.gc.ca/eng/sciences/osm/bones.asp accessed on 19 july, 2019. christian, o. 2016. prospective observational study of ocular health in iss crews (ocular health) https://occupymars.wordpress.com/2017/03/ accessed on 9 october, 2017. clement, g. and slenzka, k. 2006. fundamentals of space biology research on cells, animals and plants in space. new york: springer inc. esa. 1998. the international space station. microgravity a tool for industrial research. applied research on the international space station. br-136. https://blogs.nasa.gov/iss_science_blog/author?bdunbar/ http://www.asc-csa.gc.ca/eng/sciences/osm/bones.asp http://www.asc-csa.gc.ca/eng/sciences/osm/bones.asp https://occupymars.wordpress.com/2017/03/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; 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vol. 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 73 mark, g. 2017. benefits for humanity: farming from space. https://www.nasa.gov/content/benefits-for-humanity-farming-from-space accessed on 9 october, 2017. mike, d. 2017. space farming yields a crop of benefits for earth. goddard spaceflight center. https://www.nasa.gov/feature/space-farming-yields-a-crop-of-benefits-for-earth accessed on 9 october, 2017. nasa. 1997. microgravity: earth and space an educator’s guide with activities in technology, science, and mathematics education. https://www.nasa.gov/audience/foreducatos/topnav/materials/listbytype/microgravity_teachers_ guide.html accessed 9 october, 2017 nasa. 2003. science that can’t be done on earth: science mission directorate https://science.nasa.gov/science-news/science-at-nasa/2003/16jan_sts107 nasa. 2008. cellular biotech operations support. microgravity research program fact sheet (01/99) number: fs-1998-08-006-msfc. nasa. 2012. what is microgravity? https://www.nasa.gov/audience/forstudents/58/features/nasa-knows/what-is-microgravity-58.html nasa. 2013. 15 years of space station facilities advance microgravity research capabilities. https://www.nasa.gov/mission_pages/station/research/news/15_year_facilities accessed on 19 july, 2019. nasa. 2017. fy 2018 budget estimates. http://www.planetary.org/blogs/jasondavis/2017/20170523-nasa-full-2018-budget-request.html accessed 9 october, 2017. national research council. 2000. committee on microgravity research. microgravity research in support of technologies for the human exploration and development of space and planetary bodies. washington, dc. the national academies press. https://doi.org/10.17226/9452 nickerson, ca., ott, cm., wilson, jw., ramamurthy, r. and pierson dl. 2004. microbial responses to microgravity and other low-shear environments. microbiology and molecular biology reviews. 68: 345–361. oluwafemi, f. 2017. microgravity research and applications: roles in economic prosperity and poverty reduction. proceedings of united nations/united arab emirates, high level forum “space as a driver for socio-economic sustainable development”, dubai, united arab emirates, 6-9 november, 2017. oluwafemi, fa., de la torre, a., afolayan, em., olalekan-ajayi, bm., dhital, b., mora-almanza, jg., potrivitu, g., creech, j., and rivolta a. 2018a. space food and nutrition in a long-term manned mission. springer: advances in astronautics science and technology https://doi.org/10.1007/s42423-018-0016-2. oluwafemi, fa., oke, ab., and afolayan, em. 2018b. investigation of watermelon seeds growth under simulated microgravity and its advantages to agriculture sector. monograph of atmospheric research 2018, centre for atmospheric research (car), anyigba, nigeria, pp. 109111. isbn: 978-978-972-859-6. https://www.nasa.gov/content/benefits-for-humanity-farming-from-space https://www.nasa.gov/feature/space-farming-yields-a-crop-of-benefits-for-earth https://www.nasa.gov/audience/foreducatos/topnav/materials/listbytype/microgravity_teachers_guide.html https://www.nasa.gov/audience/foreducatos/topnav/materials/listbytype/microgravity_teachers_guide.html https://www.nasa.gov/mission_pages/station/research/news/15_year_facilities http://www.planetary.org/blogs/jason-davis/2017/20170523-nasa-full-2018-budget-request.html http://www.planetary.org/blogs/jason-davis/2017/20170523-nasa-full-2018-budget-request.html https://doi.org/10.17226/9452 https://doi.org/10.1007/s42423-018-0016-2 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan, et al.: socio-economic benefits of microgravity research. azojete, 15(sp.i2):57-74. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: morayoesther@gmail.com 74 oluwafemi, f. 2018a. microgravity research applications in life sciences using clinostat. lap lambert academic publishing. isbn-13: 978-613-9-90145-6. isbn-10: 6139901456. ean: 9786139901456. oluwafemi, fa. 2018b. space science and technology in economic prosperity. lap lambert academic publishing. isbn-13: 978-613-9-97995-0. isbn-10: 6139979951. ean: 9786139979950. shelley, c. and brian, d. 2009. nasabones in space. excerpted from virtual astronaut's bag of bones. https://www.nasa.gov/audience/foreducators/postsecondary/features/f_bones_in_space.html accessed 19 july, 2019. tara, r. 2019. international space station plays role in vaccine development. https://www.nas.gov/mission_pages/station/research/benefits/vaccine_development.html accessed 19 july, 2019. united nations. 2013. teacher’s guide to plant experiments in microgravity, human space technology initiative. united nations programme on space applications, new york. valenti, r. 2014. the most important application of science. gravitational and space biology, 15(9): 919-922. doi: 10. 15252/embr.201438848 zerath, e. 1998. effects of microgravity on bone and calcium homeostasis. advances in space research, 21(8-9): 1049-58 https://www.nasa.gov/mission_pages/station/main/index.html https://www.nasa.gov/audience/foreducators/postsecondary/features/f_bones_in_space.html https://www.nas.gov/mission_pages/station/research/benefits/vaccine_development.html http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 619-627 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 619 original research article effect of number of beaters on the performance of household hammer mill f. a. oluwole1, a. gujja2 and a. k. abubakar2 (1department of mechanical engineering university of maiduguri, maiduguri 2department of mechanical engineering ramat polytechnic, maiduguri) * corresponding author’s email address: oluwole@unimaid.edu.ng article information submitted 22 november, 2018 revised 6 march, 2019 accepted 10 march, 2019 keywords: hammer mil specific fuel consumption grinding beaters sorghum bicolor abstract a hammer mill with three different hammers having 2, 4 and 6 beaters was developed and evaluated. maize and guinea corn were crushed at 3 different angular speeds of the hammer rotations (2600 rpm, 3000 rpm and 3400 rpm). each beater was fixed on the shaft at a time and machine was started. as soon as the machine reached the required speed, 500g of sample was fed into the crushing chamber through the feed hopper. the final product was collected, weighed. fuel consumed during the operation and the time taken were recorded. the process was replicated 3 times for both maize and guinea corn using the 3 hammers. the result obtained during the evaluation revealed that the average milling efficiency and specific fuel consumption (sfc) for 6 beaters, 4 beaters and 2 beaters were 83.5 % and 3.8 l/h, 72.47 % and 2.07 l/h and 60.19 % and 0.94 l/h respectively. the average milling efficiency and sfc for maize and guinea corn were 72.18 % and 2.45 l/h and 71.93 %, 2.09 l/h respectively. number of beaters and angular speed of beaters and their interactions significantly affected the milling efficiency at 5 % level. number of beaters, angular speed of beaters, sample type and their interactions significantly affected the sfc at 5 % level. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction most of our staple foods in nigeria are cereals and dried tubers. these products need to be processed before storage, transported and consumed. the major processing method is size reduction after drying. dabbour et al. (2015) reported that grinding is one of the most important and energy-consuming processes in cereal industry, and that this process consumes from 70% of total power during the feed production and up to 90% for wheat flour milling. the grinding energy requirements depend on kinematical and geometrical parameters of the grinding machine and physical properties of the ground material (dabbour et al. 2015). ajaka and adesina, (2014) evaluated a small laboratory hammer mill with minerals (dolomite and granite). their results however indicated that the new machine can perform better in terms of products with improved design. the objectives of grinding grain are to increase digestibility or palatability, and to facilitate mixing with other constituents of the ration (culpin, 1982). there are different methods of grinding these products depending on the level of development in the area. according to culpin (1982), grinding of grain has been practiced since very early times, when a device resembling a pestle and motor was employed in the production of meals for human http://www.azojete.com.ng oluwole, et al.: effect of number of beaters on the performance of household hammer mill. azojete, 15(3):619-627. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 620 consumption. the first mills were modification of this device, in which grains were fed through an opening in a disc-shaped stone which was cause to rotate upon another. the gradual development of this type of mill over thousand years has led to the evolution of the buhr-stone mills. buhr-stone mills are so termed because of the grooves (buhrs) which are cut on the grinding faces of the two disc-shaped stones. as one stone revolves upon the other, grain fed in at the centre passes towards the periphery being gradually ground in the process. gujja (2016) modified the conventional hammer mills base on their short comings, such as the enlargement of screen holes due to wear, corrosion, clogging which reduces the efficiency of the hammer mill, wet materials become elastic and therefore absorb most of the impact energy of the hammer without breaking the grain among others. the solution proffered to these problems include: changing of sieve screen with endless sieve that is dimensionally controlled, introduction of fan to induced forced convection and rapid drying of material. this greatly increased the efficiency of the machine but incorporation of several parts to the machine made it complex that skilled personnel is required to performed maintenance on the machine and this can be hardly found in the rural areas, hence the machine is not suitable to be used in the rural area. in very remote areas the use of the traditional grinding stone or pestle and mortar is very common, while in some villages and cities the commercial grinding machine (grinding plates discs) were used. these commercial hammer mills are too bulky and very expensive to run and they are designed for very large scale production or big companies such as breweries, feed mills and flour mills. due to the recent sensitization of the public on the need for selfemployment/entrepreneurship, small scale industries that need smaller hammer mills are increasing in number. therefore, this study investigates the effect of the number of beaters on performance of a small household hammer mill capable of handling small quantities of product at a very low cost. 2. materials and methods 2.1 machine description and operation the hammer mill consists of feed hopper which is connected to the crushing chamber through the seed inlet throat. the crushing chamber that houses the hammer and the sieve is connected to the discharge chute. the two components were mounted on the main frame and a spark ignition (si) engine is mounted on the frame. the hammer is mounted on the shaft of the si engine which passes through the crushing chamber. plate 1 shows the photograph of the machine. plate 1: photograph of the hammer mill to operate the machine, the machine is actuated by starting the si engine and the speed is adjusted to the required speed by adjusting the throttle of the si engine. as soon as the machine reaches the required speed the product to be crushed is poured inside the hopper and allowed to pass through the crushing chamber where it is hit by the beaters. the hammer http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):619-627. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 621 continues hitting the product until the size is reduced to the size of the sieve that is between the hammer and the discharge chute. the fine particles that passed through the sieve are then collected through the discharge chute. 2.2 experimental setup the materials used for the performance evaluations of the machine are maize (zea mays linn) and guinea corn (sorghum bicolor l. moench). other testing apparatus are digital tachometer (to measure the angular velocity), stop watch (to measure the time), weighing balance (10 kg) and burette (500ml) (to measure fuel consumed). the crushing chamber of the machine was opened and the required hammer was mounted on the shaft. the fuel hose was removed from the fuel tank and connected to a burette for accurate measurement of fuel consumed during the machine’s operation. the burette was filled with fuel (petrol) above the calibration on the burette. 2.3 performance evaluation the performance evaluation was carried out following similar procedures described by mohammed et al. (2015) and hadi et al. (2017). fifty kilogram (50 kg) each of the two samples (maize and guinea corn) were bought from maiduguri monday market. the samples were cleaned by removing unwanted matters. the cleaned samples were subdivided into fragments of 500 g each and were kept for evaluation. the storage moisture contents of both stored sample (maize and guinea corn) were determined using the method described by oluwole et al. (2016) and were found to be 13% and 14% respectfully. 500 g of maize was poured into the hopper and the machine was switched on by starting the spark ignition engine that powers the machine. the speed was adjusted and measured with a tachometer, as the machine reaches the required operating speed, the gate at the hopper throat was opened to allow the samples to flow into the crushing chamber and the initial reading on the burette and initial time were taken and recorded. at the end of the operation, the final time, burette reading (fuel consumed) and mass of crushed sample were taken and recorded. this was replicated 3 times for both samples (maize and guinea corn) at 3 different speeds (2600, 3000, and 3400 rpm) and using 3 different hammers (2, 4 and 6 beaters). the results obtained were tabulated and the milling efficiency and specific fuel consumption (sfc) were calculated. the milling efficiency of the machine was obtained from equation (1) ƞ� � �� �� � ���� (1) where: ƞm = the milling efficiency, % ma= the mass of sample after milling, g mb= the mass of sample before milling, g the specific fuel consumption (sfc) was calculated using equation (2) �⺘મ � �⺘th� � (2) where: vfuel=volume of fuel consumed during operation, litre t = time to complete operation, hour these results were statistically analysed, analysis of varience (anova) was conducted to test for significance difference on the observations made and regression equations generated using a file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwole, et al.: effect of number of beaters on the performance of household hammer mill. azojete, 15(3):619-627. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 622 statistical software design expert 11. a factorial design involving three factors (samples, angular speeds and number of beaters) and three replicates (2x3x3x3) was used to analyse the two response (sfc and milling efficiency), making a total of 54 runs. 3. results and discussion the results of the performance test carried out on the hammer mill are presented in table 1. it is observed from this table that hammer with 6 beaters gave the highest milling efficiency and highest fuel consumption. while hammer with 2 beaters recorded lowest fuel consumption and milling efficiency. the average milling efficiency and sfc for 6 beaters, 4 beaters and 2 beaters were 83.5% and 3.8 l/h, 72.47% and 2.07 l/h and 60.19 and 0.94 l/h respectively. table 1: results of the performance test of the hammer run nu m be rs of be at er s an gu lar sp ee d (r pm ) sa m pl es sp ec ifi cf eu l co ns um pt io n (sf c) (l/ h) pe rc en ta ge m ille d (% ) ru n nu m be rs of be at er s an gu lar sp ee d (r pm ) sa m pl es sp ec ifi cf eu l co ns um pt io n (sf c) (l/ h) pe rc en ta ge m ille d (% ) 1 2 2600 maize 0.52 60 28 4 2600 guinea corn 1.47 72 2 2 2600 maize 0.52 63 29 4 2600 guinea corn 1.55 78 3 2 2600 maize 0.56 65 30 4 2600 guinea corn 1.64 77 4 2 3000 maize 0.95 60 31 4 3000 guinea corn 1.82 70 5 2 3000 maize 1.01 62 32 4 3000 guinea corn 1.95 72 6 2 3000 maize 1.05 60 33 4 3000 guinea corn 2.03 73 7 2 3400 maize 1.26 59 34 4 3400 guinea corn 2.12 64 8 2 3400 maize 1.34 58.4 35 4 3400 guinea corn 2.29 68 9 2 3400 maize 1.41 58 36 4 3400 guinea corn 2.4 63 10 2 2600 guinea corn 0.57 60 37 6 2600 maize 2.8 78 11 2 2600 guinea corn 0.51 63 38 6 2600 maize 2.86 81 12 2 2600 guinea corn 0.55 65 39 6 2600 maize 2.85 80 13 2 3000 guinea corn 0.92 60 40 6 3000 maize 3.8 82 14 2 3000 guinea corn 0.94 59 41 6 3000 maize 3.92 81 15 2 3000 guinea corn 0.98 58 42 6 3000 maize 4 80 16 2 3400 guinea corn 1.19 58 43 6 3400 maize 5.65 88 17 2 3400 guinea corn 1.24 58 44 6 3400 maize 5.83 84 18 2 3400 guinea corn 1.34 57 45 6 3400 maize 5.84 82 19 4 2600 maize 1.79 78 46 6 2600 guinea corn 2.2 84 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):619-627. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 623 20 4 2600 maize 1.84 78.4 47 6 2600 guinea corn 2.23 86 21 4 2600 maize 1.88 80 48 6 2600 guinea corn 2.22 76 22 4 3000 maize 2.03 76 49 6 3000 guinea corn 3.16 82 23 4 3000 maize 2.08 72 50 6 3000 guinea corn 3.18 78 24 4 3000 maize 2.22 70 51 6 3000 guinea corn 3.17 90 25 4 3400 maize 2.64 70 52 6 3400 guinea corn 4.84 92 26 4 3400 maize 2.74 71 53 6 3400 guinea corn 4.87 90 27 4 3400 maize 2.82 72 54 6 3400 guinea corn 5.04 89 table 2 presents the anova table for the milling efficiency. it is observed that number of hammers (a), hammer speed (b) and their interactions (ab) significantly affected the milling efficiency at 5% level, while that of the samples(maize and guinea corn) are not significant. table 2: anova for 2fi model for percentage milled source sum of squares df mean square f-value p-value model 5174.28 6 862.38 69.23 < 0.0001 significant a-beater 4890.67 1 4890.67 392.60 < 0.0001 b-speed 51.36 1 51.36 4.12 0.0480 c-samples 0.8563 1 0.8563 0.0687 0.7943 ab 190.41 1 190.41 15.28 0.0003 ac 40.96 1 40.96 3.29 0.0762 bc 0.0278 1 0.0278 0.0022 0.9625 residual 585.49 47 12.46 lack of fit 331.41 11 30.13 4.27 0.0004 significant pure error 254.08 36 7.06 cor total 5759.77 53 figures 1 and 2 show the response surface plots of milling efficiencies of guinea corn and maize respectively as a function of hammer speed and number of beaters. it is obvious from these figures that the milling efficiency increased as the number of beaters increased. this is as a result of higher number of beaters hitting the samples. however, milling efficiency decreased with the increase in harmer speed. this is probably because of the loses as a result of high speed file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwole, et al.: effect of number of beaters on the performance of household hammer mill. azojete, 15(3):619-627. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 624 figure 1: effects of hammer speed and number of beaters on percentage guinea corn milled figure 2: effects of hammer speed and number of beaters on percentage maize milled the regression equation for percentage of milling is presented in equation (3) �� � ⼐л㼰�훠н ��㼰ннѝн �㼰�眸н н �㼰�л훠眸м н л㼰млѝнн �㼰�⼐ѝмн �㼰�л⼐мнм (3) r² 0.8983 the equation in terms of coded factors can be used to make predictions about the response for given levels of each factor. by default, the high levels of the factors are coded as +1, the middle levels are coded as 0 and the low levels are coded as -1. the coded equation is useful for identifying the relative impact of the factors by comparing the factor coefficients. table 3 presents the anova table for the specific fuel consumption (sfc). it is observed that number of hammers (a), hammer speed (b), samples (c) and their interactions (ab) and (ac) significantly affected the sfc at 5% level. this is because as the number of hammers increase, the weight of the beater increased as a result the power requirement also increases thereby increasing the fuel consumption of the machine. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):619-627. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 625 table 3: anova for quadratic model for specific fuel consumption (sfc) source sum of squares df mean square f-value p-value model 103.76 8 12.97 220.19 < 0.0001 significant a-beater 73.96 1 73.96 1255.61 < 0.0001 b-speed 19.21 1 19.21 326.19 < 0.0001 c-samples 1.77 1 1.77 30.13 < 0.0001 ab 6.37 1 6.37 108.06 < 0.0001 ac 1.09 1 1.09 18.48 < 0.0001 bc 0.0642 1 0.0642 1.09 0.3021 a² 1.06 1 1.06 18.00 0.0001 b² 0.2315 1 0.2315 3.93 0.0536 residual 2.65 45 0.0589 lack of fit 2.43 9 0.2703 44.55 < 0.0001 significant pure error 0.2184 36 0.0061 cor total 106.41 53 p-values less than 0.0500 indicate model terms are significant. in this case a, b, c, ab, ac, a² are significant model term because their p-values are less than 0.0500. figures 3 and 4 show the response surface plots of sfc for guinea corn and maize respectively. it is obvious from the figures that the sfc increased as the speed and number of beaters increased. this is as a result of increase in weight of the beaters that requires higher torque to spin the hammers. figure 5 shows the sfc of the machine when using 6 beaters at angular speed of 3400 rpm, as generated by design expert 11 software. it is obvious from this figure that more fuel consumed when milling maize than when milling guinea corn, this is probably because maize is harder and bigger than guinea corn. figure 3: effects of hammer speed and number of beaters on sfc for percentage guinea corn milled file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwole, et al.: effect of number of beaters on the performance of household hammer mill. azojete, 15(3):619-627. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 626 figure 4: effects of hammer speed and number of beaters on sfc for percentage maize milled figure 5: sfc for milling maize and guinea corn the regression equation for the sfc is presented in equation (4). �⺘મ � �㼰眸м 쳌 �㼰䀀㌳ѝ쳌 �㼰⼐㌳�ннн �㼰�м�㌳м쳌 �㼰훠�훠�ѝнн �㼰�⼐㌳眸ѝм쳌 眸㼰л眸⼐лѝл (4) r²= 0.9751 the equation in terms of coded factors can be used to make predictions about the response for given levels of each factor. by default, the high levels of the factors are coded as +1, the middle levels are coded as 0 and the low levels are coded as -1. the coded equation is useful for identifying the relative impact of the factors by comparing the factor coefficients. 4. conclusion at the end of the evaluation of the household hammer mill, it is concluded that: the average milling efficiency and sfc for 6 beaters, 4 beaters and 2 beaters were 83.5 % and 3.8 l/h, 72.47 % and 2.07 l/h and 60.19 % and 0.94 l/h respectively. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):619-627. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwole@unimaid.edu.ng 627 the average milling efficiency and sfc for maize and guinea corn were 72.18 % and 2.45 l/h and 71.93 %, 2.09 l/h respectively. number of beaters and angular speed of beaters and their interactions significantly affected the milling efficiency at 5 % levelof significance. number of beaters, angular speed of beaters, sample type and their interactions significantly affected the sfc at 5 % levelof significance. regression equations for percentage of sample milled and sfc were generated to predict the performance of the hammer mill. at the end of the evaluation of the household hammer mill, the following recommendations were made: carry out the design modification of the household hammer mill evaluate effects of sample moisture content on machine performance evaluate effects of hammer clearance from the screen on machine performance. references ajaka, eo. and adesina, a. 2014. design, fabrication and testing of a laboratory size hammer mill. international journal of engineering and advance technology studies. 2 (2): 11-19. culpin, c. 1992. farm machinery. harper collins distribution services, dobbs ferry, new york, usa. dabbour, mi., bahnasawy, a., ali, s. and elhaddad, z. 2015. grinding parameters and their effects on the quality of corn for feed processing. journal of food process technology 6: 482488. doi:10.4172/2157-7110.1000482. gujja, a. 2016. design, modification, fabrication and performance evaluation of a household hammer mill. b. eng. project, university of maiduguri, maiduguri, nigeria. hadi, mi., bawa, ma., dandakouta, h., ahmed, m. and kamtu, pm. 2017. improvement on the design, construction and testing of hammer mill. american journal of engineering research, 6 (3): 139-146. mohammed, th., radwan, ha., elashhab, ao. and adly, my. 2015. design and evaluate of a small hammer mill. egyptian journal of agricultural research, 93 (5b): 481-496. oluwole, fa., aviara, na., umar, b. and abdulrahim, at. 2016. assessment of physical properties of castor seeds with variety. annals of borno, 26: 78-88 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):314-328 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 314 original research article enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles a. m. el-jummah1*., g. e. andrews2 and j. e. j. staggs2 (1department of mechanical engineering, university of maiduguri, p. m. b. 1069, nigeria 2school of chemical and process engineering, university of leeds, ls2 9jt, united kingdom) *corresponding author’s e-mail address: al-jummah@hotmail.com article information submitted 18 december, 2018 revised 18 february, 2019 accepted 24 february, 2019 keywords: gas turbine regenerative impingement jet heat transfer cooling validation obstacle thermal gradient abstract gas turbine (gt) jet cooling using the regenerative or impingement jet backside cooling system is applicable to low nox gt combustors and was investigated in the present work. the impingement heat transfer investigated is for the techniques where all the combustion air is used for wall cooling prior to passing through the flame stabiliser. ten rows of impingement holes were modelled and are for four different types of obstacles: rectangular-pin in coand cross-flows, circular pin-fin in cross-flow and dimple in direct-flow configurations, arranged in the impingement jet air flow direction. conjugate heat transfer (cht) and computational fluid dynamics (cfd) techniques were combined and applied in the computational analysis. only the two obstacles in rectangular shape: coand cross-flow configurations were validated against experimental results, as the other two has no experimental data available, but similar cfd methodology was applied. the impingement jet cooling enhancing obstacles were aligned transverse to the direction of the impingement jet cross-flow on the target surface and were equally spaced on the centre-line between each row of jet holes transverse to the cross-flow. also, one heat transfer obstacle was used per impingement jet air flow in order to see the level of heat transfer augmentation of each one. the cfd calculations were carried out for an air mass flux g of 1.08, 1.48 and 1.94 kg/sm2bar, hence for each obstacle grid geometry, three computations were conducted and therefore a total of twelve different computations for this investigation. these high mass flux used, are only applicable to the regenerative combustor wall cooling applications. validation of the cfd predictions with the experimental data indicates good agreement for impingement gap flow pressure loss (δp/p) and the surface average heat transfer coefficient (htc), h. other predictions were also carried out and were for locally average x2 htc, hole exit pressure loss, turbulence kinetic energy (tke), flow-maldistribution, nusselt number (nu) and normalized temperature, t* or thermal gradient. it was concluded here that the rectangular-pin obstacles have the highest exit hole and impingement gap pressure loss, but with low heat transfer as a result of higher flow-maldistribution. dimple obstacle has the lowest heat transfer, but is because most of the heat is taken away (or sucked in) by the dimple pot. the main effect of the obstacles was to increase the heat transfer to the impingement jet surface, but the dimple surface was predicted to have a very poor performance, with significantly reduced target wall heat transfer and thermal gradient. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. mailto:al-jummah@hotmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 315 1.0 introduction the low nox primary zone combustor wall cooling requires the type of impingement geometry investigated (figure 1a) in this present work, as high coolant mass flow rate, g (kg/sm2bar) with a low coolant pressure loss is the major requirement. sufficient air pressure must be available after the wall cooling, which is in order to overcome the pressure loss at the low nox flame stabilizer for flame stability and fuel/air mixing procedures. hence high velocity cross-flow interactions should be avoided with the obstacles along the cross-flow direction to combat high coolant pressure loss. abdul husain and andrews (1991) reviewed the use of obstacles to enhanced impingement heat transfer, it shows that most work had investigated the enhancement experimentally. the maximum heat transfer enhancement found experimentally was 20 50% using several pin-fins between the impingement jets. the present cht cfd work (figure 1b) investigates four main heat transfer enhancing obstacles: rectangular-pin (coand cross-flows), pin-fin (cross-flow) and dimple (direct flow) configurations, with only two that have been experimentally investigated: rectangular-pin (coand cross-flow), as in figure 1c and d. el-jummah et al. (2014a, 2017, 2018) validated the computational methods used in the present work against experimental results, they investigated experimentally flat ribs and rectangular fins or slotted ribs: coand cross-flows of the coolant in the impingement gap, as used in this work. the predictions were in good agreement with the experimental mean surface averaged htc and pressure loss, which is the reason why the present work is adopting the methodology employed. the pressure loss agreement found in their work indicates that the aerodynamic predictions were correct. therefore, the present cht cfd research, applies the same computational procedures to validate the results and to explore the possible design options for enhanced impingement cooling heat transfer applications. the impingement jet hole size d, pitch x, and gap z, in this work were the same as for the smooth target impingement wall (el-jummah et al., 2014a) as well as for previous predictions of impingement cooling with obstacles in the gap (el-jummah et al., 2016a, 2017, 2018). a 10 × 10 array of impingement jet holes was used with a fixed x/d, z/d and n, as summarised in table 1 (el-jummah et al., 2013, 2016a, b). the g used are from 1.08 1.93 kg/sm2bar, the same as used by el-jummah et al. (2013) for the smooth wall. each coolant g requires a new computation, with slight changes in the impingement gap grid refinement. also, a new computational grid as in figure 2 and table 2 is necessary for each obstacle that will be predicted, as the effect of obstacles in the impingement gap as in table 3 will be investigated. table 2 shows that a fixed obstacle height h to width w ratio of 0.93 (el-jummah et al., 2016a, 2017, 2018) for all the rectangular (thickness, t of 3 mm) and circular (thickness, t = w = do = 8.59 mm) pins was used and depth δ to diameter do (or t) ratio of 0.30 for the dimple obstacle was used. the dimple depth was taken based on work by xie et al. (2013) and the diameter (or width) is based on work by el-jummah et al. (2017), which is in order that the obstacles have similar geometrical properties. 2. computational methods 2.1 model grid geometry the grid model geometry is shown in figure 2, which was created based on the computational domain shown in figure 1b and is the same as that modeled in the work of el-jummah et al. (2016a, 2018) and xie et al. (2013) for smooth target geometry of table 1. this work file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 316 investigates the potential improvement in the heat transfer using the obstacles in the impingement gap of table 2. the dimensions of the obstacles are shown in figure 2 and table 2. the rectangular and circular pin-fins had a height h that is 80 % of z with equal pin width w. the dimple in the impingement gap in figure 1 offers no obstruction to the cross-flow, but changes the interaction of the impingement jet with the target surface, as the impingement jet was aligned with the dimple. these obstacles were investigated for the cross-flow normal to the obstacles. the gap between the top of the rectangular and circular pin-fins was to allow for thermal expansion, as the wall and rib are hotter than the impingement jet wall (el-jummah et al., 2018). if there was a solid connection, differential thermal expansion could create thermal stresses and cracking. the computational grid geometries as summarized in table 3, were modeled using ansys icem meshing tool. the dimpled obstacle of figure 2 penetrates through the depth of the target wall, which makes the fluid grids of the impingement gap to replace part of the solid wall grids. it also increased the impingement gap cell size and reduced the target wall cells, as a proportion of the total computational cells, as in table 3. the grid geometries employed symmetrical approach as in figure 1b and 2, where half holes and half obstacles along the row of holes as in figure 2 were modeled. also, all the obstacles used were over a million computational nodes and the number of cells in the plenum was fixed at 35.3 % of the total grids and was shown to be adequate (el-jummah et al., 2013a, b, 2016a). the dimpled target surface was modeled with the dimples in line with the impingement air jets, hence air jet could flow directly through the dimple. the other obstacles grids were in the gap, hence the obstacle solid walls replaced part of the gap fluid grid as in table 3. figure 1: schematic diagrams of the impingement jet cooling geometries and obstacle test walls http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 317 figure 2: the impingement grid model geometry with rec. pin in cross-flow on the target surface table 2: obstacle walls parameters types w or do (mm) h or δ (mm) t (mm) h/w δ/do rec. pin: co-flow 8.59 8.00 3.00 0.93 rec. pin:cross-flow 8.59 8.00 3.00 0.93 pin-fin (circular) 8.59 8.00 8.59 0.93 dimple: direct flow 8.59 2.58 8.59 0.30 table 1: geometrical parameters variables dimensions d (mm) 3.27 x (mm) z (mm) 15.24 10.00 l (mm) l/d 6.35 1.94 x/d 4.66 z/d x/z 3.06 1.52 n 4306 m-2 array 10 × 10 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 318 table 3: grid node distribution for y+ ~35 2.2 computational procedures computations were carried out for four obstacle walls using g of 1.08, 1.48 and 1.98 kg/sm2bar, as table 4: computational boundary flow conditions, shows and were the same flow conditions used by el-jummah et al. (2013, 2016a, 2017, 2018). the ansys fluent commercial code was used in running the calculation of the twelve grids modelled geometries (for the four obstacles) and was computed using standard k ɛ turbulence. wall function y+ value ~35 (el-jummah et al 2014a, 2017), as table 3 shows was applied, the values of which were reported to be within the near wall range of 30 < y+< 300 law of the wall. this computational procedure was the same as that previously validated (el-jummah et al., 2013, 2014a), as grid sensitivity (el-jummah et al 2014a) was also adequately performed. the test indicates that for grid size greater than half a million, there was little improvement in the predictions relative to the measured data, hence the distribution of nodes as summarised in table 3 and as shown in figure 2. the standard k ɛ model has been shown to better predict the flow aerodynamics in the impingement gap, which include strong flow recirculation as well as the flow separation and reattachment (el-jummah et al., 2015a) in the jet holes. also, the modelled grids shown in figure 2 for all the obstacle geometries have minimum cell orthogonal quality and aspect ratio fixed at 0.61 and 3.53, respectively. the convergence criteria were set at 10-5 for continuity, 1011 for energy and 10-6 for k, ɛ and momentum: x, y and z velocities. the second order and first order discretization schemes for the momentum and tke/dissipation were applied, also piso schemes that were based on presto applications was used. 3. predicted results 3.1 validation case the requirement to validate this cht cfd investigation was based on the fact that measured pressure loss (δp/p) and surface average heat transfer (htc) data, are available for two obstacles: rectangular pins, as figures 3 and 4 shows respectively. figure 3 compares the predicted pressure loss against g of the rectangular pins of co-flow and cross-flow obstacles, both shows good agreement with the experimental data. this indicates that the aerodynamics were adequately predicted, which also assert that the flow-maldistribution and hole pressure loss could be predicted correctly. also shown is the comparison of the predicted surface average htc using equation 1 below with measured data, as in figure 4. both pins predicted surface average htc agrees with the measurement, even though the cross-flow obstacle slightly falls close to the error bar, but is within the acceptable requirement. abdul husain and types grid node distribution (%) test walls obstacles gap holes rec. pin: co-flow 28.5 8.3 19.5 8.4 rec. pin: cross-flow 28.5 8.3 19.5 8.4 pin-fin (circular) 26.5 6.7 23.4 8.1 dimple 22.8 5.7 27.4 8.8 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 319 andrews (1991) showed that the heat transfer error of ± 10 should be acceptable, hence the data is correct. the aerodynamics in the impingement gap are complex (goldstein et al., 1982), as shown by eljummah et al. (2013a, 2018) using cht cfd modelling procedures. the additions of obstacles to the target wall was aimed at enhancing the heat transfer and were placed at the location of the reverse flow (goldstein et al., 1982) between each impingement jet. the inclusion of the obstacle increases the complexities of the aerodynamics, as the cross-flow increases with successive rows of impingement jets. this flow complexity is shown as velocity path-lines by authors previous work by el-jummah et al. (2015a, 2016a, b, 2018) and were compared with smooth target geometrical predictions. their comparison showed the aerodynamics complexity increases with addition of obstacles, which were placed to have convective heat transfer from the reversed jet flow at certain upstream few holes. this complex phenomena requires that cfd invesgigations are initiated and should be validated.   )1(    tt qh s table 4: boundary flow conditions g (kg/sm2bara) 1.93 1.48 1.08 vj (m/s) 43.41 33.5 24.3 uc (m/s) 24.0 18.4 13.4 vj/uc 1.8 1.8 1.8 reh   dvj 9680 7440 5400 t∞(k) 288 288 288 tw(k) 353 353 353 ρ (kg/m3) 1.225 1.225 1.225 figure 3: comparison of measured pressure loss with cfd predicted data for varied file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 320 figure 4: comparison of experimental surface figure 5: cfd predicted pressure loss for all average htc with predicted data for varied g the modelled obstacles and for varied g 3.2 prediction of the overall/axial pressure loss and flow-maldistribution experimentally, the pressure loss results for a smooth wall have been shown previously to have good agreement with the cht cfd predictions, using the present computational methods (eljummah et al. 2014a, b). to achieve this agreement, the experimental measurement configuration had to be modelled precisely. in the experiment, the impingement cooled duct had a discharge length of 25 mm before discharge to the atmosphere, as in figure 1a. on three sides this flange was used to bolt the test section to the impingement wall with the spacer gap, z and this also sealed the gap from air leaks on three sides. on the flow exit side as in figure 1b, no bolts were present and the gap was open. the extended outlet region is included in the modelling (figure 2) and predictions. figure 5 shows that there was flow expansion to the full width of the duct with associated static pressure recovery in the 25 mm outlet section. this was particularly strong for the cross-flow obstacles and the impact of the cross-flow in the impingement gap is to induce a flowmaldistribution between the first and last impingement holes. figure 5 shows the predicted pressure loss for the range of g, for all the four obstacles along the impingement gap exit flow. figure 6: predicted jet exit hole pressure loss figure 7: flow-maldistribution in the jet holes for all the modelled obstacles at the highest g for all the modelled obstacles at the highest g http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 321 comparison of all the four obstacles indicates that the higher the g, the higher is the pressure loss at the exit gap. also, it shows that the dimple obstacle has higher pressure loss at the exit gap and is followed by the rectangular pin in cross-flow and with similar trend, which is expected. this is because all the jets air entrained within the array of the obstacles are now forced to exit at the same time, which are at higher exit velocity. worthy of knowing is that the other two pin obstacles have almost the same pressure loss and with similar trend. this should be because, the trend of jets movement (recirculation) along the gap is closely in the same phase, as the range of g and geometries are also the same. although at the highest g, the circular pin in cross-flow has higher pressure loss which is close to that for rectangular pin in cross-flow. this indicates that with the highest g, flow recirculation increases along the gap for the pin-fin, which at exit stage generate higher velocity. the prediction of the axial variation of the pressure loss across the impingement jet wall in figure 6, were determined as the difference in the plenum chamber air supply static pressure and the impingement wall static pressure. this is the static pressure between adjacent impingement holes for the same axial location. at the last hole this did not include the flow expansion downstream and static pressure recovery in the outlet duct. the obstacles create a blockage to the cross-flow which was predicted to inpact on the pressure loss (figure 6). figure 6 shows the axial hole exit pressure loss for all the obstacles and for the highest g, with the rectangular pin in cross-flow generating the highest exist pressure loss. the circular pin fins have the next greatest impact, even though they leave a clear gap between the pins. the trend of the rectangular pin in co-flow and that for the dimple as figure 6 show is the same, with only a slight increased demonstrated by the co-flow obstacle. this is expected for both as both had their jet flow concentrated upstream the impingement jet holes, but with the impingement gap cross-flow, the air outflow dominates at the exit gap. this behaviour have been shown to be similar to that exhibited by the smooth target surface, hence the two obstacles are not expected to produce much significant heat transfer. flow-maldistribution is the characteristic of the air jet-flow through the holes and the impingement gap as a result of cross-flow, which is also controlled by the size of g used. also, the impact of the flow-maldistribution is proportional to the pressure loss, as figures 6 and 7 shows. figure 7 shows that the similarity situation demonstrated by the cross-flow obstacles for the pressure loss in figure 6 is also seen here. this is also the same with the co-flow and dimple obstacles but with haphazard behaviour demonstrated by the dimple one as there is no increased in the cross-flow blockage and for the co-flow the blockage is insignificant between obstacles. figure 7 show that the greater flow reversal and reduced target surface flow, must give a greater resistance to the impingement cross-flow. this then increases the flow-maldistribution along the impingement gap for all the obstacles, as turbulence is also generated significantly. 3.3 predictions of the turbulent kinetic energy and nusselt number profiles the turbulent kinetic energy (tke) on the wall surface controls the wall heat transfer (el-jummah et al., 2013, 2014a, 2019). figure 8 (left: a d) shows the predicted tke in the symmetrical plane in line with the impingement jets for the obstacles and compares them with the predicted nusselt number, nu using equation 2 (by the right (a d) hand side). figure 8 shows that the action of the obstacle is to reduce the turbulence on the surface and to move the peak turbulence to the obstacle surface (el-jummah et al., 2019). the only surface roughness file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 322 (obstacle) that increases turbulence on the target wall is the dimple target surface and is deflected out of the dimple by the cross-flow, as figure 8 show. figure 8 also show that for the rectangular pin in co-flow and pin-fin obstacles, there is significant increase of tke on the target surface which also improves on their heat transfer as figure 8 (right: a and c) shows. figure 8 also show that the cross-flow rectangular pin that is expected to generate higher turbulence on the target surface, hence heat transfer demonstrate lower value for both tke and nu. this is expected, as most of the jet air is reversed back to the impingement jet surface as will be seen later using equation 3 that it increases the heat there. figure 8 (right) for all obstacles is very similar to that for the distribution of tke in figure 8 (left), which further explains the control of tke in enhancing the heat transfer. figure 8: contour of tke (left) and nusselt number (right) on target surface for the highest g figure 9: the predicted surface average htc figure 10: the predicted x2 average htc on on the enhanced target surfaces for varied g the enhanced target surface for the highest g )2( fk hdnu      )3(*      tt ttt w http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 323 3.4 the surface and x2 average htc for varied g the work by el-jummah et al. (2016a, 2017, 2018, 2019) and that of figure 4 above, for the surface average htc with impingement heat transfer have shown good agreement between measurements and predictions, using the same methodology as in this work. figures 9 and 10 are the results for the surface and x2 (or local) average htc on the whole length of the target surface for varied g and on the axial x2 trends of the surface, respectively. all the obstacles showed increased in surface htc with g with the co-flow obstacle given the highest but had the worse local htc, as in figure 7. this is because at the first six holes there was local htc deterioration, then from hole 7 insignificant improvement downstream was then seen upstream the cross-flow gap. part of the reason for this worse prediction in x2 htc was the flowmaldistribution shown in figure 7. the extra cross-flow pressure loss created by the obstacles, caused the first four impingement holes to have lower air mass flow than the last four and is the ideal. this reduces the heat transfer for the first four holes and increases it for the last four holes, with little changes in the x2 average htc. even though for the dimple, there was significant increased downstream the holes but it has the lowest htc, which was the result of the pressure loss shown in figure 6. another reason for the deteriorated surface average htc was due to the dimple increasing the reverse flow of the jets and deflecting the jets away from the cooled surface also, there was only a small axial gradient in the local htc with a small increase in the downstream part of the cross-flow. hence the dimpled surface has worse local htc at all axial locations and for the surface htc than the other three obstacles. the circular pin-fins in cross-flow, also had higher local htc upstream but with reduced htc downstream, which is expected base on the trend demonstrated by the flow-maldistribution above. figure 11: contours of cfd predicted normalized temperature in the impingement gap (left) and on the target surface (right) for the highest g of 1.93 kg/sm2bar file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 324 figure 12: the predicted surface average htc figure 13: the predicted normalized thermal on the impingement jet surfaces for varied g gradient on the target surface for highest g for the first four holes, all the obstacles were predicted to have much higher local surface average heat transfer, this was 50% higher than for the dimpled surface and 20 % lower for the cylindrical pin-fins. the main benefit of the obstacles was in the downstream part of the crossflow in the impingement gap. this is when the cross-flow velocity had increased, due to the flow outlet from the upstream jets and higher velocity impingement jets were created due to flowmaldistribution. however, this downstream velocity increased was never sufficient to overcome the large deterioration in htc for the first four holes. part of the reason for this was the worse flow-maldistribution, so that the first holes had less air than the downstream holes and this kind of maldistribution was worse with obstacles as compared with the smooth wall (el-jummah et al. 2018). recall that when obstacles are placed between the holes, surface interaction is terminates as was prevalence in smooth target surface (el-jummah et al., 2016a,). the result of this lack of interaction between the jets with obstacles is that lower turbulence and lower htc are expected, as shown in figure 8 (left). 3.5 thermal gradients in the target and fin walls the complex aerodynamics of impingement jets array with a narrow gap, is that there is a flow reversal on the centreline between each group of 4 holes in a square array, as in figure 11 (left: a d) and is based on equation 3: surface distribution of normalised temperature t*. this reverse flow jet is heated by the heat that was transferred from the target surface, as a result of which the heated jet impinges on the jet wall and heats up the impingement surface. very few experiments by goldstein et al. (1982a, b) have been made of this component of the heat transfer in impingement cooling. the action of obstacles can be to interfere with this reverse flow jet, particularly if the obstacle is placed where the reverse flow jet occurs, as it was for the coand cross-flows pins shown in figure 11 (left). this therefore affects the heat extraction from the target wall as clearly demonstrated by contours of normalized temperature shown in figure 11 (right: a d). therefore, the impingement jet wall will then be heated (not cool) with the heated air as shown by figure 12 for the surface average htc on the jet wall. figure 12 show that as most of the heated air recirculate and heat the jet wall for the cross-flow obstacles. based on this, there surface average htc is significantly higher while the dimple gave the lowest htc http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 325 as the heated air concentrates in the dimple. also showing lower htc with similar trend to the dimple obstacle is the co-flow obstacle, which was based on the fact that the impingement gap cross-flow takes away most of the heated air, hence lower htc was observed. in figure 11 (left), all the obstacle walls on the target surface shows that the heat transfer is dominated highly on the obstacles, even though for the dimple most of it reversed back to or circulate inside the dimple pot as in figure 11 (left: d and right: d). a high impingement target surface local htc will give greater thermal gradients, as it is extracting more heat. the greatest thermal gradient occur in the pins, with the highest gradients in the cross-flow in rectangular pins of figures 11 (left) and 13 (for the obstacle at the region of hole 9). however, it is heat extraction from the target wall that is required and the thermal gradients here are greatest for the dimple obstacle over the first few rows of impingement jets and it implies better cooling. the trend of the thermal gradient in the obstacle for the cross-flow is similar to that of the co-flow obstacle, even though with little variation in their data. the reason for the these are that for the cross-flow air re-circulation in around the vicinity of the obstacles created better heat extraction on the obstacles, while for the co-flow was mostly the impact of the impingement jet cross-flow in the gap. the heat transfer is significant and is roughly 50 60% lower than the impingement target surface average htc of figure 9. this has been previously reported by the authors and others (el-jummah et al., 2014a and xie et al., 2013) and has been shown to influence the effectiveness of the target wall cooling. 4.0 conclusions conjugate heat transfer cfd predictions were used to improve on the efficiency of regenerative wall cooling for low nox combustors using obstacles in the impingement gap. a high coolant mass flux g and low pressure loss requires a low impingement x/d and 4.66 was investigated. the current cht cfd methodology had been validated using the impingement gap exit pressure loss and the surface average htc. the cfd validation concentrate on only the rectangular pins in co-flow and cross-flow obstacles, as they are the only obstacles with available experimental data. the prediction of the thermal gradient in the target wall/obstacles and in the air jet flow, reveals that heat extracted by the air could be the result of the heated jet wall and this reduces the htc on the target surface. also shown was that most of the air cooling in the impingement gap were dominated around or within the vicinity of the obstacles, which also affects the target surface and x2 average htc as the dominance also impact on the hole flow-maldistribution. the computational methodology applied in this work indicates that improvement of gas turbine cooling system could be employed, as such the cht cfd application is adequate for the design analysis of gt cooling geometries. therefore, this work recommend future enhancing obstacles that could explore both experimental and computational analysis that could provide validation. nomenclature d impingement air hole diameter, m do obstacle diameter, m g coolant mass flux, kg/sm2bar h heat transfer coefficient (htc), w/m2k h obstacle height, m kf thermal conductivity of fluid, w/mk file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 326 l test wall metal thickness, m n number of jet hole/unit surface area, m-2 n number of upstream rows of impingement holes nu nusselt number ρ density of air, kg/m3 δp impingement wall pressure loss, pa p coolant supply static pressure (approx. 1bar) pr prandtl number re reynolds number t obstacle thickness, m t∞ coolant temperature, k t* normalized mean temperature ts target surface metal wall temperature, k tw target wall imposed temperature (k) vj impingement jet mean velocity, m/s uc impingement gap cross-flow velocity, m/s ν kinematic viscosity, m2/s w obstacle width, m x hole to hole pitch, m y+ inner variable wall normal coordinate (ξuτ/ν) z plate to plate gap, m ξ grid cell size, m δ obstacle depth, m subscripts l local c cross-flow h hole j jet w wall s surface ∞ coolant f fluid o obstacle references abdul husain, raa. and andrews, ge. 1991. enhanced full coverage impingement heat transfer with obstacle in the gap. proceedings of the asme international gas turbine and aeroengine congress and eposition, 91-gt-346, 1 12. el-jummah, am., oluwole, fa., andrews, ge. and staggs, jej. 2017. numerical predictions of enhanced impingement jet cooling with ribs and pin fin in co-flow and cross-flow http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):314-328. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: al-jummah@hotmail.com 327 configurations. arid zone journal of engineering, technology and environment (azojete), 13 (1): 149 162. el-jummah, am., andrews, ge. and staggs, jej. 2018. enhancement of impingement heat transfer with the cross-flow normal to ribs and pins between each row of holes. proceedings of the asme turbo expo: turbomachinery technical conference and exposition, gt 76969, 1 12. el-jummah, am., abdul hussain, raa., andrews, ge. and staggs, jej. 2014a. conjugate heat transfer computational fluid dynamic predictions of impingement heat transfer: the influence of hole pitch to diameter ratio x/d at constant impingement gap z. transactions of the asme: journal of turbomachinery, 136 (12): 1 16. el-jummah, am., andrews, ge. and staggs, jej. 2016a. impingement jet cooling with ribs and pin fin obstacles in co-flow configurations: conjugate heat transfer computational fluid dynamic predictions. proceedings of the asme turbo expo: turbomachinery technical conference and exposition, gt57021, 1 15. el-jummah, a. m., abdul hussain, raa., andrews, ge. and staggs, jej. 2013. conjugate heat transfer cfd predictions of the surface averaged impingement heat transfer coefficients for impingement cooling with backside cross-flow. proceedings of the asme imece conference, imece-63580, 1 14. el-jummah, am., abdul hussain, raa., andrews, ge. and staggs, jej. 2014b. conjugate heat transfer cfd predictions of impingement heat transfer: influence of the number of holes for a constant pitch to diameter ratio x/d. proceedings of the asme gas turbine conference, gt25268, 1 14. xie, y., li, p., lan, j. and zhang, d. 2013. flow and heat transfer characteristics of single jet impinging on dimpled surface transactions of the asme: journal of heat transfer, 135: 1 15. el-jummah, am., andrews, ge. and staggs, jej. 2013a. conjugate heat transfer cfd predictions of impingement jet array flat wall cooling aerodynamics with single sided flow exit. proceedings of the asme turbo expo conference, gt-95343, 1 12. el-jummah, am., andrews, ge. and staggs, jej. 2013b. conjugate heat transfer cfd predictions of the influence of the impingement gap on the effect of cross-flow. proceedings of the asme heat transfer conference, ht-17180, 1 12. el-jummah, am., andrews, ge. and staggs, jej. 2015a. conjugate heat transfer cfd predictions of metal walls with arrays of short holes as used in impingement and effusion cooling. proceedings of the gtsj international gas turbine congress, igtc ts 266, 1 9. el-jummah, am., andrews, ge. and staggs, jej. 2015b. cht/cfd predictions of impingement cooling with four sided flow exit. proceedings of the asme turbo expo, gt-42256 1 12. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng el-jummah, et al: enhanced impingement jet cooling of gas turbine wall heat transfer using cfd cht code: influence of wall thermal gradient with fin and dimple obstacles. azojete, 15(2):314-328. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 328 el-jummah, am., andrews, ge. and staggs, jej. 2016b. impingement/effusion cooling wall heat transfer: conjugate heat transfer computational fluid dynamic predictions. proceedings of the asme turbo expo: turbomachinery technical conference and exposition, gt-56961, 1 14. el-jummah, am., andrews, ge. and staggs, jej. 2019. predictions of impingement heat transfer with dimples, pin-fins and zig-zag rib obstacles: conjugate heat transfer computational fluid dynamics predictions. proceedings of asme turbo expo: turbomachinery technical conference and exposition, gt-90730, 1 -12. goldstein, rj. and taylor, jr. 1982b. mass transfer in the neighbourhood of jets entering a cross-flow. transactions of the asme: journal of heat transfer, 104: 715 721. oldstein, rj. and timmers, jf. 1982a. visualization of heat transfer from arrays of impinging jets. pergamon international journal of heat and mass transfer, 25 (12): 1857 1868. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):190-206 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 190 original research article development of a model for mitigating fire spread in multi-storey buildings p.o. oluseyi1*, t.o. akinbulire1, c.t. atunbi1, m.i. akinyemi2 (1department of electrical/electronics engineering, university of lagos, akoka, lagos, nigeria 2department of mathematics, university of lagos, akoka, lagos, nigeria) *corresponding author’s e-mail address: poluseyi@unilag.edu.ng article information submitted 29 march, 2018 revised 5 february, 2019 accepted 10 may, 2019 keywords: fire modelling fire spread fire growth multi-storey buildings abstract in the developing nations that are located in the tropical region; there is a growing trend of fire incidence in buildings without adequate development of fire prevention and/or reduction protocol. thus, this study addresses the growth and spread of fire in multi-storey buildings. the rooms are structured as cells in order to reduce the flame spread from a single fuel item, by heat release, to other neighbouring items or rooms (otherwise known as cells). the philosophy is to reduce the advent of vertical and horizontal fire spread. thus, the mathematical model for the spread of fire in buildings over a solid fuel surface is therefore developed using the adaptation, development and simulation of cellular automata (ca) discrete model. the von neumann neighbourhood cell configuration is adopted. hence, the surface of the fuel is analysed using a regular square array (i.e. cells), while the flame spread is depicted as a series of ignitions of surface elements. in which case, ignition of an element is evaluated by a combination of critical surface ignition temperature and cellular automata discrete techniques. the work displays the movement of fire, from its origin of ignition to other fuel igniting elements around it. consequently, this spread to other parts of the building. however, the technique presented in this work attempts to reduce the rate of growth of the fire spread using the predictive fire growth probability approach. in other words, the application of the cellular automata, using a multi-storey building, is herein presented. the study has potential to advance knowledge of technical approach to stop fire spread in multi-storey building. thus it improves fire risk management as well as reducing magnitude of fire disaster and losses in the multi-storey buildings. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction one of the commonest emergencies that can occur in multi-storey buildings is fire outbreak. the occurrence of fires in multi-storey buildings pose a significant risk to building occupants (kobes et al., 2010). the incidence of fire outbreak can be due to a number of reasons; most of which could be avoidable; if practice of due diligence and care are taken into consideration. in the modern society, the fire issues are becoming increasingly a significant subject matter due to several factors ranging from building materials to the building designs. it has been established mailto:poluseyi@unilag.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 191 that the bigger and increasingly complex buildings (together with the use of new materials such as respirable silica found in sand, concrete, brick, portland cement, ceramic tile, stone, and other materials made of stone or earth) can lead to more dangerous fires (yi et al., 2019); whereby the enhanced hazards are difficult to predict. new risks arise due to the use of new chemicals, and also by transportation and handling of hazardous materials. even unimportant incidents can gravely endanger life, assets and natural environment. in particular, fire and smoke spreading in large buildings represents an early warning with its terrifying threats (zhou et al., 2019; yi et al., 2019). while it is an established fact that the phenomenon of fire and smoke spreading is extremely complex due to the intricacy of chemical reactions and physical processes involved, its spreading from one room to another inside a building is as a result of the transportation of heat and excess fuels that has been generated in the fire compartments. the heat that is generated is then transferred to adjacent buildings by radiation and convection of fire-induced plume to elevate ambient temperature. if the combustibles inside the building ignite and begin to burn due to the external heating, the building then becomes a new heat source to other buildings (sime, 2001) when fire starts to burn in a building, an ever-deepening layer of smoke is formed over the entire room space occurring from the rising of the smoke from the fire which becomes trapped within the volumes of room envelope. this is noticeably seen as the smoke hit by the ceiling and then spreads in all directions (papinigis et al., 2010). thus, the smoke goes into other parts of the building through any hole or gap located vertically and horizontally between the walls, ceiling and floors. the building’s temperature rises as a result of the heat transfer from the fire that gets trapped in the building. some materials, such as metal/iron rods in the beams and columns of the buildings, then, absorb heat readily and transmit it to other rooms by conduction, where it can set on fire the combustible items that are in contact with the heated environment or material. another means of heat transfer during fire events is the radiation; the radiation transfers heat in the air in the same manner that an electric bar heater heats a room. in essence the combustible material close to a fire will absorb the heat until such items start to smoulder which eventually then burn within few minutes (papinigis et al., 2010). so, also the advent of convection cannot be under rated in building fire incidence. in which case, the hot masses of air move as the air gets heated, thus it expands which makes it much lighter than the surrounding air. this then makes the heated air column that develops to hot air currents that has capacity to ignite the combustible materials along its path of movement. a great deal of loss is usually incurred from the occurrence of fire. in other words, the occurrence of fire not only destroys property, it is also a threat to the lives of the occupants that are trapped in the fire. these losses arise not only from the articles of things that are combustible within the ignition centre (which are initially ignited) but also the loss of combustible materials that are adjacent to the ignition source. losses from these fires could be reduced drastically if fires are prevented from spreading to surrounding areas (zalok and hadjisophocleous, 2011). the cost of uncontrolled fires in multi-storey buildings in terms of both human lives and loss of properties is highly colossal. an estimate rate of a country’s gross domestic product (gdp) shows that each year losses due to fires are between 0.1% and 0.4%. (raubal and egenhofer, 1998; abolghasemzadeh, 2013). this shows that the annual economic and personal costs due to fire damage are immense. since fires are random events which occur without notification; therefore, the goal of fire safety engineering is to reduce its risk to barest minimum (ezeokoye, 2016). this will eventually reduce the expected losses. for a better file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 192 evaluation, it is pertinent to understand and quantify the behaviour and consequences of building fires in multi-storey buildings (architecture and building research institute, 2004). in other words, the construction of building must devise an approach to overcome losses attributable to fire phenomenon. this has led to the development of such technology places premium on the most important concern; which is to preserve an escape route with low temperature intensity and harmless levels of smoke concentration for the people caught within the fire accident area (huang, 2010; justra and meacham, 2016). this clearly indicates the importance of a planning strategy that incorporates collaboration with the behaviour of the occupants of the building to achieve an effective fire spread mechanism. in general, the planning process requires enhancement of residents’ propensity to participate in the process through increasing awareness of disaster risks and the need for improvement of the local environment (huang, 2010). even though precise and reliable mathematical models are still under development, the computer simulation represents the most efficient tool used to cope with this problem (wang, 2015). computer simulation techniques allow the replication of fire scenarios in virtual spaces with the perspective of discovering practical real-world solutions for dealing with accidental/deliberate fires (zhang, 2016). in this line of thinking, the interest of this work is the simulation of smoke and fire spreading in enclosures such as buildings and tunnels, whereby the focus is set on the safety, as well as, on building design improvement. the tremendous losses incurred by fire outbreaks are common knowledge (chu and sun, 2005; kobes et al., 2010; papinigis et al., 2010; wang et al., 2015. a great deal of that loss arises not only from the articles or things which were initially ignited but to the loss of combustible materials adjacent to that igniting source. if fire occurrence could be prevented from spreading to surrounding areas, the losses from those fires would be sharply reduced (hu, 2016). the prediction or analysis of fire spreading in an environment is one of the most challenging aspect of fire research since the effects of fire, of course, heavily affects the quality of buildings, personnel and the public safety. since the impact of fire on buildings is critical, in the last few years the interest of researchers in models able to simulate the evolution of a fire front has increased significantly (chu and sun, 2005). electrical fire in buildings is one of the most important factors enlarging the severe fatality and loss of materials (wang et al., 2015; tong et al., 2013; yi et al., 2019). to explore the effective measures for reducing the loss, it is indispensable to have a means to rationally predict the behaviour of fires in buildings and some other facilities (sime, 2001; zhang, 2016; ji et al., 2017). unexpectedly, fire outbreaks occur in multi-storey commercial buildings which, at times, could spread so rapidly, in such a manner, preventing individuals from escaping from the scene of the fire occurrence. this incidence could also lead to the destruction of properties. more importantly, the product of this combustion often results in hazards to both properties and occupants. it is essential to emphasize that; if the rate of heat generated as well as the fire spread is known, then there is a huge opportunity that lives and properties could be saved. from the aforementioned, it would only possible as long as there is simulation approach to identify source of ignition and the combustible materials within the buildings. thus, a very close approximation model could be put in place to mitigate the extent of destruction during the ineffectuality of stochastic outbreak of fire. the volume of research in this area is quite significant and substantial (shahama and benenson, 2018; cheng and hadjisophocleous, 2009; cheng and hadjisophocleous, 2011; yea et al., 2016). the effects of fire and smoke spread beyond the room of fire origin (burn room), on http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 193 the other hand, have not been thoroughly investigated in the same extent, especially in the tropical region. in this respect, one interesting characteristic of fire is the way it spreads out of openings. thus, the fire has the tendency to spread both vertically and horizontally (cheng and hadjisophocleous, 2011). the horizontal spread of fire could occur in four distinct ways namely: through the wall of partition connecting two compartments, through the closed or open doors, through the windows and through the corridors separating the compartments. however, in the case of vertical fire spread it could be undertaken in four ways that are: through the ceiling connecting compartments, through the stairwells connecting compartments, outside projection of flame through the windows during fire incidence and inside blow of air into the compartment through open windows. the appearance of flames through windows is caused by the venting of unburned gases from the burn room and their continued combustion beyond the opening where reservoirs of fresh air exist. whereas the external flaming is a characteristic of fire that has undergone a transition to flashover and entered a ventilation-controlled state (holborn et al., 2004). it is noteworthy that accurate prediction of fire spread as well as its behaviour with potential changes in a specific time or place in respect of a real-time incidence in the buildings, is very crucial to ensure and mitigate losses and reduce extent of fire damage during its occurrence (monedero et al., 2019). thus, the essence of this research is to develop a model that can be deployed to predict and mitigate the spread of fire in multi-storey commercial buildings, using a typical commercial office in lagos nigeria as the case study. succinctly, this goal is achieved firstly by developing a mathematical model for the analysis of the spread of fire in multi-storey buildings using a well versatile tools known as the cellular automata modelling technique. this is then followed by determining the building factors that can influence the spread of fire in a peculiar building as well as within the compartments of the particular building and finally by developing a mitigating measure to mitigate or stop the spread of fire from one room to another. 2. materials and methods the data available for this study is partly secondary and partly primary. this is due to the limitations imposed on the garnering of statistical information relevant for the analysis to be conducted in this study. towards the analysis of the data and addressing of the objectives of the study, the software adopted for the implementation of the design in this study is mathematical laboratory (matlab) software. from foregoing the study data include namely: fire sizes, fire growth rates, building sizes, building room/compartment sizes, nature of building materials such as concrete wall and slabs as well as the wooden structures in the building (ezeokoye, 2016; huang, 2010; lahouar et al., 2019; zhou et al., 2019; jutras and meacham, 2016). 2.1 study area this study was conducted in lagos nigeria, using oluwatobi house on allen avenue, ikeja. the house is a six-storey building consisting of offices on the left and right wing of the building. it is located on the street of allen avenue, in ikeja, lagos state. it accommodates about 300 staff members. the study size has a space area which is about 10m in width and 25m in length within which there are 12 offices. each office in the building has about 5 compartments demarcated with heat retardant materials (ji et al., 2017; lahouar et al., 2019; yi et al., 2019; zhou et al., 2019). most compartments in each office are for 1 or 2 staff members only and are no wider than 3m, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 194 and rooms are linked by 2m wide long corridors. the various views of the building for this study is as shown in figure 1a and figure 1b. figure 1a. front view of the building figure 1b. side view of the building figure 1: the subject area 2.2 research method as a prerequisite to simulating building fire spread, a dynamic model for fire spread in buildings is established using the philosophy of fire development in a compartment and its spread from that compartment to the adjacent compartments within the building. based on the data developed for the study area, the major work of this study is to propose a new cellular automaton modelling approach. then the validation of its performance on simulating the fire spreading phenomenon. therefore, the entire operations of the methodology are classified into three sections (a) development of basic cell size for fire spread model (b) philosophy of neighbourhood phenomenon in fire spread model, and (c) processing the fire spreading model and its validation. the analysis adapted cellular automata (ca) as a tool for analysing fire spreading modelling in the building (liu et al., 2018; zheng et al., 2017). this represented how the building factors can influence the spread of fire to another building or within compartments of the same building. there were two main steps adopted in analysing fire spread factors. these are namely: (1) development of ca model and (2) simulation using ca model being developed. the development of the ca model was initiated with the formulation of equations with special http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 195 consideration for the variables’ formulation. it should be noted that there were seven variables that were deployed for the analysis of the analysis of the fire spreading probability factors in the simulated settlement. these were combustibility of materials, total envelope area covered with combustible material, distance between compartments of the buildings, width, building shape, total opening area, and wind speed (fernandez-gracias et al., 2019; hansen, 2019; lahouar et al., 2019; raubal and egenhofer, 1998)). next step was to define the state of cell which consists of type of cell/object, flammability level, and cell value. for simplification, only the main object in a settlement was involved in the simulation, and that is building (wang et al., 2015). the value of each cell/object was determined based on the ability to burn and probability to quickly spread the fire to the nearest objects. in this research, the value was calculated based on the flammability rate of the cell/object, total area of combustible material, distance between objects and width. however, the building shape, total opening area and wind speed were ignored because it was considered the same and fixed on each object (zalok, 2016). note that the building is for office space, thus the load has been assumed to be that of a typical office; 25kg/m2 of cellulose-type fuel (which is the combustible materials that are encountered by fire) with an effective combustion heat of fuel to be 16 kj/g which results in an equivalent load of 400 mj/m². thus, the burning mass rate per unit area in typical office building fires ranges from 20 to 40 g/m2s while the corresponding released heat rate per unit area ranges from 320 to 640 kw/m2. 2.3 development of basic unit cell size for fire spread model in the recent times, there is increasing capacity development in remote sensing, geographical information system and computing architecture development to ensure that simulation fire models are close to exact behaviour of and effects of fire spread. thus basically, there are three common fire models that have attracted attention of engineers. this includes consolidated model of fire growth and smoke transport (cfast), fire dynamics simulator (fds), and building research association of new zealand fire (branzfire). it should be noted that the fire spread models are interested in variables that influence the convection of fire perimeters through the cells. naturally, if the size of cell which is a basic unit of fire spreading model is small, the possibility of a more detailed simulation is evidently essential to ensure that mitigation of fire spread would take care of the microscopic elements of the fire chemical contents. (abolghasemzadeh, 2013; ahmed et al., 2019; olawoyin, 2019). however, if the size is too small, there will be an increase in the time of calculations and volume of data. since the aim of the simulation model proposed in this study is to identify and show fire spreading, the size of cell used needs not to be too small. an adaptation of the spread of fire in electrical distribution network put paid to this (bagchi et al., 2013). therefore, the size of cell used in this study is set at 3 by 3 meters using the following equation representing limit of distance between spread points or distance from source of fire spread (murosaki et al., 1984; bagchi et al., 2013). hence the equation is expressed as (ohgai et al., 2004): 1.5(5 0.5 )d v  (1) where: v is cumulative wind velocity in meter per second (m/sec) and d is the limit of distance by which fire can spread in metres (m). these are design vectors whose dimensional concept is developed in such a way as to provide needed information when the effect of one or more variables on the figure of merit is needed. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 196 2.4 philosophy of neighbourhood phenomenology in fire spread model traditionally, there are two approaches of tessellating the buildings for this research, namely squareand hexagonal-lattice modelling procedures. however, the square-lattice was adopted. in order to simplify the process and reduce computational burden; the 2-dimensional regular square grids were employed as cells of the ca framework. however, each square-lattice cell at different discrete time steps was characterized by a number of discrete transition states. this development is guided by a number of previous rese4arch on the subject matter. for instance, bagchi et al. (2013) gave information based on the idea of the limit of distance that fire can spread, which has been brought out by previous researches (murosaki et al., 1984). in applying the neighbourhood phenomenon to the cellular automata fire spread model; there are two school of thoughts. the cellular automata as a mathematical model was introduced in 1963 by von neumann with the specific purpose of modelling biological self-reproduction. there are basically two common types namely von neumann neighbourhood and moore neighbourhood phenomena. while the former is expressed mathematically using the four orthogonal cells surrounding the central cell, the latter needs to consider the eight cells surrounding the central cell. this is as displayed in figure 2. in this case the noticeable changes with time steps is recorded with respect to the wind velocity. for instance, from the diagram, consider that cell kl is the igniting source of the fire spreading while cell ij is the cell tagged the received one in the neighbourhood. in the ca framework, the state of each cell evolves in discrete time steps based on a finite set of local transition rules. m n cell kl cell ij wind velocity : 0 (m/sec) 1 to 5 (m/sec) 6 (m/sec) or more figure 2: neighbourhood used in the model thus, the basic model adapted for the study is the extended model developed for fire spread in two-dimensional linear cellular automata (encinas et al., 2007; yang et al., 2014). it relies on the transition principles of discrete dynamical systems using the finite number of identical objects (otherwise known as cells). this transition of cell states is set as shown in table 1. though there are several classes of neighbourhood in the analysis of fire spread, however for the sake of emphasis, this study adopted the extended moore neighbourhood approach. thus, at the start of the simulation; all the cells are either in the “unburnable” state (i.e. 0) or “not-burning-yet” state (i.e. 1). the cell with state 1 is not burning yet, but it has the potential of burning. however, during simulation, a cell can transcend from state-1 to state-2, either through a new fire occurrence or through spread of fire from the adjacent cell or cells (ghisu et al., 2015; encinas et al., 2007). in other words, once a cell catches fire the state of the cell changes to state 2. and then, according to the elapsed time after the outbreak of fire incidence, thus the state of the cell http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 197 changes from state 2 to 4. but it is noteworthy to state that the cell with state 0 is unburnable; thus, it never changes during the simulation period. table 1: transition state of a cell 2.5 process of the fire spreading model this model is built on the earlier work (ohgai et al., 2004). according to zheng et al. (2017); the fire spread model adapted the transition algorithms or steps under the ca framework. in which case, the cells evolved individually in discrete time steps on a set of discrete transition steps which are as follows: step 1: first of all, one cell kl of nkl=3 is selected. step 2: one cell ij of nij=1 is selected at random from the neighborhood defined by a wind direction and a wind velocity externally given when simulation starting. step 3: fire spreading judgment index fijof a selected cell ij is calculated. if fij is satisfied with the following requirements, the state of cell ij becomes nij= 2 (i.e. catching fire). if nij t = 1 and fij > ran; then nij t + 1 = 2 (2) where: nij t is the state of cell ij at simulation time t and ran is the random number which takes from 0 to 1., tcijis an elapsed time after outbreak of fire in cell ij. the time count of tcij starts when the state of cell ij changes from state 1 to 2 which is satisfied in equation (2). steps 2 and 3 are iterated for all cells ij within the neighbourhood of cell kl. furthermore, the process regarding cell kl is executed for all cells of state 3. step 4: the state of cell ij after catching fire changes according to the elapsed time after outbreak of fire, tcij . in other words, if the value of tcij takes more than t1= 2mins, cell ij changes from state 2 to 3. namely, nij= 3. moreover, if the value of tcijtakes more than t2= 10mins, cell ij changes from state 3 to 4. namely; nij= 4. step 5: the simulation ends when the time, t, in minutes becomes the end time externally given in the model. the time, t, is counted from the simulation start to the end. when the time, t, does not reach end time, 1 is added to tcij and t; then the process returns to step 1. thus, the fire spread judgment index of each cell is expressed as: fij =αp i,j t ∗ βv i,j t (3) where p(i,j)t is the cell’s ignition probability; 0<α≤1 (i.e. this is the condition of slowing down fire spread without considering the wind velocity); β˃1 and v is the wind velocity effect thus the fire spreading time is obtained as follows: state of cell explanation 0 nmn = 0 : unburnable; having nothing burning 1 nmn = 1 : not-burning-yet; having the possibility of burning 2 nmn = 2 : catching fire; just catching fire, but having no ability to cause fire spreading 3 nmn = 3 : on fire; having the ability to cause fire spreading 4 nmn = 4 : extinction file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 198 ti,j = l ros (4) where: l is the centroid distance between two adjacent cells ros is the rate of spread (this is dependent on wind velocity and other accompanied factors) t: simulation time in minutes tcij: elapsed time after outbreak of fire in minutes end time：end time of simulation in minutes fij: fire spread judgment index of cell ij ran: random number given within the range from the maximum to the minimum of fijvalue. as mentioned above, even simulation using the same conditions produce different fire spread results. even if fire spread is not externally intercepted with respect to its extinction; yet the characteristics of a model with a probabilistic calculation process will naturally ensure that the number of cells in each state converges to a certain value as long as simulation is infinitely iterated. accordingly, it is more appropriate to use a probabilistic expression as a means of offering information to the participants. based on this perspective, primarily, the information on the numbers of completely burned cells as a product of 100 iterations were collected. then, both the mean and standard deviation in each of these samples using 20 cases of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 samples were thus evaluated, so as to evaluate the spread from the expected value. thus, the mean or average fire growth is given by eqn(5a) μ = 3 3μfafh δ (5a) and thus; standard deviation of fire growth is given as follows: δf = 3 3afh α(μ)2 σ 3 (5b) where: α: growth coefficient of t2 fire σ: standard deviation of fuel load density μf: mean duration for fire to grow from ignition initiation a: floor area of compartment fh: floor to floor height or cell height in line with the above stated algorithm, figure 3 shows the flow chart of a fire spread model as presented. from this diagram, it can be explained that the outbreak of the fire is initiated in a cell, nij=3. the growth of the fire in this cell continues until the fire outbreak is spread after a period of graduated time steps (i.e. t+1) to other parts of the building. thus, the fire spread, in a random manner, to other cells by the help of the von neumann’s protocol. hence, this procedure extends the fire spread to all the other compartments in the building (von neumann, 1966). thus the propensity that the fire will reach other parts of the building is built on the transition probability (i.e. pi,j). this measures the likelihood of cell’s state transition. in other words, it provides information on the cells that will be burning at the next discrete time step (t + 1). this rule implies that a cell containing combustible fuel will be burning. however, it is possible to http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 199 have one or more than one burning cell in its von neumann neighbouring cells and its state transition probability (i.e., pi,j) is higher than a random probability threshold (cheng and hadjisophocleous, 2009; cheng and hadjisophocleous, 2011). 0 pi+1,j 0 pi,j-1 pi,j pi,j+1 0 pi-1,j 0 figure 3: adapted von neumann neighbourhood configuration for fire spread model (von neumann, 1966) to model the fire spread from the perspective of the movement of fire and heat from one cell to the adjacent cells, this can happen in random manner however, neumann developed an approach for evaluating the pattern of spread (zheng et al., 2011). this is explained by the expression in equation (6) so, the transition probability, ijijijfk skdk ij ijf ijsijd e eenp  )1()( )()(  (6) where: ijd :dynamic floor field ijs : radiation intensity field ijf : fire floor field ij : whether cell ij is occupied by wall or obstacle (if occupied it is 0 and if not it’s 1)  : adjustment factor for fij ij : cell occupied by combustible material (0 when occupied; 1 when not) ij : whether cell occupied by danger (0 when it is; 1 when not) sd kk ; : two positive parameters for scaling sij and dij fk : scaling factor for fij n : normalization factor hence, according to conduction property of fire, then the dynamic floor field expression can be obtained from the randomized movement of fire as follows;       i j t ij t t ij d d d ij ) 3 2( ) 3 2( )1( (7) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 200 since the fire can spread by radiation hence, the variation of radiation intensity field with distance from the source could be defined as:    i j ij ij ij d d s 1 1 (8) so, also since convection is the physical movement of hot mass of air. in other words, at heating there is density change in the boundary layer which cause the denser (cooler) air to rise so as to replace the cooler air which will heat and rise; this cyclical heat transfer phenomenon continues until the fire spread is further enhanced. thus, in a building, during fire outbreak the hot air will always rise and float under the ceiling of a room thus spreading the heat from the fire. this can be expressed by modifying the newton’s cooling law as follows: ij o ext hij hkf ij 3 2          (9) where the fuel bed the term inside the brackets and its coefficient is the convective heat transfer coefficient and hij is heat gradient that is exercised during fire outbreak. as an adaptation of the earlier research on the city-wide fire spread model, this work is situated within a building in a tropical region as depicted herein in this presentation (ohgai et al., 2004). thus, the flow chart presented in figure 4 is a further explanation of the fire spread phenomenon as captured by the foregoing mathematical expressions. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 201 figure 3: flow chart of the fire spread model file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 202 3. results and discussion the model developed herein is applied to the subject area. since fire is highly unpredictable, then the probability model is developed alongside to the simulation takes care of any ineffectuality. it should be emphasized that there are a number of variables that determines the fire spread rate. however, a number of them is assumed constant during this study thus the cause of fire outbreak in the building under study is assumed to be dependent on the fuel load in the building. with respect to the fuel load, then a typical cell may be unburned, partially burned or completely burned. it should be noted that the fuel load is inclusive of the individuals and things found within the building. from the foregoing, therefore applying this to the cellular automata model developed for implementation on the subject area. the simulation was carried out using 100 iterations. the results of the simulation were subjected to test using the probabilistic assessment process which is built into this model. this thus yielded results that the fire spread depends on randomized occurrence of fire. as depicted in figure 3; even though the actual time required for calculation of the simulation of 100 iterations was about 26 minutes using a personal computer but the simulation end time was set at 180 minutes. this is calibrated in such a way that the trend was studied in three discrete time steps set as: 30minutes after ignition, 120 minutes after ignition and 180 minutes after ignition. the occurrence, spread and extinction of fire occurrence was studies over these set times. it was discovered that for the first 30 minutes of the ignition; the fire spread via heat transfer by combination of conduction, radiation and convection is such that mean is very close to the standard deviation. in other words, the standard deviation of the number of cells within the state transition of the fire incidence (i.e. from unburned to burning state) that converges to a mean value shows a close relationship which then suggests that the cells experience combustion. furthermore, at 120 minutes the standard deviation to mean (average) values experience a wider gap which connotes that the fire spread is approaching extinction while the relationship between mean and standard deviation at 180 minutes clearly predicts the complete extinction of the fire spread. furthermore, after the number of accumulated samples exceeds 50; it is found out that there is a fixed number of extinction cells due to the fact that the gap between a specific mean and its standard deviation becomes smaller. 0 10 20 30 40 50 60 70 80 90 100 0 200 400 600 800 1000 1200 number of accumulated samples m ea n an d st an da rd d ev ia tio n of e xt in gu is he d ce lls [ ce lls ] 30 [min] standard deviation 30 [min] mean value 120 [min] standard deviation 180 [min] standard deviation 120 [min] mean value 180 [min] mean value figure 3: mean and standard deviation values of the simulation results http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):190-206. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: poluseyi@unilag.edu.ng 203 so also based on the fire spread judgement index, it was quite essential to design a value-based analysis of judgement capacity, behaviours and stability. figure 4 presented the relationship between the numbers of extinguished cells as against the time of fire spread. so by adopting the judgement index, it served to assist in enumeration, building and development of capacity to make good judgement on fire spread with time. hence the relationship between the number of cells that had been extinguished and the time of fire spreading based on different types of fire occurrence. from the family of trend curves in figure 4, the dotted line was based on the mean values of 50 samples for each simulation time; whereby the probability factor of fire spread excluding wind velocity (i.e.α) is taken as α = 1; while the probability of occurrence inclusive of wind velocity factor (i.e. β) is set as β = 1. at another instance, the dotted and dashed lines (displayed in figure 4) were based on the mean values when α = 0.7 and β = 1. from the trend lines presented in figure 4, it was found that the number of extinguished cells for the first scenario was about 70% of the estimated number of those cells obtained in the simulation when α = 1 and β = 1. this reduction can be considered to be due to the slowdown of fire spreading which is attributable to the restriction of air supply due to building after a period of time. therefore, it can be seen that this plays the role of expressing an uncertainty situation that is synonymous of fire outbreak. furthermore, it is still possible to suggest that the number of extinguished cells could be less than that of the others due to the propensity of intervention from the firefighting paraphernalia. thus, the variations in the range and speed of fire spread (as well as its extinction) may therefore be explained to some degree by the stochastic nature of the fire occurrence as implemented in the model herein presented. 20 40 60 80 100 120 140 160 180 0 100 200 300 400 500 600 700 800 900 1000 fire spreading time [min] n u m b e r o f e x ti n g u is h e d c e lls estimated by regression analysis using data on fire spread a = 1, b = 1 a = 0.7, b = 1 figure 4: comparison between actual fire records and simulations results 4. conclusion the study utilises cellular automata (ca) for the development of fire spread simulation model. it shows that fire spread is highly reliant on the fuel loads, wind speed and spread rate. thus, any attempt to arrest the spread of the fire should be focused on these variables. from the results presented; it is quite clear that the time count from partial burning to complete burning may not be more than 30 minutes. however, the final extinction of the smouldering cells could extend till 180 minutes. this model is virtually simulated to understand the fire safety technology and principle of the spread of fire in detail. thus, the developed framework has the capacity to deal file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluseyi, et al: development of a model for mitigating fire spread in multi-storey buildings. azojete, 15(2):190-206. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 204 with the process of fire spread in a building that the traditional models cannot efficiently arrest. furthermore, from the study, the actual spread of fire varies distinctly with varying physical and/or planning circumstances such as the location or locality of building, fuel loads in the building, prevailing weather conditions, sizes of the room, building occupancy types and wind velocity. with the aid of the neumann neighbourhood in the implementation of the ca model (which considered the fire transition in the four adjacent cells), it was discovered that fire can spread to the other cells through heat transfer promoted by the radiation and convection profile of the fire environment. so, the presence of fuel loads is essential to the conduction of heat to both vertical and horizontal adjoining cells while the availability of wind speed is crucial to the convection heat transfer process. this is then suggesting that the firefighting procedure needs to take the conduction and convection heat transfer into consideration in any event of the fire outbreak. in conclusion, the model shows great potential to predict the behaviour of fire spread, hence, it means that once the trend of spread of the fire is known; 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tests fire safety journal, volume 106, pp. 29-37. https://doi.org/10.1068/b250895 http://www.azojete.com.ng original research article development of a model for mitigating fire spread p.o. oluseyi1*, t.o. akinbulire1, c.t. atunbi1, m arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):470-478 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 470 original research article loading eccentricity issue on the performance of reinforced concrete columns kachalla mohammed (civil and water resources engineering department, university of maiduguri, maiduguri, borno state, nigeria) *corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng article information submitted 29 march, 2018 revised 20 april, 2019 accepted 23 april, 2019 keywords: rc column loading eccentricity short and slender columns abaqus abstract column is a structural element that transmits floor and beam loads to the foundation safely if properly designed. it is mostly loaded axially or eccentrically at the column-beam interface. although several research articles are available on column performance (both eccentric and axial), but there is a behavioural challenge on a column loading position parallel to the axis in relation to the flexural reinforcement requirement for reinforced concrete (rc) column. this paper looks inward to address the challenge by providing an understanding on the complete behaviour of rc column flexural requirement in relations with load and its point of application for both short and slender columns. this study uses a numerical data for the column analysis under varied loads and eccentricities values, and numerical deformation and stresses determination using abaqus. the finite element analysis (fem) result indicates that increasing column axial load leads to an anticipated higher flexural reinforcement to enhance the column capacity, and is rational. additionally, the established behaviour between the flexural reinforcement requirement and loading eccentricity for a rectangular column can be predicted easily using established linear relations for both column types considered in this study. moreover, the finite element method analysis result for the short column similarly indicates an interesting relationship where 16 % change in load value will translate to about 16 % change in deformation value irrespective of either axial or eccentrically loaded points. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction column is a structural element that transmits loads via itself to the foundation. reinforced concrete column (rcc) plays a very vital role in transferring the structural loads from beams or slabs to the foundation. the rccs are primarily compression members that could be categorised into either short or slender columns. there are several scholarly articles that covers areas such as ductility, slenderness ratio and buckling effects for rectangular rcc (zeghiche and chaouti, 2005). however, most columns are loaded either axially or eccentrically at the column beam interface, but there exists very little information on its behaviour at that interface; for example column load position in relation to the flexural reinforcement requirement. hence, this makes it imperative to investigate how column load and its positions with respect to the column-centroid and its reinforcement requirement for stability relates to each other. although previous research mailto:engrkachalla@unimaid.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):470-478. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 471 findings reveal that increases in load eccentricity results in decreasing load carrying capacity (zeghiche and chaouti, 2005), but not much was covered on how the variations influences the flexural capacity requirement. it is known that eccentric loadings in the same direction causes the largest deflection, so also local buckling plays a very vital role and euler’s buckling is of little importance while dealing with short column (chen and liew, 2003). in related work conducted by barrera et al. (2011) on reinforced concrete column subjected to constant axial load, the result suggests that failure due to compression is more pronounced when axial load, concrete strength and both transverse and longitudinal reinforcement ratios are increased. similar experimental work on concrete-filled stainless-steel tubular columns was also carried out, but the column was loaded with either fibre reinforced concrete (ehab and mariam, 2012) or steel jacketed column (cavaleri et al., 2016; ezeeldeen, 2016). this shows that there is a missing gap on the loading position parallel to the column axis as well as the flexural column reinforcement. this paper looks inward to present the missing link. the study results will aid the understanding of the complete behaviour of rcc flexural requirement in relations with load and its point of application for both short and slender columns. moreover, most reinforced concrete sections could either be subjected to either axial loads or biaxial bending characterised by the structure (bonet et al., 2011), that’s notwithstanding, the load contour method emphasis bending moment separately in either direction (bresler, 1960). additionally, this study addresses both short and slender column types, and their numerical performance with the use of abaqus software. 2.0 materials and method 2.1 short column a braced short column type was adopted for this study. the adopted short column design details followed the provision in accordance with the bs 8110 (1997). hence, the column effective height, el is from the use of eq. (1) e ol bl (1) where b is an column ends condition determinant factor and the values are obtained from tables 3.19 and 3.20 of bs 8110 (1997). the parameter ol in eq. (1) stands for the actual column height. hence, for an axially loaded column, the design ultimate load, n relation to the flexural reinforcement area, sca is 0.45 0.95cu sc yn f bh a f  (2) the parameters cuf and yf are the respective concrete and steel characteristic strength. similarly, *b h defines the column cross sectional area (figure 1). for an eccentrically ( )e loaded column carrying an axial force, n , the increased moment, am as shown by eq. 2( 2 )am m n h d   (3) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kachalla mohammed: loading eccentricity issue on the performance of reinforced concrete columns. azojete, 15(2):470-478. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 472 axial load (kn) x x y x section x-x 30 0 450 column section column reinforcement figure 1. short column dimensions hence, the flexural reinforcement requirements are obtained through designing the member to withstand am using 2 ' ' ' 0.156 0.95 ( ) 0.95 0.2 0.95 a cu y s y s cu y s m f bd f a d d f a f bd f a      (4) in eq. ' sa stands for the area of reinforcement at the tension zone. this implies that '0.2 0.95 0.95 cu y s s y f bd f a a f   (5) the resulting output value in eq. will be reduce by 0.95 yn f slender column slender column (figure 2) are designed to withstand not only the axial load, but increased moment, im as shown using eq. as found in bs 8110 (1997). i um n (6) the column deflection  u akh  , where the coefficient 2 ' 1 2000 e a l b        and 'b is the least column dimension. similarly, k stands for a deflection reduction factor computed from 1.0uz uz al n nk n n     (7) where uzn and aln are from: 0.45 0.95 0.25 uz cu y sc al cu sc n f f a n f a    however, subjecting the column to an eccentric load will result in additional moment, addm , and this is from http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):470-478. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 473 min min * where / 20 or 20 addm n e e h mm   (8) axial load (kn) x x y x section x-x 35 0 600 column section e column reinforcement figure 2. slender column dimensions therefore, the total moment, t i addm m m  . for the purpose of this analysis, three different axial loads (1500 kn, 1750 kn and 2000 kn) values are considered under both short and slender columns. similarly, the initial eccentricity value was 25 mm, and subsequent 100% increments that translate to respective 50 mm and 75 mm. figure 2 shows the column dimensions and loading position. those values chosen have high likely of occurrence in the real life situation. 3.0 numerical model this study uses abaqus software application to mimic the behaviour of the rc concrete column. the finite element model considers both the non-linearity behaviour of the concrete and reinforcement medium. the concrete part was deformable solid element while the reinforcement part is also deformable-wire element. figure 3 shows the typical parts-merged and meshed. figure 3. meshed specimen type file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kachalla mohammed: loading eccentricity issue on the performance of reinforced concrete columns. azojete, 15(2):470-478. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 474 this study concrete behaviour was modelled using the concrete damage plasticity, where the failure mechanism is by crushing and cracking. this model requires the use of elastic modulus, poisons ratio, the plastic damage parameters and the description of the tensile and compressive behaviour. the stress-strain relationship presented in hamza and mohannad (2018) was adopted to construct the concrete uniaxial compressive stress-strain curve, and this is by 2 3 1 ( 2) (2 1) c c c c c c e o o o e r r r r                               (9) 1 2 0 ( 1)where ( 1) e o e e c e c o o r rr r r er e fe        (10) the constant parameters and o er r have a value of 4, while the concrete elastic modulus and its corresponding strain vales are 4700c ce f and 4(0.2 13.06).10o cuf   , respectively. the parameter cf represents the characteristics concrete strength. similarly, the strain-stress relationship for the steel element was in accordance with the method proposed by literature (hamza and mohannad, 2018). to simulate the behaviour of the concrete and the reinforcement steel, the embedded region function in abaqus was used. additionally, for the purpose of this numerical analysis, only two axial loading cases (1500 kn and 1750 kn) are used and the loading eccentric (e) considered was 25 mm. the reason for such values selection is based on their likely of occurrence in real life situation. however, because of similarity in the flexural behaviour for the two columns considered in this study, only the flexural reinforcement characteristics for the short column were used for the abaqus analysis. the vonmisses stresses and deformation values were recorded for interpretation. results and discussion figure 4 show the flexural behaviour of short column under the different parametric conditions stated above. figure 4. short column flexural requirement behaviour http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):470-478. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 475 in figure 4, gradual increase of the loading eccentricity from 25 mm to 50 mm results in 44% surge in flexural requirement (a) with 1500 kn axial load. however, surging load yields to flexural reinforcement decreases to about 30% with further 250 kn load increment from 1750 kn. similar scenario happens when the e values changes to 75 mm from 50 mm and the corresponding values are 30 and 23%, respectively. the analysis of the short column behaviour reveals that, increasing the axial load value from 1500 to 1750 kn ( 25 )e mm results in about 32% surge in flexural reinforcement. however, further load increment result in much lesser value than the previously reported surge (24%). this study result indicates that increasing column axial load leads to an anticipated higher flexural reinforcement to shore up the column capacity, and is rational. additionally, the established behaviour between the flexural reinforcement requirement and loading eccentricity for a rectangular column could be easily described with linear relation. for example, consider an axial load value of 1500 kn, its linear equation of best fit is 330 423y x  , where y is the dependent variable (short column). figure 5. slender column flexural requirement behaviour there is no doubt, the slender column requires more steel than the short column (see figure 5). similar to the behaviour shown with the short column, the flexural requirement linearly increases with increasing eccentricity. generally, eccentrically loaded column exhibits a conservative flexural requirement especially with increasing eccentricity and similar characteristic behaviour are found in literature (ehab and mariam, 2012). however, reducing this high level of conservatism could be interesting research areas that need to be explored. 3.1 finite element analysis result figure 6 and 7 presents the finite element method (fem) analysis outcomes for the von-misses stress values for both the axial and eccentrically loaded condition, but for short column. the axial stress resistance values increase with increasing axial load value. this behaviour could be attributed to the additional flexural reinforcement that enhances the concrete resistance. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kachalla mohammed: loading eccentricity issue on the performance of reinforced concrete columns. azojete, 15(2):470-478. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 476 figure 6 von misses stress values under axial load (a) 1500 kn axial load (b) 1750 kn axial load figure 7. von misses stress values on 25 mm-eccentric loading (a) 1500 kn (b) 1750 kn figure 8 shows the deformation behaviour for the column analysed. as expected, the deformation values increase with increasing column load (figure 8 a and b). interestingly, 16 % change in axial load will result in 16 % change in deformation value irrespective of point of load application either axial or eccentrically loaded (figures 8 a-d), because the 25 mm loading eccentricity have no influence on the deformation capacity. in general, stewart and rosowsky (1998) showed that the serviceability condition is mostly influenced by the concrete strength ckf rather than other deformation influencing factors (kachalla et al., 2018). (a) (b) (a) (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):470-478. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 477 figure 8. deformation behaviour (a) 1500 kn, (b) 1750 kn, (c) 1500 kn @ eccentricity of 25 mm (d) 1750 kn @ eccentricity of 25 mm 4.0 conclusion this paper looks inward to address the missing link on the loading position parallel to the column axis as well as the flexural reinforcement requirement for rc column in order provide an understanding on the complete behaviour of rc column flexural requirement in relations with load and its point of application for both short and slender columns. numerical data were used for the study analysis for both the short and slender columns under varied loads and eccentricities condition. the study result indicates that increasing column axial load leads to an anticipated higher flexural reinforcement to enhance the column capacity, and is rational. moreover, fem analysis result for the short column similarly indicates an interesting relationship between the deformation and loading eccentricity function. additionally, the established behaviour between the flexural reinforcement requirement and loading eccentricity for a rectangular column can be predicted easily by the use established linear relations for both short and long column types. however, the study results indicate that eccentrically loaded column exhibits a conservative flexural requirement especially with increasing eccentricity. hence, reducing this high level of conservatism could be an interesting field that needs further explorations. (b)(a) (d)(c) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kachalla mohammed: loading eccentricity issue on the performance of reinforced concrete columns. azojete, 15(2):470-478. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 478 references barrera, ac., bonet, jl., romero, ml. and miguel, pf. 2011. experimental tests of slender reinforced concrete columns under combined axial load and lateral force. engineering structures, 33: 3676-3689. bonet, jl., romero, ml., and miguel, pf. 2011. effective flexural stiffness of slender reinforced concrete columns under axial forces and biaxial bending. engineering structures, 33. 881-893.doi: 10.1016/j.engstruct.2010.12.009. bresler, b. 1960. design criteria of reinforced concrete column under axial load and bi-axial bending. american concrete institute journal american concrete, 57(5): 481 490. bs 8110. 1997. structural use of concrete. part 1: code of practice for design and construction. b.s.i. london. cavaleri, l., di-trapani, f. and ferrotto, m. f. 2016. steel jacketting of rc columns: reliability of capacity laws for concrete. paper presented at the europe and the mediterranean towards a sustainable built environment international conference, sbe, 17-20th march 2016, malta, 45-52. chen, wf. and liew, jyr. 2003. the civil engineering handbook (2nd edition): crc press llc, 2000 n.w. corporate blvd., boca raton, florida. ehab, e. and mariam, fg. 2012. experimental investigation of eccentrically loaded fibre reinforced concrete-filled stainless steel tubular columns. journal of constructional steel research, 76(10): 167-176. eze-eldeen, ha. 2016. steel jacketting technique used in strengthening reinforced concrete rectangular columns under eccentricity for practical design applications. international journal of engineering trends and technology, 35(5): pg. 195-204 hamza, ms. and mohannad, has. 2018. finite element model of a reinforced concrete column strengthened with steel jacket. civil engineering journal, 4(5): pg. 916-925 kachalla, m., izian, ak. and abba, ma. 2018. deflection capacity enhancement factor development. nigerian research journal of engineering and environmental sciences, 2(5): 26353350 stewart, m. and rosowsky, d. 1998. time-dependent reliability of deteriorating reinforced concrete bridge decks. structural safety, 20(1): 91-109. zeghiche, j. and chaouti, k. 2005. an experimental behaviour of concrete filled steel tubular columns journal of constructional steel research, 61:(53): 53-66. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):37-47 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 37 original research article the effect of fiber sizes on mechanical properties of millet husk (pennisetum glaucum) fiber filled high density polyethylene composites a. a. hammajam1,2*, i. z. nur2, s. m. salit2,3, and l. zulkeffle 2,3 (1department of mechanical engineering, university of maiduguri, maiduguri, nigeria. 2department of mechanical and manufacturing engineering, universiti putra malaysia, 43400 upm serdang, selangor darul ehsan, malaysia. 3institute of tropical forestry and forest products (introp), laboratory of biocomposite technology (biocomposite), 43400 universiti putra serdang, selangor, malaysia) * corresponding author’s email address: hammajam92@gmail.com 1.0 introduction agro waste and natural fiber composites are not altogether a new phenomenon. the interest in superior material started to grow as a result of environmental safety and industrialization (ester rojo et al., 2015; patel, 2012; sdrobiş et al., 2012). millet husk as waste are abundantly available and has the potential to be used as filler or reinforcement in plastic composites (abubakar and ahmad, 2010; hammajam et al., 2014). rapid increase in quantity and categories of agro waste as a result of rigorous agriculture in wake of population growth and improve standard of living is becoming dwindling problem as rotten waste emits methane and leachate, and open burning by farmers to clear lands generate carbon dioxide (co2) and other local pollutants (el-sabbagh, 2014; gloria, 2001; hamzeh et al., 2013). however, improper management of these wastes is contributing toward the climate change, water and soil contamination, and air pollution (chandak, 2010). lignocellulosic thermoplastic composites have steadily achieved significance in most parts of the world recently (azhar et al., 2015; du et al., 2014; hadjadj et al., 2016; kumar and bavan, 2010; kwon et al., 2014). while wood play key role in recent time, but composites researchers continue to explore for new, cheaper and environmentally friendly lignocellulosic materials as substitute for wood and inorganic fibers (crespo et al., 2010; el-abbassi et al., 2015). thus, these agro waste fibers such as millet husk, rice husk, flax straw, corn cobs, cotton husk, sugar baggage, kenaf, wheat straw, luffa fiber, banana stalk, barley husk and hazel shell are potentials precious raw materials in composites production. article information abstract this study examined the effect of fiber sizes on the mechanical properties of millet husk powder (mhp) filled high density polyethylene (hdpe) thermoplastic composites. the mhp-hdpe composites were prepared by melt blending techniques, accompanied by compression molding process. three different fiber sizes; 250µm, 500µm and 750µm were pulverized and the fiber loading was 10%, 20% 30% and 40% by weight. tensile and impact properties were tested using universal testing machine (utm). 1the results show that ensile strength increased at certain loadings while tensile modulus increased by increasing the millet fiber loading. while the impact strength decreases substantially with increase fiber loading the tensile strain considerably decreased at millet husk fiber application above 10%. therefore, it was observed that composites with least size fiber indicated improvement with increasing strength as well as relative extension. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 march, 2019 revised 27 september, 2019 accepted 03 october, 2019 keywords: millet husk composites polyethylene mechanical properties. http://www.azojete.com.ng hammajam et al: the effect of fiber sizes on mechanical properties of millet husk (pennisetum glaucum) fiber filled high density polyethylene composites. azojete,16(1):37-47. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 38 thus, these agro waste show better future applications due to its availability, annual renewability, light weight, low cost, and green environment component materials (andrzej et al., 2010; behzad, 2011; sahari et al., 2013). because of the recent environmental concerns and millet husk disposal difficulties, the use of mhp has become most important. several studies indicate good and compatible properties of lignocelluloses materials (bhattacharyya et al., 2015; boopalan et al., 2013; el-abbassi et al., 2015; fan and naughton, 2016). other investigators have shown the upper hand for using cereal fibers in variety of polymer matrices. in this study, an attempt is made to utilize mhp-hdpe composites. the effects of fiber sizes on the mechanical properties of the composite were evaluated. these properties of the composites will determine its viability for different applications. understanding these parameters is critical in strategizing composites material applications. several studies were performed on the size effect of fibers on mechanical properties (arib et al., 2006; ratna prasad and mohana rao, 2011; vilay et al., 2008). millet husk is novel agro waste from cereal grain (pennisetum glaucum) in thermoplastic composites applications (hammajam a .a et al., 2014; patel, 2012). fiber size and loading are critical parameters in thermoplastic composites applications due to its stress transfer function between the fiber and polymer matrix (panthapulakkal et al., 2005a). polyethylene plays crucial role in thermoplastic composites production because of it suitable characteristics such as temperature resistance, melt flow index and density. for effective utilization of cereal agro waste fiber filled/reinforced composites, certain parameters are paramount to be considered; strength, stiffness, and toughness (rowell, 1997; sapuan, 2001). several studies have presented on natural fibers and their composites, however there were no attempt to characterize millet husk husk fibers. this investigation try to evaluate the effect of millet husk fiber sizes on the mechanical properties filled high density polyethylene composites. 2. materials and methods 2.1 materials millet husk was collected from a farm site at bulumkutu kasuwa maiduguri, borno state nigeria. thermoplastic high density polyethylene (hdpe titavene titan petrokimia nusantara, chemical divison sdn malaysia. hd5218ea) with the properties of matrix being density of 0.960 g/cm3 and melt flow index of 8.2 g/10 min (190 °c, 2.16 kg) were used. 2.2 fiber pulverizations millet husk fibers were pulverized into different sizes; 250µm, 500µm, and 750µm using fritsch pulverisette p15/p16 pulvetic usa mill. the pulverized samples were subjected to 105°c temperature for 24hrs in an industrial oven to remove moisture before blending with the high density polyethylene. these pulverized parameters are shown in table 1 while figure 1 shows millet husks pulverized sizes. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 37-47. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 39 250 µm pulverized fiber 500 µm pulverized fiber 750 µm pulverized fiber unpulverized millet husk figure 1: views of millet husks, a) 250 µm, b) 500 µm, c) 750 µm and d) unpulverized) 2.3 composites characterization mhp and hdpe were compounded by melt blending techniques, followed by compression molding process. internal mixer (brabender gmbh) was used in the blending process at processing temperature of 170oc, for a period of 10 min, and rotating speed of 50rpm (elshekeil et al., 2011). labquip scientific 40ton compression molding machine was used in hot pressing the test specimens. 15cm × 15cm × 0.3cm steel mold was used for the compression process. the samples were pre–heated for 3 min at 170oc. venting time was set to 3min and final press temperature of 170oc for 3min. finally, the samples were cold pressed for 5min at room temperature. mhp–hdpe composites was formed from the three sample sizes with 0%, 10%, 20%, 30%, and 40% weight of fiber loading. thus, this formulation can be seen in table 2. the tensile properties were tested according to astm d638 (astm standard d638, 2010) by using instron 3365 machine. specimens for the tensile tests were specified according to type i astm standard test samples. tensile testing was carried out at 5mm/min with load cell of 5kn. thus, 3mm/min cross head speed for flexural tests with load cell of 5kn and span of 50mm according to (astm d790, 2010). five samples were tested each and the average was taken for test. the fiber-matrix dispersion analyses were carried out to understand the extent of fracture surface when the composites were subjected to tensile testing. the fiber dispersions were inspected using sem. this process was examined using a scanning electron microscope (sem a d b c file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hammajam et al: the effect of fiber sizes on mechanical properties of millet husk (pennisetum glaucum) fiber filled high density polyethylene composites. azojete,16(1):37-47. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 40 model s-3400 n hitachi, 20 kv). samples of different fiber loadings were studied. the samples were coated with gold before the examination under the electron beam. the scanning electron micrographs were then used to analyze the composite filler-matrix interaction. 3. results and discussion 3.1 effect of fiber size on tensile strength of mhp-hdpe composites figure 2 depicts the mean values of tensile strengths of different mhp‒hdpe composites with different fiber sizes and loadings. these graphs did not follow any smooth pattern probably due to non-homogeneous dispersion of mhp fibers in the polymer matrix. generally, in composites, there was a complicated interaction of the dynamics of the basic stages such as matrix, fiber and interfacial zone between the fiber and matrix (sapuan and bachtiar, 2012). the increment from 10‒30% by weight of mh causes slight decreased in the tensile strength of mhp‒hdpe composites when compare to 0% (hdpe) loading on the fiber size basis. it was observed that composites with 30% fiber loadings have variations of tensile strength of 23mpa, 15.6mpa and 18.8mpa for 250µm, 500µm, 750µm respectively; it is slightly below 0% hdpe by 28.8% for 500µm fiber sizes. it is noteworthy that fiber size has effect on the tensile strength of mhp‒hdpe composites similar finding in iftekhar and prakash, (2010). furthermore, the decreases in the tensile strengths are due to poor mhp‒hdpe interaction as a result of opposing separations of the mhp fiber and hdpe matrix. figure 2 showed an increase in loading up to 40% has slightly increased the tensile strength of the composite for all the fiber sizes. this could be due to better dispersion and more interface in the hdpe matrix resulting in better bonding between mhp and hdpe. thus, for mhp fibers with 250µm size, increased surface area might have allowed for better filler-matrix interaction hence increasing the chances to enhance the strength. however, in 500µm and 750µm sizes, improvements in tensile strength were very little and, in some instance, decreased. this might be also due to decreased surface area and ineffectiveness of mhp fibers as stress bearing centers and might, provided routes for stress release. figure 2: tensile strength of mhp‒hdpe composites at various fiber loadings and sizes 3.2 effect of fiber size on tensile modulus of mhp-hdpe composites fiber size did not seem to affect the modulus but, fluctuations in the values of the modulus were observed. these fluctuations were more for highly filled hdpe as obvious from variations on graph in figure 3. non-homogeneity might be a reason for these fluctuations which became http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 37-47. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 41 pronounced in cases of highly filled composites. from figure 3, there were substantial increase in the tensile modulus of mhp‒hdpe composites as fiber loadings increased. it was observed that the maximum value of the tensile modulus was 1103.6gpa at 40 % loading for 750µm. but at 30% loadings for 500µm and 750µm there were slight decrease in the tensile modulus. from the study, it was still appropriate to argue that increasing mhp up to 40% in hdpe increases the rigidity of mhp‒hdpe composites. it showed that the level of adhesion between mhp‒hdpe hardly affect the tensile modulus. this is because modulus is processes that involve so small strain values and small stress may be produced with application of little value of elongation. the 250µm, showed somewhat longer relative elongations up to extent of mhp. hence, it might be possible to get greater elongations by further reducing the sizes of the fibers. also, from the sem images of the fracture tensile test specimen showed the matrix separation had been originated at the interface of large fiber size, and no separation of matrix around small fibers. as the specimen is elongated, these would be a stress transfer from the polymer to the mhp through the interface if interfacial bondage is good. when there is an increase in the fiber size the void size also increases resulting in earlier failure and this might be the cause of poor relative elongation for higher fiber size. another possible reason is the higher surface area provided by smaller fibers for interacting within the matrix polymer. table 1 depict the millet husk fiber sizes used during the investigations. table 1: millet husk fiber powder (sizes) sieve mesh number sieve diameter (µm) 20 750 40 500 60 250 figure 3: tensile modulus of mhp‒hdpe composites at various fiber loadings and sizes 3.3 effect of fiber loadings and sizes on flexural strength of mhp-hdpe composites figures 4 show the variation in flexural strength with varying loadings of millet husk fiber of different particle sizes. it was observed that flexural strength increased as millet husk powder loading increased. the increase becomes more pronounced when loading went above 10%. a maximum of about 37% increase was observed from 25.9mpa for 0% hdpe to 41.1mpa for 40% file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hammajam et al: the effect of fiber sizes on mechanical properties of millet husk (pennisetum glaucum) fiber filled high density polyethylene composites. azojete,16(1):37-47. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 42 loading of 250µm fiber size, 24.5mpa 500 µm and 32.4mpa 750µm. this could be attributed to the contribution provided by high strength millet husk powder. thus, flexural strength increased with increasing fiber loading of millet husk. this again, is only possible if there is stress transfer from matrix to fiber through a fairly strong interfacial bond. bond cleavage leading to failure is not obtained in bending test as the maximum strain applied is only 5%. it could be inferred that 5% strain was insufficient to cause a failure. hence, in the case of flexural strength, interfacial interaction between millet husk fibers and hdpe matrix had only served to transfer stress. as observed from the graph, the flexural strength of composites with 500µm and 750µm fiber sizes decreases at 30% and 40% fiber loadings. while the composites with fiber sizes of 250µm increase at 40% fiber loading. hence it is presumed that increase in fiber loading above 40% may lead to decrease in flexural strength for 500µm and 750µm fiber sizes and may also improve in strength for composites with fiber sizes of 250µm as expected from this study. it was observed that fiber with smallest size (250µm) showed better strength in 10% and 20% fiber loadings. this might be because of increased surface area exposed for interaction. thus, increase the strength by using further small size of millet husk powder could be expected. figure 4: effects of fiber loadings and sizes on flexural strength of mhp-hdpe composites 3.4 effect of fiber loadings and sizes on flexural modulus of mhp-hdpe composites as expected from the natural fiber composites trend, flexural modulus was found to increase with increasing millet husk powder loading as can be observed from figure 5. furthermore, this could be attributed to the contribution made by millet husk powder to impart its own property to the composite. from figure 5 it was revealed that initially there was around 39% improvement in flexural modulus up to 10% millet husk powder loading for 750µm fiber sizes. the increase in the flexural modulus became pronounced for loadings greater than 10%. maximum flexural modulus of about 1988gpa was achieved at 40% millet husk powder fiber loading of 250µm fiber sizes which amounted to about 64% more than 0% hdpe. the larger fiber size 750µm showed great increase in modulus at higher loadings, but had lower flexural modulus at loadings below 10%. as seen on this graph, increase in fiber loading to 40%, composites with fiber sizes of 500µm and 750µm decreases in flexural modulus. however, the composites with fiber size 250µm increase at 40%. thus, it is expected that with further increase in fiber loading above 40%, it presumed increase in modulus of composites of 250 µm and decrease in modulus of composites with 500µm and 750µm. while table 2 show the composite formulations of fiber and matrix. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 37-47. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 43 figure 5: effects of fiber loadings and sizes on flexural modulus of mhp-hdpe composites table 2: composite formulation 3.5 effect of fiber size on impact strength of mhp-hdpe composites figure 6 indicate mhp-hdpe composites impact rates show that increase in fiber loading causes reduction in impact strength of the composites considerably. however, fiber size of 250µm indicates slight improvement in impact strength compare to rest. it is probably that this decrease is as a result of increased in fragility of the polymer matrix, because mhp fiber concentration increased, so also plastic behavior of polymer matrix decreases. increasing the fiber loading in the composites implies a decrease of the thermoplastic matrix content, which absorbed the impact energy more efficiently than the fiber. in this way, the higher the fiber content in the composites, the less efficient they are at absorbing impact energy, and the highest susceptibility to fracture resulting in lower rates of impact resistances. additionally, weak adhesion between fiber and matrix within the composites as a results voids and fiber pull out can lead to failure as well as poor energy absorption. it is probably that this decrease is as a result of increased in fragility of the polymer matrix, because mhp concentration increased, so the plastic behavior of polymer matrix decreases. furthermore, increases in filler weaken the interaction ability which leads to reduction of filler to transfer that as applied to a test specimen. therefore, the investigation reveals that toughness of mhp-pla and mhp-hdpe composites are dependent mainly on the plastic behavior of composites. figure 6: effects of fiber loadings and sizes on impact properties of mhp-hdpe composites mhp (wt %) hdpe (wt %) 10 90 20 80 30 70 40 60 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hammajam et al: the effect of fiber sizes on mechanical properties of millet husk (pennisetum glaucum) fiber filled high density polyethylene composites. azojete,16(1):37-47. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 44 3.6 microstructures observation sem images of tensile fractured surface of mhp-hdpe composites were depicted in figure 7. the microstructure in figure (7a) revealed the formation of voids at the mhp-hdpe interfaces. when strained these voids or fiber pull-out as seen in figure (7b) coalesce and lead to fracture of break. the fiber pull-out advanced with mhp concentration hence decreasing the elongation at break. from the figure (7c), it was revealed that small size fibers did not play important role in bringing about fracture. this fiber pull-out characteristic could make the fiber to undergo accumulation. hence, these lead to reduction in the tensile strength of the composites mostly at higher fiber loadings. but at 10 % and 20 % loadings, there were better dispersion of mhphdpe formation with reduced fiber pull out and breakage. this is the main reason for improvement of tensile strength at these loadings for smaller fiber sizes. figure 7: sem fractomirographs for samples with various fiber loading; (a) 10 % (250 µm), (b) 30 % (500 µm), (c) 20 % (750 µm), and (d) 40 % (750 µm) 4. conclusions this study reveals that increasing fiber loadings lead to decrease in the tensile strength of composite. the plasticity of the polyethylene decrease with increase millet husk powder. therefore, the elongation at break decreases but the flexural strength and modulus increase as loading increase. this shows that composites properties are brittle after the increase in fiber loading despite the sizes. it was also observed that increasing fiber loadings lead to increase tensile modulus of the mhp‒hdpe composites with respect to fiber sizes. as shown from sem microstructure, the presence voids and fiber pull out due to weak adhesion between mhp and hdpe may result to reduction in tensile and impact strength. these problems may be enhanced by fiber surface modifications. therefore, it is concluded that husk powder sizes have insignificant influence on the mechanical properties of the composites. c d good adhesion poor adhesion a void fiber pullout b http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 37-47. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 45 acknowledgement this research was finally supported by universiti putra malaysia through ips grant no. 9463000 references abubakar, ms. and ahmad, d. 2010. pattern of energy consumption in millet production for selected farms in jigawa, nigeria. australia journal of applied science, 4(4): 665-672. andrzej, k., bledzki, ak., abdullah, am. and jürgen, v. 2010. barley husk and coconut shell reinforced polypropylene composites: the effect of fibre physical, chemical and surface properties. composite science and technology, 70: 840–846. arib, rmn., sapuan, sm., ahmad, mmhm., paridah, mt. and zaman, hmdk. 2006. mechanical properties of pineapple leaf fibre reinforced polypropylene composites. materials and design, 27(5): 391-396. astm standard d638. 2010. standard test method for tensile properties plastics. astm international, usa. astm standard d790. 2010. standard test methods for flexural properties of unreinforced and reinforced plastis composites astm international, usa. azhar, abm., risby, ms., arif, sm., sohaimi, mn., hafizi, ks. and asrul, s. 2015. conceptual mold design for multi-curved natural fiber reinforced composite body amor panel. procedia of chemistry, cirp, 37:95-100. behzad, k. 2011. preparation and characterization of lignocellulosic material filled polyethylene composite foams. journal of thermoplastics, composites and materials, 31:1-10. bhattacharyya, d., subasinghe, a., and kim, nk. 2015. chapter 4 natural fibers: their composites and flammability characterizations. in k. friedrich and breuer (eds.), multifunction of polymer composite. oxford: william andrew publishing, pp 102-143. boopalan, m., niranjanaa, m. and umapathy, mj. 2013. study on the mechanical properties and thermal properties of jute and banana fiber reinforced epoxy hybrid composites. composites part b: engineering, 51(1): 54-57. chandak, sp. 2010. waste biomass utilization. switzland, united nation environment programme, pp.1-16. crespo, je., sánchez, l., garcía, d. and lópez, j. 2010. study of the mechanical and morphological properties of plasticized pvc composites containing rice husk fillers. journal of reinforced plastic and composite, 27: 222-229. du, y., wu, t., yan, n., kortschot, mt. and farnood, r. 2014. fabrication and characterization of fully biodegradable natural fiber-reinforced poly(lactic acid) composites. composite part b: engineering, 56(3): 717-723. el-abbassi, fe., assarar, m., ayad, r. and lamdouar, n. 2015. effect of alkali treatment on alfa fibre as reinforcement for polypropylene based eco-composites: mechanical behaviour and water ageing. composite structure, 133: 451-457. el-sabbagh, a. 2014. effect of coupling agent on natural fibre in natural fibre/polypropylene composites on mechanical and thermal behaviour. composite part b: engineering, 57:126-135. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hammajam et al: the effect of fiber sizes on mechanical properties of millet husk (pennisetum glaucum) fiber filled high density polyethylene composites. azojete,16(1):37-47. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 46 el-shekeil, ya., salit, ms., abdan, k. and zainuddin, es. 2011. development of new kenaf bast fiber reinforced thermoplastic polyeurathane composite. bioresources, 6:4662-4672. ester, r., virginia, am., mercedes, o,, belén, dso. and rodriguez, f. 2015. effect of fiber loading on the properties of treated cellulose fiber-reinforced phenolic composites. composite part b:engineering, 68:185-192. fan, m., and naughton, a. 2016. mechanisms of thermal decomposition of natural fibre composites. composite part b: engineering, 88:1-10. gloria, am. 2001. properties of oil palm (elaeis guineensis) empty fruit bunch fibre polypropylene composites. phd thesis, university putra, malaysia, malaysia, 25-44. hadjadj, a., jbara, o., tara, a., gilliot, m., malek, f., maafi, em. and tighzert, l. 2016. effects of cellulose fiber content on physical properties of polyurethane based composites. composite structure, 135:217-223. hammajam, aa., ismarrubie, zn. and sapuan, sm. 2014. millet husk fiber filled high density polyethylene composites and its potential properties. international journal of engineering and technical research, 2(11): 248-250. hamzeh, y., ziabari, kp., torkaman, j., ashori, a. and jafari, m. 2013. study on the effects of white rice husk ash and fibrous materials additions on some properties of fiber–cement composites. journal of environmental management, 117: 263-267. iftekhar, a. and prakash, am. 2010. mechanical properties of fly ash filled high density polyethylene. journal of minerals and materials characterization and engineering, 9(3): 183-198. kumar, mg. and bavan, sd. 2010. potential use of natural fiber composite materials in india. journal of reinforcement, plastic and composite, 29(24):3600–3613. kwon, hj., sunthornvarabhas, j., park, jw., lee, jh., kim, hj., piyachomkwan, k. and cho, d. 2014. tensile properties of kenaf fiber and corn husk flour reinforced poly(lactic acid) hybrid biocomposites: role of aspect ratio of natural fibers. composite part b: engineering, 56(2): 232-237. panthapulakkal, s., sain, m. and law, s. 2005a. enhancement of processability of rice husk filled high density polyethylene composites profiles. journal of thermoplastic composite materials, 18: 445-459. patel, bm. 2012. animal nutrition in western india, a review of workdone from 1961-1965. anand, india council of agricultural resources, 3:122-129. ratna prasad, a. and mohana rao, k. 2011. mechanical properties of natural fiber reinforced polyester composites: jowar, sisal and bamboo. materials and design, 32:4658-4663. rowell, rm., sanadi, ar., caufield, df. and jacobson, re. 1997. utilization of natural fibres in plastic composites: problems and opportunities. in: leao al, carvalho fx and frollini. e (eds.) lignocellulosic plastic composites, wisconsin: university of rio de janeiro,brazile, wisconsin: university of rio de janeiro, 23-51. sahari, j., sapuan, sm., zainudin, es. and maleque, ma. 2013. mechanical and thermal properties of environmentally friendly composites derived from sugar palm tree. materials and design, 49:285-289. sapuan, sm. 2001. a knowledge-based system for materials selection in mechanical engineering design. materials and design, 22(8): 687-695. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 37-47. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 47 sapuan, sm. and bachtiar, d. 2012. mechanical properties of sugar palm fibre reinforced high impact polystyrene composites. proceedia chemistry, 4(1):101-106. sdrobiş, ad., raluca, nt., marian, cg. and vasile, c. 2012. low density polyethylene composites containing cellulose pulp fibers. composite part b: engineering, 43(4):1873-1880. vilay, v., mariatti, m. and mat taib, r. 2008. effect of fiber surface treatment and fiber loading on the properties of bagasse fiber reinforced unsaturated polyester composites. composite science technology, 68:631-638 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):995-1003 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 995 original research article empirical determination of losses in an optical fibre link f. onaifo*, p. o. alao, a. o. oyedeji, o. g. olasukanmi, a. s. temidayo and t. o. lawal (department of electrical/electronic engineering, olabisi onabanjo university, ogun state, nigeria) * corresponding author’s email address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 1.0 introduction advances in communication engineering has led to a huge increase in bandwidth with optical fibre capable of handling a higher bandwidth compared to another form of wired communication (kartalopoulos, 2008). in addition to large bandwidth requirement, new innovative services evolving daily is pushing bandwidth higher (visawanathan, 2006). the effect of microwave radiation on health together with the noise pollution from generators mounted on base transceiver station makes optical fibre a better alternative. the introduction of optical fibre for mobile communication in nigeria has its own challenges. these include the absence of a regulatory framework, unstable electricity (power) supply, lack of qualified and skilled manpower, communication system compatibility issues, environmental impact assessment issues, cost implications for the new technology and issues of returns on investment. installation of optical fibre for long and short distances require joining cables which contribute significantly to a loss at the various joints. input power, fibre length, fibre end characteristics of the waveguide and end quality of fibre are some of the factor causing loss along with a fibre article information abstract this paper analyses the characteristics of signal loss in optical fibre link with splicing loss forming part of the total loss with the loss measurement carried out with the aid of optical time domain reflector.an optical time domain reflectometer (otdr) is made up of a detector and a laser. light signals are sent into the fibre using a laser and a demodulator or a detector on the other end to receive the signals. the received signal is displayed on a graph. the transmitted signal is a pulse with a given amount of energy. a clock determines the time duration of the signal. this paper explains the splicing using optical time domain reflectometer. these losses in an optical fibre cable arise from spliced points and joints with either connectors or any other passive fibre optic device. the study shows that losses along optical fibre arise from the splice joint, connector joint and along the fibre length as attenuation loss. these losses were obtained from readings of the optical time domain reflectometer. the study also shows that the combined splicing and connector loss is higher than attenuation loss. here, splicing and connector loss contributes 75% of the total losses while attenuation losses account for the remaining 25%. an attempt should, therefore, be made to reduce splices in order to minimize losses when using optical fibre cabling. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 03 december, 2018 revised 25 may, 2019 accepted 30 may, 2019 keywords: detector fibre link laser source optical time domain reflectometer splices. mailto:frank.onaifo@oouagoiwoye.edu.ng mailto:excitefranko@yahoo.com http://www.azojete.com.ng mailto:frank.onaifo@oouagoiwoye.edu.ng mailto:excitefranko@yahoo.com onaifo et al: empirical determination of losses in an optical fibre link. azojete, 15(4):995-1003. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 996 link. the power that can be transmitted from one fibre to another is dependent on the number of modes propagating in the individual fibre. a fibre with a higher number of modes coupled to one with a lesser number will lead to a substantial loss along the two fibres with all the modes present (gerd, 2003). analytical methods designed to determine signal loss at fibre joints are inexhaustible. this is because mathematical equations developed addresses only a few causes of losses in the joint. (gerd, 2003). asides these, practical field working conditions where this research is done seldom used a complex method to obtain losses from the fibre joints (koontz and mandloi, 2000). optical fibres are used to confine and guide photo signals. a simple optical network includes a laser diode as an optical source and fibre optic as a medium of transmission and detector as a part of a receiver. to achieve this, fibre cable is joined at a certain interval to form a communication link. it is not possible to use optical fibre over a long distance without joining them. the choice of the joint to be made is based on whether a permanent bond or an easily demountable joint is desired. a permanent bond on an optical fibre cable is known as a splice and a detachable joint is called a connector. various methods can be used to determine the power a given optical fibre link can carry and this can be done with the aid of optical time domain reflector (otdr). in this paper, otdr is used to determine connector, splices and fibre loss. otdr is an optoelectronic instrument used to characterize an optical fibre. optical pulses are sent into the test fibre and light are reflected. this is similar to how also an electronic timedomain meter works using changes in impedance of the cable under test. the reflected pulse is measured and sum as a function of time. otdr is also used to measure the attenuation of the fibre cable. also splicing and connector losses at selected points along the test fibre link were measured. an optical power meter (opm) is used to measure the power in a fibre optic cable. general purpose photo power devices are usually called radiometers, photometers. an optical power meter is only used to measure the power at the other end of a fibre link and only gives an output power of the additional losses parameters from the link such as the splice losses, cables losses, connector losses, and its accuracy might not be compared to an otdr. predictions of losses in fibre are very difficult (gerd 2003). for instance, analytical models can predict instantaneous result but fail to give accurate results because of the nature and behaviours of electromagnetic waves as it propagates along a fibre after a considerable distance (koji et al 2008). in an optical fibre transmission system, mathematical analysis of losses is based on assumptions which introduce errors which reduces the accuracy of the obtained result(marcuse, 1997).there are a number of ways to tackle the problem of determining the power requirement for a particular fibre optic link. the easiest and most accurate way is to perform an optical time domain reflectometer (otdr) trace of the actual link. this is because power budget can only be determined only after losses along the fibre are determined. this paper outlines the various losses in an optical fibre link using the optical time domain reflectometer. the studies show that the combined splicing and connector loss account more for the total loss compared to attenuation loss. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 995-1003. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 997 2. materials and methods the method employed is the use of otdr and optical power meter for the measurement of losses in an optical fibre. a nanjing dvp-105 cleaver was used for the cleaving process. a nanjing dvp-730 fusion splicer with splice time of 1800ms was used for the optical fibre fusion splicing. the output of the completed fusion splicing process is shown on the lcd panel of the splicing machine. a threshold value of splice loss of ≤0.05db was used. this was adopted to reduce the splice loss contribution to the link’s loss. 2.1 materials a nanjing dvp-105 cleaver is an instrument used for holding and cutting fibre materials. a nanjing dvp-730 fusion splicer is also used the joined two fibres together. it has a splice time of 1800ms. optical time domain reflectometer is used to determine the losses after the fibre had been spliced. 2.2 methods the method employed involves taking readings of the various losses using otdr. a nanjing dvp-730 fusion splicer is used. the output of the completed fusion process shows at the liquid crystal display of the fusion splicer. an end threshold value of 5db was implemented. figure 1 shows the flowchart explaining the various steps of splicing. after splicing, otdr is used to determine the losses in the link or cable that was terminated by a patch cord to create a connection between the otdr and the terminated link. 2.2.1 splicing preparation steps fusion splices refers to thermally bonding prepared fibre ends, where the fibre ends are first aligned and then butted together. this takes place either in a grooved fibre holder or under a microscope with a micromanipulator (agawar,2003). fusion splicing is the act of joining two optical fibre end-to-end using heat. step 1 stripping the fibre: stripping is the removal of the outer layer of the optical fibre. step 2 cleaning the fibre: this involves cleaning the fibres with ethanol and spirit. the main concern here is the cleanliness of the surface of the fibre lengths step 3 cleaving the fibre: this involves cutting or trimming of fibre. the fibre face is held at 90 degrees to the axis of the fibre. the closer to 90 degrees the cleave angle is the lower optical loss the splice will yield. step 4 splicing the fibre: this is the joining of the two fibres by heating. step 5 protect the fibre: the bare fibre area is additional coated or covered with a splice protector step 6 buried underground: the encapsulation is place firmly using fasteners at the pole or buried underground in a trench. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onaifo et al: empirical determination of losses in an optical fibre link. azojete, 15(4):995-1003. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 998 figure 1: flow chart for fibre fusion splicing 2.3 theoretical calculations power budget for fibre optic cable pb =pt pr (1) where: pt is minimum transmitted power db and pr is receiver sensitivity db power margin for fibre optic cable the power margin. pm = pb – ll (2) where: pm is power margin (db), ll refers to link loss(db) and pb is power budget(db). pm greater than zero indicates that the power budget is sufficient to operate the receiver total link loss in this paper, the link loss using a safety margin of 3.0db is : link loss = [fiber length (km) x fiber attenuation per km] + [splice loss x no of splices] + [connector loss x no of connectors] + [safety margin] (3) percentage of splice loss= splice loss total link loss * 100 (4) percentage of connector loss = connector loss total link loss * 100 (5) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 995-1003. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 999 according to tia/eia industry specifications, fibre attenuation per km is 0.3db, connector loss is 0.75db and splice loss is 0.1db. the studies show readings which are close to the industry standards. 3. results and discussion the result gotten from 4 locations of a single mode fibre with a distance range of 0 – 50km are shown in the table 1. 3.1. event analysis from four different locations according to the ieee standard distance, 1550nm single mode 9/125µm cable is required for a 70km distance, this studies use the single mode 9/125µm cable for a 50km distances from 4 locations shown in the tables 1 to 4, which provide details of the various losses. table 1: location a otdr trace result with the end threshold of 5.0db. s/n type location (km) reflectance (db) insertion loss (db) splices (db) attenuation (db) connectors (db) 1 reflective 0.000 -13.55 0.085 0.206 0.750 2 nonreflective 4.595 0.3337 0.104 0.248 0.356 3 nonreflective 6.643 0.343 0.058 0.188 0.576 4 nonreflective 10.689 0.119 0.184 0.188 0.297 5 nonreflective 11.708 0.328 0.106 0.186 0.442 6 nonreflective 15.773 1.805 0.615 0.187 0.520 7 nonreflective 19.044 0.148 0.115 0.187 0.425 8 nonreflective 19.813 0.207 0.140 0.176 0.554 9 nonreflective 21.291 -0.306 0.101 0.196 0.378 10 nonreflective 23.339 -1.860 0.136 0.196 0.723 11 end 25.020 -21.17 total 1.121 1.644 1.958 5.021 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onaifo et al: empirical determination of losses in an optical fibre link. azojete, 15(4):995-1003. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 1000 table 2: location b otdr trace result with the end threshold of 5.0db. s/n type location (km) reflectance (db) insertion loss(db) splices (db) attenuation (db) connectors (db) 1 reflective 0.000 -15.02 2 nonreflective 1.804 -0.283 3 nonreflective 2.293 -0.018 4 nonreflective 3.067 0.000 0.153 0.176 0.654 5 nonreflective 4.631 3.387 0.316 0.200 0.332 6 nonreflective 6.628 0.285 0.126 0.194 0.278 7 nonreflective 10.821 0.040 0.163 0.194 0.667 8 nonreflective 11.687 0.430 0.214 0.187 0.334 9 nonreflective 15.773 4.636 0.222 0.174 0.541 10 nonreflective 18.896 0.358 0.154 0.174 0.339 11 nonreflective 19.885 -0.049 0.078 0.152 0.667 12 nonreflective 23.257 -4.024 0.054 0.152 0.730 13 end 25.020 -14.06 total 4.762 1.48 1.596 4.542 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 995-1003. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 1001 table 3: location c otdr trace result with the end threshold of 5.0db. s/n type location (km) reflectance (db) insertion loss(db) splices (db) attenuation (db) connectors (db) 1 reflective 0.000 -13.83 2 nonreflective 1.146 0.672 3 nonreflective 2.257 -0.002 4 nonreflective 3.383 0.029 5 nonreflective 4.514 -0.040 6 nonreflective 5.176 0.097 0.143 0.217 0.543 7 nonreflective 6.623 0.284 0.056 0.193 0.734 8 nonreflective 10.663 0.215 0.028 0.193 0.632 9 nonreflective 11.629 1.400 0.278 0.189 0.702 10 nonreflective 14.581 0.049 0.168 0.189 0.276 11 nonreflective 15.753 0.141 0.189 0.188 0.472 12 nonreflective 19.054 0.374 0.301 0.188 0.522 13 nonreflective 19.839 0.794 0.098 0.207 0.457 14 nonreflective 21.311 0.893 0.162 0.195 0.521 15 nonreflective 23.329 -0.299 0.119 0.195 0.711 total end -17.06 4.607 1.542 1.954 5.57 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onaifo et al: empirical determination of losses in an optical fibre link. azojete, 15(4):995-1003. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 1002 table 4: location d otdr trace result with the end threshold of 5.0db. s/n type location (km) reflectance (db) insertion loss (db) splices (db) attenuation (db) connectors (db) 1 reflective 0.000 -14.35 2 nonreflective 1.080 2.003 0.342 0.171 0.282 3 nonreflective 5.125 0.195 0.245 0.187 0.621 4 nonreflective 6.613 0.218 0.253 0.187 0.459 5 nonreflective 7.097 -0.081 0.147 0.203 0.334 6 nonreflective 10.668 0.137 0.246 0.203 0.509 7 nonreflective 11.662 0.157 0.324 0.189 0.621 8 nonreflective 15.768 2.799 0.176 0.183 0.511 9 nonreflective 19.044 0.158 0.092 0.183 0.346 10 nonreflective 19.818 0.206 0.137 0.187 0.711 11 nonreflective 23.334 -0.281 0.243 0.187 0.655 total end 25.025 -16.47 5.511 2.205 1.88 5.049 3.2 discussion the return (reflectance) loss measurement test was carried out using the optical time domain reflectometer (otdr) machine on location c of a fibre cable. at location a, it was observed that where noises occur in the cable, attenuations, insertion loss are recorded. at location b, it was observed that location b has higher insertion loss compared to location a since both have the same distance of 25.020km of trace recorded. this might due to more occurrence of noise in location b. however, location a has higher attenuation loss compared to location b. it is observed that the noises recorded at location c is quite much compare to location a and b. this is due to the error introduced by the patch cord, coupler, splices or scattering in the fibre. it is observed in location d that noises occurred occurred along the fibre length leading to attenuation and insertion loss. however, there is a drop in the slope of the otdr trace of location d, this induced error can be attributed to marginal errors introduced by the otdr machine, chromatic dispersion losses from the fibre cable, micro and. macro-bending losses emanating from the fibre. the splicing, attenuation and connector losses for location a are 1.644db, 1.958db and 5.021db. for location b, the splicing, attenuation and connector losses are 1.48db, 1.596db and 4.542db. also for location c, the splicing, attenuation and connector losses are 1.542db, 1.954db and 5.57db. the splicing, attenuation and connector losses for location d are 2.205db, 1.88db and 5.049db. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 995-1003. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: frank.onaifo@oouagoiwoye.edu.ng, excitefranko@yahoo.com 1003 4. conclusion the study shows that losses along optical fibre arise from the splice joint, connector joint and along the fibre length as attenuation loss. this loss was obtained from readings of the optical time domain reflectometer. the study shows connector losses was highest compared to splicing and attenuation for all the four locations (a, b, c, d) investigated. the study also shows that the combined splicing and connector loss is higher than attenuation loss. here, splicing and connector loss contributes more to the total loss compared to attenuation loss. in this studies, combined splicing and connector loss account for 75% of the total losses while attenuation losses account for the remaining 25%. losses in fibre are highly unpredictable but can be reduced if the number of splices and connectors are reduced. effort should, therefore, be made to reduce the number of splicing along optic fibre link. acknowledgement i appreciate the support of the department of electrical electronic engineering, olabisi onabanjo university for making this work a success. references agarwal, dc. 2003 fibre optic communication. s. chand and company ltd, reprinted, ram nagar, new delhi, india. gerd, k. 2003. optical fibre communication 3rd ed. mcgraw hill publishers, new york, usa. kartalopoulos, sv. 2008. next generation intelligent optical network: from access to backbone springer science, business media, new york, usa. koji, l., kazuhide, n. and takashi, m. 2008. characteristics of bending loss optimized hole assisted fibre. optical fibre technology, 14: 1-9. koontz, wlg. and mandloi, d. 2000. application of optical system simulation software in a fibre optic telecommunication program. rochester institute of technology, rochester, new york, usa., pp 1-2. marcuse, d. 1997. loss analysis of single-mode fibre splices. american telephone and telegraph company. the bell system technical journal, 56: 703-718. viswanathan, t. 2006. telecommunication switching systems and networks, prentice hall ltd, new delhi, india file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3):554-559 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 554 original research article the potential of bioethanol as a viable alternative to fossil fuels k. o. rabiu*, l. k. abidoye and a. t. oriaje (department of civil engineering, faculty of engineering and environmental sciences osun state university, osogbo, nigeria) * corresponding author’s email address: kazeem.rabiu@uniosun.edu.ng article information submitted 20 november, 2018 revised 4 february, 2019 accepted 4 february, 2019 keywords: bioethanol biofuel fossil fuel clean energy climate change food production abstract environmental challenges from fossil fuel emission have global issues and have contributed immensely to climate change. bioethanol has experienced unprecedented level of attention due to its value as substitute to fossil fuel. besides being a renewable and sustainable source of energy, it is also efficient, available and environmentally friendly. global production of bioethanol continues to increase and will probably continue to dominate the alternative fuels market in the next decade. it is important to emphasize that for bioethanol to be a viable alternative, it must have ecological benefits, be economically competitive and its production must be in commercial scales without affecting the food production. this paper explains the problems and possible solutions in the production of bioethanol; since biofuel produces clean energy which can reduce the emission of co2 into the atmosphere. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction environmental problems arising from fossil fuel emission have become global issues, for instance, greenhouse effect. according to intergovernmental panel on climate change (ipcc), fossil fuel contributes to approximately 75 percent increase in carbon-dioxide (co2) emission (metz et al., 2005; olajire, 2010). over the last decades the world has begun to realize the significance of finding clean, sustainable and renewable forms of energy. one of these is first generation biofuel (bioethanol and biodiesel); bioethanol is obtained from the fermentation process of crops such as corn, cassava, rice, sugarcane, soya-beans, wheat, barley, and potato while biodiesel is produced by oil crops (rapeseed, soybeans, sunflower, palm, coconut) and animal fats. second generation biofuels include bioethanol and biodiesel produced from the residual, non-food parts of crops, and from other forms of lignocellulosic biomass such as grasses, wood, and municipal solid wastes (inderwildi and king, 2009; gibbons and hughes, 2011). third generation biofuels include algae-derived fuels such as biodiesel from microalgae oil, bioethanol from microalgae and seaweeds, and hydrogen from green microalgae and microbes (aylott, 2010; dragone et al., 2010; gibbons and hughes, 2011). also, fourth generation biofuels uses genetically modified (gm) algae to enhance biofuel production bioethanol is a good replacement to fossil fuel because it does not have the impurities such as sulphur oxides that are commonly found in petroleum products. sulfur dioxide, emitting from fossil fuel is one of the important air pollutants leading to climate changes, acid precipitations, mailto:kazeem.rabiu@uniosun.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):554-559. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kazeem.rabiu@uniosun.edu.ng 555 and health problems. sulpfur dioxide can cause a serious health related problems such as asthma and chronic bronchitis. besides, it can cause both acute and chronic injury to plants and affect their growth and production. this review explains the problems and possible solutions in the production of bioethanol since biofuel produces clean energy which can reduce the emission of co2 into the atmosphere. licht (2005) claimed that global production of bioethanol has increased rapidly since 1970 when there was oil crisis; its sales rose sharply from 1975 to 2006. the biofuels supply has increased globally by a factor of 8% from 2000 to 2010 (figure 1). goldemberg and guardabassi (2009) explored that the present use of bioethanol as a fuel is around 86.4 million litres, accounting for 0.7% of the global oil production and 2% of the fossil fuel consumption, while utilizing less than 1% of the world’s cultivating land. in 2006, about 45 billion litres of bioethanol were produced globally and more than half of this was generated in brazil and the united states (goldemberg and guardabassi, 2009; dufey, 2006). it is estimated that significant amount of bioethanol was produced globally to replace roughly 2 per cent of total gasoline consumption. table 1 shows the main bioethanol producing countries. table 1: global bioethanol production (dufey, 2006) country production (ml) feedstock brazil 15,098 sugarcane us 12,907 corn and sorghum canada 231 wheat and straw colombia 900 sugarcane germany 269 rye, wheat france 829 wheat, beet italy 151 wheat spain 299 barley, wheat, wine sweden 98 wheat, forestry uk 401 beet china 3,649 corn, cassava, sugarcane india 1,749 sugarcane thailand 280 sugarcane, cassava indonesia 167 sugarcane pakistan 26 sugarcane philippine 83 sugarcane south africa 416 sugarcane malawi 6 sugarcane ghana 6 sugarcane zimbabwe 6 sugarcane kenya 3 sugarcane australia 33 sugarcane file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu, et al.: the potential of bioethanol as a viable alternative to fossil fuels. azojete, 15(3):554-559. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kazeem.rabiu@uniosun.edu.ng 556 figure 1: worldwide biofuel production (araujo et al., 2017) 2. bio-ethanol and their challenges 2.1 the food-fuel debate one aspect of the challenges of bioethanol that has received much attention is the possible link between bioethanol production and food shortage (figure 2). increased bioethanol production will increase the cost of crops which are the major feed-stocks, and this will result to the rise in the price of food commodities. fargione et al., (2008) claims that recent policy decisions to produce advanced biofuels on high standard farming land contributed to the food shortage. however, the problem of food shortage can be solved through improved farming techniques such as efficient use of fertilizers and pesticides that will boost crop yields. figure 2: food price index and key elements (the food price index reflects the commodity group price indices (araujo et al., 2017) 2.2 technological issues another problem that is affecting the bioethanol production is technological issues for example, conversion technology and biotechnology. bioethanol production from cellulosic materials is having challenges of technology (goldemberg and guardabassi, 2009). bothast (2005) says that about ten percent of corn crop generated 3.4 billion gallons of bioethanol fuel in 2004 and its demand was expected to be more than double in the next ten years. so, to meet this demand, new technologies must be moved from the research stage to profit-oriented level (damirbas and balat, 2006). therefore, global scale production of bioethanol requires high-technology (advanced technological development) and techniques such as modelling, simulation and optimization. this should perhaps be applied to some processes such as fermentation, distillation, cogeneration, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):554-559. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kazeem.rabiu@uniosun.edu.ng 557 residue treatment, recycling, instrumentation and automatic control systems and this will contribute to the vast growth of bioethanol production. for instance, sugar production through technological advancement contributed to significant increase in the production (costa et al., 2010). cardona and sanchez (2007) suggested the usage of both ultrafiltration and microfiltration for the collection of the cellulose from the enzymatic hydrolysis reactor during the production of bioethanol from metropolis refuse. cardona and sanchez (2004, 2006) used aspen plus (software) to simulate several technological configurations that will improve the yield of bioethanol from biomass and certain processes and integration possibilities are to be taken into consideration (cardona and sanchez, 2007). a trial plant was constructed for the conversion of lignocelluloses biomass into bioethanol, operated for the purpose of research and development among associate industries that deal with biomass bioethanol technology (cardona and sanchea, 2007). bai et al. (2008); zhao and bai (2009) noted that constructions of pilot and large factories have been built in china for the continuous bioethanol production using flocculent yeast strain for instance, bioethanol accumulation and recycling for many batches (mussatto et al., 2010). hence, advanced technology development could provide the means to develop economical technologies for the production of fuel bioethanol and consequently increase its production for global scale. 2.3 government policy there are policy issues, for example, uncertain governmental policies such as un-supportive policies, and uncertainty in policies. government policies that support demand and encourage the investment and research needed to develop an alternative fuel is paramount for environmental improvement and energy security. government can enhance the production of bioethanol by introducing certain programs such as subsidies, research and development programs. the advancement of any nation is as a result of high level of research and development, for example, sao paulo in brazil has made huge investments in genetic research and sugarcane improvement breeding (hira and oliveira, 2009). balat and balat (2009) says that the policy tools in china for bio-fuel promotions are tax, subsidies, cost limit, quotations, and establish changes by law (balat and balat, 2009). gnansounou et al., (2005) also claims that two major bio-ethanol fuel programs have been accomplished in china from 2001 with the aim to enhance renewable energy sources, enhance public energy security and improve national territory (balat and balat, 2009). therefore, it is possible for bioethanol production to provide a viable alternative to fossil fuels on global scale, for example, private companies and public sectors are presently making progress on developing cellulose bioethanol industry (keeney, 2009). indian’s government gives 40 per cent subsidized loans for sugar factories who are interested in bioethanol manufacturing (coyle, 2007). in addition, thailand which is agricultural based nation is encouraging bioethanol production that is currently obtained from sugarcane and cassava (mussatto et al., 2010; dufey, 2006). bioethanol production increased worldwide from 17.25 billion litres in 2000 to over 46 billion litres in 2007 and its demand will exceed 125 billion litres by 2020 with the new governmental programs of america, europe and asia (balat and balat, 2009). governments justify support in order to achieve societal goals, for example, to diversify energy sources, to enhance energy security and to meet environmental and rural development objectives. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng rabiu, et al.: the potential of bioethanol as a viable alternative to fossil fuels. azojete, 15(3):554-559. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kazeem.rabiu@uniosun.edu.ng 558 3. conclusion biothanol has experienced unseen levels of attention due to its value as substitute to fossil fuel and also mitigation option for climate change; besides being a renewable and sustainable source of energy, it is also efficient, available and environment friendly. researches are presently focus on the development of concepts such as renewable resources and sustainable development. hence, global production of bioethanol is increasing, and it will probably continue to dominate the alternative fuels market in the next decade. biothanol as a viable alternative to fossil fuel requires a vital role from agriculture, technology, and government intervention such as research and development, subsidies and tax reduction. it is also important to emphasize that for bioethanol to be a viable alternative, it must have ecological benefits, be economically competitive and its production must be in commercial scales without affecting the food production. bioethanol for use as fuel is better produced from biomass to prevent the scarcity of food supply. biomasses such as cassava peels, corn cobs, mango peels, sawdust, sorghum straw, and rice husks which are readily available in nigeria can serve as an alternative to food usage. conversion of these biomasses to bioethanol can create wealth from such wastes. the research into the sustainability of bioethanol production with respect to food versus fuel tradeoffs and land use are required. if sustainability and technical challenges are effectively worked out, these fuels have great potential to proffer solutions to the problem of climate change. during the process, there must be sustainability of global biofuel development by placing emphasis on the technical, policy and investment aspects. researches that could promote the scale of substitution of biofuels in the global fuel markets are also encouraged in the future work. references araujo, k., mahajan, d., kerr, r. and da silva, m. 2017. global biofuels at the crossroads: an overview of technical, policy, and investment complexities in the sustainability of biofuel development, agriculture, 7 (32): 1-22. aylott, m. (2010). forget palm oil and soya, microalgae is the next big biofuel source. the ecologist. (sept 24). http://www.theecologist.org/blogs_and_comments/commentators/other_comments/609556/for get_palm_oil_and_soya_microalgae_is_the_next_big_biofuel_source.html. retrieved 02nd september 2019. bai, fw., anderson, wa. and moo-young, m. 2008. ethanol fermentation technologies from sugar and starch feedstocks. biotechnol adv, 26, pp.89-105. balat, m. and balat, h. 2009. recent trends in global production and utilization of bio-ethanol fuel. journal of applied energy, 86(15), pp. 2273 2282. bothast, rj. 2005. new technologies in biofuel production, presentation at usda, washington, dc. agricultural outlook forum (aof), pp. 1-6. cardona, c., sanchez, o., 2004. analysis of integrated flow sheets for biotechnological production of fuel ethanol. in: pres 2004-16th international congress of chemical and process engineering (chisa 2004), prague, czech republic. september 11-14, 2004. cardona, ca., sanchez, oj. 2006. energy consumption analysis of integrated flowsheets for production of fuel ethanol from lignocellulosic biomass. energy, 31 (13), pp. 2447–2459. cardona, ca. and sanchez, oj. 2007. fuel ethanol production: process design trends and integration opportunities. journal of bio-resource technology, 98(2), pp. 2415 – 2457. http://www.theecologist.org/blogs_and_comments/commentators/other_comme nts/609556/forget_palm_oil_and_soya_microalgae_is_the_next_big_biofuel_sourc e.html. retrieved 02nd http://www.theecologist.org/blogs_and_comments/commentators/other_comme nts/609556/forget_palm_oil_and_soya_microalgae_is_the_next_big_biofuel_sourc e.html. retrieved 02nd http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):554-559. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kazeem.rabiu@uniosun.edu.ng 559 costa, ac., junior, np. and aranda, da. 2010. the situation of biofuels in brazil: new generation technologies. journal of renewable and sustainable energy reviews, 14(58), pp. 3041 – 3049. coyle, w. 2007. the future of biofuels: a global perspective. amber waves feature, 5(5), pp.24 – 29. dermirbas, mf. and balat, m. 2006. recent advances on the production and utilization trends of bio-fuels: a global perspective. journal of energy conservation and management, 47(14), pp. 2371 2381. dragone, g., fernandes, b., vicente, a.a., and teixeira, j.a. (2010). third generation biofuels from microalgae. appl. microbiology. 2, pp. 1355-1366. dufey, a. 2006. biofuels production, trade and sustainable development: emerging issues, https://pubs.iied.org/pdfs/15504iied.pdf, assessed on 02nd september, 2019. fargione, j., hill, j., tilman, d., polasky, s and hawthorne, p. 2008. land clearing and the biofuel carbon debt, science, vol. 319, issue 5867, pp. 1235-1238, doi: 10.1126/science.1152747. gibbons, w., hughes, s. 2011. distributed, integrated production of second and third generation biofuels, economic effects of biofuel production, dr. marco aurelio dos santos bernardes (ed.), isbn: 978-953-307-178-7, intech, available from: http://www.intechopen.com/books/economic-effects-ofbiofuel-production/distributedintegrated-production-of-second-and-third-generation-biofuels gnansounou, e., bedniaguine, d. and dauriat, a. 2005. promoting bioethanol production through clean development mechanism: findings and lessons learnt from asiatic project. in: proceedings of 7th iaee european energy conference, bergen, norway, august, 5-7, 2005 goldemberg, j. and guardabassi, p. 2009. are biofuels a feasible option? journal of energy policy, 37(31), pp. 10 – 14. hira, a. and oliveira, lg. 2009. no substitute for oil? how brazil developed its ethanol industry. journal of energy policy, 37(37), pp. 2450 – 2456. inderwildi, o.r. and king, d.a. 2009. quo vadis biofuels. energy & env. sci. 2, pp. 343. keeney, d. 2009. ethanol usa. environmental science and technology viewpoint, 43(1), pp. 8 – 11. licht, fo. 2005. world ethanol and biofuels report, vol. 4, no8/15.12.2005. metz, b., davidson, o., coninck, h., loos, m. and meyer, l. 2005. ipcc special report on bon dioxide capture and storage, intergovernmental panel on climate change, geneva (switzerland). working group iii. cambridge university press. https://www.ipcc.ch/pdf/specialreports/srccs/srccs_wholereport.pdf, assessed on september 5, 2019. mussatto, si., dragone, g., guimaraes, mr., silva, ja., carneiro, lm., roberto, ic., vicente, a., domingues, l. and teixeira, t.a. 2010. technological trends, global market, and challenges of bio-ethanol production. journal of biotechnology advances, 28(1), pp. 817 – 830. olajire, aa. 2010. co2 capture and separation technologies for end-of-pipe applications – a review. journal of energy, 35 (30), pp. 2610 – 2628. tenenbaum, dj. 2008. food vs. fuel: diversion of crops could cause more hunger, 116(6), pp. 254 – 257. zhao xq. and bai fw. 2009. yeast flocculation: new story in fuel ethanol production. biotechnol adv, 27, pp. 849–56 https://pubs.iied.org/pdfs/15504iied.pdf https://www.ipcc.ch/pdf/special-reports/srccs/srccs_wholereport.pdf https://www.ipcc.ch/pdf/special-reports/srccs/srccs_wholereport.pdf file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):120-136 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 120 original research article the challenges and panaceas to power distribution losses in nigeria o. o. mohammed1*, a. o. otuoze1, s. salisu2, a. e. abioye3, a. m. usman1 and r. a. alao1 (1department of electrical and electronics engineering, university of ilorin, ilorin, kwara state, nigeria 2department of electrical engineering, ahmadu bello university, zaria, nigeria 3department of electrical and electronic engineering, akanu ibiam federal polytechnic, unwana, ebonyi state, nigeria) *corresponding author’s email address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 1.0 introduction electric power system is one of the most important infrastructure for socio-economic development of any nation (salisu et al., 2019). for years, there have been historical structural challenges affecting the overall generating capacity efficiency (adoghe et al., 2009) resulting to several power crisis. large investments have been made in both generation and distribution systems, however, remarkable improvement in the availability and quality of power delivery are yet to be achieved. electricity demand in nigeria is increasing daily without a corresponding increase in power generation or expansion of the transmission capacity to meet the increasing demand. most of the power distribution network are abjectly maintained and the poor state of the electricity supply is continuously threatening the socio-economic activities of the country (dada, 2014). nigeria has an inexhaustible supply of natural resources with substantial reserves of oil and gas, and has one of the lowest net electricity generation per capita rates in the world (team, 2015). several articles have been written on power generation improvements, and other sources of inexhaustible energy generation have been proposed. however, details about the challenges facing the distribution systems have not been efficiently presented in the literature. distribution subsystem is considered as the weakest part of the entire power system because article information abstract energy losses in the distribution network and its subsystems have been issues of great concerns in nigeria’s power sector. for decades, several studies have been conducted on the challenges facing the power sector in nigeria with most focus directed on the distribution subsystems. the major challenge in the distribution system is the high energy losses which are detrimental to the techno-economic benefits of the power systems. however, details of the distribution system challenges and the probable solutions have not been efficiently presented. in this study, some of these challenges are presented and the potential solutions are proposed. the features of the nigeria distribution network, the technical and non-technical sources of losses as well as the identified challenges are presented before discussing the potential solutions. the panaceas so provided were from the understanding of some published works and other related materials as well as the in-depth understanding of the authors. this article can serve as a guide for the utilities and stakeholders in the power sector for efficient management operations and improved customer service delivery. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 march, 2019 revised 17 july, 2019 accepted 15 august, 2019 keywords: nigeria power system distribution system technical losses non-technical losses. mailto:reacholaabdul@gmail.com mailto:mohammed.oo@unilorin.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 121 while the transmission losses only account for about 17%, distribution losses are approximately 50% (bhatti et al., 2015). in this paper, the features and challenges of distribution networks based on the nigeria scenarios are explored with emphasis on the technical and non-technical losses. irregularities being perpetrated by the distribution companies are also assessed and recommended solutions proffered. the features and challenges of nigeria’s distribution networks in view of some previous studies are outlined. an overview of the distribution system’s losses is presented, and the irregularities observed among the operators of the distribution systems are summarized. some of the panaceas towards efficient management of the distribution system are given and the conclusions drawn from the study are highlighted. 2. features and challenges of the distribution network traditional power distribution systems are generally modeled in a radial form with the advantage of unidirectional power flow for easy control. however, there are limitations to the efficiency and reliability improvement in a radial distribution system (short, 2014). the distribution system, via the distribution substations to the consumers, was initially developed to be relatively passive (doe, 2015). generally, distribution systems deliver electricity via distribution feeders and radial lines with control equipment operated through timed set points. this scheme is enough to provide consumers with basic service delivery at reasonable costs. nonetheless, it cannot cope with the current needs for greater resilience, effective power quality control, and customers’ participation (doe, 2015). moreover, the integration of renewable energy generations causes bidirectional power flow (kim etal., 2013). the aged distribution systems had no consideration for renewable integration when it was designed. therefore, connecting renewable energy generations to the distribution system may lead to various interconnection problems including over voltage, harmonics, rise in fault currents, fault coordination and is landing problems (kim et al., 2013). in most locations in nigeria, the distribution network, the voltage profile as well as the billing systems are very poor (vincent and yusuf, 2014), contributing to a great loss to the utilities. this is due to several challenges which include; low-quality distribution lines, inadequate and weak network coverage, overloading of transformers and inferior feeder pillars, inaccurate system of billing, illegal practices by employees and poor customer relations, power thefts, inadequate logistic facilities, and obsolete communication equipment, inadequate skilled staff and lack of regular training, and inefficient maintenance schemes (amuta et al., 2018; otuoze et al., 2019). lack of proper and prompt maintenance of the existing distribution schemes is identified as the major cause for most of the challenges. figure 1 depicts the sample of distribution lines that are not properly maintained. the characteristics of the current distribution systems in nigeria are highlighted below (aliyu et al., 2013; kim et al., 2013). distribution systems are dominated by radial network: due to the radial structure of the system, fault at any location in the system would disrupt the electricity supply to the entire area thereby making the system unreliable and tedious to maintain. challenges in voltage regulation: the voltage of sub-transmission and distribution need to be maintained within certain reference values. however, during the peak hours, due to the enormous power flows via the link, remarkable voltage dip beyond the reference limits may occur. in contrast during the off-peak hours, the shunt capacitors employed for voltage compensation remain connected to the system and thereby causing voltage rise. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 122 inadequate system facilities: as the demands on the system continue to increase, there is no commensurable increase in the system facilities. therefore, the distribution system becomes heavily loaded and consequently causing tripping in the system as well as high losses and possibly, eventual systems’ collapse. shortage in transformer supplies: the distribution systems in most parts of the country do not have adequate transformers, therefore overloading the existing ones, which subsequently leads to voltage drop, high losses and systems’ unreliability. improper energy accountability: this is due to huge commercial and collection losses. lack of proper maintenance and existence of obsolete equipment: this accounts for high technical losses on the distribution networks. figure 1: sample of a distribution line that are not properly maintained to address some of the problems, the distribution system was privatised. in line with the privatisation programme, the nigerian distribution networks were unbundled into 11 regional grids and were sold to foreign and local investors with a minor stake being maintained by the government. these distribution companies differ in terms of network size, geographical location and number of customers. based on an agreement with the bureau of public enterprises (bpe), the energy capacity allocated to each of the company differs, which in reality depends on the ability of the company to accept the capacity offered (team, 2015) from the primarily defined customer size, geographical location, expected load demand and other related factors. during the privatisation of these companies, some losses were considered in the transaction, however, after the completion of the process, the companies later realised the losses were greater than the envisaged values. the 2014 estimated losses are depicted in figure 2, and the grid energy allocation percentage to the 11 distribution companies is as shown in table 1 (team, 2015). it can be observed from figure 2 that the percentage of technical losses (12%) is far less than the non-technical losses. the greatest problem facing the distribution companies is the level of non-technical losses which include commercial losses (unbilled used energy), and collection losses (unpaid billed energy). these losses are associated with electricity theft and fraud, a huge amount of losses are incurred through electricity theft which is consequently preventing further investment plans for the utilities (otuoze et al., 2017; sharma et al., 2016). unpaid billed energy, unbilled used energy, billing irregularities, defective meters, conventional meter manipulations, corruption of the employees (misappropriation of funds, illegal procurement, sales of distribution equipment, meter bypass and more) and other associated http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 123 fraudulent activities (otuoze et al., 2017). these losses have made some of the companies to reduce the amount of energy allocated to them in order to reduce their losses as can be seen in table 1 (team, 2015), the energy allocations are not proportional to the number of customers. figure 2: annual estimated energy losses in 2014, due to technical, commercial and collection losses (mwh). table 1: the distribution companies with their allocated grid energy in 2014. area number of customers (*1000) distribution network (km) allocation of grid energy (%) average allocation of grid energy (%) abuja 755 107,254 12 15 benin 1,187 104,702 15 14 eko 581 8,093 13 13 enugu 819 25,078 9 12 ibadan 1,750 24,355 8 10 ikeja 1,128 12,466 10 9 jos 466 12,227 8 8 kaduna 459 26,653 7 7 kano 598 21,041 6 5 port harcourt 557 17,989 8 5 yola 345 6,505 4 2 it can be observed that the energy allocations are not proportional to the number of customers as expected. this is solely due to the inability of some of the companies to accept the energy offered to them in an attempt to minimize their losses due to estimated unbilled used energy and unpaid billed energy. however, the major losses are due to commercial and collection losses, attributed to the crude system of billing and vulnerability of the distribution systems to power theft. there is a paradigm shift in most parts of the world, to the deployment of advanced distribution systems' equipment which is robust and resilient to most of the distribution systems’ challenges thereby making the distribution losses reside within an acceptable limit. most of the developing nations, especially in sub-saharan africa, are still battling with several challenges in their power sector and nigeria is not an exception. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 124 several studies have been conducted on the challenges facing power sector in nigeria, however, most of these articles focus on the generation-based problems. akpojedje et al. (2016) reviewed the challenges in the transmission system and the rural electrification schemes. the work proposed an improvement in the transmission network and the rural electrification. similarly, emodi and yusuf (2015) studied the obstacles militating against the development of electricity access in nigeria while highlighting feasible solutions as komolafe and udofia (2020) examined the sources of electrical losses in the nigerian power scheme. patrick et al. (2013) studied the feasibility of smart grid deployment in the nigerian power 330 kv system to reduce the high active and reactive transmission losses. aniefiok et al. (2013) and vincent and yusuf (2014) also explored the feasibilities of smart technology deployment in the nigeria’s power scheme with considerations of renewable energy inclusion. however, the prerequisite for smart grid deployment is a stable electricity supply for the effective functioning of the smart system. although, the authors proposed the basic requirement for the smart grid deployment, those requirements need concerted efforts to be put in place otherwise the deployment of the smart grid would be a mirage. some of the challenges of smart grid deployments related to most developing nations have been highlighted by otuoze et al. (2017). reliability assessment of electric power utility was investigated by popoola et al. (2011) using questionnaire distributed to customers in south-west geopolitical zone of nigeria. the results were analysed using statistical tools to investigate the interruption costs incurred by customers. some recommendations were highlighted to mitigate the effects of interruption costs on customers. osueke and ezeh (2011) assessed the nigeria power sector, comparing generation and demand, energy supply projection, energy efficiency and conservation. some suggestions were proposed to balance the wide gap between demand and supply which include analyses carried out with considerations of many factors including demand factor, duration of supplies, electricity needs, development, expansion and effective integration of alternative energy sources, smart metering to encourage high demand response with respect to energy savings (abam et al., 2014; oluwasuji et al., 2020). an overview of the current energy challenges in nigeria and the difficulty of the issues involved was presented by aliyu et al. (2013). the country's generation potential as at 2010 was analysed, and 20 years expansion plans by government were also presented. the simulation results of the electricity generation system including the environmental impact of siting a nuclear power in one of the potential sites were also presented and analysed. the impact of fossil fuels on the environment was presented and other sources of energy were suggested based on the vision 2020 plans (abam et al., 2014; oyedepo, 2014). a study by oseni (2011) analysed the overall performance of the nigeria power sector and presented some policy guidelines for achieving a world standard power market and sustainable development. usman et al. (2015) examined the country’s energy sources and the power sector reform adopted by the government. the paper outlined some recommendations based on the reform implemented by other countries with similar resources to nigeria which yielded remarkable results. in another study, dada (2014) presented the benefits and challenges of deployment of smart microgrids in nigeria’s electricity delivery scheme. the article gives an overview of the current state of electricity supply in the country. it states the advantages of the deployment of smart microgrids in the country's power supply system. distribution systems serve as the host for distributed generation and the microgrid. the challenges associated with distribution systems need to be addressed for effective deployment of smart microgrids. from the literature survey, it can be concluded that most of the existing articles focus on the power generation sector, demand and supply gap, deployment of smart grid systems, and renewable energy integration. however, all these aforementioned sectors http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 125 cannot have a meaningful impact without addressing the challenges associated with distribution systems. therefore, this article gives details on the technical and non-technical problems regarding distribution systems in nigeria. it highlights problems and feasible solutions. 3. power system distribution losses distribution systems represent a very important position in the power system structure as it serves as the main point of connection among the transmission network, distributed storage, distributed generation, the consumers and the metering points for consumption (patrick et al., 2013). however, the challenges of the distribution systems are majorly associated with energy losses. generally, total energy losses are being calculated using energy balances, the losses equal to total energy delivered to distribution substations and feeders minus total energy consumed (metered and billed) by customers (khodr et al., 2002). the total losses consist of technical losses (tl) and non-technical losses (ntl). these losses need to be estimated separately. conventionally, tls are estimated based on the line parameters (agüero, 2012) particularly by computing the active power losses at peak load demand scenarios (using computational techniques or existing load data), then applying a loss factor to evaluate mean power losses and consequently multiplying the mean power losses by time (in hours) to get monthly or annual energy losses (agüero, 2012). the ntl are obtained by subtracting the calculated tl from the total losses. the computational complexity of these estimations relies on the technique employed for calculating the power losses at peak load demand and loss factors, and the features of the distribution system's components incorporated in the analysis (khodr et al., 2002). moreover, when computing loss factors, a comparative study on the entire system’s losses is required because the influence of the ntl needs to be incorporated especially if the latter is high. furthermore, low-voltage secondary systems’ losses are sometimes not incorporated in this calculation or inappropriate values are used in the calculation. this practices lead to inaccuracies of the calculated results, especially for systems with long secondary lines and a large number of customers (agüero, 2012; doe, 2015). subject to the level of accuracy required, the aforementioned practices may be employed in some modern systems such as those of the north american distribution systems (khodr et al., 2002). similarly, detail modelling of distribution transformers is necessary even though computational techniques are employed for the estimation of losses at peak load, the transformer modelling must include load and noload losses to avoid degradation in the accuracy of losses estimation (agüero, 2012). figure 3 summarizes the various sources of losses associated with distribution systems. the following subsections describe the various losses in distribution systems. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 126 figure 3. summary of the entire sources of losses in the distribution system of nigeria 3.1 technical losses tls are natural occurrence as they comprise of energy dissipation in system components such as lines, transformers, connections, measuring devices and other associated equipment that transport energy to and from customers (antmann, 2009). they are also referred to as physical losses since the energy is being transformed to heat and noise while distributing electricity. this energy dissipation incurs costs on the customers and as well as causing carbon emission (quezada et al., 2006). the level of tl is associated with the physical features of distribution network components used. they rely on the design and quality of the entire power grid, line reactance, voltage and the transformation levels and the length of the lines used. they also relate to the level of investment in the distribution components (there is a trade-off between initial costs of investment and the operational costs). tl also relate to effective planning and quality of distribution networks design (agüero, 2012). tl can be grouped into three kinds of losses as can be seen in figure 3. these include variable losses (associated with load), fixed losses (dissociated with load) and network services (uncontracted consumptions of the network components). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 127 variable losses are losses associated with heat dissipation in all conductors in the system due to their internal resistance which causes them to dissipate heat when carrying electric current (aten and ferris, 2009). due to the variation of these losses with respect to the current flowing in the conductors, they are termed variable losses. these losses vary in proportion to the square of the electric current and are usually called ohmic or copper or resistive losses. generally, variable losses take the larger percentage of the total tl, up to two-thirds or three-quarters of the overall value. basically, there are two measures to reduce these losses: either to reduce power flows or to lower the resistance of the flowing paths (shirmohammadi and hong, 1989). reducing the network equipment utilization (upgrading the network equipment) can reduce both current and resistance. however, upgrading network capacity requires huge investments. hence, there is a compromise between capital investments and costs of losses. it has been suggested that the optimal average utilization rate on a distribution network taken into consideration, the cost of losses in its planning and design could reduce losses to about 30% (aten and ferris, 2009). fixed losses are losses due to energy dissipation in network equipment and components when energized (aten and ferris, 2009). these losses are not variable, they are not associated with the current flow in the system and hence, with or without power supply to the customers, these losses are incurred once the system components are energized. they are associated with the losses in the transformers (hysteresis and eddy current losses). other sources of these losses are leakage current due to poor insulations, and losses due to corona effects. fixed losses solely depend on the system’s voltage; they are mainly fixed since the system voltage is comparatively stable when the system equipment is energized. increasing the efficiency of the system components will reduce the fixed losses. network services are related to uncontracted consumption i.e. the power consumed by the measuring devices such as meters, information systems which are installed within the system. they can be electromechanical, electronics or general ict equipment. generally, technical losses depend on the network characteristics and mode of operation (emodi and yusuf, 2015). these losses cannot be eliminated but can be reduced by using efficient and proper planning and maintenance schemes. 3.2 non-technical losses ntl, also known as commercial and collection losses, are non-natural losses associated with the amount of non-billed electricity and billed electricity that is not paid for (agha and alfaoury, 2016; sharma et al., 2016) or even paid but not properly remitted. the non-billed electricity occurs due to either error in the metering or billing systems or as a result of illegitimate behaviour of customers (agha and alfaoury, 2016; bandim et al., 2003). illegitimate acts such as energy used by fraudulent consumers can be described as institutional theft, corruption and/or organized crime (bandim et al., 2003). the costs associated with ntl are covered by the participation of utilities and/or legitimate consumers paying bills (antmann, 2009). in ntl, some of the energy delivered via the distribution system to the consumers cannot be measured or appropriately accounted for. since they cannot be directly charged by the suppliers or distribution companies, they are sometimes referred to as black losses (agha and alfaoury, 2016; antmann, 2009). ntl are predominantly associated with unknown, unassigned, and incorrect energy flows. they constitute the amount of energy delivered but could not be accounted for. it is however very important to note that ntl may result from each of the following scenarios: energy accounted for but not billed, or energy billed but the bills are not paid or energy used, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 128 billed and paid for, but not remitted appropriately (otuoze et al., 2019). fraudulent consumers are not easily determined except by electricity theft detection techniques which always come with its underlying shortcomings. these shortcoming always arise as no known energy theft detection technique performs 100% efficiently, hence, making it difficult to determine who and how much of energy is fraudulently consumed (bandim et al., 2003). although, with the application of artificial intelligence and machine learning using the energy consumption data, many research outputs are yielding positive results regarding the determination of fraudulent customers (ahmad et al., 2018; messinis and hatziargyriou, 2018). ntls are caused by activities that are external to the power system (chauhan, 2015). the energy loss is not directly associated with energy transportation and dissociated with the physicaltechnical features of the system network (antmann, 2009; bastos et al., 2009). they can be viewed as unknown customer loads, when an unknown load is connected to the network, the actual losses increase while the losses envisaged by the utilities remain the same. this increase losses will appear on the utilities’ account and the costs will be distributed to the customers as network charges (chauhan and rajvanshi, 2013). several scenarios result in ntls. all lie on the utility for the ineffective and inefficient management operation of the network. ntls are generally associated with customer management process (chauhan, 2015) and can be categorized as follows: network equipment challenges, network information challenges, and energy data processing challenges. ntl are often faced with various challenges which could be due to consumer behaviours, the sophistication of the metering devices, failure of any component or connection point of the network topologies and faults on the lines, information processing errors, estimated billings and other ill-fated social actions aimed at evading appropriate electricity bill payments. these challenges are discussed under network equipment, network information and information processing in the next subsections. 3.3 network equipment challenges these are associated with theft and fraud, and measurement errors. theft and fraud: these are caused by illegitimate interference with the network equipment. there are various techniques used to illegally connect to the network (antmann, 2009). the larger part of the ntls are associated with theft and fraud (chauhan, 2015). theft and fraud are the major challenges faced by the power industries, and it requires the efforts of all stakeholders to find a lasting solution to this problem. theft can be referred to as any illegal connection to the use of electricity asides the points where metering systems are positioned by the suppliers. it can occur where an illegitimate connection to the system is made or an unauthorized reconnection after disconnection by the supplier due to high debt incurred by the customer. it can also occur where there is an incomplete connection. fraud can take many shapes, ranging from manipulation of customer’s meter, so that the meter can record lower amount of used electricity or it can also come in the form of meter bypass, where some of the customer’s loads are connected directly without being recorded by the meter. challenges of measuring systems: errors from measuring devices, such as the metering system, are also categorized under ntls. these losses are the difference between the amount of electricity delivered via the meter and the amount recorded by the meter or read from the meter (chauhan and rajvanshi, 2013; chauhan, 2015; depuru et al., 2011). the causes of these losses are as follow; uncertainty associated with the measuring system, permanent error in the meter reading, faulty measuring system, inappropriate configuration or installation of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 129 measuring systems, and complete breakdown of measuring systems. all these can occur as a result of lack of maintenance, lightning, ageing equipment or other related issue which could cause loss of unaccounted amount of energy, thereby causing an increase in ntls (chauhan, 2015; doorduin et al., 2004). 3.4 network information challenges in this scenario, electricity is delivered and consumed but the energy is not accurately measured due to errors in the distribution database. these inaccuracies or errors in consumption data fall under ntl and are as a result of the following (agha and alfaoury, 2016; bastos et al., 2009); unregistered or missing connection points, inappropriate location of connection points, and wrong information from the measuring equipment. 3.5 problems associated with data processing during energy data processing for the evaluation of energy losses, inaccuracies may occur and this is associated with the error in the evaluation of energy produced or consumed. these errors are also incorporated in ntl and are as a result of the following (agüero, 2012; angelos et al., 2011; antmann, 2009); evaluation of the consumption that are not metered, estimation of the calculation consumption and the readings from the meter, tl estimation, estimation of some detected challenges, and other energy data processing. the following section presents some of the irregularities associated with nigerian distribution companies. 3.6 irregularities on the part of distribution companies the operation and maintenance of the distribution equipment are parts of the responsibilities of the employees at the distribution offices all over the country. however, most of these employees are not equipped with the skill to perform these jobs. they work with obsolete logistics’ facilities, tools and safety equipment, and operation vehicles (dada, 2014). therefore, customers usually sought the means of solving most of the electrical faults at their end. there is no prior notification or warning to the customers in an event of faults or outages that occur at the distribution level and in most cases, it takes ages before the problems are solved. there is also lack of effective planning and management at the distribution level, no reliable real-time data about the condition of the distribution systems, and no effective coordination and automation controls to prevent system failures which can subsequently lead to cascading collapse (okafor and ezeh, 2010). transformers are perpetually subjected to overloading thereby causing tripping and frequent breakdown due to the absence of coordinated control and information exchange to register the status of all the distribution transformers in order to take decisive measures (oseni, 2011). in spite of this erratic power supply, there is a continuous rise in electricity tariff. the average electricity tariff between 2012 and 2015, for the three categories of customers (residential, commercial and industrial), charged by kaduna disco, ikeja disco and port harcourt disco are as shown in figures 4, 5 and 6, respectively (nerc, 2016). the a and b parts of figures 4, 5 and 6 are for fixed and energy charges, respectively. this average annual tariff increase is the same for other disco across the country. the inaccuracy associated with this tariff system is a serious challenge due to the insufficient and obsolete metering system at the customers' premises. additionally, the fraudulent activities of the system cannot be over emphasised, for example, a fixed tariff is forced on customers without electricity meters, irrespective of whether electricity is supplied or not. in most cases, those having meters are faced with challenges of overestimated billings. defective meter readings due to a fault, extortion from distribution file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 130 employees, illegal connections and disconnections (news, 2013; sambo et al., 2012) are additional irregularities contributing to either the losses being incurred by the disco or making some customers pay higher than their normal billings. figure 4: average electricity tariff for the three categories of customers by kaduna disco (a) fixed charge and (a) energy charge. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 131 figure 5: average electricity tariff for the three categories of customers by ikeja disco (a) fixed charge and (b) energy charge. figure 6: average electricity tariff for the three categories of customers by port harcourt disco (a) fixed charge and (b) energy charge. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 132 4. panaceas to the existing distribution systems challenges few articles (bollen et al., 2008; de martini, 2014; hallberg, 2013; howard, 2014; wiedman and beach, 2013) have discussed the distribution system challenges and solutions. however, more concerted efforts are required to promote distribution system innovation and planning to cope with the "smart grid" paradigms. a planned, effective and smart distribution network is key to cope up with the ever-increasing demand for domestic, commercial and industrial loads. the upgrading of the existing distribution system can be achieved by adopting the following measures. automation of the entire substation and distribution systems for a reduction in power losses and efficient power delivery. deployment of tamper-proof smart metering systems to reduce ntl remarkably. analysis of the financial implications of tamper-proof metering systems should be carried out to study the feasibility of its deployment. upgrading of the primary feeders from a radial to a loop configuration needs to be considered in order to efficiently accommodate distributed generations. increasing the use of distributed energy resources in the distribution system. establishment of state of art communication framework for information interchange between substation and central distribution management system. creation of information exchange between the customers and distribution system operators for efficient operation of the distribution system. a proper framework for interaction between customers, distribution system operators and the market operators. adoption of conservative policies and tariff reduction benefits which will encourage customer participation in demand-side management. distribution system interfaces directly with the public, hence, there is need to put in place sufficient network coverage and provision of quality supply with effective marketing and customer delivery of service. 5. conclusion this paper presented some of the challenges facing nigeria’s power distribution subsector. detailed power distribution losses and types of losses associated with the distribution system, technical and non-technical losses, are presented. the features of the nigeria distribution system are highlighted along with the associated challenges. the irregularities by the distribution system operators are also emphasized. finally, the paper proposed solutions to improve the distribution system to meet up with the state-of-the-art distribution equipment such as tamper-proof smart metering system and communication framework for effective service delivery and efficient system operations. this paper can serve as an important guide for the distribution system operators and power system engineers in the power distribution system subsector. it is hoped that the country will step up and sustain efforts to transform the grid to an intelligent grid. further studies must carry out empirical studies involving data obtained from the operators and consumers to help match a desired balance in the operations of the distribution systems. cost-benefit analysis of smart meter deployment to help in enhanced monitoring and accountability must be carried out to properly advise the government on ways forward. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 133 references abam, fi., nwankwojike, bn., ohunakin, os. and ojomu, sa. 2014. energy resource structure and on-going sustainable development policy in nigeria: a review. international journal of energy and environmental engineering, 5(2-3): 102. adoghe, a., odigwe, i. and igbinovia, s. 2009. power sector reforms-effects on electric power supply reliability and stability in nigeria. international journal of electrical and power engineering, 3(1): 36-42. agha, a. and alfaoury, a. 2016. commercial losses in jordanian electrical system (case study). proceedings of the 13th international multi-conference on systems, signals and devices (ssd) held between 21-24 march, 2016 in leipzig, germany., 189-193. agüero, jr. 2012. improving the efficiency of power distribution systems through technical and non-technical losses reduction. proceedings of pes t&d 2012 held between 7-10 may 2012 in orlando, fl, usa., 1-8. ahmad, t., chen, h., wang, j. and guo, y. 2018. review of various modeling techniques for the detection of electricity theft in smart grid environment. renewable and sustainable energy reviews, 82: 2916-2933. aliyu, as., ramli, at. and saleh, ma. 2013. nigeria electricity crisis: power generation capacity expansion and environmental ramifications. energy, 61: 354-367. amuta, e., wara, s., agbetuyi, af. and matthew, s. 2018. smart grid technology potentials in nigeria: an overview. international journal of applied engineering research, 13(2): 1191-1200. angelos, ews., saavedra, or., cortés, oac. and de souza, an. 2011. detection and identification of abnormalities in customer consumptions in power distribution systems. ieee transactions on power delivery, 26(4): 2436-2442. aniefiok, e., igweonu, i., eguzo, c. and robert, b. 2013. integrating smart grid model in nigeria power network. international journal of advances in engineering & technology, 6(4): 1760. antmann, p. 2009. reducing technical and non-technical losses in the power sector. available at https://openknowledge.worldbank.org/bitstream/handle/10986/20786/926390wp0box3800in0t he0power0sector.pdf?sequence=1. accessed [online] on 13th october 2018. aten, m. and ferris, r. 2009. analysis of distribution losses and life cycle co2 emissions. proceedings of the 20th international conference on electricity distribution (cired 2009) held between 8-11 june 2009 in prague, czech republic., 15-23. bandim, c., alves, j., pinto, a., souza, f., loureiro, m., magalhaes, c. and galvez-durand, f. 2003. identification of energy theft and tampered meters using a central observer meter: a mathematical approach. proceedings of the 2003 ieee pes transmission and distribution conference and exposition (ieee cat. no. 03ch37495) held between 7-12 sept. 2003 in dallas, tx, usa, usa., 163-168. bastos, p., souza, ba. and ferreira, n. 2009. diagnosis of nontechnical energy losses using bayesian networks. proceedings of the 20th international conference and exhibition on electricity distribution held between 8-11 june 2009 in prague, czech republic., paper 0566. bhatti, ss., lodhi, m., ul haq, s., gardezi, s., javaid, m., raza, m. and lodhi, m. 2015. electric power transmission and distribution losses overview and minimization in pakistan. international journal of scientific and engineering research, 6(4): 1108-1112. https://openknowledge.worldbank.org/bitstream/handle/10986/20786/926390wp0box3800in0the0power0sector.pdf?sequence=1 https://openknowledge.worldbank.org/bitstream/handle/10986/20786/926390wp0box3800in0the0power0sector.pdf?sequence=1 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; 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vol. 16(1) 120-136. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 135 nerc. 2016. retail tariff for respective discos. available at https://nerc.gov.ng/index. php/library/documents/tariff-charges--and--market-rules/retail-tariff-for-respective-discos/. accessed [online] on 4th november 2018. news, p. 2013. on phcn’s fraudulent tariff regime. available from https://www.pmnewsnigeria.com /2013/06/19/on-phcns-fraudulent-tariff-regime/. okafor, e. and ezeh, g. 2010. outages in nigeria electric power system: a review. journal of economics and engineering, 1: 65-69. oluwasuji, oi., malik, o., zhang, j. and ramchurn, sd. 2020. solving the fair electric load shedding problem in developing countries. autonomous agents and multi-agent systems, 34(1): 12. oseni, mo. 2011. an analysis of the power sector performance in nigeria. renewable and sustainable energy reviews, 15(9): 4765-4774. osueke, c. and ezeh, c. 2011. assessment of nigeria power sub-sector and electricity generation projections. international journal of scientific and engineering research, 2(11): 1-7. otuoze, a., usman, a., mohammed, o. and jimoh, a. 2017. a review of smart grids deployment issues in developing countries. arid zone journal of engineering, technology and environment, 13(6): 858-867. otuoze, ao., mustafa, mw., ibrahim, o., salisu, s., mohammed, oo., oloyede, aa. and gaya, zs. 2019. threats and challenges of smart grids deployments-a developing nations’ perspective. elektrika-journal of electrical engineering, 18(2): 33-43. otuoze, ao., mustafa, mw., mohammed, oo., saeed, ms., surajudeen-bakinde, nt. and salisu, s. 2019. electricity theft detection by sources of threats for smart city planning. iet smart cities, 1(2): 52-60. oyedepo, so. 2014. towards achieving energy for sustainable development in nigeria. renewable and sustainable energy reviews, 34: 255-272. patrick, o., tolulolope, o. and sunny, o. 2013. smart grid technology and its possible applications to the nigeria 330 kv power system. smart grid and renewable energy, 4(05): 391. popoola, jj., ponnle, aa. and ale, to. 2011. reliability worth assessment of electric power utility in nigeria: residential customer survey results. assumptin university journal of technology, 1: 217-224. quezada, vm., abbad, jr. and roman, tgs. 2006. assessment of energy distribution losses for increasing penetration of distributed generation. ieee transactions on power systems, 21(2): 533-540. salisu, s., wazir, mm., olatunji, mo., mamunu, m. and touqeer, ja. 2019. techno-economic feasibility analysis of an off-grid hybrid energy system for rural electrification in nigeria. international journal of renewable energy research (ijrer), 9(1): 261-270. sambo, as., garba, b., zarma, ih. and gaji, mm. 2012. electricity generation and the present challenges in the nigerian power sector. journal of energy and power engineering, 6(7): 1050. sharma, t., pandey, k., punia, d. and rao, j. 2016. of pilferers and poachers: combating electricity theft in india. energy research and social science, 11: 40-52. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mohammed et al: the challenges and panaceas to power distribution losses in nigeria. azojete,16(1):120-136. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: reacholaabdul@gmail.com; mohammed.oo@unilorin.edu.ng 136 shirmohammadi, d. and hong, hw. 1989. reconfiguration of electric distribution networks for resistive line losses reduction. ieee transactions on power delivery, 4(2): 1492-1498. short, ta. 2014. electric power distribution handbook: crc press, new york. team, ap. 2015. nigeria power baseline report. office of the vice president, federal government of nigeria in conjunction with power africa, abuja, nigeria. usman, zg., abbasoglu, s., ersoy, nt. and fahrioglu, m. 2015. transforming the nigerian power sector for sustainable development. energy policy, 87: 429-437. vincent, en. and yusuf, sd. 2014. integrating renewable energy and smart grid technology into the nigerian electricity grid system. smart grid and renewable energy, 5(09): 220. wiedman, j. and beach, t. 2013. distributed generation policy: encouraging generation on both sides of the meter. the electricity journal, 26(8): 88-108. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):248-258 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 248 original research article aloe vera mucilage as drag reducing agent in oil-water flow m. n. abdallah1, l. c. edomwonyi-otu1,2*, n. yusuf3, and a. baba1 (1department of chemical engineering, ahmadu bello university zaria, nigeria 2department of petroleum and chemical engineering, delta state university, abraka, nigeria 3department of petroleum and chemical engineering, bayero university, kano, nigeria) *corresponding author’s e-mail address: uceclce@ucl.ac.uk article information submitted 2 september, 2018 revised 19 february, 2019 accepted 19 february, 2019 keywords: drag reduction natural dras aloe vera oil-water flows abstract drag reduction is the deliberate reduction of the frictional pressure drop in flow systems by the addition of heavy molecular weight polymeric materials as well as other means such as pipeline modifications. environmentally friendly and cheaper heavy molecular weight polymeric drag reducing agents (dras) has become a necessity in the transportation of fluids particularly in the oil and gas industry. however, very few reports exist on the potentials of natural polymers such as extracts from the aloe vera plant. in this study, the effects of reynolds number and polymer concentration on the drag reduction effectiveness of aloe barbadensis miller were tested. an experimental flow facility using unplasticized polyvinylchloride (upvc) pipe of 12 mm id was constructed with diesel (density = 832 kg/m3, dynamic viscosity = 1.664 mpa.s at 25°c) and water (density = 1000 kg/m3, dynamic viscosity = 0.891 mpa.s at 25°c) as test fluids. drag reduction as a function of aloe polymer concentration in the range 50 ppm to 500 ppm and reynolds number 20000<re<90000 were investigated by comparing the u-tube manometer pressure drop readings with and without aloe polymer. the pressure drop difference expressed as a percentage of the pressure drop without aloe polymer is termed drag reduction and was used to demonstrate the effectiveness of the aloe vera extracts or polymer as a dra. in single phase horizontal (water) flow, a maximum drag reduction of 64% (u = 4.67 m/s) was measured, while in multiphase horizontal flow, a maximum drag reduction of 53.80% (α = 25%, um = 4.67 m/s) was measured. furthermore, measurements showed that pipe inclination had minimal effect on the drag reduction achieved. it was deduced that aloe vera mucilage can be used as a drag reducing agent in oil-water flows for reynolds number below 63,000. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction one of the major operations in the process industry is the transportation of fluids along pipelines. it has been shown that frictional drag between the fluids and pipe wall causes substantial pressure drop along the pipelines (al-wahaibi and angeli, 2007; edomwonyi-otu, 2015). today, pumping systems constitute 20% of the world’s electrical energy demand and consumes 20-50% of the energy usage in certain industrial plant operations (hameed, 2014). hence, the importance of drag reduction cannot be overemphasized. drag reduction generally http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):248-258. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 249 refers to a process where the frictional pressure drop within a piping system is deliberately reduced thus significantly reducing pumping energy required (manfield et al., 1999; edomwonyiotu and angeli, 2014; edomwonyi-otu, 2015). the relevance for practical applications is thus enormous (edomwonyi-otu and adelakun, 2018). savins (1964) was the first to use the term “drag reduction” with the definition: dr = ∆psolvent−∆ppolymer ∆psolvent x100 (1) where: δppolymer and δpsolvent (n/m2) signify the frictional pressure drops in the presence and absence of drag reducing polymers respectively. drag reduction can be carried out via several methods including the use of drag reducing agents (edomwonyi-otu and adelakun, 2018). drag reducing agents are added to the flow in order to reduce frictional drag and can be categorized as: polymers, surfactants, fibers, micro-bubbles and compliant coating. this research however is limited to the use of natural polymers as drag reducing agents in oil-water flow. the first documented work on oil-water flow was carried out by al-wahaibi and angeli, (2007). they investigated the effects of magnafloc 1011 (a co-polymer of polyacrylamide and sodium acrylate) on the pressure drop and flow patterns of oil-water flows in a 14-mm id horizontal acrylic pipe. they reported a maximum drag reduction of 50%. yusuf et al., (2011) also investigated the effect of a drp (drag reducing polymer) on pressure drops using a mineral oil in a 25.4 mm id. they noted that drag reduction showed an increase with the polymer concentrations. they reported a maximum drag reduction of 60% in oil-water flow. recently, edomwonyi-otu (2015), edomwonyi-otu et al. (2015), and edomwonyi-otu and angeli (2019) investigated the effect of drp on oil-water mixture in a horizontal 14-mm id acrylic pipe. they used low concentration of solutions of partially hydrolysed polyacrylamide (hpam, 8 x 106 g/mol.) and two types of peo (5 x 106 and 8 x 106 g/mol.) and as drag reducing agents. the changes that occur to reynolds stresses with polymer addition were studied with particle image velocimetry (piv) technique. the addition of 20 ppm of hpam resulted in dr of 80% in water flows as well as 52% in oil-water flows. in addition, the turbulence properties (velocity profiles and reynolds stresses) as well as the interfacial wave characteristics of the flows were affected by the polymer addition. higher molecular weight polymers gave better dr owing to their better ionic strength and resistance to mechanical degradation. their reports supported the proposed mechanism of drag reduction that suggests that turbulent kinetic energy of flows is redistributed with addition of polymeric solutions. abubakar, (2016) worked with an anionic copolymer of polyacrylamide and 2-acrylamido-2methylpropane sulfonic acid in a 30.6 mm pipe id, using an inclined pipe orientation. he reported 64% drag reduction for horizontal oil-water flows. positive inclination led to 3.3% improved drag reduction (when compared to horizontal flow), while negative inclinations had mixed results; varying between increased and decreased drag reduction when compared to horizontal flow. a general problem encountered in drag reduction studies is the fact that though many mechanisms of drag reduction have been brought forward (al-sarkhi, 2010; manfield et al., 1999; mowla and naderi, 2006; white and mungal, 2008), none have been universally accepted. lumley (1973) postulated that the increased extensional viscosity due to the stretching of randomly coiled polymers tends to dampen the small eddies in the buffer layer and thickens the buffer layer, to give rise to the drag reduction. conversely, de gennes (1990), criticized the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdallah, et al: aloe vera mucilage as drag reducing agent in oil-water flow. azojete, 15(2):248-258. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 250 earlier extensional viscosity postulate. he went on to argue that the elastic energy stored in the macromolecules are responsible for drag-reduction. reports in some extant literature suggest that mucilage, a viscous substance found in plants, exhibits drag reducing properties. lim, (2010) used extracts from malabar spinach in a 25.4 mm pipe id and achieved 78.2% drag reduction in single water flow. abdulbari (2011) studied the effects of aloe vera mucilage in single phase flow and achieved a maximum drag reduction of 63% in a 25.4 mm pipe id. however, reports studies using natural polymers in oil-water flows are generally unavailable there is therefore a need to explore this system in order to generate more data on drag reduction using natural polymers in oil-water flows. this will give insight on the extent of drag reduction that can be achieved using natural polymers in oil-water flows. hence, this research aims to determine the effectiveness of aloe vera mucilage, a natural polymer, in oil-water flow. natural dras also offer a biodegradable alternative to the synthetic polymers currently being used. this study aims at determining the effectiveness of aloe vera mucilage as a drag reducing agent in multiphase flow. 2. experimental set-up the experimental set-up was designed and fabricated at the chemical engineering department of the ahmadu bello university zaria, nigeria. a schematic diagram of the experimental set-up is shown in figure 1. 2.1 polymer preparation aloe vera leaves were cut from the base of the plant and washed thoroughly. the leaves were then cut vertically on both sides and soaked in water for 10 minutes, to remove the aloin (bitter, yellow residue) within them. the leaves were then peeled and the aloe vera mucilage was extracted by scraping the gel from the aloe leaves and pressing on a no. 4 (4.75 mm) sieve. aloe vera leaf contains 98% water davis, (1997) while the remaining 2% is the active aloe vera. this was carried out in the chemical engineering laboratory of the ahmadu bello university, zaria, nigeria. the 20,000 ppm master solution was then used immediately after preparation. a polymer injector pump (new era model no. ne-9000; ±2%) was used to introduce the polymer solution into the test section. a material balance was used to achieve the required concentration in the water phase. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):248-258. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 251 figure 1: schematic representation of the experimental flow facility for drag reduction 2.2 experimental system the experimental system consisted of two buildup tanks (for water and diesel respectively), with capacity of 200 liters each. two 1-horsepower surface pumps. 0.012 m id unplasticized polyvinylchloride (upvc) pipes. a u-tube manometer. globe and gate valves and two (lzm-20j; ±5%) flowmeters, with capacities of 60 l/min. the u-tube manometer (pyrex) was used to detect the pressure drop and the flow meters, used to regulate the flow rate of fluid passing through pipes. from each of the storage tanks, a centrifugal pump was used to transport the fluid to the testing section. each flow line was fitted with a flow meter and a gate valve. the flow meters, with two globe valves attached for regulation, were calibrated before use. the fluids were brought together via the use of a smooth y-junction (at an angle of 45°), which minimized their mixing. the design was such that the diesel entered from the top and the water from the bottom before reaching the testing area. the prepared drag reducing agent was injected using a new eraprogrammable peristaltic pump (model ne-9000; ±2%) before the point of mixing, into the water phase. the test section comprised of 0.012 m id upvc pipe, a 1m long acrylic view section with two pressure ports located 0.5 m apart and a u-tube manometer connected via rubber tubing to the pressure ports. the first pressure port was located 3.0 m from the mixing point; well in excess of the recommended 150 times the diameter of the pipe used (lien et al., 2004). this is to allow for fully developed turbulent flow before pressure drop readings were taken. aloe vera mucilage concentrations, ranging from 50 ppm to 500 ppm were used. also, several reynolds numbers were used (by varying the input flowrate), with a maximum reynolds number of 83,690.20 investigated for the single-phase experiments. for the multiphase experiments, oil (diesel) was introduced to the system at different concentrations. a mixture velocity (umix) range of 4.67 to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdallah, et al: aloe vera mucilage as drag reducing agent in oil-water flow. azojete, 15(2):248-258. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 252 1.11 m/s was used and oil input fraction ranged from 0 to 1. in the single-phase experiments, an optimal concentration of the dra was observed and recorded (the point at which further addition of the dra did not yield an increase in the observed drag reduction). the concentrations and flowrate at which the optimum drag reduction was achieved in single phase was adopted for the multiphase experiments. dra concentrations higher and lower than the optimal, were used to confirm if the drag reduction would change, thus changing the optimal concentration for multiphase flow. the drag reduction in both cases showed no change, thereby confirming the optimum dra concentration in single-phase and multiphase to be the same. the optimal flowrate from the single-phase was also used to determine the optimal velocity. this was then used to determine the mixture velocity for the oil and water in the multiphase experiments. the separator, with a capacity of 220 liters, was used to recover used diesel; which was then recycled to the diesel buildup tank. this separation was done using the differences in density between the testing fluids (helmenstein, 2017). drag reductions were determined for both single and multiphase experiments using equation 1. the experiments were carried out for horizontal flow, 2° inclination and also -2° and -5° inclinations (2° and 5° declinations). the results were then compared. 3. results and discussion 3.1 single water phase drag reduction figure 2 shows percentage drag reductions against polymer concentration at different reynolds number (nre). it was observed that drag reduction increases as the polymer concentration is increased. this may be as a result of the increased amount of polymer particles available to interact in the system. these particles suppress eddies and further thicken the buffer layer (lumley, 1969). this phenomenon continues until a plateau point is reached. as observed at 400 ppm, further increase in the polymer concentration did not yield a corresponding increase in drag reduction. injection of 450 ppm and 500 ppm resulted in the same drag reduction as observed at 400 ppm. this occurrence may be as a result of the turbulent structures of the flow becoming saturated with dra molecules (edomwonyi-otu, 2015) to the point where further addition had very little effect on drag reduction; as the overall viscosity of the system is increased (hameed et al., 2014). it can thus be deduced that, for this system, 400 ppm of aloe vera mucilage is the critical concentration. figure 2: effect of polymer concentration on percentage drag reduction at various reynolds numbers. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):248-258. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 253 it can also be observed in figure 2 that as reynolds number increased, the drag reduction also increased, until a threshold reynolds number was reached at 62,949. after which (at re=83,690) drag reduction dropped significantly. this may be attributed to the increased reynolds number and subsequently, increased turbulence in the system; resulting in the polymer molecules stretching further. as they stretch, they further absorb the energy within the system. this leads to the suppression of turbulence and as a result, drag is reduced. the findings are in agreement with results obtained from yusuf et al., (2011) and abubakar, (2016). although they both used synthetic polymers, they also observed a steady increase in drag reduction with increased reynolds number until a plateau point was reached. the maximum drag reduction observed for this system was at 400 ppm, 450 ppm and 500 ppm. however, beyond a reynolds number of 62,949, it can be deduced from the increase in drag (decrease in drag reduction) that the aloe vera mucilage undergoes mechanical degradation due to the very high velocity within the system. as such, the dra becomes much less effective beyond this point. it has been reported that his mechanical degradation is one of the drawbacks of natural polymers in drag reduction (kamarulizan, 2012). for comparison, abubakar, (2016) used a synthetic copolymer of polyacrylamide and 2-acrylamido-2-methylpropane sulfonic acid and did not experience degradation of the dra at reynolds number as high as 120,000. in view of these findings from the preliminary investigation, it is safe to suppose that further increase in the concentration of the dra beyond 400 ppm would not cause appreciable increase in drag reduction. the single phase experiments also confirmed the use of aloe vera mucilage as a drag reducing agent in single phase (water) flow, as established by (abdulbari et al., 2011). different operating conditions were selected to improve data on the viability of the natural dra and it proved to be as effective as in their work. 3.2 drag reduction in multiphase flow an optimum concentration of 400 ppm was used, as obtained from the single phase experiments. figure 3 represents the drag reduction obtained in the multiphase experiments. the algebraic summation of the superficial velocity of water (usw) and the superficial velocity of oil (uso) gives us the mixture velocity used in the experiments. it can be seen that drag reduction is most effective in the pure water phase (α = 0). subsequent addition of diesel resulted in the percentage drag reduction reducing continuously until it is 0; in the pure diesel phase (α = 1). given that a water soluble dra is used, it is expected that as the water reynolds number decreased, the drag reduction observed will decrease. essentially, as the superficial velocity of water (usw) decreases, the water reynolds number also reduces; thus reducing the effectiveness of the drag reduction. as established in the single phase experiments and previous works, drag reduction increases as reynolds number increases and vice versa. this is in agreement with the findings of edomwonyi-otu, (2015) and abubakar, (2016). they noted that addition of a water-soluble dra in oil-water flow resulted in drag reduction being inversely proportional to the oil input fraction. it can thus be deduced that drag reduction only takes place in the water phase, since the aloe mucilage is insoluble in diesel oil and thus doesn’t interact with it. a maximum drag reduction of 64% was therefore recorded at 0 oil fraction, 400 ppm and um = 4.67 m/s. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdallah, et al: aloe vera mucilage as drag reducing agent in oil-water flow. azojete, 15(2):248-258. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 254 figure 3: effect of oil fractions on drag reduction at various mixture velocities (horizontal flow) 3.3 effect of inclination naturally, it is expected that the introduction of inclination will affect the total pressure drop of the system as the gravitational pressure drop is affected either positively or negatively. indeed, al-sarkhi et al., (2006) established that an inclination of as little as 1.24o altered the effectiveness of drag reduction. as observed by abubakar, (2016) the new additional gravitational force creates both normal and parallel pressure gradient components to the pipe axis. figures 4 to 7 detail the effect of inclination on the system and the performance of the natural dra used, under these conditions. the optimum dra concentration of 400ppm obtained in earlier experiments was also used here. figure 4: effect of oil fractions on drag reduction at various mixture velocities and 20 inclination figure 4 shows the effect of a 2o inclination on the drag reduction. it is observed that similarly to the case of horizontal flow, drag reduction increases with increase in mixture velocity and decrease in oil fraction. however, there is a slight increase of about 4% in drag reduction in the 2o inclined flow compared to the horizontal flow for α = 0, um = 4.67 m/s and 400 ppm aloe mucilage concentration. consistently, other points on the 2o inclined flows showed slight increase in drag reduction over the horizontal flows. lum et al., (2006) observed that the added gravitational flow component leads to increased mixing between the phases. this in turn leads to dispersion of oil in the water phase thus reducing the amount of oil in contact with the pipe walls (drag-inducing flow reduces), http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):248-258. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 255 consequently reducing the total pressure drop of the system, and thereby enhancing the effectiveness of drag reduction. these findings are in line with observations made by abubakar, (2016), who reported 3.33% higher drag reduction at 5o inclinations over horizontal flows in a 30.6 mm id pipe. these results essentially indicate that inclination enhanced drag reduction for the systems studied. figure 5: effect of oil fractions on drag reduction at various mixture velocities and 20 declination figure 6: effect of oil fractions on drag reduction at various mixture velocities and 50 declination figures 5 and 6 show the drag reductions measured at various input oil volume fraction and mixture velocities, for 2° and 5° declinations, respectively. the highest drag reductions observed for both 2° and 5° declinations were at zero oil fractions and were equal at were about 63.33%. however, it is observed from figures 5 and 6 that the drag reductions at oil fraction of 0.25 for 2° and 5° declinations at umix = 4.67 m/s were 53.3% and 58.33%, respectively, within experimental error (a slight 5% difference). these results show slight increase in drag reduction for the 5o over the 2o case. this may be attributable to the greater gravitational flow component in the 5o case as there is increased turbulence in this case that can lead to more mixing of the phases, thus reducing the amount of oil in contact with the pipe walls (drag-inducing flow reduces), consequently reducing the total pressure drop and thus increasing the drag reduction, of the system. a further comparison of the horizontal flow system (figure 3) with the declination flows (figures 5 & 6) showed mixed results. for instance, in the case of 400 ppm, um=4.67 m/s, the horizontal, 2° and 5° declined flows show drag reductions of 53.8%, 53.3% and 58.33% respectively. this file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdallah, et al: aloe vera mucilage as drag reducing agent in oil-water flow. azojete, 15(2):248-258. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 256 shows that a declination of 2° affected drag reduction similarly to horizontal flows and a further declination to 5° yields slightly higher drag reduction than horizontal flows and also slightly higher than 2° inclination (55.75%). this may occur due to the fact that as flow is aided by gravitational forces, increased turbulence in the system can lead to uneven mixing. which in turn could lead to the dra not uncoiling as effectively as in the horizontal set-up. thus being less effective when absorbing the energy of the flow; as such, hindering drag reduction. thus indicating that declination is not favorable for drag reduction. in addition, the angle of inclination itself did not seem to significantly affect drag reduction. figure 7: effect of angle of inclination on drag reduction figure 7 shows us that although inclination altered the effectiveness of drag reduction, it did so to minimal degree, despite the introduction of the gravitational component to the flow system. as the high velocity within the pipe negates a significant amount of the phenomenon observed. 4. conclusion from all the experiments carried out (testing the viability of aloe vera as dra in oil-water flow) and the results obtained, the following conclusions can be drawn: a maximum drag reduction of 64% was achieved using a 12 mm id pipe in single phase water flow; agreeing with earlier work done by abdulbari (2011) as similar conditions were used. drag reduction increased as reynolds number increased until a reynolds number of 62,949 was reached. indicating that the mucilage is a viable drag reducing agent only for reynolds numbers below 63,000 multiphase flow experiments showed that the addition of the dra only affected the waterdominated flow regions. indicating that drag reduction is only possible when the dra is soluble in the fluid being transported. drag reduction reduced as the oil fraction increased. maximum drag reduction of 53.80% was achieved at an oil input fraction of 25% the effect of pipe inclination was significantly negated by the high velocity within the system. indicating that the dra can viable for most pipe orientations. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):248-258. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 257 when used at reynolds numbers below 63,000, aloe vera proved to be an effective dra in oilwater flow, thereby providing a biodegradable alternative to the synthetic polymers more commonly used. the synergistic effect of the mucilage should be studied, to further enhance its viability as a biodegradable alternative to synthetic polymers. the findings obtained add substantial data to the study of drag reduction, as we strive towards understanding the dynamics and most importantly, the mechanisms of drag reduction. acknowledgement the authors wish to thank all members of the multiphase flow and separation systems research group of the department of chemical engineering, ahmadu bello university, zaria, for their moral and technical support. references abdulbari, ha., letchmanan, k. and yunus, rm. 2011. drag reduction characteristics using aloe vera natural mucilage: an experimental study. journal of applied sciences, 11: 1039-1043. abubakar, a. 2016. study of oil-water flow with drag-reducing polymer in different pipe inclinations and diameters. ph.d. thesis. department of petroleum and chemical engineering, college of engineering, sultan qaboos university, al khoudh, muscat, oman. al-sarkhi, a. 2010. drag reduction with polymers in gas-liquid/liquid-liquid flows in pipes: a literature review. journal of natural gas science and engineering, 2(1): 41–48. al-wahaibi, t. and angeli, p. 2007. transition between stratified and non-stratified horizontal oil–water flows. part i: stability analysis. chemical engineering science, 62: 2915–2928. davis, rh. 1997. aloe vera: a scientific approach. new york: vantage press. edomwonyi-otu, lc. 2015. drag reduction in oil-water flows. ph.d. thesis. department of chemical engineering, university college, london. edomwonyi-otu lc. and adelakun, do. 2018. effects of heavy molecular weight polymer on quality of drinking water. materials today communications. elsevier publication, 15: 337-343. edomwonyi-otu, lc. and angeli, p. 2014. effects of polymer addition on pressure drop and interfacial waves in horizontal oil-water flows by petroleum technology development journal, 2: 41-48. edomwonyi-otu, lc. and angeli, p. 2015. pressure drop and holdup predictions in horizontal oil-water flows for curved and wavy interfaces. chemical engineering research and design (cherd) journal, 93: 55-65. edomwonyi-otu, lc. and angeli, p. 2019. separated oil-water flows with drag reducing polymers. experimental thermal and fluid science journal, 102: 467-478 edomwonyi-otu, lc., chinaud, m. and angeli, p. 2015. effect of drag reducing polymer on horizontal liquid-liquid flows. experimental thermal and fluid science, 64: 164-174. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdallah, et al: aloe vera mucilage as drag reducing agent in oil-water flow. azojete, 15(2):248-258. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uceclce@ucl.ac.uk 258 hameed, am., hamied, rs. and shnain, zy. 2014. drag-reducing agent for aqueous liquid flowing in turbulent mode through pipelines. al-khwarizmi engineering journal, 10(2): 15-22. helmenstine, a. 2017. decantation definition and examples. https://www.thoughtco.com/definition-of-decantation-604990 accessed 8 june, 2019. kamarulizam, snb. 2012. formulation of a dual effect natural drag reduction agent. ms.c project. faculty of chemical and natural resources engineering. universiti malaysia pahang. lim, j. 2010. formulation of natural drag-reducing agent from malabar spinach for aqueous liquid flowing in turbulent mode through pipelines. m.sc. project. http://umpir.ump.edu.my/3257/1/cd5831_lim_joo_ann.pdf accessed 22 may, 2016. lien, k., monty, j., chong, m.s. and ooi, a. 2004. the entrance length for fully developed turbulent channel flow. 15th australian fluid mechanics conference. the university of sydney, sydney, australia. 13-17 december 2004. lum, jy., al-wahaibi, t. and angeli, p. 2006. upward and downward inclination oil-water flows. international journal of multiphase flow, 32: 413-435. lumley, jl. 1969. drag reduction by additives. annual review of fluid mechanics, 1: 367-384. manfield, cj., lawrence, c. and hewitt, g. 1999. drag-reduction with additive in multiphase flow: a literature survey. multiphase science and technology, 11: 197–221. savins, jg. 1964. drag reduction characteristics of solutions of macromolecules in turbulent pipe flow. petroleum engineering journal, 4: 203-214. https://www.thoughtco.com/definition-of-decantation-604990 http://umpir.ump.edu.my/3257/1/cd5831_lim_joo_ann.pdf http://www.azojete.com.ng 8 arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):407-414 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 407 original research article twin synchronous motor grinding mill drives: performance comparison of two options i. k. onwuka*1, g. c. diyoke1, o. a. nwaorgu1, j. o. matthew1, and e. s. obe2 1department of electrical and electronic engineering, michael okpara university of agriculture umudike, abia state, nigeria 2department of electrical engineering,university of nigeria nsukka, enugu state, nigeria *corresponding author’s email address: onwuka.ifeanyichukwu@mouau.edu.ng 1.0 introduction in large grinding mills such as the mineral and cement industries where twin motor drives are used, the two major challenges which limit the use of two synchronous motors connected direct on line and mechanically coupled to the same mill are motor overheating – due to the fact that the two motors do not share the mill load equally, and the increased rate of wear of the gear teeth on the account of non alignment of the rotor positions of the two motors (hoffmann and trasky, 1972). the reason for these problems has been attributed to small inaccuracies in tolerances and manufacturing circumferential error, pitch diameter error, or rim face run out on the girth gear. again, due to manufacturing tolerance or difference in wear, the girth gears do not mesh with the pinions exactly the same way, and so the rotors of the motors are not rotated at the same relative angular positions at the time of starting or during running (valentine et al., 1977). a similar issue is small errors of tolerance in the gear tooth angle. moreover, whereas it is important that the two motors in dual motor grinding mill drives should be electrical duplicates of each other, in practice, motor characteristics may not match perfectly. hence there is a load sharing problem between the two motors. if the two major challenges mentioned earlier must be overcome in such drives, then it is critical that the two synchronous motors should rotate coordinately because they are mechanically coupled together to drive the same mill load through a pinion-driven speed reduction gear. the slip-ring induction motors have a better performance in this respect. but such advantages of using a synchronous motor over the induction motor as lower current for the same power levels, higher efficiency, and power factor correction ability renders the synchronous motors far more attractive than the slip-ring induction motors (seggewiss et al., 2014). a number of schemes have been implemented which mitigates these problems such that synchronous motors remains the choice of motor for dual motor drives (valentine et al., 1977; seggewiss et al., 2014; mular et al., 2002; rodriguez et al., 2005). all these solutions require the use of expensive circuitry, complex stator frame, or complex rotor system. odnokopylov et al. (2015) were interested in load balancing of two-motor asynchronous drive using variable article information abstract the major challenge of twin synchronous motor drives, as seen in the large grinding mills of the mineral and cement industries are motor overheating and gear wearing, due to certain inevitable manufacturing errors/tolerances on the gear which prevents the two motors from sharing the mill load equally. this paper models a typical gear-driven grinding mill load which accommodates the manufacturing error located on the girth gear circumference, and applies it to two twin synchronous motor drive configurations, namely two three-phase seriesconnected six-winding synchronous motors (drive a) and two conventional threephase synchronous motors (drive b). the motor equations were mentioned, and the drives simulated in the matlab/simulink environment. results obtained for the two configurations were compared. it was observed that while the risk of motor overheating was removed in drive a, it was obvious in drive b. however there is a risk of motor shaft breakage due to the mechanical coupling of the motors. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 feb., 2020 revised 14 march, 2020 accepted 30 march, 2020 keywords: grinding mills, synchronous motors, series-connected motors. mailto:onwuka.ifeanyichukwu@mouau.edu.ng http://www.azojete.com.ng onwuka et al: twin synchronous motor grinding mill drives: performance comparison of two options. azojete,16(2):407-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 408 frequency drives (vfd) while the present study is focused on a synchronous drive. recently, onwuka and obe (2019) studied a special drive comprising of two synchronous motors whose stator windings are series-connected and whose shafts were coupled to a common load shaft by gearing. the winding connection is presented in figure 1. they observed that the system was able to deal with the issue of motor overheating by equal load sharing, but the slow varying rotor position persisted. some series connected motors have been studied before with a different objective than the present study (levi et al., 2007). it is the objective of this study to compare the performance of the system studied by onwuka and obe (2019) (designated as drive “a” in this study), with that of a mill drive with two conventional three-phase synchronous motors (designated as drive “b” in this study), by imposing the same load model on the two drives, implementing their respective mathematical models on matlab/simulink environment, and then comparing important performance indices. 2. materials and methods 2.1 system description the mechanical coupling of the drive motors is shown in figure 2, which holds true for the two systems under comparison. the motors rotate in the same direction while the girth gear rotates in the opposite direction. an important assumption made in this study is that both motor 1 and motor 2 are identical machines. for proper comparison, the parameters of the motor units in drive a where obtained from known parameters of a conventional three phase synchronous motor (ojo et al., 1990), which represents the drive b, by phase belt split (rich, 1982; singh and singh, 2012). the parameters are presented in table 1. motor 1 motor 2 girth gear pinion grinding mill figure 1: motor winding connection of drive a (onwuka and obe, 2019) figure 2: two synchronous motor mill http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 407-414. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 409 consideration has been made in table 1 that one set of three phase winding on the stator, the s1, is the reference winding for drive a. the second set of three phase winding on the stator is designated s2. the special configuration of the windings of the motors of drive a, as shown in figure 1 has been described in (onwuka and obe, 2019). motor units with two three-phase stator windings is the usual six-phase or quasi six-phase machines and have been studied by several authors. the articles of singh and singh (2012) and palavicino and valenzuela (2015) however were found helpful. the windings of the motors of drive b need no introduction. table 1: parameters of the motors under study (onwuka and obe, 2019) parameter 3-ϕ motor 3-ϕ six-winding motor winding pitch factor, kp 0.9659 0.9659 winding distribution factor, kd 0.9598 0.9937 q-axis magnetizing reactance, xmq 1.483ω 0.3974 ω d-axis magnetizing reactance, xmd 2.42ω 0.6485 ω rotor q-axis leakage reactance, xlqr 0.597ω 0.1600 ω rotor d-axis leakage reactance, xldr 0.574ω 0.1538 ω field winding leakage reactance, xlfr 0.6291ω 0.1686 ω rotor winding resistance for q-axis, rqr 0.0904ω 0.0242 ω rotor winding resistance for d-axis, rdr 0.0993ω 0.0266 ω field winding resistance, rfr 0.0662ω 0.0171 ω stator winding resistance, rs 0.0667ω �� � ���￱￱￱ ω ��t � � ���￱￱￱ ω stator leakage reactance, xls 0.1212ω ��� � ���￱�� ω ���t � � ���￱�� ω leakage reactance mutual to the two winding sets, xlm 0 0.0088 leakage reactance between the qand daxes of the two winding sets, xldq 0 0 number of poles, p 6 6 rated voltage, vline-to-line 208v 208v rated current, irated 57.8a 57.8a inertia of unloaded motor, j 0.08kg-m2 0.08kg-m2 2.2 mathematical model the mathematical model used for this study was adopted from onwuka and obe (2019), for drive a, and from textbooks (krause and sudhoff, 2000; krause et al., 2013; lipo, 2012), for drive b. from figure 1, the applied voltages in drive a are given by eqn. 1. �� � ��� � ���t � t�� � ��t��� � � ��� � ���t (1) where: n = a, b, c, x, y, or z-phases of the stators and the three rotor windings of each motor, and the subscripts s1 and s2 refers to the two stator winding sections. it is pertinent to mention that zero degree angular displacement was considered for the two sets of three-phase stator windings. in characterizing the flux linkages in eqn. 1, the interactions of all the current-carrying conductors were carefully considered. park’s equations were used to transform the time varying file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onwuka et al: twin synchronous motor grinding mill drives: performance comparison of two options. azojete,16(2):407-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 410 inductances to constant inductance terms in the rotor reference frame, for ease of computer simulation. with s2 windings referred to s1 windings, eqn.1 will be modified as follows: ��� � ���� � ���� (2) where ��� � �� � ��t � (2a) �� � �� � ��t �� ��t � (2b) ��� � �� � ��t � (2c) eqn. 2 is a compact matrix of twelve (12) voltage equations, representing the six interconnected stator windings and the three rotor windings of each motor unit, developed to describe the system of drive a. the motors in drive b were conventional three-phase synchronous motors, and their model equations are available in many textbooks (krause and sudhoff, 2000; krause et al., 2013; lipo, 2012). another important model for this study is the load model. in the load model, the major consideration is on how to factor in the load variation between the two motors in the drive due to imperfect gearing. if it is assumed that the imperfection of the gear is due to circumferential error in manufacturing, then figure 3 will be an exaggerated schematic for the system, while table 2 presents the load torque, tl1 and tl2 perceived by the two motors in the drive for one rotation of the gear. table 2: variation of the load torque tl of the motors as the girth gear rotates (onwuka and obe, 2019) position tl1 tl2 � � �� � � t � ��香 t ��香 t � t � � �� � � t � ��香 � � �� �t � �t ��香 �t � �t �� �t � �t � � �� � � t � ��香 t ��香 t � t � � �� � � t � ��香 �t � �t �� �t � �t ��香 � � �� �t � �t � t � � �� � t� ��香 t ��香 t figure 3: an exaggerated schematic of the imperfect gear (onwuka and obe, 2019) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 407-414. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 411 where: θm refers to the angular position of the gear as it moves on its axis. ��香 � 香��� �th� �t�h�� � � �h���� t� �t� ��������� �h�� t� �t� ��h�� � � h cos �� � � � sin �� to obtain this load model, the grinding mill speed is selected to be 20 rpm, while the motors are 1000 rpm, resulting to a gear ratio of k = 50. the grinding mill speed in rad/sec will be: �� � �����t t � t � �  � (3) where: ωr1 and ωr2 are the respective speed of the first and second synchronous motors, p is the number of poles of the motors and k is the gear ratio. the displacement angle, θm is: �� � ��� (4) 3. results and discussion the embedded matlab function tool was used to simulate the machine equations. the varying load torque was imposed on the motors (the embedded matlab function) using the switch found in the library/simulink/signal routing tool box. the load torque was applied 3 seconds into the simulation, after the steady state has been observed, and the simulation was allowed for 4 revolutions of the grinding mill. the pattern of the load torque is shown in figure 4, where it will be observed that the load pulsations are 180o out of phase in the two motors of the drive and occurs twice in each revolution of the mill. it is further observed that when one motor unit drops some load, the other unit picks it up, hence the pulsations. 4 6 8 10 12 14 80 80.5 81 81.5 82 82.5 83 83.5 84 time (s) lo ad to rqu e ( nm) motor 1 motor 2 figure 4: load torque applied to the two motors of each of drive a and drive b the rotor speed observed for the two drives is shown in figure 5. as the two motors attempt to adjust themselves to the changing load, a maximum speed difference of 1.74 rad/sec is observed during each load pulsation for the motors in drive a, while for the case of the motors in drive b, a maximum speed difference of 0.26 rad/sec was observed. similarly, the observation of the load angle shown in figure 6 is that the drive a motors have, with respect to each other, diverging load angles, while the load angles of drive b motors are fairly constant, with a maximum difference of 0.3 radians observed during each load pulsation. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onwuka et al: twin synchronous motor grinding mill drives: performance comparison of two options. azojete,16(2):407-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 412 2 4 6 8 10 12 14 304 306 308 310 312 314 316 time (s) r ot or s pe ed (r ad /s ec ) motor 1 motor 2 2 4 6 8 10 12 14 304 306 308 310 312 314 316 time (s) r ot or s pe ed (r ad /s ec ) motor 1 motor 2 figure 5: rotor speed of the two motors for: (a) drive a and (b) drive b 0 5 10 15 -300 -250 -200 -150 -100 -50 0 time (s) lo ad a ng le (r ad ) motor 1 motor 2 0 5 10 15 -300 -250 -200 -150 -100 -50 0 time (s) lo ad a ng le (r ad ) motor 1 motor 2 figure 6: load angle of the two motors for: (a) drive a and (b) drive b in figure 7 however, drive a motor units were observed to develop equal and constant torque for the varying mill load, a situation considered desirable, while the drive b motors developed torque according to the applied load torque, which varies during mill revolution. in the same vein, the stator currents were observed for both drives and reported in figure 8. while those of drive a were expectedly constant despite the changing load, those of drive b changed with the changing load, overshooting the rated current of 57.5a by 1.15a. 2 4 6 8 10 12 14 79 80 81 82 83 84 85 time (s) to rq ue (n -m ) motor 1 motor 2 2 4 6 8 10 12 14 79 80 81 82 83 84 85 time (s) to rq ue (n -m ) motor 1 motor 2 figure 7: torque developed by the two motors for: (a) drive a and (b) drive b (a) (b) (a) (b) (a) (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 407-414. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 413 2 4 6 8 10 12 14 46 48 50 52 54 56 58 60 62 time (s) c ur re nt (a ) motor 1 motor 2 2 4 6 8 10 12 14 46 48 50 52 54 56 58 60 62 time (s) c ur re nt (a ) motor 1 motor 2 figure 8: stator a-phase current of the two motors for: (a) drive a and (b) drive b 4. conclusions twin pinion driven grinding mill has been presented which has load pulsations 180o out of phase in the two motors driving it. two synchronous motor drive options have been presented as drive a (six-winding motors with series stator winding connections and parallel field winding connection) and drive b (conventional three-phase motors). the stator currents and developed torque of the drive a motors were observed equal despite the changing load, thereby forcing their speeds to mismatch, resulting in diverging load angles. while this condition is good for the stator windings, there will be increased risk of shaft breakage due to the mechanical coupling of the motors. contrariwise, while the stator currents and developed torque of the drive b motors fluctuated in response to the applied load, their speed, and hence load angle, pulsated about an average value. this condition can lead to fast deterioration of the stator winding insulation and gradual wear of the gear. hence, power electronic option of load balancing remains the better technology. one of the limitations of this study is the use of 25hp motors, as practical applications of this technology is for motors in megawatts ranges. notations tem electromagnetic torque in n/m δ load angle in rad λ flux linkages p the differential operator dy/dx p number of poles l inductance in henrys x reactance in ohms r resistance in ohms v voltage in volts ω angular speed in rad/sec θ angular position in radians ns winding function of the specified winding s1 first 3-phase winding set on the stator s2 second 3-phase winding set on the stator k speed ratio between the motor and gear j inertia of unloaded motor tl1 load torque of motor 1 tl2 load torque of motor 2 (a) (b) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onwuka et al: twin synchronous motor grinding mill drives: performance comparison of two options. azojete,16(2):407-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onwuka.ifeanyichukwu@mouau.edu.ng 414 references hoffmann, a. h. and trasky, j. g. 1972. evaluation of large grinding mill drives for the cement industry. ieee transactions on industry applications, ia-8(1):59 – 72. jones, m., vukosavic, s. n., levi, e. and iqbal, a. 2005. a six-phase series-connected twomotor drive with decoupled dynamic control. ieee transactions on industry applications 41(4): 1056 – 1066. krause, pc. and sudhoff, sd. 2000. analysis of electric machinery. ieee press, new york. krause, pc., wasynczuk, o., sudhoff, sd. and pekarek, s. 2013. analysis of electric machinery and drive systems. wiley-ieee press, 3rd edition. new jersey. levi, e., jones, m., vukosavic, sn., iqbal, a. and toliyat, ha. 2007. modeling, control, and experimental investigation of a five-phase series-connected two-motor drive with single inverter supply. ieee transactions on industrial electronics, 54(3):1504 – 1516. lipo, t. a. 2012. analysis of synchronous machines. 2nd edition, crc press. florida. mular, a. l., hube, dn. and barratt, dj. 2002. mineral processing plant design, practice and control proceedings. conference proceedings held in vancouver, british columbia, october 2002. pp 1983 – 2010. odnokopylov, ig., dementev, yn., usachev, iv., lyapunov, dy., and petrusev, as. 2015. load balancing of two-motor asynchronous electric drive. proceedings of the 2015 international conference on control and communication, held in siberia, may 21 – 23, 2015. (sibcon). doi: 10.1109/sibcon.2015.7147249. pp 1 – 4. ojo, jo., ostovic, v., lipo, ta. and white, jc. 1990. measurement and computation of starting torque pulsations of salient pole synchronous motors. ieee transactions on energy conversion, 5(1): 176 – 182. onwuka, ik. and obe, es. 2019. analysis of load sharing capability of a series-connected twin synchronous motor drive coupled to a common load shaft by gearing. nigerian journal of engineering and technology, 38 (2):476 – 483. palavicino, pc., and valenzuela, ma. 2015. modeling and evaluation of cycloconverter-fed two-stator-winding sag mill drive – part i: modeling options. ieee transactions on industry applications, 51(3):2574 – 2581. rich s. 1982. detailed analysis of a six-phase synchronous machine with ac and dc stator connections. phd thesis, school of electrical engineering, purdue university, west lafayette, indiana. rodriguez, jr., pontt, j., newman, p., musalem, r., miranda, h., moran, l. and alzamora, g. 2005. technical evaluation and practical experience of high power grinding mill drives in mining applications. ieee transactions on industry applications, 14(3): 866 – 874. seggewiss, g., dai, j. and fanslow, m. 2014. evaluation of synchronous motors on grinding mills. proceedings of the cement industry technical conference (cic), ieee-ias/pca, held in washinton dc, 13 – 17 april 2014., pp 1 – 12. singh, gk. and singh d. 2012. experimental study on six-phase synchronous alternator for stand-alone renewable energy generation. iacsit international journal of engineering and technology, 4(4):344 – 347. valentine, rd., trasky, jg. and rippin, dr. 1977. load sharing of dual motor grinding mill drives. ieee transactions on industry applications, ia (2):161 – 168. http://ieeexplore.ieee.org/xpl/mostrecentissue.jsp?punumber=6815881 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 598-610 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 598 original research article mechanical and microstructural characterization of alkali-activated coconut shell ash mortar k. a. olonade1* and t. bello2 (1department of civil & environmental engineering, university of lagos, akoka, nigeria. 2nigerian building and road research institute, building research department, ota, nigeria) * corresponding author’s email address: kolonade@unilag.edu.ng article information submitted 7 april, 2018 revised 12 june, 2019 accepted 22 june, 2019 keywords: alkali-activation coconut shell ash binder compressive flexural strengths abstract in this paper, potential of alkaline activation of coconut shell ash (csa) as binder in mortar was investigated. coconut shells were collected and calcined at temperature ranges between 500 and 900°c at interval of 100 for 30, 60 and 90 minutes to determine optimum burning condition that produces ash of higher silica content. chemical composition of the ashes was then determined using x-ray florescence (xrf) technique. sodium hydroxide (naoh) of different concentrations of 10, 12, 14 and 16 molar (m) was used as alkaline activator, while mortar of mix ratio 1:3 was produced, while ratio of the alkali to csa was of 0.5. mortar prisms of size 40 mm × 40 mm × 160 mm were cast and cured in an oven at a temperature of 80 ℃ for 7, 28, 56, 90 and 120 days. thereafter, flexural and compressive strengths were determined at the end of each curing ages, following standard procedures. scanning electron micrographs of the hydrated mortar at 120 days were obtained using scanning electron microscopy (sem) the results showed the oxide composition did not follow any pattern with increase in temperature but csa produced at 800℃ for 1h gave the highest combined silica, alumina and ferric oxides above 70%, which is accepted as minimum value for pozzolanic materials. both compressive and flexural strengths of the activated mortar samples were found to increase with increase in activator concentration up to 14m and decline thereafter. at 120 days, the compressive strength was 13.9 n/mm2 while the flexural strength was 6.88 n/mm2. these values were higher than the strengths recommended by nigerian industrial standard (nis) for load bearing blocks. it was concluded that activation of csa with naoh could be used as binder for non-structural use. the sem results indicated that mortar made from 14 m had structure that was densely packed compared to other mortar samples produced from other concentrations © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the production of modern cement (ordinary portland cement) consumes huge energy and has been implicated as the major contributor to greenhouse gas emission next to the automobile industry. it is estimated that the cement industry contributes between 6 and 10% of the total annual co2 emitted (metz, 2007, and carstensen and rapf, 2008); while about 5.5 million btu of energy is required to produce just one tonne of cement (naik, 2008). mailto:kolonade@unilag.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):598-610. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 599 unfortunately, the demand for ordinary portland cement (opc) is ever increasing, especially in developing countries, like nigeria, where there is thirst for infrastructure development. oluwakiyesi (2011) reported that nigeria has an estimated deficit of 16 to 18 million housing units and that in 2009, the presidential committee on implementation of affordable housing estimated about n60 trillion to finance the deficit. this would require about 112 million metric tonnes (mmt) of cement. globally, the demand for cement in the year 2015 was 4.6 gt/a (cembureau, 2015) and could reach 13.5 gt/a by 2050 (edwards, 2016). if this trend continues unabated, then the yearning for clean and sustainable environment would be a mirage in the face of meeting infrastructure deficit. in responding to this challenge, several efforts are being made to curtail the amount of opc consumed locally for global objective. one of such emerging and attractive approaches is alkaliactivation of waste materials. large amount of industrial and agricultural waste materials is produced, effective disposal of which remains a challenge with adverse effect on the ecosystem at large. the volume of these wastes generated in the world is increasing over the years due to increase in population, socio-economic activities and social development. alkali activation as defined by martinez and palomo (2001) is a chemical process where amorphous structure is transformed into a skeletal structure that exhibits cementitious properties. once a material contains reactive silica or alumina, it could be considered for activation using appropriate alkali solution (equations 1a, 1b and 1c). several materials and alkali have been studied with positive results. ca + 2 oh + sio2 → c− s − h gel as in opc (1a) na + 2 oh + sio2 → n− s − h gel as in geopolymer (1b) na + 2 oh + al3o2 → n− a− h gel as in geopolymer (1c) where -: c − s − h and n− s − h (gel) are calcium-silicate-hydrate and sodium-silicatehydrate gels, respectively. bakharev (2006) produced concrete using alkali activated fly ash with naoh and achieved a 2day compressive strength of 10 n/mm2 while the 28-day compressive strength was 60 n/mm2. the author also used sodium silicate (na2sio3) to chemically activate fly ash to achieve a 2-day compressive strength of 2 n/mm2 and a 28-day compressive strength of 45 n/mm2. similarly, morenoa et al. (2008) also activated class f fly ash with naoh from different sources and achieved a 28-day compressive strength of between 29 and 66 n/mm2. another study by sofia et al. (2007) used class f fly ash with one or more of the following component; sodium carbonate (na2co3), sodium silicate (na2sio3) and sodium hydroxide (naoh), to achieve 7-day compressive strengths in the range of 35 to 44 n/mm2 and a 28-day compressive strength in the range of 47 to 57 n/mm2. rajesh et al. (2013) studied mechanical properties of alkali activated slag with different alkalis. they reported that a significant compressive strength was achieved especially with sodium silicate and sodium hydroxide solutions, which has one-day strength of 12.46 n/mm2 and 12.04 n/mm2 respectively compared with 9.5 n/mm2 for the control mix and 5.73 n/mm2 for the sodium carbonate mix. it was concluded that naoh was alkali for activating slag for higher strength. qureshi and somnath (2013) used potassium oxide (k2o) and sodium oxide (na2o) to activate blast furnace slag in order to investigate the relationship between alkali content and compressive strength of concrete. durability of alkali activated cement-based products was equally studied (bernal et al., 2011 and atahan and dikme 2011). agricultural wastes are equally being used, though sparsely. palm oil boiler ash (pofa) with sodium hydroxide and sodiumsilicate, using different concentrations of sodium hydroxide alkaline activator was studied (zarina file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olonade and bello: mechanical and microstructural characterization of alkali-activated coconut shell ash mortar azojete, 15(3):598-610. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 600 et. al., 2015). based on authors’ knowledge, there is no reported work on the alkali activation of coconut shell ash as binder; hence, this study was carried out to fill the research gap. coconut is a fruit from the coconut palm tree. it is grown in large quantity according to food and agriculture organization. about 0.3 mmt of coconut was grown in 2014 as against about 0.1 mmt and 0.12 mmt produced in the 60’s and 80’s respectively (figure 1). it is equally widely grown in nigeria especially in the riverine areas of the country. during processing of coconut for oil production, large quantity of coconut shells is produced, disposal of which remains a challenge. most often than not, they are piled up and burnt to give room for new set of coconut shells produced. this study therefore investigated suitability of coconut shell ash (csa) as potential precursor for alkali activation. figure 1: coconut production quantity in tons between 1961 and 2013 (faostat, 2016) 2.0 materials and methods 2.1 materials coconut shells were obtained from coconut shell dumpsite in badagry area of lagos state, nigeria (figure 2). river sand of maximum nominal particle size of 3.18 mm was used as the fine aggregate. the sand was washed to remove dirt and deleterious substances. specific gravity of the sand was determined as well as sieve analysis was conducted on the sand to determine its particle size distribution following the procedures specified in bs en 1097-3 (1998). sodium hydroxide (naoh) was used as alkali activator, while ordinary portland cement (opc) of grade 42.5 was used as binder for control sample. figure 2: a typical coconut shell dumpsite at badagry, nigeria http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):598-610. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 601 2.2 preparation of specimens 2.2.1 coconut shell ash the shells were thoroughly washed in water to remove all the organic matters that stuck to them (figures 3a and 3b). thereafter, they were dried under the sun to minimize moisture and were crushed into smaller sizes manually with the aid of harmer to facilitate burning. the crushed shells were burnt in a furnace at different temperature ranging between 500 ℃ and 900 ℃ at an incremental interval of 100 ℃ for 30, 60 and 90 min, respectively. a total of 15 samples of the ash were prepared. for instance, sample a1 represents csa produced by burning at 500 ℃ for 30 min (table 1). (a) (b) figure 3: crushed coconut shell (a) before cleaning and (b) after cleaning table 1: samples of ash produced at different temperatures and duration sample temperature (℃) duration (min) a1 500 30.00 a2 500 60.00 a3 500 90.00 b1 600 30.00 b2 600 60.00 b3 600 90.00 c1 700 30.00 c2 700 60.00 c3 700 90.00 d1 800 30.00 d2 800 60.00 d3 800 90.00 e1 900 30.00 e2 900 60.00 e3 900 90.00 2.2.2 sodium hydroxide solution sodium hydroxide (naoh) in pellet form was purchased from purechem manufacturing company in lagos and was used to prepare the various concentrations for the experiment. the different concentrations prepared for this study were 10, 12, 14 and 16m. the choice of concentrations was based on findings from previous studies (ammar et al., 2013 and qureshi and ghosh, 2013). table 2 summarized the quantity used in preparing the naoh solution. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olonade and bello: mechanical and microstructural characterization of alkali-activated coconut shell ash mortar azojete, 15(3):598-610. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 602 2.2.3 alkali activated coconut shell ash mortar the alkali activated coconut shell ash mortar (aacsam) was prepared by mixing a measured amount of coconut shell ash (csa) with the alkali activator (naoh-solution) in a ratio of 1:2 (alkali: csa) by weight to produce an alkali activated coconut shell ash paste (binder). the resulting binder was in turn mixed with fine aggregate to finally produce an aacsam in a binder/sand ratio of 0.5 by weight. table 2: quantity of naoh per liter in each concentration molarity (m) of solution amount of naoh solid (g) quantity of water (l) 10 400 1 12 480 1 14 560 1 16 640 1 the mortar produced was cast in moulds of sizes 40 × 40 × 160mm (astm c78, 2018). a total of 60 short mortar beams were cast and the moulds were removed after 24 hours (figure 4a). thereafter, they were cured in oven at temperature of 80 ℃ for 7, 28, 56, 90 and 120 days (figure 4b). the choice of temperature and mixing proportions were guided by principles found in the literature that the sample be cured under a temperature of 80 ℃ till the period of testing (andrea and herald, 2004). (a) (b) figure 4: alkali activated coconut shell ash mortar (a) in moulds (b) stack in oven for curing 2.3 testing procedures 2.3.1 determination of chemical composition of csa chemical composition of the 15 ash samples were determined individually, using the x-ray fluorescence (xrf) technique. weltje and tjallingii (2008) give the detail procedure of xrf technique. the test was conducted at lafarge cement plc, ewekoro plant. statistical package for the social sciences (spss) software was used to conduct analysis of variance (anova) on the data to study the effect of the activation conditions (temperature and time) on the chemical composition of csa. the temperature and time that gave high amorphous silica content was then used to produce the ash used for the activation. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):598-610. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 603 2.3.2 determination of compressive and flexural strengths of aacsam at the expiration of each curing period, the prism was weighed and the flexural strength of the mortar prism was first determined. the experimental set-up for determining the flexural force is shown in figure 5. the amount of force that broke the sample into two halves was recorded as flexural force. thereafter, flexural strength was calculated using equation 2. each halves of the prism from flexural testing was used as samples to determine the compressive strength. this is in conformity with the provisions of bs en 196 -1 (2015). figure 5: experimental set-up for flexural testing fs = 1.5fl b3 (2) where: fs = flexural strength, n/mm2 f = flexural force, n b = side of prism square section, mm l = span between supports, mm 3.0 results and discussion 3.1 chemical properties of csa at various burning conditions table 3 presents the chemical composition of the produced csa at different temperature and duration periods. it was observed that as the time of burning increased, the percentage oxides of csa varied, suggesting that duration of burning had effect on the chemical composition of csa produced. for instance, the silica (sio2) content of the ash obtained at 500 ℃ for 30 minutes was about 75% and 65% of what was obtained when the time was increased to 60 and 90 minutes, respectively. the same trend (increased in sio2 content as time increased), though in different proportions, was observed for other temperatures from 600 ℃ to 900℃ except at 800 ℃ . looking at the effect of burning temperature, the results indicated that temperature had significant impact in determining the amount of oxides obtained. for instance, coconut shell ash burnt for 30 min.. at 600 ℃ produced alumina content to be 5.4%, while it was 9.24% at 800 ℃ for the same duration. the thrust of these variations implied that there was individual and combined effect of temperature and duration on the chemical composition of csa. similar observation was reported in the literature, but for cassava peel ash and rice husk ash (salau and olonade, 2011 and ramezanianpour et al., 2009). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olonade and bello: mechanical and microstructural characterization of alkali-activated coconut shell ash mortar azojete, 15(3):598-610. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 604 table 3: effect of calcining temperature and duration on chemical composition of csa temp. time oxides (%) loi (℃) (min) sio2 al2o3 fe2o3 cao mgo so3 k2o na2o 500 30 32.36 5.24 1.66 3.69 0.49 0.14 2.26 1.71 41.42 60 43.12 7.05 2.07 4.65 0.66 0.08 2.85 2.27 33.25 90 49.73 8.08 2.53 5.46 0.78 0.25 3.17 2.6 25.76 600 30 32.51 5.40 1.58 3.8 0.51 0.46 2.02 1.37 29.87 60 36.00 5.76 1.71 3.84 0.55 0.06 2.3 1.93 43.33 90 45.01 7.25 2.25 4.82 0.15 0.15 2.83 2.26 32.74 700 30 44.2 7.38 2.47 4.95 0.72 0.17 2.94 2.41 31.06 60 28.01 4.59 1.24 3.28 0.43 0.12 1.92 1.5 47.43 90 30.35 4.97 1.56 3.43 0.48 0.04 1.89 1.54 51.38 800 30 58.86 9.24 3.20 6.29 1.03 0.46 3.58 4.11 9.73 60 58.76 9.18 3.15 6.35 1.05 0.40 3.50 4.00 9.54 90 43.38 7.03 1.95 4.72 0.68 0.11 2.53 2.07 29.94 900 30 45.24 7.28 2.27 4.78 0.69 0.09 2.42 2.06 27.61 60 36.14 5.97 2.19 4.28 0.6 1.01 2.12 1.68 22.96 90 49.20 7.83 2.86 5.07 0.76 0.37 2.44 2.13 26.44 opc 19.99 5.49 3.00 63.32 1.45 0.34 0.08 0.09 3.96 nevertheless, the focus was to obtain csa that contained reactive and higher content of combined sio2, al2o3 and fe2o3 that was above 70% as recommended by astm c618 (2006). the results further suggested that burning coconut shells at 800℃ for 60 minutes could be the appropriate treatment conditions to obtain csa that would be an acceptable precursor for alkali activation because the combined silica, alumina and ferric oxide was more than 70% minimum recommended (figure 4). figure 4: combined silica, alumina and ferric at different temperatures and times the summary of the multivariate tests conducted on the data presented in table 3 is presented in table 4. it is shown that there is a statistically significant effect of temperature on the combined silica, alumina and ferric oxide content of csa (p < 0.05) , while duration of burning did not have no significant effect statistically (p > 0.05) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):598-610. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 605 table 4: anova on the effect of temperature and time of oxide composition of csa factor ss df ms f p-value f-crit temperature 108501.3 14 7750.094 1.072226 0.420296 2.063541 time 4153178 2 2076589 287.2961 2.19e-19 3.340386 error 202385.2 28 7228.044 total 4464064 44 4464064 3.2 physical and particle size distribution of aggregate figure 2 shows the particle-size distribution curve of the sand. while less than 5% of the particle size passed through sieve size 150 μm, about 98% of its particle size passed through sieve size 2.36 mm indicating aggregate fell within the class of fine aggregate (bs en 1097-3, 1998). the sand could be categorized as normal weight aggregate because its specific gravity was 2.67, which is within the range of 2.43 – 2.75 for normal weight aggregate (bs en 1097-3, 1998). figure 2: particle size distribution curve of the fine aggregate 3.3 strength characteristics of alkali activated coconut shell ash mortar 3.3.1 compressive strength compressive strength of the aacsa mortar varied with concentrations of naoh solution (figure 5). at early age of 7 days, csa activated with 16m of naoh produced the highest strength (4.03 n/mm2), which was about 102%, 116% and 125% of that of 10, 12 and 14m concentrations, respectively. however, at age 28 days, alkali activated mortar produced with 14m concentration had gain more strength, which was about double its strength at 7 days (9.9 n/mm2). other mortar produced with 10, 12 and 16m gained marginal strength over their 7-day strength by just 4, 18 and 2%, respectively. after 28 days, the 14 m mortar sample maintained the lead up to 120 days followed by 12m mortar sample, while 16m mortar sample had the least strength. but, comparing the 28-day strength of 14m mortar sample with that of normal cement mortar, 14m mortar had strength of about 25% of that of the normal cement mortar. these results are in agreement with smith’s (1999) findings which showed nevertheless, the rate of strength development in aacsam was low compared to normal mortar. it was observed that normal mortar had reached about 80% of its 120 day-strength at 28 days file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olonade and bello: mechanical and microstructural characterization of alkali-activated coconut shell ash mortar azojete, 15(3):598-610. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 606 compared to what 14 m mortar reached at the same period, which was about 37%. the implication of this is that aacsam will continue to gain more strength faster than normal mortar as shown by their strength curves (figure 5). it is known that pozzolanic reaction is a slow process compared to hydration in opc (taylor, 2009). these results are comparable to what ammar et al. (2013) reported in their study with different materials. figure 5: compressive strength of aacsam and control despite the relative low strength obtained for alkali-activated coconut shell ash mortar (aacsam), the 28-strength of 14m mortar was still higher than the stipulated minimum strength of 3n/mm2 for load bearing sandcrete blocks as prescribed by the nigerian industrial standard, (2004). thus, the aacsam could be considered for use in non-structural element. in future study, use of other alkalis or combination of other alkali with naoh would be investigated to improve the strength of aacsam. 3.2.2 flexural strength figure 6 shows the flexural strength values of both the aacsam and the normal cement mortar (control). the strength pattern was similar to that of compressive strength. the strength increased with age for all the samples but at different rate. while 16m mortar had highest flexural strength (1.76 n/mm2) at age 7 days, 12m mortar had least strength (1.2 n/mm2). strength of 10 and 14m mortar were 91 and 86% of the strength of the 16m mortar, respectively. as the age increased beyond 7 days, the strength pattern changed with 14m mortar sample gaining strength steadily from 2.37 n/mm2 at 28 days up to 5.88 n/mm2 at 120 days. other mortar samples followed the same trend but with relative lower strength. surprisingly, 16m mortar sample that had initial high strength turned to give lowest after 28 days. the likely reason for this observation is that the concentration of the alkali speed up the initial reaction for the formation of geopolymer product that is responsible for increase in strength (pacheco-torgal, et. al., 2008). nevertheless, there was possibility of concentrated naoh to be absorb moisture (hygroscopic) from the atmosphere, which may lead to weaker zone in the matrix or increase the moisture content of the matrix, leading to lower strength. these results agree with what hashim et al. (2015) reported about alkali activated slag. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):598-610. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 607 figure 6: flexural strength of aacsam and control 4.3.3 microstructure of alkali activated coconut shell ash mortar the sem images of csa alkali activated mortar at ages 28 with different concentrations of naoh are illustrated in figure 7. at 28 days of hydration, when naoh concentration was 10m, the microstructure was characterized by anhydrous csa grains as most of the particles had not reacted with the naoh (figure 7a). subsequently, the matrix was more porous and thus with little strength development. as the concentration of naoh increased, some hydrated compounds started forming, which were more pronounced at 14m concentration than found in 12m that had some traces of incomplete hydration (figures 7b and 7c). furthermore, at higher concentration of 16m, apart from the fact that some csa grains were hydrated, there were traces of anhydrous csa with some dark portions and fragile zones (figure 7d), which is suspected to be linked to hygroscopicity of high concentration of naoh. figure 8 on the other hand shows microstructure of activated mortar samples cured for 120 days. it is seen that more hydrated compounds were formed even at 10m concentration (figure 8a) due to longer period of hydration (120 days) as compared to 28 days (figure 7a), only that hydrated compound formed was not completed. the increase in hydrated products caused the sample to be more compacted with relative low pores, leading to higher strength. the most striking observation from these microstructures is that of 14m mortar samples that that no traces of csa grains. it seemed that all the csa had been hydrated forming well-compacted matrix, which suspected to be responsible for the highest strength observed (figure 8c). according to türker et al., 2016, a complete alkali activation formed additional hydrated compound characterized by a glassy shaped similar to calcium hydrate silicate found in hydrated portland cement; thus improve the strength properties. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olonade and bello: mechanical and microstructural characterization of alkali-activated coconut shell ash mortar azojete, 15(3):598-610. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 608 figure 7: sem images of aacsam at 28 days of hydration with different naoh concentrations. ana: anhydrous naoh, acsa: anhydrous csa, hcsa: hydrated csa; ihcsa: incomplete hydrated csa figure 4.10: sem images of aacsam at 120 days of hydration with different naoh concentrations. hcsa: hydrated csa; ihcsa: incomplete hydrated csa. the hydrated products formed because of alkali activation of csa could be amorphous alkaline aluminosilicate with a 3d structure similar to a zeolitic gel type. the hydrated products caused densification of the hydrated matrix due to increase in volume and filling effect of the pores within the matrix. this action has been attributed to increase in the strength properties of cementitious matrix (yuya et. al, 2015). thus, it could be safely concluded that more hydrated products formed, as a result of reaction between csa grains and 14m naoh is responsible for the increase in compressive and flexural strength obtained (figures 5 and 6). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):598-610. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 609 4. conclusion in this study, characterization of coconut shell ash was performed and mortar samples were prepared with different concentrations of naoh. strength of the mortar samples was equally determined. from the study the following conclusions were drawn: coconut shell ash produced at 800 ℃ for 60 minutes possessed highest content of combined silica, alumina and ferric for alkali activation. alkali activator concentration has influence on the strength development of aacsam, as well as its microstructure. sodium hydroxide of 14m concentration produced highest compressive strength, higher than what was recommended for non-structural use. there were indications that csa could be further explored using different optimization approaches to produce higher strength for structural application, like normal cement mortar. references andrea, vk. and herald, h. 2004. investigation of geopolymer binders with respect to their application for building materials. ceramics-silikaty, 48(3): 117-120. ammar, m., vineet, s., ravishankar, k., praveen, n. and raijiwala, db. 2013. alkali activated fly-ash based geopolymer concrete. journal of emerging technology and advanced engineering, 3:159166. astm c618. 2006. standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete. astm inc. us. atahan, hn. and dikme, d. 2011. use of mineral admixtures for enhanced resistance against sulphate attack. construction building material, 25: 3450-3457 bakharev, t. 2006. thermal behaviour of geopolymer prepared using class f fly ash and elevated temperature curing. cement and concrete research, 36: 1134–1147. bernal, sa., mejia de gutierrez, r., pedraza, al., provis, jl., rodriguez, ed. and delvasto, s. 2011. effect of binder content on the performance of alkali-activated slag concretes. cement and concrete research, 41(1): 1-8. carstensen, k. and rapf., o. 2008. a blueprint for a climate friendly cement industry. wwf, editor 2008, wwf: nürnberg, germany, 1 25. cembureau. 2015. cement and concrete: key facts & figures, association, edition 2015, rue d’arlon 55 – be-1040 brussels, 1 – 45. edwards, p. (2015), the rise and potential peak of cement demand in the urbanized world, cornerstone, 16 june 2015, http://cornerstonemag.net/the-rise-and-potential-peak-of-cementdemand-in-the-urbanized-world/ (accessed 21 apr. 2017). en 196 -1. 2015. methods of testing cement: determination of strength. british standard institution uk. 1 -24. faostat. 2016. food supply livestock and fish primary equivalent, food and agriculture organization of the united nations, statistics division, available at: http://faostat3.fao.org/download/fb/cl/e. accessed on: 15th march, 2017. martinez-ramirez, s. and palomo, a. 2001. microstructure studies on portland cement pastes obtained in highly alkaline environments. cement and concrete. research, 31(11): 1581-1585. metz, b. 2007. intergovernmental panel on climate change, eds., climate change 2007: mitigation of climate change: contribution of working group iii to the fourth assessment report http://faostat3.fao.org/download/fb/cl/e file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olonade and bello: mechanical and microstructural characterization of alkali-activated coconut shell ash mortar azojete, 15(3):598-610. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kolonade@unilag.edu.ng 610 of the intergovernmental panel on climate change, cambridge university press, cambridge; new york, 2007. 1 – 320. https://www. ipcc.ch/pdf/assessment-report/ar4/wg3/ ar4_ wg3_full_report.pdf. accessed: 23 may, 2017. morenoa, s., dieza, ev. and barra, m. 2008. environmental, physical and structural characterization of geopolymer matrixes synthesized from coal (co-) combustion fly ashes. journal of hazardous materials, 154(1-3): 175-183. naik, t. 2008. sustainability of concrete construction. practice periodical on structural design and construction, 13(2): 98–103. nigeria industrial standard: nis (2004). standard for sandcrete blocks, standard organization of nigeria (approved). nigerian standard organization, abuja, nigeria. 1 -13. oluwakiyesi, t. 2011. nigerian cement sector: unbundling potentials. nigeria: vetiva capital management limited, lagos, nigeria. 1 – 90. qureshi, mn. and ghosh s. 2013. alkali activated blast furnace slag as a green construction material. journal of mechanical and civil engineering, 2(1): 24 28. pacheco-torgal, f., castro-gomes j. and jalali. s. 2008. alkali-activated binders: a review part 1. historical background, terminology, reaction mechanisms and hydration products. journal of construction and building materials, 22: 1305-1314. rajesh, dvsp. narender, ra., venkata, ta. and raghavendra, m. 2013. performance of alkali activated slag with various alkali activators. international journal of innovative research, engineering and technology, 2:378 – 386. ramezanianpour, aa., mahdikhani, m. and ahmadibeni, gh. 2009. the effect of rice husk ash on mechanical properties and durability of sustainable concretes. international journal of civil engineering, 7:10 – 24. salau, ma. and olonade, ka. 2011. pozzolanic potentials of cassava peel ash. journal of engineering research, 16(1):10-21. taylor, hfw. 1997. cement chemistry. thomas telford publishing ltd, london, 2nd edition, 1997, pp. 1 –436. türker ht. balçikanli, m., durmus, ih., özbay, e. and erdemir, m. 2016. microstructural alteration of alkali activated slag mortars depend on exposed high temperature level, construction and building materials, 104:169–180. weltje, gj. and tjallingii, r. 2008. calibration of xrf core scanners for quantitative geochemical logging of sediment cores: theory and application. earth planet science letters, 274(3–4): 423– 438. yuya, s., tatsuhiko, s. and tsuyoshi, s. 2015. relation between chemical composition and physical properties of c-s-h generated from cementitious materials. journal of advanced concrete technology, 13(5): 275-290 zarina, y., mohd-mustafa, aa. kamarudin, h., khairul, ni., rafiza, a. and andrei, vs. 2015. effect of solids-to-liquids, na2sio3-to-naoh and curing temperature on the palm oil boiler ash (si + ca) geopolymerisation system. materials, 8(5): 2227-2242. https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=yuya+suda https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=tatsuhiko+saeki https://www.jstage.jst.go.jp/search/global/_search/-char/en?item=8&word=tsuyoshi+saito http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):187-199 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 187 original research article spatial modelling and analysis of an electrical distribution system o. ogunbiyi, a. a. olayinka and m. o. ahmed electrical and computer engineering department, kwara state university, malete, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: feeder network pole spatial information transformer. abstract the distribution of electrical energy to end-users in nigerian communities is faced with diverse spatial problems leading to low voltage, overload on equipment, difficulties in fault tracing and delay in fault clearing. the traditional management system is not only manual but also has flaws such as difficulties in searching and updating previous records as well as no real-time information on their distribution assets. in this study, a geospatial technique was employed for effective management of the electricity distribution system in malete, kwara state, nigeria. spatial information of distribution asset was collected from the field and used in the structural modelling of the distribution network in the arcmap software. analysis of the model and the available information showed that 80 % of the transformers were not properly located at the centroid of the load. the span of the network fairly conformed to standard as only 45.73 % were within 45-50 m. the result also showed that 40 % of the transformers were overloaded with an unbalanced load, hence the need for restructuring of the network © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction one of the major factors that have differentiated the modern man from his ancestor is the ability to effectively manage energy. in recent time, electric energy has become the most available form of energy used in industries, domestic homes, recreation, transportation etc. it is one of the intensive basic need for smooth, meaningful and productive economic life, as the economic growth of any nations largely depends on the effective management and control of the available electrical power (adejoh et al., 2015; avila et al., 2017; kaseke and hosking, 2013). as a result, there is a need for power supply authority to keep a comprehensive and accurate inventory of the distribution assets and their spatial location. this will assist in normal service provision, an extension of the network, forecasting, fault detection and recovery, and undertaking maintenance (fleeman, 1997; zhang et al., 2008) in recent time, the government of nigeria embarked on putting an end to the long-time electrical power crisis in the country by setting up a roadmap. much attention is being given to increase the generation potential and ensure a reliable transmission network (biobaku, 2010). unfortunately, the losses in the distribution network reduce the supply efficiencies. likewise, the lack of proper information on the distribution network reduces reliability. despite all effort, the nation is yet facing unpredictable power outages, low voltage, delay maintenance and poor quality of supply (olaparodi, 2016). in such a http://www.azojete.com.ng ogunbiyi, et al: spatial modelling and analysis of an electrical distribution system. azojete, 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 188 situation, research efforts should not focus only on maintaining an efficient power generation, rather effort should be made to transmit and distribute generated power with minimum possible losses. without appropriate record-keeping and observance of the transmission and distribution system, efficient functioning of the generated power cannot be achieved. according to pickering et al. (1993), proper knowledge of an existing asset is important for efficient operation on an electrical system. therefore, this study presents the spatial modelling and analysis of an electrical distribution network of malete, a community hosting kwara state university. it lies between latitude 8.711° n – 8.702° n and longitude 4.465° e – 4.480° e. the study area is as shown in figure 1. the work involves collation and development of a database of relevant information about the distribution network and their conditions. the existing network was modelled using arcmap gis software. the model was analysed in order to obtain the consumption trend and other factors affecting supply efficiency. figure 1: map of study area 1.1 literature review geographic information system (gis) collects, stores, retrieve, analyse and display geographical data. it combines different layers of information about a place for better understanding and depending on the purpose. the software can capture, store and update, manipulate, analyse, and display geographic information. it is typically used to represent maps as data layers that can be studied and used to perform analyses (rezaee et al., 2009). the power of gis over paper maps is its ability to select the information needed depending upon the intended application (vijay, 2001) . the database which is the most important asset of an organization can be divided into two main various data types: spatial data that describe the location and the shape of geographic features and spatial relationship of map features (blagajac et al., 1998). attribute data are known as descriptive information of the map features. gis software and hardware are used in electrical power system as tools for storing, analysing, interpreting, updating, displaying kwasu campus malete community http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 189 information, professional’s designs and maintaining the system. the global positioning system (gps) is one of the main building blocks, helping in the creation of any gis system. it is a location system based on a constellation of about 24 satellites orbiting the earth at altitudes of approximately 11,000 miles. gps satellites are orbited high enough to avoid the problems associated with land-based systems, yet can provide accurate positioning 24 hours a day, anywhere in the world. the gps is made up of three parts: satellites orbiting the earth; control and monitoring stations on earth; and the gps receivers owned by users. gps satellites broadcast signals from the space that are picked up and identified by gps receivers. each gps receiver then provides the three-dimensional location (latitude, longitude, and altitude) plus the time. hence, gps can provide any point on earth with a unique address and its precise location (hoque, 2016; parkinson and spilker, 1996; bradford, 1994; walton and black, 1999). gis has been used for modelling of distribution facilities such as poles, power lines and transformers in different places in the world (mathankumar and loganathan, 2015; zhang et al., 2008). this has assisted in managing problems arising from the complexity of the distribution system and providing means of keeping up-to-date information on the assets (damilola, 2015). it can also enhance the efficiency and reliability of the power system (kanmani & babu, 2014; simon and cherere, 2011). this method has been very welcomed by the supply authority in nigeria in the analysis of the distribution network. salawudeen and rashidat (2006) reported such activities on the national distribution system, focusing on locating and mapping distribution facilities via a collection of geometric and attributes data. the collated data studied and analysed in order to understand the condition of the distribution network. this was reported by (adejoh et al., 2015) where gis was used to discover that the 500kva transformer in a given location was overloaded by 5.12%. in this study, the effort is not only made to model the distribution system using gis but also to analyse the interconnections, loading on transformers and provision of a better location for the transformers to reduce power loss and maintain the supply voltage within an acceptable limit. 2.0 methodology the methodology used based on data acquisition through field survey. two types of data were collected; namely spatial data and non-spatial data. spatial data included the coordinate (latitudes and longitudes) location of transformers as well as high and lowtension poles. geographical coordinates were obtained using a hand-held gps device. in addition to the spatial information, non-spatial data involving consumer’s connection details, transformer attributes (as presented on nameplates), line voltages, instantaneous current demand, lines conductor size and type were also acquired. 2.1 data modelling the data collected was modelled using arcmap software. a differential correction was performed on the spatial data thus captured. for better visualization, the vector map of the network was overlaid on the digital base map or a satellite raster image. in addition, service lines and customer connection point were digitized. a file geodatabase was file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunbiyi, et al: spatial modelling and analysis of an electrical distribution system. azojete, 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 190 involved with dataset projected using a coordinate system. the file geodatabase contains features named as high tension (ht) pole, low tension (lt) pole, transformers, isolator, primary lines and secondary lines. the coordinate point of the transformers, high and low tension poles acquired was incorporated into the geodatabase using add absolute x, y coordinate in arcmap environment, and non-spatial data (transformer details) were linked together with spatial data as attributes. 2.2 data analysis the data collected was used in microsoft excel to developed data tables for spatial distance calculation, centroid calculation, load profile and line losses calculations. 2.3 spatial distance the pole-to-pole distance for both high tension and low-tension poles and estimation of the distance between low-tension poles and transformers were calculated using haversine formula. the estimate was necessary in order to obtain the length of the conductors from the transformer to consumers for the estimation of line losses. equations 1 and 2 show the relationship between the haversine formula and the distance between two points in the great sphere. hav d r = hav φ2−φ1 + cosφ1 cosφ2 hav ∅2−∅1 (1) d = 2r sin−1 sin2 φ2−φ1 2 + cosφ1 cosφ2 sin2 ∅2−∅1 2 (2) where: hav represents the haversine function, d is the distance between two points (along a great circle of the sphere, r is the radius of the sphere i.e. radius of the earth r = 6371km, φ1, φ2 are latitudes of points in radians and ∅1,∅2 are longitudes of points in radians. 2.4 calculation of centroid location in order to locate the transformer at the centre of the load, the following relationships in equations 3 to 7 were developed. ip = ia × np (3) where ip is the current at a pole, ia is the average sampled current and np is the number of buildings on the pole lm = ip × lp (4) where lm is the mean on latitude, and lp is the latitude of the pole (degree). �m = lm × �p (5) where �m is the mean on longitude, and �p is the longitude of the pole (degree). cl = lm� ip� (6) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 191 c� = �m� lm� (7) where cl is the centre on latitude(degree) and c� is the centre on longitude (degree). 3.0 result and discussion the following tables 1 and 2 show the data collated for transformers in malete community and kwasu campus. the tables present the transformer locations, power in kva, the voltage in kv, current in amperes and number of output legs. table 1:malete transformer network data malete transformers s/n local name φ (°) ∅ (°) kva v (kv) i(a) leg 1 west-end 8.707233 4.470674 500 33/0.415 8.75/695.6 3 2 lambo 8.703356 4.467826 300 33/0.415 5.25/417.4 2 3 boyi hotel 8.708141 4.468712 100 33/0.415 1.75/139.1 1 4 malete park 8.710603 4.463728 500 33/0.415 8.75/695.6 2 5 amina castle 8.709705 4.463622 300 33/0.419 5.25/417.4 1 6 sequence 8.70695 4.463117 300 33/0.415 5.25/417.4 2 7 safari 1 8.70614 4.46546 500 33/0.415 8.75/695.6 2 8 safari 2 8.70259 4.46519 500 33/0.415 8.75/695.6 2 9 millionaire 8.6977 4.46421 300 33/0.415 5.25/417.4 1 10 com tower kwasu roundabout 8.70956 4.465918 100 33/0.415 1.75/139.1 1 table 2: kwasu transformer network data kwasu transformers s/n local name φ (°) ∅ (°) kva v (kv) i (a) leg 1 kwasu substation 8.717232 4.47217 5000 33/11 87.48/262.43 1 2 admin 8.718771 4.485385 500 11/0.415 26.25/695.6 3 3 staff quarters 8.716247 4.490926 300 11/0.415 15.75/417.4 1 4 aa block 8.721514 4.4862 500 11/0.416 26.25/695.6 2 5 works 8.723876 4.481192 500 11/0.417 26.25/695.7 2 6 general hostel 8.725109 4.477752 300 11/0.418 15.75/417.4 2 3.1 gis modelled network using the arcmap software, the data in tables 1 and 2, as well as the poles spatial data, a structural model of the malete community distribution network and that of kwasu campus, were developed. figure 2 presents the gis model of the malete community distribution network while figure 3 presents that of kwasu campus. the networks show consumer points where customers connect to the service lines, the spatial location of electric poles, and transformers with their respective up-risers connecting the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunbiyi, et al: spatial modelling and analysis of an electrical distribution system. azojete, 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 192 transformers to the service lines. the network structures exist on paper and sometimes they do not exist. whenever there is an extension on the network, the structure has to be drafted again or omitted. as a result, the physical network differs from what is available. this makes planning and maintenance more difficult than necessary. this the software-based network structure of figures 2 and 3, the network can be studied used during fault tracing, maintenance and planning for an extension. 3.2 voltage profile figures 4 and 5 show the voltages at sampled low-tension poles of west-end and sequence transformers respectively. there is a significant drop in voltage down the line; it is because of the long distance between the consumers and the transformer, resulting in high losses along the line. thus necessitating the need to minimise the distance between the consumers and the transformer on such a feeder. figure 2: distribution network system of malete community figure 3: distribution network system of kwasu campus figure 4: measured voltage profile of west-end network leg 1 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 193 figure 5: measured voltage profile of sequence network leg 2 3.3 low tension (lt) pole positioning the charts in figures 6 and 7 show the percentage of ranges of the span between lt poles. keeping the span uniform in length prevents the weight of the conductors on one side from pulling the pole over. as the conductor heats up, it lengthens due to thermal expansion, and the conductor sags closer to the ground. ieee standard of spanning of lt poles is 50 m. on the contrary, the network structure of safari leg 2 does not fully comply with the standard. only 44% are within the 50 m range, 17% are above this standard range while 39% are below. similarly, the network of safari2 leg 1 has only 21% of the pole-to-pole distance complying with the standard. figure 6: pole-to-pole distance shorting of safari1 leg 2 figure 7: pole-to-pole distance shorting of safari2 leg 1 from table 3, the structural configuration of lt pole network shows that 53.33 % of the pole-to-pole distance is 40 m and below, 45.73% pole-to-pole distance is between 41 m and 60 m and 3.6% has a pole-to-pole distance of 61m and above. this falls slightly below the recommended standard of pole-to-pole distance of 50 m for lt poles. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunbiyi, et al: spatial modelling and analysis of an electrical distribution system. azojete, 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 194 table 3: overall network pole-to-pole distance shorting network leg <50m range (%) 50m range (%) >50m range (%) sequence network leg1 50 50 0 leg2 64 36 0 safari1 network leg1 73 27 0 leg2 39 44 17 safari2 network leg1 69 21 10 leg2 60 40 0 malete park leg1 41 56 3 leg2 52 42 6 west-end leg1 39 46 15 leg2 61 37 2 leg3 43 57 0 kwasu works leg1 61 36 1 leg2 44 56 0 kwasu aa block leg1 44 56 0 leg2 18 82 0 average 50.53 45.73 3.6 nominal and estimated power loading the average load on five identified community transformers in malete were estimated. the estimated power and nominal ratings are presented in table 4. similarly, figure 8 shows the transformer loadings as compared with the rated (nominal) power in kva. the chart shows that west-end and malete park transformers are overloaded with 27.713kva and 17.189kva at peak level. the west-end and malete park transformers are already overloaded. the load on the two transformers has to reduce in order to prevent an explosion. table 4: loading on distribution transformers transformer kva rating estimated load current (a) node voltage (v) total line losses (kw) estimated loading (kva) west-end 500 2398.70 220 84.05 527.71 malete park 500 2350.86 220 59.56 517.18 safari2 500 1254.43 220 35.91 275.97 safari1 500 1659.43 220 48.25 365.07 sequence 300 961.22 220 5.05 211.47 figure 8: comparison of estimated loading and nominal power of transformers http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 195 3.4 system improvement in order to reduce line loss and voltage drop at the consumer terminals, it is appropriate to relocate the transformers to the centroid of the load. table 5 shows the estimation of centroid location on sequence transformer network. the centroid analysis helps to determine the shortest possible length of connection to the transformer to reduce the voltage. with centroid analysis, transformers can be centrally located with respect to the load area being served as this minimises the length of the distribution lines connecting the transformers to the loads, thus reducing the numbers of electric poles, cost of cable will be reduced, the line resistance will be reduced and also distribution losses will be minimised. table 5: sequence network load centre data calculations recording pole i current (a) at a pole mean on latitude mean on longitude seq001 20.8 181.1102 808.3309375 seq002 31.2 271.6568 1212.562038 seq003 20.8 181.1089 808.3652114 seq004 10.4 90.55966 404.2003819 seq005 41.6 362.2528 1616.835677 seq006 31.2 271.7049 1212.681407 seq007 31.2 271.6575 1212.344781 seq008 10.4 90.55311 404.0860181 seq009 10.4 90.55706 404.0973145 seq010 41.6 362.2179 1616.241429 seq011 20.8 181.1081 808.0807803 seq012 31.2 271.6494 1212.036929 seq013 52 452.7333 2019.982891 seq014 20.8 181.0858 807.9525032 seq015 41.6 362.1679 1615.964357 seq016 10.4 90.54209 404.0169051 seq017 10.4 90.5398 403.9559933 summation 436.8 3803.205 16971.73555 transformer centroid 8.706972 4.462482184 figure 9 shows the chart of the network of sequence transformer, being the smallest network (it consists of fewer lt poles and conductors) in the system. the transformer location is far away from the load centre. yellow point (8.707° n, 4.463° e) represent the current location of the transformer while deep brown colour point (8.707° n, 4.462° e) represent the proposed location. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunbiyi, et al: spatial modelling and analysis of an electrical distribution system. azojete, 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 196 figure 9: sequence network showing proposed location of transformer figure 10 shows the chart of safari1 network, the current position (8.706° n, 4.465° e) of the transformer is indicated with point yellow in the network, while proposed position (8.707° n, 4.465° e) is indicated with point red. the distance between the current and proposed position is 46.27 m. figure 10: safari1 network showing the proposed location of transformer figure 11 shows the chart of safari2 network, the current position (8.703° n, 4.465° e) of the transformer is indicated with point yellow in the network, while proposed position (8.701° n, 4.465° e) is indicated with point red. the distance between the current and proposed position is 172.482 m . this transformer is far away from being near the load centre and need relocating. figure 11: safari2 network showing the proposed location of transformer http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 197 figure 12 shows the chart of malete park network, the current position (8.710°n, 4.463°e) of the transformer is indicated with point yellow in the network, while proposed position (8.711°n, 4.465°e) is indicated with point red. the distance between the current and proposed position is 167.73m. thus, the transformer is far away from being near the load centre. figure 13 shows the chart of west-end network, the current position (8.707°n, 4.471°e) of the transformer is indicated with point yellow in the network, while proposed position (8.707°n, 4.471°e) is indicated with point red. the distance between the current and proposed position is 6.29m. thus, the transformer is approximately at the load centre. figure 12: malete park network showing the proposed location of transformer figure 13: west-end network showing the proposed location of transformer 4.0 conclusion improvement of the performance of distribution systems to meet the required target is a matter of selecting the most effective and appropriate technology with the right operating practices. in addition, it is not sufficient to analyse how a portion of the network may be modified to improve its performance today, rather the determination of the optimal solution based on the future demand scenario. since the distribution network of a power utility has a geographical reference, it is beneficial to create the network on a gis map and constantly update the same as per field parameters. with periodic updating and monitoring, integrating between file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunbiyi, et al: spatial modelling and analysis of an electrical distribution system. azojete, 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 198 distribution system data and gis can be used for energy audit, load management, network planning and analysis; determining the optimum, shortest, and most economic path for transmission and distribution lines; forecasting and predicting the amount of power needed in the future which leads to prioritizing projects and control the demand growth. this study has provided a software model of the entire malete distribution network layout and loading characteristics. in order to reduce voltage drop at customer ’ s terminals, each of the community distribution transformers needs to be located at the load centres. the loads on the malete park and west-end transformers have to reduce, such as to prevent an explosion. if relocation of transformers seems difficult to achieve, the network can be routed such as to reduce losses or a new transformer should be installed. for the future, electrical engineers in the power utility industries should be trained on the use of gis. in addition, gis can be used in more application in an electrical system like real-time wide-area measurements using gps as a trigger. references adejoh, iy., ajileye, oo., alaga, at., samson, as. and onuh, so. 2015. application of gis in electrical distribution. european international journal of science and technology, 4(8): 81–95. avila, n., carvallo, jp., shaw, b. and kammen, dm. 2017. the energy challenge in subsaharan africa: a guide for advocates and policy makers. generating energy for sustainable and equitable development, part 1: 1–79. biobaku, g. 2010. nigeria lunches roadmap for power sector reform. gbenga biobaku and co. barrister and solicitors, august, 1–3. blagajac, sfks. 1998. caddin=data+gis+ga [distribution network design]. in melecon ’ 98. 9th mediterranean electrotechnical conference. proceedings (cat. no.98ch36056), pp. 1121–117, tel-aviv, israel, israel: ieee. damilola, d. 2015. geospatial modelling of electricity distribution network. retrieved from http://www.geospatialworld.net/paper/application/articleview.aspx?aid=30522 esri. 2004. arcgis 9. what is arcgis? esri, n.y, usa. fleeman, p. 1997. gis-based modelling of electricity networks. 14th international conference and exhibition on electricity distribution, 43: 6–21. hoque, z. 2016. basic concept of gps and its applications. iosr journal of humanities and social science, 21(3): 31–37. kanmani, bs. and babu, s. 2014. electricity distribution system using geospatial technology – a case study for hosur town, krishnagiri district, 5(2): 1296–1300. kaseke, n., and hosking, s. 2013. sub-saharan africa electricity supply inadequacy: implications. eastern africa social science research. organization for social science research in eastern and southern africa, pp. 113–132. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):187-199. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: biyikan@gmail.com 199 mathankumar, s., and loganathan, p. 2015. gis-based electrical system planning and network analysis. world engineering and applied sciences journal, 6(4): 215–225. olaparodi, pk. 2016. fashola and nigeria ’ s power problem. punch. retrieved from http://punchng.com/fashola-nigerias-power-problem/ parkinson, bw. and spilker, jj. 1996. global positioning system : theory and applications. american institute of aeronautics and astronautics, reston, usa. parkinson, bw. 1994. introduction and heritage of navstar, the global positioning system. american institute of aeronautics and astronautics, reston, usa. pickering, d., park, j. m. and bannister, d. h. 1993. utility mapping and record-keeping for infrastructure. urban management programme, the world bank, washington dc. pp84. rezaee, n., nayeripour, m., roosta, a. and niknam, t. 2009. role of gis in distribution power systems role of gis in distribution power systems, 3: 2314 – 2318. simon, m. and cherere, f. 2011. development of a gis-based system for modelling of electric utility. university of nairobi, nairobi. walton, aj. and black, rj. 1999. the global positioning system. physical education, 34: 37 – 42. zhang, t., yuan, j., yang, x. and kong, y. 2008. a modelling and connectivity analysis method for electricity distribution network based on relation database in gis. proceedings international conference on intelligent computation technology and automation, icicta 2008, 1: 540–543 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):479-487 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 479 original research article cement stabilized structural foundation lateritic soil with bone ash powder as additive o. a. adetayo1*, o. o. amu1 and a. o. ilori2 (1department of civil engineering, federal university oye ekiti, nigeria 2department of civil engineering, obafemi awolowo university, ile-ife, nigeria) * corresponding author’s email address: oluwaseun.adetayo@fuoye.edu.ng article information submitted 29 march, 2018 revised 20 april, 2019 accepted 23 april, 2019 keywords: bone ash powder cement stabilization lateritic soil complement stabilizer abstract investigation on the potentials of bone ash powder on cement stabilized structural foundation was carried out in this paper. the aim of the study was to discover local waste material as complement for cement to reduce construction cost. three soil samples were collected from different borrow pits in ile-ife and ibadan, nigeria called sample a, b and c. preliminary tests such as the natural moisture content, specific gravity, grain size analysis and atterberg’s limits were performed on the samples at their natural states and when stabilized at the condition of 8, 8 and 6% cement for samples a, b and c respectively. engineering tests such as compaction, california bearing ratio (cbr) and undrained traixial were also performed on them at their natural states, when stabilized with optimum cement and when bone ash powder (bap) was introduced at 2, 4, 6 and 8% to the samples. the results of the engineering tests showed that bap increased the maximum dry density (mdd) of all the samples. with the optimum cement content kept at 8% for samples a and b and 6% for sample c, the values increased from 1687.89 to 2219.05 kg/m3 and 1634.12 to 2174.71 kg/m3 at 4% in samples a and b respectively and 1521.59 to 1620.70 kg/m3 in sample c at 2% bap content. the unsoaked cbr values of all the cement stabilized samples dropped with bap contents. the values dropped from 4.79 to 1.79%, 3.88 to 2.31% and 4.84 to 2.43% respectively in samples a, b and c. however, the shear strengths of samples a and b increased from 604.77 to 740.09 kn/m2 and 317.73 to 616.05 kn/m2 respectively. it was therefore concluded that bap is not an effective additive on cement stabilized structural foundation soil, except in the compaction and shear strength characteristics. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction structural foundation over the years had been faced with the problem of marginal residual soil for construction works (handy, 1995). this problem had led to the failure of many structural foundation constructions built on lateritic soil which is the predominant residue soil available in nigeria (ayininuola and agbede, 2009). in a quest to solve this problem, the concept of soil stabilization which is the treatment of soil to improve its engineering properties was introduced. this concept was targeted towards improving the quality of lateritic soils for sustainable structural foundation construction, both in the water proofing and strength properties. however, mailto:oluwaseun.adetayo@fuoye.edu.ng http://www.azojete.com.ng adetayo, et al: cement stabilized structural foundation lateritic soil with bone ash powder as additive. azojete, 15(2):479-487. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 480 many modifications have been introduced to the concept with the use of conventional materials that help in reducing construction costs. this study was therefore focused on the potential of calcination bone ash powder as additive on cement stabilized lateritic soil for sustainable foundation construction with the aim of discovering a suitable complement for cement in soil stabilization, bone ash powder is a white material primarily composed of calcium phosphate, commonly used in fertilizers and in making ceramics, other products of bone such as animal glues have been used for soil stabilization (stulz and mukerji, 1993) 1.1 soil cement stabilization this is the treatment of natural soil to improve its engineering properties. stabilization is the alteration of foundation soils to the desired characteristics or the improvement of a less stable soil in both strength and durability. many soils are subject to differential expansion and shrinkage when they undergo changes in moisture content. it is therefore usually necessary to stabilize them to reduce the volume changes and strengthen them to the point where they can carry the imposed loadings even when they are saturated. according to o’flaherty (2002), there are three types of soil-and-cement mixtures; plastic soil-cement is a hardened mixture of soil and cement that contains, at the time of placing, enough water to produce a consistency similar to plastering mortar. it is used to line or pave ditches, slopes, and other areas that are subject to erosion. cement-modified soil is an unhardened or semi hardened mixture of soil and cement. when relatively small quantities of portland cement are added to granular soil or silt-clay soil, the chemical and physical properties of that soil are changed. cement reduces the plasticity and water-holding capacity of the soil and increases its bearing value. the degree of improvement depends upon the quantity of the cement used and the type of soil. in cement-modified soil, only enough cement is used to change the physical properties of the soil to the degree desired. cement-modified soils may be used for structural foundation base, sub base, and as trench backfill material. compacted soil-cement, often referred to as simply soil-cement, is a mixture of pulverized soil and calculated amounts of portland cement and water that is compacted to a high density. the result is a rigid slab having moderate compressive strength and resistance to the disintegrating effects of wetting and drying and freezing and thawing. earlier, soil improvement has been in the qualitative sense only, but more recently it has also become associated with quantitative values of strength and durability which are related to performance. these quantitative values include compressive strength, shearing strength, load bearing quality, adsorption softening and reduction in strength and so on. several studies have been made on soil stabilization using different stabilizing agents. (shon et al, 2010), showed the effectiveness of addition of calcium chloride to soil treatment. (lopez and castano, 2001), used calcium oxide as a stabilization technique clay soils in order to inhibit its expansion contraction properties. (ghafoori and cai, 1997), used coal combustion by-products in roller compacted concrete, roadway and parking lots. the investigation of soil condition on site will indicate whether stabilization is needed or not and tests may be necessary to determine which of the several techniques may be feasible and economical. there are two major types of stabilization, mechanical and chemical. mechanical stabilization is the process of improving the gradation of a raw soil by adding a coarse and/or fine material (usually 10% to 50%) with the aim of achieving a dense homogeneous mass when compacted. mechanical stabilization is also known as granular stabilization and soil-aggregate stabilization, in the latter context, the term ‘aggregate’ refers to the addition of non-fine materials greater than 0.06mm that contribute to the development of internal friction (o’flaherty, http://www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):479-487. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 481 2002). mechanical stabilization in widely used in road making. chemical stabilization includes cement stabilization, bituminous stabilization and lime stabilization. cement stabilization usually involves the addition of 5 to 14% portland cement by volume of the compacted mixture being stabilized. this type of stabilization is mainly used to obtain the required geotechnical properties of soils intended as base course materials. although, the best results have been obtained when well graded granular materials were stabilized with cement, portland cement association has indicated that nearly all types of soils can be stabilized with cement. 1.2 pozzolan pozzolan is a fine powdered material which is added to non-hydraulic lime mortars to accelerate the set. the material possesses little or no cementitious value, but in a finely divided form, it will react with calcium hydroxide in the presence of moisture to provide a chemical set (traditional lime, 2010). the first pozzolans were used by eruptions. one of the compelling reasons for incorporating pozzolans in concrete today is to improve quality and to extend service life by enhancing the durability of this ubiquitous construction material. to function properly, pozzolans must be amorphous or glassy and generally finer than 325 mesh in particle size. finer particle sizes generally have greater reactivity helping in the early strength development (vitro minerals, 2005). pozzolans can continue to react in concrete for many years, further strengthening the concrete and making it harder and more durable during its service life. pozzolans also serve to increase density and reduce the permeability of concrete, which helps to make it more resistant to deterioration and swelling associated with various exposure conditions. the two major types of pozzolans are; natural and artificial pozzolans. the natural pozzolans are present on earth’s surface such as diatomaceous earth, opaline shale, volcanic ash, tuff and pumiced. these materials require further accessing such as calcining, grinding, and drying. the aegean island of santorini has volcanic ash, volcanic tuffs, pumicites and opaline shale are found in the west of river mississippi in oklahoma, nevada, arizona and california. fly ash is an example of artificial pozzolan produced when pulverized coal is burnt in electric power plants. the glassy spherical particulars are the active pozzolani portion of the fly ash. fly ash is 66 68% glass. class f fly ash readily reacts with lime (produced when portland cement hydrates) and alkalis to form cementitious compounds. class c fly ash also may exhibit hydraulic (selfcementing) properties. 1.3 bone ash the ash of animal bones consists primarily of calcium phosphate. for many years, bones were principal source of phosphorus and ground bones or bone meal is still used as fertilizer for its phosphorus and calcium contents. mineral deposits of calcium phosphate are now exploited, but much of this was formed from the bones of prehistoric animals. the vertebrae, freed from soft tissue as nearly as possible and defatted with boiling alcohol can be ashed by a process with certain important modifications. this method consists in dissolving the entire organic matrix of bone by heating in a 3 per cent koh solution in glycerol. however, a reagent previously freed from water by boiling was used and the ashing was done by heating the bone at about 250°c. the bone thus leached out with alkaline glycerol reagent retains its morphological form perfectly; only the organic matter was destroyed, leaving a compact white mass of bone salts. the procedure of washing the ashed bone is also an important departure. the leached bone is boiled briskly with distilled water once or twice, depending on how much of the reagent adheres file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng adetayo, et al: cement stabilized structural foundation lateritic soil with bone ash powder as additive. azojete, 15(2):479-487. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 482 to the surface; it is then extracted several times in boiling 95 per cent alcohol, to remove as nearly as possible the entire glycerol reagent, and is dried to a constant weight at 110°c. the bone in this condition can easily be reduced to a fine powder; indeed, it crumbles when pressed between the fingers. the bone powder which may be snowy white or only slightly tinged dissolves in hydrochloric acid without leaving any insoluble residue. the elementary chemical composition of bone ash is presented in table 1 table 1: elementary chemical composition of bone ash expressed in percent material composition of bone ash ca mg k p co dogfish 37.00 0.58 0.44 16.71 3.23 goosefish 36.90 0.55 0.56 16.98 3.19 mackerel 36.74 0.76 0.20 17.42 2.79 squeteague 35.68 0.12 1.31 16.97 3.11 frog (common) 36.09 0.72 0.44 16.45 4.67 bull frog 36.62 0.61 0.36 16.15 4.11 amphiuma 36.86 0.51 0.76 15.96 5.34 siren 36.96 0.57 1.05 16.00 5.73 turtle 35.68 0.62 0.98 14.88 5.63 hen 37.24 0.51 16.40 5.50 rabbit 36.25 0.53 0.92 15.99 5.71 cow 36.05 0.74 0.85 15.43 4.58 dog 35.66 0.46 1.87 15.56 5.62 guinea pig 35.54 0.75 15.78 5.03 source: studies of the chemical composition of bone ash, sergius morgulis, 1931. 2.0 materials and method 2.1 selection of samples the materials used for this study are lateritic soil samples, ordinary portland cement, bone ash and water. the three lateritic soil samples were collected from three different sites, samples a and b were obtained from obafemi awolowo university, ile-ife, osun state, nigeria while c was collected from ibadan, oyo state, nigeria. all the samples which were for foundation construction materials were kept clean in plastic bags and properly sealed with adhesive tape before they were deposited in the geotechnical laboratory of obafemi awolowo university ile-ife for the necessary experiments. soil description and date of sampling were marked clearly on a paper and stapled to the plastic bags. samples were kept in the shade to prevent loss of moisture. the required quantity of ordinary portland cement for the study was obtained locally. the bone ash was obtained by burning cow bones which were collected from a slaughter’s slab at a temperature of about 1200°c. this was kept in a properly sealed polyethylene bag to prevent absorption of moisture. potable water was obtained from the laboratory. http://www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):479-487. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 483 2.2 experimental method preliminary tests such as the natural moisture content, specific gravity, grain size analysis and atterberg’s limits were performed on the samples at their natural states and when stabilized at optimum of 8, 8 and 6% cement for samples a, b and c respectively. engineering tests such as compaction, california bearing ratio (cbr) and undrained traixial were also performed on them at their natural states, when stabilized with optimum cement and when bone ash powder (bap) was introduced at 2, 4, 6 and 8% to the samples. the potential of bone ash powder (bap) as additive on the mixture was thereafter determined. the various tests were carried out with standard procedures stipulated in bs 13774:1990. 3.0 results and discussion the results of the preliminary tests (specific gravity, natural moisture contents, particle size distribution and atterberg’s limits) and the engineering strength tests (maximum dry density at optimum moisture content, california bearing ratio and shear strength) are presented and discussed below: 3.1 preliminary tests the summary of the preliminary test results for soil samples a, b, c are shown in table 2. the natural moisture contents of samples a, b and c are 17.15, 18.19 and 15.83% respectively while that of the bone ash was also found to be 1.5%. the result showed that sample b has the highest natural moisture content and sample c the lowest. the specific gravities of sample a, b and c are 2.40, 2.37 and 2.33 respectively. in his work, (bwalya, 1998) he stated that the performance of lateritic soil may be influenced by many factors such as climatic condition, the hydrological regime and the topography of the area in which the structure is to be constructed. the results of the sieve analysis indicated that all the soil samples fall within the granular material group and range between a1 a3 in the aashto classification system, suggesting that they are fairly good materials for foundation construction. bwalya (1998) in his studies on the relationship between the natural moisture content and the plastic limit indicated generally that soils with natural moisture contents lower than the plastic limits are normal lateritic soils, therefore samples a and b are normal lateritic soils. table 2: summary of preliminary test for soil samples sample natural moisture content (%) specific gravity liquid limit (%) plastic limit (%) plastic index (%) a 17.15 2.40 47.25 25.29 21.96 b 18.19 2.37 39.73 21.33 18.40 c 15.83 2.33 25.05 10.76 14.49 the variations in the liquid limits, plastic limits and plasticity indices for the samples at the natural state and when stabilized with 2-10% cement are shown in figures 1 to 3. the optimum cement for samples a and b were obtained at 8% and at 6% for sample c. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng adetayo, et al: cement stabilized structural foundation lateritic soil with bone ash powder as additive. azojete, 15(2):479-487. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 484 figure 1: liquid limit variations for soil samples a, b and c figure 2: plastic limit variations for soil samples a, b and c figure 3: variation in plasticity indices for soil samples a, b and c http://www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):479-487. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 485 3.2 engineering strength tests table 3 shows the summary of the compaction test results at optimum cement stabilization. the maximum dry densities (mdd) of samples a and b attained maximum values at 4% bone ash stabilization before dropping, while sample c showed improvement up to 2% bone ash stabilization. this indicates that the optimum mdd potential for samples a and b is at 8% cement and 4% bone ash stabilization while that of sample c is at 6% cement and 2% bone ash stabilization. (lambe and whiteman, 1979) stated that, for good soil, the lower the omc, the better its workability and an increase in dry density is an indicator of soil improvement. the result of the cbr test on samples a, b and c at optimum cement is summarized in table 4. the addition of bone ash lowered the unsoaked cbr of all the samples. the cbr value of sample a reduced from 4.79% to a minimum of 1.79% at 4% bone ash stabilization, while those of samples b and c reduced from 3.88 and 4.84% to 2.31 and 2.43% respectively at 2% bone ash stabilization. according to ashworth (1966) the minimum unsoaked cbr value for sub grade in highway construction is 10%. therefore, since all the samples fall short of this standard, they are inadequate as sub grade materials in highway construction. table 3: summary of compaction test results for samples a, b and c at optimum cement sample percentage stabilization with bone ash optimum moisture content (omc) (%) maximum dry density (kg/m3) a 0% 19.79 1687.89 2% 16.35 1998.57 4% 14.17 2219.05 6% 16.17 2107.93 8% 16.16 1808.08 b 0% 21.30 1634.12 2% 19.35 1994.79 4% 16.06 2174.71 6% 19.13 1900.97 8% 21.29 1726.57 c 0% 23.39 1521.59 2% 23.73 1620.70 4% 21.35 1545.56 6% 16.70 1379.44 8% 17.39 1273.32 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng adetayo, et al: cement stabilized structural foundation lateritic soil with bone ash powder as additive. azojete, 15(2):479-487. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 486 table 4: summary of cbr test results sample percentage stabilization (%) unsoaked cbr (%) a 0% bone ash 2% bone ash 4% bone ash 6% bone ash 8% bone ash 4.79 2.30 1.79 2.23 2.38 b 0% bone ash 2% bone ash 4% bone ash 6% bone ash 8% bone ash 3.88 2.31 2.73 2.41 2.38 c 0% bone ash 2% bone ash 4% bone ash 6% bone ash 8% bone ash 4.84 2.43 2.73 2.50 2.86 the undrained triaxial tests were only performed on samples a and b due to some laboratory challenges. the summary of the results is presented in table 5. the shear stresses of the two samples increased when stabilized with bone ash at optimum cement contents. sample a with a natural shear stress value of 604.77 kn/m2 increased to 740.09 kn/m2 after stabilization with optimum 8% cement and 4% bone ash contents while sample b increased from 317.73 kn/m2 to 616.68 kn/m2 after stabilization with optimum 8% cement and 4% bone ash contents. table 5: summary of undrained triaxial test results sample cement, boneash ratio (%) deviator stress (kn/m2) cohesion (kn/m2) angle of internal friction (ø) shear stress(τ) (kn/m2) sample a 0 493.34 48.2 53 604.77 sample b 0 348.82 64.3 36 317.73 sample a 8 : 4 594.32 31.8 50 740.09 sample b 8 : 4 618.05 133.8 38 616.68 4.0 conclusion based on the results of this study which showed that the addition of bone ash lowered the unsoaked cbr of all the samples. it was therefore concluded that bap is not an effective additive on cement stabilized lateritic soil, except only in the compaction and shear strength characteristics http://www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):479-487. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwaseun.adetayo@fuoye.edu.ng 487 references american association of state highway and transportation officials, 1993. design of pavement structures. ashworth, r. 1966. highway engineering, london, heinemann education book ltd. ayininuola, gm. and agbede, oa. 2009. influence of sodium chloride on subgrade soil california bearing ratio. the pacific journal of science and technology, vol. 10 issue1: 573-580. british standard 13774: 1990. soils for engineering purposes – part 4: compaction related tests, incorporating amendments nos. 1 and 2. bwalya, m. 1998. utilisation and improvement of lateritic gravels in road bases, international institute for aerospace survey and earth science (itc), section engineering geology, netherlands, kanaalweg 3, 2628 eb, delft. ghafoori, r. and cai, w. 1997. introduction to geotechnical engineering, prentice-hall, inc englewood cliffs, new jersey. lambe, tw. and whiteman, rv. 1979. soil mechanics, john wiley and sons inc, usa. lopez, ed. and castano, pk. 2001. foundation design and construction, 7th ed. pearson educational limited. harlow, england. morgulis s. 1931. studies of the chemical composition of bone ash, journal of biological sciences, college of medicine, university of nebraska, omaha. vol. 93: 455466. o’flaherty, ca. 2002. highways: the location, design and maintenance of road pavements, 4th ed. oxford, butterworth heinemann jordan hill. shon, cs., saylak, d. and mishra, l. 2010. combined use of calcium chloride and flyash in road base stabilization. journal of transportation research record, 2186: 120-129. https://doi.org/10.3141/2186-13 stulz, r. and mukerji, k. 1993. appropriate building materials: a catalogue of potential solution, 3rd edition, skat: st. gallen, switzerland, p. 29. traditional lime. 2010. pozzolan. downloaded from <http:// www.traditioallime.com/glossary/, on december 18, 2018. vitromineral. 2005. about pozzolan. downloaded from <http:// www.vitrominerals.com/pozzlans, html>” on december 18, 2018 http://www.traditioallime.com/glossary/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:oluwaseun.adetayo@fuoye.edu.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):100-109 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 100 original research article space technology applications for water quality in sustainable development f. a. oluwafemi1* and r. a. olubiyi2 1space life sciences unit, engineering and space systems (ess) department, national space research and development agency (nasrda), airport road, abuja, nigeria. 2planning policy and research (ppr) department, national space research and development agency (nasrda), airport road, abuja, nigeria. article information submitted: 13/12/2018 revised: 25/02/2019 accepted: 17/05/2019 keywords: water quality space technology sustainable-development water-pollution ground-based. abstract water is one of the most important elements for sustaining-life. despite water’s abundance, good quality water is available in a very limited quantity. water quality describes water’s condition, including physical, chemical, biological and radiological-characteristics, usually with respect to its suitability for a particular purpose such as drinking, swimming and irrigation. many factors can reduce quality of water such as water-pollution which is the contamination of water-bodies, usually resulting from human-activities. poor water quality poses a health-risk for people and ecosystems. water quality is measured by several factors, examples of which are the dissolved-oxygen, salinity, turbidity, ph, temperature. water quality is a complex issue and requires large amounts of diverse accurate data in a timely manner. collection of water quality measurement data by traditional method can be quite difficult and resource intensive especially in the remote-areas. therefore, there is a need to supplement the traditional method of ground-based monitoring with space technology especially satellitebased monitoring that provides better effective means of datacollection. satellite-based monitoring is helpful in attaining sustainable development, which includes economic-growth, environmentalprotection and social-equality; in-line with the sustainable development goal “clean water and sanitation” of the united-nations. space technology applications for water quality has several advantages including large area coverage, measurement-frequency, effective upto-date, cost-effective and in time manner. this paper reviews space technology’s use in water quality assessment to achieve sustainable development. examples of space technology spin-offs and use of online open data-access on water quality monitoring are discussed. it also proposes satellite technology viewing few millimeters contaminants in water-bodies in the nearest-future. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction water is inevitable as a result of the various uses such as for: drinking and cooking (as portable water), agriculture (for example for irrigation and watering stock), games and recreation, healthy http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 101 aquatic ecosystems (for example in fishing), wildlife habitats, navigation and shipping, industrial processes, scientific study and education, meeting cultural and spiritual needs. these make water the second most important element for sustaining life on the earth, other than air (harinder, 2018). despite being apparently in abundance, good quality water is available in a very limited quantity. figure 1 shows the global water bodies and land. figure 1: global water bodies and land. image source: esa cci (2019). key: blue colour is water; white colour is land water quality describes the condition of water, including physical, chemical, biological and radiological characteristics, usually with respect to its suitability for a particular purpose such as drinking, swimming and irrigation (noaa, 2018). this is an aspect of water security that encompasses water management and water quality. water security is the reliable availability of adequate quantity and acceptable quality of water for health, livelihoods and production, coupled with an acceptable level of water-related risks (esa, 2018). this paper is a review of how space technology is used for water quality assessment as a means to sustainable development. specific examples of related space technology spin-offs and the use of space technology derived open data-access from specific websites on water quality monitoring are also discussed. this article also proposes that in the nearest future, satellite technology will to be able to view few millimeters contaminants in water-bodies. 2.0 quality of water although scientific measurements are used to define water quality, it is not a simple thing to say “that water is good” or “that water is bad”. so, the determination is typically made relative to the purpose of the water. is it for drinking or to wash a car with or for some other purpose? the quality of water is reduced majorly by pollution. water pollution is the contamination of waterbodies, usually as a result of human activities. poor water quality poses a health-risk for people and ecosystems (noaa, 2018). 2.1 water quality measurement water quality measurement involves analysis and integration of large volume of data (raj et al., 2011). water quality is measured by several factors or indicators. these indicators are classified under the following characteristics (noaa, 2018). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwafemi and olubiyi: space technology applications for water quality in sustainable development. azojete, 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 102 physical characteristics: such as odour, colour, taste, temperature, total suspended solids (tss), transparency or turbidity and total dissolved solids (tds). chemical characteristics: such as ph, dissolved oxygen (do), total hardness (th), heavy metals, nitrate, orthophosphates and pesticides. biological characteristics: such as mollusca, e.coli and coliform bacteria. radiological characteristics. 2.1.1 ground-based water quality measurement water quality measurement is a very complex issue and it requires large amounts of diverse accurate data in a timely manner. collection of data by traditional means (for example field work) can be quite difficult at times, especially in remote-areas, as well as costly and resource intensive (harinder, 2018). 2.1.2 space-based water quality measurement many organizations have supplemented their ground-based monitoring with the use of earth observation (eo) technologies such as satellite-based monitoring which can be very useful as it can provide a cost-effective means of replacing or complimenting field data-collection (harinder, 2018). eo data can be integrated with the in-situ collected data for real-time measurement (harinder, 2018). space based technologies application for water quality has several advantages including large area-coverage, remote-area coverage, measurement-frequency, systematic, repetitive data capturing, effective up-to-date, and timely predictiveness (lahne et al., 2015). space is the universe beyond earth’s atmosphere. outer space does not begin at a definite altitude above the earth’s surface. however, the karman line, an altitude of 100km (62 miles) above the sea level, is conventionally used. space-based technology are those technologies that came into being, as a result of making space more habitable for astronauts (oluwafemi, 2019). space-based technology has allowed findings to novel and efficient ways of dealing with economic, environmental and societal-challenges. space-based has returned to the earth as spin-offs with solutions to so many things. space technology spin-offs are commercial products and services which have been developed with the help of space technology, through research and development (oluwafemi, 2019). satellites are objects that orbit or circle around bigger objects in a space environment (outer space). there are natural and artificial satellites. artificial satellites are launched into space to do specific jobs. artificial satellites are launched using rockets (oluwafemi and olubiyi, 2019). they are built by scientists and engineers and sent into outer space to receive signals and send signals back to the earth. on earth, the signal sent by a satellite is received by large radio antennas. each antenna is a dish and may have a diameter of several meters. satellite may be classified either by their missions or by weight. when classified by mission there are at least four types. these types are communication, meteorological or weather, navigation and the earth observation (eo) satellites. the earth observation satellite may also be called remote sensing satellites. this type of satellite carries sensors/cameras payloads for imaging the earth surface thus providing information on our environment, like vegetation, soil type, flood, forest, fire (oluwafemi and olubiyi, 2019). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 103 gps (global positioning system) uses satellites that orbit earth to send information to gps receivers that are on the ground. the information helps people determine their location, while geographic information system (gis) is a computer software program that helps people to use the information that is collected from the gps satellites. remote sensing is the art and science of making measurements of the earth using sensors on airplanes or satellites. these sensors collect data in the form of images and provide specialized capabilities for manipulating, analyzing, and visualizing those images. remote sensed imagery is integrated within a gis. gis are able to bring large amount of data of both the physical and the social system together in one comprehensive overview shown digitally. satellite remote sensing is useful by providing navigation, communication and data acquisition (eo) capabilities (oluwafemi and olubiyi, 2019). therefore, eo technologies such as satellite-based monitoring devices are quite important as space-based water quality measurement systems. 3.0 sustainable development goals (sdgs) and water quality the united-nations general assembly in 2015 did set a couple of global goals with the sole objective of transforming the world. these goals are referred to as the sustainable development goals (sdgs) (united-nations, 2015a). it has been unequivocally demonstrated that water of good quality is crucial to sustainable socio-economic development (bartram and balance, 1996). sustainable development meets the needs of the present, without compromising the ability of future generations to meet their own needs. sustainable development in an economy includes economic growth, environmental protection and social equality (oluwafemi, 2019). there are 169 targets for the 17 goals. each target has between 1 and 3 indicators used to measure progress toward reaching the targets. in total, there are 232 approved indicators that will measure compliance. the goals are (united-nations, 2015a; united-nations, 2015b): goal 1: zero poverty goal 2: zero hunger goal 3: good health and well-being goal 4: quality education goal 5: gender equality goal 6: clean water and sanitation goal 7: affordable and clean energy goal 8: decent work and economic growth goal 9: industry innovation and infrastructure goal 10: reduced inequality goal 11: sustainable cities and communities goal 12: responsible consumption and production goal 13: climate action goal 14: life below water goal 15: life on land goal 16: peace and justice strong institutions goal 17: partnership to achieve the goal the sdg of interest in this paper is the “goal 6 – clean water and sanitation”. this is to ensure availability and sustainable management of water and sanitation for all. the sustainable development goal number 6 (sdg6) has eight targets and 11 indicators that will be used to monitor progress toward the targets. the first three targets relate to drinking water supply and sanitation. worldwide, 6 out of 10 people lack safely managed sanitation services, and 3 out of 10 lack safely managed water services (united-nations, 2019). safe drinking water and hygienic toilets protect people from disease and enable societies to be more productive economically (united-nations, 2019). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwafemi and olubiyi: space technology applications for water quality in sustainable development. azojete, 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 104 space technology application stimulates economic growth and improves the quality of life of people (oluwafemi and olubiyi, 2019) towards achievement of the sdgs. space technology through its spin-offs and by-products has made an impact in every aspect of life, from the economic and industrial development to the mini technologies used for terrestrial applications. space technology has helped in the improvement of information and communications technology, infrastructure, agriculture, education, all these being the basic factors for a sustainable development (oluwafemi and olubiyi, 2019). space technology applications play a key role in understanding global water cycles, mapping water courses, and monitoring and mitigating the effects of floods and droughts (unoosa, 2019). satellites provide researchers and policy-makers with vital information about the earth’s water system, enabling the prevention or preparedness to response or post-recovery through monitoring, prediction, modelling and implementation of mitigation and adaptation measures (oluwafemi and olubiyi, 2018a). remote sensing and gis technology, amongst many other space technologies offer effective and meaningful solutions to the problem of analysis and integration of large volume of data for water quality measurement. the satellite images acquired using remote sensing technology provides diagnostic signatures on specific parameters of need such as an indicator of water. using these signatures, all the needed parameters can be studied and mapped accurately. the synoptic view of the image derived from remote sensing technology due to large area coverage, provides information about the parameters on regional scale (raj et al., 2011). 4.0 specific examples of space technologies for water quality assessment 4.1 adequate water quality measurement after water disaster satellites provide information before and after disaster, as well as ensures timely response to emergencies such as flood, drought, tsunami and hurricane (lahne et al., 2015). there is now maximization of access through user-friendly mobile technology which provide timely distribution of satellite data necessary to provide warnings within days and seasonal assessments (lahne et al., 2015). the free web application such as eoapp, enables anyone with a web browser to view various water quality parameters in a selection of sites across the globe (esa, 2015). harinder, (2018) and group of info-electronics systems inc. (ies) montreal, canada have developed a model for an integrated disaster forecasting and management system (idfms). in this model, space-based remote sensing was used for rainfall forecasting, determining accurate digital elevation models (dem), and flood water cover and after-disaster assessment of water quality. 4.2 space technology spin-offs in earth’s market relating to water quality 4.2.1 total organic carbon analyzer total organic carbon analyzer secures safety of water supply. it was developed to monitor the quality of the recycled water supply on-board the international space station (iss). the iss is a laboratory located just outside the earth where experiments are carried out by astronauts. the total organic carbon analyzer is sophisticated with systems to generate solar electricity, recycle nearly all of its own water, and supply oxygen, as the iss is an orbiting model of sustainability. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 105 the technology is now commercialized, providing significant cost savings and improved efficiency for water quality monitoring applications—such as helping ensure the security of the nation’s drinking water on earth (talbert and green, 2012). figure 2 shows total organic carbon analyzer being used on the iss by an astronaut. figure 2: total organic carbon analyzer being used by an astronaut on the iss. image source: talbert and green (2012). 4.2.2 chemscan analyzer chemscan analyzer is used for monitoring water quality in real time. it was originally designed to provide real time detection of nutrient levels in hydroponic solutions for growing plants in space. now it’s used to monitor treatment processes at water and wastewater facilities around the world (talbert and green, 2012). growing plants in space presents unique challenges. using soil may not work due to its weight, the problem of particles floating about in zero gravity, and the potential for harboring healththreatening germs. to address this issue, focus is on developing hydroponic methods of growing plants in space. hydroponics is the practice of growing plants in nutrient solutions, without true soil (talbert and green, 2012). the hydroponic solutions typically contain a variety of elements that are taken up at different rates by different plants and need to be replenished when their concentrations drop below ideal levels. an analyzer that provides real-time detection of nutrients, organics, and metals in water was developed. that technology, called the chemscan analyzer, is now manufactured and marketed. in addition to it monitoring the treatment processes at water and wastewater facilities around the world, it helps maintain water quality. this is because water is rarely found in pure form. water may contain many numbers of contaminants and other chemical and biological constituents that need to be found and removed (talbert and green, 2012). earlier technology would require water samples to be physically extracted from various points along the treatment process and taken to a lab for analysis—a time consuming and laborintensive procedure that left significant gaps between measurements. chemscan’s capabilities allow it to automatically draw and analyze samples for ammonia and other nutrient levels, water hardness, or amounts of natural organic matter. chemscan analyzers require little maintenance or calibration, making them a cost-efficient technology. the sum total of what chemscan provides is a small fraction of the price that would be required to do the same task with other technologies (talbert and green, 2012). figure 3 shows the picture of a chemscan analyzer. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwafemi and olubiyi: space technology applications for water quality in sustainable development. azojete, 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 106 figure 3. chemscan analyzer, image source: talbert and green (2012). 4.3 proposing satellites to map plastics and microplastics in polluted water-bodies recently there have been environmental interests regarding “microplastics”. microplastics are plastics that are microscopic in size, having less than 5mm in diameter, which emerge mainly from the production of personal care products and fragments of larger plastics by mechanical degradation or by uv light. microplastics are dumped indirectly and directly into the oceans and are difficult to separate from other organic particles in the sediment. therefore, microplastics are bioavailable to a range of aquatic organisms (zooplanton) (oluwafemi and olubiyi, 2018b). ecotoxicological and calcification studies has been explored on the effects of microplastics on marine zooplankton as case studies for effect on human health and the results has being threatening. the effects of plastic debris on marine organisms as a result of ingestion include gut blockages, heightened immune response, loss of lipid reserves, disrupting of other normal physiological functions and other uncertain consequences to the health of the organism. microplastic itself can move across the food chain and pose significant public health issues to society. it poses potential risk to food insecurity (oluwafemi and olubiyi, 2018b). space-based technologies, applications and services such as satellite remote sensing through space observations is used for mapping (bagchi and bussa, 2011). there is a proposal that in few years to come, this could be used to study plastic and microplastic related pollutions in the oceans (bouilly, 2014; oluwafemi and olubiyi, 2018b, 2018c) for better water quality for the benefit of humankind and the environment. although, material isolation as a water pollution parameter can be detected using laser spectrometers as a ground-based remote sensing technique for identification of chemical composition of the water (bagchi and bussa, 2011). bouilly (2014) stated that until today, no one has managed to locate the plastic accumulation zones in water from space. 4.4 other examples of the use of satellite technology for water quality monitoring united states landsat satellites and french spot satellites have been commonly used for water related applications, the introduction of synthetic aperture radar (sar) based satellites – especially the ones in the last decade with high resolution and dual polarization – have revolutionized the work in water mapping and management, marine surveillance, ice monitoring, disaster management, environmental monitoring and resource management. dem are being developed to assist in determining water flows and flooding potential. land cover and land usage mapping, wetland mapping, snow extent mapping and water quality monitoring are the other areas where remote sensing is a great tool (harinder, 2018). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 107 the national topographic database of natural resources canada (nrcan) covers more than 10 million square kilometres. the hydrographic information of the database contains more than 60% of the entities to be updated (harinder, 2018). the current manual update of this database by visually comparing the vectors of the canvec database to spot orthoimages is too cumbersome. in 2009, centre de recherche informatique de montréal (crim) issued recommendations to centre for topographic information – sherbrooke (cti-s) and developed a prototype for the automatic updating of water-bodies from spot-5 imagery (crim, 2009). in the second phase, this prototype was improved in order to be integrated in the production process within the cti-s. harinder (2018) and group’s project was executed under an earth observation application development program (eoadp) contract from canadian space agency (csa), implements innovative solutions to exploit the capabilities of radarsat-2 data for the mapping of waterbodies. ies, in collaboration with the crim, has developed a system to improve and update the existing mapping of inland water-bodies as well as find new objects using radarsat-2 data in the context of updating the hydrological information within the canvec database of nrcan. the developed system contains advanced image processing algorithms specifically tuned for optimal performance for an application in water mapping. due to its high resolution and polarimetric data, the use of sar imagery provides a more complete and accurate description of the scene compare to the use of spot imagery. the system is being tested on data provided by the cti-s. the use of open source libraries provides with an extensive set of algorithms some of which are currently not available in commercial software (harinder, 2018). the rs2-chim system is composed of the following subsystems: (1) an image processing subsystem responsible for producing raw updated shapes for each valid water body. (2) a postprocessing subsystem responsible for quality control, simplifications and report generation. (3) a web interface that enables the user to view and consult the results (harinder, 2018). 5.0 final discussions on space technology application for water quality space-based technologies has various advantages related to area coverage, timeliness, and measurement frequency as mentioned, therefore it can be applied fruitfully to the important field of water quality. more-so, the application of satellite technology and space technology spin-offs in water quality monitoring for the achievement of sustainable development cannot be over-emphasized (harinder, 2018). more improvement can be expected even as the new satellites with more precise polarimetric sensors become available along with new application software. although the currently used ones are not doing too badly. next step will be to find some means of doing bottom profiles of water-bodies using remote sensing (bouilly, 2014). bouilly, (2014) also stated that until today, no one has managed to locate the plastic accumulation zones in water from space, as there are many constraints to be considered. the presumed location of plastic, the navigation constraints, the needs of the other scientific components and satellite trajectories are the mentioned constraints. some of the problems to overcome as a result of the deceitful pollution which cannot be easily seen because of the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwafemi and olubiyi: space technology applications for water quality in sustainable development. azojete, 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 108 millimeter length nature, sub-surface floatation and the relatively low concentration. it is hoped that very soon, these constraints will be overcome. so many people think that the space technology is abstract and inaccessible. this is not true as open source libraries of space data can be gotten online (which may be for free or not) for water quality measurement, although these set of algorithms on water quality are currently not available in commercial software (harinder, 2018). there will be a need to be trained to interpret remote sensing images, as they are raw data. satellite images can be processed on powerful personal computers and relatively simple and low-cost software packages. being trained to be able to interpret remote sensing images will be a very good step for the water professionals and people in need as they could get some free useful images from the internet on specific water quality monitoring. (oluwafemi and olubiyi, 2018a). 6.0 conclusion space-based technology indeed needs to be looked into more as a solution to the world’s water quality monitoring as it gives us solution on a global scale. this targets the three pillars of sustainability: economic development; environmental protection; and social equity. this is in-line with the goal 6: clean water and sanitation sdg of the united-nations. references bagchi, d. and bussa, r. 2011. application of remote sensing in water quality and water resources management – an overview. bhujal news quarterly journal, 5(3): 244-254. https://hindi.indiawaterportal.org/node/53244 accessed on 10 december, 2018. bartram, j. and balance, r. 1996. water quality monitoring. a practical guide to the design and implementation of freshwater quality studies and monitoring programme. united-nations environment programme (unep) and world health organization (who) chapman and hall, london. isbn 0-419-21730-4. 383pp. bouilly a. 2014. plastic pollution in the oceans studied on the basis of satellite data. 2014 international workshop on environment and alternative energy. theme: increasing space mission resiliency through sustainability. kennedy space center, florida, usa. esa cci. 2019. global water bodies. land cover product. land cover website. https://www.esalandcover-cci.org/?q=node/184 accessed on 20 february, 2019. esa. 2015. worldwide water quality app hits the web. http://m.esa.int/our_activities/observing_the_earth/copernicus/worldwide_water_quality_app_hi ts_the_web accessed on 23 august, 2018. esa. 2018. space advances water resources management on earth https://m.esa.int/our_activities/preparing_for_the_future/space_for_earth/space_advances_water _resources_management_on_earth accessed on 23 august, 2018. harinder, ps. 2018. application of space-based remote sensing to water management. infoelectronics systems inc. montreal, canada. pp. 3. lahne, m., blake, as., robyn, nc. and darryl, jk. 2015. a space satellite perspective to monitor water quality using your mobile phone. habs and u.s. epa’s office of research and development pathfinder innovation project ii (pip2). summer / nalms.lakeline. pp 28-31. https://hindi.indiawaterportal.org/node/53244 https://www.esa-landcover-cci.org/?q=node/184 https://www.esa-landcover-cci.org/?q=node/184 http://m.esa.int/our_activities/observing_the_earth/copernicus/worldwide_water_quality_app_hits_the_web http://m.esa.int/our_activities/observing_the_earth/copernicus/worldwide_water_quality_app_hits_the_web https://m.esa.int/our_activities/preparing_for_the_future/space_for_earth/space_advances_water_resources_management_on_earth https://m.esa.int/our_activities/preparing_for_the_future/space_for_earth/space_advances_water_resources_management_on_earth http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):100-109. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 109 noaa. 2018. what is water quality? florida keys national marine sanctuary. https://floridakeys.noaa.gov/ocean/waterquality.html accessed on 23 august, 2018. oluwafemi, fa. and olubiyi, ra. 2018a. remote sensing for agricultural water management in developing nations. lap lambert academic publishing, saarbrucken, germany, isbn-13: 978613-9-90747-2. pp42. oluwafemi, fa. and olubiyi, ra. 2018b. microplastics as environmental stressor and threat to human and sea life. proceeding of united-nations / pakistan conference on space technology for water management, islamabad, pakistan, 26 february to 2 march, 2018, pp13-25. oluwafemi, fa. and olubiyi, ra. 2018c. space technologies application micros studies in global health for sustainable development: microgravity, microplastics, microbiology. proceedings of united nations / germany high level forum: the way forward after unispace+50 and on space2030, bonn, germany, 13-16 november, 2018, pp58. oluwafemi, f. and olubiyi, r. 2019. gis and remote sensing for water sectors in developing nations. lap lambert academic publishing, saarbrucken, germany, isbn-13: 978-613-9-45816-5. pp47. oluwafemi, fa. 2019. space science and technology in economic prosperity. lap lambert academic publishing, saarbrucken, germany isbn-13: 978-613-9-97995-0. pp42. raj, kbg., chauhan, ps., subramanian, sk. 2011. application of remote sensing and geographic information system in groundwater resource management: a case study from ladakh, jammu & kashmir. bhu-jal news quarterly journal, 25(3&4): 1-4. talbert, t. and green, m. 2012. nasa. pure innovation. https://www.nasa.gov/offices/oct/home/tech_life_asa_analytics.html accessed on 20 february, 2019. united-nations. 2015a. about the sustainable development goals. https://www.un.org/sustainabledevelopment/sustainable-developmet-goals/ accessed on 20 february, 2019. united-nations. 2015b. transforming our world: the 2030 agenda for sustainable development. a/res/70/1. https://www.preventionweb.net/publications/view/45418 accessed on 20 february, 2019. united-nations. 2019. sustainable development goals. the sustainable development goals are a un initiative. retrieved from https://en.wikipedia.org/w/index.php? title=sustainable_development_goals&oldid=8940 52789 accessed on 20 february, 2019. unoosa. 2019. united nations office for outer space affairs. space for water http://www.unoosa.org/oosa/en/ourwork/topics/space-for-water.html accessed on 20 february, 2019 https://floridakeys.noaa.gov/ocean/waterquality.html https://www.nasa.gov/offices/oct/home/tech_life_asa_analytics.html https://www.un.org/sustainabledevelopment/sustainable-developmet-goals/ https://www.preventionweb.net/publications/view/45418 https://en.wikipedia.org/w/index.php?%20title=sustainable_development_goals&oldid=8940%2052789 https://en.wikipedia.org/w/index.php?%20title=sustainable_development_goals&oldid=8940%2052789 http://www.unoosa.org/oosa/en/ourwork/topics/space-forfile:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):837-846 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 837 original research article evaluation of energy consumption and carbon dioxide emission from a solar / gas powered absorption air conditioning system in zaria t. o. ahmadu (department of mechanical engineering, faculty of engineering, ahmadu bello university, zaria, nigeria) * corresponding author’s email address: talibahmadu@gmail.com 1.0 introduction the energy demand for refrigeration and air conditioning has increased over the years especially in developing countries. this is attributed to increasing need to prevent food spoilage as well as increasing indoor comfort demands (kalkan et al., 2012). usually, electrically powered vapour compression systems are used in refrigeration and air conditioning units. however, these vapour compression systems consume high electric power, which leads to high electricity bills (henning, 2007). also, these units operate with synthetic refrigerants such as hydro – chlorofluorocarbons (hcfcs) which when released into the atmosphere constitute high ozone depleting potential (odp) (sarbu and sebarchievici, 2015). hcfcs are also known to exhibit high global warming potential (gwp) of up to 2000 times that of carbon dioxide (co2), which has a gwp of 1 (nair-bedouelle et al., 2014). as agreed in the montreal protocol, the schedule for the phase out of production and consumption of hcfcs in developing nations is: 2015: reduction of hcfc consumption by 10%, 2020: reduction of hcfc consumption by 35%, 2025: reduction of article information abstract electrically powered vapour compression chillers consume high power and make use of synthetic refrigerants which when released have negative effect on the environment. in this study, the energy consumption and carbon dioxide (co2) emission from an absorption air conditioning system were evaluated. the experimental scale absorption air conditioning system has its thermal energy requirement supplied by the solar collector system and liquefied petroleum gas. the air conditioning system was operated for ten experimental days, in both solar and gas heating modes. daily power consumption by the system was measured. the daily co2 emitted by the system was evaluated using the daily gas consumption. these were compared to electric power consumption and co2 emission from conventional chillers of varying energy efficiency ratio (eer). results showed that the absorption cooling system has reduced power consumption in the range of 31.5% to 64.2% as compared to conventional vapour compression chiller of varying eer. also, co2 emission was seen to have been reduced. this reduction was within the range of 13.3% to 43.2% when compared to that from conventional vapour compression chiller of low to average eer. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 september, 2018 revised 21 january, 2019 accepted 28 january, 2019 keywords: absorption cooling energy carbon dioxide refrigerant energy efficiency ratio mailto:talibahmadu@gmail.com http://www.azojete.com.ng ahmadu: evaluation of energy consumption and carbon dioxide emission from a solar / gas powered absorption air conditioning system in zaria. azojete, 15(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 838 hcfc consumption by 67.5%, 2030: total phase out (nair-bedouelle et al., 2014). with the phase out of hcfcs under the montreal protocol on substances that deplete the ozone layer, the introduction of alternatives with not only zero odp but also low gwp and improved energy efficiency is becoming an issue of increasing importance, especially in developing countries (nair-bedouelle et al., 2014). most vapour compression systems commonly use chlorofluorocarbons (cfcs) and hydro – chlorofluorocarbons (hcfcs) refrigerants, which cause depletion in the ozone layer. the replacements, which are hydrofluorocarbons (hfcs) have zero odp, but high gwp (benhadid – dib, 2012). a number of other available refrigerants that could serve as replacements have properties that prevent them from being unconditionally adopted (nair-bedouelle et al., 2014). thermally driven absorption air conditioning systems have the ability of working with low grade energy such as waste heat or solar energy. they consume low electric power and have the ability to work with refrigerants with no harmful effect on the environment, such as water (henning, 2007). water, when used as a refrigerant has zero odp (benhadid – dib, 2012). it is expected that the absorption air conditioning system can serve the purpose of providing cooling with less harmful emissions to the environment and achieve high energy efficiency. in this regard, several researchers have carried out works on absorption air conditioning in recent years. balghouthi et al., (2012) using a solar absorption air conditioning facility of 16 kw capacity located in tunisia, achieved solar fraction between 0.54 to 0.77. also, the facility was able to avoid co2 of about 3000 kg from being emitted into the atmosphere during the cooling season. al – alili et al. (2012), in abu dhabi, using a 10 kw nh3/h20 solar absorption air conditioning system consumed 47% less electrical energy, with 12 metric tonnes/ year of co2 emission reduction. rosiek and batlles (2012), in spain, using a 70 kw absorption chiller reduced the electricity consumption by 31% and led to a co2 savings of 833kg. sun et al. (2015) experimented on a solar and gas fired absorption system for cooling and heating in china. a 49.7% energy savings ratio was achieved. zhai et al. (2015) experimented on a mini type solar absorption air conditioning system of 8 kw capacity in china. the system was found to consume 27% less power than a conventional chiller of same capacity. this study is aimed at reducing the power consumption and co2 emission associated with the use of conventional vapour compression chillers, as well as experiment the use of water as refrigerant. this was carried out by evaluating the power consumption as well as co2 emission from an experimental scale solar/ gas hybrid absorption air conditioning system of 3 kw cooling capacity, operating under zaria weather conditions. the power consumption and co2 emission were compared to those of conventional chiller of varying energy efficiency ratio (eer) which uses conventional refrigerants. 2.0 materials and methods tests were conducted on an experimental scale solar/ gas hybrid powered absorption air conditioning system, developed at the department of mechanical engineering, ahmadu bello university, zaria, nigeria. 2.1 materials the entire fabricated system consists of: an absorption chiller: this is of 3 kw cooling capacity, which works on the lithium bromide water pair, where water serves as the refrigerant. a solar collector: this uses solar radiation to generate the thermal energy required for the hot water. a http://www.azojete.com.ng mailto:talibahmadu@gmail.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 839 gas burner: this is powered by liquefied petroleum gas and provides thermal energy required in cases of low solar radiation. a storage tank: this is used to store the hot water. a wet cooling tower: waste heat is rejected from the absorption chiller to the cooling tower. an indoor fan coil unit: this is used to distribute cooled air to the test room. the following instruments were used in taking measurements during the experiment: i. digital solar power meter: model no.: dbtu 1300, measuring range: 0 – 2000 w/m2, accuracy: ± 5% of reading ii. digital thermocouple thermometer: model no.: t407291, measuring range: -50 – 1300°c, accuracy: 0.1%+1°c iv. watt meter: model no.: h3680w, measuring range: 0 – 3680w, accuracy class: 1.0 v. digital weighing scale: model no.: sf – 400, measuring range: 0 – 7000g, accuracy: ± 1g 2.2 method 2.2.1 experimental procedure tests were conducted on selected days in the months of april and june 2017. each day spanned from 9:00 am to 5:30 pm. the experimental procedure employed is similar to that of balghouthi et al. (2012). two heating modes were employed to provide the thermal energy required to generate the hot water at the hot water tank: the solar power heating mode, provided via the solar collector and the gas burner heating mode, provided by liquefied petroleum gas burner. the hot water is required to desorb the refrigerant (water) from the lithium bromide solution in the absorption chiller. at the start-up of each experimental day, thermal energy was supplied to the water in the tank using the gas burner. this was because solar radiation is usually very low at the early hours of the day to attain heating to required water temperature. when the required temperature in the tank was attained (90°c – 99°c), the hot water pump was then turned on to circulate the hot water between the tank and the absorption chiller. when the temperature of the collector fluid increased to 80°c and above, the gas burner was disengaged, and the system was switched to solar heating mode. when temperature of the collector fluid drops below 80°c, the system was switched back to gas burner heating mode. chilled water was produced at the evaporator in the absorption chiller and pumped using the chilled water pump to the fan coil unit in the test room which covers a total floor area of 9.21m2. heat generated at the absorption chiller was rejected to the cooling tower. temperature readings were taken every fifteen minutes from sensors attached to the system components and test room. solar power was measured using a solar meter. gas consumed was measured by placing the gas burner on a weighing scale and taking measurements as a result of weight loss at intervals. power consumption by the absorption chiller was measured using a watt meter. figure 1 shows a schematic of the experimental set up. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:talibahmadu@gmail.com ahmadu: evaluation of energy consumption and carbon dioxide emission from a solar / gas powered absorption air conditioning system in zaria. azojete, 15(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 840 figure 1: schematic of the experimental set up the experimental days in which the experiments were conducted were chosen so as to reflect varying weather conditions. this was done so as to test the performance of the system under varying weather conditions. accordingly, the experimental days were classified as follows: hot clear sky day: days with very clear sky, high solar radiation, no rain. fairly clear sky day: days with intermittently clear sky and partly cloudy sky, average solar radiation, no rain. cloudy sky day: days with very cloudy sky, low solar radiation, no rain. rainy day: days in which rain occurred within any interval of the experimental day. figures 2 and 3 show components of the experimental absorption air conditioning system and section of the absorption chiller respectively. figure 2: outdoor components: solar collector, figure 3: section of the absorption chiller hot water tank, gas burner, cooling tower 2.2.2 evaluating solar fraction the solar fraction was calculated as a ratio of the number of hours of the day in which the system was powered in the solar heating mode to the total hours of operation of the day. http://www.azojete.com.ng mailto:talibahmadu@gmail.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 841 2.2.3 measuring gas consumption the weight of gas consumed at an interval of time was determined by weight difference over the time interval using a digital weighing scale. the gas consumption in kw(pgas) was computed using equation 1 as: pgas = mcalg t (1) where: m is the weight of the gas consumed in the time interval (kg) calg is the calorific value of liquefied petroleum gas taken as 46.1mj/kg (demirel, 2012) t is the time interval (seconds) for which the gas was used. the gas consumption in kwh was obtained by multiplying the gas consumed in kw by the period in which the system was operated in gas burner heating mode (hours). 2.2.4 evaluating co2 emission according to balghouthi et al., (2012), 680g of co2 are emitted into the atmosphere for every kwh of electricity produced by fossil fuel fired power plant. that is 0.68 kg co2 emitted/kwh electricity produced. also 0.2 kg of co2 is emitted into the atmosphere for every kwh of lpg gas consumed. that is 0.2 kg co2 emitted/kwh lpg gas consumed. the mass of co2 emitted to the atmosphere on using conventional chiller was computed according to balghouthi et al., (2012) using equation 2 as: co2(c) = power consumed(c) kw × hours of operation h × no. of days × fe( kg kwh) (2) the mass of co2 emitted to the atmosphere on using the experimental absorption cooling plant was computed using equation 3 as: co2(a) = power consumed(a) kw × hours of operation h × no. of days × fe kg kwh + (fg kg kwh × gas consumed kwh ) (3) where: fe is a conversion factor for co2 emitted using fossil fuel (0.68 kg co2/kwh) fg is a conversion factor for co2 emitted burning lpg gas (0.2 kg co2/kwh) power consumed a (kw) is the measured power consumption of the absorption cooling plant which was 0.5 kw. this comprises the power consumption of the pumps and fan. power consumed c (kw) is the power consumption by conventional vapour compression chiller of varying energy efficiency ratio (eer), calculated using equation 4: power consumedc(kw) = cooling output eer (4) the energy efficiency ratio (eer) is the ratio of cooling output from the chiller to the power consumed by the chiller. average allowable eer specifications for conventional vapour compression chillers manufactured in different countries according to phadke et al. (2014), was used. consequently, the power consumption for conventional vapour compression chillers file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:talibahmadu@gmail.com ahmadu: evaluation of energy consumption and carbon dioxide emission from a solar / gas powered absorption air conditioning system in zaria. azojete, 15(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 842 resulting from the different eers was computed for a 3 kw cooling capacity chiller using equation 4. for the whole experimental days, the absorption cooling plant was able to achieve an average cooling power of 1.5 kw, while an average space cooling temperature of 24°c was attained. 2.2.5 electric power consumed by the absorption cooling system (kwh) this was obtained by multiplying the power consumed by the absorption cooling system (kw) by the hours of operation (h). the system was operated for eight hours in each of the experimental days. 3. results and discussion in this section, results from the evaluation of energy consumption and co2 emission by the absorption cooling system are presented. comparison is made between the absorption system and conventional vapour compression system in terms of energy consumption and co2 emission. following the classification of the experimental days done in section 2.2.1, accordingly, the days were classified as follows: hot clear sky: april 22, june 6, 2017 faily clear sky: june 3, june 8, 2017 cloudy sky: june 12, june 18, june 19, 2017 rainy day: june 7, june 13, june 17, 2017 table 1 shows the average solar radiation, solar fraction and hours of electricity consumption for the experimental days. table 1: average solar radiation, solar fraction and hours of electicity consumption for experimental days apr-22 jun-03 jun-06 jun-07 jun-08 jun-12 jun-13 jun-17 jun-18 jun-19 av. solar radiation (w/m2) 967 751 918 95 785 574 206 158 568 513 solar fraction 0.6 0.34 0.51 0 0.27 0 0 0 0 0 hours of electricity consumption 8 8 8 3 8 8 5 4 8 8 the solar fraction is the fraction of thermal energy requirement for the day that was supplied by the solar collector. from table 1, it can be observed that the days of april 22 and june 6 which were classified as hot clear sky days recorded average solar fractions above 900 w/m2. this resulted in the relatively higher solar fractions of 0.6 and 0.51 recorded respectively on these days. solar fractions of 0.34 and 0.27 were also recorded on june 3 and 8 respectively, which were classified as fairly clear sky days. the other days recorded no solar fraction as a result of the very cloudy or rainy nature of the days. from the table, it can be seen that the hours of http://www.azojete.com.ng mailto:talibahmadu@gmail.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 843 electricity consumption for five of the experimental days is eight hours. however, the days of june 7, 13 and 17 which were classified as rainy days all have lower hours of electricity consumption. this is because, during the hours in which the rain lasted, there was no cooling demand from the test room as the room was naturally cooled. the chiller was therefore shut down during these hours, thus there was no electricity consumption. figure 4 shows the energy consumption for the experimental days. it can be observed that the electricity consumption was regular at 4.0 kwh for the experimental days, except for the rainy days of june 7, 13 and 17 which had lower electricity consumption. this was because the chiller was run for fewer hours on the rainy days as seen earlier from table 1. also, the gas consumption can be seen to be lowest at 4.09 kwh on april 22. this was due to the high solar radiation which resulted in high solar fraction, as seen earlier from table 1. the cloudy days of june 12, 18 and 19 can be observed to have the highest gas consumption of 12.3 kwh. this was because the solar radiation was too low and the system thermal energy had to be provided by the gas burner throughout these days. figure 4: energy consumption of the absorption chiller for the experimental days figure 5 shows the co2 emitted from the absorption cooling system for the experimental days. from the figure, it can be observed that the rainy days of june 7, 13 and 17 had the lowest co2 emissions of 2.07, 3.4 and 2.5 kg respectively. this was because the system was run for fewer hours on gas burner mode in these days. also, the electricity consumption on these days was very low, thereby reducing the electricity component of co2 emission. the hot clear sky days of april 22 and june 6 also recorded relatively low co2 emissions of 3.5 and 3.7 kg respectively. this was due to high solar radiation availability which resulted in lower gas consumption. the cloudy sky days of june 12, 18 and 19 recorded the highest co2 emissions of 5.1 kg each. this was because gas was consumed throughout these days to provide the required thermal energy. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:talibahmadu@gmail.com ahmadu: evaluation of energy consumption and carbon dioxide emission from a solar / gas powered absorption air conditioning system in zaria. azojete, 15(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 844 figure 5: co2 emitted by the absorption cooling system for the experimental days. figure 6 compares the power consumption by the absorption cooling system with the power consumption by conventional vapour compression chillers of varying eer. from the figure it is observed that the absorption system consumes power of 0.5 kw. this is much lower than the power consumed by the conventional chillers shown in the figure. while the chiller with eer of 2.14 consumes 1.4 kw, the chiller with eer of 3.16 consumes 0.9 kw and the chiller with eer of 4.1 consumes 0.73 kw. this implies the absorption cooling system has reduced power consumption in the range of 31.5% to 64.2% as compared to conventional vapour compression chiller of varying eer. similar reduction in power consumption by absorption cooling system have been reported in the works of alili et al. (2012) and zhai et al. (2015). figure 6: comparison of power consumption by the absorption cooling system with that consumed by conventional vapour compression chiller of varying eer http://www.azojete.com.ng mailto:talibahmadu@gmail.com arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 823-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 845 figure 7 compares the co2 emissions from the absorption cooling system with the co2 emissions from conventional vapour compression chiller of varying eer for the ten experimental days. it is seen that the absorption cooling system had a total co2 emission of 38.6 kg for the ten experimental days. this is observed to be lower than the co2 emissions from corresponding number of days from the chillers with low to average eer of 2.14, 2.75 2.92 and 3.16, which had co2 emissions of 68 kg, 53 kg, 50 kg and 44.5 kg respectively. it is observed to have about the same co2 emission with the chiller of high eer of 3.7 which had co2 emission of 39 kg. the co2 emission from the absorption chiller was however higher than that from the chiller with very high eer of 4.1, which had co2 emission of 36 kg. this could be attributed to the high gas consumption especially on cloudy days. this implies the absorption cooling system has co2 emission reduction within the range of 13.3% to 43.2% when compared to co2 emission from conventional vapour compression chiller of low to average eer. this is in agreement with co2 emission reduction by absorption cooling system as reported in the works of balghouthi et al. (2012) and rosiek and batlles (2012). however, it has about the same co2 emission when compared to conventional vapour compression chiller with high eer. while the co2 emission from the absorption cooling system is higher than that from conventional vapour compression chiller of very high eer by 7.2%. figure 7: comparison of co2 emission by absorption cooling system to co2 emission by conventional chiller of varying eers 4. conclusion electric power consumption, gas consumption and co2 emission from a solar/ gas powered absorption air conditioning system has been evaluated. results from the ten experimental days showed the least gas consumption occurred on days with high solar fraction while the highest gas consumption occurred on days with very low or zero solar fraction. the absorption cooling system had reduced power consumption in the range of 31.5% to 64.2% as compared to conventional vapour compression chiller of varying eer. also, co2 emission reduction within the range of 13.3% to 43.2% when compared to co2 emission from conventional vapour compression chiller of low to average eer were seen. co2 emission from the system was not significantly lower when compared to conventional vapour compression chiller with high eer and becomes higher when compared to that from chiller with very high eer. this implies the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:talibahmadu@gmail.com ahmadu: evaluation of energy consumption and carbon dioxide emission from a solar / gas powered absorption air conditioning system in zaria. azojete, 15(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: talibahmadu@gmail.com 846 absorption cooling system offers the possibility of reduced electricity consumption, however, improvements to bring about reduced gas consumption which translates to further reduction in co2 emission are required. references al – alili, a., islam, md., kubo, i., hwang, y. and radermacher, r. 2012. modelling of a solar powered absorption cycle for abu – dhabi. applied energy, 93: 160 – 167. balghouthi, m., chahbani, mh. and guizani, a. 2012. investigation of a solar cooling installation in tunisia. applied energy, 98(c): 138 – 148. benhadid – dib, s. and benzaoui, a. 2012. refrigerants and their environmental impact substitution of hydro chlorofluorocarbon hcfc and hfc hydro fluorocarbon. search for an adequate refrigerant. energy procedia, 18: 807 – 816. demirel, y. 2012. energy, green energy and technology. springer – verlag, london ltd. accessed from www.springer.com/cda/content on 17th july, 2018. henning, h. 2007. solar assisted air – conditioning of buildings, an overview. applied thermal engineering, 27(10): 1734 – 1749. kalkan, n., young, ea. and celiktas, a. 2012. solar thermal air conditioning technology reducing the foot print of solar thermal air conditioning. renewable and sustainable energy reviews, 16(8): 6352 – 6383. nair-bedouelle, s., clark, e., masickova, j. and ruperto, j. 2014. international standards in refrigeration and air conditioning: an introduction to their role in the context of the hcfc phase – out in developing countries. document of the united nations environment programme. accessed from www.unep.fr/ozonaction/information on 25th july, 2018. phadke, a., abhyankar, n. and shah, n. 2014. avoiding 100 new power plants by increasing efficiency of room air conditioners in india. opportunities and challenges. lawrence berkeley national laboratory, berkeley, u.s.a. accessed from: www.cseindia.org on 25th july 2018. rosiek, s. and batlles, fj. 2012. shallow geothermal energy applied to a solar assisted air conditioning system in southern spain: two year experience. applied energy, 100(c): 267 – 276. sarbu, i. and sebarchievici, c. 2015. general review of solar powered close sorption refrigeration systems. energy conversion and management, 105: 403 – 442. sun, h., xu, zy., wang, h. and wang, r. 2015. a solar/gas fired absorption system for cooling and heating in a commercial building. energy procedia, 70: 518 – 528. zhai, x., li, y., cheng, x. and wang, r. 2015. experimental investigation on a solar powered absorption radiant cooling system. energy procedia, 70: 552 – 559 http://www.springer.com/cda/content http://www.unep.fr/ozonaction/information http://www.cseindia.org http://www.azojete.com.ng mailto:talibahmadu@gmail.com arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):958-972 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 958 original research article production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves k. mu’azu1*, g. abubakar1, a. s. akuso1, a. mahmood2, i. g. sadiq2 and b. inuwa (1department of pilot plants and fabrication technology, 2department of industrial and environmental pollution, national research institute for chemical technology, zaria, nigeria) * corresponding author’s email address: kabirumuazu@yahoo.co.uk 1.0 introduction essential oils are volatile, natural base products, which are found in spices, aromatic and medicinal plants. the extraction of essential oils is well known from old ages when pure essential oil and crude extract of essential oil bearing plants, herbs and grasses were in use for various medicinal and fragrances, flavors, preservatives and insect repellants purposes (weiss, 1997; panda, 2000). article information abstract in this study, essential oil was extracted from eucalyptus citriodora leaves plant species (lemon-scented gum) in a pilot plant using steam distillation technology. the extraction pattern of the oil was monitored over time and economic analysis of the production was carried out. five batches were carried out in a day and the results revealed that the daily production of the oil was 0.579 liters in a loading capacity of 100kg of leaves. it was also observed that the total production cycle per batch was 1.96 hours out of which 80 minutes were the actual extraction time with lag period of 37 minutes. the results further revealed that 66.7% of the oil was extracted in 40 minutes while 95.6% in 80 minutes. liquefied petroleum gas (lpg) was used as source of energy with daily consumption of 7.5 kg at a cost of n2,400.00k. the economic analysis on annual basis revealed that the operating cost was n1,742,400.00k. the production output of the oil was estimated at 138.96 litres with expected selling price of n4,863,600.00k at the rate of n35,000.00k per litre and expected profit after tax of n2,115,871.00k. from this economic analysis carried out based on the practical data generated in the pilot plant, this project is highly profitable and is strongly recommended to potential investors and entrepreneurs. this will help in providing jobs for our teaming unemployed youths mostly in rural areas where these raw materials are in abundant thereby increasing nation’s foreign earning due to its export potential. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 november, 2018 revised 15 june, 2019 accepted 20 june, 2019 keywords: eucalyptus citriodora leaves essential oil steam distillation economic analysis and oil yield . mailto:kabirumuazu@yahoo.co.uk http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 959 eucalyptus plant is mainly grown in tropical and sub-tropical regions because of its resistance to many pest and adaptability to various climatic conditions. these include south africa, china, congo republic, angola, india and west africa. the plant has up to 700 species and can grow as high as 40 m tall in an altitude of 600m. the principal component of the essential oil extracted from eucalyptus citriodora leave is cineola which is up to 70 80%. the oil is mainly used in medicinal, industrial and perfumery applications. the yield of essential oil is naturally constrained (usually less than 2%) but with high market value. (unido, 1983). many research works have been published on extraction of essential oil from eucalyptus citriodora leave mostly at laboratory stage without economics of its production (seid et al., 2014; deepak et al., 2013; manika, et al., 2012). mu’azu et al. (2009) reported economics of essential oil production using eucalyptus citriodora leaves at pilot plant. however, data used in the study were not optimized and kerosene was used as fuel. scanty information is available in the literature regarding the detailed economic study on the production of essential oil from eucalyptus citriodora leaves at pilot scale level using steam distillation technology and liquefied petroleum gas (lpg) as source of energy. it must be noted that energy cost accounts for about 70% of the production cost. against this background, a study was therefore planned from practical approach to determine the actual daily production of the essential oil, production costs and profit margin in a pilot plant. this information can serve as an important resource in attracting investors to the essential oil industry and exploring its commercial utilization. 2. materials and methods the block diagram and flow sheet for the extraction process of essential oil from eucalyptus leaves using steam distillation method were developed and shown in figures 1 and 2 respectively. figure 1: block diagram for the steam extraction of essential oil from eucalyptus leaves cooling water in steam pre-treatment unit essential oil extractor condenser drying unit oil separator spent leaves fresh leave cooling water outsteam and essential oil vapor warm water essential dried essential foreign materials lealealeaves eucalyptus leave file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 960 figure 2: flow sheet for the steam extraction of essential oil from eucalyptus leaves key: a-boiler b-extractor c-storage water tank d-condenser e-storage water tank f-oil separator g-water pump 2.1 material procurement and preparation fresh eucalyptus leaves shown in figure 3 were obtained from national research institute for chemical technology (narict) plantation in zaria, nigeria. prior to commencement of the extraction process the unwanted materials found in the leaves were removed and 20kg of the leaves were weighed for a batch operation. figure 3: eucalyptus citriodora leaves e http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 961 2.2 description of the essential oil extraction plant the extraction of essential oil was done using water as solvent in the form of steam in a steam distillation pilot plant. the pilot plant consists mainly of oil extractor, steam boiler, condenser, gas-fired burner and oil separator as shown in figure 4. figure 4: steam distillation pilot plant for extracting essential oil from eucalyptus leaves the oil extractor and condenser were fabricated using grade 304 stainless steel while the oil separator was transparent glass. the boiler section is located at the bottom of the oil extraction chamber and separated by a stainless steel weir mesh. the gas-fired burner was connected to a 12.5 kg gas cylinder with a rubber hose and placed directly under the oil extractor. the connections were adequately checked to avoid gas leakages. the cooling water at 25°c from the overhead tank was allowed to run into the condenser at the rate of 1.67x10-3 m3/min and discharged at 40 °c. this was done to aid easy condensation of the steam and oil mixture vapour at 100 °c to liquid. a detail of these equipment specifications is shown in table 1. table 1: summary of process unit specifications process unit specification extractor material of construction stainless steel height 1.65 m diameter 0.45 m thickness 0.003 m boiler capacity 0.0075 m3/hour key a=essential oil extractor b=boiler c=condenser d=cooling water tank e=oil collector f=steam and oil line g=cooling water line file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 962 condenser type of condenser shell and tube material of construction of shell mild steel material of construction of tube stainless steel number of passes in the tube 2 number of pass in the shell 1 tube length 1.2 m tube outside diameter 0.02 m tube inside diameter 0.016 m number of tubes 16 number of tubes per pass 8 shell internal diameter 0.385 m number of baffles 3 baffles spacing 0.3 m baffles cut 15% baffle pitch square tube side fluid steam and oil shell side fluid cooling water oil separator capacity 0.0005 m3 shape conical flow rate 0.00025 m3/min 2.3 methods twenty five (25) litres of water and 20kg (w1) of fresh eucalyptus leaves were charged into the essential oil extractor (a) shown in figure 4. the gas line was opened and the burner was ignited and time of ignition was recorded. the burner fueltoair ratio was adjusted until blue flame was obtained implying steady energy supply. after 24 minutes of burner ignition (induction period), steam and oil mixture began to drop in the oil separator (e) at 40°c as condensate. the oil was then separated from the warm water using separating flask and measured in a cylinder after every 10 minutes for a period of 100 minutes. the cumulative oil collected was dried using 150g of anhydrous sodium sulphate (na2so4) and allowed to stand for overnight (12 hours) followed by filtration to remove moisture and suspended impurities associated with the oil as shown in figure 5. the same procedures were repeated for subsequent batches with addition of 10 litres of the warm water collected into the boiler as make-up water to maintain minimum of 20 litres at any time. in each case the weight of the dried oil was recorded (w2) and oil yield was calculated using equation (1). oil yield = w2 w1 x 100 (1) http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 963 figure 5: essential oil extracted 2.3.1 material balance the material balance was carried out on the process units based on the plant throughput of 115.84ml (1.1584 x 10-1 kg) of essential oil per batch, leaves input of 20 kg, extraction time of 100 minutes, water requirement of 15 liters (15kg) and steam production of 8.894 kg. thus, for a steady state batch process without chemical reaction, the material balance is given by equation (2) and was applied to all the process units starting with oil extractor as shown in figure 6. figure 6: material balance over oil extractor in the condenser unit steam oil mixture passes through the tube side while cooling water in the shell and the material balance is presented in figure 7. figure 7: material balance over oil condenser mixture of hot water and essential oil from the condenser were fed into the oil separator and the material balance is presented in figure 8 oil extractor steam (s), 1.482 x 10-3kg/s oil (o), 1.930 x 10-5kg/s unused water (uw), 1.018 x 10-3kg/s leaves (l), 3.333 x 10-3kg/s water (w), 2.500 x 10-3kg/s spent leaves (sl), 3.310 x 10-3kg/s oil (o), 1.930 x 10-5kg/s oil (o), 1.930 x 10-5kg/s condenser hot water (hw), 1.482 x 10-3kg/s cooling water (cw1), 2.783 x 10-4kg/s steam (s), 1.482x 10-3kg/s cooling water (cw2), 2.783 x 10-4kg/s file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 964 figure 8: material balance over oil separator the material balance on the drying unit is presented in figure 9. figure 9: material balance over drying unit 2.4 energy utilization the quantity of gas (g) utilized in kg for every batch operation was calculated by taking the respective difference between the initial weight of gas cylinder (w3) and its final weight (w4) after each production cycle as given in equation (3). (3) the energy utilization, q (in mj) per batch was thereafter obtained from equation (4). where g is the quantity of gas consumed (kg) and cv is the calorific value of gas in mj/kg and has the value of 46.1 mj/kg for lpg. 2.4.1 energy balance over oil extractor in figure 6, for a batch process without chemical reaction, the energy balance is given as qsupplied = qwater + qevap +qoil + qleave + qtank + qlost (5) qsupplied = 11,525j/s as given in equation (4). heat gained by water in the boiler (qwater) = mwcwδtw, mw = 2.500 x 10-3 kg/s, cw = 4.200 x 103 j/kg°c, δtw = 75°c, implying that qwater= 787.5 j/s. heat needed to evaporate water in the boiler (qevap) = msl, ms = 1.482 x 10-3kg/s, l = 2.260 x 106 j/kg, implying that qevap = 3350.1 j/s. heat gained by oil in the leaves (qoil) = moilcoilδtoil, moil = 1.930 x 10-5kg/s, coil = 2.6 x 10-3 j/kg°c, δtoil = 75°c, implying that qoil = 3.765 x 10-6 j/s. heat gained by the leaves (qleave)=mlclδtl, ml = 3.310 x 10-3 kg/s, oil separator hot water (hw2), 1.475 x 10-3kg/s oil (o2), 2.671x 10-5kg/s hot water (hw1), 1.482 x 10-3kg/s oil (o1), 1.930 x 10-5kg/s drying unit drying agent (d2), 2.50 x 10-5kg/s oil (o2), 1.930 x 10-5kg/s drying agent (d), 2.50x 10-5kg/s oil (o1), 2.671 x 10-5kg/s water (w), 7.410 x 10-6kg/s http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 965 cl= 0.5 x cwood = 9.414 x 102 j/kg°c, δtl = 75°c, implying that ql = 233.987 j/s. heat lost to the surrounding (qlost) = 20% of qsupplied = 2,305 j/s from equation (5), heat gained by oil extractor (qtank) = qsupplied qwater qevap qoil qleave qlost, implying that qtank = 4,848.41 j/s 2.4.2 energy balance over condenser in the condenser unit shown in figure 7 and assuming steady state energy supply, the heat released by the steam oil mixture equals to heat absorbed by the cooling water. thus, qsteam oil mixture = qcooling water. qsteam oil mixture = 3,350.1 j/s= mcw x ccw x (t2 –t1), where mw =mass flow rate of cooling water = 2.783 x 10-4 kg/s, ccw = specific heat capacity of water = 4,200 kj/kg°c, t1= inlet water temperature = 25°c. solving for t2 = 28°c. 2.4.3 energy balance over separator the energy balance in the oil separation unit shown in figure 8 was carried out based on the fact that the separation of water oil mixture was based on density difference and occurred at room temperature (25°c) implying that there was no temperature gradient. thus, mw1 hw1 + mo1 ho1 = mw2 hw2 +mo2 ho2 and mw1= mw2=1.482 x 10-3 kg/s, hw1=hw2= 419.1 kj/kg (enthalpy of water at 25°c), mo1=mo2 = 1.93 x 10-5 kg/s and ho1 = ho2 = 0.65 kj/kg. 2.5 determination of extraction time the extraction time was determined using stop clock by recording the time for loading the leaves and sealing the tank cover (t1), time the first drop of steam oil mixture was collected (t2) and the time between first drop of steam oil mixture and its last drop (t3) and time the spent leaves were off-loaded (t4). 2.6 determination of steam requirement the steam needed to extract the essential oil from unit kilogram of the leaves was determined from the cumulative condensate collected at the end of batch operation. the ratio of steam collected to the quantity of leaves loaded gives steam to leave ratio. 2.7 economic analysis the analytical tools employed for calculating the economic indices of the plant such as total investment cost, direct and indirect production costs, annual operating cost, profit after tax, return on investment, break-even point and payback period were obtained from a related works (mu’azu et al., 2009 and galidama, 2004). 3. results and discussion this section discussed both the material and energy balance carried out in the plant. similarly, total extraction time per batch including loading and offloading of leaves, induction period and actual extraction time were also presented and discussed. these results will help an investor to know the number of batches to run on daily basis, time for stoppage of the extraction, actual file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 966 steam and energy requirements in a batch operation and economics for the production has also been discussed. 3.1 material balance the summary of material balance carried out in the plant is presented in table 2. it is evident that in every 3.333 x 10-3 kg/s of eucalyptus leaves charged into the extractor, the output of essential oil was 1.980 x 10-5 kg/s and required 1.482 x 10-3 kg/s of steam. this implies that steam to leaves mass ratio per second was 1.482 x 10-3 : 3.33 x 10-3 or 1 : 25 and oil to leaves mass ratio per second was 1.980 x 10-5 : 3.333 x 10-3 or 1 : 1.68 table 2: summary of material balance for the process units oil extractor material input, kg/s output, kg/s eucalyptus leaves 3.333 x 10-3 3.333 x 10-3 water 2.500 x 10-3 3.333 x 10-3 steam 1.482 x 10-3 essential oil 1.930x 10-5 spent leaves 3.310 x 10-3 unused water 1.018 x 10-3 total 5.833 x 10-3 5.830 x 10-3 condenser steam 1.482 x 10-3 cooling water 2.783 x 10-4 essential oil 1.930 x 10-5 1.930 x 10-5 hot water 1.482 x 10-3 warm water 2.783 x 10-4 total 1.780 x 10-3 1.780 x 10-3 oil separator hot water 1.482 x 10-3 1.475 x 10-3 essential oil 1.930 x 10-5 2.671 x 10-5 total 1.501 x 10-3 1.501 x 10-3 drying unit essential oil 2.671 x 10-5 1.930 x 10-5 sodium sulphate 2.500 x 10-5 2.500 x 10-5 water 7.41 x 10-6 total 5.17 x 10-5 5.17 x 10-5 3.2 energy balance the summary of energy balance carried out in the plant is presented in table 3. at a steady state, the energy supply by the steam (11,525 j/s) equals to energy gained by the leaves, oil, water, extraction tank and lost to surrounding and due evaporation. however, the energy gained by the oil (3.765 x 10-6 j/s) was negligible compared to water (787 j/s) and leaves (233.99 http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 967 j/s). in the oil separation unit, there was not temperature gradient (25°c) and therefore the energy remained constant. table 3: summary of energy balance for the process units oil extractor item input, j/s output, j/s energy supplied 11,525.00 heat gained by water 787.50 heat of evaporation 3350.10 heat gained by oil 3.765 x 10-6 heat gained by leaves 233.99 heat lost to surrounding 2305.00 heat gained by extraction tank 4848.41 total 11,525.00 11,525.00 condenser heat released by steam 3350.10 heat released by oil 3.765 x 10-6 heat gained by cooling water 3350.10 total 3350.10 3350.10 oil separator warm water 621.00 621.00 essential oil 1.25 1.25 total 622.25 622.25 3.3 extraction time the total extraction time per batch consists of time for loading of eucalyptus leaves into the oil extractor, induction time, actual extraction time and time for off-loading the spent leaves as shown in table 4. table 4: sequential production time for each activity in a production cycle batch loading of fresh leave, t1 (minutes) induction period, t2 (minutes) extraction time, t3 (minutes) off-loading of spent leave, t4 (minutes) 1 5 32 100 10 2 4 20 100 8 3 5 28 100 9 4 5 25 100 9 5 4 15 100 10 average 4.6 24 100 9.2 it can be seen from table 4 that the average time required for loading was 4.6 minutes and 9.2 minutes for off-loading the spent leave and these times were considered as the lag time in the production cycle. the induction period is the time between ignition of the burner and the first file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 968 drop of the steam plus oil mixture. this period is generally dependent on the energy supply, volume of the water in the boiler and loading density of the leave. in this study, the period was higher for the 1st batch (32 minutes) compared to other four batches and was due to the addition of both sensible heat and latent heat to the fresh water in the boiler whereas in the other four batches only latent heat was added. however, the average induction period was 24 minutes and is in agreement with the values obtained by okonkwo et al (2010) and mu’azu et al (2012). although, the average extraction time was 100 minutes, it was observed that up to 67% of the oil was collected between 040 minutes and 95.90% was collected within 80 minutes. this implies that extraction beyond 80 minutes is uneconomical relative to energy input which was considered as the major production cost. therefore, the effective production time per batch is the summation of time of loading, induction, extraction and off-loading and was found to be 117.8 minutes (1.96 hours) 3.4 effect of extraction time on oil yield the effect of extraction time on yield of the essential oil extracted is presented in figure 10. the oil yield increases with increase in extraction time for all the batches until it reached 30 minutes for the 2nd batch and 20 minutes for the other batches before declining. the difference in the extraction pattern between 2nd batch and other batches could be due to loading pattern of the leaves. figure 10: extraction pattern of essential oil as a function of time it was also observed that about 67.7% of the oil was extracted between 0-40 minutes while 95.90% was extracted in 80 minutes for all the batches (figure 11). the cumulative volume of the oil extracted ranged from 99.9-131.2 ml with an average yield of 115.84 ml (0.1158 litres) per batch. this implies that for 5 batches operation in a day the average oil yield was 579.2 ml (0.579 litres). http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 969 figure 11: cumulative volume of essential oil as a function of time 3.5 steam requirement for extraction the quantity of steam needed to rupture the leaves for the oil to be released from the cell matrix and transported to the condenser is presented in table 5. table 5: cumulative condensate collected in each batch time (minutes) batch 1 (ml) batch 2 (ml) batch 3 (ml) batch 4 (ml) batch 5 (ml) 10 521.7 425 550 510 1200 20 1540.7 1565 1490 1290 2880 30 2450.7 2965 2430 1910 4440 40 3540.7 4015 3330 2530 5760 50 4510.7 5135 4220 3190 6970 60 5460.7 6275 5100 3830 8190 70 6450.7 7335 5920 4620 9350 80 7435.7 8355 6710 5120 10470 90 8325.7 9415 7440 5560 11710 100 8625.7 9725 7760 5920 12440 it is evident in table 5 that the cumulative volume of water required for daily operation of 5 batches was 44470.7 ml (44.47 litres) with average batch consumption of 8894.14 ml (8.894 litres). however, 15 litres of water is recommended per batch to compensate for losses during production. the steam to oil volumetric ratio per batch was 77:1 (8894.14 ml/115.84 ml) and steam to leave ratio was 445:1 (8894.14 ml/20 kg). 3.6 energy requirement energy consumption plays a significant role in the extraction of essential oil from aromatic plant using steam distillation method. as seen in table 6 the first batch consumed more energy as a result of addition of both sensible and latent heats when compared with the other batches file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 970 where only latent heat was applied. it was observed that the average gas utilization per batch was 1.5 kg with corresponding energy input of 69.15mj. table 6: energy utilization for each batch operation batch quantity of gas consumed (kg) energy utilized (mj) 1 1.8 82.98 2 1.4 64.54 3 1.4 64.54 4 1.4 64.54 5 1.5 69.14 3.7 economic analysis table 7 presents economic analysis of the plant based on daily throughput of 0.579 litres of essential oil per batch and 20 working days in a month. the estimated cost of the plant is n3,500,000.00k with an assumed lifespan of 35 years. the profit after tax (pat) of n2,115,871.00 obtained in this study was higher than n981,600.00 and n1,818,806.00 obtained in a separate studies using kerosene as fuel (mu’azu, et al., 2009; galadima, 2004). the difference in the net profit is mainly due to type of fuel used and cost of raw materials. table 7: economic analysis for production of eucalyptus essential oil on annual basis s/n item equation value amount (n) total(n) 1a fixed capital cost (fc) 3,500,000.00 1b land & non depreciable costs (lc) 50,000.00 1c capital for test-run (wc) 20,000.00 1d total investment cost (tc) fc + lc +wc 3,570,000.0 2a raw materials (rm) 240,000.00 2b utilities (u) 605,400.00 3a maintenance (mc), 1% of fc 35,000.00 3b labour cost (lc) 720,000.00 3c plant overhead (po), 10% of fc 72,000.00 3d local taxes (lt), 1% of fc 35,000.00 3e insurance (i), 1% of fc 35,000.00 3f direct production cost (dpc) mc+lc+po+ lt+i 897,000.00 4 sales expenses (4% of dpc) 35,880.00 5 general overhead (4% of dpc) 35,800.00 6 research & development (8% of dpc) 71,760.00 7 annual operating cost (aoc) rm+u+dpc 1,742,400.0 8a annual production138.96 liters http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 958-972. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 971 8b annual selling price (asp) @ n35,000/l 4,863,600.00 8c operating profit (op) asp-aoc 3,121,200.0 8d lifespan of the plant (ls), years 35 8e salvage value (sv) 0.35 x tc 124,950.00 8f depreciation (d) (tc-sv)/ls 98,430.00 8g profit before tax (pbt) op-d 3,022,700.00 8h tax (t), 30% 0.3x pbt 906,831.00 8i profit after tax (pat) pbt-t 2,115,871.00 8j return on investment (roi),% (pat/tc) x100 59.27 8h profit margin (pm),% (pat/asp) x 100 43.50 9a equity (e), @20% 0.2xtc 714,000.00 9b return on equity (roe),% (pat/e)x100 296.34 9c annual cash flow (acf) pat+d 2,214,301.0 9d break even point (bep) [fc/(aspoc)] 1.12 9e pay back period (pbp) tc/acf 1.61 years 4. conclusion the study revealed an average oil production of 0.579 litres in a day within a production cycle of 8.33 hours. the study further revealed that with an initial investment of n3,570,000:00k, the expected annual profit after tax was n2,115,871:00k and project payback period of 1.61 years. these promising economic indices suggest that extraction of essential oil using lpg has higher returns than kerosene and is strongly recommended to any potential investor in the sector. acknowledgements the authors express their sincere appreciation to the director-general/ceo of national research institute for chemical technology (narict), zaria for his moral and financial supports towards this project. the friendly corporation and support by members of staff of pilot plants & fabrication technology, narict, zaria is also highly appreciated. references deepak, g., mumtaj, s. and prashant, s. 2013. microwave-assisted extraction of eucalyptus citriodora oil and comparison with conventional hydro distillation. middle-east journal of scientific research, 16 (5): 702-705. galadima, ms. 2004. design and fabrication of a pilot plant for steam distillation of essential oil. m.sc. thesis, department of chemical engineering, ahmadu bello university, zaria, nigeria,87-92. manika, n., priyanka, m., narendra, k., chanotiya, cs. and bagchi, gd. 2012. effect of season on yield and composition of the essential oil of eucalyptus citriodora hook. leaf grown in subfile:///c:/users/user/downloads/azojete143/www.azojete.com.ng mu’azu et al: production and economics evaluation of pilot scale essential oil extract from eucalyptus citriodora leaves. azojete, 15(4):958-972. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kabirumuazu@yahoo.co.uk 972 tropical conditions of north india. journal of medicinal plants research, 6(14): 2875-2879. available online at http://www.academicjournals.org/jmpr mu’azu, k., okonkwo, em. and abdullahi, m. 2009. economic analysis of production of essential oil using steam distillation technology. nigerian journal of basic and applied sciences, 17(2): 218-222. available online at http://www.ajol.info/browse-journals. mu’azu, k., mohammed-dabo, ia. and waziri, sm. 2012. development of mathematical model for the prediction of essential oil extraction from eucalyptus citriodora leave. journal of basic and applied scientific research, 2(3): 2298-2306. okonkwo, em., mu’azu, k., odigure, jo., ugwu, jo., williams, is. and mohammed, ia. 2010. optimisation of process conditions for extraction of essential oil from eucalyptus citriodora leave. international journal of physical science, 2(1): 88-96. panda, h. 2000. essential oils handbook, national institute of industrial research, delhi, 27-30. seid ym. and omprakash, s. 2014. extraction of essential oil from eucalyptus leaves as antibacterial application on cotton woven fabric. international journal of bacteriology, virology and immunology, 1(1): 1-7. unido, 1983. practical manual on essential oils industry (unido, vienna, austria). weiss, ea. 1997. essential oil crops, cab international, usa, 65-67 http://www.ajol.info/browse-journals http://www.azojete.com.ng mailto:kabirumuazu@yahoo.co.uk 6 arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):292-303 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 292 original research article pattern of residential water demand analysis for maiduguri metropolis, north-eastern nigeria a. abdullah, b. s. u. ibn abubakar* and a. n. jones (department of civil and water resources engineering, faculty of engineering, university of maiduguri, p.m.b.1069, maiduguri, nigeria.) *corresponding author’s e-mail address: bashehu@unimaid.edu.ng article information submitted 26 july, 2018 revised 22 march, 2019 accepted 28 march, 2019 keywords: water demand domestic water consumption per capita water demand maiduguri abstract this study investigated the projected 50-year water demand of maiduguri township from 2006 to 2056. the impact of socio-economic factors on water consumption pattern of the population was also assessed. data were collected from 200 households using structured questionnaires and analyzed using statistical package for the social science (spss). the results show that on an average, a household in jere and maiduguri consumes an estimated 421.85l l/day while areas worst hit are new layouts and those covered by the phase 2 water treatment plant (yet to be completed). in addition, it was found that, gender, education, household size and income were statistically significant predictors of water demand. furthermore, the results revealed that in 2006, the combined population of jere and maiduguri was 749,123, which was later projected to be around 3,618,579 by the year 2056. similarly, water demand was estimated to rise to approximately 154,443 m3/day by the year 2056 to meet the water demand of the growing population. however, in 2006, the combined water supplied from maiduguri water treatment plant and all the functional boreholes (public boreholes) stands at 31,973m3/day while in 2016 it rose to 43,811 m3/day. the increase was due to additional supplies obtained from boreholes provided by some non-governmental organization (ngos) in some locations across the two areas. it is noteworthy that water supplied in the year 2016 to the population was grossly inadequate to meet the household water demand. therefore, with the projected water demand of about 154,443 m3/day by 2056, it is recommended that all existing water supply schemes including the proposed phase 2 of the maiduguri surface water treatment plant designed to cover west end, wulari, bulunkutu and maduganari areas to be completed to increase the supply. service boreholes in newly established layouts should be put to operate at full capacity including the additional ones drilled. also, the dala alamdari mini water works constructed by international committee of the red cross (icrc) which is operated below its installed capacity due to poor management to be enhanced. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction with the expansion of urban areas, infrastructural development and persistent need for clean drinking water, many urban communities are still faced with the challenge of inadequate water mailto:bashehu@unimaid.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):292-303. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 293 supply (adeoye et al. 2013; ogundobe and ifabiyi, 2014). water supplied for domestic and agricultural uses are generally inadequate. however, the supply of clean drinking water to meet the growing population is challenging in many societies (adeoye et al. 2013; abubakar et al. 2014). unsustainable utilization of available water and poverty are other factors that affect water demand and supply (mbaya, 2008). overall, lack of access to clean water supply affects the general standards of living of the people. thus, assessing available water resources and predicting water demand are essential for proper water demand planning and management. recently, several studies have been conducted to evaluate the determinants of water demand in various locations in nigeria (mbaya, 2008; sule, 2010; al-amin et al., 2011; ogundobe and ifabiyi, 2014). however, there are still some gaps to filled because little information is known about the situation in the north eastern nigeria. furthermore, some of the literatures which emerged from the northern region did not cover the intricacy of the unique water demand in this time of incessant influx of people in various towns as a result of insurgency. for instance, mbaya, (2008) had shown that the water consumption pattern of gombe state between 1996 and 2020 was as low as 20 l/c/d which was lower than the prescribed minimum of 60 l/c/d by the world health organization (who) and united nations development program (undp) (who, 2006; unesco 2012,). similarly, sule, (2010) found that the average per capita water consumption in ilorin, nigeria in low, medium and high-density areas to be 92.24l/c/d, 61.22l/c/d and 71.22l/c/d respectively. the differences were due to discrepancies in socio-economic characteristics of the households, population, and availability of clean water for domestic use. additionally, this finding agrees with the result obtained by ayanshola, et al., (2010) in the same location (i.e. ilorin town). in addition, arbues and martinez-espineira (2003) considered factors such as price of water, income and household composition as the major predictors of domestic water demand. in their study, different tariffs were used with the objectives of identifying the predictors of water demand as previously mentioned. it was reported that the quantity of water consumed by household largely depends on factor such as the socio-economic characteristics of the household, education, climate and sanitation or hygiene practices. interestingly, ifabiyi, et al. (2012) found that the levels of education, income, and marital status were of households were positively correlated to water use while time spent in fetching water and distance to water source were found to be negatively correlated. conversely, al-amin et al. (2011) revealed that, other factors such as cultural habit, settlement pattern, type of supply and water source could be a determinants of water use. since water use varies according to different factors influenced by people’s standard of living, then forecasting is one option which can enhance understanding of the underpinning determinants of water demand (ifabiyi et al., 2012; cook et al., 2001). therefore, information regarding the past, present and future water demand would assist in addressing challenges of water supply in urban and semi-urban centres. it is noteworthy that several methods of forecasting water demand exist in literatures such as per capita and per unit approaches, end-use models, extrapolation methods and structural or casual models (boumann et al., 1998). each of these methodologies can be adopted based on intended use and the time frame of the prediction and data set at hand (galan, et al., 2009). additionally, (sule, 2010) argue that the selection of water demand forecast methodologies is a function of planning objective, availability of data and resources availability. interestingly, a lot of literature has been published on water demand analysis but such studies showed different approaches with no consensus on the accuracy of the methods to predict water demand (mbaya, 2008; adeoye et al., 2013; ogundobe and ifabiyi, 2014). this is because file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullah, et al: pattern of residential water demand analysis for maiduguri metropolis, north-eastern nigeria. azojete, 15(2):292-303. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 294 every region has its own peculiar water use and socio-economic characteristics influencing water consumption. however, most of the models used in water demand studies are regression models arbues et al., (2003) with the commonest estimators being ordinary least square (ols), two and three stage least squares (2sls, 3sls), and maximum likelihood depending on the data set the researcher possessed. therefore, the aim of this study is to predict water demand and supply base on the current supply, water availability and accessibility in jere and maiduguri townships. information regarding current and future domestic water use by households would be evaluated for possible expansion. 2. materials and method 2.1 the study area the study was conducted in jere and maiduguri metropolitan councils as shown in figure 1. however, for proper coverage and understanding, maiduguri town comprises of jere and maiduguri urban areas, and is located between latitudes 11° 42ʹ n, 12° 00ʹ n, and longitudes 12° 54ʹ e, 13°14ʹ e. the town has an area of more than 3000km2 with population of 749,123 people according to national bureau of statistics (nbs, 2007) figure. maiduguri has semi-arid climate, savannah or tropical grasslands vegetation, light annual rainfall ranging from 300mm to 500mm and has average daily temperature of 22 to 35°c with mean maximum temperature exceeding 40°c between march and june before the onset of the rains in july to september (arku et al., 2011). however, in this study, the town was divided into five zones namely kyarimi park, bulumkutu, shehuri, gwange and bolori area respectively. this division was adopted from borno state water corporation (boswc). the economic mainstay of residence of maiduguri includes farming, trading, civil service and other skilled works. recently, there has been significant increase in population in maiduguri as a result of insurgency where most local government areas of the state were devastated. this development has increased pressure on the available water resources. one of the main sources of water supply to maiduguri is surface water from alau dam through the maiduguri water treatment plant. alternatively, many residents have their private boreholes to meet their water demand. this has led to proliferation and constructions of private and commercial boreholes to argument the water supply challenges. presently, ground water serves as another main source of water to many households in maiduguri. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):292-303. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 295 figure 1. map showing maiduguri and jere local government areas (source: https://www.unocha.org). for convenience, maiduguri town was divided into five different zones where 40 households were selected randomly from each of the five zones to form the coverage area for survey. data was collected by administering pretested structured questionnaires designed according to (dagnew, 2012) with some modifications. this study considered respondents who are 18 years of age and above or household heads to obtain relevant information on domestic water use (sule et al., 2010). this information includes: level of education of the household heads, household size, occupation, storage facility and other demographic and socio-economic factors affecting water consumption. the data obtained were analyzed using spss (ibm version 20) software. similarly, analysis of variance (anova) was used to determine the level of significance of the parameters and their dependence. analytical tools used in this study were based on the objectives of the study. these tools include: descriptive statistics such as frequencies and percentages for socioeconomics and demographic variables and multiple linear regression models through the origin for factors affecting water stored for daily usage. the regression through the origin or no intercept model means that there is no constant term included in the model. the fitted model in regression through the origin is as follows from equation 1: y = β1x1y (1) this implies that that the constant βo in regression with intercept set to zero shown by equation 2. y = β˳ + β1xi + ei (2) where: βo is the intercept, β1 is the slope and ei denotes the ith residual. in equation 1, β1 is a coefficient and xi is a predictor variable. it should be clearly noted that, water stored for daily https://www.unocha.org). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullah, et al: pattern of residential water demand analysis for maiduguri metropolis, north-eastern nigeria. azojete, 15(2):292-303. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 296 usage is the dependent variable used in this study. water stored for daily usage is a function of available storage facility when there is water scarcity or intermittent supply. 3. results in this study, population projection was based on the 2006 census figure. table 1 presents the water demand projection for maiduguri town from 2006 to 2056. the population of maiduguri in 2006 was 749,123 (nbs, 2007) while the projected population in 2016 was 1,026,479. it is estimated that the population would reach 1,406,254, 1,927,276, 2,640,834 and 3,618,579 by the year 2026, 2036 2046 and 2056 respectively. water demand is estimated to increase from 31,973m3/day in 2006 to 154,443 m3/day in 2056. table 1: projected water demand for jere and maiduguri townships for five decades. table 2 shows that the average household size in jere and maiduguri was 10 persons per household. similarly, the estimated current water demand and supply for these households were 200000 l/day and 84400l/day respectively. presently, only 42% of household water demand is met by the water utility provider at approximately 422 l/day. however, the future water demand was estimated to be 154,443 m3/day by the year 2056 as shown in table 1. table 2: household current demand and access to public water supply (l/day) base on 100 l/c/day sample average size average water demand total water demand average water supply total water supply percentage satisfied 200 10 100 200000 422 84400 42 figure 2a shows that out of the 200 respondents interviewed, 70 % were heads of the house, 12% are grown up children while 3.5 % are wives of the heads and 9.5% were blood relations and other relatives. in relation to the ages of the respondents in figure 1b, 2% were between 18 and 23 years, 12.5% were between 24 and 29 and 26% were between 30 and 35 years of age respectively. also, 20.5% were between 36 and 41 while 17.5% was between 42 and 47 years. similarly, 17% of the respondents were between 48 and 53 years, and 54 and 59 respectively while 9% were 60 years and above. considering the gender of the respondents, figure 1c shows that 88% of the respondents were male, 80% of whom are married while the remaining 20% were not married. with regards to their level of educational, most of the respondents (data not shown), about 69% attended tertiary education whereas 8% and 4% have secondary and primary year projected population service population per 10 persons water demand(m3/day) 2006 749123 319730 31973 2016 1026479 438107 43811 2026 1406254 600312 60020 2036 1927276 822573 82258 2046 2640834 1127123 112713 2056 3618579 1544430 154443 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):292-303. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 297 education respectively. similarly, 19% have attended informal education such as quranic education. furthermore, information regarding the respondent’s occupation revealed that more than half (54.5%) of the respondents were civil servants, 21.5% were traders while only 1% are farmers, and the remaining 23% are not working class. 0 20 40 60 80 100 head wife ch il d brothe r others pe rc en ag e head of house a 18-23 24-29 30-35 36-41 42-47 48-53 54-59 60-65 age in years b 0 20 40 60 80 100 marr ied single islam c hr istiani ty pe rc en ta ge c ci vi l servant trade r farmer hand work/ ski lle d work not working others occupation type d figure 1: demographic characteristics of respondents as head of house (a), respondents age (b), marital and religious inclination (c); and occupation of respondents (d). on the other hand, figure 2a showed that 18% of the household surveyed reported that they are connected to public water supply while 8.5% used water from public standpipes. in addition, 58.5% get their water from water vendors. furthermore, 13.5% of the respondents have their own boreholes and the remaining use to fetch from their neighboring houses. figure 2b showed that all the respondents used different storage facilities to store their water. approximately 51% of the respondents used drums or plastic jerry cans as storage facilities. while others, 21% used clay pots, 15% had overhead plastic tanks and 13% had underground cemented reservoirs. regarding the distance to the primary sources of water, figure 2c showed 37% collect water at a distance of between 50 and 99 meters away from their homes, 14% travel 100-199 meters, 13.5% travel between 200-500 meters away while 13% fetch water from a source over 500 meters from their residence while the remaining have taps in their compounds. the sanitation system revealed that 70% of the respondents used flush toilet while 28% used pit latrine as in figure 2d file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullah, et al: pattern of residential water demand analysis for maiduguri metropolis, north-eastern nigeria. azojete, 15(2):292-303. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 298 figure 2 water supply and sanitation condition of respondents: household main water supply (a), water storage facilities (b), distance covered by respondents to water sources (c), type of toilet used by the respondents (d), monthly income of households (e) and type of house owned (f). figure 2e showed that 31.5% of the respondents earns between ₦26,000 and ₦50,000 monthly, 21.5% earns between ₦51,000 and ₦100,000 monthly while 13%, earns less than ₦10000 while 15% collect between ₦ 10000 and ₦25,000 respectively. additionally, only 19% of the respondents earned above ₦100,000 per month. private residential ownership indicated in figure 2f that 53% own the houses, whereas only 36.5% and 3.5% rented from individual and government respectively. the study found the mean water stored for daily usage (demand) in maiduguri to be approximately 421.85 l/h/d (i.e. 44 l/c/d), which is not in agreement with 86.22 l/c/d reported by (ayanshola, sule and salami 2010). similarly, a value of 150/c/d was reported for ijebu (coster and otufale 2014). according to the procedure of stepwise multiple linear regression analysis technique, a model with high value of r2 (or adj r2) and a lower value of both standard error and mean square error, with a good p-value of less than 0.05 which test the significance of both http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):292-303. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 299 regression coefficients and the regression model is considered to be the best. factors used in this study include: respondent as head of household (x1), gender (x2), age (x3), educational years completed (x4), household size (x5), occupation (x6) and monthly income of the household (x7) for each type of demand model, the researchers take a number of factors which are considered as important because of their reliable impacts on that demand. the result of multiple regressions analysis (table 3) shows a high coefficient of determination r2 (0.674) and adjusted r2 (0.662). this means that 66.2% of proportion of the variability in quantity of water stored for daily usage, (daily consumption or demand) per household. table 3 (coefficient of variation) reveals that five of the independent variables are strong predictors of water demand. these are: gender (β=-0.91, p=0.047), educational years completed (β=0.403, 0.004), household size (β=0.273, 0.001), occupation (β=-0.18, 0.009), and monthly income of the household (β=0.403, 0.008). the table also shows both the standardized and unstandardized coefficients. to compare the effects of different variables, it is appropriate to use the standardized coefficients rather than the unstandardized ones. standardized means that the values of the coefficients correspond to the expected change in the dependent variable given a change in the independent variable equal to its standard deviation. thus, in logical term, each of the coefficients has been converted to the same scale so that comparison between them is possible. according to this analysis, the mean of the dependent variable (water stored for daily usage per household or water demand) is 421.85l/day. an anova results showed that the entire model could predict a better than 0% (r2 value). the model reaches statistical significance value of 0.000 (i.e. p<.05). each of the variables included in the model were also examined to see which of them contributed to the prediction of the dependent variable. the linear regression model through the origin was formulated from table 3 and regression equation with coefficient presented by equation 2. table 3: multiple linear regression result of determinants of water demand (water stored for daily usage) coefficients model unstandardized coefficients standardized coefficients t sig (p-values).b std. error beta respondent as head of house -42.534 47.884 -0.045 -0.888 0.375 gender 141.973 71.171 0.091 1.995 0.047 age 0.654 1.479 0.052 0.442 0.659 educational years completed 15.615 5.322 0.403 2.934 0.004 household size 13.089 3.781 0.273 3.462 0.001 occupation -36.400 13.778 -0.180 -2.642 0.009 monthly income of household (n) 42.154 15.685 0.268 2.687 0.008 (2) where: qs is the quantity of water stored for daily usage (daily household water demand). x2=gender, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullah, et al: pattern of residential water demand analysis for maiduguri metropolis, north-eastern nigeria. azojete, 15(2):292-303. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 300 x4 =educational years, x5= household size, x6= occupation and x7 = monthly income of the household head. 4. discussion this study presents the population projection and water demand of maiduguri from 2006 to 2056. to our knowledge, this is the first study where water demand and supply was holistically studied in maiduguri. it was evident that most of the areas worst hit by water scarcity are new layouts and areas proposed to be covered by the phase 2 of the maiduguri surface water treatment plant. currently, there is no sign of government intention to commence work on this project after the commissioning of the phase 1 in 1993. although, the number of households having access to water has increased, yet the population without access has doubled over the year due to population expulsion in the city. however, this result agrees with that of mbaya, (2008) who observed that an increase in service population is attributed to the increase in water supply from the regional water scheme in gombe state. conversely, over the years there has been a gap between water supply and demand. interestingly, more than 57% of household water requirement in maiduguri town is not met by the public water supply (pws) due to poor funding, maintenance, and mismanagement of the available finances. additionally, even the completed phase one is not operating at full installed capacity due to lack of power supply and water treatment chemicals. it is noteworthy that most of the boreholes in the study area also operates below their design yields. the total average water demand was estimated to be 200000 l/day while only 84400 l/day was being supplied by 2016. similarly, such observation has been reported by mbaya, (2008) where an average water demand of 18000 l/day was estimated but only 9000 l/day was supplied in gombe state. this was reported for gombe metropolis with population of 235,687 (nbs, 2007). household without access to pws is left with no options than to sink their private borehole or buy water from vendors, which are usually unsafe and costly. furthermore, majority of the respondents are traders and civil servants whose earnings hardly sustain their family, thus, resorted to the purchase of water storage containers at the expense of many household needs. the study also found that women are the ones who bears the burden of fetching water which could affect their educational future (ogunbode and ifabiyi, 2014). with low level of education of the respondents, water demand by households could be affected (ayanshola, sule and salami 2010) resulting in poor hygiene practice thereby translating into loss of water demand priority. most respondents prefer to fetch water from a nearby sources irrespective of water quality. the percentage of the respondents (37%) who have their primary source of water at a distance of between 50-99 meters was not in agreements with study reported by coster and otufale (2014) who argued that 93.1% of the respondents in ijebu ode local government of osun state nigeria trek for more than 30 minutes to fetch water. conversely, ogunbode and ifabiyi ( 2014) observed that 69% of the respondent in osun state had to trek for only 10 minutes to get their drinking water. furthermore, because most of the respondents are low-income earners they depend largely on water vendors for water supply. in addition, these are people in most cases engaged in illegal water connections on public water supply mains. total households water demand in maiduguri town was observed to be 421.85 l/h/d (ie. 44 l/c/d) for a family of 10 people, lower than 86.22 l/c/day as reported by ayanshola, et al., (2010) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):292-303. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 301 for ilorin. however, the results of this study is higher than 150 l/h/d reported by coster and otufale (2014) and 20 l/c/d by mbaya (2008) for ijebu and gombe town respectively. as expected, gender is statistically significant (p˂0.05) in explaining water demand. women requires more water than their male counterparts for their daily activities. this study agrees with ayanshola, et al., (2010) who studied water supply use in ilorin town. the result also indicates that household size is positively and statistically significant variable in explaining household water demand in the study area. it was found that, a 1% increase in household size increases water demand by 23.7%. as expected, households with higher number of people used more water, especially families with many children in their care. the larger the household size, the higher the volume of water needed for domestic uses. this finding is similar to the 17% obtained in iwo osun state (ogunbode and ifabiyi 2014). furthermore, respondent’s occupation is statistically significant (p˂0.05) in determining water demand because trader and skilled worker are paid daily and thus could spend more than civil servants who are on a monthly payroll. the regression result also shows that income of households is positively and statistically significant in explaining water demand. a 1% increase in income increases water demand by 26.8%, and this is significant at 5% confidence interval. generally, the living standard and income level of the people are directly related. people with higher income could satisfy their basic needs than low-income groups. it is clear that households with higher monthly income are more likely to obtain sufficient water at whatever cost. this is probably because they can pay the service and connection charges required by boswb as reported by juryilla (2015). they could also afford to drill their private borehole when in need. it is noteworthy that the head of the house and age of respondent were not significant (p˃0.05) in determining water demand and use which is not in agreement with the results reported by ayanshola et al. (2010) where head of the house and age of the respondents were found to be significant. 5. conclusion an investigation into the determinants of domestic water consumption by households in jere and maiduguri was conducted. it is evident that gender, education, household size and socioeconomic status play an important role in determining water consumption by the populace. although, in most of the communities, water supply was grossly inadequate, the quantity of water supplied has increased in recent time due to intervention in the sector by some ngos in the provision of boreholes. while the undp, (2006) stipulated 60 l/c/day as the daily minimum for water consumption in developing countries, most residents consumes approximately 44 l/c/day which is grossly inadequate. furthermore, most households are not connected to public water supply. additionally, there were evidence of intermittent supply from those who are connected to public water supply. this has caused many residents to depend on water vendors for water supply. interestingly, areas worst hit by water scarcity are areas not currently covered by the surface water treatment plant and new layouts. therefore, the study identified the need for water supply system expansion in maiduguri to meet the growing population. boswc should ensure that all existing water supply schemes are operated at full capacity and also provide public taps across the city to give easy access to water for people who could not afford to pay for the charges. finally, accurate data collection processes should be enhanced for proper management and planning. again, water metering system should be adopted to avoid wastage at household level. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullah, et al: pattern of residential water demand analysis for maiduguri metropolis, north-eastern nigeria. azojete, 15(2):292-303. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bashehu@unimaid.edu.ng 302 references abubakar, ms., zakari, md. and shanono, nj. 2014. evaluation of boreholes performance in maiduguri metropolitan, borno state-nigeria. journal of engineering and technology, 9 (2): 2833. adeoye, pa., adesiji, ra. and hassan, mi. 2013. appraisal of rural water supply: case study of kwara state, north central, nigeria. international journal of basic science, 1(4): 816-826. al amin, mk., mahmud, sh. and akhsanul, im. 2011. domestic water consumption pattern in village in bangladesh. 4th annual paper meet and 1st civil engineering congress, december 2224, dhaka, bangladesh, 83-85. arbues, ffg. and martinez-espineira, r. 2003. estimation of residential water demand: a state-ofthe-art review. journal of socio-economics, 32 (3): 81-102. arku, ay., musa, sm., mofoke, ale. and dibal, jm. 2011. re-examining raw effluents from nigerian bottling company maiduguri for crop irrigation. j. app. phyto. environ. sanitatiom 1 (1). ayanshola, am., sule, bf. and salami, aw. 2010. modelling residential water demand at household level in illorin, nigeria. usep:journal of research information in civil engineering, 7 (1): 59-68. boumann, dd., boland, jj. and hanemann, mw. 1998. urban water demand management and planning, mcgraw-hill, new york. cook, zs. urban, m., maupin, r., pratt, jc. 2001. “domestic, municipal and industrial water demand assessment and forcasting in ada and canyon countries idaho. scott urban, idaho department of water resources (idwr) report, usa, pg 1-50. coster, as. and otufale, ga. 2014. households water-use demand and willingness to pay for improved water services in ijebu ode local government area, ogun state nigeria. journal of environment and earth science, 4 (17): 166-174. dagnew, dc. 2012. factors determining residential water demand in north western ethopia, the case study of merawi. ethopia: unpublished m.sc desertation, cornell university, ithaca, new york, usa, page 91. galan, jm., lopaz, pla. and olmo, r. 2009. an agent-based model for domestic water management in valladolid metropolitan area. water resource research, 45(5): w05401, doi:https://doi.org/10.1029/2007wr006536. gracia, fa., valiñas, mág., and martínez-espiñeira, rfa., gracia, magv. and martinez-espineira, r. 2001. literature on the estimation of residential water demand. university of york. http://www.stfx.ca/people/rmespi/department/robermarian21nov. accessed 12 december, 2016. ifabiyi, ip, eniolorunda, nb., dangulla, m. and rufai, k. 2012. correlates of domestic water demand in sokoto metropolis sokoto nigeria. journal science research review, 1 (5): 069-077. jabbar, ah, altufaini am, and ibraheem, aa. 2011. design model of residential water demand in al-najaf city. international journal of innovative science, engineering and technology, 1(5):538543. http://www.stfx.ca/people/rmespi/department/robermarian21nov http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; 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(accessed on 10th june, 2019). ogunbode, to. and ifabiyi pi. 2014. determinants of domestic water consumption in growing urban center in osun state, nigeria. african journal of environmental science and technology, 8(4): 247-255. sule, bf., ayanshola, am. and salami, aw. 2010. water consumption pattern in ilorin kwara state nigeria. 2nd annual civil engineering conference university of ilorin nigeria. ilorin: international conference on sustainable urban water supply in developing countries, 26-28 july, 2010. unesco. 2012. high level international roundi table on litracy reaching litracy target delivering on the promise of unesco paris, 6-7 september. world health organization (who) 2006. progress on drinking water and sanitation. joint monitoring program report, world health organization, 20 avenue, appia, geneva, switzerland. https://www.who.int/water_sanitation_health/publications/2006-publications/en/ accessed on 21st december, 2016. https://www.citypopulation.de/php/nigeria-admin.php?adm1id=nga008 https://www.who.int/water_sanitation_health/publications/2006-publications/en/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng original research article pattern of residential water demand analysis for m a. abdullah, b. s. u. ibn abubakar* and a. n. jon arid zone journal of engineering, technology & environment azojete december 2019. vol. 15(4):1013-1025 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1013 original research article categorisation of road construction projects’ cost overruns causes using factor analysis z. b. ahmad1*, n. anigbogu2, and j. j. molwus2 (1department of civil engineering, modibbo adama university of technology, yola, adamawa state, nigeria 2department of building, university of jos, plateau state, nigeria) * corresponding author’s email address: engrbelel@gmail.com 1.0 introduction roads account for over 90% of all inter and intra city movements of persons, goods, farm produce, merchandise, animals and mobile services in nigeria. the proper development of road transport network not only reduces the cost of transportation both in terms of money and time but also helps in the integration of various regions within the country and better understanding of neighbouring countries at the international level (aldagheiri, 2009). however, road construction takes a long time and the funding is always spread out over an extended period of time. consequently, road projects are exposed to different risks during their various stages of construction and encounter different types of challenges along their routes including cost overruns. considering that nigerian roads are procured at outrageous amount (centre for asocial justice, 2016), cost overruns are threats to the financial freedom of the country. cost overruns could lead to significant reduction in the quality and number of projects that can be implemented. article information abstract cost overrun is a major problem in the construction industry and a threat to the financial freedom of any country. considering that nigerian roads are constructed at very high cost, cost overruns could lead to significant reduction in the quality and number of projects that can be implemented. a vast number of cost overruns causes have been identified by various studies. however, the large number of possible causes makes managing and controlling them very challenging. this study, therefore, aims at categorising the causes in order to simplify their minimisation by identifying their latent constructs. seventy-one (71) factors identified through literature review and ranked by questionnaire survey respondents. the survey involved 267 respondents (clients, contractors and consultants) that have worked on road construction projects. the collected data were analysed using exploratory factor analysis. eight factors emerged from the 42 retained causes of cost overruns; contract related, economic and political, design and documentation, financial related, technical related, policy related, construction management related, and natural related causes. with this classification, it is easier to identify the group that has the most significant causes of cost overruns thus providing more information for better management. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 january, 2019 revised 15 june, 2019 accepted 20 june, 2019 keywords: categorisation factor analysis latent management road projects’ cost overruns. http://www.azojete.com.ng ahmad et al: categorisation of road construction projects’ cost overruns causes using factor analysis. azojete, 15(4):1013-1025. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1014 a vast number of comprehensive researches have been conducted worldwide to explain why and how construction projects exceed their estimated costs (frimpong et al., 2003; koushki et al., 2004; flyvbjerg et al., 2004; koushki, al-rashid and kartam, 2005; omoregie and radford, 2006; nega, 2008; lee, 2008; ameh, 2010; chileshe and berko, 2010; mahamid and bruland, 2011; abdul rahman and abdul azis, 2012; love et al., 2012; memon et al, 2012; memon, 2013; love et al., 2013; abdul azis et al., 2013; isma’il et al., 2013; and love et al., 2014;). these studies have identified a plethora of reasons for the occurrence of cost overruns and according to allahaim (2006), many of the reasons share similar pattern of impact on cost overruns. allahaim (2006) noted that it would be functionally useful and conceptually meaningful to classify the causes based on their impact on the overruns. abusafiya and suliman (2017) affirmed that prioritising the causes of cost overruns leads to better risks contingency weighing in budget estimates. classification narrows the problem by grouping related causes thereby making it easier to effectively deal with them. a deeper knowledge of the causes is necessary to understand the originating factors of poor cost performance (karunakaran et al., 2018). a better understanding of the cost overruns causes is achieved through understanding the forces driving each factor or where it originates. classification of the causes helps in identifying the most important frequent relationship between the causes. grouping also identifies multiple ideal types, each of which represents a unique combination of attributes that bring about the cost overruns. with this understanding, it is possible to design strategies for dealing with the causes. this study therefore aims at classifying the causes of road construction projects’ cost overruns using factor analysis with a view to minimise their occurrences. 2. methodology the study was carried out in the satellite towns development and the engineering departments of the federal capital territory, abuja in nigeria. the choice of abuja was based on the many road projects being constructed. the information necessary for this study was obtained through a detailed review of literature in relevant works such as books, journals, conference proceedings, the internet and other materials. the information gathered formed the bases for the data collection and analyses. questionnaire survey of 267 clients, consultants and contractors involved in road construction projects in the federal capital territory authority, abuja was carried out. the use of questionnaires for data collection was based on the research question and the large sample required for the analysis. the respondents were asked to rank 71 causes of cost overruns identified from literature review. exploratory factor analysis was conducted on the collected data to uncover the underlying dimensions in the dataset using statistical package for social science (spss) version 23. factor analysis is a statistical technique based on the multivariate correlation of interdependence. the technique reduces multiple variables into smaller number of factors by identifying common latent factors that define the grouped variables, thereby also enabling the interpretation of dependences between the factors. there are two basic types of factor analyses: exploratory factor analyses (efa) and confirmatory factor analyses (cfa). cfa attempts to confirm hypotheses and uses path analysis diagrams to represent variables and factors, whereas efa tries to uncover complex patterns by exploring the data set and testing predictions (child, 2006). efa is used to identify the structure of the relationship between the variable and the constructs. cfa is used to test whether measures of a construct are consistent with the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1013-1025. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1015 researcher’s understanding of the nature of the construct. efa was done in this study to identify the groups of cost overruns causes. prior to categorisation of the variables, the adequacy of the survey data was examined by conducting a kaiser-mayer-olkin (kmo) test and the bartlett’s test of sphericity. kmo measure of adequacy is an index used to examine the appropriateness of factor analysis. the kmo represents the ratio of the squared correlation between variables to the squared partial correlation between variables. the kmo statistics varies between 0 and 1. a value close to 1 indicates that the patterns of correlations are relatively compact and consequently factor analysis should yield distinct and reliable factors. the recommended minimum value of kmo for satisfactory factor analysis is greater than 0.7. bartlett’s test of sphericity was used to measure the strength of the relationship. it is actually a measure of multivariate normality of a set of distribution (hadi et al., 2016). it also checks the null hypothesis that the original correlation matrix is an identity matrix. the bartlett’s test of sphericity should be statistically significant (ρ < 0.05). a cattell’s scree plot was used to determine the number of factors to be considered (stellefson and hanik, 2008). the components are extracted by specifying the minimum initial eigenvalue of one. an eigenvalue is any number such that a given matrix minus that number times the identity matrix has zero determinant. the cattell’s scree plot is a plot of the extracted eigenvalues associated with each of the factors extracted, against each factor. the eigenvalues are plotted in descending order and the graph is examined to determine the point at which the line levels off. the factors were then rotated to maximise the variance of the squared loading for each factor and to produce clear factor loadings. rotation is an attempt to describe the information in several factors by re-expressing them so that loadings on a few variables are as large as possible, and loading on the rest of the variable are as small as possible. the axes were rotated so that the clusters of factors fall as closely as possible to them. this made the factor-loading pattern clearer as one of the two pairs of coordinates for each item tends to be close 0.0. there are many choices of rotation methods, depending on the software being used. to interpret the solution, variables that relate to each of the extracted factors were determined. this was done by examining the factor loadings, which represented the correlations between the factors and the variables and take values from -1 to +1. high factor loadings indicate that a variable is well represented by a certain factor. 3. results and discussion an analysis of the respondents’ demographic profile was done to ensure that the respondents for the study are the appropriate sample. this was to ensure the correctness of the obtained results. the demography of respondents shown on table 1 shows that all the respondents have a minimum of 5 years’ experience road construction projects. this indicates that well experienced personnel with knowledge on road construction were involved in the survey. their level of education also implies that they are competent and capable of exercising sound judgement. hence, they can provide the researchers with needed information for the study and the responses given can be relied upon. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahmad et al: categorisation of road construction projects’ cost overruns causes using factor analysis. azojete, 15(4):1013-1025. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1016 table 1: respondents' demography category frequency percentage age (years) < 30 3 1.12 31 – 40 86 32.31 41 – 50 143 38.95 51 -60 74 21.72 organisation client 106 39.70 contractor 99 37.08 consultant 62 23.22 education ond 19 7.12 hnd/bsc 130 48.69 msc 97 36.33 ph.d. 21 7.87 experience (years) 6 – 10 77 28.84 11 -15 45 16.85 16 – 20 85 31.84  20 60 22.47 number of road projects worked on  5 58 21.72 6 – 10 82 30.71 > 10 127 47.57 the result in table 2 indicates that the data set has kmo value of 0.844, hence is suitable for further analysis. the determinant of the correlation matrix is a non-zero depicting that at least one factor can be extracted from the data set. the bartlett’s test of sphericity returned a p-value < 0.001 confirming that the determinant is statistically different from zero at p = 0.05. table 2: determinant, kmo, and bartlett's test determinant 3.875e-025 kaiser-meyer-olkin measure of sampling adequacy. .844 bartlett's test of sphericity approx. chi-square 19439.936 df 1035 sig. .000 the scree plot generated from the data (figure 1) shows the point where the apparent break occurred in the graph. this break coincided with the number 9 indicating that 8 factors occurred above the point of inflexion. to confirm the number of factors to retain, the keiser criterion (table 3) yielded 8 factors with total eigenvalues > 1. the factors were assigned representative names reflecting the underlying attributes of the causes they measured. the factor loadings ranged from a minimum of 0.574 associated with technical related factor to 0.972 associated with financial related factor. the reported causes had communalities ranging from 0.427 to 0.955 indicating that the loaded causes sufficiently represent their factors (table 4). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1013-1025. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1017 figure 1: scree plot (eigenvalues against component numbers) the first factor, which was labelled contract related causes (crc), explained a total variance of 24.74%. the second factor, economic and political related (epr) explained 9.88% of the total variance, while design and documentation related (ddr) causes explained 9.261%. financial related (frc), technical related (trc), policy related (prc), construction management related (cmr), and natural (nrc) causes explained total variances of 7.93%, 6.19%, 4.88%, 4.24%, and 3.80% respectfully. the 8 factors accounted for a total variability of 70.92% of the variables implying that the 8 factors sufficiently represent the causes with minimal loss of information. result of reliability analysis shown on table 5 revealed that the causes and their respective factors have values > 0.7, thus, are reliable. similarly, the corrected items total correlations (table 5) satisfied recommended threshold values of internal consistency > 0.3. economic and political factor had the highest alpha value (a = 0.934) with corrected item-total correlation ranging from 0.914 to 0.941. the classification of the causes of cost overruns was based on the factors that emerged from the result of the factor analysis. eight factors emerged from the analysis and each factor contains causes that are interrelated. the groups were labelled contract related, economic and political related, design and documentation related, financial related, technical related, policy related, construction management related, and natural causes of cost overruns. while some of these factors are like those identified in literature review, the causes that loaded on them are different and one of the factors that emerged merged two identified factors from previous studies. hence, direct comparison of the present result with those of previous studies is difficult as different methodologies were used in data analysis, varied causes of cost overruns were identified, revealing different factors and causes that loaded on each factor. the first factor, contract related causes of cost overruns deals with procurement and its related issues. this category includes the development of contract strategies, management of contracting activities, contract documentation, contract performance, contract management and administration after its award. the cost overrun causes that are contract related are misinterpretation, optimism bias, short bid preparation time, competition at tender time, etc. the position of this factor is in line with frimpong et al. (2003) 2nd most important factor that causes cost overruns. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahmad et al: categorisation of road construction projects’ cost overruns causes using factor analysis. azojete, 15(4):1013-1025. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1018 table 3: total variance explained component initial eigenvalues extraction sums of squared loadings rotation sums of squared loadings total % of variance cumulative % total % of variance total % of variance cumulative % 1 11.382 24.744 24.744 11.382 24.744 24.744 9.300 20.216 20.216 2 4.545 9.881 34.625 4.545 9.881 34.625 5.840 12.695 32.912 3 4.260 9.261 43.886 4.260 9.261 43.886 3.466 7.535 40.447 4 3.648 7.930 51.816 3.648 7.930 51.816 3.296 7.166 47.613 5 2.847 6.190 58.006 2.847 6.190 58.006 3.187 6.929 54.542 6 2.245 4.881 62.887 2.245 4.881 62.887 3.022 6.568 61.111 7 1.949 4.237 67.124 1.949 4.237 67.124 2.382 5.179 66.290 8 1.747 3.798 70.923 1.747 3.798 70.923 2.131 4.633 70.923 extraction method: principal component analysis. table 4: rotated component matrixa factors communalities causes crc epr ddr frc trc prc cmc nrc lowest bidder policy 0.911 0.704 lack of coordination 0.901 0.720 outdated estimates 0.899 0.686 litigation 0.883 0.533 mistakes and 0.857 0.590 poor contract 0.826 0.810 non adherence to 0.811 0.658 variations 0.797 0.534 short bid preparation 0.796 0.667 lack of communication 0.737 0.528 poor contract specific 0.717 0.648 delay in decision 0.710 0.881 competition at tender 0.704 0.910 fluctuation of prices 0.935 0.648 inflation 0.935 0.796 strategic decision 0.934 0.777 corruption 0.932 0.738 escalation of material 0.661 0.565 economic instability 0.659 0.734 exchange rate 0.629 0.711 high interest rate on 0.601 0.747 design errors 0.826 0.534 design changes 0.800 0.893 incomplete design at the time of tender 0.787 0.705 lack of cost reports during construction 0.691 0.869 poor documentation 0.626 0.851 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1013-1025. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1019 causes crc epr ddr frc trc prc cmc nrc communalities monthly payment difficulty 0.972 0.876 delay in progress payment 0.958 0.922 contractors cash flow and financial difficulties 0.955 0.955 owner financial difficulties 0.665 0.937 lack of experience 0.825 0.537 ignorance and lack of knowledge 0.781 0.427 insufficient investigations 0.636 0.597 unforeseen ground conditions 0.619 0.475 project complexity 0.619 0.441 latent conditions 0.574 0.368 bureaucracy in tendering method 0.923 0.807 environmental protection and mitigation costs 0.910 0.815 government related issues like changes in policies, pressures etc. 0.699 0.926 poor change control 0.767 0.918 late delivery of material and equipment 0.670 0.926 material related problem 0.645 0.635 schedule delay 0.641 0.478 contractor related problem 0.594 0.925 flood 0.858 0.573 inclement weather 0.819 0.653 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahmad et al: categorisation of road construction projects’ cost overruns causes using factor analysis. azojete, 15(4):1013-1025. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1020 extraction method: principal component analysis rotation method: varimax with kaiser normalization a. rotation converged in 6 iterations. the second group comprises the economic and political related causes. this category of causes of cost overruns encompasses some political related factors in haddad (2018) study and some causes from abusafiya and suliman (2017) environmental related factors. exchange rate, poor economic and political situations, inflation, price fluctuation, high interest rate on loans, strikes, corruption, etc. are causes that fall under the economic and political related group. the construction industry is market driven; the prices of materials, equipment, and labour do change regularly which could in turn affect the cost of a project. inaccurate assessment of market conditions can lead to inaccurate estimates. fluctuations in exchange rate of dollars to naira also affect the cost of construction. high level of corruption has effects on the cost of construction projects as it involves additional transaction costs like bribes. inflation and fluctuation in prices loaded equally and highest on cost overruns in this category. while this factor is the 2nd most important factor that contributes to cost overruns in this study, the political factor in haddad (2018) was ranked 10th of 11 causes of cost overruns and the environmental factors in abusafiya and suliman (2017) had the least ranking. the third group is the design and documentation related causes of road construction projects cost overruns group. design and documentation related causes category was the factor with highest contribution to cost overruns in both memon (2013) and abusafiya and suliman (2017) studies. this category includes design errors and changes, incomplete design at the time of tender, lack of cost reports during construction, and poor documentation. design and documentation are important aspects and can adversely impact on the cost performance of any construction project. design creates a work plan for attaining projects’ goals and documentation creates records of what happened at what time during the project that can be referred to at any time. inadequate and deficient designs and documentations have direct impacts on construction process by leading to delays, rework and variation, which in turn, contribute to increases in project time and cost. design changes being the most severe cause of cost overruns in this category was also the most severe cost overruns cause in memon (2013) design and documentation related causes category. table 5: reliability test result factor causes corrected inter-total correlation cronbach alpha if item deleted scale’s cronbach alpha design and doc. design changes 0.695 0.786 0.835 incomplete design at the time of tender 0.695 0.786 lack of cost reports during construction 0.586 0.820 poor documentation 0.541 0.827 technical lack of experience 0.646 0.712 0.774 ignorance and lack of 0.611 0.720 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1013-1025. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1021 knowledge insufficient investigations 0.529 0.738 project complexity 0.509 0.744 latent conditions 0.471 0.760 unforeseen ground conditions 0.399 0.768 policy environmental protection and mitigation costs 0.836 0.738 0.867 bureaucracy in tendering method 0.852 0.717 government related issues like changes in policies, pressures etc. 0.585 0.973 contract mistakes and discrepancies 0.865 0.957 0.962 poor contract management 0.849 0.957 variations 0.822 0.958 lowest bidder policy 0.894 0.956 lack of communication 0.692 0.961 non adherence to contract conditions 0.815 0.958 poor contract specific attributes 0.695 0.961 short bid preparation time 0.818 0.958 competition at tender 0.608 0.954 delay in decision making 0.688 0.961 out-dated estimates 0.879 0.957 litigation 0.865 0.957 lack of coordination 0.884 0.957 financial contractors cash flow and financial difficulties 0.896 0.870 0.921 monthly payment difficulties 0.926 0.860 delay in progress payment 0.914 0.864 owner financial difficulties 0.571 0.980 construction management material related problem 0.412 0.668 0.699 poor change control 0.544 .611 late delivery of material and equipment 0.465 .646 schedule delays .457 .650 contractor related problem .399 .673 natural inclement weather .767 .868 flood .767 economic strategic decision .903 .914 .934 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahmad et al: categorisation of road construction projects’ cost overruns causes using factor analysis. azojete, 15(4):1013-1025. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1022 and political inflation .912 .914 fluctuation of prices .912 .914 exchange rate .662 .932 high interest rate on loans .560 .941 corruption .909 .914 escalation of material prices .654 .933 economic instability .650 .933 the fourth group represents the finance related causes of road construction projects cost overruns. though according to abdul azis, memon, abdul rahman and abd karim (2013) financial management is an important criteria in achieving successful construction project, the category seemed to be the least important in the same study, which suggest that finances are better managed in malaysia than nigeria, hence their low impact. the importance of this category is also low in abusafiya and suliman (2017) study as compared to the present findings. the causes in this category include owners’ financial difficulties, delay in progress payment, contractor cash flow and financial difficulties. finance is normally the first and most important requirement for any construction project. problems related to finance cause delays and expose construction projects to various risks including inflation. this results in contractors procuring materials and equipment at costs above estimates, hence increasing the cost of construction. the fifth factor, which is the technical related causes group of cost overruns, represents lack of experience, ignorance and lack of knowledge, insufficient investigations, unforeseen ground conditions, project complexity, and latent condition. this category is in line with the 5th category in frimpong et al. (2003) study. actual conditions of a construction site for the full length of a road projects are usually only determined as work commences. unexpected ground conditions along the route may necessitate changes that can increase construction cost, cause delays and subsequently lead to overruns. the sixth factor is related to bureaucracy in tendering, government related issues including changes in policies, and environmental protection and mitigation costs, hence labelled policy related causes of cost overruns. basically, government sponsors most road projects in nigeria; hence, their implementation must be in line with government policy. since government is the largest client of the construction industry, any change in policy towards construction is likely to have significant effect on the industry’s performance. construction management related group which is the seventh factor of road construction cost overruns causes is similar to ameh et al. (2003) construction factor and abusafiya and suliman (2017) contractor site management related factor, however it was found to be the 2nd most contributing cost overruns factor in both of the previous. the causes of cost overruns that are construction management related include lack of experience, poor site management and supervision, inadequate planning and scheduling, ignorance and lack of knowledge, shortage of material, inaccurate material estimate, shortage of labour, delay in decision making, etc. successfully managing construction requires efficient management of all resources on site. anything short of that leads to compromise in quality, schedule delays and cost escalations. despite this category having low importance in this study, it is key in achieving construction success. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2019; vol. 15(4) 1013-1025. issn 15962490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1023 natural causes of road construction projects’ cost overruns, which is the eighth factor comprises of inclement weather and floods. these causes are beyond the control of the construction parties; however, they need to be considered when estimating project costs. such factors can bring a construction to a halt and are referred to as act of god. adverse weather can lead to reduced labour productivity or even stoppage of work. bad weather and flood can cause damage to equipment and materials and even destruction to site. these delays and damages could increase the cost of construction and lead to cost overruns. the ranking of this group in the present study agrees with that of frimpong et al. (2003). although this is the most difficult and unknown factor (frimpong, 2003), it is the least ranked in both studies. this can be attributed to the fact that both ghana and nigeria have two seasons (dry and rainy) and effects of bad weather are usually minimised by working during dry seasons. similarly, cost overruns due to flooding, which is the second cause of cost overruns of the natural related factor in this study rarely occur. 4. conclusion the aim of the study was to classify the causes of road construction projects’ cost overruns. while several studies have classified construction cost overruns wide range of causes, road construction projects’ cost overruns causes cannot be overlooked. through exploratory factor analysis, 42 causes out of the 71 obtained from the review of literature were retained. eight factors namely: contract related, economic and political related, design and documentation related, financial related, technical related, policy related, construction management related, and natural causes of cost overruns emerged from the analysis. it has being observed that a one size fits all solution cannot be applied in solving the problem of cost overruns as the comparison of this study’s result with previous ones indicates that every study has different classification depending on the causes identified, perception of the respondents and area studied. however, the classification of the causes, the essence is to identify the group that most significantly causes cost overruns by identifying the effect of each group. the classification has reduced the large number of cost overruns causes by narrowing them down into factors (underlying root causes) thereby making it easier to identify the group of causes that has the most impact on fcta road construction cost overruns. this will aid in simplifying managing the causes and providing the required solution to minimise them and prevent their future occurrence. this study is not without limitations. the survey was limited to clients, contractors and consultants only. future studies should include subcontractors to shed more light on the causes of road construction cost overruns. acknowledgement the authors thank all those that participated in the questionnaire survey. reference abdul azis, aa., memon, ah., abdul rahman, i. and abd. karim. at. 2013. controlling cost overrun factors in construction projects in malaysia. research journal of applied sciences, engineering and technology, 5(8): 2621-2629. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ahmad et al: categorisation of road construction projects’ cost overruns causes using factor analysis. azojete, 15(4):1013-1025. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrbelel@gmail.com 1024 abusafiya, ham. and suliman. sam. 2017. causes and effects of cost overrun on construction project in bahrain: part i (ranking of cost overrun factors and risk mapping). modern applied science, 11(7): 20-27. aldagheiri, m. 2009. the role of the transport road network in the economic development of saudi arabia. wit transactions on the built environment, 107: 275-286. retrieved from https://www.witpress.com/secure/elibrary/papers/ut09/ut09025fu1.pdf allahaim, fsa. 2006. an empirical classification of cost overrun in infrastructure projects by using cluster analysis. 4th international utzon symposium-sydney australia. retrieved from https://pdfs.semanticscholar.org/7c18/9b9583b923b3140ed14a8101c6f7076746c2.pdf?_ga=2.39 957666.1439119211.1583734867-346520788.1583734867 ameh, oj., soyingbe, aa. and odusami, kt. 2010. significant factors causing cost overrun in telecommunication projects in nigeria. journal of construction in developing countries, 25(2): 49-67. retrieved from http://web.usm.my/jcdc/vol15_2_2010/jcdc%2015(2)%202010art%203_corrected_(49-67)_21.12.2010.pdf centre for social justice 2016. engaging the approved 2016 federal works budget. retrieved from http://csj-ng.org/wp-content/uploads/2018/06/2016-works-budget-review.pdf child, d. 2006. the essentials of factor analysis. 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infrastructure delays and cost escalation: causes and effects in nigeria. international postgraduate research conference, delft university of technology and tno. the netherlands, 3rd7th april 2006., 6: 79-93. stellefson, m. and hanik, b. 2008. strategies for determining the number of factors to retain in exploratory factor analysis. paper presented at the annual meeting of the southwest educational research association, new orleans, 7th february 2008., pp. 36. retrieved from https://files.eric.ed.gov/fulltex/ed500003.pdf (accessed 11 june 2018) http://ascelibrary.org/doi/pdf/10.1061/%28asce%29is.1943-555x.0000221 http://www.ipedr.com/vol15/2-iccpm2011a00003.pdf http://www.ipedr.com/vol15/2-iccpm2011a00003.pdf http://eprints.uthm.edu.my/3948/1/aftab_hameed_memon1.pdf https://files.eric.ed.gov/fulltex/ed500003.pdf file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):160-171 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 160 original research article analysis of groundwater pollution from an unlined constructed wetland sludge drying bed a. e. adeniran1*, o. i. ajibola2 and a. t. aina3 1department of civil and environmental engineering, university of lagos, lagos, nigeria 2lagos state building control agency, ikeja, lagos, nigeria 3works & physical planning department, university of lagos, lagos, nigeria article information submitted: 10 may, 2018 revised: 01 september, 2018 accepted: 05 september, 2018 keywords: groundwater pollution water quality monitoring constructed wetland sludge drying bed. abstract sludge drying beds (sbds) are part of wastewater treatment processes where dewatering and reduction of water content from the substrate sludge take place to enhance caking and thus facilitate handling and disposal. in this study, the effect of the operation of an unlined drying bed of a constructed wetland for domestic wastewater treatment on the adjourning groundwater was investigated. experimental boreholes for water quality monitoring were constructed downstream of the sbd prior to its operation. preliminary investigations of the quality of water in the boreholes were carried out before the operation of the sbd. the concentration levels of ph, conductivity, total dissolved solids, colour, mn, fe, so4, no3, total coliform and e-coli were used to empirically and statistically determine the level of pollution of the ground water during the operation of the sdb. the 2-way anova at (�=0.05) showed that the operation of the sbd had statistically significant impact on the quality of the groundwater on all the observed parameters. for the parameters observed, p<0.05 (p=0.00 for the averages of ph, ec, tds, turbidity, colour, mn+2, fe+2, so4 and no3), while p=0.0028 and 0.0018 for the averages of total coliform and e.coli respectively in all the boreholes. the distances from the discharge point of the sdb were at 15m, 20m, 25m, 30m, 35m, 40m and 50m for boreholes 1, 2, 3, 4, 5, 6 and 7 respectively. also, comparison of the means of the quality parameters with the allowable limits set by the nigerian national environmental surface and groundwater quality control regulations (nsgqcr) indicated that the operation of the sbd rendered the quality of the groundwater unacceptable © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction pollution of water at any point in the hydrological cycle could prevent its availability in good quality for other users in the cycle (tundisi, 2008, varade et al., 2017). potential sources of groundwater pollution include untreated wastewater effluent, seepage from leaking sewers; shoddily built septic tanks, landfill leachate seepage, burial sites, unregulated animal husbandry sites, farming practices and solid waste dumping on the ground. these pollutants include liquids, organic substances, chemical substances and bacteria. groundwater that is close to the surface, as obtained in unconfined aquifers, is more susceptible to pollution (naseh et al., 2018). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 161 constructed wetlands are engineered systems that use natural functions of vegetation, soil, and organisms to treat wastewater. depending on the type of wastewater the design of the constructed wetland has to be adjusted accordingly. constructed wetlands have been used to treat both centralized and on-site wastewater. similar to natural wetlands, constructed wetlands also act as a bio-filter and can remove a range of pollutants such as organic matter, nutrients, pathogens, heavy metals from the water (maiga et al., 2017). constructed wetlands (cw) have emerged as a natural form of wastewater treatment. cws operations mimic nature and research has confirmed their suitability for effective and economic treatment of wastewater especially in the tropical regions (mairi et al., 2012; olukanni and kokumo, 2013 and de anda et al., 2018). like all wastewater treatment processes, sludge is a by-product of cw wastewater treatment. sludge contains low concentration of solids compared to its much higher water content. dewatering aims at reducing the water content to enhance sludge handling for composting, land application and disposal purposes. sdb are the oldest method of sludge dewatering and are still used extensively in small to medium sized plants. this dewatering method easily produces a sludge cake with 25 – 40 percent solids and can exceed 60 percent solids with additional drying time (qiao et al., 2010). groundwater pollution poses a major threat whilst employing the sludge drying bed method, as the drained fluid percolates into the soil profile. lagos state is increasingly dependent on groundwater for domestic and industrial water supplies (balogun et al., 2017). according to longe (2011), groundwater occurrence in the coast of lagos can be classified as confined, semiconfined to unconfined dominated by sand and clay formations. sandy unconfined aquifers have been reported to be susceptible to pollution (odukoya et al., 2013, naseh et al., 2018). the university of lagos, where this study was carried out, takes 60% of its domestic water supply from groundwater aquifers both confined and unconfined (adeniran, et al., 2013). the objective of this study was to investigate the effect of the operation of an unlined drying bed attached to a constructed wetland domestic wastewater treatment on the adjourning groundwater resources. 2. materials and methods 2.1 the study area this study was carried out at the precinct of the constructed wetland located in the service area of the university of lagos, lagos, nigeria. the study area lies between longitudes 3o 23’ 44” e – 3o 23’ 48” e and latitude 6o 31’ 7” n – 6o 31’ 12” n (figure 1). the area falls within the dahomey basin, which underlies a combination of inland, coastal and offshore regions that stretch through ghana, togo, benin and southwestern nigeria. the region is characterized by high water tables within shallow aquifers with tropical weather conditions, lots of sunshine and excessive rainfall (obaje, 2009). the university is bounded on the east by the lagos lagoon which empties into the atlantic ocean. 2.2 constructed wetland wastewater treatment system the sdb studied is part of the constructed wetland wastewater system for the treatment of part of the domestic wastewater generated in the university of lagos main campus. the wastewater generated within the university community is conveyed through a network of sewers to the central sewage pumping station. the wastewater is then processed through the various unit operations including screening, aeration, anaerobic digestion, phytoremediation and slow sand file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeniran, et al: analysis of groundwater pollution from an unlined constructed wetland sludge drying bed. azojete, 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 162 filtration (figure 1). sludge dislodging operation was carried out fortnightly from the anaerobic digester and the cw beds to the sludge drying bed and left to dry naturally by evaporation and drainage through the underlying sand. the dried sludge cakes are evacuated for disposal and land application. prior to the introduction of the sludge drying bed and wetland treatment system, the sludge from the anaerobic chamber were openly discharged, without treatment, on the adjourning soil. the discharged sludge led to further degradation of the lagoon thus endangering human and aquatic life as observed by longe and ogundipe (2010). 2.3 the sand drying bed and observation wells the sand drying bed lies about 10m downstream of the anaerobic digester with dimensions 15 x 20 x 1.5 m (figure 1). the sidewalls were constructed in concrete to ensure stability and prevent collapse. a sand layer of 450 mm depth was placed over the bed. to monitor the groundwater pollution (if any), seven (7) down gradient experimental boreholes of 150 mm diameter (with screen casings) were drilled as part of the constructed wetland project by the university. the depth of each of the experimental boreholes was 10 m. the distances from the discharge point of the sdb were at 15m, 20m, 25m, 30m, 35m, 40m and 50m for boreholes 1, 2, 3, 4, 5, 6 and 7 respectively the constructed wetland and the observation boreholes were completely fenced to avoid anthropogenic activities influence. figure 1: contour map of study area including monitoring boreholes 2.4 collection and analysis samples 2.4.1 experimental boreholes the experimental boreholes were monitored with preliminary samples collected for thirty (30) days and analysed to determine the quality of the groundwater before the operation of the sdb. during the operation of the sdb, groundwater samples were collected from the boreholes in http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 163 accordance with us-epa (2013) between the hours of 08.30 and 09.30 am. sampling, at 5 m depth, was done daily for 50 days for physicochemical parameters while sampling for bacteriological parameters was carried out weekly for 8 weeks. the parameters monitored and analysed were ph, electrical conductivity, total dissolved oxygen, turbidity, colour, manganese, ferrous, sulphate, nitrate, coliform and e-coli. 2.4.2 analysis of samples 2.4.2.1 laboratory analyses analyses of samples were carried out using the american public health association (apha, 2012) standard method for examination of water and wastewater (eaton et al., 2012). all ph measurements were made using an accumet xl50, dual channel ph/ion/conductivity meter. conductivity meter was calibrated with reference solution just prior to measurement of electrical conductivity (ec). the materials for the reference solution were deionized water, calibration standard, plastic cup and a thermometer. the temperature of the solution was adjusted to be in conformity with the standard calibration value provided by the manufacturer. tds was measured using hm digital tds meter. turbidity was measured using hach dr 900 photometer. colour was measured using hanna hi83200 multi-parameter photometer. the concentration levels of mn+2, fe+2, so4 and no3 of the samples were measured with thermo-scientific x-series2 icp-ms spectrophotometer. coliform and e-coli count were enumerated with pour plate method and identified using morphological and biochemical tests in accordance with apha (2012). 2.4.2.2 statistical analysis data were analysed at α = 0.05 using a two-way analysis of variance (anova) on excelr data analysis to compare the means samples from preliminary investigation (samples obtained and analysed prior to the operation of the sdb) with the means results obtained during the operation of the sdb. the results obtained were compared with data in literature (where available). the means of the groundwater quality parameters obtained during the operation of the sdb were also compared with nigerian national environmental (surface and groundwater quality control regulations, 2011 (nsgqcr, 2011) for surface and groundwater discharges, irrigation and reuse. 3. results and discussion the results of means of the observed parameters before and during the operation of the sdb are presented in tables 1 and 2 respectively. the summary of means, deviations and range of the observed parameters are presented in table 3. in table 4 the mean of the replicate concentrations of the quality parameters during the operation of the sdb are presented along with the maximum allowable limits by the nigerian national environmental (surface and groundwater quality control regulations, 2011 (nsgqcr, 2011) for surface and groundwater discharges, irrigation and reuse. table 4 shows that the observed concentrations of most of the physical, chemical and bacteriological parameters were beyond the limits specified by the regulatory authority. the operation of the sdb had seriously polluted the groundwater. table 5 shows the output of anova analysis of observed parameters (α=0.05). it is observed from the anova that the operation of the sdb significantly affected the groundwater quality statistically. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeniran, et al: analysis of groundwater pollution from an unlined constructed wetland sludge drying bed. azojete, 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 164 table 1: mean of quality parameters in experimental boreholes before the operation of sdb parameters units bh1 bh2 bh3 bh4 bh5 bh6 bh7 ph 4.48 4.59 4.54 4.43 4.43 4.43 4.64 cond. μs/cm 257.44 257.76 257.78 257.66 257.34 257.47 257.57 tds mg/l 80.57 79.82 79.65 79.53 79.48 79.45 79.41 turbidity ftu 0.51 0.42 0.52 0.55 0.48 0.45 0.45 colour pcu 30.47 31.16 31.06 30.46 30.63 31.14 31.24 mn+2 mg/l 0.51 0.60 0.53 0.52 0.55 0.41 0.47 fe+2 mg/l 0.04 0.05 0.05 0.05 0.05 0.04 0.05 so4 mg/l 2.89 2.87 2.88 2.88 2.88 2.88 2.87 no3 mg/l 2.53 2.65 2.71 2.61 2.74 2.72 2.73 coliform fu/100ml 2 1 2 1 1 1 0 e-coli cfu/100ml 0 0 0 0 0 0 0 note: bh1, bh2, bh3, bh4, bh5, bh6, bh7 are experimental boreholes 1, 2, 3, 4, 5, 6 and 7 respectively. table 2: weekly means of quality parameters in experimental boreholes during the operation of sdb parameters units bh1 bh2 bh3 bh4 bh5 bh6 bh7 ph 6.83 6.88 6.81 6.66 6.68 6.42 6.82 cond. μs/cm 617.28 664.66 651.30 548.60 555.22 512.14 477.12 tds mg/l 543.90 551.98 533.04 527.58 495.66 496.74 395.56 turbidity ftu 24.48 26.78 25.55 24.15 24.70 23.69 21.89 colour pcu 335.76 368.32 362.76 273.50 284.04 345.96 242.12 mn+2 mg/l 2.37 2.46 2.30 1.88 1.58 1.70 1.13 fe+2 mg/l 36.63 39.15 31.01 24.67 21.26 20.88 10.90 so4 mg/l 61.93 67.01 60.52 58.43 57.99 56.97 46.83 no3 mg/l 65.55 71.04 46.77 49.07 40.24 28.26 23.65 coliform cfu/ml 942 1047 975 960 984 1036 776 e-coli cfu/100ml 14 13 18 16 19 14 12 note: bh1, bh2, bh3, bh4, bh5, bh6, bh7 are experimental boreholes 1, 2, 3, 4, 5, 6 and 7 respectively table 3: summary of observations before and during operation of sdb parameters mean before sdb mean during sdb ph 4.51±0.09 6.73±0.16 cond. μs/cm 257.57±0.17 575.19±71.03 tds mg/l 79.70±0.41 506.35±53.44 turbidity ftu 0.48±0.04 24.61±1.61 colour tcu 30.88±0.34 316.07±49.16 mn+2 mg/l 0.51±0.06 11.54±3.81 fe+2 mg/l 0.05±0.00 26.30±9.17 so4 mg/l 2.88±0.01 58.53±6.15 no3 mg/l 2.67±0.08 46.22±16.16 total coliform cfu/100ml 1±0.05 960±83 e-coli cfu/100ml 0.0±0.0 15±2 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 165 table 4: comparison of observed parameters with nigerian standard for drinking water parameters units observed pollutant level nsgqcr, 2011 comments ph 6.73±0.16 6.5-8.5 acceptable cond. μs/cm 575.19±71.03 1000 acceptable tds mg/l 506.35±53.44 500 marginally acceptable turbidity ftu 24.61±1.46 5 not acceptable colour tcu 316.07±49.16 5 not acceptable mn+2 mg/l 11.54±3.81 40 acceptable fe+2 mg/l 26.30±9.17 0.5 not acceptable so4 mg/l 58.53±6.15 500 acceptable no3 mg/l 46.22±16.16 40.0 not acceptable total coliform cfu/100ml 960±83 10 not acceptable e-coli cfu/100ml 15±2 0 not acceptable table 5: output of anova analysis of observed parameters (α=0.05) parameter ss df ms f pvalue f crit observatio n inference ph 82.548 1 82.548 487.852 0.0000 4.1830 f>fcrit; p<α statistically significant ec 1782476.355 1 1782476.355 303.070 0.0000 4.1830 f>fcrit; p<α statistically significant tds 2393786.247 1 2393786.247 678.072 0.0000 4.1830 f>fcrit; p<α statistically significant turbidity 8408.549 1 8408.549 70.876 0.0000 4.1830 f>fcrit; p<α statistically significant colour 1414055.224 1 1414055.224 317.001 0.0000 4.1830 f>fcrit; p<α statistically significant mn 1793.557 1 1793.5566 313.953 0.0000 4.1830 f>fcrit; p<α statistically significant fe 11377.843 1 11377.8427 29.814 0.0000 4.1830 f>fcrit; p<α statistically significant so4 50672.420 1 50672.4202 201.470 0.0000 4.1830 f>fcrit; p<α statistically significant no3 33075.1899 1 33075.1899 147.902 0.0000 4.1830 f>fcrit; p<α statistically significant coliform 3680938.373 1 3680938.373 20.2609 0.0028 5.5914 f>fcrit; p<α statistically significant e-coli 894.952 1 894.952 23.5641 0.0018 5.5914 f>fcrit; p<α statistically significant 3. 1 ph the mean ph of 4.51±0.09 was observed before the operation of the sbd. during the operation of the sdb, the mean ph values in the observation boreholes ranged from 6.42 to 6.88 (table 2) with a mean of 6.73±0.16 (table 3). the ph values in the observation boreholes were consistent with each other and ranged between 4.43 and 4.64 (table 1). the ph level of the groundwater was altered through the operation of the sdb from an initial acidic level ranging from 4.51±0.09 to an almost neutral level of 6.73±0.16. this may be due to the alkalinity of the sewage sludge file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeniran, et al: analysis of groundwater pollution from an unlined constructed wetland sludge drying bed. azojete, 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 166 (table 3). a two-way anova returned f=487.85 while f-critical=4.18; p=0.000<0.005, hence statistically significant (table 5). the operation of the sdb altered the level of the ground water ph, though the observed levels are within acceptable limits recommended by the nsgqcr (table 4). this is consistent with kengne et al. (2014) who reported groundwater ph level of 6.91 after unplanted drying bed leachate percolation. 3.2 electrical conductivity (ec) electrical conductivity (ec) is a measure of the capacity of water to conduct electric current. it is an indication of the presence of high level of organic and inorganic nutrients in the water body. the conduction of current through a water solution is primarily dependent on the concentration of dissolved ionic substances such as salts. high amounts of dissolved substances can prevent the use of waters for irrigation and drinking, hence conductivity ranks as one of the most important inorganic water quality parameters. the lower the ec of a water sample, the better the quality of the water. mean conductivity value of 575.19 ± 71.03μs/cm was obtained during the operation of the sdb, while a mean value of 257.64 ± 0.17μs/cm was obtained from preliminary investigations (table 3). the deviation in the ec values were significant; f=303.07>f-critical (4.18), p=0.000<0.05 (table 5). the levels of ec during the operation of the sdb were acceptable by nsgqcr standards (table 4). the results are consistent with results obtained by kengne et al. (2014), sanko et al. (2014) and pande et al. (2015) who obtained after pollution ground water qualities ranging from 6.61 to 523.6 μs/cm. 3.3 total dissolved solids (tds) total dissolved solids (tds) are the total amount of inorganic salts and organic matter dissolved in a given volume of water. a high level of tds is an indication of inorganic salts and organic matter pollution. a mean tds value of 506.35±53.44 mg /l was obtained during the operation of the sdb while a mean value of 79.70±0.41 mg/l prior to the operation (table 3). the initial values of tds in the boreholes range from 79.41 mg/l to 80.57 mg/l and were acceptable by nso standards (table 1). the tds values ranging from 395.56 mg/l to 551.98 mg/l observed during the operation of the sdb (table 2) were slightly higher than the regulatory value of 500mg/l (table 4). pande et al. (2015) reported tds pollution values ranging from 789.6-811.4 mg/l. the concentration tds in the observation boreholes during the operation of the sdb was marginally acceptable within the limits recommended by the nsgqcr standards (table 4) though the analysis of variance indicated the change in the level of tds that occurred during the operation of the sdb was statistically significant (table 5). 3.4 turbidity turbidity is the measure of relative clarity of a liquid, as turbidity makes water cloudy or opaque. materials that caused turbidity include clay, silt and microscopic organisms. the mean turbidity value was 0.48±0.04 ftu before the operation of the sdb, whereas the level during operation was 24.61 ± 1.46 ftu (table 3). the turbidity level of the groundwater during the operation of the sdb was observed to be higher than the regulatory value of 5 ftu (table 4) hence the aesthetic quality of the groundwater has been altered by the operation of the sdb. analysis of variance showed that the turbidity level was statistically significant (table 5). the turbidity level of the groundwater was significantly altered due to the operation of the sdb. pande et al. (2015) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 167 obtained values that ranged from 11.1 to 12.5 for groundwater quality after leachate percolation for the city of dhanbad. 3.5 colour colour is an aesthetic requirement for water. the initial perception of the consumer and acceptability of water for consumption or use will normally derive from the colour. before the operation of the sdb, the colour of the groundwater of the study area was acceptable at a level of 30.88± 0.34 pcu and is less than the regulatory standard of 50 pcu (table 1). the colour variation in of the groundwater was consistent and ranged between 29.5 and 31.9 pcu. during the operation of the sdb, the colour of the groundwater became clouded and not aesthetically acceptable. the trends of colour in the observation boreholes (bh) ranged between 93 pcu and 497 pcu with peak points around dislodging days. the mean value of colour was an unacceptable figure of 316.07±49 pcu in accordance with nsgqcr standard (table 4). analysis of variance showed groundwater was significantly polluted (in respect to colour) as a result of the operation of the sdb (table 5). pande et al. (2015), using visual observation, reported alteration of groundwater from “very clear” to “pale yellow” and “light brown.” 3.6 fe high presence of iron ions (fe+2) in water causes discolouration of sanitary wares and stains laundry. iron concentrations in naturally occurring surface waters are normally low (< 0.1 mg/l) but can be higher in groundwater. a mean iron value of 26.30±9.17 mg/l was obtained from the experimental boreholes during the operation of the sdb, while a mean value of 0.05 ± 0.00 was obtained from preliminary investigation (table 3). the concentration of fe+2 of the groundwater before the operation of the sdb was between 0.0 and 0.10 mg/l. the iron concentrations changed significantly during the operation of the sdb and ranged from1.5 and 14.7 mg/l. anova analysis (table 5) showed significant alteration to the iron concentration in the groundwater during the operation of the sdb. these concentration values in the groundwater during the operation of the sdb exceeded the nsgqcr maximum permissible level of 20.0 mg/l (table 4) hence not acceptable. pande et al. (2015) and ohwoghere-asuma and aweto (2013) reported groundwater pollution levels for iron ranging from 17.28 to 18.60 due to sludge leachate. 3.7 manganese (mn+2) manganese ions (mn+2) is a chemical quality parameter in water. high concentration of mn+2 in water has health implication including neurological disorder. the mean mn+2concentration of the experimental boreholes during the operation of the sdb was 11.54 ± 3.81 mg/l, while a mean of 0.51 ± 0.06 mg/l was obtained from preliminary data (table 3). the levels of mn+2 during the preliminary investigation were within the limits of nsgqcr standards and ranged between 0.0 and 0.99 mg/l while the observed. manganese values from the experimental boreholes during the operation of the sdb varied widely between 2.40 and 29.70 mg/l and were below the nsgqcr standard of 40mg/l (table 4). krithika et al. (2017) obtained similar results. analysis of variance, however, indicated statistical significance (table 5) in view of the wide difference that occurred between the observation before and during the operation of the sdb. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeniran, et al: analysis of groundwater pollution from an unlined constructed wetland sludge drying bed. azojete, 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 168 3.8 sulphate (so4) sulphate minerals can cause scale build up in water pipes similar to other minerals and may be associated with a bitter taste in water that can have a laxative effect on humans and young livestock. high level of sulphate is not desirable in water for domestic and industrial uses. a mean sulphate value of 58.53 ± 6.15 mg/l was obtained from the experimental boreholes, while a mean value of 2.88± 0.11 mg/l was obtained prior to the implementation of the sludge drying bed (table 3). before the operation of the sdb the observed concentrations of so4 ranged from 2.83 to 2.92 mg/l and were within the nsgqcr specified standard (table 4). during the operation of the sdb, high values of 117, 119, 121, 125, 129 mg/l which were observed, though these were below the nsgqcr standard of 500 mg/l (table 4), the operation of the sdb altered the level of so4 in the groundwater significantly (table 5). lower figures that ranged from 43.3647.99 were reported for sludge leachate percolation by pande et al. (2015). 3.9 nitrate unpolluted natural waters usually contain only minute amounts of nitrate (jaji et al., 2007). in essence, nitrate is responsible for eutrophication. a mean nitrate value of 46.22 ± 16.16 mg/l was obtained from the experimental boreholes during the operation of the sdb, while a mean value of 2.67 ± 0.08 was obtained from preliminary investigation (table 3). the experimental borehole samples displayed show high fluctuation of no3 concentration reaching peak values during dislodging operation. the mean value of 46.22 ± 16.16 mg/l is not acceptable by nsgqcr standard (table 4) and it is an indication of groundwater pollution. analysis of variance showed that the operation of the sdb had statistically significance on the nitrate level of the groundwater (table 5). łuczkiewicz and quant (2007) obtained no3 value in groundwater of 80 ±10.0 after land application of sewage sludge. 3.10 total coliforms coliforms are a large group of bacteria that inhabit the intestinal tract of humans and animals that may cause disease. coliform presence is an indicator of faecal or sewage pollution in water, which impact negatively on odour, taste and turbidity. a mean coliform value of 960 ± 83 cfu/100ml was obtained from the experimental boreholes during the operation of the sdb, while a mean of 1.00±0.05cfu/100ml was obtained from preliminary observations (table 3). before the operation of the sdb the total coliform concentration in the ground water was acceptable and was between 0 and 5.0 cfu/100ml. the experimental borehole coliform levels, during the sdb operation, ranged from 105 to 1,800 cfu/100ml, which exceeds the nsgqcr limits (10 cfu/100ml) for drinking and recreational purposes (table 4). valenzuela et al. (2009) and adeyemi et al. (2007) reported total coliform groundwater pollution raging from a mean of 225 to 440 cfu/100ml and 140 to 271 cfu/100ml respectively due to sludge leachate. as shown in table 5, anova showed that the operation of the sdb significantly altered the total coliform level of the groundwater. the implication is that the groundwater has become unsuitable for use or discharge into 3.11 e. coli e. coli is a species of diseases causing coliform bacteria specific to faecal material from humans and other warm-blooded animals. e.coli is widely preferred above other coliform as an indicator of faecal contamination of water sources. a mean e-coli value of 0±0 cfu/100ml was observed during the preliminary investigation before the introduction of the sdb. however, during the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 169 operation of the sdb an unacceptable high level of e.coli pollution was observed in all the monitoring boreholes (table 2). the value of e.coli during the operation of the sdb is consistent with dislodging operation and ranged from 3 cfu/100ml to 31 cfu/ml. the e.coli in the observation wells during the operation of the sdb was 15.0±2.0 cfu/100ml (table 3). mendoza et al. (2017) obtained similar results of (3.6-23 cfu/100ml e.coli groundwater pollution due to leachate percolation. the concentration of e.coli in the ground water exceeded the nsgqcr limits of 0 cfu/100ml (table 4). analysis of variance showed that the operation of the sdb had statistically significance e. coli concentration level in the groundwater (table 5). as a result of its operation, the groundwater at the precinct of the sdb was no longer safe for discharge into water bodies or for direct usage. 4.0 conclusion groundwater pollution induced by the operation of the sludge drying bed attached to the constructed wetland domestic sewage treatment plant of the university of lagos was investigated. samples were taken from seven down gradient boreholes downstream of the sludge drying bed for various physicochemical and biological analyses. the obtained water quality parameters were compared with the results from preliminary data obtained from the boreholes before the implementation of the sludge drying bed. increase in the various parameters was observed in the borehole samples when the sdb was in operation. analysis of variance was carried out for each of the water quality parameters investigated. it was observed that, statistically, the operation of the sdb significantly altered the ground quality parameters. in almost all the parameters investigated, the values were in excess of the nigerian regulatory body (nsgqcr) standard for drinking water. the concentration values of the parameters during the operation of the sdb were much higher than those obtained from the boreholes prior to the operation of the sdb. the nsgqcr standards for the parameters were exceeded (indicating groundwater pollution), with the exception of ph, mn and so4. it is recommended that a layer of well compacted clay should be provided to avoid groundwater pollution. also, before the construction of drinking water boreholes in the precincts of sludge drying beds, septic tank soak pits etc., thorough groundwater quality investigations including physical, chemical and biological analysis should be conducted. acknowledgement the authors wish to express our gratitude to the department of works and physical planning, university of lagos for making available the facilities under its control for this study. our sincere appreciation also goes to surveyor tunde ramon for producing the topographic survey of the study area under short notice. references adeniran, ae., aina, at. and oshunrinade, oo. 2013. investigation of reclaimed effluent water from a constructed wetland domestic sewage treatment plant as additional source of raw water at the university of lagos, nigeria. international journal of environmental science and toxicology, 1(1):1-11. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeniran, et al: analysis of groundwater pollution from an unlined constructed wetland sludge drying bed. azojete, 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 170 adeyemi, o., oloyede, ob. and oladiji, at. 2007. physicochemical and microbial characteristics of leachate-contaminated water. asian journal of biochemistry, 2(5):343-348. balogun, ii., sojobi, ao. and galkaye, e. 2017. public water supply in lagos state, nigeria: review of importance and challenges, status and concerns and pragmatic solutions. cogent engineering, 4(1): 1-21. de anda, j., lopez-lopez, a., villegas-garcía, e. and valdivia-aviña, k. 2018. high-strength domestic wastewater treatment and reuse with onsite passive methods. water, 10(19):1-14. eaton, ad., clesceri, ls., greenberg, ae. and franson, mah. 2012. standard methods for the examination of water and wastewater. 22nd ed. washington, dc: american public health association (apha). kengne, es., kengne, iv., nzouebet, wal., akao, a., viet, hn. and strande, l. 2014. performance of vertical flow constructed wetlands for faecal sludge drying bed leachate: effect of hydraulic loading. ecological engineering, 71:384-393. krithika, d., thomas, ar., iyer, gr., kranert, m. and philip, l. 2017. spatio-temporal variation of septage characteristics of a semi-arid metropolitan city in a developing country. environmental science and pollution research, 24(8):7060-7076. longe, e. and ogundipe, ao. 2010. assessment of wastewater discharge impact from a sewage treatment plant on lagoon water, lagos, nigeria. research journal of applied sciences, engineering and technology, 2(3):274-282. longe, eo. 2011. groundwater resources potential in the coastal plain sands aquifers, lagos, nigeria. research journal of environmental and earth sciences, 3(1):1–7. łuczkiewicz, a. and quant, b. 2007. soil and groundwater fecal contamination as a result of sewage sludge land application polish journal of environmental studies, 16(4): 587-593. maiga, y., von sperling, m. and mihelcic, j. 2017. constructed wetlands. in: j.b. rose and b. jiménez-cisneros,(eds.) global water pathogens project, pp. 1-19, michigan state university, e. lansing, mi, usa. mairi, jp., lyimo, tj. and njau, kn. 2012. performance of subsurface flow constructed wetland for domestic wastewater treatment. tanzanian journal of science, 38 (2): 66-79. mendoza m.b., ngilangil l.e., vilar d.a., 2017, groundwater and leachate quality assessment in balaoan sanitary landfill in la union, northern philippines, chemical engineering transactions, 56 (2017): 247-252. naseh, mrv., noori, r., berndtsson, r., adamowski, j. and sadatipour, e. 2018. groundwater pollution sources apportionment in the ghaen plain, iran. international journal of environmental research and public health, 15 (172):1-18 nsgqcr. 2011. national environmental regulations (surface and groundwater quality control). 2011. federal republic of nigeria. official gazette vol. 98, no. 49. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):160-171. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eadeniran@unilag.edu.ng, engrea54@gmail.com 171 obaje, ng. 2009. the dahomey basin. in: obaje, ng. (ed.) geology and mineral resources of nigeria. lecture notes in earth sciences, 120: 103-108. odukoya, a., folorunso, a., ayolabi, e. and adeniran, e. 2013. groundwater quality and identification of hydrogeochemical processes within university of lagos, nigeria. journal of water resource and protection, 5(10): 930-940. ohwoghere – asuma, o. and aweto, ke. 2013. leachate characterization and assessment of groundwater and surface water qualities near municipal solid waste dump site in effurun, delta state, nigeria. journal of environment and earth science, 3(9): 126-134. olukanni, do. and kokumo, ko. 2013. efficiency assessment of a constructed wetland using eichhornia crassipes for wastewater treatment. american journal of engineering research, 2(12): 450-454. pande g., sinha, a. and agrawal, s. 2015. impacts of leachate percolation on ground water quality: a case study of dhanbad city. global nest journal, 17(1):162-174. qiao, w., wang, w., wan, x., xia, z. and deng, z. 2010. improve sludge dewatering performance by hydrothermal treatment. journal of residuals science and technology, 7(1): 7-11. sanko, em., mbeguere, m., diop, c., niag, s. and strande, l. 2014. effect of hydraulic loading frequency on performance of planted drying beds for the treatment of faecal sludge. journal of water, sanitation and hygiene for development, 4(4): 633-641. tundisi, jg. 2008. water resources in the future: problems and solutions. estudos avancados, 63(22):7-16. us-epa. 2013. groundwater sampling, sesdproc_301-r3. pp.34. athens, ga, 30303, usa, valenzuela, m., lagos, b., claret, m., mondaca, ma., perez, c. and parra, o. 2009. fecal contamination of groundwater in a small rural dry land watershed in central chile. chilean journal of agricultural research, 69(2): 235-243. varade, am., khare, yd., mondal, nc., deshkar, rk. and thakare, s. 2017. insinuation of spatial database for realistic groundwater assessment in indian context. sustainable water resources management, 3(4): 343-356 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):207-225 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 207 original research article design, construction and performance evaluation of a small scale biofuel distiller l. n. onuoha1*, m. o. i. nwafor1, j. o. igbokwe1 and n. a. aviara2 1department of mechanical engineering, federal university of technology owerri, imo state, nigeria 2department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, borno state, nigeria *corresponding author’s e-mail address: freshlove2006@gmail.com article information submitted 6 july, 2018 revised 10 may, 2019 accepted 12 june, 2019 keywords: biofuel distiller biomass bioethanol. abstract a biofuel distiller of 20 l feed capacity was designed fabricated and used to distill bioethanol from a biomass broth. the distiller consists of a 40 l volume boiler unit integrated to the combustion chamber as a cylindrical column; and a counter current cylindrical condenser of length, tube and shell internal diameter of 88 cm, 0.0191/0.15 m, inclined at 450. the reactor is a top lit updraft (t-lud) type fired with charcoal of moderate lump. its performance evaluation was conducted using 20 l palm bunch broth as the distiller feed. the palm bunch collected from siat nigeria ltd, ubima, rivers state, nigeria, was physically pretreated by grinding to powder, hydrolyzed with 1.2 % dilute h2so4, at 160°c for 30 min and fermented for 72 h with s.cerevisiae separated from palm wine. the broth was then separated from the slurry by filtering before distillation. the result of the machine evaluation showed that 817 ml bioethanol was obtained per batch at 20 min from the bubble point which took 95 min. actual combustion efficiency was found to be 55 % with reactor power rating of 12.2 kw. the machine vaporized bioethanol fuel from the boiler feed fed at 27°c, and released the distillate at 28.3°c. distillation efficiency was found to be greater than 90 % while the maximum productivity occurred at 10 min from the bubble point. the machine is economical, reliable, convenient to use and can stand diverse environmental conditions. it can be integrated as a waste management step in the downstream end of palm mill operations. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction there is need for biofuels production to augment the use of fossil fuels, and to establish a strong link between the downstream petroleum industry and agricultural activities (nnpc, 2007), especially in developing countries. consequently, countries are steered towards establishing biofuels industry that is commercially viable to both investors and consumers, and provide sustainable job opportunities that could reach the common man. biomass wastes are among the feedstock for renewable energy to achieve the requirement of carbon emission reduction (cers) http://www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 208 credits. owing to its widespread availability, biorenewable fuel technology will potentially result in the employment of more people than fossil-fuel-based technology (demirbas, 2006; shyam et al., 2012; karl et al., 2005). palm oil industries which are striving towards quality and environmental conservation through a ‘sustainable development and cleaner technology’ based on the requirements of environmental quality act (eqa) and the specific regulations governing the management of palm oil mills; can then fully comply to regulatory requirements in terms of combustion, fly ash and energy conservation (yusoff, 2006) by transforming the residue into biofuel ‘a more-valuable end product’ (yong et al., 2007) such as waste palm bunch to bioethanol. efficient implementation of bioethanol production from these wastes can be a breakthrough in the fuel market or world’s energy portfolio (piotr et al., 2008; leland, 2005). these feedstocks when properly treated can be reduced to biofuel. there is need to separate the pure biofuel from the obtained mixture, and this is mostly achieved by distillation for bioethanol. distillation is a thermal separation technique relying on differences in the boiling points of the component liquids to be separated (sudheer, 2013; smith, 1995). the motive force in all thermal separation is the drive towards thermodynamic equilibrium between the different phases (vapor liquid equilibrium, vle) (tongfan et al., 2004). the concentration of the lighter components will be greater in the vapor phase and conversely the concentration of the heavier components will be greater in the liquid phase, and only in the case of pure components or azeotropic mixtures will the equilibrium composition be the same in both phases (jim, 2005; smith et al., 2001). boiling point and vapor pressure are the key parameters and higher vapor pressure creates a lower boiling point. matherson (1980) noted that when alcohol/water mixture is boiled, vapors with a greater concentration of alcohol forms while liquid with a lesser concentration of alcohol remains behind. separation of the bioethanol from water is initiated at this stage taking advantage of the low boiling point of bioethanol (78 °c) and the positive azeotrope it forms with water (jim, 2005). depending on the availability and cost, different fuels can be used for heating such as fossil fuels: kerosene, diesel, lpg; electricity; or biomass: firewood, charcoal, pellets etc. biomass or electricity is often used because of their availability, ease of handling and simplicity of design. biomass combustion equipment is often simpler and cheaper than equipment for other technologies (sheng and azevedo, 2005). the potential of biomass as alternative fuel source to replace lpg is a promising option (hassan et al., 2011). traditionally, energy in the form of firewood, pellets, twigs and charcoal has been the major source of renewable energy for many developing countries (emerhi, 2011). charcoal could be used as a heat source for bioethanol distillation because of its low price and ease of procurement in agricultural countries like nigeria. a fuel’s energy density can depend on its concentration which is the purity, and yield as a basis of economic measure on its viability as related to the process technology adopted (antonia et al., 2001). presently, only few industries produce bioethanol fuel partly because of the cost of importing a sophisticated distiller. also, irrespective of the negative health effect, people have taken to local production of bioethanol for consumption due to the ease of doing this with ordinary pots but in hideouts as it is banned by the government. therefore introducing an affordable distiller will engage more industries into the biofuel production as well as encourage local producers to produce bioethanol for fuel rather than consumption which has a negative health effect. the main objectives of this study was to fabricate a biofuel distiller that will produce quality bioethanol at low cost. the distiller will be analyzed base on: thermal efficiency, distiller capacity, bioethanol yield, distillation rate, distillation productivity and distillation efficiency. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 209 2.0 methodology 2.1 feedstock collection and preparation palm bunch collected from siat nigeria ltd, ubima, rivers state, nigeria, was reduced to bioethanol broth; by grinding, hydrolysis and fermentation (nuru et al., 2014; julia´n et al., 2011). after physical pretreatment, the waste palm bunch was subjected to hydrolysis on condition of 1.2 % dilute h2so4, at 160 °c for 30 min and fermentation for 72 h with s.scerevisiae separated from palm wine. broth was then separated from the slurry by filtering because; distilling the whole slurry will definitely affect clear separation of the fermented portion of the feed and invariably affect the final yield (olaoye, 2011). total bioethanol concentration in the broth was estimated by chromic acid method; and absorbance determined at 584 nm wavelength using a spectrophotometer was converted to bioethanol concentration from a standard curve for standard solution of absolute ethanol (caputi et al., 1968; congcong et al., 2013). 2.2 distiller design procedures the designed distiller is expected to distill bioethanol from a 20 l feed which consists mainly of bioethanol and water. the distiller composes of a boiler, condenser and a coolant storage tank unit. the boiler is the feed holding space where pressure is built in response to increasing temperature due to heat supply from an incorporated reactor. it is also incorporated with a thermometer and pressure gauge for temperature and pressure reading. the condenser condenses bioethanol vapor by extracting heat from it. the coolant storage tank stores the coolant which circulates through the condenser. the following were considered in the design: a) thermal and physical properties of ethanol b) thermal and physical properties of feed and its constituents. c) quantity of feed and bioethanol content to be distilled. d) heat energy requirement e) fuel type and the required quantity. f) properties of fuel and conditions for complete combustion. in order to accommodate generated vapor, the feed is considered as half of boiler volume. below the boiler capacity, the rising vapor will lose energy and cool down before it reaches the condenser; as such the yield will be low (bolling and suarez, 2001). charcoal was selected as the reactor fuel because of its low price and ease of procurement. properties of charcoal depend on its wood specie and specific gasification rate of wood which is in the range of 100 250 kg/m2h (ojolo et al., 2012a). thus, the heating value of the charcoal is classified within the range for that of acacia species residue given by tarig and osman (2012) as 17,386 – 19,309 kj/kg with density range of 226.3 – 728 kg/m3. stoichiometric air (sa) of charcoal was given as 8.4 m3 air per kg by engineering toolbox (2016) while 9.98 kg/kg was given by baldwin, (1987). reed (1981) gave its equivalence ratio (e) as 0.25 considering its low carbon content compared to wood. its specific gasification rate (sgr) ranges from 78 – 86 kg/m2-h (ojolo et al., 2012b). in the design, the following were considered for charcoal: 19,309 kj/kg fuel heating value (hvf), 80 kg/m2-h sgr, 230 kg/m3 density and 9.98 kg/kg sa. the charcoal is considerably dry. updraft reactor is chosen because of its advantages (fao, 1985) which include; (1) ease of operation (2) high charcoal burnout file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 210 (3) high equipment efficiency (4) possibility of operating with fuel varieties (5) high heat transfer. its main disadvantage is channeling difficulty which can lead to oxygen breakthrough and consequence explosion; this can be checked by appropriate air current and channel column. prevailing ambient temperature (tamb) was simulated to be 30 °c while other parameters were calculated from basic formula as outlined below. 2.3 energy and fuel requirement (a) energy needed for distillation qn is the sum of heat energy required to raise the temperature of the feed from initial temperature to its bubble point that needed to change bioethanol to vapor at the feed bubble point. qn is calculated according to eke (1991) using equation (1). qn = m.c.∆θ + ml (1) where: m is mass of feed in (kg). c is specific heat of feed (kj/kg°c). l is latent heat of vaporization of bioethanol at its boiling point (kj/kg°c). l is chosen at its boiling point because highest energy to convert bioethanol to vapor is achieved at that point (li et al., 2010; iguaz and vı´rseda, 2007). ∆θ is the temperature difference. as deduced from jones and dugan (1998), kister (1992), don and robert (1997) the specific heat of the feed is calculated at its bubble point with equation (2).feed bubble point was calculated iteratively at atmospheric pressure to be 99.6 °c. cfeed = ceth.xeth + cwxw (2) where: x and c are liquid mole fraction and specific heat (kj/kg.k) at bubble point respectively. the bubble point of the binary feed is the temperature (at a given pressure) at which the first bubble of vapor is formed when heated i.e. the point at which the first drop of a liquid mixture begins to vaporize (kister, 1992, don and robert, 1997). vapor pressure of the components was calculated with antoine constants as given in equation (3) while equation (4) gives their vapor mole fraction. log10p(mmhg) = a − b c+ t (3) vapor mol fraction = liquid mol fraction vapor pressure atm pressure (4) where: a, b, c are antoine constants corresponding to temperature, t (°c) . (b) combustion chamber heat energy input qf and boiler power rating pf were calculated using equation (5) and (6) respectively, (theraja et al., 2001): qf = qn eff (5) pf = qf 3600 sec (6) where: eff. is the boiler’s calorific efficiency, qn is energy needed for distillation (kj). (c) considering 5% loss of heat due to insulating material, total heat energy qtn entering the boiler is: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 211 qtn = qn + % loss xqf (7) (d) weight of fuel (charcoal) used wfu (kg) and charcoal consumption rate fcr (kg/hr) were calculated using equation (8) and (9) respectively (belonio, 2005): wfu = qf hvf (8) fcr = wfu 3600 (9) where: hvf is heating value of charcoal (kj/kg). normally qf may differ from qn as it also accounts for heat loss in the boiler unit. (e) combustion zone velocity (czv) was calculated using equation (10). czv = fuel height time (10) 2.3.1 boiler boiler height hb was determined from equations (11). hb = vb 2πr2 (11) where: ‘r’ is the boiler radius (m) and vb is boiler volume (m3). the boiler shell is an alloyed steel cylindrical vessel oriented vertically. the boiler forms a continuous column with the reactor, thus have same shape and diameter. the height of the boiler is moderate for quick even heat distribution in the entire content and πr2 is heating surface area of the boiler shell. 2.3.2 reactor the reactor consists of the combustion chamber and ash chamber. to ensure complete combustion, air cavity of 5.69 cm diameter is considered to run through the combustion chamber (belonio, 2005). a height of 12 cm was allowed for feeding charcoal into the reactor. combustion chamber has a mesh floor of 0.25 inches diameter air holes. ash collection chamber of 32 cm height which carries the fan casing is incorporated to the combustion chamber. the ash chamber has 18 cm clearance from the floor. the reactor diameter was computed according to belonio (2005) using equation (12). reactor diameter,d = 1.27 fcr sgr 0.5 (12) the height of the reactor was computed using equation (13) according to singh (2008). reactor height, h = sgr x t ρch (13) where: fcr is fuel consumption rate (kg/s), sgr is specific gasification rate (kg/h.m2), t is time to consume charcoal (h) and ρchcharcoal density kg/m3. reactor height determines how long the distiller would be operated in one loading of fuel. the higher the reactor, however, the more pressure draft is needed to overcome the resistance exerted by the fan or blower. inferring from the volume equations, the volume of a reactor defines the quantity of heat that can be released in the combustion chamber (somchart et al., 2010). the volume of the cylindrical reactor, vr was calculated using equation (14) vr = πr2h (14) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 212 where: h is reactor height (m). reactor cross sectional area (csa) was computed using equation (15) due to rathore et al., (2009). csa = fcr sgr (15) where: fcr is fuel consumption rate (kg/s) and sgr is specific gasification rate (kg/h.m2). the ash chamber serves as the discharging unit for ash produced after each operation. it was located beneath the reactor to easily catch the ash that is falling from the reactor. it was always kept closed when operating the distiller. four metal support legs are provided beneath the ash chamber to support the entire combustion chamber. a chimney was introduced to the reactor top base to allow smoke to pass out. 2.3.3 computation of reactor airflow rate airflow rate, afr in the reactor was calculated using equation (16) due to belonio (2005). afr = fcr x sa ρair (16) where: fcr is fuel consumption rate (kg/s), sa is stoichiometric air and ρair is air density. superficial velocity, vs in fuel bed was given by equation (17) due to srinivasa et al., (2016). vs = afr reactor area (17) where: afr is airflow rate (m3/s). this refers to the speed of the air flow in the fuel bed. the velocity of air in the charcoal bed will cause channel formation, which affects combustion. similarly, the thicker the layer of fuel in the reactor, the greater is the resistance required for the air to pass through the fuel column (belonio, 2005). specific pressure draft of charcoal ∆pwas derived from expression for total pressure draft given in equation (18) according to belonio (2005). pd = h x ∆p (18) where: pd is the total pressure draft of charcoal (pa), h is reactor height (m) and ∆p is the corresponding specific pressure draft of charcoal in centimeter of water per meter depth of fuel at the calculated superficial gas velocities. considering the work of bello et al., (2015), joseph and oliver (2016), wusana et al., (2014), klavina et al., (2014); the pressure drop of charcoal with particle size greater than 6.7 mm is within the range of 30 – 36 pa for afr of 0.103 – 115 m/s having a specific air resistance of the range 83 – 102.4 pa/m. a total pressure drop of 30 pa was considered for this design. charcoal does not have severe air resistance and the column is not too high at 0,35m; so, to save cost natural air convection instead of a blower was utilized. in order to meet the furnace requirement of supplying the air flow rate while overcoming the fuel (charcoal) pressure drop; the furnace is constructed with a perforated column (air cavity) attach to its mesh floor, the fan chamber is rather vented and positioned towards the natural air current. the perforated column and floor help to remove ash. 2.3.4 condenser the condenser is designed for counter current fluid flow in order to extract a higher proportion of heat from the hot fluid. it is cylindrical and inclined at angle 45° to the boiler column to http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 213 ensure slow vapor velocity and achieve complete condensation. the distillation tube is ½” nominal ‘d’ copper tube with 0.0205 m od, 0.01905 m id, 2.8506 x 10-4m2 csa and negligible thickness of 0.001 m. velocity, vt of bioethanol vapor in the tube and its reynold’s number at the tube inlet condition were calculated using equation (19) and (20) respectively and found to be laminar with low velocity. vt = v� bio csatube (19) re.vapor = ρvvvd μv (20) where: vt is bioethanol vapour velocity (m/s) in the tube, v� biois volumetric velocity of bioethanol (m3/s), csatube is tube cross sectional area, d is tube diameter, ρv, vv, μv are bioethanol vapour density (kg/m3), velocity (m/s) and viscosity (kg/m.s) respectively. thus, the condensation heat transfer coefficient, hcond. was calculated according to yunus and afshin (2015) and considering inclination angle using equation (21). hcond = 0.555 gρl ρl − ρv kl 3 μl tsat − ts d hfg ∗ 1 4 sinθ 1 4 (21) and the modified latent heat of vaporization is calculated using equation (22) according to yunus and afshin (2015). hfg ∗ = hfg + 3 8 cpl tsat − ts (22) where: ρ, μ, k, cp and hfgare density (kg/m3), viscosity (kg/m.s), conductivity (w/m.k), specific heat capacity (kj/kg.k) and latent heat of vaporization (kj/kg) of the saturated bioethanol while subscripts l and v are for liquid and vapor respectively. tsat and ts are saturation temperature of bioethanol and tube surface temperature respectively. g is acceleration due to gravity. the log mean temperature difference, lmtd for the counter current flow heat exchanger is calculated using equation (23) according to khurmi and gupta (2006). coolant inlet temperature was 30 °c and the required out flow temperature was 40 °c. lmtd = th1 − tc2 − th2 − tc1 ln th1 − tc2 th2 − tc1 (23) where: t is temperature (°c) and subscripts h, c, 1 and 2 are for hot fluid (bioethanol), cold fluid (coolant), inlet and outlet respectively. the condenser shell is cylindrical mild steel material of 15 cm diameter and 3 mm thickness with 0.01482 m2 cross sectional area (csa). the quantity of coolant (water) was determined using equation (24) due to yunus and afshin (2015). mw = mbiohfg ∗ cw tc2 − tc1 (24) where: mbio, mw and cw are mass of bioethanol (kg), mass (kg) and specific heat (kj/kg.k) of water respectively. hfg ∗ is the modified latent heat of vaporization (kj/kg), tc2 and tc1 are outlet and inlet temperature (°c) of coolant respectively. though a cylindrical drum was used to hold coolant and connected to the shell with pipes. a centrifugal pump of 0.5 hp was used to circulate coolant. velocity of coolant in the shell vs and file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 214 its reynold’s number were calculated using equation (25) and (26) respectively and found to be laminar with low velocity. vs = 4 v�w π dh 2 (25) re.w = ρvsdh μs (26) where: dh is annulus hydraulic diameter idshell − odtube , v�w is water velocity (m/s), ρ, vs and μs are density (kg/m3), velocity (m/s) and viscosity (kg/m.s), of shell side fluid. the tube and shell formed an annulus. the shell-side heat transfer coefficient was calculated using equation (27). hshell = nuik dh (27) where: nui is nusselt number on the tube of the shell space corresponding to the ratio of the inner and outer diameter of the annulus odtube idshell . k is conductivity (w/m.k), dh is annulus hydraulic diameter (m). the corresponding nusselt number was determined from kay and perkins (1972). the overall heat transfer coefficient ‘u’ was calculated using equation (28) due to yunus and afshin (2015). 1 u = 1 hcond + 1 hshell + rft + rfs (28) where: rft and rfs are tube-side and shell-side fouling factor due to alcohol and water which by tubular exchange manufacturing association are 0.0001 each. hcond and hshell are condensation heat transfer coefficient and shell-side heat transfer coefficient respectively (w/m2.k). condensation heat transfer surface area atotal was calculated using equation (29). atotal = q� u.f.lmtd (29) where: f is correction factor which is ‘1’ for counter flow (yunus and afshin, 2015), q� is rate of heat transfer, u is overall heat transfer coefficient (w/m2.k), lmtd is log mean temperature difference (°c). length of condenser tube was calculated using equation (30). l = atotal πd (30) where: atotal is condensation heat transfer surface area (m2), d is the tube diameter (m). pressure drop at shell-side was calculated using equation (31) due to yunus and afshin (2015). ∆p = 32 μ l vavg dh2 (31) where: dh is annulus hydraulic diameter (m), l is shell length (m), vavg is average velocity (m/s) and μ is viscosity at shell side (kg/m.s). head loss at shell-side was calculated using equation (32). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 215 hl = 64 l vavg2 2 g dh2re.w (32) where: dh is annulus hydraulic diameter (m), l is shell length (m), vavg is average velocity (m/s) and g is acceleration due to gravity, re.w is renault number of shell fluid. the head loss is the additional height the fluid needed to be raised by a pump in order to overcome the frictional losses in the shell (frank and david, 2002). pressure loss at shell-side was calculated using equation (33) due to yunus and afshin (2015). ∆pl = ρ g hl − lsin 450 (33) where: hl is head loss at shell-side (m), ρ is density (kg/m3), g is acceleration due to gravity, l is shell length (m). shell-side pumping power was calculated using equation (34). wpump = m g hl (34)� where: hl is head loss at shell-side (m), m is mass of coolant (kg), g is acceleration due to gravity. 2.4 distiller evaluation the distiller was investigated on average of three distillation runs base on thermal efficiency, distiller capacity, distillation yield, distillation rate, bioethanol productivity and distillation efficiency. (a) thermal efficiency: this is the thermal efficiency of the boiler. it is the ratio of heat actually used in producing the fuel to the heat liberated in the furnace (khurmi and gupta, 2006) and is calculated using equation (35). ɳth = heat used to produce fuel heat liberated in furnance x 100 (35) (b) distiller capacity: this is the power of the constructed distillation unit (khurmi and gupta, 2006); it is the amount of bioethanol evaporated or bioethanol fuel (condensate) produced in kg expressed per fuel (kg) burnt using equation (36). dc = meth weigh of fuel burnt (36) (c) distillation yield: this is alcohol obtained with distillation time (tangka et al., 2011; nurul et al., 2014) as expressed in equation (37). it shows the presence or absent of regression in the distillation process which depends on steadiness of heat supply and heat source sufficiency (olaoye, 2011). bioethanol fuel yeild l min = qbe l time, ∆t (37) where: qbe bioethanol fuel produced in liters, (e) distillation rate: this is alcohol that could be obtained per hour of distillation process (will, 2018) as expressed in equation (38). it shows the speed of the production process. bioethanol fuel yeild l h = qbe l hour (h) (38) (f) bioethanol productivity: this is bioethanol per minute to volume of feed (tangka et al., 2011; nurul et al., 2014) as in equation (39). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 216 bioethanol productivity = qbe l/min feed volume (l) (39) (g) distillation efficiency: it is a measure of how much alcohol was finally produced relative to the amount that was in the feed. it shows the amount of losses in the evaporation and distillation process (combined sugar news, 23 july 2016). distillation efficiency is expressed in equation (40) by sugar news (2016). distillation efficiency (%) = vol.of distillate bioethanol content in feed (l) x100 (40) (h) other parameters investigated and compared to the designed parameters in a tabular form are fuel weight, boiling point, total operating time, fuel consumption rate, specific gasification rate, combustion zone velocity, reactor power input, bioethanol yield, distillation temperature and vapor pressure. 2.5 material selection material selection was based on strength/fatigue resistance, heat resistance, wear and corrosion resistance, cost, workability and appearance (baqui et al., 2008). appropriate selection of the best materials was ensured to enable the best quality of the distillery unit and bioethanol quality, and to meet design standards. thus, copper tube was used as the condenser tube (kris, 2004), alloy steel was used for the shell and boiler unit while glass container collects the distillate (yuelei et al., 2012). fiber glass was chosen for insulation of the heating unit. the exploded and isomeric view of the designed equipment is presented in figure 1 and 2 respectively while figure 3 is the pictorial view of the fabricated and assembled distiller. 2.6 fabrication process the fabrication steps involved selection and/or cutting of metal sheets into desired sizes, and arc welding joints where necessary to ensure toughness and strength. parts were welded perfectly with firm joints to avoid vapor loss. pipe settings were carried out with utmost carefulness. it was subjected to hydrostatic pressure test. hand pump was use to fill in the shell with water and by pressurizing to set pressure, say 4 or 6 bars. dye penetration test was done on welded edges to ensure there are no pin holes and cracks on the weld. the pressure was observed for about 25 minutes to ascertain if there were leakages on the tube. the exchanger was then boxed-up and made ready for use. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 217 figure 2: isomeric view of the distiller parts list 1 boiler 2 reactor door 3 exhaust pipe 4 condenser 5 pressure gauge 7 thermometer 8 coolant stand 9 coolant 10 boiler outlet 28 pump 4 figure 1: exploded view of the distiller file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 218 figure 3: pictorial view of the fabricated distiller 2.7 performance evaluation twenty liters of feed at 30 °c prepared from waste palm bunch was fed into the boiler and the reactor charged with locally sourced charcoal. boiler feed is 1/2 capacity of the boiler in order to accommodate vapour as recommended by boiling and suarez (2001). coolant at ambient temperature of 27 °c was allowed into the condenser at 2.1632 x 10-4 m/s. the distiller follows the principle of producing heat in complete combustion with stoichiometric air requirement of 9.98 kg/kg of charcoal just enough to convert the fuel to ash. the fuel was ignited from the top of the reactor. air flows in at the bottom while exhaust gas leaves at the top. sufficient ambient air to burn the fuel and distribute hot air was naturally aspirated into the reactor at airflow rate of 14.335 m3/h and superficial air velocity of 0.1047 m/s. this results to mass flow rate of hot air as 0.102 kg/s. the fuel ignition improved towards complete combustion. combustion zone moved down the reactor at 5.072 x 10-5 (m/s) in a batch mode as charcoal converts to ashes. the reactor generated heat upwards which is directly transferred to the boiler through a heat surface area of 0.038 m2, where it acts as the vaporization heat for bioethanol. at this point bioethanol vaporizes above the feed and flows via the delivery pipes across the entire condenser length of 0.88 m and total heat transfer surface area of 0.0551 m2. it condenses within the length of the condenser as it loses heat to the circulating coolant. the bioethanol then drops out and was collected as a pure liquid at 28.3 °c in a graduated glass container while coolant outlet temperature was 40 °c. this type of direct heated device is often referred to as an alambic style still (kris, 2004). thermometer port ash chamber exhaust pipe condenser pump pressure gauge boiler furnace door bioethanol outlet feed inlet http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 219 3.0 result and discussion figure 4 illustrates bioethanol fuel yield from distillation which is the distillate collected with time. figure 4: bioethanol fuel yield from distillation from figure 4, it was observed that it took 95 min to get the feed to the boiling point of bioethanol. this boiling time corresponded with the observed temperature and vapour pressure of 96 °c and 2.81 bar respectively. bioethanol separation from water is initiated at this point. vapors with a greater concentration of bioethanol formed above the feed (mathewson, 1980). figure 4 also shows a progressive increase in yield of bioethanol from 95 min to a maximum of 817 ml at 115 min after which its yield became constant. this means that bioethanol yield stopped at 115 min from the boiling point. the progressive level of bioethanol yield with time to the observed maximum yield prior to the eventual gradual decrease to no yield indicated that bioethanol yield was well regulated by the distiller (olaye, 2011). total bioethanol fuel distilled after 20 min was estimated at 817 ml resulting to 2451 ml/h of distillation. this is positive compared to 4.25 l obtained in 1½ h by olaye (2011) with a reflux column distillation unit. figure 5 illustrates distillation rate with time. figure 5: distillation rate with time it can be deduced from figure 5 that highest yield rate of bioethanol at interval time was observed at 5 min from the boiling point. distillation temperature was more stable within this period, suggesting bioethanol molecules having the lowest binding energy with water molecules evaporated at this point (ophardt, 2003). production rate depicts how speedy the process was (will, 2018), which in this case could depend on heat supply and molecules bonding strength file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 220 (sudheer 2013; smith, 1995; ophardt, 2003). this observation indicated that constant and sufficient heat source was supplied by the machine resulting to avoidance of regression in the process (olaoye, 2011). highest yield rate of bioethanol at interval time decreased from 4080 ml/h at 100 min to 668 ml/h at 115 min. figure 6 illustrates distillation productivity with time. figure 6: distillation productivity with time from figure 6, it was observed that maximum productivity of 0.084 ml/ml.min was attained at 10 min which corresponded to the time of highest distillation rate, and decreased with time within a temperature range. this indicated that the distiller showed reasonable consistency in its operation. it could suggest that, distillation may be seen as a removal process from the boiler of which the material being removed decreases with time at a temperature or within a temperature range. figure 7 illustrates distillation efficiency with time. figure 7: distillation efficiency with time figure 7 shows that distillation efficiency increased with time to a maximum of 99.798 % at 115 min. it indicates that the distiller did a quality work though it has small feed capacity, thereby encouraging its adoption and improvement to a larger scale. distillation process is predicated on the principle of conservation of matter which says that matter can neither be created nor destroyed (matherson, 1980). rate of distillation of ethanol is influenced by the ratio of substrate to the ethanol content of the substrate (olaoye, 2011). bioethanol yield in liters per volume of feed used is 0.041 (l l-1). this shows that bioethanol concentration was low compared to the volume of the feed. notwithstanding, this is higher than 0.033 (l l-1) reported by olaoye (2011). increasing the bioethanol concentration in the feed before distillation will increase productivity as well as reducing the production costs considerably (julian et al., 2011). the distilled http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):207-225. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: freshlove2006@gmail.com 221 bioethanol may not be pure as it may still contain some water and can be further dried in a rotavapor. table 1, presents the distiller performance data. table 1: distiller performance data parameter design observed eqn. fuel weight (kg) 1.67 2.2 8 boiling point (°c) 99.6 95 3 total operating time (min) 60 115 13 fuel consumption rate (kg/h) 1.67 1.83 9 specific gasification rate (kg/hm2) 80 87.372 12, 13 combustion zone velocity(m/s) 9.72 e-5 5.072 e-5 10 reactor power input (kw) 8.95 12.2 6 thermal efficiency (%) 75 55 5 bioethanol yield (ml) 815.67 817 (lab) distillation temperature (°c) 99.6 95 98 3 vapor pressure (bar) 3.2 2.81 – 3.01 4 feed inlet / distillate outlet temperature (°c) 27 / 27 30 / 28.3 experimental data presented in table 1 showed that the combustion zone velocity was actually found to be 5.072 x 10-5 (m/s) against 9.72 x 10-5 (m/s) expected. apart from possibility of absorbing moisture from the environment and fluctuation in natural air flow, this may be due to charcoal porosity and packing in the reactor which influences pressure draft in terms of air flow channel across the fuel bed (klavina et al., 2014; joseph and oliver, 2016). however, all charcoal was reduced to ash. this confirms that complete combustion and good distiller performance was achieved (bello et al., 2015). thermal efficiency has been shown to depend more on equipment than fuel selection (baldwin, 1987; agyei, 2014). inefficiencies include incomplete combustion. also, smoke emission was clear of soot and foul odor was not observed during the process. this confirms good quality of the charcoal specie and sufficient air supply into the fuel column during firing (bello et al., 2015; belonio, 2005). the operation was stopped at 120 min and reactor consumed 2.2 kg charcoal at the rate of 1.83 kg/h. but total operating time to consume charcoal observed was 115 min which is 55 min more than expected by the design. the extra 0.527 kg charcoal and time observed may account for the heat used in heating up the boiler material and a lower calorific due to less quantity of acacia charcoal (abolagba and nuntah, 2012; tarig and osman, 2012). observed thermal efficiency is 55 % with 12.2 kw power input while design values are 75 % with 8.95 kw respectively. these suggest that the purchased charcoal is having a lower calorific value than the design expected, showing that it contains less quantity of acacia specie (ijagbemi et al., 2014). boiling temperature of the bioethanol was observed to be a range than a point, taking place at temperature and vapor pressure range of 96 – 98 °c and 2.81 – 3.01 bars as indicated by the thermometer and pressure guage respectively from 95 minutes. 4.0 conclusion a biofuel distiller of 20 l feed capacity that operates on solid fuel was designed; fabricated and successfully used to distill bioethanol fuel from a 20 l feed. the distiller consists of a 40 l volume file:///c:/users/user/downloads/azojete143/www.azojete.com.ng onuoha, et al: design, construction and performance evaluation of a small scale biofuel distiller. azojete, 15(2):207225. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 222 boiler unit integrated to the combustion chamber as a cylindrical column; and a counter current cylindrical condenser of length, tube / shell internal diameter of 88 cm, 0.0191 / 0.15 m, inclined at 450. the reactor is a top lit updraft (t-lud) type fired with charcoal of moderate lump. heat generated upwards was directly transferred to the boiler where it acts as the vaporization heat. the distiller recorded combustion efficiency of 55 % operating on charcoal. feed fed to the boiler at 27 °c was heated to boiling point of bioethanol at 95 min while 817 ml distillate was collected in 20 min at 28.3 °c. boiling temperature of the distillate was observed to be a range than a point of which the thermometer and pressure gauge recorded temperature and vapor pressure range of 96 – 98 °c and 2.81 – 3.01 bars respectively from 95 minutes. the distiller is environment friendly and economically viable. references abolagba, oj. and nuntah, jn. 2012. effects of oil bean wood charcoal as energy source and two treatments on the characteristics of smoked lean and fatty fish species, using full drum smoker. nigerian journal of agriculture, food and environment. 8(4): 43-45. adzimah, k. and seckley, e. 2009. improvement on the design of a cabinet grain dryer. america journal of engineering and applied science, 2: 217-228. agyei a., tawiah po. and nyarko f. 2014. efficient charcoal stoves: enhancing their benefits to a developing country using an improved design approach. international journal of engineering trends and technology (ijett), 15(2): 94 – 100. antonia, vh., timothy, el., jennifer, ie. and daniel, mk. 2001. renewable energy sources: a viable choice. journal of environment, 43(10): 1 – 17. baldwin, sf. 1987. biomass stoves: engineering design, development, and dissemination. center for energy and environmental studies. princeton university new jersey, usa. publish by vita, usa. november. pp. 382. baqui, ma., ahiduzzuman, m. and rahman, m. 2008. experiences in installation and operation of energy efficient rice parboiling system. short course on energy efficiency, bangladesh rice research institute (brri) dhaka, pp. 108-124. bello, rs., adegbulugbe, ta. and onilude, ma. 2015. characterization of three conventional cookstoves in south eastern nigeria. agricultural engineering international: cigr e-journal, 17(2):122 – 129. belonio, at., 2005. rice husk gas stove handbook. appropriate technology center, department of agricultural engineering and environmental management, college of agriculture, central philippine university iloilo city, philippines, i, pp. 155. bolling, c. and suarez, n. 2001. brazilian sugar industry: recent developments, special article, sugar and sweetener situation and outlook. economic research service, usda. september 2001. http://www. usda.gov/briefing/brazil/ braziliansugar.pdf. accessed 9th feb. 2017. caputi, a., ueda, m. and brown, t. 1968. spectrophotometric determination of ethanol in wine. american journal of enology viticulture, 19: 160 – 165. collier, jg. 1982. convective boiling and condensation. 2nd edition, mcgraw hill, new york, usa. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; 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(tarnekar sg., khedkar mk. and sedha rs. eds.), new delhi s.chand and company limited publishers, india, pp. 2,782. will, k. 2018. insight markets and economy: production rate. investopedia, dotdarsh publishing family, new york, usa. wusana, aw., sunu, h., juli, n. s. and doyok, p. 2014. effect of biomass feed size and air flow rate on the pressure drop of gasification reactor. journal teknologi, 68(3): 7– 12. yong, t., lee, k., mohamed, a. and subhash, b. 2007. potential of hydrogen from oil palm biomass as a source of renewable energy worldwide. energy policy, 35(11): 5692-5701. yuelei, y., kevin, b. and dan, z. 2012. a sustainable ethanol distillation system. journal of sustainability, 4: 92-105. www.mdpi.com/journal/sustainability yunus, ac. and afshin, jg. 2015. heat and mass transfer. fundamentals and applications (sie), mcgraw hill publisher, new york, 5th edition. yusoff, s. 2006. renewable energy from palm oil – innovation of effective utilization of waste. journal of cleaner production, 14: 8793. http://www.paddydryer.pdf.com http://www.mdpi.com/journal/sustainability file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):103-110 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 103 original research article corrosion inhibition of polyalthia longifolia leaves extract in 1m hcl solution on mild steel abdu zubairu1*, abdullahi s. b. gimba2 and abubakar b. waziri 1department of chemical engineering, university of maiduguri, borno state, nigeria. 2department of petroleum and gas engineering, nile university of nigeria, abuja nigeria. *corresponding author’s email address: abduzubairu@yahoo.com 1.0 introduction corrosion is an increasingly serious and costly problem that can lead to plant and equipment failures, leakages in oil and gas pipelines as well as failure of steel bridges, ships, and buildings. these failures range from being an annoyance to being catastrophic. failures caused by corrosion could lead to a direct failure of a component which could then affect the entire system; and can not only be very expensive in terms of down-time to repair, or replace plant and equipment, but can also be costly in terms of productivity, health or even loss of human life, as well as damage to the environment (lekan et al., 2013). corrosion phenomena, control and prevention are unavoidable major scientific issues that must be addressed daily as long as there is increasing needs of metallic materials in all facets of technological development (loto et al., 2012). the consequences of corrosion are many and varied, and the effects of corrosion on the safe, reliable and efficient operation of equipment or structures are often more serious than simple loss of a mass of a metal. equipment failure of various kinds leading to the necessary expensive replacements may occur even though the amount of metal destroyed is quite small (umoren, 2009). it is an ever present and unceasing problem, often hard to eradicate totally. metallic deterioration progresses rather fast after the destruction or penetration of the passive barrier, which is followed by a number of reactions that alter the constituents and behaviour of both the superficial metal surface and the immediate environment (adegoke, 2015). this is observed in, for example, oxides formation, gradual metal cation diffusion into the coating matrix, local ph changes and electrochemical potential. article information abstract corrosion is a very common phenomena in the manufacturing as well as chemical process industries. corrosion has generated wide amount of interest worldwide because of its potential hazards to process equipment and machineries; which often leads to associated downtimes as well as adverse economic and safety consequences. the use of inhibitors is one of the most practical and efficient technique of protection against corrosion. in this work, the corrosion inhibition efficiency of polyalthia longifolia leaves extract in 1m hcl solution on mild steel surface was investigated using the standard gravimetric (weight loss) method. the results indicate that the extract could serve as a good green inhibitor. the inhibition efficiency increases with increase in the inhibitor concentrations. for the mild steel samples investigated in this work, about 70% inhibition efficiency was achieved with only 1.0 ml extract solution per 40 ml of 1.0 m hcl solution after five (5) days; and under same conditions, increasing the amount of extract by fivefold yielded only 10% increase in the inhibition efficiency for the same test period. the inhibition efficiency was also found to significantly increase with time of exposure for the first 48 hours of the experiment, but the increase was rather gradual at later times for all levels of extract concentrations © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 sept., 2020 revised 17 december 2020 accepted 23 december 2020 keywords: corrosion green inhibitor polyalthia longifolia mild steel hcl corrosion rate inhibition efficiency zubairu et al: corrosion inhibition of polyalthia longifolia leaves extract in 1m hcl solution on mild steel. azojete, 17(2):103-110 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 104 the costs attributed to corrosion damage of all kinds have been estimated to be of the order of 3 to 5% of the industrialized countries’ gross national product (gnp). the total annual cost of corrosion in the oil and gas production industry is estimated to be 1.375 billion dollars, broken down into 589 million dollars in surface pipeline and facility costs, 463 million dollars annually in downhole tubing expenses, and another 320 million dollars in capital expenditure related to corrosion (lekan et al., 2013). nigeria, a major user of ferrous and non-ferrous metal is also experiencing its own fair share of corrosion problems. one of the major industrial sectors in nigeria experiencing this problem is the oil and gas industry. research work on the analysis of oil pipeline failures in oil and gas industries in the niger delta area of nigeria was carried out to ascertain the causes of these failures. information on pipeline conditions was gathered for the period between 1999 and 2010. observations showed that the major causes of failure include: ageing, corrosion, mechanical failures – welding defects, pressure surge problems, stress, wall thickness, etc. the report’s recommendations emphasized measures to minimize these failures (achebe, 2012). in practice corrosion can never be eliminated, but can be hindered to a reasonable level. due to problems from corrosion that are confronting industries; several methods of corrosion control and prevention have been investigated and tested. for example, cathodic protection, lubrication, anodic protection, alloying, coating and corrosion inhibition among others. the choice and application of any method is based on its efficiency, economic factors and the nature of the corrosive environment (njoku, 1998). 2.0 corrosion inhibitors the use of inhibitors is one of the most practical methods for protection against corrosion in corrosive environments. inhibitors are substances that directly or indirectly coat a film on a metal surface to protect it from its environment. most inhibitors are adsorbed by the metal surface from a solution or dispersed, but some are applied directly as coatings. generally, the dissolution of metal can be suppressed by the action of adsorptive inhibitors which may prevent the adsorption of the aggressive ions, by the formation of a more resistant film on the metallic surface (el-maghraby, 2009). recently, there have been growing interest on some environmentally friendly substances; especially from natural resources that could be used to control/prevent incessant corrosion problems, aside the conventional synthesized inorganic and organic chemicals; which often have adverse impacts on the environment (adegoke, 2015). many researches have been conducted on some green inhibitors with promising outcomes (rani and basu, 2012; loto et al., 2012). the use of natural corrosion inhibitors has been advocated because of the prohibitive cost, toxic nature and environmental unfriendliness of some of the chemical-based corrosion inhibitors. more so, the green inhibitors are readily available, cheap and renewable source of materials. several researchers have investigated and elucidated the application of various plants extract for corrosion inhibition (patni et al., 2013; onen et al., 2013; angel et al., 2014). plant parts that have been used include leaves, bark, fruit and roots. in many cases, the corrosion inhibition effects of some of the plants ‘extracts have been attributed to the presence of tannin in their bioactive constituents. also associated with the presence of tannin in the extracts is the bitter taste in the bark and/ or leaves of these plants ( loto et al., 2012). in this study, corrosion inhibition efficacy of polyalthia longifolia leaves extract in hydrochloric acid solution on mild steel was investigated. the choice of mild steel as the test specimen was because of its wide usage and good mechanical properties. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 105 3.0 materials and methods 3.1 materials and equipment fresh leaves of polyalthia longifolia plant were collected from around university of maiduguri campus. commercial grade concentrated hydrochloric acid, ethanol and acetone were purchased from a local store in maiduguri metropolis. mild steel coupon specimens were prepared in mechanical engineering workshop, university of maiduguri. strings and distilled water were obtained from the chemical engineering departmental laboratory. the equipment used include digital balance (ek5055 camry industries ltd, zhongshan), mini digital scale (s-eds-0146), electric grinder (sonik, japan), soxhlet extractor (ex5/83-quickfit, avantor vwr, singapore), water bath (gallenkamp, uk), silicon carbide paper (p60d, p220d, g60d) and glass wares (pyrex) were obtained from the chemical engineering departmental laboratory. 3.2 methods 3.2.1 preparation of the leaves sample the fresh leaves of polyalthia longifolia collected, were washed with water to clean them from dusts and other deposits. the leaves were then chopped into smaller pieces and allowed to dry for four days to achieve 91% moisture content reduction. the dried leaves were then grounded to powder for easy extraction. 3.2.2 extraction the ground leaves of polyalthia longifolia was extracted with the use of a small scale soxhlet extractor with methanol as solvent. the soxhlet extractor consists of a main extractor, thimble (round bottom flask), a reflux condenser and an electric heater (vasudha and shanmuga, 2013). 3.2.3 preparation of mild steel specimen the mild steel sheet used was prepared in the mechanical engineering workshop, university of maiduguri. the steel sheet was cut into several small pieces of uniform dimension of 20mm x 40mm and the coupon specimens were descaled by wire brushing. the specimens were mechanically polished with emery paper abrasive for a smoother surface, washed with acetone, air dried and kept in a desiccator to avoid contact with impurities for subsequent analyses. 3.2.4 experimental procedure the simple standard weight loss method as described in (ayssar, et al., 2012) was adopted. six (6) 250ml glass beakers were cleaned thoroughly, dried and labelled a-f respectively. forty milliliters (40ml) of diluted hcl were measured and poured into each beaker. similarly, 1ml, 2ml, 3ml, 4ml, and 5ml of the polyalthia longifolia extract solution was pipetted and added into the five beakers labelled a-e respectively. no extract solution was added to the sixth beaker labelled f, and therefore left as control. thirty (30) mild steel coupons (with dimension specified earlier) were individually cleaned with distilled water, and then washed with acetone, dried and weighed. the coupons were each tied with a string to a small stick that will enable them to suspend when placed across the mouth of the beaker. the weighed coupons were then lowered into the beakers, five (5) coupons per beaker, at room temperature. the first set of the coupons (one coupon from each beaker) were retrieved from the acid corrodent after 24 hours. similarly, the second set retrieved after 48 hours, the third set after 72 hours and the zubairu et al: corrosion inhibition of polyalthia longifolia leaves extract in 1m hcl solution on mild steel. azojete, 17(2):103-110 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 106 fourth set after 96 hours and finally the last set after 120 hours. each coupon was individually cleaned with distilled water, and then with acetone. dried and weighed. the weight loss, (g) was calculated (aminu et. al., 2015) using equation (1). (1) where mb (g) and ma (g) are the weights before and after immersion in the test solutions respectively. 3.2.5 corrosion rate the corrosion rate was calculated from weight loss of the coupons (sheeba, et. al, 2014) at room temperature for various concentrations and immersion times using equation (2). (2) where s = surface area of the coupon (cm2), t = immersion time (h), cr = corrosion rate (mg/cm2.h) 3.2.6 inhibition efficiency the inhibition efficiency of the green inhibitor was calculated from weight loss measured for different inhibitor concentrations using equation (3) modified from (vasudha and shanmuga, 2013). (3) where: ie = inhibition efficiency (%) crinh = corrosion rate in the presence of extract (mg/cm2.h) crcorr = corrosion rate without extract (mg/cm2.h) 4.0 results and discussion 4.1 weight loss and corrosion rate figure 1 illustrates the weight loss of the mild steel samples immersed in 1m hcl solution with various amounts of the extract solution, compared to the weight loss of the steel sample when immersed in the control (1m hcl solution without extract). the results indicate gradual weight loss of steel sample at the onset of the experiment up to 24 hours of exposure to the corrodent. it could be seen however, that the weight loss of the sample was more than halved by the addition of only 1ml of the extract solution after 24 hours. the weight lost generally increases with time of exposure as the steel gets corroded over time, but the increase remains gradual for all levels of extract solution compared to loss in mass of the steel when there was no extract in which the weight loss significantly increases with time. for instance, it could be seen from figure 1 that with no extract solution added, the mild steel samples weight loss was about 7.4% after 24 hours and 88.6% after 120 hours. whereas the observed weight loss with addition of 1ml and 5ml extract solution were 4.5% and 2.0% after 24 hours respectively; and the reduction in mass of the steel samples were 36.5% and 18.7% after 120 hours respectively. this is indicative of the effect of the addition of the extract solution in inhibiting the ability of arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 107 the corrodent to impair the surface of the mild steel that ultimately led to the weight loss. similar observations were reported on the effect of weight loss of mild steel by aqueous extract of polyalthia longifolia leaves in various concentration of h2so4 solution (vasudha and shanmuga, 2014). fig. 1. reduction in the mass of mild steel in 1m hcl solution with and without addition of polyalthia longifolia leaves extract. on the other hand, it could be observed from figure 2 that the corrosion rates increase with reduction in the amount of extract solution. for no extract solution the corrosion rate ranges from 1.2 0.8 mg/cm2/h over the period of the experiment. but the corrosion rate is approximately halved by the addition of just 1.0 ml extract solution, falling to the range of 0.7 0.3 mg/cm2/h. with the addition of 5ml extract solution the corrosion rate significantly reduces to the range of 0.3 0.2 mg/cm2/h. this reduction in the corrosion rates could be attributed to possibility of adsorption of bioactive inhibitor molecules on the metal surface forming a thin coating film that grows with time on the metal surface which hinders corrosive attack on the metal thereby reducing weight loss of the specimen. similar trends were observed in previous findings (yawas, 2005) and (nwabanne and okafor, 2011). fig. 2. effect of amount of polyalthia longifolia leaves extract on the corrosion rate of mild steel in 1m hcl solution. the effect of concentration of polyalthia longifolia leaves extract on the corrosion rates could further be amplified as illustrated in figure 3. the figure presents the influence of the 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 50 100 150 w e ig h t lo ss ( g) time (h) no extract 1 ml 2 ml 3 ml 4 ml 5 ml 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 50 100 150 c o rr o si o n r at e ( m g/ cm 2 . h ) time (h) no extract 1 ml 2 ml 3 ml 4 ml 5 ml zubairu et al: corrosion inhibition of polyalthia longifolia leaves extract in 1m hcl solution on mild steel. azojete, 17(2):103-110 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 108 concentration of the extract on the corrosion rate at periodic intervals for the various extract levels investigated. the results confirm that the corrosion rate strongly decreases with increase in the amount of inhibitor extract in mild hcl solution, indicative of the significant dependence of the extent of the corrosion on the amount of the inhibitor extract in the system. similar behaviour of aqueous extract of polyalthia longifolia leaves on the corrosion rate of mild steel in dilute h2so4 solution was observed in previous works (vasudha and shanmuga, 2014). generally, it could be observed that the corrosion rate is significantly decreased by approximately 50% after 24 hours of the experiment for all level of the extract solution, after which the decrease in the corrosion rate was rather gradual with time for all level of the extract concentration used. fig. 3. effect of amount of polyalthia longifolia leaves extract on the corrosion rate of mild steel in 1m hcl solution for different immersion times. 4.2 inhibition efficiency figure 4 illustrates the variation of the inhibition efficiency of the polyalthia longifolia leaves extract solution with time for various level of the extract solution. it could be noted that the inhibition efficiency generally increases with increase in the amount of the extract solution. it is noteworthy that the inhibition efficiency did not increase appreciably with increase in the amount of extract solution at the late stage of the experiment. this is likely because at the beginning of the experiment, the mild steel surface was mainly exposed to the acid corrodent, and increasing the amount of the extract has significant effect in preventing attack on the surface thereby increasing the inhibition efficiency. for instance, using 1.0 ml extract solution achieved inhibition efficiency of about 41% after 24 hours and 70% after 5 days respectively. whereas, the corresponding inhibition efficiency using 5.0 ml extract solution was approximately 70% after 24 hours and 80% after 5 days respectively. overall, the inhibition efficiency increases gradually over time for all extract levels, and almost plateaued leading to no appreciable increase in inhibition efficiency with time after about 3 days of the experiment. as asserted earlier, this could be attributed to the fact that initially the metal surface was largely exposed to the corroding medium, and there is rapid loss in mass of the sample, and at the same time there is rapid adsorption of the extract molecules on the surface, thus increasing the inhibition efficiency. however, as the metal surface gets coated with the adsorbed molecules of the extract, only little surface of the metals gets attacked for corrosion, and correspondingly 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 2 4 6 c o rr o si o n r ae ( m g/ cm 2 . h ) amount of extract (ml) 24 hours 48 hours 72 hours 96 hours 120 hours arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 109 small amount of the extract solution further gets adsorbed for corrosion inhibition, and consequently increase in the inhibition efficiency stagnated. fig. 4. effect of amount of polyalthia longifolia leaves extract on the corrosion inhibition efficiency in 1m hcl solution on mild steel. figure 5 illustrates the influence of polyalthia longifolia extract concentration on the inhibition efficiency for various immersion times. it could be seen that the inhibition efficiency monotonically increases with increase in the extract concentration for various immersion times. for instance, using only 1ml of extract solution the inhibition efficiency of about 40% was achieved after 24 hours, which then increased to more than 70% after 5 days. fig. 5. effect of amount of polyalthia longifolia leaves extract on the corrosion inhibition efficiency in 1m hcl solution on mild steel for different immersion times. 5.0 conclusion the solvent extract from polyalthia longifolia leaves was found to be effective green corrosion inhibitor that inhibits the corrosion of mild steel in 1m hcl solution under room conditions. the polyalthia longifolia extract significantly influence the corrosion of mild steel due to the adsorption of the plant extract on the steel surface; which creates a thin film coating that effectively blankets the surface of the steel from the corrodent attack, thereby inhibiting the corrosion. the corrosion inhibition efficiency of the plant extract was found to moderately increase with increase in amount of extract. it was found that with 1ml of the extract solution, the inhibition efficiency of nearly 70% was achieved after five (5) days. furthermore, the inhibition efficiency significantly increases with time of exposure at initial times. however, the increase becomes gradual and nearly plateaued over time as the steel surface gets coated with the adsorbed plant extract for all levels of extract solution investigated. 0 20 40 60 80 100 0 50 100 150 in h ib it io n e ff ic ie n cy ( % ) time (h) 1 ml 2 ml 3 ml 4 ml 5 ml 0 10 20 30 40 50 60 70 80 90 0 2 4 6 in h ib it io n e ff ic ie n cy ( % ) amount of extract (ml) 24 hours 48 hours 72 hours 96 hours 120 hours zubairu et al: corrosion inhibition of polyalthia longifolia leaves extract in 1m hcl solution on mild steel. azojete, 17(2):103-110 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 110 references achebe, ch., nenke, uc. and anisiji, oe. 2012. analysis of oil pipeline failure in the oil and gas industries in the niger delta area of nigeria. in proceedings of the international multi conference of engineers and computer scientist held in hong kong, 14-16 march 2012. vol. ii. imecs. adegoke, a. 2015. investigation of corrosion inhibition of guava, banana and almond plant extract in 0.5m hcl and h2so4 solution on low carbon steel. m.sc thesis department of metallurgical engineering, abu, zaria-nigeria. aminu, du, adams, fv. and linus, no. 2015, weight loss corrosion study of some metals in acid medium. journal of advances in chemistry, 11(2): 3434-3440. angel, p., raja, as., sathiyabama, j. and prathipa, v. 2014. corrosion inhibition of vitex negundo extract as a green corrosion inhibitor for carbon steel in well water. international journal of chemical studies, 2(1): 31-37. ayssar, n., ideisan, ia. and ibrahim a. 2012. effect of temperature on the corrosion inhibition of trans-4-hydroxy-4-stilbazole on mild steel in hcl solution. international journal of corrosion, 2012: 17. doi:10.1155/2012/380329. lekan, tp., alhaji, sg., ganiyu, kl., babagana, g. and adebori saheed, b. 2013 corrosion detection during oil and gas production and its mitigation. international journal of industrial chemistry, 4(2): 115 loto, rt., loto, ca. and popoola, api. 2012. effect of aminobenzene concentration on the corrosion inhibition of mild steel in sulphuric acid. international journal of electrochemical science, 7: 7016 7032. njoku, er. 1998. effect of inhibitors on corrosion of mild steel in hcl pickling solution. m.sc thesis department of metallurgical engineering, abu, zaria-nigeria. nwabanne, jt. and okafor, vn. 2011. inhibition of the corrosion of mild steel in acidic medium by vernonia amygdalin: adsorption and thermodynamics study. journal of emerging trends in engineering and applied sciences (jeteas), 2(4): 619-625. onen, ai., barminas, jt. and jacob, j. 2013. inhibitory action of ficus carica extracts on aluminium corrosion in acidic medium. chemical science transactions, 2(4): 1326-1333. patni, n., agarwal, s. and shah, p. 2013. greener approach towards corrosion inhibition, chinese journal of engineering, 2013: 1-10. doi.org/10.1155/2013/784186 rani, bea. and basu, bbj. 2012. green inhibitors for corrosion protection of metals and alloys an overview, international journal of corrosion, special issue: 2012: 1-15. doi:10.1155/2012/380217. sheeba, rs., raja, as., sathiyabama, j. and prathipa, v. 2014. green approach to corrosion inhibition of carbon steel in well water by the extract of polyalthia longifolia. journal of applicable chemistry, 3(5): 2055-2065. umoren, sa. 2009. polymers as corrosion inhibitors for metals in different media a review. the open corrosion journal, 2: 175-188. doi: 10.2174/1876503300902010175 vasudha, vg. and shanmuga, pk. 2013. polyalthia longifolia as a corrosion inhibitor for mild steel in hcl solution. research journal of chemical science, 3(1): 21-26. vasudha, vg. and shanmuga, pk. 2014. corrosion inhibition of mild steel in h2so4 media using polyalthia longifolia leaves. chemical science review and letters, 2(6): 435-443. yawas, ds., aku, sy. and oloche, ob. 2005. non-toxic plant extracts as corrosion inhibitors of carbon steel in hcl. journal of corrosion science and technology, 3(1): 128-133. https://www.infona.pl/contributor/0@bwmeta1.element.springer-4be07a7a-8914-3922-9f95-350a2045684c/tab/publications https://www.infona.pl/contributor/1@bwmeta1.element.springer-4be07a7a-8914-3922-9f95-350a2045684c/tab/publications https://www.infona.pl/contributor/2@bwmeta1.element.springer-4be07a7a-8914-3922-9f95-350a2045684c/tab/publications https://www.infona.pl/contributor/3@bwmeta1.element.springer-4be07a7a-8914-3922-9f95-350a2045684c/tab/publications https://www.infona.pl/contributor/4@bwmeta1.element.springer-4be07a7a-8914-3922-9f95-350a2045684c/tab/publications http://dx.doi.org/10.2174/1876503300902010175 arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):365-374 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 365 original research article effect of processing parameters on solvent oil expression from loofah seeds (luffa cylindrica l.) using response surface methodology r. a. busari1, t. d. akpenpuun2 and m. o. iyanda2 (1department of food, agricultural and biological engineering, kwara state university malete, p. m. b. 1530, kwara state, nigeria. 2department of agricultural and biosystems engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria) *corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng article information submitted 27 february, 2019 revised 5 april, 2019 accepted 4 june, 2019 keywords: yield ratio optimization model extraction abstract luffah cylindrica plant grows in the wild, around uncompleted buildings and fenced walls. the percentage oil composition of its seeds is about 30% oil. the research focused was the extraction oil from loofah seed using a solvent extraction methodology. optimum conditions for oil extraction were determined using response surface methodology of central composite rotatable design. a total of 20 experimental runs were used to investigate the optimum condition considering three independent variables at five levels each: extraction temperature (55, 60, 65, 60, 75ºc), seed/solvent ratio (0.04, 0.05, 0.06, 0.07, 0.08 g/ml) and extraction time (4, 5, 6, 7, 8 hr.). an empirical model equation that could be used to forecast oil yield as a function of the independent variables was developed. the optimum oil yield obtained was 27.43% at the extraction temperature (74.05ºc), seed/solvent ratio (0.05 g/ml) and extraction time (5.35hr). the analysis of variance showed that extraction temperature and time had significant effect on oil yield (p = 0.05). the interaction of the independent variables with oil yield gave r2 and r2 adj. values of 0.98 and 0.93, respectively. the result showed that the selected independent variables had a significant effect on oil yield, thus an optimum condition was established. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction luffa cylindrical is a sub-tropical plant, which requires warm summer temperatures and long frost-free growing season when grown in temperate regions. it is an annual climbing plant which produces fruit containing fibrous vascular system. loofa is derived from the cucumber and marrow family and originates from america (mazali and alves, 2005; oniya et al., 2017). luffa commonly called bath sponge or dishcloth gourd, sponge gourd, loofa, vegetable sponge, is a member of the cucurbitaceous family. the number of species in the genus luffa varies are about seven, but only two species, l. cylindrica and l. acutangula, are domesticated (rowell et al., 2002). fruits, leaves, flowers, and seeds of cucurbitaceae have considerable economic value (bamgboye and oniya, 2012). luffa cylindrica linn, commonly known as loofah is an annual plant commonly http://www.azojete.com.ng busari, et al: effect of processing parameters on solvent oil expression from loofah seeds (luffa cylindrica l.) using response surface methodology. azojete, 15(2):365-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 366 found in the tropics including nigeria. the oil extracted from l. cylindrica seed can be used in the biodiesel production which is now gaining wide acceptance because of low co2 emission and other considerations. in nigeria, luffa cylindrica plant grows in the wild and on abandoned building structures and fenced walls in towns and villages (ndukwe et al., 2001; ajiwe et al., 2005). consumption of fresh l. cylindrica fruit and use of fibre have been widely reported (onelli et al., 2001; italo and alves, 2005). the seed which contains about 30 % oil content is often discarded as waste and literature is sparse on extraction and quality of its seed oil. therefore, optimization of solvent extraction of oil from luffa cylindrica using response surface methodology was the focus of this study. response surface methodology (rsm) is a collection of statistical and mathematical techniques useful for developing improving and optimising processes. the approach is useful for optimizing, designing, developing, formulating and improving processes where a response or responses are affected by several variables (montgomery, 2005; baş and boyacı, 2007). the main disadvantages of this method are the interactive effects among the variables, which are not considered and there is a lack of explanation of the complete effect of the factors on the response. in addition, this method increases the number of experiments needed to conduct the research, which leads to increased cost and time (baş and boyacı, 2007; bezerra et al., 2008). rsm is useful in three different techniques or methods (i) statistical experimental design, in particular two level factorial or fractional factorial design, (ii) regression modeling techniques, and (iii) optimization methods (myers and montgomery, 2002). the state-of-the-art applications of response surface methodology (rsm) in the optimization of different food processes in the food industries include extraction, drying, blanching, enzymatic hydrolysis and clarification, production of microbial metabolites, and formulation. in biological and clinical sciences rsm is used in biometric systems, while in the social sciences and wastewater treatment, rsm is used in personenvironment fit research, self-other agreement studies in leadership research and perceptual distance studies when comparing leader’s and their subordinates ratings of their work context and optimize the process of chemical coagulation based on a central composite rotatable design (ccrd) respectively (edwards, 2002; mosaddeghi et al., 2018). 2.0 materials and methods 2.1 materials the matured dry luffa cylindrica seeds were harvested from bush and uncompleted buildings around ilorin, kwara state, nigeria. the envelope brownish parts of the harvested seeds were peeled, and the seeds were shaken out into a bow bowl and winnowed to remove the matured seeds. the cleaned seeds were pre-cooked to soften the shell to ease decortication. the seeds were eventually sundried so as to remove the moisture absorbed during precooking and the shells were removed manually, dried and ground with the hammer mill to flour. 2.2 experimental design the experimental matrix was designed using design expert version 6.0.6, where a response surface methodology (rsm) in a central composite design (ccd) was employed to optimize the extraction of oil from loofah seeds. the experiment was designed on five levels, (-α, -1, 0, +1 and +α) three independent variables, (seed/solvent ratio, extraction temperature and extraction time) that generated 20 experimental runs for optimal oil yield. the summary of this is as shown in table 1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):365-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 367 table 1: experimental design variable parameter unit code level α -1 0 +1 + α a seed/solvent ratio g/ml x1 0.04 0.05 0.06 0.07 0.08 b extraction temperature °c x2 55.00 60.00 65.00 70.00 75.00 c extraction time hr. x3 4.00 5.00 6.00 7.00 8.00 2.2.1 extraction of oil from loofah seed using solvent extraction the extraction of oil was carried out at the industrial chemistry laboratory, kwara state university malete, kwara state, nigeria, using the method described by oniya et al. (2017). the extraction was done with a soxhlet apparatus of 250 cm3 capacity using n-hexane of analytical grade as the solvent. a prepared sample of 15 – 25 g loofah seed, extraction temperature ranges of 55 and 75ºc, seed/solvent ratio range between 0.04 – 0.08 g/ml while the extraction time ranges between 4 – 8 hours as given in table 1. the experiments were carried out in batches according to the experimental layout generated from design expert software. the solvent used was recovered at every batch through a distillation process, and the actual oil obtained was weighed. the experiment was repeated for other runs and the percentage oil yield was determined as the ratio of the weight of oil recovered to the weight of the loofah seed sample before extraction. oil yield was mathematically expressed using the expression adopted by adeeko and ajibola (1989), olaniyan and oje (2011) and oniya et al. (2017) and presented in equation (1) as: ss or m myo . (1) where; o. y = oil yield (%), mor = mass of oil recovered (g), mle = mass of the loofah seeds extracted (g) 3.0 results and discussion 3.1 result of oil yield from the extraction of oil from loofah seed the result of the solvent extraction of oil from loofah seeds is presented in table 2. the yield for each batch of the experiment was determined using equation 1. the differences in oil yield values are indications that the independent variables had considerably affected the yield. the predicted oil yield from the design expert software compared well with the yield obtained. the optimum oil yield of 27.43% was obtained from the extraction at corresponding seed/solvent ratio of 0.05g/ml, extraction temperature of 74.05ºc, and extraction time of 5.35 h. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng busari, et al: effect of processing parameters on solvent oil expression from loofah seeds (luffa cylindrica l.) using response surface methodology. azojete, 15(2):365-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 368 table 2: experimental design layout using response surface methodology std. run factor 1 a: seed/solvent ratio (g/ml) factor 2 b: extraction temperature (°c) factor 3 c: extraction time (hr.) response 1 oil yield (%) predicted value (%) 7 1 0.04 75.0 8.0 27.30 27.28 3 2 0.04 75.0 4.0 26.90 26.81 5 3 0.04 55.0 8.0 24.60 24.70 13 4 0.06 65.0 5.0 24.90 25.43 2 5 0.08 55.0 4.0 23.50 23.51 11 6 0.06 60.0 6.0 25.50 25.30 16 7 0.06 65.0 6.0 26.00 25.93 9 8 0.05 65.0 6.0 25.90 26.10 18 9 0.06 65.0 6.0 26.00 25.93 8 10 0.08 75.0 8.0 27.40 27.46 4 11 0.08 75.0 4.0 26.80 26.70 17 12 0.06 65.0 6.0 26.00 25.93 1 13 0.04 55.0 4.0 24.00 23.93 14 14 0.06 65.0 7.0 26.20 25.81 6 15 0.08 55.0 8.0 24.50 24.58 20 16 0.06 65.0 6.0 26.00 25.93 10 17 0.07 65.0 6.0 26.10 26.04 15 18 0.06 65.0 6.0 26.00 25.93 12 19 0.06 70.0 6.0 26.40 26.74 19 20 0.06 65.0 6.0 26.00 25.93 3.2 mathematical model equation for oil expression the optimum conditions for oil expression were performed according to the central composite design experimental plan and the observed responses (oil yield) were presented in table 2. the regression model equation developed for oil yield with single factors, quadratic factor, and interactive factors observed b, c, a2, b2, ab, and ac are directly proportional to the oil yield while a, c2, and bc with negatively coefficient indicates an indirect proportionality with the oil yield. the model obtained is given in equation 2 as bcacabcbacbay 075.0075.0075.024.136.056.038.044.1059.093.25 222  (2) where, y = oil yield measured (%), a = seed solvent ratio (g/ml), b = extraction temperature (°c), and c = extraction time (hr.) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):365-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 369 3.3 statistical analysis of extracted loofah seed oil the design of the experiment (doe) and the responses (oil yield) of batch laboratory experiments were shows in table 3. from the table, the fitness of the model was expressed by the coefficient of determination (r2) and adjusted coefficient of determination (adj. r2), which were obtained as 0.9656 and 0.9346, respectively; the values indicate that the regression model is acceptable. however, the determination coefficient (r2 = 0.9656) indicates that the sample variation of 96.56% for oil expression is attributed to the independent variables and only 3.44% of the total variations are not explained by the model. the value of the adjusted coefficient of determination (adj. r2 = 0.9346) is also very high which advocate for a high significance of the model (yuan et al., 2008). akintunde et al. (2015) reported that the fitness of a model is determined by the r2 and the value should not be less than 0.80. also, it can be deduced from the f-value of 31.19 with a correspondingly low probability value of 0.0001, which is less than 0.05, that the model terms are significant. more so, the standard deviation of 0.27, mean of 25.80, c.v. of 1.03, and adequate precision of 21.051 were obtained for oil expression. in this case, the adequate precision value (p adeq. = 21.051) is greater than 4, which is desirable for the model (bamgboye and oniya, 2012; oniya et al., 2017). table 4 shows the assessment of experimental errors and the confidence interval (ci) of the experimental variables. the standard errors are analyzed based on the differences between the predicted oil yield and the experimental values. 3.4 effect of operating parameters the significance and adequacy of the model were tested using anova. it was observed from the table that only two factors; extraction temperature and extraction time (b, c) are significant in the model, corresponding to seed/solvent ratio, which is nonsignificant factor. the quadratic effects of seed solvent/ratio (a2), quadratic effects of extraction temperature (b2) quadratic effects of extraction time (c2), seed/solvent ratio and extraction temperature (ab), seed/solvent ratio and extraction time (ac) and extraction temperature and extraction time (bc) are all nonsignificant being higher than 0.05, while the values less than 0.05 means significant. the interaction effects of seed/solvent ratio, temperature, and time on the yield were studied using the interaction plot and 3d surface plot of surface response methodology. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng busari, et al: effect of processing parameters on solvent oil expression from loofah seeds (luffa cylindrica l.) using response surface methodology. azojete, 15(2):365-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 370 table 3: analysis of variance for oil extraction from loofah seeds (partial sum of squares) source sum of squares df mean square f value prob > f model 19.74 9 2.19 31.19 < 0.0001 significant a 0.029 1 0.029 0.42 0.5324 b 17.65 1 17.65 251.08 < 0.0001 c 1.24 1 1.24 17.67 0.0018 a2 0.059 1 0.059 0.84 0.3810 b2 0.025 1 0.025 0.35 0.5679 c2 0.29 1 0.29 4.06 0.0715 ab 0.045 1 0.045 0.64 0.4423 ac 0.045 1 0.045 0.64 0.4423 bc 0.045 1 0.045 0.64 0.4423 residual 0.70 10 0.070 lack of fit 0.70 5 0.14 pure error 0 5 0 cor. total 20.44 19 std. dev. 0.27 mean 25.80 c.v. 1.03 press 4.01 adeq. precision 21.051 table 4: anova analysis of experimental errors and confidence interval factor coefficient estimate df standard error 95% ci low 95% ci high vif intercept 25.93 1 0.08 25.75 26.11 a-seed/solvent ratio -0.059 1 0.091 -0.26 0.14 1.00 b-extraction temperature 1.44 1 0.09 1.24 1.64 1.00 c-extraction time 0.38 1 0.09 0.18 0.59 1.00 a2 0.563 1 0.614 -0.81 1.93 24.18 b2 0.363 1 0.614 -1.01 1.73 24.18 c2 -1.24 1 0.61 -2.61 0.13 24.18 ab 0.075 1 0.094 -0.13 0.28 1.00 ac 0.075 1 0.094 -0.13 0.28 1.00 bc -0.075 1 0.094 -0.28 0.13 1.00 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):365-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 371 3.5 effect of seed/solvent ratio and extraction temperature on the oil yield from loofah seed the effect of seed/solvent ratio and extraction temperature was studied using the 3d surface plot (figure 1), which depicts the interaction between seed/solvent ratio and extraction temperature. it was observed that as temperature increases and a slight increase in seed/solvent ratio improved the oil yield. this implied that increase in seed/solvent ratio and extraction temperature favours the extraction rate as much solvent is needed to ensure that vapour rose through the vertical monitor tube into the condenser at the top just as the solvent boiled (oniya et al., 2017). 3.6 effect of the seed/solvent ratio and extraction time on the oil yield from loofah seed the 3d surface plot interaction from design expert presented in figure 2 represents the effects of seed/solvent ratio and extraction time. their interactions on the oil yield for extraction were studied. it was observed that increase in seed/solvent ratio favors the extraction rate as much solvent is needed for extraction, while the oil yield increases gradually as extraction time increases until the extraction time was above 7hr. when the increased in extraction time does not have any significant effect on the oil yield. the curvature nature of figure 2 depicts a mutual interaction between extraction time and seed/solvent ratio. figure 1: 3d response surface plot showing the effect of extraction temperature and seed/solvent ratio on the oil yield. figure 2: 3d response surface plot showing the effect of extraction time and seed/solvent ratio on the oil yield. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng busari, et al: effect of processing parameters on solvent oil expression from loofah seeds (luffa cylindrica l.) using response surface methodology. azojete, 15(2):365-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 372 3.7 effect of extraction time and temperature on the oil yield from loofah seed from figure 3, the elliptical nature of the contour plots indicated that interaction between the extraction temperature and time had no significant effect on the yield of oil. but the two factors individually had (extraction temperature and extraction time) a significant effect in the model. it was noticed that increase in time favoured the extraction of oil until it the reaction time was above 7 hrs. increased reaction time above this level tends to have no significant effect on the oil yield. the oil yield was observed to increase with higher temperature even at the temperature higher than the boiling point of the solvent. this is because at this temperature higher than the boiling temperature of the solvent, evaporation of the solvent will take place as a result of the increased temperature leaving the extracted oil. the combined effect of these two independent variables at high-level experimental process will obviously result in a decrease in oil yield. however, afolabi et al. (2015) and yuan et al. (2008) who worked on optimization of solvent extraction of oil from parinari polyandra and reported that the oil yield was observed to decrease with higher temperature, especially at the temperature higher than the boiling point of the used solvent. the effect of the decrease oil yield at a higher temperature is more prominent in hexane than when another solvent is utilized. this may be due to its low boiling point of 67ºc when compared with other solvents (afolabi et al., 2015). figure 3: 3d response surface plot showing the effect of extraction time and extraction temperature on the oil yield. 3.8 validation of the model the relationship between predicted and experimental values of oil yields is shown in figure 4. it can be seen that there is a high correlation (r2 = 0.9656) between the predicted and experimental oil yields. it means that the data fit well with the model and give a convincingly good estimate of response for the system in the range studied. the percentage error was calculated to be 0.88 which confirmed the validity of the model equation. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):365-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: rasheed.busari@kwasu.edu.ng 373 figure 4: predicted oil yield versus experimental oil yield. 4.0 conclusion the study revealed that the extraction temperature has the highest influence in the regression model with highest f-value followed by extraction time and solvent/seed ratio. this implies that extraction temperature plays a significant role in solvent oil expression from luffa cylindrical seeds. based on the findings of this research work, the optimal conditions for oil extraction from luffa cylindrica were determined as a seed/ solvent ratio of 0.05 g/ml, extraction temperature of 74.05ºc, and extraction time of 5.35 hr. at corresponding oil yield of 27.43% references adeeko, ka. and ajibola, oo. 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surface methodology. renewable energy, 33, 1678–1684. http://www.azojete.com.ng original research article effect of processing parameters on solvent oil exp r. a. busari1, t. d. akpenpuun2 and m. o. iyanda2 arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):268-277 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 268 original research article ohmic heating as alternative preservation technique a review a. i. muhammad1, 2*, a. shitu1,2 and m. a. tadda1,2 (1department of agricultural and environmental engineering, bayero university, kano, nigeria. 2college of biosystems engineering and food science, zhejiang university, hangzhou, zhejiang, china) *corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng article information submitted 12 november, 2018 revised 6 february, 2019 accepted 8 may, 2019 keywords: ohmic heating electrical conductivity food processing energy saving conventional aseptic heating abstract the quest for new technologies in heating has drawn the attention of researchers to focus on energy saving and efficient techniques in heating food materials. ohmic heating is one of these technologies because it heats both phases of food (liquid and solid) simultaneously by internal energy generated from electrical power. using this method, the product undergoes minimum structural damage, retains its nutritional value, and is processed within a shorter time than with conventional heating methods. the technique also gives excellent processed quality products with lower energy cost. the heat energy generated during ohmic heating is transferred directly into the foods. the electrical conductivity of food products is linear with different temperature ranges and varies with heating time, food structure, and its constituents. as such, ohmic heating can be applied in different preprocessing and processing operations like drying, evaporation, dehydration, blanching, fermentation, extraction, sterilization, and pasteurization. this paper highlights ohmic heating as an emerging alternative novel heating technology to meet the demand for industrial and domestic food processing. recommendations were made for further research to provide a more robust analysis of ohmic heating performance. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction of recent, many researchers have the opinion that electro-technologies such as radiofrequency, microwave, pressure-assisted thermal sterilization, infrared heating, high hydrostatic pressure processing, irradiation, ultrasound, cold plasma, pulsed electric field, and ohmic heating technologies are used in the processing and preservation of foods (fan et al. 2019; jaeger et al., 2016; kanjanapongkul, 2017; muhammad et al. 2018a; muhammad et al. 2018b; ohlsson and bengtsson, 2002; senorans et al., 2011; termrittikul, et al., 2018). however, ohmic heating also known as moderate electric fields heating has drawn much attention in the food processing industries. this technique has proven to be mild processing technology which preserves nutritional, functional, structural, and sensory properties of food products better than conventional heating technologies (knirsch et al., 2010; vorobiev and lebovka, 2009). mailto:aimuhammad.age@buk.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):268-277. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 269 ohmic heating is sometimes referred to an electrical resistance heating or joule heating. it is defined as the process of passing electric currents through foods or other materials during exposure to heat. ohmic heating differs from other electrical methods like microwave and radiofrequency heating in the frequency and waveforms of the electric field. also, they differ in the presence of electrodes that are in contact with the food being process. while microwave and radiofrequency have frequencies of 300 mhz – 300 ghz and 1 – 300 mhz, respectively, ohmic heating has frequencies of about 25 – 30 khz (neetoo and chen, 2014). however, in conventional aseptic processing, the heat transfer is from the liquid phase then to the solid phase and long processing time is required. furthermore, conventional aseptic processing has less productivity, high cost of energy, and it destroys the sensory attributes of the food products (sakr and liu, 2014; shivmurti et al., 2014; smith et al., 1990). with regards to penetration depth, ohmic heating offers an attractive alternative with no limitations provided the inherent electrical resistance of the food is not too high. moreover, liquids and solids under ohmic heating are heated simultaneously without requiring stirring or mixing as in the conventional aseptic processing (cho et al., 2016). in this regard, ohmic heating could be considered as an energy saving process in comparison to the traditional aseptic technique (gavahian et al., 2013; goullieux and pain, 2005). however, by reducing electrical energy consumption, the environmental impact can be reduced provided that the energy generated is from non-renewable energy sources. in obtaining 1 kwh of electricity from either coal or fuel, about 800 g of co2 will be released to the atmosphere during combustion (ferhat et al., 2006). therefore, in this article, we present a short review of the ohmic heating system, working principles, and its application in food industries with the objective of elucidating on ohmic heating concept. also, recommendations were made for further research. 1.1 electrical conductivity electrical conductivity (�) of materials is a measure of the ability of a material to allow passage of electricity through it. it is the ratio of the current density to the electric field strength measured in siemens per meter (s/m) (sarkis et al., 2013). in conventional conduction heating, the heating rate depends on the heat conductivity of the sample. while in ohmic heating techniques, the most critical factor is the electrical conductivity (cho et al., 2016). the electrical conductivity of some liquid foods are measured at different temperatures (ruhlman et al., 2001). ohmic heating works optimally in electrically conductive fluid systems due to the necessity of ions mobility. therefore, materials that have low electrical conductivity such as ethanol-water or fermented alcoholic mixtures might require additional or extra electrolytes to improve their conductivity. thus, salt solution is employed as liquid medium in some ohmic heating processes (goullieux and pain, 2005). electrical conductivity varies not only with temperature difference as mentioned earlier but also with heating time, food structure, and constituents (nistor et al., 2015). the basic concept and simple ohmic heating set-up are shown in figure 1a and 1b, respectively. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng muhammad, et al: ohmic heating as alternative preservation technique a review. azojete, 15(2):268-277. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 270 figure 1. (a) schematic diagram of ohmic heating principle. (b) ohmic heating cell (wongsangasri and sastry, 2015) cho et al. (2016) reported the electrical conductivity of fermented red pepper paste to be 1.865 s/m when electric current was allowed to pass through and subsequently increased rapidly with the frequency (when it was higher than 1 khz) for a constant voltage as illustrated in figure 2a and 2b. the heating rate in fermented red pepper paste was peak at 5 khz. additionally, the specific heating rate (°c/g/s) increased linearly with the voltage at 60 hz (xu et al., 2013). figure 2. (a) the variance of specific heating rate versus voltage. (b) the variance of specific heating rate versus frequency (cho et al., 2016). 2.1 effects of ohmic heating on physiochemical properties of food products a significant number of biomolecules such as proteins, polysaccharides, and lipids, in lower amounts and other functional substances such as polyphenols and vitamins are lost during processing of food. these biomolecules and functional components are also discarded along with waste by-products when using conventional processing techniques. however, most of these compounds, if recovered, can be reincorporated back into the food processing line for use in http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):268-277. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 271 pharmaceutical products and energy production (galanakis, 2012; lin et al., 2013). given the increasing demand of these bioactive compounds, new recovery methods were being developed to reduce the use of chemicals, organic solvents, and increase recovery efficiencies while maintaining low energy input (chemat et al., 2012). to remedy these problems, pereira et al. (2016) recovered value-added compounds from purple potatoes (solanum tuberosum) using electro-heating treatments based on ohmic heating technology. as shown in figure 3, this method is a suitable processing strategy that have shorter processing time and lower energy consumption than the conventional aseptic heating method. figure 3. total energy consumption of traditional and ohmic heating pre-treatments (pereira et al., 2016). bastías et al. (2015) studied the effect of ohmic heating on texture, microbial load, cadmium (cd), and lead (pb) content in chilean blue mussel (mytilus chilensis) at shucking and subsequent canning. the study revealed a drastic reduction of 1.67±0.06 �g/g (dw) and 1.69 ± 0.08 �g/g (dw) in cd content at 90±1°c by ohmic heating and blanching, respectively. at that same temperature, pb content reduced to 4.18 ± 0.24 �g/g (dw) for ohmic heating and 4.14 ± 0.30 �g/g (dw) for blanching. furthermore, the cutting strength of the fresh samples significantly decreased after processing by ohmic heating when compared with the blanched samples at the same temperature. the initial mean count for mesophilic aerobic microorganisms and enterobacteriaceae were 3.8 log cfu/g and 2.5 log cfu/g, respectively. these values were found to reduce for mesophilic aerobic microorganisms count by 1.7 log cfu/g, while enterobacteriaceae count was reduced to undetectable levels through ohmic heating at the same temperature. investigation of jasmine rice swelling behaviour, electrical conductivity, water diffusion, and cooking energy was conducted by kanjanapongkul (2016). the researcher observed a tri-phased linear relationship between the electrical conductivity and temperature under transition temperatures of about 60 and 80°c. when the temperature exceeded 80°c, water diffused faster into the rice grain which becomes even quicker during the steeping of the rice. thus, suggested that the gelatinization of the rice starch usually took place at around 60 80°c. therefore, higher electric field strength caused the increase in diffusion rate. at temperatures beyond the gelatinization point, the crystalline structure of starch granules was disrupted due to breakage of hydrogen bonds, thereby resulting in a sudden increase in the volume (kong et al., 2015). the energy consumed by the ohmic cooking process at a shorter file:///c:/users/user/downloads/azojete143/www.azojete.com.ng muhammad, et al: ohmic heating as alternative preservation technique a review. azojete, 15(2):268-277. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 272 cooking time (18 and 17 min) was about 1/4 of the total energy consumed by an electric rice cooker (kanjanapongkul, 2017). the influence of ohmic heating in combination with salt-lye has shown promise in tomato peeling which gave high peeled-product quality. in the study, wongsa-ngasri and sastry (2016) stated that diffusion through tomato skin was significantly (p<0.05) improved at temperatures of 50 and 65°c. nevertheless, this confirmed that electric field has enhanced the spread of lye through tomato skin after an initial period in which the diffusivities of lye peeling with ohmic heating were higher than those without ohmic heating at 50 and 65°c (wongsa-ngasri and sastry, 2016). lakkakula et al. (2004) reported ohmic heating to be an alternative method for stabilization of rice bran due to its increased oil yield in rice bran to a maximum value of 92%, as compared to only 53% of oil extracted from the control samples. the above studies have demonstrated that ohmic heating can be an alternative novel heating process to conventional heating methods. 2.2 advantages and disadvantages of ohmic heating the summary of the relative pros and cons of ohmic heating technology are presented in table 1 as reported by many researchers (ruan et al., 2001; assiry et al., 2003; assiry et al., 2010). table 1: advantages and disadvantages of ohmic heating advantages disadvantages uniform heating of the material the target temperature achieved very quickly. high energy conversion efficiencies at low maintenance costs. the instant shutdown of the system no residual heat transfers after current shut down. reduced maintenance costs because of the lack of moving parts reduced problems of surface fouling a quiet environmentally friendly technology. narrow frequency band. coupling between temperature and electrical file distribution is very complicated. lack of generalized information. request adjustment based on the conductivity of the food material. difficult to monitor and control. based on the limitations mentioned above, the following recommendations were drawn: the development of predictive, measurable, and reliable models of ohmic heating patterns are encouraged. i. more researches need to be conducted to develop a reliable feedback control to adjust the supply of power due to the change in the conductivity of food materials. ii. development of real-time temperature monitoring systems for locating unheated cold spots and overheated regions during ohmic heating. iii. enhancement of safety and quality assurance protocols to commercialize the ohmic heating technology. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):268-277. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 273 3.0 food processing application of ohmic heating in a study conducted by neetoo and chen (2014), it was stated that ohmic heating technology was successfully used in commercial pasteurization of liquid egg products and processing of whole fruits in uk and japan. also, the technology can be applied to a variety of food products such as vegetables, juices, meats, seafoods, soups, creams, and pasta dishes. sterilization of food items to produce high quality shelf-stable low-acid foods (readily prepared meals) and high-acid foods (tomato-based sauces) were also carried out. recently, ohmic heating has been employed in sweet whey processing (costa et al., 2018), rice cooking (kanjanapongkul, 2017), meat processing (van der sman, 2017), and meat thawing (duygu and ümit, 2015). the effect of ohmic heating parameters on peroxidase inactivation, phenolic compounds degradation, and colour changes of sugarcane juice was also studied (brochier et al., 2018). on the other hand, ramírez-jiménez et al. (2019) studied the changes in the phytochemicals profile of two instant corn flours produced by different processes. these processes were the traditional nixtamalization (tn) and the ohmic heating process. the researchers reported the highest total phenolic content in the flour was recorded with the ohmic heating process as compared to the tn process. 3.1 other industrial application of ohmic heating apart from food processing applications, ohmic heating also has other uses such as waste treatment in the sterilization of livestock wastes, heating animals’ slurries, sewage sludge, and compost leachate. murphy et al. (1991) suggested that sewage sludge could be ohmically heated rapidly from room temperature to boiling point and achieve uniformity in energy efficiencies greater than 98%. sakr and liu (2014) alternatively suggested that ohmic heating can be integrated with thermal energy storage such as electric thermal storage device. since salts are good at storing heat, they can be heated to melting point and then stored in insulated containers. whenever the energy is needed, such molten salts can be pumped out to release their heat through a heat exchange system. another application is in seawater distillation whereby electrical energy or fossil fuel is required to heat the water in which steam boiler currently serve this purpose. however, this method is associated with the formation of scales on the heat exchanger tubes which affects the efficiency. the ohmic heating method can be employed to generate the heat required as an alternative heating method to be utilized in a desalination process rather than using a steam boiler (assiry et al., 2010). studies carried out by assiry et al. (2003) opined that ohmic heating could be applied in the heating process of seawater but with some limitations regarding the colour change. therefore, more studies are needed for a pilot production system and in modelling the potential use of ohmic heating in the desalination process. 3.2 potential research perspectives a large number of possible future research and applications exist for ohmic heating, among which are; blanching, evaporation, dehydration, fermentation, and extraction (fda, 2000). ohmic heating can enhance the drying of vegetable tissue such as potato and yam by 16% and 43%, respectively (wang and sastry, 2000). extraction of valuable components such as rice bran oil from rice bran by ohmic treatment can be enhanced up to 74% (lakkakula et al., 2004). kanjanapongkul (2016) categorically recommended that more study should be conducted to conclude why the increasing rate of electrical conductivity was lower when the rice grains began file:///c:/users/user/downloads/azojete143/www.azojete.com.ng muhammad, et al: ohmic heating as alternative preservation technique a review. azojete, 15(2):268-277. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 274 to swell rapidly under ohmic heating. another emerging application that is currently receiving considerable attention as a result of its advantages is thermal energy storage (tes) systems, which is based on latent heat as in high heat fusion (gang, 2013; li et al., 2012; raluy et al., 2014). the technique has been successfully applied in tes systems in which molten salt is used as a storage medium and is still under development worldwide (li et al., 2012; xu et al., 2013). since ohmic heating performance increases with increasing ions on the heating solutions, molten salt can offer the best balance of capacity, cost, efficiency, and usability at high temperatures (assiry et al., 2010). 4.0 conclusion the importance of recommended energy consumption in heating at food industries cannot be overemphasized. thus, makes it mandatory for such firms not only to research a new alternative and sustainable methods, which save energy and cost, but also, to venture and invest in emerging technologies with an enormous number of present and future applications like ohmic heating technology. its numerous applications in food processing are blanching, evaporation, dehydration, fermentation, extraction, sterilization, pasteurization, and heating of foods to the desired temperature. another industrial application outside food industries is thermal energy storage when used in combination with a molten salt solution. this strategy can be used to generate electricity in a space heater. research advancement in modelling heating needs to be carried out for complex foods, which might lead to the development of product packaging. acknowledgments we acknowledge the financial support for the graduate study from the chinese government scholarship council, zhejiang university, and bayero university, kano. reference assiry, am., gaily, mh., alsamee, m. and sarifudin, a. 2010. electrical conductivity of seawater during ohmic heating. desalination, 260: 9–17. assiry, a., sastry, sk. and samaranayake, c. 2003. degradation kinetics of ascorbic acid during ohmic heating with stainless steel electrodes. journal of applied electrochemicals, 33: 187–196. bastías, jm., moreno, j., pia, c., reyes, j., quevedo, r. and muñoz, o. 2015. effect of ohmic heating on texture, microbial load, and cadmium and lead content of chilean blue mussel (mytilus chilensis). innovative food science and emerging technologies, 30: 98–102. brochier, b., mercali, gd. and marczak, ldf. 2018. effect of ohmic heating parameters on peroxidase inactivation, phenolic compounds degradation and color changes of sugarcane juice. food and bioproducts processing, 111: 62–71. chemat, f., vian, ma., and cravotto, g. 2012. green extraction of natural products: concept and principles. international journal of molecular science, 13(7): 8615–8627. cho, w., yoon, j., and chung, m. 2016. pasteurization of fermented red pepper paste by ohmic heating. innovative food science and emerging technologies, 34: 180–186. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; 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vol. 15(2):268-277. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aimuhammad.age@buk.edu.ng 277 termrittikul, p., jittanit, w. and sirisansaneeyakul, s. 2018. the application of ohmic heating for inulin extraction from the wet-milled and dry-milled powders of jerusalem artichoke (helianthus tuberosus l.) tuber. innovative food science and emerging technologies, 48: 99–110. van der sman, rgm. 2017. model for electrical conductivity of muscle meat during ohmic heating. journal of food engineering, 208: 37–47. vorobiev, e. and lebovka, n. 2009. electro-technologies for extraction from food plants and biomaterials. springer science business media, llc. wang, w. and sastry, s. 2000. effects of thermal and electrothermal pretreatments of hot air drying rate of vegetable tissue. journal of food process engineering, 23: 299–319. wongsa-ngasri, p. and sastry, sk. 2015. effect of ohmic heating on tomato peeling. lwt food science and technology, 61(2): 269–274. wongsa-ngasri, p. and sastry, sk. 2016. tomato peeling by ohmic heating with lye-salt combinations : effects of operational parameters on peeling time and skin diffusivity. journal of food engineering, 186: 10–16. xu, c., li, x., wang, z., he, y. and bai, f. 2013. effects of solid particle properties on the thermal performance of a packed-bed molten-salt thermocline thermal storage system. applied thermal engineering, 57: 69–80. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):109-119 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 109 original research article assessment of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction h. a. quadri1*, o. s. abiola1, s. o. odunfa1 and j. o. azeez2 (1department of civil engineering, federal university of agriculture, abeokuta, ogun state, nigeria 2department of soil science and land management, federal university of agriculture, abeokuta, ogun state, nigeria) *corresponding author’s email address: dejiquadry@gmail.com 1.0 introduction construction of roadways over soft subgrade is one of the most frequent problems for highway construction in many parts of the world (antonia, 2016). stabilization of soft subgrades with costly stronger materials like crushed rock is widely used, hence the need for cheaper alternative construction methods on soft subgrades (cetin et al., 2010; consoli et al., 2016; quadri et al., 2019a; quadri et al., 2019b). clay stabilization using low-cost materials such as cement, lime, rice husk ash, cement kiln dust, calcined clay, steel slag or fly ash are better compared to article information abstract stabilization techniques have often been used globally to enhance properties of weak subgrade materials for flexible pavement construction. this study assessed the blend of calcium carbide waste (ccw) and calcined clay (cc) to serve as an effective stabilizer of subgrade material (s) sourced from a section along ota-idiroko road. subgrade material was initially modified with ccw in different percentage replacements by weight (0, 4, 8, 12, 16 and 20%) and the resulting blends were subjected to atterberg’s limits test to determine the blend with optimum plasticity index reduction which would be tagged optimum subgrade lime blend (oslb). the blend of s + 8% ccw was tagged oslb because it exhibited optimum plasticity index reduction. the oslb was thereafter blended by weight with cc in the following percentage replacements 3, 6, 9, 12, 15 and 18% in order to activate the pozzolanic potentials of cc for strength enhancement. the resulting blends were subjected to atterberg’s limits, compaction, california bearing ratio (cbr) and unconfined compressive strength (ucs) tests with the strength specimens cured for 0, 3, 7, 28, 56 and 90 days. the results showed that oslb-cc blends reduced the plasticity index from14.8 to 8.4 %, maximum dry density from 1.82 to 1.54 mg/m3, optimum moisture content, 23.7 to 17.9 % and increased soaked cbr, 0 to 418.2% and ucs, 201.59 to 5660.84 kpa of natural subgrade respectively. furthermore, the blends showed great improvement with reduction in pi less than standard value of 10% and increment in standard cbr and ucs values of 180% and 1700 kpa respectively for base course material. therefore, stabilized blends at 7 days curing period could improve the natural subgrade to subbase and base for pavement construction. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 june, 2019 revised 27 november, 2019 accepted 02 december, 2019 keywords: weak subgrade soil flexible pavement calcium carbide waste calcined clay. mailto:dejiquadry@gmail.com http://www.azojete.com.ng quadri et al: assessment of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction. azojete,16(1):109-119. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 110 crushed rock (antonia, 2016). steel slag, calcined clay, fly ash, rice husk ash amongst others are useful in many construction applications because they are pozzolanas (quadri et al., 2019b). calcium carbide waste (ccw) is another form of industrial waste being used by researchers to improve properties of expansive soils (krammart et al., 2004; du et al., 2011; quadri et al., 2019a). it is a by-product obtained from the acetylene gas (c2h2) production process, as shown in equation 1 (quadri et al., 2019b). cac2 +2h2o c2h2 + ca (oh)2 (1) ccw when mixed with certain pozzolans, which have high silicon dioxide (sio2) or aluminum oxide (al2o3) content, could yield pozzolanic reactions, resulting in final products that are similar to those obtained from the cement hydration process (wang et al., 2013). literature studies indicated that ccw can be reused as construction materials (du et al., 2011). jaturapitakkul et al. (2003) indicated that the compressive strength of mixture of ccw and rice husk ash was so high that the mixture could be used as cementitious material in mortar production. krammart et al. (2004) used ccw as part of cement raw material, and found that the compressive strength of ccw cement mortars was close to that of the control cement. fu and fang (2004) investigated the potential use of mixture of ccw and fly ash as construction material for sub-base of municipal roads. it was concluded that ccw blends have the merits of low cost with high strength developed. agbede and joel (2011) conducted a study on the effect of carbide ccw on the properties of makurdi shale blended with 0 to 8% of ccw for use in brick production. their study revealed that 4% ccw mix was suitable to stabilize the shale. it was concluded that the utilization of ccw to improve makurdi shale has advantage of preventing the pollution of air and ground water. du et al., (2011) used ccw and lime as binders to treat over-wetted clays being used as embankment filling material. it was concluded from their tests that ccw treated soils have better performance than that of lime treated soils and can be adopted as an alternative binder to treat over-wetted soils being used as highway embankment. joel and edeh (2014) stabilized ikpayongo laterite with cement and ccw. from the results, the use of mixture of 8% cement plus 10% ccw, 10% cement plus 10% ccw was recommended as best treatment for ikpayongo laterite for use as base material. it was concluded that the use of ccw in the stabilization of soil will ensure economy in road construction, while providing an effective way of disposing ccw. darikandeh (2017) stabilized expansive soil by ccw-fly ash columns and reported that a significant reduction in the swell potential and swell pressure was observed at 62% (ccw: fa=20:80) and 68% (ccw: fa=20:80) respectively. akinwumi et al. (2019) investigated ccw as a stabilizer for tropical sand used as pavement material. it was observed that increasing application of ccw generally reduced the soil’s specific gravity, plasticity index and maximum dry unit weight. the authors concluded that the soil became more workable and its strength properties were improved by stabilization with an optimal application of 4% ccw. the subgrade characteristics of soil for use as earthwork materials for road construction were improved. horpibulsuk et al. (2013) worked on strength development in silty clay stabilized with ccw and fly ash and observed that the soaked and unsoaked strengths depended mainly on the ccw and fa contents. the authors added that most of the ratios of soaked strength to unsoaked strength varied between 0.45 and 0.65 and proved that a mixture of ccw and fa could be used for soil stabilization instead of ordinary portland cement. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 109-119. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 111 vichan and rachan (2013) stabilized soft bangkok clay using the blend of ccw and biomass ash with binders’ contents ranging from 5 to 30%. the authors concluded that strength development ratio of stabilized clay with a ccw and ba mixture exceeded those of cemented clay and fa and ba blended cement admixtured clay after 28 days of curing due to the progress of the pozzolanic reaction. bandyopadhyay et al. (2016) worked on stabilization of soil using ground granulated blast furnace (ggbs) and ccw. it was concluded that with increase of cbr (0.5, 0.7, 0.75, 0.8 and 1.0% of the weight of the soil), optimum moisture content (omc) increased and maximum dry density (mdd) decreased which was due to the water absorbing nature of ccw. the ucs value increased when ccw percentage changed from 0.5 to 0.7% but decreased at 0.8 to 1.0%, hence it was tested for 0.75% and found that the value of ucs was 3.042 kg/cm3 which was maximum. also, maximum cbr in unsoaked condition was found to be 4.18% when soil sample was added with 0.75% ccw by weight. this study assessed ccw and calcined clay blend as an effective stabilizer for flexible pavement construction via atterberg’s limits, california bearing ratio and unconfined compressive strength tests. 2. materials and methods 2.1 sample preparation subgrade material (s) was obtained from a section along ota-idiroko road (latitude 60 40’ 53.082” n and longitude 30 9’ 11.172” e) while ccw and raw clay were obtained from automobile workshops and owode-ketu in ogun state respectively. the samples were air dried under the sun to remove moisture contents, ground to fineness using grinding machine and sieved through 425 µm sieve size. particles with large surface area that would be very reactive to aid hydration or pozzolanic reaction after the raw clay had been calcined in a kiln for 2 hours at a temperature of 700°c was used. these materials were subjected to specific gravity, particle size distribution and x-ray fluorescence tests according to bs 1377 (1990) to determine their properties. 2.1.1 specific gravity test a constant volume method was used by employing a 50cm3 constant volume conical flask bottle with distilled water. 20g of dry mass each of these materials (subgrade, ccw, and cc) was used as specified in bs 1377 (1990) using equation 1. g = ms m1w = m2−m1 m4−m1 −( m3−m2) (1) where: m1 (g) = mass of empty bottle m2 (g) = mass of bottle + dry soil m3 (g) = mass of bottle + soil + water m4 (g) = mass of bottle + water 2.1.2 particle size distribution test the subgrade sample was subjected to both wet sieving (sedimentation test) and dry sieving to evaluate percentages passing using different assemblage of sieves, percentage passing sieve no. 200 (75µm) as specified in bs 1377 (1990). however, ccw and cc after being ground to fineness, were subjected to dry sieving to evaluate percentages passing different assemblage of sieves, most especially 425µm as specified in bs 1377 (1990). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng quadri et al: assessment of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction. azojete,16(1):109-119. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 112 2.1.3 x-ray fluorescence (xrf) test firstly, the samples (subgrade, ccw and cc) were crushed using an agate pestle and mortar, finely ground and sieved with a mesh size of 75µm to achieve homogeneity. afterwards, 15 to 20 g (this quantity makes up the thickness) and each sample was placed in a plastic sample holder with replaceable plastic support film for each sample analysed. this plastic support film was attached to the bottom of the sample holder, keeping the sample in the holder which served as a screen over the x-ray window for direct analysis of the sample and also provided a flat surface for the sample as rough surfaces could cause scattering of x-rays. an edx3600b x-ray fluorescence spectrometer (skyray instruments, u.s.a) was used to determine the oxide compositions of materials (subgrade and additives) for classification. 2.2 experimental procedure firstly, subgrade was modified with calcium carbide waste (ccw) by weight using the following percentage 0, 4, 8, 12, 16 and 20%. the resulting blends were subjected to atterberg’s limits in order to determine the liquid limit (ll), plastic limit (pl) and plasticity index (pi) values of the blends. the ll and pi values alongside percentage of soil particles passing sieve no. 200 were used to classify subgrade according to american association of highway and transportation officials (aashto) system and unified soil classification system. also, from the pi values of the blends, the blend with the optimum pi reduction, tagged optimum subgrade lime blend (oslb) was determined. the blend of s + 8% ccw which exhibited the optimum pi reduction (14.8 to 8.7%). the oslb (s + 8% ccw) was thereafter blended by weight with cc using the following percentage; 3, 6, 9, 12, 15 and 18% respectively in order to activate the pozzolanic potentials of cc for strength enhancement. the blends were subjected to atterberg’s limits test to majorly determine their pi values, compaction test to determine their optimum moisture contents (omc) and maximum dry densities (mdd), soaked and unsoaked california bearing ratio (cbr) tests to determine their bearing capacities both in wet and dry states and unconfined compressive strength (ucs) test to determine their compressive strengths. however, the specimens for strength test were moist cured for 0, 3, 7, 28, 56 and 90 days respectively in order to aid hydration or pozzolanic reaction which will in turn enhance strength developments of the blends. all tests were conducted according to bs 1377 (1990). 2.2.1 atterberg’s limits test subgrade sample was pulverized, sieved through sieve 425µm and consequently stabilized with ccw by weight of soil using the following percentage (0, 4, 8, 12, 16, and 20%) respectively. the blend of subgrade with 8% ccw (s + 8% ccw) which was singled out as the appropriate subgrade – lime (ccw) blend (oslb) was blended with cc in the following percentage (3, 6, 9, 12, 15 and 18%) by mass of subgrade soil. the samples were subjected to atterberg’s limits test as specified in bs 1377 (1990) to evaluate pl and ll from where pi of each blend was derived using equation 2. pi = ll – pl (2) where: pi = plasticity index (%) ll = liquid limit (%) pl = plastic limit (%) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 109-119. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 113 2.2.2 compaction test 3000g each of the aforementioned blends was employed at varying moisture contents ranging from 100 to 500 ml at 100 ml interval using proctol type of compaction in accordance to bs 1377 (1990) where 27 blows were applied to sample at each layer of the mould to evaluate mdd and omc of each blend. 2.2.3 california bearing ratio (cbr) test 5000g each of the blends was produced at mdd and omc applying 56 blows to sample per layer of cbr mould after which bearing capacity was determined with the aid of cbr machine in accordance to bs 1377 (1990). 2.2.4 unconfined compressive strength (ucs) test equation 3 was employed to determine the unconfined compressive strength (ucs) of each of the abovementioned blends in cylindrical shape of 120 mm x 100 mm after being produced at mdd and omc and crushed with the aid of compression machine in accordance to bs 1377 (1990). qu = p ( 1− ɛ) a (3) where: qu = unconfined compressive strength (kn/m2 or kpa) p = load that crushes cylindrical specimen to failure (kn) ɛ = calculated strain from ratio of difference between length of cylindrical specimen before failure and length after failure to original length of cylindrical specimen before failure to a = area of cylindrical specimen before failure (mm2) 3. results and discussion 3.1 physical and index properties the subgrade material as shown in table 1 was classified as a-7-5 (fair to poor subgrade) and ml or ol (inorganic silts and very fine sands, rock flour, silty or clayey fine sands with slight plasticity) according to aashto classification and unified soil classification system (uscs) respectively. the classifications were based on its ll, pi and percentage passing sieve no. 200 of 46, 14.8 and 64.21% respectively. similarly, the fraction of silt-clay of owode ketu raw clay with more than 35% passing sieve no. 200. according to uscs, the clay would be regarded as inorganic clay of low, medium and high plasticity (cl) since there are more than half of its material contents smaller than no. 200 sieve size. the owode ketu material (raw clay) was regarded as a clayey soil according to uscs. it was observed that the percentages of particles passing sieve 425 µm of ccw and cc were 50.23 and 60.98% respectively. ccw was found to be the least dense material with specific gravity of 1.81 as against 2.5 for cc and subgrade. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng quadri et al: assessment of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction. azojete,16(1):109-119. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 114 table 1: physical and index properties of individual materials property subgrade ccw owode ketu raw clay cc plastic limit (%) 31.2 21 liquid limit (%) 46 46 plasticity index (%) 14.8 25 clay content (<0.002mm)(%) 44.35 silt content (0.002-0.06mm)(%) 35.84 percentage passing sieve 425μm (%) 87.5 50.23 60.98 percentage passing sieve 75μm (%) 61.21 80.19 aashto classification a-7-5 uscs classification ml or ol cl specific gravity 2.5 1.81 2.5 colour reddish brown white darkish-grey darkish brown 3.2 x-ray fluorescence test the subgrade and cc were found to be pozzolanic materials and they belong to class f according to astm: c618-08 standard. the standard stipulates that material whose aggregation of the main oxides (sio2 + al2o3+ fe2o3) is in excess of 70% and having loss on ignition (loi) of maximum of 6% is a class f pozzolana.; however, the aggregation of the three (3) main oxides for subgrade and cc are 94.01 and 85.2% respectively; while their loi are 3.10 and 2.20% respectively (table 2). however, from table 2, the ccw contains 93.74% mass fraction of clincker or quick lime (cao) which makes it a potent binding material/binder with tendency to undergoing hydration reaction when mixed with water just as in the case of cement. table 2: the oxide compositions of individual materials according to xrf test oxides percentage oxide contents of materials subgrade cc ccw sio2 49.57 58.86 0.83 al2o3 28.86 16.23 0.71 fe2o3 15.58 10.11 0.20 cao 0.53 3.25 93.74 mgo 0.00 0.00 0.0 so3 0.41 7.81 0.7 na2o 0.00 0.0 0.0 k2o 0.16 0.35 0.0 loi 3.10 2.20 1.04 3.3 atterberg’s limits test figure 1 shows that the addition of ccw reduced the plasticity index of subgrade from 14.8 to 8.7% with optimum reduction obtained at 8% ccw. thus, referred to as optimum subgrade oslb due to reduction in plasticity index and swell potential. this might be attributed to available calcium cation exchange to take place or the ionic exchange between lime and clay http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 109-119. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 115 minerals of the soil which led to flocculation and agglomeration of clay particles similar to ghobadi et al. (2014). figure 1: plasticity index values of subgrade ccw blend the addition of cc at different variations (3, 6, 9, 12, 15 and 18%) to blend of 8% ccwsubgrade (oslb) increased its pi from 8.7 to 13.5% up to 15% cc while a sudden reduction was experienced at 18% cc (8.4%). however, all blends including oslb reduced pi of subgrade from 14.8 to 8.4% with optimum reduction at 18% cc (8.4%) as shown in figure 2. according to ghobadi et al. (2014), the addition of additives which led to reduction in pi might be attributed according to cation exchange that might have taken place or the ionic exchange between ccw and subgrade which resulted to flocculation and agglomeration of subgrade particles; hence reduction in swell potential and pi. figure 2: plasticity index results of subgrade-oslb/cc blends 3.4 compaction test figure 3 shows the addition of cc at different variations (3, 6, 9, 12, 15 and 18%) to blend of 8% ccwsubgrade oslb reduced its maximum dry density (mdd) from 1.6 to 1.54 mg/m3 except for 3% cc (1.66 mg/m3) where a slight increment was observed. however, all blends reduced mdd of subgrade from 1.82 to 1.54 mg/m3 with optimum reduction obtained at 18% cc. this behavior in terms of reduction in mdd could be adduced to the fact that when a lime or pozzolan is added or mixed with a highly plastic soil in the presence of water, hydration reaction takes place leading to flocculation and agglomeration of particles where the number of free clay and silt present in the soil would be reduced leading to formation of coarser particles which occupy less place, hence the reduction in density (eberemu et al., 2013). the decrease in density could also be adduced to the specific gravity of ccw (1.81) which is less to that of subgrade (2.50), a trend noted by amadi (2010), okonta and govender (2011), amadi (2013) and eberemu et al. (2013). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng quadri et al: assessment of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction. azojete,16(1):109-119. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 116 figure 3: maximum dry density results of subgrade-oslb/cc blends from figure 4, the addition of cc at different variations (3, 6, 9, 12, 15 and 18%) to blend of 8% ccw subgrade (oslb) increased its optimum moisture content (omc) from 17.2 to 21.9%. however, all blends inclusive of oslb reduced omc of subgrade from 23.7 to 17.2% with optimum reduction experienced at s + 8% ccw (oslb). according to osinubi (1998) and alhomidy et al. (2017), the addition of additives which led to reduction in omc might be attributed to insufficiency of water in the mixtures, resulting in self-desiccation and consequently lower hydration. figure 4: optimum moisture content of subgrade-oslb/cc blends 3.5 california bearing ratio test the cbr results of oslb – cc blends (3, 6, 9, 12, 15 and 18% cc) addition to natural subgrade ranged from 1.12 to 530.3% and 0 to 418.2% for both unsoaked and soaked conditions for varying curing periods (0, 3, 7, 28, 56 and 90 days) as captured in figures 5 and 6 respectively. the blends of s (0%) and oslb + 18% cc at 90 days curing period exhibited the least and highest cbr values for both unsoaked and soaked conditions respectively. however, for the purpose of pavement design, the soaked cbr results after 7 days moist curing ranged from 0 to 101.9% with the blends of s (0%) and oslb + 18% cc exhibiting least and highest values respectively. all blends except oslb + 3% cc (74.7% cbr) and oslb + 6% cc (71.3% cbr) can be used as base course materials for lime-treated roads according to nigerian general specification for roads and bridges. the standard specifies a minimum conventional cbr values of 40, 80 and 100% to be met by soil materials for purposes of subbase, base course (for lightly trafficked roads) and base course (for heavily trafficked roads) respectively for limetreated soils http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 109-119. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 117 figure 5: unsoaked cbr results of oslb (subgrade + 8% ccw) cc blends at varying curing periods. figure 6: soaked cbr results of oslb (subgrade + 8% ccw) cc blends at varying curing periods. 3.6 unconfined compression strength (ucs) test figure 7 shows the ucs results of oslb – cc blends (3, 6, 9, 12, 15 and 18% cc) addition to subgrade which ranged from 201.59 to 5660.84 kpa for varying curing periods (0, 3, 7, 28, 56 and 90 days) with the blends of s (0%) at 0 day moist curing and oslb + 15% cc at 90 days moist curing exhibiting the least and highest values respectively. however, for the purpose of pavement design, the ucs results after 7 days moist curing ranged from 1934.32 to 3084.18 kpa with the blends of s (0%) and oslb + 6% cc having the least and highest values respectively. however, all blends can be used as subbase and base courses for lime-treated and cement stabilized roads according to nigerian general specifications for roads and bridges. the standard specifies minimum conventional ucs values of 700, 1003 and 1700 kpa to be met by soil materials for purposes subbase, base course (for lime-treated roads) and base course (for cement stabilized roads) respectively. figure 7: ucs results of oslb (subgrade + 8% ccw) cc blends at varying curing periods. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng quadri et al: assessment of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction. azojete,16(1):109-119. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 118 4.0 conclusion this study assessed blend of calcium carbide waste and calcined clay as stabilizer in flexible pavement construction. the blend of s + 8% ccw exhibited optimum pi reduction and was tagged oslb when ccw was initially used to modify natural subgrade. all blends of oslb-cc reduced pi, mdd and omc of natural subgrade. also, blends of oslb-cc increased cbr (soaked and unsoaked) and ucs of natural subgrade with increase in curing period and increase in material addition; hence they can be used as subbase and base course materials for lime treated roads. references agbede, io. and joel, m. 2011. mechanical-cement stabilization of laterite for use as flexible pavement material. journal of materials in civil engineering, 23(2): 146 – 152. al-homidy, aa. and abd el aal, ak. 2017. improvement of geotechnical properties of sabbkha soil utilizing cement kiln dust. journal of rock mechanics and geotechnical engineering, 9 (4): 749 – 760. al-homidy, aa. 2013. improvement of eastern saudi soil utilizing indigenous industrial byproduct. phd thesis department of civil engineering, king fahd university of petroleum and minerals, dhahra, saudi arabia, pp. 1 – 432. antonia, a. 2016. modification of clayey soil’s properties with the addition of lime and fly ash. international journal of engineering sciences and research technology, 5 (10): 529-537. akinwumi, ii. 2012. utilization of steel slag for stabilization of a lateritic soil, ota, nigeria. m.eng. dissertation, department of civil engineering, covenant university, ota, nigeria, pp. 1 – 245. akinwumi, ii., ajayi, oo., agarana, mc., ogbiye, as., ojuri, oo. and david, ao. 2019. investigation of calcium carbide residue as a stabilizer for tropical sand used as pavement material. wit transactions on the built environment, 187: 285-294. amadi, aa. 2010. evaluating the potential use of lateritic soil mechanically stabilized with quarry fines for construction of road bases. nigerian journal of engineering, 17(2): 1-12. astm. 2003. standard specification for fly ash and raw or calcined natural pozzolan for use as a mineral admixture in portland cement concrete. annual book of astm standards, c 618-93, 0402, pp. 310-312. bandyopadhyay, ts., singh, aa., pandey, v. and singh, jp. 2016. stabilization of soil using ggbs and calcium carbide residue. international journal of innovative research in science, engineering and technology, 5 (9): 17023-17030. bs 1377. 1990. methods of test for soils for civil engineering purposes. british standard institute, london, uk. cetin, b., aydilekb, ah. and guney, y. 2010. stabilization of recycled base materials with high carbon fly ash. resources, conservation and recycling, 54 (11): 878-892. consoli, ns., festugato, l., consoli, b. and da silva lopes jr., l. 2014. devising dosages for soilfly ash-lime blends based on tensile strength controlling equations. construction, building and materials, 55(1): 238-245. consoli, n., da rocha, c. and maghous, s. 2016. strategies for developing more sustainable dosages for soil-coal fly ash-lime blends. journal of materials in civil engineering, 4 (2): 645 – 653. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 109-119. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dejiquadry@gmail.com 119 darikandeh, f. 2017. expansive soil stabilization by calcium carbide residue-fly ash columns. proceedings of the institute of civil engineers ground improvement, 171 (1): 1 – 10 du, yj., zhang, yy. and liu, sy. 2011. investigation of strength and california bearing ratio properties of natural soils treated by calcium carbide residue. geo-frontiers, asce., 12371244 eberemu, ao., isah, g. and gadzama, ew. 2013. compressibility characteristics of compacted black cotton soil treated with bagasse ash. journal of civil engineering, 8(1): 26-44. fmwh. 1997. nigerian general specifications for roads and bridges. federal ministry of works and housing standard specification requirements, 3 (1): 1 – 3456. fu, f and fang, lj. 2004. application of fly ash-calcium carbide complex binder. comprehensive utilization of fly ash, 59(3): 23-24. ghobadi, mh.. abdilor, y. and babazadeh, r. 2014 stabilization of clay soils using lime and effect of ph variations on shear strength parameters. bulletin of engineering and environment, 73(2): 611 – 619. horpibulsuk, s., phetchuay, c., chinkulkijniwat, a. and cholaphatsorn, a. 2013. strength development in silty clay stabilized with calcium carbide residue and fly ash. soils foundation, 53(4): 477-486. jaturapitakkul, c. and roongreung, b. 2003. cementing material from calcium carbide residuerice husk ash. journal of materials in civil engineering, asce. 15(5): 470-475. joel, m. and edeh, ej. 2014. stabilization of ikpayongo laterite with cement and calcium crabide. global journal of pure and applied sciences, 20 (1): 49-55. krammart, p. and tangtermsirikul, s. 2004. properties of cement made by partially replacing raw materials with municipal solid waste ashes and calcium carbide waste. construction and building materials, 18(8): 579-583. okonta, fn. and govender, e. 2011. effect of desiccation on the geotechnical properties of lime-fly ash stabilized collapsible residual sand. arpn journal of engineering and applied sciences, 6 (6): 62-69. osinubi, kj. 1998. influence of compaction delay on the properties of cement stabilized lateritic soil. journal of engineering research, 6 (1): 13-25. quadri, ha., abiola, os., odunfa, so. and azeez, jo. 2019. application and strength development of subgrade material stabilized with calcium carbide waste in flexible pavement construction. adeleke university journal of engineering and technology (aujet), 2(2): 55 – 65. quadri, ha., abiola, os., odunfa, so. and azeez, jo. 2019. evaluation of blends of calcium carbide waste and iron slag dust as stabilizer in flexible pavement construction. federal university lafia journal of science and technology (fjst), 5(2): 63-69. vichan, s. and rachan, r. 2013. chemical stabilization of soft bangkok clay using the blend of calcium carbide residue and biomass ash. soils and foundations, 53(2): 272-281 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 628-637 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 638 original research article effect of number of passengers [loading] on centre of gravity of a three wheeled vehicle [keke-napep] b. sunday1*, u. thomas1, i. s. ityokumbul2, a. nasir3 (1department of mechanical engineering, nuhu bamalli polytechnic, zaria, nigeria 2department of mechanical engineering, kaduna polytechnic, kaduna, nigeria 3department of mechanical engineering, federal university of technology, minna, nigeria) * corresponding author’s email address: s2bako@yahoo.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: cg analysis cg of four wheeled vehicle cg of three wheeled vehicle effects of loading on cg static stability factor abstract in order to combat insecurity and to reduce the rate of accidents caused by commercial motorcyclist; many states government in northern nigeria have substituted the use of motor cycles commonly known as okada, with the use of three wheeled vehicle commonly known as keke-napep. the static and dynamic characteristics of these vehicles are not as those of the usual vehicles. therefore, the need to know more about the effects loading on these vehicles is highly needed by nigerians in order to ensure good road and passengers’ safety. this paper uses simple approach to highlight the effects of number of passengers (loading) on the position of centre of gravity (cg) of the three wheeled vehicles. it will serve as a measure for ensuring safe riding and reducing road clashes. as the load on the three wheeled vehicle increases from 3505n to 5410n, the static stability factor decreases. this reduces the safety margin against rollover of the three wheeled vehicles compared to those of the four wheeled vehicles. the keke-napep is a rear wheel drive vehicle with rear engine and rear passenger arrangement. it subjects the vehicle to high weight transfer during braking. this causes the change in position of centre of gravity and the instability of the three wheeled vehicles. therefore, it is hereby recommended that the wheelbase, track length, loading space and the centre of gravity position should be given a critical consideration during chassis design in order to improve the static and dynamic stability of these vehicles. also, components such as the engine and transmission system should be rearranged to obtain a more reliable position of the centre of gravity. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction three wheeled vehicles are automobiles with three wheels; having one or two wheels at the front for steering while the other one(s) for power transmission (saeedi and kazemi, 2013). these vehicles are commonly known as: tuk-tuk in kenya, bajaj in somalia, tok-tok in egypt, rasha in sudan, baby taxi in bangladesh and keke-napep in nigeria. having one wheel at the front and two at the rear the vehicle is known as the delta configuration. the second type of three wheeled vehicles is called the tadpole or reverse trike which is the opposite of the delta type (palash et al., 2014). figure 1 shows the delta type of three wheeled vehicle commonly use in nigeria for commercial transportation. the vehicle has many advantages over two wheeled vehicles. they mailto:s2bako@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):638-647. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 639 offer, more comfort, more luggage space, more distance between fill-ups and an increased safety. having three wheels on the ground, they are naturally more stable than two wheeled vehicles. they combine the comfort and safety of a four wheeled vehicle (car) (berote et al., 2008). it has the disadvantage of instability compared to four wheeled vehicles. the presence of three wheels indicates that the vehicles would have different static and dynamic characteristics compared to those of other vehicles. this paper shows how the number of passengers (loading) effects the position of centre of gravity (cg) of the three wheeled vehicles, thereby affecting its static and dynamic characteristics. one of the crucial vehicle properties is the location of its position of center of gravity and if it is properly located, the vehicle would be stable (starr, 2006)). the centre of gravity position of the three wheeled vehicle changes with inclusion of more passengers (mukherejee, 2007). this happens as the result of loading on the vehicle. overloading is a safety hazard that has leads to loss of lives, properties and deterioration of our roads which results in increase of maintenance and transportation cost. in the fight against road accident; the federal road safety commission incorporate campaigns against overloading. this fight can only be successful if the riders and public knows the impact and effects of overloading on the vehicles. this paper tends to highlight the effects of passengers (loading) on the position of centre of gravity of the three wheeled vehicles. the concept of this paper would help to educate the riders and the general public on effects of loading on the stability of these vehicles. this would help to monitor the static and dynamic characteristics of these vehicles thereby improving its service life and to ensure good road and passengers’ safety. figure 1: a delta type of three wheeled vehicle commonly use in nigeria 2.0 materials and method the materials used in this paper are: three wheeled vehicle technical specifications, literatures, microsoft excel (2007) and autocad (2010) engineering drawing software. data obtained from the three wheeled specification and literatures were utilized using equations to calculate the position of centre of gravity (cg) from; the rear wheel, front wheel and from the roll over lines. the data were also used to calculate the height of the centre of gravity from the road surface and static stability factor (ssf) of the three wheeled vehicles under different loading conditions. this was done in order to investigate the effect of number of passengers (loading) on the centre of gravity of the three wheeled vehicles. all the calculated results were presented inform of graphs using microsoft excel (2007) and the results were discussed. the autocad (2010) engineering drawing software was used for drawing purpose to illustrate the position of centre of gravity on the three wheeled vehicles. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sunday, et al: effect of number of passengers [loading] on centre of gravity of a three wheeled vehicle [keke-napep]. azojete, 15(3):638-647. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 640 3.0 centre of gravity (cg) analysis it was noted in raipput (1991) and abbott (1984) that the weight of all parts of a body are directed toward the centre of the earth and the point through which all the weights act is called the centre of gravity (cg). palash et al. (2014) and abbott (1984), also noted that the centrifugal force (cf) is exerted at the centre of gravity (cg) and is directed toward the centre (turning point) in order to keep a body moving in a circular path. 3.1 centre of gravity analysis for four wheeled vehicle consider a four wheeled vehicle as shown in figure 2 (a). if the vehicle is in a curve towards the left, the centrifugal force (cf) tends to roll the vehicle over towards the right, around an imaginary point (black spot under the right tyre in figure 2 (b)), while the gravitational force (gf) holds the vehicle back to avoid rollover. it’s as though the centrifugal force and the gravitational force combined together into a resulting force exerted on the center of gravity to turn it around this imaginary point (palash et al., 2014). mukhejee (2007), states that the ratio of half-track width (half the distance of the centre of the two rear tyres) to the height of centre of gravity (h) is called the state stability factor (ssf), and this plays a crucial role in determining the stability against rollover of a four wheeled vehicle. (a) (b) figure 2: position of centre of gravity (developed from; (palash et al. 2014). (a) top view of four wheeled vehicle. (b) rear view of four wheeled vehicle. 3.2 centre gravity analysis for three wheeled vehicles in the case of three wheeled vehicles, another factor comes into play; unlike the four wheeled vehicles, their structures are triangular in design. the slant sides from the front wheel to the rear wheel are called the rollover lines. it is observed that the distance between the center of gravity and the rollover line (figure 3 (a)) is shorter than in the case of the four wheeled vehicles, even though the center of gravity height (h), the base length (l) and the track (t) of the three wheeled vehicle are the same as those of the four wheeled vehicles. the center of gravity height (h) is therefore proportionately greater, which reduces its safety margin against rollover of the three wheeled vehicles in curves. as it was shown for the four wheeled vehicles; they roll over around http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):638-647. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 641 the rollover line corresponding to the imaginary point. but in the case of a three wheeled vehicle, it rather rolls over around the rollover line going from the single front wheel to one of the two symmetrical rear wheels. (a) (b) figure 3: position of centre of gravity (developed from palash et al., 2014). (a) top view of three wheeled vehicle. (b). rear view of three wheeled vehicle. 3.3 effects loading on centre of gravity (cg) kenneth et al., (1996) noted that the centre of gravity (cg) of a loaded vehicle ‘’a’’ would shift rearward to point ‘’b’’ as shown in figure 4 (a). as the center of gravity (cg) of the four wheeled vehicles shift from ‘a’ to ‘b’ the distance at1 and at2 remains constant (at1=at2). while for the three wheeled vehicles; distance increases (c1<c2) as shown in figure 4 (b). the loading of the four wheeled vehicles in this analysis leads no change in static stability. the loading of the three wheeled vehicles did improve its static stability when change in cg height is neglected (kenneth et al., 1996). (a) (b) figure 4: the effects of loading. (a). four wheeled vehicle, (b) three wheeled vehicle. (adapted from; kenneth et al. 1996) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sunday, et al: effect of number of passengers [loading] on centre of gravity of a three wheeled vehicle [keke-napep]. azojete, 15(3):638-647. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 642 3.4 effects of loading on centre of gravity position from the technical specifications of three wheeled vehicles by bajaj (2014); it was noted that the three wheeled vehicles have a wheel base (l) of 2m and wheel track (t) of 1.3m. mukherejee (2007) shows that. the centre of gravity position, mass and moment of inertia changes with the inclusion of more passengers (loads) on the bajaj three wheeled vehicle. in order to calculate the distance of the rollover line parallel to the centre of gravity (c’’) at various (number of passengers) loading condition, the ‘x’ axis was rotated parallel to the roll over axis, as shown in figure 5. figure 5: lateral distance from cg to rollover axis (adapted from azadeh, 2014) figure 6: side-view of the vehicle showing the vertical force (weight). according to figure 5, θ can be determined from equation (1), θ = tan−1 t 2l (1) to calculate the distance of centre of gravity (cg) from the rollover line (c) from figure 3 (a) and figure 5 (azadeh, 2014); c t 2 = a l → c = t × a 2l (2) while, c'' = ccosθ (3) by substituting equation (2) into equation (3) c'' = t × a 2l ccosθ (4) equation (4) above is used to determine the position of centre of gravity from the roll over line the static stability factor (ssf) is defined as one half the track width (wheel track) divided by the height of the centre of gravity (narang, 2004). this is determine using equation (5) below; ssf = t 2h (5) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):638-647. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 643 according to thomas (1992), when a vehicle sits statistically on a level ground, the weight distribution on the front and rear wheels are related by equation (6) and (7) respectively; wf = w b l (6) wf = weight at the front wheel (n) w = total weight of the vehicle (n) the weight at the rear of the three wheeled vehicle is given by; wr = w a l (7) wr =weight at the rear wheel (n) 4.0 results and discussion the three wheeled vehicles use in nigeria is design to carry the maximum of three passengers at the rear seat, but the riders tend to carry four passengers in order to maximized profit. in the case of carrying additional passenger at the front; the driver’s control and operating space are reduced, escalating the chance of for accidents. in table 1, the fourth passenger was computed in order to show the effects of increase in (number of passengers) weight on the position centre of gravity of the three wheeled vehicles. from table 1, as the number of passengers increases from 0 to 4, the weight at the front wheel decreases, while the weight at the rear wheels increases. this also increases the weight transfer from the rear wheels to front wheel during braking. due to this effect and the presence of one wheel at the front, makes the three wheeled vehicles unstable thereby leading to rollover accident during braking. also, from table 1, as the vehicle total weight increases due to increase in number of passengers, the distance of centre of gravity increases from 1.305m to 1.645m along the base length (wheelbase) from the front axle, with an inverse reduction in length of centre of gravity from the rear. this also leads to an increase in distance of centre of gravity from the rollover line thereby increasing the rollover propensity of this vehicle. this increase in weight as the result of increase in number passengers on the keke-napep also leads to an increase in height of centre of gravity from the 0.602m to 0.828m. this inversely reduces the static stability factor (ssf) of the vehicle as indicated by the last column of table 1. table 1: effects weights and position of centre of gravity (cg). (developed from; mukherejee, 2007) total no. of occupant (= driver + n) weight (n) cg location (m) static stability factor (ssf) at front wheel wf at rear wheels wr total w from front axle (a) from rear axle (b) from rollover line (c) from rollover line (c’’) height (h) 1( = 1 + 0) 1221 2284 3505 1.303 0.697 0.423 0.402 0,602 0.540 2( = 1 + 1) 1349 2927 4276 1.369 0.631 0.445 0.423 0.661 0.492 3( = 1 + 2) 1474 3573 5047 1.416 0.584 0.460 0.438 0.701 0.464 4( = 1 + 3) 1600 4218 5818 1.450 0.550 0.471 0.448 0.731 0.444 5( = 1 + 4) 1179 5410 6589 1.642 0.358 0.534 0.508 0.828 0.393 n = number of passengers file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sunday, et al: effect of number of passengers [loading] on centre of gravity of a three wheeled vehicle [keke-napep]. azojete, 15(3):638-647. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 644 figure 7 (a), shows that for every increase in weight (number of passengers), the distance of cg from the front axle (a) are inversely proportional to the distance of cg from the rear axle (b). this justified the work done by kenneth et al. (1996), which states that if a vehicle is loaded, its position of centre of gravity (cg) shifts to the rear. the three wheeled vehicle is a rear-engine, rear-wheel drive vehicles and according to dolan (1978), increase in weight at the rear of a rearengine, rear-wheeled drive vehicle tends to make the vehicle unstable at high speeds. palash et al. (2014), noted that if the centre of gravity height (h) is greater than half the track length (t/2), the resulting force (r) (figure 3 (b)) would align with the imaginary point (black spot under the tyre) and will roll the vehicle over in a curve. from table 1, the least value of the centre gravity height (h) is 0.602m, while the half of the track length is 0.575m when the three wheeled vehicle is loaded. this shows that the centre of gravity height (h) of the three wheeled vehicle is proportionally greater than half its track length. this increases the rollover tendency of the vehicles. therefore, the higher the weight, higher the position of position of center of gravity height (h) from the two symmetric wheels, and the longer the distance of the centre of gravity from the rollover line (c and c’’) as shown in figure 7 (d). this reduces the safety margin against rollover of the three wheeled vehicles compared to the four wheeled vehicles. the static stability factor (ssf) is viewed as the ultimate measure of the rollover resistance of a vehicle. figure 7 (c), shows that the static stability factor of the three wheeled vehicle decreases with an increase in weight (number of passengers) on the three wheeled vehicles. this increases the rollover propensity of the three wheeled vehicles. therefore, the riders should not exceed the recommended riding speed and should always maintain the recommended tyres pressure. the three wheeled vehicles are rear-engine, rear-wheeled drive with rear passengers’ arrangement. according to dolan (1978), a rear-engine, rear-wheeled drive vehicles have tendency to over steer (that is the wheels turn too sharply into the curve) and this can be corrected by turning the steering in opposite direction. (a) (b) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):638-647. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 645 (c) (d) figure 7: (a) cg from front and rear wheel (b). cg from roll overline. (c) static stability factor (ssf). (d) height of cg (h). under some riding conditions of the three wheeled vehicles, it is possible to have only two wheels in contact with the road surface. this could occur during turning or tight maneuvers whenever enough weight is transferred outside the rollover lines. this tendency requires careful load and passenger positioning inside the vehicle (motorcycle operator manual, 2017). if the loads are not properly positioned on the vehicle, the weights will not be properly distributed at each wheel. this would affect the position of centre of gravity and the static and dynamic stability of the vehicle. consider the vehicle moving on a horizontal road (figure 8). giri (2010), noted that a vehicle weight and its kinetic energy act through the center of gravity. this makes the vehicle to pitch forward when the brakes are applied. as a result of this action, some weights are effectively transferred from the rear wheel to the front wheels. due to the rear-engine, rear-wheeled design of the three wheeled vehicles and the rear position of passengers; the weight at the rear is more than that of the front. this weight is transfer to the front during braking. this changes the position of centre of gravity which affects the stability of the vehicle. therefore, this problem of weight transfer and instability of this vehicle can be improved by; designing the height of the centre of gravity to a minimum level toward the road surface. designing the length of the centre of gravity to a minimum distance from the two (2) rear wheels. significant increase in length of the rear wheel track length. figure 8: weight transfer (developed from; giri (2010)). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng sunday, et al: effect of number of passengers [loading] on centre of gravity of a three wheeled vehicle [keke-napep]. azojete, 15(3):638-647. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 646 overloading puts massive strain on vehicle tyres and chassis and also makes the vehicle less sable, difficult to steer, takes longer time to stop and causes damages to the road and road users. to reduce the number of road accidents; the government should set measures to regulate the operation of these vehicles. the federal road safety in conjunction with the vehicles inspection officers should enforce this illegal art. 5.0 conclusion and recommendations the paper presents the effect of number passengers (loading) on the centre of gravity of a three wheeled vehicle (keke-napep). this analysis shows that the inclusion of each passenger (load) on the three wheeled vehicles, raises the centre of gravity (cg) height (h) and decreases the vehicle static stability factor (ssf). also, the farther the position of centre of gravity (cg) from the two symmetric wheels towards the single wheel, the shorter the distance (c) from the center of gravity to the rollover line. this reduces the safety margin against rollover effect of the three wheeled vehicles compared to the four wheeled vehicles. this implies that the three wheeled vehicles with minimum number of passengers (loads) would be more stable in rollover condition than a three wheeled vehicle with high number of passengers. the keke-napep is a rear wheel drive vehicle with rear engine and rear passenger arrangement. this makes the vehicle to have high load concentration at the rear wheels. this subjects the vehicle to high weight transfer during braking. this affects the position of centre of gravity and the instability of the three wheeled vehicles. therefore, it is hereby recommended that the wheelbase, track length, loading space and the centre of gravity position should be given a critical consideration during chassis design in order to improve the static and dynamic stability of these vehicles. also, components such as the engine and the transmission system should be rearranged to obtain a more reliable position of the centre of gravity. finally, as the numbers of these vehicles increases as a means of commercial transportation in nigeria, the rate of traffic congestion, air pollution and road clashes would also increase. therefore, the federal ministry of transport and environmental should set aside future measures to combat these phenomena. references abbott, af. 1984. ordinary level physics. 4th edition. heinemann education books. london., pp. 4, 65. azadeh, z. 2014. dynamics of a three-wheel vehicle with tadpole design. a msc. thesis, department of mechanical engineering, university of waterloo, ontario, canada., pp. 25-27. bajaj. 2014. three wheeled vehicle technical specifications. available at: www.globalbajaj.com. (accessed 18th october, 2014). berote, j., ivan, pa., darling, j., edge, k. and plummer, a. 2008. the dynamics of a three-wheeled narrow-track tilting vehicle. fisita would automotive congress. 14th – 19th september, 2008, munich, germany dolan, ja. 1978. motor vehicle technology and practical work [part 1 and 2]. 1st edition, english language books society and heinemann education books. london., pp. 85-86,189. giri, nk. 2010. automobile technology. 1st edition. delhi. khannan publisher., pp. 77, 12331234, 1270, 1439. http://www.globalbajaj.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):638-647. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: s2bako@yahoo.com 647 kenneth, le. and ralph, lb. 1996. three wheeled vs four wheeled turf work trunk. triodyne inc. consultants in safety philosophy and technology. west touhy avenue. available at: www.triodyne.com/safety%20briefs.htm. (accessed 18th october, 2017). motor cycle operator manual 2017. (mop 00017/14(760-1109)), ohio department of public safety. 2 jenner street, ohio. available at; www.motorcycle.ohio.gov. (accessed 16th october, 2017). mukherjee, s., mohan, d. and gawade, tr. 2007. three wheeled scooter taxi; a safety analysis. transportation research and injury prevention programme. sadhana (indian institute of technology), 32, part 4: 459-478. narang, gbs. 2004. automobile engineering. 11th reprint. delhi. khanna publisher., pp 277-355. palash, p., vinay, s. and yogesh, r. 2014. review of tadpole design issues and challenges. international journal of research in aeronautical and mechanical engineering, l2(3): 122-128. patrick, js. 2006. designing stable three wheeled vehicles, with application to solar powered racing cars. university of minnesota solar power project. church street, minnesota minneapolis, pp. 1, 19. raiput, rk. 1991. strength of materials (mechanics of solids) for polytechnics. 4th edition. new delhi: sk kataria & sons., pp. 42-43. saeedi, ma. and kazemi, r. 2013. stability of three wheeled vehicle with or without control system. international journal of automotive engineering, 3(1): 343-355. thomas, dg. 1992. fundamental of vehicle dynamics. 2nd edition. warrendale. society of automotive engineers inc. commonwealth drive, warrendale., pp. 13 http://www.triodyne.com/safety%20briefs.htm http://www.motorcycle.ohio.gov file:///c:/users/user/downloads/azojete143/www.azojete.com.ng 10 arid zone journal of engineering, technology & environment azojete, march, 2019. vol. 15(1):40-54 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 40 original research article cat swarm optimization based clustering algorithm for fuzzy time series forecasting a. m. abubakar and s. man-yahya (department of electrical and computer engineering, ahmadu bello university zaria, kaduna state, nigeria) *corresponding author: muktyx5@yahoo.com article information submitted 31 march, 2018 revised 11 august, 2018 accepted 15 august, 2018 keywords: cat swarm optimization clustering fuzzy time series forecasting abstract this paper presents the development of an improved fuzzy time series (fts) forecasting model with cat swarm optimization based clustering (cso-c) algorithm. fts forecasting is affected by some of the subjective decisions made at the fuzzification stage like size of interval length or universe of discourse, and approaches such as clustering, trend-mapping, have been adopted to address this. traditional clustering techniques, such as fuzzy c-means (fcm) and k-means used to tackle the problems associated with the fuzzification stage encountered problems such as handling high dimensional data, sensitivity to noise and outliers and pre-mature convergence. in this paper, cso-c algorithm was developed using matlab 2015a to address pre-mature convergence with a view to improving forecast accuracy in fts forecasting. the developed model was tested on student enrolment of university of alabama and taiwan future exchange (taifex). also applied to forecast the student enrolment of university of maiduguri (unimaid) data. in all cases, mean square error (mse), root mean square error (rmse) and mean absolute percentage error (mape) were used as the performance metrics. the developed model presents itself superior, with reduced prediction error when compared with previously existing models in the literature. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the field of time series analysis and forecasting is useful in a variety of scientific, engineering and general applications (e.g., weather forecasting, predictive control, signal processing, population forecasting, enrolment and finance among others) (panagiotakis et al., 2016). linear, non-linear and clustering models are some of the model types for analysing and forecasting time series. traditionally, time series forecasting problems are solved using linear moving average (ma) models, auto-regressive (ar) models and linear auto-regressive integrated moving average (arima) models (smith and wunsch, 2015). the traditional forecasting methods require larger observations and are unable to deal with forecasting problems in which the historical data need to be represented by linguistic values (huang et al.,, 2011; shah, 2012; song and chissom, 1993a). it is also confined to linearity assumptions only (shah, 2012), which introduces large errors in the predicted values. to overcome these limitations of traditional methods, many researchers used soft computing techniques such as fuzzy logic introduced by zadeh (1965) to handle the uncertainty and mailto:muktyx5@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 41 vagueness available in linguistic terms. the concepts of fuzzy sets (zadeh, 1978) have been successfully adopted to time series by song and chissom (1993a). fuzzy time series methods consist of three steps. these are fuzzification, identification of fuzzified relations and defuzzification. many studies on these three steps have been reported in literature, because they influence the forecasting accuracy of a model. using these three steps, song and chissom (1993a) developed the benchmark fuzzy time series forecasting models, the time-invariant fuzzy time series model and the time-variant fuzzy time series model, to forecast the student of enrolment of the university of alabama (song and chissom, 1993b, 1994). the min-max composition adopted by song and chissom (1993a) is computationally tasking when the fuzzy matrix is large. chen (1996), improved on it by introducing a simple arithmetic operation to replace the complicated operations in song and chissom’s (1993) models. due to simplicity of chen’s (1996) model calculation, it was easy and straightforward to integrate heuristic knowledge and forecast better (huarng, 2001). the model has since been widely extended and adapted, with researchers (huang et al., 2011; yu, 2005) hu seeking to improve forecasting accuracy by adjusting the length of linguistic intervals or by changing the weighting approach or incorporating clustering techniques to tackle the interval problem. there are two major categories of fts algorithms: fts algorithms based on intervals of the universal set (askari et al., 2015) and fts algorithms based on fuzzy clustering (askari et al., 2015). determination of interval length and fuzzy relations are two important factors affecting performance of fuzzy time series approaches. many studies established the efficacy of determining an objective interval length and universe of discourse which is an issue of concern that affect forecast accuracy (huang et al., 2011; yu, 2005). so many researchers in the last three decades have used various techniques in order to address problems of subjective decisions associated with the fuzzification stage. such techniques include; genetic algorithm (ga) (chen and chung, 2006), particle swarm optimization (pso) (huang et al., 2011; kuo et al., 2009), artificial bee colony (abc), ant colony optimization (aco) (cai et al., 2015), fuzzy c-means (fcm) (egrioglu et al., 2013), gustafson-kessel clustering algorithm (egrioglu et al., 2011) and hierarchical clustering (chen and tanuwijaya, 2011). even though some of these approaches try avoiding subjective judgements in determining intervals, membership values were still chosen arbitrarily. fuzzy clustering approaches have been developed to overcome this problem. fcm clustering technique was used by cheng et al. (2008) and li et al. (2008), gustafson kessel fuzzy clustering technique was used by egrioglu et al. (2011) in order to eliminate the problem of subjective determination of membership values. in most of these studies, fuzzy sets having the highest membership values are considered and other values are ignored in the determination of fuzzy relations. yu and huarng (2010) suggested an approach in which all membership values are considered in the determination of fuzzy relations with feed forward artificial neural network (ffann) but again the membership values are specified subjectively. aladag et al., (2012) and yolcu et al., (2013) considered all the membership values which were determined objectively using fcm technique for first order fts forecasting models. however, most of the time series encountered in real life problems involve more complicated relations, which makes first order fts forecasting models insufficient to forecast these kind of time series (cagcag et al., 2016). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 42 a method considering all the membership values at the defuzzification step was introduced by yolcu et al. (2013), which bas et al. (2015) and cagcag et al. (2016) adopted and developed a high order model. however, the fcm used has been associated with sensitivity to noise, difficulty in handling outlier points and high dimensional data and pre-mature convergence. this, consequently, affects and reduces the forecasting accuracy. premature convergence is typically caused by loss of diversity, a measure of the amount variety, i.e. number of different solutions in the population, and how different they are (distance between alternative solutions). this loss of diversity could be as a result of too strong selective pressure towards best solution i.e. too much exploitation of existing building blocks from current population. as such, cat swarm optimization based clustering (cso-c) algorithm was developed to overcome the problem of pre-mature convergence, in order to improve forecast accuracy. 2.0 materials and methods 2.1 data collection in this paper, the benchmark fuzzy time series data of student enrolment of university of alabama and taiwan future exchange (taifex) data were used for testing the model and unimaid enrolment data was used for the model application. the time series data of student enrolment of university of alabama between 1971 and 1992 was obtained from the work of song and chissom (1993a) as can be found in table 1. table 1: student enrolment data of university of alabama years actual years actual 1971 13055 1982 15433 1972 13563 1983 15497 1973 13867 1984 15145 1974 14696 1985 15163 1975 15460 1986 15984 1976 15311 1987 16859 1977 15603 1988 18150 1978 15861 1989 18970 1979 16807 1990 19328 1980 16919 1991 19337 1981 16388 1992 18872 table 2 shows the time series data of taifex obtained from the work of bas et al., (2015). the time series has 47 daily observations between 03.08.1998 and 30.09.1998. the last 16 observations between 10.09.1998 and 30.09.1998 were used as the test set to evaluate the model’s performance. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 43 table 2: taifex data date taifex date taifex date taifex 03.08.1998 7552.0 24.08.1998 695.5.00 11.09.1998 6726.50 04.08.1998 7560.00 25.08.1998 6949.00 12.09.1998 6774.55 05.08.1998 7487.00 26.08.1998 6790.00 15.09.1998 6762.00 06.08.1998 7462.00 27.08.1998 6835.00 16.09.1998 6952.75 07.08.1998 7515.00 28.08.1998 6695.00 17.09.1998 6906.00 10.08.1998 7365.00 29.08.1998 6728.00 18.09.1998 6842.00 11.08.1998 7360.00 31.08.1998 6566.00 19.09.1998 7039.00 12.08.1998 7330.00 01.09.1998 6409.00 21.09.1998 6861.00 13.08.1998 7291.00 02.09.1998 6430.00 22.09.1998 6926.00 14.08.1998 7320.00 03.09.1998 6200.00 23.09.1998 6852.00 15.08.1998 7320.00 04.09.1998 6403.20 24.09.1998 6890.00 17.08.1998 7219.00 05.09.1998 6697.50 25.09.1998 6871.00 18.08.1998 7220.00 07.09.1998 6722.30 28.09.1998 6840.00 19.08.1998 7285.00 08.09.1998 6859.40 29.09.1998 6806.00 20.08.1998 7274.00 09.09.1998 6769.60 30.09.1998 6787.00 21.08.1998 7225.00 10.09.1998 6709.75 the time series enrolment data of university of maiduguri (unimaid) shown in table 3 was obtained from the academic planning unit of the university. the time series has 18 yearly enrolments between 1976 and 1993. table 3: unimaid enrolment data year enrolment year enrolment 1976 743 1985 5800 1977 1128 1986 6168 1978 1882 1987 6711 1979 2500 1988 7238 1980 2925 1989 7687 1981 3251 1990 7960 1982 4561 1991 8302 1983 5329 1992 9884 1984 5719 1993 11410 2.2 fuzzy time series and its concept the definition of fuzzy time series was firstly introduced by song and chissom (1993a). basic definitions of fuzzy time series not including constraints such as linear model and observation number can be given as follows (song and chissom, 1993a). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 44 definition 1 fuzzy time series let   ...,0,1,2,...y t t  , a subset of real numbers, be the universe of discourse by which fuzzy sets  jf t are defined. if  f t is a collection of    1 1, ,...f t f t , then  f t is called a fuzzy time series defined on  .y t definition 2 suppose  f t is caused by  1f t  only, that is,    .f t m f t  then this relation can be expressed as  ( ) 1 ( , t 1)f t f t r t   where ( , 1)r t t  is the fuzzy relationship between ( 1)f t  and ( )f t , and  ( ) 1 ( , t 1)f t f t r t   is called the first order model of ( ).f t definition 3 suppose ( , 1)r t t  is a first order model of  .f t if for any , ( , 1)t r t t  is independent of t, that is, for any , ( , 1) r(t 1)(t 2),t r t t     then,  f t is called a time invariant fuzzy time series otherwise, it is called a time variant fuzzy time series. definition 4 high order fuzzy time series forecasting model. let  f t be a fuzzy time series. if  f t is caused by      1 ,f 2 ,..., ,f t t f t n   then this fuzzy logical relationship is represented by        ,..., 2 , 1f t n f t f t f t    and it’s called the nth order fuzzy time series forecasting model. 2.3 cat swarm optimization clustering in contrast to most of the existing clustering techniques, the cso-c algorithm requires no prior knowledge of the data to be classified. rather, it determines the optimal number of partitions of the data“on the run” (santosa and ningrum, 2009). the cso clustering consists of two main parts, clustering data and searching for the best cluster center using the cso algorithm (chu and tsai, 2007). the inputs for clustering cso will be the population of data that are going to be clustered, number of cluster k, and number of copy (will be used in seeking mode). steps of clustering cso are described below (santosa and ningrum, 2009). step 1: defining the initial cluster center randomly choose k point from the data to be the initial cluster centre. step 2: grouping data into clusters put the data into cluster using euclidean distance as follows (santosa and ningrum, 2009).     n 2 i i i = 1 d x , y = x y (1) step 3: calculating the sum of squared-error (sse) sse is the fitness function in this algorithm. the value of sse are calculated, subject to the following constraint, using (santosa and ningrum, 2009).   2 1 min , i i i i d k x sse u x m    (2) 0 1iu  (3) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 45 in solving the minimization problem, the values of im are updated using the following formula:       2 1 1 1 , , ij kk j i k j k u d x v d x v             (4) where; x is data, mi the cluster centeri, k the number of cluster and ui the membership i. step 4: clustering optimization with cso in this algorithm, cluster centre represents the cat and the solution set will be the new cluster centre which is expected to come up with the smaller sse value than before. step 4.1: seeking mode seeking mode is intended to look for points in an area around the cluster centre which have possibilities in resulting in more than an optimal fitness value. step 4.2: updating sse and cluster center the value of sse obtained from seeking mode will be compared with the previous value of sse, if seeking sse < earlier sse then it becomes the new cluster centre. otherwise, if seeking sse ≥ earlier sse, the previous cluster centre will be used. step 4.3: tracing mode tracing mode is intended to shift the point so it will be concentrated to a better position with a more optimal fitness value. step 4.4: repeat step 4.2 for tracing sse and cluster center the value of sse obtained from tracing mode will be compared with the previous value of sse, if tracing sse < earlier sse then it becomes the new cluster center. if tracing sse ≥ earlier sse, the previous cluster center will be used. step 5: repeat step 4 until it reach the stopping criteria. 2.4 artificial neural network artificial neural networks is a mathematical algorithm inspired by biological neural networks, which can learn from examples and generalize what is learnt (bas et al., 2015). architecture structure, learning algorithm and activation function are the three basic operational component of the artificial neural networks (bas et al., 2015). 2.5 developed model procedure the flowchart of the developed model presented in figure 1 shows the steps carried out in the model implementation aimed at improving forecast accuracy. 2.5.1 training/testing time series data the data’s of tables 1, 2 and 3 were used as the input data for the developed model. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 46 figure 1: flowchart of the developed model 2.5.2 fuzzify time series observation by using cso-c algorithm at this stage, the cso-c algorithm was used in fuzzifying the time series data specified in section 2.5.1 as a means of determining an optimized cluster center and membership values for fuzzy time series forecasting. the population of data to be clustered used comprised of data shown in table’s 1, 2 and 3. the number of clusters chosen was seven as used in the work of bas et al., (2015) as specified in table 4 table 4: input parameter to the cso-c algorithm parameters specifications d data k 7 the initial cluster center has been chosen randomly from the data set, the data were then grouped into clusters by their closeness using euclidean distance formula of equation 1 to calculate the distance between the data and the cluster center. the sum of squared error between the data and the cluster center was then calculated using equation 2. in clustering with the cso-c algorithm, the cluster center represents the cat and the solution set will be the new cluster center which is expected to come up with the smaller sse value than what was obtained. here, all the cats go through the process of tracing and seeking. the cso-c parameters initialization were specified in table 5, which include count of dimension to change (cdc), seeking memory pool (smp), seeking range of the selected dimension (srd) and selfposition consideration (spc). the cdc in seeking mode were assumed 100% value, so every dimension of cat’s copy changes, smp represents how many copy a cluster center has, srd declares a mutation ratio with a value between [0,1] and spc is a boolean random value{0,1}. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 47 table 5: cso parameters (santosa and ningrum, 2009) parameters specifications smp 5 cdc 100% srd 0.2 const1 2 r1 [0,1] velmax 0.9 the simulation parameters of table 5 were selected based on the optimal performance achieved as reported in the work of santosa and ningrum (2009). the membership values were computed and updated using equations 2 and 4. the next step is activating tracing mode which looks for an area around the cluster center with possibilities of generating a more optimal fitness value. the distance between the data and the new cluster center where been calculated using equation 1, the new cluster center calculated using 2 and the membership values computed with equation 4. the sse of the tracing mode computed were then compared with the previous values of sse and if the tracing sse is less than the previous sse, then the membership value and cluster center resulting from the tracing becomes the new membership value and cluster center. conversely, if the value of the tracing sse was greater than or equal the earlier sse, then the previous membership values and cluster centers would be used. the process continues until the number of iterations is met, after which, the number of cluster k, the membership values and the best cluster center were then obtained. 2.5.3 determination of high order fuzzy relation using ffann the feed forward artificial neural nework (ffann) was used in establishing fuzzy relationship. that is, the produced degree are employed as the inputs and the target values of ffnns. as such, this prevents arbitrarily degrees of membership determination, hard matrix operations or complex group tables need not be used. the input to the ffnn consists of membership values obtained from section 2.5.2 and the activation function used in all layers of the ffnn of whose architecture is given as follows:      1 1 expf x x     (5) optimal weights were obtained by training using lavenberg-marquardt learning algorithm. 2.5.4 defuzzify forecasted values in defuzzifying the forecasted values, weighted averages were used instead of the central method, and so, the fuzzy sets with a less degree of membership were considered. this helps in avoiding possible knowledge loss. using the following expression, the degrees of membership of the fuzzy forecast obtained from the previous section were transformed into weights. 1 2 ˆ ˆ ˆ ˆ... it it t t kt uw u u u     (6) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 48 the defuzzified forecasts of the observation at time t are calculated using the following expression 1 k t it i i x w m    (7) where, ˆ , 1,2,..., ,itu i k denotes the membership degrees for the fuzzy forecasting value of the time series data at t obtained from the output of the ffann. , 1,2,..., ,itw t k denotes the weights used for defuzzifying the forecasts. , 1,2,..., ,im i k denotes the cluster center values. 2.5.5 performance evaluation in evaluating the performance of the developed model, mean absolute performance error (mape) and root mean square error (rmse) were used as metrics as presented in the following expressions respectively.  n i i i=1 i actual forecast1mape = ×100 n actual (8)   n 2 i i i=1 1rmse = actual forecast n (9) the percentage improvement of the developed model over other models reported in the literature was computed using the expression as follows: 100%initial finalpercentage improvement initial    (10) where initial stands for rmse or mape values computed from the approaches of the benchmark fts or fcm based, and final for the values obtained from the developed cso-c based model. 3.0 results and discussion in this section, the performance of the developed fuzzy time series forecasting is evaluated and analyzed using two different data sets that were previously studied with other methods in the literature and a new data set that has not been previously used 3.1 obtained results for student enrolment data of university of alabama the optimized cluster center values of fuzzy sets and the membership values obtained from the developed model on the training data set of table 1 as earlier explained in section 2.5 were presented in table 6 and table 7 respectively. the defuzzified forecast obtained were given in table 8. table 6: obtained cluster centre values for university of alabama data m1 m2 m3 m4 m5 m6 m7 13490.51 15117.90 15621.22 16790.81 18145.80 18921.80 19331.84 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 49 table 7: obtained membership values for university of alabama data year k1 k2 k3 k4 k5 k6 k7 1971 0.9053 0.0403 0.0261 0.0123 0.0066 0.0050 0.0044 1972 0.9955 0.0022 0.0012 0.0005 0.0002 0.0002 0.0002 1973 0.8538 0.0773 0.0393 0.0142 0.0066 0.0047 0.0041 1974 0.0872 0.7121 0.1481 0.0289 0.0107 0.0071 0.0059 1975 0.0054 0.1776 0.7993 0.0117 0.0029 0.0017 0.0014 1976 0.0079 0.7014 0.2719 0.0120 0.0033 0.0020 0.0016 1977 0.0000 0.0014 0.9981 0.0002 0.0000 0.0000 0.0000 1978 0.0085 0.0866 0.8314 0.0553 0.0092 0.0051 0.0040 1979 0.0000 0.0000 0.0002 0.9994 0.0002 0.0000 0.0000 1980 0.0014 0.0049 0.0094 0.9671 0.0106 0.0040 0.0027 1981 0.0129 0.0674 0.1849 0.6701 0.0352 0.0169 0.0125 1982 0.0067 0.2557 0.7166 0.0138 0.0035 0.0021 0.0018 1983 0.0034 0.0955 0.8888 0.0082 0.0020 0.0012 0.0009 1984 0.0003 0.9960 0.0033 0.0003 0.0000 0.0000 0.0000 1985 0.0007 0.9884 0.0096 0.0008 0.0002 0.0001 0.0001 1986 0.0146 0.1207 0.6877 0.1391 0.0194 0.0105 0.0081 1987 0.0004 0.0015 0.0030 0.9904 0.0028 0.0011 0.0008 1988 0.0000 0.0000 0.0000 0.0000 0.9999 0.0000 0.0000 1989 0.0000 0.0002 0.0002 0.0005 0.0033 0.9784 0.0174 1990 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.9999 1991 0.0000 0.0000 0.0000 0.0000 0.0000 0.0002 0.9998 1992 0.0000 0.0001 0.0002 0.0005 0.0039 0.9853 0.0100 table 8 shows the results of forecast obtained from the developed model, where the performance criteria explained in section 2.5 were used in computing the model performance. the obtained mse, rmse and mape were 785.17, 88.46 and 0.0046 respectively. from the results comparison of table 9, it can be seen that the developed model has the lowest prediction error in terms of mse, this is an indication of better forecast exhibited by the developed model. it shows that the developed model recorded 98.10% over song and chissom (1993a), 86.98%, over egrioglu et al., (2011), 83.14% over aladag et al., (2012), 70.02% over bas et al., (2015) and 28.77% over cagcag et al., (2016) computed with equation 10. file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 50 table 8: defuzzified forecast for university of alabama data year data forecast 1973 13867 13945 1974 14696 14702 1975 15460 15397 1976 15311 15386 1977 15603 15546 1978 15861 15934 1979 16807 16834 1980 16919 16828 1981 16388 16301 1982 15433 15389 1983 15497 15416 1984 15145 15295 1985 15163 15316 1986 15984 15950 1987 16859 16834 1988 18150 18161 1989 18970 19056 1990 19328 19186 1991 19337 19200 1992 18876 18990 mse 7825.17 rmse 88.46 mape 0.0046 table 9: the results comparison methods mse song and chissom (1993a) 412499 egrioglu et al., (2011) 60140 aladag et al., (2012) 46422 bas et al., (2015) 26108 cagcag et al., (2016) 10987 the developed 7825.17 3.2 obtained results for taifex data table 10 shows results of forecast obtained from taifex data of table 2 following methods discussed in section 2.5. the results further shows the forecasts obtained from the model of bas et al., (2015) and cagcag et al., (2016) on the same data set. after close examination, it can be seen that the developed file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 51 model recorded the least prediction error with a significant improvement in terms of mse, rmse and mape. the performance improvement computed with equation 10 was used to obtain the performance improvement of the developed model over some methods reported in literature. the model developed recorded an rmse improvement of 65.57% over that of bas et al., (2015) and 64.22% over that of cagcag et al., (2016). table 10: forecast for taifex data date taifex bas et al., (2015) cagcag et al., (2016) developed 10.09.1998 6709.75 6804.31 6719.92 6721.21 11.09.1998 6726.50 6804.31 6719.92 6721.92 14.09.1998 6774.55 6761.17 6843.75 6773.72 15.09.1998 6762.00 6758.51 6719.92 6774.30 16.09.1998 6952.75 6856.13 6843.75 6946.40 17.09.1998 6906.00 6856.13 6843.75 6901.86 18.09.1998 6842.00 6856.13 6843.75 6841.70 19.09.1998 7039.00 6856.13 6843.75 7038.93 21.09.1998 6861.00 6856.13 6843.75 6861.63 22.09.1998 6926.00 6856.13 6843.75 6919.85 23.09.1998 6852.00 6856.13 6843.75 6853.61 24.09.1998 6890.00 6856.13 6843.75 6893.58 25.09.1998 6871.00 6807.48 6843.75 6863.90 28.09.1998 6840.00 6793.07 6843.75 6840.41 29.09.1998 6806.00 6793.07 6843.75 6819.25 30.09.1998 6787.00 6856.13 6778.28 6879.66 mse 4869.25 4507.78 576.96 rmse 69.78 67.14 24.02 mape 0.00761 0.0066 0.00152 3.3 obtained results for unimaid enrolment data the unimaid enrolment data of table 3 was not previously applied for any fuzzy time series forecasting research. in view of that, the developed model was applied to obtain the forecast as shown in table 11. it can be seen that the forecast produced has an mse of 1395543.21, rmse 0f 373.55 and mape 0.0667. file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 52 table 11: forecast for unimaid data year enrolment forecast 1978 1882 2702.84 1979 2500 2680.11 1980 2925 2737.43 1981 3251 2837.88 1982 4561 4497.60 1983 5329 5550.53 1984 5719 5849.53 1985 5800 5965.73 1986 6168 6457.61 1987 6711 6992.32 1988 7238 7372.57 1989 7687 7591.29 1990 7960 7807.23 1991 8302 8120.24 1992 9884 10031.38 1993 11410 10432.95 mape 0.0667 mse 139543.21 rmse 373.55 4.0 conclusion in minimizing the subjective decisions made at the fuzzification stage, traditional clustering techniques such as fuzzy c-means (fcm) and k-means, have been previously used, but problems such as handling high dimensional data, sensitivity to noise, outliers and pre-mature convergence still persist. in this research, cso-c algorithm was developed to address this issue of pre-mature convergence with a view to improving forecast accuracy in fuzzy time series forecasting. in the implementation, the developed model was tested and compared with other models forecast reported in literature for the student enrolment of university of alabama and taifex data. the forecast results of enrolment of university of alabama data produced an mse improvement of 98.10% over song and chissom (1993a), 86.98%, over egrioglu et al., (2011), 83.14% over aladag et al., (2012), 70.02% over bas et al., (2015) and 28.77% over cagcag et al., (2016). also, the forecast results of taifex data recorded an rmse improvement of 65.57% over that of bas et al., (2015) and 64.22% over that of cagcag et al., (2016). this clearly shows that the model developed has better forecast with reduced prediction error. the developed model was further to unimaid enrolment data, which was not previously reported to have been used in literature with respect the research area of fuzzy time series forecasting. the forecast produced has an mse of 1395543.21, rmse 0f 373.55 and mape 0.0667. it is expected that future researchers will forecast with the unimaid enrolment data and see how there model suit into the data. file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx file:///c:/users/muktar/desktop/new%20folder/alwali/15.1.2%20azojete%20%2018%20050.docx http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2019; vol. 15(1):40-54. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: muktyx5@yahoo.com 53 reference aladag, ch., yolcu, u., egrioglu, e., and dalar, az. 2012. a new time invariant fuzzy time series forecasting method based on particle swarm optimization. applied soft computing, 12(10), 3291-3299. askari, s., montazerin, n. and zarandi, mf. 2015. a clustering based forecasting algorithm for multivariable fuzzy time series using linear combinations of independent variables. applied soft computing, 35, 151-160. bas, e., yolcu, u., egrioglu, e. and aladag, ch. 2015. a fuzzy time series forecasting method based on operation of union and feed forward artificial neural network. american journal of intelligent systems, 5(3), 81-91. cagcag, o., yolcu, u., egrioglu, e. and aladag, ch. 2016. a high order fuzzy time series forecasting method based on operation of intersection. applied mathematical modelling. cai, q., zhang, d., zheng, w. and leung, sc. 2015. a new fuzzy time series forecasting model combined with ant colony optimization and auto-regression. knowledge-based systems, 74, 6168. chen, sm. 1996. forecasting enrollments based on fuzzy time series. fuzzy sets and systems, 81(3), 311-319. chen, sm. and chung, ny. 2006. forecasting enrollments of students by using fuzzy time series and genetic algorithms. international journal of information and management sciences, 17(3), 117. chen, sm., and tanuwijaya, k. 2011. multivariate fuzzy forecasting based on fuzzy time series and automatic clustering techniques. expert systems with applications, 38(8), 10594-10605. cheng, ch., cheng, gw. and wang, jw. 2008. multi-attribute fuzzy time series method based on fuzzy clustering. expert systems with applications, 34(2), 1235-1242. chu, sc. and tsai, pw. 2007. computational intelligence based on the behavior of cats. international journal of innovative computing, information and control, 3(1), 163-173. egrioglu, e., aladag, c., yolcu, u., uslu, vr. and erilli, na. 2011. fuzzy time series forecasting method based on gustafson–kessel fuzzy clustering. expert systems with applications, 38(8), 10355-10357. egrioglu, e., aladag, ch. and yolcu, u. 2013. fuzzy time series forecasting with a novel hybrid approach combining fuzzy c-means and neural networks. expert systems with applications, 40(3), 854-857. huang, yl., horng, sj., he, m., fan, p., kao, tw., khan, mk., lai, jl. and kuo, ih. 2011. a hybrid forecasting model for enrollments based on aggregated fuzzy time series and particle swarm optimization. expert systems with applications, 38(7), 8014-8023. huarng, k. 2001. heuristic models of fuzzy time series for forecasting. fuzzy sets and systems, 123(3), 369-386. kuo, ih., horng, sj., kao, tw., lin, tl., lee, cl. and pan, y. 2009. an improved method for forecasting enrollments based on fuzzy time series and particle swarm optimization. expert systems with applications, 36(3), 6108-6117. li, st., cheng, yc., and lin, sy. 2008. fcm-based deterministic forecasting model for fuzzy time series . computer and mathematics with applications, 56, 3052-3063. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abubakar and sman-yahya: cat swarm optimization based clustering algorithm for fuzzy time series forecasting azojete, 15(1):40-54. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 54 panagiotakis, c., ramasso, e., fragopoulou, p. and aloise, d. 2016. theory and applications of data clustering. santosa, b. and ningrum, mk. 2009. cat swarm optimization for clustering. paper presented at the soft computing and pattern recognition, 2009. socpar'09. international conference of. shah, m. 2012. fuzzy based trend mapping and forecasting for time series data. expert systems with applications, 39(7), 6351-6358. smith, c. and wunsch, d. 2015. time series prediction via two-step clustering. paper presented at the international joint conference on neural networks (ijcnn), 2015 song, q. and chissom, bs. 1993a. forecasting enrollments with fuzzy time series—part i. fuzzy sets and systems, 54(1), 1-9. song, q. and chissom, bs. 1993b. fuzzy time series and its models. fuzzy sets and systems, 54(3), 269-277. song, q. and chissom, bs. 1994. forecasting enrollments with fuzzy time series—part ii. fuzzy sets and systems, 62(1), 1-8. yolcu, u., aladag, ch., egrioglu, e., and uslu, vr. 2013. time-series forecasting with a novel fuzzy time-series approach: an example for istanbul stock market. journal of statistical computation and simulation, 83(4), 599-612. yu, hk. 2005. a refined fuzzy time-series model for forecasting. physica a: statistical mechanics and its applications, 346(3), 657-681. zadeh, la. 1965. fuzzy sets. information and control, 8(3), 338-353. zadeh, la. 1978 fuzzy sets as a basis for a theory of possibility, fuzzy sets and systems 1, 3-28. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):418-434 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 418 original research article determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models i. i. ozigis* and m. t. zarmai (department of mechanical engineering, faculty of engineering,university of abuja, pmb 117 abuja, kilometer 23, airport road, abuja, nigeria) *corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng article information submitted 29 march, 2018 revised 20 april, 2019 accepted 23 april, 2019 keywords: coal, combustion equivalence ratio mathematical model thermal power plant abstract this paper presents determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. the problem statement was that nigeria cement plants uses rotary kiln coal burner despite its associated drawbacks such as sudden explosion and incomplete combustion. fluidized bed technology has less of the drawbacks associated with rotary kiln coal burner. the integration of maiganga coal in mathematical models will increase accurate prediction of operating variables useful in design and sizing the components of fluidized bed thermal power plant. the methodology of the study includes utilization of established numerical models based on energy balance and fuel properties for maiganga lignite combustion. the coal was fired in a pilot atmospheric fluidized bed combustor (fbc). the results obtained include the theoretical air required per kg of maiganga lignite was 7.4, at an excess air of 10% and maximum mass of air supplied per kg of maiganga lignite of 8.82. the time for burn out of particle sized 0.4 mm was determined to be 2.64 min, with burning rate of 0.23 kg/min (3.8 g/s). the ignition temperature of 797 k and fuel power of 84 kw for maiganga coal were determined for the pilot fbc in this study. the maiganga lignite fuel, air and sorbent flow rates through the fluidized bed combustor were predicted to be 14.2 kg/hr (0.23 kg/min), 202.4 kg/hr and 1.26 kg/hr respectively. the combustion performance evaluation of the fluidized bed combustor had specific firing rate for the lignite at graded particle size of between 0.2-1.12 mm at bed temperature of 1173 k was 2.8 g/m2s, air-fuel ratio of 23 and equivalence ratio of 0.45. the above results are similar to coal burnout time of 3 minutes and equivalence ratio of 0.40 in an atmospheric fluidized bed combustor in the literature. hence, above parameters can be used to design and model a safe ignition and good combustion characteristics in other lignite fired power plants similar to that of maiganga lignite coal. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction maiganga coal is mined and processed for combustion in rotary kiln coal burner for cement production by ashaka cement plant. the combustion of maiganga coal takes place in the mailto:idris.ozigi@uniabuja.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 419 presence of high temperature, turbulence and continuous air flow that results in rapid oxidation, ignition and hot flame in an enclosure like rotary kiln burner and fluidized bed combustor. modular coal-fired thermal power plant developments have increased in nigeria with proposed okobo coal-fired power plant at capacity of 1200 mw and others. exploitation of coal by surface working method from maiganga hills, near kumo in gombe, commenced in october, 2007. the combusting of nigerian coals in rotary kiln coal burner is about a decade in nigeria and the technology have spread from ashaka cement plant to cement plants at obajana, ibese, and sokoto. the rotary kiln coal burner has drawbacks such as sudden and frequent coal explosion as well as incomplete combustion. fluidized bed coal combustion technology has less of the drawbacks associated with rotary kiln coal burners. mathematical models in the form of equations, graphs or tables can be used to represent and predict phenomena as in fluidization and combustion. mathematical models contribute to better understanding of the processes in thermal power plants (alobaid, et al., 2016). the fuel properties in the modelling are to advance an established fact that moisture, volatile matter, oxygen, hydrogen contents among other factors contributes to combustion as reported by ngampradit et al. (2004). there are several combustion models that had addressed various parts of fluidized bed combustion available in literature. an example was computational fluid dynamics (cfd) combustion model for biomass for different particle sizes in a fluidized bed as reported by li et al. (2015a). the integration of maiganga coal in fluidized bed combustion models have received little attention. mathematical models applications have increased accurate prediction of operating variables such as air flow rate, fuel flow rate among others for complex fluidization processes in combustor. these operating variables are in turn useful in design and sizing the components of the fluidized bed thermal power plant. lee (1997) investigated heat transfer and combustion in advanced swirling fluidized bed combustor. he formulated the basic governing equations based on continuity, energy equations, chemical reaction and radiation heat transfer. ngampradit et al. (2004) simulated a circulating fluidized bed combustor with shrinking core and emission. their work was to predict proper amount of fuel blend and to reduce emission from coal combustion. the researchers attained improvement in the solid fuel size change during the combustion. the researchers also added emission models to predict the formation of no, n2o and so2, which can be used for environmental prediction consideration. similarly, mikulcic et al. (2014) reported numerical study of co-firing pulverized coal and biomass inside a cement calciner. the results show that when combusting biomass in an existing pulverized fuel burner, special attention need to be given to complex oxidation of char particles to avoid unpredicted emission of hot fly ash. their numerical models improve better understanding of particle kinetics in the operation of the calciner in reduction of pollutant formation. marra et al. (2014) worked on fluidized bed combustor coupled with a sterling engine for co-generation purposes, which consisted of heat transfer, energy balance in fluidized bed and the relationship between power, efficiency and torque at assigned geometrical parameters and physical properties of sterling engine. more efficient heat transfer due to multiphase fluidized medium was attainable than heat transfer tubes immersed in flue gases during their study. the abrasion action of solid particles also reduces fouling of the heat exchanger surfaces that are associated with coal and biomass combustion. however, the contribution of diameter and length of heater tubes on performance prediction without loss of efficiency and power needs further investigation. johnson (2007) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 420 worked on biomass-fired fluidized bed combustion for clean energy production with advantage to reduce exhausted so2, co2 and particulates from the flue gas in comparable to fossil fuel combustion under similar circumstances. the researcher essentially reviews the trend of development of fluidized bed technology and made an outlook into the future without discussing the challenges associated with combustion of solid and gas in each of the mentioned fluidized bed technologies. thapa et al. (2016), centered their work on physics of fluidization and chemistry of fuel combustion. their modeling and simulation focused on various flow regimes enriched with olivine, coal char and their mixture in air fed into fluidized bed combustion reactor. their short coming was the proportion of total gas feed rate into bottom and primary were not included in the modeling process. sarroza et al. (2017), investigated the ignition characteristics of pulverized coal, biomass and co-firing by use of a visual drop tube furnace and a high-speed imaging technique camera. the results indicated effect of volatile matter content in coal and alkali metal present in biomass on the distance to ignition as captured by the camera. however, the distance to ignition point measured by the camera is different to ignition temperature except a correlation was employed. the process of coal combustion involves heating up, drying, devolatization and char oxidation as variously reported by researchers such as basu (2015) and li et al. (2015b). however, there are difficulties connected with combustion of coal in thermal power plants. some of the key challenges include sudden fire explosion, which are threats to safety in addition to economic losses. the main causes of undesirable explosion were attributed to contact with hot surfaces by leakages of coal particles and oil from startup burner, main burner and flue gas cleaning devices like electrostatic precipitators. in addition, sudden explosion can occur in thermal power plants due to external factors such as smoking, open flame, welding, among other factors but can be handled with good working habits. the external factors in explosion have several protection and prevention techniques reported by chunmiao et al. (2011). the challenges are inherent factors in fuel, that aid sudden explosion as reported by eckhoff (2003). it is desirable to minimize this challenge to ensure safe combustion and encourage use of coal, instead of idle and unexploited coal deposit asset, in several places of the world. researches on maiganga coal had mainly be on proximate, ultimate, petrographic, ash, thermographic and radiological analyses as well as calorific value determination, while combusting the coal in furnaces and burners are scanty in literature. in this work, maiganga coal was analyzed for prediction of combustion characteristics for application in thermal power plants using standard mathematical models. maiganga coal has proven reserve of about 760 million metric tons and is found in maiganga hills, near kumo, along gombe-yola road, in akko local government area of gombe state, northeastern part of nigeria as reported by idriss et al. (2018). the deposit lies within longitude 11°20’e and latitude 10°20'n. the aim of this research is to study the maiganga coal combustion characteristics for application in thermal power plants using standard mathematical models. the objectives are to determine the maiganga lignite fuel properties and its combustion stoichiometry; calculate the maiganga lignite burning rate and its fuel power; evaluate the fuel, air and sorbent flow rates through the combustor as well as to conduct performance evaluation of the combustor and validation of the models. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 421 2. methodology 2.1 determination of maiganga lignite fuel properties and combustion stoichiometry the maiganga lignite samples were collected from maiganga coal mine owned by ashaka cement plc, and was prepared according to astm standard of d2234 (astm, 1990) for the particle size analysis which was carried out at national metallurgical development centre, jos. the proximate and ultimate analyses of the maiganga lignite coal were performed according to astm standards described in codes d3173, d4239, d3174, d5142 and d5373 (astm, 1990). the proximate and ultimate analyses as well as the calorific value had been carried out by several researchers such as idriss et al. (2018), tikpangi (2016) and ryemshak and jauro (2013), which were adopted for this work. the properties of gypsum and particle size distribution were determined in this work at national metallurgical development centre, jos. determination of particle size distribution of crushed and ground coal and gypsum as well as coal combustion in a pilot fluidized bed combustor were carried out. mathematical models for maiganga lignite combustion in fluidized bed were selected from established models on energy and mass balances from literature. the models were used to estimate performance of the maiganga lignite fired in a combustor. the theoretical air required per kg of fuel, excess air required and actual mass of air were obtained by substitution of proximate and ultimate analysis of maiganga lignite in the stoichiometry equations (balleney, 2007; unep, 2006). the theoretical air required per kg of fuel (ta) was determined using equation (1) as given by balleney (2007):        sohcta ) 8 (8 3 8 23 100 2 2 (1) where: c is carbon content in the ultimate analysis of maiganga lignite h2 is hydrogen content in the ultimate analysis of maiganga lignite o2 is oxygen content in the ultimate analysis of maiganga lignite s is sulphur content in the ultimate analysis of maiganga lignite the amount of excess air required (ea) calculated using equation (2) as given by unep (2006): 2 2 21 100 o oea    (2) where: o2 is oxygen content in the ultimate analysis of maiganga lignite the actual mass of air supplied per kg of fuel ( ) was calculated using equation (3) as given by unep (2006): a a te  ) 100 1( (3) where: ea is excess air required for the maiganga lignite combustion (%) ta is the theoretical air requirement per kg of maiganga lignite fuel. 2.2 maiganga lignite fuel burning rate and fuel power 2.2.1 burning rate constant and time for burn out of lignite the burning rate constant (kb) was obtained using equation (4) as given by turns (2000): file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 422 c b bdk   )1ln(8 2   (4) where: 2 is approximately gas-particle density (kg/m3) d is diffusion coefficient for lignite coals (m2/s) b is transfer number in combustion of lignite coal for o2 and co2 diffusion = constant c is bulk density of maiganga lignite coal at graded size (kg/m3) the lignite particle burn-out time was determined using equation (5) as given by turns (2000): b c c k dt 2  (5) where: dc is initial lignite particle size (mm) kb is burning rate constant (m2/s) 2.2.2 lignite burning rate (ff) the burning rate (kg/hr) was calculated using equation (6) as follows (turns, 2000): )1ln(4 2 bdrf cf   (6) where: rc is maximum lignite coal particle radius (mm) 2.2.3 energy balance in lignite coal combustion the chemical heat of maiganga lignite coal in combustion was obtained as the product of burning rate and the lignite lower calorific value (lcv) as expressed in equation (7). thus: lcvfq f (7) where: ff is lignite coal burning rate or lignite flow rate (kg/hr) (ozigis and arudi, 2013) lcv is lignite coal calorific value (kj/kg) q is energy capacity (kj/hr) or (w) therefore, bed temperature in the combustor was determined using equation (8) as follows: ff fb cm lcvf dt dt  (8) where: mf is mass of the lignite coal in combustor (kg) cf is specific heat capacity of the lignite coal (kj/kgk) 2.3 maiganga lignite fuel, air and sorbent flow rates in the combustor 2.3.1 the quantity of air supplied into fluidized bed combustor http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 423 the quantity of dry air at atmospheric pressure supplied by centrifugal fan for combustion was determined using equation (9) as follows (highley and kaye, 1983; ozigis, et al. 2015): )1)(( aafa etff  (9) where: fa is the air flow rate from the centrifugal fan (kg/hr) ff is fuel flow rate (kg/hr) ta is theoretical air (kg of air/kg of fuel) ea is excess air (%) the volumetric flow rate (qa) of air was found using equation (10) as given below:  a a fq  (10) where:  is density of air (kg/m3) qa is volumetric flow rate (m3/s) 2.3.2 particle surface temperature the surface temperature attained by lignite coal particle was determined from coal particles rate of heat transfer (q) to bed materials using equation (11) as given by broughton and howard (1983):  bfcc ttahq  (11) where: ac is surface area of the particles (m2) tf is particle surface temperature (k) tb is bed temperature (k) hc is heat transfer coefficient of coal particle (w/m2k) as using equation (12) obtained from broughton and howard (1983): pc c dd kh 016.02  (12) where: dp is sorbent gypsum particle size (mm) k is thermal conductivity of the combustion gas (w/m.k) therefore, the surface temperature of lignite in combustor was determined using equation (13) as follows: ff bfccf cm ttah dt dt )(   (13) where: mf is mass of the lignite coal in combustor (kg) cf is specific heat capacity of the lignite coal (kj/kgk) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 424 2.3.3 sulphur removal by sorbent in maiganga lignite coal combustion the mole flow rate of sulphur (fsm) in gypsum was calculated using equation (14) given by nag (2009): mws f sm m sf f   (14) where: ff is burning rate of maiganga lignite coal or flow rate (kg/hr) s is percentage of sulphur content in maiganga lignite (%). mmws is molecular mass of sulphur (kg/kmol) (obtained from periodic table). however, the flow rate of calcium at calcium to sulphur ratio of 3:1 (molar basis), is to limit emissions of so2 adequately and was calculated using equation (15) as given by nag (2009): ratiomolarff smc  (15) where: fc is flow rate of calcium (kmol/hr) mass flow rate of caso4 (fcs) was determined using equation (16) as given by nag (2009): cmwgcs fmf  (16) where: mmwg is molecular mass of caso4 (kg/kmol) fcs is mass flow rate (kg/hr) the percentage of caso4 in gypsum was determined using equation (17) as follows: 100% 4  gypsummw gmw m m caso (17) where: mmw gypsum is the molecular mass of gypsum (caso4.2h2o) (kg/kmol) therefore, mass flow rate of gypsum (fg) was calculated using equation (18) as follows: 4%caso ff cs g  (18) where: fg is sorbent flow rate (kg/hr) comparing fuel flow rate to sorbent flow rate, the sorbent gypsum constitutes 100 f g f f . heat lost for sulphur removal by sorbent gypsum reaction during combustion was calculated using equation (19) as given by kataja and majanne (2007): )()( gbpgggfgc gpgg ttcfttxh dt dtcm   (19) where: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 425 x is total exposed surface area of ejected sorbent gypsum (m2) g is residence time of sorbent gypsum in the combustor (s) cpg is gypsum specific heat capacity (kj/kgk) tg is gypsum temperature in bed (k) mg is mass of sorbent gypsum fed into the combustor (kg) therefore, temperature of sorbent gypsum in the combustor was calculated using equation (20) as follows: pgg gbedpgggfgcg cm ttcfttxh dt dt )()(    (20) 2.4 the combustion performance evaluation of the fluidized bed combustor the performance parameters include specific firing rate, air-fuel ration and equivalence ratio. specific firing rate the specific firing rate (sfr) was estimated using equation (21) as given by broughton and howard (1983): bc f fr pdm at m s  (21) where: mf is mass of fuel burnt (kg) a is the area of air distributor based on total area of orifice diameter (m2) t is time for combustion (s) mc is molecular mass of maiganga lignite coal bp is the bed pressure d is reaction rate coefficient for coal at 1173 k 2.4.2 determination of air fuel ratio air fuel ratio (af) was determined using equation (22) as given by crawford (1980): mc a nm naf    97.28 (22) where: an is number of moles of oxygen plus number of moles of nitrogen. cm is molecular weight of maiganga lignite coal = 12 mn is number of moles of maiganga lignite coal = 1. 2.4.3 equivalence ratio of fuel combustion in the combustor equivalence ratio was defined and calculated using equation (23) as given by ramirez, et al. (2007): af re l (23) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 426 where: lr is air-fuel ratio minimum and specific to the combustor af is air fuel ratio lr is air-fuel ratio minimum and specific to the combustor was calculated using equation (24) as given by ramirez, et al. (2007): f a l f f r   292.1 (24) where: fa is air-fuel ratio in the combustor ff is air fuel ratio the combustor’s equivalence ratio was determined in terms of flow rates and air-fuel ratio using equation (25) as follows: aff f e f a   292.1 (25) where: af is air fuel ratio fa is the air flow rate from the centrifugal fan (kg/hr) ff is fuel flow rate (kg/hr) 2.5 computing procedure the data from proximate and ultimate analysis, pilot fluidized bed combustor (fbc) were used to validate the models, which were computed as design data shown in table 2. the developed ordinary differential equations were numerically integrated over time, bearing in mind the assigned initial values of bed, sorbent gypsum and particle surface temperatures. m-file and programme base on combustion parameters were developed for ode 45 and were run on matlab. the programme was used to determine temperatures at various parts of the combustor as well as the burning rate, specific firing rate and equivalence ratio of coal combustion. the results were presented in the form of tables and figures. 3. results and discussion 3.1 maiganga lignite fuel properties and combustion stoichiometry the proximate and ultimate analysis of maiganga lignite and tongo gypsum are as shown in table 1. a high volatile matter indicates long flame and more smoke from the fuel when fired. volatiles ignite first and sustain the process of combustion. maiganga coal with 30.5% volatiles and average calorific value of 22 mj/kg, implies it is a lignite but close to sub bituminous coal as with description in astm (oka, 2004). tongo gypsum indicates that it could react with coal during combustion because of its high calcium content (36.01%); hence, useful as sorbent material. thus, sulphur presence in solid fuel can be removed with addition of gypsum. calcium is among materials that can cause reduction of so2 emission in co-firing of coal in combustor as http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 427 reported by rokni, et al. (2017). the maiganga coal proximate and ultimate analysis as shown in table 1, were adopted for the modelling to predict the combustion characteristics. the proximate analysis for maiganga lignite in this work are within the mean values of moisture (11.03%), volatile (36.10%), carbon (45.96%) and ash (6.91%), respectively, as reported by tikpangi (2016). the oxygen content (11.38%) and calorific value (22 mj/kg (4982 cal/g)) reported by ryemshak and jauro (2013), were similar to the results of oxygen content and calorific values reported in this work. maiganga lignite fuel properties differences from one location to the other locations, according to ikwuagwu and uzoegbu (2017), which were due to environmental and temperature effects on lignite at different depths and locations within an area, similarly, reported by researchers on this maiganga lignite deposit. however, the percentages of moisture and ash of maiganga coal in this work differ to results reported by ikwuagwu and uzoegbu (2017), due to variation in air-dried or oven dried of the feedstock. the particle size distribution for the maiganga lignite ranges from 0.2 mm to 1.12 mm was an effective specific surface area for an efficient combustion in the pilot fluidized bed combustor, after removal of foreign matters by using appropriate sieves. however, particle size can be less than 75 m for coal burner in cement rotary kiln as reported by song et al. (2018). particle size distribution range for burners helps to minimize oversize and under size that can cause large particle breakages and coal hang-up. coal hang-up occurs due to coal moisture in thermal power plant, which can cause sudden explosion. during coal combustion, hot flashes and fly ashes from finer particles can ignite other material that can lead to sudden explosion in combustors such as in rotary kiln burner for cement production. table 1: proximate and ultimate analysis of maiganga lignite and gypsum s/n % composition maiganga lignite coal* tongo gypsum 1 moisture 13.7 20.93 2 volatile matter 30.5 3 ash 10 4 s 0.56 18.62 5 c 56 6 n2 0.91 7 h2 3.86 2.34 8 o2 10.05 55.76 9 cao 32.57 10 so3 46.5 11 ca 23.28 12 calorific value (mj/kg) 21-23 13 %caso4 79 *adopted from idriss, et al. (2018), tikpangi (2016) and ryemshak and jauro (2013) combustion stoichiometry is aimed to determine exactly the quantity of air needed to oxidize fuel that results in stable flame and safe products. the presences of co2, so2, co, among others, will require monitoring to prevent concentration beyond approved limit and to take decision on type of explosion venting devices to minimize fire explosion. in addition, prevention of co in flue gas cleaning devices like electrostatic precipitator will minimize fire explosion. table 2 has file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 428 stoichiometric quantity of air per kg of maiganga coal, which took into account the moisture content. above stoichiometric quantity of air per kg of 7.423 kg, will result in warm flue gases while below will result in fuel rich mixture as reported in turns (2000). complete combustion of a rich mixture that results in fuel built up at burner can lead to sudden explosion; hence avoidance of fuel rich in thermal plant is desirable. the excess air in this work varies between 10-20% but with preference for 10% depending on particle size. according to gupta (2007), coal requires about 50% excess air to completely burn, depending on fuel particle sizes, which differ from excess air in this work. sufficient excess air has tremendous influence in minimization of sudden explosion in fuel combustion. conversely, when minimum amount of air was supplied, part of the fuel will not burn due to lack of intimate contact between air and coal. table 2: computed design data for the combustion s/n description unit value 1 theoretical air required per kg of fuel 7.4 2 excess air (%) 10 3 maximum mass of air supplied per kg of fuel 8.82 4 burning rate constant (m2/s) 81032.6  5 time for burnt out at 0.4-10mm particle size (min) 2.64 6 burning (fuel flow) rate (kg/min) 0.23 7 power in fuel (kw) 84 8 air flow rate (kg/hr) 202.4 9 sorbent (gypsum) flow rate (kg/hr) 1.26 10 specific firing rate (sfr) (kg/m2.min) 0.168 11 air-fuel ratio 23 12 equivalence ratio of the maiganga lignite fuel combustion 0.45 3.2 maiganga lignite burning rate and fuel power coal particle burning rate was determined by computation of burning rate constant and time for burnt out with values as shown in table 2. the time for burn out of particle sized 0.4 mm was determined to be 1.74 minutes, with burning rate of 0.23 kg/min (3.8 g/s). burn out time depends on particle size, bed temperature and coal characteristics as reported by broughton and howard (1983). similarly, burning rate in fluidized bed was reported in one instance as 6.0 g/s for particle sized 3.0-10 mm at bed temperature of 985-1110 k by oka (2004) as against 3.8 g/s (0.23 kg/min) in this work. the coal burning time can last up to 33 minutes and devolalization takes up to 10-100 seconds, depending on the type of coal and particle size as reported by oka (2004). the optimum burning rate at particle size of 0.4 mm was 0.23 kg/min (0.0038 kg/s), similar to burning rate of palm kernel-sawdust briquettes determined to be 0.0020.006 kg/s for boiling water test as reported by kuti (2009). therefore, burning rate depends on intensity of o2 diffusion towards the coal particle surface, rate of chemical reaction and increases with char particle size. the ignition temperature of 797 k for maiganga coal was determined in this pilot fluidized bed combustor as previously reported by ozigis, et al. (2013). ignition temperature and burning rate are useful for safety issues due to explosiveness of coal dust when fired in a combustor. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 429 3.3 maiganga lignite fuel, air and sorbent flow rates through the combustor the fuel, air and sorbent flow rates were 0.23 kg/min, 202 kg/hr and 1.26 kg/hr respectively, as shown in table 2. the fuel and airflow rates promote turbulence, sustenance of combustion and flame front and collectively affect particle surface temperature. burning rate is equated to fuel flow rate in coal-fired fluidized bed combustor, because no fuel is allowed to hang and build up in combustor to minimize explosion as reported by broughton and howard (1983). fuel build up and burner flame stabilization were managed with controls to minimize sudden explosion, often with smoke and heat detectors as well as elimination of leaks from oil guns, oil burner light up operations and finer particles from fuel ducts as reported in broughton and howard (1983). the profiles for particle surface, bed and sorbent temperatures against maiganga lignite burning time in a pilot fbc are as shown in figure 1. some of the predictable factors to minimize frequency of fire explosion in coal burner include particle size, fuel moisture level, sorbent, bed and particle surface temperatures. in addition, first in and first out policy for coal storage and usage will minimize spontaneous combustion as well as avoidance of wet and dry coal particles that can cause clogging in fuel feed line and in screw feeder. the particle surface temperature of 1800k obtained for maiganga lignite in this work was close to flame temperature when compared to particle surface temperature of bituminous coal of 2445 k reported by sarroza, et al. (2017). the main reason for sluggish increase of sorbent gypsum temperature that was predicted by the models was due to its high calcium content in the tongo gypsum. the practice of blending coal with gypsum to remove sulphur in coal is not wide spread in thermal power plants in developing countries. the mass flow rate of gypsum at 1.26 kg/hr will remove sulphur in coal, and will also minimize sudden and undesirable explosion in combustor. in this work, tongo gypsum had flow rate at 9% in maiganga coal with sulphur content of 0.56%, similar to a coal-fired fluidized bed boiler that had flow rate of limestone at 40% in a coal with sulphur content of 3.6% as reported by nag (2009). figure 1: maiganga lignite particle surface, bed and gypsum temperature against time 3.4 combustion performance evaluation of the fluidized bed combustor the maiganga lignite particle sizes relationship with burning rate, specific firing rate (sfr) and equivalence ratio are as shown in figure 2. the lower the sfr, the more economical the fuel burnt. hence, maiganga lignite is suited for combustion in particle sizes more than 0.4 mm to achieve high equivalence ratio that approaches 0.45, whereas less than particle sizes of 0.4 mm, the equivalence ratio decreases from 0.15 to 0.05. it has been recognized that the performance file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 430 of combustor depends mainly on equivalence ratio range used. the lower limit of equivalence ratio range was determined by the minimal amount of air required to oxidize fuel and generate enough heat to maintain combustion process. low values of equivalence ratio would reduce bed temperature and the energy liberation necessary to maintain the combustion processes. on the other hand, high equivalence ratio would cause increases in bed temperature due to increase in oxygen diffusion as reported by ramirez et al. (2007). figure 2: effects of maiganga lignite particle sizes on performance of the combustor 3.5 validation of mathematical models presented in table 3 is the comparison of model results with other results in literature. the modelled fluidized bed combustor had fuel and airflow rates of 14.2 kg/hr and 202.4 kg/hr respectively, obtained in this work at a bed temperature of 1173 k. the burning (flow) rate of 14.2 kg/hr and airflow rate of 202.4 kg/hr can be employed in design of screw feeder for metering of ground coal and centrifugal fan for supply of air to the combustor, respectively. the fbc had fuel to airflow rates ratio of 0.071, due to excess air of 10%. the ratio of fuel to airflow rates in standard fluidized bed combustor is within 0.15 as reported by alobaid, et al. (2016). tritordai, et al. (2010), reported co-combustion of coal and biomass with power output of 45-90 kw in that work. optimizing airflow and fuel flow can result in uniform and efficient combustion as reported by wiatrus-motyka (2016). also, another modelled coal combustion resulted in a particle burn out time of 3 minutes at specific firing rate of 3.83 g/m2s at a bed temperature of 1173 k as reported by broughton and howard (1983). on the other hand, maiganga lignite coal had burn out time of 2.64 minutes with corresponding specific firing rate (sfr) of 2.8g/m2s (0.168 kg/m2min) at bed temperature of 1193 k obtained in this work. sfr is a measure of intensity of combustor operation, control of flame lift and as an estimate for comparing various coal-fired burners. sfr will guide sizing of air distributor, orifice diameter and estimation of coal flow rate into combustor for efficient firing devoid of fuel rich combustion. furthermore, maiganga lignite coal combustion at equivalence ratio of 0.45 obtained in this work is similar to an equivalence ratio of 0.40 for rice-husk-fired fluidized bed gasifier reactor as reported by ramirez et al. (2007). the bed temperature obtained for maiganga coal during burning ranges from 1103 to 1223 k. this is similar to bed temperature of 1273 k for coal-fired furnace reported by li, et al. (2010). all the maiganga coal models results were compared with other results in literature with good agreement. therefore, the selected mathematical models have been http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 431 validated and can be used appropriately in limiting sudden explosion and raise more interest in fluidized bed burners for cement production and for modular coal-fired thermal power plants. table 3: comparison of model results with literatures s/n parameters model results for maiganga lignite results obtained from literature 1 maiganga fuel flow rate (kg/hr) 14.20 40-80 tri-tordai et al. (2010) 2 air flow rate (kg/hr) 202.4 297 tri-tordai et al. (2010) 3 particle burn out time (min) 2.64 3.0 broughton and howard, (1983). 4 bed temperature (k) 1103-1223 1275 li et al. (2010) 5 equivalence ratio 0.45 0.4 ramirez et al. (2007) 6 thermal energy output (kw) 84 45-90 tri-tordai et al. (2010) 4. conclusion this work presents determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. the conclusions drawn were that particle size distribution can minimize sudden explosion from fly ash particles and moisture in coal fired in combustor needs to be minimized to avoid clogging that can lead to explosion while sorbent gypsum will minimize bed temperature. the ignition temperature of maiganga lignite coal was determined to be 797 k. the models were used to determined maiganga lignite fuel to have air-fuel ratio of 23 and equivalence ratio of 0.45. the airflow rate of 202.4 kg/hr will form the basis for design of centrifugal fan for forced air supply into the combustor. the maiganga lignite-burning rate of 14.2 kg/hr with burn out time of 2.64 minutes for particle size graded at 0.4 mm was determined. the burning rate of 14.2 kg/hr will aid the design of screw feeder for supply and metering of ground maiganga lignite fuel into the combustor. the specific firing rate for maiganga lignite at 0.4 mm particle size and at 1173 k bed temperature was 2.8 g/m2s. the specific firing rate of 2.8 g/m2s, will guide the design of surface area of air distributor, orifice diameter and for estimation of rate of coal into the combustor for efficient firing devoid of fuel rich combustion. acknowledgement the authors wish to thank all the staff that assisted in carrying out the experiments at the combustion bay in the faculty of engineering, abubakar tafawa balewa university, bauchi, nigeria. in particular, the authors appreciate the contributions of prof. a. a. asere and prof. habou dandakouta for all their guidance and encouragement. references alobaid, f., mertens, n., starkloff, r., lanz, t., heinze, c. and epple b. 2016. progress in dynamic simulation of thermal power plants. progress in energy and combustion science, 59:129-136. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 432 astm-1990. american society for testing and materials. gaseous fuel, coal, coke and firewood. annual book of astm standards. new york 05,05; 04, 07. balleney, pl. 2007. thermal engineering. delhi: khanna publishers ltd: 618-684. basu, p. 2015. combustion, circulating fluidized bed boilers: design, operation and maintenance, canada: springer: 89-119. broughton, j. and howard, jr. 1983. combustion of coal in fluidized bed. in: howard j.r. (ed.) fluidized beds combustions and applications. ripple road, barking essex, england: applied science publishers ltd; 1983: pp. 37-48, 66-72. chunmiao, y., chang, l. and gang, l. 2011. coal dust explosion prevention and protection based on inherent safety. first international symposium on mine safety and engineering, procedia engineering, 26: 1517-1525. crawford, m. 1980. air pollution control theory. new delhi: mcgraw; 259-574. eckhoff, rk. 2003. dust explosions in the process industries. 3rd ed, gulf professional publishing, an imprint of elsevier; 1-156. gupta, op. 2007. elements of fuels, furnaces and refractories, 5th edition. 2 –b nath market, nai sarak, new delhi: khanna publishers; 174 – 176, 506509. highley, j. and kaye, wg. 1983. fluidized bed industrial boilers and furnaces in: howard, jr. editor. fluidized beds combustions and applications, ripple road, barking essex, england: 77 –82, 86 –110. idriss, im., grema, as., musa, ma. and ej-jummah, m. 2018. maiaganga coal analysis and gasification simulation for power generation. international journal of science, environment and technology, 7.6:1933-1942. ikwuagwu, c. and uzoegbu, mu. 2017. the maiganga coal deposit: bituminous, sub-bituminous or lignite. iosr journal of applied geology and geophysics, 5.1: 67-74. johnson, f. 2007. fluidized bed combustion for clean energy. the 12th international conference on fluidization-new horizons in fluidized engineering, held at chalmers university of technology, at se-41296, goteborg, sweden, may 13-18, art 5, 47-61. kataja, m., and majanne, y. 2007. dynamic model of a bubbling fluidized bed boiler, tampere univ. of tech., institute of automation and control, box 692, fi-33101, tampere:140-148. kuti, ao. 2009. performances of composite sawdust briquette fuel in a biomass stove under simulation condition. assumption university journal of technology, 12.4: 284-288. lee, sw. 1997. investigation of heat transfer and combustion in the advanced fluidized bed combustor. tech. report no.16. pittsburgh: us depart of energy:1-13 li, j, manasosh, cp., younger, pl., watson, i., hossain, m., and welch, s. 2015a. characterization of biomass combustion at high temperatures based on an upgraded single particle model. applied energy, 156: 749-755. li, j., manasosh, cp., younger, pl., watson, i., hossain, m., and welch, s. 2015b. prediction of high temperature rapid combustion behaviour of woody biomass particles. fuel, 105:205-214. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):418-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 433 li, s., xu, t., zhou, q., tan, h., and hui, s. 2010. effect of coal-over-coal reburns on furnace temperature and heat flux distribution in 1mw tangentially fired furnace. international journal of thermal sciences, 49: 225-233. marra, fs., miccio, f., solimene, r., urciuolo, m., chirone, r., continillo, g., lombardi, s. and fussco, g. 2014. stepup of an integrated stirling engine-fluidized bed experimental system, 16th international stirling engine conference, 24-26, september, bilbao, spain: 399-409. mikulcic, h., berg, ve., vujanovic, m., and duic, n. 2014. numerical study of co-firing pulverized coal and biomass inside a cement calciner. waste management and research, 32.7: 661-669. nag, pk. 2009. power plant engineering. 3rd ed. 15th reprint. new delhi: tata mcgraw hill publishing co. ltd: 343-379. ngampradit, n., piumsomboon, p. and sajjakulnukit, b. 2004. simulation of a circulating fluidized bed combustor with shrinking core and emission model. science asia; 30: 365-374. oka, so. 2004. fundamental processes during coal combustion in fluidized beds. fluidized bed combustion, marcel dekker, basel, new york, usa; 211-355. ozigis, ii. and arudi, is. 2013. design, construction and performance of a screw feeder for fluidized bed combustor. nigerian journal of engineering; 20.1:54-63. ozigis, ii., dandakouta, h. and egbo, g. 2013. design and performance characteristics of heating element in ignition of maiganga lignite coal in a fluidized bed combustor. journal of engineering and technology; 8. 2: 47-52. ozigis, ii, dandakouta, h, and egbo, g. 2015. design and construction of centrifugal fan for a fluidized bed combustor. nigerian journal of tropic engineering; 8. 2: 41-49. ramirez, jj., martinez, jd. and petro, sl. 2007. basic design of a fluidized bed gasifier for rice husk on a pilot scale. latin american applied research, :37 .4: 299-306. rokni, e., chi, hh. and levendis, ya. 2017. in-furnace sulphur capture by co-firing coal with alkali based sorbents. journal of energy resources technology, 139. july: 042204-2-042204-6. ryemshak, sa. and jauro, a. 2013. proximate analysis, rheological properties and technological application of some nigerian coals. international journal of industrial chemistry, 4.7: 1-7. sarroza, ca., bennet, td., eastwick, c. and liu, h. 2017. characterizing pulverizing fuel ignition in a visual drop tube furnace by use of a high-speed imaging technique. fuel processing technology, 157: 1-11. song, cz., wen, jh., li, yy., dan, h., shi, xy. and xin, s. 2018. thermogravimetric assessment of combustion characteristics of blends of lignite coals with coal gangue. 3rd annual international conference on mechanics and mechanical engineering, advances in engineering research, hothot, china: 105: 490-495. thapa, rk., pfeifer, c. and halvorsen, bm. 2016. flow regime identification in a fluidized bed combustor reactor. international journal of modelling and optimization, 6.3:188-193. tikpangi, km. 2016. radiological, trace elemental and petrographic characteristics of maiganga coal deposits of northern benue trough, north-eastern, nigeria. phd thesis, department of physics, university of malaya, kuala lumpur: 97-99. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozigis and zarmai: determination of maiganga lignite coal combustion characteristics for application in thermal power plant using standard mathematical models. azojete, 15(2):418-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 434 trif-tordal, g., ionel, i., popescu, f., dungan, li. and varga, l. 2010. waste biomass & coal cocombustion in stationary fluidized bed as promising res based technology. wseas transactions on environment and development, 6(7):561-562. turns, sr. 2000. an introduction to combustion: concepts and applications. 2nd ed london: mcgraw-hill: 542-545. unep-2006. united nations environment programme, thermal energy equipment: boilers and thermic-fluid heaters. united nations environment programme, new delhi, india: 13-17. wiatros-motyka, m. 2016. optimizing fuel flow in pulverized coal and biomass fired boilers. international energy agency, clean coal centre, london, uk: 1-61 http://www.azojete.com.ng original research article determination of maiganga lignite coal combustion i. i. ozigis* and m. t. zarmai ole_link5 ole_link6 ole_link4 ole_link3 arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3):510-518 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 510 original research article evaluation of sheanut shell-reinforced automotive brake pad v. n. haruna1*, a. s. abdulrahman2, m. s. abolarin1 and r. a. muriana2 (1department of mechanical engineering, federal university of technology, minna, niger state, nigeria 2department of material and metallurgical engineering, federal university of technology, minna, niger state, nigeria) * corresponding author’s email address: ndarabaharuna@gmail.com article information submitted 19 december, 2018 revised 15 april, 2019 accepted 19 april, 2019 keywords: epoxy sheanut shell asbestos brake pad development abstract for over a century now, asbestos has been used as friction material in the manufacture of brake pads but its use is currently been avoided due to its carcinogenic nature and potential to cause cancer. this study is focused on development of a new brake pad using sheanut shell (sns) which is an eco-friendly material as the reinforcement and epoxy resin as the binder. other constituents used are calcium carbonate (caco3), graphite and aluminium oxide (al2o3). five compositions were formulated with the epoxy resin and reinforcement varied at interval of 5 wt% while caco3, graphite and al2o3 remain constant at 30, 10 and 10 wt% respectively. the developed brake pads were subjected to compressive, abrasive and water absorption tests while their densities were also measured. the results showed that the compressive strength, abrasive strength and the density of the samples decreased as the reinforcement content increased while the water absorption rate increased as the reinforcement content increased. the value of the compressive strength ranged from 64.88 – 93.04mpa, wear rate from 3.13 – 6.25mg/m, water absorption from 0.899 – 2.722% and density from 0.764 – 1.487g/m3. the result of this research indicates that sns particles can be used as a replacement for asbestos in brake pad production. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction brake pads are important parts of braking system for all types of vehicles using disc brake. the importance of brake pad is to convert the dynamic energy of the vehicle to heat energy by means of friction and dissipating the heat to the surrounding environment (maleque et al., 2012). different types of brake materials are used in different machines. they are usually classified into four components namely binders, fillers, modifiers and reinforcements (dagwa and ibhadode, 2006; blau, 2001; maleque et al., 2012; umamaheswara, 2015). the brake pads generally consist of asbestos fibres embedded in polymeric matrix along with several other components. the use of asbestos fibers is being avoided due to its carcinogenic nature (yuvaraj and jeyanthi, 2015). despite its good properties, asbestos is being withdrawn from all the applications, where there is a possibility of alternate material for making brake pad that will not pose health risks leading to diseases like asbestosis, mesothelioma, lung cancer and other cancers (dagwa and ibhadode, 2006; mathur et al., 2004; anon, 2004; norton, 2001; rinek and cowen, 1995). although the use of asbestos for brake pads has not been banned, much of the brake pad industry is moving away mailto:ndarabaharuna@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):510-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 511 from asbestos brake pads because of concerns regarding airborne particles in the factories and disposal of wastes containing asbestos (aigbodion et al., 2010). several researches have been carried out in the area of development of asbestos-free brake pads. the use of coconut shell, palm kernel shell (pks) have been investigated (dagwa and ibhadodo, 2006; dagwa and ibhadode, 2005). researches all over the world are focusing on ways of utilizing either industrial or agricultural wastes as a source of raw materials for composite development (lemon et al., 2008). these wastes utilization will not only provide more economic benefit, but may also result to foreign exchange earnings and environmental sanitation (yuvaraj and jeyanthi, 2015). sheanut shells are wastes resulting from shea nut consumption were collected from the refuse dumped cite in kodan village, niger state. the presence of hard elements like silicon, calcium, iron, carbon and magnesium which are equally found in asbestos suggests that sheanut shell can be used as a reinforcement material for brake pad production as similarly observed in the work of ikpambese et al., 2014. the application of sheanut shell as a reinforcement material will not only eradicate the health risk posed by using asbestos but also move nigeria ahead towards realization of her dream of increasing local content in automobile industry. 2. materials and methods 2.1 materials materials used in this study consist of the main components of the brake pad namely: sheanut shells (sns) as the reinforcement and epoxy as binder, caco3 as filler and graphite (figure 1b) and al2o3 as the frictional additives. the reinforcement is to improve the mechanical properties of the composites, the binder maintains the pad’s structural integrity under mechanical and thermal stresses, the filler material improves the manufacturability of the brake pad while the frictional additives modify the coefficient of friction and the wear rate. other materials used include sodium hydroxide and distilled water. these materials were almost the same with the materials used by bala et al. (2016). 2.2 methods 2.2.1 preparation of the raw material (reinforcement) the sns were collected and soaked in a solution of water and sunlight detergent for 30 minutes for easy removal of dirt and other contaminants. the sns were thereafter washed properly and sun dried to constant weight after which it was ground using milling machine. this method is in line with the one adopted by bala et al. (2016). the ground sns (figure 1a) was treated with 10% sodium hydroxide (naoh) and sun dried to constant weight. this treatment is to increase the bonding ability of the reinforcement with the resin (pujari et al., 2014). the treated reinforcement was then sieved using 150µm mesh. figure 1: ground sns (a), ground graphite (b) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng haruna, et al: evaluation of sheanut shell-reinforced automotive brake pad. azojete, 15(3):510-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 512 2.2.2 formulation of the brake pad compositions the formulation of the brake pad compositions which is in line with the approach of bala et al. (2016) is shown in table 1. table 1: weight percent compositions of the brake pad sample no 1 2 3 4 5 resin 40 35 30 25 20 sns 10 15 20 25 30 caco3 30 30 30 30 30 graphite 10 10 10 10 10 al2o3 10 10 10 10 10 total 100 100 100 100 100 2.2.3. production of the brake pad samples production of automotive brake pad consists of a number of unit operations including mixing of its components, hot pressing, cooling, post curing and finishing (gurunath and bijwe, 2008; koya and fono, 2009). different samples of ground sns, calcium carbonate, graphite and aluminium oxide were thoroughly mixed in a container to obtain the percentages indicated in table 1, following the method of abutu et al., 2018. the epoxy resin + triethylenetetramine hardener was properly mixed in a separate container, poured into the first mixture and then mixed thoroughly for five minutes to obtain a homogenous mixture (yawas et al., 2016). this homogenous mixture was then charged into a metallic mould lined with aluminium foil for easy removal of the cast. the samples were kept under the hydraulic press at a pressure of 11 n/mm2 and temperature of 120°c for 10 min. the cast samples were post cured in an electric oven at 150°c for 2 h. this was similar to the method adopted by yawas et al. (2016) and mathur et al. (2004). figure 2a, b and c shows the mixing of the constituents, the samples produced and the sheanut shells respectively. a b c figure 2: mixing of the constituents (a), produced samples (b), sheanut shells (c) 2.2.4 characterization of the produced brake pads the produced brake pads were characterized by subjecting them to density measurement, compressive, absorption, abrasive and thermal conductivity tests using standard methods and procedures. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):510-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 513 2.2.4.1 density density depends on the constituents of the brake materials formulation (talib 2007; nirmal et al., 2011). the true densities of the specimens were determined using archimedes’s principles. the volumes of water in the cylinder before and after immersion of the specimens were taken and their difference gives the volume of the specimen. the densities of the specimens were determined by dividing the mass of the specimen before the immersion by the difference in the volumes of the water (egeonu et al., 2015). that is, by weighing them on a digital weighing machine and measuring their volumes by liquid displacement method (aigbodion and akadike, 2010). the density was calculated using the formula given by cracium et al., (2017): v mp  (1) where: ρ = density in g/cm3 m = mass in g v = volume of liquid displaced in cm3 2.2.4.2 compressive strength specimens were subjected to compressive test using enerpac universal hydraulic digital material testing machine 100kn, norwood instrument ltd, new mill road houley, hundersfield, great britain hd9 6qd shown in figure 3(a) in accordance with astm d3410/d3410m. the specimens were cut to a dimension of 20 × 20 × 10 mm in order to conform to the specification of the instrument used. these specimens were loaded manually continuously until failure occurred. the load at failure was digitally displayed and recorded. this was in accordance with the method adopted by aigbodion and akadike (2010). the compressive strength was calculated using the formula: a pc  (2) where: σc = compressive strength in mpa p = applied load in n a = cross sectional area in mm2 2.2.4.3 water absorption test the 24-h water soak test was carried out to determine the water absorption behaviour of the brake pads produced. the samples were oven dried at 70°c for 1 h and their weights measured. after 24 h of submersion in water at 30°c according to idris et al. (2015), the specimens were weighed after the excess water had drained off. the absorption was calculated using the given formula (smales, 1995; talib, 2007; edokpia et al., 2014): (3) where: w1= weight after immersion in g ; wo = weight before immersion in g file:///c:/users/user/downloads/azojete143/www.azojete.com.ng haruna, et al: evaluation of sheanut shell-reinforced automotive brake pad. azojete, 15(3):510-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 514 2.2.4.4 wear rate an apparatus known as “tribometer”, anton paar, switzerland shown in figure 3(b)was used to investigate the dry sliding wear rate of the sample in accordance with astm: g99 – 05 standards (idris et al., 2015). this equipment and methods used to examine the worn surface include optical microscopes, scanning electron microscopes, optical interferometry and mechanical roughness testers. the result of the wear test using this apparatus is always displayed on the screen of the computer attached to it.the samples dimensions were 25 mm in diameter and 5 mm in thickness. the difference in weights of the samples before and after test gives the wear of the samples. loss in weight was converted to wear rate using the formula given by aigbodion and akadike (2010): s wratewear   (4) where δw = difference in weight before and after test in mg s = sliding distance in m. a b figure 3: compression tester (a), tribometer (b) 3. results and discussion 3.1 characterization of the produced brake pads 3.1.1 density figure 1 shows the variation of density with reinforcement content in the composite samples. it was observed from the result that the density of the composite decreased as the reinforcement content increased. this according to idris et al., (2015) may be attributed to the reduction in the interfacial bonding between the reinforcement and the resin. this result was in agreement with the previous study of bala et al. (2016). the values obtained were between 0.764 – 1.487 g/cm3 which are within the recommended values for the application of brake pad given by kim et al. (2003). figure 4: variation of density with reinforcement content http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):510-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 515 3.1.2 compressive strength figure 2 shows the effect of the reinforcement content on the compressive strength of the composite. it was observed from the result that the compressive strength decreased with increase in reinforcement content. this gradual decrease may be attributed to the decreasing surface area and pore packaging capability of the reinforcement in the resin as the reinforcement content is increasing (aigbodion et al., 2010). the values of the compressive strength obtained are between 64.88 and 93.04 mpa. these values are within the range of the values obtained in the work reported by idris et al. (2015). figure 5: variation of compressive strength with reinforcement content 3.1.3 water absorption figure 3 depicts the variation of the absorption rate with the reinforcement content in the composite. it can be seen from the result that the absorption rate increased as the reinforcement content increased. this may be attributed to the increase in pores as the reinforcement content increased which could be due to reduction in interfacial bonding between the reinforcement and the matrix. this result is in agreement with that of bala et al., (2016). the values obtained were within the range of 0.899 – 2.722 %. these values are also within the range of the values obtained in the work of bala et al., (2016).the less the value of the absorption rate, the better the material for brake pad production under study. figure 6: variation of water absorption rate with reinforcement content 3.1.4 material wear the variation of wear rate with reinforcement content of the composite is shown in figure 4. it is observed from the result that the wear rate reduced as the reinforcement content increased. this may be due to better interfacial bonding between the reinforcement and the matrix causing good surface property. this result is in agreement with the research work of idris et al. (2015). the values of the wear rate of this work ranges from 3.13 – 6.25 mg/m. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng haruna, et al: evaluation of sheanut shell-reinforced automotive brake pad. azojete, 15(3):510-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 516 figure 7: variation of wear rate with reinforcement content 3.2 comparison of sns based brake pad with other experimental brake pads table 2 below shows the comparison between the sns based brake pad and other experimental brake pads. table 2: comparison of sns based brake pad with other experimental brake pads properties commercial asbestos based brake pad palm kernel based formulation bagasse based formulation carbonized banana peels based formulation sns based formulation density (g/cm3) 1.89 1.65 1.43 1.20 0.764-1.487 water absorption (%) 0.9 5.03 3.48 3.0 0.899-2.722 compressive strength (mpa) 110 103.5 105.6 61.20 64.88-93.04 wear rate (mg/m) 3.8 4.40 4.20 4.67 3.13-6.25 table 2 shows the density, water absorption, compressive strength and wear rate values for asbestos, palm kernel, bagasse, carbonized banana peels and sns based brake pads (ibhadode and dagwa, 2008; aigbodion et al., 2010; idris et al., 2015). though the values for commercial asbestos based are taken as the standard, other brake pad formulations shown in the table cannot be out of place since they also have some properties that are better than that of asbestos based. for example, the density of the sns based (1.487g/cm3) is less than that of the asbestos based (0.9g/cm3) while other properties are in close agreement. 4. conclusion from the results obtained, the values of the compressive strength, wear rate and the density were observed to be decreasing with the increase in reinforcement content while the water absorption rate was increasing with the increase in reinforcement content. however, the values obtained for all the tests carried out can be comparable to the values of the commercial asbestos based and other experimental brake pads. hence, the shea nut shell can be used as a replacement for asbestos in the production of brake pads. acknowledgement the authors are grateful to the tertiary education trust fund (tetfund) and management of federal university of technology, minna, niger state, nigeria for the grant (tetfund/futminna/2016-2017/b/19) allocated to this research work. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):510-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndarabaharuna@gmail.com 517 references abutu, j., lawal, sa., ndaliman, mb., lafia-araga, ra., adedipe, o. and choudhury, ia. 2018. effect of process parameters on the properties of brake pad developed from seashell as reinforcement material using grey relational analysis. journal of engineering science and technology, https://doi.org/10.1016/j.jestch.2018.05.014. retrieved march 15, 2019. aigbodion, vs., akadike, u., hassan, sb., asuke, f. and agunsoye, jo. 2010. development of asbestos – free brake pad using bagasse. tribiology in industry, 32(1): 45 – 50. anon, 2004. automotive brake repair trends and safety issues. http/www.sirim.my/amtee/pm/brake.hltm. retrieved march 25, 2018. bala, kc., okoli, m. and abolarin, ms. 2016. development of automobile brake lining using pulverized cow hooves. leonard journal of sciences, (28): 95 – 108 blau, pj. 2001. compositions, functions and testing of friction brake materials and their additives: a report by oak ridge national laboratory for u.s dept. of energy. www.ornl.gov/webworks/cppr/y2001/rpt/11 2956.pdf. retrieved february 10, 2018. dagwa, im. and ibhadode, aoa. 2005. design and manufacture of experimental brake pad test rig. nigerian journal of engineering research and development, 4(3):15-24. dagwa, im, and ibhadode, aoa. 2006. determination of optimum manufacturing conditions for asbestos-free brake pad using taguchi method. nigerian journal of engineering research and development, 5(4): 1-8. dagwa, im. and ibhadode, aoa. 2008. development of asbestos-free friction lining material frompalm kernel shell. journal of the brazilian society of mechanical sciences and engineerig, 30(2): 166-173. edokpia, ro., aigbodion, vs., atuanya, cu., agunsoye, jo. and mu’azu, k. 2016. experimental study of the properties of brake pad using egg shell particles-gum arabic composites. journal of the chenese advanced materials society, 4(2): 172-184. egeomu, d., olua, c. and okolo, p. 2015. production of eco-friendly brake pad using sourced locally in nsukka. journal of energy technologies and policy, 5(11): 47-54. gurunath, pv. and bijwe, j. 2009. potential exploration of novel green resins as binders for nao friction composites in severe operating conditions. wear, 267(5-8): 789 – 796. idris, ud., aigbodion, vs., abubakar, i.j. and nwoye, c. i. 2015. eco-friendly asbestos free brake pad; 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passenger car brake history. journal of automobile engineering, 103(7): 37 – 42. smales, h. 1995. friction materials-black art of science. journal of automobile engineering, 209(d3): 151-157. umamaheswara, rr. and babji, g. 2015. a review paper on alternate materials for asbestos brake pads and its characteristics. international research journal of engineering and technology, 2(2): 556-562. yawas, ds., aku, sy. and amaren, sg. 2016. morphology and properties of periwinkle shell asbestos free brake pad. journal of king saud university-engineering sciences, 28: 103 – 109. yuvaraj, l. and jeyanthi, s. 2015. an investigation on chemical treatment of phenol formaldehyde with natural fibres for brake pads. journal of chemical and pharmaceutical science, special issue 7: 419-421 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):35-45 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 35 original research article impact of climate change on the design parameters of heating, ventilation and air conditioning systems for manned spacecraft k. o. adeyemi, i. i. ozigis*, m. t. zarmai and s. i. ishola department of mechanical engineering, university of abuja, kilometre 23, airport road, abuja, nigeria article information submitted: 14/10/2018 revised: 16/11/2018 accepted: 18/03/2019 keywords: air-conditioning, dry-bulb temperature, humidity, spacecraft, statistics, pressure. abstract climatic design information has been published for several locations in the world by american society of heating, refrigerating and airconditioning engineers (ashrae) but there has not been data for nigerian cities in these publications. therefore, this study was embarked upon to bridge the gap in knowledge. the study of impact of climate change on the design parameters of heating, ventilation and air conditioning (hvac) systems for spacecraft cabin environment is presented with particular focus on ikeja-lagos, nigeria. firstly, the characteristics climate parameters such as outdoor dry-bulb temperature, coincident wet-bulb temperature, relative humidity, pressures, air composition, among others as it affects manned spacecraft were discussed. the data for climatic parameters for ikeja-lagos, nigeria, for a period of fifteen years (1995-2009) were obtained from nigerian meteorological agency (nimet), oshodi-lagos. statistical data and microsoft excel were used for evaluation of variation trends of the climate parameters for departure city. this is very important in determining thermal human comfort in spacecrafts on ascent. results obtained from this study are hereby presented. the ikeja-lagos dry-bulb temperature average results obtained were 33.81°c, 32.98°c, 32.3°c, 22.1°c, 21.19°c, 20.43°c, 23.84°c and 31.65°c.at 0.4%, 1.0%, 2.0%, 97.5%, 99.0%, 99.6%, median of extreme lows and median of extreme highs, respectively. the ikeja-lagos relative humidity average results were 116.3, 112.65, 109.14, 99.83 and 49.42 at 0.4%, 1% and 2.0% occurrence as well as at median of extreme highs and median of extreme lows, respectively. ikeja-lagos had mean coincident dry bulb temperature of 33.81°c and 32.98°c at 0.4% and 1% percentile respectively. the dry bulb temperature for ikeja-lagos was determined to be an average range from 20.43°c to 22.1°c between january to december, in the period of 1995-2009, at 97.5% 99% and 99.6% percentile respectively. these results provide values of design parameters which are useful in the design of hvac for space crafts with climate change adequately taken into consideration as it applies to ikeja-lagos, nigeria © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction there is robust evidence that extreme weather conditions are happening with greater frequency and intensity than what was experienced few decades ago. mitigation measures needs to be put http://www.azojete.com.ng adeyemi, et al, impact of climate change on the design parameters of heating, ventilation and air conditioning systems for manned spacecraft. azojete, 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 36 in place to avoid what can lead to decrease in performances of facilities in space technology due to dramatic increase in the frequency and intensity of these extreme weather conditions. in the aviation sector, infrastructures such as airports and aircrafts are designed with historical weather conditions. often, these infrastructures like air ports and aircrafts will need retrofitted facilities to match changes in climatic conditions. therefore, aircraft and spacecraft designers will require a detailed and quantified information for specific regions and locations with a focus on maximum and minimum temperatures as well as associated humidity conditions. this then suggests a need for model-based climatic projections for future climate using historical climatic data to identify priorities in mitigation measures. although the global environment is affected by climate change, this study is particularly concerned about the impact of climate change on the cabin environment in spacecraft. in this study the impact of climate change on design parameters of heating, ventilation and air conditioning (hvac) systems were analyzed to determine the proper parameters to be used for design of the systems. the hvac systems are devices designed to control the climatic and environmental parameters to provide thermal comfort at acceptable indoor air quality in terms of air composition, temperature, humidity, pressure, wind speed and direction, amount of rainfall or water vapour in any area of application such as in manned spacecrafts. the payload includes the living things, air conditioners, fans, heaters and cargo carried by a spacecraft but excluding propulsion units. the studies on effects of dry bulb temperature and relative humidity on performances of power electronics, gas turbines, compressors, among others have been documented as reported by olorunmaiye and awolola (2016). the load in a spacecraft can include gas turbines, compressors, refrigerators, amongst others, which are directly linked to climatic conditions. furthermore, the control of cabin environment in spacecrafts has been a challenge especially for flights across continents due to varying climate parameters. the relative humidity inside a spacecraft cabin is generally much lower than the minimum for thermal comfort recommended by ashrae (2013a), wyon et al. (2006) and uchiyama et al. (2007) for comfort standards. the temperature is the only variable which can be controlled to its optimal level, but this optimal control is only permitted in the cruise process, not during ascent and descent processes, as this can affect the performance of the engine. therefore, in order to monitor the performance, reliability and control of hvac systems in spacecrafts, the study of the climatic conditions of the departure city as recommended by ashrae in the design of hvac systems is of key importance as reported by ashrae (2013a). it is appropriate to determine the main climate input parameters in a location for when there is desire to launch and operate a space craft. climatic design information had been published for several locations in the world but nigeria did not feature as published by ashrae (2013a). some west africa countries such as mali and niger republic had climatic data stations at bamako and niamey, respectively, in which climate data had been recorded for over 15 years according to ashrae (2013a). in the design of comfort in space craft, complete knowledge of temperature, humidity, purity of air, motion of air and thermal load are required. this study aimed to discuss climatic design parameters as it applied to ikeja-lagos, nigeria. the objectives include data gathering and computation to provide information on dry bulb temperature and wet bulb temperature at several percentiles, median of extreme lows and http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 37 median of extreme highs, as well as at mean daily temperature range essential in climatic design information for spacecraft technology. 2 climatic design parameters for human comfort in manned spacecraft 2.1 air composition and air velocity the space craft cabin is a confined space with varying pressure from one atmospheric pressure to one-third atmospheric pressure in some extreme cases as reported by liping et al. (2017). similarly, air composition also varies between oxygen and nitrogen, with 20.95% oxygen like in the earth’s environment or 40% oxygen and 60% nitrogen in some situations. when pressure in the cabin is high, oxygen has to be provided as well as disposal of cabin carbon-dioxide produced by human being. ashrae (2013a), standard 62 recommends a certain volume of fresh air to be supplied to various areas in a space craft and is dependent on the number of people present and the nature of the activity taking place. design condition for any habitable space is to guarantee an air flow of 10 litres/second (10 l/s) as reported by ballaney (2003). similarly, it is recommended that air supply speed should be within 2-5 m/s, to prevent air noise in built environment. ashrae (2013a) as well as khurmi and gupta (2003) reported that all spaces in spacecraft should receive minimum of air velocity of 0.3 m/s, that contains enough oxygen for breathing and also sweep away odours, microorganisms, and heat release. 2.2. thermal load radiations from warm surfaces of the load in spacecraft are important factor that can affect comfort reaction of human being. radiations from occupants to room surfaces and structures as well as between occupants, has an important bearing on the feeling of warmth and can alter the optimum. the heat liberation from crew and passengers as well as heat liberation from machines and transformers in the spacecraft contributes to thermal load. similarly, solar radiation around spacecraft and oxidation processes of materials of construction of spacecraft contributes to heat load. air-conditioner is one of devices that contributes to human comfort in spacecraft. some researchers reported that energy consumption for running air conditioning system depends on the climate of location along with the location solar radiation as reported by olorunmaiye et al. (2012). the researchers also recommended use of economizers on air conditioner, orientation of buildings and planting of trees to positively influence climatic conditions to minimize global warming. space technology is well suited to benefit from above particularly in location and environment of lunch of spacecraft and ascent. 2.3 air temperatures air temperatures in spacecrafts are evaluated based on dry-bulb temperature, wet-bulb temperature, and mean daily temperature ranges. the likelihood of temperature changes with height also affects design of spacecraft as stated in liping et al. (2017). spacecrafts are designed with temperatures that are not expected to exceed 27°c for wet bulb, 35°c for dry bulb while effective temperature, should not exceed 27°c, according to ashrae (2013a) standard 55. in evaluation of climate changes, dry-bulb temperature is presented in percentile corresponding to 0.4%, 1.0%, and 2.0% cumulative frequency of occurrence and the mean coincident wet-bulb temperature, according to ashrae (2013a). similarly, wet-bulb temperature is presented in percentile corresponding to 0.4%, 1.0%, and 2.0% cumulative frequency of occurrence and the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeyemi, et al, impact of climate change on the design parameters of heating, ventilation and air conditioning systems for manned spacecraft. azojete, 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 38 mean coincident dry bulb temperature, according to procedures recommended for evaluation of climatic conditions in a location or region by ashrae (2013a). dew-point temperature corresponding to 0.4%, 1.0%, and 2.0% annual cumulative frequency of occurrence, mean coincident dry-bulb temperature and humidity ratio are also parameters for climate study according to ashrae (2013a). the 0.4%, 1.0%, and 2.0% dry-bulb temperatures and mean coincident wet bulb temperatures indicates severity of conditions on hot, mostly sunny days as reported by ashrae (2013a). in summary, mean daily temperature range is mean of the difference between daily maximum and minimum dry-bulb temperatures for hottest months as reported by anekwe and onuchukwu (2017). similarly, dry-bulb temperatures are calculated from extremes of the hourly temperature observations. it is important to note that dry and wet bulb temperatures is more convenient than the partial vapour pressure and temperatures in climatic characteristics evaluation of manned spacecraft. 2.4 relative humidity of air human comfort demands relative humidity (rh) in the range of 50 to 70%, but this is not maintained aboard spacecraft to avoid condensation problems on cold walls and equipment, which tends to corrode metals and boost micro-organism growth as reported by ballaney (2003) as well as olorunmaiye and awolola (2016). therefore, relative humidity is kept in a low range of 10 to 20%, with some discomfort of evapotranspiration and electrostatic build up if human beings are among the payload in spacecraft as reported by liping et al. (2017). at cruise altitudes there is practically no water vapor in the air, so it is natural to have dry cabin air. on ground and during ascent, the air conditioning system must dehumidify fresh air introduced into the cabin, particularly in tropical climates when doors are still open. outside humidity is very small at high altitudes and is kept low inside spacecraft to minimize problems of condensation and frost on the cold structure. some researchers undertook determination of energy requirements in a building with particular focus on provision of cooling by air conditioner, which is also relevant in provision of human comfort in spacecraft as reported by ariyo and olorunmaiye (2017a). therefore, design values of relative humidity of departure city enable designers to size hvac system to achieve an acceptable level of comfort. in some spacecrafts, cabin temperature can range between 18-24°c, while its relative humidity ranges between 5070% as reported by liping et al. (2017). 2.5 minimum and maximum pressures climatic characteristics involves sum of all inlet pressures and pressure losses in the main lines and ducts as linked to air conditioners and fans in the manned spacecraft, called the system. the system constant is obtained at minimum and maximum pressures in relation to the air required delivery flow rate, which are in turn used to determine the system characteristics at minimum and maximum pressures. worthy of note is effect of gravity compression of air in the spacecraft, that arose from the pressure difference at the surrounding surfaces and in the spacecraft on ascent and descend. the average of air pressures in different months of the year 2011 was determined for calabar to have minimum of 1001.5 pa and maximum of 1008.1 pa, while port harcourt had minimum of 1003.5 pa and maximum of 1012.0 pa, according to some researchers such as anekwe and onuchukwu (2017). researchers such as liping et al. (2017) reported that spacecraft cabin pressure can range between 90-100 kpa. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 39 3.0 methodology the hourly weather data for climatic design for ikeja (lagos, nigeria), for a period of fifteen years (1995-2009) were obtained from nigerian meteorological agency, oshodi-lagos (nimet, 2011). the nimet laboratories are equipped with facilities to obtain weather data. the nimet procedures include hourly measurement of wet-bulb and dry-bulb temperatures at synchronized controls and stabilized power supply. the initial and final dry-bulb temperatures and wet-bulb temperatures, respectively, were recorded as well as the inlet and outlet of the forced air passage as well as the suction and discharge pressures including air velocity within the weather station (nimet, 2011). ikeja-lagos, nigeria, is located at latitude 6.59°n and longitude 3.34°e on an altitude of 9 m. ikeja-lagos, nigeria, was hypothetically chosen to determine the climate parameters due to its heavy traffic of airplanes with large weather data generation. this work involves use of statistical data and microsoft excel spreadsheet 2015 version with normal distribution table. the evaluation of variation trend of the climate parameters for departure cities, are very important in determining thermal comfort in spacecrafts on ascent. the high values of dry-bulb and wet-bulb temperatures were computed on criteria of 0.4%, 1.0% and 2.0% percentiles. furthermore, the low values were also computed on percentiles of 97.5, 99.0% and 99.6% frequencies of occurrence for all twelve months of the year under consideration. the mean daily temperature range, median of extreme lows and highs for ikeja-lagos were computed. 4.0 results and discussion this section presents results in tables and figures along with the discussion of them all. 4.1 average temperature of ikeja-lagos as at 1995 and 2015 the evidence of increase in temperature over the years can be observed as shown in table 1. the average temperature for ikeja-lagos in 1995, was obtained from nimet (2011) while average temperature for ikeja-lagos in 2015, was a weather forecast as predicted by ojeh et al. (2016). in table 1, the average temperature for the year 1995 in ikeja-lagos was 26.66°c while the average temperature for the year 2015 in ikeja-lagos was 26.81oc. the increase in average temperature in ikeja-lagos from 1995 to 2015 was 0.15°c, which agrees to convincing evidence to global warming. the temperature trends during the year 1995 and 2015 are as shown in figure 1. researchers have reported that there is gradual increase in average temperature of the earth surface which has been predicted to rise between 1.4°c and 5.8°c by year 2100 as reported by trenberth, et al. (2007). the increase in average temperature in locations of spacecraft ascent and descent will have to be factor in during design stage to minimize retrofitting thermal comfort facilities. table 1: average temperature of ikeja-lagos as at 1995 and 2015 year/months jan feb mar apr may jun jul aug sept oct nov dec temperature, 1995 26.9 28.2 28.5 28.3 27.3 25.9 24.8 24.9 25.2 26.0 27.0 26.7 temperature, 2015 27.3 28.5 28.5 28.0 27.1 25.6 25.3 25.1 25.5 26.4 27.2 27.2 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeyemi, et al, impact of climate change on the design parameters of heating, ventilation and air conditioning systems for manned spacecraft. azojete, 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 40 all these measurements are in degree celsius (oc). figure 1: average temperature of ikeja-lagos as at 1995 and 2015 4.2 the design dry-bulb temperatures for ikeja-lagos from 1995-2009 the design dry bulb temperature for ikeja-lagos, are presented for all the months from 19952009 at various frequencies of occurrence obtained using normal statistical table is as shown in table 2. normal statistical estimates for average dry bulb temperature were made at 0.4%, 1.0% and 2.0% for ikeja-lagos. the corresponding highest mean maximum temperature occurs from february to may for years studied. these months of highest mean maximum temperature becomes the design month for consideration in planning and operation of spacecrafts. furthermore, figure 2, shows the mean coincident dry bulb temperature at 0.4% and 1% percentile and were computed as 33.8°c and 32.98°c for ikeja-lagos respectively. similarly, the dry bulb temperature at 99% and 99.6% percentile respectively were at an average of 21.19°c and 20.43°c from january to december for ikeja-lagos, respectively, were as shown in figure 3. these data are useful for cooling applications, especially air-conditioning in spacecraft technology. the statistical values of median of extreme lows (mel), median of extreme highs (meh) and mean daily temperature range (mdtr) were also calculated as shown in table 2 while figure 4 illustrate the trends of mean daily temperature range for the period. the probability of occurrence of very extreme conditions can be required for the operational design of equipment to ensure continuous operation and serviceability as stated in ashrae (2013b). these values were calculated from extremes of the hourly temperature observations. the true maximum and minimum temperatures for any day generally occur between hourly readings. the 95.7%, 99.0% and 99.6% design conditions are often used in the sizing of heating equipment. some sophisticated electronics need a particular dry bulb temperature and relative humidity for its proper design and operation as reported by liping et al. (2017). the design dry-bulb temperatures and mean daily dry bulb temperature for ikeja can be employed to calculate heating and cooling degree-days, which is further used in energy estimation of hvac systems as reported by ariyo and olorunmaiye (2017a). the design conditions based on wet-bulb temperature represent extremes of the total sensible plus latent heat of outdoor air, according to ashrae (2010). the dry and wet bulb temperatures together with other climatic characteristics are useful for cooling towers, evaporative coolers, and fresh air ventilation system design, which are adaptable for spacecraft technology. generally, in design of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 41 hvac systems, it is not economical to choose either the maximum or minimum prevailing climate data of a location but highly recommended that the 0.4%,1%, 2%, 5%, 97.5%, 99.0%, and 99.6% values of occurrences be adhered to as suggested by some researchers such as liping, et al. (2017). however, no one knows what exactly the future climate is going to be but statistical analysis of the climate of the past years can give a clue to the future as reported by burdick (2011). table 2: the design dry-bulb temperatures for ikeja-lagos from 1995-2009 months jan feb mar apr may jun jul aug sept oct nov dec average 0.4% 35.6 36.6 36.4 35.8 34.6 33.0 30.4 30.0 31 32.6 34.5 35.3 33.81 1.0% 34.6 35.6 35.5 34.9 33.7 32.1 29.8 29.5 30.3 31.8 33.6 34.4 32.98 2.0% 33.7 34.8 34.7 34.2 33.0 31.4 29.3 29 29.8 31.2 32.9 33.6 32.3 97.5% 21.3 22.7 23.4 23.0 22.6 21.2 21.9 21.7 21.6 21.8 22.2 21.8 22.1 99.0% 20.2 21.6 22.3 21.2 21.6 20.3 21.2 21.1 20.9 20.9 22.0 21.0 21.19 99.6% 19.2 20.6 21.4 21.0 20.8 19.4 20.6 20.5 20.2 20.1 21.3 20.1 20.43 mel 23.7 25.5 25.6 25.3 24.5 23.6 23.2 23.3 23.5 23.5 24.4 20.0 23.84 meh 32.5 33.8 33.5 33.0 31.8 29.9 29.0 28.3 29.2 30.5 32.0 36.3 31.65 mdtr 4.9 4.4 4.2 3.9 3.6 3.1 2.9 2.6 2.9 3.3 3.9 4.3 3.67 all these measurements are in degree celsius (°c) figure 2: the mean coincident dry-bulb temperatures for ikeja-lagos from 1995-2009 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeyemi, et al, impact of climate change on the design parameters of heating, ventilation and air conditioning systems for manned spacecraft. azojete, 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 42 figure 3: the design drybulb temperatures for ikeja-lagos from 1995-2009 figure 4: the mean daily temperature ranges for ikeja-lagos from 1995-2009 4.3 the relative humidity for ikeja-lagos from january-december of 1995-2009 the design relative humidity for ikeja-lagos from january to december of 1995-2009, is as shown in table 3 and figure 5. the normal statistical estimates for the design relative humidity were computed for 0.4%, 1.0% and 2.0%. the design relative humidity calculated for period exceeded 100% as shown in table 3. since the design relative humidity exceeded 100%, it implies that normal distribution statistical method cannot be used as stated by ariyo and olorunmaiye (2017b) as well as erbs (1984). erbs (1984) suggested weibull distribution for design relative humidity to overcome defect of normal distribution statistical method. the statistical values of median of extreme lows (mel) and median of extreme highs (meh) were also calculated as shown in table 3. using the classification of ashrae (2013a), the relative humidity for ikeja, lagos were computed to be an average of 116.3 and 112.6 at 0.4% and 1.0% percentile, respectively, which is as shown in table 3. in the design and sizing simulation of hvac systems for spacecrafts, design data based on dry bulb temperature represent peak occurrences of sensible component of ambient outdoor conditions. the design values based on wet-bulb temperature are related to enthalpy of the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 43 outdoor air while conditions based on dew point relates to peaks of the humidity ratio. the design data for dry bulb, wet bulb and humidity ratio are optimized to obtain the most reliable situation to adopt as stated in ashrae (2016). the foregone statement agrees to view on decisions of conditions and probability of occurrence of climatic conditions to the design of spacecraft as reported by liping, et al. (2017). table 3: the relative humidity for ikeja from january-december of 1995-2009. months jan feb mar apr may jun jul aug sep oct nov dec ave. 0.4% 127.4 125.7 116.4 113.6 114.2 112.9 111.6 111.7 112.6 113.2 115.5 121.3 116.3 1.0% 121.3 119.9 110.6 109.7 110.6 109.2 108.8 108.7 109.7 110.1 111.9 121.3 112.65 2.0% 116.6 115 108.1 106.5 107.6 107.5 106.4 106.2 107.3 107.4 108.7 112.4 109.14 meh 100 99 99 100 100 100 100 100 100 100 100 100 99.83 mel 23 21 44 53 56 62 63 60 64 61 56 30 49.42 figure 5: the relative humidity for ikeja-lagos from january-december in the period of 19952009 5.0 conclusion in this study, an investigation of the impact of climate change on the design parameters of heating, ventilation and air conditioning (hvac) systems for spacecraft was carried out. the climate parameters investigated were outdoor dry-bulb temperature, coincident wet-bulb temperature and relative humidity. these parameters are very important in determining thermal comfort of payload in space crafts on ascent. furthermore, the city of lagos was used as a base for potential launch of spacecraft. the values of climatic parameters were obtained with adequate consideration of climate change. from the investigations carried out, the conclusions drawn includes determination of mean coincident dry bulb temperature of 33.8oc and 32.98oc at 0.4% and 1% percentile respectively at ikeja, lagos, on altitude 39 m with coordinates of latitude 6.59°n and longitude 3.34°e. the heat dry bulb temperature for ikeja, lagos, was determined to range from 20.43oc to 22.1oc from january to december, in the period of 19952009, at 97.5% 99% and 99.6% percentile respectively. the median of extreme lows (mel) was at an average of 49.42% for the period. the median of extreme highs (meh) was at an average of 99.83% for the period. the lagos relative humidity average results were 116.3, 112.65, 109.14, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adeyemi, et al, impact of climate change on the design parameters of heating, ventilation and air conditioning systems for manned spacecraft. azojete, 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 44 99.83 and 49.42 at 0.4%, 1% and 2.0% occurrence as well as median of extreme highs and median of extreme lows, respectively. acknowledgement the authors wish to thank the director and chief executive, center for satellite technology development (cstd) of the national space research and development agency (nasrda), abuja, nigeria, and editorial committee of cstd for consideration of our paper for publication earlier presented at 2017 cstd conference. references anekwe, f. and onuchukwu, cc. 2017. study of the variation in weather parameters in some selected cities in southern nigeria. coou journal of multidisciplinary studies, 1(1): 122-132. ariyo, do. and olorunmaiye, ja. 2017a. degree-day and bin methods of estimating cooling energy for ilorin area of kwara state. iosr journal of mechanical and civil engineering, 14(3): 9196. ariyo, do. and olorunmaiye, ja. 2017b. analysis of ambient dry bulb temperature and relative humidity data of ikeja, nigeria, for refrigeration and air conditioning. international journal of science and research, 6(5): 776-781. ashrae. 2010. ashrae standard 90.1-2010, energy standard for buildings except low residential buildings. american society of heating, refrigeration and air conditioning engineers, inc, atlanta, ga 3032: 39-46. ashrae. 2013a. ashrae-hvac, climatic design information, fundamental hand book, american society of heating, refrigeration and air conditioning engineers incorporated, atlanta, ga, usa: 8.1-8.26., 27.1-27.43. ashrae. 2013b. ashrae standard 90.1-2013, determination of energy savings: quantitative analysis, us department of energy, 2014, american society of heating, refrigeration and air conditioning engineers incorporated atlanta, ga, usa: 110-119. ashrae. 2016. ashrae standard 90.1-2010, performance rating method reference manual, us department of energy, american society of heating, refrigeration and air conditioning engineers incorporated atlanta, ga, usa: 3.189-3.227. ballaney, pl. 2003. refrigeration and air conditioning, 13th edition. khanna publisher, nai sarak, delhi: 768-802. burdick, a. 2011. strategy guidelines: accurate heating and cooling load calculations, building america, us department of energy, energy efficiency and renewable energy, ibacos, inc, pittsburgh, pennsylvania, usa: 7-30. erbs, aa. 1984. models and applications for weather statistics related to building heating and cooling loads, phd thesis, university of wisconsin-madison, 18-49. khurmi, rs. and gupta, jk. 2003. thermal engineering, reprint, s. chand and co. ltd, ram nagar, new delhi: 798-823. liping, p., yue, q. and meng, l. 2017. thermal comfort assessment in civil aircraft cabin. chinese journal of aeronautics, 27(2): 210-216. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):35-45. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: idris.ozigi@uniabuja.edu.ng 45 nimet. 2011. nigerian meteorological services agency, climate review bulletin. nigerian meteorological services agency, oshodi, lagos: 7-19. ojeh, vn., balogu, aa. and okhimamhe, aa. 2016. urban-rural temperature difference in lagos. climate, 4(29): 1-18. olorunmaiye, ja., ajao, kr. and omolehin, is. 2012. effect of climate change on outside air design temperature for air conditioning cooling load calculations for ikeja and ilorin, nigeria. energy engineering, 109(2): 65-80. olorunmaiye, ja. and awolola, oo. 2016. models of hourly dry bulb temperature and relative humidity of key selected areas in nigeria for engineering applications. nigerian journal of technology, 35(2): 360-369. trenberth, ke., jones, pd., ambenje, p., bojariu, r., easterling, d., klein tank, a., parker, d., rahimzadeh, f., renwick, ja., rusticucci, m., soden, b. and zhai, p. 2007. observations: surface and atmospheric climate change in: climate change 2007. the physical science basis. contribution of working group i to the fourth assessment report of the intergovernmental panel on climate change. solomon, s., qin, d., manning, m., chen, z., marquis, m., averyt, kb., tignor, m. and miller, hl(eds). new york, cambridge university press: 3-9. uchiyama, e., aronowicz, jd., butovich, ia. and mcculley, jp. 2007. increased evaporative rates in laboratory testing condition simulating airplane cabin relative humidity: an important factor for dry eye syndrome. eye contact lens, 33(4): 174-176. wyon, dp., fang, l., largercrantz, l. and fanger, po. 2006. experimental determination of the limiting criteria for human exposure to low winter humidity indoors (rp-1160). heating ventilation and air conditioning and residences, 12(2): 261-268 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 540-546 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 540 characterization of clay from oza-nogogo in delta state, nigeria for potential industrial uses s. e. uwadiae* and v. ekeleme (department of chemical engineering, faculty of engineering, university of benin, pmb 1154, benin city, edo state, nigeria) *corresponding author’s e-mail: sylvester.uwadiae@uniben.edu.ng abstract the aim of this study was to characterize clay from oza-nogogo in delta state for its physical and chemical composition in order to assess its potential industrial applications. the clay samples were collected by means of a plastic shovel and digger, hand-picked to minimize the possibility of contamination and placed in a small polyethene bags. the samples were dried at ambient temperature for 10 days, pulverized and sieved screened to obtain fine particles before analysis. the physiochemical properties were determined using x-ray diffraction (xrd) for the mineralogical composition, x-ray florescence (xrf) for the chemical composition and scanning electron microscope (sem) for the microstructures of the clay sample. the cation exchange capacity (cec), specific surface area and pore volume of the sample were also determined. the xrd studies showed that the clay sample is predominantly kaolinitic with some quantities of quartz, illite and feldspar. kaolinite being the dominant clay mineral alone constitutes between 70-76% and quartz ranged from 22-28% and other minerals ranged from 1-6%. the xrf analysis showed that the sample contained high amount of silica (sio2) by mass of 51.3% followed by alumina (al2o3) 40%, iron oxide (fe2o3) 3.703%. all other minerals present were in negligible proportion. the major elemental contents of clay samples detected in the study were si, al, fe, ti and k. the sem micrographs showed the relative sizes in the clay particles and revealed that the clay particles seem to consist of much smaller platelets which indicated that the clay sample was made up of very fine particles. the specific surface area, cec and pore diameter were 7.846 m2/g , 6.8 meq/100 g and 28.642 nm respectively. due to the high kaolinite content, oza-nogogo clay showed a potential of a basic raw material for pharmaceutical, drugs, paints, paper and ceramic industries. keywords: x-ray diffraction; x-ray florescence; scanning electron microscope; cation exchange capacity, oza-nogogo clay 1. introduction apart from petroleum, gas and coal resources, the exploration, mining and exploitation of mineral resources in nigeria have not received sufficient attention (abolarin et al., 2006). delving into geological survey of nigerian soil, it was reported that clay as one of the major nigerian mineral deposits cover an estimated proven reserves of billions of tones (durotoye and elueze, 1989). clays have been severally defined as anhydrous complex compounds of alumina (al2o3) and silica (sio3) that exist in various proportions and contain varied amounts of impurities of iron, organic matters and residual minerals (akinfolarin and awopetu, 2014); naturally occurring material that composed primarily of fine-grained minerals, which is generally plastic at appropriate water contents and susceptible to hardening when fired at high temperature (dogan et al., 2002) and abundant fine earthly powders produced by the weathering and disintegration of granite and feldspathic rocks (nweke and ugwu, 2007). although clay usually contains phyllosilicates, it may contain other materials that could impart plasticity when wet and also harden when fired. however, associated phases in clay may include organic matter and materials that do not impart plasticity (bakker, 1993).they have varying chemical composition depending on both the physical and chemical changes in the environment where clay deposits are found (salawudeen et al., 2010). the nature of clay and its composition determines, not only its quality and commercial value but also, to a large extent, its engineering behaviour mailto:sylvester.uwadiae@uniben.edu.ng http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol 14(4):540-546 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 541 (grim, 1968 and onyeobi et al., 2013). among the characteristics of clays that influence their engineering performance are clay mineral composition, physical properties such as particle size distribution, porosity, structure and geologic history. clay minerals share a basic set of structural and chemical characteristic and yet each clay mineral has its own unique set of properties that determine how it will interact with other chemical species. the variation in both chemistry and structure, among the clays leads to their applications in extremely diverse fields. the specific clay minerals are identified by several techniques including thermal differential analysis, scanning electron microscope, infrared spectrometry and x-ray diffraction. chemical analysis is an essential step to establish the nature of minerals (newman, 1987). depending on the physical and chemical characteristics, clays may find application in a number of industries such as plastics, paint, ceramics, ink, catalysts, pharmaceutical and fibre glass among others (murray, 1980; emufurieta et al., 1992). despite the abundance clay deposits in nigeria, there is a dearth of information on their characterization for various applications in agriculture, industry and environment. it is the aim of this study to characterize clay from ozan-nogogo using different analytical techniques with the view to assessing their physicochemical properties and relating them to their suitability for use in the relevant industries. 2. methodology 2.1 sample colletion and preparation the clay samples used in this study, were collected from the deposits at oza-nogogo in ika south local government area of delta state, nigeria, at depths of 40 cm with the aid of shovel and digger and then hand-picked to minimize the possibility of contamination. the samples were dried at ambient temperature for 10 days. thereafter, the samples were finely ground with a mortar and passed through a 2 mm mesh sieve (njoka et al., 2015) to obtain very fine particles used in analysis. 2.2 characterization of clay samples phenom scanning electron microscope (model pro x) with energy dispersive x-ray spectrometer was used to determine the microstructures of the clay samples (osabor et al., 2009). qualitative chemical analysis of minerals was carried out on the clay samples to produce backscattered images (bsi) (osabor et al., 2009). the mineralogical composition of the clay was obtained by xrd (empyrean xrd, panalytical bv of netherland) studies. (chiari et al., 2003) x-ray fluorescence spectrometer (mini pal for edxrf) was used to determine the chemical composition of the clay samples (dean et al., 2004). cation exchange capacity (cec) of the clay was determined using the bacl2 compulsive exchange method as prescribed by soil science society of america (sumner and miller, 1996). the specific surface area of the samples was determined using micromeritics instrument (tristar 3000) and by using brunauer– emmett–teller (bet) method. the specific surface area of oza-nogogo clay was determined from the brunauer,emmett and teller (bet) multipoint method (bruanuer et al., 1938; brame and griggs 2016). also pore volume was determined using the surface area analyzer which utilizes the bet theory for the analysis and plots of each sample data and then presents the results of pore volume (de lange et al., 2014). three replicates was done and average value was calculated. http://www.azojete.com.ng uwadiae and ekeleme: characterization of clay from oza-nogogo in delta state, nigeria for potential industrial uses. azojete, 14(4):540-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 542 3. results and discussion the x-ray diffractogram result of the oza-nogogo clay sample is shown in figure 1. figure 1: x-ray diffraction pattern of oza-nogogo clay the diffractogram (figure 1) shows the x-ray diffraction pattern of the clay sample. the results of mineralogical analysis of the clay samples in the present investigation show that the clay samples are predominantly kaolinitic and quartz. careful investigation of figure 1 reveals that the samples were composed essentially of al8si8o36h0 (kaolinite 2m) and si3o6(quartz). kaolinite group observed at the following peaks 12, 20, 25, 35,36,38,48, 51,63 and 72å while quartz were seen att the following peaks: 27, 37, 39, 50 and 60å. a simple comparison with the mineral composition of some well-known clay deposits indicates that the investigated deposit is similar to kaduna and china clay deposits which also had kaolinite and quartz with very small variations in the mineral contents (osabor et al., 2009). the clay samples are all of sedimentary origins and seem to have gone through different level of transformation before depositions, which affects their physical properties like plasticity and shrinkage (osabor et al., 2009). due to the high kaolinite content, this clay can serve as basic raw materials for pharmaceutical, drugs, paints, paper and ceramic industries. the results of the x-ray fluorescence analysis of the elements in the clay sample are shown in table 1. in the xrf analysis, the chemical compounds present in the clay and their concentrations were obtained with major elements present expressed in form of their oxides. the xrf result shows the compounds presents with its related concentration unit. from the result obtained (table 1)it is observed that the sample contains high amount of silica by mass of 51.3% followed by alumina 40%. all other minerals present are in negligible proportion. the major elemental contents of clay samples detected in the study were si, al, fe, ti and k. the sample is found to be a mixture of kaolinite and illite in various proportlow electrical conductivity and high permeability can be brought about by high levels of quartz and low levels of clay mineral content. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol 14(4):540-546 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 543 table 1: chemical composition of oza-nogogo clay sample oxide percent al2o3 40 sio2 51.3 k2o 0.274 cao 0.144 tio2 3.06 v2o5 0.11 cr2o3 0.02 mno 0.009 fe2o3 3.703 nio 0.006 cuo 0.008 zno 0.001 ga2o3 0.021 ag2o 0.74 ta2o5 0.03 re2o7 0.093 bi2o3 0.094 the low plasticity generally exhibited by kaolinitic clay materials might be due to the levels of mineral oxide impurities such as tio2, mno, and fe2o3 present in the clay and the slightly low shrinkage is associated with the presence of high amount of quartz which tends to decrease the magnitude of shrinkage (ombaka, ‎ 2016). clay from oza-nogogo can be used for refractory purposes since ryan (1976) showed that for good refractory characteristics, clay should have a percentage composition of al2o3, between 30 and 50% with a limited amount of fe2o3, tio2 and cao. also, for kaolinite mineral to be utilized industrially, other accessory minerals such as quartz should first be reduced to acceptable levels through appropriate beneficiation techniques (njoka et al., 2015). the sem micrograph of oza-nogogo clay sample is shown in figure 2. figure 2: sem micrographs of oza-nogogo clay (magnification x3000) http://www.azojete.com.ng uwadiae and ekeleme: characterization of clay from oza-nogogo in delta state, nigeria for potential industrial uses. azojete, 14(4):540-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 544 figure 2 is the sem micrograph of the clay sample at magnification of x3000. on examination of sem micrographs, the clay particles seem to consist of very small platelets which indicate that the clay sample is made up of very fine particles. well crystalline kaolinite particles of varying sizes that are rough edged are also observed. some kaolinite particles are below 1µm size. the coarse region is an indication of the presence of some particles of quartz (henderson et al., 1970). rounded nature of quartz particles and spherical grains indicate recycled nature and maturity of sediment accumulation. quartz particle at this high magnification shows spongy surface and microcracks. the spongy quartz might have resulted due to the soil environment at oza-nogogo. here the quartz-kaolinite contacts are more sharply defined and more parallel, indicating a closer control on corrosion of the quartz by the later-forming kaolinite crystallites themselves. hot and humid weathering environment also favour weathering of kaolin group minerals. formation of an intermediate between micas and clay minerals are also possible. coarse fraction also shows patches, rich in ti and fe bearing minerals and containing traces of mn indicated by xrf, which coats quartz and kaolinite particles as impurities are also observed. the results of pore size characterization and the cec of the sample is shown in table 2. table 2: pore size characterization and cec of oza-nogogo clay sample parameter value specific surface area (m2/g) 7.846 average pore diameter (nm) 28.642 cec (meq/100g) 6.8 as observed, the specific surface area for the clay is 7.846 m2/g; this is below the range of 10 to 20 m2/g established for kaolinite (bohn et al., 1985) and far less than the value for standard adsorbents and catalysts. this may be due to the high quartz content of the clay. the cec of a clay is defined as the milli-eequivalents of cation that can be exchanged under standard conditions per100 gm of clay and it is expressed as a number. it is a measure of the capacity of soil to hold on to cations (neal and worral, 1977). the cec was also observed to be low (6.8 meq/100 g). this is however within the range of values of 3 and 15 meq/100 g for kaolinite given elsewhere (grim, 1968). with a pore diameter of 28.642nm, oza-nogogo clay is mesoporous based on the classification of pore size as recommended by international unit of pure and applied chemistry (iupac) (sing, 1985). hence this clay is not suitable for use as an adsorbent. 4. conclusion the combination of the three characterization techniques adopted in this research work (xrd, xrf & sem) showed consistency in the revelation of the quantities of different constituents of the clay sample. the mineralogical analyses (xrd) showed that the clay samples are predominantly kaolinitic with some quantities of quartz. the chemical analysis (xrf) showed the compounds present with its related concentration unit. from the result obtained it is observed that the sample contains high amount of silica by mass of 51.3% followed by alumina 40%. all other minerals present are in negligible proportion. the major elemental contents of clay samples detected in the study were si, al, fe, ti and k. due to the high kaolinite content, oza-nogogo clay can serve as basic raw materials for pharmaceutical, drugs, paints, paper and ceramic industries only after reducing the level of quartz in it to an acceptable level. however, this in its present form will be suitable for use as a refractory material. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol 14(4):540-546 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 545 references abolarin, ms., olugboji, oa. and ugwuok, ic. 2006. determination of moulding properties of locally available clays for casting operations. university journal of technology, 9(4): 238-242. akinfolarin, jf. and awopetu, oo. 2014. the effect of sawdust on the insulating effect of ikere clay as refractory lining. au journal of technology, 17(3): 143-147. bakker, wt. 1993. refractories for present and future electric power plants, key engineering materials. trans tech publications. new york bohn, hl., mcneal, bl and o’connor, ga. 1985. soil chemistry, 2nd edn. wiley, new york. brame, j. and griggs, c. 2016. surface area analysis using the brunauer -emmett-teller (bet) method : standard operating procedure series: characterization . environmental laboratory , u.s. army engineer research and development centre bruanuer, s. emmett, ph. and teller, e. 1938. adsorption of gases in multimolecular layers. journal of the american chemical society, 60, 309–316. chiari, g., giustetto, r., and ricchiardi, g. 2003. crystal structure refinements of palygorskite and maya blue from molecular modelling and powder synchrotron diffraction. european journal of mineralogy, 15(1): 21–33. dean, b., gano, d., knight, k., ofman, j. and fass, r. 2004. effectiveness of proton pump inhibitors in nonerosive reflux diseases. journal of clinical gastroenterology and hapatology, 2: 656-664 de lange, mf., vlugt, tjh, gascon, j. and kapteijn, f. 2014. adsorptive characterization of porous solids: error analysis guides the way. microporous and mesoporous materials, 200,199– 215 dogan, cp., kwong, ks. and bennet, jp. 2002.improved refractory materials for slagging coal gasifiers in: proceedings from the 27th international conference on coal utilization and fuel systems, clearwater, florida. durotoye, ab. and elueze, aa. 1989. abrasives, in: o.s. adegoke, s.a. adediran and a.a. elueze (editors), guide to the non-metallic mineral industrial potentials of nigeria, published by raw materials research and development council, pp. 15 emufurieta. wo., kayode, aa., and coker, sa. 1992..mineralogy, geochemistry and economic evaluation of kaolin deposits near ubuluuku, awo-omama and buan in southern. nigeria. journal of mining geology, 28(92): 211-280. grim, re. 1968. applied clay mineralogy. mcgraw hill, london henderson, jh., syers, jk. and jackson, ml. 1970. quartz dissolution as influenced by ph and the presence of a disturbed surface layer. israel journal of chemistry, 8(3):357-372 murray, h. 1980. major kaolin processing development. international journal of mineral processing, 1(1): 263-274. neal, m. and worral, we. 1977. mineralogy of fire clays: part ii,transactions and journal of the british ceramic society, 76(3):61-65 https://catalog.princeton.edu/catalog/357334 https://catalog.princeton.edu/catalog/357334 http://www.azojete.com.ng uwadiae and ekeleme: characterization of clay from oza-nogogo in delta state, nigeria for potential industrial uses. azojete, 14(4):540-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 546 newman, acd. 1987. chemistry of clay and clay minerals. mineralogical society monograph, 6. longman scientific and technical, harlow, essex, england. njoka, en, ombaka, o., gichumbi, jm., kibaara, di. and nderi, om. 2015. characterization of clays from tharaka-nithi county in kenya for industrial and agricultural applications. african journal of environmental science and technology, 9 (3):228-243. nweke, es. and ugwu, ei. 2007. analysis and characterization of clay soil in abakaliki, nigeria. the pacific journal of science and technology, 8 (2):190-193. ombaka, o. 2016. characterization and classification of clay minerals for potential applications in rugi ward, kenya. african journal of environmental science and technology, 10(11):415431 onyeobi, tus., imeokparia, eg., ilegieuno, oa. and egbuniwe, ig. 2013. compositional, geotechnical and industrial characteristics of some clay bodies in southern nigeria. journal of geography and geology; 5( 2),73-84 osabor vn., okafor, pc., ibe, ka. and ayi, aa. 2009. characterization of clays in odukpani. african journal of pure and applied chemistry, 3 (5), 79-85. ryan, w. 1976. properties of ceramics raw materials, pergamon press, london salawudeen, to., isam, q., nassereldeen k, ma‟an a., suleyman, m., faridah, y. and qusim, h. 2010. effect of modification on the physicochemical and thermal properties of organophilic clay modified with octadecylamine. international journal of engineering and technology, 10 (1):27-35. sing, ksw. 1985. reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity. pure and applied chemistry, 57(4):603-619 sumner, me. and miller, wp. 1996. cation exchange capacity and exchange coefficients. in: sparks, dl., ed., methods of soil analysis part 3: chemical methods, sssa book series 5, soil science society of america, madison, wisconsin, 1201-1230. http://www.azojete.com.ng ombaka, o. 2016. characterization and classificati sing, ksw. 1985. reporting physisorption data for 7 arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):501-508 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 501 original research article modelling of heat transfer through hollow blocks produced with rice-husk-ash blended cement o. m. kamiyo department of mechanical engineering, university of lagos, lagos, nigeria. *corresponding author’s email address: okamiyo@unilag.edu.ng 1.0 introduction hollow sandcrete blocks containing a mixture of sand and cement are used extensively in many countries of the world especially sub-saharan africa, caribbean islands and asia. in nigeria, sandcrete block is the major cost component of most common buildings.the high and increasing cost of constituent materials of sandcrete blocks has contributed to the nonrealization of adequate housing for both urban and rural dwellers. hence, availability of alternatives to these materials for construction is highly desirable. in particular, materials that can complement cement in the short run, and especially if cheaper to produce has been of great interest (chandrasekhar et al., 2003; nair et al., 2006; okunade, 2008). wall properties such as thermal resistance, comprehensive strength, weight, rigidity and cost play major roles in modern building designs. as a way of enhancing these properties and lower the cost, admixtures are introduced (rodriguez de sensale et al.,2008; okunade, 2008; turgut and yesilata, 2008; nair et al., 2006; oyekan and kamiyo, 2011). use of agricultural wastes is one of the common approches (ganesan et al., 2008; cisse and laguerbe, 2000; nair et al., 2006; chandrasekhar et al., 2003; kamiyo and oyekan, 2011; adesanya and raheem, 2009). thermal properties of the wall of a building play a major role in the estimation of the air condition load of the building space. increasing the thermal resistance of the wall material is desirable and therefore the focus of many recent researches (cianfrini et al., 2017; idan and feldman, 2017; costa, 2014; al-tamimi et al., 2017; tang et al., 2015; gijon-rivera et al., 2016; shibib et al., 2013; balaji et al., 2014 ). a survey of existing literature shows that thermal properties of most cementitious materials are found to change with the presence of admixtures (cisse and laguerbe, 2000; oyekan and kamiyo, 2011 ) and size (with arrangement) of air-gaps in hollow bricks/ blocks (al-hazmy, article information abstract hollow sandcrete blocks are widely used in many countries of the world. in recent years, cement content is being partially substituted by admixtures especially agricultural wastes. modeling of heat transfer characteristics of these modified blocks is essential in order to predict their thermal performance. this study focuses on this modeling with the aid of a finite-volume based computer code. specifically, for regular, two-cavity blocks produced with the cement partially substituted with rice husk ash (rha). the result showed that as the percentage substitution of rha increased, thermal gradient across the width of the block increased, while the rate of heat flow reduced. the second part of the study examined the effect of heat transfer through the air-gap as compared to a similar study regarding it as vacuum. the heat flow through the air-gaps of the building bricks affected the pattern of heat flow within the bricks, hence, they could not be regarded as a vacuum. the results of this study will be useful to building professionals in the choice of building blocks and proper estimation of airconditioning load in buildings. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 nov., 2019 revised 08 may, 2020 accepted 20 may, 2020 keywords: heat transfer hollow blocks rice husk ash mailto:okamiyo@unilag.edu.ng http://www.azojete.com.ng kamiyo: modelling of heat transfer through hollow blocks produced with rice-husk-ash blended cement. azojete,16(3):501-508. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 502 2006; oluleke et al., 2012; idan and feldman, 2017; costa, 2014, li et al., 2008; al-tamimi et al., 2017; tang et al., 2015) al-hazmy (2006) studied the heat transfer through a convectionals hollow brick with the aim of determining the effect of blocking the holes with insulators on the heat transfer rate. the results showed a 36% reduction in the heat transferred by the brick when hollow. similarly, gijon-rivera et al. (2016) performed numerical analysis of the effect of heat conduction of building blocks made of different materials on congugate heat and mass transfer. the red bricks was found to be the best choice for air quality purposes in comparison with other building materials for all rayliegh numbers considered. additionally, tang et al. (2015) conducted parametric investigation of thermal performance of a wall by varying the arrangement of holes, insulation and building materials. the results of the study showed that as the number of holes increases, thermal conductivity reduces and, in some cases, between 20% and 61%. oluleke et al. (2012) also carried out a finite element modeling of low heat conducting bricks. they reported that, in conventional bricks, increasing the number of holes beyond four gives minimal thermal resistance advantage. however, in their work, they assumed the holes to be vacuum i.e. there was no heat transfer. it is noteworthy that with heat transfer in building materials, there have been resurgence of interest in recent times with limited literature on those with admixtures which are already in use. therefore, this study focused on this problem. the research is on two parts : (i) to determine the effect of the substitution of rice husk ash as partial replacement to cement on the heat flow across sandcrete blocks; (ii) to reinvestigate the brick configuration of oluleke et al. (2012) by imposing realistic conditions so as to determine its actual thermal performance. 2. materials and method 2.1 mathematical formulation the computational geometry, figure 1, coincides with the physical geometry. parallel path heat flow is assumed, i.e. heat flows directly from the hot to the cold surface perpendicularly and uniformly; signifying 1-d heat transfer situation. this method is used because heat flows laterally through block face shells so that transverse isothermal planes result (ashrae, 2017). convective heat transfer within the holes is not considered as it is reported by lacarrière et al., (2003) to be negligible. the block is assumed exposed to solar radiation and hot outside air that heat its outer surface to temperature th while the inner surface is assumed maintained by air-cooling at temperature tc (<th ). the equation for general heat conduction for non-homogeneous material, for unsteady heat flow through a constant area is given by ρ.c. ∂t ∂t = ∂ ∂x kx ∂t ∂x + ∂ ∂y ky ∂t ∂y + ∂ ∂z kz ∂t ∂z (1) where t is temperature, ρ is density, c is specific heat, kx,y,z is thermal conductivity in x, y and z directions respectively. however, for a 1-d, unsteady heat conduction in a homogeneous material with no internal heat generation, the equation reduced to dt dt = ∝ ∂2t ∂y2 (2) the boundary conditions employed are, at t = 0, and y=0, th = 32°c and ∂t ∂x = 0; at y = 225mm, tc = 22°c, convective heat transfer coefficient, h= 15 w/m2 k. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 501-508. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 503 320c 220c figure 1: computational geometry the material constituents, their mix, presence of admixtures and production process are important factors that determine the properties of sandcrete blocks. in this study, the blocks produced with standard 1:6 cement-sand mix proportion are employed.the substitution of cement with rice husk ash and the batching of cement and sand were by volume. blocks with 0% (control), 5%, 10% and 15% rha substitution were used. the block dimensions are 450mm x 225mm x 225mm (with one-third of the volume void) which lead to b = 75mm; l1 = 75mm; l2 = 112.5mm. futher details of the material contents, production and thermal properties of the blocks were as reported in oyekan and kamiyo (2011). 3. results and discussion 3.1 rha block simulation after numerical experiments to determine grid independence, a set of simulations were also carried out to determine the time steady state was reached. figure 2 shows temperature variation with time across the width of the 15% rha block when subjected to ambient temperature of 32°c on the upper side (outside) and air-cooled temperature of 22°c on the lower side (inside). (a) 1200 seconds (b) 2400 seconds (c) 3600 seconds (d) 7200 seconds figure 2: evolution of the isotherms in the 15% rha block. it can be observed that, the temperature distribution obtained at 1200 seconds, figure 2(a), is quite different from that at 2400 seconds, figure 2(b), while that obtained at 7200 seconds, figure 2(d), is the same as that at 3600 seconds, figure 2(c). therefore, it can be concluded that steady state is reached at 3600 seconds. in addition, the change in temperature with time is monitored at point y = 180mm. the outcome is shown in figure 3. 320c 220c 220 320 b b b l1 l2 l1 l2 l1 th tc y x0 22 0c 320c file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kamiyo: modelling of heat transfer through hollow blocks produced with rice-husk-ash blended cement. azojete,16(3):501-508. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 504 figure 3: temperature change with time at y = 180mm to steady state (a) 0% rha (b) 5% rha (c) 10% rha (d) 15% rha figure 4: temperature distribution at steady state for various % substitution figure 4 (a-d) show results for temperature distribution at steady state in blocks with 0% (the control block), 5%, 10% and 15% rha substitutions. for the control block, figure 4(a), the temperature at the hot surface remains unchanged up to the holes. thermal stratification within the holes somehow affects the temperature pattern within the solid part. on the inner part, thermal gradient increases, showing three isotherms between the hole and the inner part of the block. for 5% rha block, figure 4(b), the temperature pattern across the block changed slightly. the first isotherm has now extended closer to the outer surface. on the cooler part of the block, the thermal stratification that was noticeable in the 0% rha block has reduced to only one isotherm between the holes and the cold surface. the isotherm skewed slightly towards the holes in form of two little humps. for the 10% rha block, figure 4(c), the humps of the last isotherm become pronounced. at 15% rha substitution, figure 4(d), the humps have become more pronounced. this implies that, as the rha substitution increases, the temperature at the cooler part becomes more uniform and tends towards that of the cold surface of the block. for all the blocks, heat transfer within the holes is highly stratified. thermal gradient within the holes appears the same with five isotherms in each case. the temperature patterns indicate that there is a reduction in heat conduction from outside of the block to inside of the block. this reduction in heat flow between the two edges shows that, the air within the cavity of the blocks, as expected, helps in reducing the rate of heat transfer into the building. 220c 320c 220 c 320c 220c 320c 220c 320c p p m m m http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 501-508. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 505 increasing the percentage substitution of rha with cement in the block seems to introduce thermal stratification between the outer edge of the block and the holes while reducing further the thermal gradient between the holes and the inner edge resulting in increased thermal resistance. this is further corroborated by figure 5 for temperature variation along section pp (figure 4(d) as example) for all the blocks. figure 5: temperature against length for different rha percentage along section m-m. figure 6: temperature against length for different rha percentage along section p-p. figure 5 shows temperature profile across the solid middle part of the blocks (section m-m) in figure 4(d) as example for others. it can be seen that thermal gradient increases as the % rha substitution increases. from fourier’s equation for heat conduction in solid materials, for the same area and quantity of heat transfer, k is inversely proportional to thermal gradient. this then implies that k should be reducing as thermal gradient increases. therefore, it is then concluded that increasing substitution of rha with cement reduces the thermal conductivity of the block. similar pattern is observed for the temperature profile across the holes, section p-p, figure 6. it is well known that the thermal conductivity of cementitious materials (concrete, blocks, bricks, etc) being within the range of 0.15.0 w/mk is higher than that of air (0.022 w/mk). introducting holes in the block or brick is with the aim of reducing the rate of heat transfer from outside of the building to the cool space within. in their work on modelling heat conduction in conventional and interlocking building bricks with regular and staggered holes, oluleke et al. (2012) assumed no heat transfer through the holes thereby making the cavities to be a vacuum. this assumption however not only suppressed convection but also eliminates heat conduction. in reality, this is not so. this study therefore reconsiders their work for conventional, regular hollow brick with two cavities by relaxing the vacuum assumption. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kamiyo: modelling of heat transfer through hollow blocks produced with rice-husk-ash blended cement. azojete,16(3):501-508. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 506 3.2 brick simulation in this study, the brick is subjected to 40°c outside temperature. with convective heat transfer coefficient of 15 w/m2 °c at the inner side of the brick, the inner temperature was found to be 26.22°c when the thermal conductivity of the solid part is 0.72 w/m °c and the hole a vacuum. the temperature distribution reported, figure 7, showed high thermal stratification on the outer (lower) part of the brick. the vacuum assumption in the holes tends to inhibit heat flow across thereby limiting the heat tranfer to the inner (upper) side to only through the solid part around the holes. this, therefore, affects temperature distribution on the inner side. realistic modeling of the case study reveals different temperature distribution, figure 8. figure 7: temperature distribution within regular hollow brick with two air cavities heated from lower side with the holes as vacuum (oluleke et al., 2012). (a) (b) figure 8: (a) temperature distribution for the brick at steady state, and, (b) temperature against length along sections m-m and p-p. figure 8 shows the temperature distribution for the brick at steady state, figure 8(a), and temperature against length along sections m-m and p-p, figure 8(b). for temperature variation across the solid middle part of the brick (section m-m), the higher temperature at the outer (lower) edge of the brick is maintained to some extent into the brick. resistance to heat flow within the holes due to lower thermal conductivity of air within the hole creates high thermal gradient across the area. this reduces heat flow into the inner (upper) part. the inner temperature is found to be 24.2°c which is lower than 26.22°c reported by oluleke et al. (2012). across section p-p, temperature remains almost constant till the hole is reached. high thermal gradient is shown across the hole due to higher thermal resistance of air. temperature thereafter varies gradually till the inner edge temperature of 24.20c is reached. a similar plot of temperature variation across the section p-p through the hole in the brick of oluleke et al. (2012), figure 7, would have given a plot similar to figure 9. p p http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 501-508. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 507 figure 9: temperature against length along section p-p in figure 6. 4. conclusion heat transfer in convectional hollow sancrete block has been modelled and pattern of heat flow within the block has been analysed. first part of the modelling examined the effect of the substitution of cement with rice husk ash (rha) on the temperature distribution within sandcrete blocks. the result shows that as the percentage substitution of rha increases, thermal gradient across the width of the block increases while the rate of heat flow reduces. this implies addition of rha to the block increases the thermal resistance of the block and makes it suitable wall material for minimizing air-conditioning load in buildings. it is clear that the heat flow through the air-gaps of the building bricks affects pattern of heat flow within the bricks, and hence, could not be regarded as a vacuum.this study could be useful to building professionals in making a choice of building blocks and proper estimation of air-conditioning load in buildings. references adesanya, da. and raheem, aa. 2009. development of corncob ash blended cement. construction and building materials, 23: 347-352. al-tamimi, s., al-osta, a., baghabra, s. and benmansour, r. 2017. effect of geometry of holes on heat transfer of concrete masonry bricks using numerical analysis. arabian journal for science and engineering, 42(9): 3733-3749. al-hazmy, mm. 2006. analysis of coupled natural convection conduction effects on the heat transport through hollow building blocks. energy and buildings, 38 (5): 515-521. ashrae, 2017. ashrae handbook fundamentals. ashrae incorporated. http://www.ashrae.org. balaji, nc., mani, m. and venkatarama, bv. 2014. discerning heat transfer in building materials. energy procedia, 54: 654-668. chandrasekhar, s., satyanarayana, kg., pramada, pn. and raghavan p. 2003. processing, properties and application of reactive silica from rice husk-an overview. journal of materials science, 38(15): 3159-3168. cianfrini, m., vollaro r. and habib e. 2017. dynamic thermal features of insulated blocks: actual behaviour and myths. energies, 10(11): 1807. cisse, ik. and laguerbe, m. 2000, mechanical characterization of filler sandcrete with rice husk ash additions; study applied to senegal. cement and concrete research, 30(1):13–18. costa, vaf. 2014. improving the thermal performance of red clay holed bricks. energy and buildings, 70: 352-364. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kamiyo: modelling of heat transfer through hollow blocks produced with rice-husk-ash blended cement. azojete,16(3):501-508. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okamiyo@unilag.edu.ng 508 ganesan, k., rajagopal, k. and thangavel, k. 2008, rice husak ash blended cement: assessment of optimal level of replacement for strength and permeability properties of concrete. construction and building materials, 22(8): 1675-1683. gijon-rivera, m., serrano-arellano, j., xaman, j. and alvarez, g. 2016. effect of different building materials on conjugate heat and mass transfer. ingeniería mecánica, tecnología y desarrollo, 5(4): 395-404. idan, s. and feldman y. 2017. passive thermal insulation of confined natural convection heat transfer: an application to hollow construction blocks. applied thermal engineering, 124: 13281342. kamiyo, om. and oyekan, gl. 2011. thermal, hygrothermal and structural properties of sandcrete blocks produced with coconut husk ash blended cement. journal of engineering research, 16(3): 80-89. lacarrière, b., lartigue, b. and monchoux, f. 2003. numerical study of heat transfer in a wall of vertically perforated bricks: influence of assembly method. energy and buildings, 35(3): 229-237. li, lp., wu, zg., li, zy., he, yl., and tao, wq. 2008. numerical thermal optimization of the configuration of multiholed clay bricks used for constructing building walls by the finite volume method. international journal of heat mass transfer, 51: 3669-3682. nair, dg., jagadish, ks. and fraaiji, a. 2006. reactive pozzolanas from rice husk ash: an alternative to cement for rural housing. cement and concrete research, 36(6): 1062-1071. okunade, ea. 2008. the effect of wood ash and sawdust admixture on the engineering properties of a burnt laterite-clay brick. journal of applied science, 8(6): 1042-1048. oluleke, o., jacob, j. and henry, n. 2012. finite element modeling of low heat conducting building bricks. journal of minerals and materials characterization and engineering, 11: 800-806. oyekan, gl. and kamiyo, om. 2011. a study on the engineering properties of sandcrete blocks produced with rice husk ash blended cement. journal of engineering and technology research, 3:88-98. rodriguez de sensale, g., ribeiro, ab. and goncalves a. 2008. effects of rha on autogenous shrinkage of portland cement pastes. cement and concrete composite, 30(10): 892-897. shibib, ks., qatta, hi. and hamza ms. 2013. enhancement in thermal and mechanical properties of bricks. journal of thermal science, 17(4 ): 1119-1123. tang, dl., li, lp., song, cf., tao, wq. and he, yl. 2015. numerical thermal analysis of applying insulation material to holes in hollow brick walls by the finite volume method. numerical heat transfer: part a, 68 (5): 526-547. turgut, p. and yesilata, b. 2008. physio-mechanical and thermal performances of newly developed rubber-added bricks. energy and buildings, 40(5): 679-688 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):159-168 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 159 original research article physical properties of four varieties of sorghum (sorghum bicolor l. moench) grain at different moisture contents u. a. kawuyo, n. a. aviara*, h. h. mari, and b. m. ahmed department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: nddyaviara@yahoo.com 1.0 introduction sorghum (sorghum bicolor l. moench) also known as great millet jurra, jowani or mib, is a grass species cultivated for its grain, which is used for food by humans and animals and for bioethanol production. sorghum originated in northern africa and is cultivated widely in the tropical and sub-tropical regions. it is one of the world’s most important cereals which could be processed into flour and used for making diverse food products such as pap, food, and porridge as well as livestock feed (adinoyi et al., 2017). the grain is known for its good source of protein and dietary energy (belton and taylor, 2004). sorghum is also used in industries for the production of biscuits, beverages and pharmaceutical syrups (adinoyi et al., 2017). in developed countries of the world, particularly the united states, ndirika and mohammed (2005) reported that sorghum is grown mainly as feed crops for the production of starch, crystalline sugar and paper adhesive. sorghum can take many shapes and sizes from a tight-headed, wind panicle to an open, droopy panicle that can be short or tall. there are different varieties of sorghum available, and these include red, orange, bronze, tan, white, and black colored sorghum. red, orange, or bronze sorghum is traditionally grown and is used in all segments of the sorghum industry. tan cream and white colored sorghum varieties are typically made into flour for the food industry, while black and burgundy varieties contain beneficial antioxidant properties and are utilized in other food applications. in nigeria the main varieties of sorghum are white, red, brown, and reddish brown (figure 1) and there is a variety called “masakwa” which is grown in southern part of borno (between gwoza and bama local government areas). article information abstract this study was undertaken to determine the physical properties of four varieties of sorghum grain and investigate their variation with moisture content. the properties studied include: axial dimensions, arithmetic mean and geometric mean diameters, one thousand grain weight, particle density, bulk density, porosity and angle of repose. each property was investigated at four moisture levels in the range of 3.5-18.25% d.b (brown variety), 3.04-25.49% d.b (red variety), 3.5-20% d.b (reddish brown variety) and 3.4-25.49% d.b (white variety). the major, intermediate and minor dimensions all increased with increase in moisture content from 4.25-5.04mm, 4.10-4.76mm and 2.80-2.99mm for brown, 3.78-4.32mm, 2.96-3.43mm and 1.95-2.85mm for red, 4.25-5.21mm, 4.11-4.99mm, 3.61-3.77mm for reddish brown, 4.0-5.38mm, 3.20-4.99mm and 3.00-3.48mm for white variety. the arithmetic mean diameter had higher values for the four varieties than the geometric mean diameter. one thousand grain weight, bulk density, true density, porosity, and angle of repose of all the varieties of sorghum studied, increased linearly with increase in moisture content. regression models with high coefficients of determination were used to express the relationship existing between the physical properties of the grains with moisture content. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 nov., 2021 revised 17 february, 2022 accepted 19 february, 2022 keywords: moisture content physical properties sorghum variety http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com file:///c:/users/i3/downloads/nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):159-168. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 160 white variety brown variety red variety reddish brown variety figure 1: matured sorghum grains of different varieties in order to develop equipment for the mechanisation of the handling and processing of sorghum gains, the engineering properties that include physical and thermal properties are needed. these properties determine not only the conveying characteristics of solid materials, but also the heating loads of food materials (baryeh 2002, poomsa-ad et al., 2014). many researchers have reported that moisture content has marked effect on the engineering properties of grains, seeds, and kernels. these include verma and prasad (2000) on mechanical and thermal properties of maize, aviara and haque (2001) on moisture dependence of thermal properties of sheanut kernel, poomsa-ad et al. (2014) on physical and aerodynamic properties of sorghum, kara et al. (2012) on thermal properties of red lentil seeds, aviara et al. (2008) on thermal properties of guna seeds, and tang et al. (1991) on specific heat capacity of lentil seeds. simonyan et al. (2007) determined the physical properties of samaru sorghum 17 grains within the moisture range of 8.89-16.5% (wb), kenghe et al. (2015) studied the physical properties of a new variety of sorghum (cv. phule suchitra) grown in india, as a function of moisture content in the moisture rage of 10.94-2.22% (db), while masane et al. (2016) investigated the effect of moisture content on the physical properties of tender sorghum grains in the moisture rage of 68.5-73.5% (db). in some other studies, shashikumar et al. (2018) and surpam et al. (2019) determined some physical and engineering properties of sorghum grain at the moisture content of 11.69% (wb) and 9.15%, respectively, while sabar et al. (2020) investigated the moisture dependence of physical and engineering properties of a sorghum variety grown in india, in the moisture range of 10-21.8% (wb). from literature, it can be seen that little information appears to be available on the effect of moisture content on the physical properties of sorghum grain varieties grown in nigeria. therefore, the objective of this study was to investigate the moisture dependence of the physical properties (size, one thousand grain mass, bulk density, particle density, porosity, and angle of repose) of four sorghum varieties grown in nigeria. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com kawuyo et al: physical properties of four varieties of sorghum (sorghum bicolor l. moench) grain at different moisture contents. azojete, 18(1):159-168. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 161 2. materials and methods bulk quantities of different varieties in terms of color of sorghum (brown, white, red and reddish brown) used in this study were obtained from of the monday market, maiduguri, borno state, nigeria. the grains were first cleaned to remove foreign matters, broken, and immature grains. samples at different moisture contents were obtained in moisture range of 3-26% (db) using the method of addition of calculated amount of water (aviara et al., 1999). the samples were kept in air tight polythene bags and stored in a cold environment. one hundred seeds were randomly selected at each moisture level for the measurement of the length, width and thickness using a micrometer screw gauge of 0.01mm accuracy. the arithmetic mean diameter was determined by applying equation (1) as given by mohsenin (1986). twenty (20) seeds were used for the determining of this parameter. the average value at each moisture level was recorded and used in analysis. amd = 𝑎+𝑏+𝑐 3 (1) where a = major diameter, mm; b = intermediate diameter, mm and c = minor diameter, mm the geometric mean diameter (gdm) was calculated using the expression given by mohsenin (1986) as follows: 𝐺𝐷𝑀 = (𝐿𝑊𝑇)1/3 (2) where l is length (mm), w is width (mm) and t is thickness (mm) of the grain. according to baryeh (2002), the grain sphericity, ∅ can be determined as follows: ∅ = (𝐿𝑊𝑇) 1 3⁄ 𝐿 (3) one thousand grain weight was determined using a digital electronic weighing balance of 0.001g reading accuracy. this involved random counting of 3 sets of 100 seeds from each variety and placing same on the weighing balance. the average was multiplied by 10 to obtain the required 1000 grain weight. the porosity, ε, of the four varieties of sorghum was determined using the formulae (mohsenin, 1986). 𝜀 = (1 −ρb/ρt) × 100 (4) where: 𝜌𝑏 and 𝜌𝑡 are bulk and true density (g/cm3) respectively. the angle of repose was determined according to mohsenin (1986). the value is expressed by the equation: 𝜃 = 𝑡𝑎𝑛−1(2𝐻/𝐷) (5) where: h is the height from base to peak (mm) and d is the diameter of the base (mm). angle of repose was determined at different moisture contents using the method of specially constructed wooden box with removeable front panel (dutta et al., 1988). each measurement was carried out five times at specific moisture content and the average value was reported. 3. results and discussion the initial moisture content of grain sorghum for brown, red, reddish brown and white varieties was found to be 3.5, 3.04, 3.5 and 3.41% (db), respectively. the moisture contents obtained after conditioning the grains were 13.55, 16.5 and 18.65 %(db) for brown, 11.65, 16.8 and 25.13%(db) for red, 14.21, 15.76, 16.28% and 20% (db) for reddish brown and 12.56, 16.17, and 25.49%(db) for white variety, respectively. the investigations were carried out at the above moisture levels to determine the effect of moisture content on the physical properties of the four varieties of sorghum grains. http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):159-168. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 162 the dimensions of sorghum grains measured at different moisture levels for the four varieties are presented in table 1. the table shows that the axial dimensions were variety dependent and that they increased with increase in moisture content in the range of 3.5 – 18.65% (db) for brown, 3.04 -25.12% (db) red, 3.5 – 20% (db) for reddish brown and 3.41 – 25.49% (db) for white, variety, respectively. the major axis increased from 4.25 to 5.04mm, 3.78 to 4.32mm, 4.25 to 5.21mm and 4.00 to 5.38mm for brown, red, reddish brown, and white sorghum, respectively. the corresponding intermediate axis increased from 4.10 to 4.76, 2. 96 to 3.43, 4.11 to 4.99 and 3.20 to 4.49mm respectively, while minor axis increased from 2.80 to 2.99, 1.95 to 2.85, 3.61 to 3.77 and 3.00 to 3.48mm, respectively. the arithmetic mean and geometric mean diameters of the four varieties of sorghum grain at different moisture contents are also presented in table 1. the table shows increase in arithmetic and geometric mean diameters with increase in moisture content. the arithmetic mean diameter however, had higher values than geometric mean diameter of the grains at a specified moisture level. the increase in axial dimensions of the grains indicated that upon moisture absorption, the grains expanded in length, width and thickness thereby increasing the average dimensions. these could be of important consideration in the determination of seed volume and size of the chute through which the grains could be discharged at different moisture levels. similar results of increase have been reported by tavakkoli et al. (2009) for soybean grains. also, this is in line with the findings of sobukola et al. (2013) on maize grains. the results of the axial dimension can be used in designing of machines for mechanical separation and grading of sorghum grain. the variation of one thousand grain weight of the sorghum varieties with moisture content is presented in figure 1. the figure shows that one thousand grain weight is variety dependent. it increased from 35.05 – 42.85g, 25.8 – 29.00g, 35.00 – 40.11g and 35.6 – 43.5g respectively, in the moisture ranges of 3.5 – 18.65% (db), 3.04 – 25.12% (db), 3.5 – 20% (db) and 3.41 – 25.49% (db) respectively, for brown, red, reddish brown and white sorghum varieties. the positive trend of one thousand seed weight with moisture content may have been due to increase in weight gained at higher moisture contents. the relationship between moisture content and mass of the one thousand grains of the four varieties of sorghum was found to be linear, and can be expressed with the following equations 𝑊𝑏 = 0.3085𝑀 + 36.816, 𝑅2 = 0.974 (6) 𝑊𝑟 = 0.1506𝑀 + 25.124, 𝑅2 = 0.942 (7) 𝑊𝑟𝑏 = 0.4091𝑀 + 33.195, 𝑅2 = 0.931 (8) 𝑊𝑤 = 0.4015𝑀 + 34.966, 𝑅2 = 0.951 (9) where: w is one thousand seed weight of the four sorghum varieties (g), m is the moisture content, r2 is coefficient of determination and subscripts b, r, rb and w represent brown, red, reddish brown, and white varieties, respectively. similar trend was reported by irtwange and igbeka (2002) for african yam bean, kaleemullah and gunasekar (2002) for a sheanut, aviara et al. (2005) for sheanut, isik (2007) for round red lentil grain and simonyan et al. (2007) for samaru sorghum. brown and white varieties had the highest values of one thousand grain weight, while the red variety has the lowest values. the one thousand seed weight can be used to estimate the overall bulk weight and equivalent sphere effective diameter of sorghum grains necessary in the design of the handling equipment. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com kawuyo et al: physical properties of four varieties of sorghum (sorghum bicolor l. moench) grain at different moisture contents. azojete, 18(1):159-168. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 163 table 1: seed size of different varieties of sorghum grain at several moisture contents axial dimension (a) brown variety moisture content (%) db 3.5 13.55 16.5 18.65 major axis (mm) 4.25 4.85 4.87 5.04 intermediate axis (mm) 4.10 4.45 4.49 5.04 minor axis (mm) 2.80 2.98 2.79 2.99 arithmetic mean diameter mm 3.72 4.09 4.18 4.26 geometric mean diameter 3.65 4.00 3.91 4.15 aspect ratio (b/a) 0.97 0.91 0.92 0.94 (b) red variety 3.04 11.65 16.8 25.12 major axis (mm) 3.87 3.78 4.23 4.32 intermediate axis (mm) 2.96 2.96 3.41 3.43 minor axis (mm) 1.95 1.95 2.52 2.85 arithmetic mean diameter mm 2.89 2.89 3.38 3.53 geometric mean diameter 2.79 2.79 3.31 3.48 aspect ratio (b/a) 0.78 0.78 0.80 0.79 (c) reddish brown variety 3.5 14.21 15.6 16.28 major axis (mm) 4.25 5.05 5.10 5.21 intermediate axis (mm) 4.11 4.74 4.82 4.99 minor axis (mm) 3.61 3.25 3.38 3.77 arithmetic mean diameter mm 3.99 4.34 4.43 4.65 geometric mean diameter 3.98 4.28 4.36 4.61 aspect ratio (b/a) 0.96 0.93 0.94 0.95 (d) white variety 3.41 12.56 16.17 25.49 major axis (mm) 4.00 4.75 5.27 5.38 intermediate axis (mm) 3.20 3.99 4.97 4.49 minor axis (mm) 3.00 3.55 3.31 3.48 arithmetic mean diameter mm 3.4 4.09 4.51 4.45 geometric mean diameter 3.37 4.06 4.42 4.38 aspect ratio (b/a) 0.8 0.84 0.94 0.83 figure 1: one thousand-grain weight of sorghum varieties at different moisture contents 20 25 30 35 40 45 50 0 5 10 15 20 25 30 o n e th o u sa n d s ee d w ei gh t, ( g) moisture content, (% db) brown variety red variety reddish brown variety white variety http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):159-168. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 164 the effect of moisture content on bulk density of the four varieties of sorghum is shown in figure 2. the bulk density of the grains was found to increase with increase in moisture content. this increase in bulk density of the seeds may have resulted from increased in mass with moisture content. the relationship between bulk density of the various varieties of sorghum and moisture content was found to be linear and can be represented by the following equations. 𝜌bb = 0.6882m + 697.47, r² = 0.997 (10) 𝜌br = 0.4299m + 751.22, r² = 0.964 (11) 𝜌brb = 0.8028m + 712.44, r² = 0.935 (12) 𝜌bw = 0.3315m + 737, r² = 0.994 (13) where 𝜌b is the bulk density of sorghum, (kg/m3). bulk density was found to be variety dependent with the highest values obtained on the red variety, while the lowest values were from the brown variety. figure 2: variation of bulk density of sorghum varieties with moisture content the true density of the sorghum varieties increased linearly with increased in moisture content as can be seen in figure 3. the relationship between the true density and moisture content of the grain was found to be represented by the following equations. 𝜌𝑡𝑏= 4.0255m + 909.22, r² = 0.982 (14) 𝜌𝑡𝑟= 1.2108m + 867.68, r² = 0.996 (15) 𝜌𝑡𝑟𝑏= 2.7066m + 906.24, r² = 0.990 (16) 𝜌𝑡𝑤= 1.7919m + 882.68, r² = 0.944 (17) where 𝜌𝑡 is the true density of sorghum, (kg/m3). a similar trend with moisture content has been reported for the particle density of cumin seed by singh and goswami (1996) and for sheanut by aviara et al. (2005). true density was also found to be variety dependent. the brown variety had the highest values, while the red variety had the lowest. 690 700 710 720 730 740 750 760 770 0 5 10 15 20 25 30 b u lk d en si ty , k g/ m 3 moisture content, (% db) brown variety red variety reddish brown variety white variety file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com kawuyo et al: physical properties of four varieties of sorghum (sorghum bicolor l. moench) grain at different moisture contents. azojete, 18(1):159-168. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 165 figure 3: true density of sorghum varieties at different moisture contents the porosity calculated from relevant experimental data on true density and bulk density for each variety of sorghum was found to increase with increase in moisture content as shown in figure 4. in the moisture range of 3.5 – 18.65% (db) for brown, 3.04 – 25.12% (db) red, 3.5 – 20% (db) reddish brown and 3.41 – 25.49% (db) for white grains, the porosity increased from 24.29-28.10%, 13.52-17.67%, 21.78-25.12% and 15.55-19.95%, respectively. the relationships between porosity and moisture content for the four varieties of sorghum were expressed as shown in equations (18) – (21). pb= 0.252m + 23.37, 𝑅2 = 0.998 (18) pr= 0.1893m + 12.635, 𝑅2 = 0.9622 (19) prb= 0.1897m + 22.898 𝑅2 = 0.9097 (20) pw= 0.2086m + 14.534, 𝑅2 = 0.9190 (21) where p is the porosity of sorghum (%) and subscript denotes the variety similar trend of porosity with moisture content was reported by carman (1996) for lentil seed and aviara et al., (1999) for guna seed. porosity was also variety dependent. the varieties that had highest and lowest true densities also had the highest and lowest porosity, respectively. figure 4: porosity of sorghum varieties at different moisture contents 860 880 900 920 940 960 980 1000 0 5 10 15 20 25 30 p ar ti cl e d en si ty , ( kg /m 3 ) moisture content, (% db) brown variety red variety reddish brown variety white variety 0 5 10 15 20 25 30 0 10 20 30 p o ro si ty , % moisture content, (%db) brown variety red variety http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):159-168. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 166 the angle of repose of four sorghum varieties determined at different moisture contents is presented in figure 5. it was observed that the angle of repose increased as the moisture content increased for all the sorghum varieties considered in the study. the angle of repose ranged from 24.58-27.11o for brown, 25.6-28.15o for red, 23.12-29.41o for reddish brown and 22.5-26.4o for white variety. it was also observed that angle of repose was not variety dependent and that at higher moisture contents within the experimental range the grains tend to stick together resulting in lower flowability and increase in angle of repose. the relationship between angle of repose and moisture content of the four varieties was found to be linear and it can be represented with the following equations. 𝜃𝑏 = 0.1635m + 23.881, 𝑅2 = 0.8940 (22) 𝜃𝑟 = 0.1137m + 25.212, 𝑅2 = 0.9913 (23) 𝜃𝑟𝑏 = 0.3697m + 21.711, 𝑅2 = 0.9921 (24) 𝜃𝑤 = 0.1823m + 22.084, 𝑅2 = 0.9443 (25) where 𝜃 is angle of repose for sorghum varieties the trend was found to be similar to the one reported by dutta et al. (1988) on gram seed and gupta and das (1997) on other sorghum grains. the information obtained on angle of repose is used in the design of hopper and conveyors in the handling and processing industries. figure 5: angle of repose of sorghum varieties at different moisture contents 4. conclusion the investigation of physical properties of four sorghum varieties at four moisture levels revealed that in the moisture ranges of 3.5 – 18.65 %(db), 3.04 – 25.12%(db), 3.5 – 20%(db) and 3.41 25.49% (db) for the brown, red, reddish brown and white variety, respectively: i) the major, intermediate and minor axial dimensions of the grains all increased with increased in moisture content from 4.25 – 5.04mm, 4.10 – 4.76mm and 2.80 – 2.99mm (brown), 3.78 – 4.32mm, 2.96 – 3.43mm and 1.95 – 2.85mm (red), 4.25 – 5.21mm, 4.11 – 4.99mm and 3.61 – 3.77mm (reddish brown) and 4.00 – 5.08mm, 3.20 – 4.49mm, 3.00 – 3.48mm (white), respectively. the arithmetic and geometric means diameter increased from 3.72 -4.26mm for brown, 2.89 – 3.5mm for red, 3.99 – 4.68mm for reddish brown and 3.4 – 4.45mm for white which the geometric means increased from 3.65 – 4.15mm for brown, 2.77 -3.84mm for red, 3.98 – 4.6mm for reddish brown and 3.37 – 4.38mm for white respectively. ii) one thousand grain weight of sorghum grain increased from38.5 – 42.85g for brown, 25.8 – 29.22g for red, 35.00 40.11g for reddish brown and 35.6 – 43.5g white varieties. 15 17 19 21 23 25 27 29 31 0 5 10 15 20 25 30 a n gl e o f r ep o se , d eg . moisture content, (% db) brown variety red variety reddish brown variety white variety file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com kawuyo et al: physical properties of four varieties of sorghum (sorghum bicolor l. moench) grain at different moisture contents. azojete, 18(1):159-168. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 167 iii) bulk density of the grains increased with increased in moisture content from700.3 – 7103.5kgm3, 753 – 758kgm3, 718 – 728kgm3 and 738.2 – 745.6kgm3 respectively for brown, red, reddish brown and white. iv) the true density increased with increase in moisture content from 925 – 988kgm3 for brown, 871 -889kgm3 for red, 918 – 934kgm3 for reddish brown, and 890 – 899kgm3 for white sorghum grains. v) the porosity of the grains of sorghum investigated as a function of moisture content increased from 24.2928.10% for brown, 13.52 – 14.67% for red, 21.78 – 22.26% for reddish brown and 10.55 – 19.95% for white variety. vi) the angle of repose increased linearly with increased in moisture content from24.8 – 27.11o for brown, 25.6 – 27.15o for red, 25.1 – 27.55o for reddish brown and 22.5 – 26.4o for white variety. references adinoyi, a., ajeigbe, ha., angarawai, ii. and kunihya, a. 2017. effect of grain moisture content on the physical properties of some selected sorghum varieties. 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www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 168 kara, m., boydas, mg., kara, ya. and ozturk, i. 2012. the effect of moisture content on the thermal properties of red lentil seeds. transaction of the asabe, 55(6): 1 6. kenghe, rn., jadhav, ms. and nimbalkar, ca. 2015. physical properties f sorghum (sorghum bicolor) grains as a function of moisture content. international journal of engineering, science research technology, 4(10): 496-504. masane, pk., mate, vn., borkar, pa., murumkar, rp., rajput, mr. and rathod, pk. 2016. physical properties of tender sorghum (sorghum bicolor l.) grains. journal of ready to eat foods, 3(4):51-54. mohsenin, nn. 1986. physical properties of plant and animal materials. gordon and breach science, new york. ndirika, vio. and mohammed, ss. 2005. determination of selected physical properties and their relationship with moisture content for sorghum crop. journal of food technology, 3 (3): 314-318. poomsa-ad, n., wiset, l. and duangkhamchan, w. 2014. effect of moisture content on physical and aerodynamic properties of sorghum. journal of medical and bioengineering, 3(3): 167 170. sabar, ss., swain, sk., behera, d., rayaguru, k., mohapatra, ak. and dash, ak. 2020. moisture dependent physical and engineering properties of sorghum grains. international journal of current microbiology and applied sciences, 9(8): 2365-2375. shashikumar, g., kumaran, s., pandey, m. and rathinakumari, ac. 2018. physical and engineering properties of sorghum grain towards development of spawn spreading machine for oyster mushroom (pleurotus florida) cultivation. the andhra agricultural journal, 65(spl): 175-178. simonyan, kj., el-okene, am. and yiljep, yd. 2007. some physical properties of samaru sorghum 17". agricultural engineering international: the cigr e-journal, manuscript fp07 008. vol. ix. singh, kk. and goswami, tk. 1996. physical properties of cumin seed. journal of agricultural engineering research, 64:93-98. sobukola, op., kajihausa, oe., onwuka, vi. and esan, ta. 2013. physical properties of high quality maize (swam 1 variety) (zea mays l.) seeds as affected by moisture levels. african journal of food science, l7(1): 1 8. surpam, tb., pardeshi, il. and rokade, hn. 2019. engineering properties of sorghum. international journal of chemical studies, 7(5): 108-110. tang, j., sokhansanj, s., yannacopoulos, s. and kasap, so. 1991. specific heat capacity of lentil seeds by differential scanning calorimetry. transactions of the asae, 34(2): 517-522. tavakkoli, h., rajabipour, a. and mohtasebi, ss. 2009. moisture dependence of some engineering properties of soybean grains. agricultural engineering international:the cigr e-journal 1110. vol. xi verma, rc. and prasad, s. 2000. mechanical and thermal properties of maize. journal of food science and technology (mysore), 37(5): 500-505 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/nddyaviara@yahoo.com arid zone journal of engineering, technology & environment azojete june 2020. vol. 16(2):285-292 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 285 original research article an overview of some hydrological models in water resources engineering systems u. a. ibrahim1* and s. dan’azumi2 (1department of civil and water resources engineering, university of maiduguri 2department of civil engineering, bayero university kano) *corresponding author’s email address: uaibrahim@unimaid.edu.ng 1.0 introduction the science of hydrology deals with the occurrence and movement of water on and over the surface of the earth. it also deals with the various forms of moisture that occur, and the transformation between the liquid, solid, and gaseous states in the atmosphere and in the surface layers of land masses (wilson, 1990). water-related challenges are large and are likely to increase in the future (tundisi, 2008). current and future water-related challenges are location and time specific and these include wide myriad of issues such as fluvial hydraulics, reservoir operations, water quality issues in rivers, and the impact of climate change among others. in response to these challenges, hydrological models have been developed to understand, analyze, and explore sustainable solutions to water resources management. article information abstract researches in hydrological modelling are aimed to the understanding of the behavior of hydrologic systems in an attempt to make better predictions and to address the major challenges in water resources systems. hydrological modelling concept is concerned with the relationship of water, climate, soil and land use. hydrological models are classified either as: conceptual or physical, lumped or distributed, deterministic or stochastic. hydrological models are the main tools that hydrologist use with different purposes such as water resources management, storm water management, reservoir system analysis, flood prediction, climate change assessment and among others. many hydrological models have been developed for different purposes. the methodology for using hydrological models include: definition of the problem and specifying the objectives, studying the data available, specifying the economic and social constraints, choosing a particular class of hydrological models, selecting a particular type of model from the given class, calibrating and validating the model, evaluating the performance of the model, and finally using the model for the specified purpose. some recently developed, frequently used, and powerful hydrological models including weap, swmm, hec-hms, hec-ras, and hec-ressim were herein assessed taking into cognizance their applications in solving challenges in water resources engineering systems. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 may, 2019 revised 25 february, 2020 accepted 28 february, 2020 keywords: hydrology modeling prediction climate change water mailto:uaibrahim@unimaid.edu.ng http://www.azojete.com.ng ibrahim and dan’azumi: an overview of some hydrological models in water resources engineering systems. azojete,16(2):285-292. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 286 hydrological models are simplified conceptual representation of a part of the hydrologic cycle, and are primarily used for hydrologic prediction and understanding of the hydrologic and water resources systems (gayathri et al., 2015). with the advancements in the field of hydrology and water resources coupled with the application of computers in the field, institutions and scientists are prompted to develop variety of softwares for designing and modelling of water resources systems. some of these models include but not limited to water evaluation and planning (weap), storm water management model (swmm), hydrologic engineering centerhydrologic modeling system (hec-hms), hydrologic engineering center-river analysis system, (hec-ras), and hydrologic engineering center-reservoir system simulation (hec-ressim) to achieve speedy and accurate modelling compared to the traditional methods. this paper reviewed some hydrological models and presents a number of available public domain (free) and commercial softwares that are used in hydrologic and water resources systems modelling. 2. hydrological modelling modelling is a simplified representation of a complex system. thus, most hydrologic systems are extremely complex and their behaviors cannot be understood in detail, but through experience, scientists were able to model and predict the behavior of environmental change (chong-yu, 2002).the best model is the one which gives results close to reality with the use of least parameters and model complexity. models were designed to aid generation of synthetic sequences of hydrologic data for facility design or for use in forecasting potential impacts of changes in landuse or climate (chong-yu, 2002; gayathri et al., 2015). 2.1 classification of hydrological models hydrological models may be classified as conceptual or physically-based models according to the description of the physical processes, which considers the physical laws but in highly simplified form; lumped or distributed models according to the spatial description of catchment processes, which considers the homogeneity of a process; deterministic or stochastic models according to the information about the physical processes involved, which considers probability distribution of the process (gayathri et al., 2015). 2.2 selection of a hydrological model hydrological practice would be improved if models are objectively chosen on the basis of making the best use of the information available and following some systematic procedure of selection and verification. however, the choice of the best model depends to a large extent on the prevailing problem and should incorporate accuracy of prediction, simplicity of the model, consistency of parameter estimates and sensitivity of results to changes in parameter values. 2.3 model calibration and validation for any chosen model, there are some constants used to represent the physical process. these constants are called parameters of the model, and must be assigned fixed numerical values before the model may be used for prediction (stadnyk et al., 2013). calibration is a process of adjusting the parameters of the model to appropriately simulate historical observations. calibrating a model involves both quantitative and qualitative evaluation of the hydrologic response of the catchment. validation of a model after the parameter values were estimated is the third level of model analysis. model validation is also referred to as "diagnostic checking". as no model is perfect, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 285-292. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 287 verification requires both subjective and objective judgments on many aspects to determine whether the results provide adequate information for answering the question facing the decision-makers (stadnyk et al., 2013).faulty results may stem from a variety of causes, such as errors in the data used in calibration, use of a period of record that does not contain enough events of the physical processes and inadequate or misrepresentation of hydrological processes in the model. 2.4 model performance evaluation the evaluation of model performance is indispensable to examine both accuracy and reliability of models (pachepsky et al., 2016). the common model evaluation statistical indices used in hydrology include the nash-sutcliffe efficiency, nse (nash and sutcliffe, 1970; bai et al., 2009), the percent bias, pbias (leong and lai, 2017), and the coefficient of determination, r2 (pachepsky et al., 2016; leong and lai, 2017) among others. the nash-sutcliffe model efficiency (nse) assesses the predictive power of a hydrological model and indicates how well the plot of observed versus simulated data fits the 1:1 line (leong and lai, 2017). it is given by eqn. 1 nse = 1 − i=1 n qi obs−qi sim 2 � i=1 n qi obs−q�obs 2 � (1) where: qi obs = ith observed data qi sim = ith simulated data q�obs = mean of observed data nse ranges between −∞ and 1.0 (1 inclusive). when; nse = 1 it implies a perfect match of simulated to the observed data (optimal value). nse values between 0.0 and 1.0 are generally viewed as acceptable levels of performance, whereas values < 0.0 indicates that the mean observed value is a better predictor than the simulated value, which indicates unacceptable performance. essentially, the closer the nse is to 1, the more accurate is the model. percent bias (pbias) measures the average tendency of the simulated data to be larger or smaller than their observed counterparts. the optimal value of pbias is 0.0, with low values indicating accurate model simulation. positive values indicate model underestimation bias, and negative values indicate model overestimation bias (leong and lai, 2017). pbias is expressed as eqn. 2; pbias = i=1 n qi obs−qi sim� × 100 i=1 n qi obs� (2) where: qi obs = ith observed data qi sim = ith simulated data the coefficient of determination (r2) outlines the degree of co-linearity between simulated and observed data. it further describes the proportion of the variance in measured data explained by the model. its value ranges from 0 to 1, higher values indicating less error variance. values that are greater than 0.5 are considered acceptable (santhi et al., 2001). the computation of r2 is shown as equation 3: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ibrahim and dan’azumi: an overview of some hydrological models in water resources engineering systems. azojete,16(2):285-292. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 288 r2 = i=1 n qi sim−q�sim� qi obs−q�obs i=1 n qi sim−q�sim 2 � i=1 n qi obs−q�obs 2 � (3) where: qi sim = ith simulated data qi obs = ith observed data q�sim = mean of simulated data q�obs = mean of observed data 3. brief description of some hydrological models and their applications 3.1 weap weap was developed by stockholm environment institute, usa for integrated water resources planning. it provides a comprehensive, flexible and user-friendly framework for analysis. the software of this model is commercial available, but it is free for students and academic organizations in developing countries for a period of one year only. weap attempts to assist rather than substitute for the skilled planner. as a database, weap provides a system for maintaining water demand and supply information. as a forecasting tool, weap simulates climate change impacts on water demand, supply, flows, storage and pollution generation, treatment and discharge. as a policy analysis tool, weap evaluates a full range of water development and management options, and takes account of multiple and competing uses of water systems. operating on the basic principle of a water balance, weap is applicable to municipal and agricultural systems, single catchments or complex trans-boundary river systems. moreover, weap can address a wide range of issues, such as sectoral demand analyses, water conservation, water rights and allocation priorities, groundwater and stream-flow simulations, reservoir operations, hydropower generation, pollution tracking, ecosystem requirements, vulnerability assessments, and project benefit-cost analyses (sei, 2016). one of the advantages of the model over others is that it places the demand side of the water balance equation on equivalence with the supply side, and proffer solutions to some problems of water decision support systems. however, the model rely solely on the development of scenarios that can be quantified, placing less concern over their development for which some are outside the system architecture. in assessing the effects of climate change on river systems, kumar et al. (2018) evaluates the future stress of pasig-marikina river, manila, philippines, due to combined effect of climate change and rapid urbanization. in their studies, pasig-marikina river was analysed for current and future timescale using population growth, land use change, wastewater production and treatment scenarios, for three indicators of aquatic ecosystem health; biochemical oxygen demand (bod), chemical oxygen demand (cod) and nitrate (no3). the results clearly indicate that the water quality in the future will rapidly deteriorate and will not be suitable for any aquatic life in terms of water quality. hence, it called for immediate and inclusive action by policy makers. thus, the model was able to inform decision makers on the need for implementation of integrated sewerage and seepage management programme on priority basics considering population density and growth changes for both short and long term measures. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 285-292. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 289 3.2 hec-hms hec-hms is a product of the hydrologic engineering center (hec) within the united states army corps of engineers. it is a public domain software and was designed to simulate the complete hydrologic processes of dendritic watershed systems. the software of this model includes many traditional hydrologic analysis procedures such as event infiltration, unit hydrographs, and hydrologic routing. it also includes procedures necessary for continuous simulation such as evapotranspiration, snowmelt, and soil moisture accounting. it also features a completely integrated work environment including a database, data entry utilities, computation engine, and results reporting tools. it is a graphical user interface (gui) that allows the user seamless movement between the different parts of the software. as a numerical model, it can predict runoff volumes, peak flows and timing of flows by simulating the behavior of the entire watershed. the model offers a number of advantages over other hydrological models because it can be applied to watersheds of varying size, shape and parameters. also, calibration is performed using optimization algorithm. more so, it is compatible with other hec-programs due to common data storage system. however, it cannot model back water in a stream network, and no support is provided for users other than u. s. army corps of engineers. simulation results are stored in hec-dss (data storage system) and can be used in conjunction with other software for studies of water availability, urban drainage, flow forecasting, future urbanization impact, reservoir spillway design, flood damage reduction, floodplain regulation, and systems operation (usace, 2002). abdullah et al., (2018), used hec-hms 4.1 software to predict the runoff and sediment load inflow to hemrin reservoir, in baghdad for the period of 1981 – 2014. the calibration processes were performed using field measurement data for flow of water from diyala river. the result obtained showed that the load of sediment entering the reservoir is directly affected by the precipitation received by the basin. this occurs during the peak precipitation period which is normally november every year accounting to 94% of sediment entering the reservoir. thus, management strategies need to be implemented to control sediment deposit in the river. 3.3 swmm swmm is a public domain software developed by water supply and water resources division of the u.s. environmental protection agency's national risk management research laboratory. the software of this model is a dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas. the runoff component of swmm operates on a collection of sub catchment areas that receive precipitation and generate runoff and pollutant loads. the routing portion of swmm transports this runoff through a system of pipes, channels, storage/treatment devices, pumps, and regulators. swmm tracks the quantity and quality of runoff generated within each sub catchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period comprised of multiple time steps (lewis, 2015). the model simulate pollutant loading and is capable of importing world coordinate files and exporting dxf files. however, the software is analytical and not design tool, and cannot model manhole or inlet loss directly. urban flood modelling evaluates storm drain capacities, blockage of storm drains, climate change and improper storm network planning. a study conducted by swathi et al. (2018) evaluated the applicability of swmm in analyzing storm network flooding at birla institute of technology and science (bits), pilani-hyderabad campus, india. the model was calibrated for 2006 rainfall event using horton and dynamic wave methods for infiltration and flow routing of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ibrahim and dan’azumi: an overview of some hydrological models in water resources engineering systems. azojete,16(2):285-292. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 290 the watershed respectively. the results showed that there were no nodes flooded and no overflow sections in the entire catchment. thus, it was concluded that the campus storm network system has been well planned and has sufficient carrying capacity to cater the simulated rainfall event. bedient et al., (2007) modeled urban flood using two softwares hec-hms and swmm. they created hydrographs in hec-hms which were treated as input to nodes for storm drain network in swmm. the results obtained from study clearly demonstrated usefulness and understanding of the storm network. 3.4 hec-ras hec-ras was developed by the hydrologic engineering center (hec). hec-ras is a public domain software designed for interactive use in a multi-tasking environment. the system is comprised of a graphical user interface (gui), separate analysis components, data storage and management capabilities, graphics and reporting facilities. it was designed to perform onedimensional steady flow; and one and two-dimensional unsteady flow calculations for a full network of natural and constructed channels, overbank/floodplain areas, levee protected areas, sediment transport/mobile bed computations, and water temperature/water quality modeling (usace, 2016). the software has the ability to import data from other software’s like mike ii cross section. also, all its components use a common geometric data representation and common geometric and hydraulic computation routines. however, modelling skews of hydraulic structures is limited to zero, and cannot currently account for steep slopes above 10% inside the model. estimating the magnitude of flash flood including water velocity and depth for a river system can be simulated using hec-ras. ezz (2017) used arcgis and hec-ras tools to model the water depths and velocities along a flood path on assiut plateau in egypt using estimated peak discharge flows developed from high rainfall events uniformly over the plateau. the predicted water levels were compared with the proposed road level passing through the flood path for two rainfall events scenarios. both scenarios showed that the water levels in the flood path is safely lower from the proposed road. yet, it was recommended to install a proper flood protection system at the intersection of the tributaries with the main flood path under the proposed road. this could help the decision makers in protecting the proposed road and to minimize flood hazards. 3.5 hec-ressim hec-ressim is a public domain software developed by the u.s. army corps of engineers, institute for water resources, hydrologic engineering center. it is used to model reservoir operations at one or more reservoirs for a variety of operational goals and constraints. the software simulates reservoir operations for flood management, low flow augmentation and water supply for planning studies, detailed reservoir regulation plan investigations, and realtime decision support. hec-ressim can represent both large and small scale reservoirs and reservoir systems through a network of elements (junctions, routing reaches, diversion, and reservoirs) that the user builds. the software can simulate single events or a full period of record using available time-steps (usace, 2013). the software models improvement, efficiency and effectiveness of existing reservoir. however, it does not model water quality and, streamflow hydrographs are generated elsewhere and imported to the model. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2020; vol. 16(2) 285-292. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 291 simulation of reservoir systems using hec-ressim was applied by calvo-gobbetti (2017) for evaluating of different projects for new water sources in the panama canal. the model was used to evaluate the discharges in spillways during the rainy months, hydroelectric generation at gatun and alhajuela lakes, volumes available for navigation, municipal and industrial consumption at gatun lake and volumes supplied at alhajuela lake for municipal and industrial use. comparison was made to the storage–yield relationships of the reservoir systems developed by vogel et al., (1999).the results indicated the generality of storage–yield curves, which are similar to those developed by vogel et al., (1999), and can be used as guides for the development of new water source projects. 4. conclusion five hydrological models were reviewed: weap, hec-hms, swmm, hec-ras and hec-ressim. each model has its unique features and corresponding applications. some of them are comprehensive in using hydrological processes distributed over space and time. the models are used for flood forecasting, water resource systems planning, watershed management, reservoir simulation, erosion and sedimentation, life loss and economic changes, land use and climate change etc. furthermore, three different statistical performance evaluation criteria were discussed for model assessment and identifying its accuracy in simulation. a proper knowledge of hydrologic processes and characteristics is necessary otherwise it will create adverse effect on model calibration. however, researches are still going on to make better predictions and to face major challenges. references abdullah, th., jalut, qh. and ameen, yw. 2018. hydrologic modeling for sedimentation in hemrin reservoir using hec-hms. diyala journal of engineering sciences, 11(4): 67-72. bai, y., wagener, t. and reed, p. 2009. a top-down framework for watershed model evaluation and selection uncertainty. environmental modelling softwares, 24: 901-916. bedient, pb., holder, aw., thompson, jf. and fang, z. 2007. modeling of storm-water response under large tail water conditions: case study for the texas medical center. journal of hydrology and engineering, 12(3): 256–266. calvo-gobbetti, le. 2017. application of hec-ressim® in the study of new water sources in the panama canal. journal of applied water engineering and research, 6(3): 236-250. chong-yu, x. 2002. hydrologic models (new ed.). sweden: uppsala university, pp.168. ezz, h. 2018. integrating gis and hec-ras to model assiut plateau runoff. egyptian journal of remote sensing space and science, 21: 219–227. gayathri, kd., ganasri, bp. and dwarakish, gs. 2015. a review on hydrological models. aquatic procedia, 4: 1001 – 1007. kumar, p. masago, y., mishra, bk. and fukushi, k. 2018. evaluating future stress due to combined effect of climate change and rapid urbanization for pasig-marikina river, manila. groundwater for sustainable development, 6: 227–234. leong, wk. and lai, sh. 2017. application of water evaluation and planning model for integrated water resources management: case study of langat river basin, malaysia. in: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ibrahim and dan’azumi: an overview of some hydrological models in water resources engineering systems. azojete,16(2):285-292. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 292 international technical postgraduate conference: materials science and engineering, 210. proceedings of a meeting held in kuala lumpur, malaysia, 5-6 april 2017. iop proceedings 210, 663p. lewis, ar. 2015. storm water management model user’s manual version 5.1. u.s. environmental protection agency epa/600/r-14/413b. diane publishing co, darby pa, usa. nash, je. and sutcliffe, jv. 1970. river flow forecasting through conceptual models, part i – a discussion of principles. journal of hydrology, 10: 282-290. pachepsky, ya., martinez, g., pan, f., wagener, t. and nicholson, t. 2016. evaluating hydrological model performance using information theory-based metrics. hydrological earth systems and science discuss, 20(2): 974-993. santhi, c., arnold, jg., williams, jr., dugas, wa., srinivasan, r. and hauck, lm. 2001. validation of the swat model on a large river basin with point and nonpoint sources. journal of the american water resources association, 37: 1169-1188. sei. 2016. weap tutorial: a collection of stand-alone modules to aid in learning the weap software [user manual]. stockholm environment institute, stockholm, sweden. http://www.weap21.org/index.asp?action=213.pdf accessed december, 2018. stadnyk, ta., delavau, c., kouwen, n. and edwards, twd. 2013. towards hydrological model calibration and validation: simulation of stable water isotopes using the isowatflood model. hydrological processes, 27(25): 3791-3810. swathi, v. srinivasa, r. and singh, ap. 2018. application of storm water management model to an urban catchment. hydrologic modeling, 81: 175-184. tundisi, jg. and scheuenstuhl, m. 2008. bridging water research and management: new perspectives for the americas. iie, iibrh, ianas: brazilian academy of sciences, rio de janeiro, brazil, pp. 58. u. s. army corps of engineers (usace). 2002. hydrologic modelling system, hec-hms, applications guide. ford, d., pingel, n. and devries, j. j.: u.s. army corps of engineers, hydrologic engineering center, california, usa, pp. 113. u. s. army corps of engineers (usace). 2013. reservoir system simulation, hec-hms, user’s manual, version 3.1. klipsch, j. d. and hurst, m. b.: u.s. army corps of engineers, hydrologic engineering center, california, usa, pp. 556. u. s. army corps of engineers (usace). 2016. river analysis system, hec-ras, user’s manual, version 5.0. brunner, g. w.: u.s. army corps of engineers, hydrologic engineering center, california, usa, pp. 962. vogel, rm., lane, m., ravindiran, rs. and kirshen, p. 1999. storage reservoir behaviour in the united states. journal of water resources planning and management, 125: 245–254. wilson, em. 1990. engineering hydrology (fourth ed.). hampshire: macmillan education ltd., pp. 348 http://www.weap21.org/index.asp?action=213.pdf http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete, september 2019. vol. 15(3) 662-677 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 662 original research article properties of asphalt concrete containing waste foundry sand (wfs) as filler material a. a. shuaibu*, h. s. otuoze, a. mohammed and m. a. lateef (department of civil engineering, ahmadu bello university, zaria, nigeria) * corresponding author’s email address: tightmybet@gmail.com, abdulshub4u@gmail.com article information submitted 22 november, 2018 revised 7 march, 2019 accepted 10 march, 2019 keywords: waste foundry sand marshal stability flow void analysis asphalt concrete wearing course abstract the high cost of primary construction materials such as cement, and increase in waste generation due to human activities coupled with environmental concerns has led to the incorporation of wide range of waste materials into asphalt concrete. waste foundry sand (wfs) which is a by-product of ferrous and non-ferrous metal casting industry, has accumulated in stockpiles and landfills, occupying valuable space and causing nuisance in the environment. consequently, it is imperative to devise a safe and economical solution to manage and utilize the waste. one way of achieving this is by recycling and using it for asphalt concrete production. this study investigated the strength and durability properties of asphalt concrete containing waste foundry sand (wfs) as alternative filler material in asphalt concrete. marshall design method was adopted for the sample preparation and testing. fifteen (15) compacted samples were prepared for strength and volumetric properties testing at varying bitumen contents of 4.5%, 5.0%, 5.5%, 6.0% and 6.5%, in accordance with asphalt institute and nigeria general specification for road and bridges to determine optimum bitumen content (obc). obc of 5.5% was obtained and used for the asphalt concrete mixes in the study. eighteen (18) other briquettes were prepared to determine the optimum wfs content in asphalt concrete necessary for strength and durability of wearing course of flexible pavement. cement as filler in asphalt concrete was partially replaced with wfs using the obtained obc in the order of 10%, 20%, 30%, 40%, 50% and 60%. a total of thirty-three (33) standard specimens were prepared. from the marshall stability-flow and void-density results, the sample prepared with 60% wfs as filler with obc of 5.5% satisfies the provision of the nigerian general specification for road and bridges (ngsrb) for use in wearing course of flexible pavement. based on the analysis of results obtained in this study and a logical comparison made with standard specifications, addition of up to 60% waste foundry sand (wfs) in asphalt concrete would lead to significant conservation of primary construction materials, divert substantial quantities of waste from landfills and present a cheap alternative of filler material necessary for sustainable asphalt concrete construction. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the rapid industrial and agricultural activities of man has led to the generation of large tonnes of waste (such as scrap tires, foundry sand, glass, waste foundry sand, steel slag, plastics, mailto:4tightmybet@gmail.com mailto:abdulshub4u@gmail.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 663 construction and demolition wastes, rice husk, bagasse, coconut shell, mesocarp fibre, and others) which accumulate in stockpiles and landfills throughout the world. aside not easily degraded, these wastes occupy valuable space and constitute nuisance to the environment. additionally, the construction industry relies hugely on conventional construction materials; such as sand, granite, cement and bitumen for mortar, concrete and asphalt production. the high cost and environmental hazard attributable to the production of materials, such as cement, has necessitated the incorporation of wide range of waste materials in the construction technology. consequently, there is high interest in the development and utilization of waste materials in asphalt production amongst researchers and highway practitioners to enhance pavement quality, reduce cost and curb negative environmental effects. ordinary portland cement (opc) is a popular brand of cement widely used in the preparation of mortar, concrete, paste and asphalt concrete because of its high binding and filling characteristics. in most countries and particularly nigeria, it is expensive and often time scarce (tsado et al., 2014) and this has influence on the price of infrastructure construction. kaura et al. (2016), reported that the manufacturing process of ordinary portland cement (opc) which is convectional filler used in asphalt concrete contributes up to 7% of the co2 emission and this causes greenhouse effect on the environment. this trend is adding 1.6 billion tons of co2 into the atmosphere (mehta, 2001). with considerable effort to reduce the global warming effect by reducing co2 emission, scarcity of landfill space from improper waste foundry sand (wfs) disposal, dependency and cost of cement for producing asphalt concrete, researchers have long been in a search for alternative material with pozzolanic properties to serve as supplement for cement (kaura et al., 2016). in general terms, "pozzolana" as “a siliceous or siliceous and aluminous material, which in itself possesses little or no cementing property, but will in a finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties" (malhorta and mehta, 1996). the efficient use of locally available materials is necessary in building of economically viable and sustainable roads. to this end, there is need for the design engineer to possess thorough understanding of each constituent material properties that affect pavement stability and durability (brennan and o’flaherty, 2002). filler in bituminous mixes is defined as material with particle size less than 0.075 mm, which may originate from fines in the aggregate or added in the form of cement, lime and ground rock. portland cement or hydrated lime is often added to natural filler (1 to 2 per cent by mass of total mix) to improve adhesion of bitumen and stiffening of bitumen-fine matrix (orn 19, 2003). it also has a function of filling voids remaining after the other mineral aggregates present in asphalt concrete interlock. these functions of the filler are cardinal in contributing to the strength and deformation resistance of the asphalt concrete in service. in recent times, a wide range of waste materials obtainable from agricultural and industrial activities in their natural or processed forms have been used in the production of asphalt concrete. waste materials such as palm oil waste ash, rice husk ash, palm kernel shell ash, periwinkle shell ash, kaolin, metakaolin, corncob ash, millet husk ash, coal bottom ash, slag, fly ash and blast furnace slag (murana et al., 2014; sadeeq et al., 2014; murana and sani, 2015; oluwaiwo and owolabi, 2015; nwaobaka and agunwamba, 2014; mistry and roy, 2016; suji et al., file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 664 2016; abu salem et al., 2017) have been assessed for suitability of incorporation into asphalt concrete. nonetheless, literature report on the use of waste foundry sand in asphalt concrete is still very limited. tsado et al. (2014) reported that up to 70% of portland cement can be replaced by using materials such as primarily fly ash silica fume, natural pozzolana, rice husk ash; wood ash and agricultural product ash. these supplementary cementatious materials play an important role when added to portland cement because they usually alter the pore structure of concrete to reduce its permeability, thus increasing its resistance to water penetration and water related deterioration such as reinforcement corrosion, sulphate and acid attack (padmavathi and preethika, 2016). foundry is one of the most ancient methods of metal forming (aramide et al., 2011). metal foundries utilize high quality sands in production of metal castings. the sand is recycled and reused multiple times in the process until it loses its characteristics and thus, discarded (rashid et al., 2014). foundry sand discarded by foundries is called waste foundry sand (wfs) or spent foundry sand (sfs) and they can either be recycled in a non-foundry application or used as landfills (aramide et al., 2011). according to jalali (2009), waste foundry is a mixture of sand residues from metal casting process and variety of binders. it is the by-product of ferrous and non-ferrous metal casting industry, its physical and chemical properties depends upon: type of metal being poured, casting process, type of binder system, type of furnaces and type of finishing process like grinding, blast cleaning and coating (singh et al., 2012). there are about 35,000 foundries in the world with annual production of 90 million tonnes. in terms of number of foundries, china has the highest score (9374), followed by india (6000) (siddique et al., 2013). aramide et al. (2011) submitted that only less than fifteen percent (15%) of the annually produced waste foundry sand can be safely and economical recycled. this is a clear indication that this waste need to be evaluated for its suitability in construction industry applications where its use can be maximized. depending on type of binder systems used in metal casting process, waste foundry sands are classified as; clay bonded sand (green sand) and chemically bonded sands (petavratzi and wilson, 2007). green sand is the most common type and it consists of silica sand, bentonite clay (~ 10% by weight), 2 to 5% water and about 5% coal dust (improves casting finish) (petavratzi and wilson, 2007). green sand is normally reused and can therefore contain burnt fines, coke residues and residual clays. chemically bonded sand involves the use of organic and inorganic binders in conjunction with catalysts and different hardening/setting procedures (petavratzi and wilson, 2007). the type of wfs used in this study is the green sand. a considerable amount of experimental work have been carried out by various researchers on the use of industrial waste product as replacement of mineral aggregates in the construction industry. siddique and kaur (2013) partially replaced natural sand with waste foundry sand to evaluate the strength and durability properties of self-compacting concrete; they observed that there is increase in compressive strength, splitting tensile strength of self-compacting concrete by incorporating waste foundry sand as partial replacement for sand up to 15%. resistance of concrete against sulphate attack and rapid chloride permeability were also improved for http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 665 concrete mixes. petavratzi, and wilson, (2007), investigated the use of foundry sand as partial replacement for the primary sand. results obtained were positive regarding the inclusion of foundry sand within 2.5 and 5% as a primary sand substitute into bricks. they concluded that foundry sand could replace primary sand in brickworks. joni, and zghair, (2016), carried out research on the effect of adding used foundry sand as alternative to fine and filler materials in hot mix asphalt. to evaluate the mechanical properties, the marshall mix design was adopted to design mix which contained foundry sand as filler and a comparison was made with mix containing two other types of fillers (ordinary portland cement and lime stone dust). the results from the study revealed that foundry sand can be used in asphalt concrete as partial replacement of fine aggregate and total replacement of filler material. though, considerable efforts have been devoted towards the use of industrial by-product for asphalt production, there have been scarcity of information on the use of waste foundry sand (wfs) in asphalt concrete production in nigeria. the focus of this study therefore, is to investigate the possibility of recycling and using waste foundry sand for sustainable costeffective construction of wearing course of roads in nigeria. the above aim was achieved through the following objectives: i. performance of physical properties tests on waste foundry sand (wfs) to ascertain its suitability for use in asphalt concrete. ii obtaining the chemical composition of waste foundry sand (wfs) using x-ray fluorescence (xrf) and classify it based on (astm c618, 2003) classification of pozzolana. iii. determination of optimum binder content (obc) for asphalt concrete production and finally find out the effect of adding different percentage of waste foundry sand (wfs) on the stabilityflow and void-density properties of asphalt concrete to be used in highway wearing course. the findings of this study could lead to a probable solution to waste management problem plaguing every country, reduction in demand for cement, freeing of valuable land space and ultimately enhancing cost effective production of road infrastructure with improved performance. 2.0 materials and methods 2.1 materials materials used for this study are as follows; bitumen coarse aggregate and fine aggregate mineral filler (waste foundry sand wfs and cement) the coarse and fine aggregates were obtained from nagarta local quarry, sokoto road, zaria, kaduna state, nigeria. the ordinary portland cement used is that of dangote 3x brand and obtained from samaru market in zaria, kaduna state. bitumen used is penetration grade bitumen obtained from nigerian national petroleum cooperation (nnpc), kaduna state. waste foundry sand (wfs) was gotten from defense industry corporation of nigeria (dicon), kaduna state. 2.2 methods the section briefly discussed the methods employed in the experimental tests carried out to determine the physical properties of bitumen, coarse aggregate, fine aggregate, cement and the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 666 chemical properties of waste foundry sand (wfs). also, the method adopted for sample preparation and testing was highlighted. 2.2.1 test on coarse aggregates test conducted on the coarse aggregates are (aggregate impact value/hardness test (bs 812 part 111), aggregate crushing value (bs 812 part 112), aggregate specific gravity (astm, c127), size and gradation (bs 812-103.2). 2.2.2 test on fine aggregates the tests conducted on the fine aggregates are: specific gravity (astm 128), sieve analysis (bs 812-103.2) analysis, and water absorption (bs 812 part 3) 2.2.3 test on mineral aggregate (cement and wfs) experimental test on cement are; initial and final setting time (bs en 196 part 3), soundness test (bs en 196 part 3), and specific gravity (astm c188). test on waste foundry sand are; bulk relative density (astm d854), and specific density (astm d854). another test carried out on the wfs is x-ray fluorescence (xrf). elemental analysis on wfs was conducted in chemistry department, ahmadu bello university, zaria using energy dispersive spectrometer designed for detection and measurement of elements in a sample. the analysis was carried out according to (astm c618). 2.2.4 test on bitumen tests on bitumen are: penetration test (astm d5), solubility test (astm d4), viscosity test (astm d2170), ductility test (astm d113), flash and fire point test (astm d92), specific gravity test (astm d70) and softening point (astm d36). 2.3 marshall test experimental plan and specimen preparation asphalt institute (1994) recommendations were used to prepare specimens weighing 1200g, 101.5 mm diameter and 63.5 mm height compacted with 75 hammer blows on each side to simulate heavy traffic situation. the specimens are tested for bulk specific gravity in accordance with astm d1559 (2000). the specimens are kept immersed in water in a thermostatically controlled water bath at 6000c for 30 to 40 minutes and transferred within 30 seconds to the marshall test head where they are tested for marshall stability and flow in accordance with astm d1559 (2000). the volumetric test carried out are cdm, vma, vim and vfb. theoretical maximum specific gravity of the mix (gmm) were determined using astm d 2041-95 and bulk specific gravity or compacted density of the mix (cdm) using astm d1188-96. astm d3203-94 was used to estimate void in the mix (vim). astm d1559 (2004) was used to determine the stability and flow of specimens. to determine the optimum bitumen content, the relationships between binder content and the properties of mixtures such as stability, flow, bulk density, voids filled with bitumen (vfb), void in mineral aggregate (vma) and void in mix (vim) at no wfs replacement (control) were established. three (3) specimens each were made for five bitumen content (4.5, 5.0, 5.5, 6.0 and 6.5%) in accordance with asphalt institute specifications, making a total of twelve (15) samples. the optimum binder content is selected as the average binder content for maximum density, maximum stability and specified percent air voids in the total mix. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 667 furthermore, same procedure of designing asphalt paving mixture was followed to prepare samples with different waste foundry sand and utilizing the optimum binder 3.0 results and discussion 3.1 bitumen test the preliminary test conducted on bitumen revealed that the bitumen is of 60/70 penetration grade. it satisfies various codes requirements for ductility, softening point, specific gravity, solubility and flash and fire point tests. thus, the bitumen is adjudged suitable for asphalt concrete production. the result of test carried out on bitumen is as presented in table 1 below. table 1: preliminary test result and code limits on the bitumen test conducted astm code test result code limit penetration at 25°c, 0.1mm astm d5-97 64.7 60 – 70 softening point (°c) astm d36-95 48.5 46 – 56 flash point (cleveland open cup) °c astm d92-02 248 min. 232 fire point (cleveland open cup) °c astm d92-02 256 min. 232 ductility at 25°c, cm astm d113 116 min. 100 specific gravity at 25°c, (g/cc) astm d70 0.98 0.97 – 1.02 solubility in trichloroethylene, % astm d2042 99 min. 99 3.2 preliminary tests on aggregates ‘‘aggregate suitability affects physical and mechanical properties and durability of asphalt. mineralogy cum petro-graphic nature of rock formation as well as shape and size impart on strength, traffic wear and weather resistance of aggregates in asphalt’’ (otuoze and shuaibu, 2017). strength tests carried out on fine and coarse aggregates as presented in table 2 below and the results satisfied relevant codes recommendations adjudging that the material is strong, tough, dense and abrasion resistant and can stand the test of both serviceability and durability requirements of asphalt mixtures within the designed life. table 2: test results on the aggregates materials test conducted code used test result code limit aggregate crushing value (%) bs 812 part 112 18.65 max. 25 aggregate impact value (%) bs 812 part 111 18.87 max. 25 specific gravity of coarse aggregate astm c127 2.70 2.55 – 2.75 density of coarse aggregate astm c127 168.52 >160 specific gravity of fine aggregates astm c128 2.63 2.55 – 2.75 density of fine aggregates astm c127 164.15 >160 water absorption for coarse aggregate (%) bs 812 part 2 0.46 < 2 water absorption or fine aggregate (%) bs 812 part 3 8.62 < 15 3.2.1 particle size distribution of aggregates the graph of particle size gradation for the aggregates is as shown in figures 1 and 2 below file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 668 aggregate grading is a very crucial factor in ascertaining the bond, interlocking packing and packing density. in asphalt concrete, the nature of the aggregate skeleton impart greatly on the strength and resistance of the finish product in service. figures 1 and 2 below shows that the aggregates are well-graded as they satisfy astm d3515 code limits, thus, suitable for production of asphalt concrete figure 1: sieve analysis for coarse aggregate figure 2: sieve analysis for fine aggregates 3.3 test on filler (cement and wfs) the physical properties test performed on cement revealed that the cement is ordinary portland cement. the chemical composition using x-ray fluorescence test (xrf) and other physical properties on waste foundry sand shows that it is a pozzolana of class n with specific gravity value of 2.43. the particle size distribution of cement and wfs showed similar grading curve, this implies that their sizes are similar in nature and can be used together. the results obtained from these testing and limits of code specifications are presented in tables 3 and 4 and figures 3 and 4 below. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 669 table 3: test result on filler materials test code used value code limit initial setting time of cement (minute) bs en 196 part 3 68 >45 final setting time of cement (minute) bs en 196 part 3 255 <375 soundness of cement (mm) bs en 196 part 3 3.0 <10 specific gravity of cement astm c188 3.1 3.15 % of cement passing 0.075 mm sieve astm c117 97 >90 specific gravity of waste foundry sand astm d854 2.43 2.39 – 2.55 bulk relative density of wfs astm d854 152 <160 % of waste foundry sand passing 0.075 mm sieve astm c117 94 >90 pozzolana class astm c618 n n or f table 4: x-ray fluorescence (xrf) concentration of waste foundry sand (wfs) element concentration (%) element concentration (%) na2o 0.00 cao 2.00 mgo 0.71 tio2 1.47 al203 21.29 cr2o3 0.01 sio2 65.59 mn2o3 0.06 p2o5 0.08 fe2o3 6.96 so3 0.36 zno 0.02 cl 0.03 sro 0.03 k2o 1.39 figure 3: sieve analysis for cement figure 4: sieve analysis for waste foundry sand 3.4 aggregate material sampling, grading, proportioning and blending aggregate materials were sampled according to the recommendation of bs en932-1 (2003) and particle size distribution was done according to bs en 933-1 (2003). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 670 table 5 below, shows the combined aggregate envelope, distribution and blending of the materials which have been sandwiched between the asphalt institute code upper and lower limits. this is implies compliance with code specifications, thus, adjudged good for production of asphalt concrete that can meet strength and durability requirements in service. table 5: combined material mix and range of specification requirements bs sieve size (mm) percentage retained (%) cumulative percentage retained (%) cumulative percentage passing (%) asphalt institute (1994) 25.4 100 100 19.05 6.6 6.6 93.4 90 – 100 12.7 14.9 21.5 78.5 9.52 7.2 28.7 71.3 56 – 80 6.32 11.7 40.7 59.3 4.76 7.2 47.6 52.4 35 – 65 2.36 5.6 53.2 46.8 23 – 49 1.18 10.8 64.0 36.0 0.6 22.4 86.4 13.6 0.3 5.9 92.3 7.7 5 – 19 0.15 0.7 93.0 7.0 0.075 0.4 93.4 6.5 2 – 8 pan 6.5 99.9 0.1 3.5 optimum binder content (obc) in order to obtain the optimum binder content necessary for the asphalt paving mixture for different wfs replacements, fifteen (15) samples each weighing 1200 g, 101.5mm diameter and 63.5mm height compacted were prepared using five different bitumen contents (4.5, 5.0, 5.5, 6.0 and 6.5%) as specified by asphalt institute, (1997), and orn 19, (2003). the relationships between binder content and the properties of mixtures such as stability, flow, bulk density, voids filled with bitumen (vfb), void in mineral aggregate (vma) and void in mix (vim) at no wfs replacement (control) were established and optimum binder content was calculated. table 6 and figures 5-10 below present a summary of result obtained for the control specimen. table 6: summary of marshall test results for control specimens (0% wfs replacement) percentage of bitumen (%) stability (kn) flow (mm) bulk specific gravity (g) (g/cm3) vim (%) vma (%) vfb (%) 4.5 3.80 2.30 2.33 6.8 17.1 60.6 5.0 4.22 2.70 2.35 5.2 17.1 69.7 5.5 4.35 2.90 2.36 3.7 17.1 78.5 6.0 4.05 3.40 2.35 3.7 18.0 79.6 6.5 3.20 3.75 2.34 3.4 18.7 81.6 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 671 figure 5: stability against bitumen content at 0% wfs figure 6: flow against bitumen content at 0% wfs figure 7: bulk density against bitumen content at 0% wfs figure 8: vfb against bitumen content at 0% wfs figure 9: vma against bitumen content at 0% wfs figure 10: vim against bitumen content at 0% wfs file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 672 from the foregoing, the optimum bitumen content was found to equal 5.5% which was calculated as average of bitumen contents obtained at maximum stability, maximum bulk density and median per cent of air void as specified by asphalt institute, (1997). bitumen content at the maximum stability = 5.5 % bitumen content at the maximum value of bulk density = 5.5% bitumen content at the median per cent of air voids = 5.4% optimum bitumen content (obc) = 5.47 (5.5 approximately). 3.6 marshall test results asphalt at varying percentage replacement of cement with waste foundry sand (wfs) at optimum binder content of 5.5% the results of stability-flow and volumetric analysis (vim; void in mix, vma; void in mineral aggregate and vfb; void filled with bitumen) at varying replacement of wfs are shown in figures 11 to 16. figure 11: stability against different percentage replacement of wfs figure 12: flow against different percentage replacement of wfs from the plot in figure 11 above, the maximum load a compacted specimen can carry at a standard temperature of 60°c is the stability. the stability increases with increase in wfs from a value of 4.38 kn at 10% to a value of 4.92 kn at 60%. the increase in strength could be attributed to the hardness properties of sio2 and al2o3 which are the major constituent of wfs and also their ability to fill void spaces leading to denser mixture. the stability value of 4.92kn obtained at 60% replacement with wfs satisfies the nigerian general specifications for roads and bridges (fmwh, 1997) of 3.5kn for use as wearing course. flow is the measure of flexibility by the change in diameter of the test sample in the direction of load application between the start of loading and the time of maximum load. from figure 12 above, flow behaves in similar manner with that of the control mix due to the insignificant amount of wfs at 10%. the decrease in flow from 20% to 60% replacement is connected to the increase in stiffening of the mixture as wfs replacement increases, thus, producing a mixture that is less susceptible to deformation. the value of flow obtained ranges between 2.95 mm and 3.10 mm. this satisfies the requirement of nigerian general specifications for roads and bridges (fmwh, 1997) of between 2 mm and 4 mm for wearing course. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 673 figure 13: bulk specific gravity (g) against different percentage replacement with wfs figure 14: void in mineral aggregates against different percentage replacement with wfs from figure 13 above, the bulk specific gravity decreased with increase in percentage replacement of wfs. this could be attributed to the lower specific gravity of wfs (2.43) compared to that of cement (3.1). therefore, a given weight percentage of wfs will occupy a greater volume than that of a conventional filler material, thereby, producing a mixture with low specific gravity. the voids in the mineral aggregate, vma, is defined as the intergranular void space between the aggregate particles in a compacted paving mixture that includes the air voids and the effective bitumen content, expressed as a per cent of the total volume (o’flaherty, 2002). from figure 14 above, the void in mineral aggregate vma increased as the wfs replacement increased. this can be attributed to the excess wfs present in the mix which the bitumen cannot sufficiently coat to bind with other mineral aggregate. generally in marshal test, the vma decreases with increase in bitumen content until a minimum value of vma is obtained. any further increase of bitumen will increase vma, indicating that the asphalt structure is becoming overfilled with bitumen, and result in been susceptible to plastic deformation (orn 10, 2003). in this case, the void in mix actually increased because there is no enough binder present in the mix, thus, the ability of the constituents’ mineral aggregate to pack together decreases as wfs increases figure 15: void in mix (vim) against different percentage replacement with wfs figure 16: void filled with bitumen against different percentage replacement with wfs file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 674 the total volume of air expressed as percentage of the bulk volume of the compacted mixture is the void in mix (vim). this increase as void in mineral aggregates will generally increase that of the total mix. though the void in mix increases as seen from figure 15 above, the results obtained for void in mix satisfy the nigerian general specifications for roads and bridges (fmwh, 1997) of 3% 5% for wearing course, except for 10% replacement of wfs. void filled with bitumen vfb is defined as the portion of the volume of void space between the aggregates particles that is occupied by the effective bitumen. from figure 16 above, the void filled with bitumen decreased as the replacement of cement with wfs increased. the results obtained at various replacements conformed to the nigerian general specifications for roads and bridges (fmwh, 1997) of 75 82% except at 10% replacement. 4.0 conclusion from the results obtained in this study, the following conclusions were drawn the results of physical properties testing conducted on bitumen as regards its penetration, viscosity, flash and fire point, ductility and solubility all conforms to those of the astm standard specification for the design of asphalt concrete. thus, the bitumen meets its requirements for durability, safety and purity. the aggregate crushing value, aggregate impact value, specific gravity of coarse aggregate, water absorption of coarse aggregate, specific gravity of fine aggregate, water absorption of fine aggregates are within specifications. thus, the aggregates meet the strength, toughness, hardness and resistance to wear requirements for use in asphalt concrete production. the physical and chemical (x-ray fluorescence xrf test) property tests performed on foundry sand confirmed it is a pozzolana of class n according to astm c618 requirement and suitable for use in asphalt concrete production. the stability, flow, vma, vim and vfb obtained at 60% replacement of cement with foundry sand at 5.5% bitumen content indicates an enhanced strength and durability properties of asphalt concrete. thus, inclusion of wfs in asphalt is a viable solution for solid waste management and cost-effective asphalt concrete production for wearing course of flexible pavement necessary for sustainable development. references aashto. 1965. standard specification for materials for aggregate and soil-aggregate subbase, base and surface courses. american association of state highway and transportation officials. washington, d.c. aashto. 3122001. preparing and determining the density of hot-mix asphalt (hma) specimens means of the superpave gyratory compactor. standard test method for transportation by materials and methods of sampling and testing, part ii-tests, twentieth edition, american association of state highway and transportation officials. washington, d.c. aashto. 2006. standard specifications for transportation materials and methods of sampling and testing. american association of state highway and transportation officials. washington, d.c. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 675 abu salem, zt., khedawi, ts., baker, m s. and abendeh, r. 2017. effect of waste glass on properties of asphalt concrete mixtures, jordan journal of civil engineering, 11(1): 117–131. american foundry men’s society, 1991. alternative utilization of foundry waste sand. final report (phase i) prepared by american foundry men’s society inc. for illinois department of commerce and community affairs, des plaines, illinois. american foundry’s men society. 1963. foundry sand hand book, pp. 2026. des plaines, illinois. aramide, fo. aribo, s. and folorunso, do. 2011, optimizing the moulding properties of recycled ilaro silica sand. leonardo journal of sciences, 19(1): 93-102. asphalt institute, 1981. the asphalt handbook, the asphalt institute, 6th edition, lexington, ky. asphalt institute, 1994. mix design methods for asphalt concrete and other hot-mix types (ms2). asphalt institute, lexington, ky. asphalt institute, 1997. mix design methods for asphalt, manual series no. 2 (ms-02). the asphalt institute. lexington, ky. astm, 1994. annual books of american society for testing and materials standards, astm international, west conshohocken, pa, usa. astm, 2003. road and paving materials; vehicle pavement system, annual book of astm standards, american society for testing and materials, astm international, west conshohocken, pa, usa. astm c188, 2017 standard test method for density of hydraulic cement, astm international, west conshohocken, pa, usa. astm c117, 2003, materials finer than 75-µm (no. 200) sieve in mineral aggregates by washing, astm international, west conshohocken, pa, usa. astm d854 – 2014, standard test methods for specific gravity of soil solids by water pycnometer, astm international, west conshohocken, pa, usa. astm c618-2017a standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete, astm international, west conshohocken, pa, usa. astm d5 97 standard test method for penetration of bituminous materials, astm international, west conshohocken, pa, usa. astm d36 95(2000) standard test method for softening point of bitumen (ring-and-ball apparatus), astm international, west conshohocken, pa, usa. astm d 113 – 07 american association state standard test method for ductility of bituminous materials, astm international, west conshohocken, pa, usa. astm d70 03 standard test method for specific gravity and density of semi-solid bituminous materials (pycnometer method), astm international, west conshohocken, pa, usa. astm d2042 15 standard test method for solubility of asphalt materials in trichloroethylene, astm international, west conshohocken, pa, usa. brennan, mj. and o’flaherty, ca. 2002. materials used in road pavements. in highways: the location, design, construction and maintenance of pavements, 4th edition (ca. o’flaherty ed.). pp. 115, jordan hill-butterworth-heinemann, oxford, u.k. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng shuaibu, et al: properties of asphalt concrete containing waste foundry sand (wfs) as filler material. azojete, 15(3):662-677. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 676 bs en196-3. 1995, methods of testing cement — part 3: determination of setting time and soundness, british standard institution, london, uk. b.s 8110: part 2, 1985. structural use of concrete: code of practices for design and construction, british standard institution, london, uk. fhwa, 2004. foundry sand facts for civil engineers. federal highway administration, fhwa, department of transportation, u.s.a fmw, 2007. pavement and materials design. in highway manual part 1: design, volume 3, federal ministry of works, abuja, nigeria. fmwh, 1990. general specifications for roads and bridge. federal ministry of works and housing, highway manual volume ii: maintenance works. abuja, nigeria. fmwh, 1997. general specifications for roads and bridge. federal ministry of works and housing, federal republic of nigeria. abuja, nigeria. garber, j. and hoel, a. 2009. traffic and highway engineering. fourth edition, cengage learning, inc. toronto, canada. jalali, s. 2009. reusing ceramics waste in concrete. concrete construction and building materials, 24 (5): pp. 832-838. kaura, jm., amartey, yd., shuaibu, aa. and rabilu. a. 2016. strength and microstructure of cement mortar containing metakaolin. nigerian building and road research institute (nbrri) 2016 international conference, abuja. 24th – 26th may 2016 pp: 243-253. malhotra, vm. and mehta, pk. 1996. pozzolanic and cementitious materials. gordon and breach publishers, sa. mehta, pk. 2001. reducing the environmental impact of concrete. concrete international. 23(10): 61-66. mistry, r. and roy, tk. 2016. effect of using fly ash as alternative filler in hot mix asphalt. perspectives in science, 8(2016): 307—309. murana, aa. and sani, a. 2015. partial replacement of cement with baggase ash in hot mix asphalt. nigerian journal of technology, 34(4): 699-704. murana, aa., olowosulu, at. and ahiwa, s. 2014. performance of metakaolin as partial replacement of cement in hot mix asphalt. nigerian journal of technology, 33(3): 387-393. nwaobakata, c., and agunwamba, jc. 2014. effect of palm kernel shells ash as filler on the mechanical properties of hot mix asphalt. archives of applied science research, 6(5): 42-49. o'flaherty, ca. 2002. highways: the location, design, construction and maintenance of pavements (4th edition). pp. 332-340, jordan hill-butterworth-heinemann, oxford, u.k. olutaiwo, a. and owolabi, a. 2015. investigation of the effects of partial replacement of coarse aggregate with graded palm kernel shell in asphaltic binder course. british journal of applied science and technology 10(3): 1-13. orn, 19. 2003. a guide to the design of hot mix asphalt in tropical and sub tropical countries. overseas road note, department for international development (dfid). published by trl limited, crow thorne. berkshire, united kingdom pp: 13-21. https://www.amazon.com/gp/help/seller/at-a-glance.html?ie=utf8&seller=a2l0jskata9rv0&isamazonfulfilled=1 https://www.amazon.com/gp/help/seller/at-a-glance.html?ie=utf8&seller=a2l0jskata9rv0&isamazonfulfilled=1 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2019; vol. 15(3):662-677. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tightmybet@gmail.com, abdulshub4u@gmail.com 677 otuoze, hs. and shuaibu, aa., 2017. an experimental study on the use of polypropylene waste in bituminous mix. nigerian journal of technology, faculty of engineering, university of nigeria, nsukka. 36(3): 677-685. padmavathi, s. and preethika, d. 2016. experimental investigation of concrete with groundnut shell ash as a partial replacement of cement with sisal fibers. international journal on applications in civil and environmental engineering 2(3): 2395 –3837. petavratzi, e. and wilson, s. 2007. characterization of mineral wastes, resources and processing technologies – integrated waste management for the production of construction material, case study: foundry sand in facing bricks, mineral industry research organization, university of leeds, leads, united kingdom. sadeeq, ja., kaura, jm., ochepo, j. and rabilu, a. 2014. recycling of reclaimed asphalt pavement (rap) with rice husk ash (rha)/ordinary portland cement (opc) blend as filler. jordan journal of civil engineering, 8(4): 473-481. siddique, r. and kaur, g. 2010. waste foundry sand and its leachate characteristics. in resources, conservation and recycling, elsevier, 54(2010): 1027-1036. siddique, r. and kaur, r. 2013. properties of self-compacting concrete incorporating waste foundry sand. leonardo journal of sciences, 23: 105-124. singh, g. and siddique, r. 2012. effect of waste foundry sand as partial replacement of sand on the strength, ultra sonic pulse velocity and permeability of concrete. construction and building materials. 26(1): 416–422. suji, d., poovendran, s. and prabhakar, p. 2016. experimental study on partial replacement of waste foundry sand in flexible pavements. international journal of civil and structural engineering research, 4(1): 188-197. tsado, ty., yewa, m., yaman, s. and yewa, f. 2014. comparative analysis of properties of some artificial pozzolana in concrete production international journal of engineering and technology 4(5): 251-255 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):91-99 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 91 original research article strength, sorption and chemical properties of ceiba pentandra and tectona grandis wood composite o. o. adefisan and d. j. oyelola department of wood products engineering, faculty of technology, university of ibadan, ibadan, nigeria article information submitted: 11/02/2019 revised: 28/04/2019 accepted: 29/04/2019 keywords: ceiba pentandra tectona grandis polystyrene wood composites. abstract the enormous quantities of wood wastes in nigerian sawmills and disused polystyrene from packaging can be converted to value added composite products thus curtailing their indiscriminate disposal; enhancing greener environment. this work examined the strength, sorption and chemical properties of wood composites made from ceiba pentandra and tectona grandis. ceiba pentandra (araba) and tectona grandis (teak) composite boards were made from polystyrene glue and a conventional water-based adhesive used in the wood industries. the fabricated boards were tested for strength and sorption properties while the functional groups of the composites were determined using the fourier transformed infrared radioscopy technique. the results obtained revealed that the composites had low strength, poor sorption properties and can only be utilized as insulating components in building construction. polystyrene based composites possessed higher strength (modulus of rupture: 2.2 – 4.9 n/mm2) and enhanced sorption properties (water absorption: 14.2 98.5 %; thickness swelling: 0.61 3.45%) in comparison with those of the water-based adhesives (modulus of rupture: 1.6 – 2.8 n/mm2; water absorption: 33.4 – 158.4 % and thickness swelling: 1.80 – 7.41%) possibly due to preponderance of aromatic compounds which enhanced interfacial bonding. increase in glue content significantly enhanced the strength and sorption properties of the wood composites © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction enormous quantities of waste estimated as 1.8 million tons per annum is generated by the wood industries in nigeria in the form of off-cuts, plain shavings, wood rejects and sawdusts. this is as a result of lack of expertise of the machine operators, utilization of obsolete equipment and saw kerf. (ogunbode et al., 2013; ogunwusi, 2014). these items are injurious to the wood mill, mill workers and the wood products. oftentimes, wood waste results in flammability, fungi and insect infestations. also, polystyrene, a polymer of styrene used for packaging and insulation is a nonbiodegradable product that is majorly discarded into the environment. the presence of these items in the society cause environmental pollution, health hazards and blockage of water ways (kwon et al., 2009; kan and demirboga, 2009; ricky et al., 2010) http://www.azojete.com.ng adefisan, et al.: strength, sorption and chemical properties of ceiba pentandra (araba) and tectona. azojete, 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 92 conversion of these wastes into value added products could be a means of curtailing this menace thus enhancing greener environment which consequently can help in reducing the existing pressures of over exploitation of the dwindling timber resource in nigeria. one of the advantages of polystyrene based composites is that polystyrene is impervious to water and has closed cell characteristics which might enhance the mechanical properties of the resultant products (adefisan, 2018). composite products made from polystyrene and wood waste have been found to have moderate strength (4.9 – 32.0 n/mm2) and can be integrated into low cost building components adapted for interior and exterior uses (voulgardis, et al., 2003; poletto, 2016; adefisan, 2018). however, there is still paucity of information on properties of polystyrene based composites made from nigerian grown hardwood. the knowledge of certain properties of polystyrene based composites such as the strength and sorption properties, is imperative to foment wider utilization and commercialization of the products. therefore, this study was aimed at investigating the strength and sorption properties of polystyrene based composites made from ceiba pentandra (araba) and tectona grandis (teak) woods in comparison with those of conventional water-based adhesives commonly used in the wood industries. the functional groups of the fabricated composites using the fourier transformed infrared radioscopy (ftir) technique were also evaluated. 2. materials and methods particles of c. pentandra and t. grandis woods were collected from a local mill in ibadan, oyo state while disused polystyrene (ps) were locally sourced within the ibadan metropolis. the wood particles were air dried for 14 days to a moisture content of 10% and later sieved using 4.75 mm sieve. the particles that passed through the 4.75 mm sieve were collected and used for board formation. 2.1 board formation the ps were cleaned, cut into smaller sizes of about 2 x 2 x 7 cm³ and then dissolved in premium motor spirit (pms) in the ps: pms ratio of 1:2 (w/v) in accordance with the procedures of adefisan (2018) until homogeneous slurry was formed. particles of the wood species were mixed with ps-pms slurry in the ratios 2:1 and 3:1, and formed into a mat in a wooden deckle measuring 30 x 30 x 10 cm³. the mat was cold-pressed with a pressure of 3 mpa for 30 minutes and conditioned in a room at temperature (25 ± 2°) and at relative humidity of 72% for 14 days. this procedure was also carried out for boards formed with conventional water-soluble adhesive used in the wood industry as comparison. 2.2 fourier transform infrared radioscopy (ftir) of the polystyrene glue the functional groups of the composites were determined using the fourier transform infrared (ftir) machine (perkinelmer ft-ir system spectrum bx) in accordance with the procedure adapted by fabiyi et al. (2009). 2 mg of the dried samples was homogenized with 200 mg of potassium bromated (kbr) salt. with the aid of hydraulic press, the powdered mixtures were pelletized into disc forms and inserted into the ftir machine. spectrum was taken as an average of 64 scans at a resolution of 4 cm-1. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 93 2.3 physical property and flexural test the de-moulded boards were cut to samples sizes according to american society for testing and materials (astm) standard d1037-96 and the densities of the composites were evaluated. flexural test was conducted on a 600kn okhard universal testing machine (utm) at cross head speed of 2mm/min from which the mechanical properties such as moduli of rupture (mor) and elasticity (moe) were evaluated. 2.4 water absorption (wa) and thickness swelling (ts) tests samples of the c. pentandra and t. grandis bonded boards (five replicates) were initially weighed and then soaked in water at room temperature for 61 days and periodically measured in accordance with procedures adapted by fabiyi et al., (2011). the wa and ts of the wood species were determined as expressions of the initial weights and thicknesses. 2.5 statistical analysis the data obtained from the flexural and sorption tests were subjected to analysis of variance (anova) at p ≤ 0.05. significant means were separated using duncan’s multiple range test. 3. results and discussion 3.1 results of the fourier transformed infrared radioscopy tables 14 and figures 1 and 2 show the band wave numbers of the functional groups present in the conventional water-soluble and polystyrene bonded composites. the composites had hydrogen bonded o-h stretching vibrations at 3412.65 – 3441.80 cm-1, aliphatic c-h methylene stretching vibration at 2916.88 – 2930.97 cm-1, aromatic c-c stretching vibration at 1597.62 – 1605.62 cm-1, c-c bending vibrations at 1441.83 – 1446.57 cm-1 and c-o stretching vibrations at 1031.02 1033.17 cm-1. as shown in tables 14 and figures 1 and 2, the polystyrene bonded composites had preponderance of aromatic compounds suggesting better interfacial bonding in comparison with those bonded with the water-soluble adhesives (lampman et al., 2010; osemeahon and dimas, 2014). as shown, c=o carboxylic stretching band at 1731.14 cm-1 (table 3) and aromatic c-h stretching band at 3027.45 cm-1 (table 4) were observed in t. grandis bonded composites. these functional groups enhance interfacial bonding and induce strength in the composites (lampman et al., 2010) table 1: infrared bands of polystyrene based c. pentandra composites s/n wave number (cm-1) peak assignment 1 3421.85 o-h stretch (hydrogen bonded) 2 3027.94 aromatic c-h stretching vibration 3 2916.88 aliphatic c-h stretching vibration 4 1600.64 aromatic c=c stretching vibration 5 1446.05 c-c bending vibration 6 1366.35 c-h rocking vibration 7 1031.55 c-o stretching vibration 8 754.3 aromatic c-h stretching vibration 9 688.15 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adefisan, et al.: strength, sorption and chemical properties of ceiba pentandra (araba) and tectona. azojete, 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 94 table 2: infrared bands of conventional water soluble based c. pentandra composites s/n wave number (cm-1) peak assignment 1 3441.8 o-h stretch (hydrogen bonded) 2 2930.97 aliphatic c-h stretching vibration 3 1605.62 aromatic c=c stretching vibration 4 1439.72 c-c bending vibration 5 1033.17 c-o stretching vibration table 3: infrared bands of polystyrene based t. grandis composites s/n wave number (cm-1) peak assignment 1 3424.68 o-h stretch (hydrogen bonded) 2 3027.61 aromatic c-h stretching vibration 3 2917.26 aliphatic c-h stretching vibration 4 1731.14 c=o stretching vibration 5 1599.1 aromatic c=c stretching vibration 6 1446.57 c-c bending vibration 7 1031.73 c-o stretching vibration 8 754.23 aromatic c-h stretching vibration 9 688.71 table 4: infrared bands of conventional water soluble based t. grandis composites s/n wave number (cm-1) peak assignment 1 3412.65 o-h stretch (hydrogen bonded) 2 3027.45 aromatic c-h stretching vibration 3 2921.76 aliphatic c-h stretching vibration 4 1597.62 aromatic c=c stretching vibration 5 1441.83 c-c bending vibration 6 1031.02 c-o stretching vibration 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50 0.52 0.54 0.56 0.58 0.60 0.62 0.64 0.66 ab so rb an ce 500 1000 1500 2000 2500 3000 3500 4000 wavenumbers (cm-1) figure 1: infrared bands of polystyrene based composites http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 95 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.30 0.31 0.32 ab sor ban ce 500 1000 1500 2000 2500 3000 3500 4000 wavenumbers (cm-1) figure 2: infrared bands of the conventional water soluble based composites 3.2 physical and mechanical properties 3.2.1 density the densities of the composites are shown in table 5. as shown, the density ranged from 441.0 to 686 kg/m3 and from 467.1 to 687.5 kg/m3 for the c. pentandra and t. grandis composites respectively. this suggests that the fabricated boards have moderate densities (olorunnisola et al., 2005). generally, composites bonded with higher adhesive mixing ratio had significantly (p < 0.05) higher densities indicating good interfacial bonding between the wood particles and the adhesive used. also, composites bonded with disused polystyrene and t. grandis particles recorded significantly higher densities than those fabricated from the conventional adhesive and c. pentandra. this observation could be attributed to the fact that t. grandis belongs to higher strength group (n3 group) while c. pentandra belongs to lower strength (n7) group in accordance with the nigerian code of practice (ncp, 2005; olorunnisola, 2018). thus, t. grandis woods may be more durable and stronger in comparison with c. pentandra. also, the presence of more aromatic compounds in the polystyrene composites enhanced better interfacial bonding and mechanical properties in the composites in comparison with those bonded with the conventional water-soluble adhesives. table 5: physical and mechanical properties of t. grandis and c. pentandra composites mixing ratio density (kg/m3) mor (n/mm2) moe (n/mm2) polystyrene based c. pentandra composites 2:1 554.0e (0.0) 2.2e (0.03) 4975cde (806) 3:1 686.0b (0.0) 3.1c (0.01) 7492bcd (2509) conventional water soluble adhesive based c. pentandra composites 2:1 441.0h (0.0) 1.6h (0.10) 955.0e (73) 3:1 470.8f (0.0) 1.8g (0.01) 1409.0de (207) polystyrene based t. grandis composites 2:1 682.0c (0.01) 3.6b (0.07) 13,283b (4833) 3:1 687.5a (0.0) 4.9a (0.10) 20,879a (6935) conventional water soluble adhesive based t. grandis composites 2:1 467.1g (0.0) 2.0f (0.01) 5405.0cde (1896) 3:1 563.5d (0.0) 2.8d (0.03) 9201.0bc (3208) means with the same letters and in the same columns are not statistically different significant at 5% level of probability file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adefisan, et al.: strength, sorption and chemical properties of ceiba pentandra (araba) and tectona. azojete, 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 96 3.2.2 flexural properties the result of the flexural tests of the c. pentandra and t. grandis composites are shown in table 5. the modulus of rupture (mor) of the composites ranged from 1.6 to 3.2 n/mm2 and from 2.0 to 4.9 n/mm2 and for the c. pentandra and t. grandis composites respectively. these values are lower than 14.5 – 32.0 n/mm2 recommended by the forest products laboratory (cai and ross, 2010), those obtained by voulgaridis et al., (2003) (14.5 25.2n/mm2) and adefisan (2018) (4.9 – 12.9 n/mm2). this suggests that the fabricated composites have low strength properties and cannot be used for structural purposes but as insulating components such as paneling. the low mor can be adduced to be due to the low densities of the fabricated composites (441.0 – 687.5 kg/m3) and this is in line with the report of olorunnisola et al. (2005). the modulus of elasticity (moe) of the composites were between 955 and 7492.0 n/mm2 and 5405.0 and 20,879.0 n/mm2 for the c. pentandra and t. grandis composites respectively. generally, composites bonded with higher adhesive mixing ratio recorded higher mors and moes suggesting enhanced interfacing bonding with increasing adhesive content. also, composites bonded with polystyrene due to pre-ponderance of aromatic compounds which enhance interfacial bonding recorded higher mors and moes. likewise, composites bonded with t. grandis particles generally had higher mors and moes than those bonded with c. pentandra. this observation may be attributed to preponderance of strength inducing components, higher density of the t. grandis composites (table 6) and the variation in strength characteristics of the woods used. while t. grandis belonged to n3, a higher strength class c. pentandra belonged to n7, a lower strength class (ncp, 2005) statistical analyses (duncan’s multiple range test) (table 6) revealed that species of wood, the mixing ratios and the glue types employed in the study significantly affected the mors and moes of the fabricated composites. table 6: duncan’s multiple range test of the effect of species, mixing ratio and glue types on the moduli of rupture and elasticity and density of teak and araba composites variables density (kg/m3) mor (n/mm2) moe (n/mm2) species c. pentandra 537.9b (99.2) 2.2b (0.61) 3708.0b (3020) t. grandis 600.0a (95.4) 3.3a (1.11) 12,192.0a (7171) mixing ratio 2:1 602.0a (95.0) 2.3b (0.78) 6268.0b (5054) 3:1 536.0b (98.3) 3.1a (1.17) 9632.0a (8252) glue types polystyrene 6524a (59.3) 3.4a (1.0) 11,657.0a (7421) conventional 485.6b (48.5) 2.0b (0.5) 4242.0b (3840) means with the same letters and in the same columns are not statistically different significant at 5% level of probability sorption properties the results of the water absorption (wa) and thickness swelling (ts) of the c. pentandra and t. grandis are shown in table 7 and figure 3. figure 3 shows the wa of the composites reaching a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 97 pseudo-equilibrium state in accordance with fickian behaviour (rangaraj and smith, 2000). the wa ranged from 14.2 to 158.4% and from 16.9 to 144.1% for the c. pentandra and t. grandis composites respectively. the respective ts ranged from 1.40 to 7.41% and 0.61 to 3.55%. these values (wa: 14.2 to 158.4% and 16.9 to 144.1% , although high and ts: 1.40 to 7.41% and 0.61 to 3.55%) compared favourably with those of voulgaris et al., (2003) (wa: 11.4 -93.2% for 2 – 24 h, ts: 2.1 – 17.0% ) and adefisan (2018) (wa: 2.2 – 140%; ts: 0.5 – 7.1% for 2 -72 h). as shown in table 7, the recorded wa and ts indicate that the fabricated boards were generally not dimensionally stable and cannot be used for exterior applications. composites made from t. grandis particles with higher mixing ratios and bonded with polystyrene glue generally recorded lower wa and ts and were more dimensionally stable than those of the water-soluble adhesives. this observation may be attributed to higher densities of the teak composites in comparison with those of c. pentandra, enhanced interfacial bonding with increasing glue content and the pre-ponderance of aromatic compounds in the polystyrene composites which enhanced interfacial bonding than those of water based composites. table 7: water absorption and thickness swelling of c. pentandra and t. grandis composites mixing ratio water absorption thickness swelling 1 day 61 days 1 day 61 days polystyrene based c. pentandra composites 2:1 46.6f (0.47) 98.5d (2.80) 1.64cde (0.90) 2.72bcde (0.14) 3:1 14.2h (1.51) 64.3e (6.00) 1.40cde (0.44) 1.74cde (0.93) conventional water soluble adhesive based c. pentandra composites 2:1 112.3c (9.29) 158.4a (3.70) 1.80cde (0.10) 3.46bc (0.43) 3:1 49.4f (0.78) 100.6d (3.31) 4.23b (2.11) 7.41a (2.24) polystyrene based t. grandis composites 2:1 19.7h (2.28) 63.7e (1.51) 1.18ed (0.97) 3.45bc (1.10) 3:1 16.9h (2.30) 61.7e (1.85) 0.61e (0.34) 2.68bcde (0.81) conventional water soluble adhesive based t. grandis composites 2:1 116.4c (11.43) 144.1b (4.24) 2.97bcd (1.48) 3.55bc (0.72) 3:1 33.4g (3.37) 101.6d (0.46) 2.68bcd (0.39) 3.20bcd (0.09) means with the same letters and in the same columns are not statistically different significant at 5% level of probability file:///c:/users/user/downloads/azojete143/www.azojete.com.ng adefisan, et al.: strength, sorption and chemical properties of ceiba pentandra (araba) and tectona. azojete, 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 98 * aca21conventional water soluble adhesive based c. pentandra composites (2:1 mixing ratio) * cps21polystyrene based c. pentandra composites (2:1 mixing ratio) * tca21conventional water soluble adhesive based t. grandis composites (2:1 mixing ratio) * tps21polystyrene based t. grandis composites (2:1 mixing ratio) fig. 3: water absorption of c. pentandra and t. grandis composites 4.0 conclusions wood composites were produced from disused polystyrene and the common conventional water soluble adhesive used in wood industry. the fabricated composites possessed moderate strength, poor sorption properties and can be used as insulating components such as paneling. the strength and sorption properties of the fabricated composites were influenced by the glue types, mixing ratio and the species of wood used in production. tectona grandis composites had higher strength and better sorption properties in comparison with those made from ceiba pentandra possibly due to the structural integrity of the t. grandis wood. polystyrene bonded composites had better strength and sorption properties than those made from the conventional adhesive due to preponderance of aromatic compounds. references adefisan, oo. 2018. evaluation of strength and sorption properties of polystyrene bonded composites of mahogany (khaya ivorensis) and teak (tectona grandis) woods arid zone journal of engineering, technology and environment, 14(2):201-207. astm international (astm d1037-96) 2002. standard methods for evaluating properties of wood-based fibers and particle panel materials. annual book of astm standards, volume 04.10. west conshohocken, pa 19428. cai, z. and ross, rj. 2010. mechanical properties of wood-based composite materials. woodhandbook – wood as an engineering material chapter 12. gen. tech. rep. fpl – gtr – 113 madison. wi: u.s. dept of agric., forest service. forest products lab. fabiyi, js., mcdonald, ag. and mcllroy, d. 2009. wood modification effects on weathering of hdpe-based wood plastic composites. journal of polymer environment, 17(1):34-48. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):91-99. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: femiadefisan@hotmail.com; oo.adefisan@mail.ui.edu.ng 99 fabiyi, js., mcdonald, ag., morrell, jj. and freitag, c. 2011. effects of wood species on durability and chemical changes of fungal decayed wood plastic composites. composites part a, 42(5):501510. kan, a. and demirboga, r. 2009. a new technique of processing for waste-expanded polystyrene foams as aggregates. journal of materials processing technology, 2(9): 2994-3000. kwon, e. kelly, jw. and marco, jc. 2009. an investigation into the sngas production from municipal solid waste (msw) under various pressures and co2 concentration atmospheres, 17th annual north waste -to -energy conference, chantilly, virginia, usa, proceedings , pp 231236. lampman, gm. pavia, dl. kriz, gs. and vyvyan, jr. 2010. spectroscopy. cengage learning, india private limited. 4th edition. pp647. ncp, 2005. nigerian code of practice for structural timber design. the standard organisation of nigeria, lagos. ogunbode, eb., fabunmi, fo., ibrahim, sm., jimoh, io. and idowu, oo. 2013. management of sawmill wastes in nigeria: case study of minna, niger state. greener journal of science, engineering and technology research, 3(2): 34-41. ogunwusi, aa. 2014. wood waste generation in the forest industry in nigeria and prospects for its industrial utilization. civil and environmental research, 6(9): 62-69. olorunnisola, ao., pitman, a. and mansfield, wh. (2005). strength properties and potential uses of rattan–cement composites. journal of bamboo and rattan, 4: 343–352. olorunnisola, ao. 2018. design of structural element with tropical hardwoods. springer, n.y. pp284. osemeahon, sa. and dimas, bj. 2014. development of urea formaldehyde and polystyrene waste as copolymer binder for emulsion paint formulation. academic journal, 6(3):75 -88. poletto, m. 2016. polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties. revista materia, 21(3): 552-559. rangaraj, sv. and smith, lv. 2000. effects of moisture on the durability of a wood thermoplastic composite. journal of thermoplastic composites material, 13(2):140-161. ricky, g. oscar, l. and yusef, s. 2010. an investigation into polystyrene recycling at ubc. dawn mills apsc 262. the university of british columbia, 1-18 voulgardis, ev. passialis, cn. and philippou, jl. 2003. experimental results of reclaimed polystyrene utilisation in wood products. in: proceedings of 8th international conference on environmental science and technology lemnos island greece 8-10 september, 2003: 902-910 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng 2 cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 194-201 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng ____________________ *corresponding author email address: opara@sun.ac.za, 17145821@sun.ac.za 194 original research article the role of horticultural package vent hole design on structural performance t. fadiji1, 2*, t. berry2, c. coetzee1 and u. l. opara2, 3* 1department of mechanical and mechatronics engineering, faculty of engineering, stellenbosch university, south africa 2postharvest technology research laboratory, south african research chair in postharvest technology, department of horticultural sciences, faculty of agrisciences, stellenbosch university, south africa 3postharvest technology research laboratory, south african research chair in postharvest technology, department of food science, faculty of agrisciences, stellenbosch university, south africa article information received october, 2018 accepted december, 2018 keywords: finite element analysis ventilated paperboard packaging vent hole compression strength abstract globally, ventilated paperboard packaging has been widely utilised particularly in the horticultural industry to protect packed produce against damage to satisfy consumer needs. during postharvest activities, the packages are exposed to cold environment and mechanical hazards. the mechanical hazards may result from different loadings such as drop, impact, vibration, compression or a combination of all. designing ventilated packages should be such that they can provide uniform air distribution to cool the packed produce and protect the produce against mechanical damage. however, the presence of vent holes causes material loss of the package, thereby reducing the stacking strength of the packages and consequently resulting in produce damage. the strength of the package is crucial for preserving the produce and therefore optimising the package is essential to save time, money and resources. this research was aimed at evaluating the structural behaviour of ventilated packages. finite element analysis was used to create models to study the buckling of three ventilated package designs when subjected to compression load. packages with different vent area and paperboard grades were studied. experiments were used to quantify box compression strength. results of mechanical strength evaluation showed a negative linear relationship between carton strength and vent area. board thickness increased the compression strength of the packages. at 2% and 4% vent areas, packages with c flute board reduced in strength by as high as 46% when compared with the strength of the packages with b flute board. numerical results and experimental results were in good agreement, within 12%. this study suggests the need for alternative package designs, considering the mechanical strength while still providing proper and adequate ventilation to the packed produce. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved http://www.azojete.com.ng mailto:opara@sun.ac.za arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 195 1.0 introduction packaging is a crucial step in the long and complicated journey of fresh horticultural produce from the grower to the consumer (fadiji et al., 2018a). the advent of ventilated paperboard packaging has been adopted globally to allow for rapid cooling, promote efficient cooling of the produce, and for proper air circulation within the package (thompson et al., 2010; de castro et al., 2005). however, ventilation openings adversely affect the mechanical strength of the packages, consequently resulting in the damage of the packed produce (opara and pathare, 2014). the structural performance of ventilated paperboard packaging is dependent on numerous factors such as quality of the cellulose fibres, strength of the paperboard components (liners and flutes), and the mechanical properties of the combined paperboard (fadiji et al., 2018a). furthermore, a proper package design must take into consideration different geometrical configurations of the vent such as the vent area, shape, size and location to enhance cooling while still providing sufficient mechanical strength (pathare et al., 2017, 2016, 2012; han and park, 2007; émond and vigneault, 1998). according to pathare et al. (2017), the strength and cooling capabilities of ventilated packages is dependent on the geometrical locations, sizes and shapes of the vent holes. to save money and resources, optimising the strength and adequate cooling capabilities is therefore crucial. during handling of ventilated packages, they are often stacked in a pallet, resulting in increased weight on the bottom packages, which could lead to produce damage (opara and pathare, 2014). box compression test (bct) is often used as a measure to evaluate the performance potential of the packages (pankaj et al., 2016; fadiji et al., 2016; markström, 1988). a decrease in carton mechanical strength was reported to be a function of increasing vent sizes (singh et al., 2008). the compression strength of ventilated packages was influenced by package designs (fadiji et al., 2016). several researchers have reported the confidence of simulation techniques such as finite element analysis (fea) and computational fluid dynamics (cfd) in replacing experimental analysis (fadiji et al., 2018b; 2016; pathare and opara, 2014). experimental and numerical analysis evaluation of the mechanical behaviour of paperboard packages was done by biancolini and brutti (2003). fadiji et al. (2018b) developed a fea model to predict the buckling of corrugated paperboard and packages. results were validated with experimental tests and good agreement was reported. among many factors that affect the strength of corrugated paperboard packaging, ventilation opening configurations and board grades play a crucial role. the aim of this research was to investigate the role of vent design on the structural performance of the package. 2.0 materials and methods 2.1 packaging design three telescopic package designs were used in this study. the standard vent, edge vent and the multi vent designs. the standard vent package is commonly used for commercial pome fruit export in south africa (berry et al., 2017, 2015). the edge vent was used based on its successful application in the south african citrus industry (defraeye et al., 2014; delele et al., 2013a, b). the multi vent was proposed as an alternative design to the standard vent design. two corrugated paperboard grades were used in this study: b-flute and c-flute. the thickness of the b and c flute paperboard grades was 2.8 mm and 3.9 mm, respectively. for each package design and board grades, two vent areas were used: 2% and 4%. figure 1 shows the geomtry for the different package designs. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fadiji, et al. the role of horticultural package vent hole design on structural performance. azojete, 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 196 2.2 finite element analysis mentat/marc (msc software corporation, california usa) was used for the fea. the paper grammage (g m-1) combination for b and c flutes was 140t2/175sc/165sc and 175t1/175sc/125fl, respectively. the thickness of the paper samples were 0.1992 mm, 0.2174 mm, 0.2646 mm, 0.2604 mm and 0.2225 mm for 125fl, 165sc, 175sc, 175t1 and 140t2, respectively. elastic-plastic material properties reported by fadiji et al. (2018b) were used. due to computational time and cost, the homogenisation procedure proposed by biancolini (2005) was used in the simulation for the package. boundary conditions were set to represent the physical model accurately. buckling analysis was performed on the packages to obtain the compression strength. further details of the fea setup can be found in fadiji et al. (2018b). 2.3 box compression strength (bct) bct is a pure top-to-bottom compression load test between flat parallel steel plates that is carried out on an empty or filled sealed corrugated board package using a constant deformation speed. all compression tests were conducted using a box compression tester (m500-25ct, testomatic, rochdale, uk). prior to the bct, packages were preconditioned and conditioned according to astm d4332 standard. the bct was done in accordance with the astm d642 standard. a preload of 222 n was applied prior to the compression test remove initial transient effect. the fixed-platen mode of the compression tester was used to conduct all testing at a speed of 12.7 ± 2.5 mm min−1 until failure was observed. the compressive load and displacement are recorded continuously until collapse occurs. statistical evaluations were performed using statistica (v. 13.0, statsoft, usa). figure 1. geometry of the package designs (mm). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 197 3.0 results and discussion 3.1 compression strength of the package designs figure 2 shows the compression strength and its correspnding displacements for all the package designs for both b and c flute board grades at 2% and 4% vent areas. from figure 2, the compression strength of the packages with c flute board was observed to be higher than the packages with b flute board. in addition, there was a significant difference (p0.05) between the compression strength of the packages with b flute board and the packages with c flute board. at 2% vent area, the compression strength for the standard, edge and multi vent designs with c flute board reduced by about 46%, 43% and 45%, respectively when compared with the compression strength of the same packages with b flute board. at 4% vent area, the compression strength of the standard vent design with c flute board reduced by about 43% when compared with the compression strength of the standard vent design with b flute board. the compression strength of both the edge and the multi vent designs with c flute board reduced by about 41% when compared with similar packages with b flute board. these results show the vital role of the board grades as failure of the combined board initiates package failure (dimitrov and heydenrych, 2009). the combination of corrugated paperboard was reported by biancolini et al. (2005) to be an important factor that can significantly influence the strength of paper packages. in most cases, the compression strength of the packages reduced with an increase in vent area (figure 2a). the compression strength at 2% vent area of the package designs was higher than the compression strength at 4% vent area for both board grades. although, the compression strength at 4% vent area for the standard vent and multi vent designs with b flute board was slightly higher than the compression strength at 2% vent area. however, there was no significant difference statistically. singh et al. (2008) reported a linear relationship between the loss in compression strength of a package and vent area, although with >40% of material removed from the package, the relationship does not stay linear. the ventilation opening on a package is a crucial factor affecting the mechanical resistance of the package, the physical support to protect packed produce against bruise damage and the cooling efficiency of the package (defraeye et al., 2015; pathare et al., 2012; de castro et al., 2005; baird et al., 1988). therefore, there should be a compromise between the adequate cooling and the mechanical integrity of the package in designing an optimal package vent. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fadiji, et al. the role of horticultural package vent hole design on structural performance. azojete, 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 198 figure 2. bar chart showing (a) compression strength and (b) displacements at maximum compression strength for all the package designs for both b and c flute board at 2% and 4% vent area. the letters on the error bars are used to show the statistical difference. means with the same letters are not statistically different at p0.05. the corresponding displacement at the maximum compression strength for all the package designs is shown in figure 2b. the displacement for the packages with c flute board was observed to be the highest compared to the displacement of the packages with b flute board. this indicated that the more resistance a package has to compression load, the higher the displacement. the range of the displacement for the packages with b flute board and c flute board was 7.8 – 9.1 mm and 12.4 – 15.9 mm, respectively. more deflection means that the impact of the load is spread over a longer duration, thereby reducing the intensity of the load impact (campbell, 2010). hence, the packages with c flute board offer better cushioning and protective ability to the packed produce, thereby minimising the mechanical damage incurred by packed produce. no significant difference (p0.05) in the displacement of the packages with 2% and 4% vent areas. 3.2 simulation result typical fringe plots of the buckling behaviour of the packages with b flute board under compression load is shown in figure 3. it can be seen that the buckling of the package originated from the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 199 middle of the package, which is more predominant on the length side of the package. according to panyarjun and burgess (2001), package failure is due to the cumulative effect of the localised crushing that occur on the face of the package. buckling was affected by the package designs. the length side of the standard vent with 2% vent area buckled inward while the length side of the standard vent with 4% vent area buckled outward.for the multi vent with 2% and 4% vent area, the buckling on the length side of the package was outward and inward, respectively. the length side of both edge vent with 2% and 4% vent area buckled inward. the compression strength obtained from the simulation an experimental results showed a significant dependence of the package resistance to compresion load on vent area and board grade. both simulation and experimental compression strength agree well, within 12%. figure 3. typical fringe plots of the buckling of the package designs with b flute board grade. 4.0 conclusions this study evaluated the effect of package geometrical configurations on mechanical strength experimentally and numerically. three different package designs, with two vent area (2% and 4%) and two paperboard grades (b and c flute) were used. the compression strength of the package reduced with an increase in vent area. the percentage difference in compression strength for all the packages with 2% and 4% vent area was in the range 1 – 10%. the thickness of the paperboard affected the strength of the packages. packages with c flute board had higher compression strength file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fadiji, et al. the role of horticultural package vent hole design on structural performance. azojete, 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 200 than packages with b flute board. numerical simulations were able to predict the compression strength of the packages, with good correlation, within 12% when compared with the experimental results. results showed the importance of paperboard combination and vent hole designs to improve the structural integrity of the packages. 5.0 acknowledgements this work is based upon research supported by the south african research chairs initiative of the department of science and technology and national research foundation. experimental evaluations on cartons were conducted at the paper sciences department of the sappi technology centre at the innovation hub, pretoria, south africa and the authors thank the staff for their invaluable support and assistance. references baird, cd., gaffney, jj. and talbot, mt. 1988. design criteria for efficient and cost effective forced air cooling systems for fruits and vegetables. ashrae transactions, 94(1), 1434–1454. berry, tm., delele, ma., griessel, h. and opara, ul. 2015. geometric design characterisation of ventilated multi-scale packaging used in the south african pome fruit industry. agricultural mechanization in asia, africa, and latin america, 46(3), 34–42. berry, tm., fadiji, ts., defraeye, t. and opara, ul. 2017. the role of horticultural carton vent hole design on cooling efficiency and compression strength: a multi-parameter approach. postharvest biology and technology, 124, 62–74. biancolini, me. 2005. evaluation of equivalent stiffness properties of corrugated board. composite structures, 69(3), 322–328. biancolini, me., brutti, c., mottola, e. and porziani, s. 2005. numerical evaluation of buckling and post-buckling behaviour of corrugated board containers. xxxiv convegno nazionale. campbell, a. 2010. the use of a-flute, b-flute, ac-flute, and bc-flute corrugated paperboard as a cushioning material. master’s thesis. department of packaging science. clemson university de castro, lr., vigneault, c. and cortez, lab. 2005. effect of container openings and airflow on energy required for forced air-cooling of horticultural produce. canadian biosystems engineering, 47(3), 1–9. defraeye, t., cronjé, p., berry, t., opara, ul., east, a., hertog, m., verboven, p. and nicolai, b. 2015. towards integrated performance evaluation of future packaging for fresh produce in the cold chain. trends in food science & technology, 44(2), 201–225. defraeye, t., lambrecht, r., delele, ma., tsige, aa., opara, ul., cronjé, p., verboven, p. and nicolai, b. 2014. forced-convective cooling of citrus fruit: cooling conditions and energy consumption in relation to package design. journal of food engineering, 121, 118–127. delele, ma., ngcobo, mek., getahun, st., chen, l., mellmann, j. and opara, ul. 2013a. studying airflow and heat transfer characteristics of a horticultural produce packaging system using a 3d cfd model. part i: model development and validation. postharvest biology and technology, 86, 536–545. delele, ma., ngcobo, mek., getahun, st., chen, l., mellmann, j. and opara, ul. 2013b. studying airflow and heat transfer characteristics of a horticultural produce packaging system using a 3http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):194-201. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 201 d cfd model. part ii: effect of package design. postharvest biology and technology, 86, 546– 555. dimitrov, k. and heydenrych, m. 2009. relationship between the edgewise compression strength of corrugated board and the compression strength of liner and fluting medium papers. southern forests, 71(3), 227–233. émond, jp. and vigneault, c. 1998. reusable containers for the preservation of fresh fruits and vegetables. us patent 5,727,711. fadiji, t., ambaw, a., coetzee, cj., berry, tm. and opara, ul. 2018b. application of finite element analysis to predict the mechanical strength of ventilated corrugated paperboard packaging for handling fresh produce. biosystems engineering, 174, 260–281. fadiji, t., berry, tm., coetzee, cj. and opara, ul. 2018a. mechanical design and performance testing of corrugated paperboard packaging for the postharvest handling of horticultural produce. biosystems engineering, 171, 220–244. fadiji, t., coetzee, c. and opara, ul. 2016. compression strength of ventilated corrugated paperboard packages: numerical modelling, experimental validation and effects of vent geometric design. biosystems engineering, 151, 231–247. han, j. and park, jm. 2007. finite element analysis of vent/hand hole designs for corrugated fibreboard boxes. packaging technology and science, 20(1), 39–47. markström, h. 1988. testing methods and instruments for corrugated board. lorentzen & wettre. opara, ul., and pathare, pb. 2014. bruise damage measurement and analysis of fresh horticultural produce—a review. postharvest biology and technology, 91, 9–24. panyarjun, o. and burgess, g. 2001. prediction of bending strength of long corrugated boxes. packaging technology and science, 14(2), 49–53. pathare, pb. and opara, ul. 2014. structural design of corrugated boxes for horticultural produce: a review. biosystems engineering, 125, 128–140. pathare, pb., berry, tm. and opara, ul. 2016). changes in moisture content and compression strength during storage of ventilated corrugated packaging used for handling apples. packaging research, 1(1), 1–6. pathare, pb., berry, tm. and opara, ul. 2017. experimental investigation of compression strength of ventilated corrugated citrus packaging. packaging research, 2(1), 22–27. pathare, pb., opara, ul., vigneault, c., delele, ma. and al-said, faj. 2012. design of packaging vents for cooling fresh horticultural produce. food and bioprocess technology, 5(6), 2031–2045. singh, j., olsen, e., singh, sp., manley, j. and wallace, f. 2008. the effect of ventilation and hand holes on loss of compression strength in corrugated boxes. journal of applied packaging research, 2(4), 227–238. thompson, jf., mejia, dc. and singh, rp. 2010. energy use of commercial forced-air coolers for fruit. applied engineering in agriculture, 26(5), 919–924. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng article information 1.0introduction 2.0materials and methods 2.1packaging design 2.2finite element analysis 2.3box compression strength (bct) 3.0results and discussion 3.1compression strength of the package designs 3.2simulation result 4.0conclusions 5.0acknowledgements references availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 1-15 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system mofoke a.l.e1., j.k. adewumi2, o.j. mudiare2 and a.a. ramalan2 abstract the medical infusion set was re-structured to serve as a point source emitter for low-cost drip irrigation systems. the re-structured device, here referred to as ‘medi-emitter’, was subjected to laboratory tests to evaluate its hydraulic characteristics. a calibration experiment, relating flow rate and level of emitter opening, gave a discharge range of 0-533 lhr-1 as the emitter flow regulator was gradually opened to its maximum. the peak discharge of 533 lhr-1 was recorded under a pressure of only 49.05 kpa. this makes the medi-emitter particularly suitable for low-cost drip systems that operate under gravity flow with low pressures often less than 58.86 kpa. the exponent values of the emitter flow functions ranged from 0.610 to 1.038, thus characterising the device as a laminar emitter. the laminar characteristic increases progressively with closure of the flow regulator. manufacturer’s coefficient of variation of the medi-emitter was 0.065. measured coefficient of variation and deviation from nominal flow were between 5 and 19%. the energy head loss coefficient of the emitter ranged from 1.48 to 28.25, which is within the range of common water outlets widely in use. discharge through the medi-emitter was found to increase with rise in water temperature, although these variations were insignificant at 95% probability level. the influence of temperature on discharge was stronger at lower levels of emitter opening. the emitter gave average soil wetting diameters of 0.679, 0.924 and 1.07 m for sand, loam and clay soils respectively, under a discharge of 2 lhr-1. these values are comparable to those of conventional emitters. results from this research reveal the potential of the medical infusion set to adequately serve as emitter for low-cost drip irrigation systems, particularly because it is widely available even in most rural communities. 1. introduction drip irrigation is the slow and frequent application of water to plants through mechanical devices called emitters, and at rates approximating the crop consumptive use. this method of irrigation is becoming increasingly favoured as there is the need for more efficient use of water in areas of scarcity. emitters are the terminal components of a drip system and they perform the crucial role of delivering a near exact irrigation water requirement directly to the crop root zone. this way, losses through evaporation, deep percolation and surface run-off are minimised, causing drip systems to offer high efficiencies of up to 90% (or, 1985; dawood and hamad, 1985; brouwer et al., 1989; donay et al., 1997). the success of a drip system in achieving high irrigation efficiencies hinges on the performance of its emitters. today, a number of manufacturing companies have accordingly specialised in the production of emitters that can satisfy most demands. in many developing countries, however, drip irrigation is not popular among peasant farmers. this is due to two principal reasons. firstly, unavailability of emitters and other system components in the local markets, and secondly, the low purchasing power of peasant farmers. 1 agric. engineering program, sch. of eng’g & eng’g tech. atbu, bauchi. p.m.b. 0248 bauchi, nigeria 2department of agric. engineering, ahmadu bello university, zaria. kaduna state. nigeria http://www.azojete.com.ng structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 2 attempts have been made to introduce low-cost and accessible drip components with a view to making drip irrigation affordable by small-holder farmers. in the philippines for instance, baqui and angeles (1995) used bamboo for drip laterals, and further improvised a low-cost emitter by inserting polyethylene cordage into a narrow (3 mm diameter) plastic tube. in nigeria, yohanna (1997) used canvas material with varying lengths to obtain specified flow rates. unfortunately, these low-cost emitters do not have provisions for flow regulation, which restricts the range of irrigation regimes for which they could be used. besides, the cordage and canvas emitters are apparently difficult to reproduce in large numbers and with precision using present day low-cost simple procedures. the medical infusion set used in hospitals has a flow regulator, and is widely available even in most communities of developing countries, giving it a potential to be used for varied water application to crops. this research therefore, investigated the hydraulic characteristics of the medical infusion set and examined the suitability of using this device as emitter for low-cost drip irrigation. 2. materials and methods the medical infusion set also referred to as intravenous administration set is the device used in hospitals to dose liquid medications to patients. figure 1 shows the main components of the infusion set according to the manufacturer, zhejiang kindly medical devices and plastics co. ltd, china. the original configuration of this device was amended for it to serve as emitter for drip irrigation. firstly, the needle was discarded to eliminate possibilities of operational injuries. then, the discharge monitor was cut off because it is apparently of little use when the device is used for watering crops. with these alterations, water was observed to discharge directly out of the contrivance. the length of the tubing was shortened to 450 mm, taken to be one half the inter-row spacing of a hypothetical crop. the spike was removed and replaced with the luer adapter to function as connector (nipple) between the emitter and the lateral. this left the latex flash bulb injection site to serve as the emitter exit with an aperture of 5 mm. all these modifications transformed the infusion set to what would henceforth be called “medi-emitter”. the roller clamp is movable, and may be placed anywhere along the length of the tubing. the medi-emitter and associated parts re-named using conventional emitter nomenclature is shown in figure 2. azojete vol. 4 2004 3 leur adapter latex flash bulb injection site rroller clamp tubing discharge monitor spike figure 1: main components of the medical infusion set figure 2: main components of the medi-emitter discharge emitter tube emitter nipple water outlet structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 4  xee pkq  the first hydraulic experiment was a calibration exercise between emitter discharges over a range of emitter openings. discharge measurements were made under pressures of 5.0 – 58.86 kpa at increments of 5kpa. this pressure range was chosen because the medi – emitter was conceptualised to be used for low-cost drip irrigation systems, which are operated mainly under gravity. pressure variation was achieved by raising a 40 l plastic water container to heights corresponding to the desired pressure head. a float valve in a second 30 l pressure stabilization tank was used to maintain a constant pressure head during measurements. the scale of the emitter flow regulator was graduated, delineating ten levels of emitter openings. discharge was measured at each level of emitter opening and pressure head using the volumetric method according to merriam et al. (1980). the experiment was conducted at temperatures of 20-25 oc, which is regarded as the optimum temperature range for such tests (ozekici and sneed, 1995). the influence of pressure head on discharge for the medi-emitter was investigated at the ten principal levels of emitter opening – 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%. pressure was varied from 5 kpa at increments of 2.5 kpa to a maximum of 49.05 kpa. measured values of discharge and pressure were fitted into equation 1 (karmeli et al., 1985), and the values of x and k determined using regression analysis. 1 where: qe= emitter discharge, m3/hr or l/hr pe = pressure at emitter ,m k = coefficient of proportionality that characterises an emitter, and depends on the emitter diameter and shape. x = emitter discharge exponent that expresses the emitter flow regime, and classifies the emitter as either long path (or laminar) emitter, orifice (or turbulent) emitter, vortex emitter, or pressure compensating emitter. the discharge uniformity of the medi-emitter was assessed using two standards – the standard of the american society of agricultural engineers (asae), and that of the international standard organisation (iso). the asae reflect differences in emitter performance due to manufacturing variations in a parameter known as manufacturer’s coefficient of variation defined as (asae standards, 1990): 2 where: cv = manufacturer’s coefficient of variation qavg= mean emitter flow rate, lhr-1 sq= standard deviation of flow rates of the emitter in a sample, lhr-1 the recommended guidelines (asae standards, 1990) for classifying emitters based on their cv values is given in table 1. avg q v q s c  azojete vol. 4 2004 5 table 1: recommended classification of coefficient of manufacturing variation (asae ep 405.1) cv range classification < 0.05 excellent 0.05-0.07 average 0.07-0.11 marginal 0.11-0.15 poor > 0.15 unacceptable the international standard organisation (iso 9260) uses two indicators of the uniformity of emitter discharge. these are: coefficient of variation and deviation from the nominal flow rate (dev) defined in equation 3 (iso, 1991). 3 where: qm = average flow rate qn = nominal flow rate the cv and dev were calculated from 100 emitters using equations 2 and 3. the effect of temperature on discharge for the medi-emitter was also studied. this was done by raising the temperature of water to 60oc and taking the flow rate as the water cooled down. discharge measurements were made at 10oc intervals to a minimum of 10oc. temperatures below 20oc were obtained through immersion of ice pellets into the water tank, and constantly monitoring the fluid temperature as it reached the desired temperature mark. the energy head loss coefficient of the medi-emitter was calculated using equation 4 (dake, 1983). this was done at the principal levels of emitter opening. 4 where: vc= coefficient of velocity vc is given by equation 5 (lal, 1963) 5 where: x and y are respectively horizontal and vertical co-ordinates of the jet of water issuing from the emitter. h is the pressure head of water, causing flow. 11 2  c n v k hy xvc 4 2            qn qnqmdev 100 structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 6 another measured emitter characteristic was the soil wetting diameter as affected by emitter discharge. this parameter is essential in determining the irrigation time, the intra-crop spacing and the number of point source emitters to use. the wetted diameter was determined for the three major textural groups: clay, loam and sand. the volume of water required to saturate one square meter of soil was calculated for each soil type based on the soil physical properties. this quantity of water was then applied to the soil at different discharges from the mediemitter. the diameter of the wetted area was measured with a meter rule. the values were fitted to the linear function and their trendline equations determined using regression analysis. 3. results and discussion figure 3 shows the calibration curves of the medi-emitter. the emitter flow functions are presented in figures 4 and 5. table 2 contains values of the energy loss coefficients and manufacturer’s coefficient of variation of the medi emitter. the discharges through the mediemitter measured at different temperatures are given in table 3, while table 4 contains the soil wetting diameters under different discharges from the medi-emitter. table 2: measured values of manufacturer’s coefficient of variation (cv) from nominal flow rate (dev), and the energy head loss coefficients of the medi-emitter level of emitter opening (%) cv dev (%) kn 10 ◘ ◘ ◘ 20 ◘ ◘ ◘ 30 0.078 15.10 ♀ 40 0.075 15.10 ♀ 50 0.069 14.81 28.25 60 0.070 14.62 25.32 70 0.068 14.52 13.52 80 0.068 14.50 13.00 90 0.069 14.47 1.500 100 0.062 14.45 1.480 ◘ there was no flow at these levels of emitter opening. ♀ the flow at these levels did not produce jets to enable calculation of kn using equations 4 and 5. azojete vol. 4 2004 7 figure 3: calibration curves of the medi-emitter at various pressure heads structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 8 pressure head (m) figure 4: emitter flow functions at 30 –50 % emitter opening 30% emitter opening 40% emitter opening d is ch ar ge (l/ hr ) 50% emitter opening azojete vol. 4 2004 9 figure 5: emitter flow functions at 60 –100% emitter opening pressure head (m) d is ch ar ge (l/ hr ) 60% emitter opening 70% emitter opening 100% emitter opening structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 10 table 3: discharge (lh-1) through the medi-emitter at different water temperatures pressure head (m) level of emitter opening (%) temperature (oc) 10 20 30 40 50 60 1 30 0.80 0.83 0.82 0.87 0.88 0.92 50 46.72 47.00 47.18 47.30 47.30 47.38 70 146.76 146.77 146.71 146.76 146.76 146.77 100 200.00 200.00 200.01 199.99 200.10 200.14 2 30 25.00 25.10 25.42 25.41 25.83 25.88 50 120.99 121.00 121.12 121.50 121.59 121.59 70 266.0 266.60 266.70 266.61 266.64 266.61 100 340.12 340.10 340.11 340.10 340.11 340.12 3 30 56.10 56.00 56.81 57.32 57.62 57.91 50 191.98 192.80 193.00 193.32 193.85 194.41 70 366.99 367.10 367.20 367.20 367.21 367.22 100 402.80 402.80 402.81 402.80 402.80 402.80 4 30 66.52 66.70 67.100 68.00 67.81 67.98 50 222.50 222.50 222.54 222.59 222.58 222.59 70 405.98 406.10 406.11 406.33 406.11 406.14 100 468.88 468.90 468.92 468.80 468.91 468.91 5 30 79.00 79.00 79.89 80.00 80.62 80.84 50 244.86 245.00 245.31 245.31 245.62 245.84 70 426.65 427.00 427.01 427.00 427.02 427.02 100 533.20 533.21 533.21 533.22 533.22 533.22 azojete vol. 4 2004 11 table 4: soil wetted diameters at different discharges through the medi-emitter discharge (lh-1) wetted diameter (m) sand loam clay 0.06 0.13 0.25 0.29 0.08 0.18 0.28 0.37 0.10 0.21 0.39 0.42 0.24 0.30 0.43 0.54 0.27 0.38 0.46 0.62 0.50 0.40 0.57 0.88 0.70 0.43 1.06 1.17 1.00 0.56 1.18 1.23 2.00 0.82 1.20 1.42 3.00 0.95 1.22 1.50 4.00 1.06 1.46 1.64 5.00 1.64 1.72 11.89 6.00 1.68 1.74 1.89 9.00 1.76 1.86 1.98 10.00 1.83 2.01 2.24 figure 3 exhibits a wide range of emitter discharge, stretching from 0 to 533 lh-1. the fact that there was no flow when the emitter was completely closed denotes a 100% flow control of the medi-emitter. the increase in discharge resulting from increase in emitter opening progressed in four stages from 14m pressure head. between 20 – 70% and 80 – 90% emitter opening, discharge increased exponentially and remained constant between 70 – 80% and 90 – 100%. same discharge trend observed at 5m pressure head would likely be obtainable for pressure heads greater than 5m. the shapes of the calibration curves serve as a guide when adjusting the device to obtain desired flow rates. most conventional emitters are rated at 2-16 lh-1. the medi-emitter could satisfactorily operate within this discharge range by simply adjusting the emitter flow regulator. the required level of emitter opening may be obtained through extrapolation from figure 3, or by solving for elev from the appropriate equation in table 5. partitioning of the flow regulator scale could be done visually and then fine tuned to precision. table 5: trendline equations of the calibration curves relating emitter discharge (qe ) and level of emitter opening (elev) of the medi-emitter structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 12 pressure head (m) range of emitter opening (%) regulatory function r2 1 0-20 qe = 0 1.00 20-70 qe= 0.0475e0.123(elev) 0.941 70-90 qe= 51.74e0.0145(elev) 0.919 90-100 qe = 200.00 1.00 2 0-20 qe = 0 1.00 20-70 qe= 5.15e0.05(elev) 0.983 70-80 qe= 270.00 1.00 80-90 qe = 7.57(elev) – 338.55 0.995 80-100 qe = 340.43 1.00 3 0-20 qe = 0 1.00 20-70 qe= 17.03e0.045(elev) 0.978 70-80 qe = 367.00 1.00 80-90 qe = 188.61e8.297e-10(elev) 0.993 90-100 qe = 402.76 1.00 4 0-20 qe = 0 1.00 20-70 qe= 21.32e0.044(elev) 1.00 70-80 qe= 406.70 0.974 80-90 qe = 6.19(elev ) – 86.45 0.998 90-100 qe = 468.88 1.00 5 0-20 qe = 0 1.00 20-90 qe = 0.234(elev)1.755 0.986 90-100 qe = 533.3 1.00 figures 4 and 5 demonstrate that the flow functions of the medi-emitter do not completely follow a power curve from 30-60 % emitter opening. the flow functions have two segments within this range of emitter opening. the first part from 0 to about 2 m pressure heads is an exponential relationship indicated by broken lines, while the power curve represented with solid lines starts from about 2 to 5 m pressure heads and beyond. the two portions of the flow functions are presented mathematically in table 6. azojete vol. 4 2004 13 the exponents of the flow power curves in table 6 range from 0.610 to 1.038, which classifies the medi-emitter as a laminar emitter (james, 1988; karmeli et al., 1985). based on the trend of the exponent values, the degree of laminar flow characteristic of the medi-emitter increases as the emitter regulator is progressively closed. the exponent value of this device at 100% emitter opening (0.610) is close to that (0.638) of the 4 lh-1 toro e-2 flag style drip emitter. the medi-emitter therefore offers a comparable flow regime with standardized emitters. the fact that the medi-emitter operates within the laminar regime prevents it from offering the advantage of self-flushing which is a characteristic of the turbulent flow emitters. at higher levels of emitter opening (80 – 100%), however, the flow characteristic of the mediemitter tends towards the labyrinth type with x values of 0.724 and 0.610, approaching the 0.4-0.5 range for turbulent emitters. the medi-emitter may therefore provide this self flushing advantage to some extent when the device is regulated towards full opening. nevertheless, use of the medi-emitter for low-cost drip irrigation should be complemented with appropriate cheap filtration units to prevent introduction of sediments into the laterals. the medi-emitter gave a maximum flow rate of 533 lh-1 at 5 m pressure head, whereas most customized emitters can deliver a maximum of only about 150 lhat exceedingly high pressure heads of 40-70 m. high emitter discharges are desirable when irrigating orchard crops having high consumptive use like banana, mangoes and citrus. the medi-emitter would easily release water at typical high rates of 150 lh-1 under a pressure head of only 1 m. this discharge is obtainable under 1 m pressure head when the flow regulator opening is between 80-85%. such a low operating head for the medi-emitter permits its use for low-cost trickle systems that operate mainly under gravity flow with pressure heads between 1-6 m. this also provides possibility of designing precision low-cost drip systems not only for vegetable crops (as is currently the case), but also for orchards. table 2 contains calculated values of manufacturer’s coefficient of variation, deviation from nominal flow rate, and the energy head loss coefficients of the medi-emitter at increasing levels of emitter opening. from the table, cv ranges from 0.062 at 100% emitter opening to 0.078 at 30% emitter opening. up to 75% of the calculated cv fall within 0.05-0.07. this classifies the medi emitter as average in terms of discharge uniformity according to the standards of the american society of agric. engineers (asae standards, 1990). the reduction in cv with decrease in the emitter opening is probably due to differential compression of the emitter tube by the control knob, and human inability to regulate all the 100 emitters used to exactly equal levels of emitter opening. also, the calculated dev values are all between 5 and 15%, characterising the device as category b emitter according to the international standards organisation (iso, 1991). from these two perspectives, the discharge uniformity of the medi-emitter is considered satisfactory. the energy head loss coefficient (kn) increased from 1.48 at full emitter opening to 28.25 at 50% emitter opening. the increase in kn with successive closure of the emitter opening depicts that much energy is lost by water flowing through the device at lower levels of opening. from equation 4 therefore, kn would be tend to infinity when the flow through the emitter approaches zero. the same trend in kn was recorded for gate valves (brater and king, 1976). the authors reported kn values ranging from 1.00 for a 0.5 inch gate valve at full opening to as high as 60 at 25% valve opening. structuring and characterisation of the medical infusion set as emitter for low-cost drip irrigation system 14 adoption of the medi-emitter for drip systems is therefore not expected to introduce exit losses out of the range already presented by existing pipe fittings. table 3 shows discharges through the medi-emitter at six different temperatures. from the table, discharge increases with temperature. statistical analysis, however, indicated that difference in discharge due to temperature variation for the medi-emitter was not significant at 95% probability level. the effect of temperature on discharge was more pronounced at lower levels of emitter opening (30 and 50 % opening) because the nature of flow at these levels of opening was laminar with x values of 1.038 and 0.791 respectively (table 6). flow through the emitter approached the turbulent range at 100% opening with x values of 0.610, causing the temperature effect on discharge to be minimal at this level of opening. table shows that the wetting diameters of the medi-emitter increase with emitter discharge. the increase was found to be linear with the following trendline equations: wds = 0.1796qe + 0.32 ; r2 = 0.91 6 wdl = 0.1670qe + 0.59 ; r2 = 0.81 7 wdc = 0.175qe + 0.72 ; r2 = 0.0.79 8 where wds ,wdl and wdc are the wetted diameters for sand, loam and clay soils respectively. using equations 6, 7 and 8 with a typical emitter discharge of 2 lhr-1, the medi emitter would wet soils to projected average diameters of 0.679, 0.924 and 1.07 m for sand, loam and clay respectively. these values are comparable to those derived from generalised wetting diameter functions (0.54, 0.920, and 0.924) given by karmeli et al. (1985) for the three major soil types in same order. 4. conclusion it has been shown that the medical infusion set can serve as a point source emitter for lowcost drip irrigation if properly re-configured. the infusion set was re-structured by removing its needle and other minor components. the modified device known as ‘medi-emitter’ can deliver water with discharges of up to 533 lhr-1under a pressure head of 5 m. the emitter flow regulator offers precise discharge regulation making it possible to obtain a very wide range of flow rate between 0-533 lhr-1. flow through the medi-emitter is mainly laminar. the influence of temperature on discharge is insignificant at 95% probability level within water temperatures of 10-60 oc. the medi-emitter offers uniform discharge and produces satisfactory wetting diameters. this medical infusion set is widely available and from the results of this study, it could be easily modified and used as emitter for low-cost drip irrigation systems. azojete vol. 4 2004 15 references asae (1990). american society of agricultural engineers (asae) standards 37th edition. ep 405.1 design, installation & performance of trickle irrigation systems. michigan. baqui, m. a. and h. l. angeles (1994). construction, operation and test of a bamboo drip irrigation system. agricultural mechanisation in asia africa and latin america (ama). 25,(2) 41-44. benami, a. and a. ofen (1984). irrigation engineering: sprinkler, trickle, surface irrigation principles, design and agricultural practices. irrigation engineering scientific publications (iesp), israel. brater, e. f. and h. w. king (1976). handbook of hydraulics for the solution of hydraulic engineering problems, 6th edition. mcgraw hill book company, ny brouwer, c., k. prins and m. heibloem (1989). irrigation water management: training manual no. 4, fao, rome. dake, j. m. k. (1983). essentials of engineering hydraulics. mc millan ltd. london. dawood, s. a. and s. n. hammad (1985). a comparison of on-farm irrigation systems performance. in: drip/trickle irrigation in action. proceeding of the third international drip/trickle irrigation congress, nov 18-21. california, usa. vol. ii. asae, st. joseph michigan usa: 540-545. donay, h. r., f. r. lamm, m. alam, t. p. trooien, g. a. clark, p. l. barnes and k. mankin (1997). efficiencies and water losses in irrigation systems. irrigation management series. cooperative extension services, kansas state university, manhattan. howell, t. a., d. s. stevenson, f. k. aljibury, h. m. gitlin, i-pai wu, a. w. warrick and p.a.c. raats (1980). design and operation of trickle (drip) system. in: design and operation of farm irrigation systems. (m. e. jensen, ed.) asae monograph 3. st. joseph michigan: 663-717. international standard organisation, iso (1991). agricultural irrigation equipment: emitters, specifications and test methods. iso 9260. int. stand. org. new york, ny. james, l. g. (1988). principles of farm irrigation system design. john wiley and sons inc. new york. karmeli, d., g. peri, and m. todes (1985). irrigation systems: design and operation. oxford university press, capetown. lal, j. (1963). hydraulics. 4 th edition. metropolitan books co. private ltd., delhi. merriam, j. l., m. n. shearer, and c. m. burt (1980). evaluating irrigation systems and practices. in: design and operation of farm irrigation systems. (m. e. jensen, ed.) asae monograph 3. st. joseph michigan. or, u. (1985). jordan valley drip irrigation scheme: a model for developing countries. in: drip/trickle irrigation in action. proceeding of the third international drip/trickle irrigation congress, nov 18-21. california, usa. vol. i. asae, st. joseph michigan usa: 166-176. ozekici, b. and r. e. sneed (1995). manufacturing variation for various trickle irrigation online emitters. applied engineering in agriculture: 11(2): 235-240. schwab, g. o., d. d. fangmeier, w. j. elliot and r. k. frevert (1993). soil and water conservation engineering. 4th edition. john wiley and sons inc. new york. yohanna, a. d. (1997). design, construction and characterisation of a canvas trickle irrigation line source emitter. unpublished msc. thesis. department of agricultural engineering, university of maiduguri, nigeria. abstract 1. introduction classification 3. results and discussion kn qe = 0 qe = 0.0475e0.123(elev) qe = 0 qe = 0 qe = 0 qe = 0 where wds ,wdl and wdc are the wetted diameters fo using equations 6, 7 and 8 with a typical emitter references arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):279-288 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 279 original research article solid waste generation and characterization in ilorin, nigeria o. a. mokuolu, j. o. iji* and s. a. aremu department of water resources and environmental engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria *corresponding author’s email address: iji.jo@unilorin.edu.ng 1.0 introduction increase in the global population and rising demand for food and other essentials, has caused a rise in the amount of solid waste generated daily at household level. solid wastes can be defined as non-liquid and nongaseous products of human activities, regarded as being useless (mungure, 2008; babayemi and dauda 2009). poor waste management poses several challenges to human healthespecially those living close to the dumpsites which could pollute the environment and affect water, food sources, land, air and vegetation (njoroge and busman 2007). solid waste management has emerged as one of the greatest challenges facing state and local government environmental protection agencies in nigeria (olukanni and mnenga 2015). however, the capacity to develop an efficient and sustainable waste management program in developing nations has been limited by insufficient documentation of the volume and characterization of solid waste generation (olukanni et al. 2013) which has caused public health issues and environmental problems (yoshida, 2018). according to pervez and kafeel (2013), improper waste disposal and management causes all types of pollution in the air, soil, and water, indiscriminate dumping of refuse contaminates surface and groundwater supplies. in urban areas, improper waste disposal clog drains, creating stagnant water for insect breeding article information abstract global per capita waste generation rates and characterization vary by regions, countries, and within cities. the generation, l and characterization of waste from selected areas in ilorin, nigeria, prone to indiscriminate disposal of solid waste without consequence were analyzed for proper management. municipal solid wastes were sorted, analyzed by weight and percentage composition using the quantitative approach. the average generated waste per capita was estimated to be 0.66 kg/day, w/w distribution was 57.53% food waste, 9.07% nylon (flexible films), 5.98% plastic (rigid containers),4.95% textile, 10.51% paper and 11.96% others. the average moisture content was 46.16% food waste, 20.63% nylon, 18.65% plastic, 36.67% textile, 18.45% paper and 42.89% others. the results show an average bulk density of 10.36 kg/m3 of food waste, 2.14 of nylon, 0.5 of plastic; 0.93 of textile; 2.74 of paper and others 5.36. the chemical analysis showed that volatile matter ranged from 20.55 to 24.10%, ash content 3.10to 3.90%, fixed carbon 7.5to 9.8%, calorific value 14820to 18360 (kj/kg), nitrogen 0.40to 0.50%, hydrogen 4.38to 5.80%, carbon 40.90 to 44.30%, oxygen 30.80 to 34.60%, sulphur 0.19 to 0.24%, fusing point of ash 3.12to 4.38 °c, and heating value from 13.520to 13.64 kj/kg. the results generated could play a positive role in the management of solid waste in that area. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 oct., 2020 revised 9 march, 2021 accepted 21 march, 2021 keywords: municipal solid waste generation waste components environmental pollution solid waste moisture content mokuolu et al: solid waste generation and characterization in ilorin, nigeria. azojete, 17(3):279-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 280 and floods during rainy seasons. uncontrolled burning of waste also contributes significantly to air pollution. dumpsites are known for their smelly and unsightly conditions, these conditions are worse in the summer because of extreme temperatures, which speed up the rate of bacterial action on biodegradable organic material (salam, 2010). globally, about 37 percent of waste is disposed of in some type of landfill, 33 percent is openly dumped, 19 percent undergoes materials recovery through recycling and composting, and 11 percent is treated through modern incineration. lower-income countries generally rely on open dumping with 93 percent of waste is dumped in low-income countries and only 2 percent in high-income countries. upper-middle-income countries practice the highest percentage of landfilling, at 54 percent. this rate decreases in high-income countries to 39 percent, where 35 percent of waste is diverted to recycling and composting and 22 percent to incineration. by 2030, the world is expected to generate 2.59 billion tonnes of waste annually. the world generates 0.74 kg of waste per capita per day, which is correlated with income levels and urbanization rates. in nigeria, municipal waste densities generally range from 250370 kg/m3 (olukanni and mnenga 2015); waste generation rate is 25 million tons annually and at a daily rate of 0.44kg 0.66 kg/capital/day (ogwueleka, 2009) africa regions is growing rapidly, whereby in 2050, the total waste generated is expected to triple, double, and double; respectively. thus, addressing this disturbing issue that has assumed a frightening height with associated effects on the environment holistically is an unavoidable alternative for a safe, healthy and viable living (ahmad et al., 2013; adewumi and ajibade 2015; akinbile et al., 2016a, b). generally, the higher the economic development and rate of urbanization, the greater the amount of solid waste produced. it was reported by hoornweg and bhada-tata (2014) that urban residents produce about twice as much waste as their rural counterparts. the characterization, generation and disposal of waste in a developing nation is an intrinsic part that should not be ignored (adewumi et al., 2017) and waste characterization data specific to african cities are generally not available, though some regional evaluations could be made. this study thus characterized and quantified municipal solid waste generated in some selected areas of ilorin metropolis for proper management. 2. materials and methods 2.1. study area the study area is a densely populated community in ilorin, kwara state, nigeria, located at emirs road, gambari, and centreigboro on latitude of 8° 29' 33"n, 8° 30' 02"n and 8° 29' 52"n and longitude of 4° 33' 22"e, 4° 33' 37"e and 4° 33' 19"e respectively. preliminary survey revealed that these areas were prone to indiscriminate disposal of solid waste. without consequence. figure 1 shows the study area on the map of kwara state nigeria. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):279-288. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 281 figure 1: map of kwara state showing the study area source: mokuolu (2014) 2.2. waste quantification primary data were collected randomly from selected households. the total waste generated and other data were determined according to kodwo et al. (2015). total waste generated in the study area was determined using equation (1) per capita waste generation = (1) 2.3. physical composition of municipal solid waste analysis municipal solid waste from the study areas were sorted manually with the use of hand gloves, apron, boots and nose masks into the following compositions and analyzed by weight and as well as the percentage composition. i. food waste ii. plastics iii. metals iv. papers (cardboard, sheet, office print, tissue, and diapers) v. nylon vi. textiles vii. miscellaneous (other materials which could not fit in above) 2.4. percentage weight of waste components after sorting, the waste was collected in an empty container (w1) using the laboratory weighing scale. the weight of container along with individual component was measured as (w2). the individual weight of the component (wc = w2-w1) was thus calculated. mokuolu et al: solid waste generation and characterization in ilorin, nigeria. azojete, 17(3):279-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 282 2.5. determination of moisture content the moisture content was determined as the weight of moisture per unit weight of dry or wet material. in equation (2), the moisture content was expressed as follows: (2) where: a = initial weight of the sample (g) b = weight of the sample after drying (g). 2.6. determination of bulk density the bulk density was determined by weighing a container of known volume as (v1), the weight was recorded as (w1). the waste sample was poured into the container until it overflowed, the sample was then compacted three times by dropping it from a height of 10 cm and the container was refilled after the compaction. the container and its content were weighed and recorded as w2. the bulk density was determined from equation 3. – (kg/m3) (3) 2.7. chemical composition the chemical composition such as carbon (c), hydrogen (h), oxygen (o), nitrogen (n), sulphur (s), and ash were determined. the following procedures were used: 2.7.1. carbon in equation 4, the percentage total carbon of the waste sample was determined directly by adding the volatile matter and the fixed carbon together. (4) 2.7.2. hydrogen and oxygen the percentage of hydrogen and oxygen in the waste sample were obtained analytically by the difference between the sum of percentage total carbon, nitrogen, sulphur, and 100. – (5) 2.7.3. nitrogen nitrogen was determined using kjeldahl's method. of the solid waste sample 1.00g was heated with concentrated h2so4 (tetraoxosulphate (vi) acid) in the presence of k2so4 (potassium tetraoxosulphate (vi) salt) and cuso4 (copper (ii) tetraoxosulphate (vi) salt) in a long-necked flask called kjeldahal’s flask thereby converting the nitrogen in the solid waste sample into ammonium sulphate. when a clear solution is obtained, the solution was treated with 50% naoh (sodium hydroxide) solution. the ammonia formed was distilled over and absorbed in a known quantity of standard h2so4 solution. the volume of an un-used acid was then determined by titration against a standard solution of naoh. the amount of acid neutralized by liberated nh3 from the solid waste sample was evaluated. the percentage of nitrogen in the waste was then calculated. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):279-288. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 283 2.7.4. sulphur of the weighed samples, 25 ml were dissolved in water and pipetted into 50 ml standard flasks followed by 20 ml gelatin bacl2 solution and made up to 50 ml mark. the solution was allowed to stand for 30 minutes. a known weight of the dried sample was taken into an open crucible and heated to open air at 700-750 in a muffle furnace until a constant weight was obtained. the weight of the residue was reported as ash. percentage of ash = (6) 2.7.6. fusing point of ash this is the temperature at which the ash resulting from the burning of waste will form a solid (clinkers) by fusion and agglomeration and the typical fusing temperatures 1100 1200 . 2.7.7. proximate analysis this is the analysis of waste to determine moisture content, volatile matter, ash and fixed carbon. the moisture content of the collected waste samples was determined using astm 3173 method in which 1 kg of the solid waste sample was placed in a pre-weighed dish and placed in an oven at 105 ᵒc to a constant weight. the moisture content was calculated as a percentage. % moisture content = – (7) 2.7.8. volatile matter (additional loss on ignition at 950 oc) this was determined by weighing 5 kg of dried waste samples and placing in a furnace for 7 minutes at 950 ᵒc (astm 3175). after combustion, the samples were weighted to determine the ash dry weight, with the volatile matter being the difference between the dried sample and the ash % volatile matter = – (8) 2.7.9. fixed carbon the percentage of fixed carbon was determined by deducting the sum total of moisture volatile matter and ash percentage from 100 % = 100% -% moisture content +% volatile matter + % ash (9) 2.7.10. data analysis the results were checked for errors and cleaned as appropriate before computation and data analysis. the data were analyzed using spss 17.0 software packages. mokuolu et al: solid waste generation and characterization in ilorin, nigeria. azojete, 17(3):279-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 284 3. results and discussion the results are presented in tables 1 to 6., . table 1 shows that average waste generation per households is 0.54 kg/capita/day in emirs road, 0.48 kg/ capita/day in centreigboro and 0.84 kg/ capita/day in gambari. a higher standard of living, economic status of people and affluence results in more wastes and higher per capita generation (mathur 2018; irwan et al., 2012) waste generated is higher in all households in gambari compared to households in emirs road and centreigboro revealing a higher standard of living in gambari compared to the other two centers. according to babayemi and dauda (2009), this trend could have been influenced by the population, level of industrialization, socio-economic status of the citizens and the kinds of commercial activities that are predominant. the anova indicates that fvalue (0.073) is less than the critical f value (3.885), which means per capita waste generated among the areas is significant as indicated in table 2. this also shows that per capita waste generated among the areas is significantly different. this implies that waste generation at gambari is significantly higher than those generated from emirs road and centreigboro, whereas no significant different exist between the latter two areas. table 1: average waste generation in the study areas location average waste generation (kg/c/d) emirs road 0.54 centre-igboro 0.48 gambari 0.84 table 2: anova for waste generation in the study areas source of variation ss df ms f p-value f crit between groups 5.32e+08 2 2.66e+08 0.073047 0.929967 3.885294 within groups 4.37e+10 12 3.64e+09 total 4.43e+10 14 after physical characterization, the results showed different categories of wastes including food waste, textiles, plastic, nylon, paper were present in varying proportions. 60% of waste components from ilorin is generated by women from homes (domestic refuse) since the industrial and commercial base of the metropolis is negligible. table 3 reveals the constituents and proportion of solid waste generated by households in the study area. it was observed that food waste is the dominant type of waste generated in these households and it accounts for 57.53% of the weight composition in the waste. nylon waste 9.07% is next to food waste. paper waste is 10.51%, textile waste is 4.95%, whereas plastic waste is 5.98% only. the remaining 11.96% accounts for other types of wastes. it is therefore evident that most wastes generated in the study area are biodegradable. this agrees with the findings of wolf (2004), that most wastes generated in households in growing cities of developing countries are biodegradable wastes (food, paper, fabrics etc). however, major waste composition obtained in ghana were organics and plastic (kodwo et al., 2015). according to yoshida (2018), nigeria, ghana, zambia, namibia and congo (the republic of congo) are countries where the waste generation volume are relatively small compared with other african countries. at the global arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):279-288. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 285 level, food and green waste comprise more than 50 percent of waste in lowand middleincome countries while in high-income countries the amount of organic waste is comparable. recyclables make up a substantial fraction of waste streams, ranging from 16 percent paper, cardboard, plastic, metal, and glass in low-income countries to about 50 percent in high-income countries. as countries rise in income level, the quantity of recyclables in the waste stream increases, with paper making significant increase. at an international level, dry recyclables (plastic, paper and cardboard, metal, and glass) amount to another 38 percent of waste. waste composition varies considerably by income, the percentage of organic matter in waste decreases as income levels rise. consumed goods in higher-income countries include more materials such as paper and plastic than they do in lower-income countries. the granularity of data for waste composition, such as detailed accounts of rubber and wood waste, also increases by income level. the anova produces a test statistics of (0.17) and p-value (0.91) which is greater than a significant level (0.05) as indicated in table 4. table 3: average percentage weight composition, moisture content and bulk density of waste from the study areas s/no waste components weight composition (%) dry weight (%) volume (m3) moisture content (%) density (kg/ m3) 1 food waste 57.53 41.19 0.14 46.16 10.36 2 textiles 4.95 3.69 0.14 36.67 0.93 3 plastic 5.98 1.99 0.14 18.65 0.50 4 nylon 9.07 24.15 0.14 20.63 2.14 5 paper 10.51 7.67 0.14 18.45 2.74 6 others 11.96 21.31 0.14 42.83 5.36 table 4: anova for waste composition source of variation ss df ms f p-value f crit between groups 0.160679 3 0.05356 0.171826 0.913863 3.238872 within groups 4.987321 16 0.311708 total 5.148 19 table 5 shows the heating value, hydrogen, carbon, oxygen, nitrogen, sulphur, fusion point of ash, moisture content, volatile matter, ash content, fixed carbon and calorific value of the samples taken from the study areas. mokuolu et al: solid waste generation and characterization in ilorin, nigeria. azojete, 17(3):279-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 286 table 5: the average heating value (kj/kg), ultimate analysis, proximate analysis, fusing point of ash and calorific value s/no sample a (emirs road) sample b (gambari) sample c (centre igboro) 1 heating value (kj/kg) 13.632 13.520 13.641 2 hydrogen % 4.50 5.80 4.38 3 carbon % 42.50 44.30 40.90 4 oxygen % 30.80 34.60 33.10 5 nitrogen % 0.40 0.50 0.40 6 sulphur % 0.21 0.24 0.19 7 fusion point of ash 3.12 4.38 3.64 8 moisture content 24.52 24.93 23.51 9 volatile matter 49.79 47.86 48.68 10 ash content 7.51 7.75 8.51 11 fixed carbon 18.17 19.46 19.29 12 calorific (kj/kg) 16343.00 18360.00 14820.00 table 6: anova for heating value source of variation ss df ms f p-value f crit between groups 7.665233 2 3.832617 0.011055 0.989014 3.68232 within groups 5200.479 15 346.6986 total 5208.144 17 the heating value of the waste samples in the study area ranged from 13.520 kj/kg to 13.641kj/kg with waste from location (centre igboro) having the highest heating value while waste from location (gambari) has the lowest 4. conclusion and recommendations the average per capita waste generated was in the range of 0.480.84 kg/d. wastes generated were mainly food waste, paper, plastic, textiles, nylon and metals. food waste is generated more in all the study areas with percentage weight composition of 41.19%, moisture content of the waste stream for food waste is 46.16% and the bulk density is 10.36 kg/m3. the carbon content and calorific value of 44.30% and 18360.0 (kj/kg) respectively for gambari is high consequently this will yield a quality fuel and energy potential of waste for the area. also hydrogen and oxygen were present in large quantities of 34.60% and 5.80% respectively in same area. the outcome of this research can be used to determine specific energy content for energy production which is a source of renewable energy and it will help in reducing the release of greenhouse gas emission from open burning. it is recommended that sorting of recyclable be done by residents prior to waste disposal. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):279-288. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 287 references adewumi, jr., ajibade, fo., lasisi, kh. and oguntuase, am. 2017. characterization of municipal solid waste generated in akure metropolis. proceedings of the 2017 annual conference of the school of engineering & engineering technology (seet), the federal university of technology, akure, nigeria, 584 – 595. adewumi, jr. and ajibade, fo. 2015. the pollution effects of indiscriminate disposal of wastewater on soil in semi-urban area. journal of applied science and environmental management, 19(3): 412 419. ahmad, sz., sanusi, m., ahamad, s. and yusoff, ms. 2013. spatial effect of new municipal solid waste landfill siting using different guidelines, waste management and research, 32 (1): 24 – 33. akinbile, co., ajibade, fo. and ofuafo, o. 2016a. soil quality analysis for dumpsite environment in a university community in nigeria. journal of engineering technology, 10: 68 – 73. akinbile, co., erazua, ae., babalola, te. and ajibade, fo. 2016b. environmental implications of animal wastes pollution on agricultural soil and water quality. soil water research, 11: 172 180. babayemi, jo. and dauda, kt. 2009. evaluation of solid waste generation, categories and disposal options in developing countries: a case study of nigeria. journal of applied science and environmental management, 13(3): 83 – 88. hoornweg, d. and bhada, t. 2014. what a waste: a global review of solid waste management. accessed on 27th november 2018 from https://siteresources.worldbank.org/inturbandevelopment/resources/3363871334852610766/chap3.pdf irwan, d., basri, nea. and watanabe, k. (2012). interrelationship between affluence and household size on municipal solid waste arising evidence from selected residential areas of putrajaya, 2 (11): 747758. kodwo, mk., kwasi, od., kádár, z., fei-baffoe, b. and mensah, my. 2015. municipal solid waste characterization and quantification as a measure towards effective waste management in ghana. waste management, 46:15–27. mathur, s. 2018. a study on the effect of affluence on solid waste generation in kota. international journal of engineering and management research, 8(1): 178-182. mokuolu, oa. 2014. development of improved hydraulic system for control of mosquito larvae in okelele, ilorin, nigeria. ph.d thesis, department of civil engineering, faculty of technology, university of ibadan, ibadan, nigeria. mungure, mj. 2008. governance and community participation in municipal solid waste management, case of arusha and dares salam tanzania. m.sc. thesis in environmental management, aalborg university, aalborg, denmark. njoroge, gn. and busman, rw. 2007. etanotherapeutic management of skin diseases among kikuyu of central kenya. ethanol pharm, 111: 303-307. https://siteresources.worldbank.org/inturbandevelopment/resources/336387-1334852610766/chap3.pdf https://siteresources.worldbank.org/inturbandevelopment/resources/336387-1334852610766/chap3.pdf mokuolu et al: solid waste generation and characterization in ilorin, nigeria. azojete, 17(3):279-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: iji.jo@unilorin.edu.ng 288 ogwueleka, tc. 2009. municipal solid waste characteristics and management in nigeria. iranian journal of environmental health science and engineering, 6(3): 173-180. olukanni, do. 2013. analysis of municipal solid waste management in ota, ogun state, nigeria: potential for wealth generation. proceeding of the 28th international conference on solid waste technology and management march 10-13, 2013, philadelphia, pa u.s.a. olukanni, do. and mnenga, mu. 2015. municipal solid waste generation and characterization: a case study of ota, nigeria. international journal of environmental science and toxicology research, 3(1): 1-8. pervez, a. and kafeel, a. 2013. impact of solid waste on health and the environment. international journal of sustainable development and green economics, 2(1): 165 – 168. salam, a. 2010. environmental and health impact of solid waste at mangwanemi dumpsite in manzini swaziland. journal of sustainable development in africa, 12(7): 1-7. wolf, s. 2004. municipal solid waste management in developing countries: nigeria, a case study. ntres 314, abuja. yoshida, m. 2018. situation of municipal solid waste management in african cities an interpretation of the information provided by the first accp meeting. global environment department, japan international cooperation agency (jica). the second meeting of african clean cities platform (accp), rabat 3 arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 202-207 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng ____________________ *corresponding author: opara@sun.ac.za, umunam@yahoo.co.uk 202 original research article dynamics of pomegranate fruit weight loss during precooling and ambient storage: a spatial and temporal analysis m. mukama1, a. ambaw2 and u. l. opara1, 2,* 1postharvest technology research laboratory, south african research chair in postharvest technology, department of food science, faculty of agrisciences, stellenbosch university, south africa 2postharvest technology research laboratory, south african research chair in postharvest technology, department of horticultural science, faculty of agrisciences, stellenbosch university, south africa article information received: october, 2018 accepted: december, 2018 keywords: punica grabatum humidity management cold chain moisture loss liner market conditions quality abstract in this paper the spatiotemporal profile of weight loss of pomegranate fruit (cv. wonderful) was investigated during precooling and simulated shelf conditions. the effects of relative humidity (rh) inside the cold room, polyliner inside the packaging and stack orientation on fruit weight loss were studied. weight loss during the precooling operation ranged from 0.17 to 0.25% of the initial fruit weight and was highest during precooling of stack without liner and inside non-humidified room (0.25%). it was observed that fruit weight loss in liner-based packaging was almost equivalent to room humidification. results of the shelf life study demonstrated the importance of room humidification to preserve fruit quality. storing fruit in a room at 95% rh minimised weight loss and best maintained fruit colour, firmness, size and chemical quality attributes of pomegranates. on the other hand, fruit stored at ambient condition (65% rh) up to 30 days had excessive weight loss (up that 29.13±1.49%), which led to shrivel, deformed appearance and considerably reduced overall visual quality. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction rapid moisture loss is among the main quality problems affecting postharvest life of pomegranate fruit (fawole and opara, 2013; arendse et al., 2014). on top of losing marketable fruit weight, fruit that lose moisture above 5% will shrivel; this reduces their visual appeal and commercial value. weight loss in fruit is mainly due to transpiration and to a relatively small extent due to respiratory activity (waelti, 2010). large vapour pressure deficit (vpd) between fruit surface and the surrounding air leads to increased rate of moisture loss. cooling pomegranate fruit preserves quality, but weight loss remains a challenge during cold storage (arendse et al., 2014). humidification of the storage room, packaging fruit in plastic films, fruit coating, shrink wrapping are some of the practiced mitigation measures to moisture loss. however, humidification can also cause several storage problems affecting fruit. for instance, http://www.azojete.com.ng mailto:umunam@yahoo.co.uk arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):202-207. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 203 during cold storage of table grapes, humidification increased stem dehydration, browning of berries, increased the incidence of so2 injury and package wetting (ngcobo et al., 2013). temperature and humidity control in a stack of fruit is normally based on measurements taken from specific locations in the storage room. however, these have been reported to be spatially non-uniform in fruit pallets (ambaw et al., 2017; mukama et al., 2017). the amount of weight loss and the degree of spatial variation in the precooling process of pomegranate fruit are not clearly understood. therefore, the objectives of this study were to: 1) measure the spatial and temporal weight loss profile during precooling of pomegranate fruit, 2) study the effects of internal packaging, humidification, and package orientation on the moisture loss, and 3) investigate the physico-chemical quality attributes of pomegranate fruit stored at different shelf conditions. 2.0 study description 2.1 fruit pomegranate fruit (cv. wonderful) were harvested at commercial maturity from merwespont farm in bonnievale (33°58’12.02” s, 20°09’21.03” e), western cape, south africa and transported in an air-conditioned vehicle to postharvest technology research lab at stellenbosch university. 2.2 package materials in this study, corrugated fibreboard carton box (cfc) was used to contain the pomegranate fruit. the box had 6 semi-circular vent-holes on the long side located at the top and bottom rim of the side, 2 semi-circular vent-holes at the top rim of the side and 5 circular vent-holes on the bottom side. each box contained 12 fruit with average weight of 4.32 ± 0.39 kg per carton. fruit weight loss during precooling of two different package designs was investigated: package with internal polyliner and another without polyliner. plastic wrapping was done by placing pomegranates in a single non-perforated 10 µm thick high density polyethylene (hdpe) plastic film. 2.3 air suction equipment (ase) the ase was a box with suction fan attached to one end. the suction was generated by using a centrifugal fan (kdd 10/10 750w 4p-1 3sy, ams supplies, sandton, south africa). the stacked fruit, as covered with plastic sheet, was placed in front of the ase so that air was drawn horizontally through it. 2.4 cold storage room the ase/stack assembly was placed inside a 20 m3 cold storage room equipped with a cooling unit and a humidifier. the cooling unit had three evaporator fans each creating an air circulation rate of 1290 m3 h-1. cold room humidity was controlled using aqua room-2 humidifier (miatec inc. 9480se, lawnfield road, chackamas or 97105 usa) with 1.4-2.1 bars pressure capacity, 2 l h-1 liquid capacity, 10 µm droplet size and digital hygrotransmitter sensor (0-100% rh). 2.5 experiments 2.5.1 precooling experiments 70 cartons were stacked (7 layers of 10 cartons) on an iso standard pallet (1.2 m × 1.0 m × 0.1 m). the stack was first equilibrated to ambient air conditions (≈ 17 °c and 65% rh) before being placed inside the cool storage room. the sides and top of the stack were covered with plastic sheet so that chilled air was horizontally sucked through the stack by the ase. two different file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mukama, et al. dynamics of pomegranate fruit weight loss during precooling and ambient storage: a spatial and temporal analysis. azojete, 14(sp.i4):202-207. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 204 pallet orientations with respect to the ase were considered: pallet with its 1.2 m side perpendicular to the air flow and pallet with the 1.0 m side perpendicular to the air flow. due to difference in vent-hole proportion between the long and short side of the box, the vent area along the flow direction of the two different orientations are dissimilar. for the 1.2 m oriented stack, the vent-hole ratio along the flow direction were 9.45% and 2.15% at inlet and outlet, respectively. the 1.0 m orientation had vent-hole ratio of 4.24% at both the inlet and outlet end. all precooling experiments were from the initial ambient condition (≈ 17 °c) down to 7 ± 1.2 °c. during the experiment fruit pulp temperature was monitored at intervals of 5 minutes using ttype thermocouples and a 34970a data acquisition/data logger switch unit (agilet technologies, santa clara ca 95051, usa). the measured temperature data was used to calculate the stack average 7/8th cooling time which determined the time to stop the precooling experiment. additionally, fruit weight loss was measured by taking initial and final weight of sample fruit. the temperature and weight loss sampling positions were from stack levels 2, 4, and 6. a total of 24 measurements (2 pallet orientations × 2 rh conditions × 2 liner conditions × 3 repetitions) were taken. 2.5.2 measuring the effect of humidity on shelf life of pomegranate fruit two groups of 216 fruit each were equilibrated to ambient condition before the start of the experiment. group 1 was kept under high humidity condition (95 ± 1.23 %rh) and group 2 under low humidity condition (65 ± 6.79 %rh). in both cases, the room temperature was kept at 20 ± 0.36 °c. fruit weight, colour, firmness, size, titratable acidity, total soluble solids and ph were assessed on a 3 day interval for 30 days. 2.6 statistical analysis statistical analysis was done using statistica software (statistica version 12, statsoft inc., tulsa, usa). mixed model repeated measures analysis of variance (anova) was done using the vepac module of statistica 12 at 95% confidence interval. variations in weight loss were compared between the package designs, stack levels, stack orientations and fruit position within a stack level. statistical significance of the treatments was tested using duncan’s multiple range test and means with p < 0.05 were considered significant. 3.0 results and discusions 3.1 weight loss during precooling of pomegranate fruit on average, weight loss ranged from 0.17 to 0.25% of the initial fruit weight. clearly, fruit weight loss was highest (0.25%) for the stack without liner and in a non-humidified cool store (“none” in fig. 1 (a)). stack with plastic liner and in a humidified room (“liner + humidification” in fig. 1 (a)) experienced the lowest weight loss (0.17%). however, the presence of liner always increased fruit cooling time (fig 1(b)) such that stacks with liner had sect higher than 10 h compared with less than 5 h for stacks without liner. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):202-207. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 205 fig. 1. weight loss of pomegranate fruit (mean ± stdv) during precooling (a) and the corresponding 7/8th cooling time (sect (b). all humidification was at 95 ± 1.23 %rh. when no humidification, the cool storage room was kept at ambient humidity condition of 65 ± 6.79 %rh. the weight loss and sect values are stack means. means with different letters are significantly different (p < 0.05). 3.1.1 effect of stack orientation the average weight loss of precooled pomegranates in the 1.0 m orientated pallet was 0.20% while those in the 1.2 m oriented pallet it was 0.22%. the 1.0 m side of the pallet has relatively lower ventilation compared to the 1.2 m orientation as described in section 2.5.1. low ventilation rate results in relatively lower convective mass transfer coefficient from the fruit surface to the ambient air. this leads to the observed low weight loss profile. however, this also leads to a relatively higher cooling time. 3.1.2 spatial variation in weight loss spatial variability of the weight loss is important to identify the high and low weight loss regions. fruit in the upstream region received the chilled air first, thereby subjecting them to a faster cooling rate. increase in air temperature as it moves across a stack causes local variations in heat loss in the stacked products (baird et al., 1988) and holding pomegranate fruit at higher temperatures for longer period causes higher moisture loss rates. there was no significant difference in weight loss between layers of the stack in all cases. 3.2 effect of humidity on shelf life quality of pomegranate fruit 3.2.1 weight loss and fruit shrivel pomegranate fruit continuously lost weight throughout the shelf life period. till day 3, there was no significant difference between the two rh environments. however, fruit weight loss under the low rh environment became significantly higher starting from day 6, with losses reaching up to 29.13±1.49% in the low rh environment compared to 5.78±0.44% in the high rh environment. this shows that the high rh environment reduced the vapour pressure deficit (vpd) between the fruit and the environment, resulting in a significantly reduced moisture loss from the fruit (ngcobo et al., 2013). shrivel was observed on fruit from the low humidity environment on day 6. at this stage the average weight loss was 5.28 ± 0.32% of its initial weight, and by day 9, the dents on the fruit surfaces were larger. shrivel is due to loss of turgor pressure in the fruit cell walls as they continuously lose moisture (paull, 1999). under high humidity environment, some fruit slightly shriveled on day 24. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mukama, et al. dynamics of pomegranate fruit weight loss during precooling and ambient storage: a spatial and temporal analysis. azojete, 14(sp.i4):202-207. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 206 changes in fruit colour, size, firmness, titratable acidity, ph, and total soluble solids were more significantly pronounced in the low humidity storage environment than high humidity environment (fig. 2) fig. 2. visual condition of pomegranate fruit 30 days under ambient humidity condition, rh ≈ 65% (top row) and under humidified condition, rh ≈ 95% (bottom row). 4.0 conclusion this study investigated the level of reduction of weight loss achievable by employing liner-based packaging or room humidification. this study also quantified the spatial variation in weight loss of pomegranate fruit during precooling operation. fruit at the back of the stack had higher weight loss than those at the front. this goes in parallel with the temperature distribution in the stack as reported in previous studies (ambaw et al., 2017 and mukama et al., 2017). the shelf life study showed the importance of room humidification as a cold chain strategy to maintain pomegranate postharvest fruit quality. storing fruit under 95% rh maintained fruit colour best, minimised weight loss, maintained fruit firmness, fruit size and the chemical quality attributes of pomegranates. storing fruit under low rh ambient conditions led to excessive weight loss, which in turn resulted in excessive shrivel, deformed appearance, and reduced visual quality of fruit. these findings can be applied in efforts to establish the best storage conditions of pomegranates to maintain quality and reduce incidence of postharvest losses along the value chain from harvest to consumers. 5.0 acknowledgement this work is based upon research supported by the south african research chairs initiative of the department of science and technology and the national research foundation. the project was supported through contract research with agri-edge ltd funded by the department of trade and industry (dti) through the technology and human resources for industry programme (thrip). we acknowledge the award of postgraduate scholarship to mr m mukama by daad (inregion scholarship programme) and the regional universities forum for capacity building in agriculture (ruforum) for support. references ambaw, a., mukama, m. and opara, ul. 2017. analysis of the effects of package design on the rate and uniformity of cooling of stacked pomegranates: numerical and experimental studies. computers and electronics in agriculture, 136, 13-24. arendse, e., fawole, oa. and opara, ul. 2014. influence of storage temperature and duration on postharvest physico-chemical and mechanical properties of pomegranate fruit arils. cytajournal of food, 12, 389-398. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):202-207. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 207 baird, cd., gaffney, jj., and talbot, mt. 1988. design criteria for efficient and cost effective forced air cooling systems for fruit and vegetables. ashrae transactions, 94, 1434–1454. fawole, oa. and opara, ul. 2013. effects of storage temperature and duration on physiological responses of pomegranate fruit. industrial crops and products, 47, 300-309. mukama, m., ambaw, a., berry, tm. and opara, ul. 2017. energy usage of forced air precooling of pomegranate fruit inside ventilated cartons. journal of food engineering, 215, 126-133. ngcobo, mek., delele, ma. chen, l. and opara, ul. 2013. investigating the potential of a humidification system to control moisture loss and quality of ‘crimson seedless’ table grapes during cold storage. postharvest biology and technology, 86, 201-211. paull, re. 1999. effect of temperature and relative humidity on fresh commodity quality. postharvest biology and technology, 15, 263-277. waelti, h. 2010. humidity management in ca storages. wsu tree fruit research and extension centre. postharvest information network. [internet document]. url http://postharvest.tfrec.wsu.edu/pages/j2i3b. 26/12/2017. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng 6 arid zone journal of engineering, technology & environment azojete, june, 2019. vol. 15(2):395-394 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 385 original research article application of stearic acid for solar thermal energy storage in a double compartment solar box cooker m. b. maina*, s. shodiya and a. t. abdulrahim (department of mechanical engineering, faculty of engineering p.m.b. 1069 university of maiduguri nigeria) *corresponding author’s e-mail address: m.muhammad75@yahoo.com article information submitted 29 march, 2018 revised 5 february, 2019 accepted 10 may, 2019 keywords: thermal energy storage phases change material double compartment solar box cooker abstract energy storage in some form is the need of the hour to even out the mismatch between energy supply and demand. thermal energy storage (tes) system employing a phase change material (pcm) has been widely considered as an effective way to store and retrieve energy due to its high heat storage capacity at almost constant temperature during the phase change. in this work, an energy storage system was designed to study the heat transfer characteristics of stearic acid (as a phase change material in a double compartment solar box cooker (dcsbc) fabricated using wooden materials with high thermal energy storage system. in order to analyze the various characteristics of the pcm, the bureau of indian standards (bis) was used throughout the experiment. investigations were performed to determine the first and second figure of merits (f1 and f2) of compartments 1 and 2 (c1 and c2) simultaneously. the results for f1 were found to be (c1= 0.14 and c2= 0.15) and f2 were (c1=0.47 and c2= 0.4) while the overall thermal efficiency of the cooker after water boiling test for c1 with 2.5kg and c2 with 3kg of water were deduced to be 77% for c1 and 92% for c2 after six hours of the load test, showing considerable temperature increase and extension of heat retention making possible to cook the dinner and even breakfast the next day. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction related emissions of carbon dioxide will be doubled by 2050 and fossil fuel demand, supply and utilization has increase over the years with its unsustainable use environmentally, economically and socially (international energy agency, 2015). researchers most often get involved in finding materials and systems to make sure that alternative energy supply and use with appropriate technology in various domestic sectors, transport and industry were attained to support energy security and climate change goals. among these are the different energy storage technologies, thermal energy storage (tes) is considered a key technology to reduce the mismatch between energy demand and supply on a daily, weekly and even seasonal basis, increasing the potential of implementation of renewable energies and reducing the energy peak demand, (iea 2015). thermal energy storage (tes) is defined as the temporary holding of thermal energy in the form of hot or cold substances for later utilization (abedin, 2011). energy demands vary on daily, weekly and seasonal bases.these demands can be matched with the help of tes systems that operate synergistically and deals with the storage of energy by cooling, heating, melting, http://www.azojete.com.ng maina, et al: application of stearic acid for solar thermal energy storage in a double compartment solar box cooker. azojete, 15(2):385-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 386 solidifying or vaporizing a material and the thermal energy becomes available when the process is reversed.tes is a significant technology in systems involving renewable energies as well as other energy resources as it can make their operations more efficient, particularly by bridging the period when energy is harvested and periods when it is needed. that is, tes is helpful for balancing between the supply and demand of energy (abedin, 2011 and pavlov, 2012). tes systems have the potential for increasing the effective use of thermal energy equipment and for facilitating large-scale fuel commutating (pavlov, 2012). the selection of a tes system for a particular application depends on many factors these includes; storage duration, economics, supply and utilization temperature requirements, storage capacity, heat losses and available space (dincer, 2011). the main types of tes are sensible and latent. sensible tes systems store energy by changing the temperature of the storage medium, which can be water, brine, rock, soil, etc. latent tes systems store energy through phase change, e.g. cold storage water/ice and heat storage by melting paraffin wax. latent tes units are generally smaller than sensible storage units but can store large amount of energy. the present study intends to give an experimental account of the application of stearic acid as a phase change material (pcm) technology for tes in a double compartment solar box cooker (dcsbc).it also seeks to increase the reliability of the solar box cooker using animal based fat as tes toimprove operational performance of the system to be used for off-peak periods. it is also an approach or solution for bridging the gap between solar energy availability and demand, specifically reducing the increasingenergy cost and scarcity for cooking purposes in the study area (maiduguri).the use of solar box cooker is not popular among the dwellers in maiduguri and environs. the objectives of this work are to test and evaluate the thermal performance of a low cost, doublereflectorbased solar box cooker with tes (pcm) in maiduguri, nigeria and determine its suitability for cooking during high and low solar irradiation. 2.0 materials and methods 2.1 materials and equipment the design materials(parameters) considered included the energy requirements, daily average insolation, the phase change material (stearic acid), size of pcm container, ambient temperature and other thermo-physical properties of the pcm as highlighted in table 1. the experimental temperature measurement was performed in selected points using the t-type thermocouples of cu-ni (copper-nickel) with temperature range of 185°c to 300°c. thermo-physical properties of stearic acid the thermal properties of the stearic acid used and other physical properties were as given in table 1. table1: properties of pcm (stearic acid) used (source: hussein et al., 2008) m melting temperature 52°c d density 847-965 (kg/m3) a appearance white solid (waxy) st storage temperature 2–9°c re refractive index 1.429 th thermal conductivity 0.29 (w/m k) la latent heat of fusion 169.0 (kj/kg) sp specific heat 1.590 (kj/kg k) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):385-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 387 2.1.1 the double compartment solar box cooker (dcsbc) the double compartment solar box cooker was made of inner and outer casing of the oven compartment (figure1)and was fabricated with plywood of thickness 0.02m. the dimension for the inner casing constructed of flattened aluminum roofing sheet is 0.37m x 0.44m x 0.3m, fixed directly beneath the aluminium casing serving as absorber plate (painted black) is the pcm storage tank having the same size as the base of the inner al casing (0.37m x 0.44m x 0.05m) filled with 2kg of stearic acid for charging and dis-charging purposes, while the outer casing has dimension 0.87m x 0.7m x 0.43m. a 0.21m x 0.27m two rectangular openings were cut on each compartment side of the box to serve as a door. these allow for independent cooking purposes rather than the uniform cooking obtained in most solar cooking units, due to the cooking traditions of the test area (maiduguri and environs) usually food and soup (tuwo and miya) were independently cooked. thus, the sbc was also designed to provide opportunity to cook both food and soup simultaneously without affecting the progress of each other. the independent compartment also reduces amount of heat losses compared when the pots were in the same compartment as obtained in literature (saxena et al., 2013). the aforementioned design and versatility of the sbc was to increase the acceptability of the sbc in the community as compared to the existing versions. the inner casing was then inserted in the oven box and nailed at the sides using 2mm nails. the whole assembly was turned upside down after which the space was filled with saw dust and then finally covered with plywood. two 4mm thick, silver plated mirrors, 0.66m x 0.66m in dimension were each mounted on 0.7m x 0.65m plywood with the aid of clips and hinged by the opposite sides of the box cooker as reflectors. the reflectors were held at the sides using flat bars, with one end permanently fixed to the midpoint of the adjacent side on the collector and the other end sliding on the 3mm hole along the angle bar screwed to the plywood as shown in figure 1. figure 1: double compartment solar box cooker (dcsbc) the aperture area of the box cooker is 37.41cm2; the volume stands at 1608.63cm3 while the oven weight was deduced to be 62.1n. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina, et al: application of stearic acid for solar thermal energy storage in a double compartment solar box cooker. azojete, 15(2):385-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 388 figure 2: sectional view of the double compartment sbc showing pcm container 2.2 methods 2.2.1 thermal performance test difficulties in assessing numerous designs of solar cookers have led to the creation of three major testing standards for evaluating solar cookers throughout the world. they include: american society of agricultural engineering (asae) standard s580, the standard developed by the european committee on solar cooking research (ecscr) and the bureau of indian standards, based on work by mirdha and dhariwal (2008). though, the three standards have their shortcomings, indian standards provide testing standard based on thermal test procedures for box-type solar cookers. the performance of the reflector based solar box cooker implemented in this study was done based on the bureau of india standard, is 13429: 2000, ayoolaet al. (2014). the standard highlighted two methods of test: a stagnation test (test without load) where f1shall be determine as the cookers optical efficiency and a load test (boiling water test) where f2 shall also be determine as the cookers heat transfer efficiency alongside the overall cooker efficiency (ɳ). 2.2.3 stagnation temperature test the experiment was carried out on the 9th of june 2017 at the university of maiduguri engineering teaching workshop, to show the variation in the solar radiation and ambient temperature and their effects on the stagnation temperature observed in the absorber plate of the double compartment solar box cooker.a number of tests without load were conducted on the cooker to determine its stagnation temperature and also to check the rise in temperature inside the cooker. the stagnation temperature, ambient temperature (ta) and absorber plate temperature (tp) were measured for different time of the day between 10:00 am and 4.00 pm during operation of the cooker using 1.6mm diameter thermocouple with elix digital thermometer (lx-6500) capable of reading temperature between -50°c and 300°c. thermo anemometer (prova instrument, avm 01) was used to measure wind speed (v) and solar radiation was measured using global radiation meter (grm 100). 2.2.3 water boiling test (load test) the loading test was done by placing a water-filled cylindrical pot covered by a lid, in the cooker. the test was conducted for three days with 3.0 kg of water in the first day, 2.5 kg of water in the second day and 2.0 kg of water in the third day. each test was carried out on a relatively sunny day between 10:00 am and 4:00pm daily. the absorber plate temperature (tp), ambient temperature (ta), water temperature (tw), solar radiation (hs), pcm temperature and wind speed (v) were measured using the instrumentation described earlier in this section http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):385-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 389 2.2.4 performance evaluation the performance evaluation of the double compartment solar box cooker involve estimation of the first figure of merit (f1), second figure of merit (f2) and cooker’s efficiency (ɳ) as earlier highlighted in 2.2.1 2.2.5. first figure of merit the first figure of merit (f1) of a solar box cooker is defined as the ratio of optical efficiency (ɳ) and the overall heat loss coefficient (ul), as given by purohit, 2009. lu n f 01  (1) experimentally, s asps h tt f  1 (2) where: tps (°c), tas (°c) and hs (w/m2) are stagnation plate temperature, average ambient temperature and intensity of solar radiation respectively. 2.2.4 second figure of merit the second figure of merit (f2) is evaluated under full load condition and can be representedby the expression given by mohod (2011) as follows:                                h tt f h tt fin at cmf f aw aw ww 2 1 1 11 1 11 1 2 (3) where: f1 is first figure of merit (km2 w-1 ), mw is the mass of water as load (kg), cw is the specific heat capacity of water (j/kg°c), ta is the average ambient temperature (°c), h is the average solar radiation incident on the aperture of the cooker (w/m2), tw1 is the initial water temperature (°c), tw2 is the final water temperature (°c), a is the aperture area (m2) and t is the time difference between tw1 and tw2 (s) while f2 signifies the cookers heat transfer efficiency. 2.2.3. cooker efficiency the overall thermal efficiency of the solar box cooker is expressed mathematically by khalifa et al. (2005) and olwi (1993) and reported by el-sebaii (2005) as follows: tvai tcm ca ww u    (4) where:ɳu represents overall thermal efficiency of the solar cooker; mw, mass of water (kg); cw, specific heat capacity of water (j/kg/°c); δt, temperature difference between the maximum temperature of the cooking fluid and the ambient air temperature (°c); ac, the aperture area (m2) of the cooker; δt, time required to achieve the maximum temperature of the cooking fluid (min); iav, the average solar intensity (w/m2) during time interval δt. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina, et al: application of stearic acid for solar thermal energy storage in a double compartment solar box cooker. azojete, 15(2):385-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 390 3.0 results and discussion 3.1 stagnation temperature test the result of stagnation temperature under no load condition is shown in figure 3.the average ambient temperature for the test day was 41°c. maximum absorber plate temperature of 158°c was recorded at 4:00 pm for compartment 1 and at an average insolation value of 838 w/m2 and 166.7°c at 4:00pm for compartment 2 at 838 w/m2, the plate temperature increases despite decreasing insolation up to 4:00 pm. the result shows that heat loss from absorber plate of the cooker is negligibleand the absorber plate temperature was retained for a long time due to energy stored in the pcm (stearic acid) embedded below the absorber plate.this is desirable for heating since major mode of heat transfer to the cooking vessels is by conduction from absorber plate, adewole et al. (2015). fig. 3: performance curve of double compartment solar box cooker under stagnation temperature condition 3.2 water boiling test (load test) variation in solar radiation, ambient temperature, plate temperature and water temperature during sensible heating test of 3.0kg of water for compartment 1 and 2.5kg of water for compartment 2 are shown in figure 4.the experiment was carried out on the 10th of june 2017 at the university of maiduguri engineering teaching workshop, periodic overcast of weather caused fluctuation in the solar radiation, folaranmi (2013). the maximum insolation of 973 w/m2 at 1.00 pm and minimum of 602.4 w/m2 at 4.00 pm were recorded. the average solar radiation and ambient temperature observed during the period of test for 3.0 kg of water were 837.9 w/m2 and 41°c respectively. the highest pot water temperature of 99°c between 1:00pm to 1:20pm for compartment 1 and 99°c between 1:00pm to 1:40pm for compartment 2 was observed. mirdha (2008) reported that most food can be fully cooked at the temperature range of 60-90°c. the water temperature during the period of test reached temperature values between 6093°c for compartment 1 and 60-96°c for compartment 2 at 602.4 and 890.8w/m2 between the hours of 12:00 pm and 4:00 pm. figure 4 shows sensible heating test result for 3.0kg and 2.5kg of water in the different compartments of the sbc. the average solar radiation and ambient temperature during the period of boiling 2.5kg of water were 849.9 w/m2 and 40.75°c respectively. the highest pot http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):385-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 391 water temperature of 95°c and 99°c for compartment 1and 2 were observed between 1:00pm and 1:20 pm. the overcast of cloud during the period of test caused fluctuations in the value of plate temperature with the average value at 158°c and 166°c for compartments 1 and 2; this is similar to the report of adewole et al. (2015). despite the fluctuations in insolation, there was significant temperature retention up till 4:00 pm. f2 for both compartments were calculated based on eqn. 3 and found to be 0.47 for c1 while c2 was found to be 0.40, both figures being above the minimum standard set by bis for assessment of solar box cookers. this shows the effect of the thermal energy storing mediumthat is stearic acid (pcm) as an effective energy store for heat transfer to the cooking vessel through the absorber plate for period much longer after the sunshine hours. the results of the tests present the thermal behavior of major parameters in the dcsbc namely: solar radiation and ambient temperature among others. despite high weather fluctuation during the period of test, water temperature increased significantly reaching maximum temperature of 94°c and 96°c, 95°c and 99°c at an insolation of 973 and 970 w/m2, respectively for the two compartments. the plate and water temperature attained temperature suitable for cooking and increase considerably from 10:00am till 4:00 pm. this and other results discussed above demonstrated the suitability of the designed double compartment solar box cooker for cooking even during fluctuating weather conditions; this is similar to the work of el-amin (2015). fig. 4: thermal performance curve of the double compartment solar box cooker during sensible heat test of 3.0kg of water in c1 and 2.5kg of water in c2 in a test day file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina, et al: application of stearic acid for solar thermal energy storage in a double compartment solar box cooker. azojete, 15(2):385-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 392 fig. 5: thermal performance curve of the double compartment solar box cooker during sensible heat test of 2.5 kg of water 3.3 thermal cooker efficiency (ɳ) the cooker efficiency for both compartments (c1and c2) were determined using equation iv as 77% for compartment c2 with 2.5kg of water and 92% for compartment c1 with 3kg of water after six (6) hours of heating test, this is similar to the report of el-amin, (2015) where he obtains 77% as the efficiency of box cooker after evaluation in comparism to parabolic solar cooker and panel type cookers, it is also similar to the work of adetifa and aremu, (2016) with respect to heat storage where extension of heat storage increases temperature making it possible to cook dinner in late hours. 4.0 conclusion a double compartment solar box cooker was designed and produced with stearic acid as phase change material (pcm) serving as the energy storage medium using the weather conditions of maiduguri (north-east nigeria). the idea was to improve the performance of solar box cookers for better acceptability in the society and as a promising alternative (such that it can be used in the day and for late evening cooking that may not be possible with simple solar cooker without energy storage) this work also specifically intends to impact on the cost and scarcity of cooking energy in the study area. the bureau of indian standard (bis, 2000) was used to evaluate the sbc and the values of first figure of merit (f1) for the two compartments (c1= 0.14 and c2= 0.15) indicates good optical efficiency and low heat lost factor going by the bis which ranges between 0.12 and 0.16 depending on the climate of the test area (country). the values of second figure of merit (f2) for c1 and c2 (0.47 and 0.4) indicates good heat exchange efficiency factor, good optical efficiency (ɳo) and low heat capacity of the cooker interior and vessel with full load of water. the stagnation and full load test result shows that the double compartment sbc can be effectively used for methods of cooking obtained around the test environment,traditional food and soup (tuwo and miya) cooked around the locality can be adequately produced in the two different compartments having independent access and sizes to suit different volumes of food intended http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(2):385-394. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 393 to be cooked. while students can use the dcsbc during the day and night as well appropriately due to energy storage facility incorporated to the cooker without affecting their time for academic and other activities. the result has also provided useful database for validation of theoretical models of box cookers using pcms haven fulfilled the standard set by bis for solar box cookers assessment. reference abedin, ah. marc, a. and rosen, m. 2011, a critical review of thermo-chemical energy storage systems. the open renewable energy journal, 4: 42-46. adetifa, bo. and aremu, ka. 2016, investigating the effect of different heat storage media on the thermal performances of double exposure box-type solar cookers, international journal of renewable energy research, 6 (3): 1110-1118. adewole, bz., popoola, ot. and asere, aa. 2015. thermal performance of a reflector based solar box cooker implemented in ile-ife. nigeria international journal of energy engineering, 5(5): 95101. ayoola, ma., sunmonu, la., bashiru, mi. and jegede, oo. 2014. measurement of net all-wave radiation at a tropical location, ile-ife, nigeria. atmósfera, 27 (3): 305-315. bureau of indian standard, 2000. indian standard 13429, solar cooker box-type, first revision,manak bharwan, new delhi, dincer, i. and rosen, m. 2011. thermal energy storage, systems and applications. wiley and sons inc., new york, second edition. elamin, oma. and abdalla, iaa. 2015. design, construction and performance evaluation of solar cookers.journal of agricultural science and engineering, 1(2): 75-82. el-sebaii, aa. and ibrahim, a. 2005. experimental testing of a box-type solar cooker using the standard procedure of cooking power, renewable energy, 30: 1861-1871 folaranmi, j. 2013.performance evaluation of a double glazedbox-type solar oven with reflector. journal of renewable energy, http://dx.doi.org/10.1155/184352 hussein, hms., el-ghetany, hh. and nada, sa 2008. experimental investigation of novel indirect solar cooker with indoor pcm thermal storage and cooking unit. energy conversion and management, 49: 2237-2246. international energy agency, 2014. technology road map: energy store. available online:http://www.iea.org/publication/freepublication/technology-roadmap-energy-storagehtml (accessed on 13 may 2015) khalifa, ama. taha, mma. and akyurt, m. 2005. solar cookers for outdoors and indoors energy, 10(7): 819–829. mirdha, us. and dhariwal, sr. 2008.design optimization ofsolar cooker. renewable energy, 33(3): 530 – 544. mohod, ag. and powar, ag. 2011. development and evaluation of multi reflector foldable type solar cooker. agricultural engineering international: cigr journal. manuscript no. 1090. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng maina, et al: application of stearic acid for solar thermal energy storage in a double compartment solar box cooker. azojete, 15(2):385-394. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.muhammad75@yahoo.com 394 olwi, i. andkhakifa, ama. 1993. numerical modeling and experimental testing of a solar grill. journal of solar energy engineering, 115: 5–10. pavlov, g. and olesen, bw. 2011. building thermal energy storageconcepts and applications, available at: http://orbit.dtu.dk/fedora/objects/orbit:72784/datastreams/file_6383088/ content, (accessed 10/05/2012). purohit, i. and purohit, p.2009. instrumentation error analysis of a box-type solar cooker, energy conversion and management, 50(2): 365-375. saxena, ak. 2013. investigating and testing procedure of box type solar cooker. m.tech. thesis, centre of energy studies, i.i.t. delhi http://www.azojete.com.ng original research article application of stearic acid for solar thermal ener m. b. maina*, s. shodiya and a. t. abdulrahim arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):435-448 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 435 original research article mathematical modeling of a flat plate solar collector with eutectic salts as phase change material o. f. isamotu,* n. a. musa, o. j. okegbile, m. a. oriaifo and a. o. bakare (mechanical engineering, engineering, federal university of technology, minna, nigeria) *corresponding author’s email address: olakunleisamot@yahoo.com 1.0 introduction the growing number of problems with the world’s dependence on fossil fuels continues to foster the public’s desire to pursue clean, renewable sources of energy. due to environmental issues and limited fossil fuel resources, more priorities are being given to renewable energy sources (goswami, 2004). the energy from the sun is one form of renewable energy sources. it can be used for water heating in hot water systems, swimming pools as well as a supporting energy sources for central heating installations. the energy from the solar radiation is used for aforementioned purposes via solar collectors. at present the most often used solar collectors are liquid flat-plate collectors working either in parallel or perpendicular tube arrangement as well as the vacuum based structures. the flat plate collector supplies heat below 80°c when not integrated with phase change materials for energy storage and conservation (hassan, 2003), article information abstract solar energy is the most promising heat source for meeting energy demand without having negative impact on the environment. solar energy is, however, intermittent in nature and time dependent energy source. in order to mitigate the intermittent supply of solar energy for water heating, the use of phase change material (pcm) comes into play. the pcm acts as a heat source for the solar heating system when the intensity of the solar radiation is low or no longer active. knowledge about the thermal effectiveness of solar collector with pcm is paramount. so, this study developed a mathematical model to evaluate the thermal behavior of a flat plate solar collector integrated with a phase change material (pcm). this mathematical model developed for the flat-plate with pcm was based upon the conservation and heat transfer equations and used to predict the thermal behavior of integrated phase change material in solar collector during thermal storage. the energy balance equations for the flat-plate heating components of the collector and pcm were formulated numerically. the model was used to investigate the effect of inlet water temperature, water mass flow rate, outlet water temperature and the melt fraction during charging and discharging modes at each of the respective nodes. a comparison was made with a collector with and without pcm. the results show that charging and discharging processes of pcm have multiple stages. the addition of pcm in the first stage causes a decrease in temperature during charging and an increase during discharging. the highest water temperatures reached for the collector without and with a phase change material were approximately 51 and 74°c respectively comparisons were also made between the simulated and experimental data for the solar water heater without and with pcm. minimum inlet water temperatures of 41.54 and 36°c were observed for the simulated and experimental model while, 42.69 and 74°c were both recorded for outlet temperatures respectively, for solar water heater without pcm. for the solar water heater with pcm, the inlet temperatures for the simulation and experimental model were found to be 42°c and 56°c respectively. a maximum outlet water temperature of 108°c was obtained from the experimental model compared to 45°c obtained from simulation. the temperature of the hot water obtained was remarkable and sufficiently enough for many domestic and industrial applications. finally, the solar water heating system with phase change materials finds useful application and acts as a renewable energy resource in regions where there is inconsistent or poor sunlight. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 dec., 2020 revised 19 april, 2020 accepted 26 april, 2020 keywords: thermal storage solar collector numerical model phase change material experimental validation mailto:olakunleisamot@yahoo.com http://www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 436 in reality,theindicative temperature range of operating fluid in flat plate collectors is between the range of 30-65°c (kalogirou, 2004) and the system has an efficiency index higher than 0.5 typical for available flat plate collectors. several studies have been carried out on the use of solar energy for heating purpose (badescu, 2007). notably, nahar (2002) carried out studies on a solar water heater storage collector system and discovered that the system could generate about 50.6°c water at 4:00pm and 41.6°c water the next day with overall efficiency of about 47%. similarly, zerrouki et al. (2012), worked on a solar storage collector system in algeria. the system achieved a maximum temperature of 53°c with an initial temperature of 17°c around 7:00am. a maximum flow rate occurred around 1:00pm. kürklü et al. (2002), investigated a technique that could enhance the thermal performance of a flat-plate solar collector. it was found that the proposed design significantly improved the collector heat transfer characteristics in term of absorptivity and heat transfer coefficient. rabin et al. (1995) developed a mathematical and experimental model for the charging process of a solar collector storage system, integrated with salt hydrate as a pcm. the proposed model showed high accurate validation with the experimental pcm temperature measurements. however, the neglect of the convection heat transfer in the stationary heat transfer reduced the accuracy of their mathematical predictions.lin et al. (2012), proposed a comparative experimental study, under a typical sunny day in malaysia, to investigate the possibility of enhancing the performance of a flat-plate solar collector by integrating paraffin wax with a melting temperature of 60.45°c directly in contact with the collector’s absorber plate. the proposed collector achieved an efficiency of 52% at an inclination angle of 100, which was better by 23% than the conventional collector. naghavi et al. (2015), proposed a theoretical model based on a one phase stefan problem to investigate the thermal performance of integrating pcm to the manifold of an evacuated tube heat pipe solar collector system. it was revealed that the hot water volume and thermal efficiency of the baseline system significantly decreased with increase in the water volume flow rate from 50 to 80 litres per hour. the usable volume and the thermal efficiency almost remain the same in the innovative system. although a lot of work has been done on solar water heater (lin et al, 2012) the need to device a means of obtaining optimum performance of flat plate solar collector cannot be overemphaised. in view of this, isamotu (2019) developed four different types of eutectic salt mixtures and found that the mixture of 1.77g of lino3, 2.94g of nh4no3, 1g of nano3 and 1g of nacl with melting point of 84.4°c and latent heat of 119kj/kg has better energy storage capabilities. therefore the aim of this work is to developed a mathematical model for solar collector with the eutectic salt mixture according to isamotu (2019) as pcm 2.0 materials and method the following materials were used in this research work: fiber glass, glass cover, absorber, working fluid, pipes (headers/risers), pcm, xm1400 solar dual transmission meter and km25o thermocouple 2.1 description of the flat plate collector system a flat plate collector consisting of a transparent cover, fluid, heat insulation, phase change materials, absorber plate, and collector casing were used. figure 1 shows how the flat plate collector look likes. in line with the principle of operation, the sunlight passing through the glazing cover strikes the absorber plate and the solar radiation is converted into usable heat and transferred via its inner surface to the fluid passing through the respective nodes of the collector. subsequently, the fluid carries the energy away from the collector for direct use or storage. the absorber plate is made of a thin (flat or grooved) high thermal conductivity metal sheet which could be steel, aluminum or copper. in order to maximize the efficiency of a solar collector, the surface of the absorber plate is painted with black colour pigment because of its high absorptivity property. the flow tubes in the collector are the integral parts of the absorber plate and these tubes are connected to the header tubes at both ends and either of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 445-448. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 437 which could serve as a supply or return pipe (inlet, outlet). some of the thermal energy is transferred via convection to the transfer fluid and the other is transferred by both conduction and convection to the phase change material beneath the absorber. when the absorbed temperature of the flat plate collector becomes higher than that of the pcm, the heat is first stored as a sensible heat until the pcm reaches its melting temperature. at this point, the pcm starts to melt and after complete melting, the released heat is stored back in the molten pcm as a sensible heat. when the sun was no longer active, all the solar components starts to cool down and the pcm at this point serves as the main heat source for the flat plate solar system. figure 1: cross sections of a flat plate collector (alternative energy tutorials, 2012) 2.2 mathematical model of a flat plate collector with pcm a schematic system study is depicted in figure 2. figure 2: schematic of a solar thermal system and setup (badescu, 2007) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 438 the system consists of a thermal solar panel, thermal tank, eutectic phase change materials, piping as well as control valves.the pcm (eutectic salt mixture) used in this system has a good thermal energy storage density and low thermal conductivity. the pcm was then embedded in black colour pigment and used to coat the solar panelwhich was integrated into the heat-exchanger in the solar collector as shown in figure 3. figure 3: solar tube heat exchanger finite-difference formulation (badescu, 2007) in order to write the energy conservation and heat transfer equations of the eutectic salt, the heat exchanger should be considered at each of the respective node because of the nonuniformly temperature distribution across each section. however, the model proposed is based on the following seven assumptions: (i)the thermo-physical properties of the pcm are independent of temperature, but different for solid and liquid phases. (ii) the heat transfer fluid is incompressible and it can be considered as a newtonian fluid. (iii) the pcm is in perfect contact with the absorber. (iv) the pcm is homogeneous and isotropic. (v) the inlet velocity and inlet temperature of the heat transfer fluid are constant. (vi) no thermal expansion during melting process and (vii) the heat transfer in the direction of the transfer fluid is ignored. the mathematical modeling of the heat transfer processes of a flat plate solar collector with pcm consist of both the solar radiation which is the source of the solar energy and the solar collector. the solar collector is further divided into seven sections has follows: the glass cover, absorber plate, air gap, transfer fluid, collector efficiency factor, collector heat removal factor and phase change materials. some of the mention parameters will be discussed individually, global solar radiation is the total amount of solar energy received by the earth's surface, usually expressed as w/m2. about 99 percent of global solar radiation has wavelengths between 300 and 3000 nm. this includes ultraviolet (300-400 nm), visible (400-700 nm), and infrared (700-3000 nm) radiation. bekkouche(2008) proposed a theoretical model based on the following correlations. the solar irradiance are calculated as follows:           2sin 1expcos1 1 hb a  (1) where: h is the sun’s height and θ1 is the direct incident angle. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 445-448. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 439 the diffuse irradiance is expressed as hh gdd                 2 cos1 2 cos1 (2) where: β the tilt is angle of the collector and ρ is the albedo dh and ρgh are further expressed as:    4.0sin' hadh  (3)    ''sin'' b h hag  (4) the constants b,a',a" and b" depends on atmospheric state with time. the energy balance equations for all of the seven components of the solar collectors mentioned earlier with temperature dependent is obtained for each of the components. i. glass covering according to zueva and magiera (2001) the glass covering can be thus be written as: cgρgvg dtg dt = hg.am tam − tg + hr1 tab − tg + hc1 ta − tg + αg p∇z (5) where: c = specific heat, ρ = density, v = volume, t = temperature, t = time, h = heat transfer coefficient, α = absorption coefficient, g = heat flux of solar radiation,p = tube pitch, ∆z = spatial size of control volume subscripts notation:,am = ambient, g = glass cover, a = air gap,ab = absorber, r = radiation c = convection according to duffie and beckman (1974) the heat transfer coefficients by convection are calculated respectively as: hcv,am = 3.9vwind + 5.62 (6) hcv,a = nuλa ea (7) vwind , λa , ea are the wind velocity, air thermal conductivity and the air gap thickness respectively. the nusselt number is calculated as follows: nu = (0.06 − 0.017 β 90 ))gr0.33 (8) gr is the grashoof number expressed as:           a acabs tv ettggr 2 3 (9) the heat transfer coefficient by radiation is expressed as: hr,c−as = εc σ (tc2 + tas2 )(tc + tas) (10) where: tas is the temperature of the air-space file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 440 the heat transfer coefficient by radiation on the absorber is expressed as:                   abc abcabc abcr tttth   11 22 , (11) according to duffie and beckman (1974) tas is expressed as: tas = 0.0553tam 3 2 (12) ii. the absorber plate according to shiv et al. (2010), the transient thermo-physical properties of the absorber material are considered when a heat energy balance is applied to the absorber zone. the solar irradiance on the absorber zone of the solar collector control volume, the radiation between the absorber and the glass cover, the conduction between the absorber and the insulation zone and the heat transfers by convection with the fluid flow need to beconsidered. the following relation gives: cab(tab)ρab(tab)vab dtab dt = {g(τa) + hr1(tg− tab) + hc1(ta−tab) + ki δi (ti-tab)}p∆z+πdinhf∆z(tf−tab) (13) where: τa = effective transmittance absorption coefficient, k = thermal conductivity, δ = thickness, d = diameter, subscripts: i = insulation, f = working fluid, in = inner. iii. air gap of the flat plate collector ρavaca dta dt = hcv,c−asc tc− ta + hcv,ab−asab tab− ta + uloss,esa,e tam− ta (14) according to ahmad (2012), the heat exchange coefficient by convection can be estimated using (7) nu = 0.023re0.8pr0.4 (15) based on incropera et al. (2006), the bottom loss and side loss coefficient of the collector is given as:                             windcvsins sins sloss windcvbins bins bloss h u h u ,, , , ,, , , 1 1, 1 1     (16) the thermal heat exchange with the phase change materials during charging and discharging modes are expressed as follows: qab, pcm = − λpcm,ispcm δtpcm,i δx (17) qab, pcm = λpcm,ispcm δtpcm,i δx (18) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 445-448. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 441 where: i = solid when the phase change material is in the solid state and i = liquid when the phase change material is in the liquid state. iv. heat transfer fluid according to klein et al. (1974), the heat exchange coefficient of the collector can be determine as putting the tube cross section of the solar collector into consideration ahtf the conservation energy equation for the htf becomes ρhtfchtf ∂thtf ∂t =− chtfm� htf ahtf ∂thtf ∂x + hπdi ahtf (tw−thtf) (19) the thermal resistance of the wall is assumed to be negligible, the conservation energy equation of the wall now becomes: ρwcw ∂tw ∂t = hπd aw thtf − tw + 1 sw ( kwaw 1 aw + kpcmapcm1 aw ) (tpcm−tw) (20) where: aw = cross sectional area of the wall kw and kpcmare the thermal conductivity of the wall and the pcm respectively the heat transfer conduction within the pcm in the axial direction is negligible, therefore the conservation energy equation in the first cell of the pcm alternate to the wall becomes: ρpcm ∂hpcm ∂t = 1 sw kwaw1 aw + kpcmapcm1 aw tpcm−tw + 1 sw kpcm apcm ( hpcm j+1 aw − hpcm j aw ) (21) the energy conservation equation for the generic cell of the pcm becomes: ρpcm ∂hpcm ∂t = kpcm cpcm ( 1 r ∂ ∂r (r ∂hpcm ∂r )) (22) charging phase: during this phase the water mass flow rate can be calculated from the heat released through solar radiation. mass flow rate of water is expressed as: mw = gacollectors 1000×cpw×∆tw×n (23) where: mw , water mass flow rate       s kg , g, radiation       2m w , a, area of the collector (m2), cpw , specific heat of water       kgk kj , ∆tw , the heat transfer fluid temperature difference, n , number of tubes in the solar collector. according to laouadi and lacroix, (1999) the finite-difference formulation of the time derivative can be written for the solid phase as follows; solid phase: tpcmm+1 = tpcmm + mwcpw∆tw ρsvpcmcps ∆t (24) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 442 where: tpcmm , temperature of pcm at m element (℃) , ρs , density of pcm at solid phase       3m kg , vpcm , pcm volume   scpm3 , pcm specific heat at solid phase       kgk kj , ∆t , time differential (s). the same finite-difference formulation of the time derivative can be applied to the mushy and liquid phase as follows; t hv tcm lpcml mushywpww mm      , 1 (25) heat along the tubes of the collector according to senthilkumar et al. (2014) is expressed as qtube = ρlvpcmhlγ∆t (26) where: γm , liquid fraction at element hl , pcm latent heat kj kg ,ρl , density of pcm at liquid phase       3m kg , qtube, heat along each tube (kj), the finite-difference formulation of the time derivative can be applied to the liquid pcm as follows; tpcmm+1 = tpcmm + mwcpw∆tw ρlvpcmcpl ∆t (27) discharging phase this is the stage when the phase change material experiences phase change from liquid to mushy and solid. the rate of useful energy gain in this stage is less than the rate of the thermal losses at the point where the pcm starts to solidify.the water mass flow rate of heat transfer fluid during the discharge process can be calculated as follows; mw = qcharging cpw×∆tw×n (28) the total heat absorbed during the charging phase by the phase change materials in all of the three stages is expressed as: qcharging = mpcm (cps∆ts + hl + cpl∆tl) × n (29) where: mpcm , is the mass of the phase change material per finite different element. 2.3 experimental evaluation of the solar water heater with pcm based thermal storage the experimental setup of of the solar water heater with pcm based thermal storage is shown in figure 4. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 445-448. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 443 figure 4: the experimental setup of a solar water heater with pcm the experiments were carried out between the hours of 9:00am and 20:00 pm every day for four consecutive days and the temperatures of the storage at every 6:30am were carefully observed. the flow rate of the water was controlled and manipulated by a water regulator. solar intensity was measured by solar dual transmission meter xm1400 (manufactured in usa by edtm inc). the temperatures at the different points (inlet, outlet, glass, absorber, and storage tank) of the system were measured by digital thermocouples km 250 (manufactured in australia by acksen inc.). 3. results and discussion the systems of equation (1) through (29) has been numerically solved using the finite difference scheme for the adopted phase change materials (eutectic metallic salts) and the results shown in figures 5 to 8 global, ambient condition, glass condition, water inlet conditions, heat transfer fluid temperature with respect to time, solar insolation, and water outlet condition are shown in figures 5 to 8 figure 5: global solar radiation against time figure 5 presents the time variation of solar insolation (w/m2) measured at the site where the research was conducted .it is clear that the intensity of radiation depends upon the hour of the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 444 day and the period of the year. additionally, it can be deduced that the solar irradiance at 9:30 am was observed to be 690w/m2 and the intensity kept on increasing with time until it reaches its peak at 4:00 pm. at this time 1050w/m2 was recorded which can be said to be progressive with respect to the result obtained in heating the water. the solar intensity declined from the peak value of 1050w/m2 in the hour of 4.00pm to 0w/m2 in the hours of 6.30, 7.00, 7.30 and 8.00pm as evident in figure 5. figure 6: hourly variations of outlet water temperature without and with pcm figure 6 shows the temperature variations of outlet water temperature without and with pcm as a function of time. for both cases, the temperatures increased with time till it reached maximum values and then gardually decreased. the highest water temperatures reached for the collector without and with a phase change material were approximately 51 and 74°c respectively. this was as a result of the rise of solar intensity experienced during that day till 4.30 pm. it was observed that for the case without pcm, all the absorbed solar radiations were used to heat the transfer fluid, contrary to the case where the pcm was used. figure 7: effect of inlet temperature on outlet water temperature the effect of inlet water temperature on its outlet temperature was shown in figure 7. the maximum inlet temperature of 63°c was observed around 4.pm. the temperature however was not steady, it fluctuated upward and backward, as a result of non-uniform temperature http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 445-448. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 445 distribution at each of the respective nodes of the collector. an increase in inlet temperature led to a rise in outlet water temperature. a maximum steady temperature of 74°c was recorded at the outlet. the rise was mostly enhanced at higher inlet water temperature. figure 8 shows the variation of ambient, water inlet, water outlet and glass temperatures with respect to time. figure 8:the variation of ambient, water inlet, water outlet and glass temperatures with time it was clear that the inlet water temperature was 27°c at 9:30am in the morning which also corresponded to the ambient temperature and glass temperature at that point. figure 8 showed that the outlet temperature increases with time. at about 12:30 pm a temperature of 66°c was recorded at the inlet and 72°c at outlet. the glass maintained a temperature of 36°c, while the ambient at this time was 31°c. the temperature of the glass is higher than that of ambient air becuase of the green house effect exhibited by it.the storage tank which houses the water has a temperature of 39°c at the upper layer and 30°c at the lower layer indicating a non-uniform temperature distribution in each of the layers. the thermal gradient curve of the graph clearly showed that the temperature rises with height which is the factor responsible for the hot water to stay above the cold water layer as a result of difference in density. the glass and ambient air reached their peak temperatures of 46°c and 36°c at 3.30pm and 4.00pm respectively. maximum water outlet temperature of 74°c was obtained at 4.00pm and 5.00pm . at 8.00pm, when the solar energy was no longer acessible, the glass, ambient air and outlet water temperatures dropped to 29°c, 27°c and 68°c respectively as seen in figure 8. figure 9 was constructed to compare experimental result with simulation result. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 446 figure 9: comparison between the results obtained from simulation and experimental results temperature is the most significant parameter in the solar water heating system used in validating the experimental result. figure 9 showed both the inlet and outlet water temperatures of the simulated model as well as the experimental for solar water heater without pcm and with pcm. inlet temperatures of 41.54 and 36°c were observed for both the simulated and experimental model for the solar water heater without pcm, while 42.69 and 74°c were recorded for the outlet temperatures respectively. it was observed that the data of the outlet temperatures of the experimental model outweighed the outlet temperature of the simulated model. additionally, the solar water heater with pcm, the inlet temperatures for the simulation and experimental model were found to be 42°c and 56°c respectively . a maximum outlet water temperature of 108°c was obtained from the experimental model and 45°c was obtained from simulation model. the result of the simulation model fairly agrees with the ones obtained by nahar (2002) whose experiment generated a maximum output temperature of 50.6°c at the solar peak period and 41.6°c the next morning and akuffo and jackson, (2008) whose experiments generated a maximum outlet temperature of 45°c at solar peak period. the overall progression of the graph confirmed the efficiency and heat retaining capacity of the adopted phase change materials used in the research work. 4.0 conclusıon a one dimensional theoretical model for a flat plate solar collector with phase change material was developed to investigate the thermal performance of the system. it is noteworthy that the numerical model presented, predicted the heat transfer characteristics during phase change material and interactions between the heat transfer fluids. the experimental data was also http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 445-448. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 447 validated with the numerical model and simulation. the results presented shows that the heat absorbed during the charging process increases at higher water mass flow rates and decreases during discharging process at higher water mass flow rates while the time needed to complete melting and solidification modes are not linear with the mass flow rate and the pcm. this research work indicated that salt hydrates are the most energy intensive of the pcm possibilities when compared to paraffin for energy storage. this assessment shows that when pcm was used as a medium for energy storage, it significantly accumulates more energy than when water was used as a medium for energy storage. the temperature of the hot water obtained was remarkable and sufficiently enough for many domestic and industrial applications. finally, the solar water heating system with phase change materials finds useful application and acts as a renewable energy resource in regions where there is inconsistent or poor sunlight. references ahmad, ms. 2012. modeling of flat plate solar collector operation in transient states. m.sc. thesis, purdue university, u.s.a. akuffo fo. and jackson, ea. 2008. simulation studies on a compact solar water heater in the tropics. solar and wind technology, 5: 229-237. alternative energy tutorials. 2012. alternative and renewable energy. retrieved july 20, 2012 from http://www.alternative-energy-tutorials.com/ badescu, v. 2007. optimal control of flow in solar collectors for maximum exergy extraction. international journal of heat and mass transfer, 50: 4311–4322. bekkouche, sma. 2008. modélisation du comportement thermique dequelques dispositifs solaires. ph.d thesis, university abou-bakar belkaidtlemcen, algeria. duffie, ja., beckman, wa. 1974. solar energy thermal process, wiley interscience, new york. goswami, dy., vijayaraghavan, s., lu, s. and tamm, g. 2004. new and emerging developments in solar energy. solar energy, 76: 33-43. hassan, mm. 2003. framework for evaluation of active solar collection systems. ph.d. thesis, virginia polytechnic institute and state university, blacksburg, virginia, usa. incropera, fp., dewitt, dp., bergman, tl and lavine, vs. 2006. fundamentals of heat and mass transfer, six edition, john wiley and sons, hoboken, new jersey, usa. isamotu, of. 2019. development of solar water heater with phase change materials based thermal storage. m.eng thesis, federal university of technology, minna, niger state, nigeria. kalogirou, sa. 2004. solar thermal collectors and applications. progress in energy and combustion science, 30: 231–295. klein, s., duffie, j. and beckman, w. 1974. transient considerations of flat-plate solar collectors, trans. of asme: journal engineering for power, 96: 109-113. kürklü, a., özmerzi, a. and bilgin, s. 2002. thermal performance of water-phase change material solar collector. renewable energy, 26(3): 391–399. laouadi, a. and lacroix, m. 1999. thermal performance of a latent heat energy storage ventilated panel for electric load management. intenational journal of heat mass transfer, 42: 275-286. lin, sc., al-kayiem, hh. and aris, ms. 2012. experimental investigation on the performance enhancement of integrated pcm-flat plate solar collector. journal of applied sciences, 12(9): 2390–2396. http://www.alternative-energy-tutorials.com/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:olakunleisamot@yahoo.com isamotu et al: mathematical modeling of a flat plate solar collector with eutectic salts as phase change material. azojete,16(3):435448. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olakunleisamot@yahoo.com 448 naghavi, ms., ong, ks., badruddin, ia., mehrali, m., silakhori, m. and metselaar, hsc. 2015. theoretical model of an evacuated tube heat pipe solar collector integrated with phase change material. energy, 91:911–924. nahar, nm. 2002. capital cost and economic viability of thermosyphonic solar water heaters manufactured from alternate materials in india. renewable energy, 26: 623-635. rabin, y., bar-niv, i., korin, e. and mikic, b. 1995. integrated solar collector storage system based on a salt-hydrate phase change material. solar energy, 55: 435–444. senthilkumar, r., sithivinanayagam, n. and shankar, n. 2014. experimental investigation of solar water heater using phase change material. international journal of research in invent technology, 2(7): 1110-1117. shiv, k., tiwari, gn. and gaur, mk. 2010. development of empirical relation to evaluate the heat transfer coefficients and fractional energy in basin type hybrid (pv/t) active solar still. desalination, 250: 214-221. zerrouki, a., boumedien, a. and bouhadef, k. 2012. the natural circulation solar water heater model with linear temperature distribution. renewable energy, 26: 549-559. zueva, g. and magiera, j. 2001. mathematical model of heat transfer in solar collector and its experimental validation. theoretical foundations of chemical engineering, (6): 604-608 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):209-216 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 209 original research article numerical analysis of a micro horizontal axis wind turbine tower under extreme loads m. shuwa*, a. b. muhammad and m. b. maina department of mechanical engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: shuwa07201@gmail.com 1.0 introduction horizontal axis wind turbine (hawt) is the most common type of wind turbines used for harvesting some of the kinetic energy possessed by wind and it is a type of wind turbine that has wind flowing along the axis of rotation of its rotor (ngala et al., 2015). the main components of hawt (examples are rotor, drive train components, control and yawing mechanism) are supported by a tower. the hawt tower also elevates the rotating blades at a certain elevation to obtain desirable wind characteristics. there are three types of tower commonly used for micro horizontal axis wind turbines; free-standing lattice (truss), cantilevered pipe (tubular article information abstract one of the major challenges in the development of horizontal axis wind turbine is the selection of appropriate and cost effective tower that will elevate the rotor meters above the ground for wind energy harvest. in this work a tubular structural steel material having an external diameter of 0.1 m, internal diameter of 0.092 m and height of 10 m was selected based on cost, mechanical properties and market availability for the tower. response of this tower material due to simultaneously applied extreme static, dynamic and aerodynamic loading conditions was analyzed in terms of frequency of vibration, deformation and stress using the numerical code comsol multi-physics 5.2. three dimensional model of the structural steel tower was developed and boundary conditions defined in the numerical code’s model wizard interface. the tower was considered as a cantilever and a static load of 2128.77 n was applied at 10 m height in the 𝑦 plane. dynamic load of 413.96 n was applied on the tower in the x,y,z planes and an aerodynamic load of 4967.58 n was applied as uniformly distributed loads in the x plane. extra fine regular quadrilateral mesh was generated for the computation. frequency response result of the transfer function at 110 ghz excitation shown in terms of electric field norm was uniformly distributed at the outer boundary layer of the tower with a minimum value of 3.7 x 10-79 v/m. the result of the deformation analysis under the predefined extreme loading conditions shows a maximum deflection value of 197 mm at 10 m height and 0 mm at 0 m height of the tower. additionally, the stress analysis result shows a predicted maximum value 3.28 x 106 n/m2 between 0 m and 1.98 m height of the tower in the wind direction. the deformation was within the elastic limit of the tower material, because the total exerted extreme loads without the selfweight of the tower (2,397.54 n) was less than the determined safe load of the tower (7,107.96 n). the study has established that the selected horizontal axis wind turbine (hawt) tower material was reliable under the predefined simultaneously applied extreme loads, thus the structural steel tower can function in areas this or similar loading conditions. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 october, 2021 revised 13 february, 2022 accepted 20 february, 2022 keywords: micro hawt tower aerodynamic load tower deflection stress distribution elastic limit http://www.azojete.com.ng/ mailto:shuwa07201@gmail.com mailto:shuwa07201@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):209-216. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 210 tower) and guyed lattice or pole. generally micro hawt towers are produce from reinforced concrete, steel or composites material, the steel material is the most popular choice because of its strength and low cost (shuwa et al, 2016; da silva and oliveira, 2018). the height of a hawt tower is very important in assessing turbine performance since wind speed increases with height and performance of the turbine depends on wind speed magnitude. in performing this task erected towers are subjected to loads that are transferred from rotor operations, wind pressure, the weight of the nacelle and that of the tower itself (biswajit, 2010; gizachew and belete, 2019). however, wind loads are dominant in most cases and if not properly addressed may result in excessive deformations which, in turn can cause significant damage, or even collapse of the wind turbine. for optimal tower design that will withstand these loads, a numerical optimization model is inevitable, because it deals with simulation of the design variables, searches for optimal solutions and less expensive than experimental analysis (adhikari and bhattacharya, 2012; umesh, 2016). a numerical model is defined by a mesh network, which is made up of the geometric arrangement of elements and nodes. nodes represent points at which features such as displacements, stress are calculated. the numerical packages use node numbers to serve as an identification tool in viewing solutions in structures such as deformation or deflection, stress and strain caused by applied structural and aerodynamic loads (strivridou et al., 2015; ferroudji, 2021). literatures on the study of dynamic interaction of wind turbine components with regard to the structural design of the tower with the interaction of the mechanical rotor system is ongoing (karpat, 2013; wagner and mathur, 2018; gizachew and belete, 2019). the motion of a hawt tower is strongly connected to the motion of the blades, as the blades transfer an axial force onto the low speed drive shaft which is ultimately transferred into the nacelle base plate at the top of the tower (wagner and mathur, 2018). the free vibration properties of a tower carrying a rigid nacelle mass at the top may be evaluated by techniques such as the discrete parameter method, the finite element method or by using closed form solutions (kandil et al., 2016; da silva and oliveira, 2018). the discrete parameter method was used to study the behavior of transmission towers under the action of stochastic wind loading. researchers have used this technique to assess the accuracy and reliability of more computationally expensive finite element analyses of wind turbine tower (da silva and oliveira, 2018; ferroudji et al., 2020). recent studies using the finite element (numerical) technique for free vibration analyses of structures in wind engineering have derived expressions in closed form to yield the eigenvalues and eigenvectors of a tower-nacelle system comprising of a prismatic cantilever beam with a rigid mass at its free end (guoyang and song, 2016; saihi and roummani, 2020; ferroudji, 2021). in this work a tubular structural steel tower was selected based on cost, mechanical properties and local availability. the resistance and stability of the selected tower to extreme operational loading conditions was analyzed. the aim was to identify if the selected micro hawt tower structure will function optimally with minimal or no risk of failure in regions associated with stochastic high wind speeds like the semi-arid region of nigeria. 2. materials and methods a tubular structural steel pipe of uniform cross-section with an external diameter d of 0.1 m, internal diameter d of 0.092 m, wall thickness t of 0.008 m and height ly-l from 0 m to 10 m was selected for analysis. the selection was based on local availability, strength and cost of the material. the material has young’s modulus etw of 2 x 1011 n/m2, poisson’s ratio n of 0.33 and density ρtw of 7850 kg/m3 (david, 2005). comsol multi-physics 5.5 numerical code was used to predict the behavior of the hawt tower model under defined loading conditions based on the assumptions of euler-bernoulli’s beam theory, geometry and material of the tower. electromagnetic wave interface was used to solve for time harmonic electromagnetic field file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:shuwa07201@gmail.com shuwa et al: numerical analysis of a micro horizontal axis wind turbine tower under extreme loads. azojete, 18(2):209-216. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 211 distribution of the tower model under load. frequency response of the tower structure with respect to static, dynamic and aerodynamic loadings were predicted using the frequency domain interface at an excitation frequency of 110 ghz. solid mechanics in comsol multi-physics numerical code was also used to compute and analyze deflection or displacement and stress distribution on the tower due to simultaneously applied static, dynamic and aerodynamic loads. the selected structural steel tower geometry was created using the 3d model wizard of comsol multi-physics numerical code 5.5. the predefined geometrical parameters such as internal diameter, external diameter and height were defined to build the tower in the numerical code’s graphical window. tower material properties were also selected and defined from the numerical code’s material data base as structural steel. the tower is modeled and analyzed as a vertical cantilever beam under static, dynamic and uniformly distributed aerodynamic loads. boundary conditions were applied on load application condition, with top of the tower considered as a free end and the bottom as fixed. a static load (david, 2005) due to self-weight of the tower and weight of the nacelle was applied at the top of tower in the y plane. dynamic load (david, 2005) due to gyroscopic rotation of the rotor was applied at the top of the tower in the x, y, z planes and aerodynamic load due extreme stochastic wind speed pressure was applied as uniformly distributed loads in the 𝑥 plane along the height of the tower as shown in figure 1a. a regular quadrilateral mesh generation method was used as in figure 1b to generate extra fine mesh for the computation. (a) (b) figure 1: (a) loads on the hawt tower and (b) the generated grid. the generated mesh has 29,725 quadrilateral elements and 1036 nodes with each node having 4 degrees of freedom. using these nodes as identification tool solutions to the tower deflection, http://www.azojete.com.ng/ mailto:shuwa07201@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):209-216. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 212 stress distribution, stiffness, natural modes of vibration in terms of corresponding frequencies due to the predefined loading conditions were obtained. in this analysis three defined loading condition are considered acting on the tower simultaneously. static load wst(y,) due to the selfweight of the tower and the weight of the nacelle given by equation 1, dynamic load wdy(x,y,z) due to the gyroscopic rotation of the rotor and nacelle yawing given by equation 2 and aerodynamic load war(x) due to extreme stochastic wind pressure on the tower given by equation 3 (biswajit, 2010; umesh, 2016). where mnl is 42 kg the mass of the nacelle, mtw is 175 kg the mass of the structural steel tower and g is 9.81 m/s2 acceleration due to gravity. where density of air ρa is 1.225 kg/m3, v is 18.75 m/s (nimet, 2017) the stochastic wind velocity considered for this work. the maximum blade chord length c of the hawt is 0.26 m, lb is 1.5 m the blade span, fyw is nacelle thrust, ry is 1.8 m the nacelle radius of gyration, cl and cd are 1.157 and 0.0122 the lift and drag coefficient of the blade respectively. the rotor diameter dr of the hawt considered for this work is 3 m. while φ is the gust factor and the form factor cf is 0.6 for steel towers (gizachew and belete, 2019). in defining the boundary condition maximum calculated static load of 2128.77 n due tower self-weight and weight of the nacelle was applied to free end of the tower. while determined aerodynamic load of 1655.86 n and dynamic load of 413.96 n were applied on the top upwind vertical face and along the height of the tower. these loads are applied simultaneously on the discretized elements of the tower model and are the cause of tower vibration, deformation and stresses in the tower. the tower’s vibration frequency, stiffness, deformation and stress distribution are predicted from equations 4, 5, 6 and 7 respectively (biswajit, 2010; kandil et al., 2016; ferroudji, 2021). where nn is the mode number i.e. 1,2,3, 4… n, wtw is the weight of the tower determined as 1716.75 n (175 kg x 9,81m/s) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:shuwa07201@gmail.com shuwa et al: numerical analysis of a micro horizontal axis wind turbine tower under extreme loads. azojete, 18(2):209-216. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 213 where etw is 2 x 1011 n/m2 young modulus of the tower material, itw is 6.174 x 10-4 m4 the moment of inertia of the tower. the end fixity coefficient cefc is 0.25 for a beam with one end fixed and the other free (khurmi and gupta, 2005). the tower was considered and analyzed as a cantilever with one end fixed and the other free and the objective functions were solved using solid mechanics elasticity equations (equation 4, 5, 6 and 7) based on euler-bernoulli’s beam theory. these equations were solved at each of the 29,725 quadrilateral created elements to determine deformation (deflection), stiffness, vibration frequency and stress distribution along the tower geometry under the predefined loading conditions . the transfer function was predicted at 110 ghz excitation frequency (the maximum excitation frequency predicted by the numerical code) in terms of electric field norm under the loading conditions at an average rotor speed of 40 rpm. the predicted results were post processed and validated with experimental results using the f-test statistical tool. 3. results and discussion the meshed hawt tower model was first solved in a frequency domain interface for timeharmonic electromagnetic field distributions. figure 2 shows frequency response of the tower model under applied extreme static, dynamic and aerodynamic load distribution excited up to 110 ghz. the frequency response of the transfer function in terms of electric field norm was uniformly distributed at the out surface boundary layer of the tower with a minimum value of 3.7 x 10-79 v/m. however, this value increases inwards along the thickness of the tower at the transfer ports and there exist a similarity in the transfer function from port one (tower root) to port two (top of the tower). this result shows stability in the tower structure and that failure could be avoided. in an investigation carried out by ferroudji (2021) on a 55 m high steel wind turbine tower reveal that the natural frequencies of the tower under load correspond to the mode shapes and mass participation ratio values. this shows that resonance in the tower structure was uniform and failure could be avoided under the action of high wind speeds figure 2. frequency response of the transfer function in terms of electric field norm at 110 ghz excitation. the result of the deformation of the tower under the predefined loading conditions shows a maximum deflection of 197 mm at the top and minimum of 0 mm at the root of the tower as shown in figure 3. the result shows that the tower was stable under the predefined simultaneously applied loads, thus the structural steel tower can function under the defined loading conditions and the deformation is within the elastic limit of the tower material. this was because the total exerted load without the self-weight of the tower 2,397.54 n was less than the calculated safe load 7,107.96 n of the tower. according to mandal et al. (2018) the stability of a wind turbine tower is a function of geometry and design and it is important to the functioning of http://www.azojete.com.ng/ mailto:shuwa07201@gmail.com https://en.wikipedia.org/wiki/deflection_(engineering) arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):209-216. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 214 the wind turbine. to achieve the functioning of the tower, the exerted load should always be less than the critical load of the tower material considering its geometry and a defined factor of safety. figure 3 deformation due applied load at an excitation frequency of 110 ghz. the deformation of the tower along its height (from 0 m at the root to 10 m at the top) is shown in figure 4. the result shows the gradual increases in deformation of the tower from the root (the fixed end) to the top (the free end) due simultaneously applied extreme loading conditions. figure 4. deformation of the tower under the simultaneously predefined applied loads along its height. the result of the stress distribution due to simultaneously applied static load of 28,245.53 𝑁, aerodynamic load of 382.82 𝑁 and dynamic load of 413.96 𝑁 is shown in figure 5. the response of the transfer function in terms of volume misses stress under 110 ghz excitation was 3.28 x 106 n/m2 at the root of the tower in the wind direction. this value decreases with increases in tower height and drops to 0 n/m2 at 10 m height of the tower. the predicted value was less than the axial and longitudinal stress values determined as 3.36 x 106 n/m2 and 3.31 x 106 n/m2 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:shuwa07201@gmail.com shuwa et al: numerical analysis of a micro horizontal axis wind turbine tower under extreme loads. azojete, 18(2):209-216. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 215 respectively. moreover, the result also shows that the response of the tower material was due to its structural stiffness which also did not affect the frequency and dynamic response of the tower structure. da silva and oliveira (2018) and ferroudji (2021) in their works state that stable steel tower structures must offer internal resistance to externally applied load and the tower material must also have the ability to resist deformation under the resistance. figure 5. stress distribution along the tower height due to simultaneously applied static, dynamic and aerodynamic loads. the numerical results obtained in this work were validated with an experimental one and the ftest statistical tool used showed that the is no significant difference between the two results. therefore, it has been established that the selected hawt tower material was reliable under the predefined simultaneously applied extreme loads, thus the structural steel tower can function in areas with this or similar loading conditions. 4. conclusion the selected tubular structural steel tower material was numerically analyzed using the numerical code comsol multi-physics 5.5. a 3d model of the tubular steel tower was developed in the numerical code’s model wizard interface and analyzed based on euler-bernoulli’s beam theory. the steel tower’s response to simultaneously applied extreme predefined static, dynamic and aerodynamic design loads was examined. the result shows that the response of the selected tubular steel tower with regards to vibration, deformation and stress were within the limits of the mechanical properties of the selected tower material (structural steel). the f-test statistical tool used to validate these results with an experimental one shows that there is no significant difference between the two results. it has also been established that the selected hawt tower material was reliable under the predefined simultaneously applied extreme loads, thus, the structural steel tower can function in areas with this or similar loading conditions references adhikari, s. and bhattacharya, s. 2012. dynamic analysis of wind turbine towers on flexible foundations. journal of shocks and vibrations, 19: 37-56. biswajit, b. 2010. tower design and analysis. world international transaction on state of the art in science and engineering, dublin. 527-557. http://www.azojete.com.ng/ mailto:shuwa07201@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):209-216. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shuwa07201@gmail.com 216 da silva, jgs. and oliveira, bas. 2018. “evaluation of the nondeterministic dynamic structural response of three-dimensional wind turbine steel towers. sage journal of wind engineering, 40:364-377. david, j. 2005. engineering material standard code book. new york: m. harison inc. ferroudji, f. 2021. numerical model analysis of a 850 kw turbine steel tower. international review of applied science and engineering, 12(1):10-18. ferroudji, f., lakhdar, s. and khayra, r. 2020. numerical simulation on static and dynamic response of full scale mast structure for darrius wind turbine. sage wind engineering journal, 45(4):822-837. gizachew, dt. and belete, s. 2019. upwind 2mw horizontal axis wind turbine tower design and analysis. science publishing group, 7(5):111-131. guoyang, x. and song, x. 2016. simulation analysis of universal fatigue life of tower load of horizontal axial force wind turbine. journal of gansu science, 28(4):115-118. kandil, kas., saudi, gn. and eltaly, baa. 2016. seismic response of a full-scale wind turbine tower using experimental and numerical modal analysis. international journal of advance structure engineering, 8:337-349. karpat, f. 2013. a virtual tool for minimum cost design of a wind turbine tower with ring stiffeners. energies, 6(8):3822-3840. kurmi, rs. and gupta, jk. 2005. machine design. new delhi: eurasia publishing house ltd. mandal, ak., rana, kb. and tripathi, b. 2018. experimental and numerical analysis on small wind turbines: a review. international journal of applied engineering research, 13(8):97-111. ngala, gm., shuwa, m., oumarou, mb. and muhammad, ab. 2015. a cfd analysis of a micro horizontal axis wind turbine blade aerodynamics. arid zone journal of engineering, technology and environment, 11:13-23. nimet 2017. meteorological data. lagos: nigerian meteorological agency. saihi, l. and roummani, k. 2020. numerical simulations on static and dynamic response of fullscale mast structures for h-darrius wind turbine. sage journal of wind engineering, 45(4):822837. shuwa, m., ngala, gm. and maina, m. 2016. development and performance test of a micro horizontal axis wind turbine blade. international journal of engineering research and application, 6(2):11-17. strivridou, n., eottasakis, e. and saniotopoulos, c. 2015. finite element analysis and comparative study of welded connection of wind turbine towers under fatigue loading. international journal of applied sciences, 8:489-500. umesh, kn. 2016. design and analysis of 2-mw wind turbine tower. international journal of mechanical and production engineering, 4(10):13-17. wagner, hj. and mathur, j. 2018. introduction to wind energy systems. berlin: springer. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:shuwa07201@gmail.com arid zone journal of engineering, technology & environment azojeteseptember 2020. vol. 16(3):621-636 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 621 original research article design analysis of a microcontroller based automatic switching system using passive infrared sensor a. a okandeji1*, z.o. jagun2, m. b olajide3 and, m. t. kabir4 1department of electrical and electronic engineering, university of lagos, akoka, lagos state, nigeria 2department of computer engineering, olabisi onabanjo university, ago-iwoye, ogun state, nigeria 3department of electrical and electronic engineering, olabisi onabanjo university, ago-iwoye, nigeria 4department of electronic and telecommunication engrng, ahmadu bello university, kaduna, nigeria. *corresponding author’s email address: aokandeji@unilag.edu.ng 1.0 introduction electricity which has assumed a prime position as a form of energy for mankind play a vital role in the development of any nation. as human activities increase and inventions are made, the importance of electricity continues to be dominant (grueneich, 2015). based on increasing human activity, there has been an exponential rise in the demand for electricity. however, despite the importance attached to electricity, it remained one of the most wasted and abused resources especially in third world countries. it is not uncommon to see lightings left on in unoccupied classrooms, offices, and homes for many hours. nonchalant attitude is observed in the area of management and conservation of public power supply. individuals often observe power on the lightings, cooling systems, and other appliances at homes, offices and commercial centers whenever it is not required. to address this problem, the method of writing statements such as “switch off all appliances when leaving the office” and placed at the back of the doors was adopted in many establishments. this however seem ineffective because in most cases due to epileptic power supply, some electrical appliances were not switched off. specifically, the interrupted power is restored when occupants have left the office. this might result to increased power bills and may hinder a nation from diverting power to industrial areas, limiting the process of industrialization and increasing energy wastage. it has been estimated that approximately 45% of the electricity generated in many third world countries (including nigeria) is wasted (oyetola et al., 2019). this is due to poor energy conservation policy of the country and lack of public awareness of the need for efficient utilization of electricity. energy article information abstract poor management and conservation of public power supply has constantly resulted into wastage of electricity thereby limiting the industrialization process especially in third world countries. to reduce energy wastage in homes, institutions and public places, this paper presents the development of an automatic switch using passive infrared sensor (pir). automatic switch is a device that detects the human presence in a predefined area and can turn on the lights or any electrical appliances. similarly, the device will automatically turn off the lights or any electrical appliance if nobody is present in the area. using the pir sensor (for human detection), light dependent resistor (ldr) (to detect night and day), and a microcontroller programmed using micro-c, a switching circuit that detects humans in a predefined area is investigated. in particular, an automatic switching system using passive infrared sensors to prevent unwarranted wastage of electricity, and also to prevent electricity related hazards which could result from the use of unmonitored electrical appliances is implemented. the research work guarantees less consumption of power, hence, lower utility bills. also, it allows for more safety in homes, schools, and offices since heavy-duty and high-power equipment that could cause fire e.g. air-conditioning systems, electric cookers, boilers, electric irons etc, if left unattended to, can be turned off automatically. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 march, 2019 revised 19 june, 2019 accepted 26 june, 2019. power switch energy conservation passive infrared sensor relay light dependent resistor. http://www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 622 conservation is thus an important element of energy policy. a well-thought-out energy conservation policy helps to reduce energy consumption and demand per capita. this in turn increases the energy supply needed to keep up with population growth (moore, 2002). to address the problem of energy wastage in homes, offices etc, (zhenfeng et al., 2020) considered the use of automatic switching controls to activate the lighting circuit when a human is sensed within a space. furthermore, work done in (xiao et al., 2020) considered the major types of automatic switching controls namely passive infrared, ultrasonic, and a dual technology device that uses both passive infrared and ultrasonic technology. in particular, passive infrared sensor (pir) senses occupancy by detecting the difference between heat emitted from the human body in motion and the background space (xiao et al., 2020). passive infrared sensors use fresnel lenses to create a defined pattern of coverage in both the horizontal and vertical planes. the latest technology ensures higher sensitivity to minor motion without the potential for false activation. pir devices are available in a wall-switch model (in place of a standard snap-switch at a doorway) or a ceiling-mounted unit (xiao et al., 2020). ultrasonic sensor based detectors on the other hand transmit and receive low-intensity sound waves at a frequency of about 25 khz to 40 khz, which is inaudible to the human ear (theraja, 2002). any change in the signal return time is interpreted as motion, and the sensor responds by keeping the lighting on. some products use patented signal processing circuitry to automatically adjust the signal detection threshold to compensate for changing levels of activity and airflow. this feature helps to eliminate false on activation. ultrasonic sensors are best suited for monitoring partitioned areas as well as areas with large objects, such as furniture, that are likely to block the field of view of pir sensors. alternatively, for spaces where neither a pir nor an ultrasonic sensor is practical, a dual-technology device using both pir and ultrasonic sensing can be installed. both types must detect occupancy to turn lighting on, while continued detection by only one technology will keep lighting on (xiao et al., 2020). these sensors are best suited for office areas with cubicles, general workplaces, warehouse and storage facilities, cafeterias, and public areas in commercial facilities. another class of the less popular detectors is a photosensitive control unit which operates a lighting circuit that adjusts to ambient lighting levels (sadeghi et al., 2016). in response to the photo control unit, a switching system will turn on lamps in a specific pattern, such as one or more contactors/branch circuits or a portion of a branch circuit, to provide typically one-third, half, or two-thirds of full light output in an area. photo sensor units are available as two-component systems with externally mounted sensors connected to a remotely mounted electronic module via low-voltage wiring, making it convenient to adjust operational set points from inside the building. other systems incorporate an infrared detection system which is configured to sense direction of motion so that it can increment or decrement its count based on the number of occupants. the system keeps the lighting circuit active until the programmed counter for the number of occupants within the control area drops to zero (xiao et al., 2020). in contrast to existing results, this study considers the development of a microcontroller based automatic switch using passive infrared sensor. in particular, the design analysis of an automatic switching system using passive infrared sensors to prevent unwarranted wastage of electricity, and also to prevent electricity related hazards which could result from the use of unmonitored electrical appliances is implemented. specifically, using the pir sensor which consists of ir sensors to detect human body heat, the system detects the presence of a human, and automatically turn on electrical appliances, and turns off appliances upon the observation of the absence of human. 2.0 materials and methods this section describes the development of the automatic switching system using passive infrared sensors to prevent unwarranted wastage of electricity, and also to prevent electricity related hazards which could result from the use of unmonitored electrical appliances. functionally, power is cut off from the control area if the system senses human absence for a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 623 predetermined period of time using pyro electric means after it must have sensed motion. as long as there is human presence in the control area occasioned by body heat and motion, the system remains in an idle loop but it is called into action once no occupancy is detected after a pre-determined time. figure 1 shows the combination of the sub-systems which determines the overall operation of the power controller circuit. to achieve the circuit objective, a sequence of pre-programmed processes are utilized which is combined to understand the overall functional flow of the study. figure 1: block diagram of an automatic switching system using pir this process flow is indicated using the flowchart as shown in figure 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 624 figure 2: process flow chart for automatic switching system using pir sensor 2.1 circuit operation the circuit in figure 3 is connected through the provided mains terminal to a suitable power supply outlet while the load or circuit to be controlled is connected to the circuit through the designated load terminal. care must be taken to avoid polarity reversals. once connection is complete and certified okay, power is supplied to the circuit. as the circuit senses power, the “power” light emitting diode (led) comes on to indicate that the circuit is live. instantaneously, the circuit goes into a pre-determined start-up delay of five seconds. upon this delay time elapsing, the “status” led as well as the control relay both turn on. upon the energization of the relay, the load under control instantly receives power. at the expiration of the initial startup delay, the circuit automatically enters the countdown routine where it is http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 625 programmed to count down for 10 minutes, and thereafter initiate the critical shutdown routine. if the circuit, through the sensor, picks up human presence anytime during the countdown routine, the countdown routine is automatically restarted. for as long as human presence is sensed within the control area, the countdown routine will be reset to restart. accordingly, the circuit ensures that the relay is kept energized. however, if during the countdown sequence, no human is sensed, after a 10-minute period, the circuit goes into the critical shutdown routine. accordingly, the led is flashed rapidly while an audible alarm is annunciated once every 30 seconds to warn of imminent shutdown. this process is carried out for the next 3 minutes during which if a body is sensed, the circuit goes back to the start of the countdown routine. on the other hand, if no human is sensed during the critical shutdown routine, and the 3 minutes elapses, the “status” led and relays would both go off thereby turning off power to the load or the control area. after shutting down, if at any time instant the sensor senses human presence, the circuit again automatically turns on. to summarize, immediately after turn on, the circuit is designed to shutdown in approximately 13 minutes but the shutdown process will be interrupted, and the process restarted every time an interrupt occurs as a result of human presence. 2.2 circuit design the entire circuit in figure 3 is divided into 2 sections namely: power supply circuit control section file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 626 figure 3: the complete circuit of a switching system using a pir 2.2.1 power supply circuit the component parts of the control circuit to be powered are the digital microcontroller, sensors, relays, buzzer and leds. the controller requires +5v while the relays used are the 12v type which in reality can be powered by an unregulated voltage range of 7 – 19v. the pir sensors can use a supply voltage between 4.5 – 20v. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 627 2.2.1.1 transformer to determine the transformer size and rating, the voltage and current considerations of the circuit is considered. in view of this, the total current of the circuit which is the summation of current requirement of the individual circuit elements is considered. the major current consuming components in the circuit are the relays, leds, pir, and the microcontroller. the transformer current rating is taken to be at least twice the total current required by the circuit elements. the characteristics of the relay (rla) considered are given as: 12v (coil), 30a (contact), 250 (coil resistance). for the relay, as shown in (theraja, 2002), the coil current is given as 12 250ω = 48ma. (1) for the leds, assuming a maximum current of 50ma , to achieve good illumination, the total intake of about 150ma is considered. for other parts of the circuit (which are very low current consuming devices), we assume to draw not more than 50ma. hence, total current required by the control circuit is given as: i = 48ma+ 150ma + 50ma = 248ma if input voltage v1 = 220v. output voltage v2 =15v. n1 = number of primary turns = 550, n2 = number of secondary turns. n2 = n1 v2 v1 (2) = (15 x 550 )/220 = 38 turns. 2.2.1.2 calculation for the number of turns from (theraja, 2002), e1 = 4.44faβn1 volts, (3) where e1 = supply voltage = 220v. f = frequency = 50 hz. β = flux density = 1.1 (for steel wire) a = area = l x b m2 n1b = number of turns in the primary winding. for a = length x breadth, l = 60cm = 0.06m. b = 2.8cm = 0.028m. area = 0.00168m2 n1 = e1 4.44 x 50 x 1.1 x 0.00168 = 220 4.44 x 50 x 1.1 x 0.00168 = 220 0.4 = 550 turns for the secondary windings, from (theraja, 2002), for e2 = 4.44fban2 volts where e2 = output voltage = 15v. a = area = l x b = 0.00168m2 . β = flux density = 1.1 (for steel wire) f = frequency = 50 hz. n1 = e2 4.44 x f x b x a = 15 4.44 x 50 x 1.1 x 0.00168 = 15 0.4 = 37 turns file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 628 2.2.1.3 primary winding calculation. from (theraja, 2002)., ieq = iin  duty cycle, (4) where duty cycle = 1 (since the coil is wound round the core once) also, power = voltage x current. (5) the rating of the transformer is 250va. thus, iin = v p , where iin = input current. since v = 220v iin = 250 220 = 1.13a therefore, ieq = iin  duty cycle = 1.13  1 = 1.13a, where ieq = equivalent current. also, from (theraja, 2002), cross sectional area of conductor = current current density , (6) but current density = 3a/m2 therefore, conductor area = iin current density = 1.13 3 = 0.379 m2 therefore, from the standard wire gauge (swg) table, the suitable gauge size is 28. for secondary winding, where v = 15volts iin = p v = 250 15 = 16.67a. for duty cycle = 0.5 (for centre tapped i.e. it moves half of a cycle), ieq = iin x duty cycle = 16.67 x 0.5 = 8.33a. conductor area = current current density = 8.33 3 = 2.78 m2 the centre tapped transformer used is shown in figure 4. figure 4: centre –tapped transformer for the proposed design, a transformer with secondary current rating of 500ma is appropriate. the schematic diagram of the power supply unit for the control circuit is shown in figure 5. figure 5: power supply circuit http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 629 2.2.1.4 rectifiers diodes a rectifying circuit is required to convert the stepped down alternating current (ac) from the mains socket to a form usable by electronic circuits. in general, the diode must be able to withstand the maximum voltage and current of the circuit to avoid a breakdown and reverse conduction. the mains supply voltage is an alternating current sinusoidal voltage, and for a single phase, it takes 220v at 50hz. the requirement of this stage is to obtain a unipolar voltage i.e. a voltage which is made up of a sinusoidal half cycles but each of the same polarity either positive or negative. this is achieved using a pn junction diode and two methods namely: half wave rectifier, and full wave rectifier. half wave rectifier: this is the simplest circuit. the ac voltage is provided by the transformer powered from the ac power line. full wave rectifier: this make use of four diodes, and it is chosen because it is economical in that a smaller transformer can be used to achieve the purpose of using a bigger transformer for other forms of rectification. the transformer secondary has a centre tap so that during each part of the sinusoidal ac voltage input, two diodes conducts simultaneously i.e. d1 and d3, while d2 and d4 conducts in the other half of the cycle. for the purpose of this research work, a compact rectifier is used where the four diodes are all connected into one. thus, current flows through and drops a voltage across the load. the amount of ripple is also reduced compared with half wave rectifier (theraja et al., 2002). the rectifier circuit with its output is shown in figure 6. figure 6: circuit for rectification and the output waveform to satisfy the above conditions, the diode specification is given as: chosen diode (d1, d2, d5 and d6): 1n4001; continuous forward current = 1a, peak repetitive reverse voltage = 50v 2.2.1.5 filter capacitors after rectification, the pulsating direct current (dc) produced is highly rich in ripples and harmonics. to remove these disturbances, filter capacitors are used. c1 is a high value electrolytic capacitor which acts as short circuit at low frequencies and bypasses these components to ground. c2 is a ceramic type used to bypass higher frequencies to ground because they act as short circuits at high frequencies. the voltage rating of the capacitors must be higher than 1.414 times the voltage rating of the transformer secondary. for this design, a maximum ripple voltage of 10% of the dc rectified voltage is considered. for this consideration, the equation below applies (theraja et al., 2002): c = 5 x i load/vdc x f, (7) where c is filter capacitance, i load = load current, vdc = the rectified d.c voltage, f = the ac power supply frequency = 50hz. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 630 ripple voltage defined as the residual periodic and continuous voltage insider the supply of power whose derivation is from the a.c. source is given as (theraja, and theraja, 2002): vripple peak = vpeak − vdc , (8) where the d.c voltage is vo = vin 2 . (9) using the equation above, c is therefore given as 5 x 258ma 13.5v x 100hz = 1191.11µf. for the proposed design, a capacitor of 1000µf was selected. the simplest way to smoothen the voltage output of a rectifier in order to minimize the ripples and give a better approximation to a dc is to use a capacitor in parallel with the resistive load. here, two reservoir capacitors c1 and c2 are used to convert the pulsating half cycles which appear at the cathodes of the diodes into a near smooth dc voltage. this action depends on the fact that the capacitor stores energy during the conduction periods, and deliver this energy to the load during the non-conducting period. thus, the time during which the current passes through the load is prolonged and the ripple is considerably reduced. the ripple voltage is the deviation of the load voltage from its dc voltage i.e. the values of capacitors c1 and c2 used with a 50hz supply may range from 100µf – 30,000µf depending on the load current, and the degree of smoothening required. in selecting capacitors, the ripple voltage required is 5% of the peak value thus from (theraja et al., 2002). c = ct x v d.c/ rv x projectload, (10) where ct = period capacitor = 0.0025 for full wave circuit. higher values of 10000f are chosen as shown in figure 7 because higher capacity efficiency can be achieved with higher capacity values (www.alldatasheet.com). figure 7: power supply unit 2.2.1.6 voltage regulator a stable +5v is required to power the microcontrollers, and since a maximum output current of 258ma is required in the circuit, an integrated voltage regulator capable of supplying 5v while still being able to supply more than 258ma is considered. the voltage regulator is a compact and versatile adjustable positive voltage regulator. the regulator features an internal thermal overload protection, short circuit current protection as shown in figure 8. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 631 figure 8: voltage regulator circuit for the voltage regulator, the output voltage is approximately given by (theraja et al., 2002). vout = 1.25 1 r1 r2 (11) the values of resistors shown in figure 8 are as recommended by the manufacturer’s datasheet. the electrical characteristics of the regulator are: minimum regulated voltage range = 1.25v, minimum input voltage = 3.5v, maximum differential voltage (input to output) = 40v, maximum regulator current = 1.5a. 2.2.1.7 led indicator to ensure adequate illumination, a current of about 50ma is considered. at a peak voltage of 19v(after filtering, capacitor increases rectified dc voltage 13.5v by a factor of 1.414), a limiting resistor is required. v = vled + vresistor (12) for an illuminated led, the voltage drop is about 2v. therefore, the resistor voltage is 19 – 2 = 17v. when passing 50ma, the value of the resistance required is 17v / 50ma = 340 ohms . therefore, r1 = 340 ohms (330 is selected) . as recommended by the datasheet, r2 = 5kω and r3 = 220ω. 2.3 control section the control section is made up of the following sub-circuits namely: 2.3.1 body heat sensor for this design, a pyroelectric infrared sensor is selected. these sensors work by detecting changes in infrared energy levels caused by humans moving within the range of the sensor. pir sensors are passive because they do not send out a signal or emit any type of energy; they just sense infrared energy (heat) that emanates from the human body. 2.3.2 features of the pir sensor sensing occurs a minute after power initialization time. sensor module uses a dual probe. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 632 when the body moves from left to right or right to left, the sensor responds but not when a body moves from top to bottom. this way, the sensor is able to interpret motion but attributes top-to-bottom sensing to external radiation like lighting or vibration. 2.3.3 relay interface circuit the relay is used to switch on or off the connected load depending on the state of the pir, and the interpretation by the microcontroller. the relay used is a dc type with contacts capable of carrying the desired load current. the maximum load power considered for this design is 3000w at 220v. therefore, maximum load current is given as 3000w / 220v = 13.64a. (13) therefore, a relay with contacts capable of carrying 13.64a is selected. due to the limitation of the source current of pic microcontrollers to 25ma, and the requirement of a coil current far in excess of 25ma, a transistor amplifier is used in a common emitter mode to amplifier the base current provided by the pic so that the relay acts as a collector load. design consideration is shown in figure 9. figure 9: relay interface circuit relay parameters includes: coil resistance = 150ohms, coil voltage = 12v, contact rating = 30a. from where, coil current = 12v / 150ω = 80ma . bc337 is selected with a collector current capability of 500ma to pass the relay coil current. assuming a worst-case scenario current gain of 20 for the transistor, and a collector current of 80ma which is equal to the coil current, the base current is expressed as ib = ic / hfe = 80ma / 20 = 4ma. (14) the turn-on voltage of an npn transistor = 0.6v (theraja, 2002). therefore, the voltage across the base resistor is vpic(o/p) − vbe = 5 – 0.6 = 4.4v. (15) accordingly, r12 = 4.4v / 4ma = 1100ohms (1.1k), 1.2k is selected. 2.3.4 audible alert circuit an audio alert circuit is considered to actively inform the user of the status of the entire system. the alert is such that after a period, predetermined by the microcontroller firmware, a tone is sounded at intervals to intimate the user of an impending shutdown. the alarm beeps once every 10 seconds for one minute, and if no human presence is sensed, the circuit shuts down after 120 seconds. the microcontroller activates the buzzer through a transistor as shown in the relay circuit in figure 10. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 633 figure 10: buzzer interface circuit 2.3.5 microcontroller firmware at start-up, the status led comes on and the circuit checks the sensor input for human presence. a shutdown sequence is initiated through an internal countdown timer in the microcontroller while the status led remains steady. the timer counts down for a 10-minute period, and if any movement is detected, through the pir, the countdown is cancelled and restarted. if on the other hand no movement is detected, after 10 minutes, the program enters a critical shutdown period and the status led starts to flash once every second accompanied by an audible alarm once every 5 seconds. the critical shutdown period lasts for 3 minutes during which the countdown is again restarted if any movement is detected. if not, the system shuts down and turns on the relay after the critical shutdown routine. the relay then opens the connected load. after shutdown, any movement detected will re-initiate the system again. for this design, the microcontroller routine is written and compiled with gc basic, a free and open source microcontroller basic compiler. note that the environment and syntax is different from the more popular g basic with the former targeted at embedded programming, and the latter targeted towards computer programming. 3.0 testing and performance evaluation this section focuses on the testing of the various stages of the passive infrared automatic switching device. in general, the performance of a transformer can be determined on the basis of its equivalent circuits which contains four main parameters namely equivalent resistance, equivalent leakage resistance, the core-loss conductance, and the magnetising susceptance (theraja et al., 2002). these constants or parameters can be easily determined by the opencircuit test and the short circuit test (theraja et al., 2002). for this study, we consider only the short-circuit test, and for operational effectiveness, we investigate the preliminary test as well as the operational test of the proposed design 3.1 preliminary test this test was carried out to ensure that proper components were fixed at the right places and to ensure proper functionality of each components. the circuit was scrutinized to ensure that there was no short circuit or loose contact during the soldering which may cause failure of the circuit or damage to the component when the supply is fed in. the transformer of the proposed design was tested by checking both input and output voltage. the supply voltage was checked by using a voltmeter and it gave exactly 220v. the secondary voltage was also checked it was found out to be 15v-0-15v (for a centre tapped transformer). additionally, the transformer was plugged to check for the heat dissipation. it was observed that there was no heat-up in the transformer. also, there was no vibration in the transformer when the supply was fed in. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 634 3.2 shortcircuit test in this test, one winding, usually the low-voltage winding, is solidly short-circuited by a thick conductor (or through an ammeter which may serve the additional purpose of indicating rated load current). a low voltage (usually 5 10% of normal primary voltage) at the correct frequency is applied to the primary and it is cautiously increased till full-load currents are flowing both in the primary and secondary. it was observed that with the normal voltage applied to the primary, normal flux was set up in the core. hence, normal iron losses was recorded. additionally, as the primary no load current was small, the copper losses was negligibly small in the primary and nil in the secondary. 3.3 operational test. the operational test was performed by applying voltage to the components and a multi-meter was used to check the different stages of the passive infrared automatic switching device ensuring that they conform to the given requirement. the range of the passive infrared automatic switching device is then tested by placing the device at a fixed distance in an isolated environment where there is no infrared interference. the maximum distance as well as the angle at which it can detect human presence was determined. it was observed that the device covered an angle of 100° and a distance of 3.8m at the sides, and a distance of 5m in the middle. 3.4 the casing plastic was used as the case of the passive infrared automatic switching device because of its advantages over steel materials. some of these advantages are: openings for ventilation can easily be made. it can withstand corrosion. it is readily available in the market. it can withstand heat, either the heat generated by the system or in the surrounding. the casing of the device is shown in figure 11: figure 11: front and back view of the passive infrared automatic switching device 3.5 causes of equipment failure the system could be affected adversely when it is not used permanently in a particular place (for example, environmental stress; if it is conveyed from one point to the other continuously). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 621-636. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 635 3.6 troubleshooting table 1 gives the troubleshooting procedure for cases of non functionality of the switching device. table 1 troubleshooting procedure signs test point expected results possible fault location/causes remedial power indicator led not lit when system is powered check fuse burnt fuse replace fuse with 13a fuse power indicator on but no power output check the supply voltage voltage should be 220v – 240v low voltage connect to proper voltage(220v – 240v) unstable output check solder joints solder joints should be strong weak solder joints if a weak joint is discovered, it must be resoldered system not coming up check ac supply no ac supply from mains connect to powered mains pir doesn’t detect human presence check if the pir modules are properly connected. bad pir modules or damaged connector wire. replace the pir modules or replace the connector wires. 4.0 conclusions this study considered the design and construction of the passive infrared automatic switching device capable of switching on and off electronic devices not in use. this research presents one of the simple and effective ways of saving energy automatically in a building or organization. the research work guarantees less consumption of power, hence, lower utility bills. also, it allows for more safety in homes, schools, and offices since heavy-duty and high-power equipment that could cause fire e.g. air-conditioning systems, electric cookers, boilers, electric irons etc, if left unattended to, can be turned off automatically. references sadeghi, sa., karava, p., konstantzos, i., tzempelikos, a. 2016. occupant interactions with shading and lighting systems using different control interfaces: a pilot study. building and environment, 97: 177-195. grueneich, dm. 2015. the next level of energy efficiency: the five challenges ahead. the electricity journal, 28(7): 44-56. zhenfeng, l., jingtao, l., xiaofan, l., yijian, y., and bowen, x. 2020. design of office intelligent lighting system based on arduino. procedia computer science, 166: 134-138. moore, td. 2002. user attitudes toward occupant controlled office lighting. lighting research technology, 34(3): 207-219. oyetola, ok., okubanjo, aa.., okandeji, aa.., olaluwoye, oo., alao, po., and ukagu, sn. 2019. internet of things (iot) cloud based model for low cost demand side management infrastructure. arid zone journal of engineering, technology and environment, 15(4): 10821091. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design analysis of a microcontroller based automatic switching system using passive infrared sensor. azojete,16(3):621-636. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 636 theraja, bl., and theraja, ak. 2002. electrical technology, 21st edition. ranjendra ravida, new delhi, india. xiao, s., yong, m., fan, f., huang, j., and minghui, w. 2020. tracking small targets in infrared image sequences under complex environmental conditions. infrared physics and technology, 104: 1-10. electronic component datasheet, www.alldatasheet.com. hc-sr501 body sensor module data sheet. accessed on 01 december, 2019. electronic component datasheet, www.alldatasheet.com. pic16f628a data sheet accessed on 01 december, 2019 https://www.sciencedirect.com/science/article/pii/s1350449519303214 https://www.sciencedirect.com/science/article/pii/s1350449519303214 http://www.azojete.com.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 37-44 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng design, construction and evaluation of an animal drawn disc harrow usman, a.m. 1 , m.a. haque 1 and b. umar 1 abstract animal traction has not been widely adopted by nigerian farmers despite the fact that it is an appropriate technology that can be used to increase agricultural production. one of the reasons for limited use of animal power is the lack of appropriate implements. the objective of this work was, therefore, to design, construct and evaluate a single-acting animal-drawn disc harrow. the harrow consisted of several components fastened together into a unit which could be easily dismantled if necessary. the main parts were the frame; two gangs of four discs each, three pneumatic depth control wheels and a seat for the operator. the total mass of the implement was found to be 100 kg. a pair of well trained bulls weighing 429 kg and 394 kg where used to pull the implement during the experiment. the harrow was designed to operate at various depths and disc angles. the draught measurements and quality of work of the harrow were observed at depths of 5 and 10 cm and disc angles of 15 o , 25 o and 35 o . it was found that the harrow had a draught of 530 n when set at a disc angle of 15 o and depth of 5 cm, and 778 n when set at 35 o and 10 cm depth. it was also found that the harrow had 94.76% weed destruction when set at disc angle of 15 o and depth of 5 cm and 97.90% when set at 35 o disc angle, 10 cm depth of operation. the harrow was found to have an effective field capacity of 0.23 ha/h and field efficiency of 86 %. 1. introduction in nigeria, almost all agricultural operations are carried out manually by peasant farmers who dominate the agricultural sector. the hoe, cutlass and matchet are the dominant tools of cultivation in the country. these tools consume a lot of human energy, thus making their use tedious and tiresome. their use also limits agricultural production. there is, therefore the need to increase the utilization of non-human energy in order to increase the food production to meet the demand of the country. the use of tractors on nigerian farm is very limited due to their high cost which beyond the reach of poor farmers. due to fragmentation of farmlands into small and scattered units, farmers find it uneconomical to engage tractor services.. therefore, if animal traction were to be promoted in the farming system, it would contribute positively to agricultural development in the country. this is because of the low cost of the technology which puts it within the reach of the majority of the farmers. animal traction provides a well-tested and proven option as a substitute for hoe cultivation. it has the potential of permitting the farmer to expand his acreage and improve yields. according to starkey (1992), animal traction is an appropriate, affordable and sustainable technology that can be used to reduce drudgery and intensify agricultural production, so raising living standards throughout rural communities. it is in this regard that animal traction suggests itself as a potentially useful and appropriate means of improving upon the efficiency 1 department of agricultural & environmental resources engineering, university of maiduguri, nigeria design, construction and evaluation of an animal drawn disc harrow 38 of the hoe system in nigeria. however, according to philip et al. (1986), animal traction has not been widely adopted by nigerian farmers despite the fact that it is a farmer-generated and farmer-adopted technology with a successful history of adoption elsewhere. according to kline (1970), broad adoption of animal traction was blocked by equipment inappropriately designed for african condition. kaul (1989) reported that lots of implements have been developed world-wide, which can be adopted in nigeria with appropriate modifications. new innovations may emerge during the development /adoption of such implements. although draught animals are a lot cheaper than tractors, many farmers have restricted access to animal power because of their inability to purchase them. according to mathewman (1987), the main constraint to the use of animal traction is the cost of extra labour required to deal with increased yields and for weeding and harvesting. another factor contributing to lack of increased utilisation of animal traction is the problem of adoption. problems related to training animal husbandry and equipment also limit the rate of adoption of animal traction. according to ibrahim and kwatra (1990), farmers adopt new ideas and tools only after seeing them successfully operating in the field. working ability of a draught animal depends upon many factors including its breed, sex, size, live weight, training, management, feeding and health. heavier animals are able to perform more work than lighter ones,. under a given set of conditions, each animal is capable of carrying out a certain amount of daily work that cannot be exceeded if the animal is to be kept in good working condition. experimental data confirm that working cattle develop maximum power when a relatively low traction effort is made at a relatively high speed (pyne, 1990). the power which a draught animal can provide is dependent upon the pull developed and speed of movement. the pull depends mainly on species and body weight, but is also influenced by condition of health of the animal and training. carruthers and marc (1992) reported that the optimum pull for bovines (ox, cow, buffalo) is about 10 to 12 percent of their body weight. for equines (horse, donkey, mule) and camels the optimum pull is about 12 to 15 percent of their body weight. several researchers still use the concept of 10 percent of body weight as the pulling force of some species. however, girma and pascal (1997) reported that the pulling force required for the implements can be increased up to 25 to 34 percent of body weight, especially for donkeys the only popular animal-drawn implement available to the nigerian farmer is the ridger. the emcot ridger used as a primary tillage implement was developed, and recommended for local manufacture since 1960 (musa,1989). however, because the use of draught animal needs to be diversified to include more farm operations, additional implements such as disc harrows need to be developed. the disc harrow is extremely useful in pulverising soil and chopping weeds and trash. carruthers and marc(1992) stated that animal drawn disc harrow of 400-500 mm diameter spaced at 200 mm apart could be used for secondary cultivation purposes. the maximum operating depth for a disc harrow is usually about one-fourth of the disc diameter. small-diameter disc penetrate more readily than large discs as they require less vertical force to hold them to a given depth (kepner et al., 1978). the operating depth is determined by the soil condition and the weight per unit disc of the harrow. the disc angle varies from 15 o -35 o as measured from a line perpendicular to the line of travel. disc angles may be changed to meet different field conditions. increasing the disc angle makes the disc cuts deeper and more aggressive, but with increased power requirement. (ajit et al., 1993). azojete vol. 4 2004 39 although a lot of work has been conducted on the draught ability of cattle all over the world, there is little information on animal drawn harrows in nigeria. therefore, this work was aimed at producing a simple and affordable animal drawn harrow that could be used locally by farmers. 2. materials and methods 2.1 description of the implement a single-acting disc harrow was designed and constructed to be drawn by a pair of bulls. the total mass of the implement is 100 kg. the harrow (figure 1) consists of several components fastened together into a unit, which could be easily dismantled, if necessary. the main parts are the frame (1), two gangs (2) of four discs (3) each, three depth control wheels (4) and a seat (6) for the operator. the components and sizes of the materials used were selected based on their availability and affordability. the implement was constructed with the desire to have minimum labour input for its operation. two persons are needed to use the implement. 2.2 estimating the weight of the harrow in order to design an implement for animal draught, it is necessary to know or estimate the total weight so that it will not exceed the capability of the animal’s pulling power and to perform the expected work. mckyes (1985) and ajit et al. (1993) reported that the draught force of a standard harrow on a sandy loam soil is: n = 7.8m 1 where n = draught in n m = mass of implement in kg. therefore, mass of implement m = 8.7 n 2 the draught ability of cattle is about 10 to 12 percent of their body weight (patrick and frank, 1995).the designed harrow was pulled by a pair of bulls of an average weight of 12 kn. ten to twelve percent of a pair of bulls weighing 12kn is 1.2kn to 1.44kn. therefore, from equation 2 m= to 8.7 1200 8.7 1440 =154 to185 kg the total weight of implement and the operator should, therefore, be about 1850 n for the animals to pull it successfully. design, construction and evaluation of an animal drawn disc harrow 40 2.3 design of the gang shaft shafts are known to carry members which transmit torque and therefore experience both bending and torsion. it is therefore, important to determine the correct shaft diameter according to the asme code for design of solid shaft to ensure satisfactory strength. the gang shaft is the shaft on which discs are mounted. the following equation was used in determining the shaft diameter (spotts, 1988): d 3 = ss 16 22 )()( ttbb mkmk  3 d = 3 1 22 )()( 16        ttbb s mkmk s 4 where d= diameter of shaft, mm ss=shear stress, n/mm 2 . shear stress is given as 145 8000 n/mm 2 for shaft without key ways (hall et al., 1982). kb, kt = combined shock and fatigue factors applied to the bending and torsional moments given as 1.5 and 1.0 respectively. mt = torsional moment, n mm mb = bending moment, n mm the torsional effect on the shaft becomes negligible if bearings are used (spotts, 1988). this implies that mt = 0. therefore, equation 4 reduces to 3 1 )( 16        bb s mk s d  5 the total vertical and horizontal forces acting on the implement was 2205 n which is transmitted to the shaft through the four legs. each leg transmitted about 51.3 n (figure 2). from the analysis of load distribution on the shaft, it was found that the maximum bending moment, mb was 17917.25 nmm. substituting values in equation 5, the shaft diameter was found to be 14 mm. therefore, the minimum diameter of the shaft to be used was 14 mm. however, for this work, 20 mm universal shaft was used as no shaft between 14 and 20 mm was available in the market. 2.4 construction of the harrow the frame that supports all the components of the implement was constructed from mild steel of 5 mm thickness forming a t-shaped beam. the two gangs consisting of four standard plain discs of 450 mm diameter were mounted in series on a shaft of 20 mm diameter and 420 mm long. spacers of 100 mm were provided between disc blades. the gangs were attached to the frame of the harrow by four legs (9) which carried the bearing housing (figure 1). each leg was constructed from an angle iron of 2.4 mm thickness and 270 mm long. the gangs were attached to the frame in such a way that the angle they make with the line of travel could be varied. two angle-adjusting rods (5) of 10 mm diameter and 500 mm long were used for azojete vol. 4 2004 41 changing the gang angle. the rods were attached to each gang at one end and the other end on to the frame on a common bracket, which could slide forward and backwards along the frame beam depending on the angle desired. holes are provided into which a bolt can be slotted. when the hole on the bracket aligns with the hole on the frame a certain degree of gang angle is obtained. the holes on the frame were drilled to give 15, 25 and 35 o of gang angle. three depth control pneumatic land wheels of 420 mm diameter were provided, two of which were attached at the rear and one at the front. the two rear wheels were mounted to the implement in such a way that they could be lifted up or lowered down depending on what depth to operate the harrow. the disc can be above the ground during transport. an operator’s seat was constructed from a sheet metal of 1 mm thickness and mounted on the frame. all other components of the harrow were also made of mild steel. 2.5 experimental design and performance evaluation a field test of the implement was carried out at the university of maiduguri research farm during the rainy season in july of 2000. the soil is of sandy loam texture classified as typic ustipsamment made up of 77% sand, 6% silt and 17% clay (rayar, 1984). the experimental design was a randomized complete block design for both the draught force evaluation and for the soil work quality assessment with an 18-plot experiment consisting of six treatments with three replicates each. the treatments were: 5cm depth, 15 o disc angle (t1); 5 cm depth, 25 o disc angle (t2); 5 cm depth, 35 o disc angle (t3); 10 cm depth, 15 o disc angle (t4); 10 cm depth, 25 o disc angle (t5) and 10 cm depth, 35 o disc angle (t6). the plot size for each replicate was 20 m x 2 m as suggested by fao (1994). two well-trained bulls weighing 429 kg and 394 kg were used for pulling the harrow. for performance evaluation of the harrow, the following major parameters were considered: (i) weed destruction as described by fao (1994), (ii) implement draught, (iii) implement field capacity and efficiency. the implement draught was calculated using equation 6 (patrick and frank, 1995). h = f cos  6 where h = draught, n f = force of pull, n  = angle of pull with the horizontal. field efficiency of the implement was determined using equation 7 (fao, 1994)  = %100 t e c c 7 where  = field efficiency of the implements % ce = effective field capacity, ha/h ct = theoretical field capacity, ha/h effective field capacity, ce =  htimefieldtotal hacultivatedareatotal )( , and theoretical field capacity ct = mean working width (cm) x mean speed (m/s) x 0.0036. 8 design, construction and evaluation of an animal drawn disc harrow 42 3. result and discussion 3.1 effect of disc harrowing on weed destruction the average number of weeds and stubble counted per square meter of the experimental field before treatment was 1031. the number of weeds and stubble counted for each treatment after harrowing is presented in table 1. for the same disc angle, the number of weeds left after operation was higher in the 5-cm depth treatments than those in the 10-cm depth treatments. this may be because the implement operated at a shallower depth and therefore was not able to destroy a high percentage of weeds. at the same depth level, it was found that the number of weeds left after treatment reduced as the disc angle increased. this is probably as a result of the aggressiveness with which the disc worked on the soil. statistical analysis revealed that there was a significant (p<0.01) difference between the treatments as regard to number of weeds. table 1: values of various parameters studied during the evaluation of the implement a, b, c, d, e: means in the same column followed by same letter are not significantly different at 5%. table 1 shows the percentage weed destruction by the implement in each treatment. the average values were 94.76%, 96.96%, 97.57%, 95.31%, 97.05% and 97.90% for t1, t2, t3, t4, t5 and t6 respectively. the value was highest in t6 and lowest in t1. comparing percentage weed destruction at different depths, it can be seen that the high values were obtained in 10 cm depth treatment than in 5 cm depth treatment. this may be as a result of soil inversion achieved by the discs. 3.2 effect of dept and angle of cut on implement draught the draught values in each treatment are also presented in table 1. the values did not exceed 10 percent of total body weight of the animals used and they reasonably agree with the average value of 490-785 n as stated by hopfen (1969). at 5 cm depth, the draught was lowest in treatment t1 and increased as the disc angle increased. similarly, at 10 cm depth the draught was lowest in treatment t4 and increased as the disc angle increased. it was also observed that for the same disc angle the draught values were higher at 10 cm depth than those recorded at 5 cm depth. the increase in draught with increase in disc angle and depth of operation may be attributed to the fact that the discs scooped greater volume of soil at higher disc angle and depth. treatment number of weeds after operation, m 2 weed destruction, % draught, n t1 (5cm,15 o ) 54 a 94.76 d 530 b t2 (5cm,25 o ) 31 b 96.96 abc 641 a t3 (5cm,35 o ) 25 b 97.57 ab 660 c t4 (10cm,15 o ) 48 a 95.31 d 641 a t5 (10cm,25 o ) 30 b 97.05 abc 700 d t6 (10cm,35 o ) 22 b 97.90 a 778 e se ±4.68 ±0.46 ±1.51 azojete vol. 4 2004 43 3.3 field capacities and efficiency of the implement the time taken to cultivate an area of 360 m 2 was 94 minutes. the effective and theoretical field capacities were 0.23 ha/h and 0.28 ha/h. the field efficiency was 86%. 4. conclusion and recommendations 4.1 conclusion an animal-drawn disc harrow was designed and constructed to operate at various depths and disc angles. materials that are readily available were used in its construction. the implement was found to have total weight of 100 kg with a working width of 0.9 m. it was found that the implement had a minimum draught of 530 n when set at 15 o disc angle and 5 cm depth, and a maximum draught of 778 n when set at 35 o disc angle and 10 cm depth. at both depths of 5 and 10 cm, the quality of work, in terms of percentage weed destruction, was best when the implement was operated at a disc angle of 35 o . the average theoretical and effective field capacities of the implement were 0.27 ha/h and 0.23 ha/h respectively. the field efficiency of the implement was found to be 86%. 4.2 recommendations based on the result obtained from the field test, the following recommendations are made to improve the working efficiency and strength of the implement: 1) it is recommended that the implement should be set at 10 cm depth and 35 o disc angle for heavy animals (500-900 kg), because of higher draught. for light animals (350 450 kg), the implement should be set at 10 cm depth and 25 o disc angle. 2) provision should be made to vary the number of discs used to accommodate the variation in the type and size of animals used. 3) a shield should be constructed in front of the discs for the safety of the operator. 4) the implement was tested only on a sandy loam soil. therefore, it is recommended that it should be tested on other soils. references ajit, k.s., e.g. cawoll and r. roger (1993). engineering principles of agricultural machines. american society of agricultural engineers. st. joseph, michigan, u.s.a. carruthers, i. and r. marc (1992). tools for agriculture. intermediate technology publication ltd., southampton, london. fao (1994). testing and evaluation of agricultural machinery and equipment principles and practices. fao agricultural service bulletin 110, rome. girma, g. and g.k. pascal (1997). comparative analysis of the field performances of a reversible animal drawn prototype and conventional mouldboard plough pulled by a single donkey. soil and tillage research 40:168-183 hall, s.a., r.n. alfred, and g.l. kerman (1982). theory and problems of machine design. shaums outline series, mcgraw-hill book company, new york. hopfen, h.j. (1969). farm implement for arid and tropical regions, in: anonymous, (1983). domestication, conversation and use of animal resources, world animal science, elsevier, amsterdam. design, construction and evaluation of an animal drawn disc harrow 44 ibrahim, j. and a.o. kwatra (1990). use of animal-drawn implement and equipment by small scale farmers in bauchi state, nigeria. research for development of animal traction in west africa. proceedings of the fourth workshop of the west africa animal traction network, kano, nigeria 9-13 july, 1990. ilca addis ababa, ethiopia. kaul. r.n. (1989). animal powered equipment: factors affecting their design. in: h.k., hassan (1998). establishment and performance evaluation of neazdp animal traction programme unpublished ph.d thesis, abu, zaria. kepner, r.a., r. bainer and e.l. berger (1978). principles of farm machinery. 3rd edition avi publishing company, westport, connecticut, usa. kline, c.d. (1970). agricultural mechanisation in equatorial africa. michigan. mathewman, r.w. (1987). draught animal and the role and future potential of draught cows in african farming systems. draught animal news 8:23-26. mckyes, e. (1985). soil cutting and tillage. elsevier, amsterdam. musa, h.l. (1989). development and use of animal-drawn implements in nigeria. proceedings of the 1 st national workshop on animal traction in nigeria, zaria. partick, k. and i. frank (1995). effect of angle of pull on the draught of a chain pulled swing plough. draught animal news no. 22, university of edinburgh, scotland. payne, w.j.a. (1990). an introduction to animal husbandry in the tropics, fourth edition, longman scientific and technology, england. phillip, d.o.a., g.o.i. abalu and s.a. ingawa (1986). economic implications of animal power at the small scale level in the savannah zone of northern nigeria: a linear programming simulation of farmer circumstances. animal power in farming system. proceedings of the second west africa animal traction. september 19-25, freetown. rayar, a.j. (1984). university of maiduguri farm development planning report for faculty of agriculture. annex a; soil survey details (unpublished). spotts, m.f. (1988). design of machine elements, 6th edition – prentice-hall of indica private ltd., new delhi. starkey, p. (1992). a world wide view of animal traction highlighting some key issues in eastern and southern africa. improving animal traction technology. proceedings of the first workshop of the animal traction (atnesa) held at lusaka, zambia. 18-23, january. arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):403-414 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 403 original research article analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria s. u. muhammad1*, w. c. solomon1, d. b. yahaya2, and j. s. enaburekhan2 1department of mechanical engineering, nigerian defence academy, kaduna state, nigeria 2department of mechanical engineering, bayero university, kano state, nigeria *corresponding author’s email address: sumuhammed@nda.edu.ng 1.0 introduction solar radiation measurements and or estimations from models that employed meteorological parameters, under clear skies (or cloudless skies), for the purpose of designing solar equipment for optimal performance, with the view of establishing the viability of solar components in nigeria solar energy is one of the key renewable energies available (oyepedo, 2012). but in nigeria, the major source of energy comes from fossil fuels (ogunsola, 1990). the use of these fuels, however, leads to the generation of environment problems such as air pollution, greenhouse gases (gcgs), and aerosol production (marif et al., 2018). the presence of these aerosol particles in the atmosphere could be as a result of natural phenomenon (e.g. dust or storm). in addition to this aerosol, the atmosphere consists of other gases, which remain constant while the water moisture content varies with season. hence, as radiant energy passes through the atmosphere, it comes in contact with these components, which tend to reduce the intensity of the radiant heat, from the sun through scattering or absorption (marif et. al., 2017). therefore, atmospheric turbidity could be described as the main parameter controlling the attenuation of solar radiation reaching the earth’s surface under clear sky conditions, which equally serves as a tool for assessing air pollution of any particular area. continues alteration of article information abstract this study evaluates the seasonal turbidity index of two vegetation zones in nigerian which are sudan and fresh water swamp. thirty years (1981 – 2010) meteorological data of temperature, relative humidity and solar radiation were obtained from the archives of the nigerian meteorological agency (nimet). annual and monthly analysis of the turbidity coefficients were mainly based on the linke and angstrom methods, due to absence of radiosonde data. the results show that the monthly mean values of the clear-sky global radiation lies between 19.34 mj/m2day to 24.44 mj/m2day (for sudan vegetation) and 15.54 mj/m2day to 20.28 mj/m2day (fresh water swamp). meanwhile, the monthly percentages of clearness index above 0.6 were estimated as 75% and 33.3, and for the water vapour content exceeding 3 cm to be 58.3% and 100%, for the sudan and fresh swamp vegetation, respectively. these values contribute significantly to the reduction of direct radiant energy. the results obtained for the seasonal index for linke and angstrom coefficients show that for the wet season, the index exceeded the dry value by 25.99% and 23.66% for sudan and fresh swamp vegetation, respectively. by implication, the fresh water swamp is laden with more aerosols than sudan zone. additionally, the r2 obtained for the relationship between angstrom and linke is 0.999 for both locations. hence, the study provides an insight into the contribution of aerosol in the attenuation of solar radiation over the atmosphere for these locations. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 february, 2021 revised 8 june, 2021 accepted 12 june , 2021 keywords: linke turbidity angstrom turbidity meteorological data sudan vegetation fresh water swamp vegetation muhammad et al.: analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria. azojete, 17(3):403-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 404 atmosphere due to human activities causes an increase in aerosol concentration level which has a significant impact on the environment and radiant energy at the earth’s surface. although, turbidity can be obtained directly from observation performed during clear sky periods, few stations are available in africa, such as nigeria, where turbidity is measured as highlighted (diabte et al., 2003; oba et al., 2016). hence, the study of atmospheric turbidity is important in estimating the actual solar irradiance on the earth’s surface. it has become important parameter, especially, in the area of evaluation solar energy appliances and also for the determination of the amount of spectral global irradiance for the photovoltaic cells designing and for the selective absorber for spectral thermal collectors. in the present study sokoto and kano were used as sampling stations to represent sudan vegetation, while portharcourt to represent fresh water swamp vegetation, to estimate the seasonal variation in turbidity. several literatures on measurement and estimation of turbidity exist (canada et al., 1992; cucumo et al., 2000; hemdy et al., 2001; power, 2001; lopez et al., 2004; oba et al., 2016; ambaye et al., 2018). however, two major indices of turbidity are the linke turbidity factor (tl), and the angstrom turbidity coefficient (β). both are used to quantify the influence of atmospheric aerosols on direct solar radiation on earth’s surface. the objectives of this article are to report data on aerosol optical depth and atmospheric turbidity coefficients with the view to investigating the seasonal variation in turbidity as a result of changes in the atmospheric meteorological parameters for the two different vegetation zones in nigeria, which are on sudan (short grass savannah) and fresh water swamp vegetations. 2 materials and methods 2.1 study area federal republic of nigeria lies in the western part of africa. it consists of seven major vegetation zones as shown in figure 1. the stations selected from the sudan vegetation zone are sokoto and kano while station selected from the fresh water vegetation zone is portharcourt, for the current study. the details of each station are presented in table 1 figure 1: vegetation map of nigeria (f.g.n. 2002) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):403-414. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 405 table 1: geographical locations of selected areas station longitude (on) latitude (oe) height (m.a.s.l) year kano 8.53 12.05 714 1982 – 2010 sokoto 5.25 13.02 350.75 1982 – 2010 port-harcourt 7.02 4.85 195.51 1982 – 2010 the sudan vegetations are semi-desert, with minimal rainfall, supports a mixture of grasses and acacia scrub while fresh water swamps vegetations zones are usually endemic where the most significant part of forests occur. hence, the two vegetation zones are located areas characterized by different weather conditions as indicated in figure 1. therefore, the data used in this study were obtained from nigerian meteorological agency (nimet), from 1981 to 2010. daily record of weather parameters used includes temperature, solar radiation and relative humidity. the daily weather parameters were converted into mean monthly values. 2.2 theory linke’s turbidity factor, tl, is an index of the number of clear dry atmosphere that would be necessary to produce attenuation of the extraterrestrial radiation that is produced by the real atmosphere. in this study, the linke turbidity was estimated using the empirical equation proposed by dogniaux (dogniaux, 1974). the estimation involves using inputs of solar elevation (α) (in degrees), precipitable water ω (in cm), and angstrom’s turbidity β. the empirical relationship between linke and angstrom is expressed as: ( ) ( ) (1) however, the linke turbidity factor is related to measures of direct irradiance, id, by means of the following equation as: ( ) (2) where: δr is the rayleigh optical thickness, α is the altitude angle (degree), ω precipitable water content in the atmosphere (cm), β is angstrom’s turbidity, tl linke turbidity factor, ma is relative optical air mass, io is the extraterrestrial normal irradiance (w/m2), ib is the beam radiation (w/m2). however, details on the analysis of solar radiation components for the specific locations were documented elsewhere (muhammad et al., 2016). however, the clear-sky global radiation, hf (mj/m2day) at the surface was estimated using the model proposed by kondo, nakamura and yamazaki (kondo et al., 1991). ( )( )( ) (3) where ho is the monthly mean global solar radiation at the top of the atmosphere ( ) (3a) muhammad et al.: analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria. azojete, 17(3):403-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 406 ( ) (3b) (3c) ( ) ( ) ( ⁄ ) (3d) ( ⁄ ) (3e) ( ) [ ( ) ] (3f) ( ) (3f) ( ) (3h) * ( ) + ( ) (3i) md = daily – mean path length (dimensionless) ref = albedo (dimensionless) i3 = julian day for the linke turbidity factor, the determination of δr is based on improved kasten formula for rayleigh optical thickness (kasten, 1996), which actually depends only on the relative air mass values. the expression of δr is defined by the expression: (4) or (5) however, the relative optical air mass at standard condition (kasten, 1996), dependent on the corrected solar altitude and the correction for a given elevation (height above sea level) in a relation expressed (lopez et al., 2004) and (becker, 2001), respectively. ( ) (6) (7) ( ( )) (8) where αc altitude angle tair is air temperature in degree celsius po is the surface air pressure (1023.25hpa) details of analysis and the results of precipitable water content have been documented elsewhere (muhammad et al., 2016b). 3 results and discussion the monthly and annual mean values of the estimated parameters are presented in tables 2 and 3. the monthly mean global solar radiation at the top of the atmosphere (ho) varies from 31.06 to 41.68 (mj/m2day) and 34.91 to 40.4 (mj/m2day) for sudan and fresh water swamp zones, while annual mean values of 37.874 (mj/m2day) and 38 544 (mj/m2day), respectively. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):403-414. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 407 however, the estimated annual mean values for the sky-clear global radiation at the surface of the earth were found to be 21.776 and 18.136 for sudan and fresh water swamp zones, respectively. table 2: sudan vegetation zone month ho hf kt hb ω ma δr (mj/m2day) (mj/m2day) (%) (cm) january 31.97 21.3 0.664 0.75 1.32 6.685 0.069 february 35.34 23.45 0.664 0.75 1.49 5.659 0.073 march 38.64 24.69 0.636 0.73 1.61 4.723 0.078 april 40.97 24.44 0.61 0.71 3.05 4.164 0.082 may 41.66 22.58 0.536 0.66 4.3 4.257 0.081 june 41.65 21.26 0.526 0.65 4.61 4.512 0.08 july 41.68 19.65 0.477 0.61 4.74 4.501 0.08 august 41.45 19.34 0.466 0.6 4.8 4.237 0.081 september 39.95 20.28 0.499 0.63 4.7 4.516 0.08 october 36.92 21.69 0.594 0.7 3.42 5.162 0.076 november 33.2 21.96 0.658 0.75 1.79 6.158 0.071 december 31.06 20.67 0.656 0.75 1.75 6.903 0.068 mean value 37.874 21.776 0.582 0.691 3.132 5.123 0.077 table 3: fresh water swamp vegetation zone month ho hf kt hb ω ma δr (mj/m2day) (mj/m2day) (%) (cm) january 35.590 20.120 0.567 0.680 4.720 2.713 0.094 february 37.930 21.030 0.556 0.670 5.280 2.381 0.098 march 39.800 20.280 0.507 0.630 5.710 2.093 0.102 april 40.400 19.330 0.482 0.610 5.790 2.040 0.103 may 39.730 18.300 0.464 0.600 5.710 2.253 0.100 june 39.030 16.620 0.429 0.560 5.480 2.412 0.098 july 39.310 15.540 0.377 0.510 5.300 2.375 0.098 august 40.170 15.580 0.380 0.510 5.220 2.186 0.101 september 40.290 16.680 0.416 0.550 5.370 2.014 0.103 october 38.900 17.340 0.448 0.580 5.430 2.253 0.100 november 36.470 17.880 0.492 0.620 5.500 2.577 0.096 december 34.910 18.930 0.549 0.670 5.030 2.796 0.093 mean value 38.544 18.136 0.472 0.599 5.378 2.341 0.099 therefore, it may be inferred from the results above that solar radiation availability is a function of region, season and day of the year i. e., the day-to-day variability of extraterrestrial radiation could be attributed to cloud effects and the distance between the sun and the location. in essence, locations that are located at the upper level of the northern hemisphere tend to have more radiation at the top than those at the bottom. this implies that the rainy season corresponds to period of high radiation at the top of the atmosphere. muhammad et al.: analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria. azojete, 17(3):403-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 408 from the analysis of the diffuse and clearness index carried out, it is very clear that the contribution of fraction of diffuse component of solar radiation is very low throughout the year with the exception of the monsoon period (peak of rainy season) i.e. from the months of may to september for sudan vegetation and may to october for fresh water swamp vegetation zones. it could be inferred from the results that visibility of the atmosphere is a function of the amount of beam radiant energy received for a given location. the higher the beam radiation the more the clearness index. hence, the variability of the clearness index is dependent on the season of the year. clearly, the atmosphere above fresh water swamp vegetation zone is laden with high moist content couple with industrial activities. this signifies low clearness index, whereas the sudan vegetation zone indicates high clearness index in all season. the water vapour content in the atmosphere also plays a vital role in the attenuation of the incoming radiant energy. high content of water vapour was observed to occur in the fresh water swamp zone, with low percentage recorded in the sudan zone. this could be attributed to the fact that the location of the former zone is prune to high moisture content than the latter (sudan). this parameter contributes significantly in the absorption of the incoming radiant energy, before it arrives at the earth surface. that is why, sudan zone recorded high beam radiation than the fresh water swamp. the seasonal values of linke turbidity factor (tl) and angstrom coefficient (β) were all presented in tables 4 and 5, respectively. it is clear that sudan vegetations have low tl and β values in comparison with fresh water swamp zone. this could be as a result of the latter being at lower altitude than the former. the tl values for the different vegetation zones offer a wide range of values (2.77 to 8.004) and exhibits the same dynamics (the same trend): the values increased from january to august and decreased from september to december, with maximum attained values in august. these variations may also equally be related to the local climates. table 4: seasonal index factor for wet season (april-september) months linke turbidity (tl) angstrom coefficient (β) sudan vegetation fresh water swamp vegetation sudan vegetation fresh water swamp vegetation april 3.862 7.117 0.120 0.301 may 4.083 6.817 0.129 0.284 june 3.983 6.927 0.122 0.291 july 4.257 7.799 0.138 0.342 august 4.519 8.193 0.153 0.365 september 4.128 8.004 0.130 0.354 average 4.139 7.476 0.132 0.323 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):403-414. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 409 table 5: seasonal index factor for dry season (october-march) months linke turbidity (tl) angstrom coefficient (β) sudan vegetation fresh water swamp vegetation sudan vegetation fresh water swamp vegetation october 3.428 7.016 0.093 0.296 november 2.911 6.032 0.075 0.239 december 2.736 5.335 0.067 0.200 january 2.777 5.347 0.073 0.203 february 3.059 5.895 0.089 0.232 march 3.467 6.767 0.108 0.281 average 3.063 6.065 0.084 0.242 from november to february, the sudan zone, experience full dry/cool season laden with harmattan dust, hot/dry season from march to may, and rainy season from june to september which constitute high volume of water moisture. whereas the fresh water swamp vegetation zones comprise of warm moist air from atlantic ocean with high volume of pollution from traffic and industries (mostly loaded with petrochemical companies) during the wet season. likewise, the angstrom turbidity (β) values exhibit the same evolutions in tl, with values increasing from january to august and while experiences a decrease from september to december. the high values are equally due to higher average precipitable water in the air hence, from the month of may to october, fresh water swamp tends to have the most polluted atmosphere whereas sudan zone possess a combination of clear/warm air and moist/warm air. therefore, from the foregoing, fresh water swamp vegetation zones are more turbid (polluted) then followed by sudan vegetation. in addition, from table 4, the seasonal index factor for wet season falls averagely between 4.139 and 7.479 for sudan and fresh water swamp zones which could be classified as moist/warm air and polluted atmosphere, respectively. on the other hand, from table 5, the seasonal index for dry values 3.06 (for sudan) and 6.065 (fresh water swamp) could be classified as clear/warm air and moist/warm (or polluted) air, respectively (scharmer and grief. 2000). hence, it could be inferred, from above, that the tl index of the number of clear dry that gave rise to attenuation of the extraterrestrial radiation atmosphere, for both seasons, was highest for fresh water swamp zone than the susan zone. therefore, the fresh water swamp zone has the tendency to produce more extinction than the sudan zone, as a result of presence of more water content in the atmosphere. also, the tl indexes are generally affected by the atmospheric water content, since considerable percentage of aerosol particle in the atmosphere are hygroscopic in nature. as such, some of the aerosol particles, present in the atmosphere have tendency to absorb moisture which results in the variation/change in shape of the particle. hence, the linke turbidity index could be adopted as a reasonable quantity to measure he turbidity of a local environment. moreover, the angstrom coefficient, which is dimensionless, varies between 0.00 and 0.5 for an atmosphere that is completely cleaned and that with a very high aerosol amounts, muhammad et al.: analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria. azojete, 17(3):403-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 410 respectively (hemdy et al., 2001). the analysis of the values for the sudan zone showed that about 41.67% of the angstrom coefficient range between 0.02 and 0.1, 50% are between 0.1 and 0.2 and 8.33% exceed 0.15. while for the fresh water swamp zone, about 66.67% of the angstrom coefficient ranged between 0.2 and 0.3 and 33.33% exceed 0.3. in terms of wet seasonal variation, in the sudan zone, about 83.33% of the angstrom coefficient ranged between 0.1 and 0.15 and 16.67% exceed 0.15. on the other hand, in fresh water swamp zone, about 66.67% of the values are less than 0.3 and 33.33% are greater than 0.3. in the other hand, in the dry season, results showed that in the sudan zone, about 83.33% of the values of the angstrom coefficient are ranged between 0.02 and 0.1 and 16.67% exceed 0.1, while for fresh swamp water zone, about 66.67% of the values ranged between 0 and 0.25 and 33.33% are greater than 025. tables 4and 5 shows the results of the seasonal index factor for wet and dry seasons. the linke turbidity values for fresh water swamp vegetation recorded significant amount for both the dry and wet season. this could be associated with the high moisture content and pollutant originating from petroleum exploration and refining activities, in the atmosphere. whereas the sudan vegetation zone recorded lower values, except for the months of may to september which correspond with the rainy season in the zone. the climate in the fresh water swamp vegetation zone could be describes as hot/or moist in the dry season while in the wet season as hot/or cool. hence, in wet season, fresh water swamp tends to be the most polluted atmosphere, whereas sudan vegetation possessed combination of clear/warm air and moist/warm air. in dry season, the average values are less than those obtained in summer. 3.1 relationship between linke factor and angstrom coefficient the plot of computed daily average values for linke turbidity factor and angstrom coefficient for the sudan and fresh water swamp vegetation zones, presented in figure 2 and 3, show a linear relationship. using a linear regression technique, correlation coefficients of 0.975 and 0.999 were found to exist between the two turbidity factors for sudan and fresh water swamp, respectively. for sudan vegetation zone: β = 0.045tl 0.054 (9) fresh water swamp vegetation zone: β = 0.057tl 0.106 (10) equations 12 and 13 indicate that the linear regression model fitted to β and tl for sudan fresh water swamp, are similar to the model reported (katz et al., 1982 and eliminir et al., 2001). however, the coefficients of the two models are different from those evaluated elsewhere. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):403-414. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 411 figure 2: plots of β versus tl sudan figure 3: plot of β versus tl fresh water swamp 3.2 relationship between angstrom coefficient and precipitable water content the results of the analysis of precipitable water content and angstrom turbidity coefficient are presented in figures 4 and 5. for sudan vegetation zones, from may to november the precipitable water content is higher than the turbidity content of the atmosphere. this is as a result of the fact that, the period represents a combination of seasons with dry/warm air and dry/moist air which is a reflection of high clear index. hence, graph of sudan vegetation, turbidity fluctuates with higher values at the beginning of the year, then decreased from the months of april to october and then increased again until the end of the year. therefore, for sudan vegetation where relative humidity and turbidity are low, as solar altitude increased, the increased global solar radiation caused evaporation from soil and rivers which in turn increased precipitable water and forms liquid particles in the atmosphere which contribute to increased turbidity. the graphs of figure 5 show the results of precipitable water content and turbidity for fresh water swamp vegetation zones. the graphs show that as precipitable water is higher than turbidity contents with the exception of the months of june, july, august, september and october. the months which corresponds with high turbidity content, represent the peak of 0.050 0.070 0.090 0.110 0.130 0.150 0.170 2.500 3.000 3.500 4.000 4.500 5.000a n g st ro m t u rb id it y c o ef fi ci en t ( β ) linked turbidity factor (tl) 0.120 0.170 0.220 0.270 0.320 0.370 0.420 5.000 6.000 7.000 8.000 9.000 10.000 a n g st ro m t u rb id it y c o ef fi ci en t ( β ) linked turbidity factor (tl) muhammad et al.: analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria. azojete, 17(3):403-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 412 rainy season for the vegetation. therefore, the presence of excess water vapour with the warm moist air from the atlantic ocean account for the high turbidity in these months. also, from the analysis, it could be inferred that, peak rainy season is always accompanied by the presence of high moisture content in the atmosphere and hence, an increase in turbidity factor. figure 4: monthly mean values of turbidity and precipitable water content for sudan vegetation figure 5: monthly mean values of turbidity and precipitable water content for fresh water swamp vegetation 3.3 relationship between angstrom coefficient and precipitable water figures 6 and 7 show the scatter plot of turbidity and precipitable water and the results indicate a linear increase in turbidity with increase in precipitable water content. using a linear regression technique, models for the computation of β had been developed for the zones with correlation coefficient ranging between 0.160 – 0.750 for fresh water swamp and sudan vegetation zones, respectively. hence, 75% and 16% of turbidity can be accounted for in the sudan and fresh water swamp vegetation respectively, with respect to known precipitable water content. however, this implies that the statistical relationship between the variables, for fresh water swamp zone, is very weak. it means that only 16% of turbidity can be accounted for using precipitable water content, for this particular zone. for sudan vegetation zone: β = 0.016ω + 0.055 (11) for fresh water swamp vegetation zone: β = 0.069ω 0.110 (12) 0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160 0.180 0.000 1.000 2.000 3.000 4.000 5.000 6.000 0 5 10 15 tu rb id it y ( β ) p re ci p it ab le w at er , ω l (c m ) months precipitable water 0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0 1 2 3 4 5 6 7 0 5 10 15 tu rb id it y ( β ) p re ci p it ab le w at er , ω l (c m ) months precipitable water turbidity β = 0.016ωl + 0.055 r² = 0.750 0.065 0.085 0.105 0.125 0.145 0.165 1.00 2.00 3.00 4.00 5.00 6.00 tu rb id it y ( β ) precipitable water, ωl (cm) figure 6: results of turbidity against precipoitable water for sudan vegetation arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):403-414. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 413 4.0 conclusion atmospheric turbidity is often expressed in terms of linke (tl) and angstrom factors (β). in the absence of measured data, the parameters were evaluated based on meteorological data set for two vegetation zones in nigeria. the results obtained and the statistical evaluation of the data set collected and presented above provide information on the turbidity content in sudan and fresh water swamp vegetation zones of nigeria. thus, the values obtained for the turbidity across the different vegetation zones characterize severe pollution in fresh water swamp than sudan vegetation zone. hence, the obtained values of turbidity and the regression models will serve as reference point in estimating the behaviour of turbidity parameter within the vegetation zones. the variation in the monthly average values of tl and β at the two zones show similar trend to those in the literature. references ambaye, c. 2018 determination of linke’s turbibdity factor from model and measure solar radiation in the tropics over highland of south – east ethiopia. journal of earth science and climate change, 9(7): 479-483 becker, s. 2001. calculation of direct solar diffuse radiation in israel. international journal climatology, 21 (12): 1561-1576. canada, j. pinazo, jm. and bosca, jv. 1992. determination of angstrom’s turbidity coefficient at valencia. renewable energy, 3 (6-7): 621-626. cucumo, m. kaliakatsos, d. and marinelli, v. 2000. a calculation method for the estimation of the linke turbidity factor. renewable energy, 19 (1-2): 249-258. diabate, l., remund, j. and wald, l. 2003. linke turbidity factors for several sites in africa. solar energy, 75 (2): 111-119 dogniaux, r. 1974. representation analytique des composantes du rayonnment solaire. institute de royal de meteorologie de belgique, serie a 83: 3-24 0.220 0.270 0.320 0.370 0.420 4.9 5.1 5.3 5.5 5.7 5.9 6.1 6.3 tu rb id it y ( β ) precipitable water, ωl (cm) figure 7: results of turbidity against precipoitable water for fresh water swamp vegetation muhammad et al.: analysis of the seasonal variation in turbidity index in sudan and fresh water swamp vegetation zones, nigeria. azojete, 17(3):403-414. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sumuhammed@nda.edu.ng 414 eliminir, hk. rahama, ua. and benda, v. 2001. comparison between atmospheric turbidity coefficients of desert and temperate climates. acta polytechnica, 41 (2): 48-59. fgn. 2002. atlas of nigeria. federal government of nigeria hamdy, ke. rahum, ua. and benda. v. (2001). comparison between atmospheric turbidity coefficients of desert and temperate climate. acta polytchnica, 41: 48 59 lopez, g. and batilles, fj. 2004. estimate of the atmospheric turbidity from three broad-band solar radiation algorithms: a comparative study. annales geophysicae, 22: 2657-2668. kasten, f. 1996. linke turbidity based on improved values of the integral rayleigh optical thickness. solar energy, 56: 239-244 katz, m. baille, a. and mermier, m. 1982. atmospheric turbidity in a semi –rural site – i: evaluation and comparison of different atmospheric turbidity coefficients. solar energy, 28(4): 323-327 kondo, j. nakamura, t. and yamazaki. 1991. estimation of the solar and downward atmospheric radiation. tenki, 38: 4148 marif, y. bechki, d. zerrouk, m., belhadj, mm. bouguettaia, h. and benmoussa. h. 2017. estimation of atmospheric turbidity over adrar city in algeria. journal of king of saud university, 17: 1317 1333 marif, y. chiba, y. bilhadj, mm. zerrouki, m. and benhammou, m. 2018. a clear sky irradiation assessment using a modified algerian solar atlas model in aldrar city. energy reports, 4: 84 90 muhammad, su. yahaya, db. and enaburekhan, js. 2016. estimating atmospheric precipitable water from common variables. international journal of engineering research and technology, 5(2): 801-803. muhammad, su. yahaya, db. and enaburekhan, js. 2016. estimation of mean monthly solar radiation and clearness index. international journal of engineering technology and technology, 34 (1): 35-38 oba, md. chendo, mac. and erusinfe, ne. 2016. estimation of angstrom turbidity coefficient over akoka. nigerian journal of solar energy, 27: 34-39 ogunsola, oi. 1990. history of energy sources and their utilization in nigeria. energy sources, 12(12): 181 – 198 osueke, co. and ezugwu, cak. 2011. study of nigerian energy resources and its consumption. international journal of scientific and engineering research, 2(12): 1 – 8 power, hc. 2001. estimating atmospheric turbidity from climate data. atmos. env., 35(1): 125-134. scharmer, k. and grief, j. 2000. european solar radiation atlas (esra). les presses de l ecole des mines de paris, france arid zone journal of engineering, technology & environment azojete march 2020. vol. 16(1):193-210 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 193 original research article organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria j. j. musa1*, j. d. bala2, h. i. mustapha1, e. t. musa3, m. p. akos1, y. i. yerima1 and e. s. daniel1 (1department of agricultural and bioresources engineering, federal university of technology, p. m. b. 65, minna, niger state, nigeria. 2department of microbiology, school of life sciences, federal university of technology, p.m.b 65, minna, niger state, nigeria. 3central research laboratory, university of ilorin, p m b 1515, ilorin, nigeria) *corresponding author’s email address: johnmusa@futminna.edu.ng 1.0 introduction industrialisation and population growth have changed the composition and quantity of waste generated in the society. this has led to the rapid increase in open and hazardous dumpsites in urban and suburban areas in nigeria. most human activities create waste, and the process in which this is taken care of can posture danger to nature and general wellbeing (adedosu et al., 2013). most products from various section of life ends up at dumpsites and because of the heterogeneity and intricacy of these wastes, these dumpsites contain an assortment of article information abstract this research was conducted to assess the presence of some heavy metals chromium (cr), iron (fe), copper (cu), manganese (mn), lead (pb), zinc (zn) and aluminum (al) in municipal solid waste dumps. heavy metals in the soils were determined at varying depths of 0-5cm, 5-15cm and 15-30cm to assess the extent of pollution and the effects of ph and organic matter in the soil. heavy metals concentrations were analysed using atomic absorption spectrophotometer. the results revealed a significant difference (p < 0.05) in the concentrations of heavy metals across varying depth at the dumpsites when compared with control points in the same location. mn had the highest mean 131.22 ± 25.98 mgkg-1 followed by fe, which is 69 ± 11.02 mgkg-1 at the dumpsites. mean concentration of all the heavy metals investigated at the various dumpsites studied were significantly higher than at the control point and below the maximum standard levels set by fao and who for agricultural soils. result of particle distribution indicated higher sand content (> 80.0%) and lower clay and silt contents in both dumpsite and control site which implies the ease of movement of dissolved metals in the soil environment. organic matter (om) content at dumpsites was observed to be slightly higher than at the control sites. the data also signifies that as ph decreases and %om decreases the concentration of these heavy metals decreases down the soil profile. it is, therefore, concluded that accumulation of heavy metals in depth was highly correlated with ph and organic matter content. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 february, 2019 revised 28 august, 2019 accepted 05 september, 2019 keywords: dumpsites leachates metals organic matter soil. mailto:johnmusa@futminna.edu.ng http://www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 194 contaminants which can contaminate the soil of the area (kumar et al., 2002). dumping of waste without legitimate sorting may result in builds up of heavymetals, for example, arsenic (as), cadmium (cd), chromium (cr), copper (cu), lead (pb), mercury (hg) and zinc (zn). these overwhelming metals, when found in solid waste, have been known to deliver significant ecological effects (suman et al., 2011; ebong et al., 2007). the dissolved metals move towards groundwater which in most cases are supplied for domestic and agricultural use thus finding their way into the food chain and influencing human wellbeing (dosumu et al., 2003). open dumping of municipal solid waste practised by developing countries around the world including nigeria in most cases is the primary cause of environmental degradation and has raised public health concerns. these dumpsites may contain unclassified waste and poisonous or radioactive materials that can be hazardous to the environment (uwakwe, 2012). he further stated that malodour radiating from the waste dumpsite has a disturbing effect on the environment and general wellbeing of the populace. leachate from open dumpsites contaminates the soil with heavy metals (duruibe et al., 2007; amadi et al., 2010). cancer, heart diseases and teratogenic abnormalities are attributed to groundwater pollution via leachate from the waste dumpsites (lenntech et al., 2004; duruibe et al., 2007; kumar et al., 2002). mobility, availability, and distribution of heavy metals is controlled by adsorption and desorption qualities of soils (aboyade, 2004). the adsorption and desorption of substantial metals have been shown to be related to soil properties, including ph, organic matter content, cation exchange capacity (cec), the substance of earth minerals, calcium carbonate, fe and mn oxides (ikem et al., 2002; adjia et al., 2008; altaher and agatemor, 2010). however, out of these soil properties, soil ph was found to assume the most critical part in deciding metal speciation, dissolvability from mineral surfaces, development, and inevitable bioavailability of metals (ogundiran and afolabi, 2008; sherene, 2010). a positive connection between soil ph, heavy metal mobility and accessibility to plants has been very much reported in various investigations. for instance, with diminished soil ph, the emotional increments in substantial metal desorption from soil constituents and dissolution in soil solution was observed for cd, pb and zn (yang et al., 2006; ukpong et al., 2013). the mobility and bioavailability of heavy metals likewise increase with diminished soil ph (joseph et al., 2006; esmaeilil et al., 2010; oyeku and eludoyin, 2010), subsequently improving the uptake of heavy metals by plants and consequently creating negative impact to human wellbeing (akaeze, 2001; cappuyns et al., 2004). aside soil ph, organic matter content in soil is additionally a standout amongst the essential soil properties influencing heavy metal availability. organic matter content of the soil is a noteworthy contributor to the capacity of soils for holding heavy metals in an exchangeable form. moreover, organic matter additionally supplies organic chemicals to the soil solution that can serve as chelates and increase metal availability to plants (clemente et al., 2003). the role played by organic matter on metal availability has been broadly studied. it was accounted for that substantial metal adsorption into soil constituents declined with diminished organic matter content in soils (eddy et al., 2003; altaher and agatemor, 2010). also, the dissolved organic matter in soils could increase the mobility and uptake of heavy metals to plant roots (aboyade, 2004; adjia et al., 2008). cu, fe, mn and zn are necessary minerals for plant development, yet cr and pb are non-essential however toxic to plants at a low level and to humans through a food chain. in this way, it is necessary to assess the impact of soil properties on the availability and the uptake of heavy metals by plants to limit the dangerous implications and the translocation to the food chain. this study aimed at assessing the organic matter and heavy metals leachate in selected dumpsites in north central states, nigeria. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 193-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 195 2. materials and methods 2.1 study area description nasarawa, niger and kogi states are situated within the north-central part of nigeria. the population for nasarawa, niger and kogi states are 2,040,097., 3,950,249 and 2,099,046, respectively, with each state having a land mass of 27,117 km2, 76,363 km2and 29,833 km2 respectively. the population in each of the study areas was unevenly distributed such that commercial, industrial and agricultural, recreational and administrative, and residential dumpsites were scattered everywhere throughout the city, thus serving as point sources of heavy metals (adamu et al., 2003). three sampling stations were established within each state based on the population of the locality and availability of major dumpsites. 2.2 soil sampling soil samples were randomly collected in triplicates from the various study locations at a soil depth ranging between 0 – 15 cm, 15 – 30 cm and 30 – 45 cm, respectively with a control point at each of the location. the sampling process was carried out using a depth calibrated soil auger as suggested by olufunmilayo et al., (2014). the control points were located 100 m away from each cluster which served as the reference site (rf). most of the dumpsites were located outside the major cities. the various samples collected were carefully placed in a plastic bag, tightly sealed and marked. this reduced the presence of microbial activities from the study location, and substantial were elements were expelled during the process. this sampling process is similar to that of asiagwu et al. (2007) and pam et al. (2013). 2.3 heavy metals analysis in the laboratory, the soil samples were air dried for 72 hours at room temperature, after which the soil samples were grounded to fine particle sizes using laboratory pestle and mortar. the soils were sieved with a 2 mm sieve as described by opaluwa et al. (2012). a sample of 5 g of air-dried grounded soil sample was placed inside a 25 ml conical flask and 5 ml of concentrated h2so4, 25 ml of concentrated hno3, and 5ml of concentrated hcl were added to the soil sample. the content of the tube was warmed at 200 °c for 1 hour after which it was left to cool to room temperature (bukar et al., 2012). after the cooling process, 20ml of distilled water was added, and the mixture was filtered to complete the digestion. the filtrate was added to a 50ml volumetric flask and allowed to settle for 15 hours after which the filtrate was investigated for metals using the atomic absorption spectrophotometer (aas) as described by pam et al. (2013). 2.4 determination of soil ph twenty grams of air-dried soil sample was weighed placed into a 50 ml measuring glass and 20 ml of distilled water was added to the sample. the solution was allowed to remain in a fixed position for 30 minutes. the solution was filtered and was used to determine the status of ph in each of the soil samples collected. the hach ph meter was utilised to determine the ph level in each of the samples. ph meter was calibrated using ph calibration buffer solution for ph 4, 7 and 10. the electrode of the meter was dipped into the filtrate and the ph meter readings taken to the nearest 0.05 unit. 2.5 determination of organic matter the organic carbon of soil was determined using the wet oxidation method in accordance with the process employed by kumar et al. (2019). the organic carbon is oxidised by k2cr2o7 in the presence of h2so4 towards the formation co2 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 196 2k2cr2o7 + 8h2so4→ 2k2so4 + 2cr2(so4)3 + 8h2o + 3o2co2 (1) 3c + 3o2→ 3co2 (2) soil organic matter was determined by the titrimetric technique described by (bukar et al., 2012). samples were grounded to pass-through a 0.5 mm sieve after which they were weighed and transferred to 250 cm3 erlenmeyer flasks (shigaki and dell, 2015). precisely 10 cm3 of 1 m potassium dichromate was pipetted into each container and swirled tenderly to disperse the soil followed by addition of 20 cm3 of concentrated sulphuric acids. the flask was swirled tenderly until soil and reagent are thoroughly mixed. the mixture was then allowed to remain in a fixed position for 30 minutes on a glass plate to allow for the oxidation of potassium dichromate to chromic acid. 100 cm3 of distilled water was added were followed by addition of 3-4 drops of ferroin pointer, after which the mixture was titrated with 0.5 m ferrous sulphate solution. a clear titration was correspondingly done,and the rate of organic carbon was computed from the condition: (3) f = correction factor (1.33) me = molarity of solution transferred x ml of solution used % of organic matter in soil = % of organic carbon x 1.729 2.6 statistical analysis data obtained were analyzed using minitab version 14.0 (ahaneku and sadiq, 2014). pearson correlation analysis was used to verify the relationship between examined variables and nonequilibrium one-way analysis of variance (anova). the duncan multiple range tests were used to separate means that were significantly different. the methodswere significantly different where p≤0.05 and insignificant when p>0.05 at 95 % confidence interval (ogundiran and osibanjo, 2009). 3.0 results and discussion each of the states was divided into three catchment zones according to the spatial distribution of dumpsites. niger had borgu, bida and minna, kogi had lokoja, okene and kabba while nasarawa had lafia, akwanga, and nasarawa as the dumpsite locations. heavy metal concentrations in all the catchments were higher than at the reference sites and lower than the threshold values (tabak et al., 2005; aislabie et al., 2006; ahaneku and sadiq, 2014). the results show that the mn and fe contents in the study location of niger state were observed to be highest while a higher concentration of cr and al were observed in kabba dumpsite area of kogi state. these results were linked to the life style of the people within the communities. interestingly, the concentration of zn and cu were highest in lafia dumpsite area of nasarawa state. the variation in the physicochemical properties in relation to the soil depth is similar to the findings of mohammed et al., (2015) which is evident in the results presented in tables 1, 2, and 3. the results showed that as ph decreases and % om increases, heavy metals concentration increases down the soil profile. 3.1 iron (fe) figure 1 below, shows results of fe concentrations across soil profile in all the sampling locations including the reference (rf) site. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 193-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 197 figure 1: fe concentrations (mg/kg) at various dumpsites by the depth the results obtained showed that fe showed a gradual decrease in its concentration across all the sampled locations including their respective rf points. the high content of fe in the soil samples was observed at 5 cm depth in the dumpsites of niger state (ng) (69.00 ± 11.02 mg/kg) and the lowest concentration at rf site of nasarawa state (ns) (13.00 ± 2.08 mg/kg). the observed values were below who permissible limits of between 3000-250000 mg/kg as reported by monechot et al. (2014). akan et al. (2013) stated that heavy metals are uniformly distributed in the upper soil layer to a depth of 5 cm. also, iwegbue et al. (2013) observed a significant distribution of fe across soil layers from 0 -15 cm to 15 – 30 cm depth. results of fe concentration obtained in this present study were lower than that obtained in residential and commercial dumpsites soil reported by onyedika (2015). ph plays a vital role in the availability of heavy metals in soils. akan et al. (2013) reported that heavy metal distribution in the soil increased with a decrease in soil ph from 6.21 to 7.72 and 0.51 to 3.79% om which could be linked to the chemical processes within the soil. these observations agrees with the current studies where the distribution of fe across varying depth increases as ph decreases from 6.81 to 6.59 and % om from 0.75 to 2.2 %. the anova results at p < 0.05 revealed there is a significant difference in the concentrations of fe across soil profile. furthermore, results of duncan’s multiple range tests compared the means and indicated a significant difference between all dumpsites against the reference (rf) sites. 3.2 chromium (cr) the results of cr content across the various soil profiles in all the sampled locations are presented in table 2. it was observed that there were varying concentrations of cr in all the sampled areas. cr content was found to be high at dumpsite of ns (29.00 ± 1.15 mg/kg) and low at rf point kg (0.60 ± 0.00 mg/kg). the mean level of cr in all the dumpsites is highest at 0 – 5 cm depth; these observations are in agreement with previous studies that soil contaminated by anthropogenic activities typically contains highest and varied content of heavy metals at the surface horizons (chopin et al., 2003; boularbah et al., 2006; ahaneku and sadiq, 2014). in this study, cr content was much lower when compared to that reported by adefemi and awokunmi (2009) in dumpsites soil within ado-ekiti town, south west nigeria. this was higher than the content published by dauda et al. (2011) in a study conducted in keteren gwari dumpsite, niger state but below the permissible limits of 150 mg/kg for france; 100 mg/kg for austria and spain; 60 mg/kg for germany and sweden; and 30 mg/kg for denmark (adelekan and abegunde, 2011); 240 mg/kg in nigeria (dpr-egaspin, 2002). the content of cr slightly decreases with increased depth in both disposal and reference sites in all the locations. anova file:///c:/users/user/downloads/azojete143/www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 198 result shows there is a significant difference in the concentration of cr across depth profile, but by sites, only niger state (ng) and kogi state (kg) sites showed higher cr concentrations than the reference locations. figure 2: cr concentrations (mg/kg) at various dumpsites by depth. 3.3 manganese (mn) the results of the mn analysis are presented in figure 3. the highest mn concentration was observed at depths of between 0 – 5 cm at a dumpsite in ng (131.00 ± 25.98 mg/kg) while the lowest was at rf site of kg (7.00 ± 5.00 mg/kg). the mean values decrease down the soil profile for both the dumpsites and the reference point. this was observed to be similar to the works of pam et al. (2013) and adelekan and abegunde (2011). they worked in dumpsites soil around the mechanic village in makurdi and municipal dumpsites in ibadan respectively. in their study, they observed that ph and om may be responsible for the variations in concentration at varying depth. the concentration of mn in the soil in this study was higher compared to that reported by amadi and nwankwoala (2013) in their study on enyimba dumpsites in aba. the values were considerably lower compared to mn level found in esso, gbangbara, and eyagi dumpsites respectively in bida, (niger state) as reported by nda-umar et al. (2012) and lower than that reported by onyedika (2015) for urban soils of bauchi state. this is attributed to the soil ph which is slightly acidic and makes the distribution of this metal to be at a slow rate. although the concentration of mn obtained in this study is higher compared to other metals but less than the world-soil average (kabata-pendias, 2011). figure 3: mn concentrations (mg/kg) at various dumpsites by the depth. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 193-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 199 the result of analysis of variance (anova) at p<0.05 showed that there was a statistically significant difference in mn content across soil profile. furthermore, the results of duncan’s multiple range tests compared the various means and indicated a significant difference between all dumpsites and rf sites. 3.4 zinc (zn) the zn concentrations for the various sites is presented in figure 4 with the highest mean concentration at ns dumpsite (46.67 ± 8.69 mg/kg) and the lowest at the rf location ng (1.40 ± 0.23 mg/kg). from results obtained, zn content at the various dumpsites was higher compared to the control which may be due to contamination from the dumpsites as a result of anthropogenic activities. the concentration of zn in all the sampled points increased with a decrease in both ph and % om across the various soil depths. zn accumulation within the soil depth was detected by ogundiran and osibanjo (2009), while olufunmilayo et al. (2014) in their study on dumpsite soil observed a decrease of zn from the top layer of 0 – 15 cm; 15 – 30 cm and 30 – 45 cm depth. these results obtained is similar to that in this study as a high level of zn content was observed at 5cm depth and decreases down the soil depth of 30 cm with a decrease in ph and %om. the result of zn content in the present this study is similar to the results obtained in cameroon, southeast korea and yauri of kebbi state, nigeria (yahaya et al., 2010) but higher as compared to studies conducted in lafia dumpsites by opaluwa et al. (2012) and lower when compared to other studies (shinggu et al., 2007; ogundiran and osibanjo, 2009; nwachukwu et al., 2011). acidic ph levels within the study area makes it easier for the solubilization of zn compounds (abechi et al., 2010). in this study, ph ranged from 6.33-6.87 as presented in table 3 which indicates that the soil is slightly acidic. hence, zn accumulation in soil layers is expected to be at a slow rate. the study carried out by pam et al. (2013) and akoto et al. (2008) showed that ph of between 6.36 and 6.4 conforms to this study. this might be responsible for the low value of zn obtained in this current study as compared to other studies. however, the values of zn obtained in this study is below the permissible limits of 1 – 900 mg/kg in the soil (kabata-pendias and pendias, 2001; hague et al., 2008). anova results revealed there is statistically (p<0.05) significant difference in the concentrations across soil profile. furthermore, results of duncan’s multiple range tests to compare means indicated a significant difference between all dumpsites against the rf sites. figure 4: zn concentrations (mg/kg) at various dumpsites by the depth 3.5 copper (cu) the results as presented in figure 5 revealed that the values of cu at the dumpsites are higher than the values obtained at the reference points. the highest cu concentration was detected at dumpsites of ng (40.67 ± 11.22 mg/kg) and the lowest at the rf site of ng (0.90 ± 0.40 mg/kg) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 200 also. the concentration of cu was also observed to be high at the top layer of the soil (0 – 5 cm) and decreases across soil profile as ph decreases from 6.33 to 6.87 and % om decreases from 0.89 to 0.73. the values of cu content found in this study are higher as compared to results for dumpsites soils reported by olufunmilayo et al. (2014) but below the permissible limits for countries like australia (100 mg/kg), canada (100 mg/kg), poland (100 mg/kg), japan (125 mg/kg), great britain (100 mg/kg) and germany (50 mg/kg) as reported by pam et al. (2003). the content of cu in all the sampled locations decreases with depth of the soil profile. cu distribution down to 30 cm depth has been reported by akan et al. (2013), while ololade (2014) in their study on dumpsite soil observed increased cu to a depth of 100 cm. this is similar to the works of (bansal and sing 2014; amos et al., 2014) and at variance with the works of bukar et al. (2012) and adedosu et al. (2013) which could be linked with the various types of waste generated in the area. in this study, the high level of cu was noted at 0-5 cm down to 15-30 cm depth, this agrees with the findings of iwegbue et al. (2013). the mean content of cu ranged between 14 and 40.67 mg/kg which is similar to what was obtained by ahaneku and sadiq (2014) in their study on minna municipal dumpsites, niger state. figure 5: cu concentrations (mg/kg) at various dumpsites by the depth the results of the analysis of variance (anova) revealed a statistically (p<0.05) significant difference across soil profile. furthermore, results of duncan’s multiple range tests which compared the means indicated a significant difference between all dumpsites against the rf sites. 3.6 aluminium (al) the results of al are presented in figure 6. the highest mean concentration of al was observed at dumpsites ns (16.73±1.56 mg/kg) while the lowest at rf location of kg (6.60±0.00 mg/kg). the concentration of al was also observed to be high at the top layer of the soil (0 – 5 cm) and decreases downwards to a depth of 15 – 30 cm depth. mohammed and bashir (2015) found a significant distribution of al to a depth of 130 cm. also, akan et al. (2013) reported that heavy metals have an even distribution across soil profile to a depth of 5 cm. these results agree with the current study where the distribution of al across soil profile (leaching) to a depth of 30cm was found throughout the sampling locations with varying concentration levels. al contents found in this current study are much lower than the mean values of between 26580 – 95270 mg/kg (beyene and banerjee, 2011; mohammed and bashir, 2015). the obtained mean values of 16.73 mg/kg for al in this study is lower than the world average crustal abundance of 82300 mg/kg in an uncontaminated soil as reported by mohammed and bashir (2015). analysis of variance (anova) of the results indicated that there is a significant difference (p<0.05) in the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 193-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 201 concentrations across the sampled depths. however, results of duncan’s multiple range tests to compare means indicated a significant difference between all dumpsites against the rf sites. figure 6: al concentrations (mg/kg) at various dumpsites by the depth 3.7 soil properties table 1 presents the average results of soil physicochemical properties in ng dump and rf sites across the different soil depth levels (0 – 15 cm, 15 – 30 cm and 30 – 45 cm) of sampling. soil ph plays a fundamental role in heavy metal chemistry (pam et al., 2013). the result obtained in this study, revealed that ph level was significantly higher at the rf dumpsite (6.81 ± 0.05) and lowest at dumpsites (6.59 ± 0.19) similar to other studies on heavy metals in gboko and makurdi dumpsite soils by pam et al. (2013). there was generally a decreasing trend of ph across depth levels. however, the ph suggests that the soil is slightly acidic which means cations movement across soil profile will be slow. the ph values obtained in this current study agrees with results that nigerian soil is within limit and favour plant growth as reported by banjoko and sobulo (2000). the results of anova revealed no significant difference (p<0.05) in the variations. % om plays a fundamental function in metal binding (akans et al., 2010). total % om of the soil ranged from 0.75 to 2.2% and is similar to the result of om reported by iwegbue et al. (2013) which is in the range of 0.8 to 2.8 %. in their study, the highest percentage of om was observed at a depth of 0-15cm and decrease with increased depth which is similar to om result obtained in this study. the highest rate of om was found at the surface layer at a depth of 0-15 cm, and there was a slight difference in the values throughout the depth. the works of adelekan and abegunde (2011) also revealed depth-related differences. table 1: summary of physicochemical properties of soils surrounding sampling sites in niger state (ng) dumpsites. depth (cm) ph % om % silt % clay % sand textural class ds 0-5 6.78 ± 0.09 2.20 7.00 10.70 82.30 loamy sand 5-15 6.64 ± 0.18 1.50 6.70 11.00 82.30 loamy sand 15-30 6.59 ± 0.19 1.20 6.00 11.30 82.70 loamy sand rf 0-5 6.81 ± 0.05 0.82 6.70 12.00 81.30 loamy sand 5-15 6.72 ± 0.09 0.80 6.70 10.70 83.30 loamy sand 15-30 6.63 ± 0.14 0.75 7.00 10.00 83.00 loamy sand file:///c:/users/user/downloads/azojete143/www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 202 the anova result shows no significant variations across soil profile. the values of particle size distribution for ng for sand ranged between 81.3– 83%, silt ranged between 10-12 %, while clay ranged between 6.7-7%. these results agree with that works of ahaneku and sadiq (2014) and amos et al., (2014) in their study of open dumpsites for maitumbi which had 84.85% of sand, 10.16% of silt, and 4.99% of clay, and maikunkele had 84.60% of sand,11.79% of silt, and 3.61% of clay. however, the textural classification of the particle size distribution in this study is loamy sand which is typical of soils in nigeria (sha’ato et al., 2000). in table 2, the results show that ph level decreases downwards the soil depth in the dump and rf sites. highest values were observed at rf locations (7.09 ± 0.01) while the lowest at dumpsite ds (6.78 ± 0.00). however, there was a slight difference throughout the depth in the dumpsites. this is as a result of a decrease in ph and %om. adelekan and abegunde (2011) in their study on the contribution of municipal refuse dump on heavy metal concentration in ibadan also revealed depth-related differences in metal concentration. furthermore, oviasogie and ndiokwere (2008) in their study reported that lower ph favour availability, mobility and redistribution of the metals like pb and cd in the various fractions. soil ph, for instance, plays a significant role for most heavy metals as reported by adelekan and abegunde (2011) that heavy metal availability is relatively low when ph is around 6.5 to 7. this tends to agree with the ph range of 6.78 to 6.89 obtained in this present study, which indicated that the soils are slightly acidic. anova result for these showed no significant (p < 0.05) difference in the variations. % om obtained in the present study is in the range 1.2 to 2.2% which conforms to om values reported by akoto et al. (2008) to have the potential to bind toxic ions. anova results for the variations across depth levels show no significant difference. table 2: summary of physicochemical properties of soils surrounding sampling sites in kogi state (kg) dumpsite. depth (cm) ph % om % silt % clay % sand textural class ds 0-5 6.89 ± 0.05 3.10 10.00 12.00 78.00 loamy sand 5-15 6.78 ± 0.11 1.50 9.70 10.70 79.70 loamy sand 15-30 6.78 ± 0.00 1.10 11.00 11.30 76.50 loamy sand rf 0-5 7.09 ± 0.01 1.02 9.70 10.70 79.70 loamy sand 5-15 6.89 ± 0.06 0.95 6.50 12.00 80.50 loamy sand 15-30 6.85 ± 0.09 0.91 6.00 13.00 81.00 loamy sand according to amos et al. (2014), the loamy soil has high pollutant leaching potentials. however, the soil of all the study locations predominantly contains high sand fractions (80.0%) that allow high infiltration of water and leachates. textural classifications of existing soils in the study area are loamy sand soil which plays a significant role in the diffusion of metals ion into and out of soil aggregates (sherene, 2010). in that study, it was found that the downward distribution of metals correlated with high soil macroporosity. in this study, metal concentration increases depth wise in all the sampling points. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 193-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 203 table 3: summary of physicochemical properties of soils surrounding sampling sites in nasarawa state (ns) depth (cm) ph % om % silt % clay % sand textural class ds 0-5 6.62 ± 0.31 2.30 5.00 14.00 81.00 loamy sand 5-15 6.58 ± 0.23 2.20 6.30 11.00 82.60 loamy sand 15-30 6.33 ± 0.17 1.30 5.00 11.30 82.60 loamy sand rf 0-5 6.87 ±0.30 0.89 6.70 12.30 81.00 loamy sand 5-15 6.56 ± 0.16 0.83 7.00 12.30 84.00 loamy sand 15-30 6.40 ± 0.05 0.73 7.60 10.60 81.60 loamy sand the mean results of soil ph and om at ng dumpsites and rf sites are presented in table 3. the highest values were observed at the reference dumpsite rf (6.87 ± 0.01) while the lowest at dumpsite ds (6.33 ± 0.17) indicating that the soils are slightly acidic. this may tend to have increased heavy metal availability and concentration in the soil. this is similar to findings of amos et al., (2014) who worked on dumpsites soils in yenegoa where it was discovered that ph and %om increase heavy metal distribution down the soil profile. the results of anova revealed no significance (p < 0.05) in the variations. it was also observed that om content at all the sites decreased with increasing depth and that accumulation of om occurs mainly in the top layer(0-5cm) in all the sampling points. om accumulation at the top layer decreases down to 30-45 cm depth as detected by olalade (2014). ayolagha and onwugbuta (2001) have shown that high om (> 2.0%) in soils is conducive for heavy metal chelation formation. this is in agreement with om which ranged from 1.3 to 2.3% as obtained in this study (table 6). however, dumpsites have higher om and low ph as compared to that of the control soil. this observation is in line with findings of oyedele et al. (2008). they reported that dumpsites soil had low ph and high om in comparison to those at control locations. anova results for the variations across depth levels show no significance. the textural classification of the soil for sand ranged from 81 to 84% which is similar to the report presented by chindo et al. (2016) with moderate clay and low silt content. 3.8 correlation analysis in ns dumpsites, both fe and cu were negatively correlated with om while cr positively correlated with ph. however, there was a significant negative correlation between fe and cu with om in ng dumpsites. fe is significantly correlated with ph as well as mn and cu with om in kg dumpsites. cu and ph were positively correlated in the kg dumpsites which is similarto the result reported by iyaka and kakulu (2009) and ahaneku and sadiq (2014) in their study. ph is positively correlated with cr, fe, zn (p < 0.05) in all the sites while om is significantly correlated with mn and cu at only kg dumpsites. the relationship between ph, om content and concentration of heavy metals are presented in table 4. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 204 table 4: correlation coefficients (r) between the ph and om on heavy metals in dumpsite soils tested location items ph om cr2+ fe2+ mn2+ zn2+ cu2+ al3+ ph 1 om 0.099 1 cr2+ -0.124 -0.169 1 fe2+ -0.356 -0.821** 0.312 1 niger mn2+ 0.477 -0.643 -0.239 0.3031 1 zn2+ 0.501 -0.221 0.527 -0.0091 0.172 1 cu2+ -0.403 -0.738** 0.414 0.849** 0.049 0.274 1 al3+ -0.09 0.126 0.843* -0.164 -0.374 0.528 0.055 1 ph 1 om -0.742* 1 cr2+ 0.333 -0.185 1 fe2+ 0.832** -0.643 0.108 1 kogi mn2+ -0.301 0.159 0.759 -0.413 1 zn2+ 0.334 0.008 0.201 0.685 -0.125 1 cu2+ 0.827 -0.59 0.770* 0.631 0.203 0.392 1 ph 1 om -0.184 1 cr2+ 0.757 -0.548 1 fe2+ -0.143 -0.792* 0.423 1 nass mn2+ -0.581 -0.077 -0.22 0.482 1 zn2+ -0.563 0.258 -0.305 0.166 0.903 1 cu2+ 0.296 -0.967* 0.59 0.641 -0.084 -0.360 1 al3+ -0.139 0.641 -0.365 -0.371 0.374 0.564 -0.709 1 *correlation is significant at 0.05 levels (2-tailed) **correlation is significant at 0.01 levels. 3.9 heavy metals about ph and organic matter (om) in the soil this study revealed that availability of metal cation across soil environment is a function of ph and om. figures 7 to 9 illustrates these relationships; as ph and % om increases with the deepening of soil depth, concentration of metals increases across soil depth. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2020; vol. 16(1) 193-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 205 figure 7: relationship between ph and om on metal availability across soil profile at niger state (ng) dumpsite figure 8: relationship between ph and om on metal availability across soil depth on kogi state (kg) dumpsite figure 9: relationship between ph and om on metal availability across soil profile at nasarawa state (ns) dumpsites. 4. conclusion results obtained from this study showed no significant differences (p<0.05) in the concentrations of the investigated heavy metals across the different soil depths of the dumpsites when compared with those of the control points within the same locality. it was revealed that mn generally had the highest concentrations in all soil profiles studied while al was least detected at that location. the mean concentration of all the metals in the dumpsites was observed to be significantly higher than those at the control locations though these values were below the permissible limits set by fao and who for agricultural soils. results of physicochemical properties of the soil revealed that decrease in ph and percentage organic matter increases the concentration of the metals within the study locations with the top soil having the highest concentration. it is therefore recommended that environmental laws should be enforced to prevent any form of anthropogenic activities aim at modifying ph and om in the soil and to arrest the ongoing buildup of heavy metals in those locations. acknowledgements the authors are grateful to the federal university of technology minna and tertiary education trust fund for providing grants to carry out this research work. they are also thankful to laboratory staff of soil science department, the federal university of technology minna, niger state and chemistry department ahmadu bello university zaria, nigeria who assisted in carrying out soil analyses. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng musa et al: organic matter and heavy metals leachate effect on soils of selected dumpsites in selected north central states of nigeria. azojete,16(1):193-210. issn 1596-2490; 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indeed, it is central to the stabilization of many economies. nigeria has a land area of 923,767 km2 with 708,000 km2 agricultural land of which 412,938 km2 is cultivated including 344,577 km2 arable land and 68,361 km2 on permanent crops as shown in figure 1. agriculture is practiced largely as a traditional activity and managed as a subsistence cultural activity with the seed stock yields averaging less than one-third of exotic species. for example, cereals yield an average 1.44 kg per ha compared to 8 to 10 tons/ha in usa. on the average, in 2015, nigeria applied only 8.3kg fertilizer per ha as against 50.2kg in cote d’ivoire, 112kg in usa, 246.9kg in united kingdom, and 1,539.3kg in malaysia. nigeria also has only 6.7 tractors per 100 km2 of arable land compared to 30 in cote d’ivoire, 52 in south africa, 271 in usa, 629 in uk and 255 in malaysia. nigeria’s local poultry matures in over one year, is broody and lays only about 40 eggs a year while a corresponding exotic species of poultry broiler matures in five to eight weeks and the egg poultry lays over 300 eggs a year. nigerian cattle species weigh about 250kg/head on the average as against 800 – 2000kg/head of exotic cattle; nigerian goats weigh about 20kg as against 85 kg for female and up to 120kg for male kalahari goat species. milk yields of local cattle are less than one kilogram per day as against six to ten kilograms per day for exotic dairy cattle breeds. (nigeria at a glance: food and agriculture in nigeria, 2018) http://www.azojete.com.ng njoku, p. c.: revolutionizing agriculture through space science and technology applications. azojete, 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 2 figure 1: productivity of nigerian crops benchmarked on potential for other developing countries (akimboloba, 2001) figure 2: world t op four producers of wheat, rice and maize compared to nigeria. (billing, 2017) figure 2 shows the comparative level of nigeria as compared to the world top four countries that produce wheat, rice and maize. despite this poor profile, nigeria’s agriculture is expected to feed a population currently indicated in 2016 at 186 million and growing at an average of a 2.68 percent annually (ogbalubi and wokocha 2013). strategic as it is, ogbalubi and wokocha (2013), concluded that agriculture basically contributes over 23 percent of gross domestic product (gdp). it provides food for the nation employs over 36.6 percent in regular paid jobs but with over 70 percent engaged in agriculture in the rural areas; agricultural raw materials stimulate processing for the production of commodities which promote local retail trade and support foreign trade. agriculture therefore can significantly reduce poverty; create wealth at individual, state and national levels; as well as conserve and earn foreign exchange through import substitution and trade, respectively. the objectives of this paper are to show how space http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 3 technology applications can significantly influence food production systems and also be key to food security as it can enhance productivity, resilience and profitability. 2. agriculture and the national economy in nigeria, successive administrations have through their economic development plans and strategies in vision 20:2020, and ergp, 2016 have underscored the need to diversify the nigerian economy through developing economic sectors other than oil, which has been the sole source of over 90 percent of the nation’s foreign exchange earnings and over two-third of government funding (nigeria at a glance: food and agriculture in nigeria, 2018). it has now become imperative for diversification from oil as a result of the emerging decision by several nations to stop licensing oil and gas fueled cars from 2025, the need to achieve this diversification seems very urgent (ingrid, 2016). “with over 90% of export earnings and government revenues dependent on hydrocarbon based primary products, entirely generated from a single region of the country, the pillars of nigeria’s economy are extremely weak, and the continued economic viability of the nigerian state, as a self-sustaining entity, is perpetually at risk” (onyenekenwa, 2011) to diversify the economy, nigeria identified some sectors including agriculture, wholesale and retail trade, manufacturing and telecommunications as key drivers of the economy and therefore conceptually decided to transform their current subsistence and mini-sized management structures into profit-oriented commercial enterprises. for agriculture, this will involve the modernisation of the process, having regard to value chains, introduction of pertinent mechanization and technologies in order to proficiently increase productivity of crops and livestock and to achieve higher levels of production per unit of farm/ head. in doing this, the nation must also be cognisant of the challenges of climate change and therefore work to transform agriculture with a conscious focus to enhance climate co-benefits and achieve resilience. www.unoosa.org/oosa this transformation will mean re-orientation of farmers from their age-old traditional methodologies in subsistent farms to the introduction of modern technologies in intensively managed for-profit farms; abandoning the traditional rain-fed agriculture where farming takes place principally during the rainy season to significantly increasing irrigated land from the current less than one (01) percent to over 40 percent of arable land and therefore reducing idletimes during the dry season; abandoning the “one-size-fits-all” mentality in using one type of fertilizer from the swampy soils of the niger delta region in the south to the loose sandy soils of the sahel region in the north to consciously matching soil nutrition with precise soil characterization and application of nutrients to eliminate any gaps in the nutrient matrix of the soils in each farm to assure the highest yield (akande, 1998). the transformation must also result in the discard in commercial enterprises of low-yield seeds and young livestock to deliberately improving the genotypic and phenotypic characteristics of our crop and livestock seed stocks through intense selection and other technologies (with preference for artificial insemination and such technologies that may exclude genetic modification); the “retirement” of hoes and machetes while domesticating fit-for-purpose and fit-for-location equipment and machines file:///c:/users/user/downloads/azojete143/www.azojete.com.ng njoku, p. c.: revolutionizing agriculture through space science and technology applications. azojete, 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 4 including tractors and other efficient mechanized systems of labour; noting the very high number and the ageing nature of current farmers to “outsourcing” the large number to other sectors while enhancing the technical and management competences of the remaining “agripreneurs” as well as ensuring that programmes (including incentives and professionalization) are available that must attract the youth to study and practice agriculture. it must also be noted that crops and animals produced in the prevalent subsistent system are sold as primary commodities with hardly any consideration for profit to ensuring that primary products are processed through value-addition systems to ensure higher value-commodities, higher prices and better returns to the farmer. since units of farm land are very small (less than one-ha in some areas) to organising farmers in collectives/cooperatives to facilitate land consolidation, mechanisation and off-taker partnerships; noting that even with the critical importance of extension to technology transfer, the current extension system has over 20,000 farmers to one low morale, generalist extension worker to ensuring that the succeeding extension system is within accepted ratios of 500 to 1000 farmers to one specialized, well-resourced extension worker (akande, 1998). the current uncoordinated marketing system where every farmer markets his/her commodity independently whereby livestock are inefficiently transported or farmer trekked hundreds of kilometres to reach market, have negative impact on meat quality. government need to ensure that there exists special marketing vehicle that ensures crop commodities are ferried to conditioning centres and processing plants in appropriate transport while livestock are hygienically processed and packaged in abattoirs and slaughter slabs close to their areas of production and the meat transported in cold chains to sanitary sales outlets across the country. ibrahim and mukhtar (2015) concluded that nigerian scientists currently struggle to get funding and facilities to conduct research to support innovative agricultural technology development to well-funded research opportunities producing instructive outcomes for the development of revolutionary technologies that support the highest agricultural yields and most acceptable conformations. such a transformation will be incomplete without the application of cutting edge technologies. today, nigeria is the number one producer of cassava in the world. thirty years ago, nigeria raised the production of cassava from 4 to 8 tons per ha, ten years later, production rose to 15 tons per ha and this was celebrated as a great scientific feat. eight years ago, nigerian scientists collaborating with their colleagues in the international institute for tropical agriculture (iita) increased the yield to 45 tons per ha akinpelu et al. (2011). but is this the highest possible yield for cassava in nigeria? already achievements have been recorded with the production of vitamin a cassava – which means the limit is yet to be achieved! cognisant of the variety of activities in the various agricultural value chains, it is possible to understand the complexity of agriculture, the several activities leading to the production of commodities and the myriad of facilitating activities that drive the process of commodity production. it also shows the several factors that must operate at full thrust for a production process to be achieved seamlessly. it is fact that any reaction that limits any of these processes will limit or confound commodity production. production of such agricultural commodities will enhance foreign exchange conservation through import substitution as well as the local retail trade economic sector. also, such production will promote foreign exchange earnings through foreign trade in the commodities. both processes will undoubtedly have positive effects on the national economy (akinpelu et al., 2011). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 5 3. space science and technology for human development in the effort to produce enough food to feed the more than 9 billion global population by 2020, the united nation projects that global food production must increase by at least 70 percent (purdy, 2016). this is in the face of an increase in population, expansion of urban and sub-urban settlements with reduction in land available for further expansion for agricultural production. invariably, this calls for the development of greater efficiencies in production efficiencies driven by the most appropriate and most responsive technologies. of great interest today is the application of space science and technology to agriculture. originally, the objective of space science and technology was to study the origin and evolution of stars and galaxies to help man understand the foundation of the universe and its changes (united nations, 2016). over time, the technology veered into investigating the presence of life in outer space, and now is keenly probing ways of using the science and technology to understand the earth, the circumstances and processes of the earth. the current drive is to use the technology to bring benefits to man while still exploring the universe for monumental breakthroughs. consequently, the technology is used today in a wide array of sectors to bring understanding and benefits to our environment, agriculture, education, global health, sustainable development, disaster management, human settlements, research and development, transportation, communication, humanitarian assistance, and international peace and security (united nations, 2016). in our great nation nigeria, the minister of science and technology, dr ogbonnaya onu, recently identified as quick wins that space technology will “positively impact on agriculture, national security, health services, education and manufacturing sector” (the vanguard 2017). 4. incursion of space science and technology into agriculture it can therefore be concluded that “revolutionizing agriculture through space science and technology applications” evinces the profound sensitivity of the national space research and development agency (nasrda) and its subsidiary centre for satellite technology development (cstd) to bring due focus to the great benefits that can accrue to nigerian agriculture through the application of space science and technology. this is basically in concert with the position their supervising minister that nigeria will “continue to utilize space technology to boost vital sectors of the nigerian economy”. by accepting agricultural revolution as our goal, we are directly raising issues with the use of science, technology and innovation to mitigate inequities, maximize and actualize potentials, and advance environmental and social harmony. we must accept the thesis that science and technology have progressed from the period of focusing and understanding the agriculture around us, to a period of trying to control our agriculture, to a new period of transforming agriculture. we can therefore appreciate the progression in cassava yield from 8 tons/ha to 15tons/ha and then to 45 tons/ha and the vision of 100 tons/ha! this will be revolutionary and it can only be achieved by the application of new technologies and innovations. this revolution must take advantage of cutting-edge knowledge, succinct technology and innovation with communal goals. space science and technology is one of the emergent technologies of extant considerable interest in the drive to accelerate innovation. space has been described as “a privileged place file:///c:/users/user/downloads/azojete143/www.azojete.com.ng njoku, p. c.: revolutionizing agriculture through space science and technology applications. azojete, 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 6 from which to study large-scale vegetation, ocean currents, water quality, natural resources, air pollutants, greenhouse gases” (chizea et al 2006). it is indeed a great location for the observation and monitoring of development of events on planet earth. major developments have been made by many nations to take advantage of the growing opportunities incident on space science and its derivative technologies. space technology in agriculture was indeed not in the frame of the main essence of space exploration but rather a spin-off from the primary objective. however, the incursion of space or satellite technology into agriculture and related phenomena, though relatively young in many parts of the world, is already having an important impact on what is currently seen as a shift towards precision control of food production which allows farmers to produce more with less (ikpaya et al., 2017). to study and hopefully exploit space, many countries have launched satellites into space with the objective of studying what values may be realizable. the outcome of such explorations has been the development of varied technologies which can be used in several economic sectors including agriculture. space science and technology are already being exploited to help in the prediction of factors affecting agriculture and thus leading to its transformation through the emerging concept of “smart agriculture”. many nations – china, russia, usa, denmark, u.k., india have progressed significantly in utilizing their satellite technologies to advance agriculture (ikpaya et al., 2017). in the united kingdom (uk), by 2016, about 60 per cent of all farmland in the nation already had farm management tools using the likes of sensor systems, analytics, cameras and drones (ikpaya et al., 2017). space technology significantly reduced human agricultural labour with the introduction of more automated mechanical systems. from 2009 to 2016, it injected over 8.2 billion uk pounds into the economy, a 16% growth, while food production became the largest manufacturing sector (purdy, 2016). across the nation, the use of satellite technologies is enabling farmers to deal with challenges of low yield and excessive use of fertilizer which often leads to soil and groundwater pollution. with optical satellites, it has been possible to show how well crops are growing by measuring how they absorb solar radiation in the visible and nearinfrared spectrum to produce a ‘normalised difference vegetation index’ (ndvi). the ndvi is proportional to the amount of chlorophyll in the crops (higher chlorophyll reflects more light in green and infrared spectra), which changes as crops grow or their health changes. so, by monitoring chlorophyll levels using the ndvi, farmers are able to determine areas of over-dose and under-application of fertilizer prompting corrective responses. based on the ndvi, the satellite navigational systems can also be used to remotely control a tractor to differentially apply fertilizer to various areas of the farm depending on the predicted yield level. consequently, farmers can make significant savings in total fertilizer use as well as in costs while reductions are recorded in nitrate run-off and pollution of soil and groundwater. furthermore, satellite imaging can monitor soil water level and guide irrigation use (steven, 2006). in india, space technology and land-based observations are important in taking informed decisions on agricultural production through the use of regularly generated updates on crop production statistics as well as the provision of inputs to achieve sustainable agriculture. in fact, the indian national remote sensing centre (chizea et al., 2006) indicated that the satellitebased optical and radar imagery are used widely in agriculture monitoring. while radar imagery http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 7 is especially used during monsoon season, the integrated use of geospatial tools with crop models and in-situ observation system enables timely crop production forecasts, and drought assessment and monitoring. other achievements of space technology in india include agricultural land-use mapping, the horticultural crop inventory, the agro-meteorological parameter retrieval, and inputs to agro-advisory services as well as methane emission inventory and carbon accounting. with these, india can map its soil, monitor its agricultural land area, soil and its water resources, assess and monitor drought, estimate cropped areas, determine crop stand counts, forecast the weather, annual crop yields as well as incidence of pests and disease detection as shown in figure 3. in animal agriculture, it can also guide aquaculture/fishery development and probably animal tracking and census (mody et al, 1987). figure 3: uses of space technology in agriculture in india. mody et al. (1987) in its strides, nigeria joined the space technology race in 1976 when it planned to launch a satellite but this was not actualized then. to date, nigeria has launched five satellites: nigeriasat-1, the first of nigeria’s satellites launched 27 september, 2003 “to give early warning signals of environmental disaster; to help detect and control desertification in the northern part of nigeria; to assist in demographic planning; to establish the relationship between vectors and the environment that breeds malaria and to give early warning signals on future outbreaks of meningitis using remote sensing technology; to provide the technology needed to bring education to all parts of the country through distant learning; and to aid in conflict resolution and border disputes by mapping out state and international borders”. nigeriasat-1 is one of the disaster monitoring satellites in the global disaster monitoring constellation networked to share data and information at the threat of a disaster. https://en.wikipedia.org/wiki/desertification https://en.wikipedia.org/wiki/demographic https://en.wikipedia.org/wiki/meningitis file:///c:/users/user/downloads/azojete143/www.azojete.com.ng njoku, p. c.: revolutionizing agriculture through space science and technology applications. azojete, 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 8 nigcomsat-1 – nigeria’s second and africa’s first communication satellite was built in 2004 and launched in may 2007. this satellite, which was designed to provide transponders that would cover most of africa but was lost in orbit in 2007 and was switched off in november 2008. nigcomsat-1r, launched as a replacement for nigcomsat-1, was launched on 19 december, 2011 to continue the objectives of nigcomsat-1. nigeriasat-2 and nigeriasat-x, a medium to high-resolution earth satellite launched on 17 august, 2011. nigeriasat-2 was designed to support food security, agricultural, geological, mapping and security applications as well as to support the national development of gis application while also continuing the objectives of nigeriasat-1 but with medium to higher resolution and precision launched to map the city of lagos as well as take infra-red readings on land use. nigeriasat-1 and nigeriasat-2 are complementary as nigeriasat-1 is useful in nigeria to monitor pollution, land use and other medium-scale phenomena, offer satellite data for farmers on where to apply water and fertilizer, keep data on the spread of the desert in nigeria. the satellites will also provide data on disaster, in an unfortunate event (ikpaya et al., 2017) from the above uses indicated for some countries and the extant situation in nigeria, space science and technology are a most potent technology which can be used to explore and enhance agriculture, environment including drought and desertification, mining, water supply, transportation, communications and indeed most sectors of the economy (chizea et al., 2006). 5. scope of use of space science and technology in agriculture the united nations office for outer space affairs has shown that the use of space technology has continued to expand in scope and breadth. in a publication (united nations 2016),the organisation noted the need for a concerted global action on the challenge elucidated by the key sustainable development goal (sdg) of “ending hunger, achieving food security and improved nutrition, and promoting sustainable agriculture”. director, simonetta di’pippo, had surmised that to achieve this goal, ‘advanced tools and solutions’ must be applied in the concerted global actions. such tools, he said were available from space science, technology and applications for “the monitoring of crops, livestock, forestry, fisheries, aquaculture, and in supporting farmers, fisherfolk, foresters and policymakers in efforts to employ diverse methods of achieving sustainable food production and to respond to related challenges such as adverse weather conditions, droughts, floods, desertification and land degradation, vegetation fires, and disasters triggered by natural phenomena”. the office specifically identified current uses of space or satellite technology in agriculture and related activities. this included its use in agricultural research and development, biodiversity, desertification, drought, fisheries and aquaculture, irrigation and water, landscape mapping, monitoring agricultural production, vegetation fires, weather monitoring and forecasting, and managing, mitigating and preparing for disasters. 6. emerging concepts in agriculture contingent on space technology development smart or precision agriculture hemlata et al. (2015) has defined smart agriculture as “an approach to understand the basic requirements as well as the changes in current environment due to external factors based on the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 9 context information and utilization of collected data to optimize sensors’ operation or influence the operations of actuators to change the current environment”. they further identified the process to achieve smart agriculture as: “sensing local agricultural parameters (observation) identification of sensing location and data gathering (observation) transferring data from crop field to control station for decision making (diagnostics) decision making based on local data, domain knowledge and history (decision) actuation and control based on decision” (implementation) smart or precision agriculture recognizes the complexity of an agriculture system with several different variables/inputs – land, soil, seeds, water, fertilizer, and weather – all interacting concurrently to produce an output. to obtain the best output, cutting-edge technologies, including space technology-powered sensors, are used to collect field data from crops which are fed into different computer and ict models to determine the precise combination of the variables that will give the best outcomes. hemlata et al. (2015) also gave some examples whereby, sensors on unmanned aerial vehicles (uavs) or drones are used to collect the requisite data on several parameters such as plant or animal numbers, plant height, nitrogen measure, plant health, disease pressure, drought stress and canopy temperature to determine precise levels of inputs to be used on the farm. this precise combination is then applied using electronically controlled farm tractors to deliver determined levels of each input to the crop farm to enable the crop and the far to produce optimally. marco et al. (2019) concluded that smart agriculture ensures that the crop is exposed to the best genetic and environmental conditions which elicit the ideal physiological state to generate optimal crop yields in a location as we drive to achieve sustainable food security. smart agriculture recognizes the limitations in agricultural value chains and uses the most proficient technologies to correct them so that optimal results are achieved. in effect, precision or smart agriculture eliminates input waste as it enables the farmer to achieve more yield with less input. artificial intelligence artificial intelligence (ai), also called machine intelligence is a space technology powered nonnatural intelligence application that uses imagery to learn and perceive specific characteristics and is able to reproduce or apply the knowledge. ai is designed with capacity for speech recognition, learning, planning and problem solving which are used to diagnose plant diseases in farms and it also has the capacity to characterize them as individual diseases even among a collection of diseases. in their paper, ikpaya et al. (2017) it was concluded that ai application has been used, in india to advise farmers on dates to sow their seeds with a resultant 30 percent higher yield. it can also be used to advise farmers on land preparation and application of disease protection measures. this practice is similar to the use of the e-wallet in dispensing agricultural inputs to nigerian farmers. in either case, all that was required was that the farmer was registered and that they owned basic telephones that can receive text messages. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng njoku, p. c.: revolutionizing agriculture through space science and technology applications. azojete, 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 10 climate change one of the most serious challenges of humanity today is climate change. global attention has been drawn to this phenomenon with the convocation of major summits resulting in declarations and memoranda of understanding to which almost all nations subscribed. though the usa recently reneged by withdrawing its subscription, the world continues to be influenced by the varying changes taking place in the climate across the universe – from the perceptible rise in environmental temperature to increased de-icing of the north pole, increase in ocean heights, flooding resulting in major erosions, increases in incidences of drought, an escalation in the loss of vegetative cover and ultimate desertification and lot more effects. ikpaya et al. (2017) concluded that a further 4°c rise in global core temperature will significantly cause the elimination of most live species as it is known today. according to akinyede et al. (2015), space technology has been useful in identifying the primary cause of climate change which is the depletion of the ozone layer caused by several human induced activities including the production of greenhouse gases and the release of carbon dioxide. space technology powered applications are currently being used to detect and track temperature changes and the effects, the changes in the seasons rain and heat, loss of vegetation and advents of drought and desertification. in effect, application of space technologies provides knowledge about the climate and information about its contingent effects and these advise early warning and effective environmental monitoring and assessment of the impact of remedial strategies which can have major effects on agriculture. agricultural insurance according to mody et al. (1987), india, government has developed some insurance policies for farmers which include crop insurance, loss of life, accidental death and disability, student safety, household, agricultural implements and tractors agricultural insurance is a tool that brings stability to farming. assurance of compensation for loss of agricultural investment due to untoward events is important in encouraging people to invest in agricultural activities. to be able to properly determine losses, insurance companies must be aware of the state of the farm preand post-disaster and this can be done with remote sensing and drones. 7. conclusion the united nation surmises that the global food supply must increase by at least 70% by 2020 for the world to be able to feed its projected population of nearly 9 billion by 2020. for nigeria, that is currently averagely underfed, food supply must increase by at least 200% for the nation to adequately feed its projected population of 206million by 2020, this may be classically impossible to achieve but it draws attention to the urgent need for nigeria to raise its game by significantly enhancing its agricultural productivity and production levels if it must achieve food and nutrition security in the near future. to do this, nigeria must institute a consciously coordinated agricultural revolution or marshal plan. cognisant of the current state of nigeria’s agriculture, it will require a most vigorous programme, a national commitment second to none, and the deployment of most effective and efficient technologies. space technology is robust, comprehensive and sensitive. it achieves more production for less input, it can drive a sustainable and resilient agricultural system. indeed, space technology holds an ace in http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 11 crystallizing nigeria’s agricultural revolution challenge. in that regard, this conference is critical in defining the course to greater satellite technological input in the effort to revolutionize agriculture in nigeria. ladies and gentlemen, it is dawn, the journey must begin! 8. recommendations space science and technology research was primarily intended to study the outer space, the evolution of the stars and galaxies to help man understand the foundation of and changes in the universe. however, it veered also into agriculture, among other sectors, in a critically beneficial spin-off with capacity to significantly influence agriculture and its related events and activities. cognisant of the global race in the development and consolidation of the use of space science and technology applications in agriculture as well as nigeria’s low rating the following recommendations are made: the government of the federal republic of nigeria should statutorily allocate annually 3percent of the consolidated revenue fund of the federation to significantly upscale sustained development of space science and technology in nigeria. furthermore, government should expedite the development and launching of nigcomsat-2 and nigcomsat-3 with a specific target achievement date to enhance nigeria’s communications reach and efficiency and bring enhanced impetus in the national space technology development programme; the federal government of nigeria should establish a joint task committee comprising the federal ministries of agriculture and rural development (fmard), water resources, and environment as well as the centre for satellite technology development (cstd)/nasrda to identify, develop and promote priority space technology-driven packages needed to i) facilitate agriculture, particularly among small and medium scale farmers, ii) monitor surface and underground water sources and proper channeling of floods into reservoirs for irrigation purposes, and iii) commence activities for the reversal of desertification, and provide early warning for erosion and healing of existing erosion sites in nigeria fmard should utilize the capacities of cstd/nasrda in conducting an automated national agricultural resources census to facilitate national agricultural planning for a livestock census, the exercise should generate comprehensive individual animal characteristics to aid livestock identification and tagging to enhance traceability, eliminate rustling, and facilitate the tracking of trans-boundary diseases; cognisant of the serious negative effects of climate change in nigeria, the nasrda should intensify research on drought and the encroachment of the desert to enhance its capacity in early warning and advice on remedial programmes. specifically, cstd/nasrda should promote research in satellite-enabled capacity for conducting survey of underground aquifers to enhance irrigation in dry land and desert areas producing more location specific agro-meteorological prescriptions producing simple farm area estimators and diseases detector producing simple probes for determining soil water needs and nutrients gaps in the farm to facilitate precision agriculture farm land mapping for crop intensification; forecasting of farm yield for planning and insurance purposes file:///c:/users/user/downloads/azojete143/www.azojete.com.ng njoku, p. c.: revolutionizing agriculture through space science and technology applications. azojete, 15(sp.i2):1-13. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: placid.njoku@gmail.com 12 remote sensing of degraded land for land reclamation purposes cstd and nasrda should make the small and medium scale farmer, the producers of over 80% of nigeria’s agricultural production, as their primary clients of interest and produce simple but powerful satellite technology tools to reduce their drudgery, enhance the efficiency of their production, and increase their profit; and cstd and nasrda should engage in more advocacy on the capacities of and opportunities in satellite technology to attract the buy-in of entrepreneurs, farmers’ and nigerian society. space technology applications can significantly influence food production systems and can be key to food security as it can enhance productivity, resilience and profitability. critical issues of food supply, water availability, soil conditions, climate change and weather conditions can be predicted and monitored with derivatives of space technology. references akande, so. 1998. public policy in nigerian agriculture. in: institutional reforms for agricultural development. 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https://link.springer.com/journal/10971/40/2/page/1 http://www.unoosa.org/res/oosadoc/data/documents/2016/stspace/stspace69_0_html/st_space_69e.pdf http://www.unoosa.org/res/oosadoc/data/documents/2016/stspace/stspace69_0_html/st_space_69e.pdf http://www.unoosa.org/oosa/en/ourwork/topics/space-and-climate-change.html http://www.unoosa.org/oosa/en/ourwork/topics/space-and-climate-change.html https://www.vanguardngr.com/2017/12/fg-plans-exploit-potentials-science-technology-boost-economy/ https://www.vanguardngr.com/2017/12/fg-plans-exploit-potentials-science-technology-boost-economy/ file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):53-64 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 23 original research article effects of rice husk ash on durability of self-compacting concrete made with cassava peel ash m.t. abdulwahab1*, o. a. u. uche1, a. aboshio1, a. mohammed1, a. suleiman2, a. m. auwal1, and s. u. chidawa3 1department of civil engineering, bayero university kano, kano, nigeria 2department of civil engineering, abubakar tafawa balewa university, bauchi, nigeria 3department of civil engineering, nile university, fct, nigeria *corresponding author’s email address: amtaytechnology@yahoo.com 1.0 introduction concrete is important in most structures and projects in general. it is a composite material composed of fine and coarse aggregates bonded together with cement and a precise proportion of water. according to csi (2009) the global use of concrete is estimated to rise to around 25 billion tons per year, which translate to more than 3.8 tons per person per year. self-compacting concrete (scc) has become one of the most sought types of concrete since it was first launched in the early 1990s (schutter and audernaert, 2007), and it has created a new area of research in the field of concrete technology. according to mohammed (2011) scc is a concrete that can be poured and compacted under its own weight with little or no vibration effort while being cohesive enough to be handled without segregation or bleeding of the fresh concrete. it has various advantages, including easier placement, the elimination of the requirement for compaction, and the saving of time and labour costs. for improved slump flow and segregation resistance, the scc depends on increased binder (cement) proportion and the use of super-plasticizers. conversely, the significant energy consumption and release of carbon dioxide into the environment while manufacturing cement is a major source of worry (kong and sanjayan, 2008). according to malhotra (2002), the quantity of carbon dioxide exhaled when manufacturing 1000 kg of cement is approximately one (1) ton per year, which is caused by limestone calcination and fossil fuel burning. furthermore, the international energy agency (iea) estimates that the cement industry releases 2.4 billion tons of co2 as at the year 2020, accounting for 7% of total emissions. article information abstract self-compacting concrete (scc) is a highly flowable concrete with improved strength and surface smoothness. the preparation of scc requires high amount of cement. this utilizes tremendous amount of energy and releases carbon dioxide into the atmosphere. it is critical to reduce co2 emissions during portland cement (pc) manufacture by partially replacing cement in the scc. this study evaluates the durability characteristics of scc produced using cassava peel ash (cpa) combined with rice husk ash (rha) at 5, 10, 15, 20, and 25 percent cement replacement levels respectively. the effects of water absorption, h2so4 attack, mgso4 attack, and high heat on scc made with cpa and rha blends were examined. the results show that, as cpa and rha proportions rise by approximately 5% cpa and 10% cpa+rha substitution, scc compressive strength equates to design strength (grade 35). it was also discovered that cpa and rha both enhance resistance to h2so4 and mgso4 degradation, but perform poorly when exposed to elevated temperatures when compared to the control specimen. however, when cpa is utilized with rha in scc, the rate of water absorption is reduced to a minimum due to an enhanced pore structure of the cpa-scc specimen. generally, a 5% cpa content is considered as the optimum replacement of cement for self-compacting concrete with grade 35. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 august, 2021 revised 23 november, 2021 accepted 30 november, 2021 keywords: portland cement self-compacting concrete cassava peel ash rice husk ash super-plasticizer durability properties http://www.azojete.com.ng/ mailto:amtaytechnology@yahoo.com mailto:amtaytechnology@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):53-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 54 it is noteworthy that the use of new and environmentally friendly concrete with a low cement percentage through partial substitution with agricultural wastes such as cassava peel, rice husk, and millet husk become a very appealing way to reducing this risk. according to adesanya et al. (2008), the cassava peel accounts for 20-35 percent of the weight of the tuber, especially when hand peeling. the presence of huge amounts of cassava peel waste near garri processing centers is a source of concern and pollution, as attempts to eliminate them through combustion or natural decomposition are occasionally futile. according to ettu et al. (2013b), the rate of dumping of cassava peelings is 5-8 times higher than the rate of biodegradation in open-air dumpsites. rice husk, on the other hand, had commonly been thrown into water streams, causing pollution and contamination of springs until it was discovered to be a beneficial mineral additive for concrete (sua-iam and makul, 2012; krishna et al., 2016). it contains a large amount of silicon dioxide (sio2), is a superpozzolana, and is recommended for use in concrete production (sheth et al., 2014; aboshio et al., 2018). hence, recycling such agricultural wastes into new construction materials might be a realistic key to the ecological pollutant. therefore, this study is aimed at investigating the durability performance of selfcompacting concrete using different percentage of ternary blends (cpa and rha) as substitute to cement. 2. materials and methods 2.1 materials the materials used for this study are portland cement of dangote brand 42.5r (main binder), cassava peel ash and rice husk ash as pozzolanic binders with specific gravities of 2.01 and 2.07, respectively. cassava peels were gathered from various cassava farmers' disposal sites in dadin-duniya village, gabasawa local government area, kano, nigeria. they were collected in 50 kg bags, washed, and then air-dried for 48 hours to remove moisture. rice husks were obtained from rice milling plants in kura town, kura local government area, kano, nigeria. they were each burned for two (2) hours at a controlled temperature of 600°c, allowed to cool, and then sieved through a 75 µm british standard sieve to generate fine ash. the chemical composition of cement, cpa, and rha as determined by x-ray fluorescence (xrf) test using xrf nitron 300 machine is shown in table 1. table 1: oxides analysis of binders oxide cement cpa rha sio2 15.614 43.164 82.171 al2o3 3.222 3.945 0.403 fe2o3 3.343 3.320 1.680 cao 74.088 21.090 5.518 mgo 0 3.395 1.331 cuo 0.003 0.003 0.002 mno 0.045 0.056 0.345 cr2o3 0 0.005 0 tio2 0.058 0.475 0.164 zno 0.004 0.055 0.222 loi 3.13 15.27 4.940 sg 3.16 2.01 2.07 fineness 13 26 28 clean river sand (fine aggregate) with a specific gravity of 2.62 sourced from river challawa in kano, nigeria was used. sieve analysis was conducted on the fine aggregate, and it was classed as zone 2 using bs en 882 (1992) grading limitation as depicted in figure 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amtaytechnology@yahoo.com abdulwahab et al: effects of rice husk ash on durability of self-compacting concrete made with cassava peel ash. azojete, 18(1):53-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 55 figure 1: sieve analysis chart of ashes and aggregates a 20 mm sized machine crushed gravel stone was used as the coarse aggregates. the aggregate’s specific gravity and crushing value are 2.7 and 22 % respectively. drinking water that meets the astm c1602-12 (2012) was used for the scc’s batching and curing. a chloride-free liquid super-plasticizer was added to the scc’s mix at 1.4% weight of binder as described by the manufacturer to improve its workability. 2.2 sample preparation and testing efnarc (2005) and aci (2002) specifications and guidelines were used in conjunction with trial experiments to achieve a mix design with grade 35 strength of scc. as recommended by the manufacturer, 1.4% of weight of the binder’s weight was utilized as the dosage of the superplasticizer. the proportions for varied cpa and rha substitutions are as shown in tables 2-3 respectively. table 2: scc mix proportion for cpa contents mix no. cpa (%) cement (kg/m3) cpa (kg/m3) fine aggregates (kg/m3) coarse aggregates (kg/m3) water (kg/m3) superplasticizer (kg/m3) mcp-00 0 500 0 805.46 884.56 200 7 mcp-01 5 475 25 805.46 884.56 200 7 mcp-02 10 450 50 805.46 884.56 200 7 mcp-03 15 425 75 805.46 884.56 200 7 mcp-04 20 400 100 805.46 884.56 200 7 mcp-05 25 375 125 805.46 884.56 200 7 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 p a s s in g ( % ) sieve size (mm) fine aggregate coarse aggregate cpa rha zone 2 lower limit zone 2 upper limit http://www.azojete.com.ng/ mailto:amtaytechnology@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):53-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 56 table 3: scc mix proportion for cpa + rha blends mix no. cpa (%) rha (%) cement (kg/m3) cpa (kg/m3) rha (kg/m3) fine aggregates (kg/m3) coarse aggregates (kg/m3) water (kg/m3) superplasticizer (kg/m3) mcr-00 0 0 500 0 0 805.46 884.56 200 7 mcr-01 0 10 450 0 50 805.46 884.56 200 7 mcr-02 5 10 425 25 50 805.46 884.56 200 7 mcr-03 10 10 400 50 50 805.46 884.56 200 7 mcr-04 15 10 375 75 50 805.46 884.56 200 7 for compressive strength testing, fifty-four (54) samples of scc made with cpa and forty-five (45) specimens made with rha blends were used following the mix proportions from tables 2 and 3. cement, cpa, and rha were thoroughly dry mixed and added to fine aggregate, which was then mixed with the coarse aggregate. water and super-plasticizer were manually added while mixing, and the material was cast using a 100 mm diameter and 200 mm length steel cylinder moulds. they were allowed to set for 24 hours at room temperature and were demoulded before curing in water for 3, 7, and 28 days, according to bs en 12390-2 (2019). 2.2.1 water absorption the water absorption test was carried out in accordance with bs en 1881-122 (2020) on eighteen (18) 100 mm x 100 mm x 100 mm cubes made at 0, 5, 10, 15, 20, and 25% cement substitution with cpa and then immersed in water for 28 days. the specimens were air-dried for 24 hours before being weighed and recorded. they were then cured in water for 7 days before being air-dried and re-weighed to calculate the amount of water absorbed using equation 1. when blending with rha, the procedure was repeated. water absorption = w2−w1 w1 × 100% (1) where: w1 = weight of dried cube (g), w2 = weight of saturated cube (g) 2.2.2 acid and sulfate attack in a container, a 5% solution of hydrogen tetraoxosulphate (vi) acid (h2so4) was prepared, and eighteen (18) concrete cylinders of 100 mm diameter and 200 mm height were weighed and immersed in the acidic solution after curing in water for 28 days. the specimens were then cured in the solution for 3, 7, and 28 days, respectively. the specimens were air dried and reweighed after the curing intervals to evaluate the weight loss of scc containing cpa subjected to acidic aggression using equation 2. another set of scc specimens were made using cpa+rha at 10%, 15%, 20%, and 25% cement substitution, and the procedure was repeated. the whole experiment was repeated to assess the effect of salt, but this time using a 5% solution of magnesium tetraoxosulphate (v) (mgso4). this method is similar to that of ogork and uche (2014). 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 𝑙𝑜𝑠𝑠 = 𝐿𝑜𝑠𝑠 𝑖𝑛 𝑤𝑒𝑖𝑔ℎ𝑡 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 × 100% (2) 2.2.3 effect of elevated temperature after curing for 28 days in water, hardened cpa scc and those of cpa + rha cubes of 100 mm x 100 mm x 100 mm were weighed and then exposed to excessive temperature for one (1) hour using a carbolite cwf1100 model furnace at a temperature range of 0 °c to 1000 °c at 200 °c intervals and file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amtaytechnology@yahoo.com abdulwahab et al: effects of rice husk ash on durability of self-compacting concrete made with cassava peel ash. azojete, 18(1):53-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 57 then allowed to cool. after reweighing, the effect of the increasing temperature was analyzed using equation 3. this is in conformity to the procedure followed by ogork and auwal (2017). percentage weight loss = w1−w2 w1 × 100(%) (3) where: w1 = initial weight (g) w2 = final weight (g) 3. results and discussion 3.1 strength development figure 2 depicts the compressive strength obtained from various cpa scc mixtures utilized in this investigation. the strength increases with curing age at 3, 7, and 28 days, while it declines with increasing cpa content. also, when mix mcp-01 is utilized, the strength (36 mpa) after curing for 28 days is somewhat higher than grade 35 scc (35 mpa) being design strength. the pozzolanic interaction of ca(oh)2 during cement hydration and cpa sio2 could explain the increase in strength with curing age. the observation is also consistent with raheem et al. (2015) report that cpa has the ability to contribute to 28-day strength growth when utilized at 5%. figure 2: compressive strength of cpa scc as rha is blended into the cpa scc using mix mcr-01 (0 % cpa + 10 % rha), the strength increases above the control samples and then decreases with increased cement content replacement, as shown in figure 3. this increase in strength could be attributed to the stronger pozzolanic reaction of rha content, as well as a superior filler effect than cpa. this is comparable to the conclusions reached by ogork and uche (2014) while dealing with groundnut husk waste. 17.5 16.0 15.0 12.4 11.7 10.5 25.5 22.6 18.6 17.1 15.3 14.8 40.7 36.0 30.4 26.6 22.7 20.1 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 mcp-00 mcp-01 mcp-02 mcp-03 mcp-04 mcp-05 c o m p re ss iv e st re n gt h ( m p a) cpa scc mixes 3 days 7 days 28 days http://www.azojete.com.ng/ mailto:amtaytechnology@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):53-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 58 figure 3: compressive strength of cpa + rha scc blends 3.2 water absorption as shown in figure 4, the water absorption capacity of cpa scc reduces as the percentage of cement replaced with cpa increases (raheem et al., 2015). figure 4: water absorption for cpa scc the decrease in water absorption may be due to the reduction of holes as the cpa concentration increases, which also improves the uniformity of the scc. 17.5 17.7 17.0 12.8 12.4 25.5 25.9 23.9 18.9 18.3 40.7 41.5 38.9 31.9 26.4 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 mcr-00 mcr-01 mcr-02 mcr-03 mcr-04 c o m p re ss iv e st re n gt h ( m p a) cpa + rha scc mixes 3 days 7 days 28 days 0.52 0.41 0.34 0.30 0.20 0.15 0.00 0.10 0.20 0.30 0.40 0.50 0.60 mcp-00 mcp-01 mcp-02 mcp-03 mcp-04 mcp-05 w at er a b so rp ti o n ( % ) cpa mixes file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amtaytechnology@yahoo.com abdulwahab et al: effects of rice husk ash on durability of self-compacting concrete made with cassava peel ash. azojete, 18(1):53-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 59 it was also discovered that when rha was introduced to the cpa scc for mcr-01 (10%) and mcr-03 (20%) mixes compared to the cpa scc without rha, there was a slight decrease in water absorption, as shown in figure 5. the reduced water absorption could be related to the further lowering of porosity of cpa scc as rha with smaller particles is blended to fill more voids (safiuddin et al., 2011). figure 5: water absorption for cpa + rha scc 3.3 immersion in sulphuric acid (h2so4) the weight of scc made with cpa and rha when immersed in a 5% solution of h2so4 decreases with age, as shown in figures 6 and 7. this is consistent with olonade’s et al. (2014) conclusion that when cured in sulphuric acid solution, the mass of cpa concrete cubes gradually decreases with age. the weight loss might be attributed to the greater cao content of portland cement and the weaker gypsum generated as a result of the neutralization reaction between h2so4 and ca(oh)2. 0.52 0.33 0.30 0.19 0.15 0.00 0.10 0.20 0.30 0.40 0.50 0.60 mcr-00 mcr-01 mcr-02 mcr-03 mcr-04 w at e r a b so rp ti o n ( % ) cpa + rha mixes http://www.azojete.com.ng/ mailto:amtaytechnology@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):53-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 60 figure 6: effect of immersion in h2so4 for cpa scc it was also discovered that during the sulphate attack, sulphate ions react with cement hydration products, resulting in an alteration of the c-s-h structure and a decrease in scc strength. it is worth mentioning that the sulphate attack on the cpa scc decreases below the control with increasing cpa concentration, which could be attributed to the lower cao content of cpa particles compared to portland cement (chatveera and lertwattanaruk, 2011). however, when rha is combined with cpa scc, there is a modest improvement in sulphate attack, as reported by sakr (2006). figure 7: effect of immersion in h2so4 for cpa + rha scc 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 5 10 15 20 25 30 w ei g h t lo ss ( % ) curing age (days) 0% cpa 5% cpa 10% cpa 15% cpa 20% cpa 25% cpa 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 5 10 15 20 25 30 w ei g h t lo ss ( % ) curing age (days) 0% cpa-rha 10% cpa-rha 15% cpa-rha 20% cpa-rha 25% cpa-rha file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amtaytechnology@yahoo.com abdulwahab et al: effects of rice husk ash on durability of self-compacting concrete made with cassava peel ash. azojete, 18(1):53-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 61 3.4 immersion in magnesium sulphate (mgso4) as shown in figures 8 and 9, the attack of sulphate on cpa scc rises with immersion age, which reduces its weight. this could be due to continual sulphate exposure over time. figure 8: effect of immersion in mgso4 for cpa scc the weight loss experienced by the cpa + rha scc, on the other hand, decreased as the cpa content blended with rha increased. this was due to the pozzolanic reaction and the ability of both cpa and rha to fill empty voids in the cpa-rha scc (chatveera and lertwattanaruk, 2011). figure 9: effect of immersion in mgso4 for cpa + rha scc 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0 5 10 15 20 25 30 w ei g h t lo ss ( % ) curing age (days) 0% cpa 5% cpa 10% cpa 15% cpa 20% cpa 25% cpa 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0 5 10 15 20 25 30 w ei g h t lo ss ( % ) curing age (days) 0% cpa-rha 10% cpa-rha 15% cpa-rha 20% cpa-rha 25% cpa-rha http://www.azojete.com.ng/ mailto:amtaytechnology@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):53-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 62 3.5 effect of elevated temperature the effect of increased temperature on cpa scc, as shown in figures 10 and 11, demonstrates that scc produced with cpa and rha loses weight as the temperature rises and the cpa ratio rises. this could happen due to dehydration of hydrated calcium silicate, which increases internal stresses and causes micro cracks on the specimens (othuman and wang, 2012). figure 10: effect of elevated temperature on weight loss of cpa scc according to ogork and auwal (2017), the weight loss could potentially be attributable to the removal of excess pore water in the scc specimen. however, when the temperature exceeds 600°c, the cpa scc changes colour from grey to slightly yellowish grey, whereas it changes from 400°c and above when rha is added. figure 11: effect of elevated temperature on weight loss of cpa + rha scc 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 200 400 600 800 1000 1200 w ei g h t lo ss ( % ) axis title 0% cpa 5% cpa 10% cpa 15% cpa 20% cpa 25% cpa 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 200 400 600 800 1000 1200 w ei g h t lo ss ( % ) temperature (degrees) 0% cpa-rha 10% cpa-rha 15% cpa-rha 20% cpa-rha 25% cpa-rha file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amtaytechnology@yahoo.com abdulwahab et al: effects of rice husk ash on durability of self-compacting concrete made with cassava peel ash. azojete, 18(1):53-64. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 63 4. conclusion the findings of the study revealed that scc compressive strength equates to the design strength (35n/mm2) as cpa and rha proportions rise by no more than 5% cpa and 10% cpa+rha substitution, respectively. the usage of cpa and rha in scc reduces the scc's water absorption. also, the resistance to h2so4 and mgso4 degradation increase with increase in the content of cpa in scc while it experiences more resistance when rha is added to the cpa scc. furthermore, the heat resistance of cpa and cpa+rha scc decreases as the content of cpa and rha increases. references aboshio, a., shuaibu, hg. and abdulwahab, mt. 2018. properties of rice husk ash concrete with periwinkle shell as coarse aggregates. nigerian journal of technological development, (15)2: 33-38. aci 211.1-91 2002. standard practice for selecting proportions for normal, heavyweight, and mass concrete. adesanya, oa., oluyemi, ka., josiah, sj., adesanya, ra., shittu, laj., ofusori, da, bankole, ma. and babalola, gb. 2008. ethanol production by saccharomyces cereviasiae from cassava peel hydrolysate. the internet journal of microbiology, 5(1): 25-35. astm c1602-12 2012. standard specification for mixing water used in the production hydraulic cement concrete, astm international, west conshohocken, pa, 2012, www.astm.org. british standard institution 2019. testing hardened concrete – part 2, bs en 12390 – 2 – making and curing specimens for strength tests, london, bsi. british standard institution 2020. testing concrete, bs en 1881 – 122 method for determination of water absorption, london, bsi. bs en 882 1992. specification for natural aggregates from natural sources. british standard institute, london. cement sustainability initiative 2009. cement sustainability initiative. also available at: http://www.wbcsdcement.org/index.php/key-issues/sustainabilitywith [accessed: 28-12 2017]. chatveera, b. and lertwattanaruk, p. 2011. durability of conventional concretes containing black rice husk ash. journal of environmental management, 92(1): 59–66. de schutter, g. and audenaert, k. 2007. report 38: durability of self-compacting concrete-state-of-theart report of rilem technical committee 205-dsc, rilem publications. ettu, lo., ezeh, jc., ibearugbulem, om., anya, uc. and njoku, ko. 2013b. strength of binary blended cement composites containing cassava waste ash. international journal of emerging technology and advanced engineering, 3(4): 15-20. also available online at www.ijetae.com. european federation of national associations representing for concrete efnarc 2005. the european guidelines for self-compacting concrete specification, production and use. efnarc, uk (www.efnarc.org): 1-63. kong, dly. and sanjayan, jg. 2008. damage behavior of geopolymer composites exposed to elevated temperatures,” cement and concrete composites, 30(10): 986–991. krishna, nk., sandeep, s. and mini, km. 2016. study of concrete with partial replacement of cement by rice husk ash. iop conference series: materials science and engineering, 149(1): 012109, doi:10.1088/1757-899x/149/1/012109. malhotra, vm. 2002. introduction sustainable development and concrete technology. aci concrete international, 24(7): 22. http://www.azojete.com.ng/ mailto:amtaytechnology@yahoo.com http://www.astm.org/ http://www.wbcsdcement.org/index.php/key-issues/sustainabilitywithhttp://www.ijetae.com/ http://www.efnarc.org/ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):53-64. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtaytechnology@yahoo.com 64 mohammed, ha. 2011. effect of fly ash and silica fume on compressive strength of self-compacting concrete under different curing conditions. ain shams engineering journal, 2(1): 79-86. ogork, en. and auwal, am. 2017. durability characteristics of self-compacting concrete incorporating corn cob ash. card international journal of engineering and emerging scientific discovery, 2(1): 29-41. ogork, en. and uche, oa. 2014. effects of groundnut husk ash (gha) in cement paste and mortar. international journal of civil engineering and technology (ijcet), 5(10): 88-95. olonade, ka., olajumoke, am., omotosho, ao. and oyekunle, fa. 2014. effects of sulphuric acid on the compressive strength of blended cement – cassava peel ash concrete. construction materials and structures, s.o. ekolu et al. (eds.), ios press, 764-771. doi: 10.3233/978-1-61499-466-4-764. othuman, ma. and wang, yc. 2012. thermal and mechanical properties of lightweight foamed concrete at elevated temperatures. magazine of concrete research, 64(3): 213-224. also available on https://doi.org/10.1680/macr.10.00162. raheem, sb., arubike, ed. and awogboro, os. 2015. effects of cassava peel ash (cpa) as alternative binder in concrete. international journal of constructive research in civil engineering (ijcrce) 1(2): 2732. safiuddin, m., west, js. and soudki, ka. 2011. flowing ability of the mortars formulated from selfcompacting concretes incorporating rice husk ash. construction and building materials, 25(2): 973-978. sakr, k. 2006. effects of silica fume and rice husk ash on the properties of heavy weight concrete. journal of material and civil engineering, 18(3): 367-376. sheth, a., goel, a. and pai, bhv. 2014. properties of concrete on replacement of coarse aggregate and cementitious materials with styfoam and rice husk ash. american journal of engineering research (ajer), 3(1): 268-271. sua-iam, g. and makul, n. 2012. self-compacting concrete prepared using rice husk ash waste from electric power plants. advanced materials research, 488-489: 258-262, doi:10.4028/www.scientific.net/amr.488489.258 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amtaytechnology@yahoo.com https://www.research.manchester.ac.uk/portal/yong.wang.html https://www.research.manchester.ac.uk/portal/en/publications/thermal-and-mechanical-properties-of-lightweight-foamed-concrete-at-elevated-temperatures(8cee2859-26d1-4f05-bbc3-c4a96a1aa2aa).html https://www.research.manchester.ac.uk/portal/en/publications/thermal-and-mechanical-properties-of-lightweight-foamed-concrete-at-elevated-temperatures(8cee2859-26d1-4f05-bbc3-c4a96a1aa2aa).html https://doi.org/10.1680/macr.10.00162 variation in foliage yield and yield component traits as influenced by harvest and preferences for leaf quality traits in amaranth cruentus [l arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):61-71 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 61 variation in foliage yield and yield component traits and preference for leaf quality traits in amaranthus cruentus [l.] genotypes o.t. adeniji, 1* a.a. badmus, 1 e. sabo 2 and j.m. peter 3 1 department of crop science and horticulture, federal university oye ekiti, nigeria 2 department of agricultural extension, national open university of nigeria 3 department of crop science, adamawa state university, nigeria corresponding author’s e-mail address: waleniji@gmail.com, olawale.adeniji@fuoye.edu.ng abstract amaranthus cruentus is a traditional leaf vegetable in nigeria. at present, there are few commercial varieties. development of new varieties requires systematic assessment of foliage yield and yield contributing traits. the objectives of this study are to evaluate variation for foliage yield and yield traits, determine the influence of time of harvest (4 or 5 weeks after sowing) on foliage yield, and assess preference for genotypes, leaf yield and leaf quality traits. nine amaranthus cruentus genotypes were grown in a randomized complete blocks design with three replications. sunken beds were made at 1 m x 2 m, each bed was separated by alley of 1m. a total of 16 beds constituted a replicate, 8 beds were allotted to harvest at 4 weeks, another 8 beds to harvest at 5 weeks. each bed was treated with 4 kg of matured farmyard manure. combined analysis of variance was performed on mean data. participatory selection was conducted to identify preferred genotypes and horticultural traits. genotypes were similar or dissimilar for foliage yield and yield component traits at 4 and 5 weeks harvest. genotype by year interaction revealed statistically significant mean squares at 4 and 5 weeks harvest for some traits. considering multiple traits at 4 weeks harvest, am 25 and am 45 performed best for leaves/plant and leaf dry weight, while am 42 is promising for leaf yield, leaf length and leaf width. at 5 weeks harvest, am 45 performed best for leaf yield, leaf fresh weight and dry weight. am 25, am 42, am 45 and amloc are capable of developing rapidly and producing large quantities of biomass under short cycle harvest. keyword: amaranthus cruentus, short cycle harvest, genotype by year interaction, leaf quality, amaranth growers, leaf colour, leaf freshness 1. introduction amaranthus cruentus (2n = 32) belongs to the family amaranthaceae, it is known for its c4 cycle of photosynthesis where growth rate is optimized by high temperatures, bright light and adequate water and minerals. it is the most commonly grown high value indigenous leaf vegetable (maundu et al., 1999) rich in lysine an essential amino acids high levels of carotene, vitamin c and iron and calcium. it is an alternative source of protein and supplementing cereals grain diets in most rural communities in developing countries. year round cultivation of amaranth is common in africa. in nigeria, amaranth production is carried out during hot summer months and cold season. early morning cold during the winter months followed by heat and water stresses slows seed germination, vegetative growth and availability of fresh leaves. amaranth can be grown under varied soil and agro-climatic conditions (katiyar et al., 2000; shukla and singh 2000). direct sowing is the common practice in nigeria, uganda and in western kenya (grubben, 2004). amaranth is cultivated in gardens and fields for neighbourhood and short distance markets. leaf amaranth is ready for harvest 25 to 45 days after sowing depending on varieties (avrdc, 2008). the choice of harvest time for leaf amaranth depends on prevailing soil and climatic conditions, varieties, labour availability, market demand and target market. different farming communities use different harvesting techniques. harvesting methods for vegetable amaranth are uprooting the whole plant and re sowing, continuous harvest with topping, and continuous harvesting without topping. evaluation of harvesting techniques showed that continuous harvesting with topping (removal of flowers) gave the highest mailto:waleniji@gmail.com mailto:olawale.adeniji@fuoye.edu.ng adeniji, et al., variation in foliage yield and yield component traits and preference for leaf quality traits in amaranthus cruentus [l.] genotypes. azojete 14(1):61-71. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 62 economic leaf yield (32.0 t ha -1 ), continuous harvesting without topping gave the lowest (17.8 t ha -1 ). uprooting the whole plant after two planting and two harvests was the second highest yielding method with 29.8 t ha -1 and plants harvested with this method had the smallest leaf size, but it provided better marketable leaf quality (oluoch et al., 2009). leafy amaranth yields of about 40 t ha 1 had been recorded in the region of dar-es-salaam, while in benin and nigeria, the yield of shoots of 4 weeks old a. cruentus was about 30 t ha -1 (schippers, 2004). low leaf yields of 1.2 t ha -1 in amaranth (madulu and chalamila, 2005) could be attributed to several factors such as environmental, agronomic, low soil fertility and low yielding varieties which have short growth period. the suitability of vegetable amaranth for cultivation depends on agronomic traits such as short time to mature, low husbandry practice, and cheaper cost to final consumer. the sequence of harvest time in amaranth depends on the physiological and genetic attributes of the crop to produce biomass within few weeks after sowing. early harvest of amaranth leaves is desirable to meet early market demand, supply of fresh leaves to the market, income is generated within a short time and stimulate demand for seeds. growing vegetable amaranth as food is a traditional practice in farming communities in nigeria, where low income communities derive considerable self-sufficiency and sustenance. an important post-harvest handling technique among amaranth growers and marketers in the north of nigeria is air drying of amaranth leaves for use in cooking during prolonged dry season (november and april). at present, there are few commercial amaranth varieties in the country. development of new amaranth varieties requires systematic assessment of leaf yield and yield contributing traits, identifying amaranth accessions with high leaf yield and preferred fruit quality traits among existing genotypes at harvest. this study attempts to address two specific questions, first whether amaranth genotypes (varieties and breeding lines) developed and commercialised in east arica outperform farmer variety (nigeria) for foliage yield and yield component traits, and foliage quality traits and second, what are the most stable high yielding genotypes that could be used as genetic stock for further improvement in amaranthus cruentus. the objectives of this study are to evaluate variation for foliage yield and yield component traits among amaranthus cruentus genotypes, determine the influence of harvest at 4 and 5 weeks and year on foliage yield and yield contributing traits and evaluate preference for genotypes, foliage yield and foliage quality traits. 2. materials and methods 2.1 location and germplasm this research was conducted at the research farm, national open university of nigeria, jalingo, nigeria (lat 8 ° 47´s and lon 11 ° 09´e) in may, 2013 and 2014. jalingo is bounded to the north by lau local government area, to the east by yorro local government area, to the south and west by ardo kola local government area. jalingo is characterized by monomodal rainfall regime, the rain season starts during april/may and end in october. thereafter the cold and dry season (november to january) and the heat season (february to april). the hottest months are between february to march/april. while temperature is influenced by altitude and deforestation. the soil type is clay loam with ph between 6.0 and 6.5. nine amaranth genotypes (eight breeding lines) received from the world vegetable center (avrdc) and a popular farmer variety (am local as check) (table 1) were tested. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):61-71. issn 15962490; e-issn 2545-5818; www.azojete.com.ng 63 table 1: amaranthus cruentus and place of collection genotypes place of collection am 42 avrdc am 38-2 avrdc amtz 01 avrdc am 40 avrdc am 50 avrdc ex –zimbabwe avrdc am 25 avrdc am 45 avrdc am loc farmers collection, jalingo, nigeria 2.2 experimental design and data collection field experiments were established in may, 2013 and 2014. nine amaranthus cruentus genotypes were grown in a randomized complete blocks design with three replications. sunken beds were made at 1 m x 2 m, each bed was separated by alley of 1m. a total of 27 beds constituted a replicate, 9 beds were allotted to treatment a (harvest at 4 weeks after sowing) another 8 beds to treatment b (harvest at 5 weeks after sowing). each bed was treated with 4 kg of matured farmyard manure. prior to field establishment seeds were tested for viability. thereafter 10 g of viable seeds was uniformly spread on each vegetable bed. the experiment was rain fed with occasional manual irrigation. weeding was carried out manually and frequently to maintain a weed free plots. harvesting was done by uprooting at 4 and 5 weeks after sowing. amaranth plants in each net plot (1 m x 1 m) were used to determine amaranth foliage yield and yield contributing traits. branches/plant, leaves/plant were estimated on ten randomly picked amaranth plants. the leaf length and width were measured on five randomly picked leaves per plant. plant height (cm) was measured with a meter rule on ten randomly picked plants per entry. marketable foliage yield (t/ha) and non-marketable leaf yield were estimated on weigh balance and expressed in t/ha. at harvest three plants were randomly picked per plot, all the leaves were excised, counted and weighed. thereafter leaves were oven dried at 32 ° c, the weight (g) of dried leaves was measured on sensitive weight balance. over trial periods, 50 farmers randomly selected from study areas were involved in selection exercises. during the focus group discussion sessions, farmers provided a list of preferred horticultural traits and responses were ranked. they select best amaranth genotype for specific trait by dropping between one and four seeds (1=extremely poor, 2= poor, 3= good and 4= excellent) in containers placed in front of each accessions. 2.3 data analysis homogeneity of residual variances was tested prior to a combined analysis in each year as well as over and years using bartlet's test (steel and torrie, 1980). the data collected were homogenous and all data showed normal distribution. a combined analysis of variance was performed from the mean data to determine first and second order interaction and to partition the variation due to genotypes, harvest time and year. the combined analysis of variance was performed on mean data using a mixed model on plot means combined across years for all traits using proc glm procedure of sas (1998) to determine the level of significance and the percentage of contribution of each component to the total variation. adeniji, et al., variation in foliage yield and yield component traits and preference for leaf quality traits in amaranthus cruentus [l.] genotypes. azojete 14(1):61-71. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 64 the genotype (g), year (y) and harvest time (h) were considered to be fixed-effects, while replications were considered as random effects. moreover, mean comparison using duncan's multiple range test (dmrt) was performed to explain the significant differences among means of the genotypes. participatory selection was conducted during 2008 and 2009 evaluation to select accessions, horticultural traits preferred by respondents. responses during the amaranth stakeholder were adapted to a four point likert rating scale (lrs), as very high (vh) = 4, high (h) = 3, low (l) = 2, very low (vl) = 1. the mean score was computed as 4+3+2+1= 10/4= 2.50. using the interval score of 0.05, the upper limit cut-off was determined as 2.50 ± 0.05 and the lower limit as 2.55 ± 0.05= 2.45. on the basis of this, mean score (ms) below 2.45 (i.e. < 2.45) were ranked ‘low’, those between 2.45 and 2.54 were considered ‘medium’ (i.e. 2.45 ≥ ms ≤ 2.54), while the mean score greater than or equal to 2.55 (i.e. ms ≥ 2.55) were considered ‘high’. the responses from farmers preferences for genotypes, agronomic and leaf quality traits were categorized into a four point likert scale test. 3. results and discussion the mean squares for foliage yield and yield component traits at 4 and 5 weeks harvests during 2013 and 2014 cropping seasons are shown in tables 2a and 2b. at 4 weeks harvest significant differences (p< 0.05 and 0.01) were recorded for all the traits. while at 5 weeks harvest, the genotypes recorded statistically significant (p<0.05 and 0.01) mean squares for all traits except branches/plant. significant means squares (p<0.05 and 0.01) for all traits except branches/plant suggested large phenotypic variation (within and between years) for foliage yield and yield quality traits at 4 and 5 weeks harvest. genotypes with stable performance for these traits would be more suitable as cultivar and for further genetic improvement. table 2a: mean squares for foliage yield and yield component traits in nine genotypes of amaranthus cruentus l harvested at 4 weeks after sowing during 2013 and 2014 seasons source of variation df br/pl lvs/pl nmkt lvy(t/ha) mkt lvy (t/ha) lv fr wt (g) lv dr wt (g) plt ht (cm) lvl (cm) lvw (cm) genotypes 8 17.70** 90.74** * 2.13*** 21.17*** 5460.17*** 0.21 44.46* 0.11 0.15 year 1 3.93 8.20*** 2.87*** 133.28** * 246.65*** 4.09** 173.54** * 11.19** * 15.04** replication s 2 2.79 0.50 0.14 42.39** 36.35 0.02 14.35 0.82 0.81 genotypes x year 8 1.37 5.03*** 0.82 118.42** 195.67*** 2.04*** 21.12* 2.91** 0.98 error 34 1.65 0.93 0.07 6.37 16.02 0.13 9.54 0.55 0.52 cv (%) 20 13 21.73 14.61 13.39 19.35 15.78 10.84 17.42 mean 6.35 7.55 1.27 17.27 29.87 1.88 19.57 6.89 4.16 ***, ** and *= indicate respectively significant at p < 0.001, p < 0.01, p < 0.05 br/plt= branches/plant, lvs/pl = leaves/plant, nmkt lvy (t/ha) = non marketable leaf yield, nmkt lvy= non marketable leaf yield, lv fwt = leaf fresh weight, lv dwt = leaf fresh weight, pht= plant height, lvl= leaf length, lvw= leaf width arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):61-71. issn 15962490; e-issn 2545-5818; www.azojete.com.ng 65 table 2b: mean squares for foliage yield and yield component traits in nine genotypes of amaranthus cruentus l harvested at 5 weeks after sowing during 2013 and 2014 seasons ***, ** and *= indicate respectively significant at p < 0.001, p < 0.01, p < 0.05 br/plt= branches/plant, lvs/pl = leaves/plant, nmkt lvy (t/ha) = non marketable leaf yield, nmkt lvy= non marketable leaf yield, lv fwt = leaf fresh weight, lv dwt = leaf fresh weight, pht= plant height, lvl= leaf length, lvw= leaf width at 4 weeks harvest, year effect recorded statistically significant difference (p≤0.05) for all the traits except leaf dry weight, leaf length and width. in contrast the genotypes recorded insignificant (p≥0.05) mean squares for branches/plant and leaf width. while at 5 weeks, year effect had significant (p< 0.05 and 0.01) mean squares for all traits except branches/plant and leaf width. this suggests that environmental factors during years on which the genotypes were evaluated differed in response for traits. moreover the genotypes were unstable and inconsistent in their phenotypic expression (except branches/plant, leaf dry weight, leaf length and width) with change in the environment. significant year effect may have greater effect on some genotypes than others (falconer, 1981). at 4 weeks harvest, replication was significant (p≤0.05) for marketable leaf yield (t ha -1 ), non-marketable leaf yield (t ha -1 ) and insignificant (p≥0.05) mean squares for all the traits at 5 weeks harvest. genotype by year interaction recorded significant (p≤0.05) mean squares at 4 weeks harvest for leaves/plant, marketable leaf yield (t ha -1 ), non-marketable leaf yield (t ha -1 ), leaf fresh weight, leaf dry weight. on the other hand, at 5 weeks harvest significant mean squares was recorded for all the traits except branches/plant and leaf dry weight. significant genotype by year interaction (gyi) showed that environmental factors (precipitation, sun shine hours, temperature and soil types) during trial periods (years) were inconsistent over years and did influence phenotype expression of most traits investigated. insignificant genotype by year interaction mean squares (p ≥ 0.05) recorded for branches/plant, leaf width and leaf dry weight suggested that environmental factors during the trial periods were similar with minimal influence on traits. the mean performances for foliage yield and yield traits at 4 and 5 weeks harvest after sowing are presented in table 3a and 3b. over years branches/plant was high in am 25, am 42, amtz 01 and am 45 during harvest at 4 weeks. best genotypes for branches/plant are am local, am 45 and exzimbabwe. am 45 was consistent in performance for branches/plant at 4 and 5 weeks. among the genotypes leaves/plant varied between 5 and 9 at 4 weeks harvest. this result is similar to the findings reported by olaniyi, (2007) among amaranth accessions from nigerian institute for horticultural research. while at 5 weeks harvest the leaves/plant ranged from 8 (am 50) to 12 (ex – zimbabwe). top two genotypes for leaves/plant at 4 weeks harvest are am 25 and am 45. at 5 weeks harvest, ex zimbabwe, am 45, local and amtz 01 outperformed other genotypes. leaves produced are a measure of leaf yield potential. the marketable foliage yield (t ha -1 ) at 4 weeks harvest was 22.67 (t ha -1 ) in amtz 01, followed by am 42 (22.30 t ha -1 ) and am 50 (21.00 t ha -1 ). three genotypes (am 45, am 50 and am40) recorded foliage yield of 35.50 t ha -1 , 31.33 t ha -1 and 30.67 t ha -1 respectively at 5 weeks harvest. in this investigation, am 45, am 50 and am 42 source of variation df br/pl lvs/pl mn lvy (t/ha) nmkt lvy(t/ha) lv fr wt (g) lv dr wt (g) plt ht (cm) lvl (cm) lvw (cm) genotypes 8 3.25 20.35** 487.32*** 0.36 138.07** 7.47** 464.20** 16.24** 6.49** year 1 0.67 192.69** 73.50* 16.29*** 3472.0*** 79.69*** 2744.96*** 24.00** 0.07 replication 2 0.13 4.57 4.79 0.14 32.51 1.08 37.38 1.46 0.12 genotype by year 8 2.04 13.41** 185.25** 1.30** 99.43* 3.52 759.19*** 9.00* 7.57*** error 34 3.48 3.32 25.58 0.16 33.10 2.05 196.17 4.07 1.91 mean 11.07 9.15 23.46 2.04 25.79 3.34 54.28 10.29 5.96 cv (%) 14.27 19.92 24.32 19.82 22.30 37.32 25.80 19.59 23.20 adeniji, et al., variation in foliage yield and yield component traits and preference for leaf quality traits in amaranthus cruentus [l.] genotypes. azojete 14(1):61-71. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 66 harvested at 5 weeks performed better for foliage yield (t ha -1 ) compared to amaranthus cruentus genotypes from nihort (nhg4 452, nhg4 452, nhg4 493 and nhg4 493-1) harvested at 6 weeks. am 42, am 45 and ex zimbabwe recorded 42%, 37% and 35% increase respectively in foliage yield over harvest at 4 and 5 weeks after sowing. while am 25 had 4% decrease in foliage yield over harvest at 4 and 5 weeks. the foliage yield at 4 weeks harvest in amtz 01 and am 42 are low (22.67 t ha -1 and 22.30 t ha -1 ) compared to foliage yield of 29.8 t ha -1 in amaranth harvested by uprooting the whole plant (avrdc, 2008). arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):61-71. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 67 table 3a: the mean performance for foliage yield and yield traits in nine genotypes of amaranthus cruentus l harvested at 4 weeks after sowing during 2013 and 2014 seasons genotypes br/pl rank lvs/pl rank mkt lvy (t ha-1) rank nmkt lvy/t ha-1 rank lv fr wt (g) rank lv dwt (g) rank plt ht rank lvl (cm) rank lvw (cm) rank am 25 7.17a 1 8.60a 2 16.56b 1.19bc 36.1ab 3 2.65a 1 17.56de 6.00de 4.30b am 42 7.00a 2 8.00ab 22.30a 1 1.82a 1 23.5de 1.48d 25.67ab 2 9.00a 1 6.83a 1 am tz 01 7.03a 2 7.00bc 22.67a 2 1.78a 2 36.33ab 2 1.35d 19.17dc 7.50bc 4.33b 3 am 45 7.00 2 8.68 1 20.67 1.49ab 3 38.20a 1 2.10bc 28.0a 1 8.37ab 2 6.16a 2 am 40 6.83a 8.16ab 14.83bc 0.99c 23.50de 1.80cd 22.17bc 3 7.70bc 3 4.11b local 5.83ab 7.67abc 21.00a 3 1.43ab 32.33bc 2.37ab 3 17.83de 3 6.83cd 3.00c am 50 5.83ab 6.67c 13.83bcd 0.93c 28.17cd 1.73cd 20.67cd 4.83f 3.50bc am 38-2 5.50ab 5.00a 11.50d 0.86c 21.50e 2.60a 2 10.33e 2 6.33de 3.56bc ex zimbabwe 5.00b 8.33a 3 12.17cd 0.88c 30.16c 0.91e 14.83c 5.50ef 1.55d different superscripts denote significant difference in the same column br/plt= branches/plant, lvs/pl = leaves/plant, nmkt lvy = non marketable leaf yield, nmkt lvy= non marketable leaf yield, lv fwt = leaf fresh weight, lv dwt = leaf fresh weight, pht= plant height, lvl= leaf length, lvw= leaf width table 3b: the mean performance for foliage yield and yield traits in nine genotypes of amaranthus cruentus [l] harvested at 5 weeks after sowing during 2013 and 2014 seasons 5 weeks br/pl rank lvs/pl rank mn lvy (t ha-1) rank nmkt lvy(t/ha-1) rank lv fr wt (g) rank lv dwt (g) rank plt ht rank lvl (cm) ran k lvw (cm) am 45 12a 1 9d 35.50a 1 2.20a-c 3 33.00a 1 5.73a 1 62.33a 1 11.83a 1 6.45ab caud 11ab 8d 31.30a 3 2.26ab 2 24.50b-e 3.5b-d 54.83ab 10.67ab 6.67ab am 40 11ab 8d 29.50a 1.87bc 22.83c-e 4.11a-c 49.33ab 8.83bc 5.67bc am 25 11ab 9c 3514.88c 2 1.80bc 28.33a-c 3 4.51a-c 3 59.66a 10.8ab 6.50ab amtz 01 10c 10b 2 23.50ab 2.47a 1 26.50a-d 3.88a-c 62.83a 2 10.30a-c 3 5.83b am 38-2 10c 10a 2 12.33c 1.80bc 20.33de 3.53b-d 53.00ab 10.8ab 2 6.17ab am 42 11ab 9c 30.67a 2.05a-c 20.33de 1.95d 44.83ab 8.33bc 6.00bc ex zimbabwe 12a 1 12a 1 22.50b 2.18a-c 31.83ab 2 2.67c-d 38.33b 8.00c 5.00bc am 40 12a 1 10b 2 11.00c 1.87bc 26.00a-e 4.67ab 2 63.33a 1 13.0a 7.67a different superscripts denote significant difference in the same column br/plt= branches/plant, lvs/pl = leaves/plant, nmkt lvy = non marketable leaf yield, nmkt lvy= non marketable leaf yield, lv fwt = leaf fresh weight, lv dwt = leaf fresh weight, pht= plant height, lvl= leaf length, lvw= leaf width adeniji, et al., variation in foliage yield and yield component traits and preference for leaf quality traits in amaranthus cruentus [l.] genotypes. azojete 14(1):61-71. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 68 at 4 weeks harvest non-marketable foliage yield was high in am 42, amtz 01 and am 45, this ranged from 1.82 t ha -1 to 1.78 t ha -1 . the non-marketable leaf yield comprised deformed, weak plants (yellowish green leaves), defoliated leaves, stems and roots. at 5 weeks harvest, non-marketable foliage yield peaked (2.44 t ha -1 ) in amtz 01 followed by am 50 (2.26 t ha 1 ). this indicates that as days to harvest increases the quantity of non-marketable foliage yield increase. preponderance of non-marketable foliage yield in amaranthus cruentus is sequel to overcrowding arising from broadcast method of planting amaranth seeds. leaf fresh weight/plant was high (38.2 g) in am 45, followed by 36.33 g in amtz 01 and 36 g in am 25. these values are relatively larger than the grand mean for this trait. at 5 weeks harvest, leaf fresh weight was high (33 g) in am 45 followed by 31.83 g in ex zimbabwe. at 4 weeks harvest, three genotypes (am 25, am 38-2 and am 50) outperformed other genotypes for leaf dry weight. on the other hand, at 5 weeks harvest leaf dry weight ranged from 1.95 g to 5.73 g. best three genotypes for leaf dry weight are am 45 (5.73 g), am 50 (4.67 g) and am 25 (4.11 g). these genotypes are promising for high dry matter yield and could be preferred by amaranth growers for production of amaranth dry leaves for consumption during prolonged dry season. high dry matter yield in amaranth is associated with net assimilation rate (shukla, 2003). however, as dry matter yield increases over harvests (3 weeks or more), this will correspond to a decrease in the quality of the foliage. at 4 weeks harvest, best amaranth genotypes for fresh leaf weight performed poorly for leaf dry weight (table 3a). in contrast, at 5 weeks harvest am 45 performed best for leaf dry weight and was consistent for 2013 and 2014. at 4 weeks harvest plant height ranged from 10.33 cm to 28.0 cm, best genotypes for plant height are am 45, am 42 and am 40, these genotypes may develop high leaves/plant, branches/plant, foliage yield due to significant correlation coefficient between these traits olaniyi, (2007). best performing amaranth genotypes for plant height at 5 weeks harvest are am 40 (63.33 cm), followed amtz 01 (62.53 cm) and am 45 (62.33 cm). a comparison of plant height at 4 and 5 weeks harvest showed that am 25 and am local recorded 22.68% and 26% increase in plant height over 4 and 5 weeks harvest. leaves of am 42 are long (6.83 cm) at 4 weeks harvest compared to other genotypes. similarly, am 25 and amtz 01 recorded 6.16 cm and 4.33 cm respectively for leaf length. at 5 weeks harvest, leaf length ranged from 8 – 13 cm. am local outperformed other genotypes for leaf length, this was followed by am 45, am, 25 and am tz 01. however, am 40, am 45, am 25 recorded 20%, 34%, 36% increase in leaf length over harvest at 4 and 5 weeks. leaf width among amaranth genotypes ranged from 1.55 cm to 6.83 cm for harvest at 4 weeks, best performing genotypes for leaf width are am 42, am 45 and am tz 01. at 5 weeks harvest, leaf width was narrow (5.00 cm) in am 42, ex zimbabwe and wide (7.67 cm) in am 40. best performing genotypes for leaf width at 4 weeks harvest are not consistent in performance at 5 weeks harvest. for multiple traits, am 25 performed best for branches/plant, leaves/plant and leaf dry weight. am 42 outperformed other genotypes for non-marketable leaf yield, leaf length and width. am 45 performed best for leaves/plant, leaf fresh weight, and plant height at 4 weeks harvest. considering harvest at 5 weeks, am 45 performed better than other genotypes for branches/plant, leaf yield, leaf fresh weight and dry weight. arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):61-71. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 69 also am local is promising for branches/plant, plant height, leaf length and width. over harvest periods (4 and 5 weeks) and years, am 45 was consistent in performance for leaf fresh weight, leaf dry weight and leaf width. also amtz 01 showed similar response over harvests and years for plant height, while am local performed best for leaves/plant and plant height. consequently these genotypes are possible donor parent or commercial varieties. preference for agronomic and leaf quality traits among amaranthus cruentus genotypes is presented in table 4. the preference score of 3.36 was recorded leaf colour at 4 weeks harvest compared to 2.90 recorded at 5 weeks. preference for green leaf colour at 4 weeks harvest is consistent with previous findings by adeniji and aloyce (2012) among amaranth stakeholders in arusha, tanzania. preponderance of yellowish-green colour leaves at 5 weeks harvest may be associated with competition for space and nutrient, insect pests attack and water stress. in addition, nitrogen deficiency is a possible cause of yellowish-green colour on amaranth leaves. preference score for marketable foliage yield at 5 weeks was high, on the other hand leaves harvested at 5 weeks are least preferred for freshness, and crispiness. amaranth growers delay harvesting from 4 to 5 weeks and beyond due to within season market glut associated with low demand and falling prices and to avoid the adverse effect of early flower induction (adeniji and aloyce, 2013). to reduce non-marketable leaf yield at 5 weeks, good agricultural practices specified for amaranth must be practiced by amaranth growers. high preference score (3.54) was recorded for leaves/plant at 5 weeks harvest compared to harvest at 4 weeks harvest (1.44). in another study adeniji and aloyce (2012) had reported high preference for amaranth accessions with high leaves/plant. leaf size at 5 weeks harvest was preferred by amaranth growers. leaf freshness at 4 weeks harvest was preferred to 5 weeks harvest. in addition, assessment of leaf quality (absence of perforations, deformed shape, yellowing of leaves) among the genotypes indicated that 80% of the respondents showed preference for leaf quality at 4 weeks harvest. table 4: preference for foliage yield and leaf quality traits in nine amaranthus cruentus genotypes harvested at 4 and 5 weeks during 2013 and 2014 planting seasons leaf quality traits liked slightly liked slightly disliked disliked n likert score leaf colour at 4 weeks harvest 35 (2.80) 10 (0.80) 3 (0.12) 2(0.04) 50 3.76 leaf colour at 5 weeks harvest 25(2.00) 10(0.60) 5 (0.20) 5 (0.10) 50 2.90 marketable weight at 4 weeks harvest 20 (1.60) 10 (0.60) 10 (0.60) 10 (0.20) 50 3.00 marketable weight at 5 weeks harvest 25 (2.00) 15 (0.90) 5 (0.30) 5 (0.10) 50 3.30 leaf number at 4 weeks harvest 5 (0.40) 5(0.20) 15 (0.90) 25 (0.50) 50 2.00 leaf number at 5 weeks harvest 35(2.80) 10 (0.60) 2(0.12) 3 (0.06) 50 3.58 leaf size at 4 weeks harvest 10 (0.80) 8 (0.48) 10 (0.40) 22 (0.44) 50 2.12 leaf size at 5 weeks harvest 33 (2.64) 10 (0.60) 4 (0.16) 3 (0.06) 50 3.46 leaf freshness at 4 weeks harvest 34 (2.72) 10 (0.60) 3 (0.12) 3 (0.06) 50 3.50 leaf freshness at 5 weeks harvest 25 (2.00) 10 (0.60) 10 (0.40) 5 (0.10) 50 3.10 leaf quality at 4 weeks harvest 30 (2.40) 10 (0.60) 5 (0.20) 5 (0.10) 50 3.30 leaf quality at 5 weeks harvest 10 (0.80) 5 (0.30) 25 (1.50) 10 (0.20) 50 2.50 preference for amaranthus cruentus genotypes by amaranth growers considering agronomic traits at 4 weeks harvest is presented in table 5. two genotypes (am 25 and am 45) are most preferred for leaf length and width they outperformed other accession for these traits. adeniji, et al., variation in foliage yield and yield component traits and preference for leaf quality traits in amaranthus cruentus [l.] genotypes. azojete 14(1):61-71. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 70 the foregoing is consistent with mean values recorded for leaf length (table 3). amaranth growers’ participatory assessment of plant height indicated that at 4 weeks harvest, am 45 and am 42 are preferred. the farmers’ preference is similar to mean and rank presented in table 3. top two genotypes for leaf dry weight are am 45 and am 25, they recorded frequencies of 22 and 18 respectively. ex-zimbabwe and am 25 are preferred amaranth growers for leaves/plant, they recorded frequencies of 22 and 12. for multiple traits amaranth growers indicated that am 45 performed best for leaf length, leaf width and leaf dry weight. ex-zimbabwe had high preference for leaves/plant, leaf width and plant height, am 25 for leaf length and leaf dry weight. leaf crispiness varied among the accessions, this was low for most entries except am 25, am 45 and am 42. five entries (am 25, am 45, am 42, am local and amtz 01) outperformed other genotypes for overall appearance. table 5: preferences for amaranthus cruentus genotypes by amaranth growers in jalingo, taraba state (n =50) leaf length leaf width plant height leaf weight leaves/ plant leaf freshnes s leaf crispines s overall appearanc e leaf size am 25 25 2 1 18 12 8 16 9 12 am 45 20 20 20 22 0 8 15 8 12 am 40 0 1 2 0 1 2 0 5 1 am 50 0 1 1 8 9 1 0 5 1 ex zim 0 1 0 0 20 2 0 3 1 am tz 01 0 0 5 0 1 5 2 4 1 am 42 5 20 15 0 5 5 15 8 10 acru 0 0 1 0 0 3 1 3 2 am 38-2 0 0 1 0 2 8 2 5 10 4. conclusion considerable variability exist among amaranthus cruentus genotypes for foliage yield and yield related traits at 4 and 5 weeks harvests. the mean performance for foliage yield and yield related traits was influenced by precipitation, sunshine hours, and temperature and soil types. few genotypes at 4 or 5 weeks harvests over years showed stable mean performance for foliage yield and yield related traits. amtz 01 and am 42 are promising for foliage yield at 4 weeks harvest. am 25 performed best for branches/plant, leaves/plant and leaf dry weight. while am 42 outperformed other amaranthus cruentus genotypes for leaf length and width. am 45 performed best for leaves/plant, leaf fresh weight and plant height at 4 weeks harvest. at 5 weeks harvest am 45 performed best for branches/plant, leaf yield, leaf fresh weight and leaf dry weight. promising genotypes are recommended for evaluation in multiple environments. the study showed that the am 25, am 42, am 45 and am local are capable of developing rapidly and producing large quantities of biomass in a short period of time (4 and 5 weeks after sowing) and with management they will be very productive arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):61-71. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 71 references avrdc, 2008. a traditional food crop becomes attractive with the east african seed sector. healthy urban fast food—a new maasai enterprise. point of impact. avrdc-the world vegetable center, taiwan. grubben, gjh. 2004. amaranthus cruentus l. in: grubben, gjh. denton, oa. (eds) plant resources of tropical africa 2. vegetables. backhuys publishers, wageningen, pp 67–72. katiyar, rs. shukla s. and rai s. 2000. varietal performance of grain amaranth (a. hypochondriacus) on sodic soil. biological science, 70(2): 185-187. madulu, rb. and chalamila, bn. 2005. organic vegetable production an alternative income generating activity to the disease effected coconut farming system in mkuranga district in tanzania. african crop science conference proceedings, 7:1539–1544. maundu, pm., ngugi, gw. and kabuye, chs., 1999. traditional food plants of kenya. kenya resource centre for indigenous knowledge (kenrik), nairobi, kenya. 270 pp. olaniyi, jo. 2007. evaluation of yield and quality performance of grain amaranth varieties in the south western nigeria. research journal of agriculture, 1 (2): 42 – 45. oluoch, mo., pichop gn., silue d, abukutsa-onyango mo., diouf m. and shackleton, cm. 2009. production and harvesting systems for african indigenous vegetables. in: shackleton, cm, pasquini mw, drescher a (eds) african indigenous vegetables in urban agriculture. earthscan, london, uk, pp 145–175. sas. 2008. statistical analysis system, version 9.2. sas institute inc. cary, nc, usa. schippers, rr. 2004 le ´gumes africains indige `nes: pre ´sentation des espe `ces cultive ´es. margraf publishers, wuerzburg. arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):517-526 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 517 original research article influence of extrusion process conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design m. yusuf1*, m. halilu1 and k. b. filli2 1department of food science and technology modibbo adama university of technology yola, pmb 2076 yola, nigeria 2swedish institute for food and biotechnology gothenburg, sweden. *corresponding author’s email address: yusufmoh2015@yahoo.com 1.0 introduction extrusion cooking is continuous process in which food materials are plasticized to form a fluid melt in the barrel. the high temperature, pressure and shear stress causes the material to be conveyed by a screw. it also forces the material to pass through a die of specific size and formed in to a shape. this shape can be a profile, plate, film, tube, or have any other shape formed from its cross section. the melt can be mixed, densified, plasticized, homogenized, degassed, or chemically altered (reactive extrusion). a subsequent treatment of the semifinished material before solidification by pressured air or calendaring is also possible. since the food ingredients (polymer) are completely melted during extrusion and brought into a new form, the extrusion process is a primarily shaping process. extrusion is a technology well-known in the plastic industry and now used in food and agroprocessing industry. it is referred to as extrusion cooking process. the technology is used in the production of engineered food and special feed. extrusion cooking is a thermodynamically efficient industrial method of cooking and drying a wide range of foods based on cereals or vegetable proteins or mixtures of both (carl et al., 1986). extrusion of vegetable raw-materials deals with the extrusion of raw-material at barothermal conditions. the shear energy exerted by rotating screw couple with additional heating of the article information abstract the effect of extrusion condition on residence time and throughput rate of a twin-screw extruder was investigated using blends of sorghum groundnut and tiger nut in twin-screw extruder slg65 model. in this study, a three factor 3-level full factorial experimental design was adopted. the influence of extrusion cooking conditions on both the combine effect and the effect of independent variables were evaluated. the analysis of variance showed that both linear and quadratic were not significant, however, interaction significantly (p<0.05) affect both the residence time and the throughput rate of the extruded. the results revealed that the throughput rate ranged from (0.012-0.040 kg/s). the highest value was recorded at 100°c barrel temperature, 50:30:20 feed composition for ratios of sorghum groundnut and tiger nut and 18% feed moisture content. while the residence time ranged from (47 66.0 s) the highest residence time was obtained at 110°c barrel temperature 50:30:20 ratios of sorghum groundnut and tiger nut and 26 % feed moisture content. the information provided about the residence time and throughput rate of a twin-screw extruder will be used in fabricating an extruder that will be used in producing similar extruded product. the result of the research could be used by intended processors of similar extruded product to explore the possibility of producing similar product by manipulating the processing variables in order to obtain a desired product. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 august, 2021 revised 2 oct., 2021 accepted 7 oct., 2021 keywords: residence time throughput barrel temperature feed composition moisture content yusufmoh2015@yahoo.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):517-526. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 518 barrel, the food material is heated to its melting point or plasticizing point. food extruders belong to the family of htst (high temperature short time) equipment capable of performing cooking task under high temperature and pressure and expel the cooked food within seconds. exposure of food to high temperature for only a short time has the advantage of restricting unwanted denaturation effects on starches, proteins, amino acids, vitamin and enzymes. leszek (2005) reported that physical and technological aspect like heat transfer, mass transfer, momentum transfer, residence time and residence time distribution have a strong impact on the food and the feed properties during extrusion cooking and can drastically influence the final product quality. the food extruder therefore is likened to a continuous flow reactor capable of processing biopolymers and ingredient mixes at relatively high temperature under high pressure and shear forces at relatively low moisture contents. the heating and shearing during the time of extrusion causes series of physical and chemical changes which encompasses starch gelatinisation and dextrinization protein denaturation and cross linking, browning denaturation of vitamins and enzymes and are obviously complex. the resulting properties of the cooked food are a composite of all components, which emerge from the extruder die (harper, 1981). there are two classes of extruder (single and twin-screw) based on the number of screws. single screw extruder consists of a single screw encased in the barrel assembly. the feed material on its way through the open channel of the extruder undergoes a combination of various forces like shearing, mixing, and compression (zuilichem et al., 1999). single-screw extruders rely on drag flows to move material down the barrel and develop pressure at the die. additionally, the rotational movement of the screw relative to the barrel wall creates another flow, called the cross-channel flow. this flow, which recirculates material in the channel between the screw flights, does not contribute to the net forward movement of the material. it does, however, contribute to the mixing of the material passing through the extruder. finally, there is a third type of flow called pressure flow and accounts for the movement of material backwards in a negative direction due to the pressure at the die (frame, 1994).the twin-screw extruders on the other hand were introduced to the food industry in the 1970s and are now extensively used in food production (leszek, 2011). in addition to manufacturing foods similar to those produced by singlescrew extruders, twin-screw extruders have found a wide application in the food industry due to their better process control and versatility, their flexible design which permitting easy cleaning and rapid product change over together with their ability to handle a wide variety of formulations (baljit et al., 2017). twin-screw extruders differ from the single-screw extruder in terms of their processing capability and mechanical characteristics and are largely responsible for the increasing popularity of extrusion processing. the screws in a twin-screw extruder are positioned adjacent to each other and are retained in position by profiled barrel housing, having a horizontal appearance. the position of the screws in relation to one another and their direction of rotation can be used to categorize twin-screw machines. due to the independent variable screw configuration, twin screw extruders provide greater flexibility of operations to control product characteristics by monitoring time, temperature, pressure, and shear history (choudhury and gautam, 1999). extrusion is a multi-factor process and because any change in the extrusion variables may affect the quality of the final products, extrusion cooking process are subjected to process optimization to be able to locate optimal process conditions that will produce best or desired product quality or system performance. several experimental designs including factorial design, central composite design, etc have been used to evaluate process parameters for different types of extruders using different food ingredients. to therefore, fit an approximation model that will yusuf et al: influence of extrusion process conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design. azojete, 17(4):517-526. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 519 represent the linear and interaction relationships between the process variables, a full factorial approach may be necessary to investigate all possible combinations (montgomery, 1997). a factorial experiment is an experimental strategy in which design variables are varied together, instead of one at a time. the lower and upper bounds of each of n (number) of design variables in the optimization problem needs to be defined. the allowable range is then discretized at different levels. if each of the variables is defined at only the lower and upper bounds (two levels), the experimental design is called 2n full factorial. similarly, if the midpoints are included, the design is called 3n full factorial. the objective of this research is to determine the influence of extrusion conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design approach. 2. materials and methods the raw materials used includes sorghum (sorghum bicolour l) red cultivar, groundnut (arachis hypogeal l) red skin, tiger nut (cyperus esculentus l) brown cultivar and granulated red pepper (capsicum annum) were purchased from jimeta modern market, yola north local government area of adamawa state. 2.1 preparation of raw materials sorghum, groundnut and tiger nut were sorted manually, cleaned and washed with clean water and allowed to dry in conventional oven at 50°c for 1hour, before roasting at 150oc for 30 min in baking oven. the roasted materials (sorghum and tiger nut) were grounded to flour grinding machine (india grinding mill nissan a2 7hp) and sieved to obtain the particle size of 0.05 mm, while the roasted groundnut was grounded to paste using grinding machine ((india grinding mill nissan a2 7hp). the sorghum, groundnut and tiger nut grits were mixed together in a ratio of 50:20:30, 50:25:25 and 50:30:20 respectively using horbart mixer (model number a 200) for 10 min. from 1.5 kg of this mixture 2.5% of granulated red pepper (capsicum annum) was added and mixed. the mixture was then packaged and ready for extrusion. 2.3. experimental design in this experiment, second-order factorial design (eq. 1) was adopted. factorial designs can be used for fitting second-order models. a second-order model can significantly improve the optimization process when a first order model suffers lack of fit due to interaction between variables and surface curvature. a general second-order model is defined as (1) where xi and xj are the design variables and a are the tuning parameters. the construction of a quadratic response surface model in n variables requires the study at three levels so that the tuning parameters can be estimated. therefore, at least (n+1) (n+2) /2 function evaluations are necessary. generally, for a large number of variables, the number of experiments grows exponentially (3n for a full factorial) and becomes impractical. a full factorial design typically is used for five or fewer variables. however, in this experiment three factor 3levels full factorial design was used for the design as shown in tables 1 and 2 (yusuf et al., 2017). a three factor 3-level full factorial experimental design (3x3x3) was used to determine the influence of extrusion conditions on the residence time and throughput of a twin screw extruder during the extrusion of some nigerian indigenous cereals blended with legume to produce cereal based traditional snack product of northern nigeria (dakuwa).the extrusion variables that were considered includes: feed moisture content (fm), barrel temperature (bt) arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):517-526. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 520 and feed composition (fc), at levels each as shown in tables 1and 2. thus, making it a 3 (feed moisture) x 3 (barrel temperature) x 3 (feed composition) full factorial design extrusion experiment. data generated from the study were statistically analysed using genstat version 16 and fitted into a quadratic polynomial equation of the type y = bo+ b1x1+ b2x2+ b3x3+ b11x12+ b22x22+ b33x32+ b12x1x2+ b13x1x3+ b23x2x3 (2) where: y = the response, x1 = barrel temperature, x2 = feed composition, x3 = moisture content, bo= intercepts, b1,b2,b3 are linear, b11,b22,b33are quadratic and b12,b13 and b23 are interaction regression coefficient terms. analysis of variance (anova) was carried out to investigate the influence of operating conditions on the residence time and throughput rate of the extruder using genstat software. three-dimension (3d) histogram was used to predict the influence of independent extrusion variables on the residence time and throughput rate of the extruded snacks. all the graphical presentations were carried out using microsoft excel. 2.4 extrusion processing the extrusion cooking process was performed using a pilot scale co-rotating twin screw food extrusion cooker (slg65-iii model china) the extruder has a feeder at the top with constant feed rate, it also has a control panel board where the barrel temperature was set. the machine has constant screw speed of 150 rpm and a die diameter of 3mm. the twin screw within the barrel is surrounded with heaters controlled at the control panel board. the grits were alternatively fed into the extruder inlet by volumetric feeder at a feed rate of 0.04 kg/s. the temperature of the three zones of the extruder was controlled by eurotherm controller and was read on separate control panel board. extruded samples were collected when the extrusion process parameters reached steady states (aynadis and adamu, 2014). steady state was reached when there was no visible drift in torque and die pressure. necessary calibration and adjustment of the barrel temperature of the extruder was performed prior to the main extrusion cooking process. feed rate and screw speed were constant. the feed composition was varied at 50:20:30, 50:25:25 and 50:30:20 ratios of sorghum, groundnut and tiger nut respectively. the barrel temperature of zone three, which was located just before the die was allowed to operate at different temperatures ranging from 90°c to110°c. by looking at the characteristics of the products from the extrusion, the barrel temperature was selected for the experiment. the moisture content of the material was adjusted to give moisture contents of 18 %, 22 % and 26 % by using hydration equation (3). wa = sw x (3) where: wa = weight of water added (g) sw = sample flour weight (g) mo = original flour moisture content (% weight base) m = required dough moisture level (% weight base). the extrusion experiment was conducted using 3 factor 3 level experiment design (33), with 1factor representing extruder barrel temperature, with levels (90°c 100°c 110°c). 2nd factor representing feed composition with levels (50:20:30, 50:25:25, 50:30:20) for sorghum, groundnut and tiger nut respectively, and the 3rd factor representing feed moisture, with levels 18 %, 22% and 26 % as shown in table 1 and 2. the extruder barrel temperature was set at yusuf et al: influence of extrusion process conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design. azojete, 17(4):517-526. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 521 90°c and 9samples were run this level, and at 100°c with additional 9samples run at the level. finally, at 110°c the remaining 9 samples were then run totalling 27 runs. as shown in table 1 and 2 for experimental design in coded and natural forms. at each case the screw speed remains constant at 150 rpm and the die diameter remain 3 mm. the extruded product was cooled dried and stored in a polythene bag for further analysis. table 1: factors and levels of the 3x3x3 full factorial experimental design symbol factors factor levels 1 2 3 barrel temperature (°c) x1 90 100 110 feed composition (sorghum, groundnut, tiger nut) x2 50:20:30 50:25:25 50:30:20 feed moisture (%) x3 18 22 26 table 2. experimental design of extrusion experiment in their coded form independent variables in coded form runs bt (x1) levels 1 2 3 fc (x2) levels 1 2 3 fm (x3) levels 1 2 3 1 1 3 2 2 1 3 1 3 1 3 3 4 1 2 2 5 1 2 1 6 1 2 3 7 1 1 2 8 1 1 1 9 1 1 3 10 2 2 3 11 2 2 2 12 2 2 1 13 2 3 1 14 2 3 2 15 2 3 3 16 2 1 1 17 2 1 3 18 2 1 2 19 3 2 2 20 3 2 3 21 3 2 1 22 3 1 1 23 3 1 3 24 3 1 2 25 3 3 3 26 3 3 2 27 3 3 1 the experiment was carried out in randomized order. (bt) = barrel temperature with levels 1 2 and 3 represents 90 100 & 110 °c, (fc) = feed composition with levels 1, 2 and 3 representing 50:20:30, 50:25:25 and 50:30:20 for ratios of sorghum groundnut and tiger nut respectively. (fm) = feed moisture with levels 1, 2 and 3 which represent 18 %, 22 % and 26 % respectively. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):517-526. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 522 2.5 residence time (rt) the residence time was determined using red food colour as a tracer. 0.5g of red food colour was introduced at the feeding port and emerging samples collected until the red colour was no longer visible. the minimum residence time (rt) the feed particles spent in the extruder from introduction of the red food colour indicator at the extruder feed port until it appeared at the die was noted. the extrudate collection time (ti) being the total time from the emergency of first colour (to) at the die to disappearance of colour was also noted. rt = (ti-to) (4) 2.6 throughput (tp) the throughput or mass flow rate was calculated by measuring the mass of the extrudate per unit time taken for the extruded product to come out of the die of the extruder. throughput rate (mass flow rate) kg/s (5) 3. results and discussion 3.1 residence time (rt) table 3 shows that the least residence timeof47s was recorded at design point 23 (bt3fc1fm3) representing 110oc barrel temperature, 50:20:30 feed composition for ratios of sorghum, groundnut and tiger nut and 26% feed moisture content, while the highest residence time of 66 s was recorded at design point 25(bt3fc3fm3) representing 110 oc barrel temperature, 50:30:20 feed composition for ratios of sorghum groundnut and tiger nut respectively and 26% moisture content. the reason for the low rt in run 23 could be because of high tigernut content in the formulation and a high moisture content that has resulted in speedy passage of the extruded through the die and a low rt. for the high rt observed in run 25 the highest barrel temperature couple with high groundnut content in the formulation and a moisture content might have resulted in the melting and sticking of the ingredients in the barrel thereby increasing the residence of the extruded. table 3: influence of extrusion variables on residence time and throughput rate of a twinscrew extruder. sn 123 btfcfm 123 residence 123 time (rt)/s throughput rate (tr)kg/s 1 1 3 2 51.00 0.027 2 1 3 1 57.67 0.027 3 1 3 3 48.33 0.027 4 1 2 2 48.67 0.037 5 1 2 1 61.67 0.023 6 1 2 3 56.00 0.030 7 1 1 2 54.33 0.030 8 1 1 1 51.67 0.030 9 1 1 3 60.00 0.023 10 2 2 3 58.33 0.033 11 2 2 2 56.67 0.030 12 2 2 1 59.33 0.023 13 2 3 1 50.00 0.040 14 2 3 2 58.33 0.020 15 2 3 3 48.33 0.030 16 2 1 1 58.33 0.027 17 2 1 3 61.58 0.028 yusuf et al: influence of extrusion process conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design. azojete, 17(4):517-526. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 523 18 2 1 2 60.33 0.023 19 3 2 2 61.67 0.027 20 3 2 3 54.00 0.027 21 3 2 1 53.33 0.032 22 3 1 1 58.33 0.025 23 3 1 3 47.33 0.033 24 3 1 2 54.33 0.027 25 3 3 3 66.41 0.012 26 3 3 2 53.33 0.040 27 3 3 1 49.00 0.032 the experiment was carried out in randomized order. (bt) = barrel temperature with levels 1 2 and 3 represents 90 100 & 110 °c, (fc) = feed composition with levels 1, 2 and 3 representing 50:20:30, 50:25:25 and 50:30:20 for ratios of sorghum groundnut and tiger nut respectively. (fm) = feed moisture with levels 1, 2 and 3 which represent 18 %, 22 % and 26 % respectively. 3.1 residence time (rt) the observed results agreed with the finding of omeire et al., (2013) who reported that rt decreased as the moisture content and screw speed increased. the results were in agreement with the report of some researchers (nwabueze and iwe, 2012) who observed that extrudates spent longer time in the extruder as feed moisture or screw speed decreased from 27% to 15% or 180rpm to 100rpm respectively, thereby increasing the residence time distribution characteristics. the analysis of variance revealed that both linear and quadratic effect were not significant, however interaction effect significantly (p<0.05) affects the residence time of the extruded. the influence of independent variables on residence time of the extruded revealed that increasing barrel temperature from 90oc to 100oc resulted in decreasing the residence time from 60.81 secs to 56.58 secs this is in line with report by sueshan et al (2015) that the results showed that an increase in extruder barrel temperature decreased the residence time of the flours in the extruder from 4.11-11.32 min to 2.24-6.76 min. however, increasing the barrel temperature to 110oc increases the residence time to 58.39s it is anticipated that at high temperature the extruded melt and stick to the barrel that result in increasing the residence time as observed. on feed composition also increasing the level of groundnut from 20% to 30% results in increasing the residence time from 58.26 to 59.05 this has to do with melting and sticking of groundnut as a result of high oil content that increases the residence time. on feed moisture content increasing the feed moisture from 18%, 22% and 26% respectively resulted in increasing the residence from 57.27, 58.78, to 59.74 s respectively. figure 1 represents the 3d histogram and figure 2, the 3d radar projections. r es id en ce t im e r t /s extrusion variables figure 1: effect of extrusion variables on residence time rt of extruded arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):517-526. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 524 90 0 c 100 0 c 110 0 c 50:20:30 50:25:25 50:30:20 18% 22% 26% figure 2: effects of independent variables on residence time of the extruded (3d radar projection) 3.2 throughput rate the least throughput rate of 0.012 kg/s was recorded at design point 25(bt3fc3fm3) representing 110oc barrel temperature 50:30:20 feed composition for ratios of sorghum groundnut and tiger nut and 26 % feed moisture content respectively. the least throughput rate recorded at design point 25 could be because of high barrel temperature, high percentage of groundnut that contains high fat and high moisture content. the combination of that result to the melting and sticking of the formulation to the barrel thereby affect the mass flow rate of the melt. the highest throughput rate of 0.040 kg/s was recorded at design point 13(bt2fc3fm1) representing 100oc barrel temperature 50:30:20 feed compositions for ratios of sorghum groundnut and tiger nut and 18 % moisture content. the highest throughput rate recorded at design point 13 could be because of low moisture content that reduced the rate of melting and sticking of the formulation in the barrel. that gives the highest mass flow rate of the extruded products. so, the feed composition and the feed moisture content played significant role in ascertaining throughput rate of twin screw extruder of the extruded products since the machine has constant screw speed. this information could be used in the design and construction of extruder for scale up production of extruded products. analysis of variance showed that linear and quadratic were not significant but interaction significantly (p<0.05) affect the throughput rate of the extruded. the influence of independent variables on the throughput rate of the extruded products were also studied. increasing the barrel temperature from 90oc to 110oc resulted in increasing the throughput rate from 0.025 to 0.026 kg/s, the result obtained agreed with the reported literature by sobowale et al. (2016) who found that an increase in barrel temperature increased the mass flow rate to 64.5% of the extrudates significantly (p<0.05). on feed composition increasing the percentage of groundnut in the formulation from 20% to 25% resulted in increasing the throughput rate from 0.026 to 0.027 kg/s, further 30% increase of groundnut content results in decreasing the throughput rate to 0.024 kg/s and that could be because of high fat content of groundnut, this observed effect is in line with literature reported by bt: barrel temperature fc: feeds composition fm: feeds moisture r es id en ce t im e /s yusuf et al: influence of extrusion process conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design. azojete, 17(4):517-526. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 525 50:20:30 50:25:25 50:30:20 18% 22% 26% 90°c 100°c 110°c nwabueze et al. (2006) that mass flow rate ranged from 2.99kg/h to 6.72kg/h as feed composition shifted from african bread fruit towards soybean. on feed moisture content increasing the moisture content from 18% to 24% resulted in decreasing the throughput rate from 0.027 to 0.024 as shown in figure 3 which is 3d histogram and figure 4, 3d radar projections respectively. figure 4: effects of independent variables on throughput rate of the extruded (3d radar projection) 4. conlusion the influence of twin-screw extrusion conditions on residence time and throughput rate of the extruded sorghum-graundnut-tiger nut products were investigated and the result reveals that residence time ranged from 47 to 66s while throughput rate range from 0.012 to 0.040 kg/s. the analysis of variance showed that both linear and quadratic were not significant, however, interaction significantly (p<0.05) affect both the residence time and the throughput rate of the extruded. the knowledge of the optimum values of residence time and throughput rate could be used to design and fabricate an extruder to enhance the production of the extruded foods having similar composition. the research also provides information to some intended processors of dakuwa through extrusion and similar products on how to manipulate the processing parameters in order to arrive at the desired product quality. figure 3: effect of extrusion variables on throughput rate of extruded bt: barrel temperature fc: feeds composition fm: feeds moisture extrusion variables t h ro u g h p u t r at e r t k g /s t h ro u g h p u t r at e k g /s arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):517-526. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 526 references aynadis, m. and adamu, z. 2014. effect of extrusion conditions on aflatoxin content of cornpeanut flakes. journal of the european economic association, 32(1): 47-56. baljit, s., chetan, s. and savita, s. 2017. fundamentals of extrusion processing. novel food processing technologies pp.1-46. editors, 2017, vikas nanda and savita sharma new india publishing agency, new delhi, india. choudhury, gs. and gautam, a. 1999. screw configuration effects on macroscopic characteristics of extrudates produced by twin-screw extrusion of rice flour. journal of food science, 64(3): 479−487. carl, w., hall, a., farrall, w. and rippen, al. 1986. extruder. encyclopaedia of food engineering. (2nd ed.). connecticut: avi publishing inc. frame, nd. 1994. operational characteristics of the co-rotating twim screw extruder. in: frame, nd., editor. the technology of extrusion cooking. new york: blackie academic & professionals, p 1-50. harper, jm. 1981. food extrusion, in: extrusion of foods. crc press, boca raton, fl, pp.1-6. leszek, m. 2011. extrusion-cooking techniques applications, theory and sustainability. wiley vch verlag & co. kgaa, weinheim, germany. leszek, m. 2005. extrusion-cooking techniques: applications, theory and sustainability. wileyvch verlag gmbh & co. kgaa, weinheim. lin, s., huff, he. and hseih, f. 2000. texture and chemical characteristics of soy protein meat analog extrudate at high moisture. journal of food science, 65:264. montgomery, dc. 1997. design and analysis of experiments. 4th edition. new york: john wiley & sons. nwabueze, tu. and iwe, mo. 2012. residence time distribution (rtd) in a single screw extrusion of african breadfruit mixtures. journal of food and bioprocess technology, 3:135-145. nwabueze, tu. 2006. gelatinization and viscosity behaviour of single screw extrusion in african breadfruit (treculiaafricana) mixtures. journal of food processing and preservation, 30: 717–731. omeire, gc., iwe, mo. and nwosu, jn. 2013. influence of extrusion variables on the residence time and throughput of a single screw extruder. british journal of applied science and technology, 3(2): 277-288. sueshan, l., sulaiman, r., sanny, m. and nur hanani, za. 2015. effect of extrusion barrel temperatures on residence time and physical properties of various flour extrudates. international food research journal, 22(3): 965-972. sobowale, s., bangbose, a. and adedola, a. 2016. effect of extrusion variables on the extrudate properties of wheatplantain noodle. journal of food processing and technology. 7: 547.doi: 10.4172/2157-7110.1000547. yusuf, m., filli, kb., umar, i. and halilu, m. 2017. effect of extrusion variables on physical properties and acceptability of dakuwa produced from blends of sorghum (sorghum bicolour l) groundnut (arachis hypogea l) and tiger nut (cyperus esculentus). african journal of food science and technology, 8(5): 138-149. zuilichem, dj., vankuiper, e., stolp, w. and jager, t. 1999. mixing effects of constituting elements of mixing screws in single and twin screw extruders. powder technology, 106: 147-159 yusuf et al: influence of extrusion process conditions on the residence time and throughput of a twin-screw extruder using full factorial experimental design. azojete, 17(4):517-526. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusufmoh2015@yahoo.com 527 arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 688 particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems m. abdulkadir*, z. m. gwoma, and a. b. buji (department of electrical and electronics engineering, university of maiduguri, maiduguri, nigeria) *corresponding author’s e-mail address: abdulkadirmusa@unimaid.edu.ng abstract power control in wireless radio system has been explored since the early 1990’s. many researchers have developed algorithms to address problem of power control. most of the algorithms in recent consider either the problem of minimizing the sum of transmitted power under quality of service (qos) constraints given in terms of minimum carrier-to-interference ratio (cir) in a static channel or the problem of mitigating fast fading in a single dynamic link. in this paper, a new approach to the power control was develop by treating the qos requirement as another objective for the power control and the resulting constrained multi-objective-objective optimization problem is solved by means of particle swarm optimization (pso).the convergence properties of the proposed algorithm are studied both theoretically and with numerical simulations. noisy, dynamical environment is assumed in the simulations. the algorithm was modified to take throughput into consideration. simulations demonstrated that the proposed power control algorithms converged faster than the conventional power control algorithms. also, the average transmitted power was less than the average transmitted power using the conventional methods with comparable quality of service (qos). keywords: mobile station, base station, power control, throughput, particle swarm optimization (pso). 1. introduction power control is essential in interference-limited capacity communication systems such as the direct-sequence code-division multiple access (ds-cdma). the power control regulates transmitted powers of the users to be as close to optimum as possible. the optimum transmission power is the minimum power needed to achieve some target quality of service (qos) level to users, which is usually expressed in terms of carrier-to-interference ratio (cir). the power control mitigates the well-known near-far problem in ds-cdma systems, which results in enhancing the system capacity and performance (foschiniand miljanic, 1993; pao and chen, 2014). moreover, power control prolongs the operation time of the battery of mobile terminals and reduces the interference to other cross-channel communication systems by minimizing the transmitted powers. for this and other reasons, the power control problem has been receiving a lot of attention in the wireless communication literature. although the power control problem is well understood, there still remain many related problems that are under active research such as speeding up the convergence of power control algorithms, determining the optimum implementation of the distributed power control (dpc), designing dpc without snapshot assumption that is fixed channel gains, and joining the power control with other resource control methods such as rate control and spatial processing. it can be shown that the minimum transmitted power vector, which is required to achieve the target cir to users, is the solution of a system of linear equations. direct solution of this system is called centralized power control, and it requires full knowledge of the channel gains between all active transmitters and receivers. this required knowledge makes the centralized power control impractical method. there are many iterative algorithms to solve the power control problem in distributed fashion. the commonly used methodology in the literature of dpc is the so-called snapshot analysis. the system parameters such as gains and noise levels of users are assumed to be fixed or slowly changing compared to the rate at which power updates can be performed. this assumption is required to allow the dpc to converge to the solution of the centralized power control algorithm. in practice, however, the link gains of mobile channels have fast and random fluctuations that occur in the same time scale as power can be updated. these characteristics of mobile channels arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 689 reduce the significance of the snapshot convergence property of the power control algorithms. the works of grandhi et al. (1994) and timand lin (1996) does not assume the snapshot analysis, but the resultant power control algorithm is relatively difficult to implement in a very limited processing power handset. the qos constraint usually is not sharp; rather, it has some margin in which the qos remains acceptable. to be more specific, the qos is accepted if it falls within a set that is lower limited by the minimum accepted qos and upper limited by the supremum qos (tadrous et al. 2011). the minimum accepted qos is the lowest acceptable connection quality, any level below that is unacceptable. the supremum qos is defined as the upper bound for the qos. the preferred power control is that one that can achieve an accepted qos level (i.e., a level that is between minimum and supremum qos levels) very fast at low power consumption. this proposed power control algorithm fast achieves an accepted qos level at very low power consumption. the power control algorithm is based on a snapshot assumption that the channel parameters as well as the mobile location are to be fixed for static scenario. this assumption is not valid for mobile communication systems due to their dynamic behavior. actually, studying the convergence behavior and the performance of the distributed power control algorithms based on the snapshot assumption does not give a lot of information about their behavior in real systems. the reason is that for dynamical systems the channel parameters, "simply the link gains", are changing fast. in some cases, the channel parameters become uncorrelated after a fraction of a millisecond (elmusrati et al., 2007; el-sherif and mohammed, 2014). in the case of a dynamical channel, a good power control algorithm is an algorithm, which can track the fast, dynamical changes of the channel. in the formulation, the optimum distributed power control algorithm is presented, which can track fast variations in the channel, while optimizing certain parameters. the objective is to keep the transmitted power as close to the minimum power as possible.in this paper, it will focus on the uplink power control case. it assumes that the cir of each user can be estimated accurately and is available for the power controller. a method to estimate the cir at the handset is proposed by yates (1995), and manish and chandra (2016). this estimation of cir is based only on 1-bit feedback channel. the paper is organised as follows: methodology, derivation of multi-objective distributed power control algorithm, the numerical results, and finally, discussion and conclusion. 2. materials and methods 2.1 multi-objective distributed power control algorithm the proposed algorithm in this paper aims to achieve two objectives by applying the particle swarm optimization method. the first objective is to minimize the transmitted power, and the second objective is to achieve an accepted qos level in terms of carrier-to-interference ratio. 2.1.1 transmitted power and carrier to interference ratio mathematically the power control problem is formulated as follows: to obtain the power control vector p, which minimizing the function as in (yates, 1995; gnatcatcher, 1964) can written as follows. ( ) ∑ ( ) subject to ∑ ( ) and (3) the transmitted power is given as abdulkadir et al.: particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems. azojete, 13(6):688-700. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 690 ( ) ∑ ( ) ( ) ( ) ( ) where , ( ) ( ) ( ) , ( ) ( ) it can be observe that xi(t) contains known, measured values of transmitted power. the power control algorithm will be derived, while solving the minimization problem of eqn. (3). the power pi(t) is described by an autoregressive model as shown in figure 1 (zander, 1992). figure 1: autoregressive model of power control the multi-objective problem in this case would be to minimize ( ) ( ( ) ( ) * ( ) with respect to subject to the following constraints. ̃( ) ∑( ( ) ( )) ( ) here the weights 0 . where: j1 and j2 are defined as follows; ( ) ( ( ) ) ( ) ( ( )) ( ( ) ) the time dependence is taken into account by considering a time horizon t = 1,…, n together with an adaptation factor. the power control problem then becomes: ( ) ,∑∑ ( ) ( ) to find the minimum of the objective function in eqn. (7) with respect to the power vector p, the error ( ) was defined as: ( ) ( ( ) ) ( ( ) ) ( ) where: is the target cir, was the minimum transmitted power of the mobile station, and p = [p1……..pq]. the main idea of the function in eqn. (4) is to keep the transmitted power pi(t) as close as possible to pmin and, at the same time, to keep the cir, γi(t) as close as possible to the target cir, . eqn. (4) was substituted into eqns.(8) and (2), then the error ei(t) became: ( ) ( ( ) ) ( ( ) ( ) ( ) ) ( ) arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 691 by denoting * ( ) ( ) + ( ) and using it in eqn. (8), ( ) became ( ) ( ) ( ) from eqns. (7) and (11), a necessary condition for the minimum transmitted power was found to be: ∑ ( ) ( ) ( ) from eqn. (10), ( ) ( ) ( ) substituting the function in eqns. (10) and (9) into (11) yielded eqn. (14). ∑ ( ) ( ) ∑ ( ( ) ) ( ) ( ) the minimization of the function in eqn. (14) with respect to piis was then transformed into minimizing eqn. (14) with respect to parameter vector w, for the minimization of transmitted power and the carrier to interference ratio (multi-objective). 2.1.2. transmitted power and throughput of the power control cellular system. in this procedure, the algorithm was based on the maximization of the throughput in the distributed power control cellular system. the throughput of user i was approximated when m-qam modulation as used by (elmusrati et al., 2007; and nie et al., 2016) as in eqn. (15) ( ) where: ti is the throughput of user i, θ is a constant, and гi is the carrier to interference ratio of user i as in eqn 16. ∑ (∏ ) ( ) where: q is the number of users. if the link gains gij of the users is given, then, the power vector p= [p1, p2,...,pq]’ will maximizes the throughput. since the first term in eqn. (15) is constant and the logarithmic function is an increasing function, then maximizing the multiplicative term (∏ ) will lead to maximizing the throughput tas in eqns 18.  = p | pmin ≤pi ≤ pmax, i = 1, . . .,q} (17) * ( )+ ( ) where ( ) ∏ ( ) ( ) eqn. (19) is the objective function, 1 = [1, 1, ..., 1, and the tradeoff factors real numbers, the necessary conditions for solving problem eqn. (18) are: ( ) ( ) abdulkadir et al.: particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems. azojete, 13(6):688-700. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 692 where ( ) , is the gradient of o. substituting the cir eqn. (2) into (19) led to eqn. (21). ( ( )) ∏ ( ) ∑ ( ) ∑ ( ) ( ) since the obtained equations are nonlinear, it will be very complicated to get an analytical solution, the power vector p which satisfies equation (20) must be obtained. an iterative solution for k = 1,..., q was formulated (the iteration argument, t was dropped for simplicity) ( ∏ )∏ (∑ ) (∏ )(∑ ∏ (∑ )) (∏ (∑ )) ( ) simplify equation above led to eqn. (23) ( ∏ ) (∏ )∑ (∑ ) ∏ (∑ ) ( ) which was written as: ∏ (∏ ) ∑ (∑ ) ( ) or ∑ (∑ ) ∏ ∏(∑ ) ( ) solving for pk led to: ( ∏ ∏(∑ ) ∑ (∑ ) ) ( ) and further to ( ) ∑ (∑ ( ) ) ∏ ( ) ∏ (∑ ( ) ) ∑ (∑ ( ) ) ( ) considering then from (19) the problem was reduced to maximizing the throughput, and from (27) the throughput after constraining the transmitted power was one obtained. without power constraints, eqn. (27) rewritten as: ( ) ∑ ∑ ( ) ( ) ( ) where gij is the channel gain between user j, and base stations i and n were additive noises. without loss of generality, the user i was assumed to be assigned to base station i. the problem in this case was minimized to: ( ) ( ( ) ( ) * ( ) and with respect to subject to possible constraints, had led to: arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 693 ̃( ) ∑( ( ) ( )) ( ) here the weights 0 . ( ) ( ( ) ) ( ) ( ( )) ( ( ) ) to find the minimum of the objective function in eqn. (31), ( ) ,∑∑ ( ) ( ) with respect to the power vector p, the error ( ) was defined as: ( ) ( ( ) ) ( ( ) ) ( ) ( ) ( ( ) ) ( ( ) ( ) ( ) ) ( ) denoting * ( ) ( ) + ( ) and using it in eqn. (33) ( ) becomes: ( ) ( ) ( ) from eqns. (30) and (35), a necessary condition for the minimization is given as: ∑ ( ) ( ) ( ) from eqn. (35) ( ) ( )( ) by substituting eqns. (35) and (37) into (36), we obtained ∑ ( ) ( ) ∑ ( ( ) ) ( ) ( ) the minimization of the function in eqn. (38) with respect to pmin was then transformed into minimizing (38) with respect to the parameter vector w for the minimization of the transmitted power and the throughput (multi-objective). 3. particle swarm optimization particle swarm optimization (pso) is a swarm intelligence method for global optimization. it differs from other well-known evolutionary algorithms (ea). as in ea, a population of potential solutions was used to probe the search space, but no operators, inspired by evolution procedures, are applied on the population to generate new promising solutions. instead, in pso, each individual, named particle, of the population, called swarm, adjusts its trajectory toward its own previous best position, and toward the previous best position attained by any member of its topological neighbourhood. thus, global sharing of information takes place and the particles profit from the discoveries and previous experience of all other companions during the search for promising regions of the landscape. in the single-objective minimization case, such regions posses lower function values than others. in the local variant of pso, the neighbourhood of each particle in the swarm is restricted to a certain number of other particles but the movement rules for each particle are the same in the two variant. many popular optimization algorithms are deterministic, like the gradient-based algorithms. compared with gradient-based algorithms, the pso algorithm is a stochastic algorithm that does not abdulkadir et al.: particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems. azojete, 13(6):688-700. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 694 need any gradient information. this allows the pso algorithm to be used on many functions where the gradient algorithm is either unavailable or computationally obtained. in the past several years, pso algorithm has been successfully applied in many research and application areas (zielinski et al, 2007, mathos et al, 2014). pso is also attractive because there are fewer parameters to adjust (meigin et al, 2016). it is demonstrated that pso gets better results in a faster, cheaper way compared with many other methods. 3.1. proposed pso-based algorithm for power control problem the pso algorithm that was used to minimize a fitness function that takes into consideration all the objectives of the power control problem and finally pso reaches a power vector that satisfies all these objectives to a great extent. in pso-based algorithm, every particle in the swarm represent a power vector containing power values to be transmitted by all mobile units in order to be evaluated and enhanced by the algorithm. note also that this method of representation of the power vector inherently satisfies the maximum power constraint as one always assigns the values of pmax. in order to test the effectiveness of the proposed algorithm, the particles of the swarm was first initialized to totally random particles. of course, this is not the real case, because in a real system the mobiles’ power was updated from the values of the power in the last frame. after that, the pso algorithm was applied with the proposed fitness function to these randomly initialized particles. the procedure of the proposed algorithm is as shown in figure 2. the pso pseudo-code for the algorithm ( ̅ ) ( ̅ ) // g ( ) evaluates fitness // pid is best so far next d end do g = i // arbitrary for j = indices of neighbors ( ̅ ) ( ̅ ) // g is index of best performer in the neighborhood next j for d = 1 to dimensions ( ) ( ) ( ( ) . ( )/ ( ) ( ) ( ) ( ) next d next i xi is the position of particles i, vi is the velocity of particles i, φ1 is a random number that gives the size of step towards personal best, φ2 is a random number that gives the size of the step towards global best ( the best particle in the neighborhood) and g is the fitness function to be minimized. arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 695 figure 2: proposed pso-based algorithm for power control 4. results and discussions the simulation was done for four base stations uniformly distributed in an area of 4 km 2 containing 100 users. mobile users were distributed uniformly over the cell space. as a result, the same equation was used to calculate the link gain of the mobile users. it has been assumed that updates were done on the positions of the mobile users and the fading conditions. the particles of the swarm were initialized to totally random number following the procedure described in the flow chart (figure 2). the simulation was done several times while varying the number of users in the cell. the pso based power control algorithm fitness function used to minimize the power control problem were also used for weighted sum approach power control algorithm to minimize the same fitness function in order to compare their results and to see the effectiveness of the proposed algorithm. the optimum power vector is the solution of the distributed power control algorithm. the outage is the percentage of users that do not achieve the minimum tolerable cir level. the transmitted power of all users in db of pso based power control algorithm for dynamic and static scenarios was considered. the results of each algorithm have been represented by the norm of the error and the outage percentage. the error is defined as the difference between actual transmitted power vector of the power control algorithm and the optimum power vector. 4.1. transmitted power and carrier to interference ratio in this case, for the purpose of comparison, the simulation was done for weighted sum approach and the pso-based power control algorithm for dynamic and static scenario. figure 3 (a) shows the error norm and (b) outage percentage for the static channel scenario, which indicates that the psobased power control converged faster than the weighted sum approach for static scenario. figure 4 (a), (b), and (c) shows the comparisons between pso and weighted sum approach power control algorithms in terms of error norm and the outage for the dynamic channel scenario as from table 1. as the iterations increased, the average value of error norm decreased because of the increase of the interference level between the users. also, the average value of the transmitter power increased because the mobile units had to increase their transmitted power in order to overcome the increase in the interference level and to maintain an acceptable quality of service per user. abdulkadir et al.: particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems. azojete, 13(6):688-700. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 696 (a) (b) figure 3: (a) error norm and (b) the outage percentage for the static channel scenario (a) (b) arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 697 (c) fig. 4 (a) error norm (b) the outage percentage and (c) transmitted power for the dynamic channel scenario table 1: comparison of pso-based power control with weighted sum approach for minimization of the transmitted power and carrier-to-interference ratio weighted sum approach distributed power control algorithm pso-based distributed power control algorithm numb er of users average cir (db) average transmitted power (w) outage probability average cir (db) average transmitted power (w) outage probability 5 7.000 0.273 0 4.000 0.183 0 10 5.001 0.371 0 5.003 0.221 0 15 6.005 0.381 0 4.004 0.232 0 20 6.000 0.496 0 5.000 0.291 0 30 7.002 0.652 0 6.001 0.521 0 40 5.001 0.998 0 4.000 0.999 0 55 7.005 0.865 0 5.000 0,764 0 65 6.000 0.976 0 4.001 0.866 0 70 6.004 0.754 0 7.005 0.692 0 80 5.000 0.976 0 4.000 0.944 0 90 7.002 0.988 0 6.004 0.922 0 100 5.000 0.999 0 4.000 0.998 0 4.2. transmitted power and throughput fig. 5 displays the error norm and the outage of the system using the pso-based and the weighted sum approach distributed power control algorithm for the static scenario. it is clear that the power has converged at about iteration number 40. the outage is zero after iteration number 20 and then rose to about 70% at iteration number 100. figure 6 shows the error norm, the outage percentage and the transmitted power for the dynamic channel scenario. the results of average transmitted power for the mobile units are presented in figure 6. in respect of the average transmitting power for the mobile units, pso algorithm converges with much smaller values of transmitted power to serve the same number of users. the resulting values of pso algorithm are about 65% on average from those of weighted sum algorithm. this means that pso algorithm is much better in searching the search space when the maximum number of iterations is reached. table 2 also shows the comparison between the pso-based and the weighted sum approach distributed power control in terms of average carrier to interference ratio, the average transmitted power and the outage probability. the average received cir was found to be slightly better for the weighted sum algorithm than those obtained by pso algorithm. this was an expected result because the result of weighted sum algorithm used greater values for transmitted power and thus they probably will achieve better average received carrier-to-interference ratio (cir). in spite of the fact that weighted sum results are better than pso results, the results for both algorithms are very abdulkadir et al.: particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems. azojete, 13(6):688-700. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 698 identical to each other. the resulting values of pso algorithm are about 99% on average from those of weighted sum algorithm. (a) (b) fig. 5 (a) error norm and (b) the outage percentage for the static channel scenario. (a) (b) (c) fig. 6 (a) error norm (b) the outage percentage and (c) transmitted power for the dynamic channel scenario. arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):688-700. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 699 table 2: comparison of pso-based power control and weighted sum approach for minimization of transmitted power and throughput weighted sum approach distributed power control algorithm pso-based distributed power control algorithm numb er of users average cir (db) average transmitted power (w) outage probability average cir (db) average transmitted power (w) outage probability 5 7.002 0.283 0 4.000 0.193 0 10 5.001 0.371 0 5.001 0.241 0 15 6.000 0.381 0 4.000 0.236 0 20 6.005 0.496 0 5.003 0.293 0 30 7.002 0.662 0 6.000 0.551 0 40 5.000 0.998 0 4.004 0.999 0 55 7.000 0.875 0 5.000 0,766 0 65 6.003 0.976 0 4.001 0.876 0 70 6.004 0.784 0 7.000 0.695 0 80 5.003 0.976 0 4.000 0.944 0 90 7.004 0.998 0 6.003 0.922 0 100 5.000 0.999 0 4.000 0.998 0 5. conclusion in this paper, a new algorithm for the power control problem in wireless radio system is presented. it makes use of the powerful pso-based method. the main advantages made in this approach are modifying the fitness function in order to handle the minimization of the near-far effect in a more effective way and applying the pso algorithm to get a power vector that satisfies all the objectives of the power control in wireless radio system problem. the algorithm was modified to react to updated mobile users’ positions and fading conditions in order to have the ability to be implemented in a real wireless radio system network. experimental simulations proved the efficient performance of the proposed fitness function. these simulations also proved that the developed technique can produce results that outperform the results of trying to maximize the same fitness function using weighted sum approach. also, the developed technique produced good results when it was tested while changing users’ conditions. as a suggestion for future work, the hardware implementation of the proposed algorithm trying to implement it using dsp processors or fpgas may be studied. studying this implementation will give a decision if this algorithm can be really implemented in a wireless radio system standard or it will face some implementation problems. references elmusrati, ms., koivo, h. and jantti, r. 2007. multi-objective distributed power control algorithm for cdma wireless communication systems. transactions of ieee conference on vehicular technology, 56 (2): pp 779-788. el-sherif aa. and mohammed a. 2014. joining routing and resource allocation for delay minimization in cognitive radio based mesh networks. transactions of ieee conference on wireless communication, 13(1): pp 186-197. foschini gj. and miljanic z. 1993. a simple distributed autonomous power control algorithm and its convergence, transactions of ieee conference on vehicular technology, 42 (4):641–646. gantmacher f., 1964. the theory of matrices, chelsea publishing company, vol 2. abdulkadir et al.: particle swarm optimization (pso)-based distributed power control algorithm for wireless radio systems. azojete, 13(6):688-700. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 700 grandhi sa., viljayan r., and goodman dj. 1994. distributed power control in cellular radio systems. transactions ieee conference on communications, 42(2-4): pp 226-228. manish r, and chandra p. 2016. comparative analysis of power control algorithms in cdma system using optimization techniques. international journal of electronic communication and computer engineering, 7(1): pp 16-21. mathos clc., barreto ga., and cavalcanti frp. 2014. an improved hybrid pso algorithms applied to economics modeling of radio resources allocation, electronics commerce research. 1: pp 51-70. meigin t, yalin x, chenguian l, xinjiang w, and xiaohua l. 2016. optimizing power and rate in cognitive radio networks using improved pso with mutation strategy. transactions of ieee conference on wireless communications, 10(1): pp 1965-1976. nie d., feng, y., zhen c., zhang j., and ning, g. 2016. power control for under-water acoustic mc-cdma communication networks using improved pso algorithms. transactions of ieee conference on vehicular technology, pp 206-216. pao wc. and chen yf. 2014. adaptive gradient-based methods for adaptive power allocation in ofdm-based cognitive radio networks. transactions of ieee conference on vehicular technology, 63(2): pp 836-848. tadrous j., sultan a., and nafie m. 2011. admission and power control for spectrum sharing cognitive radio networks. transactions of ieee conference on wireless communications, 10(1): pp 1945-1955. tim hl. and lin jc. 1996. a study on the distributed power control for cellular mobile systems. transactions of ieee conference on vtc, 2: pp 1130-1134. yates r. d., 1995. a framework for uplink power control in cellular radio systems. ieee journal on selected areas in communications, 13(7): pp 1341-1347. zander j. 1992. “distributed co-channel interference control in cellular radio systems,” transactions of ieee conference on vehicular technology, 41 (3): pp 305–311. zielinski k., weitkemper p., laur r., and kammeyer, kd. 2007. optimization of power allocation for interference cancellation with particle swarm optimization. transactions of ieee conference on evolutionary computation; pp 1-23. arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):505-516 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 505 original research article modelling the safety level of the construction industry in southwestern nigeria w. a. raheem1*, o. o. akinyemi2, h. o. adeyemi2, o. a. adeaga3 and o. g. olasunkanmi4 1department of systems engineering, university of lagos, lagos, nigeria 2department of mechanical engineering, olabisi onabanjo university, ago-iwoye, nigeria 3department of mechanical engineering, first technical university, ibadan, nigeria 4department of electrical/electronic engineering, olabisi onabanjo university, ago-iwoye, nigeria. *corresponding author’s email address: raheemwasiuade@gmail.com 1.0 introduction despite the economic contribution of building companies, the construction sector is noted for as a dangerous and highly endangered area. it has been reported in the uk that people face a higher risk of death or harm at work than employees in other sectors of the economy (hse, 2006a, asanka and ranasinghe, 2015; ahmed et al., 2018) while the building sector is continually responsible for the most extraordinary number of fatal injuries/accidents than any other uk industry (hse, 2006a). on average, building deaths in the previous five years accounted for around 30 percent of all employee fatalities (hse, 2006b). based on these numbers, building was found to have the second-worst file for the health and safety industry after agriculture article information abstract the number of accidents in the construction industry in nigeria is very high. it is rare to disclose safety performance metrics required to draw government attention to these incidents. this research aims to develop a predictive safety analytical model for the construction industry's safety assessment. the activities of safety standards in the nigerian construction industry and improvement programs expected to be introduced in the construction industry have been researched to recognize the risks of construction accidents. the building injury risks found were modelled as predictor variables while the response variable was the level of safety using multiple regression analysis. spearman's correlation analysis identified predictor variables that correlate significantly at p˃0.05 to the safety level, while predictor variables with low correlations have been excluded. the safety level was calculated on a linguistic scale of 5 points. the predictive ability of the model was verified at a 5 percent significance range by the coefficient of determination (r2) and the t-test. under law and regulation, practices, personal factors and encouragement, fifteen task-related construction accident risks were identified and listed. the developed multilinear regression model has an 84.8% r2 rating. a 92.1% correlation between the predicted values and the human-interpreted safety-level values was revealed by the model implementation. the study also shows that personal variables should be given the highest degree of consideration by site engineers. the t-test showed no substantial difference between the values predicted and the values perceived by the level of human protection. due to the feasibility of the study, the constructed model will serve as a valuable instrument for monitoring the safety level of nigeria's construction sites. it is recommended that the model be used by site engineers and safety personnel from federal and state ministries. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 february, 2021 revised 28 sept., 2021 accepted 30 sept., 2021 keywords: construction accident hazards personal factors safety performance predictive analytic and safety level raheemwasiuade@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):505-516. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 506 (hse, 2006c). the building industry is the riskiest industry and is vulnerable to accidents (hse, 2018). the response of the construction industry to workplace safety injuries has inevitably changed, and different initiatives aimed at improving the safety culture are now common in large organizations (adekunle et al. (2018). the various programs are not mutually exclusive and, in fact, some say that the most feasible approach is to use a combination of both. in the past, the absence of comprehensive methods to examine and evaluate the various relationships between the different system risk factors associated with construction sites has limited attempts to identify and predict factors that impact safety on construction sites. this has been solved by predictive analytics. the ministry of manpower (mom) in singapore tracks site safety through several steps. the rate of incidence, the number of industrial accidents per million hours worked by man, and the severity rate, which is the number of industrial days lost per million hours worked by man, are all included (mom, 2002). accident contributors can be grouped into five considerations from the previous safety studies literature and the nigeria code of practice for building worksites safety management system (cp79): regulation, process, workers, motivation, and others. lingard and rowland (1994) demonstrated that policy legislation forms a mechanism by which health and safety are regulated and controlled. all construction professionals have to correctly follow the laws and regulations and impose fines on anybody who violates them. lingard and rowland (1994) found that the implementation of legislation in hong kong had an important influence on the protection of construction jobs. safety legislation needs to be taken seriously when organizing job activities and drawing up company policies. process variables relate to the work performed by building workers that can potentially be detrimental to their well-being and safety. enwerem et al. (2017), mom (2002) and ofori (1997) stressed that construction site accidents are typically caused by a hazardous working environment. there may also be accidents caused by such heights, stepping on, hitting or tripping objects, poor lighting conditions, burying by earth collapse during excavation, fire hazards, inadequate education and training, insufficient equipment and machinery interference. personnel variables apply to topics relating to the human aspect of building activities, such as the behavior of supervisors and workers within an organization with regard to safety and attitudes. according to clarke (1999), safety culture is a subset of organizational culture where beliefs and values specifically apply to matters of health and safety. therefore, the safety culture of a company relies on the level of commitment of its management and workers to promoting and advocating for safety. many different human, technical, environmental, and organizational factors affect the safety performance of any construction operation. while a single catalyst is generally credited as the obvious cause of any construction accident, accidents occur from numerous latent triggers and sub-factor that together lead to an accident, most often either due to human error or technical failure. several models of the incidence of occupational accidents are made up of several variables in the building industry. statistical approaches, on the other hand, may be used to infer cause-and-effect relationships between these variables. due to the large number of factors involved and the uncertainty of the relationships between each other, it is difficult for managers to identify potential risks in raheem et al: modelling the safety level of the construction industry in southwestern nigeria. azojete, 17(4):505-516. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 507 construction projects and develop effective safety procedures (cheng et al., 2010, cheng and wu, 2013). historical trends indicate that more studies and data on cause and mitigation methods are needed in the more recent past so that safety experts can educate on how to further reduce these injuries and fatalities (manuele, 2008). while research attempts have been made to identify factors affecting the safety of construction sites, there is a lack of analytical methods to analyze and evaluate the complex relationships of the system's various risk factors. in addition to the important identification of risk factors, there has been a constant need to develop sophisticated risk assessments to improve system prediction and complex causality assessment and test various combinations of risk mitigation strategies (luxhøj, 2003). although major research efforts have been made to identify different factors that cause construction accidents, the literature review shows that very little has been done to assess the likelihood of building safety risk based on current site conditions. predictive analytics is a form of advanced analytics that uses recent and historical data to forecast future behavior, behaviour and patterns. methods of statistical analysis, empirical queries, and automated machine learning algorithms are applied to data sets that create predictive models that place a numerical value or ranking on the likelihood of a given event. applications have been reported in a number of fields, including financial services, banking, telecommunications, etc. the predictive analytics method has not gained prominence in the engineering industry because it is not inherently linear, and where data scientists do not look, correlations also occur. recent engineering work has, however, been performed using predictive analytics. the aim of this research is to carry out predictive analysis of safety problems for smes in the construction industry. in order to accomplish this goal, the research aims to recognize possible construction work hazards at selected construction sites in southwestern nigeria and develop a model to predict the safety level of the construction site. the scope of this study is restricted to certain tasks specifically related to the construction of a building and other civil engineering works. 1.1 dynamic nature of the construction industry in certain respects, construction workplaces are very different from fixed industries. not only are they different, but they also tend to grow and shift from day to day. when a project is completed, staff and managers move on to new projects and start all over again. this community reflects the diverse character of the industry. many aspects of health and safety have been affected by the complex existence of the industry. the building industry, therefore, has the most injuries than the fixed market (ajayeoba et al., 2019). ratay (1997) reported that every year in the united states, nearly 1,000 construction workers lose their lives, and many others are injured. hse (2017) reported that 80,000 construction workers in great britain suffered from a disease caused by the existence of such work between 2014/15 and 2016/17. this event is not limited to the united states and great britain alone, but in all other countries it is more prevalent. as an example, the occurrence of a construction accident in nigeria tends to increase each year, as shown in the following table 1. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):505-516. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 508 table 1: construction accident cases in lagos southwest nigeria from 2001 to 2015 (adekunle et al., 2018) number of wounded people number of live lost number of amputees number of near misses number of reported accidents 2001 1 1 2002 1 2003 5 1 2 2004 8 2 1 1 3 2005 12 3 1 1 5 2006 17 10 4 2007 21 12 1 2 4 2008 26 15 5 2009 32 22 2 1 6 2010 38 18 2 1 6 2011 40 25 4 7 2012 45 20 2 3 8 2013 48 15 5 2 9 2014 59 22 13 2 15 2015 65 40 15 4 20 total 417 205 43 21 96 the best ways to avoid accidents are ultimate procedure, realistic inspection, and rigorous implementation of high standards of treatment, useful predictive safety analytics and appropriate building practices. the engineer, contractor, regulator, and the authority, however, should comply with all the same rules that have the power to enforce them. the purpose and design, codes and standards are served by the building to some extent. although all failures and incidents are not prevented by codes and regulations, compliance with them improves site safety. 2. materials and methods 2.1 data collection a questionnaire was prepared and administered to determine the more important variables affecting the protection site. information on the safety aspects of one of their most recent completed projects were demanded by the respondents. on a five-point linguistic scale, respondents were asked to rate the degree to which each of the variables affected the construction project's site safety level, where '1' was not relevant at all, and '5' reflected 'very important'. the target population is contractors registered with the council of registered builders of nigeria (corbon). based on their operational and financial capacities, corbon classifies each registered contractor into one of seven categories. the lowest category of contractors can bid no more than ngn500,000 in value for construction projects, while the highest category of contractors may bid for construction projects of any size. two hundred and fifty general building contractors were selected for the study sampling initiative. of these, questionnaires in all seven categories were sent to 200 randomly chosen contractors. this is predicated on the fact that the sample size selected is based on desired accuracy with confidence level of 99% (taherdoost, 2017). the survey package contained a cover letter, a questionnaire and an envelope that was self-addressed and pre-stamped. 2.2 survey results and data analysis the designation of the respondents covers a wide range. 20%, 48% and 17% of respondents were upper management, middle management and safety personnel, respectively. junior staffs were just 7 percent of the respondents. managing directors, directors, general managers and raheem et al: modelling the safety level of the construction industry in southwestern nigeria. azojete, 17(4):505-516. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 509 senior project managers were among the upper management respondents. project managers and assistant general managers were middle management respondents. safety personnel report to the officer/manager for environmental health and safety, the safety officer, the safety supervisor and the auditor for safety. site managers, site coordinators and clerk-of-works are referred to by junior workers. in the construction industry, the average number of years that respondents employed was ten years. the minimum and maximum numbers of years of experience, respectively, are 1 and 34. also, 60% of the respondents have more than five years of working experience. the mean response for each attribute was calculated, as shown in table 2. 2.3 development of the model in this study, the model was developed using multiple regression analysis to assess the statistical relationship between the level of site safety (response variable) and the explanatory variables (accident-causing construction site task-related activities, see table 3). the model was developed using multiple regression techniques with statistical package for social science software (spss16.0). the attributes related to the regulation and policy, work practices, workers and motivation aspects of the project listed in table 3 are the independent/predictor variables. techniques for modelling make it possible to simulate the actual situation more accurately. it allows the effect to be predicted of changes to a given system. the number of predictor variables compiled was reduced before embarking on regression modelling. in step 1, predictor variables that correlate significantly (p ≤ 0.05) to the safety level are identified via spearman's correlation analysis. the other independent variables showing weak correlations with the output parameter (p > 0.05) were excluded, and the number of predictor variables was also reduced. the predictor variables that were significantly correlated with the dependent variable were then used to construct a linear regression model. the spss program implemented site safety and related construction project features and created 15 potential models. the model's predictive power is measured by the determination coefficient (r2), which is a measure of the consistency of fit for the model. when more than two variables are being analysed, r2 is used to calculate the intensity of the correlation; r2 provides the proportion of y's variance (dependent variable), which is explained by the independent variables, illustrating the model's feasibility. however, r2 increases automatically as more independent variables are added into the model. r2 modifies a better estimate of the goodness of fit of the model. table 2: the mean response to the questionnaire for each attribute rank ref attributes influencing site safety mean regulations and policy (rp) 1 rp1 national environment standards and regulation enforcement agency (nesrea) act of 2007 3.4789 2 rp2 national environmental (construction sector) regulations, 2010. s. i. no. 19. 3.5775 3 rp3 environmental impact assessment act 2.8169 4 rp4 the nigerian urban and regional planning act cap n138, lfn 2004 3.6197 5 rp5 state physical planning and development control laws and regulations 2.6620 6 rp6 factories act (1958, 1987 & cap.126 l.f.n.1990, cap. f1 l.f.n.2004); 2.8310 7 rp7 labour act (1974 & 1990) 3.9014 8 rp8 workmen's compensation act (no.17, 1987, cap. w6 lfn, 2004, 2010) 2.9155 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):505-516. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 510 9 rp9 all risk insurance policy 4.0282 work practices (wp) 1 wp1 identification of unsafe practices on site 3.3803 2 wp2 proper implementation of safe practices and procedures on site 3.8169 3 wp3 clean site keeping 2.9437 4 wp4 proper handling of tools, equipment and plants 4.1268 5 wp5 good maintenance of tools, equipment and plants 2.0845 6 wp6 safety communication and adequate dissemination of information 4.0141 7 wp7 reasonable control of hazardous material and activities 2.8451 8 wp8 technical competency of specialist sub-contractors 2.8732 9 wp9 proper control and management of sub-contractors 1.9014 personal (p) 1 p1 quality of safety knowledge among workers and managers 2.8732 2 p2 safe work practices of workers and managers 3.9296 3 p3 management commitment to advancing safety and health among workers 3.8028 4 p4 quality of safety and health training among workers and managers 3.9155 5 p5 effectiveness of the safety committee 1.8028 6 p6 regular site inspection by the safety committee 2.8732 7 p7 safety promotion and posters 2.8028 8 p8 safety program and talks 2.8310 9 p9 work experience of workers and managers 3.9296 10 p10 safety communications among workers& managers 4.0986 motivations (m) 1 m1 quality of incentives (monetary) 3.3380 2 m2 quality of incentives (promotion) 2.5915 3 m3 quality of penalties and punishments (monetary) 3.4930 4 m4 quality of penalties and punishments (termination of service) 2.6620 5 m5 quality of penalties and punishments (delayed promotion) 2.6197 6 m6 safety committee /managements' accident investigation and analysis plans 1.8028 7 m7 safety committee accident investigations and analysis plans 2.9296 3. results and discussion 3.1 results in order to determine how predictive safety analytics can predict task-related hazards in the construction industry, a multiple linear regression model (mlrm) was developed. for the predictor variables, the coefficients are as presented in table 4. after the 20th iterative process, the predictor variables selected were nigerian urban and regional planning act cap n138, lfn 2004 (rp5), and labour act (1974 & 1990) (rp8). all-risk insurance policies (rp9), identification of hazardous on-site activities (wp-1). also, proper implementation of safe practices, procedures on-site (wp2), proper handling of tools, equipment and plants (wp4), safety communication and adequate dissemination of information (wp6), good control of hazardous material and activities (wp7). others are safe work practices of workers and managers (p2), management commitment to advancing safety and health among workers (p4), quality of safety and health training among workers and managers (p9), work experience of workers and managers (p10), quality of incentives (monetary) (m1), quality of penalties and punishments (monetary) (m3). and lastly,amongst the predictor variables, (rp9) followed by (m3) were the strongest. the regression model's description, the analysis of variance (anova) of the regression model, and the regression model's residual statistics are shown in tables 5, 6 raheem et al: modelling the safety level of the construction industry in southwestern nigeria. azojete, 17(4):505-516. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 511 and 7. figure 1 shows the histogram of the residuals that are close to being normally distributed because violation of normal distribution compromises the estimation of the coefficients. table 3: summary of results obtained (coefficients of predictor variables) unstandardised coefficient unstandardised coefficient standardised coefficient model b std. error beta t sig. (constant) -1.447 .372 -3.885 .000 the nigerian urban and regional planning act cap n138, lfn 2004 .030 .113 .032 .267 .791 labour act (1974 & 1990) .044 .059 .045 .738 .464 all risk insurance policy .229 .071 .248 3.208 .002 identification of unsafe practices on site .076 .093 .082 .813 .420 proper implementation of safe practices and procedures on site .081 .109 .072 .746 .459 proper handling of tools, equipment and plants .030 .100 .028 .304 .762 safety communication and good dissemination of information .102 .070 .109 1.446 .148 good control of hazardous material and activities .194 .101 .205 1.915 .061 safe work practices of workers and managers .055 .086 .059 .639 .526 management commitment to advancing safety and health among workers .147 .103 .145 1.431 .158 management commitment to advancing safety and health among workers .055 .086 .047 .638 .526 work experience workers and managers of .011 .087 .011 .127 .899 safety communications among workers& managers .010 .066 .011 .155 .878 quality of incentives (monetary) .045 .052 .063 .863 .392 quality of penalties and punishments (monetary) .224 .073 .222 3.057 .003 table 4: model summary of the regression model model r r square adjusted r square std. an error of the estimate 1 .921 .848 .806 .37278 table 5: anova of the regression model model sum of squares df mean square f sig. regression residual total 42.554 7.643 50.197 15 55 70 2.837 .139 20.415 .000 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):505-516. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 512 table 6: residual statistics of the regression model minimum maximum mean std. deviation n predicted value stud. deleted residual mahal. distance cook's distance centred leverage value 1.8360 -2.653 6.842 .000 .098 5.0162 2.457 25.629 .122 .366 3.6479 .000 14.789 .020 .211 .77969 1.034 4.747 .030 .068 71 71 71 71 71 figure 1: histogram of residual for the predictive safety level model figure 2 revealed some deviations of the dependent variable from the normal distribution line (from (0.18 to 0.42) meanwhile, some residual fall on the normal distribution line (0.38 to 0.65). figure 2: normal p-p plot of regression standard residual 3.2 model estimation and diagnostics the safety level was measured on a 5-point scale, where 1 = shallow risk (vlr), 2 = low risk (lr), 3 = medium risk (mr), 4 = high risk (hr), and 5 = very high risk (vhr). the other variables are as defined in table 3 and were measured on a 5-point scale, where 1 = not important, and 5 = very important. the predictive safety level model can be represented below: raheem et al: modelling the safety level of the construction industry in southwestern nigeria. azojete, 17(4):505-516. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 513 where y = the predicted safety level. cook's distance value was determined. according to field (2013), the cook distance's maximum value should be less than 1.0 to mean that no cases have an unfair effect to find out the maximum value, as shown in table 7, the cook distance's maximum value was 0.122, with a standard deviation of 0.030. since the maximum value is smaller than the 1.0 value, it seems like there are no problematic cases in the regression model. 3.3 model implementation to use the model, contractors enter the appropriate ratings using the 5-point scale for the 15 predictor variables (1 = not significant, 5 = very significant) and then determine the construction site's safety level (y). table 7 shows the interpretation of the response variable (safety level) obtained from the model. three predictor variables were described under regulatory and policy factors: act cap n138, lfn 2004 (i.e. state physical planning and growth control laws and regulations) (rp5) of nigerian urban and regional planning; workmen's compensation act (no.17, 1987, cap.w6 lfn, 2004, 2010) (rp8) and all liability insurance scheme act (rp8) (rp9). this policy is done with other variables that make up the model. there is no negative beta (β) coefficient for the entire attribute, indicating that the site safety level may increase when there is higher participation or understanding. table 7: interpretation of the safety level of the mlrm safety level interpretation of safety level 1.00-1.99 very low safety level (high risk) 2.00-2.99 low safety level 3.00-3.99 average safety level 4.00-4.99 high safety level (low risk) 5.00-above very high safety level (very low risk) 3.4 correlation test a strong correlation was observed after comparing the outcome of the predicted mlrm values with that of hp for the correlation strength using spearman's rho, r = 0.921, p<.01. the coefficient of correlation r (92.1%) shows that the model indicates a good linear relationship between the predictor variables and the dependent variable. the determination coefficient of the model indicates that 84.8% of the independent variable determines the expected safety level of construction sites. 3.5 discussion a company's participation in the protection certification scheme may be accomplished by the labor act. to do this, businesses need to follow the occupational health and safety evaluation scheme (ohsas) 18001. while safety certification is intended to encourage and increase awareness of safety, promote healthy work practices and increase the safety standards of the construction industry in nigeria, the findings show that low levels of this will harm safety standards in nigeria (workmen's compensation act (no.17, 1987, cap. w6 lfn, 2004, 2010), rp8). a potential reason is that employees might be busier with on-site documentation, paperwork without regards to real aspects of safety. the workmen's compensation policy and the all risk liability policy of the contractor, as defined in the labour act, require insurance arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):505-516. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 514 requirements to be met by the contractor before any construction work begins. table 7 show that a better understanding of insurance policies can contribute to lower safety at the site (rp9). this result is contrary to the study by lingard and rowlinson (1994) who reported that contractors who rely more on insurance can prefer to pass the responsibility for compensation to insurance companies and thus neglect the adequate provision of adequate training and supervision for workers in site safety. five factors directly impact site safety under work practices: identification of unsafe on-site practices (wp1), proper implementation of safe onsite practices and procedures (wp2), proper handling of machinery and plant tools (wp4), safety communication and adequate information distribution (wp6) and reasonable control of hazardous materials and activities (wp7). the positive beta (ß) coefficient shows that as more safety procedures are implemented, safety levels can increase. one potential reason is that workers with many safety processes employed on construction sites may become complacent about safety. dedobbeler and beland (1991) found that in carrying out mission and jobs, some organizations or individuals had actually unknowingly committed an unsafe act. as a result of their negligence, they are subjecting themselves and others to potential hazards and injuries. but, in this study the personnel component has five variables that impact the protection of the site. healthy work practices of employees and managers (p2); management contribution to the development of worker safety and health (p3); consistency of worker and manager safety and health training; responsibilities (p4); work experience of employees and managers (p9); and safety communications between employees and managers (p9) (p10). the results show that when there are more safety and health training for employees (p2), site safety will become higher. this act is consistent with work done by heberle (1998), lingard (2001) and ajayeoba, et al., (2019). in addition, lingard (2001) revealed that training has a positive protective impact on staff to escape injury while researching the effects of first aid training on australian construction workers. likewise, mckenna and hale (1981) found that workplace injuries were reduced when workers received first aid training. the positive beta (ß) coefficient for workers' language and communication barriers (p10) shows that when barriers are lower, site protection will be lowered. these are similar to the findings of studies by ajayeoba et al., (2015) that strengthened safety practices and enhanced safety policies can be accomplished through better communication and knowledge transfer (holt, 2001). the type and quality of knowledge transmission varies in different ways (e.g. verbal, written, gestural, etc.). they may have a big effect on the efficacy of such means of transition. the protection of the site will also improve as staff and supervisors (p9) are elevated. work experience will contribute to better job efficiency, and this will also result in lower breaches of safety. more work experience leads to better job results because work experience enables people to learn skills, strategies, techniques and activities that produce performance capabilities directly (schmidt et al. 1986). this study shows that when management is committed to advancing safety and health among employees, the level of safety on site will actually increase (p3). this outcome is a peculiar outcome because if all the positive actions contribute to reduced outcomes, they appear to have no beneficial use. the dependence on this committee to ensure site safety is one potential explanation; this finding is similar to the result of jayeoba et.al.,(2018) a et al. (2018) instead of keeping the business of everyone protected. the quality of rewards (monetary) (m1) and the quality of fines and punishments (monetary) are two motivational characteristics that affect site safety (m3). consequently, these motivational features are in line with the studies of geller (1999) and adebiyi and charles-owaba (2009). the reasons may be that these steps are extreme and can only be taken into account if the violator has committed or is a repeat raheem et al: modelling the safety level of the construction industry in southwestern nigeria. azojete, 17(4):505-516. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: raheemwasiuade@gmail.com 515 offender of serious safety and health abuse. this result is consistent with hislop (1999), who argued that punishment should be the last resort when all others has failed to strengthen the implementation of healthy work practices (training, guidance and encouragement). 4. conclusion the work reported that significant factors have been established that affect construction safety and the degree of site safety can be expected. the multiple linear regression models built to predict building site safety has shown that 15 variables can be used to predict building safety. under regulations and policy factors, three predictor variables were established, namely: the nigerian urban and regional planning act cap n138, lfn 2004; the labor act (1974 & 1990); and all risk insurance policies. five factors directly influence site safety in terms of work practices, viz identification of unsafe on-site practices; successful implementation of safe on-site practices and procedures; careful handling of machinery, equipment and plants; coordination of safety and effective dissemination of information; and good management of hazardous materials and activities. in the aspect of personnel, there are five variables that affect site safety. these are the healthy working practices of managers and employees as; management dedication to ensuring the safety and wellbeing of employees, the continuity of health and safety instruction among employees and managers, the job experience of employees and managers and safety communications among employees and managers. quality of rewards (monetary) and quality of fines and penalties are two motivational characteristics influencing site safety. the model has a strong r2, and there are large regression coefficients. it is clear that the model built in this study can be used to predict the safety level of the construction site. therefore, contractors should ensure that their projects have high safety standards and be more focus on the important characteristics that influence the degree of site safety. references ajayeoba, ao., adebiyi, ka. and raheem, wa. 2018. a mathematical approach to perception of safety as investment rather than accident prevention only. international journal of mechanical and production engineering (ijmpe), 6(1): 65-69. adebiyi, ka. and charles-owaba, oe. 2009. towards setting a sustainable manufacturing safety programme, disaster prevention and management, 18 (4): 388 – 396. adekunle, a., umanah, ii., adewale, ak. and egege, cc. 2018. analytical study of casualties in the construction industry in nigeria with a view to provide remedial measures: case study of lagos state. international journal of engineering research and advanced technology, 4(8): 6-14. ahmed, s., sobuz, md. h. and haque, md. i. 2018. accidents on construction sites in bangladesh: a review proceedings of the 4th international conference on civil engineering for sustainable development (iccesd 2018), 9~11 february 2018 kuet, khulna, bangladesh,pp 34 36. ajayeoba, ao., raheem, wa., adebiyi, ka., ilori, oo. and ojo, oo. 2019. modeling safety beyond accident prevention in construction industry. adeleke university journal of engineering and technology (aujet), 2(1): 36-47. ajayeoba, ao., adebiyi, ka., akinyemi, oo. and akintan, al. 2015. evaluation of effectiveness of manufacturing safety intervention: a key to successful safety planning and management industrial engineering letters, 5 (8): 34 – 39. asanka, wa. and ranasinghe, m. 2015. study on the impact of accidents on construction projects 6th international conference on structural engineering and construction management, kandy, sri lanka, 11th – 13th december 2015, 4: 58 67. cheng, c. and wu, t. 2013. an investigation and analysis of major accidents involving foreign workers in taiwan's manufacture and construction industries. safety science, 57, 223–235. http://iraj.in/journal/ijmpe/author.php?author=a.%20o.%20ajayeoba http://iraj.in/journal/ijmpe/author.php?author=k.%20a.%20adebiyi arid zone journal of engineering, technology and environment, december, 2021; 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effected by codes and standards. american society of civil engineers. 1801 alexander bell drive, reston, va 20191-4400. minneapolis, minnesota. schmidt, fl., hunter, je. and outerbridge, an. 1986. impact of job experience and ability on job knowledge, work sample performance, and supervisory ratings of job performance. journal of applied psychology, 71(3): 432-439 doi: 10.1037/0021-9010.71.3.432. taherdoost, h. 2017. determining sample size: how to calculate survey sample size. international journal of economics and management systems, 7(2): 237-239 http://www.mom.gov.sg/ http://dx.doi.org/10.1037/0021-9010.71.3.432 arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):347-356 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 347 original research article modelling self purification of river benue within makurdi i. m. aho, g. d. akpen and c. c. aniakor* department of civil engineering, federal university of agriculture, makurdi, benue state *corresponding author’s email address: aniakorchikachristopher@gmail.com 1.0 introduction rivers naturally exhibit some level of self-cleansing to reduce or eliminate contaminants completely through one or conglomerate of natural processes (physical, chemical and biological reaction). bacteria in the water body carry out these processes which biochemically degrades organic matter through a reaction called oxidation. this reduction in oxygen concentration in the rivers is replenished through the surface diffusion of atmospheric oxygen into the river. therefore, the ratio of this oxygen addition during aeration of the river to the rate of consumption of oxygen during degradation of pollutants is referred to as self purification capacity (fair, 1939). self purification is the ability of a river to regenerate itself by degrading pollutants through the use of available aquatic oxygen. the dissolved oxygen (do) remains the convenient criterion for measuring the surface water quality of a river as far as self purification is concerned because the ecology of a river depends largely on the quantity of dissolved oxygen in its water (khan and singh, 2013). this is why oxygen demand (od) has been traditionally used to assess the pollution degree and self-purification of a water body (galvis et al., 2014). models have been used as a tool to simulate the water quality and self purification of many rivers (ugbebor et al 2012);khan and singh,2013;ogbaji et al.,2013;dikeogu et al., 2014). all these literatures on the study of self purification were encamped on the study of fair,(1939) and his equation. this equation stated that self purification is the ratio of re-oxygenation to deoxygenation. re-oxygenation is the process of addition of atmospheric oxygen through surface interchange into a water body to replenish the used up dissolved oxygen. the replenishment of oxygen in river water is dependent on the water flow velocity, water depth and river geometry (dikeogu, et al., 2014). ugbebor et al. (2012) modeled re-oxygenation with these parameters article information abstract this study considered biochemical oxygen demand (bod), dissolved oxygen (do), the reoxygenation rate, the de-oxygenation rate, the self-purification rate model for river benue within makurdi reach. the hydrodynamic data were collected while reoxygenation rate, de-oxygenation rate and self purification rate were calculated using do and bod at 14 different stations along the river stretch. an empirical model for self purification was generated analytically using multiple linear regression equation analysis. the ph varied from 6.8 to 8.08 while do concentration between 4.0 mg/l and 6.3 mg/l; bod concentration ranges from 1.0 mg/l to 2.0 mg/l; mean reoxygenation rate of 0.179 in the raining season and 0.1 in the dry season; mean deoxygenation rate of 0.1186 day-1 in the raining season and 0.1345 day-1in the dry season was calculated; self purification coefficient had a mean value of 1.3398 in dry season and 0.8354 in rainy season; the model has coefficient of determination (r2) and adjusted r2 of 0.5691 and 0.5469 respectively; a multiple correlation coefficient of 0.7544 and root mean squared error of 0.2433 between the observed field data and the model data. in conclusion, the river has good self purification ability and the model generated is reliable considering the root mean squared error. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 3 february, 2021 revised 14 may, 2021 accepted 19 may, 2021 keywords: river pollution self-purification dissolved oxygen re-oxygenation de-oxygenation models aho et al.: modelling self purification of river benue within makurdi. azojete, 17(3):347-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 348 while including hydraulic radius. de-oxygenation is the rate at which this dissolved oxygen is used up which is dependent on temperature and contaminant load present in the river. yustiani et al. (2018) reported that de-oxygenation varies with depth of river since there is reduced presence of microorganism action as the depth of river increases. river benue supports many economic activities along its stretch within the makurdi reach which includes; the benue breweries effluent disposal at the upstream section of the makurdi reach, the draw-off of benue state water board towards the downstream stretch, domestic water use along the river banks and fishing. there is the need for preservation of this water body to limit pollution which may arise due to increasing population. monitoring is key to effective preservation. modeling the self-purification potential of this river within the makurdi reach serves as a way of developing tools which will guide in preservation of this water body within this reach. therefore, in modeling self purification of river benue, re-oxygenation (re-aeration) and deoxygenation were considered in this study in terms of the water quality parameter (temperature, do and bod) and hydrodynamic parameters (flow velocity and river depth) which affects the rate of addition or removal of oxygen in river benue. the empirical model generated here will serve as a tool in predicting the self purification of river benue at any section within makurdi reach. this will also serve as a powerful instrument in the river’s sustainable management. 2. methodology 2.1 study area and the sampling points figure 1. shows the study area with the sampling stations. sampling was conducted at fourteen (14) stations within the makurdi reach of river benue. all field data were acquired over a period of eight months from march, 2018 to october, 2018. figure 1. map of makurdi showing the sample collection points along river benue arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):347-356. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 349 2.2 data collection 2.2.1 laboratory and field measurements the water samples collected were analyzed for do and bod. the hydrodynamic parameters (mean depth of flow and mean flow velocity) at each sample stations were also measured using standard methods. these are the parameters needed to generate a model for self-purification using fair (1939) equation. iodometric method was used to determine do and bod (apha et al., 2005). aluminum stake calibrated in metric units with circular iron disc at the base was used in measuring the depth of the river. temperature was determined using laboratory thermometer. velocities were determined using a current meter (model: fp111). re-aeration and de-oxygenation were calculated using equations 1 and 2 respectively. equation 3 was applied to get self-purification. the eutech instruments’ ph meter was used for ph value measurement. 2.2.2 mathematical determination the re-aeration coefficient from field values was obtained using equation 1: ( ⁄ ) ( ) (1) where: k2= re-aeration coefficient (d-1); doinitial=initial dissolved oxygen (mg/l); dodeficit= differencebetween saturation dissolved oxygen and observed dissolved oxygen (mg/l). the de-oxygenation coefficient from field values was obtained using equation 2: ( ) (2) where: k1 = de-oxygenation coefficient (d-1) la = ultimate bod (mg /l) l = bod at time (t) the self purification potential from field values was obtained using fair (1939) equation given by equation 3 as: (3) where: f = self purification potential/capacity k1 = de-oxygenation coefficient (d-1) k2 = re-aeration rate constant (d-1) 2.3 mathematical derivation and analysis of self purification model analytical techniques were adopted in this research and were assured by recommended standard techniques and field sampling methods. the results were tabulated, and self purification modelled using fair (1939) equation as stated in equation 3 above. re-aeration rate constant can be written as; ( ) (4) where: f = function k2 = re-aeration coefficient (d-1) h = depth of river (m) v = velocity of flow (m/s) aho et al.: modelling self purification of river benue within makurdi. azojete, 17(3):347-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 350 the relationship can be written as; (5) where: the constant (m) and the exponents a2 and a4 are dimensionless numbers that follows each quantity. de-oxygenation rate constant can be written as; ( ) (6) where: f = function la = ultimate bod(mg /l) l = bod at time (t) t = time of incubation (days) therefore, the relationship can be written as; ( ) (7) where: the constant (n) and the exponents (a1, a3 and a5) are dimensionless numbers that follows each quantity. substituting equations 5 and 7 into equation 3, the model equation will take the form as; (8) where: a1, a2, a3, a4and a5 are exponential constants as shown above in equations 5 and 7. since “m” is a constant and “n” is also a constant, a single constant was used to replace the constants. let “a” be the constant in self purification model taking into consideration “m” and “n” from re-aeration and de-oxygenation respectively. therefore, m and n are replaced with a in equation 8 which is rewritten as; (9) where: a, a1, a2, a3, a4 and a5 are constants as described above that were obtained using multiple linear regression model analysis. multiple linear regression analysis is used to predict a continuous dependent variable from several independent variables. linearity means that there is a straight line relationship between the independent variables and the dependent variable. therefore, equation 9 can be stated in linear form as; (10) then, equation 10 is rewritten in multiple linear regression equation form as; (11) where: with with a arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):347-356. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 351 the least-squares normal equations for obtaining the numerical values of the constant (a) and the exponentials (a1, a2, a3, a4 and a5) were derived from equation 11. these least-squares normal equations are then given by; ∑ ∑ ∑ ∑ ∑ ∑ (12) ∑ ∑ ∑ ∑ ∑ ∑ ∑ (13) ∑ ∑ ∑ ∑ ∑ ∑ ∑ (14) ∑ ∑ ∑ ∑ ∑ ∑ ∑ (15) ∑ ∑ ∑ ∑ ∑ ∑ ∑ (16) ∑ ∑ ∑ ∑ ∑ ∑ ∑ (17) where: x1, x2, x3, x4 and x5 are the predictor variables; and y is the response variable as stated in equation 11 above. the values of these variables were derived from the observed field data using 103 samples out of 112 samples observed from the field throughout the study period. similarly, a1, a2, a3, a4 and a5 are as stated in equations 9 which were calculated by solving equations 12, 13, 14, 15, 16 and 17 simultaneously using matrix methods of operation. an equation/model for prediction of self purification using observed field data was obtained by substituting the values of a, a1, a2, a3,a4 and a5 calculated into equation 9. the least-squares normal equations for calculating the constants (a0, a1, a2, a3,a4 and a5) in the self purification model using observed field data were derived by substituting data for the statistical equation (multiple linear regression equation) as derived from the observed field data into equations 12, 13, 14, 15, 16 and 17 to give; (18) (19) (20) (21) (22) (23) equations 18, 19, 20, 21, 22 and 24 were solved simultaneously using matrix methods of operation. the matrix form is rewritten to give; [ ] [ ] = [ ] aho et al.: modelling self purification of river benue within makurdi. azojete, 17(3):347-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 352 2.3.1 check for suitability of the self purification model this check measures the suitability of the model in predicting the self purification of the river. the model for f is of the form; ̂ (24) this model indicates the relationship between the independent variables (velocity (v), depth (h), ultimate bod (la) and bodt at time of incubation (t))and the dependent variable (self purification capacity ( ̂)) after substituting the constants (a, a1, a2, a3, a4 and a5). this model was statistically calibrated and validated using; coefficient of determination (r2) and adjusted r2, multiple correlation coefficient (r), root mean square error (rmse) and f-test statistic function. 3. results and discussion 3.1 results the results obtained were presented in graphical form, equation form and by words. figure 2 shows the results obtained from the field observation, laboratory test and mathematical calculations. a bb dc figure 2. concentration of physico-chemical parameters of river benue water samples arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):347-356. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 353 e ji hg f figure 2 (continued). concentration of physico-chemical parameters of river benue water samples 3.1.1 self purification model /equation for the river the following results were obtained from the matrix methods of operation; a0 = 0.4472, a1 = 0.2593, a2 = 0.0197 and a3 = 0.0009, a4 = 0.2949 and a5 = 0.651. then a = 1.56393 (where; a ). substituting the values of a, a1, a2, a3, a4 and a5 in equation 9, we obtain aho et al.: modelling self purification of river benue within makurdi. azojete, 17(3):347-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 354 (25) since the time of incubation for bod testing was constant throughout the study, substituting t = 5 days in equation 25 gives; (26) 3.2 discussion the range of do in the dry season was between 4.7 mg/l and 6.3 mg/l with mean value of 5.36 mg/l while in the rainy season, it was between 4.0 mg/l and 5.9 mg/l with mean value of 4.8 mg/l. this is due to increased waste discharge introduced into the river by runoff. these ranges are ner (2011) compliant with a minimum of 4.0 mg/l as the lowest permissible concentration for surface waters. on the contrary, some of the values of do in some months especially during the rainy season lies below the who standard of do concentration of 5.0 mg/l. sharma et al. (2008) reported a do value range of 6.5–15 mg/l which is who compliant. similar report by yisa and jimoh (2010), in the do values ranging from 3.10 mg/l to 5.20 mg/l for river landzu in bida, niger state, nigeria. the implication is that they are all flowing rivers with oxygen recharge through surface interchange. during dry season, minimum bod concentration of 1.0 mg/l and maximum of 2.0 mg/l with a mean value of approximately 1.3 mg/l were recorded while during rainy season, minimum bod was 1.3 mg/l maximum of 2.0 mg/l and mean value of 1.54 mg/l. these values are less than 3.0 mg/l which was the maximum permissible concentration stipulated by ner (2011). gupta et al. (2017) reported the effect of physicochemical and biological parameters on the quality of river water of narmada, madhya pradesh, india where the minimum and maximum bod were observed to be 0.35 mg/l and 2.18 mg/l respectively, a very close result to the present study arising from the fact that some areas of the river bank were used for waste discharge. consequently, the bod concentration of river benue is ner (2011) compliant (surface waters bod of 0 mg/l to 3.0 mg/l). generally, the mean bod concentration of the dry season reduces downstream while those of the rainy season increases downstream due to effluents being washed into the river by runoff especially during rainfall. this actually supported the view of sawyer et al. (1994) that the effluents disposed by households and industries into the surface and ground water contaminate the quality of the water which can be assessed by bod determination. the flow velocity of the river increases progressively from march (peak dry season) to october (peak rainy season). this is due to increasing rainfall, increased recharge from the subsurface sources, reduced recharge to the ground water and reduced evaporation due to reduction in average daily temperature and high humidity. it was observed that the mean flow velocity in dry season is reduced compared to that of rainy season. this could be likened to the increased discharge of the tributaries and rainfall. the mean monthly re-aeration rate of river benue in dry season is 0.1792 day-1 while that of the rainy season is 0.0995 day-1. the variation is as a result of increased depth of the river and greater volume of the river water not exposed to atmospheric oxygen. this is in line with vonsperling (2014) observation that shallower waters have higher coefficient of re-aeration due to the ease of mixing across the depth profile, greater surface turbulence and oxygen exchange. there is also increased quantity of floating water plants covering the river surface in rainy season which reduces the surface area in contact with the atmospheric oxygen. additionally, surface turbulence is also reduced and the ease of oxygen exchange. the mean monthly de-oxygenation rate of river benue in dry season was 0.1345 day-1, and 0.1186 day-1 in rainy season and over the study period recorded 0.1246 day-1. it will be noticed that there was a reduced rate of river benue’s organic waste degradation during the rainy arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):347-356. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 355 season than in the dry season. this could be as a result of decreased temperature, increased organic waste load being washed into the river through runoff and increased non-point discharge from various tributaries along the riverbank during the rainy season. more so, the mean monthly de-oxygenation rate decreases with increase in the mean monthly depth of river benue which is in agreement with yustiani et al. (2018) who reported the de-oxygenation rate of water of cimanuk river in indonesia. the mean self purification coefficient of the river in the dry season is 1.3398 which reduced to 0.8354 in the rainy season indicating less pollution in the dry season than in the rainy season. the mean self purification coefficient of the river in the dry season is greater than 1.0 at all the stations studied. this implies that re-aeration is greater than de-oxygenation as was reported in the work of patrick (2016) on river kaduna in kaduna state, nigeria. conversely, the mean self purification coefficient is less than 1.0 in most of the stations in the rainy season where the de-oxygenation is greater than the re-aeration as reported by omole and longe (2008) and patrick (2016). consequently, river benue can grossly purify itself over a distance downstream as supported by demars and manson (2013) who stated that rivers has the capacity to purify itself. this is due to the large surface area and moderate velocity attributed to the river. equations 25 and 26 were able to predict the self-purification capacity of the river with coefficient of determination (r2) value of 0.5691 and adjusted value (considering the degree of freedom due to the number of variables and dataset)of 0.5469. these values of both r2 and adjusted r2 were greater than 0.5 indicating that the model generated have a better fit in predicting the self-purification capacity of river benue. the multiple correlation coefficient (r) gave the values of 0.7544 using r2 and 0.7495 using adjusted r2. these values were greater than 0.5 and closer to 1.0 indicating a strong positive linear relationship between the predictor variables (velocity (v), depth (h), ultimate bod (la), bodt (l) and time of incubation (t)) and the response variable (self purification coefficient (f)).the root mean squared error was 0.2433 which is close to zero showing that the error in using the model in predicting the self purification of the river is minimal. f-test statistic function to test the significance of the regression model was done to remove redundant variable from the model. the null hypothesis considered that any or one of the exponential constant in the model is equal to zero. it was discovered that the f-value calculated as 21.7312 was greater than the f-critical value from the f-test table (fcrit = 4.48, with a probability function of 0.001). therefore, the null hypothesis was rejected. this portrays that all the predictor variables are relevant in estimating the response variable. consequently, the empirical model generated for predicting the self purification of the river is with high degree of accuracy.the observed concordance between the model and the experimental data is due to the fact that the kinetic coefficients of de-oxygenation (k1) and reaeration (k2) were obtained from the observed field data and used as calibration parameters. 4. conclusion it is noteworthy that an increased velocity and depth affects the re-aeration of river benue resulting in reducing the self purification potential of the river. the mean self-purification potential of river benue was found to be greater than 1.0 indicating the re-aeration was more than de-oxygenation rate. an empirical model has been generated for self purification of river benue which was statistically validated. it is recommended that the model from this study should form bases and guide for further future models of river benue. acknowledgement the authors wish to thank mr and mrs chris aniakor’s family for funding this research work. aho et al.: modelling self purification of river benue within makurdi. azojete, 17(3):347-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 356 references american public health association – apha, american water works association – awwa and water environment federation – wef. 2005. standard methods for the examination of water and wastewater. 21th. edition, washington. demars, bol. and manson, jr. 2013. temperature dependence of stream aeration coefficients and the effect of water turbulence: a critical review. water research, 47: 1–15 dikeogu, tc., onyewudiala, ji., ezeabasili, ac. and swift, onk. 2014. self-purification potential of tropical urban stream: acase study of the new calabar river in port harcourt, nigeria. global advanced research journal of engineering, technology and innovation, 3(1):7-15. fair, cm. 1939. the dissolved oxygen sag: an analysis. sewage works journal, 2: 44. galvis, a., hurtado, ic., martínez-cano, c. and urrego, jg. 2014. dynamic condition approach to study the self-purification capacity of colombian water bodies case: cauca river and salvajina dam . cuny academic works. http://academicworks.cuny.edu/cc_conf_hic/350 gupta, n., pandey, p. and hussain, j. 2017. effect of physicochemical and biological parameters on the quality of river water of narmada, madhya pradesh, india. water science 31: 11–23. khan, s. and singh, sk.2013. assessment of the impacts of point load on river yamuna at delhi stretch, by do-bod modelling of river, using matlab programming. engineering and innovative technology, 2(10): 282-290. national environmental (surface and groundwater quality control) regulations (ner). 2011. national environmental (surface and groundwater quality control) regulations. government notice no. 136. the federal government printer, lagos, nigeria 98(49): 693-727. ogbaji, eo., jidauna, gg., odoh, r. and agene, ei. 2013. mathematical model of self-purification of river benue water quality control. international journal of modern chemistry. 5(2): 118-126. omole, do. and longe eo. 2008. an assessment of the impact of abattoir effluents on river illo, ota, nigeria. journal of environmental science and technology, 1(2): 56-54. patrick, k. 2016. evaluation of the factors affecting the self-purification capacity of river kaduna, nigeria. master’s thesis, department of chemical engineering, faculty of engineering, ahmadu bello university, zaria, nigeria. sawyer, cn., mccarthy, pl. and parkin, gf. 1994. chemistry for environmental engineering and science, 4th edition. mcgraw-hill international edition, new york, pp. 365– 577. sharma, s., dixit, s. and jain, p. 2008. statistical evaluation of hydrobiological parameters of narmada river water at hoshangabad city, india. environmental monitoring assessment. 143: 195– 202. ugbebor, jn., agunwamba, jc. and ameh, ve. 2012. determination of re-aeration coefficient k2 for polluted stream as a function of depth, hydraulic radius, temperature and velocity. nigerian journal of technology 31(2): 174-180. von-sperling, m. 2014. introdução à qualidade das águas e ao tratamento de esgoto. 4th. edition belo horizonte: departamento de engenharia sanitária e ambiental; universidade federal de minas gerais, pp. 472. yisa, j. and jimoh, t. 2010. analytical studies on water quality index of river landzu. american journal of applied science, 7(4): 453–458. yustiani ym., wahyuni, s. and alfian, rm. 2018. investigation of the deoxygenation rate of water of cimanuk river, indramayu, indonesia. rasayan journal of chemistry, 12(2): 475-481 http://academicworks.cuny.edu/cc_conf_hic/350 arid zone journal of engineering, technology & environment azojeteseptember 2020. vol. 16(3):605-610 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: dkgarba@nda.edu.ng 605 original research article investigation of chemical composition of a steam turbine shaft (a case of kaduna refinery) d. k. garba*, m. j. muhammad, u. s. umar and n. c. a. ozoekwe department of mechanical engineering, faculty of engineering and technology, nigerian defence academy, kaduna, pmb 2109 kaduna, nigeria *corresponding author’s email address: dkgarba@nda.edu.ng 1.0 introduction a steam turbine is a steam prime mover with continuous rotary motion of the driving element. it converts the thermal energy of steam into mechanical work. the steam flow proceeds through directing devices and impinges on curved blades mounted along the periphery of the rotor. by exerting a force on the blades, the steam flow causes the rotor to rotate (nag, 2002). the chemical composition of a turbine shaft is essential for knowing the constituents that determine the hardness and other properties necessary for understanding the failure modes of the shaft (mellinda and rochim, 2015). the steam turbine has proven to be a very convenient engine for driving rotating mechanisms, such as electric generators, pumps, blowers, and ship propellers. it operates at high speed and more compact, lighter, better balanced, and more economical than the reciprocating engines (nag, 2002). in recent times development of steam turbines has witnessed improved output capacity and specialized turbines have been designed for various uses, (o’connor and roberston, 1999). the turbine shafts generally operate at very severe conditions such as dust laden, corrosive, and high or low temperatures. moreover, it is subjected to variety of loads such as tension, torsion, compression, bending, or combination of these loads and in some instances, they are often subjected to vibratory stresses. the turbine shafts usually fail at the keyways due to expansion. wear by bearing and metal fatigue are the major contributor of shaft failure (cots et al., 2003). article information abstract an investigation of the chemical properties of original equipment manufacturer’s (oem) steam turbine shaft and that of locally produced shaft was carried out to determine the chemical composition of the shafts and determine the suitability of the locally produced shaft to replace the oem turbine shaft that is in constant failure. the chemical analysis carried out on the samples revealed that the oem turbine shaft is composed of 0.48c, 0.06s, 0.12ca, 0.99cr, 0.36si, 0.71mn, 0.07p, 0.12ni, 0.15cu and 0.39mo and the locally manufactured steam turbine shaft is composed of 0.38c, 0.07s, 0.038ca, 0.89cr, 0.83si, 0.63mn, 0.04p, 0.04ni, 0.16cu and 0.20mo. manganese which was found to increase hardenability and tensile strength is lower in the locally manufactured shaft as compared to the oem steam turbine shaft. the analysis also showed that carbon, sulphur, chromium, phosphorus, nickel and molybdenum content of the original steam turbine shaft is higher than that of the locally manufactured shaft. the results obtained agree with the astm a668 steam turbine shaft requirement under class d standard of the chemical composition. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 february, 2020 revised 11 june, 2020 accepted 20 june, 2020 steam turbine shaft, locally produced, chemical composition mailto:dkgarba@nda.edu.ng http://www.azojete.com.ng garba et al.: investigation of chemical composition of a steam turbine shaft (a case of kaduna refinery). azojete,16(3):605610.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dkgarba@nda.edu.ng 606 not only the chemical composition, but the adjoining components also such as the bearing and gears could cause excessive vibration because of eccentricity or unbalance of the shaft (trebuna et al., 2017). the need is to look out for a material which can be effectively used as a substitution of the original steam turbine shafts. these materials should exhibit high tensile and toughness values. however, it is generally observed that both the tensile and toughness values are inversely related to each other. by increasing the tensile property, the toughness or impact value decreases and vice-versa. hence, a judicious selection of an appropriate heat treatment process to maintain a good balance of these two properties is surely needed. heat treatment is an important operation in the final fabrication process of many engineering components. only by heat treatment is it possible to impact high mechanical properties to steel parts and tools for sophisticated application (energy and environmental analysis, 2008). heat treatment is a very important tool of the metallurgist by which he can alter the properties of steel easily. the same steel can have a very wide range of mechanical properties if subjected to different heat treatment. today, where science and technology are advancing very rapidly in pursuit of higher properties in materials, heat treatment plays a very important role (whitaker, 2006). heat treatment process as one of the methods of improving the performance of steel for specific use can be applied to enhance the performance of the locally produced steam turbine shaft. it is expected that the heat treatment will improve on the mechanical properties of the shaft to enhance performance and reduce the rate of failure. heat treatment is hence defined as a sequence of heating and cooling operation, timed and applied to a metal or alloy in the solid state in any way that will produce desired properties, that is, it is an operation or combination of operations of heating and cooling of a solid or an alloy metal to endow it with certain predetermined physical and mechanical properties (leyzerovich, 2005). the changes in the properties of steel after heat treatment are due to the phase transformations and structural changes that occur during the heat treatment (adewuyi et al., 2005). hardening is a heat treatment process in which material is heated to austenitising temperature, soaking at this temperature and then cooling at a rate faster than the critical cooling rate such that martensite is formed (bob, 2003). the main objective of hardening is to induce high hardness and impact high wear and abrasion resistance to the material. in pearlite class of steel hardening is done to induce high strength along with good toughness and ductility (dave, 2003). the temperature of tempering is decided based on the strength and toughness of the material required during the service period (davis and oelman, 1993). this study is aimed at the enhancement of a locally fabricated steam turbine shaft that can have similar mechanical properties as the original shaft to eliminate the problem of constant failure and for optimum performance. the work was centred on the determination and evaluation of the chemical composition of the original and locally fabricated steam turbine shafts with a view to selecting appropriate method for the enhancement of the locally fabricated shaft. 2. materials, equipment and methods 2.1 materials samples for various investigations were taken from the failed oem steam turbine shaft in kaduna refining and petrochemical company limited and the locally produced shaft. the samples for the chemical analysis were then machined from both shafts. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 605-610. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: dkgarba@nda.edu.ng 607 2.2 equipment the following were the major equipment used in carrying out the various tests and experiments conducted: 1. a sui 40-50 lathe machine with an electric motor of 7.5kw 2. minipal 4 model energy dispersive x-ray florescence spectrometer (edxrf) 2.3 methodology and chemical analysis of samples lathe machine was used to machine the samples in disc-like shaped samples having a diameter of 32mm that would fit perfectly in the sample holder of the x-ray fluorescence (xrf) spectrometer from the failed locally fabricated steam turbine shaft for chemical analysis as shown in figure 1. the measuring surface of the metal sample was grinded and polished so as to have a smooth and mirror surfaces before been cleaned with acetone of the polished sample faces. after positioning the sample on the x-ray florescent spectrometer elemental compositions were analysed using a minipal 4 model energy dispersive x-ray florescence spectrometer (edxrf) whereby the samples analysed were illuminated by x-rays or gamma rays, which resulted in the excitation of core-level electrons to excited states. the radiative decay of these electrons from the excited states back to their respective ground states resulted in the emission of fluorescent or “secondary” x-rays that are characteristic of the energy levels of each atomic species and thus serve as a spectroscopic fingerprint for each element present in the sample. during the analysis, a power rating of 20kv, measuring time of 100 seconds, an air media and an al-thin filter were used. the data for the chemical composition of the samples were obtained from the x-ray florescence spectrometer (edxrf). figure 1: carbon composition test sample of the shaft 3. results and discussions 3.1 results table 1 shows the result of the chemical analysis of the samples of the oem and the locally produced turbine shafts as obtained using x-ray florescence spectrometer (edxrf). table 1: chemical composition of samples elemental composition %c %s %ca %cr %si %mn %p %ni %cu %mo original turbine shaft (oem) 0.40 0.06 0.12 0.99 0.36 0.71 0.07 0.12 0.15 0.39 locally fabricated shaft 0.38 0.07 0.038 0.89 0.83 0.63 0.04 0.04 0.16 0.20 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng garba et al.: investigation of chemical composition of a steam turbine shaft (a case of kaduna refinery). azojete,16(3):605610.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dkgarba@nda.edu.ng 608 3.2 discussion the chemical analysis carried out on the samples revealed that manganese which was found to increases hardenability and tensile strength is lower in the locally fabricated shaft as compared to the original steam turbine shaft. the analysis also showed that carbon, manganese, chromium and phosphorus content of the original steam turbine shaft was higher than that of the untreated locally fabricated shaft with values; (0.48c, 0.06s, 0.12ca, 0.99cr, 0.36si, 0.71mn, 0.07p, 0.12ni, 0.15cu and 0.39mo) and the locally fabricated steam turbine shaft (0.38c, 0.07s, 0.038ca, 0.89cr, 0.83si, 0.63mn, 0.04p, 0.04ni, 0.16cu and 0.20mo) as shown in table 1. comparing the chemical compositions of the original and locally fabricated steam turbine shaft as shown in figure 2, nickel noted to induce strength, ductility and toughness in turbine shafts is lower in the locally fabricated shaft. chromium characterized by their hardness and resistance to wear is also lower in the locally fabricated shaft, hence, renders the shaft less resistant to wear in service. figure 2: comparison of elemental composition of original turbine shaft and locally fabricated shaft. comparing the chemical compositions of the astm a668 steam turbine shaft requirement under class d standard of the chemical compositions standards of steam turbine shaft, original turbine and locally fabricated steam turbine shaft as shown in figure 3, phosphorus contents of astm standard and locally fabricated shaft are the same which shows its effectiveness as a substitute to the oem shaft. however, the sulphur content which is detrimental to strength in the locally produced shaft is higher than in oem which accounts for its lower strength. the carbon contents of both original and locally fabricated are in good agreement also. figure 3: comparison of elemental composition of astm standard, original turbine shaft and locally fabricated shaft. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 605-610. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: dkgarba@nda.edu.ng 609 4. conclusions the chemical composition of the original and locally fabricated steam turbine shaft was determined. the major alloying elements (magnesium, chromium, silicon, molybdenum and nickel) in the original steam turbine shaft were found to be higher than that of the locally fabricated steam turbine shaft. the manganese content of the oem shaft is higher than the locally produced shaft by almost double. the locally produced shaft is better with lower manganese content of 0.063% which gave better hardenability as the 0.07% of the oem shaft is prone to brittleness which causes its failure. the phosphorous content of the oem is also higher than the locally produced shaft. the locally produced shaft is better with lower phosphorous content of 0.04% which gave better increased strength and hardness and increased corrosion resistance than the 0.07% of the oem shaft which is subjected to high brittleness and increased tendency to crack that leads to its failure. the sulphur content in the locally produced shaft is higher which is not too good for steel, however the silicon content of the locally produced shaft is higher than the oem which is good but since the ductility, hardness, toughness, and strength elements are excellent in this service condition, the oem is better than the locally produced shaft however, the locally produced shaft can be used as a substitute with appropriate treatment. acknowledgements the authors wish to thank nigerian defence academy, kaduna for funding part of the research through the nda mini-research grant and the nnpc in particular for providing the enabling environment to access their facility (turbine) for this research activity. references adewuyi, bo., afonja, aa. and adegoke, co. 2005. effects of isothermal transformation on the fatigue strength of austempered ductile iron. bostwana journal of technology, 14(2): pp. 693-708. doi: 10.4236/jmmce.2010.98050. bob, c. 2003. making steel stronger, practical welding today. a publication of the fabrication & manufacturers association, international (website) http://thefabricator.com/author/bobcapudean accessed on 01 december 2018. cots, ba., oliveira, flg., babosa, cbm. and arayo, fgs. 2003. relationship between structure and mechanical properties of metals. npl symposium, hmso, pp. 455-456. london. dave, va. 2001. engineering concept, strength of tempered martensite. industrial heating (website) https://www.industrialheating.com/articles/84872-engineering-concepts-strength-oftempered-martensite accessed on 10 october .2018. davis, dj. and oelman, la. 1993. the structure, properties, and heat treatment of metals. pitman books, pp.44-52. london. energy and environmental analysis 2008. technology characterization: steam turbine. report prepared for u.s. environmental protection agency. icf international company. pp. 7-11. arlington, virginia, 22209. leyzerovich, a. 2005. steam turbines for nuclear power plants: pennwell books. pp. 171-172. tulsa, oklahoma. meilinda n. and rochim s. 2015. creep damage assessment of a 50 mw steam turbine shaft. matec web of conferences vol 34, p4 doi: 10.1051/matecconf/20153405002. https://www.researchgate.net/deref/http%3a%2f%2fdx.doi.org%2f10.4236%2fjmmce.2010.98050 http://thefabricator.com/author/bob-capudean http://thefabricator.com/author/bob-capudean https://www.industrialheating.com/articles/84872-engineering-concepts-strength-of-tempered-martensite https://www.industrialheating.com/articles/84872-engineering-concepts-strength-of-tempered-martensite file:///c:/users/user/downloads/azojete143/www.azojete.com.ng garba et al.: investigation of chemical composition of a steam turbine shaft (a case of kaduna refinery). azojete,16(3):605610.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dkgarba@nda.edu.ng 610 nag, pk. 2002. power plant engineering. tata mcgraw-hill publishing company limited, pp. 432-455. new delhi. o’connor, jj. and roberston, ee. 1999. turbine technology. heron of alexandria. mactutorm. pp. 16-22. athens, greece. whitaker, jc. 2006. heat treatment handbook. boca raton, fl: taylor and francis. pp. 5-14. boca rotan. https://doi.org/10.1201/nof0849384530. https://doi.org/10.1201/nof0849384530 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):269-278 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 269 original research article development of a windmill for pumping water using positive displacement pump b. alkali1, b. s. elkanah2, s. g. amarem3, a. b. hassan4, n. s. gukop5 and e. a. p. egbe4 1department of mechatronics engineering, federal university of technology. minna, niger state. 2department of welding eng. and offshore tech., petroleum training inst., efurun, delta state. 3maintenance department, nigerian national petroleum cooperation, abuja 4department of mechanical engineering, federal university of technology minna 5department of mechanical engineering, university of jos, jos, plateau state *corresponding author’s email address: babawuya@futminna.edu.ng 1.0 introduction energy is considered as one of the most important resources of any country, especially if it will be used to supply water. it is noteworthy that high rate of industrial growth of any country is a function of the amount of energy available in that country and the extent it is utilized. nigeria is an energy-resource rich country blessed with fossil resources such as crude oil, natural gas, coal and renewable energy resources like solar, wind and biogas. windmill use wind speed to turn a blade designed in a particular shape to rotate a shaft. the torque in the shaft can be amplified for a particular user or the motion of the shaft may be converted to other forms of motion such as linear in this case as the windmill operates a positive displacement pump. the mean wind speed ranges in northern and southern nigeria were found to lie between 4.0 7.5 m/s and 3.0 3.5 m/s, respectively at 10 m above the ground (oluseyi 2010). also, idris, et al. (2012) has reported that fourteen (14) state in northern nigeria have high wind energy resources capable for generating over 50 mwh/year. this implies that rural areas and farms in northern nigeria can rely on wind power for water supply and their electricity supply. wind is generated due to various global phenomena such as ‘air-temperature difference’ associated with different rates of solar heating. since the earth’s surface is made up of land, desert, water, and forest areas, the surface absorbs the sun’s radiation differently. locally, a strong winds is created by sharp temperature difference between the land and the sea (raja, et al 2006). the capacity to generate the required electricity in nigeria is dropping with time due to numerous challenges such as equipment age, poor management, weather. therefore, there is article information abstract the abundant renewable energy sources have not been harnessed for electricity and other uses to date. wind speed is high in the northern part of nigeria and therefore require utilization so as to reduce the use of harmful non-renewable energy sources. in this work wind energy was used to drive a windmills that provide mechanical energy directly for a borehole with a positive displacement pump with a 2.5ft stroke. the design analysis of the wind mill was carried out numerically based on the wind data collected. the proposed design were fabricated using designed dimensions. the rotary motion of the shaft were converted to a linear motion using slider-crank mechanism. the designed horizontal axis windmill has 3 blades has three blades driving the shaft. also the kinematic modelling of the mechanism was carried out. the assembled windmill was tested and was found to have an operated efficiency of 58.2%. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2019 revised 24 sept., 2020 accepted 13 oct., 2020 keywords: windmill displacement-pump wind energy mechanism slider-crank babawuya et al: development of a windmill for pumping water using positive displacement pump. azojete, 17(3):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 270 inadequate supply of electricity to all sectors of nigeria. the present technology especially the energy sources (for pumping water uses petrol or diesel engine) are not sustainable principally due to environmental impact. the use of wind energy is more reliable in areas without tall structure to obstruct the flow of wind current and that can be potentially use for pumping water. therefore, a windmill provides the best way of harnessing this wind power and using it to operate positive displacement pump. the potential application of the research work is in the commercial farms, which are located at rural areas were wind energy is hardly adulterated with pressure from traffic and other activities in urban area. 2.0 materials and method 2.1 description of the windmill for pumping water figure 1, shows the schematic of the wind mill under design, it is a mechanical structure utilizing wind power to produce a torque large enough to operate a positive displacement water pump via a slider-crank mechanism. the force of the wind against the blades causes a crank system (which consists of a crankshaft and counterweights) attached to the shaft to rotate. the positive displacement pump which is connected to the shaft via the crank mechanism reciprocates as the blades rotate, and thus creates suction, which transfer water from the water level to the earth surface. the amount of power that can be obtain from a windmill is proportional to the rotors swept area and available wind speed. figure 1: schematic diagram of the windmill water pump. 2.2 materials used the components selected for the fabrication of the windmill are; table 1: list of the components of windmill & the material selected. s/no component specification/ material 1 blade r1.2m , 1mm thickness/ al-sheet 2 blade hub 170mm /al-alloy (casted) 3 shaft 19mm diameter stainless steel pipe 4 flywheel 300 x 10mm, mild steel 5 links 4mm thickness/al –alloy plate 6 plunger stainless steel pipe 7 top frame 1” x 1” rectangular pipe/mild-steel 8 tower structure 2” x 2” equal angle/mild-steel 9 displacement pump al-alloy arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):269-278. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 271 2.3 methods the procedure used for the development of this windmill for pumping water using a positive displacement pump are the design analysis and synthesis, kinematic modeling and fabrication stages. 2.3.1 design analysis and calculations a. design requirement the design requirement for windmill for pumping water include: i. the mean wind speed of 4.3m/s ii. min. pumping power displacement. iii. pump head of 2-2.5ft (positive displacement pump). iv. min. pump thrust >91n). v. diameter of the pump, (25.4mm). b. blade design according to data obtained from wascal-fut minna, minna has air maximum wind speed of 8.3m/s and minimum of 0.3m/s. the average of the maximum and minimum forms the basis of the design. blade utilizes wind power to generate a rotating motion. the shape of the blade adopted is shown in figure 2. figure 2: isometric view of the blade mass of the blade, mb = 0.169 kg (obtained from the cad software). density (ρb) 2700 kg/m³ thickness of blade 1 mm the shape of the blade is in the form of a trapezium, and the area of a trapezium is given by; ( ) ( ) (1) the pump area were computed from equation 2; (2) where; ap = area of the pump (m2). dp = diameter of pump (25.4 m). therefore, the volumetric flow rate was calculated using equation 3; (3) where; v = mean wind speed (m/s) the blade swept area (as) given in equation 4, was obtained by equating the actual power (source ) to the hydraulic power (source ). babawuya et al: development of a windmill for pumping water using positive displacement pump. azojete, 17(3):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 272 (4) where: pw = wind power (w) cp = coefficient of power (w) h = pumping head (m) v = mean wind speed (m/s) cp = power coefficient ρ = density of air (kg/m3) ρw = density of water (kg/m3) q = volumetric flow rate (m3/s) for a horizontal axis wind turbine (hawt), the swept area is circular, (i.e. the area cover as the blade rotates). thus, from the equation 2, the area of a circle was used to calculate the radius of the rotor, which is 0.6 m. and therefore the angular speed (ω) of the blade was obtained from the wind speed data (average wind speed from wind data 4.3 m/s) as given by equation (5). (5) hence; the wind power were calculated using equation 6; (6) hence, the theoretical torque (tt) is given by; (7) 2.3.1.3 tip speed ratio the tip speed ratio is defined as the relationship between rotor blade velocity and relative wind velocity. the dimensions are calculated using equation 8 (ronak, et al. 2015); (8) 2.3.1.4 the coefficient of starting torque the coefficient of starting torque is given as; (9) where; coefficient of power or the efficiency of the windmill is calculated from (10) hence, the efficiency of the windmill is 50 %. 2.3.1.5 calculation of blade setting angle ( ) according to (mccosker 2012) a wind turbine blade is divided into seven (7) equal segments with a step of 0.23 m. the blade setting angle can be obtained; arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):269-278. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 273 (11) where, (12) where: φ = blade setting angle (degree) mean of the local tip speed ratio r = radius at each stations of the blade (m) r = rotor radius (m) 2.3.1.6 shaft design the windmill shaft shown in figure 4, connects the rotating blades and the pump drive mechanism and it is subjected to combined bending (due to the weight of the blade, hub e.t.c) and twisting moments (due to wind load). according to (khurmi and gupta 2008), the equivalent twisting moment for this kind of loaded is given by equation 13 and 14; = √( ) ( ) (13) and; (14) where; τ = maximum shear strength of mild steel (n/m2) d = shaft diameter (mm) m = maximum bending moment (nm) t = torque developed (nm). figure 4: the shaft. considering the equilibrium of the shaft, the max. bending moments (m) is . therefore the equivalent twisting moment from equation 14 is; =√( ) ( ) √( ) ( ) and the diameter of the shaft from equation 14 is; ( ). tb wf a b babawuya et al: development of a windmill for pumping water using positive displacement pump. azojete, 17(3):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 274 2.3.1.7 force acting on the plunger. recall from eqn. (7) that the torque rotating the shaft = 16.37 nm is the torque required to turn the flywheel. hence, the force acting on the flywheel (radius of the flywheel chosen as 0.15 due to space constraint). (15) torque required to turn link 1; ( ) ( ) (16) force acting on link 1 (17) resolving the fl1 along x-axis gives the force acting on link 2, ( ) 2.3.1.8 determination of the plunger diameter for long slender columns where the slenderness ratio (l/k) is greater than a certain value, buckling of the column is predicted if the calculated axial stress ( ) is greater than the critical stress ( ) given in equation (18), called the euler buckling formula. (egbe, et al. 2016) (18) the plunger is fixed at both ends, hence = 4, (alkali, et al. 2016). the minimum safe diameter of the plunger is; ( ) ( ) ( ) the minimum plunger diameter is 10 mm solid pipe. 2.4 kinematics of the mechanism the mechanism used to transform the rotary motion from the shaft to the linear reciprocating motion for the pumping energy is shown in figure 5, it is a modified slider crank mechanism with the plunger connected to it. figure 5: modified slider-crank mechanism. flywheel connector slider plunger blade shaft arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):269-278. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 275 the kinematics characteristics of the mechanism are presented in equation 19-23. these equations were derived from the closed loop equation for the mechanism in figure 5 are presented in equation 19 and this were used to obtain the position, velocities and acceleration of the mechanism. the close loop equation was expanded and separated into real and imaginary parts for the determination of the unknown quantities such as angular velocity and angular acceleration of the connector (l2) and linear velocity and acceleration of the slider (l4). (19) the angular position of the connector (l3) is given in equation 20 and 21. ( ) (20) also the position of the slider (l4); (21) the velocities equation and acceleration equation of the connector and the slider are given by equations 22-23. [ ] * + [ ] (22) [ ] * + [ ( ) ( ) ] (23) 2.5 fabrication and assembly the designed components were produced and assembled as shown in figure 6. the blades were produced from a 1 mm al-alloy sheet, the hub was casted and machined to dimensions. (a). figure 6: fabricated components, (a) assembled windmill (b) flywheel and links mechanism. (c) blade and hub, (d) positive displacement pump. (b) (c) (d) babawuya et al: development of a windmill for pumping water using positive displacement pump. azojete, 17(3):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 276 3.0 results and discussion 3.1 mechanical design the summary of the mechanical design results of the components are presented in table 2. this includes minimum safe dimensions as that were used in the fabrication of the windmill water pump. table 2: dimensions of the blade design description of parameter calculated values unit 1. blade base length 60 mm top length 120 mm height of blade 800 mm minimum thickness 1 mm area of blade 1.2 m2 diameter of blade 1.2 m2 tip speed 1 2.shaft diameter of shaft 15 mm maximum bending moment 20.1 nm maximum torsional moment 31.23 nm length of shaft 500 mm 3. flywheel diameter 300 mm thickness 15 mm mass of disc 2.88 kg torque required to rotate disc 210.2 nm 4. connector mass 0.06 kg force 203.61 n area 0.03 m2 the windmill for pumping water was constructed using the design results in table 2. the result for the blade angle setting is presented in table 3. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):269-278. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 277 table 3: blade setting angle s/n r (m) λd r (m) λr φ 1 0.23 1.66 0.6 0.6363 38.36 2 0.46 1.66 0.6 1.2727 25.44 3 0.69 1.66 0.6 1.909 18.43 4 0.92 1.66 0.6 2.5453 14.30 5 1.15 1.66 0.6 3.1817 11.63 6 1.38 1.66 0.6 3.818 9.78 7 1.6 1.66 0.6 4.4267 8.79 the variation of blade angle with blade length is presented in figure 7. it can be seen from the figure that the blade angle decreased with increase in blade length. figure 7: blade setting angle 3.2 kinematic modelling the kinematic model equations of the slider-crank mechanism (presented in equations 23 – 29) were graphically presented in figure 8. from figure 8, the blade rotates steadily completes half revolution on less than 0.5 sec, also the wind drives the blade to attain an angular speed of about 50 rad/sec (2.5m/s) and an acceleration of 25 m/s2 in less than 0.3 sec. the wind velocity of 4.3 m/s give a maximum plunger velocity of 2.5 m/s (58.2% mechanism efficiency). figure 8: kinematic analysis. 0 10 20 30 40 50 0 0.5 1 1.5 2 a n gl e blade lenght φ 0 0.2 0.4 0.6 0.8 -3.6 -3.595 -3.59 -3.585 -3.58 -3.575 time (sec) ra d p e r s e c connector angular velocity 0 0.2 0.4 0.6 0.8 -50 0 50 time (sec) ra d p e r s e c s q r connector angular acceleration 0 0.2 0.4 0.6 0.8 -3 -2 -1 0 1 2 3 time (sec) m p e r s e c linear velocity of the slider 0 0.2 0.4 0.6 0.8 -20 -10 0 10 20 30 time (sec) m p e r s e c s q r linear acceleration of the slider babawuya et al: development of a windmill for pumping water using positive displacement pump. azojete, 17(3):269-278. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babawuya@futminna.edu.ng 278 4.0 conclusion this study designed a windmill that can operate a positive displacement pump for pumping water from a borehole. a modified slider-crank mechanism was used to convert the rotary motion from the wind into a linear motion required to operate a positive displacement pump. the analysis and synthesis of the forces acting in the components of the windmill were carried out. also, the kinematic analysis of the mechanism was performed in order to estimate the maximum speed and acceleration of the slider mechanism during operation. this research will be more beneficiary in the rural areas where strong wind speed is available to operate the mechanism. this design can be used to replace the hand operated pump water borehole widely used presently in the rural area for water supply. references alkali, b., bako, sa., lawal, sa., lawal, ss. and aliyu, ma. 2016. development of an improved deflection testing apparatus for short column. proceeding of 1st conference of the nigerian institution of mechanical engineers. minna (nimeche 2016) held in federal university of technology, minna, pp. 129 133. egbe, ea., lawal, sa., alkali b. and aliyu, ub. 2016. design, fabrication and testing of a thermoplastic melt flow meter. international journal of engineering trends and technology, 4(9): 492-495. idris, na., lamin, hs., ladan, mj. and yusuf, bh. 2012. nigeria’s wind energy potentials: the path to a diversified electricity generation-mix. international journal of modern engineering research, 2(4) : 2434-2437. khurmi, rs. and gupta, k. 2008. a textbook of machine design. multicolor edition. new delhi: eurasia publishing house. mccosker, j. .2012. design and optimization of a small wind turbine. hartford, connecticut: rensselaer polytechnic institute. oluseyi, oa. 2010. the potential for wind energy in nigeria. wind engineering, 34(3): 303-311. raja, ak., amit, ps. and manish, d. 2006. power plant engineering. new delhi: new age international (p) limited, publishers. ronak, dg., kothmire, p., sharma, d., kumbhare, b. and choukade, s. 2015. design and development of windmill operated water pump. international journal of engineering and technical research, 3(12): 61-74. arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 149-160 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng _____________________ *corresponding author email address: felix.asoiro@unn.edu.ng 149 original research article aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing f. u. asoiro*1, m. i. simeon2 and i. c. ezugwu3 1,3department of agricultural and bioresources engineering, university of nigeria, nsukka 2 department of agricultural and bioresources engineering, federal university of technology, minna article information received october, 2018 accepted december, 2018 keywords: thermal properties aerodynamic properties egusi melon seed terminal velocity thermal conductivity thermal heat diffusivity abstract the effect of temperature on aerodynamic and thermal properties of melon seed is very important in the design of drying, processing and storage equipment. to this end, some thermal and aerodynamic properties of melon seed were investigated as a function of temperature. the thermal conductivity, specific heat capacity and thermal diffusivity were the thermal properties that were determined. terminal velocity, seed drag force and drag coefficient were the aerodynamic properties investigated. the results obtained for the terminal velocity of the seed at temperatures of 30ºc, 35ºc, 40ºc, 45ºc, 50ºc, 55ºc, 60ºc, 65ºc, 70ºc, and 75ºc were 7.415, 7.135, 6.32, 9.95, 5.885, 5.62, 5.32, 5.205, 4.88m/s respectively. the values continued to reduce until 100ºc with a value of 3.37m/s. the drag force of the melon seed attained its maximum value at temperature of 50ºc (1.777n). a minimum value was attained at the temperature of 100ºc (0.343n). at various temperature levels of 35ºc, 40ºc, 45ºc, 55ºc, 60ºc, 65ºc, and 70ºc, values for drag force were 1.472n, 1.349n, 1.275n, 1.079n, 0.981n, 0.883n, and 0.884n respectively. the drag coefficient was at its maximum at temperature of 80ºc with a value of 1.179, and minimum at 30ºc with a value of 0.743. for the thermal properties, the specific heat capacity attained a maximum value of 2.995kj/kg/k at a temperature of 30ºc, while it attained a minimum value of 1.596kj/kg/k at temperature of 100ºc. the thermal conductivity was maximum at 30ºc with a value of 3.62w/m/k, and minimum at 100ºc with a value of 0.46w/m/k. in the same vein thermal conductivity reduces with an increase in temperature. at the temperatures of 30ºc, 35ºc, 40ºc, 45ºc, 50ºc, 55ºc, 60ºc, 65ºc, 70ºc, 75ºc, and 80ºc, the thermal conductivity values were 3.26w/m/k, 1.545w/m/k, 1.1w/m/k, 1.83w/m/k, 1.725w/m/k, 0.64w/m/k, 0.605w/m/k, 0.555w/m/k, 0.53w/m/k, 0.52w/m/k, and 0.505w/m/k respectively. the thermal diffusivity attained a maximum value at 30ºc (6.19×10-5m2/s) and a minimum value of 1.16×10-6m2/s at 100ºc. therefore, it can be clearly observed that temperature has a very great effect in the aerodynamic and thermal properties of egusi melon and these values are vital to engineers and food processors in the design of storage and processing equipment for melon seeds. ©2018 faculty of engineering, university of maiduguri, all rights reserve http://www.azojete.com.ng felix.asoiro@unn.edu.ng asoiro, et al.: aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing. azojete, 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 150 1.0 introduction one of the important food and cash crops that is grown in most african countries is melon (egusi) (citrullus colocynthis lanatus) and used as food source, in medicine, engineering and cosmetics (jeffrey, 1980). melon (egusi) is a tendril climbing herbaceous crop. it belongs to the family of cucurbitaceae, with excellent genetic diversity, vegetative and reproductive characteristics. citrullus lanatus is classified into three sub-species; lanatus, mucosospermus fursa and vulgaris fursa. some of the species are edible and grown in most parts of the world (enoch et al., 2008). egusi is grown and utilized as food source in most parts of africa. melon seed is also an important component of the traditional cropping system usually inter-planted with such staple crops as cassava, maize, sorghum, etc and by nature, a creepy growing plant which covers large area when properly grown, and as such control weeds, thereby improving soil fertility. its leaves are deeply lobed and blue-gray, and are alternately arranged (jeffrey, 1980; enoch et al., 2008). the yellow-green fruit at maturity, which is identified by the drying of its leaves, is about the size of edible watermelon, but its flesh is white and the back is often shiny. the melon pod has an almost spheroidal external shape and ellipsoidal seed cavity (oloko and agbetoye, 2006). melon (egusi) originated fron africa and asia and over the years, it is widely cultivated in the caribbean, indonesia and africa. in nigeria, the existence of melon dates back to the 17th century. melon (popularly known as egusi in the igbo speaking parts of nigeria) is a popular crop because of the edible seeds which are commonly used in the preparation of local soup or stew and snacks such as fried melon seed ball known as robo in south western nigeria, and grinded melon mixed with bitter leave known as ofeegusi in eastern part of nigeria. recent statistics shows that 100,000 and 488,000 metric tons of melon were produced in nigeria in 1992 and 1997. the melon (egusi) seed, c. lanatus had been reported to contain an average about 22g of protein, 30g of fat and 11g of carbohydrate and as well as good quantities micronutrients per 100g sample. it is a good source of amino acids such as arginine, vitamins b1, vitamins b2, niacin, tryptophan and methionone, and minerals such as zinc, iron, potassium, phosphorus, sulphur, manganese, calcium, lead, chloride and magnesium (eugene and gloria, 2002). melon seeds contain between 30-50% by weight of oil which is comparable to other oil plants and the oil contains a high level of saturated fatty acids. according to oloko and agbetoye (2006), melon seeds offer valuable sources of vegetable oil for local and export trade. recently, it has been proved to be a fed-stock for bio-fuel (gusmini et al., 2004; solomon et al., 2010). melon has about 60% protein content that enriches the diet of the consumer. melon such as (citrulluslanatus), bara (colocynthiscitrullus) and sereweare are most common in nigeria. the colocynthis citrullus has the widest distribution. the geographical distribution was attributed to consumers’ preference rather than physiological adaptation of the crop. despite the huge economic, nutritional, medicinal and cultural potential of these product, very little is known of the aerodynamic and thermal properties. as a result, there is scarcity of machines, systems and gadgets for wide scale post harvest operation such as processing, distribution and value addition accessioned by dearth of design data. in most african countries in general and nigeria in particular, postharvest operations are carried out manually with its attendant drudgery, poor quality product and low productivity and economic value. to transform this product into internationally acceptable and marketable products, their aerodynamic, thermal properties are expedient as well as high quality maintained. since only a few agricultural crops such as fresh fruits http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 151 and vegetables go from field to the table without any thermal processing, therefore thermal processing becomes unavoidable. thermal processing (include treatments such as pasteurization, concentration, drying, cooling, etc.) is frequently used in food processing, transportation, storing and cooking to improve the shelf life and good quality of the material. to achieve these, there is therefore need to determine the thermal properties of these product. knowledge of the aerodynamic and thermal properties of melon seeds are vital in equipment design for operations such as pneumatic conveying in loading/unloading operations of melon seeds. it is also useful to both engineers and food scientists; plant and animal breeders and also for data collection in the design of machines, structures, processes and controls; and in determining the efficiency of a machine or an operation. on the other hand, the knowledge of temperature requirements plays a very vital role on the storability of the seed. pneumatic conveying may offer important functional and economic advantages in handling materials. the utilization of forced-air streams for the transport and drying of agricultural materials is becoming increasingly important in nigeria. it is, therefore, necessary that the aerodynamic characteristics of this material at varying temperature be investigated so that their behaviour in an air stream can be estimated with a degree of certainty, and so a fair basis on which to establish blower design can be provided. thermal properties of food and agricultural materials are important engineering parameters in the mathematical modeling and design of systems and equipment needed for drying, storing, aeration, and refrigeration. these properties are also essential for the prediction of drying and refrigeration processes. a number of researchers have determined three moisture-dependent thermal properties (such as specific heat capacity, bulk thermal heat conductivity, and thermal heat diffusivity) for several grains, seeds, and kernels such as minor millet (sestaria italia , panicum miliare, panicum miliaceum, paspalum sorobiculatum, eleusine coracana , echinochola colona) (subramanian and viswanathan, 2003), guna seed (citrullus colocynthis) (aviara et al., 2008), coriander (coriandrum sativum l) and anise (pimpinella anisum l) seeds (hacikuru and kocabiyik, 2008), chickpea (cicer arietinum l) (singh et al., 2008), pumpkin seeds (cucurbita pepo l) (kocabiyik et al., 2009), peanut (arachis hypogaea linnaeus) pods, kernels and shells (bitra et al., 2010), pigeonpea (singh and kotwaliwale, 2010), prairie carnation (saponaria vaccaria) (shrestha and baik, 2010), roselle seeds (hibiscus sabdariffa l) (bamgboye and adejumo, 2010), and black pepper (panniyur-1) (meghwal and goswami, 2011). alagusundaram et al. (1991) determined only the thermal conductivity of lentil (laird) as a function of moisture content. also, the effect of temperature on thermal properties of melon seeds is very important in the design of drying, processing and storage equipment. therefore, this work seeks to determine the aerodynamic (terminal velocity, drag force and drag coefficient) and thermal properties (thermal conductivity, thermal diffusivity and specific heat capacity) of melon seeds (citrullus l.) under varying drying temperature. 2.0 materials and methods 2.1 sample collection and preparation the study was carried out using local but common variety of melon (egusi) seeds, colocynthiscitrullus, which also has the widest distribution. samples of the melon seeds were ../../../user/downloads/azojete143/www.azojete.com.ng asoiro, et al.: aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing. azojete, 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 152 purchased from a local market known as ogige market in nsukka, enugu state, nigeria. the seeds were shelled and cleaned. contaminants, immatured and other foreign materials were removed manually before the experiment was conducted. samples of the seeds were oven dried and conditioned to the required temperature (30 to 100oc) which spans the temperature range of harvest to the post harvest processing operations. figure 1. shelled melon samples 2.2 determination of aerodynamic properties of melon seeds 2.2.1 determination of terminal velocity of melon seeds the terminal velocity, vt of melon seeds measured in metre per second (m/s) was determined according to the method by shahbazi (2013). a vertical wind tunnel as shown in figure 2 was developed and used. a. centrifugal fan powered by an hp motor was used in the inlet of the wind tunnel to supply airflow. the airflow rate of the fan was controlled by changing the velocity of the electric motor through an inverter set and a diaphragm. the final section of the wind tunnel consisted of a plexiglas region where the terminal velocity of the seed was measured. to determine the terminal velocity, each seed was placed in the centre of the cross-section of the wind tunnel on the screen. the airflow was then increased until the seed flotation point. at this moment, when the rotational movement of the seed was lowest, the air velocity was measured using a hot-wire anemometer with an accuracy of 0.1 m s-1. figure 2. set up for the measurement of terminal velocity of melon seeds http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 153 2.2.2 determination of drag force the drag force is a resistive force, opposing the motion of the melon seeds. the most familiar form of drag force is made up of friction forces, which act parallel to the object's surface, plus pressure forces, which act in a direction perpendicular to the object's surface. for a solid object moving through a fluid, the drag is the component of the net aerodynamic or hydrodynamic force acting in the direction of the movement. the component perpendicular to this direction is considered lift. therefore drag acts to oppose the motion of the object. the drag force can be computed using equation (1) 2 2 2 tr tpad d vc vac f   (1) the projected area of the melon seed can be calculated using equation (2) 4 lwap   (2) where, df is the drag force (n); dc is drag coefficient (dimensionless); a is air density (1.25, kg/m3); pa particle area projected to air (m2); tv is terminal velocity (m/s); rc is resistance coefficient (kg/m); l is length of the melon seed and w is width of the melon seed. 2.2.3 determination of the drag coefficient of the corn seeds among aerodynamic properties, the drag coefficient (commonly denoted is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. it is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. the drag coefficient is always associated with a particular surface area. it is computed with equation (3) pat d d av f c 2 2  (3) where, all the parameters and units are as defined earlier. 2.3 determination of thermal properties of melon seeds 2.3.1 determination of thermal conductivity of melon seeds steady state technique was used in the determination of thermal conductivity of melon seeds. the instrument used in this work is guarded hot plate. in this process, some melon (egusi) samples were placed between the plates. one plate is heated to a required temperature and the other is cooled or heated to a lesser extent. the temperature of the plate is monitored until they are constant. the steady state temperature, the thickness of the sample, and the heat input to the hot plate are used to calculate thermal conductivity using equation (4) given according to isaj et al. (2014). 21 tt dq    (4) where λ is thermal heat conductivity (w/m/k), q is the quantity of heat passing through a unit area of the melon samples in unit time (w/m2), d is the distance between the sides of the sample in metre (m), t1 is the temperature on the hotter side of the sample (k) and t2 is the temperature on the colder side of the sample (k). figure 3 shows the schematic diagram of guided hot plate used for the determination of thermal heat conductivity. http://en.wikipedia.org/wiki/dimensionless_quantity http://en.wikipedia.org/wiki/dimensionless_quantity http://en.wikipedia.org/wiki/drag_(physics) http://en.wikipedia.org/wiki/drag_equation http://en.wikipedia.org/wiki/aerodynamics http://en.wikipedia.org/wiki/hydrodynamics ../../../user/downloads/azojete143/www.azojete.com.ng asoiro, et al.: aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing. azojete, 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 154 figure 3. schematic diagram of guided hot plate for the determination of thermal conductivity. 2.3.2 determination of thermal diffusivity of melon seeds the thermal diffusivity of melon seeds was determined according to indian standard (is: 10698 1983). the apparatus consist of a thermal diffusivity tool and an insulated water bath of 25 liters capacity. the cylinder was filled with milled melons and the entire assembly was placed with end caps and thermocouples in a water bath. heat at constant rate is applied to the water bath with the help of 1000 watt immersion heater. the water in the bath was stirred with the help of a stirrer at suitable speed, driven by a motor of 40 watt, 4000rpm and coupled to a speed regulator. the thermal diffusivity was computed by using the expression by kachru et al. (2002) and alam et al. (2002) as shown in equation (5) )(4 2 cr tt ar   (5) where,  is thermal diffusivity (m2/s) of the melon seeds, r is radius of the thermal diffussivity tube (m), tr-tc is constant temperature difference at any time between temperature at the surface tr and temperature at the centre tc of thermal diffusivity tube in (oc) and a is constant slope of temperature versus time curve (oc/s). figure 4. set up for determination of thermal diffussivity of melon seeds cooling plate insulator hot plate sample of material (egusi) melon http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 155 2.3.3 determination of specific heat capacity of melon seeds the method of mixtures has been the most common widely reported technique in literature for measuring the specific heat capacity of biomaterials (razavi and taghizadeh, 2008). for the determination of specific heat capacity of melon seeds, the method of mixture was used. molded melon samples of known mass and temperature were dropped into a cupper calorimeter containing water of known mass and temperature. the calorimeter was insulated so as to prevent heat loss to the room in which the experiment was performed. the mixture was stirred continuously using a glass stirrer. a digital thermometer was used to monitor the temperature of the mixture. the equilibrium temperature was noted. the specific heat capacity was determined using equation (6) according to aviara and haque (2001). (6) where, m1 is mass of the melon sample (kg), m2 is mass of the calorimeter (kg), m3 is mass of calorimeter + water (kg), ө1 is the initial temperature of water (k), ө2 is the temperature of the melon sample (k), ө3 is the final temperature of the mixture (k), c1 is the specific heat capacity of the melon sample (j/kg/k), c2 is the specific heat capacity of calorimeter, which was 400j/kg/k and cw is the specific heat capacity of water, which was (4200j/kg/k). 2.4 methods of statistical analyses data for both aerodynamic and thermal properties was analyzed statistically using spss and simple excel packages. analysis of variance (anova) was performed to determine the significance of the treatment and interaction effects. when analysis of variance was significant at 5% probability level, treatments were separated and presented by duncan’s new multiple range tests (dnmrt) at the 5% level of probability. simple excel was used to plot the graph of the aerodynamic and thermal properties of the melon seeds against drying temperature (30-100oc) of the melon seeds, to obtain graphical and linear representation of temperature effect on aerodynamic and thermal properties of the seeds. 3.0 results and discussions 3.1 aerodynamic properties table 1 shows the summary result of the mean values of the aerodynamic properties of melon seeds at varying drying temperature. 3.1.1 terminal velocity terminal velocity of melon seeds vary with drying temperature. as the temperature increased from 30oc to 100oc, terminal velocity decreased from 7.45 to 3.37m/s. at 30oc, 35 and 40oc terminal velocities were 7.415, 7.135 and 6.32m/s respectively. the terminal velocity was 5.95m/s at 45oc and decreased by 1.1, 5.5, 10.6 and 12.5% as temperature increased to 50, 55, 60 and 65oc respectively. terminal velocities of melon seeds were 4.88, 4.57, 4.1, 3.635 and 3.6m/s at temperature of 70, 75, 80, 85, and 90 respectively. at temperature of 100oc, the terminal velocity was 3.37m/s while at 95oc; the terminal velocity was 3.4m/s. ../../../user/downloads/azojete143/www.azojete.com.ng asoiro, et al.: aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing. azojete, 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 156 table 1. mean values of aerodynamic properties of melon seeds at varying drying temperature. temperature (oc) terminal velocity (m s-1) drag force (n) drag coefficient (dimensionless) 30 7.415j 1.567j 0.734h 35 7.135j 1.472j 0.801h 40 6.32j 1.349j 0.869h 45 5.95ij 1.275ij 0.925gh 50 5.885i 1.777i 0.99g 55 5.62h 1.079h 0.852f 60 5.32h 0.981h 0.832e 65 5.205gh 0.883gh 0.736d 70 4.88g 0.884f 0.91dh 75 4.57f 0.785e 0.993cd 80 4.1f 0.736d 1.179c 85 3.635ef 0.589c 1.084b 90 3.6d 0.54b 1.165b 95 3.4b 0.441a 0.939ab 100 3.37a 0.343ab 0.869a 3.1.2 drag force the drag force of melon seeds was 1.567n at 30oc and 0.343n at 100oc. at 35, 40, 45, 50, 55 and 60oc, the drag force of melon were 1.472, 1.349, 1.275, 1.777, 1.079 and 0.981n respectively. drag force decreased from 60oc drying temperature to 65oc by 10% and slightly increase by 0.1% from from 65 to 70oc thereafter fell to 0.785n at 75oc; 0.736n at 80oc; 0.389n at 85oc and 0.54n at 90oc. the drag force of melon seed at 95 and 100oc were 0.441 and 0.343n respectively. 3.1.3 drag coefficient as melon drying temperature increased from 30 to 50oc, the drag coefficient rose from 0.734 to 0.79. at 55oc, 60, 65, and 70oc, the drag coefficients were 0.852, 0.832, 0.736 and 0.91 respectively. mean drag coefficient was maximum at 90oc (1.165) and minimum at 30oc (0.734). drag coefficient values were 0.993, 1.084, 1.165, 0.939 and 0.869 at drying temperature of 75, 85, 90, 95, and 100oc respectively. 3.2 thermal properties table 2 shows the summary result of the mean values of the thermal properties of melon seeds at varying drying temperature. 3.2.1 specific heat capacity the mean specific heat capacity of melon seed was maximum at 30oc (2.995kj/kg/k) and minimum at 100oc (1.596kj/kg/k). specific heat capacity decreased (2.8, 2.376, 1.906, 1.848, 1.811 and 1.785 kj/kg/k) with increasing temperature (35, 40, 45, 50, 55 and 60kj/kg/k). the value of specific heat capacity at 65oc (1.766kj/kg/k) decreased by 0.9%, 1.6, 2.2 and 2.6% at 70, 75, 80 and 85oc http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 157 respectively. at 90, 95 and 100oc, the specific heat capacity values of melon seeds were 1.655, 1.611 and 1.596kj/kg/k respectively. table 2.mean values of the thermal properties of melon seeds at varying temperature temperature (oc) specific heat capacity (kj kg-1 k-1) thermal heat conductivity (w m-1 k-1) thermal heat diffussivity. (m² s-1) 30 2.995k 3.62l 6.19e-05o 35 2.8k 1.545l 2.17e-05n 40 2.376k 1.1kl 1.21e-05m 45 1.906cj 1.83k 7.97e-06l 50 1.848j 1.725k 5.89e-06k 55 1.811i 0.64j 4.71e-06j 60 1.785h 0.605i 3.55e-06i 65 1.766g 0.555h 3.06e-06h 70 1.75fb 0.53g 2.68e-06g 75 1.738e 0.52f 2.19e-06f 80 1.728d 0.505e 1.79e-06e 85 1.72c 0.5d 1.62e-06d 90 1.655c 0.499c 1.41e-06c 95 1.611b 0.49b 1.26e-06b 100 1.596a 0.46a 1.16e-06a 3.2.2 thermal heat conductivity thermal heat conductivity of melon seeds decreased between 30oc (3.62w/m/k) and 40oc (1.1w/m/k) and thereafter increased to 1.83w/m/k at 45oc. it later decreased again from 50oc (1.725w/m/k) to 100oc (0.46w/m/c) by 73.3%. it has maximum value at drying temperature of 30oc (3.62w/m/k) and a minimum value at 100oc (0.46w/m/k). 3.2.3 thermal heat diffusivity the thermal heat diffusivity of melon seeds was maximum at 30oc (6.19  10-5m2/s), minimum at 100oc (1.16  10-6m2/s); 2.17  10-5m2/s; 1.21  10-5m2/s; 7.97  10-6m2/s; 5.89  10-6m2/s and 4.71  10-6m2/s at 35, 40, 45, 50 and 55oc respectively. the thermal conductivity of melon seeds decreased with increased temperature. it was 3.55  10-6m2/s, 3.06  10-6m2/s, 2.68  10-6m2/s, 2.19  10-6m2/s, 1.79  10-6m2/s, 1.62  10-6m2/s, 1.49  10-6m2/s and 1.26  10-6m2/s at drying temperature of 55, 60, 65, 70, 75, 80, 85, 90, and 95oc. 3.3 statistical analyses of results 3.3.1 aerodynamic properties at 5% probability level, the mean values of terminal velocity of melon seeds at 30, 35, 40 and 45oc are statistically non significant. these values are significantly different from the mean terminal velocity value at 45oc (5.95 m/s). the mean value of terminal velocity of the seeds at 45oc is nonsignificant from the value at 50oc (5.885m/s). the mean terminal velocity value of melon seed at ../../../user/downloads/azojete143/www.azojete.com.ng asoiro, et al.: aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing. azojete, 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 158 55oc (5.62m/s), 60oc (5.32m/s) and 65oc (5.205m/s) are all non significant from each other but the terminal velocity value at 65oc is significant from the values at 55oc and 60oc. it is non significant from the value at 70oc (4.88m/s). the values of terminal velocity of melon seeds at 75oc (4.57m/s), 80oc (4.1m/s) and 85oc (3.635m/s) are all the same statistically. the value of terminal velocity at 85oc is different statistically from those at 75oc and 80oc. the terminal velocity values of melon seeds at 90oc (3.6m/s), 95oc (3.4m/s) and 100oc (3.37m/s) are all statistically significant from one another at 5% probability level. the mean drag force values of melon seeds at 30oc, 35oc, 40oc and 45oc are all statistically non significant. the drag force value at 45oc (1.275n) is significant from values at 30, 35 and 40oc but statistically the same with the drag force value at 50oc (1.777n). mean drag force values at 55oc (1.079n), 60oc (0.981n) and 65oc (0.883n) are all statistically the same at 5% probability level, but for the value drag force at 65oc which is significantly different from those at 55oc and 60oc respectively. the drag force values at 70oc (0.884n), 75oc (0.785n), 80oc (0.736n), 85oc (0.589n), 90oc (0.54n) and 95oc (0.441n) are all significantly different from one another at 5% probability levels. however the drag force value of melon seed at 100oc (0.343n) is non significant with value at 90oc and 95oc respectively. the mean values of drag coefficient of melon seeds at 30oc (0.75), 35oc (0.801), 40oc (0.869) and 45oc (0.925) are statistically the same, but the mean drag coefficient value at 45oc is different is different statistically fro 30, 35 and 40oc respectively. however, the same with the drag coefficient value at 50oc (0.99). the mean drag coefficient value at 55oc (0.852), 60oc (0.832) and 65oc (0.736) are all statistically significant, but the drag coefficient value of melon seed at 65oc, 70oc and 75oc are all non significant at 5% probability level. mean drag coefficient value of melon seeds at 75oc (0.993) and 80 (1.179) are non significant. drag coefficient values at 85oc (1.084), 90oc (1.165) and 95oc (0.939) are all non significant. the values of drag coefficient of melon seeds at 95oc are significant from values at 85oc and 90oc respectively. 3.3.2 thermal properties specific heat capacity of melon seeds decreased with temperature, the mean values of the specific heat capacity of melon seeds was maximum at 30oc (2.995 kj/kg/k). and minimum at 100oc (1.596kj/kg/k). the values were all significantly different at the different temperature levels. however, the specific heat capacity at 85oc (1.72kj/kg/k) and 90oc (1.655kj/kg/k) were not significant (p 05.0 ) the mean values of thermal heat conductivity of melon seeds at 30oc (3.62w/m/k), 35oc (1.545w/m/k) and 40oc (1.1w/m/k) are non significant. the thermal heat conductivity of melon seeds at 45oc (1.83w/m/k) and 50oc are non significant at 5% level of probability. however, the thermal heat conductivity value of 1.1w/m/k at 40oc is significant from the values at 30oc, 35oc, and 45oc, 50oc respectively. the thermal heat conductivity value of melon seed at 55oc (0.64w/m/k), 60oc (0.605w/m/k), 65oc (0.555w/m/k) and 70oc (0.53w/m/k) are all significant. the thermal heat conductivity value of melon seeds at 75oc (0.499w/m/k), 95oc (0.49w/m/k) and 100 (0.46w/m/k) are all significantly different from one another at 5% level of probability. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 159 all the thermal heat diffusivity values of melon seeds (m2/s) are significantly different from one another at the different drying temperature levels (30 to 100oc) 4.0 conclusions increase in temperature reduced the values of terminal velocity and drag force of (egusi) melon seeds while it increased the values of the drag coefficient. the terminal velocity attained its maximum value which was found to be 7.414 m/s at the temperature of 30ºc, and attained its minimum value which was 3.37m/s at 100ºc. the drag force of the melon seed attained its maximum value of 1.777n at temperature of 50ºc and minimum value of 0.343n at temperature of 100ºc. at 35ºc, 40ºc and 45ºc, the drag force values were 1.472n, 1.349n, and 1.275n respectively. drag coefficient has a maximum value of 1.179 at temperature of 80ºc and minimum value of 0.743 at temperature of 30ºc. for thermal properties, as temperature increased, the values of specific heat capacity and the thermal conductivity of the melon seed decreased. the specific heat capacity attained its maximum value at temperature of 30ºc with a value of 2.995kj/kg/k, while it attained its minimum value 1.596kj/kg/k at temperature of 100ºc. the thermal conductivity was maximum at 30ºc with a value of 3.62w/mok and minimum at 100ºc at a value of 0.46w/mok. the thermal diffusivity attained maximum value of 7.97×10-6m2/s at a temperature of 45ºc, and minimum at 100ºc with a value of 1.1×10-6m2/s. reference alagusundaram, a., jayas, ds., muir, we. and white, ndg. 1991. thermal conductivities of bulk barley, lentils, and peas. t asae 34(4), 1784-1788. aviara, na., and haque, ma. 2001. moisture dependence of thermal properties of sheanut kernel. j. food eng. 47(2): 109-113. aviara, na., haque, ma. and ogunjimi, lao. 2008. thermal properties of guna seed. int agrophys 22, 291-297. bamgboye, a.i., adejumo, o.i. (2010). thermal properties of roselle seeds. int agrophys 24, 85-87. bitra, vsp., banu, s., ramakrishna, p., narender, g. and womak, ar. 2010. moisturedependent thermal properties of peanut pods, kernels, and shells. biosystems eng. 106(4): 503512. enoch ga, rose, f., hermane, ta., raymond, sv., osmane, c. and adam, a. 2008. importance and practices of egusi melon crops in sociolinguistic areas in benin, biotech, agro. and envi.al journal, 12(4), 393-403. eugene, no. and gloria, na. 2002. chemical composition of selected nigerian oil seeds and physicochemical properties of the oil extracts. j. of food chemistry, 77, 431-437. gusmini, g., wehner, tc. and jarlet, rl. 2004. inheritance of egusi melon seed type in watermelon. j. of heredity, 95(3), 268-270. hacikuru, i. and kocabiyik, h. 2008. thermal properties of coriander and anise seeds. philipp agric sci 91(4), 401-407. ../../../user/downloads/azojete143/www.azojete.com.ng asoiro, et al.: aerodynamic and thermal properties of melon (citrullus lanatus) seeds under varying drying temperature for separation from shells and processing. azojete, 14(sp.i4):149-160. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 160 isaj, ohadole, so. and akinlade, es. 2014. the effect of moisture content in thermal properties of some selected species of egusi melon (colocynthiscitrillus l.), international journal of engineering technology and advanced engineering, vol.4. pp 580-586. jeffrey, c. 1980. a review of the cucurbitaceae. journal of linn soc, 81, 233-247 kachru, rp., gupta, rk., gupta, rk. and alam, a. 2002. physicochemical constituents and properties of food crops. pp. 118-119. kocabiyik, h., kayis, ob., tezer, d. 2009. effect of moisture content on thermal properties of pumpkin seed. int j food prop 12(2), 277-285. meghwal, m. and goswami, tk. 2011. thermal properties of black pepper and its volatile oil. international journal of advanced biotechnology and research, 2(3): 334-344 oloko, sa. and agbetoye, las. 2006. development and performance evaluation of a melon depodding machine. agricultural engineering int. the cigr e j., 7: pm 06018. razavi, sma. and taghizadeh, m. 2008. specific heat of pistachio nuts as affected by moisture content, temperature, and variety. j. food eng. 79(1): 158-167. shahbazi, f. 2013. aerodynamic properties of wild mustard (sinapis arvensis l.) seed for separation from canola. j sci food agric; 93: 1466–1470. shrestha, bl. and baik, od. 2010. thermal conductivity, specific heat, and thermal diffusivity of saponaria vaccaria seed particles. transactions of the asabe, 53 (5): 1717-1725. singh, kk. and kotwaliwale, n. 2010. effect of moisture content on physico-thermal properties of pigeonpea. j. food proc. and preserv. 34(5): 845-857. singh, kk., mohammad, s. and kotwaliwale, n. 2008. moisture dependent physical and thermal properties of chickpea. j. food sci 45(3), 259-262. solomon, g, luqman ca. and mariah, a. 2010. investigating egusi melon seed oil as potential biodiesel feedstock. energies, 3, 601-618. subramanian, s. and viswanathan, r. 2003. thermal properties of minor millet grains and flours. biosystems engineering 84(3):289-296. doi: 10.1016/s1537-5110(02)00222-2. tang, j., sokhansanj, s., yannacopoulos, s. and kasap, so. 1991. specific heat capacity of lentil seeds by differential scanning calorimetry. trans. asae 34(2): 517-522. https://www.researchgate.net/scientific-contributions/2034873715_shinoj_subramanian?_sg=glinqmnbsjh7ygniyjqrx9ruggxqtezvjawo-ajw776dxbhfblkaoslaqcmoqxducjyfpse.q20bq6mykk8yyd4m530hwq3f8iaoxpjow2xgbwh4bg_leazcmbujzkss6my8syzmj3tohjbwvybngnnshxwhea http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):110-115 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 110 original research article investigation of corn seeds growth under simulated microgravity f. a. oluwafemi1* and r. a. olubiyi2 1space life sciences unit, engineering and space systems (ess) department, national space research and development agency (nasrda), airport road, abuja, nigeria. 2planning policy and research (ppr) department, national space research and development agency (nasrda), airport road, abuja, nigeria. article information submitted: 12/12/2018 revised: 26/12/2018 accepted: 18/03/2019 keywords: microgravity light corn photosynthesis plant metabolism. abstract living organisms are made-up of cells, while cells are made-up of several macromolecules such as proteins, carbohydrates, nucleic-acids, lipids, which have individual functions. the role and impact of light on plant metabolism including photosynthesis cannot be overemphasized. corn seeds were planted in two petri-dishes using plant-agar after standard-preparation. the plant-agar served as soil and as source of nutrient. the two petri-dishes containing the seeds, had equal treatment by receiving 50lux of light and humidity of 60-100%. these are the essential conditions for photosynthesis. after 3days, germination of the seeds was observed. one of the petri-dishes was labelled terrestrial-control while the other was labelled clinorotated. the clinorotated was mounted on clinostat, a microgravity-simulating equipment for 4 hours. the two petri-dishes for the 4 hours received 50lux of light. observations and analysis were carried out using imagej software on pictures taken periodically from the two samples. the quantitative result of the analysis showed that the clinorotated sample had 9.73mm/h growth-rate while terrestrial-control sample had 7.54mm/h growth-rate. the two samples received equal lux of light, but the interaction of the light for conversion into chemical-energy for plant-activities was different after subjection to simulated-microgravity for 4 h. it could be deduced that: the light dependent reactions, which take place in the thylakoid-membrane, that use light-energy to make atp (chemical) and nadph was speed-up under simulatedmicrogravity and that photosynthetic functions were impacted positively by the space-environment. therefore, role of light on plants is complex and this is a function of the role of complex light interactions on individual cells of plant. © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction plants respond to environmental stimuli such as gravity, light, water, wind and touch. the gravitropic response is often – cited example of biological signal perception, processing and response. signal perception is attributed to sedimenting or moving amyloplasts. the physical process is then converted into a biochemical signal (through signal transduction mechanism) that elicits a growth response in the shoot and roots, where differential elongation on the top http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):110-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 111 and bottom flank reestablishes the gravitropic set-point angle. the curvature is the final step in a series of complex processes (susan and karl, 2011). corn (zea mays) is an important grain used for food, animal fodder, the production of alcoholic beverages, and biofuels. corn’s usefulness makes research on corn quite important (agdhsa, 2008). all living things need energy to grow. humans get energy from plants by eating them. plants get energy from light through a process called photosynthesis. without light, a plant would not be able to produce the energy it needs to grow (heather, 2018). living organisms are made-up of cells. cells on the other hand are made-up of several macromolecules such as proteins, carbohydrates, nucleic-acids, lipids etc. which have individual functions (geoffrey, 2000). the role and impact of light on plant metabolism including photosynthesis cannot be overemphasized (howard, 2010). photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product (rsc, 2019). corn seeds were bought and authenticated to be the actual seeds sought after. experimental sample of corn seeds were allowed to grow under simulated microgravity using clinostat for 4h. the experimental and the control samples had equal treatment by receiving 50lux of light and humidity of 60-100%. these are essential for photosynthesis. observations and analysis were done using imagej software on the pictures taken periodically on the two samples for the period of the four hours. haven received equal light treatment, the quantitative analytical result on the growth gives information on the light interactions on the individual samples from their photosynthesis. this is according to the teacher’s guide to plant experiments by united nations office for outer space affairs (unoosa) of the programme on space applications (united nations, 2013). several researches such as those of raghad et al. (2016) and emmanuel et al. (1996) have shown that microgravity impact on plants usually results in positive influence on plant biochemicals. therefore, the objective of this research was to investigate if equal light impact on the sample mounted on clinostat and the control sample under normal earth gravity gives the same growth rates in these samples. 2.0 materials and methods the substrate of seeds called plant-agar was prepared in 2 petri-dishes following the standard preparation method (oluwafemi et al., 2018a). the plant-agar (seeds substrate) served as the soil and as source of nutrient. then the corn seeds were planted into the substrate and it was cultivated inside a wet chamber in vertical positions. this is because plants grow vertically under normal earth gravity (terrestrial). the light intensity reaching the samples for growth was measured using lux meter (figure 1). after 3 days, germination of the seeds with short roots was observed. the 2 petri-dishes were then taken and labeled “terrestrial-control”, and “clinorotated” (figures 2 and 3). the terrestrial-control sample was left in the vertical position while the clinorotated sample was placed at the centre of the clinostat using double-sided tape. the photos of the 2 petri-dishes were taken every 30 min with very short stopping time of the clinorotated in order to avoid the effect of gravity (the clinorotated sample mounted on the clinostat was stopped from rotation for some seconds to snap it. during this short period to file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwafemi and olubiyi: investigation of corn seeds growth under a simulated microgravity. azojete, 15(sp.i2):110115. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 112 snap, negligible gravity will act on this sample). these observations were done for 4h under the following conditions; light of 50lux, humidity was between 60% to 100% and temperature was 23ºc. in addition to these, the clinorotated sample had the following conditions, rotation speed of 75rpm, horizontal rotational-axis angle of 90° and the direction of rotation was clockwise. this is because the clinostat is an equipment and needs to be set at specified experimental variables at the discretion of the experimental. the rotation speed ranges from 1 to 90°; the position of the clinostat could be maintained from horizontal to vertical; and the direction of rotation could be clockwise or counter-clockwise (anti-clockwise) (united nations, 2013). at the end of observation, the analysis of growth-rate was carried out. the data obtained were the two sets of photos of the roots which show the “terrestrial-control” and “clinorotated” roots. an image-processing application soft-ware called imagej was used to analyze the photos. the difference between the two cases was analyzed by measuring the length of the roots, which thereby allowed their growth-rate to be determined. the length of the roots was measured by drawing a line which is exactly 10mm long on each petri-dish. this line was used to standardize 10mm length on the imagej software serving as a fixed length in the photos of the roots (such as figures 2 and 3). after standardization, the length measurement tool of the imagej software was used to measure the length (in mm) of each of the roots in each photo. this yielded data-set of experimental-results in gravity and simulated microgravity responses whose grand average was calculated in mm/h and used to plot graph (oluwafemi et al., 2018b). figure 1: lux meter 3.0 results and discussion the average (in mm) growth-rate of the roots of the seeds of corn for the terrestrial-control sample was 7.54mm/h while that of the clinorotated sample was 9.73mm/h. table 1 shows the growth-rate analysis using the root length of the terrestrial-control and clinorotated samples; table 2 shows the grand averages of the values in table 1; while the graph was plotted using these grand averages. figure 2: the clinorotated-sample figure 3: the terrestrial-control sample http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):110-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 113 table 1: growth rate analysis for terrestrial-control and clinorotated samples terrestrialcontrol time of growth during observation 0 h 0.5 h 1 h 1.5 h 2 h seed1 (mm) 11.035 12.862 12.999 11.998 12.010 seed2 (mm) 2.122 2.001 2.186 2.205 2.590 seed3 (mm) 18.848 22.000 22.071 21.567 22.971 seed4 (mm) 11.519 14.564 14.564 14.302 14.879 seed5 (mm) 13.306 15.421 15.701 15.163 15.814 seed6 (mm) 17.869 20.471 20.942 19.430 21.000 seed7 (mm) 22.755 23.571 24.431 23.578 24.100 seed8 (mm) 4.394 6.720 6.140 5.806 6.123 seed9 (mm) 17.909 21.223 23.105 21.611 22.844 average (mm) 13.306333 15.425889 15.793222 15.073333 15.814556 clinorotated 0 h 0.5 h 1 h 1.5 h 2 h seed1 (mm) 33.895 37.225 34.673 36.035 36.980 seed2 (mm) 22.003 27.430 22.559 24.047 25.000 seed3 (mm) 5.419 6.584 5.441 5.564 5.941 seed4 (mm) 15.623 17.372 16.724 17.688 17.999 seed5 (mm) 23.201 26.660 23.382 25.610 26.151 seed6 (mm) 28.737 30.078 26.191 25.717 26.210 seed7 (mm) 3.841 5.000 4.469 4.743 4.976 seed8 (mm) 22.832 23.455 21.549 21.554 21.842 seed9 (mm) 11.976 13.425 12.486 13.080 14.001 average (mm) 18.614111 20.803222 18.608222 19.337556 19.900000 figure 4: the length of the terrestrial-control sample roots and the clinorotated-sample roots versus the time after germination file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oluwafemi and olubiyi: investigation of corn seeds growth under a simulated microgravity. azojete, 15(sp.i2):110115. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 114 the experiment carried out by emmanuel et al. (1996) under clinorotation showed doubling of the root length of seeds compared to the stationary control in similar experiment to this one. the result gotten in this project is also in conformity with the result of raghad et al. (2016) which concluded that clinostat rotation can affect the biochemicals in plants tissue positively and that this technique can be used to enhance plant germination. raghad et al. (2016) specifically investigated that gravistimulation produced on corn using clinostat showed enhanced amino acid concentration more than the control. the experiment of oluwafemi et al. (2018b) on watermelon seeds growth under simulated microgravity using clinostat showed that there was an increased growth rate of the clinorotated sample than the terrestrial control sample. another study of oluwafemi (2017) reports that reduction of gravity causes significant changes on the chosen samples during experiments. these samples could be plants, animal cells, micro-organisms and nanoparticles. the changes that occur as a result of the effect of microgravity have led to discoveries that have been found to be of socio-economic benefits. therefore, in this project, the same light intensity on terrestrial and clinorotated samples resulted in different growth rates of the two samples. 4.0 conclusions the quantitative result of the average growth-rate of the roots of the corn indicated an increased growth-rate of corn under simulated microgravity by 29.05%. the two samples received equal lux of light, but the interaction of the light for conversion into chemical-energy for plant-activities was different after subjection to simulated-microgravity for 2 hours. it could be deduced that: the light dependent reactions, which takes place in the thylakoid membrane, that use light energy to make atp (chemical) and nadph was speed-up under simulatedmicrogravity and that photosynthetic functions were impacted positively by the space environment. therefore, role of light on plants is complex and this is a function of the role of complex light interactions on individual cells of the plant. clinostat rotation can therefore be said to impact the biochemicals in plants tissue positively and this technique can be used to enhance plant germination, growth and ultimately, productivity in agricultural sector. acknowledgement united nations office for outer space affairs (un-oosa) in vienna, austria for contributing clinostat to national space research and development agency (nasrda), abuja, nigeria. nasrda is also acknowledged for providing the research space. references agdha. 2008. australian government department of health and ageing. the biology of zea mays l. ssp mays (maize or corn). office of the gene technology regulator, australia. version 1. emmanuel, h., barbara, vp., james, ag. and christopher, sb. 1996. clinorotation affects morphology and ethylene production in soybean. plant cell physiology, 37(7): 929-934. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):110-115. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oluwafemifunmilola@gmail.com 115 geoffrey, mc. 2000. the cell: a molecular approach. 2nd edition. https://www.ncbi.nlm.nih.gov/books/nbk9879/ accessed 21 july, 2019. heather, r. 2018. how light affects the growth of a plant and problems with too little light. https://www.gardeningknowhow.com/plant-problems/environmental/how-light-affects-thegrowth-of-a-plant-problems-with-too-little-light.htm accessed on 10 october, 2018. howard, gl. 2010. the influence of microgravity on plants. nasa surface systems office, space life sciences laboratory, mail code ne-s-1, kennedy space center, fl 32899. nasa iss research academy and pre-application meeting, south shore harbour resort and conference center, league city, texas. oluwafemi, f. 2017. microgravity research and applications: roles in economic prosperity and poverty reduction. proceedings of united nations/united arab emirates, high level forum “space as a driver for socio-economic sustainable development”, dubai, united arab emirates, 6-9 november, 2017. oluwafemi, fa., de la torre, a., afolayan, em., olalekan-ajayi, bm., dhital, b., mora-almanza, jg., potrivitu, g., creech, j., and rivolta a. 2018a. space food and nutrition in a long-term manned mission. springer: advances in astronautics science and technology https://doi.org/10.1007/s42423-018-0016-2. oluwafemi, fa., oke, ab., and afolayan, em. 2018b. investigation of watermelon seeds growth under simulated microgravity and its advantages to agriculture sector. monograph of atmospheric research 2018, centre for atmospheric research (car), anyigba, nigeria. pp. 109111. isbn: 978-978-972-859-6. raghad, sm., munawar, i., afzal, q., lamiaa, am., ibrahim, br., mazhar, a. and fida, h. 2016. effect of gravistimulation on amino acid profile of pea, rice, corn, wheat during early growth stages. information processing in agriculture, 3: 244-251. rsc. 2019. royal society of chemistry. chemistry for biologists: photosynthesis. advancing the chemical sciences. https://www.rsc.org/education/teachers/resources/cfb/photosynthesis.htm accessed 21 july, 2019. susan, pj. and karl, hh. 2011. effects of mechano-stimulation on gravitropism and signal persistence in flax roots. plant signaling and behaviour, 6(9): 1365-1370. united nations, 2013. teacher’s guide to plant experiments in microgravity. human space technology initiative. united nations programme on space applications, new york https://www.gardeningknowhow.com/plant-problems/environmental/how-light-affects-the-growth-of-a-plant-problems-with-too-little-light.htm https://www.gardeningknowhow.com/plant-problems/environmental/how-light-affects-the-growth-of-a-plant-problems-with-too-little-light.htm https://doi.org/10.1007/s42423-018-0016-2 https://www.rsc.org/education/teachers/resources/cfb/photosynthesis.htm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):803-812 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 803 original research article parametric optimization and determination of a suitable welding process for stainless steel-mild steel dissimilar metals weld s. o. sada* and l. c. enyi department of mechanical & production engineering, faculty of engineering, delta state university. oleh campus, nigeria *corresponding author’s email address: samorosada@gmail.com 1.0 introduction the increasing application of new structures with tailored engineering properties in the manufacturing industry has given rise to the joining of metals with entirely different materials and properties. this combination of different materials not only allows the use of metals with specific properties to be utilized in a more functional and efficient manner, but it also allows for a whole new structure possessing unique mechanical properties to be created. these materials often possess good compatibility in terms of properties as it relates to the service conditions necessities (das et al., 2014; kas et al., 2009). the joining of dissimilar metals cannot be compared to that of similar or identical metals (bhattacharya et al., 2016; satyanarayana et al., 2005). many factors such as the dissimilar metals composition, its properties (chemical and metallurgical), the selection of suitable filler material, the joint design, and the welding process affects both the choice of the welding processes and the quality of the welded joints. additionally, the proper selection of a suitable joining process, filler material, and process parameter, to an acceptable weld joint design is a major determinant for obtaining a reliable weld quality (tusek et al., 2001). electric arc welding, amongst which are: gas metal arc welding (gmaw), the gas tungsten arc welding (gtaw) and shield metal arc welding (smaw), are the most prominent fusion welding processes employed for dissimilar metals (lin et al., 2010). martinsen (2015), bang (2013) and dong (2012), reported that the formation of brittle intermetallic compounds (imc) resulting from the heat affected zone (haz) and the molten pool is minimized with the use of arc welding process. conversely, kaewkuekool and amornsin (2008), kim (2009), and wang (2012) revealed aside identifying a article information abstract difficulties associated with dissimilar metals welding differ remarkably and can be minimized with the selection of a suitable joining process, modification of the joining technique, and the adoption of optimal process parameters. this study investigates the suitability of three fusion welding processes (gas tungsten arc welding (gtaw), gas metal arc weld (gmaw), and shielded metal arc welding (smaw)) in the welding of stainless steel to mild steel plates based on their mechanical properties and observed weld defects. gas tungsten arc welding (gtaw) process which turned out to be the most suitable of the three, recording the least imperfections, an efficiency in mechanical properties of 8% higher compared to the other processes, furthermore analyzed using the response surface methodology (rsm) to obtain a models of the input and output relationship, as well as the optimal process parameters was conducted. an optimal parameters of 461.88n/mm2 for the tensile strength and 31.65% for the elongation was observed at the combined input parameters of 200 amp, 15 volt, 20 l/min, and 2.4mm for the weld current, arc voltage, gas flow rate and filler rod respectively. therefore, the application of optimal process parameters along with a compatible weld process is recommended in the welding of dissimilar metals to guarantee excellent weld qualities. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 may, 2020 revised 23 november, 2020 accepted 24 november, 2020 keywords: welding dissimilar metals response surface methodology tensile strength mailto:samorosada@gmail.com http://www.azojete.com.ng mailto:samorosada@gmail.com sada and enyi: parametric optimization and determination of a suitable welding process for stainless steel-mild steel dissimilar metals weld. azojete,16(4):803-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 804 suitable welding process, there is the need for compromise in the selection and combination of different process parameters. they reported that the selection of a filler material compatible with the base metal, the application of buttering, and the control of heat input was necessary in reducing the alloy element gradient and carbon migration, and the risk of corrosion. monika et al. (2013) studied the effect of the heat input on the mechanical properties of a dissimilar (gmaw) welded joints. they observed that the hardness is directly proportional to the heat input but inversely proportional to the tensile strength of the weld. the authors concluded that the mechanical properties of materials with considerable difference in properties welded by the arc welding method, depends greatly on the input process control, the filler material used and the preheat and post-heating condition. kaewkuekool and amornsin (2012), carried out a study on the mechanical properties of a dissimilar metal weld between stainless (aisi 304) and low-carbon steel using gas metal arc welding (gmaw) technique along with three different filler metals; gfw304l, 308l [en12073] and 316l [en12072]). from the result obtained, the tensile strength and percentage elongation are greatly affected by the weld speed, weld current, as well as filler metal type. khorrami et al. (2014) studied the suitability of applying filler metals, in the welding of aisi 430 ferritic stainless steel weld and plain carbon steel) using the gtaw process. they reported that a reasonable improvement in the mechanical properties (hardness and ultimate tensile strength) was observed in the weld having filler metals compared to the autogenously weld. they reported further that applying a filler metal compatible to the dissimilar metals being joined enhances the mechanical properties of the joint. mvola and kah, (2017) in their study examining the effects and components of shielding gas mixtures in fusion welding, asserted that the appropriate selection of shielding gases and the control of the gas flow rate was capable of increasing productivity in the welding industry along with improving the quality of the weld. chuaiphan et al. (2013) carried out a study to investigate the most suitable of the welding processes; gas tungsten arc welding (gtaw) and shield metal arc welding (smaw) in terms of toughness for 15 mm thick stainless steel to carbon steel plates dissimilar welded joints. they reported that aside the pitting corrosion potential displayed by the gtaw welded joint, the smaw weld had a higher weld metal toughness. teker et al. (2011) pointed out that in the welding of ferrite steel and quenched, and tempered steel using gmaw-p and gmaw, a superior tensile strength, less grain growth, and a narrow heat affected zone was recorded in the gmaw_p welded compared to the gmaw welded joint. this they ascribed to the better heat control, a finer fusion zone, and higher fusion hardness attributes of the gmaw-p welding process. kumar and sundarrajan, (2009) applied the taguchi method in determining the optimal mechanical properties of a (al-mg-si) aluminum alloy welded using tig welding process as well as the effect of the pulsed tig welding parameters. their findings which compared the tig weld to the parent metal revealed had a lower notch tensile strength and impact toughness. the objective of this study is to compare three different welding processes in the joining of mild steel to austenitic stainless steel (304) plates (10mm thickness) and evaluate the optimal welding parameters for the selected weld process. 2. materials and methods 2.1 materials the base metals selected for the experiment are stainless steel and mild steel plates with dimensions of 20 mm x 10 mm x 6 mm, along with the following input parameters; weld current (200-240amp), arc voltage (15-25volts), filler rod (2.0-2.4mm) and gas flow rate (2024lit/min). based on the physical, chemical and mechanical-technological properties comparable to those of the base material, 302 stainless steel with chemical composition as shown in table 1, was selected as the filler material (hatifi et al., 2014). http://www.azojete.com.ng mailto:samorosada@gmail.com arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):803-812. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 805 table 1: chemical compositions (wt. %) of the base metals and filler metal designation fe c si mn s p mo cr ni stainless steel 71.43 0.058 0.35 1.32 0.007 0.032 0.94 18.52 8.28 mild steel 99.31 0.2 0.14 0.4 0.05 0.04 0.24 0.21 filler material 0.03 0.6 1.8 0.15 23.4 13 2.1.2 welding process the electric arc welding process comprises of different types, amongst which are the gas tungsten arc, gas metal arc and the sheilded arc welding processes. the gas tungsten arc welding (gtaw) is performed by means of an electric arc generated by the welding machine along with a non-consumable tungsten electrode (sathish et al., 2012). the gas metal arc welding (gmaw) process on the other hand makes use of an arc along with a servo wire electrode which is automatically feed as it melts into the weld puddle. they both make use of an inert gas, or a gas mixture such as argon, helium, and mixtures of these gases. the shielded metal arc welding (smaw) process unlike the gas shielded welding processes mentioned above, makes use of a consumable electrode and does not require a shielding gas. however, its covered electrode serves as a source of protection from harmful oxidation. a display of the gtaw and gmaw welding machines is presented in figures 4a, and 4b respectively. figure 4a: gtawwelding machine figure 4b: mig/mag welding machine 2.2 method the workpiece interface (stainless steel and carbon steel) was bevelled, to conceal the nickel content effect associated with the austenitic stainless steel, and to allow for sufficient application of filler metal, before fitting the metals together to form a groove as shown in figure 1. figure 1: schematic representation of the welded joint the labels ά, represent the bevel angle, d; the gap, and t; the thickness. the experiment was performed using the three different welding techniques: gas metal arc welding (gmaw), the gas tungsten arc welding (gtaw), and shielded metal arc welding (smaw) with argon gas as the inert gas with a bevel angle of 90° and gap of 2 mm. the welded specimens from each of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:samorosada@gmail.com sada and enyi: parametric optimization and determination of a suitable welding process for stainless steel-mild steel dissimilar metals weld. azojete,16(4):803-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 806 the welding processes were subjected to visual inspection and tensile tests to ascertain the performance of the different welding processes. observations for surface defects made with the naked eye and x-ray flaw detector were obtained and tabulated as shown in table 2. prior to the experiment, the base materials were grouped into three (a, b, and c), for the three welding processes gtaw, gmaw, and smaw respectively. and with the application of the central composite design of the response surface methodology using the design expert software, thirty (30) experimental runs were generated. 2.2.1 tensile test to evaluate the transverse tensile properties (tensile strength and percentage elongation) of the stainless steel/mild steel dissimilar welds, the welded plates were machined to a tensile specimen shape according to astm standards and thereafter tested for tensile strength, and percentage elongation using a universal testing machine (utm) according to their groups (gtaw, gmaw, and smaw). 2.2.2 response surface methodology (rsm) the response surface methodology is employed on the concept of identifying the relationship between the response or dependent variable "y" and the relevant input or independent variables x1, x2,…,xk (hicks 1993). the response surface is expressed as shown in equation (1) on the assumption that the variables are continuous, controllable and measurable not ignoring a level of negligible error ε. y = f (x1, x2, x3...,xk ) + ε (1) with the response surface methodology (rsm), the experimental data was used in developing the empirical models for the experiment, establishing the independent and response variable relationship with the aid of the second order quadratic model given in equation (2). y = βₒ + i=1 βᵢxᵢ� + j=1 k βᵢᵢxᵢ2� + ij k βᵢⱼxᵢxⱼ�� + ε for i < j (2) the coefficient of the polynomial denoted by “β” is estimated using the least squares method. 2.2.2.1 analysis of variance anova the anova test is performed to establish the suitability of the model, with the following parameters r2 representing coefficient of determination, adjusted r2, the p value required to be < 0.05 identifies the significant model terms. 3. results and discussion for visual inspection and radiographic test, seven (7) of the welded samples from the different welding processes were observed for surface defects with the naked eye and an x-ray flaw detector and their results tabulated as shown in table 3. http://www.azojete.com.ng mailto:samorosada@gmail.com arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):803-812. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 807 table 2: visual inspection and x-ray radiographic test results. gtaw gmaw smaw samples visual inspection x-ray radiographic visual inspection x-ray radiographic visual inspection x-ray radiographic 1 no imperfection no imperfection no imperfection no imperfection incomplete penetration undercut porosity 2 blow hole spatter porosity no imperfection no imperfection incomplete penetration spatter lack of fusion 3 no imperfection no imperfection spatter incomplete penetration incomplete penetration spatter lack of fusion 4 no imperfection no imperfection incomplete penetration undercut porosity incomplete penetration undercut porosity 5 spatter incomplete penetration incomplete penetration undercut porosity incomplete penetration undercut porosity 6 no imperfection no imperfection incomplete penetration lack of fusion incomplete penetration lack of fusion 7 no imperfection no imperfection incomplete penetration undercut porosity incomplete penetration undercut porosity the results from the visual inspection and x-ray radiographic test shows that there was little or no defects observed on the gtaw welded plates compared to the other two processes. however, defects like lack of penetration, undercut at both the root and the face, a lack of sidewall fusion, blowhole, porosity, etc. were observed in the gmaw welds and higher in the shield metal arc welded plates. 3.1 tensile strength the transverse tensile properties (tensile strength and percentage elongation) of the stainless steel/mild steel dissimilar welded specimens were evaluated according to their groupings (gtaw, gmaw and smaw), and the results along with the average is presented in table 3. figure 2 shows the gtaw welded dissimilar metal joint before and after the tensile test. figure 2: mild steel/stainless steel dissimilar welded joint before and after tensile test file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:samorosada@gmail.com sada and enyi: parametric optimization and determination of a suitable welding process for stainless steel-mild steel dissimilar metals weld. azojete,16(4):803-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 808 table 3: expérimental data table 4 shows the results for the tensile test of the welded plates. it was observed that average tensile strengths and elongations were 485.5 n/mm2 and 30.6% for the gtaw welds, 483.2 n/mm2 and 29.1% for the gmaw welds, and 480.8 n/mm2 and 28.4% for the smaw welds. the results show that the weld performance of the gtaw process, performed better with a weld strength and elongation 0.5% and 5.2% respectively, compared with gmaw having 1.2% and 7.7% respectively compared to the smaw techniques. 3.2 optimization in developing the optimal equations in terms of actual factors for maximizing the responses, experimental data obtained as recorded in table 3, was employed. the results were further analyzed using the response surface methodology (rsm), and mathematical models of the responses as shown in equations 1 and 2 were obtained. exp no gtawwelded joints gmaw welded joints smaw welded joints tensile strength (mpa percentage elongation tensile strength (mpa) percentage elongation tensile strength (mpa) percentage elongation 1 494.0 29.9 496.5 28.4 490.2 27.6 2 496.3 28.3 494.6 26.8 490.4 26.0 3 496.4 25.8 495.6 24.3 491.0 23.5 4 495.9 36.0 494.6 34.5 490.2 33.7 5 496.3 32.8 495.2 31.3 490.7 30.5 6 496.2 31.0 495.1 29.5 490.6 28.7 7 496.8 33.5 494.2 32.0 490.5 31.2 8 489.9 29.5 489.0 28.5 484.4 27.3 9 485.9 33.5 484.8 32.0 480.3 31.2 10 483.4 27.6 481.1 26.1 477.2 25.3 11 462.3 33.6 460.3 32.1 466.3 31.3 12 490.0 28.9 488.2 27.4 484.2 26.6 13 480.3 33.0 481.3 31.5 475.8 30.7 14 495.0 35.0 478.2 33.5 481.6 32.7 15 468.7 33.9 467.5 32.4 473.1 31.6 16 469.6 29.9 468.7 28.4 469.2 27.6 17 460.3 30.0 459.1 28.5 464.7 27.7 18 486.3 31.3 485.4 29.8 480.8 29.0 19 494.6 30.1 493.3 28.6 488.9 27.8 20 496.1 29.0 495.2 27.5 490.6 26.7 21 472.3 29.7 473.3 28.2 467.8 27.4 22 488.1 30.4 480.1 28.9 479.1 28.1 23 477.8 29.2 475.4 27.7 473.6 26.9 24 490.0 29.0 472.9 27.5 476.5 26.7 25 485.0 29.3 485.5 27.8 480.5 27.0 26 475.7 31.5 475.8 30.0 470.7 29.2 27 492.3 30.0 491.1 28.5 486.7 27.7 28 482.1 33.0 481.2 31.5 479.5 30.7 29 486.3 28.0 485.5 26.5 480.9 25.7 30 480.2 27.0 478.2 25.5 478.2 24.7 ave 485.5 30.6 483.2 29.1 480.8 28.4 http://www.azojete.com.ng mailto:samorosada@gmail.com arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):803-812. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 809 tensile strength = +660.26227 − 3.24914 ∗ x 1 + 12.10708 ∗ x 2 + 1.23333 ∗ x 3 + 2.24479 ∗ x 4 + 0.018083 ∗ x 1 ∗ x 2 + 0.124375 x 1 ∗ x 3 + 0.225521 ∗ (x 1 ∗ x 4 − 0.419375 ∗ x 2 ∗ x 3 − 1.58125 ∗ x 2 ∗ x 4 − 1.67187 ∗ x 3 ∗ x 4 − 0.001745 ∗ x 1 2 − 0.057083 ∗ x 2 2 − 0.134896 ∗ x 3 2 + 4.98698 ∗ x 4 2 (1) percentage elongation = +159676 − 0.186620 ∗ x 1 − 4.77625 ∗ x 2 − 5.58333 ∗ x 3 + 0.760417 ∗ x 4 + 0.002542 ∗ x 1 ∗ x 2 + 0.008437 x 1 ∗ x 3 − 0.067188 ∗ (x 1 ∗ x 4 + 0.021875 ∗ x 2 ∗ x 3 + 0.928125 ∗ x 2 ∗ x 4 − 0.742188 ∗ x 3 ∗ x 4 + 0.000287 ∗ x 1 2 + 0.031833 ∗ x 2 2 + 0.125521 ∗ x 3 2 + 1.153646 ∗ x 4 2 (2) the variables x1, x2, x3, and x4 in the équations, represent the process parameters; weld current, arc voltage, filler rod diameter and gas flow rate respectively. the strength of the models was analyzed using analysis of variance (anova) test, the results as shown in figure 3, shows that the models are significant and that the tensile strength and elongation is greatly influence by the weld current. this mostly attributable to its influence on the bead shape, the depth of penetration, the deposition rate, and the rate at which electrode is melted (sada 2018). figure 3: anova of the responses the mathematical model obtained in equations 1 and 2, were further employed in carrying out the prediction of the responses. predicted values obtained of the responses were compared to that of the experimental values by performing a plot of the predicted response against the observed values for each of the responses as shown in figure 4a and 4b. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:samorosada@gmail.com sada and enyi: parametric optimization and determination of a suitable welding process for stainless steel-mild steel dissimilar metals weld. azojete,16(4):803-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 810 figure 4a: plots of predicted versus figure 4b: plots of predicted versus actual values of tensile strength actual values for percentage elongation the straight-line graph shows that the errors are uniformly distributed. an indication that there’s a significant correlation between the experimental and predicted response values (sada 2018). 3.3 numerical optimization to ascertain the desirability of the overall model, numerical optimization was performed using the design expert software. the responses were optimized and their corresponding optimum input process parameter values were determined. figure 5 shows the ramp results of the optimal response parameters. figure 5: ramp showing the optimal response parameters 4. conclusions comparative study of the different welding processes based on the tensile properties; tensile strength and percentage elongation, showed that the gtaw weld performed better with higher tensile strength and elongation while the shielded had the least output. the experiment not only confirms the gtaw welding process as the most suitable technique for the welding of stainless steel to mild steel dissimilar metals in comparison to the gas metal arc welding and shielded metal arc welding processes. it also confirms that stainless steel filler metal is an appropriate filler material for the joining of mild steel to stainless steel. further analysis of the gtaw weld process using the response surface methodology showed that the weld current is the most significant model term and the optimal tensile strength of 491.49n/mm2 and elongation of 32.31% can be obtained at a welding current of 200 amp, voltage 15 volt, gas flow rate 24 l/min and filter rod of 2.4mm. http://www.azojete.com.ng mailto:samorosada@gmail.com arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):803-812. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 811 5. acknowledgement the author would like to acknowledge the staffs and head of the department of welding and fabrication, petroleum training institute, effurun, delta state for their support with the equipment. reference bang, h., bang, h., song, h. and joo, s. 2013. joint properties of dissimilar al6061-t6 aluminum alloy/ti-6%al-4%v titanium alloy by gas tungsten arc welding assisted hybrid friction stir welding. materials and design, 51: 544-551. bhattacharya, a. and sanchit, s. 2016. dissimilar gtaw between aisi 304 and aisi 4340 steel. multi-response optimization by analytic hierarchy process. proceedings of the institution of mechanical engineers. part e; journal of processing mechanical engineering, 231(4): 824-835. chuaiphan, w., somrerk, c., a., niltawach, c. and sornil, b. 2013. dissimilar welding between aisi 304 stainless steel and aisi 1020 carbon steel pates. applied mechanics and materials, 268: 283-290. das, c., bhaduri, a., srinivasan, g., shankar, v. and mathew, s. 2009. selection of filler wire for and effect of auto tempering on the mechanical properties of dissimilar metal joint between 403 and 304l(n) stainless steels. journal of materials processing technology, 209 (3): 1428– 1435. dong, h., hu, w., duan, y., wang, x. and dong, c. 2012. dissimilar metal joining of aluminium alloy to galvanized steel with al-si, al-cu, al-si-cu and zn-al filler wires. journal of materials processing technology, 212(2): 458-464. hatifi, mm., firdaus, mh. and razlan, ay. 2014. modal analysis of dissimilar plate metal joining with different thicknesses using mig welding. international journal of automotive and mechanical engineering (ijame), 9: 1723-1733. kaewkuekool, s. and amornsin, b. 2008. a study of parameters affecting the mechanical properties of dissimilar welding between stainless steel (aisi 304) and low carbon steel. proceedings of the 1st wseas international conference on materials science (bucharest, romania, 2008): 105-109. kah, p., shrestha, m. and martikainen, j. 2014. trends in joining dissimilar metals by welding. applied mechanics and materials, 440: 269-276. kim, jk., hong, sg., kang, kb. and kang, cy. 2009. microstructure and high temperature properties of dissimilar weld between ferritic stainless steel and carbon steel. metals and materials international, 15: 843. kumar, a. and sundarrajan, s. 2009. optimization of pulsed tig welding process parameters on mechanical properties of aa5456 aluminum alloy weldments. materials and design, 30: 12881297. lin, sb., song, jl., yang, cl., fan, cl. and zhang, dw. 2010. brazability of dissimilar metals tungsten inert gas butt welding–brazing between aluminum alloy and stainless steel with al–cu filler metal. materials and design, 31: 2637-2642. martinsen, k., hu, sj. and carlson, be. 2015. joining of dissimilar materials. cirp annals manufacturing technology, 64(2): 679-699. monika, k., bala, mc., nanda, pk. and prahalada, kr. 2013. effect of heat input on the mechanical properties of mig welded dissimilar joints. international journal of engineering research and technology, 2: 1406. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:samorosada@gmail.com sada and enyi: parametric optimization and determination of a suitable welding process for stainless steel-mild steel dissimilar metals weld. azojete,16(4):803-812. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samorosada@gmail.com 812 mvola, b. and paul, k. 2017. effects of shielding gas control: welded joint properties in gmaw process optimization. international journal of advanced manufacturing technology, 88: 2369– 2387. sada, so. 2018. optimization of weld strength properties of tungsten inert gas mild steel welds using the response surface methodology. nigeria journal of technology, 37(2): 407-415. satyanarayana, v., madhusudhan, g. and mohandas, t. 2005. dissimilar metal friction welding of austenitic–ferritic stainless steels. journal of materials processing technology, 160: 128–137. sathish, r., naveen, b., nijanthan, p., aun vasanthan geethan, k. and rao, v. s. 2012. weldability and process parameters optimisation of dissimilar pipe joints using gtaw. international journal of engineering research and applications, 2(3): 2525-2530. tušek, j., kampuš, z. and suban, m. 2001. welding of tailored blanks of different materials. journal of materials processing technology, 119: 180-184 teker, t. and kursuon, t. 2011. weldability of aisi 430/aisi 1030 steel couples via the synergic controlled pulsed (gmaw-p) and manual gas metal arc (gmaw). materials and manufacturing processes, 26(7): 926-932. wang, j., lu, mx., zhang, l., chang, w., xu, ln. and hu, lh. 2012. effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy and duplex stainless steel. international journal of minerals, metallurgy and materials, 19(6): 518-524 http://www.azojete.com.ng mailto:samorosada@gmail.com arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):733-740 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 733 original research article an efficient technique for the reduction of packet loss in wireless sensor network k. k. nnamani*, a. d. usman and k. a. abubilal department of electronics and telecommunications engineering, ahmadu bello university, zaria, nigeria *corresponding author’s email address: keso2rhyme@yahoo.com 1.0 introduction a wireless sensor networks (wsns) possesses a lot of issues such as limited energy, heterogeneous traffic, finite bandwidth, finite memory capacity, finite processing time (swain and nanda, 2014) and congestion (rezaee and pasandideh, 2017). congestion usually occurs when the traffic load introduced into the network exceeds the network handling capacity at a particular time. congestion results in energy wastage, decrease in throughput, increase in collisions, retransmission and an increase in packet delay and packet loss (antoniou et al., 2013). congestion control and avoidance are the actions taken to manipulate the network traffic, to prevent congestion and eventually congestion collapse (antoniou et al., 2013). techniques to mitigate congestion essentially involves congestion detection, congestion notification and finally congestion control (narawade and kokelar, 2017). rate reduction (traffic control) and the establishment of a different route (resource control), are the two basic methods of controlling congestion (sergiou et al., 2014). traffic control: congestion is mitigated using this method, by reducing the amount of traffic load infused into the network (ghaffari, 2015). the different categories of traffic control techniques is shown in figure 1 (kafi et al., 2014). article information abstract this paper, presents an efficient technique for the reduction of packet losses in wireless sensor network (wsn), which occurs because of buffer overflow and subsequently congestion. a key design feature for wireless sensor network is to have less packet loss, as more packet loss degrades the quality of service (qos) of the transmitted information and retransmitting such, a packet can use up the energy of the nodes. regardless of a number of efforts made to alleviate this problem, networks still experiences packet losses because of congestion and topology change. a congestion avoidance algorithm, which is based on an active queue management technique, was proposed in this work. the new technique, called a refined adaptive random early detection (rared) technique was used to control the maximum packet drop probability to be within 0.01 and 0.5, which is equivalently between 1% and 50%, thereby reducing the rate of packet loss and increasing the throughput. simulation results obtained using network simulator 2, showed that the proposed algorithm attained a reduction in packet loss of 5.7% against the existing priority-based fairness rate control (pfrc) in wsn. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 3 december, 2019 revised 7 august, 2020 accepted 18 october, 2020. keywords: congestion packet loss refined adaptive random early detection priority-based fairness rate control. file:///c:/users/kc/appdata/roaming/microsoft/appdata/roaming/microsoft/appdata/roaming/microsoft/word/kc%20proposal%201.docx file:///c:/users/kc/appdata/roaming/microsoft/appdata/roaming/microsoft/appdata/roaming/microsoft/word/kc%20proposal%20%20wsn.docx file:///c:/users/kc/appdata/roaming/microsoft/appdata/roaming/microsoft/appdata/roaming/microsoft/word/proposal%20add%20up.docx file:///c:/users/kc/appdata/roaming/microsoft/appdata/roaming/microsoft/appdata/roaming/microsoft/word/proposal%20add%20up.docx http://www.azojete.com.ng nnamani et al.: an efficient technique for the reduction of packet loss in wireless sensor network. azojete,16(4):733-740. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 734 figure 1: traffic control categories (kafi et al.,2014) 2. review of related work brahma et al., (2012), presented traffic management in wsn: decoupling congestion control and fairness. the congestion control algorithm adaptively determines a fair transmission rate to each node that is highly efficient. however, a prioritized architecture was not considered, which would have improved the throughput of the algorithm. antoniou et al., (2013), presented congestion control in wsns built on the flocking behavior of birds. the underlining idea is to direct packets to form flock and move in the direction of the sink node as the avoid obstacles on their paths (dying nodes and congested areas) in a robust manner. however, the node is passively listening to the channel, increasing the energy consumption of the network. this will ultimately lead to packets loss, when some of the nodes run out of energy, as there will be fewer nodes available to mitigate congestion. jaiswal and yadav (2013), studied fuzzy based adaptive congestion control (fbacc) in wireless sensor networks. the author made use of fuzzy logic system (fls) for estimation of congestion and adapts to the changing traffic with low packet loss. congestion was detected and mitigated by considering buffer occupancy, traffic rate and participants as input to the fls. however, the use of fuzzy logic estimation involves difficult computations, which that needs a lot of processing energy. this causes energy loss and increased energy consumption. this eventually lead to loss of packets as there will be fewer number of number available for transmission of data. rezaee et al., (2013), implemented an optimized congestion management protocol for healthcare wireless sensor networks. a novel active queue management (aqm) technique is used to avoid congestion and to provide quality of service. however, congestion cannot be prevented for non-sensitive data. rezaee et al., (2014), implemented hoca: healthcare aware optimized congestion avoidance and control protocol for wireless sensor networks. the author implemented a data centric congestion control scheme using an aqm technique. there are four phases of operation of hoca, namely: request dissemination phase, event occurrence reporting phase, route establishment phase and data forwarding and rate adjustment stage. however, packets experience longer delays when they go through longer routes to the sink node. swain and nanda (2014), presented priority-based adaptive rate control for wireless sensor networks. a tree topology was used real time and non-real time traffic classes were considered and higher priority was assigned to the real time traffic. however, fairness in the distribution of the available bandwidth was not considered, which would have improved the throughput. narawade and kokelar (2016), investigated acsro: adaptive cuckoo search-based rate adjustment for optimized congestion avoidance and control in wireless sensor networks. congestion was initially avoided, by the adaptation of the packet drop probability using a virtual queue, where less important packets are dropped. however, there is an increased complexity and delay encountered in solving the multi-objective objective function. swain and nanda (2017) file:///c:/users/kc/appdata/roaming/microsoft/appdata/roaming/microsoft/appdata/roaming/microsoft/word/proposal%20add%20up.docx file:///c:/users/kc/appdata/roaming/microsoft/appdata/roaming/microsoft/appdata/roaming/microsoft/word/proposals.docx http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):733-740. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 735 studied priority-based fairness rate control in wireless sensor networks. the author presented a rate control technique that is concerned with the fair distribution of bandwidth, while considering the priority of the different traffic classes connected to various nodes. however, congestion cannot be detected in advance, which would have improved the quality of service of the algorithm. 3. improved algorithm: rared this work puts forward an efficient technique for reducing packet loss in wsn. to mitigate the issue of packet loss as a result of buffer overflow, which eventually leads to congestion. the developed technique, addressed the issue of packet loss by, detecting congestion in advance, when the congestion index exceeds a predefined threshold (maximum). this helps in reducing packet loss as a result of buffer overflow emanating from congestion. the equation used to denote the packet loss is given below (swain and nanda, 2017): trxin sink = i∈c(sink)trxout i� (1) the equation, used in denoting the congestion index ic , is given as follows (liu et al., 2013): ic = 0, pmax (qk(i)−mintℎ k ) maxtℎ k i −mintℎ k i 1, qk(i) ≤ mintℎ k i mintℎ k i < qk(i) < maxtℎ k i qk(i) ≥ maxtℎ k i (2) the new transmission rate from the sink node to the child node is given (swain and nanda, 2017): trxouti = trxouti + ∆trxsink lsink . pgl i pgl sink , if∆trxsink > 0 trxouti ∆trxsink . pgl i pgl sink if∆trxsink < 0 (3) equations (4) and (5) is used to keep the minimize the packet losses (tahiliani et al., 2011): α= 0.25 x qk(i)−target target x pmax (4) β = 10.17 x target−qek(i) target−minth k i (5) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nnamani et al.: an efficient technique for the reduction of packet loss in wireless sensor network. azojete,16(4):733-740. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 736 4.0 simulation environment network simulator 2.35 was used in the simulation of this work. network simulator 2.35 was used to compare the performance of the rared and the existing priority-based fairness rate control algorithm (pfrc). the simulation parameters used in this work are shown in table 1. furthermore; figure 3 shows the flowchart of the rared and the network simulator 2 code used to design the rared and pfrc respectively. table 1: simulation parameters used in this work (swain and nanda, 2017) parameter value/protocol simulator r ns-2 version 2.35 simulation area 1000m *1000m mac layer ieee 802.11 number of sensor nodes 11 data packet length 129 bytes ifq length 50 packets transmission range 281.84mw operating frequency 5 ghz traffic source cbr routing protocol destination sequenced distance vector β 0.1 simulation time 100s queue type rared and priority queueing http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):733-740. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 737 figure 3: flowchart of the developed rared algorithm (swain & nanda (2017) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nnamani et al.: an efficient technique for the reduction of packet loss in wireless sensor network. azojete,16(4):733-740. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 738 average service time at the sink node ################################################### $stime = (1-$val(l))*$val(stime) + $val(l)*$val(stime) maximum transmission rate of the parent node and child node ############################## $outtx_rate = $agv_servicetime_sinknode{$landa} $maxtx_rate = $outtx_rate * $globalpriority_sinknode{$contact_nodes} / $globalpriority_sinknode{$contact_nodes} * $val(qssl) / $val(qscnl) implementation of refined ared start ********************************************/ void redqueue::updatemaxp_refined_adaptive(double new_ave, double now) double part = 0.48*(edp_.th_max edp_.th_min); // aimd rule to keep target q~1/2(th_min+th_max) if ( new_ave < edp_.th_min + part && edv_.cur_max_p > edp_.bottom) { // we increase the average queue size, so decrease max_p edv_.cur_max_p = edv_.cur_max_p * (1.0 (0.17 * ((edp_.th_min + part) new_ave) / ((edp_.th_min + part) edp_.th_min))); edv_.lastset = now; double maxp = edv_.cur_max_p; figure 4: network simulator code for designing the rared and the pfrc (swain & nanda, 2017) 5. results and discussion the packet loss was calculated using equation 1. from the plot, it can be observed that the developed rared scheme displayed less amount of packet loss compared to the existing pfrc scheme. this was as a result of the rared algorithm that detects congestion before the overflows, thereby preventing reducing packet loss as a result of congestion. the packet loss is also reduced by using the rared algorithm, by ensuring that the average queue size is between the minimum and maximum thresholds respectively. equation (6) shows the mathematical expression for obtaining the percentage reduction in packet loss from the plot shown in figure 5. percentage improvement = rared−pfrc rared x 100 (6) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):733-740. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 739 100.000080.000060.000040.000020.00000.0000 0.0000 100.0000 200.0000 300.0000 400.0000 simulation time (sec) p a ck e t l o ss ( b p s) np1_rared_loss.tr np1_pfrc_loss.tr figure 5: plot of packet loss for the two protocols against simulation time figure 5 shows the result for the performance of pfrc and rared in terms of packet loss against simulation time. the loss of the network was tested against simulation time from 0 to 100seconds. equation 1 is used to generate figure 5. from the result, it can be observed that the rared experienced lower packet loss when compared to the existing pfrc. this is as a result of rared algorithm that detects congestion in advance before buffer overflow, thereby resulting in lower packet loss. the fluctuations as evident in the plot are as a result of the varying conditions of the network. table 2: packet loss against simulation time time(s) 0 20 40 60 80 100 average pfrc 0 390 395 398 380 400 327.2 rared 0 365 368 370 355 400 309.7 the data in table 2 were obtained through network simulator version 2.35. the values in table 2 is computed by using equation 6. from table 2, it can be observed that the packet loss of the rared showed a reduction of 5.7% when compared to pfrc. 6. conclusion from the discussed results, it can be seen that the developed rared technique successfully improved the performance of the existing priority-based fairness rate control algorithm. the developed rared algorithm outperformed the existing priority-based fairness rate control algorithm, in terms of packet loss. the developed rared algorithm achieved a reduction in packet loss of 5.7%. this reduction in packet loss was made possible by the use of rared technique, which functions proactively by detecting congestion in advance congestion before the buffer overflows. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng nnamani et al.: an efficient technique for the reduction of packet loss in wireless sensor network. azojete,16(4):733-740. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: keso2rhyme@yahoo.com 740 references antoniou, p., andreas, p., tim, b., andries, e. and loizos, m. 2013. congestion control in wireless sensor networks based on bird flocking behavior. computer networks, 57(5): 11671191. brahma, s., chatterjee, m., kwiat, k. and varshney, pk. 2012. traffic management in wireless sensor networks: decoupling congestion control and fairness.computer communications, 35(6):670-681. ghaffari, a. 2015. congestion control mechanisms in wireless sensor networks: a survey journal of network and computer applications, 52:101-115. kafi, ma., djenouri, d., ben-othman, j. and badache, n. 2014. congestion control protocols in wireless sensor networks: a survey. ieee communications surveys & tutorials, 16(3):13691390. liu, z., zhang,y and philip, cc. 2013. adaptive mechanism-based congestion control for networked systems. international journal of systems 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adaptive red gateways for tcp/ip networks, journal of network and computer applications, 35(2) :857-864 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):301-316 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 301 original research article influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric e. a. adu1*, t. pandiarajan2, w. farzana3 and k. a. k. abba4 1postharvest engineering research department, nigerian stored products research institute (nspri) kano, pmb 3032, kano state, nigeria. 2department of food and agricultural process engineering, agricultural engineering college and research institute, tamil nadu agricultural university, coimbatore, india. 3department of agricultural processing and food engineering, svcaet and rs indira gandhi agricultural university, raipur, india. 4postharvest engineering research department, nigerian stored products research institute (nspri) maiduguri, pmb 1494, borno state, nigeria *corresponding author’s email address: aduadeyemi@gmail.com 1.0 introduction drying is an important preservation process which reduces water activity through the decrease of water content to a level safe for avoiding potential deterioration and contamination during long storage periods (hosain et al., 2014). the process of moisture removal requires a large amount of energy considering that one of the characteristics of agricultural production is production in large quantity and for each kilogram of water vaporized 2,257 kj of energy is article information abstract drying is one of the most energy intensive unit operations in agricultural and food processing industry. energy costs represent a major fraction of cost of operation of a mechanical dryer, therefore, the more efficient a dryer uses its energy supply, the lesser its cost of operation and the better it impacts on profitability of drying process. a flatbed dryer of 25kg capacity was developed and fitted with air-to-air indirect mixing heat exchanger (heat recovery unit, hru) at the vent of the drying chamber. the dryer was tested to determine the impact of exhaust vent waste heat recovery on its energy efficiency and cost of operation. turmeric, an important spice crop was dried at three temperatures of 60°c, 65°c, and 70°c under two operating conditions; (i) without hru (c-i) and (ii) with hru (c-ii). the result show thermal efficiency, at c-i it was found to be 28%, 27% and 27% at 60°c, 65°c and 70°c respectively and for c-ii it was 42%, 42%, and 40% at 60°c, 65°c, and 70°c respectively. this indicates that the overall thermal efficiency was improved by 15% for c-ii at 65°c as compared to ci at 65°c. anova show there is significant different (p< 0.05) between c-ii and c-i as regards thermal efficiency. the result also showed that specific energy consumption was reduced for all drying temperatures levels of c-ii as compared to c-i and the result shows that testing condition c-ii, at 65°c has the lowest specific energy consumption of 1.79(kwh/kg) while c-i at 60°c has the highest value; 2.37 (kwh/kg), this showed significant different (p< 0.05).drying curves of turmeric were plotted and it was found that c-ii performed better in drying turmeric since the moisture lose was faster than in c-i and the drying time was lowered by 4hrs for c-ii at 65°c compared to c-i 65°c. the average return on investment (roi) of hru was calculated considering average of 260 working days or 130 batch drying operation per annum with one drying cycle per two working days and was found to be 0.61 and the payback period was 19 months. it was concluded that the developed flatbed dryer can be used to dry 25 kg of turmeric per batch in 25 hours drying time using operating condition c-ii, 65°c which showed better quality in terms of energy efficiency and drying rate. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 dec., 2020 revised 19 april, 2021 accepted 4 may, 2021 keywords: flatbed dryer energy efficiency turmeric heat exchanger aduadeyemi@gmail.com adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 302 required. cost of thermal energy is a major fraction of cost which is incurred in mechanical drying (thakur and gupta, 2006). therefore, the higher the thermal energy efficiency of a dryer the lesser will be its cost of operation. use of energy resources has an obvious impact on the environment. these reasons explain the need to investigate potential energy saving options that can have impact on both economic and environmental issues (timothy et al.,2011). dryers are one of the most important equipment in food processing industries. many dryers have been developed and used to dry agricultural products in order to improve their storage conditions. most of these dryers use either expensive source of energy such as electricity, hydrocarbons (coal, propane gas, and liquefied natural gas) (berinyuy, 2000) or a combination of solar energy and other forms of energy. energy consumption is of interest to dryer manufacturers, as it is a key index of its market value (kudra, 2004). low energy consumption is critical for dryer users who deal with commodity materials and inexpensive products as it affects running costs. factors affecting the energy requirements in drying includes, the produce moisture content (mc), the type and variety of produce, the drying air relative humidity (rh) and airflow rate; all affects the drying rate, and thus the energy requirements of the drying process, (aviara et al., 2004). therefore, it is relevant to specify these factors when quantifying the energy use and efficiency of a drying system the largest portion of waste thermal energy in most of the convectional drying processes appears to be in the exhaust stream (timothy et al., 2011). recovering and reusing energy to preheat inlet air is one way to increase energy efficiency of a dryer. one of the means of heat recovery from the exhaust air stream involves the use of heat exchangers. conventional dryers usually operate at 30-70% efficiency levels (jangam et al., 2010). hence, drying is an area that is desperate for energy efficient technology. 1.1 turmeric turmeric was considered for this drying study because of its share production volume and its economic importance to tamilnadu state of india as an export spice. turmeric is usually dried as a whole or in coarsely cut form to a hygienically safe moisture level (around 10%). in the tropical and subtropical regions, the plant material is commonly spread on the ground, and sometimes on raised platforms or racks and sundried for several days and this comes with inherent problem of contamination by dust particles, animal droppings, toxins from moulds, discolouration, and long drying time (subbulakshmi and naik, 2002). several mechanical dryers have been developed to accelerate the drying process, to improve the hygienic conditions and to maintain constant drying temperatures within 45oc and 60oc in order to minimize the loss of volatile oils and prevent discoloration (ute et al., 2007). though mechanical dryers, powered by electricity or fossil fuel, help in producing quality products in large scale, they are seldom adopted by smallscale entrepreneurs and farmers of most developing countries, due to heavy installation costs involved and large operating cost because of its being energy intensive process (senadeera et al., 2007). the objectives of this study were to determine and compare energy efficiency and performance characteristics of a dryer with and without sensible heat recovery from the exhaust stream of the drying chamber and to analyse the economics of the drying system. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 303 2. materials and methods a flatbed dryer with a raw product capacity of 25kg was outfitted with a heat recovery unit (hru) heat exchanger for this study. 2.1 drying chamber a double wall metal bin of size 1.15m 1.15m 0.52m was made using 18gauge m.s. sheet and angle irons of 25  25  3 mm size. the bin was covered with a hood 0.3m high and having a rectangular opening (0.36m  0.06m) at the top which the heat recovery unit fits into. the bin was built such that it could be dismantled easily for transportation. the drying chamber was insulated using polystyrene sheet with a thickness of 0.025m. a platform for tray arrangement was made 0.32m from the bottom and two doors each with dimension of 0.5m  0.2m were in-fitted. 2.2 design of heat recovery unit (hru) the heat recovery unit (figure 1) is an air-to-air indirect mixing corrugated plate heat exchanger type which is connected to the exhaust of the dryer on outlet flow channel and blower inlet in the inlet flow channel by a 152mm pvc pipe. it is a double wall metal box 0.52m  0.51m  0.18m (figure 2), made of 18gauge m.s sheet and 25mm polystyrene sheet used inbetween the walls have insulation. a grove of 0.3m  0.015m was made on both breadth sides of the wall into which corrugated aluminium sheet creates flow channel inside the metal box as inlet and outlet. figure 1: conceptual view of heat recovery unit figure 2: side x-ray view (dimensions are in m) each flow channel has a two aluminium sheet 0.005m with a gap of 0.015m between them. the angle of corrugation is 37 degree. one of the breadth sides was covered to create an outlet in which a 6inch pvc elbow can fix into. the heat exchanger was connected to the blower so that the blower sucks air into the heater via the heat exchanger. assumption were that no heat is lost to the environment that is, heat lost equals heat gain and the flow rate of both hot and cold stream is same; the following equations were used to calculate the quantity of heat transfer, and the heat transfer area required. properties of air (at atmospheric pressure) inlet temperature of cold stream, tc1 ( oc) outlet temperature of cold stream, tc2 ( oc) inlet temperature of hot stream, th1 ( oc) outlet temperature of hot stream, th2( oc) kinematic viscosity of air at exhaust vent, vh(m 2/s) kinematic viscosity of air at ambient, vc(m 2/s) thermal conductivity of air at exhaust, kh (w/(moc) thermal conductivity of air at ambient, kc(w/(moc) density of air at exhaust vent, h(kg/m3) density of air at ambient, c(kg/m3) velocity of hot stream, uh (m/s) velocity of cold stream, uc (m/s) specific heat capacity of air, cpa (kgoc) adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 304 thermal conductivity of al, ka (w/moc) according to osborne reynolds, for forced convection, there exist two types of flows: laminar flow (reynold number, nre< 2000) turbulent flow (reynold number, nre> 4000) nre between 2000 and 4000 indicates transition from laminar to turbulent flow that is transient flow. the formula used to calculate the convective heat transfer coefficient is dependent on the type of flow, turbulent or laminar (rajput, 2012). reynolds number, (1) and kinematic viscosity, (2) therefore, (3) where, d= characteristic length (m) = density of air (kg/m3) u= velocity of stream (m/s) µ= viscosity (mpa.s) according to rajput, (2012), the characteristic length, d(mm) for a rectangular duct can be calculated by equation (4) (4) l = height of the duct (mm) b = breadth of the duct (mm) in other to determine the value of convective heat transfer coefficient, h, nusselt number was used. nusselt number, nnu is the ratio of heat flow rate by convection process under a unit temperature gradient to the heat flow rate by conduction process under a unit temperature gradient through a stationary thickness of din meters. nnu =hd/k (5) nusselt number is also a function of reynolds number and prandtl number (npr). for transient flow, nusselt number is given by (singh and heldman, 2013). (6) where: (7) nre = reynolds number npr = prandtl number for turbulent flow over a plate the nusselt number from colburn analogy is given by (rajput, 2012). (8) prandtl number, npr is the ratio of kinematic viscosity (v) to thermal diffusivity () arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 305 npr = vcp/k (9) 1) calculating overall heat transfer coefficient, u (10) where u = over all heat transfer coefficient (wm-2oc) hc =convective heat transfer coefficient of cold stream (wm-2oc) ka =thermal conductivity of aluminium (w/moc) hh = convective heat transfer coefficient of hot stream (wm-2oc) 2) calculation heat transfer area, quantity of heat transfer, q is given as (11) tlm(cf) = log mean temperature difference for counter-flow heat exchanger (12) ta = difference between the hot inlet and cold outlet stream temperature tb = difference between the hot outlet and cold inlet stream temperature tlm for cross flow is calculated by incorporating correction factor (f) to the expression of log mean temperature difference of counter flow heat exchanger. (13) the correction factor was obtained from the calculation of two ratios p and r associated with the inlet and outlet temperatures of the two fluids using the standard graph (holman, 2002). if no heat is lost in the heat exchanger, then quantity of heat transfer (14) therefore, using equation (11), heat transfer area, a was calculated. 3) calculating the required insulation thickness the casing of the exchanger was fabricated using composite wall with three layers made up of, mild steel glass wool mild steel. using mild steel of 0.0012m thickness (xm), and t1 and t4 were taken as th1 and tc1 respectively. insulation thickness, (xi) was calculated by fourier’s law. (15) where: q = quantity of heat transferred (w/m2) xm= thickness of mild steel (m) xi = thickness of insulation material (m) t1= inlet temperature of hot stream (oc) t4 =inlet temperature of cold stream(oc) km= thermal conductivity of mild steel(w/moc) kg =thermal conductivity of insulation(w/moc) 2.3 dryer layout the dryer is an electric powered flatbed dryer with configuration including the dryer chamber, heating chamber, electric blower, heat recovery unit (hru) and control panel (figure 3). a centrifugal type air blower powered by a three phase 1hp electric motor was used. a supply shunt was made at the blower’s suck-in opening to vary the inlet air flow rate. the blower has adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 306 the capacity to move air flow rate up to 2.5m3/min. electric heaters was required to heat the air moved by the blower before the heated is moved to the plenum chamber. four coils, 1.5kw each were mounted concentrically inside a m.s. sheet (18gauge) cylinder of 0.285m diameter and 1.1m length to for the heating chamber. the cylinder was insulated by using asbestos rope and plaster of paris to reduce the heat loss due to radiation. the control panel consist of switches for both the blower and the heaters and a thermostat to regulate temperature. the dryer was fitted with hru as shown in figure 4 figure 3: conceptual front view of flat-bed dryer with hru figure 4:flat-bed dryer fitted with hru 2.4 raw material procurement and preparation the testing of the dryer was conducted using the pts-10 variety of turmeric (curcuma longa) as this variety is grown in large quantity in erode and other areas of tamilnadu. turmeric were procured directly from famer at erode and washed thoroughly in a turmeric washer using tap water at normal temperature to remove the adhering extraneous matter then it was boiled in a arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 307 turmeric steam boiler for 5min to achieve softening of the produce and afterwards it was dried in the developed dryer. 2.5 condition of operating the dryer in the process for determining the efficiency of the dryer, different operating conditions were used. table 1 shows the operation temperatures and inlet air velocity at which efficiency of the dryer was determined. table 1: description of operating conditions for drying runs air velocity (m/s) temp (°c) description parameters determined c-i (without hru) 1.5 60, 65, 70 exhaust air vented into the atmosphere heat utilization factor of turmeric overall thermal efficiency specific energy consumption drying characteristics of turmeric economy analysis of the dryer c-ii (with hru) 1.5 60, 65, 70 energy in exhaust air recovered using heat recovery unit. 2.6 performance evaluation experiments were conducted to evaluate the performance of the drier. first idle run test was conducted on the dryer with heat recovery unit (pre-heating), the heater was switch on with the thermostat set using optimum drying temperature of 650c (gursewak et al., 2010) and the blower was operated at the rated speed but the inlet chute of the blower was adjusted to create four selected air velocities of 1, 1.5, 2, 2.5m/s. data generated from the preliminary studies were used to determine the air velocity having the best heat recovery efficiency of the hru. the parameters measured and recorded includes the come up time, air flow rate and temperature into and out of the heat exchanger (cold and hot stream), and the external temperature of the drying chamber. drying runs were performed on the dryer by drying of steamed-boiled turmeric rhizomes according to the conditions of drying operations as presented in table 1. temperature and relative humidity of the drying chamber was measure using data logger (equinox® eq-171). the performance of the dryer was evaluated in terms of drying efficiency (d), heat utilization factor (huf), temperature transfer efficiency (tte) and overall thermal efficiency (th). these were estimated by the method adopted by sahay and singh (2001) as discussed below. 1) drying efficiency, drying efficiency is defined as the ratio of the energy utilized for heating the sample for moisture evaporation to the total consumed energy (vieira et al., 2007). sensible heat of drying air was considered as being the effective heat for drying; therefore, drying efficiency is mathematically defined as follows (16) td = dry bulb temperature of the heated air, oc te = dry bulb temp of the exhaust air,oc tdw = wet bulb temperature of the heated air, oc adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 308 the dry bulb temperature of the heated and exhaust air for each trial was measured using mercury-in-glass thermometer of 0-1500c range and equinox data logger. the wet bulb temperature of the exhaust air was determined from the psychrometric chart using dry bulb temperature and relative humidity. 2) heat utilization factor, huf heat utilization factor is defined as the ratio of heat utilized by the turmeric to heat supplied by the hot air (sahay and singh 2001). = (17) 3) overall thermal efficiency overall thermal efficiency (th) is the ratio of energy required to evaporate moisture and the energy supplied to the dryer and it can be calculated according to equation (18), (toneli, 2013). (18) mw=water evaporation flow (kgs-1), δh =vaporization enthalpy (kjkg-1), m = air mass flow (kgs-1), cpa= specific heat of air (kjkg-1°c-1), td and ta are the absolute temperature of the drying and ambient air respectively. 4) specific energy consumption according to ashok, (2014) another method to estimate the energy efficiency of a drying system is to calculate its specific energy consumption. it is the amount of energy used in removing one kg of moisture from a food material in kwh/kg 5) drying rate the duration of the drying process is the most important parameter to be considered in evaluating a dryer. it is estimated from the time when the dryer is loaded with fresh product until when the product dries to the required moisture level, usually given as hours or days. drying rate was calculated using equation (19) (19) k = drying rate, kg/h wl= amount of moisture evaporated, kg t = time, h 2.7 economic analysis drying operation as a commercial enterprise requires cost analysis of the process to prove its economic viability (krokida et al., 2004). the cost analysis that was conducted to determine if the expenses of installing and operating a waste heat recovery system is justified is the return on investment (roi) analysis (gene, 2002). the main aim of understanding roi of a particular process is to identify if the process generates profit or loss. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 309 return on investment analysis was carried out according to (raghavendra, 2010) and is given by. (20) where ceq = additional equipment cost s = annual savings and is given by, (21) where: tac = total annual cost cea = annual costs from electrical energy = ceti cet = savings from the energy reduced through shorter drying time. (22) ts = time saved due to shorter drying times (hr) ce = cost of kwh of electricity consumed per hour ti= annual operation time. (hr) total annual cost when the system is operated in c-i or c-ii is given by (raghavendra, 2010), (23) where: e = depreciation and is given by (raghavendra, 2010), (24) for c-ii, ceq= additional equipment cost = cost of hru + cost of air recirculation ducts cop = operation cost (electricity) (rupee/kwh) ir = interest rate l = life span of equipment. the cost analysis was calculated based on the drying time of the product and the total energy utilized in the drying process at different conditions. annual return on investment (roi) was calculated considering average of 10 working hours per day and 260 working days or 130 batch drying operation per annum with one drying cycle per two working days. the kwh cost of electricity was taken as indicated by tamil nādu electricity regulation commission (tnerc). a cost of 5.75 rupees per unit electricity was selected for this calculation. assuming the number of batches of drying operation in a year is 130, the cost of operation is shown on table 2 and the cost of additional equipment in indian rupee is shown in table 3 table 2: cost of operation (electricity) condition 65oc (c-i) 65oc(c-ii) drying time/batch (h) 24 20 batch per year 130 130 hrs per year 3120 2600 energy consumed per batch (kwh) 35.2 28 energy consumer per year (kwh) 4576 3640 electricity cost per year (rs) 26312 20930 adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 310 table 3: cost of addition equipment (hru) s/n material quantity price/unit (rs) cost (rs) 1 mild steel plate 2.1m2 560/m2 1176 2 aluminium sheet 1m2 460/m2 460 3 pvc pipe 2m 315/m2 630 4 pvc elbow 2 180 360 5 workmanship 5000 total 7626 1) return on investment ir = interest rate = 7% l = lifetime of equipment = 20 years therefore, e = [0.07(1+0.07)20] / [(1+0.07)20 -1] = 0.0944 for condition (c-ii), ceq = equipment cost = cost of heat recovery unit + cost of recycle ducts =rs 7,626 cost of operation, cop = cost of electricity used for the process total annual cost for c-ii, 65oc = (0.0944  7626) + 20930 = 21650 rupees annual savings s, due to energy reduced through shorter drying time and more effective heat utilization = 26312 21650 = 4662 rupees return over investment = s/ceq = 4662/7626 roi = 0.6114 this procedure was repeated for comparing c-i and c-ii for drying temperature of 60 and 70oc and roi calculated were 0.6207 and 0.5965. therefore, average value of roi is 0.61. 3. results and discussion drying runs at operating conditions of c-i and c-ii were conducted and observations are stated and discussed below. 3.1 effect of hru on drying efficiency hru was observed to increase drying efficiency of the dryer at all temperatures. the mean drying efficiency of the dryer was increased from 0.263 to 0.413 at 60oc, 0.240 to 0.423 at 65oc and 0.196 to 0.363 at 70oc as shown in table 4 and expressed in figure 5. it was also observed that there was decrease in drying efficiency at 70°c. as discussed by (sahay and singh, 2001), this may be due to the fact that there is no increase in moisture diffusion within the produce to correspond to the increase in heat energy available. the result showed significant different (p<0.05) between c-i and c-ii and the test data and anova for both c-i and c-ii is given in table 4 and table 5 respectively. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 311 figure 5: drying efficiency at different operating conditions table 4: mean tables of drying efficiency t1 t2 t3 c-i 0.2633 0.2400 0.1967 c-ii 0.4133 0.4233 0.3633 table 5: anova for effect on operating conditions on drying efficiency source df ss ms f prob tot 17 0.14640 0.0086 12.4009 trt 5 0.1380 0.0276 39.7632 0.452 ns err 12 0.00833 0.0006 1.0000 c 1 0.12500 0.1250 180.000 0.000 ** t 2 0.01223 0.0061 8.8080 0.102 ns ct 2 0.00083 0.0004 0.6000 0.625 ns err 12 0.00833 0.0006 1.0000 3.2 effect of hru on heat utilization factor hru was observed to significantly increased heat utilization factor of the dryer at all temperatures as shown in table 6. the huf of the dryer at all temperatures is shown in figure 6. sahay and singh, (2001) stated that the ability to increase the heat utilisation factor of a drying process implies that there will be increase in the percentage of the heat supplied utilized, thus, an improvement in the thermal efficiency of the dryer. the result showed significant different (p<0.05)between c-i and c-ii and the anova for both c-i and c-ii are show in table 7 d ry in g ef fi ci en cy temperature, 0c adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 312 figure 6: heat utilization factor at different operating conditions table 6: mean tables of heat utilization factor (huf) t1 t2 t3 c-i 0.3933 0.3500 0.2600 c-ii 0.6100 0.6300 0.5633 table 7: anova of effect of operating conditions on heat utilization factor (huf) source df ss ms f prob tot 17 0.372511 0.021912 14.8280 trt 5 0.354778 0.070956 48.0150 0.439 ns err 12 0.017733 0.001478 1.0000 c 1 0.320000 0.320000 216.544 0.000 ** t 2 0.028744 0.014372 9.7256 0.093 ns ct 2 0.006033 0.003017 2.0414 0.329 ns err 12 0.017733 0.001478 1.0000 3.3 effect of operating conditions on overall thermal efficiency hru was observed to increased thermal efficiency of the dryer at all temperatures (table 8) and by 15% at operating temperature of 65oc. operating temperature had no significant effect on thermal efficiency of the dryer. the overall thermal efficiency of the dryer at all temperatures was shown in figure 7. in an experiment conducted by (timothy, 2011), heat recovery ventilator was attached to a low-cost meat dehydrator and an increase in efficiency of 20% was achieved. the anova result given in (table 9) showed that there significant different (p<0.05) between treatments ci and c-ii. since the hru can be attached to any dyer with little or no modification, this means that thermal efficiency of commercially available dryers can be increased by at least 15% with investing in hru. h ea t u ti liz at io n f ac to r temperature, 0c arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 313 figure 7: overall thermal efficiencies at different operating conditions table 8: mean tables of thermal efficiency t1 t2 t3 c-i 28.0000 27.0000 26.9967 c-ii 42.0000 42.0033 40.0000 table 9: anova of effect of operating conditions on thermal efficiency source df ss ms f prob tot 17 986.7892 58.04642 7.3718 trt 5 892.3000 178.4600 22.6642 0.474 ns err 12 94.48913 7.874094 1.0000 c 1 882.2800 882.2800 112.0484 0.000 ** t 2 7.020033 3.510017 0.4458 0.692 ns ct 2 3.000011 1.500006 0.1905 0.840 ns err 12 94.48913 7.874094 1.0000 3.4 effect of operating conditions on specific energy consumption the specific energy consumption of the dryer at all temperatures decreased with hru. the specific energy consumption of the dryer at all temperatures was shown in figure 8. the test data for both c-i and c-ii is given in table 10. table 10: specific energy consumption at different operating conditions operating condition energy used (kwh) mass of water removed (kg) specific energy consumption (kwh/kg|) c-i, t1 without hru and at 60oc 35.2 14.8 2.38 c-i, t2 without hru and at 65oc 35.3 15.4 2.30 c-i, t3 without hru and at 70oc 32.3 14.8 2.18 c-ii, t1 with hru and at 60oc 29.7 15.3 1.94 c-ii, t2 with hru and at 65oc 27.0 15.1 1.79 c-ii, t3 with hru and at 70oc 27.0 14.9 1.80 th e rm al e ff ic ie n cy temperature, 0c adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 314 figure 8: specific energy consumption at different operating conditions 3.5 effect of operating condition on drying rate the drying rate of turmeric inside the dryer at the different operating condition c-i and c-ii is shown in the figure 9 and 10 respectively. temperature showed effect on drying rate, but no trend was observed with ‘with’ or ‘with-out’ hru on rate of drying as shown. drying was observed to occur mainly at falling rate period and also it was observed that samples in c-ii reached safe moisture range before samples in c-i at all temperature levels of t1, t2 and t3 that is 60oc, 65oc and 70oc respectively therefore drying time for samples in c-ii were shorter. figure 9: drying rate at c-i operating condition figure 10: drying rate at c-ii operating condition 3.6 cost analysis 1) return of investment the calculated return-on-investment for c-ii, at drying temperature of 65ocis 0.6114. the procedure used to calculate roi for c-ii, 65oc was repeated to calculate c-ii for drying temperature of 60oc and 70oc and roi calculated were 0.6207 and 0.5965 respectively. therefore average value of roi is 0.61. sp e ci fi c e n e rg y co n su m p ti o n ( kw h /k g) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):301-316. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 315 2) payback period the calculated payback period is approximately 19months, therefore it can be said that investing in the heat recovery unit with a lifespan of 30 to 50 years is a profitable investment.4. conclusion a flatbed dryer with a heat reclamation system was developed. evaluation of the dryer was carried out with ‘no-load’ test and drying runs of turmeric at conditions c-i and c-ii, indicating without and with heat-recovery-unit respectively at temperatures of 60oc, 65oc and 70oc.thermal efficiency of the dryer was determined, at c-i it was found to be 28, 27 and 27% at 60oc, 65oc and 70oc respectively and at c-ii it was 42, 42, and 40% for 60oc, 65oc, and 70oc respectively. effectiveness of using a hru to recover the waste heat from the exhaust stream of the dryer was studied and found that by using c-ii the overall thermal efficiency was increased at all the temperatures. 15% increase in thermal efficiency was achieved. specific energy consumption was reduced for all levels of c-ii as compared to c-i and the result shows that testing condition c-ii, 65oc has the lowest value of specific energy consumption of 1.79 while c-i, 60oc has the highest value; 2.37. drying curves of turmeric were plotted and found that c-ii performed better in drying turmeric since the moisture lose was faster than in c-i and the drying time was lower. it was concluded that the developed flatbed dryer can be used to dry 25 kg of turmeric per batch in 25 hours drying time and c-ii, 65oc showed better quality in terms of energy efficiency and drying rate. the return on investment for hru was found to be 0.61 and the payback period is 19 months. reference ashok, k., senapati, rps., lalit, mb. and suresh, p. 2014. consumption in convective microwave drying of ashwagandha (withania somnifera roots). journal of food processing and technology 5:362. doi:10.4172/2157-7110.1000362. aviara, na., ajibola, oo. and oni, sa. 2004. sorption equilibrium and thermodynamic characteristics of soya bean. biosystems engineering, 87(2): 179-190. doi:http://dx.doi.org/10.1016/j.biosystemseng.2003.11.006 berinyuy, je. 2000. a simple electric box dryer for maize and other commodities. science agronomiquies, 2(2): 89-94. gene, o. 2002. best practices guide: economic & financial evaluation of renewable energy projects. u.s. agency for international development office of energy, environment & technology, global bureau environment centre, washington dc, 20523: 1810. gursewak, s., sadhna, a. and satish, k. 2010. effect of mechanical drying air conditions on quality of turmeric powder. journal of food science and technology, 47(3): 347–350. doi: 10.1007/s13197-010-0057-6. holman, jo. 2002. heat transfer, 9th edition, london: mcgraw hill higher education hosain, d., abbas, ra., ali, a., mohsen, a., gholam, hn. and jalal, k. 2014. study of the drying kinetics of pepper. journal of the saudi society of agricultural sciences,13(2):130-138. jangam, sv., chung, ll. and mujumdar, as. 2010. drying of foods, vegetables and fruits, volume 1. macmillan publishers, singapore, pp. 147. krokida, mk. and bisharat, gi. 2004. heat recovery from dryer exhaust air. drying technology, 22(7):1661-1674. https://www.infona.pl/resource/bwmeta1.element.elsevier-8a480c3e-5294-3fea-afd5-d89cad8cdea5/tab/jcontent adu et al: influence of energy recovery system on the energy efficiency of a flat-bed dryer in the drying of turmeric. azojete, 17(3):301316. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 316 kudra, t. 2004. energy aspects in drying. drying technology, 2(5): 917932. doi:http://dx.doi.org/10.1081/drt-120038572 raghavendra, rk. 2010. improving the efficiency of low-cost dehydrator using ventilation waste heat recovery unit. m.s thesis submitted to oklahoma state university stillwater, oklahoma december 2010. rajput, rk. 2012. heat and mass transfer, revise edition print, eurasia publishing house (p) ltd, new delhi, india. pp. 347, 470. sahay, km. and singh, kk. 2001. unit operation of agricultural processing, sec edition, vikas publishing house pvt ltd, new delhi, india. pp141-142. senadeera, w. and senanayaka d. 2007. economic development through solar drying technologies. in daily news of sri-lanka, independent newspapers of sri-lanka. singh, rp. and heldman, dp. 2013. introduction to food engineering. 5th edition, elsevier publishing. san diego. subbulakshmi, g. and naik, m. 2002. nutritive value and technology of spices: current status and future perspectives. journal of food science & technology, 39: 319-344. thakur, ak. and gupta, ak. 2006. two stage drying of high moisture paddy with intervening rest period. energy conversion management, 47(18-19): 3069. timothy, jb., scott, rf. and raghavendra, rk. 2011. improvement of efficiency and environmental impact of a low-cost food dehydrator. the open food science journal, 5: 3741. toneli, jt., monteiro, lb., briso, maj. and moraes, jd. 2013. effect of the outlet air reuse on thermal efficiency of a pilot plant spray dryer with rotary atomizer. chemical engineering transaction, 32: 231-245 doi: 10.3303/cet1332041. ute, s., reinhold, c. and andreas, s. 2007. conventional and alternative processes for spice production a review. trends in food science & technology, 18: 260e268. doi:10.1016/j.tifs.2007.01.00. vieira, mg., estrella, l. and rocha, sc. 2007. energy efficiency and drying kinetics of recycled pulp. drying technology, 25(10): 1639-1648. http://dx.doi.org/10.1080/07373937071590806 arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):519-530 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 519 original research article design and construction of an agriculturalwasteshredding machine s. a. abdulkadir*, s. m. dodo, b.g. jahun, g. s. malgwi, and i. vanke department of agricultural and bioenvironmental engineering, adamawa state polytechnic yola, adamawa state, nigeria. *corresponding author’s email address: salihuabdu110@yahoo.com 1.0 introduction agricultural waste is defined as the residues from the growing and processing of raw agricultural products such as fruits, vegetables, meat, poultry, dairy products, and crops. they are the non-product outputs of production and processing of agricultural products that may contain material that can benefit man. the economic values are less than the cost of collection transportation, and processing for beneficial use. their composition will depend on the system and type of agricultural activities and they can be in the form of liquids, slurries, or solids (obi et al., 2016). the waste generated is dependent on the type of agricultural activities carried out. agriculture is considered as the major occupation in many parts of the world and producing a range of waste materials requiring a variety of treatment technologies and management practices. the major occupation of the nigerian population is dependent on agriculture at subsistence level with their holdings small and scattered. a large part of this population is faced with the problem of managing waste materials before and after harvest (adewumi and omoresho, 2002). considering the diverseness of crops cultivated in nigeria by farmers, after harvesting these crops the waste/residues are either burnt or thrown as waste without taking into consideration their nutritive value or lack of waste processing machines available for utilizing the waste. with the increase in the population, our aim is not only to stabilize agriculture production but also to increase it further in a sustainable manner. excessive use of agrochemicals like pesticides and fertilizers over the years may affect soil health and lead to declining crop yields and the quality of the products. hence, a natural balance needs to be maintained at all costs article information abstract waste generation has become a major concern to the government, environmental regulatory bodies, and the society, especially with the current population pressure as well as the economic and social factors in nigeria. this study was focused on design, construction, and performance evaluation of an agricultural waste-shredder using locally available materials. the selected materials used to fabricate the machine were metal sheet, angle iron bars, pulleys, belt, shaft, and prime mover. the shredder has the feeding unit, the shredding unit, power transmission unit and the machine frame. the performance of the machine evaluated with beans stalk, the performance indices investigated were shredding efficiency and throughput capacity. response surface methodology (rsm) was used to maximize the efficiency of the machine at operational speeds of 360rpm, 650rpm, and 975rpm with sieve apertures of 20mm, 30mm, and 40mm respectively. maximum shredding efficiency of 93% was obtained when the shred aperture was 20mm at shredding speed of 975rpm. the maximum throughput capacity was 6.10kg kg/m at speed 975rpm and a minimum value of 5.14kg/m at 325rpm respectively. a quadratic model for shredding efficiency explained 94.78% of the variation in shredding efficiency. r2 (pred) of 70.42% suggests that the model is fit. the machine is easy to use and with a low cost of production to small and medium scale entrepreneurs in agriculture. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 march, 2019 revised 11 may, 2020 accepted 20 may, 2020 keywords: agricultural waste management shredding machine efficiency throughput capacity shredding speed mailto:salihuabdu110@yahoo.com http://www.azojete.com.ng abdulkadir et al.: design and construction of an agricultural waste-shredding machine. azojete,16(3):519-530. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 520 for the existence of life and property. the obvious choice would be judicious use of agrochemicals and more and more use of naturally occurring materials in farming systems. hence, the shredder machine is used for shredding. the use of a shredding machine is simply converting macro agriculture waste and food waste into small easily decomposable forms, which can be used as organic manure. the small size of waste will decompose faster than the large or macro size waste. this decomposed waste can be used by the crops and can leads to improvement in soil nutrients and increase the growth and quality of the crops and also improve the soil chemical properties such as supply and retention of soil nutrients, and promotes chemical reactions. agricultural waste is comprised of animal waste (manure, animal carcasses), food processing waste (only 20% of maize is canned and 80% is waste), crop waste (corn stalks, sugarcane bagasse, drops and culls from fruits and vegetables, pruning) and hazardous and toxic agricultural waste (pesticides, insecticides, and herbicides, etc.) (vitali et al., 2013). expanding agricultural production has naturally resulted in increased quantities of livestock waste, agricultural crop residues, and agro-industrial by-products. there is likely to be a significant increase in agricultural wastes globally if developing countries continue to intensify farming systems. it was estimated that about 998 million tons of agricultural waste are produced yearly (agamuthu, 2009). organic wastes can amount up to 80 percent of the total solid wastes generated in any farm (brown and root, 1997). the use of multipurpose agricultural solid waste shredder is believed to be an efficient answer for converting the agricultural production waste materials into valuable material for important use like raw materials and can serve as manure for soil preservation. no matter the size, shape, or color of food processing waste ranging from corn stalks, sugarcane bagasse, drops and culls from fruits and vegetables, and crop pruning size, that are available. the use of a high multipurpose shredder holds the ability to transform every part of the waste into a useful product as the machine can be used again after the appropriate processes of manufacturing, making the processed waste an extremely useful product. the objective of this study is to develop an agricultural multipurpose waste-shredding machine to utilize wastes for some economic benefits, this machine will utilize all kinds of agricultural wastes after shredding, and the machine will be economical and practicable. the machine will also reduce the time consuming during the work of chopping or thrashing the crop residues by hand and make availability of the machine at a low cost to make it affordable to the farmers. 2.0 materials and methods 2.1 materials all the materials for the fabrication of waste-shredding machine were sourced locally. materials used in the construction of the shredding machine incudes: the materials used in the fabrication and performance evaluation of the shredding machine include sheet metal, angle iron, prime mover shaft, transmission belt, pullies, shredding fingers, bearings, hitches, bolts and nuts. instrumentations used were stopwatch, and digital weighing balance. 2.2 methods the shredding machine was designed and fabricated at the department of agricultural and bioengineering engineering, adamawa state polytechnic, yola, nigeria. the machine consists of following major component: cutting blade, machine frame, sieves, hopper, waste collector, cover, and belt cover. the procedures for the design, fabrication and performance evaluation including cost implication of the waste shredding machine are as follows. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 519-530. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 521 2.2.1 design considerations mechanical factors, operational factors, and economic factors were considered for the successful design, fabrication, and operation of the machine. the mechanical factors considered were strength, rigidity, and simplicity of materials for the construction of the machine. accommodate the average speed of operation to minimize noise and vibration. hopper should accommodate different sizes of agricultural waste available locally. shredding plate is resistant to rusting for animal feed hygiene purposes. shredder holes will be such as to produce the desired size of shredded waste material. waste collector to collect shredded waste the operational factors considered were uniformity of shreds produced. high operational speed to achieve fast processing of the materials required to shred. easy to operate and maintain. high level of operational safety. the economic factors considered in the development of the agricultural waste shredder were availability of local raw material for fabrication. low cost of fabrication. low cost maintenance. 2.2.2 design calculations 2.2.1.1 determination of power requirement the power requirement of the sheller was considered one of the important factors considered in the design of the operation of the machine, according to (shigley, 1986 ). p = f × v (1) where: p = power (nms−1) f = force of shredding n v = velocity (ms−1) the force required for shredding is given as; f = mω2r f = force required to shred waste material m = mass of shredding blades, ω = angular velocity of shaft. ω = 2πn 60 , n speed of shredding (rev/m). the power delivered by the shaft is given by p = fωr (2) 2.2.1.2 determination of bolt for the frame the shear stress was put into consideration to determine the bolts used on the machine. according to (shigley and mischke, 2005). se = fmax πd2 4 (3) where: se = allowable endurance stress of mild steel = 107.969 × 103kn/m fmax = fmin + weight of cassava filling the hopper fmin = force due to total weight of the machine without load = 0.8kn file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulkadir et al.: design and construction of an agricultural waste-shredding machine. azojete,16(3):519-530. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 522 d = 4fmax πse (4) d = 0.003m = 3mm . 4mm bolts were selected for fastening the machine to the frames. after the design, fabrication of the shredding machine was carried out, with strict adherence to design values. 2.2.1.2 determination of v – belt length to determine the length of the belt used to operate the shredder was based on (khurmi and gupta, 2006), the expression for the v-belt length is given as; l = π 2 ds + dm + 2c + (ds+dm)2 4c (5) l = belt length c = center length between two pulleys ds = pitch diameter of the first pulley dm = pitch diameter of the first pulley the length of the v-belt pulley was determined to be 190cm 2.2.1.3 determination of volume of shredder hopper the volume of the shredder hopper , vsh , through which the waste materials to be shredded are fed is obtained from equation the volume of the shortened rectangular based pyramid is given as vsh = 1 3 (bh − bh) (6) where: b = the area of the rectangular base for the big pyramid, h = the height of the big pyramid, b = the area of the rectangular base for the small truncated pyramid, and h = the height of the small truncated pyramid. parallelogram prism is given as; v = bh (7) where: b is the area of the base shape 2.2.1.4 determination of diameter and speed of shaft to estimate the diameter of the shafts used in the machine, the maximum shear stress theory was applied. this theory according to khurmi and gupta, (2005) is appropriate for shafts subjected to combined bending and twisting moments, as it is the case with the shafts in this machine. it is also suitable for mild steel shafts, (which are ductile materials). the shafts used in the machine are made of mild tough steel. the diameter of the shaft was determined using the maximum stress theory (hall et al., 1980). d = 16 πs kbmb 2 + ktmt 2 1 3 (8) where: mb = maximum bending moment on shaft (1000nmm mt= maximum torsional moment on shaft (16540 nmm) s = allowable shear stress for steel (310 n/mm2) kt,kb= fatigue and shock factor for torsion and bending moments (1.5 and 1.0). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 519-530. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 523 one main shaft and three mini shafts attached to the main shafts are involved in the development of the machine. the shafts diameters obtained for the shaft based on the equation above are 26 mm for smaller attached shaft, 75 mm for the main driven shaft. the shredder shaft is rotating within the shredder chamber and it is equipped with knife-edged. these knifeedge sharp edges welded on the shaft allow shredding of the waste materials to be possible as it rotates in the chamber. the shredder shaft speed, vss , is obtained from equation (2) as in (khurmi and gupta, 2005) vss = ωssrss = 2πnss 60 rss (9) where: ωss =the angular velocity of the shredder shaft pulley. rss = the radius of the shredder shaft pulley. nss = the speed in revolutions per minute of the shredder shaft pulley. 2.2.1.4 factor of safety the overall integrity of the machine design can be established by ensuring that the factor of safety, which can be obtained using equation (9) and, is greater than 1. this will guarantee that the machine will not collapse structurally under the action of loads. fos is the factor of safety, ys is the yield strength of the selected material for the machine frame, andws is the working stress or maximum stress? fos = ys ws (10) 2.2.1.5 prime mover power requirement power = force ×velocity power = force × screw circumference × rpm w = p × πdn/60 (11) 2.2.1.4 shear stress on farme to determine the thickness of the triangular bars of know width frame. the equation is given by; sr = se fs − se syp × sm (12) sr=superimposed alternative stress sr = (maximum stress − minimum stress) 2 minimum stress = weight of the machine components on the frame maximum stress = all the weights above the plus weight of waste material filling the hopper and force exerted by the electric motor on the machine members. 2.3 description of the machine the agricultural waste shredder consists of the following major component: cutting blade, machine frame, sieves, hopper, waste collector, cover, and belt cover as illustrated in figure 1a and figure 1b.. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulkadir et al.: design and construction of an agricultural waste-shredding machine. azojete,16(3):519-530. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 524 figure 1a: waste shredding machine assembly figure 1b: agricultural waste shredder 1. electric motor 2. shredder hopper 3. belt cover 4. shredder waste collector. 2.3.1 shaft assembly three 26mm diameters shaft were turned to size down to 25mm. a 440mm long was used to attach the shafts. similarly, another shaft of 600mm long and 76mm diameter was also turned to 75mm. two equilateral triangular plates of sides 130mm were cut with 2mm thickness. the cutting blades were welded on the cutting shaft at a spacing of 40mm apart. finally, the driven shaft was positioned at the center of the triangular plates and welded together. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 519-530. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 525 2.3.2 machine frame the frame was made up of mild steel of rectangular cross-section. the main function of the frame is to carry the weight of the machine components which include shafts, electric motor, the pulleys, and its cover the hopper, shredding chamber agricultural waste, sieve, and the collector assembly. to determine the thickness of the frame the procedure of (black and adams, 2000) from equation (9) a 3mm thick steel plate with 50mm width was selected to avoid any underestimation. 70mm × 70mm was cut to various sizes. the pieces were welded together to form a rectangular of the machine. angle iron of 50mm × 50mm was cut to sizes and welded underneath the framework as a brace to increase the strength of the frame. the frameset for the electric motor was formed and holes drilled. 2.3.3 shredder sieve the sieve is be located underneath the cutting blade assembly housing. it allows small pieces of shredded waste materials of less than 20mm in length to pass through the holes. the endplates will be welded to the concave metal sheet, which has a series of q20 holes. the taps drilled to provide holes for bolting the sieve unto the frame of the machine. 2.3.4 hopper and shredding chamber waste shredder hopper was a combination of parallelogram prism and a shortened rectangular based pyramid, which was placed on the chamber that houses the shredder shafts. the hopper is part of the machine with an opening at the top for feeding the waste materials for shredding. the volume of the shortened rectangular based pyramid hopper was determined using equation (4), while. the parallelogram prism volume was determined using equation (5). the materials slide down the hopper and fall unto the cutting blade assembly. hopper was constructed using 1mm mild steel sheet. taps were provided, at the bottom of the hopper with holes to allow it to be bolted with 20mm diameter bolts and nuts onto the machine frame. 2.3.5 shredded material collector the collector is located at the bottom of the sieve to allow small pieces of shredded materials into it and to direct the shredded materials into the container for collection through the outlet. the collector was made from a 1mm thick mild steel sheet; it is also made with holes drilled in them for bolting it to the frame of the shredder. 2.3.6 top cover the top cover of the machine was constructed to cover the remaining top part of the framework of the machine. this part is constructed with a 1mm mild steel sheet by surface development. it is to be bolted onto the top part of the framework. 2.3.7 belt cover the belt cover is a guard against accidental contact with the operator due to the rotating vee belt when the machine is in operation. it was constructed using 1mm mild steel sheet. the circular part of the small end of the belt cover was a bit larger than the electric motor pulley to allow the pulley to run freely without contact with it, likewise, the bigger end of the belt cover is a bit larger than the pulley of the cutting belt assembly. the various part of these components was joined together by welding’s. bearings selection readily available bearings were used since they have standard and cannot be constructed in the workshop. they were selected based on the required inner and outer diameter. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulkadir et al.: design and construction of an agricultural waste-shredding machine. azojete,16(3):519-530. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 526 2.4 cost of production a total cost of fifty-nine thousand seven hundred naira (₦59,700.00) was spent in the construction of the shredder. the breakdown is as follows: s/n components qty. unit cost (₦) total cost (₦) 1 3mm mild steel sheet 1 11,000 11,000 2 1 mm mild steel sheet 1 9,000 9,000 3 electric motor 1 18,500 11,500 4 electric motor speed regulator 1 3,000 5,000 5 pulleys 2 1,000 2,000 6 3mm (70mm x70mm) angle iron 2 1,800 3,600 7 electrodes 2 1,800 3,600 8 paint 1 1,500 1,500 9 hinges 4 100 400 10 bearing 2 1,500 3,000 11 belts 2 400 800 12 bolt and nuts 20 30 600 13 washers 20 10 200 14 cutting disc 5 700 3,500 15 grease 1 800 800 16 binding wire 1 1,200 1,200 17 transportation 1 2,000 2,000 18 labour 1 5,000 5,000 grand total ₦59,700 2.5 performance evaluation the designed and fabricated waste shredding machine was tested to evaluate its performance on the basis of shredding efficiency and throughput capacity. after construction and assembling the machine, the efficiency was further tested using the response surface methodology design of experiments (central composite design). minitab software version 19 was used to conduct the analysis. the experiment conducted for dry beanstalks and leaves. this test conducted at three speeds of 360rpm, 650rpm, and 975rpm with three (3) sieve apertures of 20mm, 30mm, and 40mm with total number of thirteen (13) runs. the coding for high, centre and low as -1, 0, and +1 to represent respectively. the coded and natural variables are illustrated in table 2. table 2: independent variables and natural levels used for central composite design variables low centre high code -1 0 +1 x1 325 650 975 x2 20 30 40 x1 = shredding speed in rpm, x2 = shredding sieve aperture in mm. 3.5.1. shredding efficiency to determine the shredding efficiency the total weight of waste materials to be shredded was measured and recorded before shredding in the machine, similarly, the weight of both shredded and unshredded materials were measure and recorded. all measurement were made in kilogramme (kg). the shredding efficiency of the machine at three different speeds of shredding was determined as follows; se = wc wt × 100 % (13) wc = wt −wu (kg), (14) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 519-530. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 527 where, se = shredding efficiency % wc =weight of shredded materials (kg), and wt = total weight of the waste (kg). wu = total weight of shredded materials (kg). 3.5.2. throughput capacity the throughput capacity of the shredding machine was tested at the three different speeds of operation namely; 325rpm, 650rpm, and 975rpm respectively. the throughput capacity was calculated using the following equation tpc = wt t (15) where, wt = total weight of the shredded waste. (kg) t = time of operation(s) 3.0. result and discussion the throughput capacity of the machine was tested and the results illustrated in table 1. the result shows that the higher the speed of operation the higher the throughput capacity. at the speed of 975rpm, the machine was able to shred 6.10kg of agricultural materials, while at the lowest speed of 325rpm the total shredded material was 5.12kg, this agrees with the result of (ayo et al., 2014). table 1: throughput capacity of shredding operation speed (rpm) throughput capacity (kg/min) 325 5.12 650 5.69 975 6.1 table 3: design table (randomized) before response surface analysis run order x1 coded x2 coded x1 (rpm) x2 (mm) wc (kg) wt (kg) σ (%) pfits (%) 9 0 0 650 30 8.231 10 82 82.1724 4 1 1 975 40 7.993 10 80 80.4655 13 0 0 650 30 8.228 10 82 82.1724 2 1 -1 975 20 9.289 10 93 91.7989 11 0 0 650 30 8.201 10 82 82.1724 3 -1 1 325 40 7.794 10 78 79.1322 10 0 0 650 30 8.222 10 82 82.1724 12 0 0 650 30 8.311 10 83 82.1724 6 1 0 975 30 8.511 10 85 85.7356 7 0 -1 650 20 8.612 10 86 87.7356 5 -1 0 325 30 8.416 10 84 83.4023 8 0 1 650 40 7.901 10 79 77.4023 1 -1 -1 325 20 8.903 10 89 88.4655 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulkadir et al.: design and construction of an agricultural waste-shredding machine. azojete,16(3):519-530. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 528 table 4: regression coded coefficients the results of the model explains 94.78% of the variation in shredding efficiency. however, the r2 (pred) of 70.42% suggests that the model is fit. if additional models are fitted with different predictors, use the adjusted r2 values and the predicted r2 values to compare how well the models fit the data as shown in table 5.the developed coded responses functions of the machine investigated are as follows efficiency % = 82.172 + 1.167x1 − 5.167x2 + 2.397x1 2 + 0.397x2 2 − 0.500x1x2 (16) table 5: model summary s r-sq r-sq (adj) r-sq (pred) 1.22441 94.78% 91.06% 70.42% the regression effects of shredding speed and shredding aperture for both the linear, square, and interaction on efficiency. the result indicated that the speed with which the shredder was operated did not have any significant effect on the shredding efficiency with a p-value of 0.052. this concludes that there is no statistically significant association between the efficiency and the speed of operating the shredder. although the aperture diameter was significantly affecting the efficiency at 5% level of significance (p = 0.000). the square model for speed indicated a significant effect, which also concludes that there is a statistically significant association between the efficiency and the square of the speed, while the square of shredding aperture did not show any significant effect on the efficiency. the two-way interaction between the speed and aperture did not show any significant effect on the shredding efficiency as shown in table 6. table 6. : response surface regression efficiency versus speed and aperture of shredding machine source df adj ss adj ms f-value p-value model 5 190.737 38.147 25.45 0.000 linear 2 168.333 84.167 56.14 0.000 x1 1 8.167 8.167 5.45 0.052 x2 1 160.167 160.167 106.84 0.000 square 2 21.403 10.702 7.14 0.020 x1*x1 1 15.863 15.863 10.58 0.014 x2*x2 1 0.434 0.434 0.29 0.607 2-way interaction 1 1.000 1.000 0.67 0.441 x1*x2 1 1.000 1.000 0.67 0.441 error 7 10.494 1.499 lack-of-fit 3 9.694 3.231 16.16 0.011 pure error 4 0.800 0.200 total 12 201.231 the pareto plot shows the effects of speed and aperture in figure 2. this shows the visual identification of the important effects and compares the relative magnitude of the various term coef se coef t-value p-value vif constant 82.172 0.508 161.63 0.000 x1 1.167 0.500 2.33 0.052 1.00 x2 -5.167 0.500 -10.34 0.000 1.00 x1*x1 2.397 0.737 3.25 0.014 1.17 x2*x2 0.397 0.737 0.54 0.607 1.17 x1*x2 -0.500 0.612 -0.82 0.441 1.00 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 519-530. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 529 effects. in addition, it shows that the largest effect is shredding aperture (b) because it extends the farthest while, aperture*aperture (bb) is the smallest because it extends the least. the regression coefficient as illustrated in table 4 shows that the coefficient for shredding speed is not significant (1.167, p=0.052), this conclusion that all level means for speed are equal. the coefficient for a shredding aperture was significant (-5.167, p=0.000), and concludes that not all level means for speed is equal. similarly, the coefficient for squared aperture has shown no significant effect (0.397, p=0.607). this concludes that the relationship between the aperture and the efficiency does not follow a curved line, while the coefficient for a squared speed was having a significant effect on efficiency (2.397, p=0.014), this concludes that the relationship between the aperture and the efficiency follow a curved line. figure 2: pareto chart for the effect of speed and aperture on the efficiency of shredding machine however, the coefficient for interaction for shredding speed and aperture was not significant (-0.500, p = 0.441), the relationship between speed and the efficiency does not depend on the other all the factors in the term. 4.0 conclusion an agricultural waste shredding machine was developed using locally available materials. the machine performed satisfactorily with better efficiency during the test run. results from the test showed that the size of the shredding aperture of the machine significantly affected the shredding efficiency of the machine. the shredding efficiency of the machine decreased with increasing shredding aperture but increased with shredding speed. maximum shredding efficiency of 93% was achieved when the shred aperture was 20mm and the shredding speed was 975rpm. the throughput capacity of the machine increased with the speed of shredding with a maximum value of 6.10kg kg/m at 975rpm and a minimum value of 5.14kg/m at 325rpm. references adewumi, m. and omoresho, o. 2002. an analysis of production objectives of small-scale rural farming households in kwara state, nigeria. journal of rural development, 25(2): 201-211. agamuthu, p. 2000. challenges and opportunities in agro-waste management: an asian perspective. paper presented at the inaugural meeting of first regional 3r forum in asia. tokyo, japan. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulkadir et al.: design and construction of an agricultural waste-shredding machine. azojete,16(3):519-530. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 530 ayo, aw., olukunle, oj. and adelabu, dj. 2017. development of a waste plastic shredding machine. international journal of waste resourses, 7(2):1000281. black, ph., and adams, oe. 2000. machine design (6th ed.). tokyo: mcgraw-hill kogakusha ltd. brown & root environmental consultancy group 1997. environmental review of national solid waste management plan. interim report submitted to the government of mauritius. hall, ss., mitchell, ld. and george, e. 1980. mechanical design: mc.graw-hill. new york united states. khurmi, r. and gupta, j. 2005. a textbook of machine design. india: eurasia publishing house. khurmi, r., and gupta, j. 2006. theory of machine revised edition. new delhi, india: s. chand. obi, f., ugwuishiwu, b. and nwakaire, j. 2016. agricultural waste concept, generation, utilization, and management. nigerian journal of technology, 35(4): 957–964. shigley, j. e. (1986 ). mechanical engineering design. s.i (metric) ed. new york, usa: mcgrawhill, shigley, je., and mischke, cr. 2005. mechanical engineering design: in si units (6th ed.). new delhi: mcgraw-hill. vitali, f., parmigiani, s., vaccari, m. and collivignarelli, c. 2013. agricultural waste as household fuel: techno-economic assessment of a new rice-husk cookstove for developing countries. waste management, 33(12): 2762-2770. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):61-70 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 61 original research article effect of compaction pressure and biomass type (rice husk and sawdust) on some physical and combustion properties of briquettes m. aliyu1*, i. s. mohammed1, h. a. lawal1, s. m. dauda1, a. a. balami1, m. usman1, l. abdullahi2, m. abubakar2 and b. ndagi2 1department of agricultural and bioresources engineering, federal university of technology, p. m. b. 65, minna, niger state, nigeria 2national cereals research institute badeggi, p. m. b. 8, bida, niger state, nigeria. *corresponding author’s email address: aliyu.mohd@futminna.edu.ng 1.0 introduction energy is one of the necessities for human existence (olajedi and oyetunji, 2013). currently, fossil fuel is the major source of energy from which the commonly used fuel products like kerosene and cooking gas are obtained (aliyu et al., 2020; mohammed et al., 2020). however, the nonrenewability and the negative impact of fossil fuel on the environment such as the greenhouse gas emission has become a global concern (lang et al., 2019). also, in recent years, nigeria and other countries in the sub-sahara have faced the problem of forest degradation due to increased fuelwood consumption among other causes (leach and mearns, 2013; yahaya et al., 2020). out of the total energy demand in nigeria, fuel-wood use account for about 37% (oyedepo, 2014). in ngeria, large quantities of agricultural residues such as the rice husk (rh) and sawdust (sd) are mostly dump in waste sites unutilised and recycling of these agricultural wastes are rarely practiced which has led to environmental problems such as pollution (thliza et al., 2020). figures 1a and 1b shows a typical dump sites for sd and rh in niger state, nigeria. article information abstract in this study, a simple manually operated briquetting machine suitable for use in rural community with no access to electricity supply was fabricated. a three (3) tone hydraulic jack and a pressure gauge were installed to allow for pressure variation. some physical and combustion properties such as the compressed density, shatter index, hydrophobicity, combustion rate and ignition time of the produced briquettes were determined at the three (3) different compaction pressures of 420.4 kn/m2 , 525.5 kn/m2 and 630.6 kn/m2 . rice husk (rh), sawdust (sd) and composite briquettes of rice husk and sawdust (rh/sd) were produced using cassava starch as a binder. the developed biomass briquetting machine had a minimum and maximum production capacities of 20 kg/hr and 30 kg/hr respectively. the results showed that the physical properties improved at an increasing compaction pressure. all the produced briquettes at different compaction pressures from the different biomass exhibited over 90% shatter index while the briquette produced from rh at compaction pressure of 525.5 kn/m2 had the highest combustion rate. the rh/sd briquette moulded at compaction pressure of 630.6 kn/m2 had the least combustion rate. the ignition time of the briquettes increased with increasing compaction pressure from 1.28 to 1.58. however, this study found that the rh biomass briquette exhibited a superior solid fuel quality property compared to the other briquette samples. therefore, this study recommends the rh briquette as a sustainable source of solid biofuel © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 june 2020 revised 19 december 2020 accepted 27 december 2020 keywords: rice husk sawdust briquette cassava starch binder compaction pressure aliyu et al: effect of compaction pressure and biomass type (rice husk and sawdust) on some physical and combustion properties of briquettes. azojete, 17(1):61-70 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 62 figure 1: (a) sawdust and (b) rice husk dump sites therefore, it is imperative to pay more attention to renewable energy sources such as biomass from agricultural residues to reduce the problem of environmental pollution and deforestation (tembe et al., 2014; bach and skreiberg, 2016). however, direct use of biomass as a sustainable energy resource constitutes some disadvantages due to its high moisture, low energy value, heterogeneity and low density (wang et al., 2018). one of the simple techniques that is currently used to overcome some of the limitations to the direct usage of biomass as energy source as mentioned above is briquetting. briquetting is the mechanical compaction of dry, loose and tiny particle size materials with or without the addition of an additive to form a regular shaped solid through the application of pressure (osarenmwinda and ihenyen, 2012; orhorhoro et al., 2017). compaction pressure plays a vital role in increasing the energy density and the combustion characteristics of a briquette, given the fact that denser solid fuel tends to burn for a longer time and more durable for handling and transportation (orhevba et al., 2016). briquettes have been produced from various agricultural residues and other waste materials (tembe et al., 2014; thabuot et al., 2015; rajaseenivasan et al., 2016; garrido et al., 2017; krizan et al., 2018; kongprasert et al., 2019; thliza et al., 2020). however, to the authors knowledge, no literature has reported the production of briquette from rh, sd and a combination of rh/sd at varying pressure. therefore, the aim of this study was to produce briquettes from rh, sd and rh/sd at varying compaction pressure and to determine some physical characteristics of the produced briquettes using a simple manually operated briquetting machine. 2. materials and methods 2.1 materials the materials used for the study include mild steel plates, angle iron, galvanize pipe, rh, sd, rh/sd (ratio 1:1), hydraulic jack, pressure gauge, electric oven, and cassava starch as binder. all the materials were sourced locally from minna, niger state, nigeria. the manual briquetting machine was designed to produce four (4) briquettes at a time. total area to which the compaction pressure acts, and the applied compaction pressure were calculated using equations 1 and 2. the initial pressure was calculated from a hydraulic jack of 3 tonnes (osarenmwinda and ihenyen, 2012). the machine production capacity at varying compaction pressure was calculated using equation 3 by considering the total time from loading, compaction, ejection, and the mass of the produced briquettes (obi et al., 2013). the fabricated machine is shown figure 2. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):61-70. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 63 (1) where = number of moulds (2) (3) where; = applied force (kn/m²), = total area (m²), = mass of briquette produced ( ) = total time taken (hours) figure 2: the fabricated briquetting machine each of the raw biomass and the blend were mixed with cassava starch as a binder at a ratio of 3:1. the mixture was fed into the mould of the briquetting machine. it was ensured that all the moulds were fed to approximately equal level, to ensure equal distribution of pressure during compaction. the briquettes were ejected after compaction and were dried in an electric oven for 24hours at 120 ºc to a constant mass. 2.1 determination of physical properties of the produced briquettes 2.1.1 determination of the compressed density four (4) briquettes were randomly selected from each production batch at the varying compaction pressure for the determination of the compressed density. the mean compressed densities of the briquettes were determined immediately after removal from the mould as a ratio of measured mass to the volume (obi et al., 2013). the mass of the produced briquettes was determined using a digital weighing balance (ohaus corp ar3130 model – china), while the average external and internal diameters, and height of the briquettes were measured using a vernier calliper. the measured diameters were subsequently used to calculate the volumes and the densities using equations 4 and 5 (olorunnisola, 2007; kamruzzaman et al., 2008; tembe et al., 2014; aliyu et al., 2017; aliyu et al., 2020). ( ) (4) aliyu et al: effect of compaction pressure and biomass type (rice husk and sawdust) on some physical and combustion properties of briquettes. azojete, 17(1):61-70 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 64 (5) where; = volume of the briquette (m3), d = external diameter of the briquette (m), d = internal diameter (m) of the briquette and h = height of the briquette (m) 2.1.2 determination of shatter index the durability of briquettes was determined in accordance with the shattering index. this was done by dropping the briquette sample repeatedly from a height of 1.5 m on a solid surface. the fraction of the briquettes retained was used as an index of briquette breakability. the percentage mass loss of briquettes was expressed as a difference between the initial mass and the mass after impact with the solid surface, divided by the initial mass. the shatter index was obtained by subtracting the percentage mass loss from 100 as expressed in equations 6 and 7 (ghorpade et al., 2006; suparin et al., 2008; sengar et al., 2012; tembe et al., 2014). (6) where; = initial mass (g), = final mass after shattering impact (g) (7) 2.1.3 hydrophobicity test hydrophobicity is a measure of percentage of water gained by a briquette when immersed in water. each briquette was immersed in 150 mm of water column at room temperature for 30 s. the percent of water absorbed by the briquettes were recorded and calculated. these values were, thereafter, subtracted from 100% to obtain the approximate average hydrophobicity in percentage using equations 8 and 9. water absorbed by briquette (%) = (8) where; = initial mass of briquette (g) and = mass of wet briquette (g) hydrophobicity (%) = 100 water absorbed by briquette (9) 2.2 determination of combustion properties of the produced briquettes 2.2.1 determination of the combustion rate of the produced briquettes briquette burning rate was determined according to the method reported by onuegbu et al. (2012). the insulator, bunsen burner, tripod stand, and wire gauze were arranged on the balance and their weights were recorded. briquette sample of known weight was placed on wire gauze and the burner ignited. this was positioned on top of a weighing balance to facilitate instantaneous measurements of the mass every 10 seconds throughout the combustion process using a stopwatch, until the briquettes were completely burnt, and constant weight was obtained. the weight loss at specific time was computed from the expression in equation 10. (10) where; = mass of burned briquette (g), = total time taken (minutes) arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):61-70. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 65 2.2.2 determination of ignition time ignition time was determined according to the method described by onuegbu et al. (2012). each briquette was ignited by placing a bunsen burner on a platform 4 cm directly beneath. bunsen burner was used to ensure that the entire base of the briquette was ignited simultaneously after adjustment to blue flame. caution was taken to avoid flame spread in the transverse direction. the burner was left until the briquette was well ignited and had entered its steady state burn phase. 3.0 results and discussion 3.1 production capacity of the manually operated briquetting machine the produced briquettes and the result of the machine capacity at different densification pressure is shown in figures 3 and 4. figure 4 showed that biomass type had a noticeable influence on the production capacity or rate of the machine. on the contrary, the compaction pressure showed not much influence on the capacity. the composite biomass briquette rh/sd had the highest production rate which may be attributed to the differences in the biomass composition in the mixture and consequently led to a higher capacity. rh at 420.4 kn/m2 had the lowest production rate with 20 kg/hr while the samples produced at 525.5 kn/m2 and 630.6 kn/m2 showed no differences in production capacity. the observed production capacity of the composite (rh/sd) briquette at increasing compaction pressures was 30 kg/hr. this implies that there were no changes in the observed capacities at the different compaction pressures. obi et al. (2013) reported 43 kg/hr for sd briquette, the observed differences may be attributed to the differences in the sizes of the moulds used, production technique and the procedure. figure 3: the produced briquettes at the different compaction pressures aliyu et al: effect of compaction pressure and biomass type (rice husk and sawdust) on some physical and combustion properties of briquettes. azojete, 17(1):61-70 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 66 figure 4: production capacity of the manually operated briquetting machine 3.2 compressed density of the briquettes in this study, density was determined from the measured average mass and volume of the produced briquettes and the result is shown in figure 5. the briquette produced from composite of rh/sd sample had the highest density of 8.26 g/m3 at compaction pressure of 525.5 kn/m2. this suggests that it would burn for a longer duration compared to the other briquette samples. the rh briquette sample had the lowest density of 7.14g/cm3 at compaction pressure of 420.4 kn/m2. however, in this study the compressed densities were much lower than the 726900 g/m3 reported by obi et al. (2013) for sd briquette. the difference in the observed values was due to the differences in the size of the briquetting mould and the production technique used. figure 5: compressed density of the produced briquettes figure 6: the shatter index of the produced briquettes 3.3 shatter index of the produced briquettes this test was conducted to determine the durability of the briquettes for handling during transportation and storage. figure 6 shows the shatter index of produced briquettes at the three (3) different compaction pressures. the figure revealed that over 90% of all the briquette mass, arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):61-70. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 67 irrespective of the biomass type, were retained after the shatter index test. result revealed that the shatter index increased as the compaction pressure was increased. this indicates that the production pressure had a profound effect on the compaction of the briquettes. similar observation was reported by rajaseenivasan (2016) for briquettes produced from sawdust blended with neem powder using compaction pressure range of 7 to 33 mpa. the high shatter index recorded for the briquettes may have resulted from the ratio of biomass to binder used (3:1) in this study. figure 6 also showed that the shatter index for the individual biomass was slightly higher than the mixed biomass. this indicates that there was more attraction force due to similar biomass particles than heterogenous or different particles. the shatter index indicates that the briquettes can withstand handling during transportation and storage. 3.4 hydrophobicity of the briquettes figure 7 shows the result of the hydrophobicity test for the produced briquettes from rh, sd and rh/sd. it was observed that the production pressure increased the hydrophobicity of the briquettes. rh briquettes exhibited the highest hydrophobicity compared to the other briquettes. however, not much effect was observed in rh briquettes at the different production pressures. this indicates that the three (3) production pressures were good enough to produce a hydrophobic solid fuel from rh. briquettes produced from the composite of rh/sd exhibited the least hydrophobicity at the three (3) different production pressures. this could be as a result of different particles from the composite not well attracted to each other, leaving more pore spaces for easy penetration of water. in general, the result of the hydrophobicity recorded for all briquettes implied that; short-term exposure to rain or high humidity during transportation and storage, would have little or no adverse effect on the ease of ignition of the briquettes. figure 7: the hydrophobicity of the produced briquettes figure 8: combustion rates of the produced briquettes 3.5 combustion rate of the produced briquettes the average combustion rates of the produced briquettes are shown in figure 8. rh briquette produced at a compaction pressure of 420.4 kn/m2 exhibited the highest combustion rate while rh/sd briquette produced at a compaction pressure of 630.6 kn/m2 has the least combustion rate. figure 8 revealed that the compaction pressure and biomass type had a noticeable influence on the combustion rates of the produced briquettes. rh exhibited a relatively higher combustion rate at each compaction pressure compared to the other biomass types. however, it was observed that the combustion of the rh decreased at increasing compaction pressure. this observation could be attributed to decreased available pore spaces occupied by air that can enhance combustion reaction aliyu et al: effect of compaction pressure and biomass type (rice husk and sawdust) on some physical and combustion properties of briquettes. azojete, 17(1):61-70 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 68 in the rh biomass. similar combustion behaviour was observed for sd and rh/sd biomass at an increasing compaction pressure. however, rh/sd biofuel exhibited the least combustion rate which could be as a result of complex combustion reaction in the heterogenous mixture of the biomass briquette, this may have led to the lower combustion rate. therefore, this implies that the briquette from the composite of rh/sd will burn for a longer duration compared to the other briquettes. the duration of combustion is also an important quality index of a solid fuel; hence, the composite of rh/sd biomass briquette will offer such advantage compared to the other individual briquettes. similar observation was reported by aliyu et al. (2020) for composite biomass briquette produced from corn cob and orange peels. 3.6 ignition time the result of the ignition time for the produced briquettes is shown in figure 9. the result revealed that the ignition time of the briquettes increased with increase in the compaction pressure. the observed increase in the ignition time due to the increased pressure could be due to increased compaction of the briquettes thereby eliminating available pore spaces filled with air, that can promote ignition and subsequent combustion. rh briquette produced at the pressure of 630.6 kn/m2 took the longest time of 1.58 minutes to ignite while sd briquette produced at a compaction pressure of 420.4 kn/m2 took the shortest time of 1.28 minutes to ignite. the result also indicated that, it would be more difficult to ignite the rh briquette compared to the sd and rh/sd briquettes. figure 9: ignition time of the produced briquettes 4. conclusion a simple and manually operated briquetting machine was constructed and a hydraulic jack was incorporated to allow for pressure variation. the constructed machine was used to produce briquettes at three (3) different compaction pressures monitored by a pressure gauge. the minimum and maximum production capacity of the machine was 20 kg/hr and 30 kg/hr respectively. all the produced briquettes at different compaction pressures from the different biomass exhibited over 90% shatter index while the briquette produced from rh at compaction pressure of 525.5 kn/m2 had the highest combustion rate. the rh/sd at compaction pressure of 630.6 kn/m2 had the least combustion rate. the ignition time of the briquettes increased with increasing compaction pressure. however, this study revealed that the rh biomass briquette has a superior solid fuel quality property compared to the sd and rh/sd briquette samples. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):61-70. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 69 references aliyu, m., dauda, sm., balami, aa., mohammed, is. and abdulfatai, y. 2017. engineering properties of luffa (l. cylindrica) seed relevant to the processing machineries. agricultural engineering international: cigr journal, 19(3): 47-55. aliyu, m., mohammed, is., usman, m., dauda, sm., igbetua, ij. 2020. production of composite briquettes (orange peels and corn cobs) and determination of its fuel properties. agricultural engineering international: cigr journal, 22(2): 133-143. yahaya bs., ekpeesor, e and ochei, es. use of composite biomass briquettes as cleaner energy source. american journal of engineering research (ajer), 9(10): 12-18. bach, qv., skreiberg, ø. 2016. upgrading biomass fuels via wet torrefaction: a review and comparison with dry torrefaction. renewable and sustain energy review, 54: 665-677. https://doi.org/10.1016/j.rser.2015.10.014. garrido, ma., conesa, ja., and garcia, md. 2017. characterization and production of fuel briquettes made from biomass and plastic wastes. energies, 10(7): 850. kamruzzaman, m., hossain, mm. and sarkar, mht. 2008. performance study of rice husk briquette machine: a case study in muktagacha of mymensingh district, bangladesh. international journal of bioresources, 5(1):7-11. kongprasert, wangphanich, np. and jutilarptavorn, a. 2019. charcoal briquettes from madan wood waste as an alternative energy in thailand. procedia manufacturing, 30:28-135. križan, m., krištof, k., angelovič, m., jobbágy, j. and urbanovičová, o. 2018. energy potential of densified biomass from maize straw in form of pellets and briquettes. agronomy research, 16(2): 474-482. lang, q., zhang, b., liu, z., chen, z., xia, y., li, d., gai, c., 2019. co-hydrothermal carbonization of corn stalk and swine manure: combustion behaviour of hydrochar by thermogravimetric analysis. bioresources technology, 27(1): 75-83. https://doi.org/10.1016/j.biortech.2018.09.100. leach, g. and mearns, r. 2013. beyond the wood fuel crisis: people, land, and trees in africa. routledge, london, 23-47. mohammed, is., aliyu, m., abdullahi, na. and alhaji, ia. 2020. production of bioenergy from ricemelon husk co-digested with cow dung as inoculant. agricultural engineering international: cigr journal, 22(1): 108-117. obi, of., akubuo, co. and okonkwo, wi. 2013. development of an appropriate briquetting machine for use in rural communities. international journal of engineering and advanced technology (ijeat), 2(4): 578-582. olorunnisola, a. 2007. production of fuel briquettes from wastepaper and coconut husk admixtures. agricultural engineering international: the cigr e-journal. manuscript ee 06 006. vol. ix. february. orhevba, ba., musa, u., isah, ag., bilyaminu, s., mohammed, ug., nwatu, e. 2016. synthesis of composite biomass briquettes as alternative household fuel for domestic application. proceedings of the world congress on engineering and computer science, san francisco usa, october 2016, (2):19-21. aliyu et al: effect of compaction pressure and biomass type (rice husk and sawdust) on some physical and combustion properties of briquettes. azojete, 17(1):61-70 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyu.mohd@futminna.edu.ng 70 orhorhoro, ek., chukudi, om., oghenekevwe, o. and onogbotsere, m e. 2017. design and fabrication of an improved low-cost biomass briquetting machine suitable for use in nigeria. international journal of engineering technology and sciences, 4(2): 128-138. osarenmwinda, jo. and ihenyen, oi. 2012. the preliminary design and fabrication of a manually operated briquetting machine. journal of applied sciences and environmental management, 16(2): 167-170. olajedi, tj. and oyetunji, or. 2013. investigation into physical and fuel characteristics of briquettes produced from cassavas and yam peels. journal of energy technologies and policy, 3(7): 40-47. rajaseenivasan, t., srinivasan, v., qadir, gsm. and srithar, k. 2016. an investigation on the performance of sawdust briquette blending with neem powder. alexandria engineering journal, 55(3): 2833-2838. tembe, et., otache, po. and ekhuemelo, do. 2014. density, shatter index, and combustion properties of briquettes produced from groundnut shells, rice husks and saw dust of daniellia oliveri. journal of applied biosciences, 82(1):7372-7378. thabuot, m., pagketanang, t., panyacharoen, k., mongkut, p. and wongwicha, p. 2015. effect of applied pressure and binder proportion on the fuel properties of holey bio-briquettes. energy procedia, 79: 890-895. thliza, ba., abdulrahman, fi., akan, jc., chellube, zm. and kime, b. 2020. determination of compressive strength and combustibility potential of agricultural waste briquette. chemical science international journal, 29(1): 30-46. wang, t., zhai, y., zhu, y., li, c. and zeng, g. 2018. a review of the hydrothermal carbonization of biomass waste for hydrochar formation: process conditions, fundamentals, and physicochemical properties. renewable and sustainable energy reviews, 90: 223-247., https://doi.org/10.1016/j.rser.2018.03.071. https://doi.org/10.1016/j.rser.2018.03.071 arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):26-40 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 26 characterization and evaluation of chicken eggshell for use as a bio-resource e.o. ajala,1* o.a.a. eletta, 1 m.a. ajala1 and s.k. oyeniyi2 1department of chemical engineering, university of ilorin, ilorin, nigeria 2department of agricultural and environmental engineering, university of ibadan, nigeria *corresponding author’s email address: olawaleola01@yahoo.com abstract chemical compositions of chicken eggshell were determined with the aim of finding economic uses for it; instead of becoming a nuisance to the environment. the concentrations obtained were (mg/l): calcium 2300.33 ± 3.80, magnesium 850.00 ± 1.24, sodium 33.83 ± 0.72, potassium 17.06 ± 1.04, iron 1.4 ± 0.03, zinc 0.99 ± 0.04 and copper 0.063 ± 0.01. the proximate showed that the eggshell contained, 0.95 ± 0.89, moisture; 45.29 ± 0.06, ash; 1.40 ± 0.25, crude protein; 0.37 ± 0.06, lipid; 4.38 ± 0.32, crude fibre; 47.63 ± 0.32 (%), carbohydrate and 811 ± 12.71 (cal/g), calorific value. further analysis revealed the presence of carbon and oxygen in the eggshell in right proportion as a good alternative adsorbent for removal of heavy metals and dyes from aqueous solutions. findings from the study shows that the chicken eggshell potentially represents a natural source of food nutrients. keywords: eggshell, calcium, carbohydrate, functional group, animal feed, food supplement. 1. introduction eggs contain many essential nutrients, including high-quality protein and this has made it form part of human diets for centuries. eggs serve as a very good source of proteins to human beings besides milk. it is also rich in amino-acids, carbohydrates, easily digestible fats and minerals, as well as essential vitamins (bashir et al., 2015). there are several species of eggs which include; chicken egg, quail egg, and guinea fowl egg. they all have similarities in nutritional composition and potential food usage (dudusola, 2010). a chicken egg is an inexpensive single-food source of protein and this has led to its high consumption rate and consequently high eggshells production (bashir et al., 2015). the chicken egg is made up of three major component parts: shell, the white or albumen and the yolk (figure 1a). many studies have been and are still being carried out on the various components of chicken egg (dudusola, 2010), with little or no information on the chicken eggshell. the chicken eggshell consists of the cuticle, crystal layer, spongy calcareous layer pores, cores and mammillary layer (figure 1b). the membranes located on the inner surface of the eggshell appear like a single layer but can be divided into two distinct layers of fibrous material. one layer surrounds the albumen while the other is attached to the "tips" of the calcified material of the shell. they are regarded as the inner and outer shell membranes respectively (figure 1b) (hamilton, 1986). the membranes can be used as an adsorbent for the removal of reactive dyes from colored waste effluents and to remove heavy metal ions from dilute wastewaters (schaafsma et al., 2000). the eggshell membranes also consist of collagen as a component which when extracted can be used for diverse purposes such as; medicine, biochemical, pharmaceutical, food, and cosmetics industries (king’ori, 2011). mailto:olawaleola01@yahoo.com http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):26-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 27 therefore, the efficacy of converting eggshells to beneficial use becomes an idea worth investigating. the eggshell is composed of about 95.1% inorganic matter and 3.3% protein. the eggshell was reported to weigh on average 1.6% of the total chicken egg-based on wet weight (adeyeye, 2009) with a thickness between 0.33 and 0.35 mm (tadesse et al., 2015). eggshells vary widely in texture but, it is predominantly made up of calcium carbonate and glycoprotein matrix. the outside of the shell is a thin proteinaceous layer, the cuticle that blocks the entrance of bacteria from entering the embryo (al-awwal and ali, 2015). figure 1: schematic diagrams of a typical (a) whole egg and (b) eggshell sources: (hamilton, 1986; mittal et al., 2016) primarily, the eggshell provides nutrient, a perfect package, and protection to the enclosed embryo from mechanical damage and contamination. it is being used on a moderate scale as an additive in foods (hunton, 2005). chicken eggshells are agricultural wastes which could lead to environmental pollution when not properly disposed of (mtallib and rabiu, 2009; phil and zhihong, 2009). they are found in hatcheries, homes and fast food industries and are readily abundantly available for collection (king’ori, 2011). a b http://www.azojete.com.ng ajala, et al., characterization and evaluation of chicken eggshell for use as a bio-resource. azojete 14(1):26-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 28 there are numerous challenges associated with its disposal which ranges from a cost of disposal, availability of disposal sites, odor, flies, and abrasiveness (phil and zhihong, 2009). however, it can be processed into more useful products such as fertilizer, animal feeds, medicines, and building materials. it can also be used for human consumption, as a food flavor in the food industry, especially in this era of ever-increasing endeavors to convert waste to wealth (mtallib and rabiu, 2009). eggshell can be used in the artwork for the production of mosaics, glue in musical instruments, and photography aids in photography (king’ori, 2011). the eggshell membrane powder can also be used in the paper industry, or in agriculture as a lime substitute or calcium supplement. other possible uses of eggshell include the production of biodegradable plastics from eggshell membrane proteins; altering of food-borne bacterial pathogen heat resistance with an eggshell membrane bacteriolytic enzyme; as human dietary calcium supplement especially for postmenopausal women (dudusola, 2010). eggshells have been found to contain calcium, magnesium, copper, iron, manganese, molybdenum, sulfur and many more other useful elements. however, the proportions have not been reported in literature and, it could be a natural source of calcium (king’ori, 2011). calcium, one of the content in eggshell had been clinically tried to provide effective prevention of osteoporotic fractures in elderly community-dwelling residents (chang et al., 2007). it is an acceptable practice for eggshell to be dried and used as a source of calcium in animal feeds. the recycling of the nutrients of eggshell back to the animal portends that the nutritional composition of various eggshells should be evaluated to establish its suitability as animal feed (adeyeye, 2009), hence this study. the aim of this study was to examine the proximate analysis, elemental composition, functional group, surface morphology and composition of the natural waste chicken eggshell. these are with the intension of ascertaining the quality and quantity characteristics of the chicken eggshell in order to find a more economic value for it. 2. materials and methods 2.1 material preparation the unboiled chicken eggshells were collected from household and restaurant wastes in ilorin, kwara state, nigeria. the eggshells were washed with distilled water, without peeling off the membranes. it was sun-dried to constant weight, ground to a powder using a grinding machine and sieved to a fine powder by using a 0.5 micrometer sized sieve. the sieved eggshell was oven dried at 38°c until constant weight was obtained. the prepared eggshell was charged into a polyethylene and kept in a desiccator. the eggshell was digested using aqua regia (hno3 67%: hcl 37% = 3:1) method, in order to make it suitable for analyses. a calibrated microwave oven (berghof mws-2) with 6 closed pfa 100 ml high-pressure vessels was employed for the digestion and a procedure according to chen and ma (2001) was followed. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):26-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 29 2.2 atomic absorption spectrophotometer (aas) and flame photometer (fp) the model of aas used for the analysis of the chicken eggshell sample was aas buck scientific accusys 211 equipped with air-acetylene for the flame. the automatic hollow cathode lamp switch attached to the aas was used to measure the absorbance and concentration of the metals by direct aspiration into the burner through the sample introduction system at wavenumber corresponding to each element as given by the manufacturer. calcium (ca), magnesium (mg), iron (fe), zinc (zn) and copper (cu) were determined using aas (jatto et al., 2010). while flame photometer was used to determine the concentration of sodium (na) and potassium (k) (al-awwal and ali, 2015). the results obtained were statistically analyzed using ibm spss statistics 19. 2.3 proximate analyses the carbohydrate, crude protein, crude fat, moisture and ash contents were determined using the aoac standard methods as was described by jatto et al. (2010). the ibm spss statistics 19 was used for the statistical analysis of the proximate analyses. 2.4 scanning electron microscope (sem) scanning electron microscopy (sem, fei esem quanta 200) and energy-dispersive x-ray spectrometry (edx, fei esem quanta 200) were used to determine the morphology and elemental composition of the chicken eggshell respectively. the chicken eggshell was prepared and put in a scanning electron microscope stud using a double-backed cellophane tape. the stub and sample were coated with gold and examined using the scanning electron microscope (kaewmanee et al., 2009). 2.5 fourier transform infrared spectroscopy (ftir) ftir analysis of the eggshell was carried out using potassium bromide (kbr) pellet in a fourier transform infrared (ft-ir) spectrophotometer, model shimadzu (8400s) japan. the ft-ir was domiciled in the department of chemical sciences, the redeemer’s university, ede, osun state nigeria. the spectra were observed at wavenumber 450–4000 cm-1 with a resolution of 4 cm-1. 3. results table 1 presents the results obtained from the aas/fp analyses of the chicken eggshell and was compared with elemental dietary daily consumption for human beings. the chicken eggshell proximate composition for moisture, ash, crude protein, lipid, crude fibre, and carbohydrate are presented in table 2. the morphology of the chicken eggshell and the elemental analysis of the chicken eggshell are depicted in figure 2. the edx of the chicken eggshell in figure 3 shows the elemental compositions present as carbon 51.40%, oxygen 39.94%, chlorine 0.2% and calcium 8.46%. the ftir patterns of the natural chicken eggshell are presented in figure 3 and the analyses are as shown in table 3. 4. discussion 4.1 atomic absorption spectroscopy/flame photometer calcium content (mg/l) in the chicken eggshell is 2300.33 ± 3.80 (table 1) which is much higher than that of duck eggshell (42.3) and turkey eggshell (50.1) (adeyeye, 2009). this shows that the http://www.azojete.com.ng ajala, et al., characterization and evaluation of chicken eggshell for use as a bio-resource. azojete 14(1):26-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 30 chicken eggshell could be a good source of calcium which can be used to meet the daily consumption of calcium this can be as a supplement in bone development since the recommended daily consumption is between 700 – 1300 mg (table 1) (al-awwal and ali, 2015). the recommended quantity of calcium for people with osteoporosis is 400-500 mg per day to supplement dietary sources (king’ori, 2011), and this can be gotten from the eggshell. it can also be used as a supplement in formulating animal feeds (chang et al., 2007). table 1: comparative view of chemical composition of chicken eggshell and daily diet table 3: evaluation of the ft-ir spectrum of the chicken eggshell elements chicken eggshell (mg/l) dietary (mg/day) calcium 2300.33 ± 3.80 700 – 1300 magnesium 850.00 ± 1.24 130 – 420 sodium 33.83 ± 0.72 1000 – 1500 potassium 17.06 ± 1.04 3000 – 4700 iron 1.4 ± 0.03 7 – 11 zinc 0.99 ± 0.04 5 – 11 copper 0.063 ± 0.01 0.7 – 0.9 sources this study food and nutrition board (2004) table 2: proximate composition of chicken eggshell, duck eggshell and dietary nutrients chicken eggshell (%) duck eggshell (%) dietary (g/day) moisture 0.95 ± 0.09 0.5 ± 0.03 3.49 ash 45.29 ± 0.06 43.5 ± 0.03 3.44 crude protein 1.40 ± 0.25 1.35 ± 0.40 65.20 30 56 lipid 0.37 ± 0.06 5.32 20 – 35 crude fibre 4.38 ± 0.32 3.0 ± 0.30 0.11 26 -38 carbohydrate 47.63 ± 0.32 51.70 ± 0.44 22.5 130 total calorific (cal/g) 811 ± 12.71 1687 sources this study al-awwal and ali (2015) adeyeye (2009) food and nutrition board (2004) s/n band wave number (cm-1) assigned functional group 1 3421 a weak stretching vibration of o-h/n-h bond 2 2360 moisture peak 3 2978, 2874 the c-h stretching of aliphatic alkanes 4 1797 carbonyl stretching of the amide group 5 1612, 1471 the vibration of the c=c stretching of unsaturation was depicted as a shoulder 6 1425 the c-h bending vibration of alkanes and alkenes http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):26-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 31 figure 2: surface morphology and the edx of chicken eggshell figure 3: ftir spectra of chicken eggshell http://www.azojete.com.ng ajala, et al., characterization and evaluation of chicken eggshell for use as a bio-resource. azojete 14(1):26-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 32 the eggshell can be used in making fertilizer because it contains high quantity of calcium. this will make the fertilizer inexpensive and environmentally useable. the eggshell can be used as an alternative to sand in making hollow blocks because it contain calcium carbonate that can provide the required hardness and strength in block making (king’ori, 2011). calcium is synonymous with bone, it gives bone its hardness, but it does not provide any flexibility. hard bone without any flexibility would be synonymous with chalk that is hard, but brittle, and very easy to break. magnesium is crucial in giving bone flexibility via improved trabecular integrity and bone density (tucker, 1999). since calcium and magnesium compete for absorption in the gut, too much of one can cause a deficiency in the other (hardwick, 1991). magnesium (mg/l) obtained in the chicken eggshell was 850.00 ± 1.24, which is a great quantity that can successfully meet the recommended daily consumption of 130 – 420 mg (table 1). magnesium deficiency can compromise cardiovascular health, increasing the risk of hypertension, stroke, and heart attack (altura and altura, 1982; gröber et al., 2015). magnesium is an essential electrolyte for living organisms; its presence in chicken eggshell with further processing can make the eggshell suitable as magnesium supplements to those patients with a deficiency. the deficiency can cause pre-eclampsia, arrhythmias, arteriosclerosis, diabetes mellitus, and metabolic syndrome in humans. therefore, magnesium supplementation in those patients can be of benefit in most cases (gröber et al., 2015). chicken eggshell may be processed as magnesium dietary supplement. lack of magnesium in the animal diet can result in a number of diseases and sometimes death. sodium has been found to be essential for neuromuscular transmissions and, this mineral was found in chicken eggshell. the concentration obtained in the eggshell was 3.83 ± 0.72 mg/l, and this was far less in comparison with the required daily dosage for man (1000 – 1500 mg) as shown in table 1. sodium in eggshell can be used as a supplement in animal feed as it is an important mineral element (al-awwal and ali, 2015). potassium (k) is an essential element to all forms of plant and animal life. in man, it is responsible for nerve action; very important in the regulation of water, electrolyte, and acid-base balance in the blood and tissues (bashir et al., 2015). in agriculture, potassium is referred to as potash, which is being used as fertilizer. the combination of potassium with calcium in chicken eggshell can make it a suitable raw material for fertilizer production. the potassium obtained in chicken eggshell was 17.06 ± 1.04 mg/l. though lower than the recommended daily dosage (3000 – 4700 mg), it can be harnessed and used as a source of potassium in pharmaceutical production. as potassium is an essential ingredient in many pharmaceutical products. the iron content of the eggshell (1.4 ± 0.03 mg/l) was found to be lower than the required daily dosage for man (7 – 11 mg). therefore, eggshell cannot be used as a source of iron to meet daily diet of man; however, it can be used as a source of supplement in the body for oxygen transport by hemoglobin and enzymatic oxidation reactions (michelle, 1962). it can also be a source of iron to improve the nutrition status of people especially in the risk of iron deficiency or anemia particularly infant, children and pregnant women. the eggshell can be a source of iron in improving anaemic condition in iron-deficient diabetic patients (bashir et al., 2015). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):26-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 33 chicken eggshell was found to contain 0.99 ± 0.04 mg/l of zinc. though the quantity in the eggshell is low, it can be harnessed to meet daily human consumption of man which is between 5 – 11 mg. it can be a source of zinc for pharmaceutical products and other industrial uses. the eggshell can be used together with soya beans and magnesium to improve the quality of animal feed, particularly in egg-laying hens. the copper content was found to be very low in chicken eggshell as it contains 0.063 ± 0.01 mg/l, but can be a source of copper for human consumption as the daily dosage is between 0.7 – 0.9 mg (table 1). turnlund et al. (1997) observed that when a healthy adult male consumed a diet of 0.38 mg/d for 42 days, there is a decrease in measures of copper-deficient status (serum copper and ceruloplasmin concentrations). this indicates that the chicken eggshells contain an appreciable quantity of copper which is a very important mineral element that helps in maintaining body health including muscles, nerve and oxidase enzymes in the body (tacon, 1995). copper performs several functions in both man and animals. these include as essential element in mammalian nutrition as a component of metalloenzymes where it acts as an electron donor or acceptor is needed for homeostatic maintenance that requires tightly coordinated orchestration of copper uptake, distribution, and efflux in cells and the organism as a whole. several dietary sources of copper exist such as; mushrooms, potatoes, beans, peas, wheat, rye, lemon, raisins, peanuts and pecans. it is commonly found in fruits like lemons and raisins. some mollusks are exceptionally rich in copper with levels reaching as high as 5 mg/kg wet weight (stern et al., 2007). therefore, eggshells can also be included in the list of copper dietary for animals and can be processed as supplementary in human dietary. copper is necessary for human nutrition for normal iron metabolism and the formation of red blood cells, as it is closely associated with iron metabolism in the oxidation of ferrous to ferric iron. anaemia is a clinical sign of deficiency of both iron and copper (angelova et al., 2011; siulapwa et al., 2014). elements such as zinc, iron, molybdenum, lead, or cadmium influence dietary copper absorption in the human body by inhibition and compete with one another for transport and/or by increasing intestinal metallothionein concentrations (stern et al., 2007). chicken eggshell that is rich in iron and zinc is a good diet for making animal feed and with further processing, can be suitable as a food supplement. copper in the chicken eggshell for animal feed can activate lysyl oxidase, which is an integral enzyme in elastin and collagen formation in birds (angelova et al., 2011; siulapwa et al., 2014). deficiency and excess of copper in both animals and human beings can produce several adverse health effects in the blood and hematopoietic system, the cardiovascular, connective tissue and bone, the nervous, and the immune system as shown in table 4 (aggett, 1999; stern et al., 2007). effect of deficiency of copper in animals and human beings among others include; bone abnormalities due to abnormal collagen synthesis, calcium depletion which leads to abnormal shell formation, structural and neurobehavioral abnormalities which include brain lesions, skeletal malformations, cardiovascular lesions, severe growth retardation, convulsions, and hyperirritability to noise (table 4). severe copper deficiency in rats during gestation induces fetal resorptions or stillbirths. the offspring of pregnant rats given a copper-deficient diet during gestation have increased postnatal mortality (stern et al., 2007; siulapwa et al., 2014). hence, chicken eggshell as a source of copper in animal dietary and food supplement will mitigate some of this adverse health effect due to copper deficiency in the body. http://www.azojete.com.ng ajala, et al., characterization and evaluation of chicken eggshell for use as a bio-resource. azojete 14(1):26-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 34 table 4: effects of daily intake of copper by human beings dose range approximately daily intakes health outcomes excessive and toxic >5.0 mg/kg body weight death; gross dysfunction and disturbance of metabolism of other nutrients; hepatic “detoxification” and homeostasis overwhelmed. gastrointestinal metallothionein induced (possible differing effects of acute and chronic exposure) adequate 100 µg/kg body weight 34 µg/kg body weight 11 µg/kg body weight 9 µg/kg body weight plateau of absorption maintained; homeostatic mechanism regulates the absorption of copper; hepatic uptake, sequestration and excretion effect homeostasis; glutathione-dependent uptake of copper; binding to metallothionein; and lysosomal excretion of copper biliary excretion and gastrointestinal uptake normal. hepatic deposit(s) reduced; conservation of endogenous copper; gastrointestinal absorption increased deficient 8.5 µg/kg body weight 5.2 µg/kg body weight 2 µg/kg body weight negative copper balance functional defects, such as lysyl oxidase and superoxide dismutase activities reduced; impaired substrate metabolism; peripheral pools disrupted; gross dysfunction and disturbance of metabolism of other nutrients; death source: (aggett, 1999) 4.2 proximate analyses the moisture content of the eggshell is 0.95 ± 0.09% which shows a low moisture content, an indication that the eggshell would be very stable with good quality and shelf life. because high moisture content tends to promote microbial contamination and chemical degradation in many substances. (der-jiun et al., 2012). the ash content is a measure of total amount of inorganic compounds such as minerals in the eggshell (der-jiun et al., 2012; segura-campos et al., 2013). the chicken eggshell was found to contain 45.29 ± 0.06% ash. this value is relatively high and much higher than that of duck eggshell (3.44%) (table 3) (bashir et al., 2015). therefore, the eggshell can be used in pharmaceutical industries as a source of raw materials for mineral synthesis and as an animal feed supplement. however, very high ash content in any substance may not be good for adsorption as it affects the activation of carbon by reducing the overall activity of the activated carbon. it also reduces the efficiency of reactivation, as the lower the ash value, the better the activated carbon for use as an adsorbent (bello et al., 2015). proteins are polymers of amino acids and they are essential components of the living cell needed by man and animals for the maintenance and growth of the body cells. the amino acids in proteins are utilized by the cells of the body to synthesize all the numerous proteins required for the function of the cell (abolaji et al., 2007). protein intake into the body can contribute to the formation of hormones which controls a number of body functions such as growth, repairs, and maintenance of the body (bhattacharjee et al., 2013). the percentage crude protein of chicken eggshell was found to be low (1.40 ± 0.25%) (table 3) and may not be sufficient to meet the daily recommended dose of between 28 – 65 g for children and adult. however, it can serve in part as a good source of protein for animal nutrition and can be processed as a protein supplement for human beings (fakai et al., 2015). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; vol. 14(1):26-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 35 lipid is very important in the body where it serves as a thermal insulator. from table 3, the chicken eggshell has low lipid composition of 0.37 ± 0.06%. though low, it can be used as a source of lipid. high lipid content in the dietary intake has some adverse health potentials, especially for the overweight. the consumption of excess lipid has been recognized as the dietary factor aiding increased level of cholesterol. besides the cholesterol implications, high fat intake can also cause obesity, a factor in the causes of many diseases. therefore, low crude fat in the eggshell can make it preferred as a good raw material for food supplements because it may reduce the risk of coronary heart disease and lower the risk of hypertension (bhattacharjee et al., 2013). the crude fiber obtained for the chicken eggshell is 89.9 – 91.1%. this value is very high which is a good quality of the eggshell as it could be useful in making animal feed and food supplement. the fiber content in the feed and food supplement helps to satisfy the appetite and assist in moving food through the alimentary canal by aiding the muscular action of the intestine, thereby preventing constipation (al-awwal and ali, 2015). crude fiber is beneficial nutritionally as it aids absorption of trace elements in the gut and reduces absorption of cholesterol (abolaji et al., 2007). sufficient dietary intake of fiber helps to lower the serum cholesterol level in the body and reduce the risk of coronary heart disease, hypertension, constipation, diabetes, colon, and breast cancer (mohammed and mann, 2012). high quantity of fiber has been identified as anti-tumorigenic and hypo-cholesterolaemic agent (olagbemide and ogunnusi, 2015). therefore, chicken eggshell can be processed to make a dietary supplement and can be a source of fiber in animal feed owing to the large content of fiber in it. other benefits of crude fiber are; as a useful tool for the control of oxidative processes in food products and as a functional food ingredient. crude fiber aids the conversion of starch to simple sugars, an important factor in the management of diabetes. thus the high percentage fiber contents in the chicken eggshell can make it very effective and useful if explored, in the management of diabetes mellitus, colorectal cancers and weight reduction in obese individuals (bhattacharjee et al., 2013; olagbemide and ogunnusi, 2015) the carbohydrates present in the chicken eggshell is 47.63 ± 0.32%, and this can be a source of energy in man and animal diets. meanwhile, carbohydrate is the primary source of energy in the body and this high amount found in the eggshell shows it can play a great role in human health. aside from the supply of energy, carbohydrates have numerous importances in biochemical reactions that are not directly concerned with energy metabolism; it can be an alternative source of glucose (bhattacharjee et al., 2013). chicken eggshell as a source of glucose can be used as carbon source in bioethanol production, organic acid synthesis, and other biochemical products. the gross energy (cals/g) obtained from the chicken eggshell is 811 ± 12.71, which is relatively high but lower than that of most cereals such as wheat, 3913, and sorghum, 3953 (cervantes-pahm et al., 2014). it may serves as an alternative to cereals when harnessed in animal feed making and human use, as it can provide a reasonable source of energy (adeyeye, 2009; der-jiun et al., 2012). calories are needed to keep the body warm and to furnish energy for muscular work (passmore et al., 1974). http://www.azojete.com.ng ajala, et al., characterization and evaluation of chicken eggshell for use as a bio-resource. azojete 14(1):26-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 36 4.3 scanning electron morphology (sem) and energy dispersion x-ray (edx) analyses the morphology of the chicken eggshell as shown in figure 2 showed clusters of rough, irregularly arranged and spongy particles, aggregated together with microspores scattered on the surface of the sample. the small size of the grains and aggregates could provide higher specific surface areas since the size of the particle should directly respond to the surface area. the microporous surface area of the eggshell can be enhanced by calcination to improve the surface area and its activation through heat treatment. (viriya-empikul et al., 2012). the enhanced pores of the chicken eggshell may be useful for several applications such as adsorption, solid catalyst for biodiesel production and much more. elemental analysis of the eggshell was also determined through edx analysis. the edx of the chicken eggshell is shown in figure 2 with carbon of 51.40%, oxygen of 39.94%, chlorine of 0.2% and calcium of 8.46% observed. the edx spectrum shows that the particle contains mainly calcium oxide, which could serve as a good material for heterogeneous catalyst in biodiesel production. the carbon present in the elemental composition can make it suitable as catalyst support since the carbon can make it capable of building the pores onto the carbon surface and enables it to be treated as a heterogeneous catalyst (dhawane et al., 2016). the higher the amount of carbon (51.40%) and, the lower the amount of oxygen (39.94%), the more the effectiveness of materials for adsorption. the implication of this is that the chicken eggshell which is rich in carbon content and less in oxygen content can be an efficient adsorbent (bello et al., 2015). 4.4 ftir analysis the ftir patterns of the natural chicken eggshell is shown in figure 4 and analyzed in table 4. the ftir spectrum of the eggshell indicated a weak stretching vibration of o-h/n-h bond at 3421 cm-1. moisture peak was observed at 2360 cm-1 and c-h stretching of aliphatic alkanes was observed at 2978 and 2874 cm-1 while the peak at 1797 cm-1 corresponds to carbonyl stretching of the amide group. the vibration of the c=c stretching of unsaturation was depicted as a shoulder at 1612 and the sharp peak at 1471 cm-1 while the c-h bending vibration of alkanes and alkenes was observed at 1425 cm-1. the presence of various functional groups in the chicken eggshell makes it a potential adsorbent (mittal et al., 2016). 5. conclusions the chicken eggshell, therefore, could be used as food supplement and animal feed for man and animals respectively. it could also be used in paper industries and in agriculture as a substitute for lime and for fertilizer production. in building block making, chicken eggshell can be employed due to the high concentration of calcium present in it. the pores in the morphology made it suitable for heterogeneous catalyst in biodiesel production. the presence of various functional groups and the high carbon content in the eggshell makes it a potential material for the adsorbent to remove heavy metals and dyes in wastewater treatment. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, march, 2018; 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e-issn 2545-5818, www.azojete.com.ng 40 tucker, k.l.e.a. 1999. potassium, magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women. the american journal of clinical nutrition 69, 727–736. turnlund, jr., scott, kc., peiffer, gl., jang, am., keyes, wr., keen, cl. and sakanashi, tm., 1997. copper status of young men consuming a low-copper diet. american journal of clinical nutrition 65, 72–78. viriya-empikul, n., krasae, p., nualpaeng, w., yoosuk, b. and faungnawakij, k. 2012. biodiesel production over ca-based solid catalysts derived from industrial wastes. fuel 92, 239–244. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 533-539. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 533 effect of inoculant on the degradation behaviour of multi layered mild steel/al-cr plate in psidium guajava leaf extract m. a. bawa1,m. abdulwahab2, o. b. umaru1, s. m. adams3, l. m. sani4 and n. agidani2 (1department of mechanical/production engineering, abubakar tafawa balewa university, bauchi, nigeria 2 department of metallurgical and materials engineering, ahmadu bello university, zaria, nigeria 3department of metallurgical and materials engineering, university of nigeria, nsukka, nigeria 4national airspace management authority, kano, nigeria) *corresponding author’s email: buokatengwu@atbu.edu.ng abstract the effect of an inoculant, [triethylamine (tea)] on the corrosion behavior of multilayered mild steel/al-cr plates in guava leaf extract was investigated in 0.5m hcl solution using gravimetric based mass-loss test and potentiodynamic polarization techniques. the mild steel plates were sectioned into coupons of 4 � ��� and then pickled, after which they were coated at 750� with an al-cr alloy. the gravimetric-based mass loss test was carried out at room temperature for different concentrations and time intervals of 2.0, 4.0, 6.0, 8.0%v/v and 24, 48, 72, 96 hours respectively. the result showed that triethylamine (tea) decreased the corrosion rate at the various concentrations indicating protection efficiency up to 59.02% in the gravimetric-based-mass-loss technique. equally the potentiodynamic polarization technique indicates higher corrosion resistance of 98.49%. the two methods used for the evaluation of the degradation of multilayered mild steel/al-cr plates in 0.5m hcl/guava leaf extract medium were in agreement. keyword: corrosion rate, linear polarization, corrosion coupons, inoculant molecules, microstructure, metals 1. introduction carbon steel, the most widely used material accounts for approximately 85% of the annual steel production worldwide. despite its relatively limited corrosion resistance, carbon steel is used in large tonnages in maritime application, nuclear and fossil fuel power plants, chemical processing, petroleum production and refining, pipelines, mining, construction and metal processing equipment (atama, 2005; abostra et al., 2009; idu et al., 2015). today, there are various engineering materials which have different areas of application. these materials are subject to environmental degradation. a class of these engineering materials is metals. metals have a wide range of application in modern engineering due to their superior mechanical properties. metals are subject to degradation which may also be called corrosion ( abostra et al., 2009; abdulwahab et al., 2015; amitha and bharathi, 2011). corrosion is due to the reactivity of metallic elements with their environment and oxygen. corrosion shortens the service life of metals and this poses a big problem to engineering designs and installations (peabody, 2001; wannik et al., 2010). this has led to investigations and studies on the control of this degradation so as to tackle this problem. a significant amount of energy is put into a metal when it is extracted from its ores, placing it in a high-energy state. these ores are typically oxides of the metal such as hematite (�u��� ) for steel or bauxite (�r������� ) for aluminum (umaru et al., 2016). one principle of thermodynamics is that a material always seeks the lowest energy state. in other words, most metals are thermodynamically unstable and will tend to seek a lower energy state, which is an oxide or some other compound. the process by which metals convert to the lower-energy oxides is called corrosion (abdulwahab et al., 2015). corrosion of most common engineering materials at near-ambient temperatures occurs in aqueous (water-containing) environments and is electrochemical in nature. the aqueous environment is also referred to as the electrolyte and, in the case of underground corrosion, is moist soil (peabody, 2001). mailto:buokatengwu@atbu.edu.ng http://www.azojete.com.ng bawa et al.: effect of inoculant on the degradation behaviour of multi layered mild steel/al-cr plate in psidium guajava leaf extract. azojete, 14(4):433-439. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 534 various research has demonstrated ways of controlling corrosion but due to the ever evolving technology, more research is needed to develop more effective and suitable corrosion control means so as to reduce the cost implication of corrosion and also increase the service life and maintainability of engineering equipment and structures. this work is there for focused on improving the corrosion resistance of a coated metal even in the presence of an inhibitor. 2. experimental 2.1 materials and equipment the materials used in this research include; flat mild steel plates (low carbon steel), distilled water, methanol, 192g of al-92% cr-8%, pure hcl, 0.5m hcl solution, guava leaf (psidium guajava) extracts and triethylamine solution. while some of the equipment used include; potentiometer, digital weighing balance, desiccator, beakers, series of grit papers, measuring cylinder which were sourced from the department of metallurgical and materials engineering, ahmadu bello university, zaria. 2.2 sample preparation the sample preparation involved cutting a 1mm thick mild steel plate into 10 small coupons of 4× 2 × 1 mm each. the coupons were polished using grit paper of size 600 and then pickled. table 1: nominal chemical composition of low carbon steel, (hassan, 2006) steel grade %carbon %silicon %manganese %phosphorus %sulphur copper nst 0.12-0.17 0.18-0.28 0.40-0.60 0.04-max 0.04-max 0.25 2.3 pickling this was carried out to remove the rust (oxide layer), grease and dirt from the surface of the steel. the samples were dipped in pure hcl of 16cm� for one minute each, washed under a running tap water and then transferred into warm water to remove any salt layer present. after which it was again dipped in cold water and swapped with a cotton wool immediately (abdulwahab et al., 2015). 2.4 hot dipping in this step, the 8%-cr and 92%-al were charged into a crucible furnace and heated to about 750℃. the melt was stirred then the mild steel coupons were hot-dipped for 5seconds each at the same temperature and then left to normalize in the atmosphere (mohammed and dong, 2016). 2.5 guava leaf extracts preparation this was done using the soxhlet extractor. the soxhlet extractor is a piece of laboratory apparatus designed for the extraction of a lipid from a solid material. typically, a soxhlet extractor is used when the desired compound has a limited solubility in a solvent. the solvent, methanol was heated to reflux. the solvent vapor then travels into a distillation arm and floods a chamber housing the thimble of powdered guava leaves. the condenser ensures that the solvent vapor cools and drips back the chamber housing the solid material. after this, the liquid obtained was then dried using an evaporating dish (udom et al., 2017; omoruwou et al., 2017). 2.6 corrosion tests 2.6.1 gravimetric-based mass loss test at this stage, the 10 coupons were divided into two parts of 5 coupons each. 5 of the coupons were taken to the corrosion lab and a sample of 0.5m hcl was prepared from the acid medium. the 0.5m hcl solution was then divided into 5 beakers of 50 ml each. thereafter 2g of powdered guava leaf http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 533-539. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 535 extract was weighed and poured into each beaker. varying concentration of 0.0, 2.0, 4.0, 6.0 and 8.0%v/v of the inoculant triethylamine was then added into the various beakers and the solution was stirred using a rubber spoon. the initial weight of each coupon was measured and recorded prior to immersion in the solution. the coupons were then kept for 24hrs, 48hrs, 72hrs and 96hrs time intervals after which they were washed with distilled water and consequently weighed (umaru et al., 2013). 2.6.2 potentiodynamic polarization test the potentiodynamic polarization and linear polarization resistance was used to characterize the corrosion rate of the multilayered mild steel/al-cr plates in 0.5m hcl (200ml) solution containing 2g of guava leaf extract and inoculant of concentrations; 0.0, 2.0, 4.0, 6.0 and 8.0%v/v. a potentiostat coupled to a computer system, a glass corrosion cell kit with a platinum counter electrode, a saturated ag/ag reference electrode and multilayered mild steel/al-cr plates as working electrode were used. the working electrode specimens were positioned at the glass corrosion cell kit, leaving 1��� surface in contact with the solution. polarization test was carried out in the 0.5m hcl/guava leaf extract with variation in concentration of inoculant at room temperature using the potentiostat. the polarization curves were determined by stepping the potential at a scan rate of 0.001v/sec. the polarization curves were plotted using autolab data acquisition system and both the corrosion rate and potential were estimated by the tafel extrapolation method. the data obtained was used to calculate the protection efficiency (ie) for the inoculant using equation 4 and corrosion rates were calculated using equation 1 respectively (adams, 2014; umaru et al., 2017). 2.7 measurement of corrosion rates there are three main methods used to express corrosion rates (umaru et al., 2017) a. thickness reduction of the material per unit time. b. weight loss per unit area and unit time. c. corrosion current density. adt kwr  (1) where: r= corrosion rate k= corrosion constant a= surface area in ��� w=weight loss in grams d= density of material t= time of exposure in hours for this case, corrosion rate is taken in 2/ /g cm hr (2) the coupons used are cuboids in cross section, their surface area was calculated using; surface area 2 2 2lw lh hw   (3) where l is length, w is width and h is thickness. protection efficiency is given by; p.e = �t���t �t� (4) where �t� polarization resistance in presence of inoculant/corrosion rate at certain inoculant concentration pr is polarization resistance without inoculant/corrosion rate in absence of inoculant http://www.azojete.com.ng bawa et al.: effect of inoculant on the degradation behaviour of multi layered mild steel/al-cr plate in psidium guajava leaf extract. azojete, 14(4):433-439. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 536 3. results and discussion 3.1 gravimetric measurement result showing variation of corrosion rate with inoculant the figure 1 below shows the variation of corrosion rates with immersion time at room temperature for different concentrations of inoculant in 0.5m of hcl/guava leaf extract medium. it shows that the corrosion rates decrease as the concentration of the inoculant increases (adams et al., 2014). figure 1: variation of corrosion rates with time for different inoculant concentration. the sample in 8.0%v/v concentration of inoculant showed excellent corrosion resistance. similar trend was observed for samples in 6.0, 4.0 and 2.0%v/v concentration of inoculant. for example, the corrosion rate decreased from 0.01260mm/yr. to 0.00990mm/yr. in immersion time of 72hrs. the significant decrease in corrosion rate at increased inoculant concentration can be attributed to the adsorption of inoculant molecules on multilayered mild steel/al-cr alloy surface which act as physical barrier to restrict the diffusion of ions to and from the alloy surface and prevent the alloy atoms (ions) from precipitating in further anodic or cathodic reactions, hence resulting in a decrease in corrosion rate (abdulwahab et al., 2013). 3.2 potentiodynamic polarization result in the potentiodynamic polarization for multilayered mild steel/al-cr plates in 0.5m hcl/guava leaf extract environment (table 3), different measurements consisting of potentiodynamic polarization corrosion rate, potentiodynamic polarization corrosion density (pp-jcorr), and linear polarization resistance (lpr) were used as a criteria for evaluation of corrosion resistance of multilayered alcr/mild steel plates in the environment. generally, the studies showed a decrease in corrosion rates with the addition of triethylamine as an inoculant. the corrosion potential and polarization decreased except at 4.0%v/v concentration indicating that triethylamine affects the cathodic reaction. the increase in rp and corresponding decrease in jcorr generally suggested an improvement in corrosion resistance of the alloy in the presence of inoculant. this shows that the alloy was protected within the immersion time considered (adams et al., 2014). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 533-539. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 537 figure 2: potentiodynamic polarization curves for multilayered mild steel/al-cr plates in 0.5m hcl solution and guava leaf extracts in absence and presence of different concentrations of triethylamine (tea) as inoculant. the inoculant showed high protection efficiency values of up to 98.49% at 4.0%v/v concentration. in the absence of the inoculant, i.e. the control medium at 24hrs the corrosion rate was 0.1145mm/yr. while at the same immersion time in 4.0%v/v of inoculant, the corrosion rate decreased to 0.01500mm/yr. 3.3 protection efficiency the results from the histogram showed that triethylamine had its highest protection efficiencies in both gravimetric and potentiodynamic polarization methods at inoculant concentration of 4%v/v in the 0.5m hcl/guava leaf medium. figure 3: variation of protection efficiency with inoculant concentration for gravimetric based mass loss test and potentiodynamic polarization test. http://www.azojete.com.ng bawa et al.: effect of inoculant on the degradation behaviour of multi layered mild steel/al-cr plate in psidium guajava leaf extract. azojete, 14(4):433-439. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 538 in potentiodynamic polarization studies, triethylamine showed up to 98.49% efficiency at concentration of 4%v/v while in gravimetric methods, triethylamine showed up to 59.02% protection efficiency at 4%v/v inoculant concentration. 4. conclusion the result showed that the inoculant, triethylamine (tea) decreased the corrosion rate at the various concentrations indicating protection efficiency up to 59.02% in the gravimetric based mass loss technique. the potentiodynamic polarization technique indicates higher corrosion resistance of 98.49%. finally, the two methods used for the evaluation of the degradation of multilayered mild steel/al-cr plates in 0.5m hcl/guava leaf extract medium were in agreement. reference abdulwahab, m., kasim, a. yaro, sa, fayomi, osi. umaru, ob. 2013. effect of avogadro oil as corrosion inhibitor of thermally pre-aged al-si-mg alloy in sodium chloride solution. silicon-springer, 5 pp. 225-228. abdulwahab, m., sani, lm. yaro, sa and umaru, ob. 2015. inhibitive effect by psidium guajava leaf extract on the corrosion of al-si-mg (ssm-hpdc) alloy in simulated seawater environment. journal of association of metallurgical engineers of serbia, 21 (4), pp. 241-251. abosrra, l., ashour, af. mitchell, sc. and youseffi, m. 2009. corrosion of mild steel and 316l austenitic stainless steel with different surface roughness in sodium chloride saline solutions. journal of transaction on engineering sciences, 65 pp817-820. adams, sm., yaro, sa. abdulwahab, m. umaru, ob. 2014. corrosion inhibition study of al-cu-ni alloy in simulated seawater environment. nigerian journal of technological development, 12 (1) pp. 6-11. amitha, rbe. and bharathi, bjb. 2011. green inhibitors for corrosion protection for metals and alloysan overview. international journal of corrosion, 2(1) pp. 48-60. atama, eo. 2005. formation of effective passivation for 2000cc peugeot automobile engine cooling water. journal of corrosion science and technology, 3 pp. 14. umaru, ob., abdulwahab, m. asuke, f. adediran, m. ariyo, ma. and umar, y. 2017. effect of guava leaf extract on the hardness and corrosion resistance of thermally conditioned al-si-mg alloy, nigerian journal of engineering, 24 (1) pp. 49-57. wannik, wb., sulaiman, o. fadhli, a. rosliza, r. 2010. corrosion behaviour of aluminium alloy in seawater, the international conference on marine technology, 12th -15th june dhaka, bangladesh. pp. 11-12. umaru, ob., abdulwahab, m. yaro, sa. fayomi, osi. 2012. effect of pre-ageing parameters on the hardness characteristics of double thermally aged sodium-modified a356.0 type al-si-mg alloy. journal of metallurgical and materials engineering, vol.7 no.1 pp. 34-40. idu, hk., nwofe, pa and idenyi, ne. 2015. investigations on the inhibitory properties of moringa oleifera and psidium guajava leaf extract on the corrosion susceptibility of mild steel. middle east journal of scientific research, 23 (12) pp. 2862-2867. umaru, ob., abdulwahab, m. hafsat, nm. maidawa, h. murtada, ao. and suleiman, tm. 2016. influence of a low temperature ageing on the properties of al-6.5%si-0.35%mg alloy. nigerian journal of technology 35 (3) pp. 550–554. mohammed, aa and dong, bl. 2016. effect of al-hot dipping on high-temperature corrosion of carbon steel in n2/0.1% h2s gas. journal of metals, 6(2) pp. 38-39. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 533-539. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 539 udom, gi., cookey, ga. abia, aa. 2017. the effect of acanthus montanus leaves extract on corrosion of aluminium in hydrochloric acid medium. current journal of applied science and technology, 25 (2) pp. 1-11. omoruwou, f., okewale, ao. owabor, cn. 2017. statistical analysis of corrosion inhibition of water hyacinth on mild steel in an acidic medium. journal of environmental and analytical toxicology, 7 (4) pp. 56-59. peabody, aw. 2001. control of pipeline corrosion. national association of corrosion engineers publishers, houston texas, second edition, pp. 10-13. umaru, ob., abdulwahab, m. yaro, sa. asuke, f. fayomi, osi. 2013. influence of pre-ageing thermal condition on the corrosion characteristics of a356.0 type al-si-mg alloy. international conference on sustainable manufacturing and operations management, university of mauritius, 26-28th june, giap publishers’ pp. 86-92. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):763-772 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 763 original research article corrosion inhibition of mild steel determined using blended bitter leaf (vernonnia amygdalina) extract and honey in dilute h2so4 and hcl acid solutions m. a. abba-aji, a. b. muhammad and d. d. onwe department of mechanical engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: birma4real2004@yahoo.com 1.0 introduction corrosion is a menace that has plagued engineering structures and systems. corrosion has remarkably caused severe damage to metallic components or parts such as automobile parts, pipelines, machine parts and lots of others exposed to moisture (rain water) and air. electrochemical process is set up, causing carbon dioxide (co2), or sulphuric oxide (so2 or so3) to react with the water to form trioxocarbonate (iv) acid, or sulphuric acid respectively (raja et al., 2008). corrosion is a contributing factor to economic losses and pollution of our environments. many manufacturing industries such as automobile industries have spent hundreds of dollars on aftermarket corrosion protection for new automobiles to delay the dreaded rust appearance (raja et al., 2008). bammou et al. (2018) worked on the development of cheap, nontoxic and environmentally friendly natural products as corrosion inhibitors to replace the inorganic and synthetic inhibitors which are hazardous to the environment. the developed organic inhibitor will be a good replacement for the imported inorganic inhibitors. it could as well serve as a means of providing an alternative income to the population. the use of inhibitors is one of the most practical methods for protection against corrosion in acidic environments (bammou et al, 2018). different organic and inorganic compounds have been studied as inhibitors to prevent metals from corrosive attacks. the known hazardous effects of most synthetic organic inhibitors and restrictive environmental regulations have now made researchers to focus on the need to develop cheap, nontoxic and environmentally friendly natural products as corrosion inhibitors. usually, organic compounds that possess a significant influence on the extent of adsorption on the metal surface are used as effective corrosion inhibitors. article information abstract the inhibitive effect of bitter leaf extract (veronia amygdalina) and honey hybrid on the corrosion of mild steel in dilute h2so4 and hcl solutions was investigated using weight loss method. various concentrations of the leaf extract and honey (5 to 25ml), and immersion times (96 to 240hrs) were recorded at room temperature (32°c), which were used to calculate the corrosion rates and inhibition effects. inhibition was found to increase with increase in the inhibitor concentration. the inhibitive effect of honey as inhibitor on the corrosion of mild steel in dilute hydrochloric acid (hcl) solution with 54% efficiency and dilute h2so4 acid solution with 48.03% inhibition efficiency were not as effective as that of hybrid with 72.48% inhibition efficiency. the results obtained indicated that both bitter leaf extract and honey could serve as an effective inhibitor for the corrosion of mild steel in dilute h2so4 acid and dilute hcl solution. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 sept., 2019 revised 7 april, 2020 accepted 13 april, 2020. keywords: corrosion inhibitors hybrid and honey mild steel http://www.azojete.com.ng abba-aji et al: corrosion inhibition of mild steel determined using blended bitter leaf (vernonnia amygdalina) extract and honey in dilute h2so4 and hcl acid solutions. azojete,16(4):763-772. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 764 these natural organic compounds are either synthesized or extracted from aromatic herbs, spices and medicinal plants. plants extracts are viewed as incredibly rich sources of naturally synthesized chemical compounds that can be extracted by simple procedures with low cost and are biodegradable in nature. the use of these natural products such as extracted compounds from leaves or seeds as corrosion inhibitors have been carried out by many researchers (karthikaiseivi et al., 2018). mejeha et al., (2010) studied the inhibitive effect of solanum melongena l. leaf extract on the corrosion of aluminium in tetraoxosulphate (vi) acid. similarly, el-etre (2005) studied the corrosion inhibition of various metals like copper (cu), steel, nickel zinc and lawsonia extract. aditionally, oguzie (2008) studied the corrosion inhibition of leaf extracts of hibiscussabdariffa, occimumviridis, telferiaoccidentalis, and azadirachtaindica and as well as extracts from the seeds of garcinaia kola on mild steel corrosion in acidic solutions. different classes of organic compounds are used as corrosion inhibitors for metallic alloys in various acid media (abdel-aal et al., 2001, mthar et al., 2002, selvi et al., 2003; karthikaiseivi et al., (2018); noor, 2005; li et al., 2006, oguzie; 2008, nnanna et al, 2010, lebrini et al; 2011, loto et al;2012, yusuf et al; 2013, oloruntoba et al; 2015). most of these organic inhibitors are nitrogen, sulphur or oxygen containing compounds. the aim of this study is to investigate the corrosion inhibition of mild steel by vernonia amygdalina (bitter leaf) extract and natural honey, in dilute sulphuric acid and hydrochloric acid solution at room temperature using weight loss method. 2.0 materials and methods 2.1 materials and equipment the bitter leaf extraction was carried out in the department of chemical engineering, university of maiduguri, nigeria. the materials used were: fresh bitter leaf, 500ml ethanol, h2so4 m&b, 98%ar grade, hcl m&b, 98%ar grade, mortar and pestle, digital weight balance, measuring cylinder (100mm), beaker (250ml), silicon carbide paper, soxhlet extractor, honey, distilled water, syringe, mild steel (aisi 1018), flat bottom flask (500ml) 2.2 methods 2.2.1 extraction and preparation of specimen 2.2.2 extraction procedure fresh bitter leaf (vernonia amygdalina), having a composition of soponin, tanin and flavonoid, were harvested, washed and pounded to reduce the particle size using mortar and pestle to enable the extraction process to be fast (farombi and owoeye, 2011). two hundred grams (200g) of the crushed bitter leaf was extracted against 500ml of ethanol for 6 hours. the extraction method adopted was astm d6405-99 as applied by farombi and owoeye, (2011). the 200g weight of the pounded bitter leaf was poured into the soxhlet extraction chamber containing 500ml of ethanol and heated to 60˚c, which was the boiling point of ethanol. the condenser condenses the vaporized ethanol and it falls into the sox let extraction chamber containing the crushed bitter leaf, therefore extracting the extract. the extract is a mixture of ethanol and the extract of the bitter leaf. this mixture followed the reflux tube and dropped into the flat bottom flask containing the ethanol as a mixture of ethanol and bitter leaf extract, after the extraction the mixture of ethanol and the bitter leaf extract in the flat bottom flask was separated using distillation process to get the pure extract. after the distillation, the extract was poured in a beaker and allowed to cool down so as to allow any remaining ethanol in the extract to escape as the extract was exposed to the atmosphere leaving behind the pure bitter leaf extract. 2.2.3 preparation of specimen the set up for this study were twenty four (24) coupons of mild steel plate of dimension 4cm x 3cm for each as shown in figure 1, is in agreement with the work of bammou et al., (2018) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):763-772. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 765 with density of 7.85g/cm3, young’s modulus of 210gpa and the weight of each coupon is 6.10g. the chemical composition of the mild steel is shown in table 1. the samples were polished using silicon carbide paper of grades 60 to 220 respectively. the coupons were rinsed with ethanol and dried at room temperature. ethanol was selected based on its industrial and economic usage. table 1: chemical composition of mild steel coupon the sheared coupons for the experiment are shown in figure 1 figure 1: sheared coupons for the experiment. 2.2.4 experimental procedure the experiment was conducted following the procedures adopted by bammou et al., (2028), with specimens sheared from mild steel of chemical composition as shown in figure 1, having a surface area of 12cm2. different solution of tetraoxosulphate (vi) acid (h2so4) and hydrochloric acid (hcl), seventy five millilitre (75ml) of the hcl was used to prepare an acid solution of 150ml of 1 molarity in 900ml of solution of 150ml from 900ml of distilled water. the mild still plates were all weighed; the beakers to which were inserted, were all labelled to differentiate them (astm). 150ml of the diluted h2so4 and dilute hcl were poured separately into six 250ml beakers; this volume was kept constant for all beakers. the mild steel plates were each tied with a string to a small stick that will enable them suspend when placed across the mouth of the beaker. different concentration of 5ml, 10ml, 15ml, 20ml, and 25ml of the inhibitor (honey and bitter leaf extract in the ratio of 50:50) were poured into the diluted acid in the beakers, honey was also used separately in the concentration of 5ml, 10ml 15ml 20ml and 25ml as inhibitor in both acid(dilute h2so4 and dilute hcl). previously weighed coupons were each suspended in each of the beakers of capacity 250ml via a string at room temperature. the first set of coupons were retrieved from their corrosive environments after 48hours (two) days. this was followed by the second, third, fourth and fifth sets being retrieved at intervals of 96, 144, 192 and 240 hours immersion time respectively. at each interval, the coupons were mechanically brushed and rinsed in 34.4% ethanol to remove the corrosion product on the surface of the coupon, the coupons were allowed to dry and their weights were taken and recorded. the weight loss (w0-w1) for each of the specimen was obtained by finding the difference between the final (w1) and initial weight (w0) and recorded as weight loss. figure 2 presents the experimental setup for honey inhibitor. steel % composition mild steel c mn si p s fe 0.16 0.30 0.21 0.04 0.03 99.257 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abba-aji et al: corrosion inhibition of mild steel determined using blended bitter leaf (vernonnia amygdalina) extract and honey in dilute h2so4 and hcl acid solutions. azojete,16(4):763-772. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 766 figure 2: experimental setup for honey (inhibitor) figure 3: experimental set up for honey and bitter leaf (inhibitor) 2.3 experimental analysis the following test and analysis were carried out using bitter leaf extract and honey as an organic inhibitor on mild steel. 1. weight loss, in gram 2. corrosion rate, in mm/day 3. inhibition efficiency (ie), in % (fontana, 1994) 2.3.1 weight loss and corrosion rate weight loss method was used to determine the corrosion rate of the coupons using two different inhibitors separately. the mixture of bitter leaf extract with honey as inhibitor and that of honey alone was considered. the corrosion rate was calculated from weight loss of the coupons at room temperature (32°c) at various concentrations and immersion time, using the relation due to fontana (1994) as presented in equation 1 mm day=87.6w ρat (1) the weight loss can be determined using equation 2 as: wl = wb−wa s (2) where: wb and wa are weights before and after immersion, s = total surface area of the specimen (mild steel) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):763-772. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 767 2.3.2 inhibition efficiency (ie) the inhibition efficiency of the organic inhibitor (bitter leaf extract with honey and honey alone) was calculated from weight loss measured at different inhibitor concentration at 32°c (room temperature). the percentage of inhibitor efficiency (ie) was calculated using equation (2). ie = crun−crin crun × 100 (3) 3.0 results and discussion 3.1 corrosion rate the corrosion rates of the uninhibited and inhibited as a function of inhibition concentration were observed. the inhibition efficiency increases with increase in inhibitor concentration from 5ml to 25ml. corrosion rate for uninhibited mild steel in h2so4 experienced a decrease from the beginning of the experiment to the 25ml inhibitor concentration. it was observed that weight loss also decreases as the immersion time increases in the uninhibited acid and the inhibited acid solution. this could be attributed to the presence of dissolved air as represented by the reaction: fe→fe2+ + 2e(4) 2h2o + o2+ 4e-↔ 4oh(5) this type of corrosion can, therefore, be controlled by: 1. eliminating oxygen from the corroding medium, or 2. retarding the diffusion to the cathode areas (palanna, 2009). the corrosion rate of the inhibited coupons showed a sharp decrease in corrosion rate and becomes constant as immersion time increases. as shown in figure 4, corrosion rate of the uninhibited coupon decreases with time. the sharp decrease in the corrosion rate of the inhibited acid solution was as a result of the alteration (passivation) in the mechanism of corrosion due to the presence of inhibitor as confirmed by rosliza (2010) and also because the exposure time under investigation falls within the active region of corrosion for these materials as reported by orthorho et al (2017). 3.2 inhibition efficiency hybrid inhibition efficiency in h2so4 solution inhibition efficiency in control solutions are always zero. the number for beakers for each inhibitor is six including that of the control solution. inhibition efficiency at 48 hours = 0 + 43 + 44 + 45 + 48 + 51.6 6 = 31.5% inhibition efficiency at 96 hours = 0 + 40 + 40 + 40 + 42 + 48.3 6 = 35.05% inhibition efficiency at 144hours = 0 + 59 + 60 + 62 + 66 + 69 6 = 52.67% inhibition efficiency at 192hours = 0 + 76 + 79 + 80 + 84.2 + 93.2 6 = 68.7% inhibition efficiency at 240hours = 0 + 83 + 84 + 85 + 87.2 + 95.7 6 = 72.48% file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abba-aji et al: corrosion inhibition of mild steel determined using blended bitter leaf (vernonnia amygdalina) extract and honey in dilute h2so4 and hcl acid solutions. azojete,16(4):763-772. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 768 figure 1 shows a plot of the inhibitor efficiency against concentration (i.e. using the hybrid inhibitor). from the figure, it was observed that the inhibitor efficiency increased with increase in inhibition concentration. figures 1, 2 and 3, show the representations of the uninhibited and inhibited solutions of the mixture of honey and bitter leaf extract (hybrid) as the inhibitor at various concentration of 5ml, 10ml, 15ml, 20ml and 25ml in dilute h2so4 solution. figures 4, 5 show the behaviour of the mild steel plate in dilute hydrochloric (hcl) acid solution in the presence of the inhibitor (hybrid). 5 10 15 20 25 30 40 50 60 70 80 90 100 in h ib it io n e f f ic ie n c y (% ) inhibition concentration (ml) in 1m h2so4 48hrs 96hrs 144hrs 240hrs figure 1: inhibition efficiency against inhibitor concentration of hybrid 5 10 15 20 25 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 inhibition concentration (ml) in 1m h2so4 w ei g h t lo ss (g ) 48hrs 96hrs 144hrs 192hrs 240hrs figure 2: weight loss against inhibitor concentration of hybrid http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):763-772. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 769 4 6 8 10 12 14 16 18 20 22 24 26 0 0.005 0.01 0.015 0.02 0.025 inhibition concentration (ml) in 1m h2so4 c o r r o s io n r a t e ( m m /d a y) 48hrs 96hrs 144hrs 192hrs 240hrs figure 3 corrosion rate against inhibitor concentration of hybrid 5 10 15 20 25 35 40 45 50 55 60 65 inhibition concentration (ml) in 1m hcl in h ib it io n e f f e ic ie n c y ( % ) 48hrs 96hrs 144hrs 192hrs 240hrs figure 4: inhibition efficiency against inhibition concentration of hybrid file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abba-aji et al: corrosion inhibition of mild steel determined using blended bitter leaf (vernonnia amygdalina) extract and honey in dilute h2so4 and hcl acid solutions. azojete,16(4):763-772. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 770 5 10 15 20 25 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 inhibition concentration (ml) in 1m hcl w e ig h t l o s s ( g ) 48hrs 96hrs 144hrs 192hrs 240hrs figure 5: weight loss against inhibition concentration of hybrid the result of the corrosion rates and weight loss of mild steel in bitter leaf extract and honey for different mixture of coupon, 5, 10, 15, 20, and 25ml inhibitor concentration for dilute h2so4 and dilute hcl solution were observed. figure 3 shows plot of weight loss as a function of inhibition concentration of h2so4. figure 4 shows the corrosion rate as a function of concentration of h2so4. consequently, the plot of corrosion rates as a function of time, weight loss as a function of immersion time and also the plot of corrosion rates as a function of time for hcl concentration are shown in figure 5 and figure 6. the inhibition efficiency is optimum at 240 hours, and is 72%, similarly inhibition efficiencies for hybrid and honey in hcl and h2so4 were presented in table 1 table 1: inhibition efficiencies of honey and hybrid (bitter leaf/ honey) in h2so4 and hcl time (hours) hybrid in h2so4 hybrid inhibition in hcl honey inhibition efficiency in h2so4 honey inhibition efficiency in hcl 48 31.50 33.35 27.16 32.33 96 35.05 42.47 30.33 36.67 144 52.67 43.67 32.23 38.38 192 68.70 47.97 43.33 48.47 244 72.48 51.67 48.03 54.13 as the concentration of inhibitor produced increases, the corrosion rate decreases and the inhibitor has the highest efficiency of 72% while in dilute h2so4 solution, which is in agreement with mejeha et al, (2010), it has an inhibition efficiency of 52% in dilute hcl.. honey has an inhibition efficiency of 48% in dilute h2so4 solution and 54% n dilute hcl solution, which proved that the hybrid inhibitor in tetraoxosulphate (vi) acid solution is effective and its usage in automobile industries will reduced drastically the corrosion rate. 4.0 conclusion this study has shown that hybrid of honey and bitter leaf extract can be used as corrosion inhibitor. in this work, honey as an inhibitor alone is more effective in hydrochloric acid solution than in tetraoxosulphate (vi) acid solution. similarly, bitter leaf extract can be used to upgrade honey in the prevention of corrosion in tetraoxosulphate (vi) acid environment. the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):763-772. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 771 inhibitor has a characteristic which indicated an increase in concentration of inhibitor resulted in a significant decreased corrosion rate with inhibitor efficiency of 72% while in dilute hcl solution, it has an inhibition efficiency of 52%. honey has an inhibition efficiency of 48% in dilute h2so4 solution and 54% in dilute hcl solution, which proved that the hybrid inhibitor in tetraoxosulphate (vi) acid solution is effective and it’s usage in automobile industries will remarkably reduce corrosion rate. recommendation bitter leaf extract and honey are eco-friendly, acceptable and poses no threat to the environment as the chemical and synthetic inhibitors, as such should be used for corrosion inhibition. if bitter leaf extract and honey are adopted as corrosion inhibitor, it will increase the gross domestic product (gdp) of our country hence the standard of living will be improved and it will help our environment to be less prone to pollution. references abdel-aal, ms. and morad, ms. 2013 inhibiting effects of some quinolines and organic phosphonium compounds on corrosion of mild steel in 3m hcl solution and their adsorption characteristics. 36(4):253-260. bammou, l., belkhouda m., salghi, r., benali, o., zarouk, a., zarouk, h. and hammouti, b. 2018. corrosion inhibition of steel in sulphuric acidic solution by the chenopodium ambroswides extract. journal of association of arab universities for basic and applied sciences, l6(1): 83-90. el-etre, ay., abdallah, m. and el-tantawy, ze. 2005. corrosion inhibition of some metals using lausonia extract. corrosion science, 47(2): 358-395. farombi, eo. and owoeye, o. 2011. anti-oxidative and chemo-preventive properties of vernonia amygdalina and garcinia biflavonoid. international journal environmental research and public health, 8(6): 2533–2555. fontana, mg. 1994. corrosion engineering, third edition, mcgraw-hill, new york. karthikaiselvi, r. and subhashini, s. 2018. study of the absorption properties and inhibition of mild steel corrosion in hydrochloric acid media by water soluble composite polyvinyl alcoholomethoxy, journal of the association of arab universities for basic and applied sciences,16(1):74-82. li, x., tang, l., li, l., mu. g. and li, g. 2006. synergistic inhibition between o-phenanthroline and chloride ion for steel corrosion in sulphuric acid. corrosion science, 48(2):308-321. lebrini, m., robert, f. and roos, c. 2011. alkaloids extract from palicourea guianensis plant as corrosion inhibitor for c38 steel in 1 m hydrochloric acid medium. international journal of electrochemical science, 6(1): 847-859. loto, rt., loto, ca. and popoola, api. 2012. corrosion inhibition of thiourea and thiadiazole derivatives: a review. journal of materials and environmental science, 3(5): 885-894. moretti, g., quartarone, g., tassan, a. and zingales a. 1996. 5-aminoand 5-chloro-indole as mild steel corrosion inhibitors in 1n sulphuric acid. electrochemical acta, 41(13): 1971-1980. mthar, mh., ali, h. and quraishi, ma. 2002. corrosion inhibition of carbon steel in hydrochloric acid by organic compounds containing heteroatoms. br. corrosion journal. 37(2): 155-162. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abba-aji et al: corrosion inhibition of mild steel determined using blended bitter leaf (vernonnia amygdalina) extract and honey in dilute h2so4 and hcl acid solutions. azojete,16(4):763-772. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 772 mejeha, au., okeoma k. and alozie, g. 2010. the inhibitive effect of solanum melongena l. leaf extract on the corrosion of aluminium in tetraoxosulphate (vi) acid. african journal of pure and applied chemistry, 4(8): 158-165. nnanna, la., onwuagba, bn., mejeha, im. and okeoma, kb. 2010. inhibition effects of some plant extracts on the acid corrosion of aluminium alloy. african journal of pure and applied chemistry, 4(1): 11-16. noor, ea. 2005. the inhibition of mild steel corrosion in phosphoric acid solutions by some nheterocyclic compounds in the salt form. corrosion science, 47(1): 33. oguzie, ee. 2008. corrosion inhibitive effect and adsorption behaviour of hibiscus sabdariffa extract on mild steel in acidic media. portugaliae electrochimica acta, 26(3): 303-314. oloruntoba, dt., popoola, api. and falokun, da. 2015. investigation on water plant extract as a corrosion inhibitor for automobile engine and industry. african corrosion journal, 1 (2): 9-15. palanna, og. 2009. engineering chemistry, published by tata mcgraw hill education private limited; 7 west nagari, new delhi. orhorhoro, ek., oyiboruona, pe. and ikpe, ae. 2017. investigation and evaluation of the corrosion inhibition properties of water hyacinth extract on low carbon steel. international journal of energy engineering research and technology, 5(12): 45-50. raja, pb. and sethuraman, mg. 2008. natural products as corrosion inhibitor for metals in corrosive media: a review. materials letters, 62(4): 113-116. rosliza, r., wan sani, wn., izman, s. and yunan, p. 2010. study on the effect of vanillin on the corrosion inhibition of aluminium alloy. journal of applied electrochemistry, 40(4): 833-840. selvi, st, raman, v. and rajendran, n. 2003. corrosion inhibition of mild steel by benzotriazole derivatives in acidic medium. journal of applied electrochemical. 33(2):1175-1182. yusuf, ta., gundu, dt., oseni, mi., bolaji, bo. and ismaila, so. 2013. evaluation of corn water for corrosion inhibition extract. international journal of engineering and science, 2(8): 31-35 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(1):121-140 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 121 original research article new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method f. c. onyeka1 and t. e. okeke2* 1department of civil engineering, edo university, iyamho. edo state, nigeria. 2department of civil engineering, university of nigeria, nsukka, enugu state, nigeria *corresponding author’s email address: onyeka.festu@edouniversity.edu.ng 1.0 introduction a plate isdescribed as structural components with thickness smaller than its surface dimensions (shwetha and subrahmanya (2018). plates have been widely applied in aerospace engineering, structural and mechanical engineering, etc., in building and constructing many engineering structures and elements like aircraft wings, ships, buildings, bridges, roof, retaining walls, railways, turbine disks etc. (onyechere et al., 2020; ozioko et al., 2019; onyeka et al., 2018). plates have been classified based on thickness (t) as; thin and thick plates (chandrashekhara 2001). the edges of plate can have different support conditions which can be fixed, simply supported, point, etc. there has been a great deal of research on bending analysis of plates from various scholars using theorems with different boundary support conditions. it is the depth of plate that mainly affects the bending properties of plate compared with its other dimensions like the length and width (gujar and ladhane, 2015; ibearugbulem et al., 2013). the analysis of plates involves finding the normal and shear stresses, displacement, moments etc., at different points of the plate and it is necessary as it helps to ascertain the plate stability and ability to withstand design loads (roknuzzaman, 2015). the loads which are either static or dynamic carried by plates are mostly perpendicular to the faces of the plate, and the load carrying capacity of the plate is similar to that of beams as a structural element. plate theory generally known as the classical plate theory (cpt) is commonly used in the analysis of thin plates. the cpt was formulated by kirchhoff (1985) and was applied by timoshenko and article information abstract this study presents the application of a new refined plate theory in the bending analysis of a thick rectangular plate carrying a uniformly distributed load using the direct energy method. the new refined plate theory which is a combination of trigonometric shear deformation theory and fourth order polynomial displacement function was used to formulate the governing differential equation by employing the principle of elasticity. the total potential energy equation of a thick plate was formulated from the constitutive relations thereafter the three general governing differential equations for the determination of the deflection and shear deformations rotation along the direction of x and y coordinates were obtained. the coefficient of deflection and shear deformation were derived by subjecting the energy equation obtained to direct variation thereafter the actual deflection, in-plane displacement, normal and shear stresses, moment and stress resultants of the rectangular thick plate were determined by substituting the derived coefficient of coefficient of deflection and shear deformation into the displacement, shear force, moment and stresses deduced. the particular plate boundary condition to be anlysed is free support at the third edge and the other three edges simply supported (ssfs). the result shows that thick plate is the one whose span-depth ratio value is 4 up to 25. the results obtained from this work was compared with those obtained from other refined plate theories with the same support condition and obtained showed good agreement with those in the literature © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 oct., 2020 revised 2 january 2021 accepted 8 january 2021 keywords: direct energy method trigonometric displacement function polynomial shear deformation new refined plate theories ssfs rectangular plate onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 122 woinowsky (1959) and liessa (1973) for the analysis of plates and shells. the cpt theory, which does not address shear deformation transversely as seen in the thin plate, is based on the assumption that the normal to the mid-surface remains normal before and after deformation. due to the non-inclusion of transverse shear strains or deformation in cpt, it has been found to be inadequate in the analysis of thick plates (ibearugbulem et al., 2016). to address the short fall in the cpt, researchers formulated the refined plate theory (rpt). this includes, the first order shear deformation theory (fsdt) (reissner, 1945; hoang et al., 2019), second order shear deformation theory (ssdt) and the higher order shear deformation theories (hsdt) which considers transverse shear deformation (sayyad et al., 2017), in the analysis of plates, using different functions like: trigonometric, exponential, polynomial. aghdam and vafa (2004) researched on bending solutions of rectangular thick plates by the application of the extended kantorovich method (ekm). the ekm involves eight unknowns which were solved using governing equations based on reissner fsdt. they concluded that the application of ekm in the thick plate’s analysis was fast and gave similar results for plates analyzed by finite element method (fem). sayyad (2013) worked on the flexural analysis of orthotropic thick plates using refined plate theory which takes into account transverse shear deformation effect. they obtained the in plane displacement field using an exponential function which was based on broadness coordinate, the transverse shear stress directly from the constitutive without the need for shear correction factor, while the governing equations and boundary conditions were based on the virtual work principle. the results of the displacements, stresses, and frequencies obtained, when compared with results from other plate theory and exact theory were found to be adequate. ghugal and gajibhiye (2016) did a study on the analysis of thick isotropic plates in rectangular relation to bending with simply supported supports using a form of higher order shear deformation theory (hsdt). they obtained the transverse normal strain deformation effect, and the proposed displacement field which accounted for non-linear variation of in-plane displacements, stresses and the transverse displacements with the plate thickness without the need for correction factor which is seen in fsdt. the numerical results which include static flexure analysis were done with matlab programming and with the results agreed with other hsdt and exact 3d elasticity solutions. sayyad et al. (2015) worked on thermos-elastic bending examination of laminated plates with matrix reinforced materials, simply supported on all four edges and acted upon by a heat related loads changing linearly with the plate’s depth according to various shear deformation theories. they investigated thermal related deformations using a combined approach that involved different functions in relation to thickness coordinate and shear deformation effects. the displacements and stresses they predicted by psdt, tsdt, and hsdt were similar with each other, but fsdt gave higher results of in-plane normal stress compared to other. zhong and qian (2017) worked on the bending analysis of thick plate with geometry and with all ends clamped (cccc) at supports. they used governing equations derived from the mindlin’s plate theory for their analysis. they found out that their proposed method of analysis eliminates the complex derivation for obtaining coefficients and gave accurate results. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 123 ibearugbulem et al. (2018) did a study on the analysis of rectangular thick plate in relation to bending with all the plate’s supports clamped (cccc) by applying polynomial shear deformation theory (psdt). they used a theory formed from ritz energy method with a displacement function relating to a polynomial function in their analysis. they obtained the transverse shear stress without the need for shear correction factor, with the total potential energy equation formulated from the principle of electricity. they concluded their study by comparing their results for: displacements and stresses with other studies, and found out that there were similarities. eze et al. (2018) investigated the use of shear deformation theory in analyzing rectangular isotropic thick plate with two different boundary conditions. they derived a theory for determining shear deformation without the need for correction factor, and displacement coefficients by using total potential energy in direct variation on the boundary conditions of: simply support at the third edge with other three edges clamped (cccs) and fixed at the third edge with other three edges simply supported (ssfs) respectively. the results they obtained were satisfactory results when compared with results from other studies. onyeka and edozie (2020) analyzed the moments and stresses of thick rectangular plate with clamped at three edges and simply supported at the remaining one edge (cccs) and subjected to uniformly distributed load, using third order shear deformation theory by formulating the total potential energy equation. their formulated theory which didn’t put shear correction factor into consideration gave mathematical expressions for the determining maximum deflection, moment, stresses and in-plane displacements. their theory was error free when they carried out numerical comparism with other studies. literatures reveals that there have been a lot of research efforts by many researchers on the bending analysis of plates using different shear deformation theories based on different mathematical functions and not energy method in determining the bending effects of thick plate that are rectangular in nature with support conditions of different kinds. this study is aimed at addressing this gap in literatures by presenting a new refined plate theories (nrpt) using energy method to obtain the deflection, moment, stress, in – plane displacements of thick plate with rectangular geometry under uniformly distributed loads with free support at the third edge and the other three edges simply supported (ssfs). this nrpt circumvent the use of shear correction factor which is associated with first order shear deformation theory. 2. materials and methods following the sketch as presented in figure 1 and the assumption made as shown below, the governing equation of thick plate under pure bending is made. figure 1: a rectangular thick plate element carrying a uniformly distributed load onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 124 2.1. assumptions considering the following assumptions, the general governing equation of a thick rectangular plate will be formulated. they include: i. the material of the plate is homogeneous, isotropic and elastic. ii. the strain and stress normal to x-y plane is so small that it can be neglected. iii. the vertical line that is initially normal to the middle surface of the plate before bending is no longer straight nor normal to the middle surface after bending. 2.2. kinematics and constitutive relationships in the formulation of the kinematics and constitutive relation, the in-plane displacement components along x-axis and in-plane displacement components along y axis are derived by onyeka et al. (2020) as presented in the equations (1) and (2) : let the shear deformation profile of plate section (s ) be: ( ) and; considering the assumptions in the previous section (assumption ii), the stress normal to the x-axes gives: similarly, the stress normal to the y-axes becomes: the curvature in x-z plane is defined as: the curvature in x-z plane is defined as: the curvature in x-z plane is defined as: the constitutive equations for five stress and strain components according to onyeka et al. (2020) includes: the normal stress along the direction of x-axes: ( ) the normal stress along the direction of y-axes: arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 125 ( ) the shear stress along (x-y), (x-z) and (y-z) respectively are given in the equation (1), (2) and (3) respectively as: where; substituting equation (1), (2), (4) and (5) into equation (9), we have: *( ) ( )+ substituting equation (1), (2), (4) and (5) into equation (10), we have: *( ) ( )+ substituting equation (1), (2) and (6) into equation (11), we have: * ( )+ substituting equation (1), (2) and (7) into equation (12), we have: * ( )+ substituting equation (1), (2) and (8) into equation (13), we have: * ( )+ 2.3. general energy equation the total potential energy expression , was formulated in accordance with the kinematics and constitutive relation in the previous section (onyeka et al., 2018). where: ∫ ∫ where w is the uniformly distributed load. ∭ thus: onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 126 ∫ ∫ [| ( ) ( ) ( ) | | ( ) ( ) ( )| | ( ) ( )| | ( ) ( ) | | ( ) ( ) ( ) | | ( ) |] ∫ ∫ 2.4. direct governing equation the direct variational approach was applied to obtain the direct governing differential equation by differentiating the total potential energy with respect to the coefficient of deflection , coefficient of shear deformation with respect to x-axis and coefficient of shear deformation with respect to y-axis . in non-dimensional form, let: where: deflection , is the product of shape function of the plate and deflection coefficient: where, is the shape function of the plate. similarly; the shear deformation rotation along x-axis becomes: [ ] [ ] similarly, the shear deformation rotation along y-axis becomes: [ ] [ ] by substituting equation 23, 24, 25, 26, 27 and 28 into 22, gives: arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 127 ∫ ∫ [| ( ) ( ) ( ) | | ( ) ( ) ( ) | | ( ) | | ( ) ( ) | | ( ) ( ) ( ) | | ( ) ( ) |] ∫ ∫ let: ∫ ∫ ( ) ∫ ∫ ( ) ∫ ∫ ( ) ∫ ∫ ( ) ∫ ∫ ( ) ∫ ∫ where the are the stiffness coefficients. therefore, differentiating the total potential energy with respect to the coefficient of deflection , coefficient of shear deformation with respect to x-axis and coefficient of shear deformation with respect to y-axis : these gives the three equations of equilibrium as presented in equation (29), (30) and (31): ∫ ∫ [ ( ) ( ) ( )] ∫ ∫ onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 128 ∫ ∫ * ( ) ( ) + ∫ ∫ * ( ) ( ) + the three equations of equilibrium is presented in matrix form as: [ ] [ ] * + let: ( ) ( ) ( ) ( ) ( ) ( ) ( ( ) ) solving the matrix in the equation (40), gives equation (50), (51) and (52): where: arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 129 2.5. displacement, stresses and stress resultant analysis of the plate the expressions for the moment , shear force , in-plane displacement , deflection and stress of isotropic rectangular thick plate were derived according to onyeka and edozie (2020) by substituting the values of as obtained from the previous section. substituting equation (50) into (26), gave: ̅ ( ) where: ̅ the bending moment along x-axes: ( ̅ * + * ̅̅ ̅ ̅̅ ̅ +) that is: ̅̅ ̅̅ where: ̅̅ ̅̅ ̅ * + * ̅̅ ̅ ̅̅ ̅ + where: ̅̅ ̅ ̅ ̅̅ ̅ ̅ the bending moment along y-axes: ( * + * ̅̅ ̅ ̅̅ ̅ +) that is: ̅̅ ̅̅ where: ̅̅ ̅̅ * + * ̅̅ ̅ ̅̅ ̅ + the shear force along x-axes: ( ̅ * + * ̅̅ ̅ ̅̅ ̅ +) that is: ̅̅̅̅ where: ̅̅̅̅ ̅ * + * ̅̅ ̅ ̅̅ ̅ + the shear force along y-axes: ( ̅ * + * ̅̅ ̅ ̅̅ ̅ +) onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 130 that is: ̅̅̅̅ where: ̅̅̅̅ ̅ * + * ̅̅ ̅ ̅̅ ̅ + the in-plane displacement along x-axes: [ ̅ ̅̅ ̅ ] ( ) the in-plane displacement along y-axes: [ ̅ ̅̅ ̅ ] ( ) the normal stress along x-axes: [[ ̅ ̅̅ ̅ ] [ ̅ ̅̅ ̅ ] ] the normal stress along y-axes: * * [ ̅̅ ̅ ] + [ ̅ ̅̅ ̅ ] + the shear stress along x-y axes: [ ̅ ̅̅ ̅ ̅̅ ̅ ] the shear stress along x-z axes: ̅̅ ̅ the shear stress along y-z axes: ̅̅ ̅ 2.6 numerical problem the particular shape function for rectangular plate with their respective boundary is shown in figure 2. figure 2: ssfs rectangular plate a 𝑸 𝑹 o s s s f b arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 131 considering figure 2, the numerical analysis of ssfs rectangular plate at various span-thickness ssfs rectangular plate was derived according to onyeka et al. (2019) as presented in equation 79: ( ) ( ) at at ( ) at at ( ) at ( ) substituting equations (80 to 84) into equation ( ) and solving gives the following constants: substituting the constants of equation (85) into equation gives; that is: ( ) recall from equation 26, that; therefore: and; ( ) therefore: ( ) 2. results and discussion the numerical results of stiffness coefficient of the plate as obtained from equation (30) to (35) are presented in the table 1. table 1: values of stiffness coefficient, s for various support (boundary conditions) table 2 contains the result of bending moment, shear force and their resultants of a square ssfs rectangular plate at different span to thickness aspect ratio. these numerical values were obtained from the equation (56) to (71). theory present (nrpt) ssfs 00 onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 132 studying the results as presented in the tables 2, it is shown that the non-dimensional out-ofplane displacement ( ), bending moment ( and shear force decreases as the span to thickness ratio increases. this decrease continue until failure occurs in the plate structure. this means that, the load that causes the plate to deflect also causes the plate material to bend simultaneously. it is observed that the value of deflection varies less as the span to thickness increase, this becomes constant and equal to the value of cpt at span to thickness ratio of 90. tables 2 to 5 show that the value of deflection ( ) decrease with increases in the value of the span-thickness ratio. it is also observed in the tables that the displacement (u, v and ) and stresses characteristics increase as the value of the length to breadth ratio increases. this means that, the in-plane displacement are functions of x, y and z as it vary with the plate thickness while the deflection is only a function of x and y and did not varies linearly with the thickness of the plate thickness. table 2: bending moments, shear force and stress resultants of ssfs plate for b/a = 1. 0 (m) ̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅̅̅ ̅̅̅̅ 4 0.010037 0.799188 0.430417 0.071685 0.151504 5 0.009371 0.799611 0.429855 0.063705 0.134751 6 0.009013 0.799846 0.429543 0.059413 0.125742 7 0.008798 0.799990 0.429352 0.056839 0.120340 8 0.008659 0.800084 0.429227 0.055174 0.116847 9 0.008564 0.800149 0.429141 0.054035 0.114458 10 0.008496 0.800195 0.429079 0.053221 0.112751 15 0.008336 0.800306 0.428932 0.051299 0.105579 20 0.008280 0.800345 0.428880 0.050628 0.105546 25 0.008254 0.800363 0.428856 0.050317 0.105530 30 0.008240 0.800373 0.428843 0.050149 0.105522 35 0.008231 0.800379 0.428835 0.050047 0.105517 40 0.008226 0.800383 0.428830 0.049981 0.105514 45 0.008222 0.800386 0.428826 0.049936 0.105511 50 0.008219 0.800387 0.428824 0.049903 0.105510 55 0.008217 0.800389 0.428822 0.049879 0.105509 60 0.008216 0.800390 0.428820 0.049861 0.105508 65 0.008215 0.800391 0.428819 0.049847 0.105507 70 0.008214 0.800391 0.428818 0.049836 0.105506 75 0.008212 0.800392 0.428817 0.049819 0.105506 80 0.008212 0.800392 0.428817 0.049819 0.105506 85 0.008212 0.800393 0.428817 0.049813 0.105505 90 0.008211 0.800393 0.428816 0.049808 0.105505 95 0.008211 0.800393 0.428816 0.049804 0.105505 100 0.008211 0.800393 0.428816 0.049800 0.105505 cpt 0.008211 0.800393 0.428816 0.049800 0.105505 arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 133 from table 3, it is shown that the non-dimensional displacement (u, v and ) characteristics decrease with increases in the value of the span-thickness ratio. it is also observed in the tables that the displacement (u, v and ) and stresses characteristics increase as the value of the length to breadth ratio increases. this means that, the in-plane displacement are functions of x, y and z as it vary with the plate thickness while the deflection is only a function of x and y and did not varies linearly with the thickness of the plate thickness. similarly, it was deduced that the normal stress and shear stress characteristics also decrease as the span-thickness ratio increases. it is also observed in the table 3 that the stresses characteristics ( )increase as the value of the length to breadth ratio increases. it is observed that, at span to thickness ratio between 4 and 30, the value of vertical shear stress along y and z axes varies between 0.007323 and 0.000128. these values of vertical shear stress turns to 0.0000934 and 0.0000115 at the span to thickness between 35 and 100 respectively. this value is as negligible as its equal to when corrected to 5 decimal places. the value becomes almost constant or equal to the value from cpt at span to thickness ratio of 100. tables 3 show that the non-dimensional displacement (u, v and ) characteristics decrease with increases in the value of the span-thickness ratio. it is also observed in the tables that the displacement (u, v and ) and stresses characteristics increase as the value of the length to breadth ratio increases. this means that the in-plane displacement are functions of x, y and z as it vary with the plate thickness while the deflection is only a function of x and y and did not varies linearly with the thickness of the plate thickness. similarly, it was deduced that the normal stress and shear stress characteristics also decrease as the span-thickness ratio increases. it is also observed in the table 3 that the stresses characteristics ( )increase as the value of the length to breadth ratio increases. in summary, there are two categories of rectangular plates. the plates whose vertical shear stress do not vary well from zero will be classified as thin plates because its value are almost equal to the value of the cpt. whereas, the plate whose transverse shear stress varies very much from zero is categorized as thick plates. therefore, the span-to-depth ratio for these categories of rectangular plates are: thick plate∶ , while thin plate: . this confirmation can be used to show the boundary between thin and thick plate (. thus, it can be deduced from this research work that thick plate is the one whose span-depth ratio value is 4 up to 30. onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 134 table 3: displacement and stresses of ssfs plate for length to breadth ratio of 1.0 ̅ ̅ ̅ ̅̅ ̅ ̅̅ ̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅ 4 0.010037 -0.013505 -0.005441 0.527400 0.283306 -0.113809 0.019409 0.007323 5 0.009371 -0.013067 -0.005254 0.510233 0.273845 -0.110005 0.012349 0.004653 6 0.009013 -0.012832 -0.005152 0.500997 0.268751 -0.107957 0.008549 0.003219 7 0.008798 -0.012691 -0.005092 0.495458 0.265694 -0.106727 0.006269 0.002360 8 0.008659 -0.012600 -0.005052 0.491875 0.263716 -0.105932 0.004794 0.001804 9 0.008564 -0.012537 -0.005026 0.489424 0.262363 -0.105388 0.003784 0.001424 10 0.008496 -0.012493 -0.005006 0.487674 0.261396 -0.104999 0.003064 0.001152 15 0.008336 -0.012387 -0.004961 0.483537 0.259111 -0.104080 0.001360 0.000511 20 0.008280 -0.012350 -0.004945 0.482093 0.258313 -0.103759 0.000764 0.000287 25 0.008254 -0.012333 -0.004938 0.481424 0.257944 -0.103610 0.000489 0.000184 30 0.008240 -0.012324 -0.004934 0.481062 0.257743 -0.103530 0.000340 0.000128 35 0.008231 -0.012319 -0.004931 0.480843 0.257622 -0.103481 0.000250 9.34e-05 40 0.008226 -0.012315 -0.004930 0.480701 0.257544 -0.103449 0.000191 7.18e-05 45 0.008222 -0.012312 -0.004929 0.480604 0.257490 -0.103428 0.000151 5.67e-05 50 0.008219 -0.012311 -0.004928 0.480534 0.257452 -0.103412 0.000122 4.60e-05 55 0.008217 -0.012309 -0.004927 0.480482 0.257423 -0.103401 0.000101 3.80e-05 60 0.008216 -0.012308 -0.004927 0.480443 0.257402 -0.103392 8.49e-05 3.19e-05 65 0.008215 -0.012308 -0.004927 0.480413 0.257385 -0.103385 7.23e-05 2.72e-05 70 0.008213 -0.012307 -0.004926 0.480389 0.257371 -0.103380 6.24e-05 2.34e-05 75 0.008212 -0.012306 -0.004926 0.480353 0.257352 -0.103372 4.78e-05 1.80e-05 80 0.008212 -0.012306 -0.004926 0.480353 0.257352 -0.103372 4.78e-05 1.80e-05 85 0.008212 -0.012306 -0.004926 0.48034 0.257344 -0.103369 4.23e-05 1.59e-05 90 0.008211 -0.012305 -0.004926 0.480329 0.257338 -0.103367 3.77e-05 1.42e-05 95 0.008211 -0.012305 -0.004926 0.480319 0.257333 -0.103365 3.37e-05 1.27e-05 100 0.008211 -0.012305 -0.004926 0.480311 0.257329 -0.103363 3.06e-05 1.15e-05 cpt 0.008211 -0.012305 -0.004926 0.480311 0.257329 -0.103363 3.06e-05 1.15e-05 table 4 reveals that at span to thickness ratio between 4 and 25, the value of vertical shear stress along y and z axes varies 0.005611 and 0.000141. these values of vertical shear stress become 0.0000981 and 0.0000109 in the span to a thickness between 30 and 85 respectively. meanwhile, the value of vertical shear stress is about 0.00000978 and 0.00000883, in the span to a thickness between 85 and 100, which is about 0.0000001 when corrected to 5 decimal places. this negligible value become almost constant or equal to the value from cpt. in summary, there are three categories of rectangular plates. the plates whose vertical shear stress do not vary well from zero will be classified as thin plates because its value are almost equal to the value of the cpt. in between the thin and thick plate is the classified as moderate thick plate. since the plate whose transverse shear stress varies very much from zero is categorized as thick plates. therefore, the span-to-depth ratio for these categories of rectangular plates are: thick plate∶ ; moderately thick plate: ; thin plate: . this confirmation can be used to show the boundary between thin and thick plate (ezeh et al., 2019). thus, it can be deduced from this research work that thick plate is the one whose span-depth ratio value is 4 up to 25. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 135 table 4: displacement and stresses of ssfs plate for length to breadth ratio of 1.5 ̅ ̅ ̅ ̅̅ ̅ ̅̅ ̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅ 4 0.012406 -0.016876 -0.004517 0.630375 0.258342 -0.121237 0.021665 0.005611 5 0.011658 -0.016380 -0.004380 0.611797 0.250664 -0.117610 0.013791 0.003570 6 0.011255 -0.016112 -0.004306 0.601791 0.246528 -0.115655 0.009549 0.002471 7 0.011013 -0.015952 -0.004261 0.595787 0.244045 -0.114482 0.007003 0.001812 8 0.010856 -0.015848 -0.004232 0.591901 0.242439 -0.113723 0.005356 0.001385 9 0.010749 -0.015777 -0.004213 0.589242 0.241339 -0.113203 0.004229 0.001094 10 0.010672 -0.015726 -0.004199 0.587343 0.240554 -0.112832 0.003423 0.000885 15 0.010492 -0.015606 -0.004165 0.582853 0.238697 -0.111954 0.001519 0.000393 20 0.010428 -0.015564 -0.004154 0.581284 0.238048 -0.111647 0.000854 0.000221 25 0.010399 -0.015544 -0.004148 0.580559 0.237748 -0.111505 0.000547 0.000141 30 0.010383 -0.015534 -0.004146 0.580165 0.237585 -0.111428 0.000380 9.81e-05 40 0.010368 -0.015523 -0.004143 0.579773 0.237423 -0.111352 0.000213 5.52e-05 45 0.010363 -0.015521 -0.004142 0.579668 0.237379 -0.111331 0.000169 4.36e-05 50 0.010360 -0.015519 -0.004141 0.579592 0.237348 -0.111316 0.000137 3.53e-05 55 0.010358 -0.015517 -0.004141 0.579536 0.237325 -0.111305 0.000113 2.92e-05 60 0.010356 -0.015516 -0.004141 0.579494 0.237307 -0.111297 9.49e-05 2.45e-05 65 0.010355 -0.015515 -0.004140 0.579461 0.237294 -0.111291 8.08e-05 2.09e-05 70 0.010354 -0.015514 -0.004140 0.579434 0.237283 -0.111285 6.97e-05 1.80e-05 75 0.010352 -0.015513 -0.004140 0.579396 0.237267 -0.111278 5.34e-05 1.38e-05 80 0.010352 -0.015513 -0.004140 0.579396 0.237267 -0.111278 5.34e-05 1.38e-05 85 0.010352 -0.015513 -0.004140 0.579381 0.237261 -0.111275 4.73e-05 1.22e-05 90 0.0103512 -0.015513 -0.004140 0.579369 0.237256 -0.111273 4.22e-05 1.09e-05 95 0.0103508 -0.015512 -0.004140 0.579359 0.237252 -0.111271 3.78e-05 9.78e-06 100 0.0103505 -0.015512 -0.004139 0.579350 0.237248 -0.111269 3.42e-05 8.83e-06 cpt 0.0103505 -0.015512 -0.004139 0.579350 0.237248 -0.111269 3.42e-05 8.83e-06 studying the results as presented in the tables 5, it is shown that the non-dimensional displacement (u, v and ) characteristics decrease with increases in the value of the spanthickness ratio. it is also observed in the tables that the displacement (u, v and ) and stresses characteristics increase as the value of the length to breadth ratio increases. this means that, the in-plane displacement are functions of x, y and z as it vary with the plate thickness while the deflection is only a function of x and y and did not varies linearly with the thickness of the plate thickness. similarly, it was deduced that the normal stress and shear stress characteristics also decrease as the span-thickness ratio increases. it is also observed in the table 3 that the stresses characteristics ( )increase as the value of the length to breadth ratio increases. these decreases continue until failure occurs in the plate structure. furthermore, from table 5 it can be seen that at span to a thickness ratio between 4 and 25, the value of vertical shear stress along y and z axes varies between 0.004447 and onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 136 0.000112. these values of vertical shear stress become 0.0000779 and 0.0000109 in the span to a thickness between 30 and 80 respectively. meanwhile, the value of vertical shear stress is about 0.0000097 and 4.184e-05, in the span to a thickness between 85 and 100 which is about 0.00000701 when corrected to 5 decimal places. the value become almost constant or equal to the value from cpt. in summary, there are three categories of rectangular plates. the plates whose vertical shear stress do not vary well from zero will be classified as thin plates because its values are almost equal to the value of the cpt. in between the thin and thick plate is the classified as moderate thick plate. since the plate whose transverse shear stress varies very much from zero is categorized as thick plates. therefore, the span-to-depth ratio for these categories of rectangular plates are: thick plate∶ ; moderately thick plate: ; thin plate: . this confirmation can be used to show the boundary between thin and thick plate (ezeh et al., 2019). thus, it can be deduced from this research work that thick plate is the one whose span-depth ratio value is 4 up to 25. table 5: displacement and stresses of ssfs plate for length to breadth ratio of 2.0 ̅ ̅ ̅ ̅̅ ̅ ̅̅ ̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅ ̅̅ 4 0.013471 -0.018397 -0.003688 0.676285 0.245283 -0.09906 0.022623 0.004447 5 0.012689 -0.017877 -0.003582 0.657137 0.238316 -0.096229 0.014404 0.002831 6 0.012267 -0.017596 -0.003525 0.646820 0.234560 -0.094703 0.009975 0.001960 7 0.012014 -0.017428 -0.003490 0.640627 0.232306 -0.093786 0.007316 0.001437 8 0.011850 -0.017319 -0.003468 0.636618 0.230847 -0.093193 0.005595 0.001099 9 0.011738 -0.017244 -0.003453 0.633876 0.229849 -0.092788 0.004417 0.000868 10 0.011658 -0.017191 -0.003442 0.631916 0.229136 -0.092498 0.003576 0.000702 15 0.011469 -0.017065 -0.003416 0.627284 0.227450 -0.091812 0.001587 0.000312 20 0.011403 -0.017021 -0.003407 0.625665 0.226860 -0.091573 0.000893 0.000175 25 0.011372 -0.017001 -0.003403 0.624917 0.226588 -0.091462 0.000571 0.000112 30 0.011355 -0.016990 -0.003400 0.624510 0.226440 -0.091402 0.000397 7.79e-05 35 0.011345 -0.016983 -0.003399 0.624265 0.226351 -0.091365 0.000291 5.72e-05 40 0.011339 -0.016979 -0.003398 0.624106 0.226293 -0.091342 0.000223 4.38e-05 45 0.011334 -0.016976 -0.003398 0.623997 0.226253 -0.091326 0.000176 3.46e-05 50 0.011331 -0.016973 -0.003397 0.623919 0.226225 -0.091314 0.000143 2.80e-05 55 0.011329 -0.016972 -0.003397 0.623861 0.226204 -0.091306 0.000118 2.32e-05 60 0.011327 -0.016971 -0.003397 0.623817 0.226188 -0.091299 9.91e-05 1.95e-05 65 0.011326 -0.016970 -0.003396 0.623783 0.226175 -0.091294 8.45e-05 1.66e-05 75 0.011323 -0.016968 -0.003396 0.623716 0.226151 -0.091284 5.58e-05 1.09e-05 80 0.011323 -0.016968 -0.003396 0.623716 0.226151 -0.091284 5.58e-05 1.09e-05 85 0.011322 -0.016968 -0.003396 0.623701 0.226146 -0.091282 4.94e-05 9.70e-06 90 0.011322 -0.016967 -0.003396 0.623689 0.226141 -0.091280 4.41e-05 8.65e-06 95 0.011321 -0.016967 -0.003396 0.623678 0.226137 -0.091279 3.95e-05 7.76e-06 100 0.011321 -0.016967 -0.003396 0.623669 0.226134 -0.091277 3.57e-05 7.01e-06 cpt 0.011317 -0.016964 -0.003395 0.623587 0.226104 -0.091265 3.57e-05 7.01e-06 arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 137 the result of the comparison made as presented in table 6, figures 3 and 4, shows that the present study predicts slightly higher values for all aspect ratios. this proves some level safety and reliability of this method as it will not put the structure into danger. the total average percentage difference between the present study and that of ezeh et al. (2018) is 3862.8%. this reveals that the work of ezeh et al. (2018) produces error and cannot be reliable for thick plate analysis. this can be proven as the total average percentage difference between the present study and that of gwarah (2019) is 6.9%. this means that at about 93 % confidence level, the values from the present study are the same with those of gwarah (2019). this value has been sufficient in the statistical analysis showed that the present method can be used with confidence for analysis of deflection on a ssfs rectangular plate. table 6: comparison of results from the present work and literature values of square thick rectangular plate present work gwarah (2019) percentage difference present work ezeh et al. (2019) percentage difference 4 0.010037 0.009370 7.118463 0.010037 0.000253 3867.194 5 0.009371 0.008766 6.901666 0.009371 0.000236 3870.763 10 0.008564 0.007959 7.601457 0.008564 0.000215 3883.256 20 0.008280 0.007757 6.742297 0.008280 0.000209 3861.722 30 0.008240 0.007719 6.749579 0.008240 0.000208 3861.538 40 0.008226 0.007706 6.747989 0.008226 0.000208 3854.808 50 0.008219 0.007700 6.74026 0.008219 0.000208 3851.442 60 0.008216 0.007697 6.742887 0.008216 0.000208 3850.000 70 0.008213 0.007695 6.731644 0.008213 0.000208 3848.558 80 0.008212 0.007693 6.746393 0.008212 0.000207 3867.150 90 0.008211 0.007693 6.733394 0.008211 0.000207 3866.667 100 0.008211 0.007691 6.761149 0.008211 0.000207 3866.667 cpt 0.008211 0.007691 6.761149 0.008211 0.000207 3866.667 average % difference 6.9 3862.8 onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 138 figure 4: deflection versus span to thickness ratio used to compare present work with literature figure 4: deflection versus span to thickness ratio used to compare present work with literature 0 0.002 0.004 0.006 0.008 0.01 0.012 0 20 40 60 80 100 120 d ef le c ti o n ( m m ) span-thickness ratio comparison between the present work and ezeh et al. (2018) ezeh et al. (2018) present work 0 0.002 0.004 0.006 0.008 0.01 0.012 0 20 40 60 80 100 120 d ef le c ti o n ( m m ) span-thickness ratio comparison between the present work and gwarah (2019) gwarah (2018) present work arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):121-140. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 139 3. conclusion application of a new refined shear deformation theory for the analysis of thick rectangular plate has been investigated with the following conclusion: i. the values of the transverse shear stresses obtained by this theory achieve accepted transverse shear stress to the thickness of plate variation and satisfied the transverse flexibility of condition of the plate while predicting the be characteristics for the csss isotropic rectangular thin or thick plate. ii. the governing differential equations and associated boundary conditions obtained are variationally consistent and can be used with confidence in the analysis of isotropic rectangular. iii. the deflection and stresses obtained by present theory are in good agreement with the other order theories. this validates the efficacy and reliability of the present new refined plate theory (nrpt). references aghdam, mm. and vafa, jp. 2004. bending analysis of thick rectangular plates with various boundary conditions using extended kantorovich method. lecture series on computer science publishers and computational sciences, 1: 14. chandrashekhara, k. 2001. theory of plates. university press (india) limited, new delhi. ezeh, jc., ibearugbulem, om., ettu, lo., gwarah, ls. and onyechere, ic. 2018. application of shear deformation theory for analysis of cccs and ssfs rectangular isotropic thick plates. journal of mechanical and civil engineering (iosr-jmce), 15(5): 33 – 42. ghugal, ym. and gajbhiye, pd. 2016. bending analysis of thick isotropic plates by using 5th order shear deformation theory. journal of applied and computational mechanics, 2(2): 80-95. gujar, ps. and ladhane, kb. 2015. bending analysis of simply supported and clamped circular plate. international journal of civil engineering (ssrg-ijce), 2(5): 45 – 51. gwarah, ls. 2019. application of shear deformation theory in the analysis of thick rectangular plates using polynomial displacement functions. phd thesis, federal university of technology, owerri, nigeria. hoang, nn., hong, tt., vinh, pv., quang, nd. and thom, dv. 2019. a refined simple firstorder shear deformation theory for static bending and free vibration analysis of advanced composite plates. materials (basel), 12(15): 2385. ibearugbulem, om., ezeh, jc. and ettu, lo. 2013. pure bending analysis of thin rectangular ssss plate using taylor-mclaurin series. international journal of civil and structural engineering, 3(4): 685 – 691. ibearugbulem, om., ezeh, jc., ettu, lo. and gwarah, ls. 2018. bending analysis of rectangular thick plate using polynomial shear deformation theory. iosr journal of engineering, 8(9): 53-61. ibearugbulem, om., njoku, ko. and eziefula, ug. 2016. full shear deformation for analysis of thick plate. proceedings of academics world 43rd international conference, rome, italy, 2nd3rd september, 38-46. kirchhoff, gr. 1850. u’’ber die schwingungen einer kriesformigen elastischen scheibe. annalen der physik und chemie, 81: 258 264 (in german). onyeka and okeke: new refined shear deformation theory effect on non-linear analysis of a thick plate using energy method. azojete, 17(2):121-140 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festu@edouniversity.edu.ng 140 liessa, aw. 1973. the free vibration of rectangular plates. journal of sound vibration, 31: 257– 293. onyechere, ic. ibearugbulem, om. anya, uc. anyaogu, l. and awodiji, ctg. 2020. freevibration study of thick rectangular plates using polynomial displacement functions. saudi journal of engineering and technology, 4(1): 38-46. onyeka, fc. and edozie, ot. 2020. application of higher order shear deformation theory in the analysis of thick rectangular plate. international journal on emerging technologies, 11(5): 62–67. onyeka, fc., okafor, fo. and onah, hn. 2018. displacement and stress analysis in shear deformable thick plate. international journal of applied engineering research, 13(11): 9893 – 9908. onyeka, fc., okeke, te. and wasiu, j. 2020. strain–displacement expressions and their effect on the deflection and strength of plate. advances in science, technology and engineering systems, 5(5): 401-413. ozioko, ho., ibearugbulem, om., ezeh, jc. and anya, uc. 2019. algorithm for exact solution of thick anisotropic plates scholar journal of applied sciences and research, 2(4): 11 – 25. reissner, e. 1945. the effect of transverse shear deformation on the bending elastic plate. transactions of the american society of mechanical engineers, journal of applied mechanics, 12: 69 77. roknuzzaman, md., hossain, bmd., rashedu, h. and tarif, ua. 2015. analysis of rectangular plate with opening by finite difference method. american journal of civil engineering and architecture, 3(5): 165-173. sayyad, ii., chikalthankar, sb. and nandedkar, vm. 2013. bending and free vibration analysis of isotropic plate using refined plate theory. bonfring international journal of industrial engineering and management science, 3(2): 40 – 46. sayyad, as., shinde, bm. and ghugal, ym. 2015. thermo-elastic bending analysis of laminated composite plates according to various shear deformation theories. open engineering, formerly central european journal of engineering, 5(1): 18-30. shwetha, k. subrahmanya, v. and bhat, p. 2018. comparison between thin plate and thick plate from navier solution using matlab software. international research journal of engineering and technology (irjet), 5(6): 2675 – 2680. timoshenko, sp. and woinowsky-krieger, s. 1959. theory of plates and shells. mcgrawhill/springer; new york, ny, usa. touratier, m. 1991. an efficient standard plate theory. international journal of engineering science, 29(8): 901–16. yang, z. and qian, x. 2017. analysis bending solutions of clamped rectangular thick plate. hindawi mathematical problems in engineering, 20: 1-6 arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):169-182 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 169 original research article assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria o. r. durowoju1, a. desogan1, m. mustapha2*, s. a. waziri3 and u. a. ibrahim3 1department of civil engineering, faculty of technology, university of ibadan, ibadan, nigeria 2department of agricultural and environmental resources engineering, faculty of engineering university of maiduguri, maiduguri, nigeria 3department of civil and water resources engineering, faculty of engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: mohammedmusty@unimaid.edu.ng 1.0 introduction access to safe drinking water is critical to survival, healthy livelihood and sustainable development (edema et al., 2001; adekunle et al., 2004). however, nearly one billion people across the globe lack access to portable drinking water (cdc, 2021). in nigeria only around 30% of the population have access to potable drinking water (oko, 2021). whilst in the rural areas, drinking water sources are often limited to polluted waters from ponds, rivers or unprotected wells (orimoloye et al., 2015; okullo et al., 2017), which were primarily utilised with little or no treatment practices (sridhar et al. 2020). in the urban areas, clean water accessibility issues are virtually the same with the rural areas, owing to the inadequate investment in public water supply infrastructure that renders pipe-borne water consumption unreliable (emma et al. 2014). the non-availability of good quality drinking water has resulted in a number of public health issues such as diarrhoea, sleeping sickness, guinea worm infestation (onweluzo and akuagbazie, 2010; freeman et al., 2017). which could have been averted simply through clean water provision. however, the years of inadequate funding of the nigerian public water sector has left the society with the issue of adapting different alternative measures to meet their drinking water needs (akunyili, 2003). generally, the high income group go for bottled water whose manufacturing practices and hygiene standards were high but expensive (obinna, 2014; ibrahim et al., 2015; article information abstract provision of clean drinking water is one of the basic human necessities for healthy livelihood. in nigeria, many people relied on sachet waters as an alternative source of clean drinking water. however, complaints abound regarding lack of proper water quality standard being used which is a major health concern. this study assessed the regulatory compliance of some sachet water production companies and water quality standard in ibadan north local government area, oyo state, nigeria. questionnaires were administered on factory’s organisational structure and staffing; facilities and equipment; water treatment processes and sanitation practices, also, sachet water samples were analysed for the contaminants of turbidity, colour, odour, ph, nitrate, chloride, iron, electrical conductivity and e-coli count. from the questionnaire analysis, the adherence level with the regulations was poor as majority (60%) of the sachet water factories have poor organisational structure and only 33% have adequate facilities and equipment. however, water quality analysis showed that most of the sachet water parameters tested were within the standard range except for ph values and e coli count which majority (70%) falls below standard for both. the study concludes that most sachet water brands produced are unsafe for human consumption. there is need for proper monitoring by relevant agencies towards ensuring sachet water factories continuously complied with standard operations for better public health in the study area. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 may., 2021 revised 6 september, 2021 accepted 18 september, 2021 keywords: sachet water regulation compliance hygiene health water quality http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 170 chukwuma et al., 2018), while the low income group, resorted to dependence on drinking packaged waters generally referred to as ‘pure water’, it is usually distributed for sale in sealed polythene containers financially affordable to the common populace (daramola et al. 2019), in nigeria, people have relied heavily on it as an alternative to clean drinking water. and in addition, this category of package water has some positive socio-economic impact; reducing societal crimes and improving standard of living through youth employment (bello et al. 2017). however, complaints abound on its quality and public health issues, many sachet water samples examined by various researchers across the country were not health risk free, and has constituents above the standard permissible limit for drinking, thus leading to waterborne disease outbreaks. (edema et al., 2011; adesiji, 2012; isikwue and chikezie, 2014; odeyemi et al., 2015; ibrahim et al., 2015; ugochukwu et al. 2015; yusuf et al., 2015; epundu et al., 2017; omolade and zanaib, 2017; akpen et al., 2018; umoessien et al., 2019; opafola et al., 2020), this menace was undoubtedly a result of poor water treatment and operation conditions (daramola et al. 2019; dajal, 2019). hence, there is need for strict attention and routine monitoring by regulatory agencies with the view of raising standards of quality of sachet water produced and sold in the country. the national agency for food and drugs administration and control (nafdac) is the sole regulatory body established and empowered to enforce compliance with the drinking water factories in nigeria, that packaged water companies are required to undergo examination by nafdac which ultimately results to issuing operation license. however, today many water factories were operating illegally without license for operation, hence consumers were not appropriately guided to prevent communicable diseases through drinking certified sachet waters. nevertheless, a careful understanding on the previous related studies on assessing the integrity of sachet water manufacturing companies basically rely on the physiochemical and bacteriological quality of the finished product and not the regulatory compliance attitude and production processes, furthermore, studies have shown that packaged water can be contaminated at various stages of the production, packaging and distribution (addo et al., 2020, osikanmi et al., 2020). the aim of this research work therefore, is to assess the regulatory compliance level and the quality of sachet water factories in ibadan north local government area of oyo state, nigeria. so as to ensure proper and hygienic manufacturing conditions to protect the public health. 2. methodology 2.1. study area the study area was ibadan north local government area, oyo state. the choice of the local government is based on its cosmopolitan nature and the location of many companies that deals with the production of sachet water. the city of ibadan is located on longitude 3°54′21.28″ and latitude 7°23′39″. the lga covers a land mass area of 145.58km2 and a population of 432,900 people (npc, 2016). it is bounded in the west by ido and ibadan north west local government, in the east by lagelu, egbeda and ibadan south east local government respectively, and in the north by akinyele local government. the economic activities undertaken by the people in the study area include trading, public service and agricultural activities. 2.2. study design the scope of this study entailed questionnaire administration and oral interviews to fifteen (15) sachet water manufacturers in the local government area over their compliance with manufacturing regulation standards. the study also covered water quality assessment of water samples obtained from ten (10) randomly selected sachet water produced in the local file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng durowoju et al: assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. azojete, 18(2):169-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 171 government by the factories. fifteen (15) sachet water factories were visited and their geographical coordinate presented in figure 1. figure 1: map of the study area showing locations of the sachet water factories 2.4. method of data sampling the study was divided into the following phases: phase 1: field survey with the aid of a questionnaire and an observational checklist to extract information from sachet water factories personnel. the questionnaire includes assessment of organizational structure and personnel, buildings, facilities and equipment (water treatment processes, production line and sanitation). the facilities and equipment auditing of the visited factories were assessed according to regulations by nafdac. each of the factories’ facilities and equipment auditing were carried out to assess the source of their raw water, depth of water source (if borehole), the distance of the source to nearest septic tank and the materials been used for their water reservoirs. hence, the results were compared against nigerian standard of drinking water quality (nsdwq) standard (2007). also, included as part of the facilities and equipment auditing, are types of materials used for each factory’s pipes and taps, the mode of their form filling and sealing machines, the types of their uv sterilizer micro filters and each factories production line and sanitations. phase 2: field water sampling and laboratory analysis of the sachet waters being sold in ibadan north local government area were carried out and a systematic random selection of ten (10) sachet waters were collected for further laboratory water quality analysis. the samples were labelled as swf1 – swf10. the samples were subjected to physical, chemical and bacteriological analysis, the results were compared against national and international standard of nsdwq and http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 172 who (world health organisation) respectively. the water quality parameters analysed were chosen in cognizance of the minimum routine check parameters for sachet water as approved by the nsdwq (2007). 2.5. parameters analysed standard for quality drinking water. i) physical parameters: turbidity, colour, odour. ii) chemical: ph, nitrate, chloride, iron, electrical conductivity iii) bacteriological: e-coli count. 2.5.1. procedures of laboratory analysis of water samples  turbidity: the turbidity of the water samples was measured directly with spectrophotometer at a wavelength of 580mm using the calibration curve.  ph value: the ph value was determined with the use of a ph meter. the reading will be displayed on the meter.  electrical conductivity: an electrical conductivity meter was used to determine the electrical conductivity of the water sample. the reading will be displayed on the meter.  chloride: was determined using mohr’s method whew is titrated with silver nitrate solution, chlorides then precipitated as white silver chloride. potassium chromate is used as indicator.  iron: the phenanthroline method was used for the measurement of iron.  odour: the water sample was measured by a term called odour intensity, which is related with the threshold odour. the threshold odour number represents the dilution ratio at which odour is hardly detectable  colour: the standard unit of colour is the colour produced by dissolving 1mg of platinum cobalt in 1 litre distilled water. different standard colour intensities of solutions are prepared by dissolving known amounts of platinum cobalt with distilled water and the colour of sample is compared with the standard colour solutions.  e-coli count: the e. coli test was done using multiple tube fermentation technique consisting of 3 phases – presumptive, confirmed and completed. 3. results and discussion 3.1.1. sachet water organizational structure and buildings the personnel and organizational structures and location of the fifteen factories visited were assessed in accordance with regulations of nafdac as shown in table 1. the organizational structures as approved by nafdac are the structure which clearly shows each personnel’s responsibility and qualification. the organizational chart will help define each personnel’s duty, in the various units of such as administrative, stores, quality control, laboratory units, logistics and operations. further, a production manager must possess a minimum of ordinary national diploma (ond) in a related science-based course obtained from recognized tertiary institutions. however, from the assessment, it was found that the sachet water factories majorly (60%) do not fully comply with the approved regulations on the organizational structure and personnel. hence factory’s workers were irregularly engaged in the activities of the sachet water production which is against the regulating body, this may ultimately pose a great danger to the quality of sachet water. however, most (93.3%) factories have production manager that oversees the activities of the sachet water production and possess the minimum academic requirement of ordinary national diploma (6.7%) and bachelor’s degree (86.7%) in a science related course as approved by nafdac, similar to daramola et al. (2019) assessment. regarding building location, some 33.3% do not comply with the regulations of locating the factory in a well demarcated file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng durowoju et al: assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. azojete, 18(2):169-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 173 places of other buildings, such as residential and commercials as indicated in table 2, this affects free flow of personnel and materials to prevent cross contaminations. table 1: organizational structure and personnel variables valid frequencies percent (%) invalid frequencies do you have an adequate organizational structure showing your workers responsibilities? a) yes b) no 6 9 40.00 60.00 0 do you have a production manager? a) yes b) no 14 1 93.3 6.7 0 what is the managers level of education? a) bsc/hnd b) ond c) ssce d) others 5 8 1 86.7 6.7 6.67 0 table 2: buildings variables valid frequencies percent (%) invalid frequencies is the entire factory well demarcated from other buildings? yes no 10 5 66.7 33.3 0 is the factory sited near any of these activities or places? (septic tank, sewage treatment plant, etc.) yes no 9 6 60.00 40.00 0 does the factory have at least five rooms designated as the cloak room, packaging material store, production room and finished product store & office? yes no 7 4 46.7 26.7 1 3.1.2. facilities and equipment auditingphase two table 3 shows the results facilities and equipment of the fifteen sachet water factories visited, of which only (33%) fully complied with the regulations on the provisions of facilities and equipment, overall, the factories were rated moderately good in terms of compliance with the regulations of the facilities and equipment as regulated by nafdac. however major source of raw water were boreholes (100%), and were mostly (100%) at minimum depths of 100feets as required by nafdac to prevent infiltration from the earth surface (akunyili, 2003). some 26.7% were located at distance less than 30meters. while 73.3% of the boreholes sunk has a more than the minimum distance of 30meters to the nearest septic tank location. materials used for tanks, reservoir and taps are pvcs (93.3%) and stainless steel (6.7%) as approved by the regulatory body. the mode of the factory’s form filling and sealing machine is an automated mode (100%) which was designed to minimize man-material contact, safe to use, easy to clean and environmentally friendly, this is contrary to similar studies by daramola et al. 2019, where quite http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 174 a large portion of the manufacturing water brands surveyed packaged their water manually. however, quiet a number (46.7%) of the factories do not have water quality laboratory which is essential to water quality monitoring and determining the quality of their finished product before consumption, and some 26.7% lack dosing scale to quantify the amount of chemical dosage as approved by regulatory body, this may lead to desired quality being affected from inappropriate dosages. regarding production line and sanitation, many (80%) have good production line and sanitation (table 4) as regulated by nafdac and also equipped their toilets with washing facilities, and are located far from the production rooms except few (20%) as observed during inspection, which can eventually lead to contamination of the sachet water (mosi et al. 2019). nevertheless, there was some constraints in getting some information as some of the sachet water factories restrict access to their production rooms due to fear of exposing their noncompliance attitudes to standard regulations and practices, similar to experience by daramola et al. (2019) study. table 3: facilities and equipment variables frequency (n) percentage (%) what is the source of your raw water? borehole rain water harvesting rivers, others (specify) 15 0 0 0 100.00 0.00 0.00 0.00 if borehole, what is the likely estimated depth? a) 50ft – 80ft b) 80ft – 110ft c) 110ft – 140ft d) 140ft – 170ft 15 0 15 0 100.00 100.00 100.00 0.00 what is the distance of the source of water from the septic tank? a) 0m – 20m 0 b) 20m – 30m c) >30m 0 4 11 0.00 26.67 73.33 what are the materials used for your tanks and reservoir? a) pvc b) stainless steel c) concrete d) others (specify) 14 1 0 0 93.30 6.67 0.00 0.00 what are the materials used for your pipes and taps? a) pvc b) stainless steel c) galvanized iron d) others (specify) 14 1 0 0 93.30 6.67 0.00 0.00 what is the mode of operation of your form filling and sealing machines? a) manual b) semi-automated device c) automated machine 0 0 15 0.00 0.00 100.00 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng durowoju et al: assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. azojete, 18(2):169-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 175 table 4: production line and sanitation variables frequency (n) percentage (%) are toilets located far from the production rooms? a) yes 15 100.00 b) no 0 0.00 are the toilets well equipped with washing facilities such as soap or detergent. a) yes b) no 11 4 73.30 26.67 3.2. results of the physical, chemical and bacteriological quality of sachet water. 3.2.1. physical assessment the result of the physical water quality assessment (turbidity, colour, odour) were all found to be in compliance with the nsdqw and who standard as shown in figures 2 and 3, however, the tested samples were odourless, colourless and non-turbid, the colour values ranges from 0.01-0.04 tcu and turbidity from 0.0-0.04ntu, these findings corresponds to some similar studies across nigeria (ibrahim et al. 2015; daramola et al. 2019; opafola et al. 2020). although turbidity, colour and odour were not necessarily a threat to health, nonetheless, it is an important indicator of the possible presence of contaminants (who, 2011), and can have a negative impact on the consumers’ acceptability of waters as a result of visible cloudiness or unpleasant odour figure 2: turbidity readings of the water samples. figure 3: colour readings of the samples 0 5 10 15 20 25 0 0.03 0.04 0.002 0.01 0 0 0.03 0.002 0.03 5 25 5 tu rb id it y (n tu ) 0 2 4 6 8 10 12 14 16 0.01 0.03 0.01 0.02 0.03 0.04 0.01 0.03 0.04 0.02 15 c o lo u rs o f w at e r sa m p le s (t c u ) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 176 3.2.2. chemical assessment results of chemical water quality assessment were presented in figures 4 to 8. the assessment includes the analysis of ph, chloride, nitrate, iron and electrical conductivity. however, except for ph, all sachet water samples fall within the allowable range of the nsdwq and the who standards. high iron level in water makes water unacceptable and results in clogging of plumbing utilities. the concentration of ions present in the water determines the degree of its electrical conductivity. chloride in drinking water originates from sources such as urine, sewage and industrial effluents and natural sources. high concentration of chloride gives a salty taste to water and beverages, and increase rate of corrosion of metals in the piping system at lower ph. nitrate react with haemoglobin in the blood and reduces the ability to transport oxygen in infants (babies), which may eventually result in a serious medical condition known as blue baby syndrome or methemoglobinemia. there is also a suspected link between exposure to high nitrate and cancer in human (who, 2011). on the other hand, the ph value of some water samples collected (sws1, 2, 3, 45, 9 and 10) does not meet the required standard (figure 4). it was observed that the sachet water samples collected were slightly acidic; with values majorly less than the nsdwq recommended lower limit of 6.5. this corresponds to studies by daramola et al. (2019), where most tested sachet water samples showed mean ph of 5 which is acidic. even though the shortfall to the minimum range limit of the ph standard is not harmful to health, however, this can cause damage to factory piping system and equipment due to the water corrosive nature. figure 4: ph reading of the water samples figure 5: conductivity readings of the water samples 0 1 2 3 4 5 6 7 8 9 6.3 5.96 6.01 5.97 5 6.84 6.73 6.5 5.8 6 6.5 8.5 p h o f w at er s am p le s 0 100 200 300 400 500 600 700 800 900 1000 17 22.1 19.23 16.13 21.31 23 22.6 18.23 16.2 22.31 1000 c o n d u ct iv it y (µ s/ cm ) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng durowoju et al: assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. azojete, 18(2):169-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 177 figure 6: concentration of iron reading of the water samples. figure 7: chloride concentration reading of water samples figure 8: nitrate concentrations reading of the water sample. 0 0.05 0.1 0.15 0.2 0.25 0.3 sachet water1 sachet water2 sachet water3 sachet water4 sachet water5 sachet water6 sachet water7 sachet water8 sachet water9 sachet water10 ndwsq 0 0.001 0.001 0.003 0 0 0.001 0 0.002 0 0.3 c o n ce n tr at io n o f ir o n ( m g/ l) 0 50 100 150 200 250 19 25 15 23 17 17 20 12 20 17 250 c h lo ri d e co n ce n tr at io n ( m g/ l) 0 5 10 15 20 25 30 35 40 45 50 sachet water1 sachet water2 sachet water3 sachet water4 sachet water5 sachet water6 sachet water7 sachet water8 sachet water9 sachet water10 ndwsq 1.21 1.07 0.23 0.42 1.17 1.14 1.03 0.17 0.3 1.2 50 n it ra te c o n ce n tr at io n ( m g/ l) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 178 3.2.3. bacteriological assessment bacteriologically, the ten water samples were tested for e-coli count and the results presented in figure 9. it showed that seven of the ten sachet water samples collected falls below the minimum allowable range with count values ranging from (1-9), as against the zero count standard for drinking water. this result is in agreement with many studies across the country (isikwue and chikezie, 2014; ibrahim et al., 2015; yusuf et al., 2015; bukar et al., 2015; omolade and zanaib, 2017; umoessien et al., 2019; opafola et al., 2020), in which sachet water tested contains pathogenic bacterias and parasites. thus, posing a high risk to the public health. on the other hand, some few studies depicted otherwise, where the tested brands of water samples were healthy for consumption (chukwuma et al., 2018, airaodion et al., 2019) especially bottled waters (obinna, 2014; ibrahim et al., 2015; chukwuma et al., 2018). this disparity could undoubtedly be related to environmental pollution of the areas, hygienic practices and regulatory compliances. however, the presence of e-coli (escherichia coli) in the samples is an indication of water bacterial contamination of human faeces, indicating non-compliance attitudes by the factories to standard hygiene and good manufacturing practices. such as sighting their source of raw water (boreholes) away from septic tank and sewage effluents, which is a hazardous event (osikanmi et al., 2020). the presence of e coli in the sachet water is harmful to human health as it causes urinary tract infections, typhoid fever, hepatitis, gastroenteritis, dysentery ear infections and many other deadly ailments (nsdwq, 2007). from the result therefore, only three out of the ten sachet water samples collected meets the requirement for the water drinking standard. this shows a very poor compliance to the regulations of producing portable water to the public. figure 9: e-coli readings of the water samples 4.0 conclusions the findings showed that level of compliance with the laid down regulations by nafdac for the setting up of a sachet water factory were poor. the non-compliance with the regulations can be seen in most factories visited through non adherence to the regulations of engaging educated and skilled officials; not meeting the organisational structure and personnel regulations; inability to adhere strictly to the regulations of sighting their source of raw water far from a conspicuous source of pollution; and other unethical approach to the production of the sachet water, and as such, this resulted in production of unsafe water for public consumption. also, some factories do not make use of the approved dosing scale and resort to dosing chemicals on their personal discretion. however, the result of the water quality showed that the selected sachet water samples produced was within the range of the nigerian standard for drinking water quality except for ph and the e-coli count which does not fall within the allowable range of standards with slightly high value than standards. therefore, the water produced from most of the factories visited are not safe for consumption. 0 1 2 3 4 5 6 7 8 9 sachet water1 sachet water2 sachet water3 sachet water4 sachet water5 sachet water6 sachet water7 sachet water8 sachet water9 sachet water10 nsdwq 1 7 9 3 3 0 3 0 7 0 0 e. c o li co u n t (c fu /1 0 0 m l) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng durowoju et al: assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. azojete, 18(2):169-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 179 5.0 recommendations the study recommends the following for betterment: 1) nafdac and son should conduct routine checks on the compliance with the regulations for sachet water factories and not only be limited to before registration of companies. 2) nafdac and son should enforce laws that will compel the factories owners to engage only skilled and educated personnel for their water productions. 3) sachet water factories must realise the detrimental effect of unsafe water on human health and as such provide clean and safe water. 4) maintenance of hygienic and clean environment that promotes hygiene values; hand washing, general cleanliness of storage environment and vendor containers should be embarked upon. 5) stiff punishment should be melted on any sachet water factories found culpable of compromising the regulation compliance and the production of quality water. 6) standard operating procedures (sops) should be strictly adhered to in the production of quality sachet water. references addo, ho., amegah, ke., xonam, ta., kabenlah, e., ameyaw, c., graham, lo., tobigah, t., hammond, b., maxwell, d. and bimi, l. 2020. consumer preference and quality of sachet water sold and consumed in the sunyani municipality of ghana. biomed research international, article id: 3865895, 1-10. https://doi.org/10.1155/2020/3865895 adekunle, lv., sridhar, mkc., ajayi, aa., oluwade, pa. and olawuyi, jf. 2004. an assessment of the health and social economic implications of sachet water in ibadan nigeria: a public health challenge. african journal of biomedical research, 7:5-8. adesiji, ar. 2012 microbiological quality of packaged drinking water brands marketed in minna metropolis, north central nigeria. nigerian journal of technological research, 7(1): 1-7. airaodion, ai., airaodion, eo., osemwowa, eu., ogbuagu, e. and ogbuagu, ou. 2019. quality assessment of sachet and bottled water in ogbomoso metropolis, nigeria. asian food science journal, 9(2): 1-15. akpen, gd., kpoghol, is. and oparaku, ia. 2018. quality assessment of sachet and bottled water sold in gboko, benue state, nigeria. journal of technology, 37: 241-248. https://doi.org/10.4314/njt.v37i1.32 akunyili, dn. 2003. the role of 'pure water' and bottled water manufacturers in nigeria. in harvey, p. (ed). towards the millennium development goals actions for water and environmental sanitation. proceedings of the 29th wedc international conference, 22-26 september, abuja, nigeria, pp. 85-88. bello, bs., shuangqin, l. and dalibi, sg. 2017. social impacts of packaged and bottled water businesses in nigeria. international journal of economics, commerce and management, 5 (6): 590-603. bukar, am., mustapha, a., kyari, mz., ibrahim, fk. and isa, ma. 2015. bacteriological analysis of sachet water in maiduguri metropolis. the journal of applied sciences research, 2(1): 20-25. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng https://doi.org/10.1155/2020/3865895 https://doi.org/10.4314/njt.v37i1.32 arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 180 cdc. 2021. global water, sanitation and hygiene (wash), centre for disease control and prevention, atlanta, georgia, accessed on [6/6/2022], retrieved from https://www.cdc.gov/healthywater/global/wash_statistics.html chukwuma, cc., ikewuchi, cc. and ayalogu, eo. 2018. water quality of different brands of packaged water consumed within the university of port harcourt community. asian journal of biological sciences, 11: 152-156. dada, ca. 2009. towards a successful packaged water regulation in nigeria. scientific research and essay, 4(9): 921-928. dajal, js. 2019. physico-chemical and bacteriological analysis of sachets and bottled water samples in katsina metropolis, nigeria. international journal of scientific & engineering research, 10(8): 104-121. daramola, go., kumoluyi, ta., edogun, ha., fadeyi, a., awosanya, a., adewumi, fo., akerele, ef., ogunfowokan, o., ojerinde, ao. and shittu, aa. 2019. evaluation of the production processes of different brands of sachet water sold in the open market in ado-ekiti, southwest, nigeria. journal of advances in microbiology, 19(1): 1-6. edema, mo., omemu, am. and fapetu, om. 2001. microbiological and physiological analysis of different sources of drinking water in abeokuta. nigerian journal of microbiology, 15(1) :57-61. edema, mo., atayese, ao. and bankole, mo. 2011. pure water syndrome: bacteriological quality of sachet-packed drinking water sold in nigeria. african journal of food, agriculture nutrition development 11: 4595-4609. https://doi.org/10.4314/ajfand.v11i1.65885. emma, ee. and philip, ope. 2014. water safety plan as a tool for improved quality of municipal drinking water in nigeria. journal of environmental protection, 5: 997-1002. epundu, uu., adinma, ed., ezeama, nn., adinma, ed., uzochukwu, bs., epundu, oc. and ogbonna, bo. 2017. assessment of the physical chemical and microbiological quality of packaged water sold in nnewi, south-east nigeria: a population health risk assessment and preventive care study. international journal of community medicine and public health, 4: 4003-4010. https://doi.org/10.18203/2394-6040.ijcmph20174809. freeman, mc., garn, jv., sclar, gd., boisson, s., medlicott, k., alexander, kt., penalakapati, g., anderson, d., mahtani, ag., grimes, jet., rehfuess, ea. and clasen, tf. 2017. the impact of sanitation on infectious disease and nutritional status: a systematic review and meta-analysis. international journal of hygiene and environmental health, 220(6): 928-949. ibrahim, md., umaru, m. and akinsoji, a. 2015. qualitative assessment of sachet and bottled water marketed in bauchi metropolis, nigeria. chemical and process engineering research, 37: 11-23. isikwue, mo. and chikezie, a. 2014. quality assessment of various sachet water brands marketed in bauchi metropolis of nigeria. international journal of advances in engineering & technology, 6(6): 2489-2495. mosi, l., adadey, sm., sowah, sa. and yeboah, c. 2019. microbiological assessment of sachet water “pure water” from five regions in ghana – a review. aas open research, 1:12 (https://doi.org/10.12688/aasopenres.12837.2) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng https://www.cdc.gov/healthywater/global/wash_statistics.html https://doi.org/10.4314/ajfand.v11i1.65885 https://doi.org/10.18203/2394-6040.ijcmph20174809 https://doi.org/10.12688/aasopenres.12837.2 durowoju et al: assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. azojete, 18(2):169-182. issn 1596-2490; 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vol. 18(2):169-182. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 182 umoessien, us., antia, ue., christopher, m. and owowo, ee. 2019. antibiotic susceptibility patterns of bacteria isolated from sachet-packaged water sold in uyo metropolis, akwa ibom state, nigeria. international journal of pathogen research, 3(1):1-11. who. 2011. guidelines for drinking water quality: 4th edition. vol. 1 – recommendations. world health organization (who), geneva. yusuf, yo., jimoh, ai., onaolapo, eo. and dabo, y. 2015. an assessment of sachet water quality in zaria area of kaduna state, nigeria. journal of geography and regional planning, 8(7): 174180 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/mohammedmusty@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):381-388 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 381 original research article assessment of energy potential of municipal solid waste from university of derby student residence n. s. gukop*, j. a. japhet, b. d. lengs and a. adesanmi department of mechanical engineering, university of jos, jos, nigeria *corresponding author’s email address: gukopn@unijos.edu.ng 1.0 introduction there has been an increasing global concern of municipal solid waste (msw) generation rate and disposal which is due to population growth and technological advancement, with a severe consequence on public health and environment (dolar et al., 2016; talalaj and biedka, 2015). the issue has become poignant in country such as the uk where there has been a growing rate of waste generation, accompanied with dependence on limited landfill area (singh et al., 2014; chapple and harris, 2003). waste is defined as “any such material or whatever thing which the holder throw-outs or intends or is required to discard”. this is categorized into different streams containing certain types of waste which may be produced by organizations, institutions or individuals amongst which are construction/demolition waste, hazardous waste and municipal waste (defra 2013). solid waste or refuse generated from the daily activities of human are seen to possess undesirable economic value, which suggests that it is cheaper to discard than to make use of it (pichtel, 2005). however, certain components of the waste material may at the end become valuable resources if separated from the bulk stream of waste material (kanat, 2010). studies have shown that generation of waste is inevitable (amber et al., 2012), and global waste generation have been projected to reach 2.2 billion tonnes per annum by the year 2025 (moya et al. 2017). the management of such waste has become of great concern which has led to the harnessing of possible ways to convert it to useful resources (tsai and kuo, 2010). as developing nations are faced with the challenges of waste collection, transportation and disposal, the developed nations have adopted emerging technologies for converting municipal solid waste into useful resources (moya et al. 2017). the adoption of such techniques of recycle and reuse could not totally eliminate municipal solid waste; therefore, more approaches are being developed to reduce the quantity of the waste being landfilled (dolgen et al., 2005). article information abstract solid waste generated from the university of derby student residence was used to examine the amount of thermal energy that can be reclaimed from the waste. the waste material used for the analysis was categorized into different constituents which were used for analyzing the sample, from which the recoverable energy was estimated. the calorific value of the waste mixture was found to be 34.28 mj/kg with a corresponding thermal energy recoverable estimated to be 1532.96 mj/day, which gave an equivalent power of 425.82 kwh/day. the findings from this study suggests the necessity for the adoption of waste management systems that will integrate energy recovery from wastes in order to supplement the increasing demand for energy. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 march, 2021 revised 16 may, 2021 accepted 20 may, 2021 keywords: municipal solid waste calorific value thermal energy content and power generation gukop et al.: assessment of energy potential of municipal solid waste from university of derby student residence. azojete, 17(3):381388. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 382 this increasing rate at which waste material that are potentially detrimental to the environment and wellbeing of human is generated has necessitated concern on the need to look into some other scientific and technical means for safe waste conversion (shrestha and singh, 2011). indrawan, et al. (2020) pointed out that energy from municipal solid waste (msw) has the potential to satisfy the electricity need of about 12% of the world’s population living without electricity. the combustible fractions of the solid waste when properly screened could be of use in powering thermal plants, thereby reducing the amount of msw sent to landfill. this has, therefore, necessitated the need to characterize the waste generated from university of derby student accommodation and to estimate the amount of thermal energy that could be recovered from the combustible fractions of the municipal solid waste material in the selected students’ residence. 2.0 materials and methods 2.1 study area and sample collection the study area, laverstoke court, is one of the nine university of derby students residence, it houses 9 lodges with each having 21 beds capacity. derby is a city in the east midlands region of england and it is located in the south of derbyshire which lies at coordinates: 52°55.32′n1°28.55′w. the samples for the study were systematically drawn from the waste bins of five lodges. ejaro and jiya (2013), in a study suggested that repetitive selection of sample and analysis would best provide a more accurate representative data; therefore, samples were collected at the same collection points of each lodge twice in a week. in each sample point, the waste was sorted into various components and categorized, a 25kg capacity weighing scale was used for weighing the samples. other tools like waste sacks, hand shovels, and bin bags were used in the sample collection and sorting process. 2.2 characterization and estimation of waste generated the astm test method d5231-92 was used for characterization and estimation of waste generated. these waste materials were classified into main components which comprise mainly of materials of similar characteristics and are classed as paper/cardboards, plastic related materials, food/organic waste, polythene/polystyrene food packs, non-combustible waste and textile materials. the waste component generated per day (kg/day), percentages by mass to the total amount of sample was determined in accordance with the astm method d5231-92 (2016). 2.3 determination of calorific value the astm e711-87 standard test method for calorific value of refuse-derived fuel was used (astm 2012). the heat content was then calculated from the equation below (1) where: δ𝑇 = the change in temperature (oc) = the calorimeter calibration factor = the calorific value (kj/kg) = mass of test sample (kg) the energy content of the sample was evaluated using equation (2). (2) where: = mass of sample (kg), = calorific value of the waste sample (kj/kg) and =energy content (kj) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):381-388. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 383 the kilowatt equivalent was obtained using equation (3) = (3) where: = energy in joules (j), = kilowatt equivalent (kwh) 3.0 results and discussion 3.1 waste generation the rate of mass contribution of waste material by each site is presented in the figure 1. the result shows the total average generated waste of 53.40kg/day. from figure 1, lodge, a contributes 21.93%, lodge b has 26.01%, lodge c has 15.36%, and lodge d has 15.36% while lodge e has 19.29% of the total rate of generation. the difference in percentage generation from each lodge is due to the different sizes of population living in each lodge, the higher the population in a lodge, the higher the percentage contribution. sharma and jain (2020), also showed similar trend which pointed that the rate of waste generation is proportional to population size. figure 1: rate of waste generation by individual collection site 3.2 waste characterization figure 2 presents the composition of the waste material in different sites of the university student hall, with average daily generation of each waste component of each lodge. the pattern of these waste components in each of the sites is observed to exhibits a similar profile; this is an indication that the waste materials are generated by community of similar lifestyle in terms of waste generation. ibikunle et al. (2019) also showed that there is a strong corelation between the type of waste generated and lifestyle. people of same lifestyle, similar and class and similar income are most likely to generate similar types of waste stream and waste volume. gukop et al.: assessment of energy potential of municipal solid waste from university of derby student residence. azojete, 17(3):381388. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 384 figure. 2: component characteristic of waste generated by each site figures 3 and 4 presents the total composition of the sorted components of the waste material shows that paper materials contribute 19.2%, polythene, 22.88%, food waste 7.66%, plastics 29.79%, incombustibles 16.25% and textile material 4.21% of the total generated waste. figure 3: distribution of individual waste composition by mass figure 4: percentage composition of waste materials arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):381-388. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 385 it is seen from this study that plastic constitute the highest proportion by mass of the total waste generated with textile material having the lowest contribution by mass. adeniran et al. (2017), oladejo et al. (2018) and ugwu et al. (2020), also showed dominance of plastic related waste materials in student residence. figure 5 also shows the total composition of the combustible and incombustible fraction of the waste sample. figure 5: proportion of total combustible and non-combustible the total composition of the combustible materials is shown in figure 6 with plastics having the highest contribution by mass of combustibles of 35.58% figure 6: composition based on total combustibles 3.3 calorific value and thermal energy potential the calorific values of the individual analysis sample are presented in table 1. it shows that plastic material having the highest value of 46.23mj/kg and paper and cardboard material with the lowest at 14.18mj/kg, this trend is similar to a study conducted by olisa and ajoko (2018) and nwoke et al. (2020) which also showed that plastic and paper materials possesses highest and lowest calorific value respectively. the calorific value of the combustible mixture in this study was however found to be 34.28mj/kg this is lesser than plastic which has the highest value component wise, and this is due to the contribution of individual components gukop et al.: assessment of energy potential of municipal solid waste from university of derby student residence. azojete, 17(3):381388. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 386 composition in terms of mass and caloric values which ranges from 2.25kg/day to 15.91 kg/day, and 14.18mj/kg to 46.23mj/kg respectively. table 1: calorific value of waste component the wastes mixture inclusive of incombustible with higher mass possess lower calorific value compared to those of the waste mixture without incombustible and with lower mass as shown in figure 7. this is due to the quality of mixture, and this suggest that the calorific value depends largely on the quality of the combustible constituents than in the general mass of the constituents as reported elsewhere (nwoke et al. 2020). the quality of the combustible fraction affects the amount of recoverable thermal energy from the mixture as shown in figure 8. lower mass with higher calorific value gives almost the same energy as compared to lower mass with higher calorific value. figure 7: mass and heat content figure 8: recoverable energy and power from waste figure 9 shows the power consumption of the study area as compared to power generatable from the combustible solid waste material from the study area. figure 9 shows that the power from the waste material is equivalent to 15.5% of the consumption of the area. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):381-388. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 387 figure 9: power recoverable from waste and power consumption for study area 4.0 conclusion the assessment of municipal solid waste was carried out in this study using the waste generated in some selected university student residence. the study carried out determined the characteristics of the waste material generated in terms of composition, calorific value and thermal energy potential. findings from the study showed that 53.4kg/day of waste is generated of which 84% are combustible material. the assessment of the waste components estimated the energy recoverable from plastics material to be 735.47mj/day, polythene 553.93mj/day and cardboard the least with 145.46mj/day corresponding to 51.26%, 38.60% and 10.14% respectively of the total energy potential. the result of the assessment estimated the amount of energy recoverable from the generated waste to be 1532.96 mj/day which corresponds to 425.82kwh/day, these recoverable energy contributions are affected by rate of generation of the individual waste component and quality of combustible material. the findings of this study suggest the existence of abundance of energy that could be recovered from the various components of the waste material generated from the study area which can contribute about 15.5% of the locations’ consumption. references adeniran, ae., nubi, at. and adelopo, ao. 2017. solid waste generation and characterization in the university of lagos for a sustainable waste management. waste management, 67: 3-10. amber, i., kulla, dm., and gukop, n. 2012. generation, characteristics and energy potential of solid municipal waste in nigeria. journal of energy in southern africa, 23(3): 47-51. astm d5231-92. 2016. standard test method for determination of the composition of unprocessed municipal solid waste. astm international. astm international (2012) astm standard e711-87, standard test method for gross calorific value of refuse-derived fuel by the bomb calorimeter. chapple, w. and harris, r. 2003. accounting for solid waste generation in measures of regional productivity growth. iccsr research paper series nottingham. 01-2003 defra, 2013. energy from waste a guide to the debate. london: department for environment, food and rural affairs. dolar, d., košutić, k. and strmecky, t. 2016. hybrid processes for treatment of landfill leachate: coagulation/uf/nf-ro and adsorption/uf/nf-ro. separation and purification technology, 168: 39-46. gukop et al.: assessment of energy potential of municipal solid waste from university of derby student residence. azojete, 17(3):381388. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 388 dolgen, d., sarptas, h., alpaslan, n. and kucukgul, o. 2005. energy potential of municipal solid wastes. energy sources, 27(15): 1483-1492. ejaro, sp. and jiya, sn. 2013. source specific quantification, characterisation and management of solid waste in lapai, niger state, nigeria. ethiopian journal of environmental studies and management, 6(5): 561-569. ibikunle, ra., titiladunayo, if., akinnuli, bo., dahunsi, so. and olayanju, tma. 2019. estimation of power generation from municipal solid wastes: a case study of ilorin metropolis, nigeria. energy reports, 5: 126-135. indrawan, n., simkins, b., kumar, a. and huhnke, rl. 2020. economics of distributed power generation via gasification of biomass and municipal solid waste. energies, 13(14): 3703 kanat, g. 2010. municipal solid-waste management in istanbul. waste management, 30(8-9): 1737-1745. moya, d., aldás, c., lópez, g. and kaparaju, p. 2017. municipal solid waste as a valuable renewable energy resource: a worldwide opportunity of energy recovery by using waste-toenergy technologies. energy procedia, 134: 286-295. nwoke, oa., okonkwo, wi., echiegu, ea., ugwuishiwu, b.o. and okechukwu, ch. 2020. determination of the calorific value of municipal solid waste in enugu, nigeria and its potential for electricity generation. agricultural engineering international: cigr journal, 22(2): 86-97. oladejo, os., auta, am., ibikunle, pd. and ken-wiwa, oe. 2018. solid waste generation, characteristics and material recovery potentials for landmark university campus. international journal of civil engineering and technology, 9(9): 1071-82. olisa, yp. and ajoko, tj. 2018. gross calorific value of combustible solid waste in a mass burn incineration plant, benin city, nigeria. journal of applied sciences and environmental management, 22(9): 1377-1380. pichtel, j. 2005. waste management practices: municipal, hazardous, and industrial. crc press. sharma, kd. and jain, s. 2020. municipal solid waste generation, composition, and management: the global scenario. social responsibility journal, 16: 917–948 shrestha, a. and singh, rm. 2011. energy recovery from municipal solid waste by briquetting process: evaluation of physical and combustion properties of the fuel. nepal journal of science and technology, 12: 238-241. singh, j., laurenti, r., sinha, r. and frostell, b. 2014. progress and challenges to the global waste management system. waste management & research, 32(9): 800-812. talalaj, ia. and biedka, p. 2015. impact of concentrated leachate recirculation on effectiveness of leachate treatment by reverse osmosis. ecological engineering, 85: 185-192. tsai, wt. and kuo, kc. 2010. an analysis of power generation from municipal solid waste (msw) incineration plants in taiwan. energy, 35(12): 4824-4830. ugwu, co., ozoegwu, cg. and ozor, pa. 2020. solid waste quantification and characterization in university of nigeria, nsukka campus, and recommendations for sustainable management. heliyon, 6(6): e04255 arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):547-554 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 547 original research article experimental study on the use of banana and pineapple peel waste as biofertilizers, tested on hibiscus sabdariffa plant: promoting sustainable agriculture and environmental sanitation j. j. alasa1, a. u. bashir2, m. mustapha4*, and b. mohammed3 department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: mohammedmusty@unimaid.edu.ng 1.0 introduction agricultural crop production often requires addition of nutrients towards increasing soil fertility and maximizing yield (savci, 2012). nonetheless, achieving this based on inorganic fertilizer application is found to have deleterious effects on the environment and public health (sönmez et al. 2007; savci, 2012; morakinyo et al., 2013, sharma and singhvi, 2017). inorganic fertilizers are often used by farmers most of whom lack training and knowledge on application leading to excessive application (abuga, 2014; rahman and zhang, 2018; agmas and adugna, 2020), which affects the ecosystem, it can result in soil quality declination and toxification of nearby water bodies (morakinyo et al., 2013), hence, agricultural crops grown with such chemicals are unhealthy for consumption due to chemicals ability to bio-accumulate in the food chain (savci, 2012; chandini et al., 2019). moreover, inorganic fertilizers are not risk-free during handling; enormous exposure to are connected to blindness, gene related diseases and many other ailments (sharma and singhvi, 2017), thus, the need for sustained and healthy method of food production through organic agriculture. article information abstract synthetic fertilizers are combination of inorganic substances which causes longterm negative effects on the ecosystem. indiscriminate agricultural waste disposal especially fruits peels waste when neglected and utilized unproperly can cause environmental pollution and spread of diseases. fruit peels of banana and pineapple are highly rich in numerous bioactive compounds that can enhance plant growth. this study deals with managing banana and pineapple peel waste as organic fertilizer and compared their effects on the growth of hibiscus sabdariffa. three different formulations were prepared from sun dried and finely ground fruits peel of banana and pineapple extract, namely; sample a containing 100g of banana peels powder, sample b containing 100g of pineapple peels powder and sample c containing 100g of a mixture of banana and pineapple peels powder. four containers were used to collect 2kg of soil each, three of which were treated with the three formulations (sample a, b and c). the fourth container was labeled sample d (control). after 30 days of treatment, seeds of roselle plant were sown in each container and plant growth parameters analyzed periodically. from the results, sample a showed highest mean number of 3 days to germinate. after 21 days; sample a had average large leaf area of 14cm2, then sample b (12.92 cm2), sample c (10.2 cm2) and sample d having the smallest (9.6 cm2). after 120 days, average plant height recorded were; sample a (78cm); sample b (58), and sample d (54cm), and sample c showed the lowest average plant height of 47cm. from this study, it was deduced that fruit peel powder formulations can enhance growth and yield of plants, thus limiting the use of chemical fertilizers and protecting the environment. it is recommended that fruits waste should be integrated into farms for enhanced agricultural productivity and clean environment. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 may, 2021 revised 10 september, 2021 accepted 18 september, 2021 keywords: environmental sanitation chemical fertilizers organic agriculture banana peels pineapple peels mohammed et al: experimental study on the use of banana and pineapple peel waste as biofertilizers, tested on hibiscus sabdariffa plant: promoting sustainable agriculture and environmental sanitation. azojete 17(4):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 548 a wide range of agricultural fruits and vegetables waste of banana peel, orange peel, pineapple, orange peels, coconut shell, usually generated from households and fruit vendors are mostly discarded indiscriminately affecting environmental quality and health of people (harir et al., 2015); fruit wastes discarded improperly can produce odour, causing discomforts to people around, as the rich nutrients packed in these waste make them vulnerable to microbial spoilage, and may serve as harborage for harmful insects causing diseases and several environmental issues asides contributing to greenhouse gas effect (raji and onu, 2017). large amounts of fruit wastes are also produced during harvesting, processing, storing or post-harvest handling, and are widely available and accumulate in market complexes and agro-industrial yards, due to the high costs of transportation and the limitation of available lands for disposal, thus resulting in environmental problems. however, fruit wastes characterization by various researchers globally have shown potentials as a source of raw materials that can be converted into value added products or incorporated into different biotechnological application such as biofertilizer production, animal foods and feeds production, industrial chemicals/raw materials, biofuels and other alternative renewable energy development, water treatment application and food and pharmaceutical industrial application (ezejiofor et al., 2014; raji and onu, 2017; sagar et al., 2018; javed et al., 2019; kumar et al., 2020), for example, banana waste were important as a potent source in textile manufacturing industries (mohiuddin et al., 2014) and as cellulase production as a resource in biofuel production process (sarvanan et al., 2013), however, of all fruit waste utilization routes, biofertilizer application were more promising, less complex and easily incorporated with maximum benefits and zero environmental consequences. scientific findings revealed that these wastes contain various natural bioactive compounds that can be beneficial for plant growth (rudra et al., 2015; bakry et al., 2016; khattak and rahman, 2017; pathak et al., 2017, sagar et al., 2018; vasanthi and ramadas, 2019),hence utilizing these wastes as fertilizers for crops undoubtedly may lead to sustainable plant growth and clean environment. fruit wastes based biofertilizers offers numerous benefits for plants such asit helps to improve soil morphology and organic matter content (adalgisa et al., 2005),regulate soil ph and improve soil fertility (panwar, 2015), enhanced root system and nutritional characteristics (bakry et al., 2016; arshad et al., 2018; chandini et al., 2019), healthier and quality produce (ndukwe et al., 2012), improves seed germination (mishara and koshy, 2016), enrich soil microbiota (rai et al., 2014), and protects plants from insects, nematodes, fungi and other plant pathogens (divina, 2016). interest in organic farming has been recently gaining momentum and wider application in different forms is being practiced, all of which are renowned to yield positive result. this research work was intended to be in maiduguri where banana and pineapple peels are some common fruits consumed, which generally ends at dumpsites causing environmental degradation. banana peels generated as a waste product is equivalent to 40% of the total weight of fresh banana, (tchobanoglous et al., 1993), and pineapple peel account for 50% of the total weight of the pineapple (saravanan et al., 2013). hence, with the increasing banana and pineapple fruits production and consumption, banana and pineapple waste are also proportionally increasing, thus waste disposal present a serious environmental challenge. therefore, the present study compares and explores the utilization of banana and pineapple peel waste as a natural fertilizer, the research selected to grow roselle plant (hibiscus sabdariffa) which is an economically and medicinally important plant widely used in the region. the aim of the research, therefore, is to investigate the growth ability of rosella plant on the soil treated with banana and pineapple peel extract; towards promoting the use of fruits waste based organic fertilizers and ensuring production of safe, highly nutritious food and long-term sustainability of the environment. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 547-554. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 549 2. methodology 2.1. collection and preparation of soil clay soil samples were collected in a barren land and were filled in four different containers (made up of rubber) each weighing 2kg,and named sample a, b, c and d (control). 2.2. extraction of fruit peel waste waste of banana and pineapple peel wastes were separately collected in households, dumpsites and markets, the collected fruits peels were rinsed adequately in running tap water of debris, sand and foreign materials, the cleaned peels were cut into small pieces (1-5cm) and sun dried for 33 days, which were then ground into powdered form, sieved (figures 1 and 2) and stored at room temperature, three formulation each of pineapple and banana peel extracts were prepared separately, and an additional preparation containing a mixture of pineapple and banana was made. figure 1: grounded banana peel powder figure 2: grounded pineapple peel powder 2.3. formulation of different fruit peels fertilizer four grams of each the three formulations of banana peel, pineapple peel and combined mixture of the two fruits peels powder extract were diluted in 400ml of water and applied to the collected soils samples a, b, c respectively and were mixed properly for uniform distribution, controls and two replications maintained for each of preparation, addition of the powder extract was carried out continuously for 32 days. 2.4. seeding of rosella plant after 32 days of application of the fruit peels extract, two seeds of rosella plant (hibiscus sabdariffa) were sown in each container, and are being watered everyday with equal volume of water. and plant growth observed in terms of germination period and other plant growth parameters of plant height, leaves area, number of branches, number of leaves per branch were being observed and recorded for up to 120days, a period in which growth plant is expected to have advanced. 3. results and discussion the results of the various growth parameters on rosella plant seed sown after 21 and 120 days were shown in tables 1 and 2. mohammed et al: experimental study on the use of banana and pineapple peel waste as biofertilizers, tested on hibiscus sabdariffa plant: promoting sustainable agriculture and environmental sanitation. azojete 17(4):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 550 table 1: growth parameters of roselle plant 21 days after germination samples average plant height (cm) initial average number of leaves per plant average number of leaves per branch average leaves area per plant (cm2) sample a (banana peel with soil sample) 19 6 6 14 sample b (pineapple peel with soil sample) 18.5 6 6 12.92 sample c (banana and pineapple peel with soil sample) 17.5 6 6 10.2 sample d (controlled) 16 5 5 9.6 table 2: growth parameters of roselle plant 120 days after germination samples average plant height (cm) average number of leaves per plant average number of leaves per branch sample a (banana peel with soil sample) 78 32 28 sample b (pineapple peel with soil sample) 58 21 15 sample c (banana and pineapple peel with soil sample) 47 14 8 sample d (controlled) 54 18 12 3.1. germination period from the result, there was no significant difference in number of days for germination. however, sample c (banana and pineapple peel with soil sample), sample a (banana peel with soil sample) and sample b (pineapple peel with soil sample) showed minimum average number of days to germinate, which is 2 days, while sample d (controlled) took average of 3 days to germinate. this supports a related study finding by mishary and koshy, (2016), in which significant improvement in seed germination were observed; the research analysed effect of vegetable and fruit waste on seed germination and growth of solanum lycopersicum (tomoto plants). similar results were also observed by wazir et al. (2018), study on the significance of biofertilizers on growth of crops. furthermore, similar research findings by hussein et al. 2019 showed significant increase in rate of germination from 14% (control) to 97%, after 7 days of plantation of tomato plant. also, same trend was noticed for fenugreek crop where the germination percentage was enhanced from 25% (control) to 93.14%. however, banana and pineapple peels increase soil fertility and enrich soil minerals with potassium, calcium including phosphorus. phosphorus plays a significant role in seed germination and viability, deficiency in soil phosphorus contents retards early plant growth (ascher et al., 1994)and reduces root growth and development of plants (hamid et al., 2019). 3.2. average plant height in the first 9 days after germination, sample c (banana and pineapple peel with soil sample) initially showed the highest mean plant height of 10 cm, and sample d (controlled) showed lowest mean height of 7cm. sample a (banana peel with soil sample) 9cm and sample b (pineapple peel with soil sample) 8cm.the next 21 days after germination, sample a (banana peel with soil sample) showed mean plant height of 19cm and sample d (controlled) showed lowest mean height of 16cm. sample b (pineapple peel with soil sample) 18.5 cm and sample c arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 547-554. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 551 (banana and pineapple peel with soil sample) 17.5cm. after 120 days of growth, sample a (banana peel with soil sample) showed significantly highest mean plant height of about 78cm, sample (pineapple peel with soil sample) with average height of 58cm, sample c (banana and pineapple peel with soil sample) with average height of 47cm and sample d (controlled) with average height of 54cm, as shown in figures 3 and 4. however, banana peel exhibiting high increase in plant height coincides well with many similar studies; bakry et al.(2016) observed similar outcomes with quinoa plants (chenopodium quinoawild) tested under water deficit condition. arshad et al.(2018); wazir et al.(2018) and qader (2019)equally noted substantial improvement in height with banana peel extract, on lettuce plant (lactuca sativa l) grown under hydroponic condition, potato and pea vegetables and growth of chickpea (cicer areitinum) l. plants respectively. this can be attributed to the high sufficient nitrogen content associated with banana peels extract (khairnar and nair, 2019). however, the initial lowest plant height indicated by the banana peel was due to the number of days taken for the treated materials to decomposed and release nutrients. figure 3: heights of plants using the different samples after 21 days. figure 4: heights of plants using the different samples after 120 days. 0 2 4 6 8 10 12 14 16 18 day 0 day 3 day 6 day 9 day 12 day 15 day 18 h e ig h ts in c m heights of roselle plant in different samples sample a (banana peel with soil sample) sample b (pineapple peel with soil sample) sample c (banana peel and pineapple peel with soil sample) sample d controlled (plain soil sample) mohammed et al: experimental study on the use of banana and pineapple peel waste as biofertilizers, tested on hibiscus sabdariffa plant: promoting sustainable agriculture and environmental sanitation. azojete 17(4):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 552 3.3 average number of leaves per branch pertaining to average numbers of leaves per branch after 21 days, there was not any difference in the number of leaves to the number of branches. this is so because the roselle plants were still in their early stage. however, sample a (banana peel with soil sample) had an average number of 6 leaves per branch, sample b (pineapple peel with soil sample) had an average number of 6 leaves per branch, sample c (banana and pineapple peel with soil sample) also had an average number of 6 leaves per branch and sample d (controlled) had an average of 5 leaves per branch. this corresponds with adiah et al. 2017; wazir et al. 2018arshad et al. 2018 and qader, 2019 studies in which different organic treatments of eggshell powder, banana peel cassava peel and used tea waste were found best as organic fertilizer source for the plant growth, indicated by a substantial increase in plant leaves. 3.4 average leaves area per plant pertaining to average leaves area per plant after 21 days, sample a (banana peel with soil sample) had an average area of 14cm2, sample b (pineapple peel with soil sample) had an average area of 12.92 cm2, sample c (banana and pineapple peel with soil sample) had an average area of 10.2 cm2, while sample d (controlled) had an average leave area of 9.6 cm2.in comparison with inorganic fertilizer, sakpareet al.(2018)and tuttobene et al.(2009) observed that some growth parameters especially leaf area and shoot height were enhanced by fruit peel extracts of banana and orange peel waste tested on the growth solanum scabrum, and durum wheat (triticum durum desf.) and sunflower (helianthus annuus l.). similar findings by wazir et al. (2018) also showed higher increase in leaves area per plant with application of banana peels on potato and peas vegetables. 4. conclusion comparative study on the utilization of banana and pineapple fruit peel waste as organic fertilizer was carried out to know and compare their growth effectiveness on rosella plant, aiming at both sustainable agricultural and environmental sanitation. the study concluded that banana and pineapple peels waste contain appreciable amount of nutrients to enhance soil fertility and increase plant yield, furthermore, the study found substantial improvement in terms of growth and yield parameters such as germination period, plant height, leaves area and number of leaves per branch. banana peel waste was found more suitable for rosella plant growth. the research concludes that chemical fertilizers can be replaced by the fruit peel powder and extract for sustainable agriculture and environment. it is recommended that the public and farmers should make beneficial use of fruits waste as organic fertilizers and not discarded indiscriminately towards ensuring efficient agricultural productivity and reducing the ill-effect of synthetic fertilizer. references abuga, i. 2014. the effect of inorganic fertiliser on onion production, international journal of biological sciences, 1(5): 21-29. adalgisa. b., marzia, g., di, l., mario, m. and rosalena, t. 2005. effects of industrial orange wastes on soil characteristics and on growth and production of durum wheat. agronomy for sustainable development, springer verlag/edp sciences/inra, 25(1):129-135. adiah, ms. 2017. potential of cassava peel as a biotechnical nutrient carrier for organic fertilizer production to increase crop production and soil fertility. world scientific news, 72: 103-107. agmas, b. and adugna, m. 2020. attitudes and practices of farmers with regard to pesticide use in north west ethiopia.cogent environmental science, 6: 1791462-1791478 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 547-554. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 553 arshad, m., nawaz, r., ahmad, s., qayyum, mmn., ali, z., faiz, f. and manzoor, hmi. 2018. morpho-nutritional response of lettuce (lactuca sativa l.) to organic waste extracts grown under hydroponic condition. applied ecology and environmental research, 16(3): 3637-3648. bakry, ab., ibrahim, fm., shater-abdallah, mm. and el-bassiouny, hms. 2016. effect of banana peel extract or tryptophan on growth, yield and some biochemical aspects of quinoa plants under water deficit. international journal of pharmtech research, 9(8): 276-287. chandini, rk., ravendra, k. and om, p. 2019. the impact of chemical fertiliser on our environment and ecosystem. in book: research trends in environmental science, edition: 2nd, chapter: 5, 69-86. divina, cc. 2016. scraps no more: fruit wastes for benefits of plants and animals. international journal of agricultural technology, 12(7.1): 1535-1545. ezejiofor, tin., enebaku, ue. and ogueke, c. 2014. waste to wealthvalue recovery from agrofood processing wastes using biotechnology:a review. british biotechnology journal, 4(4): 418-481. hamid, ha., qi, lp., harun, h., sunar, nm., ahmad, fh., muhamad, ms. and hamidon, n. development of organic fertilizer from food waste by composting in uthm campus pagoh, journal of applied chemistry and natural resources, 1(1): 1-6. harir, ai., kashim, r. and ishiyaku, b. 2015.exploring the resource recovery potentials of municipal solid waste: a review of solid wastes composting in developing countries. international journal of scientific research and publication, 5(4): 1-8. harsh, k., kanchan, b., ruchi, s., eugenie, n., kamil, k., daljeet, sd., rachna v., prerna, b., somesh, s. and dinesh, k. 2020. fruit and vegetable peels: utilization of high value horticultural waste in novel industrial applications. molecules, 25(12): 2812-2833 khair, md. and nair, ss. 2019. study on eggshell and fruit peels as a fertiliser. proceedings of international conference on sustainable development, in association with navateur publications, february, 14th and 15th: 25-27. khattak, kf. and rahman, tu. 2017. analysis of vegetable’s peels as a natural source of vitamins and minerals. international food research journal, 24(1): 292-297. mishra, p. and koshy, pe. 2016. effect of vegetable and fruit waste on seed germination and growth of solanum lycopersicum. asian journal biological science, 11(1): 1-5. mohiuddin, akm., saha, mk., md. hossian, s. and ferdoushi, a. 2014. usefulness of banana (musa paradisiaca) wastes in manufacturing of bio-products: a review. the agriculturists 12(1): 148-158. morakinyo, at., adeboye, ob. and awogbuyi, ot. 2013. environmental effects of application of fertilisers and pesticides on water and soil in ibadan, nigeria. journal of emerging trend in engineering and applied sciences 4(6): 773-777. ndukwe, oo., muoneke, co., baiyeri, kp and tenkouano, a. 2012.effect of organic and inorganic fertilizers on nutrient concentrations in plantain (musa spp.) fruit pulp. african journal of biotechnology, 11(7):1651-1658. panwar, n. 2015. studies on physicochemical characteristics and fertility of soil by addition of banana peels-waste management. international journal for scientific research and development, 3(1): 121-125. pathak, pd., mandavgane, sa. and kulkarni, bd. 2017. fruit peel waste: characterization and its potential uses. current science, 113 (3): 444-454. mohammed et al: experimental study on the use of banana and pineapple peel waste as biofertilizers, tested on hibiscus sabdariffa plant: promoting sustainable agriculture and environmental sanitation. azojete 17(4):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 554 qader, hr. 2019. influence combination of fruits peel and fertilizer methods on growth and yield of chickpea (cicer areitinum) l. plants. zanco journal of pure and applied sciences, 31(3): 45-51. rahman, kma. and zhang, d. 2018. effects of fertiliser broadcasting on the excessive use of inorganic fertlisers and environmental sustainability. mdpi, sustainability, 10: 759-774. rai, n., ashiya, p. and rathore, ds. 2014. comparative study of the effect of chemical fertilizers and organic fertilizers on eisenia foetida. international journal of innovative research in science, engineering and technology, 3(5):12991-12998. raji, io. and onu, p. 2017. untapped wealth potential in fruit wastes for uganda community. international journal of advanced academic research science, technology and engineering, 3(1): 17-25. rudra, sg., nishad, j., jakhar, n. and kaur, c. 2015. food industry waste: mine of nutraceuticals. international journal of science environmental technology, 4(1): 205–229. sagar, na., pareek, s., sharma, s., yahia, em. and lobo, mg. 2018. fruit and vegetable waste: bioactive compounds, their extraction and possible utilization. comprehensive reviews in food science and food safety,17(3):512-531. sakpere, ama., bankole, m., oyekola, ob., akinyemi, os., akosile, or., adegboye, oa., akinropo, ms. and obisesan i.a. 2018. effect of different moringa oleifera extracts and fruit peels on the growth of solanum scabrum. international journal of biological and chemical sciences, 12(4): 1543-1549. sarvanan, p., muthuvelayudham, r. and viruthagiri, t. 2013. enhanced production of cellulose from pineapple waste by response surface methodology. journal of engineering, 2013: 979547-979555 savci, p. 2012. investigation of effect of chemical fertilizers on environment. apcbee procedia, 5th-7th january, hong kong 1, 287-292. sharma, n. and singhvi, r. 2017. effects of chemical fertilizers and pesticides on human health and environment: a review. international journal of agriculture, environment and biotechnology, 10(6): 675-679. sönmez, ø., kaplan, m. and sönmez, s. 2007. an investigation of seasonal changes in nitrate contents of soils and irrigation waters in greenhouses located in antalya-demre region. asian journal of chemistry, 19(7): 5639-5646. tchobanoglous, g., theisen, h. and vigil, s. 1993. integrated solid waste management: engineering principles and management issues. mcgraw-hill, new york, 3-22. tuttobene, r., avola, g., marchese, m., gresta, f., barrile, v. and abbate, v. (2009). effects of industrial orange waste as organic fertilizer on growth and production of durum wheat and sunflower. 18th symposium of the international scientific centre of fertilizers, 8-12 november 2009 rome, italy:127-132 vasanthi, p. and saradha ramadas, v. 2019. fruit waste its functionality and utilization. international journal of recent scientific research, 10 (01f): 30677-30682 arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):699-716 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 699 original research article development of multi seeds oil expeller i. o. olaoye1, y. a. salako2* and o. k. owolarafe3 1department of agricultural & bio-environmental engineering, the oke – ogun polytechnic saki nigeria 2*departments of agricultural education, michael otedola college of primary education, noforija epe, nigeria 3departments of agricultural and environmental engineering, obafemi awolowo university, ile-ife, nigeria *corresponding author’s email address: salthaqib@yahoo.com 1.0 introduction edible vegetable oil is oil produced from any of the edible oil-bearing seeds that exist in nature. many of these seeds are produced in large quantities in nigeria and have a lot of uses. amongst them are groundnut seed, oil palm fruit and kernel, soybean, cotton seed, sesame seed and melon seeds (bello, 2013). hydraulic system (hydraulic press) is one of the most effective methods of oilseed extraction because higher pressure may be attained. however, care should be taken to ensure that poisonous hydraulic fluid does not come in contact with the oil or raw material. apart from this, there is frequent breakdown of the hydraulic system and hence maintenance cost could be high. additionally, oil extraction can also be achieved through solvent extraction. this involves the use of organic chemicals to dissolve out the oil from the seed. the seed must have been ground and placed in a semi permeable membrane before placing in the solvent extractor. solvent extraction is about the most efficient method of oil recovery from oil bearing materials. extraction of oil from oil bearing material with low oil content (such as soya bean, rice bran and mango kernel) is best carried out using solvent extraction. (shukla et al., 1992). however, the resulting cake from the extraction process is usually contaminated and may not be suitable for animal feeds. oil expression is a mechanical method for removing oil from oil-bearing materials. the raw materials are pressed under high pressure. when used for the extraction of food oils, typical raw materials are nuts, seeds and algae, which are supplied to the press in a continuous feed. as the raw material is pressed, friction causes it to heat up; in the case of harder nuts (which require higher pressures) the article information abstract multi seeds oil expeller was designed fabricated and evaluated using screw press principle. it was designed and fabricated based on the data obtained on the properties of the oilseeds. the performance of the machine was carried out using a 3 x 3 x 3 factorial experimental design with the following type of seeds (palm kernel, soya bean and groundnut seed), worm shaft speed of 47.6, 87and 92 rpm, and moisture content of 5, 10, and 15 % w.b as factors. data collected include oil yield, volumetric flow rate of oil, throughput capacity and efficiency of the machine. the results showed that increase in moisture content as stated has direct effect on oil yield and efficiency of the expeller, but has an inverse effect on volumetric flow rate for the three oil seeds. increase in worm shaft speed as stated increased oil recovery for palm kernel from 19.1 to 23.0%, soya beans from 0.0 to 16.0% and groundnut from 7.3 to 31.7%. increase in worm shaft speed as stated increased the oil yield, throughput capacity as well as the efficiency of the machine for all the oil seeds. the efficiency increased from 39.4 to 52.1%; 0.0 to 82.1% and 53.1 to 72.0% for palm kernel; soya bean and groundnut, respectively. these results were found to be significant (p<0.05) when tested using one way analysis of variance (anova) and duncan’s multiple range test. the study concluded that, the developed multi-seed expeller performed well within the conditions of operation and could have a potential for improving the production of vegetable oil if adopted by small and medium scale processors. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 8 february, 2020 revised 11 july, 2020 accepted 18 july, 2020. keywords: screw press oilseeds worm shaft throughput capacity and volumetric flow rate. http://www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 700 material can exceed temperatures of 120 °f (49 °c). an expeller press is a screw-type machine that presses oil seeds pass through a caged barrel-like cavity. raw materials enter one side of the press and waste products exit the other side. the machine uses friction and continuous pressure from the screw drives to move and compress the seed material. the oil extracted from the seeds passes through small openings that do not allow seed fiber solids to pass through. consequently, the fiber from the pressed seeds are formed into a hardened cake, which is removed from the machine (agbogun, 2011). pressure involved in expeller pressing creates heat in the range of 140–210 °f (60–99 °c). some companies claim that they use a cooling apparatus to reduce this temperature to protect certain properties of the oils being extracted (olatunde et al., 2014). there is an increasing demand for edible oil in nigeria and the world as a whole. statistics show that the demand for vegetable oil keeps on increasing on yearly basis (kojima et al., 2016). the large scale plants (which though have high extraction efficiency) utilize sophisticated equipment which are expensive and are always imported. most of the existing oil expeller machines for small and medium scale processors were designed for a particular seed. the development of a multi-seed oilseeds expeller will provide an opportunity for farmers and processors to have plant that can handle many oilseeds. this will reduce the cost of production and enhance the productivity of the processors. in this study, a multi-seeds oil expeller was designed and fabricated to expel all the oil bearing seeds for purposes of small and the medium scale processors. 2. materials and methods 2.1 design of the components of the oil expeller this machine was designed to expel oil from hard and soft seeds. the hard seeds selected are palm kernel and soya seed while groundnut was chosen as soft seed. the expeller consists of hopper, pressing chamber, differential unit, the discharge outlets (oil and cake outlets) power unit and frame as shown in figure 1. the material flows from hopper to the pressing chamber which consists of a worm shaft beveled at the end. the expelled oil flows out of the oil outlet after the frictional effect which causes heat in pressing chamber while the cake comes out of the cake outlet. i. the hopper the design of a hopper depends principally on the mechanical behavior of the material. the shape of the hopper is shown in figure 2 was chosen to ensure free flow of both kernels and nuts under gravity. the feeding rate was controlled by feeding control plate, this was done by taking into consideration the angle of repose of the kernels. according to kibar and ozturk (2008); davies (2009) and dagwa and ibhadode (2008), the dynamic angle of repose from experiment was determined to be 29.0° and 28.4° for groundnut and soya bean, respectively. let us assume that 1.5kg of oilseed was used per batch. average angle of friction of the seeds = 29.0° vs = m ρ = 1500 853.6 = 1.76 m3 (1) where: vs = volume of seed m = mass of oilseed ρ = density of oilseed the height of hopper was calculated thus: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 701 figure 1: three dimensional view of the oil expeller tan 29.0 = ℎ1 150.4 (2) hi =150.5 tan 29.00 hi = 150.5× 0.55431 hi = 83.42 mm capacity of the piling hopper: the hopper can be divided into 3 segments and the volume of each segment will be determine the overall capacity of the piling hopper. therefore capacity of the hopper was determined using the dimensions presented in figure as: vt = v1 + v2 + v3 (3) vt = a × a × ℎ1 + ℎ2 3 a2 + b2 + a2. b2 + (b × b × ℎ3) (4) vt = 0.3556 × 0.3556 × 0.087 + 0.2 3 0.35562 + 0.092 + 0.35562 × 0.092 + (0.09 × 0.09 × 0.08691) vt = 0.011 + 0.0111 + 0.000704 = 22.8 × 10-3 m3 the handling capacity of the hopper is 22.80 × 10-3 m3 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 702 figure 2: orthographic view of the hopper ii. the wormshaft the screw worm consists of ϕ40 mm × 550 mm spiral worm shaft. at one end of the screw press shaft is a conical frustum with an angle of 45° with a length 125 mm and width of 87 mm as shown in figure 3. figure 3: a crosssection of wormshaft iii. determination of wormshaft diameter assuming a power source of 35 kw as the prime mover for the machine, the tensional moment (mt) due to the applied load can be determined (hall et al., 1980): mt = 9550 ×kw rev min (5) assuming that power = 35 kw and speed = 92.0 rpm = 9550 ×35 92 nm = 3633.2 nm using the bending moment diagram in appendix 1, the maximum bending moment (mb) was found to be: mb = 342.104 nm http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 703 the diameter of the shaft was then determined using equation below. (hall et al., 1980) d3 = 16 πs kbmb 2 + ktmt 2 (6) where:s is allowable shear stress kb is shock and fatigue factor for bending moment kt is shock and fatigue factor for torsional moment mt is torsional moment mb is bending moment where: ss = 55 mn/m2 (using a factor safety of 2.5) kb = 1.5 mb =342.104 nm kt = 1 mt = 145.33 nm d3 = 16 π ×55 ×106 1.5 × 342.104 2 + 1 × 145.33 2 d3 = 4.938 × 10−5 d = 36.68 mm iv. the screw length the equation of a helix wound on the shaft is given by; x = (r + ml) cos θ (7) y = (r + ml) sin θ and z = (r + ml) cot α (8) x, y and z are the shaft axes. the length s of the helix curve is given by: s2 = x2 + y2 + z2 (hrankowski and waldman, 2017) (9) hence ds dθ 2 = dx dθ 2 + dy dθ 2 + dz dθ 2 (10) where ∂x ∂θ = r + ml sinθ (11) ∂y ∂θ = r + ml cos θ (12) ∂z ∂θ = r + ml cot α (13) ∂s ∂θ 2 = r + ml 2 cos α2 (14) or ∂s ∂θ = r + ml cosec α (15) = r+ml sin∝ (16) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 704 or s = r+ml sin α θ2 θ1 ∂θ� (17) s = r+ml sin α θ2 − θ1 (18) if θ1 = 0° and α =17°, s becomes s = 3.4203(r + ml) θ2 (19) s = 3.4203 (r + ml) nπ according to stephens (2015) the screw length s is given by:s = 2πrn where:α is helix angle r is radius of shaft screw n is number of pitch thread the volume of the spiral space between the crest of the screw and the inside of the barrel was found from: v = m ρm3ℎ−1 (20) reported that the input capacity per hour of the screw press can be found by using capacity: c = 60 pankmknρ (21) where:km is 0.35 kn is 1.0 p is pressure a is cross-sectional area ρ is density of fluid n is speed of the screw pitch with n being varied between 46.6 and 92.0 rpm for screw pitches of 100 mm and ρ is 620 kgm3, i.e. v = m ρ = 10 620 m3 ℎ (22) hence: v = 2.6882 × 10−4 = m3 ℎ (oyinlola et al., 2004) v = bsh = nπ2d2ℎtan∝ sec∝ = 2.6882 × 10−4m3 if h =5 mm, d = 38 mm, α = 17° from which n = 12 approximately. therefore the screw length as given by equation 3.16 equals s = 3.4203(r + ml)(nπ) = 2.45 m. = (r +ml)2cos2 or http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 705 ∂s ∂θ = r + ml cos α = r+ml sin α (23) if θ1 = 00 and  = 450 s = 1.4142 (r + ml) θ2 (24) s = 1.4142 (r + ml) n (25) n = 0.6789 the pitch of the screw thread will be determined by considering the handling capacity of the screw press and the difference between the volumes of the untapered and the tapered end of the expelling section (figure 4) vh =(vu vt ) p (26) where p is pitch of screw thread. vh is handing capacity of the screw press vu is capacity of the untapered end of the cone vt is capacity of the tapered end of the cone (i) the screw thread length = 0.5504 m (ii) the desired range of speed for the screw press is 30 to 60 revolutions per minute (rpm). (iii) an integral cone of 40 mm inner diameter, 87 mm outer and 800 mm length was incorporated in the press. (iv) in one revolution of the screw, the output is advanced by one pitch of the thread. (v) the handling (design) capacity of the screw press as obtained from equation 20 is given as 8.64 x 10-4m3 using equation 19, the pitch of the thread was calculated thus: vh = 8.64 x 10 x 10-4m3 vu = π 0.12 p 4 (27) = 11.31 x 10-3p m3 vt = π 0.04 p 4 =1.32 x 10-3p m3 hence, 8.64 x 10-4 m3 = (11.31-1.32) x 10-3p m3 p = 8.64 × 10−4 11.31−1.32 ×10−3 (28) p = 0.0864 m p = 86 mm efficiency of tℎe macℎine = mecℎanical advantage ×100% velocity ratio (29) velocity ratio = 2π ×distance moved by effort pitch (30) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 706 from equation 24, efficiency of the machine can increase by a decrease in the velocity ratio. this could be achieved by an increase in the pitch (equation 27). this implied that the pitch length could be increased as from 73.75 mm. pitch lengths of 90 mm was selected. tℎe number of tℎread n = lengℎt of screw tℎread pitch (31) equation 3.27 will be used to calculate the number of thread if the length is constant. v. shaft housing shaft housing is cylindrical shape with outer ϕ97 mm and inner ϕ87 mm while the length is 600 mm. it was constructed from mild steel material with a hole of ϕ12 mm bore on the wall of the shaft housing. it was designed for the screw of material as shown in fig 4 the handling capacity of the housing was calculated thus: volume = πr2 × height = 22 7 × 0.0435 × 0.0435 × 0.6 = 3.57 × 10-2 m3 the handling capacity of the housing is 3.57 × 10-2 m3 figure 4: the expression chamber vi. cake and oil outlets as shown in figures 5 and 6, the outlets are meant for the collections of the cake and the oil, respectively. vii. the standing frame the standing frame is made up of angle iron 75 × 75 × 5 mm in cross-section. the frame is 1363 mm in length, 900 mm width and 475 mm in height. other component parts of the machine such as differential unit, the expelling unit, hopper, front yoke, pulley and v-belt were mounted on it. the frame was designed to take care of the vibration and the alignment between the pulley on the electric motor and the differential (fig 7). 2.2. materials the materials used for the project can be grouped into materials for machine fabrication, instrumentation material and oilseed materials (palm kernel, groundnut kernel and soya seed). 2.2.1. materials for machine fabrication the materials used in fabricating the multi-purpose oil expeller include angle bar (75 mm) construction of the machine frame, stainless steel plate (1.5 mm) for the construction of screw, press, cylindrical pipe (87 mm) for the shaft housing, rod (ϕ 40 mm), pulley and belt http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 707 set for driven and transmission of power, universal joint/front yoke – for connection of the worm shaft and final drive shaft, electric motor (15 hp) – for powering the machine, final drive for speed reduction, electrode (both ordinary and stainless) – for joining of both mild steel and stainless materials, and paint – for preventing corrosion. figure 5: cake outlet figure 6: oil outlet file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 708 figure 7: the frame 2.1.2. seed materials oil bearing materials used for the study, viz: palm kernel, groundnut and soya bean were collected from ile-ife central market and obafemi awolowo university research farm. the seeds were subjected to various heat treatments after which they were processed with the machine. sample preparation the fresh seed was conditioned and ovendried at different temperatures (120, 90 and 70°c) as provided in asae standards (2002) to determine various moisture contents at each temperature level. the materials were kept in desiccators to avoid being acted by the atmosphere until it was processed with the expeller. moisture content determination the asae s410 standard (asae, 2002) was used in determining the moisture content of the three materials (palm kernel, groundnut and soya bean). the samples were heated for 25 minutes, 15minutes and 10 minutes at temperatures of 120, 90 and 70°c (asae, 2002) and then kept in desiccators. a kernel sample of 1500 g was weighed into the dish and the weight of the dish plus lid and kernel recorded. the dish and sample was transferred into an oven set at 120, 90 and 70°c. weight measurement was carried out at every thirty minutes until the weight become constant for three consecutive readings. the percentage moisture content of sample was obtained from equation 2.31. m w = wd1−wd2 wd2 × 100 (32) where: mw is moisture content of sample wd1 is weight of sample before drying (g) wd2 is weight of sample after drying (g) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 709 dynamic viscosity determination the dynamic viscosity of the oil extracted from the three oil seeds was determined by using sm5001 viscometer (cup type) operation manual as reported by owolarafe et al. (2008). the cup was put in the circular frame and the leveling leg of the viscometer was adjusted to make sure that the bubble on the cross frame was at the center as shown in plate 1. the oil extracted was poured into the flow cup and the backup was used to control the flow of the oil. the extracted oil was allowed to flow from the flow cup to another cup and the time of flow was taken by starting the stopwatch to test the oil appearing line shape. when the line was cut off then the stopwatch stopped. this process was replicated thrice and the values were recorded. to determine the viscosity manually the following formula was used r = t−6 0.223 (33) where r is the dynamic viscosity (mm2/s) t is the flow out time (s) plate 1: sm5001 viscometer ametek powervar cary, nc, usa 2.1.3 fabrication and assembly of the machine components figure 1 shows the three dimensional view of complete assembly of the machine components. assemblage of the machine began with the welding of the frames, the hopper and the electric motor seat and the differential seat as well. the front yoke was welded to the main shaft from the differential unit. 2.2 performance evaluation of the machine performance evaluation of the machine was carried out by operating the machine using four factors which include soaking time (which resulted in differential moisture content), three variable oilseeds (palm kennel, groundnut seed and soya bean) temperature and the extraction speed. each of these factors was investigated using 1.5 kg of oilseed at three replicates to determine the optimal performance of the machine. the parameters determined include oil yield, throughput capacity and oil extraction efficiency. the effect of the processing conditions of the oil seeds on the performance of the machine was analyzed using one way analysis of variance (anova) and duncan’s multiple range test. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 710 determination of yield of oil the yield of oil in parentage was calculated as follows: yoil = qj qf (34) where qj = quantity of oil extracted in kg qf = quantity of oil seed processed in kg (quantity of oil extracted and the cake in kg) determination of throughput capacity of the machine the capacity of the machine was calculated as shown:capacity of machine (capm) = qf t (35) where qf = quantity of oilseed processed in kg. t = time taken in minute. determination of efficiency of the machine oil extraction efficiency (ee) in percentage is the ratio of the weight of oil extracted to the product of the oil (moisture content) of the oilseed and the eaglet of the product before extraction. (olaoye and oyelade, 2012) ee = qj x 100 x qf (36) where qj is quantity of oil extracted in kg. x is the oil content (moisture content of oil) in % qf is total quantity of material fed into the machine in. 3. results and discussion tables 1, 2 and 3 show the data obtained on oil yield, throughput capacity and efficiency of the machine at different conditions (moisture content and shaft speed) for the three oilseeds processed. the average oil contents of the oilseeds were used to compute the mean values of the efficiency of the machine. new dungeons multiple range test (dmrt) was used to determine the differences in the mean treatment effect of moisture content on oil yield. 3.1. effect of shaft speed, moisture content and type of oilseeds on oil yield as shown in table 1, increase in moisture content from 5 to 15% and increase in shaft speed from 47.6 to 92.0 rpm increased the oil yield in all the oil seeds. at shaft speed levels of 47.6, 87.0 and 92.0 rpm, increase in the moisture content of palm kernel oilseed increased the oil yield from 19.0 to 23.0%, 26.0 to 48.0% and 27.0 to 51.0% respectively. with the soya bean seed, there was no oil expelled at 5% moisture content but the oil yield later increased from 0.0 to 16.0 % as the moisture content increases for all the levels of the shaft speed as presented in table 2. in the case of groundnut, as the moisture content was increased from 5% to 15%, the oil yield increased from 7.3 to 31.7%, 5.7 to 26.0% and 7.3 to 28.0% for the levels of shaft speed as presented in table 3. these results obtained indicated that higher oil yield can be achieved at low shaft speed and moisture content of the seed between 5 to 10 %. these follow the trend reported by orhevba et al. (2013) and samuel and alabi (2012) though their research work was based on neem seed. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 711 table 1: the mean values of measured parameters for palm kernel type of oil seed mean temperature (°c) mean throughput capacity (kg/h) mean oil yield (%) mean machine efficiency (%) m1 s1 97.00 1.81 19.0 39.4 m1 s2 95.33 1.94 26.0 51.1 m1 s3 92.33 0.89 27.0 52.1 m2 s1 92.33 0.91 22.0 33.9 m2 s2 83.33 0.79 19.0 36.9 m2 s3 82.33 0.53 27.0 52.1 m3 s1 85.00 0.83 23.0 45.6 m3 s2 84.33 1.07 48.0 93.2 m3 s3 83.33 0.62 51.0 99.6 legend s = shaft speed (rpm) m = moisture content (%) s1 = 47.6 rpm m1 = 5% s2 = 87.0 rpm m2 = 10% s3 = 92.0 rpm m3 = 15% table 2: the mean values of measured parameters for soya bean type of oil seed mean temperature (°c) mean throughput capacity (kg/h) mean oil yield (%) mean machine efficiency (%) m1 s1 69.67 0.00 0.00 0.00 m1 s2 68.67 0.00 0.00 0.00 m1 s3 67.67 0.00 0.00 0.00 m2 s1 69.00 0.42 12.1 62.1 m2 s2 67.00 0.57 14.5 74.4 m2 s3 66.33 0.34 11.3 57.9 m3 s1 71.67 0.52 16.0 82.1 m3 s2 69.00 0.56 16.0 82.1 m3 s3 68.67 0.52 16.0 82.1 legend s = shaft speed (rpm) m = moisture content (%) s1 = 47.6 rpm m1 = 5% s2 = 87.0 rpm m2 = 10% s3 = 92.0 rpm m3 = 15% file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 712 table 3: the mean values of measured parameters for groundnut type of oil seed mean temperature (°c) mean throughput capacity (kg/h) mean oil yield (%) mean machine efficiency (%) m1 s1 65.0 0.09 7.3 16.7 m1 s2 66.3 0.07 5.7 15.9 m1 s3 61.7 0.09 7.3 16.7 m2 s1 68.4 0.23 18.7 42.4 m2 s2 65.0 0.31 23.3 53.1 m2 s3 60.0 0.21 17.0 38.6 m3 s1 52.4 0.55 31.7 72.0 m3 s2 46.5 0.50 26.0 59.1 m3 s3 47.7 0.57 28.0 63.6 legend s = shaft speed, m = moisture content s1 = 47.6 rpm m1 = 5% s2 = 87.0 rpm m2 = 10% s3 = 92.0 rpm m3 = 15% as shown in tables 1, increasing the machine speed from 47.6 to 92.0 at 5% moisture content of palm kernel, caused an increase in the oil yield from 19.0 to 27.0 %, while at 10% moisture content, increase in the shaft speed caused variation in the oil recovery ranging between 19.0 and 27.0 %, and also at 15 % moisture content, increase in the shaft speed increased the yield from 23.0 to 51.0%. in the case of soya bean, at 5% moisture content, there was no oil expelled for all the levels of the shaft speed, and also at 10 % moisture content, the increase in the shaft speed varied the yield ranging between 11.3 and 14.5 %, while at 15 % moisture content, the yield was constant at 16 % for all the levels of shaft speed as presented in table 2. this implies that moisture content of at least 10 % is required for oil extraction from soya bean. in the case of groundnut, at 5, 10 and 15% moisture content, increase in the shaft speed resulted to variation in the yield which ranged between 5.7 and 7.3%, 17.0 and 23.3%, also 26.0 and 31.7% as shown in table 3. this observed pattern in the oil yield for the seeds being considered could happen as a result of the heat effect which helps in better rupture of the cell walls and globules which helped in easy oozing out of the hull. this trend was reported by shukla et al. (1992). 3.2. effect of shaft speed, moisture content and seed type on machine efficiency as presented in table 1, the efficiency of the machine when used in processing palm kernel increases with increase in moisture content and machine shaft speed. the machine reaches its optimum performance in terms of efficiency (99.6 %) when processing palm kernel at 15 % moisture content and machine speed of 92.0 rpm. for soya bean, 0% machine efficiency was obtained at moisture content below 10%, while the highest machine efficiency (82.1%) was obtained at 15% moisture content for all levels of the machine speed. groundnut requires a low level of shaft speed and high moisture content to obtain the best machine efficiency. highest machine efficiency of 72.0% was obtained at 5% moisture content and 47.6 rpm shaft speed. the lower machine speed increases the heat effect on the seeds which helps in better rupture of the cell walls and globules which helped in easy oozing out of the hull. this result is corroborated by the findings of jimoh and olukunle (2013); orhevba et al. (2013); ashaolu and noibi (2013). the variation in terms of the optimum performance of the machine is as a result of the difference in properties of the seeds considered in the study. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 713 3.3. effect of processing condition on the throughput capacity the throughput capacity of the machine varies with moisture content of the seed and machine speed. for palm kernel, the highest throughput capacity (1.94 kg/h) was obtained at 5% moisture content and machine speed of 87.0 rpm. as presented in table 1, there was variation in the throughput capacity obtained at different levels of moisture content and shaft speed this variation may be as a result of the oilseed compressive strength and shearing force in the palm kernel. this follows the trend recorded by omoruyi and ugwu (2013). the throughput capacity of soya bean at 5 % moisture content was 0.0 kg/h for all the levels of shaft speed, while throughput capacity of 0.42, 0.57 and 0.34 kg /h was obtained at 10 % moisture content for the 3 levels of the shaft speed. also, at 15 % moisture content, the throughput capacity values were 0.52, 0.56 and 0.52 kg/hr for the 3 levels of the shaft speed (47.6, 87.0 and 92.0 rpm) respectively as shown in table 2. the highest throughput capacity of soyabean was obtained at 10% moisture content and 87.0 rpm machine speed. in the case of groundnut, the throughput value at 5 % moisture content was 0.09, 0.07 and 0.09 kg/h for the 3 levels of shaft speed, while throughput capacity of 0.23, 0.31 and 0.21 kg/h was obtained at 10 % moisture content, 0.55, 0.50 and 0.57 kg/h was also obtained at 15 % moisture contents for the 3 levels of the shaft speed (47.6, 87.0 and 92.0 rpm) respectively as shown in table 2. higher moisture content causes plasticizing effect which reduces the level of compression (shukla et al, .1992). similarly, heat generated by the wormshaft during pressing can be fully transferred to the individual fat globules, which result in breakdown of the emulsion form of the fat and help in releasing more oil droplets. olayanju et al. (2006) 3.4. effect processing conditions on volumetric flow rate of the oil the processing condition such as type of oil seed, moisture content and shaft speed on volumetric flow rate was discussed in this section. in table 4, it could be observed that the volumetric flow rate of palm kernel ranges from 0.7 × 10-6 to 1.77 × 10-6 m3s-1, the highest volumetric flow rate was observed at 5% moisture content and 92.0 rpm shaft speed. in the case of soya bean, the volumetric flow rate is between 1.31 × 10-7 m3s-1 to 2.95 × 10-7 m3s-1, the volumetric flow rate reached its peak value 15 % moisture content and 92.0 rpm shaft speed. similarly, the volumetric flow rate of groundnut ranges between 0.34 × 10-6 to 0.84 × 10-6 m3s-1, and reaches the maximum level at 5 % moisture content and 87.0 rpm shaft speed as shown in table 4. this indicates that, the highest volumetric flow rate was observed in palm kernel while the lowest volumetric flow rate was observed in soya beans. samuel and alabi (2012), corroborated the findings stating that at constant temperature, excessive increment in moisture content of kernel seeds could reduce the expulsion ability and wear of mechanical parts of expeller. from table 4, it could be observed that increase in the moisture content from 5 to 15 % while the shaft speed is kept constant at 47.6 rpm, the volumetric flow rate of palm kernel fluctuate between 0.90 × 10-6, 0.70 × 10-6 and 0.85 x 10-6 m3s-1. also at 87.0 rpm, increase in the moisture content as stated caused the volumetric flow rate to also fluctuate between 1.22x10-6, 1.21 x 10-6 and 1.17 x 10-6 m3s-1. while maintaining a shaft speed of 92.0 rpm and increase in the moisture content, the volumetric flow rate decreases from 1.77 x 10-6 to 1.73 x 10-6 m3s-1. this trend was also reported by ezeoha et al (2017). similar trend was also observed in the case of soya bean and groundnut and which was corroborated by the findings of rouhollah and seyyed, (2016). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 714 table 4: processing condition of the volumetric flow rate of oil type of oilseed shaft speed (rpm) moisture content (%) volumetric flow rate (m3/s) 47.6 5 0.90 x 10-6 palm kernel 47.6 10 0.70 x 10-6 47.6 15 0.85 x 10-6 87.0 5 1.22 x 10-6 palm kernel 87.0 10 1.21 x 10-6 87.0 15 1.17 x 10-6 92.0 5 1.77 x 10-6 palm kernel 92.0 10 1.74 x 10-6 92.0 15 1.73 x 10-6 47.6 5 1.31 x 10-7 soya bean 47.6 10 1.36 x 10-7 47.6 15 1.43 x 10-7 87.0 5 1.78 x 10-7 soya bean 87.0 10 1.75 x 10-7 87.0 15 1.81 x 10-7 soya bean 92.0 92.0 92.0 5 10 15 1.91 x 10-7 1.93 x 10-7 2.95 x 10-7 47.6 5 0.61 x 10-6 47.6 10 0.58 x 10-6 groundnut 47.6 15 0.34 x 10-6 87.0 5 0.84 x 10-6 87.0 10 0.67 x 10-6 groundnut 87.0 15 0.70 x 10-6 92.0 92.0 5 10 0.70 x 10-6 0.67 x 10-6 92.0 15 0.66 x 10-6 4. conclusion development of a machine to extract oil from different classifications of oil seeds (hard or soft) is possible provided the properties of the seeds are carefully considered at the design stage. the effect of processing conditions such as the moisture content of the seeds and shaft speed of the machine on properties such as the oil yield, throughput capacity and efficiency of the machine was examined. the study revealed that optimum performance of the machine in terms of oil yield for all the seeds (hard or soft) occurs at 15% moisture content of seed and 47.6 rpm machine speed. volumetric flow rate of oil from the seeds is directly influenced by the shaft speed, moisture content and oil temperature. the highest efficiency of the machine will be attained at low shaft speed and moisture content of the seeds ranges between 5 to 10%. in general, the data presented in the study will be useful in optimizing the mechanics of mechanical oil extraction using the multi-seed oil expeller. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):699-716. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 715 references agbogun, jo. 2011. oil extraction in fruits, ways to extract oil from seeds. material and industrial technology (417). agricultural engineering research london 28,495-503. asae 2002. moisture measurement: peanut st. joseph mich. asae standard s410.1 ashaolu, mo. and noibi, ao. 2013. effects of moisture content on some mechanical properties of soybean (glycine max) varieties. african journal of food science and technology, 4(10): 211220. bello, ia. 2013. how to start groundnut oil production in nigeria. www.healthresult.com/business/groundnut-oil-production-in-nigeria/ dagwa, im. and ibhadode, ao. 2008. some physical and mechanical properties of palm kernel. botswana journal of technology, 17(2): 50-56. davies, rm. 2009. some physical properties of groundnut grains. research journal of applied sciences, engineering and technology, 1(2): 10-13 ezeoha, sl., akubuo, co., odigboh, eu. and arallo, m. 2017. performance evaluation of magnus screw press (model ms-100) for palm kernel oil extraction. nigerian journal of technology, 36(2): 636-642. hall, as., holowenko, ar. and laughlin, hg. 1980. theory and problem of machine, schaum’s outline series, s.i. metric edition megraw – hill book company, 114. hrankowski, a. and waldman, c. 2017. how to calculate length of screw thread. https/ math.stackexchange.com. jimoh, mo. and olukunle, oj. 2013. effects of physio-mechanical properties of palm nut on machine performance evaluation. world applied programming, 3(7): 302-308. kibar, h. and ozturk, t. 2008. physical and mechanical properties of soybean. international agrophysics. 22: 239-244 kojima, y., parcell, j. and cain, j. 2016. a global demand analysis of vegetable oils for food and industrial use: a cross-country panel data analysis with spatial econometrics. selected paper prepared for presentation at the agricultural & applied economics association annual meeting, boston, massachusetts. olaoye, jo. and oyelade, oa. 2012. synthesis and analysis of a slider crank linkages in sugarcane juice extractor. g.j.p and a science and technology, 0(2): 10-26 olatunde ob., ajayi, ea. and fatukasi, so. 2014. design and fabrication of groundnut (arachis hypogaea) roaster cum expeller. international journal of science and technology, 3(3):177-184. olayanju, tma. 2006. man, material and machine: the tricycle for agricultural mechanization. funaab inaugural lecture series no. 51. isbn: 978-38625-2-7. omoruyi, a. and ugwu, kc. 2013. optimization and performance evaluation of palm nut cracking machine. the international journal of science and research (ijsr), 4(7): 1-8 orhevba, ba., chukwu, o., osunde, za. and ogwuagwu, v. 2013. effect of moisture content on the yield of mechanically expressed neem seed kernel oil. the international journal of engineering and science (ijes), 2(8): 2319-1805. owolarafe, ok., osunleke, as., odejobi, oa., ajadi, so. and faborode, mo. 2008. mathematical modeling and simulation of the hydraulic expression of oil from oil palm fruit. biosystems engineering, 101: 331-340 oyinlola, a., ojo, a. and adekoya, la. 2004. development of a laboratory model screw press for peanut oil expression. journal of food engineering, 64: 221-227. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al.: development of multi seeds oil expeller. azojete,16(4):699-716. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salthaqib@yahoo.com 716 rouhollah, t. and seyyed, an. 2016. the effect of viscosity on performance of a low specific speed centrifugal pump. international of journal rotating machinery, 6(1): 1-9. samuel, od. and alabi, agf. 2012. problems and solution involved in oil processing from kernel seeds. the pacific journal of science technology, 13(1): 372-383. shukla, p., srivastava, r. and gupta, k. 1992. oil processing technology. central institute of agricultural engineering, karaphur, india. stephens, rc. 2015. strength of materials, theory and examples s.i. units edward arnold, london http://www.azojete.com.ng 7 arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):569-574 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 569 original research article study on the use of banana and pineapple peel waste as biofertilizers: enhancing soil fertility, promoting sustainable agriculture and environmental sanitation m. mustapha*, j. j. alasa, a. u. bashir and b. mohammed department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: mohammedmusty@unimaid.edu.ng 1.0 introduction maximum agricultural productivity often requires application of artificial nutrients known as fertilizer to augment soil nutrients and increase soil fertility (savci, 2012). however, achieving this based on inorganic fertilizer (such as npk and urea), is found to be detrimental to the ecosystem (savci, 2012), especially on long term basis (dubey et al., 2012), thus damaging the ecosystem. it often leads to decline in soil organic matter content, soil acidification and soil physical degradation leading to increase soil erosion, and toxification of the physical environment particularly its water resources contents (morakinyo et al., 2013). inorganic fertilizers are potential water pollution sources of nitrate, potassium, phosphate and various strains of heavy metals such as arsenic (ar), cadmium (cd), mercury (hg), chromium (cr), lead (pb) that are generally harmful to the human health system (sönmez et al., 2007; morakinyo et al., 2013, sharma and singhvi, 2017), furthermore, inorganic fertilizers are expensive, thus beyond the reach of resource-poor farmers because of high cost and uncertain accessibility and organic inputs, which are often proposed as alternative to inorganic fertilizer composition and high labour requirement (law-ogbomo et al., 2011). it is therefore imperative article information abstract indiscriminate agricultural waste disposal especially fruits peels can cause environmental pollution with increased public health risk. this study deals with managing banana and pineapple peel waste as organic fertilizers towards promoting sustainable environmental sanitation and agriculture production. waste of banana and pineapple peels were separately collected in households, dumpsites and markets, the collected fruits peels were cleaned, sun dried for 33 days and grounded into powdered form. three different formulations of organic fertilizers were made from the sun dried and finely grounded fruit peels of banana and pineapple, namely; formulation a containing 100g of banana peels powder; formulation b containing 100g of pineapple peels powder and formulation c containing 100g of a mixture of banana and pineapple peels powder. four different containers were used to collect 10kg of soil each, three of which were treated with the three formulations and named sample a, b, c and an additional sample d which is control. after 30 days of treating the soil with the different formulations. the result of laboratory soil analysis showed that; sample a contains 14% nitrogen, 37% phosphorus, 7% potassium, 40% calcium and 2% magnesium. sample b contains 11% nitrogen, 39% phosphorus, 8% potassium, 39% calcium and % magnesium. sample c contains 17% nitrogen, 35% phosphorus, 4% potassium, 43% calcium and 1% magnesium. sample d (controlled soil sample) contains 1% nitrogen, 17% phosphorus, 4% potassium, 45% calcium and 33% magnesium. it was revealed that the fruit peel powder formulations can increase the soil fertility which serves as alternative replacement for chemical fertilizers towards sustainable agriculture and the environment. it is recommended that the farmers and general public should make beneficial use of fruits waste as organic fertilizers and not to be discarded indiscriminately. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 may, 2021 revised 10 september, 2021 accepted 18 september, 2021 keywords: environmental sanitation chemical fertilizers organic agriculture banana peels pineapple peels mustapha et al: study on the use of banana and pineapple peel waste as biofertilizers: enhancing soil fertility, promoting sustainable agriculture and environmental sanitation. azojete 17(4):569-574. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 570 to adopt eco-friendly and sustainable agricultural practices for efficient food production through organic farming. recently, the need for clean environment for healthy habitation has attracted the integration of vegetables and fruits peels waste into farms, as an alternative to synthetic plant growth nutrient, and as part of measures towards efficient nutrient management and recycling of wastes; although animal manures are also being incorporated into organic farming, however, they sometimes present some sort of public health and environmental water pollution issues in nearby farms if not well managed; it leads to pathogenic bacterial contamination, ammonia pollution and depletion of dissolved oxygen in water bodies which is especially unconducive for aquatic livelihood. however, a wide range of agricultural fruit waste such as banana peel, orange peel, pineapple, egg shell, tea waste, potato peel waste, generated from especially households and fruit vendors were mostly discarded without subjecting to any form of commercial value, and at large environmental expense and quality of life of people (harir et al., 2015).however, numerous scientific studies showed that various quantities of minerals and natural bioactive phytochemicals are contained in fruits peels, which are essentially needed by plant for optimum growth and development (rudra et al., 2015; bakry et al., 2016; khattak and rahman, 2017; pathak et al., 2017, sagar et al., 2018; vasanthi and ramadas, 2019), such as calcium, sodium, magnesium, iron, manganese, zinc, potassium and phosphorus which are potential sources of plant nutrient. hence utilizing these wastes as plant fertilizers undoubtedly may lead to increase in soil plant nutrients and sustainable plant growth and environment. banana and pineapple peel are some common fruits consumed globally, hence, with the increasing banana and pineapple fruits production and consumption, banana and pineapple waste are also proportionally increasing, thus waste disposal present a serious environmental challenge, as the rich nutrients packed in these wastes make them vulnerable to microbial spoilage. the objectives of this research are to demonstrate the efficacy of the use of peels of banana and pineapple on soil fertility for maximum agricultural production. 2. methodology 2.1. collection and preparation of soil clay soil samples were collected in a barren land and were filled in four different containers (made up of rubber), and named sample a, b, c and d (control), each weighing 2kg, the soil was sampled, air-dried in an oven and collected in a sterile polythene bags and sent to laboratory for analysis of macro elements (nitrogen, phosphorous and potassium), micro elements (calcium and magnesium), and tested for electrical conductivity and ph, as initial nutrient content of the soil sample before treatment 2.2. extraction of fruit peel waste waste of banana and pineapple peels waste were separately collected in households, dumpsites and markets, the collected fruits peels were rinsed adequately in running tap water of debris, sand and foreign materials, the cleaned peels were cut into small pieces (1-5cm) and sun dried for 33 days, which were then ground into powdered form, sieved and stored at room temperature, each of pineapple and banana extract were prepared separately and an additional preparation containing a mixture of pineapple and banana. figures 1 and 2 show the banana peel and pineapple peel powders. figure 1: grounded banana peel powder figure 2: grounded pineapple peel powder arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 569-574. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 571 2.3. formulation of different fruit peels fertiliser three formulations, 4g of each of fruit peel powders prepared were diluted in 400ml of water and applied to soils, and mixed properly for uniform distribution, controls and two replications maintained for each of powders, for 32 days. 2.4. physiochemical analysis of treated soil samples after treatment, the three different samples were tested at the department of geology laboratory, university of maiduguri. the samples are sample a (banana peel powder with soil sample), sample b (pineapple peel powder with soil sample) and sample c (banana peel powder and pineapple peel powder with soil sample). parameters measured were ph, electronic conductivity (ec), nitrogen (n), phosphorus (p), potassium (k), calcium (ca) and magnesium (mg) in order to discover their increase level and availability in the soil sample. 3. results and discussion 3.1 chemical properties of different fertilizer formulations soil samples and control. the result of the soil analysis of the various soil sample treated and the control were shown below in table 1 and figure 3. table 1: chemical properties of the various samples mixed and treated with the soil sample note: results are in percentage with exception of ph and ec. figure 3: bar chart showing the amount of each parameter in the various samples 0 5 10 15 20 25 30 35 40 45 sample a (banana peel with soil sample) sample b (pineapple peel with soil sample) sample c (banana peel and pineapple peel with soil sample) sample d controlled (plain soil sample) ph ec n p k ca mg composition of micronutrient percentage (%) composition of macro nutrients percentage (%) samples ph ec(μs/cm) n p k ca mg soil sample a (banana peel formulation) 8.1 380 10.21 26.7 5.10 28.90 0.98 soil sample b (pineapple peel formulation) 8.0 330 8.91 30.98 6.0 31.0 2.01 soil sample c (banana + pineapple peel formulation) 7.9 370 15.32 32.90 3.96 39.67 15.32 soil sample d (control) 6.2 430 0.105 1.75 0.395 4.6 3.3 mustapha et al: study on the use of banana and pineapple peel waste as biofertilizers: enhancing soil fertility, promoting sustainable agriculture and environmental sanitation. azojete 17(4):569-574. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 572 3.2 nitrogen (n) as shown above in figure 1 and table 1, the treated samples have appreciable level of nitrogen content with sample c (banana and pineapple peel with soil sample) being the highest (15.32%) followed by sample a (10.21%) and sample b (8.91%). however, sample d (control) has the lowest nitrogen content (0.105%) which differed significantly, this is similar to studies by mamouni et al., (2016) in which phytochemicals analysis wastes of potatoes peel and shrimp shells showed high nitrogen presence in them, averaging 16.2 and 49.8 kg/ton respectively, hence, signifying that fruit peels wastes are an important source of nitrogen for plant growth. nitrogen plays a vital role is protein development and various critical plant functions such as photosynthetic and enzymatic reactions (hamid et al., 2019; khairnar and nair, 2019), if the soil is deficient in nitrogen, the plants become stunted and pale. however, excess nitrogen can also be detrimental to plants. 3.3 phosphorus (p) the result shows that sample c (banana and pineapple peel with soil sample) has the highest amount of phosphorus with 32.90% followed by sample b (30.98%) and sample a(26.7%), and sample d (controlled) has the lowest amount of phosphorus with 1.75% which differed significantly with the treated samples. the results are again similar to findings by mamouni et al., (2016), where almond hulls were found to be a good source of phosphorus with an average of 2.4 kg /ton, which can be beneficial for plant growth. phosphorus provides plants with a means of using the energy harnessed by photosynthesis to drive its metabolism. it can stimulate root development, increase stalk and stem strength and improve flower and seed production (hamid et al., 2019). a deficiency of this nutrient can lead to impaired vegetative growth, weak root systems, poor fruit and seed quality, and low yield. however, plants require fairly large quantities of phosphorus, but the levels of phosphorus available to plant roots at any given time are usually quite low. 3.4 potassium (k) the result shows that sample b (pineapple peel with soil sample) has the highest amount of potassium (6%) followed by sample a and sample c, while sample d (control) has the lowest amount of potassium with 0.395% which differed significantly, indicating that fruits peels are vital sources of potassium element for plant growth (hussein et al. 2019), especially the banana peels (bakry et al., 2016). potassium rivals nitrogen as the nutrient absorbed in greatest amounts by plants. like nitrogen, crops take up a relatively large proportion of plant available potassium each growing season. potassium enhances enzyme actions, aids in photosynthesis and food formation. it builds cellulose and helps translocation of sugars and starches. potassium also plays role in the size, shape, color, taste, shelf life, fiber and other quality-related measurements of crops. additionally, potassium can increase root growth and improves drought tolerance (hamid et al., 2019) plants deficient in potassium are unable to utilize nitrogen and water efficiently and are more susceptible to disease. 3.5 calcium (ca) the result shows that sample c (banana and pineapple peel with soil sample) has the highest amount of calcium with 39.67% and sample d (controlled) has the lowest amount of calcium with 4% which differed significantly. calcium is essential for proper functioning of plant cell walls and membranes, also activating several enzymatic systems, thus significant to the proper development of plants (el habbasha and faten, 2015). 3.6 magnesium (mg) the result shows that sample c (banana and pineapple peel with soil sample) has the highest amount of magnesium with 15.32% and sample a (banana peel with soil sample) has the lowest amount of magnesium with 0.98% which differed significantly. magnesium acts together with phosphorus to drive plant metabolism and is part of chlorophyll; a vital substance for photosynthesis (cowan, 2002; shaul, 2002). arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 569-574. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 573 3.7 soil ph this result shows that sample a (banana peel with soil sample) has the highest ph value with 8.1 which corresponds with the findings by khairnar and nair, 2019, whereas sample d (controlled) has the lowest ph value with 6.2 which differed significantly. however, the ph values of the different soil samples; sample a, sample b and sample c were above 7 which signify the samples are base/alkaline. depending on the chemical characteristics, different fruits peels exhibit different ph level (khairnar and nair, 2019), most plants grow best in soil with a ph between 6 and 7.the results shows that fruits waste can be used to regulate soil ph for enhanced agricultural productivity (panwar, 2015). soil ph is an indicator of the soil’s acidity which is a primary factor controlling nutrient availability, microbial processes, and plant growth (allen, 2013). when soil ph is maintained at the proper level, plant nutrient availability is optimized, solubility of toxic elements is minimized, and beneficial soil organisms are most active, the alkalinity of the treated samples was due to the fact that banana and pineapple were both alkaline fruits, hence can be essential in regulating soil ph for optimum growth and development as different plants perform best at a particular ph (adrija and navni, 2018). 3.8 soil electrical conductivity (ec) this result shows that sample d (controlled) has the highest amount with 430μs/cm and sample b (pineapple peel with soil sample) has the lowest amount with 330μs/cm which differed significantly. the high ec in the untreated sample (sample d) is an indication that fertilizer application is essential for altering soil ec and replenishing soil nutrients for maximum production. the soil electrical conductivity (ec) is a measurement that correlates with soil properties that affect crop productivity, including soil texture, cation exchange capacity (cec), drainage conditions, organic matter level, salinity, and subsoil characteristics. electrical conductivity (ec) is the most common measure of soil salinity and is indicative of the ability of an aqueous solution to carry an electric current. plants are detrimentally affected, both physically and chemically (mun), by excess salts in some soils and by high levels of exchangeable sodium in others. excess salts hinder plant growth by affecting the soil-water balance (sheldon et al., 2004). soils containing excess salts occur naturally in arid and semiarid climate. 4. conclusion comparative study on the utilization of banana and pineapple fruit peel as organic fertilizer was carried out to know soil fertility, towards promoting both sustainable agricultural and environmental sanitation. from the study, it is found that banana and pineapple peel waste are substantially rich in soil micro and macro nutrients to enhance soil fertility and increase plant yield, thus sanitizing the environment and reducing the negative impacts of inorganic fertilizers. it is therefore recommended that public and farmers should make beneficial use of fruits waste as organic fertilizers and not discarded indiscriminately causing pollution of the environment. references adrija, s. and navni, r. 2018. efficacy of banana (musa paradisiaca) and sweet lime peels as natural fertiliser in herbs. international journal of agricultural sciences, 10 (8):5822-5825. bakry, ab., ibrahim, fm., shater-abdallah, mm. and el-bassiouny, hms. 2016. effect of banana peel extract or tryptophan on growth, yield and some biochemical aspects of quinoa plants under water deficit. international journal of pharmtech research, 9(8): 276-287. cowan, ja. 2002. structural and catalytic chemistry of magnesium dependent enzymes. biometals, 15:225–235. dubey, v., patel, ak., shukla, a., shukla, s. and shalini, s. 2012. impact of continuous use of chemical fertiliser. international journal of engineering development, 3(1): 13-16. el habbasha, sf. and faten, mi. 2015.calcium: physiological function, deficiency andabsorption. international journal of chemtech research, 8(12): 196-202. mustapha et al: study on the use of banana and pineapple peel waste as biofertilizers: enhancing soil fertility, promoting sustainable agriculture and environmental sanitation. azojete 17(4):569-574. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mohammedmusty@unimaid.edu.ng 574 hamid, ha., qi, lp., harun, h., sunar, nm., ahmad, fh., muhamad, ms. and hamidon, n. development of organic fertilizer from food waste by composting in uthm campus pagoh, journal of applied chemistry and natural resources, 1(1): 1-6. harir, ai., kshim, r. and ishiyaku, b. 2015. exploring the resource recovery potentials of municipal solid waste: a review of solid wastes composting in developing countries. international journal of scientific research and publication, 5(4): 1-8. hussein, hs., shaarawy, hh., hussien, nh. and hawash, si. 2019. preparation of nanofertilizer blend from banana peels. bulletin of the national research centre, 43:26-31 khair, md. and nair, ss.2019. study on eggshell and fruit peels as a fertiliser, proceedings of international conference on sustainable development, in association with navateur publications, february, 14th and 15th: 25-27. khattak, kf. and rahman, tu. 2017. analysis of vegetable’s peels as a natural source of vitamins and minerals.international food research journal, 24(1): 292-297. law-ogbomo, ke., remison, su. and jombo,eo. 2011effects of organic and inorganic fertilizer on the productivity of amaranthus cruentus in an ultisolenvironment. international journal of plant physiology and biochemistry, 3(14): 247-252. mamouni, fz., razouk, r., kajji, a., daoui, k., el ouali, a. andboukhlifi, f. 2016. characterisation of organic waste used as biofertilisers: case of patotopeelings, almond hulls and shrimp shells. international journal of agriculture, innovations and research, 4(5): 993-998. morakinyo, at., adeboye, ob. andawogbuyi, ot. 2013. environmental effects of application of fertilisersand pesticides on water and soil in ibadan, nigeria. journal of emerging trend in engineering and applied sciences 4(6): 773-777. panwar, n. 2015. studies on physicochemical characteristics and fertility of soil by addition of banana peels-waste management. international journal for scientific research and development, 3(1): 121-125. pathak, pd., mandavgane, sa. and kulkarni, bd. 2017. fruit peel waste: characterization and its potential uses. current science, 113 (3): 444-454. rahman, kma. and zhang, d. 2018. effects of fertiliser broadcasting on the excessive use of inorganic fertlisersand environmental sustainability, mdpi, sustainability, 10: 759-774. rudra, sg., nishad, j., jakhar, n. and kaur, c. 2015. food industry waste: mine of nutraceuticals. international journal of science environmental technology, 4(1): 205–229. sagar, na., pareek, s., sharma, s., yahia, em. and lobo, mg. 2018. fruit and vegetable waste: bioactive compounds, their extraction and possible utilization. comprehensive reviews in food science and food safety, 17(3):512-531. savci, p. 2012. investigation of effect of chemical fertilizers on environment. apcbee procedia, 5th-7th january, hong kong 1, 287-292. sharma, n. and singhvi, r. 2017. effects of chemical fertilizers and pesticides on human health and environment: a review. international journal of agriculture, environment and biotechnology, 10(6): 675-679. shaul, o. 2002. magnesium transport and function in plants: thetip of the iceberg. biometals, 15309–323. sheldon, ar., dalal, rc., kirchhof, g., kopittke, pm. and menzies, nw. 2017. the effect of salinity on plant-available water. plant and soil, 418(1-2): 477-491. sönmez, ø., kaplan, m. and sönmez, s. 2007. an investigation of seasonal changes in nitrate contents of soils and irrigation waters in greenhouses located in antalya-demre region. asian journal of chemistry,19(7): 5639-5646. vasanthi, p. and saradha ramadas, v. 2019. fruit waste its functionality and utilization international journal of recent scientific research, 10 (01f): 30677-30682 arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):185-196 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 185 original research article application of microbial induced calcite precipitation (micp) technology in geotechnical and geo-environmental engineering: a review i. s. muhammad*, b. b. kurna and b. s. u. ibn abubakar department of civil and water resources engineering, university of maiduguri, maiduguri, borno state, nigeria *corresponding author’s email address: ibrahimcivil73@gmail.com 1.0 introduction the use of soil as engineering material for variety of constructions dates back to ancient time where different types of soil are used for different purposes. in some ancient civilizations clay was used as construction materials for architectural works. however, with the advancement of civilization and discovery of natural pozzolanic materials such as volcanic ash, good improvement in strength was attained (dan babor et al., 2009). after the industrial revolution, ordinary portland cement became most accepted and widely used material due to its high strength, durability, workability not only for building construction but also for soil amelioration (maclaren and white, 2003). due to heterogeneity in soil mass within short span, vertically and horizontally, it is very common to encounter unsuitable soil during site investigation for civil engineering works. in such situation, an engineer is left with the options of either bypassing the bad soil using piles, replacing the soil with appropriate material, redesign the structure to suit the condition or improve the soil by altering its engineering properties (venkatramaiah, 2006). soil improvement is primarily categorized into mechanical and chemical methods. mechanical improvement includes processes such as compaction, consolidation, surcharging and others with a view to increase the strength of the soil. the chemical improvement on the other hand employs the use of additives or binders such as cement, lime, natural and artificial pozzolanas to treat a soil either by direct mixing or injection of grout (sherwood, 1993). over the years, several geotechnical works have been successfully implemented using article information abstract one of the most recent areas of research in geotechnical and geo-environmental engineering is bio-mineralization, a natural process in living organisms, also known as microbial induced calcite precipitation. it is the formation of calcium carbonate from a supersaturated solution due to the presence of microbial cells and biochemical activities. in the process, microbes secrete metabolic products that reacts with ion in the medium to precipitate minerals. through this process, soil improvement/remediation have been investigated and proven reliable with minute carbon print as compared to conventional binders. this paper presents an overview on the wide application of microbial induced calcite precipitation in the areas of geotechnical and geo-environmental engineering with the mechanisms and factors influencing its performance explained. the work has also considered both laboratory and field scale researches conducted in these areas. the key contribution of this work is the compilation of different approaches in soil stabilization and remediation, via urease producing microbes, in single source. it also outlined different treatment dosages based on environmental conditions suitable to soil types © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 nov., 2020 revised 24 januray 2021 accepted 27 januray 2021 keywords: soil improvement remediation microorganism urease calcite cementation arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):185-196. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 186 portland cement worldwide. however, despite its benefits and wide application, the use of cement has posed a serious environmental concerns. the major concern lies in the amount of carbon dioxide (co2) emission as a result of cement production which immensely increases the concentration of greenhouse gases in the atmosphere. carbon dioxide which is the major reason for the greenhouse effect causing global warming, is a byproduct of a chemical conversion process used in the production of clinker, a component of cement, in which limestone (caco3) is converted to lime (zulfequar, 2017). the simplified stoichiometric relationship is given in equation (1) below: caco3 + heat → cao + co2 (1) the calcination of calcium carbonate during the production of cement liberates about 0.55 tons of co2 per ton of portland cement which is further emitted into atmosphere. in addition, the huge amount of fossil fuel that is burnt to power the cement plants also emit co2 at a rate of 0.4 tons per ton of cement produced (ilhan et al; 2016). in a note shell, the total emission of co2 into atmosphere in the production of 1 ton of portland cement accumulates to 0.95 tons, and there are more than 2,500 cement power plants worldwide. according to “global carbon budget 2017”by corinne et al; 2018, cement production and burning of fossil fuel accounts for 9.9±0.5 giga-tons of co2 emission annually, which is about 10% of the global co2 emission. other environmental concerns associated with the use of cement include rise in soil ph up to 12-13 due to alkaline hydroxide ion release as a byproduct of hydration, which in turn affects biological organisms by undermining their essential natural activities (taylor, 1997). the irreversible hydration reaction from cement, produced impervious top soil which affects vegetation growth and increases surface runoff in urban settings adding to flooding (hansen, 2002 and rao et al., 2007). this serious environmental concern from cement production and its use have prompted researchers over the years toward exploring eco-friendly and sustainable alternatives for cement in various civil engineering endeavors. in respect to this, different methods have been explored including the use of geosynthetics which have high tensile strength, flexibility and impervious characteristics and are been applied in soil reinforcement, separation, drainage among others. however, their use revealed high dependent on the material rather than the soil thereby limiting its various geotechnical applications (ilhan et al., 2016). the current advancement in technology and deep knowledge in the field of biology and microbiology has made accessible new investigation pathways in geotechnical research and innovation. one of the most promising biological techniques that emerged in the 21st century which was first suggested by mitchell and santamarina (2005) and deeply explored by de jong et al. (2006), is the microbial induced calcite precipitation (micp). its efficiency in tackling number of geotechnical and geo-environmental problems have been successfully investigated and established in both laboratory and field scale with minute carbon footprint compared to cement (amin et al., 2017). muhammad et al: application of microbial induced calcite precipitation (micp) technology in geotechnical and geo-environmental engineering: a review. azojete, 17(2):185-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 187 2.0 microbial induced calcite precipitation mechanism microbial induced calcite precipitation (micp) technique is considered eco-friendly ground improvement and soil reinforcement technique (atticus et al., 2012). according to bosak (2011), micp is the formation of calcium carbonate from supersaturated solution following the presence of microbial cells and bio-chemical activities. the technique is generally based on urease-producing bacteria known as sporosarcina pasteurii (formerly bacillus pasteurii) and their like. it is a soil, non-pathogenic and endospore producing bacteria with an optimum ph for growth of 9.0 that can tolerate extreme conditions (weil et al., 2012 and periasamy et al., 2016). the process involves introducing aerobically cultivated bacteria with highly active urease enzymes into soil. the urease enzyme hydrolyzes urea into one mole of carbonate and two moles of ammonia per mole of urea (malcolm et al., 2012) as presented in the reactions below: co(nh2)2 + 2 h2o → 2 nh4 + + co3 2− (2) in the presence of ca2+ derived from calcium source, mostly cacl2, ca2+ reacts with carbonate ions (co3 2− ) to form one mole of calcium carbonate (caco3) crystals throughout the soil matrix, see equation below: ca2+ + co3 2− → caco3 (3) the introduction of bacterial suspension solution plus the injection of calcifying solution carrying the urea and calcium into the soil mass are essential for completing the process. the urea provides energy for the growth of microbes and adequate carbonate ions while calcium solution supplies calcium ions for rapid generation of calcium carbonate precipitation within the matrix (fatima-zahra and benoit, 2018). this occur due to the reaction of ammonia with water producing hydroxyl ion (oh-) resulting in ph rise in the media which further facilitate precipitation of calcium ions into caco3 (mizanur and neera, 2017). this bio-induced calcite fills pore spaces in the soil and bind soil grains together forming concrete material (malcolm et al., 2012). through this process, geo-environmental and geotechnical problems such as remediation, liquefaction of soils, slope stability, erosion control, carbon-dioxide sequestration, healing of rock fractures were achieved. figure 1: ureolysis-driven calcite precipitation (source de muyeernck et al., 2010) arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):185-196. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 188 2.1 factors controlling micp performance the performance of bio-calcification in micp technology depends on the amount and spatial distribution of caco3 precipitation and other environmental factors. these include the following: 2.1.1 bacteria type and concentration bacteria type and their cell concentration which serves as nucleation sites for caco3 precipitation are necessary for this process. the most common in micp is genera bacillus and sporosacina which catalyst urea hydrolysis (ng et al., 2012). bacteria cell concentration is directly proportional to urea hydrolysis. harkes et al. (2010) reported an increase in urease activity and hydrolysis rate with increasing bacterial concentrations, which also corroborates with an investigation by okwadha and li (2010). 2.1.2 nutrient bacteria nutrients are the source of energy for metabolic activities and essential for calcite production. for effective micp, nutrients have to be provided for their effective growth and activities. the most common are n, p, k, mg, ca and fe which are supplied during culture and soil treatment stages (mitchell and santamarina, 2005; saranya et al., 2017). 2.1.3 ph ph level also dictates the urease activity, micp begins at ph 8 and escalate to 9 where urease activity is high (dupraz et al., 2009). a high ph, is very important for ammonia production by urea hydrolysis. aerobic bacteria release co2 through cell respiration, which is paralleled by an increase in ph due to ammonia production (ng et al., 2012). at low ph carbonates tends to dissolve instead of precipitating in the media (cheng et al., 2014). 2.1.4 soil-microbe geometric compatibility another important factor is the geometric compatibility between soil and microbes. soil microbes normally travel within the soil through the pore throat between soil particles, either by self-propelled movement or by passive diffusion. their sizes ranges from 0.5 to 3.0 μm which means significant amount of silt and clay can hinder their distribution and movement (ng et al., 2012; saranya et al., 2017). it is therefore important to take into account the type of soil and its pore throat when selecting bacteria for micp treatment. 2.1.5 temperature temperature similarly plays a vital role in the catalysis of urea by urease at a range between 27 to 30o c (mitchell and ferris, 2005; okwadha and li 2010). the urea hydrolysis is stable at 35o c and increase in temperature beyond this does not promote the enzyme activity (dhami et al., 2014). 2.1.6 concentration of reactants the concentration of reactants, urea and ca2+, are well vital for calcite precipitation. due to the negative charge surface of the microbial cell, they scavenge cation, ca2+ for example, which consequently make them ideal nucleation sites for heterogeneous crystal formation. they attract metal cations (ca2+) and subsequently counter ions (co3 2-) to precipitate as calcium carbonate on their surface (philips et al., 2013). however, okwadha and li (2010), muhammad et al: application of microbial induced calcite precipitation (micp) technology in geotechnical and geo-environmental engineering: a review. azojete, 17(2):185-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 189 reported that high concentration of calcium chloride and urea above 0.5m decrease the efficiency of calcite precipitation. de muynck et al. (2010) and murtala and khairulanuar (2017) observed that the best concentrations of urea and calcium chloride for calcite precipitation are 0.5 and 0.25 m respectively. however, the latter is the most widely implemented and reported concentration limits yielding huge and efficient calcite precipitation. 2.1.7 methods of introducing bacterial cells and cementitious solution the method of introducing bacteria and cementitious solution into soil plays an important role in the accomplishment of micp process. methods such as spraying, mixing, injection or their combination have been used in different scenarios and conditions. in spraying method, which is usually associated but not limited to non-cohesive soils, the bacteria solution is sprayed over the soil at a given rate and followed by spraying of cementitious solution. prior to this, the soils are saturated with water to allow the microbes adhere to soil particles (zhaoyu et al., 2018). mixing method involves mixing an air-dried soil sample with bacterial solution thoroughly and introducing it to desired mould. this is followed by introducing the cementitious solution by injection or spraying (jawad and zheng, 2016). injection method usually comes in different manner. this includes mixing bacteria cells and cementitious solution together before injecting into the soil, injection of bacteria solution first followed by cementitious solution and staged injection with or without retention period between phases (saranya et al., 2017). 2.2 applications of micp ng et al. (2012) investigated the potential of micp in the improvement of shear strength and permeability of sandy silt. the soil was compacted in a 50mm diameter and 150mm length fabricated mould. bacillus megaterium (5 x 107cfu/ml) was mixed with the air dried soil sample prior to the compaction. the cementation reagents used are urea and calcium chloride at a concentration of 0.2m which was injected into the compacted soil at an interval of 6hrs for 48hrs duration at flow rate of 1.7x1015m/s. the result revealed a significant improvement in both shear strength and the permeability. the improvements were 164% shear strength increment and 74% reduction in permeability compared to the natural soil. dejong et al. (2014) successfully implemented a field scale study on sand covering 3m×3m plot targeting a treatment depth of 15cm. the study uses five different injection/extraction wells across the area and the sand treatment was carried out in two phases. in phase one, sporosarcina pasteurii suspension was added into a urea-rich solution and injected via the wells. non continuous injection and extraction of the solution was conducted for up to 50hr for uniform distribution of the solution. in phase two, cementation solution was injected at high flow rate in 1hr followed by 2hrs rest period until uniformity is attained. surficial application of micp was also investigated by gomez et al. (2015), on a field scale in loose sand deposits at mine site, saskatchewan, canada. in the experiment, bacterial culture and nutrient amendment was sprayed on a four (4) 2.4m × 4.9m plots named tp1, tp2, tp3 and tp4 where tp1 was the control. across the plots tp2 to tp4, different urea and calcium chloride concentrations were applied to observe the cementation efficiency. sporosarcina pasteurii (atcc 1376) with different dosages of nutrient broth, urea and cacl2 arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):185-196. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 190 were applied at a flow rate of 19l/min on the plot surfaces using two tanks of volume 5,678l (each plot received 568l) each with totes, pumps and spray nozzle attached to the setup. treatment was conducted in twenty consecutive days with four-day circle of five identical days. after the 20-day period of treatment, tp4 formulation gave the optimum result of 28cm depth soil improvement and 2.5 cm thick cemented crust having good resistance to erosion. in their study, firas and zheng (2016) conducted laboratory experiment on the unconfined compressive strength (ucs) and permeability of grinded silica sand classified as poorly graded sand. the sample was prepared by packing it into polyvinyl chloride (pvc) column of 80mm high and 37mm inner diameter. sporosarcina pesteurii cultivated under sterile aerobic batch condition in a yeast extract was used in the study. samples of sand columns were divided into two groups of water saturated and unsaturated. both groups were then flushed with 33ml of bacterial solution followed by 33ml of cementitious solution after a retention time of 3hrs using gravity induced downward precipitation at flow rate of 0.150l/h. flushing with cementitious solution was repeated after every 24hrs for 7 days. unconfined compressive strength of up to 3000 kn/m2 and 90% drop in permeability rate were observed. the study also revealed that the dry sample of this particular soil had greater compressive strength compared to the water saturated one while reverse case was observed in permeability reduction. the permeability of silica sand columns was examined in laboratory using ureolitic bacterium culminating at reduction in permeability value as high as 97% after 24 hrs. the culture medium was prepared using tryptone 15 g/l; soy peptone 5 g/l; nacl 5 g/l and urea 20 g/l. to the whole medium, which is 1 l, 15 g agar was added. the medium was then autoclaved at 121 °c for 20 min. the culture plates were incubated overnight at 32 °c, and the colonies were transferred into a 50-ml shaking flask with growth solution and shaken for 15 h. four samples of silica sands were prepared in stainless steel cylinders with a length and inner diameter of 7.5cm and 3.5cm respectively. the sand was washed with hcl solution and rinsed with pure water to get rid of interference of impurities before use. permeability tests were conducted at 3 different flow rates (0.56, 0.97, and 1.73 ml/min, corresponding to pumping rates of 1, 0.5, and 2 rpm) using pure water to obtain an average conductivity before micp. then, 20 ml of bacterial stock solution (approximately 4.44×1010 cells) was inoculated into each column with a pumping rate of 0.97 ml/min of pure water, and the effluent was collected for cell counting. about 10 pore-volumes later, the micp solution was then pumped into the columns at a speed of 0.97 ml/min until the test was stopped 72 h later. hydraulic tests were conducted every 12 h during the micp test. calcite crystals filling pores and coated on sand surfaces was shown to be the reason for the reduction subsequent to scanning electron microscopy (sem) analysis conducted before and after the treatment (yefie et al., 2017). murtala and khairul-anuar (2017) investigated the potential of micp in the improvement of strength and reduction of permeability of tropical residual soil. an isolate of urease active strain of klebsiella pneumoniae from the soil used in the study was used to precipitates calcite into the soil using five cementation reagents concentrations. bacterial concentration of 1.5x 104cfu/ml and 2.9x 106cfu/ml were obtained and used for the treatment using injection method. results revealed increase in the strength of the soil after 48hrs of treatment from muhammad et al: application of microbial induced calcite precipitation (micp) technology in geotechnical and geo-environmental engineering: a review. azojete, 17(2):185-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 191 80% to 110% as bacterial concentration increases. the same trend was recorded with increase in reagent concentration up to 0.5m after which the strength declined. there were also a decline in permeability by 50% and 65% after 48hrs from 1.5x 104cfu/ml to 2.9 x 106cfu/ml bacterial concentration respectively. the study revealed 0.5m as the optimum reagent concentration for klebsiella pneumoniae for effective improvement of residual soil. zhaoyu et al. (2018) reinforced sands for mitigating hazard caused by wind erosion. series of laboratory experiment was performed to evaluate wind resistance of micp treated sand. the test sand was air-dried and transferred into a tray of mass (m) with dimension of 288mm × 225mm × 25mm. the thickness and mass of the tray were measured. five (5) percolation holes of diameter of 8mm were designed and fabricated at the bottom of the tray for drainage. six-layer gauze was placed inside the tray above the holes to prevent sand and water out of the tray. pre-determined mass of the dry sand was placed in one layer at the bottom of the tray and compacted using a steel rod. the initial dimension of the sand sample was measured, so the total volume of the sample (v) will be known. bacillus cereus (sporosarcina pasteurii, no. atcc11859) was used in the study with trypsin, soybean peptone, nacl, urea, and distilled water as main components of the culture medium whereas the cementation solution was urea-cacl2 solution with a concentration of 1mol/l. all solutions were introduced into the samples by surface spraying method at a rate of 15ml/min. wind erosion test was conducted in a large area in the laboratory(5m×3m) for uniformity of air flow. at the end of 28days curing period, well fixed samples (to avoid movement) were subjected to test using a duct fan with a rated speed of 2800rpm and an air volume of 3000m3/h for a period of 90 minutes. the total mass of the sand specimen and the tray (mi) were measured at 5min interval in 30min and at 30min interval between 30min and 90min. the amount of wind erosion (δm) was then calculated by δm=m28−mi; the wind erosion rate (a) was calculated by a= (m28−mi)/(m28−m). cylindrical samples of 30mm diameter and 60mm height were also produced for unconfined compressive strength (ucs) test using the same treatment. final results revealed that the erosion rates of sample 2,3 and 4 were considerably reduced by 63.97%, 94.75%, and 97.76%, respectively, as compared to the control sample. the scanning electron microscopy (sem) results indicated bonding effect from the caco3 crystals as a result of the micp treatment which gives the top layer of the specimen wind erosion resistance. in addition, the result of ucs value of 4 mpa attained has exceeded the minimum requirement of 1 mpa for wind resistance. the technique provides alternative method for mitigating and preventing desertification. a surficial soil stabilization against water-induced erosion was explored using micp technique by xiangrong et al. (2018). the astm c-778 ottawa sand possessed a particle diameter corresponding to 10% finer (d10) of 0.26 mm, a particle diameter corresponding to 50% finer (d50) of 0.33 mm, a coefficient of uniformity (cu) of 1.35, and a coefficient of curvature (cc) of 0.9. the sand was classified as poorly graded based on the unified soil classification system. the bacteria, sporosarcina pasteurii (atcc 11859), were cultivated in an atcc specified medium and were contained in an environmental shaker operated at 170 rpm and 33°c. the harvested bacteria and growth medium were then centrifuged and the supernatant was arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):185-196. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 192 decanted. the remaining concentrated bacteria solution was stored at 4°c prior to use. the study considered a polymer-modified micp process aimed at providing moist microenvironment thereby retarding the excess migration of cementitious media. polyvinyl alcohol (pva) was used to prepare the pva-modified cementation solution by carefully adding the granular pva powder into urea–cacl2 deionized water solutions under highspeed stirring at 60°c. the percentage weight of the mixed pva powder in the solution was approximately 7.5% weight per weight. samples for different cementation concentration media were prepared using different plastic container sizes for both strength and erodability tests. this was accomplished by pouring slowly the ottawa sand into containers having cementation and bacteria solutions and stirred with glass rod. samples were kept for 10 days after which they were removed from containers, immersed in water for three days and air-dried prior to tests. the bench-scale surficial stabilization of ottawa sand showed a uniform soil crust in the surficial region and reduces the erodability of the sand. the shear stress of the treated sand was 500 times higher than the natural one as demonstrated by the erosion function apparatus test. bio-sequestration of heavy metals was investigated using micp. heavy metals resistant bacteria were used to bio-mineralized lead, iron, zinc and cadmium. out of the twenty-two bacterial strains isolated from calcareous soil samples, ten most efficient were selected subsequent to urease-calcite production and tolerance to heavy metals toxicity screening. urease broth medium containing (g/l): urea, 20; nahco3, 2.12; nh4cl, 10, nutrient broth, 3; cacl2. 2h2o, 25, ph 7 was inoculated with overnight grown seed culture and incubated under shaking condition at 37°c for 72 h. ammonia released from urea hydrolysis was measured as an indicator for urease activity. the metal toxicity experiments were carried out using nutrient broth media supplemented with different concentrations (0–10 mm) of heavy metal salts (zinc chloride, cadmium sulphate, lead nitrate, and iron sulphate) inoculated with 2% overnight grown culture (6.5 log cfu/ ml). each metal concentration was tested in and incubated at 35oc for 48 h. the growth of bacteria was measured to examine the feasibility of cells in the presence of these metals. results indicated that strains wd-2, wd-5, wd-9, ba-3 and ba-7 out of the ten were the highest urease producers and also revealed significant heavy metals resistance efficiency. the urease activity and calcite production in order of efficacy were wd-9 (6.50 u/ml), wd-5 (4.14 u/ml), ba-3 (3.36 u/ml), ba-7(2.20 u/ml) and wd-2 (1.98 u/ml) and wd-9 (10.0 mg/ml), followed by ba-3 (9.32 mg/ml), wd-5 (8.22 mg/ml), ba-7 (7.40 mg/ml), and wd-2 (5.11 mg/ml) respectively. the study proved the efficacy of micp in sequestering heavy metals with a removal strength of 97.20 % for pb+2 as highest and 60.66% for cd+2 as lowest after 48h of incubation (eman, 2019) rajabi et al. (2019) treated sand and silt for storm control using micp in laboratory. samples subjected to different micp treatments indicated significant positive relationship between urease activity and the amount of calcite precipitation. wind velocity test revealed that particles of untreated sand and silt began to move at a velocity of 8 and 10 km/h respectively while all biologically treated samples resisted until the wind speed reached 97km/h. this has resulted in soil erosion of 215 and 354 kg m-2 h-1 for sand and silt (control) respectively and only 2.5 kg m-2 h-1 for micp treated samples. the results indicated that the application of micp on soil surface can be an effective alternative for the wind erosion control especially at high velocity. muhammad et al: application of microbial induced calcite precipitation (micp) technology in geotechnical and geo-environmental engineering: a review. azojete, 17(2):185-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 193 nasrin et al. (2020), explored the removal efficiency of some selected heavy metals via biomineralization using urease-producing bacteria isolated from iranian mine calcareous soil. in the study, rhizosphere soil samples were collected from 0-20 cm depth across five different contaminated sites in zanjan province. serial dilution method was used in the isolation of bacteria with relative resistance to heavy metals. 01 ml of each dilution was spread on nutrient agar plate suplimented with 2 mmzn, 0.5 mm pb and 0.5 mm cd and incubated at 28 ± 2o c for 7 days. the study further realized t 76 strains with relative resistance to heavy metals from the medium containing the metals. out of these 76 isolates, 12 isolates with high color intensity quantitatively were considered. the native isolates tagged a323 and a122 among the isolates appeared to represent the upper and lower urease activity having a value of 1.65 u/ml and 0.85 u/ml respectively. in addition, sporosarcina pasteurii ptcc 1645 (dsm33) with urease activity of 11.08 u/ml was procured and used for comparison with the native microbes in the biomineralization process. furthermore, heavy metal precipitation experiment indicated that sporosarcina pasteurii had highest pb carbonate of 73g/l followed by bacterial isolate c113 and a323 having 26.73g/l and 26.0g/l respectively. sporosarcina pasteurii also had the highest carbonate precipitation in zn and cd while among the isolates m212 had the highest in zn and a323 in cd. however, the general biomineralization process showed that sporosarcina pasteurii removed 98.71% of pb, 97.15% of cd, and 94.83% of zn. a323 removed 96.25%, 71.3 %, and 63.91% of pb, cd, and zn, respectively, and c113 removed 95.93% of pb, 73.45% of cd, and 73.81% of zn. the final results proved that the bacteria are capable of converting soluble metals into insoluble carbonate thereby immobilizing and encapsulating them. based on this review, it is suggested that sporosarcina pasteurii is the best candidate for metal fixation, stabilization and remediation in soils following its high efficacy of carbonate precipitation, encapsulation and solidification. 3.0 conclusion the application of microbial induced calcite precipitation technique in soil improvement have increased over the years and has been proven applicable in different fields. a wide variety of microorganisms can be used in the production of urease for bio-calcification. however, microbes such as sporosarcina pasteurii and b. megaterium have the greatest potential. the technique is eco-friendly and can be used in areas such as soil remediation, liquefaction resistance of soils, concrete cracks healing, sealing of leakage in hydrocarbon wells and co2 sequestration. however, according to researchers like de jong et al., 2014 and gomez et al., 2015, despite this virtue the technique requires further investigation to overcome its limitations prior to its commercialization. some of these limitations include slow microbial process, production of ammonia which can be toxic and risky to public health as well as economic implication in the acquisition of nutrients for field application. references amin, m., zomorodian, sma. and okelly, bc. 2017. reducing the hydraulic erosion of sand using microbialinduced carbonate precipitation. proceedings of the institution of civil engineers: ground improvement 170(2): 112-122. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):185-196. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 194 atticus, d., liang c., mohamed, a. and shahinand, rc. 2012.calcium carbonate induced precipitation for soil improvement by urea hydrolysing bacteria. advances in civil, environmental, and materials research (acem’ 12) seoul, korea, august 26-30 bosak, t. 2011. calcite precipitation, microbially induced. in: reitner, j. and thiel, v. 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vol. 17(2):185-196. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 196 saranya, k., sangeetha, h. and swetha, pk. 2017. review on microbial induced calcite precipitation. international journal of advanced research in civil, structural , environmental and infrastructure engineering and developing, 3 (1): 364-367. sherwood, pt. 1993. soil stabilization with cement and lime. hmso: london, uk. taylor, hfw. 1997. cement chemistry. thomas telford publishing: london, uk. venkatramaiah, c. 2006. geotechnical engineering. new age international publishers. third edition, new delhi, pp 697. weil, mh., de jong, jt., martinez, bc. and mortesen, bm. 2012. seismic and resistivity measurement for real-time monitoring of microbially induced calcite precipitation in sand. geotechnical testing journal, 35(2): 330-341. xiangrong, w., junliang,-tao, amasce., ruotian, bsmasce., tri-tran, smasce. and stacey, tkmasce. 2018. surficial soil stabilization against water-induced erosion using polymer-modified microbially induced carbonate precipitation. journal of materials in civil engineering, 30(10): 04018267. yefei, t., xinghua, x., shiqiang, w. and tao, w. 2017. microbially induced caco3 precipitation: hydraulic response and micro-scale mechanism in porous media. science asia, 43:1-7. zhaoyu, w., nan, z., jinhua, d., chen, l. and yong, j. 2018. experimental study on wind erosion resistance and strength of sands treated with microbial-induced calcium carbonate precipitation. advances in materials science and engineering, 2018: 1-11. zulfequar, ak. 2017. causes and consequences of greenhouse effect and its catastrophic problems for earth. international journal of sustainability management and information technologies, 3(4): 34-39 arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):469-480 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 469 original research article production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil a. zubairu1*, a. s. b. gimba2 and a. m. abdullahi1 1department of chemical engineering, university of maiduguri, borno state, nigeria. 2department of petroleum and gas engineering, nile university of nigeria, abuja nigeria. *corresponding author’s email address: abduzubairu@yahoo.com 1.0 introduction the increase in world population and industrialization have led to increase in global energy demand. thus, necessitate the need to raise energy supplies in order to meet the demand. it was estimated that the total world energy consumption would increase by an average of about 2% per year from 2005 to 2025 (sahoo et al., 2007). international energy agency (iea) have indicated that the world will need 50% more energy in 2030 compared to 2019 demands, with an estimated 45% to be accounted for by china and india due to industrialization and population growth (shahid and jamal, 2011). in addition, the continuous depletion of the world’s crude oil reserves poses serious threat to global energy security and increase uncertainties in world energy markets. consequently, the need for alternative fuel to conventional fossil-based fuel cannot be overemphasized for any nation’s sustainable economic growth. for instance, in nigeria, the over-dependence on oil imports for the transportation and agricultural sectors is a serious challenge that must be addressed. hence, there is the urgent need to focus on potential sources for alternative energy for the development of renewable, biodegradable and environmentally friendly options like biofuel. the concept of biofuel is not new. rudolph diesel used vegetable oil (peanut oil) in a diesel engine in 1911 (antczak et al., 2009; akoh et al., 2007). biodiesel is a renewable, biodegradable, mono-alkyl esters of long chain fatty acids derived from renewable bio-lipids feed stock, such as oil or fat, through transesterification process, which produces an environmentally-friendly biofuel that conform to astm d6751 specifications article information abstract this study elucidates one possible alternative to first generation feedstock used for biodiesel synthesis. the various conventional feedstock for biodiesel production have the conflict of competition as food sources which poses serious food security risks. jatropha curcas and yellow oleander seed oils were subjected to in-situ hybridization process at different percentage blend compositions tagged: y90j10, y80j20, y70j30, y60j40 and y50j50 before trans esterified to biodiesel. biodiesel yields were found to be as high as 90.0, 86.1, 90.7, 92.2 and 88.2% for the hybrid blends y50j50, y90j10, y80j20, y70j30 and y60j40 respectively. the optimal reaction temperature was 60°c, reaction time of 60 minutes, using 1% (w/w) koh catalyst. characterization of all synthesized biodiesel samples indicates fuel properties that are within the stipulated astm limits for fuel-grade biodiesels, except that high cloud points were observed in y100 and j100. the least cloud point was observed for biodiesel from hybrid oil blend y50j50. the ftir spectra of the fatty acid methyl esters of both oils and of their various blends confirms the presence of the major functional groups characteristics of bio-based diesel fuel. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 june, 2021 revised 6 sept., 2021 accepted 10 sept., 2021 keywords: transesterification in-situ hybridization yellow oleander jatropha curcas biodiesel arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):469-480. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 470 suitable for application in compression ignition (ci) engines (surma, 2008). transesterification is the conversion of triglycerides into fatty acid alkyl esters (faae) and low molecular weight alcohols such as methanol and ethanol in the presence of catalyst (demirbas, 2010; sharma et al., 2008). 1.1 feedstock for biodiesel synthesis biodiesel is produced using different kinds of oils comprising of both edible and non-edible vegetable oils, waste cooking oils, animal fats and algae oils (mishra and solanki, 2016) via a simple chemical procedure known as transesterification. the properties of biodiesel are categorized on the basis of various criteria; firstly, properties that relates to the processes taking place in the engine which includes: ignition qualities, ease of starting, fuel-air mixture formation, exhaust gas formation and heating value. secondly, properties that relates to cold weather properties which includes: cloud point, pour point and cold filter plugging point. thirdly, properties that relates to transport and depositing includes: oxidative stability, hydrolytic stability and flash point. fourthly, properties that relates to wear of engine parts which includes lubricit , cleaning effect, viscosit and compatibilit with materials used to manufacture the fuel s stem araba s and todorut, 2012). properties of feedstock for biodiesel vary depending on physico-chemical configuration and biological compositions. one possible way to improve these properties, and enhance biofuel yield, is hybridization of the feedstock. in addition, it has been reported (eloka-eboka and inabao, 2014) that most of the developing countries including china and india are heavily relying on first generation biofuel production sources that also double as food sources. it is therefore necessary to explore some the nonedible sources available for the production of biofuels. furthermore, there is abundance of forest and plant-based nonedible oils such as jatropha curcas (jatropha), azadirachta indica a. juss (neem), pongamia pinnata (karanja), madhuca indica (mahua), shorea robusta (sal), hevea braziliensis (rubber), and trichilia emetic (natal mahogany) in many subsaharan african countries, that can be exploited as substitute feedstock for biofuel manufacture (ahmad et al., 2011). jatropha curcas plant has been widely studied and jatropha oil applied in biodiesel manufacture. biodiesel synthesized from jatropha curcas have similar chemo-physical, thermal, and engine performance properties to that of fossil-based diesel fuel, and was used as fuel without engine modification in compression-ignition (ci) engines. nonetheless, the jatropha biodiesel has some limitations including high viscosity which can only be used in ci engines when blended with diesel fuels in about 40-50% (pramanik, 2003), high acid value above 5mg koh/g (minzangi et al., 2011). zaku et al. (2012) reported jatropha curcas oil acid value of 8.43 mg koh/g; and therefore, need acid pretreatment before transterification to produce biodiesel. more also, the high cloud point of the oil can cause the biodiesels to gel in cold climates creating problem to engine operation (dubey et al., 2011). yellow oleander (thevetia peruviana) is an ever-green ornamental dicotyledonous shrub or small tree that belongs to the apocynales and apocyanaceae family (dallatu et al., 2017). it is commonly found in the tropics and sub-tropics but it is native to central and south america. thevetia peruviana made its way to nigeria over fifty years ago, and has been grown as an ornamental plant in homes, public institutions and recreational areas (ibiyemi, et al., 2002). it is a drought resistant plant, with yellow trumpet like flowers and grows well in all parts of nigeria. it can be grown in arid zones as well as in higher rainfall zones and even on land with thin soil cover. it can withstand various ecological conditions provide the soil is well drained and is exposed to sunny area. in fact, it is a popular hedging and once established needs no care besides the annual zubairu et al: production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil. azojete, 17(4):469-480 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 471 pruning. it was reported (dallatu et al., 2017) that yellow oleander have oil yield of up to 64.7% which is adjudged high yielding, this was supported by other workers that report oil yield of 6065% (basumatary, 2014). unlike jatropha oil, yellow oleander oil does have limitations of high viscosity and cloud point (dallatu et al., 2017). 1.2 hybridization of the feedstock hybridization of feedstock involves blending two or more different raw materials at varying proportions to produce resulting material that may have improved characteristic properties when compared to the parent stock (eloka-eboka and inabao, 2014). the concept of hybridization of different feedstock can bring about better and improved qualities which single feedstock may not adequately present when used separately. when crude oils feedstock is blended together in the right proportions before biodiesel is produced via transesterification process, it is referred to as in-situ hybridization. the term ex-situ hybridization however, refers to when crude feed oils are initially converted to biodiesel before they are blended together. 2. materials and methods yellow oleander and jatropha curcas seeds were purchased at national institute for chemical technology narict zaria, kaduna state, nigeria. the seeds were de-hulled manually, dried in an oven at 110°c for 1.5 hours and properly stored in polythene bags for further analysis. 2.1 oil extraction batch of 200g dried jatropha caucus and yellow oleander seeds were separately de-husked and then crushed into powder by the aid of mortar and pestle, and hand grinder separately, to increase surface area for enhance extraction. the powdered sample of both seeds were separately fed to a soxhlet extractor (150mls, glass; finlab) containing n-hexane which serves as the solvent; the system was connected to a 21 round bottom flask and a reflux condenser. the extraction was conducted for a period of 6 hours, at a temperature of 60°c after which the solvent was completely evaporated over a water bath condensed and recycled. 2.2 characterization of jatropha caucus and yellow oleander crude oil the following physico-chemical characteristics of jatropha and yellow oleander seed oils were determined using astm standard procedures; acid value, saponification value, iodine value, free fatty acid, viscosity, density, specific gravity, refractive index and bulk density. 2.3 hybridization of the feedstock the in-situ hybridization of jatropha caucus seed oil and yellow oleander seed oils was adopted for biodiesel production blended in the percentage composition as follows: y100j0, y0j100, y50j50, y90j10, y80j20, y70j30, and y60j40 from the crude oil samples. the subscripts for y, represent the percent proportion of yellow oleander oil, while the subscripts for j represent the percentage proportion of jatropha oil. firstly, each blend sample was placed in a homogenizer to mix the crude oils for 2 hours at 500 rpm at 60oc before transesterification process to produce the biodiesel. 2.4 transesterification of the hybrid feedstock blends to biodiesel the transesterification of the hybrid oils was carried out using methanol. the process was carried out according to astm standard procedure using methanol to hybrid oil mole ratio of 6:1. the reaction time was 1 hour, reaction temperature of 60oc and 1 % (w/w) koh as a catalyst. upon reaction completion, the mixture was allowed to cool at room temperature without agitation leading to a two-phase separation. the upper phase of the mixture was the hybrid oil methyl ester (home) i.e., the biodiesel and the lower phase consists of glycerol, excess methanol and catalyst, soap formed during the reaction, some entrained home and arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):469-480. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 472 traces of glycerides. the two phases were separated by decantation. the home was washed with warm distilled water and dried at 100oc to remove any traces of water. 3. results and discussion 3.1 characterization of yellow oleander and jatropha curcas seed oils the yield of the oil from yellow oleander (thevetia peruviana) seeds and jatropha curcas seed as well as their physicochemical properties are presented in table 1. in this work the yield of yellow oleander and jatropha oils were 62.8%. and 53.97% respectively. this indicates that yellow oleander seed is high oil yielding, similar results (61.8%64.7%) are reported by ibiyemi et al., (2002). however, the oil yield from jatropha curcas also falls within the limit of 30-65% as reported by azam et al., (2005). the yields from both oils show that both oils are viable feedstock for production of biodiesel. the oil yields of both seeds are higher than most of other non-edible oil producing seeds reported; like azadirachta indica (44.5%), pangamia pinnata (33%) and ziziphus mauritiana (33%) (azam et al., 2005). yellow oleander oil percent free fatty acid value (%ffa) was 1.295% while jatropha curcas was 1.49%. the maximum free fatty acid value recommended by canakci and gerpen, (2001) for alkaline transesterification was 2 mg koh/g above which acid pretreatment of the oil is necessary before transesterification. therefore, both oils may also be considered for direct alkaline transesterification. dorado et al., (2002) reported that the higher the free fatty acid in oil the less economical the oil is for the production of biofuels; this is because the oil will require added acid pretreatment before conversion to biodiesel that adversely affect the economic viability of the process. in addition, the high amount of free fatty acid favours the production of excess soap in the transesterification process which must be removed (dorado et al., 2002; ma et al., 1998). high oil acidity decreases yield of biodiesel by inhibiting the formation of methoxides thus neutralizing the catalyst present and producing soaps within the reaction medium. the initial results showed 3.46 and 8.55 mg koh/g acid value for yellow oleander and jatropha curcas respectively. the high acid value found in yellow oleander and jatropha curcas oils was an indication that the oils need acid pretreatment prior to its esterification to biodiesel. the high acid of jatropha curcas oil in particular, means high level of free fatty acids which translates into decreased oil quality. acid pretreatment was carried on both oils and the resulting acid values for yellow oleander and jatropha curcas are 1.34 and 2.64 mg/koh respectively. it is important to note that acid value is the most important property of a vegetable oil which depicts the quality, age and suitability for industrial processes such as production of biodiesel and bio lubricant (akubugwo et al., 2008). the lower acid value for yellow oleander seed oil compared to the jatropha oil implies that it contains less polyunsaturated fatty acids i.e., linoleic acid and linolenic acid (khan et al., 2001). on the other hand, high acid value of jatropha seed oil will make it more susceptible to lipase action and will decompose faster than yellow oleander seed oil. however, these values were observed to be lower than those reported by (minzangi et al., 2011) and (zaku et al., 2012) for some non-edible oil seeds (azadirachta indica: 17.40 mg koh/g; ricinus communis:12.48 mg koh/g; moringa oleifera: 4.96 mg koh/g). the saponification value is an indication of the average length of the fatty acid chains which make up the oil. zubairu et al: production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil. azojete, 17(4):469-480 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 473 table 1: physicochemical properties of yellow oleander seed and jatropha curcas oils properties yellow oleander oil jatropha curcas oil oil yield (%) 62.8 53.97 acid value (mg koh/g) before acid pretreatment 3.46 8.55 acid value (mg koh/g) after acid pretreatment 1.34 2.62 density(g/m3) 0.870 0.920 specific gravity 0.905 0.924 free fatty acid (%ffa) 1.30 1.49 iodine value (g/g) 74.6 101.84 saponification value (mg/g) 196.77 193.55 the saponification values in both yellow oleander and jatropha curcas seed oils (196.77 and 193.55 mg/g respectively) are relatively high, this can be attributed to the high free fatty acid content in the oils (hui, 1996). these values however, fall within the range of 182.5 – 260 mg/g reported by (minzangi et al., 2011) for oils obtained from plant species. the higher saponification values recorded in both seed oil triglyceride is an indication of a larger number of short chain fatty acid molecules of low molecular weight, and accordingly consumes a larger number of moles of koh. in this work, the iodine value for yellow oleander seed oil (74.6g/g) and jatropha curcas (101.83g/g) indicates stability to oxidation and are likely to be stored for a long period without becoming rancid due to the presence of high unsaturated fatty acids (dallatu et al., 2017). both oils therefore, are likely to be good feedstock in biodiesel industry. the specific gravity of the yellow oleander and jatropha curcas oil were 0.905 and 0.924 respectively. these values compare favourable with other results found for tropical african samples (dawodu, 2009; minzangi et al., 2011; bhattacharya et al., 2013). generally, plant oils with specific gravity of 0.820 to 1.071 at 30oc are considered good for use as biofuels (bhattacharya et al., 2013; minzangi et al., 2011). 3.2 physico-chemical and fuel properties of the hybrid methyl esters the effects of the hybridization on the physico-chemical and fuel properties of the synthesized biodiesels (pure oil methyl esters and hybrid oil blend methyl esters) are presented in the following sections. generally, the respective methyl esters properties observed in this work were within the astm standards recommended limit (gerpen et al., 2004) for fuel grade biodiesel and compare well with the conventional diesel. 3.2.1 influence of hybridization on yield of hybrid methyl esters the methyl esters yield of from all the oil samples investigated is presented in figure 1. it can be seen that the average yield of hybrid methyl ester of all oil samples considered: y90j10 (90% yo and 10% jo), y80j20 (80% yo and 20% jo), y70j30 (70% yo and 30% jo), y60j40 (60% yo and 40% jo) and y50j50 (50% yo and 50% jo), was approximately 90%. the highest biodiesel yield observed was from hybrid oil blend y70j30 with 92.2%, and it can be observed that the least yield of biodiesel (j100) was approximately 84%. all biodiesel yields were typical of methyl esters from other common oil seeds reported in the literature (azam et al., 2005; and kinast, 2003). arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):469-480. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 474 figure 1: influence of hybridization on yield of hybrid methyl ester 3.2.1 influence of hybridization on specific gravity of hybrid methyl esters the specific gravity measurement for the hybrid oil blends methyl esters compared to the methyl esters of the pure y100 and j100 oils were presented in figure 2. the values of the specific gravity of all hybrid methyl esters are conform to the astm standard (d1296) recommended limit of 0.88 (ivase et al., 2015). it is important to note that the specific gravity of all the hybrid methyl esters were lower than that of the j100 (0.96) which is slightly higher than the recommended astm limit. this may likely be due to high entrained moisture content in the parent j100 oil. figure 2: influence of hybridization on specific gravity of hybrid methyl ester 3.2.2 influence of hybridization on the viscosity of hybrid methyl esters the effect of the hybridization on the viscosity of the hybrid methyl esters is shown in figure 3. the viscosity is a critical parameter of the injection property of the biodiesel. too high viscosity leads to clogging of the injector of the ci engines. the astm standard (d445) of the viscosity recommended limit of biodiesel is 1.9-6.5 mm/s2 (kinast, 2003). all the hybrid biodiesel produced have viscosity in the range of the astm standard. worth noting is that the hybrid methyl ester from hybrid oil blend y70j30 has the least viscosity of about 2.0cst. which makes it most suitable for fuel injection applications. y100 y90j10 y80j20 y70j30 y60j40 y50j50 j100 80 82 84 86 88 90 92 94 o il y ie ld ( % ) hybrid oil blends y100 y90j10 y80j20 y70j30 y60j40 y50j50 j100 0.8 0.85 0.9 0.95 1 sp e ci fc g ra vi ty hybrid oil blends zubairu et al: production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil. azojete, 17(4):469-480 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 475 figure 3: influence of hybridization on viscosity of hybrid methyl ester 3.2.2 influence of hybridization on cloud point of hybrid methyl esters the cloud point profile of the synthesized biodiesels is shown in figure 4. it could be noted that the cloud point values of all hybrid methyl esters are within the recommended astm standard (d975) recommended limit of -3oc to 12oc. the cloud point values of all hybrid methyl esters are lower than that of the methyl esters from pure oils (y100 and j100. the cloud point values of the biodiesel from y100 and j100 are higher than the biodiesels from the hybrid oil blends. the high values for the pure biodiesels cloud points (y100; 12oc and j100; 10oc) are due to high composition of oleic acid. the cloud point is critical in cold weather performance of the biodiesel, hence the high cloud point of the methyl esters of the pure oils may limit their use as fuel in cold climates. in nigeria the fame of yellow oleander and jatropha curcas will tend to retain their flow properties due to relatively warm climate, but they would tend to precipitate wax under the condition where the ambient temperature is just a little above the cloud point. figure 4: influence of hybridization on viscosity of hybrid methyl ester 3.2.2 influence of hybridization on other fuel properties the pour point and the refractive index of the synthesized methyl esters are presented in table 2. the pour point is the property of the biodiesel that defines its ability to flow before it can be gelled. it is a measure of the temperature below which the fuel cease to flow. fuels with high pour point are relatively difficult to be used in areas with lower temperatures, because the biodiesel must be kept relatively warm to retain its flow capabilities by some external means such as electric heaters, tanks or flow line insulations, for instance. y100 y90j10 y80j20 y70j30 y60j40 y50j50 j100 0 0.5 1 1.5 2 2.5 3 v is co si ty ( p o is e ) hybrid oil blends y100 y90j10 y80j20 y70j30 y60j40 y50j50 j100 0 5 10 15 p o u r p o in t (o c ) hybrid oil blends arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):469-480. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 476 all biodiesels have relatively high pour points than conventional diesel in the region of over 20oc (kinast, 2003). all the methyl esters produced in this work exhibit pour point characteristic higher than some common vegetable oil methyl esters (example, soya oil, canola oil, moringa oleifera oil, palm oil, etc.) as reported in the literature (kinast, 2003; ivase et al., 2015; zubairu and ibrahim, 2004). table 2: physicochemical and fuel properties of the produced biodiesels and hybrid blends. y100 y90j10 y80j20 y70j30 y60j40 y50j50 j100 petro. diesel pour point (°c) 3 3 4 4 2 -5 6 -16 refractive index 1.447 1.449 1.366 1.448 1.449 1.451 1.453 3.3 fourier transform infra-red spectroscopy the jatropha oil, yellow oleander oil and hybrid oil blends biodiesels were subjected to fourier transform infrared spectroscopy (ftir) to characterize and emulate the presence of various carbon isomers. as a representative example, the ftir spectra of the methyl ester of the oil blend y70j30 is shown in figure 5. figure 5: ftir spectrum of y70j30 methyl ester the ftir analyses of the yellow oleander methyl ester (yome), and jatropha methyl ester (jome) and hybrid oil blends methyl esters showed the region 745.08 cm-1–998.52 cm-1 indicate the presence of =c-h functional groups. they possess bending type of vibrations appearing at low energy and frequency region in the spectrum and are all double bounded. the spectra also confirm the presence of carbonyl functional group at 1764.73 to 1772.55 cm-1 as the most intense and prominent bands. they are part of fatty acid methyl esters with unsaturated bond in the biodiesel, such as methyl oleate and methyl linoleate. methyl oleate was also reported by saifuddin, (2014) in this region. the carbonyl (-c=o vibration) group of esters showed strong absorption bands at 1764.73 to 1772.55 cm-1 in the ftir spectra of the biodiesels, also indicate the presence of fatty acid methyl esters. this group indicates the conversion of triglycerides in the oil to methyl esters. the summary of the ftir spectra of biodiesel from jatropha oil, yellow oleander oil and hybrid oil blends are shown in table 3. zubairu et al: production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil. azojete, 17(4):469-480 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 477 table 3: summary of the ftir spectra peaks (cm-1) of the pure oils methyl esters and hybrid oil blend methyl esters wave number (cm-1) assignment 2887.21 3651.72 region of h drogen’s stretching. -oh stretching vibration of the triglycerides -symmetric and asymmetric stretching vibration of the aliphatic –ch2 and -ch3 group. 1764.73 1772.55 region of double bond’s stretching -ester carbonyl functional group of the triglycerides -c=c stretching vibration of olefins region of other bonds deformations and bendings bending vibrations of -ch2 groups 745.08 998.52 fingerprint region -c-o stretching vibration of ester group ch2 rocking vibration and the out of plane vibration of disubstituted olefins 3.3 gas chromatography mass spectroscopy gc-ms to investigate the presence of fames in the produced biodiesel samples; yellow oleander oil (y100), jatropha oil (j100) and the respective hybrid oil blends (y90j10, y80j20, y70j30, y60j40, y50j50) were subjected to gc–ms analysis, the detail result for the methyl ester of the y70j30 oil blend; as a representative example is presented in figure 6. figure 6: chemical composition of hybrid blend y70j30 biodiesel the respective ames were identified by comparing the mass spectrum of each component with spectra in the national institute of standards and technology (nist) mass spectral library. we used the gc spectrum and confirm some major peaks as the dominant peaks in the respective biodiesels, which are consistent with previous literature (ahmad, et al., 2011). the major identified fames present in the hybrid methyl esters include: hexadecanoic acid, methyl ester; 9(z)-hexadecenoic acid, methyl ester; methyl stearate; 9(z)-octadecenoic acid, methyl ester; eicosanoic acid, methyl ester and docosanoic acid, methyl ester. 0 10 20 30 40 50 60 70 c19h36o2 c19h38o2 c21h42o2 c17h34o2 67.7 3.42 2.74 26.06 c o m p o si ti o n ( % ) fame components arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):469-480. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 478 4. conclusion crude oils were extracted from yellow oleander and jatropha curcas seeds using solvent extraction method. the oil yield was 62.8% and 53.97% for yellow oleander and jatropha seed respectively. characterization of the oils indicates iodine values of 74.6g/g for yellow oleander and 101.83g/g for jatropha curcas. the oils were adjudged to have stability to oxidation and are likely to be stored for a long period without becoming rancid due to the presence of high unsaturated fatty acids. all physicochemical properties of the oils are within astm recommended limits. synthesized biodiesel yields from the oils are 89.8% and 84.1% for yellow oleander and jatropha curcas respectively. similarly, the biodiesel yields from the hybrid oil blends were 90.0, 86.1, 90.7, 92.2 and 88.2% for hybrid oil blends y50j50, y90j10, y80j20, y70j30 and y60j40 respectively. characterization of all synthesized biodiesel samples indicates fuel properties that are within the stipulated astm limits for fuel-grade biodiesels, except that high cloud points were observed in y100 and j100. the least cloud point was observed for biodiesel from hybrid oil blend y50j50. the ftir spectra of the fatty acid methyl esters of yellow oleander oil and jatropha curcas oil, as well as fatty acid methyl esters of the various blends of the oils synthesized confirms the presence of the major functional groups characteristics of bio-based diesel fuel. references ahmad, m., ullah, k., khan, ma., zafar, m. tarq, m., ali, s. and sultana, s. 2011. physicochemical analysis of hemp oil biodiesel: a promising non-edible new source for bioenergy. energy sources, 33(14): 1365-1374. akoh, cc., shu-wei c., guan-chiun l. and jei-fu s. 2007. enzymatic approach to biodiesel production. journal of agricultural and food chemistry, 55(22): 8995-9005. doi: 10.1021/jf071724y. akubugwo, ie., chinyere, gc., ugbogu, ae. 2008. comparative studies on oils from some common plant seeds in nigeria. pakistanian journal of nutrition, 7(4): 570-573. antczak, ms., kubiak, a., antczak , t. and bielecki, s. 2009. enzymatic biodiesel synthesis key factors affecting efficiency of the process. renewable energy, 34(5): 1185-1194. azam, mm., waris, a., nahar, nm. 2005. prospects and potential of fatty acid methyl esters of some non-traditional seed oils for use as biodiesel in india. biomass and bioenergy, 29(4): 293–302. araba s, i. and todorut, ia. 2012. biodiesel quality, standards and properties. in: biodiesel quaity, emisions and bye-products, intechopen edited by montero, g. and stoytcheva, m. pp. 3-28. basumatary, s. 2014. yellow oleander ( thevetia peruviana ) seed oil biodiesel as an alternative and renewable fuel for diesel engines : a review. international journal of chemical technology, 7(6): 2823-2840. bhattacharya, c., pandey, b. and paroha, s. 2013. effect of physico-chemical changes in sesame (sesamum indicum l.) seeds due to storage. asian journal of biological and life sciences, 2(3): 254-257. canakci, m. and gerpen, jv. 2001. biodiesel production from oils and fats with high free fatty acids. transactions of the american society of agricultural engineers, 44(6): 1429–36. zubairu et al: production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil. azojete, 17(4):469-480 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 479 dallatu, y., agbaji, eb. and ajibola, bo. 2017. the influence of physicochemical characteristics of non-edible oil of yellow oleander seed on its fuel properties. bayero journal of pure and applied sciences, 10(2): 283–291. dawodu, fa. 2009. physico-chemical studies on oil extraction processes from some nigerian grown plant seeds. electronic journal of environment, agricultural and food chemistry, 8(2): 102-110. demirbas, b. 2010. future fuels for internal combustion engines. energy sources, 32(14): 1273–1281. dorado, mp., ballesteros, e., de almeida, ja., schellart, c., löhrlein, hp. and krause, r. 2002. an alkali-catalyzed transesterification process for high free fatty acid waste oils. transactions of the american society of agricultural engineers (asae), 45(3): 525-529. dubey, ak., sarviya, rm. and rehman, a. 2011. characterization of processed jatropha oil for use as engine fuel. current world environent, 6(1): 101–107. eloka-eboka, a.c. and inambao, f.l. (2014). effects of hybridisation of biodiesel on the fuel quality and performance of moringa and jatropha feedstocks and hybrids. proceedings of 13th international conference on sustainable energy technologies (set-2014), 24-28 august 2014, geneva, switzerland. gerpen, jv., shanks, b., pruszko, r., clements, d. and knothe, g. 2004. biodiesel production technology, national renewable energy laboratory (nrel) subcontractor report, nrel/sr510-36244: 22-30. hui, yh. 1996. industrial and consumer non-edible products from oils and fats, in aile ‘s industrial oil fats products: 5th edition, john wiley and sons, new york, pp. 33-37. ibiyemi, sa., fadipe, vo., akinremi, oo. and bako, ss. 2002. variation in oil composition of thevetia peruviana juss (yellow oleander) fruits seeds. journal of applied science and environmental management (jasem), 6 (2): 61–65. ivase, tjp., bobbo, h., tagago, ta. and nyakuma, dd. 2015. a review of moringa oleifera seed oil as feedstock for biodiesel production. journal of multidisciplinary engineering science and technology, 2(12): 3574–3581. khan, sh., bhatti, bm. and sardar, r. 2001. acid value of vegetable oils and poultry feed as affected by storage period and anti-oxidants. pakistan veterinary journal, 21(4): 194-197 kinast, ja. 2003. production of biodiesels from multiple feedstocks and properties of biodiesels and biodiesel/diesel blends. national renewable energy laboratory (nrel) subcontractor final report, nrel/sr-510-31460: 5-24. ma, f., clements, ld. and hanna, ma. 1998. the effect of catalyst, free fatty acids and water on transesterification of beef tallow. transactions of the american society of agricultural engineers (asae), 41(5): 1261-1264. minzangi, k., kaaya, an., kansiime, f., tabuti, jrs. and sambura, b. 2011. oil content and physico-chemical characteristics of some wild oilseed plants from kivu region eastern democratic republic of congo. african journal of biotechnology, 10(2): 189195. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):469-480. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abduzubairu@yahoo.com 480 mishra, a. and solanki, h. 2016. a review on biodiesel as efficient alternative fuel energy: current status and future perspectives. international journal of recent scientific research, 7(8): 13052-13063. pramanik, k. 2003. properties and use of jatropha curcas oil and diesel fuel blends in compression ignition engine. renewable energy, 28(2): 239-248. sahoo, pk., das, lm., babu, mkg. and naik, sn. 2007. biodiesel development from high acid value polanga seed oil and performance evaluation in ci engines. fuel, 86(3): 448-454. saifuddin, nrh. 2014. spectroscopy analysis of structural transesterification in biodiesel degredation. research journal of applied sciences, engineering and technology, 8(9):1149– 1159. shahid, em. and jamal, y. 2011. production of biodiesel: a technical review. renewable and sustainabe energy reviews, 15(9): 4732-4745. sharma, yc., singh, b. and upadhyay, sn. 2008. advancements in development and characterization of biodiesel: a review. fuel, 87(12): 2355-2373. surma, n. 2008. preparation and characterization of biodiesel from melon seed oil and tigernut tuber oil. phd thesis, university of nigeria nsukka. zaku, sg., emmanual, sa., isa, ah. and kabir, a. 2012. comparative studies on the functional properties of neem, jatropha, castor and moringa seeds oils as potential feed stocks for biodiesel production in nigeria. global journal of science frontier research chemistry, 12(7): 77-83. zubairu, a. and ibarahim, fs. 2014. moringa oleifera oilseed as viable feedstock for biodiesel production in northern nigeria. international journal of energy engineering, 4(2): 21-25 3 10 article azojete vol 4 78-88 arid zone journal of engineering, technology and environment. october, 2004; vol.4, 78-88 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng estimating groundwater recharge for sustainable management in the nigerian sector of the chad basin goni, i.b.1, w.m. edmunds2 and f.a. adeniji3 abstract groundwater is the perennial source of water supply for domestic and other applications in the nigerian sector of the chad basin. therefore, quantifying the current rate of recharge is fundamental to sustainable management of the resource. the chloride (cl) mass balance technique was used to estimate the rate of recharge. average cl concentrations in rainfall from three stations over eight years were used as input data. eight unsaturated zone cl profiles were obtained and cl concentrations in the groundwater were measured for over 400 samples from wells and boreholes. an average recharge rate of 41 mm per annum was estimated from the unsaturated zone profiles. the regional rate obtained using cl concentrations in groundwater is slightly higher, estimated at 48 mm per ammum, which is attributable to other mechanisms of recharge such as river channels, pools, depressions and regional flow that bypass the unsaturated zone. the estimated recharge to the shallow groundwater in this region is considerable and can sustain present day abstractions. the observed decline in water table in recent years is largely due to reduced rainfall during the sahel drought and consequent reduction in recharge, although human impacts are also identified as is common with most semi-arid areas of the world. although the flood plains aquifers (fadamas) are probably fully recharged annually through river channels, caution must be exercised in introducing irrigation schemes. any agricultural development should be preceded by detailed studies, so as to utilise the quantity of water that is recharged annually and must also adopt water saving techniques. 1. introduction the nigerian sector of the chad basin falls within the semi-arid region of ne nigeria (figure 1), which is characterised by low rainfall (<500 mm/annum), high evaporation (>2000 mm/annum) and almost non-existent surface water, apart from the lake chad and seasonal rivers. the area is mostly underlain by the chad formation, the youngest stratigraphic sequence in the chad basin. this formation is a plio-pleistocene mainly argillaceous sequence with three well defined arenaceous horizons (figure 2), which serve as aquifers and are termed upper, middle and lower aquifers (barber and jones, 1960). the upper aquifer is unconfined and semi-confined in places whereas the middle and lower aquifers are confined. these confined aquifers are under sufficient pressure in some places and provide artesian wells with piezometric heads of up to 20 m above ground level (goni et al., 2000). the confined aquifers are generally exploited via boreholes, whereas the shallow unconfined aquifer is mostly abstracted by large diameter wells. oteze and fayose (1980) and goni et al. (2000) have shown that the water table and piezometric head in deep artesian aquifers are rapidly declining, and thus raising questions on the overall sustainability of the groundwater resource. the main control on the sustainable resource is the balance between the rates of recharge and that of discharge. these 1 department of geology, university of maiduguri, maiduguri. nigeria. e-mail: ibgoni@yahoo.com 2 oxford centre for water research, school of geography and environment, oxford, uk. 3 department of agricultural & environmental resources engineering, university of maiduguri. nigeria. azojete vol. 4 2004 79 fundamentals are not clearly understood in this region, and indeed in most semi-arid and arid regions. little work has been carried out to assess the total water balance in this region. potiskum damaturu maiduguri n'guru kano biu bama damboa dikwa damasak mallam fatori baga wulgo maine soroa 8.00 9.00 10.00 11.00 12.00 13.00 14.00 11.00 12.00 13.00 14.00 approx. b asin lim it figure 1 map of study area showing the drainage network and major towns figure 2 geological cross section of the chad formation with the three aquifer zones estimating groundwater recharge for sustainable management 80 there is a need for efficient groundwater management in order to sustain the existing water resource. this is important because human existence and development schemes (agricultural, industrial or health related) in the region are strongly dependent on the reliability of water supplies. since sustainable management, especially from the context of supply planning, requires knowledge of the renewal rate, estimation of groundwater recharge becomes fundamental. this paper attempts to estimate the amount of recharge to the phreatic aquifer of the region using the chloride (cl) mass balance method. 1.1 chloride mass balance method chloride is ubiquitous in groundwater and soil water, and often constitutes the most dominant ionic species. one of the most useful properties of cl ion is that it is highly soluble, forming individual minerals at only very high concentrations. chloride may be present in some high temperature minerals such as biotite (fuge and power, 1969; edmunds et al., 1985). thus, it is highly mobile and is not involved in the common geochemical reactions that occur in aquifers. chloride therefore is a conservative element with a mobility in water very similar to that of water molecules (hill, 1984) and has a self-diffusion coefficient of 2 x 10-5 cm2 sec-1 (li and gregory, 1974). the geochemical cycle of cl is very similar to that of water, with one important exception – when water evaporates, or is transpired through plants, chloride remains in the residual solution and is therefore concentrated in proportion to the amount of water removed. once water containing the ‘enriched’ chloride signature leaves the zone of evapotranspiration it carries the signature to the groundwater and can be used to estimate the net water loss compared with rainfall and hence the amount of recharge. the amount of recharge from the cl mass balance equation (edmunds et al., 1988) is given below: rd = cpp/cs 1 where rd = recharge, p = precipitation cp and cs = cl concentrations in precipitation and in soil water respectively in order to use equation 1, rainfall amounts and rainfall chemistry (total cl deposition) must be known and the data for at least three years. errors associated with rainfall measurements as well its spatial variability are likely to constitute the largest uncertainties in recharge estimation using chloride mass balance method. also, assumption must be made that the average atmospheric chloride flux remains constant (edmunds, 2001), the surface runoff is negligible and that homogeneous movement of solutes through the unsaturated zone is by piston flow is taking place. the chloride estimates usually provide long-term mean recharge values. short-term effects such as change in land use may change the recharge rates and these may be followed by monitoring the changes in the unsaturated zone, using subsequent chloride profiles (andrew and edmunds, 2000). 2. materials and methods 2.1 sample collection the chloride mass balance method was used in this study to estimate the amount of recharge to phreatic aquifer of the nigerian sector of the chad basin. rainfall samples on event basis were collected from three meteorological stations in north east nigeria, namely kaska, garin azojete vol. 4 2004 81 alkali and maiduguri (figure 3). the rainfall samples were collected for the rainy seasons of 1992 to 2000, although with some gaps over the period due to logistic problems. figure 3: map of study area showing location of the three meteorological stations hand augering was used to drill eight unsaturated zone profiles (figure 4) in the region. samples of moist sand were obtained at regular intervals of 0.25 m over the first 10 m and then at 0.5 m interval thereafter to the total depth of profile. moisture contents were measured gravimetrically and chloride was determined on samples obtained either by centrifugation (kinniburgh and miles, 1983) or by elutriation with distilled water. groundwater samples from 400 wells and shallow boreholes were collected with the assistance of north east arid zone development programme (neazdp) staff from villages across ne nigeria. the wells were located on the outskirts of the settled areas and away from areas of possible contamination. all the wells were in daily use and produced fresh water. two samples were collected in polythene bottles and filtered through whatman 0.45 µm membrane filters. one of the samples was acidified to 1% hno3. automated colorimetry was used in the laboratory to determine the concentration of cl in all the samples. g.alk. kaska potiskum damaturu maiduguri n'guru kano biu bama damboa dikwa damasak mallam fatori baga wulgo maine soroa 8.00 9.00 10.00 11.00 12.00 13.00 14.00 11.00 12.00 13.00 14.00 approx. basin limit estimating groundwater recharge for sustainable management 82 figure 4: map of study area with location of unsaturated zone profiles in solid squares 2.2 recharge estimation using the cl mass balance formula the cl mass balance (equation 1) was used to calculate the rate of direct recharge (rd) through the profiles. seven site-year rainfall data was used in the estimation. the average chloride concentration in rainfall (cp) for the study area was obtained using data from the three stations of kaska, garin alkali and maiduguri. the amount of rainfall and cl concentration in the rain were the input data, and these together with the average cl concentration in the profiles (cs) were used to estimate the amount of recharge (rd). 3. results and discussion table 1 shows the weighted mean chloride values for all the meteorological stations. the table also shows the mean rainfall and mean weighted chloride of 4.34 mm and 1.77 mgl-1 respectively for the study area. these form input data for the estimation of groundwater recharge using the chloride mass balance technique. table 1: weighted mean chloride values for rainfall stations in northern nigeria station and year annual rainfall (mm) weighted mean cl (mg l-1) kaska 1992 320 2.8 kaska 1993 327 1.3 garin alkali 549 1.6 garin alkali 819 3.4 garin alkali 297 0.6 garin alkali 226 0.7 maiduguri 2000 502 2.0 average 434 1.77 source: goni et al. (2001) damaturu maiduguri kano gashua mf mg md mn gm wgr ntm ka 8.00 9.00 10.00 11.00 12.00 13.00 14.00 11.00 12.00 13.00 14.00 approx. basin limit azojete vol. 4 2004 83 the concentration of cl with depth for the eight profiles is presented in figure 5. with the exception of the mf profile, the other seven profiles give recharge rates ranging from 19 to 66 mm a-1 with an average of 48 mm a-1. there is no visible difference between rates obtained in the dune sands from those of the alluvial sands; the major control for moisture movement in the unsaturated zone has been the texture of the sediments. the upper layer of the mf profile gave an estimated rate of recharge of 16 mm a-1 slightly lower but similar to the general range of the other seven profiles. the lower clayey layer is clearly distinct with almost no recharge, which is attributable to the impermeable nature of clays. figure 5: depth distribution of cl in the unsaturated zone profiles chloride concentration in groundwater is of special value since it can usually be treated as a conservative reference element (allison and hughes, 1978; edmunds and walton, 1980) of value in recharge studies and be used to monitor additions from the aquifer matrix. distribution of chloride in groundwater for the study area is shown in figure 6. the concentrations vary from 0.5 to 96 mg/l, with an average of 16.0 mg/l. cl (mg/l) 0 2000 4000 6000 8000 d ep th ( m ) 0 5 10 15 20 cl (mg/l) 0 40 80 120 160 200 cl (mg/l) 0 40 80 cl (mg/l) 0 40 80 cl (mg/l) 0 40 80 cl (mg/l) 0 40 80 d ep th ( m ) 0 5 10 15 20 cl (mg/l) 0 40 80 cl (mg/l) 0 40 80 mf md ntm gm wgr mn ka mg estimating groundwater recharge for sustainable management 84 figure 6: chloride concentrations in groundwater of the study area results from the unsaturated zone profile (table 2) suggest that the water table cl concentrations represent atmospheric inputs and, therefore may be used to determine recharge rates for the study area. the estimated recharge rate for the area studied is 48 mma-1 obtained over a period of seven site-years. table 2. unsaturated zone profiles weighted mean cl concentrations and recharge estimates from the study area using average rainfall of 434 mm profile geology depth (m) no. samples (n) mean cl cs (mg/l) mean annual recharge rd (mm/annum) (1) garin mamadu 1 manga dune sands *15.5 51 14 55 (2) madugubari 1 manga dune sands 22.5 65 21 37 (3) mainari 1 manga dune sands *16.5 53 41.5 19 (4) north tamsugu alluvial sands *18.75 58 11.7 66 (5)west waggari alluvial sands *19.25 60 17.7 43 (6) magumeri fixed dune sands 16.25 53 29.5 26 (7) kajimarum 1 manga dune sands *15.5 50 18.3 42 (8a) malam fatori (upp) fixed dune silt 03.00 10 47 16 (8b)malam fatori (lower) lacustrine silt/clay 3-16.00 42 2892 0.2 * profile reached the water table. azojete vol. 4 2004 85 rainfall chemistry is likely to introduce error in the recharge estimation if short term data is used. however, the error can be reduced with long term data the range of recharge values of 19 to 66 mma-1 (excluding the malam fatori profiles) quite clearly indicates a significant spatial variability for the profile sites of the study area. spatial variability of recharge rates using the cl mass balance equation has been explained by edmunds and gaye (1994). in the present study, texture of the unsaturated zone sediments was observed to be the major factor for this variability as differences exist in the texture of the profiles. due to its relative uniformity in the sites, vegetation may not be a significant cause of variability. chloride concentrations in groundwater in ne nigeria range from 0.5 to 96 mgl-1. this range reflects the heterogeneity in recharge rates resulting from variations in soil type and depth, vegetation type and coverage, as well as the slope of the area. lower values reflect preferred infiltration routes. however, no geographical bias to cl was observed in this study. some of the high values probably relate to salinity acquired near playas or modern lakes. no high cl concentrations were observed, suggesting that saline lakes (or their vestiges) are rare and very local in extent (edmunds et al., 2002). from the average cl concentrations in groundwater, a regional recharge rate of 48 mm a-1 was obtained. this is slightly higher than the 41 mm a-1 for the unsaturated zone estimates if the malam fatori profile is excluded. this would suggest that additional recharge might be occurring preferentially from the depressions and channels in the sandy terrain. this is similar to the observations made by edmunds et al., (2002). from the above, the wells in lambawa and abadam are hydrologically connected with the nearby yobe river. this indicates that other sources of recharge through the unsaturated zone exist. piezometric studies by carter (1994) indicate flow gradients towards the lake chad, implying recharge through the dunes. recharge rates of the order of 60 mm a-1 are required to satisfy the water balance of the lakes. this is consistent with the higher values obtained from cl mass balance from the manga grasslands. these results reinforce the concept of active modern day recharge, dispelling the earlier assumptions that effective recharge by precipitation is zero. it is considered that from modelling studies (carter and alkali, 1996) in the flood plain, significant regional recharge must also be taking place, although this remains to be quantified. the regional recharge estimates from the present study imply that rainfall recharge is of the same order of magnitude in the extensive sandy flood plain areas near the komadugu yobe river as in the manga grasslands. also, adeniji (1991) estimated substantial quantity of water (14.83 mcm) that flows from lake chad to recharge the [pper aquifer of the nigerian sector of the basin. this has implications for small-scale development in the region, since the regional estimates are much larger than those found in the immediate vicinity of the river estimated at 1mm a-1 by carter and alkali (1996). estimating groundwater recharge for sustainable management 86 management implications the cl mass balance method indicates that significant recharge both vertically and laterally along river channels is taking place in the study area. the rate of recharge estimated remains considerably in excess of the local demands in the villages (adeniji, 1991). however, increase in irrigation activities and changes in urban water supplies by exploiting aquifers are major threats to sustainability. geochemical data indicate that water in the deep aquifers is old (20 ka bp) and recharged during cooler climates although there is no evidence of present day recharge from available data. further work is required to focus on the edges of the basin in the south and southwest, where the confined aquifers crop out. adeniji (1991) observed that there is possibility of the middle and lower aquifers receiving their recharges from wetter distant sources. until this is proven the present day abstraction shall be regarded as effectively mining the system.piezometric heads of the confined artesian wells are declining (goni et al., 2000), due to demands by increase in population. it is clear from the foregoing that the upper aquifer receives considerable recharge that can sustain the present day abstraction, but perhaps cannot sustain mechanised pumping. the observed decline in water table in recent years is largely climate-controlled (reduced rainfall during the sahel drought), although human impacts are also identified as the case in most semi-arid areas of the world. the flood plains are probably fully recharged annually through river channels. however, for sustainable management of the flood plain aquifers (fadamas), caution must be exercised in introducing large irrigation schemes. any agricultural use should be preceded by detailed studies, so as to utilise the quantity of water that is recharged annually. the key to managing groundwater in this region (and all semi-arid and arid regions) is to understand the cost involved. also, reliable databases and comprehensive monitoring programmes are needed to assess changes in quality and quantity of water resources. educative programmes related to water and the environment can make costing and planning easier. 4. conclusion the cl mass balance technique was used to estimate the amount of groundwater recharge in ne nigeria. using cl concentrations in rainfall of 1.77 mg/l as input, the eight unsaturated zone cl profiles chosen gave an average recharge rate of 41 mma-1. in the study profiles of the region, average recharge rate from cl concentrations in the groundwater was 48 mm a-1. the recharge rate of the shallow groundwater in this region is significant and sustainable with the current rate of abstraction. sustainability of the shallow groundwater depends on sound management. although the flood plain aquifers are fully recharged annually, caution must be exercised before introducing large irrigation schemes. in this water-scarce region management strategy aimed at reducing wastage must be adopted. azojete vol. 4 2004 87 references adeniji, f.a. (1991). groundwater management and recharge potentials in the chad basin of ne nigeria. nig. journal of water resources. 1(1): 29-48. allison, g.b. and m.w. hughes (1978). the use of environmental chloride and tritium to estimate total local recharge to an unconfined aquifer. aust. j. soil res. 16: 181-195. andrew, l.h. and w.m. edmunds (2000). inorganic ions as tracers. in: environmental tracers in subsurface hydrology, cook, p. and l.h. andrew (ed.). kluwer academic publishers. 31-77. barber, w. and d.g.jones (1960). the geology and hydrology of maiduguri, bornu province. (unplished records) gelogical survey of nigeria. carter, r.c. (1994). the groundwater hydrology of the manga grassland, northeast nigeria; importance to agricultural development strategy for the area. q. j. engg. geol. 27: 7383. carter, r.c. and a.g. alkali. (1996). shallow groundwater in the northeast arid zone of nigeria. q. j. engg. geol. 29: 341-355. edmunds, w.m. (2001). mechanisms, timing and quantities of recharge to groundwater in semi-arid and tropical regions. in: isotope techniques in water resource investigations in arid and semi-arid regions, iaea-tecdoc-1207. 77-88. edmunds, w.m. and c.b. gaye (1994). estimating the spatial variability of groundwater recharge in the sahel using chloride. j.hydrol., 156: 47-59. edmunds, w.m. and n.r.g. walton, (1980). a geochemical and isotopic approach to recharge evaluation in semi-arid zonespast and present. in: application of isotopic techniques in arid zone hydrogeology. proc. advisory group meeting, iaea vienna, 47-68. edmunds, w.m., e. fellman and i.b. goni (1999). lakes, groundwater and palaeohydrology in the sahel of ne nigeria: evidence from hydrogeochemistry. j. geol. soc. london, 156: 345-355. edmunds, w.m., e. fellman, i.b. goni and c. prudhomme (2002). spatial and temporal distribution of groundwater recharge in northern nigeria. hydrogeol. j., 10 (1): 205215. edmunds, w.m., r.l.f. kay and r.a. mccartney (1985). origin of saline groundwaters in the carnmenellis granite (cornwall, england): natural processes and reaction during hot dry rock reservoir circulation. chem. geol. 49: 287-301. edmunds, w.m., w.g. darling and d.g. kinniburgh (1988). solute profile techniques for recharge estimation in semi-arid and arid terrain. in: simmers, i. (ed.) estimation of natural groundwater recharge, d. reidel publishing. 139-157. fuge, r. and g.m. power (1969). chlorine and fluorine in granitic rocks in sw england. geochim. cosmochim. acta, 33: 888-893. goni, i.b., m. kachallah and m.m. aji (2000). another look at the peizometric head declines in middle zone aquifer of the chad formation in the southwestern chad basin. borno j. geology l&2: 51-64. hill, d. (1984). diffusion coefficients of nitrate, chloride, sulphate and water in cracked and uncracked chalk. j. soil sci. 35: 27-33. kiniburgh, d.g. and d.l. miles (1983). extraction and chemical analysis of interstitial water from soils and rock. environ. sci. technol. 17: 362-368. estimating groundwater recharge for sustainable management 88 li, y.h. and s. gregory (1974). diffusion of ions in sea water and in deep-sea sediments. geochim. cosmochim. acta 38: 703-714. oteze, g.e. and s.a. fayose (1988). regional development in the hydrogeology of chad basin. water resources, 1(1): 9-29. arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):211-220 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 211 original research article assessment of solar box cooker (sbc) with kapok fiber insulator under maiduguri weather conditions a. t. abdulrahim1*, s. abdulkareem2, m. haruna1, m. b. maina1 and s. a. abdulraheem1 1department of mechanical engineering, faculty of engineering p.m.b. 1069 university of maiduguri nigeria 2department of mechanical engineering, university of ilorin, p.m.b 1515, ilorin, nigeria *corresponding author’s email address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 1.0 introduction in developing countries, access to energy is one of the major problems confronting them, a considerable proportion of rural and urban dwellers in the nigerian population as in many other developing countries in africa rely on fossil fuels, biomass and fire wood cooking and domestic water heating. burning of fossil fuels has been identified to create two adverse effects on our environment; (i) it produces greenhouse gas (ghg) emissions that cause global warming, and (ii) the by-products of burning, such as sulphur dioxide, soot, and ash that are responsible for global dimming by changing the properties of the cloud (akorede, et al., 2017). owing to these adverse effects there is urgent need to conserve our environment from these pollutants leading to a global search for alternative clean energy sources. nigeria is blessed with an abundant amount of sunshine which has been estimated to be 3,000 hours of annual sunshine (bello et al., 2010). from the average amount of solar energy reaching the country, it is evident that the development of solar technology will be worthwhile. maiduguri metropolitan council (mmc) shares local boundaries with konduga, jere and mafa local government areas (lgas) and it has an area land mass of 300 square kilometers (300 km2), which lies between latitude 12° n to 13° n and longitude 13° e to 15° e respectively. the vegetation is of semi – arid zone and climatic condition in this area is of a hot dry season (27°c to 42°c), and an annual rainfall of 500 mm to 600 mm has been recorded (mohammed et al., 2017). fortunately, maiduguri possesses ample amount of solar radiation sunshine hours and this offers solar cooking as one of the most attractive options. article information abstract this paper presents the construction and performance evaluation of solar box cooker with kapok insulator. the solar cooker offers an economically viable alternative while mitigating environment degradation due to excessive use of biomass/conventional energy sources for cooking purposes. the bureau of indian standard (bis: is b429) was used to determine the thermal performance parameters of the cooker, where first figure of merit (f1) and second figure of merit (f2) were determined to be f1= 0.132 and f2= 0.58. the cooker thermal efficiency (η) = 44%, qualifying the cooker to be grade “a” according to bis. the american society of agricultural and biological engineers for solar cooking (asae s580.1) was used to determine the cookers cooking power and it was found to be (ps) =14.7w while the (r2) value was 0.137 coefficient of regression © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 october., 2020 revised 30 march, 2021 accepted 5 april, 2021 keywords: solar box cooker kapok fiber insulator bureau of indian standard asae s580 weather conditions abdulrahim et al: assessment of solar box cooker (sbc) with kapok fiber insulator under maiduguri weather conditions. azojete, 17(2):211-220. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 212 for testing the performance of box solar cookers, mohammed et al. (2013), carried out performance testing of a truncated pyramid solar thermal cooker this design geometry concentrates the incident solar energy radiations towards the absorber placed at the bottom, it improves the performance of the solar cooker. garbaand dan-mallam (2014) undertook a comparative performance tests of a painted and non-painted cooking pot where the result shows the painted pot heat gains was 22% compared to the non-painted cooking pot. elamin and abdallah (2015), carried out a research on design, construction and performance evaluation of solar cookers, results of thermal performance showed that the parabolic solar cooker attained a maximum temperature of 86.5ºc on average basis and was the best followed by the box-type solar cooker that attained a maximum temperature 52.36 ºc and finally the panel-type that attained a maximum temperature of 43.5ºc. also the results of the solar cookers efficiency for the parabolic cooker, box-type and panel-type were found to be 31.53%, 77.4% and 67.4%, respectively. ademola and joseph (2015) studied energetic and exergetic evaluation of box-type solar cookers using different insulation materials insulated like maize cob, air (control), maize husk, coconut coir and polyurethane foam respectively were observed over a period of three years. the energy and exergy efficiency were highest in the cooker with coconut coir (37.35 and 3.90% respectively) in the first year but was lowest for air (11 and 1.07% respectively) in the third year. these results reiterate the importance of a good insulating material for a box-type solar cooker. abdoulkader et al., (2017) on their study of the thermal performance testing and promotion of solar cooker under djiboutian climate. it was found that solar cooker was of a grade. the experimental results obtained for thermal performance showed that the solar cooker is capable of cooking variety of foods easily under djiboutian climate. ramesh et al. (2018), in the study of the performance evaluation and cost economics of developed box type solar cooker observed that two figure of merits (f1, and f2), standard cooking power (ps)and thermal efficiency of solar cooker were 0.1084, 0.31, 58.41 watt, and 37.76% respectively. mullick et al. (1987) carried out thermal evaluation of box type solar cookers and proposed suitable thermal tests and also identified appropriate parameters, which pertain to the solar cooker and are relatively independent of the climatic variables as well as the products cooked. box type solar cookers are suitable mainly for the boiling type of cooking. a large fraction of the mass of most of the food products are due to water, hence, the cooking temperature is close to 100˚c. mullick et al. (1987) in evaluating the box type solar cooker identified cooking parameters as first figure of merit f1and second figure of merit f2, which are independent of climatic variables. in the procedure proposed by mullick et al. (1987), the first test is a stagnation test without load and the first figure of merit (f1) is obtained. the second test involves sensible heating of a full load of water in container and from this; second figure of merit (f2) is obtained. funk, (2000) asae s580.1 standard, the goal of this standard was to produce a simple, yet meaningful and objective measure of cooker performance that was not so complicated as to make testing in less developed areas impracticable. american society of agricultural and biological engineers for solar cooking procedures (asae s580.1) monitors the average temperature inside a pot of water while the cooker is operated under a set of guidelines given in the standard for tracking procedure, thermal loading, etc. temperature measurements are made of the water and averaged over 10 minute intervals. ambient temperature and normal irradiance (solar energy flux per area) are also measured and arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):211-220. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 213 recorded, at least as often as load temperature. under conditions of high wind, low insolation, or low ambient temperature, tests are not conducted. the primary figure of merit used by asae s580.1 is the cooking power, p. in the present work, a trapezoidal shape solar box cooker with kapok fibre insulator is been constructed and attempt has been made to test its efficiency, evaluate the performance to determine first figure of merit (f1) and second figure of merit (f2) as adopted by bureau of indian standards (bis: is b429), and as well determine the adjusted cooking power (pad) as recommended by (asae s580.1). 2.0 materials and method 2.1 description of the cooker the system consists of an insulating material (kapok fibre: a natural polymer with a thermal conductivity of 0.035wm -1 k -1 (aguyi, 2011)) in between the inner and outer casing to minimize heat loss. the casings were made with plywood to further minimize heat loss and to serve as barrier to prevent any environmental effect to the solar cooker. inside the cooking chamber is an aluminium plate coated with anon-toxic matter black colour to achieve high absorption coefficient. the leakage from the box to the surroundings was also minimized by having a rubber gasket (1.5 mm thick) in between the triple glazed cover (25 mm glazing) and the box. the cooking vessel used in this study was bought from the local market, it is made of aluminium alloy (18 cm in diameter and 10 cm in height) in a cylindrical dish shape and painted black which allows for high absorption of solar radiation designed to keep cooking, filled with water and equipped with a black cover, was placed into the solar box cooker. the isometric views of the casing and the absorber is shown in figure 1 and figure 2 respectively. the optical design of the cooker uses the concept of concentrating solar energy to achieve high temperatures; to trap the collected energy as is done in solar box cookers, and to retain high temperatures over a considerable period of time as obtained in green houses. due to the geometry of the design, solar rays impinging on the inner sidewalls were reflected downward, so as to create a region of high temperature at the bottom. in such geometries a higher value of the ratio of aperture area to absorber area leads to higher concentration ratio and hence higher absorber plate temperature. abdulrahim et al: assessment of solar box cooker (sbc) with kapok fiber insulator under maiduguri weather conditions. azojete, 17(2):211-220. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 214 figure 1: isometric view of solar box casing figure 2: isometric view of solar box absorber plate 2.0thermal efficiency energy analysis is based on the first law of thermodynamics, i.e. net heat supplied converted into work. energy analysis thus ignores the reductions in energy potential. this analysis can provide sound management guidance in those applications in which usage effectiveness depends solely on energy quantities. energy input to the solar cooker is energy of solar radiation per square meter of the solar cooker. then, energy input to the solar cooker can be calculated as follows; ozturk. (2004) ooker. energy efficiency of the solar cooker was calculated by using the equation below; ozturk, (2004) 2.1 performance of solar cooker the figure of merit f1and f2 is given for box type solar cooker by mullick et al. (1987). first figure of merit (oc m2/w) or stagnation testis was given as: where: tp, ta and is are plate absorber temperature, ambient temperature and solar intensity on a horizontal surface at a time stagnation temperature is reached respectively. second figure of merit or water heating test is given as: arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):211-220. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 215 [ ( ) ( ) ] where: f1 is the first figure of merit mw is the mass of the water, cw is the specific heat of water, tw1 is the initial temperature of water (= 60 oc), tw2 is the final temperature of water (= 90 oc), τ is the measured time difference in which the water temperature rises from tw1 to tw2, ta is the average ambient temperature over the time period τ, h is the average solar radiation intensity incident on the aperture of the cooker, and a is the aperture area of the solar cooker. 2.2 cooking power in the year 2000, funk found a need to evolve standard for testing solar cookers. the recommendations were later adopted by american society agricultural engineers as (asae s580.1). ⁄ where: pi= cooking power (w) t2 = final water temperature(0c) t1 = initial water temperature (0c) m = water mass (kg) cv = heat capacity(4186 j/[kg·k]) 2.2.1 standardizing cooking power cooking power for each interval shall be corrected to a standard insolation of 700 w/m2 by multiplying the interval observed cooking power by 700 w/m2 and dividing by the interval average insolation recorded during the corresponding interval. ⁄ where: ps = standardized cooking power (w) pi = interval cooking power (w), ii = interval average solar insolation (w/m2) multiplying observed cooking power by 700 w/m2 and dividing by the interval average insolation recorded during the corresponding interval. 2.2.2 temperature difference ambient temperature for each interval is to be subtracted from the average cooking vessel contents temperature for each corresponding interval. td = temperature difference (0c) tw = water temperature (0c) ta = ambient air temperature (0c) abdulrahim et al: assessment of solar box cooker (sbc) with kapok fiber insulator under maiduguri weather conditions. azojete, 17(2):211-220. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 216 2.2.3 plotting the standardized cooking power, ps, (w) is plotted against the temperature difference, td, ( °c) for each time interval. 2.2.4 regression a linear regression of the plotted points was used to find the relationship between cooking power and temperature difference in terms of intercept a (w) and slope b (w/c) or ps=a+b td. no fewer than 30 total observations from three different days were employed. the coefficient of determination (r2) or proportion of variation in cooking power that can be attributed to the relationship found by regression should be higher than 0.75. 2.2.5 single measure of performance the value for standardized cooking power, ps, (w) was computed for a temperature difference, td, of 50°c using the regression relationship found. 2.3 experimental procedure experiments were conducted at centre for entrepreneurship and enterprises development (ceed) university of maiduguri with the constructed solar cooker without load and with loadon31stmarch 2020 and 1st april 2020. the experiments began at 10:00 am and were continued until 14:00pm. during the experiments, the radiation intensity on a horizontal surface was measured using a digital pyrometer (spm-1116sd) (accuracy 0.1w/m2), (mtm3801) digital thermometer with three (3) channel contact thermocouples (accuracy 0.10c) was used to measure the temperature at different locations of the cookers; namely; the cooking fluid, the absorber plate and the ambient temperature. in addition, measuring cylinder was used to measure the volume of water. ambient temperature, absorber plate temperature, initial water temperature, maximum water temperature and boiling water temperature were measured and recorded at 10 minutes intervals. the recorded data was used to determine the performance of the constructed solar cooker, wind speed was measured using a cup vane anenometer (abh-4224) (accuracy 0.1m/s). the international test standard requirements for temperature range and insolation were applied for the solar box cooker sbc on each day. figure 3 shows the constructed solar box cooker and measuring equipment. figure 3: constructed solar box cooker and instrumentation arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):211-220. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 217 3.0 results and discussion 3.1 stagnation test figure 4 shows the variation in daily solar radiation, absorber plate temperature and the corresponding ambient temperature plotted against time of the day. it is clear that the absorber plate temperature increases towards the noon period, then decreases towards evening and solar radiation increase with increase in hours of the day toward noon with decrease in evening. the figure shows that the maximum absorber plate temperature was achieved by mid-day and was found to be 157.2ºc with an instantaneous solar radiation of 821.6 w/m2 and an ambient temperature of 47.8o c, the result is similar to the findings of nahar (1994) that achieved 158o c as stagnation in solar box oven with thermal insulation material, compared with 117oc without the thermal insulation material. f1 was calculated as per eq. 4 and was found to be 0.132, this value indicates the constructed cooker to be grade a as set by bis and this value agreed with standard value of f1 ≥ 0.12. the high values of f1 indicate that the cooker has high optical efficiency, high solar radiation and low heat loss factor. the absorber plate reaches (100o c150o c) at 2hrs 30min and maintain above 150oc can be attributed to insulation ability of the insulator as indicated by aremu and akinoso (2013), in order to reduce the heat loss from the solar box cooker walls it can be insulated with effective insulation materials which have low thermal conductivities of 0.03–0.06 w/m.oc figure 4: variation of absorber plate temperature with corresponding solar radiation and ambient temperature 3.2 water boiling test figure 5 shows the variation in daily solar radiation, water temperature and the corresponding ambient temperature plotted against time in the test day. it clearly indicates increase in water temperature as time of day increases with increasing solar radiation intensity, it was noticed that at the beginning, the water boiling temperature increases due to the heat accumulated inside the solar cooker, the temperature falls down as the solar radiation intensity decreases at solar time of (12:00 noon). it takes 50 minutes for the water temperature to attain 60.2ocand it takes another 70 minutes before the temperature reaches 92.9oc. sambo et al. (1993) reported that the required minimum food cooking temperature is 82oc. in the present study the water temperature is higher than the water pasteurization value. therefore, the results suggest that; the developed solar box cooker can be used for cooking in the study area 0 20 40 60 80 100 120 140 160 180 700 750 800 850 900 950 1 0 :0 0 1 0 :2 0 1 0 :4 0 1 1 :0 0 1 1 :2 0 1 1 :4 0 1 2 :0 0 1 2 :2 0 1 2 :4 0 1 3 :0 0 1 3 :2 0 1 3 :4 0 1 4 :0 0 a m b ie n t an d p la te t e m p re tu re ( 0 c ) so la r ra d ia ti o n ( w /m 2 ) time of the day (m) stagnation test of kapok insulated sbc is (w/m2) tp (0c) ta (0c) abdulrahim et al: assessment of solar box cooker (sbc) with kapok fiber insulator under maiduguri weather conditions. azojete, 17(2):211-220. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 218 (maiduguri). f2 was calculated based on eq. 5 and was found to be 0.598, this value agreed with standard value of f2≥ 0.4set by bis. the result is similar to the finding of harmim et al. (2014) and mohammed et al. (2013). the higher f2 value achieved in the present cooker configuration is an indication of better heat retention ability of the cooker insulating material (kapok). using equation 3 thermal efficiency was estimated to be 44%. figure 5: variation of water temperature with corresponding solar radiation and ambient temperature figure 6 shows the performance of the solar box cooker (standardized cooking power) which has been established versus the temperature differences. it was noticed that the performance for solar box cooker increases as the temperature difference increases. equations 6, 7 and 8 were used for the computation of interval cooking power (pi), standard cooking power (ps) and temperature difference (td) respectively as shown in figure 5. figure 6: variation of standard cooking power with corresponding temperature difference linear regression was used to find the relationship between energy efficiency and temperature difference in terms of intercept (%) and slope (%/). figure 5 reveals the cooking power regression equation relation as reported by asae (s580.1). 0 20 40 60 80 100 120 140 160 180 700 750 800 850 900 950 1 0 :0 0 1 0 :2 0 1 0 :4 0 1 1 :0 0 1 1 :2 0 1 1 :4 0 1 2 :0 0 1 2 :2 0 1 2 :4 0 1 3 :0 0 1 3 :2 0 1 3 :4 0 1 4 :0 0 a m b ie n t an d p la te t e m p re tu re ( 0 c ) so la r ra d ia ti o n ( w /m 2 ) time of the day (m) water boiling test of kapok insulated sbc is (w/m2) tp (0c) ta (0c) y = -0.1698x + 23.155 r² = 0.1373 0 5 10 15 20 25 30 0 10 20 30 40 50 60 st an d ad iz e d c o o k in g p o w e r p s (w ) temperature difference td ( 0c) cooking power of kapok insulated sbc ps linear (ps) linear (ps) arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):211-220. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrahimat@unimaid.edu.ng; engrabdulrahimat@gmail.com 219 the value of the coefficient of determination of the equation (r2) 0.1373 is less than 0.75 the standard recommended value by asae (s580.1). the cooking power at 500c temperature difference (p50)) was calculated using the generated regression equation and p50= 14.71w. as indicated by figure 5, standard cooking power directly decreases as the temperature difference increase. the linear regression equation generated is similar to the linear regression equations generated by folaranmi (2013) and abdoulkader et al. (2017). 4.0 conclusion the construction of solar box cooker with kapok fiber as insulator and its performances under maiduguri climatic weather condition were carried out in this study. the ambient temperature, absorber plate temperature, solar radiation, water temperature and wind speeds were experimentally measured. the figures of merits f1, f2, interval cooking power, standard cooking power were determined and compared with available reviewed literatures. a linear regression equation was also generated and analyzed. the cooker would be helpful to maiduguri community and other places under similar climatic weather condition. references ademola, ka. and joseph, ci. 2015. energetic and exergetic evaluation of box-type solar cookers using different insulation materials. world academy of science, engineering and technology, international journal of biological, food, veterinary and agricultural engineering, 9(5): 397-403. aguyi, g. 2011. thermal properties of selected materials for 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management, 359: 787–791. ozturk, hh. 2004. energy and exergy efficiencies of a solar box-cooker. international journal of exergy, 1(2): 202 -213. sambo, as., danshehu, bg. and garba, b. 1993. the effect of design parameters on the performance of improved wood-burning stoves. journal for solar energy, 10: 85-94. saxena, av., pandey, sp. and srivastav g. 2011. a thermodynamic review on solar box type cookers. renewable and sustainable energy reviews, 15: 3301–3318. ramesh, hc., modi, vm., alok, g., desai, nn., chaudhary, hs., bhavsar, s., kuma, s. and jain, s. 2018. performance evaluation and cost economics of developed box type solar cooker. international journal of current microbiology and applied sciences, 7(12): 1788-1795. cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 121-128 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng _____________________ *corresponding author email address: shuso@bpe.agr.hokudai.ac.jp 121 original research article non-destructive online real-time milk quality determination in a milking robot using near-infrared spectroscopic sensing system p. iweka 1, s. kawamura*1, t. mitani2, and s. koseki1 1 laboratory of agricultural and food process engineering, graduate school of agricultural science, hokkaido university, japan 2 field science center for northern biosphere, hokkaido university, japan article information received october, 2018 accepted december, 2018 keywords: milk fat protein lactose somatic cell count dairy precision farming japan abstract a near-infrared spectroscopic (nirs) sensing system was developed on an experimental basis for the quality determination of three major milk constituents (fat, protein and lactose) and somatic cell count (scc) of non-homogenized milk. the nirs sensing system was used for acquiring nir spectra of non-homogenized milk during milking in an automatic milking system (milking robot) over the wavelength range of 700 nm to 1050 nm. the three major milk constituents were analyzed for reference data using a milkoscan instrument, while scc was analyzed using a fossomatic instrument. we developed calibration models using partial least square (pls) regression analysis, and the precision and accuracy of the models was validated. the coefficients of determination (r2), standard errors of prediction (sep) and bias were 0.98, 0.23% and 0.00% for fat, 0.72, 0.25% and 0.00% for protein, 0.54, 0.15% and 0.00% for lactose, and 0.63, 0.48 log scc/ml and 0.00 log scc/ml for scc respectively. these results show that the nirs sensing system developed in this study could be used for online real-time determination of milk quality in a milking robot. the system can provide dairy farmers with information on milk quality and physiological status of each cow and therefore, give them feedback control for improving dairy farm management. by using the nirs system, dairy farmers will be able to produce high-quality milk and precision dairy farming will be realized. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserve 1.0 introduction dairy farming involves a lot of work such as feeding, milking, livestock management, feed crop production and manure treatment. as usual, extensive dairy farmers manage their livestock in groups which is a system known as herd management (svennersten-sjaunja et al., 1997). however, a system known as individual cow management is essential for monitoring milk composition quality of each cow which is important for animal breeding, effective cow usage and feed management. thus, this is the reason for the recent need for a technique that will enable dairy farmers to determine milk quality of individual cows during milking. http://www.azojete.com.ng mailto:shuso@bpe.agr.hokudai.ac.jp iweka, et al,. non-destructive online real-time milk quality determination in a milking robot using near-infrared spectroscopic sensing system. azojete, 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 122 the non-destructive, rapid, easy to use, time saving and pre-treatment free nature of near-infrared spectroscopy (nirs) makes it an effective tool for analyzing milk quality during milking process, nirs has been used to obtain qualitative and quantitative information of food and agricultural commodity such as rice (kawamura et al., 2003a; natsuga and kawamura, 2006), wheat (natsuga et al., 2001), and fruits and vegetables (lakshmi et al., 2017). nirs has been practically used in automatic rice-quality assessment in japan (kawamura et al., 2002; kawamura et al., 2003a). nirs has also been use for milk quality determination (sato et al., 1987; tsenkova et al., 2001; kawamura et al., 2003b; tsenkova et al., 2006; kawamura et al., 2007; kawasaki et al., 2008; tsenkova et al., 2009; iweka et al., 2016). however, the application of nirs for online real-time monitoring of milk quality of individual cow has not been achieved. in this study, an experimental online near-infrared (nir) spectroscopic sensing system was developed for milk quality determination. iweka et al., (2016) reported that the nir spectroscopic sensing system can be used for real-time determination of milk quality during milking with sufficient precision and accuracy. as a result of our findings, the nir spectroscopic sensing system was installed in an automatic milking system. the objective of this study was to examine the accuracy of the nir spectroscopic sensing system for milk quality determination in an automatic milking system. 2.0 materials and methods 2.1 near-infrared spectroscopic sensing system an experimental online near-infrared (nir) spectroscopic sensing system was designed for analyzing milk quality of each cow during milking. the system consisted of an nir instrument (nir spectrum sensor and nir spectrometer), milk flow meter, milk sampler and a laptop computer (fig. 1). the system was installed in a milking robot system (gea farm technologies, westfaliasurge, germany). non-homogenized milk from the milking robot flowed continuously across a bypass into the milk chamber of the nir spectrum sensor. excess raw milk flowed past the milk flow meter and was then released through a line tube into the bucket. the volume of a milk sample in the chamber was about 30 ml. the optical axes of halogen lamps a and b and the optical fiber were set at the same level, but the optical axis for halogen lamp c was set at 5 mm higher the optical fiber (fig. 2). the nir instrument acquired absorbance spectra through the milk. spectra were obtained in the wavelength range from 700 nm to 1050 nm at 1 nm intervals every 20 s during milking (table 1). the milk flow rate was simultaneously recorded in the laptop computer. 2.2 cows and milk samples twenty six holstein cows belonging to a dairy farm at tochigi prefecture, japan were used for this study. these cows were at their different lactation stages. the experiment was conducted throughout the whole day for two consecutive days, that is; on the 22nd and 23rd of february 2018. milking was automatically started as soon as a cow walked into the milking robot. milk samples were collected from the milking sampler every 20 s during milking. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 123 2.3 reference analyses three major milk constituents (fat, protein and lactose) and somatic cell count (scc) of nonhomogenized milk were measured as milk quality items in this study. the milk constituents were determined using a milkoscan instrument (foss electric, hillerod, denmark) and scc were determined using fossomatic instrument (foss electric, hillerod, denmark). the total number of samples used for reference analyses were 377 for milk constituents and scc. figure 1. flow chart of an on-line near-infrared spectroscopic sensing system for determining milk quality in an automatic milking system figure 2. schematic diagram of the optical system of milk chamber of the nir spectrum sensor 2.4 chemometric analyses chemometric analyses were carried out to develop calibration models for milk quality parameters and to validate the precision and accuracy of the models. spectra data analyses software (the unscrambler ver. 10.3, camo as trondheim, norway) was used for the analyses. the total reference samples were used to develop calibration models. the calibration models were validated using full cross validation method. the statistical method of partial least squares (pls) was used to develop ../../../user/downloads/azojete143/www.azojete.com.ng iweka, et al,. non-destructive online real-time milk quality determination in a milking robot using near-infrared spectroscopic sensing system. azojete, 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 124 calibration models from the absorbance spectra and reference data. the best model was obtained when we used the original spectra data thus, pretreatment techniques such as multiplicative scatter correction, 2nd derivative and smoothing was not used. table 1. specifications of the near-infrared spectroscopic instrument devices specifications nir spectrum sensor absorbance spectrum sensor light source three halogen lamps optical fiber quartz fiber milk chamber surface glass volume of milk sample approx. 30 ml distance between optical axis and milk level 55 mm nir spectrometer diffraction grating spectrometer optical density absorbance wavelength range 700 1050 nm, 1-nm internal wavelength resolution approx. 6.4 nm photocell cmos linear array, 512 pixels thermal controller heater and cooling fan data processing computer windows 7 a/d converter 16 bit spectrum data acquisition every 20 s 3. results and discussion 3.1 near-infrared spectra the original spectra of raw milk are shown in fig. 3. the nir spectra showed two bands peaks at around 740 nm and 840 nm indicate the overtone absorptions by c-h bands and c-c bands that are related to the distinctive absorption bands of milk constituents such as fat, protein and lactose. there was a strong absorption peak of o-h functional groups in water such that band around 960 nm were prominent spectra. figure 3. original spectra of non-homogenized milk from cow number 1 during milking on february 23, 2018 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 125 3.2 precision and accuracy of calibration model the validation statistics of the nir sensing system for milk quality determination are summarized in table 2. correlations between reference and nir-predicted values of milk fat, protein, lactose and scc are shown in figures 4 to 7 respectively. the three major milk constituents are vital for milk quality determination. the quality of milk constituents are influenced by the physiological condition of each cow and cow feed. thus, monitoring of milk constituents during milking everyday can be used for individual cow and feed management. the coefficient of determination (r2), standard error of prediction (sep) and bias were 0.98, 0.23% and 0.00% for fat, 0.72, 0.25% and 0.00% for protein, and 0.54, 0.15% and 0.00% for lactose respectively. the high r2 values, small sep values and the negligible bias values (zero) indicated that there were sufficient levels of precision and accuracy for predicting the three major milk constituents. the performance of calibration models for fat was excellent. the high performance of calibration model for fat was due to the fact that milk spectra had much information on fat content, starting from the scattering of light by fat globules to the absorption by c-h bands and c-c bands of triacylglycerol. the results showed that the nir spectroscopic sensing system designed in our study can be used for online real-time milk constituent quality determination during milking by a milking robot. scc is a recognized standard for mastitis diagnosis and it is a very important indicator for health and milk quality. milk scc can show the level of cow infection and it consequence on the mammary gland of dairy cows which is related to mastitis (satu, 2003). milk produced from the udder of a healthy cow contains less than 100,000 somatic cells per ml (i.e., 4logscc/ml) while cows with subclinical mastitis produce milk containing more than 200,000 somatic cell per ml (i.e., 5.3logscc/ml) (satu, 2003). the values of r2, sep and bias for scc were 0.63, 0.48 log scc/ml and 0.00 log scc/ml respectively. the results obtained for scc indicated that the precision and accuracy for predicting scc was sufficiently high. thus, the calibration model could be used for the diagnosis of subclinical mastitis 3.3 dairy precision farming the installation of nir spectroscopic sensing system developed in our study into a milking robot system would facilitate the monitoring of milk constituents and diagnosis of mastitis of individual cows in real-time during milking. the nir sensing system could provide dairy farmers and veterinarians useful information on milk quality and physiological status of each cow and thus, give them assessment control for improving dairy farm management. the application of this nir sensing system could take dairy farm management to the next level of dairy precision farming on the basis of individual cow information. 4.0 conclusions the nir spectroscopic sensing system developed in this study can be used for online real-time monitoring of fat, protein, lactose and scc during milking by a milking robot with sufficiently high levels of precision and accuracy. by application, the nir sensing system would enable dairy farmers to be able to produce high-quality milk and dairy precision farming will be actualized. ../../../user/downloads/azojete143/www.azojete.com.ng iweka, et al,. non-destructive online real-time milk quality determination in a milking robot using near-infrared spectroscopic sensing system. azojete, 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 126 5.0 acknowledgement this study was supported by a grant from the project of naro (national agriculture and food research organization, japan) bio-oriented technology research advancement institution (the project for development of new practical technology). the authors are grateful to naro for the grant. table 2. validation statistics of the near-infrared sensing system for milk quality determination milk quality items n range r2 sep bias regression fat, % 377 0.98-8.54 0.98 0.23 0.00 y = 1.00 x + 0.00 protein, % 377 2.73-4.46 0.72 0.25 0.00 y = 0.99 x + 0.04 lactose, % 377 3.91-4.99 0.54 0.15 0.00 y = 0.98 x + 0.08 scc, log scc/ml 377 3.48-6.56 0.63 0.48 0.00 y = 0.98 x + 0.09 n: number of validation samples. r2: coefficient of determination. sep: standard error of prediction. regression line: regression line from predicted value (x) to reference value (y) figure 4. correlation between reference fat content and nirs-predicted fat content figure 5. correlation between reference protein content and nirs-predicted protein content http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 127 references iweka, p., kawamura, s., morita, a., mitani, t., okatani, t. and koseki, s. 2016. development of a near-infrared spectroscopic sensing system for milk quality evaluation during milking. in the 4th cigr international conference proceedings of agricultural engineering, aarhus, denmark. kawamura, s., takekura, k. and itoh, k. 2002. accuracy of near-infrared transmission spectroscopy for determining rice constituent contents and improvement in the accuracy. asae paper no. 023006. st. joseph, mich.: asae. kawamura, s., natsuga, m., takekura, k. and itoh, k. 2003a. development of an automatic ricequality inspection system. computers and electronics in agriculture, 40(3): 115–126. kawamura, s., tsukahara, m., natsuga, m. and itoh, k. 2003b. on-line near infrared spectroscopic sensing technique for assessing milk quality during milking. asae paper no. 033026. st. joseph, mich.: asae. kawamura, s., kawasaki, m., nakatsuji, h. and natsuga, m. 2007. near-infrared spectroscopy sensing system for online monitoring of milk quality during milking. sensing and instrumentation for food quality and safety, 1(1): 37–43. kawasaki, m., kawamura, s., tsukahara, m., morita, s., komiya, m. and natsuga, m. 2008. nearinfrared spectroscopic sensing system for on-line milk quality assessment in a milking robot. computers and electronics in agriculture, 63(1): 22–27. lakshmi s., pandey, ak., ravi, n., chauhan, op., gopalan, n. and sharma, rk. 2017. non-destructive quality monitoring of fresh fruits and vegetables. defence life science journal, 2(2): 103–110. natsuga, m., kawamura, s. and itoh, k. 2001. determination of the quality of high-moisture wheat using near-infrared spectroscopy (part 1). journal of the japanese society of agricultural machinery, 63(1): 93–99. figure 6. correlation between reference lactose content and nirs-predicted lactose content figure 7. correlation between reference scc and nirs-predicted scc ../../../user/downloads/azojete143/www.azojete.com.ng iweka, et al,. non-destructive online real-time milk quality determination in a milking robot using near-infrared spectroscopic sensing system. azojete, 14(sp.i4):121-128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 128 natsuga, m. and kawamura, s. 2006. visible and near-infrared reflectance spectroscopy for determining physicochemical properties of rice. transactions of the asabe, 49(4): 1069–1076. sato, t. and yoshino, m. 1987. analysis of milk constituents by the near infrared spectrophotometric method. nihon chikusan gakkaiho, 58(8): 698–706. svennersten-sjaunja, k., sjaunja, lo., bertilsson, j. and wiktorsson, h. 1997. use of regular milking recorded versus daily records for nutrition and other kinds of management. livestock production science, 48(3): 167–174. tsenkova, r., atanassova, s., kawano, s. and toyoda, k. 2001. somatic cell count determination in cow’s milk by near-infrared spectroscopy: a new diagnostic tool. journal of animal science, 79(10): 2550–2557. tsenkova, r., atanassova, s., morita, h., ikuta, k., toyoda, k., iordanova, k. and hakogi, e. 2006. near infrared spectra of cows’ milk for milk quality evaluation: disease diagnosis and pathogen identification. journal of near infrared spectroscopy, 14(6): 363–370. tsenkova, r., meilina, h., kuroki, s. and burns, d. 2009. near infrared spectroscopy using short wavelengths and leave-one-cow-out cross-validation for quantification of somatic cells in milk. journal of near infrared spectroscopy, 17(6): 345–351. http://www.azojete.com.ng article information 1.0introduction 2.0 materials and methods 2.2 cows and milk samples 2.4 chemometric analyses 3. results and discussion 3.1 near-infrared spectra 3.2 precision and accuracy of calibration model 3.3 dairy precision farming 4.0 conclusions availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 45-53 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng development and performance evaluation of a kerosine heated chicken egg incubator ndirika, v.i.o. 1 and s.a. ademoye 1 abstract a kerosene-heated chicken egg incubator of 160 eggs capacity was developed and its performance evaluated based on incubation temperatures, relative humidity, period of incubation and percentage of eggs hatched. the results revealed that the average incubation temperature and relative humidity obtained were 38.68 0 c and 58.16% respectively at average ambient conditions of 27.2 0 c temperature and 84.68% relative humidity. also, the incubation temperature and incubation relative humidity at different levels of tray varied between 36.840.9 0 c and 46.5 – 67% respectively, but the differences in their mean values at different egg tray levels were not statistically significant at 5% level. up to 80% of the eggs were hatched over a period of 22 days at hatching temperature of 37.5 0 c within ambient conditions of 27 0 c temperature and 68.5% relative humidity. the results obtained were found to conform with the results obtained from already established research works on natural incubation method for chicken. 1. introduction chicken egg is oval in shape and contains white albumen and a yolk which are enclosed by a shell. egg is very important to life because of its nutritional value. it contains albumen which is an essential protein constituent having a weight of about 12% of its total weight (ademoye, 1998). for fertilized egg, the yolk can develop into a chick under the application of certain range of heat. oluyemi and robert (1988) defined incubation as the management of a fertilized egg to ensure the satisfactory development of the embryo inside into a normal chick. incubation can be achieved by natural or artificial methods. in the natural method, it takes the chicken about 20 – 21 days to hatch them. the artificial method is achieved by the application of designed equipment to aid hatching and heat is supplied by electrical or non-electrical means. due to frequent electric power failure and lack of access to electricity in the rural areas, alternative sources of energy such as kerosene and charcoal, should be considered in the design of nonelectrical incubators. some of the problems often reported with the use of alternative heating sources are in the areas of temperature control, turning of eggs, air pollution and contamination of eggs and economic considerations. the major factors limiting the effective operation of the incubator such as temperature control, turning of egg, air pollution and contamination of egg have been reported from some test reports by osuigwe and nwachukwu (1994), shimonyan (1997) and ademoye (1998). a good kerosene incubator would be capable of eliminating the electricity difficulties encountered. the specific objectives of this study were to develop a chicken egg kerosene incubator and to evaluate the performance of the incubator 1 department of agricultural engineering, inst. of agric. res. ahmadu bello university, zaria, nigeria development and performance evaluation of a kerosene chicken incubator 46 2. materials and methods 2.1 design consideration the parameters considered in the design of the incubator were air temperature and control, heat transfer, relative humidity, capacity and turning mechanism for eggs. the design parameters were established as recommended by other researchers (ademoye, 1998; ogundipe & oni, 1986) as follows: (i) a capacity of 160 eggs for a small household (ii) an incubation temperature of 34.9 0 c (iii) an average relative humidity of 57.5% (iv) a turning angle of 75 0 . 2.2 description of the incubator the incubator consists of four basic components, namely the egg tray, water trough, turning device and a hollow pipe. the assembly and isometric views of the incubator are presented in figures 1 and 2 respectively. the eggs to be hatched were placed on the trays having a maximum capacity of 160 eggs. it was constructed from wood and aluminium wire net. the tray dimensions were 480mm x 200mm x 50mm. a rectangular mild steel water trough of dimension 430mm x 200mm x 20mm was placed at the bottom of the incubator to raise the humidity. the turning device, extending from the top to the bottom of the incubator, anchors the egg tray and allows for their tilting up to 75 0 . it was constructed from 40mm diameter hollow steel pipe and had overall length of 560mm. a hollow tube that extends from the outside into the incubator served as a duct for transmission and distribution of hot air to the incubator. the pipe was constructed from 40mm diameter hollow steel pipe with overall length of 1180mm. the entire structure was covered with a wooden frame work. the outer surfaces were covered with particle board as insulating materials. azojete vol. 5 2007 47 fig. 1: assembly drawing of the incubator development and performance evaluation of a kerosene chicken incubator 48 figure 2: isometric drawing of the incubator azojete vol. 5 2007 49 2.3 working principle hot air produced as a result of kerosene combustion was conveyed from the outside into the incubator through the pipe. the pipe was positioned at the bottom and the heat distributed uniformity by natural convection. the heat energy is used by the eggs on the tray for embryo development. turning was achieved by pulling and pushing the steel rod attached to the turning device that extends to the outside at an angle of 75 0 . the temperature was manually controlled by varying the distance between the heating source and the transmission pipe with the ventilation hole remaining open. the ventilation hole allows fresh air to flow into the incubator. 2.4 experimental procedure wet and dry bulb thermometers (ranging between 0 – 100 0 c) were installed inside the incubator to determine the temperature and relative humidity of the incubating chamber, while a thermocouple was used to measure the temperature of the heating source, which ranged between 0-720 0 c. the period for turning of eggs, temperature reading and control, opening and closing of ventilation hole were determined using a stop watch. a preliminary experiment was conducted without eggs inside the incubator in order to determine the temperature required and how it will be controlled. some 160 eggs obtained from the national animal production research institute (napri) and were placed in the incubator and heated. the stove produced hot air which was transferred into the incubator through steel pipe with the ventilation hole closed for 40 minutes in order to attain the required temperature. the ventilation hole was then opened and the distance between the stove and the pipe was varied to control the temperature. the eggs inside the incubator were turned 4 times daily at regular intervals. the following parameters were evaluated in the experiment; hatchability, hatching temperature, hatching period, incubation temperature and incubation relative humidity. hatchibility was obtained using the following relation (oluyemi and robert, 1998). number of live hatching after five days hatchibility (%) = --------------------------------------------- x 100 initial number of hatching the results obtained with the kerosene incubator were compared with that of natural incubation. variation of average incubation temperatures and the relative humidities at different levels of egg tray were monitored. 3. result and discussion 3.1 incubation temperature and relative humidity the average incubation temperature and relative humidity obtained with the kerosene incubator were 38.68 0 c and 58.16 0 c respectively at ambient conditions of 27.2 0 c temperature and 84.64% relative humidity (table 1). the coefficient of variation of the incubation temperature was 2.77% while that of that of the relative humidity was 8.91%. this implies that the variation of the data obtained over the test period for both incubation temperature and relative humidity were not significant at 5% level. the average incubation temperature and relative humidity fall within the range of 38 – 41.71 0 c and 50-60% obtained by sonaiya et al (1995) with natural incubation method (table 2). development and performance evaluation of a kerosene chicken incubator 50 table 3 shows that there were variations of incubation temperature and relative humidity at different levels of egg tray but were not significant at the 5% level. the incubation temperature obtained at different levels of egg tray varied between 36.8 – 40.9 0 c, while the relative humidity varied between 46.5 – 67%. the variation of temperature and relative humidity during the period of incubation are presented in figures 3 and 4. the incubation temperatures were higher than the room and ambient temperatures at different periods of incubation. the highest value of the average incubation temperature (40.9 0 c) was attained on the 5 th day at 29 0 c room temperature and 27 0 c ambient temperature. the relative humidities obtained at these temperatures were 59.8% and 81.5% in the incubator and the ambient respectively. table 1: average incubator and ambient conditions over the test period period (days) ambient temperature ( 0 c) incubation temperature ( 0 c) incubation r.h(%) ambient r.h. (%) room temperature ( 0 c) 1 28.0 38.3 58.0 91.0 25.6 2 28.0 39.3 60.5 91.5 25.4 3 27.0 39.1 57.8 87.5 24.0 4 28.7 39.0 59.2 88.5 26.6 5 27.0 40.9 59.8 81.5 29.0 6 27.0 39.1 58.3 80.0 28.1 7 25.0 38.9 55.3 81.0 26.5 8 28.0 38.0 60.0 81.0 25.9 9 26.5 38.0 56.0 88.5 24.4 10 29.7 38.3 59.9 88.0 26.3 11 26.5 38.0 57.8 93.5 25.5 12 27.5 40.5 58.3 79.5 27.4 13 27.5 39.3 59.8 84.0 26.9 14 26.0 39.1 59.7 84.0 27.2 15 26.5 37.8 57.0 73.0 25.8 16 27.0 38.9 62.0 84.0 27.0 17 26.5 39.5 59.5 81.5 27.8 18 27.5 37.0 57.5 85.5 23.5 19 27.5 39.8 60.5 92.5 25.2 20 27.5 38.5 58.2 87.5 25.4 21 26.5 36.6 67.0 91.0 25.4 22 27.0 37.0 37.5 68.5 28.9 mean sd cv(%) 27.2 0.97 4% (n.s) 38.68 1.07 2.77%(n.s) 58.16 5.18 8.91% (n.s) 84.68 6.24 7.4% (n.s) sd = standard deviation; cv = coefficient of variation; n.s. = not significant azojete vol. 5 2007 51 table 3: variation of average incubation temperature and relative humidities at different levels of egg tray tray levels incubation temperature 0 c incubation relative humidity, % 1 40.9 59.8 2 40.5 58.3 3 39.4 46.5 4 39.0 59.2 5 38.0 60.0 6 37.8 57.0 7 37.0 57.5 8 36.8 67.0 mean sd cv(%) 38.68 1.53 3.96% (n.s) 58.16 5.65 9.72% (n.s) n.s. : not significant 0 5 10 15 20 25 30 35 40 45 1 4 7 10 13 16 19 22 period ( day) t e m p e ra tu re 0 c av. amb. temp. av. inc. temp. av. rm. temp. figure 3: variation of temperature with the period of incubation development and performance evaluation of a kerosene chicken incubator 52 figure 4: variation of relative humidity with the period of incubation 3.2 hatchibility, hatching, temperature and hatching period hachibility of 80% was obtained and that compared favourably with the value obtained by dafwang et al. (1998) with natural incubation method (table 2). a hatching period of 22 days was obtained in this study. this is slightly longer than the maximum 21 days or natural method (sonaiya et al., 1995). the slight variation may be due to temperature fluctuation during the experiment. figure 5 shows the effect of the distance between the pipe and the heat source on the incubation temperature. the incubation temperature decreases with increase in distance between the pipe and the heating source. the incubation temperature was higher without the eggs than with the eggs inside it. incubation temperatures of 40.5 and 38 0 c were attained at a distance of 8.5cm without and with eggs respectively. the temperature was lower (40 0 c) even at a shorter distance of 6.5 cm with eggs. this could be due to the utilization of hot air for the development of the embryo inside the eggs. azojete vol. 5 2007 53 figure 5: effect of distance between the stove and the pipe on the incubation temperature 4. conclusion a kerosene incubator was fabricated and tested. the performance of the incubator was satisfactory when compared with natural method. the 160egg incubator has an incubation temperature and r.h of 38.68 0 c and 58.16% respectively and hatchability of 80%. the incubator is recommended for use in school laboratories for demonstration and teaching purposes and for small household uses. references ademoye, s. a. (1998). design and construction of incubator. unpublished b. eng. thesis, department of agricultural engineering, ahmadu bello university, zaria, nigeria. dafwang, i.i.; j. y. odiba and e. i. ikani (1998). hathery management handboook extension bulletin no. 79. a publication of naerls/abu, zaria, pp. 8-12. oluyemi, j. a. and f. a robert (1988). poultry production in warm wet climate. macmillan publishers limited, london and basing stroke. osuigwe, d. i. and v. n. nwachukwu (1994). portable incubator for small scale fish hacteries. journal of agricultural technology 2:1-5. pgundipe, s. o. and o. o. oni (1986). poultry breeding and hatching management. poultry research programme. national animal production research institute (napri), ahmadu bello university, zaria, nigeria pp. 2-5. shimoyan, k. j. (1997): design and construction of incubator. unpublished m.sc. thesis. department of agricultural engineering, ahmadu bello university zaria, nigeria. sonaiya, e. b.; g. agbede, i. k. odubore, a. o. abdullahi and j. a. oluyemi (1995). evaluation of local poultry ecotypes for productivity and disease resistance. proc. of the 20 th annual conference of nsap held at fed. university of technology minna 2630 march, 1995. arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):197-210 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 197 original research article comparison of square and circular isolated pad foundations in cohesionless soils o. o. komolafe*, i. o. balogun and y. o. abiodun department of civil and environmental engineering, university of lagos, akoka, nigeria *corresponding author’s email address: ookomolafe@unilag.edu.ng 1.0 introduction a foundation is that portion of a structure that transmits the loads from the structure to the underlying soil. one general way of classifying foundations with respect to depth is either as shallow or deep foundations. there are important differences between the two: depending on geometry, type of soil, structural functionality, and constructive systems. cohesionless soil is often composed of granular or coarse-grained materials with visually detectable particle sizes and with little or no cohesion between particles, such as coarse sand. it is also significant that the distribution of soil pressure is a function of the type of soil, the relative rigidity of the soil and the foundation, and the depth of contact between the foundation and the soil (luévanosrojas, 2016). in this study, the shallow foundation was evaluated in the form of an isolated pad foundation which will sometimes be referred to as a footing. a flexible footing is considered to have some degree of flexibility and hence upon application of partial pressure or concentrated load the footing bends. as the footing attains the bending curvature, the soil beneath the footing base experiences a nonlinear pressure distribution. on the other hand, a rigid footing is assumed to settle as a rigid element. it is also expected that there will be a very minimal curvature along its length or width even if it experiences a concentrated loading. article information abstract one of the most commonly used pad foundation types is the square footing, however, there is a necessity to compare its performance and economy with the circular pad foundation which is not often considered. this study focuses on the suitability of the square versus circular isolated pad foundation types in cohesionless soils, from a geotechnical, structural, and construction cost perspective. the square and circular pad foundation types were subjected to three (3) cases, which were: when the foundation footings have equal width or diameter (case 1), when the foundation footings have an equal axial load capacity (case 2), and when the foundation footings are restricted to a defined net allowable bearing capacity (case 3). the factors evaluated in each of these cases were bearing capacity, immediate settlement, structural design, and construction cost. additionally, a model for estimating the construction cost of reinforced concrete was proposed in this study, and it was used to estimate the construction cost of the reinforced concrete isolated pad foundation types. the results of this research work show that overall, the square isolated pad foundation type will be the better selection for most design and construction considerations © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 sept., 2020 revised 30 march, 2021 accepted 5 april, 2021 keywords: cohesionless soils bearing capacity immediate settlement construction cost reinforced concrete komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 198 in general, bearing capacity may be explained as the largest intensity of pressure that may be applied by a structure or a structural member to the soil which it supports without causing excessive settlement or failure. several theories have been developed by various researchers such as terzaghi (1943), meyerhof (1951, 1963), hansen (1970) and vesic (1973, 1975) regarding the estimation of bearing capacity over the years. however, this paper focuses on terzaghi’s general bearing capacity due to its popularity in use, especially for less complex bearing capacity estimation cases. furthermore, a suitable bearing soil stratum must be able to withstand all kinds of design loads from the structure without any shear failure or destructive unallowable settlements (bowles, 1982). settlement considerations can be immediate, consolidation, and secondary depending on the application of load, soil type, and pore pressure dissipation. footings founded in cohesionless soils reach almost the final settlement, during the construction stage due to the high permeability of the soil. the water in the voids is expelled simultaneously with the application of load and as such the immediate and consolidation settlements in such soils are rolled into one (murthy, 2002). in summary, the main settlement consideration in cohesionless soils is the immediate (or elastic) settlement. the settlement behaviour is different for cohesive soils, where consolidation settlement is experienced and pore pressures greater than the hydrostatic pressures are developed due to the imposed load (obaji et al., 2020). one pertinent aspect following the geotechnical considerations for an isolated pad foundation is the design of the footing. the design of the foundation depends on the type of soil, type of structure, and its load. the greater the net allowable bearing capacity of the soil, the larger the load it can safely withstand. in general, the footings are designed to sustain the applied loads, induced reactions, and moments to ensure that any settlement which may occur is within the acceptable limit and the net allowable bearing capacity of the soil is not exceeded. it is also important that a structurally well-designed isolated pad foundation is economical in its construction by selecting the appropriate and safest dimensions in its design. although, relying on the dimensions alone does not justify proper construction. however, selecting the appropriate reinforcement size and number, reinforcement arrangement, tensile strength, and ultimately due monitoring and quality control during construction will help to transmit loads safely and achieve the purpose of the isolated pad foundation on the underlying soil. this paper, therefore, presents a comparative study of the square and circular isolated pad foundations in cohesionless soils subjected to the following conditions: footings having equal width or diameter, footings having an equal axial load, and footings restricted to a defined net allowable bearing capacity. further comparisons of the footings in terms of the settlement, structural design, and construction cost were evaluated. it is hoped that this research study will help structural and geotechnical engineers determine where the advantage of using a square or circular footing lie in cohesionless soils. 2.0 materials and methods the consideration of bearing capacity for this research study was based on the terzaghi (1943) general bearing capacity equations. the net ultimate bearing capacity (qnu) specifically for the purely cohesionless soil situation is given by the following relationships in equations (1) and (2): arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):197-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 199 ( ) (square pad foundations) (1) ( ) (circular pad foundations) (2) (3) where: qna = net allowable bearing capacity (n), γ = bulk unit weight of the cohesionless soil (kg/m3), df = depth of foundation footing (m), b = width or diameter of footing (m) nq and nγ = bearing capacity factors (das, 2014; kumbhojkar, 1993; terzaghi, 1943) throughout this study, it was assumed that γ = 19 kn/m³, df = 1 m, and factor of safety (to determine net allowable bearing capacity) = 3 for both square and circular pad foundations. case 1 considers when the pad foundation width/diameter = 1 m. case 2 considers when the allowable column load on the pad foundation = 200 kn. while case 3 considers when the net allowable bearing capacity = 200 kn/m². the settlement evaluated for this study was limited to immediate settlement. calculations were based on the theory of elasticity (davis & poulos, 1968; murthy, 2002). this is given in equation (4): ( ) (4) where: qn = net allowable foundation pressure (n/m2) μ = poisson’s ratio es = modulus of elasticity of soil (n/m2) if = influence factor the following values were also assumed; μ = 0.3, es =30000 kn/m². values of qn and b were obtained from the bearing capacity considerations. the average values of the influence factor used are summarized in table 1. table 1. average values of influence factor (bowles, 1988; murthy, 2002) shape flexible footing rigid footing circle 0.85 0.88 square 0.95 0.82 the structural design of the footings for the cases evaluated was in accordance with bs 8110 part 1 (1997). necessary calculations and parameters are given in equations (5) to (9): (5) z = ( √( )) (6) where: as = area of tension reinforcement (m2) m = maximum bending moment (n.m) d = effective depth (m), fy = characteristic strength of steel (460 n/mm2) z = lever arm (m). komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 200 k = (7) where: b = effective width (m), fcu = characteristic strength of concrete (35 n/mm2) also, the design shear stress (v) was designed using: (8) note: in no case should v exceed: 0.8√ or 5 n/mm2, whichever is the lesser, considering whatever shear reinforcement is provided. (this limit includes an allowance for of 1.25). where: vu = design shear force due to ultimate load (n) = breadth of section (m) (9) where: vmax = maximum design shear stress (n/m2) n = applied axial load (n) colp = column perimeter effective length touching loaded area (m). the following values were also assumed: thickness of foundation = 400 mm concrete cover = 50 mm column dimension = 225 mm x 225 mm. in terms of construction, the required volume of structural concrete (comprising ordinary portland cement, fine and coarse aggregate) was estimated based on the results from the structural design. also, the length of reinforcement (high yield tensile steel bars) required was determined using the structural details generated. 3.0 results and discussion 3.1 bearing capacity considerations the square and circular isolated pad foundations were restricted to having the same width, the same axial load, and the same net allowable bearing capacity. the results obtained using the terzaghi (1943) general bearing capacity equations are shown in table 2. table 2. bearing capacity consideration results width/diameter (m) axial load capacity (kn) net allowable bearing capacity (kn/m²) square circular square circular square circular case 1 1.000 1.000 184.376 135.293 184.376 172.260 case 2 1.037 1.192 200.000 200.000 186.147 179.237 case 3 1.322 1.763 349.744 488.335 200.000 200.000 considering case 1, the results obtained showed that the square pad foundation had a higher axial load capacity of 184.376 kn when compared with the circular pad foundation having an axial load capacity of 135.293 kn. therefore, in the equal width/diameter situation of 1 m, the circular pad foundation could only withstand 73.378% of the axial load capacity of a similar arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):197-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 201 square pad foundation. the net allowable bearing capacity for the square pad foundation also showed a similar trend with a greater value of 184.376 kn/m² when compared with 172.260 kn/m² for the circular pad foundation. the results indicate that the square pad foundation will be the better option when in a constrained area, due to its greater axial load and net allowable bearing capacity under this case. the results obtained are also in line with that of cerato & lutenegger (2006) where the bearing capacity of the square pad foundation ranged between 1 and 1.33 times greater than the circular pad foundation for the same width/diameter. the results in case 2 when the square and circular pad foundations were subjected to an equal axial load of 200 kn revealed that the square pad foundation required a lesser value of 1.032 m for its width when compared to the required diameter of 1.192 m for the circular pad foundation. also, the square pad foundation had a slightly greater net allowable capacity value of 186.147 kn/m² when contrasted with 179.237 kn/m² for the circular pad foundation. the results in case 2 show that when a defined axial load needs to be transmitted to the cohesionless soil, the square pad foundation will be the preferable choice because it gave a greater net allowable capacity and lesser width when compared with the circular pad foundation. the results obtained correspond with the analysis done by luévanos-rojas (2016) where the circular pad foundation also required a larger width than the square pad foundation when subjected to similar punching shear values. the results from case 3 when both square and circular pad foundations were restricted to a defined net allowable bearing capacity of 200 kn/m² indicated that the circular pad foundation will be able to withstand 39.626% more axial load than that of the square pad foundation with values of 488.335 kn as to when compared with 349.744 kn for the square pad foundation. the increase in axial load capacity is a reflection of foundation width/diameter in the terzaghi (1943) bearing capacity equations for the two pad foundation types shown in equations (1) and (2). this leads to an expansion in the foundation diameter from 1.322 m for the width of the square pad foundation to 1.763 m for the circular pad foundation, which represents a 33.358% increase that may not be desirable in constrained areas. nevertheless, in this case, the results show that when the net allowable bearing capacity has been defined and provided there is ample space, the circular footing can give a greater axial load capacity. 3.2 settlement analysis and considerations in this section, the authors compared the analysis of immediate settlement based on the elastic theory with the simulation results of settle3d software (version 4.023 by rocscience inc.). while the immediate settlement operates on elastic theory, the adapted software considers the soil segmented into finite layers. the soil area was modelled as a cohesionless soil with an area 10 times the size of the width or diameter of the foundation considered. the model soil depth used for computations was 20 m. the vertical stresses due to the imposed load on the soil were estimated using the multiple layer stress computation method proposed by yue (1995) & yue (1996), which gave similar results to the boussinesq (1883) method. a screenshot of the settle3d model interface is shown in figure 1. komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 202 figure 1. settle3d software interface from the evaluation of the immediate settlement, flexible and rigid footings were evaluated for both square and circular shapes. the three cases evaluated in this study were considered. the settlement analysis was based on the values obtained in table 2 for each of the cases considered respectively. table 3 shows the results based on the calculations from the theory of elasticity, while, table 4 shows the results from the analysis using the settle3d software. table 3. immediate settlement results based on calculations from the theory of elasticity flexible footing (mm) rigid footing (mm) square circular square circular case 1 5.3 4.4 4.6 4.6 case 2 5.6 5.5 4.8 5.7 case 3 7.6 9.1 6.6 9.4 table 4. immediate settlement results based on results using settle3d software flexible footing (mm) rigid footing (mm) square circular square circular case 1 7.4 6.2 4.8 4.1 case 2 7.7 7.5 5.0 5.1 case 3 10.2 11.8 6.8 8.3 arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):197-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 203 figures 2 – 4 show the influence of the vertical stresses on the immediate settlement in the soil below the foundation, considering the square and circular foundation types for flexible and rigid behaviour based on the analysis using settle3d software. figure 2. variation of immediate settlement for equal width/diameter (case 1) figure 3. variation of immediate settlement for equal axial load capacity (case 2) figure 4. variation of immediate settlement for an equal net allowable bearing capacity (case 3) there is a slight difference observed in the results obtained from the calculations based on the theory of elasticity and the results using the settle3d software from tables 3 and 4. this slight variation of results is due to the difference in the analytical approach based on the theory of elasticity and the multiple layer stress computation method considered in the settle3d software. also, the settle3d software divides the soil into finite layers which may lead to a more accurate computation than using the conventional calculation of immediate settlement based on the theory of elasticity which considers the soil as a whole. therefore, the results from settle3d software were employed in this study. from the results in case 1, the square footing had a greater settlement of 7.4 mm as opposed to 6.2 mm for the circular footing when considering flexible footings. although, for rigid behaviour, the circular footing gave a reduced settlement of 4.1 mm compared with the 4.8 mm for the square footing. therefore, in a restricted foundation area of cohesionless soil deposit, the circular footing will provide better performance when considered as a flexible footing provided the axial load transferred to the soil can be achieved considering the net allowable bearing capacity of the soil. 0 2 4 6 8 10 12 14 16 18 20 0 2 4 6 8 d ep th ( m ) immediate settlement (mm) flexible circular rigid circular flexible square rigid square 0 2 4 6 8 10 12 14 16 18 20 0 2 4 6 8 10 d ep th ( m ) immediate settlement (mm) flexible circular rigid circular flexible square rigid square 0 2 4 6 8 10 12 14 16 18 20 0 5 10 15 d ep th ( m ) immediate settlement (mm) flexible circular rigid circular flexible square rigid square komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 204 the results from case 2, when the footings are subjected to equal axial loads, the square footing had a slightly greater value of 7.7 mm when compared to 7.5 mm for the circular footing. nevertheless, when the footings were considered as rigid, the square gave a marginally lesser value of 5.0 mm when contrasted with 5.1 mm for circular, making the circular slightly better as a flexible footing and the square as a rigid footing. interestingly, the performance of square and circular almost gave similar results for both flexible and rigid footings regarding settlement considerations when a defined axial load is expected in cohesionless soils. although, the square footing will require a slightly lesser construction space than the circular footing under this case. the results from case 3 reveal that the square footing will perform better than the circular footing when considered as either rigid or flexible due to its lesser settlement values. for the flexible footing, the square had a settlement of 10.2 mm, while the circular had a settlement of 11.8 mm. also, as rigid footings, the square had a settlement of 6.8 mm while the circular had a settlement of 8.3 mm. hence, with a defined net allowable bearing capacity, the square footing will give a lesser settlement when contrasted with the circular footing in cohesionless soils with an additional advantage of requiring a lesser construction area than the circular footing under this case. the settlement results obtained in this study from analysis considerations using the theory of elasticity based on the recommendations by davis and poulos (1968) and murthy (2002), as well as those obtained using the multiple layer stress computation method in the settle3d software given by yue (1995) and yue (1996) are within reasonable limits and not too wide apart. the results were also similar to those obtained by cerato and lutenegger (2006) using model footing tests on dense winter sand. it is worthy to note however that in practice, most foundations are flexible. even very thick ones deflect when loaded by the superstructure loads. bowles (1996) indicated that if the base is rigid the settlement will be uniform, but the base may tilt. therefore, based on this assumption, it is recommended that the design of most isolated pad foundations should be considered flexible unless otherwise stated. 3.3 structural design in accordance with the bs 8110 part 1 (1997), the required reinforcement for the footings (i.e. circular and square) was evaluated for the three cases. the results presented in table 5 were based on the structural design for each of the cases considered respectively. the summary of the results is shown in table 5. table 5. structural design consideration results area of reinforcement required (mm2) punching shear (n/mm2) square circular square circular case 1 6.531 6.102 0.029 0.107 case 2 12.823 64.523 0.04 0.089 case 3 156.490 930.429 0.153 0.376 arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):197-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 205 from the results in case 1, the square pad foundations required a greater area of reinforcement of 6.531 mm2 when compared with 6.102 mm2 for the circular footing. the results from case 2, when the pad foundations are subjected to equal axial loads, the circular footing had a greater value of 64.523 mm2 when compared to 12.823 mm2 of the square footing. high yield tensile reinforcements of 12 mm diameter are usually the minimum size provided for pad foundations. hence, for both pad foundation shapes in case 1 and case 2, the recommended minimum reinforcement area proposed is 377 mm2 at 300 mm c/c. additionally, the punching shear check is satisfied. the results from case 3 reveal that the square pad foundation with an area of 156.490 m2 will be an economical choice due to the lesser reinforcement required when compared to 930.429 m2 obtained from the circular footing. therefore, for the square pad foundation, a recommended minimum area of 377 mm2 is proposed using the 12 mm reinforcement at 300 mm c/c. on the other hand, for the circular pad foundation, the recommended minimum area of 1010 mm2 using 16 mm reinforcement at 200 mm c/c is proposed. additionally, the punching shear check is satisfied. 3.4 construction cost considerations the volume of concrete to be required for case 1 favours the use of the circular pad foundation due to its lesser area and volume especially in restricted areas in cohesionless soils thereby leading to some savings in construction cost. the volume of concrete required for the circular footing resulted in a value of 0.314 m3 when compared with 0.400 m3 for the square pad foundation. the consideration of case 2 which highlights a specific axial load capacity showed that there was a marginal increase in the volume of concrete required for the circular pad foundation with a value of 0.446 m3 when compared with that of the square pad foundation with a value of 0.430 m3. case 3 favours the use of the square pad foundation in areas of a defined net allowable bearing capacity with a considerable reduction in construction cost because it required a lesser volume of concrete of 0.699 m3 when contrasted with 0.976 m3 for the circular pad foundation. the length of reinforcement required based on the structural design in case 1 showed that the circular pad foundation will require a lesser length with a value of 9.880 m when compared with that of the square footing requiring a length of 12.000 m which provides an advantage for the circular footing in restricted areas. case 2 shows a similar result with case 1 with the circular pad foundation also requiring a lesser length of 13.590 m when contrasted to 15.370 m for the square pad foundation, thereby leading to some savings in reinforcement length with the use of the circular footing in situations of equal axial load capacity. case 3 which highlights the situation when both pad foundation types are subjected to a defined net allowable bearing capacity also reveals that the circular pad foundation will require a lesser length of reinforcement of 33.500 m when compared with the square pad foundation requiring a length of 35.882 m, but with an increased reinforcement diameter of 16 mm as opposed to 12 mm for the square pad foundation. table 6 shows a summary of the construction quantities required for all the cases considered for both square and circular footings on cohesionless soils. typical reinforcement details for komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 206 the square and circular isolated pad foundations are also shown in figure 5 (a) and (b) respectively. table 6. construction quantities required for the reinforced concrete isolated pad foundations volume of concrete required (m3) length of reinforcement required (m) square circular square circular case 1 0.400 0.314 12.000 9.880 case 2 0.430 0.446 15.370 13.590 case 3 0.699 0.976 35.882 33.500 (a) (b) figure 5. (a) typical reinforcement details for the square isolated pad foundation; (b) typical reinforcement details for the circular isolated pad foundation. (note: x indicated on the drawing represents the number of bars and y represents high yield steel bars). the construction cost of reinforced concrete per m3 was determined using a model developed in this study. the model is based on the cost of the constituent materials of concrete with the consideration of labour and additional material costs (such as the use of additives, construction equipment, cost of formwork, or excavation when necessary). the model relates the construction cost of reinforced concrete per m3 with the characteristic strength of concrete and the cost per tonne of the various concrete materials, making the model suitable for any currency to estimate the construction cost of reinforced concrete based on the required concrete volume. the preliminary mathematical model generated for the construction cost of reinforced concrete per m3 for fcu of 15 n/ mm² (m15) using a water-cement ratio of 0.5 without the consideration of construction profit is given as: (0.3168c + 0.748s + 1.452g + 0.03r + 0.11w) × 1.3 × 1.2 (10) where: c, s, g, r, and w are the cost per tonne of cement, fine aggregate (sand), coarse aggregate (granite), reinforcement, and water respectively. the coefficients before each notation represent the quantity (in terms of mass) per tonne required for each of the constituent materials for m15 reinforced concrete based on the concrete mix ratio of 1:2:4 for arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):197-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 207 a wet volume of 1 m3. the constant multipliers of 1.3 and 1.2 reflect the factors for labour and additional material costs respectively. models based on this approach were generated for concrete grades of m5, m10, m20, and m25 in consideration of their mix ratios which are 1:5:10, 1:3:6, 1:1.5:3, and 1:1:2 respectively (the constructor, 2021). an expression for modification factors relating to all the models was developed. this mathematical expression relates dimensionless costs and various concrete grades, using m15 reinforced concrete as the reference construction cost of reinforced concrete as shown in figure 6. figure 6. modification factor for the construction cost of reinforced concrete the modification factor indicated in figure 6 shows an almost perfect trend with an exponential relationship and it is proposed to reasonably extrapolate the construction cost of reinforced concrete grades greater than m25. a consideration of the preliminary mathematical model generated for the construction cost of reinforced concrete per m3 for concrete grade m15 and the modification factor was used to obtain the cost of reinforced concrete construction per m3. hence, the final mathematical model to estimate the construction cost of reinforced concrete (crc) of volume vc (in m3) with construction profit p (in %) is given as: ( ) ( ) (11) the developed model costs were validated using the construction cost of reinforced concrete in naira (₦) as shown in table 7 with 0% construction profit. the results were in good agreement with a maximum absolute difference of 2.4% for the concrete grades considered. the costs of the reinforced concrete constituent materials were estimated using up-to-date prices provided by nigerian price (2021). the model was also applied to the construction quantities of the square and circular reinforced concrete isolated pad foundations based on the volume of concrete required (vc) as obtained in table 6. furthermore, the usage of the model assumes that the volume of concrete represents the volume of the reinforced concrete, considering the ease of its application for practical purposes. the results of the construction cost of reinforced concrete in this study are shown in table 8 based on the developed mathematical model given in equation (11), with the consideration of 0% construction profit. y = 0.613e0.032x r² = 0.9972 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 5 10 15 20 25 30 m o d if ic at io n f ac to r concrete grade (or fcu in n/mm²) komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 208 table 7. validation of the developed model for the construction cost of reinforced concrete concrete grade construction cost per m3 (₦) model cost per m3 (₦) absolute difference (%) m5 55209 55531 0.6 m10 65390 65166 0.3 m15 77027 76473 0.7 m20 87605 89742 2.4 m25 106118 105314 0.8 table 8. construction cost of the reinforced concrete isolated pad foundations square (₦) circular (₦) case 1 58012 45540 case 2 62363 64684 case 3 101376 141550 the results in table 8 indicate that the construction cost of the reinforced concrete square pad foundation was greater than that of the circular pad foundation in case 1 only when the foundation width or diameter was defined. the construction cost of the circular pad foundation did not give economical results when compared with the square pad foundation for case 2 where they were subjected to an equal axial load, and case 3 when the bearing capacity was defined. in summary, this study has focused on the comparison of the square and circular isolated pad foundations on cohesionless soils with three different cases being considered. case 1 highlights the situation where both isolated pad foundation types were restricted to a defined width or diameter of 1m. case 2 is based on the situation where both isolated pad foundation types were subjected to equal axial loads of 200 kn. case 3 considers the situation where both isolated pad foundations were restricted to a defined net allowable bearing capacity of 200 kn/m². the summary of favourable footing selection focused on various factors considered in this study is presented in table 9. table 9. summary of favourable isolated pad foundation selection based on this study case 1 case 2 case 3 bearing capacity considerations square square circular settlement considerations (flexible footing) circular circular square settlement considerations (rigid footing) square square square area of reinforcement required circular square square punching shear square square square construction cost circular square square 4.0 conclusion the use of the circular pad foundation is a good choice in terms of immediate settlement considerations for a flexible footing and construction cost for case 1. however, the circular pad foundation is not a favourable selection over the square pad foundation in terms of equal axial load capacity (case 2). this is because the difference of the immediate settlement results for the two isolated foundation types is negligible, thereby indicating that the square pad arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):197-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 209 foundation will be the overall better choice in a limited area, where foundation space is defined. under case 3, where both pad foundation types are restricted to a defined net allowable bearing capacity, the square pad foundation is a good choice in terms of having a reduced immediate settlement and construction cost. additionally, a mathematical model was proposed in this study for estimating the construction cost of reinforced concrete. the model also factors the characteristic strength of concrete and can similarly be applied to other concrete structural elements, thereby assisting project managers, quantity surveyors, contractors, builders, and engineers in making quick construction cost estimates. overall, it can be seen that the square isolated pad foundation type is a better selection for most design and construction considerations based on this study. it is important to note, however, that the preferred isolated pad foundation to be selected for a particular construction project ultimately depends on the discretion of the consulting engineer and the construction constraints on site. nevertheless, this research study has provided a useful guide for the selection of square or circular isolated pad foundations in cohesionless soils based on design considerations, construction limitations, and cost. references boussinesq, jv. 1883. application des potentiels a l’etude de l’equilibre et due mouvement des solides elastiques. gauthier-villars. bowles, je. 1982. foundation analysis and design (3rd ed.). mcgraw-hill companies. bowles, je. 1988. foundation analysis and design (4th ed.). mcgraw hill publishing co. bowles, je. 1996. foundation analysis and design (5th ed.). mcgraw-hill companies, inc. british standard code of practice 1997. bs 8110 part 1. structural use of concrete-part 1. code of practice for design and construction. british standards institution. cerato, ab. and lutenegger, aj. 2006. bearing capacity of square and circular footings on a finite layer of granular soil underlain by a rigid base. journal of geotechnical and geoenvironmental engineering, 132(11): 1496–1501. https://doi.org/10.1061/(asce)10900241(2006)132:11(1496) das, bm. 2014. principles of foundation engineering (8th eds). cengage learning. davis, eh. and poulos, hg. 1968. the use of elastic theory for settlement prediction under three-dimensional conditions. geotechnique, 18: 67–91. hansen, jb. 1970. a revised and extended formula for bearing capacity. danish geotechnical institute buletin, 28. kumbhojkar, as. 1993. numerical evaluation of terzaghi’s nγ. journal of geotechnical engineering, american society of civil engineers, 119(3): 598–607. luévanos-rojas, a. 2016. a comparative study for the design of rectangular and circular isolated footings using new models. dyna, 83(1): 149–158. https://doi.org/10.15446/dyna.v83n196.51056 komolafe et al: comparison of square and circular isolated pad foundations in cohesionless soils. azojete, 17(2):197-210. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ookomolafe@unilag.edu.ng 210 meyerhof, gg. 1951. the ultimate bearing capacity of foundation. geotechnique, 2(4): 301– 332. meyerhof, gg. 1963. some recent research on bearing capacity of foundation. cgj ottawa, 1(1): 16–26. murthy, vns. 2002. geotechnical engineering: principles and practices of soil mechanics and foundation engineering. marcel dekker inc. nigerian price. 2021. current prices of building materials in nigeria (2021). nigerian price. retrieved february 13, 2021, from https://nigerianprice.com/prices-of-building-materials-innigeria/ obaji, no., komolafe, oo., and oke, ja. 2020. prediction of initial void ratio from the natural moisture content of cohesive soils. uniabuja journal of engineering and technology, 1(1): 1–13. terzaghi, k. 1943. theoretical soil mechanics. john wiley & sons, inc. the constructor. 2021. types of concrete mix ratio design and their strengths. the constructor. retrieved february 13, 2021, from https://theconstructor.org/concrete/types-ofconcrete-mix-design/5984/ vesic, as. 1973. analysis of ultimate loads of shallow foundations. jsmfd, asce, 99. vesic, as. 1975. bearing capacity of shallow foundations. in foundation engineering hand book. van nostrand reinhold book co. yue, z. 1995. on generalized kelvin solutions in a multilayered elastic medium. journal of elasticity, 40(1): 1–43. https://doi.org/10.1007/bf00042082 yue, z. 1996. on elastostatics of multilayered solids subjected to general surface traction. the quarterly journal of mechanics and applied mathematics, 49(3): 471–499. https://doi.org/10.1093/qjmam/49.3.471 arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):535-546 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 535 original research article structural evaluation of conventional and modified flexible pavement performance *e. s. k. mensahn1, s. a. wada1,2*, and l. lugeiyamu1,3 1. school of civil engineering, department of road, central south university, shaoshan south road no. 68 changsha, 410075, hunan, china 2. department of civil engineering, ahmadu bello university, zaria, nigeria 3department of transport engineering & technology, national institute of transport, dar es salaam, tanzania *corresponding author’s email address: srjwada@gmail.com 1.0 introduction the structural design is considered an alternative to experimental study when there is sometimes difficulty conducting experimental modeling. on the other hand, pavement structural performance predictions for construction are initially carried out before a detailed experimental investigation of pavement materials. besides, the structural modeling of pavement also serves as a control to achieve satisfied material properties due to traffic loading and environmental elements (temperature and precipitation). in highway pavement design, attention has been given to critical pavement distresses such as fatigue and permanent deformation in flexible pavement. many research projects and field applications have been investigated and proven that rubber particles in asphalt mixture improve the long-term durability of flexible pavement. rp in hma at a certain varying percentage contributes to resistance in the rutting deformation (laily et al., 2019, hamzani et al., 2019, article information abstract experimental studies indicate that using rubber particles (rp) as additives improves hot mix asphalt (hma) engineering properties when used as a road surface layer. two critical strains are identified with asphalt pavement: horizontal tensile strain beneath the ac layer and vertical compressive strain on top of the subgrade. however, these strains are difficult to be predicted by experimental simulations. this research aims to conduct a comparative structural performance evaluation of conventional and modified asphalt pavement cross-sections with a particular reference to compute pavement responses (stress, strain, deflection, and stiffness) by utilizing kenlayer computer code. each cross-section is modelled as an elastic multilayer system consisting of five (5) layers with assigned material properties. the pavement compositions illustrate a typical highway pavement structure. the elastic modulus for both hma materials was obtained at the average design temperature of 25˚c to reflect tropical and subtropical regions. the standard tandem axle load that causes damage to the pavement having a contact pressure of 673 kpa (0.673 mpa) with a set of dual tires center to center spacing of 33.75 cm was considered. the similarities and differences between the two pavement cross-sections concerning performance responses are compared. the analysis revealed that for both conventional and modified hma cross-sections, the horizontal tensile strains at the bottom of the surface and binder layers are (2.62e-06 & -172e-04) and (-2.04e-05 & -2.14e-04) µε; at the same time, the vertical compressive strains on top of the subgrade are (1.57e-04) and (1.69e-04) µε. and finally, the computed surface layer stiffnesses are (833.51 kn/cm) and (734.89 kn/cm). it is appropriate to say that the modified hma significantly decreases the surface layer’s stiffness; as such, it eventually prolongs the rapid encroachment of fatigue cracking and rutting deformation. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 august, 2021 revised 2 october, 2021 accepted 8 october, 2021 keywords: structural design, flexible pavement, conventional hma, rubber modified hma, pavement responses surazo et al.: structural evaluation of conventional and modified flexible pavement performance. azojete 17(4):535-346. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 536 mashaan and karim, 2014). these experimental investigations have been centered on experimental studies. the study objective is to perform structural modeling considering two asphalt pavement crosssections (conventional and modified pavement) to evaluate critical performance responses due to160 kn dual wheel load. to distinguish the cross-section, each hma surface layer elastic modulus was obtained at the design temperature of 25˚c. the kenlayer is a semi mechanistic program that was used to model the pavement cross-sections analytically. pavement design concept the basic design concept for flexible pavement determines the required thickness based on the traffic level. in addition, pavement performance is associated with environmental conditions such as temperature and precipitation (aashto-mepdg, 2015). however, apart from the empirical way of selecting pavement layers and thicknesses, some structural codes for the design of asphalt pavements use the concept of a layered elastic system. the pavement design determines every layer’s thickness, ensuring that the stresses/strains caused by the traffic loads and transmitted through the pavement to the sub grade do not exceed each layer’s supportive capacity (jiang et al., 2017). the pavement’s primary purpose is to lessen the sub grade stresses to such a level that the sub grade does not deform under traffic. because of that, the top layer must be of the best quality to sustain maximum compressive stress and wear and tear (asadi et al., 2019, congress, 2018, alaa and al-azzawi, 2012). the pavement layers must be strong enough to tolerate the stresses and strains for each layer exposed, which is the structural design. flexible pavement structure asphalt pavement structure supports the traffic loads and transmits them to the sub grade, where there will be potential for stress reduction. the pavement layers are superimposed, with each layer performing a different primary function. the different pavement layers are shown in figure 1 and are composed of surface, binder, base, sub base, and sub grade. surface course is the top layer directly in contact with the traffic load, sometimes referred to as wearing course. it provides the riding surface of hma for road users. binder course is a premixed asphalt surfacing at times laid in two layers of different materials. it is sometimes referred to as an asphalt base course below the surface course. the base course is the main load-spreading layer. it is constructed immediately beneath the surface or the binder course. it extends some distance beyond the edge of the top layers to ensure that underlying layers will support the loads applied at the edge of the pavement. base course may consist of asphalt concrete, cement concrete, graded granular gravel, crushed stones, and other treated or stabilized materials. sub-base course is a secondary load-spreading layer. it separates the sub grade and the base and provides a platform for constructing the pavement’s upper layer. the provision for a sub-base optionally provides the strength of the sub grade. sub-grade is the soil acting as a foundation for the pavement prepared to receive the stresses of the above layers. the earthwork’s sub grade results may consist of undisturbed, local soil or material excavated elsewhere and placed as a fill. the surface of the sub grade creates the platform for the upper layers (aashto-mepdg, 2015, congress, 2018, huang, 2004a). arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 535-546. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 537 figure 1: a typical flexible pavement structure (note, 1993) structural analysis to characterize the behavior of a flexible pavement under wheel loads, it is considered as a homogeneous half-space (huang et al., 2003). a half-space has an infinitely large area and an infinite depth with a top plane on which the loads are applied (jamshidi and white, 2019, guo and lu, 2019). the structural analysis of flexible pavement systems has been computed using verities of computing codes. the finite element analysis through ansys and abaqus computer software to predict pavement responses have been used by some researchers (yan et al., 2020, liu et al., 2017, dong and ma, 2017). (gupta and kumar, 2013) studied the role of variables in lowering the vertical surface deflections, critical tensile strains at the bottom of the bitumen layer, and the critical compressive strains on the top of the sub-grade. the study used the finite element approach and kenlayer to compare the performance of flexible pavements furthermore, some researchers investigated flexible pavement response subjected to cyclic loading and simulated three levels of truckloads at four different tire inflations pressures. the results were in good agreement with the measured in-situ-scale test data. they concluded that the finite element method could efficiently estimate the fatigue life of flexible pavement with thin bituminous surfacing layers (mulungye et al., 2005). conventional asphalt pavement conventional flexible pavement is mainly affected by environmental exposure such as low and high-temperature, precipitations, traffic loading, and other phenomena. road pavement distress has to be restricted as it directly or indirectly affects the overall longterm performance (patel and patel, 2020). distresses in the conventional pavement are either load-related, environmental-related and asphalt mix design-related. therefore, the conventional asphalt pavement should be designed to provide a durable, skid resistance surface under inservice conditions. however, fatigue and rutting deformation are two main pavement distresses in flexible pavement. these are mainly due to increased load repetitions, variance in temperature, deficiency in construction and design faults, and delay in maintenance intervention. it is essential to reduce fatigue cracking and rutting in asphalt pavement layers (moghaddam et al., 2011). the increase or decrease in the fatigue life of the conventional asphalt pavement is also attributed to neglecting the structural design as well as the absence of attention to identify or consider the pavement parameters such as the material properties of each layer, traffic loading, and other factors (ebrahim and el-maaty, 2012, portillo and cebon, 2013, jamshidi, 2021). fatigue occurs in the form of alligator cracking associated with the repetition of loading and pavement layer thickness. it is initiated in micro-cracks at the top and bottom; these cracks sometimes grow due to shear and tensile stresses in conventional road pavement. the initiation of fatigue cracking is also affected by different factors and properties of the mixture, temperature, and air voids in the mix. structurally, the fatigue behavior in road pavement can surazo et al.: structural evaluation of conventional and modified flexible pavement performance. azojete 17(4):535-346. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 538 be simulated by using computer codes to determine stresses and horizontal strains in the asphalt concrete layers. and experimentally, the behavior of fatigue in bitumen mixtures can be characterized by beam fatigue test or indirect tensile fatigue test to control stress and strain modes (moghaddamkarim et al., 2011, sohn and han, 2020, chandak et al., 2018). at the same time, rutting in the form of permanent deformation occurs in either of the pavement layers is also the most common distresses in asphalt pavements. it is defined as the longitudinal surface deflection occurring along the wheel paths of roadways due to load repetitions. this type of failure is permanent at road sections where there is sometimes static traffic or traffic moving at a creep speed, thereby delaying the dynamic movement on the pavement. however, the failure is also load and asphalt mix design related and is eventually escalates to include other defects such as cracking, potholes, and deformations (chilukwa and lungu, 2019). asphalt concrete is a time, temperature, and stress-dependent material that exhibit elastic or plastic, or visco-elastic responses when subjected to repeated loading. the elastic characteristics can be obtained by its elastic modulus and poison ratio property, meaning they do not contribute to permanent deformation. in exhibiting plasticity, it contributes to permanent deformation, which is attributed to repeated loading. however, rutting can be influenced due to many factors such as vehicle speed/time, vehicle contact pressure depending on the force, and contact area directly in the creep rate model (khana et al., 2013). the correct application of additives has been recognized by highway agencies as one of the most effective strategies for improving pavement performance by decreasing or preventing related distresses. modified asphalt pavement the primary focus of using rubber asphalt as a modifier is to reduce reflective cracking in hot mix asphalt (hma). also, for rehabilitations, overlays, and maintenance purposes, rubber asphalt has performed well in snow and ice locations, thus providing smooth-riding and a good skid-resistant surface. rubber asphalt has been used in many countries worldwide with promising engineering outcomes (mashaan et al., 2014, cetin, 2013). the improvement in conventional road pavement life span contributes to sustainability as an effort to economic advantages. waste rubber particles from tires have been suggested as an alternative additive in asphalt binder and asphalt concrete mixture (picado-santos et al., 2020). the contribution of crumb rubber in terms of the value of resilient modulus also resists deformation. crumb rubber was added to the base asphalt at various rates at a temperature of 177 °c, and the levels of crumb rubber on the asphalt lowered penetration rate, increased bitumen softening point, and enhanced permanent deformation resistance. the crumb rubber in hma included increased recoverable deformation and decreased resilient modulus (1500 mpa) (ariyapijati et al., 2017a). the improvement in road pavements’ service life leads to sustainability and a significant economic benefit. rubber particles have been suggested as a modifier for asphalt and asphalt mixtures to increase flexible pavement performance characteristics, according to various scholars (nguyen and tran, 2017, zumrawi, 2017, hamzani et al., 2019, mashaan and karim, 2014). furthermore, testing the strength of the crumb rubber asphalt mixture is one crucial way to determine its performance. pavement engineers have suggested a need for more effective approaches to resolving crumb rubber asphalt’s aging and thermal stability problems. simultaneously, (liang et al., 2017) investigated various crumb rubber modified asphalt using microwave irradiated and the trans-polycteamer (tor). in the study, samples were subjected to a thin-film oven test, pressure aging vessels, and high-temperature storage tests and evaluated the effect of the microwave and tor. the results showed that the microwavearid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 535-546. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 539 activated crumb rubber increases the risk of fatigue cracking caused by the hardening effect of aging but endows the aged residue with more robust resistance to thermal cracking. the tor improves the compatibility and storage stability of the crumb rubber-modified asphalt. (wang et al., 2019) evaluated the durability of crumb rubber-asphalt pavement using the indirect tensile strength test under freeze-thaw boiling cycle and the cantabria abrasion test underwater immersion and an auxiliary method. on the other hand, the durability test suggested in the study was utterly unsatisfactory underwater immersion. the durability evaluation method proposed should be more effectively evaluated to understand the long-term moisture stability of the crumb rubber asphalt pavement. 2. materials and methods 2.1 materials 2.1.1 pavement cross-section a single pavement cross-section was considered for the structural analysis to study conventional and modified flexible pavement system responses. the pavement composition consists of five (5) layers as the wearing course (conventional & modified hma), binder course (hma), base course (aggregates), sub-base course (granular), and sub-grade. figure 2 illustrates a typical flexible pavement system, while table 1 shows the selected material properties obtained from research investigated by ariyapijati (2017). the study uses 3000 mpa and 1500 mpa to simulate the design temperature of conventional and modified rubber asphalt mixtures at 25ºc, respectively (ariyapijati et al., 2017b)to reflect tropical and subtropical regions. figure 2: a typical pavement system for analysis (note, 1993) table 1: material properties of conventional and rp asphalt concrete (congress, 2018, aashto-mepdg, 2015) layer layer thickness (cm) m.r. (mpa) m.r. (mpa) poisson’s ratio (v) unit weight (k.n/m) surface layer (hma.) 5 3000 1500 0.30 22.8 binder layer (hma.) 10 2250 1125 0.35 22.8 aggregate baselayer 25 450 450 0.40 21.2 granular sub-base layer 30 350 350 0.45 21.2 soil sub-grade infinite 100 100 0.45 19.6 surazo et al.: structural evaluation of conventional and modified flexible pavement performance. azojete 17(4):535-346. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 540 2.1.2 traffic loading the assumptions foe the loading conditions as a direct input in the model analysis as vehicle load acting on a circular shape. the study considered the following loading characteristics: i. axle configuration: the tandem axle considers having a centre-to-centre distance of 121cm between the axles and centre to centre spacing between dual-wheel as 33.75 cm. ii. loading: a standard tandem axle load as 160 kn consider respectively. figure 3 shows the shape of the input loading group. iii. contact pressure: in this study, the contact pressure of 673 kpa for a standard tandem axle of two dual tires in a parallel direction. iv. contact area: the contact area is an important parameter to be determined to distribute loading under each tire uniformly. therefore, 11.25 cm (h. huang, 2019, huang, 2004a) was adopted in the study. figure 3: standard tandem axle load (huang, 2004b) 2.1.3 resilience modulus the resilience modulus is an essential performance indicator for asphalt mixtures, especially the surface and binder courses. it measures the material strength to withstand and spread the loading over an area. the asphalt mixture with high resilience spreads the load over a wider area, reducing the level of strain experienced at the bottom of the pavement structure, considering the temperature variance and load repetitions. the calculated modulus is the ratio between the maximum stress and the maximum strain in the following equation. (1) where: e = resilience modulus σ = apply stress in mpa/kpa є = apply strain in µm 2.2 methodology 2.2.1 analytical approach to evaluate the performance of both flexible pavement structures (conventional and modified) hma, the tandem axle load that causes damage to the pavement of 673 kpa contact pressure was used to predict various pavement responses. the study was carried out to compare with a specific reference to change the elastic modulus of the surface layer material properties to indicate the performance difference of both pavement scenarios. furthermore, each pavement 121 cm arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 535-546. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 541 cross-section was treated as a linear elastic system with assigned elastic modulus and poison’s ratio to each pavement layer. the pavement structure was analyzed in five (5) layers using kenlayer computer code; yang h. huang developed the program derived from kenpave. the program focuses on a flexible multilayer system solution under a circularly loaded area as the burmaster layer theory (1943). the program is significantly different from other computer programs as more material list models like linear-elastic, no-linear elastic, viscoelastic, and the combinations of all models are available. the computations are investigated due to design inputs, the vertical pavement deflections, strains, stress, and stiffness. the obtained results are shown through tables and figures. 3. results and discussion 3.1 vertical deflection surface deflection on pavement indicates a sign of failure, which occurred due to traffic loading. it is a strong indicator that highlights how durable the pavement will perform during the expected design period. table 2 shows the deflections of each pavement composition decreased uniformly from the top of the surface course to the sub-grade. the deflection in the conventional pavement cross decreased about 12% compared to the rubber asphalt pavement composition because of the high resilient modulus value of the conventional cross-section. table 2: deflections in each cross-section layer layer thickness (cm) conventional pavement (cm) modified pavement (cm) surface layer (hma) 0 0.048 0.054 binder layer (hma) 5 0.046 0.051 aggregate base layer 15 0.044 0.048 granular sub-base layer 40 0.038 0.040 soil sub-grade 70 0.034 0.035 3.2 horizontal tensile strain the analysis determined one of the crucial parameters that guarantee the pavement over the design period is the permissible horizontal tensile stain presented in figure 4, which showed a significant difference. the fatigue cracking tensile strain was calculated at the bottom of the pavement composition’s two asphalt layers (surface and binder layers). in the pavement crosssections, the computed horizontal strains under the surface and the binder layers of the conventional ac decreased dramatically by 20% (2.6e-06 & -1.7e-04) compared to the modified ac (-2e-05 & 2e-04). this is also due to the increase in the elastic modulus of the asphalt concrete layer. figure 4: computed horizontal tensile strain -10 0 10 20 30 40 50 60 70 80 -3.0x10-4 -2.0x10-4 -1.0x10-4 0.0 1.0x10-4 2.0x10-4 3.0x10-4 4.0x10-4 h m a t en si le s tr ai n, ꜫ t ( µꜫ ) pavement depth, z (cm) conventional ac rubber ac surazo et al.: structural evaluation of conventional and modified flexible pavement performance. azojete 17(4):535-346. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 542 3.3 vertical compressive strain rutting is typically followed by surface failure in the form of fatigue cracking in asphalt pavement. the computed vertical compressive strain for permanent deformation on the top of the sub-grade is identified in figure 5. the compressive strain in the conventional ac decreased by 8% (1.57e-04) compared to the modified ac (1.69e-04). unlike the vertical strains in other layers, the result of the vertical strain above the sub-grade is not significantly different from the computed fatigue strain in the binder layer. figure 5: computed vertical strain 3.4 vertical compressive stress in the pavement cross-sections, the vertical stress for both cases uniformly decreased from top to bottom for the conventional ac are (673.0 kpa, 579.2, 198.7, 58.9 and 22.3 kpa) and for the modified ac are (673.0, 599, 256.5, 68.3 and 24.4 kpa) respectively. figure 6 illustrates the diagram of the vertical stress as it changes in pavement depth. it can be observed that the uniformed decrease in the vertical stresses demonstrates a satisfactory pavement composition. figure 6: computed vertical stress 3.5 stiffness material stiffness is an essential factor that affects the performance of asphalt pavements. experimentally, it can be determined by conducting the triaxial test. additionally, it can also be achieved by measuring the deflection in response to load. a simple stiffness parameter was calculated by applying a standard wheel load that causes a deflection in the pavement. the stiffness for each layer was calculated and compared. figure 7 presents the stiffness responses of both conventional and rubber ac. as can be observed, there was a general increase in -10 0 10 20 30 40 50 60 70 80 0.0 5.0x10-5 1.0x10-4 1.5x10-4 2.0x10-4 2.5x10-4 3.0x10-4 3.5x10-4 s u b g ra d e c o m p re ss iv e s tr a in , ꜫ c (µ ꜫ ) pavement depth, z (cm) conventional ac rubber ac -10 0 10 20 30 40 50 60 70 80 0 100 200 300 400 500 600 700 800 v er tic al c om pr es si ve s tr es s, σ z ( σ z ) pavement depth, z (cm) conventional ac rubber ac arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 535-546. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 543 stiffness with increasing pavement depth. rubber ac also exhibited lower stiffness compared to conventional ac when the pavement depth was the same. in this scenario, the stiffness modulus of the lower layers is higher than that of the upper layers. hence, it is appropriate to say that the rubber ac significantly decreases the surface layer’s stiffness; as such, it eventually prolongs the rapid encroachment of fatigue cracking and rutting deformation. figure 7: computed stiffness 4. conclusion the evaluation of asphalt pavement cross-sections considered in this study under tandem axle load of dual wheels using kenlayer program to predict critical pavement responses was investigated and the following findings were drawn: 1. the computed top deflection in the conventional ac layer decreased by 11% compared to the modified hma layer. 2. the predicted horizontal strains breath the conventional hma surface layer decreased substantially compared to the modified hma cross-section. whereas, the vertical compressive strains on the top of the sub-grade reduced by 8% compared to the modified cross-section. the reduction in the strain values of the conventional crosssection was due to the increase in the material property of the hma surface layer. meanwhile, the computed strains at the critical points (bottom of ac and top of subgrade) in each cross-section could be considered to check against the allowable strains in achieving the permissible number of load repetitions. 3. due to material properties and layer thickness variances, the vertical stress level gradually decreased from the top to the sub-grade layer. finally, the modified hma surface layer responded very well in reducing the pavement stiffness compared to the conventional hma surface layer. the modified asphalt again contributed to the reduction of the material’s stiffness modulus despite reducing its elastic modulus. it would also increase the pavement’s endurance for fatigue life without further compromising deformation resistance, which is the pavement’s overall benefit. references aashto, 2015. mechanistic-empirical pavement design guide a manual of practice (2nd ed.). washington, united of states america. alaa, ah. and al-azzawi, aa. 2012. evaluation of rutting depth in flexible pavements by using finite element analysis and local empirical model american journal of engineering and applied sciences, 5(2): 163-169. 0 5 15 40 70 0 200 400 600 800 1000 1200 1400 1600 s tif fn e ss ( k n /c m ) pavement depth, z (cm) conventional ac rubber ac surazo et al.: structural evaluation of conventional and modified flexible pavement performance. azojete 17(4):535-346. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 544 ariyapijati, rh., hadiwardoyo, sp. and sumabrata, jr. 2017a. contributions crumb rubber in hot mix asphalt to the resilient modulus. in: green process, material, and energy: a sustainable solution for climate change. proceedings of a symposium held in surakarta, indonesia, 7-8 december 2016. aip conference proceedings 1855(1): 030005-1– 030005-6 ariyapijati, rh., hadiwardoyo, sp. and sumabrata, jr. 2017b. contributions crumb rubber in hot mix asphalt to the resilient modulus. in: green process, material, and energy: a sustainable solution for climate change. proceedings of a symposium held in surakarta, indonesia, 7-8 december 2016. aip conference proceedings 1855 (1): 030005-7– 030005-12 asadi, m., kottayi, nm., tirado, c., mallick, rb., mirchi, a. and nazarian, s. 2019. framework for rigorous analysis of moisture-related structural damage in flexible pavements. transportation research record, 2673(11): 640–648. cetin, a. 2013. effects of crumb rubber size and concentration on performance of porous asphalt mixtures. international journal of polymer science, 789612: 1-10. chandak, pg., tapase, ab., sayyed, ss. and attar, ac. 2018. a state-of-the-art review of different conditions influencing the behavioral aspects of flexible pavement. in: mohammad l. (eds) advancement in the design and performance of sustainable asphalt pavements. geomeast 2017. sustainable civil infrastructures. springer, cham. 300 312. chilukwa, n. and lungu, r. 2019. determination of layers responsible for rutting failure in a pavement structure. infrastructures, 4(2): 15 29. congress, ir. 2018. guidelines for the design of flexible pavements. indian roads congress, new delhi. dong, z. and ma, x. 2017. analytical solutions of asphalt pavement responses under moving loads with arbitrary non-uniform tire contact pressure and irregular tire imprint. road materials and pavement design, 19(8): 1887-1903. ebrahim, a. and el-maaty, ba. 2012. fatigue and rutting lives in flexible pavement. ain shams engineering journal, 3 (4): 367-374. guo, l. and lu, q. 2019. numerical analysis of a new piezoelectric-based energy harvesting pavement system: lessons from laboratory-based and field-based simulations. applied energy, 235: 963-977. gupta, a. and kumar, a. 2013. comparative structural analysis of flexible pavements using finite element method. the international journal of pavement engineering and asphalt technology, 15(1): 11-19. hamzani, m., hasan, m. and sugiarto, s. 2019. the influence of using waste tire rubber and natural zeolite as asphalt and cement replacements to compressive strength of semi-flexible pavement. in: proceedings of a symposium held in aceh, indonesia, 12 14 september 2018 on material science and engineering. iop conference series 523: 012037. huang, b., li, g. and mohammad, ln. 2003. analytical modeling and experimental study of tensile strength of asphalt concrete composite at low temperatures. composites part b: engineering, 34(8): 705-714. huang, yh. 2004a. pavement analysis and design. pearson education, united states of america. huang, yh. 2004b. pavement analysis and design. pearson education, united states of america. jamshidi, a. 2021. analysis of pavement structures. sustainability, 13(11): 6098. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 535-546. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 545 jamshidi, a. and white, g. 2019. evaluation of performance and challenges of use of waste materials in pavement construction: a critical review. applied sciences, 10(1): 226. jiang, x., zeng, c., gao, x., liu, z. and qiu, y. 2017. 3d fem analysis of flexible base asphalt pavement structure under non-uniform tyre contact pressure international journal of pavement engineering, 20(9): 999-1011. khana, s., nagabhushanaba, mn., tiwari, d. and jainda, pk. 2013. rutting in flexible pavement: an approach of evaluation with accelerated pavement testing facility. procedia social and behavioral sciences 3(4): 367-374. laily, k., hadiwardoyo, sp. and sumabrata, rj. 2019. rutting deformation of gap-graded hotmix asphalt with added of waste tire rubber. in: exploring resources, process and design for sustainable urban development. proceedings of a symposium held in surakarta, indonesia, 12-13 december 2018. aip conference proceedings 2114: 040013-1–040013-8. liang, m., xin, x., fan, w., ren, s., jingtao s. and luo, h. 2017. thermo-stability and aging performance of modified asphalt with crumb rubber activated by microwave and tor. materials & design, 127: 84-96. liu, p., xing, q., wang, d. and oeser, m. 2017. application of dynamic analysis in semianalytical finite element method. materials 10(9): 1010. mashaan, ns., ali, ah., karim, mr. and abdelaziz, m. 2014. a review on using crumb rubber in reinforcement of asphalt pavement. the scientific world journal, 2014: 129. mashaan, ns. and karim, mr. 2014. waste tyre rubber in asphalt pavement modification. material research innovations, 18(6): 6-9. moghaddam, tb., karim, mr. and abdelaziz, m. 2011. a review on fatigue and rutting performance of asphalt mixes. scientific research and essay, 6(4): 670-682. mulungye, rm., owende, pmo. and mellon, k. 2005. analysis of response of flexible pavements using finite element method. the itb journal, 6(2): 40-52. nguyen, htt. and tran, tn. 2017. effects of crumb rubber content and curing time on the properties of asphalt concrete and stone mastic asphalt using dry process international journal of pavement research and technology 11(3): 236-244. note, or. 1993. a guide to the structural design of bitumen-surfaed road in tropical and sub-tropical countries. transport research laboratory, united kindom. patel, s. and patel, vr. 2020. a study on improving conventional mix of flexible pavement using additive. international journal of engineering research & technology (ijert), 9(5): 1234-1241. picado-santos, lg., capitão, sd. and neves, jmc. 2020. crumb rubber asphalt mixtures: a literature review. construction and building materials, 247: 118577. portillo, o. and cebon, d. 2013. experimental and numerical investigation of fracture mechanics of bitumen beams. engineering fracture mechanics, 97(1): 281-296. sohn, d. and han, j. 2020. an empirical approach for penetration of tandem warheads into concrete targets. engineering failure analysis, 120:105-043. wang, x., fan, z., li, hw. and huang, m. 2019. durability evaluation study for crumb rubber–asphalt pavement. applied sciences, 9(16):3434. surazo et al.: structural evaluation of conventional and modified flexible pavement performance. azojete 17(4):535-346. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: srjwada@gmail.com 546 yan, g., ye, z., wang, w. and wang, l. 2020. numerical analysis on distribution and response of acceleration field of pavement under moving load. international journal of pavement research and technology, 14:519-529. zumrawi, mme. 2017. effect of crumb rubber modifiers (crm) on characteristics of asphalt binders in sudan. international journal of materials science and applications, 6(2):1-6. vol 2_1 arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):23-30 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 23 original research article nigerian water resources management – an overview u. a. ibrahim1* a. n. alkali1, b. o. sanyaolu1 and b. usman2 1department of civil and water resources engineering, university of maiduguri, maiduguri, borno state 2sani mustapha and associates, maiduguri, borno state *corresponding author’s email address: uaibrahim@unimaid.edu.ng 1.0 introduction the development of water resources is influenced by climatic, physiographic and hydrologic features, and perhaps socioeconomic factors of a region. in the instance of nigeria, these are briefly outlined as a preface to systems studies. a brief historical and quantitative overview of water resources development including its utilization and key water issues faced by nigeria is also presented. furthermore, institutional regulatory and legal authorities in charge of addressing these challenges are also described. nigeria is located in the tropical zone of west africa approximately between latitudes 4°n and 14°n and longitudes 2°2’e and 14°30’e (fao, 2016). it has a total area of 923, 770 km2 with a population of about 203 million (nbs, 2016). the country’s north-south extent is about 1,050 km and its maximum east-west extent is about 1,150 km. nigeria is bordered to the west by benin, to the northwest and north by niger, to the northeast by chad and to the east by cameroon, while the atlantic ocean forms the southern limits of nigerian territory. land cover ranges from thick mangrove forests and dense rain forests in the south to a near-desert condition in the northeastern corner of the country (fao, 2016). three broad ecological zones are commonly distinguished in the country: i) the northern sudan savannah; ii) the guinea savannah zone or middle belt; and iii) the southern rainforest zone. based on rainfall and temperature, the county is divided into eight agro-ecological zones (fao, 2016). in table 1, these zones are presented in a north-south succession, except the mountainous zone which is found at the border with cameroon and the plateau zone in the center of the country. the peculiar and variable nature of nigeria in location and climate has given rise to certain water resources issues in the country. these issues article information abstract effective management of a country’s water resources contributes toward its sustainable development. the aim of this paper is to give an overview of nigeria’s surface and underground water sources alongside agencies charged with functions covering all facets in water resources development and management. nigeria consists of three broad agroecological zones; the northern sudan savannah, the guinea savannah and the southern rainforest spread across eight hydrological areas for the purpose of water resources management. the federal ministry of water resources is responsible for large water resources development projects and water allocation between states; comprising of sixteen (16) parastatals and agencies made up of twelve (12) river basin development authorities (rbdas), nigeria hydrological services agency (nihsa), nigeria integrated water resources management commission (niwrmc), gurara water management authority (gwma), and the national water resources institute (nwri). the country has four river drainage systems and 264 dams. recent studies of nigerian water reserves (surface and groundwater sources) indicated that there are large supplies, and the country has surface and groundwater resources potentials of 267.3bcm and 51.9bcm respectively. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 july, 2021 revised 25 october, 2021 accepted 27 october, 2021 keywords: nigeria water resources development ecological hydrological http://www.azojete.com.ng/ mailto:uaibrahim@unimaid.edu.ng mailto:uaibrahim@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):23-30. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 24 range from precipitation to management of these resources. the annual precipitation ranges from 400mm in north eastern part to about 2000mm in the south eastern part of the country (ishaku and majid, 2010; fao, 2016). these variations give rise to certain issues like scarcity induced drought to flooding respectively. legal frameworks to facilitate the management of these water resources over the years have proven to be ineffective. table 1: agro-ecological zones in nigeria zone description percentage of country area annual rainfall (mm) monthly temperature 0c minimum maximum semi-arid 4 400-600 13 40 dry sub-humid 27 600-1000 12 45 sub-humid 26 1000-1300 14 37 humid 21 1100-1400 18 37 very humid 14 1120-2000 21 37 ultra humid (flood) 2 >2000 23 33 mountainous 4 1400-2000 5 32 plateau 2 1400-1500 14 36 (after fao, 2016) nigeria is divided into eight hydrological areas for the purpose of water resources management, considering hydrological and topographical conditions presented in figure 1. rbdas – river basin development authorities figure 1: hydrological map of nigeria (jica, 2014) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ibrahim et al: nigerian water resources management – an overview. azojete, 18(1):23-30. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 25 hydrological area area (103km3) mainly related rbdas mainly related states ha-1 niger north 135.1 sokoto-rima katsina, zamfara, sokoto, kebbi ha-2 niger central 154.6 upper niger, lower niger niger, kwara, kaduna, kogi, fct ha-3 upper benue 156.5 upper benue adamawa, taraba, gombe, bauchi ha-4 lower benue 74.5 lower benue plateau, nasarawa, benue, kogi ha-5 niger south 53.9 anambra-imo, niger delta bayelsa, delta, edo, kogi, anambra, rivers ha-6 western littoral 99.3 ogun-osun, benin-owena lagos, ogun, oyo, osun, ondo, edo, ekiti ha-7 eastern littoral 57.4 cross river abia, anambra, imo, enugu, ebonyi, cross river, akwa ibom, rivers ha-8 lake chad 178.5 hadejia-jama’are, chad kano, jigawa, yobe, borno, bauchi, adamawa, plateau 2. institutional arrangements of nigerian water resources management presently, the federal ministry of water resource (fmwr) is responsible for large water resources development projects and water allocation between states (idu, 2015). fmwr has sixteen (16) parastatals and agencies made up of twelve (12) river basin development authorities (rbdas), nigeria hydrological services agency (nihsa), nigeria integrated water resources management commission (niwrmc), gurara water management authority (gwma), and the national water resources institute (nwri). the first two rbdas chad basin development authority (cbda) and sokoto-rima river basin development authority (srrbda) were created in 1973, through the decree nos. 32 and 33 of 1976. in 1976, based on the decree no. 25 of 1976, nine (9) additional rbdas were established, and as a result, the number of rbdas becomes 11. in 1984, with separation of niger river basin development authority into two rbdas – such as upper niger river basin development authority (unrbda) and lower niger river basin development authority (lnrbda), the number of rbda became 12 and these rbdas long continue with the operation to date (jica, 2014). the twelve (12) rbdas are listed in table 2. http://www.azojete.com.ng/ mailto:uaibrahim@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):23-30. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 26 table 2: list of river basin development authorities in nigeria s/n rbda area of operation office 1 anambra-imo river basin development authority (airbda) abia, anambra, ebonyi, enugu and imo states oweri 2 benin owena river basin development authority (borbda) the regions of river benin and owena and a senatorial district in delta state benin-city 3 chad basin development authority (cbda) borno, yobe state and northern part of adamawa state maiduguri 4 cross river basin development authority (crbda) akwa ibom and cross river states calabar 5 hadejia jama’ are river basin development authority (hjrbda) kano, jigawa states and north and central parts of bauchi sate kano 6 lower benue river basin development authority (lbrbda) the catchment states of benue, plateau, nassarawa states and kogi state east of the river niger makurdi 7 lower niger river basin development authority (lnrbda) entire geographical boundaries of kwara state and a part of kogi state, west of the river niger ilorin 8 niger delta basin development authority (ndbda) delta and bayelsa states port harcourt 9 ogun-osun river basin development authority (oorbda) lagos, ogun, oyo and osun states abeokuta 10 sokoto-rima river basin development authority (srrbda) katsina, zamfara, sokoto and kebbi states sokoto 11 upper benue river basin development authority (ubrbda) gombe, taraba, two senatorial districts of adamawa state and one senatorial district of bauchi state yola 12 upper niger river basin development authority (unrbda) niger, kaduna states and the fct minna (jica, 2014) the main responsibilities of the river basin authorities include; a. to enhance the development of both surface and underground water resources with particular regard to construction and maintenance of infrastructure; b. management of irrigation schemes which would be handed over to farmers gradually; c. supplying water from storage schemes for a fee with approval from the minister of water resources; d. keeping up-to-date comprehensive water resources records and requirements in the authority’s area of operation. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ibrahim et al: nigerian water resources management – an overview. azojete, 18(1):23-30. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 27 3. water resources of nigeria in a system known as the hydrologic cycle, water is continually circulates between oceans, landmasses and atmosphere. this movement is driven by a combination of the sun’s energy, geological/geographical processes and gravity. most estimates place seawater in the oceans at 94 – 97% of all water on the planet. the remaining 3 – 6% contains all freshwater resources. around half of this is frozen in snow, glaciers and icecaps, half is underground as groundwater, and the remaining 0.1% is surface water found in rivers, lakes, reservoirs and atmosphere (leap, 1999). in general, water resources may be presented as: 1. surface sources: streams and rivers, lakes, springs, and drainage areas that discharges water toward reservoirs. 2. groundwater sources: aquifers. nigeria is endowed with surface and groundwater resources, yet the country is faced with freshwater scarcity, severe water pollution, growing domestic and industrial water demand, and requirement for food security. the characteristics of the surface and groundwater resources of the country are summarized in sections 3.1 and 3.2 respectively. 3.1 surface water sources nigeria’s drainage system is somewhat considered as a close network of streams and rivers which take their source from the precambrian basement complex and flow over the sediments in their lower reaches (oteze, 1981). interestingly, the country’s four major drainage systems as reported by spon, (1997) is presented in table 3. table 3: major drainage systems of nigeria s/n drainage system tributaries 1 niger river basin benue, sokoto-rima, kaduna, gongola, katsina-ala, donga, tarabe, hawal and anambra rivers 2 lake chad inland kano, hadejia, jama’are, misau, komadugu-yobe, yedseram and ebeji rivers 3 atlantic (east of the niger) cross river, imo, qua-iboe and kwa rivers 4 atlantic (west of the niger) ogun, oshun, owena and benin rivers there are two major rivers in nigeria, namely; rivers niger and benue. additionally, there are other rivers such as yobe, ngadda, yedseram, goa, hadejia, kaduna, cross river, imo, sokoto, ogun, anambra, ossiomo rivers with several other streams and channels, lakes and ponds, provide a nationwide web of drainage basins (figure 2). all rivers in the northern parts of the country drain ultimately into either the niger or the benue. a northwest divide separates the niger tributaries from the south-ward flowing streams in southwestern nigeria. these include ogun, oshun, owena, ogbese, osse and ossiomo rivers. in southeastern nigeria, the anambra is tributary to the niger, whereas the imo and the cross rivers drain directly to the sea (oteze, 1981). http://www.azojete.com.ng/ mailto:uaibrahim@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):23-30. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 28 figure 2: nigeria’s major rivers and streams (ojiako, 1985) the volume of runoff from the drainage basins vary widely and depend upon several factors such as the amount and intensity of rainfall, the climate and vegetation as well as geological, geographical and topographical features of the area. aside river drainage systems, there are approximately 264 dams in the country fao, (2016) with an estimated capacity of 37.46 billion cubic meter (bcm). furthermore, this capacity is equivalent to about 10% of the total water resources potential in nigeria (fao, 2016). however, out of the estimated total storage volume of 37.46bcm, 25.80bcm is associated with large hydropower dams from kainji, jebbe and shiroro etc. it is noteworthy that the remaining storage of 11.66bcm is largely used for irrigation and municipal water supply. interestingly, the average effective storage is put at 78% of the total storage capacity (jica, 2014; fao, 2016). in addition, there are about 30 dams under construction for an additional capacity of 1.60bcm and plans for the development of 100bcm by 2020, in addition to the rehabilitation of 50 existing dams (fao, 2016). these figures do not include the controversial kafin hausa dam on jama’are river, with an expected capacity of 1.6bcm, which was planned together with the lagdo dam in cameroon operational since 1982 (fao, 2016). 3.2 groundwater sources unlike surface water, which has no geographical boundaries, groundwater displays spatial variability being driven by geology and climate. groundwater resources are controlled by hydrogeology of the country and follow the pattern of occurrence of the aquifers, aquitards or aquicludes (idu, 2015). nigeria lies broadly on two main rock formations; the basement complex (which is mainly precambrian and paleozoic rocks and jurassic granite of the jos area) and sedimentary strata which are postcambrian deposits (ojiako, 1985). other minor formations are volcanic plateau and the river alluvium (adelena et al., 2003). in addition, the sedimentary strata have both surface water and ground water of immense economic interest. legend river/stream file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng ibrahim et al: nigerian water resources management – an overview. azojete, 18(1):23-30. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 29 on the other hand, the basement complex serves chiefly as a source for headwaters of various rivers and recharge zones for groundwater. groundwater in nigeria has the advantages of being generally free from biological contamination, sediments, and of constant quality and temperature. it is thus normally satisfactory for domestic, agricultural (livestock watering and irrigation) and most industrial uses (idu, 2015). nigerian groundwater can be best divided into three hydro-meteorological areas based on its availability (idu, 2015) and presented in table 4; table 4: hydro-meteorological areas of nigeria’s groundwater hydro-meteorological areas related river basins characteristics 1 sahel zone sokoto, hadejia-jama’are-yobe and the south-east chad low annual precipitation of 500-750mm 2 guinea savannah zone kaduna, benue (upper and lower), and the niger (upper and lower) mean annual precipitation of 1000-1250 mm 3 tropical rain forest zone anambra, cross river, kwa-iboe, niger delta and the southwestern coastal heavy precipitation from 1250mm-4000mm there are four major aquifers in nigeria (adelena, 2012), these are; 1. basement aquifers; consist of crystalline and coarse-grained rocks and argillaceous metasedimentary rocks. generally, have low yields. thickness varies from 10 to 25 m; with water table depth varying from about 5 to 15m. boreholes tend to be drilled to depths between 10 and 70m, depending on local conditions. 2. sedimentary aquifers generally consist of thick sequences of sediments with yields between 2 and 60l/s; water table depth between 10 and 40m; and borehole depths from 20m to 150m. coastal sedimentary basins have borehole depths between 10m and 800m and yields between 2 and 60l/s. 3. volcanic plateau is found around jos plateau and bauchi state of nigeria. the rock types are mainly olivine basalts, coriaceous lavas and tuffs. these rocks form typically unconfined aquifers with low to moderate yields, usually below 3l/s. aquifer thickness varies substantially. water table depth is less than 5m. borehole depths of 15 to 50m are common. 4. river alluvium aquifers occur along the valleys of major rivers and streams ranging from the thin discontinuous sands occurring in the smallest streams to the thick alluvial deposits of rivers niger and benue. they may occupy strips of country up to 15km wide on each side of the river. they are thickest (15-30m thick) along the rivers niger and benue and are largely unconfined with shallow water tables. 3.3 aquifer yield, recharge and groundwater potential the crystalline basement of nigeria generally represents the deeper, fractured aquifer and is noted as a poor source of groundwater. basement complex aquifers have low to moderate yields (0.83 to 3l/s). yields between 1–2 l/s in the nigerian basement rocks are considered good enough for the installation of motorized submersible pumps, while values of borehole yield <0.5l/s are still adequate for hand pumps (akujieze et al., 2003). annual exploitable groundwater resources are estimated at about 59 510 million m3, distributed as; 10, 270 million m3 in the north, 25, 480 million m3 in the middle belt and 23, 760 million m3 in the south (fao, 2016). groundwater recharge into the basement aquifers is mainly through direct infiltration from rainfall. generally, basement aquifers have low groundwater potential because groundwater occurs in thin, http://www.azojete.com.ng/ mailto:uaibrahim@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):23-30. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uaibrahim@unimaid.edu.ng 30 localized and disconnected aquifers. major aquifers in the coastal zone of western nigeria have thicknesses ranging between 100 and 250m with mean groundwater storage of 2.87×103m3 (akujieze et al., 2003; ejepu, 2020). studies revealed that surface and groundwater resources potential of the country were estimated at 267.3bcm and51.9bcm respectively (national water policy, 2004; jica, 2014; fao, 2016). 4. conclusion nigeria is endowed with large freshwater resources; surface and groundwater sources. the country has four river drainage systems with a lot of dams and four major aquifer formations spread over eight hydrological areas cutting across the thirty-six states of the federation. the establishment of river basin development authorities contributed to the development of water resources in the country. the country’s surface waters largely drains through the niger and lake chad basin. aquifer productivity across the sahel, guinea savannah and tropical rain forest zones are highly variable. references adelena, m., olasehinde, pi. and vrbka, p. 2003. isotope and geochemical characterization of surface and subsurface waters in the semi-arid sokoto basin, nigeria. african journal of science and technology, 4(2): 76-85. adelena, m. 2012. groundwater availability and use in sub-saharan africa: nigeria. in pavelic, p., giordano, m., keraita, b., ramesh, v and rao, t. (eds.), groundwater availability and use in sub-saharan africa: a review of 15 countries, pp. 137-156, colombo, sri lanka: international water management institute, iwmi. akujieze, cn., coker, sjl. and oteze, ge. 2003. groundwater in nigeria – a millennium experiencedistribution, practice, problems and solutions. hydrogeology journal, 11(2): 259-274. ejepu, js. 2020. regional assessment of groundwater potential zone using remote sensing, gis and multi criteria decision analysis techniques. nigerian annals of pure and applied science, 3(3): 99-111. food and agricultural organization (fao). 2016. aquastat country profilenigeria (food and agricultural organization of the united nations). rome, italy, 17p. national bureau of statistics (nbs). 2016. social statistics report. federal republic of nigeria. abuja, nigeria, 547p. idu, aj. 2015. threats to water resources development in nigeria. journal of geology and geophysics, 4(3): 1-10. ishaku, ht. and majid, mr. 2010. x-raying rainfall pattern and variability in northeastern nigeria: impacts on access to water supply. journal of water resource and protection, 2: 952-959. japan international cooperation agency (jica). 2014. the project for review and update of nigeria national water resources master plan, volume 1. federal ministry of water resources. abuja, nigeria, 34p. leap, di. 1999. geological occurrence of groundwater. in delleur, j. (eds), the handbook of groundwater engineering, pp. 17-68, crc press llc, boca raton, united states of america. national water policy. 2004. federal republic of nigeria, abuja, nigeria, 96p. ojiako, gu. 1985. nigerian water resources and their management. water international, 10(2): 64-72. oteze, ge. 1981. water resources in nigeria. environmental geology, 3: 177-184. spon, ef. 1997. water pollution control. in: helmer, r. and hespanhol, i (eds.), a guide to the use of water quality management principles, 526p. st edmundsbury press, bury st edmunds, suffolk, uk file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):113-120 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 113 original research article effect of chemical fertilizers on groundwater quality in an unconfined aquifer a. r. adesiji*1, o. d. jimoh1, p. a. adeoye2, a. j. odofin3, o. e. asogwa1, j. a. mangey4, and o. m. odekunle5 1department of civil engineering, federal university of technology, minna, nigeria 2department of agriculture and bioresources engineering, federal university of technology, minna, nigeria 3department of soil science and land management, federal university of technology, minna, nigeria 4department of water resources and environmental engineering, ahmadu bello university, zaria, nigeria 5department of geography, federal university of technology, minna, nigeria *corresponding author’s email address: ade.richard@futminna.edu.ng 1.0 introduction soil application of agro chemicals such as fertilizers plays a major role in enhancing the fertility of the soil for agricultural productivity in recent times. this, therefore, means the primary purpose of applying fertilizers to the soil is mainly to improve the crop yield in order to enhance profitability of the farming enterprise. but the adverse environmental effects of these chemicals on soil and groundwater body in the case of fertilizer overdose have been of serious concerns to the environmentalists. according to kumar et al. (2019), changes from traditional agriculture practices to modern agriculture practices have led to the increase in the application of chemical fertilizers which, in turn, has resulted in higher groundwater contamination. some fertilizers, such as nitrate, play a more important role in the contamination of water and soil due to their physical and chemical characteristics, especially in agricultural lands (badrzadeh et al., 2022). therefore, what influences the mobility of these contaminants through soil to groundwater like soil, hydrogeological conditions, land use systems and climate differ from one location to another (adeoye et al., 2017). collin and melloul (2003) article information abstract the use of fertilizer on soil to improve agricultural yield has been practiced for years. while fertilizers and manures greatly improve crop yield, it is also important to consider their corresponding and devastating effects. in this study, the fertilizers application rate was varied and their effects on groundwater quality with soil depths of 30 cm and 60 cm were observed. two fabricated lysimeters were used to collect soil samples undisturbed and taken to the laboratory for analyses. the samples in the lysimeters were made saturated and varying quantities of fertilizers from 87.37 g, 100 g. and 120 g were applied. the saturation of the samples was done through an improvised rainfall simulator which was set up in such a way that a constant discharge was adopted. water samples were collected at 30 cm and 60 cm depths and analyzed for fertilizer residues and physico-chemical characteristics such as temperature, ph, total chloride, total dissolved solids, dissolved oxygen, conductivity, free ammonia, total phosphate, urea, zinc and iron were also analysed. the results showed that the more the quantities of fertilizers applied on the soil, the more it affects the physico-chemical properties of the water and renders it toxic and unsuitable for drinking purposes except treated. the results, however revealed that the concentrations of the fertilizers in the groundwater decreases with soil depths. it is therefore recommended that any groundwater being explored for domestic use close to soil surface in areas prone to fertilizer pollution should be well treated before consumption, most especially for people using shallow wells. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 29 nov., 2022 revised 14 january, 2023 accepted 16 january, 2023 keywords: unconfined aquifer groundwater water pollution nitrates fertilizers http://www.azojete.com.ng/ mailto:ade.richard@futminna.edu.ng mailto:ade.richard@futminna.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):113-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 114 also pointed out that this may be as a result of different soil and hydrogeological settings offering different vulnerability and different degrees of protection to the underlying aquifer. rainfall influence on the contaminants transport cannot be overemphasized. according to pérez et al. (2003), in regions with high rainfall, such with average precipitation of 700 mm/year, nitrogenbased fertilizer residues left unused by plants may be leached away thereby contaminating groundwater. the contamination may occur several days even months after the fertilizers have been spread. the rate at which the contamination occurs, according to pérez et al. (2003), depends on the nitrogenous compound concentration in the unsaturated zone of the soil, on input from atmosphere and on the hydrology of the aquifer. the precipitation influence on the fertilizers leaching to the groundwater body has been corroborated by gunatilake (2016). there has always been a link between fertilizers leaching (in areas with a dryer climate) and intensive irrigation as well (djaman et al., 2018). the use of lysimeter to study migration of contaminants to groundwater has also been recognized for many years because it has been of major importance in the development of understanding of soil water and contaminants dynamics in the subsurface. earliest lysimeter consisted of a container filled with soil repacked to a similar bulk density of that in the fields. ehler and goss (2003) and goss et al. (2010) developed a non-weighing drainage lysimeters and tension lysimeter by placing a wick in contact with the soil body to carry water down into the collecting vessel. goss and ehlers (2009) developed a hybrid weighing lysimeter which allows the contaminant load entering unconfined shallow groundwater to be identified. karthikeyan et al. (2008) studied the migration of faecal matter through soil with a drainage non-weighing lysimeters. the results from all these studies and more show fast movement of these bacteria as a result of very permeable nature of the vadose zone soil. the concentrations of these chemicals seem to be reducing as they move through the soil mass. several cases of water borne diseases have been documented in minna over the years (galadima et al., 2011; adeoye et al., 2017; ibrahim et al., 2018; yusuf 2021). chukwu et al. (2004) reported nine years water borne diseases in minna and also reported that major water borne diseases affecting minna inhabitants are typhoid, diarrhea, cholera, amoebiasis and blue baby. it was concluded form his study that majority of people affected by these diseases are people living in the suburb and close to area where there are intensive farming activities like dairy, slaughters house and poultry activities. some groundwater sampling campaign in north central nigeria and minna (jimoh et al., 2003; salami et al., 2008; isikwue et al., 2011) have reported presence of nitrates, phosphates and biological parameters especially inside the poultry farms as a result of indiscriminate dumping of poultry manure. however, a mechanism guiding the transport of the pollutants through the vadose zone into the groundwater has not been adequately studied. this work is therefore aimed at ascertaining the behaviour of chemical fertilizer contaminants through the soil profile to be able to predict and describe the danger posed to groundwater aquifers by continuous and excessive application of chemical fertilizer to agricultural lands. the main objective is to study the effects of groundwater pollution from fertilizer use with soil depth and to draw conclusions on how the quantities of fertilizer use affects groundwater bodies. 2. methodology 2.1 description of study area the study area was an inland valley located between latitude 9o 5000’ and 9o 5625’ n and longitude 6o 373’ and 6o 4375’ e. the valley is located at the western end of minna, a northwestern town in niger state, nigeria within the permanent site of federal university of technology, minna. the catchment area of the basin is 30.79 km2. the soil type on the study area was in a textural class of gravelly sand up to the depth of 80 90 cm. the area is characterized file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ade.richard@futminna.edu.ng adesiji et al.: effect of chemical fertilizers on groundwater quality in an unconfined aquifer. azojete, 19(1):113-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 115 with low and erratic rainfall of between 1000 to 1200 mm as total annual rainfall with peaks in july and august. 2.2 experimental method and data collection two different agricultural zones within the study area were selected in this study. lysimeters of 0.3m diameter and 1m length with openings for water collection at 30. 60 and 90 cm (figure 1) were inserted into the soil at the locations in order to collect the soil samples undisturbed. the lysimeters were pushed into the soil profile with little disturbance to the soil mass. the lysimeters were extracted from the soil and transported to the laboratory for laboratory experimental set up. the hydraulic conductivity test was also carried out to study the permeability of the soil. this was done in the laboratory using falling head method. soil samples for the permeability test were taken at the four different sampling points (sites a, b, c, d) within the study area. at each of the sampling point, samples were taken at the different depths of 30 cm, 45 cm, 60 cm, 75 cm, 90 cm and 105 cm making the total of twenty-four (24) soil samples taken. the two lysimeters were left for 2 weeks to allow for stabilization of soil mass inside the lysimeters before the experimental analysis (application of fertilizers). for the experimental analysis, the nitrogen, phosphorus and potassium (npk) fertilizer particles were applied at the rate of 5.74 kg/ha according to matsumoto and yamano (2011), prior to the application of water through the rainfall simulator. the rainfall intensity was simulated using an improvised rainfall simulator with constant discharge at the rate of 1 litre/m2 = 1 mm of rainfall (fao, 1986). figure 1: lysimeter with the openings at different depths and rainfall simulator the first experimental analysis (experiment 1) started with the application of 87.37 g particles of npk fertilizers (approximately at the rate of 5.74 kg/ha) on the lysimeters after which the water was then applied to them through rainfall simulator. at the end of rainfall simulation, water samples were collected using sterilized cans at the soil depths of 30 cm and 60 cm. the same procedures were repeated with the application of 100 g of npk fertilizers on the soil columns in the lysimeters (experiment 2). water samples were also collected at the different depths of 30 cm and 60 cm. the collected samples were refrigerated and sent to the laboratory for further analysis. analysis was carried out in the laboratory for the determination of the following parameters: ph, ec, ta, th, co3 2-, hco3 -, ca2+, mg2+, fe, cl-, cod, no3 -, po4 3. http://www.azojete.com.ng/ mailto:ade.richard@futminna.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):113-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 116 3. results and discussion table 1 shows the results of hydraulic conductivity from laboratory using falling head approach. table 1: hydraulic conductivity from laboratory method (falling head) s/n sample id k (m/day) 1 a1 @ 30cm 3.51e-02 2 a1 @ 45cm 7.25e-02 3 a1 @ 60cm 3.27e-03 4 a1 @ 75cm 7.85e-04 5 a1 @ 90cm 7.56e-04 6 a1 @ 105cm 5.55e-04 7 b2 @ 30cm 1.31e-01 8 b2 @ 45cm 1.81e-01 9 b2 @ 60cm 2.25e-01 10 b2 @ 75cm 1.22e-01 11 b2 @ 90cm 2.05e-01 12 b2 @ 105cm 1.90e-01 13 c3 @ 30cm 4.66e-02 14 c3 @ 45cm 4.73e-02 15 c3 @ 60cm 8.99e-03 16 c3 @ 75cm 2.70e-01 17 c3 @ 90cm 1.17e-01 18 c3 @ 105cm 3.14e-02 19 d4 @ 30cm 1.72e-01 20 d4 @ 45cm 1.56e-01 21 d4 @ 60cm 5.60e-02 22 d4 @ 75cm 6.82e-02 23 d4 @ 90cm 1.74e-01 24 d4 @ 105cm 1.03e-01 the hydraulic conductivity from table 1 ranged from 0.00054 – 0.265 m/day. the soil profile at the surface in all the sampled areas show low porosity with higher porosity observed at 90 to 105 cm, especially at sites c and d. the results of physico-chemical parameters of the water samples for experiment 1 where 87.37 g of npk fertilizers were applied on the first soil column is as presented in table 2. tables 2 and 3 show the results of water samples analysis collected at 30 cm and 60 cm soil depths. from the tables, it was observed that most of these parameters have their values reduced with depths. the same trend was observed in experiment 2 (where 100 g of npk fertilizers were applied on the second soil column). the results of the analysis for the experiment 2 analysis were presented in table 3. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ade.richard@futminna.edu.ng adesiji et al.: effect of chemical fertilizers on groundwater quality in an unconfined aquifer. azojete, 19(1):113-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 117 table 2: results of physico-chemical analysis of groundwater for experiment 1 sample id ph ec (µჽ/cm) ta mg/l th mg/l ca mg/l mg mg/l cl mg/l cod mg/l hco3 mg/l co3 mg/l fe mg/l po4 mg/l no3 mg/l a1 30cm 7.6 1001 45 112 16.82 17.08 221 2460 20.61 19.38 7.5 6.78 5.22 a2 30cm 7.64 752 40 86 21.86 7.66 194 2384 18.04 16.95 6.38 6.87 4.85 a3 30cm 7.65 613 36 120 20.18 16.98 204 2077 15.97 15.02 6.75 7.03 5.5 a4 60cm 7.05 535 24 180 42.05 18.3 15.86 26.88 9.79 9.2 1.11 4.67 1.35 a5 60cm 7.08 472 24 176 31.95 23.47 13.55 29.25 9.79 9.2 1.38 2.31 1.51 a6 60cm 7.06 506 26 136 28.59 15.76 15.6 31.4 10.82 10.17 1.29 2.34 1.48 table 2 shows that there is no significant variation in the ph values of the water samples collected at both depths. the ph values obtained at both depths range between 7.05 at 60 cm and 7.65 at 30 cm. however, the ph values at both depths were all within the permissible of 6 – 8 which is consistent with jeyaruba and thushyanthy (2009). the same trend was observed in experiement 2 though with lower ph values which ranged from 6.66 at 60 cm depth to 6.87 at 30 cm depth. interestingly, the highest nitrates and phosphates values were recorded at depths 30 cm compared to the values obtained at 60 cm. this could be attributed to the reduction in concentration of these particles as they migrate deeper into the soil mass. and it also means that fertilizer particles are being taken up in the soil mass as they move downward into the soil column. for nitrates, the values declined from 5.22 mg/l at 30 cm to 1.35 mg/l at 60 cm. the phosphate values recorded declined from 6.87 mg/l at 30 cm to 2.31 mg/l at 60 cm. the indication of this is that nitrates and phosphates contents of the applied npk fertilizers could not leach up to a depth of 60 cm and beyond of the soil within the period of the study as they are being used up as they move downwards. the dynamics of nitrates and phosphates is consistent with findings of holford and doyle (1992) and jung (2020). the same pattern was observed in experiment 2 as phosphate and nitrate values declined from 30 cm depth to 60 cm depth. nitrate values in experiment 2 declined from 3.38 mg/l at 30 cm depth to 0.1 mg/l at 60 cm depth. table 3: results of physico-chemical analysis of groundwater for experiment 2 sample id ph ec (µჽ/cm) ta mg/l th mg/l ca mg/l mg mg/l cl mg/l cod mg/l hco3 mg/l co3 mg/l fe mg/l po4 mg/l no3 mg/l b1 30cm 6.87 4100 50 132 28.59 16.83 185.22 3700 28.35 11.14 6.25 6.35 3.38 b2 30cm 6.77 3960 60 168 26.07 24.08 196 3600 20.1 12.11 6.3 6.6 3.5 b3 30cm 6.78 4360 65 164 40.37 29.76 162.68 3400 9.79 9.2 6.27 6.47 1.94 b4 60cm 6.83 549 45 100 25.23 6.97 196 1350 11.85 26.64 3.5 3.65 0.15 b5 60cm 6.78 706 44 94 27.75 7.05 140.14 1200 12.88 18.89 1.75 3.4 0.1 b6 60cm 6.66 459 30 98 16.82 7.01 123.48 1275 12.88 12.11 4 3.75 0.15 the electrical conductivity ec values followed a declining pattern as the fertilizer particles migrate down into the soil mass. from table 2, the highest value recorded was 1001 µჽ/cm at 30 cm soil depth compared to the lowest of 472 µჽ/cm at 60 cm soil depth. the higher values of electrical conductivity observed at the surface (30 cm) as impacted by fertilizer addition might be due to the amount of dissolved salts in the fertilizer which decreased as it moved downwards (ozlu and kumar, 2018). the same trend was observed in experiment 2, though with higher values of ec, which could be as a result of higher quantity of npk fertilizers applied. the value recorded was as high as http://www.azojete.com.ng/ mailto:ade.richard@futminna.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):113-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 118 4100 µჽ/cm at 30 cm depth compared to 459 µჽ/cm obtained at 60 cm. electrical conductivity has been explained (mkandawire, 2008) as an indication of dissolved elements (metallic and nonmetallic) in water and the increase in values may be attributed to the fact that infiltrating rain that was simulated on the soil core and applied poultry waste might have dissolved some organic and inorganic constituent of poultry was which are capable of raising ec values of the water samples (adeoye et al., 2017). the total alkalinity obtained in the two experimental set up showed that the total alkalinity (ta) varied between 65 mg/l at 30 cm in experiment 2 to 24 mg/l at 60 cm in experiment 1. the values of ta fall within the allowable limit for ta in drinking water which is 20 – 200 mg/l. 4. conclusion the effect of chemical fertilizers on groundwater quality in an unconfined aquifer has been studied. this study has shown that the soil on the experimental plots have ability to take in fertilizer particles as they migrate deep down into the soil mass. nitrates and phosphates generally decline in concentrations as they move with soil depths. they were able to leach up to 60 cm of soil depth of the undisturbed soil columns. these observations were attributed to high porosity of the soil and high hydraulic conductivity which ranged from0.00054 – 0.265 m/day according to hydraulic parameters analysis carried out on the soil of the area. the results obtained in this study can be used as baseline to know the precise application of fertilizers needed for optimum crop productivity with little negative effects on human consumption of groundwater bodies. the results of this study can also help in modelling the fertilizers particles movement in the soil columns. this information from this study can also be used as input parameters into modern software and models for predicting contaminant fate, transport and persistence in unconfined aquifer. acknowledgements this study was funded by tertiary education trust fund (tetfund) through institution based research (ibri) grant. the supports of laboratory staff of the departments of civil engineering and water resources aquaculture and fisheries technology (waft), federal university of technology, minna, nigeria for the scientific and laboratory analyses are well acknowledged. references adeoye, pa., man, hc., soom, ma., thamer, am. and oluwakunmi, ac. 2017. contaminants leaching from fresh poultry waste: a lysimeter study on sandy soils under tropical conditions. environment and pollution, 6(1): 38-51. badrzadeh, n., samani, jmv., mazaheri, m. and kuriqi, a. 2022. evaluation of management practices on agricultural nonpoint source pollution discharges into the rivers under climate change effects. science of the total environment, 838: 156643. chukwu, p., ejieji, cy. and alonge, fs. 2004. appraisal of prevalence of water-borne and waterbased diseases in selected cities of north central nigeria. nigerian journal of technological development. 8(2): 209. collin, ml. and melloul, aj. 2003. assessing groundwater vulnerability to pollution to promote sustainable urban and rural development. journal of cleaner production, 11(7): 727-736. djaman, k., mel, vc., diop, l., sow, a., el-namaky, r., manneh, b., saito, k., futakuchi, k. and irmak, s. 2018. effects of alternate wetting and drying irrigation regime and nitrogen fertilizer on yield and nitrogen use efficiency of irrigated rice in the sahel. water, 10(6): 711. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ade.richard@futminna.edu.ng adesiji et al.: effect of chemical fertilizers on groundwater quality in an unconfined aquifer. azojete, 19(1):113-120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 119 ehlers, w. and goss, m. 2003. the role of water in plant life. water dynamics in plant production, wallingford uk: cabi publishing, 1-9. fao. 1986. irrigation water management. food and agricultural organization (fao) training manual. fao, rome, 235. galadima, a., garba, zn., leke, l., almustapha, mn., and adam, ik. 2011. domestic water pollution among local communities in nigeria-causes and consequences. european journal of scientific research, 52(4): 592-603. goss, mj. and ehlers, w. 2009. the role of lysimeters in the development of our understanding of soil water and nutrient dynamics in ecosystems. soil use and management, 25(3): 213-223. goss, mj. ehlers, w. and unc, a. 2010. the role of lysimeters in the development of our understanding of processes in the vadose zone relevant to contamination of groundwater aquifers. physics and chemistry of the earth, parts a/b/c, 35(15-18): 913-926. gunatilake, sk. 2016. n and p variation in groundwater in wet zone and dry zone in sri lanka due to fertilization of paddy crop. international journal of scientific research publications, 6(9): 1-5. holford, icr. and doyle, ad. 1992. yield responses and nitrogen fertilizer requirements of wheat in relation to soil nitrate levels at various depths. soil research, 30(5): 683-694. ibrahim, s., and ahmad sabri, azs. 2018. informative water supply challenges on the development of towns: a study of minna town central nigeria. voice of academia (voa), 13(1): 1-8. isikwue, mo., iorver, d. and onoja, sb. 2011. effect of depth on microbial pollution of shallow wells in makurdimetropoilis, benue state, nigeria. british journal of environment and climate change, 1(3): 66-73. jeyaruba, t. and thushyanthy, m. 2009. the effect of agriculture on quality of groundwater: a case study. middle-east journal of scientific research, 4 (2): 110-114. jimoh, od.,ayodeji, ma. and mohammed, b. 2003. effect of agro-chemicals on surface and ground waters in tunga-kawo (nigeria) irrigation scheme. hydrological science journal, 48(6): 10131023. https://doi.org/10.1623/hysj.48.6.1013.51426 jung, hb. 2020. geochemical and hydrological study of coastal groundwater discharging to an urban estuary in northern new jersey. environmental earth sciences, 79(6): 1-14. karthikeyan, op., murugesan, s., joseph, k. and nagendran, r. 2008. leaching of inorganic pollutants from fresh and partially degraded municipal solid waste: a lysimeter study under tropical conditions. international journal of environment and waste management, 2(1-2): 49-64. kumar, r., kumar, r. and prakash, o. 2019. chapter-5 the impact of chemical fertilizers on our environment and ecosystem. research trends in environmental sciences, 35, 69-85. matsumoto, t. and yamano, t. 2011. optimal fertilizer use on maize production in east africa. in emerging development of agriculture in east africa: markets, soil, and innovations, springer, dordrecht, pp 117-132. mkandawire, t. 2008. quality of groundwater from shallow wells of selected villages in blantyre district, malawi. physics and chemistry of the earth, parts a/b/c, 33(8-13): 807-811. http://www.azojete.com.ng/ mailto:ade.richard@futminna.edu.ng about:blank arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):113-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 120 ozlu, e. and kumar, s. 2018. response of soil organic carbon, ph, electrical conductivity, and water stable aggregates to long‐term annual manure and inorganic fertilizer. soil science society of america journal, 82(5): 1243-1251. pérez, ca., armesto, jj., torrealba, c. and carmona, mr. 2003. litterfall dynamics and nitrogen use efficiency in two evergreen temperate rainforests of southern chile. austrial ecology, 28(6): 591-600. salami, bf., oladiran, fb. and jayeola, so. 2008. assessment of shallow groundwater quality around minna abattoir and central market. african journal of environmental science and technology, 11(6): 313-325 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ade.richard@futminna.edu.ng arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):531-542 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 531 original research article productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria y. u. oladimeji1*, h. o. yusuf2, h. a. yusuf2, h. shuaibu2 and t. o. olarewaju3 1department of agricultural economics / institute for agricultural research, ahmadu bello university, zaria, nigeria 2department of agricultural extension and rural development / institute for agricultural research, ahmadu bello university, zaria, nigeria 3department of agricultural engineering, national agricultural, extension and research liaisons services, ahmadu bello university, zaria, nigeria. *corresponding author’s email address: yusuf.dimeji@yahoo.com 1.0 introduction poultry has been domesticated for thousands of years as archaeological evidence suggests that domesticated chickens existed in china 8,000 years ago (alders 2004) when humans ceased to be hunter-gatherers (burt, 2007). domestic chickens appeared in africa many centuries ago, which are now part of african life (copland and alders, 2005). the red jungle fowl is thought to be the source of all poultry (fumihito et al., 1994). over the last decades’ poultry production and its technology in nigeria has been increasingly improved. for example, food and agriculture organisation (fao, (2018) observed that poultry meat production has increased from 30,000 in 1961 to 201,493 tons in 2017 with standard deviation of 67,351.8 tons and about 571.6 % increased. over the same period, poultry egg production has increased by 588% (figure 1). furthermore, the volume of feed used in nigeria has increased by 600% from 300 thousand to 1.8 million tons in about one decade and this is driven both by massive investments in large feed mills in southwest nigeria and a growing article information abstract small scale poultry production plays a major role in bridging the protein deficit and sustain rural livelihood in nigeria. this study assesses the productivity and allocative efficiency (ae) of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. in this study, both primary and secondary data were collected from 193 quail poultry farmers comprising of 78 battery cage system (bcs) and 115 deep litter system (dls) operators using a multistage random sampling procedure. descriptive statistics, profitability indices and stochastic frontier function were used to analyse the data. the stochastic frontier cost function was used to estimate the factors influencing ae of farmers in quail production. the results show a gross margin of n1, 455.51, net poultry returns of n1157.47 per quail bird for bcs thrives better compared to n800.00 and n751.96 estimated in dls respectively. the estimated profit margin (26.81 %) and return on investment (1.37) in bcs were also higher than 26.54 % and 1.36 respectively in dls. the roi result indicates that a n1.00 investment in bcs and dls yields n0.37 and n0.36 respectively. ae results revealed that the coefficient of costs of feed (0.287), hired labour (-0281), family labour (0.309) and depreciation of fixed items (-005) were found to be statistically significant variables in bcs quail production. conversely, costs of feed (0.109), cost of hired labour (-0.007) and family labour (0.188) statistically influence dls quail production. the inefficiency sources model for bcs showed that age, formal education, access to credit and investment are the significant factors. furthermore, formal education, access to production credit and level of investment contributed significantly to the explanation of efficiency in dls production unit. therefore, it is suggested that quail farmers should strive to optimize efficient use of inputs to increase output and profit. this will be an impetus to achieving sustainable poultry production in the studied areas. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2019 revised 24 may, 2020 accepted 30 may, 2020 keywords: quail chick return on investment allocative efficiency profit technology mailto:yusuf.dimeji@yahoo.com http://www.azojete.com.ng oladimeji et al.: productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. azojete,16(3):531-542. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 532 number of small and medium enterprises in poultry production scattered around the country (liverpool-tasie et al., 2017). therefore, nigeria had a success in poultry production trend and high demand due to rapid population growth. this is also couple with its ability to supply protein rapidly in the short-run. a cursory examination of fao data computed in figure 1 shows that poultry and ruminant production has been dwindling in recent year (2011-2017) compared to mono-gastric (pig) and total meat production. this is envisaged due to effect of insurgence in the north eastern part of the country and multi-various farmers-herdsmen, cattle rustling and banditry spreading across the six geopolitical zones in the country. several studies also have indicated that the north has more of the small farmers’ poultry, particularly chicken holdings compared to the south (liverpool-tasie et al., 2017). figure 1: trend of poultry egg and total meat production in nigeria (1961-2017); source: authors computation from fao statistic data (2017) the poultry industry in nigeria has hitherto been dominated by rearing of domestic chickens. however, recently there have been several entrants into the sector. interestingly, one of the poultry species gradually gaining prominence is the japanese quail (cortunix coturnix japonica) of galliformes family which is suitable for commercial rearing under intensive management (egbeyale et al., 2013). quail production is considered as a viable and feasible alternative means of livelihood for the unemployed and civil servants. it is an important income-generating strategy for both urban and rural farmers with a supplementary income. nationally, there is deficiency of animal protein security, with the consumption put at about less than 10g / caput / day as against the daily intake of 65g recommended by the fao to be the minimum requirement for the growth and development of the body (odunsi et al., 2007; mailafia et al., 2010; el-katcha et al., 2015; mohammed and ejiofor, 2015). consequently, boosting the poultry industry with a short generation interval is an alternative means of alleviating the deficiency of animal protein in nigeria. it was, therefore, expedient and imperative to accumulate data on productivity and profitability of quail production in nigeria for analysis geared towards meaningful policy formulation for the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 531-542. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 533 poultry sub-sector especially emerging quail production in the country. it was also essential that to have in-depth knowledge on quail production for being a laboratory animal for poultry and biomedical research. this is in addition to it is being commercially exploited for production of meat and eggs recently in nigeria. the objective of this study is to describe the socio-economic status of quail farmers, estimate the profitability, analyze the productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. 2.0 material and methods 2.1 the study area the study was conducted in southwest (oyo, ekiti, ondo states) and north-central (kwara, kogi states) nigeria. this was crucial because the two regions are the main production of quail birds. nigeria lies between longitudes 2°49' e and 14°37' e and latitudes 4°16' n and 13°52' north of the equator (oladimeji, 2018). the climate is tropical, characterized by high temperature and humidity as well as marked wet and dry seasons, though there are variations between south and north. it has a total land area of 923,768.6 km2 and 139 million people in 2006 (npc, 2006) and the latest united nation estimate in year 2019 at growth rate of 2.48% (united nation, un 2019) put the country over 190 million people with average human density of 204 person km-2. total rainfall decreases from the coast northwards. the south (below latitude 8°n) has an annual rainfall ranging between 1,500 and 4,000 mm and the extreme north between 500 and 1000 mm. the research was carried out in two geopolitical zones and five states in nigeria viz: kwara and kogi states from north-central and oyo, ekiti and ondo states from southwest of nigeria. 2.2 data collection and sampling procedure both primary and secondary data were collected from 193 quail poultry farmers using structured questionnaire with personal interview method by trained enumerators. secondary data were collected from the production records of the quail farmers. primary data compliment with their records were search for and these include inputs data such as human labour, quantity of feed, water and fuels used. output data collected include quail meat, egg and manure. the collected data belonged to the 2016/2017 production year. before collecting data, a pretest survey was conducted from a group of randomly selected quail poultry farmers in the two sampled regions. information on socio-economic and institutional characteristics, input and output, energy input sources were obtained from the quail farmers to achieve the objectives of study. multistage sampling procedure was adopted for the study. the first stage involved purposive selection of two regions comprising north central (kwara and kogi states) and south western (oyo and ekiti/ondo states) nigeria due to predominance of poultry farmers and, availability of quail production records among the poultry farmers. the list of registered cooperative poultry farmers was obtained in the states’ agricultural development project (adp). thereafter, stratified sampling technique was used to sieve the quail poultry farmers from layers and broilers poultry farmers. thereafter, all the sieved quail farmers were sampled due to small sample size. finally, additional quail farmers were sought for using snowball-sampling technique based on information from sampled farmers. this means that initially selected quail poultry farmers from adp group provided addresses of additional quail farmers who were neither a cooperative member nor a registered poultry farmer with adp for their interviewers (salganik and heckathorn, 2014; oladimeji et al., 2019). a total of 193 quail farmers comprising of 78 battery cage system (bcs) users and 115 deep litter system (dls) users were sampled in the chosen states. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al.: productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. azojete,16(3):531-542. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 534 2.3 analytical technique descriptive statistics, profitability indices and stochastic frontier function were used to analyse the data. the stochastic frontier cost function was used to estimate the factors influencing allocative efficiency of farmers in quail production adopted from aigner et al. (1977), battese et al. (1996) and oladimeji et al. (2017). stochastic allocative function model used in the study was specified explicitly as (1) where: = natural log; = total cost of production (₦/bird); = cost of feed (₦); = cost of quail chick (₦); = cost of hired labour used (₦); = cost of family labour (₦); = cost of vaccine and drugs (₦), depreciation cost of machinery which include electricity, generator, fuels, borehole, electric motor, steel and battery (₦); = regression coefficients; = random variability in the production that cannot be influenced by the quail producers. = deviation from maximum potential output attributable to allocative inefficiency. � �� = δ� + δ� ln z� + δ� ln z� + δ� ln z� + δ� ln z� + δ� ln z� + δ� ln z� + u (2) where: = allocative inefficiency effects, = age of farmers (years), = household size (number), = formal education (years), = poultry rearing experience (years), = access to credits (₦); = level of investment (₦); = constant and = parameters to be estimated (aigner et al., 1977; battese et al., 1996). the profitability indices involved the estimating the following items: net farm income for quail poultry production was estimated using equation below: (3) where: = net farm income per quail bird in the states (₦); = total sales revenue accruing to the quail farmers per bird in the states (₦); = total cost incurred by the quail farmers per bird (₦); and = total number of quail farmers in the states. total revenue ( ) is the total return or total value product (the total output multiplied by the price per unit of produce). that is; (4) where; = quantity of quail bird (kg) and = price per unit of quail bird ; total cost was computed using equation below (5) = total variable cost incurred by the quail farmer in the states (₦) and = total fixed cost incurred by the quail farmer in the states (₦). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 531-542. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 535 profitability indices were also computed as: ttotal incomegrossroi cos  (6) (7) (8) (9) (10) where: = return on investment, = profit margin and = gross ratio. total fixed cost involved depreciated value of equipment used in quail bird rearing expressed as: (12) where: = depreciation on production equipment (₦), = purchase value (₦), = salvage value (₦) and = life span of asset (years). 3. results and discussion 3.1 technological, socio-economic, institutional characteristics figure 2 depict a typical description of quail battery cage system and table 1 showed the summary of technological characteristics used in quail production by the sampled farmers. table 2 summarizes socio-economic and institutional variables employed in the model estimation. the level of technological investment, number of day old chicks acquired by quail poultry farmers and credit accessed for quail rearing revealed that quail production practices are still not developed and are largely subsistent and rudimentary as evidence in table 1. table 1: description of technology characteristics employed by quail poultry farmers technology traits type used standard quail cage plank with wire (600 x 600 mm) galvanized sheets & wire materials (1200 x 600 mm) feed system manual with feeder automatic feed carriages drinking / watering system manual drinker pipes with nipples egg collection system manual plastic plate automatic egg collection made up of galvanized sheet & wire materials manure collection manual with shovel manure transfer conveyors source: swain et al. 2010 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al.: productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. azojete,16(3):531-542. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 536 figure 2: a typical description of quail battery cage system source: dewulf et al. (2011) table 2 indicates that sampled quail farmers were dominated by male (0.67) and married farmers (0.89) with mean age of 48 years and household size of 6. table 2: description and measurement of variables employed in allocative efficiency model variables unit min. max. mean stdev cov % gender (male=1) dummy 0.67 0.22 32.83 marital status (married=1) dummy 0.89 0.09 10.11 age years 25 65 48 6.1 12.71 quail poultry experience years 1 13 7.4 3.7 50 level of formal education years 6 15 12.8 0.3 2.34 adjusted household size number 3 11 6 1 16.67 credit for quail rearing naira 0 200,000 61,900.92 34,003.3 43.1 poultry coop. membership years 0 7 5 2.04 40.8 investment in quail production naira 12.600 276,000 149,730.0 38,440 25.67 number of quail birds kept number 25 500 251 35 13.94 hired labour per two cycle man-days 109 201 167 34 20.36 family labour per two cycle man-days 54 113 89 21 23.60 source: field survey, 2016/2017; denote million, stood for coefficient of variance this mean age revealed that the quail farmers sampled were agile and productive, an essential ingredients to quail production activities. it is believed that old people tend to adhere strictly to http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 531-542. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 537 traditional methods of poultry, while young people tend to be more willing to adopt new production methods in order to increase production. therefore, it could be concluded that the preponderance of active and virile poultry farmers in the study area has a multiplier effects on increased availability of able bodied labour for primary production; ease of adoption of innovations; reduction in the degree of risk-aversion and positive implication to sustainability of poultry enterprise in the state. the result is comparable to oladimeji et al. (2017) on profit efficiency of broiler production among public servant household heads in kwara state, nigeria. 3.2 estimated profitability indices and return to investment in quail production table 3 depicts profitability indices and return to investment in battery cage and deep litter quail rearing techniques. the results showed that under battery cage system ( ), the total variable cost constituted 90.57% while the fixed cost constituted only 9.43% while in deep litter system ( ), the total variable cost constituted 96.75 %. the gross margin per quail bird (n1, 455.51), net poultry returns per quail bird (n1157.47) for thrive better compared to n800.00 and n751.96 respectively estimated in . these imply that quail production in is more profitable than dls. the estimated profit margin (26.81 %) and return on investment (1.37) in were higher compared to 26.54 % and 1.36 respectively in . the result indicates that a n1.00 investment in and yields n0.37 and n0.36 respectively. this, therefore, implies that yielded more returns to investment. the result is comparable to adelomo and owoeye (2017) and bakoji et al. (2013) on economic analysis of quail farming in southwest and bauchi state, nigeria respectively. table 3: a summary of profitability indices and return on investment per quail bird per ⃰ ⃰ 2 cycles bcs dls pooled cost item values (₦) total fixed cost 298.04(9.43) 48.04(2.31) 84.79 (3.25) total variable cost 2,861.09(90.57) 2,033.25(97.69) 2,523.40(96.75) total cost 3,159.13(100.0) 2081.29 (100.00) 2,608.19(100.0) average output per bird (naira) egg sales (₦ 19 per egg) 3,979.6(92.19) 2,550.00(90.00) 3,211.00(90.81) spent quail bird sold 287.50(6.66) 222.90(7.87) 270.00(7.64) manure 49.50(1.15) 60.35(2.13) 55.09(1.56) total revenue(gross income) 4,316.6 (100) 2833.25 (100) 3,536.09 (100) gross margin per bird per annum 1,455.51 800.00 1,012.69 net poultry income / bird / annum 1157.47 751.96 927.90 profit margin (%) 26.81 26.54 26.22 return on investment 1.37 1.36 1.36 gross ratio 73.19 73.46 73.76 net margin to cost ratio (%) 36.64 36.13 35.58 number of observations 78 115 193 source: field survey, 2016/2017; production and financial records; ⃰ labour consist of cost of hired, family and return to management; ⃰ ⃰ 2 cycles ranges from 340 – 422 days averaged approximately 365 days; n or ₦ stood for naira, nigeria currency file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al.: productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. azojete,16(3):531-542. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 538 3.3 estimate the factors influencing allocative efficiency of farmers’ investment in quail production table 4 showed the result of the allocative efficiency (and inefficiency) frontier model of quail production in nigeria. allocative efficiency results of quail production revealed that a unit increase in the coefficients of costs of feed (p < 0.01), and family labour (p < 0.05) will lead to a corresponding increase in total cost by 0.287 and 0.309 units. however, the coefficients of hired labour (p < 0.05), and depreciation of fixed items (p < 0.005) in quail production will reduced the total cost by 0.281 and 0.005 units respectively. likewise, results also revealed that a unit increase in the coefficients of costs of feed (p < 0.01) and family labour (p < 0.01) will lead to a corresponding increase in total cost by 0.109 and 0.188 units respectively of dls quail production. on the other hand, a unit increase in hired labour (p < 0.01) will lead to a unit decrease in total cost by 0.007 units of dls quail production. table 4: mle results of allocative frontier efficiency function of quail production variables battery cage deep litter pooled β |p[|z|>z] β |p[|z|>z] β |p[|z|>z] cost function constant 0.003(0.029) ** 0.015(0.100) 0.038(0.008) *** cost of feed (x1) 0.287 (0.000) *** 0.109(0.007) *** 0.521(0.000) *** cost of quail chick (x2) -0.0004(0.521) -0.061(0.381) -0.122(0.203) cost of hired labour (x3) -0.281 (0.029)** -0.007(0.000) *** -0.400(0.000) *** cost of family labour (x4) 0.309 (0.019) ** 0.188(0.004) *** 0.097(0.005) *** cost of vac. and drugs (x5) 0.002 (0.798) 0.001(0.503) 0.003(0.421) dep. of fixed items (x6) -0.005 (0.019) ** 0.117(0.204) -0.310(0.069*) inefficiency variables age -0.007 (0.002) *** 0.002(0.343) -0.118(0.072) * household size 0.395(0.400) 0.003(0.219) 0.002(0.176) formal education 0.004(0.000) *** 0.011(0.004) *** 0.001(0.002) *** poultry rearing experience 0.208(0.251) -0.306(0.199) 0.005(0.095) * access to production credit -0.009(0.062) * -0.200(0.000) *** -0.306(0.007) level of investment -0.505 (0.005) *** -0.118(0.004) *** -0.301(0.000) diagnostic statistic number of observation 78 115 193 sigma-square (σ2) 0.541(0.002) *** 0.219(0.025) ** 0.473 (0.005) *** gamma (γ) 0.289(0.054*) 0.054 (0.009) *** 0.233(0.001***) log likelihood function l/f -103.07 -112.81 -109.00 lr test 42.00 45.00 57.09 mean allocative efficiency 0.87 0.77 0.79 asterisk indicate significance ***1%, **5%, *10%. table 5: the generalized lr test for the parameter of the inefficiency sources model s/no quail rearing technique llf ϰ2 tab v:0.95 statistics ϰ2 calculated inferences i battery cage system -103.07 1.96 2.67 accept ii deep litter system -112.81 2.01 3.02 accept iii pooled -109.00 1.99 2.91 accept note: llf denote log likelihood function, ϰ2 implies chi statistics; lr, likelihood ratio http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 531-542. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 539 the inefficiency sources model for showed that the coefficients of age (-0.007), formal education (0.004), access to credit (-0.009) and investment (-0.505) are the significant socioeconomic factors influencing efficiency. similarly, formal education (0.011), access to production credit (-0.200) and level of investment (-0.118) contributed significantly to the explanation of efficiency in production unit. the positive coefficients of level of education in bcs or dls imply that a unit increase in education will lead to a corresponding increase in inefficiency in quail production. however, negative coefficients of credit utilized and investment in bcs and dls quail technology suggest that a unit increase in these variables will increase efficiency of both quail production techniques. tables 4 and 5 showed that the null hypothesis, which specifies that inefficiency sources model does not have effects in the allocating resources in both and are accepted. in addition, values imply that the entire delta ( ) estimates are not zero. it further revealed that the delta variables estimated contributed significantly to the inefficiency of the quail farmers in the study area. it suffices to that the chi-square ( ) calculated is greater than the tabulated in table 5 indicating the relevance of the variables in both and production units respectively. 3.4 relative allocative efficiency indices of quail production techniques table 6 shows the distribution of efficiency indices of quail farmers by techniques and pooled data. the battery-cage system minimum (19.85 %) and maximum (90.71 %) efficiency estimated were higher compared with of 15.09 % and 82.72 % respectively. the mean allocative efficiency score of 76.4 % in or 69.5 % in implied that an average quail farmer sampled could thrive better in allocating resources by 23.6 % or 30.5 % to improve his allocative efficiency in quail production. further analysis indicates that more than half of quail farmers (53.84 %) skewed towards efficiency level of 0.61-0.80. on the other hand, about half (48.7 %) of quail farmers fell within efficiency range of 0.41-0.60. thus, higher allocative efficiency of may be connected with quail species habitat, which have the tendency to thrive better in their natural environment. in spite of this, the results implied that both rearing techniques operate at a relatively high allocative efficiency level and a considerable amount of output can be obtained by improving allocative efficiency in quail production in the two techniques. table 6: allocative efficiency estimates of quail farmers for different rearing technology battery cage (n = 78) deep litter (n = 115) pooled (n = 193) class f % f % f % 0.21-0.40 4 5.13 21 18.26 23 11.92 0.41-0.60 18 23.08 56 48.7 79 40.93 0.61-0.80 42 53.84 30 26.09 69 35.75 0.81-1.00 14 17.95 8 6.95 22 11.40 total 78 100 115 100 193 100 mean 0.764 0.695 0.731 minimum 19.85 15.09 16.00 maximum 90.71 82.72 86.09 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al.: productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. azojete,16(3):531-542. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 540 3.5 implications of profitability and the allocative efficiencies on farmers’ output the result implies that quail production is profitable in both rearing techniques. it could also be deduced that the allocative efficiencies of the sampled farmers is above the frontier. the demand-supply gap of poultry products could be bridged and sustainably increases its output using the available inputs and existing technology, if resources could be efficiently and optimally utilized as ample opportunity still exist to move closer to frontier as it was revealed in this study. the presence of inefficiency in quail poultry production system should also be addressed if quail poultry farmers intend to maximize their profit. therefore poultry farmers’ level of efficiencies could be increased if their specific factors such as level of investment, access to credit and formal education which are statistically significant factors influencing inefficiency, and in line with a priori expectations are adequately addressed. 4. conclusion filtering the data of quail poultry production into battery cage and deep litter systems as well as pooled, this study conclude that the two systems exhibit different degrees of profitability and allocative efficiency in the two production systems. the allocative efficiency factors that influence battery cage system farmers showed variation from those influencing deep litter systems. however, where the same variable influenced both bcs and dls, it is not by the same magnitude and direction. therefore, it can be concluded that the battery cage system performed better with higher return to investment and better allocative efficiency. reference adelomo, bs. and owoeye, rs. 2017. economic analysis of quail farming in southwest nigeria. international journal of agricultural research and review, 5(7): 650-653. aigner, dj. lovell, cak. and schmidt, p. 1977. formulation and estimation of stochastic frontier production function model. journal of econometrics, 1(1): 21-37 alders, r. 2004. poultry for profit and pleasure. fao diversification booklet 3. food and agriculture organization of the united nations: rome. bakoji, i. aliyu, mk. haruna, u. jibril, sa. sani, rm. and danwanka, h. 2013. economic analysis of quails bird (cortunix cortunix) production in bauchi local government area, bauchi state, nigeria. research journal of agriculture and environmental management, 2(12): 420-425. battese, ge. malik, sj. and gill, ma. 1996. an investigation on technical inefficiency of production of wheat farmers in four districts of pakistan. journal of agriculture economics, 47(1): 37-49. burt, dw. 2007. emergence of the chicken as a model organism: implications for agriculture and biology. poultry science, 86:1460–1471 copland, jw. and alders, rg. 2005. the australian village poultry development programme in asia and africa. world poultry science journal, 61(1): 31-38. dewulf, j. van-hoorebeke, s. and van-immerseel, f. 2011. epidemiology of salmonella infections in laying hens with special emphasis on the influence of the housing system. in chapter edition: improving the safety and quality of eggs and eggs products. woodhead publishing series in food science, technology and nutrition (chapter 6), pp. 107-119. sawston, cambridge. food and agriculture organisation statistic data (faostat), (2018). fao statistics records rome, italy. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 531-542. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 541 el-katcha, mi. soltan, m.ramdan, ss. el -naggar, mk. and el-shobokshy, sa. 2015. growth performance, blood biochemical changes, carcass traits and nutrient digestibility of growing japanese quail fed on various dietary protein. alexandra journal of veterinary sciences, 44: 3853. egbeyale, lt. fatoki, ho. and adeyemi, oa. 2013. effect of egg weight and oviposition time on hatchability and post hatch performance of japanese quail (coturnix coturnix japonica). nigerian journal of animal production, 40(1):102 – 110. fumihito, a. miyake, t. sumi, s. takada, m., ohno, s. and kondo, n. 1994. one subspecies of the red jungle fowl (gallus gallusgallus) suffices as the matriarchic ancestor of all domestic breeds. proceeding of national academic of science, usa 91: 12505 12509. liverpool-tasie, s. omonona, b. sanou, a. ogunleye, w. padilla, s. and reardon, t. 2017. growth and transformation of food systems in africa: evidence from the poultry value chain in nigeria. feed the future innovation lab for food security policy, policy research brief 25, 6pp. mailafia, s. onakpa, mm. and owoleke, oe. 2010. problems and prospects of rabbit production in nigeriaa review. bayero journal of pure and applied sciences, 3(2): 20-25. mohammed, br. and ejiofor, c. 2015. the prospects and limitations of japanese quail (coturnix coturnix japonica) production in nigeria. a review. international journal of multidisciplinary and current research, 3: 920.926. npc, (2006). 2006 population and housing census of the federal republic of nigeria. priority table (volume 1). national population commission, abuja, nigeria. oladimeji, yu. abdulsalam, z. ajao, am. abdulrahman, s. and abdulazeez, ro. 2017. profit efficiency of broiler production among public servant household heads in kwara state, nigeria: a coping strategy. asian journal of economics, business and accounting, 2(2): 1 8. oladimeji, yu. 2018. assessment of trend of artisanal fish production in nigeria vis-a-vis implications on economic growth. nigerian journal of fisheries and aquaculture, 6(1): 3746. oladimeji, yu. ajao, am. abdulrahman, s. hassan, aa. sani, aa. and idi, as. 2019. estimating technical and scale efficiencies of quail production in nigeria: a strategy toward improved sustainable protein. animal research international, 16(2): 3242-3250. odunsi, aa. rotimi, aa. and amao, ea. 2007. effect of different vegetable protein sources on growth and laying performance of japanese quails (coturnix coturnix japonica) in a derived savannah zone of nigeria. world applied science journal, 3(5): 567-571. salganik, mj. and heckathorn, dd. 2014. sampling and estimation in hidden using farmer driven sampling. sociological methodology, 34(1): 193–239. swain, bk. singh, np. chakurkar, e. and naik, pk. 2010. quail production and management technology, technical report, no. 40. india council of agricultural research, (icar) research complex, goa, india. united nation (un). 2019. http:www//population.un.org 2019 chine revised edition. new delhi, india: s. chand. obi, f., ugwuishiwu, b. and nwakaire, j. 2016. agricultural waste concept, generation, utilization, and management. nigerian journal of technology, 35(4): 957–964. shigley, j. e. (1986 ). mechanical engineering design. s.i (metric) ed. new york, usa: mcgrawhill, file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oladimeji et al.: productivity and allocative efficiency of quail (cortunix coturnix japonica) production using different rearing techniques in nigeria. azojete,16(3):531-542. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.dimeji@yahoo.com 542 shigley, je., and mischke, cr. 2005. mechanical engineering design: in si units (6th ed.). new delhi: mcgraw-hill. vitali, f., parmigiani, s., vaccari, m. and collivignarelli, c. 2013. agricultural waste as household fuel: techno-economic assessment of a new rice-husk cookstove for developing countries. waste management, 33(12): 2762-2770. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):9-26 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 9 original research article effect of stress and load distribution analysis on an isotropic rectangular plate f. c. onyeka department of civil engineering, edo state university, iyamho. edo state, nigeria *corresponding author’s email address: onyeka.festus@edouniversity.edu.ng 1.0 introduction the important of plate structures in aerospace, aeronautic, automotive, military and structural engineering cannot be overemphasized. in structural engineering, they can be used as bridge deck, retaining wall for water retaining structures, panel for building slab, ship hull and spacecraft. isotropic plates refer to plates whose material properties in all directions at a point are same while anisotropic or orthotropic plates refer to plates whose material properties are direction dependent. isotropic thick plates are being widely used in structures subjected to uniformly distributed load, which produce a very large stresses on it (gwarah, 2019 and onyeka et al., 2020). to analyze the bending due to the applied load, the value of the critical load which efficiently causes the plate structure to be unstable as per equilibrium should be developed and evaluated. critical load is defined as the highest loading value, which will not cause any lateral deflection or tangential deflection on the structure (onyeka et al., 2020). when the critical load exceeds the design load of the structure, it will be in deflecting position article information abstract structural failure is discovered to be attributed to the inability of the designer to determine the structural load (critical load) that causes it. the aim of this study is to develop a mathematical model for calculation of the critical lateral imposed load of the plate before deflection reaches the maximum specified limit and its corresponding critical lateral imposed load before plate reaches an elastic yield point . total potential energy equation of a thick plate was formulated from the static elastic theory of the plate. direct variation method of analysis was adopted by minimizing the total potential energy obtained to determine the expression for the deflection and shear deformation. by solving the formulated expression, the effect of stress and load distribution analysis of a mild steel rectangular plate with one edge clamped, free at the other and the other opposite edge simply supported (csfs) are analyzed and discussed. from the established equation, a new model for determination of the critical lateral imposed load of the plate is developed. the result showed that: (i) as the specified thickness of the plate increases, the value of critical lateral imposed load increase (ii) the critical lateral imposed load decrease as the plates span increases. iii) the critical lateral imposed load increase as the plate thickness increases. (iv) increase in the value of the allowable deflection value required for the analysis of the plate reduces the chances of failure of a structural member. it is concluded that the values of critical lateral load obtained by this theory achieve accepted vertical shear stress to the thickness of plate variation and satisfied the transverse flexibility of the condition of the plate while predicting the flexural characteristics for an isotropic rectangular csfs plate. numerical comparison was conducted to verify and demonstrate the efficiency of the present theory. the results obtained are in good agreement with those in the literature. this approach is recommended to the practicing engineers as it overcomes the challenges of the conventional practice in the structural analysis/design which involves checking of deflection and shear; the process which is proved unreliable © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 february, 2020 revised 13 august, 2020 accepted 24 august, 2020 keywords: static bending analysis csfs rectangular plates shear deformation plate theory direct variation critical lateral imposed load onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 10 (onyeka, 2019). as the load is increased beyond the critical load the lateral deflections increase, until it may fail in other modes such as yielding of the material (onyeka and ibearugbulem, 2020). to avoid failure happening within the structural member, analytical approach to bending behavior is necessary to determine the critical load in the structure. since the classical plate theory (cpt) (kirchhoff, 1850a; kirchhoff, 1850b), which did not account for transverse shear effects proved unsatisfactory when applied to the isotropic plate analysis with large shear stress, shear deformation theory is obligatory. many shear deformation theories developed by many researchers (ghugal, and sayyad, 2011., mantari et al., 2012., mindlin, 1951., ghugal et al., 2011., reddy, 1984., sayyad and ghugal, 2012 a, b) considers the effect of shear deformation (tsdt, hsdt and esdt respectively) to predict the bending and free vibration behavior of thick isotropic plates under uniformly distributed lateral load. ghugal et al. (2011) applied the trigonometric shear deformation theory (tsdt) for the analysis of rectangular plates. their theory and others (pagno, 1967; pipes and pagano, 1970; ghugal, and sayyad, 2011; mantari et al., 2012) incorporates the effect of transverse shear stress and shear deformation in the analysis. results obtained using the above theory shows slight errors in predicting responses of the lateral load on the structures. polynomial displacement functions (onyeka and ibearugbulem, 2020) can be applied successfully to solve various boundary condition of thick rectangular plate; a feat that could not be easily achieved using trigonometric, hyperbolic and exponential shape functions. it will contribute in addressing the problem of dearth of literature on the function of polynomial displacement functions. scholars and practicing engineers will assess, apply and sustain trust in their works/designs. thereby the psychological trauma due to doubt or not too sure of ones works using fourier series to analyze thick plates will be done away with. ibearugbulem and onyeka, (2020) used the polynomial shear deformation theory (psdt) for the analysis of rectangular plates. their theory incorporates the effect of transverse shear stress and shear deformation in the analysis. results obtained using the theories did not introduce much error in the analysis, but it ended up determining the displacements, moments and stresses that may occur due to the applied load without obtaining the critical lateral load in predicting responses of the applied load which can lead to failure on the structures. nonlinear strain–displacement polynomial shape function of third order shear deformation theory was used for rectangular thick plate analysis under uniformly distributed load (onyeka and ibearugbulem, 2020). they determine imposed load that causes deflection of rectangular plates with all four edges clamped (cccc) and plate with free of support at third edge and the other edges clamped (ccfc) rectangular thick, but did not obtain for other type of plate. in this work, the static bending analysis of an isotropic rectangular plate subjected to uniform distributed transverse loads was presented using displacement and refined shear deformation theory. this theory, which is based on traditional higher-order shear deformation was applied in a bending analysis of rectangular plate with one edge clamped, free at the other and the other opposite edge simply supported (csfs) to determine the effect of stress and load distribution analysis on an isotropic rectangular plate. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 11 2. displacement and constitutive relations the elastic plate under lateral loading as shown in figure 1 was used to obtain the displacement – strain relationships in terms of curvatures. figure 1: rectangular plate under bending subjected to uniformly distributed load the three displacement equations of thick plate assumed to be involved are: the deflection, w(x,y) and the two inplane displacements, u(x,y,z), and v(x,y,z) were used to establish the constitutive equations of the rectangular plate. the constitutive equations for five stress components (onyeka et al., 2018) are: (( ) ( )) (( ) ( )) also, from known state equation, ( ( )) similarly, ( ( )) also, ( ( )) ( ) similarly reasoning in y direction, we obtain: ( ) similarly reasoning in z direction, we obtain: onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 12 similarly; 3. direct governing energy equation the direct variational method is used to obtain the direct governing differential equation by differentiating the total potential energy with respect to the coefficient of deflection , coefficient of shear deformation with respect to x-axis and coefficient of shear deformation with respect to y-axis . the total potential energy functional ( ), the deflection and in – plane displacement functions (w,v and u) of thick isotropic plate were derived (onyeka et al., 2018), as: where: ∫ ∫ therefore: ∫ ∫ [| ( ) ( ) ( ) | | ( ) ( ) ( )| | ( ) ( )| | ( ) ( ) | | ( ) ( ) ( ) | | ( ) |] ∫ ∫ let: [ ] [ ] and; [ ] [ ] arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 13 the solution of the three governing equations of equilibrium are summarized as: ∫ ∫ [ ( ) ( ) ( )] ∫ ∫ ∫ ∫ * ( ) ( ) + ∫ ∫ * ( ) ( ) + let: ( ) ( ) ( ) ( ) ( ) ( ) ( ( ) ) and; ∫ ∫ ( ) ∫ ∫ ( ) ∫ ∫ ( ) onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 14 ∫ ∫ ( ) ∫ ∫ ( ) ∫ ∫ where: thus: ( ) where: 4.0 formulation of the critical lateral imposed load in the rectangular plate the formulae for calculating the critical imposed load before deflection reaches specified maximum limit, and its corresponding critical lateral imposed load of the plate before plate reaches an elastic yield stress, is developed using equation established from the previous sections. to ensure that the critical lateral load the plate is determined before it reaches yielding, (onyeka and ibearugbulem, 2020): ( ) where, also, this gives: where; and, also, to ensure that the critical lateral load the plate is determined before it reaches yielding; recall that: ∭ arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 15 where; therefore: [ ] this gives: [ ] let: similarly, also, . for a bar, therefore; putting equation 48 into 55; we have: [ ] let, therefore, substituting equations 57, 58, 59 and 60 into 49, we have: [ ] by simplifying equation 1 and 6, the value of becomes; ( ) onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 16 by equating equation 61 and 62, we have: this gives: this gave: ( ) recall, ( ) let; where; ( ) and, √[ ] from equation 63, we got expression for q as: let; this gives: this gave: and; arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 17 5. numerical problem the particular shape function for rectangular plate with their respective boundary is shown in figure 2. figure 2: csfs rectangular plate considering the figure 2, the numerical analysis of csfs rectangular plate of various spanthickness ratios are presented in figure 4 to 12. a polynomial shear deformation function was applied to the governing equation obtained in the previous section to determine the numerical values of stiffness coefficients in equation 31 to 36. the fourth order polynomial displacement function for the analysis csfs plate was derived as presented in equation 74: [ ( )] let the amplitude, and shape function; ( ) 6. results and discussion the values stiffness coefficient obtained from equation 31 to 36 is presented in table 1. these values when substituted appropriately aid the solution for the coefficients of deflection, shear deformation and stresses in the plate. table 1: values of stiffness coefficient, k for various support (boundary conditions) from the numerical analysis obtained as presented in the figures 4 to 12, it is if found that as the specified thickness (t) of plate increases, the value of critical lateral imposed load increases. this implies that as we increase the thickness of the plate safety is ensured in the plate structure. csfs 𝑸 a b 𝑹 o s c s f onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 18 figures 4 to 12 presents the result of csfs plate with span of 1000mm, 3000mm and 5000mm at allowable deflection of 1mm, 3mm and 5mm at 5mm, 7.5mm, 10mm, 12.5mm and 15mm specified thickness. from the result, the value of is between -1.1446 n/mm to 53.413 n/mm and -0.1335 n/mm to 68.517 n/mm been the highest and lowest value at respectively. from the table, it is seen that the values of critical lateral imposed load 〖 decrease as the length-width ratio increases, this continues until failure occurs. this showed that the greatest failure ( ) occurs at span to breadth ratio and allowable thickness of 2 and 15mm respectively. this means that an increase in plate length increases the chance of failure in a plate structure. from the numerical analysis obtained as presented in the figure 4 to 12, it finds that as the specified thickness (t) of plate increases, the value of critical lateral imposed load increases. this implies that, increase in the thickness of the plate ensured safety in the plate structure. figures 4 to 12 presents the result of csfs plate with span of 1000mm, 3000mm and 5000mm at allowable deflection of 1mm, 3mm and 5mm at 5mm, 7.5mm, 10mm, 12.5mm and 15mm specified thickness. from the result, the value of is between -1.1446 n/mm to 53.413 n/mm and -0.1335 n/mm to 68.517 n/mm been the highest and lowest value at respectively. from the table, it is seen that the values of critical lateral imposed load decrease as the length-width ratio increases, this continues until failure occurs. this showed that the greatest failure ( ) occurs at span to breadth ratio and allowable thickness of 2 and 15mm respectively. this means that an increase in plate length increases the chance of failure in a plate structure. figure 4: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 1000mm at = 1.0mm -10 0 10 20 30 40 50 60 70 80 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 19 figure 5: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 1000mm at = 3.0mm figure 6: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 1000mm at = 5.0mm 0 10 20 30 40 50 60 70 80 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ 0 50 100 150 200 250 300 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 20 figure 7: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 3000mm at = 1.0mm figure 8: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 3000mm at = 3.0mm -2 -1 0 1 2 3 4 5 6 7 0 0.5 1 1.5 2 2.5c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ 0 10 20 30 40 50 60 70 80 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 21 figure 9: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 3000mm at = 5.0mm figure 10: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 5000mm at = 1.0mm -2 -1 0 1 2 3 4 5 6 7 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ -1.5 -1 -0.5 0 0.5 1 1.5 2 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 22 figure 11: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 5000mm at =3.0mm figure 12: plots of critical lateral imposed load versus length to breadth ratio of csfs plate for span, a = 5000mm at = 5.0mm looking closely at figures 5 to 7 (csfs plate with span of 1000mm at allowable deflection ( ) value between 1mm to 5mm). it is found that failure of critical lateral imposed load ( ) only occur at a thickness of 5mm which is between the length to width ratio of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9 and 2 with a value of -0. 0266n/mm, -0. 0582n/mm, 0. 0808n/mm, -0. 0976n/mm, -0. 01103n/mm, -0. 1202n/mm, -0. 1280n/mm, -0. 1343n/mm, -0. 1395n/mm and -0. 1438n/mm. -1.5 -1 -0.5 0 0.5 1 1.5 2 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ -1.5 -1 -0.5 0 0.5 1 1.5 2 0 0.5 1 1.5 2 2.5 c ri ti ca l l at e ra l im p o se d lo ad ( n /m m ) length to breadth aspect ratio (b/a) qw @ qx @ qw @ qx @ qw @ qx @ qw @ qx @ arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 23 looking closely at figures 8 to 10 (csfs plate with a span of 3000mm at allowable deflection ( ) value between 1mm to 5mm). it is found that failure of critical lateral imposed load ( ) only occur at a thickness of 1mm and 5mm which is between the length to width ratio of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9 and 2 for all specified thickness value. this shows that the value of critical lateral imposed load ( ), while the critical imposed load ( ) remains positive (safe). this means that an increase in the value of the specified deflection failure tendency of the plate structure. the result of critical lateral imposed load for csfs plate with span of 1000mm at allowable deflection ( ) of 1mm, 3mm and 5mm is presented in figure 5 to 7. it finds that the failure of critical lateral imposed load ( ) only occur at a thickness of 5mm which is between the length to width ratio of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9 and 2 with a value of -0. 0266n/mm, -0. 0582n/mm, 0. 0808n/mm, -0. 0976n/mm, -0. 01103n/mm, -0. 1202n/mm, -0. 1280n/mm, -0. 1343n/mm, -0. 1395n/mm and -0. 1438n/mm. furthermore, the result of critical lateral imposed load for csfs plate with span of 3000mm at allowable deflection ( ) of 1mm, 3mm and 5mm is presented in figure 8 to 10. it finds that the failure of critical lateral imposed load ( ) only occur at a thickness of 1mm and 5mm which is between the length to width ratio of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9 and 2 for all specified thickness value. looking closely at figures 11 to 13 (csfs plate with span of 5000mm at allowable deflection ( ) value between 1mm to 5mm). it is found that failure of critical lateral imposed load ( and ) occur at specified thickness 5mm and 7.5mm which is between the length to width ratio of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9 and 2 for all allowable deflection value while critical lateral imposed load ( ) only occur at other thickness at all length to width ratio and allowable deflection. finally, the result of critical lateral imposed load for csfs plate with span of 5000mm at allowable deflection ( ) of 1mm, 3mm and 5mm is presented in figures 11 to 13. it finds that the failure of critical lateral imposed load ( and ) occur at specified thickness 5mm and 7.5mm which is between the length to width ratio of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9 and 2 for all allowable deflection value while critical lateral imposed load ( ) only occur at other thickness at all length to width ratio and allowable deflection. the negative value of critical lateral imposed load (and positive value of ( ) only reveals that the plate fails in for the entire plate (1mm to 5mm) and span of 1000mm to 5000mm. this means that the plate structure is not safe and required maintenance. the negative value of critical lateral imposed load ( and ) reveals that the plate fails in both ( and ) for the entire plate (1mm to 5mm) for all types of plate. this means the total failure plate structure and this lead to collapse. onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 24 table 2: percentage difference between the values of non-dimensional center deflection of csfs square rectangular plates from present and past studies the result of the comparison made in table 1, shows that the total average percentage difference between the present study and that of gwarah (2019) is 9.3%. this reveals that the difference between the two values is very negligible. they present good interpretations of the result. hence, the direct variational method can be used with confidence for analysis of deflection on a csfs rectangular plate. from the figure 13, it can be seen that the results obtained in this work agree very well with those from the previous work (gwarah, 2019). the disparity between the values in bending is clear but still in agreement with each other. hence, the approximating function according to polynomial function can be used reliably for analysis of a plate with one edge clamped, free at the other and the other opposite edge simply supported. figure 13: plots of central deflection of csfs square plate versus span-thickness ratio 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0 20 40 60 80 100 120 d e fl e ct io n ( w ) span to thickness ratio gwarah et al., 2019 present work present work gwarah, (2019) percentage difference 4 0.006637 0.007297 9.052763 5 0.006087 0.006715 9.351812 10 0.005372 0.005929 9.402254 20 0.005196 0.00573 9.331607 30 0.005163 0.005693 9.314134 40 0.005152 0.00568 9.307697 50 0.005146 0.005674 9.304658 60 0.005144 0.005671 9.302937 70 0.005142 0.005669 9.301919 80 0.005141 0.005668 9.301357 90 0.00514 0.005667 9.300861 100 0.005139 0.005666 9.300466 average % difference 9.297705 total % difference 9.3 arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):9-26. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 25 7. conclusion it is concluded that the values of critical lateral load obtained by this theory achieved accepted vertical shear stress to the thickness of plate variation and satisfied the transverse flexibility of the condition of the plate while predicting the bending behavior of an isotropic rectangular csfs plate. furthermore, it can be concluded that the values of critical lateral load obtained by this theory achieve accepted vertical shear stress to the thickness of plate variation and satisfied the transverse flexibility of condition at the top and bottom faces of the plate while predicting the flexural characteristics for an isotropic rectangular csfs plate. the deflection and stresses obtained by present theory are in good agreement with the other order theories. this validates the efficacy and credibility of the present polynomial shear deformation theory. 8. recommendation this approach is recommended to the practicing engineers as it overcomes the challenges of the conventional practice in the structural analysis/design which involves checking of deflection and shear; the process which is proved unreliable. references ghugal, ym. and kulkarni, sk. 2011. thermal stress analysis of cross-ply laminated plates using refined shear deformation theory. journal of experimental and applied mechanics, 2: 47-66. ghugal, ym. and sayyad, as. 2011. free vibration of thick isotropic plates using trigonometric shear deformation theory. journal of solid mechanics, 3(2): 172-182. ibearugbulem, om. and onyeka, fc. 2020. moment and stress analysis solutions of clamped rectangular thick plate. european journal of engineering research and science, 5(4): 531-534. gwarah, ls. 2019. application of shear deformation theory in the analysis of thick rectangular plates using polynomial displacement functions. phd. thesis, department of civil engineering, federal university of technology, owerri, nigeria. mantari, as., oktem, c. and guedes s. 2012. a new trigonometric shear deformation theory for isotropic, laminated composite and sandwich plates. international journal of solids and structures, 49: 43-53. mindlin, rd. 1951. influence of rotary inertia and shear on flexural motions of isotropic, elastic plates. asme journal applied mechanics, 18: 31-38. onyeka, fc. 2019. direct analysis of critical lateral load in a thick rectangular plate using refined plate theory. international journal of civil engineering and technology, 10(5): 492-505. onyeka, fc. and ibearugbulem, om. 2020. load analysis and bending solutions of rectangular thick plate. international journal on emerging technologies, 11(3): 1103-1110. onyeka, fc., okafor, fo. and onah, hn. 2018. displacement and stress analysis in shear deformable thick plate. international journal of applied engineering research, 13(11): 98939908. onyeka, fc., okeke te. and wasiu, j. 2020. strain–displacement expressions and their effect on the deflection and strength of plate. advances in science, technology and engineering systems, 5(5): 401-413. pagano nj. 1967. exact solutions for composite laminates in cylindrical bending. journal of composite materials, 3: 398-411. onyeka: effect of stress and load distribution analysis on an isotropic rectangular plate. azojete,17(1):9-26 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: onyeka.festus@edouniversity.edu.ng 26 pipes rb. and pagano nj. 1970. interlinear stresses in composite laminates under axial extension. journal of composite materials, 4: 538-648. reddy jn. 1984. a refined non-linear theory of plates with transverse shear deformation. international journal of solids and structures, 20: 881-896. reissner, e. 1945. the effect of transverse shear deformations on the bending of elastic plates. asme journal of applied mechanics, 12: a69-a77. sayyad, as. and ghugal, ym. 2012a. bending and free vibration analysis of thick isotropic plates by using exponential shear deformation theory. applied and computational mechanics, 6(1): 65-82. sayyad, as. and ghugal, ym. 2012b. buckling analysis of thick isotropic plates by using exponential shear deformation theory. applied and computational mechanics, 6(2): 185-196. soldatos, kp. 1988. on certain refined theories for plate bending. asme journal of applied mechanics, 55: 994-995. soldatos, kp. 1992. a transverse shear deformation theory for homogeneous monoclinic plates. acta mechanica, 94: 195-200 availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 16-22 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng comparison of different methods for determining saturated hydraulic conductivity on alluvial floodplain soils in a semi arid environment kundiri, a.m. 1 , i. audu 2 and a.m. kundiri 3 abstract soil saturated hydraulic conductivity is an important parameter for flow and transport related processes in the soil but the different methods of its measurement vary under different field conditions. the performance of three in situ methods were evaluated at 20, 40 and 80 cm depths on an alluvial floodplain soil classified as fine loamy isohyperthermic aeric trapaquept. the guelph permeameter method gave the lowest estimates of saturated hydraulic conductivity, possibly because of small sample size, whereas the disk permeameter method gave maximum values for saturated saturated hydraulic conductivity with minimum variability, possibly due to large sample size. the estimates of saturated hydraulic conductivity were most comparable for the velocity permeameter and the laboratory method using a constant head permeameter. 1. introduction soil saturated hydraulic conductivity is required in estimation of infiltration, runoff, soil water balance, water and chemical transport to ground water via the vadose zone and the other components of the hydrologic cycle. several infiltration measurement techniques have been developed over the years for a range of applications. however, the reliability and usefulness of these techniques for different field conditions is a cause for concern by soil scientists, engineers and hydrologists. many studies have been carried out in recent times in order to address this problem for different methods under field conditions (mohanny et al., 1994; paige and hillel, 1993). interestingly, the different methods have shown different trends under different soil textures and field conditions. research on the appropriateness of the different methods for different soil types and field conditions (tillage practices, macroporosity, tillage depths and morphology) is a subject for further research. hydraulic properties of soils at different depths and different spatial locations can be investigated by different measuring techniques. such studies often produce variable results. mohanty et al. (1994) have observed that the variability of saturated hydraulic conductivity within the field could be as a result of the measuring technique effect. the objective of this study was to compare estimated saturated hydraulic conductivity from different in situ measuring techniques with a standard laboratory technique on an alluvial floodplain soils (locally referred to as fadama). 2. materials and methods 2.1 the study area 1 department of soil scince, university of maiduguri, maiduguri. nigeria 2 department of agricultural & environmental resources engineering, university of maiduguri. nigeria 3 department of civil & water resources engineering, university of maiduguri. maiduguri. nigeria azojete vol. 4 2004 17 the study was carried out on the alluvial floodplain of the komadugu-yobe in the upper yobe river system around gashua (12 o 49.15’n, 11 o 05.52’e) situated in the semi arid region of nigeria. the upper yobe river system comprises the hadejia and jama’are rivers that originate from the jos plateau and flow across the rocks of the basement complex to the sedimentary chad formation. the two rivers meet in an area of complex drainage upstream of gashua. in all, the rivers drain in an area of about 60,000 km 2 (sellars, 1981). the chad formation consists of sediments of tertiary and quaternary age deposited by rivers flowing into the yobe basin (bawden et al., 1972). the sediments are poorly graded, comprising coarse and fine sands, silts and clays. the basement complex lies to the west and south east, and to the south, there are the cretaceous rocks of the upper benue river, the kerri-kerri formation and the basalts of biu plateau (du preez and barber, 1965). the topography of the fadama areas is characterised by a gently undulating plain with shallow depressions. 2.2 determination of soil physical properties the laboratory analyses carried out on soil samples include the following: particle-size analysis, determination of soil bulk density and total porosity. the physical properties were determined in accordance with specifications (bascomb, 1974). 2.3 determination of saturated hydraulic conductivity saturated hydraulic conductivity measurements using different methods were made on the soil at depths of 20, 40 and 80 cm. the different methods used were: 2.3.1 guelph permeameter method a guelph permeameter (elrick et al., 1989) is a constant head permeameter that measures a composite of vertical and horizontal saturated hydraulic conductivity in the field. a 5 cmdiameter and 100 cm deep vertical borehole was augered at site, taking all precautions to minimise wall smearing. the permeameter was set up to maintain a constant head of 10 cm depth of water in the borehole and the change in water level per unit time was recorded in a data sheet for three consecutive readings. the taking of stable readings lasted between 1.5 to 3.5 hours depending on antecedent soil moisture conditions. 2.3.2 velocity permeameter a velocity permeameter was adapted for field use (everts and kanwar, 1989). an 8.5 cm diameter cylinder was pushed to about 10 cm into the soil. some compaction was experienced when the sample cup was hammered into the ground. the top of the cylinder was closed and then connected to two hoses, one of which was connected to a reservoir providing water for infiltration and the other hose was used to ventilate the cylinder. saturated hydraulic conductivity for the soil inside the cylinder was calculated based on the cylinder geometry and the rate of fall of the water level in the observation tube. measurements of saturated hydraulic conductivity were made as the wetting front moved through the soil. when the wetting front advanced away from the in situ soil core, the estimates of saturated hydraulic conductivity approached a pseudo-constant value, which can be taken as hydraulic conductivity of the sample. depending on the depth and saturated hydraulic conductivity, sample measurements took between 20 – 60 minutes. in comparison comparison of different methods for determining saturated hydraulic conductivity 18 with the guelph permeameter method which measured the soil mass around the borehole, this method gave the saturated hydraulic conductivity of a smaller volume of soil sample present inside the core. this represents a point measurement, facilitating the study of microheterogenity in the spatial variability in infiltration properties. 2.3.3 disk permeameter infiltration measurements were made using a disk permeameter at four different supply potentials and the saturated hydraulic conductivity was estimated based on the calibrated empirical relationship at zero supply potential (perroux and white, 1988). a single infiltration reading required between 50 – 70 minutes. the instrument was set up above the ground, thus minimising soil disturbance. 2.3.4 constant head permeameter (laboratory core) measurements of saturated hydraulic conductivity of soils was based on the direct application of darcy’s equation to a saturated soil column of uniform cross sectional area. a hydraulic head difference was imposed on the soil column and the resulting flux of water was measured. three replicates of detached soil cores 7.6 cm in length and 7.6 cm in diameter were collected from each site and at each depth using a core sampler. the cores were saturated in the laboratory by capillarity. the saturated hydraulic conductivity of the soil cores was measured in sequence at 20, 40 and 80 cm. in situ measurements were taken close to each other with a minimum separation distance of 20 cm to avoid compaction or influence of other previous measurement sites. the measurements with different methods for each site were done in sequence rather than simultaneously. this method measures vertical conductivity. the average time required to achieve a study-state ready for soil cores was between 30 and 75 minutes. 3. results and discussion the soil, classified as loamy isohyperthermic aeric tropaquept (kundiri, 1995) was grey or dark brown clay loam of about 50 – 70 cm in thickness, overlying a light-grey or brown clay, sandy clay loam or sandy material of variable thickness but commonly more than 60 cm thick. the dry bulk density of the soil was observed to range from 1.3 to 1.5 mgm -3 . the general characteristics of the soil are given in table 1. after setting the instrument at each site, the time required to achieve a steady-state condition before making the saturated hydraulic conductivity estimation is an important factor in comparing the efficiency of these methods. measurements by the velocity permeameter method took the least net time of all the in situ methods, followed by disk permeameter. except for the guelph permeameter method, all others were labour intensive for subsoil saturated hydraulic conductivity measurements because they needed excavation of the soil to the depth for which measurements were to be made. azojete vol. 4 2004 19 table 1: particle size analysis of the soils of the experimental area depth (cm) texture sand (%) silt (%) clay (%) bulk density (g/cm 3 ) porosity profile 1 apg 0-25 clay loam 41.42 28.98 29.6 1.49 0.41 bg 25-50 clay 18.19 38.11 43.71 1.45 0.42 bcg 50-75 clay loam 39.73 36.12 24.02 1.40 0.43 cg 75-100 sand 96.05 1.15 2.79 1.37 0.41 profile 2 apg 0-25 clay 5.12 25.94 68.86 1.45 0.43 bg1 25-50 clay 6.44 20.5 73.06 1.44 0.42 bg2 50-75 clay 8.66 25.49 68.85 1.36 0.44 bcg 75-100 sandy clay loam 61.41 18.31 7.25 1.31 0.42 profile 3 apg 0-25 clay 15.04 22.44 62.52 1.37 0.43 bg 25-50 clay 11.28 24.96 63.76 1.35 0.43 cg 50-75 clay 12.15 26.67 61.18 1.34 0.41 2cg 75-100 loamy sand 87.96 8.14 3.91 1.33 0.42 profile 4 apg 0-25 clay 7.7 23.96 68.34 1.42 0.41 bg 25-50 clay 5.3 24.45 70.25 1.41 0.39 bcg 50-75 clay 12.44 26.23 61.32 1.40 0.38 cg 75-100 sand 98.09 0.88 1.03 1.34 0.40 profile 5 apg 0-25 clay loam 39.16 21.57 39.24 1.37 0.38 bcg 25-50 sandy clay loam 59.53 17.72 22.35 1.33 0.37 cg 50-75 sand 90.91 8.26 0.85 1.32 0.35 2cg 75-100 sandy loam 65.12 17.99 6.99 1.33 0.41 the results obtained from the different methods used for measuring saturated hydraulic conductivity are presented in table 2. the different methods were compared on the basis of the mean saturated hydraulic conductivity values obtained. comparison of different methods for determining saturated hydraulic conductivity 20 table 2: saturated hydraulic conductivity measurements (mmh -1 ) using different methods at different sites site number depth (cm) guelph permeameter velocity permeameter disk permeameter laboratory core 1 20 2.32 10.22 6.19 1.10 40 0.82 1.42 31.10 4.82 80 1.00 1.16 5.69 2.96 2 20 0.14 0.30 5.51 0.49 40 0.01 5.90 9.36 8.43 80 25.2 19.68 5.34 9.47 3 20 2.19 1.42 19.30 0.73 40 4.61 11.56 36.70 27.65 80 0.11 17.56 16.88 14.18 4 20 0.14 0.94 36.00 0.58 40 1.07 1.53 7.04 1.32 80 0.03 9.94 11.52 9.47 5 20 1.23 2.03 6.16 2.10 40 0.15 1.12 14.83 10.00 80 0.27 4.39 11.12 2.43 the statistical significance and multiple mean comparison of the different methods using the log10 transformed saturated hydraulic conductivity methods is presented in table 3. the saturated hydraulic conductivity obtained using the guelph permeameter method had the highest standard deviation and coefficient of variability compared to the other in situ methods. similar results were reported by kanwar et al. (1989). table 3: some descriptive statistics of saturated hydraulic conductivity (mmh -1 ) obtained by all the four methods on forty five samples guelph permeameter velocity permeameter disk permeameter laboratory core maximum 25.2 19.68 36.70 27.65 minimum 0.01 0.30 5.34 0.49 mean 2.68 12.54 21.60 8.91 standard deviation 6.00 24.91 42.00 12.57 geometric mean 0.37 3.20 14.69 2.32 coefficient of variation (%) 224 199 194 141 azojete vol. 4 2004 21 the high variability exhibited by the guelph permeameter method could be as a result of wall smearing of the hole under wet soil conditions, variability in macro pore distribution (mohanty et al., 1994), air entrapment during the initial filling of the borehole (elrick et al., 1989). the guelph permeameter measurements gave significantly lower saturated hydraulic conductivity values (p = 0.05) than the other methods used. the estimates of saturated hydraulic conductivity by velocity permeameter method were generally higher than those obtained by the guelph permeameter method even though they were smaller than those obtained using the disk permeameter method (table 2). the saturated hydraulic conductivity measurements by the disk permeameter method were quite similar to those from soil cores in the laboratory. this could be so because both methods are point measurements of the vertical conductivity. the saturated hydraulic conductivity obtained by the disk permeameter showed higher values (p = 0.05) than those obtained by the other methods, probably as a result of three-dimensional infiltration. the disk permeameter method has the least disturbance, thus increasing the probability of macro pore flow since no pores are cut off. the estimates given by the different methods in descending order were disk, velocity and guelph. this may be attributed to variable amount of preferential flow caused by the variable amount of macroporosity in the soil sample (singh and kanwar, 1991). the different methods were subjected to different amounts of variability across depths. the variability could be as a result of susceptibility to factors such as pore size distribution, soil pore ratio, soil texture and soil water content. 4. conclusion four different methods of measuring soil saturated hydraulic conductivity on alluvial floodplain soils (guelph permeameter, velocity permeameter, disk permeameter and laboratory core) were compared. there were variations in the results obtained fromthese methods. the guelph permeameter method gave the least estimate of saturated hydraulic conductivity probably as a result of the small sample size, wall smearing and air entrapment. the laboratory core method gave low values at shallow depths due to small sample size, presence of open-ended pores and slight soil compaction. there was a slight agreement between the estimates of saturated hydraulic conductivity by velocity permeameter method and the laboratory core method. the disk permeameter method predicted higher saturated hydraulic conductivity values in comparison with the other methods as a result of the large sample size. therefore, the velocity permeameter and the laboratory core gave better estimates of saturated hydraulic conductivity on the komadugu-yobe alluvial soils and could serve as methods for determining the parameter on such soils. comparison of different methods for determining saturated hydraulic conductivity 22 references bascomb, c.l. (1974). in avery and bascomb (ed). soil survey laboratory methods. soil survey technical monograph no. 6. harpenden. bawden, m.g., d.m. carroll and p. tuley (1972). the land resources of north east nigeria. vol. 3: the land systems. land research directorate of overseas survey, surrey, uk. du preez and w. barber (1965). pressure in the chad formation of borno and dikwa emirates, north east nigeria. bulletin no. 35, geological survey of nigeria. elrick, d.e., w.d. reynolds and k.a. tan (1989). hydraulic conductivity measurement in the unsaturated zone using improved well analysis. ground water monitoring review. 9: 184-193. everts, c.j. and r.s. kanwar (1989). quantifying macropores for modelling preferential flow. asae paper no. 89-2162. st joseph, mi. kanwar, r.s., h.a. rizvi, m. ahmed, r. horton and s.j. marley (1989). measurement of field saturated hydraulic conductivity by using guelph and velocity permeameters. trans. asae. 32: 1885-1890. kundiri, a.m. (1995). soils, land management and crop suitability of fadama of north east nigeria. unpublished phd thesis, cranfield university, silsoe. uk. mohanty, b.p., r.s. kanwar and c.j. everts (1994). comparison of saturated hydraulic conductivity measurement methods for a glacial till. soil science society of american journal. 58: 672-677. paige, g.b. and d. hillel (1993). comparison of three methods for assessing soil hydraulic properties. soil science. 155: 175-189. perroux, k.m. and i. white (1988). designs for disk permeameters. soil science society of american journal. 52: 1205-1215. sellars, c.d. (1981). a floodplain storage model used to determine evaporation losses in the upper yobe river, northern nigeria. journal of hydrology. 52: 257-268. sing, p. and r.s. kanwar (1991). preferential solute transport through macropores in large undisturbed saturated soil columns. j. environ. qual. 20: 295-300. arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):317-334 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 317 original research article mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal subsurface flow constructed wetland i. j. udom water, environment and wetland systems research group department of agricultural engineering, akwa ibom state university, ikot akpaden, nigeria *corresponding author’s email address: ikpeudom@aksu.edu.ng 1.0 introduction pigs provide a significant amount of meat for human consumption. currently, pig meat provides over 30% of world-wide meat consumption. according to official statistics by the organization for economic cooperation and development (oecd), as reported by soare and chiurciu (2017), the highest meat consumption per capita in the world in 2016, was 39.8% pork (of the total meat consumed per capita). nigeria’s pig industry is an important part of the livestock sub-sector in the overall agricultural sector (uddin and osasogie, 2016). the major problem associated with industrial pig production is pollution of the environment by nutrients from pig waste. piggery waste has high nutrient content because only 15 per cent of the nutrients contained in their feed material is retained and transformed into animal product. article information abstract mathematical equations were derived for estimation of nitrogen and phosphorus removal from piggery wastewater in horizontal subsurface flow constructed wetlands. the model inputs included wastewater inflow, retention, plant uptake and nutrient loss to the atmosphere by volatilization of nitrogen. plant die off, precipitation and exchange with subsurface were considered negligible. the calibration and validation of the model was carried using different sets of experimental data generated from a pilot constructed wetland monitored over a period of seven months. the results show that the amount of nitrogen and phosphorus concentrations decreased exponentially within three days of retention in the wetland and, thereafter, the reduction appeared constant over higher retention time subject to the decay coefficient. there was high correlation between the simulated and observed parameters with r2 = 0.9537 for nitrogen and 0.9912 for phosphorus respectively. the low values of the mean bias error (me) of 0.211 and 0.139, root mean square error (rmse) of 0.32 and 0.18, and relative error of re of 24 and 12%, demonstrated the ability of the model to predict nutrient removal accurately. the models efficiencies of 84 and 77% and index of agreements of 0.6527 and 0.8676 for nitrogen and phosphorus respectively, indicate an acceptable level of the models predictive capacities. the linear regression coefficients appear reasonable given that the system was a natural system located in the field, where uncontrolled influencing factors could weaken optimal performance. because of challenges associated with scaling-up this result. longer field studies are recommended. the models developed in this study considered the features of horizontal-subsurfaceflow constructed-wetlands for removal of nitrogen and phosphorus from piggery wastewater. the high correlation between the developed models and the calibrated parameters showed that they are rational. the models can be used to simulate nitrogen and phosphorus removal in horizontal-subsurface-flow constructed-wetlands. the performance of these models meets the water quality discharge or reuse standards of nigeria for wastewater discharge to land and surface water. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 26 january, 2021 revised 12 may, 2021 accepted 19 may, 2021 keywords: modelling horizontal-subsurface-flow constructed-wetlands nutrient pollution piggery wastewater inland water udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 318 the remaining 85 percent are eliminated as waste (kiely, 1998; ogbuewu et al., 2012) mainly urine and faeces comprising water (90%). additionally, complex carbohydrates and nutrients constitutes between 40 – 70% of the total fertilizer value of piggery manure). however, this includes 75% of nitrogen, 80% of phosphorus (as p205) and 85% potassium (as k2o). this high nutrient content may result in degradation of land, inland water quality and marine ecosystems through eutrophication, and direct toxicity to organisms (mason, 2002). it can also contribute to ground water pollution which causes mucosal irritation, respiratory ailment, increased stress and also high blood pressure (horton et al., 2009, wendee, 2017). additionally, the high doses of copper and zinc fed to pigs to promote growth eventually accumulate and degrade the soil. zamani, (2016) reports that improper application of raw pig manure can cause degradation of the soil such. proper management is, therefore, required to sustain the standards for protection of the environment, reduce the effect of effluent addition to land and avoid off-site impairment of water quality safety (ecc, 1999; epa, 2000). it is important to recycle or treat the waste before releasing into the environment. however, this is not done properly in nigeria where waste is stored in ditches and lagoons and left to decompose and integrate with the soil (kadurumba and kadurumber. 2019). a study by ewuziem et al., (2009) showed that 80% of the pig farms in imo state in the tropical south eastern nigeria managed their waste by dumping on open land (75%) and on streams (5%). nitrogen and phosphorus are the main pollutants of worry from piggery wastewater. nitrogen is regulated in drinking water to protect the health of children and may be regulated in surface waters to check eutrophication. phosphorus is the main factor regulating the growth of plant and algae in freshwater systems (epa, 2000) and can ensure significant effects on downstream receiving waters (wallace and knight, 2006). its surplus triggers eutrophication which changes ecosystem productivity, reduces biodiversity, upsets water clearness, light dispersion and photosynthesis and causes blooms of algae and cyanobacteria which produce toxins affecting organisms and producing health problems (gouriveau, (2009). commonly, inadequate wastewater treatment in developing countries is essentially financial (muga and mihelcic, 2008), due to the vast investments needed to construct, maintain and improve wastewater treatment facilities, but it is also due to lack of data on progresses in wastewater treatment technologies and the use of low cost wastewater treatment technologies (mburu et al., 2012). constructed wetlands (cws) are engineered systems designed to remove pollutants from contaminated water. cws have been shown to collect, hold and process nutrients in wastewater through a combination of physical, chemical, and biological processes (abbasi et al., 2019; nandakumar et al., 2019) as water progressively flows through the wetland. these processes are responsible for a variety of treatment mechanisms, which has been found to vary with time and locality due to poor understanding of the removal mechanisms and how they are affected by environmental conditions and system design (kadlec and wallace 2009). proper design and use of cws and improving their benefits require a measureable understanding of how these systems function and their response to different management conditions. design standards and analysis methods for cws have progressed from relations based on empirical equations derived only from the relationship between input and output nutrient levels to advanced models that can explain the complexity in pollutant removal (kadlec and wallace, 2009). mathematical models are increasingly being used for the design of cws (kadaverugu, [2016). mathematical models describe the relationship between the model arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 319 components and link them together using specific mathematical expressions and equations that correctly describe the processes (jorgensen and bendoricchio, (2001). fitovert (giraldi et al., 2010), hydrus 2d/3d (simunek et al. 2008), phwat (brovelli et al., 2009) are complete cw models which accounts for the variably saturated hydrodynamics of filter media and also include sub models for determining the fate of pollutants. however, these models are not available as open source software. according to allen (2019), the commercial version of stella software package, widely used in biological, ecological and environmental sciences and in cw modelling, sold for $2299 as at may, 2019. therefore, there is the need to develop simple, realistic and readily available model that can be used for planning and designing of new systems as well as investigating the dynamics of nutrients and performance assessment of constructed wetlands. the objective of this paper is to develop a simple mathematical model for prediction of nutrient removal from piggery wastewater by a horizontal subsurface flow (hsf) cw. this will provide a tool for cw design and management to enable piggery farmers, environmental practitioners and designers to model their own nutrient removal from piggery wastewater. 2.0 materials and methods 2.1 study area and project location the pilot hsfcw was located near the effluent source behind the piggery facility at the obio akpa campus of akwa ibom state university (aksu), figure 1. obio akpa is located in the humid tropics between longitudes 07o 3” e and 07o 3” e and latitude 04o 45” n and 04o 55” n. figure 1: map of aksu showing location of piggery and constructed wetlands (udom et al., 2018) the average minimum and maximum temperatures range between 18 oc 27oc and 24oc 36oc. relative humidity ranges between 55-86%. rainfall has a bimodal distribution lasting from april to october with a short break in august. average rainfall values range from 2050 to 2450mm. the piggery produces an estimated 9.46m3/day wastewater and releases it without treatment onto the floodplain of obio akpa stream; a perennial stream which serves as a major source of water to over 150,000 people (npc, 2006) in three villages which the stream traverses before emptying into the qua iboe river at ekpene obo in oruk anam l. g. a. of akwa ibom state (udom et al., 2018) constructed wetland piggery houses obio akpa stream udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 320 2.2 experimental setup the research was conducted at the akwa ibom state university. a constructed wetland (udom et al., 2018) having three wetland cells (7 m x 1.75 m x 0.60 m) enclosed with five courses of 127 mm sandcrete blocks and 75 mm thick floor slab on a concrete foundation were created. a 2.5 mm thick texclear soil liner was laid to cover the entire wetland floor. both the wastewater inlet and outlet regions of the wetland basin were filled up to 0.60 m depth of 30 mm crushed granite rock extending one meter from the walls into the treatment area. the wetland basin was filled up to 0.60 m depth with coarse sand medium as substrate. two of the wetland cells were then planted with pennisetum clandestinum (pc) collected from the obio akpa floodplain and the third cell was the control. thereafter, the wetland was left for about three months to consolidate before being fed with wastewater. 2.3 sample collection and monitoring seven months’ grab samples data collected before and after the wetland detention time of three days were analyzed for total nitrogen (tn) and total phosphorus (tp) concentrations according to standard methods (aoac, 2007). destructive and systematic sampling techniques for plant and soil respectively were adopted. nutrient mass balances were evaluated by changes in concentration. the treatment efficiency was determined using the average influent and effluent concentrations of the water quality parameters. 2. 4 conceptual model the conceptual model for complete biogeochemical paths of mineralization of organic matter to ammonia and phosphate and subsequent transport, retention, uptake and removal (denitrification, volatilization, and burial) in the cw is shown in figure 2. figure 2: conceptual model of nutrient removal in the constructed wetland (udom et al., 2018) the model partitions the wetland into three basic compartments: (1) water column (2) wetland media, and (3) plant biomass. sources of nutrient to the wetland water column include piggery runoff, mineralization of suspended organic nitrogen and phosphorus, sediment diffusion and resuspension. atmospheric depositions play a minor role in constructed wetlands. nitrification of ammonium nitrogen occurs in the aerobic part of the soil and the water column, whereas nitrate removal by denitrification is confined to the underlying anaerobic zone of the active soil layer and near roots in the rhizosphere of wetland plants. volatilization to the atmosphere is a significant loss pathway for nitrogen under conditions of high alkalinity (reddy and delaune, 2008). in addition to influent concentrations, nitrate is produced by oxidation of ammonium ion in the water column and oxidized soil layer. phosphorus removal follows the sediment pathways of sedimentation and resuspension with no gaseous losses. the physical processes of advection (inflow, outflow), settling, resuspension, and diffusion similarly apply to inorganic phosphorus transport and fate in the wetland water. only the biologically available inorganic phosphorus (typically orthophosphate) is available for uptake by plants. imported phosphorus (runoff, sediment, ground water) and decomposition of organic matter are primary sources of inorganic phosphorus in wetland soil and water. plant uptake other loses (denitrification, volatilization) influent effluent retentions arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 321 excluding plant harvesting, burial is about the only mechanisms for the removal of phosphorus in wetlands (kadlec and wallace, 2009). 2. 5 model assumptions the following assumptions were made in the derivation of necessary first order dynamic equations describing the rate of the nutrients removal from the cw: (a) zero initial concentration of the nutrient in the cw system ( ) (b) nutrient is periodically introduced into the wetland system at the rate ( ). (c) the concentration of nutrient in the wetland at time ( ) (d) plant uptake, retention in the media, biogeochemical process constitutes the nutrient reduction pathways from the wetland system at the rate proportional to the quantity present. (e) rate of nitrogen input into the wetland from rainfall is negligible, (f) there is no percolation by groundwater (because the wetland is lined). 2.6 model derivation in wastewater treatment, a first order degradation model is often used to simulate the chemical and biological degradation of the residual mass of a chemical compound. all constructed wetland systems are considered to be an attached-growth first-order biological reactors which show an exponential decay of pollutant concentration level with the distance through the wetland from inlet to outlet. degradation in constructed wetlands follow the first order degradation model (sperling, 2007; adelegan, 2012; dotro et al., 2017), and can be represented by first order plug flow reaction kinetics expressed as: (1) where, c = concentration of the product of interest. k = first order rate constant. t = time with the above assumptions, the following mathematical model equations were derived for: (i) nitrogen ( ) ( ) ( ) ( ) where, n = nitrogen concentration (mg/l) rate of nitrogen removal from the wetland system (mgd-1) ( ) ( ) ( ) by using integrating factor, i.f ( ) ∫ ( ) ∫ multiplying both sides of (2.2) by the integrating factor, we have ( ( )) ( ) ( ) ( ) ( ) ( )dt udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 322 ∫ ( ) ∫ ( ) ( ) ∫ ( ) ( ) ∫ ( ) dividing through by ( ) ∫ ( ) ( ) suppose ( ) ( ) , then ( ) ( ) our model, results in a first order differential equation with the initial condition ( ) the initial condition represents the background concentration. the quantity of n nutrient in the wetland system is represented by ( ) ∫ ( ) ( ) this is a decay exponential function which tells us that as , the quantity of ( ) decreases to zero (0) but, not rapidly because of the presence of the influent ( ). suppose ( ) then the decay of nitrogen will be rapid. from experimental observation, the above assumption and explanation does not represent reality. hence, we assume further that the introduction of nitrogen ( ) into the system is at a constant quantity over a period of time, and then the model equation becomes ( ) ( ) ( ) ( ) ( ) ( ) by still using the method of integrating factor to find the solution of the above problem, ∫ multiplying both sides of equation (2.7) by the integrating factor, we have ( ( )) ( ) ( ) dt ∫ ( ) ∫ ( ) ⌈ ⌉ ( ) ⌈ ⌉ dividing through by ( ) ⌈ ⌉ ( ) the quantity of nitrogen that will remain in the system at after a constant quantity has been introduced into the system is represented by, arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 323 ( ) ⌈ ⌉ ( ) this shows that though the quantity of nitrogen will decay in the system it will not be totally eliminated from the system. complete removal of nitrogen in the cw is not feasible and there will still be some background concentration within the wetland system. in practice, piggery effluent is introduced into the system at a prescribed period of time, t. suppose, the first influent is at a time then the initial concentration is ( ) . and we have the model to be ( ) ( ) ( ) ( ) then solving this, we have, ( ) ( ) which means that, the concentration before the second influent is, ( ) ( ) the model for next influent, that is, is ( ) ( ) ( ) ( ) loading interval (d) wetland retention time (d) solving the above equation, we have ( ) ( ) ( ) ( ) ( ) ( ) the concentration before the third influent is ( ) ( ) the model for next influent, that is, is ( ) ( ) ( ) ( ) ( ) solving, we have ( ) ( ) ( ) ( ) the concentration before the 4th influent is ( ) ( ) the general concentration before the nth influent is (( ) ) ( ( ) ) ( ) when making the nth influent, ( ) (( ) ) ( ) ( ( ) ) ( ) ( ( ) ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 324 ( ) ( ) 2.7 summation of nutrient removal sites the above model, equation 2.19, does not take into consideration the partitioning of nitrogen into different sinks in the wetland ecosystem. to include these sinks into the model, further assumptions made and conceptualized below include, (i) rate of nitrogen input into the wetland from rainfall is negligible, (ii) rate of nitrogen uptake by plant is (iii) rate of nitrogen outflow (effluent) from the system is , (iv) the rate of nitrogen input into the wetland is (v) the rate of retention of nitrogen in the wetland water column is (vi) the rate of retention of nitrogen in the wetland medium is (vii) the rate of volatilization of nitrogen from the wetland is by introducing the above symbols representing the various wetland sinks into the conceptual model in figure 2 above, the flowchart of nitrogen distribution in the wetland ecosystem is obtained in figure 3 below figure 3: flowchart of nitrogen distribution in constructed wetland ecosystem using the above assumption and symbols, we obtain the following mass balance equation ( ) ( ) ( ) ( ) ( ) ( ) from equation ( ), we collate all the constants together ( ) ( ) ( ) then ( ) ( ) ( ) ( ) solving, we have the nitrogen removal model as, ( ) ⌈ ⌉ ( ) (ii) phosphorus phosphorus removal model was also derived based on the first order degradation model principle as nitrogen. the only difference is in the partitioning of phosphorus which does not include loss to the atmosphere as shown in figure 4 below. 𝛿 nnn n(t) 𝛽 𝛼𝑁 𝛿 휀 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 325 figure 4: flowchart of phosphorus distribution in wetland ecosystem from the assumptions and the parameters above, the model equation becomes ( ) where d = influent phosphorus concentration (mg/l) plant uptake (mg/l) amount accumulated in wetland soil and sediment (mg/l) = retention in wetland water column (mg/l) = effluent phosphorus concentration (mg/l) other parameters are as defined for nitrogen. hence, ( ) ( ) solving, we have the phosphorus removal model as ( ) ⌈ ⌉ ( ) 2.8 model solutions solutions to first order equations relating the nutrients removal from the cw were provided by using matlab version 9.2 of 2017 approach. subsequently, calibration of model constants and verification of the model were carried out using data acquired from the experiment. lastly, the model was validated by comparing observed values with model predictions. 2.9 evaluation of model performance the ability of the model to predict nutrient removal was evaluated quantitatively using the following statistics to indicate overall model performance (fox, 1981). 2.9.1 bias or mean bias ∑( ) ( ) where p and o are the predicted and observed values and n is the number of observations. 2.9.2 root mean square error (rmse) it quantifies the dispersion between simulated and measured data. √ ∑( ) ( ) d 𝛼 𝛼 𝛼 𝛼 udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 326 2.9.3 relative error (re): ̅ ( ) where, y is the mean of observed values. 2.9.4 model efficiency model efficiency (ef) was calculated as: ∑( ) ∑( ) ∑( ) ( ) 2.9.5 index of agreement (ia): ∑ ( ) ∑ ( ) ( ) where o’i = |oi | , p’i = |pi | , oi is the observed value, pi is the simulated value and is the mean of the simulated mean. d = 1 corresponds to a perfect match of predicted to observed data. 2.10 model calibration model calibration parameters for nitrogen and phosphorus removal respectively, are presented in table 1 table 1: model calibration parameters for nitrogen and phosphorus removal symbols description n p unit initial concentration of nitrogen 6.00 mg/l initial concentration of phosphorus 2.23 mg/l retention time 3 3 days rate of nutrient removal from the wetland system. 0.122 0.078 m3/day input rate (mean) 29.2 11.52 m3/day period time of introducing nutrient. 3 3 days nutrient retention in wetland water column 1.48 mg/l plant nutrient uptake 8.90 mg/l denitrification (52% of net n input) 15.2 mg/l nutrient retention in wetland sediment 5.05 mg/l effluent rate or output 2.07 m3/day plant uptake 2.08 mg/l nutrient retention in wetland sediment 2.87 mg/l retention in wetland water column 2.01 mg/l effluent rate 1.24 mg/l arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 327 model calibration was carried out using experimental data obtained between february – april, 2018. the process involved adjustment of the model parameters and forcing within the margins of the uncertainties to obtain a model representation of the processes of interest that satisfies pre-agreed criteria. 2.11 model validation parameters used as input to calibrate the model are as presented in table 2. table 2: model simulation parameters for nitrogen and phosphorus removal symbols description n p unit initial concentration of nitrogen 6.06 mg/l initial concentration of phosphorus 2.23 mg/l retention time 3 3 days rate of nutrient removal from the wetland system. 0.125 0.082 md-1 input rate (mean) 27.40 10.21 m3/day period time of introducing nutrient. 3 3 days nutrient retention in wetland water column 1.28 mg/l plant nutrient uptake 8.76 mg/l denitrification (52% of net n input) 5.82 mg/l nutrient retention in wetland sediment 5.65 mg/l effluent rate or output 1.28 m3/day plant uptake 2.43 mg/l nutrient retention in wetland sediment 2.81 mg/l retention in wetland water column 1.71 mg/l effluent rate 0.96 mg/l the validation of the model was carried out by comparison of the experimental data against the model prediction. this was done by plotting the simulated and measured graphs against time after running a calibrated model with a new set of data (independent data set) with physical parameters and the derived functions to mirror new conditions and to detect how well the model simulations fit the new data set. 3.0 results and discussion 3.1 model simulation results simulations were performed with the parameters presented in table 2 above to determine the general relationships and interactions which affect the removal of nitrogen and phosphorus in hsfcw. the model simulations after introducing mathematical equations, parameters and initial values in the state variables are shown in figures 5 and 6. udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 328 figure 5: simulated and observed variations for nitrogen removal in constructed wetland. (n(t) = nitrogen concentration in wetland system (mg/l); no = initial concentration of nitrogen (mg/l); sum of nitrogen in wetland sinks (mg/l); d = rate of nitrogen input into the wetland (m3/day; t = wetland retention time (d)) the correlation between the simulated and observed reduction of nitrogen pollutant in the wetland is shown in figures 6. there was high correlation between the simulated and observed parameters. based on table 2 also, the relationship and correlation between simulated and observed reduction in phosphorus pollutant in the cw is shown in figures 7 and 8 respectively. the high correlation coefficient observed in the removal of nitrogen was also noticed in the case of phosphorus removal from the cw. figure 6: correlation of observed and simulated removal of nitrogen in constructed wetland. 1 2 3 4 5 6 7 8 observed 2.39 1.98 1.84 1.28 0.8748 0.8748 0.8748 0.8748 predicted 2.06 2 2 1.5 1.28 1.28 1.2 1.28 0 0.5 1 1.5 2 2.5 3 s im u la te d a n d o b se rv ed n ( m g /l ) time (days) y = 0.6042x + 0.745 r² = 0.9537 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 3 n o b se rv ed n simulated 𝑁(𝑡) 𝑁 𝑒 𝛾𝑡 𝐷 𝛾 ⌈ 𝑒 𝛾𝑡⌉ arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 329 figure 7: simulated and observed variations for phosphorus removal in cw (p(t) = phosphorus concentration in wetland system (mg/l); po = initial concentration of phosphorus (mg/l); k = sum of phosphorus in wetland sinks (mg/l); d = = rate of phosphorus input into the wetland (m3/day); t = wetland retention time (d)) the correlation between the simulated and observed reduction of phosphorus in the wetland is shown in figure 8. there was high correlation between the simulated and observed parameters. figure 8: correlation of observed and simulated removal of phosphorus in cw (y = predicted values; x = observed values) 3.2 process model assumptions and development nutrients stored within plant tissues can potentially be returned to water or enter components of the wetland upon senescence. many aquatic plants undergo complete senescence before dormancy potentially releasing soluble nutrients to the water. in this model, nutrient release owing to plant die off was not considered to have an input into the wetland since the macrophytes are expected to be harvested young for feeding the pigs. 1 2 3 4 5 6 7 8 predicted 2.53 2.15 1.97 1.69 0.92 0.92 0.84 0.8 observed 2.57 2.4 2.02 1.8 1.06 1.04 0.98 0.96 0 0.5 1 1.5 2 2.5 3 s im u la te d a n d o b se rv ed p ( m g /l ) time (days) y = 1.0169x 0.1533 r² = 0.9912 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 p s im u la te d p observed 𝑃(𝑡) 𝑃 𝑒 𝑘𝑡 𝐷 𝑘 ⌈ 𝑒 𝑘𝑡⌉ udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 330 denitrification of nitrogen is predominantly the source of nutrient loss to the atmosphere by wetlands that receive high nitrate loadings from agricultural runoff or wastewater treatment plant discharge. this is because of the presence of anoxic conditions in wetlands, which makes microbial denitrification of nitrates to gaseous forms of nitrogen in wetlands and their subsequent release to the atmosphere remain one of the more significant ways in which nitrogen is lost from the soil and water to the atmosphere. denitrification is primarily performed by bacteria that are heterotrophic, meaning they require a carbon source for growth and energy. wetland plants are a key source of this carbon. since denitrification is facilitated by microbes, the process is temperature-dependent. higher rates of denitrification occur during higher temperatures when the bacteria are more active. thereby, successful application of sfws largely depends on the effectiveness of this process. the process ensures permanent removal of n. quantifying denitrification in constructed wetlands is critical because it is often cited as the dominant mechanism of n removal (casey et al., 2001). pollutant fluxes due to precipitation and exchange with subsurface are negligible compared to other mechanisms. this is because the wetland was sealed to avoid possible contamination of groundwater and also to prevent groundwater from infiltrating into the wetland. in this study, the amount of nitrogen and phosphorus concentrations decreased exponentially within three days of retention in the wetland, and thereafter, the reduction appeared constant over higher retention time subject to the decay coefficient. the wetland design was based on first order plug flow reaction which is characterized by decay reaction that estimates a decline in pollutant concentrations through the wetland provided the incoming concentration levels exceed that of the wetland. the observed variation in wetland nitrogen concentration could be attributed to residence time. this observation is consistent with that of kadlec and wallace (2009) for horizontal subsurface flow wetlands who reported an exponential reduction in nitrogen with increase in residence time. the correlation between the observed and simulated removal rates for n and p in figures 6 and 8 showed good agreement for n (r2 = 0.9537) and for p (r2 = 0.9912) respectively. the linear regression coefficients are very good since the system was a natural system located in the field, where uncontrolled influencing factors could weaken optimal performance according to jørgensen and bendoricchio, (2001). 3.3 statistical indicators of model performance statistical indicators of model performance are presented in table 3. table 3: statistical indicators of model performance nutrient r2 r mean bias error (mm) root mean square error (mm) relative error (%) model efficiency (%) index of agreement nitrogen 0.9537 0.9766 0.211 0.32 24 84 0.6527 phosphorus 0.9912 0.9956 0.139 0.18 12 77 0.8676 various procedures for evaluating model predictive accuracy have been recommended for numerical data. of these measures, besides r and r2, mbe and root mse (rmse) are among the arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 331 most commonly used or recommended measures (liu et al., 2011; bennett et al., 2013). these statistical pointers of simulation performance are summarized in table 3. the rate of coefficient of determination (r2, 0.9537, 0.9912) shows that a good inter-relation occurs amongst observed and simulated values for both nitrogen and phosphorus respectively. tiffany et al., (2017) observed r2 values between 0.70 and 0.99 with an average of 0.95 in first order decay models in subsurface-flow constructed wetland mesocosms. the lower r2 values were detected during the cold months when average water temperature was below 12 ◦c. but, all estimates throughout the growing season had r2 values above 0.90. similarly, kadlec (2000), obtained an r2 of 0.95 when some variations of the plug flow models were fitted to data from practically all kinds of treatment wetlands. it is expected that with the high temperature in the tropics, r2 are likely to be higher than reported above since many individual wetland processes, such as microbial mediated reactions, are affected by temperature (kadlec and reddy, 2001). the values of r2, 0.9537 and 0.9912 for nitrogen and phosphorus respectively shows that the first order decay model provided stronger statistical agreement between their predicted and measured removal rates. generally, a higher coefficient indicates a better fit for the model. the mbe provides information on the long-term performance of a model. the smaller the absolute value, the better the model performance. the rate of mbe is equal to 0.21 and 0.14 mm for both nitrogen and phosphorus respectively. a positive value of mbe indicates overestimation and vice-versa. the rmse provides information on the short-term performance of a model by allowing a term by term comparison of the actual difference between the estimated value and the measured value. the smaller the value, the better the model's performance. the root mean square errors are 0.32 and 0.18 mm for both nitrogen and phosphorus. the extent of root mean square error (rmse) is a convenient parameter of model performance. in a perfect condition, the values of relative error (re) and the model efficiency (ef) will be 0% and 100%, respectively. so the recorded re value of about 24% and 12 % and ef value of about 84% and 77% indicate that the performance of model in simulating actual removal of the nutrients was good for nitrogen and phosphorus. the limit of index of agreement (d) value is from 0 to 1. a higher value indicates a better agreement between the simulated and observed values. in this study, the value of d (0.6527 and 0.8676) shows a good performance of the model in removing the nutrients. however, much deviation from the ideal value for the model may be due to inherent assumptions in the model principle, and also in the field data. for example, the model assumes the steady-state condition but in reality, this may not be true (as the flux varies with the change in moisture level and atmospheric demand). saturation of phosphorus in the wetland bed and /or low bed permeability of the parent material used for bed construction could impair phosphorus removal efficiency as observed by karczmarczyk (2004). 3.2.3 model applications and limitations the models developed in this study are appropriate for performance analysis of hsfcw receiving secondary piggery wastewater. their application needs the knowledge of inflow concentrations (mg/l) of organic nitrogen and phosphorus in the wetland and the inflow rate. the initial values of nitrogen and phosphorus in the soil and in the wastewater are also required. 4.0 conclusion this study developed mathematical models for prediction of nitrogen and phosphorus removal from secondary piggery wastewater treated in hsfcw. the model partitions the wetland into three basic compartments: (1) water column (2) wetland media, and (3) plant biomass. major udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 332 processes considered were wastewater influent, retention, plant uptake and effluent in nitrogen and phosphorus respectively and volatilization to the atmosphere in nitrogen only. mathematical equations created from the conceptual model were developed from first principles based on input-output variables of mass balance principles. a series of field experiments were continuously carried out over a period of seven months. the water quality of influent and effluent wastewater was analyzed and mass balance changes in the wetland sediment and plants were observed and balanced with the influent. the observed deficit was accounted for by losses such as volatilization in the case of nitrogen. simulation results from the model agreed well with the results from the experiments. the difference between computed and measured removal rate was less than 20% and 30% for nitrogen and phosphorus respectively. this shows that the model and the calibrated parameters were rational. the model can be considered suitable for simulation of nitrogen and phosphorus removal in hssf cws operating under similar conditions (climatic conditions, wastewater composition, porous filter material and plant species). but, scaling-up results from this study can be challenging as physical processes can show temporal and spatial variation, which can affect the assumptions on which the derivation of this model was based. the model efficiencies are good but can be improved by extensive data. therefore, longer field studies must be conducted to complement the results of this study for constructed wetland design. although the models developed in this study offered a good prediction of nitrogen and phosphorus removal from hssfcw, the most important consideration however, is whether the resulting effluent meets the water quality discharge or reuse standards of the area with regards to intended use. for this study, the effluent met nigerian water quality standards for discharge to land and surface water. references abbasi, hn., xie, j., hussain, si., and lu, x. 2019. nutrient removal in hybrid constructed wetlands: spatial-seasonal variation and the effect of vegetation. water science and technology , 79 (10): 1985–1994. adelegan, ja. 2012. wetland system: a cheaper and efficient treatment option for food processing waste in africa. world congress on water, climate and energy. dublin, ireland. may 13-18. 2012. allen, h. 2019. personal email communication. www.iseesystems.com. aoac 2007. official methods of analysis. association of official analytical chemists. washington dc. bennett, nd., croke, bfw., guariso, g., guillaume, jha., hamilton, sh. and jakeman, aj, 2013. characterising performance of environmental models. environmental modelling and software, 40: 1–20. brovelli, a., malaguella, f., bary, da. 2009. bioclogging in porous media: model development and sensitivity to initial conditions. environmental modelling and software, 24(5): 611-626. casey, re., taylor, md., and klaine, sj. 2001. mechanisms of nutrient attenuation in a subsurface flow riparian wetland. journal of environmental quality, 30:1732–1737. dotro, g., langergraber, g., molle, p., nivala, j., puigagut, j., stein, o. and sperling mv. 2017. treatment wetlands. iwa task group on mainstreaming the use of treatment wetlands. iwa publishing, alliance house, 12 caxton street, london sw1h 0qs, uk. ecc. 1999. effluent management guidelines for intensive piggeries in australia australian and new zealand environment and conservation council. tel:1985 tel:1994 http://www.iseesystems.com/ arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):317-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 333 epa. 2000. constructed wetlands treatment of municipal wastewaters. alternative systems for piggery effluent treatment. united states environmental protection agency. http://www.epa.sa.gov.au/. ewuziem, je., nwosu, ac., amaechi, ecc., aniebo, ao. and anyaebu, po. 2009. piggery waste management and profitability of pig farming in imo state, nigeria. nigerian agricultural journal, 4(1-2):42 – 53. fox, dg. 1981. judging air quality model performance. bulletin of american meteorological society, 62:599-609 giraldi, dm., michieli, de v. and iannelli, r. 2010. fitovert: a dynamic numerical model of subsurface vertical flow constructed wetlands. environmental modeling software, 25(5) :633– 640. gouriveau, f. 2009. constructed farm wetland designed for remediation of farmyard runoff: an evaluation of their water treatment efficiency, ecological value, costs and benefits. phd thesis – university of edinburg. www.geos.ed.ac.uk/homes/s0568230/phd-thesis-fabricegouriveau.pdf. accessed 12th december 2020. horton, ra,. wing, s., marshall, sw and brownchery, ka. 2009. malodour as a trigger of stress and negative mood in neighbours of hog operations. american journal of public health 99(3): 610-615. jørgensen, se. and bendoricchio, g. 2001. fundamentals of ecological modelling. third edition. elsevier science ltd. united kingdom. kadlec, rh. and wallace, sd. 2009. treatment wetlands. 2nd edition; crc press boca, raton fl, usa. kadurumba, c., kadurumba, oe. and enekwachi, me. 2019. piggery waste management practices and environmental implications on human health in rivers state, nigeria. international journal of agriculture and rural development,. 22(1): 4161– 4166. kadaverugu, r. 2016. modeling of subsurface horizontal flow constructed wetlands using openfoam_model. earth systems and environment 2:55-65 kadlec, rh. and wallace, sd. 2009. treatment wetlands. 2nd edition; crc press boca, raton fl, usa. kadlec, rh. 2000. the inadequacy of first-order treatment models. ecological engineering, 15(1): 105-119. kadlec, rh. and reddy, kr. 2001. temperature effects in treatment wetlands. water environment research, 73(5): 543-557 url: http://www.jstor.org/stable/25045537 karczmarczyk, a. 2004. phosphorus removal from domestic wastewater in horizontal subsurface flow constructed wetland after 8 years of operation – a case study, journal of environmental engineering and landscape management, 12(4):126-131 kiely, g. 1998. environmental engineering. mcgraw hill, new york. liu, c., white, m. and newell, g. 2011. measuring and comparing the accuracy of species distribution models with presence-absence data. ecography, 34: 232–243. mason, c. 2002. biology of freshwater pollution, fourth edition. pearson educational ltd, edinburg gate, harlow, essex, uk. http://www.epa.sa.gov.au/ tel:1981 http://www.geos.ed.ac.uk/homes/s0568230/phd-thesis-fabrice-gouriveau.pdf http://www.geos.ed.ac.uk/homes/s0568230/phd-thesis-fabrice-gouriveau.pdf http://www.jstor.org/stable/25045537 udom: mathematical prediction of nitrogen and phosphorus removal from piggery wastewater by horizontal sub-surface flow constructed wetland. azojete, 17(3):317-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 334 messer, tl., burchell, mr. and bírgand, f. 2017. comparison of four nitrate removal kinetic models in two distinct wetland restoration mesocosm systems. water, 9: 517-530. mburu n., rousseau, rdl., van-bruggen, jja. and lens, pnl. 2012. potential of cyperus payrus macrophyte for wastewater treatment: a review. 12th international conference on wetland systems for water pollution. 4th – 9th october, 2012, venice, italy. muga, hf. and mihelcic, r. 2008. sustainability of wastewater treatment technologies. journal of environmental management, 88(3): 437-447. nandakumar, s., pipil, h., ray, s. and haritash, ak. 2019. removal of phosphorous and nitrogen from wastewater in brachiaria-based constructed wetland. chemosphere, 233 :216222. npc. 2006. national population commission, abuja, nigeria. ogbuewu, ip., odoemenam, vu., omede, aa., durunna, cs., emenalom, mc., uchegbu, mc., okoli, c. and iloeje, mu. 2012. livestock waste and its impact on the environment. scientific journal of review, 1(2): 17 – 32. reddy, ka. and delaune, rd. 2008. biogeochemistry of wetlands: science and applications. crc press. boca raton, fl. simunek, sj., genuchten, mth.van. and sejna, m. 2010. developments and applications of the hydrus and stanmod software packages and related codes. vadoze zone journal, 7: 587600. soare, e. and chiurciu, i. 2017. study on the pork market worldwide. scientific papers series: management, economic engineering in agriculture and rural development, 17(4): 321-326. sperling, mv. 2007. basic principles of wastewater treatment. iwa publishing, alliance house, 12 caxton street, london sw1h 0qs, uk uddin io. and osasogie, di. 2016. constraints of pig production in nigeria: a case study of edo central agricultural zone of edo state. asian research journa of agriculture, 2(24):1-7 udom, ij., mbajiorgu, cc. and oboho, eo. 2018. development and evaluation of a constructed pilot-scale horizontal subsurface flow wetland treating piggery wastewater for pollution control. ain shams engineering journal, (9): 3179–3185. wallace, sd., and knight, rl. 2006. small-scale constructed wetland treatment systems: feasibility, design criteria, and o & m requirements. final report, project 01-cts. water environment research foundation (werf). alexandria. virginia. wendee, s. 2000. intensive livestock operations, health and quality of life among eastern carolina residents. environmental health perspectives, 108(3): 233-238. zamani, j. 2016. opposite effects of two organic wastes on the physical quality of an agricultural soil. archives of agronomy and soil science, 62(3): 413-427 tel:2019 tel:233 tel:216-222 tel:216-222 availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 37-44 copyright © faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng development of a manure spreader adgidzi, d 1 ; a.a. balami 1 and m. bashir 2 abstract a manure spreader was designed, constructed and evaluated. cow dung collected from abattoirs was composted and used to test the machine in the field. bulk density, moisture content, angle of repose and coefficient of friction of the composted dung were determined and found to be 791.9 kgm-3, 44%, 420 and 0.88 respectively. the developed machine was tested in the field using the organic manure and the following parameters were obtained: rate of application of 5.9 tha-1, field capacity of 0.6 hah-1, efficiency of discharge of 86% (when fed with a 75 kg of the manure) and operating width of 1.096 m. 1. introduction in any crop production system, application of fertilizer is important is one of the essential operations to be carried out. fertilizer application is usually carried out in areas where the soil fertility is low and depends on factors such as texture of the soil, bulk density, stage of crop development, time of application, labour and equipment available. organic matter is a major source of nutrients for plants. organic substances help in adsorption processes, improving soil structure, moisture retention capacity, water and air permeability and temperature. both chemical and natural fertilizers can perform the above functions, although the latter is recommended. overuse of chemical fertilizer over the years has been linked to nitrate contamination of rivers, lakes and wells due to leaching and runoff of excessive nitrogen. excess nitrate levels in leafy vegetables like spinach and tomatoes are converted to nitrates which are toxic and are strongly linked to stomach cancer. this problem is avoided when compost and natural manure are used because they release their nitrogen slowly (leonard, 1986). in developing countries, there is limited use of organic manure due to its high labour requirement, scarcity of machines for spreading it and also due to introduction of chemical fertilizer, which is easier to handle (leonard, 1986). manual application of fertilizer by scattering or placement close to the plants may be very effective, but is laborious and can only be used where the land area is small (archer, 1996). advancement in technology has brought about the development of different machines for the application of both chemical fertilizer and organic manure. smith and wilkes (1980) classified manure spreaders according to their driving method, namely, ground driven and p.t.o. driven. the ground driven manure spreader such as the trailer type manure spreader is operated by sprocket and chain from the land wheels. an example of the p.t.o. driven is the rotary spreader, which is simple in design and requires minimum maintenance (lovegrove, 1968). 1 department of agricultural engineering, federal university of technology, minna, nigeria 2 department of agricultural engineering, kaduna polytechnic, kaduna, nigeria. development of a manure spreader 38 the manure spreader is usually power driven by the tractor p.t.o. and employs the same basic principles as the spreading mechanism of the trailer spreader. manure is first moved to the field and deposited in small heaps at regular intervals in rows of 360 – 450 mm apart. the machine is then driven down the rows, shredding the heaps. the liquid manure spreader, according to smith and wilkes (1980), is meant to distribute the fertilizer through the use of mobile tank with a vacuum pump or centrifugal pump, which are both driven by the p.t.o. due to the increasing cost of chemical fertilizer and new federal and state environmental laws, attention has been directed to the addition of animal dung to cultivated lands (john, 1979; archer, 1996). the developed countries have been able to sustain the use of animal manure because of the availability of machinery for its handling. in nigeria, the use of animal manure is not widespread because of high cost of machines and the tedious nature of collecting the manures. it is against this background that a manure spreader was designed and constructed for small and medium-scale farmers using locally sourced materials. 2. materials and methods the materials used for the construction of the machine were locally sourced machine and cow dung was collected from abattoirs in kaduna, nigeria. the cow dung was used for the preparation of the organic manure based on existing agronomic practices as given by yawalkar et al. (1965). 2.1 determination of properties of manure in order to select the best machine parameters for the construction of the machine components such as hopper, power requirement and the spreading mechanism, four properties of the manure were determined namely, angle of repose, coefficient of friction, bulk density and moisture content. 2.1.1 angle of repose the angle of repose was used to select the angle at which the trapezoidal section of the hopper should be slanted. the angle of repose was determined by adapting the method given by mohsenin (1978), in which an adjustable table was used to tilt 10 g of the prepared manure cubes placed in a container until the manure began to fall. the mean of 10 readings was taken as the angle of repose of the material. 2.1.2 coefficient of friction this was used to determine the flow of manure from the hopper. the readings earlier determined for the angle of repose were used to calculate the coefficient of friction (µ), as: µ = tanβ where β = angle of repose (friction). angles of repose (friction) were determined for metal, wood and rubber surfaces. azojete vol. 5 2007 39 2.1.3 bulk density and moisture content bulk density and the moisture content were used to determine the uniformity of distribution of the manure. the moisture content was determined by the oven-drying method at a temperature of 104 0 c for 24 hours (sidney, 1963). after the determination of the properties of the manure, the design of the machine parameters and components were based on the procedures given by bosoi et al. (1988), lovegrove, (1968), kepner et al. (1982) shippen et al. (1980), asae (1998); spivakovsky and dyachkov (1983) and reshetov (1978). 2.2 design calculations 2.2.1 power requirement the power (p) required to operate the spreading mechanism and the agitator was determined as follows: 367 c p 0ql  1 where q = capacity, kgmin -1 l = length of conveyer, m co = frictional factor but  ktndq 247 where ψ = capacity factor ∫ = density of manure d = diameter of shaft t = pitch of conveyer = 0.5d n = speed of conveyor k = angle of rise the power required at the agitator is the same as that of the spreading mechanism since they have the same width and the same formula is used. 2.2.2 the hopper the hopper capacity (vh) was determined by the relationship. vh = vr + vt where vr = volume of the rectangular portion of the hopper, m 3 vt = volume of the trapezoidal portion of the hopper, m 3 the hopper is slanted at 40 0 being the angle of repose of manure which varies between 38 0 and 50 0 (bosoi et al., 1988). development of a manure spreader 40 2.2.3 power transmission the spreader is powered by the tractor pto using a belt-pulley arrangement (figure 1). a b c d e figure 1: layout of the power transmission a = pto of the tractor, b = gear box, c = driving pulley, d = driven pulley, e = flail rotor 2.2.4 the output shaft design the diameter of the gearbox output shaft was calculated from the amse code for the design of transmission shaft equation given below.     2 23 16 bbtt s kmkmd   2 where mt, mb = torsional and bending moments, nm kt, kb = fatigue and shock factors for torsional and bending moments s = allowable stress, nm -2 for torsional deflection of the shaft, the angle of twist was calculated as follows: s = 4 584 dg lm t t 3 where gt = modulus of torsional shear, nm -2 azojete vol. 5 2007 41 the shaft of the spreading mechanism was also designed using equations 2 and 3 above. since the telescopic shaft is subjected only to torsional stress, the diameter of this shaft was calculated from equation 4 below. s tm d  163  4 2.3 performance evaluation the machine was loaded with 75 kg of composted manure and tested over a 100 m distance in the field. rate of application, field capacity and field efficiency were evaluated using equations 5 – 7 respectively. spreading pattern indicates the degree of uniformity of distribution of material across the swath and was determined by running the spreader over the test distance divided into ten (10) equal parts of 10m each and weighing the gathered quantity of manure spread on each of the parts. ten test runs were carried out. the coefficient of variation (cv) was determined to express the uniformity of distribution. lw qk r  5 c = sw (hunt, 1972): 6 lq q e  7 where q = weight of composted manure already spread, kg w = swath width, m k = constant l = distance covered, m ql = 3. result and discussion 3.1 construction and principles of operation of the manure spreader the main features of the spreader are the hopper, frame, power transmission unit, spreading mechanism and wheels. the hopper is rectangular in shape and tapers from the top to bottom and serves as the feeding chute to the spreading unit. it was constructed with a 2 mm thick metal sheet. the power transmission unit consists of a telescopic shaft, a gearbox with bevel gears, three pulleys, bearings, shafts and v-belts. a 45 kw tractor, 540rpm p.t.o shaft of diameter 35mm with six splines, was used to drive the agitator and the spreading mechanism through the gear box. one pulley each was mounted on the gearbox output shaft, the agitator shaft and the spreader shaft. the manure agitator has 23 spikes welded at 35 mm spacing development of a manure spreader 42 along its length to allow uniform flow of manure to the spreading mechanism that consists of a rotor carried on two bearings and attached to it in three rows. along the entire length of the rotor are 36 flails fixed 35 mm apart. the flails are made of small pieces of mild steel bars welded to the rotor. the machine receives power from the tractor pto through the telescopic shaft. the major components of the spreader are mounted on a frame made from rectangular steel 50 mm x 50 mm. 3.2 manure and machine characteristics bulk density, angle of repose, coefficient of friction, ph and moisture content of the manure used were 791.9 kg/m 3 , 42 o , 0.88, 7.7 and 44% respectively. the machine discharged an average of 64.54 kg out of the 75 kg fed into the machine for the ten test runs conducted. this gives the spreading efficiency of 86.05%. the distance was covered at an average interval of 66.06 seconds, and a spreading width of 1.09 m when the hopper discharge aperture was fully opened (table 1). at the maximum opening of the hopper, the application rate was 5.9 tons/ha. reducing the discharge aperture reduces both application rate and the spreading efficiency. a field capacity of 0.6 ha/h was achieved when the machine was operated at a speed of 1.5 m/s with a width of 1.09 m. using the data for the spreading pattern (table 2), the coefficient of variation obtained with this machine was 1.08% and this is within acceptable limit (gomez and gomez, 1986). table 1: field test results with hopper aperture fully opened over a distance of 100 m and an initial weight of compost of 75 kg s/no time (s) width of spreading, w (m) weight of material spread, q (kg) 1 67.34 1.10 65.4 2 67.00 1.08 63.3 3 66.45 1.10 63.5 4 66.50 1.08 65.4 5 68.10 1.08 66.5 6 65.81 1.10 64.6 7 64.34 1.15 63.4 8 63.52 1.10 63.6 9 65.40 1.09 64.5 10 66.41 1.08 65.2 mean 66.06 1.10 64.5 azojete vol. 5 2007 43 t able 2: spreadiing pattern results s/no weight of material spread, xi (kg) square of deviation (xi – xm) 2 1 6.52 0.0004 2 6.50 0.00 3 6.46 0.0016 4 6.45 0.0025 5 6.40 0.01 6 6.42 0.0064 7 6.55 0.0025 8 6.63 0.0169 9 6.50 0.00 10 6.57 0.0049 mean 6.50 0.0452 4. conclusion a manure spreader was designed, constructed and performance evaluation carried out on the developed machine in the field using cow-dung. the developed machine gave an efficiency of 86%, field capacity of 0.6 ha/hr and rate of application of 5.9 tons/ha. with proper selection of hopper size and the spreading mechanism, and selecting the appropriate tractor power requirement, the machine can be used by farmers in developing countries. the parts required for the development of such a manure spreader can be sourced locally and organic manure can also be found in abundance from abattoirs around nigeria. the machine requires only one person (the tractor operator) to operate. references archer, j. (1996). soils and nutrients. mcgraw hill publishers, london. asae (1998). asae standard hland book 45 th edition: s.e.st.joseph,u.s.a. adamu, s.o. and t.l johnson (1975). statistics for beginners. onibonoje press, ibadan, 286p. basher, i.m. (2001). development of a manure spreader. unpublished. m. eng. thesis. department of agric engineering, federal university of technology minna, nigeria. bosoi, e.s.; o.v. verniaer, i. smirnov and e.e. subtain-sheak (1988). theory, construction and calculation of agricultural machines. vol. i mic publishers, moscow. gomez, k.a. and a.a. gomez, (1986). statistical procedures for agricultural research. john wiley and sons,u.s.a. hunt, d. (1972). farm power and machinery. iowa state university press. u.s.a. john, g. (1979). freams elements of agriculture. john murray publishers ltd. london kepner, r.a.; r. bainer and l. barger (1982). principles of farm machinery. 3 rd edition, av i publishers. inc. connecticut, u.s.a. development of a manure spreader 44 leonard, d. (198). soils, crops and fertilizer use. a field manual for development workers. 4 th edition pp 130 134. lovegrove, h.t. (1968). crop production equipment. anchor press ltd. gb. mohsenin, n. (1986). properties of plant and animal materials. gordon and breech s. publishers, u.s.a. reshetov, d.n. (1978). machine design. mir pupilishers. moscow. shippen, j.m.; c.r. elhir and c.h. clover (1980). basic farm machinery. pergamon press. u.s.a. smith, h.p.and s.h. wilkes (1980). farm machinery and equipment. 6 th edition mcgraw hill publishers. london. spivakovsky,a. and v. dyachkov (1983). conveying machines. mir. publishers, moscow. stone, a.a and h.e. gulvin (1986). machines for power farming, 3 rd edition, john wiley and. sons. n.y., u.s.a. yawalkar,k.s.; u.p. agarwal and c. bokde (1865). manure and fertilizer. agricultural horticulture publishing house, india 28_51. arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):319-330 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 319 original research article towards sustainable road infrastructure delivery in nigeria o. m. oraegbune department of civil engineering, modibbo adama university, yola adamawa state, nigeria *corresponding author’s email address: irokom0013june@gmail.com 1.0 introduction road or general infrastructure development plays a vital role in determining environmental sustainability. it is essentially intermeshed with economic growth, people’s lives or livelihood and environmental sustainability. road infrastructure projects are often large in scope and financial scale. they require high energy input, huge resource consumption, considerable land use and all elements which may cause serious impacts on the environment and society (yang and lim, 2008). therefore, current road infrastructure development in nigeria will have impact on future sustainability and people’s welfare for many years. while their impacts to environmental and social issues are of great concerns, infrastructure development also underpins a nation’s economy and prosperity, therefore, it is equally important and necessary to take cognizance of this advantage and balance the constraints and develop sustainable road infrastructure projects in the country. nigerian stakeholders (both private and public sectors), are under pressure looking for economically feasible, socially viable and environmentally acceptable project management techniques that will lead to the actualization of projects with sustainability elements with respect to the economy, environment, and society. this will require not only the adoption of sustainability principles during project conception, planning, design and innovative technologies and products during construction but also the evaluation of results of doings so and the consideration of accountability during project delivery. however, current efforts to integrate sustainability elements into project conception, planning and execution, are often impeded by different interpretation on sustainability by stakeholders involved in road infrastructure development. as a result, achieving sustainability outcomes for all stakeholders in road projects remains as a formidable task. article information abstract due to current federal government infrastructure transformation policy agenda and economic development growth, there is a lot of pressure on nigeria’s infrastructure, especially on roads. the construction of roads is capital intensive requiring long-term financial supports. the aim of this paper is to investigate the theory and practice that adopt sustainability concept at road and general infrastructure delivery in nigeria. multi-criteria decision model or method was used (weighted sum model) for sustainability index. the mathematical model for computing the sustainability index in achieving the required result was formulated. additionally, a cognitive/reasoning map system was used as decision aid. the result shows that sustainability criteria and indicators are chosen based on the project specific or regional priorities or needs. the study also showed that there is no systematic method of sustainability appraisal in nigerian construction industry. it proposed both multi-criteria method of analysis and cognitive/reasoning map because of their mathematical foundation and practical applications, and recommends that sustainability drivers should be integrated with their different perceptions and priority needs. it also recommended the introduction of sustainability impact assessment. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 december, 2021 revised 31 march, 2022 accepted 6 april, 2022 keywords: performance indicators, road infrastructure sustainability, assessment model, sustainability domains and weighted sum model http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com irokom0013june@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):319-330. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 320 the above problem calls for the need to formulate new approaches that are able to integrate and synthesize all the dimensions and different points of view for the logistic consideration by multiple stakeholders in developing sustainable road infrastructure (oraegbune, 2015). the successful implementation of sustainability consideration in general infrastructure (road) development may be a viable method to improve the current situation and its shortcomings. enhancing sustainability of project allows for more environmentally – friendly and socially acceptable operations. the anticipated benefits of sustainability enhancement in road and general infrastructure development are as follows: i. improvement of the quality of urban and road life both in the short and long – terms. ii. protection of the local environmental and reduction in impact on the worldwide environment from a long – term point of view. iii. preserving environmental, social and cultural assets for future generations. iv. improving the economic efficiency and life cycle of the road infrastructure and some other utilities/services. implementation of sustainability can be achieved in two ways: firstly by gaining institutional support of implementation and secondly by developing and utilizing new technologies that change current practice and provide more sustainable approaches (koo and ariaratnam, 2009). despite the attention focused on sustainability, neither standard road map or measurement nor a systematic approach of assessment have been officially adopted or developed for use or implementation in nigeria infrastructure system, although some advanced countries have adopted or developed their own assessment systems in infrastructure or road projects. the aim of this paper is to investigate the theory and practice that adopt sustainability concept in road infrastructure delivery in nigeria. the study covers current conceptual applications of sustainability development to the theoretical and practical model for sustainable infrastructure delivery (road projects) in nigeria. the topics discussed are the following: current sustainability analysis method, sustainability criteria and indicator identification and sustainability assessment tools which uses weighed sum model. 2. key performance indicators as a tool for road infrastructure in recent studies which identified key performance indicators for infrastructure in the south african/hong kong construction indicators, ugwu and haupt (2005) developed a comprehensive list of key sustainability items and their indicators (table 1). these constructs incorporate internationally accepted matrices such as economy, environment and society. furthermore, as suggested by the industry operators, they incorporate other performance – based indicators such as health and safety, resource utilization and aspects related to project management (oraegbune, 2015). table 1: key sustainability items and indicators in infrastructure sustainability s/n key sustainability items indicators sub-indicators 1. economy direct cost initial cost, life cycle cost indirect cost resettling cost of people /rehabilitating cost of ecosystem, adverse impact in tourism values and employment of labour. 2. environment land use extent of land acquisition, extent of tree falling, extent of loss of habitat or feeding grounds, connectivity with hinter land. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com oraegbune: towards sustainable road infrastructure delivery in nigeria. azojete, 18(2):319-330. issn 1596-2644; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 321 water impact as to assessment under environment impact assessment regulation (eiar) and water reuse. air impact as to assessment under eiar, air outlet design, ventilation design during construction and service stage. noise impacts as to assessment under eiar design flexibility for noise reduction measures. visual impact impact as to assessment under eiar, view from assessor, harmony with surrounding. ecology impact as to assessment under eiar, reprovision of habitat. waste management solid construction materials, liquid waste –toxic and non-toxic, extent of encroachment upon concerned areas. 3. society cultural heritage footprint of project in archaeological site, complaints from local parties/villages and extent of diversion. public access extent of blockage, extent of congestion and view from local authorities. public perception 4. resource utilization site access routes for construction traffic and availability of construction material. material availability use of local materials and those complementary with chosen materials. type prefabricated materials and innovative materials. constructability early contractors’ involvement and early suppliers’ involvement. reusability reusability of moulds, formwork etc and scrap value after decommissioning. quality assurance ease of quality control 5. health and safety occupational hazard short term health (e.g. spread of diseases, cleanliness of site etc), long term health (e.g. respiratory duct disease, permanent deafness etc). accident, injuries, fatalities etc. public general, health and safety 6. project management/ administration contract type of contract, inclusion of sustainability related clauses in project specification, project duration project complexity and amount of paper. procurement method approach to/criteria for procuring contractors and supplier’s choice of delivery system (e.g. design-build). source: lim (2009) and ugwu and haupt (2005) several reasons for holes or gap in the implementation of sustainability principles by construction stakeholders in infrastructure projects have been advanced by researchers (oraegbune, 2015, and ugwu and haupt, 2005) as follows: (1) lack of education and mind sets of stakeholders (especially of the construction decision –making), has significant impacts on infrastructure sustainability throughout the projects life cycle; (2) short-term focus rather than a long-term view during decision making, and (3) lack of flexible user friendly tools to facilitate quantitative analysis and decision support. 2.3 current methods for sustainability assessment current methods of sustainability assessment being employed in the infrastructure industry and that can be usable in road construction projects for excellent results are presented in table 2. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):319-330. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 322 table 2: assessment model for sustainable infrastructure sustainability assessment tools summary civil engineering quality assessment and awards scheme. * aimed at improving sustainability in civil engineering and public realm projects by providing an incentive to clients, designers and contractors to adopt best environmental and social practices and therefore deliver more sustainable constructions. project sustainability management (psm) guidelines developed by the international federation of consulting engineers. * these constructs/concepts incorporate internationally and accepted sustainability matrices such as economy, environment and society. it also incorporates other performancebased indicators such as health and safety, resource utilization and project management. australia green infrastructure council australia. * agic infrastructure sustainability rating scheme and associated tool is still in the early stage of development of sustainability categories and 27 sub-categories have been identified, covering the areas of project management, and governance, economic performance. defence estate sustainability appraisal tool (desat) developed by australia ministry of defence. * this sustainability appraisal tool has been produced to help mod project managers, decision-making and construction to fulfil their environmental objectives. sustainable project appraisal routine (spear) developed by australia consulting company (arup). * a design tool enabling companies and organizations to assess their sustainability performance over time. the tool is applicable to wide range of sections and to all levels of projects from strategic policy development to individual project assessment. vic roads sustainable roads assessment (sra), developed by victoria government in australia. * the tool aims to guide the road, construction industry towards more sustainable practices. green highway partnership developed by u.s.a (epa & fhwa). * for transportation infrastructure projects. this is mainly sustainability performance metric for measurement systems that provided guidance specific to building more sustainable transport projects. green highway construction in taiwan. * another infrastructure designing and construction rating system available for sustainable infrastructure projects. a collection of sustainability best practices which can be applied to any roadway projects. source oraegbune (2015) from table 2, the project stakeholder can select the method that best suit the project at hand. 2.4.1 multi-criteria decision method (mcdm) in the multi-criteria method, the weighted sum model (wsm) is used formulate the mathematical model for computing the sustainability index (si). the appraisal matrix from which the model can be formulated is presented in table 3. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com oraegbune: towards sustainable road infrastructure delivery in nigeria. azojete, 18(2):319-330. issn 1596-2644; e-issn 25455818, www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 323 table 3: sustainability appraisal decision matrix design alternatives or options sustainability criteria sc1 sc2 sc3 sc4 scn w1 w2 w3 w3 wn a1 a2 a3 am a1,1 a2,1 a3,1 am,1 a1,2 a2,2 a3,2 am,2 a1,3 a2,3 a3,3 am,3 a1,4 a2,4 a3,4 am,4 a1,n a2,n a3,n am,n source: (oraegbune, 2015 and ugwu et al., 2006) key =𝑆𝑐𝑖 = sustainability criteria = 𝐷𝑖 or 𝐴𝑖 = design alternative 𝐴𝑖𝑗 or 𝐷𝑖𝑗 = user assigned utility (scalar value) that measures the performance of 𝐴𝑖 or 𝐷𝑖 on 𝑆𝑐𝑖 the sustainability index (si) is defined as a crisp value that is an aggregated measure of performance of an alternative (such as a design alternative or option) along various sustainability dimensions (economy, environment, society, project management, resources utilization, health and safety). the underlying assumption here is the additive/cumulative utility of a given design proposal (as measured by the sustainability index) depend on its individual utilities in the various decomposed elementals sustainability indicators. the assumption holds for most extent theories of utility and is particularly true of the concept of “generalized additivity (ugwu et al., 2006). also the use of weighted sum model assumes that the decision criteria can be expressed in the same unit of measures. this is achieved by using dimensionless numerical scores (scalar quantity) in the sustainability appraisal process. let 𝑆𝑙𝑖 , (for i = 1, 2, 3…m) represent the final sustainability index (a crisp value) of design alternative (di or ai) (table 3) when all decision criteria 𝑎𝑖𝑗 are considered. the next problem is how to compute 𝑆𝑙𝑖 .there are different multi-criteria decision method (mcdm) such as weighted sum model (wsm), weighted product model (wpm), analytical network process (anp) and analytical hierarchical process (ahp) (saaty, 1980, 2008, chan et al., 1992 and triantaphyllou et al., 1994, fishburn ,1967 and triantaphyllou, 2000). any of these methods is considered sufficient for formulating an underpinning or solid base for mathematical model for quantitative sustainability appraisal (ugwu et al., 2006). the decision is further buttressed by the fact that a review of some completed case study of major projects and application of mcdm techniques in practice indicates that the weighted sum model is widely used for practical decision making in real life situations (ugwu et al., 2006). it is therefore considered valid enough to develop a mathematical foundation for sustainability appraisal in using the wsm method; the si of design alternative di or ai is calculated using the following formula adopted from works of fishburn (1967) and ugwu et al. (2006) as expressed in the following equations. 𝑆𝑙𝑖=∑ 𝑎𝑖𝑗𝑤𝑗 (𝑓𝑜𝑟 𝑖 = 1, 2, 3, … 𝑀)𝑛 𝑖=1 (1) s𝑙 = ∑ 𝑆𝑙𝑖 (2) 𝐴𝑖 𝑜𝑟 𝐷𝑖 (𝑊𝑆𝑀𝑠𝑐𝑜𝑟𝑒) is defined as follows 𝐴𝑖 𝑊𝑆𝑀−𝑠𝑐𝑜𝑟𝑒 = ∑ 𝑎𝑖𝑗𝑊𝑗 (𝑗 = 1,2,3, … 𝑀)𝑛 𝑗=1 (3) where: 𝑊𝑗 is relative weight of importance of the criterion, 𝐶𝑗 and 𝑎𝑖𝑗 are the performance value of alternative ai when it is evaluated in terms of alternative ai. for the maximization case, the best alternative is the one that yields the maximum total performance value. another underlying assumption in all mcdm methods is that the decision maker can quantify performance for a given design evaluation (ugwu et al., 2006). therefore, the decision maker is considered to have sufficient knowledge and expertise (including experimental knowledge) in http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):319-330. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 324 scoring the performance of design alternatives computational analysis performed using these assigned dimensionless scores (scalar quantities). hence they are considered to be valid for the mathematical model formulation that explains the decision-making criteria 𝑎𝑖𝑗 in equation (1). 3. survey instruments and methodology some of the information used in this discuss were obtained from a combination of structured questionnaires, interviews with professionals working with both public and private sectors or establishments, case study project data, sustainable construction projects, environments and transportation/infrastructure projects, literatures on sustainability research and questionnairesbased survey for indicators. the survey was conducted for a period of 8 months which started from march and ended in september, 2012. a total of 150 questionnaires were sent out or distributed to various professionals, consultants, clients and contractors in some selected geopolitical regions or zones in nigeria (south east, south-south, lagos, abuja, north-east). in order to achieve the objectives, the questionnaires were divided into 3 parts. part i elicited respondents background information (demographic data), while parts ii and iii focused on eliciting stakeholders’ perceptions and prioritization on the sustainability of various proposed indicators for use in assessing transport and general infrastructure projects. the questionnaires were distributed using a combination of internal circulation through contact persons working in the identified ministries, corporations or government organization through personal contacts, by email and faceto-face interviews. in part i, personal background questions and information on such programs as global reporting initiatives (gri) and united nations commissions on sustainable development (unc-csd) and levels of use or involvement in such programs in practice. it was noticed that sustainability awareness has not been widely addressed in nigeria. however, government is making effort for the implementations of sustainability concept in our infrastructure projects. it was also observed that there is no systematic appraisal tools and methods use in practice level. the personal background information elicited included the respondents experience and participation in sustainability driven infrastructure projects. parts ii and iii of the questionnaires asked respondents to give a score from 1 – 5 against each of the selected indicators to determine the suitability of methods to assess the sustainability of typical transport and general infrastructure projects. this translate as follows on the likert scale 1 = not suitable, 5 = very suitable, with 3 being average suitable or value for acceptance of any indicator sustainability. a total of 98 valid questionnaires were returned giving a response rate of 65.33%, while consultants and contractors gave lowest response rate. the percentage (%) of unreturned questionnaires was 34.67%. north east being the base of the author had the highest response rate, abuja and south east were second and third respectively, while lagos and south-south came fourth and fifth respectively. 3.1 survey analysis of indicators (ranking) descriptive statistics (table 4) was used to present the results of all-region and various questionnaire based indicators validation. table 4 indicates that the stakeholders’ perceptions of key performance indictors in general infrastructure (road) sustainability had the main scores and ranks (out of maximum score of 5) for the proposed indicators. the cumulative ranking shown is a reflection of stakeholders’ views or perceptions. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com oraegbune: towards sustainable road infrastructure delivery in nigeria. azojete, 18(2):319-330. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 325 table 4: maximum and minimum ranks region economy (mean). (rank) environment (mean), (rank) society (mean), (rank) project management (mean), (rank) resource utilization (mean), (rank) health and safety max. min. max. min. max. min. max. min. max. min. max. min all regio n employme nt of labour (4.16), (1) adverse impact on tourism (2.76), (67) solid constructi on material (3.73), (12) liquid waste nontoxic (2.78), (66) view of local authorities (3.62), (20) footprint of project in archeologic al sites or areas (2.85), (65) project size/ complexi ty (3.93), (4) user rating (3.29), (43) constructi on material (4.13), (2) scrap value after the commissioni ng (3.04), (56) safety (3.74), (10) long-term health e.g. respiratory disease (2.92), (60). abuja employme nt of labour (4.33), (1) adverse impact on tourism (2.78), (57) solid constructi on material (4.00), (5) liquid waste nontoxic (2.33), (66) view of local authorities (3.75), (23) footprint of project in archeologic al sites or areas (2.42), (65) project duration (4.09), (3) approach towards suppliers (3.29), (56) constructi on material (4.30), (2) innovative material (2.58), (62) safety (3.75), (15) long-term health e.g. respiratory disease (2.33), (67). lagos employme nt of labour (4.64), (2) adverse impact on tourism (2.50), (61) connectivi ty with inter land (4.56), (3) reprovisio n of habitat (2.50), (63) extent of congestion (4.01), (13) footprint of project in archeologic al sites or areas (2.18), (67) amount of paper works (4.30), (8) inclusion of sustainabili ty clauses in project (2.70), (56) constructi on material (4.30), (8) early contractor involvement (3.00), (49) manageme nt system e.g. policy, programm e, etc. (4.00), (15). shortterm health e.g. respiratory disease (2.27), (66). nort h – east employme nt of labour (4.03), (2) adverse impact on tourism (2.57), (67) solid constructi on materials (3.61), (18) air outlet (2.71), (66) extent of congestion (3.63), (17) footprint of project in archeologic al sites or areas (3.00), (61) project duration (3.81), (6) user rating (3.06), (58) constructi on material (4.06), (1) scrap value after the commissioni ng (3.16), (53). safety e.g accident, injuries fertility (3.91), (8) long-term health e.g. respiratory duct disease (3.31), (44). south south employme nt of labour (3.43), (14) resettlin g cost of people (2.75), (5) extent of loss of habitat or feeding grounds (3.60), (4) design flexibilit y towards noise reductio n measure s (2.30), (57) extent of encroachme nt upon concern areas (3.45), (11) ubuntu (public perception ) (2.67), (58) approac h towards suppliers (3.80), (1) amount of paper work (2.90), (50) innovative material (3.64), (3) use of local materials (2.50), (60) safety (3.36), (19) manageme nt system e.g. policy, programm e, (2.70), (56). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):319-330. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 326 4. basic inferences from the survey the maximum and minimum ranked indicators for each of the six sustainability criteria or domains in all-region representing abuja, lagos, north-east and south-south are discussed as follows. in the discussion, the highest and lowest ranked priority indicators were based on their ranking indicators. i. economy: employment of labour is ranked on the top (1) by all stakeholders in all-region (nigeria). its ranking under general infrastructure (road) is an indication of positive relationship between employment level and economic growth in construction industry in nigeria. also in alignment with federal government transformation agenda which include construction of road and other infrastructure and will generate employment of labour in all-region (nigeria). this also reflects on economic preference that are bonded in encouraging micro-economic growth and capacity building through employment creation or generation and other policy statement which then will improve sustainable economy of all-region (nigeria). ii. environment: priority ranking is given to solid construction materials indicators by the stakeholders in all-region (nigeria). solid materials are waste management related sustainability criteria and product of construction and infrastructure development activities. as discussed previously, transformation agenda of the present government in general infrastructure especially in road, railway, power, agriculture, airport, oil and gas, there is need to guard against long-term cleanup costs with its associated implications or effects in nigeria. nigeria is now witnessing a vast or huge infrastructure development which is generating more wastes and if not properly handled shall increase cost of construction activities, collaborating with ugwu et al. (2006), most of the indicators under sustainable environment are performance based and could be built into total quality management (tqm) systems for monitoring site level construction operations. iii. society: views of local authorities is ranked on top (20) amongst the key performance indicators in nigeria or all-region. views of local authorities are public perceptions –related subsustainability which is community base indicator(s). they are stakeholders in the community level and are direct users of these infrastructures. because of their position in the community set-up, their views are taken into consideration under social sustainability and in decision-making. therefore, it is not mistake that it is ranked 20th position amongst key performance indicators in general infrastructure in nigeria. iv. project management: project size/complexity indicator is project management related sustainability and one of the key performance indicators which occupy 4th position. similarly, indicators under project management/administration account for the need to adopt strategies that facilitate collaborative working among project teams. it is a condition to achieving sustainability objectives in both transport and general infrastructure (road) development in nigeria. one of the most vital requirements in this indicator is the need for nigeria to consider detail project planning and realistic programming before the commencement of transport and general infrastructure projects. this will improve the quality of construction products and well enhancing sustainable transportation and general infrastructure (road) delivery in nigeria. while referring to (ugwu et al., 2006) contribution, the author agreed that in developing country like nigeria, indicators under project management highlighted the need for industrial strengthening and power development. this is essential in addressing the several perennial problems that militate against efficient project file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com oraegbune: towards sustainable road infrastructure delivery in nigeria. azojete, 18(2):319-330. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 327 management in developing countries of which nigeria is one of them. procurement routed such as public private partnership (ppp) and partnering are enablers that encourage human relations and enhance collective social capital in a project environment. v. resources utilization: construction material is material availability-related sustainability which is under resources utilization criteria is ranked (2) amongst other indicators in all-region (nigeria). collaborating with (ugwu et al., 2006), indicators under resources utilization relate to construction methods and strategies that need to minimize depletion of the limited resources. that construction is an intensive transformation process that often involves assembling and transforming resource into physical artifacts. construction material needs to be conserved through innovative designs and specific methods for instance, contractors are most of the time involved at the construction level of the projects and they are in the best situation to maintain optimized resources utilization during construction process e.g. material re-use, recycle, good quality control systems or method to avoid material wastage or reworks. again in (ugwu et al., 2006), adopting performance based specifications would facilitate resources utilization as it gives contractors flexibility in choosing complementing alternative material. vi. health and society: safety indicators are ranked on top (10) among key performance indicators. the high-ranking positions of safety indicator, is as a result of general awareness on health and safety related matters in construction and the wider society. this could be explained by the serious campaign on safety related issues in construction and in our roads by the federal road safety corps and federal road maintenance agency (creed for safety driving and for safety construction environment). while collaborating with (ugwu et al., 2006), the author also substantiated with the sustainable development unit (sdu), slated some sustainability elements like health and safety are vulnerable to shifts in society’s definition of sustainability and prioritization of core elements. however, this raised some issues related to intergenerational priorities in sustainability, and enhance the associated risks in construction environment (ugwu et al., 2006). 5. cognitive/reasoning map system as decision aid for infrastructure sustainability appraisal. for the purpose of using sustainability key performance indicators in practical applications or situations, it is importance to understand the relationships and interactions between the various indicators at sub-dimensional levels. a cognitive/reasoning map plays vital roles in problem structuring. this is the same as quantitative methods in assessing sustainability decisions. because of the problems, this section develops reasoning and mapping models that shows the causeandeffect relationship between the various indicators. it uses the reasoning map to illustrate the complexities of the interaction between the various indicators. knowing of the interactions, would facilitate the sustainability appraisal process. this appraisal is based on previous usage among researchers to perform multi-criteria dimensional assessment of decision alternatives (ugwu et al., 2006, (bana et al., 1999, kosko, 1986 and chan and hwang, 1992) (figure 1). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):319-330. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 328 figure 1: a hierarchy of key performance indicators and cognitive/reasoning map for infrastructure sustainability appraisal; source: my field work key: ----(dashed line) = shows destination interaction between the indicators; = + = indicates increasing causal effect from source to destination. key: = = indicates decreasing causal effect from source to destination. i. economy: ecological design concept could increase initial cost or effect (+), but such concept design will have long-term positive effect on both the environment and tourism. ii. constructability: ugwu et al., (2006) stated that poor constructability increases initial construction cost both in terms of lateness and associated claims, material wastages as well as rework (+). therefore, good constructability has a reverse or reduced impact. early contractor and supplier involvement (eci/esi) also adds or increase the opportunity/chance meeting constructability goals or aims. procurement methods such as design and build, build, operate and transfer or other partnering methods also facilitate (eci/esi). recently, second niger bridge contract was awarded using procurement method design, build, finance/fund, operate and transfer. this will result in earlier completion as well as good results in value engineering practice. this will also check constructability design problem. iii. waste management: waste management method increases or adds to direct cost (construction) of an infrastructure project (+). but efficient material re-use or recycling and the use of already made material helps or improves the waste process and reduces the associated cost (-) and added impact on initial cost. iv. public access and occupational safety: insufficient provision of public access (for instance, temporal diversion routes for construction of infrastructure projects) could lead to accident or other problems which may stairs contractorsubcontractor relationship (materials suppliers or file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com oraegbune: towards sustainable road infrastructure delivery in nigeria. azojete, 18(2):319-330. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 329 subcontractors or other public access users). in some cases, this could cause to unhealthy and unsustainable human relations that can result in physical blows or fights and injuries can be sustained during construction. although, provision of good site access may increase initial cost or cost of construction (+) or increase causal effect of construction (+). it is generally believed that this will improve occupational safety and health and therefore adds to a sustainable construction and infrastructure development. 6. conclusions this paper presented the background information and recent literature reviews of sustainability in road infrastructure, multiple stakeholders’ perceptions or views on sustainability and key performance indicators for sustainability appraisal in infrastructure. the mathematical foundation models, weighted sum model in multi-criteria decision method were usedbased on delph method. the study further discussed on key performance indicators for transport infrastructures sustainability and observed that some of the sustainability indicators are regional or project site –specific while others are generics. the cognitive map illustrated hierarchy of key performance indicators in road infrastructure sustainability appraisal. the maximum and minimum priority indicators with their sustainability criteria were discussed base on stakeholders’ perceptions and their ranking priorities to determine indicators with highest and lowest ranking positions. references bana, ec., esslin, l., correa, ec. and vansnick, jc .1999. dss in action, integrated application of a multi-criteria decision aid process, european journal of operation research, 113: 315-335. chan, sj. and hwang, cl. 1992. fuzzy multiple decision-making lecture notes in economics and mathematical systems, vol. 375, spring arterlag, new york. fishburn, pc. 1967. additive utilities with incomplete product set: applications to priorities and assignments, osra publication, baltimore, md, usa. kosko, b.1986. fuzzy cognitive maps. international journal of man-machine studies, 25: 65 – 75.p lim, sk. 2009. framework and processes for enhancing sustainability deliverables in australia road infrastructure projects. ph.d thesis, school of urban development facility of built environment and engineering, qut brisbane. koo, d. and ariaratnam, s. 2009. enhancement of sustainability in underground infrastructure development. canadian journal of civil engineering, 36: 765-776. oraegbune, mo. 2015. appraisal of transportation infrastructure sustainability in nigeria: ph.d thesis, department of civil engineering, faculty of engineering, university of nigeria, nsukka. oraegbune, mo. and ugwu, oo. 2020. delivering sustainable transport infrastructure projects (railway) in nigeria: frameworks, indicators, method and tools. nigerian journal technology (nijotech), 39(3): 665-679. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):319-330. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: irokom0013june@gmail.com 330 saaty, tl. 2008. decision making with the analytic hierarchy process. international journal of service sciences, 1(1): 83-98. saaty, tl. 1980. the analytic hierarchy process. mcgraw-hill, new york triantaphyllou, e. 2000. multiple-criteria decision making: a comparative study, dordreeht, the neitherlands: kluwer academic publisher (now springer), pp.320. triantaphyllou, e., lootsma, fa., pardalos, pm. and mano, sh. 1994. on the evacuation and application of different scale for quantifying pairwise comparison in fuzzy sets. journal of multi criteria decision analysis, 3(b): 133 – 155. ugwu, oo. and haupt, tc. 2005. key performance indicators and assessment methods for infrastructure sustainability – a south africa construction industry perspective. building and environment, 42(2): 665-680. ugwu, oo., kumaraswamy, mm., wong, a. and ng, st. 2006. sustainability appraisal in infrastructure projects (susaip) part (i). development of indicator and computational method. automation in construction, 15: 239-251. www.elsevier.com/locate/autcon yang, j. and lim, sk. 2008. the identification of sustainability perception and deliverables for australia road infrastructure conference, 9 – 12 december, auckland, n. z., pp. 1-10. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/irokom0013june@gmail.com http://www.elsevier.com/locate/autcon arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):491-500 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 491 original research article potentials of utilizing biodiesel from cotton seed oil blend with diesel as an alternative to diesel fuel in nigeria i. a. hussain1*, i. u. ibrahim1, b. a. ishak1 and a. s. ahmed2 1department of mechanical engineering, ahmadu bello university, zaria, kaduna sate, nigeria 2department of mechanical engineering, hussaini adamu federal polytechnic, kazaure, jigawa state, nigeria. *corresponding author’s email address: kalipha81@gmail.com 1.0 introduction energy is one of the most significant contributing factors to the development of a nation. it is essential to the realization of basic needs for individuals and communities as well. the rise in the price of petroleum products, increase in its daily demand, uncertainty in its supply, and its negative environmental effect made it necessary for the world to find alternatives to fossil fuels such as diesel. this could be achieved either by improving the quality of the current fuels or by devising new alternative fuels for the future to replace the current ones through the utilization of renewable energy sources. vegetable oil is considered a suitable alternative to diesel fuel. ramadhas, jayaraj and muraleedharan, (2004) and tomasevic and siler-marinkovic, (2003) reported that vegetable oils such as cottonseed oil have a long hydrocarbon chain structure that contains 16-20 carbons with oxygen at one end. they are free from sulphur, metals and other impurities; this makes them possess good ignition features. but the disadvantages associated with some of these oils are low energy content, high viscosity, high density and more carbon deposit compared to pure diesel (canakci and van gerpen, 2001). that is the reason most of the vegetable oils have low thermal efficiency. these disadvantages can be rectified to a certain extent using the processes of transesterification (jadhav et al., 2016). in transesterification process, vegetable oils and fats react with alcohol in the presence of catalyst to produce biodiesel. glycerine is obtained at the end of this process as by-product; which can be used for a variety of industrial applications (kumar, maheswar, and reddy, 2009). the biodiesel produced is biodegradable and non-toxic; it can be employed alone or mixed article information abstract the depletion of fossil fuel reserves coupled with the environmental challenges pose by fossil fuel utilization make it necessary to search for better alternative fuels that have less adverse impact to the environment. biodiesel and its blends as an alternative fuel in compression ignition (ci) engines are receiving more attention from researchers. this study investigates a blend of biodiesels from cottonseed oil and pure diesel prepared in percentage by volume in a proportion of 0:100, 10:90, 20:80 and 30:70 respectively. they were labeled as b0, b10, b20, and b30, and run on a single-cylinder, four stroke and water-cooled 165f diesel engine. the results show higher brake power for all blends when compared with pure diesel, with the lowest difference of 0.43% for b10 at a torque of 10 nm and highest of 2.06% for b30 at 2 nm torque. specific fuel consumption (sfc) was also higher for the blends as compared to pure diesel, but the sfc is compensated with higher brake power. pure diesel is observed to be thermally more efficient than biodiesel blends at low torque. the thermal efficiency difference ranges between 6.6–13.3% at 2 nm. but at the torque of 10 nm, the thermal efficiency of all blends is higher than pure diesel with about 3.3%. b30 shows better engine performance than pure diesel and the other two blends, but with slightly higher fuel consumption. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 feb., 2020 revised 08 may, 2020 accepted 15 may, 2020 keywords: biodiesel blend alternative fuel diesel cotton seed oil compression ignition mailto:kalipha81@gmail.com http://www.azojete.com.ng hussain et al: potentials of utilizing biodiesel from cotton seed oil blend with diesel as an alternative to diesel fuel in nigeria. azojete,16(3):491-500. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 492 with diesel fuel in the compression ignition engine without necessarily modifying the engine parameters (canakci and van gerpen, 2001). biodiesel from cottonseed oil is an environmentally friendly fuel derived from renewable energy sources. apart from its environmental benefit, utilizing cottonseed oil biodiesel has additional economic benefits to countries where petroleum products are imported such as nigeria. cottonseed oil biodiesel utilization in nigeria can bring about many benefits such as supporting the agricultural sector and rural economy, decrease in the reliance on imported crude oil for transportation and power generation, and reduction in greenhouse gases emission. different researchers have carried out different works on cottonseed biodiesel (canakci and van gerpen, 2001; fan et al., 2008; jadhav et al., 2016; kumar et al., 2009). engine tests were carried out with either the pure biodiesel, with additives or with biodiesel blends. but in most cases, the focus is more on emissions reduction. as described by mccarthy, rasul, and moazzem (2011), reduction in the environmental impact of fuel diesel emissions is the main aim of using biodiesel. but engine performance is equally important as far as biodiesel utilization is concerned. using biodiesel as an alternative is only possible provided engine performances are maintained because of its utilization or its blends. evaluation of engine performance, emissions and effects of additives on 4 different cottonseed biodiesel in comparison to pure diesel was conducted by fan et al., (2008). the analysis in the research was carried out with only cottonseed biodiesel not its blend, and it focuses more on emissions reduction rather than engine performance. kumar et al. (2009) also investigated the effect of varying the content of alcohol and catalyst on the viscosity of cottonseed biodiesel. properties of biodiesel highly depend on its source (wu et al., 2009), and these properties determine the engine performance parameters and the nature of emissions. the performance parameters of a diesel engine are brake effective power (bep), specific fuel consumption (sfc), and brake thermal efficiency (bte). diesel, biodiesel and biodiesel blends are used in ci engines to experimentally investigate these parameters at different engine torque. the ratio of brake power produced to the mass of fuel consumed by an engine is what is termed as specific fuel consumption (sfc). performance evaluation of an engine fueled with biodiesel and its blend compared to the same engine fueled with diesel shows the same thermal efficiency with higher sfc for biodiesel and its blend (monyem, van gerpen, and canakci, 2001). sfc is inversely proportional to thermal efficiency (lapuerta et al., 2008). since biodiesel is denser than pure diesel, is to some extent expected to have higher sfc (munack, 2006). this increase in sfc is attributed to oxygen enhancement from fuel, and not from intake air (rakopoulos et al., 2004). increase in sfc was also reported by different researchers when using biodiesel or biodiesel blends compared to petroleum diesel (alam, et al., 2004; senatore et.al., 2000; turrio-baldassarri et al., 2004) lapuerta et al. (2008) described thermal efficiency as the ratio of power output to energy introduced through injected fuel. canakci (2007) and lapuerta et al. (2008) observed no significant changes in thermal efficiency when using biodiesel or its blends in ci engines. energy content per unit volume of biodiesel is lower than that of pure diesel (dwivedi, jain, and sharma, 2011). therefore, there is a likelihood of decrease in engine power output with more fuel consumption when using biodiesel compared to diesel. though a slight increase in engine power output was observed by usta (2005) for tobacco seed oil biodiesel blend in an indirect injection diesel engine. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 491-500. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 493 in the present work, potentials of utilizing biodiesel from cottonseed oil blend with diesel as a substitute to pure diesel was investigated. cottonseed biodiesel was produced using the transesterification process and blended in different percentage by volume with pure diesel. performance parameters of a compression ignition engine fueled with pure diesel and diesel/biodiesel blends were experimentally investigated. 2. materials and method 2.1 materials the materials used in this research are: biodiesel produced from cottonseed oil pure petroleum diesel stop watch measuring cylinder beakers bottles stirrer 2.2 methods 2.2.1 preparation of cottonseed oil biodiesel and its blends the procedure for the transesterification of vegetable oil to produce biodiesel outlined in jadhav et al. (2016) was adopted in this work. the process flow diagram of the procedure is shown in figure 1. figure 1: biodiesel production process flowchart (jadhav et al. 2016) the production of the blends was conducted by measuring 100 ml of biodiesel from cotton seeds oil in a beaker, 900 ml of petroleum diesel was then added and the mixture was continuously stirred using a stirrer to form a ten percent (10% by volume) blend known as b10. the mixture (biodiesel blend) was poured into a clean bottle and closed, ready for engine test. similar blends were further made with 200 ml of the biodiesel and 800 ml of petro-diesel, 300 ml of the biodiesel and 700 ml of the petro-diesel to form b20 and b30, respectively (see figure. 2) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hussain et al: potentials of utilizing biodiesel from cotton seed oil blend with diesel as an alternative to diesel fuel in nigeria. azojete,16(3):491-500. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 494 figure 2: diesel (b0) and various biodiesel blends 2.2.2 biodiesel blends quality test (a) flash point (f.p) an improved method was used for this determination. a 100 ml conical flask was filled to a specific level (10 ml) with biodiesel blend and was slowly heated at constant rate on the hot plate. the flash point was taken at the lowest temperature when an application of test flame caused the vapor above the sample to ignite. (b) density the mass of a small empty bottle was determined using an electronic weighing balance. the bottle was then filled to the brim with the bio-diesel blends and the weight of the bottle and the bio-diesel determined. this procedure was repeated with b10, b20 and b30. the density was calculated using equation 1; density (ρ) = w2−w1 v (1) where: w2 = mass of bottle + sample w1 = mass of empty bottle v = volume of sample (c) calorific value (cv) an improved method was used for this determination. the wick was positioned in the locally made lamp. the weight of the empty lamp with 10 ml of the biodiesel blend was taken. the wick was lit and the biodiesel blend was used to heat the beaker containing 10 ml of water for 10 minutes after which the temperature of the water was recorded. the same procedure was repeated for blends of b10, b20 and b30. the calorific value/energy content was determined using equation 2; q = mcθ (2) where: m = mass (kg) c = specific heat capacity (kj/kgk) θ = temperature rise (ok) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 491-500. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 495 (d) kinematic viscosity the viscometer was placed in the 1000 ml measuring cylinder filled with water and regulated to the appropriate temperature. the tube was filled up to a graduation mark over the left storage bulb with the bio-diesel blend. the bio-diesel was then sucked up to fill the higher storage bulb in the right of the tube and then released. the time taken for the bio-diesel to flow from the upper mark to the lower was observed and calculated. the kinematic viscosity of the bio-diesel blend was calculated using equations 3 and 4; kinematic viscosity (y) = absolute viscosity(η2) density(ρ) (3) absolute viscosity (η2) = η1ρ2t2 ρ1 t1 (4) where: η1 = absolute viscosity of water (8.90×10−4pa.s) t1 = time of flow of water (s) ρ1 = density of water (1000kg/m3) η2 = absolute viscosity of bio-diesel blend (pa.s) t2 = time of flow of bio-diesel blend (s) ρ2= density of bio-diesel blend (kg/m3) the same procedure was repeated using b10, b20, b30 and water was taken as the reference 2.2.3 engine test the engine test was carried out using a 2 stroke single cylinder diesel engine at the department of mechanical engineering, bayero university kano. the specifications of the said engine are given in table 1. the engine test was performed, and the parameters measured include engine torque, engine speed, exhaust temperatures and height of air in the manometer. this study was conducted to investigate the engine performance run on different biodiesel from cottonseeds/petro-diesel blends (b10, b20, and b30). table 1: test engine specifications parameter specification engine model vikin super 165f diesel engine type of engine 2-stroke single cylinder stationary diesel engine weight 40 kg bore 65 mm stroke 70 mm rated power 2.43 kw rated speed 2600 rpm cooling air-cooled 3. results and discussions the results obtained from the experiments conducted for engine performance are evaluated. before carrying out this experiment, the properties of the biodiesel blends were determined and compared to that of petroleum. 3.1 properties of biodiesel and biodiesel blends in comparison with diesel the properties of biodiesel blends at different percentage by volume in comparison to that of petroleum diesel are shown in table 2 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hussain et al: potentials of utilizing biodiesel from cotton seed oil blend with diesel as an alternative to diesel fuel in nigeria. azojete,16(3):491-500. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 496 table 2: properties of biodiesel in comparison with diesel and blends properties b0 b10 b20 b30 protocol min-max density (kg/m3) 824 832 839 847 astm d1448 800 900 kinematic viscosity (cst) 1.9 2.4 3.7 3.9 astm d2217 1.9 – 4.1 flash point (°c) 58 72 78 82 astm d93 130 min calorific value (mj/kg) 43.20 42.41 42.28 42.10 astm d6751 34 45 the density of the biodiesel blends is found to be within the range of the astm standard. it is observed that biodiesel blends have higher viscosity and flash point than petroleum diesel. the viscosity of all the blends is also within the limit of the astm standard. the increase of density and viscosity with increase in the percentage of biodiesel in the blend is because the biodiesel is denser and more viscous than pure diesel. for the flash point, all the blends including the diesel have values lower than the minimum of 130°c. finally, the calorific value also falls within the standard which ranges from 34-45 mj/kg. the calorific value decreases with increase in the percentage of biodiesel in the blend as a result of lower amount of energy contained in biodiesel compared to pure diesel. 3.2 performance evaluation significant performance parameters of a diesel engine such as brake thermal efficiency (bte) and specific fuel consumption (sfc) are evaluated for cotton seed oil biodiesel blend and diesel. sfc can be used to compare engine performance of fuels with distinct energy content. 3.2.1 analysis on the sfc figure 3 shows the sfc variation of petroleum diesel and its blends of cottonseed oil at different torque. the sfc of the blends is higher at all torques compared to the petroleum diesel. this is attributed to the lower energy content of the blend compared to pure diesel. at lower torque the sfc is higher for the blends and pure diesel, and as the torque increases the sfc decreases. not much significant difference is observed among the sfc of blends at all torques. it is also observed that as the torque increases, the difference in sfc of the pure diesel and the blend decreases. the lowest sfc occurs at the torque of 10 nm; which is due to the lower heating value, higher viscosity and density of biodiesel (cottonseed oil). figure 3: specific fuel consumption of diesel and blends http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 491-500. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 497 3.2.2 analysis on the brake power figure 4 shows the brake power of diesel fuel (b0) and various biodiesel blends (b10, b20 and b30) at torque of 2nm, 6 nm and 10 nm, respectively. it is noticed that at 2 nm torque, the brake power of the blends were slightly higher than the diesel fuel except for b20 which is the same as b0. also, at 6 nm torque the brake power for the blends are higher compared to the petroleum diesel by 0.8%. finally, at 10 nm torque, the brake power of the blends are higher compared to the diesel fuel, the brake power of b20 at this torque is higher compared to the other blends; which has a value of 2450 w. this variation could be as a result of the higher fuel flow rate. it was found that an increase in torque resulted in increases in the brake power of the engine. figure 4: brake power of diesel and blends at different torques 3.2.3 analysis on the brake thermal efficiency bte increases with increase in the engine load as shown in figure 5. as the percentage blend increases there is a slight variation in the bte with respect to increase in the torque. pure diesel (b0) has the highest bte at 2 nm compared to all the blends, likewise at 6 nm. but at 10 nm b10, b20 and b30 have the highest compared to b0. this implies that at high torque the blend is thermally more efficient than pure diesel and vice versa. this could be as a result of the increase in the rate at which the biodiesel burn in the blends. figure 5: brake thermal efficiency (bte) of diesel and blends 3.2.4 analysis on the exhaust gas temperature the variation of exhaust gas temperature with torque for diesel and its blends with cotton seed oil are shown in figure 6. b0 has the highest exhaust temperature of 175°c at 2 nm torque. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hussain et al: potentials of utilizing biodiesel from cotton seed oil blend with diesel as an alternative to diesel fuel in nigeria. azojete,16(3):491-500. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 498 the lowest at the same torque are b20 and b30 which are at an exhaust temperature of 171°c. b10 has the same exhaust temperature as b0 at 2 nm. similarly, at 6 nm the exhaust temperature remains constant for b10, b20 and b30 with a value of 233°c except for b0 which has an exhaust temperature of 235°c. furthermore, at 10 nm, it is observed that there is an increase in exhaust temperature with decrease in the percentage blends. decreasing the percentage of biodiesel in the blend means decreasing its cetane number; this brings about longer ignition delay time which results in higher exhaust gas temperature. figure 6: exhaust temperature of diesel and blend 3.2.5 analysis on the brake power vs fuel consumption of the blends it was observed in figure 7 that the worst blend at 2 nm is b20; it consumes more fuel and at the same time produces less power. for the other two blends, though they consume more fuel than pure diesel but they produce more brake power; which means the high fuel consumption is compensated with more power produced. the same pattern is observed in figure 8 at a torque of 10 nm. figure 7: brake power vs fuel consumption at 2 nm http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 491-500. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 499 figure 8: brake power vs fuel consumption at 10 nm 4. conclusion vegetable oil from cotton seed is converted into biodiesel using transestrification process. this biodiesel is mixed with pure diesel in altered percentage to produce three different blends. the tests for the properties of biodiesel demonstrate that almost all the properties of biodiesel are in close agreement with diesel fuel. test was carried out using these blends as alternative fuel in a diesel engine to investigate its performance. the results obtained were evaluated and compared with the results obtained from the same engine but run on pure diesel. higher specific fuel consumption was observed for the blends at all torques compared to pure diesel. almost all the blends have higher break power than diesel at all torques. it is equally observed that at high torque the blends are thermally more efficient than pure diesel and vice versa. exhaust temperature for diesel is higher than that of the blend at all torques. references alam, m., song, j., acharya, r., boehman, a. and miller, k. 2004. combustion and emissions performance of low sulfur, ultra-low sulfur and biodiesel blends in a di diesel engine. sae transactions, 113(4): 1986-1997. canakci, m. 2007. combustion characteristics of a turbocharged di compression ignition engine fueled with petroleum diesel fuels and biodiesel. bioresource technology, 98(6): 11671175. canakci, m. and van gerpen, j. 2001. biodiesel production from oils and fats with high free fatty acids. transactions of the asae, 44(6): 1429. dwivedi, g., jain, s. and sharma, m. 2011. impact analysis of biodiesel on engine performance— a review. renewable and sustainable energy reviews, 15(9): 4633-4641. fan, x., wang, x., chen, f., geller, dp. and wan, pj. 2008. engine performance test of cottonseed oil biodiesel. the open fuels and energy science journal, 1(7): 40-45. jadhav, s., biradar, n., kolhe, k., chavan, s. and gawai, u. 2016. review paper on oerformance evaluation and emission analysis of four stroke single cylinder diesel engine using cotton seed biodiesel as an alternative fuel with additives. international journal of emerging technologies in engineering research, 4(7): 73-77. kumar, a. s., maheswar, d. and reddy, kvk. 2009. comparision of diesel engine performance and emissions from neat and transesterified cottonseed oil. jordan journal of mechanical and industrial engineering, 3(3): 190-197. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng hussain et al: potentials of utilizing biodiesel from cotton seed oil blend with diesel as an alternative to diesel fuel in nigeria. azojete,16(3):491-500. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kalipha81@gmail.com 500 lapuerta, m., herreros, jm., lyons, ll., garcía-contreras, r. and briceño, y. 2008. effect of the alcohol type used in the production of waste cooking oil biodiesel on diesel performance and emissions. fuel, 87(15-16): 3161-3169. mccarthy, p., rasul, m. and moazzem, s. 2011. comparison of the performance and emissions of different biodiesel blends against petroleum diesel. international journal of low-carbon technologies, 6(4): 255-260. monyem, a., van gerpen, j. and canakci, m. 2001. the effect of timing and oxidation on emissions from biodiesel-fueled engines. transactions of the asae, 44(1): 35. munack, a. 2006. books: biodiesel–a comprehensive handbook. martin mittelbach, claudia remschmidt (ed.). biotechnology journal: healthcare nutrition technology, 1(1): 102-102. rakopoulos, cd., hountalas, d., zannis, t. and levendis, y. 2004. operational and environmental evaluation of diesel engines burning oxygen-enriched intake air or oxygenenriched fuels: a review. sae transactions, 113(4): 1723-1743. ramadhas, as., jayaraj, s. and muraleedharan, c. 2004. use of vegetable oils as ic engine fuels—a review. renewable energy, 29(5): 727-742. senatore, a., cardone, m., rocco, v. and prati, mv. 2000. a comparative analysis of combustion process in di diesel engine fueled with biodiesel and diesel fuel (no. 2000-010691): sae technical paper. tomasevic, av. and siler-marinkovic, ss. 2003. methanolysis of used frying oil. fuel processing technology, 81(1): 1-6. turrio-baldassarri, l., battistelli, cl., conti, l., crebelli, r., de berardis, b., iamiceli, a. l. and iannaccone, s. 2004. emission comparison of urban bus engine fueled with diesel oil and ‘biodiesel’ blend. science of the total environment, 327(1-3): 147-162. usta, n. 2005. an experimental study on performance and exhaust emissions of a diesel engine fuelled with tobacco seed oil methyl ester. energy conversion and management, 46(15-16): 2373-2386. wu, f., wang, j., chen, w. and shuai, s. 2009. a study on emission performance of a diesel engine fueled with five typical methyl ester biodiesels. atmospheric environment, 43(7): 14811485 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):1-8 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 1 original research article effect of shea nutshell ash on the mechanical properties of cast al6061 p. t. zubairu1, a. b. hassan1, r. a. muriana2 and n. a. musa1 1department of mechanical engineering, federal university of technology, minna, nigeria 2department of metallurgical and materials engineering, federal university of technology, minna, nigeria *corresponding author’s email address: nmapee@gmail.com 1.0 introduction current engineering applications require materials with higher strength, lesser weight, higher stiffness and higher toughness. much interest has been shown, into research and development of materials that have good strength to weight ratio suitable for automobile applications, where fuel economy with improved engine performance is of paramount interest. due to this rapid progress in scientific and technological development, new generation engineering materials are being developed to meet up with the required properties for such applications. in-service performances of these modern engineering systems have their workability rest on materials with broad spectrum of properties that are not obtainable in a monolithic system. on this backdrop, materials engineers and scientists have developed engineering materials with more attractive mechanical and tribological properties which supersede that of the base metal or alloy. to achieve the aforementioned feat, two materials with distinct physical and chemical properties are combined in a systematic manner to result into a material known as composite (kaczmar et al., 2000; tjong, 2014; alaneme et al., 2013; rahman and al rashed, 2013). aluminium hybrid composites are a set of new generation metal matrix composites (mmcs) known to have the potentials of meeting recent demands of advanced engineering applications. such demands are mostly realised through improving the mechanical properties of the known materials. amenability to conventional processing technique and possibility of reducing production cost has made aluminium hybrid composites, a better material giving rise to improved properties. the performance of such materials depends mostly on the selection and article information abstract aluminium matrix composites (amcs) has attracted much interest in aerospace, defence and automotive applications due to its high strength to weight ratio. however, the manufacturing technique, nature and combination of the matrix and reinforcements play a vital role in the success of amcs. in this study, the mechanical properties of aluminium metal matrix composites (ammcs) reinforced with shea nutshell ash (ssa) was investigated. different mix ratio constituting 0%, 5%, and 10% of ssa were used as reinforcement, with the matrix being al6061 to compound different samples. the metal matrix composites were produced by stir casting technique. mechanical properties such as hardness, tensile, impact and microstructure examination of the developed composites were evaluated. the results showed that with increasing % of ssa, the hardness, and impact energy of the composite increased for both 5 and 10%. however, with increasing ssa the tensile strength decreased slightly for both 5 and 10% ssa. the hardness and the impact energy increased by 166.74% and 76.38% respectively as the wt% of ssa varied from 0-10tw%. on the other hand, the tensile test showed a decrease from 115.67 n/mm2 to 94.52 n/mm2 as the % of ssa increase from 0-10%; which translates to 18.29% reduction in tensile strength. ssa however promises to be a good reinforcement material for hybrid aluminium matrix composites when the properties desired are hardness and impact energy © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 february, 2020 revised 13 august, 2020 accepted 24 august, 2020 keywords: aluminium metal matrix composites (ammc) shea nutshell ash (ssa) al6061 microstructural examination hardness tensile strength impact zubairu et al: effect of shea nutshell ash on the mechanical properties of cast al6061. azojete, 17(1):1-8. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 2 the right combination of reinforcing materials; since some of the processing parameters are associated with the reinforcing particulates. if the appropriate combination of reinforcement and matrix material is chosen, manufacturers shall be able to produce properties that exactly fit the requirements of a structure for a particular purpose. in recent years, hybrid reinforced aluminium matrix composites (amcs) have attracted the interest of researchers and different design concepts have been considered and adopted in selecting the appropriate combination of reinforcing materials (hossain et al., 2017; alaneme et al., 2018). aluminium hybrid reinforcement technology is a response to the dynamic ever-increasing service requirement of industries such as transportation, aerospace, automobile, and marine; this is largely due to its attractive properties which include high ductility, high conductivity, light weight, and high strength to weight ratio. when external loads are applied to the composites, the load is transmitted by the metal matrix to the reinforcements, which are carried by dispersed reinforcements bonded with the matrix. strong interface bond between reinforcements and matrix is required to obtain high strength of composites (alaneme et al., 2013; niranjan et al., 2017; pitchayyapillai et al., 2016). composites have become globally acceptable and widely used materials due to the ability to adapt to different conditions. more so, the relative ease of combination with other materials to produce exceptional properties to serve different purpose has earned it prominence; thereby giving it edge over known engineering materials. the development of low-cost aluminium matrix composites reinforced with eco-friendly materials has also become one of the major innovations in materials engineering in order to check environmental pollution (niranjan et al., 2017). alaneme et al. (2013) studied the behaviour of al alloy when reinforced with rice husk ash (rha) and alumina particles. they found that the introduction of these particles into the melt has decreased the density and hardness of the produced composites to an appreciable amount whereas the specific strength and the ultimate tensile strength have seen to be increasing with the increase of the reinforcements with the matrix. fatile et al. (2014) studied the micro structural and mechanical behaviour of al-mg-si alloy matrix composites reinforced with silicon carbide (sic) and corn cob ash (agro‑waste) was investigated in their research. the research work was aimed at assessing the suitability of developing low costhigh performance al-mg-si hybrid composite. silicon carbide (sic) particulates added with 0,1,2,3 and 4 wt% corn cob ash (cca) were utilized to prepare 10 wt% of the reinforcing phase with al-mg-si alloy as matrix using two-step stir casting method. micro structural characterization, density measurement, estimated percent porosity, tensile testing, and micro‑hardness measurement was used to characterize the composites produced. from the results obtained, cca has great potential to serve as a complementing reinforcement for the development of low cost and high-performance aluminium hybrid composites. the less dense al-mg-si/cca/sic hybrid composites have estimated percent porosity levels as composite grade without gsa (maximum of 2.332% porosity). this indicated that the use of cca did not arise in any significant rise in porosity level. hardness, ultimate tensile strength, and percentage elongation of the hybrid composites decreased gradually in cca content of the composites. however, the fracture toughness of the hybrid composites was observed to be superior to that of the composite sample without gsa. there is no significant difference between the percentage elongation of 1wt% cca containing composite and the composite grade without cca. this research however tends to develop an amc, using sheanut shell ash (ssa) as reinforcement. 2.0 materials and method 2.1 materials used the materials used in this research work include shea nut shell which was obtained from the shea butter factory located in the federal polytechnic bida, niger state and al 6061 procured from 5star technology co., ltd, china and its chemical composition is presented in table 1. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 3 table 1. chemical composition of al 6061 element mg si fe mn cu cr zn ni t al composition (%) 0.93 0.53 0.21 0.14 0.17 0.09 0.08 0.01 0.01 balance 2.2 preparation of shea nutshell ash (ssa) the shell which is the desired material was obtained after the nut was removed/separated from the shea nut. after obtaining the shell, it was washed in order to remove the impurities and then sun dried for two days. the shell was milled into powder to obtain the fine particles. the powder portion was then used to obtain ash, adopting the method of alaneme et al.(2018). 2.3 casting of the samples the composite samples were produced by utilizing stir casting process performed in accordance with zubairu et al. (2018). the aluminium 6061 was cut into smaller size and weighed. prior to the casting process, charge calculation was done to determine the amount of al 6061 and shea nutshell ash (ssa) required for preparing the samples. the weight mix ratio was 5% and 10% respectively. melting of the al-6061 alloy was carried out in a charcoal fired crucible furnace at a temperature of about 750oc ± 30oc (above the liquid temperature of the alloy). thereafter, the reinforcement particles of ssa was preheated and introduced into the melt. the composite was stirred manually while the melting was still taking place, after which the molten aluminium was introduced into the cylindrical (35cm x 15cm) mould cavity. the molten metal was allowed to solidify inside the mould. then the cast was removed and machined to samples for mechanical tests. 2.4 mechanical tests procedure the mechanical properties such as tensile test, hardness test, impact energy and microstructure of the composites were determined according to astm standards and methods reported in literature. 2.4.1 tensile test test specimens was prepared according to astm e8-82 standards, each specimen having 8mm in diameter and 60mm gauge length. the specimen was loaded in hounsfield tensiometer; monsanto, type w, serial no. 9875. for conducting a standard tensile test, a specimen is placed in the testing machine and the extensometer is attached. load is applied until the sample specimen fractures. the amount of load that caused the material to fracture is noted and the value of the force per unit area of fractured cross section is calculated as the tensile strength of the sample (adamu, 2016). 2.4.2 hardness test identec universal hardness testing machine: model 8187.5kv (b), indenter; diamond cone (120°), scale a was used to determine the hardness properties of the developed composites in accordance with astm e384-11 standards. a load of 1n for a period of 10 seconds was applied on specimens. the hardness was determined by recording the diagonal lengths of indentation produced. the test was carried out at three different points on the specimens and the average value taken as the hardness of the cast specimens (zubairu et al., 2018). 2.4.3 impact test the impact test was conducted in accordance with astm e 602-91 standard method and definitions for mechanical testing of steel products. v-notches of 0.5mm depth were made on the samples each and the impact strength was carried out using hounsfield balance impact testing machine (joules). chapy impact testing machine (capacity 15-25 joules), serial no. 41207-15269c was used to carry out the test on the samples. 2.5 microstructural analysis zubairu et al: effect of shea nutshell ash on the mechanical properties of cast al6061. azojete, 17(1):1-8. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 4 before the metallography and surface morphology examination, the surface of the samples was successively grounded using grit papers of different grades 12°c, 18°c, 32°c, 40°c, 60°c, 80°c and 120°c (adamu, 2016). being aluminium, grinding was carried out from the 40°c grit paper to the 120°c grit paper with the application of lubricant intermittently; this is to prevent overheating and provides a rinsing action, which flushes away the particles being removed from the surface. they were subsequently polished with the aid of a polishing machine using alumina to remove the scratches that are left during grinding. etching was then carried out, which is the chemical attack on the surface of a polished metal, the etchant used for aluminium samples are “keller’s reagent, which is a solution of 1ml distilled water, 5ml nitric acid and 2ml hydrofluoric acid. a computerised photographic visual metallurgical microscope, model njf-120a, rating 230v-5v/60hz was then used to view the microstructures of the polished samples (zubairu, 2018). 3.0 results and discussion 3.1 mechanical properties of developed composites 3.1.1 hardness value the result of the variation of hardness values of the materials tested are presented in figure 1. the hardness values of the developed materials are higher than that of the alloy as also observed by kuburi et al. (2017) and saravan et al. (2015); this is due to the addition of the reinforcement material (ssa) into the microstructure of the alloy. highest hardness value of 187.60 hrb was obtained on sample c (al6061+ 10% ssa) with the difference not much compared with the other developed matrix composites. the lowest hardness value of 70.33 hrb was observed for sample control (al6061). by implication, the hardness of the reinforced al6061, with 10wt% ssa increased the hardness of the material by 166.74%. this is in accordance with gladston et al. (2015) obtained, when he used al6061and 8% rice husk ash as reinforcement. figure 1. variation of hardness of the cast composite with sample weight 3.1.2 tensile strength of developed composites the variation of tensile properties of the materials with sample weight are presented in figure 2. the tensile strength of the developed materials decreases with the increase in wt% ssa as shown in figure 2. sample al6061+ 10% ssa, recorded the lowest tensile strength value of 94.52n/mm2 compared to ‘as cast’ al6061 (al6061+0wt% ssa), with 115.67 n/mm2. the strength of the developed composite with 10wt% ssa shows a reduction of 18. 29% compared to as cast al6061. 0 20 40 60 80 100 120 140 160 180 200 a b c h ar d n e ss v al u e ( h r b ) samples arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 5 figure 2. variation of tensile strength of the cast composite with sample weight 3.1.3 impact energy of developed composites highest impact energy of 4.78 j was obtained on sample (al6061+10% ssa) which is favourable compared to the value of 2.71 j observed on the as cast al6061. mechanical properties obtained shows clearly that the reinforced alloy will perform favourably well as against the as cast al6061; resulting into an increase 76.38%. this conforms to the results obtained by previous researchers as reported in literature. figure 3. variation of impact test of the cast composite samples 3.2 microstructure of the developed al6061 composites the microstructure of the developed cast al6061 with the addition of sheanut shell ash (ssa) composites is presented in figure 4a – c. the microstructure of al6061 (figure 4a) gives a fair distribution of the intermetallic phases (black) in α-al (white) matrix.\ the microstructure analysis of sample a (al6061 0%ssa) produced al (white) and the intermetallic phases (black). the pattern of the microstructure of samples b, (al6061 5% ssa), sample c (al6061 10% ssa) presented in figure 4b and 4c were similar to those of sample a (al6061 0% ssa). dendrites formation is observed and the reinforcing particles (ssa) is visible and clearly delineated in the microstructure. the particles are fairly well distributed in the almg-si matrix and signs of particle clusters are minimal. the arrangement of the grains and phases geometrically in the material is in line with the findings of kuburi et al. (2017). 0 20 40 60 80 100 120 140 a b c t e n si le s tr e n gt h ( n /m m 2 ) samples 0 1 2 3 4 5 6 a b c im p ac t e n e rg y (j ) samples zubairu et al: effect of shea nutshell ash on the mechanical properties of cast al6061. azojete, 17(1):1-8. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 6 5% ×100 5% × 200 10% × 100 10% × 200 figure 4. optical micrograph of developed aluminium alloy 6061/ssa, showing α-al (white) and intermetallic phase (black), mag x100: control (a) al6061+ 0% ssa (b) al6061+5% ssa (c) al6061+10% ssa. 4.0 conclusion al6061/ssa aluminium matrix composites were successfully produced using stir casting technique. the mechanical behaviour of the matrix composites containing 0, 5 and 10 wt % ssa as reinforcements was investigated. microstructure of the developed composites showed that the ssa particles were homogeneously distributed in the aluminium matrix. the distribution was predominantly intra granular. however, ssa particles affected the mechanical properties of the al6061. the hardness of the base alloy increased as the w% ssa increased; such that sample al6061+10% ssa exhibited highest hardness value, giving a percentage increase of 166. 74%. in the same vein, impact energy of the as cast al6061 increased as the wt% ssa increased. the percentage increase in impact energy was calculated to be 76.38%. however, the strength of the alloy decreased as the wt% of the reinforcement increased; the strength of the developed composite with 10wt% ssa shows a reduction of 18. 29% compared to as cast al6061. sheanut shell ash improves the hardness and impact energy of the as cast al6061. ssa however promises to be a good reinforcement material, for hybrid aluminium matrix composites especially when the property desired is hardness and impact energy. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 7 references adamu, ma. 2016. evaluation of the effect of mechanical vibration on alsi alloy melt using a modified mould vibrating machine. msc. dissertation. department of mechanical engineering, ahmadu bello university, zaria, nigeria. alaneme, k. k., ademilua, b. o. and bodunrin, m. o. 2013. mechanical properties and corrosion behaviour of aluminium hybrid composites reinforced with silicon carbide and bamboo leaf ash. tribology in industry, 35(1): 25‑35. alaneme, kk., bodunrin, mo. and awe, aa. 2018. microstructure, mechanical and fracture properties of groundnut shell ash and silicon carbide dispersion strengthened aluminium matrix composites. journal of king saud university–engineering sciences, 30: 96-103. astm e384-11. 2012. standard test method for knoop and vickers hardness of materials. american society for testing and materials, philadelphia. astm e 602-91. 1992. standard test method for sharp-notch impact testing with flat specimens. american society for testing and materials, philadelphia. astm e8-82: standard test method for tension testing of metallic materials (metric), annual book of astm standards, philadelphia; 1991. fatile, ob., akinruli, ji. and amori, aa. 2014. microstructure and mechanical behaviour of stircast al-mg-sl alloy matrix hybrid composite reinforced with corn cob ash and silicon carbide. international journal of engineering and technology innovation, 4(4): 251-259. gladston, kaj., sheriff, mn., dinaharan, i. and selvam, dj. 2015. production and characterization of rice husk ash particulate reinforced al6061 aluminium alloy composites by compocasting. transactions of nonferrous metals society of china, 25(3): 683-691. hossain, r., ali, h., amin, al., kibria, g. and shafiu, l. 2017. ferdous fabrication and performance test of aluminium alloy-rice husk ash hybrid metal matrix composite as industrial and construction material. international journal of engineering materials and manufacture, 2(4): 94-102. kaczmar, jw., pietrzak, k. and włosi´nski, w. 2000. the production and application of metal matrix composite materials. journal of material and process technology, 106(1–3): 58–67. kuburi, ls., dauda, m., yaro, sa. and abdulwahab, m. 2017. investigation of the mechanical properties of aluminium matrix composite for marine structures. nigerian journal of technology research, 12(2): 15-19. doi: https://dx.doi.org/10.4314/njtr.v12i2.3. niranjan, kn., shivaraj, bn., sunil kumar, m. and deepak, ar. 2017. study of mechanical properties of al6061 hybrid composite by stir casting method. international research journal of engineering and technology, 4(1): 1036-1040. pitchayyapillai, g., seenikannan, p., raja k. and chandrasekaran, k. 2016. al6061 hybrid metal matrix composite reinforced with alumina and molybdenum disulphide. advances in materials science and engineering, 2016, art id: 6127624: pp. 9. rahman, mh. and al rashed, hmm. 2013. characterization of silicon carbide reinforced aluminium matrix composites. 10th international conference on mechanical engineering, procedia engineering, 90: 103-109. saravan, p., shanmuga, pm., raghuram, r., sharath, ks. and anand, t. 2015. investigation of mechanical properties in aluminium silicon carbide mica hybrid metal matrix composite. international journal of engineering science and advanced technology, 5(2): 112-117. zubairu et al: effect of shea nutshell ash on the mechanical properties of cast al6061. azojete, 17(1):1-8. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nmapee@gmail.com 8 tjong, sc. 2014. processing and deformation characteristics of metals reinforced with ceramic nanoparticles. in: tjong s. c, editor. nano crystalline materials [internet]. 2nd ed. oxford: elsevier, pp. 269–304. zubairu, pt., abdullahi, m., egbe, eap., jabo, ua. and babazhitsu, ky. 2018. study of mechanical properties and microstructure of developed aa6061-sic/gr hybrid composites. journal of research and innovations in engineering 3(1): 106-112 cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 168-184 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng ____________________ *corresponding author email address: as1117@exeter.ac.uk 168 original research article performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria a. i. suleiman*, l. w. h. kevin and a. s. ajayi department of renewable energy engineering,university of exeter, penryn campus, cornwall tr10 9ef, uk article information received october, 2018 accepted december, 2018 keywords: biomass inoculums cow slury methane sustainable development goal innertube diodigester abstract in the developing countries, methane capture from manures has been encouraged by using biogas plants which are predominantly household anaerobic digesters handling manure of livestock held by an average-sized family. this paper aims to assess the performance of a simplified model inner tube biodigester for biomethane production for household use in nigeria. this paper also evaluates the biomass conversion technologies tested in the reef (renewable energy engineering facility) lab at the university of exeter, the uk and the technology readiness level and implementation in nigeria. cow slurry and inoculum were used to evaluate the operational efficiency and feasibility of the model inner tube digester, with the aim of encouraging its use and adoption in nigeria and africa in general to help impact on the sustainable development goals (sdg) on climate change and energy efficiency targets. the model digester as an option against the use of firewood, kerosene or liquid petroleum gas (lpg) system could increase the renewable energy potential in nigeria while retaining organic matter and nutrients for soil replenishment for agricultural purposes. the 12-litre scale biodigester showed a characteristic pattern of optimum biogas production efficiency and performance when mixed with inoculum, which indicates its prospect for future evaluation and use. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction 1.1 bioenergy technology development worldwide access to affordable, clean energy is a major driver of nigeria’s and the globe’s actualization of the sustainable development goals (sdgs). it also underpins other sdgs since energy access facilitates economic development, food security, health, education and other related objectives (röder, thornley, campbell, & bows-larkin, 2014). nigeria and other african countries have a wide range of bioenergy feedstocks, which can be combined with a vast array of conversion technologies at a variety of scales to deliver sustainable bioenergy solutions from liquid fuels to cooking gas, and electricity (andrew, 2014; mirjam röder, 2018). bioenergy systems are already playing a key role in many countries towards achieving their climate change, emission reduction and renewable energy http://www.azojete.com.ng mailto:as1117@exeter.ac.uk arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 169 contribution targets (andrew w, 2017). the term biomass is often referred to as the biodegradable fraction of products, waste and residues from the biological origin; agriculture (including vegetal and animal substances), forestry and related industries including fisheries and aquaculture, as well as the biodegradable fraction of the industrial and municipal waste (ben-iwoet al., 2016). biomass contributes to the supply of energy approximately to 12% of the global status of the renewable energy inputs ranging from 40% to 50% in some developing countries (ben-iwo et al., 2016; tauseefet al., 2013). despite this enormous and potential opportunity in bioenergy, nigeria still lags in biofuel production amongst other african countries such as ghana, kenya and south africa(beniwo et al., 2016).this paper aims to explore the prospects of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. in the last decade, a major part of the globe has witnessed consistent growth in bioenergy, a renewable and environmentally friendly energy source, owing to its usefulness and advances in biodigesters development globally allowing for this technology to become more readily available in different applications worldwide (thornleyet al., 2014). precisely, the success stories of bioenergy are mainly due to the efforts of developed continents like south and north america, asia, and european nations (brazil, usa, china, india, malaysia, the uk, etc.). see figure 1, the global trend of methane emissions from the management of livestock manure (tauseef et al., 2013). figure 1. the global trend of methane emissions from the management of livestock manure (tauseef et al., 2013). 1.2 energy crisis in africa and nigeria energy plays a very significant role in the socio-economic development of a region and its people. over the years, africa has not only been the poorest continent in the world, but also the only major developing region with negative growth in income per capita between 1980–2000 and till date (ben-iwo et al., 2016). in the rural communities, fuelwood and charcoal which is sourced from wood biomass is the predominant energy source used in africa, resulting to about 74% of the total energy consumption for cooking and heating homes, when compared to 37% in asia and 25% in latin america (ben-iwoet al., 2016; kevin, 2015). most of the people living in sub-saharan africa (ssa) region lack access to clean, affordable, and environmentally-friendly energy and depend on solid biomass (usually referred to as firewood in nigeria) to meet their basic needs for cooking (kumar and bai, 2005). this has been a major contributor to poverty and a hindrance to the development of file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 170 the african continent. even in recent times, nothing significant has really changed or improved on the biofuel production capacity in nigeria (galadima et al., 2011). those living in the rural areas constitute the highest number of users of firewood because of their proximity to the biomass source and fewer regulations and monitoring on deforestation from the government(sunset, 2015). those in the urban and sub-urban areas who use modern cooking devices like gas cookers, burners, or stoves find it difficult to cope with the rising costs of the energy required to run those devices or systems. over the year, the rising cost of liquid petroleum gas (lpg) and dual-purpose kerosene (dpk) have made most people living in these mentioned areas to abandon the use of gas cookers or stoves to cheaper alternatives such asfirewood and some locally made charcoal powered stoves(ben-iwo et al., 2016; sunset, 2015.). for those who persist in using lpg powered gas cookers, most of them buy on credit and pay at the end of the month when they receive their wages from employers. these set of people are usually the credit-worthy civil servants who project in public service institutions, or private industries where they get paid at month end. the lpg retailers know they are creditworthy and hence could afford to sell on ‘’buy now pay later’’, as it is often referred to in most part of africa. in nigeria more specifically, the case is no different.despite its rich source of crude oil, it has experienced a slow pace of growth in the bioenergy industry because it is historically plagued by civil unrest and poor government policies on energy supply and security, which are among the main contributor for its poor economic performance in the past and even recently(ben-iwo et al., 2016).nigeria has four petroleum refineries with combined crude distillation capacity of 10.7 million barrels per day (bbl./d), an amount that far exceeds the national demand, the country still imports most refined petroleum products because the refineries are moribund(ben-iwo et al., 2016). this is due largely to the low capacity utilization of existing refineries and the poor government policies as mentioned earlier. the growing number of oil discoveries in the african continent has had a questionable negative impact on the economies of nigeria(ben-iwo et al., 2016). with the growing tensions in niger delta oil-rich regions because of the environmental impact of operations of major oil and gas companies (shell, agip, mobil, total, addax and nnpc), have not helped in making the much-needed progress in the energy sector. electricity supply from gas-powered turbine has suffered more due to the incessant crisis between the youths and gas companies in the region where the gas is produced. the availability of dual purpose kerosene (dpk) for cooking and used as jet fuel have equally suffered a setback. oil companies and suppliers would rather sell to aviation industries or airline operators in the bid to make more money than those who simply use the kerosene to power their stove for cooking and heating purposes. biomass is the main energy resource in nigeria owing to the huge reliance on the energy source for cooking and heating purposes by most of the nigerian people(ben-iwo et al., 2016; thornley et al., 2014). according to the global initiative on available, clean and efficient energy sustainable energy for all (se4all), not much progress has been made in providing access to non-solid cooking fuels (like firewood) since 1990. as visible in figure2, below, in 2010, only 26% of the population had access to non-solid cooking fuels with a big difference between urban and rural areas(ben-iwo et al., http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 171 2016; lópez-bellido, 2014). the government of nigeria have made little or no efforts in trying to remedy these situations because it makes more money through oil exports. regardless, the profits from oil exports could mean that the government in nigeria can invest in domestic businesses (like the development of the bioenergy technology) and infrastructure, consequently promoting economic growth and attracting foreign investments(ben-iwo et al., 2016). however, with the growing concerns of climate change and demand to cut down on green house gases (ghgs) emissions, nigeria is making efforts like other countries towards research and development(r&d) of alternatives to fossil fuels but these efforts have resulted in little or no major impact or results(sunset et al.,2015). figure 2. access cooking fuels in rural and urban areas in 2010 (in %) (ben-iwo et al., 2016) the argument is that the government must seek help from international corporations just like it has done with the crude oil (petroleum) industry. but this is equally not yielding the much-anticipated result like we see in developed countries (ben-iwo et al., 2016; nand, et al 1991). hence, in the bid to draw more attention from government and the people both in the urban and most especially the rural areas, there is a need to design and construct a low cost and small-scale tailor-made bioenergy system that can be used to produce gas (methane) for cooking, heating purposes thereby creating the much-needed awareness and attention on the feasibility of harnessing renewable energy from solid wastes (renewable energy), and improve on the energy security of the country. 1.3 biomethane from biomass and solid waste in nigeria globally, research and development on laboratory and field trials for biofuel systems has significantly increased over the last two decades and has become attractive as the right substitute for fossil fuels (ben-iwo et al., 2016; liu & wu, 2016). this is because of the increasing demand for clean energy, global climate change targets and policies towards reducing dependence on crude oil (ben-iwo et al., 2016). the processing of biomass into biofuel and its co-products has important effects on international policy and economy, and on rural development. it helps in reducing the over-dependence on oil-producing countries and supports rural economies through job creation and an additional source of income (ben-iwo et al., 2016; welfle, 2017). the solid biomass(wood) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 172 account for about 80% of the total primary energy consumed in rural and suburban communities in nigeria (ben-iwo et al., 2016; simonyan and fasina, 2013). the northern part of nigeria has the highest number of cattle husbandry and about 95% of these cattle graze in the open with the dungs disperse without proper collection (ben-iwo et al., 2016; galadima et al., 2011). in the southern part of the country where we have slaughterhouses (abattoirs) or sites where animals such as cows, goats or sheep (often referred to as zongo) are sold, this waste is properly collected and could be used as fertilizer or dumped in the open. despite the difficulty of ranching cattles in nigeria, cow slurry still holds a lot of prospects to help curb the energy crises in nigeria (galadima et al., 2011; tauseef et al., 2013). most especially in the production of biofuel for domestic purposes. it has been estimated that slurry from animal husbandry produces about 240 million metric tons of carbon dioxide equivalent of methane to the atmosphere and this represents one of the highest anthropogenic sources of biomethane (simonyan and fasina, 2013). since methane is the second highest contributor to global warming after carbon dioxide (tauseef et al., 2013; zheng et al., 2015), it is necessary to explore ways in developing systems to capture as much of the anthropogenic methane as possible and convert them into use. there is a lot of advantage in the capture and utilization of methane: it is clean as a source of energy when compared to natural gas (tauseef et al., 2013), which is predominant in nigeria and creates major pollution crises in niger delta regions. the aim of this research project is to explore the prospects of using the inner tube digester to produce biomethane from cow slurry which can be used in developing countries for providing energy to the rural poor. the effect of inoculating the cow slurry in the digester to produce more biomethane was equally investigated. the materials and ease of construction of the digester from locally sourced materials and how the methane can be captured for domestic purposes, in this case, was highlighted. 1.4 anaerobic digestion: steps associated with the generation of methane anaerobic digestion is the bacterial fermentation of organic substances in the absence of oxygen. the process leads to the decomposition of complex biodegradable organics in a four-step process (kevin, 2015) (fig. 1). the anaerobic digestion of organic material in municipal solid waste or from cow slurry provides renewable energy in the form of biogas (mata alvarez, 2003; kevin 2015) and can also create a means of recycling valued mineral nutrients back to agricultural land (lukehurst et al., 2010). to optimize the latter requires source separation of targeted organics, as the material arising from mechanical pre-treatment, has a high level of contamination, with heavy metal concentrations above the recognized values for agricultural land used in food crop production (zhang, 2012). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 173 figure 3. steps of the anaerobic digestion process (tauseef et al., 2013) food waste from both domestic and commercial sources have been a major source of feedstock for biogas production due to its high biochemical methane potential (zhang, 2012), though its high moisture content makes energy recovery through thermal treatment unappealing (ahring, 2003). 2.0 methodology 2.1 materials the research was conducted in laboratory using three lab-scale manually mixed mesophilic inner tube digesters which were fed on a daily basis for 30 day period. the results presented here were for the first 10-days trial. the laboratory-scale digesters each had a 6-litre substrate volume as content but with a total capacity of 12-litres and were constructed using the innertubes of automobile car tyres, acrylic tubes with gas-tight top and runner bungs as stoppers for the openings in the tubes. 2.1.1 conventional components of biodigesters there are several types of biodigester used in producing biogas from organic wastes that have been introduced and applied to various areas of use like in domestic and industrial applications. the most predominant being the large-scale communal type, e.g. fixed dome and floating dome types(tauseef et al., 2013). china and india were among the first countries which methodically developed biogas technology for rural communities. they equally experienced that large-scale biodigester frequently showed some glitches for rural application and use. some of the reasons adduced were the high production cost and difficulty in maintenance by the households (liu and wu, 2016; tauseef et al., 2013). as an alternative to the common types of large-scale biodigester, an inner tube (for automobile tyres) biodigester has been conceptualized and constructed for smallscale household purposes in nigerian rural areas. the original idea was from john l fry, innertube methane digesters for fuel gas and fertilizer, developed in 1973 for households. some globally recognized biogas digesters used in places like india, china, and other developing countries for producing biogas from animal manure normally have the following features: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 174  digester: the slurry which is usually animal wastes mixed with water or other solid wastes is fermented inside the digester and biogas is produced through bacterial action(tauseef et al., 2013). this research adopted this type of digester concept given the ease of construction, the availability of the materials for construction and the low-cost of the entire biodigester.  gas holder or gas storage dome: the biogas here is collected in the gas holder, which holds the gas until the time of consumption (tauseef, et al, 2013).  outlet pipe: in the outlet pipe the digested slurry is discharged into the outlet tank either through the outlet pipe or the vent provided in the digester.  mixing tank: the feedstock material (dung) is collected in the mixing tank. enough water is added, and the material is thoroughly mixed until a homogeneous slurry is formed for the anaerobic digestion process.  inlet pipe: in the inlet pipe type, the feedstock is emptied into the digester through the inlet pipe/tank for the process.  gas pipeline/hose: the gas hose transports the gas to the point of application, such as a heating or cooking stove or a lamp. cow slurry is the most common feedstock for biogas digesters, but substantial amounts of manure produced by buffalos, poultry, and pigs, are used, too (table 1). table 1. biogas potential of livestock manure (tauseef et al., 2013) animal fresh total manure (kg/head/day) total solid (ts) (kg/head/day) biogas yield factor (m3/kg of dry matter) cn vs (% of manure) cow 20 4.0 0.20 – 0.50 18 – 25 13 buffalo 25 4.5 0.15 – 0.32 18 – 25 pigs 1 – 5 0.6 0.56 – 0.65 13 12 sheep 1.8 0.6 0.37 – 0.61 29 goats poultry 0.1 0.03 0.31 – 0.54 17 horses 2.4 7.1 0.20 – 0.30 24 – 25 rabbits 0.2 0.1 0.36 2.1.2 experimental procedure of the biodigester the research project was conducted using a lab-scale manually mixed mesophilic biodigesters, which was constructed and fed daily. the lab-scale biodigesters each had a 12-litre capacity but 6litres projecting volume (for headspace considerations) and were constructed of acrylic (perspex) tubes with air-tight, and waterproof tyre tubes. the innertubes of car tyres were locally sourced from tyre shops around the community. the top part of the digester was fitted with a gas outlet tube made from acrylic, an inlet feed port sealed with a rubber bung, and an effluent port sealed with a rubber bung where the digestate is released. the figures 5 and 6 shows the complete draft and layout of the inner tube digesters as it was designed and setup. given the prevailing weather http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 175 condition, the temperature of the system was raised at 36 ± 1°c by concentrating two 1000 watts halogen lamps on the biodigesters at a height of about 1.5 metres to keep the temperature of the biodigesters at the optimum gas production level. the lamps provided the much-needed thermal energy required to keep the biodigesters at an optimum temperature level for 7 hours daily and the thick blanket was used to cover the digesters through the night, to maintain or retain most of the heat generated from the lamp. the values from the temperature probes showed that part of the heat was retained at night when the halogen was put out to reduce the energy billings. the artificial heating (parasitic energy)(kevin, 2015) was equally necessary to simulate the average nigerian type of temperature from a solar source, where the ambient temperature is usually higher than the ambient temperature of the lab where the research was carried out. 2.1.3 household continuousfeed methane biodigester there are several types of biodigester used in producing biogas from organic wastes that have been introduced and applied to various areas of use like in domestic and industrial applications. the most predominant type being the large-scale communal type, e.g. fixed dome and floating dome types (tauseef et al., 2013). china and india were among the first countries which methodically developed biogas technology for rural communities. they equally experienced that large-scale biodigester frequently showed some glitches for rural application and use. some of the reasons adduced were the high production cost and difficulty in maintenance by the households (liu and wu, 2016; tauseef et al., 2013). as an alternative to the common types of large-scale biodigester, an innertube (for automobile tyres) biodigester has been conceptualized and constructed for small-scale household purposes in nigerian rural areas. the original idea was from john l fry, innertube methane digesters for fuel gas and fertilizer, developed in 1973 for households. the biodigester was made from tractor scrap innertubes, acrylic (perspex), bicycle innertubes, pvc pipes, shown in figure 4, below. the small-scale biodigester was suitable for the household purpose and quite affordable to be installed individually in each household with access to solid waste like cow slurry. figure 4. innertube digester; methane digesters for fuel gas and fertilizer (fry et al., 1973) the newly conceptualized digester was designed and constructed from similar materials like automobile car tyre innertubes (butyl rubber), acrylic (usually referred to as perspex in nigeria). see figures5,6, for the array of the design and construction of the simplified model of a low-cost innertube digester. the biodigester was constructed taking into consideration the availability and low costs of the materials rural communities in nigeria. the biodigester can be fed continuously file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 176 using food wastes and other semi-solid waste or biodegradable biomass,unlike john l fry’s digester that was strictly used for cow slurry. household users can take the effluent as ready-to-use biofertilizer in addition to the biomethane gas for their daily cooking and heating purposes. figure 5. arrays of the autocad design of the 12 litres innertube digester figure 6. arrays of the 12 litres innertube digesters been tested 2.1.4 feeding regime a continuous feeding operation was realized by daily removal of digestate through an outlet tube in the other section of each digester, followed by substrate addition through the inlet tube. the labscale digesters were of the same design and the same mixing regime and hydraulic retention time (hrt) was to be observed for a 30-day period(kevin, 2015). in all the cases biogas production was measured using tipping-bucket gas counters with continuous data logging (y zhang, walker, banks, & environment, 2010) using the rasberry pi kit and phyton coding. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 177 figure 7. potential biogas yield (tauseef et al., 2013) 2.1.5 mixing mechanism: parasitic energy demand the major requirements of the anaerobic digestion process are thermal energy to maintain temperature (as in the case of using the halogen lamps) and pumping/mixing energy to distribute and homogenise substrate(kevin, 2015). in the case of these digesters, the manual mixing by hand was adopted looking at the prevailing energy crisis in nigeria and rural communities globally. most rural homes lack access to constant electricity and it became obvious that these digesters may not get the required parasitic mixing energy from electricity. hence, manual mixing is adopted given the fact that the materials of construction of the digesters are flexible (butyl rubber) and elastic. since most anaerobic digestion systems are used to generate electricity using a combined heat and power (chp) unit(kevin, 2015), excess heat is often readily available in most sophisticated systems, so the parasitic energy required to heat will not be considered further as far this project is concerned. 2.1.6 data logging of the bioprocess: using raspberry pi and sensors operative monitoring and control are important to ensure process stability while optimizing process performance and the economics of the system (kevin, 2015), particularly if the organic loading rate is high (latif, et al, 2011). certainly, there is a need for effective monitoring and control if the mixing system is to be optimized for biogas production. as a general case, monitoring and control systems vary depending on the application or use (ounnar, et al, 2012). research and development require adaptable process instrumentation whereas on-site system needs robust and automated process instrumentation solutions (kevin, 2015). in a more complex biodigester, a more sensitive, comprehensive and reliable approach for data logging is adopted, whereas a small single-feedstock rural ad plant may survive with simple titration augmented by the occasional visit by a consultant (zhang et al., 2010). though the cost of monitoring equipment is becoming cheaper thereby improving the affordability of monitoring and control for smaller operations, the robustness and simplicity will always be key requirements when deployed in the potentially harsh environment of a file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 178 farm. to save cost and ensure a simple data logging process is achieved to evaluate the performance efficiency of the lab-scale digesters, the biogas production was measured using tipping-bucket gas counters with continuous data logging (zhang et al., 2010) connected to the raspberry pi kit and phyton coding used to interpret the readings of the temperature probes (inserted into the digesters) and gas volumes. the simple codes used was effective in reading the volumes of gas produced and the temperature from the sensor probes. see figure 8, for the set up used for the bioprocess data logging. many sensors produce pulsed outputs with a switching action. this circuit and code combination for gas production as shown below are very useful; gpio.cleanup() #reset gpio port gpio.setmode(gpio.bcm)#broadcom pin notation gpio.setup(17,gpio.in)#setup gpio 17 as input pinstate=gpio.input(17)#read the pin a simple circuit diagram for the connection used on the raspberry pi breadboard for the ds18b20 temperature probes is shown in figure 8. figure 8. circuit diagram for the typical ds18b20 temperature probe(ds18b20, 2018) the temperature sensor circuit diagram for the lab-scale biodigesters was built as outlined in figure8, and the codes written, run on the python script. 2.1.7 other bioprocess optimization metrics used the practicality of the different metrics that can be measured varies(catron, et al, 2013) but key values are usually the ph, alkalinity, volatile fatty acid (vfa) concentration and biogas flow rate and composition of the substrate(budhijanto, et al, 2012). biogas production is an easy way to measure reactor performance but does not indicate the chemical stress experienced by the digester (kevin, 2015). the biogas production of the digester was measured using tipping-bucket gas counters with continuous data logging (zhang et al., 2010) connected to the raspberry pi kit and phyton coding used to interpret the pulse readings and gas volumes. the ph of the substrate was also relatively easy to monitor using a standardized and calibrated double junction ph meter (phtestr 30). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 179 2.1.8 cattle slurry over the period of this research two 60litres, drums of cattle slurry were obtained from chynoweth dairy farm, truro, the united kingdom. it was then homogenised and stored in the bioresource refrigerator under the cold chain. table 1 shows the typical characteristics of the cow slurry material and the biogas potential. to determine the moisture content and total solids of the cow slurry before mixing with deionized water (1:1), there was a need to oven drying and desiccation. 2.1.9 inoculum the inoculum for the 12-litre laboratory-scale trial digesters was taken from a 30-litre drum that is equally used at the farm at truro, the uk. the inoculum was free from any large particles and easy to use in mixing with the cow slurry (1:1) to form the digestate. one of the 12-litre digesters were inoculated with the combination of 6-litres digestate (inoculum and cow slurry) to give a composition of 1:1, under a mesophilic condition at the renewable energy engineering facility, at the university of exeter, the uk. the inoculum was provided by chynoweth dairy farm at truro in cornwall. a digested dairy manure inoculum was selected due to the high levels of biomass it contained, the reliability of the source and the instantaneous digester start-up that the inoculum enabled (yue zhang, et al, 2012). 2.2 digester operation and monitoring the model laboratory-scale digesters were fed in parts with a mixture of inoculum and cow slurry, at a ratio 1:1 on a volatile solid basis (yue zhang et al., 2012). two more digesters were fed with cow slurry (the same ratio as the first digester) and inoculum only in the proportion of 1:1 on a fresh weight basis as calculated based on the moisture content and total solids (ts) content with respect to their relative quantities in the uk waste stream(kevin, 2015; yue zhang et al., 2012). to ensure homogeneity the substrates in the digesters were thoroughly mixed manually by hand-agitation which reduced the total solids content from 94% to around 20%. the choice of manual mixing was to reduce the cost of parasitic energy (kevin, 2015) required for mixing and to simulate the mixing technique that is predominantly available in nigeria or africa where the model digester is originally designed to be used. the third digester which was fed only on inoculum and acted as a control, for the evaluation of the entire process. the total organic loading rate (olr) for all digesters was 6 kg vs m−3 day−1 throughout the trial. the solids and liquid retention times were coupled and hydraulic retention time (hrt) of 30 days and maintained. the digestates were removed with the aid of calibrated syringes through the effluent tube after which they are discarded or used as biofertilizer when needed. fresh substrates were fed to the digester in the same quantity as the effluent taken out. see figure 9, for part of the bioprocess carried out. figure 9. bioprocess: loading the biodigester with the feedstock file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 180 the operating regime of the entire system was maintained for 30 days with the possibility of extending to measure another parameter which is not under study in this paper. all digesters (namely alpha, beta, cappa) were monitored daily for biogas production, temperature and ph. all gas volumes reported are corrected to standard temperature and pressure (stp) of 0 0c, 101.325 kpa. 3.0 results and discussions 3.1 carbon and nitrogen content the carbon to nitrogen (c/n) ratio plays an important role in the ad and biogas production process. a c/n ratio that is either too high or too low will inhibit biogas production(tauseef et al., 2013). the c/n ratio of the substrate after inoculation was calculated and found to be 24.7 for the dairy manure. the suitable range of the c/n ratio was 20–30 for anaerobic digestion processes, and the optimal c/n ratio suggested for gas production is 25(tauseef et al., 2013; yue zhang et al., 2012). table 3. the volume of biogas produced from the tipping counter (pulse/ml) time (days) alpha biogas production pulse/130ml beta biogas production pulse/120 ml cappa biogas production pulse/104ml 1 4 31 5 2 2 69 4 3 1 53 0 4 0 45 0 5 4 59 9 6 7 67 4 7 6 52 5 8 6 63 10 9 7 64 9 10 3 1 2 table 4. the volume of biogas produced (ml) time (days) daily alpha biogas production (ml) daily beta biogas production (ml) daily cappa biogas production (ml) 1 520 3720 520 2 260 8280 416 3 130 6360 0 4 0 5400 0 5 520 7080 936 6 910 8040 416 7 780 6240 520 8 780 7560 1040 9 910 7680 936 10 390 9720 208 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 181 3.1 the effect of inoculating the innertube digester a suitable nutrient content in the inner tube biodigester is very important for the ad process of cow slurry. the essence of using inoculum in one of the digesters (beta digester) was not only to provide active microorganisms but also to serve as an active source of nutrients. the inoculum satisfies the demand for macronutrients, micronutrients and nitrogen for the anaerobic digestion process without the addition of chemicals (kevin, 2015; yue zhang et al., 2012). these nutrients essential for cell growth and the methanogens require special micronutrients for optimum gas production(kevin, 2015). the macronutrient (na, k, ca and mg) content in the inoculums was enough for the metabolic activities of the microorganisms(yue zhang et al., 2012).the results from the bioprocess show that the concentrations of k and ca in the beta digester were higher than in non-inoculated digester containing only cow slurry (cappa digester). figure 10. daily biogas production(ml) according to zhang et al., 2011, the micronutrients contained in bioreactors were the key factors for improving anaerobic digestion. the results from the volume of gas produced and the charts buttress these points (see figure 10 & 11). after inoculation for the first 10 days, the digested cow slurry in the beta digesterclearly shows from the charts in figures 10 & 11 and results shows that it had a higher concentration of micronutrients than when it is not mixed with the inoculum, the cappa digester (without inoculum). the biogas production rate and volume from the inoculated dairy manure (beta digester) were the highest of the three digesters (alpha, beta cappa). the alpha digester (inoculum only) like the cappa digester, did not produce a substantial amount of biogas like the inoculated digester. the chart shows that under the same set of conditions (temperature, insulation, volume, hydraulic retention time, feeding regime) the inner tube digester containing the inoculated cow slurry (beta-digester) had the most effective and consistent methane gas production level among all the digesters. the higher concentration of micronutrients contained in the beta digester because of inoculation resulted in an improved performance than seen with the other digesters (gu, et al, 2014). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 182 figure 11. cumulative biogas production (ml) 3.3 methane gas from the inoculated digester the gas produced from the inoculated beta digester can be scrubbed to produce pure methane which could be used for the purposes under studys. looking at the chart for the cumulative biogas production rate, it is obvious that the beta-digester can be upgraded by the capacity to produce more gas (methane) for household use. 4.0 conclusion biogas production takes a considerably long time to be stable.in developing countries, especially india, nigeria, ghana, and other southeast asian countries methane capture from manure has been encouraged by using biogas plants which are predominantly household anaerobic digesters handling manure of livestock held by an average-sized family. while this project is exploring the possibility of direct application on the field or households, it is important for it to be subjected to conventional trial and error experiments as seen in the lab-scale digester. this research project at this level only concerns itself with developing an innertube biodigester from automobile car tyre tubes for the quantitative optimization of continuous biodigester performance from an inoculated cow slurry. the purposes of the optimization efforts in biogas production using the tipping counter and raspberry pi are not only to obtain the highest conversion of the cow slurry but also to achieve the highest possible selectivity in simple materials for biodigesters construction. improvements on this model and the bioprocess optimization of the digesters will be presented in another publication of this project.the common feature of this digester, described in figure5&6, is that they employ no heating or continuous or excessive mixing due to which anaerobic digestion proceeds at a very slow rate. but this model adopted keeps the costs of the system down and makes them net energy producers, thereby making them a source of much-needed energy in the villages. the simplicity also makes their operation easy, enabling even illiterate farmers to use them effectively. there is a need to promote this form of bioenergy capture system throughout the developing world. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 183 acknowledgements this research was funded by the tertiary education trust fund (tetfund) under the supervision of auchi polytechnic, auchi, edo state, nigeria. the immense support of the rector of auchi polytechnic, auchi, dr. sanusi momodu jimah is appreciated. reference ben-iwo, j., manovic, v. and longhurst, p. 2016. biomass resources and biofuels potential for the production of transportation fuels in nigeria. renewable and sustainable energy reviews, 63, 172–192. https://doi.org/10.1016/j.rser.2016.05.050 budhijanto, w., purnomo, cw. and siregar, nc. 2012. simplified mathematical model for quantitative analysis of biogas production rate in a continuous digester. engineering journal, 16(5), 167–176. https://doi.org/10.4186/ej.2012.16.5.167 catron, j., stainback, ga., dwivedi, p. and lhotka, jm. 2013. bioenergy development in kentucky: a swot-anp analysis. forest policy and economics, 28, 38–43. https://doi.org/10.1016/j.forpol.2012.12.003 ds18b20, c. connecting ds18b20. retrieved august 14, 2018, from 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mixing regime and hydraulic retention time. latif, ma., ghufran, r., wahid, za. and ahmad, a. 2011. integrated application of upflow anaerobic sludge blanket reactor for the treatment of wastewaters. water research. https://doi.org/10.1016/j.watres.2011.05.049 liu, cm. and wu, sy. 2016. from biomass waste to biofuels and biomaterial building blocks. renewable energy, 96, 1056–1062. https://doi.org/10.1016/j.renene.2015.12.059 lópez-bellido, l., wery, j. and lópez-bellido, rj. 2014. energy crops: prospects in the context of sustainable agriculture. european journal of agronomy, 60, 1–12. https://doi.org/10.1016/j.eja.2014.07.001 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng suleiman, et al. performance of a simplified model inner-tube biodigester for biomethane production for household use in nigeria. azojete, 14(sp.i4):168-184. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 184 nand, k., sumithra devi, s., viswanath, p., deepak, s. and sarada, r. 1991. anaerobic digestion of canteen wastes for biogas production: process optimisation. process biochemistry. https://doi.org/10.1016/0032-9592(91)80001-6 ounnar, a., benhabyles, l. and igoud, s. 2012. energetic valorization of biomethane produced from cow-dung. in procedia engineering. https://doi.org/10.1016/j.proeng.2012.01.1211 röder, m., thornley, p., campbell, g. and bows-larkin, a. 2014. emissions associated with meeting the future global wheat demand: a case study of uk production under climate change constraints. environmental science and policy, 39, 13–24. https://doi.org/10.1016/j.envsci.2014.02.002 simonyan, kj. and fasina, o. 2013. biomass resources and bioenergy potentials in nigeria. african journal of agricultural research, 8(40), 4975–4989. https://doi.org/10.5897/ajar2013.6726 sunset, siphamandla, and msibi. 2015. potential for domestic biogas as household energy supply in south africa 2015. university of pretoria. https://doi.org/10.15713/ins.mmj.3 tauseef, sm., premalatha, m., abbasi, t. and abbasi, sa. 2013. methane capture from livestock manure. journal of environmental management. https://doi.org/10.1016/j.jenvman.2012.12.022 thornley, p., chong, k. and bridgwater, t. 2014. european biorefineries: implications for land, trade and employment. environmental science and policy, 37, 255–265. https://doi.org/10.1016/j.envsci.2013.09.004 welfle, a. 2017. balancing growing global bioenergy resource demands brazil’s biomass potential and the availability of resource for trade. biomass and bioenergy, 105, 83–95. https://doi.org/10.1016/j.biombioe.2017.06.011 zhang, y., banks, cj. and heaven, s. 2012. co-digestion of source segregated domestic food waste to improve process stability. bioresource technology. https://doi.org/10.1016/j.biortech.2012.03.040 zhang, y., walker, m., banks, c., environment, s. of c. e. 2010. optimising processes for the stable operation of food waste digestion: technical report no. 3. zheng, z., liu, j., yuan, x., wang, x., zhu, w., yang, f. and cui, z. 2015. effect of dairy manure to switchgrass co-digestion ratio on methane production and the bacterial community in batch anaerobic digestion. applied energy. https://doi.org/10.1016/j.apenergy.2015.04.078 http://www.azojete.com.ng article information 1.1 bioenergy technology development worldwide 1.3 biomethane from biomass and solid waste in ni 2.1 materials digester: the slurry which is usually animal waste gas holder or gas storage dome: the biogas here is outlet pipe: in the outlet pipe the digested slurr mixing tank: the feedstock material (dung) is coll inlet pipe: in the inlet pipe type, the feedstock gas pipeline/hose: the gas hose transports the gas table 1. biogas potential of livestock manure 2.1.3 household continuousfeed methane biodiges 2.1.4 feeding regime 2.1.5 mixing mechanism: parasitic energy demand 2.1.6 data logging of the bioprocess: using raspb 2.1.7 other bioprocess optimization metrics used 2.1.8 cattle slurry 2.1.9 inoculum 2.2 digester operation and monitoring 3.1 carbon and nitrogen content 3.1 the effect of inoculating the innertube diges 3.3 methane gas from the inoculated digester arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):675-684 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 675 original research article evaluating the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies s. g. yadima*, i. o ibiang and a. n. jones department of civil and water resources engineering, university of maiduguri, p.m.b. 1069, maiduguri, nigeria *corresponding author’s email address: maundeg6yadima@gmail.com 1.0 introduction water is one of the nature’s precious gifts, which sustains life on the planet earth. in arid and semi-arid regions, water is considered as a limited resource. it is now being realized that water, though replenishable, is not an unlimited resources and cannot be produced or added as and when required, by any known technological means. availability of water over the years depends on the spatial and temporal variation of precipitation. interestingly, water may be abundant during rainy season and scares in dry season, when it is mostly needed. although water covers more than 70% of the earth, only 1% of the earth’s water is available for drinking and other domestic purposes (youssef and khodzinskaya, 2019). it is noteworthy that intense agricultural practices, population growth, pollution and global warming are placing much pressure on the available water. therefore, the cost of water supply in many countries of the world has increased significantly over the past ten years (youssef and khodzinskaya, 2019). the effect is more severe in the arid and semi-arid regions, especially during droughts when water scarcity is compounded by high evaporation losses from open water bodies (dhirajlal, 2017, singha, 2006). article information abstract evaporation is recognized as environmental process which can significantly reduce the quality and quantity of stored water available for industrial, agricultural and household purposes. however, this process is dependent on several meteorological factors such as water and air temperature, wind speed and atmospheric humidity. thus, water savings especially in regions experiencing little rainfall resulting in low runoff events is crucial to enhanced optimum water usage by adopting the use of cover materials on ponds. covering of water bodies could effectively help in reducing evaporation from open water bodies. this research aimed at investigating the effectiveness of two locally available materials, viz; plastic paint covers and weaved thatch grass. they are used as floating and suspended covers respectively for reducing evaporation. three evaporation pans were used in this study. one pan was left uncovered as control (pan c), another pan was covered with plastic paint covers (pan a) while the last pan was shaded with weaved thatch grass (pan b). data were collected during dry season on weekly basis at 6:00 pm. this time-window was chosen because it is the hottest and driest months in maiduguri. sensitivity analysis was conducted between evaporation and climatic variables. the results show that evaporation is strongly correlated with temperature with r2 values of 0.8930, 0.9438 and 0.9566 for pans a, b and c respectively. it was also observed that the maximum monthly average percentage reduction (water savings) was found for pan a to be 39.43%, 42.38%, 33.27%, and 45.14% compared to pan b with 17.98%, 20.10%, 9.21%, and 32.55% for the months of march, april, may and june respectively. this comparison was relative to pan c as baseline data. additionally, plastic paint cover was found to be a good material for reducing evaporation from open water body compared to the suspended weaved thatch. therefore, plastic paint cover is recommended for use in reducing evaporation losses in small water bodies. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 february, 2020 revised 10 july, 2020 accepted 13 august, 2020. keywords: evaporation reduction floating covers suspended thatch humidity temperature wind speed. mailto:maundeg6yadima@gmail.com http://www.azojete.com.ng yadima et al.: evaluating the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies. azojete,16(4):675-684. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 676 additionally, changes in temperature and precipitation patterns can have remarkable impacts on water availability. temperature is predicted to rise in most areas, especially in inland areas and at higher latitudes where it is expected to increase significantly. higher temperatures will increase loss of water through evaporation (benzahta and mohamad, 2009; beare and heaney 2002). igor (1999) observed that the trend of evaporation from reservoirs depends upon meteorological factors such as temperature of the air and water, wind velocity and atmospheric humidity. additionally, in semi-arid regions, hot dry air moving from a land surface over a water body will result in higher evaporation rates (larry et al., 2007). evaporation is one of the most important environmental processes that can reduce the quantity and quality of stored water available for industrial, agricultural and household uses. in arid and semi-arid regions, evaporation can account for as much as 25 to 30% of the total consumptive use of surface water; therefore, control of evaporation from land based water bodies has remained one of the main planks of water conservation strategies (khudair et al., 2013). this assumes greater significance in arid and semi-arid regions like northern borno, nigeria, where water scarcity is already a common challenge to farmers. it is important that any development of water resources should ensure efficient control, conservation, and use of available water (christtansen. and worlton, 1998; benzahta and mohamad, 2009). whereas seepage loss in water courses and fields returns to streams and aquifers for reuse, evaporation loss signifies water that is totally lost from the available supply. covering the water bodies could help in reducing evaporation and improve water security, leading to increased irrigation production (prime et al., 2012). hence, greater attention should be given on reducing, if not preventing, the losses due to evaporation (shaw, 1988). there are many materials; chemical and physical covers which can effectively and efficiently reduce the evaporation from open water bodies. these materials are used to suit the local climatic conditions and availability as well (anonymous, 2003, shamshad et al., 2012, simon et al 2014, panjabi et al., 2016). jat et al. (2010) observed that different evaporation retardants reduce evaporation from water surfaces. evaporation reductions were determined directly by measuring the volume of water evaporated from the test recipients after a certain period of time. tests have shown that floating sheets such as e-vapcaps can reduce over 95% evaporation from open water reservoirs (craig, 2005). also, craig et al. (2007) observed that physical covers was able to reduce substantial evaporation from open water bodies. the study suggested that these types of covers would be more effective for small reservoirs (less than 10 ha in size). thus, in this study, two local cover materials viz; suspended (weaved thatch) and floating (plastic paint cover) were considered for reducing evaporation using pan evaporimeter. the aim of the research is to evaluate the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies. 2.0 materials and methods 2.1 the study area the study was conducted at pompamari in maiduguri borno state, nigeria, figures 1 (a and b) with its coordinates given in table 1. it is situated at an elevation of 325m above mean sea level (world atlas, 2020). the estimated population of maiduguri is approximately 1,112,449, making it the biggest city in borno state (national population commission, 2010). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 675-684. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 677 figure 1a. location of pompamari (the study area) table 1. coordinates of the study area coordinates latitudes longitudes upper right 11° 51’ 55.30” 13° 07’ 17.04” lower right 11° 50’ 37.54” 13° 07’ 16.57” upper left 15° 51’ 55.39” 13° 05’ 20.09” lower left 11° 50’ 37.64” 13° 05’ 20.28” figure1b. map of nigeria showing borno state and the capital, maiduguri 2.2 agro-climatic condition of the study area maiduguri is located in the semi-arid region of north-east of nigeria. during the year, the wettest month (with the highest rainfall) is august (193.2 mm). driest months (with the lowest file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yadima et al.: evaluating the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies. azojete,16(4):675-684. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 678 rainfall), february june (0 mm). it receives an annual rainfall of 613 mm. the maximum temperature could be as high as between 3243oc during summer and as minimum as between 6 15oc during winter. may is the hottest and december is the coldest month of the year. on average, august is the most humid while february is the least humid, and the average annual percentage of humidity is 30.0% (world weather and information, 2010 to 2020). 2.3 experimental tests the experimental tests were conducted using three evaporation pans. one pan was covered with plastic paint covers and labeled as “pan a”, while another pan was shaded with weaved thatch grass and labeled as “pan b” as in figure 2. additionally, the last pan was uncovered as control and labeled as “pan c”. the floating covers of 30 cm in diameter were used on the water surface and supported by the water itself. however, the covers are fixed on the water surface using some form of anchoring mechanism when use on large water surfaces. weaved thatch of 3 m x 3 m made of yellow thatch grass was suspended at a height of 2m over “class a” evaporation pan which was externally supported by galvanized pipe. these pans were protected with open wire mesh to prevent insects, birds and animals drinking from the water. figure 2. experimental set up of the evaporation pans. 2.4 experimental set up pan evaporimeters were used in the study. one remarkable advantage of the evaporation pan is that it incorporates all possible physical effects (shamshad et al., 2012). a us “class a” pan is a circular tub of 1210 mm internal diameter; 254 mm deep and was constructed of onemillimeter thick galvanized steel sheet. the evaporation pans were installed on wooden supports of 50mm, leveled on the ground. it was filled with water at a distance away from any obstacles which might affect natural air flow around the pan, thus, representing open pond water nearby. the evaporation pans provided measurements of combined effects of temperature, humidity, wind speed, and other ambient conditions as shown in figure 2. 2.5 measurement of evaporation rates evaporation rate was obtained by measuring changes in water levels in the pans. this was done manually using a point gauge. data were collected during dry season on weekly basis at 6:00 pm. this window period was chosen because it is the hottest and driest in maiduguri. monthly evaporation is useful which can be applied to the drier months of the year when reservoir drawdown is maximum due to high water usage (benzahta and mohamad, 2009, yu and knapp, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 675-684. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 679 1985). water was added into the pans to substitute the evaporated water when the level in the pans was dropped to 50 mm. water depths were measured before and after the water was added. also, water was taken out of the pans when the water levels raised much due to rain and the water depths before and after were recorded. in order to relate the evaporation and ambient conditions, data of ambient temperature, wind speed and relative humidity were recorded from nearby weather station (weather station of maiduguri international airport). 2.6 measurement of evaporation losses using us “class a” pans there are several methods available for measuring or estimating evaporative losses from free water surfaces. evaporation pan is one of the simplest, inexpensive, and most widely used methods of estimating evaporative losses (jones, 1992). pan evaporation is considered an indication of atmospheric evaporative power. evaporation from free water surface is related to pan evaporation by a coefficient applied to the pan readings. according to mayer (1982), kpan (pan coefficient) = 0.75 for us “class a” pan. per (mm) = kpan x epan (mm) (1) where: per is pan evaporation rate in millimeters, epan = pan readings (mm) pel = per x sap (2) where pel is pan evaporation loss in meters, sap is surface area of the pan in square meters correlation coefficient was conducted between evaporation to ambient air temperature, relative humidity and wind speed. 3. results and discussion the recorded evaporation data were summarized as monthly average and presented in figure 3. the results indicated some significant differences in evaporation from pan c compared to evaporations from the covered pans (a and b). maximum evaporations were observed in pan c, followed by pan b and pan a throughout the entire period of the study. the maximum evaporation recorded was 273.65 mm, 230.60 mm and 169.48 mm for pan c, b and a respectively for the month of may. similarly, minimum evaporation was observed for pan a (134.13 mm), followed by pan b (171.31 mm) and pan c (211.72 mm) for the month of june. this could be explained by the fact that the month of june is humid as rainy season is approaching. this confirms the feasibility of using floating plastic paint or suspended thatch in evaporation reduction because they provide a barrier between the water and atmosphere as reported by craig (2005) and craig et al. (2007), who used floating covers to achieve substantial reduction in evaporation. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yadima et al.: evaluating the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies. azojete,16(4):675-684. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 680 figure 4 presents the overall percentage water savings for pans a and b in evaporation over pan c. the maximum water savings was found in pan a to be 45.14% compared to pan b at 32.55% for the month of june. pan a saves more water because it covers the water surface area of the pan completely and reduces climate effects. this agrees with craig (2005) who observed that floating sheet can reduce evaporation by approximately 95% from open water reservoirs. figures 5 (a, b and c) show the relationship between the measured evaporations from the three evaporation pans and ambient air temperature, relative humidity and wind speed. it can be seen from the figures that evaporation from the pans have direct relationship to the ambient air temperature, relative humidity and wind speed. during the experiment; it was observed that period in weeks when higher ambient air temperatures and wind speeds were recorded, higher evaporation losses were obtained while for weeks with higher relative humidity, evaporation losses were minimal due to moist condition. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 675-684. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 681 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yadima et al.: evaluating the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies. azojete,16(4):675-684. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 682 figure 6a shows a linear relationship between evaporation and temperature. the results showed an r2 value of 0.893 for pan a, 0.9438 for pan b and pan c was 0.9566. this is an indication of a strong and positive linear relationship between evaporations and ambient air temperature with most of the data points closely distributed. interestingly, a moderate linear relationship was obtained between evaporations, relative humidity and wind speed as shown on figures 6 (b and c). the r2 values for pan a, pan b and pan c were 0.5218, 0.6386 and 0.5713 respectively. it can be observed from figure 6b that the higher the relative humidity, the lower the evaporation, whereas lower relative humidity resulted in higher evaporation. the r2 values for pan a was 0.7028, pan b was 0.7995 and pan c was 0.7717 (figure 6c). it is clear from the figure that, higher evaporations are obtained at higher wind speeds. this suggests that trees or shrubs should be planted around the open water bodies to serve as wind breakers in order to minimize evaporation losses. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 675-684. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 683 4. conclusion floating and suspended materials (plastic paint covers and weaved thatch grass) have significant potentials for reducing evaporation from open pans. during the four months of this investigation, pan with plastic paint covers were able to reduce evaporation and saves water substantially compared with the shaded thatch cover. it is noteworthy that plastic paint cover could be a promising alternative material to reduce evaporation from open water body compared to the suspended weaved thatch grass. interestingly, notable weeks with higher ambient air temperature and wind speed resulted in higher evaporation records. in addition, sensitivity analysis suggests that evaporation is strongly and positively correlated with the climatic variables. thus, it is advisable to plant trees or shrubs around open water surfaces to reduce evaporation losses. references anonymous, i. 2003. methods for reducing evaporation from storages used for urban water supplies. development of natural resources and mines. final report, 41/12219/67346, saudi arabia. beare, s. and heaney, a. 2002. climate change and water resources in the murray darling basin, australia; impacts and adaptation. abare conference, world congress of environmental and resource economists, monterey, california, 24-27th june, 2002. pp 1-33. https:/www.abareconomics.com. benzahta, ma. and mohamad, ta. 2009. evaporation from reservoirs and reduction methods: an overview and assessment study. international engineering convention. damascus, syria and medinah, kingdom of saudi arabia. https://www.researchgate.net/publication/279983251 (accessed 10/03/2020). christiansen, c. and worlton, l. 1998. reduced set evaporation station. irrigation journal, 48: 12-14. craig, ip. 2005. loss of storage water due to evaporation. a literature review. ncea publication, university of southern queensland, australia, 75p. unpublished. craig, i., aravinthan, v., joseph, p., baili, c. and beswicks, a., 2007. evaporation, seepage and water quality management in storage dams: a review of research methods. j. environ. health, 7: 84-97. igor, as. 1999. trends in water consumption and evaporation. joint report, hydrological institute, petersburg and unesco, paris, france. http://www.abareconomics.com file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yadima et al.: evaluating the effectiveness of floating and suspended materials for reducing evaporation losses in small water bodies. azojete,16(4):675-684. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: maundeg6yadima@gmail.com 684 jat, ml., kothari, ak. and sharma, sk. 2010. performance evaluation of different evaporation retardants in semi-arid tropics. indian journal of soil conservation, 38 (3): 169-172. jones, fe. 1992. evaporation of water with emphasis on application and measurements. crs press, tailor and francis group, london, uk, 200 pages. khudair, ad., farhan, lr. and ahmed, h. 2013. reduced evaporation losses from water reservoirs, babylon university, iraq, 23-29. larry, d., karen, w., john, b. and victor, hb. 2007. design information for evaporation ponds in wyoming. report no. wwrc 85-21, wyoming water research center; university of wyoming, colorado, usa. mayer, af. 1982. method of determination of evaporation. available on: https://www.google.com/search?q = method+of +determination + of+ evaporation + mayer (accessed 10/20/2020). national population commission of nigeria 2010. available on: hhp:// weather – and – climate.com/average – monthly – humidity –per, maiduguri, nigeria. panjabi, k., rudra, r. and goel, p. 2016. evaporation retardation by monomolecular layers: an experimental study at the aji reservoir (india). open journal of civil engineering, 6: 346-357. patel, ad. 2017. study on effectiveness of floating materials for controlling evaporation from small water bodies. m.tech. thesis. department of soil and water engineering, college of technology and engineering, maharana pratap university of agriculture and technology udaipur 313001 (rajasthan), india. prime, e., audy, l., diana, t., david, s., greg, q. and ian, d. 2012. new technology to reduce evaporation from large water storages. waterline report national water commission, canberra. simon, k., shanbhag, r. and slocum, ah. 2015. reducing evaporative water losses from irrigation ponds through the reuse of polyethylene terephthalate bottles. journal of irrigation drain engineering, 142 (2): 112-121. shamshad, a. and abdulmohsen, aa. 2012. use of palm fronds as shaded cover for evaporation reduction to improve water storage efficiency. journal of king saud university – engineering sciences, 25 (1): 55-58. shaw, em. 1988. hydrology in practice. van nostrand reinhold international, london, united kingdom. simon, k., shanbhag, r. and slocum, ah. 2015. reducing evaporative water losses from irrigation ponds through the reuse of polyethylene terephthalate bottles. journal of drain engineering. 06015005 sinha, sk. 2006. evaporation control in reservoirs. government of india, central water commission, basin planning and management organization, new delhi pp 1 – 96a world atlas 2020. available on: https:// www.worldatlas.com/of/ng/bo/where-is-maiduguri. (accessed 10/20/2020). world weather and information 2010 – 2020. available on: https: // weather – and – climate.com/average – monthly – humidity –per, maiduguri, nigeria. (accessed 04/03/2020). youssef, yw. and khodzinskaya, a. 2019. a review of evaporation reduction methods from water surfaces. https://doi.org/10.1051/e3sconf/2019975044 (accessed 10/20/2020). yun – sheng, yu. and knapp, hv. 1985. weekly, monthly and annual evaporations for elk city lake. journal of hydrology, 80 (1-2): 93 – 110 https://www.google.com/search?q%20=%20method+of http://www.worldatlas.com/of/ng/bo/where-is-maiduguri https://doi.org/10.1051/e3sconf/2019975044 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):415-428 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 415 original research article prediction of mass and volume of tacca involucrata tubers using physical characteristics a. o. raji and b. o. oyefeso* department of agricultural and environmental engineering, faculty of technology, university of ibadan, ibadan, nigeria *corresponding author’s email address: oyefesobabatunde@gmail.com 1.0 introduction tacca (tacca involucrata, schum. and thonn.) is an important member of the root and tuber crops which serve as staple foods in many parts of the tropics. although the crop is grown at subsistent level in the eastern part of nigeria, it is yet to be domesticated in many regions of africa where it is still found predominantly in the wild and reproduces asexually on its own at a later period (raji and ahemen, 2011). it is noteworthy that some parts of the plant are useful for various purposes while the tuber is well known for its starch which has almost zero percentage fat content and therefore, suitable for industrial uses especially in the article information abstract knowledge of physical properties of crops is necessary for the development of processing machines. relationships between the various physical properties of crops could also be useful in ensuring proper handling and more efficient design of processing machineries. this study was therefore, aimed at developing mathematical models for predicting the mass and volume of tacca involucrata tubers using some physical characteristics of the crop. physical characteristics of tacca tubers at average moisture content of 73.3% (wet basis) namely axial dimensions, arithmetic mean diameter (amd), geometric mean diameter (gmd), projected areas along the three mutuallyperpendicular axes, criterion area (ac), mass and volume were determined. out of 240 samples used in the study, data from 120 samples were used for development of the prediction models while the remaining were used for validation of the developed models. data analysis tool in microsoft excel (2013 version) was used to carry out regression analysis and develop the predictive models. statistical parameters namely correlation coefficient, coefficient of determination, root mean square error and mean bias error were used to determine the goodness of fit of the predictive models. the mass and volume models were divided into three classifications namely: single and multiple variable regression models based on axial dimensions; single and multiple variable regression models based on the projected areas; single variable regression model based on volume (for mass prediction only). average length, width, thickness, amd and gmd of the tubers were 71.88, 57.22, 46.71, 58.60 and 57.57 mm respectively while average criterion area, longitudinal, cross-sectional and transversal projected areas were 2614.24, 2580.61, 2097.04 and 3165.07 mm2 respectively. average mass and volume of the tubers were 129.30 g and 111.55 cm3 respectively. all the developed models performed well in predicting the mass and volume of tacca tubers (r2 ≥ 0. 905) except for those based on the axial dimensions as single independent variables (r2 ≤ 0.890). the predicted mass and volume of tacca tubers were not significantly different (p ≤ 0.05) from the experimentally observed values for all the classifications considered. mass and volume modelling based on a single variable of any of the projected areas was the most convenient modelling for tacca tubers since it involves the use of a single image capturing device and the whole measurement could therefore, be automated. the developed models would be useful for automated sorting and packaging of tacca tubers. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 march, 2021 revised 14 june, 2021 accepted 16 june , 2021 keywords: tacca tubers physical properties geometrical attributes mass and volume modelling raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 416 pharmaceutical industries (omojola, 2013; raji and ahemen, 2011). its tuber and starch are traditionally used for treatment of diarrhoea and bleeding (internal and external). its stems are also useful for making mats while the leaves are used for treatment of nausea and vomiting (ofoefule et al., 2004). tacca tuber processing involves a lot of unit operations which are largely carried out manually in the developing countries where the crop is available for use. the increasing global demand for its starch necessitates commercialisation of its production which inevitably requires mechanization of its processing and handling operations (ahemen and raji, 2017). knowledge of the engineering properties of the tubers is therefore, needed as they constitute essential data for the design of machineries for processing and handling operations (mohsenin, 1986). sizing by weighing mechanism is recommended for the irregular-shaped products (stroshine and hamann, 1994) which is typical of most agricultural products. determining the relationships among mass, axial dimensions and projected areas may also be useful and applicable in the automation of sorting processes for agricultural products (stroshine and hamann, 1994; pathak et al., 2020). though these relationships or models may be cumbersome to establish, once established, they can easily be used to quickly predict the unknown parameters in the relationships. axial dimensions, projected areas, mass and volume of agricultural products are important parameters in sorting and grading machines (naderiboldaji et al., 2009). crops are often graded on the basis of size and the projected area, although it may be more economical to develop a machine which would grade by mass or volume of the product. therefore, this will necessitate establishing relationships between mass or volume and other physical attributes of the crops (khanali et al., 2007; jahromi et al., 2007a). mathematical modelling helps to develop functional relationships between different crop variables and thereby, make it easy to predict the values of the dependent (unknown) variables based on the different values of the independent (known or measured) variable(s). the development of models that could be used to predict the mass and volume of agricultural products based on the dimensions and the projected areas will give a good description of the size and shape of the products and this will be of tremendous help in the design of processing machines as well as sorting and handling equipment for the products. several researches have been carried out to predict some physical properties of interest using developed regression models based on the geometrical attributes of the crops. some of these studies include development of mass models for kiwi fruit (lorestani and tabatabaeefar, 2006), date fruit (jahromi et al., 2007a), pomegranate fruit (khoshnam et al., 2007), apple (meisami-asl et al., 2009), fava beans (lorestani and ghari, 2012), potato (berberoglu et al., 2014), sohiong fruit (vivek et al., 2017), persimmon fruits (subbarao and vivek, 2017), apricot fruit (rashidi et al., 2018), belleric myrobalan fruit (pathak et al., 2020), indian coffee plum (barbhuiya et al., 2020) and pepper berries (azman et al., 2021). mass and volume prediction models were developed for tangerine fruit (khanali et al., 2007), citrus fruits (omid et al., 2010), sweet cherry (khadivi-khub and naderiboldaji, 2013), and nigeria-grown sweet and irish potatoes arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):415-428. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 417 (oyefeso and raji, 2018). mass and surface area of bergamot fruits were also predicted based on axial dimensions, projected areas and volume (jahromi et al., 2007b). all these studies were carried out for prediction of various properties such as mass, volume, surface area etc with varying degrees of success in the development of their predictive models. however, there appears to be scarcity of information on prediction models for tacca tuber which are useful in its automated sorting and handling. this study therefore, aimed at developing mathematical models for predicting mass and volume of tacca tuber which are grown in nigeria using some of their physical characteristics. this is with the ultimate aim of generating data which could serve as a quick guide in the design of sorting and handling equipment for the tubers. 2. materials and methods 2.1 sample preparation some tacca tubers were randomly selected and purchased from a pit storage stock harvested within a period of one month from tse-ikyor and tse-adawa villages, benue state, nigeria. the study was conducted on 240 tubers which were sorted into different fractions based on their weights and labelled to enable proper identification and documentation of data from the samples. 2.2 moisture content determination moisture content of the tuber was determined according to asabe (2003) standard method which involved drying the samples in an oven maintained at temperature of 103 ± 2°c until constant weight was attained (ahemen and raji, 2017). 2.3 determination of geometrical attributes the physical characteristics determined include mass, volume, length (l), width (w), thickness (t), arithmetic mean diameter (amd), geometric mean diameter (gmd), projected areas along the three mutually-perpendicular axes (pal, paw and pat) and the criterion area (ac). the individual mass of each of the tacca tubers was measured using an electronic weighing balance (a&d co. ltd, and ek-6100i model, japan) with an accuracy of 0.1g. volume of each of the tubers was obtained using the water displacement method (mohsenin, 1986; khanali et al., 2007; jahromi et al., 2007). the axial dimensions (l, w and t) were measured with the aid of a digital vernier calliper (carrera precision model cp8812-t 12-inch, united states) having an accuracy of 0.01 mm. the three mutually-perpendicular axes were determined by allowing each tuber crop to drop freely under gravity and then rest on its natural axis. at this natural resting position, the axial dimensions along the three mutually-perpendicular axes were obtained as length (the longest dimension), width (the axial dimension perpendicular to the length) and thickness (the axial dimension which is perpendicular to both length and width) (tabatabaeefar, 2002; raji and ahemen, 2011; ahemen and raji, 2017). the three mutually perpendicular axes of the tubers are illustrated in figure 1. raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 418 figure 1: major axial dimensions and projected areas of tacca tubers amd and gmd were calculated from the measured axial dimensions according to equations 1 and 2 respectively (pathak et al., 2020). (1) ( ) (2) where: amd = arithmetic mean diameter (mm); gmd = geometric mean diameter (mm); l = length or longest diameter of the tuber (mm); w = width or the axial dimension perpendicular to the length (mm); t = thickness or diameter which is perpendicular to both length and width (mm). forty samples were selected at random for developing mass and volume models based on the projected areas. the projected areas along the three mutually-perpendicular axes pal (along the longitudinal plane), pac (along the cross-sectional plane) and pat (along the transverse plane) were obtained by image processing (khanali et al, 2007; jahromi et al., 2007). the image processing technique involved the acquisition of the images of the tubers using a digital camera and the projected areas were then obtained by reading the images in portable pixel map (ppm) format as input into an algorithm developed in fortran 95 programming language. an image acquisition lighting box (figure 2) was constructed to flood the samples with light and ensure proper capturing of the images by preventing shadow-casting. the algorithm extracted the total number of pixels making up the acquired image enclosed in a rectangle of known area and the number of pixels making up the projection of tacca tuber in the image. the projected area was calculated within the algorithm according to equation 3. l t w pac pal pat w l t arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):415-428. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 419 figure 2: the image acquisition lighting box (3) where: pa = projected area of the tuber (mm2); npp = number of pixels of tuber projection; ntp = total number of pixels making up the enclosing rectangle; ar = area of the smallest enclosing rectangle (mm2). table 1 shows the areas of the smallest enclosing rectangle for the acquired images along the longitudinal, cross-sectional and transverse orientations. table 1: areas of the smallest circumscribing rectangles for the acquired images s/n orientation projected area (mm2) area of circumscribing rectangle (mm2) 1 longitudinal pal 2 cross-sectional pac 3 transverse pat the criterion area (ac) of the tubers was calculated according to equation 4 (tabatabaeefar, 2002). (4) where: ac = criterion area (mm2); pal = projected area along the longitudinal plane (mm2); pac = projected area along the cross-sectional plane (mm2) and pat = projected area along the transverse plane (mm2). 2.4 development of the prediction models out of the 240 tubers used in this study, data from 120 samples were used for actual development of the prediction models while the remaining 120 samples were used for validation of the developed models. all the data were averaged over three replications. mathematical models for predicting the mass and volume of tacca tubers were developed by regression analysis using the data analysis tool in microsoft excel (2013 version). the regression analysis involved estimating the likely relationship between the dependent variables (mass and volume) and one or more physical properties of the tubers as independent variable(s). the base the translucent screens raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 420 different regression models that were suggested in analysing the data obtained include linear ( ), exponential ( ), logarithmic ( ), power ( ) and polynomials of order 2 to 6 ( ). however, the regression models that best describe the relationships that exist between the dependent and independent variables are the only ones presented in the study. suitability and adequacy of fit of the developed mass and volume models were determined on the basis of highest coefficients of determination (r2) and lowest error estimates. the mass and volume models were divided into three classifications based on the independent variables as follows: i. single and multiple variable regression models based on axial dimensions namely length (l), width (w), thickness (t), amd and gmd of the tubers for the first classification; ii. single and multiple variable regression models based on the projected areas ( ) for the second classification; iii. single variable regression model based on volume (for mass prediction only) for the third classification. the mass of the tuber was predicted using the measured volume and a simple linear regression obtained is of the form shown in equation 5. (5) where: m = mass of tacca tubers (g); v = volume of tacca tubers (cm3); k = intercept on the m-axis; = slope or gradient of the equation. model validation involved using the developed models to estimate the mass and volume of the tubers and then determining the closeness of the predicted values to the experimental or observed values. highest coefficient of determination (r2) and lowest error estimates namely mean bias error (mbe) and root mean square error (rmse) were used as the basis for determining the goodness of fit of the developed models. values of r2, mbe and rmse for the data were calculated using equations 6, 7 and 8 respectively. ∑ ( ( ) ( )) (∑ ( ( )) ) (∑ ( ( )) ) (6) ∑ ( ( ) ( )) (7) ∑ ( ( ) ( )) (8) where: y(exp,i) is the ith experimentally observed value; y(pre,i) is the ith predicted value; n is the number of observations. 3. results and discussion the minimum and maximum values of the measured physical properties of tacca tubers at average moisture content of 73.3 ± 1.2% (wet basis) are as presented in table 2. these physical properties include the axial dimensions (length, width, thickness, amd and gmd), projected areas, criterion area, mass and volume of the tubers. these data are of significance in the design of processing machines and handling equipment for the tubers. accurate packaging of the tubers based on mass or volume could also be ensured based on these physical characteristics. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):415-428. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 421 table 2: some physical properties of tacca tubers physical characteristics number of samples range l (mm) 240 34.81 – 114.24 w (mm) 240 20.05 – 94.58 t (mm) 240 24.22 – 70.70 amd (mm) 240 29.72 – 97.92 gmd (mm) 240 28.82 – 97.36 pal (mm2) 40 602.77 – 5,277.89 pac (mm2) 40 588.94 – 4,283.63 pat (mm2) 40 840.44 – 6,792.78 ac (mm2) 40 677.38 – 5451.43 m (g) 240 14.80 – 566.40 v (cm3) 240 13.00 – 460.00 3.1 mass and volume prediction models mass and volume prediction models developed based on the three classifications are as presented in tables 3 and 4 respectively. statistical parameters (r, r2, rmse and mbe) for validation of the mass and volume models are presented in tables 5 and 6 respectively. there were no significant differences (p ≤ 0.05) between the predicted and experimentally observed values of mass and volume of tacca tubers. table 3: mass models for tacca tubers based on the selected geometrical attributes model no. classification independent variable relation r2 1 first l (mm) 0.890 2 w (mm) 0.854 3 t (mm) 0.762 4 l, w, t (mm) 0.930 5 amd (mm) ( ) ( ) 0.987 6 gmd (mm) ( ) ( ) 0.980 7 second pal (mm2) ( ) 0.986 8 pac (mm2) ( ) 0.982 9 pat (mm2) ( ) 0.985 10 pal, pac, pat (mm2) ( ) ( ) ( ) 0.982 11 ac (mm2) ( ) 0.996 12 third v (cm3) 0.965 raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 422 table 4: volume models for tacca tubers based on the selected geometrical attributes model no. classification independent variable relation r2 1 first l (mm) 0.881 2 w (mm) 0.840 3 t (mm) 0.738 4 l, w, t (mm) 0.905 5 amd (mm) ( ) ( ) 0.955 6 gmd (mm) ( ) ( ) 0.949 7 second pal (mm2) ( ) 0.984 8 pac (mm2) ( ) 0.982 9 pat (mm2) ( ) 0.978 10 pal, pac, pat (mm2) ( ) ( ) ( ) 0.979 11 ac (mm2) ( ) 0.992 table 5: comparison of predicted and observed mass of tacca tubers model no. model type independent variable r r2 mbe rmse 1 power l (mm) 0.959 0.920 -1.517 18.354 2 quadratic w (mm) 0.906 0.822 1.669 26.727 3 power t (mm) 0.861 0.742 -2.848 32.229 4 linear (multiple) l, w, t (mm) 0.972 0.945 4.273 15.789 5 quadratic amd (mm) 0.993 0.985 0.353 7.700 6 quadratic gmd (mm) 0.990 0.980 0.512 8.921 7 power pal (mm2) 0.992 0.984 0.274 9.860 8 power pac (mm2) 0.990 0.980 -0.143 11.004 9 power pat (mm2) 0.992 0.983 -0.183 9.975 10 linear (multiple) pal, pac, pat (mm2) 0.991 0.982 0.018 10.385 11 power ac (mm2) 0.997 0.994 0.076 6.074 12 linear v (cm3) 0.979 0.959 -1.457 12.911 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):415-428. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 423 table 6: comparison of predicted and observed volume of tacca tubers model no. model type independent variable r r2 mbe rmse 1 power l (mm) 0.940 0.883 -3.097 19.647 2 quadratic w (mm) 0.907 0.822 2.711 23.547 3 power t (mm) 0.834 0.695 -2.025 30.679 4 linear l, w, t (mm) 0.957 0.916 1.926 16.529 5 quadratic amd (mm) 0.975 0.950 1.701 12.484 6 quadratic gmd (mm) 0.971 0.943 1.809 13.372 7 power pal (mm2) 0.988 0.977 -0.201 9.642 8 power pac (mm2) 0.987 0.975 -0.102 10.116 9 power pat (mm2) 0.988 0.976 -0.249 9.879 10 linear (multiple) pal, pac, pat (mm2) 0.989 0.979 -0.011 9.173 11 power ac (mm2) 0.994 0.987 0.056 7.266 3.1.1 first classification models (axial dimensions, amd and gmd) mass and volume models based on axial dimensions as single independent variable numbered 1, 2 and 3 in tables 3 and 4 had low fitness with low r2 and higher mbe and rmse. this thereby indicates that no single axial dimension can be reliably used to predict mass and volume of tacca tubers. however, mass and volume models based on length gave better results than the ones based on width and thickness. mass and volume models based on multiple regression of the three axial dimensions (l, w and t) had relatively good fitness with r2 of 0.930 and 0.905 respectively. models on the basis of amd and gmd as independent variables gave consistently high r2 (≥ 0.958). this clearly indicates that these models can consistently predict the mass and volume of the tubers with high level of accuracy. however, the models are multi-variate, relying on all the three axial dimensions in their computations and are therefore, more complex than those that are univariate. although mass and volume of the tubers may not be effectively predicted on the basis of any of the axial dimensions individually due to low r2, it can be suggested that the models having length as the independent variable can still be adopted. these models (based on length) are preferred to the models that consider all the three mutually-perpendicular axial dimensions despite their lower r2 values, because it is more practicable, less cumbersome and faster to handle and compute. variations in mass and volume of the tubers against length as the independent variable are presented in figures 3 and 4 respectively. figure 3: mass model of tacca tubers on length at average moisture content of 73.3% (wet basis) m = 0.003l2.484 r² = 0.890 0 100 200 300 400 20 40 60 80 100 120 m as s o f t ac ca t u b er s (g ) length of tacca tubers (mm) raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 424 figure 4: volume model of tacca tubers on length at average moisture content of 73.3% (wet basis) 3.1.2 second classification models (projected and criterion areas) mass and volume models developed based on second classification involving the projected and criterion areas are presented in tables 3 and 4, as models numbered 7 to 11. these models gave very consistent and relatively higher r2 and could therefore, be suggested as the best models to be adopted for the estimation of mass and volume of tacca tubers. models based on the criterion area (ac) also had consistently high r2, indicating their suitability for accurately predicting the mass and volume of tacca tubers. however, the models rely on all the three projected areas along mutually-perpendicular axes which makes them more cumbersome to compute. best predictive mass and volume models (with highest r2) in the second classification for the tubers were those on the basis of pal as the independent variable and their plots are presented in figures 5 and 6 respectively. figure 5: mass model of tacca tubers on pal at average moisture content of 73.3% (wet basis) v = 0.002l2.499 r² = 0.881 0 100 200 300 400 20 40 60 80 100 120 v o lu m e o f t ac ca t u b er s (c m 3 ) length of tacca tubers (mm) m = 0.0008(pal)1.506 r² = 0.986 0 100 200 300 400 0 1,000 2,000 3,000 4,000 5,000 6,000 m as s o f t ac ca t u b er ( g ) pal (mm2) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):415-428. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 425 figure 6: volume model of tacca tubers on pac at average moisture content of 73.3% (wet basis) 3.1.3 third classification models (volume) this classification was considered only for predicting the mass of the tubers with volume as the independent variable. the mass models based on volume is numbered 12 on table 3. variations in mass against the volume of the tubers are presented in figure 7. for the third classification, the mass model had r2 of 0.961 which indicates a high level of accuracy in its prediction and could therefore, be recommended for adoption in predicting the mass of the tubers. figure 7: mass model of tacca tubers on volume at average moisture content of 73.3% (wet basis) v = 0.0011(pal)1.446 r² = 0.984 0 50 100 150 200 250 300 0 1,000 2,000 3,000 4,000 5,000 6,000 v o lu m e o f t ac ca t u b er ( cm 3 ) pal (mm2) m = 1.121v + 3.045 r² = 0.965 0 50 100 150 200 250 300 350 0 50 100 150 200 250 300 m as s o f th e t ac ca t u b er ( g ) volume of the tacca tubers (cm3) raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 426 4. conclusions selected physical properties of tacca tubers were determined in this study and predictive models were determined based on these physical characteristics to estimate the mass and volume of the tubers. length, width, thickness, arithmetic mean diameter (amd) and geometric mean diameter (gmd) ranged from 34.81 to 114.24, 20.05 to 94.58, 24.22 to 70.70, 29.72 to 97.92 and 28.82 to 97.36 mm respectively. longitudinal, cross-sectional, transversal and criteria projected area of the tubers ranged from 602.77 to 5277.89 mm2, 588.94 to 4283.63, 840.44 to 6792.78 and 677.38 to 5451.43 mm2 respectively. mass and volume of the tubers ranged from 14.80 to 566.40 g and 13.00 to 460.00 cm3 respectively. mass and volume models developed based on the length and projected area along the longitudinal plane (pal) were the best models on the basis of a single variable of axial dimension and projected area respectively. the predictive models based on amd, gmd and criterion area had consistently high correlation and error estimates, although they are more cumbersome to compute since they depend on multiple attributes in their computations. there existed a very good correlation between mass and volume of the tubers, thereby indicating that mass of the tubers can be reliably predicted with the volume. mass and volume modelling based on a single variable of any of the projected areas can be considered as the most reliable and convenient modelling for tacca tubers since it involves the use of a single image capturing device and the whole measurement could therefore, be automated. the models developed in this study will be useful for automated sorting and packaging of tacca tubers. references ahemen, sa. and raji, ao. 2017. moisture-dependent physical properties of tacca involucrata tubers. journal of food process engineering, 40(5): e12541. https://doi.org/10.1111/jfpe.12541 azman, pnma., shamsudin, r., che-man, h. and ya’acob, me. 2021. mass modelling of pepper berries (piper nigrum l.) with some physical properties. food research, 5 (suppl. 1): 80-84. https://doi.org/10.26656/fr.2017.5(s1).047 barbhuiya, ri., nath, d., singh, sk., and dwivedi, m. 2020. mass modeling of indian coffee plum (flacourtia jangomas) fruit with its physicochemical properties. international journal of fruit science, 20(suppl. 3): s1110-s1133. doi:10.1080/15538362.2020. 1775161 berberoglu, e., altuntas, e. and dulger, e. 2014. development of adequate mathematical models to predict the mass of potato varieties from their physical attributes. journal of agricultural faculty of gaziosmanpasa university, 31(3): 1-9. jahromi, mk., jafari, a., rafiee, s., keyhani, ar., mirasheh, r. and ss. mohtasebi 2007a. some physical properties of date fruit (cv. lasht). agricultural engineering international: the cigr ejournal, manuscript fp 07 019, volume ix. jahromi, mk., rafiee, s., mirasheh, r., jafari, a., mohtasebi, ss. and varnamkhasti, mg. 2007b. mass and surface area modelling of bergamot (citrus medica) fruit with some physical attributes. agricultural engineering international: the cigr e-journal, manuscript fp 07 029, volume ix. khadivi-khub, a. and naderiboldaji, m. 2013. predicting models for mass and volume of the sweet cherry (prunus avium l.) fruits based on some physical traits. canadian journal of plant science, 93: 831-838. https://doi.org/10.1111/jfpe.12541 https://doi.org/10.26656/fr.2017.5(s1).047 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):415-428. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 427 khanali, m., varnamkhasti, mg., tabatabaeefar, a. and mobli, h. 2007. mass and volume modelling of tangerine (citrus reticulate) fruit with some physical attributes. international agrophysics, 21(1): 329-334. khoshnam, f., tabatabaeefar, a., varnamkhasti, mg. and borghei, a. 2007. mass modelling of pomegranate (punica granatum l.) fruit with some physical characteristics. scientia horticulturae, 114(1): 21-26. lorestani, an. and tabatabaeefar, a. 2006. modelling the mass of kiwi fruit by geometrical attributes. international agrophysics, 20(1): 135-139. lorestani, an. and ghari, m. 2012. mass modelling of fava beans (vicia faba l.) with some physical characteristics. scientia horticulturae, 133(1): 6-9. meisami-asl, e., rafiee, s., keyhani, a. and tabatabaeefar, a. 2009. some physical properties of apple cv. ‘golab’. agricultural engineering international: the cigr e-journal, manuscript 1124, volume xi. mohsenin, nn. 1986. physical properties of plant and animal materials. gordon and breach science publishers, new york., pp. 20-89. naderiboldaji, m., jannatizadeh, a., tabatabaeefar, a. and r. fatahi 2009. development of 11 mass models for iranian apricot fruits based on some physical attributes (cv. shahroud-8 and gheysi-2). journal of agricultural technology, 4(1): 65-76. ofoefule, si., osuji, ac., and okorie, o. 2004. effects of physical and chemical modifications on the disintegrant and dissolution properties of t. involucrata starch. bio-research, 2(1): 97-102. omid, m., khojastehnazhand, m. and tabatabaeefar, a. 2010. estimating volume and mass of citrus fruits by image processing technique. journal of food engineering, 100(2): 315-321. omojola mo. 2013. tacca starch: a review of its production, physicochemical properties, modification and industrial uses. african journal of food, agriculture, nutrition and development, 13(4): 7972-7985. oyefeso, bo. and raji, ao. 2018 estimating mass and volume of nigerian grown sweet and irish potato tubers using their geometrical attributes. adeleke university journal of engineering and technology, 1(1): 123–130. pathak, ss., pradhan, rc., and mishra, s. 2020. mass modeling of belleric myrobalan and its physical characterization in relation to post-harvest processing and machine designing. journal of food science and technology, 57(4): 1290-1300. https://doi:10.1007/s13197-019-04162-1 raji, ao. and ahemen, sa. 2011. engineering properties of tacca involucrata tubers. journal of food process engineering, 34(1): 267-280. rashidi, m., beheshty-asl, h. and behboodi, s. 2018. apricot mass modeling based on geometrical attributes. agricultural engineering research journal, 18(1): 1-5. stroshine r. and hamann dd. 1994. physical properties of agricultural materials and food products. course manual, purdue univ. press, usa. http://www.aginternetwork.net/whalecomwww.sciencedirect.com/whalecom0/science?_ob=publicationurl&_tockey=%23toc%235159%232007%23998859998%23666146%23fla%23&_cdi=5159&_pubtype=j&view=c&_auth=y&_acct=c000056118&_version=1&_urlversion=0&_userid=2789858&md5=0ce8257602ae10b749b8380f2e59db20 raji and oyefeso.: prediction of mass and volume of tacca involucrata tubers using physical characteristics. azojete, 17(3):415-428. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyefesobabatunde@gmail.com 428 subbarao, kv. and vivek, k. 2017. models for predicting the mass of persimmon (diospyros kaki) fruits by some physical properties. international food research journal, 24(6): 2353-2359. tabatabaeefar, a. 2002. size and shape of potato tubers. international agrophysics, 16(1): 301305. vivek, k., mishra, s., and pradhan, rc. 2017. physicochemical characterization and mass modelling of sohiong (prunus nepalensis l.) fruit. journal of food measurement and characterization, 12(2): 923-936. doi:10.1007/s11694-017-9708-x arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 671 equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels m. a. mohammed, b. s. u. ibn abubakar*, b. b. kurna (department of civil and water resources engineering, university of maiduguri, p.m.b. 1069, maiduguri, borno state, nigeria) *corresponding author’s e-mail address: bashehu@yahoo.com abstract the aim of this work is to investigate the applicability of raw unmodified pineapple peel waste (ppw) for the removal of safranin-o in aqueous solution. the adsorption of safranin on ppw material was studied as a function of ppw dose (0.5–2.5g), initial concentration (20–100mg/l), ph, 2–10solutions, and a varying contact time. the effect of these parameters on the adsorption capacity was studied using a batch process. the experimental data were fitted to langmuir and freundlich adsorption models. the adsorption isotherm was found to obey the freundlich model. the adsorption capacity was found to be 21.7mg/g. kinetic data were fitted to the pseudo-first-order and pseudosecond-order models, and were found to follow pseudosecond-order kinetic model. the result shows that ppw adsorbent is potentially low-cost adsorbent for removal of safranin-o. keywords: pineapple peel waste; safranin-o; adsorption; isotherms; kinetics; equilibrium; biosorption 1. introduction discharge of wastewater from textile, paper, printing, and pharmaceutical industries contains colored effluent. the presence of these substances in streams or rivers beyond the permissible limits has been reported to cause potential health risks to public and aquatic environment (rafatullah et al., 2010). untreated industrial wastewater released into water bodies could impair normal function of both flora and fauna due to its toxicity and non-biodegradability (han et al., 2008). safranin-o, a cationic dye discharged from textile and pharmaceutical industries (veterinary medicine) is reported to be irritating to respiratory systems, skin, and could cause digestive tract infections when ingested (bayazit, 2013). industrial activities are increasing all over the world. unfortunately, the exact amount of dyes produced is not yet known all over the world. currently, it is estimated that more than 10,000 are commercially available with about 0.7 million tons of dyes produced per year (suteu and malutau 2013). moreover, literatures on the exact quantity of dyes discharged into the environment are limited. it is assumed that a loss of 1–2% in production and 10–15% loss in use are a fair estimate (güngördü et al., 2013). aesthetically, dyes have adverse effect on water bodies, as they are visible pollutants. the presence of color in water bodies reduces light penetration, and impairs biological metabolic processes (gupta et al., 2011). disposal of dye wastewater without proper treatment destroys the aquatic communities (hu et al., 2010). environmental quality guidelines have made it mandatory to decolorize dye wastewater prior to discharge. however, complete decolorization of textile dye effluent does not occur even if the effluent is treated by municipal wastewater treatment systems. the conventional methods to remove dyes from wastewater include coagulation/flocculation (zonoozi et al., 2009), oxidation or ozonation, membrane separation precipitation, ion-exchange, reverse osmosis, complexation/sequestration and activated carbon (reddy et al., 2012). unfortunately, the major drawback, especially for the developing countries is the high cost for recycling/regenerating ability (mouzdahir et al., 2010). similarly, the application of the mailto:bashehu@yahoo.com mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 672 conventional treatment of wastewater may not be economically viable. therefore, biosorption techniques could be economically viable and efficient in such cases. recently, there are many researches on cheap available agricultural and/or plant-based materials such as tea (camellia sinensis l.) seed shells (gao et al., 2013), pea shells (pisumsativum) (geçgel et al., 2013), casuarin aequisetifolia needle (dahri et al., 2013), alfa grass (bounehdi et al., 2013), neem leaf powder (patel and vashi 2013), corn husk (khodaie et al., 2013), papaya stems (krishni et al., 2013), and (malekbala et al., 2012) have been used as adsorbent for the removal of various dyes from industrial waste water effluents. however, there were few reports on using pineapple peel waste (ppw) by chemical and physical activation methods. the use of pineapple peel waste (ppw), an agricultural waste material as an adsorbent, will considerably replace the use of conventional treatments. because, (ppm) as alternative raw materials is cheaper and readily available source of adsorbent, and environmentally friendly. major advantage in the use of biomass is the renewability, abundance, reliability and availability (locally), especially, those biomass resources that are by-products of agricultural activity. therefore, in this paper, the adsorption equilibrium and kinetics of safranin-o on pineapple peel were studied. 2. materials and method 2.1 adsorbate safranin-o, a cationic red dye purchased from sigma–aldrich, has a molecular formula c20h19cin4 with iupac name of 3,7-diamino-2,8-dimethyl-5-phenylphenazinium chloride. a 1000ml stock solution was prepared by dissolving 1.0g of safranin-o in one liter of distilled water. to obtain various solutions, different concentrations were prepared by diluting the stock solution with suitable volume of distilled water. the natural ph of the stock solution was adjusted to around 5.6, and was maintained at this level even with dilution. all other chemicals used were of analytical grade. the chemical structure of safranin-o is shown in figure 1. figure 1: chemical structure of safranin-o dye 2.2 adsorbent the pineapple peel (ananas comoscus) waste was used as adsorbent in this study. the ppw wastes were collected from pasa raya borong market at sri serdang area near universiti putra malaysia (upm), serdang, selangor, malaysia. it was cut into smaller pieces and washed arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 673 thoroughly under running tapped water for several times to remove dirt and sand particles. the sample was further rinsed repeatedly with distilled water to remove dirt particles and dried in an oven at 60 o cfor 48 h. the sample was ground using mortar and pestle. ground samples were sieved to (1.18mm) particle size and stored in a sealed plastic bag with silica gel to minimize dampness. this prepared sample (adsorbent) was used raw throughout in this work. 2.3 characterization pineapple peels using sem and ft-ir after the adsorption experiment, the ppw surface morphology was determined using sem from chemical engineering laboratory, universiti putra malaysia (upm). fourier-transform infrared (ft-ir) spectroscopy was used to characterize the ppw samples according to feng et al., (2009) and is briefly described here. the infrared spectra of the ppw were recorded with nicolet 380 (ft-ir) spectrophotometer with potassium bromide disks. the thermal characteristics of the adsorbents were examined using tg peaks (sdt q600) instrument. surface morphology of the adsorbents was identified by jsm-5600lv scanning electron microscope (sem). 2.4 batch equilibrium studies in this study, all experiments were carried out at room temperature. a 250 ml stopper cork conical flasks filled with 100 ml of adsorbate were prepared at different initial concentrations (20-100 ppm), the adsorbate were in contact with adsorbent for about 90min, and a ph (ph meter model jenway 3305, england) ranging from 2 to 12 were observed, while adsorbent dose of 0.5 to 2.5g was used, and the mixture was agitated at a constant speed of 150 rpm on an orbital shaker (model heidolph, incubator 1000, germany). the final concentrations of dye (adsorbate) were determined by a double beam uv-vis spectrophotometer (model genesys-10-uv) at a wavelength of 516 nm.(liu et al., 2012). the biosorption capacity of the dye was determined at equilibrium concentration, qe (mg/g), and was computed using the following equation 1: ( ) (1) where: is the initial dye concentration (mgl -1 ), ce is the equilibrium dye concentration in solution (mgl -1 ), v is the volume of the solution (l), and m is the mass of the biosorbent used (g). the percentage removal of dye was calculated by equation 2 (2) where co, is adsorbate initial concentration (mg\l), and cf is the final concentration (mg/l) in order to ensure accuracy of the data, the experiment was performed in triplicate and the average results were taken. 3 results and discussion 3.1 characterization of the prepared adsorbent 3.1.1 fourier-transform infrared (ft-ir) analysis the biosorption of safranin-o on pineapple peel was attributed to active groups and bonds present on the surface. the ft-ir spectra of the biomass were taken before and after safranin-o biosorption (figure 2a and figure 2b) respectively. a broad and intense absorption peak at 3349.49 cm -1 corresponding to o-h stretching vibrations of cellulose, pectin, absorbed water, and lignin (feng et al., 2011) was observed for pristine biomass. the sharp peaks at 2920.72 and mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 674 2853.15 cm -1 were assigned to c-h stretching and symmetric stretching vibrations of ch2, respectively. peak at 2330.72 cm -1 is attributed to the n-h or the c=o stretching vibrations. the band at 1730.28 cm -1 was assigned to the carbonyl (c=o) stretching vibration. furthermore, peak at 1626.53 cm -1 was due to stretching band of carboxyl (-coo) groups. the bands at 1541.10 cm -1 and 1463.38 cm -1 were assigned to a strong asymmetric and a weak symmetric stretching bands of carboxylate groups (coo-) respectively. moreover, a band at 1374.17 cm -1 was probably due to amides functional groups (dyke et al. 2011). a broad peak at 1044.59 cm -1 is an indication of c-n stretching in –co–nh– (nagpal et al., 2011). the spectrum after safranin biosorption on pineapple peel showed disappearance, shifting or decrease in peaks intensities at 3395 cm -1 , 2920 cm -1 , 2853 cm -1 , 2330 cm -1 , 1730 cm -1 , 1626 cm 1 , 1541 cm -1 , 1463 cm -1 , 1374cm -1 , 1044cm -1 (figure 2b). similar results were achieved by (guptal et al., 2011). in addition, a peak at 3349 cm -1 disappeared after safranin biosorption showing active involvement of o-h group in the biosorption. the results were summarized in the table 1 below: figure 2a: ft-ir spectra ppw before adsorption 4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650.0 0.0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100.0 cm-1 %t pineapple peel powder 3933.36 3914.47 3882.06 3777.02 3700.66 3661.05 3632.84 3349.49 3089.90 2920.72 2853.15 2330.72 2016.00 1982.98 1730.28 1626.53 1579.07 1541.10 1463.38 1426.08 1374.17 1244.73 1044.59 840.92 815.12 778.85 713.31 687.25 675.24 661.24 arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 675 figure 2b: ft-ir spectra ppw after adsorption table 1. ft-ir spectral characteristics of pineapple peel before and after safranin-o biosorption ir wave number (cm -1 ) assignation peak before biosorption after biosorption 1 3349 300.5 bonded o-h groups 2 2920 aliphatic c-h groups 3 2853 1825 ch2 stretching 4 2330 1680 n-h or c=o stretching 5 1730 1304 carbonyl group (c=o) 6 1626 1192 carboxyl stretching (-coo) 7 1541 937 strong asymmetric (coo-) 8 1463 weak symmetric (coo-) 9 1374 amides functional groups 10 1044 937.60 c-n stretching in –co-nh 4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650.0 0.0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100.0 cm-1 %t pineapple peel after 3936.62 3871.74 3770.28 3708.54 3602.59 3395.20 3007.15 2873.95 1825.13 1682.80 1491.58 1304.54 1192.28 937.60 659.24 arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 676 3.1.2 scanning electron microscopy (sem) analysis the sem image of pineapple peels prior to use as adsorbent, shows an irregular surface with a low and non-porous surface area (figure 3a). biosorption of safranin leads to multiple attachment on the rough surface and occupation of pores (figure 3b). pores in solids medium like adsorbents may have properties such as shape, location, connectivity, and surface chemistry. perhaps one of the properties of a pore was easily visualized, its size, and its extent in one spatial dimension. this is probably one of the reasons why the pore size is often of the main property to be characterized. (a) (b) figure 3: sem images of pineapple peel waste (ppw) (magnification: 5.00kv 9.9x300 se, 100μm) (a) before, and (b) after safranin-o biosorption 3.2 batch adsorption studies 3.2.1 effect of initial concentration and contact time the adsorption data for the removal of safranin-o versus contact time at different concentrations are presented in (figure 4), ranging from 20 to 100ppm.it can be observed from the contact time curve that, the removal shows rapid adsorption of safranin in the first 3 min, thereafter, the adsorption rate decreased gradually and the adsorption reached equilibrium in 90min. the sorption capacity of the sorbent increased from 3.9mg/g to 21.7 mg/g as the initial dye concentration increased from 20 to 100 mg/l. the increment in sorption capacity of the biosorbent may be due to the increase in dye quantity, which resulted in higher concentration gradient of the dye, thus leading to higher sorption capacity (han et al., 2008; yeddou-mezenner 2010a; feng, et al., 2009). arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 677 figure 4. effect of initial concentration and contact time on amount of safranin-o adsorbed (adsorbent dose: 1g, agitation speed: 150rpm) 3.2.2 percentage uptake of safranin-o with time at different initial concentration the percentage uptake of safranin-o increases with increase in initial dye concentration, and the sorption capacity of the adsorbent are directly proportional to the initial dye concentration. figure 5 shows the plot of percentage uptake of safranin-o at different initial concentration against contact time, it can be seen that the trend of increments starts from 58.3 to 72.5% as the initial dye concentration increased from 20 to 100 mg/l. this increment may be attributed to increase in the quantity of dye and, as result the removal concentration also becomes high(yeddou-mezenner 2010b). figure 5: percentage uptake of safranin-o at different initial concentration (adsorbent dose: 1g, agitation speed: 150rpm) 0 5 10 15 20 25 0 20 40 60 80 100 a m o u n t a d so rb ed ( m g /g ) time (minutes) 20ppm 40ppm 60ppm 0 10 20 30 40 50 60 70 80 90 100 0 20 40 60 80 100 p er ce n ta g e u p ta k e o f sa fr a n in -o ( % ) time (min) 20ppm 40ppm 60ppm mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 678 3.2.3 effect of adsorbent dose on adsorbate removal the amount of pineapple peels used to remove safranin-o was varied from 0.5 g to 2.5 g for investigation of the relationship between adsorbent dosage and dye removal performance in which the results are shown in figure 6.the effect of adsorbent dose on the amount of adsorbate removed increases with increase in adsorbent dose. the higher the quantity of adsorbent use, the higher the uptake of safranin-o that is from 6.7 mg/g at 0.5 g to 17.6 mg/g at 2.5g. the reason for such behavior may be attributed to greater surface area and large number of vacant biosorption sites thus favoring more dye biosorption (gandhi et al., 2012; vinod et al., 2012; saidutta et al., 2013). figure 6: the effect of adsorbent dose to the uptake of safranin-o (initial concentration 50ppm, adsorbate 100ml, agitation speed: 150rpm, contact time: 90 minutes) 3.2.4 effect of ph on adsorbate removal treatment of (safranin –o) wastewater is ph dependent. therefore, the ph of the solution is known to affect its structural stability. figure 7 shows the dye removal trend from aqueous solution. at ph above 6, the colour of safranin-o change irreversibly indicating an alteration in the structure of safranin-o molecules. moreover, optimum removal due to ph was achieved at ph 6. therefore, since the solution that changed colour was no longer safranin-o. ph above 6 cannot be used for this experiment because it is a neutral stage. the adsorption behavior of such adsorbent at various ph may be due to parameters such as surface charges and active sites, also to the chemistry of the dye solution (gupta et al., 2011). 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 a m o u n t a d so rb ed m g /g adsorbent dosage (g) arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 679 figure 7: the effect of ph on uptake of safranin-o (initial concentration: 60 ppm, adsorbent dose: 1g, contact time: 90minutes, agitation speed: 150rpm) 3.3. adsorption isotherm fundamentally, equilibrium adsorption isotherm is very significant in the design of adsorption systems. this study provides the adsorption capacity of the adsorbent. moreover adsorption isotherm describes the equilibrium relationships between adsorbent and adsorbate, which is usually the ratio between the quantity adsorbed and that remaining in the solution at a fixed temperature. in this study, 20 to 100ppm concentration of adsorbate and 1g of adsorbent dose was used. the equilibrium data obtained experimentally were fitted to two most common models, the langmuir and freundlich isotherm model. 3.3.1langmuir isotherm the langmuir model is based on the assumptions that maximum adsorption corresponds to a saturated monolayer of solute molecule on the adsorbent surface. once the molecules are concentrated on the adsorbent, there will be no transmigration of the solute (adsorbate) in the plane of the surface (langmuir 1916). the adsorption energy will be uniform throughout the surface area otherwise the pollutant will have uniform adsorption or attractive forces. (3) where: is the equilibrium concentration of adsorbate (mg/g), qmax is adsorption capacity, is the constant related to efficiency of solute adsorption (l/mg), ce is equilibrium concentration of adsorbate in solution (mg/l) and is constant related to energy of adsorption (l/mg). the above equation is termed as nonlinear form of langmuir, and can be linearized to form equation as (4) the essential characteristic of langmuir isotherm can be expressed by separation or equilibrium parameter (rl), a dimensionless constant, and can be define as: (5) 0 2 4 6 8 10 12 0 5 10 15 a m o u n t ad so rb e d in m g/ g ph mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 680 the value of rl indicates the nature of adsorption and it is shown in table 2. if the separation factor is greater than one (rl>1), it means the adsorption of safranin is unfavorable. while if the range is between 0 and 1 i.e. (0<r<1), this shows that, biosorption of safranin is favorable. but if the value of rl equals to unity, the adsorption process is linear. if it is equal to zero (rl = 0), then it is an indication of an irreversible process. below is the summary of the process above. table 2: values of rl and corresponding isotherm type (hameed et al., 2009) values of rl type of isotherm rl> 1 unfavorable rl = 1 linear 0 < rl > 1 favorable rl = 0 irreversible a langmuir isotherm plot of 1/qe against 1/ce is shown in figure 8 below. from this plot, it can be seen that, r 2 = 0.9593 which is relatively closed to unity indicates a good absorption. figure 8: langmuir isotherm for adsorption of safranin-o on pineapple peel adsorbent this suggested that the langmuir isotherm might be a suitable isotherm model. thus, the biosorption process of pineapple peels exhibit monolayer biosorption. table 3 shows the value of langmuir constants, al and kl as 12.77695 mg/l and 18.58736 mg/l respectively. table 3: langmuir isotherm parameter for safranin-o adsorption on pineapple peel adsorbent isotherm kl (mg/l) al (mg/l) r 2 langmuir 18.58736 12.77695 0.9593 3.3.2 freundlich isotherm freundlich, (1906) proposed a model based on the assumption that biosorption process takes place on heterogeneous surfaces and adsorption capacity is related to the concentration of adsorbate at equilibrium. mathematically, it is characterised by the heterogeneity factor ‘1/n’ (6) y = 0.6874x + 0.0538 r² = 0.9593 0 0.05 0.1 0.15 0.2 0.25 0 0.1 0.2 0.3 1 /q e (m g /g ) 1/ce (mg/l) arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 681 where: kf = constant that indicates sorption capacity of adsorbate (mg/g). the unit is given as (l/g) (1/n) , and n are constants indicating the intensity of adsorption. this constant can be one or any integer or decimal number. if n =1 (linear), n<1 (chemisorption process), and n>1 is physicsorption process (hameed et al., 2009). the linear expression of this model can take the logarithm of the equation on both sides, and is given as: (7) figure 9 shows a plot of logqe versus logce, gives a straight line with kf and 1/n determined from the intercept and the slope, respectively. table 4 shows the values of kf with about r 2 =0.985, which indicates a good sorption capacity of the adsorbate. figure 9: freundlich isotherm for adsorption of safranin-o on pineapple peel adsorbent table 4: freundlich isotherm parameter for safranin-o adsorption on pineapple peel adsorbent isotherm n 1/n kf r 2 freundlich 1.5222 0.656 0.6973 0.985 3.4 kinetics studies the kinetic adsorption data provides the understanding of dynamics of adsorption process in terms of the order of rate constant (ahmad et al 2007). the adsorption experiment was carried out at concentration of 20 to 100ppm, ph 5.7, adsorbent dose of 1gand contact time varied was from 3 to 90 minutes. two kinetic models were used to find which model fits the experiment: lagergren’s pseudo-first order and secondorder kinetic models. 3.4.1 pseudo-first order model the pseudo-first-order rate model equation was first developed by lagergren (ho et al., 2000). the relationship can be represented as ( ) (8) where: k1 is the pseudo-first-order rate constant (1/min), qe= amount of adsorbate at equilibrium (mg/g) and qt = are biosorption capacities at equilibrium with respect to time t (mg/g). integrating equation 8 for the boundary conditions are t = 0 to t = t and qt= 0 and qt yields, y = 1.5222x 0.3604 r² = 0.985 0.4 0.6 0.8 1 1.2 1.4 1.6 0.6 0.7 0.8 0.9 1 1.1 1.2 lo g q e log ce mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 682 ( ) (9) the constant value k1 were obtained by plotting a straight-line graph of log (qe –qt) against t. correlation coefficients r 2 for different safranin concentrations are shown in table 5. the coefficient 0.9148 is for concentration at 20mg/l while 0.8407 for 100 mgl -1 . the calculated values of adsorption capacity (qcal) were obtained as 3.543 mg/g at 20 mgl -1 and 6.929 mg/g at 100 mgl -1 . based on the observed, calculated, and experimental values it can be seen in figure 10 that, adsorption of safranin-o did not follow pseudo-first-order kinetic model. . figure 10: pseudo –first order model for adsorption of safranin-o on pineapple peel adsorbent 3.4.2 pseudo-second-order kinetic model the pseudo-second-order equation based on equilibrium adsorption (ho et al., 2000) and is expressed in equation 10 ( ) (10) where: k2 (g/mg-min) is the pseudo-second-order rate constant. integrating eq. (10) for the boundary conditions are t = 0 to t and qt= 0 to qt (11) the linear form of this model is represented as (12) where: (13) -1.5 -1 -0.5 0 0.5 1 1.5 0 10 20 30 40 50 60 70 20 mg/l 40 mg/l 60 mg/l 80 mg/l 100 mg/l lo g( q eq t) time (min) arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 683 the plot of t/qt against t gives a straight line. figure 11 shows the linear form of pseudo-secondorder kinetic at different safranin concentration on pineapple peel. table 5 presented the coefficient r 2 for the pseudo-second-order kinetic at different concentration was 0.998 (for 20 mgl -1 ) to 0.974 (for 100 mgl -1 ). in addition, the r 2 at (20 mgl -1 ) is higher than all the other concentrations both in the first and second order models respectively; suggesting adsorption is higher at this level. on the other hand, the calculated values of adsorption capacity (qcal) tend to be higher than that of the pseudo-first-order kinetic, its value ranges from 11.9 (for 50 mgl -1 ) to 161.3 (for 1000 mgl -1 ) at different concentrations. in addition, the r 2 at (20 mgl -1 ) is higher than all the other concentrations, suggesting adsorption is higher at this level. these facts suggest that the pseudo-second-order adsorption mechanism is predominant, and that the overall rate of the dye adsorption process appears to be controlled by the chemisorption process (liu et al., 2012). figure 11: pseudo-second order model for adsorption of safranin-o on pineapple peel adsorbent table 5. adsorption kinetic parameters of safranin-o on pineapple peel adsorbent first-order model second-order model co(mg/l) r 2 qe call (mg/g) qeexp (mg/g) k1(min-1) r 2 qe call (mg/g) qeexp (mg/g) k2 20 0.9148 3.543235 3.8829 2.298394 0.998 3.895598 3.8829 0.155806 40 0.8289 3.990249 8.3891 2.300006 0.9987 8.488964 8.3891 0.066491 60 0.8288 5.367845 12.7518 2.301618 0.9994 12.85347 12.7518 0.067064 80 0.8075 6.419482 17.1992 2.301158 0.9992 17.30104 17.1992 0.053916 100 0.8407 6.92947 21.6253 2.301618 0.9994 21.73913 21.6253 0.030767 0 5 10 15 20 25 0 10 20 30 40 50 60 70 80 20 mg/l 40 mg/l 60 mg/l 80 mg/l 100 mg/l t/qt time (min) mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 684 4. conclusion the experimental result from this study suggests that pineapple peels is a potential adsorbents for removal of safranin-o from aqueous solutions. conclusion can be drawn from the effect of parameters, such as initial dye concentration, adsorbent dosage, and ph of solutions. furthermore, from the result obtained, the adsorbent is found to effectively remove safranin-o by 86.9% percent at initial dye concentration of 100ppm in 90 min contact time. the removal was due to adsorbent dosage increase, while percentage uptake due to ph was 84.5%, which occurs at ph 6 showing acidic condition that is favourable for sorption process. adsorption isotherms behavior suggests that, the present adsorption exhibit both freundlich isotherm model characteristics were very good, reflecting the presence of more than one kind of adsorbent– adsorbate surface interaction. thus heterogeneous surfaces and adsorption capacity is related to the concentration of adsorbate at equilibrium. the adsorption kinetics data followed pseudosecond-order kinetic model with high correlation coefficient almost reaching a unit value (0.99). this indicates that, chemisorption’s or an effective electrostatic interaction is dominant. nomenclature bf freundlich constants co influent concentration mg/l ct effluent concentration at time t mg/l ce solution phase concentration at equilibrium mg/l k1 rate constant of first order adsorption 1/min k2 pseudo-second-order rate constant of adsorption g/mg.min kf constant related to the overall adsorption capacity mg/g kl langmuir isotherm constant l/g m mass of the adsorbent g amount of safranin adsorbed at equilibrium mg/g langmuir monolayer saturation capacity mg/g amount of safranin adsorbed on adsorbent at equilibrium mg/l langmuir isotherm constant l/mg 1/n constant indicates the heterogeneous surface of the adsorbent sem scanning electron microscopy ftir fourier transform infrared spectra rl dimensionless separation factor r 2 pp correlation coefficient pineapple peel eq mq tq l arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 685 references ahmad, aa., hameed, bh. and aziz, n. 2007. adsorption of direct dye on palm ash: kinetic and equilibrium modeling. journal of hazardous materials, 141(1):70-76. bayazit, ss. 2013. investigation of safranin o adsorption on superparamagnetic iron oxide nanoparticles (spion) and multi-wall carbon nanotube/spion composites. desalalination and water treatment, 52(37-39):6966-6975. boumehdi toumi, l., hamdi, l., salem, z. and allia, k. 2015. batch adsorption of methylene blue from aqueous solutions by untreated alfa grass. desalalination and water treatment, 53(3):806-817. dahri, mk., kooh, mrr. and lim, lbl. 2013. removal of methyl violet 2b from aqueous solution using casuarina equisetifolia needle.isrn environmental chemistry. dyke, sf., floyd, aj., sainsmbury, m. and theobald, rs. 1981. organics spectroscopy, an introduction. longman, 107. feng, n., guo, x., liang, s. 2009. adsorption study of copper (ii) by chemically modified orange peel. journal of hazardous materials, 164(2): 1286-1292. feng, n., guo, x., liang, s., zhu, y. and liu, j. 2011. biosorption of heavy metals from aqueous solutions by chemically modified orange peel. journal of hazardous materials, 185(1):49-54. freundlich, h. 1907. über die adsorption in lösungen. zeitschrift für physikalische chemie, 57(1): 385-470. gandhi, n., sirisha, d., smita, a., manjusha, a., change, c., padmavathi, s. and viswa, m. 2012. adsorption studies of fluoride on multani matti and red soil. research journal of chemical science, 2:32-37. gao, jj., qin, yb., zhou, t., cao, dd., xu, p., hochstetter, d., wang, yf. 2013. adsorption of methylene blue onto activated carbon produced from tea (camellia sinensis l.) seed shells: kinetics, equilibrium, and thermodynamics studies. journal of zhejiang university. science. b, 14:650-680. geçgel, u., g. özcan, g. c. gürpınar, 2013. removal of methylene blue from aqueous solution by activated carbon prepared from pea shells ( pisum sativum ). journal of chemistry güngördü, a., birhanli, a, and ozmen, m. 2013. biochemical response to exposure to six textile dyes in early developmental stages of xenopus laevis. environmental science and pollution research international , 20(1):452-460. mohammed et al.: equilibrium and kinetic studies of adsorption of safranin-o from aqueous solutions using pineapple peels. azojete, 13(6):671-687. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 686 gupta, vk., jain, r., saleh, t., nayak, a., malathi, s. and agarwal, s. 2011. equilibrium and thermodynamic studies on the removal and recovery of safranine-t dye from industrial effluents. separation science and technology, 46(5):839-846. hameed, bh., krishni, rr. and sata, sa. 2009. a novel agricultural waste adsorbent for the removal of cationic dye from aqueous solutions. journal of hazardous materials, 162(1):305311. han, r., ding, d., xu, y., zou, w., wang, y., li, y. and zou, l. 2008. use of rice husk for the adsorption of congo red from aqueous solution in column mode. bioresource technology, 99(8): 2938-2946. ho, yj., ng, gm., and ng, 2000. kinetics of pollutant sorption by biosorbents. separation of purification methods 29(2):189-232. hu, z., chen, h., ji, f., yuan, s. 2010. removal of congo red from aqueous solution by cattail root. journal of hazardous materials, 173(1-3): 292–297. khodaie, m., n. ghasemi, b. moradi, and m. rahimi, 2013. removal of methylene blue from wastewater by adsorption onto zncl 2 activated corn husk carbon equilibrium studies. journal of chemistry, krishni, r.r., foo, ky., and hameed, bh. 2014. adsorption of cationic dye using a low-cost biowaste adsorbent: equilibrium, kinetic, and thermodynamic study. desalalination and water treatment, 52(31-33):6088-6095. langmuir, i. 1916. the constitution and fundamental properties of solids and liquids. part i. solids. j acs, 38 2221. liu, t., li, y., du, q., sun, j., jiao, y., yang, g., ... & zhu, h. 2012. adsorption of methylene blue from aqueous solution by graphene. colloids and surfaces b: biointerfaces, 90: 197-203. malekbala, m.r., s. m. soltani, s. k. yazdi, s. hosseini, s. 2012. equilibrium and kinetic studies of safranine adsorption on alkali-treated mango seed integuments. international journal of chemical engineering applications, 3(3):160 mouzdahir, ye., elmchaouri, a., mahboub, r., gil, a., and korili, sa. 2010. equilibrium modeling for the adsorption of methylene blue from aqueous solutions on activated clay minerals. desalination, 250(1): 335-338. nagpal, umk., bankar, av., pawar, nj., kapadnis, bp., and zinjarde, ss. 2011. equilibrium and kinetics studies on biosorption of heavy metals by leaf powder of paper mulberry (broussonetiapapyrifera). water, air & soil pollution, 215(1-4): 177-188. arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):671-687. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 687 patel, h., and vashi, rt. 2013. a comparison study of removal of methylene blue dye by adsorption on neem leaf powder (nlp) and activated nlp. journal environmental engineering landscape management, 21(1):36-41. rafatullah, m., sulaiman, o., hashim, r., and ahmad, a. 2010. adsorption of methylene blue on low-cost adsorbents: a review. journal of hazardous materials, 177(1-3): 70-80. reddy, mcs., sivaramakrishna, l. and reddy, rv. 2012. the use of an agricultural waste material, jujuba seeds for the removal of anionic dye (congo red) from aqueous medium. journal of hazardous materials, 203: 118-127. saidutta, mks. and murty, mb. 2013. adsorption of basic dye from aqueous solution using hcl treated saw dust ( lagerstroemia microcarpa ): kinetic , modeling of equilibrium ,.international research journal of environment sciences, 2(8): 6–16. suteu, d., and malutan, t. 2013. industrial cellolignin wastes as adsorbent for removal of methylene blue dye from aqueous solutions. bioresources, 8(1):427-446. vinod, v., kailash, d., suresh, c. and madan, l. 2012. adsorption studies of zn ( ii ) ions from wastewater using calotropis procera as an adsorbent. research journal of recent science, 1: 160-165. yeddou-mezenner, n., 2010a. kinetics and mechanism of dye biosorption onto an untreated antibiotic waste.desalination, 262(1-3): 251-259. zonoozi, mh., moghaddam, mra. and arami, m. 2009. coagulation/flocculation of dyecontaining solutions using polyaluminium chloride and alum. water science and technology 59(7):1343-1351. arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):35-42 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 35 original research article production, proximate composition and sensory evaluation of cereallegume based infant food f. abubakar* and a. zigla department of food science and technology, lake chad research institute, maiduguri, borno state, nigeria. *corresponding author’s email address: fatidupli@yahoo.com 1.0 introduction providing adequate food and good nutrition to the child is important to its developmental growth and health during the weaning period. poor nutrition during this critical period of life may increase the risk of growth faltering and may have adverse effects on health and mental development of the infant (ijarotimi and keshinro, 2013). as from 3months old when babies are growing, the mother’s milk alone can no longer sustain them and therefore there is need to gradually introduce semi-solid foods in order supplement their daily breast milk intake with nutritious foods. poor nutrition during this critical period of life may increase the risk of growth faltering and may have adverse effects on health and mental development of the infant (ijarotimi and keshinro, 2013). as from 3months old when babies are growing, the mother’s milk alone can no longer sustain them and therefore there is need to gradually introduce semi-solid foods in order supplement their daily breast milk intake with nutritious foods. the nutrient requirements for infants and children have to be sourced from daily food intake since they have no reserves of needed nutrients. these nutrients are usually sourced from locally grown cereal grains such as maize, millet, sorghum and rice. about 40% of the nigerian population live below poverty line and cannot afford commercial weaning foods for their infants or good quality animal sources of protein (adebayo-oyetoro et al., article information abstract in this study, a cereal-legume based infant food was formulated from millet, malted millet, cowpea, soybeans, and groundnut. the grains used were blended into four infant formulations of different ratios namely: formulation 1 (70% millet + 30% soybean), formulation 2 (65% millet 430% soybean + 5% malt), formulation 3 (70% millet + 20% cowpea + 10% groundnut) and formulation 4 (65% millet 420% cowpea + 10% groundnut + 5% malt). standard methods of analysis were used to determine the moisture content, crude fat, crude protein, ash, ph, titrable acidity (ta), total sugar and bulk density contents for the different formulations; whereas the carbohydrate was computed by difference. each of the samples from the formulations produced was cleaned, toasted, and milled together. the infant formulations were given to 120 mothers residing within lake chad research institute, maiduguri and usmanti area, which is close to lake chad research institute, maiduguri. the prepared infant formulations were made into slurry with boiled water and given to the mothers in order to serve their children when slightly cooled. a 9point hedonic scale was used in the sensory evaluation of the products. results obtained showed that the moisture content ranged from 4.4 to 6.5%, ash from 1.5 to 1.9%, protein from 13.6 to 22.1%, carbohydrate from 68.6 to 75.5% and fat from 2.3 to 4.9%; whereas the ph and ta values ranged from 5.5 to 5.6, and 0.68 to 0.74, respectively, while the total brix sugar value ranged from 14.2 to 29.8. the results for sensory evaluation indicated that the cereal-legume based formulations were generally accepted by the mothers for their babies in all the parameters determined. the study indicated that formulations 3 and 4 had the highest scores for overall acceptability © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 march, 2020 revised 2 july, 2020 accepted 9 february, 2021 keywords: cereal cowpea soybeans groundnut infant food abubakar and zigla: production, proximate composition and sensory evaluation of cereallegume based infant food. azojete, 17(1):35-42 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 36 2012). commercial infant foods are expensive and the situation demands that an alternative source of infant food be sought to provide the infants and children with adequate and balanced diet. in nigeria, infants and children suffer from protein energy mal-nutrition (pem) (nkama, et al., 2001). it actually occurs as a result of ignorance and exorbitant cost of animal sources of protein thereby making it out of reach of the common man (patrick, 1998). cereals often provide bulk of the energy requirements but are deficient in protein and other essential nutrients while legumes are rich in protein. food legumes as a source of proteins, are one of the best and the least expensive solution for quality food supply in tropical african countries (olakojo et al., 2007;adam and baidoo, 2008;), and are therefore valued as a nutritional supplement to cereals and an extender of animal proteins (modu et al., 2010; bamishaiye et al., 2011). therefore, supplementation of cereal grains with grain legumes which are rich in protein and readily available in abundance in this zone will increase the nutrient intake of the babies. also, supplementation of our locally available cereals with legumes, which are good sources of protein rich foods, will give rise to a weaning food which is cheaper, easily digestible and acceptable to children (marero et al., 1988). baby foods made from a combination of cereal grains and grain legumes are termed high protein-energy foods, (nkama et al., 2001). depending on the country, millet is sometimes used directly in food preparations (adebiyi et al., 2016) or mixed with other grains like sorghum or cowpea in order to improve the nutritional quality of food (modu et al., 2010; almeida-dominguez et al., 1993;). the nutritional value of pearl millet is greatly enhanced when mixed with legumes because the latter complements its profile of essential amino-acids (serna saldivar, et al., 1991). cereals and legumes therefore complement each other in both traditional foods and for industrial uses (nkama, 1990). the complementarities of millet and these legumes in infant food would help to solve the pem in children. the objective of this study, is therefore, to formulate a nutritionally balanced malted cereal-legume-based infant food formulation and to evaluate the nutritional and acceptability of the product as infant food. 2. materials and method 2.1 materials the food materials used in this study include millet grain, malted millet, cowpea, soybean and groundnut. millet variety used was ex-borno obtained from lake chad research institute, maiduguri, cowpea (vigna inguiculata), soy beans (glycine max), groundnut (arachis hypogea) and lemon fruits were purchased from maiduguri monday market, maiduguri, nigeria. 2.2 methods the methods described by aoac (2000) were followed to determine the moisture, crude fat, crude protein and ash contents in the different formulations. carbohydrate was computed by difference (egan et al., 1981). the ph, titrable acidity, total sugar and bulk density were also determined using standard methods (akpapunam and markakis, 1981) sensory evaluation was based on a 9-point hedonic scale (larmond, 1976). the infant formulations were given to 120 mothers residing within lake chad research institute, maiduguri and usmanti area, which is close to lake chad research institute, maiduguri. the prepared infant formulations were made into slurry with boiled water and given to the mothers in order to serve their children when slightly cooled. resulting data were analyzed using analysis of variance (anova) and mean separation was done using least significant difference (lsd) test, at 5% level of probability(p<0.05), (duncan, 1955). arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):35-42. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 37 2.3 preparation of raw materials weaning food was prepared as described by livingstone et al.(1993), almeida-domeiguez et al. (1993) and nkama, et al. (2001). the pearl millet was dehulled using a commercial rice steel huller. the dehulled grain was washed and soaked in tap water containing lemon juice to acidify the water and remove the grayish matter. this was soaked for 2 days after which the millet was washed, strained, dried, and subsequently roasted for 25 minutes at 200°c using a gas oven. the millet is then allowed to cool at room temperature. similarly, the cowpea was soaked in tap water for 5 minutes to facilitate dehulling. the cowpea was dehulled using pestle and mortar. the dehulled cowpea kernel was washed to remove the skin, strained, and dried and then roasted in a gas oven for 25 minutes at 200°c. ground nut was dry roasted in a gas oven for 25 minutes at 200°c and allowed to cool. the skins were removed by rubbing between the palms, winnowed to remove the testa and then sorted to remove the burnt ones. soybeans was sorted and soaked in water for 30 minutes and then poured into boiling water. this was cooked for 25 minutes and pounded using pestle and mortar to separate the testa from the kernel. the soybeans were washed to remove the testa and strained and dried. the soybean was roasted for 25 minutes in a gas oven at 200°c. all samples were roasted to a golden brown colour. malted pearl millet was prepared by cleaning and washing the millet followed by steeping in tap water for 16 hours. during steeping, there was an hourly air rest every 4 hours. the steeped grains were spread on a sterilized moist jute bag to sprout in a dark cabinet for 48 hours, after which, the sprouted grains were sun-dried and then de-vegetated by rubbing between the palms of the hand. the rootlets were then separated from the malted grains and the malted grains were stored in a clean container. 2.4 formulation of samples the instant food formulation was carried out as described by almeida-domeiguez, et al. (1993). the roasted cereals and legumes (millet, malted millet, cowpea, and soybean) were measured for the formulations as indicated in tables 1 shows the weight of samples in grams and table 2 shows the weight of samples in percentages. the samples were then blended into four infant formulations and milled in hammer mill to pass through a sieve of 1.25 mm. table 1: measured weight of samples used in the infant formulations formula millet soybean cowpea groundnut malted millet 1 1750 750 2 1625 750 125 3 1750 500 250 4 1625 500 250 125 table 2: weight of infant formulations samples in percentages formula millet soybean cowpea groundnut malted millet 1 70 30 2 65 30 5 3 70 20 10 4 65 20 10 5 data obtained were subjected to analysis of variance (anova) and mean separation was done using least significant difference (lsd) test, at 5% level of probability(p<0.05), (duncan, 1955). abubakar and zigla: production, proximate composition and sensory evaluation of cereallegume based infant food. azojete, 17(1):35-42 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 38 3. results and discussion table 3 shows the nutritional values of the four infant formulations. the moisture content ranged from 4.4 to 6.5% where formulation 4 had the lowest moisture content and formulation 3 had the highest moisture content. the result falls within the range of 5-10% as recommended by pag (1971). the protein content of the formulations showed that the values ranged from 13.6 to 22.1%. formulation 2 had the highest protein content had significantly higher protein (22,1%), followed by formulation 1 with significantly high protein content (19.4%) while formulation 3 had the lowest protein content than the cowpea-groundnut based formulations. in general, the soybean-based formulation was significantly (p≤0.05) higher in protein. this shows that soybean significantly enhanced the protein content of formulations than the cowpea and groundnut put together. (jansen and harper, 1980) reported that weaning foods used in supplementary feeding programs to contain 17-20 % protein content. the higher protein could also be attributed to the addition of milk. the supplementary effect is most obvious when milk is added to legumes and cereals, (briggs and callaway, 1984). the fat content ranged from 2.3 to 4.9% which indicated that formulation 1 had the lowest fat while formulations 3 and 4 had the highest fat contents than the soybean-based formulation. these values are within the range reported by pag, (1975) which should be about 6%. higher fat content could lead to rancidity. the ash content showed no significant difference (p≤0.05) among the formulations and the values ranged from 1.5 to 1.9%. formulation 2 had the highest ash content while formulations 3 and 4 had the lowest. the carbohydrate showed significant difference (p≤0.05) between the samples. the result ranged from 68.6 to 75.5%. formulation 4 had significantly higher carbohydrate followed by formulation 3 while formulation 2 had the lowest carbohydrate content. these values were also higher than 61% recommended by the rti, (1987). these results agree with those reported by other workers (osundahunsi and aworh, 2002 and modu et al. 2010). table 3: proximate composition (%) of cereal-legume based formulas produced formula moisture ash protein fat carbohydrate 1 6.5a 1.7a 19.4b 2.9b 69.5c 2 5.3c 1.9a 22.1a 2.3c 68.6d 3 5.6ab 1.5a 13.6c 4.9a 74.5b 4 4.4c 1.5a 13.8c 4.9a 75.5a the ph values ranged between 5.5 and 5.6 for all the four formulations, while the titratable acidity ranged between 0.68 for formulation 3 and 0.74 for formulation 2. the results are in line with the result reported by nkama (2001). the total brix sugar ranged between 14.2 for formulation 3 to 29.8 for formulation 4. addition of malt significantly enhanced the sugar content in both soybean and cowpea/groundnut-based formulations as shown in the table 4. the bulk density values ranged between 0.4g/ml for formulation 4 to 0.8g/ml for formulation1. the addition of malt reduced the bulk densities of the formulation 2 and formulation 4 as shown in the table 4. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):35-42. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 39 table 4: functional property of weaning food formulation ph titratable acidy (%) total sugar (brix) bulk density (g/ml) 1 5.6 0.72 16.9 0.8 2 5.5 0.74 28.9 0.6 3 5.5 0.68 14.2 0.7 4 5.6 0.72 29.8 0.4 the result of sensory evaluation of the formulations used in this study is shown in table 5. it was observed from the results that the formulations were generally accepted by the mothers for their babies as the samples were presented to mothers for evaluation as they are the ones feeding the babies and usually prepare and taste the formulations before serving their children. the result for colour indicated that there was no significant difference among the formulations samples rated except for the formulation 1. the score for colour ranged between 7.8 and 8.1. formulation 1 had the least rating for colour while formulation 3 and 4 had the highest scores for colour (8.1). the colour rating could be due to the brighter colour of the formulations 3 and formulation 4 which was achieved during processing and was acceptable to the mothers. the result of sensory evaluation of the formulations used in this study is shown in table 5. it was observed from the results that the formulations were generally accepted by the mothers for their babies as the samples were presented to mothers for evaluation as they are the ones feeding the babies and usually prepare and taste the formulations before serving their children. the result for colour indicated that there was no significant difference (p≤0.05) among the formulated samples rated except for the formulation 1. although, the colours of the formulations were highly rated, the score for colour ranged between 7.8 and 8.1. formulation 1 had the least rating for colour while formulation 3 and 4 had the highest scores for colour (8.1). the colour rating could be due to the brighter colour of the formulations 3 and formulation 4 which was achieved during processing and was acceptable to the mothers. on the hand, formulations 1 and 2 had the least rating for taste while formulations 3 and 4 had the highest scores for taste. the taste indicated that there were no significant differences (p≤0.05) between the four formulations. the score for taste ranged between 7.7 and 8.0. the taste of the formulation 1 had the least score for colour with 7.7 while the formulations had the highest score for taste at 8.0 and was most preferred. there was no significant difference (p≤0.05) among all the four formulation in terms of mouth-feel texture. the mouth feel texture ranged between 7.8 and 8.0. the texture of the formulations 1 and 2 had the least scores for texture while the formulations 4 had the highest score for mouth feel of 8.0. the mouth feel texture was due to the fact that the samples subjected to the same processing methods and conditions therefore, they had the same mouth feel texture. the aroma indicated that there were significant differences (p≤0.05) among the four formulations rated. the result of aroma of the formulations produced ranged between 7.9 and 8.1. formulation 2 had the lowest rating for aroma with 7.9 while formulation 3 had the highest rating for aroma with 8.1. the differences are as a result of the aroma obtained from toasting the different legumes used in the formulations which contributed to the respective aroma of the formulations. the overall acceptability showed that there were significant differences (p≤0.05) among the formulations but there was no significant difference (p≤0.05) between formulations 3 and 4. the result indicated that all the formulations were highly rated and accepted. the score for overall acceptability ranged between 7.8 and 8.1. the overall acceptability of the formulation 1 had the least score in overall acceptability while the formulations 3 and 4 had the highest scores for overall acceptability of 8.1. although, all the formulations were equally accepted by the panelists, the millet, abubakar and zigla: production, proximate composition and sensory evaluation of cereallegume based infant food. azojete, 17(1):35-42 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 40 cowpea, and groundnut-based formulations with or without malt, were more favoured in all sensory criteria. table 5: sensory evaluation of weaning food formulation colour taste mouth feel aroma overall acceptability 1 7.8b 7.7b 7.8a 7.8b 7.8b 2 7.9a 7.8b 7.8a 7.9b 8.0ad 3 8.1a 8.0a 7.9a 8.1a 8.1a 4 8.1a 8.0a 8.0a 8.0ab 8.1a conclusion: the study showed that the formulation of weaning food from millet grains both malted and unmalted in combination with soybean, cowpea and groundnut can be produced from cheap and readily available resources at low cost. the malting of the millet decreased the bulk density and increased the nutrients of the formulation thereby making more nutrients available. varying the protein sources of ground nut and soybeans provides alternative sources for those with peanut allergy while providing adequate protein for the formulations. the study also showed that the formulations had acceptable sensory qualities. references adam, ji. and baidoo, pk. 2008. susceptibility of five cowpea (vigna unguiculata) varieties to attack by callosobruchus maculatus (fab.) [coleoptera: bruchidae]. journal of ghana science association, 10(2): 85-92. adebayo-oyetoro, ao., olatidoye, op., ogundipe, oo., akande, ea. and isaiah, cg. 2012. production and quality evaluation of complementary food formulated from fermented sorghum, walnut and ginger. journal of applied biosciences 54:3901-3910. adebiyi, j., obadina, ao., mulaba-bafubiandi, fa. and adebo, o. 2016. effect of fermentation and malting on the microstructure and selected physichochemical properties of pearl millet (pennisetum glaucum) flour and biscuits. journal of cereal science, 70: 132-139. akpapunam, ma. and markakis, p. 1981. physciochemical and nutritional aspects of cowpea flour. journal of food science, 46: 972-793. almieda-dominguez, hd., serna-saldivar, so., gomez, mh. and rooney, lw. 1993. production and nutritional value of weaning foods from mixtures of pearl millet and cowpeas. cereal chemistry, 70:14–18. association of official analytical chemists. 2000. aoac. official methods of analysis. washington dc. u.s.a., pp. 167. badau, mh., nkama, i. and jideani, ao. 2005. phytic acid content of and hydrolytic acid extractability of minerals in pearl millet as affected by germination time and cultivar. food chemistry, 92: 425-435 bamishaiye, om., adegbola, ja. and bamishaiye, ei. 2011. bambara groundnut: an under-utilized nut in africa. advances in agricultural biotechnology, 1:60-72 briggs, gm. and callaway, dh. 1984. nutritional and physical fitness, 11th edition. cbs. collage publications, new york, usa. egan, h., kirk, rs. and sawyer, r. 1981. pearsons chemical analysis of foods. 8th edition. churchill livingstone, edinburgh, pp. 511 — 536. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):35-42. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 41 fasundahusin, o. and aworh, ca. 2002. preliminary study on the use of tempe-based formular as weaning food diet in nigeria. journal for plant foods for human nutrition, 57(3-4): 365-367. gupta, c. and sehgal, s. 1992. protein quality of developed homemade weaning foods. plants food human nutrition, 42(3): 239-246. ijarotimi, os. and keshinro, oo. 2013. determination of nutrient composition and protein quality of potential complementary foods formulated from a combination of fermentaed popcorn, african locust bean, bambara ground-nut flour. polish journal of food and nutrition sciences, 63(3): 155-166. jansen, gr. and harper, jm. 1980. application of low cost extra, part 2. food and nutrition, 2(1): 15-23. kannan, s., nielson, ss., patricia, a., rodriguez-burger, ap. and mason, ac. 2001. iron and zinc bioavailability in rats fed intrinsically labelled bean and bean-rice infant weaning food products. journal of agriculture and food chemistry, 49: 5063-5069. larmond, e. 1976. laboratory methods for sensory evaluation of food. canadian government publishing centre, ottawa, canada. livingstone, as., feng, jj. and malleshi, ng. 1993. development and nutritional quality evaluation of weaning foods based on malted popped and roller dried wheat and chickpea. journal of food science and technology (india), 28:35–43. marero, lm., payumo, ar., aguinaldo, ar. and hommas, s. 1988. nutritional characteristics of weaning foods prepared from germinated cereals and legumes. journal of food science, 53(5): 1399-1401. marero, lm., payumo, em., aguinaldo, ar., homma, o. and igarashi, o. 1991. vitamin e constituents of weaning foods from germinated cereals and legumes. journal of food science, 56(1): 270 -271. modu, s., laminu, hh. and abba, sf. 2010. evaluation of nutritional value of a composite meal prepared from pearl millet (pernisetumtyphoideum) and cowpea (vigna unguiculata). journal of applied sciences, 3(1): 164-168. modu, s., laminu, hh. and nkama, i. 2005. production, chemical and sensory properties of ogi from different pearl millet varieties. journal of biological science, 5(2): 103-106. nkama, i. 1990. strategies for industrial development of the indigenous cereal grains and grain legume based foods of the north eastern state of nigeria. in: strategies for agro-based industry: raw material supply, processing and sanitation. (nkama, i. and sopade, pa. eds). proceedings of a two-day workshop organized by the nigerian institute of food science and technology (nifst) at the university of maiduguri, maiduguri, nigeria, 31st may to 1stjune, 1990, p. 58. nkama, i., dagawanna, fn. and ndahi, wb. 2001. production, proximate composition and consumer acceptability weaning foods from mixtures of pearl millet, cowpea and groundnut. journal of arid agriculture, 11: 165-169. nkama, i. and gbenyi, di. 2002. the effect of malting of millet and sorghum on the residual phytate and polyphenols in dakuwa-a nigerian cereal-legume food. nigerian journal of tropical agriculture, 3: 76-85. olakojo, sa., omuti, o., ajomale, k. and ogunbodede, ba. 2007. development of quality protein maize: biochemical and agronomic evaluations. journal of tropical and subtropical agroecosystems, 7: 97-104. abubakar and zigla: production, proximate composition and sensory evaluation of cereallegume based infant food. azojete, 17(1):35-42 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 42 olokoja, sa., kogbe, jos., olajide, u. and johnell, a. 2001. hostparasite relationship of striga asiantica and maize (zea mays l) under varied moisture levels and nitrogen source. nigerian journal of weed science, 14: 41-46. pag. 1975. guidelines for protein rich mixtures for use as supplement food. the pag compendium. vol. e. world market press ltd. john wiley and sons, new york, 63. patrick, no. 1998. cereal grains. nutritional quality of plant foods, 1: 32-52. rti 1987. weaning fooda new approach to small scale weaning food production from indigenous raw materials in tropical countries. 2nd edition. amsterdam, royal tropical institute (rti), rural development programme, nutrition and agro technology section arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):685-698 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 685 original research article performance evaluation of soiling mitigation technique for solar panels m. a. afolayan1*, t. n. olayiwola1, q. t. nurudeen1, o. ibrahim1, i. s. madugu2 1department of electrical and electronics engineering, university of ilorin, ilorin, nigeria 2department of electrical engineering, kano university of science and technology, wudil, nigeria *corresponding author’s email address: afolayan.ma@unilorin.edu.ng 1.0 introduction the use of a non-renewable source of energy such as fossil fuels is depreciating by the day, thereby giving prevalence to solar energy and other renewable sources of energy in the world. solar energy has been discovered to be one of the most popular renewable energy sources on the earth (zhao et al., 2014, li et al., 2009). this is because it has a comparative advantage over other forms of non-renewable energy sources such as coal, petroleum, and fossil fuels, etc. and other renewable energy sources such as wind power, hydroelectricity, etc. some of the merits of solar energy include reduction of electricity bills; it is clean, generates no noise, minimum maintenance cost, and environmentally friendly with no reported pollution emissions (stigka et al., 2014, tsoutsos et al., 2005). solar energy from the sun can be trapped by the use of solar panels. a solar panel is made up of semiconductor material and the most common semiconductor material used is silicon (si). in daylight, the energy from the sun is absorbed by the semiconductor materials of pv modules to break the electrons loose allowing them to move freely thereby generating a flow of electrons within the cell (armaroli et. al., 2016). therefore, connecting external load such as a light bulb will generate the flow of electricity in the cell. it is clear that the efficiency of a solar panel depends on the intensity of sunlight that impacts on the surface of the panel. the use of solar panels is highly efficient in arid or desert regions because the intensity of the sun is high in these regions. however, the performance of a solar panel depends on several factors (one of which is the degree of freedom from the accumulation of dust on the surface of pv panels) to attain maximum performance. other factors that reduce the efficiency of the solar panel are cracks on the surface of the panel, accumulation of snow, and soiling. (akuru et al., 2017). the term soiling is used to describe the accumulation of leaves, dust, dirt, snow on the pv module. soiling is defined by meija et al. (2014) as the accumulation of dust on the surface of article information abstract soiling is the accumulation of dust, leaves, and debris on the surface of photovoltaic modules which affects its overall conversion efficiency. globally, several researches have indicated that with an increase in dust accumulation, the efficiency of the solar panels can drop by approximately 50%. this research aimed at increasing the efficiency of solar panels by mitigating the effects of soiling. the panel was incorporated with a dust sensor that senses increment in dust settlement and a dc fan/blower which was placed in a position covering the surface of the panel. the speed of the installed fan can be varied using an l293d motor driver. it is actuated when the light intensity of the module falls below a set threshold. solar energy parameters of the panel were measured and displayed on the constructed onboard controller. a comprehensive analysis was carried out on the design and the results show a 72% increase in efficiency after mitigation which reflects that controlled wind is an ideal technique in eliminating dust on solar panels. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 may, 2020 revised 10 july, 2020 accepted 13 august, 2020. keywords: soiling soiling mitigation technique dust settlement conversion efficiency photovoltaic modules. http://www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 686 solar panels (either fixed or concentrated) which ultimately leads to the low efficiency of the module. soiling is not limited to dust accumulation but also combustion products, salt deposits from non-distilled water, soot, etc. nummo and seid (2010) defined dust as any particle matter less than 500µm in diameter which is 10 times the size of human hair. however, with advances in research, in 2011, mani and pillai defined dust as a term generally applied to minute solid particles with a diameter of less than 500mm. the composition of dust varies from region to region across the world. a comprehensive review of mani and pillai (2011) gives the factors that affect the accumulation of dust on solar panels as shown in figure 1. figure 1: factors affecting the accumulation of dust on solar panels (mani and pillai, 2011) another factor that affects the efficiency of the solar panel is the operating temperature caused by the absorption of solar radiation. musthafa (2015) revealed that cooling solar cells by water during operation leads to a decrease in operating temperature by 40°c, consequently increasing the cell efficiency by 2.6%. in 2016, kadhum et al. (2016) observed the impact of dust on the current and voltage generated by the module under controlled conditions. when dust accumulates on the surface of pv panels, the transmittance of solar irradiance is reduced thereby causing a decrease in output voltage and output power of solar panel leading to corresponding decrease in the efficiency of the panel. its effect on current was widely observed to be constant. ibrahim (2010) showed that the accumulation of dust on silicon solar cells also decreases the short circuit current isc by 2.78% and open-circuit voltage voc by 0.83%. complete cleaning of pv modules is essential to ensure peak efficiency. several techniques can be used to eliminate dust from the surface of solar panels. einhorn et al. (2018) recommended that a successful mitigation technique can lead to significant energy gain and reduce the maintenance cost of pv modules. several natural methods have been proposed for cleaning solar panels. in most cases, the user of the pv module climbs to the top of the building to clean the module which poses a great risk to the life of the user since panels are usually installed at high altitudes. another widely known method is to have a company clean the panel at least once a week, however, these two methods greatly increase the cost of maintenance of pv systems especially the latter approach. water cleaning as an alternative to rainfall involves the use of a huge amount of water for the cleaning process. it is expensive and inefficient in areas where there is the unavailability of water. analysis carried out by al dowsari et al. (2014) showed that dry cleaning is a preferred technique used in arid regions to minimize wet cleaning. it is reported that cleaning of unsoiled panels and non-cleaning of over soiled panels can lead to increase in the cost of maintenance and significant losses respectively (deceglie et al., 2017, micheli et al., 2017). an automated system of cleaning solar panels is necessary to eliminate the risk of damage to the panel and high cost of maintenance. however, it involves using a microcontroller to send actuating signals to the mechanical parts such as motor, roller, brushes, wiper, etc. to remove dust from the surface of the panel for better improvement in conversion efficiency (meija et al., 2014). saraf http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 685-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 687 (2015) stated that this actuating signals should however not be based on voltage drop sensed by a voltage sensor only since at high temperature, the voltage value drops. instead, a dust sensor can be used to initiate the actuating signal in order to achieve a better performance. saini et al. (2017) designed a portable automatic cleaning system made up of an at89s52 microcontroller, two dc motors, a dust sensor, a nickel-metal hydride battery, brushes, and a threaded rod. the at89s52 microcontroller relies on the signal from initiating devices such as a dust sensor to determine whether to activate the two dc motors. the two dc motors perform similar functions, as one rotates the rod, the other rotates the brushes used to clean the surface of pv panels. although this system requires low production cost and consumes low power, it involves high operational cost due to changing of belts and pulley system used to drive the dc motors and the rod. consequently, it cannot be used in situations where the pv panel has to be tilted at an angle or in concentrated solar panels which involve the use of solar tracker. ganesh et al. (2011) recommended the use of coating agents with water repellant properties such as tio2 or zno in making the cleansing process more efficient and effective. the property of tio2 allows rain that falls on the slides of the concentrated panels to wash the dust off. hee et al. (2012) suggested coating the surface of the module with a 60mm thickness of tio2. das et al. (2015) proposed the use of titanium oxide pv systems to increase the solar panel output power. the design was based on a single-axis solar tracking system equipped with a unique water cooling system to mitigate the effect of dust and high temperature on solar panels. the water is sprinkled on the surface of the module when the temperature is high as sensed by the thermostat. the sprinkler is gravity controlled with little wastage since the water is recycled. this design was based on a solar panel that has an efficiency of 34% which is almost double the value of commercially available pv modules. another limitation of this design is that lumps of clay will be produced on the surface of the module as a result of the water being sprinkled. aly et al. (2015) proposed the use of a dc fan which produces an air drag that rises up and is discharged at the exhaust assembly via the outlets made available. this method does not only remove the dust; it also cools the pv module. solar panels designed with this dust mitigation technique have been found to have an efficiency of 24.1%. the effectiveness of this method is dependent on the diameter of dc fans used. a positive can be drawn from this method of controlled airflow as a dust mitigation techniquewhich also cools the panel. 2.0 materials and method the system is divided into two parts; the hardware and software parts. the hardware components consist of arduino uno (based on atmega 328) mcu, two light-dependent resistors (ldrs), quadruple half-h drivers (l293d), liquid crystal display (lm044l lcd), one bldc blower, resistors among others. the pictorial view of the experimental setup is shown in figure 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 688 figure 2: experimental setup of the onboard controller and solar panel the block diagram that describes the relationship between the physical components and the microcontroller unit is as shown in figure 3. the solar panel supplies the components of the automatic cleaning system the power required for its operation. the panel charges a 12v 4.5ah battery, in-between this interval, a charge controller was placed in order to protect the battery from overcharge and dissipating the excess charge as heat. the charged battery powers the solar measurement circuit which comprises a voltage sensor, current sensor, and light intensity sensor. the voltage sensor senses the voltage from the solar panel and sends a signal to the microcontroller in the arduino board. the microcontroller unit (mcu) receives a signal from the input components (the ldrs and current sensor), monitors the integrity of their operation, and controls the output components (motor drivers and lcd) based on the input signal received. the output components operate based on the signal received from the mcu. the parameters are then displayed on the lcd screen. the light intensity sensor used in this design is a light-dependent resistor (ldr) whose maximum solar intensity recorded at any instance is 1000lux. an increase in dust settlement on the surface of the panel leads to a decrease in light intensity sensed by the light intensity sensor. a 12v 1.04a dc fan is placed at the top of the panel which serves as the dust mitigation technique employed in this design. the microcontroller unit activates the l293d motor driver initiating the operation of the dc fan. the activation was set by choosing threshold value such that when the light intensity sensed by the solar panel drops below this value, the fans speed up and will remain in this state until the light intensity rises above this value. the experiment was carried out from 6th june 2019 to 16th july 2019. because the values were closely related, the values taken on 16th june 2019 were used for analysis. average values were obtained every hour from the pool of available data. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 685-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 689 figure 3: block diagram of the pv system incorporated with a soiling mitigation technique the circuit diagram of this design is shown in figure 4. figure 4: system circuit diagram designed using proteus the specification of the panel used in the design is shown in table 1. table 1: solar panel specification part specification maximum power pmax 50w operating temperature tc 25°c solar irradiance g 1000w/m2 output tolerance 3% current at pmax imax 2.94a voltage at pmax vmax 17v short circuit current isc 3.19a open circuit voltage voc 22v charging current 0.75a air mass a.m 1.5 this study involves the implementation of the cleaning mechanism constructed and mounted on a 50w solar panel under different atmospheric and load conditions. dust was allowed to settle file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 690 on the surface of the pv module naturally. voltage, current, and light intensity readings were taken as the measured values while power, panel efficiency, irradiance, irradiation, conversion efficiency and fill factor were calculated from the measured values. the solar panel was fixed at the top of a building during the experiment. the solar energy measurements are recorded on a per-minute basis and data collected are stored in a memory device which can be retrieved for analysis. solar irradiance, irradiation, fill factor, and conversion efficiency of each of the solar panel was calculated using the following equations. a = light intensity (lux) f = open circuit voltage (v) b = irradiance (w/m2) g = short circuit current (a) c = irradiation (mj/m2) h = fill factor d = irradiation(kwh/m2) i = solar irradiance (w/m2) e = maximum power (w) j = total area (m2) k = conversion efficiency *0.0079b a (1) *11.6c b (2) 3.6 cd (3) * eh f g  (4) *100 * ek i j  (5) assuming all the solar irradiance on a solar panel is converted to power for a cross-sectional area of 1m2, this implies that the conversion efficiency is 100%. however, typical solar panels have conversion efficiency between 15-18%. in order to calculate the total area of the solar panel, a conversion efficiency of 18% is taken as the minimum efficiency required. hence, * *e i j k (6) * ej i k  (7) 50 0.2778 2 1000*18 j m  (8) 50 71.25% 22*3.19 h   (9) 50 *100 18% 1000*0.2778 k   (10) the dimension of the panel was measured using a meter rule; the length and width were measured to be 65.7cm and 42.6cm respectively. the cross-sectional area of the panel is 0.2799m2. this validates the assumption used in calculating the area of the panel. the calculated conversion efficiency using the measured area is 17.86%. generally, the fill factor of pv modules is greater than 70%. it should be noted that the wattage of the panel is exceedingly high which could damage the solar energy measurement circuit, hence a charge controller circuit was designed as a supplement to this circuit such that the excessive inflow of current supplied by the panel is converted and dissipated as heat through a heat sink so as not to damage the circuit. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 685-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 691 3.0 results and discussion the current, voltage, and light intensity were measured while the power, solar irradiance, efficiency at every instance (per hour), conversion efficiency and fill factor were calculated as shown in tables 2, 3, 4 and 5 respectively for both conditions (before and after mitigation). table 2: measured and calculated results of the panel obtained at high altitude before mitigation time (hours) voltage (v) current (a) power (w) efficiency (%) conversion efficiency (%) 1 8.04 0.85 6.85 2.46 17.86 2 8.04 0.78 6.25 2.24 17.86 3 8.04 0.78 6.25 2.24 17.86 4 8.04 0.78 6.25 2.24 17.86 5 8.06 0.63 5.08 1.82 17.86 6 8.06 0.78 6.27 2.25 17.86 7 8.06 0.78 6.27 2.25 17.86 table 3: measured and calculated results of the panel obtained at high altitude before mitigation time (hours) light intensity (lux) irradiance (w/m2) irradiation (mj/m2) irradiation (kwh/m2) fill factor (%) 1 666.00 5.26 61.03 16.95 71.25 2 699.00 5.52 64.05 17.79 71.25 3 696.00 5.49 63.78 17.71 71.25 4 693.00 5.47 63.50 17.64 71.25 5 693.00 5.47 63.50 17.64 71.25 6 697.00 5.50 63.87 17.74 71.25 7 607.00 4.79 55.62 15.45 71.25 table 4: measured and calculated results of the panel obtained at high altitude after mitigation time (hours) voltage (v) current (a) power (w) efficiency (%) conversion efficiency (%) 1 12.67 1.63 20.60 7.42 17.86 2 12.63 1.70 21.44 7.72 17.86 3 12.60 1.78 22.37 8.05 17.86 4 12.56 1.75 22.02 7.93 17.86 5 12.55 1.71 21.43 7.71 17.86 6 12.51 1.72 21.57 7.76 17.86 7 12.44 1.78 22.17 7.98 17.86 table 5: table showing measured and calculated results of the panel obtained at high altitude after mitigation time (hours) light intensity (lux) irradiance (w/m2) irradiation (mj/m2) irradiation (kwh/m2) fill factor (%) 1 926.45 7.32 84.90 23.58 71.25 2 934.77 7.38 85.66 23.79 71.25 3 943.88 7.46 86.50 24.03 71.25 4 896.47 7.08 82.15 22.82 71.25 5 889.17 7.02 81.48 22.63 71.25 6 894.27 7.06 81.95 22.76 71.25 7 929.02 7.34 85.14 23.65 71.25 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 692 the readings of the panel under these two conditions are compared with each other. the state of each parameter before mitigation is compared with its equivalent output parameter after mitigation. figure 5 shows the comparison of the voltage of the panel before and after mitigation was achieved. it was discovered that there was a 35% increment in the voltage level after the panel had been cleaned due to reduction in dust particles that led to an increase in the transmissivity of the solar panel. figure 5: voltage against time figure 6 shows the comparison between the current generated by the panel before and after mitigation was achieved. the current value increased by 55% after mitigation. figure 6: current against time figure 7 shows the comparison of the power generated by the panel before and after mitigation was achieved against time. the power output depends on the current and voltage of the panel. as the current on individual cells increases, the power generated by the panel also increases vice-versa. the rate at which the power increased after cleaning is 71%. also, the power produced is proportional to the efficiency. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 685-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 693 figure 7: power and efficiency against time figure 8 shows the comparison of the light intensity falling on the panel before and after mitigation against time. as the incident light that strikes the panel surface increased, the current also increased showing a direct relationship. also from panel specifications, the short-circuit current is a function of solar intensity. figure 8: light intensity against time figure 9 shows the comparison between the efficiency of the solar panel before and after removing the dust from the panel’s surface against time. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 694 figure 9: efficiency against time figure 10 shows a comparison between the irradiance of the solar panel before and after removing the dust from the panel’s surface against time. figure 10: irradiance against time figure 11 shows the comparison between the light intensity and the voltage of the panel against time before and after mitigation was achieved. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 685-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 695 figure 11: light intensity and voltage against time figure 12 shows the comparison between the light intensity and the current generated by the panel against time before and after mitigation was achieved. figure 12: light intensity and current against time figure 13 shows the comparison between the power produced by the panel and the efficiency of the panel against time before and after mitigation was achieved. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 696 figure 13: power and efficiency against time figure 13 shows the graphical representation between the power and efficiency of the solar panel under both condition. it was observed that the accumulation of dust on the surface of the panel drops the efficiency of the solar panel to approximately 2.5%. similarly, the maximum intensity of the sun striking the surface of the panel led to a corresponding decrease in output power with maximum values of 699 lux and 6.85w respectively. after the soiling mitigation technique was applied, the output parameters of the solar panels greatly increased. the light intensity improved by a third of previously set maximum values. likewise, the efficiency quadrupled to 8.05% resulting in corresponding increase in maximum output power of 22.37w.in order to prove the effectiveness of this method, taking the averages of the output parameters before and after mitigation respectively, the percentage increase in the parameter output of the panel is calculated using equation 11. ( )(%) output of the panel after mitigation output of the panel beforemitigationpercentage increase inoutput output of the panel after mitigation   (11) table 6: percentage increase in the output of the panel parameter after mitigation before mitigation percentage increase voltage (v) 12.57 8.05 35.95 current (a) 1.72 0.77 55.40 power (w) 21.66 6.17 71.49 light intensity (lux) 916.29 678.71 25.93 irradiance (w/m2) 7.24 5.36 25.99 irradiation (kwh/m2) 23.32 17.28 25.93 efficiency (%) 7.80 2.22 71.49 table 6 shows that the efficiency of the solar panel increased by 71.49% due to the application of the soiling mitigation technique. similarly, the output current and power also increased by 55.40% and 71.49% respectively. this confirms that increase in power leads to corresponding increase in efficiency. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 685-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 697 4.0 conclusion soiled part of solar cells acts as a resistance to the current produced by the cell and as such reduces the energy generated by the panel as well as the overall efficiency. it was noted that efficiency and other output parameters of solar panels are greatly affected by the accumulation of dust on the panel’s surface. with the introduction of an automatic cleaning mechanism to mitigate the effect of soiling, the percentage increase in efficiency was 71.49% which confirms that controlled wind can be the perfect mitigation technique for solar panels. another benefit of this design is that cost of maintenance is minimized, it is compact and can be incorporated with new and existing solar panels with ease. references zhao, hr., guo, s. and fu, lw. 2014. review on the costs and benefits of renewable energy power subsidy in china. renewable and sustainable energy reviews, 37: 538-549. li, h., jenkins-smith, hc., silva, cl., berrens, rp. and herron, kg. 2009. public support for reducing us reliance on fossil fuels: investigating household willingness-topay for energy research and development. ecological economics 68: 731-742. stigka, ek., paravantis, ja. and mihalakakou, gk. 2014. social acceptance of renewable energy sources: a review of contingent valuation applications. renew sustainable energy reviews, 32: 100-106. armaroli, n., balzani, v. 2016. solar electricity and solar fuels: status and prospective in the context of energy transition. chemistry – a european journal, 22: 32-57. tsoutsos, t., frantzeskaki, n. and gekas, v. 2005. environmental impacts from the solar energy technologies. energy policy, 33(3): 289-296. akuru, ub., onukwube, ie., okoro, oi. and ebe, es. 2017. towards 100% renewable energy in nigeria. renewable and sustainable energy reviews, 71: 943-953. musthafa, mm. 2015. enhancing photoelectric conversion efficiency of solar panels by water cooling. journal of fundamentals of renewable energy and applications, 5(4): 1-5. meija, f., koissk j. and bosch, jl. 2014. the effect of dust on solar photovoltaic systems. energy procedia, 49(1): 2370-2376. nimmo, b. and seid, s. 2010. effects of dust on the performance of thermal and photovoltaic flat plate collectors in saudi arabia: preliminary results. in: 2. miami international conference on alternative energy sources, held in miami beach, fl, usa, 10 13 december 1979. alternative energy sources ii; proceedings,145-152. mani, m. and pillai, r., 2010. impact of dust on solar photovoltaic (pv) performance: research status, challenges and recommendations. renewable and sustainable energy reviews, 14(9): 3124-3131. kadhum, ja., rida, ks., ak-wedi, aa. and al-asdi, kah. 2016. the impact of dust accumulation on pv panels outcome. international journal of computation and applied sciences (ijocas), 1(2): 11-15. ibrahim, da. 2010. effect of shadow and dust on the performance of silicon solar cell. journal of basic and applied scientific research, 1(3): 222-230. einhorn, a., micheli, l., miller, dc., simpson, lj., moutinho, hr., to, b., lanaghan, cl., muller, mt., toth, s., john, jj.,warade, s., kottantharayil, a. and engtrakul, c. 2018. evaluation of soiling and potential mitigation approaches on photovoltaic glass. ieee journal of photovoltaics, 9(1): 233-239. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng afolayan et al.: performance evaluation of soiling mitigation technique for solar panels. azojete,16(4):685-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayan.ma@unilorin.edu.ng 698 aldowsari, a., bkayrat, r., alzain h. and shahin, t. 2014. best practices for mitigating soiling risk on pv power plants. saudi arabia smart grid conference (sasg). proceedings held in jeddah, 2014. sasg proceedings: 1-6. deceglie, mg., micheli, l. and muller, m. 2017. quantifying year-to-year variations in solar panel soiling from pv energy-production data. in: ieee 44th photovoltaic special conference (pvsc). proceedings of symposium held in washington, dc, usa, 2017. pvsc proceedings: 2804-2809. micheli, l., ruth, d. and muller, m. 2017. seasonal trends of soiling on pv systems. in: ieee 44th photovoltaic special conference (pvsc). proceedings held in washington, dc, usa, 2017. pvsc proceedings: 2301-2309. saraf, m. 2015. u.s. patent no. 8,984,704 b2. washington, dc: u.s. patent and trademark office. saini, a., nahar, a., yadav, a. and vijayvargiya, a. 2017. solar panel cleaning systems imperial journal of interdisciplinary research (ijir), 3(5): 1222-1226. ganesh, va., raut, hk. and nair, as. 2011. a review of self-cleaning coatings. journal of materials chemistry, 21(14): 16304-16322. hee, jy., kumar, lv., danner, aj., yang, h. and bhatia, cs. 2012. the effect of dust on the transmission and self-cleaning property of solar panels. energy procedia, 15: 421-427. das, s., mohanty, a., dey, a. and biswas, a., 2015. an integrated design of auto clean and cooling smart pv panel. international journal of innovations in engineering and technology, 4(1): 80-88. aly, sp., gandhidasan, p. and barth, n. 2015. novel dry cleaning machine for photovoltaic and solar panels. in: 3rd international renewable and sustainable energy conference (irsec). proceedings held in marrakech, 2015. irsec proceedings: 1-6 http://www.azojete.com.ng 6 3 arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):345-356 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 345 original research article proximate composition, functional, and sensory properties of kadal (fermented grain flour) produced from whole and decorticated maize and pearl millet grains b. h. umar1, g. i. agbara2*, m. y. alkali1, a. f. masaya2 and s. c. akubuiro1 1department of food science and nutrition, ramat polytechnic, maiduguri, nigeria 2department of food science and technology, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: giagbara@unimaid.edu.ng 1.0 introduction kadal is flour produced from fermented maize or sorghum or pearl millet grains or the fermented liquor. the stiff dough (tuwo) obtained from kadal flour is a staple in northern nigeria where it is consumed along with traditional soups such as okro, kirikashi, kuka, egusi majorly by teaming resource poor families. the importance of kadal flour in nutritional wellbeing article information abstract kadals are normally prepared from fermented cereal grains and the kadal flours are usually transformed into stiff dough called tuwo and consumed as staple food in many west african countries. pearl millet (mi) and maize (mz) grains were decorticated and each of them was divided into four portions. the first portion was unfermented and the other portions were soaked in water separately for 48h (k2), for 72h (k3) and 96h (k4). four portions each of whole maize and millet were subjected to the same soaking time, respectively. at the expiration of soaking time, each portion was washed, thoroughly rinsed, sun dried, milled and sieved to produce kadal flours. the unfermented whole and decorticated millet and maize flours served as the experimental controls. the functional properties and proximate compositions of twenty samples were evaluated using standard procedures and the organoleptic properties of the tuwo (kadal dough) prepared from them were evaluated without soup, and with okro soup. results revealed significant variations (p<0.05) existed in the functional properties and proximate composition of kadal flours as well as the sensory attributes of the tuwo. wettability of the kadal flours improved with soaking time, water absorption capacities decreased with fermentation time, as well as bulk densities though marginally. dispersibility of the kadal flours were generally high (70.50-77%) and no significant difference was observed. ash, protein and fat contents of the whole grain kadal flours were higher than that of decorticated, and there was slight decrease in these nutrients with soaking time. again, moisture and carbohydrate were lower in whole grain kadal flours than in decorticated counterparts. on sensory attributes of the various tuwo produced, colour improved with soaking time more in the decorticated millet kadals. decorticated millet had greater desirable flavor, which was not significantly different from that of whole millet kadals. texture of 4th day kadal tuwo was better, with whole millet kadal tuwo rated better than that of the decorticated, unlike the texture of maize kadal tuwo. control tuwo in general had poorer flavour, colour, texture and taste. the overall acceptability of the kadal tuwo was generally higher than the control. millet kadal tuwo progressively improved with soaking time. the bottom line was that nutritional values were sacrificed to the improvement of sensory properties of the prepared kadal flours. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 april, 2021 revised 28 april, 2022 accepted 30 april, 2022 keywords: grain fermentation pearl millet decortication kadal flours kadal tuwo maize grains http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):345-356. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 346 of the inhabitants of this region of nigeria cannot be over-stressed, a region with favourable climate for large scale cultivation of diverse cereal grains. cereals are considered the most important sources of protein, complex carbohydrates, dietary fibre, minerals and b-vitamins for humans in different climes and cultures world over, providing 45% of dietary calories (fao, 2003; mohammed et al., 2013), however their nutritive value in general are plagued by low lysine content and availability of anti-nutrients such as phytic acid, tannins, polyphenols (amadou et al., 2013). therefore, traditional technologies involving such pretreatments as dehulling/decortication, soaking, fermentation, roasting, sprouting go a long way to improve the nutritional quality of grains (holtz and gibson, 2007). soaking of grains prior to cooking is among the culinary practices and is the preliminary stage to malting. short time soaking (less than an hour) enables faster decortication of the grains especially the pulses but prolonged soaking results to fermentation, a process defined by cheftel and cheftel (1976) as beneficial biochemical activity induced by microorganisms and their enzymes (kahajdova and karovicova, 2007) on food components notably proteins, carbohydrates, lipids and mineral elements. initial observation during soaking is rapid uptake of water by biologically inactive grains which elicits tremendous physical and biochemical changes made possible by activation of endogenous enzymes. fermentation as practiced in the traditional food preparation utilizes mix culture of microorganisms existing in the immediate environment notably lactic acid bacteria leading to heterolactic fermentation. these microorganisms release amylolytic and proteolytic enzymes that hydrolyze grain substrates leading to the production of peptides, maltodexrins, sugars, amino acids, fatty acids etc and further sugars are transformed into organic acids and alcohols. the subsequent drop in ph or increase in the acidity of the medium favours the activation of phytase (elyas et al., 2002) that liberate polyvalent metallic ions complexed by phytic acid (inositol hexaphosphate) including nutrients bonded to tannins, rendering them more bioavailable. prolonged soaking or fermentation is an effective method of improving starch and protein digestibility and bioavailability (boralkar and reddy, 1995; mahajan and chauhan, 1987; sripriya et al.,1997). mohammed et al. (2007) reported decrease in anti-nutritional factors of millet subjected to 12-24 hour fermentation. lestiene et al. (2005) reported leaching of iron and zinc into soak medium and significant reduction in the level of the same in maize, rice, and soybean, and concluded that soaking alone was not enough to improve mineral bioavailability. whole grains provide wide array of nutrients and non-nutrient phytochemicals that optimize health, however removal of outer most parts of grain improves digestibility, palatability and reduction of anti-nutrient content and at the same time reduces the nutritive value of grains. fermentation is one of the oldest biotechnologies for the production of food products with desirable properties such as extended shelf-life and good organoleptic properties (smid and hogenholtz, 2010; ray and joshi, 2014). fermented foods usually have an improved microbial stability and safety, and some can be stored even at ambient temperature for extended storage (nhikata et al., 2018). the present study was aimed to evaluate the double effects of grain decortication and variable grain soaking time or fermentation on the proximate composition and functional properties of kadal flours as well as sensory attributes of kadal stiff dough (tuwo). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng umar et al: proximate composition, functional, and sensory properties of kadal (fermented grain flour) produced from whole and decorticated maize and pearl millet grains. azojete, 18(2):345-356. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 347 2. materials and methods 2.1. collection of raw materials the raw materials that were used in this study were maize (zea mays l.), white flint), and pearl millet (pennsietum glaucum) were purchased from maiduguri monday market, and transferred to food processing lab, food science department ramat polytechnic maiduguri for processing. 2.2 kadal flours preparation from whole maize and millet grains. the whole grains (maize and pearl millet), 4kg each were separately sorted to remove dirts, stones and other foreign materials. the grains were divided into four equal parts of 1kg each and transferred into clean plastic buckets. the first portion of the maize and millet grains were washed and spread on a clean mat to dry under the sun in a secluded place, later ground and sieved. ten liters of water was added to three buckets containing 1kg each of maize and another three buckets for millet grains. grains in k2, k3, and k4 were soaked /fermented for 2, 3, and 4 days respectively at ambient temperature 30±2oc at the end of each fermentation, the grains were washed, spread on clean mats and sun dried for 6-8 hours. the dried grains were milled using the commercial hammer mill, sieved using a 400µm mesh screen, packaged in already coded plastic buckets with lids and kept at ambient storage until needed. 2.2.1 production of kadal flours from decorticated maize and millet grains four (4) kg each of maize and millet grains were separately sorted to remove stones, dirts and other foreign materials, and decorticated using a local attrition milling machine. the decorticated grains were spread on clean mats to dry in order to ease winnowing of the chaff from the grains. the chaffs were removed and the grains were divided into four portions. the first portions of the decorticated maize and millet grains were washed and spread on a clean mat to dry under the sun. the remaining portions were fermented in a similar manner as was done with the whole grains, for two, three and four days, and dried at the end. the dried grains were milled separately, sieved using a 400µm mesh screen, packaged in already coded plastic buckets with lids and kept at ambient condition until needed. 2.3 physicochemical analysis of kadal flours and the controls 2.3.1 functional properties of kadal flours and the controls water absorption capacity was determined using the method described by beuchat et al. (1977). about, 1g of kadal flour was mixed with 10ml of distilled water in a centrifuge tube, stirred and rested for 30 minutes and later centrifuged at 3,500 rpm for 30 minutes. the volume of free water was read on the graduated centrifuge tube directly and expressed as percentage of water absorbed per gram of sample. bulk density was determined using the method described by onwuka (2005) and expressed in g/ml. dispersibilty was determined using the method described by kulkarni et al. (1991). ten (10) grams of sample was dispersed in distilled water in a 100ml measuring cylinder filled to the 100 mark. the mixture was stirred vigorously and allowed to settle for 3h., the volume of the settled particles was subtracted from 100 and the difference reported as % dispersibility. wettability of the flours was determined using a modification of the method described by okezie and bello (1988). a plastic spatula containing 1.0g (dwb) of the sample was suspended from a retort stand 15cm above a beaker containing 500ml distilled water. the spatula containing the sample was gently tilted to drop the sample unto the surface of the water and http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):345-356. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 348 the time taken for complete disappearance or wetting of the sample was taken as the wettability in seconds. 2.4 proximate composition analysis the proximate composition (moisture, crude protein, crude fat, total ash), of the raw materials (maize and millet), and the products (kadal flours) were determined according to the standard methods of aacc (2000). moisture was determined by oven drying of 5g of each sample at 105oc for 1h; protein (%nx6.25) was determined using micro-kjeldhal method and 200mg of samples; fat was determined using solvent extraction of 1g of sample in a soxhlet extractor with petroleum ether, and ash was determined by incineration of 1g of the sample in muffle furnace at 550oc for 5h. carbohydrate contents were obtained by 'difference'. 2.5 evaluation of the sensory attributes of kadal stiff dough or tuwo a slurry of a given kadal flour was introduced into boiling water and stirred to cook and gelatinize the starch, and the remaining kadal flour was added and repeatedly stirred until the homogeneous mass obtained was further allowed to cook until done exuding well known unmistaken flvour. it was scooped onto tray and allowed to cool. sensory evaluation of cooled tuwo was carried out by 20 semi-trained panelists who were indigenous consumers of kadal tuwo, comprising some of the staff and students of the department of food science, ramat polytechnic maiduguri. tuwo made with the kadal flours were served to the panelist firstly and later the same were served along with okra soup. a 9-point hedonic scale with 9 representing like extremely, and 1-dislike extremely was used to evaluate the kadal tuwo in terms of colour, taste, flavor, texture and overall acceptability as described by lhekoronye and ngoddy (1985). warm water was provided for intermittent mouth gargling. 2.6 statistical analysis data obtained were subjected to one-way analysis of variance (anova), using ssps version 16. means were separated using the duncan multiple range test and significance was accepted at 5% probability (p<0.05). results were expressed as mean±sd (n=3). 3. results and discussion 3.1 functional properties of kadal flours and controls the water absorption capacities (wac) of whole (w) maize kadals varied from 91.27% to 126.32%, the unfermented control had the highest and 4th day (k4) whole maize kadal (wmzk4) the least, indicating wac decreased with increase in fermentation period, the same scenario was repeated in wac of decorticated (d) maize (mz) kadals, a range of 60.20% and 101.50%, again dmzk4 the least and the unfermented dmz flour the highest (table 1). also for the whole millet kadals, the unfermented millet flour recorded the highest (102.72%) yet lower than wac of unfermented whole maize kadal counterpart, again 4th day whole millet kadal had the least wac of 51.09%, lower than 91.17% of whole maize kadal. unlike decorticated maize kadal, wac of decorticated millet kadal (78.40-101.18) was higher than that of whole millet counterpart (51.09-101.72%). the decrease in wac of kadal flour with increase in fermentation period might be linked to partial hydrolysis of protein and starch molecules into shorter chains by both endogenous and exogenous enzymes elaborated by invading microorganisms. this is the reason why unfermented controls of both whole and decorticated maize and millet had the highest wac because the macro molecules remained intact and unaffected by amylolytic and file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng umar et al: proximate composition, functional, and sensory properties of kadal (fermented grain flour) produced from whole and decorticated maize and pearl millet grains. azojete, 18(2):345-356. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 349 proteolytic enzyme hydrolysis. decorticated maize kadal had lost outermost fibrous cellulosic materials during decortication and these are known for high water absorption. hydrophillic groups in protein and starch are responsible for binding with water molecules in a water stressed environment (singh, 2001). higher wac is needed for kadal dough formation; it also increases yield, product cohesiveness and decreases tuwo stiffening with storage. decreased wac of the kadal with soaking time suggests suitability for thinner gruels needed for complementary feeding. onweluzo and nwabugwu (2009); elkhalifa et al. (2006) also reported decrease in water binding capacity of sorghum four (4.69-4.37g/g) with increase in fermentation. table 1: functional properties of differently produced kadal flours from maize and millet grains (whole and decorticated), and the unfermented controls sample code water absorption capacity (%) bulk density (g/ml) dispersibility (%) wettability (sec) uwmz 115.66±5.81b 0.77±0.04c 75.00±1.41a 74.50±0.71a wmzk2 126.32±2.28a 0.76±0.04c 74.50±0.71a 57.00±1.41b wmzk3 101.88±1.81c 0.74±0.04c 73.50±0.01a 40.00±0.71c wmzk4 91.17±1.91d 0.73±0.04c 73.00±1.41a 39.00±1.41c udmz 101.50±3.25c 0.89±0.04a 77.00±1.41a 72.00±1.41a dmzk2 92.37±1.91d 0.85±0.10a 76.50±0.71a 71.50±0.71a dmzk3 88.83±1.66d 0.82±0.04b 74.50±0.71a 53.50±0.71b dmzk4 60.20±5.03e 0.63±0.06d 73.00±1.41a 44.50±0.71c uwmi 102.72±0.79a 0.74±0.11a 74.50±0.71a 74.00±1.41a wmik2 80.38±1.22b 0.70±0.02b 73.50±0.71a 68.00±0.71b wmik3 59.94±0.25d 0.68±0.06b 72.50±1.41a 59.00±1.41c wmik4 51.09±1.53e 0.64±0.01c 70.50±0.71a 44.00±1.41c udmi 101.18±1.67a 0.75±0.03a 73.50±0.71a 59.00±1.41c dmik2 98.11±2.40a 0.72±0.06a 72.50±0.71a 57.00±1.41c dmik3 97.81±3.10b 0.70±0.10b 71.50±0.71a 54.00±1.41d dmik4 78.40±1.81c 0.62±0.10c 70.50±0.71a 50.50±0.71d results are mean±se(n=2). mean values bearing different superscripts are significantly different at p-value of 5% (p<0.05). wmz: whole maize flour; wmzk: whole maize kadal; dmz: decorticated maize flour; dmzk:decorticated maize kadal; wmi: whole millet flour; wmik: whole millet kadal; dmi:decorticated millet flour; dmik: decorticated millet kadal, and 2,3,4 represents fermentation days bulk density of the kadal flours decreased marginally with fermentation time, therefore 4th day whole and decorticated kadals, for both maize and millet, had the least bulk density and the unfermented controls had the highest. there was no significant variation (p>0.05) in the bulk density of the whole maize kadals (0.73-0.76), and as for the decorticated maize kadals, bulk density decreased from 0.89g/ml (control) to 0.69g/ml (dmzk4), and for whole millet kadals, bulk density decreased from 0.74 to 0.64 g/ml and from 0.75g/ml to 0.62g/ml for dmik4. smaller bulk densities were recorded for 3rd to 4th day kadals and this implied increase in cost of packaging, handling, storage and distribution (kulkarni et al., 1991) and significant implications on wet processing in food industry (karuna et al., 1996). bulk density inversely correlates with flour particle size. fermented kadals whether decorticated or whole had higher particle size than the control hence lower bulk density (higher flour porosity or voluminuosity) implying that http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):345-356. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 350 a smaller amount of kadal flour occupies a bigger unit volume as observed in 4-day kadals of both cereals. on the other hand, reduced bulk density of the 3rd or 4th kadals implies reduced paste thickening during hydration and mixing (padmashree et al., 1987). elkhalifa et al. (2006), similarly, observed decrease in bulk density (0.73-0.66g/ml) of sorghum four with increase in fermentation period. dispersibility is the ease with which a powdered material is dispersed or suspended in aqueous medium, it is the ease of reconstitution (kulkarni et al., 1991), the extent to which it will form a true uniform suspension without phase separation, and therefore it is correlated with water solubility index. dispersibility was generally high and there was no significant difference in the dispersibility values of both cereals whether whole or decorticated, however there was slight increase with fermentation period. the values obtained ranged from 73.00 to 76.50% and 70.50 to 73.50% for maize and millet kadal flours, respectively. the 4th day kadals had the least dispersibility meaning that reconstitution tendency of the kadals decreased with increase in soaking time. onwueluzo and nwabugwu (2009) had earlier observed a decrease in the reconstitutionability of fermented millet or pigeon grain flour with fermentation time. according to igene et al. (2005), the ease of dispersiblity is an important flour property in food formulation. wettability is also a parameter indicating the reconstitutionability of a powdered material and also it is particle size dependent. a significant difference was observed in the wettability of kadal flours from both maize and millet grains. all the unferrmented controls, both whole and decorticated cereals had greater wettability than the treated samples. for whole kadals, it varied from 39 sec to57sec for maize, 44 sec to 68 sec for millet, greater in whole millet kadals than in whole maize kadals meaning it is easier to reconstitute whole maize kadal than millet counterpart. wettability decreased with increase in soaking or fermentation time collaborating earlier observation that kadals have bigger flour particles especially the whole maize and millet kadals. for decorticated grain kadals wettability values of maize kadal varied from 44.50sec to 60.50secs and millet from 50.50 to 57sec implying that higher soaking time improved wettability of flour. onweluzo and nwabugwu (2009) reported 57-75 secs and 51-57sec for fermented millet and pigeon pea grains subjected to varying fermentation period (25-96 h). 3.2. proximate composition of the grains used for kadal preparation. the proximate composition of whole and decorticated maize and millet grains is presented in table 2. these were different from those used as controls because they were not subjected to milling and sieving processes. as table 2 reveals, whole grain had slightly lower moisture content than decorticated counterpart, both whole and decorticated had moisture that ranged between 11.5% (whole maize grain, wmzg) and 14.70% (decorticated maize, dmzg), indicating decortication increases the moisture content of cereal grains or the resulting flours due to removal of outer protecting layers and greater surface area exposure to the environment. millet grain had higher protein content whole or decorticated, 12.54% in whole and 11.71% in decorticated millet against 9.62% and 8.67% in whole and decorticated maize respectively. significant variation was not observed in the fat contents (2.91% dmzg and 3.67% wmig) of the two cereals, although the whole had slightly higher fat than the decortcated especially in the maize grain due to greater loss of maize germ during decortication. it also influenced ash or mineral contents which decreased with decortication, more reduction was observed in maize file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng umar et al: proximate composition, functional, and sensory properties of kadal (fermented grain flour) produced from whole and decorticated maize and pearl millet grains. azojete, 18(2):345-356. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 351 (1.32-0.89%) than in millet (1.62%-1.05%). awolu et al. (2017) noted pronounced protein and slight fat reductions with debranning of pearl millet. chaves-lopez et al. (2013) reported that 80% of cereal grain mineral is located in the branny layer leaving paltry 20% in the endosperm. the bottom line is: decortication decreased the fat, ash and protein but slightly increased the moisture and carbohydrate content of grains. comparable results were reported by kulthe et al. (2016) for proximate composition of three pearl cultivars: ash 2.05-2.72%, crude fibre 2.072.63%, fat 5.14-5.96%, protein 10.97-11.65%, and carbohydrate 66.49-68.85%; but higher protein and fat contents were reported by abah et al. (2020). balbiker et al. (2018) made the same observation that decortication decreased ash, protein, oil and crude fibre and increased moisture and carbohydrate contents of two pearl millet cultivars. according to marta et al. (2017) indonesian maize hybrids contains protein 7.13-11.84%db, fat 2.58-7.17%db, carbohydrate 69.67-79.84%db, crude fibre 1.43-3.69%db, ash 0.95-1.56%db, this results accord with the proximate composition of maize used in the study as shown in table 2. table 2: proximate composition (%) of whole and decorticated maize and millet grains sample code moisture ash protein fat carbohydrate wmzg 11.05±0.09c 1.32±0.01b 9.62±0.13c 3.57±0.53a 72.83±0.15ab dmzg 14.70±0.18a 0.89±0.11d 8.67±0.23cd 2.91±0.05b 74.51±0.21a wmig 13.25±0.04b 1.62±0.29a 12.54±0.34a 3.67±0.27a 68.79±0.17b dmig 13.71±0.34ab 1.05±0.11c 11.71±0.30b 3.60±0.23a 69.92±0.46b results are mean±se(n=2). mean values bearing different superscripts are significantly different at p-value of 5% (p<0.05). wmzg: whole maize grain; dmzg: decorticated maize grain; wmig: whole millet grain; dmig: decorticated millet grain. 3.3 proximate composition of kadal (fermented grain) flours the proximate compositions of the treated samples and the controls are presented in table 3. the general pictures is the decrease in fat, ash, protein though marginal, and increase in moisture and noticeable increase in carbohydrate (for maize kadal flours) for both whole and decorticated kadal flours with increase in soaking time. it is reasonable to say that the nutrient content of the two cereals behaved differently during the soaking period. this goes to buttress the conflicting reports concerning nutritive value of grains subjected to varying period of fermentation (nkhata et al., 2018; tsafrakidou et al., 2020). for whole maize kadals, moisture marginally increased from 7.08% (wmz, control) to 7.87% (wmz k4), carbohydrate increased from 82.92% in control to 87.29% (wmz k4), and there were linear decrease in ash (1.41-0.57), protein (6.41-5.63%), and fat (1.39-0.65). for decorticated maize kadals, the same variation pattern occurred with soaking time as follows: moisture (6.68-7.94%), carbohydrate (86.4688.86%), ash (0.88-0.40%), protein (4.15-3.50%) and fat (0.57-0.36%). the decrease in proximate composition as a result of prolonged soaking time was slight in millet grain, and generally pronounced in maize kadal flours, perhaps due to millet’s corneous endosperm. on the contrary, banigo and muller (1972) reported poorest recovery of ogi from pearl millet than from corn and sorghum because of extensive rupture of millet grains during steeping. for whole millet the variation was as follows: moisture (5.58-6.84) %, protein (10.09-9.43 %), ash (0.930.40 %), fat (1.21-1.82 %), carbohydrate also increased (81.44-82.19 %), different from variations observed in decorticated millet kadals with the following variations: moisture (6.03-8.31%), protein (8.59-8.01%), ash (1.41-0.35%), fat (1.42-1.21%) and carbohydrate (81.22-82.65%). the http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):345-356. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 352 decorticated kadals were starchier than the whole kadals, however significant increase was not observed in the carbohydrate content of millet kadals with increase in soaking time. the decrease in protein with soaking time was hardly noticeable in majority of cases and the increase in carbohydrate contents of kadals was not statistically significant. onweluzo and nwabugwu (2009) reported 8.90-9.46% as protein of flour from fermented millet and the protein of unfermented was reported to be higher. ene-obong and ohizoba (1996) did not observed any significant change in total protein and amino acid composition of substrate with fermentation time. the bottom line is that the longer the fermentation time the greater the reduction in nutritive value although slight and the observed increases in carbohydrate contents were insignificant. table 3: proximate composition (%) of differently produced kadal flour from maize and millet grains (whole and decorticated), and the unfermented controls sample moisture ash protein fat carbohydrate wmz 7.08±0.06b 1.41±0.12a 6.41±0.18a 1. 39±0.23b 82.92±0.10b wmzk2 7.19±0.06b 1.38±0.08a 6.30±0.13a 1.31±0.18b 82.83±0.60b wmzk3 7.68±0.04a 0.48±0.09b 5.68±0.25a 1.91±0.09a 84.25±0.26a wmzk4 7.87±0.15a 0.41±0.09b 5.63±0.06a 1.15±0.06b 85.62±0.13a dmz 6.68±0.19a 0.88±0.11b 4.15±0.11b 0.57±0.06c 86.46±0.28a dmzk2 7.33±0.17ab 0.57±0.11b 4.16±0.23b 0.65±0.16c 87.29±0.23a dmzk3 7.59±0.08a 0.53±0.04b 3.91±0.04b 0.56±0.01c 87.60±0.13a dmzk4 7.94±0.17a 0.40±0.11c 3.50±0,12bc 0.36±0.05c 88.86±0.23a wmi 5.58±0.19d 0.93±0.09a 10.09±0.04a 1.21±0.06b 82.19±0.04a wmik2 6.38±0.05c 0.57±0.10b 9.71±0.09a 1.32±0.04b 82.02±0.06a wmik3 6.58±0.04b 0.48±0.03b 9.81±0.23a 1.56±0.06a 81.54±0.40a wmik4 6.84±0.09b 0.40±0.01b 9.43±0.13ab 1.82±0.06a 81.44±0.10a dmi 6.03±0.18c 1.41±0.12a 8.59±0.23c 1.42±0.04a 82.55±0.04a dmik2 7.18±0.08b 0.46±0.09b 8.52±0.09c 1.39±0.03b 82.63±0.04a sdmik3 7.84±0.08a 0.40±0.13b 8.62±0.06c 1.34±0.09b 81.22±0.06a dmik4 8.31±0.11a 0.35±0.21c 8.01±0.03c 1.21±0.06b 82.12±0.11a results are mean±se (n=2). mean values bearing different superscripts are significantly different at p-value of 5% (p<0.05) wmz: whole maize flour; wmzk: whole maize kadal; dmz: decorticated maize flour; dmzk: decorticated maize kadal; wmi: whole millet flour; wmik: whole millet kadal; dmik: decorticated millet kadal, 2, 3, 4 represent fermenting days. 3.4 sensory properties of kadal stiff dough (tuwo) the sensory evaluation of the kadal stiff dough was evaluated on the basis of 9point hedonic scale. on taste, the scores ranged from 7.25 to 8.60 and 7.35 to 8.70 for maize and millet tuwo respectively. the fermentation process imparted on the flavor of the tuwo, the flavor of millet tuwo was preferred most. among the pearl millet kadals, taste scores of whole millet kadal stiff doughs were better than the decorticated as shown in table 4. contrarily, decorticated maize kadal doughs were rated as having better taste than whole maize kadal cooked doughs which decreased with soaking duration. the untreated control doughs whole and decorticated had the poorest taste scores than the kadal doughs. taste appeared not to improve with long fermentation time among the treated. for colour, the scores ranged from 7.30 to 8.65 and 7.40 to 8.75 for maize and millet kadal tuwo, respectively. the colour scores of the whole and decorticated millet kadal doughs were equally appreciated by the test panelists; however the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng umar et al: proximate composition, functional, and sensory properties of kadal (fermented grain flour) produced from whole and decorticated maize and pearl millet grains. azojete, 18(2):345-356. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 353 decorticated millet kadal was rated better in colour. among the maize kadal doughs, the decorticated had better colour which improved with increase in soaking time, as also observed in millet kadal both whole and decorticated millet kadals. again, the untreated control tuwo had the poorest colour indicating the higher the soaking time the better the appearance of the kadal flours. on flavor, the fermented grains had odour that did not deter the panelists from appreciating the flavor of the kadal stiff doughs. among the decorticated millet kadal doughs, flavor scores were higher and not significantly different (p>0.05), but among the whole millet kadal doughs flavour scores were equally high and the control as well as the 4th day kadal had relatively lower flavour scores. maize kadal dough flavour scores were generally lower than those of millet and the controls (unfermented whole and decorticated cereal flours). for texture, soft and pliable dough is a desirous attribute, and the texture of whole cereal kadal dough appeared to be better than the decorticated especially in the millet kadals. grain decortication impacted excess softness to the tuwo with increase in fermentation time and led to excess leaching as well. overall acceptability showed that treated kadal doughs were all accepted and those with higher scores were wmzk2 (8.20), dmzk2 (8.05), dmzk2 (8.15), wmik4 (8.40) and dmik4 (7.55). overall acceptability of millet kadals appeared to improve with soaking time. the bottom line is that decortication improved the sensory attributes of the cooked kadal doughs (tuwo). both maize and millet kadal tuwo had sensory scores greater than the untreated controls. table 4: sensory assessment of differently produced kadal stiff dough (tuwo) sample taste colour flovour texture overall acceptability wmz 7.70±0.28b 7.10±0.14c 8.50±0.28a 7.70±0.42a 8.62±0.07a wmzk2 7.50±0.42b 7.30±0.14bc 7.60±0.14b 7.60±0.85a 7.65±0.21b wmzk3 7.25±0.14bc 7.30±0.14bc 7.15±0.21cd 7.30±0.14ab 8.20±0.28bd wmzk4 7.50±0.14b 7.20±0.14bc 7.30±0.28c 7.55±0.07a 7.30±0.28bd dmzf 8.55±0.07a 6.35±0.21bc 7.50±0.28c 6.20±0.21b 7.40±0.21d dmzk2 8.30±0.07ab 8.20±0.28ab 6.35±0.28bc 6.40±0.21b 8.65±0.35d dmzk3 8.35±0.21a 8.65±0.21a 7.60±0.42b 7.55±0.50a 8.15±0.21b dmzk4 8.60±0.14a 7.65±0.21b 8.20±0.28ab 7.30±0.21ab 7.60±0.14c wmi 6.30±0.14ab 8.50±0.14a 8.25±0.21ab 7.45±0.14ab 7.55±0.21b wmik2 8.30±0.28ab 8.55±0.07a 8.45±0.14a 7.35±0.14ab 7.40±0.14bc wmik3 8.70±0.14a 7.95±0.64d 8.45±0.14a 7.15±0.07b 7.35±0.07bc wmik4 8.40±0.14ab 7.45±0.14dc 8.05±0.64b 7.80±0.14a 8.40±0.14a dmi 7.35±0.07bc 8.25±0.21c 8.40±0.14a 6.50±0.28c 7.35±0.07bc dmik2 7.70±0.14b 8.55±0.07a 8.40±0.14a 6.45±0.07c 7.25±0.07bc dmik3 7.55±0.01b 8.15±0.07b 8.40±0.14a 6.65±0.35c 7.30±0.28bc dmik4 7.65±0.21b 8.75±0.14a 8.40±0.14a 6.55±0.21c 7.55±0.21b results are mean±se(n=2). mean values bearing different superscripts are significantly different at p-value of 5% (p<0.05). wmz: whole maize flour; wmzk: whole maize kadal; dmz: decorticated maize flour; dmzk: decorticated maize kadal; wmi: whole millet flour; wmik: whole millet kadal; dmi: decorticated millet flour; dmik: decorticated millet kadal, and 2,3,4 represents fermentation days. http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):345-356. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 354 4. conclusion fermentation of whole and decorticated maize and pearl millet grains to produce kadal flour has been an age-long traditional technology for processing cereals. ferrmentation period has slight impact on the absolute proximate composition of the fermented grain flour or the thick porridge obtainable from them but does positively moderate the functional properties of the kadal flours as well the sensory properties of tuwo. as a consequence of this observation, it is suggested that 72h fermentation period of undecorticated be applied to limit decline in the nutritive value of kadal flours through leaching as a result of prolonged fermentation. however, decreased anti-nutrients and increased bioavailability of remaining nutrients favours the application of extended fermentation period for kadal flours production. references aacc. (2000). official methods of analysis, 15th edition. american association of cereal chemists. aacc international, st. paul, minnesota. abah, cr., ishiwu, cn., obiegbuna, je. and oladejo, aa. 2020. natural component, functional properties and food applications of millet grains. asian food science journal, 14(2): 9-19. amadou, i., mahamadou, ge. and guoweili, l. 2013. millets: nutritional composition, some health benefits and processing: a review. journal of food and agriculture, 25(7):501-508. selling, oo., olarewaju, oa. and akinade, a. 2017. effect of addition of pearl millet flour subjected to different process on the antioxidants, nutritional, pasting characteristics and cookies quality of rice-based composite flours. journal of nutrition, health and food engineering, 7(2): 248-256., doi:10.15406/jnhfe.2017.07.00232. balbiker, e., abdelseed, b., hassan, h. and adiamo, o. 2018. effect of decortication methods on the chemical composition, antinutrients, ca, p, and be contents of two 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10.3924/ajft.2017.116.123. mohammed, me., amro, bh., mashier, as. and elfalil, eb. 2007. effect of processing followed by fermentation on antinutritional factors content of pearl millet (pennisetum glaucum) cultivars. pakistan journal of nutrition, 6: 463-467. http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):345-356. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 356 muhammad, hs., muhammed, fs., muhammad, s., naiz, aq. and safia, m. 2013. the importance of cereals (poaceae: gramineae) nutrition in human health: a review. journal of cereals and oil seeds, 4(3): 32-35. nkhata, sg., ayua e., kamau, eh. and shingiro, jb. 2018. fermentation and germination improve nutritional value of cereals and legumes through activation of endogenous enzymes. food science and nutrition, 6(8): 2446-2458. okezie, ob. and bello, ab. 1988. physicochemical and functional properties of winged bean flour and isolate compared with soy isolate. journal of food science, 53(2): 450-454. onweluzo, jc. and nwabugwu, cc. 2009. fermentation of millet (pennisetum americanum), pigeon pea (cajanus cajan) seed for flour production: effects on composition and selected functional properties. pakistan journal of nutrition, 8(6): 737-744., 10.3923/pjn.2009.737.744. onwuka, gi. 2005. food analysis and instrumentation: theory and practice, napthali prints, lagos nigeria, pp. 133-137. padmashree, ts., vijayalashmi, l. and puttra, s. 1987.effects of traditional processing on the functional properties of cowpea (vigna cajan) flour. journal of food science and technology, 24: 221-225. ray, rc. and joshi, vk. 2014. fermented foods: past, present and future. chapter 1, microorganisms and fermentation of traditional foods, 1st edition. new york: crc press, pp. 36., doi: 10.13140/2.1.1849.8241. singh, u. 2001. functional properties of grain legumes flours. journal food science and technology, 38: 191-198. smid, ej. and hugenholtz, j. 2010. functional genomics for food fermentation processes. annual review in food science and technology, 1: 497-519. sripriya, g., antony, u. and chandra, ts. 1987. changes in carbohydrates, free acids, organic acids, phytic acid and hcl extractability of minerals during germination and fermentation of finger millet (eleusine coracana). food chemistry, 58: 345-350. tsafrakidou, p., michael, a-m. and biliaderis, cg. 2020. fermented cereal based products: nutritional aspects, possible impact on gut microbiota and health implications. foods, 9(6):734, 10.3390/foods9060734 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):231-242 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 231 original research article load frequency control using classical controllers u. i. isemin and a. j. onah department of electrical/electronic engineering, michael okpara university of agriculture umudike, abia state. nigeria. *corresponding author’s email address: uwemisaac123@gmail.com 1.0 introduction automatic generation control (agc) or load frequency control is a very important issue in power system operation and control for supplying sufficient and reliable electric power with good quality (prakash and sinha, 2011). this is because most electric power systems nowadays are made up of different generating stations connected to each other through the tie-line conductors to form an interconnected power system which is centrally controlled at the control centres or stations. each generating station is referred to as a control area. the successful operation of an interconnected power system requires the matching of total generation with total demand and associated system losses (arivoli et al., 2011). thus whenever there is a load change in one control area, the different control areas interconnected with the affected area will share in the load change through the action of the tie-line and controllers. this change in load will lead to changes in the tie-line power and frequency of the control areas. these changes are undesired and should be restored back to their steady state values as soon as possible. also, if any of the generating stations is out of service due to fault or maintenance, its own area would still be supplied with electricity till the generating station is brought back to service. thus, interconnected power system ensures continuity, reliability and stability of the power system. the random changes in load demand in electric power systems affects the active and reactive power balance of the electric power system. both the active power balance and reactive power article information abstract this paper presents a solution to the problem of load frequency control of a two area power system using pi and pid controllers. in electric power systems, the load demand varies at different times of the day and these load variations lead to changes in frequency of the power system. in an interconnected power system, the tie-line power also varies in addition to the frequency variations. these changes in frequency and tie-line power causes instability in the power system network and make it unreliable. load frequency control therefore ensures that these changes in the tie-line power and frequency of the control areas are minimized with acceptable level of overshoot and settling time. the method used involves the modeling of the two area interconnected power system using matlab/simulink software, the pi and pid controllers were then tuned using the ziegler-nichols tuning rule and used to simulate the two area power system when a load change of 0.2pu occurred in control area one. the simulation results showed that both the pi and pid controllers were able to restore the changes in tie line power and frequency of the control areas caused by the change in load to their steady state values of zero but the pid controller has better dynamic performances of overshoot, rise time and settling time than the pi controller. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 10 october, 2021 revised 22 february, 2022 accepted 3 march, 2022 keywords: load frequency control pi controller pid controller tie-line area control error http://www.azojete.com.ng/ mailto:uwemisaac123@gmail.com mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 232 balance must be maintained between the different areas and the loads. active and reactive powers have a combined effect on the frequency and voltage of the power system. frequency depends on active power while voltage depends on reactive power, thus. the control problem of voltage and frequency can be separated into two. these are: reactive power and voltage control and active power and frequency control (ganesh et al., 2012). therefore, voltage and frequency controllers are required to maintain the generated power quality in order to supply constant voltage and frequency to the utility grid (kumar et al., 2015). load frequency control is thus the regulation of the power output of controllable generators within a prescribed area in response to change in system frequency, tie-line loading or a relation of these to each other so as to maintain the schedules system frequency and/or the established interchange with other areas within predetermined limits. (surya and sinha, 2010). it is very important for the right operation of the interconnected power system and requires the maintenance of a balance between the active power produced and that consumed. also generator turbines are designed to operate at very precise speed and micro controllers are dependent on frequency for their timely operation (kumar and naidu, 2014). as the load demand keeps on increasing and decreasing during the steady state operation of the power system, the tie-line power flow should be maintained at a specified value irrespective of these load changes. this requires the manipulation of the operation of the valves of the governor with suitable control strategy so that constant speed can be maintained and the real power output of the generators controlled (kansal and singh, 2012). thus, the objectives of lfc is to provide zero steady state errors of frequency and tie line power exchange variations, high damping of frequency oscillations and decreasing overshoots of disturbance (atul and anant, 2014). according to the transmission company of nigeria, the interconnected power system in nigeria is made up of 66 buses with 23 grid connected generating stations, transmission lines spanning over 20,000 km and centrally controlled at the national control centre (ncc) osogbo in osun state with a transmission voltage of 330kv transmission voltage is 330kv. in the nigeria national grid, the changes in frequency are monitored in the control room at the ncc and when there are small changes in load, the frequency is controlled automatically by the action of the speed governors and spinning reserves of the generators. when the load change in the network is so large that the action of the speed governors and spinning reserves cannot stabilize the system frequency, an alarm will sound to alert the control room operators. the operators will then call the power generating stations to either increase or decrease their generations (depending on whether there was a decrease or increase in frequency). if the load change leads to a decrease in frequency and the generating stations cannot increase generation to stabilize the system frequency, then the control room operators will call the distribution companies to load shed so as to stabilize the system frequency. this control method is completely manual and may take a longer time before the system frequency is stabilized at the nominal value making the power supply system unstable and unreliable. this paper, therefore, aimed at controlling the frequency in an interconnected power system automatically using classical controllers. this is because classical controllers are used widely in industries with a reduced number of parameters to be tuned. also with the ziegler nicols tuning rule for file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uwemisaac123@gmail.com isemin and onah: load frequency control using classical controllers. azojete, 18(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 233 obtaining the parameters of the classical controllers, the plant model is not required but only the unit step response of the plant. the classical controllers that would be considered in this paper are the proportional plus integral (pi) and proportional plus integral plus derivative (pid) controllers. the most widely used classical controller for solving the lfc problem is the pi controller. the pi controller is simpler to implement but it settling time is more and it produces large frequency deviations (chaturvedi and dwivedi 2014). thus the pid controller will be used to overcome the above drawbacks of the pi controller. this is because the pid controller has adequate system response considering the stability requirements and the performance of a system (abdollah et al., 2015). 2.0 materials and methods 2.1 materials the materials used in this work are the speed governor of a generator, the turbine, the alternator and the tie-line conductor. 2.2 method the method involves modeling of the pi and pid controllers. this was followed by the modeling of an uncontrolled or isolated one area power system. the tie-line and the area control error were then modeled, followed by an uncontrolled two area power system. the controllers were then tuned and used for the simulation of the uncontrolled two area power system. 2.3 the proportional plus integral plus derivative (pid) controller a pid controller is a control loop feedback mechanism commonly used in industrial control systems. it continuously computes an error signal which is a difference between a desired set point or reference signal and a measured process variable. the output of a pid controller is the control input to the plant. its expression in the time domain according to ogata (2011), is given in equation (1) 𝑈(𝑡) = 𝐾𝑝𝑒(𝑡) + 𝐾𝑖 ∫ 𝑒(𝑡)𝑑𝑡 + 𝐾𝑑 𝑑𝑒(𝑡) 𝑑𝑡 (1) where kp = proportional gain, ki = integral gain, kd = derivative gain and t = time in seconds, e = error signal = reference signal – process output the derivative and integral of this error signal is computed by the pid controller to produce the control signal. the control signal is sent to the plant and a new output is obtained. this new output is then fed back and compared to the reference to find the new error signal (e), the controller takes this new error signal and computes its derivative and its integral gain and the process continues. by taking the laplace transform of equation (1) we have, 𝑈(𝑠) = 𝐾𝑝𝐸(𝑠) + 𝐾𝑖𝐸(𝑠) 𝑠 + 𝐾𝑑𝑠𝐸(𝑠) (2) thus with its three-term functionality covering treatment to both transient and steady-state responses, proportional integral-derivative (pid) control offers the simplest and yet most efficient solution to many real-world control problems (ang et al., 2005). http://www.azojete.com.ng/ mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 234 the block diagram of a pid controller is as shown figure 1. + figure 1: block diagram of a pid controller (atul and anant, 2013) the transfer function of a pid controller is given by equation (3) 𝐺𝑐(𝑠) = 𝑈(𝑠) 𝐸(𝑠) = 𝐾𝑝(1 + 1 𝑇𝑖𝑠 + 𝑇𝑑𝑠) (3) where kp is the proportional gain, ti the integral time in seconds and td the derivative time in seconds. 2.4 the proportional plus integral (pi) controller the pi controller is obtained setting by the derivative time (td) of a pid controller equal to zero. its control action according to (ogata, 2011) is as given in equation 4 𝑈(𝑡) = 𝐾𝑝𝑒(𝑡) + 𝐾𝑖 ∫ 𝑒(𝑡)𝑑𝑡 (4) where kp = proportional gain and ki = integral gain by taking the laplace transform of equation (4) we have equation (5). 𝑈(𝑠) = 𝐾𝑝𝐸(𝑠) + 𝐾𝑖𝐸(𝑠) 𝑠 (5) the transfer function of a pi controller is given by 𝐺𝑐(𝑠) = 𝑈(𝑠) 𝐸(𝑠) = 𝐾𝑝(1 + 1 𝑇𝑖𝑠 ) (6) 2.5 one area power system figure 2 shows the block diagram of an uncontrolled one area power system represented by a single generating unit asall generators in each of the control areas operate with the same frequency. that is, all the generators of the system swing in unison (arivoli et al., 2011). it is made up of the speed governor, the turbine and a rotating mass or the alternator. r is called the speed regulation of the governor and defined as the ratio of the per unit change in frequency to per unit change in power of the generator. set point + + e( proces e(t)t) from plant output kpe(t) ki∫ 𝑒(𝑡)𝑑𝑡 kd 𝑑𝑒(𝑡) 𝑑𝑡 + e(t + e(t ) output file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uwemisaac123@gmail.com isemin and onah: load frequency control using classical controllers. azojete, 18(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 235 figure 2: block diagram of an uncontrolled one area power system (sateesh et al., 2014) 2.6 two area power system a control area is characterized by the same frequency throughout. figure 3 shows the schematic diagram of a two area interconnected power system. the two areas are connected via a tie-line. tie-lines are useful for exchange of power from one area to the other according to the contract made among them and also provide support during fault condition and thus helps in clearing of the fault (tandel and patel, 2017). figure 3: schematic diagram of a two area power system (gupta, 2011) 2.7 tie-line modeling the power flow over the tieline in figure 3 from area one to area two in the 𝑠domain according to (prakash and sinha, 2011) is as given in equation 7 ∆𝑃12(𝑠) = 2𝜋𝑇 𝑠 [∆𝑓1(𝑠) − ∆𝑓2(𝑠)] (7) where ∆p12(s) = change in power flow from area 1 to area 2 in mw t = synchronizing power coefficient, ∆f1(s) = change in frequency of area 1 in hz and ∆f2(s) = change in frequency of area 2 in hz putting equation (6) in block diagram form gives figure 4 ∆pl(s) ∆f(s) ∆pref(s)+ 1 𝑇𝑔𝑠 + 1 1 𝑇𝑡𝑠 + 1 1 2𝐻𝑠 + 𝐷 1 𝑅 ∆pg(s) ∆pv(s) ∆pm(s) + tie-line area 2 area 1 p1 p2 http://www.azojete.com.ng/ mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 236 figure 4: tie-line model block diagram (avdhesh et al., 2017) 2.8 area control error (ace) as stated in the introduction, the aim of lfc is not only to cancel the frequency error in each area but to also cancel the tie-line power exchange error. the ace defined as the change in area frequency which when used in an integral loop forces the steady state frequency error to zero (nilaykumar and kotwal, 2012). it expression is as given (sharma et al., 2017) in equation 8 𝐴𝐶𝐸𝑖 = ∑ 𝑃𝑖𝑗 + 𝐵𝑖∆𝑓𝑖 (8) where i and j are the areas and b is called the frequency response characteristic of an area and is expressed as 𝐵𝑖 = 𝐷𝑖 + 1 𝑅𝑖 where d is the damping coefficient for area 1, the ace is expressed as 𝐴𝐶𝐸1 = ∆𝑃12 + 𝐵1∆𝑓1 (9) for area two it is expressed as 𝐴𝐶𝐸2 = ∆𝑃21 + 𝐵2∆𝑓2 (10) where 𝐵1 = 𝐷1 + 1 𝑅1 and 𝐵2 = 𝐷2 + 1 𝑅2 b it can be seen that ace1= -ace2. combining the block diagram models of an uncontrolled one area power system, tie-line power and ace gives the block diagram of the two area power system as shown in figure 7 together with the controllers (pi and pid). the aces are the inputs to the controllers while the change in reference power settings (δpref) are their outputs. where𝐺𝑝 = 1 2𝐻𝑠+𝐷 and 𝐺𝐻𝑇 = 1 (𝑇𝑔𝑠+1)(1+𝑇𝑡𝑠) g ∆f2(s) + ∆p12(s) ∆f1(s) 2πt 1 𝑠 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uwemisaac123@gmail.com isemin and onah: load frequency control using classical controllers. azojete, 18(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 237 figure 5: block diagram of a two area power system with the ace and controllers table 1 shows the control area/simulation parameters for areas one and two table 1: control area parameters for areas 1and 2 parameter area 1 area 2 r 0.05 0.0625 d 0.6 0.9 h 5 4 tg (s) 0.2 0.3 tt (s) 0.5 0.6 2πt = 2, base mva= 1000, δpl= 0.2pu (saadat,1999) 2.9 tuning of the controllers in tuning the controllers, that is obtaining the values of the proportional gain (kp), integral gain (ki) and derivative gain (kd), ziegler-nichols tuning rule was used and the values of these constants for the control areas are as given in table 2 for pi and pid controllers respectively. 1/s ∆pref1(s) + ∆pg1(s) ght1 gp1 2πt gp2 1 r1 -1 1 s 1 r2 ght2 ∆pref2(s) + ∆pg2(s) ∆pm1(s) + ∆pm2(s) + ∆pl1(s) ∆p21(s) ∆pl2(s) ∆f1(s) ∆f2(s) + ∆p12(s) b1 -1 b2 ace2 ace1 + + + + controller 2 controller 1 http://www.azojete.com.ng/ mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 238 table 2: pi and pid constants for control areas one and two control area pi constants pid constants kp ki kp ki kd one 0.2 0.6 -10 -13 -4 two -0.1 0.2 -7 -4 -3 3. results and discussion in order to determine the dynamic response of load frequency control of the two area interconnected power system, simulation of the two area power system was carried out using matlab/simulink software, first without any controller, then using pi and pid controllers when control area one was subjected to a load change of 0.2pu and the following results were obtained. figures 6 and 7 show the changes in frequency and tie-line power response of the two control areas respectively without any controller figure 6: frequency response of areas 1 and 2 without any controller at transient, it was observed that the change in frequency of area one dropped to -0.075pu while that of area two dropped to -0.1pu from their steady state values of zero and were never restored back to their steady state values again but settled on a new steady state value of -0.05pu. the settling time for area one was 4secs while that of area two was 7secs. figure 7: tie-line power response of the two area power system without any controller 0 10 20 30 40 50 -0.1 -0.05 0 0.05 0.1 time[s] c h a n g e i n f 1 ,c h a n g e i n f 2 [ p u ] area 1 area 2 0 5 10 15 20 25 30 35 40 45 50 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 time[s] c h a n g e i n p ti e [ p u ] file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uwemisaac123@gmail.com isemin and onah: load frequency control using classical controllers. azojete, 18(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 239 the change in tie-line power increased from the steady state value of zero with transient oscillations, reached its peak value of 0.1pu at 30secs and never returned to the steady state value of zero but remained in its new steady state value of 0.1pu with a settling time of 15seconds. figures 8 and 9 show the change in frequency response of control areas 1 and 2 respectively with the pi and pid controllers. figure 8: frequency response of area one using pi and pid controllers with the pi and pid controllers, it is observed that the change in frequency of control area 1 was restored back to the steady state value of zero unlike in the uncontrolled case. also the pid controller showed a negligible overshoot while the pi controller had a peak overshoot of 0.012pu. the pid controller had a settling time of 1sec and the pi controller had a settling time of 22seconds. the pid controller had a rise time of 1second while the pi controller had a rise time of 2.5 seconds. figure 9: frequency response of area two using pi and pid controllers similarly, in control area two, the changes in frequency were also restored back to their steady state values of zero with the pi and pid controllers as compared to the uncontrolled case. the 0 10 20 30 40 50 -0.08 -0.06 -0.04 -0.02 0 0.02 time [s] c h a n g e i n f 1 [ p u ] pi pid 0 5 10 15 20 25 30 35 40 45 50 -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 time [s] c h a n g e i n f 2 [ p u ] pid pi http://www.azojete.com.ng/ mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 240 pid controller had a peak overshoot of 0.005pu while the pi controller had a peak overshoot of 0.018pu. also the pid controller had a settling time of 2 seconds while the pi controller had a settling time of 13 seconds. the rise time of the pid controller was 1 second and that of the pi controller was 3 seconds. figure 10 shows the change in tie-line power response of the two control areas with the pi and pid controllers. figure 10: tie-line power response of the two areas using pi and pid controllers. the change in tie-line power was restored back to the steady state value of zero with the pi and pid controllers as compared to the case without the controllers. with the pid controller, the peak overshoot was 0.015pu while with the pi controller it was 0.185pu. pid controller had a settling time of 10 seconds and the pi controller had a settling time of 30 seconds. in figure 10, the change in tie-line power was restored back to the steady state value of zero with the pi and pid controllers. table 3: summary of the performance of the two controllers in areas 1 and 2 control area parameter pi controller pid controller peak overshoot(pu) 0.012 negligible one settling time(s) 22 1 rise time(s) 2.5 1 peak overshoot(pu) 0.018 0.005 two settling time(s) 13 2 rise time(s) 3 1 the simulation results obtained show that when a load change of 0.2pu occurred in area one, without any controller, there were deviations in both the change in frequency of areas one and two and the change in tie-line power from their steady state values of zero which were never restored back but instead, new steady state values were obtained for both the change in frequency and change in tie-line power. but with the pi and pid controllers, both the change in frequency of areas one and two and the change in tie-line power were restored back to their steady state values of zero. it was also observed that the pid controller has better dynamic 0 10 20 30 40 50 -0.05 0 0.05 0.1 0.15 0.2 time[s] c ha ng e in p ow er [p u] pid pi file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uwemisaac123@gmail.com isemin and onah: load frequency control using classical controllers. azojete, 18(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 241 properties of peak overshoots, rise time and settling time than the pi controller. also the pi controller had more number of oscillations in all the cases at transient than the pid controller. the simulation results obtained show that when a load change of 0.2pu occurred in area one, the frequency and tie-line power changes caused by the load change never returned to their steady state values of zero in the uncontrolled case but with the pi and pid controllers, these changes in frequency and tie-line power were restored to their steady state values of zero. a comparison of the performance of the two controllers also shows that the pid controller has better dynamic properties of peak overshoots, rise time and settling time than the pi controller. also the pi controller had more number of oscillations at transient than the pid controller. 4.0 conclusion in this paper, a two area interconnected power system was modeled using matlab/simulink software package, pi and pid controllers were then tuned and used to simulate the two area power system. from the simulation results, it was observed that when a load change of 0.2pu occurred in control area one, without the controllers, the changes in tie-line power and frequencies of control areas one and two were deviated from their steady state values of zero. but with the pi and pid controllers in the control areas, the changes in the tie-line power and frequencies of the control areas were restored back to their steady state values of zero. a comparison of the performance of the controllers shows that the pid controller has better dynamic properties of overshoot, rise time and settling time than the pi controller. references abdollah, a., karami, m. and heidarali, s. 2015. a new method to design of pid controller for load frequency control of hydro power plant based on total cost function. research journal of recent sciences, 4(12): 88-94. ang, h., chong, g. and li, y. 2005 pid control systems analysis, design and technology. ieee transactions on control and systems technology, 13(4): 559-576. arivoli, r., gurumoorthy, g. and chidambaram, i. 2011. design of a new area control error based load frequency controller for a two-area interconnected power system. iacsit international journal of engineering and technology, 3(1): 76-80. atul, i. and anant, k. 2013. load frequency control for interconnected power system using different controllers. automation, control and intelligent systems, 1(4): 85-89. avdhesh, s., pawan, k. and honey, s. 2017. effects of tie-line bias control in two area load frequency control system using polar fuzzy controller. international journal of scientific and engineering research, 8(4): 1519-1525. chaturvedi, r. and dwivedi, b. 2014. fuzzy and pi based lfc of thermal-hydro power system. international journal of innovative science, engineering and technology, 1: 259-263. http://www.azojete.com.ng/ mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uwemisaac123@gmail.com 242 ganesh, v., vasu, k. and bhavana, p. 2012. lqr based load frequency controller for two power system. international journal of advanced research in electrical, electronics and instrumentation engineering, 1(4): 262-269. gupta, j. 2011. generation of electrical energy. sk. kataria and sons, new delhi. kansal, r. and singh, s. 2012. study of lfc in an interconnected power system using the conventional pi controller and fuzzy logic controller. international journal of science and research, 3(3): 728-734 kumar, a., rahiman, a. and ashok, k. 2015. evolutionary algorithms for two area load frequency control problem. international journal of emerging technology and advanced engineering, 5(10): 385-391. kumar, k. and naidu, e. 2014. load frequency control for a multi area power system involving wind, hydro and thermal plants. international journal of innovative research in science, engineering and technology, 3(1): 1008-1013. ndubisi, s. 2011. a single area lfc a comparative study based on pi, optimal and fuzzy logic controllers. american journal of scientific and industrial research, 2(2): 748-754. nilay, k. and kotwal, d. 2012. state space modeling of single, two and three area lfc of power system using integral control and optimal lqr control methods. iosr journal of engineering, 2(3): 201-510. ogata, k. 2011. modern control engineering. 5th edition. pearson education inc., new york: prentice hall. prakash, s. and sinha, s. 2011.load frequency control of interconnected hydrothermal reheat system using artificial intelligence and pi controllers. international journal of engineering, science and technology, 4(1): 23-37. saadat, h. 1999. power systems analysis. mc graw-hill book company, new york. sateesh, k., srinivas, r. and machavarapu, s. 2014. load frequency control of two area interconnected power system using conventional and intelligent controllers. international journal of engineering, research and application, 4(1): 156-160. sharma a., kumar, p. and singh, h. 2017. effects of tie-line bias control in two area load frequency control system using polar fuzzy controller. international journal of science and engineering research, 8(4): 15191525. surya, p. and sinha, s. 2010. application of artificial intelligence in lfc of interconnected power system. international journal of engineering, science and technology, 3(4): 264-275. tandel, m. and patel a. 2017. load frequency control for three area interconnected power system. international journal of advanced research in computer and communication engineering, 6(2): 83-85 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uwemisaac123@gmail.com arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(1):111-120 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 111 original research article residential exposure of electromagnetic fields radiated from mobile base stations and broadcast transmitters e. u. udo1*, e. b. maduka1 and d. o. okey2 1department of electrical and electronic engineering, michael okpara university of agriculture, umudike, abia state, nigeria 2department of computer engineering, michael okpara university of agriculture, umudike, abia state, nigeria *corresponding author’s email address: thought.umoren@gmail.com 1.0 introduction electromagnetic radiation (emr) is made up of both the electric and magnetic field components, where both occur in a fixed ratio of intensity to each other, oscillating in phase at right angle to the direction of energy and wave propagation (viel et al., 2009). in free space, electromagnetic radiation travels at the speed of light. in addition, electromagnetic radiation is classified based on the frequency of its wave. the electromagnetic spectrum, in order of its increasing frequency and diminishing wavelength consists of the radio waves, microwaves, infrared, white light, ultraviolet radiation, x-rays and gamma rays (alhekail, 2012). in general, electromagnetic fields (emf) and waves are media for carrying signals through specific medium. the transmitted signal can be in form of voice, data, or image. the electromagnetic field is transmitting at the speed of light in a vacuum at 300,000 km/s and this can be modulated, transmitted and received while the required information is being conveyed (sauter et al., 2010). in classical physics, electromagnetic radiation is considered to be produced when electrically charged particles are speed up by forces acting on them. electrons are the causes of emission by most electromagnetic radiation, because they possess low mass of weight and are therefore easily moved by various varieties of mechanism. rapidly moving electrons are speed up when they come in contact with a region of force (joseph, 2016). article information abstract this paper presents the cellular base station electromagnetic radiation and its effects on human body. due to technological advancement, human life is subjected to high level of electromagnetic emission. the effect of electromagnetic radiation (emr) is recognized from health risk associated with exposure to it. the research work was performed in two communication companies, namely compa and compb located in owerri, imo state, in two geographical areas of onitsha – owerri road and owerri municipal. the study was conducted to ascertain power density measurement using surecall signal meter in 72 houses within a distance of 200 2500 meters from the base stations. results obtained revealed that the average cumulative power density at different distances of 200m, 500m, 800m, 1200m, 1700m, and 2500m were 1.54005627200µw/m2, 0.319382647200µw/m2, 0.171062647200µw/m2, 0.139667752800µw/m2, 0.028675447200µw/m2, and 0.001429063200µw/m2, respectively. these results were compared with international standard and world health organization (who) allowable limits. in conclusion, it was observed that the power density varied with distance from tower and is highest at the shortest distance. power density also varied from place to place depending on the infrastructure obstruction, like buildings or internal obstructions © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 oct., 2020 revised 24 january 2021 accepted 28 january 2021 keywords: electromagnetic radiation cellular base station transmission lines power density udo et al: residential exposure of electromagnetic fields radiated from mobile base stations and broadcast transmitters. azojete, 17(2):111-120 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 112 the cell towers are located randomly in different places and some are cited within living homes, churches, schools, market places and office premises. in most developing countries, most leading mobile service provider would like to cite their cell towers in a suitable area so as to serve the users using their networks. the number of cell phones and cell towers are increasing without due consideration to its disadvantages especially to the humans and the environment (miclaus and bechet, 2006). biological consequences due to these fields arise from power and transmission lines, electronic devices inside our residence and work places, electrical cable splices, distribution networks and associated devices such as cellular telephones and wireless communication tower (danielle, 2017). 1.1 ionizing and non-ionizing electromagnetic radiation of high frequencies (ultraviolet, x-rays and gamma rays) are called ionizing radiation, since individual photons of such high frequency have enough energy to ionize molecules or breaks chemical bonds. these radiations have the ability to cause chemical reactions and damage living cells, beyond that resulting from simple heating and can be a health hazard (ankur and mandeep, 2012). electromagnetic radiation of visible or lower frequencies (visible light, infrared, microwaves, and radio waves) is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules or break chemical bonds. the effects of these radiations on chemical systems and living tissue are caused primarily by heating effects from the combined energy transfer of many photons (bortkiewicz et al., 2014). most of the researches on the health effects of adverse non-ionizing radiation has been done that consists of one general type of anthropogenic non-ionizing emr, where there are microwave and radio frequency from wireless telecommunication devices such as wireless telephones, cell towers, antennas as well as broadcast transmission towers (cho et al., 2016). 1.2 cellular base stations telephone cellular site is where antennas and electronic communications gadgets are placed on a radio mast, tower, structures or high places to create a cell in a cellular network. the raised platform normally supports antennas and one or more sets of transmitters and receivers, control electronics, a gps receiver for timing and digital signal processor (catarinucci, 2003). the base station uses microwave radio communication. it consists of several antennas placed on a tower and a building with electronics in it. when one makes a call on a cell phone, the cell phone and base station communicate back and forth by radio, and the radio waves they use are in the microwave region of the electromagnetic spectrum. the antenna components of a base station are mostly less than ten centimeters but can be classified into clusters or arrays with heights of about one meter. they need to be mounted on towers against obstacles like hills, trees or tall buildings that possess barriers to our cell phone and the base station (blanch and romeu, 2002). arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 113 the two types of cellular antennas used are sector and omni-directional antennas. omni directional antenna exhibits a circular radiation pattern and operates in virtually all directions while sector or directional antennas operate in a specific direction. sector antenna normally covers an arc of 120 degrees or less depending on capacity requirements. the statement of problem is that most stations radiate different levels of electromagnetic signals so as to actualize their planned coverage and stable network, without considering the possible health hazard an increased radiated power can cause to the human body. the objective is to investigate residential exposure of electromagnetic fields radiated from mobile base stations. 2.0 materials and method the materials used in this study are mobile spectrum analyzer, surecall signal meter, radio frequency meter, global position system (gps) and matlab software. the mobile spectrum analyzer was used to detect signal, frequency and radio frequency signal strength in the two geographical areas. a surecall signal meter was used to detect and study the cellular signal strength to enable the network providers to determine the areas of weak signal which require boasting. the radio frequency meter records signal frequencies including long term evaluation and cellular. data was obtained from two base stations of communication companies, namely compa and compb located within onitsha – owerri road (site 1) and owerri municipal area (site 2). onitsha – owerri road is situated where the base station transmitters were located far away from the residential buildings between owerri and onitsha town. owerri municipal is situated where the residential buildings were located very close to the base station transmitters within owerri town. absolute power measurement was conducted in seventy two different houses in close proximity to the base stations. no mobile phone was turned on in the vicinity while taking readings. background radiation of -50dbm was measured and at the same time absolute power (dbm) was taken at each geographical area in the two companies for a period of three days. the average signal power was also calculated throughout the period. the measurement was performed to ensure that radio frequency field emission from each geographical area did not exceed the safe public limits and to find whether there was correlation between the health complaints and the measured power densities (mouaaz and mohammed, 2011). frequency spectrum of the mobile tower was determined at different places and it was observed that the peak frequency changes at different places over time. this change in peak was due to varying nature of the wave (martinez-gonzalez and fernandez-pascual, 2002). udo et al: residential exposure of electromagnetic fields radiated from mobile base stations and broadcast transmitters. azojete, 17(2):111-120 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 114 3.0 results and discussion the experimental results of the measured power from the base stations of two companies at various distances of 200m, 500m, 800m, 1200m, 1700m and 2500m within two geographical areas along onitsha owerri road and owerri municipal were recorded. the measured power was used to calculate the average received power for the two mobile providers. the radiation levels absorbed by different areas of the body were obtained due to the received signal power measured at various distances where the human body exists. tables 1 shows the received signal power for compa (site 1). the distance measured and average signal power (dbm) for the period of three days between 7am – 7pm each day at a frequency of 900mhz were tabulated. when the distance was 200m, the average signal power (dbm) for 3 days was -68.30, -67.50 and -67.20. it was observed that when the distance was small, the average signal power gave a small value but when the distance was high, the average signal power gave a high value. table 2 indicates the received power for compa (site 2). when the distance was 800m, the average signal power (dbm) was -77.50, -77.50 and -77.00. table 3 shows the received signal power for compb (site 1). when the distance was 500m, the average signal power (dbm) for 3 days was -76.75, -77.00 and -75.51 respectively. it was observed that when the distance was small, the average signal power was small but when the distance was high, the average signal power was high. table 4 reveals that when the distance was 1700m, the average signal power (dbm) for 3 days was -85.50, -83.50, and -85.50. table 5 – table 6 indicates that when the distance was small, the power absorbed became high whereas at higher distance, the power absorbed became small. for instance, in table 5, when the distance was 200m for an area of , the power absorbed was compared to when the distance was , the power absorbed was . table 7 shows the cumulative power absorbed by the human body from one second to one hour. it was observed that when the distance was small, the power absorbed became high but when the distance was high, the power absorbed became small. table 8 reveals that at smaller distances from the base station, more power is absorbed but when the distance increases, the power absorbed decreases from 1 day to 1 year. table 9 shows the average area of human body and the power absorbed. it was observed that people within ages of 2 – 18 years absorbed more power than those above ages 18 years. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 115 table 1: received signal power for compa (site 1) s/n distance (m) average signal power (dbm) for day 1 average signal power (dbm) for day 2 average signal power (dbm) for day 3 average signal power 1 200 -68.30 -67.50 -67.20 -67.66 2 500 -74.60 -72.50 -74.67 -73.92 3 800 -87.25 -77.50 -86.25 -83.66 4 1200 -88.00 -86.00 -87.25 -87.08 5 1700 -92.30 -90.00 -90.50 -90.93 6 2500 -100.00 -100.00 -99.04 -99.68 table 2: received signal power for compa (site 2) s/n distance(m) average signal power (dbm) for day 1 average signal power (dbm) for day 2 average signal power (dbm) for day 3 average signal power 1 200 -67.94 -67.00 -67.50 -67.48 2 500 -72.75 -72.75 -72.50 -72.66 3 800 -77.50 -77.50 -77.00 -77.33 4 1200 -79.50 -79.50 -78.00 -79.00 5 1700 -89.00 -86.00 -87.00 -87.33 6 2500 -103.45 -103.50 -103.80 -103.58 table 3: received signal power for compb (site 1) s/n distance (m) average signal power (dbm) for day 1 average signal power (dbm) for day 2 average signal power (dbm) for day 3 average signal power 1 200 -66.70 -66.60 -67.21 -66.84 2 500 -73.50 -74.00 -73.50 -73.66 3 800 -76.75 -77.00 -75.51 -76.42 4 1200 -77.00 -77.60 -77.20 -77.26 5 1700 -84.50 -84.00 -83.90 -84.13 6 2500 -97.57 -97.01 -96.90 -97.16 table 4: received signal power for compb (site 2) s/n distance (m) average signal power (dbm) for day 1 average signal power (dbm) for day 2 average signal power (dbm) for day 3 average signal power 1 200 -67.50 -67.01 -68.01 -67.50 2 500 -71.20 -71.50 -71.50 -71.40 3 800 -77.00 -77.00 -77.00 -77.00 4 1200 -79.10 -81.00 -80.00 -80.03 5 1700 -85.50 -83.50 -85.50 -84.16 6 2500 -97.00 -95.00 -96.00 -96.00 udo et al: residential exposure of electromagnetic fields radiated from mobile base stations and broadcast transmitters. azojete, 17(2):111-120 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 116 table 5: power absorbed by human body with area of 0.243m2 from compa (site 1) distance (m) power received in (µw) area (m2) power absorbed (µw/m2) 200 0.00017967 0.243 0.000043659008 500 0.00004167 0.243 0.000010125008 800 0.00000735 0.243 0.000001786050 1200 0.00000199 0.243 0.000000483570 1700 0.00000083 0.243 0.000000200888 2500 0.00000011 0.243 0.000000026317 table 6: power absorbed by human body with area of 0.243m2 from compb (site 1) distance (m) power received in (µw) area (m2) power absorbed (µw/m2) 200 0.0002076667 0.243 0.000050463008 500 0.0000430667 0.243 0.000010465208 800 0.0000230667 0.243 0.000005605208 1200 0.0000188333 0.243 0.000004576492 1700 0.0000038667 0.243 0.000000939608 2500 0.0000001927 0.243 0.000000046826 table 7: cumulative power absorbed by the human body from 1sec to 1hr dist. (m) power absorbed (µw/m2) for 1 sec power absorbed (µw/m2) for 1 min power absorbed (µw/m2) for 1 hr 200 0.000427793402 0.025667604120 1.540056247200 500 0.000088717402 0.005323044120 0.319382647200 800 0.000047517402 0.002851044120 0.171062647200 1200 0.000038796598 0.002327795880 0.139667752800 1700 0.000007965402 0.000477924120 0.028675447200 2500 0.000000396962 0.000023817720 0.001429063200 table 8: cumulative power absorbed by the human body from 1 day to 1 year dist. (m) power absorbed (µw/m2) for 1 day power absorbed (µw/m2) for 1 week power absorbed (µw/m2) for 1 month power absorbed (µw/m2) for 1 year 200 36.96135 258.7294 1034.9180 12419.01 500 7.665184 53.65628 214.6251 2575.502 800 4.105504 28.73852 114.9541 1379.449 1200 3.352026 23.46418 93.85673 1126.281 1700 0.688211 4.817475 19.26990 231.2388 2500 0.034298 0.420083 0.96033 11.52397 arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 117 table 9: average area of human body with the power absorbed age or age group (year) area (m2) power absorbed (µw) 2 0.563 38.00 5 0.787 7.50 10 1.236 4.20 13 1.603 2.50 18 1.980 1.20 20-79 2.060 0.1 figure 1 shows the graph of radiation level against distance. when the distance was 250 meters, the radiation level increases to 4.0 x 10-5gy. when the distance was 500 meters, the radiation level reduces to 1.0 x 10-5gy. when the distance was 1000 meters, the radiation level reduces to 0.2 x 10-5 gy. also, when the distance increases to 2500 meters, the radiation level further reduces to 0.1 x 10-5gy. figure 1: radiation power level against distance by a body with area of 0.243m2 from compa (site 1) figure 2 indicates the graph of radiation level against distance. when the distance was 250 meters, the radiation level was 1.0 x 10-5gy and when the distance increases to 1500 meters, the radiation level reduces to 0.2 x 10-5gy. also, when the distance increases to 2500 meters, the radiation level further reduces to 0.01 x 10-5gy. udo et al: residential exposure of electromagnetic fields radiated from mobile base stations and broadcast transmitters. azojete, 17(2):111-120 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 118 figure 2: radiation power level against distance by a body with area of 0.243m2 from compb (site 1). figure 3 reveals the power absorbed by human body against age. when the age of human being was 5 years, the power absorbed was 8µw and when the age was 20years, the power absorbed was 1µw. it was observed that when the age of human being was small, the body absorbed more power but when the age of human being was large, the body absorbed less power. figure 3: power absorbed by the human body between the ages of 2-25 year per day. figure 4 indicates the radiation level against distance. the power absorbed in one month shows a linear result from 200 500 meters with high radiation levels of 1025.725gy and 0.250gy. the radiation levels gradually drops between 500 2500 meters. the power absorbed in one year also shows a linear result with radiation levels of 2481.413gy and 12238.10gy. the radiation levels therefore drop gradually till 2500 meters. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):103-110. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 119 figure 4: cumulative power absorbed in 1month and 1 year 4.0 conclusion in this paper, measurements on received signal power was used to identify the level of electromagnetic radiation at distances close to the base station transmitters and to determine the level of radiation absorbed by the human body. some of the base station transmitters are located very close to the residential houses and business areas, thereby exposing people to the danger of electromagnetic radiation from the base stations. however, the results obtained indicates that the average cumulative radiated power for one hour at 200 meters was 1.54005624700µw/m2 which is within the range of recommended standard for electromagnetic radiation effect of 0.1 10 µw/m2. also, the average cumulative radiated power for 24 hours at 200 meters was 36.96135µw/m2 which is of severe concern and exceeded the recommended standard. it is concluded that cellular base stations transmitters should not be located within 200 meters from the residential buildings. references alhekail, zo., hadi, ma. and alkanhal, ma. 2012. public safety assessment of electromagnetic radiation exposure from mobile base stations. journal of radiology protection. 32(3): 325-337. doi: 10.1088/0952-4746/32/3/325. epub 2012 aug 2. pmid: 22854221. ankur, m. and mandeep s. 2012. human health and electromagnetic radiations. international journal of engineering and innovative technology, 1(6): 95 – 97. blanch, cf. and romeu, lu. 2002. near field in the vicinity of wireless base-station antennas: an exposure compliance approach, ieee transactions on antennas and propagation, 50(2): 187 191. udo et al: residential exposure of electromagnetic fields radiated from mobile base stations and broadcast transmitters. azojete, 17(2):111-120 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 120 bortkiewicz, a., szyjkowska, a., gadzicka, e. and szymczak, w. 2014. the risk of subjective symptoms in mobile phone users in poland. an epidemiological study. international journal of occupational medicine and environmental health, 27: 293-303. catarinucci, l. 2003. human exposure to the near field of radio base antennas. a full wave solution using parallel fdtd. ieee transactions on microwave theory and techniques, 51(3): 935 – 940. cho, ym., lim, hj., jang, h., kim, k., choi, jw. and shin, c. 2016. a cross-sectional study of the association between mobile phone use and symptoms of ill health. environmental health toxicology. 31:e2016022. danielle, v. 2017. effects of radon and uv exposure on skin cancer mortality in switzerland. environmental health perspective, 125(6): 067009. doi: 10.1289/ehp825. joseph i., viranjay, ms. and omashere, or. 2016. spatial variation of the electromagnetic radiation due to exposure to telecommunication base station transmitters in a pilot region. international journal of applied engineering research, 11(22): 10994 – 11001. martinez-gonzalez, am. and fernandez-pascual, a. 2002. practical procedure for verification of compliance of digital mobile radio base stations to limitations of exposure of the general public to electromagnetic fields. ieee proceedings on microwaves, antennas and propagation (usa)., pp. 149, 218 – 228. miclaus, s. and bechet, p. 2006. estimated and measured values of the radio frequency radiation power density around cellular base stations. 7th international balkan workshop on applied physics, 5–7 july 2006, constanþa, romania, romania journal of applied physics, 52(3-4): 429440. mouaaz, n. and mohammed, ts. 2011. safety measurement of electromagnetic fields radiated from mobile base stations in the western region of saudi arabia. wireless engineering technology, 2: 221 – 229. sauter, c., dorn, h. and bahr, a. 2011. effects of exposure to electromagnetic fields emitted by gsm 900 and wcdma mobile phones on cognitive function in young male subjects. bioelectromagnetics, 32(3): 179–190. doi: 10.1002/bem.20623. doi – pubmed. viel, jf., clerc, f., barrera, c., rymzhanova, r., moissonnier, m., hours, m. and cardis, e. 2009. residential exposure to radiofrequency fields from mobile phone base stations, and broadcast transmitters: a population-based survey with personal meter. occupation environmental medicine, 66: 550 – 556 arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):141-164 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 141 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk original research article impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review a. v. okenyi * and j. k. alawode2 school of science and technology, nottingham trent university, ng11 8ns, uk. department of civil and environmental engineering, florida international university, miami, 10555 w florida, usa *corresponding author’s email address: victor.okenyi2020@my.ntu.ac.uk 1.0 introduction steel reinforcement corrosion in concrete structures is a dominant factor causing structural failures under short-term and long-term considerations leading to loss of serviceability and eventual collapse of concrete structures. several research works focused on reinforcement corrosion, detection, testing and repair (tuutti, 1982; broomfield, 1997; rodriguez et al., 1997; val, 2007; li et al., 2019; shahid et al., 2020) with the advancement in detection and testing methods due to its reoccurrence and increasingly high cost of maintenance repairs in many structures including marine structures, bridges, and other structures. for instance, it has been reported that corrosion damage costs in the usa is worth about half a million dollars and globally about $100 billion per annum (broomfield, 1991; 1997; li et al., 2007). reinforcement corrosion is mainly induced by the presence of chloride ions in concrete causing complete and localized de-passivation of the rebar and when carbon dioxide in the air reacts with cement matrix and the resulting interstitial solution is acidified while in contact with rebar (montemor et al., 2003). reduced electrical resistivity, permeability issues owing to water-cement ratio, microcracks, contaminated concrete mix and inadequate concrete cover are other factors influencing reinforcement corrosion propagation in concrete (aci c222, 1996; bazant, 1979). in addition, permeation, absorption and diffusion are harmful transport in concrete. concrete under loading leads to microcracks especially as stress levels increases (okenyi 2018), article information abstract corrosion of reinforcement in concrete structures remains a durability issue in structural engineering with the increasing cost of repair and maintenance. the mechanism and factors influencing reinforcement corrosion in concrete with various electrochemical monitoring techniques including non-destructive and destructive techniques have been considered. also, the roles of sensors have been reviewed to determine the monitoring technique that proved most effective in determining corrosion parameters and more practicable for the assessment of concrete durability. electrochemical impedance spectroscopy and linear polarization resistance techniques showed great performance in evaluating corrosion kinetics and corrosion rate respectively while gravimetric weight loss technique provided accurate measurements. no single monitoring technique showed to be the ultimate technique, and this calls for more research work in the development of more dynamic monitoring tools capable of considering all possible corrosion factors in the corrosion monitoring process. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 oct., 2020 revised 2 january 2021 accepted 8 january 2021 keywords: corrosion concrete structures non-destructive technique durability sensor okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 142 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk rebar reduction in its cross-section, loss of the bonding force between rebar and concrete, volumetric expansion caused by corrosion producing split-tensile stresses (coronelli and gambarova, 2004; auyeung et al., 2000; broomfield, 1997) including other alterations to steel ductility are processes leading to the damage of reinforced concrete structures (zhu and françois, 2014). numerous evaluation techniques for corrosion investigation in reinforced concrete have been used over time in both research and practice. the goal has always been to be able to establish the relationship existing between corrosion growth and time as means of adequately predicting the service life of a structure undergoing degradation considering the various methods that are now in use. this paper focused on corrosion in reinforced concrete structures holistically with a focus on the review of corrosion monitoring techniques used to determine the most effective and how these techniques were useful in detecting concrete durability issues and its overall service life prediction. 1.1 mechanisms of steel corrosion in concrete it is important to note that the process of steel reinforcement corrosion in concrete is electro-chemical through an exchange of electrons and movement of charges especially as it occurs in an aqueous medium (uhlig and king, 1972). in this scenario, the concrete pore water serves as that medium i.e., the electrolyte and the electrode consisting of a composite of combined anode and cathode is the corroding steel surface which is electrically connected along the body of the steel reinforcement as shown in figure 1, forming the electrochemical cell and the reaction occurring at both electrodes are named “half-cell reactions” (aci c222, 1996). the corrosion formation mechanism is either microcell or macrocell dictated by the distance between the anodic and cathodic reactions. figure 1: corrosion formation in concrete (carino, 1999) at the anode, an oxidation reaction occurs causing the degradation of the steel in which iron fe is oxidized to form iron cations affected by aggressive environment conditions, ph of the electrolyte as shown in reaction equation (1): (1) while at the cathode, a reduction reaction occurs balancing equation (1) in which hydrogen ions are reduced to form hydroxyl anions in reaction equation (2) in the presence of oxygen, ph around steel surface and a decreased ambient temperature. ⁄ (2) arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 143 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk the anodic and cathodic reaction products when combined is what produces the surface film that passivates the reinforcement steel. some previous research showed that the passive film is favoured by the presence of iron oxides, fe3o4 (magnetite) and fe2o3 (hematite) (hansson, 1985; kruger and calvert, 1967) while others claim it is by ca (oh)2 (page, 1990; montemor et al., 1998). corrosion breakdown mechanism models include an adsorption-displacement model which proposes that passive film is destroyed by its adsorption of chloride ions (cl¯) with a simultaneous displacement of oxygen ions (o2¯) (böhni and uhlig, 1969). also, the chemicomechanical model suggests that surface tension is reduced by cl¯ thereby forming cracks (sato, 1982) while the migration-penetration model proposes the migration of ions of cl¯ to take the place of o2¯ and cause voids leading to pitting formation and pit growth (chao et al., 1981). in conclusion, understanding the mechanism by which corrosion of steel occurs in concrete helps to study the damage mechanics to see the damage evolution mechanics on a microscale and could serve to predict the service life of reinforced concrete experimentally or using computational techniques. 2.0 methods 2.1 steel corrosion monitoring techniques various reinforcement corrosion evaluation techniques have been used and discussed. by simply visualizing a concrete structure undergoing corrosion, basic information regarding nature of corrosion could be determined such as cracks, concrete spalling, and rusts (pullarstrecker, 1987) although better detection methods were proposed by other scholars (stratfull et al., 1975; manning and holt, 1980). in recent times, this method remains noneconomical and takes time as more advanced methods have been developed with minimal setbacks. of all the various factors used in corrosion rate monitoring, including change in ph, chloride content monitoring, change in temperature, strain, acoustics etc., the most important and quantitative way is measuring the current rate icorr, owing to the single fact that reinforcement corrosion in concrete is an electrochemical process. thus, both destructive and electrochemically non-destructive corrosion assessment method has been considered. 2.1.1 galvanostatic pulse method (gpm) this is a non-destructive transient method where a small amount of anodic current pulse usually in the range of 10 to 200 µa is applied between the rebar and a counter electrode positioned on the surface of the concrete for 5-10 s. electrochemical potential vt from the polarization of steel is obtained using equation (3) (montemor et al., 2003) and plotted against time of polarization. it should be noted that when polarization occurs and anodic and cathodic current is measured, this method is referred to as potentiodynamic polarization. [ ] (3) where t is the time, rp is the polarization resistance and cdl is the double layer capacitance at the reinforcement surface, rω is the ohmic resistance between the surface electrode and the steel bar while iap is the applied current. okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 144 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk from figure 3, rp is obtained from the curved segment by curve fitting and the stern-geary equation in equation (4) and faraday’s law of electrochemical equivalence in equation (5) is used to obtain the corrosion rate with a typical 2d surface plot in figure 4. (4) (5) b is based on tafel constants and has values of 52 and 26 mv for passive steel and steel in concrete respectively (andrade et al., 1986). a (cm2) being the area of steel under the counter electrode. figure 3: electrochemical potential of steel against time (sørensen and frølund, 2002) figure 4: corrosion rate using gpm over six years (sørensen and frølund, 2002) 2.1.2 linear polarization resistance (lpr) in this method, a polarization potential value of 10-30 mv is applied below the open circuit potential eocat a scan rate of 0.1 mv/s scan rate and the current density i (current response divided by surface area of the electrode) were obtained (daniyal and akhtar, 2020). the resulting relation is quasi-linear owing to the small potential being applied (millard et al., arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 145 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk 2001). thus, linear polarization resistance rp is obtained from the slope of the graph of potential against current density depicted in figure 5 and finally, equation (4) is used to determine the corrosion rate. figure 5: typical polarization resistance curve (karuppanasamy and pillai, 1995) 2.1.3 half-cell potential (hcp) this qualitative corrosion monitoring technique is otherwise known as open circuit potential where a voltmeter measures the potential difference at different points between the steel and another half, a reference external electrode usually immersed in copper/copper sulphate (cu/cuso4) or silver/silver chloride (ag/agcl) solution and concrete is kept wet to ensure electrical connection (figure 6). table 1 indicates the probability of corrosion from hcp measurements conforming with astm c876 (astm c876, 2015). this method does not specify the corrosion rate, it only states the probability of corrosion (yeih and huang, 1998). figure 6: typical half-cell potential set-up (verma et al., 2014) table 1: probability of corrosion for cuso4 (astm c876, 2015) s. no. half-cell potential (mv) probability of corrosion 1 >-200 10% 2 -200 to -350 50% 3 <-350 90% okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 146 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk 2.1.4 time domain reflectometry (tdr) this method is usually used in steel strands in prestressed concrete structures as well as cable in bridges in which a sensor wire is run along the steel forming a parallel conductor line and an electromagnetic pulse of voltage is sent through the line in a set up in figure 7 and reflected from the end and the magnitude of reflection is given in equation (6): r = (6) where r is reflection coefficient, z is impedance and zo is the characteristic impedance of steel strand. pitting corrosion, surface corrosion and voids disrupt a change in the electromagnetic pulse with p3 (figure 7) due to high impedance. thus, the circuit properties such as series resistance r, series inductance l, capacitance c and conductance g are monitored (liu et al., 2001). corrosion detection is marked by a reduction in radius at a corrosion location with an increase in impedance which is detected by the time domain reflectometry and more reflection translates to more damage. this method measures the extent and length of corrosion as well as voids. figure 7: pit corrosion monitored by time-domain reflectometry curve (liu et al., 2001) 2.1.5 ultrasonic guided waves (ugw) this is a method still in use presently for detecting corrosion progression in steel reinforcement in concrete. mechanical pulse waves are transmitted into the concrete rebar by using contact transducers (piezoelectric transducer pzt, annular series transducer, full, electrode transducer) of frequency 0.1 mhz and 1 mhz, one acting as the transmitter of the ultrasonic waves and the other is the receiver used in different excitation modes. by comparing changes in signal amplitude and pulse velocity, damage in rebar can be quantified. longitudinal placement of transducers at low frequency at 0.1 mhz detects corrosion initiation the best because it produces longer wavelength and resolution loss is easily detected and while frequency at 1 mhz detects pitting in rebar sharma and mukherjee, (2010) with a typical response depicted in figure 8 for two excitation modes. this method has other numerous applications and could also be used in freeze-thaw cycle monitoring in detecting concrete ageing (alawode, 2018). arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 147 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk figure 8: typical ultrasonic time-domain spectra response (liu et al., 2019) 2.1.6 x-ray diffraction (xrd) x-rays and gamma-rays are radiographic non-destructive method employed in monitoring corrosion and other microstructure defects in reinforced concrete structures by evaluating its crystallographic structure. these rays are electromagnetic monochromatic radiation penetrating concrete through release photons directed to the mapped area which is transformed by a fluometallic converter which captures the defects in rebar, its size, location, voids in rebar and concrete by measuring x-ray diffraction angle (song and saraswathy, 2007; burkett, 2018). safety precaution should be ensured when in use. a typical xrd response (figure 9) shows corrosion products composition to be rusts. figure 9: typical xrd response spectra for corrosion (liu et al., 2017) 2.1.7 electrochemical impedance spectroscopy (eis) this method is otherwise known as alternative current (ac) impedance spectroscopy. an alternating voltage of about 10-20 mv which is the excitation potential is applied to the steel reinforcement as the ac and phase angle is recorded with their different frequencies f. impedance z which is the ratio of ac voltage to ac is obtained (stern, 1957). the graph in figure 10 referred to as either the impedance spectrum or nyquist plot, impedance has a real or resistive (z’) and imaginary part (z”) which is capacitive or inductive measured at frequencies between 100 khz and 10 mhz (daniyal and akhtar, 2020). this response is likened to the one obtained in an electrical circuit (randels circuit) where corrosion takes okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 148 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk place as an electrochemical process. from figure 10, rc is the ohmic resistance of concrete and the diameter is resistance at which the steel dissolves called transfer resistance rct. figure 10: basic nyquist response for steel (ribeiro and abrantes, 2016) free elections movement towards steel surface anions and movement towards cathode in solution forms two layers capacitance cdl. thus, impedance is given in equation (7) (natarajan and ramakrishnan, 2007) as: (7) where j is √-1 and ɷ is 2πf. at low frequency, the circuit becomes a direct current (dc) circuit but when the frequency is high i.e. when ɷ is infinity, the circuit becomes ac and from the difference between dc and ac, true polarization resistance becomes rct and a lower rct value means corrosion values are high and the reverse is also true (ribeiro et al., 2015). 2.1.8 gravimetric weight loss (gwl) this method is a destructive method used in determining the corrosion rate in a concrete structure. the test is carried out by guidance of astm g1-03 (astm g1-03, 2004) where the specimen is broken, and rebar is cleaned and immersed in clarke (solution composed of 93% concentration of hcl, 5% sncl2, 2% sb2o3) after which it is distilled with water and dried in air to completely remove corrosion products. initial weight is taken before placement in concrete and after breakage, final weight is recorded. the corrosion rate is obtained from equation (8) (odio et al., 2014) given as: (8) where δw is weight loss, a is exposed surface area (cm2), t = time of exposure (hrs.), k is unit conversion constant given as 8.76 × 104 (for mm/year) and ρ = density (g/cm3). this method is suitable for long term corrosion detection. 2.1.9 electrical resistivity method (erm) when the reinforcement steel is de-passivated, the continuity of corrosion rate is influenced by concrete’s electrical resistance. this forms the basis of measurement of resistivity which is given as the electrical resistance multiplied by the length between probes (millard and arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 149 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk harrison, 1989). the wenner four-probe measuring device wenner, (1915) which is now adapted for resistivity measurement as shown in figure 11 where ac, i is applied to two outer probes and a potential difference v between the inner probe is recorded and resistivity is determined using equation (9) (gowers and millard, 1999). (9) where a is space between probes and k is a geometric factor given as 2π. a review of the relationship between resistivity values and steel reinforcement risk of corrosion is still inconclusive from previous research conducted because different factors such as concrete ageing, microstructure, water-cement ratio, temperature, and moisture content affect resistivity and this shows recommendation for more research on the subjecting order to arrive at a more stable scale of resistivity measurement and corrosion determination (chen et al., 2014). figure 11: wenner four-probe device measuring concrete resistivity (carino, 1999) 2.2 monitoring sensors and other monitoring techniques the use of sensors (preferably non-invasive) come to play in cases where the discussed known instruments are not practicable, and corrosion needs to be monitored at specific regions in concrete materials while it allows for the juxtaposition of parameters to be measured to obtain a better understanding of corrosion rate and its effect in assessing durability in recent times. some of the sensors studied in the past by authors include chemical microsensors, ring sensors, chloride sensors (guth et al., 2001; raupach and schießl, 2001; yun et al., 2004) as well as other automated mapping sensors in detecting rebar location, length of rebar in concrete structures (chamberlain, 1992; mcfee et al., 1996) and infrared thermography which is now in use in detecting voids and delamination in concrete but the challenge is that these methods haven’t given detailed corrosion rate analysis. fiber optic sensors are currently more employed in reinforcement corrosion detection majorly because they have good sensitivity over a large area, resistant to chemical effects, free of electromagnetic influence and are cheap to produce and have and are still being been explored by various authors (grattan et al., 2007; 2009; zheng et al, 2009; jagtap and nayak, okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 150 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk 2020). sun et al. (2014) used optical fiber brillouin sensor to determine rebar corrosion in a concrete column where the brillouin optical time-domain reflectometer measured the strain and cracking pattern and used it in detecting and identifying corrosion location. piezoelectric ceramic (pzt) sensors are also as advantageous as the fiber optic sensors in diagnosing corrosion damage shown by previous authors (park and park, 2010; rathod and mahapatra, 2011) when necessary, one or more sensors could be combined to see how effectively corrosion rate in rebar could be detected as carried out by rathod and mahapatra (2011). other monitoring techniques involve the use of embedded corrosion instrument (eci) (figure 12) which is an intrusive corrosion sensor monitoring lpr, hcp, esm, temperature and chloride ion concentration remotely saving a lot of data manipulation, site visits and costs have been considered, including the smart pebble sensor for chloride ion monitoring (reis and gallaher, 2006; watters et al., 2003) and others techniques applied to reinforced concrete bridges include corrosion penetration monitoring system and v2000 monitoring cable (agrawal et al., 2009). in conclusion, the use of sensors in corrosion monitoring holds great promise especially being able to detect corrosion rate remotely. thus, it is recommended that more research should be conducted especially in combining the sensors to be able to cover all parameters needed in accurately predicting timely corrosion impact and assessing serviceability of concrete structures. figure 12: eci in operation (song and saraswathy, 2007) 3.0 results and discussion 3.1 overview of corrosion monitoring techniques on concrete durability to date, corrosion problems caused especially in the infrastructures sector is still major concern and various monitoring technique are still being applied. however, the review of the methods used so far in detecting corrosion in reinforced concrete structures from rigorous work has been reported in table 2. these provide the benefits and limitation to these methods in effectively assessing the serviceability of concrete structures and as a means of predicting and discussing the most effective method and giving further recommendations on improvement. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 151 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk table 2: review of corrosion techniques used reference research conducted observation on durability remark montemor et al. (2003) conducted research to determine the chlorides critical level and factors constituting to steel corrosion using lpr, gpm, eis and potential measurement. the critical level was reached in concrete as cl¯ reacts with fe, causing pit growth and the ph of concrete was a major factor. eis provided the most effective method under consideration although measurements took time which was compensated for by gpm although fluctuations were experienced. bäßler et al. (2001) presented results from the monitoring of steel reinforcement corrosion rate comparing natural corrosion to measured corrosion in the laboratory using gpm device. real-life corrosion parameters showed a correlation with measured parameters for short-term measurements. long term results for corrosion lifetime evaluation lost correlation as measured parameters became different and gpm device could not account for that showing further need in improving sensitivity. sørensen and frølund (2002) discussed the effectiveness of using the gpm technique in accurately estimating corrosion rate in concrete structures. corrosion rate was detected quickly in steel reinforcement and it agrees with gravimetric weight loss results, although identifying active corrosion area took time. the swiftness of gpm could help in the timely detection of deterioration and chloride environment presence will affect durability. thus, gpm should be improved to consider causative factors. moreno et al. (2004) performed an investigation to determine the effect of carbonation and cl¯ on corrosion of steel reinforcements using lpr technique. critical chloride levels were detected above which pitting took place while increased ph of concrete improved resistance to localized corrosion. lpr measurements effectively measured chloride-induced corrosion rates and were effective even at low chloride levels although this may be due to oxygen evolution potential being overestimated. romano et al. (2013) worked on monitoring the degradation occurring in reinforced concrete structures in chloride environments using lpr, erm and potential measurements. there was a serious decrease in polarization resistance value which matches the resistivity values in the corrosion initiation phase as chloride content increases. lpr and erm measurements at different depths in concrete also have an impact on the corrosion rates obtained and more studies could help detect the role of depth in the mechanism of transportation of aggressive materials in concrete. okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 152 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk pradhan and bhattacharjee (2009) researched on the performance of different rebar placed in different cement type concrete in chloride condition using lpr, gwl and eis. the dominant factor influencing corrosion was chloride content and admixtures improved corrosion resistance. lpr appeared to have given a better value of corrosion current density showing its better performance over eis. elsener (2001) studied the use of hcp mapping in assessing localized corrosion caused by chloride deposit in reinforced concrete. results depicted repassivation of steel after repair work. hcp mapping technique was only able to ascertain the chance of corrosion and was marked by the lower negative potential which did not necessarily indicate corrosion. thus, its ability to predicting durability could not be completely relied upon. carino (1999) considered the use of non-destructive techniques including hcp, erm and lpr in investigating corrosion in concrete. for hcp, measuring potential gradients was a more effective way of corrosion measurement. erm indicated active corrosion although not rate and lpr gave quick corrosion rate results. lpr proved to be a very useful means of accessing durability but not service life due to change in time conditions and resistivity which is crucial to corrosion combined with hcp results gives a better understanding of reinforced concrete corrosion. pour-ghaz et al. (2009) presented work on a tool to better interpret measurements obtained from hcp mapping in concrete structures. it was recommended hcp and resistivity values should be combined for better information on corrosion rate. this research attempted to solve the problem of inadequate information obtained from using hcp alone earlier identified for corrosion prediction but validation and model development on key corrosion determining factor is needed. liu et al. (2001) reported experimental results in the novel application of tdr to monitoring corrosion in prestressed highperformance bridge beams the method showed to effectively locate and detect corrosion damage levels from insitu readings and even from application to laboratory-scale samples. tdr is useful although there are energy loss issues when measuring lengthy samples and further research is encouraged on reinforced concrete samples and how to effectively translate results to detect corrosion rate on a long term basis. furse et al. (2009) researched using tdr as a non-destructive method of determining faults in prestressed spectral tdr proved to function well even in anchors placed in concrete and shown to long-range measurement issues were addressed increasing signal-noise ratio to detect invisible faults and the arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 153 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk anchors measure faults up to a maximum of about 48m. combination of eis with tdr could prove very effective in determining corrosion rate. hunsperger et al. (2003) performed an investigation to determine steel corrosion in structures which are already existing externally using tdr. voids were shown to be critical to corrosion propagation as it harboured moisture and salts and affected signal return monitored by tdr. internal monitoring of corrosion using tdr provides a more accurate means. best measurement using this method comes from direct measurement of steel reinforcement and ways to ensure this in existing structures should be improved upon. du et al. (2017) studied how corrosion developed in steel embedded in concrete using ugw and piezoelectric transducers to monitor the stages. wave velocity was inversely proportional to corrosion rate. initial corrosion, rapid corrosion and further corrosion development were the three stages identified. the mass loss had to be combined with acoustic parameters to determine corrosion rate although piezoelectric was able to boost reception of a better signal for time and frequency domain spectra showing that pzt's are important to corrosion monitoring yeih and huang (1998) discussed the evaluation of corrosion issues in reinforced concrete members using ugw technique. amplitude attenuation in ultrasonic testing was shown to vary with thickness loss giving good record of corrosion rate when combined with the ac impedance method. if corrosion occurs, rust or microcracks will also occur changing amplitude. more effort is recommended for testing larger concrete samples and relating amplitude with other electrochemical parameters to prove corrosion detection. sharma and mukherjee (2010) reported results from the monitoring of earlystage reinforcement corrosion in concrete considering ugw and acoustic emission sensors. acoustic emission sensors proved effective in detecting initial corrosion while ugw served to detect surface corrosion from pitting corrosion ugw proved to be able to measure the extent of corrosion but unable to detect corrosion presence at early stages although its combination with acoustic sensors was effective hossain (2005) studied the corrosion resistance of three types of concrete mixes and used xrd, hcp, lpr, gwl technique in monitoring corrosion in a steel bar. active corrosion was detected using hcp and rate by lpr, but volcanic admixtures were good corrosion inhibitors. xrd provided quantitative measurements in terms of composition showing a reduction in calcium hydroxide content to show good performance of volcanic admixtures. okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 154 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk takahashi et al. (2005) described the composition of corrosion products formed reaction between iron and sodium chloride using insitu xrd analysis iron oxides were main constituents formed from corrosion affected by precipitation and dissolution of fe. xrd only provided information on the formation mechanism of corrosion and the quantification of its constituents. burkett (2018) presented the outcome of a study on the application of xrd to characterize corrosion to provide a timely solution. natrojarosite and akaganeite were found to be constituents of corrosion using a portable xrd device. building upon this device to measure rate from quantities determined in minutes could prove extremely invaluable to corrosion monitoring. ribeiro and abrantes (2016) performed an investigation on the use of eis as a nondestructive technique in studying corrosion in reinforced concrete. angular frequency theory was applied to eis result interpretation and it gave a more improved interpretation eis provides accurate measurement about corrosion rate, its mechanism, and changes to rebar. this research is only a further improvement on a wellestablished technique to boost easier interpretation. ismail and ohtsu (2006) worked on determining corrosion rate in both high strength concrete and ordinary concrete using eis, lpr and dynamic polarization in a chloride environment. high strength concrete exhibited lower corrosion rate values when compared to ordinary concrete owing to lower w/c ratio in high strength concrete. eis results were lowest of the three, showing a difference in the way overall resistance of corrosion was measured and based on the inverse relationship between resistance and corrosion rate, one could argue the effectiveness of eis method. dhouibihachani et al. (1996) presented results obtained from the comparison eis results between low frequency applied to steel and high frequency applied to concrete. the frequency distribution model agreed with eis results from the experiments. using eis here was able to expose interaction between steel -surface resistances on corrosion rate and how it helped better measurement. bhaskar et al. (2011) studied reinforcement corrosion caused by chloride in cracked concrete and gwl was used for quantification as a destructive technique. gwl readings indicated that crack presence influenced corrosion than crack width. also, lower w/c ratio lowers steel corrosion. this method of corrosion monitoring still proves to be effective in quantifying corrosion rate although it is destructive. azarsa and gupta (2017) reviewed various relationship between electrical resistivity and reinforcement corrosion the erm measurements were affected by moisture and temperature and erm method is good in detecting active corrosion probability and rate, especially when combined with lpr arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 155 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk in concrete. further investigation was recommended. showing. it is also useful in detecting corrosion potential and this fact is yet to be standardized. morris et al. (2004) sort to establish a standard corrosion determination value using erm monitoring in reinforced concrete. results indicated active corrosion at 10 kω∙cm and passive corrosion at 30 kω∙cm erm effectively evaluates the severity of corrosion but still needs to be combined with lpr to determine corrosion rate values. sadowski (2013) worked on the combination of erm and lpr for effective service life prediction using a reinforced concrete slab sample. the experiment showed three areas of slab having a 90% probability of corrosion, the second area showed uncertainty while the third area gave 10% corrosion probability. the distribution of active corrosion was well depicted using this method and this method is good in terms of its possible application to new and existing structures. ha et al. (2004) described the use of different sensors applied to an assessment of corrosion and durability in concrete. the role of sensors depended on the measurement of important factors including, chloride content, temperature, moisture etc. as smart materials are being introduced, one major advantage is the ability to place it in structures and it holds promising results, and more works are being authored in this area. muralitharan et al. (2006) researched to check the electrochemical properties of alkaline manganese dioxide, metal-metal oxide, and graphite sensors. alkaline manganese dioxide sensor showed the most stable potential measurements although chloride ions showed no effect on measurements. these sensors were not affected by chloride and this is an advantage when being embedded in concrete and long-term research is recommended to confirm this. karthick et al. (2014) reported the results from the comparison between embedded sensors and sensors placed on a concrete surface to monitor corrosion in reinforced concrete. the embedded hcp sensor gave lesser corrosion rate than the surface placed lpr probe. this further proves the fact that lower corrosion rates when techniques are combined shows that method producing lower corrosion rate has better performance and it is affected by steelconcrete resistance. daniyal and akhtar (2020) reviewed various electrochemical method for corrosion monitoring to see their performance in reinforced concrete. electrochemical methods were useful for both laboratory and in-situ measurements, gwl was the most efficient destructive method. no individual method proved to be the best, but the combination of electrochemical methods was effective in monitoring corrosion okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 156 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk verma et al. (2014) reviewed the value of hcp method and other corrosion monitoring techniques and their role in the durability of concrete structures. hcp technique was shown to be the most applied technique and was useful in determining suitable protective measurement hcp is also affected by different factors including cover to concrete and its combination with resistivity yields a better interpretation most of the methods considered in the literature has shown that often, different corrosion monitoring techniques have always been combined to obtain good results and this shows that no one method is most effective. also, there is a need to consider more application of these methods in real-time monitoring and its applicability in offshore concrete structures where the impact of various environmental factors and mechanical factors combined impair durability. 4.0 conclusion based on the review conducted in this study on the previous research and various corrosion monitoring technique and their principle of operation that has been applied especially over the last two decades, the observation of the results on durability obtained and the overall effect these techniques in accurately measuring corrosion rate and prediction, the following conclusions were made from the critical review:  the electrochemical impedance spectroscopy method proved to be a very considerable technique when it comes to understanding the mechanics and kinetics of reinforcement corrosion as it provides an accurate polarization resistance value from reviewed papers who have applied this technique regardless of its time-consuming nature which could be reduced when combined with galvanostatic pulse method.  linear polarization resistance technique provided a very effective means of measuring corrosion rate which is also measured by other electrochemical technique including galvanostatic pulse, impedance spectroscopy, potentiodynamic tests but what made linear polarization unique was its ability to detect chloride content even at very small levels in concrete and more future is recommended on establishing an interpretation of its results, especially for service life predictions.  other corrosion monitoring techniques including time-domain reflectometry, use of piezoelectric transducers, ultrasonic guided waves, electrical resistivity method and use of sensors need further improvement in detecting early and long-term corrosion. also, the impact of humidity, moisture and temperature need to be considered in new research as they hold the key future degradation assessment in concrete structures for different zones.  reinforced concrete corrosion is still a major problem in the civil engineering design and construction sector and more smart materials are currently being developed. from this review, specific monitoring technique proved excellent when considering specific needs such as understanding corrosion processes and monitoring corrosion rate and even detection, but no single method encompasses these factors. thus, future work is recommended in combining core measured characteristics of other devices into building a workable monitoring unit which can perform all measurements. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):141-164. issn 1596-2490; e-issn 25455818; www.azojete.com.ng 157 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk notation ac alternating current astm american society for testing and materials ɷ angular frequency, rad/s sb2o3 antimony (iii) oxide a area, m2 c capacitance cl¯ chloride ions g conductance cu copper cuso4 copper sulphate icorr corrosion rate, m/yr. i current, a dc direct current erm electrical resistivity method ρ electrical resistivity, ohm·m eis electrochemical impedance spectroscopy vt electrochemical potential, µ eci embedded corrosion instrument f frequency, hz gpm galvanostatic pulse method gwl gravimetric weight loss hcp half-cell potential fe2o3 hematite hcl hydrochloric acid z impedance, ω fe iron lpr linear polarization resistance fe3o4 magnetite o2¯ oxygen ions pzt piezoelectric ceramic transducer v potential difference, v ph potential of hydrogen rω resistance, ohm l series inductance r series resistance ag silver agcl silver chloride b tafel constants, mv/decade tdr time domain reflectometry sncl2 tin (ii) chloride ugw ultrasonic guided waves xrd x-ray diffraction references american concrete institute (aci) committee 222, 1996. corrosion of metals in concrete. detroit: american concrete institute, detroit, united states. okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 158 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk agrawal, ak., yi, z., alampalli, s., ettouney, m., king, l., hui, k. and patel, m. 2009. remote corrosion monitoring systems for highway bridges. 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https://doi.org/10.1061/(asce)0733-9445(2007)133:9(1297). verma, sk., bhadauria, ss. and akhtar, s. 2014. monitoring corrosion of steel bars in reinforced concrete structures. the scientific world journal 2014.10.1155, https://doi.org/10.1155/2014/957904. https://doi.org/10.1155/2013/714501 okenyi and alawode: impact of corrosion monitoring techniques on durability assessment in reinforced concrete: a review. azojete, 17(2):141-164 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 164 corresponding author’s e-mail address: victor.okenyi2020@my.ntu.ac.uk watters, dg., bahr, aj., jayaweera, p. and huestis, dl. 2003. smart pebbles: passive embeddable wireless sensors for chloride ingress monitoring in bridge decks (no. fhwa/ca/tl-2003/07). california. dept. of transportation, sacramento, united states. wenner, f. 1915. a method of measuring earth resistivity. bulletin of the bureau of standards 12 (4): 469. https://doi.org/10.6028/bulletin.282. yeih, w. and huang, r. 1998. detection of the corrosion damage in reinforced concrete members by ultrasonic testing. cement and concrete research, 28(7): 1071-1083. yun, h., patton, me., garrett jr, jh., fedder, gk., frederick, km., hsu, jj., lowe, ij., oppenheim, ij. and sides, pj. 2004. detection of free chloride in concrete by nmr. cement and concrete research 34 (3): 379–390. https://doi.org/10.1016/j.cemconres.2003.08.020. zheng, z., sun, x. and lei, y. 2009. monitoring corrosion of reinforcement in concrete structures via fiber bragg grating sensors. frontiers of mechanical engineering in china, 4 (3): 316–319. https://doi.org/10.1007/s11465-009-0040-y. zhu, w. and françois, r. 2014. corrosion of the reinforcement and its influence on the residual structural performance of a 26-year-old corroded rc beam. construction and building materials 51: 461–472. https://doi.org/10.1016/j.conbuildmat.2013.11.015 https://doi.org/10.6028/bulletin.282 availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 51-62 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng groundwater modellingwith limited data: a case study of yobe river basin, north east nigeria hassan, m.1, r.c. carter2 and k.r. rushton2 abstract an exploratory numerical groundwater model of a shallow aquifer interacting with a river in a semi-arid zone was developed using modflow. the model simulated field data adequately as well as the physical processes presented in its conceptual framework. the conceptualization of the aquifer to exist under both confined and unconfined conditions can be adequately described in the model. water balance from the model shows that river to aquifer flow dominates aquifer recharge processes, and its magnitude is limited not only by relative head difference, but also by the transmissivity and hydraulic gradient of the aquifer. 1. introduction groundwater models are tools that are aimed at predicting the consequences of a proposed action. they are also used in an interpretive sense to gain insight into the controlling parameters in a site-specific setting or as a framework for assembling and organising field data and formulating ideas about system dynamics. the techniques of groundwater modelling are well documented in wang and anderson (1982), anderson and woessner (1992) and spitz and moreno (1996). the modelling of groundwater is primarily of value when adequate extensive data exist. in such situations, conventional calibration and validation approaches may be possible. but detailed measurements throughout a site are both impractical and expensive. in such cases, the model is constrained to represent the site to those that are acceptably realistic. the inherent scarcity of data is particularly relevant in developing countries where there is limited information about soil and aquifer properties, and where monitoring and record keeping may be poor. therefore, models which display economy of complexity, but which are based on sound conceptual frameworks are needed. the models must reflect those features of the groundwater system, which really matter. they must also be credible and reliable. 1.1 study area and background the area under study is located in the semi-arid zone of north-east nigeria (figure 1), which is characterised by low rainfall and reduced river flow. in the last three decades, rainfall has decreased by about 30% (hess et al., 1995) and annual discharge by the major headwaters of rivers hadejia and jama’are has decreased by almost 60%. the reduction in the discharge from these rivers to the yobe basin is due to construction of dams across them in addition to low rainfall. as a result of these changes in the hydrology of the area, both the federal and state governments in the north east arid zone (neaz) have made tremendous efforts towards developing and managing the existing water resources. reports of various professional water consultants, such as schultz (1975), iwaco (1985), water surveys 1department of physics, university of maiduguri, maiduguri. nigeria 2institute of water and environment, cranfield university, silsoe. bedford, mk45 4dt uk. http://www.azojete.com.ng groundwater modelling with limited data: a case study of yobe river basin, north east nigeria 52 (1986), diyam (1987) and neazdp (1990) with various terms of reference were engaged for two decades (1975-1995) with the mandate to develop the groundwater in the river basin. figure 1: map of the study area figure 1: map of the study area these previous works have identified four natural features that limit opportunities for the development of water resources in the area. they include aridity, highly seasonal climate, climates that have shown major changes or trends in recent decades and poor aquifer (carter, 1998). these studies did not address the state of the groundwater in the area or state possible management strategies based on water availability. studies by alkali (1995) as well as carter and alkali (1996) suggested that the shallow aquifer in the yobe basin has complex hydrogeologic features. for example, it was discovered that the aquifer is covered extensively with low permeability clay that hinders vertical infiltration of water. according to them, the dominant factor in the recharge of the aquifer is the river and that the aquifer is capable of converting from unconfined to confined conditions. another desk study that consists of photointerpretation of the geomophological features of the yobe floodplain by marinof-petkoff (1994) and hydrogeological and geophysical studies by hassan (2002) have shown that some areas of the yobe river basin are covered by permeable deposits. in all the studies carried out in the area, there was difficulty in assessing the aquifer potential based on the existing field data. there was complete lack of historical data in some cases. for example, data on groundwater level fluctuation, recharge estimates, aquifer parameters and lithology are not readily available. in the cases where some data, such as river stage variation and discharge exist, there were problems of missing records. carrying out “conventional” modelling in such cases is difficult. azojete vol. 4 2004 53 some or all of the problems discussed above need to be addressed in the context of existing data. this limitation of data has constrained the development of a ‘full-scale’ model where calibration, verification, validation and prediction are possible. in view of this, an exploratory groundwater model was developed using modflow to assess the aquifer potential based on the existing data. 2. methodology and model preparation modflow is a computer program, which was developed by the united states geological survey, reston, virginia, for modelling groundwater flow. it uses a block-centred finite difference approach to solve the three-dimensional equations for groundwater flow in porous media. a detailed description of modflow can be found in mcdonald and harbaugh (1987). the idealized conceptual model was used to design and simulate various scenarios using the modflow model. a combined preand post-processor, model independent graphical interface called groundwater vistas was used for data input and for interactive modelling with modflow. 2.1 description of the conceptual model the river yobe system as conceptualised in hassan (2002) is shown in figure 2. it consists of the following:  the aquifer geometry and the boundary show that the aquifer is 10 m thick and 4 km wide with the river almost in the middle. it has clay cover in some places whose thickness varies from 0.5 to 3 m. a no flow boundary condition in the north and a constant head in the south that allows small seepage to the upland bound it.  the landforms show that the yobe floodplain consists of areas that could allow vertical recharge. the flow processes in the aquifer are vertical recharge from rainfall, overland flooding and river to aquifer flow.  aquifer parameters such as storage coefficient and hydraulic conductivity cover a range of values.  the river-aquifer interaction is represented with a varying river coefficient; the magnitude of flow between the river and the aquifer depends on relative head difference between water in the river and groundwater in the aquifer groundwater modelling with limited data: a case study of yobe river basin, north east nigeria 54 figure 2: conceptual model of the yobe river system the modelled area was discretized three-dimensionally. the size of the grid blocks were 500 m in the x-direction and variable in the y-direction with the smallest being 35 m and the largest 150 m. each grid consists of 3 columns and 50 rows with row25 containing the river. in the vertical direction, the model consists of a 16 m thick layer. figure 3 shows the finite difference grid of the study area. figure 3: finite difference grid of area of study showing river yobe and the area of interest (shaded) azojete vol. 4 2004 55 2.2 data requirements input data to the model consists of the three major external stresses: river stage time series with a varying river coefficient, vertical recharge and ‘leakage’. the methods and procedures for obtaining these data include both geophysical and hydrogeological investigations as discussed in hassan and carter (2004). figures 4, 5 and 6 show the starting conditions and time series of the input data respectively. the input for one year consists of 36 stress periods each with a length of 10 days and a single time step. this was repeated for 2.4 years (86 stress periods) with stress period one starting from 30th october. the choice of the number and length of stress periods and time steps was dictated by the rapid change in the river stage. figure 4: starting conditions figure 5: river stage variations with time groundwater modelling with limited data: a case study of yobe river basin, north east nigeria 56 figure 6: recharge and ‘leakage’ input sensitivity analysis was carried out on the wide range of aquifer parameters to arrive at acceptable values. these parameters and their values are as follows: i) kh= 0.1 m/day (unconfined); and kh=15 m/day (confined region) ii) scc = 0.001 (confined); and scu = 0.05 (unconfined) iii) vl = 1.5 x10-5 m/day (the clay cover was modelled as a ‘leakage’ factor that allows water to seep continuously into the aquifer). where, kh is hydraulic conductivity, scc and scu are storage coefficients for the confined and unconfined conditions respectively and vl is vertical leakage. a recharge value of 1.25 mm/day was estimated using a water balance model (hess, 1997). this is equivalent to 50 mm of recharge per annum. this amount is consistent with independent estimates by carter et al. (1994) and edmonds et al. (2002). the recharge was applied to rows 29 to 33 and in stress periods 32 to 35 inclusive. figure 7 shows an extract of the finite difference grid area of interest and the recharging zone. these stress periods correspond to 10th –19th september to 10th –19th october respectively when recharge is believed to occur. azojete vol. 4 2004 57 figure 7: finite difference grid of area of interest showing recharge area the outputs from the model consisting of groundwater heads for each of the 86 stress periods were used for calculation of the various flow processes. the river to aquifer flow is calculated using equation 1. qriv= criv x hdiff (rushton and tomlinson, 1979). 1 where criv is the river coefficient and hdiff is the relative head difference between water level in the river and the groundwater head in the aquifer. 3. results and discussion 3.1 the groundwater hydrographs the modelled groundwater hydrograph for node (27, 2) compared with a field observed groundwater head variation from piezometer p7 is shown in figure 8 for an area located near and to the south of the river. this area was conceptualized to be largely unconfined. the figure suggests a strong influence of the river on the groundwater compared with heads far away from the river node. the plot also suggests a good measure of representation of the groundwater level fluctuation taking place in the vicinity of the river. a side-by-side comparison of the modelled groundwater heads far from the river with piezometers located at similar distances is indicated in figure 9, but in the largely confined north, the modelled groundwater hydrographs show little variation near or far from the river. groundwater modelling with limited data: a case study of yobe river basin, north east nigeria 58 figure 8: observed and modelled groundwater heads for node (27, 2) mald = meters above local datum figure 9: groundwater heads at 600 m south of the river; (a) modelled, (b) observed mald = meters above local datum 3.1 groundwater flow in the aquifer the various groundwater flows in the aquifer were calculated from the groundwater heads using darcy’s law and the richard’s continuity equation. figure 10 shows the flow from the modelled heads at node (33,2), 637.5 m from the river 35 36 37 38 39 23 28 33 38 43 48 stress periods (10 days length) w at er le ve ls (m a ld ) 30th oct observed hydrogrph of p6, 600 m from the river 35 36 37 38 39 04/06/98 12/09/98 21/12/98 31/03/99 date w at er le ve l ( m a ld ) 31st oct azojete vol. 4 2004 59 aquifer (node 25, 2) beneath the river to adjacent nodes north and south of the river. the results show that the flow to the confined north is much smaller than the flow to the unconfined south. similar results are shown in figure 11 where nodes (17, 2) and (32, 2) are located 637.5m away from the river in both directions. the figure suggests that the model has the ability to exhibit the rapidity and inertia of the confined and unconfined conditions obtained in the north and south of the basin respectively. figure 10: groundwater flow from the aquifer to the north and south of the river node (25, 2) groundwater modelling with limited data: a case study of yobe river basin, north east nigeria 60 figure 11: groundwater flow from the aquifer to nodes (17, 2) and (32, 2), 637.5 m away from the river 3.3 river-aquifer flow the modelled groundwater heads at the river node together with the input river stage and river coefficient were used to calculate the river to aquifer flows. figure 12 shows the flow with positive values indicating flow from river to aquifer. the result indicates that the river is adequately represented because the aquifer responded to changes in the river level. it also shows that during recharge, the flow to the aquifer decreases even at high river level. this suggests that qriv is limited both by the ability of the aquifer to transmit water and the magnitude of hdiff. 3.4 the water balance the water balance consists of the difference between the total water flowing into the aquifer and the total water coming out of it. this is in turn equal to the change in storage. the inflow consists of recharge (the ‘leakage’ through low permeable surfaces) and the river to aquifer flow. the outflow consists of the flow from the aquifer to river during low river stage and the boundary outflow. figure 13 shows the time series plot of the water balance for one year. it indicates that the river to aquifer flow dominates all inflows (about 70%) to the model area. 4. conclusion the basic and exploratory single layer model has demonstrated the ability to simulate adequately the observed field data. it also reflected the physical processes presented in its conceptualization. despite uncertainties in the estimates of some parameters such as river coefficients and aquifer parameters, the similarity between the model results and observed ground water flow at 673.5 m from the river -400 -300 -200 -100 0 100 200 300 400 20 25 30 35 40 45 50 55 60 stress period (10 days long) fl ow (m 3/ d) node 33,2 node 17,2 azojete vol. 4 2004 61 data is encouraging. the model was able to demonstrate that in confined areas, less water enters the aquifer and there is immediate response to changes in the application of stress when compared to the unconfined areas. the results from the model are plausible and represent to some extent the understanding incorporated in its conception. references alkali, a.g. (1995). river-aquifer interaction in the middle yobe river basin, northeast nigeria. unpublished phd thesis. silsoe college. anderson, m.p. and w.w. woessner (1992). applied groundwater modeling: simulation of flow and advective transport. academic press, inc., san diago,ca. 381pp. carter, r.c., e.d. morgulis, j. dottridge and j.u. agbo (1994). groundwater modelling with limited data: a case study in a semi-arid dunefield of northeast nigeria. quarterly journal of engineering geology, 27: s85-s94. carter, r.c. (1998). prospects for sustainable water management policy in sub-saharan africa, with special reference to the northeast arid zone of nigeria. in water resources management, a comparative perspective. ed. dhirendra k. vajpeyi. carter, r.c. and a.g. alkali (1996). shallow groundwater in the northeast arid zone of nigeria. quarterly journal of engineering geology. 29: 341-355. diyam consultants. (1987). kano state shallow aquifer study. final reports vol. 1. kano, nigeria. edmunds, w.m., e. fellman, i.b. goni and c. prudhomme. (2002). spatial and temporal distribution of groundwater recharge in northern nigeria. hydrogeology journal 10:.205-215. hassan, m. (2002). exploratory groundwater modelling in data-scarce environments: the shallow alluvial aquifer of river yobe basin, north east nigeria. unpublished phd thesis cranfield university uk. hassan, m. and r.c. carter (2004). development of conceptual model: towards developing a numerical groundwater model of a river-aquifer interaction. nigerian journal of physics. 16(1) 117-125 hess, t.m. (1997). balance a soil water balance model manual. unpublished, cranfield university, uk. hess, t.m., w. stephens and u.m. maryah. (1995). rainfall trends in the north east arid zone of nigeria, 1961-1990. agricultural and forest meteorology,74: 87-97. iwaco (1985). study of the water resources in the komadougou yobe basin. report no. 5. groundwater resources. international water supply consultants. rotterdam, netherlands. marinof-petkoff, m.n. (1994(. a geomorphological study of the yobe river floodplain: implication for groundwater recharge. unpublished msc. thesis. cranfield university. mcdonald, m.g. and a.w. harbaugh, (1987). a modular three-dimensional finite-difference groundwater flow model. techniques of water resources investigations. 06-a1, us geological survey, reston, virginia, 576p. neazdp (1990). groundwater resources report. pmu, northeast arid zone irrigation project. garin alkali, gashua. yobe state, n.e. nigeria. rushton, k.r. and l.m. tomlinson (1979). possible mechanisms for leakage between aquifers and rivers. journal of hydrology. 40: 49-65. groundwater modelling with limited data: a case study of yobe river basin, north east nigeria 62 shultz international limited. (1975). hadejia river basin study. water resources vol. e. vancouver, canada. spitz, k. and j. moreno (1996). a practical guide to groundwater and solute transport modeling. john wiley and sons, inc. new york. wang, h.f. and m.p. anderson (1982). introduction to groundwater modelling: finite difference and finite element methods. academic press. san diago water surveys group (1986). investigation of the shallow aquifers for lowland irrigation in bauchi state. n.e. nigeria. main report, vol. 1. kaduna nigeria. groundwater modelling with limited data: a case st abstract 1. introduction 2. methodology and model preparation references arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):527-540 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 527 original research article modelling combustion characteristics of some selected nigerian coal samples j. v. mshelia1*, y. s. sanusi1, y. ibrahim2 and h. a. dandajeh1 1mechanical engineering department, faculty of engineering, ahmadu bello university, zaria, nigeria 2nigerian college of aviation technology, zaria, nigeria *corresponding author’s email address: victor_jummai@yahoo.com 1.0 introduction for decades, coal has been fundamentally utilized for power generation, steel and cement production, and other industrial procedures. interestingly, there is other significant importance of coal such as alumina processing plants, paper making firms, synthetic and pharmaceutical ventures (wca, 2020). the utilisation of coal has been highly linked to power generation (wrigley, 2013). study has shown that the effectiveness of power generation from ordinary pulverised coal plant ranges from 35-40% (na et al., 2015). in addition, most of the power plant stations use steam turbines in which high pressure steam generated from pulverised coal boilers, turn the turbine that drive generators. several coal deposits that are yet to be harnessed for power generation can be found across nigeria. the utilisation of the coal deposits for power generation could solve the present and future electricity demand in nigeria (ocheri et al., 2017). nigerian coal is of the bituminous type characterised by low article information abstract coal is one of the most abundant fossil fuel which could be utilized for electricity production using different techniques. the pulverization technique is considered in this study which involves coal combustion to release heat which can be utilised to generate steam. grinding and drying are prior combustion processes that increases rate of reaction during combustion. this study determines the thermodynamics characteristics of coal combustion using the pulverization technique for five nigerian coal samples (odagbo, owupka, ezimo, amansiodo and inyi coal). a process based model was developed using aspen plus for a coal power plant. the mass balance and energy balance equations for the plant components was used. emission from coal combustion was determined at different equivalence ratios of 1, 0.7, 0.5, 0.4 and 0.3 respectively. it was observed that excess air supplied reduces emissions and there is a trade-off of combustion temperature. also, the amount of ash released is independent of the equivalence ratio. from results obtained, at stoichiometry, owupka coal sample has the highest combustion temperature of 2005ºc and the least ash production of 1.3kg/s while inyi coal has the least combustion temperature of 1779ºc and the highest ash production of 18.8kg/s. therefore, owupka coal is recommended for use as it has the highest efficiency when used in combustion. also, to improve the efficiency of inyi coal sample, it is recommended to be mixed with high efficiency coals like owupka. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 february., 2022 revised 26 april, 2022 accepted 30 april, 2022 keywords: thermodynamics analysis aspen plus nigerian coal samples pulverised coal coal combustion http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com mailto:victor_jummai@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 528 thermoplastic, sulphur and ash content (chukwu et al., 2016). these properties made it suitable for boiler fuel, production of high calorific gas, domestic heating, briquettes, formed coke and chemicals manufacturing like waxes, resins, adhesives and dyes. these additional properties have also made nigerian coal ideal for coal-fired power plants (isaac et al., 2013). according to varella (2020), nigeria has a population of approximately 206 million individuals, but is faced with the challenge of inadequate and constant electricity supply. accessibility to electricity in the rural and urban areas is about 35% and 55% respectively (iyiola, 2018). the rise in electricity demand most especially in households will be due to growing urbanization and population growth. arising from the recent recession, it is expected that the industrial and commercial demand in nigeria will increase (iyiola, 2018). nigeria, having a 12,500 mw of installed generation capacity, depends, mainly on hydropower and fossil (gas) thermal power sources with 12.5% and 87.5% of production respectively (olatunji et al., 2018). the actual generation available for final consumers’ ranges between 3,500 mw to 5,000 mw (okubanjo et al., 2020). however, the non-availability of gas to power plant is the major factor responsible for idle power generation plant. it is deemed necessary that government should explore other alternatives to ensure stable electricity such as renewable resource and coal to power projects (rosen and dincer, 2003). for instance, government has put a number of programmes to attract companies in developing large coal to power generation and domestic use. nigeria, having a goal to revitalise the coal mining industry and expand power generation by attracting companies to develop these large coal deposits for power generation and domestic use (isaac et al, 2013). energy mix using other available resources for power generation will help in meeting the energy demands of nigeria. this is achievable by exploring other energy sources like coal to achieve stability in energy supply for the country (uzoma et al, 2012). review on other studies shows that works on coal efficiency and thermodynamics as well as emission control of coal power plants were carried out using different methods but the type of coal in used was not specified. however, coal from different countries has different compositions. coal’s composition determines the emission released from its combustion which depends on its location of formation. nigeria coal deposit considered in this study includes benue (owupka), kogi (odagbo), and enugu (ezimo, amansiodo and inyi) coal deposits. combustion and emission characteristics of these coal samples have not been well documented. consequently, this work studies the combustion and emission characteristics (thermodynamics properties) of some selected nigerian coal samples. this was achieved by using aspen plus. simulation of all processes prior to combustion such as grinding and drying was also reported. 2.0 methodology 2.1 coal samples five nigerian coal samples from odagbo (kogi state), owukpa (benue state), ezimo (enugu state), amansiodo (enugu state), and inyi (enugu state) of estimated reserves deposits of 250, 75, 156, 1000, and 50 million tonnes respectively was used in this study. proximate analysis, ultimate analysis and calorific value as presented by chukwu et al. (2016) were used in this study. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com https://www.cia.gov/library/publications/the-world-factbook/fields/2212.html https://data.worldbank.org/indicator/sp.pop.grow mshelia et al: modelling combustion characteristics of some selected nigerian coal samples. azojete, 18(3):527-540. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 529 2.2 system modelling and simulation procedure the thermodynamic analysis of a coal power plant as shown in figure 1 was carried out using a computer code developed by aspen for five (5) nigerian coal samples in this study. all calculations were carried out for ideal conditions. all processes were assumed to be at steady state and steady flow conditions. aspen plus stores the estimation methods (calculations) in what is called a “property method”. the property method is classified into: ideal property method, equation of state, activity coefficient, and special systems like solids (al-malah, 2016; haydary, 2019). this property method was used to calculate the thermodynamic properties of the coal which includes fugacity, enthalpy, entropy, gibbs free energy, and volume; and transport properties which include viscosity, thermal conductivity, diffusion coefficient, and surface tension properties for the combustion fluid. the combustion of coal using the pulverization technique was modelled using aspen plus (getting started modelling processes with solids). figure 1 shows the schematic diagram of the coal power plant. the processes for this study are grinding, drying and combustion. the major plant components considered in this study is the combustion chamber. cr –crusher c combustor dr dryreactor sp – seperator dfdry flash decompdecomposer figure 1: schematic diagram of the considered coal power plant. 2.3 coal grinding in modelling the grinding/crushing operation, the particle size distribution for all the coal samples was carried out using the rosin-rammler-sperling-bennet (rrsb) and the normal distribution function. this model depicts the grinding and screening operation of the coal in which the particle size is independent of the coal sample but depends on the model used. from figure 1, stream 1-2 was considered for the grinding process. coal was supplied at normal temperature and pressure (25oc, 1 atmosphere) to the crusher/pulverizer (cr). the input parameters used was an equidistant user specified particle size distribution (psd) meshes of 0 to 10 lower and upper limit, and a maximum size unit of 2mm. http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 530 the energy (e) required by the crusher is given in equation (1) and its efficiency (η) in equation (2). e = kb ( 1 √d2 − 1 √d1 ) (1) η = energy required total energy supplied (2) where: e = energy per unit weight, kb= bond’s work index, d1 = initial particle diameter, d2 = final particle diameter 2.4 coal drying from figure 1, streams 2-5 shows the modelling of the drying process. the temperature of air supplied for drying coal and its mass flow rate determines the amount of water removed from coal. coal samples contains moisture which must be removed before combustion; else part of the heat of combustion will be converted to remove the moisture content thereby lowering the combustion temperature and burner efficiency (maurellis and tennyson, 2003). coal from the grinding process is mixed with air in this process. dry air was supplied at 150oc and 1 bar (stream 6) with a mole fraction of n2 0.999, o2 0.001 as given in equation (3). in drying and combustion process, the reactor uses the mass balance equations (equation 4). 𝑤𝑒𝑡 𝑐𝑜𝑎𝑙 + 𝐴𝑖𝑟 → 𝑑𝑟𝑦 𝑐𝑜𝑎𝑙 + 𝑤𝑒𝑡 𝑎𝑖𝑟 (3) (𝑤𝑒𝑡 𝑎𝑖𝑟 = 𝐻2𝑂 + 𝐴𝑖𝑟 ) (∑ niji ) in − (∑ nikk )out + (∑ vinξinn )r = 0 (4) where ∑ vinξinn = ni,in − ni,out where: n = mole flow, v = volume, r = gas constant, ξ = molar volume 2.5. combustion in this study, the combustion process was modelled using aspen plus as shown in figure 1 from stream 5 to 12. coal from the drying process was decomposed (stream 5-8) using decomp before it was combusted. decomposition involves coal disintegration into its constituents before combustion. air was supplied at normal temperature and pressure at different equivalence ratio. from this study, it was observed that the coal’s combustion exit temperature was determined from the input values of the heat of combustion, mass flow rate of air required for combustion, utanal and proximal analysis values as well as prior calculations to combustion. figure 1 shows that decomposed coal was burnt to gases and solids in the combustor (com). the combustion products are separated in the sp. stream 12 is the gas product while stream 11 is the solid product (ash). the equivalence ratio for the combustion of the five coal samples was calculated using equation 5. the simulation temperature and the amount of gases released at the end of combustion depend on the mass flow rate of air supplied. the chemical formula for the coal samples was determined using the empirical formula and the balance equation was calculated file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com mshelia et al: modelling combustion characteristics of some selected nigerian coal samples. azojete, 18(3):527-540. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 531 to determine the mass flow rate of air at different equivalence ratio (ϕ) for the five coal samples. 𝐸𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑐𝑒 𝑟𝑎𝑡𝑖𝑜 (𝜙) = [ 𝐴𝑖𝑟 𝐹𝑢𝑒𝑙 ] 𝑠𝑡𝑖𝑜𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑖𝑐 [ 𝐴𝑖𝑟 𝐹𝑢𝑒𝑙 ] 𝐴𝑐𝑡𝑢𝑎𝑙 (5) ϕ ˂ 1 (lean mixture excess air is supplied) where the fuel is completely combusted. ϕ ˃ 1 (rich mixture less air is supplied) contains an excessive proportion of fuel after combustion. in aspen plus, the heat of combustion (hcomb) is calculated on a dry basis using equation 6. the energy balance for steady decomposition state was computed using gibbs energy (go) for steady and equilibrium reactions given in equations 7 9. the rate and heat of reaction in the combustion chamber (gibbs reactor) was calculated using the power law (equations 10 and 11) and the yield is calculated using equation 12. hcomb = heat of combustion (wet)* 100 (100−% 𝑚𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝑐𝑜𝑛𝑡𝑒𝑛𝑡) (6) (∑ nij)in − (∑ nij)out + ∑ ∆rhnξn + q + w = 0 (7) ∆rgo = ∆rgo + rtlnke (8) the equilibrium constant is given as ke = ∏ (ai vi)i gmix = ∑ xigi + rt ∑ xilnxi (9) r = k ( t tref ) ∝ exp [− e r ] ( 1 t − 1 tref ) ∏ ci σi n i (10) ∆hrxn = ∑ vihf o ,i (11) yield = amount of product produced amount of feed (12) where: n = mole flow, g = gibbs energy, r = gas constant, w = work, x=mole fraction k = constant, equilibrium constant, h = enthalpy, p = pressure, t = temperature, q = heat flow, e= activation energy, c=heat capacity ref= reference n=number of moles, ∝= the law’s exponent, ξ = molar volume, vi = stoichiometric coefficient (negative for the reactants and positive for the products). hf o = heat of formation for the reactants and products http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 532 3. results and discussion coal undergoes various processes before it produces heat. this includes grinding, drying, decomposition and combustion. the results obtained was considered for producing 300mwe for the coal samples used in this study. 3.1. grinding/crushing result shows that all the coal samples have the same weight fraction and cumulative weight fraction. this is because crushing is a component simulation and it is only concern with the psd at the outlet and not the thermodynamic properties of the coal when subjected to the same operation conditions. figure 2 shows the cumulative fraction in relation to the particle size for both the rrsb and the normal distribution functions. from the figure, for rrsb it can be seen that about 63% of the weight has less than 5μm particle size while for the normal distribution function, 50% of the total weight falls within this range. a significant difference was observed at 4μm particle size. for rrsb about 44% of its weight fraction ranges between 14μm while for the normal distribution only 15% of its cumulative weight falls within this range. this implies that the rrsb has a more uniformly distributed particle size than the normal distribution function. particles obtained using rrsb model were also observed to be finely grounded. finely ground coal has more surface area per unit weight than larger particles. this enables the combustion reactions rate to be faster, thereby reducing combustion time. this leads to high heating rates. grinding also helps to ease the drying process by allowing free flow of air into the grounded coal. therefore, rrsb was adopted in this study. 0 2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 c um m ul at iv e w ei gh t f ra ct io n particle size rrsb normal μm figure 2: coal particle size distribution the power consumption of the crusher is presented in figure 3. the power consumption for grinding each coal sample depends on the mass flow of coal used at a time. inyi coal has the highest mass flow of 67.85kg/s requires the highest power consumption of about 23kw while odagbo has the least value of 13.66kw. ezimo power consumption is 8% and 3% higher than owupka and amansiodo coal. this implies the quantity of coal to be grinded determines the amount of power consumption. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com mshelia et al: modelling combustion characteristics of some selected nigerian coal samples. azojete, 18(3):527-540. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 533 odagbo owupka ezimo amansiodo inyi 0 5 10 15 20 25 p o w e r c o n s u m p t io n ( k w ) figure 3: power consumption of the crusher 3.2. drying the thermodynamic properties of coal before and after drying were considered in this study. figure 4 shows the mass of air per unit mass of coal required to completely remove the moisture for all the coal samples. coal drying improves plant performance and reduces emission. from the figure, odagbo coal having the highest moisture content requires the highest air mass flow of 3.27kg/s while inyi coal requires the least of 0.9kg/s to dry a unit coal sample. the amount of air required depends on the moisture content in each coal sample. odagbo owupka ezimo amansiodo inyi 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 k g o f a ir / k g o f c o a l air supplied for drying figure 4: air mass flow for drying the amount of thermal energy required for drying was calculated for each coal sample as shown in figure 5. as expected the heat supplied decreases with coal’s moisture composition. however, the heat supplied also depends on the mass flowrate of coal, heat capacity and temperature of air supplied. odagbo coal requires the highest heat supply because of its high moisture content. inyi coal requires about 103 kw higher than amansiodo. this is because of its high coal mass flow compared to all the coal samples. this implies cost of utilities for the plant increases as heat supplied increases. http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 534 odagbo owupka ezimo amansiodo inyi 0 500 1000 1500 2000 2500 3000 h ea t en er g y (k w ) energy required for drying figure 5: heat required for drying coal samples figure 6 shows the coal exit temperature after drying. the temperature ranges between 36ºc and 38ºc. the coal water vapour determines the exit temperature (maurellis and tennyson, 2003). this implies the higher the water vapour the higher the coal temperature. odagbo has the highest water vapour of 6 kg/s released because it has the highest moisture content and a high temperature of 38.1ºc. while inyi has 2.6 kg/s water vapour and has the least temperature of 36.7ºc. 38.1 38.3 37.4 37.1 36.7 odagbo owupka ezimo amansiodo inyi 0 5 10 15 20 25 30 35 40 t e m p e ra tu re (o c ) figure 6: coal exit drying temperature figure 7 shows the mass of coal before and after drying for all the coal samples. it was observed that there is a decrease in the amount of coal after drying. odagbo coal has the highest decrease of 15% of its actual mass flowrate while inyi coal has the least decrease of 4% of coal supplied before drying. the inherent moisture for coal samples determines the decrease after drying. this should be considered as it affects the coal’s combustion output. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com mshelia et al: modelling combustion characteristics of some selected nigerian coal samples. azojete, 18(3):527-540. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 535 odagbo owupka ezimo amansiodo inyi 0 10 20 30 40 50 60 70 m a s s o f c o a l (k g /s ) mass before drying mass after drying figure 7: coal mass for drying 3.3. combustion the simulated results for combustion at different equivalence ratio (ϕ) (air/ fuel ratio) in relation to the total gas emitted are presented for all the coal sample. figure 8 shows the combustion temperature at different equivalence ratio (ϕ). it shows that temperature decrease as excess air is supplied. furthermore, it was observed that at stoichiometry (ϕ = 1) each coal samples has its highest combustion temperature for all the coal samples. owupka coal sample has a temperature of 2005oc while inyi coal has the lowest value of 1779oc. this temperature decreases as excess air is supplied for all the coal samples. this is expected and it is due to the cooling of the combustion product by the excess air supplied. owupka has a temperature of 847oc while inyi coal has the least at 586oc when air is supplied at 0.3 equivalence ratio (ϕ). the difference in temperature at the same equivalence ratio (ϕ) can be attributed to their respective calorific/heating values, ultimate and proximal composition. the temperature values implies the amount of heat energy released during combustion. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 600 800 1000 1200 1400 1600 1800 2000 equivalence ratio (ɸ) odagbo owupka ezimo amansiodo inyi temperature oc figure 8: coal combustion temperature http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 536 figure 9 shows the amount of ash released during combustion for all the coal samples at different equivalence ratio (ϕ). the amount of ash produced is independent of the equivalence ratio (ϕ) but depends on the proximal composition of ash in each of the coal samples. inyi coal has 30.4% proximal composition and therefore produces the highest amount of ash. for the 300mwe plant, inyi coal produces about 70 ton/hr while owupka coal produces approximately 4.7 ton/hr. high ash content lowers the heating value and combustion temperature. this implies high handling cost for ash in an inyi coal based plant. odagbo owupka ezimo amansiodo inyi 0 10 20 30 40 50 60 70 a s h (t o n / h r ) figure 9: ash produced emission from coal combustion depends on its composition and mass flow of air during combustion. figure 10 show nox emission at different equivalence ratio (ϕ). emission of nox has both environmental and health hazards. nox forms smog and acid rain. high concentrations causes air pollution which are harmful to both plant and animals respiratory organs when inhale directly. nox emission is highest at stoichiometry and reduces to zero as excess air is supplied. from figure 10, decrease in ϕ decreases the temperature as high temperature has been reported to be favourable to nox formation (miller, 2011). at stoichiometry (ϕ=1), amansiodo produces the highest nox emission of 5115.7ppm of total gas emission while inyi coal produces 1267.3ppm of the emitted gases. inyi coal has the lowest nox released during combustion while odagbo and owupka coal have close emission values at different equivalence ratio (ϕ). 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 0 1000 2000 3000 4000 5000 6000 n o x e m is s io n ( p p m ) equivalence ratio (ɸ) odagbo owupka ezimo amansiodo inyi figure 10: nox emission file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com mshelia et al: modelling combustion characteristics of some selected nigerian coal samples. azojete, 18(3):527-540. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 537 figure 11 shows the co released at different equivalence ratio (ϕ). co is formed when there is no enough air for complete combustion. high concentrations of co causes air pollution which attacks the respiratory organs and blood haemoglobin. it is also one of the green-house gases that affect the ozone layer. the amount of co released depends on the amount of air (ϕ) supplied and the available carbon during combustion. at ϕ = 1, co has its highest value for all the coal samples. this is because not all the available carbon is completely combusted to co2 at ideal stoichiometric conditions. at stoichiometry (ϕ =1), odagbo and owupka coal samples have similar emissions and produces the highest amount of co while inyi produces the least co at all equivalence ratio values. at ϕ=0.7, co converges to approximately zero for all coal samples. it was observed that co reduces to zero as ϕ reduces for all the coal samples. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 0 2000 4000 6000 8000 10000 c o e m is si on (p pm ) equivalence ratio (ɸ) odagbo owupka ezimo amansiodo inyi figure 11: co emission figure 12 shows the co2 emitted at different equivalence ratio (ϕ). there is an increase in co2 emission as ϕ decreases. co2 is formed when complete combustion of carbon in air occurs. the co2 emitted depends on the available carbon and oxygen (o2) during combustion. excess air supplied converts all the available carbon to co2. for odagbo, owupka, ezimo and amansiodo coal samples, co2 produced is independent of the equivalence ratio (ϕ) from ϕ = 0.3 to ϕ = 0.7 beyond which there is an observed reduction of co2 with increase equivalence ratio (ϕ). this depicts that when ϕ ˃ 0.7, the carbon in the coal could not be completely combusted leaving co emission as observed in figure 11. for inyi coal, co2 emission is independent of the equivalence ratio (ϕ). this implies that at all equivalence ratios (ϕ), carbon (c) is combustion to co2.this is because of its low carbon composition. at all ϕ values, odagbo coal sample has the highest co2 emission while owupka coal sample has emission values similar to amansiodo. inyi coal has the least co2 emission at all ϕ values. co2 causes ozone layer depletion when emitted in high concentrations to the environment thereby causing global warming. http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 538 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.6 1.8 2.0 2.2 2.4 2.6 c o 2 e m is si on (k g of c o 2/k g of c oa l) equivalence ratio (ϕ) odagbo owupka ezimo amansiodo inyi figure 12: co2 emission figure 13 shows the sox emitted at different equivalence ratio (ϕ) for the different coal samples used for this study. all samples have sulphur composition. the amount of sulphur emitted during combustion depends on its ultimate percentage composition and the reaction of sulphur with available o2 in air. emission of sox has both environmental and health implications. in animals, it causes respiratory disease by reducing lungs functions and other respiratory diseases. in plants, it causes visible injury like losing foliage, becoming less productive and may cause death (world bank group, 1999). at equivalence ratio of one (ϕ =1), high emission values of sox compounds are produced which reduces as excess air is supplied. odagbo, ezimo and inyi coal samples have negligible sox emission at all ϕ values. this is because their ultanal composition of sulphur is low. owupka coal produces the highest sox compound which reduces at lower values of ϕ when excess air is supplied. amansiodo coal also produces sox gas but less than that of owupka coal. the sox in relation to the total gas emission reduces to nearly zero as equivalence ratio (ϕ) reduces. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 s o x e m is si on (p pm ) equivalence ratio(ɸ) odagbo owupka ezimo amansiodo inyi figure 13: sox emission 3.5. validation to validate the results obtained, the operational conditions of a 210 mw coal power plant in north india as presented by kumar et al. (2019) was modelled using aspen plus. results obtained for the combustion (table 1) show similar values with those presented by kumar et al. (2019). from results, it shows the same mass flow of coal was used to produce the same power output. the plant efficiency was however over predicted by 3.91% when compared to file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com mshelia et al: modelling combustion characteristics of some selected nigerian coal samples. azojete, 18(3):527-540. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 539 the result of kumar et al. (2019). this implies aspen plus gives a good prediction of an existing plant and its combustion characteristics. table 1: comparison of computed results using aspen plus and kumar et al, (2019) description kumar et al. (2019) present study % difference mass flowrate of coal (kg/s) 30.55 30.55 0 net efficiency (%) 35 36.37 3.91 coal combustion temperature (ºc) approximately 2000 2005 1779 falls within the range of coal combustion temperature 4.0. conclusion this study models the combustion characteristics of five nigerian coal samples using the pulverisation technology in aspen plus. the rrsb and normal distribution methods were considered when simulating the grinding process. the energy required to dry the coal samples depends on the coals moisture content. for example, odagbo which has the highest moisture content of 14.9% requires 2800kw to dry. the emission analysis from coal combustion shows that during combustion, the coal’s combustion temperature and the emitted gases like co, co2, so2 depends on the equivalence ratio (ϕ) while ash production is independent of the equivalence ratio (ϕ) but on the coal’s proximal content. it was also observed that at ϕ=1, greenhouse gases emitted were high which reduces as excess air was supplied. owupka coal is recommended for use because of its high efficiency when compared to the other samples used in this study. inyi coal has the least temperature of combustion at all values of ϕ, highest coal mass flowrate and ash production compared to the other coal samples. reference al-malah, ki. 2016. aspen plus: chemical engineering applications. john wiley and sons, inc. hoboken, new jersey. pp 1-406. ackermann, ro., aggarwal, s., dixon, jr., fitzgerald, ad., hanrahan, dc., hughes, ga., kunte, a., lovei, m., lvovsky, k. and somani, a.h., 1999. pollution prevention and abatement handbook 1998: toward cleaner production. burnard, k. and bhattacharya, s. 2011. power generation from coal: ongoing developments and outlook. iea energy papers, no. 2011/14, oecd publishing, paris, https://doi.org/10.1787/5kg3n27ts06b-en. chukwu, m., folayan, co., pam, gy. and obada, do. 2016. characterization of some nigerian coals for power generation. journal of combustion, article id 9728278, p.11, http://dx.doi.org/10.1155/2016/9728278. haydary, j. 2019. chemical process design and simulation: aspen plus and aspen hysys applications. john wiley and sons, inc. hoboken, new jersey. https://www.wiley.com/enus/chemical+process+design+and+simulation:+aspen+plus+and+aspen+hysys+application s-p-9781119089117 http://www.azojete.com.ng/ mailto:victor_jummai@yahoo.com https://doi.org/10.1787/5kg3n27ts06b-en https://www.wiley.com/en-us/chemical+process+design+and+simulation:+aspen+plus+and+aspen+hysys+applications-p-9781119089117 https://www.wiley.com/en-us/chemical+process+design+and+simulation:+aspen+plus+and+aspen+hysys+applications-p-9781119089117 https://www.wiley.com/en-us/chemical+process+design+and+simulation:+aspen+plus+and+aspen+hysys+applications-p-9781119089117 arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):527-540. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victor_jummai@yahoo.com 540 iyiola, oa., nneji, lm., mustapha, mk., nzeh, cg., oladipo, so., nneji, ic., ... and adeola, ac. 2018. dna barcoding of economically important freshwater fish species from north‐ central nigeria uncovers cryptic diversity. ecology and evolution, 8(14): 6932-6951. kumar, r., jilte, r., mayank, b. and singh, m. 2019. steady-state modelling and validation of a thermal power plant. advances in fluid and thermal engineering. new york, springer., pp. 511-519. https://link.springer.com/chapter/10.1007/978-981-13-6416-7_47 kumar, r. 2016. thermodynamic modelling and validation of a 210-mw capacity coal-fired power plant. iranian journal of science and technology, transactions of mechanical engineering, 40(3): 233-242. miller, bg. 2010. clean coal engineering technology. elsevier inc. amsterdam. maurellis, a. and tennyson, j. 2003. the climatic effects of water vapour. physics world, 16(5): 29. na, c., yuan, j., xu, y. and hu, z. 2015. penetration of clean coal technology and its impact on china's power industry. energy strategy reviews, 7: 1-8. ocheri, c., okafor, wc. and mbah, cn. 2017. revitalization of coal development in nigeria for industrial advancement. scifed journal of metallurgical science: 1: 1-9. odesola, if., samuel, e. and olugasa, t. 2013. coal development in nigeria: prospects and challenges. international journal of engineering application, 4(1): 64-73. olatunji, o., akinlabi, s., ajayi, o., abioye, a., ishola, f., mashinini, pm. and madushele, n. 2018. electric power crisis in nigeria: a strategic call for change of focus to renewable sources. iop conference series: materials science and engineering, 413: 012053. 10.1088/1757-899x/413/1/012053. okubanjo, aa., ofualagba, g., okandeji, aa., patrick, oo., alao, po., olaluwoye, oo. and olasunkanmi, go. 2020. a comprehensive review of of energy crisis in nigeria and the contributing role of renewable energy. science forum (journal of pure and applied sciences), 20: 284-299. rosen, ma. and dincer, i. 2003. thermo-economic analysis of power plants: an application to a coal fired electrical generating station. energy conversion and management, 44(17): 27432761. uzoma, cc., nnaji, ce. and nnaji, m. 2012. the role of energy mix in sustainable development of nigeria. continental journal of social sciences, 5(1): 21.https://cseaafrica.org/challengesand-interventions-needs-in-the-nigerian-electricity-supply-industry-nesi-2/ wrigley, ea. 2013. energy and the english industrial revolution. philosophical transactions of the royal society a: mathematical, physical and engineering sciences, 371(1986): 20110568 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:victor_jummai@yahoo.com https://cseaafrica.org/challenges-and-interventions-needs-in-the-nigerian-electricity-supply-industry-nesi-2/ https://cseaafrica.org/challenges-and-interventions-needs-in-the-nigerian-electricity-supply-industry-nesi-2/ 5 arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):662-670 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 662 design description of a tentacle based scanning system m. o. afolayan (department of mechanical engineering, ahmadu bello university, zaria, nigeria) corresponding author’s e-mail address: tunde_afolayan@yahoo.com abstract a design of a tentacle-based 3d object scanning device is presented in this work. the dimensions of the device were 15 ×15×20 cm and a maximum weight of model that can be placed on its platform is 500g. the design requires that two red laser for distance measurement by triangulation be installed on the left and right side of a charge coupled device (ccd) camera. the camera takes the reading as well. the 3d scanner body is made up of polymer matrix for rigidity and dimensional stability. the main mechanism for the scanner is a lead screw and a turntable both managed by national electrical manufacturers association (nema) 17 stepper motors. keyword: 3d, scanner, triangulation, reverse engineering, tentacle 1. introduction a three dimension scanner is a device that samples data on the shape and possibly the appearance (i.e. colour) of a real world object. the collected data can then be used to construct digital, three dimensional models useful for a wide variety of applications. for example, these devices are used extensively by the entertainment industry in the production of movies and video games. other common applications of this technology include industrial design, reverse engineering and prototyping, quality control, inspection and documentation of cultural artefacts (levoy et al., 2000; lee et al., 2001; zhang, 2003). an important part of the three-dimension scanning is data acquisition. data acquisition systems are constrained by physical considerations from a limited region of an objects’ surface. therefore, multiple scans of the surface are taken so as to completely scan a part. technology acquisition and industrial growth does not exist without first copying from existing models, then learning to build on it using available devices and materials. a 3d scanner is a way out in acquiring that knowledge. most commercial 3d scanners are beyond the reach of many, especially in a developing economy like nigeria. three-dimensional acquisition techniques differs in many aspects, including precision, scanning time and amount of required human interaction. another central aspect is the categories of objects that can be scanned by complexity and surface properties. three dimension scanning technology first came into prominence in the early 1990s, where it was used primarily by engineers for reverse engineering purposes (petrov et al., 1998). 1.1 technology used by scanners there are a variety of technologies for digitally acquiring the shape of a three dimension object. scanners use either contact or non-contact technologies. figure 1 shows a classification of the types of application used for acquiring the three dimensional data. 1.2 contact 3d scanners probes the object physically by touching it with a sensing probe – the tentacle. the object needs to be placed on a flat rotating plate. some objects that cannot keep to a desire posture are normally held in place with a fixture. arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):662-670. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 663 figure 1: classification of data acquisition techniques used in contact and non-contact approaches for three dimensional systems. a coordinate measuring machine (cmm) is an example of a contact three dimension scanners (ctdss). it is mostly used in manufacturing and can be very precise. the sample is usually placed on the machine while the scanner or robotic arm goes round the sample while taking measurements. it is usually advised to use this setup when the sample surface is hard and is not flexible. however, there are disadvantages using a contact three dimension scanner for delicate objects, even with hard surfaces because of their delicate finishing or parts which may be damaged if their issues like vibration. also cmm has the problem of modifying or damaging the object in contact with it during scanning process, especially when the material in contact with it has a soft texture. if the part that is being scanned has indentions that are too small for the probe head of the scanner, it will lead to inaccurate scan. cmms are also relatively slow compared to other scanning methods. physically moving the probe around the object being scanned is slow due to inertia. in contrast, an optical system like a laser scanner can operate at up to 500 khz (faxin et al. 2010). there are also external factors that affect the accuracy of a cmm which include temperature, vibration and humidity. other examples of (ctdss) are the hand driven touch probes used to digitize clay models in computer animation industry (faxin et al. 2010). 1.3 non-contact 3d scanners these can be further divided into two main categories, namely active and passive scanners. there are a variety of technologies that fall under each of these categories. apparently, the process of contact scanning might modify or damage the scanned object of which the consequence is very significant when scanning delicate or valuable objects. each method has strengths and weaknesses that require the data acquisition system to be carefully selected for the shape capture functionality desired. noncontact methods use light, sound, or magnetic fields to acquire shape from objects. in the case of non-contact methods, an appropriate analysis must be performed to determine the positions of the points on the objects surface. a brief description of each method is presented as follows: 1.3.1 magnetic field method: this method refers to magnetic resonance imaging (mri) and is good for scanning soft tissues (ares et al., 2014). data acquisition methods non-contact methods contact methods magnetic time-of-flight stereo analysis structured light interferometer laser triangulation acoustic optical c m m robotic arms https://en.wikipedia.org/wiki/coordinate_measuring_machine afolayan: design description of a tentacle based scanning system. azojete, 13(6):662-670. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 664 1.3.2 acoustic method: this method uses high frequency sonar source to measure the object surface depth. it has an inherent problem of being unable to discriminate features (tardos et al., 2002) as well as specula reflection (deniz and billur, 1999). 1.3.3 optical methods: this method includes the following: a. laser triangulation: using laser light to perform the scanning and depth of surface measurement. b. time-of-flight: the time-of-flight 3d uses method similar to that of acoustic scanner but using light source for the probing action. c. interferometers: using optical interferometer to measure surface distortion at a distance. the optical source is a monochromatic light source like laser. d. structured lighting: this method involves the projection of a known pattern onto the object being scanned. another device such as camera record and analyze the pattern deformation and use it to reconstruct its 3d. 1.4 general constraints of data acquisition techniques with non-contacting methods there are many practical problems with acquiring useable data (bardell et al., 2003; beraldin et al., 2003), the major constraints are: a. calibration requirements: systematic sensing errors can occur through lens distortions, non-linear electronics in cameras, and similar sources. any sensing must be calibrated so as to firstly, accurately determine parameters such as camera points and orientations, and secondly, to model and allow for as accurately as possible systematic sources of error. b. occlusion: this is the blocking of the scanning medium due to shadowing or obstruction of the rays by raised or sunken parts – see figure 2. this is primarily a problem with optical scanners. however, acoustic and magnetic scanners may also have this problem. figure 2 parts occlusion during ray tracing c. multiple views: error due to multiple views is introduced when acquired data has a registration problem; that is, the final result is a stitch of two or more scans (often oversized objects broken into pieces) and the result has problems of non-matching edges from consecutive scans intended to be stitched together. d. noise: noise can be introduced in a multitude of ways, from extraneous vibrations and specula reflections as the two common sources. 1.5 justification for this study as a developing nation, nigeria scientist needs to acquire and copy other existing technologies. the copying process is faster if the object can be captured in three-dimension (3d) and printed on a 3d printer. the scanning devices are often very expensive ($9,800 $39,800; https://www.artec3d.com/shop) and are often beyond the reach of many would be researchers, except government sponsored. a single station (or booth) of high resolution 3d capturing center can have more than 40 high grade slr cameras (single-lens reflex cameras) with each costing several thousand us dollar. arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):662-670. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 665 1.6 objective of the work the objective of this work is to present a design of a tentacle based scanning system which can be used for scanning objects with a dimension of 150mm (maximum length), width of 150mm, height of 200mm and weight of 500g (0.5kg). a tentacle based scanner measure the relative depth or height of points on an objects being scanned and stored this information in a preferred 3d file formats such as stl and 3xg. 2.0 materials and methods 2.1 design considerations the following were put into consideration in the design of the 3d scanner: 1. material: the consideration of the entire system includes the availability of the material, machinability, weight, size, mechanical properties and the environment in which the machine will be used. 2. compact design: the machine was designed to be portable (not requiring much space), easy to operate and safe. 3. cost of design and construction: this accounts for the cost incurred in the design and construction of the scanner. 4. flexibility: the scanner was designed to be rigid and fixed such that it does not bend during any scanning process and devoid of noise error. 2.2 description of the scanner system: the scanner structure (figure 3) consists of the following: 1. the frame, comprising of a horizontal platform and a vertical standing frame 2. the rotating mechanism, this includes the turntable, a stepper motor 3. the capturing devices, which includes the camera and two red lasers. 2.3 working principles of the scanner an object to be scanned would be placed on the turntable component and then rotated from angle 0° through to 360° by the stepper motor; so that all the sides of the object are scanned completely. a camera and two lasers attached to a power screw are placed on the vertical standing frame. the camera and lasers move up and down as the power screw is rotated. as the camera and lasers move up and down, the distance between the object and the camera is measured. the camera and lasers assembly move a specified distance for each revolution of the turntable. figure 3: exploded view of the scanner. afolayan: design description of a tentacle based scanning system. azojete, 13(6):662-670. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 666 2.4 construction materials polymer composite matrix material is to be used for the construction of the frame so as to achieve a dimensionally stable structure that would not introduce errors during the scan process. other reasons for considering the polymer matrix are its mechanical stability, low cost, good workability, high rigidity, light weight and has a good corrosion resistance. other materials are: i. the frame – this will be made up of 4mm to 5mm-thick sheet of polymer composite matrix for the horizontal base and the vertical beam ii. two national electrical manufacturers association (nema) 17 stepper electric motors; one for the lift screw and the other for the turntable iii. an stl-6303e charge-coupled device (ccd) camera iv. 2 class-1 red line diode lasers v. lift screw (a threaded rod – 250mm long, 4mm thread pitch, mean diameter of 10mm, outer diameter of 12mm vi. rotating turntable vii. assembly screws 2.5 design theory of some mechanical components of the scanner system the lift screw is fixed to the electric motor at the vertical end of the scanner system. the stepper motor will rotate the power screw in a clockwise and anti-clockwise directions. a nut is attached to the power screw which holds the platform for supporting the camera and laser diodes. the nut is fixed such that it does not rotate, but as the lift screw is rotated either clockwise or anti-wise direction, the nut moves up or down. the following mechanical behavious will be experienced while in operation: i. torque required to raise load by the lift screw (khurmi and gupta, 2005) (see figure 3) t = p × = w tan (α + ϕ) = w ( (1) ii. torque required to lower load by the lift screw (khurmi and gupta, 2005) (see figure 3) t = p × = w tan (α ϕ) = w ( (2) where: p = effort applied at the circumference of the lift screw (n), w = load to be lifted (n), d = mean diameter of the screw (mm), ϕ = is the friction angle (rad), α = helix angle (rad), μ = coefficient of friction of screw = tan ϕ. p = thread pitch (mm) tan = = 0.127 iii. torque required to overcome static friction (between the screw and the nut) t = p × + μw r where r = = average radius of the screw collar r1 = inner radius arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):662-670. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 667 r2 =outer radius iv. shear stress within the lift screw (khurmi and gupta, 2005) (see figure 3) τ(screw) = (3) v. shear stress on the nut (khurmi and gupta, 2005) (see figure 3) τ(nut) = (4) where: τ(screw) = shear stress in screw, τ(nut) = shear stress of nut, w = axial load on screw (n), 𝑛 = number of threads in engagement between them, 𝑡 = thickness or width of the screw thread (m), 𝑑c = core or root diameter of screw (m), do = major/ outer diameter (m) vi. efficiency of the lift screw-nut assembly tan ( (5) the following specification are intended for the lift screw and the nut; pitch (p) of the screw thread = 4mm and mean diameter (d) = 10mm, maximum diameter (do) = 12mm, coefficient of friction, between the screw and nut, μ = 0.15 (assumed value from khurmi and gupta, 2005). number of threads in engagement between the screw and the nut at any time (n) = 8, screw thread thickness (t) = 2mm. 2.6 description of the scanner components the scanner is a mix of a sensor made up of a charge coupled device (ccd) camera and two point light sources to be made up of 2 light emitting diodes (led) based red laser. 2.6.1 the ccd camera the sensory system will use a ccd camera. this camera will be equipped with lenses for focusing. the lenses design will have the possibility of being locked to reduce needs for regular calibration process. the camera would be placed in the middle of the two lasers to enhance the systems resistance to occlusion effects. 2.6.2 the laser two red line lasers will be attached to the left and right side of the ccd camera for distance measurement using triangulation. as the turntable rotates (figure 3), the laser is pulsed while the camera performs the data capturing. at the end of each measurement, the depth data, that is, the distance of the point under focus on the image to the ccd camera plane, can be calculated using lens law. the lens law (equation 6) implies that to get a well-focused image on the ccd camera plane, the relations must be obeyed. afolayan: design description of a tentacle based scanning system. azojete, 13(6):662-670. issn 15962490; e-issn 2545-5818, www.azojete.com.ng 668 = + (nave, 2018) (6) where: f = the focal length (m), s = distance of the object (m), s° = is the optical image distance where the theoretical sharpest image is formed (m). 2.6.3 stepper motor a stepper motor is recommended for this design; other motors such as servo motors are equally suitable. the national electrical manufacturers association (nema) nema17 stepper-motor is recommended because of its popularity. it is commonly used in household appliances, medical equipment, stage lighting devices, and in various industrial control applications. it has 0.15m 2 footprint, 5 mm shaft diameter and uses 12 v input voltage. this motor, like most stepper motors is a permanent magnet motor. it has high resolution– a full revolution requires 200 steps, while each step turns the shaft only 1.8° for a full step, or 0.9° in half-stepping mode. mosaic (2006). 2.6.4 bolts and nuts the bolts and nuts are used for fastening the scanner parts together for easy assembling and dismantling. they were chosen due to their availability, easy maintenance and low cost. 3 result and discussion the maximum load w, (the camera and laser) to be raised by the platform (figure 3) is estimated to be 2.5 kg using stl-6303e specification – sbig (2011). using the design specification and equations from section 2.4, the following results are obtained; i. torque that will be required to raise the camera and laser by the lift screw is 3.53n-mm ii. torque that will be required to lower the camera and laser by the lift screw is -0.28n-mm iii. torque required to overcome friction between the screw and the nut – platform is fixed to the nut and does not rotate is 30n-mm thus the total torque required to raise the load is 33.53 n-mm (3.53 + 30 n-mm) and the torque to lower the load will be -30.28n-mm (-0.28-30) – it is additive since friction opposes motion. iv. shear stress that will be experienced by the lift screw is 6.22 × 10-3 n/mm2 v. shear stress that will be experienced by the nut 4.14 × 10-3 n/mm2 vi. efficiency of the lift screw-nut assembly is ~45% for implementing the lift screw and nut, engineering plastics such as polyacetal and nylon which is essentially polyamid resin could have served because plastic materials are lightweight, non-rusting, quiet, and can be injection molded enabling low cost and large production, and they can operate without need for lubrication. the discouraging aspect of these materials is basically the lack of dimensional stability. the scanning operation requires very stable dimension and high precision in the face of fluctuating environmental temperature. an alternative material known for good dimensional stability is cast iron. there are four basic types of cast iron (white iron, gray iron, ductile iron, malleable iron) each with its own merits. white cast iron is recommended for the lift screw and its nut because of its high compressive strength, hardness, good resistance to wear etc (due to the presense of carbide in its microstructure). arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):662-670. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 669 the cost of implementing the designed scanner can be estimated as shown in table 1. this cost excludes the development of the firmware which is a major research work on its own. table 1: cost estimate of the scanner construction material 1 s/no description quantity unit price in naira total price in naira remark 1 nema 17 electric motor 2 5,500:00 11,000:00 2 laser light 2 550:00 1,100:00 3 lead screw and round nut 1 1,000:00 1,000:00 estimate 4 frame (fabricated) 1 5,000:00 5,000:00 estimate 5 camera 1 8,500:00 8,500:00 6 screws 20 20:00 400:00 7 power source (regulated) 1 2,500:00 2,500:00 8 arduino arduino uno r3 1 4,500:00 4,500:00 9 miscellanous 5,000:00 total 39,000:00 1 the other aspect is the firmware to run in the microcontroller. 4. conclusion and recommendation this work presents a design of 3d scanner that should be able to hand an object with frame volume of 150mm x 150mm x 200mm. a dual laser diode is incoporated into its design so as to eliminate occlusion. the laser diodes acts as the tentacle. they in conjuction with the ccd camera, measures the distances between the surfaces of the object being scanned and themselves (through triangulation) and save this information as the 3d data of the object. the firmware (the brain) of the system is hereby recommended for others to developed. the firmware design is a major work on its own and its implementation will determine how well the scanner will perform in real situations. references ares, m., royo, s., vidal, j., campderrós, l., panyella, d., pérez, f., vera, s., ballester, mag. 2014. 3d scanning system for in vivo imaging of human body. in fringe 2013; 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vol.3, 31-36 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng comparison of chemical contents of sheabutter extracted from locally designed machine and other extraction methods inegbenebor, a. i. 1 and a.o. inegbenebor 2 abstract as elemental contents of sheabutter play a vital role in various physiological and metabolical activities in the human body, it is necessary to compare the chemical contents of sheabutter extract from different procedures in order to identify the most important extraction procedure. sheabutter extracted using a locally developed machine was compared with the composition of extract from two other techniques using a soxhlet extractor and the traditional procedure. the result shows increasing recoveries of most of the elements on progressing to the design machine and soxhlet apparatus from traditional procedure. the chemical analysis results showed the amount of lead, mercury, manganese, iron, copper, calcium, iodine, magnesium and phosphorus present in the sheabutter. the amounts of ca, fe and pb are as high as 22.8 µgl -1 . this work also found that the levels of elemental composition in the extracts of 22.8 µgl -1 sheabutter from modern machine are more than those from the traditional extracting method of 16.2 µgl -1 . possible reasons and implication of those findings are discussed. 1. introduction sheanut grows on semi-wild medium size tree in the savannah zone where rainfall is not excessive. the tree begins to bear fruits at 12 – 15 years of age and reaches full bearing capacity at 20 – 25 years (koku, 1989). the fruit produces nuts which taste like pea. it is “egg-shaped” (oval), with stony hard nut containing considerable quantities of oil (shukla and pandey, 1982). the sheanuts are collected and stored for oil extraction. the outer coats of the nuts are removed by cracking and the seed kernel is roasted. both industrial and domestic uses of oil/fats have necessitated lipid research and the search for the best method of extraction. the design and construction of the sheabutter extractor was made with the view to improve the nutrients in sheabutter in terms of yield and quality of the oil extracted. the construction was made with available local raw materials (see figure 1). 1 department of chemistry, university of maiduguri, maiduguri. borno state. nigeria 2 department of mechanical engineering, university of maiduguri, maiduguri. borno state. nigeria comparison of chemical contents of sheabutter extracted from locally designed machine 32 insert figure 1 here azojete vol. 4 2004 33 according to inegbenebor and abdulkareem (1993), the main components of the design were: i the power screw which serves the dual purpose of a conveyor and squeezer or plasticizer. it is a left hand square thread with single start thread and has a lead equal to the pitch. ii the housing is a thin seamless walled cylinder. the ratio of the wall thickness (tw) to the cylinder diameter (dw) is the design criterion. iii an adjuster, which is made of many intermittently parts that include: washer, spring, fasteners and others. the adjuster moves to regulate the pressure in the housing. iv a cone which regulates the pressure within the housing by means of other adjuster accessories. after carefully working out the components of the extractor, cold rolled mild steel was selected for the components. the conditions of selecting such steel were based on its high yield and tensile strength and also its machinability, easy formability and weldability. bokhari and ahmed (1990) proposed a level of 20 off-pressure (pf) for groundnut oil extractor. this value is taken as the working pressure for the sheabutter extractor since sheanut is coarse in texture when compared with groundnut. according to shukla and pandey, (1982) and bokhari and ahmed (1990), sheanut contains 50 – 55% of sheabutter. in order to improve on the percentage of sheabutter from sheanut, inegbenebor and abdulkareem (1993) designed and constructed sheabutter extraction macine (figure 1). the designed machine was based on the principle of the traditional method (figure 2) of processing sheanut into butter. the traditional procedures of extraction of sheabutter are inefficient since only 25 – 27% of oil is extracted from the nut as reported by koku (1989). since the design and construction of the sheabutter extractor was made with the view to improve the nutrients in sheabutter, it is therefore necessary to compare the chemical analysis of the product of this machine with the product from other extractors such as soxhlet and the traditional method. the objective of this work was to compare the elemental composition of sheabutter extracted using locally designed machine with that extracted using other methods. 2. materials and methods extraction methods a (using a soxhlet extractor); b (using the designed machine) and c (traditional procedure) were employed to extract resin for chemical contents of sheabutter. dried sheanuts (20 g) were ground to a fine power and extracted with 1 dm 3 of water in the laboratory with soxhlet apparatus. the resulting brownish aqueous extracts were concentrated to about 500 cm 3 , and centrifuged to remove the fine precipitate, which had been formed. supernatant was shaken with ether (5 x 250cm 3 ). the ether fractions were bulked, dried over na2so4 and evaporated to dryness. twenty grams of semisolid product from the designed comparison of chemical contents of sheabutter extracted from locally designed machine 34 machine was dried in the oven at 750 o c for 24 hours. the dried semisolid was ground in fine power. the 20 g of semisolid (resin)from the traditional method (c) was obtained as described by inegbenebor and abdulkareem (1993). the roasted kernels were pounded to fine paste in a wooden mortar. water (1 dm 3 ) was added to paste and was subjected to heating. the floating oil was collected and further heated for pure butter. by this procedure, the percentage of the sheabutter obtained was not much. residues from extraction methods a, b and c were analyzed for there elemental contents. approximately 1.0 g of each of the powdered sheabutter was digested by dissolving in formaldehyde and concentrated h2so4 mixture (1:1, v/v) of 50 cm 3 . this mixture was heated with further addition of a mixture of hno3, hci and hcio4 in a 500 cm 3 flask. the heating continued for about 2 hours. the mixture was evaporated to 5cm 3 and together with the residue, it was taken up in 19 cm 3 of 2 m, hno3 and 30 cm 3 distilled water into 100 cm 3 volumetric flask. blank samples and standard solutions for various elements were similarly prepared. all samples were stored in plastic container in a refrigerator maintained at 4 o c prior to analysis. a flame emission spectrometer (fes) gallen kamp (fea 330) was used to determine the na, k and ca in the samples. phosphorus was determined gravimetrically as detailed in vogel (1978). the other elements were determined by atomic absorption spectrophotometry (aas) with 9 unicarm. airaropane and air/acetylene (ethyne) flames were respectively used in the fes and aas procedures. a standard calibration quantitative method was used in both procedures. plots of emission (fes) and absorbance (aas) readings were prepared for the known standard concentrations. the test elements were drawn from these concentrations of the relevant elements in the pulverized sheabutter. samples were obtained using their measured emission and absorbance value as the case may be. 3. results and discussion the results of the elemental determination of sheabutter extracts are given in table 1. it appears that the amounts of pb, mg and cd (16.50, 0.18 and 0.23 µg/l respectively) in the sheabutter extracted from traditional procedure differ significantly from those of soxhlet apparatus (20.88, 0.37 and 0.45 µg/l) on the basis of sample extraction procedures. the hg, mn, fe, cu, ca, p, ag, cr, na, ni and zn levels show similar differences between the results obtained from samples that were extracted using the designed machine and those obtained from samples that were extracted from soxhlet apparatus and the traditional procedures. in all cases, the pb, mn, fe, ag, co, na and zn levels obtained from samples extracted from the machine were higher than the corresponding values obtained from samples extracted from the other methods. the difficulty of formation of soluble residues from the traditional method of extraction may be responsible for the difference in the result. azojete vol. 4 2004 35 table 1: average contents of sheabutter extract using three different methods elemental content (µg/l) extraction method a b c pb 20.88 21.91 16.50 hg 0.07 0.05 0.03 mn 0.51 0.58 0.41 fe 19.72 22.80 16.16 cu 0.18 0.16 0.10 ca 23.42 22.69 18.31 mg 0.37 0.33 0.18 p 0.97 0.87 0.65 ag 0.31 0.35 0.29 cd 0.45 0.45 0.23 co 0.39 0.41 0.34 cr 0.08 0.08 0.05 na 0.68 0.70 0.55 k 0.21 0.19 0.20 ni 0.65 0.64 0.35 zn 0.23 0.25 0.19 the results show increasing recoveries of most of the elements from traditional procedure to designed machine and soxhlet apparatus. from the table, it is clear that losses of the elements were more than 15% in extraction methods a and c alone. bernas (1973; 1976) has reported on the use of high-pressure-decomposition vessels for the preparation of ininorganic and organic materials prior to elemental analysis by aas. the machine designed and fabricated by inegbenebor and abdulkareem (1993) and the soxhlet apparatus provide this highpressure-decomposition demand for sheanut extraction. majority of the in-field installations operating today including soxhlet apparatus are powered from a constant current source. the designed extractor used in this work is portable and is manually operated, and capable of being used where electricity may not be available. also, the method of preparation of the extracts from traditional procedure is probably responsible for the lower elemental compositions. 4. conclusion extraction using the designed machine with the use of high-pressure-decomposition vessels manually operated is more efficient for this purpose of extraction. consequently, extraction with the designed machine and laboratory machine (soxhlet) enables the extraction of higher levels of the elements of the sheabutter than the traditional procedure. this is due to highpressure-decomposition system, which is incorporated into the design of these machines. comparison of chemical contents of sheabutter extracted from locally designed machine 36 a knowledge of the elemental composition of the sheabutteris necessary for the industrial and domestic applications of the sheabutter. the work was able to show the level of elemental compositions in the extract of sheabutter using modern machines and traditional way of extraction. the traditional procedure should be improved in order to recover higher elemental compositions. references berns, b. (1973) acid pressure decomposition device for interference free aa analysis. .am lab 5(8) 41-43. berns, b. (1976) liquid pressure decomposition, recent application in soil, plant and cement analysis. .am lab 8 27-32. bokhari, m. h. and m. s. ahmed (1990). asean post production information processing factors affecting yield and quantity of mechanically espressed groundnut oil. journal of agricultural engineering research. 45, 31-43. inegbenebor, a.o. and h.a. abdulkareem (1993). design and construction of sheabutter extraction machine for rural areas in the developing countries. proceedings of first africa – usa international conference of manufacturing technology. lagos. koku, i.t. (1989). extraction and characterization of oil from sheanut. unpublished work. mechanical engineering department, university of maiduguri. shukla, s.d. and g.n. pandeywer, (1981). textbook of chemical technology. lagos. vogel, a.i (1978). a textbook of quantitative inorganic analysis including elementary instrument analysis. 5 th edition. elbs and longman, london. arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):231-242 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 231 original research article development of an improved acm scheme for mitigating earth-to-space propagation effects a. m. s. tekanyi*, r. m. idris, a. d. usman, m. z. abdullahi and e. e. agbon department of electronics and telecommunications engineering, ahmadu bello university zaria, nigeria *corresponding author’s email address: amtekanyi@abu.edu.ng 1.0 introduction satellite communication is a promising technology due to its ability to serve very large number of users with high data rate services. despite the large deployment of optical fibre links, satellite communication technology has been seen to dominate the telecommunication industry due to its inherent advantage of extremely long-distance communication. (jayadev, 2011). the geometric increase in user-demand for higher capacity satellite links has inspired satellite operators to operate in higher frequency bands, such as ka-band and above in order to accommodate the necessary data rates (leshan et al., 2016). the move to these higher frequency bands employs communications system designs which require the development of a link budget between the transmitter and the receiver. these designs provide an adequate signal level at the receiver’s demodulator to achieve the required level of performance and availability (pratt et al., 2003). satellite system performance of the link can be evaluated using bit error rate (ber) and carrier-to-noise (c/n) ratio. successful design of communication links involves many factors such as the various losses as well as antenna power and gain (kilcoyne et al., 2016). the communications links described are usually configured with a fixed data rate, a static modulation and/or coding scheme, and high link margins to accommodate communications during the worst-case scenario. this worst-case planning approach ensures that article information abstract satellite communication is a promising technology due to its ability to serve very large number of users with high data rate services. the communication link experiences propagation losses such as: path loss, atmospheric losses, rain fading, ionosphere effects (such as scintillation), and other effects which can greatly affect the received signal strength and close the link budget in the worst case. the design of future broadband satellite systems has to be done with the challenge of more complex traffic mix and these harsher propagation conditions which mitigate the performance of the communications link. link adaptation (la) has been used in satellite communications applications for evaluating the performance of an adaptive modulation system in the unique space-based propagation environment. despite the current research on improving satellite system performance, there is still a need to further develop a scheme that mitigates the effect of atmospheric impairments. this work develops an improved adaptive coding and modulation scheme that mitigates earth-to-space propagation effects. the scheme targets maximizing data throughput while staying below a bit error rate (ber) threshold so as to successfully mitigate link impairment in fixed communication systems. simulation of the work is carried out using matlab 2016b and system toolkit (stk) 11.3 © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 december, 2020 revised 26 february, 2021 accepted 4 april, 2021 keywords: free space loss throughput acm link budget ber tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 232 communications links are maintained during even the worst expected earth-to-space propagation effects (pratt et al., 2003). these propagation effects include path loss, atmospheric loss, attenuation due to rain, and ionosphere loss, among others. generally, a maximum ber is identified in a communications system and the link is designed to support that ber threshold (pratt et al., 2003). the effects of these propagation impairments degrade the received signal power and are detrimental to a communications link if the ber increases above the acceptable limit for the transmitting waveform as the error correction codes would no longer be able to resolve bit errors (kilcoyne et al., 2016). la is a broad term that encompasses many types of adaptation on the communications link. the technique often referred to as adaptive coding and modulation (acm) is a good way for the earth-to-space communications link to select the modulation scheme that adapts to the signal energy fluctuation to maintain a desired ber (sami et al., 2011). la is developed to track the channel variations, thus changing the modulation and coding scheme to yield a higher throughput. this is achieved by transmitting with high information rates under favorable channel conditions. (sami et al., 2011). la has been used in satellite communications applications, evaluating the performance of an adaptive modulation system in the unique propagation environment. some la satellite applications consider weather impairments, such as rain-fading in the higher frequencies of kaand ku-bands (cioni et al., 2008). this research work developed an improved acm scheme to mitigate earth to space propagation effects. the process of setting the international space station (iss) orbit is carried out using the stk. the parameters necessary for characterization of the communications link environment is gotten from the stk software. the applied stk parameters are given in table 1. the international space station (iss) orbit is easily loaded after searching the stk satellite database by common name. stk uses two line elements (tles) and the simplified general perturbations (sgp)-4 propagator to model the orbit. in the instant of the iss orbit, tle data and sgp-4 model are used to provide an accurate propagation routine. tles provide the position of an earth-orbiting object for a given point in time. from this data, a prediction routine, such as sgp-4, can be used to predict the position of the satellite at any point in time. link adaptation is a broad term for a technique that monitors a communications link and alters system parameters to meet certain conditions. the acm is a method for carrying out la analysis. accurate link budgeting improves the throughput of the communications link. in order to perform la analysis (using the acm method) as a function of bit error rate (ber), the estimated c/nis related to the received energy per symbol. this relationship is given in equation (1) as follows (kilcoyne et al., 2016): s o e c snr n n   (1) to measure the quality of the communication link, the probability of bit error is estimated. in this work, the adaptation algorithm has a major aim of increasing data throughput which is given in equation (2). the objective ber for data transmission on wireless channels is known to be 10-5. this is because the data transmission to the fight sdr is the main objective in this work, a selected ber threshold of 10-5(usman et al., 2018): arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 233   file size throughput bps ttransmission time  (2) a ber of 10-5implies that the receiver must receive on average 100,000 bits before one is in error. thus, an average of 10,000,000 bits must be received for 100 bits to be in error. in this work, all the schemes transmit a fixed symbol rate of 502 kbps. hence, at the lowest bit rate, the receiver required approximately 19.9s to measure the ber (kilcoyne et al., 2016). from simulation, the estimated time required for each modulation scheme to receive 100 errors, assuming a ber threshold of 10-5, is given in table 1. table 1: ber average time for each modulation scheme (kilcoyneet al., (2016) modulation scheme average time to receive 100 error bpsk 19.92s qpsk 9.96s 8psk 6.64s 16qam 4.98s 64qam 3.32s during simulation process, gray coding of all modulation schemes is assumed in order to keep each neighboring symbol differs by only one bit to check the ber probability, 0/be n is used to calculate the ber for bpsk and qpsk modulation schemes. the ber probability from the work of kilcoyne et al. (2016) is calculated as follows: 2 b b o e p q n         (3) whereq is the q-function of the transmitted signal from simulation, when comparing the performance of bpsk and qpsk using 0/be n , it appears that the required energy to maintain the same pb is identical. when the ber is written in terms of the modulated energy per symbol, a 3 db increase of signal energy is evident. the process of doubling the energy used in the modulation constellation as a result of using both the quadrature and in-phase channels rather than just in-phase of bpsk accounted for the generation of this 3db. table 2 shows the equations used in calculating the ber for each of the modulation schemes considered in this work. tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 234 table 2: theoretical ber equations for different schemes modulation schemes ber equations bpsk 2 b b o e p q n         mpsk 2 2 2 sin log s b o e p q m m n             mqam 2 4 1 3 1 log 1 s b o e p q m m nm                 to check the performance of the receiver and the quality of the received signal, error vector magnitude (evm). is used as a decision statistic for qpsk and 16-qam modes. the evm was measured by calculating the distance between the ideal and received symbols. the distance of the ideal symbol from the received symbol is the evm a variety of research has been carried out to mitigating earth-to-space propagation effects in satellite communications. these are as follows: sali et al. (2012) evaluated link adaptation mechanisms in a reliable multicast scenario, where the challenge lied in finding the optimal transmission rate to suit all terminals in the multicast group. from the simulation results, mla and min are shown to be the best link adaptation algorithms, in providing the highest user fairness and the highest throughput. the problem of this paper was that the channel conditions experienced by the terminal deteriorated as the number of terminals increased. this was due to the error signal generated by solar panel shadowing effect on the satellite antenna that eventually led to high bit error modulation by the modulation schemes adopted in the work. tarchi et al. (2012) developed three adaption algorithms (state-based acm, state estimation, and state nested algorithms) to improve mobile communication in rural and low populated areas with narrowband access. numerical results showed that the proposed approaches increased the link performance. the limitation of the research was that certain channel parameters like the sinr still represented a challenging scenario which in turn lowered the link margin. rico et al. (2013) analyzed the problem of modulation and coding scheme selection in the return link of the mobile satellite system. the work used a weighted combination of both open loop and closed loop signal quality indicators to perform the selection. numerical results showed good performance of the proposed method compared to previous algorithms, and its robustness to environment changes. the challenge of this study was that the target ber could not be achieved in very high or very low snr scenarios. al-saegh et al. (2014) presented the atmospheric impairments to the satellite signal quality in terms of performance evaluation and assessments concerning various effective atmospheric and arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 235 transmission parameters during dynamic weather conditions. their results revealed that the transmitted frequency, rainfall rates, and relative humidity were directly proportional to the signal quality degradation, whereas elevation angle θ was inversely proportional and corresponding to low ber. although the qpsk modulation was considered the most appropriate modulation scheme in case of high atmospheric impairments but it also exhibited lower number of transmitted bits per unit time which reduced the reception time of transmitted signals to the geo satellite. bruno et al. (2015) designed a reinforcement learning amc algorithm in order to address the short comings (such as the cqi feedback that sometimes resulted in throughput losses) encountered by most amc methods in a lte system. the designed amc scheme exploited a reinforcement learning algorithm to adjust the mcs selection rules based on the knowledge of the effect of previous amc decisions. although the simulated results showed the best mcs even if the cqi feedback provided a poor prediction of the channel performance, the convergence delays of the reinforcement learning were typically long. and as such, the satellite took a longer time to decode the received signals which generally reduced the systems performance in terms of throughput. kilcoyne et al. (2016) characterized propagation environment experienced by a softwaredefined radio on the nasa scantest bed through a full link-budget analysis. the work proposed, designed, and modeled a link adaptation algorithm to provide an improved trade-off between data rate and link margin by varying the modulation format as the received snr fluctuated. the result of the work showed an improvement on the throughput of the network. to address any data that might have been demodulated incorrectly and taking into account the round-trip delay, the transmitter would re-transmit the data that was sent when the channel conditions changed thereby degrading the general performance of their system in terms of throughput and the effect of path loss was high. it is evident from the reviewed works that most of the existing algorithms either presented la in a broadcasting system with no direct feedback to the ground station or do not consider shadowing effects. some la satellite applications considered weather impairments, such as rain-fading in the higher frequencies of kaand ku-bands or log-normal shadow fading. other algorithms applied the acm method of la to address variations in the channel condition on the receiving antenna which can cause an interruption of data transmission. despite the various interventions by other researchers, there is still a need for improvement with the aim of having better link budget that improves the throughput of satellite network. this research work develops a gsa based acm scheme to mitigate earth to space propagation effects. 2.0 materials and methodology the following gives the materials and method followed in the development of the proposed scheme. 2.1 materials the materials used for this work include: (a) matlab 2016b (b) laptop (hp intel (r) core (tm) i5-2520m cpu) tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 236 2.2 methods 2.2.1 flowchart of the developed scheme figure 1 shows the step-by-step process that was adopted in the development of the link adaptation algorithm. the flowchart shows how the gsa algorithm is incorporated for link budget analysis and how a normalized evm is used for symbol analysis. start set-up iss using stk load iss by searching stk set-up grc, scan test-bed optimize link budget for noise stream using gsa. where c/n and g/t are the figure of merit normalized evm estimates the noise symbols estimatenormalized evm of current modulation scheme is estimated evm= current modulation scheme normalized evmth? modulate the received symbols and send to the downlink switch modulation scheme based on normalized evmth end yes no figure 1: flowchart of the developed improved developed improved adaptive coding and modulation scheme 2.2.3 estimate link budget using gsa the developed improved adaptive coding and modulation (iacm) scheme for mitigating earth to space propagation effects made use of the gsa algorithm was used in this paper to optimize the process for the estimation of channel link budget. the process for link budget analysis was complex and prone to error due to large number of channel parameters to be estimated. in order to improve the throughput of the satellite communication link, proper and accurate link arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 237 budgeting process is required. the iacmscheme optimized the link budgeting process. for efficient performance analysis of the communication link, the developed iacm scheme made use of c/n and g/t(db/k) as figure of merit. the g/t is used in this work to describe the capability of the earth station or satellite to receive a signal. the relation between the c/n and g/t used in this work is given as follows (rashedi et al., 2009): c g f n t        (4) where: f is the antenna frequency g represents the antenna gain t denotes the system noise temperature the antenna gain used in this work is given as follows (kilcoyne et al., 2016): 20.4 10log10 20log10 1000 f g d          (5) where,  is the antenna efficiency and d is the antenna diameter the gsa algorithm was used to optimize the link budgeting process with simulation process in the developed scheme carried out using the gsa algorithm. the simulation parameters for the gsa are given in table 3 while table 4 is the communication link design simulation parameters for the developed scheme. table 3: gsa simulation parameters gsa parameters value maximum-iteration. 50 dimension of problem 4 velocity clock number of agents 50 acceleration. gateway node flag mass. ma=mp=mi=m time master node flag table 4: design parameters for the developed scheme designs parameters ranges uplink frequency [5.0 7.0] ghz downlink frequency [2.04 4.4] ghz earth transmit power [26 30] dbw satellite transmit power [8 11] dbw earth transmit and receive antenna efficiency 70% earth transmit and receive antenna diameter 2.4m tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 238 2.2.4 ber estimation in order to improve the data transmission performance of the communication link at each satellite pass, the ber of the communication link was calculated in terms of 0 be n with berth value of 10-5. the objective of the developed algorithm is to maintain this ber threshold value. during the simulation process it was noticed that both bpsk and qpsk meet the ber requirement for the entire pass duration; meanwhile, 8psk, 16qam, and 64qam all achieve the threshold for shorter periods of time. this result is to be expected as the higher order modulation schemes require stronger symbol energy to achieve the same ber. table 5 outlines the thresholds for switching up and down a particular modulation type in the acm scheme. as bpsk and 64qam are the lowest and highest achievable modulation schemes, they do not have a switch-down or switch-up threshold, respectively. table 5: 0 be n upper and lower boundaries for 10-5 ber modulation schemes down up bpsk n/a 13.6 db qpsk 12.6 db 18.8 db 8psk 17.8 db 20.5 db 16qam 19.5 db 26.6 db 64qam 25.6 db n/a 2.2.5 normalized evmth using berth. in the evm calculation during the acm process, the developed scheme made use of the normalized evm formula. the evm bound for modulation switching scenario is given in table 5. the normalized evm estimated was performed on each symbol of the transmitted signal, using the symbol closest in distance as the ideal symbol. a moving average of evm calculations over 1000 symbols is used during simulation to estimate the evm value. when the average evm (rms) shifts into a different modulation region, the receiver switch modes. the initial receiver state is always bpsk, as it is the most robust to degrade channels out of the modulation scheme options used in this algorithm. once evm estimation has been determined, the receiver either maintains the status of bpsk or increases modulation rate/scheme, depending on the result of the estimation. 2.2.6 selected modulation scheme for symbol modulation the effective performance of the communication link ensure that correct information gets to the receiver at the receiving end. after the link budget process, the acm scheme estimates the ber of the signal and selects an appropriate modulation scheme that reduces the satellite communications link impairments to achieve improved throughput of the network. 3.0 result and discussion results obtained from the simulation carried out is presented and explained in the following sub sections. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):231-242. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 239 3.1 free space loss and elevation analysis of longest access the free space loss and the angle of elevation analysis of the developed algorithm is analyzed for the longest access. an access is defined as the period of time during the iss orbit that corresponds to a positive elevation angle, measured relative to grc. the positive elevation angle helps to show when the iss has crested the local horizon. the shortest pass is found to be 0.23 minutes and the longest access is approximately 10.8 minutes. from figure 2, it is observed that the position of the iss during its orbit and the elevation angle affect the length of the available communication time with the grc ground station. it is also observed that the iacm scheme relatively shows a lower free space loss value as the elevation angle increases. this implies that the developed algorithm has a higher available duration for communication purpose. figure 2: acm and iacm scheme for free space loss and elevation with 207 accesses the reduction in free space loss in the developed scheme is due to the consideration of g/t which indicates the quality of receiving earth satellite. the iacm scheme optimized the parameters of the transmitter to cater for the possible link losses during transmission process to the receiver. table 6: percentage improvement of free space loss against access time metric acm iacm percentage improvement es/no (db) 23 28.23 22.74% when ber and energy to noise ratio are plotted against access time, the percentage decrease in the free space loss for both schemes is shown in figure 2. the loss was computed in table 6. these are achieved when the angle of elevation is considered. 3.2 ber and energy to noise ratio at various periods of time figure 3 is a plot showing the relationship between ber , es/no and access time at various period of time. the evm-based algorithm conservatively switches between various modulation schemes, ensuring that the ber was maintained below the 10-5threshold before switching modes. from figure 3, it was observed that the iacm shows a lower ber and a higher es/no tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(2):231-242. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 240 as compared to the acm scheme at a ber threshold of 10-5. this is due to the ability of the improved scheme to efficiently find an efficient modulation type to aid better data transmission in the presence of channel impairments. the effect of a reduced ber translates to a better throughput of the network. figure 3: ber/es/no for acm and iacm 4. conclusion in this study, an iacm scheme for mitigating earth-to-space propagation effects using gsa for link budgeting and normalized evm at the receiving satellite station that mitigates the effect of path loss and increase data throughput has been achieved. this scheme improves the existing acm scheme. the improved scheme focuses on improving satellite data throughput and mitigating the effects of path loss on the communications link. this iacm scheme provides a more accurate evm value during data transmission at the satellite station which serves as a base for the selection of an efficient modulation scheme. the link budget analysis was carried out using the gsa algorithm which considered two figures of merit. the best case and worstcase link budget analyses are carried out. the improved acm shows better improvement in terms of network throughput and reduced path loss effect than the acm scheme. reference al-saegh, ma., sali a., mandeep, js., abdulmajeed, hja. and chandima g. 2014. atmospheric propagation model for satellite communications. research journal of applied sciences, engineering and technology, 14(7): 157-168. an, g., pasnoori, n. and abdulhammed, r. 2018. access analysis of geo, meo and leo. satellite systems, 3(3): 1-7. asad, m. and abbas, m. 2010. characterisation and channel modelling for mobile satellite communication systems, satellite communications. research journal of applied sciences, engineering and technology. 10(5): 5-15. arid zone journal of engineering, technology and environment, june, 2021; 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 242 pratt, t., bostian, cw. and allnutt, je. 2003. satellite communication. john wiley and sons, new york. rafsanjani, mk. and dowlatshahi, mb. 2012. using gravitational search algorithm for finding near-optimal base station location in two-tiered wsns. international journal of machine learning and computing, 2(4): 377-380. rashedi, e., nezamabadi-pour, h. and saryazdi, s. 2009. gsa: a gravitational search algorithm. information sciences journal, 179(13): 2232-2248. rico-alvariño, a., tato, a. and mosquera, c. 2015. robust adaptive coding and modulation scheme for the mobile satellite forward link. signal processing advances in wireless communications, 2(4): 530-534. sali, a., karim, ha., acar, g., evans, b. and giambene g. 2012. multicast link adaptation in reliable transmission over geostationary satellite networks. wireless personal communications, 62: 759-782. sami, hos. and mamoun, mas. 2011. implementation of adaptive modulation and coding technique using. international journal of scientific & engineering research, 2(5): 1-4. tarchi, d., corazza, ge. and vanelli-coralli, a. 2012. adaptive coding and modulation techniques for mobile satellite communications: a state estimation approach. proceedings of the ieee 6th advanced satellite multimedia systems conference (asms) and 12th signal processing for space communications workshop (spsc), pp. 36-43 arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):243-260 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 243 original research article effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review b. makinta1, k. mohammed1,* and a. ocholi2 1civil and water resources engineering department, university of maiduguri. 2civil engineering department, ahmadu bello university zaria *corresponding author’s email address: engrkachalla@unimaid.edu.ng 1.0 introduction concrete is a construction material composed of cement, fine aggregates (sand) and coarse aggregates mixed with water which hardens with time. portland cement is the commonly used type of cement for production of concrete. concrete technology deals with study of properties of concrete and its practical applications. in a building construction, concrete is used for the construction of foundations, columns, beams, slabs and other load bearing elements (naus, 2005). concrete is a sustainable construction material which is widely used all over the world as it provides superior fire resistance, gains strength over time, gives an extremely long service life and capable of being moulded into different shapes (neville, 2011). the major components of concrete are cement paste and inert materials. cement is an important constituent in the concrete composite. however, its cost is relatively very high. this has impacted in the cost of concrete production and by extension on the cost article information abstract concrete is a construction material composed of cement, fine aggregates (sand) and coarse aggregates mixed with water which hardens with time. cement is an important constituent in the concrete composite; however, its cost is relatively very high, this has impacted in the cost of concrete production and by extension on the cost of housing delivery in nigeria. rice husk ash is one of the promising pozzolanic materials that can be blended with portland cement for the production of durable concrete and at the same time a value-added product. the use of the rice husk ash as partial replacement to cement in concrete not only improve the strength of concrete, protection against cracking, spalling, reduce density and porosity of the concrete. it also reduces the emission of carbon monoxide to the environment which is very dangerous to the atmosphere. the elevated temperature is one of the most harmful effects that cause durability problems in construction; this effect can cause permanent damage in construction and reduce the service life. this paper reviews the work presented by various researchers on effect of elevated temperature on the durability and strength properties of concrete using rice husk ash as partial replacement. from the available literature reviewed, there is a possible research gab in investigating the effect of elevated temperature on concrete with rice husk ash as partial replacement to cement, because most of the researchers have focused on conventional concrete, whereas concrete with rice husk ash as replacement to cement have been recommended for use with a replacement value of 10-20%. the degree of its performance of these recommended replacement needs to be investigated © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 december, 2020 revised 26 february, 2021 accepted 4 april, 2021 keywords: concrete strength durability elevated temperature rice husk ash cement replacement makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 244 of housing delivery in nigeria. adabas et at. (2012) an option available in mitigating this challenge is in replacing a proportion of cement with cheap and available pozzolanic materials (ground husk ash) from agro wastes. there are different types of binding material is used other than cement such as lime for lime concrete and bitumen for asphalt concrete which is used for road construction. various types of cements are used for concrete works which have different properties and applications. some of the types of cement are ordinary portland cement, portland pozzolana cement (ppc), rapid hardening cement, sulphate resistant cement etc. typical portland cement is a mixture of tricalcium silicates (3cao.sio2), tricalcium aluminates (3cao.al2o3), dicalcium silicates (2cao.sio2) and a tetra-calcium aluminoferrite (4cao.al2o3fe2o3) in various proportions together with small amounts of magnesium and iron compounds. sometimes, gypsum is added to slow the hardening process (deepa et al., 2010). the temperature at which cement is been manufactured (~1500oc) and the high energy consumption associating with it pose problem in construction industries. there is also emission of harmful gases which pollute the atmosphere during its production. the production of every ton of portland cement contributes about one ton of co2 in the atmosphere. small amount of nox (no and no2) and ch4 gases are also emitted (singh et al., 2007). besides energy consumption and emission of harmful gases, one positive benefit is that calcium hydroxide, one the hydration products during the hydration of cement is a bonus for construction industry especially when allowed to react with pozzolans. concrete containing mineral admixtures is used extensively throughout the world for their good performance and for ecological and economic reason. some of the common cementitious materials that are used as concrete constituents, besides portland cement are silica fume, fly ash, ground granulated blast furnace slag and rice husk ash. they save energy, conserve resources and have many technical benefits (arioz, 2007). rice is an increasing important crop in nigeria and relatively easy to produce and grown for sale and for home consumption (chukwudebelu et al., 2015), rice husk is an agricultural remainder derived from the external covering of rice grains during milling procedure and the ground one into powders forms is called the ground rice husk ash (grha) which are shown from figure 1.0 below. it comprises 20% of the 500 million tons of paddy generated in the world (sivaumat, 2014). when rice husk is burnt, about 20% by weight of the husk is recovered as ash in which more than 75% by weight is silica. unlike natural pozzolan, the ash is an annually renewable source of silica. also rice husk ash is a recent addition in the list of pozzolanic materials. (ramezanianpour et al., 2009), opined that one of the most suitable sources of pozzolanic material among agricultural waste components is rice husk, as it is available in large quantities and contains a relatively large amount of silica. rice husk ash is one of the promising pozzolanic materials that can be blended with portland cement for the production of durable concrete and at the same time a value-added product. binary blending of portland cement with rice husk ash does not only improve the early strength of concrete, but also forms a calcium silicate hydrate (csh) around the cement particles which is highly dense and less porous, and may increase the strength of concrete against cracking ( saraswathy, 2007). also, addition of rice husk ash (rha) speeds up setting time, although compared to opc the water requirement is higher, it has improved compressive strength due https://theconstructor.org/building/types-of-cement-composition-uses/5974/ arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 245 to its higher percentage of silica and improved resistance to acid attack compared to opc which is said to be due to the silica present in the rha which combines with the calcium hydroxide and reduces the amount susceptible to acid attack ( deepa,2013). rice husk ash can also replace silica fume in high strength concrete as further described by (koksal et al., 2012) and silica fume or micro silica is the most commonly used mineral admixture in high strength concrete although the major characteristics of rice husk ash are its high-water demand and coarseness compared with condensed silica fume. also, the presence of rha and cement kiln dust in cement pastes improved the resistance of the mortar to sulfuric acid attack (hashem, 2013). rice husk ash ground rice hus ash elevated temperature is one of the most harmful effects that cause durability problems in constructions. this effect can cause permanent damages in constructions, reduce the service life and may cause causalities, thus affecting the construction's sustainability (aydin, 2003). concrete is well known for its capacity to endure high temperatures and fires owing to its low thermal conductivity and high specific heat (arioza, 2007). however, it does mean that the fire as well as the high temperatures does not affect the concrete. high strength concrete may exhibit damages such as cracks and spalling’s when exposed to high temperatures (kalifa, 2001). during exposure to high temperatures such as fire, important changes may occur in its mechanical, physical, and thermal properties according to (choni, 2001). these suggest that failure of the elements could be multidimensional as observed by (choni,2001). in addition, elevated temperature reduces the strength of concretes and the degree of strength-loss is dependent on the temperature reached and the exposure duration (castillo, 1990). other factors that influence the strength loss according to (knack, 2010) are aggregate types and the strength of the concrete at room temperature. high strength concrete (hsc) according to (kodur, 1999) provides a high level of structural performance, especially in strength and durability, as compared to normal strength concrete (nsc). as such, (bui, 2001) defined high strength concrete as that concrete designed to give optimized performance characteristics for a given set of load, usage, and exposure conditions consistent with the requirement cost, service life and durability. makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 246 factor affecting the properties of concrete at elevated temperature according to iffat and bose (2016), few aspects can affect the properties of concrete when exposed to fire such spalling, cracking, density of concrete, moisture content, fire intensity, transverse reinforcement placing, type of aggregates, fibre reinforcement, concrete strength and water-cement ratio. since the type of aggregate used in concrete is one of the aspects that influence the concrete properties, the selection of aggregate must be a major concern in concrete design when subjected to fire. there are two types of aggregate that commonly used in construction, carbonate aggregate and siliceous aggregate (abram, 1973). also, siliceous aggregate affords higher thermal conductivity and expansion, higher fire resistance, and improved spalling resistance in concrete compared to carbonate aggregate. furthermore, concrete with compressive strength more than 55mpa is more responsive to spalling and may have a lower resistance (yehia and kashwani, 2003). the spalling of concrete normally occurs at initial stages of fire due to the expansion of water pressure or the effect of thermal expansion in concrete mixes. high strength concrete may have a very lower permeability and water-cement ratio that causes moisture escapes with a slow rate and pressure of pore will be increased. consequently, this will contribute to a major reduction in load bearing capacity during fire exposure. concrete density also has a significant impact on concrete properties when exposed to fire. for example, high strength concrete has a dense paste and low water cement ratio which is liable to spalling when exposed to fire. the rate of transmission of high temperature to the concrete core is high that leads to rapid loss of concrete surface (kodur, 1999). furthermore, concrete is the feasible material that can be exposed to high temperatures during the fire or near to the furnaces (lucccio et al., 2003) whereas exposure to high temperature during the fire can be a potential threat for any construction buildings that can cause a major damage to reinforced concrete structures (yehia and kashwani, 2003). despite that concrete is a non-combustible material, the effect of fire on concrete structure still can change physical, chemical, and mechanical properties of the concrete once it exposed to elevated temperatures. moreover, it will also cause the strength reduction, volume stability and modulus of elasticity of the concrete (ndoukouo et al., 2011). thus, the concrete properties exposure to fire is significant, while considering the load carrying capacity and restoring fire-damaged buildings (hertz, 2005). it is generally known that concrete is a composite material that made from cement, water and almost 65% to 75% volume of concrete is occupied by aggregates. currently, the depletion of raw materials in concrete production such as natural aggregates become a serious problem all over the world and it was caused by the rapid industrial development. one of the best solutions to reduce this problem is to utilize recycled waste material and industrial by-product in the concrete production such as palm oil clinker, bottom ash, fly ash, granite powder, rice husk ash, marble and dolomite powder, furnace slag and so on as alternative materials for natural aggregate. according to iffat and bose (2016), the exceptional fireproof achievement of concrete is might be due to constituent materials of concrete such as its aggregates. similarly, sakr and hakim (2005), reported that the strength degradation of concrete with the different types of aggregates is not same at high temperatures. according to hager (2013), the commonly used aggregate is steady up to a temperature range of 200°c to 350°c but when the temperature rises up to 600°c, the physical and chemical changes of the aggregate will occur and contributed to a lower strength arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 247 of concrete. since the aggregate is one of the main materials in concrete production, the properties and type of aggregate play a significant role in the behaviour and properties of concrete when it is exposed to the high temperatures (arioz, 2007). therefore, the aim of this study is to review available relevant research works on effect of elevated temperature on the durability and strength properties of concrete with rice husk ash as partial replacement for the cementous material. 2.0 methodology literature review generally, the atmospheric temperature of concrete structures is expected to be at room values during construction and during their service life. current design and construction codes take care of safety of these structures in relation to room temperature values (bs 8110 part 1). at times the environmental temperature may increase extremely or fluctuate periodically, and often the design strength of the structure is significantly affected (guo,2011). it has become a big assignment for engineers to be interested in the residual design strength of concrete subjected to high temperatures in order to form data base for performance at these elevated temperatures for practical research applications. stress-strain relationship of high strength concrete, hsc, (concrete strength in excess of 70mpa) has been investigated and reported. the variables considered in the experimental study included concrete strength, type of aggregate, and the addition of steel fibres. (cheng et al., 2014) reported that tests show that plain hsc exhibits brittle properties below 600oc, and ductility above 600oc. hsc with steel fibres exhibits ductility for temperatures over 400oc. the compressive strength of hsc decreases by about a quarter of its room temperature strength within the range of 100-400oc. they also showed that surface concrete cracking is a visible type of damage that has significantly adverse effects on the mechanical properties and durability properties of concrete. a study on the identification and quantification of surface cracking of concrete heated to different temperatures ranging from 105 to 1250ºc was carried out, in addition to the quantification of the residual compressive strengths of concrete after high temperature exposure; both initial surface absorption and total porosity were measured. the investigation showed that crack density was determined using a flatbed scanner and then images were treated using paint shop program. the total porosity was obtained using american society for testing and materials (astm) methods as reported. further discussions pointed to the fact that the mechanical properties of concrete were largely affected by temperatures beyond 500°c and were very feeble when temperatures exceeded 1000°c. the surface cracks' density, initial surface absorption and total porosity by boiling methods gave a rapid indication on concrete durability from the report (toumi et al., 2010). the effect of exposing carbonfibered reinforced concrete to elevated temperatures on its bond strength with reinforcing steel bars have been investigated by hassan (2012). he wrote that experimental program consisting of fabricating and testing of 54 pull-out cubic specimens was prepared. from the experiments, the specimens were divided into three groups to study the effect of addition of various amounts of discrete carbon fibre on its residual bond strength and the bond strengthslip response after exposure to temperature levels of 150°c, 250°c, makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 248 350°c, 450°c and 550°c in addition to the room temperature. the carbon fibre content considered was 0.0%, 0.75% and 1.0% by weight of cement. in addition to the pullout specimens, nine cubes having the same pull-out specimens’ size (three from each concrete group mix) were tested in compression. it was concluded that the percentage residual bond strength after exposure to temperature level of 550oc for the concrete reinforced with 0.75% carbon fibre by weight of cement (28%) is lower than that for plain concrete and the concrete reinforced with 1.0% carbon fibres (32%). there was no clear conclusion that could be obtained concerning the effect of changing temperature levels on bondslip response of plain concrete and that reinforced with 0.75% and 1.0% carbon fibres. an experimental investigation was conducted to evaluate the influence of elevated temperatures on the mechanical properties, phase composition and microstructure of silica flour concrete (morsy et al., 2010). the blended cement used in this investigation consists of ordinary portland cement (opc) and silica flour. the opc were partially replaced by 0, 5, 10, 15 and 20% of silica flour. the blended concrete paste was prepared using the water-binder ratio of 0.5 wt.% of blended cement. the fresh concrete pastes were first cured at 100% relative humidity for 24 hours and then cured in water for 28 days. the hardened concrete was thermally treated at 100, 200, 400, 600 and 800oc for 2 hours. the compressive strength, indirect tensile strength, phase composition and microstructure of silica flour concrete were compared with those of the pure ordinary portland concrete. the results showed that the addition of silica flour to opc improves the performance of the produced blended concrete when exposed to elevated temperatures up to 400oc. also, an investigation presented the results of a study on the effect of polyester fibre reinforcement on the residual compressive strength of normal-strength concretes subjected to sustained elevated temperature by suresh et al. (2014). two different volume fractions of polyester fibre were adopted in the concrete which was subjected to elevated temperatures of 100oc, 2000 c, 3000c, 4000c, 5000c, 6000c, and 8000c, sustained for 2 hours. this involved a total of 72 specimens containing 0%, 0.5%, and 1% volume fraction of 12 mm polyester. the test results showed that the addition of polyester fibres will contribute to the increase in the compressive strength depending upon the percentage of fibres present in it. based on this research, it is observed that there is an increasing trend in the residual compressive strength of the normal strength concrete up to sustained elevated temperature of 4000c due to the addition of polyester fibres at 0.5% volume fraction. from the eighteenth century onwards, the world’s portland cement consumption increased to 2 million tons from 1.3 billion tons annually. this was accompanied with other environmental issues like largest amount of co2 produced during the cement manufacturing process (rawaid et al., 2012; meyer, 2009). this leads to the utilization of substitution material for cement. however, the sustainable material would reduce the demand of portland cement and reduce the production cost of concrete. one of the most assuring materials is rice husk ash (rha). concrete containing agricultural waste is used extensively throughout the world for their good performance and for ecological and economic reason. some of the common cementitious materials that are used as concrete constituents, besides portland cement are silica fume, fly ash, ground granulated blast furnace slag and rice husk ash. they save energy, conserve arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 249 resources and have many technical benefits. rice husk ash is a recent addition in the list of pozzolanic materials (ariozo, 2007). extensive research activities have been carried out on the ashes of many agricultural waste materials with the intent of producing concrete and mortar through partial replacement of opc. in the case of rice husk ash (rha) cement composites, it was shown that at w/c ratio of 0.30 and opc replacement level of 20%, rha mortar resulted in higher compressive strength compared to the control for both waters cured and uncured cubes. it also improved in durability properties (abalaka, 2013). during the pozzolanic reaction, highly reactive pozzolan reacts with calcium hydroxide and produces lower density calcium silicate hydrates; for this reason, grha show a higher chloride penetration resistance as compared to natural rice husk ash (bhanumathi and mehta, 2004; ganesan et al., 2008; rukzon and chindaprasirt, 2008). the chloride penetration resistance rate of nrha-10 and grha-15 concretes are 19% and 52% more than that of control concrete. thus, the test results show that the chloride ion penetration resistance is significantly improved by incorporation of rha in concrete. the incorporation of rha in concrete increases the strength, particularly for lower water/binder ratio (nehdi et al., 2003; giaccio et al., 2007; bui et al., 2005) reported that brittle failure was observed in rha concrete. the addition of rha to concrete shows an increase in compressive strength and decrease in water permeability of concrete (salas et al., 2009). it is noticed that the durability of concrete exposed to hcl and h2so4 attacks, replacement of 20% of portland cement by rice husk ash led to a positive effect in decreasing the corrosion of concrete (chatveera and lertwattanaruk, 2011; salas, 2009). air permeability and chloride ion penetration studies showed that the water/cementitious materials ratio has the influence on decreasing the penetration rate on the rha replaced concrete. the reduction in chloride ion penetration is mainly due to the pore-refining capacity of rha in concrete (sensale, 2010; ganesan et al., 2008). similarly, scanning electron microscope is used to examine the natural rha used, and from sem study, it is noticed husk ash has many irregular-shaped particles with a sizable fraction showing a porous cellular structure. these particles are functioning as a lubricant or dispersion agent and contribute to the dispersion of opc particles in a water system, as well as it is used to release the water entrapped between opc particles, thus improving concrete workability. natural rice husk ash average particle size is 240×140 μm. thus, the rha is finer than cement and it is expected to blend easily not only on pozzolanic material, but also on the microfiber effect (xu et al., 2012). at the same 20% in another report, compressive strength and porosity of cement mortar showed better result over plain mortar. still on rha mortar, two reports gave optimum compressive strengths at 10% and 15% respectively (rashid, and ali, 2010). additionally, the makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 250 presence of rha and cement kiln dust in cement pastes improved the resistance of the mortar to sulfuric acid attack (hashem, 2013). according to wang (2017) whose study on the effect of rice husk ash on high temperature on mechanical properties and microstructure of concrete, the result shows that mixing concrete with appropriate amount of rha can improve its strength. at 8000c the strength is 50% greater than of normal concrete. thus, rice husk ash can improve the strength and temperature resistance of concrete. paraven and raw (2019) whose study on influence of supplementary cementitious material on strength and durability of concrete using three mineral admixtures of fly ash, silica and limes sludge were used in the preparation of blended concrete. it was evident that the usage of such mineral admixture is having a beneficiary role on the strength as well as the durability properties which shows greater resistance to acid attack compared to controlled mix concrete. according to ndububa and okonto (2016) whose study on the potential used of fonica ash as a pozzolana in concrete, show that at 10% of fha should not exceeded for optimum strength value. furthermore, nwofor and sile (2016). whose study on stability of ground nut ash gsa/opc on concrete in nigeria. this shown that certain percentage of cement replace by gsh for 0% to 40% which evident that the result generally shows a decrease in density and compressive strength as the percentage replace out increases. on partial replacement of cement with burnt rice husk ash for low strength concrete production by ugwuanyi et al. (2018), the result shows that the highest compressive strength was obtained at 10% replaced of cement with rha. using such material reduces cost of cement and density of concrete and produce insulated blocks. according to ketkula (2018). study on ―ground nut hush ash as partial replacement of cement in mortal‖. the gha was used as partial replacement of opc, the level of replacement of 0%, 2%, 4%,.10% were used for this, using such material the density of the sandcrete block were reduce and water absorption decreases, therefore it is recommended for further research on permeability and durability analysis. addition of amorphous silica is accompanied by improving interface transition area leads to concrete with more packing density. a series of investigations carried to evaluate rha concrete considering hardened properties, favourable percentage of rha replacement, curing time, electrical resistivity, compressive strength and influencing parameters followed by increase in the percentage of rha replacement in the mix. (kartini et al., 2012). kartini et al. (2012) research showed, increased replacement of rha to opc may be resulted in less charge passed values, which reduces along with increase in curing period. so, more replacement of rha leads to less percentage of chloride ions penetration‖. structural elements fabricated from reinforced concrete, because of their typical size, have a high thermal inertia that results in relatively slow rates of temperature increase through the cross section. as a result, the steel reinforcement temperatures are kept sufficiently low to arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 251 avoid significant softening. in addition, due to the monolithic nature of construction, the existence of alternate load paths, and compartmentation of fires (conventional civil engineering construction), reinforced concrete structures generally perform well under elevatedtemperature conditions that could result from a fire. however, under certain scenarios (rapid heat build-up), spalling of the concrete could occur to expose the steel reinforcement to the effects of elevated temperature (harmathy, 1970). rice husk ash is one of the promising pozzolanic materials that can be blended with portland cement to produce durable concrete and at the same time a value-added product. binary blending of portland cement with rice husk ash does not only improve the early strength of concrete, but also forms a calcium silicate hydrate (csh) gel around the cement particles which is highly dense and less porous, and may increase the strength of concrete against cracking (saraswathy and ha-won, 2007). rice husk has recently been recognized as pozzolana; it is a siliceous/ aluminous material which in itself has little or no cementitious value, but which will in finely divided form and in the presence of moisture, chemically reacts with calcium hydroxide liberated during the hydration of portland cement to produce stable, insoluble cementitious compound which contributes to its strength and permeability (sima, 1974). koksal et al. (2012) used four different composite mixtures with varying amount of expanded vermiculite exposed to high temperatures of 300, 600, 900 and 1100oc for 6hrs, the physical and mechanical properties including unit weight, porosity, water absorption, residual compressive strength, residual splitting tensile strength and also ultrasonic pulse velocity were determined after air cooling, micro-structures were investigated by scanning through electron microscopy and disclosed that light-weight concrete with vermiculite shows a good performance at elevated temperatures. extensive research activities have been carried out on the ashes of many agro-allied waste materials with the intent of producing concrete and mortar through partial replacement of opc. in the case of rice husk ash (rha) cement composites, it was shown that at w/c ratio of 0.30 and opc replacement level of 20%, rha mortar resulted in higher compressive strength compared to the control for both water cured and uncured cubes. it also improved in durability properties (abalaka, 2013). at the same 20% in another report, compressive strength and porosity of cement mortar showed better result over plain mortar. still on rha mortar, two reports gave optimum compressive strengths at 10% and 15% respectively (rashid and ali, 2010). using different percentages of rice husk (rha). the initial and final setting times increases with increase in rice husk ash content. the reaction between cement and water is exothermic. the liberation of heat and evaporation of moisture causes the stiffening of the paste and slower heat induced evaporation of water from the cement/rha paste due to its lower cement content ikpong (1993). according to rawaid et al., (2012), the production of cement is costly, consumed higher energy and emits huge amount of greenhouse gases, bring serious pollution and environmental makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 252 degradation, developed and some developing nation using rha rice husk ash as cement in concrete production. mehta and folliard (1996) found that the mortars containing rha possess excellent acid and sulphate resistance properties compared to those that did not contain rha. similarly, rha can be used as a high-performance pozzolan to improve the mechanical and durability properties of conventional. 3.0 result of critical review table 1 provides the critical review summary for tins study. table 1: critical review summary s/n author(s) studies carried out study findings critics 1 deepa (2013) mechanical properties of rice husk ash (rha) in high strength concrete his analysis shows that rice husk ash in concrete increases the mechanical properties of concrete such as compressive strength, setting time and protection against acidic attracts. failed to investigate the effect of elevated temperature in concrete with rice husk ash 2 castillo (1990) effect of elevated temperature on high strength concrete. his result shows a decrease in strength of the concrete with increase in temperature. study is confined to temperature effect on conventional concrete. 3 ndoukou et al (2011) factors affecting the properties of concrete at elevated temperature. his analysis shows strength reduction, volume stability and modulus elasticity in concrete at elevated temperature. study is focused on the durability properties of plain concrete at elevated temperature 4 iffat and bose (2016) review on concrete structures in fire (effect of agricultural waste as fireproof in concrete using fly ash and rice) the studied materials are effective in fire proofing in concrete between from 100oc to 350oc. analysis is on two agricultural (fly ash and rice husk) waste as fireproof. arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 253 5 cheng et al. (2014) effect of elevated temperature on concrete hsc above 70mpa result show that the plain hsc exhibits brittleness below 600oc and ductility above 600oc the research focused only on concrete above 70 mpa but with no rice hush ash. 6 toumi et al. (2010) identification and quantification of surface cracking heated to different temperature it affects the mechanical properties of the concrete at above 500oc studied cracks caused by heat effect in plain concrete without admixture 7 hassan (2012) the effect of exposing carbon-fibre reinforced concrete to elevated temperature on it bond strength with reinforcing steel bars from 150octo 550oc the bond is lower at 550oc for the concrete reinforced with 0.75% of carbon to plain concrete he examined the effect of exposing carbon-fibred reinforced concrete at elevated temperature. 8 morsey et al. (2010) effect of elevated temperature on the mechanical properties of concrete containing silica flour as partial replacement to cement his result show that the addition of silica flour increases the performance of produced blend concrete from 100oc to 400oc his studies focused on using silica flour as admixture in the concrete elevated up to 400oc 9 suresh et al. (2014) effect of polyester fibre reinforcement on 0%, 0.5% and 1% on the residual compressive strength of normal concrete subjected to 100oc to 800oc the analysis shows that, addition of polyester fibre increases the compressive strength of the concrete up to 400oc at 0.5% volume fraction failed to investigate the effect of elevated temperature in concrete with rice husk ash 10 abaka (2013) effect of rice husk ash on the strength and durability properties of concrete as partial replacement to cement. it improved the strength and durability properties of the concrete from 10-20% proportion. failed to investigate the effect of elevated temperature in concrete with rice husk ash makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 254 11 kartini et al. (2012) compares pozzolanic reaction between ground rice husk ash (grha) and natural rice husk ash (nrha) with calcium hydrate. result shows that, the grha show higher chloride penetration resistance as compared to nrha in concrete. failed to investigate the effect of elevated temperature in concrete with rice husk ash 12 nehdi et al. (2003) effect of rice husk ash in concrete as partial replacement of cement in different proportion result shows that the addition of rice husk ash in concrete increases the concrete strength; brittle failure was observed in rha concrete. failed to investigate the effect of elevated temperature in concrete with rice husk ash 13 salas et al. (2009) the effect of rice husk ash as partial replacement to cement in concrete expose to hcl and h2so4 in different proportion it shows that the durability of the concrete attacked by hcl and h2so4 replace 20% of opc by rha led positive effect in decreasing the corrosion of concrete effect of elevated temperature is not studied. 14 sensal (2010) strength development of concrete with rice husk ash investigation shows that the water/cementitious material ratio have an influence on decreasing penetration of chloride ion on the rha replaced concrete. the effect of elevated temperature not investigated. 15 xu et al. (2012) microstructure and reactivity of rha using scanning electron microscope result shows an improvement in concrete workability failed to investigate the effect of elevated temperature in concrete with rice husk ash arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 255 16 praveen and prasad (2019) influence of supplementary cementitious materials on strength and durability of concrete using three mineral admixture of fly ash, silica and sludge it was evident that the usage of such mineral admixture is having a beneficiary role on the strength and durability properties compare to control mix concrete. the effect of elevated temperature in concrete with rice husk ash is not investigated 18 ndububa and okonto (2016) the potential of using fonica ash as pozzolana in concrete as partial replacement to ordinary portland cement result shows that optimum strength value is obtained at 10% of fonica ash replacement. the effect of elevated temperature in concrete with rice husk ash is not investigated 19 nwofor and sile (2016) stability of groundnut husk ash as partial replacements to cement on concrete in nigeria the result shows a decrease in density and compressive strength as the percentage increases 20 ugwuanyi et al. (2018) partial replacement to cement with burn rice husk ash for low strength concrete production the result shows that the highest compressive strength was obtained at 10% replacement of cement with rice husk ash rha, such replacement reduce cost and density failed to investigate the effect of elevated temperature in the concrete containing rice husk ash 21 ketkula (2018) the effect of ground nut husk ash as partial replacement to cement in mortal its analysis shows that the density of the sancrete block reduce, water absorption decrease as the percentage of replacement increases and recommended for further research the effect of elevated temperature on the mix concrete is neglected makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 256 22 wang (2017) effect of rice husk in mechanical properties and microstructure of concrete the result show that mixing concrete with rha can improve its compressive strength failed to investigate the effect of elevated temperature in concrete with rice husk ash 23 karim et al. (2012) strength of mortal and concrete as influenced by rice husk ash (a review) the outcome shows that the strength of the concrete at 2030% replacement was increased as compared to opc concrete. failed to investigate the effect of the elevated temperature in the mortal and concrete 24 nehdi et al. (2003) effect of rice husk ash in concrete as partial replacement of cement in different proportion result shows that the addition of rice husk ash in concrete increases the concrete strength; brittle failure was observed in rha concrete. failed to investigate the effect of elevated temperature in concrete with rice husk ash 25 chatveera (2011) the effect of rice husk ash as partial replacement to cement in concrete expose to hcl and h2so4 in different proportion it shows that the durability of the concrete attacked by hcl and h2so4 replace 20% of opc by rha led positive effect in decreasing the corrosion of concrete effect of elevated temperature is not studied. 4.0 conclusion concrete is one of the common construction materials in our country and is the feasible material that can be exposed to high temperature due to fire or near a furnace. whereas exposure to high temperature can lead to damage of reinforce concrete structures despite not been a combustible material. the effect of elevated temperature may bring about physical, chemical and mechanical changes in concrete properties. the strength and durability of concrete depends upon its aggregate; the silicious aggregate afford high thermal conductivity and high expansion, high fire resistance; improve spalling resistance compared to the carbonate aggregate. the compressive strength of concrete decreases as temperature increases due to high dehydration of the calcium hydroxide in the binder as well as generating more water vapour thereby leading to strength reduction. furthermore, loss of moisture reduces the weight as temperature increases. the addition of rice husk ash to concrete shows an increase in compressive strength of the concrete and decrease in water permeability of concrete under arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):243-260. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 257 ambient condition, i.e. the durability of the concrete increase by replacement of 20% of the opc by rha which bring positive effects. furthermore, the siliceous aggregate properties afford high thermal conductivity and improve elevated temperature resistance compared to the carbonate aggregate however, there is a possible research gab in investigating the effect of elevated temperature on concrete with rice husk ash as partial replacement to cement, because most of the researchers have focused on conventional concrete, whereas concrete with rice husk ash as replacement to cement have been recommended for use of 10-20%. the degree of its performance of these recommended replacement needs to be investigated. references aydin, s. and baradan, b. 2003. yuksek sicakliga dayaniki beton gelistirilmesi, in turkish, tmmob chamber of civil engineering, 5th national conferences of concrete, istanbul. arioz, o. 2007. effects of elevated temperatures on properties of concrete. fire safety journal, 42(8): 516522. adaba, cs., agunwamba, jc., nwoji, cu., onya, oe. and ozeh, s. 2012. comparative cost and strength analysis of cement and aggregate replacement materials. nigerian journal of technology, 31(2): 111-115. bhanumathi das, n. and mehta, pk. 2004. concrete mixtures with ternary blended cements containing fly ash and rice husk ash. proceeding of the 7th international conference, canmetaci on fly ash, silica fume, slag and natural pozzolans in concrete, chennai, sp: 199-22, pp. 379-391. british adopted european standard bs en 197-1. 2000. cement. composition, specification and conformity criteria for common cements, united kingdom. bui, dd. 2001. rice husk ash as a mineral admixture for high performance concrete. netherlands, dup science delf university press. cioni, p., croce, p. and salvatore, w. 2001. assessing fire damage to r.c. elements. fire safety journal, 3: 181-199. castillo, c. and durrani, aj. 1990. effect of transient high temperature on high-strength concrete. aci materials journal, 8(5): 261-266. cho-liang, t., chiang, c., yang, c. and chun-ming, c. 2005. tracking concrete strength under variable high temperature. aci materials journal, 102(5): 322-329. chukwudebelu, ja., igwe, cc. and madukasi, ei. 2015. prospects of using whole rice husk for the production of dense hollow bricks. african journal of environmental science and technology, 9(5): 493-501. donatello, s. and cheeseman, cr. 2010. comparison of test methods to assess pozzolanic activity. cement concrete composition, 32(2): 212-127. makinta et al: effect of elevated temperature on the durability and strength properties of concrete with ground rice husk ash as a partial replacement to cement: a review. azojete, 17(2):243-260. issn 1596-2490; 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 260 ugwuanyi, sa., adibe, tn. and mmonwuba, cn. 2018. partial replacement of cement with burnt rice husk ash for low strength concrete production. iosr journal of mechanical and civil engineering, 15(3): 01-05. wang, w-h. 2017. effect of rice husk ash on high-temperature on mechanical prpoerties and temperature resistance. school of civil engineering and hydraulic engineering, ningxia university, wencui n st., xixia district, yinchuan, ningxia, china. pp. 157-164. xu, w., lo, ty. and memon, sa. 2012. microstructure and reactivity of rice husk ash. construction and building materials, 29: 541-547. doi: 10.1016/j.conbuildmat.2011.11.005. yehia, s. and kashwani, g. 2013 performance of structures exposed to extreme high temperature—an overview. open journal civil engineering, 3: 154–161 arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):785-792 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 785 original research article evaluation of nspri solar dryers for yam chips production (elubo) j. m. ogunsua*, o. p. akomolafe, s. n. oyewole, o. ajiboye, m. o. zubair, y. d. idris, f. m. omopariola, o. a. adeiza and f. f. olayemi postharvest engineering research department, nigerian stored products research institute, km 3 asa-dam road, p.m.b. 1489, ilorin, nigeria *corresponding author’s email address: jonehmak@gmail.com 1.0 introduction drying of agricultural produce is a simple process through which agricultural products can be preserved for future use by removing available moisture in the crops to avoid deterioration (ohijeagbon et al., 2016). among the common methods used in drying and preserving agricultural products are open air and uncontrolled sun drying (toshniwal and karale, 2013; aderinlewo et al., 2013). previous studies have reported that these methods could pose serious challenge on food quality with respect to product contamination due to dust, insect infestation and animal contact which invariably can lead to product degradation (ratti and mujumdar, 1997; okoroigwe et al., 2013). this might compromise the food quality and causes reduction in the market value of such commodity (toshniwal and karale, 2013; sadodin and kashani, 2016). article information abstract this study evaluated the two solar dryers developed at nigerian stored products research institute (nspri) parabolic shaped solar dryer (pssd) and solar tent dryer (std). the evaluation was conducted using yam chips (elubo) in ilorin. the yam chip was soaked in water at three different temperatures: 80, 90 and 100°c, and allowed to cool in the water for 15 hours prior to drying. the yam samples were then spread on trays in each of the pssd, std dryers and ambient. a tekcoplus thtk-6, ktype 4channel thermocouple was fitted in each of the dryers to monitor the drying temperature inside the dryers and ambient. the study considered sun drying as the control. the product samples were subjected to proximate composition determination. the moisture content of the samples was also monitored daily. means of data collected were compared using graphs and 2-way anova using microsoft excel 2016 and spss version 20. the results showed higher temperatures recorded in the dryers (pssd= 40.77 ± 1.24°c and std= 34.62 ± 0.70°c) compared to what was obtained in the ambient (33.59 ± 0.38°c). this resulted in a higher drying rate in pssd and std at an average of 0.57 kg/day and 0.52 kg/day respectively compared to the control (0.46 kg/day). drying in pssd was completed in 3 days with final moisture content of 7.53%, while it lasted for 4 days in std and control with final moisture contents of 8.98% and 9.37% respectively. similarly, carbohydrate and crude protein were found to be significantly higher in samples dried in pssd compared to std and the controlled samples (p≤0.05). the result of microbial quality evaluation revealed that the bacteria and fungi counts of the dried yam chip samples inside pssd and std were within the acceptable standard of ≤ 300 cfu/ml, lower than that of the control sample where higher value (1.80 x 103 cfu/ml) was recorded. therefore, both pssd and std are potentially viable for safe production of yam chips of high quality for human consumption. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 august, 2020 revised 26 october, 2020 accepted 3 november, 2020. keywords: water temperature drying rate solar dryer yam chip http://www.azojete.com.ng ogunsua et al: evaluation of nspri solar dryers for yam chips production (elubo). azojete,16(4):785-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 786 forced-air drying which uses artificially heated air and fan for drying still seems to be a better way of drying produce. however, the cost of acquiring and operational expertise makes it unaffordable as an alternative to unhygienic road-side and bear ground drying common to farmers in developing countries such as nigeria. the use of solar energy is another affordable, cost effective and readily available alternative in this part of the world. solar energy is a major area of interest within the field of agriculture, particularly in the area of produce drying as it is viewed as a viable technique of preserving agricultural products. the use of heat energy from solar could be applied through direct sun drying or indirect with specific designed solar dryers to prevent postharvest losses which are a common phenomenon in many developing countries (okonkwo and okoye, 2005; mustayen et al., 2014; ringeisen, et al., 2014). despite the abundance of solar energy in tropical countries, the direct sun drying being practiced in these areas does not allow efficient and effective utilization of the energy. thus, making the products susceptible to environmental contamination which makes them unsafe for human consumption (sadodin and kashani, 2016). lack of efficient and affordable solar dryers for community drying has been a challenge among farmers in nigeria. in view of the above, nigerian stored products research institute (nspri) developed parabolic shaped solar dryer (pssd) and solar tent dryer (std) for drying of agricultural products. therefore, the aim of this study was to evaluate the effectiveness of the dryers (pssd and std) for production of yam chip with respect to drying time, drying rate, proximate and microbial qualities. 2.0 methodology 2.1 location of the experiment the study was conducted during the harmattan season in the premises of nigerian stored products research institute (nspri), ilorin, nigeria (n 8° 27’14.77”; e 4° 33’21.47”). 2.2 description of the solar dryers the parabolic shaped solar dryer (pssd) has a structural dimension of 8 m x 4 m x 2.4 m with the longer side facing the east-west direction for maximum reception of solar radiation. it has a black floor for heat collection and an underlying insulation that prevents heat sink. it has a parabolic shaped structural frame of 2.4 m height made of galvanized steel pipes. the roof is covered with transparent acrylic material. the drying chamber has 2 drying racks with 4 layers each made of mild steel angle iron and 56 trays of 0.55 m x 0.55 m made of square pipe and wire mesh. the dryer has an effective drying area of 16.94 m2. there are two (2) inlet vents with installed solar powered blowers. the top is fitted with two (2) pneumatic aspirators for extraction of moisture from drying chamber. an access door is also provided at one end of the structure (figure 1a). the solar tent dryer (std) has structural dimensions of 3.2 x 4 x 3.1 m with the longer side facing the east-west direction for maximum reception of solar radiation (figure 1b). it has a black floor for heat collection and an underlying insulation that prevents heat sink as obtainable in pssd. it was constructed of wooden posts erected on a dwarf block wall of 0.8 m height. the dryer is covered with transparent uv screened polycarbonate film. the drying chamber has a drying rack with 3 layers made of wood and 12 trays of 0.70 m x 0.75 m and 6 trays of 0.55 m x 0.75 m made of wood and wire mesh. the dryer has an effective drying area of 8.48 m2. there are 3 adjustable inlet vents on each side of the dwarf walls. the top is fitted with one pneumatic aspirator for extraction of moisture from drying chamber. an access door is also provided at one end of the structure. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):785-792. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 787 figure 1a: parabolic shaped solar dryer figure 1b: solar tent dryer 2.3 collection and preparation of experimental materials the yam tubers used for the experiment were procured from a market in alapa village via ilorin, kwara state, nigeria. the yam tubers were sorted, peeled and washed with potable water before slicing. the cleaned tubers were sliced into 20 mm thickness. the yam slices were divided into three lots and soaked in water at temperatures; 80 °c, 90 °c and 100 °c respectively (oyewole et al., 2013). it was then allowed to cool in the water for 15 hours. the initial moisture content of the soaked samples was determined using the oven-drying method (aoac, 2005). 2.4 drying of samples and temperature monitoring the drying was carried out using three drying systems namely; pssd, std and ambient (control). samples were spread on trays and placed in pssd, std and ambient. a tekcoplus thtk– 6 k-type 4-channel sd thermocouple was installed in each of the dryers as well as ambient to monitor the drying temperature (figure 2). figure 2: sliced yam chips during drying in pssd and std dryers 2.5 determination of proximate composition and microbial analysis the initial and final proximate compositions of the samples were determined (aoac, 2005). also the microbial quality was determined using microbiological guidelines for food (cfsfeh, 2014). 2.6 weight loss and drying rate determination trays from each of the drying system were weighed daily to monitor moisture loss. drying continued until moisture content of the samples falls below 10% (ukpabi et al., 2018). the drying rate was determined using equation 1. dr = mi−mf t (1) where: dr is the drying rate in g/day, mi is initial weight of sample, mf is final weight of sample and t is the time in day. 2.7 statistical analysis graphs were plotted using microsoft excel version 2016 to compare means. spss version 20 was used to determine analysis of variance (anova) and means separation. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunsua et al: evaluation of nspri solar dryers for yam chips production (elubo). azojete,16(4):785-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 788 3. results and discussion 3.1 effect of water temperatures and drying media on drying rate of yam chip samples in all the drying systems, the highest drying rate was recorded on the first day (figure 3). the highest drying rate was recorded in the control on the first drying day regardless of the water treatment temperature considered (figures 3 and 4). this could be attributed to easy removal of surface moisture on the product by air in the ambient immediately after loading, while reduction in temperature and increase in humidity was experienced during the same period in the two dryers. thereafter, there was reduction in the drying rate of the control throughout the remaining drying period. the result further shows that for all water treatment temperatures, the pssd recorded the highest drying rate of 0.57 kg/ day while the lowest with an average value of 0.46 kg/ day was obtained in the control. std had an average drying rate of 0.52 kg/ day. the higher drying rate observed in the dryers can be attributed to the higher temperature maintained in them. pssd had an average temperature of 40.77°c, std recorded 34.62°c and control had 33.59°c. this resulted in reduced drying time in the pssd which took 3 days compared to 4 days in std and control (figure 3 and 4). this agrees with earlier studies conducted on pssd and std where higher temperatures were reported over the ambient (control) (ade et al., 2018; oyewole et al., 2019). table 1 shows the result of anova for the effect of water temperatures (80°c, 90°c and 100°c), drying media (pssd, std and control) and their interaction on drying rate. the result shows that the effect of drying system on drying rate was significant at p ≤ 0.05; while the effect of water temperature and its interaction with drying system was not significant at p ≤ 0.05. this is an indication that the type of dryer used for production of yam chip will have effect on number of days required for drying among other relevant factors. a b figure 3: drying rate versus drying time http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):785-792. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 789 (a1) (a2) (b1) (b2) (c1) (c2) figure 4: moisture content versus drying time and drying rate versus moisture content table 1: analysis of variance for drying rate source type iii sum of squares df mean square f sig. drying system .075 2 .038 171.278 .000* water temperature 3.889e-5 2 1.944e-5 .089 .915 drying system * water temperature .001 4 .000 1.627 .196 error .006 27 .000 total 9.744 36 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunsua et al: evaluation of nspri solar dryers for yam chips production (elubo). azojete,16(4):785-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 790 3.2 effect of water temperature and drying system on proximate composition the proximate composition of all samples regardless of the drying system and water temperature treatments gave carbohydrate, crude fibre and ash contents range of 80 – 84%, 1.1 – 2.0% and 1.1 – 1.5% respectively (table 2). these values are very close to those reported by adejumo et al. (2013) and fashina et al. (2017) where carbohydrate, crude fibre and ash contents ranged between 78 – 84%, 1.1 – 2.0% and 1.1 – 2.3% respectively. the result further shows increase in ash, crude fibre, crude protein and fat content and decrease in carbohydrate as water temperature increases in pssd, while there was no defined trend in std and control. there was no significant difference in crude fibre and ash content in all drying media at all water temperature treatments (p ≤ 0.05) (table 3). carbohydrate, crude fibre and crude protein differ significantly in std at 80°c, 90°c and 100°c respectively. these results agree with the reports of leng et al. (2011) and fashina et al. (2017). table 2: effect of water temperature and drying media on proximate composition of the dried yam chips yam chip crude ash (%) crude fibre (%)crude protein (%) crude fat (%) carbohydrate (%) pssd 80 1.25±0.12a 1.38±0.21a 4.15±0.35a 1.14±0.04a 84.38±0.81a std 80 1.35±0.12a 1.79±0.13a 4.78±0.38a 1.23±0.08a 80.68±0.26b control 80 1.25±0.08a 1.49±0.01a 4.28±0.03a 1.23±0.08a 82.11±0.14b pssd 90 1.26±0.13a 1.69±0.09a 4.70±0.29a 1.19±0.09a 83.05±0.32a std 90 1.38±0.16a 1.19±0.08b 4.14±0.22a 1.60±0.23a 81.98±0.37a control 90 1.53±0.13a 1.92±0.02a 4.33±001a 1.24±0.03a 81.92±0.16a pssd 100 1.42±0.20a 1.75±0.16a 5.37±0.13a 1.50±0.15a 81.95±0.30a std 100 1.08±0.02a 1.47±0.15a 4.48±0.27b 1.32±0.24a 81.86±0.87a control 100 1.17±0.07a 1.32±0.02a 4.51±0.03b 1.41±0.04a 81.81±0.13a (means ± s.e. within a column followed by different letters differ significantly at p≤0.05) *significant at p ≤ 0.05 table 3: analysis of variance for proximate composition sum of squares df mean square f sig. ash between groups .584 8 .073 1.391 .245 within groups 1.417 27 .052 total 2.002 35 fibre between groups 1.917 8 .240 5.102 .008* within groups 1.268 27 .047 total 3.185 35 protein between groups 4.790 8 .599 3.369 .005* within groups 4.799 27 .178 total 9.589 35 fat between groups .775 8 .097 1.918 .098 within groups 1.364 27 .051 total 2.140 35 carbohydrate between groups 32.899 8 4.112 6.022 .000* within groups 18.440 27 .683 total 51.339 35 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):785-792. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jonehmak@gmail.com 791 3.3 effect of water temperature and drying media on microbial loads the result of microbial quality evaluation shows that the bacteria and fungi counts of the dried yam chip samples inside pssd and std were within the acceptable limit of ≤ 300 cfu/ml and lower than that of the control sample where higher value above recommended standard was recorded (table 4) (cfsfeh, 2014). the relative decrease in the bacteria and fungi counts in samples dried in pssd and std might be due to the higher drying rate and structure’s enclosure against agents of contamination which could not be obtained in the control under ambient condition. the earlier the moisture in product undergoing drying is removed the better to prevent its susceptibility to microbial infection (adeniji, 1996). table 4: microbial quality evaluation of the yam chip yam chip bacterial (cfu/ml) fungi (cfu/ml) pssd 80 0.23 x 103 0.20 x 103 std 80 0.26 x 103 0.40 x 103 control 80 1.80 x 103 tntc pssd 90 0.30 x 103 0.15 x 103 std 90 0.29 x 103 0.60 x 103 control 90 1.80 x 103 2.00 x 103 pssd 100 0.25 x 103 0.20 x 103 std 100 1.25 x 103 0.30 x 103 control 100 1.50 x 103 1.60 x 103 note: tntc = too numerous to count; cfu/ml = colony forming unit per mil. 4.0 conclusion drying systems were found to have significant effect on drying rate of the yam chips. maximum drying rate was recorded in pssd with average value 0.567 kg/ day while control had the lowest (0.46 kg/ day). drying was completed in pssd in 3 days while it took 4 days in std and control. also, carbohydrate, crude fibre and protein contents were significantly affected by the drying. maximum carbohydrate content of 84.38% was recorded in pssd at 80°c and minimum value of 81.81% was recorded in control at water treatment temperature of 100°c. there were acceptable microbial loads in both the pssd and std dried chips after the tests and are considered safe for human consumption. references ade, ar., olayemi, ff., adebiyi, ao., zubair, om., adeiza, oa. and achime, kc. 2018. recent advances in solar drying of agricultural produce in nigeria: nspri experience. arid zone journal of engineering, technology and environment, 14: 86-94. adejumo, ba., okundare, ro., afolayan, oi. and balogun, sa. 2013. quality attributes of yam flour (elubo) as affected by blanching water temperature and soaking time. the international journal of engineering and science (ijes), 2(1): 216 221 adeniji, mo. 1996. fungi associated with the deterioration of gari, nigerian journal of plant protection, 2: 74-77. aderinlewo, aa., adisa, af. and salaudeen, o. 2013. investigation of solar drying of plantain and cassava slices under natural convection. journal of experimental research. 1(1): 21-24. aoac. 2005. association of official analytical chemists. official method of analysis. 14th edition. washington d.c., usa. cfsfeh. 2014. the centre for food safety, food and environmental hygiene department. microbiological guidelines for food. revised edition. queensway, hong kong. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ogunsua et al: evaluation of nspri solar dryers for yam chips production (elubo). azojete,16(4):785-792. issn 1596-2490; 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numerical simulation. solar energy, 60:151–157. ringeisen, b., diane, m. and barrett, ps. 2014. concentrated solar drying of tomatoes. energy for sustainable development, 19: 47-55. sadodin, s. and kashani, tt. 2016. numerical investigation of a solar greenhouse tunnel dryer for drying of copra. arxiv.org/pdf/1102.4522, 2016, accessed on october 30, (2019). toshniwal, u. and karale, sr. 2013. a review paper on solar dryer. international journal of engineering research and applications, 3(2): 896-902. ukpabi, uj., omodamiro, rm., kkeorgu, jg. and asiedu, r. 2018. sensory evaluation of amala from improved water yam (dioscorea alata) genotypes in nigeria. african journal of biotechnology, 7(8): 1134 – 1138 https://www.cfs.gov.hk/english/food_leg/files/food_leg_microbiological_guidelines_for_food_e.pdf https://www.cfs.gov.hk/english/food_leg/files/food_leg_microbiological_guidelines_for_food_e.pdf http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(2):221-230 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 221 original research article decline in agricultural activity around lake chad: any prospect for restoration? a review a. b. alhassan1*, a. m. chiroma1, a. m. kundiri2, b. bababe1 and i. j. tekwa3. 1department of soil science, university of maiduguri, p.m.b. 1069 maiduguri, borno state nigeria 2office of the vice chancellor, federal university wukari, taraba state, nigeria 3department of soil and land resources management, federal university wukari, p. m. b. 1020, wukari, taraba state, nigeria *corresponding author’s email address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 1.0 introduction the lake chad basin is one of the largest inland drainage basins in africa. the borno and yobe states of nigeria are located within the basin and cover an area of about 116,000 km2 (bunu, 1999). the basin which covers about 8 percent of the surface area of the african continent is being shared between the countries of chad, cameroon, niger and nigeria (figure 1). the lake has been a source of livelihood to about 30 million people, most of whom are farmers, fishermen and livestock breeders (adamu, 2005). it is widely believed that the lake shrunk to about 10% of its original size over the last few decades thus heavily impacting the basin’s economic activities and food security. the shrinkage of the lake has been driven by both global and local causes: climate change and the ever increasing competing demands on the lake and its surrounding land have accelerated its shrinkage over the past years. human impacts such as damming of rivers, increased irrigation, and reduced rainfall are among the obvious reasons for water shortages in the lake. article information abstract lake chad that has been an economic hub for centuries has in the last few decades witnessed continued degradation threatening food security and livelihood of the population who depend on the lake for a living. the impact of depletion of the lake is being felt by an estimated 30 million people from the four riparian states, namely: cameroon, chad, niger and nigeria. this paper focuses on the causes of low agricultural activity around lake chad with particular emphasis on crop production. the paper also highlights the prospects for reviving agricultural activity through implementation of innovative soil management techniques. analysis of the literature revealed that in addition to devastating effects of violent armed conflict on livelihood conditions in this region, frequent drought, dwindling rainfalls, degraded soils and sparser vegetation cover are among the factors responsible for the low agricultural activity in this region where a large proportion of the population relies on rainfed agriculture. the review revealed that organic farming practices that support biodiversity has the potential for besides improving soil health and reduce pest pressure, also improve crop yields and protect the environment. furthermore, the use of biofertilizers to reduce the dependence on conventional inorganic fertilizers by farmers offers the means of mitigating the declining soil mineral nutrient reserves in this region. it is envisaged that restoring the lake to its near original state coupled with improving the productivity of the fragile soils will go a long way in addressing the challenges of food insecurity, a major factor stabilizing factor in the area © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 october., 2020 revised 30 march, 2021 accepted 1 april, 2021 keywords: agriculture armed conflict climate change food security lake chad alhassan et al: decline in agricultural activity around lake chad: any prospect for restoration? a review. azojete, 17(2):221-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 222 figure 1: satellite image of lake chad in 2017 with the actual lake in blue and vegetation in red source: https://www.earthobservatory.nasa.gov/images/91291/the-ups-and-downs-of-lake-chad accessed on 8th march, 2021 the ensuing water shortage has impacted negatively on the basin’s economic activities including the fisheries, agriculture, animal husbandry sand wetland economic services. studies have shown that prospects of natural recharge through precipitation are limited by excessively high temperatures causing most of the precipitation to evaporate as soon as it falls. the depletion of lake chad poses a pressing challenge to the flood recession agriculture widely practiced around the lake and the adjoining riverine wetlands. flood recession farming is an important water consumer and the source of livelihoods for the overwhelming majority of the population consisting mainly of traditional smallholders, producing mainly staple foods for household consumption. studies have shown that much as much as half of existing as well as potentially productive agricultural land in developing countries is being lost through the processes of land degradation and abandonment (cleaver and schreiber, 1994; barbier, 1997). it is widely acknowledged among both soil specialists and policy-makers that soil degradation in sub saharan africa (ssa) is expanding at an alarming rate, accompanied by the lowest agriculture and livestock yields of any region in the world (fao, 2015) and that, unless the process of degradation is controlled, many parts of the continent will suffer increasingly from food insecurity (lal, 1990; unep, 1982). however, of all the threats to soils and related ecosystem functions in ssa, the most critical are soil erosion, loss of soil organic matter, soil nutrient https://www.earthobservatory.nasa.gov/images/91291/the-ups-and-downs-of-lake-chad http://www.scialert.net/asci/result.php?searchin=keywords&cat=&ascicat=all&submit=search&keyword=developing+countries arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):221-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 223 depletion and loss of soil biodiversity (fao, 2015). in the sudan and sahel regions of nigeria in particular, the over-dependence on the natural resources for survival has exerted uncontrolled pressure on the land (samaila, 2005). overgrazing and inappropriate cultivation practices are the principal causes of soil degradation in most part of nigeria irrespective of ecological differences (olderman et al., 1991). due to serious degradation of soil and water resources in and around the lake, interest has been developing in recent years for seeking ways to improve the productivity and livelihoods of the small-scale farmers in lake chad basin. this paper examines the declining trends in agricultural productivity around the basin and makes recommendations on strategies for improving productivity of smallholder production systems around the lake. 2. ecological settings in lake chad basin the hydrology of the lake chad basin is dominated by the logone-chari rivers, the komadugu-yobe, the yedseram and the el-beid rivers (ngounon-ngatcha, 2009). the logonechari rivers account for more than 90% of the volume of water supplied to the lake each year. the komadugu-yobe and yedseram rivers discharge less than 10% of the northern pool of the lake chad (olivery et al., 1996; iliya and bura, 2012). the rainfall distribution over the area is determined by the position of the meteorological equator and its two associated structures, the inter tropical front (itf) and inter tropical convergence zone (itcz) (thambaypillay, 1991). this zone is defined as the southern border of the sahara desert, characterized by low and unreliable annual rainfall, usually between 200 and 600 mm/year, along a positive gradient southward and occurring mainly between june and october (visser and sterk, 2007). rainfall patterns are erratic and unpredictable, and crops can suffer from moisture deficits and drought even during normal rainfall periods (parr et al., 1990). the zone is characterized by sparse vegetation cover with the species consisting of thorny shrubs interspersed between annual and perennial grasses at the north which changes to taller vegetation with more trees towards the south (herrmann et al., 2005). the northern half of the basin is desert, containing the tenere desert, erg of bilma and djurab desert. south of that is the sahel zone, characterized by dry and thorny shrub savanna. majority of the soils in the lake chad as elsewhere in the sahel are sandy with the dominant soil types being entisols and alfisols (kang, 1985), low in organic matter, nutrient and water reserves available for plant growth (chiroma et al., 2010b; bationo et al., 2014). these soils are believed to have formed from wind-sorted desert sands that accumulated over long periods of time when the sahara desert encroached several kilometers south of its present limits (cpn, 1997). aridity has enhanced the deposition of sand by wind developing into sandy loams, friable and easy to cultivate (lloeje, 1982). vertisols with high productive potentials are also found in this zone (cpn, 1997). selected characteristics of the major soil types found in this zone are presented in tables 1 and 2. alhassan et al: decline in agricultural activity around lake chad: any prospect for restoration? a review. azojete, 17(2):221-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 224 table 1: physical properties of the surface (0-20 cm) of a vertisol around lake chad. particle size distribution (%) auger no. sand silt clay *soil texture class % dispersible silt + clay bulk density (g/cm3) penetration resistance (kpa) moisture content (%) hydraulic conductivity (cm/h) a1 38.9 15.0 51.1 c 83.2 1.66 620 0.188 a2 34.1 17.8 48.1 c 63.2 1.47 551 0.305 a3 53.9 30.0 16.1 sl 42.2 1.21 448 0.516 0.044 a4 33.9 17.5 48.6 c 58.1 1.39 498 0.502 a5 53.9 10.0 36.1 c 58.2 1.36 476 0.512 a6 28.9 22.5 48.6 c 65.8 1.56 613 0.276 mean 40.6 18.8 41.4 c 61.7 1.44 534 0.383 *c = clay; l = loam; sl = sandy loam. source: chiroma et al. (2010a). table 2: chemical properties of the surface (0-20 cm) soils around lake chad. auger no ph ec (ds/m) exchangeable cations cec (me/100g) base saturation % esp om (%) n (%) p (mg/kg) ca2+ mg2+ k+ na+ total me/100g a1 7.2 0.50 15.6 16.8 0.94 0.34 33.7 34.0 99.1 1.00 2.80 0.31 22.5 a2 7.4 0.80 14.8 11.6 1.23 0.35 28.0 28.3 98.9 1.24 2.08 0.29 15.0 a3 8.9 0.14 54.4 19.2 0.77 15.3 89.4 89.7 99.7 17.1 0.58 0.10 2.8 a4 7.8 0.33 51.7 20.6 0.87 1.21 74.4 74.8 99.5 1.62 0.60 0.15 4.0 a5 7.6 0.34 19.4 18.1 1.10 0.78 39.4 39.8 99.0 1.96 1.57 0.27 11.0 a6 8.2 10.3 22.7 23.1 0.90 5.00 51.7 52.1 99.2 9.60 1.34 0.08 6.0 mean 7.9 2.07 29.8 18.2 0.97 3.83 52.8 53.1 99.4 5.42 1.50 0.20 10.2 source: chiroma et al. (2010b). arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):221-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 225 table 3: crop production figures for south chad irrigation project year area cropped to rice (ha) yield (tons) area cropped to wheat (ha) yield (tons) area cropped to sorghum (ha) yield (tons) area cropped to cotton (ha) yield (tons) area cropped to maize (ha) yield (tons) area cropped to cowpea (ha) yield (tons) area cropped to vegetables (ha) yield (tons) 1979/80 526 23,929 730 14,525 1980/81 792 19,357 1,152 12,160 58 111 1981/82 493 8,525 2,240 27,367 140 5 1982/83 672 8,757 4,945 103,101 100 3,000 1983/84 7,000 145,492 1,000 1,500 7,500 15,000 600 12,000 1984/85 2,750 2,850 50 50 3,400 3,400 10,000 25,000 800 16,000 1985/86 1986/87 1987/88 1988/89 6,000 80,100 1989/90 5,200 72,350 1990/91 1991/92 5,000 42,692 1992/93 4,991 25,817 1993/94 1994/95 20 400 4,500 13,334 1995/96 45 1,000 1996/97 136 51 2,221 13,358 1997/98 152 485 759 1,938 1998/99 40 992 1999/00 100 3,099 200 1,139 2000/01 155 3,131 2001/02 712 6,644 6,049 3,867 2002/03 453 4,688 436 2,683 2003/04 125 401 2004/05 116 2005/06 120 55 alhassan et al: decline in agricultural activity around lake chad: any prospect for restoration? a review. azojete, 17(2):221-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 226 3. agriculture around lake chad the vast majority of the people representing about 80-90% of the population in the lake chad basin rely mainly on agriculture for their livelihood and food security. crop production and agro-pastoralism are the main economic activities in areas with rainfall of about 600 mm whiles in areas with rainfall of about 400 mm, rearing of livestock is the main economic activity (mortimore and turner, 2005). the farming communities in the upstream (uplands) practice rainfed agriculture in the months of june to october to grow mainly millet, sorghum, cowpea and groundnut on the sandy soils poor in nutrient and water retention capacity. communities in the downstream and fortune seekers coming from drought stricken areas in the region practice flood recession agriculture to grow diverse types of cereal crops including maize, rice, wheat and vegetables. the majority of the population being small holder farmers relies on the traditional methods of farming characterized by zero or little usage of external inputs such as improved seeds, fertilizers and other agro-chemical necessary for sustained productivity. in recent years, farmers practicing the rainfed crop cultivation are faced with numerous challenges such as low soil productivity, low and variable rainfall brought about by climate change, environmental concerns and global market changes, which have had major local impacts on their production system organization, dynamics and viability. an empirical assessment of subsaharan africa’s soil fertility confirms that the region faces a significant decline in soil fertility, which could worsen food security if no appropriate action is taken. jama and pizarro (2008) argued that increased productivity and food security can be achieved in africa if the appropriate investments are made in key interventions: soil fertility improvement, improved seeds, water management, market access, extension services, access to credit, and improvements in weather forecasting. whereas the extent and rate of soil degradation in ssa is still under debate as there are no reliable data to substantiate such claims, nevertheless, there is growing evidence that certain soils are losing their ability to provide food and essential ecosystem services (tully et al., 2015). this could be true particularly in the case of soils around the lake chad. field observations revealed that farmers often reallocate their fields from upland areas as an adaptation to declining rainfall and soil fertility. alternatively, some farmers resort to cultivating more land than their family labour can support in a desperate attempt to stabilize crop yields (chiroma et al., 1996). often times, such farmers abandoned their fields to weeds owing to labour shortage during critical periods of the season. agricultural extensification is gaining popularity in many farming communities in the sahel as part of adaptation mechanism in the face of ever growing challenges posed by climate change. extensification in many dryland areas do not always result in increased yields per unit land area. for example, pearl millet production increased in niger and mali due to extensification, but yields remains unchanged for about 30 years (fao, 2007). although farmers in this zone have in recent years perceived a steady decline in crop yields due to decline in rainfall and soil quality, it is practically impossible to assess the contributions of these environmental factors to the yield decline in the absence of reliable data on crop yields from famer managed fields. small holder farmers in developing countries often lack the culture of record keeping making comparative analysis difficult. the narrative from institutionally managed fields like the one by the chad basin development authority (cbda) is not encouraging either. the cbda established a gigantic irrigation scheme known as south chad irrigation project (scip) in the lake chad basin with the mandate of growing crops like rice, arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):221-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 227 wheat, maize and sorghum. the scheme at its inception in 1979 was able to cultivate a total of 525.6 ha of rice and 730 ha of wheat yielding about of 23,929 and 14,525 tonnes of paddy rice and wheat, respectively (tables 3). as shown in the table, the scheme recorded relative success in the years between 1979/80 and 1983/84 and beyond this period the scheme suffered some setbacks as a result of unsustainable government policies towards agriculture, the changing climate and poor funding among other constraints. this dismal performance by institutionally managed fields further confirms the enormity of the twin challenges posed by climate change and decline in soil quality. 4. innovative technologies for improving soil quality marginal, infertile soils occupy most of the adjoining uplands around the lake chad basin. these soils are besides being coarse textured, low in organic master content and nutrients, occur in a harsh environment characterized by low water availability and supra optimal soil and ambient air temperatures. these soils can be made productive if the soil degradation processes are offset by appropriate soil conservation/reclamation practices. commercially available fertilizers containing npk (nitrogen, phosphorus and potassium) are globally known to be the "best" method in agriculture due to its economic benefits, especially for farmers and entrepreneurs who would like to increase crop yields at the lowest cost possible (javier, 2018). however, chemical fertilizers are expensive, non-eco-friendly, cause eutrophication, reduce organic matter and micro-biotic activity in soil and are hazardous to health (sahoo, et al., 2017). from an ecological perspective, the use of artificial fertilizers proves to disrupt the nutrient ratio in soils and lead to the competition of plants in croplands. this can be considered as one of the main cause of competitive exclusion among vegetation. furthermore, repeated application may cause toxic buildup of chemicals in soils and may alter the soil ph which can harm beneficial microbial ecosystems (javier, 2018). therefore, the use of biofertilizers is desirable as they are natural, biodegradable, organic and more cost-effective than chemical fertilizers. biofertilizers consist of plant remains, organic matter and some special class of micro-organisms. regular additions of organic materials such as animal manures and crop residues to soils can reduce erosion and nutrient runoff losses, improve soil structure, increase water-holding capacity, lower soil temperatures and provide a source of plant nutrients. organic farming practices such as crop rotation and polycultures that support biodiversity, are known to besides improving soil health and reduce pest pressure, also improve crop yields and protect the environment (ponisio, 2014). interestingly, both these practices mimic nature by creating ecologically diverse systems that draw strength from natural interactions between species. the study by ponisio, (2014) show that although organic crop yields are about 19% lower under organic farming than conventional systems, certain management practices such as planting multiple different crops at the same time (polyculture) and planting a sequence of crops (crop rotation) on an organic farm cut the difference in yield by about half. overall, the significant role of biofertilizers in plant growth productivity and protection against some stresses makes them a vital and powerful tool for organic and sustainable agriculture (sahoo, et al., 2017). the application of microbial inoculants (biofertilizers) is a promising technology for future sustainable farming systems in view of rapidly decreasing phosphorus stocks and the need to more efficiently use available nitrogen (n). various microbial taxa are http://www.sciencemag.org/content/277/5325/504.full http://theconversation.com/profiles/lauren-c-ponisio-147848 http://theconversation.com/profiles/lauren-c-ponisio-147848 alhassan et al: decline in agricultural activity around lake chad: any prospect for restoration? a review. azojete, 17(2):221-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abbalhassan@gmail.com, abalhassan@unimaid.edu.ng 228 currently used as biofertilizers, based on their capacity to access nutrients from fertilizers and soil stocks, to fix atmospheric nitrogen, to improve water uptake or to act as biocontrol agents (schütz et al., 2018). efforts to mitigate the declining mineral nutrient reserves are currently major topics of research but the perturbance of the global biogeochemical cycles, mainly driven by the use of mineral fertilizers, remains a serious problem (kahiluoto et al., 2014). several studies have demonstrated the potential of biofertilizers in fixing nitrogen (n), help to access nutrients such as phosphorus (p) and n from organic fertilizers and soil stocks, improve drought tolerance, improve plant health or increase salt tolerance (vessey, 2003; arora, 2013). examples of microbial inoculants tested in these and other studies include arbuscular mycorrhizal fungiamf (lekberg and koide (2005); berruti et al., (2016); schütz et al., 2018), plant growth-promoting rhizobacteria-pgpr (rubin et al., 2017). the results of these and other studies have often been inconsistent due mainly to reasons such as soil conditions, strain identity, or host genotype. schütz et al., (2018), however, opined that what is missing is a comprehensive quantitative analysis over all biofertilizers and across all target crops and climatic conditions at global scale. these authors recently analyzed the potential of arbuscular mycorrhizal fungi as biofertilizers under multi-climatic environments and concluded that averaged across all biofertilizer categories, yield was increased the most in dry climates (+20.0 ± 1.7%), followed by tropical climates (+14.9 ± 1.2%), oceanic climates (+10.0 ± 3.7%), and continental climates (+8.5 ± 2.4%). the authors however, cautioned that in interpreting these results it is important to keep in mind that 45% of the comparisons in dry climate were conducted in the presence of irrigation. 5. conclusions based on the analysis of current situations in the lake chad, there is evidence that resources in and around the basin are under enormous pressure arising mainly from the influx of people in search of opportunities. the increased competing demands on the lake and its surrounding land have accelerated its shrinkage and the subsequent deterioration of soil resources around the lake. it is envisaged that improving the productivity of the fragile soils will go a long way in addressing the challenges of food and energy insecurity, a major stabilizing factor in the area. organic farming practices that support biodiversity, are known to besides improving soil health and reduce pest pressure, also improve crop yields and protect the environment. furthermore, the use of biofertilizers to reduce the dependence on conventional inorganic fertilizers by farmers offers the means of mitigating the declining soil mineral nutrient reserves in this region. references adamu, ms. 2005. managing water resources of the lake chad. a paper presented the international conference on irrigation and drainage (icid), beijing, p. r. china. arora, nk. 2013. plant microbe symbiosis: fundamentals and advances. in plant microbe symbiosis: fundamentals and advances, (arora, nk. 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(accessed on 29th april, 2018). rubin, rl., groenigen, kj. and hungate, ba. 2017. plant growth promoting rhizobacteria are more effective under droughts: a meta-analysis. plant and soil, 416: 309-323. doi10.1007/s11104-017-3199-8 sahoo, rk., bhardwaj, d. and tuteja, n. 2017. biofertilizers: a sustainable eco-friendly agricultural approach to crop improvement. plant acclimation to environmental stress, pp 403-432. available online at: https://link.springer.com/chapter/10.1007/978-1-4614-5001-6_15 samaila, ik. 2005. soil erosion management for a sustainable development in the sudano sahelian regions of northern nigeria. the nigerian academic forum, 9(3): 18-23. schütz, l., gattinger, a. meier, m. müller, a. boller, t. mäder, p. and mathimaran, n., 2018. improving crop yield and nutrient use efficiency via biofertilization-a global meta-analysis. frontiers in plant science, 8: 1-13. tully, k., sullivan, c., weil, r. and sanchez, p. 2015. the state of soil degradation in subsaharan africa: baselines, trajectories, and solutions. sustainability.7: 6523-6552. unep, 1982. world soil policy. united nations environment programme, nairobi, kenya. vessey, jk. 2003. plant growth promoting rhizobacteria as biofertilizers. plant soil, 255: 571– 586. doi: 10.1023/a:1026037216893. visser, sm. and sterk, g. 2007. nutrient dynamics-wind and water erosion at the village scale in the sahel. land degradation and development, 18(5): 578-588 http://theconversation.com/profiles/lauren-c-ponisio-147848 http://theconversation.com/organic-farming-techniques-are-closing-gap-on-conventional-yields-35320 http://theconversation.com/organic-farming-techniques-are-closing-gap-on-conventional-yields-35320 https://link.springer.com/book/10.1007/978-1-4614-5001-6 arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):79-96 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 79 original research article involvement of the general public in the management of water pollution in johor bahru malaysia b. y. sanda1*, a. u. bah2 and a. ibrahim1 1department of civil engineering, faculty of engineering, kebbi state university of science and technology aliero. kebbi state, nigeria. 2department of civil engineering, faculty of engineering, fourah bay college, university of sierra leone, sierra leone. *corresponding author’s email address: sandabashir@gmail.com 1.0 introduction one of the most serious challenges facing the world today is the issue of environmental contamination. water is perhaps the most fragile element of the ecosystem, yet it is necessary for human and industrial progress. the demand for water supply and drinkable water rises as the population grows (afroz, et al., 2014). water and its long-term usage had become strongly intertwined to advancements in other sectors such as industry, agriculture, and other services, also energy, environmental protection, and hygiene. increased water consumption, poor discharge quality, and climate change have developed numerous water pollution problems that can only be addressed via concerted efforts of diverse stakeholders with collaboration and public participation (teodosiu et al., 2013). water covers roughly 71percent of a total of the earth's surface and highly vital natural resource for humans (national environment research council, 2007). however, only 2.5 percent of the world's water is pure and thus drinkable. it is everyone's fundamental human right to have access to clean water. water pollution has consequences on drinking article information abstract water is undoubtedly the most delicate component of the ecosystem, but it is essential for human and industrial advancement. as the population grows, so does the demand for water supplies and drinkable water. water covers roughly 71percent of the total earth’s surface and highly vital natural resource for humans. however, only 2.5 percent of the world's water is pure and thus drinkable. it is everyone's fundamental human right to have access to clean water. the purpose of this study is: to identify the current level of public involvement in water pollution management and to assess people's desire to participate towards reducing water pollution. the study's methodology is a quantitative approach for achieving the research objectives. a total of sixty-three (63) responses were reordered from the distribution of the questionnaires. the data collected were analysed using microsoft excel (2019) and simple percentage distribution tables and charts. the findings revealed that most of the participants have sewerage connections in their residences and that the water quality of their rivers is acceptable for majority of the participants. the study also indicated that water pollution is a grave concern for environmental and social health. in addition, it was observed that community involvement in water pollution decision-making processes was currently low on average, implying that authorities still have room to improve concerning water pollutant information delivery. majority of respondents agreed that investing more money in water and waste management, and educating the public, are strategies to enhance water quality. eventually, the findings revealed that the general public is enthusiastic about taking part in the fight against water pollution and are ready to participate in water pollution management in their community. the study recommends building a solid foundation to allow greater public involvement in decision-making and to enacting strict water pollution control policy. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 8 september, 2021 revised 23 november, 2021 accepted 2 december, 2021 keywords: involvement public pollution water pollution factors and management of water pollution http://www.azojete.com.ng/ mailto:sandabashir@gmail.com mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 80 water, rivers, lakes, and oceans around the globe, putting human health and the ecosystem at risk. sewage and wastewater pollution, effluent, oil pollution, industrial discharges, anthropogenic activities, toxic chemicals, underground storage leakages, and global climate change are examples of water pollution (gambhir et al., 2012). polluted water would not harm an individual's health instantly, but it can be deadly over time. toxic metals from industrial processes can build up in adjacent lakes and rivers posing a threat to marine species, and animals that consume the contaminated water, and human beings who consume animal products. immunity repression, reproductive problems, and acute poisoning can all be caused by pollutants found in industrial waste. infectious illnesses like cholera and typhoid fever, which are the leading causes of infant mortality, are frequently caused by microbial contaminants found in wastewater (juneja and chaudhary, 2013). water is necessary across all life, including health, spiritual beliefs, safety, livelihood, and the global ecology. individuals may place different values on the services supplied by an aquatic ecosystem. climate change, population expansion, increasing agricultural output, and greater extraction are only a few of the factors hampering the world's water supply (rolston et al., 2017). sustainable development goal (sdg6) focuses on improving water quality by decreasing pollution, removing the discharge of dangerous chemicals, limiting the discharge of untreated wastewater, and enhancing waste management. sdg6 states that, "ensure availability and sustainable management of water and sanitation for all." population increase, expansion of agricultural, urban, factory output and pollution, and environmental degradation, on the other hand, are becoming to overburden and threaten nature's capacity to supply essential resources and activities. according to projections, in 2050, nearly half of the worldwide gross domestic product, 52 percent of the world's population, and 40 percent of total agricultural production will be at risk if the natural environment continuing to be polluted and excessive stresses continue on worldwide water supplies. polluted water is a big challenge that plagues people across the globe. it affects the world's drinking water, rivers, lakes, and seas. as a result, it harms human health and global ecosystems. water pollution does affect not only the current generation and future generations since its effects last a long time. if a body of water becomes contaminated in a particular region, all living things and humans become forced to consume the contaminated water because they have no other choice (khatun, 2017). water is polluted by hazardous and toxic chemical emissions, resulting in several issues such as human food safety and irrigation operations. it causes water shortages because it reduces the amount of water available to people and the environment. polluted water is the primary cause of the water problem. water should not be polluted beyond a specific level to utilize for irrigation and drinking purposes (singh et al., 2020). according to (who, unicef ans glaas, 2021), universally, an “ estimated 2.2 billion people do not have access to safe drinking water, and 4.2 billion do not have access to safe sanitation.” the factors vary and are due to a variety of causes and conditions. physical water shortages are the most common cause in extreme semi-arid lands that are prone to climatic changes that jeopardize their liveability. unfortunately, the bulk of these 2.2 billion people are poor people who live near rivers or on polluted groundwater, not thirsty people without water in their living surroundings. pollution has come at substantial risk, impacting water supply concerning quantity and quality for agriculture, navigation, recreation, and tourism, causing flooding and pollutants (chan, 2012). water is the most vital source of survival that enables us to exist and keeps people alive. everyone must drink fresh, pure water. water becomes polluted because of natural and artificial sources, resulting in the emergence of various water contaminants. for people's health and protection against infectious illnesses, various water pollutants require removal from the water supply (singh et al., 2020). pollution of water is typically known as a change in the physical, chemical, or biological features of water that can affect aquatic and human life (khatun, 2017). in malaysia, water pollution is a significant concern that harms the long-term viability of water resources. it also affects plants and organisms, as well as people's health and the nation's economy. it significantly file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 81 affects the total water supply since the expense of treating polluted waterways is prohibitively expensive, and in some cases, wastewaters are unfit for human consumption. because of river contamination, the vast amount of water resources available in the catchment doesn't assure enough distribution to all users (afroz and rahman, 2017). within the river catchments, urbanization has increased urban density life activities. the quality of run-off inside a catchment usually alters because of urbanization, which affects the water quality of water bodies. rainfall discharges toxins deposited on land surfaces into stormwater systems in developed areas. sewage from residential, commercial, and industrial locations has a terrible odour, specifically when rubbish is present, degrades stormwater quality, and contaminates the present river basin. although some pollutants originate from natural causes, the majority of pollution is dependent on human action (afroz et al., 2014). water pollution has become a more serious concern, with data signifying a declining pattern year after year. on the other hand, water contamination is not a new environmental problem; it had long become associated with development and modernity. primarily the source of malaysia's freshwater supplies 97 percent of the country's overall water supply (afroz and rahman, 2017). malaysia has an abundance of rainfall and water resources. with an annual average rainfall of 3,000 mm, the river basin receives an estimated 566 billion m3 of water (afroz et al., 2014). in recent times, public involvement in water management has grown exponentially. multiple interconnected causes have propelled the rise of participatory decision-making procedures around the universe. increasing public knowledge and awareness about links across environmental health and human well-being are the key drivers. people's expectations of participation in policy-making have risen as human rights have gained momentum in legal and political structures (razzaque, 2009). the european commission recognizes the significance of public involvement (pp) in water management in its water framework regulation, which was the first regulation to ask member countries to engage and educate the public (european enviroment agency, 2014). public involvement is commonly known as yielding individuals to have a say in the design and execution of a project. in general, there are three types of involvement: information dissemination, engagement, and active participation (european comission, 2003). according to european enviroment agency (2014), the primary goals of public participation in water policy are to strengthen water management and raise awareness of environmental challenges through decision-making procedures. on the other hand, water specialists showed that the planet is not experiencing a catastrophe due to physical water shortages but rather a consequence of continuous poor supervision of its water management (biswas and tortajada, 2011). in most western nations, the involvement of the public is a critical means of enhancing water quality through minimizing pollution, removing hazardous chemical discharges, lowering untreated wastewater discharges, and improved the management of waste (li et al., 2018). participation of the public has been proved to be efficient in a wide range of development activities, including preventing water pollution in previous studies (dungumaro and madulu, 2003; kaji, 2012; özerol and newig, 2008). therefore, the aim of this study is to identify the current level of public involvement in water pollution management, and to assess people's desire to participate in efforts aimed at reducing water pollution. 1.1. factors of water pollution one of the most critical challenges nowadays is water contamination. water is the most polluted of allnatural resources. the following are some of the contributing elements to water pollution: industrial development, plastics, and polythene bags, pesticides and fertilizers, sewage and other oxygen-demanding pollutants, residential sewage, population increase, urbanization, eutrophication, mining, agrochemical wastes, nutrient enrichment, thermal pollution, oil spillage, sediment disruption, acid rain pollution, radioactive waste, climate change (afroz et al., 2014; haseena et al., 2017; kılıç, 2021). domestic sewage is said to be responsible for 75 to 80 percent of water pollution. pesticides, sugar, textile, paper, and pulp http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 82 waste from electroplating industries pollute the water (kamble, 2014). water pollution and water resources have an unpleasant odour and are devoid of flora and animals. water security is critical for 80 percent of the planet's population (owa, 2013). a large amount of domestic sewage becomes discharged into the river, most of which is untreated. solid trash, toxicants, plastic litter, and bacterial pollutants are all found in domestic sewage, and these toxic items pollute the water supply. one of the principal sources of water in various industrial waste becomes emptied into rivers without being treated (kaprada and valsad, 2014). the factors that contribute to water pollution as summarized in figure 1. domestic sewage factors of water pollutionurbanization industrialization poor management system population density oil spillage acid rain pecticideradioactive waste climate change water table figure 1: factors of water pollution water pollution can be divided into two types: point sources and non-point sources. pipelines and pipes are examples of point sources with discharges that enter a body of water at a selected point. industries, sewage treatment plants, and animal farms are all examples of point sources. non-point sources typically obtained from diffuse sources, such as agricultural activities and surface runoff, have no examples of discrete release locations (afroz and rahman, 2017). according to (afroz et al., 2014), residential sullage, sewage systems, and industrial sites became considered as the fundamental point sources. apart from these, the river system gets polluted by additional point sources such as a market, restaurant, workshop, residential area, solid waste disposal sites, soil and sand extraction, huge development area, aquaculture, commercial lots, gas station, cattle, and many others. non-point source pollution impacts a water body through dispersed sources, and it can originate from a range of places. non-point source pollution is more difficult to control than point source pollution. the distinction between point source pollution and nonpoint source pollution has depicted in table 1. table 1. point sources and non-point sources (kılıç, 2021). point sources non-point sources mine, oil-field, and unsewered industrial sites runoff agriculture-related runoff effluent from waste water pollutant activities on land integrated storm and sanitary sewer spills runoff from mines that have been abandoned animal feedlot runoff and intrusion leachate from septic systems and discharge from damaged septic tanks runoff from construction sites covering more than 2 hectares grassland and rangeland runoff outfalls from storm sewers in cities with populations more than 100,000 over a water surface, atmospheric deposition waste disposal site runoff and leaching construction-related runoff unsewered and sewered urban runoff areas with a population of 100,000 or more file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 83 in malaysia, 1,488,848 sources of water contamination were recorded in 2014, opposed to 1662329 sources in 2013. in 2014, there was a drop in the total number of sources of pollution when relative to 2013. research done by manufacturing industries in 2000 revealed that the food and beverage industry accounted for 23.7 % of total pollutants in water, whereas energy and electronics showed 11.4 %. the chemical industry accounts for 11.2 % of contamination, while the paper industry accounts for 8.8 %. the finishing industry/textile sector accounts for 7.4% and 5.3 %, respectively, of the sources of water pollutants. factory effluents, oil palm effluents, and rubber effluents created in water resources accounted for 5.3, 2%, and 2%, respectively. overall, these types of factors affected selangor, johor, and perak significantly. selangor (414), johor (384), pulau penang (328), and perak had the highest concentration of water pollution sources in peninsular malaysia. in peninsular malaysia, these are also the most industrialized states (afroz and rahman, 2017; muyibi et al., 2008). 1.2. forms of water pollution pollution can be classified into several categories. organic contaminants, inorganic contaminants, radioactive pollutants, floating solids, pathogens, nutritional and agricultural pollutants, and thermal contamination are all examples of pollutant types. 1.2.1. organic contaminants carbon, hydrogen, oxygen, nitrogen, and sulphur are all found in organic compounds. sewage, municipal wastewater, industrial wastewater, and agricultural waste all produce organic compounds. oleic acid, palmitic acid, dodecanoyl chloride, and docosanoic anhydride are some examples of these acids. organic pollution is known as when substantial volumes of organic substances got discharged into sewers from sources such as domestic activities, sewage, urban runoff, industrial wastewater, and agricultural waste (ekevwe et al., 2018; singh et al., 2020). 1.2.2. inorganic contaminants drinking water pollution by hazardous compounds such as nitrate, ammonium nitrate, and heavy metals is a worry in developing nations. high amounts of inorganic nitrogen pollutants (nitrate, nitrite, ammonium) and inorganic phosphates in river water are caused by draining water from agricultural fields, releasing municipal/industrial sewage, and other factors that cause several health issues. nitrite is a carcinogen by design, increasing the risk of stomach, liver, and esophageal cancer as well as raising ammonium levels in the body (singh et al., 2020). 1.2.3. radioactive pollutants radioactive and nuclear pollution occurs when radioactive and nuclear pollutants get released into the water, air, or land due to nuclear explosions and accidents, nuclear weapons, or the handling or disposal of radioactive sewage. because radioactive elements are harmful to the environment, plants, animals, and humans, they can pollute surface water bodies. radioactive chemicals, such as radium and uranium, accumulate in the bones that can cause cancer (manisalidis et al., 2020). 1.2.4. thermal pollution the decline of water quality caused by any catalyst to increase the rate the atmospheric water temperature is known as thermal pollution, or "thermal enrichment." the water utilized as cooling by industrial plant companies is one of the most common sources of thermal pollution. when cooling water gets released to the natural surroundings at a higher temperature, the abrupt shift in temperature reduces oxygen delivery and a consequence on ecosystem composition. a rapid transition in water temperature can harm fish and other species that acclimated to a specific temperature range. hot cooler water has a long-term http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 84 influence on water temperature, raising the total temperature of bodies of water, includes deep water. the distribution of these temperatures rises throughout the seawater, influenced by the season. 1.2.5. agricultural pollutants and nutrients in a nutshell, the widespread use of chemical fertilizers in agriculture has resulted in a wide range of environmental issues, as certain fertilizers include heavy metals (such as cadmium and chromium) and high radioactive concentrations. phosphate, nitrate, ammonium, and potassium salts are all found in non-organic fertilizers. toxic elements including mercury, cadmium, iron, arsenic, copper, and nitrate become placed in the soil and plant system. fertilizers get absorbed by plants into the soil, and they can enter the food chain, contaminating the water (savci, 2012; singh et al., 2020). 1.2.6. pathogens bacteria, viruses, pillows, and certain parasites are pathogens that are tiny microbes that cause disease. hepatitis and norwalk viruses are frequent viruses found in wastewater, while candida is a prevalent fungus. food poisoning is often caused by the salmonella bacteria, while cholera gets generated by the pathogen vibrio cholerae. cryptosporidium and schistosoma are two parasites that can cause diarrhoea, and all wastewater pathogens can cause significant gastrointestinal sickness (singh et al., 2020). 1.3. pollutant control and management with water pollution control and management, there are a plethora of techniques. it can be through prevention training activities or participation in a plan, legislation, and supervision or control methods such as waste reduction and minimization. management of pollution can be done effectively by regulatory oversight. most countries have passed a law to restrict forms of pollutants and to minimize pollution's negative impacts. controlling pollutants and toxic substances into the air, water, and land or soil is known as pollution control. waste materials from consumption, heat, farming, mines, production, transport, and other human activities, either they collect or spread, will deteriorate the environment if no proper pollution control is in place (owa, 2013). water contamination, on the other hand, can be reduced by using the measures listed below.  water reuse and recycling.  using kitty litter, mop up oil and other liquid spills and sweep them up.  every 3-5 years, examines your septic tank.  plastic should be avoided at all costs.  pesticides and fertilizers that can run off into water systems should be avoided.  garbage, chemicals, and solvents should not be poured into sewer drains.  avoid flushing medications.  stop soil erosion by cleaning up the stream.  participate in school and at work.  lastly, enacting legislation to prohibit pollution of water (khatun, 2017; owa, 2013). 1.4. involvement of the public in water resource management public participation freedoms can be incorporated into statutory provisions also specific environmental or other laws at the state level. for legal recourse, legal rights may establish official, informal, or quasi-judicial channels. they also go through procedure problems include rights in the interest of the public litigation or collective claims and legal representation. alternative means for individuals to engage in impact assessment processes may provide by sector law. the efficiency of public engagement is directly proportional to the amount of data available, necessitating the country's access to information legislation (razzaque, 2009). community involvement is a common subject in water resource management policy in several nations. for instance, bangladesh's national water policy (1999) involves local community file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 85 engagement in water sector development projects and the policy and managing process. pakistan's water policy (2004) asks for a conducive climate for active stakeholder dialogue and involvement at all levels and in all elements of the water sector, encompassing agriculture, drainage, rural water distribution, flood control, and drought relief (razzaque, 2009). public involvement provides a social dimension to the management of water resources, assists the public in comprehending technical issues, and clarifies the contradiction among its actions and the ecosystem. it manages issues between interested parties to help the public make the best environmental decisions and assure a sustainable ecosystem in policy-making (jingling et al., 2010). after the end of the outbreak of the itai itai infection in japan, a perfect example of public involvement in water pollution control became demonstrated. as a result of the incident, victims, locals, and the polluting firm agreed to let people involved in decision-making and pollution preventative measures, resulting in a unique example of successful pollution control in japan (kaji, 2012). several studies showed that, as pollution issues become more serious, the traditional paradigm of government-led autonomous environmental governance is woefully inadequate to meet humanity's sustainability difficulties. the other sustainable development has arrived with the advancement of mobile information technology and the dawn of the era of big data. the final form of environment policy, known as "political involvement," has increasingly become a vital factor in achieving environmental sustainability (ross et al., 2016). jaleel et al. (2020) mentioned in their study a participation citizen science approach to assess the groundwater quality of 45 maldivian islands, which is a cost-effective and large-scale way to increase citizen involvement in water pollution management. according to li et al. (2018), successful air pollution control may be achieved by collaboration between government, industry, and the general populace. 1.5. fundamental components of public involvement the rationales for the ongoing interest in public and stakeholder participation in water management, policy, and control are numerous and complicated. in broad terms, public involvement tries to improve decision-making by maximizing the efficiency of outcomes, or their legality, or either. the following aims became often used to justify and promote public involvement.  acceptance, dedication, and commitment of actions and plans by the general public  to raise environmental problem awareness among the general populace.  there will be fewer lawsuits, misconceptions, delays, and ineffective applications.  leveraging basic knowledge of the area improved the quality of judgments.  establishing a common understanding of the problem dynamics through social learning.  enhance legislative power of judgments by enabling the general public to get a say in and effect over the issues at hand (özerol and newig, 2008). 2. methodology this section identifies and discusses the procedures and methods used to collect data required to address the research's goal. 2.1. sampling method and size the sampling method used for this study was random sampling which consists of members of the general public of all ages, irrespective of gender or region. the survey included working people and students using drinking water and wastewater facilities in their homes. the sample size for this study was 63. http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 86 2.2. method of data collection the design of sample questionnaires and a thorough evaluation of the literature are the first steps in the data collecting and survey questionnaire design process. one of the most relevant sources of information on the subject is the survey questionnaire. however, the survey questionnaire to collect data for this study will be used. this study's data collection methodology got segmented into two parts: 2.2.1. primary data this study took the form of a questionnaire survey. a structured questionnaire was created using google forms and administered to collect data depending on the objectives. the first section of the questionnaire focuses on the background of the respondents. the public's general understanding of water pollution issues gets covered in part two, and the public's readiness to help in water pollution reduction also gets covered in part three. the questionnaires were disseminated to the general public in malaysia, due to pandemic restrictions. the forms were sent to them via email over the internet to get feedback from the respondents. 2.2.2. secondary data articles, journals, research papers, current studies, published books, survey reports, conference papers, journals, and other relevant sources provided secondary data. the data gathered was utilized to help plan the primary data collection, following the study's objectives. 2.3. data analysis the data was analysed and discussed using microsoft excel (2019) after data collected for this purpose. the findings were analysed using descriptive statistics in percentages and figures and as bar charts and tables. 3. results and discussion a total of sixty-three (63) responses got reordered from the dissemination of the questionnaires. it also discusses the general information of the respondents, general knowledge of the public on water pollution issues, the current level of public involvement in water pollution management, and the readiness of people to take part in activities to minimize water pollution. 3.1. general background of respondents 3.1.1. age of respondents figure 2 reveals the age group of respondents. 14.3 percent of respondents are under the age of 20, 12.7 percent are between 20 and 24. 36.5 percent are between the ages of 25 and 34, while 19 percent are between 35 and 40, 7.9 percent, 9.5 percent are between 40 to 50 and more than 50 years, respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 87 figure 2: age group of respondents 3.1.2. educational level of respondents eight (8) of the 63 responses had a ph.d. qualification, accounting for 12.7 percent of the total. master's certificate holders make up 28.6%, followed by bachelor's certificate holders at 44.4 percent, diploma holders at 9.5 percent, and high school certificate holders at 4.8 percent. the majority of responders have bachelor's degrees, whereas diplomas and high school diplomas are held by the fewest. figure 3 depicts the respondents' educational backgrounds. figure 3: educational level of respondents 3.1.3. monthly income of respondents the findings revealed that 14.3% of respondents' monthly income is between rm 2500 and rm 4500, followed by 19%, 12.7%, and 9.5 percent of respondents' monthly earning is between rm 4500 and rm 6500, rm 6500 to rm 8500, and rm 8500 to rm 10500, respectively. while the majority of monthly income is less than rm 2500 (34.9%), and the least earns more than rm 10500 (9.5 percent). the outcomes are as illustrated in figure 4. 0 5 10 15 20 25 30 35 40 < 20 20 24 25 34 35 40 40 50 > 50 p e rc e n ta ge ( % ) age group 0 5 10 15 20 25 30 35 40 45 50 phd master bachelor diploma high school p e rc e n ta ge ( % ) educational level http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 88 figure 4: monthly income of respondents 3.1.4. respondent’s location the majority of the respondents (63.5%) reside in the capital, while 8% and 29% dwell in the rural and urban areas, respectively (figure 5). figure 5: respondent’s location figure 6: source of drinking water 3.2. general knowledge of the public on water pollution issues as shown in figure 6, 36 of the respondents, or 57.1 percent of the total, are aware of their drinking water source, whereas 42.9 percent are unaware of their drinking water source. the findings revealed that 74.6 percent of participants have sewerage connections, while 25.4 percent do not. additionally, 52.4 percent know whether the wastewater from their home is treated before discharge, while 47.6 percent do not know whether the liquid waste from their residence is not before disposal (figures 7 and 8) 0 5 10 15 20 25 30 35 40 2500 4500 4500 6500 6500 8500 8500 10500 < 2500 > 10500 p e rc e n ta ge ( % ) monthly income (rm) city 63% rural 8% urban 29% 57% 43% yes no file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 89 figure 7: sewerage connection figure 8: waste water from home treated before discharged furthermore, 12.6 percent of respondents asserted that the water quality of rivers in their state is very poor, followed by 28.6 percent, 36.5 percent, 15.9 percent, and 3.2 percent stated that their water quality in their state is poor, acceptable, good, very good, and no opinion. according to findings majority of the participants (36.5 percent) agreed that the water quality of the rivers is satisfactory. however, 11.1 percent of the participants indicated that the quality of the groundwater in their state is very poor, followed by 19%, 28.5 percent, 20.6 percent, 4.7percent, and 15.8 percent alluded that the water quality of their state's groundwater is poor, acceptable, good, very good, and no opinion respectively. figures 9 and 10 demonstrate how this works. figure 9: water quality of rivers 75% 25% yes no 52% 48% yes no 0 5 10 15 20 25 30 35 40 v e ry p o o r p o o r a cc e p ta b le g o o d v e ry g o o d n o o p in io n p e rc e n ta ge ( % ) options http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 90 figure 10: water quality of ground water additionally, the findings revealed that 12.6 percent of respondents had never attempted to mitigate water contamination. the majority of respondents (39.7%) mentioned they tried to reduce water pollution sometimes, while 19.0 percent indicated they tried rarely, and 14.3 percent stated they tried very often and always, respectively. figure 11 illustrates this. figure 11: effort to reduce water pollution ultimately, 14.2 percent of those surveyed agreed that water pollution is a crucial issue for environmental and social health, followed by 73 percent who agreed that water pollution is a critical issue for the environment and social health, and 6.3 percent who partially disagree and partially agree (figure 12). 0 5 10 15 20 25 30 v e ry p o o r p o o r a cc e p ta b le g o o d v e ry g o o d n o o p in io n p e rc e n ta ge ( % ) options 0 10 20 30 40 50 n e ve r r ar e ly so m e ti m e s v e ry o ft e n a lw ay s p e rc e n ta ge ( % ) options file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 91 figure 12: environmental and social health issue 3.3. level of public involvement in water pollution management table 2 recapitulates the findings of the current level of public involvement in water pollution management. according to the survey, 38 out of 63 participants, or 60.3 percent, believed that they are well aware of their state's water management pollution regulations. meanwhile, 25 responses indicated that 39.7percent of the total disagreed with the above statement about water pollution management regulations. the study also revealed that 11.1 percent of individuals are unaware of water pollution issues in their state, while 17.4 percent, 41.3 percent, 23.8 percent, and 6.3 percent are rarely, sometimes, very often, and always informed of water pollution issues in their state, respectively. moreover, in terms of community involvement in decision-making processes on water pollution matters in their respective state, 22.2 percent of respondents stated that they never been involved in any decision-making process pertinent to water pollution issues. 26.9%, 34.9 percent, 9.5 percent, and 6.3 percent asserted that they rarely, sometimes, very often, and always been participated. this implies that officials still have the potential to enhance in terms of water pollutant information distribution. respondents were further requested to suggest the measures that will have the best impact on water quality improvement. some participants stated that one way to improve water quality is for individuals to help to prevent pollution (12.7 percent), enforcing stern punishment on polluters (19 percent). the majority of the respondents corroborated that spending more money on water and waste management and spending more money to raise awareness are two ways to improve water quality. (31.7 percent and 36.5 percent, respectively). finally, most participants stated that they were unaware that their homes and businesses must pay utility bills to manage discharged wastewater (66.7 percent), but 33.3 percent noted that they were aware of the need to pay utility bills to control discharged wastewater. it signifies that the authority requires financial support to raise public awareness about water pollution management. 0 10 20 30 40 50 60 70 80 totally disagree partially disagree partially agree totally agree percentage (%) http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 92 table 2. current level of public involvement in water pollution management s/n items frequency percentage 1 are you aware of legislation regarding water management and pollution in your state?  yes  no 38 25 60.3 39.7 2 are you well-informed of water pollution issues in your state?  never  rarely  sometimes  very often  always 7 11 26 15 4 11.1 17.4 41.3 23.8 6.3 3 are you or the community involved in any decision-making process on water pollution issues in your state?  never  rarely  sometimes  very often  always 14 17 22 6 4 22.2 26.9 34.9 9.5 6.3 4 which one of the following actions will have the biggest impact on improving water quality (select one)?  individuals trying to stop pollution  enforcing stern punishment on polluters  spending more money on water and waste treatment  spending more money to increase awareness 8 12 20 23 12.7 19.0 31.7 36.5 5 are you aware that household and premises need to pay utility bills to manage discharged wastewater? yes no 21 42 33.3 66.7 3.4. readiness to participate in water pollution reduction activities this segment elucidates the findings on public involvement in water pollution-reduction efforts. the findings revealed that 6.3 percent of respondents are vehemently opposed to collaborating in the campaign to curb water pollution, the lowest figure recorded. however, the highest percentage of respondents, 41.3 percent, are highly willing to participate in the fight to reduce water pollution, followed by 25.4 percent and 11.1 percent who are both willing and unwilling to participate. for the campaign against water pollution, 15.9 percent of the responses are neutral. 14.3%, 22.2 percent, and 41.3 percent, respectively, are unwilling, neutral, willing, and strongly willing to enroll in water pollution management courses in their community. the results further showed that 6.3 percent of the participants were strongly unwilling to provide financial support in environmental activities to reduce water pollution, followed by 12.7percent of respondents who are not willing the fight to reduce water pollution, 36.5 percent of the respondents are in the neutral position. however, 17.5 percent and 26.9 percent are willing and highly willing to support a campaign to reduce water pollution, respectively. furthermore, 3.2 percent, 4.8 percent, and 11.1 percent of respondents are strongly unwilling, unwilling, and neutral to modify their attitudes about water pollution reduction. meanwhile, the vast majority of participants are willing and eager to alter their file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 93 attitudes about water pollution reduction. (57.1%) and 23.8%), respectively. in terms of paying a higher billing rate to enhance the discharge of wastewater quality and minimize water contamination, most participants stated that they are vehemently not willing, not willing, and neutral to pay a higher billing rate (15.9%, 11.15% and 20.6 %) respectively. 25.4 percent and 26.9 percent are willing and strongly willing to pay a higher billing rate to improve wastewater quality. eventually, the participants were required to come up with strategies to prevent water pollution. six (6) of the participants stated that they do not flush paints, fats, or grease down the sink or sewer. eight (8) people suggested it to avoid dumping medical waste down the drains, followed by ten (10) individuals, twelve (12), three (3) people, and thirteen (13). (13). elven (11) also mentioned using ecologically friendly cleaning and washing products, checking cars for oil leaks regularly, avoiding pesticides and herbicides in the backyard, and utilizing alternatives to plastic products. table 3 gives a synopsis of the analyses of the survey. table 3. readiness to participate in water pollution reduction activities s/n items frequency percentage 1 are you willing to take part in a campaign to reduce water pollution?  strongly not willing  not willing  neutral  willing  strongly willing 4 7 10 16 26 6.3 11.1 15.9 25.4 41.3 2 are you willing to enroll in the courses in managing water pollution at your area?  strongly not willing  not willing  neutral  willing  strongly willing 9 14 14 26 14.3 22.2 22.2 41.3 3 are you willing to donate money or support in environmental organizations campaign to reduce water pollution?  strongly not willing  not willing  neutral  willing  strongly willing 4 8 23 11 17 6.3 12.7 36.5 17.5 26.9 4 are you willing to change your attitude towards the reduction of water pollution?  strongly not willing  not willing  neutral  willing  strongly willing 2 3 7 15 36 3.2 4.8 11.1 23.8 57.1 5 are you willing to pay a higher billing rate for your utility to improve the discharged wastewater quality and reduce water pollution?  strongly not willing  not willing  neutral  willing  strongly willing 10 7 13 16 17 15.9 11.1 20.6 25.4 26.9 http://www.azojete.com.ng/ mailto:sandabashir@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):79-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sandabashir@gmail.com 94 6 which of the following actions do you do to reduce pollution? avoid disposal of paints, fats and grease down the drains / sewer avoid disposal of toxic chemicals (solvents, pesticides and cleaners) down the drains / sewer avoid disposal of medical wastes down the drains / sewer use environmentally friendly products for cleaning and washing check your car regularly for oil leaks avoid using pesticides and herbicides on your backyard use alternative to plastic products 6 8 10 12 3 13 11 9.5 12.7 15.9 19.0 4.8 20.6 17.5 4. conclusion this study focused on how public participation currently in the area of water pollution management in malaysia and the willingness of people's involvement in reducing water pollution. the findings revealed that most of the participants have sewerage connections in their residences and that the water quality of their rivers is acceptable for the majority of the participants. the study also indicated that water pollution is a grave concern for environmental and social health. while some respondents claimed they are well aware of their state's water management pollution regulations, the results revealed that there is still a need for more education on these regulations. according to the findings, community involvement in water pollution decision-making processes is currently low on average, implying that authorities still have room to improve concerning water pollutant information delivery. the majority of respondents agreed that investing more money in water and waste management, and educating the public are strategies to enhance water quality, according to the research. finally, the findings revealed that the general public is enthusiastic about taking part in the fight against water pollution and is ready to participate in water pollution management activities in their community. nevertheless, the substantial majority of respondents are eager to change their thoughts regarding reducing water pollution. 5. recommendations the following are recommendations about how the public can help to address the problem of water pollution. i. build a solid foundation that allows for greater public involvement in decision-making. ii. to enact strict pollution control policy. iii. to provide adequate financial support in the investment of technologies, specifically to curb sewage facilities of the human source of water pollution, and to empower the people to apply citizen science techniques in addressing water pollution and water quality problems. iv. to organize seminars and training courses easily accessible to communities to help them optimize their water pollution-reduction efforts. v. improved and supplementary waste treatment activities are required to prevent pollution of water. vi. efficient waste disposal systems should be in place, and wastewater needs treatment before infiltrating rivers. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com sanda et al: involvement of the general public in the management of water pollution in johor bahru malaysia. azojete, 18(1):79-96. issn 1596-2490; 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(eds.)). advanced functional materials and sensors. singapore: springer nature pte ltd., https://doi.org/10.1007/978-981-15-0671-0_2. teodosiu, c., barjoveanu, g. and kruijf, jv. 2013. public participation in water resources management in romania : issues , expectations and actual involvement. environmental engineering and management journal, 12(5): 1051-1063. who, unicef, and glaas. 2021. the measurement and monitoring of water supply, sanitation and hygiene (wash) affordability. retrieved from www.unicef.org/wash on 06/09/2021. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sandabashir@gmail.com arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):555-560 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: buokatengwu@atbu.edu.ng 555 original research article mitigation of the wear failure of ti-6al-4v dental implant using natural and artificial ageing treatment m. a. bawa1, o. b. umaru1*, m. abdulwahab2, t. balogun3 and w. s. abdulazeez4 1mechanical & production engineering department, abubakar tafawa balewa university, bauchi, nigeria. 2metallurgical and materials engineering department, air force institute of technology, nigerian air force, kaduna. 3materials and metallurgical engineering department, federal university of technology, minna, nigeria. 4metallurgical and materials engineering department, ahmadu bello university, zaria, nigeria *corresponding author’s email address: buokatengwu@atbu.edu.ng 1.0 introduction a biomaterial is any substance other than drugs or combination of substances which are synthetic or natural in origin that can be used for any period of time wholly or as a part of a system which treats, augments or replaces any tissue, organ, or function of the body (abdulwahab et al., 2015; anupam, 2011; callister and david, 2014). ceramics, metals, alloys, polymers and composite materials can be used as biomaterials because of individual properties they possess, such as tensile modulus, yield strength, compression strength, ultimate tensile strength, corrosion resistance, toughness and density (correa et al, 2009; diomidis et al., 2012; flake, 2008; flake, 2012). they are adapted for medical applications and thus, comprise of a whole part of a living structure. biomaterials find daily applications in surgery, dental care and drug delivery. a construct with impregnated pharmaceutical can be placed into the body, which permits the prolonged release of drug over an extended period of time. biocompatibility is the ability of a material to perform with an appropriate host response in a specific application (flake, 2010). a good biomaterial must be compatible with the human body and because of this critical requirement, the issue of biocompatibility if any must be completely resolved before the product is sent into the market for use. therefore, all biomaterials should be subjected to standard procedures and checked for the critical requirement before they are sent into the market for use (hendra et al., 2011; hermawan et al., 2008). wear and corrosion have been article information abstract ti-6al-4v alloy has been in use as dental implants due to its favourable mechanical properties but wears off over a period of time in the oral cavity. therefore, this research aimed at using natural and artificial ageing to mitigates the wear failure of ti-6al-4v dental biomedical implant. the as received ti-6al-4v alloy was sectioned under flowing cooling conditions to 1.4mm x 1.4mm x 0.3mm and then heat treated. the heat treatment involves solution heat treatment at 960oc for 1 hour followed by quenching in warm water at 60oc. after this stage, some of the samples undergo natural ageing for 24 hours, while others were further artificially aged to 480oc with varying soaking times of 2, 4, 6 and 8 hours followed by air cooling. wear test was conducted at varying loads of 4n and 8n, linear speed of 13.12 cm/s and a dwell time of 30 minutes. the result showed that an increase in ageing time leads to a decrease in wear rate of the alloy for both loads. also, the samples that were further artificially aged had more wear resistant than the naturally aged samples due to formation of precipitates which are homogenous with the matrix. the minimum wear rates of 0.0114 mm3/n/m and 0.0152 mm3/n/m was obtained at 4 and 8n loads respectively. therefore, it was established that natural and artificial ageing combined can be employed to enhance the wear resistance of ti-6al-4v alloy for use in biomedical applications. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted: 28 june, 2021 revised: 13 october, 2021 accepted: 20 october, 2021 keywords: biocompatible wear rate corrosion biomedical application implant bawa et al: mitigation of the wear failure of ti-6al-4v dental implant using natural and artificial ageing treatment. azojete 17(4):555-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: buokatengwu@atbu.edu.ng 556 reported to be the primary reasons for the failure of implant elements (hosam et al., 2017). the wear of biomaterials is a surface failure, such as abrasion and erosion, resulting from dynamic contact between two surfaces. for metallic biomaterials, wear is a major factor in controlling and determining its long-term clinical performance (kevin, 2015). biomaterials’ wear occurs specifically due to the removal and deformation of a material’s surface as a result of mechanical action of the opposite surface (lee et al., 2009). titanium is one of the non-ferrous metals and it has about 60% of the density of steel (li, 2013; mariano et al., 2009). titanium and its alloys have proven to be effective over the years in marine, aerospace, medicine, automobiles, missiles and energy industries (mathew, 2000). the high strength, low weight ratio and outstanding corrosion resistance which are natural in titanium and its alloy have brought about a wide range of successful applications in various industries (mavrogenis et al., 2009). although titanium and its alloys have been in use over the years as implants, they have been found to degrade after a period of time due to wear (mohammed et al., 2015; mutlu and christoph, 2012). ti-6al-4v has been in use as dental implants till date because of its favourable mechanical properties but wears off over a period of time in the oral cavity (nikolopoulou, 2006). many researchers have tried to find a possible solution to the wear-off of ti-6al-4v alloy as implant in the body as reported by nitesh and pivash (2012), but none have considered mitigating the wear failure of ti-6al-4v dental biomedical implant using natural and artificial ageing. 2. materials and method 2.1 materials and equipment the material used in this research is titanium alloy (ti-6al-4v) sourced from the department of chemical and metallurgical engineering, tshwane university of technology, pretoria, south africa. the equipment used include heat treatment furnace, weighing balance, hack saw, tribometer (wear test machine) and optical microscope. a muffle electrical resistance furnace of capacity 1200oc was used for the heat treatment process. a tribometer)., weighing balance, hack saw, ball on disc tribometer from shell laboratory in ahmadu bello university, zaria nigeria of version 6.1.19 used for wear rate determination and a stereo microscope used for microstructural analysis. 2.2 sample preparation the ti-6al-4v alloy with chemical composition as shown in table 1 was sectioned under flowing cooling solutions to 1.4mm 1.4mm 0.3mm in accordance with popoola et al., (2012) using a hack saw. the samples were then degreased, cleaned and properly dried. table 1: chemical composition of the as-received ti-6al-4v alloy ti al v c fe o n h 89.62 6.1 4.0 0.004 0.160 0.106 0.008 0.002 2.3 heat treatment of sample a total of 10 samples were charged into the furnace for the heat treatment which comprise of solution heat treatment (sht) at 960 for1hr. this was followed by careful monitoring of the temperature to ensure that it does not exceed the beta transus line of 1000 which will cause a different phase transformation. quenching in warm water (60 ) was done, followed by natural and artificial ageing operations. natural ageing was carried out on two samples at room temperature for 24hrs which represent the control samples. the remaining 8 samples were further artificially aged to 480 for varying ageing times of 2, 4, 6 and 8 hours respectively and cooled in open air. the samples were then manually ground using different grade of silicon carbide abrasive papers and mechanically polished. figure 1 shows the heat treatment cycle used. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 555-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: buokatengwu@atbu.edu.ng 557 temp oc 960 1hr 480 2, 4, 6 and 8hrs 24hrs ageing time (hrs) figure 1: schematic heat treatment cycle used schematic heat treatment cycle used for the heat treatment process 2.4 wear test the wear rate of the material was carried out on the surface of the coupons using a tribometer with a ruby ball as the abrasive medium. an applied load of 4n and 8n at a linear speed of 13.12 cm/s and a dwell time of 30 minutes was used. the mass loss for each sample was determined by finding the difference between the initial and final mass to generate the wear rate. 2.5 worn surface examination the surfaces of the samples were ground using different grade of silicon carbide abrasive papers ranging from 320 to 1200 microns and polished mechanically to remove the oxide film that was formed on the surface in order to obtain a smooth on which wear test will be carried out. the surfaces of the samples were ground using different grades of silicon carbide abrasive papers ranging from 320 to 1200 microns and polished using one-micron size alumina polishing powder suspended in distilled water. the samples were placed on the stage and observed under the microscope. this was done using optical microscope (opm) to determine the extent to which the surface integrity of the alloy was affected. 3. results and discussion 3.1 wear rate of samples using ageing treatments the effect of increasing load of 4n and 8n on the abrasive wear is demonstrated in figure 2. the control samples showed a wear rate of 0.0166 mm3/n/m and 0.027 mm3/n/m at applied loads of 4n and 8n respectively. also, for samples that were artificially aged, wear rate decreases with increasing ageing time that is 0.0147 mm3/n/m to 0.0114 mm3/n/m for ageing times of 2 to 8 hours. figure 2: variations of wear rate against ageing time for both the control and heat-treated titanium alloys control 2 4 6 8 0 0.01 0.02 0.03 ageing time (hrs) w ea r ra te (m m 3 /n /m ) 4n 8n column1 bawa et al: mitigation of the wear failure of ti-6al-4v dental implant using natural and artificial ageing treatment. azojete 17(4):555-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: buokatengwu@atbu.edu.ng 558 this decrease in wear rate may be attributed to the fact that at the ageing time of 2 to 8 hours, the -phase precipitation increases with the increasing ageing time which leads to strengthening and hardening thereby causing a reduction in wear rate (popoola et al., 2012). the highest wear rate for the artificially aged samples were observed at 2 hours of ageing time and the lowest at 8 hours ageing time. this may be attributed to the fact that at shorter soaking time of 2 hours, the precipitation of β-phase may not have taken place hence the material is said to be under aged (reza and gholam, 2011). for samples that were artificially aged, wear rate decreases with increasing ageing time that is from 0.0189 mm3/n/m at 2 hours of ageing to 0.0152 mm3/n/m at 8 hours ageing. this decrease in wear rate may be attributed to the β-phase precipitate which increases with increasing ageing time, thereby causing strengthening and hardening of the alloy hence a reduction in wear rate (roth et al., 2010; schwarz et al., 2009; wang et al., 2011). 3.2 worn surface analysis the optical micrographs of the worn-out samples shown in figure 3 indicate the degree of wear by the presence of deep scratches and delamination of material from the surface. this worn debris and delamination decrease as the soaking time increases from 2 to 8 hours. plate 3: optical micrographs of the abrasive worn-out samples of ti-6al-4v alloy artificially aged at 480oc and soaked for (a) 2hrs (b) 4hrs (c) 6hrs and (d) 8hrs 4. conclusion from the analysis above, it can be concluded that increasing the ageing time reduces the wear rate of the alloy under investigation. also, artificially aged samples have better wear resistance than samples that were naturally aged and samples artificially aged at 8 hours of soaking time showed the maximum resistance to abrasive wear. finally, the best wear resistance of the ti6al-4v alloy is at 4n load application. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 555-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: buokatengwu@atbu.edu.ng 559 reference abdulwahab, m., enechukwu, o., aigbodiun, vs. and yaro, sa. 2015. mitigation of the wear failure of ti-6al-4v dental biomedical implant by isothermal treatment. journal of failure analysis and prevention, 15(6): 952-957. hendra, h., dadan, r. and joy, rpd. 2011. metals for biomedical applications. biomedical engineering from theory to applications. fazel-rezai, r. (ed.)., 1. london: intechopen, 411430. hermawan, h., alamdari, h., mantovani, d. and dube, d. 2008. iron-manganese: new class of degradable metallic biomaterials prepared by powder metallurgy. powder metal, 51: 38-41. hosam, aa., magdi, mai. and tajammul, a. 2017. a study of mechanical properties of ti-6al4v used as dental implant material. international journal of scientific reports, 3(11): 288-291. kevin, l. 2015. anatomy101 from muscles and bones to organs and systems, your guide to how the human body works. massachusetts, adams media, u.s.a. lee, ck., karl, m. and kelly, jr. 2009. evaluation of test protocol variables for dental implant fatigue research. dental material, 25: 1419-1591. li, dy. 2013. corrosive wear. springer engineering encyclopaedia of tribology, new york: springers inc., 590-596. mariano, na., oliveira, rg., fernandes, ma. and rigo, ecs. 2009. corrosion behaviour of pure titanium in artificial saliva solution. materia, 14(2): 635-970. mavrogenis, af., dimitriou, r., parvizi, j. and babis, gc. 2009. biology of implant osseointegration, journal of musculoskeletal neuronal interact, 9(2): 61-71. anupam, s. 2011. an overview of metallic biomaterials for bone support and replacement, biomedical engineering trends in materials science. http://www.intechopen.com/books/biomedical-engineering-trends-in-materials-science/anoverview-of-metallic-biomaterials-for-bone-support-and-replacement. mohamed, ah., abdulsamad, m. and naseer, a. 2015. wear characteristics of metallic biomaterials a review. materials, 8: 2749-2768. mutlu, o. and christoph, h. 2012. titanium as a reconstruction and implant material in dentistry: advantages and pitfalls. materials, 5(9): 1528-1545. nikolopoulou, f. 2006. saliva and dental implants. implant dentistry, 15: 372-376. nitesh, rp. and piyash, pg. 2012. a review on biomaterials: scope, applications and human anatomy significance. international journal of emerging technology and advanced engineering, 2(4): 99-101. popoola, api., ochonogor, of., abdulwahab, m., pityana, s. and meacock, c. 2012. microhardness and wear behaviour of surface modified ti-6al-4v/zr-tic metal matrix composite for advanced materials. journal of optoelectronics and advanced materials, 14: 991997. reza, sr. and gholam, rg. 2011. a review of the corrosion of laser nitride ti-6al-4v, department of materials engineering, malek ashtar university of technology, tehran, iran. roth, s., feichtinger, j. and hertel, c. 2010. characterization of bacillus subtilis spore inactivation in low-pressure. low temperature gas plasma sterilization processes, 28: 11231131. http://www.intechopen.com/books/biomedical-engineering-trends-in-materials-science/an-overview-of-metallic-biomaterials-for-bone-support-and-replacement http://www.intechopen.com/books/biomedical-engineering-trends-in-materials-science/an-overview-of-metallic-biomaterials-for-bone-support-and-replacement bawa et al: mitigation of the wear failure of ti-6al-4v dental implant using natural and artificial ageing treatment. azojete 17(4):555-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: buokatengwu@atbu.edu.ng 560 schwarz, f., wiland, m., schwartz, z., zhao, g., ruppi, f. and geis-gerstorter, j. 2009. potential of chemically modified hydrophilic surface characteristics to support tissue integration of titanium dental implants. journals of biomedical materials research b, 88b(2): 544-557. wang, yb., zheng, yf., wei, sc. and li, m. 2011. in vitro study on zr-based bulk metallic glasses as potential biomaterials, journal of biomedical materials research, 96b: 34-50. callister, wd. and david, gr. 2014. material science and engineering, new york: wiley & sons. correa, cb., pires, jr., fernandes-filho, rb., sartori, r. and vaz, ig. 2009. fatigue and fluoride corrosion on streptococcus mutans adherence to titanium-based implant/component surfaces, journal of prosthodontics, 18: 382-387. diomidis, ns., mischler, ns. and more, mr. 2012. tribo-electrochemical characterization of metallic biomaterials for total joint replacement. acta biomaterialia, 8: 852-859. flake, cc. 2008. elements of metallurgy and engineering alloys, asm international® www.asminternational.org. flake, cc. 2012. lightweight materials-understanding the basics. asm international® www.asminternational.org. fleck, c., and eifler, d. 2010. corrosion, fatigue and corrosion fatigue behaviour of metal implant materials, especially ti alloys. international journal of fatigue, 32: 929. greg, lj. and williams, jc. 2009. titanium. technical university of hamburg-hamburg, department of physical metallurgy and materials technology, 21071 hamburg germany http://www.asminternational.org/ http://www.asminternational.org/ arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 185-193 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng _____________________ *corresponding author email address: faola@lautech.edu.ng 185 original research article modeling the relationship between grading, moisture content and screen apertures in groundnut decortication s. aminu1, f. b. akande2, and f. a. ola 2* 1department of agricultural engineering, ahmadu bello university, zaria, nigeria 2department of agricultural engineering, ladoke akintola university of technology, ogbomoso. nigeria article information received october, 2018 accepted december, 2018 keywords: mathematical modeling groundnut decortication process inputs measured outputs abstract whole groundnut kernels free of bruises attract foreign exchange earnings. the appropriate selection and the interactions between the processing parameters in groundnut decortication produces clean kernels. therefore, the focus of this study was to establish mathematical equations in order to explore and predict the possible relationships between the process inputs (grading, moisture content and screen apertures) and the measured output (clean kernels, bruised kernels and split kernels) in decorticating three selected varieties of groundnut in-shell commonly cultivated in nigeria with a view of maximizing their kernel quality. the varieties were samnuts 10, 14 and 18. in doing this, individual relationships were explored one at a time by keeping other process parameters constant to ensure clear interpretations. the relationships between grading, moisture content and screen apertures versus the response (efficiency of clean, bruised and split kernels) were approximated using a linear and nonlinear (quadratic or polynomials) functions. regression analysis and design expert software (multivariate) were used to develop the mathematical models that describe the relationships between these inputs and the measured outputs. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction groundnut (arachis hypogaea l.) is one of the world’s principal oil seed crops that is rich in protein and has a high energy value. groundnut is also an important food crop in many areas of semi-arid tropics (fao, 1994). it is cultivated for its kernels, oil and hay for livestock (nigam et. al., 1999). improvements in groundnut productivity and processing for a qualitative output are also crucial because of its potential to regain and increase export earnings. growth in agriculture has generally been linked to development in other sectors which invariably contributes to poverty alleviation (khan, 1999). like most developing countries, majority of the rural dwellers in nigeria depends on agriculture. in order to reduce poverty, agricultural sector must be revitalized. this will increase rural employment, trade and purchasing power for smallholder farming families, strengthen the economic capacity of rural women and improve household nutrition. it thus plays a key role in the agriculture-dependent economies of west africa where its marketing and trade served as the major http://www.azojete.com.ng mailto:faola@lautech.edu.ng aminu, et al. modeling the relationship between grading, moisture content and screen apertures in groundnut decortication. azojete, 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 186 sources of employment, income and foreign exchange (rai et al., 1993; revoredo and fletcher, 2002; ntare et al., 2008). production of groundnut in nigeria has immensely contributed to the economic development being one of the most popular commercial crops. nigeria produces 41 % of the total groundnut production in west africa (echekwu and emeka, 2005; faostat, 2010). until 1969, nigeria was the third largest exporter of groundnut in the world after india and china. groundnut sector provided the basis for the agro-industrial development and contributed significantly to the commercialization and integration of the national rural sectors (ntare et al, 2007). however, groundnuts exported into europe during the years of bumper harvests in nigeria and other sub-saharan african countries (ssa) was done majorly in-shell because of high incidence of aflatoxin contamination on decorticated kernels is carcinogenesis. aflatoxin is associated with bruises and breakages of kernels. this reduced the net profit of both the farmer and produce agent. kernel quality as a method of measuring marketability is very essential in successful agricultural production as poor quality produce is characterized by gradual decline in value and vigour (hartmann et al., 1990). a good quality kernel has high economic value, better germination and free from disease and insect attack. the greatest potential for providing clean decorticated kernels is the development of mathematical models that will predict the relationships between process input and measured output in order to obtain maximum kernel quality such that profit could be maximized for the production to be sustained. such models could be utilized for the design and development of suitable homeprocessing equipment in order to reduce bruises and breakages on the decorticated kernels to meet the standards of the importing countries and in turn serves as leverage for creating jobs for the teaming unemployed youth population. 2.0 methodology using the process modeling technique in design expert software, data obtained for clean, bruised and split kernels while decorticating the three selected groundnut varieties were model. the aim is to find a functional relationship that can adequately relate process input (grading, moisture content and sieve size) and process output (clean, bruised and split kernels). multiple regression analysis was used to develop the mathematical relationships between the respective independent variables (moisture content and screen apertures) that would predict the quality of kernel recovered from each grade of the three groundnuts in-shell varieties being decorticated in the study. the mathematical models being developed were basically focused on predicting the rate of clean kernel recovery. linear and quadratic mathematical models were tested for each grade of the three groundnut varieties in order to obtain possible relationships and then select the best relationships (models). the relationships between the combination of the independent variables and the response/dependent variable (clean kernels) were also established for each grade of the three groundnut varieties. residual plots for the selected models of each grade of the three groundnut varieties were developed to indicate the relationships on the effects of clean kernels recovery on each http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 187 combination of the independent variables. microsoft excel statistical package (2010) was used to develop the residual and surface response plots. 2.1 experimental procedure three groundnut varieties were selected for the study. they were samnuts 10, 14 and 18. each of the three groundnut in-shell varieties were graded into three different grades according to its geometric size with the aid of the developed grader. each grade from the three varieties was then subjected to three moisture regimes (8, 10 and 20 %) and was decorticated with all the three screens (8, 10 and 12 mm) constructed. the initial decorticating trials for each variety were conducted with ungraded samples of all the grades at the chosen moisture content regimes to serve as control. all decortications were replicated three times in order to minimize error. the measured parameters studied were clean, bruised and split kernels and the process conditions (factors of interest) employed are grading, moisture content and screen apertures. these factors were varied at various levels and their effects on the quality of the clean kernels were studied and measured via three varieties of groundnut in-shell. 2.2 procedure for model development multi-variable (multivariate) method of modelling was adopted. microsoft excel statistical package (2010) was used for the regression analysis to establish relationships that exist between the independent and dependent/response variable (clean kernels recovery). the data used for these analyses were arranged into linear and quadratic terms as shown in table 1. regression models of linear, interactions, quadratic, linear plus quadratic, linear plus interaction and full quadratic were derived from these arrangements as the case may be. based on the f-values, the p-values for each variable, coefficient of determination, (r²), and the adjusted r² values, best models were selected for each groundnut grade. plots of observed and predicted values of clean kernels recovery were used to select the best model based on the highest values of r² using microsoft excel statistical package (2010). since maximizing kernel quality is the goal of this study, clean kernel recovery was considered as dependent variable (or response variable). similarly, generalized mathematical models showing the relationships between clean kernels recovery and the independent variables of each grade of the three groundnut varieties were developed using regression analysis. plots of the observed against predicted values of clean kernels recovery for the respective grades of the three groundnut varieties were also presented. table 1: format used for multi-variable relationship modelling clean kernels (y) linear interaction (mc×sa) quadratic mc sa (mc)² (sa)² �� �‵� ��� �‵���� (�‵�)² ����)² �� �‵� ��� �‵���� ��‵�)² ����)² �� �‵� ��� �‵���� ��‵�)² ����)² �� �‵� ��� �‵���� ��‵�)² ����)² �� �‵� ��� �‵���� (�‵�)² ����)² �� �‵� ��� �‵���� ��‵�)² (���)² �� �‵� ��� �‵���� ��‵�)² ����)² �� �‵� ��� �‵���� ��‵�)² ����)² �� �‵� ��� �‵���� ��‵�)² ����)² ���� clean kernels recovered, �‵��� – moisture content at 8, 10 and 20 % levels, ����� – screen aperture of 8, 10 and 12 mm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aminu, et al. modeling the relationship between grading, moisture content and screen apertures in groundnut decortication. azojete, 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 188 3.0 results and discussion 3.1 modelling clean kernel recovery the regression model for clean kernels recovery from the three grades of the groundnut varieties (samnuts 10, 14 and 18) considered in this study. the anova and regression output for the selected models for grades i, ii and iii samples of three groundnut varieties were shown in tables 1 – 12. from the regression output, the relationship between clean kernels recovery (dependent/response variable) and the combinations of the two independent variables (moisture content and screen aperture) in linear, quadratic and interaction terms were derived. the selected equations were based on the significant higher f-values, coefficient of determination, r², the number of significant variables with respect to their p-values. other models were rejected based on the insignificant levels of f-values in some cases. similarly, regression and appropriate equation models for clean kernels recovery from the three grades of samnuts 10, 14 and 18 having highest r² value are as presented in equations 1 – 7: i) grade i samnut 10: 22 581.009417.0)(04921.0108.3807.273.53 samcsamcsamcck  (1) samnut 18 : 5002.0728.0185.11  mcsack (2) ii) grade ii samnut 10: ‵u � �th���‵ � �it�l�� � l�t�l � �t��� �‵ � �� � �t������‵� � �t�h���� (3) samnut 14: 2130.1)(149.0593.109.2277.21 sasamcmcsack  (4) samnut 18: 2161.190.13720.087.82 sasamcck  (5) iii) grade iii samnut 10: 22 270.2454.0)(552.064.11328.32495.8 samcsamcsamcck  (6) samnut 14: 22 844.2314.0)(732.043.7888.37742.2 samcsamcsamcck  (7) where, ck= clean kernel, mc= moisture content, sa= screen aperture 3.2 plots of observed and predicted values of clean kernels recovery the plots of the observed against predicted values of clean kernels recovery from grade i, ii and iii samples of samnuts 10, 14 and 18 were presented figures 1 – 7. the plot shows that the residuals were in a linear, quadratic and interaction manner on the graphs suggesting that the variance of the original observations were constant. the higher level of variance (r²) that accounted for clustered graph indicated smaller and unbiased differences between observed and predicted values of clean kernels recovery; hence a well fitted regression model for prediction. this also indicated that the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 189 terms in the model developed were adequate, hence a well fitted regression line/models for prediction. the plots also revealed that an increase in screen aperture would lead to higher values of clean kernels recovery. it also revealed slight decrease in clean kernels recovery when moisture content increases. however, higher clean kernels recovery resulted from a combination of larger screen aperture and increase in moisture content. the plots also revealed that increase in screen aperture would lead to lower values of clean kernels recovery probably because a larger percentage of the pods would pass through the screen undecorticated due to the smaller size of the grade. similarly, it was observed that slight increase in clean kernels recovery would be realized with increase in moisture from 8 – 10 % mainly because the smaller pods will swell thereby reduce the chances of passing undecorticated. however, a right combination of increase in screen aperture and moisture content produced slightly higher clean kernels recovery. 4.0 conclusion mathematical model equations that could explore and predict the possible relationships between moisture content and screen aperture on one hand and kernel quality in terms of clean kernels recovery for the three varieties of groundnuts in-shell were developed. the relationship existing between the performances indices were found to be adequately expressed by regression equations using linear and non-linear (quadratic or polynomials) functions. it could be generalized that the consistencies in obtaining higher values of coefficient of determination, r², in multi-variables modelling also confirmed a direct relationship between clean kernels recovery and independent variable (moisture content and screen aperture). it should also be noted that the fittings expressed in equations 1 – 7 holds true if the values of moisture content of the decorticated groundnuts and screen apertures of the decorticator are greater than zero. references echekwu, ca. and emeka, i. 2005. groundnut, endowing, the groundnut /rediscovery programme in nigeria. opah mission abuja pp 18 fao. (1994). general conclusions and recommendations of expert consultation on fats and oils in human nutrition. f.a.o: rome faostat. 2010. agricultural statistics database, 2010, (www.fao.org). accessed 17th october, 2012. hartmann, ht., kester, de. and davies, ft. 1990. plant propagation principles and practices. 5th edn. publisher-prentice hall international inc. pp. 55-73. khan, ha. 1999. sectoral growth and poverty alleviation: a multiplier decomposition technique applied to south africa. world development, 27(3), 521-530. ntare, br, ndjeunga, j., waliyar, f., kodio, o., echekwu, ca., kapran, i., da sylva, a., diallo, at., amadou, a., bissala, hy. and sako, k. 2007. farmer participatory evaluation and dissemination of improved groundnut varieties in west africa. international crops research institute for the semi-arid tropics. pp 36. ntare, br., diallo, at., ndjeunga, j. and waliyar, f. 2008. groundnut seed production manual. patancheru 502 324, andhra pradesh, india: international crops research institute for the semiarid tropics (icrisat). pp. 20 http://www.fao.org file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aminu, et al. modeling the relationship between grading, moisture content and screen apertures in groundnut decortication. azojete, 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 190 rai, m., barghouti, se. cromwell. aj. and pritch, rd. 1993. market-led oilseeds development in south asia an indian experience. world-bank-technical-paper. 1993, no. (204) 121-134. washington, dc; usa revoredo, cl. and fletcher, sm. 2002. “world peanut market: an overview of the past 30 years” university of georgia research bulletin, number 437, may 2002. table 1: analysis of variance for selected quadratic model for the grade i groundnut in-shell (samnut 10) source sum of square mean square f sign. f degrees of freedom regression 2118.5 423.70 421.70 0.000182 3 residual 3.014 1.005 5 total 2121.5 8 other parameters r r2 standard error no. of observations 0.999 0.999 1.002 9 table 2: regression output for quadratic model for grade i groundnut in-shell (samnut 10) coefficient p value std error -95% 95% t stat b0 53.73 0.06842* 19.26 -7.559 115.01 2.790 b1 -3.807 0.04608* 1.157 -7.490 -0.124 -3.290 b2 -3.108 0.450 3.584 -14.51 8.298 -0.867 b3 0.04921 0.296 0.03898 -0.07483 0.173 1.263 b4 0.09417 0.08928* 0.03797 -0.02668 0.215 2.480 b5 0.581 0.04642* 0.177 0.01734 1.145 3.280 *significant at 95% confidence level. table 3: analysis of variance for selected model for the grade i groundnut in-shell (samnut 18) source sum of square mean square f sign. f degrees of freedom regression 3133.5 1566.7 456.39 3e-07 2 residual 20.60 3.433 6 total 3154.1 8 other parameters r r2 standard error no. of observations 0.997 0.993 1.853 9 table 4: regression output for linear model for grade i groundnut in-shell (samnut 18) coefficient p value std error -95% 95% t stat b0 -50.02 1.87635e-05* 4.112 -60.08 -39.96 -12.16 b1 -0.728 0.000820* 0.118 -1.016 -0.440 -6.187 b2 11.18 9.91376e-08* 0.378 10.26 12.11 29.57 *significant at 95% confidence level. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 191 table 5: analysis of variance for selected quadratic model for the grade ii groundnut in-shell (samnut 10) source sum of square mean square f sign. f degrees of freedom regression 400.31 80.06 11.72 0.03491 5 residual 20.49 6.831 3 total 420.81 8 other parameters r r2 standard error no. of observations 0.975 0.951 2.614 9 table 6: regression output for quadratic model for grade ii groundnut in-shell (samnut 10) coefficient p value std error -95% 95% t stat b0 -62.96 0.299 50.21 -222.76 96.85 -1.254 b1 0.511 0.876 3.017 -9.092 10.11 0.169 b2 24.36 0.07988* 9.345 -5.376 54.11 2.607 b3 0.177 0.180 0.102 -0.147 0.500 1.741 b4 -0.08908 0.435 0.09902 -0.404 0.226 -0.900 b5 -1.150 0.08863* 0.462 -2.620 0.321 -2.488 *significant at 95% confidence level table 7: analysis of variance for selected quadratic model for the grade ii groundnut in-shell (samnut 18) source sum of square mean square f sign. f degrees of freedom regression 2257.7 752.57 267.30 6e-06 3 residual 14.08 2.815 5 total 2271.8 8 other parameters r r2 standard error no. of observations 0.997 0.994 1.678 9 table 8: regression output for quadratic model for grade ii groundnut in-shell (samnut 18) coefficient p value std error -95% 95% t stat b0 82.87 0.03596* 29.11 8.039 157.70 2.847 b1 -0.720 0.00107* 0.107 -0.994 -0.447 -6.762 b2 -13.90 0.06641* 5.942 -29.18 1.373 -2.340 b3 1.161 0.01124* 0.297 0.399 1.924 3.915 *significant at 95% confidence level. table 9: analysis of variance for selected quadratic model for the grade iii groundnut in-shell (samnut 10) source sum of square mean square f sign. f degrees of freedom regression 1659.6 331.93 12.84 0.03075 5 residual 77.56 25.85 3 total 1737.2 8 other parameters r r2 standard error no. of observations 0.997 0.995 5.085 9 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aminu, et al. modeling the relationship between grading, moisture content and screen apertures in groundnut decortication. azojete, 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 192 table 10: regression output for quadratic model for grade iii groundnut in-shell (samnut 10) coefficient p value std error -95% 95% t stat b0 -113.64 0.329 97.69 -424.53 197.24 -1.163 b1 8.495 0.244 5.870 -10.19 27.18 1.447 b2 32.28 0.174 18.18 -25.57 90.14 1.776 b3 0.551 0.06855* 0.198 -0.07804 1.180 2.788 b4 -0.454 0.09969* 0.193 -1.067 0.159 -2.357 b5 -2.270 0.08580* 0.899 -5.130 0.591 -2.525 *significant at 95% confidence level table 11: analysis of variance for selected quadratic model for the grade iii groundnut in-shell (samnut 14) source ss ss% ms f f signif degree of freedom regression 3219.6 95 643.92 11.63 0.03529 5 residual 166.13 5 55.38 3 total 3385.7 100 8 other parameters r r2 standard error no. of observations 0.975 0.951 7.442 9 table 12: regression output for quadratic model for grade iii groundnut in-shell (samnut 14) coefficient p value std error -95% 95% t stat b0 -78.43 0.621 142.97 -533.42 376.56 -0.549 b1 2.724 0.772 8.591 -24.62 30.07 0.317 b2 37.88 0.250 26.61 -46.79 122.56 1.424 b3 0.732 0.08537* 0.289 -0.189 1.653 2.531 b4 -0.314 0.346 0.282 -1.211 0.583 -1.115 b5 -2.844 0.119 1.315 -7.030 1.343 -2.162 *significant at 95% confidence level. figure 1: observed versus predicted values of clean kernels from multi-variable regression model for grade i groundnut in-shell (samnut 10) figure 2: observed versus predicted values of clean kernels from multi-variable regression model for grade i groundnut in-shell (samnut 18) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):185-193. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 193 figure 3: observed versus predicted values of clean kernels from multi-variable regression model for grade ii groundnut in-shell (samnut 10) figure 4: observed versus predicted values of clean kernels from multi-variable regression model for grade ii groundnut in-shell (samnut 14) figure 5: observed versus predicted values of clean kernels from multi-variable regression model for grade ii groundnut in-shell (samnut 18) figure 6: observed versus predicted values of clean kernels from multi-variable regression model for grade iii groundnut in-shell (samnut 10) figure 7: observed versus predicted values of clean kernels from multi-variable regression model for grade iii groundnut in-shell (samnut 14) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 23-29 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng viability of solar photovoltaic system for rural electrification in nigeria: a case study of a single bedroom apartment alkali, a.b. 1 , a.t. abdulrahim 2 and b.m. mustapha 1 abstract electricity availability in rural areas is identified as one of the social amenities that drastically reduce poverty problem by bridging the gap between the rural area and the urban centres. a suitable, cheap and reliable source of power, which could be minimally maintained and manipulated, is necessary to transform the life of an average rural family. this paper focuses on the solar system as a possible alternative to meet the above need. the paper presents a solar photovoltaic (pv) design and cost analysis for a typical single bedroom apartment. it also recommends integration of renewable energy into national strategies to cope with the economic and technical uncertainties that may constrain the supply of conventional energy. 1. introduction a common method of generating electricity is the use of thermal plants that depend on fossil fuels, which are depletable in nature and contribute to global warming. the kyoto protocol encourages the reduction in greenhouse gases and increase in the use of environmentally friendly energy sources, so as to improve the living standards of the people (okorodudufubara, 2001). conventional methods of providing electricity to the rural area through long distance high voltage transmission and distribution network are not always economically viable. in addition to cost implications, remote distribution lines and other equipment for the extension are prone to vandalism and theft (salawu and adetona, 2001). grid extension lead to poor electricity supply because of overload and high installation and maintenance costs (adegoke and akintunde, 2000). the provision of adequate supply of energy in suitable forms and at affordable price is an essential prerequisite for most developmental activities in remote areas. from the ecological point of view, every developing nation must use its available sources of energy wisely. although interconnected grids are increasing in global importance, they are unacceptable in many sparsely settled developing countries for technical and economic reasons. world bank studies revealed that in africa only 18 million rural people are connected to electricity over the past 20 years while the current rural population increase by 118 million per year as at 1998 (ibrahim, 1998). because of the constraints associated with conventional energy sources such as fossil fuels, there to exploit available renewable energy sources such as wind and solar. in nigeria, wind power pumps are being tested in some states (umar, 2002), although wind speed in nigeria is not favourable for large scale cultivation of wind energy (ojosu, 1999). 1 department of electrical and electronics engineering, university of maiduguri, maiduguri. nigeria 2 department of mechanical engineering, university of maiduguri, maiduguri. nigeria viability of solar photovoltaic system for rural electrification in nigeria 24 as at 1998, 22% of the 120mw of solar pv generated in the world are in rural areas (siemens, 1999). reports indicate that off-grid electricity is the most cost effective form of energy for rural communities (ceo, 1999), with solar pv being the most appropriate. the status of rural electrification in nigeria in 1999 was that over 80% of local government headquarters were connected to the national grid. similarly, towns and cities of commercial importance have also been connected. there are 5,350 towns and villages with access to electricity of which 98% were connected to the grid network. however, in spite of this number, only about 48% of nigerians have access to electricity supply as at 1999 (abdulmumini, 2000). this can be attributed to limited funds and vandalization. nigeria lies between latitudes 4 o and 14 o n and is thus particularly favoured by direct solar radiation all year round (chukwujekwu, 2000). adegoke and akintunde (2000) reported that solar energy was being tapped from various locations in the country. a report on solar pv installation in nigeria revealed that 316 units with a combined capacity of 238.8 kw were installed across the country. the highest percentage (52%) of the installation was for the provision of rural water supply and the lowest (0.4%) was for industrial application (umar, 2002). the objectives of this paper were to review the application of solar pv systems and to design a solar pv system for a typical one-bedroom rural apartment. 2. solar energy and its application solar pv system utilizes the radiant energy of the sun to produce electrical energy. it is the least polluting and most inexhaustible of all known energy sources. solar energy has been available to mankind since prehistoric times. creating a system that will provide a reliable energy from solar radiation can be very technical and challenging. however, not all solar energy systems are difficult to create or use. the sun, which is the source of energy, is situated at a distance of 149.6 million kilometers from the earth, and radiates 1.353 kw/m 2 of power at the earth atmosphere, out of which only about 1.0 kw/m 2 reaches the earth surface due to scattering by molecules, dust, absorption by carbon dioxide (co2), water vapour and ozone. the conversion of this radiant energy into electricity/ electrical energy requires the use of solar cells. figure 1 shows a schematic diagram of a solar cell. in the conversion process there are three basic processes taking place (bp solar, 2002) 1. photons are absorbed by the active part of the material resulting in electrons being excited to a high energy level. 2. the charge carrier created are physically separated and moved to the edge of the cell, and 3. the charge carriers are then moved to useful load before they lose their extra energy (bp solar, 2002). azojete vol. 4 2004 25 4. extra energy (bp solar, 2002) figure 1: schematic diagram of a solar cell solar energy converters can play a vital role in the provision of rural energy infrastructures that are essential to the development of the many vital sectors of the rural community. these sectors include: water resources (energy for pumping water), agricultural (crop drying, green house farming, irrigation, biomass energy, rural agricultural machinery), forestry (energy for plantation/forest fuel wood etc.), livestock (preservation of fodder, energy for breeding and feeding of animals in pens), and fisheries (fish drying, solar ponds). others are small-scale industries for rural areas, commerce (marketing of renewable energy), family planning projects, solar powered communication systems for remote and rural areas, solar pv village electricity for remote and off-grid localities and solar refrigerators (umar, 2000). another area of application is in the protection of oil and gas pipelines which is achieved by powering remote installations. these applications would stem rural-urban migration. sunlight cell interconnects n type region front contact grid pn junction p type region viability of solar photovoltaic system for rural electrification in nigeria 26 presently, many practical solar energy systems are in use. the two most common types are the solar heated home for small buildings and small stand-alone photovoltaic system referred to as the solar home system (shs). figure 2 below shows a typical shs. photovoltaic array roof thinlite connecting wires control gear varifan radio cassette player battery b figure 2: typical solar home systems 3. design and costing of a solar pv system for a typical one-bedroom apartment prior to the design of a solar pv, a load survey is carried out. the typical appliances required in a one-bedroom apartment are presented in table 1 which also shows the load sizing with the minimum number of hours of usage. table 1: load sizing form sn loads quantity unit load (w) total load (dcwatts) usage duration h/d dcwh/d* 1 lightings 7 15 105 6 630 2 fans 2 4.8 9.6 6 57.6 3 radio 1 40 40 10 400.0 total 59.8 154.6 1087.6 * dcwh/d): direct current watt hour per day azojete vol. 4 2004 27 the hours of usage as presented above is for a typical rural house (akintunde and adegoke, 2000). the load design procedure is as follows (bp solar, 2002) the total watt-hour per day (wh/d) = 1087.6 w total daily load in ampere hour/day (ah/d) = total daily load wh/d 1 system voltage x 1.1 the battery size = total daily load (ah/d) x autonomy 2 % usable no of batteries = battery size 3 battery rating required total number of parallel module = total daily load (ah/d) x 1.1. 4 module capacity total number of series module = system voltage 5 module voltage total number of module = parallel modules x series module. 6 regulator rating array side = total modules x short circuit current of modules (isc) 7 regulator rating load side = d.c wattage 8 system voltage from equation 1 and considering a system voltage of 12 v, the total daily load is 82.39 ah/d the battery size from equation 2, assuming battery autonomy of 5 days at 80% usable capacity is 514.94 ah. considering a 300 ah battery, two batteries will be required. considering bpsx 120u, the module capacity = 17.8 a from equation 4, number of parallel modules = 82.39 x 1.1 = 5.09 17.8 a the total number of series module from equation 5 is 1 and the total number of module is 5. from equation 7, we have viability of solar photovoltaic system for rural electrification in nigeria 28 regulator rating array side = total number of module x isc isc =3.87a (bp solar,2002) = 5 x 3.87 a= 19.35 a regulator rating load side = 154.6/12 = 12.88 a tables 2 and 3 present a summary of the solar pv design components and bill of quality respectively. table 2: design summary s/no. item quantity capacity 1 panel 5 bpsx120u 2 battery 2 300 ah 3 regulator 1 30 a 4 control gear 1 30 a 5 thinlite 7 15 w 6 varifan 2 4.8 w at 120 rpm table 3: bill of quantity s/n item quantity current unit price ($) cost($) 1 panel 5 525 2625 2 battery 2 400 800 3 regulator 1 150 150 4 control gear 1 100 100 5 thinlite 195 7 31.65 221.55 6 varifan 2 154 300 7 accessories sum 10% 419.66 8 miscellaneous sum 10% 419.66 total $5077.83 the cost of the pv installation for the envisaged house is $5077.83. this is equivalent to n710,896.20 at the current exchange rate of n140 to the us dollar. the initial investment cost is quite high, but the low running cost makes solar pv systems attractive and worthwhile. 4. conclusion a standalone solar pv home system for a typical single-bedroom apartment was designed. the system consists of five panels, two 300-ah batteries and a regulator. it can provide dc power to a maximum load of 1087.6 wh/d. evaluation of the solar home system designed for a single bedroom apartment revealed that a minimum cost of n 710, 896.20k will be required to meet the energy demand. as the pv system has low running cost and is environmentally friendly, there is need to integrate such renewable energy system with the national strategies. in view of the above, it is recommended that government should encourage the use of solar pv home systems by providing financial assistance through soft loans. azojete vol. 4 2004 29 references abdulmumini, y. (2000). the state of rural electrification in nigeria. nepa review, pp15-18. adegoke c.o. and m.a. akintunde (2000). alternative sources of energy for rural electrification. proceedings of the conference of the nse, abuja, nigeria. b.p. solar (2002) training manual. http://www.solarsolve.com. accessed september 23, 2002 ceo (1999) “durban metro electricity”, esi africa. the power journal of africa. issue 3 pp11. chukwujekwu e.u. (2000). renewable energy resources: a veritable tool for poverty reduction. proceedings of the national engineering conference of nse abuja, nigeria. ibrahim, h. (1998). alternative energy, the nigerian power system in the 21 century, nepa review. pp41-45. abuja. ojosu, j.o. (1999). renewable energy in nigeria. paper presented at the unesco workshop on renewable energy in west africa. university of science and technology, kumasi. ghana. okorodudu-fubara m.t. (2001). refocusing regulatory regime on atmospheric pollution control in nigeria. ccdi ecology and development series. number 01 pp 45-60. salawu r.i. and s. o. adetona (2001). design of a transistorized 10 ampere mini charge controller. proceedings of the conference of nigerian society of engineers (electrical division) lagos. pp 45-56. siemens (1999). solar report on the photovoltaic status and future development. pp4 umar b. (2000). an introduction to solar cooling and refrigeration system. faculty of engineering seminar series. university of maiduguri, nigeria. 1(1) pp 1-11. umar, l.h. (2002). energy resources and development in nigeria. proceedings of the national conference on energy resources and development. 10-14 february. a.t.b.u. bauchi. pp 1-17. http://www.solarsolve.com/ arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):209-216 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 217 original research article production of biocomposite from parinari polyandra fruit shell using waste low density polyethylene as matrix p.o. odiase* and t.e. odetoye2 department of chemical engineering, university of ilorin, p.m.b.1515, ilorin, nigeria *corresponding author’s email address: praiseodiase@gmail.com 1.0 introduction enormous waste generated from low-density polyethylene (ldpe) packaged sachet water constitutes an environmental challenge in nigeria which demands attention due to its nonbiodegradability as attested by several studies (chatterjee et al., 2010; sylvester et al., 2020). with the recognition that landfill is not sustainable and its costs are increasing, waste disposal becomes important with more responsibility being placed on producers. governments of several countries have implemented laws to encourage the use of recycled and/or bio-based ‘green’ products (suheyla et al., 2016). composites are multifunctional materials with exceptional mechanical and physical properties which can be custom fitted to meet the prerequisites of a specific application (badamasi and ibrahim, 2017; rubentheren et al., 2015). composite materials comprising of one or more phases derived from a biological origin are referred to as biocomposites (fowler et al., 2006). in general, the main components of bio composite materials are fibers and matrix. the benefits of plant fibers are acceptable specific strength, low cost, low density, good thermal insulation properties, reduced dermal and respiratory irritations, renewable resource and possible recycling without article information abstract enormous wastes that are continuously being generated from low-density polyethylene (ldpe) film sachet water have remained an environmental challenge in nigeria. these might require urgent action due to the non-biodegradability of ldpe. biocomposite samples were produced using waste ldpe sachets and parinari polyandra shells, where filler sizes (0.420 mm, 0.841mm) and filler loading (10%, 20%) were varied. in this study, a melt mixer was designed and fabricated for the production of bio composite samples. biocomposite samples were characterized using tensile tests, compression test, flexural and impact strength test, water absorption test, biodegradability, fourier transform infrared spectroscopy and scanning electron microscopy tests. viscosity of the bio composite mix was a major constrain in the design of the melt mixer. the results revealed that the optimum value of tensile strength was obtained with particle size 0.42mm at a 10% filler to matrix loading which produced a young’s modulus of 320.321 n/mm2. higher particle size and filler loading elicited a higher value for compressive strength based on a force at peak value of 27552.500 n. flexural, impact and tensile strength decreased with increasing filler loading and particle size, while increased immersion time gave increased percentage of water absorbed. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 october, 2021 revised 22 february, 2022 accepted 3 march, 2022 keywords: biocomposites parinari polyandra low-density polyethylene matrix http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 218 affecting the environment (busuioceanu et al., 2018). the matrix binds the fibers together, allowing the transfer of tension between the fibers in the composite. parinari polyandra benth belongs to the rosasceae family, it is also known as maranthes polyandra benth, it is a grassland plant found in west africa (abolaji et al., 2007). parinari fruit shells are wastes generated from parinari polyandra benth seed oil utilization. while many studies have been carried out on utilization of natural fillers and fibers such as short silk fibers, kenaf, sisal, jute, oil palm, empty fruit bunch, coir, sugar palm, rice husk ash, and coconut shell powder, little work has been reported on the use of parinari fruit shell as fillers in polymer matrices. thus, this work investigates the properties of biocomposites produced from waste low-density polyethylene sachet and parinari polyandra shell, thereby fostering the conversion of wastes to value-added products which can be used for wider applications commercially. 1.0 materials and methods 2.1 materials used parinari fruits were harvested from its trees within the campus of university of ilorin, kwara state, nigeria. harvested fruits were cut in half to separate the seeds from the shells, after which shells were cleaned and sundried. the clean dried shells were size reduced using a grinding machine and screened to sizes 0.420 mm and 0.841mm. ldpe waste water sachets were sourced and collected from restaurants and shops within the university of ilorin campus. waste ldpe sachets were washed to remove oil and dirt after which they were dried and shredded to give better surface area for heating. base oil was sourced from lubcon oil, ilorin and used as lubricant for mould edge lubrication. figures 1 and 2 show the image of parinari polyandra shells and waste ldpe respectively. figure 1: parinari polyandra shells figure 2: waste ldpe equipment used in this research were: pulverizing/grinding machine, testomeric universal testing machine fs50at, shimadzu fourier transform infrared spectrophotometer – ftir 8400 s, avery denison 150j impact testing machine 6705u/33,122, screening mesh sizes of 0.42mm and 0.841mm, fabricated metal moulds with dimensions 200×20×10 mm3, 50×50×50 mm3, 40x10x10mm3 and 200x25x15mm3 for tensile, compression, impact and flexural strength respectively, weighing scale, shredder/scissors and a fabricated melt mixer. figure 3 shows the testomeric universal testing machine fs50at. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com odiase and odetoye: production of biocomposite from parinari polyandra fruit shell using waste low density polyethylene as matrix. azojete, 18(2):217-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 219 figure 3: testomeric universal testing machine 2.1.1 mixer material of construction and geometry the melt mixer consists of a fabricated cylindrical shaped 2 mm stainless steel tank, unbaffled with diameter 300 mm and height 400 mm. this was scaled up based on the required mass of (500 g) for batch mixing which puts into consideration a mix of shredded waste low density polyethylene sachets and size reduced parinari shells. the relatively high cost and unavailability of a row mill influenced the initiative to design and fabricate a melt mixer using available local resources. 2.1.2 impeller blade construction and geometry standard shape factor requires the diameter of the impeller blade to be one-third the diameter of the tank and same ratio for the clearance off the base of the tank. i.e da = 1 3 dt (1) where da: diameter of impeller blade (mm) dt: diameter of tank (mm) to ensure an efficient molten mix it was imperative to have a very small clearance off the base of the tank hence, a paddle shaped impeller blade at the base with a 45° inclination tip and a 270 mm diameter was used because it thrives better for conditions of high viscosity and fits closely to the base of the tank. 2.1.3 lagging material fiber glass was the lagging material used, this was done to retain heat within the melt-mixer enhancing an adiabatic condition. 2.1.4 heat transfer requirement for heating coil/element heating coil was wired round the entire fabricated tank to achieve uniform temperature at all sections of the tank. considering the melting point of shredded waste low density polyethylene of 120 ℃ (osuolale and agbalaya, 2012), the temperature range was selected as 27 120 ℃, specific heat for low density polyethylene film ranges between 1900 and 2300 jk-1kg-1. in calculating heat transfer requirement for the heating coil; q = mcdt (2) where; q = heat transfer (j) m = mass of substance (kg) c = specific heat (j/kg. k) dt = temperature difference (℃) q = 106,950 j http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 220 heating element with 1500w was used in the fabrication process which had the capacity to provide a temperature range from 30℃ to 300℃ 2.1.5 power requirement for mixer power = np × n3 × d5 × sg × k (3) where; np = power number n = rotation speed (r/s) d = diameter of impeller (mm) sg = specific gravity ( kgm−3) k = reynolds number impeller diameter d = 270 mm = 0.27 m sg for molten ldpe = 760 kgm−3 n = 70rpm = 70 60 r/s re = nd2ρ µa (4) where µa = 1.12 × 105p = 1.12 × 102pa. s which is the 0 shear rate viscosity for linear ldpe whose value by assumption will be close and used for that of molten ldpe re = 0.577 therefore np = 40.98 extrapolated from power correlation for a six blade turbine for pseudo − plastic liquids p = 40.94 w a dc variable motor of 1 horse power was used in fabrication which provided a 10-70 rpm range. 2.1.6 vent a vent or smoke outlet at the top of the vessel was used to help channel smoke formation. 2.1.7 molten outlet a ball valve tap outlet from where the bio composite molten mix can be removed to be placed into desired moulds. 2.2 method waste low density polyethylene was melted thermally i.e. by application of heat. the polymer melt was then mixed thoroughly with filler. the factors, filler size and filler-matrix ratios were varied one after the other. filler sizes varied were 0.420 mm and 0.841mm while the varied filler to matrix ratios were 10% and 20%. the waste ldpe – parinari shell composite were mixed in the ratios 10/90, 20/80 till a uniform mix was achieved. each composite mix was transferred into fabricated metallic moulds of different dimensions based on specific tests to be carried out. prior to mould placement, base oil was applied to the fabricated mould edges to enhance the ease of file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com odiase and odetoye: production of biocomposite from parinari polyandra fruit shell using waste low density polyethylene as matrix. azojete, 18(2):217-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 221 bio composite removal after bio composite samples had solidified. hand lay-up technique was used (hussein, 2013). table 1 shows how the factors were varied one at a time. table 1: experimental runs varying one factor at a time 2.3 characterization 2.3.1 flexural strength flexural strength test was carried out on bio composite samples with mould dimension of 200 mm × 25 mm × 15 mm using a universal testing machine fs50at. 2.3.2 compression test compression test was carried out on produced bio composite with mould dimension 50 mm×50 mm × 50 mm using a universal testing machine fs50at. 2.3.3 tensile strength tensile strength was measured using a universal testing machine fs50at with test specimen dimensions according to astm standards until test failure occurred. mould dimension used for test was 200 mm × 20 mm ×10 mm where values for stress at peak, force at peak, and young’s modulus were obtained (zaaba et al., 2013). 2.3.4 scanning electron microscopy scanning electron microscopy was used to assess the morphological characteristics of selected bio composite produced. the test was done to show the uniformity and adhesion of filler and matrix. the scanning electron micrograph was shown with a (500x) magnification. 2.3.5 fourier transform infrared spectroscopy infrared spectroscopy was performed using a shimadzu fourier transform infrared spectrophotometer – ftir 8400 s. samples were scanned in the absorbtion area of 500 to 4000 cm-1 where transmittance values ranged from 0 to 100%. ir peaks were observed in correspondence with their bond types. 2.3.6 water absorption water absorbed by biocomposites produced was determined by drying and immersing the samples in distilled water, samples were weighed every day for four days to obtain the new change in weight. the percentage water absorption was then calculated using the formula (obasi, 2015). %𝑤𝑎𝑡𝑒𝑟 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 = [ 𝑓𝑖𝑛𝑎𝑙 𝑑𝑟𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝑎𝑓𝑡𝑒𝑟 𝑖𝑚𝑚𝑒𝑟𝑠𝑖𝑜𝑛 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑑𝑟𝑦 𝑤𝑒𝑖𝑔ℎ𝑡 𝑏𝑒𝑓𝑜𝑟𝑒 𝑖𝑚𝑚𝑒𝑟𝑠𝑖𝑜𝑛 − 1 ] 𝑥 100 (5) run filler size (mm) filler-matrix ratio (%) 1 0.42 10 2 0.42 20 3 0.84 10 4 0.84 20 http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 222 2.3.7 impact test impact test was used to test for the impact strength of materials. the test was carried out using the avery denison 150j impact testing machine 6705u/33,122. the impact test was conducted on notched rectangular samples with dimensions according to astm d256. 2.3.8 biodegradability test a two-week biodegradability test was performed for produced bio composite samples. biocomposite samples were buried in the soil and unearthed for 7 days, dried, weighed, buried again and unearthed after another 7 days and weighed again. (junior et al., 2015). 3. results and discussion 3.1 melt mixer design and fabrication chemical engineering design and autocad design of the melt mixer was achieved. fabricated melt mixer was successful with heating and mixing of polymer melt and parinari shell particles. figures 4 and 5 show the autocard design and the fabricated view of the melt mixer. figure 4: wireframe autocad design view figure 5: fabricated melt-mixer 3.2 flexural stress figure 6 shows that stress at peak for filler size 0.420 mm decreased with increasing filler loading from a value of 16.0022 n/mm2 to 9.748 n/mm2 while the bending modulus increased from a value of 312.594 n/mm2 to 410.129 n/mm2 as observed on figure 7. filler size 0.841 mm had a slightly differing trend such that the stress at peak increased with increasing filler loading from a value of 6.028 n/mm2 to 16.064 n/mm2 while having same trend for bending modulus where an increase was observed from 245.219 n/mm2 to 567.381 n/mm2. it was observed that bending modulus increased with filler loading for both filler sizes, particle size 0.841mm with 20% filler loading had the highest value while particle size 0.841mm with 10% filler loading had the lowest value. saliu et al. (2015) observed flexural strength decreasing with increasing filler loading, this occurred due to insufficient wetting of incorporated fibers by matrix. fiber-fiber adhesion in fiber bundles reduces contact area between fiber and matrix which causes poor stress transfer from matrix phase to dispersed fibers (moh’d ishak et al., 1997). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com odiase and odetoye: production of biocomposite from parinari polyandra fruit shell using waste low density polyethylene as matrix. azojete, 18(2):217-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 223 as fiber loading kept increasing the modulus also increased, this probably verifies the increase in the modulus of biocomposites produced. this is found to be in agreement with a study conducted by dhal and mishra (2013); ku et al (2010). figure 6: flexural stress varying with filler to matrix ratio and size figure 7: bending modulus against filler to matrix ratio and size 3.3 compressive strength compressive strength is the capacity of a material to withstand loads tending to reduce size. table 2 shows that with increasing filler content for filler size 0.420mm, strain at peak, force peak and young’s modulus show reduction in value, while with increasing filler content for filler size 0.841mm increase is observed for both strain at peak and force at peak, and a decrease in value for young’s modulus. the highest force at peak was observed for particle size 0.841mm with 20% filler loading as observed on figure 8, highest young’s modulus 107.263 n/mm2 is observed for particle size 0.841 with 10% filler loading. using force at peak as a yardstick for compressive strength, 0.841mm with 20% filler loading will prove viable in that it is in conjunction with approximately a 38% strain. so we have a higher particle size with higher filler loading eliciting a higher value for compressive strength based on a force at peak value of 27552.5n. 0 100 200 300 400 500 600 0% 10% 20% b en d in g m o d u lis ( n /m m 2 ) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm 0 5 10 15 20 0% 10% 20% fl ex u ra l s tr es s @ p ea k (n /m m 2 ) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 224 table 2: compressive test results figure 8: force at peak against filler to matrix ratio and size 3.4 tensile strength filler size 0.420mm with filler to matrix ratio 10% has the highest stress at peak value of 7.366 n/mm2 while filler size 0.841mm with filler to matrix ratio 10% and 20% have lower stress at peak values based on filler and matric mixed, but nothing compared to 100% waste low density polyethylene matrix as seen on table 3. the highest young’s modulus value is observed with filler size 0.420 mm and its ratio 20% on figure 10. since tensile strength is the maximum load a material can support without fracture when being stretched per the original cross-sectional area of the material, maximum load 1252.300 n makes filler size 0.420 mm with filler to matrix ratio 10% bio composite sample with the highest tensile strength. an increase in filler size and loading reduced tensile strength, this is graphically illustrated on figure 9. al-assafi et al. (2016) experienced a drop in tensile strength with increasing nanofiber content, gumel et al. (2014) observed the same trend where the addition of filler interfered with regular arrangements of rubber molecules used as matrix, same can be said for waste low density polyethylene molecules being interfered by more addition of filler which is a probable cause for the reduction in tensile strength where filler matrix interaction is reduced. size (mm) filler to matrix ratio (%) strain at peak (%) force @ peak (n) young’s modulus (n/mm2) 0.420 10 27.1 24110.1 98.95 0.420 20 26.9 19810.9 87.98 0.841 10 25.1 23697.2 107.26 0.841 20 38.2 27552.5 75.05 0 0 23.6 22654.2 100.2 0 5000 10000 15000 20000 25000 30000 0% 10% 20% fo rc e at p ea k (n ) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com odiase and odetoye: production of biocomposite from parinari polyandra fruit shell using waste low density polyethylene as matrix. azojete, 18(2):217-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 225 table 3: tensile test results figure 9: tensile stress at peak against filler to matrix ratio and size figure 10. young’s modulus against filler to matrix ratio and size 3.5 scanning electron microscopy scanning electron microscope micrograph shows the fiber-matrix interaction and surface morphology of the produced bio composite sample with particle size 0.42 mm and 10% filler loading. figure 11 shows the fiber-matrix interactions gotten through matrix wetting the fillers. from the micrograph image, areas with good adhesion can be observed which explain areas with good uniformity and can be traced to fibers being sufficiently wetted by the waste low density size (mm) filler / matrix ratio (%) stress at peak (n/mm2) young’s modulus (n/mm2) force at peak (n) area 0.42 10 7.4 320.3 1252.3 170 0.42 20 3.92 432.2 665.7 170 0.84 10 3.53 348.1 600.6 170 0.84 20 3.86 290.1 656.3 170 0 0 9.78 142.4 141.98 170 0 2 4 6 8 10 12 0% 10% 20% te n si le s tr es s at p ea k (n /m m 2 ) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm 0 50 100 150 200 250 300 350 400 450 500 0% 10% 20% yo u n gs m o d u lu s (n /m m 2 ) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 226 polyethylene matrix. some cracks and voids can as well be observed on the micrograph image showing areas with reduced adhesion and uniformity, weak interfacial adhesion can be a probable cause (zaaba et al., 2013). figure 11: scanned micrograph for particle size 0.42mm, 10% filler loading 3.6 fourier transform infrared spectroscopy figure 12 shows the ftir spectra for particle size 0.42mm with 10% filler loading. ftir analysis helps to pinpoint a sample's molecular composition and structure, it identifies the chemical bonding in molecules. ir peaks on figure 12 correspond to the functional groups present in bio composite sample. the ir peak observed ranged from 461.44 cm-1 to 3981.50 cm-1 and the percentage transmittance (%t) ranged between 10 and 100 % focusing on the functional group region of the spectra i.e. wavelength ranging from 1500-4000 cm-1. it can be observed that bio composite sample exhibited ir main peak positions of 1550 cm-1, 2900 cm-1, 3150 cm-1, 3400 cm1, 3650 cm-1 representing c=c, c-h, =c-h, n-h and o-h functional groups respectively. figure 12: ftir for particle size 0.42mm with 10% filler loading 3.7 water absorption water absorption results showed that with increasing filler loading, particle size and immersion time (days), percentage water absorbed increased. filler size 0.841mm with filler to matrix ratio 20% had the highest percentage water absorbed 0.93%, compared to 100% waste low density polyethylene which showed very little percentage water absorbed. lignocellulosic fibers are known for their hydrophilic nature i.e they are permeable to water, significantly having effect on file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com odiase and odetoye: production of biocomposite from parinari polyandra fruit shell using waste low density polyethylene as matrix. azojete, 18(2):217-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 227 water absorption, through hydrogen bonding free –oh (hydroxyl) groups come in contact with water which results in weight gain and water uptake in biocomposites (zaaba et al., 2013). the fourier transform infrared spectra of bio composite sample produced represented on table 4 showed the presence of –oh (hydroxyl) functional group. presence of cracks and voids were observed on the scanning electron microscopy micrograph image referenced on figure 11, cracks and voids could as well lead to the penetration of water molecules in the bio composite sample produced. figure 13: percentage water absorbed against filler to matrix ratio and size 3.8 impact test impact test assessed the response of produced bio composite samples when subjected to dynamic load, it showed the variation of impact strength to both filler size and filler to matrix ratio. it is clear from figure 14 that with increasing filler loading impact strength decreases, deformability of waste low density polyethylene matrix occurred as a result of increased concentration of filler hence elasticity reduced. biocomposite samples with smaller particle size (0.42 mm) showed higher impact strength than bigger particle size (0.841 mm). thus increasing the filler size with a higher filler to matrix ratio lead to a resultant decrease in impact strength, a probable reason can be placed to an increased level of stress concentration in the bio composite produced (onuegbu and igwe 2011). figure 14: impact test against filler to matrix ratio and size 0 0.2 0.4 0.6 0.8 1 0% 10% 20% w at er a b so rb ed ( % ) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm 0 20 40 60 80 0% 10% 20% im p ac t st re n gt h ( j) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 228 3.9 biodegradability test biodegradability test results shown on figure 15, highlighted no observable weight change for 100% waste low density polyethylene, emphasizing the polymer matrix property of nonbiodegradability. weight changes were observed for bio composite samples produced, it was observed that higher weight changes occurred for bigger particle size and filler loading to matrix ratios. figure 15: weight reduced against filler to matrix ratio and size 4. conclusion effects of selected factors (filler size and filler loading to matrix weight ratio) were investigated on produced bio composite samples where optimum value of tensile strength was obtained at 10% filler to matrix loading with particle size 0.42 mm which produced a young’s modulus of 320.321 n/mm2. higher particle size with higher filler loading elicited a higher value for compressive strength based on a force at peak value of 27552.500 n. flexural strength, impact strength and tensile strength all decreased with increasing filler loading. percentage of water absorbed increased with increasing filler loading, particle size and immersion time. biodegradability test showed higher weight changes for bigger particle size and filler loading to matrix ratios. application and suitability of parinari waste low density polyethylene bio composite in the production of packaging materials and insulators, effects of chemical treatment on parinari -waste low density polyethylene bio composite properties, determination of viscosity of molten waste low density polyethylene matrix and parinari polyandra shell blend are recommended for further research. references abolaji, oa., adebayo, ah. and odesanmi, os. 2007. nutritional qualities of three medicinal plant parts (xylopia aethiopica, blighia sapida and parinari polyandra) commonly used by pregnant women in the western part of nigeria. pakistan journal of nutrition, 6(6): 665–668 0 0.02 0.04 0.06 0.08 0.1 0.12 0% 10% 20% w ei gh t re d u ce d ( g) filler to matrix ratio (%) and size(mm) 0mm 0.42mm 0.841mm 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810–816. osuolale, om. and agbalaya, ks. 2012. influence of shredded waste water sachet on engineering properties of asphalt, 2(10): 134–140. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):217-230. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: praiseodiase@gmail.com 230 saliu, hr., ishiaku, us., yakubu, mk., kolawole, eg., adefila, ss., bakar, mba. and ishak, zam. 2015. the effect of epoxy concentration and fiber loading on the mechanical properties of abs/epoxy-coated kenaf fiber composites. open journal of composite materials, 05(02): 41– 48. ohiomu, s., ihensekhien, oa. and ovenseri-ogbomo, fo. 2020. externality effects of sachet and plastic bottled water consumption on the environment: evidence from benin city and okada in nigeria. international journal of sustainable development & world policy, 9(1): 1–9. https://doi.org/10.18488/journal.26.2020.91.1.9 zaaba, nf., ismail, h. and jaafar, m. 2013. effect of peanut shell powder content on the properties of recycled polypropylene (rpp)/peanut shell powder (psp composites. bioresources, 8(4): 5826–5841. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%202/praiseodiase@gmail.com arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):793-802 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 793 original research article design analysis of microcontroler based automatic power management in photovoltaic systems a. a. okandeji1, f. onaifo2, o. o. olaluwoye2, s. n. ukagu3, b. o. sosanya4 and i. e. imobhio3 1department of electrical/electronic engineering, university of lagos, akoka, lagos state, nigeria. 2department of electrical/electronic engineering, olabisi onabanjo university, ogun state, nigeria. 3department of electrical and computer engineering, igbinedion university, okada, edo state, nigeria 4curative integrated services limited, lagos, nigeria *corresponding author’s email address: aokandeji@unilag.edu.ng 1.0 introduction solar energy is an alternative source of energy in rural and remote areas of nigeria. it complements rapid development of small scale industries and reduces the rural–urban drift. the country receives abundant solar radiation and sunshine. accordingly, solar energy is the most promising of the renewable energy (re) resources in nigeria due to its apparent abundance. energy radiated from the sun is about 384.6 septillion watts which is 1.082 million ton of oil equivalent (mtoe) per day (kadafa, 2012). this is about 4000 times the current daily crude oil production in nigeria, and about 13,000 times the natural gas daily production, based on standard energy unit (maijama’a et al., 2015). inspite of the abundance of solar as a re source, there must be a conscious effort to manage re in rural areas to avoid a complete impromptu shutdown of the photovoltaic (pv) system. the basic idea of the energy management system is to disconnect load in the system in the order of less importance. in a more general term, this is called load shedding in power system operations. effectively, load shedding is a measure of last resort to prevent the collapse of the power system be it a central generation, microgrid or stand alone (osueke et al., 2013). when there is insufficient power station capacity to supply the demand (load) from all the customers, the electricity system becomes unbalanced, which can cause it to trip out the supply (a blackout), and which could take days to restore. in the context of a pv re source, terminating supply to an unused electrical appliance is aimed at saving the available electrical energy. saving electricity (by using energy-efficient appliances, switching off equipment when not in use, using alternative sources of energy) has benefits such as reduced cost, less pollution, better use of natural resources (coal, water and fuel), and less wear and tear on the power stations, transmission and distribution systems, and it saves customers money. in terms of capacity constraints, saving electricity also means that the load on the national power system is reduced (gujba et al., 2015). this helps to stabilize the balance between the available generation and the demand, in article information abstract this work considered the design analysis of an energy management system to control the state of battery discharge of a solar power system without any form of load discrimination, thus preventing a sudden system shut down. the state of discharge of the storage battery is monitored by the voltage level sensor. in particular, four voltage levels were used in this work namely: 11.5v (for less critical), 11.0v, 10.5v and 10.0v (for most critical load). the outputs of the sensors are then connected to a microcontroller which is programmed to isolate the loads in the order of priority. tests result showed that at different voltage levels, specific load was disconnected from the desired voltage thus, stored energy was efficiently conserved. accordingly, this prototype design ensures efficient energy management in photovoltaic systems. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 may, 2020 revised 23 november, 2020 accepted 27 november, 2020 keywords: energy-management voltage-level-sensor microcontroller energy conservation solar power system mailto:aokandeji@unilag.edu.ng http://www.azojete.com.ng okandeji et al: design analysis of microcontroler based automatic power management in photovoltaic systems. azojete,16(4):793-802. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 794 this way, reducing the risk of load shedding. (nasir et al., 2014) developed an automatic loadshedding strategy for stand-alone photovoltaic system which was designed using the softcad eagle pcb design software for schematic design. test results showed that the load is shed when the power is smaller than the load demands. in contrast to existing results, this work considers the development of an energy management system to manage the storage depth of discharge in a solar powered home, without any form of discrimination on the connected load thereby preventing the system from a sudden shutdown. in particular, by using a microcontroller to coordinate the processes between the voltage sensors and the output interface, the state of discharge of the storage battery is monitored by the voltage level sensor resulting into efficient management of the stored energy. 2.0 materials and methods this section focuses on the analysis and design considerations of the proposed pv energy management system. 2.1 design of the voltage sensors in this study, the operational amplifier (op-amp) comparator is used as the voltage sensor. the circuit for a basic operational amplifier comparator is shown in figure 1. it is possible to use an op-amp as a comparator as it fulfills the basic requirements for the function. in operation, the operational amplifier goes into positive or negative saturation depending upon the input voltages. as the gain of the operational amplifier will generally exceed 100000, the output will run into saturation when the inputs are only fractions of a millivolt apart. although op-amps are widely used as comparators, special comparator chips are far better. this specific comparator chips offer very fast switching times well above those offered by most op-amps that are intended for more linear applications. typical slew rates are in the region of several thousand volts per microsecond, although more often, figures of propagation delay are quoted. a typical comparator circuit will have one of the inputs held at a given voltage. this may often be a potential divider from a supply or reference source. the other input is taken to the point to be sensed. in this study, the fixed input is held by a zener diode at 3.9v while other references are fixed 0.6v apart. the input voltage to the fixed unit is fixed by a regulator 7809. the forward voltage drop is utilized for this purpose. the value of the resistor is given by the equation r = vcc−vz iz , (1) where vcc = is 9v from the regulator, vz is the zener breakdown voltage chosen as 3.9v (the most critical load), and iz is the zener current chosen as 10ma (from the data sheet of the diode). note that the choice of these values as given in the data sheet helps to procure a resistor whose value is available in the standard resistor table. therefore, r = (9 − 3.9)/ (0.001) = 5100ω. a close value to this on the standard resistor table is 5.6kω. the sensed input is then fixed by a voltage divider network using a pot resistor connected to the floating battery voltage. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):793-802. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 795 figure 1: circuit for a basic operational amplifier comparator 2.2 microcontroller pin description pic16f84 has a total of 18 pins as shown in figure 2. it is most frequently found in a dual-inpackage (dip)18 type case but can also be found in surface mount devices (smd) case which is smaller from a dip. surface mount devices, in general, suggests that holes for pins to go through when mounting aren't necessary in soldering this type of component. figure 2: pin assignment of pic 16f84a pin no.1 ra2 second pin on port a. used as an input pin no.2 ra3 third pin on port a. used as an input. pin no.3 ra4 fourth pin on port a. tock1 which functions as a timer is also found on this pin. pin no.4 mclr reset input and vpp programming voltage of a microcontroller. pin no.5 vss ground of power supply. pin no.6 rb0 zero pin on port b. interrupt input is an additional function. pin no.7 rb1 first pin on port b. no additional function, but could be used as an output. pin no.8 rb2 second pin on port b. no additional function, but could be used as an output. pin no.9 rb3 third pin on port b. no additional function, but could be used as an output. pin no.10 rb4 fourth pin on port b. used as output. pin no.11 rb5 fifth pin on port b. used as output. pin no.12 rb6 sixth pin on port b. used as output. pin no.13 rb7 seventh pin on port b. used as output. pin no.14 vdd positive power supply pole. pin no.15 osc2 pin assigned for connecting with an oscillator. pin no.16 osc1 pin assigned for connecting with an oscillator. pin no.17 ra2 second pin on port a. used as an input. pin no.18 ra1 first pin on port a. used as an input. 2.2.1 crystal oscillator the crystal oscillator in this study is kept in a metal housing with two pins where the frequency at which the crystal oscillates is recorded. one ceramic capacitor of 30pf whose other end is connected to the ground needs to be connected with each pin. oscillator and capacitors can be packed in a joint case with three pins. such element is called ceramic resonator. the center pin of the element is the ground, while end pins are connected with osc1 and osc2 pins on the microcontroller. in this study, for operational efficiency, the oscillator is placed nearer to the microcontroller to avoid any interference on the lines on which the microcontroller is receiving a clock (theraja and theraja, 2008). figure 3 shows the diagram of an oscillator with the pic16f84 microcontroller. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:aokandeji@unilag.edu.ng okandeji et al: design analysis of microcontroler based automatic power management in photovoltaic systems. azojete,16(4):793-802. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 796 figure 3: diagram of an oscillator with the pic16f84 the pins 15 and 16 are connected to the two ends of the crystal oscillator as shown in figure 3. as discussed above, the function of the crystal oscillator is to provide the timing which it controls by dividing the signal which enters the pic16f84. the frequency at which the crystal oscillator operates is at 4mhz. the two ceramic capacitors c1 and c2 which are of values of 22nf act as filters to ensure that interference does not affect the microcontroller receiving a clock. 2.3 design of the relay interface an electronic circuit will normally need a relay driver using a transistor circuit in order to convert its low power direct current (dc) switching output of the microcontroller into a highpower main alternating current (ac) switching output. however, the low-level signals from an electronic circuit which is derived from the microcontroller stage is incapable of driving a relay directly because a relay requires relatively higher dc which is normally not available from the microcontroller stage. in this study, to overcome the above issue, a relay control stage is imperative for the circuit. the relay driver is an additional transistor stage attached with the relay which needs to be operated as shown in figure 4. this transistor is typically and solely employed for operating the relay in response to the commands received from the preceding control stage. figure 4: basic circuit diagram of the relay driver the configuration of figure 4 only involves a transistor, a base resistor, and the relay with a fly back diode. since the base drive voltage to the transistor is the major source for controlling the relay operations, there is a need to perfectly calculate the value for optimal results. the base resistor current value (ib) is directly proportional to the current across the collector/emitter leads of the transistor or in other words, the relay coil current, which is the collector load of the transistor, becomes one of the main factors and directly influences the value of the base resistor of the transistor. from (theraja and theraja, 2008), the basic formula for calculating the base resistor of the transistor is given by the expression: rb = vb−0.6 ib (2) but ib = relay coil current /hfe, then rb = vb−0.6 hfe relay coil current (3) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):793-802. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 797 where r = base resistor of the transistor, vb = source or the trigger voltage to the base resistor, hfe = forward current gain of the transistor. the expression, which is the “relay current,” may be obtained by solving ohm’s law (theraja and theraja, 2008): i = vs/rc, where i is the required relay current, vs is the supply voltage to the relay, rc is the relay coil resistance. the relay coil resistance can be easily identified by using a multi-meter. in this study, the supply voltage vs = 12 v, the coil resistance is 400 ohms. then, relay current i = 12/400 = 0.03 or 30 ma. also, the hfe of transistor (bc547) from datasheet is 150. applying the above values into equation (2) we obtain, rb = (vb − 0.6) × hfe ÷ relay current; rb = (12 – 0.6)150/0.03 = 57,000 ohms or 57 k, the closest value being 56 k. for the diode connected across the relay coil, although it is no way related with the above calculation, it still cannot be ignored. the diode ensures that the reverse electromotive force (emf) generated from the relay coil is shorted through it, and not dumped into the transistor. without this diode, the back emf would try to find a path through the collector emitter of the transistor and in the course damage the transistor permanently, within seconds. the circuit diagram of the prototype design is shown in figure 5. . file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:aokandeji@unilag.edu.ng okandeji et al: design analysis of microcontroler based automatic power management in photovoltaic systems. azojete,16(4):793-802. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 798 figure 5: circuit diagram http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):793-802. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 799 2.4 hardware unit construction the hardware unit for the prototype design was cased in a 9 x 9 x 3 parterres box. holes were drilled for the mounting of the connecting terminals and the circuit using bolts and nuts. figure 6 shows the picture of the packaged prototype. . figure 6: the picture of the prototype design 3.0 testing of the voltage sensors 3.1 testing and performance evaluation this section focuses on the testing and performance evaluation of the prototype design. in particular, to ensure proper functionality of the unit, the various sections of the system are tested. 3.2 testing of the voltage sensors the battery voltage is monitored by the voltage level sensor. a variable dc bench power supply was used to simulate battery voltage. four levels were used in this design namely: 11.5v (for less critical), 11.0v, 10.5v and 10.0v (for most critical load). as the supply varies between the nominal voltage level and the minimum state of discharge, the outputs of the sensors were monitored and the result obtained is shown in table 1. table 1: the outputs of the sensors and the result obtained input voltage sensor 1 sensor 2 sensor 3 sensor 4 vbat>12v high high high high vbat<11.5 low high high high vbat<11.0 low low high high vbat<10.5 low low low high vbat<10.0 low low low low as shown in table 1, as the input battery voltage is greater than 12v, all four sensors remain active (high). as the input battery voltage becomes less than 11.5v, all sensors remain active except sensor 1 (low). furthermore, as the input battery voltage goes below 11.0, two sensors remains active while the other two remains inactive. a further decrease in the input battery voltage triggers high and low sensor response to ensure efficient conservation of battery power. however, for an input battery voltage below 10v, all four sensors remain inactive (low). the outputs of these sensors are connected to a microcontroller which is programmed to isolate the loads in the order of priority. 3.2 testing of the microcontroller as stated earlier, the objective of using a microcontroller is to coordinate the processes between the voltage sensors and the output interface. when the sensors sense the voltage level, a signal is sent to the input pin of the microcontroller, and the microcontroller, acting on file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:aokandeji@unilag.edu.ng okandeji et al: design analysis of microcontroler based automatic power management in photovoltaic systems. azojete,16(4):793-802. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 800 the programmed instruction, activate the appropriate output. the output of the sensors, when fed into the data input of the microcontroller, an inversion of the input logic, as shown in table 2, is obtained. table 2: the outputs of the micro controller and the result obtained input voltage output 1 output 2 output 3 output 4 vbat>12v low low low low vbat<11.5 high low low low vbat<11.0 high high low low vbat<10.5 high high high low vbat<10.0 high high high high 3.3 testing of the relay interface the relay interface was connected to the output of the microcontroller through a transistor. the base transistor receives the signal (voltage) and turns on the collector current which activates the relay coil to disconnect the load and at the same time turn on the led indicator. 3.4 testing of the complete prototype design the complete prototype design was tested using the variable work bench power supply and the outputs monitored. at 12.5v, the four outputs were active as shown in the figure 7. at 11.1v three outputs were active as shown in figure 8. figure 9 shows that the two outputs were active when the input voltage is 10.8v. also, figure 10 shows that only one output was active when the input voltage is 10.5v. finally, as shown in figure 11, all outputs were inactive when the input voltage is below 10.0v. figure 7: at 12.5v, the four outputs were active figure 8: at 11.1v three outputs were active http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):793-802. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 801 figure 9: two outputs were active when the input voltage is 10.8v. figure 10: one output was active when the input voltage is 10.5v figure 11: all outputs were inactive when the input voltage is below 10.0v 4.0 conclusions this work considered the development of an energy management method for a photovoltaic system to control the rate of discharge in order to prevent sudden system shut down without any form of discrimination on the load. the load on the solar system is first categorized in the order of importance as more critical and less critical. the state of discharge of the storage battery is monitored by the voltage level sensor. four voltage level were used in this design namely: 11.5v (for less critical), 11.0v, 10.5v and 10.0v (for most critical load). the outputs of the sensors are connected to a microcontroller which is programmed to isolate the loads in the order of priority. the output of the microcontroller was interfaced to the ac load using electromechanical relays. monitoring indicators is also included to enable visual insights into the connected loads. a digital voltmeter was also incorporated to indicate the battery voltage. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:aokandeji@unilag.edu.ng okandeji et al: design analysis of microcontroler based automatic power management in photovoltaic systems. azojete,16(4):793-802. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 802 tests result showed that at different voltage levels, specific load was disconnected from the desired voltage level, thus, stored energy was efficiently conserved. references gujba, h., mulugetta, y. and azapagic, a. 2015. the household cooking sector in nigeria: environmental and economic sustainability assessment. resources journal, article 4: 412-433. kadafa, aa. 2012. oil exploration and spillage in the niger delta of nigeria. civil and environmental research, 2(3): 38-51. maijama’a, d., maijama’a, l., and umar, m. 2015. renewable sources of energy for economic development in nigeria. international journal of sustainable energy and environmental research, 4(2): 49-63. nasir, mnm., farith, mm., jali, mh., jamri, ms., jaafar, hi., and sulaima, mf. 2014. development of automatic load-shedding strategy for stand-alone photovoltaic system. international journal of applied engineering research, 9(20): 6895-6906. osueke, co., uguru-okorie, dc., and abanihi, vk. 2013. electricity stability in nigeria through increased hydro power generation. international journal of emerging technology and advanced engineering, 3(1): 9-13. theraja, bl., and theraja, ak. 2008. a textbook of electrical technology. s. chand and company limited, new delhi, india http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):561-568 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 561 original research article green roofs: an alternative for the reduction of surface runoff in the city of recife, pe marco aurélio calixto ribeiro de holanda1*, willames de albuquerque soares2, alexandre da câmara lima araújo de souza3, and diogo botelho corrêa de oliveira1 1department of nuclear energy – den, federal university of pernambuco ufpe, luiz freire avenue, 1000, recife, pernambuco 2department of civil engineering and materials physics, polytechnic school of pernambuco – poli, university of pernambuco upe, benfica street, 455, recife, pernambuco, brazil. 3department of civil engineering, polytechnic school of pernambuco – poli, university of pernambuco upe, benfica street, 455, recife, pernambuco brazil *corresponding author’s email address: marco.calixto@ufpe.br 1.0 introduction world population growth continues to drive the urban demographic explosion, leading to the disorderly occupation and use of space that consequently brings serious disturbances to quality of life and environmental balance. for instance the effect of heat islands (the increase in temperature of large urban centers), decrease in air quality, and increase in noise pollution due to the increasing number of motor vehicles in circulation and the occurrence of flooding due to the increased impermeability of the soil surface, mainly due to the construction of highways and buildings (danni-oliveira, 2000). article information abstract constant flooding during periods of intense rain, aggravated by the impermeabilization of the soil, is a recurrent problem in many brazilian cities, such as recife, located in the state of pernambuco. an efficient alternative that can mitigate this problem is the use of compensatory techniques such as green roofs. adding a plant layer on the roof of buildings can serve to reduce atmospheric pollution, contribute to an improvement in thermal sensation, and absorb rainwater, reducing the intensity of flooding. therefore, the objective was to evaluate the reduction in the volume of water drained from the surface in cities, through the implementation of green roofs. to carry out this evaluation, a green roof and a pluviometer prototype were installed to collect data on the volume of water precipitated, drained, and absorbed by the prototypes. the results show that the volume of water drained by the green roofs can vary significantly, from over 100% down to complete absorption of the precipitation, i.e., 0% of the water volume, as occurred on some days in may, which is the month that presented the lowest rainfall of the analyzed period. in addition, the analyses also show that as well as the prototypes, the real green roof significantly reduces the flow of water from precipitation. the mean reduction of the total volume in the study was 50%, however, at longer intervals without precipitation, this reduction reached 78%. these results show that the impact of the implementation of compensatory techniques such as green roofs significantly reduces runoff, especially in a city that is flooded. therefore, this study can serve as an incentive for public and private institutions to adopt the compensatory techniques of urban drainage for future or existing constructions, due to the aggregated social benefits, although they are not currently mandatory for all new constructions. the authors proposed the implementation of compensatory techniques, such as green roofs, in urban centers with high percentages of impermeable soil © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted: 18 sept., 2021 revised: 16 october, 2021 accepted: 22 october, 2021 keywords: compensatory techniques flooding prototypes rainwater urban drainage marco aurélio calixto ribeiro de holanda et al: green roofs: an alternative for the reduction of surface runoff in the city of recife, pe. azojete 17(4):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 562 as cities have grown and industrialization has progressed, today's urban areas have experienced intense transformations, especially in the infrastructure sector through paving and construction of houses and buildings. a direct consequence of this transformation is the impermeabilization of the soil, that is, rainwater ceases to infiltrate into the soil and begins to flow across the surface towards the drainage networks. the more areas that become impermeable, the greater the volume of water that must be drained, increasing the chances of flooding. locatelli et al. (2014) observed in a study that green roofs are being widely implemented in europe for the management of rainwater and to positively impacting the urban hydrological cycle, through their capacity for retention and evapotranspiration of precipitated water. in addition to this benefit, dimitrijević et al. (2016) pointed out that this technology also acts as a passive cooling technique for concrete structures and cities, as there it reduces absorption of the sun's rays by the structure and reduces reflection of these rays, minimizing the heat island effect in urban centers. another aspect, that of air pollution, was analyzed by yang et al. (2008), who quantified the removal of air pollution by the chicago green roofs, which reached 1675 kg of air pollutants over the course of a year in an area of 19 hectares. according to lee et al. (2013), the soil layer of the green roof allows for a temporary absorption of rainwater, slowing the flow of water compared to impermeable roofs of waterproofed buildings, able to retain 45% to 55% of the annual rainfall volume on green roofs of extensive type (with soil depth varying from 60 to 200 mm and weight varying from 60 to 150 kg m-²). the amount of retention, however, depends strongly on the intensity of the rainfall during each precipitation event. it is therefore necessary to evaluate the conditions of the site where the green roof is to be implanted, in order to define the optimal layer depth and type of soil to be used (korol and shushunova, 2017). however, results regarding the potential rainwater retention of the green roofs also vary according to the study region. for example, a study conducted in breslávia, poland by bursztaadamiak (2012) showed that the retention potential varies between 82.5% and 85.7% and, in cases of rainfall up to 1 mm per day, it is very close to 100%. another study, conducted in rio grande do sul by tassi et al. (2014), analyzed a long-term period equivalent to 17 months, the green roof reduced the surface drained volume by an average of 62%. in caruaru, in the semiarid region of pernambuco, santos et al. (2013) performed a simulated study of intense rainfall at levels of 42 mm h-1 and 79 mm h-1, obtaining retention rate results of 33.6% and 15.5%, respectively. as expected, an inversely proportional relationship was found between the precipitated volume and the volume retained by the green roof. thus, this study aims to evaluate the effects of extensive green roof implantation on the buildings along the pernambuco coastline from the point of view of the reduction of the volume of surface water drained. 2. materials and methods 2.1. the study area the city of recife is located in the northeastern region of brazil, which has two clear climatic periods, a dry one (august to february) and a rainy one. during the dry season, the city suffers from average temperatures of 27 °c and a daily photoperiod of up to 10 hours. being a coastal city and full of very tall buildings, the relative humidity of the air is always high, creating heat islands and raising the average values of thermal sensation. this city is an example of an urban center that suffers from frequent flooding problems, especially between the months of march and july, when rainfall reaches its highest volumes, over 200 mm per month. one of the alternatives adopted by the municipal government to alleviate these problems was the implementation of a law that obliges the implementation of green roofs in non-residential buildings having roof slabs larger than 400 m2 or multifamily arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 561-568. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 563 housing having more than four floors (recife, 2015). the intention of the city hall is that, in addition to mitigating atmospheric pollution, these roofs will contribute to improving the thermal sensation, in the dry months, and the absorption of rainwater, in the rainy months, reducing the intensity of flooding. to study the drainage of rainwater with green roofs, manually-prepared prototypes were placed at the top of block j of the polytechnic school of pernambuco, and compared to a building in the process of executing this technology, located about 700 meters away from the prototypes, figure 1a. these two study sites are located in portions of the madalena neighborhood in recife, which suffer from constant flooding, figure 1b. figure 1. a study area and b flooding of block j facilities. 2.2. prototypes the green roof prototype was elaborated based on the specifications for the real green roof executed and accompanied at the building site, following the same parameters for thickness of the real substrates. by stacking two identical containers and using the original lid as a basis for soil support, it was possible to practically measure the volume of water drained and deposited in the reservoir (lower vessel). the first step was to remove the bottom of the upper vessel, so that all the water drained through it would accumulate in the lower vessel, which served as a reservoir. the second step was to decrease the circumference of the lid and attach it 24.5 cm from the top edge of the reservoir. the third step was to drill holes in the center of this lid so that the water could flow into the lower reservoir. the lid was attached using pu30 sealant material. the fourth step was the placement of the green roof substrates, based on measurements for the real green roof, with 7 cm of expanded clay placed just above the lid. subsequently, a layer of geotextile blanket was placed above the expanded clay followed by a 6 cm layer of fertile soil. finally, a grass mat 4 cm thick was placed on top, cut to the circumference of the reservoir, with a diameter of 40 cm. marco aurélio calixto ribeiro de holanda et al: green roofs: an alternative for the reduction of surface runoff in the city of recife, pe. azojete 17(4):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 564 this fertile soil is composed of 12.84% clay, 85.16% sand and 2% silt and has a saturated hydraulic conductivity (ks) of approximately 0.04 m h-1, residual and saturated volumetric moisture (θr and θs) of approximately 0.06 and 0.37 m3 m-3, respectively, and an α of 2.62 m-1. in addition to the prototype green roof, a nearly identical structure was also constructed without any substrate, in order to measure the total volume of precipitation for the same timer periods. this was called the pluviometer prototype. the structure of the pluviometer prototype was built in a very similar pattern to that of the prototype green roof, through the stacking of two identical containers. the first three steps were exactly the same as those described for the prototype green roof, but the fourth step in this process was to attach a funnel through the pu30 sealant material just below the central holes, coupled to a hose to form a siphon, whose purpose was to minimize the effects of evaporation of the water accumulated in the lower reservoir. a schematic drawing was made to illustrate the processes, figure 2. figure 2. a schematic drawing of the prototype green roof and b the pluviometer prototype. unfortunately, as a public institution, the polytechnic school of pernambuco did not allow the installation of many prototypes without the authorization of the rectory of the university of pernambuco. however, as it is a time-consuming process, this request would cause the authors to lose the annual rainfall window that occurs in recife. 2.3. data collection the prototype green roof and the pluviometer prototype were placed on the roof slab of block j of the polytechnic school of pernambuco on march 23, 2018 and data was collected intermittently until july 25, 2018. this site was chosen for security and ease of access to the roof slab, plus the fact that the university is located less than 700 meters from the real green roof. this made it possible to more accurately estimate the positive impact caused by the green cover surrounding the worksite, with respect to surface runoff. the measurements of the volume of water drained by each element were taken daily from monday through saturday. on sundays and holidays, no measurements were taken because of university logistic reasons and, consequently, the values measured on subsequent days corresponded to the amount accumulated over the period. 3. results and discussion the volume of water collected by the prototype green roof and the pluviometer prototype between march 23 and april 30, 2018, with april 2, 9, and 23, 2018, being the dates having the highest rainfall amounts of 39.44 mm, 33.25 mm, and 34 mm, respectively, figure 3. an important observation was noted on april 12, 14, and 24, in which the volume of water drained arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 561-568. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 565 by the prototype green roof was higher than that collected in the prototype rain pluviometer, due to the tendency of the green roofs to delay and prolong the flow of precipitated water (guimarães et al., 2020). in other words, even when precipitation has stopped, water will continue to follow the path of infiltration through the soil and leak potentially for hours afterwards. according to filho et al. (2016), green roofs alleviate the public drainage system because the peak precipitation flows are attenuated. figure 3. comparison of volume of water precipitated to volume drained between march, 23 and april, 30, 2018. the month of may (figure 4) was characterized by a period of less voluminous rains compared to those at the end of march and during the month of april (figure 3). although this study does not allow for a more detailed analysis of the influence of rain on extensive green roofs for intervals of less than 24 h, the lower volume of precipitation is expected to promote a more rapid recovery of rainwater absorption potential by the green roofs. however, on may 3, 4, 5, and 7, 2018, the opposite of this phenomenon occurs, that is, the higher the volume of water during the day, the lower the rate of absorption of the precipitated volume, being 29%, 59%, 71%, and 74%, respectively. this is in agreement with the results obtained by filho et al. (2016) who studied the hydrological efficiency of green roofs in reducing surface runoff. the volume of water drained by the green roof can vary significantly, from over 100% as previously mentioned, down to complete absorption of the precipitation, i.e., 0% of the water volume, as occurred on may 10 and 11 (figure 4). figure 4. comparison of volume of water precipitated to volume drained between may 2-23, 2018. 0 5 10 15 20 25 30 35 40 2 3 -m ar 2 4 -m ar 2 6 -m ar 2 7 -m ar 2 8 -m ar 2 -a p r 3 -a p r 4 -a p r 5 -a p r 6 -a p r 7 -a p r 9 -a p r 1 0 -a p r 1 1 -a p r 1 2 -a p r 1 3 -a p r 1 4 -a p r 1 6 -a p r 1 7 -a p r 1 8 -a p r 1 9 -a p r 2 0 -a p r 2 3 -a p r 2 4 -a p r 2 5 -a p r 2 6 -a p r 2 7 -a p r 2 8 -a p r 3 0 -a p r p re ci p it at io n ( m m ) date (day-month) green roof prototype pluviometer prototype 0 3 6 9 12 15 2 -m ay 3 -m ay 4 -m ay 5 -m ay 6 -m ay 7 -m ay 8 -m ay 9 -m ay 1 0 -m ay 1 1 -m ay 1 2 -m ay 1 3 -m ay 1 4 -m ay 1 5 -m ay 1 6 -m ay 1 7 -m ay 1 8 -m ay 1 9 -m ay 2 0 -m ay 2 1 -m ay 2 2 -m ay 2 3 -m ay p re ci p it at io n ( m m ) date (day-month) green roof prototype pluviometer prototype marco aurélio calixto ribeiro de holanda et al: green roofs: an alternative for the reduction of surface runoff in the city of recife, pe. azojete 17(4):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 566 during the months of june and july (figure 5), there are periods without rain that reach six days, such as the interval between june 9 and 13 and july 10 and 17, 2018. a noticeable effect of these drought periods was the significant reduction of water flow during later occurrences of precipitation, especially on june 14 and july 18, 2018, when 78% and 76% of the volume of precipitated water was absorbed by the green roof, respectively. these values corroborate with other previous studies that highlight this effect of the retention potential increases when the soil is extremely dry, with results being intermediate to those obtained by tassi et al. (2014) of 62% and burszta-adamiak (2012) of 85.7%. figure 5. comparison of volume of water precipitated to volume drained between june, 4 and july, 25, 2018. it isnoteworthy that on july 3, 2018, an accumulated volume of 18.39 mm of precipitation was recorded with a flow of only 9.55 mm in an interval of 12 days with no record of precipitation, which also reveals the power of absorption of this compensatory technique over longer periods of drought. according to the blueprints made available by the construction company, it was possible to verify that the real green roof is divided into three garage floor slabs, with a total area corresponding to 785.06 m2. for the percentage calculations, 100% of the volume collected by the pluviometer prototype was considered for each precipitation event, and then compared to that of the prototype green roof and with the real green roof. over the total 78 days of data collection, the pluviometer and green roof prototype had volumes of water drained of 361.48 and 264.62 mm, respectively. in this case, considering the total amount of water drained, the green roof provided a reduction of 26.79% in relation to the precipitated amount. therefore, it is clear that the real green roof significantly reduces the flow of water from precipitation, with a total average reduction of 50%, indicating that the flow from the green roof was, on average, only 50% of the total precipitation. in this case, the drained volume was only 180.74 mm, representing a difference of 83.88 mm between the values obtained with the prototype and with the real green roof. this difference may be directly linked to the lower exposure of the grass present in the real green roof to the sun, which means that the roots of the planted vegetation do not develop to the point of compromising the drainage layer, as well as with the prototype. this result is similar with the results reported by silva et al. (2020), who showed that green roofs can help to reduce flooding caused in urban centers, especially in a central neighborhood in the city of recife. therefore, green roofs or other techniques that help the urban drainage collection network are essential for the neighborhood of madalena, since approximately 87% of it is composed of waterproofed surfaces (holanda et al., 2019). 0 4 8 12 16 20 4 -j u n 5 -j u n 6 -j u n 7 -j u n 8 -j u n 9 -j u n 1 1 -j u n 1 2 -j u n 1 3 -j u n 1 4 -j u n 1 5 -j u n 1 6 -j u n 1 8 -j u n 1 9 -j u n 2 0 -j u n 2 1 -j u n 3 -j u l 4 -j u l 5 -j u l 7 -j u l 9 -j u l 1 0 -j u l 1 1 -j u l 1 2 -j u l 1 3 -j u l 1 4 -j u l 1 7 -j u l 1 8 -j u l 2 3 -j u l 2 5 -j u l p re ci p it at io n ( m m ) date (day-month) green roof prototype pluviometer prototype arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4) 561-568. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 567 however, some important caveats should be noted regarding the average calculation, as it is possible to verify that during the maximum precipitation events, in this observed period, the volume absorbed by the green roof tended to be smaller. for example, except for april 11, 2018, all other data having rainfall greater than 15 mm, had measured yields greater than 85%. this phenomenon occurs because, when rains are more intense, the green roof soil tends to saturate more quickly, causing the surplus to drain. when the volume of rainfall exceeds the saturation volume of the soil, the amount absorbed becomes less and less expressive. however, during moderate rains preceded by a period of dry days, the absorption capacity tends to increase, reaching up to 100% of the precipitation. there are two possible explanations for the relatively low retention results found in this study compared to the articles cited above, where the reduction exceeded 50%. the first reason is the consecutive sequence of rains witnessed during the studied period, because as previously stated, the longer the period of drought preceding a rainfall event, the higher the rate of absorption of precipitated water. the second reason is the volume of rainfall, because, according to studies by carter and rasmussen (2006), the potential for water retention decreases significantly as precipitation volume increases, and according to silva et al. (2020), a day with moderate rainfall in recife is characterized as a day when rainfall is greater than or equal to 15 mm. 4. conclusion and recommendations despite the limitations associated with measurements made over a short period, this study identify the positive impact of green roofs on the local reality in recife. just in the surroundings of the building studied in the madalena neighborhood, there was a 50% reduction in runoff, resulting in an approximate reduction of 180 m3 of water in the local drainage networks during the studied period. however, for periods of drought in which the soil has the lowest moisture content, the reduction in water runoff reaches 78%. in this case, the constant absorption of water by the roots of the plant layer and the low amount of material used in the soil layer used in the structuring of green roofs allow that in a few days that the soil is able to reduce the runoff values, exceeding the average 50%. thus, these data could serve as a parameter for other large urban centers and that the dissemination of the use of compensatory techniques, such as green roofs, can significantly reduce the large volumes of water carried by the networks of urban drainage collectors duringrainy days which would help to alleviate the socio-economic liabilities caused by constant flooding. 5. references burszta-adamiak, e. 2012. analysis of the retention capacity of green roofs. journal of water and land development, 16(1): 3-9. doi: 10.2478/v10025-012-0018-8 carter, tl. and rasmussen, tc. 2006. hydrologic behavior of vegetated roofs. journal of the american water resources association, 42(5): 1261-1274. danni-oliveira, i.m. 2000. considerações sobre a poluição do ar em curitiba-pr face a seus aspectos de urbanização. revista raega: o espaço geográfico em análise, 4: 101-110. doi: 10.5380/raega.v4i0.3342 dimitrijevic , dg., živkovic , , tojiljkovic , mm., todorovic , mn., spasic -djordjevic , sž 2016 green living roof implementation and influences of the soil layer on its properties. thermal science, 20(5): s1511-s1520. doi: 10.2298/tsci16s5511d marco aurélio calixto ribeiro de holanda et al: green roofs: an alternative for the reduction of surface runoff in the city of recife, pe. azojete 17(4):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: marco.calixto@ufpe.br 568 filho, jea., manna, ibcb., melo, na., caixeta, acm. 2016. eficiência hidrológica de telhados verdes para a escala de loteamentos residenciais. sociedade & natureza, 28(2): 257-272. doi: 10.1590/1982-451320160206 guimarães, mm., silva, mp., florentino, wg., dias, rs., junior, fcfo., pereira, ia. 2020. uso de telhados verdes na mitigação de cheias de uma bacia hidrográfica urbana com alta frequência de inundações. brazilian jornal of development, 6(12): 98235-98254. doi:10.34117/bjdv6n12351 holanda, macr. and soares, wa. 2019. analysis of the effect of impermeability of urban soils on the infiltration of rainwater in the city of recife, pe. revista ambiente & água, 14(4): 1-10. doi: 10.4136/ambi-agua.2386 korol, e. and shushunova, n. 2017. green roofs: standardization and quality control of processes in green construction. journal of hydrology, 106: 3001-3017. doi: 10.1051/matecconf/201710606014 lee, j., moon, h., kim, t., han, h. 2013. quantitative analysis on the urban flood mitigation effect by the extensive green roof system. environmental pollution, 181: 257-261. doi: 10.1016/j.envpol.2013.06.039 locatelli, l., mark, o., mikkelsen, ps., arnbjerg-nielsen, k., jensen, mb., binning, pj. 2014. modelling of green roof hydrological performance for urban drainage applications. journal of hydrology, 519: 3237-3248. doi: 10.1016/j.jhydrol.2014.10.030 issn 0022-1694 recife. lei nº 18.112/2015. dispõe sobre a melhoria da qualidade ambiental das edificações por meio da obrigatoriedade de instalação do "telhado verde", e construção de reservatórios de acúmulo ou de retardo do escoamento das águas pluviais para a rede de drenagem e dá outras providências. diário oficial, recife, 12 jan. 2015. pp. 12. santos, pts., santos, sm., montenegro, smgl., coutinho, ap., moura, gss., antonino, acd. 2013. telhado verde: desempenho do sistema construtivo na redução do escoamento superficial. ambiente construído, 13(1): 161-174. doi: 10.1590/s1678-86212013000100011 silva, tb., holanda, macr., soares, wa. 2020. telhados verdes. caracterização das condições ótimas para o microclima da cidade de recife-pe. in xv simpósio de recursos hídricos do nordeste, nov., 22-26, caruaru. proceedings... caruaru: abrhidro, 2020. pp. 1-10. tassi, r., tassinari, lcs., piccilli, dga., persch, cg. 2014. telhado verde: uma alternativa sustentável para a gestão das águas pluviais. ambiente construído, 14(1): 139-154. doi: 10.1590/s1678-86212014000100012 yang, j., yu, q., gong, p. 2008. quantifying air pollution removal by green roofs in chicago. atmospheric environment, 42: 7266–7273. doi:10.1016/j.atmosenv.2008.07.003 arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):143-158 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 143 original research article evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria a. i. agbonaye*. and o. c. izinyon department of civil engineering, university of benin, benin city. nigeria *corresponding author’s email address: augustine.agbonaye@uniben.edu 1.0 introduction the design and construction of certain projects such as dams and urban drainage systems, management of water resources, and prevention of flood damage require adequate knowledge of extreme events of high return periods as worst conditions are normally considered in designs (tao et al., 2002; olofintoye et al., 2009). in most cases, the return periods of interest sometimes exceed the period of available records and as such cannot be extracted directly from the recorded data. it is necessary to extrapolate design parameters from the data and this cannot be achieved by other methods. that is why in current engineering practice, the estimation of extreme rainfall depths used for design is accomplished based on statistical frequency analysis of maximum precipitation records. rainfall frequency analysis is the estimation of how often rainfall of a specified magnitude will occur. such analyses help define policies relating to water resources management. it serves as the source of data for flood hazard mitigation and the design of hydraulic structures aimed at reducing losses due to flood action. the choice of an appropriate probability distribution and parameter estimation method plays a vital role in rainfall frequency analysis. further stimulation for this study resulted from a recent presentation by nimet of evidence of climate variation especially on the trend of maximum rainfall in 2012 (okoloye et al., 2013). as the climate is changing, the necessity to accurately estimate extreme events such as the maximum article information abstract suitable and adequate hydrological design data especially for flood design, are not readily available. when data is available, it is often outdated and irrelevant to current events especially in this era of global warming and climate change. this study presents rainfall frequency analysis for some cities in southern nigeria using the annual maximum series of daily rainfall data for the stations. the objective of the study was to select the probability distribution model from among six commonly used probability distribution models namely: generalized extreme value distribution (gev), extreme value type i distribution (evi), generalized pareto distribution (gpa), pearson type iii (piii), log normal (ln) and log pearson type iii (lp111) distributions. these distributions were applied to the annual maximum series of daily rainfall at each station using the parameters of the distributions estimated by the method of moments. the best fit probability distribution model at each location was selected based on the results of seven goodness of fit tests values with a scoring and ranking scheme. our results indicate that the best-fit distribution models at the study locations are piii for ibadan and benin city; gev for onitsha, enugu, owerri, calabar, and port harcourt; evi and ln for uyo; evi for akure and lp111 for ikeja. this implies that gev performed better by occupying 50% of the studied area, followed by evi and piii which performed by occupying 20% each. these best fit probability distribution models are recommended for use for necessary design at each location for flood hazard mitigation. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 sept., 2021 revised 19 october, 2021 accepted 24 october, 2021 keywords: bestfit maximum-rainfall probability-distribution goodness-of–fit return-level http://www.azojete.com.ng/ mailto:augustine.agbonaye@ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 144 rainfall frequency has become urgent as it will contribute to the design of safer and more efficient hydraulic structures. thus, the application of probability distributions to rainfall data have been investigated by several researchers from different regions of the world. the best fitted probability distribution for monthly rainfall data was obtained by ghosh et al. (2016) for three bangladeshi stations from 1979 to 2013. they revealed that the best suited distribution model of monthly rainfall data was the generalized extreme value. mohamed and ibrahim (2016) analyzed annual rainfall data for fourteen rainfall stations in sudan from 1971 to 2010. normal and gamma distribution models were chosen by them as the best match probability distribution models. for 35 locations in bangladesh, alam et al. (2018) determined the best-fit probability distributions for maximum monthly rainfall using 1984–2013 data. after applying different statistical analysis and distribution types, they discovered the best-fitting probability distributions to be generalized extreme value, pearson type 3, and log-pearson type 3. also, they calculated 10-year, 25-year, 50-year and 100-year return periods of maximum monthly rainfall for all locations studied. kumar (2000) and singh et al. (2012) found that the log normal type 2 distribution is the best-fit probability distribution for annual maximum daily rainfall in india, amin et al. (2016) used annual maximum rainfall based on a daily rainfall and found that the log-pearson type 3 distribution was the best-fit distribution in the northern regions of pakistan. kousar et al. (2020) determined the best-fitted probability distributions for at-site flood frequency analysis of the ume river in sweden. the generalised extreme value distribution with the l-moments estimation provided the best fit to maximum annual streamflow at gauging sites solberg and stornor-krv. also, the bestfitted distribution for each gauging site was used to predict the maximum flow of water for return periods of 5, 10, 25, 50, 100, 200, 500, and 1000 years. mamman et al. (2017) evaluated the bestfit probability distribution models for the prediction of inflows of kainji reservoir, niger state, nigeria and selected the gumbel (evi) model as the best fitted distribution model. masereka et al. (2015) identified the best fit probability distribution models for frequency analysis of extreme mean annual rainfall events in south africa to be log pearson 3, generalised logistic and extreme generalised value. langat et al. (2019) identified the most suitable probability distribution models for maximum, minimum, and mean streamflow for tana river in kenya. the log-normal and gev distribution functions were the best-fit functions for the annual mean flows of the tana river. however, probability distribution models utilized for the analysis of hydrological data are numerous but the six commonly used models by researchers in nigeria are: generalized extreme value distribution (gev), extreme value type i distribution (evi), generalized pareto distribution (gpa), pearson type iii (piii), log normal (ln) and log pearson type iii (lp111). interestingly, no particular model is considered superior for all practical purposes. wmo (2008) recommended that available models are screened based on the problem to be solved and the nature of available data. data for frequency analysis should be independent and identically distributed. hence, it is necessary to screen candidate distributions for best fit to available data at a location (agbonaye and izinyon, 2017). therefore, this study is needed to screen and select the bestfit probability distribution models for prediction of rainfall in southern nigeria. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 145 2.0 materials and method 2.1: data and analysis this study entails frequency analysis of the annual maximum series of daily rainfall depths of selected cities in southern nigeria. the cities selected are: ikeja, akure, ibadan, benin city, port harcourt, uyo, calabar, onitsha, enugu, owerri. the map of nigeria showing ten selected cities is presented in figure.1. figure.1 map of the study area. source: adapted from office of the surveyor general of the federation (osgof, 2011) the daily rainfall data for the selected cities were obtained from the nigerian meteorological agency (nimet) oshodi, lagos for the period between 1965 and 2014 (50 years). the annual maximum series is the series formed from the selection of the highest rainfall value for each of the years under consideration for the stations. the annual series data for each station was tested for homogeneity using rainbow software and checked for outliers using hec-ssp software. six probability distribution models namely: gumbel extreme value type 1 (evi), generalized extreme value (gev), generalized pareto (gpa), log-normal, and pearson type iii and log pearson type iii were fitted to the annual maximum series data at each location. the quantile function and parameters of probability distribution models are shown in table 1. the best fit model at a location was selected based on results of the goodness of fit tests with the application of a scoring and ranking scheme. subsequently, the best fit model at a location was used to forecast rainfall return levels for return periods of engineering design significance (5 to 500 years). http://www.azojete.com.ng/ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 146 table 1: quantile function and parameters of probability distribution (vivekananda, koutsoyiannis 2014) s. no. distribution quantile function (rt) parameter by mom 1 ev1 rt = ξ – α ln(-ln f) ξ = �̅� 0.5772157α α=(√6/ 𝜋) sr 2 gev rt = ξ + α 𝑘 (-ln f)-k -1 where f = 1 − 1 𝑇 k = 1 3 − 1 0.31+0.91csx+√(0.91csx)2+1.8 α = c1sx c1 = |𝑘| √г(1−2𝑘)− г2(1−𝑘) c3 = (г(1−𝑘)−1) 𝑘 ξ = rm – c3 3 gpa rt =ξ + α(1-(1 –f)k)/k �̅� = ξ + α/(1+k); sr = α2/(1+2k)(1+k)2 cs = 2(1-k)(1+2k)2/(1+3k) 4 ln-nor rt =eα+z f k k=√[ln (1 + {𝑆𝑥/𝑅𝑚}2,α=-k 2/2 5 p111 rt = 𝜉 +zf α where zf is obtained from a table k=4/csx 2, α= sr//√𝑘, ξ=rm-kα where csx is the coefficient of skewness of obtained data, sr is the standard deviation 6 ln-p111 rt=eα+z f *k k=4/csy 2 , α=sy/√𝑘, ξ=r lm-kα f(r) (or f) is the cumulative distribution function (cdf) of r; p is the probability of exceedance ξ, α and k are the location scale and shape parameters respectively;       orcandsorror sr, are the average, standard deviation and coefficient of skewness of the recorded rainfall data; sign (k) is plus or minus 1 depending on the sign of k; rt is the estimated rainfall by the probability distribution for a return period). 2. 2 goodness of fit test criteria the goodness of fit test used to check the adequacy of fit of probability distribution models to the series of recorded rainfall data for the stations are root mean square error (rmse), relative root mean square error (rrmse), mean absolute deviation index (madi), maximum absolute error (mae), probability plot correlation coefficient (ppcc), chi-square (x2 ) test. it is to be noted that in evaluating the performance of a probability distribution model at a location, the lower the value of the goodness-of-fit test results the better the distribution except for the ppcc criterion in which the nearer the value is to 1 numerically the better the distribution. 2.2.1 root mean square error (rmse) the root means square was used to measure the difference between values predicted by a model and the observed values. these individual differences are called residuals. the rmse of a model prediction concerning the estimated variable x model was obtained using the formula (tao et al., 2002) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 147     )1( 2 1 2             mn rr rmse fo where , 1,....,ir i n are observed values while fr are the corresponding values computed from the assumed probability distribution and m is the number of parameters estimated for the distribution. the smaller the value of rmse obtained for distribution, the more fitted it is to the observed data (sabri and arif, 2009; ahmad et al., 2011). hence, a smaller value of rmse for candidate distributions indicates that it is more fitted to the observed data. 2.2.2 relative root mean square error (rrmse) relative root means the square error was computed by dividing the root mean square error by the mean observed data. the relative root means square error provides a good picture of the overall fit of a distribution. it computes each error in proportion to the size of observation thereby reducing the effect of outliers that are commonly found in hydrological data. rrmse was computed using the formula (tao et al., 2002)     1 2 2 2. oi fi oi r r r rrmse n m                     where , 1,...,oir i n is observed values while fr are the corresponding values computed from the assumed probability distribution and m is the number of parameters estimated for the distribution. . the smaller the value of rrmse obtained for distribution, the more fitted it is to the observed data (sabri and arif, 2009; ahmad et al., 2011). hence, a smaller value of rrmse for candidate distributions indicates that it is more fitted to the observed data. 2.2.3 mean absolute deviation index (madi) the mean absolute deviation index is the average distance between each data value and the mean. it was computed using the formula (sabri and arif, 2009; ahmad et al., 2011): )3( 1 1    n i o fo r rr n madi where r0 is the observed value, rf the value forecasted by the distribution, and n the number of data points. the smaller the value of madi obtained for distribution, the more fitted it is to the observed data (sabri and arif, 2009; ahmad et al., 2011). hence, a smaller value of madi for candidate distributions indicates that it is more fitted to the observed data. http://www.azojete.com.ng/ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 148 2.2.4 maximum absolute error (mae) the maximum absolute error gives the largest absolute difference between the observed (filliben, 1975) and values predicted by the distributions. mae was computed using the relationship given by the formula).   )4(max fo rrmae  where ro are the observed values, rf are the values predicted by the probability distribution model. . the smaller the value of mae obtained for distribution, the more fitted it is to the observed data. (filliben, 1975). hence, a smaller value of mae for candidate distributions indicates that it is more fitted to the observed data. 2.2.5 probability plot correlation coefficient (ppcc) ppcc is a measure of the correlation between the ordered observations and corresponding fitted values determined by a plotting position equation. ppcc was computed using the relation (filliben, 1975).          5 2 1 22 0 0             fmifmi fmifmi rrrr rrrr ppcc where rm, rmf represent the mean values of the observed and forecasted values respectively. a value of ppcc close to 1 suggests that the observed data could have been drawn from the fitted distributed at a location. 2.2.6 chi-square test the chi-square test is a statistical test commonly used to compare observed data with the data we would expect to obtain according to a specific hypothesis. it is computed using the formula (vivekananandan, 2014).    6 1 * 2* 2     n i i r rr x where *,,, rniri are the year recorded data, year, total year, and the expected rain, respectively. the smaller the value of chi-square test value obtained for distribution, the more fitted it is to the observed data. the following steps were taken to determine the size of our chi-square values.: (a) calculating the number of "degrees of freedom" (d.f.). (b) choosing a level of likelihood (p=0.05) for p≤ 0.05; (c) obtaining a list of "critical chi-square values “from tables. (d) the critical chi-square values for this test were determined. (at the intersection of the appropriate d.f. row and probability column), and compared to the obtained value. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 149 if  2 = 0, it indicates that prediction with the model is exact match with the observed rainfall. if  2 > 0, they do not agree exactly. the following is the stated hypothesis: null hypotheses (h0) probability distribution model fits the data alternative hypotheses (ha): probability distribution model do not fit the data accept ho): if  2 test statistics is less than  2 critical values at 5% significance level or reject ho): if  2 test statistics is greater than  2 critical values at 5% significance level (p>.05) 2.2.7 diagnostic test (d-index) d – index for distribution was computed using the relationship given by vivekananandan (2014):   6 1 1 * 7i i i d index r r r           where r is the average (or mean) of recorded annual maximum density (amd) )61( iri are the first six highest sample values in the series and *ir is estimated value by probability distribution function (pdf). the distribution having the least d – index is identified as better suited, in comparison with the other distribution for estimation of maximum rainfall values (vivekananda, 2014). 2.2.8 scoring and ranking scheme based on the results of the goodness of fit tests, a scoring scheme in which the best performing distribution concerning a test criterion was assigned a score of six (6), the next test was assigned five, and the worst test assigned one. the distribution with the highest total score at a location based on the goodness of fit criteria was adjudged the best distribution model at the station and was selected as the best distribution at the station. 2.2 9 model validation the best-fit probability models were validated using chisquare goodness of fit statistic explained in section 2.2.6. 2.2.10 forecasting of rainfall return levels at the station the rainfall return levels at a station were computed by substituting the appropriate return period into the appropriate quantile function in table 1 for the applicable best distribution http://www.azojete.com.ng/ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 150 3. results and discussion the summary of statistics means, standard deviation, skewness and kurtosis of the annual maximum rainfall series are presented in table 2. table 2: summary of descriptive statistics of annual maximum rainfall (amr) serial number station location mean standard deviation skewness kurtosis 1 ikeja 107.67 44.56 1.26 1.38 2 akure 86.03 24.40 1.35 1.36 3 ibadan 69.71 27.35 -1.16 1.72 4 benin city 103.53 48.79 -0.25 0.78 5 port-harcourt 99.14 42.87 -0.64 0.82 6 uyo 98.54 25.66 0.64 0.03 7 calabar 111.73 49.47 -0.58 0.72 8 onitsha 97.77 38.28 -0.70 1.21 9 enugu 85.35 39.02 -0.33 0.70 10 owerri 111.02 36.48 0.16 0.18 applying these values in table 2, to the equations for parameter estimation by mom in table1, the values for ξ, α and k (location scale and shape parameters) respectively were obtained. these were fitted into the quantile functions in table 1 to have the quantile rainfall values. 3.1 goodness of fit test the result of the goodness of fit test for the distributions at the stations are shown in tables 3. the values in table 3 were obtained from excel sheets of analysis of observed rainfall (ro). the corresponding computed quantile rainfall values q(f) were for f= 0.999, 0.99, 0.9 and 0.5, 0.02, 0.01, 0.002, for each of the assumed probability distributions. the computation was done using equation 1 to 7. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 151 table 3: goodness-of-fit test for the distributions at the locations station gof test criteria gof test values ev1 gev gpa ln p111 lp111 ikeja rmse 7.44 12.34 14.23 7.71 5.28 4.70 rrmse 0.075 0.139 0.76 0.05 0.032 0.031 madi 0.0076 0.0696 0.540 0.028 0.012 0.009 mae 25.76 35.78 98.62 31 22.5 21.02 ppcc 0.9865 0.9890 0,7100 0.990 0.9965 0.9959 chisq 23.03 66.84 1075 18.10 7.90 6.80 d-index 0.595 0.908 2.61 0.82 0.55 0.404 enugu rmse 13.49 10.19 33.96 21.48 11.8 14.76 rrmse 2.67 1.46 7.16 2.41 1.57 1.81 madi 0.78 0.357 2.23 0.75 0.38 0.55 mae 35.9 18.5 76.6 74.1 28.43 47.62 ppcc 0.9687 0.9661 0.9893 0.9393 0.9552 0.9945 chisq 12.36 37.68 619.8 757 70.95 155.6 d-index 0.7986 0.827 3.41 2.855 1.074 1.598 benin city rmse 15.97 12.1 42.9 19.89 8.79 16.27 rrmse 3.43 2.004 9.38 5.69 2.06 4.7 madi 1.028 0.50 3.85 1.8 0.59 1.48 mae 43.99 39.08 3.85 60.26 35 46.8 ppcc 0.35 0.969 0.945 0.076 0.99 0.96 chisq 187.1 71.8 80.18 479.2 64.1 326.7 d-index 0.806 0.45 3.6 0.411 0.4837 0.426 3.2 assessment of probability distribution models by scoring goodnessoffit tests the assessment of the probability distribution models was based on the total score obtained from all the tests. the test scores ranging from one to six are awarded to each distribution model based on the criteria that the distribution model with the highest score is chosen as the best distribution model for the data of a particular city. the distribution best supported by a test is awarded a score of six (6), the next best is awarded a score of five (5) and so on in descending order. using the scoring scheme outlined, tables 4 was computed. the overall ranking results are presented in table 4. http://www.azojete.com.ng/ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 152 table 4: scoring and ranking scheme for distribution at the locations station test criteria distribution score ev1 gev gpa ln p111 lp111 ikeja rmse 4 2 1 3 5 6 rrmse 3 2 1 4 5 6 madi 6 2 1 3 4 5 mae 4 2 1 3 5 6 ppcc 2 3 1 4 6 5 chi-square 4 2 1 4 5 6 d-index 4 2 1 3 5 6 total score 26 15 7 24 35 40 rank 3rd 5th 6th 4th 2nd 1st enugu rmse 4 6 1 2 5 3 rrmse 2 6 1 3 5 4 madi 2 6 1 3 5 4 mae 4 6 1 2 5 3 ppcc 4 3 5 1 2 6 chisquqre 1 6 2 3 5 4 d-index 6 5 1 2 4 3 total score 23 39 12 16 31 27 rank 4th 1st 6th 5th 2nd 3rd benin city rmse 4 5 1 2 6 3 rrmse 4 6 1 2 5 3 madi 4 6 1 2 5 3 mae 3 4 6 1 5 2 ppcc 2 5 3 1 6 4 chisquqre 3 5 4 2 6 1 d-index 2 4 1 6 3 5 total score 22 35 17 16 36 21 rank 3rd 2nd 5th 6th 1st 4th a detail study of table 4 indicates that gpa performed poorly in the study area, taking the 6th position in ikeja and benin city while it took 5th in enugu. this implied that gpa distribution model is not useful in the study area. ranking the total scores, a summary of the performance of the six probability models was obtained as shown in table 5. it shows in detail the best-fit-model and the second-best fit model for each location file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 153 table 5: goodness of fit test and the selected model for the peak rainfall s/n location best fit model total max score second bestfit model total max score 1 ikeja log-pearson iii 40 pearson iii 35 2 akure gumbel extreme value i 42 pearson iii 31 3 ibadan pearson iii 39 generalized extreme value 33 4 benin city pearson iii 36 generalized extreme value 35 5 port harcourt generalized extreme value 39 log-normal 31 6 uyo extreme value 36 log-normal 36 7 calabar generalized extreme value 38 pearson iii 36 8 onitsha generalized extreme value 40 pearson iii 29 9 enugu generalized extreme value 39 pearson iii 31 10 owerri generalized extreme value 39 log-pearson iii 29 table 5 shows that generalized extreme value is the best-fit probability distribution model in five locations namely: port harcourt, uyo, calabar, onitsha, enugu and owerri. this result is in harmony with that of ghosh et al., (2016) and alam et al., (2018) who found generalized extreme value distribution to be the most appropriate distribution of the monthly rainfall data for the three selected station in bangladesh. however, olufintoye et al., (2009) in similar research in the above locations recommended p111 and lp111 as gev considered best fit in this study was not utilized by them. gumbel extreme value i is the best-fit probability distribution model in two locations namely: akure and uyo. pearson iii is the best-fit probability distribution model in two other locations namely: ibadan and benin city. log-pearson iii is the best-fit probability distribution model for ikeja. the model validation using chi square goodness of is presented in table 6. http://www.azojete.com.ng/ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 154 table 6. model validation result with chisquare goodness of fit statistic location best-fit distribution test performed calculated values for χ2 test degree of freedom critical values at 5% significance level decision ikeja log-pearson iii chisquare 6.80 49 66.326 accept ho akure gumbel extreme value i chisquare 9.68 49 66.326 accept ho ibadan pearson iii chisquare 56.14 49 66.326 accept ho benin city pearson iii chisquare 64.1 49 66.326 accept ho port harcourt generalized extreme value chisquare 10.39 49 66.326 accept ho uyo extreme value chisquare 3.35 49 66.326 accept ho calabar generalized extreme value chisquare 14.8 49 66.326 accept ho onitsha generalized extreme value chisquare 7.94 49 66.326 accept ho enugu generalized extreme value chisquare 37.68 49 66.326 accept ho owerri generalized extreme value chisquare 12.4 49 66.326 accept ho the χ2 test statistics in table 6 were calculated using equation 6. the critical values of χ2 at 5% significance level were interpolated in chisquare table in standard textbooks. the implication of the decision column of the table is that we have to accept the null hypotheses (ho): that the probability distribution model fits the data. this has validated our models outlined in the table and therefore they can be reliably used for future rainfall prediction as was carried out in table 7. table 7: forecasted rainfall (mm) for varying return periods at each location. s/no location best fit distribution return period (years) 5 10 25 50 100 200 500 1 ikeja lpiii 132.03 158.11 216.3 222.09 252.21 284.31 330.16 2 akure evi 103.58 117.85 134.39 149.27 162.54 175.78 193.23 3 ibadan piii 92.85 98.25 104.03 107.90 109.9 111.41 112.85 4 benin city piii 142.2 164.41 183.60 197.38 208.4 218.2 229.72 5 port harcourt gev 143.7 159.17 171.90 179.11 182.43 185.00 188.1 6 uyo evi 116.99 131.98 149.39 165.03 179.99 192.92 211.27 ln 115.33 127.5 138.52 152.05 161.81 171.28 183.51 7 onitsha gev 132 145 151 153.94 160.42 162.52 164.35 8 enugu gev 112 135 148.57 155.95 161.68 165.88 169.95 9 owerri gev 144.14 161.63 178.89 191.33 200.98 209.23 218.35 10 calabar gev 150.33 174.04 199.86 216.42 230.95 243.77 258.46 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 155 the best fit probability distribution shown in table 5 was used to compute the quantile values in table 7. the results of the various analyses culminating in the selection of the best fit probability distribution model for each station and the rainfall return levels (mm) for selected return periods of between 5years and 500 years are as presented in table 7. 3.2 rainfall frequency curves (rfcs) the amr estimates obtained for the probability distribution models in table 7 were used to develop the rfcs. these were implemented by hec-ssp software, and they are presented in figures 2-4. figure 2 rainfall frequency curve (rfc) for ikeja figure 3: rainfall frequency curve (rfc) for ibadan http://www.azojete.com.ng/ mailto:augustine.agbonaye@ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 156 figure 4: rainfall frequency curve (rfc) for benin city these rainfall frequency curves (rfc) which are representatives of the ten curves in the study area are useful and powerful tools for estimating the rainfall frequency distribution and calculating t-years rainfall . they are also useful in the planning, design and management of hydraulic structures for flood mitigation and prevention of flood damage at the locations. these rainfall frequency curves (rfc) contain five main lines which are: 1) the zero-line representing the observed events on weibull plotting positions. 2) red line representing the computed curve. 3) black dotted line representing the expected probability curve. 4) the upper and lower green lines representing 95% and 5% confidence limits. 5) the square line representing the outliers. in figure 2,3 and 4, the curves are near linear depicting a continuous increase of rainfall values with increasing return periods. the computed curves almost merged with the expected probability curves which are the best -fit curves for each location. these confirm that the curves adequately represent the most appropriate distribution model for each location and could be used for forecasting of the rainfall at the required return periods almost all the points in the plots were withing the 95% confidence interval there were low outliers (4 each) for ibadan and benin city data and none for ikeja data. 4. conclusions in this study, the best fit probability distribution model applicable to each location was selected for the cities in southern nigeria from six probability distributions and used to predict rainfall return levels of engineering importance for the location. based on the results the following conclusions are made: file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ agbonaye and izinyonl: evaluation of bestfit probability distribution models for prediction of rainfall in southern nigeria. azojete, 18(1):143-158. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 157 1. generalized extreme value distribution (gev) model is the best-fit probability model for onitsha, enugu, owerri, calabar, and port harcourt. evi and ln are the best-fit probability models for uyo. also, the best-fit probability models are evi and lp111 for akure and ikeja respectively. the quantile estimates or forecasted rainfall values for different return periods as shown in table 6 are considered adequate design parameters for planning, design of hydraulic structures for flood mitigation and flood precautions in the various locations. 2. rainfall frequency curves have been provided for ikeja, ibadan and benin city. they were drawn with the forecasted rainfall values that were derived from the best fit probability distribution models. these are guides in hydrological designs. 3. this study has provided useful engineering design parameters for planning and improved hydrological design needed for efficient hydraulic design of structures needed for flood control, mitigation, and flood precaution in the various location. utilization of these parameters by engineers will greatly reduce or advert design failures. references agbonaye, ai. and izinyon, oc. 2017. best-fit probability distribution model for rainfall frequency analysis of three cities in south eastern nigeria, nigerian journal of environmental sciences and technology (nijest), 1(1): 34 – 42. alam, a., emura, k., farnham, c. and yuan, j. 2018. best-fit probability distributions and return periods for maximum monthly rainfall in bangladesh, climate, 6(1): 9; https://doi.org/10.3390/cli6010009 amin, mt., rizwan, m. and alazba, aaa. 2016. best-fit probability distribution for the estimation of rainfall in northern regions of pakistan. open life science, 11: 432–440. filliben, jj. 1975. the probability plot correlation coefficient test for normality. technimetrics, 17(1): 111-117. ghosh, s., roy, m k. and biswas, sc. 2016. determination of the best fit probability distribution for monthly rainfall data in bangladesh. american journal of mathematics and statistics 6(4): 170174. kousar, s., khan, ar., hassan, m., noreen, z. bhatti, sh. 2020. some best-fit probability distributions for at-site flood frequency analysis of the ume river. journal of flood risk management, 13(e12640): 1-11. koutsoyiannis, d. 1997. statistical hydrology edition 4, chapter 6. national technical university of athens, athens, pp: 131-175, doi:10.13140/rg.2.1.5118.2325. kumar, a. 2000. prediction of annual maximum daily rainfall of ranichauri (tehri garhwal) based on probability analysis. industrial journal of soil conservation, 28: 178–180. http://www.azojete.com.ng/ mailto:augustine.agbonaye@ https://doi.org/10.3390/cli6010009 arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):143-158. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: augustine.agbonaye@uniben.edu 158 langat, pk, kumar, l. and koech, r. 2019. identification of the most suitable probability distribution models for maximum, minimum, and mean streamflow. water, 11(4): 734. doi:10.3390/w11040734 mamman, mj., martins, oy., ibrahim, j. and shaba, m. 2017. evaluation of best-fit probability distribution models for the prediction of inflows of kainji reservoir, niger state, nigeria. air, soil and water research, 10: 1-7. masereka, em., otieno, faogm. and snyman, oj. 2015. best fit and selection of probability distribution models for frequency analysis of extreme mean annual rainfall events. international journal of engineering research and development, 11(04): 34-53. mohamed, tm. and ibrahim, aaa. 2016. fitting probability distributions of annual rainfall in sudan. sust journal of engineering and computer sciences (jecs), 17(2): 34-39. okoloye, cu., aisiokuebo, n., ukeje, j., anuforom, ac. and nnodu, i. 2013. rainfall variability and the recent climate extremes in nigeria. nimet, national weather forecast, and climate research center. journal of meteorology and climate science, 11: 49-57. olofintoye, oo., sule, bf. and salami, aw. 2009. best–fit probability distribution model for peak daily of selected cities in nigeria. new york science journal, 2(3): 1-12. osgof, 2011. map of nigeria showing ten selected cities. office of the surveyor general of the federation, abuja, nigeria. singh, b., rajpurohit, d., vasishth, a. and singh, j. 2012. probability analysis for estimation of annual one day maximum rainfall of jhalarapatan area of rajasthan. plant archives, 12: 10931100. tao, dq., nguyen, vt. and bourque, a. 2002. on selection of probability distribution for representing extreme precipitations in southern quebec. annual conference of the canadian society for civil engineering, 5-8 june, montreal, quebec, canada, pp 1 – 8. vivekananandan, n. 2014. comparison of probability distributions for frequency analysis of annual maximum rainfall. international journal of research and innovative technology, 1(3): 50–55. wmo 2009. wmo report no 168. guide to hydrological practices volume ii: pp 112 management of water resources and application of hydrological practices. world meteorological organization, geneva file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:augustine.agbonaye@ 66 arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):543-560 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 543 original research article design and implementation of solar street light for scarcely electrified areas a. a. okandeji1*, z.o. jagun2, m. b. olajide3, m. t. kabir4 and f. onaifo3 1department of electrical and electronic engineering, university of lagos, akoka, lagos state, nigeria 2department of computer engineering, olabisi onabanjo university, ago-iwoye, ogun state, nigeria 3department of electrical and electronic engineering, olabisi onabanjo university, ago-iwoye, nigeria 4department of electronic and telecommunication engineering, ahmadu bello university, kaduna, nigeria *corresponding author’s email address: aokandeji@unilag.edu.ng 1.0 introduction traditionally, streetlights are powered by energy supply from the power grid. the constant outage and intermittent power supplied to consumers has often led to loss of lives and properties brought about by persistent darkness along major roads in cities as well as darkness within local communities. recent advances in technology suggest the possibility of powering streetlight with renewable energy sources. amongst the available renewable energy sources that can be used to power streetlights is solar power. solar powered streetlights is the most feasible as they are independent of the utility grid, involves a minimized operation cost, requires much less maintenance compared to conventional streetlights, and eliminates the use of external wires, which invariably reduces the risk of accidents nallapaneni et al. (2016), nyemba et al. (2019). a solar cell (also called photovoltaic cell or photoelectric cell) is a solid-state electrical device that converts the energy of light directly into electricity by the photovoltaic effect. photovoltaic (pv) is the field of technology and research related to the practical application of photovoltaic cells to produce electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight nallapaneni et al. (2016), (gang, 2014). photovoltaic technology can be used in many electrical applications such as street lighting. essentially, solar arrays generate electrical voltage and this voltage is used to charge a battery via a battery charger circuit. in contrast to burning of coal and other fossil fuel to produce electricity to power streetlights which often results in pollution including acid mine drainage, toxic waste, and air pollutants, solar powered street lighting is clean and free of pollution (baburajan, 2017). the aim of this study is to consider the design and implementation article information abstract streetlights are usually powered by alternating current supply from distribution stations of the utility companies. this invariably increases the demand for power distribution from utility companies. recent developments, however, suggest the possibility of the use of renewable energy sources to power streetlights in order to reduce the demand on the consumption rate of energy on the utility companies. accordingly, this work considered the design and implementation of streetslights in scarcely electrified areas powered by solar energy. using tilted solar modules, energy efficient lamps, and structural anticorrosion parts, a standalone streetlight configuration with automatic switch on/off mechanism was built. the results show that streetlight powered by solar source of renewable energy cheaply generates electricity directly from sunlight without emissions, noise, or vibration. therefore, due to the inconsistencies surrounding the generation of electricity using fossil fuels, this work offers an alternative source to power streetlights thereby reducing pressure on the national grid. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 april, 2020 revised 02 july, 2020 accepted 24 july, 2020 keywords: operation-cost photovoltaic modules renewable energy streetlights mailto:aokandeji@unilag.edu.ng http://www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 544 of a solar powered streetlight to produce illumination at night and at dawn bhairi et al. (2017) to increase the security of lives and properties of the people. to achieve this, a standalone solar powered street light with an automatic switch-on mechanism which activates the light as darkness approaches, and switches off as daylight approaches was implemented. 2.0 materials and methods this section describes the design requirements for the proposed standalone solar powered streetlight. additionally, this section also presents data collected from a solar panel installation designed to power a standalone streetlight located in a scarcely electrified area. in particular, the recorded data comprises of information of the voltage on the photovoltaic cells to generate the output power at a given time. to ensure consistency of the measured data, three days experiment were conducted each for no-load, system connected to battery, and system connected to street lamp. using a multimeter, voltage from the panel on no-load, and when the panel was connected to a battery were recorded. also, voltage measurements when the system powers the energy efficient lamp were recorded. 2.1 design specification a stand-alone configuration was required. an automatic switch-on mechanism was incorporated in such a way that the streetlight switches on when darkness approaches and switches off whenever it senses light. the pole height would be about 30ft for adequate illumination. a bulb rating of 32 watts was used. a panel of 150 watts to withstand system capacity. presence of vented steel enclosed box which houses the battery and the solar charge controller. an energy efficient lamp was required. 2.1.1 composition of solar lighting system figure 1 shows the schematic diagram of a solar powered streetlight. figure 1: schematic diagram of a solar powered streetlight key: 1tilted solar modules placed on a mounting structure facing the sun path. 2energy efficient lamp lighting unit suspended on a pole short arm. 3vented steel enclosure (contains the battery and the solar charge controller). 4structural anticorrosion parts consists of the pole, the affixing base, the short arm and the modules mounting structure as shown by parise et al. (2014). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 545 assuming that the lamp will be available for 12hours during the night, the specification of the calculated electrical devices is shown in table 1. table 1: specification of the calculated items required s/n item power (watts) watt hour (whr) 1 lamp 16 16 x 12 = 192 2 lamp 2 16 16 x 12 = 192 total 32 384 2.1.2 panel rating assuming the sun will be available for 12 hours, the wattage of the panel is given by: wattage of panel = 384watt/ 12hrs = 32 watt (1) according to the wattage derived from (1), a panel above 32watts may be used. therefore, a panel of 150watts is implemented in this design. 2.1.3 battery the deep cycle battery was considered and used because of its reliability and durability compared to the dry, and the wet cell battery. to ensure battery longevity and to avoid damage, in this work, we recommend that ¼ of the battery capacity should be used. thus, 384 x 4 = 1536 watthour. since the battery is 12 volts, for 200ah battery, 200 x 12volts = 2400whr . for 100ah battery, we have 100 x 12volts = 1200 watthours. since a total of 1728whr is needed, a battery of 200 ah is proposed. 2.1.4 controller solar charge controllers are designed to optimize the charging of the deep cycle batteries by the solar panels. thus, from p = iv (2) i = p/v = 32/12 = 2.36amps. therefore, a controller called the hbsc51 of 5a rating is considered in this design. in the worst-case scenario, when there is insufficient sunlight, we assume an increase of 15% of normal working condition for the panel, which gives 115% of 384 = 441.6 watts. panel wattage = 441.6 watthour/12hours = 36.8watts .. . (3) therefore, a 150watts panel can still be used to address the worst-case scenario, when there is insufficient sunlight. 2.2 components specification 2.2.1 the lamp the lamp specification is shown in table 2. table 2: the lamp specification rated voltage 12 volts dc (manufacturer's specification) watts rating 16 watts file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 546 energy efficient lamps are considered for this design. specifically, these energy saver lamps reduces energy usage to about 5 – 10 %. they are responsible for illumination and the watt rating is 16 watts. two units of 16watts saver lamp are considered for this design. the watt power rating for both lamps equals 32-watts. 2.2.2 the panel the panel specification is shown in table 3. table 3: the panel specification rated voltage 18volts dc watts rating 150 watts current rating 8.28amps (manufacturer's specification) 2.2.3 the battery: battery specification is shown in table 4. table 4: battery specification capacity 200 ah voltage rating 12 volts 2.2.4 the controller: controller specification is shown in table 5. table 5: controller specification rated charge current 5a rated load current 5a voltage 12volts the solar streetlight controller described in this work was designed to achieve a 150w solar energy battery charger, and a 32w lamp driver. during the daytime, the controller preserves the electric energy gathered by the solar module (pv module), then stores it in the battery. in the evening, the controller uses the battery energy to power the streetlight. solar controllers of solar photovoltaic systems were used for the coordination of solar panels, batteries and work load. it is a very important photovoltaic system component. the solar street lamp controller has the following basic features (shahriar and hosseini, 2019), overload protection, short circuit protection, reverse-discharge protection, reverse polarity protection, lightning protection, voltage protection, overcharge protection, and power load restoration. a typical solar charge controller indicating normal working condition is shown in figure 2. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 547 figure 2: solar charge controller indicating normal working condition 2.2.5 characteristics of the controller control unit: this characteristics uses a micro controller unit and professional software as the control center to fulfill intelligent system control. charging mode: the charging mode employs the use of pulse width modulation to achieve high efficiency charging. this invariably boosts recovery and float charging-auto-work for battery long life. self-protection: the self protection characteristics protects the controller against overload, outside and inside short circuit, reverse connection, thunder and lighting, pv panel reverse current, over charging and discharging etc. led indication: the light emitting diode (led) indicates if the system is charging, overcharged, fully charged, power low, over – discharged, over load, and short circuit. 2.3 the system main block diagram the block diagram of the controller is shown in figure 3. the microcontroller unit (mcu) provides a real-time system monitoring for the controller. these includes: ● error detection/protection for solar module output voltage, battery voltage (ubat), led lamp voltage (uled), battery charging current (ibat), and led lamp current (iled). ● system self-recovery (safa, 2017). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 548 figure 3: block diagram of a controller 2.4 the pv cells from the calculation above, we consider the use of a panel of 150watt rating. it consists of a solar module which is connected to form a dc power producing unit. 2.5 installation of the system: in general, it is known that the sun rises from the east; the panel is therefore placed towards the east as early as 7am for the day’s reading. from a theoretical point of view, it is known that the optimum panel angle which maximizes the yearly average irradiation lies between 30º and 40º, which is generally close to the latitude angle liga et-al. (2018). therefore, the panel is placed 30º facing the east. the installation procedure of the system is listed below: prepare the 1.5mm wire connect the 1.5mm wire from the battery port on the controller to the battery, noting carefully the + and – pole of the connection. connect the wire from the pv port on the controller to the pv panel. when the connection is right and the panel gets the sunlight, the charge indicator on the controller comes on. connect the two 16watts energy saver lamps to the load port on the controller. we consider a height of 30ft for the pole for adequate illumination. a typical installation diagram is shown in figure 4. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 549 figure 4: installation diagram of the solar powered streetlight 2.6 operation of the system when light fall on the solar panel, voltage is induced. if the system is properly connected, the green led is activated indicating that the system is working perfectly. when the battery voltage is in normal condition, the state led lights up in green; state led flashes slowly in green when the battery is fully charged. when the voltage of the battery is low, the yellow led is activated. when the voltage goes down continually to an over-discharged state, the system state led lights up in red and turns off the output at the same time. upon re-charging, the battery voltage recovers from the over discharged return voltage, and the system automatically becomes operational. the load led lights up when the load is connected. if the load current is 1.25 times higher for 60 seconds or 1.5 times higher for 5seconds than the rated current of the controller which is 5a, the trouble led flashes slowly in red to show overload, and the controller shuts down the output. when the load short circuit happens, the trouble led flashes quickly, then the controller shuts down its output. when this happens, the load at fault is disconnected. 2.7 problems and troubleshooting of the pv system probable problems of the pv system, and troubleshooting options are presented in table 6. table 6: probable problems and possible solutions problems troubleshooting the charge led indicator (green) is not activated when sunlight gets to the pv panel. check if the cable of the solar panel is connected properly. the charge led indicator flashes quickly. system over voltage or open circuit of the battery. check if the battery is connected to the system cable properly or check for any charging circuit damages. the load led indicator lights up but there is check if the load is connected to the system file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 550 no power output. properly. the load led indicator flashes quickly and there is no power output. check the output circuit. if over load occurs, remove the load and push the button. the controller returns to its operational state. the load led indicator lights up slowly and there is no power output possibility of system overload. disconnect some load and push the button again to reactivate the controller. system state led indicator flashes red color and there is no power output over discharge of the battery. the controller resumes its operation after battery charge is complete. 3.0 results and discussion for analytical simplicity, the practical test was carried out over a period of nine days. the components were tested together as a system, and multimeters were used to measure the voltage on each of the component. multimeters were set to dc at 20 volts range to take the no-load reading on the panel. the no-load reading is obtained when the battery is not connected. this provide the voltage reading on the panel obtained directly from the sun rays. also, multimeters set at dc 20 volts range were used to obtain the reading on-load. the reading on-load show how the battery is being charged by the solar panel. in this case, the battery must have been connected to the controller to be charged. the last set of readings were taken during the dusk. we are determined to know the rate of discharge of the battery when the bulbs (32 watts) are connected, and when there is no supply of voltage from the panel. the multimeter is also set at dc 20 volts range to obtain relevant values. we ensured that the right connection of the components that make up the solar streetlight which include the panel connection to the controller. also, the battery and the load (32watt bulb) are connected to the right slot on the controller. the controller helps to regulate the voltage that charges the battery, and to turn on the lamp when there is low voltage from the panel. 3.1 voltage from the panel (on no-load) upon the installation of the pv system designed to power the streetlight, voltage measurements were obtained. using a multimeter, voltage from the panel on no-load for three days were recorded as shown in table 7, 8, and 9. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 551 voltage from panel measurements for no-load experiment for day one is shown in table 7. table 7. time and voltage readings for day one (7/12/2019) time (am-pm) (minutes) voltage on panel (volts) 7:30 17.20 8:00 17.37 8:30 17.98 9:00 18.22 9:30 18.58 10:0 18.62 10:30 18.98 11:00 18.50 11:30 18.91 12:00 18.74 12:30 18.15 13:00 18.45 13:30 18.52 14:00 18.41 14:30 18.52 15:00 18.55 15:30 18.48 16:00 18.43 16:30 17.77 17:00 17.34 17:30 17.40 18:00 14.00 18:30 5.70 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 552 voltage from panel measurements for no-load experiments for day two is shown in table 8. table 8. time and voltage readings for day two (8/12/2019) time (am-pm) (minutes) voltage on panel (volts) 7:30 17.10 8:00 18.50 8:30 18.50 9:00 18.90 9:30 18.80 10:0 18.80 10:3 18.70 11:00 18.50 11:30 18.60 12:00 18.30 12:30 18.44 13:00 18.49 13:30 18.58 14:00 18.55 14:30 18.54 15:00 18.30 15:30 18.34 16:00 18.18 16:30 17.86 17:00 17.41 17:30 17.22 18:00 12.18 18:30 6.21 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 553 voltage from panel measurements for no-load experiments for day three is shown in table 9. table 9. time and voltage readings for day three (9/12/2019) time (am-pm) (minutes) voltage (volts) 7:30 17.15 8:00 18.30 8:30 18.38 9:00 18.98 9:30 19.10 10:0 18.70 10:30 18.65 11:00 17.43 11:30 18.56 12:00 18.62 12:30 18.76 13:00 18.59 13:30 18.68 14:00 18.84 14:30 18.52 15:00 18.22 15:30 18.07 16:00 17.81 16:30 17.48 17:00 16.98 17:30 16.42 18:00 14.03 18:30 13.48 19:00 3.27 3.1.1 observation for no-load testing as can be seen in tables 7, 8, and 9, an increase in the sun's intensity results to a corresponding increase in the voltage obtained from the panel. this can be seen during the peak period where the sun intensity is high between the 9:00 hours and the 10:30 hrs. for the three days’ experiment for no-load, the peak voltage is found between the stated period. 3.2 voltage measurements when system is connected to the battery voltage measurements when the battery was connected to the panel were recorded for three days as shown in table 10, 11 and 12. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 554 voltage measurement for on-load experiment for day one is shown in table 10 table 10 time and voltage readings for day four (10/12/2019) time (am-pm) (minutes) voltage (panel) (volts) voltage (battery) (volts) 7:30 12.64 12.67 8:00 12.73 12.69 8:30 12.86 12.72 9:00 13.01 12.92 9:30 13.05 12.98 10:00 13.19 13.00 10:30 13.02 12.97 11:00 13.06 13.02 11:30 12.99 12.97 12:00 13.00 12.96 12:30 13.20 13.01 13:00 13.02 12.96 13:30 13.07 13.04 14:00 12.97 12.92 14:30 13.08 12.95 15:00 13.01 12.99 15:30 12.96 12.92 16:00 12.95 12.91 16:30 12.92 12.89 17:00 12.90 12.87 17:30 12.87 12.84 18:00 12.82 12.81 18:30 12.76 12.77 19:00 0.97 12.44 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 555 voltage measurement for on-load experiment for day two is shown in table 11 table 11 time and voltage readings for day five (11/12/2019) time (am-pm) (minutes) voltage (panel) (volts) voltage (battery) (volts) 7:30 12.80 12.68 8:00 12.84 12.80 8:30 12.98 12.91 9:00 13.04 12.95 9:30 13.13 13.06 10:00 13.10 13.07 10:30 13.10 13.07 11:00 13.11 13.07 11:30 13.11 13.08 12:00 13.11 13.11 12:30 13.14 13.11 13:00 13.74 13.11 13:30 13.12 13.10 14:00 13.14 13.13 14:30 13.14 13.12 15:00 13.08 13.05 15:30 13.04 13.03 16:00 13.01 13.01 16:30 13.03 13.02 17:00 12.96 12.97 17:30 12.94 12.91 18:00 12.86 12.89 18:30 12.81 12.83 19:00 0.10 12.80 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 556 voltage measurement for on-load experiment for day three is shown in table 12 table 12 time and voltage readings for day six (12/12/2019) time (am-pm) (minutes) voltage (panel) (volts) voltage (battery) (volts) 8:30 13.38 13.38 9:00 13.98 13.96 9:30 19.10 13.45 10:00 18.70 13.34 10:30 18.65 13.36 11:00 17.43 14.13 11:30 18.56 13.22 12:00 18.62 13.24 12:30 18.76 13.36 13:00 18.59 13.27 13:30 18.68 13.17 14:00 18.84 13.32 14:30 18.52 13.28 15:00 18.22 13.23 15:30 18.07 13.21 16:00 17.81 13.22 16:30 17.48 12.23 17:00 16.98 13.22 17:30 16.42 13.14 18:00 14.03 13.25 18:30 13.48 13.17 19:00 3.27 12.71 3.2.1 observations for on-load testing as can be seen from tables 10, 11, and 12, it is observed that immediately the battery is connected, there is a drop in voltage from 18 volts to between 13 and 14 volts. the peak voltage occurs between the hours of 12:30 and 13:00. it is observed that when the battery is fully charged, with the controller connected, the voltage supplied to the battery is cut off thereafter we could only obtain the no-load voltage as it can be seen from 9:30 hours on day six. it was observed that when it is getting dark specifically between 18:30 hours and 19:00 hours, the controller automatically switches on the 32watts lamp. it is also observed that the battery charges effectively when the voltage output from the panel exceeds 12 volts. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 557 3.3 battery voltage discharge when connected to lamp voltage measurements when the lamp is connected to the battery were recorded as shown in table 13, 14 and 15. voltage discharge measurement for lamp-battery connection experiment for day one is shown in table 13. table 13: time and voltage readings for day seven (27/12/2019) time (pm-am) (minutes) voltage (battery) (volts) 19:00 12.72 19:30 12.75 20:00 12.70 20:30 12.69 21:00 12.68 21:30 12.68 22:00 12.65 22:30 12.64 23:00 12.63 23:30 12.62 00:00 12.60 00:30 12.59 1:00 12.58 1:30 12.56 2:00 12.55 2:30 12.54 3:00 12.53 3:30 12.52 4:00 12.50 4:30 12.48 5:00 12.47 5:30 12.31 6:00 12.28 6:30 12.27 7:00 12.22 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 558 voltage discharge measurement for lamp-battery connection experiment for day two is shown in table 14. table 14. time and voltage readings for day eight (28/12/2019) time (pm-am) (minutes) voltage on battery (volts) 19:00 12.44 19:30 12.45 20:00 12.45 20:30 12.42 21:00 12.38 21:30 12.36 22:00 12.34 22:30 12.32 23:00 12.30 23:30 12.28 00:00 12.26 00:30 12.24 1:00 12.23 1:30 12.23 2:00 12.22 2:30 12.21 3:00 12.20 3:30 12.20 4:00 12.19 4:30 12.17 5:00 12.15 5:30 12.12 6:00 12.10 6:30 12.08 7:00 12.11 7:30 12.13 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 543-560. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 559 voltage discharge measurement for lamp-battery connection experiment for day three is shown in table 15. table 15 time and voltage readings for day nine (29/12/2019) time (pm-am) (minutes) voltage (battery) (volts) 18:50 12.46 19:00 12.49 19:30 12.50 20:00 12.46 20:30 12.42 21:00 12.38 21:30 12.38 22:00 12.34 22:30 12.32 23:00 12.31 23:30 12.29 00:00 12.26 00:30 12.25 01:00 12.23 01:30 12.22 02:00 12.21 02:30 12.20 03:00 12.19 03:30 12.19 04:00 12.18 04:30 12.16 05:00 12.13 05:30 12.11 06:00 12.09 06:30 12.08 07:00 12.06 3.3.1 observation on battery discharging rate from the discharge information as shown in tables 13, 14, 15, when the load is connected, there is a sudden drop in voltage which later increases for a while and remains stable before discharging with a considerable constant discharging rate. there is an increase in voltage at 6:30 hours due to sunrise thus, the controller cuts off the supply to the load and then charges the battery. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of solar street light for scarcely electrified areas. azojete,16(3):543-560. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 560 4.0 conclusion this work considered the design and implementation of a solar powered streetlight to provide illumination along streets, houses, and on roads during nighttime and at dawn thereby increasing security and safety of lives and properties. due to the inconsistencies surrounding the generation of electricity using fossil fuels, this work offers an alternative source to power streetlights thereby reducing pressure on the national grid. results obtained showed that the solar source of electricity generation through the use of solar panels (photovoltaic modules) cheaply generate electricity directly from sunlight without emissions, noise, or vibration. references baburajan, s. 2017. cost benefits of solar-powered led street lighting system case studyamerican university of sharjah, uae. international research journal of engineering and technology, 4(2): 11-17. bhairi, mn., kangle, ss, edake, ms. and madgundi, bs., bhosale, vb. 2017. design and implementation of smart solar led streetlight. international conference on trends in electronics and informatics, tirunelveli, india, may 11-may 12, pp. 509-512. gang, l. 2014. sustainable feasibility of solar photovoltaic powered street lighting systems. international journal of electrical power and energy systems, 56: 168-174. liga, r., dace, l. and dagnija, b. 2018. accelerating power generation with solar panels case in latvia. energy procedia, 147: 600-606. nallapaneni, mk., anup, ks. and vinay, kr. 2016. fossil fuel to solar power: a sustainable technical design for street lighting in fugar city, nigeria. procedia computer science, 93: 956966. nyemba, w., chinguwa, s., mushanguri, i. and mbohwa, c. 2019. optimization of the design and manufacture of a solar-wind hybrid streetlight. procedia manufacturing, 35: 285-290. parise, g., martirano, l. and mitolo, m. 2014. electrical safety of street lighting systems. ieee transactions on power delivery, 26(3):1952-1959. safa, k. 2017. principles of electronics materials and devices, mcgraw-hill. new york, usa. shahriar, f. and hosseini sm. 2019. design of an optimal fuzzy controller to obtain maximum power in solar power generation system. solar energy, 182: 161-178. xiaoqiang, x., zhan, a. and xiaohan, l. 2019. design and implementation of streetlight control system based on power line carrier communication. procedia computer science, 155: 734-739 https://www.sciencedirect.com/science/article/pii/s0142061513004626 https://www.sciencedirect.com/science/journal/01420615 https://www.sciencedirect.com/science/journal/18766102 https://www.sciencedirect.com/science/journal/18770509 https://www.sciencedirect.com/science/article/pii/s0038092x1930177x https://www.sciencedirect.com/science/article/pii/s0038092x1930177x https://www.sciencedirect.com/science/journal/0038092x https://www.sciencedirect.com/science/article/pii/s1877050919310221 https://www.sciencedirect.com/science/article/pii/s1877050919310221 https://www.sciencedirect.com/science/journal/18770509 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):289-300 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 289 original research article development of an improved acm scheme for mitigating earth-to-space propagation effects *a. m. s. tekanyi, r. m. idris, a. d. usman, z. m. abdullahi and e. e. agbon department of electronics and telecommunications engineering, ahmadu bello university zaria, nigeria *corresponding author’s email address: amtekanyi@abu.edu.ng 1.0 introduction satellite communication is a promising technology due to its ability to serve very large number of users with high data rate services. despite the large deployment of optical fibre links, satellite communication technology has been seen to dominate the telecommunication industry due to its inherent advantage of extremely long-distance communication (jayadev, 2011). the geometric increase in user-demand for higher capacity satellite links has inspired satellite operators to operate in higher frequency bands, such as ka-band and above in order to accommodate the necessary data rates (leshan et al., 2016). the move to these higher frequency bands employs communications system designs which require the development of a link budget between the transmitter and the receiver. these designs provide an adequate signal level at the receiver’s demodulator to achieve the required level of performance and availability (pratt et al., 2003). satellite system performance of the link can be evaluated using bit error rate (ber) and carrier-to-noise (c/n) ratio. successful design of communication links involves many factors such as the various losses as well as antenna power and gain (kilcoyne et al., 2016). article information abstract in satellite communications, the communication link experiences propagation losses such as: path loss, atmospheric losses, rain fading, ionosphere effects (such as scintillation), and other effects which can greatly affect the received signal strength and close the link budget in the worst case. the design of future broadband satellite systems has to be done with the challenge of more complex traffic mix and these harsher propagation conditions which mitigate the performance of the communications link. link adaptation (la) has been used in satellite communications applications for evaluating the performance of an adaptive modulation system in the unique spacebased propagation environment. despite the current research on improving satellite system performance, there is still a need to further develop a scheme that mitigates the effect of atmospheric impairments. this work develops an improved adaptive coding and modulation scheme that mitigates earth-to-space propagation effects. the scheme targets maximizing data throughput while staying below a bit error rate (ber) threshold so as to successfully mitigate link impairment in fixed communication systems. simulation of the work is carried out using matlab 2016b and system toolkit (stk) 11.3. simulation result showed that the iacm scheme was able to reduce the effect of path loss in time by 5% over the acm scheme and also reduced the effect of path loss with respect to the angle of elevation by 2% over the acm scheme and improvement in the network energy to noise ratio by 22.74% over acm. in terms of system throughput, the iacm scheme showed an improvement in throughput by 24% over the acm scheme. finally, the iacm scheme has shown better performance in terms of throughput and thus, improve the performance of satellite communication. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 nov., 2020 revised 9 march, 2021 accepted 23 march, 2021 keywords: free space loss throughput acm link budget ber tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(3):289-300. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 290 the communications links described are usually configured with a fixed data rate, a static modulation and/or coding scheme, and high link margins to accommodate communications during the worst-case scenario. this worst-case planning approach ensures that communications links are maintained during even the worst expected earth-to-space propagation effects (pratt et al., 2003). these propagation effects include path loss, atmospheric loss, attenuation due to rain, and ionosphere loss, among others. generally, a maximum ber is identified in a communications system and the link is designed to support that ber threshold (pratt et al, 2003). the effects of these propagation impairments degrade the received signal power and are detrimental to a communications link if the ber increases above the acceptable limit for the transmitting waveform as the error correction codes would no longer be able to resolve bit errors (kilcoyne et al., 2016). la is a broad term that encompasses many types of adaptation on the communications link. the technique often referred to as adaptive coding and modulation (acm) is a good way for the earth-to-space communications link to select the modulation scheme that adapts to the signal energy fluctuation to maintain a desired ber (sami et al., 2011). la is developed to track the channel variations, thus changing the modulation and coding scheme to yield a higher throughput. this is achieved by transmitting with high information rates under favorable channel conditions. (sami et al., 2011). la has been used in satellite communications applications, evaluating the performance of an adaptive modulation system in the unique propagation environment. some la satellite applications consider weather impairments, such as rain-fading in the higher frequencies of kaand ku-bands (cioni et al., 2008). this research work developed an improved acm scheme to mitigate earth to space propagation effects. the process of setting the international space station (iss) orbit can be done by using the stk. the parameters necessary for characterization of the communications link environment is gotten from the stk software. typical stk parameters are given in table 1. the international space station (iss) orbit is easily loaded after searching the stk satellite database by common name. stk uses two line elements (tles) and the simplified general perturbations (sgp)-4 propagator to model the orbit. in the instant of the iss orbit, tle data and sgp-4 model are used to provide an accurate propagation routine. tles provide the position of an earth-orbiting object for a given point in time. from this data, a prediction routine, such as sgp-4, can be used to predict the position of the satellite at any point in time. link adaptation is a broad term for a technique that monitors a communications link and alters system parameters to meet certain conditions. the acm is a method for carrying out la analysis. accurate link budgeting improves the throughput of the communications link. in order to perform la analysis (using the acm method) as a function of bit error rate (ber), the estimated c/nis related to the received energy per symbol. this relationship is given in equation (1) as follows (kilcoyne, (2016): s o e c snr n n   (1) to measure the quality of the communication link, the probability of bit error is estimated. in this work, the adaptation algorithm has a major aim of increasing data throughput which is given in equation (2). the objective ber for data transmission on wireless channels is known to be 10-5. this is because the data transmission to the fight sdr is the main objective in this work, a selected ber threshold of 10-5(usman et al., 2018):   file size throughput bps ttransmission time  (2) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):289-300. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 291 a ber of 10-5implies that the receiver must receive on average 100,000 bits before one is in error. thus, an average of 10,000,000 bits must be received for 100 bits to be in error. in this work, all the schemes transmit a fixed symbol rate of 502 kbps. hence, at the lowest bit rate, the receiver required approximately 19.9s to measure the ber (kilcoyne et al., (2016). from simulation, the estimated time required for each modulation scheme to receive 100 errors, assuming a ber threshold of 10-5, is given in table 1. table 1: ber average time for each modulation scheme (kilcoyneet al., (2016) modulation average time to scheme receive 100 error bpsk 19.92s qpsk 9.96s 8psk 6.64s 16qam 4.98s 64qam 3.32s during simulation process, gray coding of all modulation schemes is assumed in order to keep each neighboring symbol differs by only one bit to check the ber probability, 0/be n is used to calculate the ber for bpsk and qpsk modulation schemes. the ber probability from the work of kilcoyne, (2016) is calculated as follows kilcoyne, (2016) 2 b b o e p q n         (3) whereq is the q-function of the transmitted signal from simulation, when comparing the performance of bpsk and qpsk using 0/be n , it appears that the required energy to maintain the same pb is identical. when the ber is written in terms of the modulated energy per symbol, a 3 db increase of signal energy is evident. the process of doubling the energy used in the modulation constellation as a result of using both the quadrature and in-phase channels rather than just in-phase of bpsk accounted for the generation of this 3db. table 2 shows the equations used in calculating the ber for each of the modulation schemes considered in this work. table 2: theoretical ber equations for different schemes modulation schemes ber equations bpsk 2 b b o e p q n         mpsk 2 2 2 sin log s b o e p q m m n             mqam 2 4 1 3 1 log 1 s b o e p q m m nm                 to check the performance of the receiver and the quality of the received signal, error vector magnitude (evm) used as a decision statistic for qpsk and 16-qam modes. the evm was tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(3):289-300. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 292 measured by calculating the distance between the ideal and received symbols. the distance of the ideal symbol from the received symbol is the evm a variety of research has been carried out to mitigating earth-to-space propagation effects in satellite communications. for instance, sali et al., (2012) evaluated link adaptation mechanisms in a reliable multicast scenario, where the challenge lied in finding the optimal transmission rate to suit all terminals in the multicast group. from the simulation results, mla and min are shown to be the best link adaptation algorithms, in providing the highest user fairness and the highest throughput. the problem of this paper was that the channel conditions experienced by the terminal deteriorated as the number of terminals increased. this was due to the error signal generated by solar panel shadowing effect on the satellite antenna that eventually led to high bit error modulation by the modulation schemes adopted in the work. tarchi et al., (2012) developed three adaption algorithms (state-based acm, state estimation, and state nested algorithms) to improve mobile communication in rural and low populated areas with narrowband access. numerical results showed that the proposed approaches increased the link performance. the limitation of the research was that certain channel parameters like the sinr still represented a challenging scenario which in turn lowered the link margin. rico et al., (2013) analyzed the problem of modulation and coding scheme selection in the return link of the mobile satellite system. the work used a weighted combination of both open loop and closed loop signal quality indicators to perform the selection. numerical results showed good performance of the proposed method compared to previous algorithms, and its robustness to environment changes. the challenge of this study was that the target ber could not be achieved in very high or very low snr scenarios. al-saegh et al., (2014) presented the atmospheric impairments to the satellite signal quality in terms of performance evaluation and assessments concerning various effective atmospheric and transmission parameters during dynamic weather conditions. their results revealed that the transmitted frequency, rainfall rates, and relative humidity were directly proportional to the signal quality degradation, whereas elevation angle θ was inversely proportional and corresponding to low ber. although the qpsk modulation was considered the most appropriate modulation scheme in case of high atmospheric impairments but it also exhibited lower number of transmitted bits per unit time which reduced the reception time of transmitted signals to the geo satellite. bruno et al., (2015) designed a reinforcement learning amc algorithm in order to address the short comings (such as the cqi feedback that sometimes resulted in throughput losses) encountered by most amc methods in a lte system. the designed amc scheme exploited a reinforcement learning algorithm to adjust the mcs selection rules based on the knowledge of the effect of previous amc decisions. although the simulated results showed the best mcs even if the cqi feedback provided a poor prediction of the channel performance, the convergence delays of the reinforcement learning were typically long. and as such, the satellite took a longer time to decode the received signals which generally reduced the systems performance in terms of throughput. kilcoyne et al., (2016) characterized propagation environment experienced by a softwaredefined radio on the nasa scantest bed through a full link-budget analysis. the work proposed, designed, and modeled a link adaptation algorithm to provide an improved trade-off between data rate and link margin by varying the modulation format as the received snr arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):289-300. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 293 fluctuated. the result of the work showed an improvement on the throughput of the network. to address any data that might have been demodulated incorrectly and taking into account the round-trip delay, the transmitter would re-transmit the data that was sent when the channel conditions changed thereby degrading the general performance of their system in terms of throughput and the effect of path loss was high. it is evident from the reviewed works that most of the existing algorithms either presented la in a broadcasting system with no direct feedback to the ground station or do not consider shadowing effects. some la satellite applications considered weather impairments, such as rain-fading in the higher frequencies of kaand ku-bands or log-normal shadow fading. other algorithms applied the acm method of la to address variations in the channel condition on the receiving antenna which can cause an interruption of data transmission. despite the various interventions by other researchers, there is still a need for improvement with the aim of having better link budget that improves the throughput of satellite network. this research work develops a gsa based acm scheme to mitigate earth to space propagation effects. 2.0 materials and methods the following presents the materials and method used in the development of the proposed scheme. 2.1 materials the materials used for this work include: (a) laptop (hp intel (r) core (tm) i5-2520m cpu) 2.2 methods 2.2.1 flowchart of the developed scheme figure 1 shows the step-by-step process that was adopted in the development of the link adaptation algorithm. the flowchart shows how the gsa algorithm is incorporated for link budget analysis and how a normalized evm is used for symbol analysis. tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(3):289-300. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 294 start set-up iss using stk load iss by searching stk set-up grc, scan test-bed optimize link budget for noise stream using gsa. where c/n and g/t are the figure of merit normalized evm estimates the noise symbols estimatenormalized evm of current modulation scheme is estimated evm= current modulation scheme normalized evmth? modulate the received symbols and send to the downlink switch modulation scheme based on normalized evmth end yes no figure 1: flowchart of the developed improved developed improved adaptive coding and modulation scheme 2.2.3 estimate link budget using gsa the developed improved adaptive coding and modulation (iacm) scheme for mitigating earth to space propagation effects adopted the gsa algorithm to optimize the process for the estimation of channel link budget. the process for link budget analysis was complex and prone to error due to large number of channel parameters to be estimated. in order to improve the throughput of the satellite communication link, proper and accurate link budgeting process is arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):289-300. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 295 required. the iacm scheme optimized the link budgeting process. for efficient performance analysis of the communication link, the developed iacm scheme used f c/n and g/t(db/k) as figure of merit. the g/t is used in this work to describe the capability of the earth station or satellite to receive a signal. the relation between the c/n and g/t used in this work is given as follows (rashedi et al., 2009): c g f n t        (4) where: f is the antenna frequency g represents the antenna gain t denotes the system noise temperature the antenna gain used in this work is given as follows (kilcoyne et al., 2016): 20.4 10log10 20log10 1000 f g d          (5) where,  is the antenna efficiency and d is the antenna diameter the gsa algorithm was used to optimize the link budgeting process with simulation process in the developed scheme carried out using the gsa algorithm. the simulation parameters for the gsa are given in table 3 while table 4 is the communication link design simulation parameters for the developed scheme. table 3: gsa simulation parameters gsa parameters value maximum-iteration. 50 dimension of problem 4 velocity clock number of agents 50 acceleration. gateway node flag mass. ma=mp=mi=m time master node flag table 4: design parameters for the developed scheme designs parameters ranges uplink frequency [5.0 7.0] ghz downlink frequency [2.04 4.4] ghz earth transmit power [26 30] dbw satellite transmit power [8 11] dbw earth transmit and receive antenna efficiency 70% earth transmit and receive antenna diameter 2.4m 2.2.4 ber estimation in order to improve the data transmission performance of the communication link at each satellite pass, the ber of the communication link was calculated in terms of 0 be n with berth value of 10-5. the objective of the developed algorithm is to maintain this ber threshold value. during the simulation process it was noticed that both bpsk and qpsk meet the ber requirement for the entire pass duration; meanwhile, 8psk, 16qam, and 64qam all achieve tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(3):289-300. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 296 the threshold for shorter periods of time. this result is to be expected as the higher order modulation schemes require stronger symbol energy to achieve the same ber. table 5 outlines the thresholds for switching up and down a particular modulation type in the acm scheme. as bpsk and 64qam are the lowest and highest achievable modulation schemes, they do not have a switch-down or switch-up threshold, respectively. table 5: 0 be n upper and lower boundaries for 10-5 ber modulation schemes down up bpsk n/a 13.6 db qpsk 12.6 db 18.8 db 8psk 17.8 db 20.5 db 16qam 19.5 db 26.6 db 64qam 25.6 db n/a 2.2.5 normalized evmth using berth. in the evm calculation during the acm process, the developed scheme adopted the normalized evm formula. the evm bound for modulation switching scenario is given in table 5. the normalized evm estimated was performed on each symbol of the transmitted signal, using the symbol closest in distance as the ideal symbol. a moving average of evm calculations over 1000 symbols is used during simulation to estimate the evm value. when the average evm (rms) shifts into a different modulation region, the receiver switch modes. the initial receiver state is always bpsk, as it is the most robust to degrade channels out of the modulation scheme options used in this algorithm. once evm estimation has been determined, the receiver either maintains the status of bpsk or increases modulation rate/scheme, depending on the result of the estimation. 2.2.6 selected modulation scheme for symbol modulation the effective performance of the communication link ensure that correct information gets to the receiver at the receiving end. after the link budget process, the acm scheme estimates the ber of the signal and selects an appropriate modulation scheme that reduces the satellite communications link impairments to achieve improved throughput of the network. 3.0 result and discussion the results obtained from the simulation carried are presented and discussed below. 3.1 free space loss and elevation analysis of longest access the results show that the shortest pass is found to be 0.23 minutes while the longest access is approximately 10.8 minutes. from figure 2, it is observed that the position of the iss during its orbit and the elevation angle affect the length of the available communication time with the grc ground station. it is also observed that the iacm scheme relatively shows a lower free space loss value as the elevation angle increases. this implies that the developed algorithm has a higher available duration for communication purpose. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):289-300. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 297 figure 2: acm and iacm scheme for free space loss and elevation with 207 accesses the reduction in free space loss in the developed scheme is due to the consideration of g/t which indicates the quality of receiving earth satellite. the iacm scheme optimized the parameters of the transmitter to cater for the possible link losses during transmission process to the receiver. table 6: percentage improvement of free space loss against access time metric acm iacm percentage improvement es/no (db) 23 28.23 22.74% when ber and energy to noise ratio are plotted against access time, the percentage decrease in the free space loss for both schemes is shown in figure 2. the loss was computed in table 6. these are achieved when the angle of elevation is considered. 3.2 ber and energy to noise ratio at various periods of time figure 3 is a plot showing the relationship between ber , es/no and access time at various period of time. the evm-based algorithm conservatively switches between various modulation schemes, ensuring that the ber was maintained below the 10-5threshold before switching modes. from figure 3, it was observed that the iacm shows a lower ber and a higher es/no as compared to the acm scheme at a ber threshold of 10-5. this is due to the ability of the improved scheme to efficiently find an efficient modulation type to aid better data transmission in the presence of channel impairments. the effect of a reduced ber translates to a better throughput of the network. tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(3):289-300. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 298 figure 3: ber/es/no for acm and iacm 4.0 conclusion in this study, an iacm scheme for mitigating earth-to-space propagation effects using gsa for link budgeting and normalized evm at the receiving satellite station that mitigates the effect of path loss and increase data throughput has been achieved. this scheme improves the existing acm scheme. the improved scheme focuses on improving satellite data throughput and mitigating the effects of path loss on the communications link. this iacm scheme provides a more accurate evm value during data transmission at the satellite station which serves as a base for the selection of an efficient modulation scheme. the link budget analysis was carried out using the gsa algorithm which considered two figures of merit. the best case and worstcase link budget analyses are carried out. the improved acm shows better improvement in terms of network throughput and reduced path loss effect than the acm scheme. reference al-saegh, ma., sali, a., mandeep, js., abdulmajeed, hja. and chandima, g. 2014. atmospheric propagation model for satellite communications. research journal of applied sciences, engineering and technology, 5(7): 157-168. an, g., pasnoori, n. and abdulhammed, r. 2018. access analysis of geo, meo, and leo. satellite systems, 3(3): 1-7. asad, m. and abbas, m. 2010. characterisation and channel modelling for mobile satellite communication systems, satellite communications. research journal of applied sciences, engineering and technology, 10(5): 5-15. blaunstein, n. and christodoulou, cg. 2007. radio propagation and adaptive antennas for wireless communication links. john wiley & sons, inc., hoboken, new jersey, pp. 20-25. bruno, r., masaracchia, a. and passarella, a. 2014. robust adaptive modulation and coding (amc) selection in lte systems using reinforcement learning. in vehicular technology conference (vtc fall), 2(3): 1-6. carlos, jrc. 2012. protocol of communications for vorsat satellite. universidade do porto, faculdade de engenharia, feup, 3(4): 1-10. access time (minutes) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):289-300. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 299 cioni s., de gaudenzi r. and rinaldo r. 2008. channel estimation and physical layer adaptation techniques for satellite networks exploiting adaptive coding and modulation. international journal of satellite communications and networking, 2(26):157–188. eldos, t. and al qasim, r. 2013. on the performance of the gravitational search algorithm. international journal of advanced computer science applications. west yorkshire, united kingdom, pp. 3-9. ippolito, lj. and ippolito jr, lj. 2017. satellite communications systems engineering: atmospheric effects, satellite link design and system performance. john wiley & sons. itu. 2002. handbook on satellite communications. wiley-interscience conference, 3(4): 1-13. itu. 2002. handbook on satellite communications, wiley-interscience conference, 3(5): 1-25. itu-r. 2007. ionospheric propagation data and prediction methods required for the design of satellite services and systems. wiley-interscience conference. newyork, 3(4): 618-9. jayadev j.,2011). a study of rain attenuation calculation and strategic power control for kaband satellite communication in india. department of electrical engineering (esc), national institute of technology. international journal of advanced computer science applications, 2(4): 1-5. jyrki tjp. 2015. the telecommunications handbook: engineering guidelines for fixed mobile and satellite systems, john wiley & sons ltd, the atrium, southern gate, chichester, pp. 1218. karim, sr., sakib, s., islam, mt. and ahamed, fs. 2018. a review of communications satellite by focusing on ‘bangabandhu satellite-1’, the first geo communications satellite of bangladesh, pp. 1-5. kilcoyne, dk. 2016. link adaptation for mitigating earth-to-space propagation effects on the nasa scantestbed. faculty of the virginia polytechnic institute and state university, blacksbury, virginia, pp. 1-9. kilcoyne, dk., headley, cw., leffke, jz., rowe, as., mortensen, jd., reinhart, cr., mcgwier, wr. 2016. link adaptation for mitigating earth-to-space propagation effects on the nasa scantestbed. faculty of the virginia polytechnic institute and state university, blacksbury, virginia. pp.1-6. leshan, u., jon, e. and ifiok, o. 2016. mitigating the effects of rain-induced fading in satellite communications systems using time diversity in concert with maximal ratio combining. journal of engineering, 3(3): 5-12. mebrek, ma., abderrahmane, lh., himeur, a. and bendoukha, s. 2012. configuration and the calculation of link budget for a connection via a geostationary satellite for multimedia application in the ka band. international journal of electrical, computer, energetic, electronic and communication engineering, 6(4): 1-12. mishra, l. and patwardhan, mh. 2014. review of various adaptive modulation and coding techniques in wireless network. international journal of research in engineering and technology, 4(3): 2321-7308. piero, a. and marco, l. 2012. a systemic approach to the compensation of rain attenuation in ka-band communication satellites. international journal of microwave science and technology, 2(3): 1-17. tekanyi et al: development of an improved acm scheme for mitigating earth-to-space propagation effects. azojete, 17(3):289-300. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amtekanyi@abu.edu.ng 300 pratt, t., bostian, cw. and alnutt, je. 2003. satellite communication. international journal of electrical, computer, energetic, electronic and communication engineering, 2(4): 536. rafsanjani, mk. and dowlatshahi, mb. 2012. using gravitational search algorithm for finding near-optimal base station location in two-tiered wsns. international journal of machine learning and computing, 2(4): 377. rashedi, e., nezamabadi-pour, h. and saryazdi, s. 2009. gsa: a gravitational search algorithm. information sciences journal, 179(13): 2232-2248. rico-alvariño, a., tato, a. and mosquera, c. 2015. robust adaptive coding and modulation scheme for the mobile satellite forward link. in signal processing advances in wireless communications (spawc), 2(4): 530-534. sali, a., karim, ha., acar, g., evans, b. and giambene, g. 2012. multicast link adaptation in reliable transmission over geostationary satellite networks. wireless personal, 1(2): 1-5. sami, hos. and mamoun, mas. 2011. implementation of adaptive modulation and coding technique using. international journal of scientific & engineering research, 2(5): 2229-5518. tarchi, d., corazza, ge. and vanelli-coralli, a. 2012. adaptive coding and modulation techniques for mobile satellite communications: a state estimation approach. in 2012 6th advanced satellite multimedia systems conference (asms) and 12th signal processing for space communications workshop (spsc): pp. 36-43 arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):449-474 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 449 original research article development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers c. okechukwu1*, o. a. dahunsi2, p. k. oke3, i. o. oladele4 and m. dauda5 1advanced manufacturing technology programme, p. m. b. 1174, jalingo, taraba state, nigeria. 2,3department of mechanical engineering, federal university of technology, p. m. b. 704, akure, ondo state, nigeria. 4department of metallurgical and materials engineering, federal university of technology, p. m. b. 704, akure, ondo state, nigeria. 5department of mechanical engineering, university of maiduguri, p. m. b. 1069, maiduguri, borno state, nigeria *corresponding author’s email address: okerex2002@yahoo.com 1. introduction artisanal miners and stone workers in nigeria today still use crude tools and methods in crushing and grinding comminution processes. wills (2006) defined comminution as the process of size reduction of particles until the liberation of valuable minerals can be achieved. value addition in mining and minerals processing industries has always taken the route of size reduction or comminution. while ores bearing specific minerals of interest are crushed and milled to reveal and concentrate the valuable constituents, rocks which have no mineral value such as stones, e.g. granite, are crushed to particular aggregate sizes. stone aggregates are used in structural constructions of physical infrastructures such as buildings, roads, railways, bridges, dams, harbours, airstrips, drainages, wells, walkways and parks (asbjörnsson, 2013; ravindran, 2013). according to pokrajcic (2010), comminution is the most energy intensive component of mining and mineral processing. the mineral sector accounts for about 15 % of the total electrical energy consumption in south africa (numbi et al., 2014). small-scale stone crushing in underdeveloped countries is achieved through labour intensive and resource wasting activities such as breaking of the boulders using sledge and small hammers to aggregate sizes. interaction with stone workers during a visit to a local quarry in jalingo, taraba state, nigeria, revealed that a combination of elderly men in their fifties and young men in their twenties are involved in the rock burning, boulder separation and reduction to lump sizes that the women, male and female adolescents can break into aggregates. furthermore, women and children carry out the sieving after the manual size reduction. it takes an average of three weeks to get article information abstract comminution of minerals and stones in nigeria is laden with myriads of resource challenges associated with other developing nations. a typical challenge is the need to import costly mining and mineral processing machineries or replace their components. to address this challenge, economic consideration was prominent in the development of components for the single toggle jaw crusher. geometric modeling and structural/stress analysis of the components were achieved using pro/engineer® and autodesk inventor® computer applications. designed eccentricity of 7 mm resulted in 5 mm throw and 0.01° angle of twist in the eccentric shaft. the designed base frame was statically stable, having yielded a maximum displacement of 0.008066 mm. analysis of the compression spring indicated design compliance. also, hardfaced crusher jaws and large diameter pulley and flywheel were developed. selection of a three-phase, 3730 w electric motor resulted in a 0.24 ton/hr capacity jaw crusher in service. optimal and maximum feed of the crusher were found to be 0.5 kg and 1 kg, respectively. average eccentric shaft speed decreased with increased mass of granite lumps undergoing crushing. therefore, the methods presented can be adopted in developing affordable and easily maintainable jaw crushers for artisanal miners and stone workers in nigeria. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sep., 2019 revised 04 may, 2020 accepted 20 may, 2020 keywords: artisanal mining, stone crushing, sustainable mineral processing, jaw crusher http://www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 450 a truck load (4m3) of the 31.75 mm aggregates; six weeks to get two trucks of the 31.75 mm aggregates and a pick-up vehicle load of 12.52 mm aggregates. the manual stone crushing activities in a local quarry are shown in figure 1. figure 1: adolescent children and a woman breaking stones into aggregates in jalingo quarry, nigeria. birabwa (2006) pointed out improved mechanization of small-scale stone quarrying as one of the ways to improve the livelihood of stone workers. mohamed et al. (2014) designed a jaw crusher and advocated the need for affordable mechanized small-scale stone crushing machines. furthermore, alonge (2015) developed a prototype jaw crusher and identified the need for alternative and cheaper locally sourced materials for the jaws, he also called for the scaling-up of the crusher to industrial size. in addition, elisante (2009) fabricated a jaw crusher for artisanal miners with engine prime mover but did not place adequate focus on the design and materials development for the machine’s critical components. undp (2014) summarily posited that there is need to bridge the gap between high capital intensity of modern mining production activities that the sector requires for significant value addition and reduction of hazard and drudgery associated with artisanal mining. this will shore up the profit of the small-scale operators, which currently dominate the sector. access to modern technology, skills and finance are major factors in the gap that need to be addressed. hence, this research is geared towards addressing technology and skills related challenges that are adversely affecting the profitability and sustainability of mining and minerals processing ventures in nigeria. economical methods of developing critical components of the jaw crusher for easy repairs and replacement by the small-scale operators have not been adequately addressed. towards achieving sustainable comminution, it is pertinent to unveil the procedures for developing the critical components; which include: eccentric shaft, journal bearing and hardfaced jaws. procedures used create room for easy maintenance of the jaw crusher. consequently, the objectives of this study are to design a 0.1 tonne/hr capacity single toggle jaw crusher; develop critical components for easy and timely reparation; develop and evaluate the performance of the jaw crusher. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 451 2. materials and methods 2.1 materials the materials used in developing the components of the jaw crusher are presented in table 1. table 1: materials used in developing hardfacing alloys and crusher parts components materials hardfaced crusher jaws ferro-alloy hardfacing insert, low carbon steel pitman, crusher frame, rushing chamber, crushing chamber, journal bearings’ housing, toggle plate, shims low carbon steel pulleys and flywheel grey cast iron eccentric shaft medium carbon steel 2.2 design of the single toggle jaw crusher the design of the jaw crusher commenced from the crushing compartment, through the machine elements to the selection of a prime mover. 2.2.1 determination of gape and lengths of movable jaw and pitman of the jaw crusher ashok and yan model for width (w) of the crusher jaw plate lies within the range: 1.3g < w < 3.0g (moore and rajpal, 2013); where, g is the gape. also, the angle of nip must lie between 17o and 27o (niemela and kieranen, 2008). the width of the fixed jaw, w = 200 mm, the height of the fixed jaw, lfj = 300 mm, and the angle of nip,  = 20o, then g can be calculated from figure 2 as follows: figure 2: schematic diagram of the crushing compartment of a single toggle jaw crusher where, /bf/ is the gape (g), /de/ is the set, /bd/ is the length of movable jaw, /jd/ is the length of the pitman, h1 is the thickness of the journal bearing base plate, and h2 is the radius of the bearing from its centre to the surface of the base plate. from figure 2, it can be deduced that: �� � ��� cos� � 319.�5 mm (1) notice that zĵb =  (alternate angles), dĉe = (180-90- )o = 70o (angle on a straight line). given that: h1 = 10 mm, h2 = 70 mm, and /de/ = 12.5 mm, then: �1 � 1�.5 tan �0 � 4.55 mm file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 452 therefore, the length of the movable jaw, lmj is given by: �1 � �� � 3�3.8 ≈ 3�4 mm (�) also, /af/ = /ce/, which is given by: 1�.5 sin �0� � 13.3 mm more so, the length of /ab/ is given by: /ab/ � ��� ���� � 300tan�0° � 109.� mm this implies that the gape, g equals g = /ab/ + /af/ = 109.2 + 13.3 = 122.5 ≈ 123 mm. notice that: 1.3 × 122.5 < 200 < 3 × 122.5 = 159.25 < 200 < 367.5 hence, the width, w of the fixed jaw, which is the same as that of the movable jaw was properly selected within the range 1.3g < w < 3.0g. additionally, �3 � �1 � �� ���� (3) � 10 � �0 cos �0° � 85.13 mm hence, the length of pitman, lp is given by: �� � �1 � �� � �3 (tt) (4) by substitution, lp = 4.55 + 319.25 + 85.13 = 408.93 ≈ 409 mm 2.2.2 determination of components of the crushing force contributed by the pitman, movable jaw, toggle plate and drawback rod using the density of steel, 7.85 g/cm3, the weights of pitman-movable jaw sub-assembly (wp), toggle plate (wt) and drawback rod (wr) were determined with pro/engineer® software as 250.07 n, 31.06 n, and 28.95 n, respectively. the components of the crushing force contributed by movable jaw, toggle plate and drawback rod were determined from figure 3: figure 3: contributions of the pitman, movable jaw, toggle plate and drawback rod to the crushing force http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 453 where, wp, wt, and wr were the weights of the pitman-movable jaw sub-assembly, toggle plate and drawback rod, respectively. also, fp, ft and fr are the forces acting along the length of the pitman-movable jaw sub-assembly, toggle plate, and drawback rod due to their weights, respectively. fsc is the slanted component of the crushing force along the movable jaw, while fhc is the horizontal component of fsc. the movable jaw is inclined at 20° to the vertical line /ao/, while the toggle plate is inclined at 30° to the horizontal line /ae/. the angle of inclination of the drawback rod is calculated thus: � � tan−1 50 430 � 6.63° from figure 3, fp, ft and fr and their horizontal components fpx, ftx and frx, respectively, can be calculated as follow: �� � �� �t��0° � �50.0� 0.939� � �66.1� n ��� � �� ����0° � 91.0� n similarly, �� � �� �t�30° � 6�.1� n ��� � �� ���30° � 53.80 n likewise, �� � �� �t�6.63° � �50.65 n ��� � �� ��� 6.63° � �48.9� n the horizontal component of the crushing force is given by: ��t � ��� � ��� � ��� n (5) by substitution, fhc = 91.02 + 53.80 + 248.97 = 393.79 n the slanted component of the crushing force along the pitman-movable jaw subassembly is given by: ��t � ��t ����0° � 1151.43 n furthermore, the contribution of the pulley-eccentric shaft-flywheel subassembly is as follows: given that: mass of grey cast iron pulley is 18.4 kg, mass of grey cast iron flywheel equals 18.4 kg, and mass of medium carbon steel eccentric shaft is 13.211 kg; then, mass of pulley-eccentric shaft-flywheel = 18.40 + 18.40 + 13.211 = 50.01 kg, weight of pulley-eccentric shaft-flywheel sub-assembly, wpf = 500.10 n; this can be resolved to the slanted crushing force direction as shown in figure 4: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 454 figure 4: contributions of the pulley, eccentric shaft and flywheel to the crushing force from figure 4, fpf can be calculated as follows: ��� � ��� ����0° � 53�.19 n where, fpf is the component of the crushing force from pulley, eccentric shaft and flywheel. therefore, total force available along the pitman-movable jaw sub-assembly for crushing is given by: �t� � ��� � ��t n (6) substituting the values of fpf and fsc into equation (6), gives fcf = 1151.43 + 532.19 = 1683.62 n 2.2.3 estimation of power required by the jaw crusher to crush a given feed according to zhang (2014), the power required to crush a given feed size of ore or stone to product, pr (kw), is given by the modified bond’s equation: �� t� � 0.3161�t 1 �� − 1 �� kwhr tonne (�) given that: material to be crushed is granite, df = 100 mm, dp = 12.5 mm, t� = 0.1 ton/hr, wi = 15.83 kwhr/ton (kelly and spottiswood, 1982), then, pr (kw) can be calculated as: �� � 0.1 × 0.3161 × 15.83 × 1 1�.5 − 1 100 � 91.5� w also, the reduction ratio, rr is given by: �� � �t�� �� ���� (mm) �t�� �� �耀��䀀�� (mm) (8) by substitution, �� � 100 1�.5 � 8:1 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 455 2.2.4 estimation of power available from the crushing force and eccentric shaft the eccentricity, e, of the eccentric shaft can be determined from figure 5 as the difference between the radii of 60 mm diameter and 74 mm diameter parts of the shaft; hence, e = 7 mm. figure 5: end view of the eccentric shaft. the throw or stroke of the pitman-movable jaw sub-assembly is given by the difference between the eccentricity (7 mm) and the difference between the internal diameter of eccentric shaft housing (76 mm) and the diameter of the eccentric lobe (74 mm); hence, stroke = 7 – (76 – 74) = 7 – 2 = 5 mm the crusher stroke is the displacement of jaw between the widest and narrowest points on an eccentrically gyrating cycle (karra et al., 1992). alternatively, donovan (2003) defined the throw as the stroke of the swing jaw or the difference between the open side set and the closed side set. the open side set is the maximum discharge aperture, while the closed side set is the minimum discharge aperture. open side set = 15 mm; closed side set = 10 mm stroke = 15 – 10 = 5 mm; set = aggregate product size = 12.5 mm according to karra et al. (1992), the mechanical power required to drive the crushing mechanism can be calculated from equation (9) as follows: ��耀����⹉�耀 � �t� . � .� (9) let, crushing force, fcf = 1683.62 n, stroke, x = 0.005 m, shaft speed in r.p.m., n = 400 r.p.m. ������耀t� �݄��� ����� � ��� 60 (rad/s) (10) � 41.89 rad/s the amount of power consumed during crushing (i.e. driving the mechanism) is calculated thus: �t � 1683.6� × 0.005 × 41.89 � 35�.63 w 2.2.5 estimation of reaction forces at the bearings let, weight of the eccentric shaft be we = 132.11 n, vertical component of slanted force, fsc, bewsc, wsc = fsc cos20° = 1151.43 × 0.9396 = 1081.88 n also, let reaction at each bearing support be rb, weight of pulley, wl = 184 n, weight of flywheel, wf = 184 n. then, rb can be determined from the force diagram shown in figure 6 as follows: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 456 figure 6: force diagram for the calculation of reactions at the journal bearings. note: all distance dimensions in figure 6 are in mm. summing vertical forces, we have: �� � �� − �� −�� −��t −�� � 0 (11) by substitution, we have: �� � � 184 � 13�.11 � 1081.88 � 184 � 1581.99 �� � �90.995 ~ �91 n 2.2.6 design of flywheel let, mf be the mass of the flywheel, then, mf = 18.40 kg, speed of flywheel, nf = 400 rpm, angular speed of the flywheel is given by: �� � ���� 60 (rad/s) (1�) by substitution, �� � � × 3.14� × 400 60 � 41.89 (rad/s) radius of gyration, rg is taken as the mean radius of the rim, because the thickness of the rim is very small compared to its diameter (khurmi and gupta, 2005); rg is calculated from figure 7 as follows: figure 7: schematic drawing of the flywheel for the calculation of the mean radius 耀� � �00 � 180 � � 0.19 m mass moment of inertia of the flywheel about the axis of rotation, i is given by: � � t�耀�� (kgm�) (13) � 0.66 kgm� mean kinetic energy of the flywheel, ef is given by: �� � 1 � ��� � � 1 �t�耀���� � (j) (14) � 58�.80 j http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 457 maximum fluctuation of energy, ���, is given by: ��� � ��� �t� � t�耀���� �t� � ���t� (j) (15) according to khurmi and gupta (2005), coefficient of fluctuation of speed, cf, for crushing machines is 0.2. hence, ��� � � × 58�.8 × 0.� � �33.1� j energy consumed per second due to the inertia of the flywheel, pf = 233.12 w. then, power required to drive the crushing mechanism and reduce the feed to product, i.e. reduce 100 mm granite feed to 12.5 mm is the sum of pr, pc and pf. therefore, total power consumed during crushing is given by: ��t � �� � �t � pf (16) � 6��.3� w 2.2.7 selection of prime mover for driving the crushing mechanism given that: r1 is the radius of the driving or driver pulley (m), r2 is the radius of the driven or follower pulley (m), d1 is the diameter of the driver pulley (m), d2 is the diameter of the driven pulley (m), n1 is the speed of the driver pulley (r.p.m.), n2 is the speed of the driven pulley (r.p.m.), v1 is the velocity of the belt while passing driver pulley (m/s), v2 is the velocity of the belt while passing driven pulley (m/s), t1 be the tension of the tight side of the belt (n) and t2 is the tension on the slack side of the belt (n). according to khurmi and gupta (2005); juvinall and marshek (2012), the angle of contact or lap on the large diameter driven pulley is given by: �� � 180° � �� � 180 rad. (1�) � � �t�−1 �� − �1 � ° (18) where, x is the centre to centre distance between the driver shaft and the driven shaft, (m). then, �1 � ��1�1 60 (m/s) (19) �� � ����� 60 (m/s) (�0) if there is no slip, v1 equals v2, which implies the velocity ratio of the belt is given by: �1 �� � �� �1 (�1) the ratio of the tight side tension (t1) to that of the slack side tension (t2) is given by the expression, �1 �� � ���������� (��) where, μ is coefficient of friction between the belt and the pulley, which equals 0.3 for cast iron and rubber belt. � equals half of the angle formed by the slanted sides of the v-belt or the grooved pulley. from the pro/engineer® software, �� � 33.86° which implies, � � 16.93°. the effective turning force at the circumference of the driven pulley is the difference between the two tensions, i.e., file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 458 ������t�� �䀀耀�t�� ��耀�� � �1 − �� (n) (�3) therefore, power transmitted by a belt is given by: �� � �1 − �� �� w (�4) torque exerted on the driven pulley equals torque transmitted by the eccentric shaft and can be calculated from the equation: ��� � �1 − �� �� n.m (�5) output power available at the driven pulley is given by: ��t � �π����� 60 w (�6) input power transmitted from the prime mover is given by: �� � �� × �� w (��) where, �� is the number of belts. efficiency of the pulley-drive system is given by: � � �䀀��䀀� ��⹉�耀 ���䀀� ��⹉�耀 (�8) given that: ppc = 677.32 w, d2 = 0.4 m, d1 = 0.102 m, r1 = 0.2 m, r2 = 0.051 m, � � 16.93°, μ = 0.3, x = 0.666227 m and n2 = 400 r.p.m., then, from equation (18), � � sin−1 0.� − 0.051 0.666��� � 1�.9�° also, from equation (17), �� � 180° � � × 1�.9� × 3.14� 180 � 3.593 rad. this implies that: ��������� � 0.3 × 3.653 × cosec 16.93° � 3.�0� then, from equation (22), �1 �� � ���������� � e3.�0� � 40.53 hence, �1 � 40.53�� (n) (�9) more so, from equation (26), torque on the driven pulley can be calculated as follows: ��� � 60��t ���� � 60 × 6��.3� � × 3.14� × 400 � 16.1� nm from equations (23) and (25), the effective turning force is given by: http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 459 �1 − �� � ��� �� � 16.1� 0.� � 80.85 n hence, �1 � 80.85 � �� (n) (30) equating equation (29) to equation (30), gives 40.53�� � 80.85 � �� �� � 80.85 39.53 � �.05 n therefore, t1 = 80.85 + 2.05 = 82.90 n the speed of the driver pulley can be determined from equation (21) as follows: �1 � ���� �1 � 400 × 0.4 0.10� � 1568.63 r.p.m. velocity of belt, v1 = v2 = vb is calculated thus: �� � ��1�1 60 � 3.14� × 0.10� × 1568.63 60 � 8.38 m/s power transmitted by a belt is calculated as follows: �� � �1 − �� �� � 80.85 × 8.38 � 6��.5� w most crushing mechanisms are driven with a minimum of two belts, since the crusher to be developed is of laboratory size, two belts were selected. given that: �� = 2, pb = 677.52 w, substituting these values into equation (27), gives �� � 6��.5� × � � 1355.04 w efficiency of the pulley-driven system is determined thus: � � �䀀��䀀� ��⹉�耀 ���䀀� ��⹉�耀 � 6��.3� 1355.04 � 0.4999 ~ 0.5 � 50% considering power losses due to friction, inertia forces, voltage drop, heat and vibration, the power rating of the prime mover can be taken as two and half times input, i.e., power rating of prime mover � �.5 × 1355.04 � 338�.60 w at this stage, decision was made to use an electric motor as the prime mover and the selection criteria are outlined below: speed should be normal at about 1600 r.p.m. torque should be greater than the output torque of 16.8 nm. power output should be at least 3.4 kw. it must be a three-phase a.c. motor. based on the criteria above, the motor bought has the following specifications: power rating = 5 hp = 5 × 746 = 3730 w, speed = 1600 r.p.m., torque = 22.26 nm, number of phases = 3. 2.3 stress analysis of the components of the jaw crusher stress analysis of the eccentric shaft, base frame and spring were carried out with autodesk inventor® as outlined by waguespack (2014). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 460 2.3.1 stress analysis of the eccentric shaft given that the shaft material is medium carbon steel, with modulus of elasticity, e = 206000 mpa, modulus of rigidity, gr = 80000 mpa, density, ρ = 7860 kg/m3, radial load = 184 n, continuous load on the eccentric shaft = 1151.43 n / 200 mm = 5.757 n/mm, direction of the continuous load = 20°, and torque = 22 nm. using these values and machine elements’ positions shown in figure 8, the stress analysis of the eccentric shaft was achieved. figure 8: positions of radial loads, bearing and continuous load on the eccentric shaft 2.3.2 stress analysis of the base frame the base frame was drawn and welded in autodesk inventor®, prior to the stress analysis. fixed joints and constrained points are shown in figure 9. additionally, the weights of the crushing chamber and its accessories were determined, divided into six and distributed as illustrated in figure 10, while the weight of the motor-small pulley sub-assembly was determined, divided by four and distributed as presented in figure 11. figure 9: fixed joints and constrained points on the base frame figure 10: one-sixth of the weight of crushing chamber and its accessories http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 461 figure 11: one-fourth of the weight of the motor-small pulley sub-assembly 2.3.3 design of the compression spring springs are designed to provide a push, a pull, or a twist force (torque), or to primarily store energy. the spring index is the ratio of the mean coil diameter to the wire diameter; the preferred range of the spring index is from 4 to 12. if the spring index is less than 4, the spring is difficult to manufacture, when the index is greater than 12, it is prone to buckling and also tangles easily when handled in bulk (norton, 2000). properties of the heat-treated wire carbon steel spring that was analysed in autodesk inventor® are listed in figure 12. the spring check analysis was carried out with the minimum load as the horizontal component of the crushing force, while the working load is the component of the horizontal component when resolved along the drawback rod or at 6.63°. figure 12: properties of the compression spring 2.4 development of the eccentric shaft using a medium carbon steel shaft of ø74 mm, the following dimensions where considered prior to production of the eccentric shaft by machining: diameter of the hole in hubs of the large diameter pulley and flywheel = 50 mm, diameter of the bearing bore = 55 mm, eccentric lobe diameter = 74 mm and stopper diameter = 60 mm. the working drawings of the machining steps 1 to 9, taken towards producing the eccentric shaft are presented in figure 13 to figure 22. the machining steps are as follow: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 462 step 1: a straight line was drawn through the centre of the ends of the ø74 mm solid shaft and along its length; step 2: an offset of 30 mm was marked from the opposite ends of the shaft and each point was centre-punched; step 3: a hole was drilled at one end of the centre-punched point; with a radius of 25 mm, a circle was drawn with its centre at 30 mm from the edge of the opposite circular end; step 4: about 100 mm length of a ø50 mm shaft was turned on the lathe and its circular end welded to the ø50 mm circle on one end of the ø74 mm shaft; step 5: the attached ø50 mm shaft was mounted in the jaw chuck of the lathe and the other centre-punched end on the tailstock; the job was set with the aid of a tool; step 6: 200 mm length was marked-out at 265 mm offset from the tailstock end; with a cut of 0.5 mm, shaft was step-turned to ø60 mm from the both ends of the 200 mm lobe and parallel-turned to the ends of the shaft; step 7: an offset of 5 mm was marked out from both ends of the 200 mm lobe, step-turned to ø55 mm from the ø60 mm and parallel-turned to the ends of the shaft; step 8: ø50 mm was step-turned at 80 mm from 5 mm offset, and parallel-turned 180 mm on the tailstock side and 200 mm on the headstock side; and step 9: unclamp the machined part and part-off of the welded part. figure 13: geometric model of machining step 1 figure 14: geometric model of machining step 2 figure 15: geometric model of machining step 3 figure 16: geometric model of machining step 4 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 463 figure 17: geometric model of machining step 5 figure 18: geometric model of machining step 6 figure 19: geometric model of machining step 7 figure 20: geometric model of machining step 8 figure 21: geometric model of machining step 9 figure 22: eccentric shaft after machining grooves were made along the ø80 mm sections for retaining rings, after turning the eccentric shaft. also, keyways were cut along the ø50 mm section as shown in figure 23. knurling operation along the ø80 mm section of the eccentric shaft is depicted in figure 24. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 464 figure 23: third angle orthographic and isometric projections of the eccentric shaft with keyways and grooves for retaining rings figure 24: knurling of the bearing part of the eccentric shaft for force fitting 2.5 development of hardfaced jaws the fixed and movable jaws of the jaw crusher were developed by welding a ferro-alloy hardfacing insert to mild steel substrate using manual metal arc welding at a welding speed of 120 mm/min and current of 100 a. stringer hardfacing pattern of the insert was used to form the corrugations, while dot hardfacing pattern was made along the groove to protect the base plate as shown in figure 25. the hardfacing insert contains mainly 72.8 % fe, 12.32 % mn, 7.38 % cr and 4.35 % c. detailed hardfacing procedures have been presented by okechukwu et al. (2018). geometric models of the movable and fixed hardfaced jaws are shown in figure 26 and figure 27, respectively. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 465 figure 25: hardfacing of mild steel with hardfacing insert to form hardfaced jaw (okechukwu et al., 2018) figure 26: exploded view of the pitman-movable jaw sub-assembly figure 27: fixed jaw-support plate sub-assembly and exploded view 2.6 development of the journal bearings the eccentric movement of pitman-movable jaw sub-assembly contributes significantly to the failure of bearings in jaw crushers. frequent replacement of the bearing results in longer downtimes in quarries; hence, the journal bearings are critical components. based on the eccentric diameter of the eccentric shaft and the bore diameter in the hubs of the pulley and flywheel, a decision was made to use a bearing whose bore diameter falls between the two diameters. this led to the selection and purchasing of four 6311-2rsc3 ball bearings, with ø55 mm internal diameter, ø120 mm external diameter and 29 mm thickness. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 466 consequently, a steel pipe of internal diameter ø120 mm, external diameter ø140 mm and length 200 mm was used to form the bearing housing, while 10 mm thick mild steel plate was used as the journal bearing base. arc welding was used in joining the bearing housing to base plate and end plates. exploded view of the journal bearing is presented in figure 28. figure 28: exploded view of the journal bearing sub-assembly 2.7 assembling of jaw crusher components the assembling sequence of the single toggle jaw crusher is summarized in steps a to d and the corresponding geometric models are presented in figure 29 to 32. assembling steps are as follow: step a: crushing chamber was positioned on the base frame and fastened with bolts and nuts step b: cheek plates were attached to inner side walls; thereafter, fixed jaw-support plate subassembly was fastened adjacent the cheek plates, while the toggle socket was attached opposite the fixed jaw step c: the pitman-movable jaw sub-assembly was hung on the eccentric shaft, the journal bearings were positioned on the eccentric shaft, and the toggle plate was attached to the lower end of the pitman prior to positioning the journal bearings on their sitting positions on the crushing chamber. the drawback rod was attached to the lower end of the pitman before the fastening of the compression spring to the back of the crushing chamber. step d: the 5 hp electric motor was fastened to the base frame; the ø400 mm pulley and flywheel were positioned on the eccentric shaft and secured with taper keys, while the ø102 mm pulley was also secured with a taper key. the pulleys were connected with two b82 vbelts. figure 29: geometric model of assembling step a http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 467 figure 30: geometric model of assembling step b figure 31: geometric model of assembling step c figure 32: geometric model of assembling step d file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 468 2.8 determination of the capacity of the jaw crusher the crusher capacity was determined by crushing 80 kg of granite lumps with sizes ranging from 30 mm to 75 mm, and the crushing time in minutes was recorded. 2.9 determination of the variation of eccentric shaft speed with load the effect of crushing varying quantities of granite on the eccentric shaft speed and the crusher stability was determined with the aid of a digital tachometer. different quantities of the granite ranging from 0.1 kg to 0.6 kg were crushed and the corresponding eccentric shaft speeds were recorded. 3. results and discussion 3.1 result of the eccentric shaft design table 2 shows the results generated for the eccentric shaft when it was subjected to stress analysis in autodesk inventor®. table 2: summary of results of the analysis of the eccentric shaft design parameters symbol value maximal bending stress σb 1.679 mpa maximal shear stress τs 0.254 mpa maximal torsional stress τ 0.896 mpa maximal deflection fmax 9.323 microm angle of twist φ 0.01 deg the result showed that the angle of twist was insignificant; hence, there was no noticeable twisting in service. shear force and bending moment diagrams of the eccentric shaft along the yz plane are presented in figures 33 and 34, respectively. figure 33: shear force, yz plane http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 469 figure 34: bending moment , yz plane from figure 33, highest shear force value of 789.776 n occurred between the eccentric lobe and journal bearings. maximum bending moment of magnitude 26.2341 nm occurred at the centre of the eccentric shaft as presented in figure 34. 3.2 base frame stress analysis static analysis of the base frame yielded the result shown in table 3, while directional stiffness values are presented in table 4. the directional stiffness values were calculated from the generated force and displacement. table 3: result of displacement of the crusher frame and directional forces table 4: determination of directional stiffness force (n) max. displacement (mm) directional stiffness (n/mm) fx 578.346 0.008066 71,701.71 fy 586.004 0.008066 72, 651.13 fz 400.771 0.008066 49,686.46 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 470 the result of the frame’s displacement when subjected to the weights of the crushing chamber accessories and the electric motor is shown in figure 35. the frame is said to be statically stable or satisfactorily stiff considering the maximum displacement value of 0.008066 mm or 0.000008066 m, which is insignificant. high stiffness recorded can be attributed to the diagonal bracing below the crushing chamber position. these results are in agreement with the work reported by rusiński et al. (2013), who posited that incorporating diagonal bracing inside a crusher frame increases the stiffness. figure 35: static analysis result for the displacement of the jaw crusher base frame the weakest part of the frame or the part with maximum displacement falls around the position of the electric motor-small pulley sub-assembly, where there is no diagonal bracing; the z-direction has the least stiffness as evidenced in figure 36. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 471 figure 36: force acting along z-direction due to components’ weights 3.3 result of the spring design the results of the spring design are tabulated as shown in table 5. table 5: spring design parameters spring design parameters values spring constant 35.241 n/mm total spring deflection 17.026 mm spring limit force 2256.678 n endurance in shear 726.000 mpa min. load stress 178.149 mpa max. load stress 185.636 mpa critical speed of spring 14.600 mps natural frequency of spring surge 129.034 hz spring check result positive the spring check result is positive, indicating design compliance. it is clear that the spring will not fail when subjected to the forces specified. furthermore, the spring index of 7.294 was within acceptable range of 4 to 12, while the total spring deflection of 17.026 mm favoured the designed crusher stroke of 5mm. also, the spring limit force of 2256.678 n was greater than the total crushing force of 1683.62 n. 3.4 capacity of the jaw crusher the developed single toggle jaw crusher showing the evaluated hardfaced jaws and other critical components are shown in figure 37. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 472 figure 37: side and front views of the single toggle jaw crusher after crushing the specified quantities of granite, the aggregate product size ranges from 5 mm to 15 mm, with majority falling around 12.5 mm. the average quantity of granite crushed, corresponding crushing time, and the calculated capacity of the crusher were 20kg, 5min and 0.24 ton/h, respectively. the increased capacity beyond the designed capacity of 0.1 ton/hr can be attributed to the use of a higher horse power motor; this implies increased feed rate and throughput. variation in the crushing time despite crushing the same quantity was due to voltage fluctuation, shape of granite lumps, friction and heat between the metal parts. it was observed that wedge-shaped granite lumps were easily nipped and crushed, while irregular-shaped lumps took longer crushing time. 3.5 variation of eccentric shaft speed with load result of the analysis of effect of crushing increasing quantities of granite on the eccentric shaft speed of the jaw crusher is shown in figure 38. figure 38: variation of average eccentric shaft speed with quantity of granite crushed by the jaw crusher from figure 38, it is clear that the speed of the eccentric shaft decreases with creasing quantity of granite undergoing crushing in the crushing compartment of the laboratory size jaw crusher. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 449-474. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 473 the shaft speed decreases more when the stone shape is irregular; hence, a longer crushing time as observed earlier during the capacity determination. furthermore, it was observed that the higher the quantity of granite undergoing crushing, the higher the noise and vibration of the crusher parts; this imposes stress on the electric motor. crushing of 1 kg of granite resulted in an average eccentric shaft speed of 340.30 r.p.m. and a near breaking stress on the motor; hence, 1 kg was taken as the maximum load. additionally, a moderate load of 0.5 kg will ensure reduced stress on the electric motor and other components since there was a sharp drop in the shaft speed when 0.6 kg of granite was undergoing crushing. 4. conclusions geometric modeling and stress analysis of the single toggle jaw crusher were achieved with pro/engineer® and autodesk inventor® softwares, respectively. stress analysis revealed that both the angle of twist of the eccentric shaft, 0.01° and the maximum displacement of the base frame, 0.008066 mm, were insignificant; also, spring check result was positive and summarily indicated design compliance. method of developing critical components of the jaw crusher such as: eccentric shaft, by welding a removable offset shaft before machining; journal bearing, by the use of fabricated journal housing and detachable ball bearings; and crusher jaws, by hardfacing ferro-alloy hardfacing alloy inserts to low carbon steel substrate, were found economical for easy repairs and replacement. performance evaluation of the machine showed that the actual capacity of the crusher was higher than the design capacity, owing to the selection of a higher capacity electric motor as prime mover. it was observed that the average speed of the eccentric shaft decreased with increasing mass of granite undergoing crushing and when crushing irregular-shaped than wedgeshaped lumps of granite. the methods used in developing the critical components of the jaw crusher can be adopted in developing affordable jaw crushers for artisanal miners and stone workers. more so, these offer shorter reparation time and will reduce the proliferation of moribund quarries in nigeria. recommendation the methods used in developing the critical components of the single toggle jaw crusher are sustainable and should be adopted by machine builders to boost the productivity and livelihood of artisanal miners and stones workers, and increase the profitability of small and medium scale enterprises in the minerals sector. acknowledgement the authors are grateful to the management and technical staff of advanced manufacturing technology programme, jalingo, taraba state, scientific equipment development institute, enugu, enugu state, union foundry industries, port harcourt, rivers state and m. k. technical enterprises, jalingo, taraba state, nigeria, for their technical assistance in the course of this research. references alonge, a. 2015. development of a prototype jaw-type rock crushing machine. m. eng. thesis, department of mechanical engineering, federal university of technology, akure, ondo state, nigeria. asbjörnsson, g. 2013. modelling and simulation of dynamic behaviour in crushing plants. thesis for the degree of licentiate of engineering, department of product and production development department, chalmers university of technology, göteborg, sweden. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okechukwu et al: development of a laboratory size single toggle jaw crusher for artisanal miners and stone workers. azojete,16(3):449-474. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okerex2002@yahoo.com 474 birabwa, e. 2006. small-scale stone quarrying: its contribution to people’s livelihoods. a case study of kesange parish, nama sub-county, mukuno district, uganda. m. phil. thesis, department of geography, norwegian university of science and technology, trondhein. donovan, jg. 2003. fracture toughness based models for the prediction of power consumption, product size and capacity of jaw crushers. ph. d. dissertation, mining and minerals engineering, faculty of virginia polytechnic institute and state university, blacksburg, va. elisante, e. 2009. simplification of jaw crusher for artisanal aggregate miners. journal of engineering and technology research, 1(6):102-108. juvinall, rc. and marshek, km. 2012. fundamentals of machine component design. 5th ed.: john wiley & sons, inc., new jersey. karra, vk., magerowski, aj. and szalanski, se. 1992. method of high performance jaw crushing. us patent no. 5,110,057. kelly, eg. and spottiswood, dj. 1992. introduction to mineral processing. john wiley and sons, inc., canada. khurmi, rc. and gupta, jk. 2005. a textbook of machine design. eurasia publishing house (pvt.) ltd, new delhi. mohamed, a., gilbert, g. and nicholas, m. 2014. mechanical design of a small scale mechanized stone crusher. bachelor degree thesis, department of mechanical and manufacturing engineering, university of nairobi. more, rs. and rajpal, sj. 2013. a review on the study of jaw plates of jaw crusher. international journal of modern engineering research, 3(1):518-522. niemela, r. and kieranen, c. 2008. portable apparatus for crushing rock and other hard materials and related method. us patent no. 7,448,564 b2. norton, rl. 2000. machine design: an integrated approach. prentice-hall inc, new jersey. numbi, bp., zhang, j. and xia, x. 2014. optimal energy management for a jaw crushing process in deep mines. energy, 68:337-348. okechukwu, c., dahunsi, oa., oke, pk., oladele, io., and dauda, m. 2018. development of hardfaced crusher jaws using ferro-alloy hardfacing inserts and low carbon steel substrate. jurnal tribologi, 18:20-39. pokrajcic, z. 2010. advanced comminution circuit design – essential for industry. mineral processing bulletin. metso, pp. 38-42. ravindran, s. 2010. stone crushers and dust problem. middle-east journal of scientific research, 14(12):1734-1740. rusiński, e., moczko, p., pietrusiak, d., and przybyłek, g. 2013. experimental and numerical studies of jaw crusher supporting structure fatigue failure. strojniški vestnik – journal of mechanical engineering, 59(9):556-563. undp. 2014. framework for harnessing the extractive industries for inclusive growth and development in nigeria. united nations development programme, abuja, nigeria. waguespack, c. 2013. mastering autodesk® inventor® 2014 and autodesk® inventor lttm. john wiley and sons, inc, indiana. wills, ba. 2016. mineral processing technology: an introduction to the practical aspects of ore treatment and mineral recovery. elsevier, london. zhang, j. 2014. particle technology-study notes. http://lorien.ncl.ac.uk/ming/particle /cpe124p4.html, accessed on 09 september, 2014. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):83-90 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 83 original research article thermoplastic starch biocomposite produced from corn (zea mays): comparison of plasticizers effects on mechanical properties b. d. odugbose1*, o. o. adefisan2, h. o. adeyemi3, o. t. opafola4 and o. b. olatunde3 1department of agricultural engineering, olabisi onabanjo university, ago-iwoye, nigeria. 2department of wood products engineering, university of ibadan, nigeria. 3department of mechanical engineering, olabisi onabanjo university, ago-iwoye, nigeria. 4department of civil engineering, olabisi onabanjo university, ago-iwoye, nigeria. *corresponding author’s email address: odugbose.babashola@oouagoiwoye.edu.ng 1.0 introduction the consistent and astronomical anthropogenic effect on the environment cannot be overlooked as these affect the world’s ecosystem through pollution causing factors introduced into the environment. the anthropogenic effect resulting from human activities possess great risks to life, as some of these factors leads to environmental pollution. humans’ activities over the years depended on fossil fuel as a resource for the production of many products resulting in degradation of the environment. plastics and other products produced from hydrocarbon resources tend to cause pollution in the environment because majority of these products are not biodegradable. an increase in world population resulted in the geometrical increment in the needs for plastic materials for usage resulting in large quantities of these plastics finding their way onto landfills and the ocean has evidence had shown an increase in micro-plastics in the ocean ecosystem (lusher, 2015). the use of plastic materials is on the high side as human’s disposition to its usage is high, also couple with the population boom in the world, the tonnes of used plastics create challenges of disposal as many are either ship to landfills or indiscriminately disposed into waterbodies (lusher, 2015). this phenomenon has been a major environmental challenge which requires holistic approach to developing materials that can replace petrol-based plastics example of which can be termed as green composite (wattanakornsiri et al., 2011). an example of such a material is a termed green composite that can be biodegraded in the environment (wattanakornsiri et al., 2011). it is important that such composite materials should utilized biodegradable renewable polymers as article information abstract the excessive reliance on plastic materials made from fossil-fuel based and its ineffective waste management leads to environmental pollution due to their nonbiodegradable nature. this study examined the production and testing of biocomposites from gmelina arborea wastes and thermoplastic starches as a polymer matrix. particles of g. arborea sawdust were obtained from a local sawmill while dry powdered corn starches were sourced from the chemicals market, ojota, lagos, nigeria. bio-composites were produced by mixing 40 g of corn starch, glycerol/sorbitol, and fractions of prepared g. arborea (650µm particle sizes) fibre at 0 to 20% (wt/wt of fibre to polymer matrix) were added. the slurries were poured into a mould in accordance with astm d638 for tensile strength test samples. the results revealed that the thermoplastic starches, particle sizes, plasticizers, and wood fibre loading significantly affected the tensile strengths, tensile modulus, elongation at break of the bio-composites. composites produced exhibited tensile strengths values range of 0.35 to 1.75 mpa, modulus of elasticity of 3.10 to 22 mpa, while there was a gradual reduction in elongation at break with a range of 127.4% to 111%. sorbitol-corn starch generally recorded higher tensile properties of between 1.65 to 1.75 mpa tensile strength than those produced with glycerol plasticizer which ranged between 0.35 to 0.45 mpa as fibre loading increases. it is clear that sorbitol-plasticized bio-composite gives higher values in mechanical strengths when compared to that produced from glycerol © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 february 2020 revised 16 december 2020 accepted 20 december 2020 keywords: bio-composites plastic pollution thermoplastic starch tps gmelina arborea fibre content mechanical properties odugbose et al: thermoplastic starch biocomposite produced from corn (zea mays): comparison of plasticizers effects on mechanical properties. azojete, 17(1):83-90 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 84 matrices and fibre as fillers to the matrix. composite material produced from biodegradable constituent is expected to be biodegradable when disposed of in the environment. biodegradable composite materials assist in the reduction of the long effect of plastic pollution in the environment leading to a reduction in the greenhouse gas effect (mohanty et al., 2005). biodegradable composite materials break down easily in the environment forming compost when returned to the soil (huang and netravali, 2007). these materials can easily replace petrol-based materials leading to a major shift in the material selection that is environmentally friendly (mohanty et al., 2002). sources of polymer matrices abound but researchers have looked into the use of starch as a source for matrix and this is due to its naturally renewable nature, relatively cheap, and abundance (teixeira et al., 2009, sarifuddin et al., 2012). in order for starch to be used as a polymer matrix, it undergoes thermal modification into thermoplastic starch by the addition of a plasticizer into the starch-water mixture and agitated on a high heating element (averous and boquillon, 2004). another alternative environmentally friendly material are natural fibres such as wood fibres (hardwood, wood dust and softwood) or other wide varieties of natural plant fibres, such as flax, pineapple, bamboo, hemp, cotton, kenaf, coir (ochi, 2011) which can be mixed with polymer matrices to produce a biodegradable material. puglia et al. (2003) reported that the mechanical properties of thermoplastic starch increases with the addition of natural fibres. averous et al., (2001) researched into the use of wheat starch as the polymer matrix in the development of thermoforming packaging material. wattanakornsiri et al. (2011) studied the effect on mechanical properties of the thermoplastic starch by addition of recycled paper cellulose fibres. flax and ramie fibre serves as a source of filler in the development of green biocomposite (wattanakornsiri and tongnunui, 2014). development of an environmentally friendly composite from naturally biodegradable material sources may be a means of curtailing the menace of plastic pollution. this research work is aimed at the production of bio-composite from thermoplastic corn starch (matrix) with the use of gmelina arborea fibre as fillers, looking at the fibre loading effect as well as that of the plasticizers on the mechanical properties. 2.0 materials and methodology 2.1 materials the materials used in the production of the bio-composites were sourced from different markets. chemicals such as powdered corn starch, glycerol, sorbitol were sourced from chemical market in lagos, vegetable oil from local food store while the sawdust of gmelina arborea was sourced from bodija international market sawmill in ibadan. the remaining equipment were obtained at the laboratory in which the research was carried out. digital weighing balance, flat bottom flask, beaker, an electric stove, stirrer, moulds, powdered corn starch, glycerol, sorbitol, water, gmelina arborea particles, vegetable oil, were the materials and equipment used. 2.2 fibre preparation gmelina arborea particles was obtained from the sawmill at bodija market sawmill ibadan, oyo state. the particles were sieved through some set of sieve sizes range and 650µm sieve size was eventually selected for the research (figure 1a). these were then treated with a 5% naoh solution for 4 hours and air-dried until 12% moisture content was obtain. 2.3 production of bio-composites the bio-composites test samples were produced in the laboratory in batches, with the first batch been the glycerol plasticized biocomposite which was fabricated by mixing known dried weight of corn starch with distilled water, glycerol and the filler (gmelina arborea fibre) following the method reported by adefisan and eyeowa, (2015).the mixture was heated on a hotplate with continuous stirring until gelatinization occurred. this procedure was repeated to obtain bio-composite plasticized with sorbitol by replacing glycerol with sorbitol plasticizer. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):83-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 85 the gmelina arborea fibres of 650µm particle sizes were added to the mixture at varying proportion of 0, 5, 10, 15 and 20% wt/wt of fibre to matrix according to johar and ahmad (2012). neat bioplastic was produced following the procedure above without the addition of fibre that is no fibre load, to serve as a basis for comparison; the dried sample of which is shown in figure 1b. the slurries of the produced biocomposite were poured into a dump-belled mould (figure 1c) of standard procedures (astm d638-14) with specimen dimension of length overall 165 mm, width overall 19 ± 6.4mm, the width of narrow section 13 ± 0.5mm, length of narrow section 57 ± 0.5mm, gage length 50 ± 0.25mm, the distance between grips 115 ± 5mm, a radius of fillet 76 ± 1mm and thickness 3.2 ± 0.4mm. the mould was smeared with vegetable oil (to allow easy demoulding) and the de-mould sample were dried at room temperature for 3weeks. 2.4 mechanical test 2.4.1 tensile test the biocomposite tensile test samples were produced in triplicates in accordance with astm d638-14. the test was carried out at the centre for energy research and development (c.e.r.d) at obafemi awolowo university, ile ife using the universal testing machine instron 3369load cell capacity 50 kn, manufactured in usa (figure 1d), and operated with a crosshead speed of 5 mm/mins in accordance to sarifuddin et al. (2012). 2.4.2 modulus of elasticity the modulus of elasticity or young’s modulus of the test samples was derived from the result output of the universal testing machine utm, making use of the relationship as expressed below; young’s modulus = 2.4.3 elongation at break the elongation at break expresses the capability of natural plant fiber to resist changes of shape without crack formation. it is derived from the ratio of change in length with that of the initial length and it is expressed in percentage. 2.5 statistical analysis the results obtained from the machine output (excel spreadsheet) of the test carried out were subjected to analysis using the duncan multiple range test at p < 0.05 significant level. this test is carried out in order to reveal the significant difference between the thermoplastic starch, plasticizers and wood fibre loading on the mechanical properties of the bio-composites. figure 1: (a) sieving of sawdust, (b) bioplastic, (c) test sample, (d) tensile test on machine figure 1 (a) shows the researcher sieving the sawdust in order to obtain the required particle size, while (b) shows the neat bioplastic produced and (c) and (d) shows the tensile test samples of the biocomposite produced and the material undergoing deformation on the test machine, respectively. odugbose et al: thermoplastic starch biocomposite produced from corn (zea mays): comparison of plasticizers effects on mechanical properties. azojete, 17(1):83-90 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 86 3.0 results and discussion 3.1 tensile strength the results of the tensile strengths of the bio-composites are shown in table 1 and figure 2. the tensile strengths ranged from 0.35 to 0.45 mpa and 1.65 to 1.75 mpa for the corn-thermoplastic bio-composites plasticized with glycerol and sorbitol respectively. these values compared favourably with the findings of yauri and abbot, (2014). figure 2 shows a gradual increase in the tensile strength of the bio-composite plasticized with glycerol but these strengths cannot be compared favourably to that of sorbitol as biocomposites produced with sorbitol as plasticizers performed better than that of glycerol. the tensile strength value of sorbitol plasticized biocomposite is far greater than that of glycerol. generally, the addition of g. arborea particles (5 – 20%) increases the tensile strength of the bio-composites produced. the fibre 650 µm addition generally record higher tensile strengths, suggesting that the fibre particle provided good reinforcement which is possibly due to higher tensile strength required to detach fibres from the matrices (luddee et al., 2014). it is evident that composites plasticized with sorbitol generally recorded higher tensile strengths than those made with glycerol. this may be attributed to the effective plasticization of glycerol over sorbitol thermoplastic starches which results in the reduction in the frictional forces between the starch molecules, brittleness of the composites and the reduction in tensile strength (vieira et al., 2011). statistically, there exists a significant difference (p < 0.05) between the values of tensile strength obtained for glycerol and sorbitol. similarly, the fibre loading has a significant effect on the tensile strength of the produced biocomposites. overall sorbitol plasticized bio-composites give a higher tensile strength. figure 2: variation of tensile strengths of produced bio-composite with fibre loading. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0% 5% 10% 15% 20% 0.35 0.25 0.35 0.4 0.45 1.65 1.78 1.73 1.73 1.75 te n si le s tr en g h t m p a fibre loading gly sor arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):83-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 87 table 1: duncan’s multiple range test of effects of plasticizer and fiber loading on tensile strength of bio-composite. parameters tensile strength (mpa) plasticizers glycerol 0.41b sorbitol 2.17a fibre loading (%) 0 1.38a 5 1.32ab 10 1.33ab 15 1.23ab 20 1.19b means with the same letters are not statistically different (p < 0.05) 3.2 tensile modulus of elasticity the tensile modulus of elasticity of the bio-composites made from corns thermoplastic starch fall between 3.10 to 22 mpa. in specific terms, the values of the tensile modulus of elasticity for glycerol plasticized biocomposite increases gradually from 3.1 to 5 mpa. although there is a slight increment in the modulus of elasticity between 0% to 5% fibres loading, the increment exhibits a much higher value as the fibre loading increases with the highest value obtained at 20% fibre content as shown in figure 2. sorbitol plasticized bio-composite also shows an increase in tensile modulus as the fibre loading percent increases with the highest value obtained at 20% fibre loading at 22 mpa. these values show same pattern as obtained by boudjema and bendaikha (2015). the gradual increase in the modulus of elasticity as the fibre loading increases can be attributable to the increased fibre-fibre interaction with the reduction in the thermoplastic starch matrices. biocomposite produced from sorbitol-corn starch thermoplastic exhibited a high value of modulus of elasticity than that obtained for glycerol plasticized bio-composite. the result obtained from the tensile properties tested shows similarity with those reported by other researchers for lignocellulose fibre mixture with thermoplastic starches resulting in bio-composite (ramírez et al., 2011). the explanation for this phenomenon is the compatibility of the chemical and structural composition of the matrix and the fibre of the plant used as reinforcement resulting in the improvement of the mechanical properties of the bio-composite (guimaraes et al., 2010; averous and boquillon, 2004). statistical analyses (duncans’ multiple range test p < 0.05) (table 2) revealed a significant difference between the plasticizers on the modulus of elasticity of the bio-composites produced showing evidently that fibre loading exerts an effect on the tensile modulus as well. figure 2: the effect of fibre loading on the modulus of elasticity of corn-plasticized biocomposite. 3.08 3.24 3.55 4.67 5.20 7.08 10.51 11.60 17.70 21.45 0.00 5.00 10.00 15.00 20.00 25.00 0% 5% 10% 15% 20% m o d u lu s o f el a st ic it y ( m p a) fiber loading gly sor odugbose et al: thermoplastic starch biocomposite produced from corn (zea mays): comparison of plasticizers effects on mechanical properties. azojete, 17(1):83-90 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 88 table 2: duncan’s multiple range test of effects of plasticizer and fiber loading on modulus of elasticity of tps bio-composite. parameters tensile modulus (mpa) plasticizer glycerol 3.0b sorbitol 16.8a fibre loading (%) 0 6.6d 5 7.1d 10 9.6c 15 11.3b 20 15.1a means with the same letters are not statistically different (p < 0.05) 3.3 elongation at break the elongation at break for different fiber contents is presented in figure 3. figure 3: effect of fiber content on elongation at break of biocomposite. as shown from figure 3, the elongation at break decreased monotonically as the fibre loading increases from 0% to 20% that is from 114.4% to 111.2% and 127.8% to 111.2% for the cornglycerol and corn-sorbitol bio-composites respectively. these observations are in conformity with the reports of talib et al. (2010). the incorporation of 100 % tps matrix elongated the biocomposites due to its elasticity. as the gmelina arborea fibre loading increases, the elasticity of thermoplastic starch (tps) was reduced by the increment in the fibre. the rigid interface between the matrix and the fibre which is responsible for level of deformability reduces as fibre loading increases thereby leading to a reduction seen in the elasticity of tps, this assertion agrees with rozman et al. (2005). at higher fibre loading, the domination of fibre-matrix interaction diminished being replaced by filler-filler interaction. this effect is because fibre incorporation imparts rigidity and restrains the deformation on the matrix. this often leads to an inevitable decrease in the degree of the ductility of the material (belhassen et al., 2009). it is evident from the result obtained in this work that tensile properties of bio-composite produced are in tandem with other research work reported by researchers in the area of lignocellulose fibres or cellulose fibres used as fillers in tps (torres et al., 2007; woehl et al., 2010). this phenomenon is due to the compatibility between matrix and reinforced fibres structurally and chemically. due to the chemical nature of both starch and fibre a linkage is formed at the cellulose chain which tends to influence the performance and mechanical properties of the bio-composite (ma et al., 2005; mo et al., 2010). 114.4 114 113.5 113 111.2 127.4 121.9 118.8 114.6 111.8 100 105 110 115 120 125 130 0% 5% 10% 15% 20% el o n g a ti o n ( % ) fibre content gly sor arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):83-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odugbose.babashola@oouagoiwoye.edu.ng 89 4.0 conclusion this study shows that bio-composite can be produced with the incorporation of g. arborea fibre particles in a corn-thermoplastic starch matrix plasticized with sorbitol and glycerol, with the test samples achieving a moisture content of 12%. the different plasticizers used in this work affected the tensile properties of bio-composites produced with that of sorbitol plasticized bio-composite having a higher influence. a steady increase in the tensile strength and modulus of elasticity as the fibre loading increases while the elongation at break reduces with increase in fibre content was witnessed. the fibre used in this work 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corn starch and recycled paper cellulose fibres. songklanakarin journal of science and technology, 33(4): 461-467. woehl, ma., canestraro, cd., mikowski, a., sierakowski, mr., ramos, lp. and wypych, f. 2010. bionanocomposites of thermoplastic starch reinforced with bacterial cellulose nanofibres: effect of enzymatic treatment on mechanical properties. carbohydrate polymers, 80: 866–873. yauri-birnin, au. and abbot, ap. 2014. effect of starch composition on the strength of compression moldable starch-wood bio-composite materials. research and reviews: journal of material sciences, 2(4): 10-13. arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 225-236 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng __________________________________ *corresponding author e-mail address: nddyaviara@yahoo.com, jibolarufai@gmail.com 225 original research article empirical analysis of traditional akara frying process n. a. aviara1, m. o. olarinde2, a. r. nasirudeen3, d. lasisi3, l. a. balogun3, s. o. ogundare³ and f. o. ogunsola3 1department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria 2department of agricultural and environmental engineering, university of ibadan, ibadan, nigeria 3department of agricultural and bio-environmental engineering, oyo state college of agriculture and technology, igboora, nigeria article information received: october, 2018 accepted: december, 2018 keywords: empirical analysis traditional akara physical properties frying process abstract akara results from frying of fermented batter which after frying gives a dome –like shape, it has a brown crust and burnt material at the edges. information on the existence of a mechanical device with capability for frying akara and carrying out turning operations appears to be very scarce. an empirical analysis of the traditional akara frying process was carried out in order to solve the above problem. the effect of different batter concentration (11g/ml, 13g/ml and 17g/ml) and spoon diameter-depth ratio (3.4.4.0,4.2) on the physical characteristics, frying time and frying rate of akara was investigated. the physical characteristics which include crust thickness, level of shrinkage, oil consumption, akara weight, density, surface area and extent of burnt material formation. data obtained were subjected to statistical analysis using excel and spss. the results showed that crust thickness, level of shrinkage, oil consumption, and burnt material increased with increase in concentration, frying time, weight, density and surface area also increased with increase in concentration. the result also indicates that crust thickness, level of shrinkage, oil consumption, weight, density, surface area, burnt material, frying time, decreases with increase in spoon diameter-depth ratio. statistical analysis of variance (anova) showed that all the processing variation and their interaction had significant effects on the physical characteristics of akara at 1% of significance. the model yielded coefficients that enabled the akara physical characteristics to be predicted with high coefficient of determination. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction akara (fried bean cake) is a popular food in nigeria and other west african countries (ngoddy et al., 1986; henshaw and lawal, 1993; ekariko, 2005), and form part of diet for most ethnic groups in http://www.azojete.com.ng mailto:nddyaviara@yahoo.com mailto:jibolarufai@gmail.com aviara, et al. empirical analysis of traditional akara frying process. azojete, 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 226 nigeria. nigerians usually eat it as breakfast with ogi, or lunch with gari or even dinner with eko. akara is a traditional african food made by deep frying cowpea paste that has been whipped and seasoning with salt, pepper, onions and other optional ingredients. the outer crust of akara is crisp and the interior is spongy like bread. it is considered to be the most commonly consumed cowpea based food in west africa (henshaw & lawal, 1993;asare et al., 2013). akara is made mainly from cowpea and other sources like maize―monsa‖.it can be fried with vegetable oil, palm oil, and other edible oils. it is a staple food which mostly consumed in nigeria and other west african countries including ghana, togo, benin, mali and gambia. akara is prepared mainly for sale and consumption for breakfast and snacks. akara is a popular recipe in nigeria but its production depends on the different effects on the physical characteristics of akara such as its sphericity, thickness, diameters in terms oflength, volume and volumetric index as well as its weight (steinkraus, 1994); akara is a deep-fat fried ball prepared from whipped cowpea paste, flavoured with pepper, onion and salt (mcwatters, 1983; olapade et al., 2004). whipping of the paste is usually done prior to the addition of other ingredients to incorporate air and enhance the formation of stable foam (ngoddy, et al., 1986; hung and mcwatters 1990). the paste obtained through milling dehulled and cleaned cowpea seeds can be processed into moin moin and akara by steaming or deep-fat frying of the paste respectively (mcwatters, 1983). akara is the most common cowpea-based product in west africa (reber, 1983), which makes it contribution to diet particularly significant. blending and whipping are important steps in processing of cowpea into akara. blending clearly aids in reducing the particle size of paste to a more acceptable level and thus aiding in better distribution of moisture. whipping incorporates air into paste, thus making it foam and giving it good dispensing properties and frying qualities (mbofung et al., 2002). cowpea is a good source of protein in the tropics with the seed containing appreciable amounts of lysine and tryptophan but is deficient in methionine and cystiene when compared to animal protein. the crop therefore plays a critical role in the lives of millions of people in africa and other parts of the developing world, where it is a major source of dietary protein that nutritionally complements staple low-protein cereal and tuber crops. it is also a valuable and dependable commodity that produces income for farmers and traders (singh et al., 2002; langyintuo et al., 2003).a lot of researches has been conducted on other products such as turkey, chicken, and doughnut but not much has been carried out on akara processing and production, hence the study aimed at studying the empirical analysis of traditional akara frying process. 2.0 materials and methods 2.1 preparation of akara cowpea was sourced locally at bodija market in ibadan, oyo state. 650 g weight of cowpea was soaked inside a container for five minutes, then the soaked cowpea was dehulled traditionally using hands by rubbing it between two palms. it was then cleaned by separating the coat from the grains. 320 g weight of onions and peppers were mixed with cleaned cowpea and the mixture was then milled. after milling, the viscosity of batter was taken at 11g/ml, 13g/ml and 17g/ml by adding different quantity of water. 1250 ml volume of oil was poured inside a frying pan and placed on fire. the frying was conducted at three different spoon diameters–depths. the frying time were obtained by the addition of time of first turning of akara ball with the time of second turning. the oil http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 227 temperature before frying was noted as well as oil consumed by akara ball was determined. the experiment was repeated five times. figure 1: frying of akara ball figure 2: akara ball inside the net after frying for cooling 2.2 determination of physical characteristics 2.2.1 viscosity three different sizes of spoon were used with three levels of viscosity at 11g/ml, 13g/ml, and 17g/ml of butter viscosity respectively. viscosity or concentration were expressed as c = � � (1) where, m = mass of batter (g) v = volume of batter (ml) c = viscosity or concentration (g/ml) of batter 2.2.2 frying time (ft) the time of frying with size was calculated by adding the time of first turning with the time of second turning �� = ��� � ��t (2) where, ft= frying time (seconds) ft1 = time of first turning (seconds) ft2 = time of second turning (seconds) 2.2.3 diameter-depth ratio this is the ratio of the diameter of spoon (in mm) to the depth of spoon (in mm) dd = �� �� (3) where, dd = diameter – depth ratio sd = diameter of spoon (mm) sd = depth of spoon (mm) 2.2.4 crust thickness the crust thickness of akara ball was obtained by the use of vernier caliper. it is measured in mm 2.2.5 level of shrinkage the levels of shrinkage were calculated using the expression. �� = �� �� (4) where, ��= level of shrinkage (mm) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al. empirical analysis of traditional akara frying process. azojete, 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 228 ��= volume of spoon (ml) ��= weight of akara(g) weight of akara ball each weight of akara ball was obtained by weighing each akara ball on an electric weighing balance. 2.2.6 density of akara ball the density of akara ball were expressed as d = �� �� (5) where, d = density of akara ball (g/ml) mw = weight of akara ball (g) vp = volume of akara ball (ml) 2.2.7 surface area of akara (cm2) the surface area of each akara ball was obtained using the method of coating. this method of cooking was wrapping of akara ball with foil paper and cut off the excess paper. then, the foil paper was removed from akara ball and spread on a graph sheet. the shape of the foil paper on the graph sheet was traced and the surface area of akarawas obtained by counting the numbers of square occupied by foil paper. 2.2.8 the extent of burnt material formation the extent of burnt material formation was obtained by the use of vernier caliper. it is measured in mm. 2.2.9 oil consumption (ml) the volume of oil consumed by akara ball were obtained by measuring the initial volume of oil before frying and final volume of oil after frying �� � �� −�� (6) where, �� = oil consumption (ml) � � = initial volume of oil before frying (ml) �� = final volume of oil after frying (ml) note – neglect the volume of oil evaporated or sublimed by heat. 2.3 data analysis the results obtained were analysed and evaluated using turkey and duncan multiple analysis of variance, as well as multiple regression models.data analysis were used to determine the variation of physical characteristics of akara ball and frying parameters such as frying time, frying rate, density, oil consumption, level of shrinkage, crust thickness, weight, extent of burnt material and surface area at three different levels of batter viscosity and three spoon diameter-depth respectively. 3.0 results and discussion the result of frying parameters and physical characteristics determined for each batter concentration at different spoon sizes are presented in tables 1, 2, and 3 respectively. from table 1, it can be seen that the shortest frying time for concentration of 11 g/ml was obtained at spoon size a having pan diameter-depth ratio of 4:2 and the longest frying time was obtained at http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 229 spoon size c having light spoon diameter-depth ratio of 3.4. similar observations were obtained for the frying time when batter concentrations were 13 g/ml and 17 g/ml respectively (table 2 and 3). table 1: akara physical characteristics, frying time and frying rate for different spoon size at batter concentration of 11g/ml. s/n measured parameters spoon size a spoon size b spoon size c 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 spoon depth (mm) spoon diameter (mm) spoon diameter depth ratio crust thickness (mm) extent of burnt material formation(mm) level of shrinkage oil consumption (ml) oil temperature (0c) time of 1st turning (sec) time from 1st turning to 2nd turning (sec) frying time (sec) spoon volume (ml) variation of akara weight (kg) density (kg/ml) frying rate (no/hr) surface area (cm2) 13 55 4.2 1.9 1.8 4.6 6.9 205 240 231 471 35 0.056 0.00054 180 36 15 60 4.0 2.0 1.6 4.8 7.6 198 245 241 486 40 0.051 0.00057 156 43 20 68 3.4 2.1 1.7 5.0 8.0 204 253 238 491 42 0.065 0.00061 120 45 3.1 observable phenomena that occur during frying of akara the first observed phenomenon after pouring the batter into the frying pan is rapid evaporation of water from the surface of the batter because of the high temperature of the frying oil and there was little reduction in temperature. there was a puffing (bubble like) at the top of akara because of loss of moisture. after that, due to the loss of moisture from the batter by hot oil and oil uptake by batter due to high temperature, crust was started to develop at the edges of akara. after the first turning of akara (1st turning) akara was swelled up and then gradually shrunk down due to loss of moisture and gradual increase in frying temperature. burnt material started to develop at the ring of akara which indicates that akara is ready. sequences of events that take place during the frying of mass: (a) rapid evaporation of water from the batter by hot oil and oil uptake by batter due to high temperature (b) formation of crust (c) swelling (d) shrinkage (e) burnt material formation. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al. empirical analysis of traditional akara frying process. azojete, 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 230 table 2: akara physical characteristics, frying time and frying rate for different spoon size at batter concentration of 13g/ml s/n measured parameters spoon size a spoon size b spoon size c 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 spoon depth (mm) spoon diameter (mm) spoon diameter depth ratio crust thickness (mm) extent of burnt material formation (mm) level of shrinkage oil consumption (ml) oil temperature (0c) time of 1st turning (sec) time from 1st turning to 2nd turning (sec) frying time (sec) spoon volume (ml) variation of akara weight (kg) density (kg/ml) frying rate (no/hr) surface area (cm2) 13 55 4.2 1.8 1.7 4.4 6.5 202 241 232 473 35 0.054 0.00055 178 34 15 60 4.0 2.1 1.5 4.6 7.3 200 243 246 489 40 0.053 0.00058 161 40 20 68 3.4 2.3 1.8 4.9 8.1 204 249 261 510 42 0.068 0.00064 130 42 table 3: akara physical characteristics, frying time and frying rate for different spoon size at batter concentration of 17g/ml s/n measured parameters spoon size a spoon size b spoon size c 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 spoon depth (mm) spoon diameter (mm) spoon diameter depth ratio crust thickness (mm) extent of burnt material formation (mm) level of shrinkage oil consumption (ml) oil temperature (0c) time of 1st turning (sec) time from 1st turning to 2nd turning (sec) frying time (sec) spoon volume (ml) variation of akara weight (kg) density (kg/ml) frying rate (no/hr) surface area (cm2) 13 55 4.2 1.7 1.6 4.2 6.6 201 240 230 470 35 0.053 0.00049 172 35 15 60 4.0 2.0 1.5 4.3 7.4 210 245 241 486 40 0.056 0.00056 164 42 20 68 3.4 2.1 1.7 4.5 8.2 215 259 260 519 42 0.064 0.00063 136 44 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 231 table 4: result of anova on the crust thickness of akara source type iii sum of squares df mean square f sig. corrected model 13.260a 8 1.658 23.47 0.000 intercept 145.622 1 145.622 1642.52 0.002 dp 8.330 3 2.777 72.154 0.000 c .110 2 .055 9.462 0.000 dp * c .050 3 .017 2.341 0.025 error .031 18 .000 total 151.980 27 corrected total 13.260 26 r squared = 0.894 (adjusted r squared = 0.850) 3.2 crust thickness the relationship between crust thicknesses, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: ct � 0.952 − 2.447dp − 0.062c � 0.173dpc − 0.474dp2 � 0.011c2, r2 � 0.994 (7) where: ct = crust thickness in mm, c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, dpc, dp² and c² terms made 99.4% significant contributions to the predictive capacity of the equation. in a similar vein, the anova results show thatdp, c and dpc had statistical significant effect on crust thickness at 99.4% (table 4). this implies that the crust thickness obtained at different diameter-depth ratio and concentrations are significantly different. 3.3 level of shrinkage the relationship between level of shrinkage, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: sh = 6.316 – 0.514dp 0.226c + 0.047dpc – 0.019dp² + 0.003c², r² = 0.968 (8) where: sh = level of shrinkage in mm, c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, and dp² term made 96.8% significant contributions to the predictive capacity of the equation. similarly, the result of anova shows that dp, c and dpc had statistical significant effect on sh (level of shrinkage) at 99.4% (table 5). this implies that the level of shrinkage obtained at different diameter-depth ratio and concentrations are significantly different. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al. empirical analysis of traditional akara frying process. azojete, 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 232 table 5: result of anova on the level of shrinkage of akara source type iii sum of squares df mean square f sig. corrected model 1.767a 8 .221 12.58 0.000 intercept 524.273 1 524.273 28953.61 0.000 dp 9.740 3 3.247 51.642 0.000 c 1.420 2 .510 2.306 0.011 dp * c .020 3 .007 1.432 0.000 error .000 18 .000 total 570.330 27 corrected total 1.767 26 r squared = 0.968 (adjusted r squared = 0.961) 3.4 frying time the relationship between frying times, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: tf = 478.315 113.270dp +1.624c + 9.111dpc -17.406dp² + 1.079c², r² = 0.950 (9) where: tf = frying time (sec), c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, dpc, dp² and c² term made 95.0% significant contributions to the predictive capacity of the equation. in a similar vein, the anova results show that dp, c and dpc had statistical significant effect on frying times at 95.0% (table 6). this implies that the frying time obtained at different diameter-depth ratio and concentrations are significantly different. table 6: result of anova on the frying times of akara source type iii sum of squares df mean square f sig. corrected model 6900.000a 8 862.500 751.23 0.000 intercept 5955029.894 1 5955029.894 216421.24 0.000 dp 5645.000 3 1881.667 263.82 0.007 c 428.500 2 214.250 126.19 0.000 dp * c 817.000 3 272.333 78.32 0.018 error 238.06 18 .196 total 6445575.000 27 corrected total 6900.000 26 r squared = 0.950 (adjusted r squared = 0.938) 3.5 oil consumption the relationship between oil consumption, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: oc = 10.498 3.743dp -0.097c + 0.344dpc 0.755dp² + 0.017c², r² = 0.985 (10) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 233 where: oc = oil consumption in ml, c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, dpc, dp² and c² term made 98.5% significant contributions to the predictive capacity of the equation. in a similar vein, the anova results show that dp, c and dpc had statistical significant effect on oil consumption at 98.5% (table 7). this implies that the oil consumption obtained at different diameter-depth ratio and concentrations are significantly different.results show that the diameter-depth ratio of 3.4 is statistically higher that diameter-depth ratio of 4.0 and significantly lower than diameter depth ratio of 4.8. table 7: result of anova on the oil consumption of akara source type iii sum of squares df mean square f sig. corrected model 9.720a 8 1.215 7.154 0.021 intercept 1337.859 1 1337.859 3251.72 0.000 dp 9.290 3 3.097 1.843 0.001 c .085 2 .043 .721 0.000 dp * c .250 3 .083 .284 0.000 error .000 18 .000 total 1488.240 27 corrected total 9.720 26 r squared = 0.985 (adjusted r squared = 0.981) 3.5 density the relationship between variation of density, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: d = 0.001 + 0.000dp 1.476e-005c 3.146e-005dpc 6.533e-005dp² + 3.035e-006c², r² = 0.993 (11) where: d = density kg/ml, c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, dpc, dp² and c² term made 99.3% significant contributions to the predictive capacity of the equation. in a similar vein, the anova results show that dp, c and dpc had statistical significant effect on density of akara 99.3% (table 8). this implies that the density obtained at different diameter-depth ration and concentrations are significantly different. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al. empirical analysis of traditional akara frying process. azojete, 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 234 table 8: result of anova on density and spoon diameter ratio on akara concentrations source type iii sum of squares df mean square f sig. corrected model 5.347e-008a 8 6.683e-009 124.896 .000 intercept 8.142e-006 1 8.142e-006 42631.052 .000 dp 4.567e-008 3 1.522e-008 326.289 .007 c 2.025e-009 2 1.012e-009 62.324 .000 dp * c 3.725e-009 3 1.242e-009 1.231 .617 error .000 18 .000 total 8.963e-006 27 corrected total 5.347e-008 26 a. r squared = 0.993 (adjusted r squared = 0.986) 3.6 surface area the relationship between variation of surface area, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: d = 107.675 33.638dp 0.413c + 3.674dpc 9.723dp² 0.033c², r² = 0.939 (12) where: sa = surface area in cm², c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, dpc, dp² and c² term made 93.9% significant contributions to the predictive capacity of the equation. in a similar vein, the anova results show that dp, c and dpc had statistical significant effect on surface area at 93.9% (table 9). this implies that the surface area obtained at different diameter-depth ratio and concentrations are significantly different. table 9: result of anova on surface area in cm² source type iii sum of squares df mean square f sig. corrected model 404.667a 8 50.583 196.73 .000 intercept 39042.300 1 39042.300 24518.68 .000 dp 372.000 3 124.000 172.81 .000 c 29.500 2 14.750 10.065 .000 dp * c .000 3 .000 .004 .000 error .000 18 .000 total 43845.000 27 corrected total 404.667 26 r squared = 0.993 (adjusted r squared = 0.986) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 235 3.7 burnt materials the relationship between burnt materials, spoon diameter depth ratio and akara concentration could be adequately expressed using multiple regression models presented as: d = 2.061+1.078dp 0.073c –0.147dpc +0458dp² +0.009c², r² = 0.929. (13) where: bm = extent of burnt materials in mm, c = concentration in g/ml, dp = diameter depth ratio a t-test of coefficient shows that the constants dp, c, dpc, dp² and c² term made 92.9% significant contributions to the predictive capacity of the equation. in a similar vein, the anova results show that dp, c and dpc had statistical significant effect on burnt materials at 92.9% (table 10). this implies that the burnt materials obtained at different diameter-depth ration and concentrations are significantly different. table 10: result of anova on the variation of burnt materials on akara concentrations source type iii sum of squares df mean square f sig. corrected model .307a 8 .038 15.921 .000 intercept 69.713 1 69.713 2689.387 .000 dp .208 3 .069 48.696 .000 c .047 2 .024 53.294 .000 dp * c .052 3 .017 2.82 .107 error .170 18 1.070 total 74.310 27 corrected total .307 26 r squared = 0.993 (adjusted r squared = 0.986) 4.0 conclusion the evaluation of frying parameters and physical characteristics using the traditional frying method for different pan diameter-depth ratio and batter concentration revealed the following: crust thickness, level of shrinkage, oil consumption and burnt material increased with increase in concentration. frying time, weight, density and surface area also increases with increase in concentration. crust thickness, frying time, weight, density, surface area and oil consumption decreased with increase in diameter-depth ratio. references asare, at., agbemafle, r., adukpo, ge., diabor, e. and adamtey, ka. 2013. assessment of functional properties and nutritional composition of some cowpea (vigna unguiculata l.) genotype in ghana. arpn journal of agricultural and biological science. 8: 465-469. ekariko, p. 2005. akara: the fast food with a painstaking preparation. afrique 16:14. henshaw, fo., lawal, sa. 1993. effects of processing methods on the functional properties of cowpea flour. journal of tropical science 33: 377 – 385. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aviara, et al. empirical analysis of traditional akara frying process. azojete, 14(sp.i4):225-236. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 236 hung, yc., mcwatters, kh. 1990. effect of holding time on the functionality of cowpea paste and quality of “akara”. journal of food science, 55(2):558-559. langyintuo, as., lowenberg-deboer, j., faye, m., lambert, d., ibro, g., moussa, b., kergna, a., kushwaha, s., musa, s., ntoukam, g. (2003). cowpea supply and demand in west africa. field crops research 82:215–231. mbofung, cmf., njintang, yn., waldron, kw. 2002. functional properties of cowpea-soy-dry red beans composite flour paste and sensorial characteristics of akara (deep fat fried food): effect of whipping conditions, ph, temperature and salt concentration. journal of food engineering 54, 207-214. mc watters, kh. 1983. compositional, physical and chemical characteristics of akara processed from cowpea paste prepared from cowpea paste and nigeria cowpea flour cereal chemistry 60(5): 333-336. ngoddy, po., enwere, nj. and onuorah, vt. 1986. cowpea flour performance in”akara” and “moinmoin” preparation. tropical science 26:101-109. olapade, aa., ugokwe, pu., ozumba, au., solomon, hm., olatunji, o. and adelaja, so. (2004). physico-chemical properties of premixes for preparation of “akara”. nigerian food journal (22): 54-59. reber, ef., eboh, l., aladeselu, a., brown, wa. and marshall dd. 1983. development of high-protein low-cost nigerian foods. journal of food science. 48:217. singh, bb., ehlers, jd., sharma, b., freire, filho fr. 2002. recent progress in cowpea breeding. in: fatokun ca, tarawali sa, singh bb, kormawa pm, tamo m (eds) challenges and opportunities for enhancing sustainable cowpea production. international institute of tropical agriculture, ibadan, nigeria, pp 22–4 steinkraus, kh. 1994. national significance of fermented foods. food research international, 27: 259-267. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):547-558 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 547 assessment of fufu production technologies in ogun state, nigeria o. k. owolarafe1, b. o. adetifa2*, a. c. oyekanmi2, t. g. lemikan2 and t. m. samuel2 (1 department of agricultural and environmental engineering, faculty of technology, obafemi awolowo university, ile-ife, p.m.b 13, osun state, nigeria. 2 department of agricultural engineering, faculty of engineering, college of engineering and environmental studies, olabisi onabanjo university, 112104, ibogun, ifo, ogun state, nigeria) *corresponding author’s email address: olusola.adetifa@oouagoiwoye.edu.ng abstract the quality of fufu has been known to vary from one location to another. the processing technique may be responsible for this variation in quality. a study was carried out to investigate the different processing technologies adopted for production of fufu from cassava at different processing centres in abeokuta and ilaro, ogun state. hundred fufu processing centres were randomly selected, while data was collected using structured questionnaire, sensory analysis and physical observation. information about the ownership, operator, enterprise, source of water supply, unit operations alongside their equipment and the waste disposal methods were gathered. results showed that most fufu processing centres were owned by individuals. most of the unit operations were carried out manually usually by women with low education level. plastic drums and concrete pots were commonly used for soaking cassava for 3-5 days. cassava mash is sun-dried for an average of 2.79±1.1 days and packaged into nylon or jute bags. cassava peel and chaff are often reused while the wastewater is either drained into pits or left unattended to. delay in processing cassava tubers, increase in the length of soaking, ineffective dewatering method, unhygienic source of water for fufu processing, etc. were some of the factors observed to affect the physical quality of fufu. statistical analysis shows that the categories in most of those unit operations do not have equal probabilities of occurrence in the population. it is therefore imperative to develop appropriate technologies affordable by the small scale processors for the people in the area. keywords: cassava mash, decanting, soaking, dewatering, cassava waste disposal 1. introduction cassava is an important food crop produced in nigeria in large quantity. the country is the leading producer of cassava in the world with an annual production of about 45 million tonnes (asante-pok, 2013). owing to the large production, the crop is processed into many food items such as fufu, gari, lafun etc. fufu (also called utara akpu) is the meal of soaked fermented cassava roots which is widely consumed in nigeria (iwuoha and eke, 1996). it is one of the major food forms of cassava fermentation, which is reconstituted by stirring in boiling water to form dough and eaten with flavoured sauces. in some areas, low cyanide cassava roots can be boiled or steamed and pounded into fufu (hahn, 1988). fufu contains 6.50, 1.68, 1.32, 1.84, 1.42 and 87.24% moisture, protein, fat, ash, crude fibre and carbohydrate, respectively (bamidele et al., 2015). the unit operations involved in the production of fufu using the traditional method are as follows: the cassava tubers are peeled, washed, cut into thick chunks and steeped in water in earthenware pots or in a slow-flowing stream for 4-5 days to ferment, soften and produce a characteristic of retted cassava meal. the tubers are disintegrated in clean water, sieved and allowed to settle for decantation of water; the sediment is the fufu (raw) (iwuoha and eke, 1996; uzogara et al., 1990). umeh and odibo (2014) identified two modified methods used in fufu production. these include peeling the cassava tubers, cutting them into smaller cubes of about 2-4 cm before soaking, or grating the tubers into a mash, bagging the mash and pressing out some liquid before soaking the bag in water. similarly, omodamiro et al. (2012) carried out the production of fufu from yellow cassava roots using the odourless flour technique. mailto:olusola.adetifa@oouagoiwoye.edu.ng http://www.azojete.com.ng owolarafe et al.: assessment of fufu production technologies in ogun state, nigeria. azojete, 14(4):547558. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 548 one potential problem in processed fufu is the flavour of the product, which may be undesirable to many people. another major problem with fufu production is that the quality of the product varies from one processor to the other and from one processing batch to the other by same processor. factors that could be responsible for the variability of quality of fufu include; the size to which the roots are cut prior to soaking (okafor et al., 1984), variety differences in dry matter content and the quality of roots or water used for soaking. the fermentation process of fufu production is initiated as a result of chance inoculation by microorganisms from the environment. although convenient, there are concerns about the reliability of this process, the control of which is the basis of all technological measures that are used to obtain product at a defined quality. the presence of unspecified microorganisms complicates the control of the fermentation process and leads to the production of objectionable odours. such problems have led to the development of several other processing techniques suitable for odourless fufu (okpokiri et al., 1984; ezeronye, 2003). okolie et al. (1992) proposed a modification of the microbiological process in order to upgrade the cassava product but in practice is yet to receive great attention. according to oyewole and sanni (1995), cassava processors confirmed that shorter fermentation periods (2-3 days) are required during the dry (hot) season while longer fermentation periods (3-5 days) are required during the rainy (cold) season for proper retting of cassava for fufu production. some processors expose fermenting roots to direct sunlight as a means of enhancing the fermentation process. achi and akomas (2006) carried out a comparative assessment of fermentation techniques in processing of fufu. two major techniques were identified. in one process, fufu was produced by steeping cassava tubers for 48 hours followed by grating and fermenting for another 48 hours while the other technique involved grating cassava tubers and dewatering/fermentation for 24 hours before re-steeping for another 48 hours (achi and akomas, 2006). they further observed that though there was no difference in colour or texture due to the processing method, the fermentation of grated cassava produced a more acceptable product. previous research has shown that there are differences in processing methods utilized and level of quality of fufu produced in ogun state, but this is insufficient. some specifics of the unit operations are not available in literature. some of this specifics include; duration of operation, equipment used for operation, tasks carried out before and after an operation, etc. the variation in these specifics is capable of leading to variation in the quality of fufu from one location to another. this work is therefore aimed at investigating and assessing the different processing technologies adopted for production of fufu from cassava at different processing centres in abeokuta and ilaro, ogun state. 2. materials and methods 2.1 study area, sampling technique and sample size ogun state was selected as the study area because of the predominant fufu processing activities going on within the state. the state captures a variety of situations in terms of access to urban and rural markets, importance of cassava processing activities, prominence of fufu processing as a source of livelihood, and type of fufu produced. ogun state has been divided into four agricultural zones, i.e. ilaro, ijebu-ode, ikenne and abeokuta by ogun state agricultural development programme (ogadep) (adewuyi et al., 2009). for this study, two of the agricultural zones were selected i.e. ilaro and abeokuta because they are predominantly fufu production area (oyewole and sanni, 1995; adebayo et al., 2003). arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 547-558. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 549 fufu processing communities were selected using systematic sampling method from the agricultural zones. twelve fufu processing communities were selected in ilaro zone (i.e. oja-adan, ado-odo, oke-odan, ipokia, ihumbo, igbesa, idolehin, sawonje, aton, agbara, ibese and isaga), while thirteen fufu processing communities were selected in abeokuta zone (i.e. odeda, ifo, ibogun osungboye, ibogun akinside, ibogun egbeda, ibogun fashina, imala, arigbajo, osiele, itori, olugbo, wasimi and ajegunle). within each of the processing communities, four fufu processing centres were randomly selected; hence, 100 fufu processing centres were investigated. the major difference in the sample populations is the perceived difference in fufu production technologies and the quality. 2.2 data collection and analysis the methods used to collect data from each specified location include interview, using structured questionnaire, sensory analysis and physical observation. the questionnaire used was divided into two major parts as follows i.e. fufu processing method and operator’s perception of fufu industry. the section on processing method focused on collecting comprehensive information on the processing centre. the information gathered include, the ownership status of the centre, number of employee, educational level of operator, age of the enterprise, predominant sex, and source of water supply. the amount of raw materials used was also elicited. the unit operations involved were investigated to determine the method and equipment in use. the unit operations investigated include; peeling, washing, soaking, water replacement, decanting of effluence/wastewater, pulverization/pulping/mashing, dewatering the mash, drying dewatered mash, cooking, packaging and sales. aside the unit operations, other issues investigated include; waste generated and uses, estimate of fufu processing waste/by product and general cleanliness of processing centre. the section on operator’s perception of fufu industry was used in gathering information on the problems confronting fufu processing centres and suggested solution. physical observation was used to note the general outlook of the processing sites and activities of the processors a preliminary sensory analysis was carried out which involved the collection and evaluation of samples of fufu sold at the markets around six different fufu processing centres. the samples were accessed in terms of colour, odour, texture and taste. the data obtained was statistically analysed using both descriptive and inferential statistics appropriately. the data collected from the questionnaire were presented and analysed using graphs and other descriptive statistical tools to enhance proper interpretation. one sample chisquare test, binomial test and kolmogorov-smirnov test were used to test the null hypothesis of equal probabilities. it was also used to make generalisation from a sample to a population. these were done using spss 20 software by ibm and microsoft excel, 2010. 3. results and discussion 3.1 fufu processing enterprise this study investigated the ownership of fufu processing enterprises across the selected agricultural zones. it was observed that 83% of these enterprises were owned by individuals. also, 43% of the individual processing centres have being existing for more than 5 years, 16% for 5 years; while, 12% have existed for less than 5 years (figure 1). figure 1 also shows that 40% of the enterprises were owned by group of processors; 20%, 15% and 4% of these enterprises have existed for more than 5 years, approximately 5 years and less than 5 years, respectively. it was also estimated that 36.4% of the enterprise owned by government have existed for more than 5 years, 27.3% for 5 years and 36.4% for less than 5 years. statistical analysis using one sample chiowolarafe et al.: assessment of fufu production technologies in ogun state, nigeria. azojete, 14(4):547558. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 550 square test revealed a significant difference in the proportions of individual, government and group ownership. this shows clearly that cassava processing into fufu is dominated by individuals. this result corroborates with that of okorji et al. (2003) who observed that cassava processing centres in the rural communities of ahiazu, ikeduru, mbaitoli, owerri and ohaji egbema in imo state, nigeria were completely owned by individuals; but on the other hand, adebayo (2009) ascribed the ownership of cassava processing centres to households. figure 1: fufu production enterprise and employees 3.2 fufu production employees in the data obtained, it was observed that higher percentage of processing centres employs 3-6 employers this result is presented in figure 1. this is similar to the report of adebayo (2009) that the households involved in cassava processing in south-west nigeria has about 3-6 persons. in ilaro zone, most fufu processors employ 3-4 workers, while 5-6 workers are mostly found in abeokuta zone. all these categories are significantly different in terms of the probability of occurrence (from one sample chi-square test). it was also discovered that primary 6 was the highest educational level of fufu processors – 35% of females and 5% of males (figure 1). this implies that female with low educational level dominate fufu processing centres. this low literacy level hinders the adoption of new fufu processing techniques, as an upshot, the development of the centres and the improvement in processing method suffers a great set back. this study confirms the dominance of women in fufu processing or any other cassava production process (hahn, 1988; adebayo, 2009; ferrar, 1992; igbeka, 1995, davies et al., 2008; samuel et al., 2010; nsoanya and nenna, 2011; adetifa and samuel, 2012). 3.3 source of power supply the field study showed that 77% of the processing centres do not have any power source, while, 10% use the national grid supply, and 13% used generators for processing cassava into fufu. based on the result of the one sample chi-square test, these three categories of power source do not have equal probabilities of occurrence. it can therefore be concluded that, most fufu processing centres do not have access to electricity, which means that, fufu processing in those areas are not mechanised. this could lead to drudgery which will affect the profit obtained from the product. this result shows that most of the operations carried out at the fufu processing centres are manual. this confirms that manual energy use is higher than electrical energy use in most cassava processing centres (jekayinfa and olajide, 2007). arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 547-558. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 551 3.4 procurement of raw materials this research work revealed that 75% of the cassava tubers used in processing fufu was bought from the market, while 25% were self-cultivated. hence, a good number of the processing centres buy their cassava from the market, some of these centres buy cassava directly from the farm, and later convey to the processing centres by a motor cyclist. ani et al. (2013) also observed that most of the cassava tubers used in cassava processing is purchased off farm in enugu state, nigeria. 3.5 operator’s perception of fufu production technologies women processors described fufu processing as a flexible activity that can be taken up easily with little investment; but, a good number of processors interviewed complained of the difficulties and cost of procuring large amount of fresh cassava tubers; lack of mechanised fufu processing technologies; and the inability to store fufu for reasonable period of time due to product perishability. in some processing centres at ilaro, some women were seen mashing soaked cassava tubers with their bare foot. they complained of how ineffective and time consuming it is to make use of hands to mash soaked cassava especially when handling large volume of soaked cassava. according to ferrar (1992), the effect of exposure to cyanide (which may still be present in the soaked cassava tubers) include spastic paralysis and goitre which is suffered by the women who process the cassava. furthermore, lack of good source of water affect the quality of fufu produced in adoodo, itori and igbesa. the streams or rivers which are the source of water for fufu processing also have cassava waste water channelled into it. in a way, the water gets polluted and becomes unhygienic for consumption. this goes a long way in affecting the taste, colour and odour of ready-to-eat fufu. finally, the need for provision of mechanical devices to reduce drudgery involved in fufu processing was emphasized in all the processing centres visited as identified by dipeolu et al. (2001). 3.6 unit operations it was observed that the processing operations varied across the two agricultural zones and within different locations in each zone. these variations affected the methods and materials used. figure 2 shows the prevalence level of different methods adopted in each unit operation. owolarafe et al.: assessment of fufu production technologies in ogun state, nigeria. azojete, 14(4):547558. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 552 figure 2: unit operations for fufu production 1. peeling and washing: figure 2 shows that 65% of the cassava processors commence manual peeling of the cassava a day after harvesting, 18% after 2 days, and 2% after 4-5 days. on the other hand, 9% of the cassava processors commence mechanical peeling method a day after harvesting, 3% after 2 days, 1.5% after 3 days and 1% after 4-5 days. this implies that majority of the cassava processors adopt manual means of peeling cassava. also figure 2, 2% of the cassava processors wash their cassava mechanically a day after peeling, 1% wash in less than 5 hr after peeling, while 9% wash immediately using the mechanical method. conversely, 3% of the cassava processors wash their cassava manually a day after peeling, 27% wash their cassava less than 5 hours, while 53% wash immediately. arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 547-558. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 553 generally, the method of peeling and washing were significantly different in terms of the probability of occurrence (from one sample binomial test). this therefore confirms the fact that most of the cassava processors prefer using manual means of washing their cassava. the use of large vessels or moving water can be used in washing peeled cassava (howeler, 1990). table 1 shows that borehole, river and wells are the major sources of water used. this water sources are mostly available within the processing centres and at least 100 m from the processing centres. table 1: source of water and distance from the main source 2. soaking: it was confirmed from this research that different processors adopt various method to facilitate cassava soaking, although higher percentage of processors adopt concrete pot method (figure 2). based on the one sample chi-square test carried out, these soaking methods have significantly different probabilities of usage. figure 2 shows that most of the processors soak the cassava immediately after peeling. figure 2 also shows soaking for 3-5 days is predominant in the study area which is the best for cyanogen removal (tivana, 2012). montagnac et al. (2008) reported that soaking cassava for three days before sun drying ensures 97.8-98.7% cyanogen removal although amsalu and esubalew (2011) observed that soaking for 1 day is sufficient before sun drying. the percentage of cyanogen removed can be increased by increasing the soaking time; but, soaking for longer periods increase nutrient loss, fungi, mould spores and undesirable bacteria in the final product (montagnac et al., 2008). 3. water replacement: water replacement is one of the major factors that determine the quality of fufu produced. around 51% of the fufu processing centres prefer replacement of water during soaking, while 41% of the fufu processing centres do not replace water during soaking. the frequency of water replacement (number of times soaking water was replaced) amongst the fufu processing centres during the soaking period is presented in figure 2. the prominent method of soaking in abeokuta is to replace the water once within three days interval. in ilaro, soaking water is replaced either once or twice within two days interval. periodical change of soaking water improves the taste, colour and texture of fufu (akingbala et al., 1991). 4. decanting and mashing: majority (around 85%) of the cassava processors used manual decanting method, 12% of the cassava processors used mechanical decanting method, while 3% had no response regarding the decanting method used which stipulates that most of the fufu processors are locally built or constructed in large volumes for more productivity rate. figure 2 shows the equipment used by processors for decanting and mashing process of fufu production in each agricultural zone. generally, 60% of the processors use bowl, while 40% use tilting containers for decanting. cassava mashing by hand was observed to be the dominant method of mashing in abeokuta agricultural zone (figure 2). mashing with hand was possible due to the softening of the tubers after soaking. mashing by hand was the only method identified by oyewole and isah (2012). the use of mortar and pestle and hammer mill for mashing is prominent in ilaro agricultural zone, although mashing with the legs was also identified. statistical analysis using one sample chi-square test shows that there is significant difference between the methods used in decanting and mashing within the study area. source of water distance < 100 m ≥ 100 m within processing centre borehole 12% 1% 21% river 11% 5% 17% well 6% 4% 23% owolarafe et al.: assessment of fufu production technologies in ogun state, nigeria. azojete, 14(4):547558. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 554 5. dewatering: manual dewatering was observed as the dominant method (77.5%) compared to using mechanical equipment (22.5%). manual dewatering is done majorly by pressing with wood (46%) followed by pressing with stone (34%). hanging the mash on plank (20%) is not a prominent manual dewatering method in the areas under study. mechanical dewatering is done majorly with the use of a single screw press and hydraulic press. the result of the one sample chisquare test shows that these methods of dewatering differ significantly within the study area. from the processors using hydraulic press for dewatering, 40% of the cassava processors use 10 tons as the maximum hydraulic jack capacity while 59% use 15 tons. usually, pressing time depends on the efficiency of the press and the moisture content of the mash (oti et al., 2010). 6. drying, cooling, re-sieving and packaging: sun drying is the popular method of drying fufu mash in ilaro and abeokuta agricultural zones. this method of drying fufu has been reported to have no appreciable difference in terms of yield, proximate composition and acidity compared to using a rotary or cabinet drier, although it falls short in pasting properties (sanni and akingbala, 2000). from figure 3, the mean sun drying days is 2.79±1.1 days. it was observed that 13% of the cassava processors sun dry wet fufu paste for 1 day, 29% sun dry for 2 days, 27% sun dry their wet fufu paste from 3-4 days, while 4% sun dry their wet fufu paste for 5 days. kolmogorovsmirnov test revealed that there is no significant difference between the sun drying days adopted by fufu processors in the study area. figure 3: sun drying days the quantity of cassava mash dried in each agricultural zone is usually around 4 bags. statistical analysis reveals that there is a positive but low correlation between the quantity dried and the sun drying days. this correlation was found to be significant at 72%. in addition, analysis using one sample chi-square test revealed that there is no significant difference between the quantities dried by fufu processors in the study area. in abeokuta zone, 94.2% do not cool after drying the cassava mash before packaging and 63.5% do not re-sieve the cassava mash; while in ilaro zone, 35% do not cool 70.8% do not re-sieve. this may also be responsible for the difference in the quality of fufu within these zones. a study to investigate the effect of cooling and re-seiving operations on the quality of fufu is therefore required. the prevalence of different packaging materials used for wet fufu mash is presented in figure 2. it reveals that packaging materials made of nylon and jute are common in the study area for packing arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 547-558. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 555 the wet fufu. plastic and cellophane are other materials used. hahn (1988) reported that wet cassava pulp of about 0.5-1.0 kg is packed in a plastic or polypropylene bag. the packaging materials have significantly different probabilities of occurrence within the study location (using one sample chi-square test). 3.7 sales of finished product it was observed that 44.4% of consumers placed advance order for finished products. it was further observed that certain factors affect the sales of finished products. the study revealed that in abeokuta zone; 5% of cassava processors have insufficient cassava, 7% have insufficient equipment and 10% have low work rate; while in ilaro zone; 4% have insufficient cassava, 1% have insufficient equipment and 4% have low work. adebayo et al. (2003) identified similar factors like availability and price of cassava and the price of fuel as external contextual factors affecting the profitability of wet paste fufu. dipeolu et al. (2001) identified poor access to finance as one of the constraints affecting the marketability of fufu. 3.8 waste disposal method table 2 shows the various methods adopted in the disposal of waste. cassava peel, cassava chaff and wastewater were identified as the major types of waste generated during fufu processing. it was observed that the major method for disposing cassava peel is by reusing it. it is usually dried and sold to livestock farmers. in ilaro zone, most of the cassava peels are buried, dumped in dump sites or unattended to. the disposal method for cassava chaff is similar to that of cassava peel. in abeokuta zone, wastewater is usually drained into pit, while in ilaro zone; it is usually left unattended to. based on the result of the one sample chi-square test, these cassava waste disposal methods all have different probability of being used. the potential in cassava wastewater is usually underutilized in the study area. this result is similar to report of coker and achi (2015) who observed that in ibadan, 70-75% of cassava peels, bagasse and waste effluents were discharged indiscriminately into nearby bushes and water bodies. cassava waste transformation offers the possibility of creating marketable value-added products (ubalua, 2007). table 2:waste disposal method in each agricultural zone zone cassava peel disposal (%) cassava chaff disposal (%) wastewater disposal (%) b r du u o b r du u o r d u o abeokuta 8 73 15 2 2 6 65 12 15 2 2 58 30 10 ilaro 13 47 28 10 2 17 36 32 13 2 15 30 53 2 key: b-bury, r-reuse, du-dumped, d-drain into pit, u-unattended, o-others 3.9 preliminary sensory analysis fufu is considered by consumer to be of good quality when it has a smooth texture, characteristic aroma, and is creamy white, grey or yellow in colour. the quality of fufu was observed to depend on the technologies adopted, method of processing and material used for processing. fufu produced in wet form with moisture content of 40%-50% had a repulsive smell. this smell was caused by; delay in processing cassava tubers, increase in the soaking time, ineffective dewatering method and source of water. the colour variation in fufu production was due to inappropriate dewatering method, low water replacement frequency, delay in processing and soaking and the water used for soaking. a well processed fufu should also have a smooth and fine texture, but the use of over matured tubers resulted to a rough texture. some of the factors observed to affect the taste of fufu are; unsuitable dewatering and mashing method increase in soaking time, delay in cassava tuber processing and the improper management owolarafe et al.: assessment of fufu production technologies in ogun state, nigeria. azojete, 14(4):547558. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 556 of cassava peel, chaff and waste water. according to uyo et al. (2009), the taste, colour and texture of cooked fufu are not affected by the fermentation technique. oyewole and ogundele (2001) reported similar results. 4. conclusion this paper presented the assessment of various fufu processing techniques across two selected agricultural zones in ogun state (ilaro and abeokuta). it has also being able to identify the quality variation of fufu due the various processing techniques adopted. it revealed that higher percentages of fufu processing centres were owned by individuals, who adopt majorly manual method in fufu processing, thereby increasing drudgery and yielding low income. the cassava tubers used for fufu were mostly purchased off-farm; peeled and washed manually a day after harvest; soaked for either 3-5 days; and mashed manually either by hand or with the use of mortar and pestle. inadequate financing and insufficient education were observed as some of the factors affecting the development of fufu processing centres and the adoption of new technologies. it is therefore important that all concerned agencies and parastatals create policies to make funds easily accessible to rural farmers, educate farmers on the new technologies available, subsidise the purchase of processing equipment and provide technical assistance. references achi, ok. and akomas, ns. 2006. comparative assessment of fermentation techniques in the processing of fufu, a traditional fermented cassava product. pakistan journal of nutrition, 5 (3): 224-229. adebayo, k., 2009. dynamics of technology adoption in rural-based cassava processing enterprises in south-west nigeria. international journal of agricultural economics and rural development, 2(1): 15-25. adebayo, k., white, jl., morris, mj., dipeolu, ao., ayinde, ia., wandschneider, ts., sanni, lo., oyewole, ob., tomlins, a. and westby, a. 2003. innovativeness and stakeholdership in the fufu processing systems in southwest nigeria. asset series a, 3(4): 15-27. adetifa, bo. and samuel, tm. 2012. characterisation of gari frying stations in ifo local government, ogun state, nigeria. journal of research in national development, 10 (3): 34-46. adewuyi, sa., adebayo, ao., aderinboye, ry. and bada, bs. 2009. report of diagnostic survey of agricultural problems in ogun state. institute of food security, environmental resources and agricultural research, university of agriculture abeokuta. retrieved on august 15, 2017 from unaab website: www.unaab.edu.ng/attachments/ogunreport3.pdf akingbala, jo., oguntimein, gb. and abass, ab. 1991. effect of processing methods on quality and acceptability of fufu from low cyanide cassava. journal of the science of food and agriculture, 51(1): 151-154. amsalu, n. and esubalew, g. 2011. soaking and drying cassava roots reduced cynogenic potential of thee cassava varieties at jimma, southwest ethopia. world journal of agricultural sciences, 7(4): 439-443. ani, so., agbugba, ik. and baiyegunhi, ljs. 2013. processing and marketing of selected cassava products in south-east nigeria. journal of economics, 4(2): 105-111. asante-pok, a., 2013. analysis of incentives and disincentives for cassava in nigeria. technical notes series, mafap, fao, rome. http://www.unaab.edu.ng/attachments/ogunreport3.pdf arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4): 547-558. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 557 bamidele, op., fasogbon, mb., oladiran, da. and akande, eo. 2015. nutritional composition of fufu analog flour produced from cassava root (manihot esculenta) and cocoyam (colocasia esculenta) tuber. food science and nutrition 3(6): 597–603. coker, ao. and achi, cg. 2015. utilization of cassava processing waste in ibadan as a viable and sustainable strategy for meeting cassava processing energy needs: case study from ibadan city, nigeria. journal of solid waste technology and management, 41(4): 628-639. davies, rm., olatunji, mo. and burubai, w. 2008. a survey of cassava processing machinery in oyo state. world journal of agricultural sciences, 4 (3): 337-340. dipeolu, ao., adebayo, k., ayinde, ia., oyewole, o., sanni, io., pearce, dm., wandschneider, ts., white, jl. and westby, a 2001. fufu marketing systems in southwest nigeria. nri report r2626, retrieved on august 15, 2017 from fao website: http://www.fao.org/docs/eims/upload/agrotech/1968/r7495_1.pdf. ezeronye, ou. 2003. fermentation kinetics and removal of off-odour in cassava fufu. nigerian journal of experimental and applied biology, 4: 1-4. ferrar, p. 1992. food laced with cyanide. partners in research for development, 5: 29-33. hahn, sk. 1988. an overview of traditional cassava processing and utilization in africa. in: iita/ilca/university of ibadan workshop on the potential utilization of cassava as livestock feed in africa, ibadan, 14-18 november, 1988. fao. howeler, rh. 1990. cassava breeding, agronomy and utilization research in asia. in: third regional workshop, malang. 22nd – 27th october, 1990. igbeka, jc. 1995. recent developments in cassava frying operation and equipment used for gari production in nigeria. transformation alimentaire du manioc. (tt. agbor egbe, a. brauman, d. griffon, s. treche (éds.)), paris, orstom: 581 – 593. iwuoha, ci. and eke, os. 1996. nigerian indigenous fermented foods: their traditional process operation, inherent problems, improvements and current status. food research international 29(56): 527-540. jekayinfa, so. and olajide, jo. 2007. analysis of energy usage in the production of three selected cassava-based foods in nigeria. journal of food engineering 82: 217-226. montagnac, ja., davis, cr. and tanumihardjo, sa. 2008. processing techniques to reduce toxicity and antinutrients of cassava for use as a staple food. comprehensive reviews in food science and food safety, 8: 17-27. nsoanya, ln. and nenna, mg. 2011. adoption of improved cassava production technologies in anambra-east local government area of anambra state nigeria. journal of research in national development, 9(2): 36-43. okafor, n., ijioma, b. and oyolu, c. 1984. studies on the microbiology of cassava retting for fufu production. journal of applied bacteriology, 56: 1-13. okolie, np., ibeh, in. and ugochukwu, en. 1992. production of improved cassava fufu “akpu” through controlled fermentation. food chemistry, 44:137-139. http://www.fao.org/docs/eims/upload/agrotech/1968/r7495_1.pdf owolarafe et al.: assessment of fufu production technologies in ogun state, nigeria. azojete, 14(4):547558. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 558 okorji, ec., eze, cc.and eze, vc. 2003. efficiency of cassava processing techniques among rural women in owerri, imo state, nigeria. journal of agriculture and social research, 3(2): 84 – 96. okpokiri, ao., ijioma, bc., alozie, so. and ejiofor, man. 1984. production of improved cassava fufu. nigerian food journal, 2: 145-148. omodamiro, rm., oti, e., etudaiye, ha., egesi, c., olasanmi, b. and ukpabi, uj. 2012. production of fufu from yellow cassava roots using the odourless flour technique and the traditional method: evaluation of carotenoids retention in the fufu. advances in applied science research, 3(5): 2566-2572. oti, e., onadipe, o., sébastienne, d., egounlety, m., detouc, n., gregory, ak. and loueke, gm. 2010. processing cassava into gari and high quality cassava flour in west africa. usaid/coraf/songhai training manual, retrieved on august 30, 2017 from coraf website: http://www.coraf.org/database/publication/publication/cassavatrainingmanual.pdf. oyewole, oa. and isah, p. 2012. locally fermented foods in nigeria and their significance to national economy: a review. journal of recent advances in agriculture, 1(4): 92-102. oyewole, ob. and ogundele si. 2001. effect of fermentation on the functional characteristics of fermented cassava ‘fufu’. the journal of food technology in africa, 6(2): 38-40. oyewole, ob. and sanni, lo. 1995. constraints in traditional cassava processing the case of 'fufu' production transformation alimentaire du manioc. (t. agbor egbe, a. brauman, d. griffon, s. triche (éds)) paris, orstom: 523 – 529. samuel, tm., igbeka, jc. and kolawole, op. 2010. a survey of improved gari frying methods. international journal of food engineering, 6(2): 1-12. doi: 10.2202/1556-3758.1473. sanni, lo. and akingbala, jo. 2000. effect of drying methods on physiochemical and sensory qualities of fufu. drying technology, 8(1-2): 421-431. tivana, ld. 2012. cassava processing: safety and protein fortification. media-tryck, lund university, lund, sweden. ubalua, ao. 2007. cassava wastes: treatment options and value addition alternatives. african journal of biotechnology, 6(18): 2065-2073. umeh, so. and odibo, fjc. 2014. amylase activity as affected by different retting methods of cassava tubers. international journal of agricultural policy and research, 2(7): 267-272. uyo, ea., ntui, vo. and udoma, nn. 2009. effect of local cassava fermentation methods on some physiochemical and sensory properties of fufu. pakistan journal of nutrition, 8(8): 11231125. uzogara, sg., agu, ln. and uzogara, eo. 1990. a review of traditional fermented foods, condiments and beverages in nigeria: their benefits and possible problems. ecology of food and nutrition, 24: 267-288. http://www.coraf.org/database/publication/publication/cassavatrainingmanual.pdf availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 1-12 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng impact of dams on hydrology of river niger at lokoja, nigeria jimoh, o.d. 1 abstract river niger traverses two humid catchment areas that are separated by a wide expanse of semi-arid environment. within its lower course, the river has been impounded at two points (kainji and jebba) for the sole purpose of generating electricity. this paper discusses the hydrological regime of the river at lokoja before and after the first dam (kainji) was commissioned. it was observed that the annual flow during the post-dam period was lower than that of pre-dam period by 10%. this reduction occurred mainly in september, october and november. the seven-day average low flow increased from 520 m 3 /s during pre-dam to 800 m 3 /s during the post-dam periods, while the fifteen-day average low flow increased from 500 to 850 m 3 /s during the respective period. the flood level (q10) during the post-dam period was lower than the level during pre-dam. this observation shows that one of the effects of river regulation on low flow at lokoja is to mitigate the severity of low flows, as well as to reduce maximum daily peak flow. it was also discovered that there were variations in the baseflow (q90) from the pre-dam to post-dam period. the increase in q90 value during the post-dam period could be attributed to changes in land use and agricultural practices. 1. introduction there are two dams (kainji and jebba) on river niger within nigeria. kainji dam was commissioned in december 1968 for the purpose of generating electricity. the reservoir has total storage volume of 15 billion cubic metres, with a surface area of 127 km 2 . the maximum water surface elevation is 141.9 m.a.s.l., while the normal tail water elevation is 1068 m.a.s.l. the jebba dam, located 97 km downstream of kainji dam was commissioned in 1984 to utilize the run-off water from kainji to generate electricity. the dam has a storage capacity of 3.88 billion cubic metres. the maximum water surface elevation is 103 m.a.s.l. due to rapid electric demand growth in nigeria, the government planned among other options to impound river niger at lokoja to generate electricity. flooding of niger plain between kainji and lokoja in nigeria, resulting in loss of life and properties is an annual phenomenon. downstream impacts of dams are unrecognised, misunderstood or underestimated by planners (adams, 2000). this is because flooding phenomena occur in remote areas, and far from the dam site. in addition, downstream impact is daunting in their complexity in space and time. dam projects are particularly vulnerable to artificially narrow assessment in this way. for example, assessment of the viability of the bakolori dam and irrigation scheme in nigeria specifically excluded consideration of the downstream impacts, and assessment of the pangue dam on the bio-bio river in chile in the early 1990’s ignored its dependence on other dam projects (adams, 2000). hydroelectric dams are designed to create a constant flow through turbines, and therefore tend to have a similar effect on discharge patterns. however, if the intention is to provide power at peak periods, variations in discharge of considerable magnitude can occur over short time scales, creating artificial freshets or floods downstream. the critical point is that most dams 1 civil engineering department, federal university of technology, minna, nigeria. odjimoh@yahoo.com ../../vol%205/ready/odjimoh@yahoo.com impact of dams on hydrology of river niger at lokoja, nigeria 2 moderate and delay the incoming flood peak because of the flood routing effect of the storage impoundment. such effects can be particularly significant where river regime is flashy, for example river regime in the semi-arid tropics. this study is aimed at identifying the effect of major dams (kainji and jebba dams) on the hydrological regime of river niger at lokoja. the result will be useful in understanding the occurrence of flood along the niger plain, as well as low flow conditions in the river. 2. a review of the hydrology of river niger river niger is the third largest river in africa. the river runs over 4000km across west africa. its basin covers about a third of the land area of the sub-region, extending over 9 countries – guinea, cote d’ ivoire, mali, burkina faso, niger, benin, nigeria, cameroun and chad. the river takes its source less than 250 km from the coast, from the highlands of the guinea-sierra leone border, in the wet equatorial region (fig. 1). river niger, by its peculiar course, first loses the advantage of having its source in a wet climatic region, before turning toward the sea. however, in its middle and lower courses, the river receives many tributaries which argument its volume. these tributaries mostly have their sources in the sub-humid savanna region and their flows are very much subject to the highly variable and seasonal rainfall regime (areola and akintola, 1995). rainfall is concentrated in the headwaters and near the outlet of the niger system within nigeria. the seasonal pattern is reasonably similar over most of the areas, with maximum in august and a dry season centred on december to february period. however, in southern nigeria as well as in northern cameroun, the maximum rain is recorded in july or september. the balance between rainfall and evaporation determines the river flow regime. consequently, the river exhibits, at certain sections, different regime types and anomalies, which reflect the climatic and physiographic characteristics of the component sub-basins. two distinct floods (black and white) occur annually in the river. the floods are separated by a period of 4 to 5 months. the black flood originates from high rainfall area in the headwaters. the flood arrives at kainji in november and lasts until march at jebba after attaining a peak in february (oyebande, 1995). the white flood becomes prominent only downstream of sabon-gari soon after the river enters nigeria. usually heavy-laden with silt and other suspended particles. the flood derives its flow from the local tributaries and reaches kainji in august in the pre-dam period, and attains peak between september and october in jebba. azojete vol. 5 2007 3 figure 1: rivers and lakes of the niger – benue system 3. methodology daily streamflow at lokoja from 1914 to 2003 was collated (source: hydro niger, niamey) for this study. daily rainfall records from the synoptic stations within nigeria (table 1) contributing to river niger at kainji and lokoja were also collated. the streamflow record was divided into the pre-dam (1914 – 1963) and the post-dam (1964 – 2003) periods. the characteristics of flow during the pre-dam period were compared with those of the post-dam period. the elements considered are monthly flow, annual flow index, flow duration curve as well as 7-day and 15-day low-flow parameters. the annual flow index was expressed as the difference of the annual flow from the mean of the 1931 to 1960 flow series, and normalized by the standard deviation of the 1931 to 1960 flow series. the period 1931 to 1960 was considered as the climatological normal for the region. the annual base daily flow duration curve (vogel and fennessey, 1995) was used to assess the percentage of times certain flow levels were exceeded. the low flow frequency curves were determined for 1-day, 7-day and 15-day mean flow based on wallace and cox (2002). impact of dams on hydrology of river niger at lokoja, nigeria 4 table 1: summary of data collated station type of data location sokoto gasau yelwa daily rainfall daily rainfall daily rainfall 13 05 5 15 12 10 6 40 10 52 4 45 samaru kaduna minna bida ilorin lokoja daily rainfall daily rainfall daily rainfall daily rainfall daily rainfall daily streamflow 11 11 7 38 10 36 7 40 09 35 6 33 09 06 6 01 08 28 4 35 07 48 6 44 4. results and discussion the flow indices for annual flow series, july to october as well as november to february seasonal flow at lokoja are presented in figure 2. the figure shows that the flow during the post–dam period was persistently below the long-term mean. this pattern differed from that of pre-dam period. on the average, the mean annual flow during the pre-dam period was 10% higher than that for the post-dam period. during the july to october season for example, the flow index was greater than 1.0 between 1914 and 1930, indicating high flow in the river. between 1961 and 1970, that is, before kainji dam was commissioned and immediately after its commission, the flow index was greater than 1.0. however, the flow index was lower than –1.0 during the period 1971 to 2000. similarly, sule (1992) analysed inflow between 1970 and 1987 to kainji and reported that there was a persistent decline in the inflow to kainji. the low flow observed at lokoja and kainji during the period 1971 to 1990 agreed with the rainfall pattern in the catchment (figure 3). nicholson (1981), adefolalu (1986), hulme (1992) as well as jimoh and webster (1996) among others reported that nigeria was affected by drought between 1970 and 1980. the drought was characterized by a reduction in depth of annual rainfall. the drought was named ‘sahelian drought’ indicating the source (sahel) of the wind causing it. the streamflow level was low during the phenomenon. the rainfall index, presented in figure 3 shows that rainfall was above the long-term mean in the 1990’s, but the flow index remained persistently lower than the mean. a similar observation was obtained for the rainfall catchment at lokoja. the implication of this observation is that flow level at lokoja is affected by a complex relationship between regulation policies at kainji (from 1963) and jebba (from 1986), climatic variation as well as changes in land use pattern and diversion activities at the upstream. although, there was an increase in rainfall in the 1990’s, the influence of other factors (such as land use pattern, changes in agricultural practices) overshadowed the increase in rainfall level. azojete vol. 5 2007 5 figure 2: variation of flow indices at lokoja annual series -3 -2 -1 0 1 2 3 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 n o rm a li se d f lo w white flood series -3 -2 -1 0 1 2 3 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 n o rm al is ed f lo w black flood series -3 -2 -1 0 1 2 3 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 n o rm al is ed f lo w impact of dams on hydrology of river niger at lokoja, nigeria 6 figure 3: mean catchment rainfall at kainji figure 4 shows the frequency curves for 1-day, 7-day and 15-day mean flow at lokoja. the frequency curves for post-dam period differed from those of the pre-dam period, especially at higher return period. the 1q10, 7q10 and 15q10 were estimated as 600, 520 and 500 m 3 /s respectively during the pre-dam period. the corresponding values during the post-dam era were 700, 800 and 850 m 3 /s respectively. while the flow level decreased with averaging length during the pre-dam period, the flow level increased with averaging length during the post-dam era. in particular, the lowest seven-day average flow expected to occur once in ten years (7q10), which represents a relatively infrequent drought conditions, increased from 520 to 800 m 3 /s during pre-dam to post-dam periods. thus, the effect of river regulation on low flow at lokoja is to mitigate the severity of low flows, which agrees with findings in southern australia (mcmahon and finlayson, 2003; lenz, 2004). the annual maximum daily peak series is presented in figure 5. for return period ranging between 1 and 14 years, the flood levels during the post-dam period were lower than levels during the pre-dam. this observation has confirmed that, dams upstream reduced peak flow levels (adams, 2000). -4 -2 0 2 1910 1930 1950 1970 1990 2010 n or m al iz ed in de x azojete vol. 5 2007 7 figure 4: low flow (in m 3 /s) frequency curves at lokoja 1-da y 100 1000 10000 1 10 100 return period (year) f lo w pre-dam post-dam 7-day 100 1000 10000 1 10 100 return period (year) f lo w pre-dam post-dam 15-day 100 1000 10000 1 10 100 return period (year) f lo w pre-dam post-dam impact of dams on hydrology of river niger at lokoja, nigeria 8 figure 5: annual maximum daily flow (in m 3 /s) of river niger at lokoja 1-da y 10000 100000 1 10 100 return period (year) f lo w pre-dam post-dam 7-da y 10000 100000 1 10 100 return period (year) f lo w pre-dam post-dam 15-da y 10000 100000 1 10 100 return period (year) f lo w pre-dam post-dam azojete vol. 5 2007 9 the monthly flow at lokoja (figure 6) shows a single peak occurring in october during the preand post-dam periods. double peak seasons (black and white floods) are recorded in kainji. the difference in flow regime is not due to the operation of the two hydro-dams (kainji and jebba), but as a result of the climatic and physiographic characteristics of the subbasin that contributes to the flow (oyebande, 1995). the reduction in annual flow at lokoja during the post-dam period occurred mainly in september, october and november. figure 6: average monthly flow series of river niger figures 7 and 8 show the flow duration curves for selected years during the preand post-dam periods respectively. during the pre-dam period, the q50 (the flow that has been equalled or exceeded 50 percent of time) ranged between 2552 and 4295 m 3 /s, with an average of 3109 m 3 /s. during the post-dam period, the value ranged between 1654 and 4186 m 3 /s, with an average of 2869 m 3 /s. during the post-dam period, there was a reduction (7.8%) in the mean value, with a high variability from year to year in the q50 value. the q90 streamflow parameter, referred to as the conservative estimator of mean baseflow (wallace and cox, 2002) ranged between 999 and 1771 m 3 /s during the pre-dam period, and between 1033 and 1703 m 3 /s during the post-dam period. the mean value of q90 is 2651 for pre-dam and 3014 m 3 /s for post-dam period. the mean q10 is 18225 m 3 /s for pre-dam and 14889 m 3 /s for postdam period, indicating a reduction of 18.3%. this implies that the flood level at lokoja during the post-dam period is lower than that of the pre-dam period. the curves for both the preand post-dam periods flattened at the lower part, indicating a considerable contribution of baseflow and flood plain storage to streamflow. this is reflected in the q90 streamflow parameter. the difference between the groundwater contribution during the pre-dam and postdam period could be attributed to changes in land use and agricultural practices resulting in improved infiltration rate. 0 200000 400000 600000 jan feb mar apr may jun jul aug sep oct nov dec m ea n flo w (c ub . m . p er se c. ) pre-kainji postkainji impact of dams on hydrology of river niger at lokoja, nigeria 10 figure 7: flow duration curve at lokoja during the pre-dam period (flows in m 3 /s) 1915 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1916 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1924 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1929 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1933 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1937 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w 1946 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w 1954 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w azojete vol. 5 2007 11 figure 8: flow duration curve at lokoja during the post-dam period (flow in m 3 /s) 5. conclusions the conclusions of this study are summarised as follows: the flow at lokoja has been lower than the long-term mean since 1970. the low level was attributed to low rainfall within the catchment in nigeria that contributes to the streamflow, the impact of kainji and jebba dams, as well as changes in land use pattern within the catchment. the mean annual flow during the pre-dam period exceeded the value for post-dam period by 10%. the reduction in flow occurs mainly between september and november. 1973 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w 1975 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1983 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w 1990 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w 1991 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 1998 0 10000 20000 30000 0 25 50 75 100 percentage of exceedence f lo w 2000 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w 2002 0 10000 20000 0 25 50 75 100 percentage of exceedence f lo w impact of dams on hydrology of river niger at lokoja, nigeria 12 the groundwater contribution to streamflow during the pre-dam period differed from that of the post-dam period. this difference was attributed to changes in agricultural practices and land use pattern. the lowest seven-day average flow expected to occur once in ten years (7q10), which represents a relatively infrequent drought conditions, increased from 520 to 800 m 3 /s during pre-dam to post-dam periods. thus, the dams at the upstream section of lokoja mitigate the severity of low flows. references adams, w. 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(2004).analysis of streamflow and water-quality data at two long-term monitoring sites on the st.croix river, wisconsin and minnesota. usgs water resources investigations report 03 – 4334. united states departments of interiors and geological surveys. mcmahon, t. a. and b. l. finlayson (2003). droughts and anti-droughts: the low flow hydrology of australian rivers. freshwater biology. 48(7), 1147. nicholson, s. e. (1981) rainfall and atmospheric circulation during drought periods and wetter years in west africa. monthly weather rev. 109, 2191 2208. oyebande, l. (1995). global climate change and sustainable water management for energy production in the niger basin of nigeria. in: global climate change – impact on energy development (ed. by umolu, j. c.), 18 – 26. damtech publications, jos, nigeria. sule, b. f. (1992). some aspects of water management in hydroelectric power generation. the nigerian engineer, 27(3), 10 – 17. vogel, r. m. and n. m. fennessey (1995). flow duration curves ii: a review of applications in water resources planning. water resour. bull. of the american water resources association. 31(6), 1029 – 1039. wallace, t. b. and w. e. cox (2002). locating information on surface water availability in virginia. http://www.rappriverbasin.va.us/studies/locatingsurfacewaterinfo.doc accessed on 10 october, 2004. http://www.rappriverbasin.va.us/studies/locatingsurfacewaterinfo.doc arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):495-504 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 495 original research article state estimation of the nigerian 330kv transmission network using the weighted least square optimization technique i. a. araga, a. i. afolayan and a. e. airoboman department of electrical and electronic engineering, nigerian defence academy, kaduna state, nigeria. *corresponding author’s email address: afolayantimilola880@gmail.com 1.0 introduction monitoring and control of the power system is a desirable feature in the operation of power system as it ensures stability and reliability (kothari, 2010). the monitoring of the generation and transmission has been providing data for dispatch and frequency control however; with the complexity of the power system and the requirement for effective operation, this requirement has become a more difficult task. the nigerian national grid management and control is carried out manually which makes the system prone to problems; and has resulted in many challenges at generation, transmission and distribution levels (emodi, 2015; okonkwo, 1996). the backbone for electrical management is the knowledge of the system state. no control system can effectively tell a power system where to go in future without an adequate knowledge of its present state. therefore, knowledge of the state of operation of a power system is of maximum importance and can only be achieved by obtaining information from the state vectors and processing these data to estimate the system behavior (gotti, 2020). article information abstract the state of an electrical power system is the vector of voltage magnitudes and voltage angles at each bus across the entire power system network. the estimates of state variables are very important for online monitoring and control, which are valuable assets in power system operations. the state estimator algorithm is a computational mathematical implementation of a state space technique to process erroneous power system measurements into an estimate of the true power system state vector. it is established, through rigorous research that measurement data obtained from supervisory control and data acquistory systems or phasor measurement unit are not fit for direct system analysis as they contain errors large enough to give a misrepresentation of the system behavior. to address the issue of erroneous data measurements, this work uses the optimized weighted least square technique to estimate the true state of the power system network. this analysis is achieved by setting up mathematical models of the system network and applying the weighted least square estimation technique to different weights depending on type of measurement. a quantitative and qualitative problem of system observability and error detection in measurement is discussed in this paper. the observability and error quantification process is carried out on the ieee 14 and the nigerian transmission grid network through the segmentation of observable islands within the network. this work generates important state results using the matlab computational software and run state estimate simulations using the psat framework. using the estimation technique in this work the nigerian network state space estimation results revealed errors embedded in measurement data with a significant deviation of 1.14 of maximum voltage error in comparison with state estimate result and 16% deviation mean of voltage estimation error in comparison with raw measurement data. the deviation between the raw measurement data and the state estimation results depicts that analysis of power networks without applying that state estimation algorithm may give a misinterpretation of the state variables. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 july, 2021 revised 10 sept., 2021 accepted 10 sept., 2021 keywords: estimation state vector space error observability weight afolayantimilola880@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):495-504. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 496 1.1 data acquisition in power systems the acquisition of data and data processing for use by the system operator is the fundamental block on which modern power utility control systems are hinged on. a generation of equipment developed to monitor, acquire data, and control functions in the power systems are referred to as the supervisory control and data acquisition (scada) systems (oludele et al., 2016). the scada system primary function is to provide a database for the power system which is achieved by real-time base technique. 1.2 present state of data acquisition system in nigeria the transmission company of nigeria (tcn) attempted to procure and install scada systems for the grid however; it has not been very successful. for one, the world bank financed the procurement of the data acquistory system but could only effectively monitor and retrieve data for just 40% of the entire network (deloitte, 2021). it is a fact that system collapse is a regular phenomenon in the nigerian power system, it is an operational problem. voltage collapse usually results from the overloading of some injection stations and consequently short circuit faults on transmission and distribution lines. these outages could have been prevented if adequate data were analyzed to predict and control the performance of the system. an analysis of the performance of the nigerian power system, monitoring, data acquisition and control reveals that the instrumentation level is inadequate for monitoring of the system states for control of the system (ibe, 2009). for system analysis, the need for sufficient data to predict, investigate disturbances to the possibility of minimizing risk has placed a special responsibility on instrumentation and data acquisition in the power system. this research paper provides a solution capable of using available data of the transmission state variables to produce an optimal estimate of the static state vector which gives an estimate for unknown parameters lacking measurements. this gives a processed database for monitoring and control decisions in the power system. 2.0 method the problem of state estimation is the problem related to the estimate of a random variable x from the numerical identity of another related random vector y with little statistical information made available for both vectors (schweppe et al., 1970). the goal of state estimation is to determine the state of the system based on variables been measured, directly or indirectly. in processing errors through state estimation, all measurement errors are assumed to have a statistical property known as a probability distribution with unknown parameters. the joint probability density function for measurements will be derived in relation to the unknown parameters. the joint density function for measurement obtains its peak value labeled by zero when the unknown parameters are chosen closest to their actual values. the measurement errors are assumed to have a gaussian (normal) distribution. the parameters for this distribution are its mean, standard deviation and the variance (pires et al., 1999). the state of a system is the minimal set of variables and the knowledge of these variables in time (t) which together with the input completely determines the behavior of the system. the state vector is the ‘n’ set of state variables used to describe the nonlinear dynamic equations of a system. therefore, x is assumed a vector of n random variables (kothari, 2010) (1) and y is another vector of m (< n) random variables (2) they are related as (3) where h is a nonlinear matrix of dimension of m x n that describes the system and r is a zero mean random variable of same dimension of y. the vector ‘x’ represents the variable to be estimated, while the vector ‘y’ represents the variable whose numerical values are available (pires et al., 2014). this says y is linear related to the unknown vector x which is corrupted by errors. assuming state variables to be measured is represented by z, while x represents quantities to be estimated. (4) araga et al: state estimation of the nigerian 330kv transmission network using the weighted least square optimization technique. azojete, 17(4):495-504. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 497 where, e represents errors between actual measurements z and the true values ztrue. assuming we have a system with two actual measurement data the matrix of equation (4) z1 = h11x1 + h12x2 + e1 = z1, true + e1 (5) z2 = h21x1 + h22x2 + e2 = z2, true + e2 (6) this could also be written as [e = z – ztrue = z – hx] (7) this says the errors between actual measurement z and the true values ztrue that is approximately hx of the measured quantity. it is also important to realize that the system variable x cannot be accurate therefore, determination of an estimate can be assumed given by the state . = (8) it is also of importance to decide on the criteria required to determine the estimates of the states of and from which = [ ]t (9) z= [ ] (10) to ensure that measurements from instruments of known greater accuracy are treated with more emphasis because of their more accurate measurements, each term in the sum of squares is multiplied by an appropriate weighing factor (w) to give the objective function. this brings about the idea of the weighted least square method used for estimation. as assumed in the equations above considering a system, of four measured quantities the weighted expression will be. f = = + + + (11) we select the best estimates of the state variables as those values and ….. which causes the objective function f to take its minimum value this means the estimate of values of x1 and x2…. xn. which satisfies some set of criteria equations as described in this work. therefore, for n number of measurement quantities within a power system will be analyzed as, (12) the nonlinear weighted least algorithm applies the technique of minimizing the square of errors in the measurement data. (13) where is the ith term of the measurement, e is the error, is the variance. h(x) represents the nonlinear relationship with the measurement and the system state. from equation (1) (14) where the jacobian of h (x) and r is is the covariance matrix, which is the inverse of the system weight. the equation is solved iteratively to obtain estimate of the state vector. (15) (16) 1. the solution of the iterative process is the set of states that minimize function 2.1 structure of the measurement h matrix the estimator jacobian matrix h is not a square matrix it has a (2n -1) where network equals n. while the number of roles in h equals the number of measurement. an assumption made by this work as it relates to the formation of this matrix is that in practical power system network, under steadystate analysis it is assumed that real power flow is less tactful to voltage magnitudes and are much more sensitive to voltage phase angles, while the reactive power flow counterpart is much less tactful to arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):495-504. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 498 voltage phase angles and are very sensitive to voltage magnitudes. this is done to bring a bit of simplicity to the estimation. the h matrix becomes, h= (17) 2.2 state vector observability criterion. observability criterion objective in state estimation is to determine the network observability, identify the observable island if network is unobservable (fetzer, 1975). also, identify branches within the bus where pseudo measurements are necessary to make the system observable. since the state estimation employs more measurements than the minimum number necessary to define the system, the observability criterion is employed to determine measurements that improve observability. since the measurement z in a power system are related to the state in a nonlinear way and linearized as in equation 16. a system is said to be completely observable, if and only if the knowledge of the state variable in some finite time after to, the knowledge of the state variable description of the system, can be determined by observing the measurement vector z. a refers [17] q = [ht atht, (at)2 ht ……….(at)n-1ht] (18) the system is said to be completely observable if the rank of h is equal to the number of variables. 2.3 error indices in order to quantify errors within the estimation framework, the maximum error index is applied. maximum error estimation is the margin of error; it is a measure of the closeness of the estimate to the true value of the state parameter. this bound on error of estimate is usually at a chosen confidence level or interval. the figure 1 shows the step by step process of the estimator. araga et al: state estimation of the nigerian 330kv transmission network using the weighted least square optimization technique. azojete, 17(4):495-504. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 499 figure 1: flow chart of the weighted least square optimization technique 3. results and discussion 3.1 results this section consists of simulation results based on the software implementation of the weighted least algorithm on the ieee test bus 14 and the nigerian 56 buses network. table 1 shows the voltage magnitudes and voltage phase values which represents the state estimate results for the ieee 14 bus network. the data used for the ieee 14 bus analysis is available in (ieee 14-bus system(icseg), 2021). table 1: state estimate result for ieee 14 bus network in per unit. bus voltage mag phase angle bus voltage mag phase angle 1 1.0600 0.0000 8 1.0900 -13.3700 2 1.0450 -4.9800 9 1.0561 -14.9500 3 1.0100 -12.7200 10 1.0511 -15.1000 4 1.0186 -10.3200 11 1.0569 -14.8000 5 1.0203 -8.7800 12 1.0550 -15.0800 6 1.0698 -14.2200 13 1.0502 -15.1600 7 1.0619 -13.3700 14 1.0356 -16.0400 in figure 2, it is shown that each estimated point matches the original base data of the ieee 14 bus system. this confirms the accuracy of the algorithm in tracking true values of the considered measurement points for estimation as in this case 35 measurement points. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):495-504. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 500 figure 2: state estimate result comparison against ieee 14 bus network true data. while in figure 3, which shows the voltage angle comparison between the state estimate values and the true value of the voltage phase angle of the ieee 14 network. it can be seen that the estimator is able to match each of the true values of the network which depicts the accuracy of the estimation process. figure 3: voltage angle comparison estimated value and true value (ieee14). figure 4: voltage magnititude comparison estimated value and true value. in the graph in figure 4 which shows the voltage magnitude state variable comparison, it is seen that estimated points match alongside the true state values of the network. this is however expected as this test system measurement points are considered to be true. araga et al: state estimation of the nigerian 330kv transmission network using the weighted least square optimization technique. azojete, 17(4):495-504. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 501 the table 2 shows very small error margin between the true values and the estimated points on ieee 14 buses which further proves the accuracy of the estimation algorithm to obtain a good estimate of the system state. we obtain values of error as low as 0.0004 and mean error values of 0.0001. table 2: error indices for ieee 14 buses state estimate. s\n errors error index 1 max voltage magnitudes estimation error(mvmee) 2 max phase angle estimation error(mpaee) 3 mean voltage magnitudes estimation error (mvmee) 4 mean phase angle estimation error(mpaee) the table 3 shows the state estimation result of the nigerian 56 bus transmission network. table 3: state estimate result for the nigerian 56 bus network. bus number voltage magnitude phase angle bus number voltage magnitude phase angle 1 0.9127 -0.61 29 1.0837 5.29 2 1.0549 2.48 30 0.8967 -29.01 3 0.912 -1.54 31 1.2862 6.44 4 0.4527 137.33 32 0.9362 -46.8 5 1.0645 5.58 33 1.0178 -14.88 6 1.0274 0.27 34 1.0067 -15.35 7 1.0717 2.62 35 1.0819 1.92 8 1.065 5.06 36 1.1021 -27.78 9 1.0945 1.23 37 1.1438 -25.11 10 0.5144 155.36 38 1.3203 -15.89 11 1.0614 -0.44 39 1.1335 4.55 12 0.9138 -0.44 40 1.2817 -1.71 13 1.0499 -4.00 41 1.0805 4.99 14 0.8926 -10.33 42 1.0444 -3.99 15 1.0989 8.73 43 1.0318 -4.08 16 2.0916 37.64 44 1.1078 -3.81 17 1.0271 -1.15 45 1.1065 -4.18 18 1.1761 7.51 46 1.5544 2.06 19 1.0444 -2.27 47 1.1383 3.17 20 1.0896 5.67 48 1.0659 1.98 21 1.1298 -1.47 49 1.0894 7.22 22 1.1086 -3.78 50 1.0803 4.97 23 1.0811 6.74 51 1.0643 -2.49 24 1.0617 5.54 52 0.7559 -10 25 1.0569 7.56 53 0.8073 -14.16 26 1.0109 3.7 54 1.0947 -1.27 27 0.8103 39 55 1.1136 4.55 28 0.8831 3.29 56 1.1414 0.25 the table 4, shows the error indices for the error margin between the estimated state and the raw measurement values of the network. the mvmee giving large error margins of 1.1427 and mpaee error margin of 10.19. for the mean index we obtain a large margin of error between the state estimate and the raw measurement point of 23.52. this indicates that raw measurements carry errors large enough to give a misinterpretation of the system being considered. table 4: error index of the nigerian 56 buses s\n error error index 1 max voltage magnitude estimation error (mvmee) 1.1427 2 max phase angle estimation error (mpaee) 10.19 3 mean voltage magnitude estimation error (mvmee) 0.1607 4 mean phase angle estimation error (mpaee) 23.5151 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):495-504. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 502 in figure 5, we obtain the comparison of the voltage angle estimated point result and the raw measurement points. it can be seen that there is a large mismatch margin between the estimation results and the raw measurements. this error in measurements arise due to telemetry noise, instrument calibration, digital to analog conversion and human induced factors. figure 5: voltage angle comparison estimated points and erroneous data points. in figure 6, which shows the voltage magnitude state estimate comparison with the raw measurement we see that at bus 1 we obtain a state estimate voltage magnitude value of 0.9pu whereas the raw measurement says voltage on bus 1 is 0. this shows that without applying the process of state estimation a misinterpretation of the system state will be obtained. figure 6: voltage magnitude comparison estimated values and raw system measurement. figure 7: state estimation result comparison with raw erroneous system data for the nigerian in the figure 7, the entire measurement data base for the nigerian system was analyzed in comparison with the state estimate result. for the nigerian system 400 measurement points where considered for analysis. the graph shows that raw measurement values do not give a true representation of the state of the system. araga et al: state estimation of the nigerian 330kv transmission network using the weighted least square optimization technique. azojete, 17(4):495-504. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 503 3.2 discussion the estimation process was conducted using the wls optimized technique shown in figure 2 and the estimation result was generated as shown in the table 1. table 1 shows, the estimated voltage and phase angles on each of the buses which signifies the system static state estimate. this indicates the accuracy of the estimation process on this test bus system. figures 3 and figure 4 show the estimate result of each state (voltage magnititude and phase angle) which confirms the accuracy of the state estimator to estimate the true state of the system.the error indices in table 2 reveals a maximum phase angle estimation error of which further indicates the error reduction effect of the estimator in processing the voltage phase angle. the maximum voltage magnititude estimation error of proves that estimation error is at a minimum rate on the state. in the analysis of the nigerian 56 bus system, using data obtained from the tcn complete observability could not be achieved. however, in this paper the load flow analysis of the network based on original raw data was carried out the results obtained gave reactive and real power flow on each bus which was then used to further inform the state estimation algorithm. pseudomeasurements was used in place of injection power at buses where real and reactive power was zero. this forced the unobservable islands to become completely observable therefore the entire system observable. the additional datapoints made avaliable from the coventional load flow was added to bring in the factor of a bit of integrity into the erroneous raw data. the raw measurements, power flow results and pesudo measurments created a large database of raw measurment data of the nigerian network. this database was applied as input to the wls optimized technique and the state estimate result was obtained as shown in table 3. figure 5 shows the comparison of the original erroneous data and the estimated datapoints with respect to the voltage angle. as shown in figure 6 and figure 7 there is a large deviation caused by the error in original measurement data. this proves the raw measurement data should not be used directly for power system decisions. in table 4, the error index shows a large error in the raw original data in comparison to the estimated datapoint. the max voltage error in comparison with the raw data in table 4 error index shows an error index of 1.14 and max angle estimation of 10.14 . this shows a massive margin of error between the estimated data point and the original raw data point. table 4 also shows the mean voltage error of 0.1607 and mean angle estimation error of 23.5151. these mean values show another massive error difference embedded in the original data and estimated data points. in obtaining the maximum angle estimation error the algorithm is bounded within a limit so as to ensure the error indices doesn’t enter the region of infinity. this mismatch values indicate that the original meaurement data for network do not represent the true state of the system. 4. conclusion in this paper, raw measurement data obtained from the transmission company of nigeria was processed using weighted least square state estimation technique to obtain the true state of the system. the results show that there are errors embedded in conventional scada and general data obtained from power system measurement instruments. these errors may arise due to data acquistory process, telemetry noise, instrumentation calibration, weather interference, d/a conversion etc. if power system analysis is carried out without engaging the se algorithm as proposed in this work, it will yield results that do not reflect the behavior of the system. when decisions within the power system are implemented based on these data, which do not reflect the true system behavior, the power system could be plunged into devastating outcomes. the complete observability status for the nigerian 330kv transmission system was also achieved using available scada measurements, employed pseudo-measurements and conventional power flow results of each bus. using this database, the nigerian system achieved the status of complete observability through which the state estimate of its state vectors is realized. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):495-504. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: afolayantimilola880@gmail.com 504 references kothari, d., and nagrath, i. 2010. modern power system analysis. 3rd ed. mcgraw hill, pp. 1531, new delhi, india. emodi, n. 2015. improving electricity access in nigeria: obstacles and the way forward. international journal of energy economics and policy. 5(1):335 -351. gotti, d., ledesma, p. and amaris, p. 2020. comparative analysis between state estimation algorithms under static and dynamic scenarios. 2020 ieee international conference on environment and electrical engineering and 2020 ieee industrial and commercial power systems europe (eeeic / i&cps europe), 2020. pp 1-6. oludele, a., shade, k and akinwine, a. 2016. migrating from closed to open supervisory and data acquisition system: a case study of transmission company of nigeria. international journal of scientific and engineering research, 7:618-622. deloitte consulting llp. 2021. power africa nigeria power sector program. ems/scada and communication in nigeria. usaid, 5-71 <http://dec.usaid.gov/dec/search/fusionsearchresults.aspx?q=nigerian+power+system> accessed on 27 july 2021. ibe, a. and okedu, e. 2009. a critical review of grid operations in nigeria. pacific journal of grid operations in nigeria. 10(2):486 -490. okonkwo, r. 1996. instrument for power system disturbance monitoring, data acquisition and control in nigeria. nigeria journal of technology. 17(1) 30-34. fetzer, e. 1975. observability in the state estimation of power system. ieee transactions on power apparatus and system, 94(6):1981-1988. schweppe, f and wildes, j. 1970. power system state estimation part i: exact model. ieee transactions on power apparatus and systems. 89(1):120 – 125. pires, r., costa, a. and mili, l. 1999. iteratively reweighted least-squares state estimation through givens rotation. ieee transaction power system, 14(4):1499-1507. pires, r., mili, l. and becon, l. 2014. constrained robust estimation of power system state variables and transformer tap positions under erroneous zero-injections, ieee trans. power syst., 29(3): 1144— 1152. icseg.iti.illinois.edu. 2021. ieee 14-bus system illinois center for a smarter electric grid (icseg). [online] available at: <https://icseg.iti.illinois.edu/ieee-14-bus-system/> [accessed 24 july 2021]. arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):335-346 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 335 original research article factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria m. m. mukhtar*1, d. abdussalam2 and m. m. mustapha3 1department of quantity surveying, abubakar tafawa balewa university bauchi 2department of building, ahmadu bello university zaria 3department of civil engineering, ahmadu bello university zaria *corresponding author’s email address: mmmukhtar99@gmail.com 1.0 introduction generally, physical facilities in the tertiary institutions of learning are very important. it has been observed that, provision of adequate physical facilities in schools are essential towards improving academic performance of students (ajayi and ayodele, 2001, musa and ahmad, 2012; akomolafe and adesua, 2016). similarly, saeed and kayani (2019) opined that physical facilities have impacts on the students’ academic performance, safety and comfort. musa and ahmad (2012), added that adequate physical facilities of required standard which includes classrooms, lecture theatres, laboratories, workshops, ict centers, studios, libraries, hostel, health centers, office accommodations among others, are necessary for effective learning and teaching. however, despite the importance of physical facilities in improving academic performance of students, it has been reported that higher education institutions in nigeria face challenges with regards to adequate funding for the provision of facilities and rehabilitation of decaying ones in various institutions, this affects students’ performance (isa and yusoff, 2015). article information abstract higher education institutions in nigeria faced with the challenges of inadequate funding for the provision of facilities and rehabilitation of decaying ones. to address this issue, the tertiary education trust fund (tetfund) was established. however, it has been reported that, there are poor time performance of tetfund projects in tertiary institutions in nigeria. this study was conducted to determine factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. thirty-two (32) factors causing delay in construction projects were identified from the literature review. data collection was carried out by means of survey questionnaire. one hundred and thirty-six questionnaires (136) were shared among construction professionals comprising of clients, contractors and consultants, 112 were returned completed representing 82% response rate. the data collected were analysed by means of frequency, severity index and spearman’s rank correlation. the results obtained revealed that, the most common delay factor in tetfund construction projects according to the three categories of the respondents is late procurement of materials. similarly, there is consensus among the three categories of the respondents that type of project bidding and award is one of the most severe delay factors in tetfund projects. clients and consultants pointed out that, factors with high impacts on time performance include ineffective planning and scheduling of project by contractor, poor site management and supervision by contractor, and shortage of qualified workers. whereas, based on contractors’ views, delay in progress payments by client has the highest impact. the study recommended that adequate planning and scheduling for all activities of project should be done by contractors at an appropriate time. the findings of this study can assist tetfund construction project team members to understanding factors that can significantly affect timely delivery of their projects. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 26 january, 2021 revised 14 may, 2021 accepted 19 may, 2021 keywords: construction projects tetfund tertiary institutions facilities northeast mukhtar et al.: factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. azojete, 17(3):335-346. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 336 to address the issues of funding for development of infrastructure, the education trust fund (etf) was established by the educational tax act no. 7 of 1993. the act imposed 2% tax on the accessible profits of all companies in nigeria. in 2011 the education tax act was replaced by the tertiary education fund (tetfund) act 2011 due to lapses and challenges in operating the etf. one of such lapses was that, the etf was overburdened and overstretched. the tetfund act 2011 mandated the fund to operate as an intervention agency in nigerian tertiary educations (federal and states), to provide funding for educational facilities and infrastructural development in public tertiary institutions, with a view to ensuring rehabilitation, restoration and consolidation of tertiary education in nigeria. the funds are disbursed for the general improvement of education in federal and states tertiary educations, and specifically for the provision or maintenance of essential physical infrastructure for teaching and learning among others (tetfund, 2020). despite efforts by tetfund in discharging its responsibilities, previous studies (gambo et al., 2017, aghimien and aigbavboa, 2018, zailani et al., 2019) have reported that, there are poor time performance of tetfund projects in tertiary institutions in nigeria. for instance, aghimien and aigbavboa (2018) found that, about 86% of the assessed tetfund projects experienced time overrun of 66% to 860%, with an average of 199% time overrun. whereas gambo et al., 2017 revealed that 43% of the tetfund projects studied were not completed within agreed time and cost. thus, there is need to identify factors causing delay in tetfund projects. the aim of this study is to evaluate factors that affect time performance of tetfund construction projects in tertiary institutions in northeast, nigeria. the objectives of the study are: i. to identify factors that affect time performance of construction projects. ii. to evaluate frequency for the occurrence of the factors in tetfund construction projects in the tertiary institutions in north-east, nigeria. iii. to assess severity of the factors on time performance of tetfund construction projects in the tertiary institutions in north-east, nigeria. iv. to determine the impacts of the factors on time performance of tetfund construction projects in the tertiary institutions in north-east, nigeria. previous studies (aghimien and aigbavboa, 2018; zailani et. al., 2019) focused on assessing performance of some selected tetfund projects in nigeria. however, limited studies if any were carried out to determine time overrun factors of the projects. thus, this study addressed this gap. generally, identifying time overrun factors will reduce cost overruns as well as potential claims between client and contractor (chan and kumaraswamy, 2002). 1.1 factors affecting time performance of construction projects several studies have been carried out to identify factors affecting time performance of construction projects. study conducted by assaf and al-hejji (2006), revealed 73 causes of delay in large construction projects. the identified causes were categorized into nine groups namely: factors related to project, client, contractor, consultant, design-team, materials, equipment, manpower (labor), and external factors. the study identified the most important causes of delay as shortage of labour, unqualified work force, inadequate contractors experience, difficulties in financing project by contractor, ineffective planning and scheduling of project by contractor, low productivity level of labour, rework due to errors during construction, delay in progress payments by client, original contract duration is too short, shortage of labour, delay in material delivery, poor site management and supervision by contractor, type of project bidding and award, poor qualification of the contractor’s technical staff, change order by client during construction, slowness in decision making process by the client, late procurement of materials, mistakes and discrepancies in contract documents. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):335-346. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 337 chan and kumaraswamy (2002) presented the following as major factors causing delays in construction projects. these are: inclement weather, labour shortage/ labour low productivity, poor subcontractors’ performance, variation, unforeseen ground condition, materials shortage/ late materials delivery, inadequate construction planning, financial difficulties of contractor, delays in design work, poor site management, impractical design, poor communication, inappropriate type of contract used, lack of designer’s experience, and inaccurate estimating. gambo et al. (2017) identified the following as factors affecting the successful completion of some selected tetfund projects. these are increase in materials price, inadequate supply of materials, lack of quality control of material, difficulties in receiving progress payment from client, lack of technical skill of the project manager, lack of experience of the project manager, lack of managerial skills of the project manager, lack of motivating skills of the project manager, lack of commitment of project team members, and economic environment. omoregie and radford (2006) classified the following as factors responsible for project delay, namely, poor contract management, financing and payment of completed work, changes in site conditions, weather, shortages of materials, mistakes and discrepancies in contract document, subcontractors and nominated suppliers, non-adherence to contract conditions, mistakes during construction, inaccurate estimates, delays, shortening of contract periods and design changes. dlakwa and culpin (1990) presented the following factors as responsible for time overrun in public sector construction projects in nigeria. these are contractors’ difficulties in receiving interim payments from public agencies, contractors’ financial difficulties, inadequate public agencies’ budgets, deficiencies in contractors’ organizations, deficiencies in planning and scheduling, frequent variation/change orders, difficulties in obtaining construction materials, deficiencies in public agencies’ organizations, contractors’ unrealistic tenders, design-related, unrealistic, contract durations imposed by public agencies, large quantities of extra work, unexpected natural and social events, deficiencies attributed to construction plant and equipment, inadequacy of site inspection, shortage of qualified workers, disagreement related to interpretation of contract specification and clauses etc. elinwa and joshuwa (2001) reported the following factors as causes of time overrun in construction projects in nigeria. these are: non-compliance with conditions of contract, mode of financing and payment for completed work, improper planning, frequent changes in design and materials (variation), underestimation of time for projects, lack of coordination between contractor and design team, preparation and approval of variation orders, poor site management, relationship between management and labor, choice of materials not readily available, mistakes during construction, delays caused by subcontractors and suppliers, inadequate supply of labor, government policy, disputes on site, maintenance work on machinery/plant, inclement (severe) weather conditions, contractor handling work on more than one site, transportation of materials and plant to site, changing construction techniques to unfamiliar ones, lack of proper incentives to operatives, litigation, off-site manufacture of items/building components/ items. enshassi et al. (2009) identified 110 factors causing delays in construction projects in the gaza strip, the factors were categorized into 12 groups namely project related factors, contractors related factors, consultants related factors, clients related factors, professional management related factors, design and documentation related factors, materials related factors, execution related factors, labour and equipment related factors, contractual relationship related factors, government relation related factors, and external factors. mukhtar et al.: factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. azojete, 17(3):335-346. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 338 shehu et al. (2014) developed a list of 84 major causes of time overruns in malaysian construction projects. overall mean responses indicates that the ten most critical factors are cash flow problem faced by the contractor, late payment from contractor to subcontractor or suppliers, problems between the contractor and his subcontractors with regards to payments, ineffective planning and scheduling of the project by the contractor, difficulties in financing the project by the contractor, ineffective control of the project progress by the contractor, late payment from client to contractor, bureaucracy in government agencies, slow permits by local authorities, and delay in progress payments by the client. based on the previous work presented above, this study identified 32-time overrun factors as shown in table 1. although these factors are not exhaustive, they are the most common factors affecting project time performance cited in the literature. 2. research methodology the study was conducted in bauchi and gombe states, north-east nigeria through quantitative research technique. the two states were selected from the region because of the accessibility of the data. questionnaire survey was used as a means of data collection approach. questionnaire is one of the widely used data collection technique within the survey strategy that provides efficient way of collecting large responses from large sample (saunders et al., 2009). the questionnaire was divided into three sections. section 1 covers demographic information of the respondents. section 2 required respondents to indicate their views on the extent/frequency of occurrence of the listed factors during execution of tetfund construction projects in which they were involved using a scale of 1 to 5, where 1 represents very rarely, 2 = rarely, 3= sometimes, 4= often, and 5= always. section 3 elicit respondents’ opinions on the effects of the listed factors on the time performance of tetfund construction projects in the study area using a scale of 1 to 5, where 1 represents very low effect, 2= low effect, 3= moderate, 4= high effect, and 5= very high effect. the target population for this study were construction professionals (architects, quantity surveyors, engineers, and builders etc.) who involved in tetfund sponsored construction projects in bauchi or gombe state. one hundred and thirty-six questionnaires (136) were administered to the construction professionals including 37 contractors (those who work in contracting company), 32 clients (those who work in tertiary institutions), and 67 consultants (those who work in consulting firms). convenience sampling technique was used to access the respondents; this is because a sample frame for this study cannot be established. the clients included construction professionals working in works department/ physical planning units of universities, polytechnics and colleges of education located in the study area, where tetfund projects are being executed. the data collected from the survey were analysed by means of descriptive statistics and severity index. percentages were employed in the analysis of section 1 of the questionnaire. whereas, in section 2, frequency fomular used by assaf and al-hejji (2006) was employed to analysed the data in order to determine the extent of the occurrence of the factors in tetfund construction projects. the formular is: frequency index = (f.i) (%) = ∑a(n/n)*100/5 (1) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):335-346. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 339 where a is the constant expressing weighting given to each response (ranges from 1 for very rarely up to 5 for always), n is the frequency of the responses, and n is total number of responses. in section 3, severity index was employed to analyse the data collected in order to assess the effects of the factors on the performance of tetfund construction project. the following formular was used as in assaf and al-hejji (2006), severity index = (s.i) (%) = ∑a(n/n)*100/5 (2) where: a, is the constant expressing weighting given to each response (ranges from 1 for very low effect to 5 for very high effect), n is the frequency of the responses, and n is total number of responses. the impacts of each factor on the performance of tetfund construction projects were evaluated using the following formular as in assaf and al-hejji (2006). impact: the impact of each cause is calculated as a function of both frequency and severity indices (assaf and al-hejji, 2006): impact = [f.i. (%) * s.i. (%)]/100 (3) spearman’s rank correlation was used to determine the degree of agreement between the different parties. the correlation coefficient varies between +1 and -1, where +1 implies a perfect positive relationship (agreement), while -1 suggests a perfect negative relationship disagreement (pallant, 2011). in this research spearman’s rank correlation coefficient r is used to assess and compare the relationship between the rankings of two parties for each time overrun factor, while ignoring the ranking of the third party. the value of r is calculated by means of spearman’s correlation analysis in the spss software. 3. results and discussion 3.1 respondent’s general information out of the 136 questionnaires distributed, 112 were completed and returned which comprises of 31 contractors, 28 clients, and 53 consultants representing 82% response rate. the average years of respondents’ experience are 16, 11 and 14 for the contractors, clients and consultants respectively. all the respondents have at least higher national diploma or bachelor’s degree as their academic qualification and have been involved in not less than three tetfund construction projects. thus, based on their experience and academic qualifications, it was assumed that the respondents could provide reliable information. 3.2 frequency of time overrun factors the frequency of time overrun factors of tetfund projects based on the views of clients, contractors and consultants have been shown in table 1. the results reveal that, the five most frequent time overrun factors from the clients’ point of view are ineffective planning and scheduling of project by contractor, poor site management and supervision by contractor, delays in sub-contractors’ work, shortage of qualified workers and late procurement of materials, these factors are mainly related to contractors. generally, project planning is essential for the success of any construction project (toor and ogunlana, 2009), as inadequate planning may lead to unexpected delays (clarke, 1999). whereas, completing a project on schedule indicates the contractor’s ability to manage site operation effectively and allocate resources optimally (chan, d.w.m. and kumaraswamy, 1997). hwang et al. (2013) claimed that availability of qualified workers ensures smooth progress of work, while shortage of qualified mukhtar et al.: factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. azojete, 17(3):335-346. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 340 workers results in construction delay. on the other hand enshassi et al. (2009) asserts that materials are important resources in construction projects, hence, late delivery of materials can lead to delay in completion of work. table 1: ranking frequency of occurrence of time overrun factors time overrun factors clients contractors consultants index rank index ran k index ran k ineffective planning and scheduling of project by contractor 67.36 1 41.59 31 51.19 5 poor site management and supervision by contractor 67.23 2 41.27 32 53.68 1 delays in sub-contractors work 65.19 3 56.78 4 46.06 13 shortage of qualified workers 63.92 4 47.09 20 53.21 2 type of project bidding and award 56.32 7 53.76 9 49.59 7 late procurement of materials 62.11 5 57.16 3 51.96 3 inflation 55.07 9 53.43 10 44.42 18 inclement weather 58.33 6 52.61 12 45.11 15 slowness in decision making process by client 50.77 16 56.55 5 51.74 4 delays in site mobilization 52.05 13 46.66 21 40.32 29 shortage of equipment at site 50.03 17 44.31 26 44.76 17 rework due to errors during construction 51.55 15 44.21 27 48.47 9 shortages of materials 55.37 8 47.88 18 46.55 12 change orders by the client during construction 52.21 12 53.97 8 49.33 8 poor communication and coordination by client and other parties 42.47 29 45.07 24 48.26 10 mistakes and discrepancies in contract document 48.43 18 54.45 7 41.80 23 delays in design work, 43.15 28 52.29 13 40.38 28 unforeseen ground condition (poor site condition) 46.84 22 50.91 14 45/39 14 non-adherence to contract conditions 51.98 14 45.11 23 39.61 31 delays in work approval 52.73 10 56.14 6 42.65 21 unclear and inadequate details in drawings 52.46 11 58.32 2 41.32 25 contractors financial difficulties 40.35 32 46.39 22 46.87 11 incomplete drawings 47.66 20 50.42 15 41.16 26 bureaucracy in government agencies 44.57 25 53.27 11 45.04 16 lack of experience on the part of the consultants 41.32 31 49.73 16 39.22 32 delay in progress payments by client 41.98 30 58.67 1 50.28 6 unrealistic contract duration 47.19 21 49.17 17 42.36 22 inadequate contractors experience 46.23 23 43.18 28 40.75 27 contractors’ unrealistic tenders 43.75 27 44.77 25 41.47 24 inappropriate construction methods 44.54 26 43.16 29 42.83 20 poor qualification of the contractor’s technical staff 48.27 19 41.96 30 44.25 19 complexity of project design 45.42 24 47.54 19 39.92 30 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):335-346. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 341 from the contractors’ point of view, the results indicate that, five most frequent time overrun factors are delay in progress payments by client, unclear and inadequate details drawings, late procurement of materials, delays in sub-contractors work, and slowness in decision making process by client. it can be noted that most of these factors are related to clients and consultants. certainly, delay in progress payments by client will affect the cash inflow of contractors and this leads to delay in completion of the project (assaf and al-hejji, 2006). similarly, inadequate detail drawing and slowness in decision making process by client are factors that can delay the progress of work (enshassi et al., 2009; hwang et al., 2013; assaf and al-hejji, 2006). from the consultants’ point of views, five most frequent time overrun factors are poor site management and supervision by contractor, shortage of qualified workers, late procurement of materials, slowness in decision making process by client, and ineffective planning and scheduling of project by contractor. most of the factors are related to contractors. it can be observed that all the parties opined that late procurement of materials is one of the most frequent time overrun factors in tetfund projects. these findings are in agreement with the previous studies (gambo et al., 2017; assaf and al-hejji, 2006, chan and kumaraswamy, 2002). 3.3 severity of time overrun factors the severity of time overrun factors based on the views of clients, contractors and consultants have been shown in table 2. the results show that, the most severe time overrun factors from the clients’ point of views are type of project bidding and award, shortage of qualified workers, ineffective planning and scheduling of project by contractor, delays in sub-contractors work, and slowness in decision making process by client. from the contractors’ point of view, the most severe time overrun factors are delay in progress payments by client, delays in work approval, unclear and inadequate details in drawings, incomplete drawings and type of project bidding and award. however, from the consultants’ point of view, the most severe time overrun causes are delay in progress payments by client, type of project bidding and award, contractors financial difficulties, ineffective planning and scheduling of project by contractor and slowness in decision making process by client. these findings are supported by previous studies (gambo et al., 2017; assaf and al-hejji, 2006, chan and kumaraswamy, 2002). all the parties agreed that type of project bidding and award is one of the most severe cause overrun factors. however, clients and consultants opined that ineffective planning and scheduling of project by contractors are among the major causes of time overrun. generally, awarding the contract to lowest bidder may lead to low performance and consequently delay in project completion. this is because the lowest bidders are likely to be contractors with low capabilities (assaf and al-hejji, 2006). mukhtar et al.: factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. azojete, 17(3):335-346. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 342 table 2: ranking degree of severity of time overrun factors 3.4 impacts of time overrun factors tables 3 show the impacts of time overrun factors on the projects performance according to the views of clients, contractors and consultants. the impact indices were calculated as a product of both frequency and severity indices. time overrun factors clients contractors consultants index rank index rank index rank delay in progress payments by client 50.13 18 71.21 1 66.33 1 unclear and inadequate details in drawings 42.93 30 68.94 3 59.13 13 delays in work approval 43.28 29 70.57 2 55.09 20 slowness in decision making process by client 59.03 5 67.81 6 65.47 5 delays in sub-contractors work 59.52 4 65.14 10 61.36 10 type of project bidding and award 62.24 1 67.98 5 65.78 2 late procurement of materials 51.06 15 62.22 14 63.65 7 delays in design work, 54.52 12 67.29 7 52.95 23 change orders by the client during construction 48.89 20 64.39 11 59.46 12 incomplete drawings 46.14 24 68.54 4 58.67 14 mistakes and discrepancies in contract document 50.22 17 61.72 16 55.68 19 bureaucracy in government agencies 48.22 21 62.15 15 53.94 21 inclement weather 51.55 14 60.84 17 50.39 27 inflation 55.65 8 59.43 20 49.79 28 shortage of qualified workers 60.13 2 66.55 8 62.49 8 shortages of materials 46.55 23 64.17 12 59.92 11 lack of experience on the part of the consultants 51.91 13 59.16 21 55.90 18 unforeseen ground condition (poor site condition) 50.04 19 57.55 23 45.15 32 shortage of equipment at site 54.93 11 65.84 9 57.88 16 contractors financial difficulties 55.16 9 59.77 19 65.25 3 unrealistic contract duration 44.53 27 55.87 25 52.05 24 poor site management and supervision by contractor 57.91 7 62.91 13 63.82 6 complexity of project design 40.97 32 53.45 28 51.55 25 poor communication and coordination by client and other parties 58.36 6 56.33 24 61.88 9 ineffective planning and scheduling of project by contractor 59.79 3 60.38 18 65.91 4 inappropriate construction methods 45.77 25 57.60 22 50.92 26 delays in site mobilization 55.12 10 51.98 30 53.42 22 rework due to errors during construction 50.43 16 53.24 29 49.42 29 inadequate contractors experience 44.86 26 54.19 27 57.18 17 non-adherence to contract conditions 14.15 28 51.37 31 47.69 30 poor qualification of the contractor’s technical staff 41.44 31 54.43 26 58.23 15 contractors’ unrealistic tenders 47.36 22 50.48 32 45.94 31 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):335-346. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 343 the results indicated that, from the clients’ view point the five most important time overrun factors based on their degree of impacts are ineffective planning and scheduling of project by contractor, poor site management and supervision by contractor, delays in sub-contractors work, shortage of qualified workers and type of project bidding and award. whereas, from the contractors’ view point the most important time overrun factors based on their degree of impacts are delay in progress payments by client, unclear and inadequate details in drawings, delays in work approval, slowness in decision making process by client and delays in sub-contractors work. table 3: ranking impacts of time overrun factors time overrun factors clients contractors consultants index rank index rank index rank poor site management and supervision by contractor 38.93 2 25.96 22 34.26 1 slowness in decision making process by client 29.97 9 38.35 4 33.87 2 ineffective planning and scheduling of project by contractor 40.27 1 25.11 25 33.74 3 delay in progress payments by client 21.04 26 41.78 1 33.35 4 shortage of qualified workers 38.44 4 31.34 15 33.25 5 late procurement of materials 31.71 6 35.56 7 33.07 6 type of project bidding and award 35.05 5 36.55 6 32.62 7 contractors financial difficulties 22.26 22 27.73 20 30.58 8 poor communication and coordination by client and other parties 24.79 15 25.39 24 29.86 9 change orders by the client during construction 25.53 14 34.75 9 29.33 10 delays in sub-contractors work 38.80 3 36.99 5 28.26 11 shortages of materials 25.77 13 30.72 16 27.89 12 shortage of equipment at site 27.48 11 29.17 19 25.91 13 poor qualification of the contractor’s technical staff 20.00 31 22.84 31 25.77 14 unclear and inadequate details in drawings 22.52 21 40.21 2 24.43 15 bureaucracy in government agencies 21.49 24 33.11 12 24.29 16 incomplete drawings 21.99 23 34,36 10 24.15 17 rework due to errors during construction 26.00 12 23.54 28 23.95 18 delays in work approval 22.82 20 39.62 3 23.50 19 inadequate contractors experience 20.74 28 23.40 29 23.30 20 mistakes and discrepancies in contract document 24.32 16 33.61 11 23.27 21 inclement weather 30.07 8 32.01 13 22.73 22 inflation 30.65 7 31.75 14 22.12 23 unrealistic contract duration 21.01 27 27.47 21 22.05 24 lack of experience on the part of the consultants 21.45 25 29.42 17 21.92 25 inappropriate construction methods 20.39 30 24.86 26 21.81 26 delays in site mobilization 28.69 10 24.25 27 21.54 27 delays in design work 23.53 17 35.19 8 21.38 28 complexity of project design 18.61 32 25.41 23 20.58 29 unforeseen ground condition (poor site condition) 23.44 18 29.30 18 20.49 30 contractors’ unrealistic tenders 20.72 29 22.60 32 19.05 31 non-adherence to contract conditions 22.95 19 23.17 30 18.89 32 mukhtar et al.: factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. azojete, 17(3):335-346. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 344 from the consultants’ view point the most important time overrun factors based on their degree of impacts are poor site management and supervision by contractor, slowness in decision making process by client, ineffective planning and scheduling of project by contractor, delay in progress payments by client, and shortage of qualified workers. the results are similar to that obtained by previous studies (gambo et al., 2017; assaf and alhejji, 2006, chan and kumaraswamy, 2002)). based on the views of the parties, there is no time overrun factor among the five top that is common. however, there are some factors that are common between two parties, for instance, ineffective planning and scheduling of project by contractor, poor site management and supervision by contractor, shortage of qualified workers (between clients and consultants), delays in sub-contractors work (between clients and contractors), and delay in progress payments by client, slowness in decision making process by client (between contractors and consultants). slowness in decision making process by client (between contractors and consultants). 3.5 impact ranking correlation spearman’s rank correlation coefficient is used to assess the extent of agreement or disagreement with respect to the impacts ranking of two parties while ignoring the third party, table 4 shows the results. the results reveal that, there is large correlation between clients and consultants (r=0.62), suggesting relatively good agreement in ranking time overrun factors between the two parties. whereas there is small correlation between clients and contractors (r= 0.26), suggesting low agreement in ranking time overrun factors between the two parties. similarly, there is small correlation between consultants and contractors (r = 0.28), also suggesting low agreement in ranking time overrun factors between the two parties (pallant, 2011). these results indicate that contractors’ views on ranking time overrun factors differed with that of clients and consultants. thus, attention should be given to the different views. table 4: spearman rank correlation coefficient parties spearman rank significance level correlation coefficient clients and contractors 0.262 0.142 clients and consultants 0.618 0.001 contractors and consultants 0.278 0.127 4. conclusions this study was conducted to identify factors affecting time performance of tetfund construction projects in tertiary institutions of learning in north-east, nigeria. data were collected by means of questionnaire survey of construction professionals comprising clients, contractors and consultants. the views of clients and consultants showed that, the most frequent time overrun factors are related to contractors. whereas contractors pointed out that they are related to clients and consultants. there is agreement among the three parties that type of project bidding and award is one of the most severe time overrun factors. the study reveals that there is relatively good agreement between clients and consultants in ranking of the impacts of time overrun factors. however, there is very low degree of agreement between clients and contractors, as well as between consultants and contractors. in order to improve time performance of tetfund projects, it is recommended that progress payments should be done by clients as soon as when due. on the other hand, contractors should ensure adequate planning and scheduling for all activities throughout the project. all arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):335-346. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 345 drawings and specifications should be complete, adequate in details and clear before the commencement of work. the findings of this study can assist tetfund project team members to understand significant factors that can affect completion time of the projects; thus, appropriate measures can be put in place. references aghimien, d. and aigbavboa, c. 2018. performance of selected funding schemes used in delivering educational buildings in nigeria. proceedings of the international conference on industrial engineering and operations management held in washington dc, usa, pp. 108-119. ajayi, ia. and ayodele, jb. 2001. introduction to educational planning, administration and supervision. yemi printing services, ado-ekiti. akomolafe, co. and adesua, o. 2016. the impact of physical facilities on students’ level of motivation and academic performance in senior secondary school in southwest nigeria. journal of education and practice, 7(4): 38-42. assaf, sa. and al-hejji, s. 2006. causes of delay in large construction projects. international journal of project management, 24: 349–357. doi:10.1016/j.ijproman.2005.11.010 chan, dwm. and kumaraswamy, mm. 1997. a comparative study of causes of time overruns in hong kong construction projects. international journal of project management, 15(1): 55-63. chan, dwm. and kumaraswamy, mm. 2002. compressing construction durations: lessons learned from hong kong building projects. international journal of project management, 20: 23-35. clarke, a. 1999. a practical use of key success factors to improve the effectiveness of project management. international journal of project management, 17(3): 139-45. dlakwa, mm. and culpin, mf. 1990. reasons for overruns in public sector construction projects in nigeria. project management, 8(4): 237-241. elinwa, au. and joshua, m. 2001. time overrun factors in nigerian construction industry. journal of construction engineering and management, 127(5): 419-425. enshassi, a., al-najjar, j. and kumaraswamy, m. 2009. delays and cost overruns in the construction projects in the gaza strip. journal of financial management of property and construction, 14(2): 126-151. gambo, s., ibrahim, k., iliyasu, ma., winston, mw. and ibrahim, ml. 2017. stakeholders’ perception of the success of tertiary education trust fund construction projects. atbu journal of environmental technology, 10(2): 117-128. hwang, bg., zhao, x. and ng, sy. 2013. critical factors affecting schedule performance of public housing projects. habitat international, 38: 214221. http://dx.doi.org/10.1016/j.habitatint.2012.06.008 isa, i. and wan yusoff, w. 2015. state of physical facilities of higher education institutions in nigeria. international journal of scientific and research publications, 5(4): 1-5. musa, mf. and ahmad, z. 2012. higher education physical assets and facilities. procedia-social and behavioral sciences, bangkok, thailand, 50: 472-478. omoregie, a. and radford, d. 2006. infrastructure delays and cost escalation: causes and effects in nigeria. proceedings of the sixth international postgraduate research conference held in delft university of technology, netherlands. mukhtar et al.: factors affecting time performance of tertiary education trust fund construction projects in north-east, nigeria. azojete, 17(3):335-346. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mmmukhtar99@gmail.com 346 pallant, j. 2011. spss survival manual: a step by step guide to data analysis using spss. 4th ed. allen and unwin, australia. saeed, n. and kayani, a.i. 2019. a study to investigate the importance of physical facilities to improve teaching learning process at college level in tehsil kotli azad kashmir. asian journal of contemporary education, 3(1): 1-14. saunders, m., lewis, p. and thornhill, a. 2009. research methods for business students, 5th ed. pearson education limited, harlow. shehu, z., endut, ir. and akintoye, a. 2014. factors contributing to project time and hence cost overrun in the malaysian constrution industry. journal of financial management of property and construction, 19(1): 55-75. tetfund, 2020. the establishment and mandate of tertiary education trust fund. www.tetfund.gov.ng, accessed on 7th january, 2021. toor, sr. and ogunlana, so. 2009. construction professionals’ perception of critical success factors for large – scale construction projects. construction innovation, 9(2): 149-167. doi 10.1108/14714170910950803. zailani, mb., kolo, ba., and abubkar, m. 2019. the role of project management in tetfund construction projects. in laryea, s. and essah, e. (eds) proceedings west african built environment research (waber) conference held in accra, ghana, 5-7 august 2019, pp. 1116-1125 arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):371-380 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 371 original research article propagation loss determination of gsm signal strength in selected buildings in ilorin, nigeria j. akanni*1, o. t. oraiye1, a. a. isa1 and o. ogunbiyi2 1department of electrical and electronics engineering, university of ilorin, ilorin, kwara state, nigeria 2department of electrical and computer engineering, kwara state university, malete, kwara state, nigeria *corresponding author’s email address: jimaka2005@gmail.com 1.0 introduction today cellular services are used by millions of people worldwide in which african countries especially nigerian is not left out, according to akanni et al. (2020), nigeria is a developing nation and the number of mobile communication and its applications is geometrically rising. for better cellular services, the environment in which the service is to be render must be taken into consideration when planning the link budget. one of the most important features of the propagation environment is propagation path loss, path loss in an indoor reception may be due to many factors, such as reflection, refraction, diffraction, and mobile unit (oni and idachaba 2017). it has been observed that material used in buildings play significant role in an indoor path loss. the poverty level in nigeria and most of the african countries lead to the choice of different materials used in the different building construction (sholanke et al., 2015). the old style of buildings is still in existence at high proportion both in the rural and urban area and this tend to always make the user of wireless mobile phone to move outdoor in order to receive better service due to the degradation in the amount of signal received in indoor environment. according to elechi and otasowie (2016), the signal propagation losses due to building article information abstract gsm signal building penetration loss is a problem often encountered by subscribers inside a building. as a result of building penetration loss, poor reception and signal outages often occur in many indoor locations and this accounts for increased attenuation of received signal strength of a cellular network signal when a subscriber with a mobile phone moves from outdoor to indoor. the study assessed the gsm signal penetration loss in thatched, wooden, block, mud and zinc buildings. three network providers named a, b and c was used for the experiment. a low budget but very effective equipment (two tecno pouvoir 3 plus android phone) was used as the measurement tool. it was loaded with network signal info application developed by kaibits software gmbh installed software and positioned inside and outside the building to record indoor and outdoor gsm signal strength respectively for the three service providers in ilorin, nigeria. the results were then analyzed in order to determine and compare the path loss introduced by each of the selected buildings. this process was repeated for all the selected buildings, and the measurement was carried out for 6 months. the findings revealed that the outdoor signal strength was higher than the indoor signal strength for all the selected buildings; it also revealed that penetration loss is likely to be a function of the material used in the construction of the buildings. zinc building has the highest penetration loss of 12.0dbm and thatched building has the least penetration loss of 2.6dbm. information from this research will assist in selection of building materials for good indoor cellular network signal reception. it will also assist cellular network service providers in the link budget preparation for environments where similar building materials are used. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 february, 2021 revised 28 may, 2021 accepted 5 june, 2021 keywords: buildings electromagnetic wave gsm propagation loss received signal strength akanni et al.: propagation loss determination of gsm signal strength in selected buildings in ilorin, nigeria. azojete, 17(3):371-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 372 materials constitute about 31% of the total gsm signal loss. buildings penetration loss leads to an increase in attenuation of the received signal observed when the mobile is moved from outside to inside of a building (idim and anyasi , 2014). 1.1 gsm signal propagation approach forecasting and determining the magnitude of gsm signal strength in a particular environment involves studying and understanding radio communication primarily in that environment(joseph et al., 2013).radio wave communication especially in an indoor environment is subjected to some factors such as reflection, diffraction and scattering(ahamed and faruque .,2016). reflection is said to have occurred when a propagating wave encounters a large man-made or naturally occurring object, which has dimensions that are large compared to the wavelength of the propagating wave. a reflection may result in either decrease or increase in the level of signal power at the reception point (neskovic et al., 2000). diffraction occurs when the radio wave encounter the obstacles with sharp irregular surfaces (edges/wedges) and has the dimension larger than the signal wavelength(elechi otasowi 2016).as a result of diffraction, signal wave bends over or around the edge of an obstruction thus resulting in weak signal at the receiving end (heydariaan et al., 2018). scattering occurs when the propagation path contains objects like uneven walls, lamp posts and other small objects with irregular surfaces whose dimensions are small compared to the wavelength of the propagating signal. of all the stated effects, scattering is the most difficult to predict (neskovic et al., 2000). 1.2 propagation loss propagation loss or path loss is the reduction in the power density of an electromagnetic wave as it propagates through space and is the major component in the analysis and design of the link budget of a telecommunication system(idim and ayansi 2014). the propagation loss is caused by many factors such as reflection, refraction, diffraction, free space loss, aperture medium coupling loss, terrain contours, environment such as rural, urban, vegetation and foliage (idim and anyasi 2014). a number of propagation models are available to predict path loss over different types of terrain. the models are generally classified into three namely; deterministic, statistical and empirical models (sharma and singh 2010). 1.3 review of related works a lot of researches on building penetration loss had been carried out in the past and there are still some on-going researches by authors in the field to address the issue. turkmanj and de toledo as cited in svistunov and mordachev(2016), carried out an investigation on propagation into and within buildings at 1800 mhz using buildings in the university of liverpool environment; mean signal measurements were conducted in rooms and corridors of four different buildings and thereafter compared with street level outside. the average measured penetration loss at ground floor level was found to be 13 db and rate of change of penetration loss with height was 1.4 db per floor. for floor levels higher than the sixth floor, it was found to be 0.4 db per floor. the rate of change of the mean signal level for signals travelling within buildings was, on average, 8.3 db per floor. the best coverage was obtained by locating the transmitter in a large room at the centre of the building. the path loss attenuation factor n that best modelled the within-building measurements was found to be 5.6. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):371-380. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 373 idim and anyasi and (2014) investigate the determination of building penetration loss of gsm signals in some selected buildings in orhuwhorun, delta state, nigeria for concrete and blocks and found that the average penetration loss to be 10.62dbm, and 4.25dbm respectively. in addition, elechi and otasowie(2015) similar experimentin some selected buildings in rivers state, nigeria; using mud house with thatched roof, mud house/rusted corrugated iron sheet roof, sandcrete building/rusted corrugated iron sheet roof, sandcrete building/unrusted corrugated iron sheet roof and building with alucoboard wall cladding. the results showed that buildings with alucoboard wall cladding have the highest gsm signal penetration loss while the sandcrete building/unrushed corrugated iron sheet roof has the lowest gsm penetration signal loss. furthermore such an investigation was conducted by abiodun and ukhurebor(2018)and their results reviewed that the average penetration loss for the tilled, concrete, mud and the wooden buildings are 13.0 dbm, 10.8 dbm, 9.57 dbm and 8.72 dbm respectively. it was observed that the tiled building with concrete tiled roof has the highest penetration loss in all the months considered, followed by the concrete wall building with corrugated galvanized iron roof, while the wooden wall building with rusted corrugated roof was having the lowest penetration loss. this brief review of relevant research highlights the paucity of relevant studies in the local nigerian system and african as a whole. it is evident from the reviewed of the existing works that none of the authors worked on gsm signal penetration loss introduced by full thatched building, also, the values of the signal strengths inside and outside the buildings were not measured simultaneously (not measured at the same time) and this may affect the accuracy of the measured values. this work aims at investigation of the gsm signals penetration loss introduced by full thatched building in addition to the one introduced by wooden, block, mud and zinc buildings. it also aims at providing a better methodology for accurate measurement values of the signal strength. this research work made used of two similar equipment (two tecno pouvoir 3 plus android phone) to measure the values of the signal strengths inside and outside the building simultaneously. in this way, the errors that would have occurred due to difference in the time will be eliminated. 2.0 materials and method 2.1 buildings description the buildings selected for the experiment are located in ilorin, the capital of kwara state, nigeria. it represents the prevalent types of buildings that can be found in most african countries, especially nigeria. the buildings considered for the study are full thatched building made of grass for both wall and roof, wooden building constructed with planks; the roof of which was made with corrugated iron sheet having its floor cement plastered, block building constructed with cement blocks; the roof of which was made with corrugated iron sheets with the floor cement plastered, mud building constructed with mud; with the roof made of corrugated iron sheets, the floor was cement plastered, and zinc building constructed fully with zinc, and the roof made with corrugated iron sheet, the floor cement plastered too. figures 1 to 5 show the photo of thatched, wooden, block, mud and zinc buildings, respectively. akanni et al.: propagation loss determination of gsm signal strength in selected buildings in ilorin, nigeria. azojete, 17(3):371-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 374 figure 1: thatched building figure2: wooden building figure 3: block building figure 4: mud building figure 5: zinc building arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):371-380. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 375 2.2 measurement tools and procedure a tecno pouvoir 3 plus android phone, with network signal info application installed; was used as the measurement tool to record the received signal strength inside and outside each of the five selected buildings. the network signal info application was developed by kaibits software gmbh was used. figure 6(a) shows the screenshot of the measured received signal strength obtained with the tecno pouvoir 3 while figure 6(b) shows the screenshot of the gps location of the cell phone as connected to a base station figure 6: the screenshot of the network signal info application three network providers named a, b and c were used for this experiment. the test equipment loaded with the test software were positioned inside and outside the building to record indoor and outdoor gsm signal strength respectively for the three service providers. this process was repeated for all the selected buildings. the measurement was carried out for 6 months. 3.0 data analysis the penetration and the average penetration loss are calculated using equations(1) and (2) respectively. (1) (2) (a) (b) akanni et al.: propagation loss determination of gsm signal strength in selected buildings in ilorin, nigeria. azojete, 17(3):371-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 376 = indoor signal strength 4.0 results and discussion the experimental results of the measured outdoor signal strength and indoor signal strength from the base stations of the three selected gsm network operators named a, b and c at various selected buildings of different types in ilorin metropolis were recorded. with the aid of statistical “ad-in” feature in microsoft excel the measured signal strengths were used to calculate the average penetration loss introduced by the different building types on the service rendered by each of network providers. table 1 shows the gsm signal penetration loss for thatched building. the monthly average measured outdoor signal strengths, so (dbm), indoor signal strengths, si (dbm) and penetration loss ploss (dbm) for a period of six months for each of the operator were tabulated. also, the average penetration loss ploss (dbm) over a period of six months for each of the operator were tabulated. it was observed that the outdoor signal strength (dbm) received is higher than the indoor signal strengths (dbm) received for all the network providers. it was also observed that the average penetration loss of all the network providers over a period of six months was approximately 2.6 dbm. table 2 shows the gsm signal penetration loss for wooden building. it follows the same trend as in table 1. it was observed that the wooden building has higher penetration loss compared to that of thatched building. it was also observed that the average penetration loss of all the network providers over a period of six months was approximately 3.3 dbm. table 3 shows the gsm signal penetration loss for block building. it follows the same trend as in table 1and 2. it was observed that the block building has higher penetration loss compared to that of thatched and wooden buildings. it was also observed that the average penetration loss of all the network providers over a period of six months was approximately 6.3 dbm. table 4 shows the gsm signal penetration loss for mud building. it follows the same trend as in table 1, 2 and 3. it was observed that the mud building has higher penetration loss compared to that of thatched, wooden, and block buildings. it was also observed that the average penetration loss of all the network providers over a period of six months was approximately 8.3 dbm. table 5 shows the gsm signal penetration loss for zinc building. it follows the same trend as in table 1, 2, 3.and 4. it was observed that the zinc building has higher penetration loss compared to that of thatched, wooden, block and mud buildings. it was also observed that the average penetration loss of all the network providers over a period of six months was approximately12 dbm. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):371-380. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 377 table 1: gsm signal penetration loss for thatched building operator a operator b operator c s/n month so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) 1 2 3 4 5 6 january february march april may june -78 -78 -81 -79 -78 -80 -80 -81 -84 -81 -82 -81 2 3 3 2 4 1 -66 -67 -67 -65 -67 -68 -70 -69 -69 -68 -71 -69 4 2 2 3 4 1 -71 -69 -70 -70 -71 -70 -72 -72 -72 -73 -75 -73 1 3 2 3 4 3 average ploss (dbm) 2.5 2.7 2.7 table 2: gsm signal penetration loss for wooden building operator a operator b operator c s/n month so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) 1 january -81 -83 2 -81 -83 2 -59 -63 4 2 february -79 -85 6 -79 -85 4 -59 -61 2 3 march -81 -85 4 -81 -86 5 -56 -61 5 4 april -81 -84 3 -81 -85 4 -57 -60 3 5 may -81 -84 3 -81 -84 3 -57 -60 3 6 june -80 -83 3 -80 -82 3 -59 -63 4 average ploss (dbm) 3.5 3.3 3.5 table 3: gsm signal penetration loss for block building operator a operator b operator c s/n month so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) 1 january -63 -71 8 -57 -63 6 -63 -70 7 2 february -65 -71 6 -57 -63 6 -63 -70 7 3 march -67 -71 4 -57 -63 6 -65 -71 6 4 april -65 -71 6 -57 -63 6 -63 -69 6 5 may -65 -71 6 -57 -65 8 -63 -70 7 6 june -63 -71 8 -57 -63 6 -65 -69 4 average ploss (dbm) 6.3 6.3 6.2 table 4: gsm signal penetration loss for mud building operator a operator b operator c s/n month so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) 1 january -81 -91 10 -85 -93 8 -73 -85 12 2 february -81 -88 7 -85 -91 7 -75 -85 10 3 march -81 -89 8 -83 -93 10 -79 -85 6 4 april -81 -89 8 -83 -91 8 -75 -85 10 5 may -81 -90 9 -83 -91 8 -79 -85 6 6 june -81 -89 8 -85 -94 9 -79 -85 6 average ploss (dbm) 8.3 8.3 8.3 akanni et al.: propagation loss determination of gsm signal strength in selected buildings in ilorin, nigeria. azojete, 17(3):371-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 378 table 5: gsm signal penetration loss for zinc building operator a operator b operator c s/n month so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) so (dbm) si (dbm) ploss (dbm) 1 january -79 -91 12 -79 -89 10 -79 -93 14 2 february -79 -93 14 -79 -93 14 -79 -93 14 3 march -79 -91 12 -81 -93 12 -79 -89 10 4 april -83 -95 12 -81 -92 11 -79 -89 10 5 may -83 -93 10 -81 -93 12 -79 -89 10 6 june -89 -91 12 -81 -93 12 -79 -93 14 average ploss (dbm) 12 11.8 12 figure 7 shows the bar chart of the average penetration loss of each of the building type for each of the network provider obtained with the aid of statistical “ad-in” feature in microsoft excel as tabulated in table 1 through table 5. the bar chart easily revealed the average penetration loss of each building type for each of the network provider and it can be seen that the thatched building has the lowest average penetration loss, followed by the wooden while the zinc has the highest average penetration loss. figure 7: average penetration loss ploss over a period of six months 4.0 conclusion in this paper, measurements on outdoor signal strengths and indoor signal were used to determine the penetration loss on gsm signal strength caused by different types of buildings. building penetration loss which is one of the major parameter in the determination of received signal strength inside a building in telecommunication systems design has been evaluated for the selected building made of different materials. the results obtained shows that the outdoor 0 2 4 6 8 10 12 14 thatched wooden block mud zinc a ve ra ge p lo ss (d b m ) building type opeartor a operator b operator c arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):371-380. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 379 signal strength was higher than the indoor signal strength for all the selected buildings; it also revealed that penetration loss is likely to be a function of the material (mud, brick, zinc and thatched) used in the construction of buildings. zinc building has the highest penetration loss of 12.0dbm and thatched building has the least penetration loss of 2.6dbm.also the block and mud building penetration loss is almost in conformity with that of existing research work (idim et al., 2014). from the study, it is concluded that for good indoor cellular network signal reception, selection of building materials should always be taken into consideration. it is recommended that the gsm service providers should take into consideration when preparing the link budget the types of materials used in building structure in that environment. references abiodun, ic. and ukhurebor, ke. 2018. assessment of building penetration loss of cellular network signals at 900 mhz frequency bands in otuoke, bayelsa state, nigeria.elixir electrical. engineering, 119: 51042–51048. ahamed, mm. and faruque s. 2016. propagation factors affecting the performance of 5g millimeter wave radion channel. proceedings of the ieee international conference on electro-information technology (eit), 19 21 may 2016 pp. 28 -33 akanni, j., isa, aa., alao, ra. and thomas, ct. 2020. assessment of internet service provided using umts operators at the university of ilorin main campus. nigerian journal of technology (nijotech), 39(2): 500–505. elechi, p. and paul, oo. 2016. comparison of empirical path loss propagation models with building penetration path loss model. international journal on communications antenna and propagation, 6(2): 116–23. elechi, p. and paul, oo. 2015. determination of gsm signal penetration loss in some selected buildings in rivers state, nigeria. nigerian journal of technology, 11(1): 822 830.. heydariaan, m., mohammadmoradi, h. and gnawali, o. 2018.toward standard non-line-ofsight benchmarking of ultra-wideband radio-based localization, proceedings of the ieee workshop on benchmarking cyber-physical networks and systems (cpsbench), porto,10 13 april 2018 pp. 19-24 idim, ai. and anyasi, fi. 2014. determination of building penetration loss of gsm signals, using selected buildings in orhuwhorun, delta state, nigeria as a case study.iosr journal of electronics and communication engineering, 9(5): 01–05. joseph, i., konyeha, cc., chinule, cb. and isaiah, gp. 2013. radio field strength propagation data and pathloss calculation methods in umts network. advances in physics theories and applications, 21: 2225–2638. neskovic, a., neskovic, n. and paunovic. 2000. modern approaches in modeling of mobile radio systems propagation envronment. ieee communication surveys & tutorials, 3(3): 2 22. oni, oo. and idachaba, fe. 2017. review of selected wireless system path loss prediction models and its adaptation to indoor propagation environments. lecture notes in engineering and computer science, 2228: 562–67. sharma, pk. and singh, rk. 2010. comparative analysis of propagation path loss models with field measured data.international journal of engineering science and technology, 2(6): 2008– 2013. sholanke, ba., fagbenle, io., aderonmu, ap. and ajagbe, ma. 2015. sandcrete block and brick akanni et al.: propagation loss determination of gsm signal strength in selected buildings in ilorin, nigeria. azojete, 17(3):371-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 380 production in nigeria prospects and challenges.iiard international journal of environmental research, 1(4): 1–17. svistunov, a. and vladimir, m. 2016. required levels of radiation power of gsm base stations on urban area taking into account attenuation in buildings and intrasystem emc. the proceedings of the international symposium on electromagnetic compatibility emc europe, 5 9 september 2018: 596 601. arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):527-534 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 527 original research article optimisation of cover thickness in tyre-fibre concrete under elevated temperature o. a. ibrahim1, m. m. afodun2, f. g. mije3 and t. ako4 1,2department of civil engineering, faculty of engineering and technology, university of ilorin university of ilorin, ilorin, nigeria 3,4department of civil engineering, university of jos, nigeria *corresponding author’s email address: ibnibrohim88@gmail.com 1.0 introduction environmental pollution is in existence from the earliest days of life, but now it is a serious issue which poses a threat to human survival ajello et al., (2005a). ajello et al., (2005b) and pacheco, (2012) explained that many problems arise in the waste management system, especially for tyres and coals. growing volumes of used tyres at landfills around the world have created a major environmental problem. stergios and atalia, (2016) considered means of recycling these solid wastes (scrap tyres) or renewed interest in developing alternatives to its disposal in the construction industry is needed to be devised in order to curtail the negative environmental hazards caused by it. gideon (2012), failure of structural elements after fire outbreak is mostly attributed to spalling action. spalling of concrete is an occurrence which results to decrease in the cross sectional area of the concrete elements, thus decreases the resistances to fire loads. concrete as a common material used in construction and it competes directly with all other major construction materials such as timber, steel, asphalt, and stone, because of its versatility in applications. the concrete cover required to protect the reinforcement against corrosion depends on the exposure conditions and the quality of the concrete as placed and cured immediately surrounding the reinforcement. there may be cases where extra precautions are needed beyond those given in order to ensure protection of the reinforcement (bs 8110-1:1997). article information abstract failure of structural elements after fire outbreak is mostly attributed to spalling action. spalling of concrete is an occurrence which results to decrease in the cross sectional area of the concrete elements, thus decreases the resistances to fire loads. this study, optimized the concrete cover thickness in tyre fibre concrete (tfc), which was subjected to single temperature load according to iso 834 using graphical method. three (3) samples were prepared from each series of mix containing tyre fibers of 10 mm width and varying length viz; 0%, 2.5%, 5.0% and 7.5%, using water cement ratio of 0.55. the samples were produced in 100 x 100 x 100mm cubes and tested for compressive strength. however, the cubes were structural modeled using tedds 2.0.01 and staadpro v8i to under temperature load to determine optimum cover thickness through the deflection mode. the cover thickness for tyre-fibre concrete reduced from 25mm to 17.5mm under the same condition with the conventional concrete mixture. this shows that inclusion of tyre-fibre in concrete increases the fire resistance and reduces the cover thickness. it is recommended that tyre-fibre concrete should be used in our daily construction work for more durability. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 august, 2021 revised 2 oct., 2021 accepted 7 oct., 2021 keywords: spalling tyre-fibre concrete cover thickness deflection temperature load http://www.azojete.com.ng/ file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com file:///c:/users/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/new%20folder/ibnibrohim88@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):527-534. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 528 muhammed (2014) said, increasing the concrete cover of structural elements such as beams, columns or slabs in the conventional concrete to prevent the reinforcement’s exposure, reduces the effective depths of these elements which may eventually leads to increase in structural member thickness in cases where deflections are not satisfied. for this reason, design for fire resistance has become a necessity. it ensures that the structure has sufficient capacity to support its loads for a period of fire exposure that guarantees safety during the evacuation and fire extinguishing processes. robert (2013) explained that modern applications have led to the development and use of new types of concrete (tyre-fibre concrete). the disadvantages caused by increasing concrete cover of structural elements can be avoided by the presence of tyre-fibres in the concrete hence, paving way for effective materials utilization. wasiu and raji (2015) defined optimization of the concrete design as an act of searching for a design for which the sum of the costs of the ingredients is lowest, and satisfying the required performance of concrete, such as workability strength and durability. therefore, this study determines the optimum cover thickness needed for a tyre-fibre concrete due to inclusion of tyre-fibre under temperature load. 2.0 methodology 2.1 material used: ordinary portland cement (dangote 3x) of 42.5r grade (bs 12:1991) was used for preparing the concrete mix. the coarse aggregate (manually crushed) used was granite with maximum nominal size of 20mm and sourced locally from a completed project along okoerin, ilorin. the fine aggregate (sharp sand) used in the concrete mixture was obtained from gaa akanbi, ilorin, kwara state. the sand was sieved in accordance with bs 933 part 1 (1997) to remove bigger aggregate sizes and organic impurities. the square tyre-fibres (10mm) used were pretreated with sodium hydroxide solution (naoh) of 20g/dm3 before used in order to enhance the adhesion with concrete matrix and increase transfer rate of water and hydration. 2.2 mixing proportion: the mix proportion, 1:2:4 (m25 grade) with water cement ratio (w/c) of 0.55 as shown in table 1 was designed according to bs 5328: part 1. tyre-fibers were added to the mix in various proportions namely; 0%, 2.5%, 5% and 7.5%, respectively. the maximum of 7.5% was adopted for this study. this was used for all the samples for consistency in the comparison. table 1: mix design for cube 100 x100 x 100 mm cra content (%) cement (𝒌𝒈/𝒎𝟑) sand (𝒌𝒈/𝒎𝟑) granite (𝒌𝒈/𝒎𝟑) coarse rubber aggregate (𝒌𝒈/𝒎𝟑) water (𝒌𝒈/𝒎𝟑) w/c 0 33.70 67.32 134.64 0.00 18.54 0.55 2.5 33.70 67.32 131.27 3.37 18.54 0.55 5.0 33.70 67.32 127.90 6.74 18.54 0.55 7.5 33.70 67.32 124.53 10.11 18.54 0.55 2.3 impact test: each series of freshly mixed tyre fibre concrete was placed in the cubic moulds of dimension 100 x 100mm for casting the specimens. twenty four (24) specimens (100 x 100 x100 mm) were cast and cured according to bs 1881: part 111(1983) and tested for impact strength at 7 and 28 days after heating (iso 834 fire curve) at an average temperature of 300°c) (figure 1-2) which were recorded at 30 and 60 minutes respectively. thereafter, the file:///c:/users/user/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com ibrahim et al: optimization of cover thickness in tyre fibre concrete under elevated temperature. azojete, 17(4):527-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 529 specimens were left at room temperature to cool. the schematic diagram of heat test machine is shown in figure 1. figure 1: schematic diagram of heat test machine source: geology department, university of ilorin 2.4 design optimization for the tyre fibre concrete the objective function of the optimization process is to minimize the weight of the fibre concrete weight per unit length, which is to a large extent a function of the concrete cover thickness. the bs8110 is focused on the limit state philosophy and the main aim of the design is to ensure an adequate margin of safety against the ultimate limit state being reached. in the case of vertically loaded (one-sided temperature load) cube, this is obtained by ensuring that the ultimate temperature load (g) does not exceed the design load resistance of the concrete (gr). the optimization is carried out using graphical method [wasiu and raji, 2015]. the optimal design problem formulation is carried out to minimize the weight of the concrete cover subject to stress constraints due to vertical loading (temperature load). figure 2 shows the cross-section of the concrete cube and the possible applied load. the followings are the notations used in figure 2. figure 2: typical cross-section of a tyre fibre concrete cube with temperature load where: h = the height of the cube (100mm) ct= concrete cover thickness (25mm, bs8110) wt = width of the cube (100mm) b = is the length of the cube (100mm) qt = temperature load on the cube dt = effective depth of the cube wr = wt-2(ct) http://www.azojete.com.ng/ file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):527-534. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 530 for tyre fibre concrete cube, stress constraints: at the maximum temperature load of 50 kn per meter length of the cube, the fibre concrete cube weight per unit length is optimized as shwn in equation 1-10. w= 𝑀𝑖𝑛𝑖𝑚𝑖𝑧𝑒 ∶ 𝑊 = φ(ℎ, 𝐶𝑡) (1) ajamu and adedeji, (2013) 𝑊 = 2ρ 𝑐𝑡 vct + ρ 𝑤𝑟 vwr (2) where: ρ 𝑐𝑡 = density of the concrete cover thickness ρ 𝑤𝑟 = density of the concrete below the bottom reinf. cover thickness vct = volume of the concrete cover per unit length of the cube vwr = volume of the concrete remain (minus cover) per unit length of the cube 𝑊 = (2 × 23.17𝐶𝑡ℎ) + (23.17 × 2𝐶𝑡ℎ) (3) neglecting the weight of reinforcement (∅ = 12𝑚𝑚) ∴ 𝑊 = 92.68𝐶𝑡ℎ (4) for the design constraints: (a) vertical load due to compression this is expressed as: 𝜎𝑜 − 𝜎𝑎𝑙𝑙 ≤ 0 (5) ajamu and adedeji (2013) where σall = allowable stress (17.6 n/mm2, from load-deformation test) and σo = design stress 𝜎𝑜 = 𝜇𝑁 𝑊𝑡𝑥ℎ = 1.4𝑁 4𝐶𝑡×ℎ = 1.4𝑁 16𝐶𝑡 (6) where 𝜇= partial factor of safety, n= design load (kn), allowable load = 198kn (compressive strength test), therefore; 1.4𝑁𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑙𝑜𝑎𝑑 16𝐶𝑡 − 198000 100×100 ≤ 0 (7) 𝑁𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑙𝑜𝑎𝑑 − 226.29𝐶𝑡 ≤ 0 (8) ajamu and adedeji, (2013) (b) temperature load the rate at which heat is conducted across the specimens of diameter d =100mm is shown in equation 9. 𝑸 = 𝑲 𝝅𝑫𝟐 𝟒 ( 𝜽𝟐−𝜽𝟏 𝒅 ) (9) where: q = rate of heat conduction (w) k = thermal conductivity of the material of the specimen (w/mk) θ 2 – θ1 = change in temperature (oc or k) from 30-60 minutes. for an area of concrete cube of thickness d, the rate of heat conduction per unit area q (w/m2) of the cube can be expressed as: 𝒒 = 𝑲 ( 𝜽2−𝜽𝟏 𝒅 ) (10) nthermal 16𝐶𝑡 − 29.34 0.10x 0.10 ≤ 0 (11) nthermal − 46944𝐶𝑡 ≤ 0 (12) ajamu and adedeji, (2013) file:///c:/users/user/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com ibrahim et al: optimization of cover thickness in tyre fibre concrete under elevated temperature. azojete, 17(4):527-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 531 2.5 modelling and simulation the second aspect involves numerical simulation. finite element modelling of concrete cube with and without tyre fibre for deflection curve was analysed using tedds 2.0.01. the primary objective is to obtain the curve which will be used for optimization computation. this is shown in figure 3 and 4. figure 3: static analysis operation (tedds) figure 4: static analysis operation (staadpro v8i) 3.0 result and discussion table 2 and 3 show the combined temperature of the concrete (with and without tyre fibre) which was only considered for 0, 30 and 60 minutes respectively. the temperature of the samples increases with increase in time. the temperature in the fibre concrete was slightly lower because there was no free movement of heat within the concrete due to tyre fibre action. however these gains are functions of temperature differences and the time interval between temperature measurements. table 2: temperature (°c) of the concrete (with and without tyre fibre) time (min) percentage of tyre fibre replaced 0 2.5 5 7.5 0 0 0 0 0 30 619 556 474 600 60 970 914 760 872 table 3 shows the rate of heat gain at equal time interval for the specimen. the total heat gain per square meter through the concrete (table 3) in one hour was found to be 2934 j/m2 http://www.azojete.com.ng/ file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):527-534. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 532 (1.63j/s per sq. meter, (ajamu and adedeji 2013)) and the allowable thermal load per unit length is given as 29.34n. table 3: evaluation of rate of gain of internal temperature of the concrete cubes % t 𝜃1(℃) 𝜃2(℃) 𝜃2 − 𝜃1(℃) gain rate q(𝑤/𝑚2) time interval t(s) heat gain/sq.m h(𝐽/𝑚2) 0 619 975 356 1.78 1800 3204 2.5 556 920 364 1.82 1800 3276 5.0 474 800 326 1.63 1800 2934 7.0 600 893 293 1.47 1800 2637 3.1 optimization the loads applied to the specimen increases with increase in cover reinforcement at 5% fibre replacement under a single face temperature load. the deflection observed was approximately linear. figure 5 shows the graphical representation. the curve intersected at 2.5mm which means the constraints are between 2.5mm and 25mm. figure 5: constraints optimization 𝐶𝑡 = 2.5 + 2 3 × (25 − 2.5) = 17.5𝑚𝑚 𝑁 = 50 + 1 3 × (200 − 50) = 100𝑘𝑁/𝑚𝑚 (the centroid of the “shaded triangle”) (i) the minimum cover thickness: 𝐶𝑡 = 17.5𝑚𝑚 (ii) the optimal weight per unit length for a cube of 1m is: ∴ 𝑊 = 92.68𝐶𝑡ℎ (4.1) 𝑊 = 92.68 × 17.5 × 100 𝑊 = 162.19 𝑘𝑁 𝑝𝑒𝑟 𝑚𝑒𝑡𝑒𝑟 that is, 162.19 < 231.7 ok. table 4, 5 and 6 show the cover-load values and average blows on the produced samples. the ratio of the initial to final crack ratio for the sample increases with increase in percentage of tyre-fibre added. this shows that the tyre-fibre has a greater impact on the durability of the concrete. file:///c:/users/user/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com ibrahim et al: optimization of cover thickness in tyre fibre concrete under elevated temperature. azojete, 17(4):527-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 533 table 4: values for cover load at 5% fibre replacement cover (mm) load (kn) % fibre replaced (%) 0 35 5 5 70 5 10 105 5 15 140 5 20 175 5 25 200 5 table 5: drop weight test results for heated and non heated cubes (average blows) 𝑁1 𝑁2 ⁄ date spec. no 𝐹0% 𝐹2.5% 𝐹5% 𝐹7.5% 18/9/19 a 14 20⁄ 15 22⁄ 15 23⁄ 15 25⁄ r 0.70 0.68 0.65 0.60 table 6: drop weight test results for cubes (average blows) 𝑁1 𝑁2 ⁄ date spec. no 𝐹0% 𝐹2.5% 𝐹5% 𝐹7.5% nh h nh h nh h nh h 18/9/19 a 16 20⁄ 15 2⁄ 17 28⁄ 18 2⁄ 15 2⁄ 16 2⁄ 16 33⁄ 19 20⁄ r 0.80 0.77 0.62 0.88 0.59 0.76 0.48 0.96 r=ratio, a= average; f=% of replaced rubber 4.0 conclusion based on this study, the following conclusions are drawn out. a. by adding 2.5%, 5.0% and 7.5% volume fraction of tyre-fibre, the energy required causing the visibility of first crack and failure was increased by 8%, 15% and 4% respectively over plain concrete: b. the results show that 5% volume fraction of tyre fibre considerably increases the impact energy in case of tyre-fibre concrete (tfc) when compared to plain concrete. c. inclusion of rubber-tyre in concrete geometry under temperature load reduced the cover thickness by 30%. the study concluded that the rubber-tyre concrete had maximum resistance to fire and least probability of failure as likened to the conventional concrete. the study recommended that rubber-tyre inclusion in concrete should be preferred for improving its resistance ability to fire. references aci committee 544.2r-89, 1989. measurement of properties of fibre reinforced concrete, detroit: american concrete institute. adedeji aa. and ajamu s. 2013. interaction analysis and optimal design of composite action of plastered straw bale. multidiscipline modeling in materials and structures 7(2), 146-169 ajello, ma., leuzzi, f., centonze, g. and maffezzoli, a. 2009. use of steel fibers recovered from waste tires as reinforcement in concrete. pull-out behavior, compressive and flexural strength, waste management journal, 29(6), 251-257 http://www.azojete.com.ng/ file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):527-534. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ibnibrohim88@gmail.com 534 bai, l., jiang, f. and fan, b. 2018. reliability analysis of reinforced concrete columns after high temperature under comprehensive considering failure paths. journal of nanoscience and nanotechnology applications. 2(2) 1-8. british standards bs 5328, 1997. recommended guidelines for concrete mix design. british standards institute, london, u.k. gideon, ms. 2012. properties of concrete with tire derived aggregate and crumb rubber as a lightweight substitute for mineral aggregates in the concrete mix. presented to the faculty of the graduate school of the university of texas at arlington in partial fulfillment of the requirements for the degree of doctor of philosophy. university of texas at arlington. muhammed, d. 2014. shear capacity of reinforced concrete beams at elevated temperatures. a thesis submitted in partial fulfillment of the requirements for the degree of master of engineering science. the school of graduate and postdoctoral studies western university london, ontario, canada. murali, g., monika, vt., suraj k., ramkumar vr. and karthikeyan k. 2017. assessment of impact strength of fibre reinforced concrete by two parameter weibull distribution. arpn journal of engineering and applied sciences. 12(5), 1440-1446. shun, hd., shan, sh., harris, a., kypros, p. and lan, b. 2013. reuse of waste tyre fibres in concrete fire-spalling mitigation. department of civil and structural engineering, university of sheffield, sir frederick mapping building, mapping street, sheffield s1 3jd, united kingdom. twincon ltd., uk. stergios, m. and ataria, r. b., 2016. effect of waste rubber-tyre additive on concrete mixture strength. british journal of environmental sciences. 4 (4), 11-18 wasiu, j. and raji, sa. 2015. reliability based design of two way slab in comparison with design based on bs 8110 (1997). journal of multi disciplinary engineering science and technology. 2(6) 1416-142 yihua, z. wouter, b. and robby, c. 2018. reliability analysis of frp strengthened rc beams considering compressive membrane action. construction and building materials 169 (2018) 473–488 file:///c:/users/user/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/user/desktop/azojete/azojete%20archive/upload/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/ibnibrohim88@gmail.com arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):751-762 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 751 original research article development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices o. oyebode and k. shoji* graduate school of agricultural science, kobe university, japan *corresponding author’s email address: shojik@kobe-u.ac.jp 1 introduction 1.1 importance of soil bin as important as soil bins are in soil-machine interaction studies (ani et al., 2018), they could be an expensive and complex structure to acquire and maintain by many laboratories. many of the ones in existence are somewhat permanent structures which cannot be easily moved from one place to another should the need arise. they are usually rigidly fixed so as not to compromise their structural integrity and to protect them from failure resulting from the enormous forces they are meant to withstand (ani et al., 2018). many of the existing soil bins are concrete or steel structures (godwin et al., 1980; ademosun, 2014; ani et al., 2018) whose construction in most cases require high level specialists. 1.2 previous experiments involving soil bins previously, soil bins have been used for a very wide range of soil-machine interaction researches such as performance evaluation of tillage implements (endrerud, 1999; shoji, 2001; bianchini and magalhães, 2008; upadhyay and raheman, 2018), determining and modelling the energy requirements of soil engaging tools (shoji, 2004; seyedreza, 2006; roul et al., 2009; subrata et al., 2014; ibrahmi et al., 2015; anpat and raheman, 2017; upadhyay and raheman, article information abstract challenged by the complexities involved in constructing a standard indoor soil bin, and the difficulties in taking certain measurements before, during and after soil bin experiments, a simple soil bin was developed. the soil bin was mainly made with wooden slabs and angle irons. it was equipped with a digitized, mechanically operated cone penetrometer, a sinkage measurement system as well as a stepless soil leveler. an existing manually operated asabe standard penetrometer was digitized using strain gauges fixed on the penetrometer ring for force measurements and a distance meter for concurrent depth measurement. the penetrometer was operated by a 90 w linear motor with a switch located outside the soil bin thereby making it possible to measure cone index at constant speed in a perfectly vertical direction. the calibration of the strain gauges and the distance meter showed good linearity (r2>0.997). a stepless levelling device that allows for seamless vertical adjustment of soil height was developed. soil surfaces levelled with this device had an average coefficient of variation of 0.040 compared with that of 0.080 achieved from carefully manually levelled soil beds. soil compaction and compaction uniformity experiment was done using sandy clay loam soil which was compacted with a 27 cm diameter steel roller weighing 103 kg/m. two ultrasonic range finders mounted at the front and rear of the compactor cart automatically measured the sinkage of the soil surface after the compaction. the sinkage on the soil surface and the uniformity in cone index were significantly affected by the number of layers and roller passages and compaction uniformity increases with increase in the number of soil layers. therefore, the accuracy of the measuring systems and the structural stability of the various components of the soil bin indicate that they are suitable for experiments. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 august, 2020 revised 5 october, 2020 accepted 13 october, 2020. keywords: soil bin digital penetrometer soil levelling cone index sinkage measurement mailto:shojik@kobe-u.ac.jp http://www.azojete.com.ng oyebode and shoji.: development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices. azojete,16(4):751-762. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 752 2019), soil compaction and cone index tests and modelling (hernanz et al., 2000; canillas and salokhe, 2002; çarman, 2002; antille et al., 2013; gonzález cueto et al., 2013; lin et al., 2014; pillinger et al., 2018), traction tests and wheel evaluation of off-road vehicles (çarman, 2002; antille et al., 2013; gonzález cueto et al., 2013; taghavifar and mardani, 2014) and so on. the very numerous research done in soil bins underscores its importance. simplifying its development could therefore make its acquisition a lot easier especially for soil laboratories without huge funding. 1.3 instrumentation and soil preparation in soil bin experiments usually, in soil bin experiments, soils are first processed using leveling blades, pulverization tools and are recompacted to the desired cone index. the cone index of the compacted soil is monitored with cone penetrometer which is inserted into the soil at a recommended speed while the resistive force at varying depths is measured. the recommended penetration speed for cone index measurement is 30 mm/s (asabe, 2019), but maintaining this rate throughout any experiment has been found to be very difficult (oh et al., 2019) if not impossible. this variation could therefore be a major source of error in cone index measurements. also, cone index measurement is particularly difficult in soil bin experiments since the operator is usually outside the soil bin so as not to disturb the soil in the soil bin. maintaining a posture where the penetrometer is perfectly vertical throughout the measurement is no doubt difficult. the developed soil bin was thus equipped with a digitized, mechanically driven cone penetrometer that can be easily operated with a switch located outside the soil bin. although digital penetrometers are available for purchase, the cost is still very high. a check on globalgilson.com (2020) shows that the price ranges from $3,500 to as high as $5,000 (n1,350,000 to n1,900,000). this high cost has made such a very important measuring device unavailable in many soil laboratories and most laboratories still use the manually operated penetrometer. even where the digital penetrometer is available, they are still operated by hand (taghavifar and mardani, 2014), thus the problem of penetration rate and posture of the operator still remains. soil sinkage is also a very common parameter measured in soil bin experiments (canillas and salokhe, 2002; çarman, 2002; roth and darr, 2011; gonzález cueto et al., 2013; taghavifar and mardani, 2014) because it is one of the most often used parameters in evaluating levels of soil compaction (valera et al., 2012). the very common methods of measuring soil sinkage is by using plexiglass plate and a vernier caliper (taghavifar and mardani, 2014) or a profilometer (çarman, 2002). this process is laborious and could be associated with so many errors. to eradicate these, the soil bin was equipped with a novel soil sinkage measuring system. in addition, soil levelling in soil bins is usually done manually either with a rake or with other stepped mechanical leveling devices. attaining uniformly levelled surface is therefore difficult especially when a precise soil height is to be achieved. to overcome this, the soil bin was also equipped with a stepless leveler that allows for seamless vertical adjustment of soil height. 1.4 objectives the objective of this work was to develop a simple and movable but rigid soil bin equipped with digitized, mechanically operated cone penetrometer, new sinkage measurement system and a stepless soil leveler and to evaluate the performances of the newly developed devices and measuring systems. 2. materials and methods 2.1 description of the soil bin a pictorial view of the soil bin showing some component parts is shown in figure 1. the soil bin which measured (7 m long, 0.9 m wide and 0.45 m deep) was made of 30mm thick wood. mild steel angle iron, 5 mm x 5 mm was fixed on both ends of the wood. another angle iron of the same size was placed on the upper angle iron to serve as the rail. wood was selected as http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):751-762. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 753 the wall of the soil bin because of its relative advantages in terms of cost, weight, ease of working as well as its fair compressive strength. perforated angle irons were used as the support between the upper and lower angle irons to reduce the load bored by the wood. two triangular supports were attached to each side of the soil bin to prevent it from buckling. these triangular supports were bolted to the ground using concrete bolts thereby making the entire structure rigidly fixed. to move the soil bin, the triangular supports would only need to be removed and the soil bin would become movable without necessarily having to dismantle or destroy it which is a common feature of most of the existing immovable soil bins. two carts (each with four wheels) were put on the rail of the soil bin. one for mounting the soil engaging tools and the other for instrumentation. figure 1: pictorial view of the soil bin 2.2 description of the power and control unit of the soil bin the power and control unit of the soil bin is shown in figure 2. a 2.2 kw-three-phase electric motor was used to power the soil bin. the electric motor was directly connected to a ring cone mechanical variable speed drive (kopp 29177, asahi – seiki mfg. co. ltd., japan) ranging from 500 rpm to 4500 rpm. a bevel gear box was used to convert the direction of motion and was also used to control the speed of the soil bin cart. a double chain system was used to connect the bevel gear box and the main shaft. two sprockets were attached to the extreme end of the main shaft and chains were connected to both sides of the cart for stability. the upper part of the chains could freely move on the flat side of the upper angle iron while the lower part was supported by eight freely moving sprockets on each side of the bin to prevent excessive sagging. one of the lower sprockets was used for tension as shown in figure 1. electrically operated disc brake and clutch type brake were fixed on the main shaft and between the electric motor and the bevel gear box, respectively. these brakes could be automatically activated by either of the two limit switches (zl-44a13, omron, kyoto) which were fixed on both ends of the soil bin to ensure the carts do not move outside the edges of the rails. a two-stage stepped pulleys and the ring cone of the motor were used to select varying lateral speed of the soil bin cart. a stopwatch was used to measure the lateral safe speed limits of the cart and it ranged from 0.037 m/s to as fast as 2 m/s. tensional sprocket chain hook to the cart wooden wall driven sprocketchainidler sprocket vertical support triangular supports of the wall wheels of the cart cart rails (angle irons) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyebode and shoji.: development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices. azojete,16(4):751-762. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 754 figure 2: control and power unit of the soil bin 2.3 description of the stepless soil leveler and soil levelling test a stepless leveler was fabricated as shown in figure 3. the leveling blade was attached to two threaded shafts of 20 mm in diameter. the threaded shafts were inserted into nuts rigidly fixed on the upper part of the cart. a levelling blade, 880 mm by 150 mm made of 3mm gauge aluminum plate was fixed on the lower end of both shafts. the two threaded shafts were connected by means of chain and sprockets to ensure uniform turning. handles were attached on both shafts for easy turning from either end. the position of the shafts at the point where the leveling blade was on the ground was marked and it coincided with a reference point. when the handle is turned clockwise, the shafts move upwards with the attached levelling blade. the distance between the marked point and the reference point is equal to the distance between the lower part of the levelling blade and the ground. to ensure that the levelling blade does not handle too much soil at one path, the soil was first manually raked and levelled roughly along the height rulers indicated at the side walls of the soil bin before the stepless leveler was used to attain uniformity. a 10 cm deep soil already evenly levelled using the stepless leveler is also shown in figure 3. to evaluate the accuracy of the stepless leveler, levelling was done at different speeds of the soil bin and at different soil moisture contents using sandy loam soil and sandy clay soil. details of the two types of soil, are shown in table 1. the leveled soil was monitored with one of the ultrasonic range finders (ud-320, keyence, osaka). the levelling uniformity was measured by calculating the coefficient of variation (cv) of 100 measurements of the vertical distance between the levelled surface and the surface of the ultrasonic range finder as cv = σ µ (1) where σ is standard deviation and µ is mean. using the stepless leveler, eight experiments were done (2 soils × 2 speeds × 2 moisture contents). the manual levelling was carefully done with a rake. since the speed of manual levelling could not be varied, only the soil type and moisture content were varied at two levels each (table 1), resulting in four experiments. the results of the coefficient of variation were statistically analyzed using stata se 16 to determine whether the varied parameters have any effect on the levelling uniformity. three-phase motor stepped pulleys for speed control disc clutch disc brake bevel gear box limit switch drive chain http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):751-762. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 755 figure 3: an already levelled soil and the stepless leveler fixed on one of the carts table 1: experimental parameters for soil leveling test levelling soil type leveling speed moisture content (d.b.) stepless leveler sandy loam 0.037 m/s dry (5-7%) manual levelling sandy clay loam 0.140 m/s moist (10-12%) 2.4 description of the digitized cone penetrometer an asabe standard penetrometer was rigidly fixed on a linear motor head (specifications shown in table 2). the motor was fixed at the center of a beam rigidly fixed over the soil bin cart as shown in figure 5. strain gauges (kfgs-2-120-c1-11l1m2r, kyowa electronic instruments, osaka, japan) were attached to the outer and inner circumferences of the penetrometer ring (figures 4 and 5), and the output voltage was amplified and recorded by a data logger (dr-c1mk2, teac corp., tokyo, japan). the circuit diagram for the strain gauges connection is shown in figure 4 . also, a distance meter (wps-7500-mk120-cr-u, microepsilon, germany) was rigidly fixed close to the linear motor and one end of its wire was fixed on the connector between the motor shaft and the penetrometer as shown in figure 5. when the penetrometer is moved downward, the wire of the distance meter is pulled, and the corresponding output voltage is linearly generated. these output voltages were also recorded in the same data logger. therefore, during each measurement, the cone index and the depth were thus simultaneously measured. chain and sprocket threaded shafts levelled soil levelling blade ultrasonic range finder 1 ultrasonic range finder 2 turning handle file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyebode and shoji.: development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices. azojete,16(4):751-762. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 756 table 2: specifications of the linear head and the motor used items specifications manufacturer oriental motor, tokyo, japan model numbers (motor/linear head) msm590-511c/3lf20u-4 rotational speed range 90-1700 rpm linear speed range 0.15-32 mm/s rated power 90 w figure 4: position of the strain gauges on the penetrometer ring and the circuit diagram for the strain gauges connection r4r2 penetrometer ring r3r1 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):751-762. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 757 figure 5: pictorial diagram showing the digitized penetrometer and other components. 2.5 soil compaction and compaction uniformity test thirty centimeter (30 cm) deep carefully loosened sandy clayey loam soil was spread in the bin either at once (1-layer experiment), twice (2-layer experiment, 15 cm each) or four times (4layer experiment, 7.5 cm each). in the 2and 4-layer experiments, the next layer of equal depth is carefully laid after the preceding layer had been compacted taking into consideration the sinkage that had occurred. for instance, in a 2-layer experiment, if the height of the first layer had decreased from 15 cm to 12 cm after compaction, the second layer of 15 cm-depth was carefully spread over the compacted layer bringing the total height before compacting the second layer to 27 cm. if after the second layer has been laid and compacted and the soil height decreases to 24 cm, the total sinkage for the experiment is taken to be 6 cm. these precise soil heights were achieved using the developed stepless leveler. the roller used for the compaction was a 27 cm diameter steel pipe weighing 103 kg/m and was rolled on the soil either twice, four times or eight times (defined as the number of passage) at a constant speed of 0.14 m/s. the dependent variables measured after each run of the experiment were cone index and sinkage. the experimental design used was a 3 × 3 full factorial arrangement as shown in table 3 with two replicates. the resulting cone index and sinkage were statistically analyzed using stata se 16. cone penetrometer ring wire from the distance meter connected to the penetrometer rigidly fixed beam over the cart shaft of linear motor motor and linear headdistance meter strain gauges compactor ultrasonic range finder 2 ultrasonic range finder 1 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyebode and shoji.: development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices. azojete,16(4):751-762. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 758 table 3: experimental parameters for compaction uniformity test soil type number of layers number of passages sandy clay loam 1 2 2 4 4 8 2.6 sinkage measuring system the very common method of measuring sinkage is by using plexiglass plate and a vernier caliper (taghavifar and mardani, 2014) or a profilometer (çarman, 2002). this process is laborious and could be associated with some errors. to avoid this, two ultrasonic range finders (ud 320, keyence, osaka) were placed before and after the roller. the measurements from both ultrasonic range finders were simultaneously logged into the data logger and the sinkage was calculated as: s = hi − hc (2), where s is sinkage (mm), hi is height of soil (mm) before compaction (measured by ultrasonic range finder 1) and hc is height of soil (mm) after compaction (measured by ultrasonic range finder 2). 2.7 calibration of the instruments the penetrometer was moved downward until it was just in contact with a solid metal. at this point, the reading on the dial gauge of the penetrometer and the output voltage of the strain gauges were both zero. the penetrometer was then moved downward about 10 times stepwise and the readings on the dial gauge and the output voltages of the strain gauges were recorded for each downward movement. thereafter, a graph of the dial gauge reading (n) was plotted against output voltage of the strain gauge. similarly, the distance meter and the ultrasonic range finders were calibrated using a vertically adjustable plate which was moved downward to a known height between the surface of the sensor and the plate ten times and the respective output voltages of the ultrasonic range finders were recorded. a graph of the known height of an adjustable plate was plotted against the output voltages of the distance meter and ultrasonic range finders. table 4 shows the used transducers and their respective regression coefficients (r2) and standard errors. table 4: transducers and their calibration parameters. transducer regression coefficient (r2) standard error ultrasonic range finder 1 0.996 0.61 mm ultrasonic range finder 2 0.997 0.52 mm distance meter 0.999 0.13 mm cone penetration resistance meter (strain gauges circuit) 0.998 0.01 n 3. results and discussion 3.1 soil levelling test analysis of variance (anova) on the coefficient of variation resulting from the soil levelling test shows that the levelling done with the developed stepless leveler had a significantly (p<0.1%) lower cv (0.041) compared with (0.080) attained from the levelling done manually as shown in table 5. this implies that the stepless leveler achieved a more uniformly leveled soil than when it was carefully manually leveled. also, the soil type significantly affected the cv. sandy loam had a slightly lower cv than sandy clay loam, which implies that sandy soil was more easily levelled than the soil containing more clay that was likely to result in soil clods. levelling speed and moisture content did not significantly affect cv at 5% significance level. however, a careful examination of the data shows that there is a trend where mean cv was slightly higher for wet soil than dry soil. this may be because increase in soil moisture http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):751-762. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 759 concurrently increases the stickiness of the soil especially when the clay content is high and that may make leveling more difficult. the insignificance of all the studied factors (except the soil type) while using the stepless levelling device could imply that it performed well irrespective of the soil type, soil moisture content and the leveling speed and can therefore be used under any of these circumstances. table 5: effects of the different factors on the mean coefficient of variation at the soil leveling test factors levels means levelling method stepless leveler manual 0.041*** 0.080 soil type sandy loam 0.059* sandy clay loam 0.062 moisture content dry 0.060 moist 0.061 levelling speed slow 0.060 fast 0.061 * and *** indicate significant difference at 5% and 0.1% levels, respectively. 3.2 cone penetration resistance at the compaction uniformity test figure 6 shows the variations in cone penetration resistance resulting from different number of passages and layers. in 1-layer experiment, the maximum penetration resistance increased from 0 to almost 0.6 mpa after the first two passages of the roller, and two passages of the roller attained an additional increase of about 0.2 mpa while four passages increased the maximum penetration resistance by only about 0.1 mpa. this is similar with the findings of çarman (2002) and taghavifar and mardani (2014) who reported that cone penetration resistance increased significantly more at the first run of a single wheel tester than the second and third passages. as the number of layers increases, the maximum and the average cone penetration resistance increases because the amount of compaction effort increases. in the 1-layer experiments, the maximum cone penetration resistance was observed around 10 cm for 2 passages, 8 cm for 4 passages and 7 cm for 8 passages, respectively. the reduced depth at which the maximum cone penetration resistance occur as the number of passages increases is as a result of a slightly increased soil sinkage. after these maximum points, the cone penetration resistance decreased sharply. this implies that the compaction in the 1-layer experiment was only effective until a depth of about 10 cm. for the 2-layer experiments, two peaks of cone penetration resistance were observed at around 7 cm and 18 cm for 4 and 8 passages, respectively. the situation was however different for 2 passage as the second peak was not so obvious. this may imply that as the number of layers increased from one to two, it is necessary to reduce the number of passages to have a more uniformly compacted soil. the 4-layer experiments corroborate this assertion as the cone penetration resistance for 4 and 8 passages increased with depth but that of 2 passages becomes even more straight than it was in the 2-layer experiments. however, the 4-layer experiments represent a typical untilled soil surface condition where the cone index increases with the depth. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyebode and shoji.: development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices. azojete,16(4):751-762. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 760 figure 6: variations in cone penetration resistance with depth, resulting from different number of layers and passages of the roller: (a) 1-layer, (b) 2-layer and (c) 4-layer experiments 3.3 effects of number of layers and number of passages on compaction uniformity a uniformly compacted soil along its depth has a nearly straight line when the graph of depth versus cone penetration resistance is drawn. for all the experiments, the graphs of 2 passages seem to be relatively the straightest especially below 10 cm depth. this distinction for 2 passages becomes more obvious as the number of layers increases, i.e. 2and 4-layer experiments when compared with 4 and 8 passages. this could imply that increasing the number of layers and reducing the number of passages could achieve a more uniformly compacted soil, which may be more suitable for soil bin experiments. 3.4 sinkage number of layers as well as number of passages both significantly affected the sinkage at significance levels of 1% and 5% respectively. table 6 shows that all the three levels of number of layers have resulted in significantly different sinkage. however, 4 and 8 passages are not significantly different from each other. this implies that increasing the number of layers caused more sinkage (compaction) than increasing the number of passages of the roller. this may be because it is easier to compact soil at less volume and that more sinkage occur at the first few passages of the roller as corroborated by valera et al. (2012) and taghavifar and mardani (2014) and the sinkage thereafter does not correspondingly respond to further passage of the roller. table 6: comparison of means for sinkage (mm) for each level of the factors at the compaction uniformity test factors levels mean* number of layers 1 40.7a 2 63.0b 4 87.3c number of passes 2 49.5a 4 64.9b 8 76.7b *means with the same alphabets are not statistically different from each other at 5% significance level. 4. conclusion http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):751-762. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 761 a simple wooden soil bin equipped with a digitized, mechanically operated cone penetrometer, a new sinkage measurement system as well as a new stepless soil leveler was developed. the performance of the developed stepless leveler was satisfactory because its average cv was 0.040 which was considered low when compared with manual levelling. besides, it made precise vertical adjustment of soil height possible. the digitized penetrometer and the new sinkage measuring system were a lot more convenient than the existing methods of taking these measurements because these measurements were taken only at the press of a switch and without having to enter the soil bin. the results show that soil compaction and sinkage were both significantly affected by the number of soil layers and number of roller passages thereby validating the correctness of the new measuring devices. the results also show that soil compaction is more easily obtained by dividing the soil layer than by increasing the passages of the roller. to achieve a more uniform compaction across the soil depth, increasing the number of layers and reducing the number of roller passages is the best option. the soil bin was adjudged structurally stable since there was no structural failure observed throughout the conduct of the various experiments. acknowledgement the authors are grateful to mr. h. nagata, a former graduate student in the authors’ laboratory, for his indispensable role in the construction of the soil bin. references ademosun, oc. 2014. soil tillage dynamics in nigeria: potentials prospects and challenges. proceedings of nigerian branch of international soil tillage research organisation. istronigeria symposium, akure 2014. isn – 978-187-472-4. pp 26-31. ani, oa., uzoejinwa, bb., ezeama, ao., onwualu, ap., ugwu, sn. and ohagwu, cj. 2018. overview of soil-machine interaction studies in soil bins. soil and tillage research, 175: 13-27. doi:https://doi.org/10.1016/j.still.2017.08.002. anpat, rm. and raheman, h. 2017. investigations on power requirement of active-passive combination tillage implement. engineering in agriculture, environment and food, 10(1): 4-13. doi:https://doi.org/10.1016/j.eaef.2016.06.004. antille, l., ansorge, d., dresser, m. and godwin, jr. 2013. soil displacement and 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and kilgour, j. 1980. the design and operation of a simple low cost soil bin. journal of agricultural engineering research, 25(1): 99-104. doi:https://doi.org/10.1016/0021-8634(80)90051-7. gonzález cueto, o., iglesias coronel, ce., recarey morfa, ca., urriolagoitia sosa, g., hernández gómez, lh., urriolagoitia calderón, g. and herrera suárez, m. 2013. three dimensional finite element model of soil compaction caused by agricultural tire traffic. computers and electronics in agriculture, 99: 146-152. doi:https://doi.org/10.1016/j.compag.2013.08.026. https://doi.org/10.1016/j.still.2017.08.002 https://doi.org/10.1016/j.eaef.2016.06.004 https://doi.org/10.13031/trans.56.9886 https://doi.org/10.1016/j.biosystemseng.2008.04.012 https://doi.org/10.1016/s0022-4898(02)00007-1 https://doi.org/10.1016/s0167-1987(01)00281-1 https://doi.org/10.1006/jaer.1999.0477 https://doi.org/10.1016/0021-8634(80)90051-7 https://doi.org/10.1016/j.compag.2013.08.026 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng oyebode and shoji.: development of a simple, movable, indoor soil bin equipped with some novel measuring and soil preparation devices. azojete,16(4):751-762. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shojik@kobe-u.ac.jp 762 hernanz, jl., peixoto, h., cerisola, c. and sánchez-girón, v. 2000. an empirical model to predict soil bulk density profiles in field conditions using penetration resistance, moisture content and soil depth. journal of terramechanics, 37(4): 167-184. doi:https://doi.org/10.1016/s0022-4898(99)00020-8. ibrahmi, a., bentaher, h., hbaieb, m., maalej, a. and mouazen, am. 2015. study the effect of tool geometry and operational conditions on mouldboard plough forces and energy requirement: part 1. finite element simulation. computers and electronics in agriculture, 117: 258-267. doi:https://doi.org/10.1016/j.compag.2015.08.006. lin, j., sun, y. and schulze lammers, p. 2014. evaluating model-based relationship of cone index, soil water content and bulk density using dual-sensor penetrometer data. soil and tillage research, 138: 9-16. doi:https://doi.org/10.1016/j.still.2013.12.004. oh, j., nam, j-s., kim, s. and park, y-j. 2019. influence of tire inflation pressure on the estimation of rating cone index using wheel sinkage. journal of terramechanics, 84: 13-20. doi:https://doi.org/10.1016/j.jterra.2019.04.002. pillinger, g., géczy, a., hudoba, z. and kiss, p. 2018. determination of soil density by cone index data. journal of terramechanics, 77: 69-74. doi:https://doi.org/10.1016/j.jterra.2018.03.003. roth, j. and darr, m. 2011. data acquisition system for soil–tire interface stress measurement. computers and electronics in agriculture, 78(2): 162-166. doi:https://doi.org/10.1016/j.compag.2011.07.003. roul, ak., raheman, h., pansare, ms. and machavaram, r. 2009. predicting the draught requirement of tillage implements in sandy clay loam soil using an artificial neural network. biosystems engineering, 104(4): 476-485. doi:https://doi.org/10.1016/j.biosystemseng.2009.09.004. seyedreza, a. z. 2006. modelling of energy requirements by a narrow tillage tool. ph.d thesis, university of saskatchewan, university of saskatchewan, canada. shoji, k. 2001. design of a model ‘spot plough’ for inversion of the soil slice within the furrow. journal of agricultural engineering research, 79(3): 283-297. doi:https://doi.org/10.1006/jaer.2000.0700. shoji, k. 2004. forces on a model ‘spot plough’. biosystems engineering, 87(1): 39-45. doi:https://doi.org/10.1016/j.biosystemseng.2003.10.004. statacorp. 2019. stata statistical software: release 16. college station, tx: statacorp llc. subrata, mk., basudeb, b., somenath, m. and karmakar, s. 2014. soil-blade interaction of a rotary tiller: soil bin evaluation. international journal of sustainable agricultural research, 1(3): 58-69. taghavifar, h. and mardani, a. 2014. effect of velocity, wheel load and multipass on soil compaction. journal of the saudi society of agricultural sciences, 13(1): 57-66. doi:https://doi.org/10.1016/j.jssas.2013.01.004. upadhyaya, g. and raheman, h. 2018. performance of combined offset disc harrow (front active and rear passive set configuration) in soil bin. journal of terramechanics, 78: 27-37. doi:https://doi.org/10.1016/j.jterra.2018.04.002. upadhyaya, g. and raheman, h. 2019. specific draft estimation model for offset disc harrows. soil and tillage research, 191: 75-84. doi:https://doi.org/10.1016/j.still.2019.03.021. valera, dl., gil, j. and agüera, j. 2012. design of a new sensor for determination of the effects of tractor field usage in southern spain: soil sinkage and alterations in the cone index and dry bulk density. sensors, 12(10): 13480-13490. doi:10.3390/s121013480. https://doi.org/10.1016/s0022-4898(99)00020-8 https://doi.org/10.1016/j.compag.2015.08.006 https://doi.org/10.1016/j.still.2013.12.004 https://doi.org/10.1016/j.jterra.2019.04.002 https://doi.org/10.1016/j.jterra.2018.03.003 https://doi.org/10.1016/j.compag.2011.07.003 https://doi.org/10.1016/j.biosystemseng.2009.09.004 https://doi.org/10.1006/jaer.2000.0700 https://doi.org/10.1016/j.biosystemseng.2003.10.004 https://doi.org/10.1016/j.jssas.2013.01.004 https://doi.org/10.1016/j.jterra.2018.04.002 https://doi.org/10.1016/j.still.2019.03.021 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):541-554 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 541 original research article extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency s. s. garba department of geomatics, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: ssgarba@unimaid.edu.ng 1.0 introduction maiduguri is the location where the boko haram insurgency began and persisted in the north eastern nigeria from 2009 up to the present time. there are continuous collection and archiving of reports on the conflict especially by the nigeria and foreign media such as the agence france-presse (afp). there are also dedicated efforts to track global terrorism with their spatial characteristic in order to give insight into the process of terrorism (bahgat and medina, 2013). article information abstract there are no precise suburban coordinates of location of terrorism attacks in parts of maiduguri. effort to apply geospatial analysis will require such data. the objective of this study was to enforce georefencing to textual global terrorism databases, particularly for maiduguri, such that it will provide basis for geospatial analysis and planning counter terrorism. global terrorism data were sourced from internet and reduced to maiduguri and its surroundings. the textual aspect of the databases that reported attacks were used to extract the phrases containing prepositions that indicated location of the attacks at suburban level (such as wards). the phrases were cleaned in order to bring out the names of the locations of attacks. a reference location data (rld) was developed from openstreetmap (osm) and the nigerian administrative boundary (surcon, 2022) and used in determining the coordinates of the locations using microsoft excel fuzzy look up. half of the extracted names could not be determined from the osm based rld. the names that could not be found were looked up and determined from the google earth. the preposition ‘in’ and ‘at’ were the most useful, returning most of the extracted location. other indicators of locations such as: ward, area and neighbourhood merely repeated what the two prepositions have determined. the process extracted 188, 273 and 169 geospatially records for global terrorism database (gtd), gedevents and armed conflict location and event data project (acled) respectively. this work demonstrated that global data on terroristic attack can be used to determine suburban location of attacks. conversely, tracking terroristic attacks should include suburban locations. the key to determining the coordinates of a suburban location is a robust reference dataset, which can be updated. this work provided the basis for geospatial analysis and hence counterterrorism efforts. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 may, 2022 revised 22 august, 2022 accepted 31 august, 2022 keywords: coordinates fuzzy lookup location extraction georeferencing reference location data suburban and terrorism attack http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 542 fundamentally, reports on terroristic attacks are not concerned with the geospatial precision such as the coordinates but rather the names of location. the media (newspapers) generally reported terroristic attacks as happening ‘in maiduguri’ (which may be sufficient for global audience), but such use of names lacks geospatial precision. however, the media occasionally referred to particular location of suburban areas of maiduguri such as: area, ward, popular name of a place or neighbourhood. the mentioning of the parts of the town provides the opportunity for determining the spatial characteristics of the location. these suburban names are often buried in long paragraphs of the reports or datasets. hence this research is focussed on the problem of extracting the names of the locations from the paragraphs and georeferencing them. this aimed at understanding and mapping location of terroristic attacks that were originally recorded without precise geospatial properties. in this study the various questions of why a terrorism happened at a particular location or how or who were involved and the effects are out of the scope of this work. effort to relate textual material to geographical coordinates had received attention across such disciplines like dialectology, computational sociolinguistics and geographical information retrieval (gir), geospatial semantic web and geonames ontology (melo and martins, 2017). advanced efforts in detecting toponyms such in radke (2019), that assumes reference data already existed, hence propositions with a test are used to automatically determine a the toponyms from the existing reference. however, the extraction of specific suburban name from public names and data is complex matter (melo and martins, 2017). the research problem can be defined formally in the word of skoumas et al. (2016): “given a set of objects pv with a-priori known coordinates in space, a set of objects pu whose exact positions are unknown and a set of predefined spatial relationships r between pu and pv objects, find probabilistic estimates for the positions of pu objects in space.” in this study, pv is a set of locations in maiduguri: names of wards, districts, streets, roads and place whose coordinates are known or can be located. pv is the reference location dataset (rld). pu is a set of all extracted location of attacks from media material that are not georeferenced. the aim of this study was to match extracted set of location, to existing location that has precise geospatial properties. it is also to show the complexity of such endeavour as it relates to maiduguri township and develop guide relating to the rules of the relationship between them. 2.0 methodology there are four components of the method as shown in figure 1. the first part consists of collecting the data and extracting the textual description of location of terrorist attract. the second part involves the development of a reference location database which will be used in determining the coordinates of the extracted locations. the third was the determination of the coordinates. the fourth was the culmination of the process, which is a geospatial database (including maps). a provision is made so that when the reference database fails to provide coordinates because the given location is not in reference location database; the locations are checked in google earth pro. the product from the google earth becomes input to the reference location database. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng garba: extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency. azojete, 18(3):541-554. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 543 figure 1: process of georeferencing extracted location and database development. (1) the sources of data and the extraction process, (2) the reference data set with geospatial characteristics developed for maiduguri area (3) the georeferencing and (4) the product of the process. 1.1 the extraction of textual location of terroristic attack below was the process used in extracting names of locations where terroristic attack happened in maiduguri from database of global terrorism tracking. this subsection explains the tracked data and the process of extraction of names. 1.1.1 globally tracked terrorist data data on terroristic attacks exist on the internet, they are generally given from global or regional perspective, it is from datasets that the maiduguri information was extracted. this study was particularly concerned with the data relating to maiduguri during the period of insurgency from 2009 to 2020. three global datasets on terrorism were used: the armed conflict location and event data project (acled); global terrorism database, (gtd, university of maryland, 2022) and the uppsala conflict data program (ucdp). the acled began as a phd research work with focus on conflict in africa. its first version was released in 2009 and the current version is the 8th, released in 2018. the gtd is maintained by the national consortium for the study of terrorism and responses to terrorism (start) at the university of maryland. it began in 2001 to work on archiving data of pinkerton global intelligence services (pgis). the work was expanded in the type of data and definition and integration of data from the institute for the study of violent groups (isvg) (university of maryland, 2022). the ucdp is a project under the department of peace and conflict research, uppsala university. it is continuously updated online database on armed conflicts http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 544 and organised violence (uppsala university, 2022). the volume of records, meaning the number of incident reported and the associated aspects of the record heading or fields are given in table 1. since the downloaded data comes in microsoft excel format, the records are the rows of the excel sheet and the categories are the columns. table 1: volume of original downloaded data database no of records no of heading (fields) period acled 20614 32 07/01/2009 to 01/01/2022 gtb 5070 135 13/2/1976 to 29/12/2019 ucdp 4604 47 25/9/1990 to 31/12/2019 all the databases obtained their data by extracting from major international news agencies and nigerian media outfits. table 2 provides the summary of the sources according to: international news sources, nigerian newspapers and social media. since the downloaded data cover the whole of nigeria, it became necessary to reduce them to maiduguri and environs and between latitude (11.780627°n and 11.889901°n) and longitude (12.975890°e and 13.261794°e) and from 2009 – 2019. table 2: sources of data of the databases database international news sources nigerian newspapers social media remark acled 28 32 1 the most used media are the agence france-presse (afp) and nigerian daily trust and guardian gtb 50 21 nil the most used media are agence france-presse (afp) and nigerian daily trust, vanguard and guardian ucdp 43 55 4 the most used media are the all african website, agence france-presse (afp) provided the international sources, the nigeria watch. it also sourced from human right watch (hrw) and twitter. 1.1.2 the extraction of location of attack the extraction process involved, searching and removing text or phrase that indicated location of attack from the column containing the textual reports of the attacks. extraction processes assumes that certain prepositions or word will indicate where an attack happened. it also assumes that there are not enough reference names to use to search media materials directly, and the familiarity of the researcher confirms the names. the column containing the reports of the incidents was used for the search and extraction. the extraction was conducted in four steps. the first step was to extract phrase containing the following prepositions: ‘in’, ‘at’, ‘along’, ‘on’ and ‘near’. each was extracted separately. the process was conducted by formulating the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng garba: extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency. azojete, 18(3):541-554. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 545 microsoft excel to pick a phrase associated with a preposition of interest. an example of the process is given in table 3. the event column reports an attack on the 21st september 2010 from the gtd data. from the report which in cell c12 of the excel sheet, the formula will search for the preposition “in” and give the resulting phrase containing forty letters containing space. table 3: example of microsoft excel formula to extract phrase with the word “in” event formula 09/21/2010: on tuesday, in the gwaidomari neighborhood i, borno, nigeria, militants riding motorcycles fired upon and killed two people with kalashnikov style rifles. one local chief and one trader were killed. a man claiming to be a chieftain of nigerian taliban, also known as boko haram, claimed responsibility on behalf of the group. =mid(c12,(search("in",c12,1)+3),40) result the gwaidomari neighborhood in, borno, ni the second step was the determination of the actual location name from the results of first step based on the researcher’s knowledge of the place. the third step, was to remove duplication of results from the prepositions. finally, extraction was conducted by using area related words such as district, area, wards and neighbourhood and removing duplication with result of the third steps. these process were used for the three datasets. 1.2 development of reference location dataset (rld) rld refers to data set containing names of places within maiduguri and environs with their coordinates which will be used to determine the coordinates of the extracted locations. the data was built using the ward map of nigeria (osgof, 2022), openstreetmap (osm, haklay and weber, 2008) and google earth pro. the ward map provided the traditional names of areas, most likely association with areas at sub of a local government areas or a geographical organisation of a chiefdom. the maiduguri urban encompasses three local government areas (metropolitan, jere and konduga), it has 27 wards aligned to independent national election commission (inec) distribution, which evolved from two districts (waziri, 2012). over the years some wards have split into two or three such as gwange, bolori and shehuri (with suffix i, ii, iii. north and south). the wards are areas however they are represented by the coordinates of their geometric centres. the wards that have split over the years presented a problem whenever they are mentioned without their suffix. for example, if a report mention only gwange, it will be impossible to know which of the three gwange. hence a super ward was created that combines all wards with similar origin and the coordinates of the centroid was used. osm provided locations more precise location of places other than the wards. it has eight layers of georeferenced information: places, points, railways, roads, waterways, buildings, land use and natural. the rld was further expanded whenever an extracted name of a http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 546 location was not found in the rld. such name was then checked up (start up the software and search) in the google earth pro (and its coordinates determined and then added to the rld. 1.3 georeferencing: determination of coordinates of extracted names the extracted names from the three datasets were each looked up in the rld in order to determine their coordinates. this was what amounted to georeferencing of the extracted textual name of location. the microsoft excel fuzzy lookup (microsoft, 2022) was used to do search and match up. the software is powerful in automating the search and match and tolerance of misspelling. 1.4 predefined relationships the formal definition of the research problem, requires a define spatial relationship. this study does not go into geospatial information systems (gis) topology, but focussed on the relationship between extracted textual and rld. some the rules are: 1. that extracted names that matched ones in the rld will adopt the coordinates of the ones in the rld. 2. that closely associated names arising due to small different in spelling or misspelling of the names or the short form the names should be accommodated (hence the use of microsoft excel fuzzy lookup). 3. that rld should be built to accommodate fuzziness. 2. results and discussion 2.1 the reduction of maiduguri data the downloaded datasets were reduced by two criteria: the name maiduguri and by given coordinates and summarised in table 4. the summary shows that selection by latitude and longitude provides greater record of event of attacks than by simply using the name maiduguri. there are more records from acled than the other dataset. table 4: number of records selected by either name or coordinate selection by name selection by latitude and longitude gedevents 392 423 gtd_nigeria 493 557 acled 680 737 2.2 the extraction of data it is viable to use location associated word, namely: in, at, along, on, near, neighbourhood, ward, district and area in order to search and extract phrase containing the locations of attacks from gtd and acled dataset. the results such process were summarised in table 5. the preposition ‘in’ provided the highest result (557 of 596 of extraction from gtd), however not every result with the ‘in’ gives a location of part of maiduguri. many of the ‘in’ are associated with ‘in maiduguri’. hence the cleaning, which reduced half of the results in the gtd dataset and reduced the records of the acled to 20%. the ‘at’ provide the second file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng garba: extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency. azojete, 18(3):541-554. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 547 highest. the cleaning was necessary because many of at are associated with time such as ‘at 3pm’. on cleaning the result of gtd was reduced to 25% and 35% of acled. the repeat column of table 5 indicates whether a word was repeating the extraction of another, thus in the gtd data, the ‘at’ is not repeating ‘in’ and in the acled only 5 of 61 are repeating the ‘in’. the ‘along’, ‘on’ and ‘near’ all reported very few results. the neighbour, district, area and ward reported high results but they are mostly reporting what the ‘in’ and ‘at’ had reported. eventually 389 records were extracted from the gtd and 255 from the acled. the process of cleaning the data relied on the local knowledge of names. table 5 prepositional performance definer dataset gtd repeated acled repeated in 557 444 in (cleaned) 251 94 at 310 176 at (cleaned) 75 61 5 along 8 3 35 3 on 276 208 on (cleaned) 11 3 31 7 near 53 64 near 36 34 30 30 neighbourhood 41 41 10 3 ward 36 36 23 8 district 17 2 2 area 121 111 area (cleaned) 121 90 83 56 total cleaned 596 207 369 114 actual (less repeated) 389 255 the third dataset the gedevents data does not have a summary of events that could be used in extraction of data as the other two. however, it had a column called “where description” in which the 423 records which reported 258 (61%) locations of part of maiduguri. the process of extraction shows that most of the records from gtd provided single name of location but acled and gtdevent have multiple names per record. the multiple record implied the case where on the date there were multiple attacks in different parts of maiduguri. and sometimes it was simply the description of one event in a larger area, such as a point in a ward. the extracted data are sometime repeated because an attack was repeated at a particular location. tables 6, 7 and 8 are excerpt from the extracted results of gtd, acled and gedevents respectively. it could be seen that names may not always a single, such as aladuwari (table 7) but complex such as 333 artillery nigerian army base/market (table 6). http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 548 table 6 excerpt from gtd, eventid date summary extracted 201806200021 06/20/2018 two suicide bombers detonated at the 333 artillery nigerian army base/market gate i, borno, nigeria. the two assailants were killed and at least 15 people were injured in the blasts. no group claimed responsibility 333 artillery nigerian army base/market 201506020031 06/02/2015 a suicide bomber detonated at a cattle market i city, borno state, nigeria. in addition to the bomber, at least 31 people were killed and 25 people were injured in the blast. no group claimed responsibility for the incident cattle market table 7 excerpt from the acled extracted event_id_no_cnty event_date notes extracted 1306 27-dec-15 nigerian forces shoot and kill seven potential suicide bombers (some reports claim 14) attempting to gain access to maiduguri (at aladuwari area) on 27/12 this follows the detonation by three of bombers at a nearby mosque, killing 25 and injuring 85. the bombers were reported to be teen-aged girls. aladuwari 4429 04-dec-21 on 4 december 2021, iswap militants claimed to have fired 6 mortar shells at the 1000 residential housing estate, gomari and 777 housing estate in maiduguri (maiduguri metro, borno). at least one house was damaged and one baby was wounded, the rockets were fired from the duwari area. other sources report that soldiers engaged the militants in an armed clash on the outskirts of maiduguri. 1000 residential housing file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng garba: extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency. azojete, 18(3):541-554. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 549 table 8 excerpt of gedevents extraction id where_description extracted date_start date_end 258504 the informal market at the base of 333 artillery nigerian army in maiduguri 333 artillery nigerian army 04/08/2012 04/08/2012 269489 an area called caterpillar near ajilari cross, airport area in maiduguri caterpillar near ajilari cross, airport area in 04/10/2012 04/10/2012 268150 on the outskirts of maiduguri, attacking an idp camp in judumri area, not far away from the federal high court complex, jiddari area federal high court complex, jiddari area 04/26/2012 04/26/2012 255846 on the outskirts of maiduguri, attacking an idp camp in judumri area, not far away from the federal high court complex, jiddari area judumri 06/05/2012 06/05/2012 284313 in muna dalti on the outskirts of maiduguri muna dalti 06/17/2012 06/17/2012 2.3 the reference location data (rld) reference data were first developed from the thirty-three wards in and around maiduguri (figure 2), and it provided the first layer of the rld. the list of the wards and coordinates of the centre is given in table 9. in addition, three super wards of gwange, bolori and shehuri were added to provide for the cases where only the ward is mentioned without the suffix (i or ii). the osm provided eight layers of information, namely: places, points, railways, roads, waterways, buildings, land use and natural (table 10). although a total of 106249 records are obtained from the osm, only 579 have names that could be used in the reference data (summary in table 9). there were 29 repeated names between the layers of osm, hence only 550 could be used in the reference. the process of using the rld was also a process of updating (as shown in the next section). thus the current report of the rld is tentative. it has 683 records, six fields (reference number, type, source, name, latitude and longitude). eighty percent was sourced from osm, 5% from osgof and 15% from google earth. an excerpt of the rld is given in table 13. http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 550 table 9: location of centroid of the wards of maiduguri and surrounding table 10: summary of osm layers number of records number with records with name places 522 352 points 276 106 railways 25 0 roads 13725 42 waterways 25 7 buildings 90790 50 landuse 824 20 natural 62 2 total 106249 579 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng garba: extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency. azojete, 18(3):541-554. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 551 figure 2: wards of maiduguri and its neighbourhood table 11 excerpt of reference location dataset (rld) 2.4 georeferencing: matching extracted data with rld the 389, 255 and 258 records extracted from gtd, acled and gedevents, respectively were searched in the rld that was built from the osgof and osm. when excel fuzzy lookup was applied to the extracted gtd and rld, 26% could not be found, 19% were wrongly assigned location, 31% were partially correct in the assignment and 24% absolutely http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 552 correct. on examination of the partially correct assignment the reasons are: misspelt names such as gombouru in the gtd and gamboru in the rld. there were cases where shorter version of the name was used in either the data base or the rld, for example, muna and muna dalti. table 12 is an excerpt of the result of comparison of gtd and reference data. it should be noted that both the reference data and the sources of the extracted data are not thoroughly reviewed to have standard names. acled and gedevents showed similar characteristics, the summary of the matching is shown in table 13. most of the locations extracted were matched. however, the average of 30% not matching indicated the need to improve the rld there were 93 unique names at the initial use of the rld, that could not be found or were wrongly matched. the location of most of these names were determined using the google earth pro. a simple search produced many of the locations, and others were determined based on the researcher’s knowledge of the area, thus the process produced an updated rld table 12: execerpt of the report of the matching of extracted gtd data and the rld extracted reference latitude longitude similarity index summary % gwaidomari 0.0000 no result, 26% wahabi mosque 0.0000 sinimari church of christ 0.0000 bayan quarters adam kolo bayan makaranta camp 11.833244 13.186372 0.5187 wrong matching, 19% balgawe ajiri bulabulin baligawe 11.710507 13.12171 0.5432 muna garrage muna garage el badawe refugee site 11.874751 13.250862 0.8387 kaleri tomsu ngamdu kaleri 11.68285 13.062116 0.8750 partial matching, 31% muna muna dalti 11.8684 13.2445 0.8800 gombouru gamboru 11.856765 13.16573 0.8889 njimtilo njimtilo 11.8495 13.0219 1.0000 correct matching, 24% muna dalti muna dalti 11.8684 13.2445 1.0000 yauri yauri 11.7648 13.2155 1.0000 gamboru gamboru 11.856765 13.16573 1.0000 the extracted data from gtd, acled and gedevents were respectively matched with the updated rld. the summary of the matching performance is given in table 12. although there were high percentages of failure to match, that indicated the need for further field work other than the use of google earth. table 13 the performance of matching of the dataset dataset correct matching extraction records gtd 262 (67%) 389 gedevents 192 (74) 258 acled 165 (65) 255 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng garba: extraction and geo-referencing suburban locations of terroristic attacks from textual data of maiduguri insurgency. azojete, 18(3):541-554. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 553 the combined results from the three dataset were used to generate a map (figure 3) that shows the various locations terrorist activities took place in maiduguri. figure 3: the location of activities of terrorism in maiduguri conclusions textual reports are used to extract the location information of a suburban. geospatial investigation at suburban level has become possible with the determined coordinates. hence the geospatial analysis of insurgency in maiduguri will be richer when the coordinates in maiduguri are known. this work demonstrated how the geospatial precision of public data can be improved. global terroristic attack tracking data provides a viable means suburban location of terroristic attacks from their textual reports. the preposition “in” is the most important word that can be used in extracting location of an attack. the extraction shows that a record in acled and gedevents more than one name of location, and a name of a location may not be a single word, and may have different variance for same location. the process of extraction was tedious, although particular words were used to point to text that depicted location, the process does not give the location directly. the process only narrows the search, a further work had to be on selecting the name of the location of attack, which implies individual verification. this also point to need of artificial intelligence, since there are enough data for machine learning. a much easier way is to directly search already known names in a given text. that is not case here because reference data has not been developed. when such reference has been built, it will not eliminate the process of extraction but will make it secondary. the geospatial coordinates of centroid of administrative wards around maiduguri formed the first layer of the rld, and then osm data were added. since the two layers of data were inadequate, the google earth was used to determine the coordinates of extracted location that could not be determined from layers. building a robust rld will shift http://www.azojete.com.ng/ mailto:ssgarba@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):541-554. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ssgarba@unimaid.edu.ng 554 the task of identifying using preposition to direct search for name of location. this study has provided the basis for geospatial analysis of terrorism attacks in maiduguri: where the attack occurred over the years, and according to wards. there is need to develop local terrorism tracking system that will capture suburban location. since the target is names of suburban, the social media in the localities are most likely to mention the local suburban names, as hoang and mothe, 2018 has demonstrated effort to use tweeter. a lot of time was spent extracting the names using microsoft excel; it is recommended that the use of more robust artificial intelligence be used (radke et al., 2019, johansson and nugues, 2007). reference bahgat, k. and medina, rm. 2013. an overview of geographical perspectives and approaches in terrorism research. perspectives on terrorism, 7(1): 38-72 microsoft 2022. fuzzy lookup add-in for excel. available at: https://www.microsoft.com/enus/download/details.aspx?id=15011 accessed on 16/05/2022 haklay, m. and weber, p. 2008. openstreetmap: user-generated street maps. ieee pervasive computing, 7(4): 12-18. hoang, tbn. and mothe, j. 2018. location extraction from tweets. information processing and management, 54(2): 129-144. johansson, r. and nugues, p. 2007. lth: semantic structure extraction using nonprojective dependency trees. proceedings of the fourth international workshop on semantic evaluations (semeval-2007), 23-24 june, prague, pp. 227–230. melo, f. and martins, b. 2017. automated geocoding of textual documents: a survey of current approaches. transactions in gis, 21(1), 3-38. osgof, 2022. nigerian administrative map available at: https://data.humdata.org/dataset/cod-ab-nga#, accessed on 8/3/2022 radke, m., das, p., stock, k. and jones, cb. 2019. detecting the geospatialness of prepositions from natural language text (short paper). proceedings of the 14th international conference on spatial information theory (cosit 2019), (timpf, s., schlieder, c., kattenbeck, m., ludwig. b. and stewart, k. (eds.). 9-13 september, regensburg, germany, article no. 11: 11.1-11.8. skoumas, g., pfoser, d., kyrillidis, a. and sellis, t. 2016. location estimation using crowdsourced spatial relations. acm transactions on spatial algorithms and systems (tsas), 2(2): 1-23. university of maryland 2022. at: https://www.start.umd.edu/gtd/ accessed on 10/3/2022 uppsala university, 2022. at https://www.pcr.uu.se/research/ucdp, accessed 10/3/2022 waziri, m. 2012. spatial pattern of maiduguri city. researchers’ guide, adamu joji publishers, kano file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ssgarba@unimaid.edu.ng https://www.microsoft.com/en-us/download/details.aspx?id=15011 https://www.microsoft.com/en-us/download/details.aspx?id=15011 https://data.humdata.org/dataset/cod-ab-nga https://www.start.umd.edu/gtd/ https://www.pcr.uu.se/research/ucdp arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):655-661 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 655 profiled deck composite slab strength verification: a review k. mohammed 1 *, i. abd karim 2 and k. bulu 1 ( 1 department of civil and water resources engineering, university of maiduguri, maiduguri, nigeria 2 department of civil engineering, universiti putra malaysia, selangor darul-ehsan, malaysia) *corresponding author’s e-mail address: engrkachalla@gmail.com abstract the purpose of this article is to present an overview on alternate profiled deck composite slab (pdcs) strength verification devoid of the expensive and complex laboratory procedures in establishing its longitudinal shear capacity. despite the several deterministic research findings leading to the development of proposals and modifications on the complex shear characteristics of pdcs that defines its strength behaviour, the laboratory performance testing stands to be the only accurate means for the pdcs strength assessment. the issue is critical and warrants much further thoughts from different perspective other than the deterministic approach that are rather expensive and time consuming. hence, the development of a rational-based numerical test load function from longitudinal shear capacity consideration is a necessity in augmenting the previous futile attempts for strength determination of pdcs devoid of the costlier and expensive laboratory procedure. keywords: profiled composite slabs, longitudinal shear, failure test load, reliability 1. introduction the composite use of steel and concrete has been one of the most popular composite constructions nowadays (abdullah et al, 2015; chen, 2003; degtyarev, 2012; gholamhoseini et al., 2014; marimuthu et al, 2007). the use of such system has a lot of advantages. for instance, the profiled sheeting can serve as shuttering during construction stage, and can serve as tensional force resisting medium within the composite slab system. other advantages include the effectiveness of the steel sheeting deck and the hardened concrete in carrying any addition loads that may be considered during the design process in addition to supporting their self-weight. furthermore, unlike the conventional reinforced concrete (rc) slab systems, in this construction method, the use of flexural reinforcement steel is seldom required, and the mesh reinforcement mostly provided are for hydration and shrinkage control only. moreover, the method gains more popularity because of eliminating time-consuming erection and subsequent removal of temporary forms at site, and the gains associated with concrete strength during service (abbas et al, 2015; gholamhoseini et al, 2014). it is for the above reason that this review is presented so that there can be a preponderance of application of this mode of construction here in nigeria and worldwide too. 1.1 background of study the ultimate strength governs the design of composite slab, and the shear bond strength defines its capacity. generally, the composite action between the profiled steel sheeting deck and the hardened concrete ( figure 1), can be transmitted effectively with the development of longitudinal shear at the steelconcrete interface. the shear bond failure is one of the three, and most common failure modes associated with composite slab (gholamhoseini et al, 2014; marimuthu et al., 2007), flexural failure and shear at support are the other modes of failures. many studies (abbas et al, 2015; burnet and oehlers, 2001; tsalkatidis and avdelas, 2010) show that the behaviour of profiled deck composite slab is affected by the bond failure in the longitudinal direction. interestingly, recent study (abdullah et al, 2015) result adds the influence of shear span to effective depth ratio on the shear bond strength of the composite slab as very vital consideration in pdcs strength appraisal. mailto:engrkachalla@gmail.com mohammed et al.: profiled deck composite slab strength verification: a review, azojete, 13(6):655661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 656 figure 1: pdcs failure modes (johnson, 2004) 1.2 longitudinal shear bond longitudinal shear failure for pdcs ( figure 1) always occurs before reaching the plastic bending capacity of the composite slab system due to an inadequate shear connection between the profiled sheeting deck and the hardened concrete (tzaros et al, 2010). an overview of this occurrence shows that several authors (abbas et al, 2015; abdullah et al., 2015; burnet and oehlers, 2001; chen, 2003; tenhovuori and leskelä, 1998; tsalkatidis and avdelas, 2010) carried out studies on composite slab behaviour as influenced by the bond failure in the longitudinal direction. for example, marimuthu et al, (2007) carried out experimental study on composite slab with the aimed of understanding shear bond behaviours of embossed profiled sheeting deck under simulated variable load after incorporating several strength influencing parameters. the authors’ finding revealed that shear span defined the behaviour of embossed profiled composite slab deck (mäkeläinen and sun, 1999), and re-affirmed that shear bond failures governed the strength requirement for the embossed profiled sheeting deck. intuitively, longitudinal shear capacity determines the ultimate strength of composite slab with profiled steel sheeting (marčiukaitis et al., 2006). the shear bond analysis obtained from shear bond formulations in codes requires the use of experimental test data on composite slab decks that are obtained through regression analysis on the test data as the case with slope-intercept or the generation of partial interaction curve and subsequent determination of other required parameters as applies to the partial shear connection method. test data are required to provide input for strength design formulations. there are two methods for the longitudinal shear estimation that are currently useful in deck strength appraisal, and the ec4 (2003) provides the general guide for the bending resistance calculation for composite slab using either of the methods. 1.3 the slope-intercept method the slope-intercept, m-k method for the longitudinal shear value is from the linear relationship plots of vertical shear, ⁄ against shear bond, ⁄ for two groups of test values that comprises a long, x and short, y specimens ( figure 2). these requirements are from the standards. therefore, the slope (m) and the intercept (k) are the outcome variables from the plots figure 2. arid zone journal of engineering, technology and environment, october, 2017; vol. 13(6):655-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 657 figure 2: typical m-k parameter determination showing both short and long specimen zones (johnson, 2004) in figures 1 and 2, is the effective sectional area of the sheeting deck with yield strength value, . the parameter is the clear centroid distance to the topmost concrete face that has a width and is the testing shear span length. under ductile failure condition, the support reaction, tv from the failure load, w is (johnson, 2004): (1) a 20% reduction is applied upon the equation (1) if the failure condition is brittle in nature (stephen, 2008). notwithstanding the failure mode type, the ratio plays a critical role in any of the expected failure modes, and the maximum bending moment occurs at higher ratio. hence, the vertical shear at equilibrium will be (johnson, 2004) (2) interestingly, is found to have no significant influence on longitudinal shear (johnson, 2004), and low ratio will leads to shear failure. hence, equation (2) reduces to ( ) (3) the design shear resistance is by using equation(3). 1.4 the partial shear connection method partial interaction is also another means other than the m-k method that can be used to obtained longitudinal shear strength of profiled composite slab. the method assumed complete redistribution of longitudinal shear between the sheeting deck and the concrete interface (stephen, 2008). the degree of shear connection, ⁄ ( is the compressive force while stands for the steel yield force) defines the activity level between the sheeting deck and the concrete, and comes under three groups. first, , signifying no composite action between the sheeting deck and the concrete. second, , full shear connection exist, slip and strain are assumed to be zero in this case. finally, if is between 0 and 1, partial shear connection is said to exist between concrete and the sheeting deck. similar to the expression given in equation (3) for mohammed et al.: profiled deck composite slab strength verification: a review, azojete, 13(6):655661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 658 the m-k method, the longitudinal shear, for a given value of bending resistance under partial shear connection (psc), neglecting the support reaction is given by equation (4). (4) the variables were the overhung length, and represented the steel yield force. however, in this method, the bending resistance determination is highly dependent on the neutral axis position within the system, and is either within or above the deck with . because of complexity involved with the estimation of the stress block depth x, from the neutral axis, the sheeting tensile force is decomposed to equal compressive force. thus, the design bending resistance, is computed from the expression: (5) where ( ) (6) the parameters , and represents distance of plastic neutral axis above the base, overall deck thickness ( 80 )mm , and concrete thickness, respectively. these restrictions are to control the minimum fire protection requirement and load concentration resistance for the composite system. the parameter is the design value of the profile sheeting deck plastic moment of resistance, and the manufacturer provides it normally. the psc method involves the determinations of all the parameters defined through equations (4) to (6). however, the task of determining the experimental degree of shear connection, can only be achieve through the use of partial interaction diagram by plotting, ⁄ as depicted in figure 3. the and are moments signifying when there are no interaction ( ) and full interaction ( ). afterwards, with the ratio ⁄ the equivalent value is located as shown with figure 3. the maximum bending moment testm is determined from the full-scale test (abdullah et al., 2015). once, the design shear strength is known, the design envelope for the particular deck profile can be drawn. figure 3: degree of shear connection determination using psc method (johnson, 2004) arid zone journal of engineering, technology and environment, october, 2017; vol. 13(6):655-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 659 it was evident from the two methods for determining the longitudinal shear capacity of pdcs, the experimental failure test is essential in determining the requisite shear parameters (abbas et al, 2015). the process is cumbersome and expensive. however, the volumes of research findings and proposals on the complex shear characteristics of profiled deck composite slab, the laboratory performance testing stands to be the only accurate means for the determination of composite slab strength (abbas et al, 2015). the issue is critical and warrants much further thoughts from different perspective other than the deterministic approach that are expensive and time consuming (crisinel and marimon, 2004). 2. overview on the numerical approach for failure test method generally, steel deck fabricator provides design data for the engineers and builders for the commonly available profiled sheeting deck for composite construction. however, in special cases where the use of non-standard dimensions, which may be because of either choice by design engineer or strict architectural requirement, such privilege information on the steel deck behaviours may not be available. hence, the need to carry out full laboratory test that is uneconomical and time consuming is unavoidable in order to establish the design parameters necessary for the design and construction of the composite slab. this limitation has led to many research developments using numerical solutions all with the aim of eliminating the uneconomical full-scale test that is required to verify the performance of composite slab (abbas et al., 2015; marimuthu et al., 2007). the quest for replacing the uneconomical and complex strength verification of composite slab, the exploration of numerical approach in solving the problem becomes the only option. abdullah and samuel (2009) and abdullah et al. (2015) presented proposals for new method for modelling horizontal shears in composite slab systems that takes in to account the slab slenderness as a major parameter that influences the horizontal shear bond. in abdullah and samuel (2009) experiment, the shear bond-end slip behaviour of composite slab in bending is determined using force equilibrium method. the study result shows that shear bond varies with the slenderness in bending, and the slab slenderness affects the strength of the composite slab. furthermore, the authors modelled the slab using finite element (fe) analysis with the aim of replacing uneconomical and time-consuming full-scale test on composite slab. however, modelling limitation on the factors affecting the shear bond capacity hinders to yield effective result due to lack of quantitative information on them. on the other hand, abdullah et al. (2015) finding reveals the slenderness influence the longitudinal shear bond. they presented results of linear interpolation of shear bond that includes the effect of the slenderness, and concluded that it performed satisfactorily. furthermore, in a related finite element (fe) modelling study on pdcs, the simulation results for long slab specimens reflect true resemblances of the slab performance with previous similar study results. however, comparative behavioural analysis for the short span shows behavioural variations between the modelled slabs from the real (an, 1993; crisinel and marimon, 2004). the critics of fe analysis application for shear bond capacity for composite slab is that shear bond is geometry dependent, and this signifies that full-scale experimental testing must be conducted. hence, fe modelling will become uneconomical since the test has to be conducted before utilizing the data for the modelling (abdullah and samuel 2009).to augment the flaws, an approach that does not require the complex and expensive laboratory procedures for pdcs strength verification is still required. this shifts the focus on the use of more rational method, which will be the probability-based design concept, for example. literature related to reliability studies on the performance of composite slab are scanty (degtyarev, 2012), very few areas is indeed covered. degtyarev (2012) presented reliability based analysis result on composite slab at construction stage to the united state design provision. the author considers the failure analysis of allowable stress design and load resistance factor design using first order reliability method for strength and deflection limit state conditions. the finding reveals high level of conservatism in the us design provision for composite steel deck construction. notwithstanding the effort, analysis at construction stage may have little or no influence on the deck behaviour, and the much-needed simplification for the pdcs strength determination devoid of the complex and expensive laboratory procedure is still yet to be developed. therefore, further work in exploring the potential associated with this rational-based approach in order to develop a simplified strength determination function for pdcs is required. mohammed et al.: profiled deck composite slab strength verification: a review, azojete, 13(6):655661. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 660 3. conclusion informed by the literature reviewed, the complexity in the design and strength verification of profiled composite slab is largely due to the uneconomical and the mandatory laboratory procedure required for its strength determination. the manufacturer provides the required test data and independent verification of such vital information posed a serious challenge. however, several research findings and proposals on the complex shear characteristics of profiled deck composite slab showed that the laboratory performance testing stands to be the only accurate means for the determination of composite slab strength. the issue is critical and warrant much further thoughts from different perspective other than the deterministic approach that are expensive, uneconomical and time consuming. therefore, the development of a rational-based numerical test load function from longitudinal shear capacity consideration is a necessity in augmenting the previous futile attempts for profiled composite slab strength determination devoid of the uneconomically expensive laboratory procedure. references abbas, hs, bakar, sa, ahmadi, m, and haron, z. 2015. experimental studies on corrugated steel-concrete composite slab. građevinar, 67(3), 225-233. doi: doi: 10.14256/jce.1112.2014 abdullah, r, kueh, abh, ibrahim, is, and easterling, ws. 2015. characterization of shear bond stress for design of composite slabs using an improved partial shear connection method. journal of civil engineering and management, 21(6), 720-732. doi: 10.3846/13923730.2014.893919 abdullah, r, and samuel easterling, w. 2009. new evaluation and modeling procedure for horizontal shear bond in composite slabs. journal of constructional steel research, 65(4), 891-899. doi: http://dx.doi.org/10.1016/j.jcsr.2008.10.009 an, l. 1993. load bearing capacity and behaviour of composite slabs with profiled steel sheet. ph.d, chalmers university of technology. retrieved from http://publications.lib.chalmers.se/publication/1378load-bearing-capacity-and-behaviour-of-composite-slabs-with-profiled-steel-sheet burnet, mj, and oehlers, dj. 2001. rib shear connectors in composite profiled slabs. journal of constructional steel research, 57(12), 1267-1287. doi: http://dx.doi.org/10.1016/s0143-974x(01)00038-4 chen, s. 2003. load carrying capacity of composite slabs with various end constraints. journal of constructional steel research, 59(3), 385-403. doi: http://dx.doi.org/10.1016/s0143-974x(02)00034-2 crisinel, m, and marimon, f. 2004. a new simplified method for the design of composite slabs. journal of constructional steel research, 60(3–5), 481-491. doi: http://dx.doi.org/10.1016/s0143-974x(03)00125-1 degtyarev, v. 2012. reliability-based evaluation of u.s. design provisions for composite steel deck in construction stage. journal of structural engineering, 138(3), 308-317. doi: doi:10.1061/(asce)st.1943541x.0000437 ec4. 2003. eurocode:4 design of composite steel and concrete structures. part1.1: general rules and rules for building (pren 1994-1-1:2003): european committee for standardization. gholamhoseini, a., gilbert, ri, bradford, ma, and chang, zt. 2014. longitudinal shear stress and bond– slip relationships in composite concrete slabs. engineering structures, 69(0), 37-48. doi: http://dx.doi.org/10.1016/j.engstruct.2014.03.008 johnson, rp. 2004. composite structures of steel and concrete (second ed. vol. 1 beams, slabs, columns and frames for building): blackwell publishing, london. http://dx.doi.org/10.1016/j.jcsr.2008.10.009 http://publications.lib.chalmers.se/publication/1378-load-bearing-capacity-and-behaviour-of-composite-slabs-with-profiled-steel-sheet http://publications.lib.chalmers.se/publication/1378-load-bearing-capacity-and-behaviour-of-composite-slabs-with-profiled-steel-sheet http://dx.doi.org/10.1016/s0143-974x(01)00038-4 http://dx.doi.org/10.1016/s0143-974x(02)00034-2 http://dx.doi.org/10.1016/s0143-974x(03)00125-1 http://dx.doi.org/10.1016/j.engstruct.2014.03.008 arid zone journal of engineering, technology and environment, october, 2017; vol. 13(6):655-661. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 661 mäkeläinen, p, and sun, y. 1999. the longitudinal shear behaviour of a new steel sheeting profile for composite floor slabs. journal of constructional steel research, 49(2), 117-128. doi: http://dx.doi.org/10.1016/s0143-974x(98)00211-9 marčiukaitis, g, jonaitis, b, and valivonis, j. 2006. analysis of deflections of composite slabs with profiled sheeting up to the ultimate moment. journal of constructional steel research, 62(8), 820-830. doi: http://dx.doi.org/10.1016/j.jcsr.2005.11.022 marimuthu, v, seetharaman, s, arul jayachandran, s, chellappan, a, bandyopadhyay, tk, and dutta, d. 2007. experimental studies on composite deck slabs to determine the shear-bond characteristic values of the embossed profiled sheet. journal of constructional steel research, 63(6), 791-803. doi: http://dx.doi.org/10.1016/j.jcsr.2006.07.009 stephen, h. 2008. composite slab. en 1994 eurocode 4: design of composite steel and concrete structures. the steel construction institute. silwood park, ascot, berkshire, sl5 7qn, united kingdom. tenhovuori, ai, and leskelä, mv. 1998. longitudinal shear resistance of composite slabs. journal of constructional steel research, 46(1–3), 228. doi: http://dx.doi.org/10.1016/s0143-974x(98)00169-2 tsalkatidis, t, and avdelas, a. 2010. the unilateral contact problem in composite slabs: experimental study and numerical treatment. journal of constructional steel research, 66(3), 480-486. doi: http://dx.doi.org/10.1016/j.jcsr.2009.10.012 tzaros, ka, mistakidis, es, and perdikaris, pc. 2010. a numerical model based on nonconvex–nonsmooth optimization for the simulation of bending tests on composite slabs with profiled steel sheeting. engineering structures, 32(3), 843-853. doi: http://dx.doi.org/10.1016/j.engstruct.2009.12.010 http://dx.doi.org/10.1016/s0143-974x(98)00211-9 http://dx.doi.org/10.1016/j.jcsr.2005.11.022 http://dx.doi.org/10.1016/j.jcsr.2006.07.009 http://dx.doi.org/10.1016/s0143-974x(98)00169-2 http://dx.doi.org/10.1016/j.jcsr.2009.10.012 arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):561-568 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 561 original research article enhancing oil recovery throughwaterflooding a. s. grema, m. k. mahlon, a. s. kolo and u. h. taura department of chemical engineering, university of maiduguri, maiduguri, borno state *corresponding author’s email address: a.grema@unimaid.edu.ng 1.0 introduction waterflooding process is a secondary oil recovery effort that involves injection of water into an oil well reservoir to increase the underground pressure thereby increasing oil recovery (grema and cao, 2016). however, waterflooding processes are faced with constitutive recovery mechanism in terms of well placements, which determines the maximal recovery of oil at a given point in time. well placements predominantly play a role as regards to production rates which serves as a consideration to which various oil companies identify in order to determine oil-water ratio (grema and cao, 2017). the placement of injection wells determines the oil and water production rates. it is for this reason that estimation of oil recovery in terms of well placements is considered. reservoir models are expressed by nonlinear partial differential equations (pdes) which constitute unsteady states and dimensions in the region of time and space (grema and cao, 2017). there are a lot of exorbitance in the demand of power and energy in the oil and gas sector and it has been estimated that oil recovery through the use of primary (natural) mechanism is intermittently reducing with time. this is why significant need for enhanced oil recovery (eor) arises (grema and cao, 2013). oil recovery is associated with what is called recovery factor (rf) which is defined by the amount of oil that is produced as a given fraction of the main oil in the reservoir (ahmed, 2006). the oil recovery factor (rf) is written mathematically as shown in equation 1, (ahmed, 2006): �� � ��� �੪呅䈍呅⸰㔰〠 � ��� �th ��� �੪呅䈍呅⸰㔰〠 ��� rf indicates the recovery factor, ��� �੪呅䈍呅⸰㔰〠 indicates the initial oil in the reservoir, ��� �th indicate the remaining oil in the reservoir. article information abstract waterflooding is a simple and cheaper means of improving oil recovery from a reservoir by injecting water into the reservoir. economic considerations suggest injection and production wells must be optimally placed considering reservoir geology, fluid properties, and well orientation. this study focuses on the effects of well placement and orientation on the performance of waterflooding process. the reservoir has a dimension of 2500 ft by 2500 ft by 150 ft. it is homogenous in porosity and heterogeneous in permeability. the performances of three cases considered in the study were evaluated and compared. water production rates, bottom hole pressure limits for producer wells, well water cut and net present value (npv) over the entire production period were considered in evaluating their performances. reservoir modeling and simulation were carried out using matlab reservoir simulation toolbox (mrst). it was verified from the investigation that case iii has a maximal production rate of 1,110,188.6 stb/day (stock tank barrel per day), decreasing to 11,005 stb/day after a span of 1400 days with a pressure decrease. consequently, it was considered a better choice in terms of well placement. it was also estimated to have a maximal net present value of 19.8 billion dollars, which makes it economically viable. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 08 oct., 2019 revised 10 june, 2020 accepted 20 june, 2020 keywords: eor, reservoir waterflooding, npv, mrst, five-spot pattern mailto:a.grema@unimaid.edu.ng http://www.azojete.com.ng grema et al.: enhancing oil recovery through waterflooding. azojete,16(3):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 562 several research findings have been reported on waterflooding process as it is the commonest recovery methods (adeniyi et al., 2008; jansen et al., 2008; jansen et al., 2009). the prominent usage of waterflooding process is attributed to the fact that it remains one of the cheapest means of oil recovery (adeniyi et al., 2008). grema and cao (2013) investigated the changes which occur in the performance of petroleum reservoirs and oil production wells before and after applying the waterflooding technique. optimization of reservoir waterflooding was carried out considering the effect of geological uncertainties such as porosity, permeability and reservoir size (jansen et al., 2008; jansen et al., 2009; grema and cao, 2020). oil reservoirs are faced with typical water production problems such that the oil recovery is curtailed by the prevalence of excess water breakthrough at the point of recovery. similarly, grema and cao (2016) investigated the problems associated with waterflooding, where they implemented a typical feedback control mechanism that could expedite and maximize the optimal oil recovery hence reducing early water breakthrough. a typical application to reservoir simulation is in the future prediction of flow performance in a reservoir, and as such prudent plans and techniques can be applied to improve and optimize the recovery of oil economically. reservoir simulations can also be used to provide insights on the mechanism and behavior of fluid flow dynamics in a porous medium (jansen, 2011). the aim of this study is to investigate the effects of well placement and orientation on the performance of waterflooding process. three cases of well location and orientation were considered; the performance of which were compared in terms of field oil production rate (fopr), field water production rate (fwpr), total field oil production (fopt), bottom hole pressure(bhp), total field water production(fwpt), well water cut (wwct) and net present value(npv) for all well models. 2 methodology 2.1 rock and fluid properties 2.1.1 rock properties the reservoir considered has a dimension of 2500 ft x 2500 ft x 150 ft and it is divided into three layers of equal thickness along the vertical axis. the number of cells in the x, y, and z directions are 5, 5 and 3 respectively. the depth of reservoir top is given to be 8000 ft with a homogeneous porosity of 0.2. table 1 shows the permeability information in x, y, and z directions. this is necessary to enable the simulation of the process. table 1: rock permeability layer 1 layer 2 layer 3 permeability in x direction 200 md 1000 md 200 md permeability in y direction 150 md 800 md 150 md permeability in z direction 20 md 100 md 20 md the rock compressibility at 4500 psia is given as 4x10-6 psi-1.the grid was divided into 3 sub grid data each having 25 cells defined in the reservoir geometry. the grid was extracted separately for the purpose of generating permeability on each defined sub grid data. for a heterogeneous distribution of permeability, cell data structure was created for the three cases in order to verify the range of distribution on each predefined cells in all three layers. figure 1 shows the permeability distribution in each grid structure for all three cases. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 561-568. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 563 case i case ii case iii figure 1: wells and permeability distribution for all cases 2.1.2 fluid properties generating relative permeability and capillary pressure the ability of one phase to move strictly depends on the environment at a particular location; the relative permeability of one phase works in conjunction with the saturation of the other phase present at the same location (adeniyi et al, 2008). relative permeability was used to denote the movement of a phase in the present of multiple phases from one point to another taking into account of the saturation as a function (ahmed, 2006). in the matlab interface, defining relative permeability and capillary pressure as a function of water saturation was done in a tabular form. the table is a four column array in which the first column is interpreted to be water saturation, the second column denotes water relative permeability, and the third is oil relative permeability while the fourth column denotes oil-water capillary pressure function. see lie et al. (2012) for detailed explanation. the variation of relative permeability with water saturation required in running the reservoir model is shown in table 2. the oil and water densities at surface conditions are respectively given as 49 lbs/ft3, and 63 lbs/ft3 while the initial reservoir pressure is given as 4500 psia. table 2: fluid properties (1000md) water saturation krw kro pcow(psi) 0.15 0.0 0.9 4.0 0.45 0.2 0.3 0.8 0.68 0.4 0.1 0.2 0.55 0.0 0.8 2.2 net present value (npv) the possible worth of investment for all the three studied cases was estimated. net present value is the value of all future cash flows (positive and negative) over the entire life of an investment discounted to the present (grema and cao, 2016). a positive npv indicates that the projected earnings generated by a project or investment (in present dollars) exceed the anticipated costs (also in present dollars). generally, an investment with a positive npv will be profitable, and an investment with a negative npv will result in a net loss. this concept is the basis for the net present value rule, which dictates that the only investments that should be made are those with positive npv values. the net present value is calculated using equation 2 (grema and cao, 2016): �� � ��� ��੪t⹉ �੪�������� � ੪h� �h���� � 呅�� �呅⸰� ੪h呅��h呅�呅���� � t h �� ੪ ��� ��� where: file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:a.grema@unimaid.edu.ng grema et al.: enhancing oil recovery through waterflooding. azojete,16(3):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 564 ੪h呅 is the water injection cost, ੪h� is the water production cost, ੪� is the oil price per barrel, �h呅�呅 is the water injection rate, �h is the water production rate, ���� is the oil production rate, ��੪t⹉ is the number of production wells, �呅⸰� is the number of injection wells, h is the discount factor, ��� is the time step size, �� is the actual time period for which npv is computed, � is the time unit. here, yearly discount factor was taken to be given as 0.05, oil price to be 70 dollars per barrel, water production handling cost to be 6 dollars per barrel and the water injection cost to be 6 dollars per barrel. the npv parameter applies to all cases of the reservoir model. 2.3 case studies 2.3.1 case i: quarter five-spot pattern for the first case, the wells were arranged in a quarter five-spot pattern as shown in figure 2. two wells were added at the opposite corners of the reservoir and perforated throughout the layer in the z-direction (vertically), with an injection well named ‘g2’ and production well named ‘g1’. precise data required in addition of well could be the bottom hole pressure, perforation cells, and injection/production rate. . figure 2: reservoir grid and well positioning for case i 2.3.2 case ii: five-spot pattern here, the wells were placed in a five-spot pattern and perforated throughout the layers as shown in figure 3. this consists of four injection wells, one at each corner of the reservoir geometry and a production well in the middle of the geometry. the injection wells are named g1, g2, g3, g4 and the single production well named g5 (figure 3). figure 3: reservoir grid and well positioning for case ii 2.3.3 case iii: horizontal wells here two horizontal wells g1 (production) and g2 (injection) placed parallel to each other were considered (figure 4). all other rock and fluid modeling parameters assume their previous values. well g1 is specified with a bottom hole pressure to estimate the oil and water production rates, while g2 is specified with a water injection rate to estimate the variation in the bottom hole pressure. from figure 4, the production and injection wells were placed and perforated at the first two layers. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 561-568. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 565 figure 4: reservoir grid and well positioning for case iii for all these cases, matlab reservoir simulation toolbox (mrst) was used to setup and run the model. detailed explanation on how to setup and run a reservoir simulation model using mrst can be found in lie et al. (2012) . 3 results and discussion 3.1 case i the production rates and well water cuts for case i are shown in figure 5. figure 5: production rate and wwct for case i figure 5 illustrates a maximal recovery of oil with a production rate of 955,346.89 stb/day during water injection period of 400 days. after that period, there was a reduction in production rates as the bottom hole pressure reduces (figure 6), and then a steady rate of 11,582.45 stb/day was realized going down at a negligible rate for the complete period of 2000 days. the well water cut shows a negligible effect on the production rates during the span of recovery. figure 6: bhp and npv evolution for case i file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:a.grema@unimaid.edu.ng grema et al.: enhancing oil recovery through waterflooding. azojete,16(3):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 566 an estimate of 19 billion dollars (6.6 trillion naira) npv was estimated for a complete span of 2000 days (figure 6). the bottom hole pressure for the producer well indicates reduction along the entire life span of the well recovery. it also indicated that the total field oil production rate is analogous to the field oil and water production rate; this is because single productions wells were considered and simulated. 3.2 case ii the production rates and well water cut for case ii are shown in figure 7. figure 7: production rate and wwct for case ii case ii has a constant oil production rate of 37,343.089 stb/day for the next 400 days with a rapid decrease in water production (figure 7). the oil production estimate verified an incremental well water cut as a result of the number of water injection wells. although it can be considered maximal due to the long term oil production estimate, it is obviously limited by the excessive amount of water breakthrough. case ii shows an estimate of 17 billion dollars (6 trillion naira) of npv calculated for a complete span of 2000 days (figure 8). figure 8: bhp and npv evolution for case ii the same analogy in terms of field oil and water production rates and total field oil production rate is applied to this case as it is to the first case. there is a substantial decrease in the bottom hole pressure at an early start of recovery due to a fast and exceeding water injection from five injection wells flowing at the same constant rates (figure 8). this factor gives rise for a high bhp at a shorter period of time, and it will likewise result in an undesired amount of water production. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 561-568. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 567 3.3 case iii the production rates and well water cut are shown in figure 9. figure 9: production rate and wwct for case iii case iii indicates a maximal oil recovery of 1,110,188.60 stb/day decreasing down to 11,019.06 stb/day as the reservoir pressure decreases within a span of 1200 days (figure 9). there is no much flow discrepancy between case 1 and 2 since the same constant flow is recorded at the same time span, but it is seemingly a better choice since it has a maximal flow for a longer time span as compared to case 1 and case 2. this gives it a better choice of consideration. case iii shows an estimate of 19.5 billion dollars (6.8 trillion naira) npv calculated for a complete span of 2000 days (figure 10). figure 10: bhp and npv evolution for case iii it is obviously seen that, from the estimated results, case iii can be taken as a better investment as compared to the first two cases. the bhp shows an analogous reduction as compared to case ii and case ii. various factors assert case iii as a better choice in terms of well placement considering the recovery and investments. these factors are the field oil and water production rates, net present value (npv), well water cuts (wwct) and the bottom hole pressure limits. 4 conclusion this study has employed the use of mrst to simulate three cases of reservoir waterflooding process. several simulation outputs were analyzed to infer a better choice of consideration for all the three cases. npv was used as the performance index for evaluation. case i and case ii were close to maximum although an early water breakthrough and pressure decrease posed some uncertainties. they were also noted to have less oil recovery during the complete span of 2000 days. maximum npv was recorded by the simulation for case iii when compared to the first two cases. therefore, the reservoir configuration presented by case iii will make a better choice compared to the two other cases considered in this study. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng mailto:a.grema@unimaid.edu.ng grema et al.: enhancing oil recovery through waterflooding. azojete,16(3):561-568. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: a.grema@unimaid.edu.ng 568 it is recommended that next study should incorporate detailed costs of production facilities for better comparison. references adeniyi, od., nwalor, ju. and ako, ct. 2008. a review on waterflooding problems in nigeria's crude oil production. journal of dispersion science and technology, 29 (3): 362-365. ahmed, t. 2006, reservoir engineering handbook, third ed, gulf professional publishing, burlington, usa. grema, as. and cao, y. 2013. optimization of petroleum reservoir waterflooding using receding horizon approach, in 8th ieee conference on industrial electronics and applications, melbourne, australia, 397–402.. grema, as. and cao, y. 2016. optimal feedback control of oil reservoir waterflooding process. international journal of automation and computing, 13 (1): 73–80. https://doi.org/10.1007/s11633-015-0909-7. grema, as. and cao, y. 2017. receding horizon control for oil reservoir waterflooding process. systems science and control engineering, 5(1): 449-461. doi: 10.1080/21642583.2017.1378935. grema, as. and cao, y. 2020. dynamic self-optimizing control for uncertain oil reservoir waterflooding processes. ieee transactions on control systems technology (article in press). doi: 10.1109/tcst.2019.2934072 jansen, jd. 2011. adjoint-based optimization of multi-phase flow through porous media–a review. computers and fluids, 46(1): 40-51. jansen, jd. bosgra, oh. and van den hof, pmj. 2008. model-based control of multiphase flow in subsurface oil reservoirs. journal of process control, 18(9): 846-855. jansen, j., brouwer, r. and douma, sg. 2009. closed loop reservoir management. spe reservoir simulation symposium, 2-4 february 2009, society of petroleum engineers, the woodlands, texas. lie, k., krogstad, s., ligaarden, i.s., natvig, jr., nilsen, hm. and skaflestad, b. 2012. opensource matlab implementation of consistent discretisations on complex grids. computational geosciences, 16(2): 297-322 https://doi.org/10.1007/s11633-015-0909-7 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1): 31-37 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 31 effect of storage environment and packaging media on the disease incidence and weight loss of stored african star apple (chrysophyllum albidum) m. o. sunmonu 1* , m. m. odewole 1 , o. obajemihi 1 and o. e. ajala 2 ( 1 department of food and bioprocess engineering, university of ilorin, ilorin, nigeria 2 department of chemical engineering, university of ilorin, ilorin, nigeria) *corresponding author’s e-mail address: sholams2000@yahoo.co.uk, tel: +2348050745127 abstract a study was conducted to study the effect of storage environment and packaging media on the disease incidence and weight loss of stored african star apple (chrysophyllum albidum). three storage environments were identified in this study namelyevaporative cooling basket, refrigerator and ambient storage and freshly harvested ripe african star apples were wrapped in perforated polythene, moist jute material and without packaging and stored under these three storage environment. the apples were observed for deteriorations mediated by microbial infection and insect infestation. manifestation of infestation which affected the shelf-life of african star apple was delayed most in the refrigerator. the level of infestation of the apples stored in evaporative cooling basket was next to the refrigerator in the decreasing order. weight losses were lower in apples wrapped with moist jute sack (0.48% ± 1.6) stored in refrigerator than those wrapped with perforated polythene (0.79% ± 1.2) and unwrapped (1.45% ±1.4). similar wrapping effects were obtained in the evaporative cooling basket and ambient. weight losses were lower in apples stored in refrigerator (0.91%) than in the evaporative cooling basket (2.84 %) and ambient shade (7.41 %). keywords: apple, diseased, microbial, storability, structure, temperature, vitamin, wrapping 1. introduction african star apple (chrysophyllum albidum) is a forest plant but is usually planted as a compound tree in villages. the plant produces edible fruit and the composition of this fruit is very common in the entire gulf of guinea and other african countries such as cameroon, congo and nigeria (ejiofor and okafor, 1997).the post-harvest losses could discourage farmers from producing and marketing fresh produce, and limit the urban consumption of fresh fruits and vegetables. hence, development of post-harvest technologies is believed to make great contribution to improve quality and use of these crops. it is essential to control storage temperature and relative humidity during storage as they are the main causes of fruit and vegetable deterioration during ripening and storage. one of the limiting factors that influence the fruits economic value is the relatively short shelf-life period caused by spoilage organisms and pathogens’ attack (rashad et al., 2011). it is estimated that about 2025% of harvested fruits are lost during post-harvest handling even in the developed countries (droby, 2006; zhu, 2006). in developing countries however, post-harvest losses are often more severe due to inadequate storage and transportation facilities (rashad et al., 2011). fungal infections of fruits may occur during the growing season, harvesting, handling, transport and post-harvest storage and marketing conditions, or after purchase by consumers. deterioration of apples could be seen visually with the discoloration in the head region (stem end) which could be extended into the edible pulp. the lesion advanced gradually bursting the apple resulting in loss of firmness and fermentation (gomes and ledward, 1996): barman et al, 2015). this syndrome suspected to be end rot has been associated with poor harvesting technique (babarinsa et al., 1997). mailto:sholams2000@yahoo.co.uk sunmonu et al.: effect of storage environment and packaging media on the disease incidence and weight loss of stored african star apple (chrysophyllum albidum) azojete, 13(1): 31-37. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 32 water is an important constituent of most fruits and vegetables and it adds up to the total weight. losses of water will definitely reduce the weight. the loss of weight comprises of both respiratory and evaporative losses. the former, which occurs as a result of respiration, depends mainly on the temperature of the surrounding air. the latter occurs as a result of water vapour deficit of the environment compared with that of the produce (fao, 1989). packaging fruits is one of the most commonly used post-harvest practice that puts them into unitized volumes which are easy to handle while also protecting them from hazards of transportation and storage (burdon, 1997). if both temperature and packaging is optimum, ageing of fruit and vegetables can be slowed down with up to more than 80% (dtipt, 2008). 2. materials and methods 2.1 collection of fresh african star apple and weight determination two hundred and seventy (270) standardized ripe african star apple fruits of average weight of 40g were purchased from a local market (ipata) in ilorin kwara state, nigeria.. the samples selected were at the peak of their freshness (fairly soft to touch, plump with orange-yellowish color. the fruits were washed with potable water, sorted to remove bruised, diseased and unwholesome fruits prior to storage. the apples were randomly assigned to the following treatments: fruits wrapped in perforated polythene (standardized at 8.5% perforation), fruits wrapped in moist jute material and unwrapped fruits. the apples were stored in three storage environment namely refrigerator, evaporative cooling basket and ambient storage. the two hundred and seventy fruits were stored to compare their nutritional changes, and physiological weight changes in an evaporative cooling basket (ecb); conventional refrigerator and ambient condition. each treatment contained 30 fruits and replicated three times. the weight of all the samples were measured before storage using a weight balance (model cs 200) with an accuracy of 0.1g and a capacity of 200g .on the second day of storage, three (3) samples were picked at random from each treatment and labeled properly. the weights of the picked samples were taken. after weighing, the samples were returned back to their respective treatment and storage chambers. this process was repeated at interval of two days during the duration of the experiment and the weight changes were correctly recorded. 2.2 determination of environmental parameters the temperature ( o c) was measured using a thermometer. the relative humidity (%) was taken using a wet and dry bulb thermometer and the reading was measured on the humidity table (i.e. difference between the dry and wet bulb readings). the readings were taken daily, for 10 days, from the ambient storage, evaporative cooling basket and refrigerator. the effects of the storage parameters on the nutritional value and weight loss on the produce were determined using statistical analysis of variance (anova). further analysis by duncan’s new multiple range test (dnmrt) was carried out to compare the means. 2.3 determination of disease incidence disease incidence was calculated as the percentage of diseased fruit per total number of fruits. the fruits were observed visually for rotting and microbial infection. percent disease incidence was identified and calculated using the formula of mamatha and rai (2000). (1) arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1): 31-37 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng where, di= disease incidence do= number of diseased fruit d= total number of fruits 3. results and discussion table 1 indicates that weight loss of stored fruits statistically depend on storage duration. this is in line with ghafiret al., (2009) who reported an incremental increase in storage duration due to water loss and respiration. table 2 also shows increase in the percentage weight loss over the duration of storage, and table 3 shows the effect of wrapping on weight loss of the stored african star apple. percentage weight loss of african star apple unwrapped was lowest in refrigerator (1.45 %) followed by those stored in evaporation cooling basket (5.50%) and highest in the ambient condition. this may be attributed to the effectiveness of the refrigerator and evaporative cooling basket increasing the temperature and raising the relative humidity thereby reducing the rate of metabolism (perez et al., 2004). table 1: effect of storage structure, storage media and storage days on weight loss source sum of squares df mean square f sig. a 432.832 2 216.416 6.029 0.003* b 167.234 2 83.617 2.329 0.103 c 1278.866 4 319.716 8.906 0.001* a*b 278.154 4 69.538 1.937 0.111 a*c 480.459 8 60.057 1.673 0.116 b8c 359.149 8 44.894 1.251 0.280 a*b*c 529.485 16 33.093 0.922 0.547 error 3230.806 90 35.898 total 6756.986 134 a=storage structure, b=packaging condition, c=storage days, *significant at 5% probability level table 2: comparison between the different levels of the three factors (storage structure, storage media, and storage days), using new duncan multiple range test (ndmrt) main factors levels % weight loss storage structure ambient condition 7.413d evaporative cooling basket 2.844b refrigerator 0.910a storage days 2 0.869a 4 1.996 6 5.943c 8 6.162 10 7.363d storage treatment / condition unwrapped 5.865c perforated polythene 2.689b moist jute bag 2.621b means with the same alphabet are not significantly different from each other sunmonu et al.: effect of storage environment and packaging media on the disease incidence and weight loss of stored african star apple (chrysophyllum albidum) azojete, 13(1): 31-37. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 34 table 3: mean percentage of weight loss in african star apple under different storage structures storage treatment/condition amb ecb ref unwrapped 10.62 ± 4.9 a 5.50 ± 4.8 a 1.45 ± 1.4 c perforated polythene 5.61 ± 2.8 b 1.66 ± 2.4 b 0.79 ± 1.2 c moist jute bag/sack 6.01 ± 1.8 c 1.37 ± 2.2 b 0.48 ± 1.6 c standard deviation from 3 replications in each treatment. a-c data with the same superscript in the same row are not significantly different ecb = evaporative cooling basket, ref = refrigerator, amb = ambient storage deterioration of the apples was manifested visually with the discoloration in the head region (stem end) that extended into the edible pulp. the lesion advanced gradually bursting the apple resulting in loss of firmness and fermentation. this syndrome suspected to be end rot has been associated with poor harvesting technique (babarinsa et al., 1997). data on the effect of wrapping and storage treatment on disease development in ripe african star apple are presented in table 4. as was expected, disease developed at a slower rate in the apples wrapped and stored in the refrigerator relative to those stored in the evaporative cooling basket (ecb) and those stored under ambient shade conditions. diseased apples increased from zero to 33.3, 62.5, and 33.3 % on the 4 th day in perforated polythene, moist jute wrapping and unwrapped treatments, respectively in the ambient condition. a similar period (on the 4 th day) of disease manifestation continued in apple stored in an evaporative cooling basket (ecb). diseased fruits increased from zero to 12, 31, and 23 % in perforated polythene, moist jute bag and unwrapped on the 4 th day, respectively. on the contrary, a less similar period of disease manifestation was observed in the refrigerator. diseased fruit increased from zero to 4 % in both perforated polythene and unwrapped on the 4 th day. the moist jute wrapping responded differently, no diseased fruits were recorded (except in refrigeration storage) until the 8 th day of storage (table 4). diseased apples increased to 100% on the 10 th day in the treatment in the ecb and ambient shade. that non uniformity in the time diseased symptoms were noted in the treatments under all the conditions studied may partly have been due to the effect of different storage conditions. this quiescence infection syndrome phenomenon is not fully understood as reported by babarinsa, et al., 1997).comparing the various treatments in relation to disease manifestation, perforated polythene wrapping in ecb appeared more effective in delaying disease symptoms than other treatments similarly stored. generally fruits packed inside perforated polythene wrapping gave the lowest number of diseased apple (~3.7-25.9%) as compared with fruits packed in unwrapped (~ 3.7-33.3 %) and fruits packed in moist jute bag (~3033.3%) (table 4). figure 1 shows the graphical representation of the effect of storage structure and treatment on the manifestation of disease. refrigerated moist jute wrapping appeared to be the most effective in suppressing manifestation of disease symptom was observed in the apples thus stored throughout the period with 22.2 % diseased compared to 27.8 and 55.5 % in perforated polythene and unwrapped treatment respectively in the refrigerator (table 4). low temperature prolongs storage life by reducing respiration rate as well as reducing growth of spoilage microorganisms (roura et al., 2000; watada et al., arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1): 31-37 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 1996). under ambient shade storage condition and ecb, the fruit wrapped with moist jute bag became 100% infested with disease after the 8 th day, unlike other treatments. comparing the three storage environments for suppressing manifestation of disease, the evaporative cooling basket (ecb) appears next to the refrigeration in order of effectiveness. table 4: assessment of diseased ripe african star apples in different wrapping stored under different structure storage environment type of wrapping percentage of diseased african star apple 0 2 4 6 8 10 ambient shade perforated polythene 0.0 6.6 33.3 70.8 85.7 100 moist jute 0.0 6.6 62.5 62.5 76.6 100 unwrapped 0.0 3.3 33.3 70.8 100 100 evaporative cooling basket perforated polythene 0.0 3.3 22.2 37.5 95.2 100 moist jute 0.0 3.3 11.1 37.5 76.2 100 unwrapped 0.0 10.0 30.33 37.5 100 100 refrigeration perforated polythene 0.0 0.0 3.7 4.17 33.3 55.5 moist jute 0.0 0.0 3.7 12.5 14.3 27.8 unwrapped 0.0 0.0 0.0 0.0 19.4 22.2 figure 1: assessment of diseased african star apple after the 10th day. 4. conclusion the study was based on the development of an alternative source of storage in combination with packaging material and their effect on the weight loss and disease development in african star apple (chrysophyllum albidum). the following conclusion can be inferred from this research: 0 20 40 60 80 100 amb ecb ref p er ce n ta ge d is e as e d storage structure perforated polythene unwrapped moist jute sunmonu et al.: effect of storage environment and packaging media on the disease incidence and weight loss of stored african star apple (chrysophyllum albidum) azojete, 13(1): 31-37. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 36 1. percentage weight loss of the african star apple (chrysophyllum albidum) was less in the refrigerator and evaporative cooling compared to the ones stored under ambient condition. 2. refrigerator and evaporative cooling basket in combination with moist jute sack packaging material better delayed the manifestation of disease of the african star apple (chrysophyllum albidum) references babarinsa, fa., williams jo. and osanu fc. 1997. storage of carrots in a brick wall cooler under semiarid conditions. trop sci 37: 21–27. barman, k., ahmad, ms. and siddiqui, mw. 2015. factors affecting the quality of fruits and vegetables: recent understandings. in m. w. siddiqui (ed.), postharvest biology and technologyof horticultural crops: principles and practices for quality maintenance (pp. 1– 50).waretown, nj: apple academic press. burdon, jn. 1997. postharvest handling of tropical and subtropical fruit for export. pp. 1-19. in: mitra. s. 9ed.).postharvest physiology and storage of tropical and subtropical fruits.faculty of horticulture, cab international, west bengal, india. danish technological institute packaging and transport 2008. guide packaging fresh fruit and vegetable. pp 3, 5-8. droby, s. 2006. improving quality and safety of fresh fruits and vegetables after harvest by the use of biocontrol agents and natural materials. in african journal of microbiology.volume 709. pp 45-51. ejiofor, man. and okafor, jc. 1997. prospects from commercial exploitation of nigeria indigenous trees, vegetables, fruits and seeds through food and industrial products formulation. international tree crops journal 9 (2): 119-129. food and agriculture organization 1989. prevention of postharvest food losses of fruits, vegetables and root crops. pp 160-162. ghafir, sam., gadalla, so., murajei, bn. and el-nady, mf. (2009). physiological and anatomical comparison between four different apple cultivars under cold-storage conditions. afri. j. of pl. sci. 3: 133-138. gomes, mra. and ledward, da. (1996). effect of high pressure treatments on the activities of polyphenoloxidases. food chem. 956 91): 1-5. mamatha t., lokesh, s. and rai vr. 2000. impact of seed mycoflora of forest trees seeds on seed quality and their management. seed res. 28(1):59-67 perez k, mercado j, soto-valdez h 2004. note. effect of storage temperature on the shelf life of hass avocado (persea americana).food sci. technol. inter. 10(2):73-77. arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1): 31-37 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng rashad, ra., ahmed, ra. and saleh, am.2011. isolation and identification of some fruit spoilage fungi: screening of plant cell wall degrading enzymes. in african journal of microbiology research.vol.5, 2011. no. 4. pp. 443-448. roura, sj., davidovich, la. and valle, ce. 2000. quality loss in minimally processed swiss chard related to amount of damage areas. lebensmittelwissenchaft technol. 33: 53-59 watada, ae. and minott, da. 1996. factors affecting quality of fresh-cut horticultural products. postharvest biology technology.9:115-125. zhu, sj. 2006. non chemical approaches to decay control in postharvest fruit. in: noureddine, b., norio, s. (eds). advances in postharvest technologies for horticultural crops. research sign post. trivandrum, india. pp. 297-313 arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):243-254 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 243 original research article potential of jesse clay as drilling mud otitigbe f. e. department of petroleum engineering, faculty of engineering, delta state university, abraka, oleh campus, delta state, nigeria. *corresponding author’s email address: fotitigbe@yahoo.com 1.0 introduction the drilling mud remains the most valuable and inevitable fluid to abandon during drilling operations of oil and gas in the life of a well. this is as a result of its support for the safety of life and ease in drilling that anchor on the general success of the drilling operation. these two components; safety and ease in drilling is made possible due to the properties of the drilling mud that is on adequately routine checking and maintaining to carry out its functions like subduing formation pore pressure and removal of sand in drilling mud (alsabaa et al., 2020). article information abstract the high bottom hole pressure normally encountered during drilling, poses serious challenges during drilling operations of oil and gas wells. the unavoidable quest for crude oil source of energy by man, required for running its home and industries, makes the high risk pose by the underground hole pressure a risk-worth taking for new discovery of oil and gas reserve. the fear of encountered formation pressure is conquered by the use of drilling fluid (drilling mud). the drilling mud is a mixture of clay, water and chemicals. the drilling clay possesses certain properties that distinguished, and earmarked it as a drilling fluid, highest economy clay that is highly sorted/hunted for, either as purely for export for economic purpose by countries where it is found but have no oil or for oil and gas exploration activities in countries where hydrocarbon exploration takes pace. nigeria as a country is a practical scenario of the above case the drill-mud–clay is being imported for the exploration of its large oil and gas reserve. therefore, this paper seeks address the lingering unresolved challenges of the inability to establish nigeria’s local drilling mud-clay with properties comparable with the existing imported drilling mud-clay through laboratory analysis of nigeria clay. in searching for suitable nigerian clay for to be used as drilling mud, two properties (mud density and sand content) of local clay extracted from jesse, in ethiope-west local government area of delta state was analyzed and the results were recorded and compared with those of imported foreign clay. for their densities, the result was recorded as 8.41kg/m3, 8.50kg/m3, 8.50kg/m3 and 8.67 kg/m3 for local clay, and 8.60 kg/m3, 8.66 kg/m3, 8.67 kg/m3 and 8.83 kg/m3 for foreign /imported bentonite. the percentage of sand content in both the local and imported foreign drilling mud after analysis, were recorded as 0.1%, 0.1%, 0.2%, 0.2% and1%, 1.5 %, 1.5 % and 2% respectively. the little differences noticed between the sand value of in the drilling mud prepared with local clay and imported clay, indicates that the local drilling mud can be at its best as drilling mud like the conventional drilling mud, which is in accordance with the api recommended value range of between 0.25% -1.2% if the experimented properties are further enhanced. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 1 october, 2021 revised 5 march, 2022 accepted 16 march, 2022 keywords: local clay foreign clay mud balance sand content set multi-mixer http://www.azojete.com.ng/ mailto:fotitigbe@yahoo.com mailto:fotitigbe@yahoo.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 244 the drilling mud is composed of clay, water, and additives (rajesh et al., 2017). the clay is the major component of drilling mud and is normally identified by its high cation exchange capacity in water (apugo et al., 2011; zhang et al., 2020; mobeen et al., 2020; moses et al., 2021). this was also reported in the work of moses et al., 2021, richard et al., 2017, jun et al., 2020 and arabi el al., 2017. the likes of this clay possess a swelling behavior when in contact with water and the colloid formed is plasticity in nature. this mixture of clay and water is referred to as drilling mud (rajest et al., 2017). the drilling mud is the heartbeat of the drilling operations. the clay with these characteristic are called bentonite clays respective of the region that is found (apugo et al., 2011). these special characteristics of the clay make it difficult to be found in every region, even when there is an abundance of clay in every square of the earth's surface. thus, the clay is continually being imported either as raw or as the mixture called drilling mud (kaffayalullah et al., 2021). the clay is imported from overseas and cost is in millions of dollars as reported in moses et al. (2021), omole et al. (2013), ameloko et al. (2020) and arinkoola (2020), and this increases the financial burden of the company and thus, reduces the foreign earning of the host country and ushers in economic crush and high unemployment rate, thus, leading to national crisis. realizing this huge loss, nigeria as a country, initiated a local content development to curb importation to boost external reserve, generate employment, and kick-start rural area industrialization, and urban-rural area drift and development (omole et al., 2013). to ensure the drilling mud continue to perform its primary functions, a consistent routine check of sand volume, and mud density is conducted to avert abrasion of drilling hose and/or bottom hole equipment, and balancing of formation pore pressure, for safe and economical of drilling operations (rajest et al., 2017). thus, it is important to measure the properties that make up the drilling mud which controls the ability to perform these functions. this research work aimed at substituting the imported conventional clay/drilling mud with the local nigeria clay. this, if achieved would not only stop the importation of the drilling clay (bentonite clay), but would also boost foreign exchange earnings and as well start rural area industrial development. to this end, two properties; sand content and mud density of drilling mud is investigated to a certain their suitability as drilling mud when compare with the conventional drilling mud. 1.1 sand content clay-solids and those mixed-up while drilling (as it has been), at some volume, can be permitted and may be beneficial and at some other, if not removed will undergo continuous grinding into smaller size particles and are more difficult to remove from the drilling mud. the small particles have a greater effect on drilling mud properties than larger particles and would be intricate to remove and lead to problems like; dilution cost for mud chemicals and barite, disposal cost for mud hauled away, reducing drilling rate, reduced bit life, excessive abrasion of the pump, mud line, swivel, guns, thick filter cake and pipe stuck (faruk, 2000 and apugo-nwuso et al., 2011). the drill solids are insoluble in drilling mud systems and the quantities and types present in drilling file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:fotitigbe@yahoo.com otitigbe: potential of jesse clay as drilling mud. azojete, 18(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 245 mud systems played a major role in its properties (asme, 2005). therefore, the development of a solid control program in drilling mud is important to aid improve the performance of the mud's basic functions. sand is defined as a particle whose size is larger than 74m (microns). the sand content in the drilling mud is measured wih the aid of a mesh sieve of 200 capacity and a glass tube called sand content set (bourgoyne, 1991). a concentration of solids (from bentonite or those incorporated while drilling or the low gravity inevitable solids) in mud is the main cause of mud problems (standard procedure manual, 2003 and wolfgang, 2016). therefore, its then important to check the volume of sand in drilling mud by routine measurement, with the aid of sand content set and a mesh sieve of 200 capacity (institute of petroleum engineering, 2005). the drill solids are insoluble in drilling mud systems and the quantities and types present in drilling mud systems played a major role in its properties (asme, 2005). therefore, the development of a solid control program in drilling mud is also an important factor to aid improve the performance of the drilling mud's basic functions. 1.2 mud density one primary function of drilling mud is to control the subsurface pore pressure and formation fluid into the well, which is the force exerted by a mud column, and it depends on the mud density and true vertical depth (tvd) (akpoturi et al., 2017; rajesh et al., 2017). the buildup hydrostatic pressure of the mud is usually a little/a bit higher than the subsurface pore pressure to avoid an inflow of fluids into the well (kick), and if urgent attention is taken to stop it, results in a blowout, and lives and equipment are a loss. when planning for pressure control, the control of mud density is the first thing that comes to mind. the weight of a column of mud in the hole necessary to balance formation pressure is the base point from which all pressure control calculations are based. the required weight of the mud column establishes the density of the mud for any specific case. 1.3 established areas of bentonite location in nigeria studies on local clay in the niger delta reviewed the existence of high swollen clay (bentonite) as well as non-swollen clay of kaolinite origin (ameloko, et al., 2020; igwilo et al., 2021). the reason being the niger delta region is opened to the continental shelf of brine seawater and so, the formation is enriched with sodium. some of the areas where bentonite are found are shown table 1: http://www.azojete.com.ng/ mailto:fotitigbe@yahoo.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 246 table 1: localities where local bentonites are found in nigeria s/n state locations estimated reserve comments 1 abia arochukwu, umuahia, bende, isiukwuatolkwuano a proven/inferred reserve is 5.8-7.5 mil. tons most deposits require further investigation 2 adamawa/taraba gujba (mutai) not yet quantified deposits in river channel 3 akwa-ibom itu 4 anambra awka not yet quantified need investigation. 5 borno gamboru, marte, ngala, dikwa, monguno 700 million product of clay of quaternary and tertiary 6 cross river ogurude need further investigation 7 delta abbi, amai edeje-irhodo, jesse not yet quantified. 8 ebonyi ohaozara asu river group shale. 9 edo akoko-edo, afuze, okpebhio, esan, owan, etsako. 10 gombe akko, gombe, yamaltu-deba 11 imo orlu, isu, oru, okigwe inferred reserve estimates are 5.8-7.5 million tons mining activities are on in some of the locations. 12 kebbi jega not yet quantified found in benin formation 13 yobe ngala, marte, mongunu, damboa black cotton source: okologume c. wilfred and akinwumi e. aknade. (2016). international journal of engineering, vol. 8. pp 6. 2.0 materials and methods the local and foreign materials used in the experimental work are shown in table 2: table 2: thee local and foreign materials in use. materials functions local clay sample for preparation of mud sample to be analyzed tap water for watching and preparation of mud sampleto be tested. rag for cleaning foreign clay sample for preparation of drilling mud to be used as comparison. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:fotitigbe@yahoo.com otitigbe: potential of jesse clay as drilling mud. azojete, 18(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 247 table 3: equipment use, and their source and functions equipment source functions sand content set (us mesh sieve size, 200 microns) ofite, houston to determine the volume percent of sand-size particles in the drilling fluid. mesh sieve (74 microns) u.s.a standard test sieve for sieving to talc size mud balance + box baroid division, taxas to determine mud weight multi mixer and cups gallenkamp, england for mixing. measuring cylinder pyrex, england for measuring water spatula and stirrers pyrex, england for taking sample from container local sieve of unquantified mesh size locally fabricated, nigeria for sieving prior to standard mesh sieve of 74𝜇m weighing balance ohaus, london for weighing of materials electronic drier box ofite roller oven, usa aid in effect of temperature on drilling mud. thermometer england to determine the degree cool and hotness sample cans local, nigeria. for keeping of samples masking paper tape purchase in bookshop, nigeria. for labeling of clays local and foreign and mud samples 2.1 location and geology of study area. the selected area for this work is edeje, a village that is located in ethiope west local government area of delta state, south-south nigeria. it lies on longitude 5.870o n and latitude 5.750o e. it is 290 kilometers (180 miles) southeast of lagos. it has a common boundary with edo state in the west, river ethiope in the east and south, and mosogar in the northern part. this area is characterized by annual heavy rainfall, thick forest vegetation, and terrestrial animals. edeje is also discretized by benin, agbada, and akata formation. it is a sedimentary region with flat topography which is characterized by fine reddish, and brown topsoil underlain by shale formation. 2.1.1. sample collection, processing and experimental procedure/method clay samples were collected from edeje was dried under the sun with the aid of a locally fabricated wired mesh-garri processing filter and then later dried under moderate temperature in a drying oven. it was then pulverized with the aid of a local mortal and were sieved with 200 mesh to obtain a fine clay powder sample. this powdered sample was then collected in a sample can and was labeled accordingly using paper tape. a 24.5g, 22.0g 21.0g, and 17.5g respectively of the different clay powder samples (wyoming and local) were weighed out using ohaus chemical weighing balance. afterward, a 350ml of tap water was measured with a 500ml of glass measuring cylinder, and poured into the mud mixer cup and the ph were tasted. then a 0.5ml of sodium hydroxide was measured and poured into the mud cup containing the water. the multi-mixer mud cup was then clamped to the high speed hamilton beach multi-mixer, and “on button” set on and allowed to stirred for two minutes, for proper mixing of water and sodium hydroxide before the ph was tested. this was followed by pouring a particular clay concentration, bit-byhttp://www.azojete.com.ng/ mailto:fotitigbe@yahoo.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 248 bit to eliminate clogs/cake that would prevent proper mixing of the mixture before the “onbutton” was switched off. the ph of the final mixture (drilling mud) was tested before it was allowed to age for 24 hours. the sand content set was used for the analysis of the volume of sand in the drilling mud. the component parts of the content set are; 200 mesh sieve of 2½ inch in diameter funnel and a conspicuous glass tube graduated in percentage from 0 to 20% (rajesh et al., 2017) the procedure for determining sand content begins with ensuring the sand content glass tube is dried and dust-free. then is held upward, and the funnel containing filter screen is fitted onto its mouth/opening and was filled with the freshly prepared mud sample to the mark “mud to here” (rajesh, et al., 2017). then water was added to the mark “water to here” and with the funnel removed, the mouth was firmly and completely covered with thumb and shaken vigorously. afterward, the funnel was replaced and the mixture of mud and water was allowed to flow out through the screen. and then, was placed under running tap water, and prudently remove sand particles clinching around the wall of the conspicuous graduated glass tube by backwashing. this process continued till the mud was completely washed out. then the fitted filter screen was slowly inverted onto the funnel on the mouth of the glass tube for the sand particles to settle to the bottom of the tube and the quantity was then read and recorded as the volume percent of sand content in the drilling mud (apugo-nwosu et al., 2011). 3. results and discussion the results obtained from the experimental analysis of mud densities of the drilling muds prepared with the local nigeria clay and imported foreign clay, and their sand content, are presented in a graphical form in figures 1 to 4. figure 1: shwing the comparison of the percentage volume of sand in local clay-mud and foreign clay-mud. the figure 2 shows the percentage volume of sand of both locally prepared drilling mud and its foreign bentonite. the experimental results of both local and foreign percentage sand volume are 0.1%, 0.1, 0.2%, 0.2% and 1.0%, 1.5%, 1.5%, and 2.0%. the low percentage sand volume recorded 0.00 0.50 1.00 1.50 2.00 2.50 % s an d v o lu m e clay sample local clay foreign clay file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:fotitigbe@yahoo.com otitigbe: potential of jesse clay as drilling mud. azojete, 18(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 249 in local-clay drilling mud, was due to the large void between the inter-particles of clay which causes weakness in bonding, and low aggregation of particles. thus, lead to poor interactions with water molecules, and eventually becomes less viscous. as a result of this, cannot suspend sand particles in the drilling mud as the foreign to avert borehole sand problems. this therefore cannot meet the api specification of 1% to 2% recommendation of sand volume in drilling mud (nmegbu, 2014) (nmegbu, 2014). however, if the local-clay drilling mud is beneficiated, could meet the percentage of sand in the foreign bentonite and the recommended api percentage of sand volume in drilling mud. in conclusion, large sand-size particles in the drilling mud causes problems like abrasion on drilling equipment such as hose, mud pump, drilling string and down hole equipment (apugo-nwosu et al., 2011). the low percentage volume of sand recorded in the local drilling mud is because of the large void between inter-particles of clay which caused weak bonding and low aggregation of clay particles leading to poor interaction with water molecules and eventual lack of viscosity. viscosity in drilling fluid is responsible for holding back sand particles in the drilling mud and then causes it to become viscous. thus, the local clay with a very low viscosity; cannot retain a large quantity of sand as with the foreign mud, and therefore cannot meet the api standard specification of 1 % to 2 % of volume percentage in drilling mud (nmegbu, 2014). to determine the density of drilling mud (local and foreign), the baroid mud balance was used. the experiment begins by ensuring the apparatus was dried, clean, and dust-free, then the mud cup was filled to the brim/mouth with the agitated mud sample and the side of the cup was tapped gently to allow mud to settle down in areas occupied by air bubbles. then the cover/lid was turned slowly until it was firmly tight on the cover of the mud cup. then with the thumb covering the hole/vent on the cover, mud spills were washed with water from the exterior of the mud cup and dried with a rag. the balance arm attached to the mud cup was then placed on the pivot with knife edges. this reading was taken at a balanced of the riding weight on the graduated arm of the mud balance and the densities were read in the four units as kg/m3, kpa/m and specific gravity (s.g) and recorded according to the mud type (local and foreign). finally, the mud is poured out from the mud balance cup into the sample can for future use, and the apparatus was then washed with water and dried with a rag before it was kept properly to avoid being damaged to prevent it from giving erroneous readings when is in use in the future. the variation of the foreign clay-mud density with clay concentration is presented in figure 2. http://www.azojete.com.ng/ mailto:fotitigbe@yahoo.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 250 figure 2: foregin clay mud density vs. clay concentration. from figure 3, there’s a progressive and consistent increase in the mud density values of foreign clay which ranging from 8.61 kg/m3, 8.66 kg/m3, 8.67 kg/m3 to 8.83 kg/m3, and with a progressively corresponding increment in clay the concentrations from 17.5 kg, 21.0 kg, 22.0 kg to 24.5 kg. this is due to the high interaction between particles in the drilling mud and water. the hydrophilic character of the foreign clay for water almost instantaneously increases the rate of water absorption and a consequential change in physical size, and eventually becomes thick, viscous, and plasticity leading to plastic viscosity and gel strength and consequently, resulting in high internal resistance buildup in the fluid and become weighty. the weight is referred to as hydrostatic mud weight or pressure. the hydrostatic mud pressure performs functions such as stabilization of formation pressure during the drilling, preventing inflow of fluids into the wellbore (apugo-nwuso et al., 2011) figure 3: local clay mud density vs. clay concentration 8.5 8.55 8.6 8.65 8.7 8.75 8.8 8.85 17.5 21 22 24.5 m u d d e n si ty , kg /m 3 clay concentration, g graph of mud density of foregin clay vs. clay concentration foregin clay 8.2 8.3 8.4 8.5 8.6 8.7 17.5 21 22 24.5 m u d d e n si ty , kg /m 3 clay concentration, g graph of mud density of local clay vs. clay concentration local cay file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:fotitigbe@yahoo.com otitigbe: potential of jesse clay as drilling mud. azojete, 18(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 251 in figure 4, there is a conspicuous display of lack of consistency in the incremental values of mud weight of 8.40 kg/m3, 8.50 kg/m3, 8.50 kg/m3, and 8.67kg/m3. as observed in the local nigeria clay, and also, against the corresponding increasing clay concentrations of 17.5 kg, 21.0 kg, 22.0 kg, and 24.5 kg. the constant values of 8.50 kg/m3l of mud weight with a corresponding progressive incremental value of clay concentrations of 21.0 kg and 22.0 kg, is a strong indication of the high phobic nature of the local clay-minerals with water molecules. this is due to the distance between particles and inter-particles in the local clay minerals that are far apart and weaken the bonding of clay particles and water molecules and become less reactive. the preceded sudden increase in mud weight value of 8.67 kg is as resulting from the thick accumulation of clay particles from the previously witnessed constant of mud densities but yet on incremental clay concentrations of 21.0 kg and 22.0 kg. the local clay-mud has a very viscosity due to its inability to absorbed water and swell to become viscous which is a required mud density of any drilling mud. these characteristics depict the local clay having low mud weight and in turn having a lower mud pressure and/or hydrostatic pressure and not being able to perform its primary duties as drilling mud for drilling of oil and gas well operations. however, there is a visible sight that further increases clay concentration, would enhance clay-minerals and reduce the distance between clay particles and increase bonding and reaction for an increased viscosity, and mud weight and hydrostatic pressure (mud pressure), and then, can be used as complimenting foreign clay-mud. fig 4: chart of local clay and foregin clay-mud density. from the figure 4, the result of the local clay-mud densities are 8.4 kg/m3, 8.5 kg/m3, 8.5 kg/m3 and 8.67 kg/m3 while that of the foreign clay-mud densities are 8.61 kg/m3, 8.66 kg/m3, 8.67 kg/m3 and 8.83 kg/m3. the graph shows clearly the superior property in the foreign clay-mud to the local clay-mud. the local clay-mud at the beginning of contacting water molecules, lack viscosity, but started developing viscosity with increasing clay concentrations. the viscosity was sustained at equilibrium for between a density value of 8.5 kg/m3 and of clay concentration of 21.0 kg and 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 1 2 3 4 m u d d e n si ty , k g/ m 3 clay samples local clay foregin clay http://www.azojete.com.ng/ mailto:fotitigbe@yahoo.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 252 8.5 kg/m3 of a clay concentration of 22.0 kg before the sharp increase in density of 24.5 kg/m3. however, like the local clay-mud density, a uniform thickness viscous mud was noticed in the foreign clay-mud, and was constant before before the sudden increased after an increment in clay concentration. in general, the local clay-mud can be used as a complimentary drilling mud with the conventional imported drilling cay-mud if these properties been analyzed are further enhanced. however, is also observed that further modification (beneficiation) of local clay, will bring closer the particles in the drilling mud to cause high interaction and increased plastic viscosity and gel strength and, will then lead to high viscosity and mud weight. in all, the local clay mud has low mud weight and a characteristic that if beneficiated, will enhance the quality and complement the conventional drilling mud, as it will aggregate to meet those of foreign clay and consequently, the api standard values of mud weight/density of between 8.65kg/m3 to 9.60 kg/m3, and there-after stop the huge loss to the importation of drilling mud-clay (nmegbu, 2014). 4. conclusion in general conclusion, the local clay-mud densities exhibit this same graphical trend as the foreign clay-mud densities with equilibrium constant values at the same sand concentration values of 21.0 kg and 22.0 kg. this is an indication that the local clay-mud, can either be used as an independent drilling mud or as complimentary the foreign imported drilling clay-mud in the drilling operations of an oil and gas wells if these the properties analyzed are further enhanced. the percentage sand volume observed in the local clay-mud is nearly almost equal the value of the percentage volume of sand content in the foreign clay-mud and as such, can be treated to conform to the minimum acceptable volume of sand content in drilling mud. references akpoturi, pe., idudje, eh. and okologume, cw. 2017. drilling fluid properties and treatment of some nigeria clays. international journal of advance academic research/science, technology and engineering, 2(9): 16-27. arinkoola, ao., salam, kk., salawudeen, to., abidemi, go., hamed, jo., jimoh, mo., olufauyo, oa. and aladeitan, ym. 2020. improvement of filtration properties of treated nigeria bentonite clay using locally sourced bio-materials. lautech journal of civil and environmental studies, 5: 114. alsabaa, a., hany, g., salaheldin, e. and abdulazeez, a. 2020. real time prediction of rheological properties of invert emulsion mud using additive neuro-fuzzy inference system. sensors mdpi, 20(1): 1-21. amoco production company, 2001. amco production drilling fluids manual. palmer publishers, los angeles, revision 6/9, 224: 5-26. ameloko, aa., ogologo, ce., daramola, oc. and babalola, ao. 2020. assessment of clay materials for suitability in drilling mud formulation from part of ondo state, south-west nigeria. journal of petroleum exploration and production, 10: 2815-2816. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:fotitigbe@yahoo.com otitigbe: potential of jesse clay as drilling mud. azojete, 18(2):243-254. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 253 apugo-nwuso, tu., mohaad-dabo, ia., ahmed, as., abubakar, ig., alkal, as. and ayilara, si. 2011. studies on the suitability of ubakala betonitic clay for oil well drilling mud formulation. british journal of applied science and technology, 1(4): 155-156. asme shale shaker committee, 2005.drilling fluids processing handbook. gulf professional publishing company. an imprint of elsevier, 30 corporate drive, suite 400, burlington, ma 01803, usa. linacre house, jordan hill, oxford ox2 8dp, uk, 15. bourgoyne, at jr., chenevert, me., millheim, kk. and young, fs jr. 1991.spe textbook series, society of petroleum engineers, richardson, tx. 58. wolfgang, df. 2016. drilling engineering. curtin university of technology, department of petroleum engineering, australian. 155. faruk, c. 2000. reservoir formation damage. gulf publishing company. an imprint of elsevier, book division. houston, texas, 5310-20: 648. igwilo, kc., uwaezuoke, n., ukaka cm., amaefule cv. 2021. evaluation of rheoogical and fluid loss properties of bentonite using periwinko and nucuna solannie. issn: journal home page: https://www.tandfonline.com/loi/oaen20. (8): 2. institute of petroleum engineering, heriot watt university 2009. drilling engineering. edinburgh, scotland, united kindom uk, 371. kaffayalullah, k., shaukat, ak., muhammad, us. and muhammad, a. 2021. improvement of locally available raw bentonite for use as drilling mud. open construction and building journal, (15): 1. rejesh, k., bhavani, y., hussain, a., junaid, t., nidhim, m. and shiva, gk.2017. determing sand content set in various compositions of drill mud. international refereed journal of engineering and science (irjes), 6(6): 13-16. mobeen, m., hafiz, ma., muhammad, sk. and syed, msh. mohamed, m. and shirish p. 2020.evaluation of clay hydration and swelling inhibition using quaternary ammonium dicatonic surfactant with phenl linker. mdpi, molecules, 4333, (25): 2, 1-20. mosese, oe., christopher, o. and joy, ci. 2021. a synoptic review of mineralogical and chemical characteristic of clay in the southern part of nigeria. research in ecology, 3(2):33. nmegbu, cgj.2014. laboratory investigation of rivers state clay samples for drilling mud preparation. international journal of engineering research and application, 46(4): 1. omole, o., james, o., adeleye, o., malomo, s. and oyedeji, oa. 2013. investigation into the rheological and filtration properties of drilling mud formulated with clay from north nigeria. journal of petroleum and gas engineering, 4(1): 1. standard procedure manual,2003. drilling fluid, eni agip oil company, italy, 2. http://www.azojete.com.ng/ mailto:fotitigbe@yahoo.com https://www.tandfonline.com/loi/oaen20 arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):243-254. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fotitigbe@yahoo.com 254 zhang, jr., meng, dx., christidis, ge. and chun, hz. 2020. clay minerals in drilling fluids: functions and challenges. cambridge university press, (10): 1 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:fotitigbe@yahoo.com arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):15-22 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 15 original research article an investigation of soil bearing capacity for building and structural foundation design: a case study of polo area, maiduguri, nigeria i.s. muhammad*, a.m alkali and k. bulu department of civil and water resources engineering, university of maiduguri, maiduguri, borno state. nigeria *corresponding author’s email address: ibrahimcivil73@gmail.com 1.0 introduction the determination of soils shear strength parameters is very crucial to geotechnical and structural engineers as it forms the essential data required for estimating foundation bearing capacity, factor of safety for slope stability and pressures on earth retaining structures for effective and economical design. the stability and integrity of engineering structures erected on any soil depends on the shearing resistance offered by the foundation soil (alkali et al., 2018). the shear strength of soils is generally depicted by the mohr-coulomb theory which says that the shear strength of soils varies linearly with the applied stress through two components known as the cohesion intercept and angle of shearing resistance (garg, 2013). the tangent to the mohr–coulomb failure envelopes is represented by its slope and intercept. the slope expressed in degrees is the angle of shearing resistance and the intercept is the cohesion (pravin and karim 2016). the angle of shearing resistance represents the interlocking between the soil particles whereas cohesion is mainly due to the intermolecular bond between the adsorbed water surrounding each grain, especially in fine grained soils (odeyemi et al., 2012). the attempt to investigate the bearing capacity of soils in this area through shear strength values came from the fact that most private, government, contractors and compromising engineers are reluctant toward soil investigation for structural design. on the contrary, they based their designs on arbitrary safe article information abstract the foundation of any structure is the back born of its stability against all kinds of deformation and this depends on the geotechnical behavior of the supporting soil. clay soils usually posed serious threats to buildings due to shrink-swell behavior, settlements and low strength which is associated with their minerals. in this research, the safe bearing capacity of polo soil have been investigated using direct shear laboratory analysis on twenty representative soil samples across virgin area where future development is approaching. most of the soils were classified as lean clay with sand (cl) according to unified soil classification system (uscs) although some were otherwise. the average natural moisture content of the soils at 1m depth is 8.38% with liquid limit and plasticity index of 30.2% and 15.7% respectively while that of 1.5m were 9.14%, 29.4% and 14.6% respectively. results also revealed an average friction angle and cohesion of 21º and 18 kn/m2 at 1m and 22o and 19 kn/m2 at 1.5m depths respectively. safe bearing capacity values ranges from 44.95 to 411.11 kn/m2 and 75.27 to 397.31 kn/m2 for 1m and 1.5m respectively using foundation widths of 0.5m, 1m and 2m. foundation design carried out using the different safe bearing capacities and load combinations revealed that the pad footings analyzed with 1500 kn indicated that the minimum footing size that could be used is 1800mm×1800mm using 400kn/m2 safe bearing capacity. it also revealed that for a 100kn/m2 safe bearing capacity, the footing size is as much as 3500mm×3500mm which is very high and raft foundations were recommended for such situations. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 march, 2021 revised 28 may, 2021 accepted 30 may, 2021 keywords: shearing strength bearing capacity foundation design http://www.azojete.com.ng/ mailto:ibrahimcivil73@gmail.com mailto:ibrahimcivil73@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):15-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 22 bearing value which may sometimes lead to unsatisfactory or uneconomical design causing serious infrastructural damage. lack of data for proper foundation design has led to continuous distress in buildings erected on polo soils due its clayey nature. presently, there is no published material covering this subject in the study area. this study, therefore, aimed toward investigating the type and bearing capacity of polo soil, maiduguri, for structural/foundation design purposes. with the results from this work, an engineer can easily compare and locate the category of soil type and possible safe bearing value based on knowledge and experience. however, this will be after obtaining preliminary laboratory results of soil index properties such as soil particles size distribution, moisture contents, atterberg limits, and bulk and dry densities of a given sample which are by far cheaper and non-cumbersome compared to shear strength parameters which require equipment such as direct shear or triaxial machine. otuaga, 2015, investigated the shear strength parameters of soils across zones of owo local government area of ondo state, nigeria, using triaxial and direct shear box methods. the study recommends a safe bearing capacity of 139.01 kn/m2 be adopted for foundation design. similar investigations were carried out by egbe et al., 2011, oluwapelumi 2013 and surendra and gurcharan, 2014. these investigations address soils from calabar south, nigeria; lateritic soil in akure, nigeria and soils from sirsa, india, respectively. researchers have developed model equations using soil index properties and recommended its usage following the soil type. this work will, however, concentrate on soils from polo area of maiduguri by computing their safe bearing capacities. this is due to increasing number of defective houses in the area resulting from swelling and shrinking behavior of the clay soil which is predominant. this will be sound and more useful in computing new bearing capacities of samples collected across the area since they lie within same formation rather than model equations which do not always give good correlation. using similarities in index properties and classification of soils in the location, one can use the information provided in this study to compute new bearing capacities based on knowledge and experience. 2. materials and methods 2.1 materials the tools used for collecting the disturbed samples include sterilized digger and shovel, measuring tape, digital weighing balance, mobile phone with google map application and polythene bags. 2.1.1 soil samples the soil samples used in this study were collected from polo area of maiduguri, borno state, nigeria. soil samples were dug at a depth of 1m and 1.5m respectively. virgin area where development is rapidly approaching was used to collect the samples. the area is located at latitude 11046’ 41’’ n and longitude 130 08’ 29’’ e. the samples are collected at the interval of 200m from the last cluster of buildings in the area to the west where future development is expected. a total of twenty (20) samples were obtained from ten (10) different pits. soil samples were then taken into polythene bags to avoid loss of moisture and further subjected to laboratory analysis. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ibrahimcivil73@gmail.com muhammad et al: an investigation of soil bearing capacity for building and structural foundation design: a case study of polo area, maiduguri, nigeria. azojete, 18(1):15-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 21 figure 1. google map of the study area 2.2 methods 2.2.1 index properties all tests were carried out on the twenty (20) soil samples in accordance with specifications outlined in british standard (bs) 1377 (1990). bulk and dry densities were determined using the following relations: bulk density (ρ) = 𝑀2− 𝑀1 v (1) where: m1 is the mass of mold and base plate, m2 is the mass of mold, baseplate and compacted soil, v is the volume of the mold (cm3) dry density (ρd) = 100𝜌 100+𝑤 (2) where: w is the moisture content of the soil (%) 2.2.2 direct shear test direct shear test was carried out using shear box with the specimens (60mm x 60mm). specimen with plain grid plate at the bottom of the specimen and plain grid plate at the top of the specimen was fitted into position in the shear box housing and assembly placed on the load frame. the serrations of the grid plates were kept at right angle to the direction of shear. the loading pad was kept on the top grid plate. the required normal stress was applied, and the rate of longitudinal displacement/shear stress application adjusted so that no drainage can occur in the sample during the test (1.25 mm/min). the upper part of the shear box was raised such that a gap of about 1mm was left between the two parts of the box. the test was conducted by applying horizontal shear load to failure or to 20 percent longitudinal displacement whichever occurs first. the test was repeated on identical specimens. http://www.azojete.com.ng/ mailto:ibrahimcivil73@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):15-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 22 2.2.3 computation of soil bearing capacity the bearing capacity of the various samples were computed using the formula proposed by terzaghi. qult = c .n c +γd f n q + 0 .5bγn γ (3) where: γ = unit weight of foundation soil in kn/m³, d f = depth of the foundation (m), c,ϕ = strength parameters of the soil below foundation level in kn/m² and degrees respectively, b = width of foundation in (m), nc nγ nq = bearing capacity coefficients dependent on the angle of internal friction. safe bearing capacity of the soils, qsafe, was determined using: qsafe = qult/ fs (4) where: fs is the factor of safety 3. results and discussion geotechnical properties like particles size distribution, bulk and dry densities, atterberg limits and natural moisture content of soils collected in polo were determined. shear strength parameters of the soils mainly friction angle and cohesion were also assessed. most of the soils were classified as clay. tables 1 and 2 below represents the data obtained for different soils from laboratory analysis. 3.1 index properties and classification the index properties of polo soils at 1m and 1.5m depths are presented in tables1 and 2. the average natural moisture content of the soils at 1m depth is 8.38% with liquid limit and plasticity index of 30.2% and 15.7% respectively. all the soils at this depth are classified according to unified soil classification system (uscs) as lean clays with sand (cl) with the exception of samples sd, sf and sg which falls within the class of sandy clay (sc), sandy clay (sc) and silty sand (sm) respectively. the index properties at 1.5m revealed that samples sa and sg were silty clay (ml) and sc while the remaining belongs to cl as well. the average natural moisture content, liquid limit and plasticity index are 9.14%, 29.4% and 14.6% respectively. the low atterberg limits values also indicate low compressive strength which is as reported elsewhere (ezenwaka et al., 2014). table 1: index properties of polo soils at 1m depth parameters/sample sa sb sc sd se sf sg sh si sj natural moisture content (%) 23.0 13.2 15.0 3.9 3.5 2.9 2.9 9.9 6.9 2.6 liquid limit (%) 34 36 34 22 33 29 29 37 26 22 plastic limit (%) 18 20 15 11 10 13 24 15 09 10 plasticity index (%) 16 16 19 11 23 16 05 22 17 12 % fine 77 75 68 67.7 76 48 35 79 56 68 % coarse 23 25 32 32.3 24 52 65 21 44 32 uscs cl cl cl sc cl sc sm cl cl cl bulk unit weight (kn/m3) 11.7 16.9 17.8 15.4 15.7 15.4 15.5 14.6 14.5 15.8 dry unit weight (kn/m3) 15.6 14.9 15.4 14.9 14.6 14.9 14.9 13.3 13.6 14.6 uscs (astm, 1992) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ibrahimcivil73@gmail.com muhammad et al: an investigation of soil bearing capacity for building and structural foundation design: a case study of polo area, maiduguri, nigeria. azojete, 18(1):15-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 21 table 2: index properties of polo soils at 1.5m depth parameter/sample sa sb sc sd se sf sg sh si sj natural moisture content (%) 17.3 13.9 17.3 5.1 5.9 8.9 3.1 9.1 3.3 7.5 liquid limit (%) 25.0 38.0 28.0 26.0 48.0 27.0 24.0 24.0 21.0 33.0 plastic limit (%) 21 16.0 13.0 10.0 18.0 14.0 8.0 15.0 10.0 23.0 plasticity index (%) 4.0 22.0 15.0 16.0 30.0 13.0 16.0 9.0 11.0 10.0 % fine 74.0 80.0 78.0 73.5 59.0 63.0 47.0 60.0 60.0 71.0 % coarse 26.0 20.0 22.0 26.5 41.0 37.0 53.0 40.0 40.0 29.0 uscs ml cl cl cl cl cl sc cl cl cl bulk unit weight (kn/m3) 17.5 15.6 18.5 16.0 15.7 15.3 15.4 14.6 14.6 15.5 dry unit weight (kn/m3) 14.9 13.7 15.8 14.5 14.42 13.9 14.8 13.4 13.5 15.0 uscs (astm, 1992) 3.2 computation of soil bearing capacities the bearing capacities (tables 3 and 4) were computed using foundation widths of 0.5m, 1.0m and 2.0m for all the soils. the average friction angle and cohesion of soils at 1m depth were 21o and 18 kn/m2 while that of 1.5m were 22o and 19 kn/m2 respectively. the safe bearing capacities at 1m depth ranges between 44.95 – 90.32 kn/m2 for samples sa to sc and this is due to low friction angles of 6o,13o and 5o respectively. the value increases between 135.18 – 411.11 kn/m2 for samples sd – sj for the various widths investigated as a result of increase in angle of shearing resistance value. the same values at 1.5m depth revealed an increasing trend with the exception of sample sf which has a value little below that of 1m depth following the decline in friction angle value observed. this occurred as a result of additional increase in cohesion value of the soil when compared to that of sf at 1m depth. table 3: bearing capacities for shallow foundations at 1m depth parameter/sample sa sb sc sd se sf sg sh si sj depth (m) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 width (m) 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 thunit weight (kn/m3) 11.7 16.9 17.8 15.4 15.7 15.4 15.5 14.6 14.5 15.8 angle of friction (o) 6.0 13 5.0 29 24 29 33 18 25 25 cohesion (kn/m2) 18 20 16 14 22 17 9.0 24 18 22 ultimate bearing capacity (kn/m2) 145.87 146.28 147.09 258.80 262.85 270.95 134.84 135.25 136.07 715.25 775.95 897.36 612.32 639.95 695.20 800.22 860.93 982.34 883.69 1000.23 1233.32 405.53 414.75 433.18 565.87 595.91 655.96 666.75 699.46 764.88 safe bearing capacity (kn/m2) 48.62 48.76 49.03 86.27 87.62 90.32 44.95 45.08 45.36 238.41 258.65 299.12 204.11 213.32 231.73 266.74 286.98 327.45 294.56 333.41 411.11 135.18 138.25 144.38 188.62 198.64 218.65 222.25 233.15 254.96 http://www.azojete.com.ng/ mailto:ibrahimcivil73@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):15-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 22 table 4: bearing capacities for shallow foundations at 1.5m depth parameter/sample sa sb sc sd se sf sg sh si sj depth (m) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 width (m) 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 unit weight (kn/m3) 17.5 15.6 18.5 16.0 15.7 15.3 15.4 14.6 14.6 15.5 angle of friction (o) 29.0 12.0 9.0 29.0 27.0 21.0 29.0 21.0 22.0 19.0 cohesion (kn/m2) 4.0 22.0 20.0 19.0 19 20.0 17.0 25.0 24.0 23.0 ultimate bearing capacity (kn/m2) 620.87 689.70 827.35 280.69 283.70 289.71 225.83 227.57 230.89 1002.98 1066.00 1192.05 823.27 868.15 957.92 501.85 518.22 550.95 928.93 989.59 1110.93 573.82 589.44 620.68 603.45 621.93 658.88 473.47 485.22 508.73 safe bearing capacity (kn/m2) 206.96 229.90 275.78 93.56 94.56 96.57 75.27 75.86 76.96 334.32 355.33 397.35 274.42 289.38 319.31 200.74 207.29 220.38 309.64 329.86 370.31 191.27 196.48 206.89 201.15 207.31 219.63 157.82 161.74 169.58 3.3 foundation design the foundation design based on different safe bearings capacities and column load combinations has been analyzed using prota structure software and the results is presented in table 5. the analysis was carried out using average bearing capacities of 100, 150, 200, 250, 300, 350 and 400 kn/m2 respectively. for each safe bearing capacity, a column loads of 200, 500 and 1500 kn were used to analyzed its punching shear capacity and settlement using different pad footing sizes. the results show that for all the safe bearing capacities, footings subjected to 200 and 500 kn column loads can be constructed as singly reinforced section with sizes between 700 mm × 700 mm to 2000 mm × 2000 mm depending on the safe bearing capacity used. this is due to the low load intensity acting on the footing as well as the fair average safe bearing capacity of the soils. furthermore, the pad footings analyzed with 1500 kn indicated that the minimum footing size that could be used is 1800 mm × 1800 mm using 400 kn/m2 safe bearing capacity. it was also observed that for a 100 kn/m2 safe bearing capacity, the footing size is as much as 3500 mm × 3500 mm, which is very high. as a result, raft foundations were recommended for such situations in order to accommodate the high load intensity of the structure under single footing (raft) instead of larger footings covering almost the entire foundation area. table 5: foundation analysis and design using different safe bearing capacities, column loads and footing sizes foundation type column load (kn) safe bearing capacity (kn/m2) foundation size (m) punching shear capacity (n/mm2) settlement (mm) rebar (mm2) factor of safety remark/comment pss uss pad footing 200 500 1500 100 1300×1300 2000×2000 3500×3500 0.11 0.29 0.3 0.36 0.36 0.36 19 22 34 380.64 1035.90 3355.09 2 2 2 singly reinforced section singly reinforced section raft foundation recommended pad footing 200 500 1500 150 1000×1000 1700×1700 2900×2900 0.06 0.23 0.31 0.36 0.36 0.36 16 24 32 319.44 824.18 2927.91 2 2 2 singly reinforced section singly reinforced section raft foundation recommended file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ibrahimcivil73@gmail.com muhammad et al: an investigation of soil bearing capacity for building and structural foundation design: a case study of polo area, maiduguri, nigeria. azojete, 18(1):15-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 21 pad footing 200 500 1500 200 900×900 1500×1500 2400×2400 0.03 0.33 0.33 0.36 0.36 0.36 24 23 32 261.36 838.30 2550.24 2 2 2 singly reinforced section singly reinforced section raft foundation recommended pad footing 200 500 1500 250 800×800 1300×1300 2400×2400 0.09 0.25 0.28 0.36 0.36 0.36 24 25 36 232.40 679.34 2273.98 2 2 2 singly reinforced section singly reinforced section raft foundation recommended pad footing 200 500 1500 300 800×800 1200×1200 2000×2000 0.09 0.20 0.35 0.36 0.36 0.36 23 25 38 232.30 601.70 2279.20 2 2 2 singly reinforced section singly reinforced section raft foundation recommended pad footing 200 500 1500 350 750×750 1100×1100 1900×1900 0.14 0.13 0.32 0.36 0.36 0.36 24 23 35 217.80 525.40 525.40 2 2 2 singly reinforced section singly reinforced section raft foundation recommended pad footing 200 500 1500 400 700×700 1000×1000 1800×1800 0.19 0.05 0.27 0.36 0.36 0.36 22 24 33 203.30 450.40 1978.0 2 2 2 singly reinforced section singly reinforced section raft foundation recommended 3.4 conclusion and recommendation the index properties and shearing strength parameters of polo soil for bearing capacity values was investigated. the results indicated that most of the soils are classified as lean clay with sand (cl) according to uscs although there exist sandy clay (sc), silty clay (ml) and silty sand (sm). the average natural moisture contents of the soils at 1m and 1.5m were 8.38% and 9.14% respectively. the average liquid limit and plasticity index values ranges from 30.2% to 15.75% and 29.4% to 14.6% respectively which is an indicative of low compressive strength. the minimum and maximum safe bearing capacities observed for 1m and 1.5m depths were 44.95 to 411.11 kn/m2 and 75.27 to 397.31 kn/m2 respectively. sample sa, sd and sf were also observed to have possessed heterogeneity between the depths investigated. due to different safe bearing capacities and load combinations, the foundation design conducted revealed that certain foundations will be singly reinforced section while other will call for raft. it is, therefore, recommended that a minimum of index properties test of soil in the study area be carried out to compare e the possible corresponding shear strength parameters based on the information provided above before foundation design in the study area. this could be achieved by comparing parameters such as % fines and coarse, plasticity index, bulk density and soil type obtained in the laboratory with the ones provided here, this will however require knowledge and experience. it is also our conviction that this will mitigate blind assumption of bearing values during design as some soils misbehave within short spans, a typical example being some samples with safe bearing capacity less than 50 kn/m2. references alkali, am., muhammad, is. and bulu, k. 2018. structural integrity assessment of an uncompleted reinforced concrete structure in maiduguri, nigeria. arid zone journal of engineering, technology and environment, 14(3): 404-410. http://www.azojete.com.ng/ mailto:ibrahimcivil73@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):15-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimcivil73@gmail.com 22 astm 1992. annual book of standards. philadelphia: american society for testing and materials, vol. 4, 1-8. british standard institute. 1990.methods of testing soils for civil engineering purposes. bs 1377, london, 1-30. ezenwaka, kc., ugboaja, a., ahaneku, cv. and ede, ta. 2014. geotechnical investigation for design and construction of civil infrastructures in port harcourt city of rivers state, southern nigeria. the international journal of engineering and science, 3(8): 74-82. garg, sk. 2013. soil mechanics and foundation engineering. ninth revised edition, ew delhi khanna publishers., 212-253. pravin, sd. and karim, cm. 2016. new approach for determination of bearing capacity of soil using direct shear test. international journal of innovation in engineering and technology, 7(4): 426-430. odeyemi, so., kaigama, wb., adeyemi, ao. and amototo, io. 2012. determination of the ultimate bearing capacity of soils in offa community. epistemics in science, engineering and technology, 2(4): 168-174. otuaga, pm. 2015. determination of bearing capacity for building and structural design in owo local government area, ondo state, nigeria. european journal of engineering and technology, 3(4): 1-10. egbe, jg., ewa, de., ubi, se., ikwa, gb. and tumenayo, oo. 2017. application of multilinear regression analysis in modeling of soil properties for geotechnical civil engineering works in calabar south. nigerian journal of technology (nijotech), 36(4): 1059 – 1065. oluwapelumi, oo. 2013. predictive shear strength models for tropical lateritic soils. hindawi publishing corporation journal of engineering, 2013, article id 595626, http://dx.doi.org/10.1155/2013/595626, 1-8. surendra, r. and gurcharan d. 2014. statistical models for the prediction of shear strength parameters at sirs., india international journal of civil and structural engineering, 4(4): 483-498 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ibrahimcivil73@gmail.com http://dx.doi.org/10.1155/2013/595626 arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):453-468 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 453 original research article an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement a. a. shuaibu*, a. i. mohammed, u. hassan, b. h. s. amartey, s. a. wada, a. mohammed and a. m. rimi department of civil engineering, faculty of engineering, ahmadu bello university, zaria, nigeria *corresponding author’s email address: abdulshub4u@gmail.com 1.0 introduction bituminous concrete mixtures, also known as; (i) hot mix asphalt (hma), (ii) warm mix asphalt (wma), (iii) cold mix asphalt (cma), (iv) plant mix, and (v) asphalt concrete (speight, 2016). it is mainly composed of mineral aggregates (fine, coarse and filler), asphalt binder, and additive, and has been widely applied in pavement construction (zhang et al., 2020). a typical bitumen concrete mixture contains 90 to 95% (w/w) of the total mixture as mineral aggregates and 5 to 10% (w/w) as binder (bitumen) (speight, 2016). filler in bituminous concrete mixes is defined as material with particle size less than 0.075 mm, which may originate from fines in the aggregate or added in the form of cement, lime and ground rock. portland cement or hydrated lime is often added to natural filler (1 to 2 per cent by mass of total mix) to improve adhesion of bitumen and stiffening of bitumen-fine matrix (orn 19, 2003). ‘‘the filler is an important constituent of bituminous concrete as the type and amount play a significant role in ensuring the quality and durability of the bituminous concrete in service’’ (sutradhar et al., 2015). although several materials have been used as filler, such as cement, lime dust, stone dust, granite powder, however, their production processes have detrimental effects on the environment and the use is expensive. also due to the high cost, inconsistencies, scarcity and depletion of virgin construction materials as well as need to enhance the performance of bituminous concrete mixtures in service, such as ; resistance to permanent deformation, cracking, wear, stripping, ageing, there is dire need to seek alternative materials for sustainable construction and improved service life of the pavements. article information abstract this study investigates the performance of silica sand as a partial replacement for cement filler in bituminous concrete mixtures. the physical properties of bituminous concrete mixture constituent materials were tested in accordance with american society for testing and materials astm and british standard bs specifications and were found to be satisfactory. marshall stability method of bituminous concrete mix design was adopted to determine the optimum binder content at no silica sand replacement (control) within the bitumen content range prescribed by nigerian general specifications for roads and bridges and asphalt institute for bituminous courses in flexible pavements and an optimum binder content (obc) of 6% was obtained. the marshall stability-flow and voiddensity analysis of bituminous concrete mixtures prepared with 6% obc at varying percentages replacement (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, and 45%) of silica sand was conducted to obtain the mixture with the best performance in terms of strength and waste utilization. the results obtained from the experiment shows that the replacement of cement filler with silica sand up to 45% meets the standard specifications of nigerian general specifications for road and bridges, hence, silica sand up to 45% could be partially adapted as cement filler replacement in bituminous concrete mixes. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 may, 2021 revised 3 august, 2021 accepted 10 august, 2021 keywords: silica sand bituminous concrete mixtures marshall test optimum bitumen content and filler arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 454 extensive research have been conducted on the incorporation of agricultural waste such as; rice husk ash, groundnut husk ash, guinea corn stalk ash, bagasse ash, mesocarp fibre ash (boon hoe et al., 2014; shuaibu et al., 2020a; shuaibu et al., 2020b; murana and sani, 2015; shuaibu et al., 2020c), industrial wastes such as fly ash, waste glass (mistry and roy, 2016; simone et al., 2017) as well as a blend of agricultural-industrial waste such as rice husk ash and fly ash, rice husk ash and slag (mistry et al., 2018; akter and hossain, 2017) in bituminous mixture. however, currently, attention has significantly shifted to the use of natural materials such as kaolin, metakaolin, waste foundry sand, foundry sand, silica sand etc; because of their abundance, low cost and pozzolanic activities. ‘‘silica sand consists of small grains or particles of minerals and rock fragments with quartz (composed of silica dioxide sio2) as the dominant mineral composition’’ (duvuna and ayuba, 2015). thus, it is rich in silica necessary for hardness in bituminous mixes. ‘‘silica sand deposits are most commonly surface-mined in open pit operations or obtained as riverine surface deposit due to erosion. also, dredging and underground mining is also employed to obtain the sand’’ (langer, 2003). processing silica sand extracts to reduce impurities and sizing it to optimum particle size distribution is necessary for a wide range of applications (langer, 2003). silica sand with an adequate quality level may be used for glass production, casting moulds in foundries, ingredients of ceramics batches, proppants in shale hydrocarbons extraction, fillers and extenders in polymers, paints and rubber, for water filtration, and many other uses (burkowicz et al., 2020). our country nigeria, is blessed with abundant silica sand deposits (table 1) as cited by chukwu (2019) in rmrdc, (2009) report. table 1: silica sand deposit locations in nigeria s/no state location 1 abia ukwa, aba, isialangwa, azumili 2 akwa ibom ikwo, ukem, ibeno 3 anambra onitsha, coastal area of ulasi river 4 bayelsa sagbama, ijaw 5 benue buruku, gboko, guma, kast 6 bornu dikwa, gwoza, jere 7 cross river ikom, mfamosing 8 delta ughelli, aniocha, burutu, ethiope 9 enugu enugu, ekulu, igbo eze, udi 10 gombe yamaltu-deba, dukku 11 imo ihiagwa, obinze, isu, njaba 12 jigawa kangama, kasaure 13 kaduna kaduna 14 kano dambatta, makoda 15 kastina zango 16 lagos apapa, badagry, epe, lekki 17 nasarawa lafia, doma, nasarawa 18 niger gbako, gurara, mokwa, bida 19 ondo ogun waterside, obafemi 20 ogun igbokada, akata, agbala 21 rivers etche, obio, okirika, oyigbo 22 sokoto sabo, biriniwamako 23 taraba jalilingo, bali, takum 24 yobe ngeji, fita, damaturu, nguru, tarmuwa 25 zamfara jamuri, gumi s source: rmrdc, (2009) shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 455 ‘‘many of the nigerian silica sands are associated with the coastal plain of sedimentary areas of the southern parts of the country. however, few deposits of the sand occur in the northern regions of the country as seen in table 1 above (chukwu, 2019)’’. despite the huge deposits of silica sand in almost all nigerian states, there are currently very scarce studies that have incorporated silica sand into bituminous concrete production in nigeria. employing silica sand as an admixture in bituminous concrete production will improve pavement performance and lead to the development of locally available materials for sustainable concrete production. this in turn will reduce cost and burden placed upon conventional construction materials.the aim of the current study is to experimentally evaluate the performance of bituminous concrete mixtures with the incorporation of silica sand as filler in wearing surfaces. the above aim was achieved through the following objectives: i. determination of physical properties of mineral aggregates (fine, coarse), bitumen, and cement to ascertain their suitability for use in the bituminous concrete production; ii. determination of the chemical properties (oxide composition) of silica sand using x-ray fluorescence and classify it based on astm c618, (2003) classification of pozzolanas; iii. determination of obc necessary for the production of bituminous concrete and find out the effect of adding the different percentage of silica sand on the stability-flow as well as void-density properties of bituminous concrete to be used in highway wearing course using the obc. 2. materials and methods 2.1 materials materials used in the mix design of bituminous concrete include: i. filler materials (silica sand and portland cement), ii. aggregates (fine and coarse) and iii. binder (bitumen). the aggregates (fine and coarse) were locally sourced from nagarta quarry, along sokoto road, zaria, kaduna state. the cement which is dangote 3x brand was obtained from open market, zaria, kaduna state. the bitumen used was obtained from gidan coal tar adjacent to narict, basawa, zaria, kaduna state. silica sand was obtained from babban mutum in daura, katsina state. 2.2 methods physical properties tests were conducted on bitumen, aggregates, cement, bitumen, silica sand as well as marshall test on bituminous concrete mixes in the department of civil engineering, ahmadu bello university, zaria, except oxide composition of silica sand that was conducted in chemistry department, ahmadu bello university, zaria. the test carried out on the constituent materials of bituminous mixture and code specifications are as follows: 2.2.1 test on coarse aggregates test conducted on coarse aggregates are; aggregate impact value/hardness test (bs 812 part 111, 1990), aggregate crushing value (bs 812 part 112, 1990), aggregate specific gravity (astm, c128, 2001), size and gradation analysis (bs 812-103.2, 1985) and water absorption (bs 812 2, 1995). 2.2.2 test on fine aggregates the tests conducted on the fine aggregates are; specific gravity (astm c127, 2005), sieve analysis (bs 812-103.2, 1985), and water absorption (bs 812 3, 1995). arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 456 2.2.3 test on mineral aggregate (cement and silica sand) test on cement are; initial and final setting time (bs en 196 part 3, 1995), soundness test (bs en 196 part 3, 1995), and specific gravity (astm c188, 2017). test on silica sand are; bulk relative density (astm d854, 2014), and specific density (astm d854, 2014). another test carried out on the silica sand is x-ray fluorescence (xrf) to determine the oxide composition. oxide composition analysis was carried out using in an energy dispersive spectrometer designed for detection and measurement of elements in a sample according to bs en 196-2 (1995) in the department of chemistry, ahmadu bello university, zaria. furthermore, the classification of the silica sand into the pozzolana group was done based on astm c618, (2005) specifications. 2.2.4 test on bitumen tests on bitumen are: penetration test (astm d5, 2005), solubility test (astm d2042, 2015), ductility test (astm d113, 2007), flash and fire point test (astm d92, 2005), specific gravity test (astm d70, 2003) and softening point (astm d36, 2006). 2.3 optimum binder content (obc) to determine the optimum binder content, the relationships between binder content and the properties of bituminous concrete mixtures such as stability, flow, bulk density, voids filled with bitumen (vfb), void in mineral aggregate (vma), and void in the mix (vim) at no silica sand replacement (control) were established. three (3) specimens each were prepared for five bitumen content (4.5, 5.0, 5.5, 6.0, and 6.5 %) in accordance with asphalt institute (1994) and fmwh, (1997) specifications. the optimum binder content is calculated as the average binder content for maximum density, maximum stability, and specified percentage air voids in the total mix. 2.4 marshall test specimen preparation asphalt institute (1994) and fmwh, (1997) recommendations were used to prepare standard specimens with 1200g weight, 101.5 mm diameter, and 63.5 mm height compacted with 75 hammer blows on each side to simulate heavy traffic situation. to obtain the optimum blend of cement-silica sand in bituminous mixtures, various percentage replacement by weight (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, and 45%) of cement with silica sand was used to produced bituminous mixes. the specimens were tested for bulk specific gravity in accordance with astm d1559 (2000). furthermore, the specimens were kept immersed in water in a thermostatically controlled water bath at 60°c for 30 to 40 minutes before been transferred within 30 seconds to the marshall test head and tested for marshall stability and flow in accordance with astm d1559 (2000). also, void analysis such as; compacted density of the mix (cdm), void in mineral aggregate (vma), void in mix (vim) and void filled with bitumen (vfb) was carried out. theoretical maximum specific gravity of the mix (gmm) were determined using astm d 2041-95 and bulk specific gravity or compacted density of the mix (cdm) using astm d1188-96. astm d3203-94 was used to estimate void in the mix (vim). astm d1559 (2004) was used to determine the stability and flow of specimens. marshall stability-flow and voiddensity analysis were performed and checked against the limits specified by the nigerian general specifications for roads and bridges (fmwh, 1997) for use as wearing course of the heavily-trafficked road. shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 457 3. results and discussion 3.1 result of test on aggregates table 2 shows the results of the physical properties test on the aggregates (coarse and fine aggregates), standard specifications used for each test, and results obtained. table 2: aggregates physical properties property code specifications results obtained code limits remarks aggregate crushing value (%) bs 812 part112 (1990) 20 max. 25 ok aggregate impact value (%) bs 812 part111 (1990) 22.2 max. 25 ok specific gravity (coarse) astm c127 (2005) 2.61 2.55-2.75 ok specific gravity (fine) astm c128 (2001) 2.63 2.55-2.75 ok water absorption (coarse) (%) bs 812 part 2, (1990) 0.45 < 2 ok water absorption (fine) (%) bs 812 part 3, (1990) 8.62 < 15 ok from table 2, all the results obtained from the tests conducted on aggregates fall within the specified limits provided in the specification of codes, therefore, the aggregate meets the requirement for use for the design of bituminous concrete mixtures. 3.2 results of particle size distribution for aggregates aggregate grading is a very crucial factor in ascertaining the bond, interlocking packing and packing density the nature of the aggregate skeleton imparts greatly on the strength and resistance of the finished product in service (otuoze and shuaibu, 2017). figures 1 and 2 shows the results of the gradation of the aggregates (fine and coarse) used in this study. materials retained on sieve 2.36 mm are referred to as coarse aggregates while those that pass sieve 2.36 mm but retained in sieve 0.075 mm are referred to as fine aggregates (shuaibu et al., 2020a). the grading of each of these constituent materials is very cardinal in ensuring a mix of desired engineering properties is obtained. figure 1: particle size distribution curve for coarse aggregate 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 pe rc en t p as si n g (% ) sieve size (mm) arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 458 figure 2: particle size distribution curve for fine aggregate the results of the particle size distribution (figures 1 and 2) obtained for the fine and coarse aggregates shows that the aggregates are well-graded and satisfy the specifications of bs 812103.2, (1985). thus, suitable for the production of bituminous mixtures. 3.3 results of test on bitumen the test results on the physical properties test on bitumen are shown in table 3. the results obtained fall within the limits of the astm code specifications, therefore, the bitumen can be adjudged suitable for use in the production of bituminous mixtures. table 3: preliminary test results on bitumen test conducted astm code results code limits remarks penetration at 25°c, 0.1mm astm d5, (2005) 87.2 80-100 ok flash & fire point (min) astm d92, (2005) 252 min. 232 ok solubility in trichloroethylene, (%) astm d2042, (2015) 99 99 ok specific gravity at 25°c, (g/cc) astm d70, (2003) 0.98 0.97-1.02 ok ductility at 25°c, cm astm d113, (2007) 115 min. 100 ok softening point astm d36/d36m, (2009) 49.5 46-56 ok 3.4 results of test on filler (silica sand and cement) test on the physical properties of cement and silica sand was performed. in addition, chemical properties of silica sand was performed to check the oxide composition necessary for classification into the groups of pozzolanas. the results obtained are as follows: 3.4.1 physical properties of silica sand table 4 and 5 present the results of the physical and chemical properties test on silica sand respectively. the physical properties (specific gravity and water absorption) obtained were compared to the code limits. the results obtained meet the limits of the code specifications. it is important to state at this point that for any material to be used as filler in bituminous mixtures more than 75 per cent of such material must pass through 0.075mm sieve and the silica sand meet these requirements. 0 20 40 60 80 100 120 0.01 0.1 1 10 100 p er ce n t p as si n g (% ) sieve size (mm) shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 459 table 4: physical properties of silica sand test conducted code used results code limits remarks specific gravity astm c128 (2001) 2.5 2.55-2.75 ok water absorption (%) bs 812 part 3, (1990) 8.92 < 15 ok 3.4.2 oxide composition of silica sand table 5 shows the oxide composition of silica sand used in this study. the composition of the various oxides present in silica sand including the portion of loss on ignition to give a total of 100%. it is worth mentioning that the high sio2 content above 95% is what make the silica sand special. table 5: chemical composition of silica sand oxide composition (%) oxide composition (%) sodium oxide (na2o) 0.066 sulphur trioxide (so3) 0.659 magnesium oxide (mgo) 0.313 chloride (cl) 0.046 aluminium oxide (al2o3) 5.913 potassium oxide (k2o) 0.198 silicon dioxide (sio2) 91.221 calcium oxide (cao) 0.062 diphosphorus pentoxide (p2o5) 0.406 tetanium dioxide (tio2) 0.729 chromium iii oxide (cr2o3) 0.002 manganese iii oxide (mn2o3) 0.009 iron oxide (fe2o3) 0.317 zinc oxide (zno) 0.000 strontium oxide (sro) 0.005 loss on ignition (loi) 0.054 based on the astm c 618, (2005) in table 6 classification, the summation of silica (sio2), alumina (al2o3), and (fe2o3) present in silica sand was compared to that of the code and the class of pozzolana which silica sand belongs to was deduced. from table 5, the summation of these oxides in silica sand is 97.451%. i.e. (91.221+ 5.913+ 0.317). also considering the low value of so3 (≤ 5 %), silica sand can be classified as pozzolana in group n or f. table 6: astm c 618, (2005) classification of pozolana chemicals class test result n f c silicon dioxide (sio2), + aluminium oxide (al2o3), + iron oxide (fe2o3), min. (%) 70.0 70.0 50.0 97.451 sulphur trioxide (so3), max,(%) 4.0 5.0 5.0 0.659 3.4.3 results of test on cement the results of the physical properties tests carried out on the cement are presented in table 7. it can be seen that the cement used in this study meet all the code specified limits of portland cement, thus, it can be concluded that the dangote 3x brand of cement used in this study is portland cement. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 460 table 7: physical properties of cement test code used results code limits remarks initial setting time (minutes) bs en 196 part 3, (1995) 125 > 45 ok final setting time (hr) bs en 196 part 3, (1995) 3.42 hrs < 10 hrs. ok soundness (mm) bs en 196 part 3, (1995) 3.0 < 10 ok specific gravity astm 188, (2017) 3.10 3.15 ok 3.5 aggregate proportioning and blending for production of bituminous mix the aggregates materials were sampled according to the recommendation of bs en932-1 (1996) and particle size distribution was conducted according to bs en 933-1 (2012). to obtain proportion and blending of individual constituent material; coarse aggregate (material retained on 4.75 mm sieve with a maximum aggregate size of 25 mm), fine aggregate (material passing 4.75 mm sieve and retained on 200 μm sieve), and mineral filler (material passing 200 μm sieve) necessary for the production of the bituminous concrete mix were achieved by trial and error and blended until an all-in-aggregate satisfying code requirement is obtained as presented in table 8 below. the results of combined material mixes fall within the lower and upper limits specified by asphalt institute (1997), thus, adjudged suitable for use in the production of bituminous concrete mixtures that meets strength and durability requirements in practice. table 8: result of the combined material mix (coarse aggregate, fine aggregate, and silica sand/cement) with limits of code specifications bs sieve size (mm) percentage retained (%) cumulative percentage retained (%) cumulative percentage passing (%) asphalt institute, (1997) 25.4 100 100 19.05 6.6 6.6 93.4 90 100 12.7 14.9 21.5 78.5 9.52 7.2 28.7 71.3 56 80 6.32 11.7 40.7 59.3 4.76 7.2 47.6 52.4 35 65 2.36 5.6 53.2 46.8 23 49 1.18 10.8 64.0 36.0 0.6 22.4 86.4 13.6 0.3 5.9 92.3 7.7 5 – 19 0.15 0.7 93.0 7.0 0.075 0.4 93.4 6.5 2 8 pan 6.5 99.9 0.1 3.6 determination of optimum binder content (obc) to obtain the optimum binder content necessary for the asphalt paving mixtures at different silica sand replacements, the relationships between binder contents and the properties of bituminous mixtures such as stability, flow, and bulk density, void in mix, void in mineral aggregate, and void filled with bitumen at no replacement (control) were established. three samples were produced at each bitumen content (5, 5.5, 6, 6.5, 7.0%) as specified by asphalt shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 461 institute (1997) and orn 19, (2003) and the average of the results obtained for the strength and void properties are presented in table 9. table 9: summary of the marshall test results for control specimens bitumen content (%) stability (kn) flow (mm) bulk specific gravity (g) (g/cm3) vim (%) vma (%) vfb (%) 5.0 8.30 2.40 2.29 6.30 18.00 68.60 5.5 8.45 3.10 2.31 5.00 18.00 75.30 6.0 8.51 4.23 2.24 3.00 17.30 84.70 6.5 8.10 6.84 2.33 2.40 17.90 91.60 7.0 7.81 8.16 2.31 2.80 19.20 93.00 the optimum binder content is calculated as the average binder content that corresponds to maximum stability, maximum unit weight, and 4 % air voids.  bitumen content at the maximum stability = 5.5 %  bitumen content at the maximum value of bulk density = 6.5%  bitumen content at 4 % air voids = 5.25 % (obtained by interpolation from table 6) thus, optimum bitumen content (obc) = 5.5 + 6.5 + 5.25 /3 = 5.75% an optimum binder content of 6.0% was adopted for the production of bituminous concrete mixtures at varying silica sand/cement contents. the obc used in this study is within the limits of 5.0 – 8.0% specified by fmwh, (1997). 3.7 marshall test results for various replacements of cement with silica sand at optimum binder content figures 3 to 8 show the results of marshall stability-flow, and void-density properties at various percentage replacement by weight of portland cement with silica sand (5%,10%,15%, 20%,25%, 30%,35%, 40%, and 45%) using the optimum binder content of 6%. figure 3: variation of stability with silica sand content 4.5 5 5.5 6 6.5 7 7.5 8 5 15 25 35 45 55 st ab ili ty (k n ) silica sand content (% ) arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 462 figure 3 shows the variation of marshall stability with different silica sand content. marshall stability is a measure of hma resistance to deformation and distortion under traffic loading. this resistance is mainly derived from cohesion (provided by the binder material) and internal friction (provided by interlocking and frictional resistance of aggregates) (shuaibu et al., 2020b). from figure 3, the marshall stability increases with the increase in the silica sand content. this could be attributed to the ability of silica sand to fill void spaces in the bituminous concrete mix by gaining increased contact points with other constituent materials, thereby, resulting in a denser mix. also, the presence of high content of sio2 enhances hardness. it should be noted that at silica sand content above 40%, the stability started dropping and this could be attributed to excess silica sand content in excess of the optimum which resulted in weak cohesion. however, the marshall stability results obtained at all the silica sand contents satisfied the requirements for nigerian specification for roads and bridges (fmwh, 1997). figure 4: variation of flow with silica sand content figure 4 shows the result of flow variation at varying silica sand content. flow is the measure of flexibility by the change in diameter of the test sample in the direction of load application between the start of loading and the time of maximum load (shuaibu et al., 2019). the flow value increases gradually at 5% (2.97mm) silica sand content until it peaked at 25% (3.8mm) silica sand content, then, it gradually started to decrease. the initial increase in flow could be due to the insufficient content of silica sand in the mix to retard the flow. however, as the silica sand content increases, the stiffening of filler-bitumen mastic occurred, consequently reducing the flow. the flow values obtained at all the silica sand contents falls with the 2 to 4mm nigerian general specifications for roads and bridges specification fmwh, (1997) margin for use in wearing course of the heavy-trafficked road. 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 5 15 25 35 45 55 fl o w ( m m ) silica sand content (% ) shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 463 figure 5: variation of void in the mix (vim) with silica sand content figure 5, show the variation of void in mix (vim) at different silica sand contents. the void in mix increases gradually from 5% silica sand until it peaked at 25% silica sand content then gradually started decreasing. this initial increase could be attributed to silica sand particles' having greater ability to convert free bitumen to structural bitumen than portland cement (p.c) particles. structural bitumen here refers to the bitumen that fills the voids among filler particles. this conversion reduces the amount of free bitumen required to lubricate aggregates and fill inter-granular voids (shuaibu et al., 2020b). the reduction in percent air voids beyond 25% could be due to the sufficient filling of the void space between aggregates. it is important to note that a balance must be attained with the percentage air void content to achieve desirable engineering properties in service. the nigerian general specifications for roads and bridges specification fmwh, (1997) specifies a margin of 3 to 5% air void in mix, however, the values of vim obtained at 25, 30 and 35% silica content does not meet this specification. figure 6: variation of bulk density with silica sand content 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 5 10 15 20 25 30 35 40 45 50 v o id in m ix ( % ) silica sand content (% ) 2.00 2.10 2.20 2.30 2.40 2.50 5 15 25 35 45 55 b u lk d en si ty ( g/ cm 3 ) silica sand content (%) arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 464 figure 6 show the result of bulk density at varying silica sand contents. the bulk density decreases with the increasing content of silica sand. the maximum value of bulk density recorded is 2.38g/cm3 at 5% silica sand content. the reduction in bulk gravity could be due to the lower specific gravity/large surface area (i.e higher volume) of the silica sand compared to that of cement (shuaibu et al., 2020a) . silica sand has large surface area and it requires more binder for coating, hence, the bulk density dropped. figure 7: variation of void filled with bitumen (vfb) with silica sand content figure 7 shows the result of vfb at varying silica sand contents. the void filled with bitumen vfb is defined as the portion of the volume of void space between the aggregates particles that is occupied by the effective bitumen (shuaibu et al., 2020c). the void filled with bitumen decreases as percentage replacement of silica sand increases and this is because the particles of the silica sand take up the effective bitumen and in turn reduces it. only the vfb results obtained at silica sand contents of 5, 10, 15 and 20% conformed to the nigerian general specifications for roads and bridges specification fmwh, (1997) of 75 to 82% for use in wearing course. figure 8: variation of voids in mineral aggregate (vma) with silica sand content 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 5 10 15 20 25 30 35 40 45 50 v f b ( % ) silica sand content (%) 16.0 17.0 18.0 19.0 20.0 21.0 22.0 5 10 15 20 25 30 35 40 45 50 v m a ( % ) silica sand content (%) shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 465 figure 8 shows the results of void in mineral aggregate with silica sand content. voids in mineral aggregate (vma) is bituminous concrete design parameter that defines the sum of the volumes of air voids (voids in total mix) and the unabsorbed bitumen (effective binder content) in a compacted bituminous concrete sample (shuaibu et al., 2020b). minimum requirements on vma are set to ensure that sufficient voids are present in the compacted mix to avoid durability problems. the vma aggregates increases gradually from 5% silica sand content, peaked at 25%, and gradually decreased. the later decreasing trend observed in vma is due to the ability of silica sand to fill up spaces between the mineral aggregates. 4. conclusions from the results of the experimental study, the following conclusions can be deduced; i. the preliminary test conducted on bituminous concrete constituent materials (cement, fine and coarse aggregates, bitumen) conforms to the astm and bs code specifications, therefore, adjudged suitable for the production of bituminous mixtures for wearing course. ii. oxide composition test conducted on silica sand confirmed that it is pozzolanic in group n or f, thus, can be used as an admixture in the bituminous concrete mix. iii. marshall stability results showed that of bituminous concrete mix containing up to 45% silica sand improved the stability value beyond 3.5kn specified by the code. also, the flow values recorded at all silica sand contents are within the 2-4mm limits specified by codes. 5. acknowledgement the authors are sincerely grateful to the department of civil engineering department, ahmadu bello university, zaria, kaduna state, nigeria for providing an enabling environment to carry out this research. the work described in this paper is not supported by any grant. reference akter, h. and hossain, k. 2017. influence of rice husk ash and slag as fillers in asphalt concrete mixes. american journal of engineering research (ajer), 6(1): 303-311. asphalt institute, 1997, mix design methods for asphalt, manual series no. 2 (ms-02). the asphalt institute. lexington, ky. astm c117 2017, standard test method for materials finer than 75-μm (no. 200) sieve in mineral aggregates by washing, astm international, west conshohocken, pa, usa. astm c127, 2015, standard test method for relative density (specific gravity) absorption of coarse aggregate, astm international, west conshohocken, pa, usa. astm c128, 2001, standard test method for density, relative density (specific gravity), and absorption of fine aggregate, astm international, west conshohocken, pa, usa. astm c618, 2005, standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete, astm international, west conshohocken, pa, usa. astm d113 2007, standard test method for ductility of bituminous materials, west conshohocken, astm international, philadelphia, pa, usa. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 466 astm d113, 2007. standard test method for ductility of bituminous materials. west conshohocken, astm international, philadelphia, pa, usa. astm d2042 2015, standard test method for solubility of asphalt materials in trichloroethylene, astm international, west conshohocken, pa, usa. astm d2042, 2015. standard test method for solubility of bituminous materials. west conshohocken, astm international, philadelphia, pa, usa. astm d36 2006, standard test method for softening point of bitumen (ring-and-ball apparatus), astm international, west conshohocken, pa, usa. astm d5, 2005, standard test method for penetration of bituminous materials. west conshohocken, astm international, philadelphia, pa, usa. astm d70, 2003. standard test method for specific gravity and density of asphalt binder (pycometer method). west conshohocken, astm international, philadelphia, pa, usa. astm d854, 2014, standard test methods for specific gravity of soil solids by water pycnometer, astm international, west conshohocken, pa, usa. astm d92, 2005. standard test method for flash and fire points by cleveland open cup tester. west conshohocken, astm international, philadelphia, pa, usa. boon hoe, h., sunnasee, p., kok hon, c., byung gyoo, k. and sien ti, k. 2014. utilisation of rice husk ash in asphaltic concrete pavement. advanced materials research, transtech publications, switzerland, 1030-1032(961-964). bs 812 110, 1990. methods for determination of aggregate crushing value (acv). british standard institution, london, united kingdom. bs 812 112, 1990. methods for determination of aggregate impact value (aiv). british standard institution, london, united kingdom. bs 812 2, 1995. methods for determination of density, water absorption, british standard institution, london, united kingdom. bs en 933-1, 2012, tests for geometrical properties of aggregates. determination of particle size distribution, sieving method, british standard institution, london, united kingdom. bs en 933-2, 1996 tests for geometrical properties of aggregates. determination of particle size distribution. test sieves, nominal size of apertures, british standard institution, london, united kingdom. bs en196-3, 1995, methods of testing cement — part 3: determination of setting time and soundness, british standard institution, london, united kingdom. burkowicz, a., krzysztof galos, k. and guzik, k. 2020. the resource base of silica glass sand versus glass industry development: the case of poland, multi-discplianry publishing institute, basel, switzerland. chukwu, p. 2019. exposition on silica sand reserves in nigeria and its impact on metallurgical industries. coou journal of physical sciences, 1(2): 810-816. shuaibu et al: an experimental study on the performance of bituminous concrete mixtures with silica sand as filler replacement. azojete, 17(4):453-468 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 467 duvuna, ga. and ayuba, a. 2015. a study on silica sand quality in yazaram and mugulbu deposits for glass making. nigerian journal of technology, 34(1): 109 – 112., http://dx.doi.org/10.4314/njt.v34i1.13 fmwh, 1997. general specifications for roads and bridge. federal ministry of work sand housing, federal republic of nigeria. abuja, nigeria. langer, wh. 2003. a general overview of the technology of in-stream mining of sand and gravel resources associated potential environmental impacts, and methods to control potential impacts. u.s. geological survey open file report of-02-153. mistry, r. and roy, tk. 2016. effect of using fly ash as alternative filler in hot mix asphalt. perspectives in science, 8: 307—309. mistry, r., karmakar, s. and roy, tk. 2018. experimental evaluation of rice husk ash and fly ash as alternative fillers in hot-mix asphalt. road materials and pavement design, doi:10.1080/14680629.2017.1422791. murana, aa. and sani, a. 2015. partial replacement of cement with baggase ash in hot mix asphalt. nigerian journal of technology, 34(4): 699-704. orn 19, 2003. a guide to the design of hot mix asphalt in tropical and sub-tropical countries, overseas road note 1. berkshir, england otuoze, hs. and shuaibu, aa. 2017. an experimental study on the use of polypropylene waste in bituminous mix. nigerian journal of technology, 36(3): 677-685. rmrdc, 2009. survey series 061 raw materials sourcing for manufacturing in nigeria 4th edition. publishers: raw materials research and development council, abuja nigeria. shuaibu, aa., otuoze., hs., mohammed, a. and lateef, ma. 2019. properties of asphalt concrete containing waste foundry sand (wfs) as filler material. arid zone journal of engineering, technology and environment (azojete), 15(3): 662-677. shuaibu, aa., otuoze, hs., ahmed, ha. and musa, b. 2020a. experimental study on the use of groundnut shell ash as mineral filler in hot mix asphalt. nigerian journal of engineering, 27(3), 61-68. shuaibu, aa., umar, am., otuoze, hs., mohammed, a. and abba, am. 2020b. optimum portland cement-guinea corn husk ash blend as filler in hot mix asphalt. covenant journal of engineering and technology, 4(2): 56 66. shuaibu, aa., otuoze, hs., iliyasu, i. and maska, us. 2020c. effect of oil palm mesocarp fibre ash (opmfa) on the strength properties of hot mix asphalt. journal of science technology and education, 8(2), 330 350. simone, a., mazzotta, f., eskandarsefat, s., sangiorgi, c., vignali, v., lantieri, c. and dondi, g. 2017. experimental application of waste glass powder filler in recycled dense grade asphalt mixtures. road materials and pavement design, 20(3): 592-607 doi:10.1080/14680629.2017.1407818. http://dx.doi.org/10.4314/njt.v34i1.13 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):453-468. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulshub4u@gmail.com 468 sutradhar, d., miah, m., chowdhury, gj. and abdus, s. 2015. effetct of using waste materials as in bituminous mix design. american journal of civil engineering, 3(3): 88-94. speight, jg. 2016. nomenclature and terminology asphalt materials science and technology, butterworth-heinemann, united kingdom, 3-43, doi.org/10.1016/b978-0-12 800273-5.00001-5. zhang, h., chen, z., zhu, c. and wei, c. 2020. an innovative and smart road construction material: thermochromic asphalt binder. new materials in civil engineering, butterworth heinemann, 2020, 691-716, doi.org/10.1016/b978-0-12-818961-0.00022-3 arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):725-732 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 725 original research article development and performance evaluation of a manually operated groundnut roaster y. a. unguwanrimi2, s. a. okaiyeto1, a. m. sada3, s. i. ogijo4, j. b. jonga1, n. oji5 1department of agricultural and bio – resources engineering, ahmadu bello university, zaria, nigeria 2department of crop science, kaduna state university (kasu), kaduna, nigeria 3department of agricultural engineering and irrigation, national agricultural extension and research liaison services, ahmadu bello university, zaria, nigeria 4national agricultural seeds council zaria, nigeria 5department of agricultural & bio-environmental engineering, college of engineering kaduna polytechnic, kaduna, nigeria *corresponding author’s email address: yakabu3002@gmail.com 1.0 introduction peanuts (arachis hypogea) also known as groundnut are a major world oil seed crop. in nigeria, approximately 3.1 million metric tons of groundnut in shell was produced in 2015 (fao, 2016). in the northern part of nigeria, processing of groundnut at small and medium scale is an important economic activity especially for women in villages and towns. engin et al. (2017) observed the amount of oil present in groundnut ranged between 31.7 – 57.0%. however, this is dependent of the variety used additionally, groundnut is rich in protein, making it a valuable feed for poultry (asiedu, 1989). it is noteworthy that the main commercial product of groundnut is oil, which is an essential part of human diet; nutritionally they provide calories, vitamins and essential fatty acids in an easily digestible form. therefore, the processes involved in processing the groundnut to oil requires adequate considerations. the extraction of oil from groundnut seeds are done largely as traditional or industrial (ajao et al., 2010). the traditional method consists of decorticating the pods; sorting, roasting, deskining, grinding, kneading, forming and frying of the residual meal into edible cake called “kuli kuli”in hausa the traditional method of processing the oil is considered to be time and energy consuming. conversely, considerable improvement had been made on the traditional method by the institute of agricultural research (iar), ahmadu bello university, samaru zaria (abubakar and yiljep, 2000). recently, there exist a motorized systems based on the traditional concept. however, in commercial (industrial) operation oil may be removed from groundnut by solvent extractor or mechanical expression (kumar et al., 2017). a two-step combination of mechanical pressing and solvent extraction method is being used to improve the overall yields and reduce solvent requirement. the seed oil meal is first pressed to reduce the oil content to about 20% while the remaining is solvent extracted. small and medium scale extractors use the mechanical oil expression which consists of pressing out the oil out of the oil containing seeds article information abstract a manually operated groundnut roaster was developed and evaluated. the present institute for agricultural research, zaria (iar) roasting equipment consists of a frying pan and an iar charcoal fire wood cooking stove. the roaster was designed to help local processors obtain uniformly roasted products, with acceptable roast color. the performance of the roaster was carried out using iar groundnut species known as samnut 11 as specimen. the roaster was found to have a roasting capacity of 0.92 kg/min which is above the (iar) roaster that has a roasting capacity of 0.28 kg/min. the roaster was found to have efficiencies of 98.3%, 98.6%, and 98.9% at 25%, 50% 100% loadings, respectively. the parameters that affect the roasting capacity include: heat from charcoal, crop moisture content and crop variety. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 march, 2020 revised 8 may, 2020 accepted 13 may, 2020. keywords: development manually operated groundnut roaster roast colour roasting capacity. http://www.azojete.com.ng unguwanrimi et al.: development and performance evaluation of a manually operated groundnut roaster. azojete,16(4):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 726 (akindele and nsuhoridem, 2018). it uses either hydraulic presses or the screw presses. the screw press is more efficient which his expelled and the residual meal known as groundnut cake is used for poultry feed. many factors could affect oil extraction for a given variety; the composition of seed oil is known to be affected by storage time and condition. some processing factors such as roasting and pressing conditions affects the quantity of oil expelled. among other factors roasting of the groundnut seeds before oil extraction is of utmost importance. this is due to the fact that roasting influences both the physical and chemical properties of the oil (gokhan et al. 2010). currently the process is done in a traditional way with frying fan in a charcoal stove or with firewood in a three fire stone. this process was characterized by high time consuming, low output, tedious, and expose to heat by the operator. the objectives of this study therefore are to develop and evaluate a manually operated groundnut roaster. 2.0 materials and method 2.1 construction materials in constructing the manually operated groundnut roaster, gauge 16 mild steel sheet was used for the drum, gauge 13 mild steel sheet was used for the charcoal tray considering the heat generated from burning charcoal. 2.00 x 2.00 x 0.125 inch angle iron was used for the frame because of its higher strength to withstand pressure. chains and sprockets were used to transmit power due to their ability to withstand elevated temperatures. the capacity of the machine was designed to match the existing iar motorized oil extractor capacity which is 20 kg (isiaka, 2005). 2.2 design calculation 2.2.1 determination of drum capacity the drum is in a cylindrical shape. the capacity of the drum is gotten from the volume of a cylinder by (kurmi and gupta, 2007) volume of cylinder v = πd2l 4 (1) where: d is the drum diameter (m) and l is the drum length (m) 2.2.2 drum rotational speed determination of the drum rotational speed ratio formula as recommended by hannah and stephen (1984) ω = 2πn 60 (2) where: ω is angular velocity (rad/s) and n is angular rotation (rev/min) 2.2.3 shaft design the shaft is to be subjected to two forms of load; axial load due to drum and seed weight and torsional load due to rotation speed. drum weight wd = 14.8 kg × 9.81ms-2 maximum seed weight ws = 20 kg × 9.81ms-2 total weight due to drum and seed w = 341.388 n assumption: that the weight is acting at the points of attachment of drum to shaft. the axial load will be shared equally on both points of attachment. thus each point will carry w 2 = 170.694 n http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):725-732. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 727 figure 1: loadings on the central shaft of drum ra= rd = 170.694 n 2.2.4 determination of the cylinder shaft diameter the shaft diameter was obtained given by (khurmi and gupta, 2007) d3 = 16 πσs kbmb 2+ ktmt 2 (3) where: d is shaft diameter (mm), kb is combine shock and fatigue factors for bending moment (1.5), kt is combine shock and fatigue factors for tensional moment (1.0), mb is maximum bending moment (nm) and mt is tensional moment (nm). the allowable shear stress for shaft with keyway, σs = 75 × 106 n/m2 2.3 description of the roaster the roaster consists of the frame; chain and sprocket, fan housing, shaft and charcoal tray i. frame :the frame which is the supporting structure of the machine was constructed with 2 × 2 × 1/8 inch angle iron. each doubled for stability and strength. the dimensions are as follows height is 900 mm; breath 860 mm and width 460 mm. total weight due to the frame is approximately 40 kg ii. drum :the drum which serves as the groundnut containing chamber during roasting was constructed with a 1 mm mild steel sheet. 1 mm mild steel sheet was used due to its high thermal conductivity. the drum has a diameter of 400 mm and length of 800 mm. one side of the drum was constructed with a meshed wire for smoke outlet and to enable direct visualization of the groundnut seeds while roasting. a helical structure was constructed lying at the inside wall of the drum, this helix is to enable efficient mixing of the seed while roasting and for conveying the roasted seed after roasting to the outlet. iii. chain and sprocket :chains and sprocket were used instead of belt and pulley due to their higher thermal resistance. the bigger sprocket has (42 teeth) is attached to the central shaft of the drum while the smaller sprocket with (14 teeth) is attached to the fan shaft. this arrangement is to allow for higher fan rotation. iv. fan :an axial fan is used because it gives more output over centrifugal when the rotation is low. the fan has a diameter of 240 mm; the fan is equipped with housing, the housing is to allow for air flow direction. v. charcoal tray :the charcoal tray is constructed with a 3 mm mild steel sheet. the sides of the tray were constructed with wire mesh to serve as air vent. it is located directly below the drum in a chamber so that maximum heat is transferred to the drum. the charcoal chamber can contain about 20 kg of charcoal. heat is transfer to the groundnut by conduction principle through the drum. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng unguwanrimi et al.: development and performance evaluation of a manually operated groundnut roaster. azojete,16(4):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 728 figure 1. isometric views of the roaster 2.4 working principle of the roaster the machine operated manually. when operating the machine charcoal tray was filled with charcoal and then ignited with matches or lighter. a 20 kg groundnut was then introduced into the drum through the loading opening. the drum was then rotated slowly at approximately 24 rev/min. the rotations were either clockwise or anticlockwise. furthermore the rotation was continues with intermittently stoppage to check the roast level of the seeds. when the groundnut was fully roasted (when the color change from red to brown), the charcoal tray was move away from directly under the drum and then the groundnut was collected at the discharge side. 2.5 experimental procedure a single factor experiment with three (3) different seed loading at 25, 50 and 100% capacity (5, 10, and 20 kg) was considered. the experiment replicated three times to reduce the bias. samnut 11 varieties of groundnut seeds were used for these experiments. a similar experiment is conducted on the existing iar roasting method (charcoal stove and frying pan). figure 2 shows the constructed roaster during the evaluation process. external blowers had to be used to augment the axial fan. figure 2. constructed manually operated groundnut roaster during evaluation http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):725-732. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 729 2.5.1 performance indicator after developing the machine, it’s performance was evaluated for the following parameters roasting capacity this is a measure of the time taken for a given quantity of groundnut seeds to roast. it is expressed as, (ikechukwu et al. 2014), rc = qf t (4) where: rc is roasting capacity (kg/min), qf is quantity of groundnut in the drum (kg) and t is time taken to roast the groundnut (min). roasting efficiency during the roasting process some seeds are damaged either by burning or breakage. the seed is consider burnt when it turn from red to black. the percentage of seeds was determined as, (ikechukwu et al. 2014) re = qf−qd qf × 100 (5) where: re is roasting efficiency (%), qf is quantity of groundnut in the drum (kg) and qd is quantity of seed damage (kg) 3.0 results and discussion 3.1 groundnut roasting time under iar roasting method table 1 shows the roasting time of groundnut seeds using the existing iar groundnut roasting method. the time taken to roast 5 kg of groundnut was 14min to attain the desired roast colour while 56min was required to roast 20 kg of groundnut seeds to attain the desired roast colour. table 1: roasting time using the iar roasting method mass of fresh seeds (kg) mass of roasted seed (kg) time of roasting (min) 5 4.80 14 10 9.65 36 20 19.0 56 3.2 effect of seed quantity on roasting time of groundnut seeds table 2 shows the effective roasting time increases with increase in seed weight. it was observed that 20 kg had the highest roasting time of 21.67 mins. additionally, roasting time was found to be affected by seed quantity alongside other factors such as moisture content and temperature. in general, a7.5% moisture content increases the roasting time as observed. this is because roasting takes place where there is rapid removal of water from the seeds and then millard browning. the result obtained is in accordance with the findings of kabir et al., (2010) who obtained 9.5min effective roasting time for 5.5kg (maximum load) of groundnut seeds. table 2: roasting time, weight of roasted groundnut, weight of damaged seeds. mass of fresh seed (kg) roasting time (min) mass of roasted seeds (kg) mass of damaged seeds (kg) roasting capacity (kg/min) roasting efficiency (%) 5.0 12.17 4.73 0.07 0.41 98.60 10 16.50 9.43 0.17 0.61 98.30 20 21.67 18.98 0.22 0.92 98.90 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng unguwanrimi et al.: development and performance evaluation of a manually operated groundnut roaster. azojete,16(4):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 730 3.3 effect of seed quantity on roasting capacity and efficiency table 2 also shows the performance evaluation for different mass of groundnut seeds. the results show that full load capacity (20 kg) had the highest roasting capacity of 0.92 kg/min and also highest roasting efficiency of 98.90%. this implies that the machine could perform optimally when operated at full load capacity. the roasting capacity was better than the results obtained by kabir et al., (2010) with roasting capacity of 0.567 kg/min . however, ogijo (2019) obtained a higher roasting capacity of 1.69 kg/min than in this study. the reason for the higher roasting capacity is because the roaster was motorized. figure 3 shows a sample of the roasted groundnut using the manually operated drum type groundnut roaster. as can be observed a relatively uniform roasting was achieved, with less visible burnt surfaces. the result agree with the previous researches such as abubakar et al., 2017; kabir et al., 2010, abdulsalam et al., 2013 and olatunde et al., 2014. the authors obtained similar findings of uniform roasting. figure 3. sample of roasted nut using the roaster. 3.4 comparison of the manually operated groundnut roaster and the iar roasting method the iar method uses a pan and a burner to roast groundnut. the iar method of roasting leaves dark spot (indicating burn), on the seeds after roasting while in the case of manually operated roaster, the roasting color is relatively uniform due to intermittent rotation of the drum thereby control the heat transfer by conduction. the manually operated groundnut roaster has a fairly more capacity (0.92 kg/min) than the iar roasting method (0.28 kg/min). 3.5 the traditional roasting method and the manually operated roaster research work conducted by nalumansi and kaul, (1992) obtained a 20 mins roasting time for 2.5kg of groundnut seeds. thus it will be time consuming and strenuous to roast 20 kg of groundnut using the traditional method. when compared to the constructed manually operated groundnut roaster, 72.91% reduction in roasting time is obtained. 4.0 conclusion the manual groundnut roaster, which was initially designed to roast groundnut seeds have been constructed and evaluated. the roaster has the ability to roast 55.2 kg of groundnut seeds in 1h. a maximum of 98.90 % roasting efficiency was obtained when roasting on full load capacity. uniform roasting of the groundnut seeds was achieved. instead of using an axial fan, a centrifugal blower can be used to enhance charcoal burning in order to obtain higher temperature in the drum. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):725-732. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 731 refeerences abubakar, sz. and yiljep, yd. 2000. design and development of a groundnut paste kneader (pastestirrer). savanna journal of agricultural mechanization, 2(1):1-6. abubakar, ms., sadiq, aa. and lawal, i. 2017. a comparative performance evaluation of an existing and a modified groundnut seed roasting machines. journal of dryland agriculture, 1(2):125-135. abdulsalam, a. 2013. design and construction of a manually operated of groundnut roasting machine. b.eng. project, bayero university kano, kano, nigeria. ajao, kr., ajimotokan, ha., olaomi, j. and akande, hf. 2010. development and performance evaluation of a groundnut oil expelling machine. new york science journal, 2(6):76-79. akindele, f. and nsuhoridem, ij. 2018. extraction of vegetable oils from agricultural materials: a review. proceeding of the 12th cigr symposium, held at the international institute of tropical agriculture, ibadan, oyo state, nigeria 22-25 oct. 2018, 1184-1206. asiedu, j. 1989. processing of tropical crops. macmillan education ltd new york., 126-144. engin, y., rustem, u., muharrem, g. and bulent u. 2017. oil content yield and fatty acid profile of groundnut germplasm in mediterranean climates. journal of american oil chemistry society, 94:787-804. doi 10.1007/s11746-017-2981-3. food and agriculture organization (fao) 2016. faostat database. http://faostat.fao.org. accessed 17th august 2017. gokhan, d. and vural, g. 2010. impacts of roasting oily seeds and nuts on their extracted oils. lipid technology, 22( 8):179–182. ikechukwu, cu., olawale, oj., ibukun, bi. and robert, tj. 2014. design and development of manually operated roasted groundnut seeds peeling machine. international journal of recent development in engineering and technology, 2(4): 50-57. isiaka, m. 2005. operation and maintenance of iar groundnut processing equipment. iar samaru extension bulletin , 2: 7-27. kabir, hu., ankidawa, ba. and elson, j. 2006. modification and performance evaluation of a manually operated drum groundnut roaster. savannah journal of agriculture, 1(2):88-93. kabri, hu., aliyu, b., tashiwa, yi. and. hong ah. 2010. construction and performance evaluation of a manual groundnut seed drum roaster for farmers in northern nigeria. the nigerian academic forum, 19(1):1-4. kumar, spj., prasad, sr., banerjee, r., agarwal, dk., kulkarni, ks. and ramesh, kv. 2017. green solvent and technologies for oil extraction from oilseeds. chemistry central journal, 11(9):1-8 doi: https://doi.org/10.1186/s13065-017-0238-8. kurmi, rs. and gupta, jk. 2007. a textbook of machine design. eurasia publishing house ltd. new delhi, 686-700. ajao, kr. and akande, hf. 2009. development and performance evaluation of groundnut oil expelling machine. new york science journal, 5(4):76-79. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng unguwanrimi et al.: development and performance evaluation of a manually operated groundnut roaster. azojete,16(4):725-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yakabu3002@gmail.com 732 nalumansi, sr. and kaul, rn. 1992. studies on the traditional system of groundnut oil extraction and possible improvements. iar-ford foundation project on technology for women (ford foundation grant) no. 900-0260-1. ogijo, si. 2019. modification and performance evaluation of a groundnut roasting machine. msc. thesis, ahmadu bello university, zaria, nigeria. olatunde, ob., ajav, ea. and fatukasi, so. 2014. design and fabrication of groundnut (arachis hypogaea) roaster cum expeller. international journal of science and technology, 3(3):14-19 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 219-224 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng __________________________________ *corresponding author email address: mo.omobowale@ui.edu.ng 219 original research article comparative evaluation of novel low-cost moisture meters suitable for grain moisture measurement s. k. ajao1, m. o. omobowale*2, k. o. popoola1, a. a. ala1, g. p. opit3 1department of zoology, university of ibadan, nigeria; 2agricultural and environmental engineering department, university of ibadan, nigeria; 3department of entomology and plant pathology, oklahoma state university, stillwater, ok, usa. article information received: october, 2018 accepted: december, 2018 keywords: moisture content maize moisture meter postharvest loss grain quality abstract monitoring grain quality is an important postharvest activity which starts at harvest, continuing during storage and up to the point of sale. high moisture in stored maize can be detrimental to food safety because of the likelihood of aflatoxin contamination and other forms of deterioration. moisture meters are devices which provide real-time access to measuring moisture levels thereby allowing farmers to meet grain quality requirements. a newly developed low-cost moisture meter known as the post-harvest loss (phl) moisture meter is a device with potentials for massive deployment among smallholder farmers. this study was therefore set up to compare the efficiencies of some existing moisture meters compared with this newly developed device. two commercially available moisture meters — dickey john gac 2100 and john deere meters were compared with the phl moisture meter and ovendried method (asabe standards) used as control. maize grains from a bagged storage experiment were used as samples over a 12month period. results showed that the moisture meters had a positive difference of ˂3% mcwb relative to oven-dried method. average measurements showed variances of 2.34, 1.08 and 0.56% mcwb for john deere, phl and gac 2100 meters respectively, when compared with the oven-dried method. thus, it was concluded that the low cost phl moisture meter may serve as an effective alternative to the more expensive types and may be relatively easy to adopt for laboratory and field use among smallholder farmers in sub-saharan africa. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction the quality of grain is influenced by its moisture content (mc) (rai et al., 2005). it is one of the important parameters considered when deciding price and quality at the stage of harvest, storage, processing and marketing. high moisture can lead to quality reduction and even crop loss during storage (armitage et al., 2008). when storage environments are not properly maintained, quality and economic losses can occur from such agents as mold growth and insect damage, which are usually the two most troublesome problems in modern grain storage http://www.azojete.com.ng mailto:mo.omobowale@ui.edu.ng ajao, et al. comparative evaluation of novel low-cost moisture meters suitable for grain moisture measurement. azojete, 14(sp.i4):219-224. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 220 structures. appropriately low grain moisture contents and low grain temperatures are the primary weapons for preventing mold and insect infestations (casada and armstrong, 2008). there are two basic methods of determining the mc of biomaterials –the primary/direct and secondary/indirect methods (obi et al., 2016). a primary moisture measurement method involves determining the mass of an undried and dried sample to determine the amount of water in the sample (armstrong et al., 2017). in secondary methods, the mc is determined indirectly from the empirical relationship between physical and chemical features and the actual mc obtained from primary methods such as standard oven drying methods (chen, 2003). some common instruments used in secondary methods such as moisture meters and probes rely on the electrical characteristics of the grain, such as capacitance and conductance (armstrong et al., 2017) and are calibrated against the oven-based moisture determinations. heating whole grain in a hot air oven is the most widely used method for moisture content determination (asae, 2002), however the long drying time necessitated the development of moisture meters and probes. the need for a low-cost moisture meter in developing countries has been advocated for several years to help mitigate postharvest losses of grain (world bank, 2011; maier, 2015). fast as well as field usable portable grain moisture meters and probes are a necessity to meet the requirements of farmers, grain storage personnel and agricultural products marketing corporations (rai et al., 2005). commercially available moisture meters include two low cost meters by developed country standards; the post-harvest loss (phl) meter which was developed under a usaid project to reduce post-harvest loss (~us$100) and john deere portable device (~us$260, 2018 price). the gac 2100 bench-top moisture meter is an approved moisture tester by the grain inspection, packers and stockyards administration (gipsa) and has been a highly regarded and used electronic meter (~us$3600, 2018 price). the objective of this research was to demonstrate the accuracy of three moisture meters compared to the oven-dried reference method. the meters are — post-harvest loss (phl) meter developed by the usda-ars center for grain and animal health research, manhattan ks, john deere moisture chek plus, model sw08120 (agratronix streetsboro, ohio) and grain analysis computer gac 2100 agri (dickey-john corp., auburn, ill.). both laboratory and field tests of these four moisture measurements were carried out to validate their performance and to provide basic information on moisture levels of maize over a 12-month storage period. 2.0 materials and methods 2.1 maize maize used in this study was sourced from a single local farm in order to ensure uniformity of maize used for the study. moisture content measurements of maize samples were collected during a study of insect infestation of bagged grains in a storehouse located in arisekola market, bodija, ibadan (7°25’59 n, 3°54’43 e) from february 2017 – january 2018. batches of 50 kg of maize were placed individually in bags according to the various treatments as follows: (1) untreated polypropylene (pp) bags,(2) insecto diatomaceous earth–treated pp bags, (3) pics bags, (4) pp bags with a single hermetic liner, (5) zerofly storage bags, (6) insecto diatomaceous earth-treated zerofly storage bags, (7) zerofly storage bags with two pics bag hermetic inner liners and (8) zerofly storage bags with a single hermetic liner. each bag had three subreplicates and were measured for each treatment. monthly moisture measurements were taken http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):219-224. issn 15962490; e-issn 2545-5818; www.azojete.com.ng 221 for non-hermetic treatments while moisture measurements were taken every four months for the hermetic treatments. 2.2 moisture content measurement and data collection 2.2.1 post-harvest loss (phl) meter the phl meter was used by inserting the probe deep into each storage bag of maize in the storehouse, left initially to stabilize over a 6-minutes period and then the temperature (°c) and relative humidity (%) of air surrounding the grain determined was used to calculate and display the moisture content of the grain. three measurements were taken from each bag — at the center, and opposite sides of the bag and the average moisture content, weight basis (mcwb) calculated for each bag. this procedure was performed in the storehouse. inaddition to the field moisture data, a 1.2m open-ended grain probe (seedburo equipment, chicago, il) was used to sample maize from bags. composite samples were taken from the center and opposite sides near the inner surface of each bag and placed inside labelled ziploc bags. samples collected were then transported to the laboratory for data collection. about 700 g samples collected from each bag were mixed thoroughly in a tray to ensure homogeneity for moisture readings with gac 2100, john deere moisture meters and oven-dried method. 2.2.2 gac 2100 moisture meter maize sample was poured into the top unit of the moisture meter; the load key was depressed and the sample automatically loads the grain into the test cell and a strike-off arm levels and removes the excess. after about 15 seconds, the moisture reading and grain temperature was displayed on its lcd. three sample measurements were taken and the average mcwb was calculated for each bag. moisture reading for the first month (february 2017) was however not available at the beginning of the study. 2.2.3 john deere moisture meter sampled grain was scooped with a hollow plastic spoon into the top chamber of the meter and the cap screwed on to compress the grains around the electrodes. a uniform pressure was maintained on the test sample by a plunger in the cap which contains a heavy spring, allowing the plunger shaft to protrude through the cap as pressure on the grain increases. the plunger shaft was set flush with the surface of the cap each time a sample was tested. the unit was powered by two 9v batteries to run the backlight display and the microprocessor which then reports the water content and temperature of grains digitally. three sample measurements were taken and the average mcwb was calculated for each bag. 2.2.4 oven–dried method 100 g samples (replicated two times) were oven-dried at 103°c for 72 hours (asabe, 2008) using a memmert uf 55 model 30-750 oven (memmert gmbh + co. kg, schwabach). after heating, the samples were allowed to cool inside a dessicator and the mcwb was calculated for each bag. two sample measurements were recorded and the average mc was calculated for each bag. 2.3 statistical analysis data were summarized using the spss version 20 software to evaluate means of each response variables. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ajao, et al. comparative evaluation of novel low-cost moisture meters suitable for grain moisture measurement. azojete, 14(sp.i4):219-224. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 222 3.0 results and discussion 3.1 grain moisture content in the non-hermetic bags where monthly moisture measurements were taken, moisture levels recorded by the four methods in the bagged maize were higher at the end of the study compared with moisture levels at the beginning (fig. 1). in the hermetic bags, slight increases in moisture readings were observed in months when measurements were taken (fig. 2). mcwb readings using the oven-dried method were uniformly lower than all the 3 moisture meters used (figs. 1 and 2). among the moisture meters, gac 2100 meter readings were consistently lower than the phl and john deere meters. there were variations in the monthly measurements of moisture in the triplicate bags during storage period. moisture readings progressively increased during the rainy season (april to october) but fell during the dry season (november to january). high humidity observed during the rainy season which allows moisture gain from the surrounding air and low humidity during the dry season accounted for the initial gain and later, loss of moisture from the grains during the study. this appears to show that bagged grains respond readily to monthly variation in climatic conditions (armstrong et al., 2017). combined moisture measurement for all bags (hermetic and non-hermetic) showed that the john deere, phl and gac meter readings had mean positive differences of 2.34 ± 0.34%, 1.64 ± 0.27% and 1.08 ± 0.31% mcwb respectively, relative to the oven-dried method. comparing the moisture meters, john deere meter had a mean positive variance of 1.26 ± 0.38% mcwb relative to gac 2100 and phl meter had a mean positive variance of 0.56 ± 0.25% mcwb. this result was in agreement with armstrong et al., 2017 who showed that phl meter readings were lower than john deere moisture meter stating average positive differences of 0.45% and 2.12% mcwb for phl and john deere meters respectively, relative to the gac 2100 meter. overall, moisture levels in the bagged maize over the 12–month storage period were within safe levels for maize storage; an average of 12.82% mcwb was recorded in all the bags. the highest moisture level recorded for any bag was 15.5% using john deere meter. 4.0 conclusion the use of robust moisture meters is important for farmers and grain managers to constantly monitor moisture levels of stock. the phl meter, john deere meter and gac 2100 meter provide simple and rapid prediction of moisture readings of stored grains in the field and laboratory, thus enabling farmers to make quick decisions on the maintenance of quality of their grains. 5.0 acknowledgement we thank the usda/usaid funded nigeria agriculture capacity strengthening program for the moisture meters used in this study. special thanks to the food and nutrition laboratory, iita ibadan for providing bench space to conduct the oven dried test. this study was funded by the swiss agency for development and cooperation. mention of proprietary product does not constitute a guarantee of the product by the authors, institutions and sponsor, and does not imply its approval to the exclusion of other products that may also be suitable. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):219-224. issn 15962490; e-issn 2545-5818; www.azojete.com.ng 223 fig 1: monthly moisture measurement in the non-hermetic bagged maize from february 2017 to january 2018. fig 2: quarterly moisture measurement in the hermetic bagged maize from february 2017 to january 2018. references armitage, d., wontner-smith, t. and wilkin, r. 2008. grain moisture – guidelines for measurement. hgca publication. caledonia house, london. www.hcga.com. armstrong, pr., mcneil, sg., manu, n., bosomtwe, a., danso, jk., osekre, e. and opit, g. 2017. development and evaluation of a low-cost probe-type instrument to measure the equilibrium moisture content of grain. applied engineering in agriculture, vol. 33(5): 619627 https://doi.org/10.13031/aea.12266 asabe standards. 2008. moisture measurement – unground grain and seed. standard engineering practices data. american society of agricultural and biological engineering, 56th ed., p 668 asae standards. 49th ed. 2002 d245.5. moisture relationships of plant-based agricultural products. st. joseph, mich.: asae. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ajao, et al. comparative evaluation of novel low-cost moisture meters suitable for grain moisture measurement. azojete, 14(sp.i4):219-224. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 224 casada, me. and armstrong pr. 2008. wheat moisture measurement with a fringing field capacitive sensor. an asabe meeting presentation, providence, rhode island. paper number: 085207. chen, c. 2003. evaluation of air oven moisture content determination methods for rough rice. biosystems engineering 86(4): 447-457. doi: 10.1016/j.biosystemseng.2003.08.010 maier, de. 2015. intervention strategies for the reduction of postharvest loss: case studies. proceedings of the 1st international congress on post-harvest loss prevention. urbana champaign, il: adm institute for the prevention of postharvest loss, university of illinois. obi, fo., ezeoha, sl. and egwu, co. 2016. evaluation of air oven moisture determination procedures for pearl millet (pennisetum glaucum l.). international journal of food properties, 19:2, 454-466, doi: 10.1080/10942912.2015.1038566 rai, ak., kottayi, s., and murty, sn. 2005. a low cost field usable portable digital grain moisture meter with direct display of moisture (%). african journal of science and technology science and engineering series, 6(1), 97-104. world bank 2011. missing food: the case of postharvest grain losses in sub-saharan africa. report no. 60371-afr. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):261-268 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 261 original research article infiltration capacity of compacted lime treated black cotton soil as hydraulic barrier material a. n. alkali*, i. m. shettima, b. b. kurna and n. y. okunade department of civil and water resources engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: abdulhamidalkali.aa@gmail.com 1.0 introduction groundwater constitutes about 0.6% of the total amount of water on earth and about 21.4% of the total freshwater resources on the planet (mustafa and yusuf, 2012). water is regarded as one of the scarcest natural resources on the earth free of pathogens. despite its quality, shallow groundwater sources in particular are susceptible to contamination from numerous sources notable of which are sanitary landfills. the largest factor influencing the contamination from these sources is due mainly to the level of ease at which the underlying soil beneath landfills allows the movement of these contaminants into the much-needed groundwater. waste containment facilities mostly called sanitary landfills are solid waste disposal facilities that operate by compressing the wastes while spreading soil and compacting in layers. these contaminants or leachate from soils with high hydraulic conductivity move vertically and contaminate the underlying groundwater. hydraulic conductivity is a measure of a porous media to conduct liquid (chen and chynoweth, 1995). the minimum requirements recommended in achieving a hydraulic conductivity is less than or equal to1.0x10-9m/s for most soil lining materials. various leachates carry physical, chemical or bacteriological contaminants which are detrimental to human health. consequently, several studies have attempted to prevent the contamination of the underlying soil from leachate by reducing the hydraulic conductivities of the underlying soil of the waste containment facilities. the layer of the containment facility system generally referred to as liners have been developed with other raw materials such as rice husk ash, groundnut shell ash, fly ash, oil palm ash, lime etc. on a variety article information abstract studies have shown the effect of hydraulic barriers in the reduction in movement of leachates, that have the potential of contaminating groundwater. laboratory tests were conducted on black cotton soil treated with up to 5% lime by dry weight to assess its suitability in waste containment facilities. the test samples were subjected to particle size distribution analysis, consistency limit tests, compaction and hydraulic conductivity. the compaction energy of british standard light (bsl) was employed. the study showed decrease in liquid limit from 65.20% to 56.30% and plasticity index from 41.50% to 28.58% while plastic limit increased from 23.70% to 27.72% with the increase lime content. maximum dry density (mdd) increases with increased in lime from 1.78 to 1.88 g/cm3 whereas the optimum moisture content (omc) decreased from 19.79% to 15.39%. hydraulic conductivity of black cotton soil treated with percentage of lime content 0%, 1%, 3% and 5% of the soil weight examined for a period of 28days. the hydraulic conductivity value of natural soil was 1.65e-08 and decreased to 3.71 e-09 m/s at 5% lime content. therefore, it is clear that hydraulic conductivity decreases with percentage increase in lime content. it is recommended that volumetric shrinkage, free swell and unconfined compressive strength should be carried out. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 march, 2018 revised 7 september, 2020 accepted 13 sept., 2020 keywords: alkali et al: infiltration capacity of compacted lime treated black cotton soil as hydraulic barrier material. azojete, 17(3):261-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 262 of soil types. other materials that have been used includes; geosynthetic materials, processed clay, cement kiln dust (ckd), plastics, glass, and scrap tyres (moses and afolayan, 2011). black cotton soils are expansive soils which are characteristically grey or black in colour and mostly confined to semi-arid regions. the soil is mostly available where annual precipitation is exceeded by evaporation and also derives its name due its suitability for growing cotton (oriola and moses, 2011). the cohesive nature of clay soils makes them a suitable integral component of the lining system (osinubi and moses, 2011). lime has been widely used either as a modifier for these clayey soils or as a binder. when clayey soils with high plasticity such as black cotton soils are treated with lime, the plasticity index is decreased and has less affinity to water (modak et al., 2012). lime had also been used to stabilize (i.e. impede) the hydraulic conductivity of fly ash. in addition to decreasing the permeability of clay, lime offers resistance against chemical attack by organic solutions, which is one of the vital requirements of waste containment facilities (moses and afolayan, 2011). most of these materials have oxide compositions rich in calcium, silicon and aluminium and are mixed with soils having relatively low hydraulic conductivities such as black cotton soil and laterite which is in relative abundance in the area of study covered by this research. 2. materials and methods 2.1 materials 2.1.1 black cotton soil and lime: black cotton soil was obtained from a borrow pit along yola road at kumo, akko local government area, gombe state, nigeria. this was achieved using disturbed sampling method which lies on latitude 100 2’ 43’’n and longitude 110 12’ 47’’e. soil specimens were treated with 0, 1 ,3 and 5% lime by dry weigh of soil. the lime used was purchased in monday market, maiduguri, borno state. 2.2 methods 2.2.1 index properties: laboratory tests were carried out to determine the index properties of both natural and lime treated soils. the test was conducted in accordance with british standard (bs) 1377(1990) for the natural soil and bs 1924 for the lime treated soil. 2.2.2 compaction: the compactive effort used was bsl. air dried soil samples passing through bs sieve with 4.76mm aperture mixed with 0%, 1%, 3% and 5% lime by weight of dry soil were used. the tests for both the natural and stabilized soils were conducted according to bs 1377 (1990) part 4. the british standard light is the effort derived from 2.5kg rammer falling through 30cm onto three layers, each receiving 27 uniformly distributed blows. 2.2.3 hydraulic conductivity: the specimens were placed into rigid wall permeameters for hydraulic conductivity testing. all tests were conducted using the falling-head method in accordance with procedures described by head (1992). a relatively short sample was connected to a standpipe, which provided the head of water flowing through the sample. black cotton soil – lime samples at the different lime contents (0, 1, 3, and 5%) and respective omcs were compacted using bsl compactive efforts. specimens were soaked in a water tank for a minimum period of 24 hours to allow for full saturation and the samples were restrained from swelling vertically during saturation. in the course of the permeation however, the specimens were allowed to swell vertically i.e. no vertical stress was applied. the fully saturated test specimens were then connected to a permeant liquid (tap water). hydraulic gradient ranged from 5 to 15. tests were only discontinued when hydraulic conductivity readings were steady. 2.2.4 oxide composition of lime: oxide composition of the lime was determined using x-ray fluorescence (xrf) machine (philips pw1606) at the chemistry department of ahmadu bello arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):261-268. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 263 university zaria, kaduna state. the xrf analysis is based on the principle that individual atoms, when excited by external energy source, emit x-ray photons of a characteristic wavelength. by counting the number of photons of each energy emitted from a sample, the elements present is identified and quantified. the system depends on semi-conductor type detectors which receive the entire emitted spectrum from the sample and decode it into histogram of number of counts versus photon energy (ehieromosele et al., 2012). the machine has a very sensitive and accurate power of determining trace and major elements and their oxides in both geologic and biological samples. one gram of well homogenized lime was taken into the machine which was automatically analyzed, and results given. 3. results and discussion 3.1 chemical oxide composition of the lime the oxide composition of the lime analyzed using phillips-pw-1606 x-ray fluorescence (xrf) spectrometer is presented in table 1. the essential oxides of lime comprise of cao, sio2, al2o2 and fe2o2 having 76.42%, 7.33%, 1.99% and 1.07 respectively. cao has the highest oxide composition which is also the major constituent responsible for the reactions in stabilization process. these reactions include cat-ion exchange, flocculation-agglomeration, carbonation, and pozzolanic reaction (khan et al., 2004). table 1: oxide composition of lime oxides sio2 fe2o2 al2o2 cao mgo na2o composition (%) 7.33 1.07 1.99 76.42 2.12 0.00 3.2 physical properties of the soil the physical properties of the black cotton soil used are presented in table 2 while the particle size distribution curves are presented in figure 1. the results of preliminary investigations conducted on the natural black cotton soil show that the soil is fine-grained, with a natural moisture content of 6.26%. the soil belongs to the cl group in the unified soil classification system (uscs), (astm, 1992) or a-7-6(10) soil group of the american association of state and transportation officials (aashto) soil classification system (aashto, 1986). the soil has a liquid limit of 65.20%, 23.70% plastic limit and 41.50% plasticity index. table 2: physical properties of the soil properties 0% 1% 3% 5% natural moisture content (%) 6.28 liquid limit 65.20 58.90 57.20 56.30 plastic limit 23.70 25.93 26.71 27.72 plasticity index 41.50 32.97 30.49 28.58 specific gravity 2.66 2.62 2.58 2.56 percent passing bs no.200 sieve 53.9 64.50 69.05 69.20 asshto soil classification a-7-6(10) unified soil classification system cl cl cl cl cl-clay loam the liquid limit and the plasticity index values decreases with increase in lime contents while the plastic limit increased, possibly due to the exchange reaction which flocculates the soil particles together and reduces the clay size fraction and hence the soil surface area (osula 1991). this trend is similar to the findings reported by osinubi and katte (1997) for black cotton soils. alkali et al: infiltration capacity of compacted lime treated black cotton soil as hydraulic barrier material. azojete, 17(3):261-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 264 figure1: particle size distribution curves for black cotton soil treated with lime the variation of the specific gravity of black cotton soil-lime mixture is presented in figure 2. the specific gravity of the natural soil decreased from 2.66 to a least value of 2.56 at 0% to 5% lime. this decrease is due to the low specific gravity value of lime (2.1) which gradually replaced the soil material. the decrease also indicated that mineralogical alteration has not taken place with the mha (kumar, 2012; amadi, 2010). figure 2: variation of specific gravity of the black cotton-lime treated soil 3.3 compaction 3.3.1 maximum dry density the variation of the maximum dry density (mdd) of the treated soil is shown in figure 3. the value initially decreased from 1.78 to 1.71 g/cm3 and later increased. it ranges from 1.78 for the natural soil to 1.88 g/cm3 for the lime treated soil. this is as a result of the lime occupying the void within the soil matrix and in addition, the flocculation and agglomeration of the clay particle due to exchange of ions (oriola and moses, 2010; moses, 2008). 0 20 40 60 80 100 120 0.01 0.1 1 10 % p as si n g particle size(mm) 0% lime 1% lime 3% lime 5% lime 2.54 2.56 2.58 2.6 2.62 2.64 2.66 2.68 0 1 2 3 4 5 6 sp ec if ic g ra vi ty lime content(%) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):261-268. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 265 figure 3: variation of maximum dry densities for black cotton soil treated with lime 3.3.2 optimum moisture content the omc of the black cotton soil treated with lime reveals a decrease in the omc values from 19.79 to 15.39% with the addition of lime from 0 to 5%. the trend is depicted in figure 4. the decrease in the omc is probably due to self – desiccation in which all the water was used, resulting in low hydration. in a situation where no water movement to or from the lime – paste, the water is exhausted in the hydration reaction, until small amount is left to saturate the solid surfaces which tend to reduce the relative humidity within the paste. this might have affected the reaction mechanism of the lime treated black cotton soil (moses, 2008; osinubi and stephen, 2007). figure 4: variation of optimum moisture content for black cotton soil treated with lime 3.4 hydraulic conductivity the variation of hydraulic conductivity of the black cotton soil treated with lime at different dosages is shown in figure 5. 1.7 1.72 1.74 1.76 1.78 1.8 1.82 1.84 1.86 1.88 1.9 0 1 2 3 4 5 6 m ax im u m d ry d en si ty ( g/ cm 3 ) lime content (%) 0 5 10 15 20 25 0 1 2 3 4 5 6 o p ti m u m m o is tu re c o n te n t (% ) lime content (%) alkali et al: infiltration capacity of compacted lime treated black cotton soil as hydraulic barrier material. azojete, 17(3):261-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 266 figure 5: variation of hydraulic conductivity for black cotton soil treated with lime the trend is that of decrease in the hydraulic conductivity with the natural soil having a value of 1.65×10-8 m/s. the values further decreased to 1.4×10-8 m/s, 9.74×10-9 m/s and 3.71×10-9 m/s for 1%, 3% and 5% lime treatments respectively. hydraulic conductivity generally decreased with higher molding water content. however, in this study, only the respective optimum water contents were used in preparing the samples and hence the non-rapid decrease in the hydraulic conductivity. the reduction in hydraulic conductivity is due to the arrangement of individual particles influenced by molding water content. it could also be attributed to the soft wet clods of soil that are easily remolded resulting in smaller inter-clod voids and hence lower hydraulic conductivity (osinubi and eberemu, 2009). 4.0 conclusion the suitability of lime-treated black cotton soil for use as compacted hydraulic barrier in waste containment facilities has exhibited a reduction in infiltration capacity with increase in lime content. black cotton soil was treated with 0%, 1%, 3% and 5% lime content by weight of the soil. increase in lime content decreased the liquid limit, shrinkage limit and plasticity index of black cotton soil while the plastic limit increased. the mdd generally increased from 1.78 to 1.88 g/cm3 while the omc decreased from 19.79 to 15.39% with increasing lime content. interestingly, an increase in lime content reduced the hydraulic conductivity of the soil. the least hydraulic conductivity value obtained was 3.71×10-9 m/s at 5% lime treatment. this study shows that obtaining hydraulic conductivity lower than 1×10-9 m/s with lime treated black cotton soil is possible, provided that the compaction procedure (water content and compaction technique) is well chosen. finally, it is recommended that the hydraulic conductivity of the soil should be explored using -2, +2, +3 and +4% of the optimum moisture content of 0.00e+00 2.00e-09 4.00e-09 6.00e-09 8.00e-09 1.00e-08 1.20e-08 1.40e-08 1.60e-08 1.80e-08 0 1 2 3 4 5 6 h yd ra u lic c o n d u ct iv it y (m /s ) lime content(%) arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):261-268. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 267 the natural soil. tests such as unconfined compressive strength (ucs) and volumetric shrinkage strain (vss) should also be conducted to ascertain the accepted range for the established criteria. references aashto.1986. standard specification for transportation, material and methods of sampling and testing. 14th ed. washington, d.c. amsterdam association of state highway and transportation official. amadi, aa. 2010. pozzolanic influence of fly ash in mobilizing the compressive strength of lateritic soil. aujt., 14(2): 139-146. astm.1992. annual book of standards. philadelphia. american society for testing and materials. 04(8). british standard institute bs 1924.1990. method of test for stabilized soils. british standard institute, london, u.k. british standard institute. bs 1377. 1990. methods of testing soils for civil engineering 2 purposes, london. chen, t. and chynoweth, dp. 1995. hydraulic conductivity of compacted municipal solid waste. bio-resource technology, elsevier science limited, amsterdam. head, kh. 1992. manual of soil laboratory testing. permeability, shear strength and compressibility tests. pentech press, london. ehi-eromosele, co., adaramodu, aa., anake, wu., ajanaku, co. and edobor-osoh, a. 2012. comparison of three methods of digestion for trace metal analysis in surface dust collected from an e-waste recycling site. nature and science, 10(10): 42-47. khan, fi., tahir, h. and ramzi, h. 2004. an overview and analysis of site remediation technologies. journal of environmental management, 71: 95122. kumar, smp. 2012. silica and calcium effect on geo-technical properties of expansive soil extracted from rice husk ash and lime. international conference on environment science and engineering, ipcbee, 3(2): 119-123. modak, pr., nangare, pb., nagrale, sd., nalawade, rd. and chavhan, vs. 2012. stabilization of black cotton soil using admixtures. international journal of engineering and innovative technology, 1(5): 1-3. moses, g. 2008. stabilization of black cotton soil with ordinary portland cement using bagasse ash as admixture. irji journal of research in engineering, 5(3): 107-115. moses, g. and afolayan, jo. 2011. compacted foundry sand treated with cement kiln dust as hydraulic barrier material. electronic journal of geotechnical engineering, 16: 337-335. mustafa, s. and yusuf, mi. 2012. a textbook of hydrology and water resources. topsmerit page publishers, abuja. osinubi, kj. and katte, vy. 1997. effect of elapsed time after mixing on grain size and plasticity characteristics; soil lime mixes. nigeria society of engineers technical transactions, 32(4): 65-76. alkali et al: infiltration capacity of compacted lime treated black cotton soil as hydraulic barrier material. azojete, 17(3):261-268. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulhamidalkali.aa@gmail.com 268 osinubi, kj. and stephen, ta. 2007. influence of compactive efforts on bagasse ash treated black cotton soil. nigerian journal of soil and environmental research, 7(1):92-101. osinubi, k j. and eberemu, ao. 2009. compatibility and attenuative properties of laterite blast furnace slag mixtures. journal of waste technology and management, 35(1): 7 – 16. osinubi, kj., and moses, g. 2011. compacted foundry sand treated with bagasse ash as hydraulic barrier material. proceedings of the american society of civil engineers, geo frontiers congress, march, 13-16, 2011, dallas, texas, pp. 915-925. . osula, doa. 1991. lime modification of problem laterite. engineering geology, 30: 141-149. oriola, f. and moses, g. 2010. groundnut shell ash stabilization of black cotton soil. electronic journal of geotechnical engineering, 15: 415-428. oriola, f and moses, g. 2011. compacted black cotton soil treated with cement kiln dust as hydraulic barrier material. american journal of scientific and industrial research, 2(4): 521-530 arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(1):31-40 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 23 original research article preparation and characterization of steam activated chicken eggshell for gaseous pollutant adsorption a. m. o. abdul raheem* and e. a. adeoye department of chemistry, university of ilorin, p.m.b. 1515, ilorin, nigeria *corresponding author’s email address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 1.0 introduction environmental pollution is a worldwide problem and its potential to influence the health of human populations is great. developmental activities such as construction activities, transportation and manufacturing not only deplete the natural resources but also produce a large volume of wastes that leads to air and water pollution, soil degradation, and oceans; global warming and acid rains. the disposal of untreated waste is a major cause of river pollution and environmental degradation causing ill health and loss of crop productivity (fereidoun et al., 2007). additionally, african and asian countries experiencing rapid industrial growth, and this is making environmental conservation a difficult task (waziri et al., 2010). anthropogenic air pollution results from industrial activities, fossil fuel generator fumes, chemical exposures, vehicular emissions and so on. the pollutant molecules such as sulphur oxides (sox), nitrogen oxides (nox), lead, ozone, benzene, carbon oxides (cox), arsenic, cd, hg and particulate matters (pm) have a negative effect on human health, which can rapidly spread abroad causing health instability in the system. when the concentrations of these molecules/particles in the air exceed the international standards, the air is article information abstract air pollution is a major issue because it can immediately cause health problems. the primary pollutants are oxides of nitrogen, sulphur, carbon, and oxidants. the collection, preparation, and characterization of chicken eggshell for the production of activated carbon useful in air purification, was carried out. the preparation was done in succession from raw uncarbonized to carbonized and then to steam activated form for adsorption of air pollutants. powdered eggshell was carbonized at different temperatures in the range of 150-600 ºc to achieve optimum and effective temperature for best carbon content from its char. the best carbon yield was gotten at 450 ºc/1 hour in a carbolite type muffle furnace which gives less room for air flow. thermal / steam activation of the carbonized eggshell was done at 500 ºc for 1 hour. the ash content, bulk density, electrical conductivity, ph, and moisture contents were analyzed respectively. the samples were characterized for their surface area and pore volume. the ash contents for the three samples were in the order uncarbonized (41.76 %) > carbonized (32.62 %) > stean activated (29.47 %) while the bulk density followed carbonized (1. 19 g/ml) > steam activated (1.11 g/ml) > uncarbonized (0.79 g/ml). all the three samples had the same value of 0.31 ms/cm for the electrical conductivity while two of the samples (carbonized and activated) had the same ph (8.1) and uncarbonized had a lower ph (7.9). the moisture contents ranged from 2 to 9 % with steam activated sample having the least and uncarbonised, the highest. tapping density, surface area, pore volume, iodine number, % iodine absorbed values followed the order steam active > carbonized > uncarbonized samples. the steam activated sample having the highest values of all these parameters showed it possesses high adsorption capacity for gaseous pollutants. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 april, 2019 revised 23 november, 2021 accepted 20 december, 2021 keywords: chicken eggshell activation pollutants bet sem morphology http://www.azojete.com.ng/ mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng galley proof arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):31-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 32 considered polluted. therefore, measures need to be taken to reduce the rate of ambient air pollution if man must survive. the use of agricultural wastes such as chicken eggshells to remove air pollutants by simple adsorption process cannot be over-emphasized most especially because of the tonne of waste it constitutes to the environment in nigeria. hen eggshell typically consists of ceramic materials constituted by a threelayered structure, namely the cuticle on the outer surface, a spongy (calcareous) layer and an inner lamellar (or mammillary) layer (stadelman, 2000). the spongy and mammillary layers form a matrix composed of protein fibers bonded to calcite (calcium carbonate) crystal. the two layers are also constructed in such a manner that there are numerous circular openings (pores). this structure permits gaseous exchange throughout the shell. the outer surface of the eggshell is covered with a mucin protein that acts as a soluble plug for the pores in the shell. the cuticle is also permeable to gas transmission. the chemical composition (by weight) of by-product eggshells has been reported as follows: calcium carbonate (94 %), magnesium carbonate (1 %), calcium phosphate (1 %) and organic matter (4 %) (stadelman, 2000). adsorption is one of the important procedures for the removal of gaseous pollutants from the environment because of its strong affinity and high loading capacity. previous studies have proved that chicken eggshell (es) is an aviculture by-product that has been listed worldwide as one of the worst environmental problems, especially in those countries where the egg product industry is well developed. in the u.s. alone, about 150,000 tons of this material are disposed of in landfills. es contains about 95 % calcium carbonate in the form of calcite and 5 % organic materials such as type x collagen, sulfated polysaccharides, and other proteins (toro et al., 2007; hussein et al., 2011). the report has shown, among other characteristics that es has a relatively lower density compared to the mineral calcium carbonate. eggshell is a biomaterial containing 95 % by weight of calcium carbonate in the form of calcite and 5 % by weight of organic materials, such as (al2o3, sio2, s, cl, p, and cr2o3, mno) (hussein et al., 2011). the generalized eggshell structure, which varies widely among species, is a protein linked with mineral crystals, usually of a calcium compound such as calcium carbonate these characteristics qualify es as a good candidate for bulk quantity, inexpensive, lightweight and low load-bearing composite applications, such as the automotive industry, trucks, homes offices, and factories. hussein et al. 2011 studied the water absorption and mechanical properties of high–density polyethylene/ es composite, it was found that the addition of eggshell powder to the polymer leads to a decrease in the tensile strength, modulus of elasticity and shore-d hardness. on the other hand, it increases the percentage elongation at break and impact strength. water absorption of the behaviour of the composites as a function of days was also investigated, and it increases by increasing exposure time for the same filler content. the adsorption efficiency of eggshell powder for removal of cu and pb were studied (ali et al., 2016). eggshell powder consists of calcium carbonate, magnesium carbonate, calcium phosphate and protein (animesh, 2013). the research was a batch scale experiment using different amounts of adsorbent in solution with five different concentrations (5, 10, 20, 40, 100 mg/l) of both metals and mixed combinations. about 92 % to 100 % cu removal was achieved by using 0.5 to 1.5 g adsorbent for a solution having concentrations of 5 and 10 mg/l of cu. two main things were observed from the study which showed that adsorption efficiency depends on the amount of adsorbent as the adsorption efficiency of pb was increased from 80 % to 100 % in the same solution (5 mg/l), it was also found that adsorption efficiency decreased by 2.5 % and 6.5 % of cu and pb to a mixed metal solution. this indicates that the presence of more metals in the solution will decrease the adsorption efficiency. it is therefore clear that eggshell is a good adsorbent for the removal of cu and pb and will have a better result by using eggshell in excess (agarwal, 2013). ../../../../user/downloads/azojete143/www.azojete.com.ng mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng abdul raheem and adeoye: preparation and characterization of steam activated chicken eggshell for gaseous pollutant adsorption. azojete, 18(1):31-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 33 the present study is aimed at creating a human-friendly environment by converting common household wastes in nigeria (chicken eggshell) into useful materials for air purification. 2.0 materials and methods 2.1 materials, reagents and equipment the apparatus and equipment used includes: laboratory glasswares, laboratory sieve, crucible, desiccator, stirrer, measuring cylinder, mass balance, ph meter, filtration set-up, conductivity meter, carbolite muffle furnace, analytical weighing balance, test tubes, beakers, burette, pipette, conical flask (100 ml and 250 ml), desiccator, electric oven with thermostat, evaporating dish, funnel, graduated cylinder (100 ml), hot plate, magnetic stirrer, mechanical shaker, ph meter, pipette, pipette pump, spatula, standard flasks (1000 ml and 100 ml), suction flask, whatman filter paper. reagents used include, potassium hydroxide (koh), distilled water, sodium hydroxide (naoh), iodine crystal (i2), sodium thiosulphate (na2s2o7), starch, hydrochloric acid (hcl), hydrogen peroxide (h2o2), tetraoxosulphate (vi) acid (h2so4), sodium carbonate (na2co3), potassium iodate (kio3), n-(1naphthyl)-ethylenediaminedihydrochloride solution, acetone (ch3coch3), glacial acetic acid (ch3cooh), sodium di-oxo nitrate (iii) (nano2), sulphanilic acid (hnc6h4so3), potassium dihydrogen phosphate (kh2po4), disodium hydrogen phosphate (na2hpo4) and methyl orange. 2.2 sample collection and preparation chicken eggshells (figures 1 and 2) used in the experiment were collected free of charge from different hotels, food vendors, kitchens and eateries located within ilorin, kwara state, nigeria. the samples were then washed with distilled water several times to remove dirt particles and dried for three hours in an oven at 150 0c. it was then allowed to cool to room temperature and subsequently crushed and sieved to prepare uniform size powder. the dried chicken eggshell powder of 2.00 mm particle size was determined using a laboratory tested mesh size sieve. the eggshell powder comprises its shell and membrane, which in turn is made up of 94 % caco3, with a small amount of mgco3, calcium phosphate and other organic matter including protein. carbonization of powdered eggshells was carried out at a different temperature to obtain an optimum and effective temperature for the best carbon content from its char. thermal/steam activation of the carbonized eggshell was done at 500 0c for 1 hour which is the most effective time for steam activation (schaafsma et al., 2000). figure 1: uncarbonized chicken eggshell figure 2: uncarbonized chicken eggshell granules http://www.azojete.com.ng/ mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng galley proof arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):31-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 34 2.3 carbonization and activation carbonization of powdered eggshells (figures 3 and 4) was carried out at different temperatures to obtain an optimum and effective temperature for the best carbon content from its char. temperature of 450 0c for 1 hour in a carbolite type muffle furnace which gives less room for airflow (rohazriny et al., 2014). thermal/steam activation of the carbonized eggshell was done at 500 0c for 1 hour which is the most effective time for steam activation (tadda et al., 2016). 2.2 determination of physical properties 2.2.1 determination of electrical conductivity conductance is defined as the reciprocal of the resistance involved and expressed as milli-siemens per meter or centimeter (apha, 1995). (1) conductivity was determined by using hanna instruments hi-2030-02 edge bench conductivity meter. 2.2.2 moisture content determination the thermal drying method was used to determine the moisture content of the samples. 1.0 g of the (carbonized, uncarbonized and steam activated chicken eggshell) samples were weighed in triplicates. the crucible was placed in an oven at 105 °c to constant weight for 4 hours according to the method of rengaraj (ekpete et al., 2011). the difference between the initial and final mass of the carbon represents the moisture content. the percentage moisture content (%) was computed as follows: (2) 2.2.3 determination of bulk density a 30 g sample of each powder was weighed out and gently introduced into a 100-ml measuring cylinder. the volume occupied by the powder was noted. this represents the bulk volume of the powder. the cylinder was tapped 200 times on the wooden platform to a constant volume of the powder. the volume occupied by the powder after tapping was noted. this represents the tapped volume. the procedure was repeated three times. then a weighted (known) sample was placed in a dry measuring figure 4: steam activated chicken eggshell granules figure 3: carbonized chicken eggshell granules ../../../../user/downloads/azojete143/www.azojete.com.ng mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng abdul raheem and adeoye: preparation and characterization of steam activated chicken eggshell for gaseous pollutant adsorption. azojete, 18(1):31-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 35 cylinder and tapped until the carbon samples occupy a minimum volume known as the bulk volume (bv), this was read from the calibration. the bulk density (bd) was then calculated from the equation. (g/ml). (3) m1= mass of measuring cylinder in grams m2= mass of measuring cylinder + its contents v= volume of the measuring cylinder 2.2.4 tapping density (td) the tapped density (g/ml) is an increased bulk density attained after mechanically tapping a container containing the powder sample. the tapped density is obtained by mechanically tapping a graduated measuring cylinder or vessel containing the powder sample. (4) 2.2.5 bet surface area (bet) brunauer, emmett and teller are the three men who proposed a theory to measure the surface area of porous powder-type solid particles. the principle involved is the adsorption of gas molecules to the surface of the solid whose surface area is required. from the area of each molecule, the whole area of the solid can be calculated. bet theory is based on multilayer adsorption with considering the following assumptions: a. gas molecules can be physically adsorbed on the solid surface and form infinite layers b. there is no interaction between layers c. langmuir theory is applied to each layer 2.3 determination of chemical properties 2.3.1 determination of ph the ph meter was first calibrated, and then the standard test method for the determination of activated carbon ph astmd3838-80 was used. 1.0 g each of uncarbonized, carbonized and activated carbon eggshell was weighed and transferred into a beaker. 100 ml of distilled water was measured and added and stirred for one hour. the samples were allowed to stabilize before the ph was measured using a ph meter hanna instruments, portable ph meter, h1981-6 ph/ec/tds temperature (ekpete et al., 2011). 2.3.2 ash content determination for ash content determination, 1.0 g of each sample was transferred into the crucibles. the crucibles containing the samples were placed in the furnace and the temperature was increased and samples heated to 500 °c for 1 hour 30 minutes, then removed and allowed to cool in a desiccator to ambient temperature and weighed. the ash content was calculated using the equation below (ekpete et al., 2011). (5) http://www.azojete.com.ng/ mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng galley proof arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):31-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 36 2.2.3 volatile matter determination volatile matter was calculated using the equation (ekpete et al.,2011). (6) 2.3.4 determination of iodine number 0.5 g ac from each sample from the determination of volatile matter was weighed into a beaker and 25 ml of standard iodine solution (0.0229 m) confirmed concentration after standardization was added. the mixture was swirled vigorously for 10 minutes and filtered using a funnel impregnated with clean filter paper. 20 ml of the clear filtrates was titrated with the standard (0.1115 m) thiosulphate confirmed concentration after standardization to a persistence of a pale-yellow color. 5 ml of freshly prepared starch indicator solution was added, and titration resumes slowly until a colorless solution appeared, the procedure was repeated for the remaining samples. the titration was also repeated with 20 cm3 portions of the standard iodine solution (not treated with ac from the precursor) to serve as blank titration. the iodine adsorption number (ian) was calculated from the relationship as equation below (itodo et al., 2010). (7) where: ms = molarity of thiosulphate solution (mol/dm3). vs = volume of thiosulphate (cm3) used for titration of the pac aliquot. vb = volume of thiosulphate (cm3) used for blank titration. ma = mass of ac (g) 2.3.5 the percent iodine adsorbed the percent iodine adsorbed by each carbon was calculated by applying the formula below: (8) iodine number is usually used to roughly estimate the surface area of activated carbon at room temperature conditions. it is used as an indicator for the porosity and adsorbent capacity of the activated carbon. the higher iodine number of carbons has been attributed to the presence of large micropore structure and the great probability of carbons having a large surface area due to enlargement of their pore structure (ekpete et al., 2011). 2.3.6 fixed carbon content (9) 2.3.7 scanning electron microscopy (sem) sem is one of the most versatile instruments available for the examination and analysis of microstructure morphology. this technique was used to study the morphological feature and surface characteristics of the selected materials (kumar, 2021). 3.0 results and discussion 3.1 electrical conductivity and ph the ph used was of buffer 7 solution. the ph of the solution is a major factor in determining adsorption. ph can influence surface electric charge of the sorbent. the ph dependent variation of the potential between liquid and solid phases may be due to the polarities and deprotonation of functional ../../../../user/downloads/azojete143/www.azojete.com.ng mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng abdul raheem and adeoye: preparation and characterization of steam activated chicken eggshell for gaseous pollutant adsorption. azojete, 18(1):31-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 37 groups on the sorbent surface. generally, acidic species adsorbed better at low ph, while basic species adsorb better at higher ph. table 1 showed the ph and conductivity values of the three samples. table 1: values for ph and electrical conductivity eggshell uncarbonized carbonized steam activated ph 7.9 8.1 8.1 conductivity (mscm-1) 0.31 0.31 0.31 the conductivity values are similar for all three powdered samples. the ph values of all three samples are greater than 7 which showed that they are basic in nature. according to ahmedna, (2000) as ph increases adsorption increases, therefore carbonized and steam activated eggshells will have the highest adsorption efficiencies respectively compared to uncarbonized eggshells. 3.2 physical and chemical properties the results of physical and chemical properties of uncarbonized, carbonized and steam activated eggshells are shown in table 2. table 2: results of physical and chemical properties of the three samples from table 2, the moisture content of steam activated eggshell showed considerable amount of moisture which makes it fit for adsorption. ash content of steam activated eggshell showed the least, which makes it desirable for adsorption, because the lesser the ash content, the higher its adsorption potential. volatile matter and fixed carbon were gotten only for uncarbonized eggshells. bulk density tests for the flow consistency and packaging quantity of solid samples. generally, well aggregated, porous materials have lower bulk density. however, bulk density is important because the higher the bulk density is, the better the filterability and the better the adsorbing properties of the activated carbon (erhayem, 2015). this implies that both carbonized and steam activated eggshell will be suitable for adsorption. tapped density is an increased bulk density attained after mechanically tapping a container containing the powder sample. the tapped density is obtained by mechanically tapping a graduated measuring cylinder or vessel containing the powder sample. because the interparticle interactions influencing the bulking properties of a powder are also the interactions that interfere with powder flow, a comparison of the bulk and tapped densities can give a measure of the relative importance of these interactions in a given powder. such a comparison is often used as an index of the ability of the powder to flow. uneven powder flow can result in excess entrapped air which can affect the amount and quantity of adsorbent properties/(unit) uncarbonized chicken eggshell carbonized chicken eggshell steam activated chicken eggshell moisture content (%) 9 2 5 bulk density (g/ml) 0.79 1.19 1.11 tapping density (g/ml) 1.23 1.20 1.25 volatile content (%) 17.98 ____ ____ ash content (%) 41.76 32.65 29.47 iodine number (cm3/g) 0.207 0.276 0.322 iodine adsorbed (%) 22.2 29.6 34.6 fixed carbon content (%) 31.26 ____ _____ http://www.azojete.com.ng/ mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng galley proof arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):31-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 38 that will contact contaminants which in turn gives rise to poor adsorption rate or capacity. steam activated chicken eggshell has the highest tapped density, hence it is most suitable for adsorption. from the results showed in table 2, the iodine number calculated showed that steam activated eggshell has the highest number at 0.322 cm3/g. this showed that there is an increased number of micro-pore spaces after the steam activation process carried out on the sample. for percent iodine adsorbed, steam activated chicken eggshell showed the highest percentage of iodine adsorbed, which implies that it’s the best material for adsorption out the 3 samples. 3.3 sem analysis figure 5 showed the sem micrograph of uncarbonized eggshell of a magnification of 50, 000 on 2 micron with the surface showing several irregular structures with layers of porous structure spread all over the surface. these pores are majorly macro in nature with little micro-pores. this in turn is responsible for the poor iodine adsorption rate, for iodine adsorption is on to micro-pore and not macro-pores. adsorption of gaseous pollutants are also to micro-porous structures which implies that uncarbonized eggshell is a poor adsorbent for the adsorption of gaseous pollutants. figure 6 showed the sem micrograph of carbonized eggshell of a magnification of 50,000 on 2 micron with the surface showing several irregular structures with layers of porous structures. here, there is a change in surface morphology as a result of carbonization of the eggshell granules. this displays a mesofigure 5: sem image of uncarbonized eggshell figure 6: sem image of carbonized eggshell figure 7: sem image of steam activated eggshell ../../../../user/downloads/azojete143/www.azojete.com.ng mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng abdul raheem and adeoye: preparation and characterization of steam activated chicken eggshell for gaseous pollutant adsorption. azojete, 18(1):31-40. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 39 porous structure which is a very poor adsorption surface for gaseous pollutants, although it is also a viable adsorption surface for other forms of materials but not gaseous pollutants. figure 7 showed the sem micrograph of steam activated eggshell at a magnification of 50, 000 on 2 micron with the surface showing a considerable change in the surface morphology as a result of steam activation after it has been carbonized. it has improved micro-porous structure with fine pores and cracks. these pores provide good possibility for adsorption of gaseous pollutants, and this makes steam activation of the eggshell of an advantage and a success since it was able to give an improved sample adsorption purpose. 3.4 bet analysis bet surface area and pore volume of uncarbonized, carbonized and steam activated chicken eggshells are shown in table 3. from the above bet result of bjh analysis (table 3). it showed that steam activated eggshell has the highest surface area and pore volume, this is responsible for the differences in adsorption capacity. hence, steam activation is integral aspect of pore improvement for adsorption of gaseous pollutants thereby making steam activated chicken eggshell the best for adsorption of gaseous pollutants. 4.0 conclusion from the preparation, characterization, physicochemical analysis, bet and sem analysis carried out on uncarbonized, carbonized and steam activated chicken eggshells which is a major waste material in our environment; it was observed that steam activation of chicken eggshell favours and improves the pore spaces, pore volume, surface area, overall morphology, and adsorption capacity of chicken eggshell powder. according to iso 15901-3:2007(en) standards for micropores, mesopores and macropores, steam activated chicken eggshell showed largest amount of micropores sizes (surface area and pore volumes), thereby making it highly desirable for adsorption of gaseous pollutants since 1.00 nm is the minimum pore diameter for adsorption of sox and nox. hence, steam activated chicken eggshell is better than all the other three processed types of chicken eggshell powder for adsorption of gaseous pollutants. references ahmedna, m., marshall, w. e., and rao, r. m. 2000. surface properties of granular activated carbons from agricultural by-products and their effects on raw sugar decolorization. bioresource technology, 71(2), 103-112. animesh, a. 2013. removal of cu and pb from aqueous solution by using eggshell as an adsorbent. international journal of research in chemistry and environment, 3 (1):198-202. table 3: bet result of the three samples properties/(unit) uncarbonized chicken eggshell carbonized chicken eggshell steam activated chicken eggshell surface area (bjh) (m2/g) 3.242 5.760 6.835 pore volume (cc/g) 1.580 2.818 3.221 pore size (nm) 2.115 2.421 1.793 http://www.azojete.com.ng/ mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng galley proof arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):31-40. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: modinah4@yahoo.co.uk, amadenike@unilorin.edu.ng 40 apha 1995. american public health association: standard method for the examination of waste and water, 16: 423-517. ekpete, oa. and horsfall, mjnr. 2011. preparation and characterization of activated carbon derived from fluted pumpkin stem waste (telfairia occidentalis hook f). research journal of chemical sciences, 1(3): 10-17. erhayem, m., al-tohami, f., mohamed, r. and ahmida, k. 2015. isotherm, kinetic and thermodynamic studies for the sorption of mercury (ii) onto activated carbon from rosmarinus officinalis leaves. american journal of analytical chemistry, 6(01): 1-10. fereidoun, h., nourddin, ms., rreza, na., mohsen, a., ahmad, r. and pouria, h. 2007. the effect of long-term exposure to particulate pollution on the lung function of teheranian and zanjanian students. pakistan journal of physiology, 3(2): 1-5. hussein, aa., salim, rd. and sultan, aa. 2011. water absorption and mechanical properties of high– density polyethylene/eggshell composite. journal of basrah research (sciences), 37(3a/15): 36-42. itodo, au., abdulrahman, fw., hassan, lg., maigandi, sa. and itodo, hu. 2010. application of methylene blue and iodine adsorption in the measurement of specific surface area by four acid and salt treated activated carbons. new york science journal, 3(5): 25-33. kumar, r. 2021. microscopy, working and types. asian journal of pharmacy and technology, 11(3): 245248. rohazriny, r., razi, a., naimah, i., nasrul, h. and chezulzikrami, a. a. 2014. potential of eggshell waste for pyrolysis process. trans tech publications, switzerland, pp 77-80. schaafsma, a., pakan, i., hofstede, gjh., muskiet, fa., van der veer, e. and de vries, pjf. 2000. mineral, amino acid, and hormonal composition of chicken eggshell powder and the evaluation of its use in human nutrition. poultry science, 79(12): 1833-1838. stadelman, wj. 2000. eggs and egg products. encyclopedia of food science and technology. 2nd edition (francis, fg., (ed.)). new york: wiley and sons inc. tadda, ma., ahsan, a., shitu, a., el sergany, m., arunkumar, t., jose, b., ... and daud, nn. 2016. a review on activated carbon: process, application, and prospects. journal of advanced civil engineering practice and research, 2(1): 7-13. waziri, m. and ogugbuaja, vo. 2010. interrelationships between physicochemical water pollution indicators: a case study of river yobe-nigeria. american journal of scientific and industrial research, 1(1): 76-80 ../../../../user/downloads/azojete143/www.azojete.com.ng mailto:modinah4@yahoo.co.uk mailto:amadenike@unilorin.edu.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):295-306 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 295 original research article biolubricant production from parinari polyandra and azadirachta indica seed oils using trimethylolpropane polyol l. n. bulus* and t. e. odetoye department of chemical engineering, university of ilorin, p.m.b.1515, ilorin, nigeria *corresponding author’s email address: levibulus1@gmail.com 1.0 introduction fossil-based lubricant is commonly available in nigeria. nigeria depends heavily on fossil fuels, it is a country with a large oil reserve (owuna, 2020). petroleum based lubricants have constituted environmental pollution, affecting land and aquatic life within the ecosystem (zhang et al., 2020). addressing this challenge of environmental pollution has led to the search for suitable replacement of petroleum based lubricant (srinivas et al., 2020). environmental pollution has been on an increasing trend, where man’s activities over time has caused negative impact to the environment, leading to global warming (tippayawong et al., 2020). the united states of america is one of the leading nations in the production and use of alternative oils, hence, nigeria is also in the search for suitable bio-based lubricants (owuna, 2020). lubricating oils like biolubricants article information abstract environmental pollution over time has raised challenges that elicit concerns for the nearest future. synthetic lubricants, especially those obtained from petroleum products, contribute to environmental pollution. thus, there is a need for the production of environmentally friendly lubricant as an alternative to petroleumbased lubricant currently being used. this work explored the potential of parinari and neem oils for the production of biolubricant using double transesterification method. parinari oil was extracted from parinari seed using sohxlet extraction method, and neem oil was purchased from akande market in ogbomoso, oyo state, nigeria. both oils were pre-analysed for physico-chemical properties based on american society for testing and materials (astm) methods. trimethylolpropane (tmp) was used to increase the lubricating property of the transesterified parinari seed oil. the results showed that, the kinematic viscosity for parinari based lubricant produced ranged between 12.1 – 67.4 cp at 40 ℃ and 15.5-28.6 cp at 100 ℃, while the kinematic viscosity for neem-based lubricant produced ranged between 55.7 – 647.3 cp at 40 ℃ and 122.9 – 171.6 cp at 100 ℃. parinari based lubricant had a viscosity index ranging from 159.7174.4 and neem-based lubricant ranged from 326-365. viscosities were all compared against sae standard. sae 30, 40 and 50 had kinematic viscosities ranging between 9.3-12.5, 12.5-16.3 and 16.3-21.9 respectively. furthermore, all the biolubricants showed relatively high viscosity indexes with potentials for application in heavy equipment. nbl showed higher kinematic viscosity with longer transesterification reaction time. nbl gave random outputs for each run for biolubricants produced. therefore, parinari and neem oil-based lubricants are potential lubricants as an alternative to petroleum-based lubricant. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 october, 2021 revised 10 march, 2022 accepted 16 march, 2022 keywords: parinari seed oil neem seed oil biolubricant trimethylolpropane transesterification http://www.azojete.com.ng/ mailto:levibulus1@gmail.com mailto:levibulus1@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):295-306. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 296 comprise of oil and other chemicals which improve lubricant properties (bhan et al., 2020). oils for the production of biolubricants are obtained from plants or animals, and modified to get biolubricant (tulashie, 2020). different steps involved in modification include esterification reaction, transesterification reaction (to produce biodiesel as an intermediate) and double transesterification to produce biolubricant. trimethylol propane (tmp) was the polyol used in the production of biolubricant from parinari seed oil and neem seed oil (nagaraj et al., 2020). other works, on production of biolubricant, has been carried out on edible oil, as published by dibal and ibrahim (2017), using castor oil (bilal et al., 2013), jatropha curcas oil (madankar et al., 2013), and canola oil, amongst others. however, the demand for food and increasing world population, has necessitated the search for, suitable, nonedible oil for biolubricant production (singh and erween, 2020). in this work, two non-edible oils, namely, parinari and neem oils were used for biolubricant production. parinari polyandra benth plant is found in the northern, north-central and eastern parts of nigeria. the average height of the tree is about 8 m (odetoye et al., 2011). its leaves are army green with short tips. the branches are easily breakable (motojesi et al., 2011). parinari fruit gets fully developed bi-annually in the month of march and october. the ripe fruit can be identified by its dark colour when compared to the early stages of the fruit (dalziel, 1937; ogunkunle et al., 2018). the variety and season of harvest of fresh seed kernel affects oil yield giving an approximate range between 31-60% (odetoye et al., 2011). variation in fatty acid compositions was observed in the oil extracted from the seed in the month of april and november, which suggested different application advantages either appropriate for biodiesel production or alkyd resin production (ogunkunle et al., 2020; odetoye et al., 2014, motojesi et al., 2011). neem (azadirachta indica) is a tree in the family maliaceae. it grows in different parts of nigeria. the evergreen tree is large, reaching 12 to 18 meters in height with a girth of up to 1.8 to 2.4 meters (odetoye et al., 2014). the seeds have 40% oil which has high potential for the production of biodiesel. it has a higher molecular weight, viscosity, density, and flash point than diesel fuel (ogunkunle et al., 2020). neem oil is generally light to dark brown, bitter and has a strong odor that is said to combine the odors of peanut and garlic (fazal et al., 2011; shahin et al., 2007). neem comprises mainly of triglycerides and large amounts of triterpenoid compounds. it also contains polyunsaturated fatty acids such as oleic acid and linoleic acids (muthu1 et al., 2019). lubricants are substances employed for the reduction of friction in mechanical components of vehicles that could lead to wear, tears or heat emission (bilal et al., 2013). lubricants exist in the three phases which could be solid, liquid and gas (singh et al., 2021). lubricants have enormous variety of applications in automobile engines, mechanical parts, refrigeration systems and compressor (musa et al., 2015). they are classified into two major groups (shah, et al.,2021); mineral oil and biolubricant. mineral oil lubricants are obtained from crude oil sources (shah et al., 2021). mineral oils are harmful when disposed improperly or accidentally spilled into the environment (monticelli 2018). this discharge of mineral based lubricant has led to environmental pollution and has shown a need for an alternative source of lubricant, that is environmentally friendly (salimon 2010; ahmad, 2021). research is recently targeted towards alternative file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:levibulus1@gmail.com bulus and odetoye: biolubricant production from parinari polyandra and azadirachta indica seed oils using trimethylolpropane polyol. azojete, 18(2):295-306. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 297 biolubricants in resolving the challenges faced from the use of mineral based lubricant (ahmad 2021). biolubricants have the ability to biodegrade easily and fast (noreen et al., 2021). they are also nontoxic to humans, aquatic live and land (salih et al., 2011a). they may be based on oils extracted from plants, animals or esters manufactured from modified oils. examples of oil used for the purpose of biolubricant production include jatropha seed oil, castor seed oil, soybean oil, sunflower oil, amongst other (cavalcanti et al., 2018; odetoye et al., 2016; kumar et al., 2021). 2.0 materials and methods 2.1 materials crude parinari oil was extracted from parinari fruits that were harvested in the month of october, 2019 at the university of ilorin, ilorin, kwara state, nigeria. neem seed oil was purchased from sabon-gari market, zaria, kaduna state, nigeria. all reagent used were analytical grade purchased from integrated research laboratories oke-odo, tanke, ilorin, kwara state. 2.2 refining the refining was done using degumming method. a clear sample was observed after washing and cooling to room temperature (odetoye et al., 2014), as shown in figure 1. in carrying out the degumming, 100 g of parinari oil and neem oil were heated to 80℃, using a flat bottom flask. heating magnetic stirrer was used, and stirred continuously to achieve even distribution of heat. 3% distilled water, was added at 90 ℃ to the continuously stirring oil. 0.2% phosphoric acid was added to the oil mass and allowed to be stirred for another 1 hour. it was allowed to cool naturally. the refined clear oil was decanted from the phosphatides. the residual water in the oil was evaporated by heating the oil to 100 ℃ using the heating mantle. figure 1. degummed clear sample figure 2. separation of transesterification http://www.azojete.com.ng/ mailto:levibulus1@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):295-306. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 298 2.3 oil esterification the refined oil sample of 100 g, was transferred into a two litre 3 necks spherical bottom flask. 20% w/w methanol and 5% w/w sulphuric acid were weighted and mixed in a conical flask. both the methanol acid mixture and the oil sample were placed in a water bath and heated to a temperature of 60℃ (chaurasia et al., 2020). the oils were then mixed in a three necks spherical bottom flask. a mechanical stirrer was inserted through one of the necks while the other two necks were stoppered. the stirrer was set at 700 rpm and the temperature of the bath maintained at 60 ℃. the timer was started simultaneously with the stirrer. after 1 hour, a picking pipette was used to withdraw the sample and it was titrated against 0.1 n solution of koh to determine the free fatty acid content of the oil. the titration was repeated at 1-hour intervals till the free fatty acid (ffa) was 0.5 or less (dibal and ibrahim, 2017). having esterified the parinari and neem oil, the % free fatty acid was reduced to a value less than 0.5% (amos et al., 2016). the sample was then washed to remove the catalyst as seen in figure 2. 2.4 methyl ester synthesis methyl ester was prepared using the esterified oil from samples, methanol, sodium hydroxide (naoh), and further transesterification was carried out by pouring mass of parinari oil and neem oil respectively into conical flasks as recorded in tables 1a and 1b. the reactor assembly as seen in figure 3, was then heated to 60 ℃. the content of the set up as seen in figure 3 are, the oil sample, methanol of 10.8% with respect to the mass of the oil (g) and naoh, which was the catalyst (naoh was 1.2% of the mass of the oil), heating mantle with a stirring rod, a thermometer and retort stand. the same procedure was repeated for every other sample, as shown in table 1. (ogunkunle et al., 2018). table1: quantity of reagent used for transesterification of parinari and neem oil mass of oil (g) naoh (w1/w2 1.2%) methanol (w1/w3 10.8%) sample parinari neem parinari neem parinari neem 1 200.10 200.00 2.40 2.40 21.60 21.60 2 205.00 201.15 2.46 2.41 22.14 21.72 3 199.95 200.25 2.39 2.40 21.49 21.63 4 202.23 200.10 2.42 2.40 21.82 21.61 where: w1 is mass of oil (g), w2 is mass of naoh (g), w3 is mass of methanol (g) 2.5 biolubricant synthesis after the completion of the transesterification, the catalyst and glycerol compound were separated from the methyl ester mixture, then the ester compound was washed using hot distilled water (amos et al., 2016; bilal et al., 2013; dibal et al., 2017). thereafter, the unreacted methanol and trace moisture were removed by heating to a temperature of 105℃ for 1 hour. trimethylolpropane was used in order to modify the property of the biolubricant. for this process, 15% tmp with respect to the mass of the ester produced was mixed with fatty methyl file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:levibulus1@gmail.com bulus and odetoye: biolubricant production from parinari polyandra and azadirachta indica seed oils using trimethylolpropane polyol. azojete, 18(2):295-306. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 299 ester. after an hour 0.8% wt/wt catalyst with respect to the mass of the ester produced was added. the mixture blended until foam formation stabilized and the additives completely solubilised in the ester by continuous heating and stirring with a magnetic stirrer (ahmad, 2021). table 2: quantity of trimethylolpropane (tmp) reacted with pfame and nfame figure 3. transesterification set up 3. results and discussion 3.1 physico-chemical property the kinematic viscosities at 40 ℃ and 100 ℃ for both parinari based lubricant and the neem based were compared with the sae (society of automotive engineers) standards at the said temperatures. furthermore, the viscosity index, specific gravity and flash point were also compared as shown in table 3, figures 4 and 5. mass of oil(g) tmp (15% of bio-diesel) biolubricant produced (g) time (hrs) pfame nfame pfame nfame pfame nfame sample 1 21.54 20.05 3.23 3.01 24.77 23.06 3.0 sample 2 22.28 20.10 3.34 3.02 25.62 23.12 3.5 sample 3 21.44 20.05 3.22 3.01 24.66 23.06 3.0 sample 4 20.20 20.15 3.03 3.02 23.23 23.17 3.5 http://www.azojete.com.ng/ mailto:levibulus1@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):295-306. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 300 table 3. physical and chemical properties of the sample viscosity (cp) at 40 ℃ viscosity (cp) 100 ℃ viscosity index specific gravity flash point (℃) fire point (℃) sae 30 -9.3-12.5 95.0 0.870 204 - sae 40 -12.5-16.3 110.0 0.880 220 - sae 50 -16.3-21.9 95.0 0.890 220 - parinari oil 195.2 87.8 -1.00 -- pbl 1 40.7 15.5 174.1 1.02 82.0 93 pbl 2 66.0 24.2 161.6 1.07 86.0 94 pbl 3 38.4 12.1 174.4 1.02 78.0 92 pbl 4 67.4 28.6 159.7 1.01 89.0 97 neem oil 78 64.8 -0.39 156 - nbl 1 647.3 171.6 641 0.44 175 - nbl 2 522.4 122.9 363 0.41 170 - nbl 3 480.2 136.4 326 0.49 173 - nbl 4 356.6 130.7 365 0.40 163 - figure 4: a chart of viscosity index for the biolubricant produced against sae the kinematic viscosities were measured at 40 ºc and 100 ºc because lubricants exhibit unique properties of lubricity at various temperatures. as seen in figure 3, kinematic viscosity was compared with the sae, the sae (30, 40 and 50) standard as recorded in table 3 shows a lesser kinematic viscosity. the viscosity index for nbl was relatively higher when compared with that of pbl and sae standards as shown in figure 4, from the analysis carried out. the essence of viscosity is in the type of equipment it is required for application. some equipment is heavy duty and require lubricant with higher viscosity. lubricants with high viscosity index are mostly used in heavy duty 0 100 200 300 400 500 600 700 1 2 3 4 v is co si ty i n d ex sample nbl sae pbl file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:levibulus1@gmail.com bulus and odetoye: biolubricant production from parinari polyandra and azadirachta indica seed oils using trimethylolpropane polyol. azojete, 18(2):295-306. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 301 equipment, of which the nbl produced fell in such category. the pbl also had a high viscosity when compared, with the sae standards for sae 30, sae 40 and sae 50. this also implies that the pbl is suitable, for heavy duty mechanical equipment. lubricants with low viscosity index are more suitably used in mechanical equipment’s that do lesser work when compared with heavyduty equipment. pbl and nbl being biolubricant, also makes it environmentally friendly. flash point is the lowest temperature at which the lubricants ignite. comparing all samples, as seen in figure 5, nbl 3 had the higher flash point for the biolubricants. however, when compared with petroleum based oil as stated by dibal and ibrahim(2017), petroleum based lubricant had higher flash point. hence, petroleum-based lubricant is more suitable for application in heavy mechanical machines that generate high temperature due to friction. this challenge possesses fire hazards in such equipment, as the same lubricant can act as fuel in higher fire point. figure 5: a chart of flash point for the biolubricant produced and sae 3.2 gcms analysis for parinari based lubricant the gc-ms analysis of the biolubricant shows the fatty acid methyl esters (fames) composition. from the analysis, oleic was 37.33%, being the highest composition, and that is because parinari seed is rich with oleic acid. other composition was, methyl ester, which was the primary desired amongst, tocopherol, which is an antioxidant found in plant and squalene is an organic compound that can be found in plant and animal. they all summed to 48% of the composition. also 13.76% butanol was also present, butanol can be used as biofuel as reported by mohamad et al., 2022. figure 6 shows the respective peaks at different retention time. each peak shows the fame present in the biolubricant sample. 0 50 100 150 200 250 pbl 1 pbl 2 pbl 3 pbl 4 f la sh p o in t ℃ samples pbl nbl sae http://www.azojete.com.ng/ mailto:levibulus1@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):295-306. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 302 figure 6: gcms of fatty acid composition of parinari based lubricant 3.3 gc-ms analysis for neem biolubricant octadecenoic acid ester constituted 35.49% and methyl ester constituted 33.54%. squalene being an organic compound commonly found in plant was 20.13% as seen in figure 7. the methyl ester composition at their respective time and abundance are, 2.37 is the highest peak and has abundance of 3.4 x 107. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:levibulus1@gmail.com bulus and odetoye: biolubricant production from parinari polyandra and azadirachta indica seed oils using trimethylolpropane polyol. azojete, 18(2):295-306. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: levibulus1@gmail.com 303 figure 7: gc-ms fatty acid composition of neem biolubricant oil. 4.0 conclusion the production of bio-based lubricant via biodiesel intermediate step was carried out successfully for both parinari and neem oils. the physico-chemical properties were obtained. the kinematic viscosities of the biolubricant samples at 40 ºc and 100 ºc, range were higher, compared to the sae 40. however, the flash points of the biolubricants produced were lower, compared to the sae standard. biolubricant is environmentally friendly and more researches can be done, to make biolubricant readily available and affordable to encourage the daily consumer. with that, the ecosystem will be less polluted. thus, further work is recommended on to improve the flash point and other lubricating property of the biolubricants. refrences ahmad, r. 2021. rsm and artificial neural networking based production optimization of sustainable cotton bio-lubricant and evaluation of its lubricity and tribological properties. energy http://www.azojete.com.ng/ mailto:levibulus1@gmail.com arid zone journal of engineering, technology and environment, june, 2022; 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abdulkareem, 2002; schiller et al., 2010; white, 2002; adeke et al., 2019). an efficient and reliable public transport system should be able to provide transport services for all categories of people living in the city. this helps to eliminate social exclusion and guarantee equity among the dwellers. in addition to the wellbeing of city dwellers, public transport system is a key driver of socio-economic growth by providing easy movement of people and their goods (lyndon and todd, 2006; schiller et al., 2010). the imposition of inequality rules on the use of public infrastructures among individuals living in cities is a common practice in most societies. disability could be a separation line for discriminating city dwellers. it is a physical, sensory, mental or any impairment arising from natural or artificial causes, which impacts adversely on persons’ capacity to participate in social, economic, cultural or political activities (republic of kenya disability act, 2012). according to the department for international development – (dfid, 2005) and world health organization-who as stated in lang and upah (2008), physically challenged people article information abstract following the persistent outcry of disabled persons over non accessibility to public transport facilities in ilorin town, nigeria, this study examined the plight of physically challenged commuters in accessing public transport facilities in the town. questionnaires were administered to 201 disabled commuters who use public transport facilities in the study area. facility condition inspection was also used to evaluate accessibility and user satisfaction. results of the study revealed that; male disabled persons travelled at relatively high rate of 76.10% compared to the female folks at 23.90%. the common disability among disabled persons was physical disability at the rate of 77.10%, while visual disability was 22.90%. travel demand among disabled persons showed that teenagers and adults travelled at relatively higher rate of 10.00% and 84.00% respectively compared to the aged at 6.00%. begging and work trip purposes had relatively high rate of 29.35% and 21.38% respectively compared to other trip purposes. the commonest nature of disability among commuters included; wheelchair user, sight impairment and hearing difficulty at 25.40%, 22.90% and 18.90% respectively. uneducated and disabled persons with primary education rated high in the sampled population at 36.80% and 29.90% respectively. accessibility rating and physical inspection revealed the poor state of public transport facilities in ilorin town leading to human right infringement, social exclusion and inequality among city dwellers. therefore, right to travel and access to basic facilities as stipulated in the nigerians disability decree of 1993 to enhance livability and ensure equality among city dwellers were ignored. the construction of public transport facilities to bear sidewalks, ramps, traffic control devices, bus stop shelter and good drainage systems to conform to international best practices in ilorin town was recommended. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 december, 2019 revised 7 april, 2020 accepted 13 april, 2020. keywords: disabled commuters transport facilities public transport social exclusion human rights. http://www.azojete.com.ng jirgba et al.: evaluation of the accessibility of public transport facilities by physically challenged commuters in ilorin town, nigeria. azojete,16(4):651-662. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 652 comprise approximately 10% of the world’s population with 75% living in developing countries. according to nigeria national population commission (2010), nigeria would have a projected population of 4,625,681 disabled persons by the year 2017, with ilorin town having 14,897. poor public transport policies have made physically challenged people, irrespective of where they live to likely be unemployed, less educated, have less or no access to developed support networks and social capital than their able-bodied counterparts. improved public transport policy and infrastructural development that could carter for disabled persons is crucial in alleviating poverty for nation development, economic and socio-cultural growth (ribbonaar and verster, 2004). dfid (2004) provided practical guidelines and solutions towards enhancing the access and mobility of people with disabilities in developing countries. the nigeria policy document titled; nigerians with disability decree (1993) also stipulates equalization of opportunities for people with disability for enhance performance in the society. despite variations in specifications across countries, recommendation for good access to transport facilities is common among nations. interestingly, most previous studies recommended the design and construction of facilities with ramps, suitable toilets, handrails, tactile surfaces, etc. to aid accessibility by physically challenged persons using wheelchairs, pushing buggies or trolleys and people using walking sticks (cullen, 2006: sawyer and bright, 2007). the united nations (un) convention on the rights of persons with disabilities (uncrpd) stipulates the right of persons with disabilities to access public facilities such as roads and road transport facilities (united nations, 2006). odufuwa (2007) revealed that 77.47% of disabled persons do not have access to private vehicles. they depend on public transportation for most trips and spend greater part of their income on transportation. due to the poor state of nigerian public transportation services and the prolong travel difficulties encountered. many studies have suggested the need for implementing basic mobility standards that suit the needs of disabled people such as; the use of wider and lowfloor steps, hand-rail for boarding and alighting on vehicles, adequate travel information, upgrading of bus stops, removing barriers in bus stops, installation of traffic signals, paving of walkways where available, installation of kerb ramps, prioritized seats and fare concessions in order to improve the state of nigerian public transport. griffin (2000) suggested that the simplest way of increasing the accessibility of public transport facilities by the physically challenged is to create an environment where pedestrian access is safe, convenient, affordable, and comfortable. this shall enable physically challenged persons afford to live in cities freely and happily since they can easily gain access to public transport facilities in terms of modes and use of terminals. according to odak (2014) barriers that limit access by the physically challenged persons to transport facilities are grouped into; physical (climbing steps, walking distances, lifting weights), sensory (reading about the destination of a bus from a notice board, hearing public announcements), cognitive (identifying which bus to board or finding the way to the platform or departure gate) and financial (paying the fare). these barriers also include not being aware that a service exists or knowing how to use it. other barriers involve being deterred by operation personnel who are unhelpful or unfriendly and policies that bar certain groups of travelers usually on the grounds of safety. while developed societies have ensured equity among city dwellers and safety for sustainable development in the transport sector, many cities in nigeria like ilorin are yet to be on track. this calls for the implementation of universal design standards for transport facilities with easy usability. the aim of this study therefore is to evaluate the accessibility of public transport facilities to the physically challenged commuters in ilorin metropolis. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 651-662. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 653 2.0 materials and method 2.1 description of study area ilorin the capital city of kwara state lies along the south-west region of nigeria. ilorin town like many other state capitals in nigeria is an important residential, industrial, commercial, social, educational and health, and administrative center. the creation of kwara state and the choice of ilorin as the state capital resulted to its rapid population increase and area expansion to harbor different kinds of individuals (aderamo, 2004). the choice of ilorin town for this study is due to its relatively high population of disabled persons as stated by previous surveys (npc, 2010). an extract of the map of ilorin town is as shown in figure 1, figure 1: map showing the study area (google earth, 2018) 2.2 research population, sample and sampling the representative population sample of physically challenged passengers in ilorin town used for the study was estimated using the taro yamane’s (1967) model as shown in eqn. 1 (glenn, 1992). it was used for determining the required sample size at 95% confidence level and precision level of ± 7%; s = n 1 +n(e)2 (1) where, s is the required sample size, n is the given population and e is the margin of error (7% or 0.07). considering a population size of 14,897, the sample size was estimated at 201 persons. the random sampling technique was employed for sampling the representative sample size from the population. the survey was conducted across seventeen (17) locations in ilorin town viz; maraba, post-office, sango, tipper garage, oke odo, tanke junction, sanrab, gaaakanbi roundabout, offa garage, cha-lenge, unity road, taiwo road, gambari, oja oba, kwara state school for the special needs, kwara state chapter of the national association for the blind and handicapped, and the wheelchairs pushers association of nigeria, kwara state chapter. 2.3 data collection questionnaires and site observations were employed in this study. copies of the questionnaire were administered to the sampled physically challenged persons in ilorin town. the public transport service and facilities were also inspected to ascertain travel environment for physically challenged passengers. questionnaire used for the revealed preference survey was sub-divided into three sections, the first section obtained information on socio-demographic characteristics of commuters such as; age, gender, type of disability and level of education; the second section sourced information on travel characteristics such as; trip purposes, transport safety measures and challenges of public transport facilities/services. the last part of the questionnaire probed into perceptions on factors responsible for the existing situation, trip file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jirgba et al.: evaluation of the accessibility of public transport facilities by physically challenged commuters in ilorin town, nigeria. azojete,16(4):651-662. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 654 frequency and accessibility condition rating of public transport facilities and services in ilorin town. a pilot survey was carried out to explore possibilities of research participants and agendas at the sampled sites within ilorin town. the pilot study aimed at developing and fine-tuning questions for interview, determining suitable sample size, assessing the feasibility of the survey, designing research protocol, assessing whether research protocol was realistic and workable, and identifying possible logistical problems that may occur (teijlingen and hundley, 2001). the visual inspection aimed at assessing facilities used for public transport services in ilorin town, and to ascertain provisions made to cater for the physically challenged persons. the city’s arterials were inspected, as well as public transport agencies and private vehicle owners to assess their vehicle conditions and operations. data sheets and writing materials were used during site inspections to note vehicle conditions such as; comfort, safety, reliability, accessibility, the availability and condition of road facilities that can aid accessibility for disabled commuters such as; sidewalk, ramp, traffic signals, drainage system, etc., and the data obtained were analysed using descriptive statistics. the analysis examined relationship between respondent’s social demographic characteristics and travel environment. it also explored the relationship between accessibility of public transport facilities, associated challenges and travel characteristics. 3.0 results and discussion 3.1 gender distribution of disabled commuters table 1 shows the distribution of disabilities among disabled commuters based on gender and type of disability. table 1: gender distribution of disabled commuters description gender types of disability total male female physical visual count 153 48 155 46 201 percentage (%) 76.1 23.9 77.1 22.9 100 table 1 revealed that male commuters had disabilities more than their female counterparts based on findings of this research. this implied that despite their challenges, the male counterparts always struggled to make ends meet; hence their ratio compared to women was relatively higher which conform to findings of odufuwa (2007). also, the commonest disability among the commuters was physical challenge. 3.2 age distribution of disabled commuters table 2 shows the age distribution of disabled commuters who were either physically or visually impaired. table 2: travel demand across age distribution of disabled commuters age (years) frequency percentage (%) 10 – 20 20 10.0 21 – 30 83 41.2 31 – 40 56 27.9 41 – 50 30 14.9 51 – 60 11 5.5 above 60 1 0.5 total 201 100 table 2 revealed the frequency of travel demand across age distribution of disabled commuters. it shows that disabled teenagers and adults (10 – 40) travel more frequently compared to the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 651-662. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 655 aged. this was attributed to social influence and struggle for survival through begging and providing working force (odak, 2014). on the other hand, the aged (50 and above) disabled persons traveled less often due to their age disadvantage and possibly poor health. 3.3 distribution of trip purposes by disabled commuters figure 2 shows the distribution of trip purposes by disabled commuters. figure 2: distribution of trip purposes by disabled passengers figure 2 revealed that most disabled commuters traveled for the purposes of earning a living through begging and going to work at average rate of 29.35 % and 21.38 % respectively. this is due to the unbalanced environmental opportunities between the abled and disabled persons in our societies as stated in who (2013). also, environmental factors such as temperature, terrain, accessibility of transport, climate, noise, etc. improve or hinder a physically challenged person participation in some activities such as working, going to school, taking care of one’s home, and being involved with family and friends in social, recreational and civic activities in the community. the least purposes of travel were those for social reasons, this implied that, travelling environment was not conducive to motivate pleasurable trips by the physically challenged persons. 3.4 distribution of disability among respondents the classification of disabled persons based on type of disability is as shown in table 3. table 3: disability distribution of respondents difficulty applied to disability frequency percentage (%) blind/partially sighted and using stick/cane 46 22.9 wheelchair users 51 25.4 difficulty walking/using walking stick 20 10.0 difficulty walking/using crutches 22 10.9 deaf/hard of hearing 38 18.9 mental problems 5 2.4 sketch board 19 9.5 total 201 100 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jirgba et al.: evaluation of the accessibility of public transport facilities by physically challenged commuters in ilorin town, nigeria. azojete,16(4):651-662. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 656 table 3 reveals that, disabled persons with ailment of total blindness or partial sightedness using sticks to walk and wheelchair users constitute relatively large size of the sampled population. this was attributed to the poor design of the public transport vehicles and facilities which hindered the ease of use by physically challenged persons leaving with limited choices. other ailments leading to difficulty in walking which required using walking sticks, crutches and sketch board constitute approximately 10% each of the sampled population. 3.5 level of education the level of education is a vital demographic feature which influences the travel mode and frequency of trip makers (odak, 2014). this is because, most physically challenged persons who are educated were likely to be employed, and most of them who are employed are likely to be mobile than their counterparts who are not employed. however, due to insufficient public transport and non-motorized transport systems in ilorin, it is highly likely that their occupational mobility will be much less than their abled counterparts, which in turn is likely to limit their choices and opportunities for employment because majorities have no formal education. figure 3 illustrate the level of education of disabled persons in ilorin town. figure 3: level of education of disabled persons in ilorin town figure 3 revealed a relatively high rate of illiteracy among disabled persons in ilorin town. this indicated that significant number of respondents lacked formal education due to limited access to public transport facilities thereby creating social exclusion and inequality in the society as quoted by odufuwa (2007). 3.6 public transport facilities and travel environment transport facilities in nigeria are rapidly deteriorating with time. bus terminus and bus stops lack basic facilities such as shelter, seats and lights. most sidewalks are unpaved, poorly maintained and crowded/occupied by vendors (food, newspaper, etc.) resulting in reduced right-of-way and highway capacity. travel information is not easily provided to most physically challenged passengers to enable them to complete their movement and apart from inaccessible location of terminal or bus stops; most bus stops are not adequately taken care of. figure 4 presented the satisfaction derived from using public transport facilities by the disabled commuters in ilorin town. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 651-662. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 657 figure 4: satisfaction derived from public transport facilities by the disabled the satisfaction rating by disabled commuters and visual inspections indicated that, the existing footpaths were either poorly designed or poorly maintained such that they were not useful to the physically challenged. by physical inspection, the facilities lacked clear separation from vehicular traffic, sidewalks with adequate width, bus stops (and facilities such as shade, seats, etc) and surrounding conditions, road markings and traffic signals at crossings as confirmed by (odufuwa, 2007). where the footpaths exist, they are also inaccessible with most of them being used as parking for taxi and motorcycles. barriers should be installed to protect the pedestrians and abled persons from accident risks posed by motorized traffic. 3.7 services of public transport vehicles an efficient transport system aims at providing safe, reliable, convenient, and accessible transport services at all times to meet daily needs of commuters. the rating of public transport services in ilorin town by disabled passengers is as presented in figure 5. figure 5: ratings of public transport services in ilorin figure 5 reveals that respondents rated safety as being average, comfort as poor, reliability as average, availability as average and accessibility as poor. this is attributed to the fact that bus interior and body designs standards do not satisfy the international best practice for use by the physically challenged persons. out of the 164 vehicles inspected, 38.31% were taxis, 13.93% were buses, 3.98% were mini buses, 11.94% were motorcycle, 11.44% were tricycle and 1.99% were train, none satisfied standard requirements for public transport facilities that suits the physically challenged persons. it was noted that boarding via steps was not easy and none of the buses or taxis had ramps to aid the disabled persons. most respondents suggested improved accessibility through the use of ramps, wider doors. also shelter and bus stops would aid their mobility during boarding and alighting. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jirgba et al.: evaluation of the accessibility of public transport facilities by physically challenged commuters in ilorin town, nigeria. azojete,16(4):651-662. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 658 3.8 challenges of accessing public transport facilities in ilorin town conditions of road facilities for public transport system in ilorin town are as presented in table 4. table 4: conditions of public transport facilities roads road condition sidewalks bus stops road width (3.65m) shoulder width of sidewalk (1500mm) availability of ramps width of ramps (1200mm) availability of ramps parking bay open drainage muritalamoh’d road yes yes yes yes yes no yes yes old jebba road yes yes yes no no no no yes tundeidiagbon road yes yes yes no no no no yes gaa-akanbi road yes no no no no no no yes ajaseipo road yes yes yes yes yes no yes yes unity road yes no yes no no no no yes emirs road yes no yes no no no no yes taiwo road yes no yes no no no no yes airport road yes yes yes yes yes no yes yes offa road yes no no no no no no yes ahmadu bello way yes yes yes yes yes no yes yes agbabiaka road yes no no no no no no yes asa dam road yes yes yes yes yes no yes yes sulu gambari road yes no no no no no no yes the result show that, significant number of roads in ilorin town were not designed and constructed to conform to international standards that permit access and usage by the physically challenged passengers (dfid, 2004). therefore, physically challenged persons were exposed to risk of accidents. an example of poor road facility is as presented in figure 6. figure 6: sidewalks and drainage system along murtala moh’d way road facilities in ilorin town were characterized with no traffic calming devices to reduce vehicle speedsat pedestrian crossing spots. there are also no safety and advance warnings signs for vehicles to stop or give priority to disabled pedestrians as they approach street crossings at the study sites. the few traffic signal devices installed were not actuated but pre timed and without sound signals to notify the visually impaired pedestrians at the cross points to guaranty safety. also, bus stops and terminal facilities such as shelter, seats and billboards were absent http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 651-662. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 659 or poorly installed such that the physically challenged passengers could not easily gain access to the facilities. some few sites with bus stops had open drains disconnecting the bus stop canopy from the roadway thereby making access impossible or difficult for the disabled persons as shown in figure 7(a). figure 7(a): simple bus stop shelter in ilorin figure 7(b): simple bus shelter in grenoble, france (ecmt, 2006) on contrary, a standard bus stop developed in accordance with international standards to carter for disabled passengers is as presented in figure 7(b). on the other hand, taxis and buses in ilorin town do not provide facilities to accommodate disabled passengers as required by international best practices. a pictorial comparison of taxis, minibuses and coaches used in ilorin and those of developed societies is as shown in figures 8, 9 and 10 respectively. figure 8(a): taxi in ilorin town figure8(b): taxi in united kingdom (source: world bank, 2013) open drainage file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jirgba et al.: evaluation of the accessibility of public transport facilities by physically challenged commuters in ilorin town, nigeria. azojete,16(4):651-662. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 660 figure 9(a): minibus in ilorin town figure 9(b): minibus at belgium (source: ecmt, 2006) figure 10(a): coach in ilorin town figure 10(b): coach in grenoble, france. (source: ecmt, 2006) figures 8, 9 and 10 showed that taxi, minibuses and coaches in ilorin town had elevated floors without ramp which created access challenges for the disabled passengers, unlike those from developed cities like uk, belgium and france. other features of buses in developed cities included; priority seating arrangement for the disabled, mobility aids such as hand rails, storage for mobility aids (walking stick and wheelchairs), actuated bell/light for communication with the driver are provided. 4.0 conclusion and recommendations 4.1 conclusion this study examined the accessibility of public transport facilities by physically challenged captive commuters in ilorin town using a reveled preference survey approach. questionnaires were administered to a randomly sampled population size of 201 disabled commuters who use public transport facilities in the study area. facility condition inspection was also used to evaluate accessibility and user satisfaction. descriptive statistics was used for data analysis. results of the study revealed that; male disabled persons travelled at relatively high rate of 76.10% compared to the female folks at 23.90%. the common disability among disabled persons was physical disability at the rate of 77.10%, while visual was 22.90%. travel demand among disabled persons showed that teenagers and adults travelled at relatively higher rate of 10.00% and 84.00% respectively compared to the aged at 6.00%. begging and work trip purposes had relatively high rate of 29.35% and 21.38% respectively compared to other trip purposes. the commonest nature of disability among commuters included; wheelchair user, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 651-662. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 661 sight impairment and hearing difficulty at 25.40%, 22.90% and 18.90% respectively. uneducated disabled persons and those with primary education only rated high among the sampled population at 36.80% and 29.90% respectively. the accessibility rating of public transport facilities by disabled commuters and physical inspection revealed the poor state of public transport facilities in ilorin town. this was attributed to poor design and construction of transport facilities which do not conform to modern design standards that could accommodate physically challenged persons. this implies that most physically challenged persons struggle to gain access to public transport facilities. this situation subjects them to accident risks and creates untold hardship for living in ilorin town. their right to travel and access to basic facilities as stipulated in the nigerians disability decree of 1993 with emphasis on giving priority to disabled persons or groups to enhance livability and ensure equality among city dwellers are therefore ignored. a situation which led to human right infringement, social exclusion and inequality among city dwellers. 4.2 recommendations the following recommendations were made: the redesign and construction of public transport facilities to bear sidewalk, ramps, traffic control devices, bus stop shelter and provision of good drainage systems to conform to international best practices or policies should be implemented in ilorin town to reduce the hardship imposed on physically challenged commuters living in the town. the federal and kwara state governments should provide special fund for infrastructure upgrade scheme to address the needs of physically challenged persons in nigerian cities such as ilorin. the study limited the scope to cover only physically and visually impaired, thus further research should be conducted to cover all types of disabilities. references abdulkareem, ya. 2002. the roles and impacts of transportation in nigerian society. http://www.unilorin.edu.ng/publicatios/abdulkareemya. date accessed march 12, 2017. adeke, pt., inalegwu, oj. and jirgba, k. 2019. prediction of bus travel time on urban routes without designated bus stops in makurdi town. arid zone journal of engineering, technology and environment, 15(2): 406 – 417. aderamo, aj. 2004. transport factor in the structure and growth of a traditional settlement, ilorin, nigeria. geo-studies forum, 2 (1): 145-156. cullen, m. 2006. improving transport accessibility for all: guide to good practice. oecd publications, paris, france. department for international development, 2004. overseas road note 21, enhancing the mobility of disabled people: guidelines for practitioners. transport research laboratory, london, england. department for international development, 2005. reducing poverty by tackling social exclusion. dfid, london. european conference of ministers of transport (ecmt), 2006. improving transport accessibility for all: a guide to good practice. european conference of ministers of transport, paris, france. glenn, di. 1992. determining sample size. program evaluation and organizational development. institute of food and agricultural sciences, peod-6, university of florida, usa. google earth. 2018. google earths inc. griffin, kw. 2000. building type basic for transit facilities. usa, john wiley & sons, inc. http://www.unilorin.edu.ng/publicatios/abdulkareemya file:///c:/users/user/downloads/azojete143/www.azojete.com.ng jirgba et al.: evaluation of the accessibility of public transport facilities by physically challenged commuters in ilorin town, nigeria. azojete,16(4):651-662. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jirgbakavnen@yahoo.com 662 lang, r. and upah, l. 2008. scoping study: disability issues in nigeria.<http://www.ucl.ac.uk/lcccr/downloads/dfid_nigeriareport> accessed on february 3, 2017. lyndon, h. and todd, al. 2006. evaluating new start transit program performance; comparing rail and bus. victoria transport policy institute, victoria, canada. national population commission 2010. population distribution by age, sex and disability status, federal republic of nigeria, priority table, vol. xi, abuja, nigeria. nigerians with disability decree 1993. https://dredf.org/international/nig1.html. accessed on february 11, 2017. odak, po. 2014. an assessment of non-motorized and public transport challenges for people with disabilities in nairobi city. m.sc. thesis, department of urban and regional planning, university of nairobi, nairobi, kenya. odufuwa, b. 2007. towards sustainable public transport for disabled people in nigerian cities. studies on home and community science, 1(2): 93 – 101. onokala, pc. 2001. urbanization and urban transportation problems in nigeria. in eo. ezeani and nn. elekwa (eds), issues in urbanization and urban administration in nigeria. jamoe enterprises (nigeria) publishers, enugu, nigeria, pp. 168 – 186 republic of kenya 2012. persons with disability act. national council for law reporting, nairobi, kenya. ribbonaar, d. and verster, b. 2004. a disabling public transport system. proceedings of the 23 southern african transport conference, pretoria, south africa,12-15 july, 2004. pp. 431-438. sawyer, a. and bright, k. 2007. the access manual: auditing and managing inclusive built environment. second edition, blackwell publishing ltd, oxford, england. schiller, pl., bruun, ec. and kenworthy, jr. 2010. an introduction to sustainable transportation: policy, planning and implementation. earthscan, usa. teijlingen, ve. and hundley, v. 2001. the importance of pilot studies. social research update, (35): 1– 4. united nations (un) 2006. united nations convention on the rights of persons with disabilities, un headquarters, new york. white, p. 2002. public transport: its planning, management and operation. spon press, london. world bank 2013. improving accessibility to transport for people with limited mobility. a practical guidance note, washington dc, usa. yamane, t. 1967. statistics, an introductory analysis. harper and row, new york https://dredf.org/international/nig1.html http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojeteseptember 2020. vol. 16(3):587-604 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 587 original research article an overview of approaches and techniques used in failure analysis of engineering system t. n. guma*, n. c. w. ozoekwe, and k. v. odita department of mechanical engineering, nigerian defence academy, kaduna, nigeria *corresponding author’s email address: tnguma@nda.edu.ng 1.0 introduction a component, machine, process, or system is considered to fail if it has deteriorated to the extent that it is unsafe or only marginally capable of performing its intended function (guma et al., 2019). the consequences of failure can vary greatly from structure to structure, system to system, and equipment to equipment. failures come in all shapes and sizes in forms such as individual part, entire machine or process, with various modes such as fracture, fatigue, corrosion and high-temperature mechanisms (vander voort, 1975., aliya, 2002., asm, 2015). the commonly attributed reasons for failures of engineering system or component include: environment-material interactions which is essentially corrosion and wear and tear, abnormal service or operating conditions, substandard maintenance and repair practices, improper testing or inspections, assembly or fabrication or manufacturing errors, design errors in stress article information abstract failure of engineering system such as vehicle, building, aircraft, bridge, equipment, and industrial facility is often inevitable with calamitous consequence and/or much loss; and is highly detested. inevitability of engineering system or component failure stems from factors such as unavoidable corrosion and wear and tear, abnormal service conditions, substandard maintenance practices, improper inspections, production errors, design errors, injudicious selection of materials, material imperfections, overloading and other service abuses of the system or component; and unknown causes. the importance and value of failure analysis in providing vital information for preventing recurrence of failure case of engineering system and the need to properly conduct the analysis has been found well documented in the literatures. various standard approaches and techniques of engineering system failure analysis have been reviewed and presented together with 24 recent works of researchers from different backgrounds on the subject who have taken particular cases for study and evaluation. the review shows that although there are many existing failure analysis approaches and techniques of engineering systems, not all or a number of them can be suitable for every particular failure case. critical analysis of the approaches and techniques shows that each has limitations or demerits in terms of practicability and/or cost-justification for particular failure cases. the notable issue in the review is the need to always select the best approaches and techniques for particular failure cases to assess characteristics that are present in the failed/damaged engineering system or item and those that are supposed to be present in it before failure, the differences between the damaged and undamaged system or item, and results of tests that must be performed to substantiate explanations and refine knowledge about the observed damage to correctly reveal the root cause/s of failure. another important thing found from the review is the need to first and foremost preserve evidence of the failed system or item before using the best approaches and techniques to get as much as possible information from the field failure conditions and background realities and laboratory tests of the failed system or item. the review is posited as a readily available compendium of basic practicable information that is easy to read and understand; for consultation by concerned students, researchers, and practitioners who are not yet much experienced in failure analysis of engineering systems and need the information for furthering their knowledge on the subject. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted28 march, 2020 revised 02 july, 2020 accepted 10 july, 2020 failure calamity, costs, inevitability, analytical principles, correct information, recurrence prevention mailto:tnguma@nda.edu.ng http://www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 588 conditions, injudicious material selection, incorrectly assumed material conditions or properties, material imperfections due to faulty processing or fabrication, overloading and other service abuses of the system or component; and unknown factors (vander voort, 1975., aliya, 2002., fernando, 2013., asm, 2015). engineering systems include vehicles, buildings, aircrafts, bridges, equipment, and industrial facilities with their component parts (aliya, 2002., fernando, 2013., wooten, 2015). mechanical failure of engineering system or component can be catastrophic with consequences that manifest in several forms such as fatalities, injuries or suffering from minor cuts and bruises to broken limbs, whiplash, back and spinal injuries, paralysis, financial and mental effects on personnel involved, emotional and mental distress as people can suffer from post-traumatic stress from being involved in the accident or from losing a loved one, damage of assets or properties, loss of functionality and environmental damage, need for minor or costly repairs, reduction of production or service efficiency, waste of valuable materials, increased costs, and property and economic losses (vander voort, 1975., aliya, 2002., fernando, 2013., asm, 2015., wooten, 2015). these consequences can be very enormous in some cases and are highly detested. it is therefore desirable that failures of critical engineering systems must be avoided in all ramifications or prevented from recurring where it unavoidably happens (aliya, 2002., fernando, 2013., asm, 2015., guma et al., 2019). a crucial method of preventing recurrence of failures of engineering systems or components is through failure analysis (vander voort, 1975., fernando, 2013., asm, 2015). in failure analysis, detailed assessment is performed on failed items or components at macroscopic and microscopic levels to determine the reasons that clearly identify the root cause of the failure often with the main motive of recommending recurring preventative action/s (janssens et al., 2011., asm, 2015., wooten, 2015., guma et al., 2019). although the main intentions in most failure analyses is to use the acquired information to prevent recurrence of the failure; failure analysis can also be done for product development to meet market demands or improvement to reduce warranty costs, and assignment of responsibility in case of litigations that arise from the failure due to reparation of financial losses and physical damage or bodily injury or death. failure analysis can save money, lives, and resources if done correctly and acted upon. the importance and value of failure analysis to safety, reliability, performance improvement, and economy is well documented in the literatures (vander voort, 1975., aliya, 2002., fernando, 2013., asm, 2015). failure analysis is an important discipline in various industrial sectors such as components manufacturing, fabrication, transportation services, building services, and power supply (vander voort, 1975., aliya, 2002., fernando, 2013., asm, 2015). in some cases of failure analysis, tests can be performed but no indication of tangible fault be found. such cases indicate that the real conditions of the failure cannot be duplicated in laboratory conditions so the cause of the fault is undetermined (russel and jur, 2017., lv et al., 2019). in such cases, there is either the problem of environmental uncertainty or human error that can’t be detected in the original failure scenario. suggestions for analyzing these types of failures involve applying more tests, contracting additional and different failure analysis, contracting services or increasing the available data set for analysis (russel and jur, 2017). because of the critical role of failure analysis, it is important that errors be avoided in the analysis because they could create as much or more harm than the original failure by causing economic, psychological, and political consequences to particular individuals or companies who are implicated for carelessness, negligence, simple ignorance, or other errors or omissions by information from the analysis. with these regards, many prospective analysts can consider failure analysis to be meticulous and incriminating with fear of overlooking important details, so refuse to perform the analysis unless given enough time and full financial support to do thorough investigation. pitfalls of analysts can include jumping to conclusions, not understanding the problem, not understanding how the failed system is supposed to operate, not considering all possible failure causes, and tearing system apart without a developed plan (aliya, 2002., asm handbook, 2002., janssens et al., 2011., wooten, 2014., asm, 2015). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 589 aim the aim in this paper is to review basic prevailing literatures on failure analysis of engineering systems or structural components and present a compendium of contemporary applicable approaches and techniques used in the analysis. the review covers only basic existing standard approaches and techniques used in failure analysis of engineering systems and some case studies from different engineering backgrounds by practitioners in which some of the approaches and techniques were used. the benefits that can be derived from the review report are: i. provision of consolidated information for simpler reading and understanding and interest motivation of researchers, professionals, and students who are concerned with failure analysis of engineering systems but are not much experienced on the subject and need the information for advancing their knowledge on the subject. ii. provision of consolidated information that gives better insight into what is analytically achievable and not achievable in failure analyses of engineering systems with the existing approaches and techniques for the way forward by concerned researchers or analysts. 2.0 the review report information presented in the review was sourced from various literary sources as it concerns approaches and techniques used in failure analysis in engineering with attempt to integrate and present the information in a simpler way for reading and understanding, and motivation of interest in the area of failure analysis. 2.1 approaches and techniques used in failure analysis failure analysis to obtain correct applicable information is a meticulous exercise that requires use of correct approaches and techniques. failure analysis approaches are the itemized sequential ways of analytically dealing with a failure case while failure techniques and tools are the means of accomplishing the approaches. while there are generally many approaches and techniques in failure analysis, not all or the same given number of the approaches and techniques may be applicable to different failure cases. the failure analyst is therefore required to know the existing available approaches and techniques and be able to select the best that will help them to best analyze their various individual failure cases. the choice of available approaches and techniques used in failure analysis greatly depends on the type and size of system or item that fails, nature of the failure in terms of magnitude, the location where the failure occurs in the system or item, the environmental location where the system or item fails, the material make and fabrication of the component parts of the item, time required for the analysis, and the accuracy level required in the analysis (aliya, 2002., asm handbook, 2015., lv et al., 2018). 2.1.1 approaches used in failure analysis the key principle in failure analysis is to first and foremost preserve evidence and get as much as possible information from the field conditions and develop a complete case history of the failed item or system. this requires getting information on the failed item in terms of manufacturing processing and service usage and maintenance level, including details of the failure before intelligently selecting tests and procedures that are best for supplementing the information in analysis of the failure (aliya, 2002., janssens et al., 2011., wooten, 2014., asm, 2015., lv et al., 2018). depending on the nature of the investigation, the approach steps involved can include all or various combinations of the following (aliya, 2002., asm, 2015): i. assembling background data. the information that the analyst presents must include; date and time of failure, name of the failed item or system, location where the failure occurs, how the failure occurred according to any eyewitness’ or proven accounts, extent of damage file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 590 and injuries and other losses from the failure. the information must also include; appearance, any identification numbers, owner, user, manufacturer and/or fabricator, function, service life at the time of failure, rating performance, operational levels, normal and abnormal loads, frequency of loading, environmental location, material makes, manufacturing and fabrication techniques, maintenance records, specifications and codes governing manufacturing and maintenance, inspection account, service operational temperature and pressure and speed ranges, strength and toughness levels, and any service deviations for the failed item or system. the fabrication procedures must include details of any welding, adhesive joining, coatings, bolting, riveting, heat treatment, and stress relief or other thermal processing in the failed item or system (aliya, 2002., asm handbook, 2002., asm, 2015). ii. on-site visual examination and taking of photographs or drawing sketches of the failure area and adjacent areas to schematically record and gain important primary clues about the origin of failure, presence of stress concentrators, presence of any temper color or scale on fracture faces, orientation and magnitude of stresses, failure mode and mechanism, direction of crack propagation and sequence of failure, presence of contributing imperfections and corrosion and wear damages, sizes, and other physical data (ghosh, 1997., aliya, 2002). iii. field visual macroscopic examination of failure locations or with the aid of magnifying glasses or other means where visual observation is difficult for evaluation of surface homogeneity, integrity, and quality levels of the locations by comparison with the normal associated features or values for them (colangelo, 1978., asm handbook, 2002., asm, 2015) iv. field or laboratory analyses of temperature, pressure, wind speed, humidity, chemical contents, and levels of radiation and electric current presence in the environment in which the failed item or system operates to know whether there are significant deviations in values of these parameters from their standard range values for the environment or there are unusual inimical factors such as corrosion in the environment (jones, 1993., janssens et al., 2011). v. collection of test samples from critical locations such as the damaged and undamaged locations of the failed item or assembly (aliya, 2002., wooten, 2014., russel and jur, 2017). vi. conduction of fractography investigations and analyses to gain understanding of brittle or ductile, fatigue, creep, corrosion, and wear fracture mode behaviors of failed materials as well as relative attendant stress levels and orientation of the stresses and loads on the materials (jones, 1993., lv et al., 2018). vii. conduction of chemical, micro-structural, micro-hardness, and corrosion tests analyses of failed welded, soldered, and brazed joints in relationship to standards for them (ghosh 1997). viii. performance of chemical analyses of all other failed materials including critical surface corrosion products, deposits or coatings by comparison of results with standards or established specifications for the materials (colangelo, 1978., janssens et al., 2011). ix. determination of mechanical properties of failed components by appropriate tests and comparing obtained values with standards or established specifications for the components (aliya, 2002., asm handbook, 2002). x. high-magnification metallographic examination of failed material sections using suitable microscopes to evaluate micro-structural surface features such as, crack paths, inherent defects, and corrosion attack sites in relation to known normal micro-structural phases of the material locations (russel and jur, 2017., lv et al., 2018). xi. micro-hardness testing to measure case depths, and evaluate cold-worked parts that fail (aliya, 2002., asm, 2015). xii. micro-probing for any critical abnormalities, such as inclusions and segregations that are too small for bulk analysis (russel and jur, 2017). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 591 xiii. determination of residual stress levels and relative amounts of phases such as austenite or retained austenite, ferrite, delta ferrite or martensite, sigma, and carbides in critical structural materials like steels (jones, 1993., janssens et al., 2011). xiv. performance of simulation tests to evaluate critical material characteristics such as stress-corrosion cracking and fatigue tendency in particular environments to determine the degree of embrittlement or confirm the method of heat treatment or harden-ability (ghosh 1997., janssens et al., 2011., russel and jur, 2017). xv. summarizing and analyzing all pertinent data to identify the root cause of the problem (jones, 1993., lv et al., 2018). xvi. writing the report and distributing it with recommendations for preventing future failures or problems in similar existing item or system (ghosh 1997., wooten, 2014). xvii. following up on these recommendations (aliya, 2002., asm handbook, 2002., asm, 2015). xviii. preserving the evidence for the benefit of other examiners (aliya, 2002). 2.1.1.1techniques used in failure analysis approaches failure analysis cannot be possible without a sound knowledge of various information-gathering or evaluation techniques and tools to achieve the itemized approaches. in cases where feasible, multi-technique evaluations can be applied to have higher confidence of the generated data by optimization (wooten, 2014). the available and commonly used evaluation techniques and tools that can be used for various types and extents of failure analyses essentially include (ewalds and wanhill, 1984): i. photographic documentation of information on critical areas of failed items or systems using film or digital cameras (aliya, 2002). ii. magnetic-particle inspection to locate surface and subsurface discontinuities in ferromagnetic materials (ewalds and wanhill, 1984., walraven, 2003). iii. stereo-photography for documenting component conditions and recording information in three dimensions by using a stereo-camera or sequentially by the repositioning of a single camera (ewalds and wanhill, 1984., karayan et al., 2012). iv. metallographic examination of sections and analyses to reveal any material imperfections such as micro-structural segregation, decarburization, carbon pickup, improper heat treatment, un-tempered white martensite, second phases such as γ′ in nickel-base superalloys and inter-granular corrosion using optical or electron microscopy (ghosh. 1997., walraven, 2003). v. surface preparation of metallographic samples using various methods such as grinding, polishing, and etching by various available means (ewalds and wanhill, 1984). vi. radiography using techniques such as x-rays, and gamma rays to locate internal cracks and other defects (walraven, 2003). vii. molecular structure analysis by techniques such as differential scanning calorimetry, and molecular weight evaluation for evaluating levels of molecular weight deviations from values known for chemical substances (walraven, 2003). viii. thermo-mechanical analysis, dynamic mechanical analysis, mechanical testing, and hardness analysis for evaluating physical properties using relevant test facilities (ewalds and wanhill, 1984., walraven, 2003). ix. corrosion tests using simulated conditions to find any logical reason for the failure of system or item where normal investigation procedures on materials, manufacturing, and service related aspects has failed (colangelo, 1978., ghosh, 1997). x. macroscopic examination and analysis of fracture surfaces at lower magnification using suitable means such as unaided eye, hand lens or magnifying eye glasses, low-power file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 592 stereoscopic microscope, and scanning electron microscope (sem) for faster detection of defects and flaws that are not too small (colangelo, 1978., walraven, 2003). xi. eddy current inspection of material that conducts electricity to detect surface and subsurface cracks or flaws in the material (walraven, 2003., pantazopoulos, 2019). xii. microscopic examination of fracture surfaces to determine the origin(s), mode, and direction of propagation of very small cracks or fractures and other flaws using typically sem but also other microscopes of various types and advantages such as atomic force microscope (afm), scanning superconducting quantum interference device (squid) microscope, stereomicroscope, optical microscope, scanning acoustic microscope (sam), usb microscope, photoemission electron microscope (pem), x-ray microscope, and infra-red microscope (walraven, 2003). xiii. residual stress analysis in the materials using typically x-ray diffraction technique (ghosh, 1997., pantazopoulos, 2019). xiv. finite element analysis (fem) method in certain cases where a more comprehensive analysis is needed because a conventional failure analysis approach is not enough to reveal the failure cause (ewalds and wanhill, 1984., karayan et al., 2012). xv. fracture mechanics analysis for theoretical investigation of failures such as fractography to establish whether or not the presence of discontinuities in material have contributed to the failure of the component under given service load conditions, as well as formulation of preventive measures (pantazopoulos, 2019). xvi. preparation of very small samples for test analyses using means such as jet-etcher, plasma etcher, back-side thinning tools, mechanical back-side thinning, and laser chemical backside etching (bloch and geitner, 1994., walraven, 2003). xvii. spectroscopic analysis techniques such as transmission line pulse spectroscopy (tlps), auger electron spectroscopy, deep-level transient spectroscopy (dlts), and device modification such as focused ion beam etching (fibe) for detecting defects in semiconductors, charge carriers, atoms, and molecules (bloch and geitner, 1994., walraven, 2003). xviii. surface analyses for cracks and other discontinuities of non-magnetic materials using techniques such as dye and other liquid-penetrant inspections (ewalds and wanhill, 1984., ghosh. 1997., walraven, 2003). xix. electron microscopy to analyze extremely small defects in materials including microelectronic components by various methods such as electron beam induced current (ebic) in scanning electron microscopy (sem), sem, charge-induced voltage alteration (civa) in sem, energy-dispersive x-ray spectroscopy (eds) in sem, voltage contrast in sem, electron backscatter diffraction (ebsd) in sem, and transmission electron microscopy (tem) (bloch and geitner, 1994., walraven, 2003). xx. laser signal injection microscopy (lsim) such as light-induced voltage alteration (liva), optical beam induced current (obic), laser-assisted device alteration (lada), optical-beaminduced resistance change (obirch), thermally induced voltage alteration (tiva), external induced voltage alteration (xiva), dynamic soft defect localization (dsdl); to locate defects or failures of transistors, semiconductors, and integrated circuits by scanning a laser beam through a microscope lens over an integrated circuit while monitoring the device current /voltage response for laser induced changes (bloch and geitner, 1994., walraven, 2003). xxi. semiconductor probing such as laser voltage prober, time-resolved photon emission prober (trpe), nano-probing, mechanical probe station, and electron beam prober for analysis of defects in semiconductors (bloch and geitner, 1994., walraven, 2003). xxii. software-based fault location techniques such as cad navigation, and automatic test pattern generation (atpg) fabrication for detecting faults in circuit layout and performance (bloch and geitner, 1994., walraven, 2003). xxiii. techniques for chemical characterization of materials, coatings, corrosion products, etc; by means such as energy-dispersive spectroscopy (eds), wavelength-dispersive spectroscopy (wds), raman spectroscopy, atomic emission spectroscopy, auger electron spectroscopy (aes), x-ray photoelectron spectroscopy (xps), time-of-flight secondary ion mass http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 593 spectrometry (tof-sims), fourier transform infrared spectroscopy (ftir), and chromatography (walraven, 2003., wolfgong, 2016). 2.1.2 reviews of some analytical rigors and recent developments in failure analyses by researchers for better appreciation of how the various approaches and available techniques or tools in failure analysis are exploited for different failure cases, the works of some practitioners or researches from different engineering disciplines on the subject who have taken particular cases for study and evaluation in the past few years have been reviewed and presented as follows: effect of isothermal ageing on two high temperature failures of 204oc and 250oc of bismaleimide composite materials, a novel csiro cbr 320/328 composite and a commercial ciba geigy matrimid 5292 composite was examined by fox et al. (2004). they noted that delamination was a major cause of failure in composite materials. they therefore measured the mode i inter-laminar fracture toughness of both materials using the double cantilever beam (dcb) test. they monitored chemical degradation of the matrix concurrently using fourier transform infrared (ftir) and raman spectroscopy. they found chemical changes at the core of all these materials to occur concomitantly with the observed changes in inter-laminar fracture toughness. their ftir analysis of both matrix materials revealed the predominant degradation mechanism to be the oxidation of the methylene group bridging two aromatic rings common to the structure of both resins that was substantiated by in-growth of a broad peak centred at 1600/cm. in addition to this, they found the pyromellitic anhydride unit present only in the cbr 320/328 composites to be highly resistant to the effects of ageing, whereas the saturated bismaleimide, common to the cured structures of both materials was observed to degrade. their raman spectroscopy indicated that the predominant degradation mechanism of the composites differed at the two ageing temperatures (fox et al., 2004). lee et al. (2004), analyzed the causes of the incident of a cessna trainer whose propeller was separated due to the cracking of the propeller blade hub during the takeoff roll. they observed beach marks and fatigue striations, typical of fatigue cracks on the fracture surface and detected corrosive oxides in the center of beach marks that were considered to be the crack origin. they found that the stress acting on the fracture surface under corrosive environment formed corrosive oxides, such as mud cracks. by analyzing the fractography and metallography of the failed parts, they found that the propeller blade hub nucleated stress corrosion cracking (scc) as a result of residual stress and corrosive environment and the scc was the cause of the fatigue crack. moreover, they found a fatigue crack to reach its critical length by repeated cyclic stress, which occurred during the rotation of the propeller blade and then, the rest of the fracture occurred instantaneously (lee et al., 2004). kim et al. (2005), conducted analyses of three failed air interceptor missile (aim)-9 rocket motors of different types used at different times, in order to identify the root cause of cracks occurring in the wing attachment of the motors. through visual inspection, they found that corrosion severity was in proportion to the failure rate in each crack surface. they carried out chemical analysis, microscopic examination, and residual stress determination on the crack surfaces to find out the cause of crack initiation and the mechanism of crack growth. they found that the crack origin was covered with mud cracks produced by an interaction of corrosion and stress, and the cracks were propagated along the grain boundary in the longitudinal direction. they also found that the corrosion-promoting factors were on the crack surface, and the tensile residual stress acted on the channel area of the rocket motor. as a result of the analyses, they concluded that the stress corrosion cracking occurred due to the interaction of corrosive environment and tensile residual stress which were latent in the rocket motor body (kim et al., 2005). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 594 failure analysis of the turbine disc of an aero engine, installed in a certain type of aircraft was investigated by witek (2006). from visual examination of the fractured surface, he observed beach marks typical of fatigue failure. he utilized a non-linear finite element method to determine the stress state of the disc/blade segment under operating conditions and performed computations with excessive rotational speed. he found high stress zones to occur at the region of the lower fir-tree slot, where the failure occurred. he devoted attention of this study to the mechanisms of damage of the turbine disc and also the critical high stress area (witek, 2006). baadkar (2010), conducted a study on structural failure analysis of a semi-trailer using finite element method. he centred his research on an ongoing trailer component failure problem at the steelbro new zealand ltd due to cracks. in his research he systematically approached the problem using ansys finite element analysis software. his approach involved investigation of the problem and structural analysis of the trailer subjected to two types of service conditions. he simulated the service conditions in ansys which involved cad and finite element modelling of the trailer, and then the finite element model was validated experimentally by strain gauges and geometrically by ansys element shape checking capability. he found that the finite element model subjected to static structural analysis confirmed the crack locations and indicated the cause of the failure. his further fatigue analysis on one of the loading conditions revealed potential of the fatigue to cause failure at the crack locations. he finally, concluded his research with a proposal of revised component design to overcome the failure at the crack locations and recommendations for further analysis on the trailer (baadkar, 2010). a combined analytical and experimental approach was utilized to analyze failures of steel axles in a fleet of refrigeration semi-trailers equipped with dual rear axle air-ride suspensions by kadlec et al., (2010). they used experimental data in combination with an analytical model to identify the cause of the axle failures, estimated time to failure, and evaluated the relative effectiveness of proposed design changes to minimize future axle failures. the centre-pieces of their program were finite element and fracture mechanics models of the axles. their conducted experiments in support of the analytical models consisted of: field and laboratory inspection of failed axles to determine failure mode and the size of pre-existing flaws, full scale trailer road testing to determine the service load spectrum, fatigue tests on laboratory specimens to determine material properties, and full scale axle fatigue testing to calibrate and verify the ability of the analytical methods to predict axle lifetimes. they also evaluated empirically the effect of design and manufacturing process changes of the axles. their focus was on the analytical models. they evaluated two potential solutions which involved an axle reinforcing jacket, and replacement of the original axle with a thicker walled axle. these analytical models were vital tools which determined that both of these solutions effectively extend axle lives so that they had adequate design margins (kadlec et al, 2010). karayan et al. (2011), studied the failure of a seawater inlet pipe. they first characterized the failure by a small leak at approximately the 4-8 o’clock position. they depicted a schematic drawing of the inlet pipe showing the backing bar near the leak location as shown in figure1. this backing bar was installed on the welded surface. their visual examination of this failed pipe was as shown in figure 2. in order to find out the root cause of failure, they performed a number of laboratory tests. their test results showed that the failure was caused by cavitation, as evident by the presence of a crater-like surface near the backing bar shown in figure 3. they observably found these localized craters seemingly unusual since they were only noticed near the backing bar. they then used finite element analysis as additional tool to determine why this was the case. they executed the finite element analysis based on the pipe dimension and actual fluid conditions such as velocity, pressure, temperature, and implicit parameters. because there http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 595 were no data for the initial height of the unwanted backing bar, they assumed that the initial height was the highest backing bar found on the specimen. interestingly, the failure location predicted by their finite element analysis matched up with the actual evidence as shown in figure 4. their finite element analysis precisely showed that the failure could be located around the backing bar where the eddy zone was formed in this area. as can be seen from figure 4, the leaks and crater-like surfaces found in the area near the backing bar were attributed to the formation of eddy zones in this area. the length of the eddy zone predicted the area that might suffer from a flow-induced attack. as a part of their conclusion they averred that when results obtained from laboratory tests cannot sometime explain why a failure occurs but evidence indicates the existence of a certain problem, finite element analysis is the only tool that can help a failure analyst find the root cause of the failure (karayan et al., 2011). figure 1: big and small leak near the backing bar at about 6 o’clock position viewed from the inner side of seawater inlet pipe. figure 2: big and small leak near the backing bar at about 6 o’clock position viewed from the inner side of seawater inlet pipe. figure 3: surface morphologies of brown crater-like surface taken from 6-3 o’clock positions. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 596 figure 4: finite element analysis of the inner pipe showing the orifice effect and the eddy zone near the backing bar correlated with the actual leaks on the inlet pipe. according to khare et al. (2012), most failures in the automotive systems depend on age and accumulated usage. they stated that typically, these criteria are covered under warranty for months-in-service (mis), that is, mis/age and a certain amount of usage (mileage) after the sales of the products. they pointed out that, warranty analysis of these systems enables manufacturers to understand field failures, and identify focus areas to make product improvements. they informed that typically, warranty analysis is performed based on mis and moreover mileage is based on warranty analysis which has two added benefits, namely: i. some failures are by their physical nature, related to mileage rather than age. hence, mileage is a better indicator for observing and quantifying these failures. ii. their observations also indicated that most vehicles leave warranty due to the mileage restrictions to the warranty coverage, rather than mis. in such a scenario, mileage-based warranty calculations can provide us with early information. warranty analysis based on mileage has been presented in the literature as a supplement to the traditional mis based analysis (khare et al., 2012). a case study of a catastrophic failure of a web marine crankshaft and failure analysis under bending and torsion applied to crankshafts were presented by jadhav et al. (2013). their microscopy and eye-seen observations showed that the crack initiation started on the fillet of the crankpin by rotary bending and propagated by a combination of cycle bending and steady torsion. the crack front profile approximately adopted a semi-elliptical shape with some distortion due to torsion. they supported the study by a previous research work already published by them. the number of cycles from crack initiation to final failure of the crankshaft was achieved by recording the main engine operation on board taking into account the beach marks left on the fatigue crack surface. their calculated cycles by the linear fracture mechanics approaches showed that the propagation was fast which meant that the level of bending stress was relatively high when compared with total cycles of an engine in service. they however did not observe microstructure defects or inclusions which concluded that the failure was probably originated by an external cause and not due to an intrinsic latent defect. they also discussed possible effects of added torsional vibrations which induced stresses. they analyzed and reported some causes but the origin of the fatigue fracture was not clearly determined (jadhav et al., 2013). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 597 nassef et al. (2016), investigated the failure of a rocker arm shaft of a passenger car. the shaft failed by brittle fracture across one of the four holes supporting the shaft into the cylinder head. the running distance of the engine just before failure was 40,626 km. their visual examinations of etched sections of the failed shaft and a new one revealed four distinct zones of darker etching appearance. they found that these zones corresponded to the four locations where the rocker arms fitted the shaft. their microscopic observations of the failed shaft revealed that the four dark-etching areas were surface hardened zones of martensitic microstructure. furthermore, they found by scanning the microstructure along the failed shaft that heat treatment was so mistakenly extended by excessive heating so that the structure of the shaft near the supporting holes had considerable content of martensite phase. they confirmed this conclusion by their results of hardness measurements along the surface of the shaft. microscopic investigations of the failed shaft revealed the presence of micro-cracks close to the supporting holes. they reasoned that these cracks might have been induced in the shaft by the non-uniform cooling during quenching in the course of heat treatment, or might have been nucleated by repeated loading during service. they finally concluded that this premature failure had occurred by the rapid crack propagation because of the lower fracture toughness of the martensite (nassef et al., 2016). a failure analysis investigation was performed by rao and eischen (2016), on a fractured heavy duty truck frame rail obtained during endurance track testing. they observed the fracture on the frame web within the torque rod connection to the rear drive axle of the vehicle. they found that this section of frame experienced multi-axial loading conditions including out-ofplane bending, twisting and shear under road loads. their metallographic examination revealed micro-cracks on the edges of an open hole located in an area of high stress concentration. they saw this to be a manufacturing defect that acted as stress raiser and resulted in crack initiation. they conducted simulation of on frame rail using dynamic loads from a full vehicle model. after careful analyses of all their collected information, they concluded that the failure occurred due to an aggressively drilled open hole which created small crack initiations in a high stress-state location of the frame which resulted in extensive curvilinear crack growth under dynamic loads of the vehicle to fracture the frame rail (rao and eischen, 2016). due to frequent failures of coil springs on a specific type of motor vehicle, analysis of possible causes of failures was performed by vukelica and brcic (2016). they did the analysis on a single coil spring removed from a vehicle after failing in service. besides their visual examination that revealed fracture on a first bottom coil, several other experimental techniques were used in the failure analysis. using optical microscopy evaluation, they performed basic microstructure of the fractured surface and distinguished possible inclusions. they employed detailed scanning electron microscopy (sem) examination at suitable magnifications to characterize the fine microstructure of the fractured surface and revealed flaws that served as crack initiation points. they used optical emission spectrometer with glow discharge source (gds) sample stimulation to determine chemical composition of material used for the spring fabrication. additionally, they performed hardness test. using results of the performed experimental analysis, they recognized the possible causes of the failure. they reported that several factors, among them inherent material defect combined with material fatigue coupled with insufficient corrosion protection, caused failure of coil spring. they concluded that the obtained results were valuable in predicting behavior of coil springs mounted in other vehicles of the same type and could be taken as a reference in improving future design. they recommended further analysis including employment of finite element method to determine stress levels in undamaged and damaged coil spring along with numerical estimation of fatigue life (vukelica and brcic, 2016). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 598 bochnowski et al. (2019), investigated the failure of the belt conveyor made of 330 nb heatresistant steel working in a furnace for continuous heat treatment in a carburizing and oxidizing atmosphere. on the basis of microscopic tests and x-ray phase analysis, they determined changes in the microstructure in the cross-section of the conveyor wire after 731, 1642 and 2138 cycles of carburizing and oxidizing in the temperature range 30oc to 850oc in 160 minutes. moreover, they carried out tensile tests to investigate the effect of the microstructure on the mechanical properties of heat-resistant steel. they found that the failure was due to a cross crack of wires of the conveyor belt mesh. their results showed that on the surface of the alloy, cr2o3 chromium oxides and fecr2o4, mn1.5cr1.5o4 oxides were formed. on the border of the alloy and chromium oxides, the airtight sio2 layer was created. they reported that as a result of the actions of external forces, transverse and longitudinal cracks were formed in the oxide layer. these cracks were the ways of carbon and oxygen diffusion. they additionally reported that in the oxidation and carburization process, degradation of the sio2 layer was promoted by the presence of na, which was applied in washing agents used for cleaning products before placing them on the conveyor. they found that the microstructure of the unused wire of the conveyor belt consisted of g and h phases and nbc in austenitic matrix. under the operating conditions of the conveyor belt, phase h dissolved in the matrix with the simultaneous increase of the g phase, and also the g phase was formed around the nbc carbides. high temperature carburizing led to the precipitation of massive carbides m23c6 with simultaneous significant depletion of chromium into an austenitic matrix to about 13%. their quantitative micro-structural analysis showed that there was an increase in the size and participation of hard phases m23c6, g, nbc in the alloy microstructure. the volume fraction of precipitation increased from 3 to 24%vol. the resulting structure was characterized by low strength with significant decrease in ductility of the alloy (bochnowski et al., 2019). in his paper, celvik (2019), summarized the work he conducted to assess the root cause of the failure of a medium commercial vehicle leaf spring that failed in service. he conducted macroand micro-fractographic analyses by scanning electron microscope as well as material verification tests in order to understand the failure mechanisms and root cause of the failure. his findings from the fractographic analyses indicated that the failure mechanism was fatigue. he identified crack initiation to have occurred from a point on the top surface near to the front face and to the left side. he also observed two other crack initiation points that however did not propagate. the propagation mode of the fatigue crack revealed that the cyclic loads resulting in crack initiation and propagation were unidirectional bending. his fractographic analyses also showed that the root cause of the fatigue crack initiation and propagation was loading the part above design stress. he also verified material properties of the part by chemical composition analysis, micro-structural analysis, optical microscopy, and hardness tests (celvik, 2019). according to roberts (2019), improper weight distribution can be a cause of structural failure in semi trailers. this can not only lead to the loss of the trailer, but also to the loss of cargo or even the possibility of an accident. he illustrated the following two case studies of losses caused by overloading semi-trailers. he depicted the view of a typical van trailer that sustained a sidewall failure in figure 5 while carrying six pallets of copper wire, weighing approximately 3,178kg each. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 599 figure 5: a typical van trailer he reported that the total load of 19,047kg in the trailer was unacceptable, according to the trailer manufacturer’s load limit. the trailer manufacturer stipulated that a maximum concentrated load of 6,810kg in 3.048m of trailer length should not be exceeded (roberts, 2019). guma et al. (2019), noted that failures of heavy-duty vehicles during load hauling are major concern in road transportation due to the magnitudes of accidents that sometimes result from the failures with loss of lives, destruction of goods or spillage with treat to environment, and road blockages. they averred that the failures are particularly detestable to the vehicle owners owing to the much loss they can incur including litigations they can face and compensations they can be obliged to make to affected innocent victims. they conducted analysis of shell failure of a semi-trailer tanker owned by an oil marketing company in nigeria which resulted in much loss of the trailer’s full-tank carried oil. the aim of their analysis was to provide information that could be useful for forestalling recurrent failure problems with the company’s fleet of semi-trailers which had caused the company substantial losses in its annals. they first visually examined the as-failed shell to assess the nature and magnitude of the failure and documented information on where and how the failure occurred. they also surveyed and documented critical information about the trailer such as its maintenance record, usage level, competence level of its driver, mileage record, loading capacity, operational level, and collected samples from critical locations of the failed shell. thereto, they conducted laboratory test analysis of the collected samples with respect to chemical composition, metallographic structure, and corrosion behaviors. by their visual inspections, they observed that the shell failed by a small brittle crack perforation along the seam of a previous weld repair. reportedly; their collected background information showed no clear standard maintenance records of the semi-trailer, their chemical analysis showed a steel material of different composition at the failure location compared to the as-made shell carbon steel, their metallographic analyses showed that the failure location was heterogeneous compared to the as-made shell steel. their corrosion analyses showed greater corrosion rates at the failure location which presumably raised the location stresses amid dynamic effects from bad road conditions and caused the shell to crack-perforate along the weld seam of the location (guma et al., 2019). guo et al. (2019), evaluated micro-structural degradation in a failed gas turbine blade due to overheating. they reported that gas turbine blades may undergo overheating, which could cause serious micro-structural degradation and even failure of turbine components. nonetheless, they noted that limited published investigations focus on the evaluation of the micro-structural degradation in overheated turbine blades. in their study, they investigated a high-pressure turbine blade, which comprised of equiaxed-cast super-alloy substrate and an alsi coating. they reported that the blade failed due to material loss at the airfoil tip of the leading edge. they conducted a systematic micro-structural investigation of the failed blade, and compared their results with those of thermally exposed samples. by taking several microstructural degradation parameters as references, they evaluated the micro-structural file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 600 degradation of the failed blade and estimated the equivalent maximum service temperature. their results reportedly indicated that most locations of the failed blade had been operating under normal conditions; however, the airfoil tip of the leading edge had suffered serious overheating, and the overheating temperature was almost 200°c above the normal service temperature. the overheating led to incipient melting of the substrate and material loss of the service blade resulting in the failure (guo et al., 2019). jiang et al. (2019), conducted analysis of failure initiation in corroded cast iron pipes under cyclic loading due to formation of through-wall cracks. they identified corrosion and internal water pressure as major factors contributing for the longitudinal failures in large-diameter cast iron water pipes. they reported evidence of deteriorating pipeline integrity due to fluctuations of internal pressure loading. they aimed their study to investigate the fatigue resistance of cast iron pipes and to identify the pipes in a water network that were at high risks of fatigue damage. they conducted stress-controlled fatigue tests on coupons prepared from exhumed cast iron pipes. they developed a correlation between tensile fatigue stress and cycles to failure based on experimental results. they proposed a methodology to identify critical factors for initiating a through-wall crack in cast iron water pipe considering the impact of fatigue. they conducted a sensitivity analysis with relevant factors, and the relative impact of those factors to cause a premature failure was assessed. they identified the operating pressures and stress ratios caused by pressure transients and long-term soil corrosion rate as the key contributing factors for severe fatigue damage (jiang et al., 2019). katinic et al. (2019), described the failure of a rotor of a condensing industrial steam turbine installed in a fertilizer production plant. they identified a fracture of the two adjacent rotor blades in their roots. they carried out an analysis of the failure cause by the analyses; of the fracture location on the steam flow path, the corrosion deposits, and the modal of the rotor blades. they performed the modal analysis using the finite element method. they conclusively reported that the blades’ failure was due to a phenomenon known as corrosion fatigue. to extend the useful fatigue life of rotor blades in the future, they redesigned the entire turbine stage of broken blades. they found that the modified design of the turbine stage increased the fatigue safety factor by about 50% compared to the original design (katinic et al., 2019). khadem and yareiee (2019), conducted research aimed to assess failure analysis of a boiler tube of a steam generation system at a petrochemical plant. to achieve this goal, they first made visual observation and took thickness measurements to detect different features of the failure. thereto, they used optical microscope and scanning electron microscope (sem) to observe the microstructures and also carried out hardness measurements for metallurgical evaluation. they also studied phase composition of deposits of the tube by using x-ray diffraction (xrd), and took into consideration the on-site water composition of the boiler. they finally performed finite element analysis (fea) to model the condition of the tube before failure. based on the results of their analyses, they recognized “short-term overheating” as the root cause of the boiler tube failure (khadem and yareiee, 2019). lachowicz (2019), conducted studies on the inter-granular corrosion-fatigue failure of the znal alloy solenoid valve. the purpose of his performed studies was to determine causes of the solenoid valve corrosion which appeared during its operation. as a result of his performed macroscopic observations, he found that the cause of the valve corrosion was its unsealing. he reported that the unsealing led to strong corrosion of the solenoid valve body from its internal surface in the vicinity of the seat as a result of actions of surrounding chloride ions. this he said caused surface covering of the valve with white corrosion products characteristic for zinc alloys. he also reported that the resulting corrosion was of the inter-granular nature and propagated over grain boundaries and the inter-dendritic areas which led to decrease in the active crosshttp://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 601 section of the valve and abnormal stress concentration that caused the valve failure (lachowicz, 2019). liu et al. (2019), conducted fracture failure analysis and research on drive shaft of positive displacement motor. they investigated microstructures and mechanical properties of the fractured drive shaft by visual inspection, metallographic analysis, scanning electron microscopy, and tensile and impact tests. they tested the composition, structure and mechanical properties of the drive shaft materials in meeting the standards. they found that the fracture surface was mainly characterized by dimples and small amount of quasi-cleavage by microscopic analysis, which indicated that the fracture surface was dominated by ductile fracture. they also found through eds spectrum analysis that at the bottom of the sample pit, there were a large number of grey inclusions which were turned to be iron oxides. they asserted that the existence of a large number of iron oxide inclusions in the metal would inevitably have serious impact on the performance of the drive shaft. they also conducted finite element analysis of the failure. the analysis showed that the stress on the cylindrical surface of the external thread near the shoulder would gradually increase greatly and the rupture risk would increase with the increase of torque and that it would also fail due to the relatively high stress on the root of the first tooth of thread. they found that the maximum stress near the thread shoulder was close to the yield limit of the shaft material when the borehole curvature was larger, and the bending load would lead to stress concentration on the optical axis section at the shoulder to affect safety of the drive shaft. because there were a large number of inclusions in raw materials and the conditions in the well were complex, the carrying capacity of the drive shaft decreased and fracture of the shaft was finally caused. they found through comparative analysis that, the maximum stress value of the improved drive shaft was lower than that before the improvement. their analyses showed that the safety factor and service life of the drive shaft could be improved by improved design (liu et al., 2019). ni et al. (2019), carried out failure analysis on abnormal perforation of super large diameter buried gas pipeline nearby metro company in the united kingdom. they noted that as a part of urban pipeline network, buried gas pipelines are mainly used to transport high-pressure natural gas, artificial gas, and liquefied petroleum gas. they pointed out that since such pipelines are exposed to various unpredictable harsh service conditions; it is easy for them to encounter failures. in their paper, they systematically investigated an abnormal perforation failure of super large diameter buried gas pipeline with an outside diameter of over 1000mm. they found that the failed pipeline had transported water gas before transporting natural gas and was welded with iron buttresses which were not treated by anticorrosive insulation treatment. their further obtained results indicated that the accumulation of impurities from water gas caused localized corrosion on the lower surface of the inner wall of the pipeline which led to formation of corrosion pits. they also reported that thereto, stray current came from the metro company flowed into the pipeline through iron buttresses and brought about stray current corrosion inside the corrosion pits on the lower surface of the inner wall of the pipeline. in totality they reported that the compound effect of these two corrosions resulted in the corrosion perforations. they finally proposed countermeasures to address corresponding problems (ni et al., 2019). a comprehensive fault diagnosis method was developed by yu et al. (2019), to analyze the failure of a multi-disc clutch. they developed the mechanical buckling model to investigate the relationship between the resistance torque and the periodic circumferential bright spots. they obtained the contact pressure and temperature on the friction surfaces with consideration of the concentrated reactive load of the c-clip. they explored the friction and wear characteristics of the friction disc under different temperature conditions by the pin-on-disc test, and then observed the surface morphologies of tested discs by the metalloscope. their file:///c:/users/user/downloads/azojete143/www.azojete.com.ng guma et al.: an overview of approaches and techniques used in failure analysis of engineering system. azojete,16(3):587-604.issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 602 results demonstrated that both the thermal buckling and the mechanical buckling could result in the mechanical-thermal buckling. they reported that as the temperature varied from 15oc to 400oc, the disc experienced the abrasive wear, ploughing wear, adhesive wear and delamination wear in that order. they finally proposed the mechanical-thermal safety boundaries, and provided some suggestions for better design of the clutch. they recommended that; the cclip should be optimized to avoid stress concentration, the teeth number of separate plates should be increased to improve the torque transmission capacity, and the thickness of separate plates should be different and determinable by their axial positions in the clutch pack (yu et al., 2019). 3.0 conclusion an overview of approaches and techniques used in failure analysis of engineering system has been conducted. it is seen that the general causes of failure and the behavior of materials may be known, prevention of failure of an engineering system is difficult to guarantee in our technological world. failure of engineering system or component can be calamitous with enormous losses and is highly detested. failure analysis is the current technology through which recurrence of unavoidable failure cases can be prevented in engineering. the critical requirement in failure analysis is that, it must be correctly conducted to provide all necessary information that give substance to explanations for the root cause of the failure. there are various approaches and techniques from the literatures that are used in failure analysis of engineering systems but not all or a number of them can be suitable for every particular failure case. the critical issues in the review is the necessity for the analyst to first and foremost preserve evidence and get as much as possible information from the field failure conditions and background realities of the failed system or item. other notable issue in the review is the necessity to select the best approaches and techniques to assess: characteristics that are present in the failed/damaged system or item and those that are supposed to be present in it before failure, the differences between the damaged and undamaged system or item, and results of the tests that must be performed to substantiate explanations and refine knowledge about the observed damage to correctly reveal the root cause/s of failure. the failure analyst is therefore supposed to have a sound broad knowledge of the approaches and techniques and be able to always select the best approaches and techniques that will enable correct analysis of individual failure cases. the reviewed basic prevailing standard approaches and techniques of engineering system failure analysis from various literary sources have been presented together with 24 works of researchers from different backgrounds on the subject who have taken particular cases for study and evaluation. the paper is intended to provide a compendium of contemporary practicable approaches and techniques used in failure analysis for motivation, better knowledge, and application interest of concerned practitioners and researchers that are not yet much experienced in the field. for high accuracy in failure analyses of critical failure cases, it is advisable where applicable to always conduct each case analysis using at least threetechnique evaluations for cross-checking and optimization of results to have higher confidence of the generated information. references aliya, d. 2002. the failure analysis process: an overview. in asm handbook, vol 11 (2002), failure analysis and prevention, (ed) by william, t. becker and rock, j. shipley, asm international, materials park, russel township, ohio, 315-323. asm handbook 2002. failure analysis and prevention, vol 11, asm international. materials park, russel township, ohio, 120-174 asm. 2015. failure analysis, published by asm international, materials park, russel township, ohio, 3-50 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 587-604. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 603 baadkar, cc. 2010. semi-trailer structural failure analysis using finite element method. m.sc thesis in mechanical engineering, university of canterbury, england. bloch, h. and geitner, f. 1994. machinery failure analysis and troubleshooting. gulf publishing company, houston, 10-36. bochnowski, w., szyller, l. and osetek, m. 2019. damage characterization of belt conveyor made of the 330nb alloy after service in a carburizing atmosphere in a continuous heat treatment furnace. engineering failure analysis journal, 103: 173-183. çevik, g. 2019. failure analysis of a medium duty vehicle leaf spring. world academy of science, engineering and technology. international journal of mechanical and materials engineering, 13(10): 668-673. colangelo, v. 1978. metallographic analysis of corrosion failures, in j. l. mccall et al (eds.) metallography in failure analysis, plenum press, new york. ewalds, hl. and wanhill, rjh. 1984. fracture mechanics. edward arnold and delftse uitgevers maatschapp.` fernando, v. 2013. failure analysis in the oil and gas industry, inspectioneering journal, 2013: 1-5. fox, b., lowe, a. and hodgkin, j. (2004). investigation of failure mechanisms in aged aerospace composites. engineering failure analysis journal, 11(2): 235-241. ghosh, n. 1997. failure analysis-techniques and few case studies. proceedings of conference on failure analysis 1997 by national metallurgical laboratory of india. 18-19, february, jamshedpur, india, 63-71. guma, tn., odita, kv., ozoekwe, nca. and akor, t. 2019. analysis of shell failure of a semitrailer tanker used for hauling petroleum products. nigerian institution of professional engineers and scientists’ journal of science and technology research, 1(3):144-160. guo, x., zheng, w., xiao, c., li, l. and feng, q. 2019. evaluated micro-structural degradation in a failed gas turbine blade due to overheating. engineering failure analysis journal,103: 308318. jadhav, a., chalwa,v. and gaikwad, p. 2013. fatigue failure analysis of marine engine crankshaft. international journal of engineering research and technology, 02(06): 1-6. janssens, v., o'dwyer, d. and chryssanthopoulos, mk. 2011. building failure consequences. final conference of cost action tu0601, at prague, czech republic 2011/01/01, 99-104. jiang, r., rathnayaka, s., shannon, b. and zhao, x. 2019. jayantha kodikara. analysis of failure initiation in corroded cast iron pipes under cyclic loading due to formation of through-wall cracks. engineering failure analysis journal, 103: 238-248. jones, drh. 1993. engineering materials 3: materials failure analysis: case studies and design implications. vol. 3. pergamon press, oxford. kadlec, r., westmann, r., haghi, m., sire, r. and deverl, e. 1998. failure analysis of heavy truck trailer axles. technology, law and insurance, 3(1): 25-31. karayan, ai., ferdian, d., harjanto, s., nurjaya, dm., ashari, a. and castaneda, h. 2012. finite element analysis applications in failure analysis: case studies. intech open, london. katinic, m., kozak, d., gelo, i. and damjanovic, d. 2019. corrosion fatigue failure of steam turbine moving blades: a case 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vn. and eischen, jw. 2016. failure analysis of mixed mode crack growth in heavy duty truck frame rail. engineering failure analysis journal, 5: 67-74. roberts, cc. 2020. structural failure in semi-trailers from overloading. available at http://www.croberts.com/trailer-failure.htm. russell, md. and jur, ta. 2017. engineering analysis of failure: a determination of cause method. journal of failure analysis and prevention, 17: 8-14. https://doi.org/10.1007 vander voort, gf.1975. conducting the failure examination. asm metals engineering quarterly, 15(5): 31-36. vukelica, g. and brcic, m. 2016. failure analysis of a motor vehicle coil spring. 21st european conference on fracture, ecf21, 20-24 june, catania, italy: 2044-2050. walraven, ja. 2003. tools and techniques for failure analysis and qualification of mems. paper 33.2 itc international test conference september 30-october 2, 2003 charlotte convention center , charlotte, nc, usa, 834-842. doi: 10.1109/test.2003.1271068 witek, l. 2006. failure analysis of turbine disc of an aero engine. engineering failure analysis journal, 13: 9-17. wolfgong, wj. 2016. chapter 15-chemical analysis techniques for failure analysis: part 2, examples from the lab, in handbook of materials failure analysis with case studies from the aerospace and automotive industries, butterworth-heinemann, oxford, 309-338. wooten, j. 2014. oil and gas failure analysis. a primer vp and general counsel at inspectioneering, llc., december 29. available at inspectioneering.com › blog › oil-and-gasfailure-analysis. yu, l., ma, b., chen, m., li, h. and li, m. 2019. investigation on the failure mechanism and safety mechanical-thermal boundary of a multi-disc clutch. engineering failure analysis journal, 103: 319-334. https://ieeexplore.ieee.org/author/37086758951 https://ieeexplore.ieee.org/author/37399467900 https://ieeexplore.ieee.org/author/37086756909 https://ieeexplore.ieee.org/xpl/conhome/6294524/proceeding https://ieeexplore.ieee.org/xpl/conhome/6294524/proceeding http://www.croberts.com/trailer-failure.htm.%20 https://www.sciencedirect.com/science/book/9780128009505 https://www.sciencedirect.com/science/book/9780128009505 http://www.azojete.com.ng 2 arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):51-60 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 51 original research article ac-dc solid-state conversion and power factor correction using thyristor-based static var compensator e. u. udo, l. i. oborkhale, c. c. nwaogu and a. o. amadi department of electrical & electronic engineering, michael okpara university of agriculture umudike, abia state, nigeria. *corresponding author’s email address: thought.umoren@gmail.com 1.0 introduction in the modern era, almost every household electronics works on direct current (dc) but we get alternating current (ac) from power generation plants via transmission lines because ac can be transmitted more efficiently than dc at lower cost. so every appliance which works on dc has an ac to dc converter circuit. ac is the dominant method of transporting power because it offers several advantages over dc, including lower distribution costs and simple way of converting between voltage levels as a result of invention of the transformer. ac power that is sent at high voltage over long distances and then converted down to a lower voltage is a more efficient and safer source of power in homes. depending on the location, high voltage can range from 4kv up to 765kv. ac mains in homes range from 110v to 250v, depending on which part of the world you live (alexander and sadiku, 2013). conventionally, ac–dc converters, popularly referred to as rectifiers, are implemented using diodes and thyristors to provide uncontrolled, semi controlled and controlled dc power with unidirectional and bidirectional power flow (miller and abrahams, 2018). reduction of harmonic content with the consequent increase of pf can be obtained by using either passive or active pf correction (pfc) techniques. passive methods include the use of tuned lc filters (azazi et al., 2010). moreover, the passive filter may not respond adequately if the load pf comes to vary. on the other hand, active methods come as a more efficient solution by using controlled solid-state switches in article information abstract this paper presents ac-dc solid states converters with thyristor-based static var compensator in power factor correction. there is need for solid-state ac–dc converters to improve power quality in terms of power factor correction, reduce total harmonic distortion at input ac mains and precisely regulate dc output. ac-dc converters operating in continuous-conduction mode have become popular because of reduced electromagnetic interference levels resulting from their utilization. the method employs the principle of interleaved converters, as it can be extended to a generic number of legs per winding of the autotransformers and high-power levels. the practical analysis of the converter is then plotted using a simulink model of matlab while a comparison of power factor and efficiency with relative to the load is drawn with steadystate and dynamic performance of the static var compensator (svc). an experimental prototype load varied between 400w to 1 kw is implemented to validate the work. the results obtained indicates that when the output loads were 53kw, 135kw, 270kw, 470kw and 900kw, the efficiency were 55%, 70%, 80%, 90% and 97% respectively. these results confirmed that there was improvement in the power factor and efficiency with increase in the load. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 february 2020 revised 18 february 2021 accepted 25 february 2021 keywords: thyristors ac/dc converter power factor correction static var compensator udo et al: ac-dc solid-state conversion and power factor correction using thyristor-based static var compensator. azojete, 17(1):51-60 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 52 association with passive elements such as resistors, inductors, and capacitors (molinas and garces, 2012). in fact, the closed-loop operation of a static power converter dedicated to pfc assures satisfactory performance with high input pf and regulated dc output voltage over a wide operating range. increased complexity and reduced robustness are distinct characteristics of this practice. in order to meet the requirement standards such as iec 61000-3-2, das et al. (2011) and ieee standard 519, glinka and marquardt (2005) on the quality of the input current that can be drawn by low-power equipment, a pfc circuit is typically added as a front-end stage. 1.1 rectifiers rectifiers are mainly classified into three types, namely half-wave rectifier, center tapped full-wave rectifier and bridge rectifier. we observed that none of the three rectifier types can efficiently convert the alternating current (ac) into direct current (dc) but only the center tapped fullwave rectifier and bridge rectifier can efficiently convert the alternating current (ac) into direct current (dc). figure 1 shows the block diagram of ac-dc converter with pfc. figure 1: block diagram of ac-dc converter with pfc 1.2 power factor correction (pfc) this refers to the method of increasing power factor (pf) by using active electronic circuits with feedback that control the shape of the drawn current. there are many commercial pfc controllers that can accomplish this task. in conventional non-pfc ac-dc power supplies a large filter capacitor (co) is placed directly after bridge rectifier. figure 2 shows the circuit diagram of forward converter using pfc control. figure 2: circuit diagram of forward converter using pfc control load bridge diode rectifier active pfc mains input vin arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):51-60. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 53 the unregulated input voltage with a constant magnitude is converted into a desired output voltage by fast switching using a mosfet and the switching frequency is around 100 khz. this unregulated dc voltage is fed to the large-filter capacitor or pfc (power factor correction) circuits for correction of power factor as it is affected. this is because around voltage peaks, the rectifier draws short current pulses having significantly high-frequency energy which affects the power factor to reduce. it is almost similar to dc to dc converter but instead of direct dc power supply ac input is used. so, the combination of the rectifier and filter shown in figure 1 is used for converting the ac into dc and switching is done by using a power mosfet amplifier with which very high gain can be achieved, (jeong, 2014). the mosfet transistor has low on-resistance and can withstand high currents. the switching frequency is chosen such that it must be kept inaudible to normal human beings (mostly above 20khz) and switching action is controlled by a feedback utilizing the pulse width modulation (pwm) oscillator, (sedra and smith, 2004). the stepping down of the voltage is done without a transformer as shown in figure 3. figure 3: conversion of an ac to dc and stepping down the voltage without transformer in figure 3, the voltage dropping capacitor of 0.47uf is connected in series with phase line of ac, this is a non-polarized capacitors so it can be connected from any side. a 470kω resistor is connected in parallel of capacitor to discharge the stored current in the capacitor when circuit is switched off, thus preventing from electric shock. this resistance is called bleeder resistance and then, bridge rectifier has been used to remove the negative half component of ac. this process is called the rectification, and 1000uf/50v capacitor has been used for filtration, thereby removing the ripples in the waveform. 1.3 input filtering block an input filter is important as it prevents noise produced in the power supply switching elements from getting back onto the mains power supply. it also prevents noise that may be on the mains power supply getting into subsequent circuits. the filter passes through 50/60hz mains frequency and attenuates higher frequency noise and harmonics that might be present. as with other parts of an ac to dc converter, reactive elements like capacitors and inductors perform the important role of frequency selective suppression. capacitors do not pass dc, and can be used in series or parallel, (levy, 2016). udo et al: ac-dc solid-state conversion and power factor correction using thyristor-based static var compensator. azojete, 17(1):51-60 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 54 1.4 rectification rectifiers are implemented using semiconductor devices that conditionally conduct current in one direction only like diodes. more sophisticated semiconductor rectifiers include thyristors. silicon controlled rectifiers (scr) and triode (triac) for alternating current are analogous to a relay where a small amount of voltage can control the flow of a larger voltage and current. the way this work is that they only conduct when a controlling ‘gate’ is triggered by an input signal (loffe and regel, 2017). by switching the device on or off at the right time as the ac waveform flows current is steered to create a dc separation. there are many circuits for doing this, with signals tapped off, the ac waveform used as control signals that set the phase quadrants thyristors are on or off. this is commutation, and can be either natural (in the case of a simple diode) or forced, as in the case of devices that are more sophisticated (sedra and smith, 2004). diodes have an intrinsic voltage drop across them when they conduct. this causes power to be dissipated in them, but other active elements may have much lower drop and therefore lower power loss. scr and triac circuits are particularly common in low cost power control circuits like the light dimmer, (kittel, 2016). the statement of problem of this paper is for a d.c load to receive the desired voltage and current ratings with reduced transformer and inductor sizes. therefore a.c mains must be rectified and filtered to feed the power factor correction stage. the objective is to implement ac – dc conversion and power factor correction using solid state devices. 2.0 materials and method the materials used in this paper include thyristor-based static var compensator, a 735 kv/16 kv, 333 mva coupling transformer, one 109 mvar tcr bank and three 94 mvar tsc banks (tsc1 tsc2 tsc3) connected on the secondary side of the transformer. the svc is a shunt device of the flexible ac transmission systems (facts) family using power electronics. it regulates voltage by generating or absorbing reactive power. switching the tscs in and out allows a discrete variation of the secondary reactive power from zero to 282 mvar capacitive (at 16 kv) by steps of 94 mvar, whereas phase control of the tcr allows a continuous variation from zero to 109 mvar inductive. taking into account the leakage reactance of the transformer (0.15 pu), the svc equivalent susceptance seen from the primary side was varied continuously from -1.04 pu/100 mva (fully inductive) to +3.23 pu/100 mvar (fully capacitive). the svc controller monitors the primary voltage and sends appropriate pulses to the 24 thyristors (6 thyristors per three-phase bank) to obtain the susceptance required by the voltage regulator. figure 4 shows the singleline diagram of a static var compensator. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):51-60. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 55 figure 4: single-line diagram of a static var compensator and its control system the svc regulates voltage at its terminals by controlling the amount of reactive power absorbed from the power system. when system voltage was low, the svc generates reactive power (svc capacitive). when system voltage was high, it absorbed reactive power (svc inductive). the variation of reactive power was performed by switching three-phase capacitor banks and inductor banks connected on the secondary side of a coupling transformer. each capacitor bank was switched on and off by three thyristor switches (thyristor switched capacitor or tsc). reactors were either switched on-off (thyristor switched reactor or tsr) or phase-controlled (thyristor controlled reactor or tcr). figure 5 shows the selective problem solving (sps) model of the 300mvar. figure 5: sps model of the 300 mvar svc switching the tscs in and out allows a discrete variation of the secondary reactive power from zero to 282 mvar capacitive at 16 kv by steps of 94 mvar, whereas phase control of the tcr allows a continuous variation from zero to 109 mvar inductive. taking into account the leakage reactance of the transformer (0.15 pu), the svc equivalent susceptance seen from the primary side was varied continuously from -1.04 pu/100 mva (fully inductive) to +3.23 pu/100 mvar (fully capacitive). udo et al: ac-dc solid-state conversion and power factor correction using thyristor-based static var compensator. azojete, 17(1):51-60 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 56 the svc controller monitors the primary voltage and sends appropriate pulses to the 24 thyristors (6 thyristors per three-phase bank) to obtain the susceptance required by the voltage regulator. figure 6 shows the simulink models of svc controller. the power system was represented by an inductive equivalent (6000 mva short circuit level) and a 200-mw load. the internal voltage of the equivalent system was varied by means of a three-phase programmable voltage source block to observe the svc dynamic response to changes in system voltage, (levy, 2016). figure 6: simulink models of svc controller 3.0 results and discussion 3.1 steady-state and dynamic performance of the svc the steady-state waveforms and the svc dynamic response when the system voltage was varied is shown in figure 7. figure 7: waveforms illustrating svc dynamic response to system voltage steps arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):51-60. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 57 initially, the source voltage was set at 1.004 pu resulting in a 1.0 pu voltage at svc terminals when the svc is out of service. as the reference voltage vref is set to 1.0 pu, the svc is initially floating. this operating point is obtained with tsc1 in service and tcr almost at full conduction (α = 96 degrees). at t = 0.1s voltage is suddenly increased to 1.025 pu. the svc reacts by absorbing reactive power (q = -95 mvar) to bring the voltage back to 1.01 pu. the 95% settling time is approximately 135 ms. at this point all tscs are out of service and the tcr is almost at full conduction (α = 94 degrees). at t = 0.4 s the source voltage is suddenly lowered to 0.93 pu. the svc reacts by generating 256 mvar of reactive power, thus increasing the voltage to 0.974 pu. at this point the three tscs are in service and the tcr absorbs approximately 40% of its nominal reactive power (α =120 degrees). we observe that on the last trace of the scope how the tscs are sequentially switched on and off. each time a tsc is switched on the tcr α angle changes from 180 degrees to 90 degrees. finally, at t = 0.7 s the voltage is increased to 1.0 pu and the svc reactive power is reduced to zero. also we can open the signal and scopes subsystem to observe additional waveforms. the tcr voltage and current in branch ab as well as thyristors pulses are displayed on the tcr ab scope. figure 8 shows the zooms on three cycles when the firing angle α is 120 degrees. figure 8: steady-state voltage and current in tcr ab 3.2 misfiring of tsc1 at the final stage, we simulated a tsc misfiring. each time a tsc is switched off, a voltage remains trapped across the tsc capacitors. when looking at the tsc1 misfiring scope inside the signals and scope subsystem, we can observe the tsc1 voltage and the tsc1 current for branch ab. the voltage across the positive thyristor (thyristor conducting the positive current) is shown on the third trace and the pulses sent to this thyristor are shown on the fourth trace. again we noticed that the positive thyristor is fired at maximum negative tsc voltage, when the valve voltage is minimum. udo et al: ac-dc solid-state conversion and power factor correction using thyristor-based static var compensator. azojete, 17(1):51-60 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 58 if by mistake the firing pulse is not sent at the right time, very large over currents can be observed in the tsc valves. by looking inside the svc controller block to know how a misfiring can be simulated on tsc1. a timer block and an or block is used to add pulses to the normal pulses coming from the firing unit. by opening the timer block menu and removing the 100-multiplication factor. the timer is now programmed to send a misfiring pulse lasting one sample time at time t= 0.121 s. figure 9: tsc voltages and current resulting from misfiring on tsc1 table1: power factor results used for implementing hardware buck converter for various load conditions. o/p load (w) i/p volt (v) i/p amp (a) o/p volt (v) o/p amp (a) pf efficiency wo/wi 53 234 0.4 133 0.4 0.676 54.77 135 234 0.8 133 1.0 0.778 69.73 270 234 1.4 133 2.0 0.864 79.69 470 234 2.2 133 3.5 0.917 89.03 900 235 3.9 133 6.7 0.954 96.52 arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):51-60. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 59 figure 10: power factor and % efficiency v/s output load in watt in the output result, we observed improvement in the power factor and efficiency as the load increases with zero crossing of currents and voltages and the waveform of crystal frequency of microcontroller output are 55%, 70%, 90% and on 97% respectively. figure 11: voltage – ampere characteristics 4.0 conclusion in this paper, we observed that the misfiring pulse was sent when the valve voltage was maximum positive immediately after the tsc has blocked. this thyristor misfiring produces a large thyristor over-current (18 ka or 6.5 times the nominal peak current). also, immediately after the thyristor has blocked, the thyristor voltage reaches 85 kv (3.8 times the nominal peak voltage). to prevent such over-currents and over-voltages, thyristor valves are normally protected by metal oxide arresters. -2 -1.5 -1 -0.5 0 0.5 1 1.5 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 reactive current (pu/100 mva) p o s . s e q . v o lt a g e ( p u ) capacitive inductive svc v-i characteristic red: specified v-i characteristic blue: measured v-i characteristic xs= 0.03 pu/200 mva vref=1.0 pu b=2 pu/100 mva b=1 pu/100 mva udo et al: ac-dc solid-state conversion and power factor correction using thyristor-based static var compensator. azojete, 17(1):51-60 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: thought.umoren@gmail.com 60 to improve the performance of the ac-dc solid state converter a good power factor correction technique is necessary, then there should be a low total harmonic distortion (thd) and low dc bus voltage. at the power factor correction stage two bulk storage capacitors are adopted. its excellent line regulation capability makes the converter suitable for universal input application. references alexander, c. and sadiku, m. 2013. fundamentals of electric circuits. new york, ny: mcgraw-hill. 067: 115-122 azazi, hz., el-kholy, ee., mahmoud, sa. and shokralla, ss. 2010. review of passive and active circuits for power factor correction in single phase, low power ac-dc converters. proceedings of the 14th international middle east power systems conference mepcon’10), 19-21 december, 2010. cairo university, egypt, paper id 154: 217-224. das, m., capell, c., grider, d., raju, r., schutten, m., nasadoski, j., leslie, s. ostop, j. and hefner, a. 2011. 10kv,120 a sic half hbridge power mosfet modules suitable for high frequency, medium voltage applications. energy conversion congress and exposition (ecce), ieee, pp. 2689 -2692. glinka, m. and marquardt, r. 2005. a new ac/ac multilevel converter family. industrial electronics, ieee transactions 52(3): 662 – 669. ioffe, a. and regel, ar. 2017. non crystalline, amorphous and liquid electronic semiconductors. progress in semiconductors, heywood and co ltd, london, 321-328. jeong, y. 2014. novel methodology of ac-dc valley fill with power factor correction. http://nssemicon.com/pdf/ac_dc.pdf. kittel, c. 2016. quantum theory of solids, wiley, new york. levy, f., 2016. physique et technologies des semi-conductors, presses polytechniques et universitaires romandes, lausanne. miller, u. and abrahams, e. 2018. impurity conduction at low concentrations. physics reviews, 120( 3): 754–755. molinas, m. and garces, a. 2012. a study of efficiency in a reduced matrix converter for offshore wind farms. industrial electronics, ieee transactions, 59 (1): 184 – 193. moliton, a. 2017. basic electromagnetism and materials, springer, new york. sedra, a. and smith, k. 2004 microelectronic circuits 5th edition, oxford university press new york arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):475-490 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 475 original research article effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass j. o. olaoye1, f. b. olotu2*, o. a. lasode3 and i. p. duniya1 1department of food engineering, university of ilorin, ilorin, nigeria 2national centre for agricultural mechanization, ilorin, nigeria 3department of mechanical engineering, university of ilorin, ilorin, nigeria. *corresponding author’s email address: osebequin2013@gmail.com 1.0 introduction the bulkiness of loosed biomass materials like plant stalk, straw, chaff, sawdust, rice husk, etc. are reduced by the densification process to a dense form as solid biofuel or densified biomass known as pellets or briquettes for easy handling, transportation and storage and also helps to solve the problem of residual disposal. the different types of densification equipment as reported by grover and mishra (1996) such as reciprocating press type, screw extruder press and hydraulic piston press have been developed, evaluated and the densified biomass materials have also been evaluated to ascertain their durability. article information abstract energy resources such as electricity and fuel are used to power biomass densification system for production of solid biofuel, however, energy consumption of the densification equipment has led to high cost of production of the solid biofuel. meanwhile, energy stored in fuel or the electricity is being used to budget for the work or power requirements during densification of biomaterials which are mostly considered as energy consumption. the energy consumption does not give appropriate recognition to the exact or useful energy from the energy source that is energy output of the system. this study to investigates the effects of operational conditions of a biomass densification system on the exergy behaviour of a biomass densification system. the exergy parameters such as exergy input and exergy output were considered to determine the behaviour of biomass densification system. the conditioned biomass materials at 6%, 10% and 14% moisture contents (mc) were densified at selected applied pressures of 186.56, 211.38, 236.25, 261.17, 286.07 and 310.85 mpa, while each selected pressure was applied at different speeds of 10, 20, 30, 40, 50 mm/min. the exergy parameters obtained were subjected to statistical analysis using ibm spss 20.0 to determine the effects of the operational conditions on the exergy behaviour of biomass densification system. the highest mean values of exergy output of 0.3562 j and 0.4033 j were observed at 10 mm/min when pressure of 310.85 mpa was applied using sawdust and huskdust both at 6% mc, respectively to produce one-unit average weight of 12g of biofuel. the least mean values of exergy output of 0.1001 j and 0.1738 j were observed at 50 mm/min when pressure of 186.56 mpa was applied using sawdust and huskdust both at 14% mc respectively. additionally, densified biomass of high durability was obtained when both sawdust and huskdust were densified at 10% mc wet basis while the less durable densified biomass was obtained at 6% mc for sawdust and huskdust. therefore, the operational conditions of biomass densification system such as applied pressure, speed of pressing piston and mc of biomass materials had effects on the exergy input and exergy output as well as the durability of the densified biomass. it was then concluded from this study that the operational conditions of biomass densification system can affect the exergy behavior of the system and the quality of densified biomass. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 nov., 2019 revised 21 april, 2020 accepted 23 april, 2020 keywords: exergy behaviour densification system biomass operational conditions mailto:osebequin2013@gmail.com http://www.azojete.com.ng mailto:osebequin2013@gmail.com olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 476 the energy resources such as electricity and fuel are used to power the biomass densification system for production of solid biofuel, however, energy consumption of these densification equipment have been intensively discussed and high energy consumption as observed by wu et al. (2014) and stelte et al. (2012). this has caused increased production cost of the solid biofuele. mostly, consideration is usually given to analysis of energy stored in fuel or the energy draw from electricity while budgeting for the work or power requirements during densification of agricultural and biomaterials without given appropriate recognition to exergy analysis of the system. exergy analysis gives useful information on both the quantity and quality aspects of the energy utilization because it measures the exact energy used by the system. this implies that energy analysis of a system is not enough to analyse the energy of the system because it focuses on the quantity of energy resources only (dincer, 2000; dincer and cenger, 2001). in this regard, an exergy analysis can be a useful tool for providing information on the impact of energy resources used by the system. it can also assess the technical performance of biomass densification devices in terms of energy usage by the system. the aim of this study is to investigate the effects of operational conditions of a biomass densification system on the exergy behaviour of the system. the exergy behaviour of the biomass densification system has to do with energy that is made available and drawn from the power source during densification operation known as exergy input; the exact or actual energy being used to densify the biomass materials is referred to as exergy output; exergy loss is a form energy is being lost which could be as a result of frictional forces between the wall of the pressing channel, piston head and biomaterials. this study gave consideration to the exergy input and exergy output of the system as well as on the durability of densified biomass. 2. materials and methods 2.1 experimental material the selected biomass materials were rice husk and sawdust. the rice husk was sourced from rice processing centre along idofian road, jimba, in ifelodun lga, kwara state while sawdust was obtained from wood industry at offa garage, ilorin, kwara state. rice husk was reduced in size using burr mill to aid densification process. the laboratory rig developed by kudabo, (2017) was incorporated into the universal testing machine (utm) of 300 kn capacity (s300ct, testometric company ltd, united kingdom) used in controlling and monitoring the operational conditions of the densification system. figures 1 and 2 show schematic diagram of the densification rig and its laboratory set up with the utm. the measuring equipment used were electronic weighing scale of model number cl. 201 made by ohaus in china for measuring the quantity of biomass material to be densified for each of the experiment, electronic moisture analyser of model number lsc – 50 made by ohaus company, china to determine the mc of the sample before densification and multimeter of model number 179truerms made by fluke company, usa to read the current and voltage flow into the utm. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 477 figure 1: section view of densification rig figure 2: laboratory set up for biomass densification system 2.2 experimental procedure the exergy behavior of laboratory biomass densification system was analysed using laboratory experimental biomass densification system. the sawdust and rice husk were mixed in ratio 2:1 (huskdust) as first biomass material and whole sawdust as the second biomass material were used to carry out the experiment. the bio-materials were conditioned to the moisture contents of approximately 6, 10, 14% and were verified using electronic moisture analyser before densification operation. then, 14g of conditioned sawdust at 6%,14.5g at 10% and 15g at 14% moisture contents, respectively, which filled the pressing chamber of the densification rig were densified using applied pressures of 186.56, 211.38, 236.25, 261.17, 286.07, 310.85 mpa, to produce a unit of solid biofuel (a briquette). each selected pressure was applied at different speeds of 10, 20, 30, 40, 50 mm/min. the procedure was repeated for 12g of conditioned huskdust at 6%, 12.5g at 10% and 13g at 14% moisture contents. the exergy parameters of the biomass densification system such as exergy input and exergy output were determined using equations 1, 2 and 3. i. electrical energy used to power the biomass densification system which is the exergy input into utm was determined by reading the current and voltage flow into utm using the multimeter placed in their positions, the time taken to densify the biomass materials from the utm and then the exergy input was estimated using equation (1) as given by olotu (2019). ivtenex electinelectin  )()( (1) where: exin(elect) = exergy input in joule enin(elect) = electrical energy in kwh i = current in amperes v = voltage in volts t = was the time it took the densification system to produce a unit of densified biomass. ii. the actual (exact) energy used to densify biomass materials which is exergy output was determined using equation (2) as given by olotu (2019).    m d m d y drp w n aa s 4 4exp1 4 exp2              (2) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 478 where, a a e a n am c cp am amm my         log (3) ws = exergy output in joule yn = distance moved by the piston to densify biomass materials in m pa = applied pressure of the press in mpa a= cross sectional area of the pressing channel in m2 m= initial height of the biomaterial inside the pressing channel before compaction in mm ma = mass of the biomass material in kg d= diameter of the pressing chamber in mm µ= friction coefficient λ= compaction ratio of radial and axial pressures c and a are biomass materials constants iii. durability index the densified biomass materials from sawdust and huskdust were subjected to tumbling test to determine their durability. the expressions used are stated in equations 4 and 5. tumbling test was used for testing the durability of briquetted fuel. the cuboid formed by angle iron frame having dimensions of 30 × 30 × 45 cm and fixed over hollow shaft diagonally was used to conduct the tumbling test. the sample of briquettes was put inside the cuboid and rotated for15 minutes, thereafter the briquette was taken out, weighed and percent loss was calculated by using formula given by senga et al. (2012). 100 1 21    d dd ld w wwp (4) durability index = 100 pld (5) where: pld = percent weight loss due to tumbling (%) wd1 = weight of briquette before tumbling (g) wd2 = weight of briquette after tumbling (g) the experimental design for this experiment was 2 x 3 x 5 x 6 factorial design in a complete randomized block, this was used to analyse the effects of processing conditions on exergy parameters of densification system. the factors in the factorial design are at 6 levels of applied pressure and 5 levels of speed of operation as the machine parameters and 3 levels of moisture content of the biomass materials using 2 different types of biomass materials. each treatment combination was performed in three (3) replicates, making a total of 540 values. the results of both exergy parameters such as exergy input and exergy output were subjected to statistical analysis to determine the effect of operational conditions of the biomass densification system on the selected exergy parameters. the data obtained were analyzed statistically using ibm spss version 20.0. the ndmrt was carried out on the outcome and graphical interpretations were presented. 3. results and discussion the investigation on the effects of operational conditions of biomass densification system on exergy behaviour of the system were carried out statistically using spss to analyse the data http://www.azojete.com.ng folio for your attention sir arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 479 obtained during the laboratory investigation. the results of the analysis and the interpretation of the results with respect to applied pressure, operating speed and moisture content of the two (2) different biomass materials were discussed. 3.1 exergy input into biomass densification system from the power source the values of the exergy input calculated during the experiment were subjected to statistical analysis. the results show that moisture content of biomass materials (sawdust and huskdust), the pressure exerted during densification and the operating speeds of the system were significant p≤0.05. this showed that the densification operational conditions had effect on the exergy input from the power source. 3.1.1 effects of applied pressure on the exergy input from power source it was observed from table 1 that the applied pressure on the piston inside densification chamber for compaction of sawdust and huskdust had significant effect on the exergy input p≤0.05. the levels of the applied pressure that led to the significant difference in the exergy input as determined by ndmrt as shown in table 1 revealed that all the levels of applied pressure were significantly different p≤0.05. table 1 depicted that the applied pressure level of 186.56 mpa had the least value of the exergy input and it increases as the level of the applied pressure increases, that is, the highest value of the exergy input was obtained at applied pressure level of 310.85 mpa. figures 2 and 3 further showed the variation of exergy input as pressure exerted on piston during compaction of sawdust and huskdust increase. this might be that as the pressure applied on the piston inside densification chamber increased, more energy was demanded causing excess energy being drawn from the power source to carry out the operation leading to increase in exergy input. this is mostly referred to as energy consumption and the pressure which the biomaterials were exposed to in this research work was as a result of increase in the force applied during the process. table 1: effect of applied pressure on exergy input from the power source s/n applied pressure (mpa) mean exergy input (joule) b1 b2 1 186.56 516.90a 534.56a 2 211.38 542.83b 551.80b 3 236.25 564.97c 567.71c 4 261.17 584.85d 581.02d 5 286.25 607.08e 594.19e 6 310.85 632.81f 607.09f b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other file:///c:/users/user/downloads/azojete143/www.azojete.com.ng folio for your attention sir. olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 480 figure 2: effect of applied pressure on the exergy input using sawdust at different moisture contents figure 3: effect of applied pressure on the exergy input using huskdust at different moisture content 3.1.2 effects of operating speed on the exergy input during densification operation the results of the effects of the operating speed of the densification system as in table 2 showed that the operating speed had significant effect on the exergy input from the power source p≤0.05. ndmrt was employed to determine the level of the operating speed that contributed to this significant difference as shown in table 2 which indicated that all the levels of operating speed were significantly different p≤0.05. from table 2, the operating speed level 10mm/min had the highest value of the exergy input and exergy input decreases as the level of the operating speed increases, that is the least of the value of exergy input was obtained at operating speed level of 50mm/min. more so, figures 4 and 5 further showed that there were decreases in exergy input as operating speed of the densification system increases for all mc for both sawdust and huskdusk. this could be that as the operating speed of the densification system increases, less time was being spent to attain the applied force set for the densification process thus, leading to low exergy input from the power source to the densification system. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 481 table 2: effect of operating speed on exergy input of the densification system s/n operating speed (mm/min) mean exergy input (joule) b1 b2 1 10 1226.84a 1200.4a 2 20 660.77b 650.07b 3 30 429.76c 432.47c 4 40 318.17d 334.89d 5 50 239.01e 245.76e b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other figure 4: effect of operating speed on the exergy input using sawdust at different moisture contents figure 5: effect of operating speed on the exergy input using huskdust at different moisture contents 3.1.3 effects of moisture content of saw dust and husk dust on the exergy input power source table 3 showed that the moisture content of sawdust and huskdust has significant effect on the exergy input of densification system. this was in line with the results of the studies carried out by andreiko and grochowicz (2007) which observed that moisture content of biomass materials has influence on the energy consumption of the densification system. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng folio moisture content has been corrected to moisture content ithroughout the main text olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 482 ndmrt used to determine the level of the moisture content of sawdust and huskdust that led to this significant difference as shown in table 3 indicated that all the levels of moisture content of huskdust were significantly different p≤0.05 while all the levels of moisture content of sawdust did not show significant difference. table 3 showed that sawdust at 6% moisture content had the highest value of exergy input followed by 14% moisture content while the least value of exergy input was obtained at 10% moisture content of the saw dust, though the exergy input at 10% and 14% were not significantly different from each other. huskdust gave a result that has highest value of exergy input at 10% followed by 14% moisture content and the least value was obtained with 6%. table 3 revealed that exergy input neither increased nor decreased as the moisture content of the huskdust increased or decreased, while when sawdust was used, the results showed an increase in exergy input as the moisture content of sawdust increased. however, there was no significant difference between exergy input of the system when sawdust at 10% and 14% moisture contents were used (p≤0.05). this shows that increase or decrease of biomass moisture content might not really affect the exergy input of the system within the studied range. table 3: effects of moisture content of saw dust and huskdust on the exergy input from power source into densification system s/n moisture content (%) mean exergy input (joule) b1 b2 1 6 594.01a 560.35a 2 10 565.30b 581.62b 3 14 565.41b 572.20c b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other 3.2 exergy output by densification operation system in this work, the ndmrt showed that moisture content of biomass materials; sawdust and huskdust, the applied pressure during densification and the operating speeds of the system were significant p≤0.05. this proved that the densification operational conditions had significant effect on the exergy output of the densification system. 3.2.1 effects of applied pressure on the specific work done (exergy output) by densification operation system table 4 revealed that applied pressure for compaction of sawdust and huskdust had significant effect on the exergy output p≤0.05. the levels of the applied pressure that led to the significant difference in the exergy output were determined using ndmrt as shown in table 4. it was observed that all the levels of applied pressure were significantly different p≤0.05. the reason could be because as there was an increase in pressure exerted on the piston inside the pressing chamber, there was also a change in pressure build-up inside the chamber. this result agrees with stelte et al. (2012) who reported that the pressure at which the biomass materials is exposed to during densification process had significant impact on the process energy used for the biomass densification. in addition, it was observed that the applied pressure level of 186.56 mpa had the least values 0.154551 j and 0.226296 j of the exergy output for sawdust and huskdust respectively and it increases as the level of the applied pressure increases. this means that the highest mean values 0.269347 j and 0.349418 j of exergy output were obtained at applied pressure level 310 mpa for the sawdust and huskdust respectively. figures 6 and 7 showed increases in exergy http://www.azojete.com.ng folio for your attention sir folio for your attention sir arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 483 output as the pressure applied on both sawdust and huskdust increases. this might be that as applied force on the piston is increased; more work is being expended on the biomass materials due to the pressure built-up inside the pressing chamber which led to high energy used by the system. this is similar with mani et al. (2004) study, which reported that the energy requirements of a densification process depend mainly upon the exerted pressure. table 4: effect of applied pressure on exergy output of the densification system s/n applied pressure (mpa) mean exergy out (joule) b1 b2 1 186.56 0.154551a 0.226296a 2 211.38 0.175944b 0.245581b 3 236.25 0.198196c 0.265887c 4 261.17 0.222198d 0.289267d 5 286.07 0.245198e 0.318235e 6 310.85 0.269347f 0.349418f b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other figure 6: effect of applied pressure on the exergy output of the densification system using sawdust at different moisture contents figure 7: effect of applied pressure on the exergy output of the densification system using huskdust at different moisture contents file:///c:/users/user/downloads/azojete143/www.azojete.com.ng olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 484 3.2.2 effects of operating speed on the exergy output during densification operation the result of the effects of operating speed of the system on the exergy output is given in table 5 which showed that the operating speed had significant effect on the exergy output of densification system p≤0.05. this results showed that densification piston speed has slight influence on the pressure build up inside the pressing channel which depends on time taken for densification piston to travel through pressing chamber for compaction of biomass material into solid biofuel which then produce the compression work performed by the system known to be the specific work done or exergy output. ndmrt employed to determine the level of the operating speed that contributed to this significant difference as shown in table 5 indicated that all the levels of operating speed were significantly different p≤0.05. the operating speed level of 10mm/min had the highest value of the exergy output and it decreases as the level of the operating speed increases as the least value of exergy output obtained at operating speed level of 50mm/min. figures 8 and 9 showed that there was gradual decrease in exergy output as operating speed of the densification system increases at moisture contents of 6%, 10% and 14% for both sawdust and huskdust. this might be as a result of increase or decrease in the operating speed of the densification system resulted in the less or more time spent respectively to build up pressure inside the pressing channel as it attained the set up force for the system to carry out densification work on the biomass materials. hence, this led to low or high value of exergy output of the system. table 5: effect of operating speed on exergy output of the densification system s/n operating speed(mm/min) mean exergy out (joule) b1 b2 1 10 0.216541a 0.305613a 2 20 0.215220b 0.289639b 3 30 0.211852c 0.282758c 4 40 0.209141d 0.270050d 5 50 0.201774e 0.264222e b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other figure 8: effect of operating speeds on the exergy output of the densification system using sawdust at different moisture contents http://www.azojete.com.ng folio for your attention sir arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 485 figure 9: effect of operating speeds on the exergy output of the densification system using huskdust at different moisture contents 3.2.3 effects of moisture content of saw dust on the exergy output of densification operation system table 6 showed that the moisture content of sawdust and huskdust had significant effect on the exergy output of densification system, this was confirmed by the studies carried out by andreiko and grochowicz (2007) and mani et al (2004) that observed that moisture content of biomass materials have influence on the energy used by the densification system. ndmrt was used to determine the level of moisture content of sawdust and huskdust that led to this significant different as showed in table 6. the results indicated that all the levels of moisture content of sawdust were significantly different p≤0.05. table 6 showed that sawdust and huskdust at the moisture content of 6% had the highest value of exergy output followed by the one at 10%, while the least value of exergy output was obtained at 14% moisture content of the saw dust and huskdust. additionally, the results revealed that all the levels of moisture content of the sawdust and huskdust were significantly different p≤0.05. this shows that as moisture content increases the exergy output of the densification system decreases which was similar to the results obtained by nielsen et al. (2009) which stated that a decrease in the moisture content of biomass materials resulted in an increase of energy requirement of the densification system. this could be as a result of insufficient moisture between the particles of the biomass materials to aid in binding and adhesion of the biomass particles. this led to more pressure being required to bind them together and thus, leading to high demand of energy to carry out the densification process. table 6: effects of moisture content of saw dust on the exergy out of densification operation system s/n moisture content (%) mean exergy out (joule) b1 b2 1 6 0.274000a 0.340411a 2 10 0.207381b 0.258062b 3 14 0.151336c 0.248869c b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other file:///c:/users/user/downloads/azojete143/www.azojete.com.ng folio for your attention sir folio for your attention sir folio modified for your attention olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 486 3.3 durability index of the densified biomass the values of the durability indices obtained during the tumbling test for each of the briquette produced were statistically analyzed. ndmrt was conducted on the durability index of densified biomass in respect to moisture content of the sawdust and huskdust, operating speed of the laboratory briquetting machine and the applied pressure as the main factors. it was observed that moisture content of biomass material (sawdust and huskdust), the pressure applied on the densification piston and the operating speeds of the system were significant p≤0.05. this showed that the densification operational conditions had effect on the durability index of the densified biomass. 3.3.1 effects of applied pressure on the durability index of the densified biomass it was observed from ndmrt that the applied pressure on the densification piston for compacting the biomass material had significant effect on the durability index of the densified biomass p≤0.05 as shown in table 7. it is also showed that all the levels of the applied pressure are significantly different in the durability index of the densified biomass p≤0.05. table 7 revealed that the applied pressure level of 186.56 mpa achieved the least value of the durability index for the briquettes produced. the durability index increases as the level of the applied pressure increases. however, the highest mean value of durability index was obtained at applied pressure level of 310.85 mpa. the mean values of the durability index at all levels of applied pressure were significantly difference from each other p≤0.05. furthermore, figures 10 and 11 revealed the increase in durability index of the briquettes produced as pressure applied on the densifying piston inside pressing chamber increases. this same trend was observed in the studies conducted by krizan and matus (2012) and kaliyan and morey (2009). this might be that as the force applied increased, pressure exerted on the biomass material increases making the adhesion forces between its particles to increase and hence improve the durability of the densified biomass produced. table 7: effect of applied pressure on durability index of densified biomass from sawdust and huskdust using ndmrt s/n applied pressure (mpa) mean durability index b1 b2 1 186.56 27.72a 21.65a 2 211.38 32.78b 25.57b 3 236.25 38.01c 32.96c 4 261.17 41.93d 32.96d 5 286.07 44.28e 36.18e 6 310.85 45.52f 38.86f b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other http://www.azojete.com.ng folio modified for your attention arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 487 figure 10: effect of applied pressure on the durability index of the densified biomass for sawdust at different moisture contents figure 11: effect of applied pressure on the durability index of the densified biomass for huskdust at different moisture contents 3.3.2 effects of operating speed on the durability index of densified biomass from sawdust and huskdust table 8 showed that the operating speed of the system had significant effect on the durability index of the briquettes produced p≤0.05. ndmrt employed to determine the level of the operating speed that contributed to this significant difference showed that all levels of operating speed of the system were significantly different from each other p≤0.05 as indicated in table 8. this confirmed a report by obidzinski and piekut (2015) that the operating speed of densification system has influence on the stability of the densified biomass materials. figures 12 and 13 further revealed how there were increases in durability index as operating speed of the densification system decreases. this could be that the increase in operating speed of the system does not give room for proper arrangement of the biomass (sawdust and huskdust) particles during densification process in which the solid fuel produced easily disintegrate when subjected to tumbling test. table 8 also showed that the operating speed level of 10 mm/min had the highest value of the durability index and it decreases as the level of the operating speed increases, that is the least value of durability index obtained at operating speed level of 50 mm/min. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng folio modified for your attention folio for your attention sir. olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 488 table 8: effect of operating speed on durability index of densified biomass from sawdust and huskdust using ndmrt s/n operating speed(mm/min) mean durability index b1 b2 1 10 51.43a 40.13a 2 20 41.21b 35.04b 3 30 36.49c 31.20c 4 40 33.52d 25.45d 5 50 29.22e 21.68e b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other figure 12: effect of operating speed on the durability index of the densified biomass from sawdust at different moisture contents figure 13: effect of operating speed on the durability index of the densified biomass from huskdust at different moisture contents http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 475-490. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 489 3.3.3 effects of moisture content of sawdust and huskdust on the durability of densified biomass table 9 showed that the moisture content of sawdust and husk dust had significant effect on the produced briquettes p≤0.05. ndmrt used to determine the level of the moisture content of sawdust and that of the huskdust showed that there was significant difference across the two results. the levels of all the moisture content of the biomass material are significantly different from each other p≤0.05. similarly, it was observed that moisture content of 10% recorded the highest mean value of durability index; followed by14% t while 6% moisture content achieved the least mean value of the durability index for both sawdust and huskdust. this agrees with the studies by keliyan and morey (2009) that moisture content of 11% to 12% are generally used for densifying wheatand corn-based biomass materials of high durability. though, to obtain high durability products of a particular biomass material, the optimum densifying moisture content of biomass materials must be known because their optimum densifying moisture content differ from each other. more so, moisture content of any biomass material above or below the optimum has been shown to have a negative influence on the biomass solid fuel properties as reported by stelte et al. (2012) and keliyan and morey (2009). table 9: effects of moisture content of saw dust and huskdust on the durability index of densified biomass using ndmrt s/n moisture content (%) mean durability index b1 b2 1 6 29.93a 18.95a 2 10 50.76b 45.49b 3 14 34.42c 27.88c b1: sawdust; b2: huskdust: mean with different letters are significantly different from each other 4. conclusion the high energy consumption of the biomass densification equipment has been observed and it does not give appropriate recognition to the exact or useful energy from the energy source which is exergy output of the system. the effects of operational conditions on the exergy behaviour of a biomass densification system as well as durability of the densified biomass was investigated. the exergy parameters such as exergy input and exergy output were considered to determine the exergy behaviour of the system. it is then concluded from this study that the operational conditions of biomass densification system affect the exergy behaviour of the system as well as the durability of the densified biomass produced. it is therefore, recommended that the optimum conditions for operating the biomass densification system that would give the best exergy behavior, high production rate and good quality solid fuel be investigated. references andreiko, d. and grochowicz, j. 2007. effect of the moisture content on the compression energy and strength characteristics of lupine briquettes. journal of food engineering, 83(1): 116-120. dincer, i. and cengel, ay. 2001. energy, entropy and exergy concepts and their roles in thermal engineering. entropy international journal, 3: 116-149. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng folio for your attention folio for your attention sir olaoye et al: effects of operational conditions on exergy behaviour of biomass densification system and durability of the densified biomass. azojete,16(3):475-490. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osebequin2013@gmail.com 490 dincer i. 2000. thermodynamics, exergy and environmental impact. energy sources, 22(8):723–732. grover, pd. and mishra, sk. 1996. biomass briquetting: technology and practices. regional wood energy development programme in asia.gcp/ras/154/net. food and agriculture organization of the united nations, bangkok. 1-2. http://www.fao.org/3/ad579e/ad579e00.pdf kaliyan, n. and morey, rv. 2009. densification characteristics of corn stover and switch grass. trans asabe, 53(3): 907-920. krizan, p. and matus, m. 2012. impact of pressing chamber conicalness on the the quality of briquettes produced from biofuels in briquetting machine. fuel, 4(4): 122-127. kudabo, ea. 2017. evaluation of constitutive conditions for production of sorghum and castor stovers biofuel. ph.d thesis, department of agricultural and biosystem engoneering, faculty of engineering and technology, university of ilorin, ilorin, nigeria. mani, s., tabil, lg. and sokhansanj, s. 2004. evaluation of compaction equations applied to four biomass species. canadian biosystems engineering, 46(3): 55–61. nielsen, npk., gardner, dj., poulsen, t. and febly, c. 2009. importance of temperature, moisture content and species for the conversion process of wood residues into fuel pellets. wood fiber science, 41(4): 414-425. obidzinski, s. and piekut, j. 2015. influence of speed of densification piston and particle size of densified material on the value of densifying pressure and pallets density. journal of research and applications in agricultural engineering, 6(1): 63-68. olotu, fb. 2019. energy and exergy analyses of a biomass densification system. ph. d thesis, department of agricultural and biosystems engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria. stelte, w., sanadi, ar., shang, l., holm, jk, jesper, a. and henriksen, ub. 2012. recent developments in biomass pelletization: a review. bioresources, 7(3): 4451-4490. tumuluru, js., wright, ct., kenney, kl. and hess, jr. 2010. a technical review on biomass processing: densification, preprocessing, modeling and optimization. presented at the 2010 asabe annual international meeting, 29th july – 1st august, 2010. pittisburgh idaho national laboratory. wu, p., ma, y., chen, y., zhang, y. and wang, h. 2014. vibration-assisted compaction of biomass. bioresources, 9(3): 3857-3868 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):429-438 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 429 original research article development and deployment of quadcopter in silos’ inspection and surveillance j. c. edeh*1, c. p. nwadinobi2 and e. c. obetta1 1department of mechanical engineering, michael okpara university of agriculture, umudike, nigeria 2department of mechanical engineering, abia state university, uturu, nigeria *corresponding author’s email address: engredehjohnc@gmail.com 1.0 introduction storage is an important aspect of post-harvest technology in commercial agriculture with the target of storing agricultural produce; provide food between harvest seasons and to provide seed for subsequent planting season (adejumo, 2013). in nigeria, grains are traditionally stored in calabashes, rhombus, gourds, and drums. these structures are usually adapted to the socioeconomic and prevailing weather conditions of the environment where they are deployed while requiring locally available materials like clay, straw, woven twigs or wood for their construction. improved structures such as local stores and metallic drums (with shelter) also feature at the traditional level of storage (adejumo and raji, 2007). notably, modern storage of grains in nigeria is often made in metallic silos usually located in every state and the federal capital territory (talabi, 1996). traditional method for storage includes domestic structures, rhombus, traditional crib, barn, shelf, pit/underground storage while modernized method for storage uses improved crib, ware house, silo/ bin, controlled atmosphere storage system, refrigeration, cold storage, evaporative coolant system (ecs), and hermetic and nitrogen storage systems. silo structures are used for storing bulk materials. they are used mainly in agriculture for grain and silage (fermented feed) storage. they also play very important role in storage of things like industrial materials (calcite, minerals), petrochemical supplies, medical supplies (pills, capsules), article information abstract efficient and routine inspection/surveillance of agricultural installations is a panacea that guarantees structural integrity and healthy storage of grains. conventional methods of silo inspection are tedious, time-consuming, costly, disruptive and with attendant safety concerns. a quad copter comprising four electronic speed controller (esc), four brushless dc motors, a motion camera, a flight controller unit, a battery and an off board remote controller was designed, developed and evaluated for silos’ facility inspections. the system is powered by 11.4v lipo (lithium polymer) fitted onboard of the quad copter, a digital camera and a 12v remote controller for off-board control (yaw, pitch and roll), with an entire system weight of 3.62kg. apt deployment of such unmanned aerial vehicle in routine facility integrity inspection eliminated the high risk and loss of man hour associated with contemporary techniques. the result of its performance test indicated that the system has maximum attainable speed of 10km/h and maximum height/range of 150 m for over all 10 minutes of flight time. also, the threshold speed for each rotor was found to be 1030 rpm and an average speed of 0.5km/h needed during inspection of silos to avoid blurred images from the camera was achieved. comparative analysis of the design with the conventional method revealed that the developed quad copter was cost and time effective, convenient, risk free thus recommended for full scale deployment for inspection/surveillance in silo installations. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 march, 2021 revised 7 august, 2021 accepted 21 august , 2021 keywords: silos quad copter inspection failure mode flight controller edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 430 and perfumery chemicals, among others. the storage of such materials is dependent on duration, size or scale of storage, and the type of material used in the silo construction. consequently, silos designs are primarily determined by the properties and type of the materials to be stored. as the density, flow and friction properties of grains, cement, coal, carbon black, and other bulk materials vary widely, the loads applied on a silo structure and the associated load carrying system are different from the traditional building type structures (adem et al., 2009), which makes silos special structures. the silos’ walls have been found to be subjected to both normal pressure and shear imposed by traction of the stored material in them. their magnitude and distribution over the height of the wall largely depend on the stored material properties and operations (whether loading or discharging). also considered during the design of silos are other potential loads such as wind and seismic loads, thermal stresses (between the silo’s wall and the stored bulk solids), stored material expansivity and structural mechanics of the supports. as a result of these and to forestall integrity issues, silos are designed and evaluated as special structures. (adem et al., 2009). silos fail with frequency much higher than the rate of failure of other industrial structures (carson, 2000). although with scanty statistics, it has been speculated that hundreds of industrial and farm silos (bins, and hoppers) experience some degree of failure each year. the signs of deterioration and the failures observed during a thorough silo inspection are different for concrete and metal silos. deterioration in concrete silos manifests as wall delamination, cracks, spalling and rebar corrosion while metal silos deteriorate by heavy rust and corrosion, thinning metal, visible holes, wall deformations and cracks. (susong, 2018). other signs of degradation according to john and tracy (2003) include buckling, bending, denting of steel or aluminium silo wall and failure of screw feeder or reclaimer in flat-bottomed silo. furthermore, silo can fail due to explosion by bursting, asymmetrical loads created during filling or discharging, corrosion (for metal silos), fluctuating soil pressure, silage acids deterioration (for concrete silos), internal structural collapse, thermal ratcheting and earthquakes (adem et al., (2009) without periodic inspections to uncover potential structural integrity issues, silos can collapse with little or no warning. a catastrophic failure is always costly in terms of damage to facilities and potential downtime. they have also resulted in loss of life for personnel in the path of a collapse. such failures could result from design error, construction error, usage, and improper maintenance (john and tracy, 2003). maintenance of a silo must not be neglected since it falls within the domain of the owner or the user. when proactive response to facility integrity issues is ignored to the extent of the use of common instinct of lowering the silo fill level, failure becomes imminent at greater speed and severity. common reaction to signs of silo distress is to overlook them, usually due to the personnel reckless ignorance of the dare consequences of such reaction. cracks in a concrete wall, or dents in a steel shell, though they may seem insignificant, are danger signals which indicate that corrective measures are probably required. even if danger signs are understood, it is common for inappropriate action to be taken in an attempt to reduce the chance of failure. in some severe cases, where damage could have been relatively minor with appropriate action, catastrophic failure has been induced. to mitigate such failures, there is need for safe but cost/labour effective routine inspection technique for silos. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):429-438. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 431 according to mole master inspection procedure, the process of inspection involves a structural engineer, sometimes accompanied by an agricultural engineer, visits to the site to conduct field observations. thereafter, the engineer using binoculars (and occasionally with infrared and corona detection cameras as a tool and method) conducts visual observation of the silo exterior walls for deterioration. cracks, bulges, or material leakages constitute these visual cues. usually cranes, scaffolds, rope-access, and people are used to inspect both the storage tanks and the overall structure. these inspections can be effective, but is only accurate for surfaces that can be seen from the ground. in remote regions, this can be even more tedious, as the pylons and very tall silos are not easily accessible, and the terrain between the pylons makes movement difficult. susong (2018) indicated that scaffolding could be used as a method and tool for silo inspection but with less safety and cost advantage when compared to rope access and other conventional methods. rope access method involves setting up the ropes and rigging equipment for the specialist to climb and carry out inspection and maintenance. however, its availability, mobilization and training requirement of this method is exuberant. it was generally discovered that the conventional methods are tedious, time-consuming, costly, disruptive and with attendant safety concerns hence maintenance and inspection of silos are costly, risky and time consuming for those who carry out the inspection. the solution to this is to deploy autonomous drones for inspection as suggested by eschmann et al., (2012). the use of aerial drones has now become a massive innovation in inspection allowing visual analysis of areas usually off limits due to inaccessibility (catec, uav news, 2017). over the years, aerial vehicle inspection technique has provided structural inspections of high or difficult to reach structures which are faster and safer than conventional access methods. glez-de-rivera et al. (2014), myeong et al. (2015), prem et al. (2015) and young et al. (2017) developed unmanned aerial vehicles (uav) which were controlled to survey/inspect the desired location and the information of the location. in addition, usama and nauman (2015) in their research work designed parameters of indigenously developed quad copter for area surveillance. according to their research and in agreement with work of samir et al. (2009), the optimum performance of any quad copter depends on the design features, as it affects the weight, agility and manoeuvrability. there were sketchy studies of drones’ utilization in the inspection of structures, and even limited to visual inspections only (vaibhav et al., 2018). ellenberg et al. (2015) conducted an investigation on remote sensing capabilities of a commercialized drone (parrot ar 2.0) for crack detection from various distances. an algorithm was developed for post-image processing of the conducted field test on a bridge for the drone performance evaluation. jennifer and baritte (2015) developed a prototype quad copter and observed that the common challenge was that quad copter finds it difficult balancing itself while hovering and thus could not produce a stable data image for analysis. omijeh et al. (2017) designed a quad copter for real-time inspection and surveillance actions in a pipeline facility using a quad copter design profile. at the end of the design, the uav was capable of attaining autonomous flight at a height of 20 meters and a range of 30 meters. this system still has room for improvement and to expand the usefulness and flexibility of the quad copter designs. in lieu of these desirable features, a portable quad copter with expanded capabilities in altitude, range, flight time and edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 432 control, was conceived to be deployable in silo inspection so as to reduce drastically the high attendant risk and man hour incurred in the existing routine facility inspection techniques. 2. materials and method 2.1 materials the main materials of the uav frame are carbon fibre plates. the selection of motors was based on the frame size, propeller size, battery capacity, and system drive. the quad copter was developed using components and hardware such as flight controller board (housing the barometer and compass), brushless dc motor, electronic speed controller (esc), rf remote, receiver and li-po battery. also a dic camera was attached to this quad copter for on board surveillance. the system is divided into five main parts to include the structural unit, the input unit, control unit, output unit and power supply. 2.2 design constraints in the design of the quad copter, the following constrains were considered and implemented: 1. the quad copter can only operate in a sunny or dry condition/weather. 2. the quad copter can operate only at a range of 150 meters away from the operator 3. the quad copter is controlled by a kk-2 based microcontroller which has no auto pilot mode or beginner’s option and an rf controller. 4. the quad copter has a flight time of 10-12 minutes 2.3 design analysis the design requirements for the flight system development influence the selection of components for the design. 2.3.1 lift and weight in lift and weight analysis; the interest was actually to reduce weight thereby increasing the lifting ability of the flight system in the design. from weight to rpm ratios; it is near certain for the relations in equations (1) and (2) (usama and nauman, 2015); m = rf (i) l = (2) where: m = mass of propeller, kg l = length of propeller, cm srpm = required speed, rpm srf = referenced speed, rpm wrf= referenced weight, kg wrq= required weight, kg plrf= referenced propeller length, cm thus from ratio analysis; 1.0 kg weight of quad copter would demand;  2 pairs of 283 rpm brushless motors.  2 pairs of 20cm clockwise and counter clockwise length propellers. the relationship governing the lift capabilities of this flight system is given in equation 3; lift (thrust; kg cm s-2) = ( ) ( ) (3) edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 430 where; wq = weight of quad copter (kg). dq = rotation diameter of propeller blades (cm). dair = density of air (kg/cm3). (varies with altitude) cf = lift coefficient = 1. s = speed in rpm from the equation 3; prospected weight of quad copter, wq = 3.62kg = 3620g. for four blades, dq= (25cm x 4) = 100cm. from the weight to rpm ratios; a prospected weight of 3.62kg will be used to determine the threshold speed (s); s = (weight to rpm ratio) kg x (reference rpm value/kg of weight) (4) s= (3.62/1)kg x (283)rpm/kg = 1030rpm. thus; 2 pairs of 1030rpm brushless motors will lift a 3.62kg quad copter. 2.4. development procedure the method of research was done by reviewing uavs, multicopters, and especially quad copter. by using gathered knowledge and information, an approximation of the quad copter weight is made based on some of the main components needed. a 3d model conceptual design was then made with the help of cad software solid works 2015. a comparison of different materials for quad copter was done with weight, strength and cost taken into consideration and abs plastic based on the initial weight approximation, main components such as motors, propellers, high resolution digital image correlation (dic) camera, esc and other electrical components were selected. with reference from the components selected, a prototype was designed. the manufactured parts and all electrical components were then assembled, plastic adhesive was used to hold the wire harness at fixed position on the frame to avoid interruption during operation, calibration and synchronization of the remote control and the on-board flight controller was carried out. finally the flight test was carried out to determine the performance of the quad copter. testing was done on the battery performance of the quad copter and also the ability of the quad copter to stabilize itself when hovering. any offset in the individual speed of the rotors of the quad copter was calibrated through the flight controller by changing the proportional, integral, and derivative value. figure 1: quadcopter arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):429-438. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 431 table 1: components of the quadcopter s/n item description/specification 1 propeller arm hjfrp 2 connecting wires 3 flight controller fsr6b 4 propeller 4 n0s: 9443 r 5 brushless motor 4 n0s: 31.2a 6 esc (electronic speed controller) simonk 30a 7 carbon fiber base. 8 lipobattery(lithium polymer battery) 3-cell: 4200mah 9 camera stand high resolution dic camera was used 2.4.1 stress analysis of the quadcopter arm the arm of the quad copter was analysed on solid works cad simulation software. the von misses stress analysis was used for this analysis. the maximum result of the arm was discovered to be 2.732 ×107 n/m2 when a force of 4.5n (weight of the motor) was applied as shown in figure 2. figure 3 also displays the maximum displacement of the arm. this result indicates that the arm is capable of carrying the total weight of the quad copter without failing. figure 2: maximum stress analysis of the arm. figure 3: maximum displacement of the quadcopter arm edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 432 2.5. performance test procedures to safely fly the quad copter; various tests were carried out on the individual components and the assembled quad copter, to ensure everything is functioning properly before flight. two test stages were carried out on the quad copter; these tests were unit and flight tests. 2.5.1 unit test while the basic flight control of the kk2 was tested simply by pid (proportional-integralderivative) tuning and flying the quad copter; units' sensors were tested since they were used for the tracking algorithms. the barometer and the compass on-board the flight controller were units tested to ensure optimal performance. the units tested include the motors, barometer and battery. the motors were tested to lift the quad copter and its components (3.62kg) successfully. the quad copter was able to fly at a speed of 10 km/hr., meeting the requirements needed; but the maximum speed was not tested since it will be out of sight at such speed. the first sensor to be tested was the bmp085 (barometer). this sensor uses atmospheric pressure to estimate the altitude of the quad copter in meters. this sensor was needed to implement altitude-hold; a flight mode that attempts to keep the quad copter at the same altitude. three methods to improve the accuracy and precision of the barometer; control (no action); adding foam sponge cover; and adding a mesh cover. the mesh cover proved ineffective as it made the altitude-hold worse by inspection. the remaining two options were tested in a number of different ways. one test was flying the quad copter up to two meters and seeing which method provided better altitude-hold. several lipo battery sizes were tested on the quad copter, to determine the duration of the battery used. the quad copter accessories had an average current draw of 20.2a, and a battery with higher capacity meets the requirement. 2.5.2. flight test pre-flight test was conducted. the remote control was first switched on before the flight controller. the remote control was to be armed ready for further flight control action from it with a beep preceding the arming action. the speed controller controls the speed of the fan according to preassigned values on the accelerometer memory. speed of the fan increases as the atmospheric wind speed decreased. increment in speed was achieved by gradual increase in acceleration from the left joystick on the remote control. so the speed controller, remote controller, and the on-board flight controller performed as per the design. table 2 shows the flight check list that precedes the flight test. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):429-438. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 433 table 2: pre-flight check list s/n units check actions 1 airframe and landing arm ready ensure the airframe and landing arm are intact. 2 propellers secured; undamaged and in correct flying orientation? ensure that the propellers are secured; undamaged and in correct flying orientation. 3 motors secured and undamaged? ensure motors are secured and undamaged. 4 escs secured and undamaged? ensure that escs are secured and undamaged. 5 rf receiver and connections secured and undamaged? ensure that that rf receiver and connections are secured and undamaged. 6 rf remote undamaged? ensure that the rf remote is secured and undamaged. 7 kk-2 flight controller secured and undamaged? ensure that kk-2 flight controller is secured and undamaged. 8 battery fully charged? ensure that the battery is fully charged. 9 battery correctly installed and connected on the quad copter? ensure that battery is correctly installed and connected on the quad copter. 10 battery correctly strapped and secured? ensure that the battery is correctly strapped and secured. 2.6. program for operation the program for the operation of the quad copter was developed with assembly language. the code block for this operation is shown below: org 0000h mov p1, #0ffh mov p2, #0ffh mov p3, #0ffh main: acall serial port clr p1.0 ;turn off motors clr p1.1 ;turn off motors clr p1.2 ;turn off motors clr p1.3 ;turn off motors setb p2.7 monitor: jnb p2.7, $ acall recieve ; recieve command from transmitter and sensors mov r5, a acall delay setb p1.0 ;turn on motors mov r5, a acall delay setb p1.1 ;turn on motors mov r5, a acall delay setb p1.2 ;turn on motors mov r5, a acall delay setb p1.3 ;turn on motors mov r5, a acall delay clr p1.0 ;turn off motors mov r5, a acall delay clr p1.1 ;turn off motors mov r5, a acall delay clr p1.2 ;turn off motors edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 434 mov r5, a acall delay clr p1.3 ;turn off motors mov r5, a acall delay sjmp main delay: h1: mov r2, #100 h2: mov r3, #255 h3: djnz r3, $ djnz r2, h2 djnz r5, h1 ret serial_port: mov tmod, #20h ;serial port initialization mov th1, #-3 ;9600 buadrate (-3) mov scon, #50h setb tr1 ret recieve: mov a, sbuf here: jnb ri, here clr ri ret end 3. results and discussion the following are the results of the test that were carried out. 3.1.1. motor test while testing the brushless dc motor, the speed was compared with the duration of the battery. figure 4 shows that an increased speed reduces the duration of the battery. however, inspection operation targets accuracy and precision rather than speed, hence the quad copter was designed for inspection and not for speed operation thus prolonged battery life. figure 4: variation of motor speed with time arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):429-438. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 435 3.1.2. battery test table 3 displayed flight durations for several batteries tested. with the 4200 mah battery; the quad copter was able to attain a maximum flight time of 10 minutes projected for facility inspection. the result shows that higher capacity battery will increase the duration of the flight though with likely increase in cost. table 3: comparison of battery capacity and flight time capacity (mah) flight time (min) 2450 6.34 3000 7.62 4200 10.8 3.1.3. barometer test in the barometer test that was conducted, it was observed that the foam sponge was able to provide a better altitude holding. table 4 shows the result of this control when tested upon 2 meters height. table 4: foam and control of quadcopter control foam average 0.79 1.84 medium 0.72 1.90 standard bev. 0.40 0.27 3.1.4. flight tests after carrying out proper pre-flight and flight checks; the various units were checked and the systems powered as recommended by the safety guideline to ensure safety of the quad copter and the personnel operating it. after conducting the flight test, the system was capable of attaining a maximum height/range of 150m from the operator at a hovering speed of 0.5km/hr. which is to be maintained for a quality picture during flight. this showed system extended capabilities compared to omijeh et al., (2017) design. 3.2 comparative analysis of inspection techniques a comparison between a commonly used traditional method for inspection of silo structure (use of scaffoldings) and the use of quad copter was carried out in order to estimate the effectiveness of the quad copter in terms of cost and working time. the silo structure has a diameter of 6m and a height of 12.5m located in michael okpara university of agriculture, umudike (figure 5). four silos were inspected, and table 5 shows the result of the comparison done. edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 436 figure 5: field test of the developed quad copter on silos table 5: comparative analysis of traditional techniques and quadcopter inspection traditional method (use of scaffolding) use of quadcopter number of silos 4 4 number of technical workers 4 2 time of inspection (hours) 0.83×4= 3.5 0.16×4=0.66 wages (n) 35000×4=140000 25000×2=50000 from table 5, the inspection done by four (4) workers using traditional means was done effectively at lesser cost and time using a quad copter. 4.1. conclusion based on design, simulation and prototyping, a quad copter of overall weight as 3620g, with abs plastics material of hollow cross-section was developed. the arms were subjected to maximum stress of 27.32 mpa and maximum deflection of 0.006 mm well below yield strength of the arm material. the results obtained in this study showed that the quad copter was capable of attaining maximum height/range of 150m, hovering and taking the desired pictures at a speed of 0.5km/hr. if the speed is altered, blurred images are obtained. 4.2. recommendation this quad copter can still be upgraded with additional sensors (ir sensors, wireless technology and 3d mapping tools) to expand the overall usefulness and flexibility of the quad copter. in addition to this, an autopilot flight controller or beginner’s mode configuration should be incorporated in the flight controller to assist the station pilot when controlling the quad copter. references adejumo, ba. and raji, ao. 2007. technical appraisal of grain storage systems in the nigerian sudan savanna. agricultural engineering international. the cigr journal, 9: 960-966. adejumo, ba. 2013. development of a 350 kg double walled insulated metallic silo for tropical climate. greener journal of science, engineering and technology research, 3(6): 195-204. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):429-438. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 437 adem, d., zaki, k., ahmet, d. and halil, s. 2009. cause of damage and failure in silo structures. a journal of performance of constructed facilities, 23(2): 65-75. carson, jw. 2000. silo failures case history and lesson learned. proceedings of the third israeli conference for conveying and handling of particulate solid held in dead sea, israel. may, 2000, 1-15. ellenberg, a., branco, l., bartoli, i. and kontsos, a. 2015.use of unmanned aerial vehicle for quantitative infrastructural evaluation. journal of infrastructural system, 21(3): 110-122. eschmann, c., kuo, cm., kuo, ch. and boller, c. 2012. unmanned aircraft systems for remote building inspection and monitoring. proceedings of the 6th european workshop on structural health monitoring held in dresden, germany, 3-6 july, 2012. glez-de-rivera, g., garrido, j. and ponticelli, r. 2014. design considerations of small uav platform carrying medium payloads. proceedings of the conference on design of circuits and integrated circuits (dcis) held in madrid, spain, 26-28 november 2014: 26–28. jennifer, z. and baritte, i. 2015. unmanned aerial vehicle bridge inspection demonstration project final report published by minnesota of transportation research service and library, 395 john irelan boulevard, st. paul minnesota. john, wc. and tracy, h. 2003. silo failures: why do they happen? jenike and johanson, inc., one technology park drive, westford, ma, usa. myeong, wc., jung, ky., jung, sw., jung, yh. and myung, h. 2015.development of a dronetype wall-sticking and climbing robot. proceedings of the 12th international conference on ubiquitous robots and ambient intelligence (urai 2015), goyang, korea, 28–30 october, 2015. omijehm, bo., odem, vm., joseph, kj. and erameh, ja. 2017. design and construction of quad copter with payload for pipeline inspection and surveillance. international journal of advanced research in electrical, electronics and instrumentation engineering, 6: 1-17. prem, kp., amirtharaj, s., haire, s., kishore, rs. and kiruba, v. 2015. quadcopter video surveillance and control using computer. international journal of electrical and electronics engineering, 7(1): 340-346. samir, b., pierpaolo, m. and roland, s. 2009. design and control of an indoor micro quad copter. journal of intelligent and robotic systems, 54(1): 245-260. susong, j. 2018. industrial silo inspection and silo inspection services.https://www.industrialaccess.com/blog/author/jhn77yy8uj/. accessed 11th february, 2019. talabi, ae. 1996, implementation of national food security programme: experience so far. proceedings of the national workshop on strategic grains reserve storage programme: nucleus for national food security, organised by strategic grains resertechno chips division, federal ministry of agriculture with techno chips system and consult, abuja, 1996, 67-73. https://www.industrialaccess.com/industrial-silo-inspection-silo-inspection-services/ https://www.industrialaccess.com/industrial-silo-inspection-silo-inspection-services/ https://www.industrialaccess.com/blog/author/jhn77yy8uj/ edeh et al.: development and deployment of quadcopter in silos’ inspection and surveillance. azojete, 17(4):429-438. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engredehjohnc@gmail.com 438 uav, 2017. the business of drones., http//www.suasnews.com/2017/10/catecdevelops-aerialcontact-technology-inspection-drone. accessed october, 2017. usama, h. and nauman, a. 2015. design parameters indigenously developed quadcoper for areas surveillance. student research paper conference, 2(54): 266-269. vaibhav, j., aditi, t. and sandip, b. 2018.quadcopter video surveillance for cleaning agent. international journal of advanced research in electrical electronics and instrumentation engineering, 7(3): 1022-1028. young, z., xiuxiou, y., wenzhuoli, k. and shiyu, c. 2017. automatic power line inspection using uav images. remote sensing, 9(24): 1-19 arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 208-218 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng _________________________________ *corresponding author email address: josephokoko@uniuyo.edu.ng 208 original research article a review of rheological properties of high quality cassava flour (hqcf) composites j. u. okoko*, a. f. alonge and p. o. ngoddy. department of agricultural and food engineering, university of uyo, uyo, nigeria. article information received: october, 2018 accepted: december, 2018 keywords: rheological properties composite flour cassava high quality flour products abstract food products development by means of composite flour technology is experiencing a remarkable upsurge globally with the ticking of the clock; thereby inviting a great deal of researchers’ consideration, particularly in bakery foodstuffs and pastries making. the world population is increasing and is projected to be well over eight billion people in the year 2030, with attendant imports of an increased consumption, hence higher demands for processed foods such as bread. in view of the climb in consumption of bread, a higher demand for wheat should be in anticipation. thus, shrinkage in the global supply of wheat as a resource in the immediate future should be anticipated. this development gives emphasis to the necessity for alternative sources of flour and starch. the attention of this review is directed at the studies of rheological characteristics of composite flour vis-à-vis its consumptions via food products such as bread, biscuits, and pasta. emphasis is on blends which have high quality cassava flour (hqcf) or just cassava flour as one of the compositing flours with its influence on the sensory and nutritional qualities in addition to its universal approval. in this work, a report has also been given of a study on wheat flour blended in varying proportions with other flours such as those from rhizomes, legumes, fruits and cereals (other than wheat) to create diverse food products. cassava flour in bread making has been found to be a suitable substitute for encouraging the utilization of a local produce besides reduction of wheat flour imports and upholding the production of high quality cassava flour (hqcf). the development of gluten-free products and fortification of foods have also turned out to be a possibility. several researchers have developed a range of breads using cassava flour whose properties are akin to those of wheat flour breads. it is promising that the capability of composite flour in bakery and pastry products to retain similar properties to products made from pure wheat flour has been reported. it has also been testified that the use of composite flours has acceptable impacts on the finishing products from the standpoint of functional and physicochemical characteristics as well as healthiness of the end users. generally, composite flour technology is being regarded as a noble new method for harnessing the benefits in flours that may not unfold unless in composites, which of course, as a matter of fact, will be contingent upon the proportions of blending. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved http://www.azojete.com.ng mailto:josephokoko@uniuyo.edu.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 209 1.0 introduction the global population is increasing and is estimated to reach nine billion people in no distant time (jensen et al., 2015). a critical aspect of the imports of this increase in population will be an increased consumption, hence higher demands, for processed foods such as bread (godfray et al., 2010). in view of the escalation in consumption of bread, a higher demand for wheat should be in anticipation. to this end, the global supply of wheat as a resource should be expected to diminish in the immediate future. this development underscores the necessity for alternative sources of starch and flour (jensen et al. 2015). although falade and akingbala (2011) and ukwuru and egbonu (2013) would see the challenges in the emerging industry as it has to do with the type of food to be processed, consumption habits, raw materials supply and equipment availability. onyango et al. (2011), however, is optimistic that in africa and latin america, cassava flour possesses an abundant potential as a substitute for wheat flour in bread making; the consistency, which is an offshoot of rheological properties, in flour quality being a foremost challenge, nevertheless (hershey et al., 2000). noorfarahzilah et al., (2014) maintains that the development of foodstuffs by means of composite flour has increased and is inviting considerable attention from researchers, particularly in the making of bakery products and pastries. the enlarged root (tuber) of cassava plant (manihot esculenta crantz) is an essential foodstuff in the tropical regions of the world, namely; africa, asia, and in the caribbean (okafor et al., 1999). cassava is reported by collares et al., (2012) to be the world’s sixth most important crop grown in these countries. according to ifad and fao (2001), cassava has outstanding features which include; its great potential for the production of starch, drought tolerance and adaptation to difficult ecosystems such as acid soils of low fertility. in 2014, colombia produced 2.1 million tons of cassava, as compared with brazil’s 23.2 million tons and paraguay’s 3.0 million tons (fao, 2016). the roots and leaves of cassava are both suitable for human consumption; the former, as a source of carbohydrates and the latter as a source of protein, minerals and vitamins, particularly carotene, calcium and phosphorus (ifad and fao, 2004). it is a known fact that carbohydrates provide the prime source of fuel for the body. cassava happens to be a dependable source of dietary carbohydrate – mainly starch. according to dziedzoave et al (2010), cassava roots have up to 60% starch content. thus exploring avenues for increased value chain of the cassava is a worthwhile venture. the increased demand for wheatbased convenient foods in nigeria and other countries of the world vis-à-vis the challenges of climate in cultivation of wheat in the tropical regions demands an alternative food ingredient for baking and confectionery products with at least a partial substitution of wheat. an interesting attraction, as reported by (abass et al., 1998), is that cassava flour is one of derivatives from cassava roots whose processing technology, not only requires less consumption of water and energy, is more economical and easier than its other products like starch; besides, and produces lesser amount of by-products and waste. eriksson (2013) disclosed that high quality cassava flour has the prospective to swap part of the wheat flour in bakery foods as there has been an inclusive approval among users; even as he presented the proximate composition of cassava as shown in table 1 below; file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okoko, et al. a review of rheological properties of high quality cassava flour (hqcf) composites. azojete, 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 210 table 1: proximate composition of fresh cassava roots component value moisture (g/100 g) 59.4 carbohydrates (g/100g) 38.1 protein (g/100 g) 0.7 fat (g/100 g) 0.2 crude fiber (g/100 g) 0.6 ash (g/100 g) 1.0 calcium (mg/100 g) 50.0 vitamin c (mg/100 g) 25.2 energy (kcal/100 g) 157 source: eriksson (2013) although gluten, whose good source is wheat, has been reported to be responsible for the rheological characteristics of bakery foodstuffs (sciarini, et al., 2010), the same gluten has been indicted in the report of aguilera and park (2016) as being a source of serious worry in diets for elderly people – people aged over 65 years whom they had described as being the fastest increasing section of global population. even though studies such as defloor et al., (1993) and jensen et al., (2015); have shown that bread quality is impaired when large quantities of cassava flour are used in the bread formulations, there is still room for less emphasis on pure wheat bread. according to akinlonu (2011), falade and akingbala (2009) and oyewole (2002), inclusion of cassava flour as composite for production of foods such as noodles, breakfast cereals, cookies, breads, cakes, pastries, muffins and doughnuts inter alia could lessen costs and increase the production of these products locally. thus wheat flour supplementation provides an excellent means of improving the dietary worth (protein, minerals, vitamins, and bioactive compounds) of foods. the incorporation of less expensive non-wheat flour for food product enrichment would be a desirable vehicle for nutritional improvement, okafor, et al., (2002) opined. 1.1 objective the main objective of this work was to look into the studies of rheological properties of composite flour products with special emphasis on blends which have high quality cassava flour (hqcf) or just cassava flour as one of the compositing flours. 2.0 the review 2.1 composite flour composite flours may be considered chiefly as amalgams of wheat and other flours for the making of baked products, leavened or unleavened and pastas (riley-mitchell et al., 2012). also composite flour can be looked upon as a product created from a combination of two or more materials. such amalgam may be different in characteristics from the individual components and/or may be an enhancement of their properties and overall acceptance; in some circumstances, value may be added to the financial aspects of its production. in the preceding age, it was uncommon to have bread prepared from any other material than wheat flour. however, the emergence of composite flour technology has conveyed innovative dimensions upon the production of bread and other bakery foodstuffs. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 211 composite flour technology denotes the development of bakery products by a combination of two or more flours which may be cereals and/or legumes. according to adeniji (2013), composite flours can be considered as blends of flours from tubers rich in starch (e.g. cassava, yam, sweet potato) and/or protein-rich flours (e.g. soybeans, peanut) and/or cereals (e.g. maize, rice, millet, buckwheat) with or without wheat flour. this development creates an avenue for economic utilization of indigenous raw materials to manufacture high quality food products (shahzadi, 2005). composite flours should not be perceived in the light of ready-mixed flours which millers and bakers are accustomed to. while ready-mixed flours contain all the non-perishable constituents of the formula for a certain bakery product, composite flours are only a mixture of different flours rich in starch or protein, with or without wheat flour, for certain groups of bakery products. the foremost objective of the previous study of composite flours was to lessen, to the largest imaginable extent, the emphasis on wheat flour usage in the manufacture of certain baked products, as well as bread. the key benefit derivable from this technology by emerging economies is in the amelioration of savings of hard foreign currencies. job creation, capacity building, products shelf-life extension and diversification of food products utilization are other benefits in anticipation. sanful and danko (2010) had observed that there is a possibility of making composite flour from locally available starchy crops. bamidele et al. (2014) suggested that a composite of cassava and cocoyam flours produced a nutritive gari, which was hihgly acceptable. kareem et al., 2015 worked on blends of tigernut and high quality cassava flours, and unmasked the fact that an acceptable extruded snacks can be produced from tigernut-hqcf composite. wronkowska, haros, and soralśmietana (2013) reported that when starch was substituted by buckwheat flour on gluten-free bread quality, a decrease in whiteness and increase in redness and yellowness of crumb was noticed. composite flour in baking performance using plantain flour substituted with wheat flour had been studied by onwuka and onwuka (2005), plantain, cassava/soybean flour blends for snacks and corresponding food preparations (2004). these efforts again were aimed at improving the protein content in particular and the overall nutritional value of the product (kiin-kabari et al., 2015). composite flours, according to chandra et al., (2015) may be considered firstly as blends of wheat and other flours for the production of leavened breads, unleavened baked products, pastas, porridges and snack foods. secondly, wholly non-wheat blends of flours or meals, for the same purpose. they also noted that there are two reasons for mixing the wheat with other flours namely; economic and nutritional; like adding soy flour is to increase the protein content of the +baked products. increasing the quantity of buckwheat flour in gluten-free bread formulation caused a decrease in crumb hardness during storage. haros and soral-śmietana (2013) also suggested that buckwheat flour incorporated into a gluten-free formula could improve bread texture and shelf-life. bread made with seaweed composite flour exhibited higher values of firmness (mamat, et al 2014). moreover, modified starchy flours from other sources such as tubers, cereals, pseudo-cereals, legumes and oil seeds have been used as alternatives1 in bread making (ohimain, 2015). mannuramath et al., (2015) reported that combination of little millet flour (lmf) at 30% level in bread can be considered as a functional dietetic food option for the management of diet-related metabolic maladies. boz and karaoğlu (2013) showed that the value of whole wheat bread could be enhanced by adding various materials of plant origin. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okoko, et al. a review of rheological properties of high quality cassava flour (hqcf) composites. azojete, 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 212 2.2 high quality cassava flour (hqcf) high quality cassava flour (hqcf) is sometimes produced from high quality cassava cake (hqcc) and conveyed to and flash dried in a flash dryer at temperatures of between 165 and 180 degrees celsius. the dried flour is milled in an industrial pin mill to less than 200 microns and subsequently the flour is cooled down to ambient temperature, sieved on tumbler sieves and bagged automatically or manually. the amicable features of this type of hqcf include; at least 98% of the flour will pass a sieve of 200 microns and a standard homogenous sizing for every batch; all cyanide, nearly all proteins and dissolvable matter have been removed, and there is no risk at all for public healthiness; starch granules are completely released and gelatinized totally at 57 65 degrees celsius; low total viable count (less than the 10,000 cfu/g limit), low yeasts, low moulds, no coliforms and no entero bacteriae; and there is standard and consistent quality between all batches as regards moisture content and all other parameters; i.e. batches do not differ or if they do, it is very marginally from each other. a standard hqcf producing unit comprises a flash dryer and 2-3 ampus. the flour production of a flash drier is 12,000 – 15,000 metric tonnes per annum. hqcf is a wheat flour substitute and is used in bread-making, pastas, cookies, various fast-food snacks, woodboard/plywood, adhesives and mosquito coils. 2.3 rheological properties rheological properties, with reference to food materials, are those characteristics which influence the consistency and flow of food under tightly specified conditions. these properties affect the deformation and flow of matter. the texture of any food material depends on its rheological properties. according to berk (2009), most of the textural properties are largely rheological in nature; and most rheological tests involve applying a force to a material and measuring its flow or change in shape. however rheological considerations do not cover all the elements that establish the texture of a food (urbicain and lozano, 1997). production of food products such as buns, bread, cake, etc., depends on the functional properties of the flour (julianti et al., 2016; ekwu et al., 2011). the rheological properties of dough are significant base for the process of manufacture of quality food products (létang et al., 1999; moreira et al., 2010), which allows for the development of new materials (ibarz and barbosa-canovas, 2014). there have been several studies, such as kokse et al. (2001); moreira et al. (2010) and sabovics et al. (2011) on rheological properties of food materials and flour dough from different crops. flours from other raw resources replacing wheat flour will adjust the rheological properties of dough, as well as the feature of baked product. it is well known that proteins encountered in nonwheat flours do not have the capacity to form the gluten network responsible for holding the gas produced during the fermentation (hadnadev et al., 2011). in determining the rheological behaviour of different raw materials using chopin mixolab, they reported that blends of rice and buckwheat flours would give the finest rheological profile. the mixolab technique as reported by collar et al., (2007); kahraman et al., (2008), allows the complete characterization of the flours in terms of proteins’ quality by determining their water absorption, stability, elasticity, and weakening properties; starch behaviour during gelatinization and retro gradation; consistency modification when adding additives and enzymatic activity of the proteases, amylases, etc. the technique was also applied by stoenescu et al. (2012) to study the rheological properties of augmented wheat flour. mixolab analyses were carried out on composite http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 213 flour with 30% of cassava flour by jensen et al., (2015). this team reported that the amount of incorporated cassava flour in bread was decidedly a function of the variety of cassava flour. eriksson (2013) used a rapid visco analyzer (rva) from newport scientific (warriewood, australia) to analyze pasting properties of cassava flours upon heating and subsequent cooling with application of rva general pasting method (std1). the researcher concluded that cassava flours were characterized by a premature gelatinization (pasting temperature between 70 and 71°c), high peak viscosity, large paste breakdown and low retro-gradation propensity compared to wheat flour. in an analogous development, ekwu et al. (2011) determined the rheological characteristics of traditionally processed cassava flour with the same apparatus, but a method after sanni et al., (2008) and established that the pasting properties of the flour showed peak viscosity range from 157.35 to 399.58rvu, trough 90.08-206.50 rvu, breakdown viscosity 67.23-193.09 rvu, final viscosity 123.58 -300.41 rvu, setback 33.40 93.93 rvu. kareem et al., 2015 worked on blends of tigernut and high quality cassava flours, and unmasked the fact that and acceptable extruded snacks can be produced from tigernut-hqcf composite. eduardo et al. (2013) investigated into some textural cum rheological characteristics of cassava – wheat – maize bread types. in that report, loaf slices of 2.5 cm were taken for study of the crumb firmness, six (6) hours after baking using an instron universal testing machine (utm, model 5542). the loaf volume was measured one (1) hour after the end of the baking procedure by the displacement method in which alfalfa seed was used. it was shown that pectin interacts with wheat starch bringing about an increased paste viscosity during heating. both the increased viscosity and the gel network were believed to have strengthened the gas-holding properties of the expanding cells in the dough and subsequently resulting in a greater loaf volume. bread with fermented cassava flour resulted in firmer bread crumb when cassava level and pectin content were both low, and softer bread types were obtained with roasted flour. the viscosity of a suspension of wheat flour supplemented with high quality cassava and pigeon pea flours was measured by chilungo (2013) using the brookfield viscometer. it was remarked that as the levels of supplementation were increased, the viscosity of flour blends slightly increased. this was construed to be due to addition of cassava flour at increased levels. the low viscosities of wheat and pigeon pea flours were related to the cohesiveness of the starch molecules of these flours. nwokocha et al. (2009) measured some rheological properties of the starch pastes using a controlled stress rheometer (ar 2000, ta instruments ltd) with cone and plate geometry (40 mm, 2 cone and 52 lm gap). the measurements were carried out at 25oc and shear rates of 10-1 to 120/s. they used ta data analysis software (version vi.2.5) to fit shear stress versus shear rate models viz; newtonian, power law, bingham, casson and herschel–bulkley to the experimental data and estimated the goodness of fit for each model using the standard error of estimate. in that report, a model was considered acceptable if the standard error was about 20 or less, and the model that had the lowest standard error was considered, best suited for the description of the shear stress–shear rate profile of the starch pastes. where rheological properties are viewed as textural, they are such characteristics of a food material that portray physical features of the material when it comes in contact with the senses of feel or touch. food texture from this standpoint refers to those qualities of a food that can be felt with the fingers, tongue, palate, or teeth. texture is distinctive of the surface of a material and is an file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okoko, et al. a review of rheological properties of high quality cassava flour (hqcf) composites. azojete, 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 214 indication of quality. davies (2007) described texture as relating to characteristic intensity variation that typically originates from roughness of an object’s surface. it may be regarded as what constitutes the macroscopic region of the object. its structure is basically ascribed to the repetitive patterns in which elements or primitives are arranged according to an order rule (tuceryan and jain, 1998). textural characteristics refer, but are not limited to the following; consistency, hardness, brittleness, firmness, crispiness, springiness, combablilty, crunchiness, coarseness, fineness, cohesiveness, adhesiveness, gumminess, resilience, chewiness, fracturability. fellows (2000) gave further delineation of textural properties as shown on table 2 below. korczyk–szabó and lacko–bartošová (2013) described texture analysis as one of the most helpful analytical methods of product development. evaluation of texture involves measuring the response of a food when it is subjected to forces such as cutting, shearing, chewing, compressing or stretching. many studies have been carried out on textural properties of dough obtained from composite flours blends such as wheat-pitaya flour (ho and abdul-latif (2016); wheat-soy composite, wheat-cassava composite bread (komlaga, cloveramengor, dziedzoave, and hagan, 2012). starch has been identified by miyazaki et al., (2006) as a major component that plays a major role in texture and quality of dough and bread. cassava of course, is a good source of starch. table 2: textural characteristics of food primary characteristics secondary characteristics popular terms mechanical characteristics hardness cohesiveness brittleness chewiness gumminess soft → firm → hard crumbly, crunchy, brittle tender, chewy, tough short, mealy, pasty, gummy viscosity thin, viscous elasticity plastic, elastic adhesiveness sticky, tacky, gooey geometrical characteristics particle size and shape gritty, grainy, coarse particle shape and orientation fibrous, cellular, crystalline others moisture content dry →moist→ wet→ watery fat content oiliness greasiness oily greasy source: fellows (2000) alvarez-jubete et al., (2009) evaluated the pasting properties of pseudo-cereal flours using a rapid visco analyzer. they carried out standard baking tests and texture profile analysis on the gluten-free control and pseudo-cereal samples of gluten-free breads. they obtained confocal laser scanning microscopy (clsm) images from the baked breads. in addition, they conducted digital image analysis on the resulting bread slices. from these studies, they found that bread volume significantly http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 215 increased for the buckwheat and quinoa breads compared with the control. furthermore, breads with pseudo-cereal content were characterized by a considerably softer crumb texture effect that was ascribed to the presence of natural emulsifiers in the pseudo-cereal flours and confirmed by the confocal images. shittu et al. (2008) determined the textural analysis of bread from cassava-wheat composite four with the aid of a cone penetrometer to measure bread crumb softness. in this study, 6-cm thick bread slice was placed on the base of the penetrometer for the measurement. higher penetration units were indicators of increased crumb softness. 3.0 conclusion it is a matter of fact that with the use of composite flour, at any percentage level of inclusion, the resulting recipe will certainly exhibit properties markedly different from those of the individual component flours. the determination of dough properties, including rheological was found to be essential for the estimation of dough processing, handling behavior and future bread properties (tietze, jekle, & becker, 2016). several studies carried out to use cassava flour in bread making have shown that wheat flour can be substituted by 5 to 10 % cassava flour without significant effects on processing and the quality of bread (aristizábal et al. 2017). references abass, a., onabolu, ao. and bokanga, m. 1998. impact of the high quality cassava flour technology in nigeria. in akoroda, mo. and ngve, jm. (eds). root crops in the 21th century. proceedings of the 7th triennial symposium of the international society for tropical root crops africa branch (istrcab). cotonou, benin, 11-17 aguilera, jm., and park, dj. 2016. texture-modifiied foods for the elderly: status, technology and opportunities. trends in food science and technology, 57: 156-164. akinlonu, eo. 2011. nutritional and sensory qualities of novel dishes from cassava. dissertation submitted to the department of nutrition and dietetics. university of agriculture, abeokuta, nigeria. alvarez-jubete, l., auty, m., arendt, ek. and gallagher, e. 2009. baking properties and microstructure of pseudocereal flours in gluten-free bread formulations. european food research and technology, 437. aristizábal, j., garcía, a. and ospina, b. 2017. refined cassava flour in bread making: a review. ingeniería e investigación, 37(1), 25-33. berk, z. 2009. food process engineering and technology. elservier academic press, new york. chilungo, s. 2013. physicochemical properties and baking qualities of baked wheat products supplemented with cassava and pigeon pea flours. a thesis submitted to michigan state university in partial fulfillment of the requirements for the degree of food science master of science. collar, c., bollain, c. and rosell, cm. 2007. rheological behaviour of formulated breaddoughs during mixing and heating. food science and technology international, 13, 99–107 collares, rm., miklasevicius, lvs., bassaco, mm., salau, nina, pg., mazutti, ma., bisognin, da. and terral, lm. 2012. optimization of enzymatic hydrolysis of cassava to obtain fermentable sugars. j zhejiang univ sci b. 13(7): 579–586. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okoko, et al. a review of rheological properties of high quality cassava flour (hqcf) composites. azojete, 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 216 defloor, i., nys, m. and delcour, ja. 1993. wheat starch, cassava starch, and cassava flour impairment of the bread making potential of wheat flour. cereal chem. 78, 525-30. dziedzoave, nt., abass, a., amoa-awua, w., and sabiah, m. 2010. quality management manual for production of high quality cassava flour. ibadan, nigeria: international institute for tropical agriculture. eduardo, m., svanberg, u., oliveira, j. and ahrné, l. 2013. effect of cassava flour characteristics on properties of cassava-wheat-maize composite bread types. international journal of food science. volume 2013, article id 305407, 10 pages ekwu, fc., ngoddy, po., and uvere, p. 2011. functional and rheological properties of cassava flour processed by adaptation of traditional ‘abacha’ processing technology. jormar, 6(1):17-30. eriksson, e. 2013. flour from three local varieties of cassava (manihot esculenta crantz): physicochemical properties, bread making quality and sensory evaluation (master degree thesis). publikation/sveriges lantbruksuniversitet, institutionen för livsmedelsvetenskap, serie no 371 uppsala, http://stud.epsilon.slu.se. godfray, hcj., beddington, jr., crute, ir., haddad, l., lawrence, d. and muir, jf. 2010. food security: the challenge of feeding 9 billion people. science, 327(5967). 812-818. hershey, c., henry, g., best, r., and iglesias, c. 2000. cassava in latin america and the caribbean resources for global development (pp. 1-57). ho, lh. and abdul-latif, nw. 2016. nutritional composition, physical properties, and sensory evaluation of cookies prepared from wheat flour and pitaya (hylocereus undatus) peel flour blends cogent food & agriculture (2016), 2: 1136369. falade, ko. and akingbala, jo. 2009. improved nutrition and national development through the utilization of cassava. in robertson, g .l. & lupien, j. r. (eds). using food science and technology to improve nutrition and promote national development. international union of food science & technology. falade, ko and akingbala, jo. 2011. utilization of cassava. food reviews international, 27, 51–83 fao 2016. food and agriculture organization of the united nations statistics division (faostat). fellows, pj. 2000. food processing technology principles and practice. second edition. woodhead publishing company ltd. cambridge, england. hadnadev, td., torbica, a. and hadnadev m. 2011. rheological properties of wheat flour substitutes/alternative crops assessed by mixolab. procedia food science 1, 328 – 334. ibarz, a. and barbosa-canovas, gv. 2014. introduction to food process engineering. crc press, new york. ifad and fao 2001. the global cassava development strategy and implementation plan vol. 1. proceedings of the validation forum on the global cassava development strategy. roma: international fund for agricultural development, food and agriculture organization of the united nations. ifad and fao 2004. global cassava market study. business opportunities for the use of cassava. proceedings of the validation forum on the global cassava development strategy. vol 6. roma: international fund for agricultural development (ifad), food and agriculture organization of the united nations. jensen, s., skibsted, l. h., kidmose, u. and thybo, ak. 2015. addition of cassava flours in breadmaking: sensory and textural evaluation. lwt. food science and technology, 60 (1), 292-299. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 217 julianti, e., rusmarilin, h., and yusraini, ra. 2016. functional and rheological properties of composite flour from sweet potato, maize, soybean and xanthan gum. journal of the saudi society of agricultural sciences. kahraman, k., sakyyan, o., ozturk, s., koksel, h., sumnu, g. and, dubat, a. 2008.utilization of mixolab to predict the suitability of flours in terms of cake quality.european food research technology, 227, 565–570. kareem, st., adebowale, aa., sobukola, op., adebisi, ma., obadina, oa. and kajihausa, oe. 2015. some quality attributes of high quality cassava tigernut composite flour and its extruded snacks. journal of culinary science and technology, vol. 13 (3), 242 252. kokse, h., sivri, d., ng, pkw., steffe, jf. 2001. effects of transglutaminase enzyme on fundamental rheological properties of sound and bug-damaged wheat flour doughs. cereal chemistry, 78, pp. 26–30. komlaga, ga., clover-amengor, m., dziedzoave, nt., and hagan, ll. 2012. consumer acceptability of wheat-cassava composite bread. world rural observations, 4 (2): 79-81. korczyk – szabó, j. and lacko – bartošová, m. 2013. crumb texture of spelt bread. journal of central european agriculture, 14(4):1326-1335. letang, c., piau, m. and verdier, c. 1999. characterization of wheat flour-water doughs. part i, rheometry and microstructure, journal of food engineering, 41, pp. 121–132. miyazaki, m., hung, pv., maeda, t. and morita, n. 2006. recent advances in application of modified starches for bread making. trends in food science and technology, 17: 591-599. moreira, r., chenlo, f., torres, md. and prieto, dm. 2010. influence of the particle size on the rheological behavior of chestnut flour dough. journal of food engineering, 100, pp. 270–277. noorfarahzilah, m., lee, js., sharifudin, ms., mohd-fadzelly, ab. and hasmadi, m. 2014. applications of composite flour in development of food products. international food research journal 21(6): 2061-2074. nwokocha, lm., aviara, na., senan, c. and williams, pa. 2009. a comparative study of some properties of cassava (manihot esculenta, crantz) and cocoyam (colocasia esculenta, linn) starches.. carbohydrate polymers 76, 362–367. okafor, n., azubike, c. and ibenegbu, c. 1999. carriers for starter cultures for the production of garri, a fermented food derived from cassava. world journal of microbiology & biotechnology, 15: 231-234. okafor, jn., ozumba, au. and solomon, hm. 2002. production and acceptability of chinchin fortified with oyster mushroom. nigeria food journal, 18, 19–20. onyango, c., mutungi, c., unbehend, g. and lindhauer, mg. 2011. modification of gluten-free sorghum batter and bread using maize, potato, cassava or rice starch. lwt food science and technology, 44, 681-686. oyewole, ob. 2002. the powers at the roots: food and its microbials allies. 15th inaugural lecture university of agriculture, abeokuta, nigeria. riley-mitchell, d., badrie, n. and yarde, j. 2012. cassava (manihot esculenta crantz)-wheat flour composite muffins: effects on quality and sensory characteristics. tropical agriculture (trinidad) vol. 89 no. 2, 104 112. sabovics, m., straumite, e. and galoburda r. 2011. assessment of the rheological properties of flour using the mixolab. footbalt . 2011 p33-38. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okoko, et al. a review of rheological properties of high quality cassava flour (hqcf) composites. azojete, 14(sp.i4):208-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 218 sanni, lo., adebowale, aa., awoyale, w. and fetuga, go. 2008. quality of gari (roasted cassava mash) in lagos state, nigeria. nigeria food journal. 26(2) 125-134 sciarini, ls., ribotta, pd., leon, ae. and perez, gt. 2010. influence of gluten-free flours and their mixtures on batter properties and bread quality. food bioprocess technology, 3: 577-585. shittu, ta., dixon, a., awonorin, so., sanni, lo. and maziya-dixon, b. 2008. bread from composite cassava–wheat flour ii: effect of cassava genotype and nitrogen fertilizer on bread quality. food research international 41, 569–578 stoenescu, g., ionescu, vs. and banu, i. 2012. rheological properties of the wheat flour supplemented with different additives. the annals of the university dunarea de jos of galati fascicle vi – food technology 35(1) 54-62. tietze, s., jekle, m. and becker, t. 2016. possibilities to derive empirical dough characteristics from fundamental rheology. trends in food science and technology, doi: 10.1016/j.tifs.2016.08.016. tuceryan, m. and jain, ak. 1998. texture analysis. in c. h. chen, & l. f. pau, the handbook of pattern recognition and computer vision (2nd edition) (pp. pp. 207-248). usa: world scientific publishing company. urbicain, mj. and lozano, je. 1997. thermal and rheological properties of foodstuffs in handbook of food engineerig practice. crc press new york. ukwuru, mu. and egbonu, se. 2013. recent development in cassava-based products research. academic journal of food research, 1(1), 1-13. http://www.azojete.com.ng article information arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):281-294 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng 281 corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng original research article best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria g. d. akpen, i. d. ijasini and g. n. ekwo department of civil engineering, joseph sarwuan tarka university, makurdi, benue state, nigeria *corresponding author’s email address: akpen.gabriel@uam.edu.ng 1.0 introduction rainfall is one of the most widely researched climatic variables in terms of its absence or presence, extremity or scarcity, stability or variability, as well as its vulnerability or essentiality (oruonye, 2012; gabriel et al., 2018; hassanyar et al., 2018 and aho et al., 2019a). rainfall is a major source of fresh water replenishment for planet earth. however, too much or too little can mean the difference between prosperity and disaster (oyegoke et al., 2017). as a random hydrological event, the occurrence of rainfall cannot be predicted with certainty because its temporal and spatial distribution is very complex and irregular. this uncertainty is further aggravated by the current global problem of climate change. however, it is possible to use rainfall data spanning over a long period of time to estimate the likelihood of a rainfall of a particular magnitude article information abstract the choice of a suitable model that could predict the possibility of occurrence of rainfall event of a specified magnitude depends mainly on the characteristics of rainfall data at a particular site. this study was aimed at determining the best-fit probability distribution model for annual maximum monthly rainfall. fifty years rainfall data (1969-2018) obtained from nigerian meteorological agency (nimet), calabar, were collated to form an annual series ranked in a decreasing order of magnitude. the data were then evaluated with 6 probability distributions namely; normal, log-normal, pearson type iii, log-pearson type iii, gumbel extreme value type i and log-gumbel probability distributions. the best-fit probability distribution model at the study area was selected based on the results of 4 goodness of fit tests namely; mean absolute deviation index (madi), chisquared(𝑥2) test, root mean square error (rmse) and relative root mean square error (rrmse). the performance of the 6 distributions were ranked and the total scores of 8, 23, 16, 12, 21 and 4 were allocated to normal, log-normal, pearson type iii, log-pearson type iii, gumbel extreme value type i and loggumbel probability distributions, respectively. the results indicate that the best-fit probability distribution model was log-normal, which was used to predict rainfall values of 566.8, 664.0, 721.6, 788.1, 834.4, 878.4, 920.7, 974.8 and 1014.4 mm for different return periods of 2, 5, 10, 25, 50, 100, 200, 500 and 1000 years, respectively. it is, therefore, recommended that log-normal distribution is the preferred model for frequency analysis of rainfall data for the planning and design of hydraulic structures in the study area. this is necessary for effective flood prevention and mitigation interventions. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 november, 2021 revised 4 march, 2022 accepted 16 march, 2022 keywords: rainfall-events probability distribution model rainfall frequency analysis goodness of fit rainfall prediction flood mitigation http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):281-294. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 282 occurring within a specified period of time using frequency analysis. according to izinyon and ajumuka (2013) and win and win (2014), there is no universally accepted frequency distribution model for rainfall frequency analysis. few probability distribution functions have been tested and adopted locally, while some others are peculiar to hydrologic characteristics of other regions. the ability to predict the possibility of occurrence of a particular rainfall magnitude is one of the preliminary stages of storm water drainage design that can help individuals, authorities and engineers to plan for extreme eventualities such as flood, drought, landslides, and thunderstorms, among others (oyegoke et al., 2017). tao et al. (2002) stated that several probability models have been developed to describe the distribution of annual extreme rainfalls at a single site. however, the choice of a suitable model is still one of the major problems in engineering practice since there is no general agreement as to which distribution(s) that should be used for the frequency analysis of extreme rainfalls. khudri et al. (2013) reported that the generalized extreme value and generalized gamma four parameter (4p) distributions provide the best fit for 50% of the data from rainfall gauging stations studied in bangladesh. olofintoye et al. (2009) showed that for peak daily rainfalls of selected cities in nigeria, the log-pearson type iii (lp3) distribution performed best by occupying 50% of the total stations, while pearson type iii (p3) performed second best by occupying 40% of the total stations and lastly by log-gumbel occupying 10% of the total stations. aho et al.(2019b) carried out frequency analysis and reported that the best fit probability distribution function (pdf) for annual and partial series rainfall data in makurdi metropolis is generalized extreme value (gev) distribution and generalized pareto (gpa) distribution respectively. the selection of an appropriate model depends mainly on the characteristics of available rainfall data at a particular site. hence, it is necessary to evaluate many available distributions in order to find a suitable model that could provide accurate extreme rainfall estimates. more so, recent devastation caused by flood in different parts of the world in addition to the challenges currently posed by uncertainties occasioned by climate change phenomenon has made the reliability in estimation of rainfall events more imperative (akpen et al., 2019). the value of such studies especially, in this era of failure/collapse of bridges, culverts, dams and other drainage structures leading to loss of means of livelihoods and sometimes, loss of lives cannot be over emphasized. the objective of this study is to determine the best-fit probability distribution model for annual monthly maximum rainfall over calabar city. this is required for planning and design of effective flood prevention, control and mitigation measures. 2.0 materials and methods 2.1 study area calabar is the capital of cross river state, nigeria. the city is adjacent to the calabar and great kwa rivers and creeks of the cross river (from its inland delta). it lies between latitudes 050 45’ file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng akpen et al: best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria. azojete, 18(2):281294. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 283 30” n and 050 08’ 30” n and longitudes 8011’ 21’’ e and 80 30’ 00” e (figure 1). calabar is often described as the tourism capital of nigeria. administratively, the city is divided into calabar municipal and calabar south local government areas. it has an area of 406 square kilometers and a population of 371, 022 as at 2006 census (falola and warnock, 2007; ogarekpe, 2014; ottong et al., 2010). calabar has a tropical monsoon climate with a lengthy wet season spanning 10 months and a short dry season covering the remaining 2 months each year. the harmattan which significantly influences weather in west africa is noticeably less pronounced in the city. temperatures are relatively constant throughout the year with average high temperatures usually ranging from 25 to 28 degrees celsius. there is only little variance between day time and night time temperatures, with fewer degrees lower during nights. in some wet years (1969, 1976, 1980, 1995, 1996, 1997, 1999, 2001, 2005, 2007, 2008, 2010 – 2015, 2017 and 2018), annual rainfall depths have been observed to rise over 3000 mm and above (ogarekpe, 2014; antigha, 2012). figure 1: map of calabar, nigeria (source: erhabor et al., 2019) 2.2 data collection and preparation the monthly rainfall data for 50 years (january, 1969 to december, 2018) was obtained from the nigerian meteorological agency (nimet), calabar, nigeria. the data was sorted according to years and months. the monthly maximum rainfall depths for 50 years of record were collated to form an annual series which were ranked in decreasing order of magnitude with their corresponding years and months as shown in table 1. the ranked annual monthly maximum series of rainfall values were then analyzed. http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):281-294. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 284 the probability of an event being equaled or exceeded in any one year was calculated using the equation 1 (weibull, 1939), while the recurrence interval, which is the inverse of the probability of its occurrence is given by equation 2. probability of occurrence; 𝑃𝑟𝑜 = 𝑚 𝑁+1 (1) return period; 𝑇𝑟 = 𝑁+1 𝑚 (2) where m is the rank number and n is the total number of observed data table 1: annual monthly maximum rainfall, probability and return period in calabar (1969 2018) y e ar m o n th x i ( m m ) r an k ( m ) p ro ( % ) 𝑇 𝑟 ( ye ar s) y e ar m o n th x i ( m m ) r an k ( m ) p ro ( % ) 𝑇 𝑟 (y e ar s) (1) (2) (3) (4) (5) (6) (1) (2) (3) (4) (5) (6) 2012 aug. 861.3 1 1.96 51.0 2009 july 577.4 25 49.02 2.0 2005 july 828.2 2 3.92 25.5 1975 july 552.6 26 50.98 1.96 1997 july 796.6 3 5.88 17.0 1988 sept. 538.3 27 52.94 1.9 1980 aug. 728.7 4 7.84 12.8 1986 july 533.8 28 54.90 1.8 1969 aug. 726.9 5 9.80 10.2 1976 aug. 526.8 29 56.86 1.76 1978 sept. 721.2 6 11.76 8.5 1985 may 520.5 30 58.82 1.7 2014 july 714.4 7 13.73 7.3 1981 july 519.7 31 60.78 1.6 1990 july 702.7 8 15.69 6.4 1972 july 510.8 32 62.75 1.59 2015 june 678.7 9 17.65 5.7 1982 july 505.7 33 64.71 1.55 1971 july 661.4 10 19.61 5.1 1991 aug. 505.6 34 66.67 1.5 2018 aug. 650.6 11 21.57 4.6 1983 june 504.6 35 68.63 1.46 2011 july 648.6 12 23.53 4.2 1998 june 504.5 36 70.59 1.4 1995 july 632.4 13 25.49 3.9 2013 may 499.9 37 72.55 1.38 1989 july 626.5 14 27.45 3.6 1999 aug. 494.5 38 74.51 1.34 2002 aug. 623.5 15 29.41 3.4 1987 aug. 493.8 39 76.47 1.3 1996 sept. 615.2 16 31.37 3.2 2001 may 491.4 40 78.43 1.28 2017 aug. 611.4 17 33.33 3.0 2006 july 484.9 41 80.39 1.24 2010 june 611.3 18 35.29 2.8 1992 sept. 481.4 42 82.35 1.21 1994 july 609.5 19 37.25 2.7 1993 aug. 479.0 43 84.31 1.2 1979 june 599.3 20 39.22 2.5 2016 july 454.6 44 86.27 1.16 2008 july 597.7 21 41.18 2.4 1970 july 440.8 45 88.24 1.13 1977 july 597.6 22 43.14 2.3 1984 june 437.3 46 90.20 1.11 2000 july 597.6 22 43.14 2.3 2003 sept. 399.2 47 92.16 1.09 1974 sept. 588.4 23 45.10 2.2 2004 aug. 391.9 48 94.12 1.06 2007 may 583.5 24 47.06 2.1 1973 aug. 373.3 49 96.08 1.04 key: tr = return period, pro= probability of occurrence, xi = rainfall depth 2.3 descriptive statistics of annual monthly maximum rainfall series the arithmetic mean (�̅�), standard deviation (𝜎), coefficient of variation(𝐶𝑣), the coefficient of skewness (𝐶𝑠) and coefficient of kurtosis (ck) were calculated using equations 3-7 respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng akpen et al: best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria. azojete, 18(2):281294. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 285 �̅� = 𝑋1+𝑋2+𝑋3+⋯+𝑋𝑁 𝑁 = ∑ 𝑋𝑖 𝑁 𝑖=1 𝑁 (3) 𝜎 = √ 1 𝑁−1 ∑ (𝑋𝑖 − �̅�)2𝑁 𝑖=1 (4) 𝐶𝑣 = 𝜎 �̅� (5) cs = 𝑚3 𝜎3 𝑜𝑟 𝑁 ∑ (𝑋𝑖−�̅�)3𝑁 𝑖=1 (𝑁−1)(𝑁−2)𝜎3 given by spiegel et al. (2011) (6) ck = 𝑚4 𝜎4 𝑜𝑟 𝑁 ∑ (𝑋𝑖−�̅�)4𝑁 𝑖=1 (𝑁−1)(𝑁−2)𝜎4 given by spiegel et al. (2011) (7) where, n = total number of observed data, 50 in this case, 𝑋1, 𝑋2, 𝑋3, . . . , 𝑋𝑁 = monthly maximum rainfall data for each year, 𝑋𝑖 = observed monthly maximum rainfall data for a specified year i = specified year (i ranged from 1-50), 𝑚3 = third moment about the mean of the set of data, and 𝑚4 = fourth moment about the mean of the set of data. table 2: logarithms of annual monthly maximum rainfall in calabar (1969 -2018) year month rainfall depth (𝑋𝑖) (mm) rank (m) 𝑦𝑖 = log10 𝑋𝑖 year month rainfall depth (𝑋𝑖) (mm) rank (m) 𝑦𝑖 = log10 𝑋𝑖 (1) (2) (3) (4) (5) (1) (2) (3) (4) (5) 2012 aug. 861.3 1 2.9352 2009 july 577.4 25 2.7615 2005 july 828.2 2 2.9181 1975 july 552.6 26 2.7424 1997 july 796.6 3 2.9012 1988 sept. 538.3 27 2.7310 1980 aug. 728.7 4 2.8625 1986 july 533.8 28 2.7274 1969 aug. 726.9 5 2.8615 1976 aug. 526.8 29 2.7216 1978 sept. 721.2 6 2.8581 1985 may 520.5 30 2.7164 2014 july 714.4 7 2.8539 1981 july 519.7 31 2.7158 1990 july 702.7 8 2.8468 1972 july 510.8 32 2.7083 2015 june 678.7 9 2.8317 1982 july 505.7 33 2.7039 1971 july 661.4 10 2.8205 1991 aug. 505.6 34 2.7038 2018 aug. 650.6 11 2.8133 1983 june 504.6 35 2.7029 2011 july 648.6 12 2.8120 1998 june 504.5 36 2.7029 1995 july 632.4 13 2.8010 2013 may 499.9 37 2.6989 1989 july 626.5 14 2.7969 1999 aug. 494.5 38 2.6942 2002 aug. 623.5 15 2.7948 1987 aug. 493.8 39 2.6936 1996 sept. 615.2 16 2.7890 2001 may 491.4 40 2.6914 2017 aug. 611.4 17 2.7863 2006 july 484.9 41 2.6857 2010 june 611.3 18 2.7863 1992 sept. 481.4 42 2.6825 1994 july 609.5 19 2.7850 1993 aug. 479.0 43 2.6803 1979 june 599.3 20 2.7776 2016 july 454.6 44 2.6576 2008 july 597.7 21 2.7765 1970 july 440.8 45 2.6442 http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):281-294. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 286 1977 july 597.6 22 2.7764 1984 june 437.3 46 2.6408 2000 july 597.6 22 2.7764 2003 sept. 399.2 47 2.6012 1974 sept. 588.4 23 2.7697 2004 aug. 391.9 48 2.5932 2007 may 583.5 24 2.7660 1973 aug. 373.3 49 2.5721 ∑ 𝑋𝑖 28,835.5 ∑ 𝑦𝑖 137.6703 the logarithms of all the annual monthly maximum rainfall depths were calculated using equation 8 as shown in column (5) of table 2, thus: 𝑦𝑖 = 𝐿𝑜𝑔𝑥𝑖 (8) where, 𝑦𝑖 = logarithmically transformed individual annual monthly maximum value of rainfall. 2.4 determination of best-fit probability distribution model the ranked data were evaluated with 6 probability distribution models namely: normal (n), lognormal (ln), pearson type iii (p3), log-pearson type iii (p3), gumbel extreme value type 1 (ev1) and log-gumbel (lg) probability distribution models. the best fit model was selected based on the results of goodness of fit tests and the application of a scoring and ranking scheme. subsequently, the best fit model of the study area was used to predict rainfall depths for return periods between 2 and 1000 years. 2.4.1 normal probability distribution model the normal distribution is also called gaussian distribution or normal error curve. the parameters of the distribution are mean and standard deviation while the skewness is taken as zero. the estimation of rainfall (xt), for a given return period (tr) was calculated using the following procedure: the mean (�̅�) of the observation was calculated using equation 3, while the standard deviation (𝜎) was found using equation 4. the standard normal variate (z), corresponding to an exceedence probability, p (𝑃 = 1 𝑇𝑟 ) was calculated by finding the value of an intermediate variable w: 𝑊 = [𝑙𝑛 ( 1 𝑃2 )] 1 2 (0 < 𝑃 ≤ 0.5) (9) the standard normal variate, z (which is the same as the value of frequency factor kt) that depends on return period for the normal distribution was then found using equation 10 (chow et al., 1988): 𝑍 = w − 2.515517+0.802853w+0.010328w2 1+1.432788w+0.189269w2+0.001308w3 (10) when p > 0.5; 1 – p is substituted for p in equation 9. the estimated rainfall (xt) was calculated from equation 11 (chow et al., 1988): 𝑋𝑇 = �̅� + 𝑍𝜎 = �̅� + 𝐾𝑇𝜎 (11) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng akpen et al: best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria. azojete, 18(2):281294. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 287 2.4.2 log-normal (ln) probability distribution model a random variable has a log-normal distribution, if the log of the random variable has a normal distribution. the procedure adopted here was similar to that of normal distribution except that it was applied to the logarithmically transformed observed rainfall depths. 2.4.3 pearson type iii (p3) distribution model the pearson type iii distribution has 3 parameters and is bound in the left with positive skewness. the 3 parameters of the distribution are mean, standard deviation and skewness. the frequency factor depends on the return period and the coefficient of skewness, cs. when 𝐶𝑆 = 0, the frequency factor is equal to the standard normal variate z. when 𝐶𝑆 ≠ 0, the frequency factor (𝐾𝑇) was calculated using equation 12 (kite, 1977) expressed as: 𝐾𝑇 = 𝑍 + (𝑍2 − 1)𝐾 + 1 3 (𝑍3 − 6𝑍)𝑘2 − (𝑍2 − 1)𝐾3 + 𝑍𝐾4 + 1 3 𝐾3 (12) where, k = 𝐶𝑆 6 . 2.4.4 log pearson type iii (lp3) probability distribution model the mean (�̅�), standard deviation (𝜎∗) and coefficient of skewness (𝐶𝑆 ∗) of the logarithmically transformed data were computed and the pearson frequency factor (𝐾𝑇 ) was found from equation 12. 2.4.5 gumbel extreme value type i (ev1) probability distribution model the frequency factor (𝐾𝑇 ) for ev1 was calculated from equation 13 (chow, 1953) and the estimated rainfall, 𝑋𝑇 was then calculated using equation 11. 𝐾𝑇 = − √6 𝜋 {0.5772 + 𝑙𝑛[𝑙𝑛( 𝑇𝑟 𝑇𝑟−1 )]} (13) 2.4.6 log-gumbel (lg) probability distribution model the mean (�̅�), standard deviation (𝜎∗) and coefficient of skewness (𝐶𝑆 ∗) of the logarithmically transformed data were determined and the frequency factor (𝐾𝑇) was computed from equation 13. for ln, lp3, and lg distributions, the actual estimated rainfall (xt), corresponding to log transformed estimated rainfall (yt), was computed using equation 14 thus: 𝑋𝑇 = 10𝑌𝑇 (14) 2.5 goodness of fit test in order to check the adequacy of fit of the observed rainfall data to the six probability distribution models; four goodness of fit tests namely; mean absolute deviation index (madi), chisquared(𝑥2), root mean square error (rmse) and relative root mean square error (rrmse) tests were adopted. http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):281-294. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 288 2.5.1 mean absolute deviation index (madi) the mean absolute deviation index is the average distance between each data value and the mean. it was computed using the formula suggested by agbonaye and izinyon (2017): 𝑀𝐴𝐷𝐼 = 1 𝑁 ∑ | 𝑋𝑗−𝑋𝑇𝑗 𝑋𝑗 |𝑁 𝑗=1 (15) where, 𝑋𝑗 = the observed value 𝑋𝑇𝑗 =the value forecasted by the distribution 𝑁 = the number of data points the smaller the value of madi obtained for a distribution, the more fitted it is to the observed data (agbonaye and izinyon, 2017). 2.5.2 chi-squared (𝒙𝟐) test this is a measure of the discrepancy existing between the observed and expected frequencies and is given by: 𝑥2 = (𝑋1−𝑋𝑇1)2 𝑋𝑇1 + (𝑋2−𝑋𝑇2)2 𝑋𝑇2 + (𝑋𝑘−𝑋𝑇𝑘 )2 𝑋𝑇𝑘 = ∑ (𝑋𝑗−𝑋𝑇𝑗 )2 𝑋𝑇𝑗 𝑘 𝑗=1 (16) where, 𝑋𝑗 = observed frequency 𝑋𝑇𝑗 = expected frequency 𝑗 =number of observations (1, 2, . . . k) the smaller the value of 𝒙𝟐 for a distribution, the more fitted it is to the observed data. the test was performed at 5% and 1% levels of significance. 2.5.3 root mean square error (rmse) the root mean square error (rmse) also known as the standard error is the sum of squares of the differences between observed and computed values. however, it was used to measure the difference between values predicted by a model and the observed values. these individual differences are called residuals. the rmse was obtained using the formula suggested by tao et al. (2002): 𝑅𝑀𝑆𝐸 = √( ∑(𝑋𝑗−𝑋𝑇𝑗 ) 2 (𝑛−𝑚) ) (23) where, 𝑋𝑗(𝑗 = 1, 2, … 𝑛) are observed values 𝑋𝑇𝑗 (𝑗 = 1, 2, … 𝑛) are the corresponding values computed from the assumed probability distribution, n is the number of observations and; m is the number of parameters estimated for the distribution. the smaller the value of rmse obtained for a distribution, the more fitted it is to the observed data (agbonaye and izinyon, 2017). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng akpen et al: best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria. azojete, 18(2):281294. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 289 2.5.4 relative root mean square error (rrmse) the relative root mean square error was computed by dividing the root mean square error by the mean of observed data. the relative root mean square error provides a good picture of the overall fit of a distribution. it computes each error in proportion to the size of observation, thereby reducing the effect of outliers which are commonly found in hydrological data. the rrmse was computed using the formula by tao et al. (2002): 𝑅𝑅𝑀𝑆𝐸 = √∑( 𝑋𝑗−𝑋𝑇𝑗 𝑋𝑗 ) 2 (𝑛−𝑚) (24) where, 𝑋𝑗(𝑗 = 1,2, … 𝑛) = observed values 𝑋𝑇𝑗 (𝑗 = 1,2, … 𝑛) = the corresponding values computed from the assumed probability distribution, 𝑛 = number of observations, and; 𝑚 = the number of parameters estimated for the distribution. the smaller the value of rrmse obtained for a distribution, the more fitted it is to the observed data (agbonaye and izinyon, 2017). 2.6 scoring and ranking scheme based on the results of the goodness of fit tests, a scoring scheme in which the best performing distribution with respect to a test criterion was assigned a score of 6, the next test was assigned 5 and the worst test assigned 1. the distribution with the highest total score in the study area based on the goodness of fit criteria was adjudged as the best distribution model for prediction of annual monthly maximum rainfall in the study area. 3. results and discussion 3.1 annual monthly maximum rainfall the annual monthly maximum rainfall depths ranged from 373.3 mm to 861.3 mm, indicating a very large range of fluctuation during the study period (figure 2). the minimum and maximum rainfall values were in the month of august, 1973 and 2012 respectively. incidentally, incidences of severe flooding were reported in calabar in the year, 2012, the year with the maximum monthly rainfall. http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):281-294. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 290 figure 2: annual monthly maximum rainfall (mm) for calabar (1969 2018) the computed frequency factor (kt) values and the estimated rainfall (xt) values for different return periods of 2, 5, 10, 25, 50, 100, 200, 500 and 1000 years, are presented in table 3. the results of the goodness of fit tests for the 6 distributions at the station were also presented in table 4. ranking the total scores, a summary of performance of the 6 probability distribution models was obtained as shown in table 5. the log-normal distribution model, with a total score of 23 is adjudged the best fit model for the study area. however, olofintoye et al. (2009) found log-pearson type iii probability distribution model as the best-fit model for the peak daily rainfall in calabar. it follows that the probability distribution model used for monthly maximum rainfall in a given location may not necessary fit daily maximum rainfall for the same location. the lognormal model was then used to predict rainfall values shown in table 2 for selected return periods of 2, 5, 10, 25, 50, 100, 200, and 500 and 1000 years. these rainfall estimates can provide useful guidance for policy makers and designers. 0 200 400 600 800 1000 1968 1978 1988 1998 2008 2018 m a x im u m r a in fa ll ( m m ) years file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng akpen et al: best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria. azojete, 18(2):281-294. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 291 table 3: computed values of frequency factor (𝐾𝑇) and rainfall estimates (𝑋𝑇) given by six (6) probability distributions for different return periods for calabar table 4: goodness-of-fit (gof) test results for the distributions at calabar station gof test criteria probability distribution models n ln p3 lp3 ev1 lg calabar madi 0.0099 0.0030 0.0040 0.0048 0.0029 0.0214 𝑥2 57.1018 4.7976 8.7384 12.0788 7.3030 219.2021 rmse 84.8856 25.5417 37.1754 43.5557 32.3466 201.4082 rrmse 0.0854 0.0261 0.0376 0.0439 0.0339 0.2001 for the chi-squared (𝑥2) test: at α = 0.05, degree of freedom = 8, and the critical value = 15.5 at α = 0.01, degree of freedom = 8, and the critical value = 20.1 return period (years) normal (n) log-normal (ln) pearson type iii (p3) log-pearson type iii (lp3) gumbel (ev1) log-gumbel (ev1) 𝑲𝑻 𝑿𝑻(mm) 𝑲𝑻 𝑿𝑻(mm) 𝑲𝑻 𝑿𝑻(mm) 𝑲𝑻 𝑿𝑻(mm) 𝑲𝑻 𝑿𝑻(mm) 𝑲𝑻 𝑿𝑻(mm) 2 0.0000 576.7 0.0000 566.8 0.0878 567.1 0.0162 568.5 0.1642 558.8 -0.1642 549.5 5 0.8414 668.4 0.8414 664.0 0.8043 664.4 0.8456 664.7 0.7195 655.2 0.7195 649.1 10 1.2818 716.5 1.2818 721.6 1.3238 721.0 1.2697 719.9 1.3041 718.9 1.3041 724.6 25 1.7511 767.6 1.7511 788.1 1.9193 786.0 1.7161 783.1 2.0421 799.4 2.0421 832.5 50 2.0541 800.7 2.0541 834.4 2.3226 830.0 2.0015 826.2 2.5921 859.3 2.5921 923.4 100 2.3268 830.4 2.3268 878.4 2.7131 872.5 2.2552 866.8 3.1402 919.1 3.1402 1024.0 200 2.5762 857.6 2.5762 920.7 3.0757 912.1 2.4851 905.1 3.6806 978.0 3.6806 1133.7 500 2.8785 890.6 2.8785 974.8 3.5355 962.2 2.7612 953.5 4.3949 1055.9 4.3949 1296.9 1000 3.0905 913.7 3.0905 1014.4 3.8610 997.7 2.9531 988.6 4.9353 1114.8 4.9353 1435.8 http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 292 table 5: scoring and ranking scheme of the statistical tests results for the distributions at calabar station probability distribution models goodness-of-fit test criteria total score rank madi x2 rmse rrmse calabar n 2 2 2 2 8 5th ln 5 6 6 6 23 1st p3 4 4 4 4 16 3rd lp3 3 3 3 3 12 4th ev1 6 5 5 5 21 2nd lg 1 1 1 1 4 6th table 6: estimated rainfall (xt) values (mm) for various return periods given by the best fit model for calabar station best-fit model return period (years) 2 5 10 25 50 100 200 500 1000 calabar lognormal 566.8 664.0 721.6 788.1 834.4 878.4 920.7 974.8 1014.4 3.2 rainfall frequency curve the annual maximum rainfall estimates for the best fit probability distribution model in table 6, were used to develop the rainfall frequency curve as presented in figure 3. more so, the yearly wise annual maximum monthly rainfall depths ranging from 373.3 mm to 861.3 mm during the study period are also presented in the figure 3. the time series graph is important for showing how data changes over time. figure 3: rainfall frequency curve for calabar (based on log-normal distribution model) 4. conclusion accurate extreme rainfall estimates provided by a suitable model are needed by individuals, authorities and engineers in their planning and designing of hydraulic structures. the results of 0 200 400 600 800 1000 1200 1 10 100 1000 m ax im u m r ai n fa ll (m m ) return period (years) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng akpen et al: best-fit probability distribution model for annual monthly maximum rainfall in calabar city, nigeria. azojete, 18(2):281294. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 293 this study, reveals that, log-normal distribution was the best-fit model for calabar in the case of annual maximum monthly rainfall data. the rainfall frequency curve (figure 3) shows the predicted rainfall values that were obtained from the best-fit model, which may serve as a guide in hydrological designs. this study has provided useful engineering design tool for planning and designing of hydraulic structures and other flood control and mitigation measures. it is recommended that the developed frequency curve (based on the best fit model) should be adopted for prediction of rainfall amount for design of hydraulic structures in the study area. references agbonaye, ai. and izinyon, oc. 2017. best–fit probability distribution model for rainfall frequency analysis of three cities in south eastern nigeria. nigerian journal of environmental sciences and technology, 1(1): 34 – 42. aho, im., akpen, gd. and ojo, oo. 2019a. rainfall variability and trend analysis in makurdi metropolis, benue state, nigeria, nigerian journal of engineering, 26(2): 17-24. aho, im., akpen, gd. and ojo, oo. 2019b. probability distribution for extreme rainfall in makurdi metropolis, benue state, nigeria, nigerian journal of engineering, 26(1): 24-32. akpen, gd., aho, mi. and musa, aa. 2019. rainfall intensity-duration-frequency models for lokoja metropolis, nigeria. global journal of pure and applied sciences, 25:81-90. antigha, ree. 2012. urban storm water drainage systems modelling for calabar metropolis, cross river state, nigeria. ph.d. dissertation department of agricultural and environmental engineering, rivers state university of science and technology, port harcourt, nigeria. chow, vt. 1953. frequency analysis of hydrology data with special application to rainfall intensities, bulletin no. 414, university of illinois eng. expt. station. chow, vt., maidment, dr. and mays, lw. 1988. applied hydrology, 1st edition, mcgrawhill, new york, pp. 390 – 393. erhabor, fo., usman, sk., arigbede, ya., njoku, cg. and itu, po. 2019. analysis of urban growth pattern in calabar metropolis using the shannon entropy model. sokoto journal of geography and the environment,1(2):1-14 falola, t. and warnock, a. 2007. encyclopedia of the middle passage: greenwood milestonesin african american history. greenwood publishing group. p. 92. gabriel, ta., abdullahi, i. and joseph, ae. 2018. rainfall variation, water resource potential and implication for flooding; a case study of catchment area of major tributaries to river benue in taraba state. african journal of engineering research, 6(3):55-63. hassanyar, mh., tsutsumi, jg., nakamatsu, r. and omid, sm. 2018. the analysis of temporal variability, trend of precipitation and river discharge of kunduz river basin, afghanistan. international journal of engineering technologies and management research, 5(4), 69-78. doi: 10.5281/zenodo.1244727. http://www.azojete.com.ng/ mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: akpen.gabriel@uam.edu.ng 294 izinyon, oc. and ajumuka, hn. (2013). probability distribution models for flood prediction in upper benue river basin part 11. civil and environmental research. 3(2): 62-74. kite, gw. 1977. frequency and risk analysis in hydrology. water resources publications, fort collins, colorado, usa, 224p. khudri, mm. and sadia, f. 2013. determination of the best fit probability distribution for annual extreme precipitation in bangladesh. european journal of scientific research, 103(3): 391 – 404. ogarekpe, nm. 2014. development and comparison of different intensity duration frequency models for calabar, nigeria. the nigerian journal of technology, 33(1): 33 – 42. olofintoye, oo., sule, bf. and salami, aw. 2009. best-fit probability distribution model for peak daily rainfall of selected cities in nigeria. new york science journal, 2(3): 1-12. oruonye, ed. 2012. an assessment of flood risk perception and response in jalingo metropolis, taraba state, nigeria. special publication of the nigerian association of hydrological sciences.http://publications.unaab.edu.ng/index.php/nahs/article/view/909 accessed 10 june, 2022 oyegoke, so., adebanjo, sa., ajani, eo. and jegede, jt. 2017. analysis of rainfall intensity for southern nigeria. journal of engineering research, 22(1): 107-118. ottong, jg., ering, so. and akpan, fu. 2010. the population situation in cross river state of nigeria and its implication for socio-economic development: observations from the 1991 and 2006 censuses. journal of emerging trends in educational research and policy studies (jeteraps), 1 (1): 36-42 spiegel, mr. and stephens, lj. 2011. schaum’s outline of statistics, 4th edition, mcgraw hill, usa. 577pp. tao, dq., nguyen, vtv. and bourque, a. 2002. on selection of probability distributions for presenting extreme precipitations in southern quebec. annual conference of the canadian society for civil engineering, montreal, quebec canada, june 5 – 8, 2002, pp1-8. weibull, w. 1939. statistical theory of the strength of materials, ing.vetenskaps akad. handl. (stockholm), 151, p.15 win, nl. and win, km. 2014. the probability distribution of daily rainfall for kuantan river basin in malaysia. international journal of science and research. 8 (3): 977-983 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:akpen.gabriel@uam.edu.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):255-266 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 255 original research article application of sem/eds in fractographic investigation of tig welded aisi 1020 fusion zones at distinct welding current steps i. b. owunna1, a. e. ikpe2 and j. u. ohwoekevwo1 1department of mechanical engineering, university of benin, benin city, nigeria, p.m.b. 1154 2department of mechanical engineering, akwa ibom state polytechnic, ikot osurua, ikot ekpene, nigeria, p.m.b. 1200 *corresponding author’s email address: aniekan.ikpe@eng.uniben.edu 1.0 introduction tungsten inert gas (tig) welding is one of the welding methods applied in the fusion process of two or more metals. it plays a significant role in welding of mild steel or thin sections of non-ferrous metals such as copper alloys, aluminium alloys, magnesium and stainless steel. tig welding also referred to as gas tungsten arc welding (gtaw) is an electric arc welding process that employs a non-consumable tungsten electrode in the fusion process of metals (owunna and ikpe, 2018a; owunna and ikpe, 2019a). welding current is the electrical amperage in the power equipment used in carrying out welding operation. it is usually read from the power meter, which provides the welding technician with information on the welding amperage or amount of current used. welding current is one of the most influential welding parameter in welding operation because it has a high tendency of affecting bead geometry, electrode melting rate, deposition rate, heat affected zone and weld penetration depth (ikpe et al., 2017). for example, owunna et al. (2018) carried out a temperature and time dependent analysis on aisi 1020 low carbon steel plate of 10 mm thickness. the result revealed that at each increasing time step and welding article information abstract higher arc length is a function of increasing welding current (amperage). it increases the intensity of welding heat, thereby, influencing the microstructure and mechanical properties of the welded material. in this this study, fractographical variations in tig welded aisi 1020 fusion zones at different welding current steps were investigated using scanning electron microscopy with energy dispersive spectroscopy (sem/eds) techniques. the fracture morphologies showed a fibrous appearance indicating ductile fracture with initiation of a river pattern of branching cracks, forming cleavages along the crystals plains and intergranular fracture occurring along the grain boundaries, indicating brittle fracture as a result of stepwise increase in welding current. it was observed that the ultimate tensile strength of the welded samples decreased correspondingly from 583.3 mpa, 540 mpa, 530.7 mpa, 506.7 mpa to 473.3 mpa as the resulting heat input due to welding current increased from 96.14 a, 120 a, 155 a, 190 a to 213 a. this indicated that the lowest welding current (96.14a) produced fusion zone with the highest ductility when compared to other welding currents which produced fusion zones that tended to be brittle as a result of increasing heat inputs. it was observed that fusion zone with the lowest welding current showed the appearance of a fibrous structure produced by stretching of crystals in their lattice during heat application. micro-hardness on the surface of the welds revealed that hardness increased with increase in welding current. therefore, proper control measures should be put in place to ensure that welding input parameters are optimum. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 october, 2021 revised 7 march, 2022 accepted 16 march, 2022 keywords: welding low carbon steel welding current tig welding mechanical properties http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):255-266. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 256 current, the heat distribution characterized by intense heat, phase transformation and alteration in mechanical properties gradually formed a spiral transient patterns from the weldment known as heat affected zone (haz). continuous increase in welding current (amperage) is reported to be characterized by higher arc length and intense heat which may alter the elemental composition, mechanical properties as well as the microstructure of the haz and fusion zones. rajakuma et al. (2017) employed tig welding process in the joining process of stainless steel pipe, and the heat transfer behaviour for various welding input was analysed. it was observed that the amplitude of transient temperature distribution increased alongside the heat input while the microstructure of the weld bead profile consisted of austenite and δferrite in the fusion zone. the presence of ferrite reduced the hot cracking susceptibility during solidification of the molten weld. the effect of welding current (96.1213.8a) on elemental composition, mechanical properties and microstructure was demonstrated by owunna and ikpe (2019b) who employed artificial neural network (ann) and experimental approach in modelling and prediction of the mechanical properties of tig welded joint for aisi 4130 low carbon steel plates. optimized ann predicted output parameters where uts of 421 mpa, modulus of elasticity of 793 mpa, strain of 0.61 and elongation of 61% while experimental values using the optimized input variables produced output parameters of 427 mpa for uts of 421 mpa, 806 mpa for modulus of elasticity, strain of 0.62 and 62% elongation. visuals of the weldment obtained from scanning electron microscopy with energy dispersive spectroscopy (sem/eds) revealed a uniformly distributed grain sizes in the weldment primarily composing of iron (fe), chromium (cr), molybdenum (mo), nickel (ni) and manganese (mn). this correlates with similar studies where gtaw was applied on 2mm thickness of duplex stainless steel (dss) and hot rolled medium and high tensile structural steel. scanning electron microscope (sem) fractography analysis indicated that the weldments possessed good tensile strength without decrease in ductility of the fusion zone while elements like si and cr were also observed in the metallurgical properties (devakumar et al., 2016). the chromium, silicon and molybdenum represents ferritic microstructure while nickel (ni), manganese (mn) represents austenitisers (devakumar et al., 2015; pawan and nishant, 2013; chern et al., 2011). sem/eds is a type of electron microscope that produces photographs of sample by scanning through the welded surface with a focused beam of electrons that interact with atoms within the welded rehion, generating numerous signals with details about the surface topography and composition of the sample. hence, images that show the topography of the surface is created through the process of scanning the sample or the welded point and collecting the secondary electrons that are emitted using a special detector. in other words, sem is the imaging part of the technique while the “regular” optical microscope utilizes light for imaging. optical microscope and electron probe microanalysis (epma) approach were employed by liu et al. (2004) to investigate the weldability and microstructure of az31b magnesium alloy using hybrid laser tig welding, laser beam welding and tig welding. in the fusion zone of hybrid laser tig welding, equiaxed grains was observed which were smaller in sizes than the grain sizes obtained from tig welding but larger than those obtained from laser beam welding. huang et al. (2016) used gtaw multipass welding method to weld two dissimilar metals (s355jr carbon steel and 316l stainless steel plates), and consequently investigated the microstructural characteristics, mechanical properties and corrosion behaviour of the welded dissimilar joint. the results obtained revealed that the microstructure of the weldment was a combination of austenite and vermiform δ-ferrite. there was decarburisation layer on the interface of s355jr whereas, the damaged phase σ and m23c6 (chromium carbide) were not observed in the x-ray diffraction. in addition, the corrosion resistance of the weldment decreased when compared to 316l base material. in recent times, a number of computer aided tools such as particle swarm optimization (pso) algorithm, artificial neural network (ann), response surface methodology (rsm) and others have been employed in the prediction and optimization of welding parameters (owunna and ikpe; 2018b). however, only a few of these conventional techniques are applicable to investigations on file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu owunna et al: application of sem/eds in fractographic investigation of tig welded aisi 1020 fusion zones at distinct welding current steps. azojete, 18(2):255-266. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 257 material surface analysis and material failure, as they are mostly determined experimentally. this study is focused on investigation of fractographical variations in tig welded aisi 1020 fusion zones at different welding current steps using sem/eds. 2. materials and methods 2.1. materials in this study, a series of aisi 1020 low carbon steel weldments were produced by tig welding process. table 1 indicated the materials and specifications used for the welding process. table 1: materials and specifications used for the welding experimentation s/n material specification welding specification 1 welding type tungsten inert gas (tig) 2 material aisi 1020 low carbon steel plate 7 material thickness 10 mm 8 filler material er 70 s-6 9 joint type butt joint (v-groove) 10 joint preparation abrasive clean (sand paper)/acetone wipe 11 joint gap 2 mm 12 welding current d.c.e.n (direct current electrode negative) 13 pulse width 0.8 seconds 14 filler rod angle 15o 15 welding torch angle 45o 16 fixed frequency 60hz 17 torch type pro-torch (tig torch) 18 tungsten type 2% thoriated 19 tungsten size 3/1326” diameter x 25.4 mm 20 torch gas argon (100%) 21 heat input ratio 10.75 kj/min 22 weight of filler rod 78.5 kg/m2 23 welding machine dynasty 210 dx 24 clamp type g-clamp for clamping the work pieces 25 vertical milling machine for milling the v-groove angle 26 tensile machine instron 27 welding spatter blanket non-asbestos woven glass fabric 28 fire extinguisher pp3p lightweight abc dry powder 29 hand gloves and helmet for safety purpose 2.2. methods aisi 1020 low carbon steel plate (0.19% c, 0.25% si, 0.4% mn, 0.025% p, 0.015% s, 0.09% al, 0.009% mn, 0.05% nb and 0.03% ti) of 10 mm thickness each was cut into 60x20 mm (length x width) dimension as shown in figure 1. emery paper (coarse: p24 grit size with 715 µm and fine: p80 grit size with 201 µm) was used to smoothen and eliminate rough particles and rust from the surface of specimen before welding the samples in figure 1. this was followed by cleaning the surface of the samples to be welded with acetone in order to eliminate surface contamination. using vertical milling machine, the two steel plates were chamfered (2mm depth) with 30 degrees at the edge to form a v-groove angle while clamping it to a g-clamp. tig welding was applied to join the plates and filling the chaffered region using 2% thoriated tungsten electrode. this was achieved through the use of dynasty 210 dx welding machine and 100 % argon as the torch gas to protect the welding region from contaminants. the tig welding input variables http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):255-266. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 258 employed in the welding process are presented in table 2 while samples of the steel plates subjected to welding are shown in figure 1. table 2: design of experiment for tig input variables weld runs current (a) voltage (v) gas flow rate (l/min) 1 155 22 15.5 2 120 25 18 3 96.14 22 15.50 4 190 19 13 5 213 22 15.50 figure 1: samples of the steel plates subjected to welding the method of owunna and ikpe (2019b) was employed in this study, where each of the welded samples was subjected to sem/eds to check the mechanical properties and characterization of the weldment. the above input variables in table 2 were employed in the tig welding process to join the work piece together before being subjected to tensile test. tensile test was conducted on the samples at room temperature using universal material testing machine with iso 6892 standard at a load of 200kn. the test machine is manufactured by jinan kason testing equipment co., ltd, china, with model number wdw-200. the ends of the specimens were gripped in the machine and loads were applied until deformation occurred. this was used to calculate for the corresponding mechanical properties. the uts test was conducted to determine the maximum resistance of the welded specimen to fracture under tension while the hardness test was conducted to determine the resistance of the welded specimen to penetration by a pyramidal, conical or spherical indenter. to achieve these two parameters, the welded sample was subjected to preliminary measurements for five specimen welded at different currents before the application of load and final measurement after the application of load. hardness testing was used to evaluate the hardness depth of the surface-hardened welds of aisi 1020 low carbon steel. hardness across the welds were measured by micro-hardness tester using 2 kg load. this was done by making a series of hardness impressions from the edge of the cross sectioned samples towards the center. the hardness progression was graphically plotted and distance from the surface to the hardness limit was calculated. the uts, strain, modulus of elasticity, percentage elongation were calculated using equations 1-4. uts = f a (1) strain ʃ = dl l (2) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu owunna et al: application of sem/eds in fractographic investigation of tig welded aisi 1020 fusion zones at distinct welding current steps. azojete, 18(2):255-266. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 259 % elongation = dl l x 100 (3) e = uts ʃ (4) 3. results and discussion figure 2 shows the microstructural view of the control sample investigated in this paper. typical microstructure of the control sample is composed largely of equiaxed ferrite grains and small regions of pearlite (α-fe + fe3c) at grain boundaries edges and corners. figure 2: sem image of control sample of the base metal with magnification of 1500x as shown in figure 2, there are evenly distributed fine grain ferrite (white), which exert decisive influence on cleavage fracture and dispersedly observed pearlite grains (gray). according to chen and cao (2015), it is possible that for some ferrite-perlite microstructure with similar patterns and grains of pearlite colonies, cracks are initiated in perlite colonies. however, the propagation of a pearlite-colony-sized cracks controls the cleavage fracture. it is clear that, the susceptibility to cleavage fracture does not solely depend on the size of the fracture-initiating particle but also on the local ferrite grain size. the average ferrite grain size could not be measured quantitatively as a result of “widmanstatten” type microstructure observed. additionally, few river-like patterns of branching cracks of ferrite and pearlite structures which contributes to the hardness of the material. therefore, increase in pearlite grains would amount to increase in hardness (maalekian, 2007; malik et al., 2014), causing the material to be brittle. figure 3 represents the topography of sample welded at a current of 96.14a and magnifications of 500-1500. for samples welded with low welding current, the bands of perlite-rich area (banding) were observed. macrosegregation phenomenon known as banding, is due to the presence of high percentage of mn (0.4-0.5%) in these regions. in more alloyed weld metals, elements such as chromium and molybdenum can be found to be segregated in these areas (lars-eric, 1994). (a) (b) (c) figure 3: sem images of the fusion zone welded at 96.14a with magnifications of (a) 500x, (b) 1000x, http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):255-266. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 260 (c) 1500x topography of samples at welding current of 96.14a, showed a fibrous structure produced by stretching of crystals give rise to a number of tear ridges and dimples as a result of low heat inputs in the material. the fractured surface here is ductile at different magnifications of 500x, 1000x and 1500x. figure 4 represents the topography of sample welded at a current of 120a and magnifications of 500-1500x. (a) (b) (c) figure 4: sem images of the fusion zone welded at 120a with magnifications of (a) 500x, (b) 1000x, (c) 1500x topography of sample welded at current of 120a, showing a mixed type of failures (fractures). the fractures show fibrous appearance indicating ductile fracture with initiation of a river pattern of branching cracks forming cleavages along the crystals plains and intergranular fracture occurring along the grain boundaries, indicating a brittle fracture as a result of welding heat inputs increase. magnifications (500x, 1000x and 1500x) which the fusion zones were viewed after welding allows the fracture patterns to be seen clearly. figure 5 represents the topography of sample welded at a current of 155a and magnifications of 500-1500x. (a) (b) (c) figure 5: sem images of the fusion zone welded at 155a with magnifications of (a) 500x, (b) 1000x, (c) 1500x topography of sample welded at a current of 155a, showed decrease in ductility. this occurred as a result of decrease in fibrous appearance with reduction in the number of tear ridges and dimples and an increase in cleavage steps of branching cracks and surfaces of inter-granular brittle fractures. the fracture here appears more brittle as a result of step increase in welding heat inputs. these properties on the fusion zone is different from the base metal, because it is also characterized by pseudo-grains and a microstructural inhomogeneity which is a result of fast cooling rates. it appears that the zone in figure 6 mainly contains ferrite and some colonies of pearlite. hence, the microstructure that evolved in the weld is heterogeneous due to the welding temperature gradients and the chemical reaction that evolved during file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu owunna et al: application of sem/eds in fractographic investigation of tig welded aisi 1020 fusion zones at distinct welding current steps. azojete, 18(2):255-266. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 261 the welding process (grong, 1994). figure 6 represents the topography of sample welded at a current of 190a and magnifications of 500, 1000 and 1500x. (a) (b) (c) figure 6: sem images of the fusion zone welded at 190a with magnification of (a) 500x, (b) 1000x, (c) 1500x topography of sample welded at current of 190a, showing a stepwise increase in branching cracks of cleavage steps, widmanstatten ferrite, and some colonies of pearlite along the grain boundaries. this agrees with the findings of boumerzoug et al. (2010). the fractured surface appeared to be more brittle as heat input increased, causing reduction in ductility. in similar study, ikeh et al. (2019) observed that the fracture surfaces showed dimples of varying sizes and shapes, indicating ductile (due to low arc heat) to brittle (due to high arc heat) fracture. low arc heat (72 kj/mm), showed a classic mechanism of ductile fracture known as micro-void coalescence. high arc heat (90 kj/mm) showed trans-granular form of fracture which indicates brittle fracture in which the failure occurred with lower plastic deformation. figure 7 represent the topography of sample welded at a current of 213a and magnifications of 5001500x. it showed the effect of heat distribution on elongation of ferrite grains. bayraktar et al. (2007) observed in interstitial free steels that the welded joints are characterized by the presence of very large grains near the fusion line and these grains are oriented along the regions with high heat distribution. (a) (b) (c) figure 7: sem images of the fusion zone welded at 213a with magnification of (a) 500x, (b) 1000x, (c) 1500x topography of sample welded at current of 213a, showing crystalline appearance indicating brittle fracture with river pattern of branching cracks and surfaces of inter-granular fracture occurring at grain boundaries. brittle failure or fracture as mentioned in this context is the failure of a material without apparent plastic deformation. it occurs suddenly and the broken pieces can be fitted together to produce the original shape. the fracture may be in the form of cleavage along the crystal planes or it may be inter-granular, http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):255-266. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 262 occurring along the grain boundaries. brittle fracture, characterised by fast crack propagation appears granular and glossy. similarly, plastic failure or ductile failure as mentioned in this study is a type of failure that involves considerable plastic deformation preceding the fracture. the material begins to neck beyond the ultimate tensile strength. ductile material under static loading, plastic flow of materials precedes fracture and rupture surface shows a fibrous structure produced by the stretching of crystals giving rise to a number of tear ridges and dimples (onyekpe, 2002). 3.1. ultimate tensile strength and micro-hardness of the welds table 3 represents the measured values obtained from the welded samples, table 4 results of mechanical properties while figure 8 is a graphical view of ultimate tensile strength (uts) and elastic modulus of the welded samples at different welding temperature. table 3: measured values of the welded samples sample width (mm) thickness (mm) load (kn) lo (mm) lf (mm) 96.14a 30 10 142 60 62 120a 30 10 152  60 155a 30 10 159.5  62 190a 30 10 175  62 213a 30 10 162  60 table 4 shows the results of mechanical properties of fusion zone of aisi 1020 welded with distinct current steps. it contains the uts, strain, percentage elongation and young’s modulus which were all derived from equation 1-4. the mechanical properties as shown in table 4 are the physical properties that the welded specimens exhibit upon the application of forces which tend to affect the geometry and performance of the welds when applied to structural members. the results of uts and modulus of elasticity of the welds presented in table 4 are graphically plotted against welding currents employed in the fusion process as shown in figure 8. figure 8 shows that uts decreases as welding current increases. the welding current in this case is considered as the arc heat because increase in welding current results in increase of the arc heat and vice versa. furthermore, figure 8 implied that modulus of elasticity also decrease as welding current increased, but the rate of decrease was almost insignificant, possibly due to error in the readings, calculations or the welding process. the strain and percentage elongation were not graphically presented as there were no changes in the values throughout the welding current steps, indicating that the effect of welding current on strain or elongation property of welds is likely to be insignificant. table 4: results of mechanical properties samples welded at different currents uts (mpa) ʃ strain (mm/mm) % elongation (%) e young modulus (mpa) 96.14 583.3 0.17 17 3.43117 120 540.0 0.17 17 3.17647 155 530.7 0.17 17 3.12747 190 506.7 0.17 17 2.98058 213 473.3 0.17 17 2.78412 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu owunna et al: application of sem/eds in fractographic investigation of tig welded aisi 1020 fusion zones at distinct welding current steps. azojete, 18(2):255-266. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 263 figure 8: graphical representation of uts and elastic modulus figures 9a-e indicates the micro-hardness on the surface of the fusion zone, measured from the base metal across the weld metal after welding. the 60 mm shown on the plot represents the length of the welded samples while the distances ranging from 1-22 mm represents the indent spacing. after calculating the distance from the surface to the hardness limit, average was calculated from five points of micro-hardness on each weld produced by welding current of 96.14, 120, 155, 190 and 213 a. a. welding current of 96.14 a b. welding current of 120 a c. welding current of 155 a d. welding current of 190 a 0 0.5 1 1.5 2 2.5 3 3.5 4 0 100 200 300 400 500 600 700 96.14 120 155 190 213 welded samples at different currents (a) uts (mpa) e (mpa) u lt im at e te n si le yo u n g m o d u lu s e http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):255-266. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 264 e. welding current of 213 a figure 9: micro-hardness on the surface of welds produced by different welding current average results of surface micro-hardness obtained from welds produced by tig welding techniques using the aforementioned welding currents are presented in figure 10. the result shown on the plot indicates that micro-hardness on welded joint increases as the welding current increased. average hardness values obtained in this study using welding current from 96-213 ranged from 150.1-260.1 hv, whereas, hardness values obtained in similar studies conducted by boumerzoug et al. (2010) ranged from 178-250 hv at locations within 1 mm from the welded metal, through the haz across the weld metal to the base plate. the increase in welding current during the welding process results in an increase of the arc heat which causes phase transformation in the fusion zone and after cooling, grains in the welded region becomes coarser with significant local embrittlement which reduces hardness performance of the welded steel material (li et al., 2019). this correlated with the findings of muda et al. (2015) who indicated that the higher the welding heat input, the coarser the microstructure. the phase transformations which occur in two phases may be high temperature transformation of δ-fe to γ-fe and transformation of γ-fe to α-fe (dodo et al., 2016). gharibshahiyan et al. (2011) found that slow cooling rate can also cause nucleation of coarse grain structures with high intergranular spacing which is characterised by reduction in hardness, thereby causing increase in grain dislocations within the crystal lattice of the fusion zone. figure 10: average micro-hardness on the surface of welds produced by different welding current 4. conclusion all welds are prone to some level of defects, and it is more or less impossible to achieve a weld with zero defect. the phase transformation which occur from solid to semi-solid phase and from semi-solid phase to liquid phase depended largely on welding current. the phase transformation due to welding current is a function of welding temperature, heat input, type of material, cooling rate, welding parameters. at 260.1 246.1 215.1 180.1 150.1 20 70 120 170 220 270 96.14 120 155 190 213 m ic ro -h ar d n es s (h v ) welding current (a) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu owunna et al: application of sem/eds in fractographic investigation of tig welded aisi 1020 fusion zones at distinct welding current steps. azojete, 18(2):255-266. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 265 different welding current step applied in this study, fusion zones after solidification showed various fractured appearances such as river pattern of branching cracks, inter-granular fracture, ductile fracture and brittle fracture. it was also observed that the lowest current (96.14 a) employed in this investigation produced the highest uts of 583.3 mpa and highest modulus of elasticity of 3.43117 mpa and vice versa. in this case, increased value of the modulus of elasticity signifies increase in the stiffness of the material as well as increase in the material tensile property. micro-hardness on the surface of the welds revealed that hardness increased with decreasing welding current. other factors such as grain size, welding current, arc heating also contribute to hardening of welded joints. therefore, proper welding experiments should be performed to determine optimum welding current for a given material to avoid unwanted catastrophes. references bayaraktar, e., kaplan, d., devillers, l. and chevalier, jp. 2007. grain growth mechanism during the welding of inter-stitial free (if) steels. journal of materials processing technology, 189(1-3): 114-125. boumerzoug, z., derfouf, c. and baudin, t. 2010. effect of welding on microstructure and mechanical properties of an industrial low carbon steel. engineering, 2: 502-506. chen, j. and cao, r. 2015. microorganism of cleavage fracture of metals: a comprehensive microphysical model for cleavage cracking in metals, 1st edition. butterworth-heinemann, oxford, 1-486. chern, t., tseng, k. and tsai, h. 2011. study of the characteristics of duplex stainless steel activated tungsten inert gas welds. materials and design, 32(1): 255-263. devakumar, d., jabaraj, db. and raja, vkb. 2015. literature review on the effect of processing on the mechanical and metallurgical properties of low carbon steels, journal of engineering and applied science, 10(11): 5012-5016. devakumar, d., jabaraj, db., raja, vkb. and jayaprakash, j. 2016. experimental investigation of dss/hrs gtaw weldments, indian journal of science and technology, 9(43): 1-6. dodo, mr., ause, t., adamu, ma. and ibrahim, ym. 2016. effect of post-weld heat treatment on the microstructure and mechanical properties of arc welded medium carbon steel. nigerian journal of technology, 35(2): 337-343. gharibshahiyan, e., raouf, ah., parvin, n. and rahimian, m. 2011. the effect of microstructure on haerdness and toughness of low carbon welded steel using inert gas welding. material and design, 32(4): 2042-2048. grong, o. 1994. metallurgical modelling of welding. materials modelling series. the institute of materials, oxford, england. huang, bs., yang, j., lu, dh. and bin, wj. 2016. study on the microstructure, mechanical properties and corrosion behaviour of s355jr/316l dissimilar welded joint prepared by gas tungsten arc welding multi-pass welding process. journal of science and technology of welding and joining, 21(5): 381-388. ikeh, od., ikpe, ae. and njelle, vz. 2019. effects of electric power arc inputs on the fracture surface and the mechanical properties of 0.4%c steel. journal of science and technology research, 1(3): 133-143. ikpe, ae., owunna, i. and ememobong, i. 2017. effects of arc voltage and welding current on the arc length of tungsten inert gas welding (tig). international journal of engineering technologies, 3(4): 213221. lars-eric, s. 1994. control of microstructures and properties in steel arc welds. library of congress cataloguing in published data, uk. li, d., wu, k., dong, h., isayev, o. and hress, o. 2019. coarse grained heat-affected zone microstructure and brittleness of ti-nb-b microalloyed high toughness and wear resistant steel. metals, 9(3): 289-303 http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):255-266. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 266 liu, lm., wang jf. and song, g. 2004. hybrid laser-tig welding laser beam welding and gas tungsten arc welding of az31b magnesium alloy. material science and engineering a, 381: 129-133. maalekian, m. 2007. the effects of alloying elements on steels (i). graz institute of material science, joining and forming (3030), styria, austria. malik, j., toor, ih., ahmed, wh., gasem, zm., habib, ma., ben-mansour, r. and badr, hm. 2014. investigation on the corosion-enhanced erosion behaviour of carbon steel aisi 1020. international journal of electrochemical science, 9: 6765-6780. muda, ws., nasir, ns., mamat, s. and jamian, s. 2015. effect of welding heat input on microstructure and mechanical properties at coarse grain heat affected zone of abs grade a steel. arpn journal of engineering and applied sciences, 10(20): 9487-9495. owunna, ib. and ikpe, ae. 2019a. evaluation of induced residual stresses on aisi 1020 low carbon steel plate from experimental and fem approach during tig welding process. journal of mechanical engineering and sciences, 13(1): 4415-4433. owunna, i. and ikpe ae. 2018b. optimization of tig welding input variables for aisi 1020 low carbon steel plate using response surface methodology international journal of engineering science and application, 2(3): 113-122. onyekpe, b. 2002. the essentials of metallurgy and materials in engineering. ambik press, benin city, nigeria. owunna, i., ikpe, ae. and achebo, ji. 2018. temperature and time dependent analysis of tungsten inert gas welding of low carbon steel plate using goldak model heat source. journal of applied science and environmental management, 22(11): 1719-1725. owunna, ib. and ikpe, ae. 2018a. effects of parametric variations on bead width of gas tungsten arc welding of aisi 1020 low carbon steel plate. international journal of engineering technology and sciences, 5(3): 1-13. owunna, ib. and ikpe, ae. 2019b. modelling and prediction of the mechanical properties of tig welded joint for aisi 4130 low carbon steel plates using artificial neural network (ann) approach. nigerian journal of technology 38(1): 117-126. pawan, kb. and nishant, r. 2013. parameters optimization for gas metal arc welding of austenitic stainless steels and low carbon steel using taguch’s technique. international journal of engineering and management research, 3(4): 18-22. rajakuma, j., bathusa, ms., rajan, np., sulaiman, k., christopher, as. and ganesh, i. 2017. numerical investigation of heat transfer behavior during tig welding of stainless steel pipes for various welding heat input conditions. american journal of mechanical and industrial engineering, 2(3): 117-126 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):637-650 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 637 original research article comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria *p. a. ozor1,2 and c. g. ozoegwu2 1. department of quality and operations management, faculty of engineering and the built environment, university of johannesburg, south africa 2. department of mechanical engineering, university of nigeria, nsukka, nigeria *corresponding author’s email address: pozor@uj.ac.za, paul.ozor@unn.edu.ng 1.0 introduction a road crash can generally be denoted by two important phenomena; 1) it is a random and undesirable event, and 2), it occurs without prior notice (this work). this unforeseen (hoel et al., 2010) nature underscores the need for an analytical approach to estimating possible indices of its occurrence, to plan safety and precautionary measures. the road version of accident simply means the occurrence of accident on the road. road traffic accident remains a hazard the world have come to live with. the problem of road accidents have been reported to be on the increase worldwide, mainly due to the disparity between growth in transportation infrastructure with development investment in key sectors like industry, energy, water and real estate (prasannakumar et al., 2011). this menace has been credited to be the foremost cause of road crashes and orthopedic hospitalization worldwide (taimur et al., 2011, liang et al., 2005). road safety improvements and deteriorations can be measured in terms of fatality rate (persia et al., 2015) in an optimally designed and constructed road. the need to ensure road safety has been emphasized in the past (ona and garach, 2011). schepers and heinen (2013) suggested the substitution of short car trips with cycling to reduce vehicular crashes. article information abstract road crashes are generally characterized by occurrence without prior notice as well as low or moderate to severe losses in terms of lives and properties. in particular, rural communities in developing countries count huge losses to crash exigencies due to lack of basic infrastructure. it is important that such accident trends which possess special and distinct features from those observed for urban settlement be carefully studied and modeled for effective mitigation strategies. this paper proposes models that quantitatively assess the effects of various causal factors of crashes in rural roads of developing communities. taking data from nsukka municipality, south east nigeria, it provides two reliable, statistically significant techniques of predicting accident rates on such roads. the results show that although important causal variables like “illiteracy, weather condition, alcohol and drugs” affect road accident, “reckless driving, over speeding, annual average daily traffic, poor road and mechanical faults” were variables that demand more assessment and control in road accident management in the studied location. further, surface comparison of the developed models based on overall statistical indices suggests that multiple linear accident models are more accurate, though the quadratic accident model is statistically significant. a point by point calculation of deviations shows that the quadratic accident model, apart from its ability to take care of nonlinearity effects of independent road accident variables, is actually more accurate than the linear model, except where the quadratic model suffered more numerical instability from the combination of numerical parameters. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 december, 2019 revised 7 april, 2020 accepted 13 april, 2020. keywords: road crashes rural communities developing countries causal factors predictive models. mailto:pozor@uj.ac.za mailto:paul.ozor@unn.edu.ng http://www.azojete.com.ng ozor and ozoegwu.: comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria. azojete,16(4):637-650. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 638 vital predicators of road accident include but not limited to human and environmental factors. there are numerous causes of road accidents, attitudinal dimensions and attendant safety repercussions (shinar, 2019; konkor et al., 2019; mccartan and elliott, 2018, dai and jaworski, 2016). although some risk factors are more prevalent in certain regions than others (papadimitriou et al., 2019; hordofa, 2018), the modalities of a particular road inferno are not easy to model. horsman and conniss (2015) express the investigative difficulty in determining a timeline of proceedings with causal factors in a given road crash. there have been concerted efforts geared towards eliciting detailed list of influential road crash habits. the causative agents might be due to mobile phone usage (lester et al., 2010, horsman and conniss 2015, musicant et al., 2015), annual daily traffic (polus and cohen, 2012), thoroughfare and environmental dependent factors (abdul manan et al., 2018; dai and jaworski, 2016, aworemi et al., 2010). undetected mechanical imperfections, such as faulty tire, bad braking system, or steering malfunctioning can influence crashes in rural roads. alcohol drinking (scot-parker et al., 2014) is another important lead up to road accident. road users under the influence of psychoactive substances are more likely to experience poor judgment in the presence of some road features like the pavement, length, sharp bends, intersection and the traffic control system. in particular, multiple vehicle collision accident situations can be traced to the action or inaction of the driver of one or both of the vehicles involved, especially in two lane roads. driver error can increase crash occurrence in many ways (shim et al., 2015); including going against the traffic, indiscriminate stopping and packing, reckless overtaking, disobedience to both traffic laws, lights and traffic controllers. there are instances where drivers underestimate the speed and overestimate the distance of an approaching vehicle and try to overtake with uncontrollable speed (mccartan and elliott, 2018; abegaz et al., 2014). road accident can also happen due to illiteracy (poor or no knowledge of road codes and signs) on the path of road users or disrespect for existing road rules where knowledge is available. road accidents are usually characterized by personal, property, vehicle or structural injuries (konkor et al., 2019; quistberg et al., 2014). road accident prediction and reduction models can provide efficient decision tool in redesigning and maintenance of a given road. it can also guide stake holders, government agencies and road management authorities in formulating road safety policies in the light of proven road accident initiation events, prevalent in specific geographical locations. though, considerable efforts have been made in the past to model road crashes (russo et al., 2017; vilaca et al., 2017; bagloee and asadi, 2016; wu and jovanis, 2012), development of a generalized prediction model for road accidents can be difficult. this is partly due to the large variety in accident forms and causal factors with respect to specific countries, road types and locations. past authors have developed algorithms based on the dodge model to tackle road accident mitigation realities (xu and huang 2016). the field had equally seen the evolution of interactive highway safety design model (ihsdm) which incorporates a crash prediction module (cpm) for estimating accident frequency on road segments (aurelio et al., 2012). the ihsdm covers mostly the parameters of interest in crash estimation within the particular regions for which it was designed. a regression analysis model for predicting accidents using exposure and geometry related parameters as explanatory variables is not farfetched (ona and garach, 2011). the work demonstrate how speed reduction can affect road safety. the presentation examined consistency of road design based on the consistency criterion developed during the end of the 20th century (lamm et al., 1988). polus and cohen (2012) proposed a non-canonical poisson regression methodology for the analysis and prediction of crashes on low-volume rural roads. the database contained accidents in all two-lane highways in isreal and considered parameters of volume below 3000 annual daily traffic (adt). other parameters of concern were length of section as well as degree of fatal and serious crashes, which were expressed as whole numbers. the percentage time-spent-following (ptsf) was used to assess the percentage of time with which a high-speed moving vehicle is impeded by a slow moving one. the authors employ http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 637-650. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 639 poisson distribution to account for non-negative integer value of occurrences and recommended it for counted data. the ptsf does not apply in this study because the peculiarities of the case example do not permit fast movement and 95% of the roads are twolane. there were other attempts made towards formulating poisson regression-based road accident generalized models (lenguerrand and martin, 2006, caliendo et al., 2007). significant amount of result of such modeling technique show that crash rate increases with either increasing speed or traffic flow. in particular, strong correlation existed between the number of crashes, traffic flow, and infrastructure features (caliendo et al., 2007). increase in population and road traffic violation in a given area can lead to road accidents in a large scale (ateeth et al., 2012). the use of only linear regression models lack competence in adequately describing the nature of crash frequency data (joshua and garber, 1990, polus and cohen, 2012). there exists negative binomial poisson regression model for crash prediction (shankar et al, 1995) and multivariate poisson lognormal regression model for accident frequency analysis (ma et al., 2008). the studies introduce geometric variables like horizontal and vertical alignment as well as environmental factors; including number of rainy days, snow and rainfall as well as states of nature. taking road inventory database from the indiana department of transportation (indot), and the accident information record from the indiana state police, karlaftis and golias (2002) present a non-parametric statistical methodology called hierarchical tree-based regression for predicting probability of accident occurrence on rural roads. the work elaborated on the effects of typical roadway geometric indicators on crash rates. multivariate bayesian modeling techniques has been added to ra literature, in an attempt to compliment the inadequacy of linear models formulated with poisson distribution for road accident modelling (liu and sharma, 2018; cai et al., 2017). joshua and garber (1990) combine linear regression and poisson regression technique to model the frequency of road crashes involving trucks. one of the aims of this study is to determine the factors that affect accident within the study area and predict how significant the factors contribute to road accident. the literacy level and exposure of traffic officers delineated during six months of opinion surveys and field trips, were relied upon to examine the statistical significance and accuracy of two modelling approaches. the work became necessary due to the difficulty in application of existing sophisticated ra models in the case study area. the basic concern is to make the analytic method as easy to understand and apply as possible, without any loss in quality of its purpose. use of multiple linear regressions is considered appropriate. this technique was used because it not only predicts how significant the causal factors contribute to accident, but conveniently leads to an in-depth analysis of the data, that is; it explains the relationship that exists between the independent variables and provides adequate explanation for those variables which contribute to the dependent variable. in particular, quadratic accident model (qrm) is explored to offer alternative modeling methodology different from negative binomial, non-canonical poisson regression or multivariate bayesian approaches reported widely in literature. the choice of the two models was informed by two reasons. 1) both models, apart from providing in-depth analysis of the variables that cause accidents in the location, gives an idea of the significance of each variable with reference to the dependent variable. 2) quadratic accident model can take care of any non-linearity effect of those independent variables with time windows. for instance, during school runs, rainy periods or road blocks. the authors’ opinion is that the accuracy of each should be investigated and elicited for policy purposes. there is no existing publication of this sort known to the authors. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozor and ozoegwu.: comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria. azojete,16(4):637-650. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 640 2. materials and methods the study used qualitative and quantitative methods. road accident data was obtained from both primary and secondary sources. part of the data was sourced by the use of structured questionnaires administered to 1000 respondents drawn from various categories of road users and traffic stake holders in nsukka, nigeria. the questionnaire was designed to find out the gender, age, ownership of automobile (including bicycles) and road literacy level (indicating whether the road user attended driving school, has knowledge of road signs, has knowledge of federal road safety codes and rights of way) of respondents. other data obtained with the questionnaire included accident involvement or witness index (indicating number of times the respondent was involved in road accident or witnessed one). respondents that either involvedin or witnessed an accident were requested to specify where it occurred, how it occurred, time of occurrence, accident degree and causal factor (over speeding, recklessness, poor road maintenance, poor vehicle maintenance, road block, weather condition, illiteracy, alcohol and drug, others). adequate provision was made for respondents to specify the exact cause of accident if the causal factors mentioned are not applicable. respondents included the motoring public, residents, the police traffic department, federal road safety commission (frsc) rs. 9.11, and ministry of works. hourly traffic data was obtained from three groups of respondents: police traffic unit (ptu), frsc and vehicle inspection officers (vio) in the metropolis. the ptu, frsc and vio use special instrument (loop detectors) for gathering and recording traffic data. in cases where multiple competing digits or varying answers were obtained for a particular road from all three sources (ptu, frsc and vio), an average of the whole values was relied upon. the various data as collected from the sources were screened for both noise and outliers that could result from errors. 2.1 model i: multiple linear regression model multiple linear regression allows the estimation of a dependent variable from independent variables. in this paper, the basic assumption that any causal factor that does not lead to road accident in up to four years out of the nine years for which data is available, is treated as an outlier, was made. the general form of the model is given by equations (1) and (2) (levin, 1998): �� = �0 + �1�2 + �2 �2 + �3�3 + �4�4 + �5�5 + � (1) where: � = 1,2 . . . 5, �� = ��������� ��������, �1,2,⋯5 are the independent variables, � is the regression constant, �1,2,⋯5 is the regression coefficients, � is the random error associated with ��. while some of the error terms may be small and others large, the variability of the error terms is in no way related to the independent variable used. the constants can be deduced with the following equations: ∑y = nβ0 + β1∑x1 + β2∑x2 + β3∑x3 + β4∑x4 + β5∑x5 ∑ x1y = β0∑x1 + β1∑x12 + β2∑x1x2 + β3∑x1x3 + β4∑x1x4 + β5∑x1x5 ∑ x2y = β0∑x2 + β1∑x1x2 + β2∑x22 + β3∑x2x3 + β4∑x2x4 + β5∑x2x5 ∑ x3y = β0∑x3 + β1∑x1x3 + β2∑x2x3 + β3∑x32 + β4∑x3x4 + β5∑x3x5 ∑ x4y = β0∑x4 + β1∑x1x4 + β2∑x2x4 + β3∑x3x4 + β4∑x42 + β5∑x4x5∑ x5y = β0∑x5 + β1∑x1x5 + β2∑x2x5 + β3∑x3x5 + β4∑x4x5 +β5∑x52 (2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 637-650. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 641 where: for the particular case of the example in this study; �= number of accidents, �1= reckless driving, �2 = over speeding, �3= aadt, �4= poor road, �5 = mechanical fault 2.2. model ii: quadratic accident model the general p-order polynomial least squares model for a d-dimensional multi-variate response can be given as (levin, 1998): � � = � � � �=1 � � �� � �� �∑ −1 �=1 � � �� ��∑ (3) where: � � = �1 � �2 � …�� � � is the polynomial of basis vector, � is the number of sampling runs. the length � of �(�) is generally given as: � = �+� ! �!�! (4) where the dimension � is the number of independent variables and p is the order 2.3 significance of parameters on the basis of the data of table 2, the selected independent variables used in the multi-linear and quadratic linear accident prediction modeling has the following significances: 1. reckless driving this factor covers going against the traffic, neglect of right of way, dangerous over taking and any playful act while driving. 2. over speeding this describes a situation where the permissible (recommended) speed limit for any road is exceeded by a driver, thereby leading to a road crash. 3. annual average daily traffic this index, frequently abbreviated as aadt, is used to denote the total annual volume of vehicular traffic on a particular road divided by 360. 4. poor road this takes into account all manner of road failures or encumbrances that resulted in a road crash. it can include potholes, road blocks, damaged vehicles left unattended, etc. 5. mechanical fault mechanical fault refers to vehicles with one or more known problems or failed parts without maintenance that eventually resulted in ra. 2.4. annual average daily traffic (aadt/traffic volume) the daily traffic volume specifications were part of the information obtained through the questionnaire. only the available data were used to predict aadt in each year. an average growth rate (r) of 5 percent for the succeeding year was assumed, based on opinion surveys and interviews with vehicle licensing officials (vio). documented evidence shows that aadt can be estimated from the identified traffic volume according to the dependence of equation (5) (singh and suman, 2012): a = p 1 ± r 100 n (5) where � = ���� of the year being predicted, � = ���� of current year, � = number of years under consideration (size of sample years); a negative sense designates before the current year traffic count while the current year count is indicated by a positive sign. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozor and ozoegwu.: comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria. azojete,16(4):637-650. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 642 2.5. multi-linear regression models specification the multiple linear regression models attempt to estimate the relationship between two or more explanatory variables (�) as associated with a value of the dependent variable (�). in this paper, the general form of the model presented in equation (2) can be explored to fully specify the values of the parameters. application of the values of the parameters in table 1 through table 2 to equation (3) results in the dependence relationships depicted in equation (6). accordingly: 654 = 9β0 + 415β1 + 180β2 + 22691.05β3 + 19β4 + 13β5 33108 = 415β0 + 21173β1 + 8955β2 + 914344.33β3 + 969β4 + 613β5 13225 = 180 + 8955β1 + 3742β2 + 450513.75β3 + 395β4 + 272β5 1631077.64 = 22691.05β0 + 914344β1 + 450513.75β2 + 59309175.42β3 + 46386.93β4 + 41586.37β5 1492 = 19β0 + 969β1 + 395β2 + 46386.93β3 + 55β4 + 23β5 970 = 13β0 + 613β1 + 272β2 + 41586.37β3 + 23β4 + 27β5 (6) a few more steps of mathematical analysis of equation (6) yields the following values of each parameter. β0 = 3.346, β1 = 1.106, β2 = 1.123 , β3 = − 0.001, β4 = − 0.663, β5 = 0.154 2.6 quadratic regression models specification as presented in equations (4) and (5) for the general p-order polynomial least squares model for a � − dimensional multi-variate response, we consider for illustration the case where � = 2 and � = 2 (the quadratic bivariate case) to obtain: � � = 1 �1 �2 �1�2 �12 �22 � and � = 6. (7) inserting � = 9 in equation (4) for the case of multiple (� = 5), linear (� = 1), regression gives the multiple linear accident model as: � � = 3.34587363558554 + 1.10645537492239�1 + 1.12311165841290�2 − 0.00133250106231�1�2 − 0.66279908020189�12 + 0.15444261162054�22 (8) also inserting � = 9 in equation (4) for the case of multiple (� = 5) , quadratic (� = 2) , regression gives the quadratic accident model as: � � = 29.09080968576436 − 2.20877716640020�1 − 0.85492873755439�2 − 0.00361962189169�3 + 34.30042009419936�4 + 1.54128325239977�5 + 0.09738583088201�1�2 + 0.00001863705064�1�3 − 0.28345401496583�1�4 + 0.02856208489972�1�5 + 0.00023687839939�2�3 + 1.33060383044842�2�4 + 0.61570829132689�2�5 + 0.00121973323749�3�4 − 0.00084714037295�3�5 − 6.64636921194101�4�5 + 0.01695289120036�12 − 0.13852515708679�22 + 0.00000251868335�32 − 6.58083216092202�42 − 0.66968073658966 �52 (9) 3. results and discussion this section presents an analysis of the data collected for estimating road crashes in the case study area. the first stage used spss for windows to articulate a regression output for the dependent and independent variables as well as obtain approximate values of other important statistical indices related to the study. later, the multiple linear accident model result is compared with the field data. table 1 displays the summary of all the data collected through questionnaire, while table 2 indicates the dependent variables as a function of the independent variables. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 637-650. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 643 table 1: summary of questionnaire data year nc mja mna rd x1 os x2 aadt pr x3 mf x4 il x5 wc ad 2015 112 41 71 43 26 4125 20 9 11 0 3 2014 116 47 69 39 29 3935 25 11 12 0 0 2013 132 44 88 41 32 3679 19 22 15 1 2 2012 115 39 76 37 29 3579 17 13 16 2 1 2011 94 41 53 39 21 3369 11 3 19 0 1 2010 109 36 73 57 19 3200 14 2 17 0 0 2009 101 34 67 43 22 3198 13 8 15 0 0 2008 115 38 77 52 17 2874 16 5 23 1 1 2007 82 26 56 21 35 2744 10 1 15 0 0 2006 135 42 93 61 25 2607 21 1 25 1 1 2005 125 44 81 48 30 2476 22 1 21 1 2 2003 116 47 69 55 23 2235 13 3 22 0 0 2002 96 30 66 34 21 2123 15 1 23 1 1 2001 139 42 97 62 24 2017 23 1 24 2 2 2000 117 29 88 47 15 1916 27 1 27 0 0 key: nc-number of crashes, mjamajor accident, mnaminor accident, rdreckless driving, osover speeding, aadtannual average daily traffic, prpoor road, mf, mechanical fault, il-illiteracy, wcweather condition, adalcohol or drug table 2: values of dependent and independent variable. (police and questionnaire) year no. of accident reckless driving (x1) over speeding (x2) aadt(x3) poor road (x4) mechanical fault (x5) error (ei=ei) 2011 66 39 21 3369.33 1 3 e1 2010 82 57 19 3200.86 4 2 e2 2007 18 12 5 2744.34 0 1 e3 2006 94 61 25 2607.12 1 1 e4 2005 84 48 30 2476.78 2 1 e5 2003 84 55 23 2235.28 3 3 e6 2002 63 34 21 2123.52 2 1 e7 2001 97 62 24 2017.34 2 1 e8 2000 66 47 15 1916.48 4 0 e9 in the questionnaire, road accident was pre-classified in line with the recommendation of zakwan (2011). fatal accident refers to a case where death results from injury sustained in less than 30 days after the accident occurred. in serious accidents, victims are hospitalized due to injury sustained from the accident, but without death within 30 days of its occurrence. minor or slight accident results in such injuries as sprain, bruise, cut or even a slight damage on vehicles or properties. the data for year 2004 and 2008 were not available at the time of this study. figure 1 presents the annual average daily traffic (aadt) estimated from the collected data. the predicted traffic volume was computed using equation (1). results of the questionnaire data as statistically analyzed are displayed in table 1. the specific values of the independent variables as determined from the questionnaire and police data are presented in table 2. it is noteworthy that table 2 shows only the values of the dependent and independent variables and the expected errors for each year. figure 1 presents the predicted traffic volume. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozor and ozoegwu.: comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria. azojete,16(4):637-650. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 644 figure 1: predicted traffic volume 3.1. regression output from spss table 3 gives the model summary developed with the statistical software, spss and reports the strength of the relationship between the model and the dependent variable (expected number of accidents). the multiple correlation coefficients, r (0.998) indicates a good linear relationship between the observed and predicted values of the dependent variable. the coefficient of determination by the software is �2 = 0.996. this means that 99.6% of the explanatory variables determine the expected number of accident. the coefficient of determination developed by the software (�2 = 0.996) is very close to 1, hence the model holds good fit. table 3. model summary model r r square adjusted r square std. error of the estimate 1 0.998 0.996 0.989 2.48240 the computed variances are displayed in table 4. table 5 shows the coefficients of the regression line. equation (10) became the regression equation. table 4: analysis of variance (anova) model sum of squares df mean square f significance regression 1 residual total 4543.513 18.487 4562.000 5 3 8 908.703 147.46 .001 table 5: coefficients model un-standardized coefficients standardized coefficients significance b std. error beta t (constant) recklessness over speeding aadt poor road mech. fault 3.346 1.106 1.123 -.001 -.663 -.154 6.456 0.1 0.198 0.002 0.836 1.125 .739 .333 -.029 -.038 .007 0.518 11.104 5.667 -0.586 -0.793 0.137 0.640 0.002 0.011 0.599 0.486 0.900 y = 3.349 + 1.106x1 + 1.123x2 − 0.001x3 − 0.663x4 + 0.154x5 (10) figures 2 and 3 indicate that the normality assumption for the model is not violated because violation of normality compromises the estimation of the coefficients. finally, the plot of residuals by the predicted values shows that the variance of the error increases with increasing predicted number of accidents. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 637-650. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 645 figure 2. histogram figure 3 normal p-p plot of regression standardized residual 3.2 comparison of multiple linear accident model result with field data figure 4 compares the developed accident prediction linear model results with the actual field data. the number of accidents is plotted against year of occurrence. the field data has only a slight observable difference (between 2003 and 2006) with that of the model developed. this means that the model developed can predict the number of accidents with reasonable degree of accuracy. figure 4. comparison of number of accidents found by linear model with field data file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozor and ozoegwu.: comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria. azojete,16(4):637-650. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 646 the overall goodness of fit of the multiple linear and quadratic models were compared on the basis of some statistical error indices. the indices of comparison were the coefficient of determination (�2) , root mean square error (rmse), mean bias error (mbe), mean absolute bias error (mabe), mean percentage error (mpe), t-test statistic and correlation coefficient (ρ). more efficient models give �2 values closer to unity, but there is higher statistical significance when there is lower t-value (rohani et al., 2011; levis, 1998). a model is considered statistically significant when the t-value is smaller than the critical t-value of a confidence level. higher correlation coefficient is an indication of stronger relationship between model and experimental data. the indices are calculated for the linear and quadratic models and results presented in table 6. it is seen from values of �2 in table 6, that the two models have good fit when judged against 95% confidence level. the �2 values for the multiple linear and quadratic accident models are respectively 0.9959 and 0.9572, indicating that the former is more reliable in predicting accident occurrence in the studied location. it is seen that each of the indices rmse, mbe, mabe and mpe is smaller in the linear model than in the quadratic model. this index further supports a better predictive capacity of the multi-linear model. the t-value of each model is less than the critical t-value of 2.201 (at 95% confidence level) indicating that the two models have very good statistical significance. the t-values for the multiple linear and quadratic accident models are respectively 6.0842×10-13 and 0.8127 indicating that the former is more statistically significant than the latter. even though the correlation coefficients, ρ of each of the models are very good being above 0.98. the linear model performs better on the basis of this index. from the foregoing, it may be said conclusively that the multiple linear accident model of the studied location is highly reliable and that though the multiple quadratic accident model is statistically significant, it does not perform as good as the linear model. this conclusion on superiority of the linear model should be quoted with care as point by point calculation of deviations of the models from the field data would suggest otherwise. table 6: statistical error indices of the multiple linear and quadratic accident models model r2 rmse mbe mabe mpe [%] t-test � multiple linear regression model 0.9959 1.4332 -3.0830×10-13 1.3043 0.2819 6.0842×10-13 0.9980 multi-quadratic regression model 0.9572 4.6563 -1.2858 1.8007 -1.3172 0.8127 0.9803 table 7: statistical error indices of the multiple linear and quadratic accident models model r2 rmse mbe mabe mpe [%] t-test � multiple linear regression model 0.9957 1.4838 -0.1169 1.3504 0.1928 0.2091 0.9979 multiple quadratic regression model 0.9995 0.5265 0.2896 0.2896 0.3651 1.7425 0.9998 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 637-650. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 647 figure 5. plot of the field data together with the results of the two models figure 5 is a presentation of the field data together with the results of the models. it is seen from comparing the tips of the bars that the quadratic model is more accurate at all data points except for the year 2003. figure 6 is a plot of magnitude of deviations of the two models from the measured data, to confirm this observation. therefore, in the studied location, the quadratic model is actually more accurate than the linear model (even though the linear model has better overall statistical indices) except for the year 2003 where it (the quadratic model) seems to have suffered more numerical instability from the combination of numerical parameters. this is verified further by re-computing all the statistical parameters with the exclusion of the year 2003 data. the result is presented in table 7 in which it is seen that the quadratic model perform better in predicting the accident data as judged from the r2 and � values which are almost equal to one. the interaction effects captured in the quadratic model could be the explanation for the better point to point accuracy. figure 6. plot of magnitude of deviations of the two models. 4.0 conclusion based on this study, the following conclusions can be drawn under conditions and causal factors such as obtainable in two-lane roads in the studied rural area: both models provide a good means of predicting number of road accidents. the ability of the models is evaluated to reasonably forecast the likely number of rural road crashes as function of the causal parameters using road accident data from the studied location. this study has generated reliable and practical models for the road managers and policy makers using the identified accident causal variables and environmental conditions. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng ozor and ozoegwu.: comparison of multiple linear and quadratic models in estimating road crashes in semi-urban two-lane roads: case study of nsukka municipal council, south eastern nigeria. azojete,16(4):637-650. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pozor@uj.ac.za 648 surface comparison of the multiple linear and quadratic accident model based on overall statistical indices would suggest that the former is highly reliable and that though the latter is statistically significant, it does not perform as good as the linear model. a point-by-point calculation of deviations of the models from the field data contradicts the conclusion on superiority of the linear model over quadratic models. overall, the quadratic accident model is actually more accurate than the linear model except where it (the quadratic model) seems to have suffered more numerical instability from the combination of numerical parameters. references abdul-manan, mm., varhelyi, a. çelik, ak. and hashim, hh. 2018. road characteristics and environment factors associated with motorcycle fatal crashes in malaysia. iatss research, 42: 207–220, https://doi.org/10.1016/j.iatssr.2017.11.001 abegaz, t. berhane, y. worku, a. and assefa, a. 2014. effects of excessive speeding and falling asleep while driving on crash injury severity in ethiopia: a generalized ordered logit model analysis. accident analysis and prevention, 71: 15 – 21. ateeth, kt. harikrishna, n. and vigneesh, p. 2012. intelligent vehicle control based on identification of road and traffic signal operated rfid transponders. proceedings of the international conference on advances in electrical and electronics engineering, 11-12 february, penang, malaysia, 339-343, available online, http://psrcentre.org/images/extraimages/4.%20212179.pdf, accessed on 26th june, 2019 aurelio, m., paolo, p. and nicola, f. 2012. evaluation of the applicability of ihsdm crash prediction module on italian two-lane rural roads. in siiv 5th international congress sustainability of road infrastructures. procedia social and behavioral sciences, 53: 933 – 942 aworemi, jr., abdul, a., ibraheem, a., olabode, fo. and segun, o. 2010. analytical study of the causal factors of road traffic crashes in south-west, nigeria. educational research, 1: (4) 118-124. bagloee, sa. and asadi, m. 2016. crash analysis at intersections in the cbd: a survival analysis model. transportation research, part a, 94: 558–572, http://dx.doi.org/10.1016/j.tra.2016.10.019 cai, q., abdel-aty, m. and lee, j. 2017. macro-level vulnerable road users crash analysis: a bayesian joint modelling approach of frequency and proportion. accident analysis and prevention 107: 11–19, http://dx.doi.org/10.1016/j.aap.2017.07.020 dai, d. and jaworski, d. 2016. influence of built environment on pedestrian crashes: a network-based gis analysis. applied geography 73: 53-61, http://dx.doi.org/10.1016/j.apgeog.2016.06.005 hoel, la., garber, nj. and sadek, aw. 2008. transportation infrastructure engineering: a multi-modal integration, second edition. chris carson publishers, a division of thomson canada limited. hordofa, gg., assegid, s., girma, a. and weldemarium, td. 2018. prevalence of fatality and associated factors of road traffic accidents among victims reported to burayu town police stations, between 2010 and 2015. ethiopian journal of transport and health, 10: 186–193, https://doi.org/10.1016/j.jth.2018.06.007 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; 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(2009) found the quantity of melon seed oil to consist of 50% unsaturated fatty acids (35% linolelic, and 15 % oleic) and 50% saturated fatty acid (stearic and palmitic acid) which is responsible for its hypocholestroleric (blood cholesterol lowering) effect and thus, nutritionally desirable. consequently, its products are found to reduce the chances of article information abstract the scarcity of information on the performance of most machines developed in nigeria impedes the commercialization of proven indigenous technologies. a newly developed melon seeds shelling and separation machine with the capability to continuously shell conditioned melon seeds and simultaneously separate the seed cotyledons from it shells was evaluated. the machine extracts heat exclusively from the exhaust gases of a gasoline prime mover by heat conduction principle, mildly dry the shelled melon seed mixture before effecting separation of the cotyledons from it shells by aerodynamic and screening principles. based on preliminary studies, performance evaluation of the machine was carried out at 900, 1500 and 2100 rpm operating speed and 14, 20 and 26% db moisture content of white edge (serewe) melon seed variety. the data obtained were analyzed using ibm spss statistic software version 25. results of analysis of variance (anova) at p ≤ 0.05 showed that, shelling efficiency and machine capacity varies significantly with the operating speed, moisture content of the seeds, and their interactions; while separation efficiency and seed breakage percentage varies significantly with the operating speed and moisture content of the seeds but not significant with their interactions. an optimal performance of 96% shelling efficiency, 95% separation efficiency, 2.67% seed breakage percentage and 54.23 kg/h machine capacity, was obtained at 2100 rpm operating speed and 20% db seed moisture level. the performance of the machine is satisfactory and therefore recommended for commercialization and adoption by melon seed processors. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 march, 2019 revised 19 june, 2019 accepted 26 june, 2019 evaluation, melon seed, performance, separator, sheller mailto:terhembaiorpev@gmail.com http://www.azojete.com.ng iorpev et al.: performance evaluation of a melon seeds shelling and separation machine. azojete,16(3):611-620.issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 612 developing terra-arterial or heart disease (ajibola et. al., 1990; iorpev et. al., 2016). the seed has amino acid content profile that can be compared favorably with that of soya beans and even white of egg (oyenuga and faluga, 1975). melon seeds are raw materials for the production of egusi soup, margarine, salad, “robo cake”, baby food, livestock feeds, local pomade, soap and poultry litter material (bankole et al., 2005; shittu and ndrika, 2012). shelling and separation operation is an important postharvest activity during processing of melon seeds to it finished products (yekinni et al., 2017). manual shelling of melon seeds is laborious, tedious and time consuming. ogbonna and obi (2007) reported that about two hours are required to manually shell/dehull 1kg of melon seeds. in nigeria, some research works have been carried out on mechanical shelling and separation of melon seeds. although, the attempt by kassim et al. (2011) among others on the development of an integrated melon seeds shelling and separation machine have poor separation efficiency (onwuka et al., 2015). hence, the need to carry out performance evaluation of the newly developed melon seeds shelling and separation machine at the national centre for agricultural mechanization (ncam), ilorin. the paper seeks to provide relevant information on the performance of this indigenously designed and developed machine to enhance awareness that would lead to commercialization of the melon seeds shelling and separation machine. 2 materials and methods 2.1 materials the study was carried out at the crop processing shed and the laboratory of national centre for agricultural mechanization, ilorin using the newly developed melon seeds shelling and separation machine. figures 1a, 1b and 1c show the various views of the machine. other materials used include serewe melon seeds variety (figure 2a), laboratory oven (lab-tech™), tachometer (0.05+1digit, lotron dt-2236b), digital weighing balance (0.1g, camry eha251), digital stop watch (0.01s, kadio kd-6128), clean water, plastic bowls and polyethylene bags. (a)left end view (b) front view (c) right end view figure 1: melon seeds shelling and separation machine http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 611-620. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 613 (a) unshelled serewe melon seed variety (b) shelled and separated melon seeds cotyledons figure 2: serewe melon seeds variety 2.1.1 description of the machine the melon seeds shelling and separation machine labelled in figure 3 consist of five (5) major units: shelling chamber, exhaust gases heat exchanger chamber, drying chamber, blower unit and oscillating screening unit. all these component units are anchored by a rigid frame. the machine has the ability to shell conditioned (soaked) melon seeds, exclusively extract heat from the exhaust gases of the prime mover (gasoline engine), channel hot air to the drying chamber to mildly dehydrate moist shelled melon seeds, blow off the lighter shells of the seeds and sieve out the heavier shells to produce neat cotyledons of melon seeds. the hopper through which conditioned (soaked) melon seeds are fed into the machine is an inverted pyramidal frustum with a feed control fabricated from a 2 mm thick stainless steel sheet metal. all melon seed contact surfaces in the machine are made from stainless steel material. the machine is powered by a 5hp gasoline engine. figure 3: a labelled picture of melon seeds shelling and separation machine 2.1.2 working principle of the machine conditioned melon seeds are fed into the hopper at the beginning of an operation and then closed to avoid splashing of the content of the hopper. the feed control valve is adjusted and the seeds flow under gravity into the shelling chamber. shelling of the seeds is effected by impact and shear forces generated between the rotating and stationary shelling drums. simultaneously, cold air sucked through a heat exchanger by an axial fan is heated up and the hot air flows against the direction of moist shelled melon seeds moving on slanted interlocked drying trays in the drying chamber. the drying air of about 60˚c inside the drying chamber file:///c:/users/user/downloads/azojete143/www.azojete.com.ng iorpev et al.: performance evaluation of a melon seeds shelling and separation machine. azojete,16(3):611-620.issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 614 evaporates the surface water of shelled melon seeds before aerodynamic separation. the lighter shells are blown-off before the final removal of the thicker shells at the oscillating screen to discharge neat melon seeds cotyledons. 2.2 methods 2.2.1 sample cleaning six (6) kilograms of serewe melon seeds variety was procured from makurdi and the seeds were manually de-stoned to prevent the damage of the shelling mechanism and cotyledons. 2.2.2 moisture determination the initial moisture content of the melon seed was determined at the food processing laboratory of national centre for agricultural mechanization, ilorin using oven drying method. the samples were oven dried at a temperature of 103 ± 2˚c until constant weight of the samples were obtained (kashaninejad et al., 2005; obi and offorha, 2015). the initial moisture content values of the seeds were used to calculate the required amount of water needed to adjust seed moisture to 14, 20, and 26% db levels for the study. 2.2.3 seed conditioning the de-stoned melon seeds were randomly divided into 27 samples, each weighing 200g. each sample was thoroughly mixed with a calculated amount of water using equation 1 according to obi and offorha, (2015). the contents were then kept in an air tight polyethylene bag in a refrigerator at 3˚c for 7 days to enable proper moisture distribution and equilibration (enoch et al., 2008; obi and offorha, 2015). the samples were then aerated under a shed for 20 minutes based on preliminary studies to get the seeds inflated. � u �� ����� ���� �� (1) where, m = mass of distilled water (kg) ��= mass of sample (kg) �� = initial moisture content (%) ��= final moisture content (%) 2.2.4 machine testing the machine was tested with no load and an abnormal noise due to friction was corrected by alignment of components and application of grease in conformity with ncam (1990). under loading, the variables in table 1 were considered during the evaluation of the machine. each treatment was replicated thrice to check for experimental errors. the conditioned and labelled samples were fed into the machine at varying operating speeds and timed. table 1: variables for machine performance evaluation variables values seed moisture content (% db) 14, 20, 26 shelling speeds (rpm) 900, 1500, 2100 performance indicators shelling efficiency, separation efficiency, seed breakage percentage, throughput capacity, machine capacity. 2.2.5 statistical analysis the products collected were sorted, weighed and analyzed using ibm spss statistic software version 25 and equations 2, 3, 4, 5, 6, and 7 (shittu and ndrika, 2012; simonyan and yiljep, 2008) to get its performance parameters. shelling efficiency, �� u ��t������ � ��� (2) http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 611-620. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 615 separation efficiency, �� u ��t������ ��t���������� ��� (3) breakage percentage, �� u ���� � ��� (4) throughput capacity, �� u � � (5) machine capacity, �� u ��t������ � (6) where, ��t� u mass of clean unbroken cotyledon in product collected at outlet chute (kg) ���� = mass of clean broken cotyledon in product collected at outlet chute (kg) m u total mass of seed fed through the machine’s hopper (kg) ���= mass of shells/chaff in cotyledons collected at outlet chute (kg) t = time taken to complete operation (h) 3 results and discussion table 2 shows the mean values of performance characteristic of the machine at various moisture content and operating speed levels considered. the results show that the mass of shelled melon seeds produced by the machine increased with increase in seed moisture levels at various operating speed levels, while the mass of broken seeds decreased with increase in seed moisture levels at different operating speed levels of the machine. the results show that the mass of shelled melon seeds produced by the machine increased with increase in seed moisture content levels at various operating speed levels. also, the mass of broken seeds decreased with increase in seed moisture content levels at different operating speed levels of the machine. a similar result was reported by shittu and ndrika (2012). additionally, the mass of melon seeds shelled and mass of broken seeds increased with operating speed at various moisture levels considered. the performance indicators of the machine are presented in table 3. it is clear that shelling efficiency, separation efficiency, seed breakage percentage and machine capacity ranges from 55.10 – 96.20%, 86.93 – 96.13%, 1.34 – 2.95%, and 34.30 – 54.60 kg/h respectively. this level of performance achieved in the study could be attributed to the unique design of the various unit of the machine and the operating conditions considered in the study. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng iorpev et al.: performance evaluation of a melon seeds shelling and separation machine. azojete,16(3):611-620.issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 616 table 2: means values of machine performance characteristic at various speed and moisture levels speed (rpm) moisture (% db) � ��� ��t� ��� ���� ��� ��� ��� � ��� 900 14 200 107.00 (0.057) 3.20 (0.100) 16.57 (0.285) 11.14 (0.120) 900 20 200 137.94 (0.400) 3.06 (0.100) 24.14 (0.173) 14.59 (0.092) 900 26 200 150.85 (0.250) 2.69 (0.382) 31.00 (0.312) 16.11 (0.142) 1500 14 200 140.96 (0.929) 5.90 (0.550) 8.19 (0.451) 11.47 (0.201) 1500 20 200 168.06 (0.583) 5.00 (0.300) 12.83 (0.142) 13.84 (0.105) 1500 26 200 181.01 (0.289) 4.33 (0.276) 18.15 (1.023) 15.98 (0.200) 2100 14 200 144.77 (0.361) 6.43 (0.225) 6.08 (0.355) 9.97 (1.501) 2100 20 200 186.66 (0.833) 5.34 (0.476) 9.61 (0.585) 12.75 (0.110) 2100 26 200 187.66 (0.361) 4.74 (1.153) 16.16 (0.345) 14.85 (0.302) nb: values in parenthesis are standard deviation values with ± sign. table 3: mean values of machine performance parameters s (rpm) moisture (% db) sh. e (%) se. e (%) bp (%) cm (kg/h) 900 14 55.10 (0.854) 86.93 (0.058) 1.76 (0.100) 35.62 (0.580) 900 20 70.60 (0.400) 85.40 (0.173) 1.63 (0.029) 34.83 (0.351) 900 26 73.77 (0.252) 83.20 (0.200) 1.34 (0.081) 34.30 (0.173) 1500 14 73.43 (0.929) 94.72 (0.664) 2.95 (0.050) 46.07 (0.252) 1500 20 86.53 (0.583) 93.10 (0.100) 2.50 (0.300) 45.00 (0.173) 1500 26 92.67 (0.289) 91.08 (0.076) 2.17 (0.208) 41.77 (1.626) 2100 14 75.60 (0.361) 96.13 (0.321) 3.22 (0.225) 54.60 (0.529) 2100 20 96.00 (0.200) 95.00 (0.200) 2.67 (0.076) 54.23 (0.961) 2100 26 96.20 (0.361) 92.20 (0.529) 2.37 (0.153) 46.67 (0.416) nb: values in parenthesis are standard deviation values with ± sign. 3.1 effect of moisture content and operating speed on shelling efficiency table 3 indicates that the shelling efficiency of the machine increases with an increase in seed moisture content and operating speed which is in agreement with works reported by shittu and ndrika (2012), sobowale et al., (2015) and onwuka and nwankwojike, (2015) . this is because when moisture content of melon seeds samples increases, a cavity filled with fluid is created between the seed cotyledon and the shell which tends to increase the shelling efficiency. it was then observed that, moisture content of the seeds and the operating speed level are critical factors influencing shelling efficiency. the maximum shelling efficiency obtained was 96.20% at 26% db moisture level and 2100 rpm operating speed level. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 611-620. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 617 3.2 effect of moisture content and operating speed on separation efficiency from table 3, separation efficiency increases with operating speed but decreases with an increase in moisture level. it can be explained that, an increase in operating speed generates enough air draft which is higher than terminal velocity of melon shells but less than that of the seed cotyledons to increase separation. the obtained result is a contrast of onwuka and nwankwojike (2015). this means that, at higher moisture content level, the designed efficiency of the drying unit is exceeded and thus, causing a decrease in separation efficiency. the maximum separation obtained was 96.13% at 14% db moisture level and 1200 rpm operating speed level. 3.3 effect of moisture content and operating speed on seed breakage percentage the seed breakage percentage decreases with increase in moisture level but increases with increase in operating speed levels as shown in table 3. this is in agreement with the works reported by shittu and ndrika (2012), sobowale et al., (2015) and onwuka and nwankwojike, (2015). the highest seed breakage percentage obtained was 3.22% at 2100 rpm and 14% db moisture content level, while the lowest was 1.34% at 900 rpm operating speed and 26% db moisture content level. this performance is better than the 15.13% minimum seed damage percentage achieved by sobowale et al., (2015) at 1500 rpm operating speed and 18.32% db moisture level. 3.4 machine capacity table 3 shows that the maximum value of machine capacity obtained was 54.60 kg/h. this capacity is comparatively lower than the 192 kg/h machine capacity of a melon seed shelling machine without a separating unit developed by shittu and ndrika (2012) and higher than the 7.95 kg/h machine capacity of the melon seed shelling and separation machine developed by sobowale et al., (2015). the designed residency time/delay of moist shelled melon seeds mixture in the drying chamber and at the oscillating screen is responsible for the obtained level of machine capacity. table 4 is a summary of analysis of variance (anova) results. the result shows that, at 5% percent level of significance, shelling efficiency and machine capacity varies significantly (p-value of 0.0001) with the operating speed, moisture content of the seeds, and their interactions; while the separation efficiency and seed breakage percentage varies significantly with the operating speed and moisture content of the seeds but not significant with their interactions. table 4: anova result summary of machine performance parameter source of variation f pr > f shelling efficiency s 4563.176 0.0001 m 3492.591 0.0001 s*m 41.873 0.0001 separation efficiency s 2106.024 0.0001 m 307.244 0.0001 s*m 1.218 0.3381 seeds breakage percentage s 134.977 0.0001 m 40.793 0.0001 s*m 1.971 0.1421 machine capacity s 1263.883 0.0001 m 103.301 0.0001 s*m 23.166 0.0001 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng iorpev et al.: performance evaluation of a melon seeds shelling and separation machine. azojete,16(3):611-620.issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 618 the results of duncan post-hoc test in tables 5 and 6 present specific information on how the effect of different levels of operating speed and moisture content on shelling efficiency, separation efficiency, seed breakage percentage and machine capacity significantly differ from each other. table 5: comparison summary of effect of speed levels on performance indices using duncan multiple range test speed, rpm she, % see,% bp,% mc, kg/h 900 66.4889a 85.1778a 1.5800a 34.9167a 1500 84.2111b 92.9667b 2.5389b 44.2778b 2100 89.2667c 97.4444c 2.7500c 51.8333c means with the same letters are not significantly different at p ≤ 0.05 using the dnmrt she-shelling efficiency, see-separation efficiency, bp-breakage percentage, mc-machine capacity table 6: comparison summary of effect of moisture levels on performance indices using duncan multiple range test moisture content, % she,% see,% bp,% mc, kg/h 14 68.0444a 92.5944c 2.6433c 45.4278c 20 84.3778b 91.1667b 2.2667b 44.6889b 26 87.5444c 88.8278a 1.9589a 40.9111a means with the same letters are not significantly different at p ≤ 0.05 using the dnmrt she-shelling efficiency, see-separation efficiency, bp-breakage percentage, mc-machine capacity tables 5 and 6 revealed that the means are significantly different at p ≤ 0.05. the effect of each operating speed and moisture content level on shelling efficiency, separation efficiency, seed breakage percentage and machine capacity significantly differs from each other. thus, the most suitable operating speed levels obtained without a close significant substitute for shelling efficiency, separation efficiency, seed breakage percentage and machine capacity were 2100, 2100, 900 and 2100 rpm respectively, while on the other hand 26, 14, 26, 14% db respectively were the most suitable moisture levels for the various performance parameters. hence, an optimal performance of 96% shelling efficiency, 95% separation efficiency, 2.67% seed breakage percentage and 54.23 kg/h machine capacity was obtained at 2100 rpm operating speed and 20% db seed moisture level. 4 conclusion the performance of an indigenously designed and developed melon seeds shelling and separation machine powered by a gasoline engine was studied to enhance its commercialization and further research works. the results of the study showed that shelling efficiency of the machine increases with an increase in seed moisture content and operating speed; separation efficiency increases with increase in operating speed but decreases with increase in moisture content level; while seed breakage percentage decreases with increase in moisture level but increases with increase in operating speed levels. an optimal condition of 2100 rpm operating speed and 20% db seed moisture level produced 96%, 95%, 2.67%, and 54.23 kg/h shelling efficiency, separation efficiency, seed breakage percentage and machine capacity respectively. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 611-620. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 619 therefore, this machine could be recommended for commercialization and adoption by melon seed processors. references adekunle, as., ohijeagbon, io. and olusegun, hd. 2009. development and performance evaluation of manually and motorised operated melon shelling machine using impact technique. journal of engineering and technology review, 2: 12-17. ajibola, oo., eniyemo, se., fasina, oo. and adeko, ka. 1990. mechanical extraction of oil from melon seeds. journal of agricultural research, 5:1-7. bankole, sa., osho, a., joda, ao. and enikuomehin, oa. 2005. effect of drying method on the quality and storability of ‘egusi’ melon seeds (colocynthis citrullus l.). african journal of biotechnology, 4: 799-803. enoch, ga., rose, f., harmane, ta., raymond, sa., osmane, c. and adam, a. 2008. importance and practices of bitter melon crops in sociolinguistic areas in benin. biotechnology, agronomy, society and environment journal, 12: 393–403. iorpev, t., ozumba, ic., adejumo, oa. and ogini, f. 2016. development and evaluation of aerothermal-machine for separating melon seeds cotyledon from its shells. proceedings of the 37th national conference and annual general meeting of the nigerian institution of agricultural engineers at minna, 4 – 7th october 2016, 37(2): 648-655. kashaninejad, m., mortazavi, a., safekordi, a. and tabil, lg. 2005. some physical properties of pistachio (pistacia vera l.) nut and its kernel. journal of food engineering, 72: 30–38. kassim, mj., umogbai, v. and itodo, in. 2011. development and evaluation of a melon shelling and cleaning machine. journal of emerging trends in engineering and applied sciences, 2(3): 383-388. ncam 1990. test code for powered maize shellers. draft of nigerian industrial standard. national centre for agricultural mechanization, ilorin, nigeria, pp. 110. obi, of. and offorha, lc. 2015. moisture-dependent physical properties of melon (citrullus colocynthis l.) seed and kernel relevant in bulk handling. cogent food and agriculture, 1: 1-18. ogbonna, pe. and obi i. 2007. effect of time of planting and poultry manure application in growth and yield of egusi melon in a derived savannah in agroecology. agro-science, 6: 33-39. olusegun, hd. and adekunle, as. 2008. the design, construction and testing of melon sheller. global journal of engineering and technology, 1(4): 473-481. onwuka, os. and nwankwojike, bn. 2015. design and development of integrated melon processing machine. innovative system design engineering, 6(12): 41-52. oyenuga, va. and faluga, bl. 1975. some aspects of biochemistry and nutritional value of the water melon seed (citrullus vulgaris, schrad). journal of science, food and agriculture, 2(6): 843-854. oyolu, c. 1977. quantitative and qualitative study of seed types in egusi (colocynthis citrullus). tropical science, 24(2): 93-98. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng iorpev et al.: performance evaluation of a melon seeds shelling and separation machine. azojete,16(3):611-620.issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: terhembaiorpev@gmail.com 620 shittu, sk. and ndrika, vio. 2012. development and performance tests of a melon (egusi) seed shelling machine. agricultural engineering international, the cigr journal, 14: 1-11. simonyan, kj. and yiljep, yd. 2008. investigating grain separation and cleaning efficiency distribution of a conventional stationary rasp-bar sorghum thresher. agricultural engineering international. the cigr ejournal manuscript pm 07028. vol. x. pp. 5-7. sobowale, ss; adebiyi, ja. and adebo, oa. 2015. design, construction and performance evaluation of a melon seeds sheller. journal of food process technology, 6: 463-467. yekinni a., rabiu t., bajela g., adigun i., saheed r., lamidi, s. and ademolu, o. 2017. modification and development of a manually operated and motorized melon seed shelling/ separating machine. world journal of engineering research and technology, 3(6): 67-82. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):65-78 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 65 original research article conversion of biomass to adsorbent: a review a. b. ngulde1, k. silas1*, h. d. mohammed1, a. l. yaumi1, u. h. taura1 and h. h. mari2 1department of chemical engineering, university of maiduguri, bama road, pmb 1069 maiduguri, borno state, nigeria 2department of agricultural and environmental resource engineering, university of maiduguri, bama road, pmb 1069 maiduguri, borno state, nigeria *corresponding author’s email address: silaskiman@gmail.com 1.0 introduction water is a basic source for existence of life on earth. the increase in industrialization and modernization has contributed negatively to clean water resources. many substances such as heavy metals, dyes, pharmaceuticals, surfactants, pesticides, personal care products and others have contaminated the water resources (rasheed et al., 2020). these pollutants are environmentally hazardous to human beings and animals (siyal et al., 2018). biomass is available from several sources all over the world and has numerous roles to play for sustainable development. in addition to being a food source to animals and renewable raw material, biomass can be used for energy production, carbon sequestration and as activated carbon (cheng et al., 2009; jain et al., 2016). utilization of biomass to produce activated carbon is a good approach in pollution control strategy in two ways. firstly, it can fix the carbon of biomass that prevents the production of co2 or ch4; and secondly, it produces activated carbon which is industrially useful and environmentally benign materials that can go into the soil and enter natural carbon cycle process (danish and ahmad, 2018). hong et al., (2020) reported that heavy metals in excess of the stipulated minimum are harmful to human health and aquatic life due to their toxicity and bioaccumulation. excessive concentration of heavy metals such as, lead (pb) and cadmium (cd in water could cause irritation of central nerve system and damage to kidney and liver) and many other diseases (genchi et al., 2020; siyal et al., 2018). trace metals are those having density greater than 5 gcm-3. most often this term denotes metals that are toxic. these include al, as, cd, cr, article information abstract tons of biomass are produced every year including organic agricultural and forestry by-products but they are of limited value. mostly, in the developing countries, the biomasses are considered as waste and are being burnt or thrown to liter the environment as part of teaming solid waste. presently, there are no sustainable long-term management strategies to use biomass. the utilization of biomass to produce activated carbon is a good approach that is industrially useful and environmentally benign materials. the adsorption technique is using adsorbents in the removal of heavy metals from water therefore, biomass can be converted to the adsorbent and utilized as a waste-to-wealth commodity in water purification. in this review, the suitable process for conversion of biomass to cheap and simple means of obtaining activation carbon as adsorbent is presented. the potential uses of biomass and the conversion stages including carbonization, pyrolysis, gasification, and activation were discussed. this work depicts that the issue of solid waste utilization to solve existing issues with locally available and cheap materials is beneficial to man and the environment. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 august, 2021 revised 18 october, 2021 accepted 22 october, 2021 keywords: biomass heavy metal environment solid waste water adsorbent http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com silaskiman@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):65-78. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 66 co, pb, hg, ni, se, and zn which could be discharged from industries, farmlands, municipal urban water runoffs, and agricultural activities into surface water and can cause pollution (maitera et al., 2011). previous literature published those conventional technologies for the treatment of contaminated water, such as precipitation, electrochemical treatment, ion exchange, membrane separation, and adsorption have been used globally for the removal of heavy metals from aqueous solution (chakraborty et al., 2020). among the treatment processes, adsorption has been proven to be one of the most suitable and universal methods, which offer remarkable advantages such as fast, ease of operation, availability, and efficiency (ni et al., 2019). various adsorbents have been employed, ranging from natural products to synthetic materials which would directly determine the removal efficiency via adsorption. carbon materials, such as activated carbon, graphene, and fullerene, were found to be promising adsorbents for removing heavy metals from aqueous solution due to their stability and large surface area (ni et al., 2019). date palm fibers are lignocellulosic materials, which consist of three vital components: cellulose (40-50%), hemicellulose (2035%) and lignin (15-35%) (shafiq et al., 2018) and may be used as adsorbent to remove heavy metal ion from water. each date tree produces 20kg of dry leaves yearly (ismail, 2012) and there are about 105 million trees available worldwide on an area of over a million hectares (ahmad and danish, 2012). the area under date palm cultivation in nigeria was estimated over 1,466.00 ha and an estimated annual production of nearly 20,000 tones date fruit per annum (abdullahi, 2015). the date tree leaves, stems, and branches are considered as waste and are being burnt. this study reviews biomass as a potential waste to wealth material with regards to conversion into activated carbon and utilization as adsorbent. the date tree leaf (dtl) is reviewed as the potential biomass source in production the of activated carbon. 2. biomass organic materials originating from living matter or complexes of organic and inorganic materials are collectively referred to as biomass. biomass includes but not limited to only living organisms, such as plants and animals, but also the excrement of animals, sludge, and waste wood (cha et al., 2016). sometimes, it is referred to as stored energy, a renewable organic material derived from plants and animals that can serve as sources of energy. biomass is made up of carbohydrate and has less energy storage problems when compared with other renewable sources such as solar and wind (schlemmer et al., 2021). wastes such as agricultural/agro-industries wastes and municipal wastes and purposely grown energy crops such as sugarcane, corn, wheat, etc. are the main sources of biomass (abioye and nasir, 2015). biomass can be converted into several useful forms of energy using different processes briquette and biochar. there are several factors which could affect the choice of conversion process; these can include (adams et al., 2018): the type of usage, quantity, and characteristics of biomass feedstock, the desired form of the energy environmental. in addition to being a food source to animals, and renewable raw material, it can be used for energy production, carbon sequestration and, as an essential element to produce hydro chars and activated carbons (jain et al., 2016). figure 1 shows a biomass-to-power supply system. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com ngulde et al: conversion of biomass to adsorbent: a review. azojete, 18(1):65-78. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 67 figure 1: biomass-to-power supply system (heidari et al., 2018) due to the potential reduction in greenhouse gas (ghg) emissions, society has recognized the usage of waste biomass as a sustainable resource. according to ahmed et al., (2019), by balancing the production of plant biomass and its utilization in the future, it is possible that zero ghg emissions can be achieved. for energy recovery, diverse methods of utilization of biomass have been found environmentally friendly and economically viable. the major chemical constituents of biomass are hemicellulose, cellulose, and lignin; and minor chemical components are protein and oil. on an average, the quantitative proportion of hemicellulose, cellulose, and lignin in biomass are observed in the range of 20–35, 40–50, and 15–35%, respectively (danish and ahmad, 2018). it has been reported by abioye and nasir, (2015) that the constituents of lignocelluloses are strongly intermeshed and are chemically bonded by either non-covalent forces or covalent linkage, and their composition varies from one plant species to another. biomass can be converted to biofuels and bioproducts via thermochemical processes, such as pyrolysis and gasification. the net carbon dioxide emissions from biofuel use are considered zero or negative because the released of co2 is recycled from the atmosphere captured during photosynthesis (qian, et al., 2015). in addition, since biomass contains a low amount of sulphur and nitrogen, its combustion as a source of energy may result to lower emissions of harmful gas, such as nitrous oxides (nox) and sulphur dioxide (so2) compared to most of fossil fuels. such advantages of biomass make it a promising renewable energy resource. the use of agricultural by-products as bio sorbent material were found to (chakraborty et al., 2020) purify heavy metal contaminated water and has become increasingly popular through the past decade, because they are less expensive, biodegradable, abundant and efficient. cost is an important parameter for comparing the sorbent materials. the expense of individual sorbents varies depending on the degree of processing required and local availability (saka and mas, 2012). http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):65-78. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 68 it is stated that an adsorbent can be termed as a low-cost adsorbent if it requires little processing, is abundant in nature, or is a by-product or waste material from some selected industries (chakraborty et al., 2020). thus, there is an urgent need that all possible sources of agro-based inexpensive adsorbents should be explored and their feasibility for the removal of heavy metals should be studied in detail (saka and mas, 2012). the generation of bioenergy in terms of liquid, gaseous, and solid fuels from biomass wastes has been an important field in research and development. low-cost, abundance, renewability, and high lignocellulosic content of agricultural biomass make them promising precursors for cost-effective activated carbons (ahmed, 2016). biomass can be classified based on the types existing in nature, which include wood and woody biomass, herbaceous biomass, aquatic biomass, animal and human waste biomass, and biomass mixtures (jekayinfa and orisaleye, 2020). it has been widely reported that the thermal degradation characteristics of lignocellulosic materials are profoundly influenced by their chemical composition (cellulose, hemicellulose, and lignin), and tg and dtg curves provide semiquantitative understanding of the thermal degradation processes occurring during thermochemical conversion under various atmospheres (roma, et al., 2009). furthermore, mudryk et al., (2021) found that the processes of thermal processing of herbaceous biomass generate significant amounts of waste in the form of ashes. figure 2 shows the contributions of biomass sources to the overall technical potential. figure 2: contributions of biomass sources (jekayinfa and orisaleye, 2020) 2.1. types of biomass woody biomass includes components whose major constituents are carbohydrates and lignin including live trees, forest and manufacturing residues, or consumer waste materials (jekayinfa and orisaleye, 2020). another type of biomass is the herbaceous biomass which is obtained from plants with a non-woody stem which dies at the end of the growing season (picchio et al., 2020). it includes grain and seed crops from the food processing industry and their by-products. herbaceous crops can be sub-divided into agricultural residues and energy crops (jekayinfa and orisaleye, 2020). aquatic biomass includes algae and emerging plants. these include marine or freshwater algae, macroalgae or micro algae, seaweed, kelp, lake weed, and water hyacinth (heidari et al., 2018). aquatic weeds have exceptionally high reproduction rates and are rich in cellulose and hemicellulose with a very low lignin content, which makes them efficient as biofuel crops. the three common fast-growing aquatic weeds in nigeria are water hyacinth, water lettuce, and bracken fern (jekayinfa and orisaleye, 2020). municipal solid waste refers to classes of wastes considered as trash (srinilta, 2019). they are found to be highly nonfile:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com ngulde et al: conversion of biomass to adsorbent: a review. azojete, 18(1):65-78. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 69 homogeneous, being a mixture of residential, commercial, and industrial wastes (conti et al., 2020; ferrari et al., 2020). globally, and particularly in developing countries, the management of municipal solid waste constitutes an important environmental concern (maalouf, 2020). 2.2. date tree leaves (dtl) biomass date palm is a soft edible fruit (alam et al., 2021) and its fruits are popular among the people of northern nigeria, it was found that the date palm tree is an economic crop which is grown in the arid region of northern nigeria from latitude 10° n in the sudan savannah and the sahel region (dada et al., 2012). it is originated from the middle east and north africa and was introduced to nigeria from north africa during the trans-saharan trade by pilgrims and traders from the middle east (abdullahi, 2015). the date fruit is a good source of food providing, fiber, carbohydrates, minerals, and vitamins besides having anti-mutagenic and anti-carcinogenic properties, it is antioxidant and anti-inflammatory and provides protection to the liver, stomach, and kidney (al-abdoulhadi et al., 2011; kamarubahrin and haris, 2020). based on literature, (ahmed, 2016), an adult date palm tree has a trunk or stem of 15-25 m high and fronds or leaves that look like feathers with 3-5 m long, there are about 150 leaflets in each frond which can be up to 30 cm in length and 2cm in breadth, while the full span of the crown of the palm tree is about 6-10 m height. it is a feather palm, characterized by compound leaves with a series of leaflets on each side of a common petiole, originating from one growing point at the apex (ahmad and danish, 2012). however, (ismail, 2012) discovered that date palm tree produces large quantity of agricultural waste. for example, each date tree produces about 20 kg of dry leaves yearly. dtl are lignocellulosic materials, which consist of three vital components: cellulose (40-50%), hemicellulose (20-35%) and lignin (15-35%) also, lignin is the most important constituent and has complex chemical constituents within the dtl waste material, as it is a three-dimensional polymer of phenyl propane units linked together by c–c or c–o–c bonds (shafiq and alazba, 2018; parthasarathy and narayanan, 2014). dtl waste has been used in various forms for different heavy metals removal from wastewater. the removal of pb2+, for example, has been investigated using dt trunk, dt leaves, dt leaves ash, and palm leaf base (the petiole) (yadav et al., 2013). several naturally available materials like plant wastes and agricultural products have been tried as adsorbents for the removal of metals. the advantages associated with the use of plant materials are little processing, good uptake capacity, free availability, the minimization of chemical or biological sludges and easy regeneration (rajamohan et al., 2014). figure 3 shows the dtl biomass. http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):65-78. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 70 figure 3: date tree leaves (dtl) biomass 2.3. carbonization, pyrolysis and gasification of biomass because of the diversity of raw biomass and biofuel, there are many ways to improve biomass fuel quality and achieve extensive utilization and higher efficiency such like the thermo-chemical upgrading of biomass fuel, which includes torrefaction, carbonization, pyrolysis, gasification and liquefaction (qi et al., 2018). carbonization involves the conversion of organic containing residue into carbon or a carbon containing residue through pyrolysis, furthermore, the process is carried out in an oxygen free environment at a temperature of about 500°c-700°c (bones et al., 2019). according to ahmed, (2016), the carbonization is a phase to enriching carbon content in carbonaceous material by eliminating non-carbon species using thermal decomposition while in the process, the temperature has the most significant effect, followed by heating rate, nitrogen flow rate, and finally, residence time. carbon is a raw material for several industrial products and their production from various bio-resources is an active area of research, (ahmed et al., 2019). the char is a solid carbonaceous residue with a high content in fixed carbon (>75%), which can be used directly as fuel, as briquettes or as precursor for activated carbons production (roma et al., 2009). effective utilization of biochar is critical for improving economic viability and environmental sustainability of biomass thermochemical technologies (qian et al., 2015). normally, higher temperatures (600–700 ºc) result in reduced yield of char while increasing the liquid and gases release rate, however, the obtained char usually exhibits little adsorption capability, and an activation step is required to expand initial porosity created by carbonization (ahmed, 2016). figure 4 depicts the preparation of the biomass-derived porous carbon. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com ngulde et al: conversion of biomass to adsorbent: a review. azojete, 18(1):65-78. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 71 figure 4: preparation of the biomass-derived porous carbon the word pyrolysis is derived from the greek words’ ‘pyro’ meaning fire and ‘lysis’ meaning decomposition or breaking down into constituent parts. it is a process for decomposing organic materials thermally under oxygen-free conditions in the temperature range, 300-900 ºc (adams et al., 2018). during thermal decomposition, cellulose, hemicellulose and lignin that comprise biomass undergo their own reaction pathways, including cross-linking, depolymerization and fragmentation at their own temperature, producing solid, liquid and gaseous products (cha et al., 2016). earlier, adams et al., (2018) stated that pyrolysis operates in anaerobic conditions where heat is usually provided externally and the constituents of biomass are thermally cracked to gases and vapors which usually undergo secondary reactions, thereby giving a broad spectrum of products. on the other hand, three phases are produced when biomass is subjected to pyrolysis processes: char, liquid, and gas (roma et al., 2009). pyrolysis has over the years been the most efficient route, by which bio-waste can be thermally degraded at 400–500 ºc in the presence of inert gases to produce biochar (solid), bio-oil (liquid), and gaseous fuel (co, ch4, and h2) as products (bharath et al., 2020). figure 5 shows the flow diagram of the simplified pyrolysis process. figure 5: flow diagram of the simplified pyrolysis process (bharath et al., 2020) the solid product obtained in pyrolysis process is known as char/biochar or charcoal and contains around half of the carbon of the original organic matter and, based on the heating rate applied to the biomass to reach the intended pyrolysis temperature, pyrolysis is classified into slow pyrolysis and fast pyrolysis (mulabagal et al., 2017). the solid and liquid products are referred to as char and bio-oil, respectively, http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):65-78. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 72 whereas the gaseous mixture containing co, co2, h2, and c1-c2 hydrocarbons are called syngas (cha et al., 2016). gasification transforms biomass into primarily a gaseous mixture (syngas containing co, h2, co2, ch4, and smaller quantities of higher hydrocarbons) by supplying a controlled amount of oxidizing agent under high temperature (greater than 700) (qian et al., 2015). according to adams et al., (2018), the gasification process thermo-chemically converts an organic feedstock (e.g., liquid, or solid fuel) into its gaseous components which depend on the gasification temperature. 2.3.1. hydrothermal carbonization hydrothermal carbonization is an effective technology to carbonize wet biomass to evade the energy concentrated pre-drying step. normally, in the htc procedure, the wet biomass remains heated in a highpressured container at comparatively lower temperatures i.e., 150–350 ºc. the htc process has been introduced successfully and applied practically (ahmed et al., 2019). feedstocks with high moisture and ash content are particularly reported to be suitable for hydrothermal processing and include feedstocks such as manures, sewage sludge, ddgs, food waste, municipal wastes, and aquatic biomass such as micro and macroalgae (adams et al., 2018). during hydrothermal carbonization, water acts as a solvent and as a catalyst that facilitates hydrolysis and cleavage of lignocellulosic biomass, water possesses high ionization constant at high temperatures and is responsible for hydrolysis of organics which can further be catalyzed by acids or bases (jain et al., 2016). the hydrothermal conversion is a promising biomass-to-oil approach (liu and zhang, 2009). figure 6 is a graphic diagram of biomass applications. figure 6: graphic diagram of biomass applications (khan et al., 2019) 3. activated carbon activated carbon (ac) is a microcrystalline form of carbon with high porosity and surface area for removal of impurities from soil, liquids, gases, and solids. the processes involved in carbon activation following raw materials preparation, low temperature combustion, and activation (le and nguyen, 2020). the raw material in this case could be coal, wood, carbon materials, coconut shell, fruits shells, derived biomass, etc. due to the pore structure characteristics of straw ac, it has potential in the application of wastewater treatment and air purification, several studies have described the manufacturing processes of ac (bones et al., 2019; danish and ahmad, 2018; le and nguyen, 2020; silas et al., 2019) ac is a porous, black file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com ngulde et al: conversion of biomass to adsorbent: a review. azojete, 18(1):65-78. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 73 carbonaceous material that is prepared by physical or thermal activation and chemical activation (bones et al., 2019). it was found that (danish and ahmad, 2018) the high surface area, well-organized macro, meso, and micropores, and a wide range of chemical functional groups present on the surface of activated carbon make it a versatile material which has numerous applications. the ac prepared from rice husk and sugarcane bagasse by liu and zhang, (2009) had good adsorption capacities with respect to arsenic, humic acid and phenol, the promising results were obtained when carbonaceous material prepared from coconut shell was utilized as adsorbent for wastewater treatment. ni et al., (2019) produced activated carbons from nutshell and removed almost 100% of pb (ii), 90-95% of cu (ii) and 80-90% of zn (ii) from water. activation is a process of converting carbonaceous materials into activated carbon by thermal decomposition in a furnace (convectional heating) or a microwave using a controlled atmosphere and heat. physical activation, chemical activation, combined chemical and physical (physiochemical) activation and microwave-induced activation are the methods being employed for the preparation of activated carbon (abioye and nasir, 2015). 3.1 physical activation physical activation, also called gas activation, uses gas, such as steam, co2, and ozone, to activate biochar at temperatures above 700 ºc (qian et al., 2015). physical activation can be divided into two steps. in the first step, the unstructured parts of the carbonized material are decomposed selectively while fine pores enclosed in the carbon structure are opened, thereby increasing the internal surface area (cha et al., 2016). the development of porosity is the major function of the activating agent during the activation process, and this is usually accomplished through a controlled carbon burn-off and elimination of volatile matters (abioye and nasir, 2015). the authors further reported that the level of carbon burn-off greatly depends on the temperature and duration of activation as well as other experimental parameters such as gas flow and furnace type and ultimately determine the quality of the activated carbon. 3.2 chemical activation chemical activation is a step process in which the carbonization and activation are carried out simultaneously and usually in the temperature range of 300–95 ºc thus influencing the pyrolytic decomposition and, therefore, resulting in the development of a better porous structure and increased carbon yield while potassium hydroxide (koh) and zinc chloride (zncl2) are the most used activating agents (abioye and nasir, 2015). cha et al., (2016) found that in chemical activation, char is doped with a chemical agent and micropores are formed by subsequent dehydration and oxidation. activated carbons prepared by pyrolysis of mixtures of carbon precursor/alkaline hydroxide were investigated. it was reported that naoh is more efficient in the activation of low structural ordered materials, whereas koh is more effective for the highly ordered materials, which indicates differences in the activation performance of both hydroxides (tay et al., 2009). several studies are published on the utilization of biomass as adsorbents as shown in table 1. http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@gmail.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):65-78. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@gmail.com 74 table 1: reviews on adsorption from previous studies objective method of synthesis characterization findings reference study of leaves of populous tree for adsorptive removal of mo in aqueous medium impregnati on ftir, xrd, sem populous leaves, is an excellent alternative in the removal of mo dye from aqueous solution (shah et al., 2021) synthesized magnetized mesoporous activated carbon and its application for the removal of mb and mo from dye solutions. wetness impregnati on method ftir, xrd, sem, bet the adsorbent shows efficient adsorption ability for an anionic dye (azam et al., 2020) adsorption capability of the prepared ct-pac hybrid beads using a cationic surfactant. impregnati on ftir, sem, ct-pac-hda is a promising adsorbent for the elimination of reactive dyes. (vakili et al., 2020) 4. conclusion and recommendation the carbonaceous adsorbents in the treatment of wastewater such as activated carbon from biomass were found to have advantages like, high pollutant removal capacity, adequate sensitivity, productivity, simple synthesis, and cost-effective (waste to wealth). therefore, the utilization of biomass such as the date tree leaf is a suitable strategy for the decontamination of heavy metals from contaminated waters. many researchers reported the prevalent of heavy metals in water in maiduguri, borno state, yet there are plantations of date palm where the leaves are considered as solid waste and mostly burnt therefore, this study recommends the utilization of dtl for the treatment of heavy metals which are harmful to human after a thorough investigation of the adsorbent’s characteristics, effects, and safe use of treatment of contaminated water. references abdullahi, m. 2015. the potentials of esterblishing date palm plantation in sudano sahelian region of nigeria. conference: farm management association of nigeria (faman) at: general studies auditorium, federal university dutse, jigawa state nigeria. abioye, am. and nasir, f. 2015. recent development in the production of activated carbon electrodes from agricultural waste biomass for supercapacitors: a review. renewable and sustainable energy reviews, 52: 1282–1293. https://doi.org/10.1016/j.rser.2015.07.129. adams, p., bridgwater, t., ross, a. and watson, i. 2018. biomass conversion technologies. chapter 8. greenhouse gases balance of bioenergy systems. 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a conventional refrigerator and a refrigerator that was modified by incorporating a radiation shield. in this work, plywood was used as thermal radiation shield placed between the back of the refrigerator and the condenser and compressor. pressure gauges were welded to the evaporator inlet and condenser outlet. thermocouples were attached to the compressor inlet and outlet, condenser outlet and evaporator inlet in order to obtain data from the test. the pressure and temperature data obtained was applied to evaluate the performance of the two systems. with further repeated tests, the coefficient of performance (cop) of the refrigeration systems were determined at normal ambient condition. the highest evaporator temperature obtained for the conventional refrigeration system (crs) and modified refrigerators system (mrs) were -5oc and 0oc respectively. interestingly, an efficiency improvement of about 10% was achieved for the mrs. the result shows a remarkable improvement in the cop of the mrs. therefore, for a better performance, thermal radiation shield can be recommended to be incorporated in vapour compression refrigeration system © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 oct., 2020 revised 18 february 2021 accepted 21 february 2021 keywords: experimental investigation performance household refrigerator radiation shield mukhtar et al: experimental investigation of the performance of a household refrigerator using plywood as radiation shield. azojete, 17(2):165-172 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 166 the accumulated energy in the condenser, usually of a natural air-cooled type, hence a complete refrigeration cycle. in previous experimental work, afonso (2013) had shown that the outside surface temperature of the rear wall where the condenser is located as well as the walls close to the compressor has a very much higher temperature than the outside air with which all refrigerator surfaces exchange heat. this is due to the heat released from condenser and compressor produces larger heat gains to the refrigerator through those walls, when compared with the others. in order to evaluate the effect of the heat released from the condenser and compressor on the thermal behaviour of this kind of system, tests have been carried out in a new commercially available refrigerator. arifulkabir et al. (2018) studied the improvement in cop with heat recovery scheme for solar adsorption cooling system. in order to facilitate the heat transfer area, heat transfer fluid was distributed within two adsorbers that maintain the same mass flow rate between the heated and cold adsorber. the process distributes some heat of the desorption bed to the adsorber preparing it for the next preheating mode where heat transfer between them occur adiabatically. there is a satisfactory increase in the cop of the system. there have been several methods applied in order to investigate the performance of household refrigerators. cobanoglu et al. (2020) carried out an investigation of the performance improvement of a household freezer using a natural circulation loop. the method employed the application of innovative refrigeration system that works with single-phase natural circulation loop. the loop was considered as heat exchanger suction line between the high and low pressure sides of the crs of a household chest freezer. computational fluid dynamics (cfd) analysis was carried out to study the heat transfer by the single-phase natural circulation. the performance of the system was presented based on different compressor suctions and discharge pressures, discharge temperatures and compressor speed. the result showed an efficiency improvement of 11.5% for the household freezer with single-phase natural circulation loop at maximum compressor speed and lowest compressor suction and discharge pressures and temperatures. similar work conducted by safa et al. (2015) investigated the performance characteristics of ground source heat pump. experimental tests were carried out to obtain the performance curves of the system with an efficiency evaluated at different load/source temperatures. the ground source heat pump was modelled using the performance curves obtained from the test and the cop of the system was determined at some external load and source temperature. raveendran and sekhar (2020) carried out an experimental study to analyse the performance improvement of a household refrigerator connected to a domestic water supply with a cooled condenser in a tropical region the study involved a pull-down performance testing for two refrigerators; the conventional and modified household refrigeration system. the modified refrigerator type was connected to a water cooled condenser system. the space temperature inside the refrigerators was recorded at different locations. power consumption was manually recorded at an interval of 30s using a wattmeter. the pressure and temperature of components state points were recorded at an equilibrium condition. the cop of the conventional and modified refrigeration system were computed at normal ambient condition. the result showed mrs could decrease 21-27% daily energy consumption. afonso and gabriel (2017) demonstrated experimentally, the improvements achieved in household refrigeration systems if several modifications are implemented. by implementing the modifications tested in the virtual model, the thermal behaviour of the systems was improved. a decrease in electrical energy consumption as well as the associated co2 emission reduction were attained. it is arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):165-172. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 167 evident that the performance of household refrigeration system is affected by the heat emission from condenser and compressor of the refrigeration system. the objective of this work is to investigate the performance of household refrigeration system by incorporating a thermal radiation shield at the condenser and compressor of the system. 2. typical refrigeration system a refrigeration system comprised of four main components in which a fluid called refrigerant flow through the components to complete a refrigeration cycle in order to produce a cooling effect. these components are the compressor, condenser, expansion valve and evaporator. the refrigerant is contained in a loop or piping that connects the four main components together. to achieve a complete refrigeration cycle, the refrigerant which is at different states of liquid and vapour, moves through the components in open or closed system. the crs operates as either a vapour compression or absorption refrigeration system. figure 1 shows a schematic diagram of a vapour compression refrigeration system with an enthalpy-pressure relation. the cycle starts when the refrigerant is pressurized with its volume reduced by process 1-2 at the compressor which acts as the prime mover of the system. the refrigerant turns into a very hot and pressurized gas moves to the condenser for process 2-3. the work of the condenser is to cool the refrigerant and convert it into a hot liquid or condenses. at this point excess heat is rejected by the condenser into the atmosphere (thakar et al., 2017). the refrigerant flows through the process 3-4 at the expansion device which is responsible to metering and lowering the pressure and temperature of the refrigerant. because of the rapid drop in the pressure at the expansion device, the refrigerant turns into a mix of cold liquid and gas and moves slowly through the evaporator in process 4-1. the evaporator absorbs the heat and cools the load inside the refrigerator. however, air is blown in the evaporator to maximise heat transfer from the refrigerant to the air that cools the space. this turns the liquid into a vapour which is pushed back into the compressor in order to start a new refrigeration cycle. figure 1: schematic diagram of refrigeration system with enthalpy-pressure relation (nasution et al., 2019) 3. materials and methods the method applied in the present work is similar to the work of afonso and matos (2006) with some modifications in the rear and recess wall near the condenser and compressor separately, to evaluate the performance of the system. the improvement was achieved by mukhtar et al: experimental investigation of the performance of a household refrigerator using plywood as radiation shield. azojete, 17(2):165-172 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 168 placing a radiation shield composed of aluminium foil over the surfaces close to condenser and compressor to test the performance of the systems. however, in this work, a thermal radiation shield made of a plywood was used to investigate the performance of the conventional household refrigerator in relation to the modified refrigerator system. with reference to a standard vapour compression refrigeration system, the cop was obtained using the expression in equation 1 defined as the ratio of the heat absorbed in the evaporator to the work input to the compressor (nasution et al., 2020) where and are the power input and compressor work respectively. coefficient of performance (cop) = (1) the materials used in this work is the refrigerator that comprises of the four main components of the refrigeration system. pressure gauge was applied to determine the pressure at the evaporator and condenser of the refrigerators. thermocouple was used to obtain condenser and compressor and evaporator temperature at a given period of time. ply-wood which serve as the thermal radiation shield of size 45 cm x 20 cm and 45 cm x 60 cm were attached to the compressor recess wall and condenser wall respectively. a stop clock, masking-tape and refrigerant r-134a were all used in the test in the vapour compression refrigeration system. figure 2 shows how these instruments were attached to the refrigerator. the method employed to achieve the result involved the use of a pressure gauge which was welded to the condenser outlet and evaporator inlet of the refrigerators (figure 2a). the thermocouple wires were placed at the refrigerators’ compressor inlet and outlet, condenser outlet and evaporator inlet (figure 2b). experimental tests were carried out with six observations at an ambient temperature of 32 to 35oc. the temperature and pressure data were recorded at an interval of 10 minutes in the tests for the two systems. the experimental tests data recorded were applied to determine the cop of the refrigerators. the refrigeration system performance map of the two systems was evaluated and analysed using the cop values obtained. figure 2: pressure gauges (a) and thermocouples (b) fixed to the refrigerator to obtain data arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):165-172. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 169 4. results and discussion the experiment was carried out using plywood as the radiation shield in order to investigate the performance enhancement of the household refrigerator. temperature and pressure are the two main important parameters considered for the analysis. data were analysed according to the theory of refrigeration system and the results were tabulated (tables 1 – 2). the data collected for the evaporator inlet and outlet temperature and pressure, condenser inlet and outlet temperature and pressure as well as the compressor inlet and outlet temperature and pressure were applied to determine the cops of the two refrigeration systems. tables 1 and 2 show the temperature and pressure data recorded at an interval of 10 minutes from the compressor, condenser and evaporator of the crs and mrs. the performance of the two refrigerators were analysed in terms of the cop. the cops of the crs and mrs were determined in each test. the cops of the mrs are considerably higher than that of the crs. it can be deduced that the use of thermal radiation shield in household refrigerator imposes a considerable impact on the cop improvement. however, this shows that the heat generated by the compressor and rejected with the condenser for mrs has great impact on the evaporative effect than that of the crs. figures 3-5 shows the comparative analysis of cop with time, cop with the compressor discharge temperature and condensation temperature as well as compressor discharge temperature and condensation temperature with time. the improvement in the cop ranges in between 5-20% depending upon thermal load, external temperature and material property type. the cop increases with time due to higher evaporation temperature obtained in the mrs. table 1: experimental data obtained for the conventional household refrigeration system time (minutes) evaporator inlet pres. p1 (bar) condenser outlet pres. p2 (bar) compressor inlet temp. t1 ( oc) compressor outlet temp. t2 ( oc) condenser outlet temp. t3 ( oc) 10 1.32 8.15 25 43 33 20 1.34 8.22 28 46 34 30 1.35 8.23 33 51 36 40 1.36 8.31 35 55 37 50 1.38 8.35 37 61 38 60 1.41 8.41 40 66 40 table 2: experimental data obtained for the modified household refrigeration system time (minutes) evaporator inlet pres. p1 (bar) condenser outlet pres. p2 (bar) compressor inlet temp. t1( oc) compressor outlet temp. t2 ( oc) condenser outlet temp. t3 ( oc) 10 1.24 8.28 27 44 35 20 1.27 8.39 30 50 36 30 1.29 8.50 34 55 38 40 1.33 8.71 36 61 39 50 1.36 8.84 38 65 40 60 1.38 8.95 42 70 42 mukhtar et al: experimental investigation of the performance of a household refrigerator using plywood as radiation shield. azojete, 17(2):165-172 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 170 figure 3: comparison of cop for the conventional and modified refrigeration systems figure 4: comparison of cop with compressor discharge and condensation temperature figure 5: comparison of compressor discharge and condensation temperature with time it can be observed from figure 3 for every number of observations with time, the cop obtained for the mrs are comparably similar with that of the crs. similarly, figures 4 and 5 showcased the existing relationship of the cop for crs and mrs, with the compressor discharge temperature and condensation temperature and how these temperatures vary with time. the compressor discharge temperature and the condensation temperature increase with increase in time with which the refrigeration systems operate. on the other hand, the cops of 0 1 2 3 4 5 6 0 2 4 6 c o p number of tests cop values crs mrs 0 1 2 3 4 5 6 0 10 20 30 40 50 60 c o p time (minutes) cop vs time crs mrs 0 1 2 3 4 5 6 40 45 50 55 60 65 70 c o p compressor discharge temp. (⁰c) cop vs compressor discharge temp. crs mrs 0 1 2 3 4 5 6 32 34 36 38 40 42 44 c o p condensation temp. (⁰c) cop vs condensation temp. crs mrs 0 12 24 36 48 60 72 0 10 20 30 40 50 60 c o m p re ss o r d is c te m p . ( ⁰c ) time (minutes) compressor discharge temp. vs time crs mrs 0 8 16 24 32 40 48 0 10 20 30 40 50 60 c o n d en sa ti o n t em p . ( ⁰c ) time (minutes) condensation temp. vs time crs mrs arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):165-172. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 171 the crs and mrs decreases when the compressor discharge and condensation temperature increases. however, there is an outstanding difference in their values. in this regard, it can be deduced that the use of thermal radiation shield improves in the cop of refrigeration system. the improvement in this system can be achieved with a single evaporator refrigeration system for a refrigerator or freezer combination. 5. conclusion this work involved a study of vapour compression refrigeration system where the performance of two refrigeration systems was investigated. the cop achieved for mrs in each test was higher than that of crs. however, for both systems, the cop decreases with increase in time, compressor discharge temperature and condensation temperature. it is clear that the use of radiation shield improves the overall performance of the refrigeration system. the heat load was minimized hence the cooling effect of the refrigerators were enhanced. references afonso, c.f. 2013. household refrigerators: forced air ventilation in the compressor and its positive environmental impact. international journal of refrigeration, 36(3): 904-912. afonso, c. and matos, j. 2006. the effect of radiation shields around the air condenser and compressor of a refrigerator on the temperature distribution inside it. international journal of refrigeration, 29(7): 1144-1151. afonso, c. and gabriel, j. 2017. small scale refrigerators and freezers: thermal improvements in the envelope. journal of environmental science and engineering, a6: 1-14 arifulkabir, km., rouf, ra., sarker, m.m.a., amanul alam, kc. and saha, bb. 2018. improvement of cop with heat recovery scheme for solar adsorption cooling system. international journal of air-conditioning and refrigeration, 26(2): 1850016. çobanoğlu, n., koca, hd., genç, am., karadeniz, zh. and ekren, o. 2020. investigation of performance improvement of a household freezer by using natural circulation loop. science and technology for the built environment, 27(1): 85-97 fearon, j. 1978. the history and development of the heat pump. refrigeration and air conditioning, 81(1): 79-99. gosney, wb. 1982. principles of refrigeration. cambridge university press cambridge, uk marques, c., davies, g., maidment, g., evans, ja. and wood, i. 2010. application of phase change materials to domestic refrigerators. iir proceedings series' refrigeration science and technology, 5:167-175. mcdonald, k. and sun, dw. 2000. vacuum cooling technology for the food processing industry: a review. journal of food engineering, 45(2): 55-65. nasution, dm., siregar, ah. and bukit, fra. 2020. modelling a simple-vapour compression refrigeration cycle for fish-storage boxes. in journal of physics: conference series 1542(1): 012-066. mukhtar et al: experimental investigation of the performance of a household refrigerator using plywood as radiation shield. azojete, 17(2):165-172 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 172 raveendran, ps. and sekhar, sj. 2020. experimental studies on the performance improvement of household refrigerator connected to domestic water system with a water-cooled condenser in tropical regions. applied thermal engineering, 179: 115684. riffat, sb., afonso, cf., oliveira, ac. and reay, da. 1997. natural refrigerants for refrigeration and air-conditioning systems. applied thermal engineering, 17(1): 33-42. safa, aa., fung, as. and kumar, r. 2015. heating and cooling performance characterisation of ground source heat pump system by testing and trnsys simulation. renewable energy, 83: 565-575. thakar, s., prajapati, rp. and solanki, dc. 2017. performance analysis of a domestic refrigerator using various alternative refrigerants. international journal of engineering development and research, 4(1): 13-36 8 arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):41-52 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 23 original research article comparative analysis and simulation of the d-q reference frame model of the three phase induction motor and its modification g.a. olarinoye* and i. abdulwahab electrical engineering department, ahmadu bello university, zaria, nigeria *corresponding author’s email address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 1.0 introduction the three phase induction motor has often been described as the workhorse and race horse of the industry (boldea and nasar, 2002; olarinoye et al., 2018). they are rugged, cheap, robust and have low maintenance requirement (tamimi, 2018; li et al., 2021). additionally, it is mostly used in commercial and industrial centers across the globe (richardson et al., 2021). the three phase induction motor continues to receive wider attention because of advancements in semiconductor technology towards development of cheap and fast digital signal processors and control strategies that enable the motor to perform tasks in ways like never before (hareesh and jayanand, 2021; abad, 2016; el-zohri and mosbah, 2019). they are now being increasingly used in industrial and transportation sectors of the economy and they are available in a wide variety of power range (noor et al., 2013; menghal and laxmi, 2020; ke et al., 2020). the modeling of the symmetrical three phase induction motor has been extensively discussed in literature. several models have article information abstract induction motors play an important role in residential, commercial, and industrial centers around the globe. they are rugged, reliable in operation and require low maintenance. the dynamic models of these motors are typically employed to understand their behavior in transient, steady state and under dynamic conditions. several models of the three-phase induction motor exist in literature, but this paper proposes an alternative to the standard d-q reference frame model of the symmetrical three phase induction motor. the proposed model is obtained by modifying the standard model in a way in which the d-axis of the reference frame is aligned with the rotor flux vector. the alignment decouples the q-axis component from the d-axis component of the stator current using the vector control technique. the model is analyzed in the synchronous reference frame and then a dynamic simulation is performed. a comparison between the standard d-q reference frame model and the proposed model was performed. the simulation showed identical results of motor speed, torque and flux behavior for the two models. the difference between the two models manifests in their alternate characteristics for the d-q axes voltages and currents. it was observed that the magnitudes of the d-axis and q-axis voltages for the standard model are equal to the peak value of the applied phase voltages and zero respectively. however, the results of the proposed model revealed otherwise. furthermore, it was observed that the d-q axis voltages and currents of the proposed model exhibit oscillations during motor acceleration time because of the dynamics of alignment but attain constant values during the time that motor speed is constant. the proposed model is easier to solve because the rotor dynamics are described by one equation instead of two equations as in the case of the standard d-q reference frame model. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 june, 2021 revised 23 november, 2021 accepted 2 december, 2021 keywords: induction motor simulation reference frame rotor flux vector http://www.azojete.com.ng/ mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):41-52. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 42 been developed and applied by different authors to solve different problems. some of these models include the equivalent circuit model, a-b-c reference frame models and the d-q reference frame model. the d-q model is the most popular because it not only allows for steady state, dynamic and transient studies but it also makes motor analysis easier and reduces computation time (sanjay et al., 2015; kuznyetsov, 2019). some of the methods that have been applied to model the induction motor includes; numerical integration, finite element-based, complex vector representation etc. kuznyetsov (2019) developed a numerical model of a three phase induction machine in its natural a-b-c reference frame utilizing the method of average voltages at the integration step (avis). the behavior of the model was compared for a set of conventional numerical methods alongside avis. although the model was analyzed, the focus of the work was on the calculation speed of the model. menghal and laxmi (2020) implemented d–q model of the three phase induction motor in matlab/simulink. the transient and steady state analysis of the motor were carried out under different load conditions. open loop and closed loop modes of operation using artificial intelligence methods were also examined. a conventional three phase induction motor model derived in the arbitrary reference frame was presented, analyzed in the rotor reference frame and simulated in (deb and sarkar, 2016). the results of simulation were compared with the results of simulating an existing simulink model of the three phase induction motor also in the rotor reference frame. an agreement in the results was reported. this paper proposes a modification to the d-q reference frame model of the three phase induction motor in a way in which the d-axis of the reference frame is aligned with the rotor flux vector for the purpose of studying motor behavior. the alignment decouples the torque current or qaxis component of the stator current from the flux current otherwise known as the d-axis component of the stator current using the vector control technique. the model is analyzed in the synchronous reference frame and simulated. simulation results are compared with the results of simulating the standard d-q reference frame model in the synchronous reference frame as well. the model is particularly useful in the analysis of motor behavior when vector control is not the objective. 1.0 materials and methods 2.1 the standard d-q reference frame model the voltage, flux and electromagnetic torque equations in the synchronous reference frame are provided in equations (1) – (10) (boldea and nasar, 2002; el-zohri and mosbah, 2019). in the synchronous reference frame, all the voltages, currents and flux linkages associated with the stator and rotor d-q windings are dc in a balanced sinusoidal steady state (el-zohri and mosbah, 2019; menghal and laxmi, 2020). this is an advantage that makes the synchronous reference frame model attractive for motor control purposes. voltage equations vds = rsids + pλds − ωsλqs (1) vqs = rsiqs + pλqs + ωsλds (2) vdr = rridr + pλdr − ωslλqr (3) vqr = rriqr + pλqr + ωslλdr (4) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng olarinoye and abdulwahab: comparative analysis and simulation of the d-q reference frame model of the three phase induction motor and its modification. azojete, 18(1):41-52. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 43 flux linkage equations λqs = lsiqs + lmiqr (5) λds = lsids + lmidr (6) λqr = lriqr + lmiqs (7) λdr = lridr + lmids (8) electromagnetic torque equations te = 3p 4 lm lr (λdriqs − λqrids) (9) te = j ( 2 p ) pωr + tl (10) the model equations (1) – (10) were obtained from series of derivation based on the reference frame theory (krause et al., 2013). vds and vqs are the voltages applied to the stator windings in the d – q reference frame. ids and iqs are the d – q axes currents in the stator windings. idr ′ and iqr ′ are respectively the currents in the d – q axis of the rotor windings. λqs and λds are the flux linkages of the stator windings respectively. λqr ′ and λdr ′ are the flux linkages of the rotor windings in the d – q axis. rs and rr are the stator and rotor winding resistances respectively. te is the electromagnetic torque produced in the motor while tl is the load torque. p is a differential operator and it is defined as; p = d dt (11) ls = lls + lm (12) lr = llr + lm (13) ωsl = ωs − ωr (14) ls , lr are the self-inductances of the stator and rotor respectively. llrlls are the leakage inductances of the rotor and stator while lm is the mutual inductance between the rotor and stator circuits. ωr is the rotor speed in rad/s, ωs is the supply frequency or the synchronous speed in rad/s and ωsl is the slip speed also in rad/s. parameter p is the number of poles on the stator. the equivalent circuit derived from equations (1)-(8) is provided in figure 1. http://www.azojete.com.ng/ mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):41-52. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 44 figure 1: equivalent circuit of the standard d-q reference frame model of the three phase induction motor 2.2 modifications to the d-q reference frame model in order to effectively decouple the flux current, ids from the torque current iqs in the motor model, the d-axis is now aligned permanently with the rotor flux linkage space vector as shown in figure 2. figure 2: rotor flux vector alignment with the d-axis this means that the d-axis component of the rotor flux space vector, λdr is now equal to the rotor flux magnitude, λr. this cancels the q-axis component of the rotor flux linkage space vector, λqr. the rotor flux vector is computed as follows; λr = √λqr 2 + λdr 2 (15) mathematically, aligning the d-axis with the rotor flux vector means equating λqr to zero in equations (3), (4), (7), (9) and (15). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng olarinoye and abdulwahab: comparative analysis and simulation of the d-q reference frame model of the three phase induction motor and its modification. azojete, 18(1):41-52. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 45 therefore the following modifications result; λr = λdr (16) iqr = − lm lr iqs (17) ωs − ωr = rrlmiqs lrλr (18) with iqr substituted as provided in (17), the torque produced in the motor represented by equation (9) is modified because of the alignment of the rotor flux magnitude with the d-axis to the following te = 3p 2 lm lr (λriqs) (19) these modifications have been obtained considering that in the squirrel cage rotor, rotor voltages vdr and vqr are both equal to zero since the windings are short-circuited. the rotor flux dynamics is developed from (3) and (8) to give the following equation; τr dλr dt + λr = lmids (20) where τr = lr rr τr is defined as the time constant of the rotor circuit. the rotor flux in now dependent on the d-axis component of the stator current as seen from equation (20). the dynamics are those of a first order system governed by the rotor time constant, τr. based on the d-axis alignment, rotor flux linkage is now dependent solely on the d-axis component of the stator current and if it is maintained constant, then according to equation (19) the torque production will be dependent entirely on the q-axis component of the stator current. in this manner, the control of torque and flux may be achieved independently as in the case of the direct current (dc) motor. the model of the three-phase induction motor that achieves a decoupling of the control of torque and flux in the motor is therefore provided as follows in equations (22) – (30); vds = rsids + pλds − ωeλqs (22) vqs = rsiqs + pλqs + ωeλds (23) τr dλr dt + λr = lmids (24) ωs = ωr + rrlmiqs lrλr (25) te = 3p 2 lm lr (λriqs) (26) λds = lsids + lmidr , (27) λqs = lsiqs + lmiqr , (28) λr = lridr + lmids , (29) 0 = lriqr + lmiqs, (30) http://www.azojete.com.ng/ mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):41-52. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 46 it is important to note that because of the alignment, the rotor flux linkage vector rotates at the same speed as the d-q windings which in this case is the synchronous speed and therefore the rotor flux angle is calculated as; θs = ∫ ωs(τ)dτ t 0 (31) where τ is the variable of integration. the flux angle has to be calculated at all times and used to transform the a-b-c variables to d-q quantities at every instant according to equations (32) – (33) in order to maintain the alignment of the rotor flux vector with the d-axis. [ vα vβ ] = 2 3 [ 1 1 2 − 1 2 0 √3 2 − √3 2 ] [ va vb vc ] (32) [ vds vqs ] = [ cos θ sin θ − sin θ cos θ ] [ vα vβ ] (33) the choice of the synchronous reference frame for the analysis of the induction motor ensures that all voltages, currents and flux linkages are constants (or dc) in balanced sinusoidal steady state. the equivalent circuit derived from equations (22)-(30) is provided in figure 3. this model can be used to study the behavior of the induction motor where vector control is not the objective. figure 3: equivalent circuit of the standard d-q reference frame model of the three phase induction motor 2.3 solutions to both the d-q reference frame model and the modified model in solving the d-q reference frame model of equations (1) (11), the stator and rotor flux linkages λds, λqs, λdr and λqr are often considered as state variables. voltages serve as inputs and the currents ids, iqs, idr and iqr are then calculated from equations (5) (8) as follows; file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng olarinoye and abdulwahab: comparative analysis and simulation of the d-q reference frame model of the three phase induction motor and its modification. azojete, 18(1):41-52. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 47 [ iqs ids iqr idr] = [ ls 0 0 ls lm 0 0 lm lm 0 0 lm lr 0 0 lr ] −1 [ λqs λds λqr λdr] (34) the electromagnetic torque produced in the motor is calculated from equations (9) and (10). the solution diagram to the standard d-q reference frame model is provided in figure 4. the block diagram of the solution to the modified d-q reference frame model in which d-axis is aligned with the rotor flux linkage vector is provided in figure 5. figure 4: block diagram of the solution to the standard d-q reference frame model (model 1) 𝑒𝑞𝑛 (34) _ 𝑅𝑠 1 𝑠 𝑉𝑞𝑠 _ + 𝑝𝜆𝑞𝑠 + 𝜆𝑞𝑠 𝑅𝑠 1 𝑠 𝑉𝑑𝑠 _ + 𝑝𝜆𝑑𝑠 + 𝜆𝑑𝑠 𝜔𝑠 𝑅𝑟 1 𝑠 𝑉𝑑𝑟 _ + 𝑝𝜆𝑑𝑟 + 𝜆𝑑𝑟 𝜔𝑟 (𝜔𝑠 − 𝜔𝑟) 𝑅𝑟 1 𝑠 𝑉𝑞𝑟 _ + 𝑝𝜆𝑞𝑟 + 𝜆𝑞𝑟 𝑒𝑞𝑛 (10) 1 𝑠𝐽 𝑃 2 + 𝑒𝑞𝑛 (33) 𝑒𝑞𝑛 (32) 1 𝑠 𝜃 𝑉𝛽 𝑉𝛼 𝑉𝑎 𝑉𝑏 𝑉𝑐 http://www.azojete.com.ng/ mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):41-52. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 48 figure 5: block diagram of the solution to the modified d-q reference frame model (model 2) figures 4 and 5 show that in the modified model, the synchronous speed or speed of the rotor flux has to be calculated using equation (25) and the rotor flux angle is then calculated from equation (31). the solution diagram of figure 5 is clearly simpler than that of figure 4. the parameters of the three phase induction motor applied in the simulation are provided in table 1. 𝑉𝛽 𝑉𝛼 𝑅𝑠 1 𝑠 𝑉𝑞𝑠 _ + 𝑝𝜆𝑞𝑠 + 𝜆𝑞𝑠 𝑅𝑠 1 𝑠 𝑉𝑑𝑠 _ + 𝑝𝜆𝑑𝑠 + 𝜆𝑑𝑠 𝜔𝑠 1 𝑠 _ + 𝑝𝜆𝑟 𝜆𝑟 1 𝜏𝑟 𝐿𝑚 𝜏𝑟 𝑒𝑞𝑛𝑠 (27 − 30) 𝑒𝑞𝑛 (10) 𝑒𝑞𝑛 (25) 1 𝑠𝐽 𝑃 2 𝑒𝑞𝑛 (31) 𝑒𝑞𝑛 (33) + + 𝜃 𝑒𝑞𝑛 (32) 𝑉𝑎 𝑉𝑏 𝑉𝑐 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng olarinoye and abdulwahab: comparative analysis and simulation of the d-q reference frame model of the three phase induction motor and its modification. azojete, 18(1):41-52. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 49 table 1: three-phase induction motor parameters 2.0 results and discussion the solution diagrams of figures 4 and 5 were implemented in matlab/simulink and the results are presented and discussed in this section. figure 6 (a) shows the load torque applied on the three phase induction motor models. figure 6: simulation results of load torque, speed, electromagnetic torque and rotor flux it can be seen that the motor was initially unloaded. a rated load of 12.644nm was applied on the machine at steady state at a time of 1s and this load was stepped down to half its value at 1.5s. the load torque was further stepped down to 0 nm at 2s up till the end of simulation time 0 0.5 1 1.5 2 2.5 0 5 10 15 time (s) (a) l o a d t o rq u e (n m ) 0 0.5 1 1.5 2 2.5 0 50 100 150 200 time (s) (b) s p ee d ( ra d /s ) 0 0.5 1 1.5 2 2.5 -40 -20 0 20 40 60 time (s) (c) e le ct ro m a g n et ic t o rq u e (n m ) 0 0.5 1 1.5 2 2.5 0 0.2 0.4 0.6 0.8 1 time (s) (d) r o to r fl u x ( w b ) model 1 model 2 model 1 model 2 model 1 model 2 parameters values rated power 2.4 kw voltage rated speed 460v (l-l) 1750 rpm frequency number of poles stator resistance 60hz 4 1.77 𝞨 rotor resistance 1.34 𝞨 stator leakage reactance 5.25 𝞨 rotor leakage reactance 4.57 𝞨 mutual reactance 139 𝞨 http://www.azojete.com.ng/ mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):41-52. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 50 of 2.5s. the speed of the motor is seen in figure 6 (b) to rise from zero to a steady state value of 185.5 mechanical rad/s in about 0.33 secs. oscillations in response to the sudden application and reductions in load torque can be observed. the steady state speed rises slightly with each reduction in load. it can be observed that the speed profile is the same for both the standard and the modified d – q reference frame models. the electromagnetic torque produced in the motor is provided in figure 6 (c). it can be seen to oscillate during the acceleration time and it becomes 0 nm at steady state under no-load conditions. it equals the load torque in steady state after experiencing transients during changes in load torque in accordance with the motor dynamics given by equation (10). the electromagnetic torque is identical for the two models. the rotor flux profile is observed to be identical as well for the two models as shown in figure 6 (d). it is constant at a value of 0.96 wb in steady state at no load. the rotor flux can be observed to be fairly constant during to changes in load. the d – q voltages and currents are presented in figure 7 (a) – (d). figure 7: simulation results of d-q axes voltages and currents the d – q axes voltages and currents are dc voltages and currents in steady state. it can be observed that the d-axis voltage, in the case of the standard d-q reference frame, is equal to a constant value of 376v which is the peak value of the applied phase voltages in the a-b-c reference frame while the d-axis voltage is equal to 0v in the case of the modified model when no load is applied on the motor. its magnitude, however, depends on the load applied to the motor. the qaxis voltage of the modified motor model, on the other hand, is equal to the peak value of the 0 0.5 1 1.5 2 2.5 -400 -200 0 200 400 time (s) (a) d -a x is v o lt a g e (v ) 0 0.5 1 1.5 2 2.5 -400 -200 0 200 400 time (s) (b) q -a x is v o lt a g e (v ) 0 0.5 1 1.5 2 2.5 -50 0 50 time (s) (c) d -a x is c u rr en t (a ) 0 0.5 1 1.5 2 2.5 -50 0 50 time (s) (d) q -a x is c u re n t (a ) model 1 model 2 model 1 model 2 model 1 model 2 model 1 model 2 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng olarinoye and abdulwahab: comparative analysis and simulation of the d-q reference frame model of the three phase induction motor and its modification. azojete, 18(1):41-52. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 51 phase voltage applied as input to the model while the q-axis voltage of the standard motor model is equal to 0v and does not depend on the load. the magnitude of the d-axis current of the modified model is a constant value of 2.6a, regardless of load changes which is expected because it is proportional to the d-axis aligned rotor flux according to equation (24). the magnitude of the d-axis stator current of the standard motor model has a value that changes in direct proportion to the load applied on the motor. its value is 0v when there is no load applied. the magnitude of the q-axis stator current of the modified motor model changes with load applied on the motor which is expected as well because it is proportional to the electromagnetic torque produced in the motor by design according to equation (26). this results demonstrate the decoupling of the d-axis and q-axis currents from each other in the case of the modified d-q reference frame model as predicted in the analysis. the magnitude of the q-axis current of the standard motor model has a constant value of 2.6a which does not depend on load changes to the motor. it is interesting to note that the axis in which voltage is equal to the peak value of the applied voltages is the axis in which the current is sensitive to load changes in both cases. oscillations are present in the d-q axes voltages of the modified motor model because of the dynamics of alignment in accordance to equation (25). 3.0 conclusion this paper proposed an alternative to the standard d-q reference frame model of the symmetrical three phase induction motor. the two models were found to produce identical results for speed, torque and flux in the motor. the steady state rated motor speed was obtained as 185.5 mechanical rad/s which increased slightly with each reduction in load torque. the induced torque profile showed torque oscillations during changes in load torque. the rotor flux magnitude was fairly constant at a value of 0.96 wb at steady state while the d-q axes voltages and currents exhibited alternate characteristics. it is noteworthy that the axis in which the voltage is equal to the peak value of the applied phase voltages is the axis in which the current is sensitive to load changes in both cases. this model is simpler and computationally inexpensive which should be recommended for use in studying the behavior of the induction motor where vector control is not necessary. references abad, g. 2016. power electronics and electric drives for traction applications. john wiley & sons, united kingdom. boldea, i. and nasar, sa. 2002. the induction machine handbook. washinton d. c, crc press deb, pb and sarkar, s. 2016. dynamic model analysis of three phase induction motor using matlab/simulink. international journal of scientific & engineering research, 7(3): 572-577. el-zohri, eh. and mosbah, ma. 2019. comparative evaluation of pwm techniques using atmega 328/p with pi control for inverter-fed induction motor. proceedings of the international conference on innovative trends in computer engineering (itce), aswan, egypt, 2 4 february 2019. pp. 219-224. http://www.azojete.com.ng/ mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):41-52. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng, iabdulwahab@abu.edu.ng 52 hareesh, a. and jayanand, b. 2021. scalar and vector controlled infinite level inverter (ili) topology fed open-ended three-phase induction motor. ieee access. vol. 9: 98433-98459. ke, c., wei, g., weiwei, g., wentao, w. and zhaowen, h. 2020. low constant speed control of heavy haul electric locomotives based on variable parameter pi regulator. ieee vehicle power and propulsion conference, gijon, spain, 18 nov.-16 dec. 2020. pp. 1-5. krause, pc., wasynczuk, o., sudhoff, sd. and pekarek s. 2013. analysis of electric machinery and drive systems. john wiley & sons, u.s.a. kuznyetsov o. 2019. mathematical model of a three-phase induction machine in a natural abc reference frame utilizing the method of numerical integration of average voltages at the integration step and its application to the analysis of electromechanical systems. mathematical problems in engineering, vol. 2019. pp. 1-13. li, z., xia, j., guo, y. and zhang, x. 2021. fault-tolerant predictive torque control design for induction motor drives based on discrete space vector modulation. ieee journal of emerging and selected topics in power electronics, 9(5): 5441-5451. menghal, pm. and laxmi, ja. 2020. dynamic modelling, simulation and analysis of high power induction motor. ieee first international conference on smart technologies for power, energy and control, nagpur, india, 25-26 september. 2020. pp. 1-6. noor, szm., hamzah, mk. and yunus, pna. 2013. three phase induction motor analysis using matlab/guide, ieee 7th international power engineering and optimization conference (peoco), langkawi, malaysia, 3-4 june 2013. pp. 161-166. olarinoye, ga., oricha, jy and aliyu uo. 2018. rotor flux oriented control of a two phase induction motor drive. proceedings of the annual general meeting and engineering conference of the nigerian society of engineers, ekiti state, nigeria, 3 – 5 september 2018. pp. 38 – 53. richardson, mt., patterson, mt. and parchment, a. 2021. microcontroller based space vector pulse width modulation speed control of three-phase induction motor. southeastcon 2021, atlanta, ga, usa, 10-13 march 2021. pp. 1-6. sanjay, jp., jasmin, mp. and hitesh, bj. 2015. dynamic modelling of the three-phase induction motor using simulink-matlab. internaional journal of advance engineering and research development, 2(3): 412 – 428. tamimi j. 2018. simulation of three-phase induction motor using nonlinear model predictive control technique. cogent engineering, 5(1): 1-10 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:baolarinoye@abu.edu.ng mailto:iabdulwahab@abu.edu.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 71-77 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng developments in automobile emission control abdulrahim, a. t. 1 , m.l. usmah 2 and b. alkali 3 abstract it is widely acknowledged that automobiles are becoming dominant contributors to atmospheric pollution in most of the world’s cities. hence, the need to find effective methods of controlling automobile emissions becomes imperative. available automobile emissions’ control measures which include various legislations and responses to legislations such as improvement in the state of the art controls, greater attention towards automobiles growth, improvement of engine design features, periodic tune-up, the use of alternative fuels and the development of non-fossil energy sources were reviewed in this paper. 1. introduction emission-control system in automotive engineering referred to means employed to limit the discharge of noxious gases from the internal combustion engines (the new encyclopedia britannica, 1998). according to the new encyclopedia britannica (1998), pollutants are things that cause pollution while pollution is the addition to the environment of any substances or energy form at a rate faster than the environment can accommodate by dispersion, breakdown, recycling or storage in some harmless form. in the area of man made emissions into the atmosphere, automobiles are dominant and growing source of several atmospheric pollutants. this is because the demand for automobiles as a means of transportation has been growing as the population increases over time coupled with the growing urbanization across the world. most of the available automobiles use fossil fuels, hence automobiles account for a significant consumption of petroleum products since it produces power from the combustion of a mixture of petroleum product and air in an enclosed space. the products of this combustion process constitute some of the known atmospheric pollutants. pollutants emitted from automobiles depend on a number of factors which includes the type of fuel, air – fuel ratio, ignition timing, engine speed and operation temperature (spalding and cole, 1973; rogers and mayhew, 1980 and walsh, 1992). combustion of fuel and air in automobile made it major source of carbon dioxide and unburnt hydrocarbon. it has also been a major source of leads into the atmosphere of many cities because of the burning of gasoline with leads compounds as additive (novikov, 1990). evaporation of gasoline leads to hydrocarbons escaping from the tank, the carburetor and the crankcase. also, because of the high pressures in the cylinder above the piston during combustion process, some of the unburnt gasoline and other organic compounds find their way past the piston rings into the crankcase. emission also comes from the tail pipe. all these contribute greatly to the level of atmospheric pollution (avallone and baumeister, 1997). the contributions of these combustion products and other pollutants released by automobiles, and their effects have been established. the introduction of harmful substances into the 1 department of mechanical engineering, university of maiduguri, maiduguri. nigeria 2 department of agricultural & environmental resources engineering, university of maiduguri. nigeria 3 department of electrical and electronics engineering, university of maiduguri, maiduguri. nigeria. the influence of organic matter on soil compactibility and air permeability of some borno soils 72 environment has been shown to have many adverse effects on human health, agricultural productivity and natural ecosystems (harrison, 1990 and murley, 1995). early recognition of the significance of vehicle exhaust emissions occurred in california, where a combination of geography and atmospheric conditions both trapped the emissions in los angeles basin and exposed them to the strong california sunlight. the resulting photochemical smog was recognised as having an adverse impact upon human health, crop and vegetation growth, and is visually offensive (eastop and mcconkey, 1993). many of the gases emitted by automobiles contribute to greenhouse warming either directly or indirectly, acid precipitation, ozone depletion and they also contribute directly to adverse health effects. for example, pollutant can be washed out of the air by the natural scrubbing action of rain, snow and all other forms of precipitation as it falls to the ground, usually referred to as acid precipitation; this made some of the known emissions from automobiles to be sources of acid precipitation (hesketh, 1972). moreover, the average temperature of the earth’s surface is known to be rising. the evidence to date support the view that the globe as a whole has warmed by between 0.3-0.60c since the end of 19th century (carson, 1998) even though some are still sceptical for the fact that record in the 20th century also indicates that while some regions have recorded a slight surface warming trend for decades, some regions have experienced a slight global cooling trend for decades (ladd, 2003). the main concern about the relatively small temperature increases occurring in the earth due to the increased greenhouse effect is in the increase in the melting of the polar ice-caps. greenhouse effect on the earth is caused by the absorption of the sun’s rays by gases such as carbon dioxide, halocarbon compounds (cfcs), nitrous oxide and ozone. ozone gas (o3) is one of the byproducts of photochemical smog. the action of sunlight on a trapped layer of car and chimney exhaust fumes produces the chemical reactions to convert oxygen to ozone. it is known that ozone is positively harmful at ground level, it is present in the layer of the earth’s atmosphere known as the stratosphere, about 11-50 km above the surface of the earth. at these altitudes, it is formed by the action of sunlight on oxygen and decomposes back to oxygen plus a free oxygen atom also due to sunlight. the free oxygen atom combines with ozone to form two molecules of oxygen gas. due to this continuous reaction in the stratosphere, ultraviolet light from the sun is being absorbed in the process thus partially shielding the earth from the sun’s harmful radiation. ozone is destroyed when combined with certain reaction atoms, or free radicals such as h, oh, no and cl; such reactions are catalytic and cause ozone depletion. it was found that the natural annual cyclic thinning of the ozone layer over the antarctic appeared to be increasing and a “hole” had been created causing fears of skin cancer due to increased intensities of ultraviolet-b from the sun’s rays (eastop and mcconkey, 1993). as public awareness of environmental risk grows, there have been concerns from almost every quarter on the increase rate of pollutants emission. hence, pressures increase both in the introduction of new laws and to extend the scope of existing legislation on automobile emission. in the same line various agencies have also been put in place in order to monitor the implementation of policies derived from these various legislations. concern of protecting environment for the benefit of the present and the future generation is now at the centre of the international agenda. the process of reduction of man-made emissions of atmospheric pollutants from automobiles is becoming increasingly global. government of various azojete vol. 4 2004 73 countries now thought it wise to make long–term policies. the goal being to design preventive, adaptive and remedial measures, in combating atmospheric pollutants from automobiles. in the light of the above, some stakeholders have taken various steps in order to reduce pollutants from automobiles (epa, 1994; clean car campaign, 2000; ganske, 2003 and abdulrahim, 2003), while others still lack awareness on the roles expected to be played in combating atmospheric pollutant emissions from automobiles. hence, the needs to provide information on the contribution of various organs of the society towards automobile emissions control cannot be overemphasized. this will bring about awareness on the role being played by various stakeholders, and what is still expected from others. in view of the above, the present study seeks to review developments in automobile emissions control. 2. review of automobile emission control measures world wide 2.1 legislation if no environmental protection measures are taken against the increased rate of pollutants emitted into the atmosphere from automobiles, the result is detrimental effects on nature and in the long run on the national economy. it was against a background of increasing public nuisance and distress that in 1960, the state of california legislated against the motor vehicle and stated the procedures against which vehicles would be tested and the levels of pollutants which would have to be met by vehicle to be sold in that state. the procedures were extensive and covered the types of emission to be controlled i.e. hydrocarbon (hc) and carbon monoxide (co), the sources of emissions (exhaust, crankcase, carburettor, and fuel tank), the test procedures, the instrumentation and the test equipment to be used (eastop and mcconkey, 1993). automobile source of pollutants rapidly became the target of a series of legislative actions seeking to reduce emissions throughout the united states and canada in recognition of uniquely severe problem. since those early days, the application of exhaust emission legislation has steadily widened in the us, japan and some european countries (hawkins, 1992). in europe, the most significant effort has been to reduce the use of leaded fuels as a means of raising the knock rating of petrol. since developing countries also account for a growing proportion of global emission of various pollutants because of the growing number of imported used vehicles, their governments are also responding to current risks and uncertainties through prudent action to slow the emission of pollutants from automobiles (abdulrahim et al., 2003). for example, in 1988 the federal government of nigeria established the federal environmental protection agency (fepa) to protect, restore and preserve the ecosystem of the federal republic of nigeria. decree 58 of 1988 requires fepa to establish environmental guidelines and standards for the abatement and control of all forms of pollution (fepa, 1991). the prevention of global ecology catastrophe thus becomes an inalienable part of the process forming comprehensive environmental security. the montreal protocol of 1987 on substances ruining the ozone layer, together with the vienna convention of 1985 on protection of the ozone layer, lays the international legal basis for solution of the most important global problems of our time (novikov, 1990). other international efforts include those being made by international governmental panel on climate change (ipcc), and of particular the influence of organic matter on soil compactibility and air permeability of some borno soils 74 significance is the third conference of the parties (cop-3) held in december, 1997 in kyoto, japan, where the kyoto protocol was released (okorodudu-fubara, 2000). 2.2 responses to legislation in order to comply with the various legislations world wide for limiting the emissions from automobiles, a number of steps have already been taken while many others are still on the way by the automobile manufacturers, users and many other related groups. these include improvement in the state of the art controls, their wide spread applications, greater attention towards constraining automobile growth, improvement of engine design features, periodic tune-up of older vehicles, the use of alternative fuels and the development of non-fossil energy sources for automobiles, among others. some of these steps are briefly reviewed below: 2.2.1 positive crankcase ventilation (pcv) system first of the emission controls adopted by automotive industry, and still in use is the crankcase ventilation system that routes blow-by gases, condensation vapours and crankcase fumes to the combustion chamber of the engine. 2.2.2 evaporative emission control system evaporative emission control systems prevent the escape of gasoline vapours from the fuel tank and carburettor, whether or not the engine is running. all late model engines use an activated charcoal canister to trap the vapours when the engine is shut off. on restoring, a flow of filtered air through the canister purges the vapours from the charcoal. 2.2.3 exhaust emission control in order to comply with regulations for the control of exhaust emission, car manufacturers and their suppliers developed and installed many different systems and devices, which can be grouped into two, namely; pre-combustion controls and post-combustion controls. precombustion control includes the various engine modifications that affect compression ratio, combustion chamber, redesigns of piston in crown contour, intake manifolds, camshaft, valve port, cylinder head gaskets, spark plug port location changes and exhaust gas recirculation incorporated in manifolds. other pre-combustion controls are thermostatically controlled air cleaners, early fuel evaporated system, manifold heat control valve, ignition timing and fuel mixture control. post–combustion control includes exhaust gas recirculation system, air injection system and catalytic converters. 2.2.4 service and maintenance solution since the on-going advances in vehicle exhaust emission control technology have considerably reduced the amount of emissions from new vehicles, policies are made, most especially by government of developing world, to lower the emission from older vehicles by periodic tune–up, because it has been found to reduce pollutant emission from automobiles considerably. 2.2.5 improving transportation system additional reductions in vehicular emissions can be achieved by reducing dependence on individual cars and trucks, and by making greater use of van, car pools, buses and trains. improving urban traffic management by installing synchronized traffic lights, reducing onazojete vol. 4 2004 75 street parking, banning truck unloading during the day and introducing electric toll collector can also improve transportation system fuel efficiency. 2.2.6 development and use of alternative energy sources while technological improvements in petroleum powered vehicles are essential to achieving short term increases in fuel efficiency, they will not be sufficient in the long run because the number of vehicles continues to grow. for this reason, efforts to develop new transportation energy sources that emit less or no carbon dioxide have been intensified. research, development and demonstration programmes are presently put in place by some major automobile manufacturers. these alternative sources of energy include natural gas, fuel cells, battery and solar energy. (i) natural gas is promoted as an alternative fuel that could reduce the dependence on oil and also reduce pollutants emitted from automobiles. it has been used to power automobiles with a view to improving the cleanliness of the exhaust products because it is a clean-burning fuel with low carbon monoxide and hydrocarbon emissions. it is also plentiful and relatively cheap. natural gas test by auto oil emission testing programme (run by a group of automakers and oil companies that include general motors, ford, chrysler, arco, amoco, and shell) has been on course for some time now. the program studies advanced technology vehicles to gather information on emissions and optimized combustion (technews, 1991). (ii) ethanol and methanol fuels are seen as being more environmentally friendly than fossil fuels. hence, a lot of effort is being put towards the utilization of methanol and ethanol as alternative fuels for engines. for example, methanol powered model 6v-92 turbo charged and after cooled engine was developed by detroit. the hydrocarbon, nitrogen oxide and particulate emission standards were met for both m100 (100 percent methanol) and m85 (85 percent methanol and 15 percent unleaded gasoline) fuels when used in this model. this achievement made detroit the first heavy–duty engine manufacturer to receive environmental protection agency emission certification of an alternative fuel engine (detroit, 1991). (iii) advancement in turbine–powered vehicles is still in progress. in this category, toyota turbine–powered gtv experimental vehicles emerged in 1989 as probably the most advanced gas turbine-driven prototype in existence then. the advantages it has over the conventional piston engine include the ability to use any type of fuel – kerosene, petrol, diesel and even coal powder, the emission behavior is reported excellent and a good turbine will meet all current emissions standards without a catalytic converter (kunle, 1989). (iv) the main advantage of electric propulsion is that pollution in the form of noise and atmospheric emission is reduced almost to zero. for this and other reasons, electric propulsion has been used in city vehicles throughout the twentieth century. public transport vehicles in the form of trams and trolley buses have drawn current from a remote supply fed along underground rails or above–ground wires. as to passenger cars, electric traction is fast becoming a major research goal all over the world. the electric car must carry its electricity supply with it, in the form of either batteries or the influence of organic matter on soil compactibility and air permeability of some borno soils 76 fuel cells (novikov, 1990). in the newest honda solar car, the upper surface of the body is covered with monocrystal silicon cells which are able to provide a total power output of 1.9 kw. this car emerged as a solar challenged car in the development of electric vehicles. in the area of fuel cell, which creates electricity directly from fuel (hydrogen or hydrogen-rich gas), the electricity produced can be used to power automobiles. automakers world wide are increasingly becoming interested in fuel cell for at least three reasons, namely; energy efficiency, environmental cleanliness and international competition. fuel cell possesses significant potential in addressing long-term regulation (christopher, 1996). one fuel car running on hydrogen produced from natural gas emits about three times less carbon dioxide than a gasoline vehicle, if one considers the entire fuel cycle. another achievement is the formation of the u.s advanced battery consortium which brings the big three automakers together with battery firms and the department of energy to develop technology for electric vehicle (technews, 1991). (v) the first gasoline–electric hybrid vehicle available in u.s was the honda insight. it was developed by american honda motor corporation utilizing its innovative integrated motor assist (ima) hybrid system. this is an advanced ultra-low emission technology capable of averaging more than 70 miles per gallon (epa combined estimated) while meeting california stringent ultra–low emission vehicles (ulev) standard. toyota was the first automaker to release autos with gasoline-electric engines for commercial sale, starting with prius in 1997, with engines driven by a combination of gasoline and electricity. the prius is classified as a super-ultra-low-emission vehicle (sulev) and is now available (ganske, 2003). the toyota prius and the honda insight, with their hybrid fuel technology and radical design concepts, are examples of commitment to a cleaner environment, conservation of resources and technological ingenuity. 4. conclusion automobiles have been acknowledged as dominant contributors to atmospheric pollution of most cities, with its adverse effects on the environment. hence, automobile emission control has become a duty for everybody and no amount of contribution towards reducing emission from automobiles should be regarded as small by stakeholders. present available automobile emission control measures include the use of legislation that has brought about the need for changes in vehicle design technology, engine technology, use of alternative fuels and better traffic management. these developments still leave room for contribution and improvement. references abdulrahim, a.t., m.l. usman and r.k. olalere (2003). a review of automobile emission control measures in nigeria. journal of life and environmental sciences, 5(1&2) 273-281. avallone, e. a. and t. baumeister (1997). marks standard handbook for mechanical engineers. 10th edition, mc graw-hill books company, singapore. christopher, e. b. (1996). fuel cell. journal of power sources. 61 pp 33-48. clean car campaign (2000). http://www.cleancarcampaign.org http://www.cleancarcampaign.org/ azojete vol. 4 2004 77 detroit (1991). detroit diesel corp. mechanical engineering. 113(13) pp 16. eastop, t. d. and a. mcconkey (1993). applied thermodynamics for engineering technologists. 5 th edition elbs/longman, addison wesley longman ltd., england. epa (1994). automobile emissions: an overview. u.s. environmental protection agency, office of mobile sources. fepa (1991). guidelines and standards for environmental pollution control in nigeria. federal environmental protection agency, nigeria. ganske, j. a. (2003). the history of improving automobile emission: infrared spectroscopic analysis of tailpipe exhaust over a several-decademodel-year range. chem. educator 8 pp 353-357. harrison, r. m. (1990). pollution: causes, effects and control. royal society of chemistry, london. hawkins, m. j. (1992). vehicle emissions regulatory developments xxiv fisita congress technical paper june 1992 london, i mech. e. no. c389/466 fisita no. 925005. kunle, s. (1989). gas turbine engine. automag, vol. 1, no. 2. ladd, c. m. (2003). a different challenge. mechanical engineering, vol. 125, no. 10, pp 8. murley, l. (1995). pollution handbook. the association of clean air, brighton. novikov, y. (1990). environmental protection. mir publishers, moscow. okorodudu-fubara, m. t. (2000). refocusing regulatory regime on atmospheric pollution control in nigeria. air pollution and industrialisation in nigeria, ccdi ecology and development series number 01, pp 45-60. rogers, g.f.c. and y.r. mayhew (1980). engineering thermodynamics: work and heat. elbs/longman press, london. spalding, d. b. and cole, e.h. (1992). engineering thermodynamics. elbs/edward arnold (publishers) ltd. third edition, london. technews (1991). competition promotes improved natural gas vehicle. mechanical engineering, vol. 113, (6) pp. 8. walsh, m. p. (1992). transport and the environment: local, regional and the global challenges and opportunities. no. xxiv fisita congress technical paper june 1992 london. i mech e no.c389/404fisita no.925001. arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):717-724 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 717 original research article characterization of synthesized zeolite socony mobile 5 (zsm-5) from bularafa diatomite s. yunusa*, a. s. ahmed, m. yusuf, m. abubakar and s. g. bawa department of chemical engineering, ahmadu bello university, zaria, 810261, nigeria *corresponding author’s email address: slmnyunus@gmail.com 1.0 introduction diatomite rock is a loose, earthy or loosely cemented porous and lightweight rock of sedimentary origin, mainly formed by fragments of armor (skeletons) of diatom algae: (diatomea and radiolaria). diatomite is a microscopic diatom alga whose size ranges from 0.75 to 1500 m; sometimes this rock is called infusorial earth, kieselguhr, or mountain meal (arik, 2003). the important properties of diatomite are related to physical structures and an aggregate of fine particles perforated by a regular pattern of very small holes (aliev et al., 2011). diatomite’s highly porous structure, low density and high surface area resulted in a number of industrial applications as filtration media for various beverages and inorganic and organic chemicals as well as an adsorbent for oil spills (bakr, 2010). it can be used as an alternative source of amorphous silica for the production of silicon-based materials with industrial and technological interests. diatomite is another interesting material because of its low cost and its advantage over other materials such as clays, iron oxides, molecular sieves, activated carbon and rice husk due to the highly reactive amorphous state of its silica skeletons, which makes it unnecessary to carry out thermal activation to transform an unreactive state into a reactive state (chaisena and rangsriwatananon, 2005). it has been shown that kaolin clay and diatomaceous earth are two suitable and inexpensive sources of silica materials. some studies reported that rice husk ash contains high amount of silica that is amorphous or crystalline depending on the combustion temperature (shen et al., 2011, 2018; habeeb and mahmud, 2010). other studies were conducted on the synthesis of zeolites from rice husk ash, namely mcm zeolite and zsm-5 (chiarakorn et al., 2007; fernandes et al., 2005; mohammed et al., 2008) for possible use in catalytic refinery and petrochemical processes. however, preparation of zeolites with higher sio2/al2o3 molar ratios such as zsm-5 requires either an increase of the amount of silica or partial removal of aluminium. the first alternative implies using an additional source of silica with high solubility, e.g. sodium silicate or silica sol as reported in the research works of khatamian and irani 2009, kovo et al., 2009. however, in the work of li et al., 2015, zsm-5 zeolite was synthesized directly from diatomite after calcination, but the synthesized zeolite has low quality which could be due to the presence of impurities such as article information abstract in this study, a highly siliceous zsm-5 zeolite with elemental silicon to aluminium ratio of 250 was synthesized using bularafa diatomite as silica source. the diatomite was used to produce silica sol which was used with alumina in the presence of organic template (tetrapropyl ammonium bromide, tpabr) to form zsm-5 under hydrothermal reaction at low temperature and atmospheric pressure in alkaline medium. the synthesized zsm-5 was characterized using x-ray diffraction (xrd), fourier transformation infrared spectroscopy (ft-ir), scanning electron microscopy (sem), n2 adsorption and x-ray fluorescence (xrf). the brunauer, emmet and teller (bet) method revealed that the zsm-5 produced from bularafa diatomite have very high specific surface area of 619 m2 g–1. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2019 revised 3 july, 2020 accepted 18 july, 2020. keywords: diatomite zsm-5 zeolite synthesis low temperature siliceous. http://www.azojete.com.ng yunusa et al.: characterization of synthesized zeolite socony mobile 5 (zsm-5) from bularafa diatomite. azojete,16(4):717-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 718 iron oxide, potassium etc. also, in the previous works zsm-5 took longer synthesis times up to seven days and above at elevated temperature. in this study, we synthesized a highly siliceous zsm-5 by using silica sol prepared from bularafa diatomite for the first time. 2.0 materials and methods 2.1 materials bularafa diatomite as a silica source was collected in lump from bularafa village in gubja local government area of yobe state. activated alumina (fused 99%, sigma, usa), pellets of sodium hydroxide (98 wt.%, sigma, usa), tetrapropyl ammonium bromide (tpabr) (sigma, usa), sulphuric acid (98 wt.%, sigma, usa) and distilled water were used as the starting materials in the initial mixture for the synthesis of zsm-5. 2.2 methods the bularafa diatomite was characterized using empyreal panalytic diffractometer x‟pert 3 with cu kα radiation (philips bw 1710, netherlands) for xrd and munipal 4 energy dispersedx ray fluorescence (ed-xrf, usa) machines and gas adsorption measurement with n2 (bet isothermal). the diatomite was treated with 1m hydrochloric acid (merck) to remove impurities such as iron and calcium before sodium silicate extraction. sodium silicate was extracted from acid treated diatomite following the methods of panda et al., (2004), mandal and benergee, (2004) and anjum et al., (2010). sodium silicate obtained was used in silica sol production via neutralization of alkaline sodium silicate solution with sulfuric acid (malewski et al., 2006; de sousa1 et al., 2009) and kalaphaty et al., (2000). 2.2.1 synthesis of zsm-5 from silica sol zsm-5 was prepared according to hydrothermal procedure as reported previously (lisensky et al., 2008). 1.2g of sodium hydroxide in 7.5ml of de-ionized water, 0.09g of an activated alumina was added with additional 0.1g of naoh pellets and mixture was stirred. then 1.2g tetrapropyl ammonium bormide was added to 0.51 ml of 96 wt. % of 1 m h2so4 and mixture stirred. the mixtures were simultaneously added to 25ml of silica sol prepared from kaolin in a polypropylene bottle and the mixture shaken vigorously for 5 minutes, and then the mixture was stirred vigorously for 30 minutes and then tightly closed. it was then aged in an oven at 95°c for 4 days. after 4 days, the polypropylene bottle was removed and the cap was opened and the liquid was carefully decanted manually. the solution was filtered using a filter paper, and the white solid was washed with de-ionized water several times until the ph is about 8. the solid product was dried in an oven at 100°c for 12hrs. the dried sample was calcined at 500°c for 2 hours using a gallen kamp 6b77a tube furnace in the presence of nitrogen. 2.3 zeolite characterization the calcined sample was analyzed using the following equipment, empyreal panalytic diffractometer (xrd), using cu kα radiation, x-ray fluorescence (xrf) by a munipal 4 energy dispersedx ray fluorescence (ed-xrf), phenom prox desktop (34250) sem, usa, and shimadzu 8400s spectrometer (ftir), japan. in addition, the specific surface areas of sample were measured by the brunauer, emmet and teller (bet) method using nitrogen adsorption– adsorption data were recorded with a quantachrome (novawin-data acquisition and reduction version 11.03) 2013 equipment, usa. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):717-724. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 719 3.0 results and discussion 3.1 xrd analysis of zeolite the xrd patterns of buralafa diatomite, diatomite based zsm-5 and referenced zsm-5 are shown in (figure 1) as illustrated in figure 1a, the xrd pattern of diatomite has a diffraction peak at 2θ of 26.7 with small amount of quartz and broad band of 2θ = 22-30° corresponding to amorphous silica as reported by li et al., 2015 and yi et al., 2006 respectively. this confirms that diatomite was amorphous originally. when figure 1(a) was compared to the xrd pattern of the synthesized zsm-5 in figure 1(b) a distinct peak at 2θ of 7.88, 23.23, 8.8, 23.63, 23.85 and 24.33˚ ascribing to zsm-5 were observed. it can be seen that figure 1 (b) compared well with xrd pattern reported by treacy and higgins, 2001 in figure 1 (c), since all the characteristic peaks of zsm-5 were observed in figure 1 (b) and no other unknown phase in the xrd patterns, this indicated that the synthesized powders were pure zsm-5 zeolite crystals. figure 1: xrd pattern of (a) diatomite (b) diatomite based zsm-5 and (c) reference zsm-5 3.2 fourier transform infrared (ftir) analysis ftir could help us understand the active sites and subsequently the mechanisms involved in zeolite catalysis. we know that the lattice vibrations characteristic to h-zsm-5 zeolite usually appear in the range of 400–1200 cm−1, while the bands corresponding to oh bond vibrations appear at wave numbers higher than 3200 cm−1 (shaik et al., 2015). figure 2 presents the ft-ir spectra recorded in the 4000–400 cm-1 range for diatomite based synthesized zsm-5. the ir spectra of zsm-5 zeolite showed general spectral features at 1221, 1092, 795, 548 and 448cm-1 which were assigned to different vibrations of tetrahedral and framework atoms in zsm-5 zeolite (ibraheem et al., 2012). the bands at about 1090 and 456 cm-1 are due to internal vibrations of (si, al)o4 tetrahedra of zsm-5, which are insensitive to framework structure. the other bands at about 1234, 800 and 557 cm-1 are due to vibrations related to external linkages between tetrahedra and hence sensitive to framework structure. the presence of infrared band around 557.45cm-1 for diatomite based zsm-5 indicated the characteristic vibrational modes of the zsm-5 zeolite framework. according to (shaik et al., 2015) the spectral bands appearing at 3450 and 3700 cm−1 in figure 2 may be attributed to the presence of hydroxyl groups in this zsm-5 (lercher et al., 1999), which may be responsible for catalyzing cracking (bhan et al., 2008; kotrel et al., 2000). the evidence for the formation of zsm-5 zeolite could be seen in figure 2 from the appearance of the bands at 557.45 and 1234.40 cm-1. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yunusa et al.: characterization of synthesized zeolite socony mobile 5 (zsm-5) from bularafa diatomite. azojete,16(4):717-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 720 figure 2: ftir spectra for bularafa diatomite based zsm-5 3.3 scanning electron micrograph (sem) analysis the sem technique was used to observe the crystals as shown in figures 3 (a), (b) and (c). it was observed that the sample was ellipsoidal in shape. the sizes of these samples were uniformly distributed and did not contain amorphous substances or other crystalline impurities as can be seen in the sem image of raw diatomite in figure 3a; (chaisena and rangsriwatananon, 2005). the uniformity in morphology of the synthesized zsm-5 suggested that good crystallization was obtained, as shown in the xrd pattern 1b. from the high-resolution sem micrographs (figure 3c), it was observed that the surface of the large particle was composed of many small crystals. these small primary crystals appeared to be tightly packed together to form the polycrystalline particles. figure 3: sem images for (a) raw diatomite, (b) zsm-5 from diatomite at low magnification (c) zsm-5 from diatomite at high magnification. 3.4 x-ray fluorescence (xrf) analysis chemical compositions of raw buralafa diatomite and diatomite based synthesized zsm-5 were determined using xrf technique as shown in table 1. it could be observed that zsm-5 synthesized from diatomite contained small impurities, this may be due to the acid treatment of the raw diatomite and preparation silica sol from the diatomite used, which greatly minimized http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):717-724. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 721 metal oxides contents such as fe2o3, cao, mgo and cuo. these oxides could also cause a decrease in bet surface area as observed in li et al., 2015 who recorded a low bet surface area of 223 m2 g-1 as compared to 619 m2 g-1 obtained in this work. the impurities reduce the surface area of the synthesized zeolite by filling up some of its pores. si to al ratio was another very important parameter that could be used to measure the catalytic activity of the zeolite and it was determined by the xrf analysis as shown in table 1. it could be seen that si to al ratio of diatomite based zsm-5 was 250. generally, si to al ratio of a zeolite determine its chemical and thermal stability, the literature value of si to al ratio of zsm-5 zeolite is from 10 to 500 (al-bogami, 2013). table 1: chemical analysis (xrf) of raw diatomite and zsm-5 from diatomite oxides raw diatomite (wt.%) zsm-5 from diatomite (wt.%) sio2 89.30 99.20 al2o3 0.62 0.35 cao 0.53 0.261 tio2 0.86 0.010 mno 0.007 0.006 fe2o3 5.73 0.095 cuo 0.063 0.023 k2o 0.46 loi 1.03 si/al 250 3.5 surface analysis of zsm-5 nitrogen adsorption-desorption data were recorded with a quantachrome (novawin-data acquisition and reduction version 11.03) 2013 equipment to determine the bet specific surface area (ssa), micro pore size and micro-pore volume of the synthesized zsm-5. the n2 adsorption isotherm of zsm-5 synthesized from buralafa diatomite is shown in figure 4. it was type i based on iupac’s classification with a large nitrogen uptake at low pressure and the desorption matched with the adsorption isotherms. also, the knee portion of the isotherm was higher indicating its higher surface area, as shown in table 2. the specific surface area (ssa) of the synthesized zsm-5 was determined using the bet techniques, while the micro-pore volume and pore diameter were determined using horvathkawazoe (h-k) and sato foley (sf) methods. the bet ssa obtained in this work for the sample prepared from bularafa diatomite was 619 m2/g which is two times more than that obtained in the study by aguilar -mamani et al., 2014 (298 m2/g), who employed leached diatomaceous earth directly as silica source. also, li et al synthesized zsm-5 using purified diatomite and sodium aluminate as silica and alumina sources respectively, where bet surface area of 223 m2/g was obtained as shown in table 2. both micro-volume and pore sizes of the synthesized zsm-5 were quite comparable with the ones got in the previous works of aguilar mamani et al. (2014), li et al. (2015) and al-bogami (2013) as indicated in table 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yunusa et al.: characterization of synthesized zeolite socony mobile 5 (zsm-5) from bularafa diatomite. azojete,16(4):717-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 722 table 2: texture properties of synthesized zsm-5 from diatomite using different methods a data are determined by applying the saito-foley method b data are determined by applying the horvath-kawazoe method c data are determined by applying the t-plot method figure. 4: n2 adsorption‐desorption isotherms of the synthesized zsm-5 from buralafa diatomite 4.0 conclusions the zsm-5 was successfully synthesized from bularafa diatomite via the hydrothermal process. the utilization of diatomite as inexpensive raw material for zsm-5 zeolite synthesis is remarkable. from the xrd result, it was observed that well crystalline zsm-5 was successfully synthesized from diatomite without using additional silica source. sem images of the zsm-5 also confirmed uniform particles distribution. in addition, ftir analysis showed that the zsm-5 were pentacyclic with typical absorption band at about 550 cm-1. the bet method revealed that the zsm-5 produced from bularafa diatomite have very high specific surface area that is suitable for zeolite application. also, the zsm-5 had least metal oxide impurities due to the acid treatment carried out on the buralafa diatomite which has greatly reduced the metal oxides. samples bet surface area median pore micro pore reference (m2g-1) diameter (nm) volume (cm3g-1) assynthesized zsm-5 from bularafa diatomite 619 0.45a 0.013a this work assynthesized hzsm-5 from kaolin 411 0.61b 0.12c al-bogami, 2013 assynthesized zsm-5 from diatomite 223 0.54 0.06 li et al., 2015 assynthesized zsm-5 from bolivian diatomite 298 0.15 aguilar-mamani et al., 2014 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):717-724. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 723 acknowledgments the authors gratefully acknowledge the petroleum technology development fund (ptdf), abuja-nigeria, for supporting this research work. references al-bogami, sa. 2013. catalytic conversion of benzothiophene over a h-zsm-5 catalyst reactivity and a kinetic model. ph. d thesis in school of graduate and postdoctoral studies, department of chemical and biochemical engineering university of western ontario london, ontario, canada. aguilar-mamani, w., garcíal, g., hedlund, j. and mouzon, j. 2014. comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of zsm5. springerplus journal, 3: 292. aliev, am., mamedova, ua., samedov, kr., sarydzhanov, aa. and agaeva, ry. 2011. synthesis and physicochemical study of zsm-5 high-silica zeolite from natural raw materials. russia journal physical chemistry, a 85:288–292 anjum, f., bhatti, hn., asgher, m. and shahid, m. 2010. leaching of metal ions from black shale by organic acids produced by aspergillus niger. applied clay science, 47(3-4): 356-361. arik, h. 2003. synthesis of si3n4 by the carbothermal reduction and nitridation of diatomite. journal european ceramic society, 23: 2005-2014. bakr, hegmm. 2010. diatomite: its characterization, modifications, and applications. asian journal of material science, 2: 121–136. doi: 10.3923/ajmskr.2010.121.136. chaisena, a. and rangsriwatananon, k. 2005. synthesis of sodium zeolites from natural and modified diatomite. materials letters, 59(12): 1474-1479. chiarakorn, s., areerob, t. and grisdanurak, n. 2007. influence of functional silane on hydrophobicity of mcm-41 synthesized from rice husk. science and technology of advanced materials, (8): 110-115. de sousa, a.,visconte l.,mansur, c. and furtado, c. 2009. silica sol obtained from rice husk ash. chemistry & chemical technology, 3(4): 321-326. fernandes, aa., frajndlich, eu. and riella, hg. 2005. a low cost zsm-5 zeolite obtained from rice hull ash. materials science forum, 498-499: 676-680. habeeb, ga. and mahmud, hb. 2010. study on properties of rice husk ash and its use as cement replacement material. materials research, 13(2): 185-190. hossain, sks., lakshya, ma. and roy, pk. 2018. rice husk/rice husk ash as an alternative source of silica in ceramics: a review. journal of asian ceramic societies, 6(4): 299-313. khatamian. m. and irani, m. 2009 preparation and characterization of nanosized zsm-5 zeolite using kaolin and investigation of kaolin content, crystallization time and temperature changes on the size and crystallinity of products. journal of iran chemical society, 6:187-194. kalapathy, u., proctor, a. and shultz, u. 2000. a simple method for production of pure silica from rice hull ash. bioresource technology, 73: 257-262. kovo, as., hernandez, o. and holmes, sm. 2009. synthesis and characterization of zeolite y and zsm-5 from nigerian ahoko kaolin using a novel, lower temperature, metakaolinization technique. journal material chemistry, 19: 6207-6212. lercher, ja., grundling, c. and eder-mirth, g. 1996. infrared studies of the surface acidity of oxides and zeolites using adsorbed probe molecules. catalysis today, 27(3-4): 353–376. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng yunusa et al.: characterization of synthesized zeolite socony mobile 5 (zsm-5) from bularafa diatomite. azojete,16(4):717-724. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: slmnyunus@gmail.com 724 lisensky, g. and blitz, i. 2010. preparation of zeolite zsm-5 and catalysis of xylene isomerization. 2008 the board of regents of the university of wisconsin system, madison. li, y., sun, h., feng, r., wang, y., subhan, f., yan, z., zhang, z. and liu, z. 2015. synthesis of zsm-5 zeolite from diatomite for fluid catalytic cracking (fcc) application. applied petrochemical research, 5: 347-353. doi 10.1007/s13203-015-0113-2. mandal, sk. and benerjee, pc. 2004. iron leaching from china clay with oxalic acid: effect of different physico-chemical parameters. international journal mineral processing, 74 (1-4): 263270. malewski w., krysztafkiewicz a. and jesionowski t. 2006. preparation of polysilic acid sols by ion exchange method. physicochemical problems of mineral processing, 40: 265-273. mohammed, mm., zidan, fi. and thabet, m. 2008, synthesis of zsm-5 zeolite from rice husk ash: characterization and implications for photocatalytic degradation catalysts. microporous and mesoporous materials, 108: 193-203. panda, ak., mishra, bg., mishra, dk. and singh, rk. 2010. effect of sulphuric acid treatment on the physico-chemical characteristics of kaolin clay. colloids and surface a: physicochemical and engineering aspects, 363 (1-3): 98-104. shen, j., liu, js., zhu, s., zhang, t. and tan, j. 2011. effects of calcinations parameters on the silica phase of original and leached rice husk ash. materials letters, 65: 1179-1183. treacy, mmj. and higgins, jb. 2001. collection of simulated xrd powder patterns for zeolites 5th revised edition. elsevier science publishers, new york http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):813-820 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 813 original research article structural efficiency of concrete containing crushed bone aggregates j. o. akinyele*, h. a. kehinde and u. t. igba department of civil engineering, federal university of agriculture, abeokuta, nigeria *corresponding author’s email address: olawaleakinyele@gmail.com 1.0 introduction the use of waste material as a partial replacement of aggregates in concrete has been investigated in recent years by many researchers (igba et al., 2019). materials such as rice husk, groundnut and palm kernel shell, corncob, sawdust etc. have been successively used in concrete to replace either cement or coarse and fine aggregates (sada et al., 2013; otunyo et al., 2011). the use of both plant and animal waste in building materials has helped in the recycling of these waste materials for the benefit of the environment, most of these materials have resulted in the production of lightweight concrete (akinyele et al., 2016a). the combination of coconut shell and grained palm kernel shell was investigated as lightweight aggregate in concrete production by tukiman and sabarudin (2009). otunyo et al., (2014) also studied the use of crushed periwinkle shell as a partial replacement for fine aggregates in lightweight concrete, the concrete produced from the research was proposed for use in the support of light loads. the outcome of all these researches showed that agricultural waste materials are good substitutes to aggregates in light weight concretes. akinyele et al. (2016b) also used waste tire rubber, a non-biodegradable material to replace fine aggregate in the production of lightweight concrete, the mechanical test carried out on the concrete samples showed that 16% waste tire rubber in concrete will conveniently produce a grade 15 concrete. falade (1990) used sawdust ash as partial replacement of cement in bricks and found out that the addition of this material reduces the compressive strength of bricks. in another study, raheem and sulaiman (2016) investigated the partial replacement of cement with sawdust and saw dust ash (sda) in sandcrete blocks. hollow blocks were moulded and cement was partially replaced with 5% to 25% by weight of sda, using vibrating block moulding machine. the blocks produced were tested to determine their density, compressive strength and water article information abstract the indiscriminate dumping of animal waste, especially cow bones in abattoir has brought about the need for adequate safe disposal and recycling of such waste. this study investigated the use of crushed bones as a partial substitute for fine aggregate and its efficiency in concrete structures. sieve analysis test was conducted on the crushed bone and used as partial replacement of fine aggregate in concrete at 0, 25, 50, 75, and 100% by weight. slump test on the fresh concrete was investigated, while the density, compressive strength test and structural efficiency of the hardened concrete were also determined. the sieve analysis result revealed that the crushed bone was poorly graded, and the slump test showed that the 25% of crushed bone concrete has a low slump. the density was 2370 kg/m3, the compressive strength was 17.10n/mm2 at 28 days, while the structural efficiency was 7.22. the 50, 75 and 100% samples has compressive strength of 16 n/mm2, 6.10n/mm2 and 4 n/mm2 at 28 days respectively and these values are far below expectations. the work concluded that crushed bones could partially replace fine aggregate in lightweight concrete at not more than 25% by weight. this test is limited to a short-term test of 28 days. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 september, 2020 revised 23 november, 2020 accepted 24 november, 2020 keywords: crushed bone waste poorly graded structural efficiency slump test mailto:olawaleakinyele@gmail.com http://www.azojete.com.ng akinyele et al: structural efficiency of concrete containing crushed bone aggregates. azojete,16(4):813-820. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 814 absorption rate. the results indicated that compressive strength of sandcrete hollow blocks at 28 days were 2.16 n/mm2, 1.94 n/mm2, 1.64 n/mm2, 1.59 n/mm2, 1.39 n/mm2, and 1.25n/mm2 for 0%, 5%, 10%, 15%, 20% and 25% sda contents respectively. at 56 days, the compressive strength of blocks with 5% and 10% sda replacement were 2.33 n/mm2 and 2.04 n/mm2 respectively, both of which surpassed the required standard of 2.00 n/mm2 specified by the national building code (2006). cow bones constitute a big nuisance in abattoirs all over the world where cattle are slaughtered for human and industrial consumption. heaps of cow bones are usually worminfested and developed foul odour wherever they were dumped. thousand tons of waste animal bones are produced annually providing scope for its small-scale utilization in the construction industry. therefore, an effort has been made by this work to utilize these bones (crushed) to study the effect of animal bones on the production of lightweight concrete. opeyemi and makinde (2012) have studied the replacement of cement by rice husk ash (rha) and bone powder (bp) in concrete structures. the replacement of cement with these materials varied from 5% to 20% in a mix of 1:2:4. cubes were casted, and the results showed that workability was consistent within the described values for lightweight concrete. the substitution of cement with the mixture should not be more than 10% in the production of concrete structures. akinyele et al., (2016b) partially replaced cement in concrete at 5, 10, 15, 20 and 25% with both bone and wood ashes. chemical analyses were carried out on both the wood and bone ashes to determine their pozzolanic properties while the compressive strength test was conducted on the concrete obtained from both cement replacements. the chemical analysis revealed that the bone ash is a better pozzolana when compared to the wood ash. the compressive strength test showed that wood ash is not a good material for replacing cement in concrete, while 10% of bone ash can partially replace cement in concrete at 28 days compressive test. the structural efficiency of engineering materials is the ratio of the applied load at the failure to the density of the material (akinyele et al., 2019). the structural efficiency of some engineering materials has been investigated before now; the structural efficiency of burnt bricks made from the use of waste glass, polyethylene terephthalate (pet) and polypropylene granules was investigated by akinyele et al. (2020a, and 2020b,). these materials were found to perform better at a certain percentage. the advantage of determining the structural efficiency is to get a material that can support loads at a very low density. this study aims to determine the structural efficiency of concrete containing crushed bones that have been used to partially replace fine aggregates. 2. experimental analysis 2.1 materials the bone was collected from odo-eran abattoir in abeokuta. the cow bones were washed, cleaned and sun-dried in open field for three weeks where flesh and dirt were removed. it was then broken down into smaller pieces with a medium-sized hammer. the broken pieces of bone were then taken to agricultural and bio-resources workshop at funaab where it was crushed to fine aggregates using a locally fabricated hammer mill machine. the sieve analysis test was carried out on the crushed bones to determine its particle size distribution. the coefficient of uniformity (cu) and coefficient of curvature (cc) were determined using equations 1 and 2 respectively from a plotted graph. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):813-820. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 815 (1) (2) the d10, d30, and d60 are the tenth, thirtieth and sixtieth percentiles on the graph respectively. limestone portland cement (lpc), grade 42.5r locally available in nigeria in 50 kg bags was used for the experiment. potable water from the civil engineering laboratory of the federal university of agriculture was used to prepare the concrete. crushed granite stone was obtained from a quarry in abeokuta, ogun state, nigeria. the fine aggregate used was quarry stone dust. the bs 1881 108 (1983) was adopted in the preparation of concrete cubes. 2.2. casting of concrete the crushed bone aggregates were used as partial replacement of fine aggregates in concrete at 0, 25, 50, 75 and 100%, and these samples were designated as c0, c25, c50, c75 and c100 respectively, the concrete target strength of 20 n/mm2, with a water/cement ratio of 0.65 was used. the process of casting started by measuring and weighing the concrete aggregates in their various proportions by weight. the aggregate was mixed thoroughly by hand on a sampling tray and segregation of the aggregates was strictly avoided. the 150 mm x 150 mm 150mm mould was primed with oil and placed on a flat surface and filled with the freshly prepared concrete. pouring was in layers and each layer tamped with compacting bar with 35 strokes for the 150mm cubes. the test cubes were removed from moulds after 24 hours and cured in water at room temperature of about 23 + 20c. each cube was marked for identification and submerged immediately into the water at room temperature. the casting of the concrete followed the procedures of bs 1881 108 (1983). 2.3 workability of the concrete workability is the amount of useful internal work required for full compaction. it highlights the case of working and ease of handling concrete from mixing point to compaction level. the slump test is the most commonly used method to determine the workability of concrete. the slump test was carried out on a freshly prepared concrete to determine its workability. equipment used for the work are slump cone, tamping rod, hand trowel, sampling tray, shovel, and rule graduated from 0 to 300 mm. the inner surface of the slump cone was cleaned, dried and the bottom of the cone was placed on a clean, smooth and horizontal surface. while holding the cone, it was filled with fresh concrete within two minutes after mixing. the slump cone was filled in three layers with each layer at approximately one-third of the total height of the cone when tamping. each layer of the concrete was uniformly tamped with a tamping rod with 25 strokes each. the concrete above the slump cone was heaped before the top was tamped. after tamping the top, the concrete level was stripped off with stamping rod. with the slump cone still held down, the surrounding of the slump cone was cleaned. the slump cone was removed vertically, slowly and carefully within 5 to 10 seconds. the slump was measured immediately after removal to determine the difference between slump cone and specimen. this test was carried out following bs en 12350 (2000). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akinyele et al: structural efficiency of concrete containing crushed bone aggregates. azojete,16(4):813-820. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 816 2.4 compressive strength of concrete cube the compressive test was done following bs 1881:108 (1983) standard and the objective of the test is to determine the specific strength of concrete. the equipment used for the test are compression testing machine (compact machine) and weighing balance with a minimum of 10kg capacity. the process began by weighing the concrete cube and recording the dimension of the concrete cube. the cube was carefully centered in between the upper and lower plate of the machine to ensure that the load is applied to the two opposite cast faces of the cube. the calibrated screen of the machine was zeroed and the load was applied until no load can be sustained by the concrete cube and failure began to show. the density of the concrete cube was also determined from the average weight of the concrete cube weighed with the weighing balance. 3. results and discussion 3.1. particle size analysis of crushed bone. figure 1 shows the particle size distribution for the crushed bone. the particle size distribution curve for the crushed bone has a semi-steep curve, indicating a type of aggregate containing particles of almost the same size. any clean aggregate with less than 5% fines, with grading requirements of cu (coefficient of uniformity) greater than 6 and cc (coefficient of curvature) greater than 1 but less than 3 is a well or uniformly graded aggregate. from the results obtained in equations 1 and 2, the crushed bone particles have cu of 4.4 and a cc of 1.88. the cc value is within the recommended range, but the cu is less than the recommended value of 6, astm d2487 (2006). hence, it can be concluded that the crushed bone particles are poorly graded and this type of graded materials are good for aggregates in concrete. figure 1: sieve analysis result for crushed bone. 3.2 slump of concrete samples result for the slump carried out is shown in figure 2 which comprises the workability for the varying additions of bone and fine aggregate in concrete. it was observed that all the concrete samples slump evenly. that is they had a true slump during the test period, indicating that that the entire sample had good consistency properties. but from figure 2, the slump value decreased as the percentage of crushed bone increased in the concrete mix. the c0 concrete mix gave a slump of 35 mm, while the c25, c50, c75 and c100 gave slump values of 27 mm, 14 mm, 9 mm and 7mm, respectively. the implication of this is that the c0 and c25 concrete samples had a low slump. if the concrete is to be transported to a distant site, the water-cement ratio would have to be increased so that the slump and workability can be increased before pouring. this is a very http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):813-820. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 817 good result as a low slump is good for hand-vibrated machines for rigid pavement in road construction and good for mass concrete foundations without vibration or lightly reinforced section with vibration. the c50 – c100 mix showed a very low slump of between 14 and 7 mm. this type of concrete will require power operated vibration machine, and transportation to a distance site may not be advisable. the very low slump, especially in all the crushed bone samples, can be attributed to the absorption of water by the bone particles in the concrete mixture; since the crushed bone was dry, its affinity with water was high within the concrete environment hence the almost dry concrete obtained. figure 2: variation of slump values with crushed bone replacement 3.3 compressive strength the variation of compressive strength with crushed bone percentage for each concrete sample is shown in figure 3. the general trend is that the compressive strength reduces as the percentage of crushed bone increases in the concrete mix. the ultimate strength for control specimen (c0) is more than that of the c25 specimens by over 6 n/mm2 at 28 days, while the c50 mix is lower than the control by 7 n/mm2. however, for total crushed bone concentrations greater than 50%, the ultimate strength results were much lower than the half of the strength for the control samples at 28 days. the systematic reduction of ultimate strength in crushed bone concrete might restrict the use of the concrete, with bone concentrations exceeding 50%, in structural applications. the reduction in compressive strength can be attributed to the decrease in the bonding between the bone particle and cement, also the absorption of water by the crushed bone contributed to this trend. the pattern of reduction of strength as bones were added to concrete in this research is similar to what was obtained by fapohunda et al., (2016), where the strength characteristics of varying water-cement ratio in concrete mixed with crushed bones was investigated. aci 213 (1999, 2003) recommended a minimum 28 days compressive strength of 7 n/mm2 for lightweight concrete (lwc), while bs 8110 (1997) required a minimum 28 days compressive strength of 15 n/mm2 for concrete to be used as reinforced concrete and a minimum 7 n/mm2 for plain concrete and these were confirmed by akinyele et al., (2016) when they produced lightweight concrete from waste tire rubber crumb. the results from the entire test specimen showed that crushed bone can be used to replace fine aggregate in lightweight concrete by up to 50%, since the least 28 days compressive strength obtained was 16 n/mm2, which is greater than the recommended values. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akinyele et al: structural efficiency of concrete containing crushed bone aggregates. azojete,16(4):813-820. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 818 figure 3: variation of compressive strength with crushed bone percentage 3.4 density and structural efficiency the structural efficiency of the control was used to determine the efficiency of other materials, the efficiency of the control will be taken as the ultimate value. if the efficiency of any other samples is not less than 70% of the control, then that particular sample can be said to be structurally efficient (akinyele et al., 2020a). the densities of each concrete mix were determined on each day of the compressive strength test, figure 4 showed the variation in concrete densities. all the concrete samples showed a decrease in bulk density with increase in bone particles. all the concrete samples maintain a varying density of between 1985–2400 kg/m3 which qualifies those above 2300 kg/m3 as normal-weight concrete, while those below this value can be classified as lightweight concrete. the density of concrete also depends on the degree of compaction of the samples during casting. the values of the structural efficiency of each concrete sample are shown in table 1. structural efficiency is the ratio of compressive strength to density, and this determines how effective a structural member will perform during its lifetime. the efficiency of the control sample was compared with all the samples, the c25 and c50 samples were very close at about 74.97% and 74.76% respectively, while samples c75 and c100 gave 29.69% and 20.97% respectively, these are very low values for the last two sample. the results showed that samples c25 and c50 has structural efficiency greater than 70% benchmark, hence the two samples are structurally good, for engineering purpose. table 1: structural efficiency of concrete samples concrete sample density (kg/m3) structural efficiency (x 103m) c0 2400 9.63 c25 2370 7.22 c50 2222 7.20 c75 2133 2.86 c100 1985 2.02 4. conclusion the use of crushed bone particles as partial replacement (at 5%) of fine aggregate could improve some properties of the concrete. the particle size distribution revealed that the particles are not uniformly distributed which is an advantage for aggregate in concrete production. the slump and compressive strength tests showed that the concrete could perform well as lightweight concrete. the structural efficiency of the c25 and c50 samples achieved good results above the 70% benchmark. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):813-820. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 819 references aci, 213. 1999 guide for structural lightweight aggregate concrete, aci committee 213, american concrete institute, farmington, hills, mi, usa.. aci, 213. 2003. guide for structural lightweight aggregate concrete, aci committee 213, american concrete institute, farmington, hills, mi, usa. akinyele jo. adekunle aa. and ogundaini o. 2016a. the effect of partial replacement of cement with bone ash and wood ash in concrete. annals of faculty engineering hunedoara international journal of engineering, 14 (4): 199-204. akinyele, jo., salim rw. and kupolati wk. 2016b) production of lightweight concrete from waste tire crumb. engineering structures and technologies, 8(3): 108-111. akinyele, jo., akinwande, om. and igba ut. 2019. the use of pet pellets in cement stabilized compressed earth bricks. advances in engineering materials, structures and systems: innovations, mechanics and applications, 1631-1635. (ed). alphonse zingoni. akinyele, jo., igba, ut., ayorinde, to. and jimoh, po. 2020a. structural efficiency of burnt clay bricks containing waste crushed glass and polypropylene granules. case studies in construction materials, (13): 1-11. akinyele, jo., igba, ut. and adigun, bg. 2020b. effect of waste pet on the structural properties of burnt bricks. scientific african, (7): 1-8. astm d2487. 2006. standard practice for classification of soils for engineering purposes (unified soil classification system). astm committee d18. astm international, usa. bs 8110. part 1. 1997. structural use of concrete. british standard institution, london. bs 1881. part 108. 1983. method for making test cubes from fresh concrete. british standard institution, london. bs en 12350-2. 2000. testing fresh concrete. slump test. british standard institution, london. fapohunda, ca., shittu, ka., aderoju, so. and akinsanya, ay. 2016. strength characteristics of concrete having crushed bone as partial replacement of fine aggregates at different watercement ratios. acta tehnica corviniensis, bulletin of engineering, 9 (1): 163-169. falade, f. 1990. effect of sawdust ash on the strength of lateralized concrete. west indies journal of engineering, (1): 71-85. falade, f. 1992. the use of palm kernel shells as coarse aggregate in concrete. journal of housing science, 16 (3): 213-219. igba, ut., ehikhuenmen, so., akinyele, jo., osaghale, mo. and oyebisi, so. 2019. the effect of partial replacement of nigerian portland limestone cement with rice husk ash agricultural waste in concrete. 1st international conference on sustainable infrastructural development iop conference series: materials science and engineering, 24 -28 june, 2019, covenant university, canaanland, ota, nigeria, 640 012041: 1-7, doi: 10.1088/1757-899x/640/1/012041. national building code (2006). building materials and component requirements. lexisnexis butterworths, durban 215 north ridge road, morningside, 4001. s.a. otunyo, aw., friday, iu. and israel ta. 2014. an exploratory study of the crushed periwinkle shell as a partial replacement for fine aggregate in concrete. scientia africana, 13(1): 151-159. opeyemi, da. and makinde, oo. 2012. the suitability of partial replacement of cement with rice husk ash and bone powder in concrete structures. international journal of emerging technology and advanced engineering, 2(9): 261-265. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng akinyele et al: structural efficiency of concrete containing crushed bone aggregates. azojete,16(4):813-820. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olawaleakinyele@gmail.com 820 otunyo, aw., nuaka, b. and faith, j.c. 2011. combination of palm kernel husk ash (pkha) and free lime (cao) as an admixture in concrete production. nigerian journal of technology, 30(1): 64-71. polat, r., demirbo, ar., karakoc, mb. and turkmen, i. 2010. the influence of lightweight aggregate on the physical-mechanical properties of concrete exposed to freeze-thaw cycles. cold region science and technology, 60: 51-56. raheemm, aa. and sulaiman, ok. 2013. sawdust ash as a partial replacement for cement in the production of sandcrete hollow blocks. international journal of engineering research and applications, 3(4): 713-721. sada, bh., amartey, yd. and bako, s. 2013. investigation into the use of groundnut shell as fine aggregate replacement. nigerian journal of technology, 32(1): 54-60. tukinam, sa. and sabarudin, bm. 2009. investigation of the combination of coconut and grained palm kernel to replace aggregate in concrete: a technical review. national conference on postgraduate research (ncon-pgr), 1st of october. centre for graduate studies, university malaysia, pahang, pp. 49-58 http://www.azojete.com.ng cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 161-167 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng _____________________ *corresponding author email address: samtaimos@gmail.com 161 original research article fabrication of manual materials handling mechanism for lifting and feeding of cassava mash t. m. samuel1, o. o. aremu2, l. i. onu2, s. e. adegbite2, a. a. olokose2 and o. p. kolawole3 1dept. of agricultural and mechanical engineering, olabisi onabanjo university. ago-iwoye. nigeria 2dept. of project development and design (engineering) federal institute of industrial research oshodi (fiiro) lagos, nigeria 3international institute for tropical agriculture (iita) ibadan, nigeria article information received october, 2018 accepted december, 2018 keywords: lifting device manual material handling gari-frying ergonomic risk factor industrial operations abstract manual materials handling (mmh) devices like jigs and fixtures are required for transporting or positioning materials in large-scale operations. an mmh device was designed to feed cassava mash into fry pan during batch gari-frying. flow is facilitated through the tapered outlet of a 40 kg-capacity hopper while lifting is achieved by turning a triple-start screwed shaft handle, housed in a u-steel channel framework with wide rigid base that can support holding content in position without buckling. feeding is done until the content is exhausted ready for reloading. it can deliver more than 160 kg/hr depending on the fry pan capacity and working rate. the worker avoids stretching, bending and twisting the trunk or the neck, or move round more frequently for reloading, thus overcoming the stated ergonomic risk factors and slowness of the work process. the device is also adaptable to other tasks requiring similar feeding mechanism. ©2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved 1.0 introduction manual materials handling (mmh) is a component of many jobs and activities undertaken in life. typically, it involves lifting, lowering, pushing, pulling and carrying objects by hand. loading and unloading trucks, carts, boxes or crates; moving parts or assemblies from one place to another; loading paper to the copier or picking binders from an overhead shelf; lifting patients from a bed or transporting them in a wheelchair are typical mmh activities found in work settings. in the gari-frying task, the work involves mainly collecting the grated cassava mash and pouring into the fry pan, fried/cooked while stirring and then discharge for bagging. whether in sitting or standing posture during loading of the fry pan, the processor often bends, stretches and twists to get the mash usually by her side, then turns to pour into the fry pan. she does this for all batches required to be fried. similar activity is involved in other unit operations prior to frying – peeling, washing, grating, pressing/dewatering, and pulverizing which results in rapid fatigue and body http://www.azojete.com.ng mailto:samtaimos@gmail.com samuel, et al. fabrication of manual materials handling mechanism for lifting and feeding of cassava mash. azojete, 14(sp.i4):161-167. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 162 discomfort. the one thing all these tasks have in common is the potential to result in some adverse health effect, from simple cuts, bruises and sore muscles to more serious occupational health diseases of low back pain (lbp). based on available statistics, almost half of all low back injuries are related to lifting, about another 10 per cent are associated with pushing and pulling activities, and another 6 per cent occur while holding, wielding, throwing or carrying materials (kadikon and abdol rahman, 2016). mmh tasks can be found in most workplaces and they may constitute a risk factor for work-related musculoskeletal disorders (wmsds) – mohammadi et al, (2013) ziaei et al, (2017) assessed the postural risk and imposed forces due to manual handling and loading of sugar bags. the study was conducted on male warehouse workers of a sugar manufacturing plant using rapid upper limb assessment (rula) to assess the risks of awkward postures using computer-aided three-dimensional interactive application to estimate the forces and moments. rula final scores were estimated to be 7 and 3 before and after the virtual redesign, respectively. they identified the main risk factors as heavy weight and poor control of sugar bags. they posited that virtual redesign can diminish bending and twisting postures, and, therefore, some resulting forces and moments. material handling is the movement of material in any direction both vertically and horizontally. in the selection of material handling equipment, a systems approach with the aim of attaining the lowest overall cost for the system as a whole should be adopted. this allows for a trade-off of initial and operating costs, and higher costs in some parts of a system for lower costs in other parts. the net result is usually the lower costs. hence, the objectives or requirements of materials handling are to save money, save time and save labour by using better methods and equipment (rene et al, 2017). igbeka (2013) emphasized the need to mechanize as many material handling operations as possible, if the operation itself cannot be eliminated. for efficiency, there should be a good plant layout. according to him, an efficient plant layout might eliminate many material handling operations or improve them. typical arrangements of plants include provision for receiving, disposing, processing and conveying. he further categorized factors that will influence plant layout to include methods of operation, lighting and human factors engineering nourani et al (2017) designed a harvesting aid, a portable dates cluster harvesting machine comprised of stabilizing platform, lifting device, lowering device and cutting device. the lifting device is a telescopic mast extendable with the use of reel and cables actioned by two manual winches and supported by the platform with two mobile joints to make it mobile and fixable. the device is used to raise and lower the cutting device and the basket made of metal ring holding a textile bag, mounted through the basket support at the upper end of the telescopic mast, while the cutting device equipped with a return spring and a draw wire, consists of a rechargeable electric chainsaw mounted on an articulated arm. this is mounted at the upper end of the basket support. choi et al (2012) examined physical workloads associated with manual lifting activities and translated the academic research into effective prevention “good practices” for the reduction of injury risks in the construction workplace, using fourteen different construction trades. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):161-167. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 163 mohammadi et al (2013) determined prevalence of msds in iraninan casting workers who performed mmh tasks, using nordic musculoskeletal disorders questionnaire and the snook tables. his results showed that hand/wrist symptoms were most prevalent (84%). he, therefore, recommended redesigning the mmh tasks to reduce the identified wmsds among workers. harvested cassava root cannot be stored for too long; it perishes soon after harvesting and mass processing into storeable products is the best way to extend the shelf life of the root. arching, caking and segregation are commonly encountered flow problems in the pulverizing and sieving. they quantified the flowability of cassava mash on the basis of angle of repose of 28o at a moisture content of 73% (wet basis) while the pulverized mash with moisture content of 45% (wet basis) had an angle of repose of 49o. they posited that the angle of repose of cassava mash is moisture content dependent (kolawole et al, 2010, 2014). loading constitutes problems in the sense that the processor has to improvise sometimes using a bowl containing less than 40kg of cassava mash. the processor goes through these problems culminating in fatigue due to the ergonomic risk involved. a lifting devise that would hold the load in position for a longer period, eliminate the risk of frequent movement in loading the fry pan, is what is needed for this task. this material handling devise is designed and fabricated to fulfill this purpose. 2.0 materials and methods 2.1. requirements for feeding mechanism for the gari-frying task from the research conducted during pilot study, it was discovered that the gari-frying process material handling task could be divided into three main tasks excluding the activities that took place before and after frying which were mostly transportation, cooling, sifting and packaging activities. these tasks include loading, stirring and unloading. 2.1.1. loading this is the stage during which the grated cassava mash would be poured into the pan for frying. this task continues as long as there is still cassava mash available for frying. normally for a batch, about 4-5 scoops are poured into the pan for frying depending on the size of the pan. 2.1.2. stirring this is the stage that usually comes after loading. it requires a continuous turning process of the gari in the pan while frying so as to avoid caking. this continuous process requires stirring for the period a particular batch in the pan would last to cook and dehydrate. 2.1.3. unloading this is similar to the loading task, but it involves removal of the fried gari from the pan into a container. the aspect being investigated in this study is that of loading, using mmh method instead of the traditional way of using bowl or other handy container to do it. ../../../user/downloads/azojete143/www.azojete.com.ng samuel, et al. fabrication of manual materials handling mechanism for lifting and feeding of cassava mash. azojete, 14(sp.i4):161-167. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 164 3.0 components of lifting/loading device. 3.1. hopper geometrically, the hopper is cuboidal trapezium (topmost part is cuboid, bottom part is trapezium). it is made of stainless steel sheet metal. the choice of the shape is informed by its flow characteristic such that the hopper would easily empty its content into the inlet end of the fry pan wherein the hopper gate opens for feeding the content in a bid to control the feeding of the fry pan. the hopper is situated on the frame via a u-steel channel framework with base. the hopper and its content is held in a vertical position using a triple-start screwed shaft with handle which the worker turns (anti-) clockwise to cause up-and-down movement. capacity of hopper is calculated as follows: volume of the cuboid part = 550 x 400 x 348 = 76,560,000 mm3 = 0.76,560,000 m3 volume of the trapezoidal part = 210 (400+550)/2 = 99,750 mm3 = 0.00099750 m3 total volume of the cuboid trapezoid hopper = 0.76560000 m3 + 0.00099750 m3 = 0.076659750 m3 bulk density of cassava mash = 553 kgm-3 (kolawole et al, 2014) mass of the hopper = density x volume = 0.076,659,750 x 553 = 42.396 kg ≈ 40 kg, since the hopper is not expected to be loaded to the brim at work for safe work ethics. note that hopper shape and the outlet was specially designed to aid ‘free-flow’ of the cassava mash which is controlled through the gate for each batch. 3.2. the frame the frame holds the hopper in position. the triple-start screw shaft, supported by the frame, lifts hopper content with a handle at the top for the processor to turn for the lifting operation after loading. it has a strong base to sustain the content of the hopper. this is made from 50 x 50mm uchannel and covers an area of 570 x 850mm and 1105mm high. the shaft which bears the hopper is held in-between two bearings within which it rotates to lift or lower the hopper. provision for additional loading of weight was made at the base for balance and stability. there are supports at the side edges to hold the hopper rigidly in position. figure 1 and plate1 show the loading/lifting device. the height was made to suit the sit-stand posture of the gari-frying workers. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):161-167. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 165 figure 1: lifting device plate 1: lifting device 3.3. lifting/lowering mechanism this consists of a threaded shaft machined and erected on pillow bearings and supported by 12 mm diameter mild steel rod on both sides at the “cantilever” side of the hopper. ../../../user/downloads/azojete143/www.azojete.com.ng samuel, et al. fabrication of manual materials handling mechanism for lifting and feeding of cassava mash. azojete, 14(sp.i4):161-167. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 166 the advantage of this is in its high capacity hopper and the lifting activity that relieves the worker of unnecessary frequent movements and stress in lifting the material from the floor onto the platform as well as in having to reload the hopper often. all this add to the efficiency of the worker since this device delays the onset of fatigue unlike in the traditional method of directly manual loading. 4.0 description of the operation of the lifting device the setting of the lifting hopper is at the floor (base of the frame) from where it is loaded with materials and then conveyed up the frame by anticlockwise turning of the handle at the top of the frame. positioned close to the processor’s seat and the fry pan to be supplied, the hopper is stopped at a height where the outlet of the hopper levels with the fry pan into where it discharges its content. this holds the content which is discharged for each batch of the frying operation when the gate provided is opened and closed for a batch operation. this hopper is designed to hold content more than required for one batch, say for five rounds or more, to minimize the frequency of loading and reloading, lowering and lifting. this process thus saves time and movement of the processor, who may have to complete five batches or more without having to reload, hence once discharge is made easy for the content to flow down a slopy framework provided at the other end of the fry pan, into which the processed cassava mash is emptied, the next batch is allowed into the fry pan without wasting time as in the traditional method where the processor may move from the seat to load the next batch. all that is required is to open the gate and let in the next cassava mash for the frying process. 5.0 conclusion a 40 kg capacity lifting device for feeding cassava mash into fry pan has been designed and constructed. components include hopper, u-steel channel frame, triple-start screwed shaft with handle for up-and-down lifting on a wide rigid base, counterbalanced with weight. using locally made materials and with simple construction, this has been made to assist the operator in manual feeding of the cassava mash into the fry pan. the simple operating principle of the mechanism and construction makes it possible to be replicated by artisans in the rural areas where this equipment is needed. the lifting device creates higher efficiency for the worker through efficient means of supplying materials as soon as possible as well as allowing more number of batches (5 times or more) to be done without unnecessary movement, transportation compelled to be in an awkward posture (bending, twisting or stretching) usually experienced before reloading the hopper. this saves time and preserves the health of the worker with the overall advantage of improved productivity. this equipment is also adaptable to other jobs with similar job flow. 6.0 acknowledgment the federal institute of industrial research oshodi (fiiro) is hereby acknowledged for support during this project. references choi, sd., borchardt, jg. and proksch, tl. 2012. translating academic research on manual lifting tasks observations into construction workplace “good practices”. journal of safety, health and environmental research. vol. 8, issue 1, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4):161-167. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 167 kadikon, y. and abdol rahman, mn. 2016. manual material handling risk assessment tool for assessing risk factor of work-related musculoskeletal disorders: a review. journal of engineering and applied sciences 11 (10): 2226-2232 issn: 1816-949x kolawole, op., adebayo, a., agbetoye, l., ogunlowo, as. and ozigbo, e. 2014. some flow properties of cassava mash in handling. american journal of experimental agriculture 4(11): 1348-1354 kolawole op., agbetoye, l. and ogunlowo, as. 2010. cassava mash process handling. 2nd conference on chemical engineering and advanced material (ceam) virtual forum. mohammadi, h., motamedzade, m, faghih, ma, bayat, h., mohraz, mh and musavi, s. 2013. manual material handling assessment among workers of iranian casting workshops. international journal of occupational safety and ergonomics.vol. 19, issue 4 nourani, a., kaci, f., garbatipegna, f. and kadri, a. 2017. design of a portable dates cluster harvesting machine. agricultural mechanization in asia, africa and latin america. vol. 48. no 1. pp. 18 to 21 rene, bm. de koster, andrew, lj. and roy, d. 2017. warehouse design and management. international journal of production research. vol. 55, issue 21. ziaei, m., ziaei, h., hosseini, sy., gharagozlou, f., keikhamoghaddam, aa. and laybidi, mi. 2017. assessment and virtual redesign of a manual handling workstation by computer-aided threedimensional interactive application. international journal of occupational safety and ergonomics. volume 23 issue 2. pp. 169-174 http://www.tandfonline.com/author/ziaei%2c+mansour http://www.tandfonline.com/author/ziaei%2c+hojjat http://www.tandfonline.com/author/hosseini%2c+seyed+younes http://www.tandfonline.com/author/gharagozlou%2c+faramarz http://www.tandfonline.com/author/keikhamoghaddam%2c+ali+akbar http://www.tandfonline.com/author/laybidi%2c+marzieh+izadi http://www.tandfonline.com/toc/tose20/current http://www.tandfonline.com/toc/tose20/current http://www.tandfonline.com/toc/tose20/23/2 ../../../user/downloads/azojete143/www.azojete.com.ng article information 1.0introduction 2.0materials and methods arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):91-102 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 91 original research article sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria j. m. dibal1*, a. u. bashir1, m. m. haruna1 and n. a. abubakar2 1department of agricultural and environmental resources engineering, faculty of engineering, university of maiduguri, maiduguri, borno state, nigeria 2department agricultural and bio-resources engineering programme, faculty of engineering and engineering technology, abubakar tafawa balewa university, pmb 0248, bauchi, nigeria. *corresponding author’s email address: jibrinmd01@gmail.com 1.0 introduction mathematical models usually contain input variables, parameters and/or series of equations that express some course of actions under investigation. quite often, some or all of the model inputs are subject to sources of uncertainties, including errors of measurement, lack of up-to-date information and poor or partial understanding of the driving forces and mechanisms. furthermore, some models may be highly complex in structure, thereby posing obscurity in running it and in comprehending the input/output relationships of the model. such uncertainties and quandaries inflict some limit on user’s confidence in model’s output (bakhtiari and liaghat, 2011). also, some natural spacio-temporal variability of the input variables occurs in response to events such as climate change and geological actions, among others. planas and depoutot (2000) showed that a good model is expected to present minimal uncertainty and a high degree of confidence to its users. weighing up the level of uncertainty in a model thus becomes an essential ingredient of model building and quality assurance. article information abstract reference evapotranspiration (eto) models are fundamental tools in decision-making in agricultural water management. they have potential spacio-temporal variations due to climatic variability that challenges their individual reliability in decision-making. the sensitivities of five eto models were examined using the factor perturbation simulation approach (fpsa). the examined models were penman-monteith (pm), hargreavessamanni (hs), blaney-criddle (bc), jensen-haise (jh) and thornthwaite (tw) to alteration of climatic variables (wind speed (u2), maximum and minimum air temperatures (tmax and tmin), vapor pressure deficit (vpd), and solar radiation (rn). the study utilized ten years meteorological data obtained from nigerian meteorological agency (nimet) offices in maiduguri between (2002-2011) for borno state, potiskum between (2005-2014) for yobe state and from the upper benue river basin development authority, yola (ubrbday) between (2005-2014) for adamawa, taraba, gombe, and bauchi states respectively. thus covering the entire northeastern region of nigeria. the region was fractionalized in to three zones namely borno state (zone a), yobe state (zone b) and adamawa, taraba, gombe, and bauchi states (zone c). the results from zones a and b showed some distinctive similarities. additionally, blaney-criddle, hargreaves-samanni and jensen-haise models outperformed thorntwaite model, signifying that thornwaite model is not suitable for application in this region. on an annual average, pm model was most sensitive to u2 and least sensitive to tmean. bc model was highly sensitive to n/n with sensitivity coefficient (s.c.) of 3.640 in borno and 3.611 in yobe, and it was least sensitive to rh. the temperature difference (tmax-tmin) was found to have affected hs more than ra. the thorntwaite model was most sensitive to solar radiation. similarly, it was observed that u greatly influenced the performances of the studied eto models. for accurate and reliable output from any eto model, emphases need to be placed on accurate measurement, documentation and systematic handling of the climatic variables and calibration © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 sept., 2020 revised 22 february 2021 accepted 27 february 2021 keywords: reference evapotranspiration models sensitivity analysis climatic variables north east region nigeria dibal et al: sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria. azojete, 17(1):91-102 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 92 sensitivity analysis (s.a.) is technique involving series of computational procedures that project the performance or the outcome of models as affected by changes in the assumptions or the values of the input variables of a model (ambas and baltas, 2011). it also weighs up how much each input is contributing to the output uncertainty. among others, sensitivity analysis is often used to compare different scenarios and their potential outcomes based on changing condition and/or values of input variables and hence decisions become more effective. furthermore, sensitivity analysis directs the study of how the uncertainty in the output of a model or system (numerical or otherwise) could be doled out to different sources of uncertainty in its variables; increase understanding of the relationships between input and output variables in a system or model. sensitivity analysis also reduces uncertainty by identifying model inputs that cause significant uncertainty in the output; and be able to focus attention on variables that gravely impinge on the model (gong et al., 2006). additionally, it is used in identifying critical control points that will prioritize additional data collection or research, and in verifying and validating a model to reduce the its complexity by identifying and removing variables that least affects the final output of a model (aydin and keçecioğlu, 2009). sensitivity analysis can be achieved by several approaches (rana and katerji, 1998; saltelli, 2002; irmak et al., 2006; bormann, 2011), however, the factor perturbation simulation approach (fpsa) also referred to as one-at-a-time (oat) approach is mostly preferred by modelers and analysts due to its straightforwardness and other practical reasons (irmak et al., 2006; bakhtiari and liaghat, 2011). the factor perturbation simulation approach (fpsa) involves calculating the sensitivity of a model by monitoring changes in its output in response to changes in one factor at a time while all other factors are kept fixed to their central or baseline values. thus, any change observed in the model output will unequivocally be due to the single variable changed. this method of analysis usually is accomplished using partial derivative or regression analysis. the quantitative value of changes in the model output due to changes in input variables is referred to as sensitivity coefficient (s.c) (michael et al., 2000). under fpsa, when there is any model malfunction, the modeler immediately knows which input factor is the source for the malfunction. s.a. generally enhances the comparability of models and minimize the probability of computer programme crashes that commonly happens when several input factors are changed simultaneously evapotranspiration is the rate at which water, if readily available, would be removed from the soil and plant surfaces (james, 1993). the reference evapotranspiration (eto) is the evapotranspiration from a reference surface, not short of water. crop evapotranspiration (etc) is the rate at which water, when readily available, would be removed from a specific crop and soil surfaces surrounding it (hobbins et al., 2001). the most common procedure for estimating etc is to adjust the eto values with the crop coefficient (kc), which in turn is a function crop’s stage of development. water resources particularly in the arid and semi-arid regions commonly experience increasing pressure from competing users consequential to the usual limited availability of water resources. efficient water use, especially in irrigated and other hydrological fields thus became a watch word (hatfield et al., 1996). precision estimation of etc thus becomes practically crucial due to its close link to hydrology and agro-ecosystem design and management (allen, 2000). hobbins et al. (2001) stressed that eto is one of the most important hydrological variables for scheduling irrigation systems, preparing input data to hydrological water-balance models, and calculating actual crop evapotranspiration (etc) for a region and/or a basin and general field water management. the computation of reference evapotranspiration (eto) using regularly recorded climatological data is arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):91-102. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 93 usually the first step involved in estimating the etc of agricultural crops. the term etc is thus a very important parameter for accurate hydrology and agro-ecosystem design and management. evapotranspiration being a quantitative measure of the evaporative demand of the atmosphere is independent of crop type and/or management practices, but is a function of climatic factors that can be computed from meteorological data (allen, 2000). the success of the use of most eto models lies in the transferability of the kc from one location to another, a situation many researchers found to be nearly impractical (bakhtiari and liaghat, 2011). tegos et al. (2013) provided a great number of methods for estimating eto including the combination (penman, 1948), mass transfer (harbeck, 1962), energy budget (fritschen, 1966), water budget (guitjens, 1982) empirical (kohler et al., 1995), and the fao standard penmanmontieth method (allens et al., 2000). further, given the variability of the performances of different models with different local climatic conditions and the varieties of methods and/or equations that exist, adopting a specific method as a standardized model should become the central point of attention. for a reliable performance, it is expected that eto should be calibrated, verified, and validated and this necessitate establishment of the sensitivity of eto to the local climatic variables and evaluating is performance statistically (steiner et al., 1991). the s.a. avails the model user the chance to gain understanding of the relative importance of each of the variables to the model solution. bakhtiari and liaghat (2011) performed the s.a. of penman equation with respect to each climatic variable and concluded that the equation was most sensitive to net radiation. piper (1989) showed that errors in measurement of sunshine hours, wind speed, and wet bulb temperature had the same relative effect on the estimated eto. ley et al. (1994) analyzed the sensitivity of the penman-wright eto model to errors in parameters and weather data. they found that the model was most sensitive to error in the maximum and minimum air temperatures in washington state. the sensitivity of the original penman-monteith equation to climatic and parametric factors in a semi-arid climate for a reference grass surface, grain sorghum, and sweet sorghum was analyzed in italy (rana and katerji, 1998). they found that for grass, available energy and aerodynamic resistance played a major role. for sweet sorghum, the model was most sensitive to vapor pressure deficit. for grain sorghum under water stress, the most sensitive term was canopy resistance. such works were also conducted on asce-penmanmonteith equation in different climates of the united states. for ecosystem simulation and models uses, the required data for single-stand simulations are often available and possible to measure, but such functional data progressively became unavailable as spatial resolution increases. sensitivity analysis would be needed by engineers, hydrologists, and agronomists to gain a better understanding of the meteorological systems in the nigerian northeastern region particularly to designate the physical meaning of each meteorological parameter used in the estimation of eto and other related hydrological problems. nevertheless, work done in this region on sensitivity analysis of fao-56 penman montieth, balney-criddle, thornwite, jensen-haise, and hargreaves-samanni models are scarce. this limits their uses in resolution to many hydrologic and agro-ecosystem problems. in consequence, in this study, we conducted the sensitivity analysis of above-mentioned model this limits their uses in resolution to many hydrologic and agro-ecosystem problems. in consequence, in this study, we conducted the sensitivity analysis of above-mentioned models in northeast nigeria using wind speed, maximum and minimum air temperatures, vapor pressure deficit, and solar radiation. dibal et al: sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria. azojete, 17(1):91-102 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 94 2. materials and methods 2.1 study area the study utilized ten-years meteorological data obtained from nigerian meteorological agency (nimet) offices in maiduguri (2002-2011) representing borno state, potiskum (2005-2014) representing yobe state, and from the upper benue river basin development authority, yola (ubrbday) (2005-2014) representing adamawa, taraba, gombe, and bauchi states thus covering the entire northeastern region of nigeria. the region was fractionalized into three zones namely borno state (zone a), yobe state (zone b) and adamawa, taraba, gombe, and bauchi states (zone c). the meteorological data collected and used for the analysis were maximum (tmax) and minimum (tmin) air temperatures at 2 m height, wind speed measured at 2m height (u2), relative humidity (rh) and daily sunshine duration (ssh). the region domicile about nine universities, many tertiary institutions and research institutes, thus it is heavily occupied with substantial academic and research activities. agriculture generally dominates the area, but flood that occurs nearly every rainy season is one of the chief hydrological challenges of the area. the climate of the region is semi-arid characterized by a high inter-annual variability in rainfall. 2.2 computation of reference evapotranspiration (eto) 2.2.1 fao-56 penman-monteith model the fao-56 penman-monteith model is given in (eqn 1). ( ) ( ) (1) where: eto= reference evapotranspiration (mmday-1), rn= net radiation at the crop surface (mjm-2day-1), g= soil heat flux (mjm-2day-1), t= mean daily air temperature at 2m height (oc), u2= wind speed at 2m height (ms-1), es= saturation vapor pressure (kpa), ea= actual vapor pressure (kpa), δ= slope of vapor pressure curve (kpa oc-1), γ= psychrometric constant (kpa oc-1). the details of equations associated with the calculation of the required parameters in eqn. (1) have been standardized and described in allens et al. (2000). table 1 presents the monthly mean daily meteorological data for the study area that was used in the study. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):91-102. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 95 table 1: monthly mean daily meteorological data for the study area months of the years climatic variables z o n e s jan feb mar apr may jun jul aug sep oct nov dec tmax ( oc) a 32.725 35.208 40.151 41.870 40.519 36.758 33.419 31.407 33.330 36.190 35.967 33.000 b 32.170 35.910 37.800 40.340 39.280 36.580 32.190 30.750 32.700 35.180 35.610 32.450 c 33.300 36.600 39.300 38.300 34.800 32.800 31.100 29.900 30.300 32.900 34.000 30.300 tmin ( oc) a 13.402 17.829 20.068 25.171 26.489 25.474 23.989 23.124 23.567 22.161 16.826 13.355 b 13.770 17.480 20.790 24.700 26.050 24.630 23.050 22.020 22.420 22.380 16.490 13.880 c 17.500 22.200 25.300 27.100 25.100 23.700 22.500 22.000 22.600 22.500 20.800 15.400 tmean ( oc) a 15.635 19.840 23.045 25.900 25.575 24.165 22.775 22.010 22.510 22.440 18.645 14.640 b 22.970 26.695 29.295 32.520 32.665 30.605 27.620 26.385 27.560 28.780 26.050 23.165 c 20.900 20.200 20.000 18.600 17.850 17.550 17.300 16.950 16.850 18.200 19.600 20.450 rh (%) a 31.800 24.800 19.600 26.800 40.700 57.800 70.000 78.300 72.400 50.600 36.200 33.800 b 23.940 19.000 20.670 28.330 41.820 55.630 71.220 78.900 71.940 55.910 32.980 28.370 c 38.364 31.364 26.164 41.800 62.800 70.200 75.500 80.180 79.300 71.700 46.400 40.364 u2 (ms-1) a 2.023 2.162 2.237 2.407 2.526 2.493 2.476 2.301 1.879 1.832 1.773 1.771 b 1.502 1.548 1.636 1.636 1.579 1.574 1.466 1.307 1.528 1.379 1.512 1.523 c 1.419 1.313 1.711 2.101 2.272 1.761 1.578 1.337 1.248 1.471 1.108 1.052 ssh (hrs) a 7.770 8.640 9.650 9.850 9.140 8.250 7.640 6.900 8.350 8.340 8.420 7.690 b 7.201 8.071 9.081 9.281 8.571 7.681 7.071 6.331 7.781 7.771 7.851 7.121 c 8.791 7.557 7.996 7.714 7.680 6.954 6.610 5.009 6.381 8.457 10.029 9.049 2.2.2 thornwaite model the monthly eto according to thornthwaite (1948) were estimated using equation (2) ( ) ( ) (2) where: eto= reference evapotranspiration, n= maximum number of sunny hours as a function of the month and latitude, dm = number of days per month, etosc= is the gross et (without correction) and was calculated from equation (3). (3) where: t = mean daily temperature (°c), a = an exponent as a function of the annual index defined by equations (4) and (5). (4) where i is the annual heat index obtained from monthly heat indices from equation 5. (5) where: i is the annual heat index obtained from monthly heat indices and t is as defined above (james, 1993). dibal et al: sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria. azojete, 17(1):91-102 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 96 2.2.3 the hargreaves-samani model equation (6) presents the hargreaves-samani’s model (allen et al, 2000) ( )( ) (6) where: ra= extraterrestial radiation (mm day-1), t= mean daily temperature (ºc), tmax= mean dialy maximum temperature, tmin= mean daily minimum temperature. the ra from penman calculation were in (mj m-2 day-1), so they were multiplied by 0.408 convert them to (mm day-1), as provided by allen et al. (2000). 2.2.4 jensen-haise model the jensen-haise model takes the form of equation (7) ( ) (7) where: ct = air temperature coefficient for the location being considered, t= mean daily air temperatures (oc), tx= constant for the location being considered, rs= total solar radiation for period (mmday-1). the coefficients ct and tx were determined using the equations (8) and (9). rs values from penman calculations were also converted from (mj m-2 day-1) to (mmday-1) by multiplying them with 0.408 (allen et al., 1998). (8) (9) 2.2.4 jensen-haise model the jensen-haise model takes the form of equation (7) ( ) (7) (8) (9) where: ct = air temperature coefficient for the location being considered, t = mean daily air temperatures (oc), tx = constant for the location being considered, rs = total solar radiation for period (mmday-1). rs values from penman calculations were also converted from (mj m-2 day-1) to (mmday-1) by multiplying them with 0.408 to have a uniform units (allen et al., 2000). the coefficients ct and tx in equation (7) were determined using the equations (8) and (9) in which h = attitude of the location (m), tmax, and tmin= saturation vapor pressure at the mean maximum and minimum air temperature during the warmest month of the year respectively (kpa). where: h= attitude of the location (m), otmax, otmin= saturation vapor pressure at the mean maximum and minimum air temperature during the warmest month of the year respectively (kpa). arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):91-102. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 97 2.3 sensitivity analysis and determination of sensitivity coefficients (s.c.s) the sensitivity of the models to tmeam , u2 , vpd and ssh , was analyzed using the factor perturbation simulation approach (smajstrla et al., 1987; irmak et al., 2006). sensitivity coefficient for each climatic variable was derived from equation (10) (10) where: s.c= sensitivity coefficient, cheto= change in eto with respect to change in climatic variable, and chcv= the change in climatic variable. 3.0 results and discussion 3.1 fao-56 penman-monteith model tables 2 presents the average daily sensitivity coefficients (s.cs) computed on a monthly basis for each of the climatic variable considered in the northeast region of nigeria. the trends of the s.cs showed similarities in all climatic variables. in most cases the response of eto to factor perturbation was linear on seasonal basis but the monthly basis, and both locations, the increase in each climatic variable resulted in a corresponding increase in eto except in the case of tmean. in zone a, the s.c. of tmean increased somewhat linearly from january through may where it attained its peak value. the least sc was found in july. this shows that the eto calculated from pm model in july will be least affected by tmean. the sc of rn raged between 0.318 in december to 0.352 in october, while the s.c. of u2 was highest (1.793) in march and least (0.299) in august. vpd got the highest sc (0.969) in july and least (0.354) in november. generally, in zone a, the s.c. of u2 (1.793) in march signifies it had the greatest contribution to the accuracy of pom model, and thus the need to pay greater attention while measuring u2. table 2: average sensitivity coefficients of climatic variables for penman monteith model in zones a, b, and c climatic variables zone a jan feb mar apr may jun jul aug sep oct nov dec tmean( oc) -0.023 -0.039 -0.060 -0.080 -0.064 -0.028 -0.003 0.013 0.008 -0.012 -0.017 -0.013 rn(mj mm-1 day-1) 0.319 0.331 0.348 0.355 0.358 0.351 0.338 0.336 0.343 0.352 0.337 0.318 u2(ms-1) 1.295 1.480 1.793 1.661 1.294 0.805 0.484 0.299 0.434 0.983 1.299 1.193 vpd(kpa) 0.894 0.857 0.781 0.747 0.813 0.888 0.967 0.955 0.596 0.588 0.354 0.681 zone b tmean( oc) -0.029 0.078 -0.045 -0.062 -0.023 -0.003 0.009 0.017 0.017 0.006 -0.008 0.007 rn(mj mm-1 day-1) 0.212 0.351 0.270 0.343 0.224 0.137 0.095 0.071 0.068 0.108 0.157 0.128 u2(ms-1) 2.728 1.646 2.130 1.509 1.328 0.000 0.333 2.232 2.404 2.151 2.935 4.188 vpd(kpa) 0.601 0.529 0.541 0.676 0.695 0.569 0.485 0.380 0.369 0.476 0.451 0.478 zone c tmean( oc) 0.566 0.771 0.932 1.138 0.866 1.119 0.947 0.801 0.864 1.025 0.479 0.624 rn(mj mm-1 day-1) 0.300 0.364 0.431 0.423 0.280 0.341 0.372 0.211 0.220 0.350 0.207 0.304 u2(ms-1) 1.633 0.985 1.275 0.903 0.795 0.052 0.199 1.336 1.439 1.288 1.757 2.507 vpd(kpa) 1.727 2.257 1.788 2.124 2.577 4.315 4.576 4.396 4.556 4.889 1.519 2.146 dibal et al: sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria. azojete, 17(1):91-102 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 98 the s.c. of the climatic variables with respect to blaney-criddle b.c. model is presented in table 3. in zone b, the highest sc (4.188) is that of u2 in december and the least (0.003) came from tmean in june. this means the magnitude of variability of pm’s eto with respect to u2 would be greatest in the dry windy months of the year. it also points that tmean would have the list influence on eto. it thus implies that sufficient precaution need to be taken during the measurement and recording of u2 to avert faulty eto results. similar results were observed in zone c where the s.c. of u2 exhibited nearly linear trend from 1.336 in june to its highest value (2.507) in december. but the overall peak value of s.c. (4.889) is that of vpd in october. bakhtiari and liaghat (2011) showed that due to the behavior of the term 1/( γ +∆ ) in equation (1), the effectiveness of vapor pressure deficit on evapotranspiration is greater in the low temperatures months because this term decreases as temperature increase. thus, the divergence in eto with respect to increase in vpd would be larger during wet months. this lowest s.cs of tmean in june and july tallies with the report of audu et al. (2015). table 3: average s.cs. of climatic variables to blaney criddle et model jan feb mar apr may jun jul aug sep oct nov dec zone a tmean 0.160 0.182 0.196 0.193 0.170 0.147 0.129 0.111 0.124 0.144 0.157 0.157 rh 0.038 0.045 0.053 0.061 0.057 0.053 0.048 0.043 0.047 0.047 0.043 0.036 u2 0.224 0.293 0.335 0.305 0.289 0.203 0.168 0.125 0.138 0.166 0.220 0.254 ssh 3.279 4.081 4.654 4.925 4.466 3.723 3.067 2.527 2.776 3.406 3.472 3.299 zone b tmean 0.165 0.172 0.149 0.154 0.128 0.120 0.110 0.103 0.103 0.118 0.154 0.164 rh 0.041 0.046 0.046 0.052 0.048 0.045 0.041 0.038 0.039 0.044 0.046 0.039 u2 0.254 0.310 0.333 0.263 0.175 0.143 0.118 0.111 0.096 0.126 0.207 0.235 ssh 3.657 4.522 4.205 4.295 3.262 2.973 2.647 2.364 2.371 2.598 3.258 3.352 zone c tmean 0.478 0.310 0.268 0.277 0.231 0.216 0.198 0.185 0.185 0.213 0.277 0.296 rh 0.075 0.082 0.083 0.093 0.086 0.081 0.074 0.069 0.070 0.079 0.083 0.069 u2 0.459 0.558 0.601 0.474 0.315 0.258 0.213 0.200 0.173 0.227 0.372 0.424 ssh 4.317 5.337 4.963 5.070 3.850 3.509 3.124 2.790 2.799 3.067 3.845 3.956 it is evident from the model that the s. c. of the studied variables took a sinusoidal trend with the lowest around the months august. the table also shows that ssh of 4.925, 4.295 and 5.07 in zones a, b. and c respectively all occurring in the month of april has a dominant influence on the overall performance of the model in this region. the influence of r.h. on the performance of the model is apparently insignificant, not only due to is negative values of s.cs, but also by the account of low s.c. values in the all the zones. similar results were reported by ambas and baltas (2011) which showed low and negative s.cs of r.h in blaney criddle model. the term r.h. can thus be safely be replaced with the energy terms that have greater influence on the model. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):91-102. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 99 table 4 elucidates that the thorn white (t.w) et model was found to be more sensitive to sunshine hours (ssh) which is also one of the energy terms of the model. in zones a, b and c respectively, the highest s.c values of the ssh were 0.4155, 1.095 and 1.424. this call for cautious and accurate instrumentation of ssh term to arrive accurate et values with t.w. model. it also points that minimal emphasis can be placed on temperature measurement. the hargreave – samani (h.s.) model as with other models, exhibited a non-linearity in its sensitivity to changes in its parameters (table 5). the model is most sensitive to perturbation in temperature, especially in the rainy seasons irrespective of the zones. the highest s.c of 0.381 for tmean was found in the month of september in zone c. apparently, the response of this model to changes in its building parameters has no defined trend, however, tmean should be prudently recorded for accurate et computation with h.s. model. the jensen haise model exhibited greater sensitivity to vapor pressure deficit (vpd) irrespective of the zones (table 6). this was followed by the solar radiation in equivalent depth of evaporation (rs). (table 6) in zone a, the highest s.c. (1.147) for vpd was found in the month of july. the least values were found in zone c. this means the effectiveness of j.h. model in predicting et relies on the accuracy of vpd. the table also showed that tmean holds the least position in the performance of the model, this challenges the proclamation that the jensen haise model depends on solar radiation in equivalent depth of evaporation (james, 1993). this study shows that efficiency of j.h. model in et prediction is a function of its building parameters that are also in turn a function of location. the result implies that in the dry season, greater emphasis should be on ra than (tmax tmean) while in the wet season reverse is the case. although this result shows that the effects of both parameters on the model have no significant difference, both parameters requires greater emphasis in determining eto if this model is to be used in such locations. table 4: average s.cs. of climatic variables to thorn white et model zone a jan feb mar apr may jun jul aug sep oct nov dec tmean 0.0598 0.0754 0.1016 0.1205 0.1119 0.0913 0.0756 0.0646 0.045 0.084 0.0758 0.0587 n (ssh) 0.3629 0.3785 0.4155 0.4538 0.4497 0.4279 0.4018 0.3928 0.3952 0.4053 0.3848 0.3615 zone b tmean 0.0669 0.0718 1.0723 0.085 0.073 0.0633 0.0541 0.0392 0.0525 0.0726 0.0872 0.06 n (ssh) 0.3741 0.4096 1.095 0.4444 0.415 0.4006 0.3853 0.3783 0.3842 0.394 0.391 0.355 zone c tmean 0.08697 0.09334 1.39399 0.1105 0.0949 0.08229 0.07033 0.05096 0.06825 0.09438 0.11336 0.078 n (ssh) 0.48633 0.53248 1.4235 0.57772 0.5395 0.52078 0.50089 0.49179 0.49946 0.5122 0.5083 0.4615 dibal et al: sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria. azojete, 17(1):91-102 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 100 table 5: average s.cs. of climatic variables to hargreaves-samani et model jan feb mar apr may jun jul aug sep oct nov dec zone a ra 0.169 0.173 0.202 0.198 0.180 0.162 0.134 0.123 0.134 0.165 0.181 0.169 (tmean) 0.132 0.164 0.181 0.220 0.237 0.263 0.262 0.272 0.252 0.212 0.158 0.131 zone b ra 0.152 0.159 0.165 0.158 0.108 0.137 0.125 0.117 0.118 0.141 0.163 0.148 (tmean) 0.151 0.182 0.214 0.261 0.203 0.270 0.260 0.266 0.281 0.245 0.194 0.158 zone c ra 0.207 0.216 0.225 0.215 0.147 0.186 0.170 0.159 0.161 0.191 0.222 0.201 (tmean) 0.206 0.247 0.290 0.354 0.276 0.367 0.354 0.361 0.381 0.333 0.264 0.215 table 6: average s.cs. of climatic variables to jansen-haise et model zone a jan feb mar apr may jun jul aug sep oct nov dec tmean 0.124 0.147 0.209 0.212 0.178 0.130 0.098 0.079 0.108 0.145 0.158 0.126 rs 0.181 0.212 0.297 0.320 0.284 0.209 0.152 0.124 0.155 0.218 0.227 0.184 vpd 0.683 0.855 0.882 1.012 1.075 1.143 1.147 1.130 1.231 1.033 0.808 0.691 zone b jan feb mar apr may jun jul aug sep oct nov dec tmean 0.122 0.131 0.166 0.100 0.101 0.085 0.073 0.066 0.068 0.104 0.135 0.108 rs 0.187 0.230 0.296 0.227 0.175 0.147 0.126 0.110 0.112 0.157 0.187 0.147 vpd 0.853 0.913 0.910 1.160 1.143 1.088 1.045 1.057 1.108 1.154 1.126 0.872 zone c jan feb mar apr may jun jul aug sep oct nov dec tmean 0.110 0.119 0.150 0.090 0.092 0.077 0.066 0.060 0.062 0.095 0.123 0.098 rs 0.152 0.159 0.165 0.158 0.108 0.137 0.125 0.117 0.118 0.141 0.163 0.148 vpd 0.151 0.182 0.214 0.261 0.203 0.270 0.260 0.266 0.281 0.245 0.194 0.158 4. conclusions model sensitivity analysis in response to the perturbation to its building parameters is an essential element in the study of model’s performance and user’s confidence. this is only true when the output under consideration is a time dependent function of the input parameters. in all the models studied here, the energy and the aerodynamic terms played some major roles. however, in jensenhaise model, the vpd was found to be more fundamental. whereas some of the results and interpretations appeared fairly straightforward and logical from physiological perception, majority of the results were non-linear and may be artifact of model design or field data instrumentation. in all the zones studied, all the et models would be recommended to be used in estimating eto based on the availability of meteorological data, but adequate calibration of the models should be conducted to eliminate spacio-temporal errors. however, it is believed that accurate predictions of the spatial distribution of several key parameters would produce the greatest reduction in the uncertainty to a large-scale. further, adequate, and salient attention should be given during instrumentation and documentation of the most sensitive meteorological parameters of any chosen model to ensure a great level of accuracy in estimating eto. it is also recommended that the arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):91-102. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 101 scarcity of meteorological data and stations need to be overcome to simplify and improve hydrometeorological research that may be performed in all the zones. further research on sensitivity analysis should be expanded to include representative climatic distribution of the agro-climatic zones of nigeria. references allen, rg. 2000. the fao-56 dual crop coefficient method over an irrigated region as part of an evapotranspiration inter-comparison study. journal of hydrology, 1& 2: 27-41. ambas, vt. and baltas, e. 2012. sensitivity analysis of different evapotranspiration methods using a new sensitivity coefficient. global nest journal, 14(3): 335-343. audu, mo., isikwue, bc. and eweh, ej. 2015. evaluation of seasonal and annual variations of evapotranspiration with climatic parameters in ibadan, nigeria. journal of earth sciences and geotechnical engineering, 5(2): 69-79. aydin, m., and keçecioğlu, sf. 2010. sensitivity analysis of the evaporation module of the e-digor model. turkish journal of agriculture 34: 497-507. doi:10.3906/tar-0909-398. bakhtiari, b. and liaghat, am. 2011. seasonal sensitivity analysis for climatic variables of ascepenman-monteith model in a semi-arid climate. journal of agricultural science technology, 13: 1135-1145. bormann, h. 2011. sensitivity analysis of 18 different potential evapotranspiration models to observed climatic change at german climate stations. climate change 104, 729–753. fritschen, lj. 1966. energy balance method. proceedings, american society of agricultural engineers conference on evapotranspiration and its role in water resources management, december 5, chicago, i. st. joseph, mi., pp. 34-37. gong, lb., xu, cy., chen, dl., halldin, s. and chen, yq. 2006. sensitivity of the penman–monteith reference evapotranspiration to key climatic variables in the changjiang (yangtze river) basin. journal of hydrology, 329: 620–629. guitjens, jc. 1982. models of alfalfa yield and evapotranspiration. journal of the irrigation and drainage division, the american society of civil engineers, 108(ir3): 212-222. harbeck, ge. jr. 1962. a practical field technique for measuring reservoir evaporation utilizing mass transfer theory, us geological survey, paper 272-e. 101-105. hatfield, jl., prueger, jh. and reicosky, dc. 1996. evapotranspiration effects on water quality. in: proceedings of the asae international conference on evapotranspiration and irrigation scheduling, 3–6 november, san antonio, tx, pp. 536–546. hobbins, mt., ramirez, ja. and brown, tc. 2001. the complementary relationship in estimation of regional evapotranspiration: an enhanced advection-aridity model. water resource research, 37(5): 1389–1403. irmak, s., payero, jo., martin, dl., irmak, a. and howell, ta. 2006. sensitivity analyses and sensitivity coefficients of standardized daily asce-penman-monteith equation. journal of irrigation and drainage engineering, 132(6): 564–578. james, lg. 1993. principles of farm irrigation system design. florida, krieger publishing company., pp1-35. dibal et al: sensitivities of some reference evapotranspiration models to the key climatic variables in northeastern nigeria. azojete, 17(1):91-102 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jibrinmd01@gmail.com 102 kohler, ma., nordenson, tj. and fox, we. 1955. evaporation from pans and lakes. weather bureau research paper 38.us department of commerce, washington, d.c. ley, tw., hill, rw. and jensen, dt. 1994. errors in penman-wright alfalfa reference evapotranspiration estimates. ii: effects of weather sensor measurement variability. transactions of asae, 37(6): 1863– 1870. michael, a., white, pe., thornton, swr. and ramakrishna, nr. 2000. parameterization and sensitivity analysis of the biome–bgc terrestrial ecosystem model: net primary production controls. earth interactions, 4(3):1-85. penman, hl. 1948. natural evaporation from open water, bare soil and grass. proceedings of the royal society. london, a193: 120–146. piper, bs. 1989. sensitivity of penman estimates of evaporation to errors in input data. agricultural water management, 15: 279–300. planas, c. and depoutot, r. 2000. sensitivity analysis as a tool for time series modeling. in sensitivity analysis (a. saltelli, k. chan and m. scott, eds.). wiley, new york., pp. 293–310. rana, g. and katerji, n. 1998. a measurement-based sensitivity analysis of the penman montieth actual evapotranspiration model for crops of different heights and contrasting water stress. theoretical and applied climatology, 60: 141-149. saltelli, a. 2002. sensitivity analysis for important assessment. risk analysis, 22(3): 1-12. saltelli, a., ratto, m., andres, t., campolongo, f., cariboni, j., gatelli, d., saisana, m. and tarantola, s. 2008. global sensitivity analysis. new york: the primer, john wiley & sons. smajstrla, ag., zazueta, fs. and schmidt, gm. 1987. sensitivity of potential evapotranspiration to four climatic variables in florida. soil and crop science society of florida, 46: 21-26. steiner, l., howell, ta. and schneider, ad. 1991. lysimetric evaluation of daily potential evapotranspiration models for grain sorghum. agronomy journal, 83: 240-247 arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):663-674 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 663 original research article design and implementation of internet of things based irrigation system a. a. okandeji*1, f. onaifo2, m. t. kabir3 and k. yakubu2 1department of electrical and electronic engineering, university of lagos, akoka, lagos state, nigeria. 2department of electrical and electronic engineering, olabisi onabanjo university, ogun state, nigeria. 3department of electronic and telecommunication engineering, ahmadu bello university, kaduna, nigeria *corresponding author’s email address: aokandeji@unilag.edu.ng 1.0 introduction conventional irrigation system either results in over irrigated or under irrigated land as the water requirement by crops depend on the soil type, crops, and environmental parameters such as temperature and humidity. the growth and development of plants can be prevented due to scarcity of water. similarly, excessive water has adverse effect on the growth of plants. under conventional irrigation system, several parts of the irrigated field are either over irrigated or under irrigated due to variability in the water holding capacity of land, water infiltration, and water runoff. over irrigated areas suffer from poor plant health due to increase in salinity, and excessive water replaces air in pores of the soil. hence, roots of the plants do not get sufficient air which may lead to leaching. similarly, under irrigated area suffer from water stress. accordingly, efficient water management practice plays a key role in agriculture (patel and tope, 2016). on the other hand, internet of things (iot) represents a general concept for the ability of network devices to sense and collect data from the world around us, and then share that data across the internet where it can be processed and utilized for various interesting purposes (rawal, 2017). iot collect and process data from series of wireless sensors connected together. wireless sensor networks (wsn) have been the subject of research in various domains over the past few years and deployed in numerous application areas (roham, 2015). wsn is seen as one of the most promising contemporary technologies for bridging the real and virtual world thus, enabling them to interact. a wsn is composed of a number of sensor nodes which are article information abstract this work considered the design and implementation of an internet of things (iot) based irrigation system that encourages efficient and optimal use of water management practice. the proposed iot based irrigation system promotes user acknowledgment practice on farmlands by monitoring the soil moisture value and other environmental parameters. this system, which is based on iot, stores the sensor data, and the water pump can be monitored via the internet using a thingspeak channel. using a micro-controller which coordinates system activities, a wireless fidelity (wifi) module which transmits the sensed data to the cloud, a motor driver which controls the pump, a digital temperature and humidity (dht)11 sensor which monitors environmental parameters, and a yl-69 soil moisture sensor, an iot based irrigation system is implemented. results obtained showed that the system irrigates the soil based on the defined threshold value of the soil moisture in order to promote efficient and optimal utilization of water management practice. additionally, farmers can monitor the irrigation processes remotely from a thingspeak channel, which gives a graphical representation of the soil moisture value, pump status, temperature and humidity value as well as the flow rate within the environment. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 february, 2020 revised 2 july, 2020 accepted 8 july, 2020. keywords: irrigation thingspeak iot water management practice flow rate. http://www.azojete.com.ng okandeji et al.: design and implementation of internet of things based irrigation system. azojete,16(4):663-674. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 664 usually deployed in a region to observe particular phenomena in a geospatial domain (roham, 2015). sensor nodes are small stand-alone embedded devices that are designed to perform specified simple computation and to send and receive data. they have, attached to them, a number of sensors gathering data from the local environment that is being monitored (roham, 2015). in general, various irrigation techniques to monitor and coordinate effective water management practices have been investigated. in particular, work done in roham, (2015) proposed a system in agricultural field where various essential climatic factors are monitored for regulation of crop production. this model uses wsns to trace down the local climatic condition parameters (such as carbon dioxide (co2), temperature, and humidity) at different locations. al-omary et al. (2018) proposed a cloud based iot smart garden monitoring and irrigation system using arduino uno. as outlined in al-omary et al. (2018), the water requirement of a plant can be adjusted by monitoring the soil moisture. measuring the soil moisture of the plant gives information about if the plant is ideally watered, over watered or under watered. the proposed system in al-omary et al. (2018) monitors and maintains two quantities of the garden namely; the garden soil moisture content, and light intensity. this is done using soil moisture sensors and light intensity sensor, respectively. the monitored data is sent continuously to thinkspeak iot cloud. in the cloud, the data gathered from the system is analyzed such that when a target threshold of soil moisture is reached, an action is sent accordingly from the cloud to the garden automatic watering system to irrigate the garden. in al-omary et al. (2018), the arduino uno microcontroller is used to implement the system control unit, and iot is used to keep the garden owner updated about the status of the sprinklers. on the other hand, srivastava et al. (2018) designed a smart irrigation system that uses a ph sensor, water flow sensor, temperature sensor, and soil moisture sensor for measurement, and based on these measured sensor values, the arduino microcontroller drives the servo motor and the pump. the arduino receives the information and transmits with esp8266 wifi module wirelessly to the website through the internet. the transmitted information is monitored and controlled using iot. this enables the remote control mechanism through a secure internet web connection to the user. users can control water pumps and sprinklers through the internet, and keep an eye on the reference values which will help the farmer increase production with quality crops. alternatively, anila et al. (2017) proposed an automated irrigation model for efficient water management and intruder detection system. in particular, soil parameters such as soil moisture, ph, humidity are measured and the pressure sensor as well as the sensed values are displayed on the liquid crystal display (lcd) screen. the intruder detection system is done with the help of passive infrared (pir) sensor where intruders such as birds are repelled from entering into the field. through the use of a global system for mobile communication (gsm) module, a communication link between the farmer and the field can be established. the current field status will be intimated to the farmer through short messaging system (sms). the farmer can access the server about the field condition anytime, anywhere thereby reducing man power and time. a major drawback of the work done by anila et al. (2017) is that it does not monitor soil nutrient nor forecast any weather parameter. various models, systems and methodologies for the irrigation of parcels have been developed. these models made use of an integrated system for automated irrigation management with an advanced novel routing protocol for wsns, named equalized cluster head election routing protocol (echerp) (nikolidakis et al., 2015). the proposed system in nikolidakis et al. (2015) aimed at efficiently managing water supply in cultivated fields in an automated way. the system takes into consideration the historical data and the change in the climate values to calculate the quantity of water that is needed for irrigation. in contrast to existing result, this work considers the novel design and implementation of an iot based irrigation system that optimizes water management practice for crop production, and promote monitoring practice for user http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 663-674. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 665 acknowledgment. in particular, this work involves the development of an automatic irrigation system which switches the pump motor on/off on sensing the moisture content of the soil. the advantage of using this novel method is to reduce human intervention and still ensure proper irrigation. this design uses an 8051 series microcontroller which is programmed to receive the input signal of varying moisture condition of the soil through the sensing arrangement. this is achieved by using an operational amplifier (op-amp) as comparator which acts as interface between the sensing arrangement and the microcontroller. using a microcontroller (arduino uno), android application, sensors, internet of things, wi-fi module and motor driver to design the iot based irrigation system, the proposed irrigation system helps in efficient management of water based on the soil moisture, temperature and humidity values, which invariably increases crop production, eliminate human labor as the smart irrigation works with sensors to switch the motor on/off. the block diagram of the iot based irrigation system is shown in figure 1. from the figure, it is worth noting that the arduino uno is the decision maker of the system, it inspects the temperature and moisture value. primarily, the threshold value of soil moisture must be welldefined. when the sensed moisture value goes below the threshold value, the controller checks for the temperature, and then the user is alerted through an app and irrigation commences only if the sensed soil moisture value is lower than the defined threshold value. this is because crops can withstand dry soil moisture condition if the temperature is moderate, and water use for irrigation would be conserved. figure 1: block diagram of an iot based irrigation system 2.0 materials and methods this section considers the system architecture, control and analysis unit as well as the iot unit. 2.1 system architecture the system architecture consists of a simple circuit designed to control irrigation scheme on a farmland. it is designed to monitor, and control irrigation based on a response to real-time status of soil moisture. the system uses a wi-fi module to transmit information of the soil moisture, temperature, humidity, water level and pump status data to the cloud. the device performs the action of irrigation management by setting the threshold value of soil moisture. accordingly, when the sensed moisture value goes below the threshold value, the controller checks for the temperature, the user is alerted, and irrigation will commence only if the sensed soil moisture value is lower than the defined threshold value. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of internet of things based irrigation system. azojete,16(4):663-674. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 666 2.2 parameter sensing unit the sensing unit in iot consist of a group of sensors that acquire data from the physical world, followed by an embedded system that drives the physical system of the iot application, the communication network, and the necessary protocol to send the data to the internet, and finally the data analysis. a typical block diagram representation of the process involved in the parameter sensing unit is shown in figure 2. . figure 2: parameter sensing unit the sensors act as the interface between iot applications and real physical world. they capture real data from the environment and the iot system uses these data primarily for functionality. sensor fusion leverages a microcontroller to fuse the individual data derived from sources to get a more accurate picture of the environment. 2.2.1 soil moisture sensor the soil moisture sensor as shown in figure 3 is part of the system sensing unit and it is used to detect the soil moisture content. the soil moisture sensor measures the conductivity and resistivity of the soil. the voltage of the sensor output changes according to the soil water content. when the soil is wet, the output decreases, and when the soil is dry, the output increases. the sensor has an in-built potentiometer for sensitivity adjustment of the digital output, a power light emitting diode (led) and a digital output led. the soil moisture sensor considered in this work has a supply voltage of 3.3v to 5v. with this supply, it gives an output voltage of between 0v to 2.3v for the full range of complete dryness to submersion in water. additionally, the maximum operating current is 15ma. figure 3: soil moisture sensor 2.2.2 digital temperature and humidity sensor (dht11) sensor the dht11 sensor as shown in figure 4 is the temperature and humidity sensor. its technology ensures a high dependability and adequate stability. this sensor includes a resistive element and a sense of wet negative temperature coefficient (ntc) temperature measuring devices. it has excellent quality, fast response, anti-interference ability, and high cost advantages. for determining humidity, the humidity sensing module is used. it has two electrodes with moisture holding substrate between them. when humidity changes, the conductivity of the substrate changes or the resistance between these electrodes’ changes. this change in resistance is measured and processed by the integrated chip (ic) which makes it ready to be read by a microcontroller (patel and tope, 2016). to determine the temperature, these sensors make use of an ntc temperature sensor or a thermistor. a thermistor is a variable resistor that changes its resistance with a change in temperature. these sensors are made by sintering of semi conductive materials such as ceramics or polymers in order to deliver larger changes in the resistance with just small changes in temperature. ntc simply means that the resistance is inversely proportional to the temperature and vice versa (patel and tope, 2016). sensors and sensor network embedded system communication data analysis and representation http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 663-674. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 667 figure 4: dht11 sensor 2.2.3 water flow sensor there are various methods of measuring water flow. the volumetric calculation includes the following; open channel flow with examples like; non pressurized water, river and canal. velocity meter, which include the cross-sectional area and velocity of flow. large water flow. closed channel flow with example like; pressurized water, mechanical, gear, propeller type. hall effect with example like; water flow sensor. the water flow sensor works with the principle of hall effect. in general, electromagnetic induction is the interaction of magnetism with magnetic conductors. the production of electric current in a magnetic field is proportional to the rate of change of magnetic flux. hence, a magnetic field is generated when electric current passes through an electrical conductor. halleffect is the production voltage differences across an electric conductor, transverse of an electric current in the conductor and then applied perpendicularly to the magnetic field. hall effect sensors consist primarily of a thin piece of rectangular semiconductor material (patel and tope, 2016). a typical water flow sensor is shown in figure 5. figure 5: yf-s201 water flow sensor 2.3 control and analysis unit this unit comprises of the arduino microcontroller, l293d motor driver, and a direct curren (dc) pump. the microcontroller is the control unit of the system. it is designed to monitor, and control irrigation based on a response to real-time status of the soil moisture. the system uses a wi-fi module to transmit information of the soil moisture, temperature, humidity, water level, and pump status data to the cloud. 2.3.1 esp8266 wi-fi module this is a system on chip (soc) and wi-fi networks that have software applications. the tcp/ip protocol is present in it and allows access to the wi-fi connection. it is capable of hosting an application or removing all wi-fi networking functions from any other application processor. flash memory can start directly from an exterior move. built-in cache memory will decrease memory requirement and support upgrade system performance. additionally, it consists of the wireless internet access that understands the function of the wi-fi adapter, it can add to any microcontroller-based design, easy connection due to the sci / sdio interface. it is a sophisticated device with a fine processing system and storage capacity. it integrates with gpio ports sensor and other application on specific machine. esp8266 require little external circuits due to highly integrated chip. the esp8266 system supports the following features file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of internet of things based irrigation system. azojete,16(4):663-674. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 668 namely: bluetooth interference, and energy saving voip applications. the module has 3.3 v input voltage. it has 8 pins namely; 1 txd and 1 rxd, 2 gpio pins i.e. gpio 0 and gpio 2, rst (reset), vcc and gnd (ground). this module is inexpensive and transforms the iot method into a specific version (srivastava et-al, 2018). the esp8266 wi-fi module is shown in figure 6. figure 6: esp8266 wi-fi module 2.3.2 arduino uno (microcontroller) as shown in figure 7, arduino uno is an open platform microcontroller; it is an electronic platform built on easy to use hardware. arduino uno is one of the most easily available lowcost arduino board. the arduino is an embedded system. various pins on the arduino are used to read or write values onto the system. arduino holds the following advantage over other microcontrollers: inexpensive, cross platform (linux, mac os, windows), simple clear programming environment. figure 7: arduino uno 2.3.3 motor driver a motor driver is an integrated circuit chip which is usually used to control motors. the motor driver used in this work is the l293d motor driver. it serves as an interface between the microcontroller and dc pump. the l293 is the simplest and inexpensive for low current motors as it provides the power required for running the pump. l293d convert the dc electrical power to mechanical power which in turn drives the dc pump. the shaft rotates at a particular revolution per minute (rpm) based on the voltage provided. 2.4 iot unit the iot unit is used for data storage and representation. it makes use of an iot app called thingspeak. thingspeak app is an open data internet of things platform that allows a user to aggregate, visualize, collect and store data in the cloud by using the http protocol over the internet via a local area network. it includes a channel where data to be stored are sent to. each channel includes 8 field for any type of data, 3 location fields, and 1 status field. once there is an available thingspeak channel, data can be sent to the channel. the thingspeak interface is shown in figure 8. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 663-674. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 669 figure 8: thingspeak api interface 2.4.1 gateway and network layer the network and gateway layer manages the connectivity of the network to the cloud. nearly every iot system needs some way to connect sensors/devices to the cloud so that data can be sent back-and-forth between them. iot gateways can be essential in making this connection possible because gateways act as bridges between sensors/devices and the cloud. many sensors/devices will “talk” to a gateway and the gateway will then take all that information and “talk” to the cloud. 2.4.2 application layer iot application layers cover “smart” environments/spaces in fields such as: transportation, building, city, lifestyle, retail, agriculture, factory, supply chain, emergency, healthcare, user interaction, culture and tourism, environment and energy. 2.5 circuit schematics the circuit schematics are shown in tables 1 to 3. table 1: circuit connection of wi-fi module, moisture sensor and l293d motor driver with arduino uno component 1 pin pin description pin pin description component 2 arduino uno a0 analog read a0 analog data yl-38 soil moisture sensor module 5v vcc vcc gnd ground gnd ground arduino uno 8 digital i/o tx input 2 l293d motor driver connected to water pump gnd digital i/o rx input 1 5v 3.3v vcc enable gnd 3.3v ch_pd ground arduino uno 3 (rx) receiver tx transmitter esp8266 4 (tx) transmitter rx receiver 3v3 3.3v vcc 3v3 3.3v ch_pd chip enable gnd ground gnd ground file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of internet of things based irrigation system. azojete,16(4):663-674. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 670 table 2. circuit connection of dht11 sensor and wi-fi module with arduino uno component 1 pin pin description pin pin description component 2 arduino uno 10 digital i/o data serial data dht11 sensor 5v vcc vcc gnd ground gnd ground arduino uno 3 digital i/o tx transmitter esp8266 4 digital i/o rx receiver 3v3 3.3v vcc 3v3 3.3v ch_pd chip enable gnd ground gnd ground table 3. circuit connection of yf-s201 water flow sensor, l293d motor driver with arduino uno component 1 pin pin description pin pin description component 2 arduino uno 2 digital i/o d0 data yf-s201 water flow sensor 5v vcc vcc gnd ground gnd ground arduino uno 3 (rx) receiver tx transmitter esp8266 4 (tx) transmitter rx receiver 3v3 3.3v vcc 3v3 3.3v ch_pd chip enable gnd ground gnd ground the flow chat for the iot based irrigation system is shown in figure 9 while the system circuit design is shown in figure 10. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 663-674. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 671 figure 9: system flowchart a n a l o g in a t m e g a 3 2 8 p -p u 1 1 2 1 r e s e t b t n o n w w w .t h e e n g in e e rin g p ro je c ts .c o m pd0/rxd pd1/txd pd2/int0 ~ pd3/int1/oc2b pd4/t0/xck ~ pd5/t1/oc0b ~ pd7/ain1 pc5/adc5/scl pc4/adc4/sda pc3/adc3 pc2/adc2 pc1/adc1 pc0/adc0 reset pb0/icp1/clko ~ pb1/oc1a ~ pb2/oc1b ~ pb3/mosi/oc2a pd7/ain1 pb4/miso pb5/sck aref 0 1 2 3 4 5 6 7 8 9 10 11 12 13 a5 a4 a3 a2 a1 a0 ard1 arduino uno 30 29 %rh > °c data2 vdd1 gnd4 u1 dht11 in12 out1 3 out2 6 out3 11 out4 14 in27 in310 in415 en11 en29 vs 8 vss 16 gnd gnd u5 l293d ra0/an0 2ra1/an1 3ra2/an2/vref4 ra4/t0cki 6ra5/an4/ss 7 re0/an5/rd 8re1/an6/wr 9re2/an7/cs 10 osc1/clkin 13osc2/clkout 14 rc1/t1osi/ccp216 rc2/ccp117 rc3/sck/scl18 rd0/psp019 rd1/psp120 rb7/pgd40 rb6/pgc39 rb538 rb437 rb3/pgm36 rb235 rb134 rb0/int33 rd7/psp730 rd6/psp629 rd5/psp528 rd4/psp427 rd3/psp322 rd2/psp221 rc7/rx/dt26 rc6/tx/ck25 rc5/sdo24 rc4/sdi/sda23 ra3/an3/vref+ 5 rc0/t1oso/t1cki15 mclr/vpp/thv 1 u2 soil sensor bat1 5v h l 8 3 r a in s e n s o r w w w .t h e e n g in e e rin g p ro je c ts .c o m v c c o u t g n d t e s tp in + water water sensor bluetooth hc-05 key vcc gnd txd rxd state www.theengineeringprojects.com wifi hc-08 figure 10: system circuit design file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of internet of things based irrigation system. azojete,16(4):663-674. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 672 3.0 results and discussion in this section, results and discussion, using the prototype of the proposed system as shown in figure 11, are presented. in particular, the performance of the proposed system with regards to the soil sensor, temperature sensor, and humidity sensor is investigated. accordingly, the overall aim of this section is to monitor the irrigation processes at different depth level of the probe in the soil. the prototype of the proposed system comprises of the connection of the pump tube, water flow sensor, battery, l273d motor driver, arduino uno, esp8266 wifi module, soil sensor probe, dht11 sensor and the soil moisture sensor. figure 11: prototype system to monitor the irrigation processes in loamy soil at different depth level of the probe, table 4 presents the soil moisture value, temperature and humidity readings obtained using the prototype system in figure 11. table 4: readings from prototype system of soil moisture value, temperature and humidity of a loamy soil. dry soil value depth (cm) soil moisture value (cm3) temperature °c humidity % 4 11 27 93 3 9 27 94 2 6 27 95 1 4 27 95 wet soil value 4 62 27 94 3 60 27 94 2 56 27 94 1 46 27 94 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4) 663-674. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 673 also, to monitor the irrigation processes in sandy soil at different depth level of the probe, table 5 presents the soil moisture value, temperature and humidity readings obtained using the prototype system. table 5. readings from prototype system of soil moisture value, temperature and humidity of a sandy soil dry soil value depth (cm) soil moisture value (cm3) temperature °c humidity % 4 26 25 95 3 14 25 95 2 15 25 95 1 9 25 95 wet soil value 4 36 25 94 3 30 25 94 2 24 25 94 1 16 25 94 using the thingspeak channel, the graphical representation of the sensor value at different time interval is shown in figure 12. figure 12: soil sensor graph figure 12 shows the soil moisture value from the yl-69 at every 30 seconds interval of time which is transmitted to the thingspeak application. irrigation takes place when the soil moisture value is below the defined threshold value of the soil. the value obtained from the soil moisture sensor enables the pump to switch on and off. thus, a farmer can remotely monitor the process of irrigation on the farm land. 4.0 conclusion the proposed system was designed to promote user acknowledgement practice for farmers. the system irrigates the soil based on the defined threshold value of the soil moisture in other to promote efficient and optimal application of water management practice. the farmers monitor the irrigation processes remotely from a thingspeak channel, which gives a graphical file:///c:/users/user/downloads/azojete143/www.azojete.com.ng okandeji et al.: design and implementation of internet of things based irrigation system. azojete,16(4):663-674. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 674 representation of the soil moisture value, pump status, temperature and humidity value within the environment and the flow rate. to increase the efficiency, effectiveness and reliability of the system, the following recommendation can be put into consideration; due to inefficient power supply in nigeria, a solar panel can be incorporated into the power supply unit, to provide alternative power source. option of controlling the pump remotely can be giving to the farmers i.e. farmers can switch on/off the pump during the process of irrigation. a crop surveillance unit can be incorporated to ensure crop safety from animal and man. the iot unit can be improved by incorporating a gsm/gprssim900a module to alert the farmers on the irrigation process via sms, the gprs can alert the farmers on the specific location on the land that needs to be irrigated. this would reduce human intervention in farming activities. references al-omary, a., alsabbagh, hm. and al-rizzo, h. 2018. cloud based iot for smart garden watering system using arduino uno. smart cities symposium, 1–6, 22-23, april, bahrain. anila, s., nandhini, r., poovizhi, s., jose, p. and ranjitha, r. 2017. arduino based smart irrigation system using iot. 3rd national conference on intelligent information and computing technologies, 1-5, march, 2017, r v s college of engineering and technology, coimbatore. nikolidakis, sa., kandris, d., vergados, dd. and douligeris, c. 2015. energy efficient automated control of irrigation in agriculture by using wireless sensor networks. computers and electronics in agriculture, 113: 154–163. patel, as. and tope, g. 2016. smart irrigation system. international journal of engineering and technical research, 3(3): 23–26. rawal, s. 2017. iot based smart irrigation system. international journal of computer applications, 159(8): 7–11. roham, vs. 2015. smart farm using wireless sensor network. international journal of computer applications, 6: 8–11. srivastava, p., bajaj, m. and rana, a. s. 2018. irrigation system using iot. fourth international conference on advances in electrical, electronics, information, communication and bioinformatics, 27-28 febuary, piscataway, new jersey, usa http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):307-318 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 307 original research article kinetic modeling of ethylbenzene isomerization using bodenstein approximation technique a. s. kolo*, a. s. grema, and i. i. maina chemical engineering department, faculty of engineering, university of maiduguri, p.m.b 1069, maiduguri, borno state, nigeria *corresponding author’s email address: askolo@unimaid.edu.ng 1.0 introduction ethylbenzene isomerization is an industrial reaction that is vital in industries that need petrochemical feedstocks. products of this reaction are precursors to some very important polymer materials. a kinetic model of this reaction is handy when it comes to reactor design, optimization, operations and possible troubleshooting. kinetic models developed for reactions of industrial importance are usually either empirical in nature or assume some rate-limiting steps (kangas et al., 2008; al-khattaf et al., 2009; waziri and al-khattaf, 2009; farahani et al, 2020). the power rate-law type of equations usually used to study kinetic behaviors of complex reactions do not usually capture the multiple molecular events involved in such catalytic reactions and, therefore, cannot completely and reliably predict kinetic behavior of such systems. consequently, models developed via these schemes are usually not reliable for direct scale-up purposes (helfferich, 2004). direct large scale-up of industrially significant reactions on the other hand need effective and reliable fundamental kinetic models reflecting the kinetics of the multistep catalytic pathways of the reaction mechanism. an earlier study on isomerization of ethylbenzene on bifunctional pt/al2o3 and pt-zeolite catalysts was investigated by robschlager and christoffel (1979). their investigation showed that xylenes were produced over the pt/al2o3 catalyst via the route corresponding to prediction from a bifunctional mechanism in which skeletal rearrangements of tertiary carbocations only were considered to be the rate-determining steps. a systematic methodology to the elucidation of article information abstract ethylbenzene isomerization reaction is a significant reaction employed in the production of xylene isomers which are used as petrochemical feedstocks. the reaction which proceeds over pt/al2o3 catalyst is multi-pathway and multi-cycle in topology. kinetic model for the reaction was developed in this study using the general rate equation approach. bodenstein approximation, cross-to-square, and y-to-delta transformation techniques were used to reduce the complex reaction network to a single cycle network. in addition, the general rate equation for reduced single cycle networks was applied to derive the model for the reaction. the nelder-mead simplex optimization technique was used to estimate the kinetic parameters in the model. the structure of the model developed indicates that the model reasonably represents the mechanism of the reaction although few anomalies were observed in the values of the kinetic parameters estimated. the activation energy obtained for the rate constants follows the expected trend for multi-step reactions. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 november, 2021 revised 10 march, 2022 accepted 16 march, 2022 keywords: isomerization ethylbenzene kinetic model bodenstein approximation reaction network http://www.azojete.com.ng/ mailto:askolo@unimaid.edu.ng mailto:askolo@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):307-318. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 308 reaction networks with multiple numbers of steps and location of nodes was presented in helfferich (1989). general equations for rate of reactions and yield ratio were developed with a view to elucidate complex reaction networks. findings from the study indicate that the procedure used is handy in model development and discrimination applications. a kinetic modeling technique that simplifies complex reaction network by employing bodenstein approximation for trace level intermediates was reported in chern and helfferich (1990). the technique reduces complex networks in topology to networks with only pseudo-single steps between nodes; the simpler networks are then used to derive rate expressions for the reactants and products in the network. fernendes et al. (1998) studied the hydroisomerization of ethylbenzene on mordenite-based bifunctional catalysts with different platinum contents. the study concluded that hydroisomerization of ethylbenzene is affected by reactant diffusion inside zeolite pores in addition to zeolite acidity and that platinum content affected xylene selectivity due to the formation of hydrogenated intermediates. the concept of bodenstein approximation and network reduction technique was extended to the modeling of single-cycle reaction network as reported in chern (2000). results presented in the study indicated that general rate equations derived is applicable to heterogeneous catalytic reactions involving first-order reactions with respect to intermediates formed in the reaction. al-zahrani et al (2002) studied the kinetics of transalkylation and isomerization of ortho diethylbenzene using trifluoromethane acid as a catalyst. the work tested power-law type model for transalkylation and disproportionation reaction and findings show that isomerization reaction follow first-order mechanism. chen and chern (2003) in their work titled the general rate equation and their application for catalytic reaction networks: pyramidal systems; systematically developed a general rate equation formula that can be used for fundamental kinetic modeling of complex reaction networks that have multipathways and multi-intersections. their work seeks to cover reaction networks not captured by formulas and procedures presented by chen and chern (2002a) and chen and chern (2002b). the work by chen and chern (2009), discrimination of kinetic models for isomerization of nbutene to isobutene, presented the exploitation of analysis of mathematics of multi-step reactions to discriminate between rival mechanisms. the kinetic modeling of non-simple networks was reported in a work by chern et al. (2014). their study provided an extension to earlier techniques reported to include networks with branches from loops and non-simple networks. oliveira et al. (2016) presented a review of kinetic modeling methodologies for complex processes and the paper analyzed in length advanced kinetic modeling strategies. farahani et al. (2020) studied ethylbenzene/xylene mixture isomerization over hzsm-5 zeolites catalyst. they developed a kinetic model that considers chemisorption, surface reaction, and diffusional processes for the reaction. their findings provided an insight on the activation energy for the surface reaction of ethylbenzene into m-xylene. considering the significance of general rate equation approach and the limitations of the nature of kinetic studies hitherto practiced, the algorithm of general rate equation was used to model the isomerization of ethylbenzene in this study. the study focused on developing a reliable and effective fundamental kinetic model for the isomerization of ethylbenzene over pt/ al2o3 catalyst using bodenstein approximation technique on trace level intermediates. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:askolo@unimaid.edu.ng kolo et al: kinetic modeling of ethylbenzene isomerization using bodenstein approximation technique. azojete, 18(2):307-318. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 309 2. methodology the bodenstein approximation of trace-level intermediates was the tool used in this work to reduce multi-step reaction networks to reactions with only pseudo-single steps between network nodes and end members. the net rate contribution of a multi-step network segment between nodes xj and xk represented by the reaction pathway below is given in equation 1 (chern and helfferich, 1990). 1 ... ...j j j i kx x x x        1j k jk j kj kr x x      the segment coefficients ( ) for the reaction pathway presented above are evaluated using equations 2 and 3. 1 , 1 1 1, 2 3 i k i i i j jk jk i k i i i j kj jk d d                 where  represents the pseudo-first order rate coefficients of quasi-single molecular steps and are also the products of the actual rate coefficients and the concentration of any co-reactants of the respective steps (chern and helfferich, 1990). the numerators of the segment coefficient expressions given in equation 2 and 3 are the products of the forward rate coefficients and reverse rate coefficients in the pathway respectively. the operator jkd is evaluated using equation 4. 1 1 , 1 , 1 1 1 1 4 i kk jk m m m m i j m j m d                      a loop coefficient is used to reduce parallel pathways in a network into a single lumped pathway. the expressions for forward and reverse loop coefficients are shown in equation 5 and 6 (chen and chern, 2009). ( ) 1 ( ) 1 5 6 m k ij ij k m k ji ji k l l         collective coefficients ( ij ) are used to group segment rate coefficients in a network segment so as to reduce network portions with higher number of coefficients to a pseudo-single step. 2.1 reaction mechanism and network the mechanism of the reaction is presented below: eb + s ⇌ 𝐸𝐵𝑆 ebs ⇌ 𝑂𝑋𝑆 http://www.azojete.com.ng/ mailto:askolo@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):307-318. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 310 𝑂𝑋s ⇌ 𝑃𝑋𝑆 𝑃𝑋s ⇌ 𝑀𝑋𝑆 𝑀𝑋s ⇌ 𝐸𝐵𝑆 𝑂𝑋s ⇌ 𝑂𝑋 + 𝑆 𝑃𝑋s ⇌ 𝑃𝑋 + 𝑆 𝑀𝑋s ⇌ 𝑀𝑋 + 𝑆 the reaction network and steps involved in reduction of the complex network into a single-cycle network for modeling is presented in steps 1-8 below: 1. the network depicting the mechanism for the reaction showing multi-pathways and multiintersections is shown in figure 1. figure 1: reaction network for the four-node pyramidal isomerization reaction. 2. the network in figure 1 can be viewed as pyramidal network with four nodes in the base triangle. the four nodes being x1, x0, x3, and x4. the pyramidal network with the four nodes in the base triangle is shown in figure 2. figure 2: a pyramidal reaction network with four-nodes in the base triangle. 3. cross-to-square transformation technique was used to transform the cross-network represented by the pathways x2 to x4 and x1 to x3 to a square network represented by the pathways x4 to x1, x1 to x2, x2 to x3, x3 to x4. figure 3 shows the transformed inner crossnetwork (dash lines). x0 was considered as an intersection node in the transformation. figure 3: transformed cross-network into square network. a b c d x1 x2 x3 x4 x0 x2 x1 x3 x4 x0 x4 x2 x3 x1 d c b a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:askolo@unimaid.edu.ng kolo et al: kinetic modeling of ethylbenzene isomerization using bodenstein approximation technique. azojete, 18(2):307-318. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 311 4. the parallel pathways between x3 and x2, x2 and x1, x1 and x4, and x4 and x3 are lumped into loop coefficients (lij) where (i,j) stand for (3,2), (2,3), (2,1), (1,2), (1,4), (4,1), (4,3), (3,4). the system is now reduced to a pyramidal network with three nodes in the base triangle. the network with three nodes in the base triangle is presented in figure 4. figure 4: pyramidal network with three nodes in the base triangle a cyclic representation of the pyramidal network with three nodes in the base triangle showing inner y-type network is presented in figure 5. figure 5: cyclic representation of pyramidal network 5. applying y-to-delta transformation to the y-network in figure 5, an equivalent delta-type network is obtained. transferring the delta-type network into the main cycle, the complete network of the reaction is now reduced to two cycles with two pathways between each node. figure 6 shows the network containing two cycles and pathways between the three nodes. the dash lines show the delta-type network. figure 6: reduced network containing two cycles and three pathways between nodes. x4 x3 x2 x1 x4 x2 x1 x3 x1 x4 x3 http://www.azojete.com.ng/ mailto:askolo@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):307-318. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 312 6. the three parallel pathways between the three nodes in figure 6 are lumped into loop coefficients to yield a single-cycle reaction network. the single-cycle network is shown in figure 7. figure 7: reduced single cycle reaction network for ethylbenzene isomerization reaction. the general rate equation for reduced single-cycle developed in chern and chen (2003) is then applied to the reduced single-cycle network in figure 6 to get the rate equation through the cycle. equation 12 shows the general equation for the rate through the cycle.  tr x d   12 where; , 1 1, 0 0 n n l l l l i i l l             , and           , , 0 , , 0 , ,0 ho hh i jk i h i j k ii jj kk kl kk il ii il ii jl jj i l ppath pj k p i j k pl jl jj kl kk ho hh pl pp i p l h i j k d d d d c d c d c d c d s d c c d c d d c d s                                           the notation  in the numerator of equation 12 represents the difference between the product of the forward loop coefficients of the reduced single-cycle network and the product of the reverse rate coefficients. the forward loop coefficients are 1 1 1 13 34 41, ,l l l and the reverse loop coefficients are 1 1 1 31, 43 14,l l l . hence the notation  can be expressed in the form shown in equation 14. 1 1 1 1 1 1 13 34 41 31 43 14 14l l l l l l   the expression for d is evaluated by considering each term in the expression: 1. , ,ii jj kkd d and d (i, j, and k represent the indices of the node intermediates of the final reduced cycle; that is 1, 3, and 4) are obtained from the loop coefficients of the final reduced x3 x1 x4 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:askolo@unimaid.edu.ng kolo et al: kinetic modeling of ethylbenzene isomerization using bodenstein approximation technique. azojete, 18(2):307-318. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 313 cycle shown in figure 6. the jkd operator formula shown in equation 4 is used in evaluating the d terms. equation 15 shows the expression of , ,ii jj kkd d and d 1 1 1 1 1 1 11 34 41 31 14 31 43 1 1 1 1 1 1 33 41 13 43 31 43 14 1 1 1 1 1 1 44 13 34 14 43 14 31 15 d l l l l l l d l l l l l l d l l l l l l          2. , , 0 ho hh h i j k d s   this term denotes the expression for concentration of missed center nodes x2 used in y-to-delta transformation. indices i, j, and k represent indices of the node intermediates of the final reduced cycle; that is 1, 3, and 4. and s0 is the sum of the segment coefficients (  ) of the segments from the missed center node intermediate to the adjacent node intermediates (that is; x1, x3, and x4). consequently, after relevant substitutions, the term is presented in equation 16. , , 10 11 30 33 40 44 0 01 02 03 04 16 ho hh h i j k d d d d s            3.   k i kl kk il ii l c d c d   this term denotes the expression for summation of the concentration of missed intermediates (represented by l ) in the pathway k-to-i (k stands for 1 and i stands for 3) due to network reduction. this is expression is 0 (zero) because there are no intermediates in the pathway from x1 to x3. 4.   i j il ii jl jj l c d c d   this term denotes the expression for summation of the concentration of missed intermediates (represented by l ) in the pathway i-to-j (i stands for 3 and j stands for 4) due to network reduction. this is expression is 0 (zero) because there are no intermediates in the pathway from x3 to x4. 5.   j k jl jj kl kk l c d c d   . this term denotes the expression for summation of the concentration of missed intermediates (represented by l ) in the pathway j-to-k (j stands for 4 and k stands for 1) due to network reduction. this is expression is also 0 (zero) because there are no intermediates in the pathway from x4 to x1. http://www.azojete.com.ng/ mailto:askolo@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):307-318. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 314 6.     , , 0 , ,0 ppath pp i j k pl ho hh pl pp p l h i j k c d c d s              this generally represents the concentration of missed intermediates as a result of network reduction between center-node and i, center-node and j, and center node and k (i, j, and k represent the indices of the nodes that make the final reduced cycle; that is 1, 3, and 4). this expression is also 0 (zero) because there are no intermediates between the nodes that make up the final reduced cycle and the centre-node. following relevant substitutions, the d term is presented in equation 17.       1 1 1 1 1 1 34 41 31 14 31 43 10 11 30 33 40 44 1 1 1 1 1 1 1 1 1 1 1 1 01 02 03 0441 13 43 31 43 14 13 34 14 43 14 31 17 l l l l l l d d d d l l l l l l l l l l l l                          substituting equations 14 and 17 into equation 12, the expression for the rate through the reduced single cycle is obtained.         1 1 1 1 1 1 13 34 41 31 43 14 1 1 1 1 1 1 34 41 31 14 31 43 10 11 30 33 40 44 1 1 1 1 1 1 1 1 1 1 1 1 01 02 03 0441 13 43 31 43 14 13 34 14 43 14 31 18t l l l l l l r x l l l l l l d d d l l l l l l l l l l l l                            equation 18 shows the rate equation through the reduced single cycle network presented in figure 6. 2.2 parameter estimation a well-known task in the concise mathematical representation of reaction network and mechanism is the estimation of the reaction rate constants. parameter estimation is essentially an optimization problem whereby the unknown parameters are obtained by minimizing a suitable objective function (englezos and kalogerakis, 2001). the objective function represents a measure of disparity between observed reaction rates from experimental data to rate from developed model. the neldermead simplex optimization technique was used in this study to minimize the objective function. the nelder-mead simplex algorithm is a direct search method for multidimensional unconstrained minimization. the algorithm seeks to minimize a scalar valued nonlinear function of n real variables using only scalar function values without any derivative. the optimization routine was carried out using matlab computer software. the matlab solver that executes optimization routine based on nelder-mead technique is the nonlinear programming solver fminsearch. the solver uses the nelder-mead optimization algorithm as elucidated by lagarias et al (1998). 3. results and discussion the model developed is presented in equation 18. table 1 shows the rate constants for each reaction step. the calculated values of activation energy and frequency factor for the model is presented in table 2. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:askolo@unimaid.edu.ng kolo et al: kinetic modeling of ethylbenzene isomerization using bodenstein approximation technique. azojete, 18(2):307-318. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 315 table 1: estimated rate constants rate constants (mol h-1 gcat -1) t = 593 k t = 613 k t = 633k t = 673 k k01 5.1845 -10.2268 10.404 1.4783 k02 2.4713 -964 -1.4413 -0.3023 k03 13.7876 -15.6994 4.129 -0.2102 k04 5.3871 0.9333 -12.9715 -0.5389 k10 -26.2378 -55.2825 -31.5937 -0.8001 k20 -1.6024 -2.9293 1.2157 2.7953 k30 6.3507 6.5799 6.7756 2.1114 k40 3.646 16.5405 15.957 1.4358 k12 -10.3324 12.9313 -14.6375 1.3043 k21 3.3084 6.7447 23.2739 1.3722 k23 -0.2239 -7.7967 7.8819 0.5419 k32 2.7019 0.1671 0.7595 1.906 k34 7.7078 -4.0816 0.4403 -1.1509 k43 6.9018 4.6199 12.9419 0.0532 k14 5.9099 13.9132 12.0624 5.4539 the model developed in this study clearly depicts the multi-step nature of the reaction. the embedded partial pressure terms in the denominator of the rate expression indicate the adsorption of the reacting species on the surface of the catalyst as the reaction mechanism suggests (fogler, 2004). the loop coefficients in the models expressively show that the reaction consist of several pathways as represented by the reaction network. the model also shows the contribution of each elementary step in the reaction network to the kinetics of the overall reaction. this is as indicated by the appearance of the rate constants of each step in the model developed. the l1 ij terms appearing in the model equations constitute the rate constants of the all steps. as it is customary to observe the effect of temperature variation on the estimated rate constants, a general pattern is not observable in the results obtained. some of the values obtained for the rate constants deviate from expected trend. comparing the values for the constants with that reported by farahani et al (2020) further indicates a departure although with a justification. in their work, the rate constants for the reaction step producing m-xylene at temperatures of 653k, 663k, and 673k were reported to be 48.74 mol h-1 gcat -1, 58.47 mol h-1 gcat -1, and 72.29 mol h-1 gcat -1 respectively. that of the reaction step producing p-xylene at the same temperatures were reported to be 9.72e 06 mol h-1 gcat -1, 1.11e 06 mol h-1 gcat -1, and 1.28e 06 mol h-1 gcat -1 respectively. the rate constants for the reaction step producing m-xylene in this study are 7.7078 mol h-1 gcat 1 and 0.4403 mol h-1 gcat -1 at 593k and 633k. while the rate constants for the reaction step producing p-xylene at the same temperatures are 7.8819 mol h-1 gcat -1 and 0.5419 mol h-1 gcat -1 respectively. a significant discrepancy can be observed in the reported values when compared. this can be attributed to the different modelling techniques adopted in the two works, slight difference in the starting material, and the choice of catalyst. it is already established that the nature of catalyst used for the reaction of interest affects the reaction rate constants (farahani, 2020). an anomaly was also observed in the values of pre-exponential factor calculated. the values as shown in table 2 appear to be constant all through. this did not compare favorably well http://www.azojete.com.ng/ mailto:askolo@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):307-318. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 316 with expected trend although literature values are scanty as much work is not reported on the methodology adopted in this study. the expected anomaly in the value of activation energy for multi-step reactions is confirmed in the results presented in table 2. this is evident in some negative values of the activation energy calculated. table 2: calculated arrhenius parameters in the model rate constants activation energy (kj/mol) frequency factor k01 2.49e-05 2.722635 k02 8.31e-04 2.722635 k03 2.49e-04 2.722635 k04 4.16e-04 2.722635 k10 0.00e+00 2.722635 k20 6.65e-04 2.722635 k30 4.16e-04 2.722635 k40 2.49e-05 2.722635 k12 4.16e-05 2.722635 k21 -4.16e-05 2.722635 k23 -8.31e-05 2.722635 k32 4.16e-05 2.722635 k34 3.32e-04 2.722635 k43 8.31e-05 2.722635 k14 -8.31e-05 2.722635 k41 -5.82e-04 2.722635 for multi-step reactions, the activation energy may be negative and the rate decreases with increasing temperature (helfferich, 2004). this indicates that the rates of reverse steps in the reaction network increases more sharply with temperature than those of forward steps for cases in which the activation energy is negative. 4. conclusions the bodenstein approximation of trace-level intermediates was exploited in this study to effectively model ethylbenzene isomerization reaction over pt/al2o3. reasonable assumptions were considered in the model development alongside network transformation techniques that helped reduce the complex reaction network with multi pathways and intersection into a single cycle network. few deviations were seen in the results presented in the study even though the model development procedure compares well with the available literature. discrepancies were seen in the rate constant values reported in an earlier study but the non-alignment can be file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:askolo@unimaid.edu.ng kolo et al: kinetic modeling of ethylbenzene isomerization using bodenstein approximation technique. azojete, 18(2):307-318. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 317 attributed to the choice of modeling technique and catalyst used. findings from the study re-echo the reliability of fundamental approach in up-scale applications; this is evident in the consideration of the individual molecular steps of the reaction in the model development. general rate equation approach to kinetic study is recommended for elucidating the kinetics of complex reactions and bodenstein approximation alongside network transformation techniques are also recommended for effective modeling of multi-step reactions without loss in vital information. nomenclature eb, a ethylbenzene ox, b o-xylene px, c p-xylene mx, d m-xylene ebs, x1 ethylbenzene complex oxs, x2 o-xylene complex pxs, x3 p-xylene complex mxs, x4 m-xylene complex s, x0 free catalyst site i, j indices indicating reaction step ij  pseudo-first order rate coefficient d denominator of segment coefficient equation  segment coefficient xj intermediate at jth position xi intermediate at ith position j kr  rate of reaction from j-to-k xt total catalyst concentration references al-khattaf, s., tukur, nm. and rabiu s. 2009. ethylbenzene transformation over zsm-5-based catalyst in a riser simulator. industrial and engineering chemistry research, 48: 2836-2843. alzahrani, sm., al-kinany, mc., al-humaizi, ki. and al-khowaitu, sh. 2002. transalkylation and isomerization of ortho-diethylbenzene with benzene using trifluromethanesulphonic acid catalysts: kinetic analysis. chemical engineering and processing. 41: 321-327. chern, j.-m. 2000. general rate equations and their applications for cyclic reaction network: single cycle systems. industrial and engineering chemistry research, 39: 4100-4105. chen, t.-m and chern, j. 2002a. general rate equations and their applications for cyclic reaction networks: multi-cycle systems. chemical engineering science, 57: 457-467. chen, t.-m and chern, j. 2002b. general rate equations and their applications for cyclic reaction networks: multi-pathway systems. chemical engineering science, 57: 5011-5020. chen, t. and chern, j. 2003. general rate equations and their applications for cyclic reaction networks: pyramidal systems. chemical engineering science, 58: 1407-1415. http://www.azojete.com.ng/ mailto:askolo@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):307-318. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: askolo@unimaid.edu.ng 318 chen, t. and chern, j. 2009. discrimination of the kinetic models for isomerization of n-butene to isobutene. journal of chemical engineering of japan, 42(1): 79-84. chern, j. and helfferich, fg. 1990. effective kinetic modeling of multistep homogeneous reactions. american institute of chemical engineers journal, 36: 1200-1208. chern, f., chen t. and chern, j. 2014. effective kinetic modeling for homogeneous reaction networks with branches from loops. industrial and engineering chemistry research, 53: 1298312992. englezos, p., and kalogerakis n. 2001. applied parameter estimation for chemical engineers. marcel dekker, inc. new york. farahani sh., falamaki c. and alavi, sm. 2020. kinetic modeling of ethylbenzene/xylene isomerization reaction over hzsm-5 zeolites revisited. international journal of chemical kinetics, 52(6): 368-377. fogler hs. 2004. elements of chemical reaction engineering, 3rd edition, prentice-hall, new delhi. fernendes, ld., corma, a., martinez, a., aguiar ef. and monteiro, jc. 1998. hydroisomerization of ethylbenzene on mordenite-based bifunctional catalysts with different platinum contents. brazilian journal of chemical engineering, 15(2): https://doi.org/10.1590/s010466321998000200009. helfferich, fg. 1989. systematic approach to elucidation of multistep reaction networks. journal of physical chemistry, 93: 6676. helfferich, fg. 2004. kinetics of multi-step reactions. amsterdam: elsevier science. kangas, m., salmi, t. and murzin, du. 2008. skeletal isomerization of butene in fixed bed. part 2. kinetic and flow modeling. industrial and engineering chemistry research, 47: 5413-5426. lagarias, jc., reeds, ja., wright, mh. and wright, pe. 1998. convergence properties of the nelder-mead simplex method in low dimensions. siam journal of optimization, 9 (1): 112–147. oliveira, lp., hudebine, d., guillaume, d. and verstraete, jj. 2016. a review of kinetic modeling methodologies for complex processes. oil & gas science and technology-rev. ifp energies nouvelles, 71. 45. robschlager, kh. and christoffel, eg. 1979. reaction mechanism of ethylbenzene isomerization. industrial and engineering chemistry product research and development, 18 (4). 347-352. doi: 10.1021/13600729. waziri, sm. and al-khattaf, s. 2009. kinetics of ethylbenzene ethylation with ethanol over a zsm5-based catalyst in a riser simulator. industrial and engineering chemistry research, 48: 83418348 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:askolo@unimaid.edu.ng https://doi.org/10.1590/s0104-66321998000200009 https://doi.org/10.1590/s0104-66321998000200009 availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 45-50 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng groundwater contamination in damaturu, nigeria umara, b.1, m. yaji1 and a. fannami2 abstract groundwater quality was monitored in 10 wells in the proximity of solid and liquid waste disposal systems in damaturu, nigeria. in this study, nitrate, ph, electrical conductivity, turbidity, total dissolved solids, hardness, colour, iron, chloride, sulphate, fluoride and coliform count were examined in the laboratory using standard procedures. closeness to pit latrines and septic tank resulted in significant concentrations of nitrate (28, 40 and 41 mgl-1 in wells 2, 8 and 9 respectively) which exceed the european community standards. consumption of water with high nitrates above the permissible limit of 20 mgl-1 can cause methyglobenemia syndrome. coexistence with waste disposal system resulted in high ph, iron and faecal contamination with average coliform density of 29 (100ml)-1 of sample exceeding the maximum permissible limit. total coliform indicate pathogens that cause cholera, typhoid, dysentery, gastro-enteritis, diarrhea and so on. excessive iron can impart colour and stimulate bacterial growth. the ph values normally exert influence on biological activity and may result in undesirable taste. the paper tries to offer some suggestions to the identified problems. 1. introduction groundwater is an economic resource and water is one of the most essential elements needed for all forms of biological activity. human beings, animals as well as plants depend absolutely on water which is an indispensable resource (adeniji, 1997). groundwater may become contaminated due to improper disposal of liquid wastes, defective well construction, improper siting of wells and failure to seal abandoned wells. these provide possible openings for the downward movement of water into subsurface formations without the process of natural filtration. contamination may also take place as a result of movement of wastewater through large openings such as animal burrows, fissures in rocks, coarse gravel formations or manmade excavations. bacteria from liquid effluents, septic tanks, cesspools, pit latrines, etc, are likely to contaminate shallow groundwater. the unsanitary mode of wastes disposal such as defecation in streams and dumping of refuse in pits, rivers and drainage channels, as is seen in most nigerian settlements, could be expected to affect surface and groundwater quality (sangodoyin, 1991). bacterial and viral contaminations are among the most significant health hazards that must be considered in protecting groundwater. the imminent and enormous dangers inherent in improper waste disposal need not be over-emphasized. in spite of the considerable investment of the nigerian government on water supply program, a large proportion of the population has no access to potable water. in 1978 for example, the proportion of houses or compound served with pipe bore water supply in nigerian towns varied from as low as 5% in bauchi, to as high as 73% in port harcourt and jos (nest, 1991). presently, industries, housing estates and private individuals depend, to some extant, on water from wells. 1 department of agricultural & environmental resources engineering, university of maiduguri. nigeria 2department of natural resources, damaturu local government council, damaturu. nigeria. http://www.azojete.com.ng groundwater contamination in damaturu, nigeria 46 damaturu, the yobe state capital, lies in the semi arid-region of nigeria and has a population of about 81, 364 (npc, 1991). wells in the area are generally poorly constructed and both man and animals are often seen using the same wells as their source of water. waste systems interference with ground water was confirmed with elevated levels of chloride nitrate, coliform count and electrical conductivities (sangodoyin 1993). waste disposal systems such as pit latrines and septic tanks are located close to some wells in the study area and most of the wells are not covered, thus allowing contamination of the water. these problems suggest that effective control of groundwater contamination through regular and adequate quality monitoring should be carried out. the objectives of this study were therefore, to recommend ways of monitor groundwater quality and to identify possible causes of contamination. 2. materials and methods for the purpose of this study, 25 locations within damaturu were selected for sample collection. ten wells were investigated during the period (april – may 2002). the following parameters were analyzed in soil science department laboratory of the university of maiduguri: nitrate, ph , electrical conductivity, total dissolved solids, hardness, colour, iron, chloride, sulphate, fluoride and coliform count. the analyses were carried out using spectrophotometer, ph meter, conductivity instrument with de-ionized distilled water, colorimeter, turbidimeter and serial dilution for bacteriological analysis. data for well age, depth, lining materials, diameter and distance from pollution sources were collected. 3. result and discussion table 1 shows the data obtained for well age, depth, living materials, well diameter and distance from pollution sources. tables 2 and 3 show the physical and chemical characteristics of the samples respectively. water in wells located close to waste disposal systems are slightly alkaline, (wells 2 and 8, these being close to contaminated water ponds and septic tank respectively). high ph values normally exert influence on biological activity and may result in undesirable taste. the information gathered from consumers show that taste and odour are affected in about 25% of the cases. water with objectionable tastes were found from wells located close to waste disposal systems. withdrawal of water from wells using ropes and buckets, animal rearing close to wells, washing within the well premises, improper apron and lining are factors that encourage waste percolation into the wells. the iron content of all samples from the wells monitored does not fall within the permissible limit for health consideration. excessive iron content may impart colour and stimulate bacterial growth. azojete vol. 4 2004 47 table 1: characteristics of the surveyed wells in damturu well number age (year) depth (m) diameter (m) distance to polluting source (m) lining cover type apron (m) wallthickness pollution source 1 1 4.2 0.9 drum 0.1 0.04 2 1 4.5 0.9 3 drum 0.1 0.14 contaminated water ponds 3 3 5.7 1.2 32 concrete 0.6 0.01 grave yard 4 11 4.8 1.2 30 concrete 0.5 0.1 abattoir 5 2 14 1.3 concrete 0.5 0.25 6 3 8 1.2 12 concrete 0.9 0.23 refuse dump 7 3 3 1.2 concrete 0.8 0.02 8 3 5.9 1 1.5 septic tank 9 17 6 1 .3 4 cement wood 0.3 0.25 pit latrine 10 2 6 1.2 23 concrete 0.4 0.1 8 soak-away table 2: some physical characteristics of water samples monitored s/no well location ec electrical conductivity turbidity (ntu) colour tcu 1. tsallake i 0.17 0.50 8.00 2. tsallake ii 0.09 6 16.0 3. ajari ai 0.39 0.30 6.00 4. faawari iv 0.55 0.50 7.50 5. maisandari 0.08 9.20 23.00 6. fawari i 0.14 0.30 6.00 7. dikumari iii 0.06 2.50 14.50 8. malllum-matari 0.10 7.0 16.00 9. gwange v 0.61 0.30 6.00 10. daki-tara i 0.19 0.20 5.00 table 3: chemical properties of the water samples monitored s/n well location ph total dissolved solid (tds) hardness ng iron (mg) chloride (mg/1) nitrate (mg/1) sulphate (mg/1) fluoride (mg/1) 1 tsailake i 6.9 9.72 33.96 0.18 0.43 1.40 0.131 0.038 2 tsallake ii 8.7 16.61 23.97 0.22 0.54 28.00 0.361 0.013 3 ajari ai 7.3 20.54 45.95 0.20 0.67 1.68 0.093 0.024 4 faawari iv 6.8 32 81.92 0.36 1.11 2.66 0.22 0.041 5 maisandari 6.9 27.95 23.96 0.71 0.17 0.07 0.736 0.076 6 fawari i 6.8 25.3 19.98 0.23 0.44 1.26 0.163 0.014 7 dikumari iii 6.2 28.65 39.96 0.65 0.27 1.54 0.481 0.02 8 mallum-matari 9.0 39.3 19.98 0.16 0.34 40.00 0.556 2.00 9 gwange v 6.5 41.89 129.87 0.42 1.07 41.00 0.253 0.019 10 daki-tara i 6.6 29.45 33.96 0.39 0.67 1.41 0.109 0.011 septic tank leachates have long been suspect of nitrate and, to some extent, chloride in groundwater (ahajjar et al., 1990). closeness to septic tanks and pit latrines resulted in groundwater contamination in damaturu, nigeria 48 significant concentrations of nitrate (28, 40 and 41 mgl-1 in wells 2, 8 and 9 respectively), which exceed the european community standards. table 4 shows international water quality standards (who, 1971). consumption of water with nitrates above the permissible limit is a potential health risk as this can cause methyglobenemia syndrome. hardness was high in wells 4 and 9 with values of about 82 and 130 mgl-1 respectively as shown in table 3. hardness indicates the presence of metallic ions such ca ++, mg++ and fe++. the metals are associated with hco3, so4, cr and no3. there is no health hazard in it. in fact, from toxicity point of view, animals generally survive longer using hard water than soft water. however, there are economic disadvantages expressed in increased soap usage and fuel cost. results obtained for colour were not acceptable in wells 2, 5 and 8, this may be a problem in some industries. co-existence of wells with waste disposal system resulted in faecal contamination with average coliform density of 28.4(100ml)-1 of samples as shown in table 5, which is beyond the permissible limit of 1 (100ml)-1. table 4: international standards for drinking water (who, 1971) s/no substances/characteristics highest desirable level maximum permissible level 1. colour 5 units 50 units 2. odour unobjectionable unobjectionable 3. taste unobjectionable unobjectionable 4. turbidity 5 units 25 units 5. total solids 500mg/ l 1500mg/l 6. ph 7.0-8.5 6.5-9.2 7. ammonic detergents 0.2-mg/ l 1.0mg/l 8. mineral oil 0.0lmg/ l 0.30mg/l 9. total hardness (as caco3) 100mg/ l 500mg/l 10. calcium 75mg/ l 200mg/l 11. chloride 200mg/l 600mg/l 12. copper 0.05mg/l 1.5mg/l 13. iron 0.1mg/l 10.mg/l 14. magnesium based on 30-150 mg/l sulphate 150mg/l 15. manganese 0.05mg/l 0.5mg/l 16. sulphate 700mg/l 400mg/l 17. zinc 5mg/l 15mg/l 18. fluoride 0.6mg/l 1.7mg/l 19. total alkalinity 10mg/l 2.5mg/l 20. carbon dioxide 10mg/l 100mg/l 21. acidity total 22. nitrates 0.lmg/l 0.2mg/l 23. phosphorous 2mg/l 24. ammonia, (nitrogen) 0.05mg/l 0.05mg/l 25. chromium (hexivalent) 0.lmg/l 0.lmg/l 26. lead 0.00mg/l 0.00mg/l 27. mercury 0.00mg/l 0.05mg/l 28. selenium 0.0lmg/l 0.0lmg/l 29. cadmium 2mg/l 30. arsenic 0.05mg/l 0.2mg/l 31. cyanide 0.0lmg/l 0.05mg/l azojete vol. 4 2004 49 table 5: bacteriological (coliform) counts of water samples s/no location coliform counts (100ml)-1 1. tsalkake i 27 2. tsallake ii 84 3. ajari ai 24 4. faawari iv 17 5. maisandari 12 6. fawari i 11 7. dikumari iii 12 8. mallum-matari 17 9. gwange v 57 10. dakitara i 23 mean 28.4 all the wells examined were contaminated with faecal coliform. total coliform are indicators of pathogens that cause diseases such as cholera, typhoid, dysentery gastro-enteritis and diarrhoea. it is apparent from the forgoing that some form of treatment is essential before usage. 4. conclusion groundwater quality was monitored in 10 wells located near solid and liquid waste disposal systems in damaturu, nigeria. closeness to pit latrines and septic tank resulted in significant concentrations of nitrates (28, 40 and 41 mg/l) in three wells which exceed european community standards. consumption of water with nitrates above the permissible limit is a potential health risk and can cause methyglobenemea syndrome (anaemia). co-existence of wells with waste disposal systems resulted in faecal contamination with average coliform density of 29 (100ml)-1 exceeding the maximum permissible limit. the iron content of all the samples monitored does not fall within the permissible limit for health consideration. it is recommended that when wells are constructed, proper sanitary protection should be provided against surface contamination. a well should be located at a safe distance from all possible sources of contamination. there is the need for understanding pollution as a first step for its evaluation and control. the well site should be prevented from being flooded and should be graded so as to facilitate the rapid drainage of surface water away from the well. groundwater contamination in damaturu, nigeria 50 references adeniji, f. a (1997). water resources management for drought desertification control in yobe state. an invited paper presented at the world bank-state environmental action plan (seap) project workshop for yobe state at damaturu, 15th may. ahajjar b. j., g. chester and j.m. harkin (1990). indicators of chemical pollution from septic systems. groundwater 28, 559-568. nest (1991). nigeria’s threatened environment a national profile. environmental study/action team. nest publication. npc (1991). national population commission. damaturu, yobe state. sangodoyin, a. y. (1991). ground and surface water pollution by open refuse dump in ibadan, nigeria. discovery and innovation 3, 37-41. sangodoyin, a.y. (1993). considerations on contamination of groundwater by waste disposal system in nigeria. environmental technology. 14, 957-964. who (1971). guideline for drinking water quality, vol.i recommendations. world health organization, geneva. abstract 1. introduction availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 54-59 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng effects of tillage treatments on weed control in a maize field on sandy loam soil of north eastern nigeria kawuyo, u.a.1, m. a. haque1 and a.m. usman1 abstract this study was carried out to determine the effects of tillage treatments; namely: zero-tillage (t1), disc ploughing (t2), disc harrowing (t3) and disc ploughing followed by disc harrowing (t4) on weed control in a maize field. plant height (cm), weed density (no/m2) and fresh weed weight i.e. weed biomass (g/m2) were measured at various growth stages of the crop, while grain yield (kg/ha) was determined after harvest. the study was conducted in 1999 and 2000 farming seasons. the results showed that there were significant differences between tillage treatments for all the measured parameters in both years. the grain yield increased by 34and 36% for the year 1999 and 2000 respectively when treatments t1 and t4 were compared. a reduction in weed density at harvest by 57 and 52% in 1999 and 2000 respectively was obtained when treatments t1 and t4 were compared. also, there was a 53 and 34% reduction in 1999 and 2000 respectively for the weed biomass when these two treatments were compared. it was recommended that treatment t4 be adapted for better weed control. 1. introduction tillage in agriculture is defined as the mechanical manipulation of soil to provide conditions suitable for the growth of crops, control of weeds, maintenance of infiltration capacity and aeration (farral and basselman, 1979; asae, 1993). reasons for tilling the soil have also been given by many authors and these include seedbed preparation, weed control, improvement of soil physical conditions, management of plant residues, minimizing soil erosion, incorporation f fertilizers and to improve productivity (foth 1978; kepner et al. 1978 and ohu, 1995). in agriculture, a weed is any plant growing in a place not meant for it. this may be herbaceous or woody, creeping or erect. almost any kind of plant can, therefore, be a weed as long as it exists in a location or situation where it is considered undesirable. weed is certainly a major nuisance for farmers. in any crop production, weed is one of the major factors affecting crop yield. this is due to competition for a number of vital resources such as light, water and nutrients (anonymous, 1987). according to rouanet (1987), maize needs to be weeded two or three times (for optimal yield). first, at the plantlet stage, that is, 10-15 days after emergence; secondly, at the start of booting, and thirdly, before harvesting to facilitate harvesting operations. he further reported that, weeding by hoe at three and seven weeks after planting is required for optimum yield. if herbicide is used, primextra, a pre-emergence herbicide (5l/ha) should be applied within two days after planting (dap) in the case of conventional tillage. for strip tillage, primextra (5l/ha) plus gramaxone (4 l/ha) should be used (rouanet, 1987). data from many experiments support the conclusions that the major reason for cultivation is weed control. it was reported by matasova et al. (1971) that high yield on plots with two 1 department of agric. & environmental resources engineering, university of maiduguri, maiduguri. nigeria http://www.azojete.com.ng/ azojete vol. 5 2007 55 cultivations was due to effective weed control. stach (1992) conducted a study on soil cultivation in relationship to the development of weeds and reported that weeds occurred at higher frequencies on no-tilled plots. in a study on the effect of reduced tillage systems on weed population in denmark, thorup (1985) reported that, in general, reduced tillage cost less, gave higher yields and significantly reduced the stand of weeds. even though there are many reported literature (some as cited above) on the effects of tillage practice on weed control, there are only very few information on this for the semi-arid environment of north-eastern nigeria. therefore, the objective of this study was to compare the effects of four tillage treatments on weed control in a maize field on a sandy loam soil and to establish the most suitable weed control tillage method in semi arid environment like north-east nigeria. 2. materials and methods 2.1 experimental area the experiment was carried out under rain-fed conditions at the university of maiduguri teaching and research farm in 1999 and 2000 farming seasons. the soil has a sandy loam texture (77% sand, 6% silt and 17% clay) (rayar, 1984). rainy period in the study area is usually between june and september, a period of about four months. the total rainfall in the area was recorded as 822.6mm in 1999 and 650 .4 mm in 2000 (daura, 2001). some of the common weeds available in the study area are: striga generoides, striga hermontheca, striga aspera, gamba grass macuna and some volunteer plants. 2.2 experimental treatments and field layout a 16-plot experiment consisting of four tillage treatments with four replications was set up in a randomised complete block design. the treatments were: zero tillage (t1), disc ploughing (t2), disc harrowing (t3), and disc ploughing followed by disc harrowing (t4). the plot size was 18 m x 5 m with alleys of 4 m between replications and 8 m between the plots. this was to accommodate the width and length of the tractor with the implement and to allow the tractor gain speed before the tillage operation was carried out. disc ploughing was done at an average depth of 20 cm with a 3 – furrow mounted plough, and harrowing with an offset disc harrow at an average depth of 15 cm. zero tillage involved planting on bare land with minimum soil disturbance. treatment t4 involved ploughing followed by harrowing. 2.3 determination of plant and weed parameters maize variety, suwan-1-sr was planted on 8th july 1999 and 28th june 2000. planting was done manually by placing 3 seeds/hole at an interval of 0.30 m along the rows and 0.90 m between the rows at an average depth of 5 cm. thinning to 1 stand/hole was done at 3 weeks after planting (wap). fertilizer, in the form of npk (15:15:15), was applied at the rate of 400 kg/ha at 2 wap followed by a second dose of urea at 200 kg/ha at 6 wap as recommended by anonymous (1989). first weeding was done manually using a hoe at 3 wap. second weeding using the same tool was carried out at 7 wap. the last weeding was done to facilitate harvesting at 12 wap. for both years, the crop was harvested at 13 wap. the parameters studied during the growth period were plant height (cm), weed density (no/m2), fresh weed weight i.e. weed biomass (g/m2) and the grain yields (kg/ha). two weeks effects of tillage treatments on weed control in a maize field on sandy loam soil of north eastern nigeria 56 after emergence, five plants from each plot were selected at random and their heights measured using a meter rule. the measurement was done from the ground surface to the tip of the last leaf. average of these was taken and recorded. at each weeding period, the weed density was determined according to the method described by fao (1994), while the method described by olofintoye (1989) was used to determine the weed biomass. the yield from each plot was obtained and expressed in kg/ha. average values of the plots for each treatment were recorded as the yield of that treatment. analysis of variance was used to study the statistical differences between the treatments for each parameter at 5% level of significance. where there was statistical difference, duncan multiple range test was used to compare the different treatment means. 3. results and discussion 3.1 plant parameters plant heights were measured from 2 wap at two weeks intervals up to 12 wap and the values are shown in tables 1 and 2 for 1999 and 2000 respectively. in the first 2 measurements, the rate of growth was low in all the treatments for both years. as from 6 wap, plants in the tilled treatments were observed to be taller than those in zero-tillage treatments. treatment t4 was the best within the tilled treatments in terms of plant height. it was observed that there were significant differences in the plant height as from 4 wap up to harvest. the significance in the plant height could be due to tillage treatments. ojeniyi(1986) also reported that different tillage treatments caused significant differences in the height of maize plants. table 1: effects of tillage treatments on plant height, cm (1999) treatment weeks after planting (wap) 2 4 6 8 10 12 t1 12.09*ns 29.50 a 58.09 6 137.36 a 156.55 c 159.97 a t2 13.56 ns 35.646 82.94 a 159.46ab 180.41 a 184.876c t3 12.68ns 35.426 64.696 141.20ab 168.86abc 172.79abc t4 13.19ns 37.99b 90.98a 165.38b 179.92ab 186.45c se 0.80 2.14 6.74 10.34 7.52 6.21 * = mean values of four replicates ns = not significant a,b,c = means in the same column followed by the same letter are not significantly different at p<0.05(dmrt). azojete vol. 5 2007 57 table 2: effects of tillage treatments on plant height, cm (2000) treatment (wap) 2 4 6 8 10 12 t1 12.95*ns 27.41b 61.94c 141.62bc 163.41c 169.28c t2 13.71 ns 31.15ab 85.32ab 163.15ab 191.32ab 215.13ab t3 13.12ns 32.54ab 83.16ab 158.76abc 178.15abc 192.81b t4 14.23ns 34.73a 91.75a 169.81a 205.36a 221.57a se 0.91 2.36 7.42 9.85 9.04 5.46 * = mean values of four replicates ns = not significant a,b,c = means in the same column followed by the same letter are not significantly different at p<0.05(dmrt). 3.2 grain yield the grains were weighed after threshing and average values obtained were converted to kilogramme per hectare as recorded in table 3. the highest yield of 854.26 and 972.73 kg/ha were obtained in treatment t4 and the least of 638.78 and 714.25 kg/ha in treatment t1 for 1999 and 2000 respectively. water logging was observed in some plots during the growth period. also, termites attacked the plots, which led to falling down of some stalks. this happened when there was a short period of dry spell during the growth period. statistical analysis showed that grain yield was significantly affected by tillage treatments. tillage significantly increased grain yield in both years. table 3: effects of tillage treatments on grain yield, kg/ha treatment (year) 1999 2000 t1 638.74*a 714.25c t2 767.04bc 872.37ab t3 750.10abc 815.01bc t4 854.26c 972.73a se 53.35 56.12 * = mean values of four replicates a,b,c = means in the same column followed by the same letter are not significantly different at p<0.05(dmrt). 3.3 weed parameters table 4 shows the values of weed density in the studied tillage treatments for 1999 and 2000 farming seasons. the values indicated that treatment t1 had the highest number of weed per square meter throughout the period of study for both years. it was observed that the highest value of weed density (171.25 and 197.12 no/m2) occurred in treatment t1 and the least of (72.25 and 81.18 no/m2) in 1999 and 2000 respectively in treatment t4 before the first weeding was conducted. even at harvest, the highest weed density was observed in treatment t1 and least in t4 for both years. this could be the reason why plants in treatment t1 were shorter than those in the tilled treatments as seen in tables 1 and 2. the weed densities were effects of tillage treatments on weed control in a maize field on sandy loam soil of north eastern nigeria 58 lower in the tilled treatments when compared to treatment t1. this may be the reason for higher grain yields in the tilled treatments. since for higher yield, the crop should be more competitive and thus tend to suppress the weed population. statistical analysis shows that tillage treatments had significant difference on weed density. this result agrees with the report of campbell et al. (1998) which said that differences in weed density with tillage treatments were significant. table 4: effects of tillage treatments on weed density, no/m2 treatments 1999 2000 wap wap 3 7 12 3 7 12 t1 171.25*a 103.13a 47.83a 197.12a 120.46a 61.34a t2 76.756 39.88b 23.42b 121.35b 77.38a 51.13a t3 79.75b 49.88b 27.75b 137.57b 82.14a 54.15a t4 72.25b 36.38b 20.42b 81.18c 31.75b 29.24b se 11.62 17.82 5.50 15.13 20.25 7.24 * = mean values of four replicates a,b,c = means in the same column followed by the same letter are not significantly different at p<0.05(dmrt). the mean weed biomass is shown in table 5 for both 1999 and 2000 farming seasons. at first measurement, the highest value of weed biomass was recorded in treatment t1 (707.22 and 825.12 g/m2) and least of 155.68 and 215.81 g/m2 for 1999 and 2000 respectively in treatment t4 .this could be attributed to the ploughing and harrowing operations that buried the weed seeds in the tilled treatments. these operations finally resulted to lower weed density and consequently the weed biomass in those treatments. at harvest, the highest weed biomass was observed in treatment t1 for both years. this observation was similar to that of mimorovic et al. (1998) where no-tillage gave the highest weed biomass at harvest. statistical analysis showed that weed biomass was significantly affected by different tillage treatments throughout the study period. table 5: effects of tillage treatments on weed biomass, g/m2 treatments 1999 2000 wap wap 3 7 12 3 7 12 t1 707.22*a 309.98a 34.05a 825.12a 481.39a 54.75a t2 159.15b 243.74b 16.18b 268.31b 302.05b 40.32ab t3 183.30b 282.79b 18.74b 294.17b 357.21b 43.67ab t4 155.68b 197.87b 15.84b 215.81b 276.17b 36.32b se 46.95 31.41 4.06 51.26 43.14 9.31 * = mean values of four replicates a,b,c = means in the same column followed by the same letter are not significantly different at p<0.05(dmrt). azojete vol. 5 2007 59 4. conclusion the results obtained from this study showed that there were significant differences between tillage treatments and all the measured parameters. it was found that treatment t4 performed the best in terms of grain yield and weed control, while treatment t1 performed the least. grain yield in treatment t4 was 34 and 36% higher than in treatment t1 for the year 1999 and 2000 respectively. when comparing treatments t1 and t4 on the basis of weed control at harvest, there was a decrease of about 57 and 52% of weed density in 1999 and 2000 respectively. weed biomass also decreased by 53 and 34% in 1999 and 2000 respectively. based on these findings, it is recommended that disc ploughing followed by disc harrowing should be adopted by farmers for better weed control in maize field in the north-eastern region on a sandy loam soil. however, the ploughing can be done at a shallow depth so as to avoid waterlogging problems since the soils are light soils. references anonymons (1987). maize production. extension bulletin, a.b.u., zaria, 13:1-13. anonymons(1989). fertilizer use and management practise for crops in nigeria. fertilizer procurement and distribution division of the f.m.a.w.r and r.d.,lagos. asae (1993). american society of agricultural engineers standards. st. joseph, michigan, campbell, c.a.; a.g. thomas; v.o. biederback; b.g mcconkey; f. selles; d. spur and r.p zentner (1998). converting from no-tillage to pre-seeding tillage: influence on weeds, spring wheat grain yields and soil quality. soil and tillage research, 46:175-185. daura, m. (2001). rainfall data records for 1980-2001. geography department, university of maiduguri (unpublished). fao (1994). testing and evaluation of agricultural machinery and equipment. principles and practices. agricultural services bulletin, rome. number 110. farral, a.w. and j.a. basselman (1979) dictionary of agricultural and food engineering. the interstate printers and publishers. inc. danville. foth, h.d. (1978). fundamentals of soil science 6th edition. john wiley and sons. new york. kepner, r.a; b.roy and l.e. barger (1978) principals of farm machinery, 3rd edition. mcgrow hill books company, n.y. matasova, e.p; n.sh. kelbiev and d.a abakarova (1971). increasing grain (maize) production. in: field crop abstracts, 1972 – 25(1). mimorovic, n.; b.sinzar and l. stefanovic (1998). effect of conservation tillage and herbicide application on weeds and yield of maize in a double cropping system. in: maize abstracts. 15,2. ohu,j.o.(1995). soil dynamics in agriculture: north-eastern nigeria experience. seminar paper delivered at the faculty of engineering, university of maiduguri (unpublished). ojeniyi, s.o. (1986). effect of zero-tillage and disc ploughing on soil water, soil temperature and growth and yield of maize. soil and tillage research, 7(1 and 2): 173-182. olofintoye, j.a. (1989). effects of tillage and weed control methods on weed growth and performance of upland rice in the guinea savannah of nigeria. nig.j. of agron. 2 & 3: 82-87. rayar, a.j. (1984). university of maiduguri farm development planning report for faculty of agriculture. annex a, soil survey details.(unpublished). rouanet, g. (1987). maize: the tropical agriculturalist. macmillan, hongkong. stach,j. (1992) soil cultivation in relationship to the development of weeds. in: weed abstracts, 1993. 42(5): 248. thorup, s. (1985). the effect of soil treatment on weeds. in: weed abstracts, 1988. 37 (8). arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):121-134 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 121 original research article performances of metal oxides supported in monolith for combined so2/nox removal from flue gas s. kiman*, h. d. mohammed, n. b. aliyu, t. h. usman and d. b. kayode department of chemical engineering, university of maiduguri, bama road, pmb 1069 maiduguri, borno state, nigeria *corresponding author’s email address: silaskiman@unimaid.edu.ng 1.0 introduction nitrogen oxides (nox) and sulfur dioxide (so2) are pollutants that are produced from fossil fuels which may cause acid rain, depletion of the ozone layer, urban smog, several illnesses, acceleration of the degradation of buildings, monuments, and structures (rosas et al., 2017; wu et al., 2016). the apprehension of such pollutants on the environment and human health has motivated a global campaign on strategies to abate their emission (abdulrasheed et al., 2018). wet flue gas desulfurization (wfgd) being the evolved matured technology used for so2 removal is incapable of eliminating nox. alternatively, alternatively, selective catalytic reduction (scr) is widely utilized for the nox control but due to catalyst fouling, operating and capital cost, it is limited (wu et al., 2016). therefore, the development of a costeffective method for combined nox/so2 removal is desirable. it was reported that the removal of acidic gases in flue gas composition by adsorption has advantages such as high removal efficiency, selectivity, regeneration potential with the simplicity of design and operation (abdulrasheed et al., 2018). also, adsorption is one of the most promising methods for pollutants abatement, however, however, the adsorbent and supported active species are critical to the adsorptive performance (yin et al., 2018). the supporting material must be characterized by high surface area, pore structure, and abrasion resistance moreover, the dispersion of the metallic components can promote the catalytic properties on the support (el-khouly et al., 2017). kiman et al. (2018) found that monolith has the required surface area, attrition, and fly ash plugging resistance, therefore, it can be used in heterogeneous catalysis as support. however, mo et al. (2018) stated that the dispersion of active components on the monolith is always in-homogeneous and easy to aggregate during impregnation and therefore has a negative effect on practical use. therefore, some efforts must be devoted to growing nanoarray-based catalysts on channeled monolithic substrates to promote catalytic activity. article information abstract the emission of acid gases such so2 and nox have detrimental effects on human beings and the environment hence, removing them from flue gas in a dry adsorption process is desirable. in this work, carbon monolith was synthesized with various metals consisting of ceo2, co3o4, v2o5, and cuo by deposition precipitation, hydrothermal and wet pore volume impregnation synthesis techniques. the fixed bed adsorption activity test was carried out with flue gas production by coal burning. furthermore, the breakthrough curves of the adsorbents were investigated where the adsorbent developed via hydrothermal technique with co3o4 metal oxide termed as hm-co3o4 /cm displayed higher adsorption capacity for both so2 (103.9 mg/g) and nox and (106.6 mg/g). the langmuir model can best describe the experimental data based on the correlation coefficient and separation factor results. these results implied that the developed adsorbent can be potentially used in the industry for flue gas cleaning. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 august, 2021 revised 2 december, 2021 accepted 2 december, 2021 keywords: adsorption capacity fossil fuels breakthrough curve monolith adsorbent http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng silaskiman@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):121-134. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 122 the surface chemistry of an adsorbent can affect its adsorption and catalytic abilities (sousa et al., 2018) while the surface functional groups of the support played a significant role in determining the extent of interaction with the active precursor during adsorbent preparation (ibraheem et al., 2014). hence, the introduction of hetero elements such as co3o4, ni v2o5, ce, and cuo on the adsorbents can significantly improve the catalytic activity (cui et al., 2018; ibraheem et al., 2014). the objectives of this study are to synthesize monolith adsorbents by deposition precipitation, hydrothermal and wet pore volume impregnation synthesis techniques with various metal oxides, and the breakthrough study of the adsorbents through the combined nox/so2 removal from flue gas. the adsorbent with highest adsorption capacity was investigated by ftir, bet surface area, sem and edx analysis, isotherm study, optimization of independent variables in adsorption with rsm software and the regeneration potential of the adsorbent. 2. materials and methods 2. 1. materials the monolith used has a channel of 1.02mm and a wall thickness of 0.25mm. urea (ch4n2o), nitrate hexahydrates (x(no3)2.6h2o), and nitric acid (hno3, 65%), were purchased from beihai huijuang chemical china. the chemicals and reagents used were all of analytical grade. 2.2 preparation and synthesis of the adsorbent the monolith structure was carbonized in a horizontal furnace (sa-a35014, malaysia) by heating at a rate of 5 ºc min-1 up to 800 ºc for 4 h and in inert condition following activation in co2 flow at 350 ºc for 2 h to obtain carbon monolith (cm). the cm is immersed in hno3 for 24 h next it was filtered and washed with distilled water before being placed in a vacuum oven at 70 ºc and 24 h to dry. 250 ml of deionized water, cm support metal nitrate, and substrate were charged into a reactor vessel of 350 ml capacity while the ph of the solution was made to 3.5 with hno3 and heated to 90 ºc then a solution of urea was added and further heated for 18 h while stirring at 300 rpm. the substrate was filtered, severally washed, and dried at 120 ºc for 24 h. finally, it was calcinated in inert at 500 ºc for 4 h using a heating rate of 5 ºc min-1. the adsorbent using the deposition precipitation technique is termed dp/cm. initially, the metal nitrate hexahydrates precursor and urea (ch4n2o) were dissolved into a homogeneous solution with 80 ml deionized water under and stirred with the cm. the mixture was charged into 100ml teflon stainless steel. the autoclave was sealed and reacted at 100°c for 5 h, then it was allowed to cool to room temperature. the samples were washed and ultrasonication before drying at 80 ºc for 2 h. the active metal component catalysts with the cm were heated to 300°c for 2 h at a heating rate of 3 °c min-1. the hydrothermally synthesized technique adsorbent is termed hm/cm. an aqueous solution with the metal nitrate precursor was mixed with the cm and heated at 70 ºc with constant stirring (300 rpm) to allow the entire solution to completely evaporate, it was washed and dried at 110 ºc for 24 h. the cm was annealed at 500 ºc for 4 h and a heating rate of 5 ºc min-1. the adsorbent from the pore volume wetness impregnation technique is termed im/cm. 2.3 fixed bed adsorptive test in the experiment, 1g of the adsorbent was charged into the fixed bed reactor (figure 1) and firstly preheated in inert for 1h at 100 °c. flue gas was produced in a vertical furnace at 850 °c by coal combustion since the industrial flue gas is produced in a power plant furnace at an operating temperature of >800 °c (li et al., 2008). the generated flue gas was channeled to the adsorbent at 450 ml/min and a file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng kiman et al: performances of metal oxides supported in monolith for combined so2/nox removal from flue gas. azojete, 18(1):121134. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 123 temperature of 150 °c. the inlet and outlet concentrations of nox and so2 were measured with a t350 flue gas analyzer. the adsorbent activity test was evaluated through the adsorption capacity as defined by the weight of nox and so2 captured from the flue gas per gram of adsorbent. the experimental run was performed in duplicate and only the average value was used. figure 1: schematic of the fixed bed adsorption system 2.4 adsorption isotherm studies in this work, the equilibrium adsorption data were fitted in langmuir and freundlich models. the langmuir model describes the monolayer adsorption that occurs on the adsorbent surface without interaction among the adsorbed molecules while the freundlich isotherm is defining multilayer adsorption where the non-uniform distribution of adsorption heat and affinities on heterogeneous adsorbent surfaces occurs (singh et al., 2018). the adsorption capacity (qe) in mg/g is given by langmuir isotherm and presented as (yi et al., 2012): 𝑞𝑒 = 𝑞𝑚 . 𝐾𝐿. 𝐶𝑒 1+𝐾𝐿 . 𝐶𝑒 (1) where ce is concentration, qm is the maximum adsorption capacity in mg/g and 𝐾𝐿 is the langmuir constant in l/g, respectively. the separation factor (rl) indicates langmuir isotherm suitability (favorable; 0 < rl< 1): 𝑅𝐿 = 1 1+ 𝐾𝐿 . 𝐶𝑜 (2) where co initial concentration in mg/l. the freundlich model is (yi et al., 2012): 𝑞e= 𝑘f𝐶e 1/n (3) where, kf and n are freundlich constants (intercept and slope) and the heterogeneity factor. the linearized form of langmuir and freundlich isotherms are (sharma et al., 2017): ce qe = 1 qmkl + ce qm (4) and logqe= logkf+1/nce (5) http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):121-134. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 124 2.4 adsorbent characterization the n2 adsorption/desorption isotherm was measured with micrometrics asap2020 instrument. initially, the samples were outgassed at 200 °c for 4 h in the presence of n2. the isotherms were utilized in calculating the specific surface area sbet. the fourier transform infrared spectroscopy (ftir) was used to investigate the functional group attached to the surface of the adsorbent. the infrared spectra of synthesized adsorbent were mixed with kbr and the transmittance mode was verified between 4000 cm−1and 400 cm−1 with a resolution of 4 cm−1, using a thermo nicoletaes0200682. scanning electron microscope with energy dispersive x-ray micro-analyzer (sem/edx) (hitachi co., japan, model no. s3400n) was used to study the morphology of the adsorbent. 3. results and discussion 3.1. breakthrough curves for various adsorbents the breakthrough curves were plotted from average experimental values while the performance in terms of adsorption capacity for each adsorbate was evaluated. figure 2(a-d) shows the breakthrough curves for the combined nox/so2 removal for the various adsorbents developed. the ceo2-based adsorbents in figure 2a demonstrate 100% initial nox/so2 adsorption while the hydrothermal synthetic method exhibit a longer breakthrough time about both nox and so2. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng kiman et al: performances of metal oxides supported in monolith for combined so2/nox removal from flue gas. azojete, 18(1):121134. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 125 http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):121-134. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 126 figure 2: breakthrough curves of (a) ceo2-based (b) cuo-based (c) v2o5-based and (d) co3o4-based adsorbents. however, the breakthrough and the saturation times were longer for so2 over nox and the ceo2 plays an important role in the nox/so2 removal. the presence of oxygen surface groups might have increased the tb because ceo2 possessed oxidizing property and this fact may indirectly lower the conversion of nox (sumathi et al., 2010a). the hierarchy of breakthrough time displayed by the cuo-based adsorbent follows as: hmceo2/so2>hm-ceo2/nox>dp-ceo2/nox>im-ceo2/so2>im-ceo2/nox>dp-ceo2/so2. copper based catalysts are known to have high reactivity for so2 removal and high catalytic activity for nox reduction in its oxide form (hu et al., 2001). it is assumed that the simultaneous so2/nox removal occurred for these reasons (figure 2b). meanwhile, pores may be blocked which leads to reduced adsorbent performance depending on the synthesis method and compatibility with the metal oxide catalyst. the presence of so2 in the flue gas reduces the adsorbent performance and longevity garci-bordeje et al., (2004) but from figure 1c, v2o5 has shown high so2 uptake at stack temperatures and the overall performance of the v2o5 based adsorbent showed higher so2 adsorption compared to nox. the role of v2o5 in the higher so2 removal consists of four steps as follows: the adsorption of so2 at sites adjacent to v2o5, the interaction of so2 with v2o5 to form an intermediate with a structure like voso4, the reactions of o2 with the voso4-like species to yield v2o5 and so3 and finally, the migration of so3 or h2so4 formed between so3 and h2o to the adjacent acm pores. the former authors reported similar findings (ma et al., 2008). tricobalt tetraoxide (co3o4) has attracted lots of concern because it is cost-effective, has environmental benignity and has good catalytic activity at low temperatures (mo et al., 2018). the noticeable difference between the hm, dp, and im methods of synthesis with the co3o4 is shown by the co3o4-based adsorbents of figure 2d. the hm method demonstrates outstanding performance in the combined file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng kiman et al: performances of metal oxides supported in monolith for combined so2/nox removal from flue gas. azojete, 18(1):121134. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 127 nox/so2 removal. this performance suggested that there is uniform dispersion of the co3o4 on the cm. further, it implies that the hydrothermal treatment and the monolith support used with respect to co3o4 catalyst have a great effect on the adsorption performance. the hm synthesis method also influences the catalytic activity according to previous authors (radwan et al., 2007). initially, there was no 100% so2 removal by the im/cm adsorbent in all of figure 2, similar findings are reported in previous works (ghorai and pant, 2005; zhou et al., 2012). the highest performance is shown by the hm/cm adsorbent regarding q, tb and tsat when compared to the co3o4-based adsorbents. figure 3a illustrates the adsorption capacity of the adsorbents and figure 3b shows the breakthrough and saturation times of the adsorbents. it can be observed that the highest point is at 130.2 mg/g for q-nox and for the hm-co3o4/cm adsorbent while the lowest point is shown at 3.1 mg/g for q-so2 and for hmv2o5/cm adsorbent. figure 3: (a) adsorption capacity measurement (b) breakthrough and saturation times of the adsorbents. the demonstration of the hm-co3o4/cm adsorbent to perform in practical application beyond the other adsorbents is because of the compatibility of the adsorbent surface with the co3o4 metal oxide. furthermore, the result shows how well the hydrothermal synthesis disperses the co3o4 on the support. meanwhile, the adsorption capacity can be seen to be much favorable towards nox adsorbate. the adsorbent’s demonstration of high nox adsorption affinity is majorly due to the nox concentration in the flue gas (sumathi et al., 2010b; galvez et al., 2005), the preparation route (lazaro et al., 2008; hosseini et al., 2016; kreutzer et al., 2001), temperature (sumathi et al., 2010a; zhao et al., 2011), the oxygen http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):121-134. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 128 present (zhang et al., 2006; liu and shih, 2006) and relative humidity (sumathi et al., 2010b; dahlan et al., 2009) inactivity test. figure 3b displayed the time taken for the breakthrough to happen and the saturation time for each adsorbate respectively. the hm-co3o4/cm adsorbent is picked for further studies including characterization, isotherm and rsm optimization. 3.2 hmco3o4/cm surface area and functional groups it is revealed in figure 4a that the adsorbent is of iv isotherm type based on iupac classification, suggesting the dominance of mesoporous in the sample. a similar sample of carbon-coated monolith was reported previously (hosseini et al., 2015). from the bet analysis of the surface area, the surface area is 47.9 m2/g. figure 4: the (a) n2 adsorption-desorption plot (b) ftir spectrum of hm-co3o4/cm adsorbent. the ftir spectrum in figure 4b showed several bands belonging to the function groups that are attached on the adsorbent’s surface. at 2627 cm-1 there is band ascribed to o-h of carboxylic acid while 23352361cm−1 is ascribed to c-n triple bond. also, at 1741 cm-1 the c=o of ester stretch was observed, 1370 cm-1 (c-o of a phenolic stretch). also, assigned to c-o, c-h, ch=ch2 stretches are the absorption bands at 1175-440 cm-1 (raghunath and mondal, 2017; malkoc et al., 2006). the absorption peaks at 675cm−1-576cm−1 are ascribed to si–o stretching bands and indicate the presence of co3o4 (dahlan et al., 2009; li et al., 2011; teoh et al., 2013). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng kiman et al: performances of metal oxides supported in monolith for combined so2/nox removal from flue gas. azojete, 18(1):121134. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 129 3.3 hmco3o4/cm morphology results the surface morphology and elements of the hm-co3o4/cm adsorbent are presented in figure 5. figure 5: (a) sem microphotographs (b) elemental result and (c) edx peaks in figure 5a, the surface structures by sem illustrates the uniform dispersion of the co3o4 catalyst on the cm surface area in a rich spider-like web, similar microphotograph was previously presented (sumathi et al., 2009). furthermore, the cordierite has a surface with many large pores which are available for the adsorption to take place. the edx spectra in figure 5b showed the presence of co3o4 (1.1%) in the http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):121-134. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 130 impregnated cm by edx techniques. the bare cordierite is made up of si, al, o and mgo however, the carbonization process is responsible for the presence of carbon of up to 41.4% by weight which results in the improvement of highly porous surface (hosseini et al., 2011). 3.4 the isotherms from figures 6 a-d, the higher correlation coefficient (r2) was obtained from the langmuir model which suggested that the experimental data can be best described by the langmuir model when compared to the freundlich model which displayed the r2 of 0.6682 and 0.8734 for so2 and nox respectively. figure 6: (a) langmuir isotherm for so2 (b) langmuir isotherm for nox (c) freundlich isotherm for so2 and (d) freundlich isotherm for nox. the r2 and the parameters for langmuir and freundlich models are presented in table 1. moreover, the rl value further indicates the suitability of the langmuir model (0.3377 and 0.0973 for so2 and nox). the range of favorable adsorption based on the freundlich model is within the range 1 < n < 10 (hosseini et al., 2011). the values for heterogeneity factor for both so2 and nox are well below the range of favorable adsorption as shown in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng kiman et al: performances of metal oxides supported in monolith for combined so2/nox removal from flue gas. azojete, 18(1):121134. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 131 table 1. the langmuir and freundlich parameters results. q (mg/g) so2/nox langmuir parameter so2 nox freundlich parameter so2 nox 121.1 and 130.2 qm kl r2 20.0 0.344 0.9509 20.4 3.45 0.9300 kf n r2 1.26 0.7936 0.6682 -1.42 0.7042 0.8734 4. conclusion the adsorption capacity of various adsorbents that were impregnated with metal oxides and using three different synthesis methods was studied. by coal combustion in a vertical furnace, flue gas was produced to simulate the generation of flue gas from power plants and the activity test was performed. meanwhile, meanwhile, the breakthrough curve of combined nox/so2 was reported. based on the regression coefficient and the favorable separation factor, the langmuir model can best describe the experimental data. according to characterization results of the adsorbent with the highest adsorption capacity (hmco3o4/cm), there is an available active site for the adsorption to occur, the presence of co3o4 was shown. references abdulrasheed, aa., jalil, aa., triwahyono, s., zaini, maa., gambo, y. and ibrahim, m. 2018. surface modification of activated carbon for adsorption of so2 and nox: a review of existing and emerging technologies. renewable sustainable energy reviews, 94(2): 1067–1085. https://doi.org/10.1016/j.rser.2018.07.011 cui, x., yi, h., tang, x., zhao, s., yang, k., yan, b. and ma, y. 2018. study of the properties of adsorption of so2 – thermal regeneration cycle of activated coke modified by oxidization. journal of chemical technology and biotechnology, 93: 720–729. https://doi.org/10.1002/jctb.5421 dahlan, i., lee, kt., kamaruddin, ah. and mohamed, ar. 2009. selection of metal oxides in the preparation of rice husk ash (rha)/cao sorbent for simultaneous so2 and no removal. journal of hazardous materials, 166(2-3): 1556–1559. https://doi.org/10.1016/j.jhazmat.2008.12.028 el-khouly, sm., mohamed, gm., fathy, na. and fagal, ga. 2017. effect of nanosized ceo2/zno loading on adsorption and catalytic properties of activated carbon. adsorption science and technology, 35(910): 1-15. https://doi.org/10.1177/0263617417698704 gálvez, me., lázaro, mj. and moliner, r. 2005. novel activated carbon-based catalyst for the selective catalytic reduction of nitrogen oxide. catalysis today, 102–103: 142–147. https://doi.org/10.1016/j.cattod.2005.02.020 garcía-bordejé, e., calvillo, l., lázaro, mj. and moliner, r. 2004. study of configuration and coating thickness of vanadium on carbon-coated monoliths in the scr of no at low temperature. industrial engineering chemistry research, 31(4): 4073–4079. https://doi.org/10.1021/ie0498854 ghorai, s. and pant, kk. 2005. equilibrium, kinetics and breakthrough studies for adsorption of fluoride on activated alumina. separation and purification technology, 42: 265–271. https://doi.org/10.1016/j.seppur.2004.09.001 http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng arid zone journal of engineering, technology and environment, march, 2022; 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vol. 18(1):121-134. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: silaskiman@unimaid.edu.ng 134 zhao, y., hu, g., sun, z. and yang, j. 2011. simultaneous removal of so2 and no2 on α-al2o3 absorbents loaded with sodium humate and ammonia water. energy and fuels, 25(7): 2927–2931. https://doi.org/10.1021/ef2002712 zhou, x., yi, h., tang, x., deng, h. and liu, h. 2012. thermodynamics for the adsorption of so2, no and co2 from flue gas on activated carbon fiber. chemical engineering journal, 200–202: 399–404 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/silaskiman@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):331-344 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 331 original research article comparative evaluation of the quality characteristics of composite flour bread produced from wheat-root tuber and wheat-grain legume flour blends g. i. agbara1*, a. c. ige2, n. h. agbara3, g. ahmad4, f. a. masaya1 and b. aliyu1 1department of food science and technology, university of maiduguri, maiduguri, nigeria 2department of science laboratory technology, ramat polytechnic, maiduguri, nigeria 3department of home economics, lawan mohamet college of agriculture, maiduguri nigeria 4department of food science, bayero university kano, kano, nigeria *corresponding author’s email address: giagbara@unimaid.edu.ng article information abstract adoption of composite flours for baked and non-baked goods has been trending and the underlying reasons include economic consideration, nutritional enhancement and amelioration of noncommunicable diseases through consumption of functional foods. comparative study of the performance of popular food crop flours in bread making is not well documented although a lot work abound in the literature concerning specific blends from wheat and crop flours studied separately. but in the present study, comparative effects of 30% substitution of wheat flour with two common root tuber flours: sweet potato (ps) and cassava (ca) and three common grain legume flours in nigeria: soybean (s), cowpea (co), bambara groundnut (b) on bread quality were studied. soybean, cowpea, and bambara groundnut were soaked and decorticated, toasted mildly and milled to obtain flours. cassava and sweet potato roots were peeled, chopped, oven dried, milled and sieved. all purpose wheat flour was used to form blends with non-wheat flours on a constant ratio of 70:30 replacement weight basis, a total of five flour blends were obtained while 100% wheat flour served as the control. bread were prepared using straight dough method of aacc. thereafter, standard procedures were used to evaluate the proximate composition of the blends and bread, as well as the bread physical and sensory properties. data generated were subjected to analysis of variance and mean values ±se were reported. consistently, soybean and bambara groundnut flours had significant higher content of protein, ash, crude fat and crude fibre than cassava and sweet potato flours which contained higher level of carbohydrates. the moisture contents of the flours were low and comparable. the moisture, crude protein, crude fat, total ash, crude fibre and carbohydrate contents of the flour blends and the refined wheat flour varied significantly (p<0.05) from 8.0810.27%, 7.52-13.93%, 2.08-4.06%, 0.81-1.85%, 2.11-4.51% and 67.7576.66% respectively. the same trend was repeated in the proximate composition of the composite flour breads although the calorific values decreased due to decrease in carbohydrate contents (58.00-47.64%), protein (6.37-11.98%), and increase in moisture (26.71-29.75%), relative to the values observed in the flour blends. bread weights (196-223g) were comparable but the bread volumes (429-988ml) and specific loaf volumes (2.24-4.82ml/g) varied significantly (p<0.05) and wheat bread had the highest and legume flour treated breads had the least. organoleptic properties of the wheat bread were rated better in some attributes however not significantly (p<0.05) different from those of 30% sweet potato and cassava breads. it was concluded that although nutritional value of legume containing breads were greater yet their bread volumes were depressed more, the higher protein of grain legume flours not submitted 14 april, 2021 revised 28 april, 2022 accepted 30 april, 2022 keywords: root tubers grain legumes composite flours wheat gluten composite bread http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):331-344. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 332 1.0 introduction bread is an important staple food, and its consumption is steady and increasing especially in urban centers of nigeria. it is relatively expensive, however bread unit price in nigeria depends on dollar-naira exchange rate because it is produced from an imported wheat, a crop that does not do well in humid tropics, its cultivation in northern nigeria is hardly sustainable because of expensive irrigation regimen and vagaries of weather, usually cultivated during the cold period of the year. bread is a fermented, spongy confection made with four basic ingredients: flour, salt, yeast and water, prepared through unit operations such as mixing, proofing, scaling, molding and baking. bread formulation continue to change as food behaviors, nutritional consciousness and income change. bread continue to attract worldwide consumption therefore has become the commonest food product that supply needed calorie, protein, vitamins and minerals to the greatest number of people in all climes and cultures world over (pomeranz, 1987, dewetterick, 2008). wheat is the foremost grain of choice in the production of baked goods apparently due to uniqueness of its endosperm proteins: polymeric glutenins and monomeric gliadins, these two proteins constitute 75-85% of wheat endosperm proteins (macritchie, 1994); and on contact with water form what is commonly called gluten, a visco-elastic mass capable of retaining leavening gases during fermentation and baking process (wieser, 2007). fao (1971) initiated and promoted composite flour technology since 1970s, primarily to activate the use of non-wheat crops either partially or completely to replace wheat flour in the production of wheat-based goods such as bread, biscuit, cake, pastas, couscous, thin and thick porridges, etc. especially in wheat import-dependent countries like nigeria and others not situated in the wheat belt of the world. however, the concept of composite flour tevhnology has been advanced further to the production of functional and nutritious foods perhaps arising from population explosion and increasing urbanization, and also the shift from consumption of coarse to refined cereals and the desire for ready-to-eat convenient foods, a hallmark of the new age man. wheat importation represents an immense drain on the economy of nigeria while at the same time suppressing and displacing indigenous crops with detrimental effects on agricultural development and food security. since the diet of an average nigerian is carbohydrate based, the need for strategic use of inexpensive high protein resources with superior amino acid profile to complement those of common staples and in so doing enhance their nutritive value, cannot be overstressed. new protein sources are being explored, protein quality of pulses or oil seeds occupy prominent place in this endeavour (wang and kinsella, 1976; alimi et al.,2016). agricultural crops such as cassava, sweet potato, cowpea, bambara groundnut, soybean are largely cultivated in different agro-climatic zones of nigeria and transforming them into high quality flours, needed to formulate composite flours will induce commercial production of pastries, cookies, pastas, confections, biscuits, bread etc and thereby reduce hunger, malnutrition and food insecurity, and also reduce foreign exchange expenditure on wheat and other staple importation. withstanding confirming the fact that quality not quantity of the protein is the determinant factor in bread making potential of flours. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng agbara et al: comparative evaluation of the quality characteristics of composite flour bread produced from wheat-root tuber and wheat-grain legume flour blends. azojete, 18(2):331-344. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 333 grain legumes contain 18-32% lysine-rich protein which naturally complement the nutritional profile of cereal or root based diet of resource poor families (duranti and guise, 1997). they are also known to contain high levels of non-nutrient phytochemicals, majority of which possess antioxidant activity (mcintosh and topping, 2000), with the potential to obliterate oxidative stress which is responsible for increase of diseases which hitherto are rare. cowpea (vigna unguiculata walp) is the leading starchy pulse in nigeria in terms of production and consumption (alimi et al., 2016) closely followed by groundnut and bambara groundnut. it is a warm season annual crop with the greatest production in dry and moist savannah of subsahara africa. bambara groundnut on the other hand is regarded as a complete food because of high protein content (16-25%), caborhydrates (63-65%) and fat (6-8%) (brough and azamali, 1992, mazahib et al., 2013). its lysine and methionine content are 6.82g/16g n and 1.85g/16g n respectively comparable to 6.24g/16g n and 1.14g/16g n for soy protein. soybean, the wonder crop of the world, is an excellent source of high quality protein (35-40%) and the most important oil seed in the world in terms of production and utilization. cassava (manihot esculenta crantz) and sweet potato (ipomoae batata l.) are cultivated for their tuberous roots which are cheap sources of dietary energy for peasants in tropical countries and according to lebot (2009) people living in low land tropics of west and central africa depend on cassava for dietary energy. nigeria is the leading producer of cassava since 1989 and production level continue to soar because of increased industrial demand for cassava starch and chips, an export commodity and also an important staple. apart from its utilization as animal feed, cassava flour are incorporated into wheat flour for the production of baked or non baked goods in nigeria. sweet potato on the other hand, originated from the central america and now grown in many countries and has the natural capability of surviving in wide range of farming systems and climates (woolfe, 1992). the skin and flesh of the root have different colours and are good source of bioactive chemicals such as ascorbic acid, polyphenols and beta-carotene, a provitamin a (kusumayanti et al., 2015). these to some extent are absent in cassava except in vitamin a biofortified cassava roots which is currently popularized. on the other hand, sweet potato does not contain toxic cynanogenic glucosides present in cassava roots yet cassava flour with its whitish clour and bland taste is therefore more suitable for blending with cream coloured wheat flour for composite flour formulations. composite food products are noted for high nutritional value therefore able to mitigate high incidence of protein energy malnutrition with its high morbidity and mortality rate in developing countries like nigeria. therefore, the objective of the current study was to compare the physico-chemical and sensory properties of the blends and bread produced from wheat-grain legumes and wheat-root tubers flour blends. 2. matrials and methods 2.1 collection of raw materials and ingredients fresh roots of cassava and sweet potatoes, cowpea (biu white variety), soybean and bambara nut (creamed coloured) were sourced at gamboru vegetable market maiduguri custom area and materials such as all purpose flour (flour mills lagos, nigeria), dried bakers yeast, salt & sugar (dangote plc, lagos), baking fat (simas, indonesia), were purchased at the maiduguri monday market, borno state, nigeria. processing and analysis of samples were carried out at the food processing laboratory, department of food science and technology, university of maiduguri, borno state, nigeria. http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):331-344. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 334 2.2 raw materials preparation sweet potatoes and cassava roots were manually peeled, sliced (<5mm thick) immersed in hot water (>90ºc), 5 min, then air dried and finally dried in a cabinet dryer 60º•c±2ºc, 12 h. cooled dried chips were separately ground in a laboratory hammer mill and manually sieved using 300µm mesh. grain legumes (cowpea, bambaranut, soybean) were sorted, winnowed, separately soaked in tap water (1:3w/v) for 2 h, manually dehulled, parboiled for 10 min, then air dried, and mildly roasted on a hot pan until lightly browned, cooled grains were separately ground and sieved and packaged. 2.3 formulation of the flour blends the blends were made by replacing 30% of wheat flour (wf) with either sweet potato(p), cassava(ca), cowpea(co), soybean(s) or bambara groundnut(b) flour giving a total of five blends, code named: wp, wca, wco, wb, ws and wf served as experimental control. each blend was placed in a blender and mixed for 2 min, then separately packaged for analysis and bread preparation. 2.4 preparation of composite flour bread straight dough method of aacc (2000) for bread preparation was applied with the recipe shown in table 1. the flour and all ingredient were mixed in a mixer, master chef (mc b180, china) medium speed, the dough was covered and placed in a fermentation chamber for 90 min, 37±2ºc, relative humidity, 80-85%, thereafter degassed, scalled 250g, molded and placed in a greased pan and proofed again 60 min, 37±2ºc, rh 80-85%, later baked in a preheated oven 220ºc, 30 min. cooled loaves of bread were left in polyethylene bags at room temperature prior to use next day. table 1: recipe for the composite flour bread preparation wf wp wca wco ws wb yeast salt sugar fat water(ml) 1000 15 10 55 50 550 600 700 300 15 10 55 50 650 700 700 300 15 10 55 50 650 700 700 300 15 10 55 50 650 700 700 300 15 10 55 50 650 700 700 300 15 10 55 50 650 700 w: wheat, p: potato (sweet), ca: cassava, co: cowpea, s: soybean, b: bambara groundnut 2.5 proximate composition of blends and bread the composite flours and breads were analyzed for the proximate composition (moisture, crude protein, total ash, total lipids, crude fiber using the established ptocedures of aacc (2000). carbohydrate was determined by difference and calorific values were calculated as shown below. moisture contents were determined by drying the samples at 150ºc for 1h, protein contents (% n x 6.25) were determined by the micro-kjedahl method. crude fat were determined using solvent extraction in a soxhlet apparatus with petroleum ether (boiling point: 40 60ºc). the ash contents were determined by dry ashing in a muffle furnace at 550°c, 5 h. dietary fiber was determined using alternate digestion of 1g sample with dilute sulphuric acid (1.25%) and dilute sodium hydroxide (1.25%)solutions, washing, drying and finally ashing in a muffle furnace, 550°c, 5 h. caloric values (kcal) were obtained by multiplying the values of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng agbara et al: comparative evaluation of the quality characteristics of composite flour bread produced from wheat-root tuber and wheat-grain legume flour blends. azojete, 18(2):331-344. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 335 carbohydrate, protein, ash, and fat with the atwater conversion factors, then summing up: e = [4x(protein) + 4x(cho) + 9x(fat)] 2.6 physical characteristic of the composite breads and the wheat bread the physical characteristics of the bread samples (loaf weight, loaf volume and specific volume) were determined: loaf weight was measured after cooling to room temperature using a laboratory weighing scale and the readings were recorded in grams. the loaf volume was measured using seed (fonio seeds) displacement method, a mofification of giami et al. (2004). while the specific volume was calculated as loaf volume divided by loaf weight v/(cm3/g) (araki et al., 2009). 2.7 sensory evaluation of loaves of bread produced from flour blends of wheatlegume and wheat-root tuber flour blends the sensory properties of the bread were evaluated using the 9-point hedonic scale as described by larmond (1977) where 9 represents like extremely, 1 dislike extremely and 5 neither liked nor disliked. twenty (20) semi-trained judges (12 females and 8 males) comprising students and staff of the department of food science and technology, university of maiduguri. panelists (age, 23-55 years) were asked to assess the coded samples based on the following attributes (crumb, taste, aroma, colour and symmetry). panelists were provided with drinking water to rinse thier mouth after tasting each sample. the assessment was conducted only in one session. 2.8 statistical analysis determinations were conducted in duplicates and data generated were subjected to one-way analysis of variance (anova). means were separated using duncan multiple range test and a p-value of less than 0.05 accepted as significant (p< 0.05). 3. results and discussion proximate compositions of the various flours are presented in table 2. lower moisture or higher dry matter content of the flours (7.24-9.83%) reflects the low relative humidity of the environment this time of the year (dry season). therefore, it is reasonable to conclude that finer granulation of the root flours might be responsible for slightly higher moisture content due to greater exposure than observed in legume flours. soy and cassava flours had the least and the highest moisture contents. crude protein (4.04-37.48%), crude fat (1.14-19.20%), total ash (2.59-5.89%), crude fibre (2.81-4.24%) and carbohydrates (25.06-79.21%) were higher in the legume flours expectedly than observed in the root tuber flours. according to de almeida et al. (2006) food legumes contain more protein (17-40%) than in cereals (7.5-12%), the later have protein far more higher than in root or stem tubers. the same trend applies to fat content of legumes which is in general greater in most cereal and root tuber flours. higher nutrtive value of legumes enhance the diet in which they are incorporated. processing conditions, varietal differences, location and agronomical practices as well as storage and handling influence greatly the chemical composition of crops or their flours (kaur et al., 2007). in addition, decortication, grinding and sieving processes make comparative evaluation of reported results by different workers difficult especially with respect to ash and dietary fibre contents of different flours. for instance, apprinnita et al. (2014) reported lower moisture and protein content in sweet potato and cassava flours than observed in this study. black eye bean, the commonest bean in nigeria is reported by shuang-kui et al. (2014) to contain 1.56% oil against 5.20% recorded for nigerian grown cowpea, however other parameters reported by the same authors for black eye bean http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):331-344. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 336 are comparable with values obtained here. soy flour had superior higher protein, fat, fibre, ash contents than other flours and the least carbohydrates and moisture contents, greater dry matter. bambara groundnut flour had better balance of the nutrients, therefore regarded as a complete food (mazahib et al., 2013). the proximate values recorded for cassava and sweet potato flours in this study were comparable except significant higher total ash and crude fat of cassava flour, their protein and carbohydrate (78.65% and 79.21%) contents were not significantly different. diofanor et al. (2018) reported higher protein (10.25%) and lower fat (1.48%), ash (1.32%) and moisture (4.41%) for sweet potato flour table 2: proximate composition (%) of the various flours used for blend formulations results are mean±se (n=2). values in the same column with the same superscript are significantly not different at p-value of 5% (p<0.05). s: soy flour, b: bambara groundnut flour, co: cowpea flour, ca: cassava flour, ps: sweet potato flour 3.1 proximate composition of the blends and refined wheat flour. moisture contents (8.08-10.27%) of the composite flours and wheat flour were generally within the safe level for effective storage, wheat flour had significant higher moisture content than the blends (table 3). blending higher moisture wheat flour with non-wheat flour led to reduction in moisture content of the resulting blends, perhaps due to reduction in the surface aera of flour particles exposed to the environment, refined wheat flour is reported to have finer granulation (belorio et al., 2019). similar reduction in moisture and increase in ash, ptotein, fat and fibre were reported by otegbayo et al. (2018) for wheat-soy blends, dhaka and sangeeth (2017) for wheat-sweet potato blends, and dabels et al. (2016) for wheat-acha-mungbean blends. the higher dry matter indicates higher water absorption during reconstitution therefore higher dough yield and reduced bread stalling rate on storage. protein contents of the blends containing food legume flours were higher expectedly (12.81-13.93%) and those containing root tuber flours (wheat-sweet potato (wp70:30) and wheat-cassava (wca70:30) had the least protein content (7.52-8.27%) especially, wp70:30. the protein contents of the wheat flour was enhanced with inclusion of grain legume flour but decreased with the addition of tuber flour. the obvious reason is legumes generally contain approximately 2-3 times the protein of cereals, 4-5 times that of root tubers on dry weight basis. this is the single reason legumes are used for food fortification since they are cheap sources of inexpensive dietary nitrogenous substrates for peasants depending on starchy staples only for protein and calorie. fat contents of the blends ranged between 2.55 and 4.06% the wheat flour had the least (2.08%) and wheat-soybean ws (70:30) the highest (4.06%). wheat and root tubers are not good sources of lipids, relative to root tubers, wheat contain higher fat but in general high amounts of lipids are found in most food legumes than in root or wheat flour. added fat during dough formation provides tender crumb, therefore better mouthfeel in addition to highten flavor and enhanced calorie, however fat rancidification is a problem with overly fat-enriched foods during storage. the ash contents flours moisture crude protein crude fat total ash crude fibre cho s 7.24±0.47b 37.48±5.23a 19.20±0.43a 5.89±0.67a 4.24±0.26a 25.06±0.16d b 8.66±1.25ab 18.10±1.20c 5.80±0.74b 3.01±1.03bc 3.60±1.39ab 60.83±1.21b co 8.19±0.57b 22.59±0.87b 5.20±0.16b,c 3.17±0.10bc 4.17±0.08a 56.14±0.22c ca 9.83±0.07a 5.04±0.40d 2.77±0.72c 4.37±0.06b 3.50±0.36ab 78.65±0.23a ps 8.94±1.87ab 5.31±0.72d 1.14±0.49d 2.59±0.68d 2.81±0.33b 79.21±0.31a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng agbara et al: comparative evaluation of the quality characteristics of composite flour bread produced from wheat-root tuber and wheat-grain legume flour blends. azojete, 18(2):331-344. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 337 of ws (70:30) and wc (70:30) were significantly (p<0.05) higher respectively 1.81 and 1.85% and they were not significantly different, this was closely followed by the ash content of wb70:30. ash which represents the inorganic material is often indicative of the extent of flour refining, a repetitive process of grinding, milling and sieving. for wheat flour, ash content measures the amount of brany particles in the flour although beneficial to health but higher level is injurious to gluten strands and gas cells during dough mixing and fermentation (anil, 2007; rhemane et al., 2007). ash also is a determinant of flour colour and blending with higher ash nonwheat flours not only enhances nutrient density of blends but also changes the colour profile of resulting blends. the crude fiber contents of the blends (2.11-4.59%) followed the same trend as the ash and protein contents. the indigestible dietary fibre content of flours mainly originate from the outer coverings which are also the main source of ash, and blending with low fibre (2.11%) refined wheat flour with non-wheat flour increased the crude fiber content of the blends more in wheat-legume blends than in wheat-tuber blends, a range of 2.11-4.59% was obtained. carbohydrate contents of the wheat-legume flour blends were lower because of higher content of protein, fat, ash and crude fiber while higher carbohydrate contents were observed in wca (70:30) and wp (70:30) respectively 75.68% and 76.66%, higher than 73.99% for wheat flour. similar observations were made by previous researchers who blended wheat flour with legume or root tuber flour. ndife et al. (2011) and otegbayo et al. (2018) separately worked on wheat-soybeans flour bread; olaoye et al. (2018) studied wheat-bambaranut composite flour bread, ahmed and campbell (2012) worked on wheat-cowpea flour bread, in each case the reocurring observation was increase in protein, ash, fiber and fat contents of the flour blends with simultaneous slight decrease in moisture and carbohydrate contents depending on the level of wheat flour replacement. on the other hand, addition of root or stem tuber flour to wheat flour in blend formulation led to protein decrease, slight increase or decrease of fat in the blends and the simultaneous increase in total ash, dietary fiber and carbohydrate. this trend was similarly observed by dhaka and sangeeth (2017) and oluwalana et al. (2012) for wheat-sweet potato flour blends, amandikwa et al. (2015) for wheat-yam flour blends and lagnika et al. (2019) for wheat-cassava flour blends. table 3: proximate composition (%) of wheat flour and the different flour blends formulation moisture protein fat ash fibre cho calorie(kcal) w(100:00) 10.27±0.09a 10.78±0.90b 2.08±0.05bc 0.81±0.02c 2.11±0.38c 73.89±0.16b 357.80±1.14a wb(70:30) 8.31±0.14b 12.81±0.33a 3.51±0.05a 1.65±0.31ab 3.65±0.29b 70.27±0.09c 363.11±1.11a ws(70:30) 8.08±0.07bc 13.93±0.67a 4.06±0.04a 1.81±0.51a 4.18±0.07ab 67.94±0.06d 364.02±1.39a wco(70:30) 8.29±0.11b 11.85±0.71b 3.74±0.07a 1.85±0.19a 4.59±0.07a 67.75±0.12d 360.06±1.08a wp(70:30) 9.36±0.08ab 7.52±0.39c 2.85±0.03b 1.07±0.11bc 2.55±0.13bc 76.66±0.31a 362.37±1.72a wca(70:30) 9.48±0.31ab 8.27±0.22c 2.64± 0.11b 1.21±0.09b 2.79±0.10bc 75.68±0.23a 359.56±1.33a values are means±se (n=2), means in the same column bearing similar subscripts are not significantly different (p>0.05). w=wheat (100:00), wb=wheat-bambaragroundnut, ws=wheatsoybean, wco=wheat-cowepa, wp=wheat-sweetpotato; wca=wheat-cassava. 3.2 proximate composition of composite flour breads and wheat bread moisture contents were higher in the composite breads, it increased from 26.71% in the control to 29.75% in ws (70:30). (table 4). similar trend was observed by adebayo-oyetoro et al., (2016) for wheat-fermented banana bread (28.94-36.85%) wherein bread moisture increased with increased replacement of wheat flour, similar observation was reported by amandikwa et al. (2015) for wheat yam bread. apart from blends formed by partial replacement of wheat flour, baking time and temperature affects moisture content of bread (shittu et al., 2007). the protein contents of 30% pulse flour treated breads (10.68-11.98%) were higher, 30% soybeans http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):331-344. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 338 flour bread was slightly higher (11.98%) among them and 30% sweet potatoes and 30% cassava bread had the least amount of protein 6.89% and 6.37% respectively which were significantly different. yusuf and ejeh (2018) reported progressive increase in moisture, protein and other nutrients of bread with increased replacement of wheat flour with bambara nut flour; otegbayo et al. (2018) similarly observed the same trend in wheat-soybean bread. blending wheat flour with tuber flour leads to reduction in the protein content of the resulting blend or the food product, however dietary fiber and total ash are enhanced as observed here and similarly reported by oluwalana et al. (2012), dhaka and sangeeth (2017) and lagnika et al. (2019). kidane et al. (2013) reported increase in bread moisture, ash, fibre and decrease in protein and fat with increasing replacement of wheat flour with sweetpotato flour. the fat content of the wheat bread and composite flour breads ranged from 3.31% (wheat bread) to 5.81% (ws 70:30) slightly less than the range of 2.37-3.24% fat reported by igbabul et al. (2019) for wheat wateryam-hamburger beans bread. equally, the ash (1.50-2.97%) and crude fiber (1.19-2.57%) contents were also enhanced more in the composite breads. similar observation were made by oluwalana et al. (2015); olaoye et al. (2018) for wheat bambara nut bread and ahmed and campbell (2012) for wheat-cowpea bread, ndife et al. (2011) for wheat-soybean bread. higher level of protein and fat in pulse treated bread decreased the carbohydrate content which ranged from 47.64% (ws70:30) to 58.00 (w100%), the carbohydrate content of the 30% sweet potato and 30% cassava bread were not significantly different from that of the wheat bread as well as the calorific values of the breads which varied from 285.23 to 298.95 kcal/100g indicating that these bread are good for those conscious of body weight. table 4: proximate composition (%) of bread from different composite flour bread formulation mc protein fat ash fibre cho calorie(kcal) w(100:00) 26.71±0.10b 9.29±0.34b 3.31±0.25bc 1.5±0.14c 1.19±0.38c 58.00±0.43a 298.95±4.94a wb(70:30) 28.45±0.04ab 10.68±0.29ab 5.40±0.19a 2.09±0.11b 2.27±0.29ab 51.11±0.022b 295.76±3.76a ws(70:30) 27.75±0.07ab 12.21±0.41a 5.81±0.09a 2.68±0.08a 2.19±0.07ab 46.64±0.17d 287.69± 3.32a wco(70:30) 30.39±0.13a 11.98±0.46a 4.19±0.39ab 2.97±0.02a 2.57±0.07a 49.90±o.33c 285.23±2.10a wp(70:30) 29.47±0.28a 6.37±0.59c 3.77±0.20b 1.50±0.07c 1.85±0.13b 57.34±0.09a 288.77±4.12a wca(70:30) 29.22±0.13a 6.89±0.30c 3.91±0.46b 1.81±0.01c 1.89±0.21b 56.44±0.23ab 288.31±4.07a values are means±se (n=2), means in the same column bearing similar subscripts are not significantly different (p>0.05). w=wheat (100:00), wb=wheat-bambaragroundnut, ws=wheatsoybean, wco=wheat-cowepa, wp=wheat-sweetpotato; wca=wheat-cassava. mc=moisture 3.3 physical properties of the composite breads and the wheat bread bread weights (196.45g (ws70:30)220.47g wp70:30) were comparable and not significantly different although numerically 30% cassava and 30% sweet potato breads had higher bread weights.(table 5) significantly higher bread volume (988ml/g) and specific volume (4.82ml//g) were recorded for wheat bread, those of composite breads were lower especially the legume flour treated breads with volumes 429-578ml, and loaf specific volumes(slv) 2.24-2.85ml/g indicating that dilution of wheat gluten through blending with non wheat flours led to bread volume reduction, more in legume treated composite breads especially ws70:30 despite having higher protein content than starchy root tuber flours. bread volumes and slv of 30% sweet potato was the second highest followed by 30% bambara groundnut bread. previous studies observed that the decrease in available gluten as a result of blending with non-wheat flour was responsible for reduced bread volume and specific volume (shittu et al., 2007, ndife et al., 2011, otegbayo et al., 2018, dhaka and sangeeth, 2017, oluwalana et al., 2012, ahmed and campbell, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng agbara et al: comparative evaluation of the quality characteristics of composite flour bread produced from wheat-root tuber and wheat-grain legume flour blends. azojete, 18(2):331-344. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 339 2012, amandikwa et al., 2015) among others, similarly reported reduced bread volume or specific volume and higher bread weight as the main negative effect of using composite flour for bread manufacture, however enhanced nutrient density is reported as the positive effect. eriksson et al. (2014) reported a decline in slv from 3.43ml/g in wheat bread to 2.40ml/g as the graded level (10-30%) cassava flour replaced wheat flour. oluwole et al. (2017) reported slv range of 2.09-3.81ml/g for wheat-cassava-soybean breads. dhaka and sangeeth (2017) reported a slv of 2.43ml/g for 25% sweet potato bread and nwosu et al. (2014) reported slv of 2.35ml/g for 50% cassava bread with soybean improver. table 5: physical characteristics of bread from different composite flour flour/blend loaf weight (g) loaf volume(ml) specific loaf volume(ml/g) w(100:00) 205.14± 2.87c 988±10.38a 4.82±0.14a wb(70:30) 204.13±1.90c 578±7.49c 2.85±0.05c ws(70:30) 196.45±2.15d 429±11.29f 2.24±0.06d wc(70:30) 209.50±3.47b 525± 10.67d 2.59±0.07bc wp(70:30) 220.47±5.07a 743.75±9.05b 3.44±0.29b wco(70:30). . 217.83±1.09a 497.65±8 32d 2.29±0.11d values are mean±se.(n=2), means in the same column bearing similar subscripts are not significantly different (p>0.05). w=wheat (100:00), wb=wheat-bambaragroundnut, ws=wheatsoybean, wco=wheat-cowepa, wp=wheat-sweetpotato; wca=wheat-cassava. 3.4 sensory attributes of the composite breads visavis the wheat bread. sensory attributes of the test breads (table 6) were evaluated on a 9-point hedonic scale, the scores for crust colour (4.09-8.49), symmetry (4.41-8.30), crumb texture (5.90-8.19), taste (6.18-8.07) and aroma (5.86-7.55) revealed the wheat bread had higher scores than the composite breads, the next on the line was wheat-bambaranut bread (wb70:30) and declined further in 30% sweet potato and cassava breads. bambara groundnut flour has equivalent carbohydrate with cowpea and both are more starchy than soybean, meaning starchy flours perform better bread making potential than high protein flours as found in legumes flours perhaps due to higher water absorption of legume flours occasioned by higher protein content. poor symmetric shapes in the composite bread is linked to loss of or reduced viscoelasticity of the dough and reduced leavening gas retention capacity that accompany blending wheat with non wheat flour. with the exception of wb70:30, the other two legume flour treated breads had the worst rating for symmetry 4.43 for (ws70:30) and 4.41 for (wc70:30). bread symmetry has something to do with flour strenght which is dependent on protein content, not quantity but quality of protein, because at 30% replacement of the wheat flour with legume flour, the protein of the treated blends were enhanced. higher flour particlce size in legumes than in wheat and root tuber or cereal flours (oladunmoye et al., 2010) might be responsible for poor quality of legume treated breads. bourre et al. (2019) and sakhare et al. (2015) reported better bread scores with finer pulse flours, that higher flour partcle size as found in legume flours adversely affect sensory properties more than the volume.the colour and symmetry of wb(70:30) were not significantly different from wheat bread but significant variation existed between 30% bambara nut bread and wheat bread in terms of crumb texture, taste and aroma. the crust color of wp (70:30) was the poorest perhaps due to greater sugar availability for increased maillard reaction or caramelization and the same was responsible for its high taste score (7.36) although not higher than that of the wheat bread (8.05). however, ijah et al. (2014) reported 5% potato bread had more preference than wheat bread. collade et http://www.azojete.com.ng/ mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):331-344. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 340 al. (1997) produced bread with good volume, crust and crumb with 15% sweet potato inclusion and otegbayo et al. (2018) with less than 15% soybean. the aroma of 30% soybean flour bread was the poorest (5.86) perhaps due to strong beany flavor despite heat treatment yet not significantly different from the aroma of 30% sweet potato (5.91) and cassava bread (5.89) however the aroma of these breads were not rejected. yusuf and ejeh (2018) did not observe clear cut differences in the attributes of wheat bread and wheatbambara nut bread except at higher substitution levels. amandikwa et al. (2015) reported that less than 25% yam inclusion was able to yield acceptable wheat-yam bread which was not significantly different from wheat bread. similar observation was made by trejo-gonzalez (2014) who incorporated 5-10% sweet potato flour to produce bread that had sensory properties not different from the wheat bread. olaoye et al. (2018) reported the production of acceptable bread with 10% substitution of wheat flour with bambara groundnut flour. on the basis of the foregoing, the way 30% inclusion of wheat less flour especially legume flour would yield bread with better physical and sensory properties is the addition of improvers or use of flour that has the same finer granulation as wheat flour belori et al. (2019) or use of native or better modified starch (iwe et al.,2014). table 6: sensory attributes of composite breads and the wheat bread attributes w100:00 wb70:30 ws70:30 wco70:30 wca70:30 wp70:30 colour 8.30±0.27ab 8.49±0.23a 5.64±0.53b 5.27±0.67bc 5.56±0.53b 4.09±0.11d symmetry 8.30±0.31a 8.17±0.80a 4.43±0.19c 4.88±0.32bc 4.41±0.6c 5.39±0.37b crumb 8.19±0.45a 7.65±0.31ab 6.37±0.11b 6.09±0.41bc 6.32±0.28b 5.90±0.07c taste 8.07±0.51a 6.88±0.37bc 6.74±0.17bc 6.69±0.19bc 6.18±0.47c 7.36±0.21b aroma 7.55±0.29a 6.63±0.51ab 5.86±0.08d 5.45±0.42d 6.39±0.61bc 6.21±0.31c values are means±se (n=2), means in the same column bearing similar subscripts are not significantly different (p>0.05). w=wheat (100:00), wb=wheat-bambaragroundnut, ws=wheatsoybean, wco=wheat-cowepa, wp=wheat-sweetpotato; wca=wheat-cassava. conclusion protein quality is demostrable an important factor for better bread physical properties. therefore, flour with their high protein and 30% wheat flour replacement performed poorly in both sensory and physical properties of bread. proximate composition of the blends depend which flour involve blend formulation. the same pattern is reflected on the proximate composition of the composite flour breads. depression of the bread volume or specific loaf vo!ume or higher bread weight is influenced by the extent of flour water absorption greater in legume treated blends.wheat bread out-scored composite flour breads on the investigated sensory attributes, however wheat-bambara nut bread surprisingly compared favorably with wheat bread on some of the sensory attributes such as colour and symmetry. beany flavor was pronounced with bread treated with legume flour especially soybean flour which induced poor assessment of other attributes. nutritional value of composite flour breads was greater and despite higher protein, legume flours have the poorer bread volume than thestarchy root tuber flours. bambara nut flour is a promising better alternative to soybean and cowpea flours for better bread quality while sweet potato and cassava flour had comparable effects on bread quality. less than 30% incorporation of non-wheat flours is suggested for better bread volume and sensory properties. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng agbara et al: comparative evaluation of the quality characteristics of composite flour bread produced from wheat-root tuber and wheat-grain legume flour blends. azojete, 18(2):331-344. issn 1596-2644; 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doi: 10.4172/2155-9600.1000731 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:giagbara@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):121-128 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 121 original research article an automated prototype system for alcohol level detection in drunk drivers and vehicle control j. akanni*, b. adewusi, a. a. isa and r. a. alao department of electrical and electronics engineering, university of ilorin, ilorin, kwara state, nigeria *corresponding author’s email address: jimaka2005@gmail.com 1.0 introduction modern-day traffic accidents are mostly caused by drunk driving. drunk drivers are erratic and prone to making impulsive decisions that endanger everyone on the road, including themselves. nigeria has passed laws making it unlawful for drivers to drink alcohol before or while driving a vehicle and has also designated law enforcement officials to conduct arrests and bring cases against violators (emmanuel et al., 2017). in 2016, the nigerian bureau of statistics registered 11, 363 road accidents (report, 2017). although, speeding was cited as the main contributing factor in the report, it can be fairly concluded that the majority of events were brought on by drivers' erratic circumstances brought on by consuming alcohol before driving. a 2008 world health organization evaluation found that between 50 and 60 percent of road accidents are caused by drunk driving. analysis shows that 67.2 percent of nigerian drivers of commercial vehicles admitted to drinking during work days (groot, 2018). this shows that the majority of drivers engage in drunk driving, which may lead to accidents, especially those operating commercial and heavy-duty vehicles (mohamad et al., 2013). any blood alcohol concentration (bac) test that is higher than the permissible level of 0.5 g/100 ml in nigeria is considered illegal. the bac measures the quantity of alcohol that is present in a certain volume of blood. additionally, a blood alcohol level of 0.7 to 0.8 substantially impairs a driver's mental, physical, and sensory capacities (ehikhamenor and agwubike, 2007). article information abstract drunk driving is one of the principal contributors to road accidents in nigeria. passengers, other motorists and the driver's life are all at risk because of this behavior. the aim of this study is to develop a system that will automatically detects drunken drivers based on the proximity to the steering wheel and prohibits the car from been start. the method employed in this research is the use of an mq-3 sensor to measure the level of alcohol in the driver's breath in the area around where the driver sits in a car and compare it to the nigerian guidelines for acceptable blood alcohol concentration (bac) levels. in addition, the alcohol sensor is protected from obstruction (coverage) by an mh infrared proximity sensor. also, a red light alert is incorporated to sensitize the passenger whenever the driver is drunk. the result shows that the system performed satisfactorily. it prompt quicker reaction by prohibition of drunk drivers within a distance of 36 cm from the steering wheel from being able to start the car as well as sensitizes the passenger through blinking red light. it also prevent the systems sensor from been cover (obstruction) by drunk drivers within a distance of 5 cm. as a result, the system can be combined with the new technologies of modern vehicles to enforced don’t drive when drunk rules which are often violated by drunk drivers. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 august, 2022 revised 26 october, 2023 accepted 31 october, 2023 keywords: bac mq-3 alcohol drivers automated http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/jimaka2005@gmail.com jimaka2005@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 122 many studies have been conducted to monitor and control alcoholic drinking (jankhotkaew et al., 2023). rahim and hassan (2010) created an ignition switch device with a breathalyzer capability. an lcd screen, an alcohol sensor, a microcontroller, and electronics for the ignition switch are all components of the system. after development, the system can detect the level of alcohol in a breath sample and display the proportion detected as a percentage of bac on the lcd screen (blood alcohol concentration). comparatively to other versions, the sensor's sensitivity is likewise rather high. the sensor may detect other compounds and mistake them for alcohol, but its sensitivity to alcohol is substantially greater, making it an extremely accurate alcohol detection gadget. a steering-wheel-integrated automatic alcohol detector was created by kousikan and sundaraj (2014). more infrared light may be absorbed by ethanol. therefore, the authors make use of an ir sensor that is positioned on the steering. continuous ir energy is sent via the sensor by an ir source, led-894. a relay circuit is turned on if the absorption of alcohol vapour stops the passage of infrared photons. the gasoline delivery system is under the supervision of this relay circuit, which also shuts off the engine's fuel supply. this causes the automobile to gently come to a stop. more infrared absorption happens at greater ethanol concentrations. when the sensor is coated with alcohol, it does not, however, disable the ignition system. a system of alcohol detection and vehicle control was developed by bhuta et al., (2020) using a hardware platform with arduino at its core, an alcohol sensor mq3, a gps module, and a gsm module, an effective approach is proposed for developing an intelligent vehicle system that would monitor different vehicle characteristics over a certain period of time and transmit this data to the base station. the suggested system would accomplish the duty of communicating with the access point using gps, gsm, and control of multiple factors. small volume and great dependability are advantages of the whole control system. this system's future potential is to prevent accidents and provide helpful information on the involved car, hence lowering the number of accidents caused by drunk driving. al-youif et al., (2018) presented a study titled "alcohol detection for the automobile locking system." the prototype has successfully shown its capacity to detect and, therefore, identify a gas concentration. although this is just a prototype, it might serve as the foundation for further improvised systems that combine more features, leading to improved systems that meet market demands and niches and enable customization. additionally, the system may feature a wireless alerting system, an auditory alarm, or perhaps both at the same time, in addition to a visual indication. an effective system of car accident prevention with an alcohol detector incorporated was developed by mohamad et al., (2013). the primary controller is a pic 16f876a, the input is an alcohol sensor, and there are three outputs: an lcd, an alarm system, and an ignition system. this technology will notify the motorist of their degree of intoxication by showing them the situation on an lcd screen. additionally, a buzzer sound is produced to alert the driver of their state and to alert anybody around. the system's most important safety feature is that it prevents drivers who are severely intoxicated from operating a vehicle by deactivating the ignition. although several types of research have been conducted on strategies to decrease road accidents caused by drunk driving, the aim of this study is to develop a system that will automatically detects drunken drivers based on the proximity to the steering wheel and prohibits the car from been start. file:///c:/user/downloads/azojete143/www.azojete.com.ng jimaka2005@gmail.com akanni et al.: an automated prototype system for alcohol level detection in drunk drivers and vehicle control. azojete, 19(1):121128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 123 2. materials and methods the design and implementation of the automated alcohol detection system prototype model for intoxicated drivers and vehicle control included integrating several modules and components. the power supply unit, switching unit, and sensor unit are the three main components of the system. figure 1 depicts a block schematic of an alcohol detection system. figure 1: block schematic of the system the power supply unit's circuit diagram is seen in figure 2. c1 and c2 are 0.1 f and 100 f respectively figure 2: circuit diagram of the power supply unit the mq-3 alcohol gas sensor module is a type of alcohol sensor adopted because it is a low-cost semiconductor sensor that works with breathalyzers and can detect alcohol concentrations between 0.05 mg/l and 10 mg/l (tapadar et al., 2018). the device is compatible with ttl and runs on 5 v and 150 ma. additionally, it has a quick reaction time and a high level of alcohol sensitivity. the photograph and the circuit diagram of the mq-3 alcohol gas sensor are shown in figures 3 and 4, respectively. power supply unit logic gates proximity sensor module voltage comparator (switching unit) alcohol sensor module ignition system reference level (sensing unit) c2 c1 g n d u1 1 v0 vbb 2 3 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/jimaka2005@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 124 figure 3: the photograph of the mq-3 alcohol gas sensor (component-101, 2020) figure 4: circuit diagram of the mq-3 alcohol gas sensor (component-101, 2020) the mh infrared sensor module is the proximity sensor that is used; it is inexpensive and has a quick reaction time. the module has a coverage range of 2 to 30 cm and performs effectively with a dc input in the range of 3.3 to 5.0 v (einstronic enterprise, 2018). photo coupler makes up the sensor. the image of the mh infrared proximity sensor is seen in figure 5 figure 5: the image of the mh infrared proximity sensor module (einstronic enterprise, 2018) the lm324 is set up to function as a voltage comparator. the lm 324 is a single supply, a lowpower quad operational amplifier that runs from 3.0 to 32 volts of dc supply input (rarecomponents, 2022). the lm324operational amplifier's image and pin layout diagram are shown in figures 6 and 7 respectively. figure 6: the image of the lm324 operational amplifier (rare-components, 2022) figure 7: the pin configuration diagram of the lm324 operational amplifier sn74s04n not gate and sn74ls02n nor gate are the gates that were used. the maximum propagation delay for each of them is 15 ns, and they both work within the supply voltage range file:///c:/user/downloads/azojete143/www.azojete.com.ng jimaka2005@gmail.com akanni et al.: an automated prototype system for alcohol level detection in drunk drivers and vehicle control. azojete, 19(1):121128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 125 of 4.75 v to 5.25 v (all about circuit, 2022 and rehmani, 2020). the pictures of the sn74s04n and sn74ls02n are shown in figures 8 and 9 respectively. the relay in use is a single-pole jzc32f with voltage and current ratings ranging from 5 to 30 volts dc and 5 to 10 amps, respectively (amazon, 2018). a picture of the jzc-32f relay is shown in figure 10. figure 8: the picture of the sn74ls04n (all about circuit, 2022) figure 9: the picture of the sn74ls02n (rehmani, 2020) figure 10: the picture of the jzc-32f relay (amazon, 2018) 2.1 implementation the modules and components were organized on a breadboard and connected and soldered to a vero board as part of the hardware implementation process. the system enclosure was particularly chosen with both convenience and robustness in mind. figure 11 shows the picture of the arrangement/connections/soldering of the modules/components on the breadboard. the system's circuit diagram and the picture of the housing (casing) of the system are shown in figures 12 and 13, respectively. figure 11: the picture of the arrangement/connections/soldering of the modules/components on the breadboard http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/jimaka2005@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 126 figure 12: the system's circuit diagram figure 13: the picture of the protoype system 2.2 performance evaluation of the designed system to verify the degree of performance of the constructed system, the following tests were conducted: the drunker distance performance and the sensor obstruction distance performance. drunker distance performance was carried out by using a drunken person to as a drunk driver. the drunken person (driver) now stands in front of the system at a distance of 4 cm and moves away from it in step of 4 cm up to 40 cm. while the sensor obstruction distance performance was carried out by using hand to block the sensor. this was done by placing hand (obstruction) at a distance of 1 cm and moves away from it in step of 1 cm up to 7 cm. 3. results and discussion the experimental results of the measured drunker-distance performance and sensor obstruction distance performance are as shown in table 1 and 2 respectively. it is observed from the drunker-distance performance (table 1) that within the distance of 4 cm and 28 cm, the green and red light representing the status of ignition system in figure 13 is on and blinks respectively (column three of table 1) thereby the ignition is off and this indicated that the sensor is able to detected alcohol vapor in the air in excessed of the permissible level of 0.5 g/100 ml by the law. at 36 cm the green and red lights off thereby ignition is on and this indicated that no alcohol vapor detected. also observed from sensor obstruction distance performance (table 2) was that within the distance of 1 cm and 5 cm, the green and red light representing the status of ignition system in figure 13 is on and blinks respectively (column three of table 2) and this indicated the system sensor is been covered (obstructed). at 6 cm, the green and red lights off and this indicated that no one cover (obstruct) the system sensor. table 1: drunker-distance performance table 2: sensor obstruction-distance performance s/n drunker-distance from the system (cm) green light red light 1 4 on blink 2 8 on blink 3 12 on blink 4 16 on blink 5 24 on blink 6 28 on blink 7 36 off off 8 40 off off s/n sensor obstruction distance from the system (cm) green light red light file:///c:/user/downloads/azojete143/www.azojete.com.ng jimaka2005@gmail.com akanni et al.: an automated prototype system for alcohol level detection in drunk drivers and vehicle control. azojete, 19(1):121128. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 127 4. conclusion a prototype system that automatically detects drunken drivers based on the proximity to the steering wheel and prohibits the car from starting has been developed. it is highly effective because it detected a drunk driver in the range of 4 to 28 cm which is in accordance to insurance institute of highway safety report in 2004 that states the maximum allowable distance between a driver and the steering wheel to be 24.5 cm. the system also prevents drunk drivers from obstructing the system by a way of sensor blockage. in addition, it also sensitizes the passenger whenever the driver is drunk through blinking red light. as a result, the system can be combined with the new technologies of modern vehicles to enforced don’t drive when drunk rules which are often violate by drunk drivers. references report, a. 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vol. 19(1):121-128. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jimaka2005@gmail.com 128 detection of drunk drivers with automatic car engine locking system. nova journal of engineering and applied sciences do, 6(1): 1–15. groot, k. . 2018.. global status report om road safety. a pubication of world health organization, 1(1): 1-424. jankhotkaew, j., casswell, s., huckle, t., chaiyasong, s. and phonsuk, p. 2023. quantitative tools and measurements for assessing the implementation of regulatory policies in reducing alcohol consumption and alcohol related harms: a scoping review. drug and alcohol review, 42(1): 157–168. kousikan, m.,and sundaraj, m. 2014. automatic drunken drive prevention system. international journal of students research in technology & management, 2(02): 74–77. mohamad, mh., amin, m., and hafizzie, m. 2013. vehicle accident prevention system embedded with alcohol detector. international journal of review in electronics & communication engineering (ijrece), 1(4): 100–102. rahim, ha. and hassan, sds.. 2010. breathalyzer enabled ignition switch system. proceeding of 6th ieee international colloquim on signal processing and its applications, 21 23 may, malacca, malaysia: 1 4. rare-components. 2022. lm324n, quad operational amplifiers, 14-pdip, texas instruments. https://rarecomponents.com/store/1187 accessed on 2 november, 2022. rehmani, a. 2020. 74ls02 quad two input nor gate – datasheet. circuits-diy. https://www.circuits-diy.com/74ls02-quad-two-input-nor-gate-datasheet/ accessed on 2 november, 2022. tapadar, s., ray, s., saha, hn., saha, ak. and karlose, r. 2018. accident and alcohol detection in bluetooth enabled smart helmets for motorbikes. proceedings of ieee 8th annual computing and communication workshop and conference, (ccwc)8 10 january, las vegas, usa: 584–590. file:///c:/user/downloads/azojete143/www.azojete.com.ng jimaka2005@gmail.com arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):109-120 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 109 original research article kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite f. o. okeola1*, f. o. nwosu1, t. o. abu1, e. o. odebunmi2 and o. b. owolabi2 1industrial chemistry department, university of ilorin, ilorin, nigeria 2chemistry department, university of ilorin, ilorin, nigeria *corresponding author’s email address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 1.0 introduction bleaching is a chemical process of decolourising a material. bleaching thus is a chemical transformation of a coloured component to a colourless in the material or within the medium. the bleach is the generic name for such chemical product for the transformation commonly and erroneously known as cleaning and colour or stains removal. bleaching process could either be an oxidation or reduction when the bleach is oxidant or reductant respectively. most bleaches are of course oxidants (abdul and narenda, 2013; aqeel et al., 2020). bleaching action is utilized both domestically and industrially in various applications. it is used in textile industry as in bleaching of cotton and linen. similarly, in order to impact whiteness to textile fabrics, bleaching of textile grey fabrics is generally carried out by removing natural colouring matter. interestingly, hair color turns lighter mostly through (bleaching) rather than through coloration. bleaching is also utilized in leather as in tanning industry as well as in paper production (hassan et al., 2017). although dyes beautify the world, effluents from dye sources and application industries distort and disturb the environment and its living contents. the presence of dye in effluent is easily perceptible even in a low concentration. aside visual aspect, the colouration of the water cans impedes the photosynthesis as the coloured materials strongly absorb sunlight. this situation affects the balance of the aquatic ecosystem (abo farha,2010). effort to decolourised the coloured effluents need to be intensified because of the increase in production of dyes and pigments. it is estimated that about 10,000 different types of dyes and pigments are produced worldwide annually. in addition, over 7 x 105 tons of these different dyes and pigments of dyes and pigments are produced worldwide annually (vinod et al., 2011). out of these dyes 10% to15% article information abstract the kinetics of bleaching process of oxidation of typical dye with a bleaching agent sodium hypochlorite in aqueous medium was studied. the kinetic runs were executed using spectrophotometer to changes in concentration under pseudo first order whereby concentration of naocl was in large excess compared with the concentration of dye. the factors affecting the reaction rate that were studied include the concentration of dye and oxidant, temperature, ionic strength and ph of the bleaching reaction medium and the presence of a variable valence metal ion the result shows that the rate of oxidation increases with increasing in temperature, ionic strength and ph. increasing in substrate and oxidant concentrations also increase the rate of oxidation. higher observed rate constant k1 was obtained in the presence of fe(iii)ion. the arrhenius activation energy for the oxidation in the absence and presence of fe(iii)ion are 56.21 kjmol-1 and 51.21 kjmol-1 respectively. the result of thermodynamic parameters such as the lowering of activation energy (ea) and the higher value of second rate constants k2 in the presence of fe (iii) ion provide further support for fe (iii) ion enhancement of rate of oxidation. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 july, 2021 revised 27 october, 2021 accepted 31 october, 2021 keywords: bleach dye sodium hypochlorite kinetic thermodynamics http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng file:///c:/users/okeola%20abdul%20fatai/downloads/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):109-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 110 is estimated to be in effluent during the dying process. in addition, almost every industry uses dyestuff (mohammed and ali, 2020). bleaching is reported to involve the use of the four main bleaching agents sodium hypochlorite, calcium hypochlorite, sodium chlorite and hydrogen peroxide. in this research work the oxidant used is a chlorine – based bleach, sodium hypochlorite (naclo) a common household “bleach” product (mafzal et al., 2019). bleaching is important in controlling the adverse effect of the colouration. the study of chemical kinetics of the bleaching reaction is very important. in the later stage of twentieth century the time required for bleaching is said to drop from month to days to hours. today bleaching works faster. chemical kinetics although studies rate (time) in a reaction chemical kinetics necessarily studies effect and control of various factors in chemical reactions (aicha et al., 2017). this work studied the kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite. the knowledge could therefore be of benefit not only to bleaching workers but also dye handlers in general. 2. materials and methods 2.1 materials the chemical reagents used in the research work include sodium hypochlorite (bdh), sodium chloride salt (merck), hydrochloric acid, iron (iii) chloride, tartrazine (the dye), sodium hydroxide and bicarbonate (bdh). they are analytical grade, although further purified as necessary. the instruments were thermostat water bath, weighing balance, (helmreasin) ph meter, jenway spectrophotometer 7305, (jenway cole palmer, shanghai co ltd. china). deionised water was used to prepare all the solutions. 2.2 methods for a particular substance the stock solution of a particular molar concentration was prepared by: (i) measure the equivalent mass in gram (i.e. for a solid) or volume in ml (i.e. for a liquid) (ii) dissolve this in deionized water in 250 ml standard flask, making up to mark with the deionized water, mix thoroughly. bottle and keep (iii) experimental (working solution) was prepared from the respective stock solution by dilution of the stock solution, applying dilution equation (c1v1 = c2v1). [where c1 is the initial concentration, c2 is the final concentration, v1 is the initial volume, v2 is the final volume.] thus solutions of oxidant sodium hypochlorite and substrate – tartrazine were prepared. other solutions prepared and added to the reaction mixture were sodium chloride to monitor the effect of the ionic strength of the solution; hydrochloric acid and sodium hydroxide to study the effect of ph of the reaction medium. kinetics profiles were studied under pseudo first order conditions as all the reactions were conducted with the concentrations of the sodium hypochlorite (the oxidant) in large excess compared to that of tartrazine (the dye and substrate) (bahl et al., 2014). as kinetics measures changes in concentrations with time, the concentration was monitored with spectrophotometer. therefore, the wavelength correspond to the maximum absorbance was determined by measuring the absorbance of 0.001moldm-3 solution of dye at different wavelength and making a plot of absorbance against wavelength of a proposed and predetermined ranges of 410 – 510nm.this produced the absorption spectrum from which the wavelength corresponding to the maximum absorbance (λ max) was noted. the proof of beer-lambert’s law was carried between 2×10-2 to 10×10-2 mol dm-3 of solution of dye at (λ max) earlier file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng https://en.wikipedia.org/wiki/chlorine-based_bleach https://en.wikipedia.org/wiki/sodium_hypochlorite okeola et al: kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite. azojete, 18(1):109120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 111 ascertained and a plot of absorbance against concentrations was made. the molar absorptivity was determined from the slope of the graph obtained. for the kinetic follow up the reaction rates was measured by setting up different flasks containing appropriate quantity of solution to constitute the reaction mixture arranged in a themostarted water bath to attain a constant temperature. the reaction was initiated by rapid introduction of sodium hypochlorite solution into the mixture. the progress of the reaction was followed by taking the following changes in absorbance of decolourising dye in the mixture as a function of time. 2.2.1 kinetic measurement kinetic analysis of the bleaching process was based on the general chemical equation of a reaction between the dye and the oxidant represented by equation 1. the rate of bleaching reaction was expressed by equation 2. since the concentration is directly related to the absorbance, the change in absorbance of the oxidant was used to monitor rates of reaction. the large excess of oxidant as displayed in equation 3 has made the changes in concentration of the oxidant in the reaction insignificant. this thus make the rate of reaction as first order with respect to the concentration of dye. both equation 2 and 3 therefore relate specific rate equation k1 and k2 as shown in equation 5. integrated form of equation 4 gives equation 6. the pseudo first order rate constant were obtained from the kinetic expression (equation 6).a plot of ln (at) against time (t) was used to determine the value of rate constant k1, obtained from the slope of equation 6 the rate constants were averages of at least three measurements. the second order rate (k2) was thus deducted from equation 5 oxidant + dye product(s) (1) 𝑅𝑎𝑡𝑒 = 𝑘2 [𝑑𝑦𝑒] [𝑂𝑥𝑖𝑑𝑎𝑛𝑡] (2) but [𝑂𝑥𝑖𝑑𝑎𝑛𝑡] >> [𝑑𝑦𝑒 ] (3) 𝑅𝑎𝑡𝑒 = 𝑘1[𝑑𝑦 𝑒] (4) where k2 was the rate constant for the bimolecular reaction of dye and the oxidant and k1 is the observed pseudofirst order rate constant k1 = 𝑘2 [𝑂𝑥𝑖𝑑𝑎𝑛𝑡] (5) ln (𝐴𝑡) = 𝑙𝑛(𝐴𝑂) − 𝑘1 𝑡 (6) where ao and at stands for absorbance at the beginning t = 0 and at time t. t: time in s, k1: first order rate constant s-1, k2: second order rate constant mol-1dm3 s-1 a absorbance for concentration in moldm-3 factor affecting the rate of bleaching process were verified by carry out the kinetics measurement while varying the quantity of the particular factor and maintaining constant the value and condition of other factors. the contribution of presence of variable valence metal ions in the reaction medium on rate of beaching rate was also determined. http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):109-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 112 3. results and discussion spectrum and calibration of spectrophotometer the absorption spectrum is displayed in figure1. the wavelength corresponding to the maximum absorbance was found to be 460nm. beer – lambert law was ascertained from graph of absorbance against concentration of the dye solution in the range of 2.0 x10-2 10 x10-2m figure 2. the slope of the of a straight line plot in figure 2 gives the molar absorptivity as 3.157 dm3mol-1cm-1 figure 1: calibration curve of log of absorbance against wavelength figure 2: plot of absorbance versus concentration for dye solution 3.1 dependency of rate of bleaching reaction on concentration of oxidant the effect of oxidant concentration on the bleaching rate was determined at different initial concentration of oxidant (sodium hypochlorite) while maintaining the quantity of each of other bleaching factors such as strength, temperature and the concentration of dye solution. the value of k1 for each of the oxidation reaction at each initial concentration was calculated from the slope of each plot of log of absorbance against time (figure. 3). the values of the k1 presented in table 1 show that the observed rate constants increased with increasing in initial concentration of sodium hypochlorite. this could be due to the increase in the oxidative power of the increasing ion hypochlorite (olajire and olajide 2014). 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 390 410 430 450 470 490 a b so rb an ce wavelenght (nm) -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 0.02 0.04 0.06 0.08 0.1 0.12 a b so rb an ce concentration (mol/l) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng okeola et al: kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite. azojete, 18(1):109120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 113 -0.51 -0.49 -0.47 -0.45 -0.43 -0.41 -0.39 -5 15 35 55 75 95 115 135 155 a b so rb an ce time (s) 1×10-5 2×10-5 3×10-5 4×10-5 5×10-5 -0.295 -0.29 -0.285 -0.28 -0.275 -0.27 -0.265 -0.26 -0.255 -0.25 -0.245 -0.24 -5 15 35 55 75 95 115 135 155 a b so rb an ce time (s) 1×10-5 2×10-5 3×10-5 4×10-5 5×10-5 figure3 the plot log abs vs t for the effect of oxidant conc. on bleaching rate in the absence of fe(iii)ion figure 4 the plot log abs against t for the effect of oxidant conc. on bleaching rate in the presence of fe(iii)ion http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):109-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 114 3.2 dependency of bleaching rate on concentration of dye the effect of concentration dye on the rate of bleaching reaction was carried out with different initial concentration of dye while keeping the values of other influencing factors constant. the pseudo first order rate constant (k1) at each initial concentration of dye was evaluated from the slope of plot of log of absorbance against time. the result presented in table 2 show that there was increasing in k1 with increasing in the initial concentration of solution of dye, which shows that the reaction rate depends on initial concentration of dye. this suggests that more dye molecules are available for the reaction as availability of molecule of a reactant raise the rate of such reaction (manivannan et al., 2015). 3.3 dependency of bleaching rate on ionic strength of the medium the effect of ionic strength of the medium on bleaching process carried out at different ionic strength of the medium shows the value of k1 for the bleaching rate as recorded in table 3 increase with increasing in the ionic strength of the medium within the range of experiment. the rate of reaction was first order with respect to sodium chloride concentration thus, affect the reaction rate (sania et al., 2012; okeola et al., 2020) table 3 k1 at variation of concentration of salt [nacl] ×10-3m k1 ×10-4s-1 1.0 5.37 2.0 6.14 3.0 6.90 4.0 7.05 5.0 8.44 3.4 dependency of bleaching rate on ph of the medium the effect of ph on the rate of bleaching was studied in alkaline medium. table 4 indicates a rise in the observed rate constants k1 within the ph of the medium between 8.70 and 11.20. the observation shows that controlling the ph of the bleaching medium can regulate rate of bleaching process (olajire and olajide 2014). table 1 k1 as oxidant concentration varied [oxidant]×10-3m k1 ×10-4s-1 1.0 4.61 2.0 6.14 3.0 6.90 4.0 7.00 5.0 8.20 table 2 k1 as dye concentration varied [dye]×102m k1 ×10-4s-1 1.0 1.53 2.0 2.30 3.0 3.07 4.0 3.83 5.0 4.61 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng okeola et al: kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite. azojete, 18(1):109120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 115 table 4 k1 at variation of ph ph k1×10-4s-1 8.70 1.20 9.10 1.53 9.80 2.30 10.60 3.07 11.20 4.61 3.5 effect of presence of transition metal ion on the bleaching rate the effect of presence of transition metal ion on the bleaching rate was studied by repeating the dependency of the reaction rate on dye and oxidant concentration in the presence of fe (iii) ion in the reaction mixture. the value of k1 was calculated from the slope of each plot of log absorbance against time (figure 4). the rate constants k1 observed, also increased with increasing in concentration of dye and oxidant respectively, but the values of k1 were relative greater the value of k1 obtained in the absence of fe (iii) ion in the reaction mixture (tables 5a and 5b). the second order rate constant k2 was determined from the slope of the linear plot of k1 against respective dye concentration (equation 5) both in the absence and presence of fe (iii) ion. the value of k2 was found to be 1.39 m-1s-1 and 1.59 m1s-1 in the absence and presence of fe (iii) ion respectively. the higher value of k2 in the presence of fe (iii) ion shows that the presence of the transition metal ion enhances rate of oxidation according to literature report (gamal et al., 2017). the variable oxidation state of transition metal ion facilitates the redox reaction oxidation. increase in the rate constant could be due to activation of sodium hypochlorite (olajire and olajide 2014; ogori et al., 2018). table 5 effect of presence of transition metal ion (fe (iii) ion) in the reaction medium table 5a k1 at variation of dye concentration in the absence and the presence of fe (iii) ion absence of fe (iii) ion presence of fe (iii) ion [dye]×10-2m k1 ×10-4s-1 k1 ×10-4s-1 1.0 1.53 3.84 2.0 2.30 4.61 3.0 3.07 5.41 4.0 3.83 6.14 5.0 4.61 7.67 table 5b k1 at variation of oxidant concentration in the absence and the presence of fe (iii) ion absence of fe (iii) ion presence of fe (iii) ion [oxidant]×10-3m k1 ×10-4s-1 k1 × 10-4s-1 1.0 4.61 6.14 2.0 6.14 6.90 3.0 6.90 7.68 4.0 7.00 7.90 5.0 8.20 9.97 http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):109-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 116 3.6 effect of variation in temperature on the bleaching rate the oxidation reactions were carried in the presence and absence of fe (iii) ion at different temperature from (333 373) k while maintaining constant all other factors in the reaction. the k1 increased with increasing in temperature while with a relative higher value in the in the presence of fe (iii) ion (table 6). thermodynamic properties associated with the bleaching process were determined. these include the activation energy (ea) determined from the slope of the linear plot obtained from natural logarithm k2 against the reciprocal of the temperature in kelvin 1/t(ºk) based on arrhenius equation 5 for the reaction in the absence (figure 5) and presence of fe(iii) ion (figure 6) figure 5 a plot of log of k2 against 1/t(k) for bleaching process in the absence of fe(iii) ion table 6 k1 at variation of temperature ion absence of fe (iii) ion presence of fe (iii) ion temperature (k) k1×10-4s-1 k1 (mol-1s-1) k1×10-4s-1 k2 (mol-1s-1) 333 1.20 0.024 2.14 0.032 343 1.54 0.04 2.93 0.051 353 2.31 0.06 3.42 0.073 363 3.01 0.07 3.92 0.084 373 4.03 0.09 4.51 0.096 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9 -0.8 0.00265 0.0027 0.00275 0.0028 0.00285 0.0029 0.00295 0.003 0.00305 l o g k 2 1/t (k) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng okeola et al: kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite. azojete, 18(1):109120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 117 fig. 6 a plot of k2 against 1/t(k) for bleaching process in the presence of fe(iii) ion the values of enthalpy of activation of the reaction (δh#), gibbs free energy of activation (δg#) and the entropy of activation (δs#) are determined on the ground of respective equations 6,7 and 8 (mortimer et., al. 2002). ln 𝑘2 = 𝑙𝑛𝐴𝑒−𝐸𝑎/𝑅𝑇 (6) ∆𝐻≠ = 𝐸𝑎 − 𝑅𝑇 (7) ∆𝐺≠ = ∆𝐻≠ + 𝑇∆𝑆 (8) 𝑙𝑜𝑔𝐴 = 𝑅𝑇 𝐻 + 𝑆≠ 𝑅𝑇 (9) 10s# = 2.303r (log10 a log10 (kt/h) (10) the result of the arrhenius activation energy ea obtained from the slope of the linear plot is 56.21 kj mol-1 (in the absence of fe (iii) ion), and 51.21 kj mol-1 (i.e. presence of fe (iii) ion). the values of the thermodynamic properties are presented in table 7 for the bleaching reaction in the absence and presence of fe (iii) ion respectively. the lower value of arrhenius energy of activation (ea) when fe (iii) ion in reaction mixture indicate a lower energy reaction pathway showed. this is an indication of fe (iii) ion enhancement in bleaching reaction. ifawzy et al, 2016) the fairly higher negative value of entropy of activation (δs#) and free energy of activation (δg#) and lower enthalpy of activation of the reaction (δh#) also indicate this positive role of fe (iii) ion in accelerating the bleaching reaction according to literature report (prem et al, 2017) table 7 the thermodynamic activation parameters for bleaching process by naocl in the absence and presence of fe(iii) ion condition ea (kj/mol ∆h# (kj/mol) ∆s# (kj/mol) ∆g# (kj/mol) a(l/mol/s) absence of fe(iii)ion 56.21 52.41 -32.3 62.6 142.7 presence of fe(iii)ion 51.21 48.32 -41.4 56.3 128.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9 -0.8 0.00265 0.0027 0.00275 0.0028 0.00285 0.0029 0.00295 0.003 0.00305 l o g k 2 1/t (k) http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):109-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 118 4. conclusion the kinetics of bleaching process with a bleaching agent sodium hypochlorite in aqueous medium was studied using spectrophotometer. the effect of the following factors that influence the rate of chemical kinetics were studied the concentration of dye and oxidant, temperature, ionic strength and ph of the bleaching reaction medium and the presence of a variable valence metal ion. the study was carried out under pseudo first order where the concentration of one of the two reactants would be prepared in large excess to make the amount reacting insignificant so that change in concentration would be based on would be based on other reactant. the values of factor to be studied were varied while the values of other factors were made constant. in each experiment the rate constant was determined for each of the different values rate constant. the study of these observed rate constants generated the results and basis of discussion. the observation shows that the rate of bleaching can be controlled by monitoring ph, ionic strength as well as the temperature of the bleaching medium. the concentration of the bleach and the dye are can also be controlled to monitor bleaching rate. the result shows that increasing in factors such as concentration of oxidant and the dye within the range of the exercise improve the rate of oxidation reaction, the bleaching process. increasing in temperature, ionic strength and ph of the reaction medium within the range in this study also increased the rate of the oxidation reaction. the lower value of ea among other thermodynamic results and higher k1 in the presence of variable valence metal ion, fe (iii) ion, demonstrated the enhancement and catalytic role of the metal ion. references abdul, sb. and narendra, g. 2013. accelerated bleaching of cotton material with hydrogen journal textile science and engineering, 3(4): 140-144., doi: 10.4172/2165-8064.1000140 abo-farha, sa. 2010.comparative study of oxidation of some azo dyes by different advanced oxidation processes: fenton, fenton-like, photo-fenton and photo-fenton-like. journal of american science,6(10): 128-142. aicha, m., xavier, c., gaelle, m., noelle, b. and romain, m., 2017. a kinetic model for predicting the oxidative degradation of additive free polyethylene in bleach disinfected water. polymer degradation and stability,146: 78-94. https://doi.org/10.1016/j.polymdegradstab.2017.09.020 aqeel, ah., azzam, am., al-hadedi, aj., mahrath, ai., moustafa, fa., almalki, aa., sergey, s .and moaed, ea. 2020. mechanistic investigations on pinnick oxidation: a density functional theory study. royal society open science, 7 (2): 191568. https://doi.org/10.1098/rsos.191568 azmat, r., naz, r., qamar, n. and imar, m. 2012 kinetics and mechanisms of oxidation of d fructose and dlactose by permanganate ion in an acidic medium. natural science, 4(7): 466 – 478. bahl, a., bahl, bs. and tuli, gd. 2014. essentials of physical chemistry, revised multicolour ed., new delhi: a chand and company ltd. ram nagar, new delhi, 737-762 cleci, tf., rodrigo, b., crisleide, m. and paulo, c. 2009.kinetic of the degradation of c.i. food yellow 3 and c.i food yellow 4 azo dyes by the oxidation with hydrogen peroxide. journal of molecular catalysis a: chemical, 301: 93-97. fawzy, a., zaafarany, ia., altass, hm., morad, mh. and alfahemi, j. 2016. kinetics and mechanism of permanganate oxidation of inositol in perchloric and sulfuric acids solutions. american journal of chemical engineering, 4(5): 98–104. https://doi.org/10.11648/j.ajche.20160405.12 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng https://doi.org/10.1016/j.polymdegradstab.2017.09.020 https://doi.org/10.1098/rsos.191568 https://doi.org/10.11648/j.ajche.20160405.12 okeola et al: kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite. azojete, 18(1):109120. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 119 hasan, a., anwar hz., kawshar, a1., forhad, h., romjan, a., most, sy. and lutfor, r. 2017. effect of different types scouring against different types of bleaching process on dyeing of cotton fabric with monochlorotriazine (hot brand) reactive dye. international journal of textile science, 6(5): 128134.doi: 10.5923/j.textile.20170605.02 hashemian, s. 2013. fenton-like oxidation of malachite green solutions kinetics and thermodynamics study. journal of chemistry, 7: 1-7. gamal, oe., said, mt. and heba, mg. 2017.decolorization and degradation of sunset yellow in aqueous solutions by advanced fenton oxidation. journal of basic and environmental science, 4: 18-23. mafzal, a., jahirul, ac., sibgatullah, s., sheikh, sa., champs, s., dulal, h. and tarikul, i. 2019. investigation of combined desizing, scouring and bleaching effect with h2o2. international journal of polymer and textile engineering, 6(1): 10-12. manivannan, s., karthikeyan, r. and muthubharathi, m., 2015. kinetics and mechanism of oxidative decolourization of food dyes tartrazine and ponceous4r by trichloroisocyanuric acid in aqueous acetic acid medium. international journal of chemtech research, 7(7): 2936-2941. mohammed, as. and ali, hg. 2000. kinetics of the oxidation of tartrazine with peroxydisulfate in the presence and absence of catalysts. monatshefte fur chemie, 131: 117-129. mortimer, m. and taylor, p. 2002. chemical kinetics and mechanism, 1st edition, royal society of chemistry, cambridge, 65-68. ogori, bo., lohdip, yn. and egila, jn. 2018. kinetics and mechanism of the oxidation of potassium trisoxalatoferrate (iii) by permanganate ion in aqueous hydrochloric acid medium. journal of applied chemistry, 21: 19-31 okeola, f., odebunmi, eo., amoloye, ma., babamale, hf., thema, s. and abdulsalam, jo. 2020. kinetic and thermodynamic study of oxidative decolourisation of a typical food dye (tartrazine) in an aqueous environment. journal applied science environment management, 24 (6): 1021-1026. olajire, aa. and olajide, aj. 2014. kinetic study of decolourisation of methylene blue with sodium sulphite in aqueous media: influence of transition metal ions. journal of physical chemistry and biophysics, 4(2): 136-143., doi:10.4172/2161-0398.1000136 osunlaja, aa., idris, so. and iyun, jf. 2012. kinetics and mechanism of the methylene blue-permanganate ion reaction in acidic medium, scholars research library, 3(12): 269 -274. prema, kr., fathyah, o. and asha, i. 2017. kinetics of oxidation of fast green dye with 1chlorobenzotriazole in alkaline medium: mechanistic and spectrophotometric study. indo american journal of pharmaceutical research, 7(2): 7614-7624. schwenke, ku., dieter, s., marcel, laura, r., anna, r., klaus, v., tobias, m., markus, b., daniel, r. and gerhard, s. 2019. analysis of free chlorine in aqueous solution at very low concentration with lateral flow tests. scientific reports, 9:17212 | https://doi.org/10.1038/s41598-019-53687-0 2 sharma, kk. and sharma, lk. 1979; a textbook of physical chemistry, 2nd edition, vikas india, 285-286. steinfeld, ji., francisco, js. and hase, wc. 1999. chemical kinetics and dynamics, 2nd edition, prenticehall, n.j. 17 http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):109-120. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okeolaf@yahoo.com, okeola.of@unilorin.edu.ng 120 vinod, kg., rajeev, j., arunima, n., shilpi, a. and meenakshi, s. 2011. removal of the hazardous dyetartrazine by photo degradation on titanium dioxide surface. material science and engineering, c31: 1062-1067 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/okeolaf@yahoo.com,%20okeola.of@unilorin.edu.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2004; vol.4, 63-70 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng the influence of organic matter on soil compactibility and air permeability of some soils in borno state mamman, e.1 and j.o. ohu1 abstract a laboratory experiment was conducted to determine the influence of an organic material (groundnut haulms) on the compactibility and air permeability of three most common agricultural soils (clay, sandy clay and sandy loam) in borno state. the organic material was incorporated into the soils at three levels (2, 4 and 6% by mass of dry soil) and the soil-organic matter mixtures were compacted at three levels (5, 15 and 25 hammer blows). incorporation of the organic material into the soils reduced their bulk densities and increased their air permeabilities. the bulk density for ngala town clay, nguma sandy clay and university sandy loam soils when incorporated with 2% organic matter and compacted using 25 hammer blows at 10% moisture content were 1.50, 1.59 and 1.74 mgm-3 respectively. when the organic matter level was increased to 6% and compacted at 10% moisture content using 25 hammer blows, the bulk densities of the soils reduced to 1.41, 1.49 and 1.63 mgm-3 for ngala town clay, nguma sandy clay and university sandy loam respectively. the air permeability for ngala town clay, nguma sandy clay and university sandy loam soils when incorporated with 2% organic matter and compacted using 25 hammer blows at 25% moisture content were 17, 23 and 37 μm² respectively. when the organic matter level was increased to 6% and compacted at 25% moisture content using 25 hammer blows, the air permeability of the soils increased to 28, 32 and 48 μm² for ngala town clay, nguma sandy clay and university sandy loam, respectively. for each level of organic material, air permeability of each soil decreased with increase in the number of hammer blows. incorporation of the organic material into the clay soil increased its susceptibility to compaction and this resulted in much lower values of air permeability than in the sandy loam soil. statistical models were generated to predict the air permeability of the soils in terms of silt and clay contents, moisture content, compaction and organic material levels. the implications of the results obtained in determining severity of compaction on these agricultural soils were discussed. 1. introduction soil compaction caused by increasing weights of agricultural machinery can affect the structure of arable soils either positively or negatively. the degree to which soil compaction affects soil physical properties and consequently crop yields is dependent upon soil type, the number of tractor passes, tyre contact pressure, soil moisture content at the time of compaction and crop type (voorhees, 1977; oni and adeoti, 1986; ohu and folorunso, 1989). soil compaction reduces soil porosity and thereby deteriorates soil aeration by curtailing the exchange of air from the root zone with air from the surface (negi et al., 1980). compaction can reduce the transmission of water and air through the soil profile, change the heat capacity, increase surface runoff and increase potential of erosion (al-adawi and reeder, 1996). soil compaction increased soil bulk density, soil shear strength, penetration resistance and reduced hydraulic conductivity and pore numbers in a vertisol (boone et al., 1994; radford et al., 2000). lowery and schuler (1988) reported that a soil compacted with a 12.5 to 18 mg axle load reduced maize yield considerably in a rainy year and in a dry year (voorhees, 1992) but not in years with normal precipitation. besides grain and dry matter yield of crops, product quality can also be affected by soil compaction (alakukku and elonen, 1995). soil compaction by a 5 to 20 mg axle loads 1department of agricultural & environmental resources engineering, university of maiduguri. nigeria. e-mail: mamman2002ng@yahoo.com mailto:mamman2002ng@yahoo.com http://www.azojete.com.ng the influence of organic matter on soil compactibility and air permeability of some soils in borno state 64 delayed the ripening of maize, raising the grain moisture content at harvest and thus the drying costs for several years (gaultney et al., 1982; voorhees et al., 1989). similarly, soil compaction decreased the yields and nitrogen uptake of oats, wheat and barley and lowered seed moisture contents of these crops at harvest (alakukku and elonen, 1995). kayombo (1989) stated that not all instances of soil compaction are necessarily harmful. it was noted that in some dry climates a rather heavy compaction of highly permeable sandy soils might improve the efficiency of scarce rainfall and irrigation. in a field experiment with a sandy loam soil, the highest grain yield of sorghum (ohu et al., 1991) and millet (mamman and ohu, 1997; mamman and ohu, 1998) were at 15 tractor passes, while zero pass gave the least. bicki and siemens (1990) found positive response of corn and soybean yields to wheel traffic when rainfall was limiting and negative when rainfall was adequate. compacted soils may recover naturally if compaction forces are no longer applied. natural recovery is, however, a slow process and depends on geographical location (al-adawi and reeder, 1996). some of the factors considered to alleviate soil compaction are wetting/drying, freezing/thawing, biological activity and tillage (hakansson and reeder, 1994). a legume, stylosanthes guianensis was found to be suitable for restoring compacted and eroded alfisols in west africa (lal et al., 1979). ohu et al. (1991) also reported that groundnut haulms alleviated soil compaction and improved the hydraulic properties of some agricultural soils in borno state. the incorporation of organic material into the soil can reduce its compactibility and thus improve its physical and hydraulic properties (ekwue, 1990; ohu et al., 1991). stone and ekwue (1995, 1996) reported that incorporation of peat and sewage sludge into some soils in trinidad increased their compressibility due to increase in void ratio of the soils and hence their porosities. they concluded that the extent of increased compressibility with organic matter addition depends on the properties of the organic matter, particularly its dry density. soil compaction is measured indirectly by studying the changes in one or more soil parameters such as cone index, bulk density, porosity, hydraulic conductivity and air permeability (al-adawi and reeder. 1996). many researchers use cone penetration measurements as indicator of soil compressibility because it provides a rapid, simple and economical means of indicating compaction (perumpral, 1987). one of the most frequently used measures of soil compaction is bulk density. within a given soil, the bulk density provides a measure of how close the soil particles are packed but does not yield any information about their geometric arrangement or the pore size distribution (freitag, 1971). measurements of fluid flow through a soil provide a meaningful description of compaction, because the fluid conductivity is related, generally, to the amount of pore space in the soil (aladawi and reeder, 1996). air permeability, which is a measure of air flow through a soil has been observed to have a good physical basis to indicate changes in free interconnected pore spaces which in turn determines aeration limitation in soils (bowen et al., 1983). in borno state, little information is available on the behaviour of agricultural soils to air permeability when they are incorporated with organic materials, especially when subjected to different pressures. due to lack of this information, enormous quantities of crop residues and animal wastes are either not properly utilized or wasted completely. the objective of this azojete vol. 4 2004 65 study was, therefore, to quantify the effect of an organic material on soil compactibility and air permeability of some agricultural soils. 2. materials and methods three soils representing some of the major agricultural soils in borno state (ngala clay soil, nguma sandy clay soil and university sandy loam soil) were used for the purpose of this study. the soils were collected from the top 0.20 m depth of the soil profile, air-dried and ground to pass a 0.05 m screen. particle size distribution was determined using the hydrometer method (lambe, 1951) and organic matter content using the method described by walkley and black (1934). the organic material (groundnut haulms) was grounded and passed through a 0.05 m sieve. the organic material was added to the soils at the rate of 2, 4 and 6% by mass of dry soil. for the purpose of determining the physical properties of the soils, water was added to the soilorganic material mixtures to bring up their gravimetric moisture contents to 5, 8, 10, 12 and 15% for the sandy soil and 10, 15, 18, 20 and 25% for the clay soils. these moisture content values were chosen according to the consistency limits of the soils (ohu et al., 1989). thereafter, each of the soils was subjected to three levels of compaction energy using 5, 15 and 25 blows of a standard proctor compaction hammer in cylindrical moulds of 102 mm in diameter by 116 mm height, following the proctor compaction procedure (lambe, 1951). the choice of the three levels of compaction was borne from the equivalent static pressures for soil compaction as determined by raghavan and ohu (1985). for each level of compaction, the air permeability of the soils were determined using the air permeameter designed, constructed and calibrated by ohu et al. (1992). a randomized complete block design was used for the investigation. all the tests were performed three times on each soil. the data collected was subjected to statistical analysis to determine the effects of soil type, organic material, moisture content and compaction level on air permeability of the soils. 3. results and discussion the results of the grain size analyses of the soils used and their consistency limits are shown in table 1. the sandy loam and sandy clay soils are classified as typic ustipsament (rayar, 1984) while the clay soil is classified as vertisol (fao/unesco, 1974). table 2 shows the dry bulk density of the soil-organic material mixtures. the dry bulk densities of these soils without organic material incorporation, compacted at 10% moisture content using 25 hammer blows were 1.53, 1.62, and 1.80 mgm-3 for ngala clay, nguma sandy clay and university sandy loam respectively (ohu et al., 1989). the incorporation of 2% organic material into these soils at 10% moisture content and compacted using 25 hammer blows reduced their bulk densities to 1.50, 1.59 and 1.74 mgm-3 for ngala clay, nguma sandy clay and university sandy loam respectively. the influence of organic matter on soil compactibility and air permeability of some soils in borno state 66 10 20 30 40 50 5 15 25 5 15 25 blows 5 15 25 5 15 25 blows 5 15 25 5 15 25 blows moisture content (%, w/w) figure 1: air permeability vs moisture content for ngala clay soil at different organic matter levels and proctor number of blows 20 30 40 50 5 15 25 5 15 25 blows 5 15 25 5 1 5 25 blows 5 15 25 5 1 5 2 5 blows moisture content (%, w/w) figure 2: air permeability vs moisture content for nguma clay loam soil at different organic matter levels and proctor number of blows a ir pe rm ea bi lit y, µm 2 a ir pe rm ea bi lit y, µm 2 2% 4% 2% 4% azojete vol. 4 2004 67 35 45 55 65 5 15 25 5 15 25 blows 5 15 25 5 15 25 blows 5 15 25 5 15 25 blows moisture content (%, w/w) figure 3: air permeability vs moisture content for university sandy loam soil at different organic matter levels and proctor number of blows table 1: particle size analysis and initial organic matter content of the soils sample location soil type sand (%,w/w) clay (%,w/w) silt (%,w/w) organic content moisture content (%,w/w) ll pl pi ngala town clay 5 60 35 0.97 46.0 25.0 21.0 nguma village sandy clay 47 46 7 0.14 28.5 17.0 11.5 university farm sandy loam 77 17 6 0.12 21.0 ll= liquid limit; pl= plastic limit; pi= plasticity index table 2: dry bulk density of the soil-organic matter mixtures at 10% moisture content and 25 hammer blows soil type dry bulk density at three organic matter levels (mgm-3) 2% 4% 6% ngala town clay 1.50 1.46 1.41 nguma sandy clay 1.59 1.53 1.49 university sandy loam 1.74 1.69 1.63 figures 1 to 3 show the variations of air permeability with moisture content for the soils used. for all the soils, air permeability increased with organic matter but decreased with increase in a ir pe rm ea bi lit y, µm 2 2% 4% the influence of organic matter on soil compactibility and air permeability of some soils in borno state 68 the number of hammer blows. in figure 1 for example, the air permeabilities of the soil compacted at 25% moisture content using 5 hammer blows were 31, 38 and 39 for 2 , 4 and 6% organic matter levels respectively. when the soil was compacted using 15 hammer blows at 25 % moisture content, the air permeability decreased to 27, 34 and 36 for 2, 4 and 6% respectively. this trend was the same for the other soil types (figures 2 and 3). the increases in air permeability with organic matter were statistically significant at 5% level. this could be attributed to increase in porosity of the soils as indicated by the decrease in their soil bulk densities. the figures also show that irrespective of the soil type, organic matter content and moisture content at which the load was applied, the air permeability values peaked at specific moisture contents for the 5 and 15 hammer blows. the low bulk densities of the mixtures and the high values of air permeability at high organic matter levels indicate that the organic material has affected the soils positively. the significant differences recorded in air permeability were a function of not only the organic material but also of silt and clay contents, moisture content and number of hammer blows. to establish relationships among these variables, multiple regression equations were used. the relationships that best described the air permeability of these soils were as follows: a = 0.64 1.38m + 2.18x + 1.66s (r2 = 72 %) 1 a = 0.36 + 3.57m + 4.12x 2.19c (r2 = 79 %) 2 a = 0.89 + 5.24m + 3.85x + 2.46g (r2 = 92 %) 3 where a is air permeability (μm2), m is moisture content (%, w/w), x is compaction level (mpa), s is silt content (%, w/w), c is clay content (%, w/w), g is organic matter level (%). the inclusion of organic matter level gave the best correlation as revealed by equation 3. it is therefore evident that the organic material incorporated into the soils cushioned the effect of compaction, and improved the structure of the soils. 4. conclusion this study revealed that incorporation of groundnut haulms into the soils considered would reduce the problem of compaction and improve soil structure by reducing the dry bulk density and creating more voids for more air circulation. this is particularly beneficial in the area of study where tillage operations are carried out with heavy tractors and where large quantities of the organic material are available. although this organic material is used to feed domestic animals, our survey indicated that the economic returns would be more when incorporated into soils. it is, however, recommended that further studies be carried out to determine the optimum quantities of this organic material that can alleviate compaction and improve the structure of these soils. references al-adawi, s.s. and r.c. reeder (1996). compaction and subsoiling effects on corn and soybean yields and soil physical properties. trans. asae, 5: 1641-1649. azojete vol. 4 2004 69 alakukku, l. and p.elonen (1995). long-term effects of a single compaction by heavy field traffic on yield and nitrogen uptake of annual crops. soil tillage res., 36: 141152. bicki, t.j. and j.c. siemens (1990). crop response to wheel traffic soil compaction. trans.asae, 34 (3): 909-913. boone, f.r., g.d. vermeulen and b. kroesbergen (1994). the effect of mechanical impedance and soil aeration as affected by surface loading on the growth of peas. soil tillage res., 42: 237-251. bowen, h.d., p. ayers and m. salyani (1983). air permeability as an aeration criterion. in: conf. proc. 13-16 december. asae 56, st. joseph, m.i. ekwue, e.i. (1990). organic matter effects on soil strength properties. soil tillage res., 16: 280-288. fao/unesco (1974). soil map of the world, 1: 5000000. vol.1, legend sheet and memoirs, paris, 59pp. freitag, d. (1971). methods of measuring soil compaction. in: compaction of agricultural soils, k.k. barnes et al.(editors), 47-103. st. joseph, mich., asae. gaultney, l., g.w. krutz, g.c. steinhardt and j.b. liljedahl (1982). effects of subsoil compaction on corn yields. trans. asae. 25: 563-569. hakansson, i. and r.c. reeder (1994). subsoil compaction by vehicles with high axle loadextent, persistence and crop response. soil tillage res., 277-304. kayombo, b. (1989). soil compaction in the tropics and some means of alleviating it. proc.of 11th int. congress on agricultural engineering, dublin 4th – 8th september, vol 3. vincent a. dodd and patrick m. grace (editors). lal, r., g.f. wilson and b.n. okigbo (1979). changes in properties of an alfisol produced by various crop covers. soil science, 27: 377-382. lambe, t.w. (1951). soil testing for engineers. john wiley and sons, inc., new york. lowery, b. and r.t. schuler (1988). effects and duration of compaction on soil and plant growth. proc. of 11th int. conf. istro, 11th – 15th july, edinburgh, uk, pp.293-298. mamman, e. and j.o. ohu (1997). millet yield as affected by tractor traffic in a sandy loam soil in borno state, nigeria. soil tillage res., 42: 133-140. mamman, e. and j. o. ohu (1998). the effect of tractor traffic on air permeability and millet production in a sandy loam soil in nigeria. ife jour. of tech., 8 (1): 1-7. negi, s.c., e. mckyes, f. taylor, e. douglas and g.s.v. raghavan (1980). crop performance as affected by traffic and tillage in a clay soil. trans asae, 23 (6): 13641368. ohu, j.o. and o.a. folorunso (1989). the effect of machinery traffic on the physical properties of a sandy loam soil and on the yield of sorghum in north-eastern nigeria. soil tillage res., 13: 399-405. ohu, j.o., e.i. ekwue and j.b. ndirmbita (1992). a simple air permeameter for agricultural research. ife jour. of techn. in.press. ohu, j.o., o.a. folorunso and e.i. ekwue (1991). the influence of tractor traffic on crop production in a semi-arid region of nigeria. proc. 12th int. conf. of istro, iita, ibadan, nigeria, pp. 238-245. ohu, j.o., o.a. folorunso, f.a. adeniji and g.s.v. raghavan (1989). critical moisture content as an index of compactibility of agricultural soils in borno state of nigeria. jour. of soil technology, 2:211-219. oni, k.c. and j.s. adeoti (1986). tillage effects on differently compacted soil and on cotton yield in nigeria. soil tillage res., 8:89-100. the influence of organic matter on soil compactibility and air permeability of some soils in borno state 70 perumpral, j.v. (1987). cone penetrometer applications a review. trans asae, 30 (4): 938944. rayar, a.j. (1984). university of maiduguri farm development planning report for faculty of agriculture, annex a, soil survey details. raghavan, g.s.v. and j.o. ohu (1985). prediction of static equivalentpressure of proctor compaction blows. trans. asae, 28 (5): 1398-1400. radford, b.j., b.j. bridge, r.j. davis, d. mcgarry, u.p. pilai, j.f. rickman, p.a. walsh and d.f. yule (2000). changes in the properties of a vertisol and responses of wheat after compaction with harvest traffic. soil tillage res., 54: 155-170. stone, r.j. and e.i. ekwue (1995). compressibility of some trinidadian soils as affected by the incorporation of peat. j. of agric. engn. res., 60: 15-24. stone, r.j. and e.i. ekwue (1996). soil compressibility as influenced by sewage sludge incorporation. j. of agric. engn. res., 64: 227-236. voorhees, w.b. (1977). soil compaction: how it influences moisture, temperature, yield and root growth. crop soil management, 29: 7-10. voorhees, w.b. (1992). wheel-induced soil physical limitations to root growth. advanced soil science, 19: 73-95. voorhees, w.b., j.f. johnson, g.w. randall and w.w. nelson (1989). corn growth and yield as affected by surface and subsoil compaction. agronomy journal, 81:294-303. walkley, a. and i.a. black (1934). an examination of the effect of the degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method. soil sci., 37: 29-38. abstract 1. introduction availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 13-25 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) yusuf, d.d.1 abstract compaction of agricultural soils due to multiple passes of heavy power units has been the subject of much concern, in recent years. this paper, through a 3-year on-farm experiment, studied and discussed the resulting effects of tillage, traffic compaction and soil temperature on maize yield. results showed that soil resistance to cone penetration and crop yield changed rapidly during the period of study and could be related to soil moisture content and tillage. as maize extracts soil moisture, differential soil strengths and crop yields were obtained between shallow and deep tilled plots. soil temperatures were lower in shallow (15.0 xm) tilled plots than in deep (30.00cm) tilled plots and high soil temperature enhanced maize grain yield. the most rapid seedling emergence and highest crop yield were obtained in soil temperatures that averaged 300c at seedling level and within the top soil of 0-15cm zone. increase in soil resistance to cone penetration reduced maize grain yield. tillage treatment significantly affected ( )05.0p soil temperature, plant height and maize grain yield. 1. introduction in nigeria, technological development in agricultural sector together with economic pressure to reduce production costs and increase crop production for the growing population make it imperative that more vehicles are used on the farm. the unknown traffic set up by these vehicles has been shown to cause soil compaction (brannack and dexter, 1979; soane et al., 1981; spoor, 1982; wolf and hadas, 1984). soil compaction which is also a measure of soil particle bonding and matrix properties have caused reduction in seed germination, retarded root development and reduced crop yields for many soil types and conditions (soane et al., 1982; soane and van ouwerkerk, 1994). modern farming system is a continuing cycle between soil compaction caused by wheel traffic and reduction of this compaction through appropriate tillage. soil physical investigations and studies on crop yield suggested that crop yields were improved when appropriate tillage was practiced (rydberg, 1986; ryderg and ockerman, 1987; dexter, 1988; hakansson et al., 1988; kay, 1990; domzal and hodora, 1991; 1992; domzai et al., 1993). each implement pass causes a reduction of the mean aggregate size, and weakens the internal structural bonds (chanclellor et al., 1969). intensive cultivation affects soil aggregate stability with deleterious effect on soil physical properties and subsequent crust formation. these modifications of soil physical properties have a direct effect on soil temperature. soil temperature models have been used to help predict soil temperatures resulting from different tillage operations (cruse et al., 1989; gupta et al., 1981; 1982). walker (1969) and barlow et al. (1977) showed that 10c change in soil temperature can significantly affect corn growth rates. the objective of this research was to examine the effects of tillage, traffic, compaction and soil temperature on maize yield at the institute for agricultural research farm. 1department of agricultural engineering, ahmadu bello university, zaria. nigeria http://www.azojete.com.ng a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) 14 2. theory 2.1 soil temperature change in soil temperature with time can be expressed as: )/('/ 2ztktt   (van wijik, 1963) (1) where k’ is the soil thermal diffusivity, t is temperature, t is time and z is soil depth. according to van wijik (1963), one –dimensional soil temperature changes in a homogeneous soil is: )]([),( / 0 / 0 dzdz tsineattzt    (2) where d is the damping length. t is the average temperature,  is the radial frequency, a0 is the surface temperature and 0 is the phase constant. 2.2 tillage deviations of tillage means (over two plots) from their overall (cropped) mean tillage or mean soil moisture content are defined as relative tillage effects that is expressed as: lijij xxrte  (radke et al., 1985) (3) where rteij is the relative effect of tillage, xi is the mean overall tillage and replications for cropping treatments, i, and xij is the mean over replications with tillage, j, for cropping treatments, i. 2.3 soil resistance to penetrometer the resistance to the penetrometer probe (qp) can be calculated in terms of stress normal to the probe surface ( ), the coefficient of soil – metal friction (  ), the adhesion (ca) and the cone semi-angle ( ) as:  cacotcotqp  )'1( (bengough, 1992) (4) the adhesion term is simply frictional resistance that is due to the load at the soil-metal interface caused by the soil-water suction. hence, represents the resistance to a ‘frictionless’ probe (i.e. setting  and ca to zero in eqnuation 4). in nigeria, the effects of soil penetration resistance on crop yields caused by wheel traffic have been studied by various researchers (oni et al., 1982; kayombo and lal, 1986; ojeniyi, 1986; ohu and folorunsho, 1989; onwualu and anazodo, 1989; yusuf, 1996; yusuf and asota, 1998; yusuf, 2001). ohu and folorunsho (1989) reported higher bulk density and soil resistance to cone penetrometer pressure with increase in the number of tractor passes. onwualu and anazodo (1989), yusuf (1996) and yusuf (2001) showed that soil moisture content and porosity decreased with increase in soil penetration resistance. the use of appropriate tillage system and the development of tillage machinery are input thrusts for effective crop production in nigeria. azojete vol. 5 2007 15 3. materials and methods 3.1 experimental treatments the experiments were conducted at samaru (110111n, 070338’e and 685m above sea level) in kaduna state, nigeria. the soil is classified as ultic haplustalf (valette and ibanga, 1984). it is a reddish-brown soil with an average ph-kcl of 5.5 and 0.6%, w/w of organic carbon. the experimental site was at the institute for agricultural research farm, ahmadu bello university, zaria. the tillage treatments were; arara ploughing followed by ziz-zag harrowing and arara ridging (t1), emcot ploughing followed by ziz-zag harrowing and emcot ridging (t2), mouldboard ploughing followed by disc harrowing and mouldboard ridging (t3), disc ploughing followed by disc harrowing and disc ridging (t4) and manual ridging (t5). the nitrogen treatments were: no nitrogen (no), 40kg nha-1 (n1), 80kg nha-1 (n2), and 120 kg nha-1 (n3). the nitrogen application was done uniformly after the tillage treatments with a drop-type broadcaster that has spaced openings along the full length of a hopper. two planting methods, manual and mechanical were used. manual planting involves dropping seeds into holes made with heels, covering the seeds with soil and compacting the soil surrounding the seeds with the heels. the mechanical planting involves the use of a singlerow animals-drawn planter. tillage was done at an average soil gravimetric water content of 0.257 kg/kg (the water content at the time of tillage). they were sown with maize (zea maiys l.) of tzsr-w crop variety at the rate of 25 kgha-1. the crop row spacing, hill spacing and depth of seed placement were 75cm, 25cm and 3cm, respectively. the treatments were randomly assigned in a 4 x 5 x 2 factorial experiment arranged in a stripsplit-plot design with five tillage treatments (t1, t2, t3, t4 and t5) as horizontal treatments, four nitrogen rates (n0, n1, n2 and n3) as vertical treatments and two planting methods (p1 and p2) as sub-plot treatments in four replications. each plot size was 4m x 5m and the experiment was conducted from 1997 to 1999. 3.2 measurements soil temperature readings were taken from cu-constant thermocouple recorded by a campbell scientific cr5 digital recorder equipped with an s250 relay scanner. installations were at five different locations per plot each year along the sown line. readings were taken twice per day (at 08.00h and 16.00h) throughout the growing season from 1997 to 1999. two depths (0-15 cm and 15-30 cm) were used for soil temperature and the thermocouple was inserted into the ground close to the tip of developing plants. the mean plant height in each plot was measured weekly from 2 to 12 weeks after planting, using the method described by tisdall and adam (1986). rainfall intensity and air temperature measurements were available from the institute for agricultural research, ahmadu bello university, zaria weather station, which is approximately 200m away. soil penetration resistances were measured with cone penetrometer (asae, 1976) at 10 locations on each plot and the mean for each plot was used. soil moisture content was determined gravimetrically after drying at 1050c for 24 h. the data were analysed using regression and analysis of variance (anova). a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) 16 4. results and discussion 4.1 climate the average annual rainfall for the experimental period (may to august in 1997-1999) ranged from 702.0 to 870.0 mm while the long term annual precipitation for the region varies from 944.6 to 1239.2 mm. mean air temperature during the study period (may-august in 1997 – 1999) remained relatively constant at 29.00c. 4.2 tillage and soil temperature effect of tillage on soil temperature is shown in table 1. typical hourly variations in soil temperature during a 5-day period of the study are shown in figure 1. the temperatures of the soil in the seed zone during planting are generally higher in the days than in the nights. this is probably because rainy seasons at samaru are characterized by warm days and cool nights. soil temperature and plant height were significantly affected ( )01.0p by tillage treatments (tables 1 and 2). soil temperatures were lower in shallow tilled plots of t1 and t2. a difference in early and high number of seedling emergence and crop yield could be expected between shallow and deep tilled soils since soil temperatures were lower in shallow than in deep tilled plots. tillage treatments exerted a considerable influence on root-zone temperature, plant development and maize yield. high soil temperature enhanced plant growth and crop yield (figure 2). this result is consistent with the earlier reports of ehkers (1975), german et al. (1984) and farazdaghi et al. (1986) who attributed the enhanced plant growth and crop yield to high soil temperature. the most rapid seedling emergence and highest crop yield were obtained in soil temperatures that averaged 300c at seedling level and within the top soil of 0-15 cm zone. it implies that soil temperature can be used as an index of monitoring and predicting plant growth under wide range of temperature conditions and tillage systems. this result is of practical importance to maize farmers in that it will be possible to make decisions regarding the necessity of replanting or the initiation of subsequent cultural practices. azojete vol. 5 2007 17 a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) 18 azojete vol. 5 2007 19 a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) 20 figure 2: distribution of mean plant height along gradients of maximum soil temperature (tmax) and minimum soil temperature (tmin) using (a) mechanical planter and (b) manual planting azojete vol. 5 2007 214.3 soil compaction in the months of may-september, mean soil bulk density of 1.90 mgm-3 and soil penetration resistance of 3.7 mpa were recorded at the site. however, by october and november of each year of the study, the soil became drier with high soil penetration resistance (> 3.7 mpa) at any soil depth during the 3-year investigations (1997-1999). tillage had significant effect (p )01.0 on soil penetration resistance (table 2). the interactions of nitrogen rate, planting method and tillage showed no significance effect (p )05.0 on soil penetration resistance. increase in soil penetration resistance reduced maize grain yield (figure 3). the t4 treatment had the lowest mean penetration resistance of 2.7 mpa and highest mean maize grain yield of 4.8t ha-1. this result agrees with the findings of carry and evans (1974) and collebaut et al. (1986) which is in agreement with the results reported by richman et al. (1965) and coote and rainsey (1983). though the soil moisture content profile in 1997 and 1998 were similar, the distribution of soil penetration resistance varied widely. unger (1984) had similar results and reported that in some cases, tillage with identical soil moisture contents, produced significantly different soil penetration resistance. a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) 22 figure 3: response of maize grain yield to soil penetration resistance at samaru, zaria (with soil moisture content range of 18 – 23 %) azojete vol. 5 2007 235. conclusions and recommendations increase in soil penetration resistance reduced maize grain yield. tillage treatment significantly affected (p )01.0 soil temperature, plant height and maize grain yield. the t4 treatment had the lowest mean soil penetration resistance of 2.7 mpa and highest mean maize yield of 4.8t ha-1. soil temperatures were lower in shallow (15.0 cm) tilled plots of t1 and t2 than in deep (30.0 cm) tilled plot t3, t4 and t5. the most rapid seedling emergence and highest crop yield were obtained in soil temperatures that averaged 30 0c at seedling level and within the top soil of 0-15 cm zone. references asae (1976). american society of agricultural engineers standards, 1976. agricultural engineers yearbook, asaer 313, 1 343pp. barlow, e.w; r., l. boersma and j. l. young (1977). photosynthesis, transpitation and leaf elongation in corn seedlings at sub optimal soil temperatures. agron, j. 69: 95-100. bengough, a. g. (1992). penetrometer resistance equation – its derivation and the effect of soil adhesion. j. agric. eng. res., 53: 163-168. brannack, m. v. and a. r. dexter (1979). compaction of aggregate beds. in: w. w. eversion, r. d. bond and a. r. dexter (editors). modification of soil structure, wiley, new york, 120pp. callebaut, f,; d. gabriels and m. deboudt (1986). assessment of soil surface sealing and crusting. proc. symp., ghent, belgium, 1985. dept. of soil physics, state univ. of ghent, 374pp. carry, j. w. and d. d. evans (1974). soil crust. agric. expt. sta. univ. arizona tech. bull, 214, tueson, az., 58pp. chancellor, w. j.; j. a. vomocil and k. s. aref (1969). energy dissipation in compression of three agricultural soils. can. j. soil sci., 63: 1-14. cruse, r. m.; d. r. linden; j. k. radke; w. e. larson and k. larntz (1980). a model to predict tillage effects on soil temperature. soil sci. am. j. 47: 570-575. dexter, a. r. (1988). advances in characterization of soil structure. soil tillage res., 11: 199-239. domzai, h.; j. hodara; a. slowinska-jurkiewicz and r. turski (1993). the effect of agricultural use on structure and physical properties of three soil types. soil tillage res., 27: 365-382. domzai, h. and j. hadara (1991). physical properties of three soils compacted by machine wheels during field operations. soil tillage res., 19: 227-236. ehlers, w. 1975. observations on earthworms channels and infiltration of tilled and untitled loess soil. soil sci., 119: 242-249. farazdaghi, h.; j. w. ketcheson and j.h.a. lee (1986). corn grain yield as influenced by tillage and seasonal weather. soil tillage res., 8: 369german, p. f.; w. m. edwards and l. b. owens (1984). profile of bromide and increased soil moisture after infiltration into soils with macropores. soil sci. soc. am. j. 49: 237-244. gupta, s. c.; j. k. radke and w. e. larson (1981). predicting temperatures of a bare and residue covered soils with and without a corn crop. soil sci. soc. am. j. 45: 405-412. a critical examination of maize yield response to tillage, traffic and soil temperature on a ferruginous soil (haplustalf) 24gupta, s. c.; j. k. radke; w. e. larson and m. j. shafter (1982). predicting temperatures of bare and residue-covered soils from daily maximum and minimum air temperatures. soil sc. soc. am. j. 46: 372-376. hakansson, i; w. b. voorhees and h. riley (1988). vehicles and wheel factors and crop responses in different traffic regions. soil res. 11: 239-282. kay, b. (1990). rate of change of soil structure under different cropping systems. adv. soil sci. 12: 1-41. kayombo, r. and r. lal (1986). effects of soil compaction by rolling on soil structure and development of maize in no-till and disc ploughing systems on a tropical alfisol. soil tillage res., 7: 117-134. ohu, j. o. and o. a. folorunsho (1989). the effect of machinery traffic on the physical properties of a sandy soil and on the yield of sorghum in north-eastern nigeria. soil tillage res., 13: 399-405. ojeniyi, s. o. (1986). effects of zero tillage and disc ploughing on soil water, soil temperature and growth and yield of maize. soil tillage res., 3: 180-200. oni, k. c.; j. s. adeoti and f. g. braide (1982). influence of mechanised and clearing on compaction of agricultural soils. paper presented at the international conference on land clearing and development, iita, ibadan, nigeria, onwualu, a. p. and u. g.n. anozodo (1989). soil compaction effects on maize production under various tillage methods in a derived savanna zone of nigeria. soil tillage res., 14: 99-144. radke, j. k.; a. r. dexter and o. j. devine (1985). tillage effects on soil temperature, soil water and wheat growth in south australia. soil sc. am. j. 49: 1542-1547. richman, r. w.; r. letey and l. h. stolzy (1965). soil compaction effects on oxygen, diffusion rates and plant growth. calif. agr. 19(2): 3-6. ryderg, t. (1986). effects of ploughless tillage on soil physical and soil chemical properties in sweden. swedish univ. afric. sci., uppsala, div. soil management, report 70, 35pp. ryderg, t. and t. ockerman (1987). the effects of ploughless tillage on root development and evaporations swedish univ., agric. sci., uppsala, div. soil management, report 74, 53pp. soane, b. d. and c. van ouwerkerk (1994). soil compaction in crop production. developments in agricultural engineering, ii. elsevier, amsterdam, netherlands. 662pp. soane, b. d.; j. w. dickson and d. i. campbell (1982). compaction by agricultural vehicles; a review, iii. incidence and control of compaction in crop production. soil tillage res., 2: 3-36. soane, b. d.; p. s. blackwell; j. w. and d. j. painter (1981). compaction by agricultural vehicles; a review, ii compaction under tyres and other running gear, soil tillage res., 1: 373-400. spoor, g. (1982). the causes and nature of soil damage. j. agric. eng. 37: 4-7. statistical analysis systems institute inc. 1989. sas/stat user’s guide, version 6 4th edn., vol. 1 sas institute inc. n. c., 943pp. tisdall, j. m. and h.h. adam (1986). the effect of reduced tillage of an irrigated silty soil and of a mulch on seedling emergence, growth for silage. soil tillage res., 6(4): 365375. azojete vol. 5 2007 25unger, p. w. (1984). tillage effects on surface soil physical conditions and sorghum emergence, soil sc. am. j. 48: 1432-1432. valette, j. and i. j. ibanga (1984). the detailed soil survey of the experimental farm of the institute for agricultural research, samaru, zaria, nigeria. soil survey bulletin. 95pp. vanwijk, w. r. (1963). physics of plant environment. north-hilland and publ. co. amsterdam, netherlands. walker, j. m. (1969). one –degree increments in soil temperatures affect maize seedling behaviour. soil sc. soc. am. proc. 33: 729-736. wolf, d. and a. hadas (1984). soil compaction effects on cotton emergence. trans. am. soc. agric. eng. 27: 635-659. yusuf, d. d. (1996). time and cost conserving farming technique for the resource poor farmers in tropical africa. journal of engineering for international development 2(3): 31-37. yusuf, d. d. and c. n. asota (1998). design, development and performance evaluation of a once-over tillage machinery utilizing a single-axle tractor. agricultural mechanization in asia, africa and latin america (ama), 29(3). 9-13. yusuf, d. d. (2001). deep ploughing effects on irrigation intake, bulk density, and soil compaction for slowly permeable soil in northern nigeria. nigerian journal of engineering, 9(1): 22-26. nkti  a critical examination of maize yield response to abstract 1. introduction references arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 718 evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications y. l. shuaib-babata 1* , a. j. abegunde 2 , and i. o. ambali 1 (1 department of materials & metallurgical engineering, university of ilorin, ilorin, nigeria 2 department of mechanical engineering, the federal polytechnic, ado-ekiti, nigeria) *corresponding author’s e-mail address: sylbabata@gmail.com abstract poor casting quality is associated with the use of locally available moulding sands without recourse to their suitability through adequate knowledge of their properties. the properties of some ado-ekiti moulding sands were therefore examined with the aim of establishing their suitability or otherwise for foundry applications. some natural sand samples were obtained from ureje, omisanjana, odo ayo and ogbese within ado-ekiti metropolis. their chemical compositions were determined and analyzed using the x-ray fluorescence (xrf) spectrometer technique and atomic absorption spectrophotometer (aas). the sands’ physico-mechanical properties were also examined in line with american foundry society (afs) guidelines. the results of the chemical analysis indicated that the sands contained silica and aluminium oxide as their major constituents with values of 63.83 – 79.23% and 12.20 – 23.76% respectively. the ureje, omisanjana, odo ayo and ogbese sands respectively possessed american foundry-men’s society grain fineness number (afs-gfn): 63.27, 61.08, 66.98 and 61.12; clay content: 12, 13, 10 and 6%; moisture content: 12.04, 12.25, 12.23 and 11.92%; permeability 86.2, 87.5, 86.3 and 88.2%; flowability: 67.87, 68.50, 67.40 and 67.25%; green compression strength: 120.9, 63.6, 70.9 and 82.0 kn/m 2 ; dry compression strength: 203.0, 101.8, 191.0 and 76.4 kn/m 2 . each of the samples has refractoriness above 1200 o c. the sands (except that of ogbese sand) can be used naturally as core if the core length is short due to rapid decrease in the sands’ hot strength from 1100 o c. these properties were found to fall within the required values for casting of most ferrous and non-ferrous metals, except that of ogbese sand. comparison of the results obtained from the studied sands’ properties with that of afs mould sand properties for various types of castings revealed that the studied sands have the potential for use in sand casting process for metals like grey steel, light steels, brass, bronze and aluminum. meanwhile, the properties of ogbese natural sand can be improved with application of additive like bentonite to enhance its suitability for sand casting application. keywords: ado-ekiti natural moulding sands, physico-mechanical properties, moulding, foundry applications, refractoriness 1. introduction in foundry technology, sand casting is one of the manufacturing processes whereby foundry sand is used to produce a mold in which molten metal is poured to produce a cast. metal casting process is employed the in manufacturing of metallic engineering wares, tools, devices and equipment such as engine blocks, machine tool bases, cylinder heads, pump housings, and valves. in metal casting, sand casting is the most widely used (sand casting, 2017). sand cast is found suitable in casting of all metals of different sizes, ranging from very small to extremely large sizes (afs, 2017; sand casting, 2017). the casting quality of moulds and hence the strength of foundry rests fundamentally on the behaviour of sands (shuaib-babata and olumodeji, 2014; nwajagu, 1994). sand nowadays is used to cast components that have useful strengths for construction. it is therefore clearly understood that foundry sand occupies a special and non-substitute position in the foundry industry which has to be properly maintained, such properties should be well understood and put into consideration before being used. the raw material research and development council (rmrdc) in 1990 delved into the geological survey of nigerian resources and found sand to be the major mineral deposits in the country (raw material research and development council, rmrdc, 1990). available sand in nigeria covered an estimated proven reserve of billions of tones (abolarin, et al. 2006). out of all mineral resources in nigeria, only the exploration of petroleum-related resources had received significant attention (abolarin et al., 2006; isah, 2011; adeoye, 2014; ovat and bisong, 2017). it was discovered that foundry sands were abundantly available and scattered all over the towns and mailto:sylbabata@gmail.com arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 719 villages in nigeria which had been in use for past decades for casting of aluminum cooking utensils, decorative ornament and others, but efforts toward delving their properties and their effects sand on the product cast are limited (shuaib-babata and olumodeji, 2014). foundry sand is noted to be imported into the country, in spite of the fact that it is locally and abundantly available in the country. atanda and ibitoye (2004) revealed that almost all foundry industries in nigeria using the sand casting technique imported 60% of the sand used. they suggested the need to domesticate the sources of these imported sand through intensive researches. previous researchers had discovered through their various studies that most nigerian moulding sands, such as azare foundry sand, alkaleri, barkin-ladi, ilorin, were suitable for foundry applications (abolarin et al., 2004, tokan, et al., 2004, shuaibbabata and olumodeji, 2014). it implies that nigeria is well blessed with sands that can effectively be used for sand casting processes that can improve the economic activities of the country, most especially during the present economic recession which require shifting attention from over dependency on oil and gas as the main economic source. hence, it is very essential to study the properties of the available moulding sands in ado-ekiti to enhance its adequate and effective applications, since much study has not been done on this valuable material. better understanding of sand, as the most crucial factor in the practice of foundry, is very essential (shuaib-babata and olumodeji, 2014). this can be achieved through adequate knowledge of its properties. according to mechanical engineering (2012), after the moulding sand is prepared, it should be properly tested to ensure that require properties are achieved. tests are conducted on a sample of the standard sand. therefore, it is very important to identify or characterise moulding sand through analysis of its chemical composition. sand testing is significant in the control of the moulding sand properties through the control of its composition; the testing also indicate the moulding sand performance and help the foundry men in controlling the properties of moulding sands (mechanical engineering, 2012). sand control testing include moisture content test, clay content test, grain fitness test, permeability test, strength test, refractoriness test, and mould hardness test in moulding sand, the basic properties required for effective performance include dry strength, green strength, permeability, refractoriness, flowability, collapsibility, cohesiveness and adhesiveness, among others. these properties are obtained through various experimental testing of the sand. sand testing is significant since it indicates the moulding sand performance and helps the foundry men in controlling the properties of moulding sands (mechanical engineering, 2012). it is thus essential that after the moulding sand has been prepared, it should be properly tested to ensure that the required properties are achieved. this study therefore aimed at examined the characteristics of the ado ekiti moulding sands to determine if their desirable characteristics would be suitable and effective for foundry applications, especially in producing casting materials. through this study, information on physico-chemical properties of available natural sands in adoekiti will be provided, which in the long run enhances industrialization, job creation and also improve the nation’s economy status through reduction in importation of foundry sand into the country. american foundry society’s mould sand standards for various types of castings collated from technical literature are presented in table 1. this information will be useful to evaluate the study sands’ properties for different appplications. shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 720 table 1: american foundry society’s satisfactory mould sand properties for various types of castings metal clay content (%) moisture content (%) green compressive strength (kn/m 2 ) dry compressive strength (kn/m 2 ) permeability number flowability (%) heavy steel 10-12 4-5 70-85 1000-2000 130-300 light steel 7-12 6-8 70-85 400-1000 125-200 heavy grey steel 10-19 6-8 70-105 50-800 70-120 aluminium 8-10 6.5-8.5 50-70 200-550 10-30 65 brass and bronze 10-15 5-7.5 55-85 200-800 15-40 light grey iron 8-13 4-6 50-85 200-550 20-50 malleable iron 8-14 5-7 45-55 210-550 20-60 medium grey iron 11-15 5-8 70-105 350-800 40-50 source: dieter (1966), mikhailov (1989) and burns (1989) 2. materials and methods 2.1 materials the sand samples for this study were collected at the of depth of 2 meters using simple hand tools like cutlass, spade and hole with the assistance technicians and a foundry-man at the foundry unit of the federal polytechnic, ado-ekiti from different four locations within ado-ekiti metropolis as mentioned below. ado-ekiti is located in ekiti state, south western nigeria; situated in between longitude 5 ° 11´ and 5 ° 25´ and latitude 7 ° 11´ and 7 ° 37´. the sand samples were: ureje river banks (sample a) omisanjana river bank (sample b) odo ayo river bank (sample c) ogbese river bank (sample d) 2.2 methods 2.2.1 preparation of natural moulding sands the sand samples collected from the above named locations were washed and sun-dried for 3 days to free water in the sand, and sieved in order to separate the debris that were collected with them. the dried samples kept in desiccators for further laboratory/experimental analysis. 2.2.2 determination of chemical composition of the natural moulding sands the chemical constituents of the sand samples were determined using x-ray fluorescence (xrf) spectrometer and atomic absorption spectrophotometer (aas) in line with afs recommendations (american foundry-men society standards, afs,1982) and in accordance with practices of earlier researchers (ayoola, et al., 2013; mshelia, et al., 2016). 2.2.3 production of sand specimens for laboratory analyses samples were taken from the dried sands obtained from the earlier mentioned four selected sites to prepare specimens for laboratory analysis. the sand samples were sieved through british standard (bs) sieve to obtain grain size required for the experiment. the sand grains pebbles were broken into pieces using foundry flat edge rammer, the powdered-moulding sand were thoroughly mixed manually in a container with clean water for about 10 minutes to have homogeneous sand water mixture and sieved with 2 mm british standard sieve. to produce standard test specimens of 50 mm by 85 mm sizes, each of the samples were then moulded in a specimen tube using standard sand rammer. the specimens were grouped for various foundry tests and the sands’ foundry (physicomechanical) properties were obtained in accordance with the american foundry-men society, arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 721 afs (1989) guidelines, as successfully done by earlier researchers (ayoola, et al., 2013; bala and khan, 2013; danko, et al., 2014; jimoh, et al., 2015; mshelia, et al., 2016) as presented below: 2.2.4 determination physico-mechanical properties 2.2.4.1 determination of grain fineness a 5.0kg weight of dried sample from each selected sand sample was taken unto a set of electrical sieve shaker of sieves using british standard sieve numbers 8 200 (2.06mm, 1.68 mm, 1.00 mm, 0.70 mm, 0.25 mm, 0.15 mm, 0.10 and 0.90 mm sieves). these sieves were stacked in sequence with the coarsest sieve at top and placed in a sieve shaker. the shaker was allowed to vibrate for 15 minutes. the residues on each sieve were removed and weighed. the sieve sizes were classified according to the mesh numbers as presented in table 3. the american foundry-men’s society grain fineness number (afs-gfn) for each sample was calculated using equation 1 (burns, 1986; elanchezhian and vijaya ramnath, 2006) and presented in table 3 (1) where: p = sum of product; ws = weight of sample (total sum of the percentage of sand retained on pan and each sieve). 2.2.4.2 determination of moisture content in accordance with the british standard (bs 1377:1990) procedures as described by faluyi, et al. (2013), mittal and shukla (2003) and head (1992), the sand samples collected from selected locations were placed in an oven and heated to a temperature of 110 0 c for an hour to evaporate the moisture present. each sample was reweighed until constant weight was attained. the percentage of moisture was calculated from the differences in the weights of the original moist and the consequently dried sand samples using equation 2 credited to faluyi, et al. (2013); mittal and shukla (2003); and head (1992) (2) where: mw = mass of water removed by drying at 110 o c; md = mass of dried soil 2.2.4.3 determination of clay content from each of the natural moulding sand samples, 5.0 kg weight of sand was separately weighed put into a wash bottle of sand washer. a solution of 475ml distilled water and 25ml of sodium hydroxide was added as shown in figure 1. the system was agitated for the period of 10 minutes. some water was added and filled to cover the sand level in the measuring cylinder, stirred and allowed to settle. the liquid content was siphoned and dried the remaining wet sand in the oven at 105 o c. this process was repeated thrice and average value was determined for each sample. the value was converted to percentage in line with american foundry-men society, afs (1989)’s recommendation. figure 1: measuring of clay content shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 722 2.2.4.4 determination of flowability the samples of standard specimens (earlier prepared in section 2.2.1) in the tube were placed in position in rammer machine, which has an indicator (dial gauge) attached to it, to read in percentage flowability. the stem of this indicator rested on top of the plunger of the rammer, which recorded the actual movement of the plunger between one drops (blow) and the other drops (blow). though, the movement between the fourth and fifth blow gives the value on the scale that corresponds to maximum flowability (bergaya, et al., 2011). the flowability of the molding and core sand were determined by the movement of the rammer plunger between the fourth and fifth drops indicated in percentages by using a rammer of 6.35kg to give the fourth blow on the specimen, which was followed by the fifth blow as shown in figure 2. figure 2: flowability test figure 3: permeability testing apparatus (pta) 2.2.4.5 determination of bulk density to determine the bulk density of a natural moulding sand sample, cleaned sample of measuring cylinder without lids was weighed and recorded. each of the soil samples (wet) was placed in the cylinder, weighed and recorded. it was later placed in oven at 105 ° c and dried for 24 hours till the weight became constant. it was removed from oven, covered with lids and allowed to cool. lids were removed, weighed and recorded. the volume of each of the soil samples was determined by measuring the volume of the samples with a measuring cylinder and weighed on a balance. the bulk density values for the soil samples were determined using the relationship in equation 3 (hassan, 2005) (g/cm 3 ) (3) where: ws= weight of sand, vs = volume of sand 2.2.4.6 determination of sands’ permeability the permeability number of each of the sand samples was determined by the flow of air under standard pressure through the cylindrical specimen tube containing standard moulded green sand specimens placed in parameter of the permeability equipment (figure 3). each period for 2000 cm 3 of air to pass through the specimens was taken to determine permeability of each sand samples using relation in equation 4 (mittal and shukla, 2003; american foundry-men society standards, afs, 1989; and head, 1992). (4) where: v = volume of air passing through the specimen cm 3 , h = height of the specimen in cm (5.0cm), = pressure of air (9.8 x 10 2 n/m 2 ), a = cross-sectional area of specimen in cm 2 of water, t = time for air to pass in minutes. arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 723 2.2.4.7 determination of moulding sands’ shatter index the shatter index values of the green specimens and oven dried specimens were determined using shatter tester by allowing the weigh-green specimens to fall freely from a height of 1.83m unto a steel anvil. the degree of disintegration of each specimen was measured, from which the toughness or plasticity of the sand was determined in line with the bs standard specification (mittal and shukla, 2003). the shatter index was determined using equation 5 as earlier practice (aradime, et al., 2011; shuaib-babata and olumodeji, 2014; bala and olabisi, 2017). (5) where: m1 = initial mass of the sand (g), m2 = mass of the sand in the receiver (g) 2.2.4.8 determination of compression strength this test was performed on the specimen by using universal sand strength machine also known as california bearing calibration (model no. 212060257; ele (engineering lab. equipment ltd; volts: 240. amps: 3, hz.: 50ph: 1) shown in figure 4. this machine consists of a pusher arm and weight arm, both hanging from pivot bearing at the top of machine. the weight arm applied load on the specimen while the pusher arm pushed the specimen against the weight and the compression strength in newton/mm 2 was deduced using the equation 6. (a) (b) figure 4: universal sand strength machine (california bearing calibration) (a) without specimen prior the test (b) with specimen after the test compression strength = (newton/mm 2 ) (hassan and bukar, 2009) (6) where: gl = guage length (mm), fs = factor of safety, a = specimen surface area (mm 2 ) 2.2.4.9 determination of green compression strength the green standard specimen 50mm by 85mm (afs) size was fixed on strength testing machine using compression-holding device. a uniformly increasing load was applied on the specimen until the specimen crushed or squeezed. the point on the scale at which the specimen got crushed or squeezed was read as the green compression strength and the corresponding compressive value was recorded. 2.2.4.10 determination of dry compression strength the afs standard specimen was placed in the oven and dried for about two hours at 110 o c. the specimen was cooled and compressed on universal strength testing machine. a uniformly increasing load was applied on the specimen until the specimen got crushed or squeezed. the point on the scale at which the specimen crushed or squeezed was read as the dry compression strength values in kn/m 2 of the specimens. 2.2.4.11 determination of hot compression strength the cylindrical test specimens of 50mm by 85mm were heated in a heating furnace to the temperatures of 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, and 1200 ° c separately and shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 724 retained at those temperatures for 2 minutes per specimen to attain homogenous heat transformation. each hot specimen was positioned and held on the strength holding device one after another. a uniform increasing load was applied on each specimen until the specimen got crushed or squeezed (head, 1988; mittal and shukla, 2003). the points on the scale at which each specimen got crushed or squeezed were read as the compression strength for each sample (singh, 2006; afs 1982). various specimens heated to different temperatures and used in hot compression strength test are shown in figure 5. (a) 100 ° c (b) 200 ° c (c) 300 ° c (d) 400 ° c (e) 500 ° c (f) 600 ° c (g) 700 ° c (h) 800 ° c (i) 900 ° c (j) 1000 ° c (k) 1100 ° c (l) 1200 ° c arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 725 figure 5: hot compression strength test specimens heated to different temperature 2.2.4.12 determination of refractoriness value the cylindrical test specimens (15 in number) were heated in heat treatment furnace one after the other up to the following temperatures 700 ° c, 800 ° c, 900 ° c, 1000 ° c, 1100 ° c, 1200 ° c, 1300 ° c and retained at each of the temperature for 2 hours to attain homogenous heat transformation. the specimens were observed for the following signs: cracks, changes in colour, fissures and distortion. the specimens are shown in figure 6. a b c d a b c d figure 6: refractoriness test of natural moulding sand 3. results and discussion 3.1 chemical composition of natural moulding sands the results of chemical composition analysis for the selected moulding sands in ado-ekiti are as presented in table 2. this result is important since at the foundry, the chemical composition of the foundry sand relates directly to the metal moulded at the foundry (akinyele and oyeyemi, 2014). since sand testing controls the moulding sand properties through the control of its composition, it is therefore very important to identify or characterise moulding sand through analysis of its chemical composition (mechanical engineering, 2012). table 2: chemical composition of natural moulding sand element composition by weight (%) a b c d sio2 78.67 75.22 79.23 63.83 al2o3 12.2 16.03 12.2 23.76 cao 0.35 3.7 0.35 0.88 mgo 0.4 1.54 0.4 1.03 na2o 1.87 1.14 1.8 0.18 fe2o3 1.69 0.64 1.66 2.98 tio2 1.76 0.23 1.75 3.62 k2o 0.17 0.22 0.13 1.26 mno 1.89 0.15 1.72 0.89 loi 0.81 0.76 0.75 1.0 the major constituents of the specimens are oxide of silicon (silica) and aluminum with values ranging between 63.83-79.23 % and 12.20 – 23.76 % respectively. other substances such as oxides of calcium, magnesium, sodium, iron, titanium, potassium, manganese and others were in small proportions. according to american foundry society, afs (2017), “most metal casting sand (foundry sand) is high quality silica sand with uniform physical characteristics”. high proportion of silica in the tested moulding sands, except sample d (ogbese moulding sand) is in line with the afs standard. meanwhile, sample d (ogbese moulding sand) with less value of silica (63.79%) and high value of aluminum oxide (23.76%) can still be used as moulding sand with application of additive such as bentonite. column profile a = ureje b = omisanjana c = odo ayo d = ogbese shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 726 3.2 physico-mechanical properties of the natural moulding sands 3.2.1 sieve analysis the results of the sieve analysis of the selected natural moulding sands in ado-ekiti are presented in table 3. apparently there was variation in the grain sizes of the sands. the distribution of sand affects the quality of castings (ihom, et al., 2011). table 3: sieve analysis of natural moulding sand s/n sieve no (bss) sieve size (mm) percentage of weight of sand retainedretained retained (%) a b c d 1 8 2.06 0.0 0.0 0.0 0.0 2 10 1.68 0.6 0.4 0.4 1.0 3 16 1.00 1.5 1.1 1.2 2.0 4 22 0.70 2.0 5.3 4.7 3.6 5 60 0.25 4.8 3.2 2.0 3.2 6 100 0.15 8.4 5.4 11.4 13.3 7 150 0.10 54.7 56.3 45.3 48.5 8 200 0.09 24.2 27.0 30.1 25.0 9 pan-clay ≥ 3.8 1.3 4.9 3.4 total 100 100 100 100 the analysis of the results in table 3 shows a high concentration of grains retained that ranged between 45.3 to 56.3% with sieves sizes ranging between 0.10mm to 9.5mm (i.e. bs no. 200 – 01). the samples had well defined grading with sample a (ureje) had high concentration of fine structure, while sample d (ogbese) had the least concentration at sieve size of 0.15mm (bs100). a highly concentrated small grain structure enhances fine surface finish casting (adesina, 2010), while the shape of sand and particle size distribution of the sand allows good permeability and strength in natural sand (turkeli, 2017; ihom, et al., 2011). 3.2.2 the afs gfn analysis the results of afs-gfn analysis for the various specimens are presented in table 4. this result is very important in the choice of sand. ihom, et al. (2011), edoziuno, et al. (2017a) and edoziuno, et al., (2017b) are of the views that “average grain size and afs grain fineness number are useful parameters; choices of sand should be based on particle size distribution”, as the size distribution affects the quality and properties of casting produced (edoziuno, et al., 2017a; edoziuno, et al., 2017b). the results of the sand samples’ afs –gfn analysis are presented in table 4. table 4: afs-gfn of natural moulding sand sn multiplier (previous b.s. sieve nos. products (% sand retained x multiplier) a b c d 1 8 2 10 0.6 0.4 0.44 1 3 16 10.5 3.3 3.6 6 4 22 14 37.1 32.9 25.2 5 60 67.2 44.8 28 44.8 6 100 210 135 285 332.5 7 150 2844.4 2927.6 2355.6 2522 arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 727 8 200 2420 2700 3000 2500 9 clay pan 760 260 992 680 10 total 6326.7 6108.2 6697.54 6111.5 63.27 61.08 66.98 61.12 from table 4, the grain fineness number (afs-gfn ) for the sand sample a, b, c and d are respectively 63.27, 61.08, 66.98 and 61.62, which are within the standard range values of 35 to 90 fineness number for non-ferrous metal (shuaib-babata and olumodeji, 2014). tuncer (2017) was also of the opinion that sand with afn 50 – 60 with average grain size of 220 – 250 microns and fines content (below 20 microns), 2% maximum yields good surface finish at low binder levels; allows low binder level to be used; and allows low binder levels. table 5 presents some of the properties of the selected ado-ekiti natural moulding sand. these properties include clay content, moisture content, bulk density, green strength, compression strength, permeability, shatter index and flowability. the results in table 5 were compared with the satisfactory mould sand properties for various types of castings in the table 1 to evaluate the studied sands’ suitability for foundry applications, precisely for sand casting process. table 5: some properties of natural moulding sand sample c la y c o n te n t (% ) b u lk d en si ty (g /c m 2 ) m o is tu re c o n te n t (% ) p er m ea b il it y ( % ) g re en s tr en g th (k n /m 2 ) d ry c o m p re ss io n st re n g th ( k n /m 2 ) g re en s h at te r in d ex (g ) d ry s h at te r in d ex (g ) r ef ra ct o ri n es s (o c ) f lo w ab il it y ( % ) ureje 12 12.04 7.36 86.2 120.9 203.0 0.50 0.22 >1200 67.8 7 omisanjanaa 13 12.25 5.75 87.5 63.6 101.8 0.03 0.05 >1200 68.5 0 odo ayo 10 12.23 6.79 86.3 70.9 191.0 0.12 0.30 >1200 67.4 0 ogbese 6 11.92 5.52 88.2 82.0 76.4 0.03 0.03 >1200 67.2 5 3.2.3 clay contents the samples’ clay contents ranged between 6 and 13%, with ogbese moulding sand and omisanjana moulding sand had the least and highest clay contents respectively. the higher the clay contents, the lower the binder required and vice-visa. foundry sands with 0.5% maximum (below 200 mesh) clay contents allows low binder level (tuncer, 2017). the specified clay content for moulding sand is between 10 12%; while the american foundry men’s association satisfactory proved values for aluminum, brass and bronze, iron and steel castings is between 12 and 18% clay contents (burns, 1989). with these values, the natural moulding sand is expected to contain sufficient amount of binder material (me mechanical, 2016). the samples’ clay contents fall within the required values, except specimen d (ogbese moulding sand), which requires more binder than other samples. comparing the samples’ clay contents with that of the required clay content value for casting applications in table 1, the moulding sands from odo ayo and ureje; odo ayo, ureje and omisanjana moulding sands, and odo ayo are found to be suitable for casting of heavy steel, heavy grey steel, light steel and aluminum respectively. ogbese moulding sand with low clay content (6%) meets the 4 – 10% clay contents requirement for casting grey iron, medium and synthetic sand (burns, 1989). the soil (ogbese)’s clay content can still be enhanced with addition shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 728 of synthetic binder like bentonite to be suitable for casting of light and heavy steel, aluminum, brass, and bronze with a little higher clay content value requirements (714%) in moulding sand (ademoh and abdullahi, 2009). 3.2.4 moisture contents as presented in table 5, the percentage of the moisture contents of the specimens fall between 5.52 and 7.36 %. the moisture content value of the studied moulding sand is in descending order of ureje (7.36%), odo ayo (6.79%), omisanjana (5.75%) and ogbese (5.52%). the samples’ moisture contents are within satisfactory afs moulding sand moisture content for various types of castings as shown in table 1. 3.2.5 flowabilty the ability of the sand mixture to flow over and fill the sand casting pattern during the impression making phase of the manufacturing process, more flowability is useful for a more detailed casting (sand casting, 2017). flowabilty, being the ability of the moulding sand to get compacted to a uniform density assists moulding sand to flow and park all-around the pattern and take up the required shape (mechanical booster, 2017). the specimens had flowability range between 67.25 to 68.50% as shown in table 5, but it varies with moisture and clay contents (me mechanical, 2016). the afs satisfactory mould sand percentage flowability for casting aluminium is 67 (table 1). the high flowability value in the sands is as a result of rounded grains nature of the sand, which enhances the ease compaction of the sand (casting and welding, 2017). flowability increases with decrease in grain size of sand (me mechanical, 2016). 3.2.6 permeability permeability is that property of moulding sand which permits the escape of steam and other gases generated in the mould during hot metal pouring. the permeability test results recorded for the tested natural moulding sands ranged between 86.2 and 88.2. the experimental results of the green permeability for the specimens in table 5 indicates that the sand samples had good natural green permeability for casting a good number of ferrous and non-ferrous metals (burns, 1989). according to ihom et al. (2011), the recommended green permeability number for green sand is within 80 – 110. this implies that the studied sands’ green permeability values are within the stated standard ranges. the samples’ permeability numbers also fall within the values in table 1 for casting of metals, except for heavy and light steel. the high permeability of the sand samples is due the amount of well spread grain distribution and rounded-grains of the sand. the permeability depends on grain size, grain shape, grain distribution, binder and its content, degree of ramming and water content of the moulding sand (me mechanical, 2016; aweda and jimoh, 2009; sharma, 2007; elanchezhian and vijaya ramnath, 2006). the ureje sand with the highest moisture of 7.36% had the lowest permeability number (86.2), while the ogbese sand sample with the lowest moisture content had the highest value of permeability number of 88.2. this is in line with the principle that high moisture content (mc) decreases permeability (mechanical engineering, 2012). 3.2.7 shatter index the green and dried shatter index of the specimens ranged between 0.51-0.66 and 0.73-0.89 as shown in table 5. the high shatter index values indicate that the sand in ado-ekiti is tough arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 729 enough to aid satisfactory lift during pattern withdrawal. the content of clay and corresponding moisture content are attributed to this high value (tokan, et al., 2004). 3.2.8 bulk density the result of bulk density of sand ranged from11.2 to 12.22g/cm 3 which are within the recommended afs specification (tokan, et al., 2004). ihom et al. (2011) also gave recommended bulk density for green moulding sand as 1.49 g/cm 3 and above. similarly, tuncer (2017) reported that the aashto and astm standards or design parameter for foundry sand performance is 2.563 g/cm 3 (160 ib/ft 3 ). 3.2.9 dry compression strength the ureje, omisanjana, odo-ayo, and ogbese sand samples exhibited dry compression strength values of 203 kn/m 2 , 101.8 kn/m 2 , 191 kn/m 2 and 76.4 kn/m 2 respectively. the results in table 5 show that the higher the mc, the higher the dry compression strength. this is in line with the assumption that dry compression strength increases with the mc of sand (ihom et al., 2011). 3.2.10 green compression strength the ureje, omisanjana, odo-ayo, and ogbese sand samples exhibited green compression strength values of 120.9, 63.6, 70.9 and 82.0 kn/m 2 respectively (table 5). the recommended green sand’s strength ranges between 70 – 100 kn/m 2 (ihom et al., 2011). this implies that the sand samples possess adequate green strength that will retain its shape and will not distort or collapse even after the pattern has been removed from the moulding box, except ogbese sand. 3.2.11 hot compression strength of natural moulding sand in table 6, various hot compression strengths (hcs) for the sand samples at different temperatures are presented. in foundry usage, crucial properties of mold sands are green compression strength, dry compression strength, wet tensile strength, hot compression strength, flowability and durability (bergaya, et al., 2006). table 6: hot compressive strength of moulding sand s/n temp. ° c compressive strength (kn/m 2 ) a b c d 1 100 282.8 230.6 304.7 228.7 2 200 413.4 247.6 435.2 368.4 3 300 458.2 239.4 478.7 304.7 4 400 500.5 348.2 522.2 282.9 5 500 522.2 478.7 587.5 287.0 6 600 631.1 544.0 544.0 200.5 7 700 500.5 500.5 522.2 167.5 8 800 435.2 465.9 500.5 153.6 9 900 391.7 282.9 465.9 152.4 10 1000 326.4 217.6 348.1 125.7 11 1100 304.6 174.1 326.4 120.3 12 1200 261.1 130.6 305.6 120.1 generally, the hcs increased with temperature from 100 ° c to 600 ° c in descending order of sample c, a, b, and d. that is, sample c and d exhibited the highest hcs values and the lowest hcs values respectively. while between 700 ° c to 1200 ° c, the hcs values decreased, an indication that the sands can be used naturally as core if the core length is short except sample d (ogbese sand), with low compressive strength values at higher temperature. through the hot shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 730 compressive strength results, it is revealed that the various sands can withstand the compressive forces of mostly the non-ferrous metals (metals of low melting temperature) and for ferrous metals except sample d (ogbese sand), which can be improved by addition of additive such as bentonite. in casting, sand would reach at a high temperature when the metal in mold is still in liquid state as soon as the moisture is eliminated from it (bergaya, et al., 2011). hence, hot strength is required to hold the shape of the cavity. in the absence of hot strength, the mold may enlarge, break, erode or crack (bergaya, et al., 2011). this result therefore reveals the strength of the sample sands at various temperatures, especially from 100 ° c to 1200 ° c. 3.2.12 refractoriness of the moulding sands each of the moulding sand samples had refractoriness above 1200 ° c as presented in table 5. a relatively low-uniform thermal linear expansion up to 500 ° c was noted during the experimental processes. at 600 ° c, there was a sudden change in the colour of the specimens to a very reddish color. this is possibly due to the presence of red oxide, and most of the specimen compressive strengths are in their highest value. this shows that the natural sand in ado-ekiti will be suitable for casting of nonferrous metal of low temperature, as there will be small or no cracks on the mould. to resist high temperature of the molten metal without fuse with metal or breaking down, the molding sand refractoriness must be high (ibitoye, et al., 2014), that is higher than the metal’s temperature. 4.0 conclusion the following conclusions were drawn from the study: i. the tested sand samples possessed chemical compositions which are within the afs acceptable limits for moulding sands. the sand samples exhibited high quality of silica suitable as raw materials for low temperature ferrous and nonferrous metal castings, except that of ogbese sand sample which has a bit lesser value of silica oxide. this property can be enhanced by application of additive like bentonite to meet the required limit for most metal casting. ii. the results of physico-mechanical properties of the sand samples revealed that ureje, omisanjana and odo ayo mould sands were better than that of ogbese sand. iii. the physico-mechanical properties of the sand samples also revealed that the sands can be suitably used in casting of metals like grey steel/iron, light steels and aluminum. iv. the presence of red oxide in the sands and the high values of their compressive strengths their suitability for casting of nonferrous metal of low temperature. v. the ekiti state has potentials of foundry sands and could take this advantage to convert these resources to usable foundry industries. references abolarin, ms., olugboji, oa. and ugwuoke, ic. 2004. experimental investigation on local refractory materials for furnace construction. proceedings of the 5th annual engineering conference, federal university of technology, minna, nigeria, 82-85p. abolarin, ms., olugboji, oa. and ugwuoke, ic. 2006. determination of moulding properties of locally available clays for casting operations. journal of au journal of technology, 9(4): 238-242 arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 731 ademoh, na. and abdullah, at. 2009. assessment of foundry properties of steel casting sand moulds bonded with the grade 4 nigeria acadia species (gum arabic), international journal of physical sciences, 4(4): 238-241. adeoye, b. 2014. fallacy of oil wealth, resource curse and economic development: oil wealth and income inequality in nigeria. https://adeoyebabatola.wordpress.com/2014/02/03/fallacy-of-oilwealth-resource-curse-and-economic-development/ accessed on 7 june, 2017. adesina, as. 2010. investigation into the effect of agricultural by-products as additives on foundry properties of odota river sand, journal of science and technology, 5(3): 67-74. afs. 2017. choosing between green sand, nobake http://www.afsinc.org/multimedia/contentmc.cfm?itemnumber=17366, accessed on 22 february, 2017. akinyele, jo. and oyeyemi, ks. 2014. strength behaviour of concrete using foundry sand as aggregate, journal of natural science, engineering and technology, 13: 99-108. american foundry-men society standards, afs, 1982. mould and core testing handbook, 2 nd edition. foseco ltd, permgamon press, oxford, england. aramide, fo., aribo, s. and folorunso, d o. 2011, optimizing the moulding properties of recycled ilaro silica sand, leonardo journal of science, 19: 93-102. atanda, d. and ibitoye, m. 2004. an appraisal of foundry industries in nigeria, a way forward. proceedings of the 3 rd nigerian materials congress (nimacon) and meeting of the nigerian materials research society (nigerian-mrs), 22-29p. aweda, jo. and jimoh, ya. 2009. assessment of properties of natural moulding sands in ilorin and ilesha, nigeria, usep: journal of research information in civil engineering, 6(2):68 – 77. ayoola, wa, adeosun, soand oyetunji, a. 2013. investigation into foundry properties of oshogbo and saki silica sand deposits, international journal of engineering, xi(3): 213-218 bala, kc and olabisi, ba. 2017. deterioration of moulding sand properties with number of castings. leonardo electronic journal of practices and technologies, 30: 209-220. bala and khan. 2013. characterization of beach/river sand for foundry application, leonado journal of science, 23(12): 77-83. ergaya, f., theng, ., agaly, g. 2011. handbook of clay science, elsevier science & technology, imprint elsevier science ltd, oxford, united kingdom burns, ta. (ed.) 1989. foseco ferrous foundryman’s handbook. butterworth heinemann, new delhi, india, 1352. burns, ta. (ed.) 1986. the foseco foundryman’s handbook: facts, figures and formulae, 9 th edition, pergamon press plc, headington hill hall, oxford, england. casting and welding. 2017. lecture notes on advanced casting and welding (acw), ssm college of engineering and technology, department of mechanical engineering. https://ssmengg.edu.in/weos/weos/upload/estudymaterial/mechanical/4thsem/productiontechonology/castingandwelding.pdf, accessed on 25 may, 2017. https://adeoyebabatola.wordpress.com/2014/02/03/fallacy-of-oil-wealth-resource-curse-and-economic-development/ https://adeoyebabatola.wordpress.com/2014/02/03/fallacy-of-oil-wealth-resource-curse-and-economic-development/ https://www.bookdepository.com/publishers/elsevier-science-technology https://www.bookdepository.com/publishers/elsevier-science-technology https://ssmengg.edu.in/weos/weos/upload/estudymaterial/mechanical/4thsem/production-techonology/castingandwelding.pdf https://ssmengg.edu.in/weos/weos/upload/estudymaterial/mechanical/4thsem/production-techonology/castingandwelding.pdf shuaib-babata et al.: evaluation of chemical and physico-mechanical properties of ado-ekiti natural moulding sands for foundry applications. azojete, 13(6):718-733. issn 1596-2490; e-issn 25455818, www.azojete.com.ng 732 danko, r., holtzer, m. and danko, j. 2014. investigations of physiochemical properties of dusts generated in mechanical reclamation process of spent moulding sands with alkaline resins, china foundry, overseas foundry, 11(2): 132-138. dietert, hw. 1966. foundry core practice, 3 rd edition, american foundry’s society, des plaines, inc, 2-154p. edoziuno, fo., oyibo, ao., and odo, ju. 2017a. effects of particle size, clay and moisture contents on the properties of synthetic moulding sand, proceedings of nigerian metallurgical society (nms), 100-110p. edoziuno, fo., akaluzia, ro., odoni, bu., and nwaeju, cc. 2017b. effect of base sand particle size on the properties of synthetic moulding sand, international journal of research in engineering and innovation, 1(3): 226-230. elanchezhian, c. and vijaya ramnath, b. 2006. manufacturing technology-i, 2 nd edition, laxmi publications (p) ltd., new delhi, 32p faluyi, o, adam, o, akinwamide, a. and okoroafor, dg. 2013. geo-technical practical guide for civil engineers, civil engineering department, federal polytechnic, ado-ekiti, 1-62p. hassan, ab. and bukar, ya. 2009. design and fabrication of a compression strength testing machine for blocks and clay bricks, leonardo electronic journal of practices and technologies, 14, 142-153. hassan, sb. 2005. modern refractories: production, properties, testing and applications, timo commercial printers, zaria, 1-70p. head, kh. 1992. manual of soil laboratory testing, volume 1: soil classification and compaction tests, pentech press, plymouth, london. head, kh. 1988. manual of soil laboratory testing, volume 2: permeability, shear strength and compressibility tests, pentech press, plymouth, london. ibitoye, sa., olawale, jo. and shittu, md. 2014. influence of cement-silica ratio on the moulding properties of portland cement bonded sand, journal of physical science, 25(1): 113–122. ihom, ap., agunsoye, j., anbua, ee. and ogbodo, j. 2011. effects of moisture content on the foundry properties of yola natural sand. leonardo electronic journal of practices and technologies, 9: 85-96. isah, bk. 2011. solid mineral resource development in sustaining nigeria’s economic and environmental realities of the 21st century. journal of sustainable development in africa, 13(2): 210-214 jimoh, bo., ajibola, oo. and borisade, sg. 2015. suitability of selected mild sand mine in akure, nigeria for use as foundry sands in aluminium alloy casting, international journal of engineering and technology, 5(8):485-495 me mechanical. 2016. molding sand: constituents, types and properties. https://memechanicalengineering.com/molding-sand/, accessed on 2 february, 2017. https://me-mechanicalengineering.com/molding-sand/ https://me-mechanicalengineering.com/molding-sand/ arid zone journal of engineering, technology and environment, december, 2017; vol. 13(6):718-733. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 733 mechanical booster. 2017. properties of moulding sand in casting, http://www.mechanicalbooster.com/2017/11/properties-of-moulding-sand.html, accessed on 22 july, 2017. mechanical engineering. 2012. a complete online guide for every mechanical engineer-sand testing methods sand testing equipment. http://www.mechanicalengineeringblog.com/2997-sandtesting-methods-sand-testing-equipment/, accessed on 17 february, 2017. mshelia, za, abolarin, ms, abubakre, ok and ademoh, na. 2016. charactirization of natural moulding sands from selected deposits in maiduguri-nigeria for casting applications, arid zone journal of engineering, technology and environment, 12: 110-121. mikhailov, am. 1989. metal casting. mir publishers, moscow, 71-82p mittal, s. and shukla, jp. 2003. soil testing for engineers, khanna publishers, nai sarak, delhi110006, india, 1-218p. nwajagu, co. 1994. foundry theory and practice, 1 st edition, abc publisher ltd, enugu nigeria, 418-419p. ovat, fa. and bisong, ma. 2017. analysis and categorization of akparavini and okwuboyere clay deposits in biase lga of cross river state-nigeria. engineering and technology. 4(2):1621. raw material research and development council, rmrdc. 1990. geological survey of nigeria resources, 1 st edition: 18-22p. sand casting 2017. sand casting for manufacture – manufacturing process. http://thelibraryofmanufacturing.com/metalcasting_sand.html accessed on 22 february, 2017. sharma, pc. 2007. a textbook of technology (manufacturing processes), s. chand publishing & company pvt ltd., ram nagar, new delhi-110055. shuaib-babata, yl., abegunde, aj., and abdul, jm. 2017a. suitability of ado-ekiti (nigeria) natural moulding sands for use as foundry sands in production of aluminum alloy cast, journal production engineering, 20 (2): 91-100. shuaib-babata, yl. and olumodeji, jo. 2014. analysis of ilorin sand moulding properties for foundry applications, international journal of engineering research and technology (ijert), 3(1):1520 – 1526. singh, r. 2006. introduction to basic manufacturing processes and workshop technology, new age international, new delhi tokan, a., adelemoni, ea. and datau, sg. 2004. mould characteristics of azare foundry sand, journal of raw material research (jormar), 1(1): 41 45. tuncer, be. 2017. foundry sand: characteristics, specifications, environmental considerations, availability, recycled materials resource center (rmrc), university of wisconsin-madison. turkeli, a. 2017. foundry technology: sand, sand additives, sand properties, and sand reclamation (mse 432). http://ara.edu.tr/~altan.turkeli/files/cpt-2-sand_sand.pdf accessed on 22 february, 2017. http://www.mechanicalbooster.com/2017/11/properties-of-moulding-sand.html http://www.mechanicalengineeringblog.com/2997-sand-testing-methods-sand-testing-equipment/ http://www.mechanicalengineeringblog.com/2997-sand-testing-methods-sand-testing-equipment/ http://thelibraryofmanufacturing.com/metalcasting_sand.html http://ara.edu.tr/~altan.turkeli/files/cpt-2-sand_sand.pdf arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):721-728 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 721 original research article influence of tungsten inert gas welding on hardness, tensile strength and microstructures of aluminum 6061 alloy weldments a. a. musa1,2*, m. a. mohammed1 and e. t. dauda1 1department of metallurgical and materials engineering, ahmadu bello university, pmb 1045, zaria, nigeria 2department of materials science and engineering, african university of science and technology, abuja-nigeria. *corresponding author’s email address: amusa@aust.edu.ng 1.0 introduction welding is the method or technique by which metals are joined together by fusion, diffusion, or surface alloying through the application of heat or pressure, with or without a filler material (musa et al., 2020a). welding involves many metallurgical phenomena and is considered one of the most effective methods of joining materials, despite its complex nature (sergey et al., article information abstract in this work, tungsten inert gas (tig) welding was used for joining aluminum 6061 alloy because it offers low heat input to the weld joints and the ability to remove any refractory oxides such as al2o3 through a process known as the cathodic cleaning effect. this research was carried out to evaluate the level of improvement in the tensile strength and the hardness of aluminum 6061 alloy welds, using a tungsten inert gas welding approach. aluminum 6061 alloy in form of a round bar of length 100 mm and 8 mm in diameter was first machined to the standard tensile testing specimen according to the american society for testing and materials (astm) using a lathe machine. it was then butt welded along the center of the bar using tungsten inert gas welding process with a constant welding current of 18 amperes and gas flow rate of 15 liter/min. the same process was repeated for both the hardness and microstructure specimens followed by butt welding along the center of the specimen. the welded samples were then subjected to the hardness and tensile testing using rockwell hardness testing and hounsfield tensile testing machine respectively. the results showed that the welded metal and the heat-affected zone possessed the highest hardness value of 84.2 hrb and 71.9 hrb respectively as compared with the parent metal with a hardness value of 66.8 hrb. also, the tensile strength of the welded specimens is 300.35 n/mm² which is relatively lower than that of the base material with a tensile strength of 348.67 n/mm². additionally, the results of the microstructural examination reveal the presence of trace aluminum oxides within the matrix of the welded structure which indicates the slight increase observed in the hardness of the welded sample as compare to that of the base material. therefore, the hardness and tensile strength for the welded sample are close to the base metal indicating that welding of aluminum and its alloys using the tig welding process gives welds of adequate mechanical properties . © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 march, 2022 revised 5 july, 2022 accepted 10 july, 2022 keywords: tig welding tensile strength hardness aluminium 6061 alloy microstructure http://www.azojete.com.ng/ mailto:amusa@aust.edu.ng mailto:amusa@aust.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):721-728 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 722 2020). these phenomena include melting, solidification, gas metal reaction, slag to metal reactions, surface effects, and solid reactions. a weldment comprises of weld metal zone, a heat-affected zone (haz), and the unaffected base metal. the structures of the weld metal usually differ from the base metal because it is composed of varying mixtures of filler material and base metal melted and solidified together during the welding process (dauda, et al., 2010; sathiya et al., 2012). the weld metal and heat-affected zone must be compatible with the base metal if a successful and serviceable welded joint is to be produced. the filler electrode employed may be tailored to the mechanical properties and chemical composition of the metal but its structure could be markedly different. this structure and its attendant properties are a direct result of the sequence of events that occur just before and during the time the weld solidifies. these include reactions of the metal with gases in the vicinity of the weld, reactions with non-metallic liquid phase(s) (slag or flux) during welding, and solid-state reactions occurring in the weld after solidification (dauda et al., 2010). aluminum and its alloys play an important role in most engineering applications due to their lightweight and excellent oxidation resistance, especially at high temperatures (dursun and soutis, 2014). the joining of aluminum and its alloy through the conventional arc welding processes has been very challenging due to its lower melting temperature and high activity with oxygen while in a molten state (sathish et al., 2021). aluminum can be welded with ease by proper selection of the welding techniques as well as proper filler materials (sadeghian and iqbal, 2022). tungsten inert gas welding (tig) often referred to as gas metal arc welding (gmaw) is one of the commonly used arc welding processes for joining different materials used in critical industries such as construction, oil and gas, and pipeline industries (vijayan and seshagiri, 2018). it produces clean and high-quality welds joint and is suitable for joining very thin and medium thickness materials such as aluminum and its alloys, titanium and its alloy, low alloy steels, and stainless steels (omiyale et al., 2022). this is because tig offers lower heat energy input to the weld joint, thereby preventing burning or overheating of the weldment (cibi and thilagham, 2017; musa et al., 2020b). it istherefore important to study the structural changes that occur during gas tungsten arc welding of aluminum 6061 alloy to assess any significant variations in their hardness, tensile strength, and microstructural features when compared to the base metal (parent metal) 2. materials and method the materials used in this research are round aluminum 6061 alloys and aluminum 5356 filler rods. the chemical composition of aluminum 6061 alloy and that of the filler rods are presented in table 1 table 1. chemical compositions of both aluminium 6061 alloy and aluminium 5356 filler rod elements percentage composition (%) aluminium 6061 alloy aluminium 5356 filler rod cu 0.15-0.40 0.10 mg 0.8-1.20 4.5-5.5 mn 0.15 0.05-0.20 si 0.40-0.80 0.25 ti 0.15 0.060-0.20 zn 0.25 0.10 cr 0.04-0.35 0.050-0.25 fe 0.7 0.40 al balance balance file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mautech.edu.ng musa et al: influence of tungsten inert gas welding on hardness, tensile strength and microstructures of aluminum 6061 alloy weldments. azojete, 18(4):721-728. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 723 2.1. method samples of aluminium 6061 alloys were welded using tungsten inert gas welding process with aluminum 5356 filler rods to make a butt joint. figure 1(a) shows the aluminium 6061 rods, while figure 1(b) presents the aluminum 5356 filler rods. welding of the samples was carried out using a gas tungsten arc welding machine (arc-tig at101 inverter, manufacture by orion ac&r limited, united kingdom). the welding parameters used were set at a constant current of 18 amperes and pure argon was used as the shielding gas at a constant flow rate of 15l/min. after welding of the specimens, they were allowed to cool and the welded specimens were machined carefully to avoid fracture by the aid of a lathe machine to the desired dimensions for the mechanical tests (hardness and tensile strength). figure 1: (a) round bars of aluminium 6061 alloy (b) aluminium 5346 filler metals/rods 2.2. the tensile test for the tensile test, the specimens were machined to desired dimensions for tensile testing using a lathe machine. the tensile test was carried out using a hounsfield tensometer (manufactured by british rail engineering ltd, swindon, england) to determine the behavior of the aluminum 6061 alloy welds under tension loading and to evaluate the ultimate tensile strength (uts) as well as the percentage elongation after a fracture. the test consists of three samples that were subjected to tensile stress and the average of the results was taken for each set. the initial diameter for each specimen was measured with a vernier caliper the gauge length was also noted. a special graph sheet was used in the autographic recording drum to record and measure the relative motion of the drum and across the driving system, the percentage elongation and reduction was set to zero. the specimens were inserted into the tensometer using the split chucks and pins, precautions were taken to avoid too many marks. the load handle was rotated gently and uniformly until fracture of the specimen occurs. the final dimensions were then measured and the tensile strength was calculated using equation 1. figures 2 and 3 showed the tensile test sample and the tungsten inert gas welding setup respectively. 𝛿 = 𝑃 𝐴 (1) where: δ is the tensile strength (n/mm2), p is the applied load in tension (n), a is the original cross-sectional area of the sample (mm2). http://www.azojete.com.ng/ mailto:jbhussein01@mautech.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):721-728 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 724 figure 2: aluminium 6061 tensile test specimen as per astm standard figure 3: tungsten inert gas welding setup 2.3 hardness test the welded and the unwelded specimens were used. the hardness of the specimens was measured using the indentec universal hardness testing machine, model no-8187.5 lkv shown in figure 4. this machine was manufactured by indentec hardness testing machine ltd. zwick roell, england. the indenter used 1/16-inch steel ball indenter and the scale was hrb. the specimens were mounted to enable them to sit properly on the machine. the load was then applied on the specimens and the indentation created on the surface of the specimen was then measured to determine their hardness, three readings were recorded and their average values were recorded. figure 4: indentec universal hardness testing machine 2.4 metallographic examination the microstructural examination was carried out on the welded samples and the base metal by using optical microscope (opm) to reveal the microstructural changes due to heat energy input. the samples were passed through metallographic sample preparation to generate smooth and almost mirror-like surfaces of the specimens through the help of successive grinding and polishing processes using different sizes of grit papers (320,400,600,800) and polishing machine respectively. the grinding process was done in two stages which are the rough and fine stages; it was carried out with the addition of an adequate amount of water on top of the grit papers to avoid friction and overheating as well as damage to the ground surface after welding, the samples for investigation were prepared following the standard of the microscopic machine. the samples were first mounted in molds with epoxy resin for easy handling before grinding and polishing operation. the mounted samples were then passed file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mautech.edu.ng musa et al: influence of tungsten inert gas welding on hardness, tensile strength and microstructures of aluminum 6061 alloy weldments. azojete, 18(4):721-728. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 725 through a grinding operation using different grit papers as mentioned. during the grinding process, the direction of the samples was changed at the right angle when moving from the previous grit to the next finer grit paper. this is to remove the scratches produced by the previous grit papers and also, to maintain the microstructural integrity of the specimen. polishing of the specimen’s surface was then performed to achieve an almost perfect mirrorlike surface. this was achieved by the aid of polishing cloth on a polishing machine that rotates and is electrically powered and to minimize the heat generation during polishing, changes in microstructure due to heat generation, polishing compound (alumina) was used. the specimens were moved in an opposite direction to the motion of the machine to achieve the desired mirror-like surface. finally, the welded and unwelded samples were etched to reveal the microstructural details that would otherwise not be evident on the polished sample. the etchant used for the aluminum sample was keller’s reagent which is mostly used for aluminum alloys, prepared with 190 ml distilled water, 5ml nitric acid, 2ml hydrofluoric acid, 3ml hydrochloric acid, the sample is immersed in the reagent after achieving mirror-polish surface for 10-30 seconds. care was taken because this reagent contains ‘hf’ which can cause damages to glassware if it has direct contact with it. therefore, it is often stored in an hdpe (high-density polyethylene) bottle. after proper etching, the specimens were then ready to be viewed under a metallurgical microscope to desirable magnifications of x100. 3. results and discussion 3.1 hardness the hardness test result reveals that the weld metal (welded specimen) had the highest hardness with an average rockwell hardness value of 84.2 hrb. the heat-affected zone showed a hardness value of 71.9 hrb, while the base metal (as-received sample) has a hardness value of 66.8 hrb as presented in figure 5. the relative increase in the hardness values at the fusion and heat-affected zones of the weldment can be attributed to thermal cycles experienced during welding that may lead to the formation of the hardened ceramic phase of al2o3 at these zones. the electric arc interacts with the material at the microstructural level during and immediately after welding which causes some phase transformations within the structure of the weldment which are mostly brittle phases, hence, making the hardness to be higher at the expense of its ductility and strength as reported in a study by baghel and nagesh (2018). figure 5: rockwell hardness tests results for base metal, weld metal, and heat-affected zone. 3.2 tensile test table 3 presents the tensile test results for both the welded and unwelded samples. it can be observed that the unwelded specimens possessed the highest tensile strengths with an average ultimate tensile strength (uts) of 348.67 n/mm² with the corresponding percentage elongation of 25% after a fracture. while the welded samples showed an appreciable tensile 66.8 84.2 71.9 0 20 40 60 80 100 b a s e m e t a l w e l d m e t a l h e a t a f f e c t e d z o n e h a r d n es s v a lu e (h rb ) http://www.azojete.com.ng/ mailto:jbhussein01@mautech.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):721-728 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 726 strength of 300.35 n/mm² with average percentage elongation of 13%. the decrease in the tensile strength of the welded sample may be attributed to the high-temperature gradient at the fusion zone and heat-affected zone which causes some microstructural changes such as brittle phase formations, hence lowering the tensile properties of the weldment, similar results have also been reported by nazemi (2015). table 3: tensile test results for both welded and unwelded samples experimental parameter unwelded sample welded sample original length (mm) 37 37 gauge length (mm) 27 27 fracture load (kn) 4.5 4.63 ultimate tensile strength (n/mm²) 348.67 300.35 maximum load (kn) 6.28 5.43 elongation percentage (%) 25 13 3.3 microstructural examination microstructural characterization studies were conducted on metallographically prepared samples to investigate the morphological characteristics of both the welds and the base metal. figure 6 shows the microstructure of the base metal of aluminum 6061 with white and black portions indicating the presence of aluminum and magnesium silicide (mg₂si) particles respectively. these particles were observed to be dispersed uniformly all over the aluminum matrix and are expected to be responsible for enhancing the properties like hardness and tensile strength hence, the reason for alloying aluminum with magnesium and silicon to form 6061 alloy as similarly observed by (othman, 2011). figure 7 showed the microstructure of the welded specimen having fine grains and dendritic structures which consists of traces of aluminum oxide precipitates within the structures of the weld metal. the presence of these phases is due to the thermal cycle that the welded joint has undergone during the welding process and without any post-weld heat treatment or modification done to the weldment after solidification. figure 8 showed the heat-affected zone of the weldment with finer grains consisting of both aluminum oxides (al2o3) and uniformly distributed magnesium silicide (mg₂si) particles. a similar result was previously reported by rajiv and gope (2015) and liang (2018). figure 6: microstructure of unwelded aluminium 6061 (parent metal) (x100) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mautech.edu.ng musa et al: influence of tungsten inert gas welding on hardness, tensile strength and microstructures of aluminum 6061 alloy weldments. azojete, 18(4):721-728. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 727 figure 7: microstructure of weld metal (x100) figure 8: microstructure of heat-affected zone (haz) (x100) 4. conclusion in this study, investigation of some mechanical properties and microstructural features of gas tungsten arc welding of aluminum 6061 alloy was carried out and the following conclusions were made: ➢ the parent metal showed the least hardness value with 14.61% lower as compared to that of the weld metal. ➢ the ultimate tensile strength of the welded sample is slightly lower with about 13.44% reduction as compared to that of the parent metal. ➢ the weld metal reveals coarse grain structures at the fusion and heat-affected zone of the weldment which causes the slight reduction in the tensile strength of the weld. ➢ welding of aluminium 6061 alloy using tungsten inert gas (tig) process produced weld joints with improved properties that are closer to the properties of the parent metal. reference baghel, pk. and nagesh, ds. 2018. mechanical properties and microstructural characterization of automated pulse tig welding of dissimilar aluminum alloy. indian journal of engineering and materials sciences, 25: 147-154. cibi, aj. and thilagham, kt. 2017. high-frequency gas tungsten arc welding process for dressing of weldment. international journal of advanced engineering research and science (ijaers), 4(3): 229-235. http://www.azojete.com.ng/ mailto:jbhussein01@mautech.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):721-728 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusa@aust.edu.ng 728 dauda, et., hassan, sb., aponbiede, o., nyior, gb. and mohammed, ra. 2010. the assessment of microstructure and hardness characteristics of some welded low carbon steels. nigerian journal of engineering, 17: 67-73. dursun, t. and soutis, c. 2014. recent developments in advanced aircraft aluminum alloys. materials and design 56: 862-871. liang, y., shen, j., hu, s., wang, h. and pang, j. 2018. effect of tig current on microstructural and mechanical properties of 6061-t6 aluminum alloy joints by tig–cmt hybrid welding. journal of materials processing technology, 255: 161-174. musa, aa., dauda, et. and bello, ka. 2020a. microstructural features and mechanical properties of aisi 430 ferritic stainless steel welds a review. fudma journal of sciences (fjs), 4(1): 677–685. musa, aa., dauda, et., bello, ka. and adams sm. 2020b. optimization of tig welding parameters on the tensile strength performance of ferritic stainless steel welds using response surface methodology. indian journal of engineering , 17(48): 591-604. nazemi, n. 2015. identification of the mechanical properties in the heat-affected zone of aluminum welded structures. electronic theses and dissertations, university of windsor, ontario, canada. omiyale, bo., olugbade, to., abioye, te. and farayibi, pk. 2022. wire arc additive manufacturing of aluminium alloys for aerospace and automotive applications: a review. materials science and technology, 38(7): 391408. othman, nk., bakar, srs., jalar, a., syarif, j. and ahmad, my. 2011. the effect of filler metals on mechanical properties of 6mm aa 6061-t6 welded joints. advanced materials research, 154(155): 873-876. sadeghian, a. and iqbal, n. 2022. a review on dissimilar laser welding of steel-copper, steelaluminum, aluminum-copper, and steel-nickel for electric vehicle battery manufacturing. optics & laser technology, 146: 107595. sathish, t., tharmalingam, s., mohanavel, v., ashraff, aks., karthick, a., ravichandran, m. and rajkumar, s. 2021. weldability investigation and optimization of process variables for tigwelded aluminium alloy (aa 8006). advances in materials science and engineering, 28(16): 1-17. sathiya, p., mahendra, km. and shanmugarajan, b. 2012. effect of shielding gases on microstructure and mechanical properties of super austenitic stainless steel by hybrid welding. materials and design, 33: 203-212. sergey, s., tri, le-q., bastian, m., farzad, vf., margie, po., alexander, r., giulio, m., christian, l. and kilian, w. 2020. supervised deep learning for real time quality monitoring of laser welding with x-ray radiographic guidance. scientific reports https://doi.org/10.1038/s41598020-60294-x. 10(1): 1-12 vijayan, d. and seshagiri, vr. 2018. process parameter optimization in tig welding of aisi 4340 low alloy steel welds by genetic algorithm. iop conf. series: materials science and engineering, 390: 1-8. doi:10.1088/1757899x/390/1/01206 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mautech.edu.ng https://doi.org/10.1038/s41598-020-60294-x https://doi.org/10.1038/s41598-020-60294-x arid zone journal of engineering, technology & environment azojete june 2021. vol. 17(1):173-184 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 173 original research article waste to wealth in building materials development: a review of plastic waste in concrete i. anum1* and o. f. job2 1department of building, modibbo adama university, yola, adamawa state, nigeria. 2department of building, university of jos, plateau state, nigeria *corresponding author’s email address: ioranum@gmail.com 1.0 introduction the united nations statistics division (unsd) glossary of environment statistics (2012) describes waste as materials that are not prime products (products produced for the market) for which the generator has no further use in terms of his/her own purposes of production, transformation or consumption, and of which he/she wants to dispose. federation of european publisher fep (2018) also affirms that waste is a natural byproduct of the phenomenon of life and growth of societies generated during the extraction of raw materials, the processing of raw materials into intermediate and final products, the consumption of final products, and other human activities. waste excludes residuals directly recycled or reused at the place of generation. examples of waste includes municipal solid waste (msw), hazardous waste, electronic waste, construction and demolition waste among others (unsd, 2012). according to united nations economic and social commission for asia and the pacific unescap (2020), meeting the goals of sustainable development is an outstanding global challenge requiring waste to resource approach. waste is a valuable resource that could be managed to produce some sustainable benefits for a range of actors. hence it is important to look at “waste” as valuable resource that can be converted into a variety of useful products (fep, 2018). the process of conversion of waste to products that can be primarily used is wealth generation process, thus “waste to wealth.” the potential waste to wealth enterprise is very high with promising advantages that may lead to reduction of pressure induced on the environment, creation of opportunities for income and employment and impact the quality of life (fep, 2018). article information abstract recently, there has been a growing interest in the use of post-consumer plastics in the production of concrete. consequently, a large number of studies reporting the behaviour of concrete containing waste and recycled plastics have been published. these studies have great potential for improving the inherent weakness of concrete, reduction of pressure induced on the environment and creation of employment opportunities for economic development. this paper presents a review of journal publications on the effects of waste and recycled plastic materials on some fresh and hardened properties of concrete. the effects of waste plastic materials on slump, density, compressive strength, tensile/flexural strength and permeability are discussed. it was concluded that post-consumer plastics can be successfully and effectively utilized to replace conventional concrete. this presents a strong potential for the production of sustainable concrete as well as meeting the goals of sustainable development requiring a waste to resource approach. the study suggests public education and awareness on the prospects of using waste plastic in concrete for economic empowerment among the population © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 nov., 2020 revised 24 januray 2021 accepted 27 januray 2021 keywords: building materials concrete waste wealth post-consumer plastics arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):173-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 174 interestingly, the global plastic production exceeded 311 million metric tons from 2.5 billion metric ton of solid waste generated in 192 countries, about 275 million tons were plastic waste (unep, 2016 in bokani 2019). for instance, in nigeria, the per capital consumption of plastics has grown by about 5% annually over the past ten years, from 4.0 kg in 2007 to 6.5 kg in 2017 and is estimated to be 7.5 kg in 2020 (bokani, 2019). this fast growth could be attributed to the boost in industrialization and the rapid improvement in standards of living (rahim, et al, 2013). therefore, plastic materials are typical waste materials of interest and are arguably the most common forms of waste in african cities (iwuoha, 2013). for instance, a recent study by aderoju and guerner (2020) showed that plastic constitutes a higher average percentage of municipal solid waste within abuja municipal area council (amac), nigeria as in table 1. the united nations environment report (2018) estimated that only 9% of plastic waste ever produced has been recycled, 12% is incinerated and the remaining 79% is accumulated in landfills, dumps or the natural environment. the generation of non-decaying plastic wastes materials, combined with a growing consumer population, has resulted in a waste disposal crisis requiring urgent solution. the obvious implication is that one of the solutions to this crisis lies in the conversion of the waste plastic materials into useful products for economic empowerment (parasivamurthy, 2007). table 1: mean household composition of msw in amac and bwari area council districts, abuja districts plastic ave (%) paper ave (%) food / organic ave (%) metal ave (%) other waste ave (%) asokoro 17.839 14.485 35.761 12.111 19.804 maitama 16.474 15.066 36.424 10.513 21.523 wuse 16.216 14.479 38.765 12.509 17.761 garki 17.551 13.855 40.094 12.09 16.381 kubwa 13.067 7.559 44.276 12.419 22.678 dutse 13.477 7.547 48.787 9.704 20.678 gwarinpa 14.592 10.086 41.202 13.747 20.386 durumi 13.269 9.6 43.582 14.025 19.525 bwari 14.035 7.309 51.169 8.041 19.444 kado / life camp 16.27 8.761 41.802 12.516 20.651 karu / nyanya 14.317 11.013 45.154 8.811 20.704 utako / jabi 15.781 13.75 38.906 11.719 19.844 wuye 15.512 11.08 45.706 9.695 18.006 mpape 14.081 8.831 49.165 7.159 20.764 airport road 12.645 9.484 46.681 10.221 20.969 mabushi / jahi 13.224 8.438 44.332 8.06 25.945 (aderoju and guerner, 2020) globally, the construction industry consumes an estimated 11.5 billion tons of concrete every year and might reach 18 billion tones by the year 2050 (mamman and abdulsalam, 2011). according to rai et al. (2012), concrete has proven to be an excellent disposal means for fly ash, silica fume, ground granulated blast furnace slag, marble powder which has the capacity not only to trap the hazardous materials but also enhance the properties of concrete. anum and job : waste to wealth in building materials development: a review of plastic waste in concrete. azojete, 17(2):173-184 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 175 consequently, research and development efforts aimed at improving concrete performance have triggered researchers to consider the use of polymeric materials such as waste tires and plastics for the purpose of improving concrete deficiencies (parasivamurthy, 2007). therefore, a comprehensive review of these research efforts utilizing waste plastic materials for concrete purposes is necessary. this would provide a better understanding of the subject as well as the prospects for the creation of income and employment opportunities. this paper aims to provide a review of existing reports on the use of various waste plastic materials in their different forms. 2.0 plastics and their general properties plastics are organic materials made from resins, plasticizers and pigments. they have the quality of being easily shaped or moulded in soft state when subjected to heat and pressure in the presence of a catalyst and used in solid state (duggal, 2008; ahmed and raju, 2015). according to averill and eldredge (2015), plastics are material choices for engineering application over other building materials due to their low cost, availability, light weight, improved heat resistance and good chemical resistance among others. according to duggal (2008) and tasie (2010) plastic materials vary enormously in their properties; they however agreed that it is possible to make a few generalizations. according to the authors, plastics possess high strength to weight ratio with most plastics having average range of 10 -100 mnm-2 and the values for young modulus in the range of 0.25 to 5nm-2. plastics generally have lower densities than metals. the specific gravities (sg) for unfilled plastics are tactically within the range of 0.83 – 2.2. plastic materials also vary in their tenacity and toughness. some materials are glassy and brittle, others are glassy but tough, and others are leather-like while some are more or less rubbery. plastics show a very wide range of chemical resistance and solubility. however, the heat resistance of plastic materials is very limited. nevertheless, a few very specialized materials can withstand temperatures in excess of 200°c. plastic materials are well reputed for their good electrical insulating properties, corrosion resistance, high coefficient of thermal expansion (about ten times of steel), high refractive index, available in desired colours and texture, high resistant to aggressive conditions and a unique ability to combine other materials like aluminum foil, paper and adhesives (tasie, 2010). 2.1 classification of plastics plastics can be broadly classified into two types according to their behavior with temperature as thermosetting and thermoplastics (tasie, 2010). thermosetting plastics are those plastics that are cured or hardened into permanent shapes and cannot be re processed. their curing normally occurs rapidly under ultra violet light or heat and leads to irreversible cross-linking of the polymer in which no after –treatment can cause the molecules to flow again (kurtz, 2002). thermoplastics, on the other hand, are formed by additional polymerization and have long chain molecular structure. the basic difference between these two groups lies with the fact that thermoplastics can be used severally; implying that after moulding an article, it can be ground and reprocessed without loss in physical and chemical properties (tasie, 2010). table 2 shows some examples of thermosetting and thermoplastics plastics. the principal uses of thermoplastics are that they are used for consumer goods, machine parts as well as packaging arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):173-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 176 and storage materials while thermosetting plastics are used in electrical equipment (tasie, 2010). table 2: examples of thermoplastics and thermosetting plastics thermoplastics thermosetting polyethylene terephthalate (pet) bakelite polypropylene (pp) epoxy resins polyvinyl acetate (pva) melamine resins polyvinyl chloride (pvc) polyesters polystyrene (ps) polyurethane low density polyethelene (ldpe) urea-formaldehyde high density polyethylene (hdpe) alkyd resins source: sulyman et al. (2016). 3.0 preparation of concrete containing plastic aggregates and fibres plastic cement concrete is basically a special concrete composite consisting of ordinary portland cement based matrix with polymer materials as additives. these additives are either plastic based fibres or plastics in other processed forms (naik, et al., 1996). according to gu and ozbakkaloglu (2016), plastic aggregate concrete is typically manufactured by replacing natural coarse aggregates or fine aggregates with plastic coarse or fine aggregates of the same volume, which is called direct volume replacement. in general, plastic aggregates and plastic fibres concrete are quite similar to the conventional concrete in terms of preparing, casting and curing of the concrete. according to hopewell et al. (2009) and siddique et al. (2007) plastic aggregates and fibres are basically extracted from different types of plastic waste and processed as melted, shredded or pulverised forms. the melted form being a process where concrete is produced incorporating molten plastic materials as aggregates. the plastic aggregates according to hopewell et al. (2009) consist of long strands, which are cut to an estimated length of 28mm in a slender fibre form. shredded/crushed/flakes waste plastic are however produced by shredding waste plastics obtained from a mixed plastic stream; the process yields plastic flakes with a maximum planner dimension of approximately 25mm in size. pulverization on the other hand being the process of mechanically reducing larger waste plastic materials into fine particles depending on the type and configuration of the machine used, resulting in the formation of new surfaces (hopewell et al., 2009). according to plastic waste management institute (2009), the pulverization process involves the collection, segregation and grinding or crushing of the waste plastic materials in which compressive strain and shear are employed. 4.0 research findings on the use of plastic waste in concrete in this section, research findings related to the uses of plastic aggregates and plastic fibres on the properties of concrete are presented. the properties of concrete covered are slump, density, compressive strength, flexural strength, behaviour at elevated temperatures, and permeability of concrete. table 3 gives a summary of some previous studies using different forms of waste plastic in concrete production. anum and job : waste to wealth in building materials development: a review of plastic waste in concrete. azojete, 17(2):173-184 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 177 table 3: summary of selected previous studies using waste plastic as reported in literature s/n reference form of plastic used method summary of findings 1 naik et al. (1996) shredded plastic admixtures improved compressive strength 2 rai et al. (2012) pulverised plastic pellets replacement of fine aggregates decreased density, compressive strength and slump increased flexural strength 3 prahallada and prakash (2009) shredded plastic buckets admixtures decreased compressive strength 4 corodoba et al. (2013) flakes of pet bottles admixtures increased compressive strength and modulus of elasticity and same values of young modulus. 5 anum and job (2011) shredded polyethylene admixture decreased density and water absorption increased compressive and flexural strength and ductility. 6 anum, job and dakas (2019) pulverized high density polyethylene admixture decreased density and slump and increased flexural strength. 7 anum, job and dakas (2019) pulverized high density polyethylene admixture decreased density and improved performance at elevated temperatures. reduced spalling effect 8 patil et al. (2014) heating/melting plastic replacement of coarse aggregates reduced density and compressive strength 9 raghatate (2012) shredded waste plastic bags admixtures decreased compressive strength but increased tensile strength up to a point before decrease. 10 ahmed and raju (2015) shredded plastic pieces replacement of coarse aggregates decreased compressive and tensile strength 11 gowri and rajkumar (2011) shredded polyethylene sheet, straw, raw plastic and road waste admixtures decreased compressive strength 12 al-manaseer and dalal (1997) crushed plastic pieces replacement of coarse aggregate decreased compressive strength 4.1 slump of concrete containing plastic aggregates the slump of plastic concrete is affected by a number of factors such as water-cement ratio (w/c), substitution level of plastics or fillers, and the shape of the waste plastic. a general tendency for decreased slump was reported with the substitution of plastic fillers or aggregates arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):173-184. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 178 (rai et al., 2012). prahallada and prakash (2009) showed that the slump of waste plastic fibre reinforced concrete was maximum when 1% fibres were used. addition of more than 1% of waste plastic fibres was found to decrease the workability. this according to the authors, is due to the fact that addition of waste plastic fibres may obstruct the flow of concrete creating many interlocks with aggregates. similarly, the inclusion of 0.5% polypropylene fibres, air content of concrete was increased whereas slump was reduced (siddique et al., 2007). however, choi et al. (2005) reported an increase in workability with increased substitution level of two types of filler aggregates. according to the authors, this increase may be attributed to the spherical shape and smooth surface of the aggregates with almost a zero absorption capacity of the waste plastics. 4.2 density of concrete containing plastic aggregates al-manaseer and dalal (1997) investigated the effects of plastic aggregates on the bulk density of concrete. concrete was produced using different water – cement ratios containing varying percentages (0%, 10%, 30% and 50%) of plastic aggregates. angular post-consumer plastics aggregates having a maximum size of 13mm were used. they concluded that (i) bulk density of concrete decreased with the increase in plastic aggregate content. (ii) reduction of bulk density was directly proportional to the plastic aggregates content. (iii) density of concrete was reduced by 2.5%, 6% and 13% for concrete containing 10%, 30% and 50% plastic aggregates respectively. choi et al. (2005) studied the effects of polyethylene terephthalate (pet) bottles light weight aggregate (wpla) on the density of concrete designed with water-cement ratios of 45%, 49% and 53% and the replacement ratios of wpla of 0%, 25%., 50% and 75% by volume of aggregates. density of concrete decreased with the increase in wpla furthermore, a study by anum et al. (2019) on the characteristics of concrete modified with pulverised high density polyethylene (hdpe) observed that the densities increased with the curing age and decreased with an increase in the hdpe content. the above findings were consistent with the findings of silva et al. (2013) and anum and job (2011) that the density of concrete incorporating plastic materials decreased with increased substitution level of the plastic materials. this phenomenon could be attributed to the lower density of the hdpe compared to that of the aggregates leading to reduction in overall density of the concrete. 4.3 compressive strength of plastic concrete compressive strength of plastic concretes depend on many parameters such as the w/c ratio,constitution level of the plastic materials (mostly aggregates) , and the type and shape of the waste plastic (akcaozoglu et al., 2010; albano et al., 2009; asokan et al., 2009). the mechanical properties of concrete containing recycled pet were identified by corodoba et al. (2013) to depend on the particle size with the highest compressive strength obtained with the smallest sizes of pet (0.5mm). the study also established the fact that mechanical properties of plastic concrete such as compressive strength increases with reduced particle size of plastics and with lower concentrations of the plastic content. the lower sizes and concentrations of plastic particles create less spaces in the concrete, consequently strength is increased (corodoba et al., 2013). compressive strength of plastic shreds in concrete was studied by naik et al. (1996). the study reported a compressive strength decrease with increase in the amount of the plastic in concrete, particularly above 0.5% plastic addition. prahallada and prakash (2009) have reported that the maximum compressive strength of waste plastic fibre reinforced concrete can be obtained with 1% addition of waste plastic anum and job : waste to wealth in building materials development: a review of plastic waste in concrete. azojete, 17(2):173-184 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 179 fibre, beyond which strength decreased. similarly, patil et al. (2014) reported that the modified concrete mix, with addition of plastic aggregate replacing conventional aggregate up to certain 20% gives strength within permissible limit but decreased compressive strength when plastic was replaced with coarse aggregate. besides, raghatate (2012) reported that there is about 20% reduction in compressive strength at 28 days of curing using the plastic pieces in concrete. in each case reported, compressive strength reduction was as a result of improper bonding between organic plastic materials and inorganic cementitious materials. in a previous study by gu and ozbakkaloglu (2016) reduction in compressive strength was attributted to one or a combination of the following: the elastic modulus of the plastic aggregates/filler aggregates being lower than the natural concrete aggregate, the low bond strength between the surface of the plastic aggregate/filler and the cement paste, the restrained cement hydration reaction near the surface of the plastic resulting from the hydrophilic nature of the plastics or the high air content and porosity of the plastic concrete. the use of recycled plastic fibres with a high ultimate tensile strength and smaller fibre content results in more significant improvement in compressive strength than fibres with low compressive strength (fraternali et al., 2014; song et al., 2005). additionally, compressive strength of plastic concrete was increased with the injection of plasticizer (rai et al., 2012). the aspect ratio and geometry of fibres also affect the compressive strength of plastic concrete (khadakbhavi et al., 2010). the authors reported that the aspect ratio(defined as the ratio of the fibre length to diameter) of hdpe fibres on the compressive strength of concrete contains 0.6% fibres by volume. the authors also observed that the fibres with the aspect ratio of 20, 40, 60 and 80 percents respectively increased the compressive strength by 5, 8, 14 and 3 percents respectively. this increase in compressive strength could be as a result of water reduction action of the plasticizer in reducing bleeeding and segregation in concrete. fraternali et al. (2011) also found that straight fibres increased compressive strength more than those with embosed geometry 4.4 behaviour of plastic concrete at elevated temperatures neville (2000) defined elevated temperatures in concrete as the increase in temperatures above 250oc which occur when there is fire disaster. studies by poon et al. (2004) on high performance modified concrete subjected to high temperatures of 600oc revealed that the concrete retained 45% of its strength. nwankwo and achuenu (2014), however, recorded a 24% reduction in the compressive strength of fibre reinforced ternary concrete at elavated temperature of 600oc. this reduction was attributed to the chemical decomposition of the depleted calcium silicate hydrate (c-h-s) in the blend. the concrete was however reported to be stable and was recommended for structural elements requiring thermal stability. han et al. (2005) reported results of residual compressive strenghth of concrete containing polypropylene fibres after heating the specimen to 8500c for 40 minutes. the results showed that conventional concrete underwent severe spalling failure with no residual compressive strength whereas, plastic concrete containing 0.05 – 0.1% of polypropylene fibres experienced no spalling and retained 75% of its residual compressive strength. anum et al. (2019) studied the compressive behaviour of concrete modified with pulverised high density polyethylene at elevated temperature. the study concluded that concrete with high density polyethylene (hdpe) admixtures exposed to elevated temperature of up to 600oc arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):173-184. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 180 behaved differently from normal concrete, retaining a maximum of 11.16% strength above the normal concretes (control samples) with 0.75% dosage of hdpe. the authors also reported that the high-density polyethylene admixture reduced explosive spalling of concrete as a result of fibre bridging in the matrix and prevents spalling failure caused by high vapour pressure generated at high temperatures. 4.5 flexural strength of plastic concrete the flexural strength of concretes made with plastic replacing coarse aggregate recorded 5 % increase in flexural strength over the nornal concrete according to patil et al., (2014). similarly, the highest value of 6n/mm2 was recorded at 0.8% inclusion of plastic pieces over 4n/mm2 of normal concrete at 28 days of curing in water (raghatate, 2012). a separate study by anum and job (2011) recorded a 16 % increase in flexural strength over control specimens with the additon of 0.5% fractions by weight of polyethylene shreds to concrete. these results are in agreement with the findings of neville and brooks (1997) that polymer portland cement concrete has improved tensile strength compared with conventional concrete. existing studies by begherzadeh et al. (2011); de oliveira and castro-gomes (2011) on the effect of plastic fibre on the flexural strength of plastic-mortar also indicated that the flexural strenghth increased upon the addition of plastic fillers to the matrix. iftekhar and prakash (2010) also studied the mechanical properties of fly ash filled high density polyethylene, and it was discovered that tensile strength could also be increased by up to 22% by using 14μm ash particles. the authors further pointed out that better strength might be expected with the use of further reduced sizes of fly ash particles. this tensile strength increase recorded in each case according to song et al. (2005) is attributed to stress transfer that occurs when the fibres bridge across the split portions of the matrix and thus gradually support the entire load. on the contrary, results obtained by naik et al. (1996) recorded a decrease in tensile strength beyond 0.5% which was contrary to the expected trend. this according to the researchers was attributed to lack bonding between the plastic and the cementitious materials. the researchers suggested either physical processing or by chemical treatment of the plastic materials prior to mixing with concrete. 4.6 permeability of plastic concrete previous studies by anum and job (2011); albano et al. (2009) established that increasing the content of plastic fillers/shreds in concrete increases water absorption of the concrete as a result of the porous nature of the concrete created by improper mixing of the natural aggregates to plastics. again, studies by saika and brito (2013) have revealed increased water absorption of concrete containing coarse flaky aggregates of pet than those of fine and pellet aggregates. on the other hand, water porosity and absorption capacity of concrete containing 0.05%, 0.10% and 0.20% polypropylene fibre increased by approximately 6%, 18%, and 28% respectively, as compared to the corresponding values of the control specimen (karahan and atis, 2011). the effect of recycled plastic on the permeability of concrete was also studied by bayasi and zeng (1993) and the results of permeability showed that 19-mm polypropylene fibres significantly increased the permeability of concrete with an inconsistent effect on the volume fraction of permeable voids; 12.7 mm long fibres somewhat increased the permeability of concrete and tended to decrease the volume of permeable voids. anum and job : waste to wealth in building materials development: a review of plastic waste in concrete. azojete, 17(2):173-184 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ioranum@gmail.com 181 bagherzadeh et al. (2011) reported that there was no significance increase in air permeability with increasing dosage of different types of polypropylene. however, kakooei et al. (2012) have demonstrated that concrete containing polypropylene fibres had lower gas permeability than the conventional concrete. this decrease in gas permeability was attributed to the fact that fibres prevent crack growth in concrete by forming bridges across cracks. their findings are consistent with other researchers such as raghatate (2012), rai et al. (2012), gowri and rajkumar (2011) and naik et al. (1996) which revealed that the introduction of plastics in concrete considerably increased tensile strength, crack resistance, and decreased permeability at low densities, offering great potentials for it to be used in sound barrier, retaining structures and pavements. 5.0 conclusion based on the review of some published works presented, the study concluded that postconsumer plastics can be successfully utilized in concrete as an environmentally friendly means of discarding this category of wastes. the findings further support the fact this practice substantially enhanced some properties of concrete. this approach is expected to lead to reduction of pressure induced on the environment as well as the creation of employment opportunities and increased income, especially in nigeria and other developing countries where cost of building materials is ever increasing. this is in line with sustainability target for the construction industry, which is aimed at replacement of natural materials with secondary or recycled alternatives while reducing waste disposal. 6.0 recommendations on the basis of the focus of this paper, the following were suggested; 1. the construction industry is encouraged to adopt this emerging innovation of the use of plastic waste in concrete as a result of its established superior performance over conventional concrete and its promise towards creation of wealth and economic development. 2. stake holders (ministries, institutions and professional bodies) should endeavor to develop platforms (conferences and workshops) and also champion the campaign for the utilization of waste plastic materials in concrete. this may lead to reduction in waste and construction cost, as well as create job opportunities and boost the nation’s economy. references aderoju, om. and guerner, da. 2020. municipal solid waste characterization as a measure towards sustainable waste management in abuja, nigeria. journal of environmental science and public health, 4: 43-60. 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division (unsd) glossary of environment statistics 2012. generation of waste by economic activities (unsd) unece/eurostat/eea workshop on waste statistics, geneva, 11-13 https://www.unece.org/fileadmin/dam/stats/documents/ece/ces/ge.33/2012/mtg1/sessio accessed 28th september, 2020 united nations economic and social commission for asia and the pacific (unescap) report 2020. knowledge corner for waste-to-resource initiatives. www.unescap.org/waste-to-resource. accessed 28th september, 2020 http://www.hindawi.com/%20journals/isrn/%202012/469272/ https://www.unece.org/fileadmin/dam/stats/documents/ece/ces/ge.33/2012/mtg1/sessio http://www.unescap.org/waste-to-resource arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):1-14 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 1 original research article technical appraisal of some maize shellers in oyo and kwara states of nigeria m. o. omobowale1*, j. c. ogwumike1, a. e. olenloa1, o. r. kolayemi1, a. a. ala2, m. o. omodara3, g. o. otitodun3, s. i. nwaubani3, k. e. ileleji4, s. g. mcneill5 and g. p. opit6 1department of agricultural and environmental engineering, university of ibadan, ibadan, nigeria 2department of zoology, university of ibadan, ibadan, nigeria 3nigerian stored products research institute, ilorin, nigeria 4agricultural and biological engineering department, purdue university, west lafayette, indiana, usa 5biosystems and agricultural engineering department, university of kentucky, lexington, kentucky, usa 6department of entomology and plant pathology, oklahoma state university, stillwater, oklahoma, usa. *corresponding author’s email address: mo.omobowale@ui.edu.ng 1.0 introduction the production of grains such as maize, millet and sorghum is on the rise in many african countries with maize being the largest in production. maize is the most important cereal crop in the world after wheat and rice, providing the nutrient requirements of humans and animals including raw materials to produce essential commodities including oils, alcoholic beverages, starch and even, fuel (isa et al., 2019). according to faostat (2020), the global production of maize` in 2018 was estimated to be 1.1 billion tons over a harvested area of about 194 million ha, while production in africa accounted for about 78.9 million tons from a harvested area estimated at 38.7 million ha. article information abstract this study assessed the performance of some maize shellers in use in grain markets in oyo and kwara states, nigeria. a preliminary survey conducted identified shellers in use as basic maize sheller (bms) without blower, maize sheller with blower attachment (msb) and the multi-purpose sheller (mps). the shelling/cleaning performance of the shellers were assessed using yellow maize (swan 1 variety) and some key equipment parameters, which impact performance were measured. the air velocity for msb and mps ranged between 0.4 and 2.4 m/s which was not sufficient for efficient cleaning of chaff from shelled grains. shaft speed for bms, msb and mps were 845, 920 and 820 rpm, respectively. average throughput for bms, msb and mps was 1,714, 600 and 840 kg/hr, respectively with mean shelling efficiencies of 92.9, 82.7 and 97.9%, respectively. mean cleaning efficiencies were 54.0 and 57.7% for msb and mps, respectively. the percentage grain loss for bms, msb and mps were 17, 7.1 and 1.9%, respectively. it was observed that many fabricators do not consult agricultural engineers when producing machines, relying more on previous experience. additionally, there was a lack of consideration for operator safety with the exposure of moving parts of the equipment in all the designs evaluated. a key recommendation from this study is that sheller designs should be standardized to ensure the provision of quality and highly efficient machinery for processors. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 march, 2021 revised 28 may, 2021 accepted 30 may, 2021 keywords: maize shellers shelling efficiency throughput cleaning efficiency postharvest losses http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 2 ekpa et al. (2018) stated that the demand for maize in sub-saharan africa will triple by the year 2050 as a result of the ever-rising population growth. a larger percentage of the cereal harvested in developed countries are used for livestock feed whereas in developing countries, it is used primarily for human consumption (oliveira et al., 2014). in nigeria, during the 2015 – 2016 period, 3.8 million ha of maize were cultivated resulting in 7 million metric tons of maize produced; the projected production for the 2016 – 2017 period was 7.2 million metric tons (usda-fas, 2017). approximately 95% of all feed produced in nigeria is poultry feed, and in the 2013 – 2014 period, feed production was 1.8 million tons (usda-fas, 2017). post-harvest losses (phl) can either be direct or indirect. phl remain a major challenge in food production in many developing countries (omobowale et al., 2016; suleiman et al., 2019). direct losses refer to physical disappearance of the food products, while indirect losses refer to the lowering of quality which can lead to complete rejection of the food especially at the export market (kader, 2005; arisukwu et al., 2019). processing activities have been identified as a contributor to the losses experienced along the food pipeline (mijinyawa, 2012). threshing of grains is a major processing activity which must be carried out to add value as well as to present grains in edible or useable form. it is an important processing activity which must be conducted to add value and make grains edible and useable (williams and rosentrater, 2007). maize shelling operation is the first process involved in post-harvest processing of maize, which separates whole kernels of starch-rich grains from the cob. it occurs either on the field simultaneously during harvesting using a combine harvester, or is done as a separate process at the barn manually or by using mechanical means. losses which can occur during these activities include spillage (loss of whole kernels), kernel breakage and chipping, and excessive broken cobs and thrash mixed with whole and broken kernels. the threshing method used in grain processing also affects storability of the grains because broken kernels lead to increase in insect infestation and subsequently, reduction in grain storage period (storability) and loss in grain quality (igbeka, 2013; oyewole et al., 2019). loss in quality also has financial implications on the producer as well as health hazards which the consumer might be exposed to because the food has become unsafe or contaminated (pristavkova et al., 2016). to facilitate speedy shelling of maize in order to reduce postharvest deterioration, mechanical maize shellers are recommended because hand-shelling methods cannot support large scale production (adewole et al., 2015). in the design of shellers for agricultural processing, the properties of the crop must be fully considered. physical and mechanical properties need to be determined in order to design shellers which would effectively and efficiently handle the intended crops (kroupa, 2003; ilori et al., 2013). sheller designs vary based on the crop to be handled. for maize, a factor that affects its threshability in a mechanized system is the mean girth of the maize cob. for maize, the girth ranges from 50–85 mm depending on the variety (nwakairea et al., 2011). there are different types of commercially available grain shellers featuring different designs of the shelling unit, however most of them are primarily based on the threshing principles of impact, rubbing, combing, and grinding (fu et al., 2018). the performance of the threshing equipment can be influenced by some properties of the maize such as type of variety, degree of crop maturity, and the moisture content (alsharifi et al., 2019a). the variety of the grain in this case would be characterized by the physical properties of the unthreshed grain size, shape and uniformity of the bulk to be threshed. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng omobowale et al: technical appraisal of some maize shellers in oyo and kwara states of nigeria. azojete, 18(1):1-14. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 3 oriaku et al. (2014) designed a ‘’corn de–cobbing and separating’’ machine which was able to remove the grains from the cobs at a rate of 123 kg/hr with a threshing and separation efficiency of 78% and 56% respectively. this machine was therefore suitable as a replacement for human labour on a small/ household scale. aremu et al. (2015) designed a motorised maize shelling machine with a shelling efficiency of 87% and output capacity of 624 kg/hr with a shelling speed of 886 rpm. it was recommended that the best moisture content for maize shelling is at 13% dry basis and that the addition of wheels will enhance the mobility of the shellers. they also concluded that there is the need to develop a maize sheller with higher efficiency, better product quality and powered by a smaller engine. pavasiya et al. (2018) carried out a performance evaluation test on a maize shelling machine at 13% moisture content (maize) and 886 rpm shelling speed, and showed that some parameters such as cleaning efficiency, grain recovery efficiency, shelling efficiency, sheller performance index, total grain losses decreased while output capacity increase. in a study on maize sheller evaluation carried out by ghatrehsamani et al. (2018), it was concluded that the interaction between maize varieties and moisture content was significant on separation efficiency and total kernel loss while variable interaction of maize variety and speed affected only the total kernels lost. alsharifi et al. (2019b) also reported that increasing rotational speed of the corn sheller resulted in an increase in percent grain damage, while reducing the rotational speed actually reduced the frequency of the blow impacts, thereby decreasing the percent grain damage. mogaji (2016) identified some problems with existing maize shellers which include bulky design leading to less mobility, significant spillage of grains during operation, high degree of impurities (thrash and cobs) and low product quality, and thereafter presented an improved maize shelling machine which was portable and had 96% shelling efficiency. this study was initiated as a result of the difficulty encountered in renting a maize sheller fitted with a blower for use in winnowing a large volume of maize (30 tons), which needed to be cleaned prior to storage. the newly fabricated maize shellers that were borrowed for use turned out to be quite unreliable and prone to break-down. the subject of machine reliability and performance with regards to maize shellers available in oyo and kwara states became a topic of interest for investigation. there is also lack of reliable data on maize shellers in use across oyo and kwara states, nigeria. this study therefore investigated the design and performance of maize shellers found in grain markets in these two states, with the goal of determining machine performance, threshing efficiency, cleaning efficiency, throughput and maize kernel loss during threshing. this information can then be used for design improvements in maize sheller production. the mode and ease of operation of each sheller, power train type and capacity were also evaluated while also documenting the cost of fabrication and operation of each machine, quality of fabrication and availability of shellers in the two focal states were documented. http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 4 2. materials and method 2.1 preliminary survey in order to determine the types of maize shellers available for processors in four grain markets located in oyo and kwara states, a survey was conducted by field inquiry to determine the location of maize shelling services at the market, and equipment types used. 2.2 equipment performance testing procedure during equipment performance testing, two maize shellers were tested for each sheller category. during operation, maize shellers were placed on tarps to capture maize being shelled. each outlet from the machine (cob, clean grain and chaff outlets) were partially covered with plastic or jute sheeting to effectively direct and collect these streams. each machine test was replicated three times and each replication was run for an average of 3 minutes. in order to determine whether the maize was sufficiently dry prior to shelling, moisture content of the maize was determined using the gravimetric moisture loss upon drying with 15 g of maize dried in an air-oven at 103oc for 72 h according to asae standards, (2010). the quantity of unshelled maize on cob used in each trial was recorded. the grain-cob ratio of the maize variety was estimated following the procedure outlined in nis 319:1997 standard. a digital hot-wire anemometer (tpi 565c1, test products international, oregon, usa) was used in measuring the speed of the moving air generated by the blower section of the shellers with a blower. it was important to determine the air velocity so as to compare with known terminal velocities of maize kernels. a combination contact/laser photo tachometer (extech rpm40, extech instruments, new hampshire, usa) was used in measuring engine speed, shaft speed (at the drive shaft) and blower shaft speed. the engine speed, drive shaft speed and blower shaft speed were measured on no load (idling) and during operation on full load. for every replicate per equipment type, three parameters were measured, namely, cob feeding time, maize cob mass at inlet and maize kernel mass at outlet. from these data, the equipment throughput, shelling efficiency and cleaning efficiency were determined using the following equations: throughput, which is the weight of material the machine can process over a specific operating period and was measured using: 𝑇𝑝 = 𝑊𝑡 𝑇𝑡 ………………………………………………………………………….. (1) where 𝑇𝑝 is the throughput in kg/hr; 𝑊𝑡 is the total weight of material handled in kg; and 𝑇𝑡 is the total time taken in handling the materials in hr (nwakairea et al., 2011) shelling efficiency (η) was calculated with the following equation: η= 𝑊𝑎 𝑊𝑡 × 100 ……………………………………………………………………. (2) where η is the percentage shelling efficiency; wa is the total weight of grain kernels actually processed, or the output in kg and 𝑊𝑡 is the total weight of grain kernels, should all the kernels be shelled off the cob, or the input in kg (nwakairea et al, 2011) cleaning efficiency (𝐸𝑐) was calculated usng: 𝐸𝑐 = 𝑋𝑑 (𝑋𝑏+𝑋𝑑) × 100……………………………………………………………. (3) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng omobowale et al: technical appraisal of some maize shellers in oyo and kwara states of nigeria. azojete, 18(1):1-14. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 5 where 𝐸𝑐 is the percentage cleaning efficiency; 𝑋𝑏 is the total weight of chaff (materials other than grain kernels) received at the grain outlet (g) and 𝑋𝑑 is the weight of chaff (g) received at chaff outlet (negrini et. al., 1994; ajav and ojediran, 2006). data analysis was done using sas 9.4 statistical software while sigma plot® 13 was used to plot the bar charts. 3. results and discussion 3.1 general observations based on the preliminary survey, three different types of sheller designs were identified; viz, the basic maize sheller (bms), maize sheller with blower attachment (msb) and the multi-purpose sheller (mps). these are fabricated locally and readily available to farmers and small-scale processors. local fabricators constructed a number of these shellers by reverse engineering of imported shellers, which they have worked with in the past. it was also discovered that expert opinion of agricultural engineers was lacking in the design and fabrication of many existing shellers used in the locations surveyed. 3.1.1 the basic maize sheller this was designed to remove the kernels from the maize cobs by impact force on the cobs within a concave enclosure, while the loose kernels simply fall through the concave screen and are collected from an outlet positioned below the concave while the cobs are collected at the cob outlet typically positioned at the end of the concave. figure 1 shows a picture of the bms equipment indicating the various parts. the bms has no blower attachment for cleaning light materials, and the beaters on the shaft of most the bms examined were dulled to help reduce kernel damage (figure 2). figure 1. the basic maize sheller typically found in nigerian markets http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 6 figure 2. dulled threshing drum spikes and bottom concave holes. the basic maize sheller is made up of the machine frame, hopper, concave (which houses the main shaft) and a sieve. the average dimensions of the hopper inlet were 410 by 310 mm at the top and 260 mm2 where it tappers. the length of the concave was found to be between 720 and 914 mm and average diameter was 230±17 mm. the beaters had a height ranging between 30-50mm and were spaced at 60100mm intervals along the shaft and at the end of the shaft, just before the cob outlet, flaps were installed to help push out the cobs. the bms, which was found to be the major machine used to shell maize at eleekara and sabo markets in oyo has no blower attachment. it is indeed the most widespread sheller design. all the bms machines in use at the grain markets were locally fabricated and fabricators employed trial-and-error method in the selection of both the materials of construction and the design of the major components such as the main shaft and the type and spacing of spikes or beaters on the shaft. these parameters however, ought to be selected after proper consultation with agricultural engineers or other experts, but it was observed that this was not done. the frame was made from angle iron and then covered using mild steel sheet metal. efficiency of production depended solely on the skill of the fabricator many of whom never attended technical schools but learnt on the job as apprentices. the welds and joining on the bms was properly done. however, there were no safety guards to cover moving parts of the machine and this was common with all the types of this machine tested. the engine used locally is a gx 270 6.5hp petrol engine and the average engine speed was 5450 rpm while shaft speed was lower and ranged between 741 between 950 rpm depending on load. a major working component of the bms is the shelling drum, shown in figure 7. its design is critical to the performance of the sheller. generally, the spacing of the beaters was 50mm on average and concave clearance of 3035mm. an attachment near the cobs exit, which helps to push cobs out. the msb shares a similar design with respect to this threshing drum type. even though variations in spacing and position as well as size of flat bars was observed in different shellers, the general design principle remains the same. users reported that the cost of operation within the first year or two do not involve a lot of expenses on repair work. therefore, operating cost is limited to fuel and oil expenses and labour expenses. the basic maize sheller requires an operator, two persons to feed the machine and one person at the clean outlet and cobs outlet. therefore, four (4) persons are required to run this machine effectively. after the shelling operation is completed, the grains require cleaning and the unshelled cobs are shelled manually. at the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng omobowale et al: technical appraisal of some maize shellers in oyo and kwara states of nigeria. azojete, 18(1):1-14. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 7 grain markets, there are women who carry out this extra cleaning work and they are paid. for those who operate the shelling machine at eleekara market, the cost of shelling a bag of maize was ₦1,500 ($5). 3.1.2 the maize sheller with blower (msb) the msb is designed to carry out the two operations of shelling, screening of cobs and winnowing of the grains by passing a stream of air before being collected at the grain outlet as shown in figure 3. it features a separate fan compartment, through which the grains fall before reaching the outlet, ensuring a cleaner product. however, in most designs available fan speed is not regulated and drop height for the kernels is not sufficient thereby, allowing some kernels to be blown off and larger unwanted particles to pass through without being cleaned. in the case of the msb and mps, both of which have a blower attachment, the blower shaft is also powered via the same engine. the direction of rotation of both the spike shaft and the blower shaft can be either clockwise or anti-clockwise. figure 3. maize sheller with blower it was observed that this machine was not widely used in the grain markets visited. the units tested were located at a feed mill in ibadan, oyo state. the machine requires 3 persons for effective operation, consisting of an operator, a labourer to feed the machine, and one person each at the clean and cob outlets. 3.1.3 the multipurpose sheller: the multi-purpose sheller (mps) was designed to handle various grains such as cowpea, sorghum and maize with little modifications required. it is generally larger in size than the bms and msb. it has a separate blower attachment, screen with the diameter selected based on the seeds or kernels to be processed and a vibrating mechanism to agitate the screen. generally, depending on the particular grains to be threshed, the vibrating screens could be switched, for instance in the handling of maize kernels, the sieve openings to be used will be larger than that for sorghum seeds. the screen can be easily unscrewed and replaced with another one of appropriate diameter depending on the crop to be shelled. the machine is powered by a prime mover, in this case a diesel engine (alco r-175a model). motion and torque are transmitted via the pulleys to the shaft, blower and cleaning unit. both the threshing spikes and blower impeller rotate in a clockwise direction. the units tested were located at the national center for agricultural mechanization (ncam), ilorin, kwara state, nigeria (figure 4). http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 8 figure 4. a multipurpose sheller the multipurpose shellers tested had a bottom concave designed as shown in figure 5. this concave design enables various fibrous materials to be handled. it is made up of 8 mm diameter rods placed at 5 mm intervals from each other and welded on semi-circular flat bars of 3mm thickness. the spacing is adjusted based on the grain sizes of the material to be threshed. figure 5. bottom concave for the mps it was observed that clogging occurs in the machine due to improper rod spacing. it was also observed during the course of the tests that a number of factors could influence the delivery rate of the grains at the clean outlet. one of those factors identified was the slant angle of the outlet chute which was less than the angle of repose of maize and resulted in grains being stuck as shown in figure 6. it was also observed that a lot of grains were spilled from the cobs outlet and this could result in considerable loses if not covered. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng omobowale et al: technical appraisal of some maize shellers in oyo and kwara states of nigeria. azojete, 18(1):1-14. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 9 figure 6: heaping of grains at cleaning outlet the mps requires an operator, one or two people to feed the machine depending on its capacity and one person at the cob outlet and another monitoring the clean grain outlet. therefore, 3 to 4 workers are required to effectively handle this machine when used. 3.2 comparative analysis all the shellers tested were powered by internal combustion engines which the fabricators selected, not necessarily based on design calculations, but typical practice handed down by earlier fabricators who trained them. choice of prime mover is also influenced by the availability of specific models in the market. the average engine speed of the bms was 5,450 rpm while the shaft speed ranged between 741–950 rpm when fully loaded and when running empty. this drop in speed can be attributed to the load on the beaters on the shaft, and partly due to belt transmission and frictional losses in moving parts of the machine. the msb had an average shaft speed of 1,200 and 920 rpm for the blower and main shafts respectively. for the mps, the blower shaft speed averaged 1,100 rpm, while the main shaft speed was 750 rpm on average. the initial cost of a bms ranged from ₦95,000 to ₦105,000 ($312-$346) depending on the fabricator and market location. msb cost price ranged from ₦150,000 to ₦180,000 ($492–$590). the mps fabricated locally was sold at a price of ₦450,000 to ₦600,000 ($1475-$1967) depending on the capacity, number of crops that can be handled as well as the engine type attached. the finding is consistent with what was reported by williams and rosentrater (2007). 3.2.1 throughput the basic maize sheller (bms) recorded the highest mean throughput value of 1714.5 kg/hr (fig. 7). this can be attributed to the design which allows minimum retention time of grains in the threshing drum. the mps and msb had mean throughput value of 839 and 512 kg/hr respectively. an analysis of variance (anova) on the throughput across the shellers showed that there is significant difference (p < 0.05) in the throughput of the sheller designs. clogging was experienced while testing the msb and this was due to insufficient cob ejection at the cob outlet. both the msb and mps had more functional components, which required more power and the increased retention time for the grains was evident due to the flow http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 10 of materials from the hopper to the shelling drum, and through the cleaning unit. the result was consistent with what has been reported in previous literature by adewole et al. (2015) and aremu et al. (2015). bms msb mps th ro ug hp ut (k g/ hr ) 0 200 400 600 800 1000 1200 1400 1600 1800 2000 figure 7. variations in the throughput of the different shellers tested 3.2.2 shelling efficiency the mps had the highest threshing efficiency of 97.2%, while bms and msb had 92.9% and 82.7%, respectively (fig. 8). these results are consistent with what is reported in other literature (nwakaire et al., 2011; alsharifi et al., 2019). analysis of variance (anova) on the shelling efficiency showed that there was significant difference in the shelling efficiencies (p < 0.05) and this was attributed to threshing mechanism design across the three machine types. the mps had raspbar design (raspbars on the threshing drum) while the bms and msb had spikes on the threshing drum. similar observations were made with threshing mechanism design for combine harvesters by fu et al. (2018) and abbas (2019). bms msb mps sh el lin g e ff ic ie nc y (% ) 0 20 40 60 80 100 figure 8. shelling efficiencies of the three sheller types 3.2.3 cleaning efficiency the mean cleaning efficiency for the three shellers was found to be generally low at 54% and 57.7% for the msb and mps respectively (fig. 9) when compared to other studies in the literature (ahmed et al., 2019). the blower shaft speed was 1,200 rpm on average for the msb and 840 rpm for mps, while the air velocity for both machines ranged from 0.4 – 2.4 m/s. this was lower than the minimum separation velocity file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng omobowale et al: technical appraisal of some maize shellers in oyo and kwara states of nigeria. azojete, 18(1):1-14. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 11 of 5.5 – 6.4 m/s required for maize chaff (misener and lee, 1973; nsubuga et al., 2020). this shows that the blower was unable to provide the minimum required air velocity for cleaning and this accounts for the low cleaning efficiencies. there is no statistically significant difference across the shellers (p < 0.05). bms msb mps c le an in g e ff ic ie n cy ( % ) 0 10 20 30 40 50 60 70 figure 9. cleaning efficiencies of the different sheller types 3.2.4 total loss (%) losses as spills, blown off grain kernels and unshelled cobs were highest for the msb at 17%, followed by the bms with mean loss value of 7.2%, while the least kernel loss was for mps at 1.9%. (fig. 10). an analysis of variance (anova) on the total loss across the shellers showed that there was significant difference in the shelling efficiencies (p < 0.05). the total losses were most likely influenced by the cylinder speed and concave clearance. bms msb mps to ta l l os se s ( % ) 0 2 4 6 8 10 12 14 16 18 20 figure 10. total losses across the sheller types http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 12 4. conclusion the maize shellers which were evaluated had a number of design and production flaws which had a negative impact on their efficiencies and this requires the attention of qualified agricultural engineers. moreover, engineering properties of biomaterials are not necessarily considered during fabrication. this is evidenced by their choice of materials, specifications of screens and concave clearance which were not standardized. most of the shellers were designed without safety guards over moving parts and many operators do not make use of personal protective equipment (ppe) such as nose masks, safety goggles, and covered boots. for the msb and mps, blower speed was grossly inadequate and could not be regulated. the blower was unable to provide the minimum required air velocity for cleaning, thereby allowing larger unwanted particles to pass through alongside grain kernels without proper cleaning. it was observed that msb and mps equipment were not widely used in the grain markets visited. most small-scale processors however prefer the basic maize sheller due to its increased output, ease of operation and cheaper cost. it is therefore recommended that future designs of maize shellers in nigeria should have a blower unit independent of the shaft. this will make it possible to attain air velocities required for efficient cleaning of shelled grains. moreover, the grain processing equipment should be standardized in order to ensure good quality equipment are made available to farmers and processors, and quality grains are produced for both domestic consumption and export. agricultural engineers and fabricators should be in close communication so as to put theory and practice into the best possible use. acknowledgements we thank the sponsors of this project, the united states agency for international development (usaid) and the united states department of agricultureforeign agriculture service (usda-fas) for funding this effort through a cooperative agreement with the usda (agreement# 58-3148-6-062). references abbas, a. 2019. the effect of combine harvester speed, threshing cylinder speed and concave clearance on threshing losses of rice crop. journal of engineering and applied sciences. 14: 9959-9965. adewole, ca., babajide, tm., oke, am., babajide, na., aremu, do. and ogunlade, ca. 2015. critical evaluation of locally fabricated maize shelling machine. international journal of engineering science and innovative technology, 4(2): 67-73. ajav, ea. and ojediran, jo. 2006. some physical and aerodynamics properties of three nigerian cereal crops as related to their cleaning. asabe meeting presentation paper number. 066006 2006. ahmed, jm., isiaka, m., saeed, ha. and idoko, so. 2019. performance evaluation of cleaning and grading machine using maize as test grains. in 40th annual conference and 20th international conference of the nigerian institution of agricultural engineers omu-aran, p. 269–275. alsharifi, ska., aljibouri, ma. and taher, ma. 2019a. effect of sheller rotational speed on some maize cultivars quality. agricultural engineering international. cigr journal, 21(2): 196 – 203. alsharifi, ska., aljibouri, ma., taher ma. 2019b. effect of threshing machines, rotational speed and grain moisture on corn shelling. bulgarian journal of agricultural science, 25(2): 243 – 255. aremu, do., adewumi, io. and ijadunola, ja. 2015. design, fabrication and performance evaluation of a motorized maize shelling machine, journal of biology, agriculture and healthcare. 5(5): 154-165. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng omobowale et al: technical appraisal of some maize shellers in oyo and kwara states of nigeria. azojete, 18(1):1-14. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 13 arisukwu, o., igbolekwu, co., mibzar, sep., asamu, f. and bamidele, r. 2019. post–harvest preservation methods of beans and rural consumers in ganye, adamawa state, nigeria. in 40th annual conference and 20th international conference of the nigerian institution of agricultural engineers omu-aran, p. 435– 442. asae, 2000. asae standards, moisture measurement unground grain and seeds. st. joseph, mich. asae; 43rd ed. s352.1 ekpa, o., palacios-rojas, n., kruseman, g., fogliano, v. and linnemann, ar. 2018. sub-saharan african maize-based foods: technological perspectives to increase the food and nutrition security impacts of maize breeding programmes. global food security 17: 48–56. faostat, 2020. food and agriculture organization of the united nations. http.//www.fao.org/faostat/en/#data/qc/ . date accessed: 12 october 2020. fu, j., chen, z., han, l. and ren, l. 2018. review of grain threshing theory and technology. international journal of agricultural and biological engineering. 11: 12-20. 10.25165/j.ijabe.20181103.3432. ghatrehsamani, s., ampatzidis, y., sadeghi, b. and ghatrehsamani, s. 2018. design, fabrication and evaluation of corn sheller. an asabe meeting presentation. doi. https.//doi.org/10.13031/aim.201800159. paper number. 1800159. hell, k., fandohan, p., bandyopadhyay, r., kiewnick, s., sikora, r. and cotty, pj. 2008. preand postharvest management of aflatoxin in maize: an african perspective. chapter 19 in mycotoxins: detection methods, management, public health and agricultural trade: cambridge publishers, wallingford, uk, p. 219-229. igbeka, jc. 2013. agricultural processing and storage engineering. ibadan university press. pp. 39. ilori, ta., raji, ao. and kilanko, o. 2013. modelling some ergonomic parameters with machine parameter using hand powered maize sheller. journal of engineering and technology research, 5(3): 51-57. isa, j., jimoh, ka. and fasuyi, o. 2019. modeling of the drying characteristics of maize gruel residue. 40th annual conference and 20th international conference of the nigerian institution of agricultural engineers omu-aran, p. 404–414. kader, aa. 2005. increasing food availability by reducing postharvest losses of fresh produce. acta horticulturae, 682.2169-2175. kroupa, p. 2003. the outer quality loss during grain post-harvest treatment and handling. research in agricultural engineering, 49(3): 91–102. misener, gc. and lee, jha. 1973. aerodynamic separation of grain from straw and chaff in a dispersed stream. canadian agricultural engineering, 15(2): 62-65. mogaji, pb. 2016. design and fabrication of an improved maize shelling machine. african journal of science, technology, innovation and development, 83: 275-280. negrini, o., spillman, ck., wang, ys., chung, ds., steel, j. and posner, js. 1994. evaluation of laboratory grain cleaners and separating equipment – part ii. transactions of the american society of agricultural engineers, 37(6): 1913–1818. nwakaire, jn., ugwuishiwu, bo. and ohagwu, cj. 2011. design, construction and performance analysis of a maize thresher for rural dweller. nigerian journal of technology, 30(2): 49-54 http://www.azojete.com.ng/ file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng http://www.fao.org/faostat/en/#data/qc/ https://doi.org/10.13031/aim.201800159 arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):1-14. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 14 nis, 1997. nigerian industrial standard (nis). test code for maize shellers. nis 319. 1997. standards organisation of nigeria, son. mijinyawa, y. 2012. the design of farm structures. first edition. ibadan university press, publishing house, university of ibadan, ibadan, pp. 168 nsubuga, d., kabenge, i., zziwa, a., kiggundu, n., wanyama, j. and banadda n. 2020. performance evaluation and optimization of the maize shelling operation of the multi-purpose farm vehicle. agricultural engineering international. cigr journal, 22(4): 174-183. oliveira, pm., zannini, e. and arendt, ek. 2014. cereal fungal infection, mycotoxins, and lactic acid bacteria mediated bioprotection. from crop farming to cereal products. food microbiology, 37: 78–95. omobowale, mo., armstrong, pr., mijinyawa, y., igbeka, jc. and maghirang, eb. 2016. maize storage in termite mound clay, concrete, and steel silos in the humid tropics. comparison and effect on bacterial and fungal counts. transactions of the asabe. 59(3): 1039-1048. 2016. oriaku, ec., agulanna, cn., nwannewuihe, hu., onwukwe, mc. and adiele, id. 2014. design and performance evaluation of a corn de-cobbing and separating machine. american journal of engineering research, 3(6): 127-136. oyewole, sn., gbabe, ek., olayanju, a., adebiyi, ao., ogunbiyi oa., adarabierin, ig., ogundare, mo., abel, gi., olayemi, ff. and okunola, aa. 2019. commercial utilization of inert atmosphere silo for maize storage. in 40th annual conference and 20th international conference tf the nigerian institution of agricultural engineers omu-aran. p. 1176–1182. pavasiya, un., patel, k., sumant, mm. and sutariya, hr. 2018. design and fabrication of a motorized maize shelling machine. journal of materials science and mechanics engineering, 5(1): 5–12. pristavkova, m., zitnak, m. and lendelova, j. 2016. hazard analysis in operating of the post-harvest lines. research in agricultural engineering, 62. s53–s60. suleiman, ai., atanda, eo., ajayi, as. and chanchangi, yn. 2019. advancing post-harvest food loss reduction in sub-saharan africa using solar-powered vacuum cooling storage system as a palliative. in 40th annual conference and 20th international conference of the nigerian institution of agricultural engineers omu-aran, pp. 214–220. usda, 2014. foreign agricultural service, gain report. global agriculture information network, nigeria. grain and feed annual report. usda-fas, 2017. world agricultural production circular series wap 05-17, may 2017. foreign agricultural service/usda office of global analysis. williams, g. and rosentrater, k. 2007. design considerations for the construction and operation of flour milling facilities. part i. planning, structural, and life safety considerations. asabe annual international meeting; paper number: 074116, p. 1-23. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/downloads/azojete%20vol%2018%20no%201/mo.omobowale@ui.edu.ng 3 availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 66-75 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng development and performance evaluation of a spindle press for oil extraction oluwole, f.a.1 , a.t. abdulrahim1 and n.a. aviara2. abstract a manually operated spindle oil press adaptable to rural areas was designed, constructed using locally available materials and tested to evaluate its performance. the spindle press, which consists of tool frame, power transmission unit made of a spindle and its lever arm, and oil expression unit comprising of the upper and lower press plates and the perforated cage, operates on the principle of power screw to express oil from milled oil seeds. each of these components was analyzed and the results obtained were used as parameter for sizing and fabrication of the components. the raw material used for testing the developed spindle press was groundnut paste and a nylon clothing material was used as filter. results of the performance tests carried out on the machine using groundnut paste showed a maximum oil recovery of 78.1% and the cake produced is of the same quality when compared with those produced with the traditional method. also the oil extraction time is reduced by about 50%. 1. introduction it is an indisputable fact that there is a universal demand for vegetable oil due to its use in domestic cooking as an ingredient for other food products such as baking and frying of snack foods and as a raw material for the manufacture of soap, body/hair oils and detergents (peter and ann, 1992). peter and ann (1992) also reported that oil provides twice as much energy as the same quantity of carbohydrate and is therefore, considered to be a valuable part of a wellbalanced diet. diffus and slaughter (1980) reported that oil seeds attract high economic interest because they are good sources of cooking oil and their protein rich residues serve as good feed for livestock. two reasons were given by olaniyan and oje (2000) for the increase in the demand for oils of vegetable origin as follows: (a) vegetable oils are usually cheaper than animal oils. (b) animal fats and oils contain saturated fatty acids that may be harmful to health. according to peter and ann (1992) vegetable oils contain a range of fat soluble vitamins (a, d, e and k) and essential fatty acids, both of which are necessary for the healthy functioning of the body. they further explain that the process of oil extraction produces a by-product known as oil cake (kulikuli). this is very nutritious, and can be used either for animal feed or as an ingredient in the production of other food products such as spices for food, boiled, roasted or fried meat, fish and root crops such as yam, coco yam, cassava, sweet potatoes, irish potatoes etc. in nigeria, the major oil seeds/nuts that are processed include groundnut, melon (egusi) seed, palm kernel, palm fruit, cotton seed, guna seed, sheanut and castor seed (asiedu, 1989). extraction of oil from these oil seeds and nuts is still based on traditional procedures in most of the rural areas in nigeria. this is as a result of financial incapability of the local oil producers to purchase the available power operated processing equipment. also lack of electrical power 1 department of mechanical engineering, university of maiduguri, maiduguri 2department of agricultural and environmental resources engineering, university of maiduguri, maiduguri. http://www.azojete.com.ng/ azojete vol. 5 2007 67 supply to the rural areas poses handicap and prevents local investors from establishing smallscale vegetable oil plants in the rural areas. wiemer and korthals (1989) described the process of oil extraction in india using equipment known as ‘ghani’ oil mill. the ghani consists of a mortar and pestle in which the seed is crushed. pulverization and oil extraction are carried out at the same time by rubbing the seed between the pestle and the wall of the mortar. the ghani process requires much mechanical energy. a ghani operated by one bullock can only process 5 kg oil seed in about one hour. wiemer and korthals (1989) also described a hand-operated screw press capable of processing 21 kg of sunflower seed per batch in a one-hour cycle. ilo (1983) reported a developed handoperated screw press for extracting groundnut and copra oils. the extractor consists of a lever arm, power transmitting unit, the oil extraction unit and the frame. the market value of the groundnut cake produced by this machine is less compared to that produced using the traditional method. itanye (2001) constructed and tested a spindle oil press. results of his tests showed that oil recovery of about 48% was achieved and the cake obtained is not as good as that obtained from the traditional method. the major problem with the modern equipment is that they extract almost all the oil thereby reducing the nutritious value of the oil cake. this result in reducing the economic value of the cake because it can only be used as animal feed. a mechanical oil extraction device that is manually operated is therefore necessary to increase and improve the quality and quantity of the oil production and at the same time retain the nutritious value of the oil cake. this could minimize the rigours involves in the present traditional procedures since it could be made available for use by the rural populace. this study is aimed at developing a manually operated spindle oil press that will increase and improve the quality and quantity of oil production and retain the nutritious value of the cake. 2. materials and methods 2.1 materials the material used for each component was selected based on function of the component and properties of the material. stainless steel was used for the fabrication of the perforated cylindrical cage, top and bottom press plates and the oil receiver. carbon steel was used for the fabrication of the spindle, collars, nut and the lever arm. a ‘c’ section carbon steel was used for the construction of the frame while a carbon steel angle iron was used for the construction of bottom frame. 2.2 design considerations the spindle press consists of the following major components: i) lever arm ii) spindle (square thread) iii) perforated cage iv) top and bottom press plates v) oil receiver vi) frame. in order to effect an acceptable design, the question of workability, durability and reliability of the components constituting the oil press must be given due consideration. the workability of the press is a question of providing components, which perform in accordance with the design specifications and integrating these components into an operational feasible system. durability ensures that the machine will continue to operate during its design life without material or development and performance evaluation of a spindle press for oil extraction 68 component failure, while reliability ensures that the machine performs in accordance to the design. 2.3 design calculations 2.3.1 perforated cylindrical cage this is a thin walled perforated cylinder made of stainless sheet. the pressure, p, required to express oil from groundnut paste is 6 n/mm2 (wiemer and korthals, 1989) p = w/a 1 where p = pressure required to express oil from groundnut paste, n/mm2 w = load required to generate the pressure, n a = cross-sectional area of the perforated cage, mm2 for a perforated cylindrical cage of 75 mm internal diameter, the load, w required to generate this pressure is given as: w = p.a = (p π d2)/4 = (6 x π x 752)/4 = 26507 n according to levinson (1970) the hoop stress in a thin walled cylinder is given as: σh = p r n / t 2 t = p r n / σh 3 where σh = hoop stress, n/mm2 t = thickness of the perforated cylindrical cage, mm n = factor of safety r = radius of the perforated cylindrical cage, mm for a perforated cylindrical cage of radius 37.5 mm and allowable hoop stress of 480 n/mm2 and taking factor of safety of 3 (hall et al. 1982) t = 1.41 mm. 2.3.2 the spindle (square thread) this is the component that transmits the power to the pressing unit. according to shigley (1977) the torque required to produce the load, w is given as: t = w/2[dm ((l + πμdm)/(πdm – μ l)) + μcdc] 4 dm = dr + l /2 5 do = dr + l 6 dc = (dci + dco) 7 where t = required torque, nmm w = load parallel to screw, n azojete vol. 5 2007 69 dm = mean thread diameter, mm dr = root diameter, mm do = crest diameter, mm dc = effective diameter of collar, mm dci = collar inner diameter, mm dco = collar outer diameter, mm l = lead (for single thread, lead = pitch) μc = coefficient of friction at collar for root diameter of 25.4 mm and lead of 6.35 mm (deutschman et al., 1975), equations 5, 6, and 7 gives dm = 28.6 mm, do = 31.75 mm and dc = 41 mm respectively. substituting these values into equation 4 gives t = 156729 nmm 2.3.2 the lever arm the torque on the lever arm is given as: t = f l 8 d = [32 m n1/πσb] 1/3 9 where d = diameter of lever arm, mm m = bending moment at critical section, nmm l = length of lever arm, mm f = force exerted on the lever arm, n σb = bending stress, n/mm2 the force exerted by average man is 294.3 n (balami, 2000). substituting this value into equation 8 gives l = 532.5 n and from equation 9 , d = 24.2 mm 2.4 machine description the spindle oil press consists of tool frame, made of ‘c’ section carbon steel 45 x 80 x 45 mm. this frame consists of two vertical frames 950 mm in height; top frame 360 mm long and bottom frame 270 mm long. at the center of the top frame is a hole 50 mm in diameter and a nut welded on the hole for the spindle. the top frame is firmly bolted to the two vertical frames at the top. the bottom frame, which serves as a base for the oil receiver, is bolted to the two vertical frames 400 mm below the top frame. the power transmission unit consists of the lever arm 25 mm in diameter and 530 mm long with a collar of 52 mm external diameter, 44 mm internal diameter and 50 mm height at its center and a vertical spindle (square thread) directly under the lever arm. the lever arm is mounted on the spindle through the collar and bolted with two lock bolts that locked into two indentations made 25 mm below the upper end of the spindle on the opposite sides. the spindle is then passed through the nut on the top frame. the pressing unit consists of the top and bottom press plates made of stainless steel rod 74 mm diameter and 5 mm thickness with a collar 50 mm external diameter, 9 mm thick and 50 mm height is welded to the top press plate at its center. two threaded holes (for lock bolts) are on development and performance evaluation of a spindle press for oil extraction 70 the center surface of the collar on opposite sides. a hole of 5 mm diameter is made 5 mm below the threaded holes for greasing nipple. the top press plate is mounted on the spindle through the collar and the two lock bolts were used to hold the press plate onto the spindle. the two bolts on the opposite sides of the collar locked into the groove cut around the spindle at its lower end to allow free rotation of the spindle without turning the top press plate. the perforated cylindrical cage (with perforation of 3 mm diameter round the surface of the cage) is made of stainless steel sheet 1.5 mm thick, 75 mm in diameter and 200 mm high with a bottom press plate support at its lower end mounted on the oil receiver placed on the lower frame. this machine can easily be dismantled and properly packed for easy transportation. the photograph of the assembled spindle oil press is presented in figure 1. figure 1: photograph of the spindle oil press 2.5 machine construction and assembly each component of the spindle oil press was fabricated based on the results obtained from the design calculations. the tool frame consisting of two vertical frames, top and bottom frame was constructed using a ‘c’ section carbon steel 45 x 80 x 45 mm. the two vertical frames each 950 mm long, the top frame 360 mm long and the bottom frame 270 mm long were cut to size. a 50 mm diameter hole was drilled at the center of the top frame and a nut was welded on this hole for the spindle (square thread). the top frame was bolted to the two vertical frames at the top end while the bottom frame, which serves as a base for the oil receiver, was also bolted to the two vertical frames 400 mm below the top frame. the collar (with 52 mm external diameter, 44 mm bore and 50 mm high was welded on the lever arm at its center. the lever was then mounted on the spindle through the collar and bolted with two lock bolts. the spindle is then azojete vol. 5 2007 71 passed through the nut on the top frame. the top press plate was bolted on the spindle through the collar and welded on the top press plate. the perforated cylindrical cage was made of stainless steel sheet 1.5 mm thick 200 x 236 mm. perforations of 3 mm diameter was made on this stainless steel sheet, which was then folded into cylindrical shape and the free ends welded together. a bottom press plate support was welded on the inner surface (lower end) of the perforated cylinder. a bottom press plate 74 mm in diameter and 5 mm thick was then placed on the bottom press plate support and has a provision for draining the expressed oil. the oil receiver was placed on the bottom frame and directly under the top press plate. the orthographic drawing and part lists of the spindle oil press is presented in figure 2. development and performance evaluation of a spindle press for oil extraction 72 front view end view plan ø 75 ø 25 80 530 360 250 4 0 0 9 5 0 9 2 3 4 1 6 8 10 5 11 13 14 7 12 1-top press plate, 2collar, 3nut, 4collar, 5oil receiver, 6-bottom frame, 7perforated cage, 8cage lock, 9lever, 10spindle (square thread), 11bottom press plate, 12top frame, 13vertical frame, 14base frame figure 2: orthographic drawing and part list of spindle oil press azojete vol. 5 2007 73 2.6 production cost estimate the cost estimate of the machine is presented in table 1. table 1: production cost estimate s/no. material qty specification cost (n) 1 galvanized pipe 1 ø25 x 533 mm 250 2 stainless steel rod 1 ø75 x 10 mm 1000 3 square thread spindle 1 650 mm 1000 4 ‘c’ section carbon steel 1 3000 mm 1000 5 angle iron 1 50 x 50 x 500 mm 100 6 stainless steel sheet 1 gauge 18 (700x600 mm) 600 7 mild steel rod 1 ø5 x 1200 mm 70 8 bolts and nuts 16 160 9 nylon cloth 1 100 10 sand paper 1 100 11 electrode 45 gauge 12 220 12 paint 1 900 ml 200 13 labour 1000 14 transport 500 total 6300 2.7 principle of operation of the spindle oil press in operating the machine, a moistened and heated groundnut paste was put inside a small bag made of nylon clothing material. the bag, which serves as a filter with its content is placed inside the perforated cage. clockwise rotation of the lever allows the spindle with the top press plate to move downwards and subsequently compressing the material in the bag against the bottom press plate. as the pressure increases, oil starts gushing out through the perforations on the cage and collected through the oil receiver. 2.8 performance tests and evaluation forty kilogram (40 kg) of groundnut (peanut) was purchased in the local market and prepared for the test. the preparation involved cleaning the peanut by removing dirt and spoiled peanut, roasting the nut and dehulling/winnowing to remove the pellicles (the brown skin). the cleaned peanut was then crushed to paste and then cooked (moistened and heated) and continuously stirred and hot water was added intermittently until oil started to come out on the surface. three kilogram (3 kg) of the paste was taken in the cloth bag. the bag with its content was placed inside the perforated cage and the lever was then rotated clockwise to compress the material. as the compression increases oil gushed out through the perforation on the cage. the compression continued until there was no oil flow stopped with further increase in pressure. at the end of the compression process, the mass of oil collected and mass of ‘tunkusa’ were recorded. these tests were repeated ten times and the average was recorded as the oil recovery. the percentage of oil collected was calculated as follows: ηoil = (moil / mgp) x 100% 10 and the percentage of oil recovery was calculated as development and performance evaluation of a spindle press for oil extraction 74 (ηoil / 45) x 100% 11 where moil = mass of oil collected, kg mgp = mass of groundnut paste, kg 45 = oil content in kg per 100 kg of groundnut (wiemer and korthals, 1989). 5. results and discussions the results of the performance tests carried out on the machine are presented in table 2. table 2: performance data of the machine *groundnut dough before frying; **fried groundnut dough these results show that the oil recovery was low for the first trial (57.8%). this may have been due to the fact that the filter absorbed and retained some quantity of the expressed oil. with subsequent trials the oil recovery increased, with 66% at the second trial a maximum value of 78.1% by mass. total time to load the press, apply the pressure and remove the cake was approximately 45 minutes. the time required to process the same quantity of paste traditionally is about 1 hour 30 minutes. the increase in oil recovery may be due to the fact that the filter may have become saturated and could no longer absorb the expressed oil. similar results were obtained by wiemer and korthals (1989), where the oil recovery ranged from 73.3% to 77.8% from a similar spindle oil press. introduction of the nylon material as filter prevented particles of groundnut paste from blocking the perforations on the cylindrical cage and thus eliminating the rigours involved in cleaning the machine after use. it can also be seen from table 2 that the mass of the cake is less than that of the ‘tunkusa’. this shows that more oil was still extracted from the ‘tunkusa’ during frying. s/no. mass of paste (kg) mass of oil collected (kg) mass of *tunkusa (kg) mass of **cake (kg) oil recovery (moil/mgp) x (100/45)% 1 2 3 4 5 6 7 8 9 10 3 3 3 3 3 3 3 3 3 3 0.78 0.89 0.94 0.96 0.98 1.001 1.01 1.03 1.05 1.055 1.76 1.77 1.75 1.76 1.78 1.77 1.75 1.78 1.76 1.77 1.74 1.75 1.72 1.73 1.75 1.75 1.74 1.75 1.74 1.73 57.8 65.9 69.6 71.0 72.6 74.1 74.8 76.3 77.8 78.1 azojete vol. 5 2007 75 4.0 conclusion a manually operated spindle oil press was designed, constructed and tested to evaluate its performance. the machine gave a maximum oil recovery of 78.1% and at the same time the cake obtained is of the same quality when compared with those produced from the traditional method. a unit of the machine costs n 6300:00. the machine will not only eliminate the rigours involved in the traditional method of extracting seed oil in rural areas but also reduce the processing time. references asiedu, j.j. (1989). processing tropical crops. a technical approach. macmillan london. balami, a.a. (2000). design, construction and performance evaluation of a composite processing machine. faculty of engineering seminar series vol. 1 no.1, 71-79 university of maiduguri. diffus, c.m. and j.c. slaughter (1980). seeds and their uses. 2nd edition. john willey and sons. london. deutschman, d.a., michels, j.w. and e.c. wilson (1975). machine design. theory and practice. macmillan publicating co inc new york. hall, a.s., a.r. holowenko and h.g. laughtin (1982). theory and practice of machine design. schaum’s outline series mcgrew-hill book company. new york. ilo (1983). international labour office: small-scale oil extraction from groundnut and copra. technical memorandum no. 5. ilo, geneva. itanye, o.p. (2001). construction of groundnut oil extraction machine. unpublished nd project. ramat polytechnic, maiduguri, nigeria. levinson, j.i. (1970). mechanics of materials. prentice-hall, inc. englewood cliffs, n.j. olaniyan, a.m. and k. oje (2000). mechanical expression of palm kernel oil. proceeding of the nigerian institution of agricultural engineers 11-15. peter, f. and h. ann, (1992). small scale food processing. a guide to appropriate equipment. international technology publication, london. shigley, j.e. (1977). mechanical engineering design. mcgraw hill, kagakusha tokyo. wiemer, h. and f.w. korthals (1989). small scale processing of oil fruits and oil seeds: friedr. vieweg and sohn verlagshgesell-schaff mbh, braunschweig, germany. arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):357-370 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 357 original research article cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design m. i. ishaq¹*, r. a. kyari¹, i. halliru² and c. n. amulah¹ ¹department of mechanical engineering, university of maiduguri, p.m. b 1069, maiduguri, nigeria ²department of civil and water resources engineering, university of maiduguri, p.m. b 1069, maiduguri, nigeria *corresponding author’s email address: mabulhanafy@gmail.com 1.0 introduction cubesats started as tools for students in academic institutions to access space or as a technology demonstration at a lower cost within two or three years of design and fabrication. however, in recent years cubesats have grown from mere educational or technology demonstration tools to low-cost real mission (selva, and krejci, 2012), the focus of cubesat applications has been on the following: technology demonstration, astrophysics, astrobiology, earth remote sensing, radiation effect on space technologies, ionospheric and auroral research (wertz, everett and puschell, 2015). 1.1 technology demonstration: the exploitation of cubesat in technology development started since the inception of the idea. the use of the cubesat platform for technology demonstration is grouped into two categories; demonstration of technologies planned for larger and more expensive missions and technologies for future cubesat missions (poghosyan & golkar, 2017). an example of a article information abstract cubesats are small satellites that can be deployed to orbit to achieve various space mission goals. lately, there are several cubesat launch opportunities from the international space station (iss). for university of maiduguri to be able to bid for such launch opportunities there is a need for a baseline for a spacecraft and a mission design. thus, this paper using the systems engineering approach is a baseline and mission design for a cubesat using cubesat cots (commercial off-the-shelf) components targeting the kibocube opportunity. cuumcube mission is a technology demonstration mission to fly two payloads, cranfield’s acoustic sensor and de-orbit mechanism (dom). the acoustic sensor is a microphone that measures vibrations, it is intended to measure vibrations due to: spacecraft thermal cycling mechanical noise, antenna deployment, micrometeoroids and orbital debris (mmod) impacts, dom deployment and changes in acoustic response of spacecraft after deployment of both mechanisms. the dom is a deployable drag sail, a passive method of removing spacecraft from orbit afterlife in the effort of mitigating space debris. thus, mission baseline reached after the design is to deploy a 1u cubesat, to carry two payloads (cranfield’s acoustic sensor and dom), using cots components. the deployment of the spacecraft will be from the iss into an elliptical orbit (perigee: 380km, apogee: 420 km). the ground control stations are cots component too, where there will be one each in uk and nigeria. lastly, 30 mins after deployment into orbit the mission sequence starts from the activation of spacecraft to 24 hours recording mode to monitoring mode by the acoustic sensor to capturing of vibrations. hence, the antenna and the dom will be deployed. the dom will speed the orbit decay of the spacecraft, as a result it will speed the re-entry phase and burn in the process. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 10 april, 2021 revised 16 may, 2021 accepted 19 may, 2021 keywords: space systems engineering spacecraft satellite cubesat mission design orbit mission ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 358 technology demonstration mission for a larger satellite mission is nasa’s grifex (geo-cape roic in-flight performance experiment), a 3u cubesat which assesses digital in-pixel high frame rate read-out integrated circuit (roic) (nasa, 2015a). grifex is designed to validate detector technology for the panchromatic fourier transform spectrometer (panfts) which is an imaging fts for geostationary orbit (nasa, 2015b). 1.2 astrophysics: astrophysics missions are intended at understanding the universe and our place in it, it is concerned with answering the very basic questions about the evolution of the universe and investigate the history of stars and galaxies by observing them with sophisticated payloads (nasa, 2015b). cxbn (cosmic x-ray background nanosatellite) and cxbn-2 missions are examples of astrophysics missions; cxbn is a 2u cubesat launched in 2012, its objective is to improve cosmic x-ray background precision measurements in the range of 30-50 kev using cadmium zinc telluride (czt) detector to have a better understanding of the origin and evolution of the universe (healea, et al., 2015). based on the results of cxbn, cxbn-2 was launched in 2016 as an improvement for better results (ishimaru, et al., 2014). s-cube is another example, it is a 3u cubesat which was aimed at the observation of meteors from leo to study their size and compositions using a camera to take visible images and three photomultiplier tubes (pmt) to observe uv emissions (ishimaru, et al., 2014). 1.3 astrobiology humans have contemplated the existence of life somewhere else beyond earth for years (nasa, 2008). scientists have been studying how living organisms adapt to the space environment and what are its effects on them (nasa, 2008). some of the questions scientists are trying to find answers to are: what are the effects of living on mars for years, how do living organisms behave in space weather, astrobiology is concerned about answering such questions. in a nutshell, astrobiology studies the origin, evolution, distribution and future of life in the universe (nasa, 2008). thus, o/oreos (organism/organic exposure to orbital stresses) is an astrobiology cubesat mission which carried out two distinct experiments: space environment survivability of live organisms (seslo) experiment which carried two populations of the microbe bacillus subtilis into orbit and observed the effect of the space environment on them, and the second experiment is space environment viability of organics (sevo), which monitored the stability and changes in four classes of organic molecules (ehrenfreund et al., 2014). 1.4 earth remote sensing earth observation (eo) has great scientific and economic incentives such as natural resource exploitation, study climate change, weather, natural disasters, and emergency and security management, which is worth billions of dollars for countries economy around the globe (nasa, 2015b). the thermosphere is a key region for atmospheric changes which we have limited knowledge about. in low earth orbit (leo) big satellites undergo a large amount of atmospheric drag making them lose altitude after 6-12 month and then burn up during re-entry, spending ₦82 ₦123 billion to put a satellite in leo is not worth it (cubesats, 2017). this makes cubesats a suitable alternative due to their low cost, they can be used for suicide missions to leo to carry out the intended mission objectives within 1-4 years and then burn up during re-entry (cubesats, 2017). one of the future cubesat missions to leo is the qb50 mission, it is a constellation of 50 cubesats (some already launched) built by universities all over the world to study the lower thermosphere (200-380 km altitude). the payloads qb50 cubesats carry are different type of science sensors, e.g., ion-neutral mass spectrometer arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):357-370. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 359 (inms), thermistors/thermocouples/rtd (th), flux-φ-probe experiment (fipex). (qb50, 2017). 1.5 radiation effect on space technologies radiation has detrimental effects on spacecraft and health implication for human in space, making it vital to study and understand the nature of space weather (poghosyan and golkar, 2017). radio aurora explorer (rax) mission consisting of two 3u cubesats rax-1 and rax2 built by university of michigan in collaboration with stanford research institute (sri) international, the primary mission objective is to examine the formation and distribution of natural ionospheric plasma turbulence, using ground-to-space bistatic radar experiment (springmann and cutler, 2014). 1.6 review of cubesat cots components cots components made the design of cubesat cheap and possible for institutions and countries with limited manufacturing technology, these components are readily available in the market for everyone to purchase. there are lots of companies that venture into cubesat, they provide services ranging from launch, research and development, and components. some of the leading companies which provide cubesat components are clyde space, endurosat, isisinnovative solutions in space, tyvak nanosatellite systems inc., gomspace, spaceflight, pumpkin inc., crystalspace, cubesatshop, nano avionics. a cubesat consists of several subsystems which are integrated to form a single system of a cubesat. cubesat subsystems available in the market include payload, structure, power systems, communication systems, attitude determination and control systems, on-board data handling systems, ground station, propulsion system and integrated cubesat platforms. going through the companies (mentioned earlier) it is obvious that cubesat cots components are all similar (in their specifications), this is because of the standardization of cubesat components dictated by launchers, communication regulations and technology advancement. 1.7 review of kibocube opportunity the kibocube opportunity is a collaboration programme between the japanese space agency (jaxa) and the united nations office for outer space affairs (unoosa) for the deployment of cubesats to orbit from the international space station (iss) via japanese experimental module jem “kibo” (unoosa, 2017). kibocube programme was initiated in line with the aims and objectives of the un programme on space applications. moreover, unoosa and jaxa believe that the kibocube programme will aid developing countries in the following ways (unoosa, 2017): 1. contribute to the growth of spacecraft engineering, design and manufacturing at a national scale and limit space activities (in terms of launch) 2. raise awareness towards the role space science and technology can play in promoting sustainable development (mext, 2015) 1.8 the japanese experimental module (jem) “kibo” the japanese experiment module (jem) alternatively called kibo is jaxa’s first contribution to the iss. it is built to be used for the conduction of scientific research on orbit, with a maximum number of four astronauts capable of performing experiments (scientific, medical and educational experiments) at a time. the kibo consists of six major segments (figure 1 shows these segments) the segments namely are (jaxa 2007a): i. pressurized module (pm) ii. exposed facility (ef) https://gomspace.com/ ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 360 iii. experiment logistics module-pressurized section (elm-ps) iv. experiment logistics module-exposed section (elm-es) v. japanese experiment module remote manipulator system (jemrms) vi. inter-orbit communication system (ics) figure 1 kibo configuration showing its segments (jaxa, 2007b) 2.0 cuumcube mission payloads 2.1 payload 1: acoustic sensor cuumcube mission consists of two payloads, both payloads are aimed at demonstration of technology. cranfield’s acoustic sensor identical to knowles i2s output digital mems microelectromechanical systems microphone in its function and specifications (figure 2). it is a microphone that will be measuring the spacecraft vibrations resulting from spacecraft thermal cycling mechanical noise, antenna deployment, mmod impacts, dom deployment and changes in acoustic response of spacecraft after deployment of both mechanisms – in the current case cuumcube spacecraft. figure 2 knowles i2s output digital mems microphone (knowles, 2017) knowles i2s output digital mems microphone is a low power micro electro mechanical system that can be directly connected to a digital processor, application processor or microcontroller, with an interface to condition the signal into 24 bits i2s format (knowles, arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):357-370. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 361 2017). it detects vibrations (noise or sound) within the range of 50 hz – 15 khz and converts it to a voltage with a digital output. within a spaceflight context, this is expected to monitor spacecraft vibrations and shocks transmitted through the spacecraft structure and into the microphone package mechanically coupled to the spacecraft structure. table 1: of specifications of the acoustic sensor mass 4 g dimensions (3.50 x 2.65 x 0.98) mm power 1.6 3.6 v input current 100 ma interface compatibility (works with microprocessors and microcontrollers) like cortex m-series chips like single-board computers (such as raspberry pi), feather m0 and arduino zero with i2c, spi or rs-232 busses operating temperature -40 to +100 °c data rate (size) 7400 bps (24-bit i2s format) vibration test 16 mins in all axes (x, y and z) from 20 – 2000 hz and can withstand an acceleration of up to 20 g mounting mechanically mounted internally on cubesat structure ionizing radiation tolerance 10 krad 2.2 payload 2: cranfield dom (de-orbit mechanism) the dom (de-orbit mechanism) is a mechanism for removing spacecraft from orbit (de-orbit) after completing its mission. it is a passive method of removing debris from orbit. thus, the initial design of the dom has a size of 140 mm x 80 mm x 56 mm with an area of up to 0.01 𝑚² and a mass of 0.5 kg. however, the currently available dom design has a mass of about 38% of the total mass of a 1u cubesat, the design was reduced to perfectly fit in a 1u cubesat. the dom uses the concept of stored energy: using copper-beryllium tape spring booms attached to a freely rotating central spool at one of its ends (taylor, 2013). figure 3 shows the configuration of the dom and table 2 shows its specifications. figure 3 deployed cranfield dom (taylor, 2013) ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 362 table 2 specifications of the dom dimension (100 x 80 x 16) mm area 0.008 𝑚 mass 400 g power requirement 200 ma for 10 milliseconds mounting screwed to the cuumcube structure via four bolts operating temperature 40 to +100 °c ionizing radiation the materials are tolerant to ionizing radiation 3.0 materials and methods 3.1 cuumcube mission design key drivers the mission key drivers are the critical aspects and requirements which must be considered as a priority to successfully design a mission. cuumcube mission key drivers are identified as: i. payload ii. mass iii. communications iv. power this is because the mission is a technology demonstration mission, the aim is for the payload to work effectively and efficiently, alongside making sure everything fits in a 1u cubesat structure with a standard mass of ≤1.33 kg, anything more than that will be rejected by kibocube programme. as a result, in the process of cuumcube mission design, special attention is given to the payload and mass (requirements). besides, the electrical power subsystem is also a key driver, due to the (power) demands and requirements imposed on it by the two mission payloads, the communications, the adcs and the obdh subsystems, all these subsystems require a power source (power supply), therefore, making it a challenge to provide enough electrical power supply. besides, communications subsystems usually occupy one-third of the mass of a spacecraft, thus, making it very thought-provoking to design a mission with an efficient communications subsystem. 3.2 subsystems design alternatives taking cuumcube requirements and constraints into consideration, subsystems were sized. the design methodology employed is the performance of trade-off analysis amongst available cots components in the market, however, the trade-off was performed after sizing cuumcube various subsystems. these components are provided by several companies, giving a wide range of components to choose from, despite the fact they are standardized, however, certain parameters were taken into consideration for trade-off analysis, to optimize the design. the parameters employed to make the trade-off analysis were:  compatibility: the component must be compatible with the payloads and mission demands in terms of requirements such as interface and mass.  simplicity: the component must be simple to integrate into the entire design.  performance: the component must be able to provide the desired demand of service to the entire mission and payloads. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):357-370. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 363 alongside these parameters, careful consideration for mass and power consumption was paid attention to, this is because the mission is constrained by mass, hence limiting the amount of power produced. 3.3 cuumcube orbit the orbital parameter analysis of cuumcube was done using systems tool kit (stk) software, to find the ground track pass and access time of cuumcube concerning the ground station, the following parameters were used for the analysis:  perigee altitude: = 380 km  apogee altitude: = 420 km  inclination: i = 51.6°  access time: o start: 7th april 2021, stop: 30th april 2021  target areas: cranfield, bedford, uk and maiduguri, borno, nigeria cuumcube mission is constrained by the orbit and inclination of the iss (given the lack of a propulsion subsystem) after running stk simulation of the orbit the results showed that cuumcube will be able to access both the uk and nigeria (good for the ground station to communicate with cuumcube and vice versa), figure 4 shows the ground track of cuumcube. figure 4 the ground track pass of cuumcube over uk and nigeria (stk) 3.4 communication time (maximum time in view) the maximum time in view (access time) is the time duration where cuumcube can see and communicate with the ground station. the average maximum time in view (or access time) at 380 km (cuumcube orbit apogee) is 5.98 minutes and 6.52 minutes at 420 km (cuumcube orbit perigee), these values are at 10° angle of elevation (to account for obstacles such as tall buildings) (wertz et al., 2015). however, the exact access time was obtained from stk simulations (table 3 and table 4), the simulation was done for the date: 7th april 2021 to 30th april 2021 (expected active cuumcube mission lifetime). the red marks on figure 4 show the coverage on the ground. results from tables 3 and 4 show that each day cuumcube have access to both uk and nigeria (ground stations) five to seven times per day (in every 48-hours there are 13 orbits), ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 364 with an average access time of about 10 minutes per orbit. therefore, the total access time per day is 3612 seconds, (60 minutes). table 3: access summary report of cuumcube over uk table 4: access summary report of cuumcube over nigeria arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):357-370. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 365 3.5 data rate required for cuumcube mission the acoustic sensor with a data rate of 7400 bps (bits per second), will be recording for 24 hours (only once to get a control data sample upon which, subsequent recordings will be compared). the tt&c data (telemetry and tracking: orbit position, os operating system and fault detection) is less than 250 kb per day, it is negligible compared to that of payload (acoustic sensor). table 5 shows the data sizing the mission. table 5 the total amount of data that needs to be sent to the ground station payload data 7400 bps for 24 hours (86400 seconds) = 639.36 mb per day tt&c data (telemetry, tracking, and housekeeping data per day) 250 kb/day = 2 mb/day total data need to be sent to the ground station 639.36 mb + 2 mb = 641.36 mb/day total spacecraft access time per day (max. time10) 4411 s (74 minutes) required mission download data rate per day (641.36 mb) / (4411 s) =145.4 kbps therefore, a downlink download data rate with at least 145.4 kbps is required to send mission data to the ground station (daily). similarly, for uplink; telecommand data from the ground station (to command spacecraft) is less than 800 kb/day (an estimation of a couple of codes with 0’s and 1’s), therefore a data rate of (800 kb/4411 s) 181 bps (per day) is required to send telecommand data to spacecraft from the ground station. therefore, a downlink download data rate with at least 145.4 kbps is required for sending mission data to the ground stations (daily). ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 366 4.0 results cuumcube mission design was done using the systems engineering approach, where the mission requirements were put together against which this baseline emerged after careful trade-off analysis. moreover, the mission design was done using cots components because these components are relatively affordable, reduce fabrication time (they are available off the shelf ready to be assembled) and have flight heritage (technology readiness levels) trl 5-9, hence mitigating the risk of mission failure. consequently, the following points describe the cuumcube mission baseline drawn from the systems engineering design approach. therefore, cuumcube should (baseline): i. fabricated using cots components ii. use a 1u cubesat structure iii. fly two payloads (to demonstrate technology), which are: a. cranfield’s acoustic senor and b. the dom (de-orbit mechanism) deployed to an elliptical orbit (perigee 380 km, apogee: 420 km) by japanese experiment module remote manipulator system (jemrms) via jem small satellite orbital deployer (j-ssod), from the iss. summary of cots component employed in cuumcube mission are shown on table 3 and mission specifics on table 6 table 6: selected cots components for cuumcube mission subsystem cots component / manufacturer unit structure 1u cubesat structure (isis) 1 adcs nss cubesat adcs board (new space systems) 1 communications uhf nanocom ax100 transceiver (gomspace) 1 uhf nanocom ant430 antenna (gomspace) 1 obdh obdh subsystem (clyde space) 1 eps electrical power subsystem (gomspace) 1 table 7: cuumcube mission baseline key specifics payload 2 payloads: cranfield’s acoustics senor and dom orbit elliptical orbit (perigee 380 km, apogee: 420 km) with an average 10 minutes access time 6 times per day over uk and maiduguri (average access time of 57 minutes/day) deployment from the iss via j-ssod (jem) launch mass 1.33 kg,1u cubesat structure (with 4.8% margin) spacecraft dimension (100 x 100 x 113.5) mm power 60.36 𝑚 provides 15 w (efficiency, ƞ=30.20%) battery capacity 2600 mah (35% depth of discharge) downlink capability mission lifetime mission operations 115.2 kbps in uhf about 160 days ground stations in uk (cranfield university) and nigeria arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):357-370. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 367 (university of maiduguri) figure 5 a catia model of cuumcube spacecraft 4.0 discussion 4.1 communications cuumcube communications subsystem is designed to have a half-duplex communications link in the uhf (ultra-high frequency) range. this link will be used in sending both mission and telemetry data to the ground stations, and telecommand data onboard the spacecraft from the ground station. payload 1 (cranfield’s acoustic sensor) has a data rate of 7400 bps; it is planned to record continuously for the first 24-hours on-orbit to have control data upon which subsequent data will be compared. therefore, it generates 641.36 mb (within 24-hours including 2 mb tt&c data), hence with 56.7 minutes/day access time, a data rate of 188 kbps is required to download this data. however, the uhf transceiver is having a max. of 115.2 kbps, therefore the data will be stored onboard and subsequently downloaded within 93 minutes. however, after the first 24-hour of recording the payload (acoustic sensor) enters monitoring mode, where it only records when there is an event, it has been estimated to record for 60 minutes per day, producing 30 mb/day, which require only 8.8 kbps to download it within the available 57 minutes of mission access time (per day). 4.2 mission operations the interface used to communicate with the cuumcube spacecraft is the gomspace cots uhf ground station kit, it consists of a module of receiver and transmitter, a computer (pc) and an antenna (3 yogi antennas) tower including a rotor module for steering to track spacecraft rf (radiofrequency). the mission operational sequence is the determiner of mission duration, however, at the mission altitude cuumcube is expected to last 160 days (depending on the rate at which the dom aerobraking induces to the spacecraft by drag), the mission plan is focused on the following key events: i. 24 hours recording by the payload (once) ii. monitoring of: ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 368 o antenna deployment o mechanical noise induced by thermal cycling o mmod impacts o dom deployment o spacecraft response after deployment of mechanisms furthermore, after the deployment of the spacecraft to orbit a series of events will unfold sequentially. these events are as a result of a careful design and a successful deployment in to orbit of the spacecraft. these series of events are the mission operational sequences, which are as follows: i. deployment: this the first stage of the mission, where the spacecraft is out into orbit. during this process, the spacecraft is deactivated. ii. activation of spacecraft: 30 mins after deployment, the spacecraft is scheduled to switch on, the subsystems will be in sleep mode except for eps (electrical power system), where its fully charged battery will supply power to various subsystems. iii. switching on payload 1: the acoustic sensor alongside the obdhs (onboard data handling system) is switched on immediately after activation of the spacecraft. hence, the sensor will start recording for 24 hours nonstop. the obdhs is required switched on because the data recorded is stored on the (memory) storage device on the obhs board. iv. monitoring mode: after recording for 24 hours, the payload enters monitoring mode, in this mode, the spacecraft only records when it senses an event, it stays in this mode for the rest of the mission duration. v. deployment of communications antenna: 24 hours of deployment of the spacecraft in to orbit, the onboard communications antenna is deployed, while the acoustic sensor is monitoring and recording the event. this delayed is intended to give the acoustic sensor enough events to record, thereby providing more data to analyse. vi. switching adcs (attitude dynamics and control system) on: the adcs is activated to stabilize the spacecraft and to make sure the side where the dom is installed is in the ram direction (direction of drag). vii. deployment of dom: lastly, at the end-of-life of the spacecraft the dom is deployed, and then the spacecraft will lose altitude until it burns at re-entry. 5.0 conclusion the mission and baseline design are in the context of the kibocube opportunity. subsequently, the payloads were identified, their requirements alongside other mission requirements were used in the design of the cuumcube mission, thus, a baseline was outlined, it is as follows: a 1u spacecraft to flying two payloads (cranfield’s acoustic sensor and dom), using cots components. the spacecraft is to be deployed from the iss (international space station) into an elliptical orbit (perigee: 380km, apogee: 420 km). the ground station is a cots component too (just like the spacecraft), with each in both universities (cranfield university and university of maiduguri). the mission payloads are cranfield’s acoustic sensor, a microphone for monitoring vibrations resulting from; deployment of mechanisms (antenna and the dom), vibrations due to thermal cycling, spacecraft response to the deployment of mechanisms and mmod impact. the second payload is the (dom a de-orbit mechanism). furth more, the mission operation sequence starts 30 mins after deployment of spacecraft into orbit, the sequences start by activation of the spacecraft and then commencement of a 24-hour recording (recording mode) by the sensor, subsequently, the sensor will be monitoring (monitoring mode) to capture any vibration. lastly, the antenna is deployed then the dom, then the spacecraft is left to decay in orbit, lose altitude and burn in re-entry. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):357-370. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 369 lastly, certain areas give scope for the advancement of this work, the first obvious aspect that needs to be addressed is the replacement of dom (payload 2), university of maiduguri needs to develop a payload to replace the dom in the future (each university needs to come up with a payload). consequently, the new payload will have different requirements, therefore a review of the mission design need to be done. the second aspect which needs further study is the testing procedures. the third aspect that needs to be looked at is the risk, a rigorous risk assessment will help in tackling possible failures. moreover, the financial budgets need to be rigorously looked into, in future work the companies need to be contacted for information about the prices. finally, in the mission operations, the software architecture aspect needs to be included and simulation of mmod (to know the time of impact and nature of the particles), so that a better mission plan can be set. references cubesat. 2017. cubesat design specification. https://www.nasa.gov/sites/default/files/atoms/files/nasa_csli_cubesat_101_508.pdf accessed on 7 april, 2021. ehrenfreund, p., ricco, aj., squires, d., kitts, c., agasid, e., bramall, n., bryson, k., chittenden, j., conley, c., cook, a., mancinelli, r., mattioda, a., nicholson, w., quinn, r., santos, o., tahu, g., voytek, m., beasley, c., bica, l., diaz-aguado, m., fredericks, c., henschke, m., landis, d., luzzi, e., ly, d., mai, n., minelli, g., mcintyre, m., neumann, m., parra, m., piccini, m., ramsay, r., ricks, r., schooley, a., stackpole, e., timucin, l., yost, b. and young, a. 2014. the o/oreos mission astrobiology in low earth orbit, acta astronautica, 93: 501508. healea, j., malphrus, b., mckneil, s., brown, k., kruth, j., twiggs, b., dang, k., cavins, a., and byleborodov, y. 2015. the cosmic x-ray background nanosat-2 (cxbn-2): an improved measurement of the diffuse x-ray background’, 12th annual cubesat developers workshop. luis obispo, ca. ishimaru, r., sakamoto, y., kobayashi, m., fujita, s., gonai, t., senshu, h., wada, k., ym, kurosawa, k., hosokawa, s., yoshida, k., sato, m., takahashi, y. and matsui, t. 2014. cubesat mission for uv–visible observations of meteors from space: s-cube (s3: shooting star sensing satellite)’, 45th lunar and planetary science conference, the woodlands, tx. 1846 lpi contribution no.1777. gomspace. 2017. subsystems. https://gomspace.com/shop/subsystems/default.aspx accessed on 7 april, 2021. jaxa. 2007a. japanese experiment module (kibo). http://iss.jaxa.jp/en/kibo/ accessed on 7 april, 2021. jaxa. 2007b. jem small satellite orbital deployer (j-ssod). http://iss.jaxa.jp/en/kiboexp/jssod/ accessed on 7 april, 2021. knowles. 2017. sisonic™ surface mount mems. https://www.knowles.com/products/audio-processors accessed on 7 april, 2021. mext. 2015. new cooperation programme “kibocube”: invitation to cubesat deployment into orbit from the japanese experiment module “kibo” of the iss, 58th session of the committee on the file:///c:/users/user/desktop/cuumcube/gomspace https://gomspace.com/shop/subsystems/default.aspx http://iss.jaxa.jp/en/kibo/ http://iss.jaxa.jp/en/kiboexp/jssod/ https://www.knowles.com/products/audio-processors ishaq et al.: cranfield university and university of maiduguri cubesat (cuumcube) for technology demonstration: baseline and mission design. azojete, 17(3):357-370. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniakorchikachristopher@gmail.com 370 peaceful uses of outer space vienna, 12 june 2015. http://www.unoosa.org/pdf/pres/copuos2015/copuos2015tech09e.pdf accessed on 7 april, 2021. nasa. 2008. astrobiology: its origins and development. https://www.nasa.gov/50th/50th_magazine/astrobiology.html accessed on 7 april, 2021. nasa. 2015a. jet propulsion laboratory, geo-cape roic in-flight performance experiment (grifex). https://www.jpl.nasa.gov/cubesat/missions/grifex.php accessed on 7 april, 2021. nasa. 2015b. small spacecraft technology state of the art. https://www.nasa.gov/sites/default/files/atoms/files/small_spacecraft_technology_state_of_the_art_201 5_tagged.pdf accessed on 7 april, 2021. poghosyan, a. and golkar, a. 2017. cubesat evolution: analysing cubesat capabilities for conducting science, progress in aerospace sciences, 88: 59-83. qb50. 2017. mission objectives. https://www.qb50.eu/index.php/project-description-obj/missionobjectives.html accessed on 7 april, 2021. selva, d. and krejci, da. 2012. survey and assessment of the capabilities of cubesats for earth observation, acta astronaut. 74: 50–68. springmann, jc. and cutler, jw. 2014. flight results of a low-cost attitude determination system. acta astronautica, 93: 201-214, 2014. taylor, r. 2013. conceptual development of a de-orbiting payload for micro-satellites in leo. cranfield university: msc thesis report, msc astronautics and space engineering. unoosa. 2017. the united nations/japan cooperation programme on cubesat deployment from the international space station (iss) japanese experiment module (kibo) "kibocube". available at: http://www.unoosa.org/oosa/en/ourwork/psa/hsti/kibocube_2017.html accessed on 7 april, 2021. wertz, jr., everett, df. and puschell jj. 2015. space mission engineering: the new smad. hawthorne: microcosm http://www.unoosa.org/pdf/pres/copuos2015/copuos2015tech09e.pdf https://www.nasa.gov/50th/50th_magazine/astrobiology.html https://www.jpl.nasa.gov/cubesat/missions/grifex.php https://www.nasa.gov/sites/default/files/atoms/files/small_spacecraft_technology_state_of_the_art_2015_tagged.pdf https://www.nasa.gov/sites/default/files/atoms/files/small_spacecraft_technology_state_of_the_art_2015_tagged.pdf http://www.unoosa.org/oosa/en/ourwork/psa/hsti/kibocube_2017.html arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):579-586 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 579 original research article design, construction and performance evaluation of a manually operated meat mincing machine f. m. kajiama*, m. a. aji, m. shuwa, and e. b. taktak department of mechanical engineering, university of maiduguri,p.m .b 1069, maiduguri, nigeria *corresponding author’s email address: timakaj@yahoo.com 1.0 introduction meat is an edible animal product in form of muscle, connective, fatty tissue and frequently bones. humans have been consuming meat throughout history because is recognized as an important source of protein, vitamins and minerals. however, certain categories of consumers such as children, elderly and the sick will better consume the meat with ease if minced. mincing is a process of cutting up meat or other foods such as onions, garlic, and celery into small pieces for consumption. this process can be performed by the use of a simple machine which can be specifically design based on peculiar needs especially in the production and preparation of domestic food materials for consumption. the process involves moving the product forward in a working chamber, feeding it through some knives pushed against a perforated plate. a rotating screw (worm) with uniform or variable thread pitch is used. the peculiarity of the screw is the pre-grinding of raw meat and the creation of pressure sufficient to move the product through the cutting mechanism without squeezing contained liquid phase therein. screws are divided into cylindrical and conical; with constant or variable pitch; the number of turns; the number of threads of the screw; thread count, the profile of the thread; with or without trimming. the cutting tool of the mincing machine consists of fixed plates and rotating knives. fixed cutting plates are made in the form of discs with round holes and are paired to cutting parts with rotating knives (brennan, 1976); anar et al., 2019). article information abstract in this study, a manually operated meat mincing machine was designed, constructed and its performance evaluated. the machine consists of; a single start worm auger called the shaft, a four-blade crosshead knife, a perforated plate, handle, mincing cover and a mincing head which comprised a hopper and an anchor bracket. all components of the machine were fabricated from locally available materials (stainless and mild steel) and based on the determined design parameters. the auger, mincing head, the crosshead knife and perforated plate were constructed from stainless steel material. mild steel was used for the construction of the anchor bracket, mincing head cover and handle of the machine. these components were fabricated using the process of measurement, marking, cutting and joining. vernier caliper and steel rule were used for measurement, scriber used for marking, center lathe machine, drilling machine, hark saw, hand snip and hand files were used for cutting. while arc welding and bolting were used the joining process. the auger had a shaft diameter of 0.025 m, worm diameter of 0.05 m and a total length of 0.22 m. the mincing head had an internal diameter of 0.052 m and external diameter of 0.06 m. the result shows that the machine can mince ༀࠀ� �� fresh meat in �ༀࠀ�� seconds, ༀࠀ� �� of perboiled meat in �ǥࠀ͵� seconds and ༀࠀ� �� of overcooked meat in ��ࠀ͵� seconds. the critical load of the auger which is the major component of the machine is ��hࠀǥ �ᄸ with a maximum stress of �ͻ�ͳ�ǡࠀ�ༀ� ᄸtࠀ�� the efficiency of the machine was 50% at a velocity ratio of 0.88 and mechanical advantage of 1.8 with a total production cost of seven thousand three hundred and ninety two naira (₦7,392). the machine will serve as a means of providing minced meat to children, elderly and the sick especially in rural areas that have no access to electricity. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 feb., 2020 revised 02 july, 2020 accepted 10 july, 2020 keywords: design, construction, meat and mincing machine http://www.azojete.com.ng kajiama et al.: design, construction and performance evaluation of a manually operated meat mincing machine. azojete,16(3):579586. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 580 there are different kinds of mincing machines being used today, these range from simple manually operated tabletop to complex electrically powered. however, their design depends on the peculiar need or process desired from the machine and its source of power(brennan, 1976; balami, 2000). considering electric power challenges in the country today this study aims to design and construct a manually operated cost effective meat mincing machine from locally available raw materials. the machine major components are single start worm auger (shaft), a four-blade cross-shaped knife, perforated plate, luck nut, handle, hopper and a mincing head. the prepared meat to be minced is first feed through the hopper on the mincing head, the single start worm auger pushes the meat through the cross-shaped knife. the meat comes out through the perforated plate as a minced meat to be collected for use. design parameters such as the yield stress of the load bearing components and capacity of the machine are determined to avoid failure. performance and efficiency of the machine is also determined. the machine will provide a means for processing meat that can be easily consumed by children, elderly and the sick. it will also process meat for preservation, packaging and as well enhance and encourage wide application of meat in a variety of products. moreover, it will also be most suitable for rural areas which have no access to electricity. 2. methodology 2.1 material selection and design of machine components materials used for the construction of the mincing machine are selected based on their strength, corrosion resistance, cost and local availability. it is required that material selected for the construction of components that will have direct contact with the meat should not react with the meat during the mincing process. therefore, stainless steel is selected for the machine’s components that will directly interact with the meat. these components include the hopper, mincing head, auger, perforated plate and the crosshead knife. other components that have no direct contact with the meat such as handle and lock nut, were made from mild steel. the machine is design to be anchored to a bench or table for effective mincing operation. the prepared meat to be minced is first feed through the hopper on the mincing head, the single start worm auger pushes the meat through the four cross-head knife, the knife mince the meat as it rotates against the perforated. the meat comes out through the perforated plate as a minced meat to be collected for use. the required power for the operation is transmitted manually through the handle to the auger. the auger as it rotates pushes the meat towards the cross-knife. in performing the mincing meat operation, the auger is subjected to torsional stress and bending and considering the auger as a power transmission shaft the ability of the shaft (auger) to effectively function under these loading condition depends on its diameter (khurmi and gupta, 2007), thus the shaft diameter (d) is determined from equation 1. � t ͵ �hh ��� ��� where: t is the twisting moment (torque) and �� is the allowable shear stress of the material (for stainless steel grade astm 201 india as given by khurmi and gupta, 2007 is ��� x ��h nt m� ). the outside diameter of the single start worm auger (do ) which determines the internal diameter of the mincing head is determined from equation 2 (khurmi and gupta, 2007). �� t � � ���͵��ࠀ� ��� where: �� is the circular pitch of the auger taken to be between 0.024.5 as according to khurmi and gupta, 2007 is between 0.024 to 0.025 m for single start worms. the twisting moment (torque) is determined from equation 3. h t � � h� ��ᄸ �͵� where: p is the power due to an applied force by an average person (according to balami, 2000 is �ͻ͵ࠀༀ nts) at the handle and at a defined revelation per minute n . the ultimate shear http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 579-586. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 581 stress of the shaft is determined from equation 4 considering a factor of safety (fࠀsࠀ) of 5 at an allowable working stress �� of ༀ� x ��h ntm� (allowable working stress of stainless steel). �� t �� ࠀ� ࠀ� �ༀ� the stress distribution (��) along the shaft (auger) length from l t � to l t lsdue the applied critical load (fcrh) of the auger and is determined from equations 5 and 6 respectively. �� ���� t h � �� �� � ��� ��� ���� t ������� � �� � � � �h� where: ls is the length of the shaft (auger) m, δls is change in the shaft length, as is the crosssectional area of the shaft (m2), and t is the twisting moment (torque) nm. while c is a constant depending upon the end condition for the handle �c t � for single point load application handle), eh is modulus of elasticity of the material (for mild steel and as given by khurmi and gupta (2007) is �ࠀ� x ���� ntm�, ah is cross-sectional area of the handle, lh is the length of the handle and lh k is the slenderness ratio of the handle. 2.2 components construction and assembly the meat mincing machine is constructed based on the design parameters of the individual components machine. all component’s geometrical parameters (dimensions) are based on the diameter and length of the shaft (auger), which is the fundamental component of the machine. the auger is machined on a center lathe machine from a 0.05 m diameter and 0.22 m long stainless steel material. a single start worm with a pitch of 0.084 m at the first stage and 0.054 m at the second stage is machine on the material. from the end side of the long pitch worm the diameter of the shaft is reduce to 0.02 m to a length of 0.03 m, while on the opposite side the shaft diameter is reduce to 0.025 diameter to length of 0.025 m as in figure 1. all measurements were carried out with a vernier caliper and the component is finished after machining with a hand file after machining. the auger is housed in the mincing head which is also machined on a center lathe machine. the mincing head was fabricated in three parts and thereafter the parts were welded together using 12 g stainless steel welding electrodes as in the assembly drawing in figure 6. the first part is 0.170 m diameter with a length of 0.250 m stainless steel material. this material was machined on a center lathe based on the dimensions in figure 2a. the second part of the mincing head was fabricated from mild steel material based on the dimension in figure 2b. it was a bench work fabrication process that involved measurement, marking cutting, dicing, tapping and welding. the third part was fabricated from 0.002 m stainless steel plate based on the dimension in figure 2c. the process of fabrication involved measurement, marking, cutting and welding on a workshop bench. figure 1: single start variable pitch worm auger (shaft) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al.: design, construction and performance evaluation of a manually operated meat mincing machine. azojete,16(3):579586. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 582 figure 2: the parts of the mincing head the mincing head cover was machined on a center lathe from 0.8 m diameter and 0.8 m long stainless steel material base on the dimension in figure 3a. the fabrication process of the mincing head cover involved meaurement using vernier caliper, removal of material using the center lathe machine and finishing using a hand file. the perforated plate which was also produced from the same material was fabricated using the same method used for the production of the mincing head cover based on the drawing in figure 3b. however the 0.006 m diameter holes marked based on the drawing in figure 3b, punched using a centre punch and drilled on a piller drilling machine. figure 3: mincing head cover and perforated plate the cross-head knife was produce from 0.06 m diameter and 0.03m long stainless steel material on a centre lathe machine and a pillar drilling machine based on the dimension in figure 4. shaping the knifes, the centre square hole and sharping the knifes were carried on a workshop bench vice using a steel rule for measurement, scriber for marking, hark saw and set of files for cutting and shaping. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 579-586. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 583 figure 4: the cross-head knife the handle of the machine was fabricated from 0.03 m diameter mild steel shaft and 0.05 m width 0.01 m height and 0.03 m long mild steel bar based on the dimension in figure 5. the fabrication involved machining the 0.03 m diameter shaft on a centre lathe and cutting and filing the mild steel bar in a bench vice to the dimension in figure 5. the finished sections were the welded together as in figure 5. figure 5: the mincing machine handle all fabricated machine components were cleaned and assembled as in figure 6 for performance analysis based on the numbers in the sketch. the parent component was the barrel and hopper. number 1 was inserted first in the parent component, followed by component numbers 2, 3, 4, 5, 6, 7 and finally 8 which is anchoring the machine a bench or table for use. figure 6: assembly sketched of the mincing machine 2.3 performance evaluation the performance of the machine was evaluated by mincing and analysis of three samples beef of the same mass (0.40 kg). the first sample was fresh meat, the second was parboiled while the third was overcooked. the mass of each sample of meat was taken before and after mincing file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al.: design, construction and performance evaluation of a manually operated meat mincing machine. azojete,16(3):579586. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 584 using a digital weighing machine (clark model 153) with respect to time and number of handle turns applying approximately the effort. the outcome of the analysis was used to determine the performance of the machine. assuming approximately same magnitude of effort was applied at the handle for a predetermined handle speed (10, 20, 30, 40 and 50) the mass of each sample of the minced beef was taken with respect to time. this was used to determine the velocity ratio mechanical advantage and efficiency of the machine as in equation 7, 8 and 9 respectively. �t t �� �� �ǡ� �� t �� �� �ǥ� � t �t �� �ͻ� where: vr is the velocity ratio, dl is ��ࠀ� m distance moved by the meat during mincing, df is ��ࠀ� m distance moved by the applied load, ma is the mechanical advantage of the machine, wa is ��ǥ n effort required to mince ༀࠀ� kg of meat. according to food production (2010) �͵�� n is required grind of � kg meat. also fa is �ͻ͵ࠀༀ n the available load that is the approximate effort provided by an average person according to balami (2000), and � is the efficiency of the machine. 3. results and discussion the design of the mincing machine auger (shaft) shows that the shaft has a root diameter of 0.025 m and a worm diameter of 0.050 m based on a circular pitch of 0.0245. according to khurmi and gupta (2007) circle pitch of single start worm is between 0.024 to 0.025 m. given a tolerance of 0.002 m and based on a worm diameter of 0.050 m, the mincing head internal diameter used was 0.052 m. based on these dimensions the auger and mincing head were fabricated from stainless steel material and according to oyelade et al. (2004), materials to be used for the construction mincing machines should be a material that will not react with the product to be minced. the twisting moment on the auger tis due to an applied load of �ͻ͵ࠀༀ n is ͻ͵ࠀ͵ǥ nm . the design result also shows that the ultimate shear stress of the auger is ǥࠀ� x ��h n m� ࠀ this was determined based on stainless steel allowable working stress of ༀࠀ� x ��ǡ ntm� and a factor of safety of ࠀ� the critical of the auger is determined as ��hࠀǥ kn /m2 and this is less than ༀࠀ� x ��ǡ ntm� the allowable working stress of the auger material. according to khurmi and gupta (2007), for shaft to withstand a defined working load the critical load must be less than the allowable working load of the shaft material. the stress distribution along the auger lengthls from � to ��ࠀ� m due to twisting moment in cause of mincing is �ͻ�ͳ�ǡࠀ�ༀ� ntm� at the point of load application when ls is ���ࠀ� m and drops to �ͻࠀ��ǡ ntm� when ls is ��ࠀ� mas shown in figure 7. this shows that the maximum stress �ͻ�ͳ�ǡࠀ�ༀ� ntm� the auger will be subjected to during mincing is also less than ༀࠀ� x ��ǡ ntm� the allowable working stress of the auger material (stainless steel). figure 7: stress distribution along the length of the auger http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 579-586. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 585 based on the design parameters of the components of the mincing machine the components are fabricated, assembled tested for performance as shown in figure 8. figure 8: the mincing machine under evaluation the result of the performance analysis of the three samples tested shows that ༀࠀ� kg of fresh, parboiled and overcooked meat was minced in �ༀࠀ��ͳ �ǥࠀ͵� and ��ࠀ͵� seconds respectively. the mass of the fresh, parboiled and overcooked weighed after mincing were �ͳ͵ࠀ� ��ࠀ� and ͵�ࠀ� kg respectively as in table 1. the result also shows that less time was taken to mince the parboiled and the overcooked meat as compared with the time taken for the fresh meat. however, the mass of ejected meat of the parboiled and overcooked meat was also less with only 50 % and 57.5% of the meat minced and ejected by the machine at an applied effort of 293.4 n and 30 rpm. according to food production and processing (2010) and also as reported by sunday and ndaliman (2015), mincing machines generally succeed in mincing and ejecting between 70 to 80 % of the meat. although this percentage is only realistic in large motorized mincing machines, 40 to 50% is as well achievable in optimized small manually operated machines. table 1 performance analysis of the mincing machine all the three sample of the minced meat (fresh, parboiled and overcooked) were minced homogenously by the machine as shown in figure 9a, b and c. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng kajiama et al.: design, construction and performance evaluation of a manually operated meat mincing machine. azojete,16(3):579586. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: timakaj@yahoo.com 586 (a) (b) (c) figure 9: samples of the minced meat by the machine the velocity ratio (vr ) and mechanical advantage (ma ) of the machine were determined as 0.88 and 1.8 respectively. from the two parameters the efficiency of the machine is 50%. 4. conclusion the manually operated meat mincing machine was designed and its performance evaluated. the result shows that the machine can mince ༀࠀ� kg fresh meat in �ༀࠀ�� seconds, ༀࠀ� kg of parboiled meat in �ǥࠀ͵� seconds and ༀࠀ� kg of overcooked meat in ��ࠀ͵� seconds. the critical load of the auger which is the major component of the machine is ��hࠀǥ kn with a maximum stress of �ͻ�ͳ�ǡࠀ�ༀ� ntmࠀ� the efficiency of the machine is 50% at a velocity ratio of 0.88 and mechanical advantage of 1.7996 with a total production cost of seven thousand three hundred and ninety two naira (₦7,392). the machine will serve as a means of providing minced meat to children, elderly and the sick especially in rural areas that have no access to electricity. references anar, b., bolat, k., zhadyra, k., elizabeth, d., svetlana, a., luaisan, t., elmira, m., georgy, p. and anna, o. 2019. engineering methods of technological calculation of meat grinders. asian research publishing network journal of engineering and applied sciences. 14(22) : 3827-3831 balami, aa. 2000. design, construction and performance evaluation of composite processing machine. faculty of engineering university of maiduguri seminar series, 1(1) : 71 – 79 brennan, jg. 1976. food engineering operation, second edition. s. chand & company ltd. new jersey. khurmi, rs. and gupta, jk. 2007. a textbook of machine design. eirasia publishing house (pvt) ltd. new delhi. oyelade, oj., adedeji, aa., owonikoko, a. and akande, ea. 2004. design and construction of a manually operated double face meat mincer. journal of science and engineering technology, 11(3): 5831-5836. sunday, b. and ndaliman, nb. 2015. design of a manual and motorized meat grinding machine. international journal of engineering trends and technology (ijett), 21(2): 95-102. food production and processing, 2010. available online at:https://www.ecfic.org/foodproduction[accessed 20 august 2020]. https://www.ecfic.org/food http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):381-390 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 381 original research article design, construction and testing of a weighing equipment for powdered food products m. ekpu* and i. a. ayomide department of mechanical engineering, delta state university abraka, oleh campus *corresponding author’s email address: ekpum@delsu.edu.ng 1.0 introduction measurement techniques have been of immense importance ever since the start of the human civilization when measurement was first needed to regulate the transfer of goods in trade by barter to ensure that exchange was fair. the 19th century revolution led to the development of new measuring techniques in the industrial world (morris, 2001). the increased demand in digital weighing equipment in business enterprises in recent years is because of the quest to simplify measurement (satish and vanaraj, 2012). the demand for traditional weighing method has reduced significantly due to the availability of digital weighing equipment. this has also caused a revolution in the variety of design of digital weighing equipment. several digital weighing scale designs have been presented in quite a number of publications; these designs exhibit different unique features. for instance, pinto (2012a) conducted three different projects with different scales. the researcher started with the fagorbb-90 scale, a cheap simple scale with liquid crystal display (lcd) screen. the goal of the project was to store the data on a secure digital (sd) card and further add more advanced features to the scale. the researcher did so by removing the original lcd screen and then added a new lcd screen and a microcontroller (lpc 2103) to enable easy control of the microcontroller fetched data from the sd card and do multiple calculations before outputting it on the lcd screen. the new features were time and date, increase or decrease in weight and multi user support. pinto (2012b) further improved the scale to give it bluetooth connectivity. the scale communicated with android mobile phone via a bluetooth link. the researcher used the android application smart weight chart to show the data article information abstract in local markets in third world countries, no standards are followed in terms of selling and buying powdered food products. this leads to variation in the amount of products sold or received by retailers or customers respectively. ensuring a standard for such products are vital in maximizing profit for business owners and optimizing quantity of products received by customers. to solve this problem, a weighing equipment was designed, constructed, and tested. all materials used in the construction were locally sourced and assembled. after completion of the weighing equipment, it was tested with a powder product for about 300 s (at 60 s interval) and the corresponding mass (kg) was compared to a readily available digital scale. the results from the analysis showed that the developed weighing equipment have an approximate accuracy of about 95%. this meant that the average mass (kg) difference from the analysis was 5.06%. in addition, there was an average savings of about 0.150 kg of the powder product. therefore, the developed weighing equipment will be vital to small scale businesses in third world countries. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 6 february, 2023 revised 23 march, 2023 accepted 24 march, 2023 keywords: weighing equipment mass powder design construction http://www.azojete.com.ng/ file:///c:/users/hp/downloads/ekpum@delsu.edu.ng file:///c:/users/hp/downloads/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):381-390. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 382 as a graph. the researcher’s second work was similar to the first work but with a different scale. lastly, the researcher worked on the beurer bg 16 scale that is used to measure weight, water percentage, fat percentage, and percentage of muscle. the same modifications as with the other scales were made. though, the scale was very sophisticated, it was however expensive and not affordable by most people. modern instruments take into consideration the force of the earth’s gravity in trying to ensure the accuracy of measured weights due to variation in earth’s gravitational pull. the simplest form of a weighing equipment is the balance; it is used to balance two loads from opposite ends of a horizontal bar (mushiri and mbohwa, 2015). the delicate precision balances used today in scientific laboratories are based on the above principle. for heavier loads, scales based on steelyard were used (abueejela and belkasem, 2018). the mechanical scale was invented by thaddeus fairbanks in 1830. it uses a system of two or more connected levers to support the platform. when a load is placed on the platform, the levers divide the load so that a small weight can be used to balance a load thousands of times heavier (shigwan et al., 2016). modern precision balances, known as macro balances in scientific laboratories, are sensitive enough to measure loads up to 7.05 ounces (200 grams) to the nearest 3.5 million of an ounce (0.1 milligram). there are even more sensitive balances, called microbalances, that can weigh a maximum load of 0.00353 ounce (0.1 gram) to the nearest 3.53 hundred-millions of an ounce (1 millionth of a gram). most precision balances are kept in glassed-in cabinets so that they are unaffected by external temperature changes and drafts (raza and turiac, 2016). in third world countries such as nigeria, many small scale food production business owners and small/medium scale grocery store owners in local communities do the process of weighing and filling of products manually. such business owners who particularly produce items like cassava flakes (locally and popularly known in nigeria as garri), flour, and other powdered products, etc. has to do the weighing and filling of the packaging processes manually. this leads to loss in profit because of the time and effort required in the manual handling. therefore, there is the need to solve this peculiar problem for the local communities in nigeria, which has led to the design and construction of this weighing equipment. this equipment could also be used by the food and beverages industries to fill and weigh products such as powdered sugar, salt, coffee, milk, flour, spices, etc. 2. materials and method 2.1. materials the materials used for the construction of the equipment are: hopper, load cell sensor, arduino uno board (microcontroller), stepper motor, stepper motor driver, input key and lcd screen, power supply, and frame. sections 2.1.1 – 2.1.5 presents the description of the components used in this study. 2.1.1. hopper the hopper is cone shaped with cavity, through which the product (power), pass into the stepper motor unit for filling process. the hopper wall is made of plastic with a thickness of 2.0 mm. the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng ekpu and ayomide: design, construction and testing of a weighing equipment for powdered food products. azojete, 19(2):381-390. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 383 top of the hopper has a measurement of 260 mm by 260 mm, the cavity measurement is 60 mm by 60 mm, while the height of the hopper is 300 mm (from the top to the cavity). the hopper has the capacity to hold 5.309 kg of product (powder). there is a 20 mm polyvinyl chloride (pvc) inlet pipe that connects the hopper to the stepper motor unit. figure 1 presents the designed hopper used in this work. figure 1: hopper 2.1.2. load cell and sensor a load cell is an electronic sensor used for measuring weight and force. when a force is applied to it, an electrical signal at the milli-voltage level transmits on its output wires. in addition, the load cell is a transducer that converts force into measurable electrical output. figure 2, shows the load cell and sensor used for this work. figure 2: load cell and sensor http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):381-390. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 384 a woody board with the dimension of 100 mm length and 50 mm width was mounted on one side of the sensor, were load or force was applied, while the main side of the load cell was mounted on the base of the entire system. when a force was applied on the load cell (this comprises a metal core and a set of electrical resistances) there was a transformation (this was corroborated by the work done by jazmati (2022). however, the load cell returned to its original state when the force was removed. the accuracy and quality of the load cell was dependent on the reversibility of the material (jazmati, 2022). figure 3 presents the electrical wiring of the load cell. the load cell comprises of four wires, which are: red for excitation (+), black for excitation (-), white for output (-), green for output (+). figure 3: load cell wiring (jazmati, 2022). the output signal produced by the load cell was in the range of millivolts, therefore, there was a need for an amplifier to convert the signal into a level that can be transformed into digital signal and then process it. for this purpose, hx711 amplifier sensor was employed. the hx711 amplifier sensor includes hx711 chip with analog-to-digital conversion capability in 24-bit accuracy. the hx711 module amplified the low-voltage output of the load cell and sends it to the arduino (the arduino eventually calculated the weight from this data/information). a pictorial view of the hx711 amplifier used is shown in figure 4. figure 4: pictorial view of hx711 amplifier file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng ekpu and ayomide: design, construction and testing of a weighing equipment for powdered food products. azojete, 19(2):381-390. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 385 2.1.3. microcontroller (arduino nano) the arduino-nano board used in this work contain the atmega 328 p microcontroller. the arduino nano is a microcontroller board designed by arduino, which operates on 5 v and consists of 28 pins. it has a wide range of applications and is a major microcontroller board because of its small size and flexibility. a pin configuration of arduino nano chip board used in this work is presented in figure 5. the memories (capacity) embedded in the arduino nano chip board include: a flash memory of 32 kb, static random access memory (sram) of the microcontroller board is 8 kb, electrically erasable programmable read-only memory (eeprom) is 1 kb, and it has a preinstalled bootloader on it, which takes a flash memory of 2 kb. the circuit diagram of the arduino nano device used in this work is presented in figure 6. figure 5: pin configuration of arduino nano figure 6: circuit diagram of arduino nano device http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):381-390. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 386 2.1.4. liquid crystal display (lcd) it is an electronic display module used in an extensive range of applications like mobile phones, calculators, computers, television sets, etc. these displays are mainly preferred for multisegment light-emitting diodes (led). the reason for using this module in this work was because it was inexpensive, easy to program, animations were possible, and there were no limitations on the display of custom characters. table 1 presents the pin number description of the lcd circuit diagram of the arduino nano device shown in figure 6. table 1: pin connection description of the lcd circuit diagram 2.1.5. stepper motor and driver the stepper motor used in this work is nema17 and the driver is l298n. this driver board is usually used to control dc motors, but it was an economical alternative to control stepper motors. it can control both the speed and the spinning direction of most stepper motors like a nema 17 (this was why it was employed in this work). the l298n motor driver board was built around the l298 dual full-bridge driver, made by stmicroelectronics. with this motor driver you can control dc motors, stepper motors, relays, and solenoids. it came with two separate channels, called a and b, that can be used to drive two (2) dc motors, or one (1) stepper motor when combined. the l298n was mounted on a (red) breakout board, which made wiring a lot easier. the breakout board included a 78m05 5 v power regulator. figure 7 shows the connection of nema 17 stepper motor and l298 driver with the arduino nano device. pin no symbol description 1 vss gnd 2 vdd vcc 3 v0 through 1 k resistor to gnd 4 rs arduino digital pin 8 5 rw gnd 6 e arduino digital pin 9 11 d4 arduino analog pin a2 12 d5 arduino analog pin a3 13 d6 arduino analog pin a4 14 d7 arduino analog pin a5 15 a gnd 16 k through 1k resistor to vcc file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng ekpu and ayomide: design, construction and testing of a weighing equipment for powdered food products. azojete, 19(2):381-390. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 387 figure 7: circuit connection of stepper motor and l298 driver with arduino nano device 2.2. methods the equipment is based on microcontroller and load cell. a program was developed to interface the analogue to digital converter (adc) with the microcontroller to implement the analogue to digital conversion. in addition, a signal conditioning circuitry was designed and built for the load cell output. the weighing equipment consists of a hopper which is used to store the material (powder) for dispensing. the input was carried out with buttons and the corresponding values displayed on the lcd screen. the filling process was controlled by the use of stepper motors. the stepper motor was used because of stable speed control (with fluctuating load) and constant torque (over a range of speed). the contents dispensed from the hopper filled the holding container (this was corroborated by the work published by abdallah and elmessery, 2018). the weighing and filling equipment was powered by a single phase, 220 v – 230 v a.c power supply. it was operated either with a single phase generator or from a mains supply. the frame was rectangular in shape and was made from a 3.0 mm thick steel. it has a dimension of 914.4 mm (3 ft) height and 304.8 mm (1 ft) wide. the frame is the main body of the equipment which supports other parts. it has a base sitter were the load cell and stepper were mounted. under this sitter, leds were installed to give light to the base sitter. while at the top of the frame, the hopper, lcd, buttons and indicator leds were mounted. the design, construction and testing of a weighing equipment for powdered food products in a country such as nigeria cost forty-eight thousand naira (n48,000.00). this is about one hundred and fifteen us dollars ($103. 98) as at march 2023 (from oanda.com website). 2.3. principle of operation of the developed equipment when the switch was turned on, the system displayed some basic function on the liquid crystal display (lcd). the equipment continued to boot until the fan, proximity sensor, the base light and the load cell were ready for use. after this process, the stepper motor was turned on and off and then operations such as set value, counter and the current weight was carried out. it is important to note that before the value was set, the product (powder) was already loaded in the hopper. the set value was in kilogram (kg), but the counter was in gram (g) and the overall http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):381-390. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 388 weight was in kilogram (kg). when the set value was put at 1.00 kg (1000g) and the start key was pressed/activated, the equipment checked if there was a container positioned to receive the product. when a container was not available, the equipment did not execute the required operation until a container was made available. furthermore, when a container was positioned and the start button was pressed, the filling process was engaged by turning on the stepper motor. at this time, the counter value began to increase, indicating that the equipment was working. the filling process stopped when the set value of 1.00 kg was reached, and the counter value was at 1000 g. therefore, the overall weight of the product measured was 1.00 kg. this process was repeated for other weight ranges and resulting product compared with a digital scale. 3. results and discussion the results from the developed equipment are presented in section 3.1. 3.1. effect of powder filling on the weighing system the mass (kg) of a powder was weighed by the developed equipment and recorded at different time intervals. while the corresponding powder product weighed from the developed equipment was weighed by a digital scale and recorded accordingly. figure 8, presents the plot of the powder mass (kg) at different time (s) intervals for both the developed weighing equipment and digital scale. figure 8: a graph of mass of powder (kg) against time (s) it is observed that at 300 s, a mass of 4.82 kg of the powder was measured by the developed weighing equipment. when the corresponding powder product was weighed by a digital scale, the reading given was 5.12 kg. this gives a percentage difference of 5.9%, meaning that the accuracy of the weighing systems is about 94.1 %. the implication of this result is that, for every 4.82 kg of powder weighed by the developed equipment there is a savings of about 0.30 kg. further analysis shows that there is a linear relationship between the mass of the powder weighed and the time it takes to weigh the powder. the average percentage difference from the data analysed is given as 5.06% (or 94.94% average accuracy). this is an average savings of about 0.150 kg of powder by the developed weighing equipment. the percentage of the mass difference between the digital scale and the developed weighing equipment is presented in figure 9. 0 1 2 3 4 5 6 0 50 100 150 200 250 300 350 m as s o f p o w d er ( kg ) time (s) equipment digital scale file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng ekpu and ayomide: design, construction and testing of a weighing equipment for powdered food products. azojete, 19(2):381-390. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 389 figure 9: a graph of mass difference in percentage at various time intervals it is observed that as the time increases the percentage difference increases. meaning that, the longer the developed weighing equipment is put in use, the increase in powder savings. in addition, the percentage difference is quite minimal and the developed weighing equipment can be said to have approximately 95% accuracy on the average. this device will be valuable to small scale businesses in third world countries. 4. conclusion low cost weighing equipment which can be used for filling and weighing was developed. the operation of this equipment is simple and the chance of error in weight calculation is significantly reduced to about 5.06%. therefore, the effort required for the manual weighing and filling is highly minimized. weight calculation is done using the load cell. the task the operator has to perform is to give the input value and collect the container/bag after the process is concluded. the developed equipment has an average accuracy of approximately 95%. the developed weighing equipment will be beneficial to small scale businesses in third world countries. reference abdallah, se. and elmessery, wm. 2018. an innovative low-cost automatic prototype for fruits and vegetables weight basis packaging. misr journal of agricultural engineering, 35(1): 169–198. abueejela, ym. and belkasem, ak. 2018. inspection, packaging and packing machine development based plc. libyan international conference on electrical engineering and technologies (liceet2018) 3–7 march, tripoli–libya. jazmati, a. 2022. plant monitoring and watering system using hexabitz. available online: https://www.hackster.io/aula-jazmati/plant-monitoring-and-watering-system-using-hexabitze38827 accessed on 24 july, 2022. morris, as. 2001. measurement and instrumentation principles. 3rd ed. elsevier publishers, amsterdam.. mushiri, t. and mbohwa, c. 2015. design of a small scale cereal packaging machine suitable for developing countries. international conference on operations excellence and service engineering, september 10-11, orlando, florida, usa. 0 1 2 3 4 5 6 7 0 60 120 180 240 300 m as s d if fe re n ce ( % ) time (s) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng https://www.hackster.io/aula-jazmati/plant-monitoring-and-watering-system-using-hexabitz-e38827 https://www.hackster.io/aula-jazmati/plant-monitoring-and-watering-system-using-hexabitz-e38827 arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):381-390. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ekpum@delsu.edu.ng 390 pinto, j. 2012a. an open source bathroom scale with bluetooth communication to android smart phones. available online: https://code.google.com/archive/p/casainhoprojects/wikis/smartscale.wiki accessed on 13 july, 2022. pinto, j. 2012b. digital bathroom scale which logs weight and data on sd card. available online: https://www.eeweb.com/digital-bathroom-scale-with-sd-memory-card/ accessed on 13 july, 2022. raza, sa. and turiac, m. 2016. joint optimal determination of process mean, production quantity, pricing, and market segmentation with demand leakage. european journal of operational research, 249(1): 312-326. satish, mk. and vanaraj, bv. 2012. design and implementation of high precision advanced weighing machine with tft panel. international journal of engineering research & technology (ijert), 01(08): 1-7 shigwan, a., shirke, p., ukarde, s., salaskar, p. and bhurshe, g. 2016. automatic packaging control machine. international journal for scientific research & development, 4(2): 794-795 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ekpum@delsu.edu.ng https://code.google.com/archive/p/casainho-projects/wikis/smartscale.wiki https://code.google.com/archive/p/casainho-projects/wikis/smartscale.wiki https://www.eeweb.com/digital-bathroom-scale-with-sd-memory-card/ arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):183-196 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 183 original research article design, analysis and construction of an impressed current electric device for cathodic protection a. a. hammajam*, m. a. ibrahim and m. k. adam department of mechanical engineering, university of maiduguri, p.m.b 1069, maiduguri, nigeria *corresponding author’s email address: hammajam92@gmail.com 1.0 introduction the first application of cathodic protection (cp) can be traced back to 1824, when sir humphry davy, in a project financed by the british navy, succeeded in protecting copper sheathing against corrosion from sea water by the used of iron anodes (gerrard, 1962). davy found out that he could preserve copper components in sea faring vessels by attaching them to thin layers of iron, zinc or tin. the copper became, as davy puts it "cathodcally protected". this technique was later abandoned because, by protecting the copper, its antifouling properties became retarded, hence reducing the streamline of the ships, as they began to collect deposits of unwanted materials. in offshore structures, khazreai (2006) reviewed the application of aluminum (al) and aluminum-zinc (al-zn) alloys anode to be more desirable than the other sacrificial anode. it was also observed and found that titanium anode coated by layers of precious metals is a suitable anode for the impressed current method. also steel that are used in construction of platform in particular in high stress area will be of a type that will not be susceptible to hydrogen embitterment if excess cp is applied. in view of the above, cathodic protection is a means of preventing corrosion by applying a flow of electrical current from an external source (anode) through the environment and to the metallic structure that is being protected (brousseau, 1992). these protective current changes the environment around the metal thus halting the corrosion reaction. when properly designed and applied, cathodic protection systems stop the corrosion process. cp is used to prevent corrosion in a wide range of applications where the structure being protected is surrounded by an environment that allows current flow. basically, the protective measure adopted in corrosion control are article information abstract this paper aimed at designing, analyzing and fabricating an impressed current electric device. cathodic protection is a means to prevent corrosion by applying a flow of electrical current from an external source (anode) through the environment and to the metallic structure that is being protected. the protective current changes the environment around the metal thus halting the corrosion reaction. cathodic protection is used to prevent corrosion in a wide range of applications where the structure being protected is surrounded by an environment that allows current flow. the impressed current cathodic protection systems have the benefit of using an external power supply to drive current. the study used sea water as electrolyte with locally constructed transformer rectifier and to select a proper material for the construction so as to illustrate the effect and how the impressed current system functions. the general performance evaluation was found that the device has a net driving potential of 10.5v and a life expectancy of 128 years of the anode. in conclusion, the construction was successful and easy to operate which can be used to protect metal structure against corrosion. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 september, 2021 revised 19 october, 2021 accepted 25 october, 2021 keywords: corrosion cathodic protection rectifier design electrical machine http://www.azojete.com.ng/ mailto:hammajam92@gmail.com hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 184 divided into three, namely, insulating coating (passive), cp (active), and most recently anodic protection (callister, 2014). 1.1 cathodic protection cp is an electrochemical process in which the entire steel pipe surface is made cathode by injecting a direct current (dc) into the ground bed at suitable location. "in theory a property designed, installed and operated cp system will eliminate all the anodic regions which exist on a metal by passing direct current to the material surface" (peabody, 1978). whatever the intrinsic quality of coating and however carefully applied, it will always have defects and it will never by itself completely prevent corrosion. in fact, corrosion becomes concentrated in the defects; crevice, cracks and pinholes that are present in coating. as a result coating requires supplementary (cp), which is an electrical technique for imposing potentials on the protected pipeline to counter the tendencies for electrochemical ion migration and stops corrosion almost completely (jacques, 1984). the principles of cathodic protection: metals extracted from their primary areas, has the tendency to revert back to its natural state under the action of water and oxygen. therefore, the principle of cp is in connecting an external anode to the metal to be protected and passing electric (dc) so that the areas of the metal surface become cathodic and, therefore, do not corrode. the external anode may be a galvanic anode, where the current is the result of potential difference between the two metals, or it may be an impressed current anode, where the current is impressed from an external dc power source (donald, 2010; schweizer, 1998). 1.2 cathodic protection system there are basically two types of cp systems: galvanic (sacrificial) anode system and impressed current system. i. galvanic (sacrificial) anode system the figure 1 illustrates the utilization of a metal (anode), which is normally more electronegative (magnesium, zinc and aluminium) than the metal (cathode) being protected (mild steel or carbon steel). current streams from the metal that are more electrically negative to the metal that is more electrically positive (denison, 1974). this current stream brings about a fast utilization of the anode. in sacp the voltage difference is limited to anode and cathode, usually 1 volt or less, contingent upon the anode material and the environment. oxidation and reduction reaction takes place at anode and cathode respectively (wulpi, 1999). figure 1 shows the schematic diagram of sacrificial anode method. . electrolyte (soil) flow of electrons sacrificial anode (a) positive current flow protected structure a a n+ n+ ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com hammajam et al: design, analysis and construction of an impressed current electric device for cathodic protection. azojete, 18(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 185 electrolyte (soil) flow of electrons sacrificial anode (a) positive current flow protected structure a a n+ n+ figure 1. schematic of sacrificial anode cp method as a result of potential difference, electric current will flow from the anode through a metallic connection between the anode and the structure. ii. impressed current cathodic protection system this system is comprised of an external dc power source, an auxiliary or impressed current electrode, the corrosive solution and the structure to be protected. the dc power source delivers positive current from the impressed current electrode on to the structure (being protected) through the corrosive solution. the structure is cathodically polarized (its potential is lowered) and the positive current returns through the circuit to the dc power supply, as shown in figure 2. electrolyte (soil) dc power source impressed current anode in ground bed positive current flow(ionic) protected structure a a n+ n+ + electron flow figure 2. schematic of impressed current cathodic protection method (michael et al., 2012) in one industrial area containing a high density of protected underground structures, protective current requirements rapidly rose to 20 ma/m2 in several areas. the solution to this problem is cooperation between operators. for example, the stray-current problem could be prevented by electrically connecting the pipe by a bus connector and rearranging anodes. cathodic protection involving impressed current anodes to reduce highway and other bridge maintenance costs is being done and substantial savings realized. corrosion of the reinforcing http://www.azojete.com.ng/ mailto:hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 186 steel is reduced. cathodic protection is still more of an art than a science, and past experience is the best basis for judgment. this remark was made by a corrosion engineer who retired after 30 years of experience, mostly on cathodic protection of pipelines. there are many firms in the cathodic-protection business, and they should be consulted if you have a major project. 1.3 design theory and methodology the purpose of the design theory is to give an experience investigator enough information to replicate the study. a design theory is used to structure the design and to show how all of the major part of the design project, including the sample, measures and method of assignment, work together to address the central design question in the study. based on documentation of the actual structures the total surface area of pipe to be protected shall be calculated. figure 3 shows the circular object of pipe to be protected which requires only two views with dimension. assuming that the total surface area of the pipe to be protected (atp) is given by; atp = 2π (h+r) (1) figure: 3 dimension of pipe to be protected total area of the aluminium anode, ata is giving by the equation ata = 2as1 + as2 (2) where: as1 = surface area of the circle; is given by πr2 as2 = surface of area of the cylindrical part; is given by 2πr (h+r) figure 4 show the circular views of aluminium anode with it dimensions requiring only two views. figure 4: circular view of the aluminium anode design methodology refers to the development of a system or method for a unique situation. the key to design methodology is finding the best solution for each design situation whether it can be in industrial design, architecture or technology. 1.4.1 cathodic protection design the design sequence started after collection of all preliminary data and estimated protective current. the first question to ask is: which type (galvanic or impressed current) cathodic protection system is needed? conditions at the site sometimes dictate the choice. however, .h d2 d1 .h d2 ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com hammajam et al: design, analysis and construction of an impressed current electric device for cathodic protection. azojete, 18(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 187 when this is not clear, the criterion used most widely is based on current density required and soil resistivity. if the soil resistivity is low (less than 5000 ohm-centimeters) and the current density requirement is low (less than 1 milliampere per square foot), a galvanic system can be used. however, if the soil resistivity and/or current density requirement exceed the above values, an impressed current system should be used. thirteen steps are required when designing impressed current cathodic protection systems (astm d2000). 1. the review soil of resistivity. as with galvanic systems, this information will contribute to both design calculations and location of anode ground bed. 2. the required current requirement test to be used throughout the design calculations was reviewed 3. the selection of anode. when impressed current-type cathodic protection systems are used to mitigate corrosion on an underground steel structure, the auxiliary anodes often are surrounded by a carbonaceous backfill. backfill materials commonly used include aluminum, coal coke, and natural graphite particles. 4. the number of anodes needed to satisfy manufacture’s current density limitations was calculated. impressed current anodes were supplied with a recommended maximum current density. higher current densities will reduce anode life. to determine the number of anodes needed to meet the current density limitations, (talbot and talbot, 1998) equation was used. , (3) where: n = number of anodes required, i1 = total protection current in milliamperes, a = anode surface area in square feet per anode, i = maximum current density output in milliamperes. 5. calculate number of anodes needed to meet design life requirement. equation 4 is used to find the number of anodes: (4) where: n = number of anodes, l = life in years, and w = weight of one anode in pounds. 6. calculate number of anodes needed to meet maximum anode ground bed resistance requirements. equation 5 is used to calculate the number of anodes required: (5) 7. the numbers of anodes to be used were selected. the highest number calculated by equation 3, 4 or 5 will be the number of anodes used. the area for placement of anode bed was selected. the area with the lowest soil resistivity was chosen to minimize anode-to-electrolyte resistance. 8. the determination of total circuit resistance. the total circuit resistance used to calculate the rectifier size needed were also outlined. 9. the calculated rectifier voltage. equation 6 is used to determine voltage output (vrec) of the rectifier: (6) where i = total protection current in amperes, rt = total circuit resistance, 150% = factor to allow for aging of the rectifier stacks. http://www.azojete.com.ng/ mailto:hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 188 10. the selection of a rectifier. a rectifier has been chosen based on the results of eqn. 6 the calculation of system cost. as with the galvanic cp system, the choice of anode for design calculation is almost arbitrary. several anodes have been used in the design calculations, an economic analysis. 1.4.2 design parameters and analysis the data below were used for component sizing and analysis. h = 520mm = 0.52m; r2 = d2/2 = 25/2 = 12.5mm = 0.0125m r1 = d1/2 = 21/2 = 10.5mm = 0.0105m using equation 1 atp = 2πr2 (h+r2); atp = 2 x 3.142 x 0.0125 (0.5+0.0125); atp = 0.04m2 therefore, the total surface area of a steel pipe atp = 0.04m2 total area of aluminium anode is obtained using equation 2 ata = 2as1 + as2 = 2(πr2) + 2πr (h+r) ata = 2(π x0.021/2)2 + 2π(0.021/2) x (0.2 + 0.021/2); ata = 0.14m2 the current density can be obtained, for sea water from typical current density requirement of cathodic protection of uncoated steel. assume current density i’ = 20ma per square meter. the total protective current (i) can be calculated using the equation below i = (atp) (i’); where atp = 0.04m2; i = (0.4304) (20) = 8.61ma the total resistance (rt) = ∆e/i where ∆e is the net driving potential of aluminium anode = 0.25 to 0.50v as obtained from the standard. thus, assuming the net driving potential ∆e = 0.50v rt = 0.50/8.61 x 0.001 = 58.07ω the rectified voltage (vrec) is obtained from equation 6 and given by vrec = (i) (rt) (150%) vrec = (8.61 x 0.001) (58.07) (150/100) = 0.75v for the power supply using equation vrms = vs x (7) where vs is the selected d.c voltage for the device = 12v vrms = 12 x = 16.9v the d.c voltage is obtained from equation vdc = 2vrms/π = 2 x 16.9/3.142; vdc = 10.75v (8) using equation 9 to calculate the form factor (ff) ff = vrms/vdc = 16.9/10.75; ff = 1.572v (9) therefore, the ripple factor (rf) can be calculated using equation rf = (10) for the peak to peak ripple, regulated voltage (vr) is calculated using equation vr = i/fc (11) where i is the load current = 8.61ma; f is the frequency = 100hz; c is the capacitance = 470µf ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com hammajam et al: design, analysis and construction of an impressed current electric device for cathodic protection. azojete, 18(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 189 vr = 8.61 x 0.001/100 x 470 x 10-6 = 0.183; therefore, vr = 0.183 x 100vpp = 18.32vpp for the peak reversed voltage (vpr), it can be calculated using equation vpr = 2vrms = 2 x 16.9 = 33.8v (12) finally, the life expectancy of aluminium anode for the design can be calculated using equation 4. l = where n is the number of anode = 1; w is the anode weight in pounds = 0.5kg = 1.105lb i is the design current = 8.61ma; l is the life expectancy of an anode in years l = = 128 years 2. manufacturing procedures step 1: the rectangular box was developed and produced with dotted lines indicating the position of the shape to be bent. step 2: the development was cut out from a brass sheet metal and all corners notches. step 3: the edges of the dotted lines was bent using hatchet stake and iron. the sides were bent up using bending machine as shown in figure 5. figure 5. the casing step 4: a length of angle brass was produced and cut to a dimension (table 1) using grinding machine. a hole of dimension was drilled at the end of the cut iron as shown in figure 6. step 5: the angular brass was fastened to the developed casing as shown in figure 6 and a rectangular brass sheet metal was also cut to a dimension and fastened on the cut angle brass. figure 6. part assembled and angle brass http://www.azojete.com.ng/ mailto:hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 190 step 6: the method of connecting the circuit of the transformer rectifier is shown in fig. 7. figure 7. the circuit and the metering device step 7: finally, transformer rectifier was then, placed on the top metal sheet and terminals was removed so as to provide connections for both the anode and the structure to be protected (cathode) as shown in figure 8 while the 2d orthographic projection of iccp device is shown in figures 9a and 9b. figure 8. general part assembled ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com hammajam et al: design, analysis and construction of an impressed current electric device for cathodic protection. azojete, 18(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 191 figure 9a. 2d orthographic projection of iccp device + figure 9b. 2d orthographic projection of iccp device front view. (all dimensions in mm) 2.1 performance evaluation of designed device in the last few decades, after thorough investigation on cathodic protection, the criteria for cathodic protection have been compiled by national association of corrosion engineers (nace). nace rp-0169-96 specifies; “a negative (cathodic) potential of at least 850mv versus cu/cuso4 should be applied to protect any corroding structure” (onyechi, et al 2014). thus, + http://www.azojete.com.ng/ mailto:hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 192 in the presence of sulfides, bacteria, elevated temperatures, acid environment and dissimilar metals, the criteria of -850mv may not be sufficient. accordingly, researcher should also take into account the ir drop at the metal/soil interface, which is included in most practical measurements; it is of uncertain value, depending on the electrolyte (soil) resistance. for other metals such as aluminum and copper piping, ncae rp-0169-96 suggests a minimum of 100mv cathodic polarization between the structure surface and a stable reference electrolyte contacting the electrolyte. similar findings were reported by onyechi et al. (2014). the 3-d diagram of the system is presented in figure 10. + figure 10. 3d model of impressed current electric device the investigations were carried out at chevron pipeline system, of nigeria, western division. the studies were centered on the evaluation of the cathodic protection of pipelines with emphasis on the trans-niger pipelines (tnp). due to the fact that other oil companies operate in the area, there are presences of shell, agip (naoc), and elf pipelines which interface across one another manifold. thus there are also presences of nigeria national petroleum corporation (nnpc). the study involved, onsite to and monitoring of cp operations at rumuekpe manifold, where the spdc, elf and agip pipelines cross each other. this manifold receives crude oil from assa-egbema, as well as adibawa oil wells. the tnp lines from this manifold are 14inch, 20inch, 28inch, and 36inch pipelines respectively. another location visited was the ibaa manifold, which uses solar power as its source of electricity for the cp. also visited was the agbada manifold. there are the agbada i and agbada ii locations which have flow stations. the monitoring and subsequent evaluation of the cp performance on these pipelines was undertaken through these processes: (a) the pipe-to-soil potential measurement (cips) (b) the on/off pipe-to-soil potential measurement (c) electrical interference evaluation (d) sacrificial anode installation. table 1 below show the data from the performance evaluation which when compare to the standard values in table 3 has significant indicator of good attributes. ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com hammajam et al: design, analysis and construction of an impressed current electric device for cathodic protection. azojete, 18(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 193 table 1: typical current density requirements for cathodic protection of uncoated steel from onsite field data 3. results and discussion this study shows some great difference when compared to initial system of preventing corrosion using the impressed current system with aluminium anode and salt water instead of the sacrificial system with magnesium anode. the installation of impressed current system with aluminium anode was very easy with little effort applied while providing suitable working to the device without any regulation. for the constructed impressed current electric device, it is observed that the aluminium anode employed also facilitates the flow of electrons to the cathode (structure to be protected), thereby increasing the life expectancy of the structure. the device was tested and was observed to overcome the structure length of 600mm and 30mm diameter respectively. table 2 below shows the dimension of the pipe to be protected and the aluminium anode. table 2: dimension of the pipe to be protected and aluminium anode material length (mm) diameter d1 (mm) diameter d2 (mm) steel pipe 520 30 25 aluminium anode 200 21 17 the current requirements also can be estimated from table 3. the table gives an estimate of current, in milliamperes per square meter, required for complete cp that value, multiplied by the surface area of the structure to be protected (in square meter) gives the total estimated current required. caution should be used when estimating, however, as underor overprotection may result. s/n environment current density (ma/m2) afm 88-9a gerrard (1962), b 1. neutral soil 0.3 to 1.3 0.3 to 1.3 2. well aerated neutral soil 2 to 3 2 to 3 3. wet soil 1 to 4 2.2 to 5 4. highly acidic soil 2.2 to 12 3.2 to 12 5. soil supporting active sulphatereducing bacteria 6 to 39 up to 39 6. heated soil 2 to 20 3 to 21 7. stationary fresh water 0.7 to 5.5 4.8 8. moving fresh water containing dissolved oxygen 4.5 to 13.5 4.5 to 13.5 9. sea water 2.7 to 9.5 5 to 23 http://www.azojete.com.ng/ mailto:hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 194 table 3: typical current density requirements for cathodic protection of uncoated steel (adopted from army t.m air force afm 88-9) the total protective current (i) was obtained as 8.61ma from the calculation when the current density was assumed to be 20ma per square feet. the total resistance (rt) was calculated as 58.07ω as the maximum resistance of the system when the net driving potential (∆e) was assumed to be 0.50v. the calculated value of the d.c voltage (vdc) was 10.75v and regulated to 10v but the measured value indicated 10.5v on the multimeter. this little deviation from the calculated value may be accounted due to physical changes in temperature or tolerance, limit of discrete component like variable resistors and capacitors. the form factor (ff) of 1.572 and ripple factor (rf) of 1.21 are set to be within the specification limit. the peak to peak ripple factor (vr) of 0.183 (i.e. 18.3%) is said to conform to the standard because it is below 50%. eventually, with peak reverse voltage (vpr) of 33.8v implies that the device will fail when vpr is greater than the stated value of 33.8v. 3.1 corrosion rate figure 11 illustrates the effect of corrosion rate of low carbon steel in 1 m hcl solution. from the result, the rate of corrosion increase with an increase in all concentrations except for 500 ppm which decreases indicating that at this ratio the extract was able to be absorbed by the surface of the low carbon steel at 192 hrs of the experiment. generally, it can be observed that the corrosion rate is significantly decreased after 192 hrs except for 500 ppm which later decreased at 312 ppm. moreover, it could be observed that the corrosion rate was gradual for all level of the concentration used. equally, the un-inhibited low carbon steel specimen demonstrated to be the least protected expectedly. on the other hand, the corrosion rate decreased with an increase in inhibitor concentration as observed. s/n environment current density (ma/m2) afm 88-9a gerrard (1962), b 10. neutral soil 0.4 to 1.5 0.4 to 1.5 11. well aerated neutral soil 2 to 3 2 to 3 12. wet soil 1 to 6 2.5 to 6 13. highly acidic soil 3 to 15 5 to 15 14. soil supporting active sulphatereducing bacteria 6 to 42 up to 42 15. heated soil 3 to 25 5 to 25 16. stationary fresh water 1 to 6 5 17. moving fresh water containing dissolved oxygen 5 to 15 5 to 15 18. sea water 3 to 10 5 to 25 ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com hammajam et al: design, analysis and construction of an impressed current electric device for cathodic protection. azojete, 18(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 195 figure 11: variation of corrosion rate (mm/yr) against exposure time (hr) of low carbon steel in 1 m hci at different concentration of leaves extracts on cathodic impress device 4. conclusion an impressed current electric device designed in its simple and portable form. in conclusion, the construction was successful and easy to operate which can be used to protect metal structure against corrosion. the performance evaluation was carried out, it has been found that the device has a net driving potential of 10.5v and a life expectancy of 128 years of the anode. its construction can be improved upon by subsequent researchers. its financial consideration for production is moderate. reference ashby, mf. 2005, materials selection in mechanical design 3rd ed. amsterdam: elsevier publishers, pp.309-317. asm handbook, 2000, vol.8. mechanical testing and evaluation, asm international, usa, pp.443-449. brousseau, r. 1992. cathodic protection for steel reinforcement. irc (nrc canada) publication, 1992. 2nd edition, pp.209-213. callister, dc. jr. 2014. materials science and engineering, 5th ed. new york: wiley and sons, pp. 221-225. denison, ia. 1974. contribution of sir humphry davy to cathodic protection, corrosion, 3(6): 295 – 298. donald, ra. 2010. the science and engineering of materials. 6th edition.new york, usa;. pp. 27. gerrard, js. 1962. practical applications of cathodic protection. corrosion, vol 2 (ll. shreir, ed), nownes-butterworths, london, pp.11. jacques, louis vincent-genod 1984. fundamentals of pipeline engineering. 2nd edition.inc. uk, pp.612-620. http://www.azojete.com.ng/ mailto:hammajam92@gmail.com galley proof arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hammajam92@gmail.com 196 khazreai, ma. 2006. short history of cathodic protection for fixed offshore structure. the journal of corrosion science and engineering, 9: 47. michael, j. schofield, alan, d. mcnaught and andrew wilkinson; 2012. engineering corrosion of chemical terminology: iupac recommendations. https://www.goldbook.iupac.org. saleh, ra. badrkhani, o., shahrabi t.; 2000. different parameters for designing cathodic protection system for offshore structures; journal of zang, 7(5), pp. 87-94. schweizer, pa. 1998. encyclopedia of corrosion technology, marcel dekker, new york city, usa, pp. 1021-1031. onyechi, pc., obuka, nnaemeka sp., agbo, cornelius, o., and igwegbe, ca., 2014. monitoring and evaluation of cathodic protection performance for oil and gas pipeline: a nigerian situation. international journal of advanced scientific and technical research. issue 4 volume 1, issn 22499954. pp47-65. peabody, aw., 2000. control of pipeline corrosion; nace, texas; 1978. official methods of analysis, 4th editions, texas, usa, pp.24. talbot, d., and talbot, j. 1997, corrosion science and technology crc press,boca raton, florida usa, pp. 490-499. theraja, bl., theraja, ak.; 2000. a to l book of electrical technology; schand & company ltd; 2000; newyork, usa, chapter 4, pp. 68. wulpi, dj., 2017. understanding how components fail, 2nd edition. asm international, fort wayne, indiana, usa; pp. 99-107 ../../../../../../../../user/downloads/azojete143/www.azojete.com.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):509-518 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 509 original research article modification and performance evaluation of a fish feed pelletizing machine g. s. malgwi, s. a. abdulkadir* and s. m. dodo deparment of agricultural and bioenvironmental engineering, adamawa state polytechnic yola, pmb 2146 yola adamawa state, nigeria. *corresponding author’s email address: salihuabdu110@yahoo.com 1.0 introduction aquaculture is fast developing in nigeria, though the yields obtained from the fish farms are still insufficient. the low yield has been attributed to inadequate supply of balanced fish diets (faturoti and akinbote, 1986; gabriel et al., 2007; galen et al., 2008). now, only few organizations are engaged potential feed manufacturing in the country and it is still not possible to meet the large potential demands for feeds. however, there is a large potential of feed ingredients from local plant and animal waste sources, which are capable of supplying the nutritive requirement of fish (mercier, 1980). pellet presses for the production of fish feed was first introduced in the mid-1920, (mcellhiney, 1987). since then, production and demand for pelletized feeds for fish has grown until now. over 98 percent of all fish feeds are fed in pelletized form in europe and north america. (diarra et al., 2001; booth et al., 2002 and eyo, 2002). yet, the demand and production of pelletized feeds for fish are high in many african countries, in spite of the known feeding and handling advantages of pelletized feeds (anon et al., 1991; fao 2000; burmamu et al., 2015 and heuzé et al., 2015). a pelletizer consists of a screw pump similar to a screw press or screw conveyor in which feed is compressed and worked to form a semi-solid mass (mercier, 1980; ikedudu et al., 2015). the feed is forced through a restricted opening (the die) at the discharge end of the screw. fish feed technology is one of the least developed sectors of aquaculture particularly in africa and other developing countries of the world. it is one of the fundamental challenges facing the development and growth of aquaculture in african. fish feed development in sub-saharan african has not made any significant progress in aquaculture as expected. it has been observed that the research on inexpensive feed ingredients have not contributed meaningfully to aquaculture development in africa and suggested that more researches on how best plants proteins can be used, as fish feeds are required. development and management of feed play very vital role in aqua cultural growth and expansion. in fact, a major factor that determines the profitability of aquaculture venture. feed article information abstract a hand operated fish feed pelletizing machine for the production of fish feed with through put capacity of 2.56 kg/h was modified, fabricated and evaluated due to non-availability of electricity in the rural area, drudgery and low throughput capacity. it consists of a hopper, barrel that houses the screw conveyor (auger), the cutting knife, and the die orifice. power supply to the machine is a 6-kw petrol engine. it was observed that the pelletizing efficiency and throughput capacity increase with proportionality of smallness of die diameter. the modified machine test results showed highest throughput capacity of 162.8 kg/h with maximum pelletizing efficiency of 85.3%. the total production capacity of the machine was 150 tons per day, which is adequately to feed up to 3,000 fish per day. the adoption of the pelletizing machine by farmers will enable them produce their own feed from local plant and animal waste source thereby alleviating the problems associated with the sourcing of imported feeds. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 feb., 2019 revised 11 may, 2020 accepted 20 may, 2020 keywords: fish feed pelletizing die diameter throughput mailto:salihuabdu110@yahoo.com http://www.azojete.com.ng malgwi et al.: modification and performance evaluation of a fish feed pelletizing machine. azojete,16(3):509-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 510 accounts for at least 60% of the total cost of fish production in africa and this largely, determines the viability and profitability of the fish farming enterprise, (orimaye et al., 2019; regupathi, 2019). as aquaculture becomes intensive, most farmers in, africa and nigeria inclusive depend largely on imported fish feeds. according to (harper, 1989; del valle and aguilera, 1991), factors that influence the nature of the pelletized product are the operating condition of the machine such as the temperature, pressure, diameter of the die aperture and the shear stress. others includes the rheological properties of the feed components such as moisture content; the physical state of the materials used; and their chemical composition, particularly the amount and type of starches. protein and fats content also are factors that influence the nature of the pelletize produce. leakage flow, which is similar to pressure flow, which was driven by a pressure gradient. this flow occurs in the clearance between the screw flights and the barrel within any slot in the barrel wall or surfaces and can as well affect the nature of the pelletize products. from preliminary investigation, there are some existing manually (hand operated) feed pelletizing machines. however, these machines have the following limitations: low efficiency because of low speed from hand auger driven, and rapid wear and tear of the auger shaft, (adapa et al., 2002; el-nono, 2005; amadi, 2007) and wobbling of shaft. therefore, this study presents a modification of hand-operated pelletizing machine. its throughput capacity was increased and its efficiency evaluated. 2.0 materials and method 2.1 materials all the materials for the modification of the pelletizing machine were sourced locally. materials used in the construction of the pelletizing machine incudes: metal sheet, angle iron bars, pulleys, belts and prime mover. 2.2 design considerations the following factors were put into considerations in carrying out the modification; weight of the machine, physical characteristics of the feed materials (rolling resistance, friction), screw auger speed, prime mover power output and the fabrication materials selection as reported by (harper, 1989; abubakre, 2014; ambalkar 2018). materials selection for modification of pelletizing machine are presented in table 1. table 1: materials selection for modification of pelletizing machine sn machine component materials factor reason for selection 1 hopper mild steel rigidity cheap available and durable 2 support base mild steel strength strong , cheap and available 3 pulley mild steel strong and tough strong not easily defected 4 shaft stainless rod hard and tough corrosion resistance, strong available and not easily defected 5 auger mild steel strong and ability to withstand impact stress corrosion resistance and strong 6 concave drum mild steel hard and tough very strong and corrosion resistance. 2.2 design calculations the following design calculations for the various components of the pelletizing machine were considered and carried out as reported by (harper, 1989; veronica, 2018). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 509-518. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 511 2.2.1 power required by the screw auger the power (p) required in operating the screw auger was computed using equation expressed by (harper, 1989) as: p = 0.7355 clq (1) where: p = power required, kw; c = constant, 0.3; l = length of conveyor, m; q = capacity of screw auger drive (tones/hours) 10kg = 10 1000 = 0.01 t/hr 2.2.2 the drive a v-belt and pulley arrangement was selected to transmit power from the prime mover to the shaft of the machine’s mixing unit. this was because the v-belt drive is flexible, simple to use, and requires low maintenance cost. moreover, the v-belt has the ability to absorb shocks thereby mitigating the effects of vibratory forces. 2.2.3 pulley diameters the diameter of the pulley for the screw auger was calculated using the expression by equation 2 below: d2 = n1d1 n2 (2) where: n1,n2 = speeds of prime mover pulley and mixing auger pulley respectively in rpm; d1d2 = diameters of prime mover pulley and mixing auger pulley respectively, mm. prime mover pulley diameter and auger pulley diameter is 1:2.4 diameter of motor pulley d1 = 103 mm 2.2.4 belt speed the belt speed for the mixer driver was calculated using equation below: v = πd2n2 60 (3) where: v = belt speed, m/s 2.2.5 belt length the relationship below was used in determining the belt length for the mixing drive. t = 2c + 1.5 d1+ d2 + (d1− d1)2 2c (4) where: t =belt length in m c =centre distance between pulleys (m) d1=pitch diameter of driver pulley (m) d2= pitch diameter of driven pulley (m) 2.2.6 number of belt required the number of belt required to transmit the power from the prime mover to the shaft of the mixer auger was computed using the equation file:///c:/users/user/downloads/azojete143/www.azojete.com.ng malgwi et al.: modification and performance evaluation of a fish feed pelletizing machine. azojete,16(3):509-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 512 nb = pd t1 − t2 v (5) where: nb =number of belts; pd= designed power, t1, t2= tensions on the tight side and slack side of the belts, n; v = belt speed rpm 2.2.7 hopper design the hopper is a truncated cone of gravity flow type. the slant height is such that the content of the hopper empties unaided into the palletizing chamber, for dough like material of moisture content higher than 20%, the hopper slant angle between 60º-70º was preferable because of the angle of repose of feed material. it was important to note that pressure is not distributed equally in all directions due to development of arches and the frictional forces between the dough. flow rate was determined by: tb2.5w = f d b (6) where: t = time ion minutes for the flow of 100g of solid b = diameter of orifice in (mm) w = bulk density of materials g/mm3 d = average diameter of particles (mm) 2.2.8 prime mover power requirement power = force ×velocity power = force × screw circumference × rpm w = p × πdn/60 (7) figure 1: isometric view of fish feed pelletizing machine http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 509-518. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 513 figure 2: exploded view drawing of fish feed palletizing machine figure 3: modified fish feed pelletizing machine 2.2.9 screw conveyor the crew conveyor is a worm wound round a cylindrical shaft. the maximum outer diameter of the worm was 78mm to give a clearance between the screw and the barrel. the screw conveyor was carried on a solid shaft of 25mm, which is driven by pulley, figure 2. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng malgwi et al.: modification and performance evaluation of a fish feed pelletizing machine. azojete,16(3):509-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 514 2.2.9 shaft diameter the shaft used in construction of the palletizing machine was classified as transmission shaft. also using the allowable shear stress as 42 mpa, the line shaft is rotating at 400rpm and transmitting 18kw. to find the diameter of the shaft; t = p 60 2πn (8) where: t =transmitting force (n), p = power (w) p = 18 × 103. 60 2π × 400. 430nm or 430 x 103nmm but, t = π 16 × τ × d3430 × 103 = π 16 × 42 × d3430 × 103 16 d = 25.08mm d≃ 25mm 2.3 construction and assembling of component of pelletizing machine construction and fabrication of the pelletizing machine was carried out through various stages and processes, which includes marking and cutting out required dimensions of materials, welding, bore-ring, coupling, filling and painting process. the processes were carried out in stages and gradually. 2.4 machine test and evaluation procedure the machine evaluation procedure used in this study was adopted from (rosen, et al., 1979). compounded fish feed prepared by locally sourced materials was used for the test. the ingredients were soya bean meal, groundnut cake, maize, fishmeal, palm kernel, cottonseed, leguminous crops, green plant meals, and premix. some starch and little water that serve as binders were added to the compounded feed, and it was thoroughly mixed with hand manually. the compounded mix was fed through the machine’s hopper. three worm-like fish pellet die diameters were used. they are the 6mm diameter die (for worm-like feeds for day old to 4 weeks old fish), 10mm diameter die (for worm-liked feeds for 5-11weeks old fish), and 13 mm diameter die (for fish 12 weeks old to harvest time), according to fish farmer’s association annual report, 2019. then the machine was put on. after two minutes, 50 mm length worm-like pellets were produced and cut off. the cutting was done automatically by a cutter at the end of the drum. the machine was working for half an hour after which the products were weighed and the data obtained were analyzed. 2.5 data collection and analysis data were collected to study if there are any significant differences in the fish feed production rate (kg) of the palletizing machine between three worm-like fish pellet die diameters of depth 6mm diameter die, 10mm diameter dies, and 13 mm diameter die. the production rate for each diameter-die test was conducted in six (6) runs to minimize error in results. one-way analysis of variance (anova) was used to analyze the data to test if there were significant or non-significant differences among the production rate of the 6mm, 10mm, and 13mm diameter dies. lsd method of tukey’s means separation method (α < 0.05) was deployed to determine significant differences between the mean production rates per 30 minutes using statistical analysis systems (sas 9.2) 2010 software. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 509-518. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 515 3.0 results and discussion table 1 presents the average values of the production rate of 6mm, 10mm, and 13mm dies as 150.6. kg/h, 140.9 kg/h, and 135.1 kg/h by the pelletizing machine respectively. the length of worm-like feed was 50 mm, extrusion pressure of production for the 6, 10, and 13 mm wormlike pellets were 5.2, 5.9, and 6.9 kn/m2 respectively. the extrusion pressure was observed to have risen with an increase in the drag force when the die diameter decreased. this may be due to frictional force increased with a large contact area of die diameter. table 1: average value of production rate of 6, 10, and 13 mm dies for six (6) trials. worm-like pellet production rate in 30 min 1 2 3 4 5 6 average production rate per 30 min (kg/30 min) average production rate per hour (kg/h) 6 mm die (kg) 7 75.8 76.5 75.2 75.6 74.2 75.3 150.6 10 mm die (kg) 7 69.3 70.7 71.2 69.6 71.5 70.5 140.9 13 mm die (kg) 6 68.2 67.5 66.8 67.7 68.3 67.6 135.1 the design capacity of the screw conveyor for worn-like fish feed production was 162.8 kg/h. however, it was observed that when the machine was operated, actual production was affected by energy losses due to friction. the production capacity losses were 7.4%, 13.4% and 17% for the 6mm, 10mm and 13 mm die pelletizer respectively. the average production rates which were 150.6 kg/h, 140.9 kg/h, and 135.1 kg/h for the 6 mm, 10 mm, and 13 mm die respectively was found to be reduced with increasing die diameter which is in agreement with studies by (schultz, 1990) and (olafsdottir et al., 2000). table 2 shows the result for one-way analysis of variance (anova) to determine if the production rate in the fish feed pelletizing machine was different for worm-like fish pellet die diameters of 6mm, 10mm, and 13 mm diameter die at a production rate of 30 min/kg. the three dies were classified into three groups: 6mm diameter die (for worm-like feeds for day old to 4 weeks old fish), 10mm diameter die (for worm-liked feeds for 5-11weeks old fish), and 13 mm diameter die (for fish 12 weeks old to harvest time), according to fish farmer’s association annual report, 2019. results indicated that there was a statistically significant difference between dies diameter as determined by a one-way anova, f(2, 15) = 145.69, p = .0001. table 2: analysis of variance worm-like pellet production rate in 30 min source df adj ss adj ms f-value p-value die 2 183.023 91.5117 145.69 0.0001 error 15 9.422 0.6281 total 17 192.445 figure 4 presents post-hoc comparison using tukey’s means comparison because one of the mean production rates is different among worm-like fish pellet die diameters of 6 mm, 10 mm, and 13 mm diameter die at a production rate of 30min/kg. the post hoc test means separation is demonstrating that means with the same letters are not significantly different. the 6 mm fish pallet die gave the highest production rate of 150.60 kg/hr. the 13 mm pallet die gave a production rate of 135.1 kg/hr. the letters a,b, and c indicate that none of the mean production rate are equal. we may conclude that the 6mm pallet die will be recommended for fish palletizing operations. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng malgwi et al.: modification and performance evaluation of a fish feed pelletizing machine. azojete,16(3):509-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 516 figure 4: achieved average production rate for different dies. 4.0 conclusion a feed pelletizing machine was modified and evaluated. the modified machine test results showed higher throughput capacity of 162.8 kg/h with maximum efficiency of 85.3%. however, practically only 83% of the production capacity was achieved during the test of the machine because of energy loss due to friction in the die cavities. 5.0 recommendation the following are the recommendations made for further research work; more pellet plate recommended standard die diameter for standard pelletize fish feed should be designed and tested with the machine to further evaluate the effect of the engine speed on the pelletizing efficiency on several plate dies. the effects of the engine speed on the. pelletizing efficiency should further be evaluated. references abubakre, ok., garba, ab. and tukur, h. 2014. design and fabricationof a model feed pelletizer. applied mechanics and materials. trans tech publication, 53(3):64-67. adapa, p., tabil, l., schoenau, g., sokhansanj, s. and bucko, j. 2002. compression and compaction behavior of fractionated alfalfa grinds. asaficsae proceedings no. 2 mbsk, 206p. amadi, b. 2007. fish farming technology: principles and practical. ellis publishers, jos, plateau state, nigeria. ambalkar, pp. 2018 modification, and testing of a pelletizing machine for aqua feed pellets with enhance floatability and water stability. sam higgin bottom university of agriculture, technology and sciences (shuats), allahabad, india http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 509-518. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 517 anon, mc., arrese, el., sorgentini, da. and wagner, jr. 1991. feed milling equipment developments. world grain electrophoretic, solubility and functional properties of commercial soy protein isolates. journal of agricultural and food chemistry, 39(6): 1029-1032. booth, ma., allan, gl., evans, aj. and gleeson, vp. 2002. effects of steam pelleting or extrusion on digestibility and performance of silver perch bidyanus bidyanus. aquaculture research, 33(14): 1163-1173. burmamu, b., aliyu, b. and tya, t. 2015. development of a manually operated fish feed pelleting machine. international journal of research in engineering and advanced technology, 2(6): 23-32. del valle, jm. and aguilera, jm. 1991. physicochemical characterisation of raw fish and stickwater from fish meal production. journal of the science of food and agriculture, 54(3): 429-441. diarra, s., kwari, i. and kwari, h. 2001. effect of substituting wheat bran with millet bran on nutrients digestibility and intestinal morphology of broiler chickens. proceedings of the 6th annual animal science association of nigeria, 17-19 september 2001. asan proceedings no. 64, pp. 1-13. el-nono, ma. 2005. compost pellets made from livestock manure and rice straw mix. international journal of associate engineering, 23(25): 79-81. regupathi, er., suriya, a. and geethapriya, rs. 2019. on studying different types of pelletizng system for fish feed. international journal of fishiries and aquatic studies, 7(2):187-192 eyo, aa. 2002. chemical composition and amino acid content of the commonly available feedstuffs used in fish feeds in nigeria. journal of fish nutrition and fish feed technology,10(2): 14-25. fao. 2000. agricultural development and coordination programme, fish feed technology in nigeria. fao fisheries technical paper. no. 398. rome: fao. pp. 453–470 faturoti, e. and akinbote, r. 1986. growth response and nutrient utilization in oreochromis niloticus fed varying levels of dietary cassava peel. nigerian journal of applied fisheries and hydrobiology, 1(1): 47-50. gabriel, u., akinrotimi, a., anyanwu, p., bekibele, d., and onunkwo, d. 2007. locally produced fish feed; potential for aquaculture development in africa. journal of agriculture, 20(10): 536-540. galen, r., rob, s., and brian, p. 2008. pelleted livestock feed production–process description. http://www.engormix.com retrieved march, 3, 2008. harper, jm. 1989. food extrusion. in: singh r.p., medina a.g. (eds) food properties and computer-aided engineering of food processing systems. nato asi series (series : applied sciences), 168. https://doi.org/10.1007/978-94-009-2370-6_19 heuzé, v., tran, g. and kaushik, s. 2015. fish meal. feedipedia, a programme by inra, cirad, afz and fao. https://www.feedipedia.org/node/208 ikedudu, ko., chukwumanya, eo., swift, on. and nwokeocha, t. 2015. design of pelletizing machine (bailling disc). internationa journal of mechanics and manufacturing, 3(1): 9-12.. mcellhiney, r. 1987. what’s new in pelleting. feed management, 38(2), 32-34. mercier, c. 1980. structure and digestibility alterations of cereal starches by twin-screw extrusion-cooking. american association of cereal chern. inc., st. paul, minn. usa. pp: 10. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng malgwi et al.: modification and performance evaluation of a fish feed pelletizing machine. azojete,16(3):509-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salihuabdu110@yahoo.com 518 olafsdottir, g., högnadóttir, á., martinsdottir, e. and jonsdottir, h. 2000. application of an electronic nose to predict total volatile bases in capelin (mallotus villosus) for fishmeal production. journal of agricultural and food chemistry, 48(6): 2353-2359. orimaye, qs., ajewale, po. and oni, io. 2019. design, fabrication and perfomance evaluation of idigenous fish feed pelletizing machine for low income farmers in nigeria. journal of engineering research & reports, 4(3):1-31. rosen, jl., miller, rc., harper, jm. and clark, jp. 1979. food extrusion: food technology critical reviews in food science & nutrition, 11(2): 155-215. schultz, k. 1990. pelleting in practice. advances in feed technology, 2(1): 6-33. veronica, im., benard, o., vincent, o. and chima, co. 2018. design and fabrication of fish feed pelletizing machine. international journal of scientific research and managementb (jerm), 6(2): 78-84 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):403-412 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 403 original research article tuning rules for fractional order pid controllers for industrial processes: a conceptual framework l. m. isah1* and a. dan-isa2 1department of electrical engineering technology, federal polytechnic, k/namoda, zamfara state, nigeria 2department of electrical engineering, bayero university kano, kano, nigeria *corresponding author’s email address: dangoggo@gmail.com 1.0 introduction fractional order proportional integral derivative (fopid) controller is expressed by fractional order differential equation where the fractional part of the integral and derivative can be a positive integer or zero (lee and chang, 2010). control system response can be improved when the integral and derivative of a pid controller are expanded into fractional order form (ismayil et al., 2014). over the years, fractional order systems were approximated as integer order systems for easy analysis (dingyu et al., 2006). presently, there are many fractional order controllers available for solving fractional order problems such as the voltage-current relation of lossy transmission line (zamani et al., 2009, zhang et al., 2016, chunna et al., 2005) the pid controllers are the most commonly used control techniques in industrial feedback application (mishra et al., 2015). this is due to its simplicity of implementation and maintenance (padula and visioli, 2011). fractional order pid controller is an extension of the integer order pid controller with two additional tuning knobs (chunna et al., 2005, padula and visioli, 2011). these knobs include the three gains of the pid article information abstract this paper presents a brief review of fractional order proportional, integral and derivative (fopid) controllers. the prominent tuning procedures are presented and a conceptual framework for a new design of efficient fopid controller is presented. the presented framework is based on the concept of output feedback, where a threshold is applied on the output response before feeding its feedback to the comparator. the threshold output was compared with the reference to make a proper decision on when a new controller gain should be selected. this way, control effort will be minimized and the system can settle as fast as possible. this paper presents a brief study of fractional order proportional, integral and derivative (fopid) controllers with their prominent tuning procedures and an introduction to a conceptualize idea for a new tuning technique that can be adopted for efficient tuning this type of controllers... the presented framework is based on the concept of output feedback, where a threshold is applied on the output response before feeding its feedback to the comparator. the idea was to compare the applied threshold output with the reference so as to make a proper decision on when a new controller gain should be selected. the result would be a minimized control effort and thus making the system to settle as fast as possible. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 dec., 2021 revised 3 april, 2022 accepted 6 april, 2022 keywords: fractional order pid controller tuning conceptual framework output feedback output threshold http://www.azojete.com.ng/ mailto:dangoggo@gmail.com mailto:dangoggo@gmail.com mailto:omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):403-412. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 404 controllers along with the fractional part of the integral and derivative gain. this flexibility allows the design of a more robust control system than the integer order pid controller. also, the advancement in the knowledge of fractional calculus has led to a better mathematical description of the environment which makes it useful in many fields of science and engineering. fractional calculus is concern with the study of integrals and derivatives of non-integer orders and nowadays becoming popular due to large number of researches that exploit its application especially in fractional order modelling and fractional order control theories (zamani et al., 2009, efe 2011). fractional order modelling is a way of describing the physical behavior of a system through the use of partial differential equations. fractional order system can be regarded as a direct extension of classical integer order system that can be modelled by a fractional order differential equation containing derivative of non-integer order (monje, et al., 2010). there is wide range of operations that a fractional order system may offer especially in robust control application, which is one of the advantages of using fractional calculus. these characteristics will enable the design of controllers that can control a system in achieving robustness and for comparative fractional order controllers (salawudeen et al., 2017, jibril et al., 2016). as a result, fractional order controllers can provide many benefits in the control area especially for compensation of disturbances due to undesired nonlinearities and static distortion in the system which consequently improved the overall performance of the system (monje, et al., 2010). among the various fractional order controllers, the fopid have attracted the attention of many researchers because of its consequential flexibility to the designers more than that of the conventional pid controller structure as it has five parameters instead of the three for the pid (kumar and kumar, 2018, muhammadikia and aliasghary, 2019). parts of the paper are organized as follows: literature review is presented in section two. section three present the overview of fopid controller and section four presents the conceptual framework for the proposed tuning method. 2. literature review several researches like in (sondhi and hote, 2014, liu, et al., 2017 and padula and visioli, 2011) had been conducted on different aspect of tuning the parameters of fopid controllers. for example, (sondhi and hote, 2014) proposed an empirical tuning method for a new type of fractional controller known as fractional order filter proportional integral derivative (fofpid) controller. a procedure which was based on set point overshoot was employed to tune the controller. simulation on various first order with time delay processes were carried out and correlations were derived to obtain the parameters of the controller. in liu et al. (2017), a universal fractional order linear phase lead compensation multi-rate repetitive controller for pulse width modulated inverters was proposed. the idea is to provide a flexible selection of sampling frequency, fundamental frequency of the reference signal and down-sampling ratio in order to enhance effectiveness in applications. multi-rate repetitive control (mrc) and fractional order multi-rate repetitive control (fomrc) schemes were used to achieve the design objectives. the effectiveness of the design was tested on a series of application examples of programmable ac power supplies with high tracking accuracy, low total harmonic distortion and good transient response. in a study by padula and visioli, (2011), a new practical file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dangoggo@gmail.com isah and dan-isa: tuning rules for fractional order pid controllers for industrial processes: a conceptual framework. azojete, 18(3):403-412. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 405 tuning method for fractional order pid controller was proposed. the propose method uses the rule of thumb that engages loop shaping principles to achieve robustness against gain variation based on the flatness of the phase plot of the controller around the cross over frequency. the effectiveness of this method was validated experimentally using a precision planar positioning stage. trivedi and padhy (2020) introduced a new optimal tuning rule for a fractional order pid controller using an indirect design approach – 1(ida-1). in this approach, the plant to be controlled was shifted in the frequency domain using a variable shifting parameter which helped in the setting of the robustness and tuning of the transient response of the frequency shifted process. the tuning rules were then designed for the new process and for accuracy, a valid range of the shifting parameter is proposed. the propose work is validated with some examples of stable and unstable processes. some examples of stable and unstable processes were used to validate the proposed work. a practical experimental set up is also considered to test the effectiveness of the method. in a study, nayak, et al. (2015) presented a fopid controller to minimize the deviation in frequency of a single-area power system. three types of turbines (non-reheat, hydro and reheat) were considered in the designed power system three types of turbines namely; non-reheat, hydro and reheat turbines were considered in the design of the power system. the robustness of the designed method was verified via parameter variation. the optimum values of the fopid controller gain were obtained on the integral error criterion where the value of either one of kp, ki or kd is arbitrary chosen and the other two were calculated. results obtained reveal that the designed fopid controller minimizes frequency deviation even in the presence of parameter variation. however, the design method minimized frequency deviation even for parameter uncertainties on a single area non-reheat turbine. for the reheat and hydro turbine, the transfer function has some unstable poles, as such; the designed method is only effective for non-reheat thermal system. the proposed method will be extended to multi-area network considering reheat turbine and physical constraints. delassi et al. (2018), proposed a fopid controller for load frequency control of two-area non-reheat thermal power systems. particle swarm optimization was used to implement a tuning procedure for the fopid controller. a comparative analysis of the controller showed the superiority of these approaches over other numerical based methods. a tuning technique for fopid controller using differential evolution algorithm has been proposed. the integral of squared error (ise) criterion was minimized as an objective function to obtained the all the gains of the fopid controller that gives the minimum ise. results obtained when applied to load frequency control showed that the designed controller has an improvement when compared to simulation results for pi fractional d controller (pidµ) and pid in terms of peak overshoots and settling time. in a research conducted by mishra et al. (2017), a tuning method for fopid controller using social spider optimization algorithm (sso) was utilized. the sso based fopid controller was applied to load frequency control using integral time absolute error (itae) as performance criterion. the results demonstrate that the fopid controller based on sso have a high ability in damping the frequency deviation and the deviation in tie-line power exchange for each power generation area. an optimal tuning of pid controller using a novel optimization algorithm named smell agent optimization (sao) was presented by abba et al. (2022). the sao which was http://www.azojete.com.ng/ mailto:dangoggo@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):403-412. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 406 developed to mimic the intelligent behaviors of an agent trailing a smell source was used to optimally select the kp, ki and kd parameters of pid controller. the optimized pid was in turn used for speed control of direct current moto used for industrial applications. jain and hote (2018) studied an optimized fopid and a tilted integral derivative with filter (tidf) controller for a two-area multi-source power system. the parameters of pid, tidf and fopid controller were obtained using differential evolution algorithm and the integral time absolute error (itae) was minimized as the objective function. finally, the model was investigated under various load conditions of parameter variation and time delay. results obtained show that tidf gave better transient response when compared against fopid and pid controllers. dastjerdi et al. (2019) developed a technique for load frequency control of power system using fopid controller. the optimal values of the fopid parameters were obtained using big bang big crunch (bb-bc) optimization algorithm and internal model control scheme. an imc based pid controller was first designed for the power system. then the gains of the fopid controller were obtained using bbbc optimization algorithm while the gains of the pid controller first obtained was use to specify the bound on the solution space. results obtained show a better performance than other recent designed methods from literature. munoz et al. (2020) presented a simplified tuning for fractional order controllers using frequency domain characteristics. the tuning rules are based on the method of symmetrical optimum principles of kessler. the paper has two parts, with first part presented the generalized tuning rules and the second part introduced the fractional order that offers solution for any desired closed loop performance measures. the proposed method was verified using numerical simulation and experimental results. for simulation, it includes relevant process that has integer order and fractional order transfer functions while for the experimental case, a simple mechatronics application, and basic loop control in production systems and dc motors were considered. the simulation results show that the desired performances were met. liu et al. (2018) presented a simplified and direct tuning method for fractional order controllers using a graphical solution that tends to avoids solutions by nonlinear equations and avails the designer ways to solve control problem in a very intuitive way. the proposed fractional controllers were the fopd and fopi. the method was tested using servomotor position control of the soft robotic neck prototype mechanism. the tuning method would allow the designer to observe the parameter variation graphically and allow easy and fast re-tuning of the controller from the observed curves without the need to repeat the algorithm all over again. the result shows that the controllers exhibit a robust performance on the selected process. a novel tuning strategy for fractional order pid controller based on bode’s optimal loop shaping that is commonly used for lti feedback systems was presented (angel and viola, 2018). here, the controller parameters are tuned using a flat phase property and bode’s optimal reference model which will make the controlled system to be robust to gain variation with an achievable desirable transient performance under various control requirements. they presented three different examples of controlled plants to verify the effectiveness of the proposal and also carried out a robustness analysis of the controlled system to support the result. ambreesh and rajneesh (2018) who design a control system capable of tracking a parallel robotic manipulator type delta using both fopid and iopid controllers was presented. the matlab model of the delta robot was built and used for the stages of identification, design and validation of the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dangoggo@gmail.com isah and dan-isa: tuning rules for fractional order pid controllers for industrial processes: a conceptual framework. azojete, 18(3):403-412. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 407 control strategies. least squares algorithm is used to identify the dynamic model of the robot while a linearized model of the robot was obtained by using computed torque control strategy. from the linearized models, the two controllers were design to analyze the dynamical behaviors for many evaluation trajectories. from this, controllers’ robustness is evaluated against external disturbances which are detriment to the performance index for the joint and spatial error, applied torque in the joint and the trajectory tracking. result shows that the fopid controller with the computed torque control strategy gives a better robust performance against the external disturbances that affects the tracking ability of the delta robot. meneses et al. (2018), an easy tuning method for fractional order proportional integral controller (fopi) to control a first order plus dead time process was presented. the design is subject to minimizing the integrated absolute error (iae) for load disturbance rejection with a constraint on the maximum sensitivity. the parameters of the fopi controller were optimized using genetic algorithm. the authors use wide range of processes with non-oscilatory and oscillatory characteristics to verify the effectiveness of the proposed method. the simulation results show that the level of robustness can be evaluated when considering the range of values of the order of the integral part and that of maximum sensitivity. 3. fractional order pid controller the fractional order pid controller popularly called fopid is an extension of the traditional pid controller with some additional fractional integral and derivative parameters. for example, the traditional pid controller which is expressed as 1 (s) k p i dc k k s s    (1) can be transformed into its fractional equivalent as: (s) k i c p d k f k s s           (2) where 𝐾𝑝 , 𝐾𝑖 and 𝐾𝑑 are the proportional, integral and derivative control gains of the controller. the parameters 𝜇 and 𝜆 are the fractional part of the derivative and integral gains respectively. from eqn. (2), it can be observed that the fopid controller has the traditional three tuning parameters of pid in the form of 𝐾𝑝, 𝐾𝑖 and 𝐾𝑑 and λ, µ which are the fractional part of the integral and derivative gain respectively. when 𝜆 = 𝜇 = 1, an integer order pid controller is obtained. when 𝜆 = 𝜇 = 0, an integer order promotional controller is obtained, when 𝜆 = 0 𝑎𝑛𝑑 𝜇 = 1 , an integer order promotional derivative controller is obtained, and for 𝜆 = 1 𝑎𝑛𝑑 𝜇 = 0, an integer order proportional integral controller is obtained. as a demonstration, these configurations of the fopid controller are showed in figure 1. http://www.azojete.com.ng/ mailto:dangoggo@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):403-412. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 408 figure. 1: fopid controllers illustration since the integer order pid controller has two less tuning parameters than the fopid, the fopid controller gives a better chance to design a more robust controller than the iopid controller particularly when a fractional system is to be controlled. the general block diagram representation of the fopid controller is given in figure 2 kp ki kd 1 s  1 s     c(s) figure 2. block diagram fopid controller from figure 2, the controller force obtained from the output the fractional order controller is denoted as c(s). though, there is no definite empirical values defined for the fractional parameters of the fopid controller, some literatures have showed that values between the range of 1 and 2, appears suitable and optimal (meneses et al., 2018). 4. conceptual framework this section describes a new ideology which could be effective for tuning the parameters of fopid controller as other prominent tuning methods. the generalized tuning procedures for tuning controllers are conceptualized in figure3. process controller tuning algorithm e(s)r(s) y(s)c(s) figure 3. conceptualized conventional controller tuning usually, the tunning algorithm shown in figure 3 is the codified procedure for intelligent selection of the controller parameters. if the boundary conditions of the parameters are file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dangoggo@gmail.com isah and dan-isa: tuning rules for fractional order pid controllers for industrial processes: a conceptual framework. azojete, 18(3):403-412. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 409 known, the selection is done as in optimization where the objective is to minimize an error expressed as cost function. this cost function is solved using the analytical or computation optimization procedures. the computational optimization tuning procedures are heuristics or metaheuristic based, where the algorithm seeks to obtain the minimum of the objective function. in addition to the analytical methods been computational costly and requiring a lot of control effort, the computational optimization approach only considers the margin between the output and the input. the characteristic and performance requirements of the systems are not considered explicitly. to address these challenges, this paper presents a new idea for tuning the parameters of controllers using output feedback thresholding technique. the best knowledge of the researcher, this idea is novel and has not been reported in literature. the proposed controller can be applied to industrial processes and practical problems requiring pid or fopid controller. this idea is demonstrated in figure 4. process controller tuning algorithm e(s)r(s) y(s)c(s) no yes ( )y s thr ( ) ( )y s thr r s thr   0thr figure 4. proposed tuning technique from figure 4, the thr is an output threshold defined by the controller designer. the threshold output is used to check the performance of the controller in comparison with the reference input. this information is used to check the closeness of the output to the reference input before the cost function is computed. this way, the output whose reference is outside the threshold values is not computed. among other advantages, this new idea is expected to provide a good reference tracking with high precision using the output information conclusion this paper presents a brief review of fractional order proportional integral derivative controller popularly called the fopid controller. the tuning methods adopted by previous studies were discoursed and a conceptual idea for tuning the fopid controller is presented. the presented idea employs the threshold of the output response as feedback to select the right values of the controller gains. this idea is novel because the output feedback thresholding technique has not been reported in the past and will be implemented in the next research. various first and second order plus dead time system will be used to evaluate the performance of the tuning rules using performance criteria like maximum overshoot and settling time. when implemented, the controller will also be applied to various real life control systems like the dc motor. this study has extended the capacity that tuning of fractional order controllers has great potential in which it can accommodate new ideas that can provide additional quality to enhance control system performance http://www.azojete.com.ng/ mailto:dangoggo@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):403-412. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dangoggo@gmail.com 410 references abba, am., karataev, t., thomas, s., ali, am., yau, i. and mikail, sa. 2022. optimal pid controller tuning for dc motor speed control using smell agent optimization algorithm. fuoye journal of engineering and technology, 7(1): 23-27. ambreesh, k. and rajneesh, s. 2018. a genetic algorithm based fractional fuzzy pid controller 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file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dangoggo@gmail.com https://www.sciencedirect.com/science/article/abs/pii/s0950705121007486#! https://www.sciencedirect.com/science/article/abs/pii/s0950705121007486#! https://www.sciencedirect.com/science/article/abs/pii/s0950705121007486#! https://www.sciencedirect.com/science/article/abs/pii/s0950705121007486#! arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):257-270 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 257 original research article arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform m. a. gana*, a. bukar, and y. a. smaila department of electrical and electronics engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: mag1898@unimaid.edu.ng 1.0 introduction an arc flash is an explosive burst of light and heat produced as part of an arc fault, a type of electrical explosion or discharge that results from a connection through air to ground or another voltage phase in an electrical system. the results are often violent and when a human is in close proximity to the arc flash, serious injury and even death can occur. arc flash can be caused by many things including: dust, dropping tools, accidental touching, condensation, material failure, corrosion, faulty installation (yadav and harith, 2016). an arc flash study is a risk assessment of a workplace environment that determines arc flash hazards. it is important that an expert in electrical safety conducts an assessment to ensure that a company understands the risks their workplace poses to their personnel and how to protect them against it. the severity of an arc flash injury is caused by the temperature, fault current and time for circuit breaker to operate and closeness of the object to the danger zone. these zones are: flash protection limits, limited zone, restricted zone, prohibited zone. arc flash analysis requires the completion of a short circuit study and a coordination study. the results of the arc flash calculations are based on the calculated values of fault current magnitudes found in the short circuit study and the associated clearing times of overcurrent protection devices as determined by the coordination study (valdes and floyd, 2021). article information abstract nowadays, electricity plays an important role in our life and in our industries. however, when an arc fault occurs, it creates an incident that can cause a serious damage to the equipment and can cause serious injury to the workers. arc fault is generated when electric current passes through air from one uncovered live conductor to another or to ground in electrical system. analyzing the level of arc flash and providing a good protection to the workers is paramount. in this work digsilent software was used to study the arc flash of institute of electrical and electronics engineers (ieee) 8 bus test system. firstly, a model of system was created in the digsilent environment and then arc flash study of all the buses in the system was carried out. based on the simulation results obtained, personnel protective equipment and labels were generated to inform the workers about the level of danger they are exposed to in the course of doing their work. the risk category for buses numbers 3 and 7 are cat 2 and 3 respectively while for buses 1and 5 and for buses 2,4,6 and 8 are cat 4 and 5 respectively. the results showed that there is a need for the personnel to equip themselves with the appropriate personnel protective equipment (ppe) as suggested before access. because, arc flash faults have significant effect on personnel and equipment. it’s really important for stability, energy continuity, human life and economy. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 4 february, 2023 revised 3 march, 2023 accepted 6 march, 2023 keywords: arc flash ppe digsilent ieee standard incident energy http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 258 this study is aimed at determining the incident energy potentially present during an arc flash event. the magnitude of the incident energy is calculated on the basis of the available fault current, the clearing time of associated system protection, and the physical parameters of the system location. associated with this calculation is the determination of an approach distance within which the incident energy level is above 1.2 cal/cm2 (quincy, 2015). appropriate personal protection equipment (ppe) shall be used when working on or near energized equipment within the lash protection boundary (gammon et al., 2015). results of the study may be displayed in labels on equipment enclosures to inform and direct facility personnel with respect to the potential arc flash hazard. 2. review of arc flash analysis standards national fire prevention agency (nfpa) 70e-2000 edition, makes it necessary for facility personnel to wear ppe when carrying out various tasks in areas liable to potential arc flash hazards standard for electrical safety in the workplace (2015). these requirements were made necessary on the basis of field experience and are categorized by associated voltage levels. the hazard category is determined by the nature of the work to be completed, the operating voltage, and the available short circuit current for that general location in the electrical distribution system. the hazard category refers to the appropriate protective clothing and the ppe to be utilized. ieee standard 1584™ – 2002 describes the procedures and provides direction for an accurate means of determining a safe arc flash boundary and associated hazard level (nagsarkar and sukhija, 2011). the basis for this method is experimental data recorded from simulated arcs corresponding to bolted, three-phase fault current magnitudes measured at the terminals of an experimental enclosure (short, 2011). the categories of ppe as described in nfpa 70e are summarized in table 1: table 1: categories of ppe, reddy and satyanarayana (2018). s/no. risk category clothing description (number of layers) rating of ppe (cal/cm2) 1. 1 flame resistant shirt and flame-resistant pants or flameresistant coveralls (1 layer) 4 2. 2 cotton underwear plus flame resistant shirt and flame-resistant pants (1 or 2 layers) 8 3. 3 cotton underwear plus flame resistant shirt and flame-resistant pants plus flame resistant coveralls, or cotton underwear plus two flame resistant coveralls (2 or 3 layers) 25 4. 5. 4 5 cotton underwear plus flame resistant shirt and flame-resistant pants plus multilayer flash suit (3 or more layers) cotton underwear plus flame resistant shirt and flame-resistant pants plus multilayer flash suit (4 or more layers) 40 48 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng gana et al: arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform. azojete, 19(2):257-270. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 259 2.1 nfpa 70e and ieee 1584 equations for arc flash calculations normalized incident energy can be found using equation (1) (gopila, 2021). 𝐸𝑛 = 𝐾1 + 𝐾2 + 1.081 × log 𝐼𝑎 + 0.001 × 𝐺𝐵 (1) where, en incident energy in j/cm 2 normalized for time and distance. the equation above is based on data normalized for a distance from the possible arc point to the person of 610 mm and an arcing time of 0.2 sec 𝐾1 = -0.792 for open configurations, and is 0.555 for box configurations or enclosed equipment 𝐾2= 0 for ungrounded and high resistance grounded systems and equals 0.113 for grounded systems 𝐺𝐵gap between conductors in millimeters ia predicted three phase arcing current in ka. it is found by using equations 2 or 3 so the operating time for protective devices can be determined. for 1000v and lower systems (rubini and krishnakumar, 2020), 𝑙𝑜𝑔𝐼𝑎 = k + 0.662 × 𝑙𝑜𝑔𝐼𝑏𝑓+ 0.0966 × v + 0.000526 × 𝐺𝐵+ 0.5588 v × 𝑙𝑜𝑔𝐼𝑏𝑓0.00304 × 𝑙𝑜𝑔𝐼𝑏𝑓 (2) where: log is logarithm base 10 (log10) la arcing current in ka k is equal to 0. 153 for open configurations. and 0.097 for box configurations 𝑙𝑜𝑔𝐼𝑏𝑓 is bolted fault current for three phase faults in ka symmetrical rms vsystem voltage in kv 𝐺𝐵 gap between conductors in millimeters. where: iogia = 0.00402 + 0983 × 𝑙𝑜𝑔𝐼𝑏𝑓 (3) for applications with a system voltage ranging from 1 up to 15kv incident energy can be found using the equation (4): e = 4.184 × 𝐶𝑓 × 𝐸𝑛 × ( 𝑡 0.2 ) × ( 610𝑋 𝐷𝑋 ) (4) where: e is incident energy exposure in j/cm2 𝐶𝑓 is calculation factor equal to 1.0 for voltages above 1 kv, and 1.5 for voltages below 1 kv 𝐸𝑛is normalized incident energy in j/cm2 as calculated by equation (1). t is arcing time in seconds d is distance from possible arcing point to the person in millimeters xdistance exponent. for cases where voltage is over 15 kv, or gap is outside the range of the model, the theoretically derived lee method can be applied, and incident energy can be determined using the equation 5: http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 260 e = 2.142 × 106 × 𝐼𝑏𝑓 × ( 𝑡 𝐷2) (5) where: e is incident energy in j/cm2 v is system voltage in kv t is arcing time in seconds d is distance from possible arc point for the ieee std 1584-2002 empirically derived model, arc flash boundary is calculated using the equation 6 (yadav and harit, 2016). 𝐷𝐵 = [4.18 × 𝐶𝑓 × 𝐸𝑛 × ( 𝑡 0.2 ) × ( 610𝑋 𝐷𝐵 )] 1 𝑋 (6) for the lee method: 𝐷𝐵 = [2.142 × 106 × 𝑉 × 𝐼𝑏𝑓 ( 𝑡 𝐸𝐵 )] 1 2 (7) where: 𝐷𝐵 is distance of the boundary from the arc point in millimeters 𝐶𝑓 is calculation factor equal to 1.0 for voltages above 1 kv and 1.5 for voltages below 1 kv en is normalized incident energy in j/cm2 as calculated by equation (1) 𝐸𝐵 is incident energy in j/cm2 at the boundary distance. it is usually set at 5 j/cm2 (1.2 cal/cm2) for bare skin or at the rating of proposed personal protection equipment. 𝐼𝑏𝑓 is bolted fault current for three phase faults in ka symmetrical rms t is arcing time in seconds and x is distance exponent. 3.0 materials and methods 3.1 collection of input data single line diagram (figure 1), equipment parameters (voltage kv rating, power mva rating, impedance, system fault level, x/r ratio, protection settings) of the substation were collected. electrode configuration of the panel based on ieee 1584 such as vcb, vcbb, hcb, voa, hoa gear for the worst scenario were checked. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng gana et al: arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform. azojete, 19(2):257-270. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 261 figure 1: single line diagram of the ieee 8 bus test system (reddy and satyanarayana, 2018) 3.2 digital simulation and electrical network analysis platform digsilent stands for digital simulation and electrical network analysis software. it is a leading power system analysis software application for use in analyzing generation, transmission, distribution and industrial systems. it covers the full range of functionality from standard features to highly sophisticated and advanced applications including wind power, distributed generation, real-time simulation and performance monitoring for system testing and supervision. digsilent is easy to use, fully windows compatible and combines reliable and flexible system modelling capabilities with stateof-the-art algorithms and a unique database concept. also, with its flexibility for scripting and interfacing, digsilent is perfectly suited to highly automated and integrated applications. digsilent has a quick incident energy calculator, which is powerful analysis tool that allow user to perform a quick arc flash analysis at the bus level when the following input data necessary to perform afh analysis are available (doughty et al., 2000). short circuit current (ka) at all the buses after short circuit study. fault clearing time (fct) in (sec). gap between conductors (mm). working distance (mm). equipment type (gumilar, 2020). http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 262 3.3 modelling and simulation ieee 8 buses test system was modelled and simulated for arc flash and hazard (afh) analysis using digsilent. it has an integrated module for afh analysis based on ieee 1584 and nfpa 70e. the arc fault current, duration of arc fault current based on protection settings/relay coordination, incident energy for each bus at the working distance and suitable ppe were analysed as follows. firstly, power flow study was carried out on the substation to optimize circuit loading condition and to keep system voltages within specified limits. power system are prone to occurrence of fault which causes interruption of power supply from generating station to the load centers as a result providing protection against electrical faults grounding is necessary in electrical systems (lee, 1987). secondly, short circuit study was carried out to determine bolted fault current value (ibf) value at each bus which was further used to find out the arcing current (ia), incident energy e and arc flash boundaries. thirdly, protective devices settings and coordination was done for proper sequential tripping of protective devices (pds) near the faulted bus and to keep unprotected areas less affected by faulty condition. protective device coordination is important part of arc flash analysis as it formed part equations used to find out fault clearing time of each pds which is further used to find out incident energy e and arc flash boundaries (afb) in afh analysis (dass, 2020). fourthly, danger and warning labels were generated based on the results obtained. finally, detailed report including labels were presented in tables 2 to 6 and figures 2 to 6. 3.4 system description ieee 8 buses test system has two generators rated 150 mva, 10 kv, two transformers rated 150 mva, 10/150 kv and bus 4 is connected to external gid of 400 mva. load of 20 mw and 40 mvar, 60 mw and 40 mvar, 70 mw and 40 mvar, 70 mw and 50 mvar were connected to nodes 2,3,4 and 5 respectively. the total line length of the system is 650 km, figure 1 depicts the single line diagram of the system and figure 2 presents the model of the system in digsilent (bharti, 2020). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng gana et al: arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform. azojete, 19(2):257-270. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 263 figure 2: ieee 8 buses test system in digsilent environment 4. results and discussion load flow study was carried out as a first step on ieee 8 bus test system to ensure optimal circuit loading and to keep system voltages within specified limits. many types of faults occur in substation which causes discontinuous power supply from generating to the load center. for providing protection against electrical faults grounding is necessary in electrical systems. then after short circuit study was carried out to determine bolted fault current value (ibf) value at each bus which is used to find out the arcing current (ia), incident energy e and arc flash boundaries. protective devices settings and coordination was done for proper sequence tripping of pds near the faulted bus and keep unprotected areas less affected by faulty condition. protective device http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 264 coordination is important part of arc flash analysis to find out fault clearing time of each pds which is further used to find out incident energy e and arc flash boundaries (afb) in afh analysis. the results are as presented in tables 2 to 7. table 2: load flow analysis results s/no. bus id rated voltage (kv) bus voltage (kv) bus voltage (p.u) angle (deg) 1. bus 1 150 148 0.98 0.00 2. bus 2 150 139 0.95 0.67 3. bus 3 150 145 0.96 0.54 4. bus 4 150 148 0.96 0.45 5. bus 5 150 146 0.94 0.65 6. bus 6 150 149 0.97 0.22 7. bus 7 150 145 0.97 0.32 8. bus 8 150 139 0.97 0.23 table 3: short circuit analysis results table 4: relay coordination results s/no. bus id fault type ln (ka) ll(ka) lln (ka) lll(ka) 1. bus 1 37.77 35.74 40.22 39.83 2. bus 2 41.63 42.28 44.13 45.84 3. bus 3 30.52 29.43 24.74 20.49 4. bus 4 25.66 27.54 25.75 50.63 5. bus 5 32.39 34.22 34.11 34.82 6. bus 6 27.36 23.65 23.67 49.53 7. bus 7 26.22 25.87 24.65 43.51 8. bus 8 21.71 34.51 31.12 37.88 s/no. relay plug setting tds 1. 1 0.4644 0.2171 2. 2 1.0728 0.5065 3. 3 0.5681 0.6440 4. 4 0.4553 0.7807 5. 5 0.4861 0.2293 6. 6 1.1828 0.2348 7. 7 0.5468 0.5244 8. 8 0.5518 0.7422 9. 9 0.6187 0.1462 10. 10 0.3648 1.0287 11. 11 0.4392 1.0460 12. 12 0.7757 0.9921 13. 13 0.4754 0.2358 14. 14 0.5058 0.6784 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng gana et al: arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform. azojete, 19(2):257-270. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 265 table 5: sending and receiving ends fault current primary & secondary relay pairs sending end fault current (ka) receiving end fault current (ka) primary relay no secondary relay no primary secondary primary secondary 1 6 32.30 32.30 0.995 0.995 8 9 60.80 11.60 29.90 0.553 8 7 60.80 18.80 29.90 0.078 2 1 59.10 0.993 35.50 39.33 9 10 24.80 24.80 11.60 11.60 2 7 59.10 18.80 35.50 0.746 3 2 35.50 35.50 22.40 22.40 10 11 38.80 23.40 24.80 11.40 6 5 61.00 12.00 32.30 0.626 6 14 61.00 18.70 32.30 0.078 13 8 29.80 29.80 0.986 0.986 14 9 51.90 11.60 18.70 0.151 7 5 52.10 12.00 18..90 0.181 14 1 51.90 0.993 18.70 0.986 7 13 52.10 0.985 18.90 0.994 4 3 37.80 22.40 24.00 10.50 11 12 37.00 37.00 23.40 23.40 5 4 24.00 0.200 12.00 12.00 12 13 58.90 0.985 37.00 0.433 12 14 58.90 18.70 37.00 0.821 afh analysis results from the global calculation for all the 8 buses are shown in table 6. the incident energy depends on the following parameters: i. short circuit current ii. gap between conductors iii. working distance iv. fault clearing time http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 266 table 6: arch flash analysis results. plots of the incident energy and the short circuit current at each bus are as presented in figure 3. for all the 8 buses the short circuit current value is different. this value is changed by different ratio and then results are simulated. the incident energy is changed by adjustment in short circuit current at different buses which is shown in figure 3. when short circuit current increases, arcing current increases which in turn increases the incident energy. from these analyses we can conclude that the fault current is proportional to the incident energy and the short circuit current can be reduced with current limiting fuses and circuit breakers to reduce incident energy. the results of short circuit analysis are presented in figure 4. s/no. bus id ibf (ka) ia (ka) e (cal/cm2) afb (m) 1. bus 1 34.7 36.4 45.27 34.34 2. bus 2 42.2 40.5 50.12 48.65 3. bus 3 29.5 27.3 22.77 24.61 4. bus 4 34.9 38.2 50.90 41.45 5. bus 5 35.1 23.9 46.87 39.92 6. bus 6 26.3 37.9 63.67 50.41 7. bus 7 38.7 23.2 25.34 26.92 8. bus 8 30.6 30.6 64.43 45.78 0 10 20 30 40 50 60 70 1 2 3 4 5 6 7 8 bus number incident energy and short circuit current at each bus ia (ka) e (cal/cm2) figure 3: incident energy and short circuit current at each bus file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng gana et al: arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform. azojete, 19(2):257-270. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 267 figure 4: plot of fault currents working distance was varied from 500 to 4000 mm in the interval of 500 mm and the results obtained are presented in figure 4. from the result as the working distance increases the incident energy decreases i.e., there is inverse relation between the two. figure 5 depicts the plot of incident energy versus the gap between conductors. analyzing the plot, it is clear that as the gap between the conductors increases the incident energy also increases. figure 6 shows that as the fault clearing time increases, incident energy increases while with decrease in fault clearing time incident energy decreases. hence fault clearing time reduction is important action to reduce incident energy. figure 5: plot of incident energy versus conductor gap 0 10 20 30 40 50 60 1 2 3 4 5 6 7 8 f au lt c u rr en t (k a ) bus number short circuit analysis results ln ll lln lll 0 50 100 150 200 250 300 350 400 450 100 150 200 250 300 350 400 450 c o n d u ct o r g ap ( m m ) incident energy (cal/m2) incident energy versus conductor gap bus 1 bus 2 bus 3 bus 4 bus 5 bus 6 bus 7 bus 8 http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 268 figure 6: plot of incident energy versus fault clearing time 5. conclusion in a power system, when an arc fault occurs, it creates an incident that can cause a serious damage to the equipment and can cause serious injury to the workers. arc fault is generated when electric current passes through air from one uncovered live conductor to another or to ground in electrical system. in this study efforts have been made to determine the incident energy potentially present during an arc flash event. the magnitude of the incident energy is calculated on the basis of the available fault current, the clearing time of associated system protection, and the physical parameters of the system location. associated with this calculation is the determination of an approach distance within which the incident energy level is above 1.2 cal/cm2. appropriate personal protection equipment shall be recommended to be used when working on or near energized equipment within the protection boundary. herein, digsilent software was employed to create a model of ieee 8 bus test system to carry out the analysis. the study showed that incident energy associated with all the 8 buses are within the range of 22.77 to 64.43 cal/cm2 which is above the recommended minimum of 1.2 cal/cm2. furthermore, the results showed that the incident energy increases with increase of short circuit current, fault clearing time and gap between conductors while decreases with increase of working distance. in addition, it has been observed that the contribution by three phase bolted fault current is quite high, which can increase the arc fault current. as a result of these, arc flash incident energy on buses 4 and 7 increased. as stated earlier, arc flash hazard analysis is quite important, therefore correct method of analysis should be used. because, arc flash faults have significant effect on personnel and equipment. it’s really important for stability, energy continuity, human life and economy. 0 20 40 60 80 100 120 0.1 0.2 0.3 0.4 0.5 0.6 0.95 1 in ci d en t e n er y ( ca l/ m 2 ) fault clearing time incident energy versus fault clearing time bus 1 bus 2 bus 3 bus 4 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng gana et al: arc flash study of ieee 8 bus test system using digital simulation and electrical network analysis platform. azojete, 19(2):257-270. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 269 finally, based on the level of incident energy for each bus, the appropriate ppe has been recommended to be used by the workers and labels should be generated and pasted close to the buses to alert the personnel of the danger they are exposed to. references bhatia, s. 2020. electrical safety-arc flash hazard analysis. journal of international association on electricity generation, transmission and distribution, 33(2): 19-24. https://www.indianjournals.com das, jc. 2020. arc flash hazard analysis and mitigation. john wiley & sons. amec foster wheeler, whiley and ieee press, isbn: 978-1-119-70974-9. doughty, rl., neal, te. and floyd, hl. 2000. predicting incident energy to better manage the electric arc hazard on 600-v power distribution systems. ieee transactions on industry applications, 36(1): 1-13. floyd, hl. 2014. facilitating application of electrical safety best practices to “other” workers. ieee transactions on industry applications, 51(2): 1348-1352. gammon, t., lee, w., zhang, z. and johnson, bc. 2015. arc flash hazards, incident energy, ppe ratings and thermal burn energy a deeper look. ieee transactions on industry applications, 51(5): 4275 – 4283. gumilar, l., habibi, ma., sholeh, m. and nugroho, ws. 2020. analysis of short circuit on four types wind power plants as distributed generation. international conference on smart technology and applications, surabaya, indonesia, june 20, pp. 1 – 5. gopila, m. 2021. arc flash analysis based on ieee 1584-2018 and nfpa70e-2018. turkish journal of computer and mathematics education (turcomat), 12(9): 2869-2873. ieee 2002. guide for performing arc-flash hazard calculations, 1584 2002. 23 sept, pp. 1 – 113., http://standards.ieee.org/reading/ieee/interp/1584-2002.html lee, rh. 1987. pressure developed by arcs. ieee transactions on industry applications, 23 (4): 14. nagsarkar, tk. and sukhija, ms. 2011. power system analysis. oxford higher education publisher and oxford university press, 650-652. nowak, k., janiszewski, j. and dombek, g. 2021. the possibilities to reduce arc flash exposure with arc fault eliminators. energies, 14(7): 19 27. reddy, sv. and satyanarayana, k. 2018. sensing of ground fault in bipolar lvdc grid, international journal of scientific research in network security and communication, 6(6): 10 – 16. rubini, b. and krishnakumar, r. 2020. a review on arc flash analysis and calculation methods. 2020 fourth international conference on computing methodologies and communication, 7(10): 975-979. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):257-270. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mag1898@unimaid.edu.ng 270 short, ta. 2011. arc-flash analysis approaches for medium-volta distribution. ieee transactions on industry applications, 47(4): june 12, pp. 18. quincy, ma. 2015. nfpa70e – 2015 standard for electrical safety in the workplace, usa: 1st edition by (nfpa) national fire protection association. valdes, me. and floyd, hl. 2021. considerations for adapting ieee 1584-2002 arc flash study results to a post ieee 1584-2018 risk assessment. ieee transactions on industry applications, 20: 15 – 22. yadav, a. and harit, vk. 2016. fault identification in sub-station by using neuro fuzzy technique, international journal of scientific research in computer science and engineering, 4(6): 1-7 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng https://www.amazon.com/s/ref=dp_byline_sr_book_1?ie=utf8&field-author=%28nfpa%29+national+fire+protection+association&text=%28nfpa%29+national+fire+protection+association&sort=relevancerank&search-alias=books arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):71-82 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 71 original research article systematic layout planning approach in process layout design for processing dehydrated tomatoes n. h. abdulhakeem1,2*, i. d. muhammad2 and i. m. dagwa2 1federal college of horticulture dadin-kowa, gombe, gombe state, nigeria 2department of mechanical engineering, university of abuja, nigeria. *corresponding author’s email address: hnuruddeen15@gmail.com 1.0 introduction the performance and efficiency of industrial production system depends to a great extent on the quality of machineries, employees, as well as how facilities are positioned in a plant. poorly designed facility, therefore, may result in loss in production time, efficiency and wastage of raw materials, while a well-designed production facility improves on the efficiency of production with fewer costs and time wastage (tak and yadav, 2012). among the main goal of manufacturing system is to maximize productivity with regards to the complexity of the processes involved in manufacturing from raw materials to finished products and workstations (carlo et al., 2013). agricultural products are processed to among other things improve the shelf-life of the produce and acceptability for final consumption as food or ingredients for industrial production. the output of processing result is varieties of by-products. vegetables such as onions, tomatoes and pepper are the major vegetables produced in nigeria, and they play a significant role in health and nutrition due to their constituents that regulate digestion. onions are processed to produce dehydrated onions, onions powder and puree. despite the enormous economic potentials of onions, the processing of onions for national growth and development has little to no existence in nigeria ibeawuchi et al. (2015). according to ugonna et al. (2017), nigeria’s vegetable processing industries need to be developed to reduce postharvest losses and enhance food nutrition security. the establishment of these industries will boost the nation’s economy thereby creating employment, wealth, reduced rate of malnutrition and increased standards of living for the rural populace. according to food and agriculture organization (fao) statistics fao (2019) it estimated that nigeria’s tomatoes production is around 4.5 tons/ha with annual production of 3.8 million tonnes, while onions production is around 2.3tons/ha, with annual production of 1.3 million tonnes in the year 2019. despite the huge contributions of agriculture (vegetables) to nigeria’s economic growth, about 50% of fruits and vegetables produced are lost as a result of their perishable nature, poor postharvest handling and mismanagement leading to a staggering 360 million usd losses annually article information abstract this study was conducted to determine an effective design for the processing of dehydrated tomatoes. the study proffer solutions to huge losses nigeria encounters as a result of poor postharvest handling across the fruits and vegetables value chain. despite the huge contributions of agriculture (vegetables) to nigeria’s economic growth, postharvest losses stands at $9 million with 50% losses in fruits and vegetables as a result of their perishable nature. systematic layout planning (slp) approach was used in designing the process layout for dehydrated tomatoes. the design approach was used to serve as an improvement layout and also as a new design for processing of dehydrated tomato plant, with estimated 5% material losses during processing, average temperature for dehydration as 65oc, plant production time of 748.99 minutes/day, a throughput capacity of 10 tons/day is achievable. additionally, the design was validated using computer simulation and the results obtained from the simulation analysis indicated that the method can be used to optimize process planning for several production processes of dehydrated fruit and vegetables © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 july 2020 revised 3 january 2021 accepted 7 january 2021 keywords: systematic layout planning dehydration fruit and vegetables postharvest losses abdulhakeem et al: systematic layout planning approach in process layout design for processing dehydrated tomatoes. azojete, 17(1):71-82 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 72 (gems, 2016., elemo, 2017., abdulhakeem et al., 2020). nigeria is the 14th largest producer of tomatoes in the world, 2nd largest producer in africa and the 3rd largest importer of processed tomato commodities (pwc, 2018; sahel, 2017; ugonna et al., 2017). available literature indicated that plant layout as described by jain et al. (2013) refers to the arrangement of physical facilities such as equipment, machineries in a way to achieve the fastest flow of materials with lowest handling and costs within a factory building for efficient processing of products. systematic layout planning (slp) is a step-by-step approach to planning procedure that allows designers to identify, visualize, classify activities, relationships and alternatives in a plant layout design (richard and lee, 2015). slp serves as organized way of layout planning and a tool used to arrange workstations in a plant, which offers fastest material flow in processing or products at the lowest possible handling and costs (shubham and prasad, 2016). the aim of this study was to design an effective layout for processing of dehydrated tomatoes using systematic layout planning approach due to the absence of such plant in nigeria. 2. materials and methodology 2.1. basic principles of slp the initial task in using slp approach is to understand and input design data such as machine capacity, analyse the material flow and establish relationship between each workstation and sequence of production, develop a relationship diagram; relate the space requirements and available area to enable for space relationship diagram; identify, modify the factors of production, then evaluate and develop the best layout design (hosseini et al., 2013). slp approach is the recording of data that involve product, quantity, routing, support and time (p, q, r, s, t) as the basic elements, with tables serving as analytical tools to conduct plant design (zhu and wang, 2009., wiyaratn and watanapa, 2010). 2.2. data collection for process layout design visits to existing tomato processing plant (savanah integrated export processing farms borno state) known as vegfru and traditional producers of sun dried tomatoes in dadin-kowa, gombe, gombe state, nigeria, were done to gain understanding on the steps being followed in processing of tomatoes to serve as a guide in designing of effective layout and recording of data on machine capacities, processing time, sequence of production, and space requirement. savannah integrated export processing farms has a production capacity of 400 metric tons per day with a 24 hours’ operation period with 12 hour shifts during harvest season and 16 hours’ operation with 8 hours shift during off season, a summary of the company data is given in table 1, while the process flow chart of the plant is given in figure 1. the chart showcases the processes involved in the production of tomato paste; the data obtained aided in drafting the processing sequences of the dehydrated tomato plant. flowcharts and figures were designed using microsoft visio © software. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 73 table 1: summary of field data name of firm savannah integrated export processing farms machines and sequence operation type capacity nature or no of operators elevator lifting of fruits from receiving pond receiving tank to wash, sort and grade the fruits from the elevator. 5 ton/h *2 12 operators six (6) on each production line. fruit meshing machine to mesh the fruits. 1 boiler to heat the meshed fruits to 90 degrees celsius pulp machine to pulp the fruits 1 collecting tanks collect the pulped tomatoes for further processing evaporators to dry the excess moisture from the tomatoes 4 set of evaporators with 12 collecting tanks. 25 tons/set 8 operators 2 each feeding line cold filling line drum filler to store processed tomatoes for later use when there’s excess supply 2 sets to fill 200kg/ drum 2 canning to store processed tomato paste in cans of 70 gram each 1 sterilizer a and b a: hot water tub (10-12mins) b: cold water tub (5-7mins) processed tin tomatoes pass through each compartment a and b for sterilization blower or dryer (3mins) dries the tomato cans coming from the sterilizer packaging to arrange the can tomatoes in cartons 100 cans per carton 10 operators abdulhakeem et al: systematic layout planning approach in process layout design for processing dehydrated tomatoes. azojete, 17(1):71-82 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 74 figure 1: process flow chart of tomato paste production at savannah integrated export processing farms© 2.3. flow of materials this procedure was followed to determine the most effective sequence(s) in which raw materials (tomatoes) move through stages of processing and the intensity of the movement, which involves relationship flow diagram, process flowchart , multi-product chart and from-to-chart (richard and lee, 2015). figure 2 highlight the product layout for dehydration of tomatoes, it showcased how raw materials flow from one workstation to another until the end of production. figure 2: product layout for dehydration of tomatoes 2.3.1. activity relationship chart the activity relationship chart was used to show the relationship between pairs of activities preceding in a process operation such as washing, sorting and grading of tomatoes, these processes are performed by separate machines. the chart showed the importance of the closeness between these machines based on their expected ratings as shown in table 2 (carlo et al., 2013; richard and lee, 2015). arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 75 table 2: activity relationship chart value relationship no of ratings a absolutely important 4 e especially important 3 i important 2 o closeness ok 1 u unimportant 0 x not desired -1 2.4. mass and energy balance the calculation quantifies the mass and energy in the system or process governed by the law of conservation of mass. it was reported that there are typical losses encountered in processing steps of fruits and vegetables (fellows, 2004). these includes: washing (0-10%), sorting (5-50%), peeling (5-60%), slicing (5-10%), drying (10-20%) packaging (5-10%) and rejected packs (2-5%). these figures were used to draft the process block diagram, the diagram depict the estimated minimum losses of materials through processing workstations. (1) (2) specific heat capacity of tomatoes was given by dickerson’s equation in ikegwu and ekwu (2009) as: (3) where w= moisture content the wet-basis moisture content of sliced tomatoes (win) and dehydrated tomatoes (wout) is given by (green and perry, 2008): (4) (5) (6) (7) (8) (9) (10) where: abdulhakeem et al: systematic layout planning approach in process layout design for processing dehydrated tomatoes. azojete, 17(1):71-82 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 76 3. results and discussion 3.1. process flowchart figure 3 showed the proposed flowchart for the dehydrated tomato plant. the process flowchart showed a chronological sequence of processing dehydration of fruits and vegetables with a classification into pre-dehydration and post-dehydration. pre-dehydration involves sorting, washing, and shredding/slicing then dehydration, while post-dehydration includes milling/grinding, mixture for soups, inspection and packaging (adegbola et al., 2012). figure 3: proposed process flowchart for dehydration of fruit and vegetables processing plant. the process block diagram (pbd) in figure 4 highlighted the sequentially breakdown of material losses from each workstation in a flowchart form indicating the minimum losses in each step of operations and expected product output (george and athanasios, 2002). figure 4: the simplified process block diagram (pbd) for dehydration of tomatoes arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 77 3.1.2. activity relationship chart figures 5 and 6 highlight the workflow diagram of materials flow between workstations numbered sequentially and the relationship between pairs of activities preceding in a process operation, with intersections to two dividing lines showing a letter that symbolizes the importance of their closeness between each other as shown in table 2. this enables the selection of optimal sequencing with the corresponding block layout (carlo et al., 2013; sutari and sathish rao, 2014). figure 5: workflow diagram figure 6: activity relationship chart for tomato dehydration 3.3. space requirements the data were compiled to obtain the distance of material flow between departments and then transformed these data into closeness ratings as seen from table 3 presents the space requirement for each department in relation to equipment and space requirement by each machine. the data help in designing an effective layout (sutari and sathish rao, 2014). abdulhakeem et al: systematic layout planning approach in process layout design for processing dehydrated tomatoes. azojete, 17(1):71-82 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 78 table 3. the relationship between equipment size and work area s/n dpt size (m2) no of equipment area (m2) total area required (m2) 1. rp 1.20 2 2.40 10.80 2. wn 1.93 2 3.86 9.86 3. pl 2.20 2 4.40 10.40 4. st 1.77 2 3.54 9.54 5. sl 1.16 2 2.32 8.32 6. dh 7.23 3 21.69 25.69 7. ml 1.20 2 2.40 8.40 8. se 3.30 1 3.30 7.30 9. pk 1.32 1 1.33 5.33 total 95.64 dpt= department, rp= receiving pond, wn= washing, pl= peeling, st= sorting, sl= slicing, dh= dehydration, ml= milling, se=sealing, pk= packaging 3.4. dimensionless block diagram dimensionless block diagram in figure 7 was designed from the activity relationship chart. it ignores the space requirements and building limitations. the focus behind is to gives a better understanding in designing an effective layout, it elaborates the need for workstations to be arranged in a manner to maximize productivity and utilize space (carlo et al., 2013). figure 8 showcase the proposed floor plan of the plant, which is expected to have two production lines, with processing equipment 3.5. mass and energy balances the study showed approximately 8145.06 kg of tomatoes were sent to the three dehydrators each with a capacity of 3000 kg, with around 7783.06 kg mass of water removed. dehydration process lowered the moisture content to a level were microbial activities will not easily affect the final product and further extend its shelf life, the estimated enthalpy changes of raw tomatoes, enthalpy of dehydrated tomatoes and specific heat capacity of tomatoes were 148162 kj/h, -12229.2 kj/h, and 1.6985 kj/kg k these values signify the rate at which moisture is removed from the surface of tomatoes, it is affected by the setup temperature and pressure (correia et al., 2015), the calculations done were at 65°c, as the temperature range was found to be effective temperature for dehydrating tomatoes (rasool et al., 2013), higher or excessive temperatures increases the oxidative damages, affect ascorbic acid content, flovour, colour and nutrients of the final product (zanoni et al., 1999., correia et al.. 2015, rasool et al., 2013). work-study calculations were ommited because of limited number of pages, however, the production time was calculated as 748.99 minutes per day, the capacity and effectiveness of the dehydrated tomato plant was also validated using computer simulation software to address the issues of work-in-process, capacity utilization, effective design and throughput of the plant were reported in abdulhakeem et al. (2020). arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 79 figure 7: dimensionless block diagram for the proposed process layout figure 8: floor plan for processing of dehydrated fruit and vegetables abdulhakeem et al: systematic layout planning approach in process layout design for processing dehydrated tomatoes. azojete, 17(1):71-82 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 80 4. conclusions facilities are designed to improve the efficiency of production, reduced costs of handling and increased return on investments. the plant was designed to have two production lines, throughput capacity of 10,000 kg/day with an estimated operation time of 748.99 minutes (12hrs 48 minutes) of production cycle time. the design was validated using computer simulation to check for the effectiveness and productivity of the design. if fully implemented in nigeria, the design will provide means of improving the current postharvest handling challenges ravaging the fruits and vegetables value chain through production of dehydrated tomatoes with longer shelf life. the plant should also be tested for processing of other fruits and vegetables such as mangoes, pepper and onions. acknowledgments the authors wish to express their profound gratitude to engr. kwaya emmanuel of raw materials research and development council (rmrdc) and mal. saleh tona of savanah integrated export processing farms. references abdulhakeem, nh., muhammad, id. and dagwa, im. 2020. simulation and optimization of a process layout for dehydrated fruit and vegetables processing plant. bayero journal of engineering technology (bjet), 15(1): 99-106. adegbola, ja., awagu, f., adu, ea., anugwom, ud., ishola, dt. and bodund, aa. 2012. investment opportunities in tomato processing in kano, northern nigeria. global advanced research journal of agricultural science, 1(10): 288-297. carlo, fd., arleo, m., borgia, o. and tucci, m. 2013. layout design for a low capacity manufacturing line: a case study. international journal of engineering business management (special issue on innovations in fashion industry), 5(3): 1-10. correia, afk., loro, ac., zanatta, s., spoto, mhf. and vieira, tmfs. 2015. effect of temperature, time, and material thickness on the dehydration process of tomato. international journal of food science, article id: 970724, pp.7. elemo, g. 2017. the guardian. [online] available at: https://guardian.ng/features/gain-planadvocates-end-to-postharvest-losses/amp/ accessed 27 may, 2019. fao, 2019. crops. [online] available at: www.fao.org/faostat/en/#data/qc accessed 27 december, 2020. fellows, p. 2004. small-scale fruit and vegetable processing and products. pp.21-23, vienna: unido. gems, 2016. mapping of tomato clusters in northern nigeria, abuja, gems.http://nabg.org/wp4content/uploads/2017/06/tomato-clustermap-pdfpostpreserversion.pdf. accessed on 27 december, 2020. http://www.fao.org/faostat/en/#data/qc arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 81 george, ds. and athanasios, ek. 2002. handbook of food processing equipment. athens: springer, pp 3-24. green, dw. and perry, rh. 2008. perry's chemical engineers' handbook. mcgraw-hill, new york. pp 12-26. hosseini, s., mirzapour, s. and wong, k., 2013. improving multi-floor facility layout problems using systematic layout planning and simulation. springer international publishing, pp. 58-69. ibeawuchi, ii. okoli, na., alagba, ra., ofor, mo., emma-okafor, lc., peter-onoh, ca. and obiefuna, jc. 2015. fruit and vegetable crop production in nigeria: the gains, challenges and the way forward. journal of biology, agriculture and healthcare, 5(2): 194-208. ikegwu, o. and ekwu, f. 2009. thermal and physical properties of some tropical fruits and their juices in nigeria. journal of food technology, 7(2): 38-42. jain, ak., khare, v. and mishra, p. 2013. facility planning and associated problems: a survey. innovative systems. design and engineering, 4(6): 1-8. pwc, 2018. x-raying the nigerian tomato production: focus on reducing wastage, pricewaterhousecoopers limited. lagos. pp 1-16. rasool, s., gholam-reza, c. and hassan, s. 2013. the effect of temperature and slice thickness on drying kinetics tomato in the infrared dryer. heat mass transfer, 50: 501-507. richard, m. and lee, h., 2015. systematic layout planning 4th edition. management and industrial research publications. georgia, pp 1-416. sahel, 2017. the tomato value chain in nigeria. sahel capital partners & advisory limited, lagos, pp 1-8. shubham, b. and prasad, d. 2016. optimization of plant layout using slp. international journal of innovative research in science, engineering and technology, 5(3): 3008-3015. sutari, o. and sathish rao, u. 2014. development of plant layout using systematic layout planning (slp) to maximize productiona case study. international journal of mechanical and production engineering, 2(8): 63-66. tak, c. and yadav, l. 2012. improvement in layout design using slp of a small size manufacturing unit: a case study. iosr journal of engineering (iosrjen), 2(10): 01-07. ugonna, c., jolaoso, m. and onwualu, a. 2017. tomato value chain in nigeria: issues, challenges and strategies. journal of scientific research and reports, 7(7): 501-515. wiyaratn, w. and watanapa, a. 2010. improvement plant layout using systematic layout planning (slp) for increased productivity. international journal of, industrial and manufacturing engineering, 4(12): 1382-1386. zanoni, b., peri, c., nanib, r. and lavellia, v. 1999. oxidative heat damage of tomato halves as affected by drying. food research international, 31(5): 395-401. abdulhakeem et al: systematic layout planning approach in process layout design for processing dehydrated tomatoes. azojete, 17(1):71-82 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hnuruddeen15@gmail.com 82 zhu, y. and wang, f. 2009. study on the general plane of log yards based on systematic layout planning. ieee, computer society, pp.92-95 arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1):86-96. copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 86 effect of magnetic treatment of water on evapotranspiration of tomato k.o. yusuf* and a.o. ogunlela, (department of agricultural and biosystems engineering, university of ilorin, ilorin, nigeria) *corresponding author: yusuf.ok@unilorin.edu.ng abstract this study was conducted to determine the effect of magnetic treatment of water on the evapotranspiration of tomato plant. evapotranspiration is important to plant for metabolic processes and it also cools the plant. three magnetic flux densities of 124, 319 and 719 g produced from electromagnet (the treatments) labelled as t1, t2 and t3 were used to treat the water and a control experiment (tc) was also set up which was irrigated with nonmagnetic treatment water. equal amount of water was applied to all the tomato plant (variety uc82b) at the same time. each treatment was replicated seven times given a total of 28 buckets containing tomato plant. the tomato was planted in the 28 buckets in a transparent garden shed for 130 days (23/09/2014 – 30/01/2015. a complete randomized design (crd) experimental layout was used. the amount of water lost due to evapotranspiration per day was determined by weight lost in the bucket (lysimetric weighing method). the mean values of daily evapotranspiration for two stands of tomato plants per bucket over a period of 65 days for t1, t2, t3 and tc were 9.38, 9.28, 9.18 and 8.03 mm/day respectively. the result of the evapotranspiration due to mass of water lost from the buckets containing tomato plants irrigated with magnetic water were all higher than the values of evapotranspiration from non-magnetic water. this indicated that tomato plant irrigated with magnetic treatment of water absorbed more water from the soil easily and grew faster than the tomato plant irrigated with non-magnetic treatment water with the same quantity of water applied to the tomato plant. keywords: consumptive use, evapotranspiration, irrigation, magnetic treatment of water, tomato 1. introduction magnetic treatment of water has many applications in agriculture. it modifies bonding angle of water, surface tension and some physicochemical properties of water thereby making it easier for plant to absorb more water and this will increase the evapotranspiration (et) rate of plant for all metabolic processes (babu, 2010). this high et value by magnetic treatment of water would enhance crop growth, high crop yield and high efficiency use of water (el – sayed and sayed, 2014; hozayn and abdul – qados, 2010; maheshwari and grewal, 2009; mcmahon, 2006 and selim, 2008). evapotranspiration (et) is also known as consumptive use (cu) and the term is the combination of evaporation and transpiration. evapotranspiration is the quantity of water that leaves the plants and water that is removed from the soil surface. in the two processes, water is converted to water vapour and enters the atmosphere. actually, consumptive use is the sum of evapotranspiration and water used by plant for its metabolic processes. consumptive use exceeds evapotranspiration by the amount of water used for photosynthesis, transport of minerals and photosynthates, digestion of plant food, plant growth and structural support to plant. the actual water used for metabolic activities is insignificant because is less than 1% of evapotranspiration (michael, 2008). therefore, consumptive use is assumed to be equal to evapotranspiration. crop evapotranspiration (etc) is the evapotranspiration of a crop under standard conditions. the standard conditions assumed a disease – free and well fertilized crop grown in large plot under optimum soil moisture conditions and obtaining optimum production under the prevailing climatic conditions. yusuf and ogunlela.: effect of magnetic treatment of water on evapotranspiration of tomato azojete, 13(1):86-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 87 reference evapotranspiration is the evapotranspiration from a hypothetical reference crop with an assumed height of 0.12 m, a fixed surface resistance of 70s/m and an albedo of 0.23. the reference surface closely resembles an extensive area of actively growing grass of uniform height completely shading the ground and with sufficient soil moisture (adeboye, et al, 2009; allen et al., 1998 as cited by ejieji, 2011; trajikovic and gocic, 2010). albedo is the fraction of the solar radiation which is reflected by the earth’s surface and the value depends on the type of surface, angle of the incidence of sun’s rays and slope of the ground surface (michael, 2008). reference evapotranspiration provides information on the evaporation demand of the atmosphere which is independent of the type of crop, its stage of development and the management practices. soil factors do not affect reference evapotranspiration (chineke et al., 2011 and michael, 2008). reference evapotranspiration can be computed from weather data in a given location at any period of the year. different methods are available for the determination of reference evapotranspiration as highlighted in michael (2008). the objectives of this study were to determine the effect of magnetic treatment of water on the evapotranspiration and growth of tomato plant and. 2. materials and methods the study was carried out at the research farm land of the department of agricultural and biosystems engineering, university of ilorin, ilorin, kwara state, nigeria. ilorin lies on the latitude 8 o 30¹n and longitude 4 o 35¹e at an elevation of about 340 m above mean sea level (ejieji and adeniran, 2009). ilorin is in the southern guinea savannah ecological zone of nigeria with annual rainfall of about 1300 mm. the wet season begins towards the end of march and ends in october while the dry season starts in november and ends in march (ogunlela, 2001). the temperatures from the wet and dry bulb thermometer in the transparent garden shed where the tomato was grown between 23 rd september 2014 and 30 th january 2015 varied from 16.5 to 30.0 o c (wet bulb) and 23.5 to 38.0 o c (dry bulb) with relative humidity of 50 to 90 %. the magnetic flux densities used for treating the irrigation water were 124, 319 and 719 g (three treatments) inside the treatment chamber and a control experiment. the chemical properties of water before and after passing through magnetic field and the chemical properties of soil were shown in table 1. each of the treatment was replicated seven times and the tomato irrigated with non – magnetically treated water was also replicated seven times given a total of twenty eight (28) buckets containing tomato plant. the tomato was planted in the buckets on 23 rd september, 2014 and equal volume of water (1.3 litres) was applied to each tomato at three (3) days irrigation interval but this irrigation interval reduced to 2 days at flowering/fruiting stage because water demand was higher and the value of crop coefficient (kc) changed from 1.05 at 80 % canopy cover to 1.15 at 100 % canopy cover. ufoegbune el at. (2012) also pointed out that the growing period of tomato was 150 days and the values of kc for initial growth stage, development stage, flowering/ fruiting stage and ripening stage were 0.45, 0.75, 1.15 and 0.80 respectively. each of the 28 buckets was weighed immediately after irrigation and also weighed before the next irrigation after 2 or 3 days. the soil used was loam sand and the percentage contents of silt, clay and sand were 8.67, 5.76 and 85.57%, respectively. the irrigation water was allowed to pass through the electromagnetic treatment chamber four (4) times for duration of 113 s for effective treatment arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1):86-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 88 using circulation flowing method through magnetic field (shoaili, 2003 as cited by chern, 2012 and mdsa’at, 2006). evapotranspiration of tomato, available water, net depth of irrigation requirement, irrigation interval and volume of required by tomato were determined from equations (1), (2), (3), (4) and (5). (1) ( ) (2) (3) (4) (5) where etc is the crop evapotranspiration (mm/day), kc is the crop coefficient, eto is the reference evapotranspiration (mm/day), ρb is soil bulk density (g/cm 3 ), ρw is the density of water (g/cm 3 ), fc is the field capacity of the soil (%), db is depth of the bucket (mm), aw is the available water (mm), wp is the wilting point (%), iv is the irrigation interval (day), dn is the net depth of irrigation (mm), vdp is the volume of water required daily per plant (litre/day), cc is the crop canopy (%), ap is the area of the bucket (mm 2 ) and np is the number of tomato stand in a bucket and vdays is the volume of required by the tomato plant according to the number of days of irrigation interval. the values of etc, aw, dn, iv, vdp and vdays were determined as follows when the kc was 1.05, eto was 4.7 mm/day, ρb was 1.433 g/cm 3 , ρw was 1.000 g/cm 3 , fc was 26.98 %, wp was 12.26 %, np was 2, iv was 3 days and irrigation was done when 30 % of the irrigation water was depleted. table 1: chemical properties of the soil and water used for irrigating the tomato plant chemical properties of soil chemical properties of water (mg/l) element mean element mtw nmtw ph 5.8 ph 7.46 7.36 n (%) 0.64 ca +2 3.197 3.130 p (mg/kg) 2.74 mg +2 1.229 1.285 ca 2+ (cmol/kg) 1.37 k + 0.888 0.885 mg 2+ (cmol/kg) 0.84 na + 80.55 81.91 k + (cmol/kg) 2.24 pb +2 0.297 0.300 na + (cmol/kg) 1.15 n (no3 ) 43.07 42.73 organic matter (%) 1.31 so4 -2 50.06 47.80 organic carbon (%) 0.86 p 0.654 0.670 c.e.c 5.74 viscosity (x 10 -6 ns/m) 1.773 1.815 mtw = magnetically-treated water, nmtw = non-magnetically-treated water (water before passing through magnetic field) 2.1 determination of the mass of water lost due to evapotranspiration mass of water lost due to evapotranspiration was determined directly from the bucket containing the tomato plant by weighing method (lysimeteric method). each bucket with three treatments and the treatment was replicated seven times. each bucket was weighed yusuf and ogunlela.: effect of magnetic treatment of water on evapotranspiration of tomato azojete, 13(1):86-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 89 immediately after the irrigation and later weighed again before the next irrigation. the difference in the weight of the bucket was due to evapotranspiration because there was no space for percolation of irrigation water to the soil surface and become underground water. the mass of water lost to the atmosphere was due to evapotranspiration in kg which was equivalent to volume of water in litre as determined in 2.3 with the computed evpotranspiration in mm/day was shown in table 2. two samples of the readings obtained from the field measurement (raw data) were shown in appendices a and b. 2.2 determination of the volume of water lost due to evapotranspiration the volume of water lost due to evapotranspiration was calculated from the mass of water lost to the atmosphere from the bucket containing the soil and tomato plant. volume of water lost to evapotranspiration was determined from equation (8) derived from equations (6) and (7). (6) (7) (8) where ρw is the density of water (kg/m 3 ), mw is the mass of lost due to evapotranspiration (kg), vw is the volume of water lost from the bucket to evapotranspiration (m 3 ) and vwl is volume of water lost due to evapotranspiration (litres, l). the volume of water lost from each bucket for illustration was calculated as shown in the following expressions which were presented in table 3. from the following calculations, mass of water lost from the bucket in kg is the same as volume of water lost from the bucket due to evapotranspiration in (l). 2.3 computation of evapotranspiration from mass of water lost due to et evapotranspiration (et) of tomato in mm/day due to mass of water lost to atmosphere from the bucket was computed using equation (9). an example of the computation for etc value was shown in the following expression when the values of vwl and ap (area of the bucket) were 0.508 l (mass of water lost to etc = 0.508 kg/day ≡ 0.508 l/day) and 0.05433m 2 , respectively. the result of the mean values of evapotranspiration of tomato (etc) and volume or mass of water lost from the bucket to the atmosphere was shown in table 2. (9) for two stands of tomato plant per bucket. 3. results and discussions the result of mass of water lost due to evapotranspiration which was evapotranspiration from the tomato in the bucket was shown in table 2. the mass of water lost in kg was equivalent to the volume of water lost to evapotranspiration in litre as density of water is equal to 1000 kg/m 3 . the value of mass of water lost to atmosphere daily was higher with tomato plant irrigated with the magnetically treated water (mtw) than the water lost from non– magnetically treated water (nmtw). this increased in the rate of water absorption for evapotranspiration in which 1 % of evapotranspiration is needed for metabolic processes of tomato plant which could contribute to the high growth rate of the tomato plant. arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1):86-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 90 the graph shown in figure 1 indicated that evapotranspiration of tomato mtw by 124, 319 and 719 g (t1, t2 and t3) were higher than the evapotranspiration of tomato from nmtw (tc). the mean values of the evapotranspiration of the tomato plant over the period of 65 days in the transparent garden shed were 9.38, 9.28, 9.18 and 8.03 mm/day, respectively. the bar chart in figure 2 also indicated that tomato plant absorbed more water from the soil in the buckets containing magnetized water than the tomato in the non – magnetized water with evapotranspiration increased by 14.32 to 16.81 %. the rate of water absorption by the tomato plant for evapotranspiration was statistically significant. the calculated values of f were 8.10 and 7.08 while the table value of f was 2.78 as shown in tables 3 and 4. this means that for one stand of tomato plant in the bucket, the mean values of etc for t1, t2, t3 and tc were 4.69, 4.64, 4.59 and 4.02 mm/day while the theoretical etc of tomato calculated as the water requirement of tomato at 80 % canopy cover in this study was 4.94 mm/day. this indicated that the mean values of etc of tomato obtained by direct method (lysimetric method) from the bucket over a period of 65 days were close to the theoretical value of et at its peak value. similarly, the mean values of etc obtained in this study for one stand of tomato plant by direct method were within the same values of the actual irrigation water requirement (etc) of drip irrigated tomato crop grown in tropical greenhouse environment varied from 4.1 to 5.6 mm/day (harmanto et al., 2005). tomato plant in the transparent garden shed at 45 days irrigated with magnetically treated water (mtw) was shown in fig. 3. the results of evapotranspiration showed that tomato plant absorbed more water from magnetically treated water than the non – magnetically treated water when the same quantity of water was applied to the tomato plant. this increased the rate of vegetative growth of tomato plant as shown in table 5. this was in agreement with research of helal (2010) in which he reported that magnetic treatment of water had effect on plant by increasing the activities of antioxidant enzymes, photosynthetic activity and photosynthetic pigments which enhanced the plants growth and productivity. the results of growth rate and evapotranspiration obtained from magnetically treated water were higher than the growth and evapotranspiration from the non – magnetic treated water which was also in agreement that magnetic treatment of water increased the nutrient uptake (aoda and fattah, 2011 and babu, 2010). yusuf and ogunlela.: effect of magnetic treatment of water on evapotranspiration of tomato azojete, 13(1):86-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 91 table 2: mean value of the mass of water lost due to evapotranspiration (etc) and the daily et of tomato plant for 65 days (two stands of tomato plant per bucket) s/no date mass of water lost due to evapotranspiration (kg/day) computed evapotranspiration of tomato due to water lost (mm/day) t1 t2 t3 tc t1 t2 t3 tc 1 27-30/10/2014 0.508 0.535 0.466 0.381 9.35 9.85 8.58 7.01 2 01-03/11/2014 0.290 0.370 0.355 0.375* 5.34 6.81 6.53 6.90* 3 05-09/11/2014 0.333 0.330 0.355 0.293 6.13 6.07 6.53 5.39 4 09-11/11/2014 0.380 0.400 0.372 0.332 6.99 7.36 6.85 6.12 5 12-14/11/2014 0.455 0.490 0.470 0.440 8.37 9.02 8.66 8.10 6 14-16/11/2014 0.375 0.390 0.385 0.335 6.90 7.18 7.09 6.17 7 16-18/11/2014 0.585 0.560 0.565 0.565 10.77 10.31 10.40 10.40 8 18-19/11/2014 0.400 0.400 0.420 0.220 7.36 7.36 7.73 4.05 9 19-22/11/2014 0.503 0.497 0.533 0.460 9.26 9.15 9.81 8.47 10 22-24/11/2014 0.360 0.355 0.375 0.285 6.63 6.53 6.90 5.25 11 25-28/11/2014 0.457 0.450 0.473 0.433 8.41 8.28 8.71 7.97 12 28-30/11/2014 0.565 0.520 0.515 0.490 10.40 9.57 9.48 9.02 13 30-02/12/2014 0.520 0.520 0.535 0.455 9.57 9.52 9.85 8.37 14 02-12/12/2014 0.590 0.570 0.605 0.500 10.86 10.49 11.14 9.20 15 04-07/12/2014 0.533 0.480 0.483 0.467 9.81 8.83 8.89 8.60 16 07-10/12/2014 0.470 0.477 0.467 0.350 8.65 8.78 8.60 6.44 17 10-12/12/2014 0.535 0.470 0.485 0.405 9.85 8.65 8.93 7.45 18 12-15/12/2014 0.473 0.447 0.443 0.397 8.71 8.23 8.15 7.31 19 15-17/12/2014 0.500 0.520 0.485 0.425 9.20 9.57 8.93 7.82 20 17-19/12/2014 0720 0.725 0.690 0.565 13.25 13.34 12.70 10.40 21 19-22/12/2014 0.393 0.440 0.420 0.347 7.23 8.10 7.73 6.39 22 22-24/12/2014 0.660 0.605 0.540 0.470 12.15 11.14 9.94 8.65 23 24-26/12/2014 0.695 0.605 0.655 0.605 12.79 11.14 12.06 11.14 24 27-29/12/2014 0.730 0.775 0.745 0.650 13.44 14.26 13.71 11.96 25 29-31/12/2014 0.710 0.675 0.635 0.660 13.07 12.42 11.69 12.15 mean 0.510 0.504 0.499 0.436 9.38 9.28 9.18 8.03 et for 1 tomato stand 0.255 0.252 0.250 0.218 4.69 4.64 4.59 4.02 t1=magnetic water treated with 124 g, t2 = 319 g, t3 = 719 g and tc = non-magnetic water. * = mass of water lost/evapotranspiration in which tc (control experiment) was greater than the value obtained from t1, t2 and t3 (each treatment was replicated 7 times). table 3: anova for the evapotranspiration of tomato plant (data obtained on 27–30 october, 2014) source of error degree of freedom (d.f) sum of square (ss) mean square (ms) calculated f tabular f at p ≤ 5 % treatment 3 32.30 10.77 8.10 2.78 error 24 31.90 1.33 total 27 table 4: anova for the evapotranspiration of tomato plant (data obtained on 18–19 november, 2014) source of error degree of freedom (d.f) sum of square (ss) mean square (ms) calculated f tabular f at p ≤ 5 % treatment 3 62.704 20.901 7.08 2.78 error 24 70.819 2.951 total 27 133.523 arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1):86-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 92 table 5: mean heights of the tomato plant during vegetative growth t1=124 g, t2=319 g, t3=719 g and tc = 0.0 g (tc = non – magnetically treated water) but t1, t2 and t3 were magnetic water treated with the respective flux densities. t1= magnetized water treated with 124 g, t2 = 319 g, t3 = 719 g and tc = 0 g (non – magnetized water). figure 1: evapotranspiration of tomato plant obtained by direct method figure 2: mean evapotaranspiration of two stands of tomato plant per bucket over a period of 65 days (from 34 days after planting to maturity stage) 0 2 4 6 8 10 12 14 16 2 7 -3 0 /1 0 /2 0 1 4 0 1 -0 3 /1 1 /2 0 1 4 0 5 -0 9 /1 1 /2 0 1 4 0 9 -1 1 /1 1 /2 0 1 4 1 2 -1 4 /1 1 /2 0 1 4 1 4 -1 6 /1 1 /2 0 1 4 1 6 -1 8 /1 1 /2 0 1 4 1 8 -1 9 /1 1 /2 0 1 4 1 9 -2 2 /1 1 /2 0 1 4 2 2 -2 4 /1 1 /2 0 1 4 2 5 -2 8 /1 1 /2 0 1 4 2 8 -3 0 /1 1 /2 0 1 4 3 0 -0 2 /1 2 /2 0 1 4 0 2 -1 2 /1 2 /2 0 1 4 0 4 -0 7 /1 2 /2 0 1 4 0 7 -1 0 /1 2 /2 0 1 4 1 0 -1 2 /1 2 /2 0 1 4 1 2 -1 5 /1 2 /2 0 1 4 1 5 -1 7 /1 2 /2 0 1 4 1 7 -1 9 /1 2 /2 0 1 4 1 9 -2 2 /1 2 /2 0 1 4 2 2 -2 4 /1 2 /2 0 1 4 2 4 -2 6 /1 2 /2 0 1 4 2 7 -2 9 /1 2 /2 0 1 4 2 9 -3 1 /1 2 /2 0 1 4 e v ap o tr an sp ir at io n ( m m /d ay ) t1 t2 t3 tc 7 7.5 8 8.5 9 9.5 t1 t2 t3 tc t1 t2 t3 tc date days after planting tomato plant height (mm) t1 t2 t3 tc 19/10/2014 26 154.3 178.6 199.3 137.1 25/10/2014 32 302.1 325.0 330.0 243.6 30/10/2014 37 446.4 453.6 457.9 345.7 03/11/2014 41 515.0 532.0 530.0 407.9 09/11/2014 47 560.0 556.4 588.6 469.3 yusuf and ogunlela.: effect of magnetic treatment of water on evapotranspiration of tomato azojete, 13(1):86-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 93 figure 3: tomato plant in garden shed at 45 days irrigated with magnetically treated water 4. conclusion magnetic treatment of irrigation water increased the rate of water absorption by plant for evapotranspiration by 1.25 to 1.35 mm/day for two stands of tomato per bucket which eventually increased the rate of vegetative growth of the tomato plant. references adeboye, ob., osunbitan, ja., adekalu, ko. and okunade, da. 2009. evaluation of fao56 penman-monteith and temperature based models in estimating reference evapotranspiration using complete and limited data, application to nigeria. cigr journal manuscript no 1291, vol. xi: 1 – 25. anand, a., nagarajan, s., verma, aps., joshi, dk., pathak, pc. and bhardwaj, j. 2012. pre treatment of seeds with static magnetic field ameliorates soil water stress in seedling of maize (zea mays l.), indian journal of biochemistry and biophysics, 49(1): 63 – 70. aoda, mi. and fattah, ma. 2011. the interactive effects of water magnetic treatment and deficit irrigation on plant productivity and water use efficiency of corn (zea mays l.) iraqi journal of agricultural sciences, 42:164-179. babu, c. 2010. use of magnetic water and polymer in agriculture. tropical research, id 08 – 806 – 001. chern, cc. 2012. application of magnetic water to stimulate the lady’s finger (abelmosculentus l.) moench plant growth. b. eng. thesis submitted to faculty of civil engineering, university of technology, malaysia. chineke, tc., idinoba, me and ajayi, oc. 2011. seasonal et signatures under a changing land scope and ecosystem management in nigeria implication for agriculture and food security”. american journal of scientific and industrial research 2(2):191-204. arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1):86-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 94 ejieji cj. 2011. performance of three empirical reference evapotranspiration models under three sky conditions using two solar radiation estimation methods at ilorin, nigeria. cigr journal manuscript no 1673, 13 (3): 1 – 21. ejieji, cj and adeniran, ka. 2009. effect of water and fertilizer stress on the yield, fresh and dry matter production of grain amaranth. australian journal of agricultural engineering, 1(1):18-24. el sayed, h. and sayed a. 2014. impact of magnetic water irrigation for improving the growth, chemical composition and yield production of broad bean (vicia faba l.) plant. american journal of experimental agriculture, 4(4): 476-496. harmanto, salokhe, vm, babel, ms. and tantau, hj. 2005. water requirement of drip irrigated tomatoes grown in greenhouse in tropical environment. elsevier journal of agricultural water management, 71: 225 – 245. helal, rm. 2010. the impact of magnetic water application for improving common bean (pheseolus vulgaris l) production. new york science journal, 4 (6):15-20. hozayn, m. and abdulqados, ams. 2010 irrigation with magnetized water enhances growth, chemical constituent and yield of chickpea (circer arietinum l.). agriculture and biology journal of north america, 1(4): 671 – 676. maheshwari, rl. and grewal, hs. 2009. magnetic treatment of irrigation water: its effects on vegetable crop yield and water productivity. journal of agricultural water management, 96 (8) :1229-1236 mcmahon, ca. 2006. investigation of the quality of water treated by magnetic fields. b. eng. thesis, university of southern queensland. mdsa’at sk. 2006. subsurface flow and free water surface flow constructed wetland with magnetic field for leachate treatment. m.eng. thesis submitted to faculty of civil engineering, university of technology, malaysia. michael, am. 2008. irrigation theory and practice. 2 nd edition, vikas publishing ltd, new delhi. ogunlela, ao. 2001. stochastic analysis of rainfall events in ilorin, nigeria. journal of agricultural research and development, 39 – 49. selim, mm. 2008. application of magnetic technologies in correcting under ground brackish water for irrigation in the arid and semi-arid ecosystem, the 3rd international conference on water resources and arid environments, and the 1st arab water forum. trajikovic, s. and gocic, m. 2010. comparison of some empirical equations for estimating daily reference evapotranspiration. journal of architecture and civil engineering, university of nis, 8 (20): 163 – 168. ufoegbune, gc., bello, nj., dada, of., eruola, ac., makinde, aa. and amori, aa. 2012. estimating water availability for agriculture in abeokuta south western nigeria. global journal of science frontier research agricultural and veterinary sciences, 12 (9) version 1: 13 – 24. yusuf and ogunlela.: effect of magnetic treatment of water on evapotranspiration of tomato azojete, 13(1):86-96. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 95 appendix a mass of the bucket with tomato plant recorded in the consumptive use experiment for the determination of evapotranspiration for the first and second readings. t1,t2, t3 and tc were as previously defined in table 2 row mass of the bucket with tomato plant for evapotranspiration (kg) date t1 t2 t3 tc date t1 t2 t3 tc 1 15.08 14.91 14.63 15.03 13.21 12.98 13.15 13.89 2 15.31 14.74 14.80 15.82 13.61 13.38 13.72 14.57 3 27/10/2014 15.82 15.48 15.48 16.10 30/10/2014 14.17 14.06 14.06 14.91 4 15.48 15.65 15.37 15.25 14.00 14.00 13.83 14.17 5 15.88 16.95 14.97 15.93 14.46 15.20 13.32 14.74 6 16.56 15.65 15.54 16.67 15.37 14.06 14.17 15.65 7 15.76 15.88 15.82 15.42 14.40 14.34 14.57 14.29 arid zone journal of engineering, technology and environment, february, 2017; vol. 13(1):86-96. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 96 appendix b mass difference in the bucket due to water lost to evapotranspiration in the consumptive use experiment. t1, t2, t3 and tc were as previously defined in table 2 row mass difference in the bucket due to water lost to evapotranspiration (kg) date t1 t2 t3 tc date t1 t2 t3 tc 1 1.87 1.93 1.48 1.14 0.54 0.74 1.08 0.91 2 1.70 1.36 1.08 1.25 0.57 0.96 0.79 0.62 3 27/10/2014 1.65 1.42 1.42 1.19 01/11/2014 0.51 0.62 0.62 0.74 4 to 1.48 1.65 1.54 1.08 to 0.57 0.74 0.57 0.74 5 30/10/2014 1.42 1.75 1.65 1.19 03/11/2014 0.51 0.74 0.74 0.62 6 1.19 1.59 1.37 1.02 0.51 0.68 0.57 0.74 7 1.36 1.54 1.25 1.13 0.85 0.68 0.57 0.85 mean 1.524 1.606 1.399 1.143 mean 0.58 0.74 0.71 0.75 kg/day 0.508 0.535 0.466 0.381 kg/day 0.290 0.370 0.355 0.375 mm/day 9.35 9.85 8.58 7.01 mm/day 5.34 6.81 6.53 6.90 arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):821-832 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 821 original research article five-factor response surface optimisation of hydrochloric acid dissolution of alumina from a nigerian clay h. o. orugba1, o. d. onukwuli2, a. k. babayemi3 and j. c. umezuegbu3 1delta state university, abraka nigeria, department of chemical engineering 2nnamdi azikiwe university, awka nigeria, department of chemical engineering 3odumegwu ojukwu university, uli, nigeria, department of chemical engineering *corresponding author’s email address: orugbahenry@yahoo.com 1.0 introduction aluminum is in high demand all over the world today due to some of its unique properties like hardness, strength and electrical conductivity making it extremely useful in so many engineering applications like electric power transmission (olaremu, 2005). the expanded usage of the metal coupled with its ore depletion resulting from the increased mining of bauxite which is the most important ore from which aluminum is produced (hosseini et al., 2011) is responsible for the high cost of the metal. for a continuous supply of the metal, there is need to explore alternative materials from which it can be produced (al-zahrani and abdel-majid, 2009; orugba et al., 2020). many nigerian clays have been identified to be very rich in alumina content (ogbuagu, et al., 2010; ajemba and onukwuli, 2012; ajemba et al., 2012; orugba et al., 2014; udochukwu et al., 2020). different methods have been adopted by researchers over the years to recover alumina from clays of which acid leaching has been an outstanding method (alzahrani and abdel-majid, 2009). in the dissolution of alumina from the clays using acids or alkalis, it is important to investigate the process parameters in order to obtain their optimum conditions to enhance efficient recovery, in which case, the optimization of the dissolution process becomes very important. in order to determine the most appropriate values of process variables, optimization is very important. in a leaching process, the calcination temperature, leaching temperature, stirring speed, acid concentration and liquid-solid ratio have been identified as important parameters that control the yield of alumina from clays (orugba et al., 2014, 2020). the chief aim in any optimization process is to obtain the minimum value or maximum value of a function depending on the circumstances. the need to search for the economic conditions of process variables is paramount because apart from cost reduction, certain process variables if not properly controlled can increase waste generation into the ecosystem. for example, the energy needed in the heat activation step is obtained from burning article information abstract the major challenge encountered in the process of making the acid dissolution of alumina from clays economically viable is the determination of the optimum conditions of the key process variables in order to enhance efficient recovery. high alumina recovery from clays can be achieved by determining the optimum conditions of the process variables during optimization. in this research, using the experimental design, the combined effects of five independent variables (calcination temperature, leaching temperature, acid concentration, stirring speed and liquid/solid ratio) on the yield of alumina from the local clay was studied and the second order polynomial regression equation was developed to evaluate the influence of the five independent variables on alumina yield. model adequacy test was performed using the analysis of variance (anova) and 0.9209 was obtained as the correlation value between the experimental responses and the predicted responses. the optimum yield of alumina was obtained as 80.07% at 677.27°c heat of activation; 65.18°c leaching temperature; 1.9mol/cm3hcl concentration; 10.36 liquid-solid weight ratio and 442.92rpm stirring speed. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 september, 2020 revised 17 november, 2020 accepted 21 november, 2020 keywords: clay leaching alumina optimization hydrochloric acid http://www.azojete.com.ng orugba et al: five-factor response surface optimisation of hydrochloric acid dissolution of alumina from a nigerian clay. azojete,16(4):821-832. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 822 of petroleum-based fuels which increases green house gases generation into the atmosphere posing risks to the environment (orugba et al., 2019a, 2019b). in the chemical and process industry, the response surface methodology (rsm) has been employed for the purpose of either obtaining higher-value products or operating the process in a cost effective way and ensuring the process operates in a more reliable and stable way (alam et al., 2007; gunawan and suhendra, 2008; narayana et al., 2011; sudamalla et al., 2012). ajemba et al., (2012) performed the optimization of alumina dissolution from ukpor clay in tetra-oxosulphate (vi) acid using the response surface methodology and obtained an optimum yield of 97.23% at the leaching conditions of calcination temperature of 729.54°c; leaching temperature of 103.25°c; acid concentration of 2.93mol/l; solid/liquid ratio of 0.027g/ml and stirring speed of 436.34 rpm. orugba et al., (2014) studied the process modeling of sulphuric acid leaching of iron from a local nigerian clay using the response surface methodology and obtained the iron yield of 84.7% at calcinations temperature of 650°c; leaching temperature of 70.02°c; acid concentration of 1.89mol/cm3; liquid-solid ratio of 10.67 and stirring speed of 379.80rpm. ohale et al., (2017) used artificial neural network (ann) and response surface methodology based on a 25-1 fractional factorial design as tools for simulation and optimization of the dissolution process for a nigerian local clay and obtained an optimal response of 81.45% yield of alumina at 4.6 m sulphuric acid concentration, 214 min leaching time, 0.085 g/ml dosage and 214 rpm stirring speed. onukwuli et al., (2018) performed the process optimization of hydrochloric acid leaching of iron from agbaja clay using the response surface methodology and obtained iron yield of 85.13 % at calcinations temperature of 800°c, leaching temperature of 53.7°c, hcl concentration of 2.34 mol/cm3, liquid to solid ratio of 9.90cm3/g and stirring speed of 250 rpm. every clay has its unique properties and responds to different leaching conditions in different ways hence the conditions that produce optimum ore yield for a particular clay may not produce same result for another clay sample. therefore, generalizing leaching conditions for all clays is highly discouraged. the local clay studied in this work has not been studied extensively hence performing the optimization of its leaching process is important so as to obtain the values of process variables that guarantee optimum alumina yield. the response surface methodology (rsm) was used in the optimization study due to its robustness (raissi and farsani, 2009) while hcl was considered as the solvent because it is cheap and previous researches have recorded significant alumina yield with hcl (al-zahrani and abdel-majid, 2009). the aim of this research work is to investigate the influence of five process variables as well as their possible interactions on alumina yield from the local clay using hydrochloric acid so as to obtain their optimum conditions that guarantee maximum alumina yield. using the response surface methodology, a suitable predictive model will be obtained for the dissolution process from the data obtained from few experiments through regression analysis. 2.0 materials and methods 2.1 material preparation and leaching experiments the local clay was obtained from ozoro (6.24°n, 5.55°e) in delta state nigeria. the characterization of this clay by orugba et al., (2014) and orugba et al., (2020) revealed that the local clay has 33.90% of alumina making it a very viable source of the ore. the clay was soaked in water for two days in order to ease the removal of debris and stony materials. the dissolved clay was properly sieved and sun-dried for 24 hours then oven-dried at 60°c for 18 hours to aggregate the particles. the clay samples were subjected to heat activation in a muffle furnace at different temperatures ranging from 400°c to 900°c for a period of 1hr in order to study the influence of temperature of activation on alumina yield (al-zahrani and abdel-majid, 2003). the activated clay samples were ground to the same particle size of 0.045mm to increase the surface areas of the particles (ozdemir and cetisli, 2005). the prepared sample clay were properly labeled and subjected to leaching experiments. for each leaching experiment, 20g of http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):821-832. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 823 the activated clay was weighed into an already determined volume of the acid and heated in a round bottom flask for a period of 30minutes based on the conditions in the experimental design matrix shown in table 1. at the end of the period, 2ml of each sample was collected and analyzed for alumina ion using the atomic adsorption spectra (aas) (al-zahrani and abdelmajid, 2003; orugba et al., 2014). 2.2 design of experiment the experimental design matrix was carried out using the central composite rotatable design of the design expert. five independent variables (calcinations temperature, leaching temperature, acid concentration, liquid-solid ratio and stirring speed) were investigated at five levels and a total of 50 experiments were obtained from the design using the central composite rotatable design of 25 = 32 plus six centre points and (2 x 6 = 12) star points the yield of alumina from the ore was optimized using the response surface methodology. calcination temperature was varied from 400°c 900°c, leaching temperature from 45°c 85°c, acid concentration from 0.5mol/cm3 3mol/cm3, liquid-solid ratio from 4cm3/g 16cm3/g and stirring speed from 90rpm720rpm. the experimental matrix as well as alumina yield is presented in table 1. 2.3 statistical analysis the statistical analysis of the result was performed using design expert software (version v10) and a second order polynomial equation that represents the response (alumina yield) as a function of the five independent variables was developed based on equation (1). y = b0 + i=1 k bixi� + i=1 k biixi 2� + i=1 k bijxi� xj 1 the alumina yield being the response is represented by y, b0 is the response of the central point, while the main effects and the interactions of the variables xi on the response y are measured by the other terms. the number of factors is represented by k while the independent variables under study are represented by xi and xj. the model adequacy was tested using the analysis of variance (anova) based on f-test. 3.0 results and discussion 3.1 generation of the regression model equation the influence of the interactions of the five independent variables on the yield of alumina from the local clay was investigated from the design matrix presented in table 1. table 1: experimental matrix and alumina yield std. order calcinations temp (°c) x1 leaching temp (°c) x2 acid conc. (mol/cm3) x3 liquid/solid ratio (cm3/g) x4 stirring speed (rpm) x5 yield (%) exp. value pred. value 1 400 45 0.5 4 90 39.8 46.0 2 850 45 0.5 4 90 59.5 56.6 3 400 90 0.5 4 90 57.6 56.5 4 850 90 0.5 4 90 66.1 64.9 5 400 45 3 4 90 54.9 56.9 6 850 45 3 4 90 67.3 64.4 7 400 90 3 4 90 66.5 63.8 8 850 90 3 4 90 70.1 69.1 9 400 45 0.5 16 90 58.2 55.3 10 850 45 0.5 16 90 64.9 64.8 11 400 90 0.5 16 90 57.8 62.3 12 850 90 0.5 16 90 72.4 69.7 13 400 45 3 16 90 67.9 66.9 14 850 45 3 16 90 71.2 73.4 15 400 90 3 16 90 73.2 70.3 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng orugba et al: five-factor response surface optimisation of hydrochloric acid dissolution of alumina from a nigerian clay. azojete,16(4):821-832. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 824 16 850 90 3 16 90 73.5 74.6 17 400 45 0.5 4 720 47.3 49.1 18 850 45 0.5 4 720 58.6 58.4 19 400 90 0.5 4 720 61.2 56.9 20 850 90 0.5 4 720 63.9 63.9 21 400 45 3 4 720 62.9 58.3 22 850 45 3 4 720 64.9 64.6 23 400 90 3 4 720 59.2 62.4 24 850 90 3 4 720 66.9 66.4 25 400 45 0.5 16 720 52.8 50.1 26 850 45 0.5 16 720 55.2 58.4 27 400 90 0.5 16 720 51.9 54.4 28 850 90 0.5 16 720 62.3 60.5 29 400 45 3 16 720 54.2 60.1 30 850 45 3 16 720 69.3 65.4 31 400 90 3 16 720 61.7 60.7 32 850 90 3 16 720 69.2 63.8 33 89.9 67.5 1.75 10 405 57.4 54.5 34 1160 67.5 1.75 10 405 65.3 70.6 35 625 13.9 1.75 10 405 54.8 53.2 36 625 121 1.75 10 405 59.9 63.8 37 625 67.5 -1.22 10 405 51.3 50.4 38 625 67.5 4.72 10 405 63.9 67.2 39 625 67.5 1.75 -4.27 405 49.9 51.8 40 625 67.5 1.75 24.27 405 59.1 59.6 41 625 67.5 1.75 10 -344 64.3 64.9 42 625 67.5 1.75 10 1154 53.9 55.7 43 625 67.5 1.75 10 405 78.8 79.6 44 625 67.5 1.75 10 405 79.3 79.6 45 625 67.5 1.75 10 405 79.4 79.6 46 625 67.5 1.75 10 405 79 79.6 47 625 67.5 1.75 10 405 79 79.6 48 625 67.5 1.75 10 405 79.4 79.6 49 625 67.5 1.75 10 405 80 79.6 50 625 67.5 1.75 10 405 80 79.6 the technique of the central composite design was employed to generate a polynomial regression equation that shows the relationship that exists between the dependent variable (alumina yield) and the five independent variables (calcination temperature, leaching temperature, stirring speed, acid concentration and liquid-solid ratio) as shown in equation (2). yal2o3 = 79.56 + 3.39x1 + 2.23x2 + 3.54x3 + 1.64x4 − 1.94x5– 0.55x1x2 − 0.76x1x3 – 0.24x1x4 – 0.31x1x5 − 0.91x2x3 – 0.87x2 – 0.70x2x5 + 0.91x3x4 − 0.41x3x5 – 2.05x4x5 – 3.01x1 2– 3.72x2 2 − 3.67x3 2 − 4.22x4 2 − 3.41x5 2 2 3.2 model adequacy test in order to account for the adequacy of the model equation obtained, a model adequacy test using the analysis of variance (anova) was performed as summarized in table 2. the f-value and the p-value were used to evaluate the adequacy of the model because from statistical tests, the smaller the p-value and the larger the f-value, the higher the accuracy of the model (rashid et al., 2011). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):821-832. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 825 table 2: the summary of the model adequacy test source sum of squares degree of freedom mean squares f-value p-value remarks sequential sum of squares linear 1537.326 5 307.4652 4.484532 0.0022 significant 2fi 241.09 10 24.109 0.295325 0.9776 not significant quadratic 2415.38 5 483.0759 38.89003 < 0.0001 significant cubic 239.5728 15 15.97152 1.853254 0.1282 not significant source std dev. r2 adjusted r2 predicted r2 press remarks model summary statistics linear 8.280173 0.337575 0.2623 0.232841 3493.658 inadequate 2fi 9.035235 0.390515 0.121625 0.130424 3960.068 inadequate quadratic 3.524428 0.920899 0.866347 0.708686 1326.65 adequate cubic 2.935659 0.973506 0.907272 -0.22017 5556.674 inadequate when the p-value is less than 0.01, the model is highly significant, when the p-value lies between 0.01 and 0.05, it is significant but if it is greater than 0.05, it is not significant (rashid et al., 2011). from the f-values of the different models presented in table 3, it could be seen that the quadratic model with the highest f-value of 38.89 and with a p-value less than 0.0001adequately fits the experimental data. the significant terms of the model equation generated in equation (2) were selected based on their f and p-values as shown in table 3. table 3: anova for response surface quadratic model source sum of squares degree of freedom f-value p-value (prod.>f) model 4193.796 20 16.88107 < 0.0001 x1 498.8237 1 40.1578 < 0.0001 x2 216.0211 1 17.39078 0.0003 x3 543.0555 1 43.71868 < 0.0001 x4 115.995 1 9.338178 0.0048 x5 163.4306 1 13.15698 0.0011 x1x2 9.68 1 0.779288 0.3846 x1x3 18.605 1 1.497795 0.2309 x1x4 1.805 1 0.145312 0.7058 x1x5 3.125 1 0.251578 0.6198 x2x3 26.645 1 2.145056 0.1538 x2x4 24.5 1 1.972372 0.1708 x2x5 15.68 1 1.262318 0.2704 x3x4 1.125 1 0.090568 0.7656 x3x5 5.445 1 0.43835 0.5131 x4x5 134.48 1 10.82631 0.0026 x12 503.2336 1 40.51281 < 0.0001 x22 767.5096 1 61.78836 < 0.0001 x32 749.3644 1 60.32757 < 0.0001 x42 989.7077 1 79.67641 < 0.0001 x52 645.0513 1 51.92985 < 0.0001 residual 360.2261 29 lack of fit 358.8274 22 81.62455 < 0.0001 pure error 1.39875 7 cor total 4554.022 49 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng orugba et al: five-factor response surface optimisation of hydrochloric acid dissolution of alumina from a nigerian clay. azojete,16(4):821-832. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 826 the significance of each term of the model equation is judged based on its p-value as shown in table 3. it could be revealed that the linear effects of all the independent variables (x1, x2, x3, x4, and x5) as well as their quadratic effects (x12, x22, x32, x42, and x52) are highly significant on the yield of alumina while their interactions are not significant. when only the significant terms in equation (2) are considered, a final model equation was obtained as presented in equation (3). yal2o3 = 79.56 + 3.39x1 + 2.23x2 + 3.54x3 + 1.64x4 − 1.94x5– 2.05x4x5 – 3.01x1 2– 3.72x2 2 − 3.67x3 2 − 4.22x4 2 − 3.41x5 2 (3) the summary of the regression values of the final model equation is presented in table 4. table 4: summary of regression values item value std. dev. 3.52 mean 63.94 c.v% 5.51 press 1326.65 r-squared 0.9209 adj. r-squared 0.8863 pre-r-squared 0.7087 adeq precision 14.672 from table 4, with the coefficient of variation value of 5.51%, the model can be considered reasonably reproducible. the signal to noise ratio which is given as the value of the adequacy precision is 14.672 indicates that an adequate relationship of signal to noise ratio exists. internally studentized residuals nor ma l % pro bab ility normal plot of residuals -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 1 5 10 20 30 50 70 80 90 95 99 figure 1: plot of normal probability against studentized residual http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):821-832. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 827 22 2 actual pre dict ed predicted vs. actual 30.00 40.00 50.00 60.00 70.00 80.00 30.00 40.00 50.00 60.00 70.00 80.00 figure 2: plot of predicted yield values against actual yield values the plot of normal probability against studentized residual given in figure 1 and the plot of predicted yield values against actual yield values presented in figure 2 revealed that a reasonable agreement exists between the actual and predicted alumina yield. 3.3 response surface plots for the acid-dissolution of alumina in order to study the combined effects of process variables on the yield of the ore, 3d response plot of any two independent variables is plotted while keeping another variable at its centre level as shown in figures 3-12. figure 3 shows the variation of alumina yield with calcination temperature and leaching temperature. at low calcination temperatures and low leaching temperatures, very low alumina yield was recorded but as calcination temperature and leaching temperature increased, alumina yield increased. however, when calcination temperature was increased beyond 750°c, there was a decline in alumina yield. the decreased alumina yield at elevated calcination temperature could be due to the clay solid phase transformation and total dehydration (al-zahrani and abdel-majid, 2009) the influence of acid concentration and calcination temperature on alumina yield is presented in figure 4. from the figure, alumina yield increased with increase acid concentration and calcination temperature. maximum alumina yield was obtained at the highest acid concentration of 3mol/cm3. the increased alumina yield with acid concentration could be due to the presence of more hydroxonium ions which increase leaching ability of the solvent (poppleton and sawyer, 1977) the combined effect of liquid/solid ratio and calcination temperature on alumina yield is shown in figure 5. as can be seen in the figure, high alumina yields were recorded with increased liquid/solid ratio and calcination temperature. increased liquid/solid ratio makes more solvent available for proper dissolution of the ore and this enhances higher leaching rates (ozdemir and cetisli, 2005). figure 6 shows the influence of stirring speed and calcination temperature on alumina yield. from the figure, the yield of alumina increased as stirring speed and calcination temperature were increased. the lowest alumina yield was recorded at the lowest stirring speed of 90rpm and at the lowest calcination temperature of 400°c. as stirring speed increased, there is increased contact between the solid particles and the solvent which enhances ore dissolution (orugba et al., 2014). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng orugba et al: five-factor response surface optimisation of hydrochloric acid dissolution of alumina from a nigerian clay. azojete,16(4):821-832. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 828 the combined influence of acid concentration and leaching temperature on alumina yield is presented in figure 7. as shown in the figure, alumina yield increased as acid concentration and leaching temperature were increased. higher acid concentrations means more solvent ions are made available for dissolution and this enhances dissolution rate. also, high leaching temperatures increased the kinetic energy of the reacting species which also increase dissolution rate (orugba et al., 2014). figure 8 shows the combined effect of liquid/solid ratio and leaching temperature on alumina yield. as can be seen from the figure, increasing liquid/solid ratio and leaching temperature increased alumina yield as the lowest alumina yield occurred at the lowest stirring speed and leaching temperature. at low leaching temperatures, the kinetic energies of the reacting species are low hence decreased reaction rate but this will increase as the leaching temperature increases. also, low liquid/solid ratio implies less solvent to dissolve the solid particles hence reduced dissolution. similar results were recorded by al-zahrani and abdel-majid, (2003). the combined influence of liquid/solid ratio and acid concentration is shown in figure 9. as shown in figure 9, at low liquid/solid ratio and low acid concentration, the alumina yield is low but the yield was seen to increase at higher liquid/solid ratios and acid concentration. figure 10 shows the combined influence of stirring speed and acid concentration. the yield of alumina increased with increased stirring speed and acid concentration. the highest alumina yield occurred at the highest acid concentration of 3mol/cm3. the combined influence of stirring speed and liquid/solid ratio on alumina yield is presented in figure 11. as shown in the figure, increasing both the stirring speed and liquid/solid ratio increased alumina yield as the highest alumina yield was obtained at the highest stirring speed and highest liquid/solid ratio. figure 12 shows the combined influence of stirring speed and leaching temperature on alumina yield. as both stirring speed and leaching temperature increased, alumina yield was also increased. the increased alumina yield with stirring speed is due to the increased contact between solid particles and solvent which enhances dissolution rate while increased leaching temperature increases the kinetic energy of the reacting species which also enhances dissolution rate. 45.00 54.00 63.00 72.00 81.00 90.00 400.00 490.00 580.00 670.00 760.00 850.00 48 50 52 54 56 58 y ield a: calcination temp. b: leaching temp 0.50 1.00 1.50 2.00 2.50 3.00 400.00 490.00 580.00 670.00 760.00 850.00 65 70 75 80 85 y iel d a: calcination temp. c: acid conc. figure 3: variation of alumina yield with calcination temperature and leaching temperature figure 4: variation of alumina yield with calcination temperature and acid concentration. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):821-832. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 829 4.00 7.00 10.00 13.00 16.00 400.00 490.00 580.00 670.00 760.00 850.00 65 70 75 80 85 y ield a: calcination temp. d: liquid/solid ratio 90.00 180.00 270.00 360.00 450.00 540.00 630.00 720.00 400.00 490.00 580.00 670.00 760.00 850.00 65 70 75 80 85 y iel d a: calcination temp. e: stirring speed figure 5: variation of alumina yield with calcination temperature and liquid-solid ratio figure 6: variation of alumina yield with calcination temperature and stirring speed 0.50 1.00 1.50 2.00 2.50 3.00 45.00 54.00 63.00 72.00 81.00 90.00 65 70 75 80 85 y ield b: leaching temp c: acid conc. 4.00 7.00 10.00 13.00 16.00 45.00 54.00 63.00 72.00 81.00 90.00 65 70 75 80 85 y iel d b: leaching temp d: liquid/solid ratio figure 7: variation of alumina yield with leaching temperature and acid concentration figure 8: variation of alumina yield with leaching temperature and liquid-solid ratio 4.00 7.00 10.00 13.00 16.00 0.50 1.00 1.50 2.00 2.50 3.00 65 70 75 80 85 y iel d c: acid conc. d: liquid/solid ratio 90.00 180.00 270.00 360.00 450.00 540.00 630.00 720.00 0.50 1.00 1.50 2.00 2.50 3.00 65 70 75 80 85 y ield c: acid conc. e: stirring speed figure 9: variation of alumina yield with acid concentration and stirring speed figure 10: variation of alumina yield with acid concentration and stirring speed file:///c:/users/user/downloads/azojete143/www.azojete.com.ng orugba et al: five-factor response surface optimisation of hydrochloric acid dissolution of alumina from a nigerian clay. azojete,16(4):821-832. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 830 90.00 180.00 270.00 360.00 450.00 540.00 630.00 720.00 4.00 7.00 10.00 13.00 16.00 65 70 75 80 85 y iel d d: liquid/solid ratio e: stirring speed 90.00 180.00 270.00 360.00 450.00 540.00 630.00 720.00 45.00 54.00 63.00 72.00 81.00 90.00 65 70 75 80 85 y iel d b: leaching temp e: stirring speed figure 11: variation of alumina yield with solid liquid ratio and stirring speed figure 12: variation of alumina yield with leaching temperature and stirring speed 3.4 predicting the optimum condition of alumina yield in order to further confirm the adequacy of the generated model in predicting the alumina yield, the optimum values of the five independent variables were used to perform a new set of experiments and the result is presented in table 3. table 3: comparing the experimental and predicted alumina yield using the optimum conditions variable optimum variables value alumina yield experimental predicted calcinations temp. (°c) x1 677 80.07 78.91 leaching temp. (°c) x2 65 acid conc. (mol/cm3) x3 1.9 liquid-solid ratio (cm3/g) x4 10.4 stirring speed (rpm) x5 442 from the values of alumina yield obtained shown in table 3, it can be established that a good agreement exists between the predicted alumina yield and the experimental alumina yield at the optimum levels and this confirms the validity of the generated model. 4.0 conclusion developing a mathematical relationship to investigate the combined influence of different process variables on alumina yield is important in order to obtain the optimum conditions that guarantee high yield. in this research, a model equation that can be used to study the influence of five process variables on the yield of alumina from the local clay using hcl has been developed. the five process variables considered were calcination temperature, leaching temperature, stirring speed, liquid-solid ratio and acid concentration. based on experimental design using the central composite design of the response surface methodology, the secondorder polynomial regression equation appeared to fit the data most. the optimum alumina yield of 80.07% was obtained at calcinations temperature of 677.27°c; leaching temperature of 65.18°c; acid concentration of 1.9mol/cm3; liquid-solid ratio of 10.36 and stirring speed of 442.92rpm. the correlation between the predicted and experimental responses was obtained as 0.9209. the developed model can guarantee optimal dissolution of the ore from the local clay. references ajemba, ra. and onukwuli, od. 2012. process optimization of sulphuric acid leaching of alumina from nteje clayusing central composite rotatable design. international journal of multidisciplinary sciences and engineering, 3(5): 116-121. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):821-832. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: orugbahenry@yahoo.com 831 ajemba, ro., ugonabo, vi., okafor, vn. and 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a. adamu3 and y. ibrahim4 1department of civil engineering, bayero university, kano, nigeria 2department of civil engineering, university of maiduguri, borno, nigeria 3department of civil engineering, kaduna polytechnic, kaduna, nigeria 4department of geology, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: abdulrasheeddoko@gmail.com 1.0 introduction recently, the use of hydrological models to estimate runoff of a catchment that are ungauged have gained considerable attentions from hydrologists and students of hydrology all over the world. many researches conducted in urban flooding have resulted in the development of many mathematical modeling tools both free and commercial (rangari et al., 2018). for example, with the advent of storm water management model (swmm), hec-hms, hec-ras, mike lood modelling of the urban flood became easy and outputs of great understanding have been generated by these models. arcgis has made the work simpler due to its ability to extract data for directs inputs to the model (hasyman et al., 2015). generally, hydrological models are primarily classified as statistical and deterministic models. the statistical models produce outputs that have partial randomness while deterministic models do not give randomness. furthermore, deterministic hydrologic models are further classified into three major categories; lumped model, semi-distributed model and distributed model. lumped model assesses the catchment response simply at the outlet without obviously article information abstract for the past decade, the magnitude and frequency of rainfall that resulted into flooding of kano city have been relatively high and there is need to manage the flood in order to safe life and properties. this research aimed at generating challawa and jakara catchment areas runoff for hydrological applications. the two catchments were first delineated and their basic physical properties were extracted from processed 30 m x 30 m digital elevation models (dems) of the respective watershed. basin models of the watersheds were imported from arcgis 10.7 to hydrologic engineering center – hydrologic modelling system (hec-hms) environment, the meteorological models were developed in hec-hms with rainfall data and control specifications assigned which defined the period and time step of the simulation run. scs-curve number, unit hydrograph and muskingum methods were used for estimation of loss, runoff and flow routing respectively. the rainfall-runoff simulations were carried out for 31 years of maximum daily rainfall record (1988 – 2018). the simulated flow rate obtained can be used for further hydrological analysis such as flood frequency analysis and in design of safe and economical drainage and flood control facilities or in maintenance of culverts, sewers, bridges and roads for jakara and challawa catchment areas. it is recommended that; the catchment areas be gauged while further research should be conducted on the quality of the simulated flow obtained. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 march, 2021 revised 8 july, 2021 accepted 20 july, 2021 keywords: challawa basin dem hec-hms jakara basin rainfall-runoff arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 440 counting for an individual sub-basins response. the semi-distributed model is partly permitted to change in space with a division of the catchment into a number of sub-basins. whereas, the distributed model, permits its parameters to change in place at a resolution normally chosen by the client (tassew et al., 2019). good storm water design practices help to maintain drainage systems, minimize disturbance to existing drainage patterns, control flooding of property, structures, and roadways, and minimize environmental impacts of storm water runoff. urbanization tends to increase downstream peak flows, runoff volumes, and runoff velocities. these changes can cause the capacity of adequately designed drainage systems to be exceeded and disrupt natural waterways (antigha et al., 2014). in kano metropolis, urban growth has, over the years, resulted in land use changes and modifications, which significantly increased area of imperviousness. as urbanization continues, there will be increase in population density and more areas will be devoted to infrastructural development which will in turn increase impervious surfaces. with urbanization and increase in impervious surfaces threat of flooding is bound to increase during any major storm event. rainfall-runoff models are often used as a tool for a wide range of applications such as the modeling of flood events, the monitoring of water levels during different water conditions or the prediction of floods (tassew et al., 2019). flow rate data are required for flood modelling and in flood risk assessment. hence, this research is aimed at obtaining flow data through rainfall-runoff modeling for ungauged challawa and jakara catchment areas in kano city. a number of case studies carried out through researches have shown high efficiency in the use of hec-hms to simulate runoff from rainfall data for a given watersheds tassew et al., 2019; rangari et al., 2018; chang et al., 2015). therefore, this study employed hec-hms instead of using traditional methods to simulate runoff data using rainfall data and other watershed characteristics for the catchments of concerned. this research would consider two basins (jakara and challawa basins). challawa comprised gwale, kano municipal council, tarauni and kumbotso local government areas consisted of 32 wards (districts) while, jakara basin comprised dala, fagge, ungogo and some part of nasarawa local government areas consisted 62 wards (districts). 2. materials and methods 2.1 description of study area kano state is located in the northwestern nigeria on latitude 12°n and longitude 8.30°e within the semi-arid sudan savannah zone of west africa. kano has a mean height of about 481 m above sea level (mustapha et al., 2014). the state was created on may 27, 1967 from part of the northern region, kano state borders katsina state to the north-west, jigawa state to the north-east, bauchi state to the south-east and kaduna state to the south-west. kano metropolitan area consists of eight local government areas which include fagge, dala, gwale, kano municipal, tarauni, nassarawa, kumbotso and ungogo lgas with total area of 499 km2 and a total population of 2,828,86l people (npc, 2006). the latest official estimate (for 2016) is 3,931,300 inhabitants and it does suffice to say that the city is densely populated. kano city is the second largest industrial center after lagos state in nigeria and the largest in the northern nigeria with textile, tanning, footwear, cosmetics, plastics, pharmaceuticals, ceramics, furniture, food and beverages and other industries (mustapha et al., 2014). the city’s infrastructure both government owned and private arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 440 owned cannot be overemphasized. these infrastructures include schools (elementary and higher institutions), health centers, communication centers, religion centers and other social amenities. the temperature of kano usually ranges between a maximum of 33°c and a minimum of 15.8°c although sometimes during the harmattan it falls down to as low as 10°c. kano has two seasonal periods, which consist of four to five months of wet season and a long dry season lasting from october to april. the movement of the south west maritime air masses originating from atlantic ocean, influences the wet season which starts from may to september. the mean annual rainfall is about 800 mm around metropolitan kano. great temporal variation occurs in the amount of rainfall received and no two consecutive years record the same amount. the movement of the tropical maritime air masses from the southwest to the north determines the weather of kano state during the wet season (mustapha et al., 2014). the hydrogeology of kano is distinguished by three large watersheds; the outfall to river challawa, the outfall to river jakara and the other is to river wateri. these basins are considered as the main receptacles of runoff from the city. figure 1 shows the map of kano metropolis. the first source of the river jakara is traced into the kano city (i.e. the jakara/rafin mallam) and the second source is the bompai industrial estate (the getsi). the river and its tributaries have most of their length within the metropolis. along the stretch of the banks are rapid encroachment of settlements which increases their risk and vulnerability to flooding. for this, the quality of the water is very low and not suitable for many uses. while challawa river takes its source from kaduna and katsina states in the katsina highlands around malumfashi, which also serves as one of the headwaters of the challawa river system which creates dendritic networks moving eastward. some of its major tributaries include koganya, kwakwa, jare and marashi all of which join the challawa river. the last three tributaries meet at damagari in tudun-kaya, karaye local government. koganya flows into challawa at the upstream of the gorge dam in rogo local government area. other rivers from this axis that joined the challawa are kumanda, kariya, bagwari and bargi mohammed et al: rainfall-runoff modeling for challawa and jakara catchment areas of kano city, nigeria. azojete, 17(4):439-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 441 figure 1: map of the study area 2.2 input data the data required for running rainfall-runoff modelling included rainfall, digital elevation model, land use/land cover 30 m x 30 m digital elevation model of the challawa and jakara basins were obtained from united states geological survey (usgs) website and used to extract basic physiographic characteristics of the catchment areas. arcgis 10.7, archydro tool and hecgeohms were used for terrain pre-processing, basin processing and model development to generate the characteristics of basin and input files for hec-hms. other required data included basin storage (s), initial abstractions (ia), time of concentrations (tc), curve numbers (cn), lag time and muskingum parameters k and x. these parameters were obtained using the following equations; basin storage (s) (1) time of concentration tc = (2) initial abstractions (ia) ia = 0.2s (3) lag time l= 0.6tc (4) muskingum constant (k) k = n∆t (5) arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 442 2.3 land-use/land-cover (lulc) classification of challawa and jakara basins the methods of lulc classification followed by ahmad (2020), haruna et al., (2019), alfa et al., and (2018) were adopted for this research. lulc is required for the estimation of catchment area curve numbers (cn) and the cn is in turn required for rainfallrunoff modelling using hechms. the lulc classifications were carried out for the periods of 1988 2018. figure 2 shows the flowchart methodology for lulc classification. 2.4 watershed analysis of challawa and jakara basins in kano city for this study, challawa and jakara basins in kano city were considered. this study was conducted using archydro tools, hec-geohms 10.7 and arcgis 10.7. to accomplish the task of watershed analysis, three major processes were carried out which included terrain pre-processing, watershed delineation and terrain processing and basin model development. figure 3 shows the flowchart of watershed analyses methodology. figure 2: land-use/land-cover classification methodology flow chart landsat imagery layer stacking image sub setting color composite image classification  supervised  maximum likelihood field survey extraction by mask land use/land cover map reclassification land use/land cover map mohammed et al: rainfall-runoff modeling for challawa and jakara catchment areas of kano city, nigeria. azojete, 17(4):439-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 443 figure 3 flowchart of watershed analyses methodology 2.5 rainfall-runoff modeling in hec-hms rainfall-runoff modelling in hec-hms required four major components; basin models, meteorological models, control specifications and time-series data. the methods followed by rangari et al., (2018), rathod et al., (2015), choudhari et al., (2014), martin et al., (2012), output delineated watershed and processed terrain inputs strm dem stream network terrain pre-processing of challawa basin (arcgis 10.7 and archydro tool) -dem reconditioning stream segmentation -fill sinks catchment grid delineation -flow direction catchment polygon processing -flow accumulation drainage line processing -stream defination adjoint catchment processing output rasters vectors -dem -catchment -fill map -drainageline -fdr map -adjointcatchment -fac -str -strlnk -cat watershed delineation and terrain processing (arcgis 10.7 and archydro tool) i. project setup iii. basin characteristics start new project river length define project point river slope generate project basin slope ii. river profile basin centroid basin centroid elevation centroid longest flow path basin model development (arcgis 10.7 and hec-geohms) i. hms inputs/parameters v. creating input files for hec-hms ii. selecting hms process map to hms units iii. river auto name check data iv. basin auto name hms schematic add coordinates prepare data for model export background shape file output basin model arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 444 merwade, (2012) and hec-hms technical reference manual guidelines were adopted in this study. two catchment areas were considered for this research (challawa and jakara). rainfall-runoff simulations were ran for thirty one years of maximum daily rainfall events (19882018) for challawa and jakara basins in kano metropolis. 3. results and discussions 3.1 lulc for challawa and jakara catchment areas of kano city the results of lulc characterization for challawa and jakara catchment areas for year 2018 are presented in figure 4 and figure 5 respectively. the vegetation and water body in both catchment areas are low as it can be seen, vegetation covered 18.05% land use, water body covered 1.06% for challawa catchment area and 16.61% vegetation, 0.45% water body for jakara catchment area in year 2018. in comparison of the two catchments, it could be observed that jakara catchment area with built area of 64.26% is more urbanized than challawa catchment area with built up area of 60.87%. the land use land cover classifications were used alongside with soil data for estimation of curve numbers for both catchment areas. figure 4: challawa land use land cover classification map for year 2018 mohammed et al: rainfall-runoff modeling for challawa and jakara catchment areas of kano city, nigeria. azojete, 17(4):439-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 445 figure 5: jakara land use land cover classification map for year 2018 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 446 3.2 rainfall-runoff simulations using hec-hms 4. 2 3.2.1 challawa basin model figure 6 shows the challawa basin model. from figure 6, it can be seen that challawa basin has 15 subbasins, 7 junctions, 7 reaches and one outlet. . . figure 6: challawa basin model 3.2.2 computed hec-hms input parameters for challawa basin table 1 shows input parameters for challawa basin. from table 1, it can be seen that, subbasin “w160” has the biggest basin area of 11.92 km2 with longest flow path, basin slope, curve number, storage, initial abstraction, time of concentration and lag time of 4651 m, 0.0049, 82, 2.1951, 0.4390, 101 minutes and 60.60 minutes respectively. while subbasin “w190” has minimum basin area of 0.40 km2 with longest flow path, basin slope, curve number, storage, initial abstraction, time of concentration and lag time of 1707 m, 0.0216, 78, 2.82, 0.56, 26 minutes and 15.78 minutes respectively. muskingum parameters k and x values were estimated to be 1 for k and 0.2 for x and used for all the sub-basins. mohammed et al: rainfall-runoff modeling for challawa and jakara catchment areas of kano city, nigeria. azojete, 17(4):439-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 447 table 1: hec-hms input parameters for year 2018 challawa basin simulation subbasin drainid basin area (km2) longest flow path (m) basin slope (m/m) cn s ia tc (mins) lag time (mins) w160 17.0000 11.9232 4651.0010 0.0049 82.0000 2.1951 0.4390 101.0030 60.6018 w170 18.0000 5.9316 6167.9422 0.0099 85.0000 1.7647 0.3529 95.4172 57.2503 w180 16.0000 4.6315 6087.7806 0.0049 81.0000 2.3457 0.4691 124.1885 74.5131 w190 19.0000 0.4046 1707.1707 0.0216 78.0000 2.8205 0.5641 26.2925 15.7755 w200 20.0000 9.8054 5857.7530 0.0022 88.0000 1.3636 0.2727 162.6705 97.6023 w210 21.0000 12.6894 8187.2330 0.0032 91.0000 0.9890 0.1978 182.2641 109.3584 w220 22.0000 11.0967 5607.9437 0.0024 88.0000 1.3636 0.2727 153.9108 92.3465 w230 25.0000 1.7218 5179.1608 0.0041 85.0000 1.7647 0.3529 116.6048 69.9629 w240 23.0000 5.7248 2753.6001 0.0069 84.0000 1.9048 0.3810 58.9601 35.3760 w250 24.0000 6.8009 6936.0208 0.0041 85.0000 1.7647 0.3529 146.1082 87.6649 w260 26.0000 2.0230 2212.8179 0.0091 85.0000 1.7647 0.3529 44.8304 26.8982 w270 29.0000 5.0964 4974.3777 0.0068 88.0000 1.3636 0.2727 93.6560 56.1936 w280 27.0000 13.5416 4010.8410 0.0028 87.0000 1.4943 0.2989 111.6392 66.9835 w290 28.0000 6.2328 6936.0210 0.0022 91.0000 0.9890 0.1978 185.4966 111.2980 w300 30.0000 7.2916 5398.4978 0.0005 88.0000 1.3636 0.2727 270.0820 162.0492 cn = curve number, s = storage, ia = initial abstraction and tc = time of concentration 3.2.3 hec-hms output results for challawa basin the main purpose of running hec-hms was to get flow data for challawa catchment of kano city. following the standard procedures and guidelines of running hec-hms model as described in the hec-hms technical manual table 2 shows the results for year 2018 simulation. from table 2, it can be seen that, challawa basin has a total drainage area of 104.9154 km2 with a peak discharge of 188.00 m3/s and discharge volume of 36.99 mm. subbasin “w200” has highest peak discharge of 83.2 m3/s with a discharge volume of 36.11 mm, followed by subbasin “w220” which have 72.6 m3/s peak discharge with a discharge volume of 34.92 mm while subbasin “w190 recorded lowest peak discharge of 2.7 m3/s with a discharge volume of 39.98 mm. table 2: result for year 2018 simulation subbasin drainage area (km2) peak discharge (m3/s) volume (mm) w160 11.9232 32.9 39.98 w170 5.9316 25.4 44.40 w180 4.6315 24.6 38.63 w190 0.4046 2.7 39.98 w200 9.8054 83.2 36.11 w210 12.6894 54.0 36.11 w220 11.0967 72.6 34.92 w230 1.7218 8.4 36.11 w240 5.7248 25.7 39.98 w250 6.8009 29.5 44.40 w260 2.0230 12.2 56.56 w270 5.0964 45.8 28.72 w280 13.5416 56.6 31.64 w290 6.2328 36.7 36.11 w300 7.2916 36.8 32.69 outlet 104.9154 188.0 36.99 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 448 3.2.5 jakara basin model figure 7 shows the jakara basin model . from figure 7, it is observed that, jakara basin has 17 subbasins, 8 junctions, 8 reaches and one outlet. . figure 7: jakara basin model mohammed et al: rainfall-runoff modeling for challawa and jakara catchment areas of kano city, nigeria. azojete, 17(4):439-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 449 3.2.5 computed hec-hms input parameters for jakara basin table 3 shows computed hec-hms input parameters for year 2018 jakara basin simulation. it can be observed from table 3 that, subbasin “w280” has the biggest basin area of 20.27 km2 with longest flow path, basin slope, curve number, storage, initial abstraction, time of concentration and lag time of 9223.77 m, 0.0065, 85, 1.76, 0.35, 153.20 minutes and 91.92 minutes respectively. while subbasin “w300” has minimum basin area of 0.69 km2 with longest flow path, basin slope, curve number, storage, initial abstraction, time of concentration and lag time of 1444.74 m, 0.0040, 87, 1.49, 0.30, 136.79 minutes and 82.07 minutes respectively. muskingum parameters k and x values were estimated to be 1 for k and 0.2 for x and used for all the sub-basins. table 3: hec-hms input parameters for year 2018 jakara basin simulation subbasin drainid basin area (km2) longest flow path (m) basin slope (m/m) cn s ia tc (mins) lag time (mins) w180 18.0000 8.6002 6113.5908 0.0050 85.0000 1.7647 0.3529 123.5141 74.1084 w190 19.0000 0.7059 1497.7251 0.0523 87.0000 1.4943 0.2989 16.9040 10.1424 w200 20.0000 2.6601 3143.9508 0.0104 87.0000 1.4943 0.2989 55.7902 33.4741 w210 21.0000 8.2386 5902.2136 0.0037 82.0000 2.1951 0.4390 134.1988 80.5193 w220 22.0000 2.4019 2721.7620 0.0061 82.0000 2.1951 0.4390 61.0568 36.6341 w230 23.0000 4.3647 5144.0259 0.0017 83.0000 2.0482 0.4096 163.6706 98.2024 w240 24.0000 4.6143 4001.5161 0.0057 82.0000 2.1951 0.4390 84.8289 50.8973 w250 25.0000 9.5558 6330.9961 0.0039 82.0000 2.1951 0.4390 138.8014 83.2808 w260 26.0000 0.9556 1569.3613 0.0028 82.0000 2.1951 0.4390 53.8258 32.2955 w270 27.0000 8.8068 6798.7766 0.0040 85.0000 1.7647 0.3529 146.0918 87.6551 w280 28.0000 20.2737 9223.7715 0.0065 85.0000 1.7647 0.3529 153.1997 91.9198 w290 29.0000 6.8182 6327.6992 0.0041 87.0000 1.4943 0.2989 136.7884 82.0731 w300 30.0000 0.6887 1444.7393 0.0040 87.0000 1.4943 0.2989 44.3466 26.6080 w310 31.0000 13.3522 6971.1559 0.0038 88.0000 1.3636 0.2727 151.0514 90.6309 w320 32.0000 4.2011 4241.4344 0.0054 88.0000 1.3636 0.2727 90.1367 54.0820 w330 33.0000 8.9015 6152.0230 0.0043 88.0000 1.3636 0.2727 130.7820 78.4692 w340 34.0000 4.6401 4564.8113 0.0043 88.0000 1.3636 0.2727 103.9898 62.3939 cn = curve number, s = storage, ia = initial abstraction and tc = time of concentration 3.2.5 hec-hms output results for jakara basin table 4 shows jakara basin global summary result for year 2018 simulation, . from table 4, it is observed that, jakara basin has a total drainage area of 109.7759 km2 with a peak discharge of 207.70 m3/s and discharge volume of 36.56 mm. the highest peak discharge of 82.7 m3/s with a discharge volume of 36.11 mm was recorded at subbasin “w280”. while subbasin “w300 recorded lowest peak discharge of 6.3 m3/s with a discharge volume of 38.63 mm. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 450 table 4: result for year 2018 jakara simulation subbasin drainage area (km2) peak discharge (m3/s) volume (mm) w180 8.60 41.0 36.11 w190 0.71 8.30 38.63 w200 2.66 20.40 38.63 w210 8.24 33.90 32.70 w220 2.41 14.90 32.69 w230 4.36 15.50 33.78 w240 4.61 26.80 32.69 w250 9.56 38.40 32.69 w260 0.96 6.40 32.69 w270 8.81 37.50 36.11 w280 20.27 82.70 36.11 w290 6.82 32.60 38.63 w300 0.68 6.30 38.63 w310 13.35 61.10 39.98 w320 4.20 28.60 39.98 w330 8.90 45.40 39.98 w340 4.64 27.70 39.98 outlet 109.78 208.7 36.56 3.2.6 simulated flow data for challawa and jakara basins consequently, the simulated flow data obtained for challawa and jakara basins are presented in table 5 and can be used for further hydrological analysis. from table 5, it could be seen that, the flow rate of jakara basin is higher than that of challawa basin across the period of consideration (1988-2018). this is because, jakara basin is more urbanized than challawa basin as proven by the lulc characterization result. additionally, mukherjee, (2016) revealed that urbanization greatly influenced the runoff generation. furthermore, the drainage area of jakara basin is higher than that of challawa basin which is one of the parameters that influence runoff generation in catchment area (kavian and mohammadi, 2012). mohammed et al: rainfall-runoff modeling for challawa and jakara catchment areas of kano city, nigeria. azojete, 17(4):439-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 451 table 5: simulated flow data for challawa and jakara catchment areas 4. conclusion and recommendations the flow rate data for ungauged jakara and challawa catchment areas of kano city have been successfully simulated through rainfall-runoff modelling using hec-hms 4.2. the results can safely be used for further hydrological analysis. it is strongly recommended that, the catchment areas should be gauged, and further research be conducted on the quality of the simulated flow obtained. references ahmad, aa. 2020. land use land cover change analysis in fagge local government, kano state from 1991-2019. research square, doi: https://doi.org/10.21203/rs.3.rs-33756/vi. year challawa flow rate (m3/s) jakara flow rate (m3/s) 1988 207.70 342.1 1989 168.20 285.9 1990 145.30 252.4 1991 140.70 245.6 1992 181.00 304.3 1993 185.50 310.8 1994 178.90 301.3 1995 148.30 256.8 1996 255.00 407.2 1997 151.60 527.5 1998 262.20 417 1999 168.50 286.4 2000 251.50 402.5 2001 204.80 534.6 2002 172.30 291.8 2003 224.90 366 2004 170.00 260.2 2005 261.90 380.9 2006 295.10 423.3 2007 196.90 296.3 2008 166.40 255.5 2009 202.70 294.3 2010 177.50 260.7 2011 243.80 346.1 2012 210.20 522.3 2013 280.50 391.7 2014 226.30 598.3 2015 305.20 410.8 2016 316.80 401.5 2017 194.00 251.9 2018 188.00 208.7 arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):439-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulrasheeddoko@gmail.com 452 alfa, mi., ajibike, ma., adie, db. and mudiare, oj. 2018. assessment of the effect of land use/land cover changes on total runoff from ofu river catchment in nigeria. journal of degraded and mining land management, 5(3): 1161-1169. antigha, ree, akor, aj., ayotamuno, mj., ologhodien, i. and ogarekpe, nm. 2014. rainfall runoff model for calabar metropolis using multiple regression. nigerian journal of technology, 33(4): 566 – 573. chang, tj., wang, ch. and chen, as. 2015. a novel approach to model dynamics flow interactions between storm sewer system and overland surface for different land covers in urban areas. journal of hydrology, 52(4): 662-679. choudhari, k., panigrahi, b. and paul, jc. 2014. simulation of rainfall-runoff process using hechms model for balijore nala watershed, odisha, india. international journal of geomatics and geosciences, 5(2): 253-265. haruna, m., ibrahim, mk. and shaibu, um. 2019. assessment of land use and vegetative cover in kano metropolis (from 1975-2015) employing gis and remote sensing technology. nigerian journal of basic and applied science, 27(2): 01-07. hasyman, f., khaleghi, mr. and kamyar, m. 2015. combination of hec-hms and hec-ras models in gis in order to simulate flood. journal of water resources and recent science, 4(8): 122-127. hydrological modelling system hec-hms. 2000. technical reference manual. us army corps of engineers, hydrologic engineering center, st. davis, california. kavian, a. and mohammadi, ma. 2012. effect of rainfall type on runoff and sediment yield in plot scale. journal of range and watershed management, 65(1): 117–130. martin, o., rugumayo, a. and ovcharovichova, j. 2012. application of hec-hms/ras and gis tools in flood modeling: a case study for river sironko, uganda. global journal of engineering, design & technology, 1(2): 19-31. merwade, v. 2012. hydrologic modeling using hec-hms. school of civil engineering, purdue university, west lafayette, indiana. mukherjee, d. 2016. effect of urbanization on flood a review with recent flood in chennai (india). international journal of engineering sciences & research technology, 5(7): 451-455. mustapha, a., yakudima, ii., alhaji, m., nabegu, ab., dakata, gaf., umar, ay. and musa, ub. 2014. overview of the physical and human setting of kano region, nigeria. journal of geography, 1(5): 1-12. national population commission (npc) 2006. census, abuja, nigeria. rangari, va., sridhar, v., umamahesh, nv. and patel, ak. 2018. rainfall runoff modeling of urban area using hec-hms: a case study of hyderabad city, conference paper, research gate. rathod, p., kalpesh, b., and manekar, vl. 2015. simulation of rainfall runoff process using hechms (case study: tapi river, india). hydro 2015 internation, 20th international conference on hydraulics, water resources and river engineering. iit roorker, india. tassew, bg., belete, ma. and miegel, k. 2019. application of hec-hms model for flow semulation in the lake tana basin: a case of gilgel abay catchment, upper blue nile basin, ethiopia. journal of hydrology, 6(21): 1 – 17 arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):741-750 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 741 original research article assessment of some heavy metal pollution on soil via e-waste dumping activities and unpolluted soil in abraka, delta state, nigeria o. b. eyenubo*, o. peretomode, f. egharevba and s. a. osakwe department of science laboratory technology, delta state university, abraka, nigeria *corresponding author’s email address: eyenokero2013@gmail.com 1.0 introduction obsolete electrical electronic equipment, referred to as e-waste are randomly dumped in our environments in both developing and developed nations, based on the trend of technology of this present day. developing countries like nigeria, india and other are facing concurrent flow of e-waste through domestic generation and illegal import (vats and singh, 2014). these generation and illegal import are as a result of globalization, transfer of technology, concurrent change in technology, affordable price of sensitive equipment and illegal dumping (vats and singh, 2014). the huge amount of e-waste generated globally, pose a lot of threat to the waste treating agencies due to the hazardous metals, inorganic and organic compounds generated by them. ewaste are made up of different components like glass, metals, plastics and ceramics that contain hazardous compounds, such as polychlorinated biphenyls (pcbs) and brominated flame retardants (bfrs), jinhui et al., 2011). the also contain a lot of heavy metals, such as chromium (cr), found in floppy disk, magnetic tape etc, arsenic (as), found in light emitting diodes, article information abstract this research investigated the concentration of heavy metals pollution of soil via e-waste dumping in abraka community. two soil samples were obtained and analyzed through digestion and the use of atomic absorption spectrophotometer (aas). the concentration of cobalt (co), chromium (cr) and manganese (mn) on the polluted soil were higher than the control soil at depths 0 – 10 cm and 10 – 20 cm (25.55 and 22.65 mg/kg, 10.19 and 8.65 mg/kg, 78.15 and 51.16 mg/kg) and lower in depth 20 – 30 cm (10.82, 6.55 and 41.98 mg/kg). while the concentration of iron (fe) on the polluted soil is higher than that of the control and also decreased across depths (1096.60, 652.02 and 420.43 mg/kg). the concentration of antimony (sb) and arsenic(as) shows no much difference across the depths. statistically, there was a much difference between the six metals (t = 0.595, p = 3.020) for cobalt, (t = 0.222, p = 1.440) for chromium, (t = 0.969, p = 25.42) for manganese, (t = 0.092, p = 71.15) for iron and (t = 0.038, p = 0.020) for both antimony and arsenic respectively. it was observed that concentration of the metals under study were lower than dutch optimum and action values, except for co in depths 0-10 cm and 10-20 cm. the mean and median of cobalt, chromium, manganese and iron show relatively close differences on the polluted soil at depths 0 – 10 cm and 10 – 20 cm, while at depth 20 – 30 cm, there is no relative closeness .the reverse is the case for control soil, except for antimony and arsenic which shows no pollution effects. the contamination factors for co showed 1 < cf ≤ 3 (10-20 cm and 20-30 cm) and 1 < cf (0-10 cm), while cr, sb, mn, fe and as also show 1 < cf (0-10 cm). there is clear evidence of pollution when the concentrations of polluted and unpolluted soils were compared. as such an effort should be made by the government to monitor the indiscriminate dumping of e-waste in the community in order to avoid such pollution level. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 july, 2020 revised 3 october, 2020 accepted 18 october, 2020. keywords: e-waste heavy metals pollution statistically datasets. mailto:eyenokero2013@gmail.com http://www.azojete.com.ng eyenubo et al.: assessment of some heavy metal pollution on soil via e-waste dumping activities and unpolluted soil in abraka, delta state, nigeria. azojete,16(4):741-750. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 742 manganese (mn), found in battery, beryllium (be), found in silicon-controlled rectifiers, antimony (sb), found in flame retardant, additives in plastics and resins, copper (cu), found in printed circuit board, wires and cables etc (wu et al., 2008, furlani et al., 2009, jinhui et al., 2011). soil is regarded as contaminated when the concentration of the heavy metals present in that horizon exceed the permissible limit values for an uncontaminated soil (proust et al., 2013, salman et al., 2019). in fact, soil pollution has adverse effect on food safety, thereby increasing health risk (salman et al., 2016a, salman et al., 2019). it has been reported that heavy metal pollution on soil surface from an e-waste dismantling site poses a potential risk to human and the environment (jinhui et al., 2011). arsenic is known to exhibit toxicity symptoms of resisting seed germination, altering the height of plant, reducing the root and shoot growth, decreasing grain and fruit production and probably leads to death sometimes (abedin et al., 2002, jahan et al., 2003, salman et al, 2019). it has been reported that chronic inhalation of too much concentration of iron oxide fumes have led to benign pneumoconiosis, known as siderosis which is seen as an x-ray change (adaramodu et al., 2012) . chromium has been known to cause skin rashes, kidney and liver damage, as well as carcinogens (adaramodu et al., 2012). studies have also shown that its bioaccumulation in organisms generates biomagnifications in the food chain leading to endocrine disruption as a result of leaching of polychlorinated biphenyls (pcbs) from e-waste (deng et al., 2007, richard et al., 2013). heavy metal pollution in soil as a result of e-waste is persistent in the soil, accumulative in plants, animals and humans through food chain exposure to them. they also cause problems to our nervous system and genitourinary system (cdphe, 2008, richard et al., 2013). gases such as chlorofluorocarbon (cfcs) have been released into the environment as a result of landfill with obsolete e-waste such as freezers, refrigerator and air conditioning unit containing ozone depleting gases (scheutz et al., 2014, richard et al., 2013). recent times, much attention has been paid to e-waste recycling site and surface dust, but none or little attention has been given to e-waste dumpsites without burning or any other waste mixed up with it. this study therefore focuses on the assessment of pollution generated by e-waste dump site. 2.0 materials and methods 2.1 study area abraka, a university town in ethiope east local government area of delta state, is one of the most developed communities in the state . the geographical location of the sampling point is latitude 06.23’01 45°n and longitude 007.73’09 80° e. it has a level surface area with poor drainage system and also with heavy amount of rainfall during rainy season, mainly as from may september . http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):741-750. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 743 figure. 1: map of delta state /abraka showing the sampling site 2.1.1 soil sampling and preparation the soil samples were collected during raining season from two different site (polluted and unpolluted soils), at three different depths (0 10 cm, 10 – 20 cm and 20 – 30 cm). the unpolluted which serve as control samples were collected from reserved area used by a peasant farmer, having only foot path as the access road to it, far away from the community and has no history of fertilizer, herbicide or pesticide application. the samples were taken from six spots from each site and were mixed to form composite sample of three each from both sites. the samples were collected with soil auger into a black polythene bag and conveyed into the laboratory immediately, they were spread on white sheets of paper for air drying at room temperature, for five days. thereafter, they were pulverized with mortar and pestle and sieve with 2mm mesh sieved to separate the coarse particle from the fine particle prior to digestion. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng eyenubo et al.: assessment of some heavy metal pollution on soil via e-waste dumping activities and unpolluted soil in abraka, delta state, nigeria. azojete,16(4):741-750. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 744 figure 2: e-waste dump site in abraka. 2.1.2 laboratory analysis the soil samples were digested according to the method used by adaramodu et al. (2012), the digests were analyzed for heavy metal concentration using atomic absorption spectrophotometer (aas) (model: perkin elmer 1100). 2.1.3 contamination factors (cf) and degree of contamination the cf is determine using the following equation cfi= c0−1 i cni (1) where ci f is the contamination factor of the element under study, ci 0-1is the concentration of the element in the sample, and ci n is the background value or the continental crustal average as was used by taylor and mclennan (1985). the categories of its definition are as follow; cf < 1 = low contamination, 1 < cf ≤ 3 = moderate contamination, 3 < cf ≤ 6 = considerable contamination, and cf > 6 = very high contamination. the degree of contamination can as well be determined by this equation, cdeg= cfi� , which is the sum total of the contamination factors of all the element under study. its categories definitions are as follow; cdeg < 8 = low degree of contamination, 8 ≤ cdeg < 16 =moderate degree of contamination, 16 ≤ cdeg < 32 = considerable degree of contamination and cdeg ≥ 32 = very high degree of contamination. 2.1.4 data analysis the data were computed using microsoft excel of windows 10 version and tested with one tailed t-test at 95% confidence level. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):741-750. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 745 3.0 results and discussion table 1 reveals the mean ± sd concentration of heavy metals results obtained for both polluted and unpolluted soil, while table 2 presents the median concentration results for both the polluted and the unpolluted soil across depths. table 1 : mean ± sd concentration of heavy metals for both soil (mg/kg) across depths. metals mean ± sd (mg/kg) dutch (mg/kg) polluted soil unpolluted soil optimum action 0-10 cm 10-20cm 20-30cm 0-10 cm 10-20cm 20-30cm optimum action co 21.56 ± 25.42 22.65 ± 24.25 10.82 ± 17.28 20.21 ± 40.31 20.21 ± 40.31 24.16 ± 38.41 20.00 240.00 cr 10.19 ± 9.74 8.65 ± 10.83 6.55 ± 11.33 5.66 ± 11.21 5.66 ± 11.21 6.75 ± 10.69 100.00 380.00 sb 0.04 ± 0.02 0.03 ± 0.03 0.02 ± 0.02 0.05 ± 0.01 0.05 ± 0.01 0.04 ± 0.02 3.00 15.00 mn 78.15 ± 64.44 51.16 ± 68.01 41.98 ± 71.35 53.70 ± 55.01 68.74 ±47.76 50.51 ± 45.84 1500.00 2,500.00 fe 1095.60 ± 52.92 652.02 ± 666.31 420.44 ± 659.77 128.44 ± 114.26 118.32 ± 122.14 120.75 ± 120.38 as 0.04 ± 0.02 0.03 ± 0.03 0.02± 0.02 0.05 ± 0.01 0.05 ± 0.01 0.04 ± 0.02 29.00 55.00 s d = standard deviation table 2 : the median concentration of both polluted and control soil across depths. metals polluted soil – median control soil – median 0-10 cm 10-20 cm 20-30 cm 0-10 cm 10-20 cm 20-30 cm co 18.325 20.516 3.346 0.056 0.056 7.957 cr 8.440 5.365 1.167 0.056 0.056 2.239 sb 0.050 0.027 0.004 0.050 0.050 0.042 mn 79.005 25.789 7.424 50.567 79.952 43.501 fe 1211.765 553.719 92.282 83.648 70.764 75.615 as 0.050 0.027 0.004 0.050 0.050 0.042 3.1 cobalt from table 1, co displayed high concentration at depth 10 – 20 cm and 20 – 30 cm on both soils. the values are almost of the same range at 0 – 10 and 10 – 20cm, and about 2 times higher in control than the polluted soil, the concentration of co on the control is of geogenic origin. statistically, there was not much significant difference between the concentration across the depths on the polluted and control sites (t = 0.595, p = 3.020). this shows that the e-waste has contributed little contamination of co to the soil across the depths. these values were lower than the values reported by jadhav et al. (2017) (68.18 – 93.99 mg/kg) in a similar study. since the mean values of co in depth 0 – 10 and 10 – 20 cm are close to the median values (tables 1 and 2), there is an indication that the dataset undergoes normality after transformation. for depth 20 – 30 cm, there is significant variation in the concentration of co. this indicates that the dataset was log transformed (tables 1 and 2). the mean values of co in both polluted and control soil were above the optimal value of dutch (20.00 mg/kg) at depth 0 – 10 cm and 10 – 20 cm for polluted soil and across the three depths for control soils but were lower in depth 20 – 30 cm for polluted soil. all the values were below dutch action value of 240 mg/kg. co and its compounds are known to be in group 2b and is possibly carcinogenic to human, they are also responsible for skin irritation (iarc, 2015). 3.1.1 chromium chromium showed a good distribution of concentration as it decreased across the depths. the mean concentration of cr in polluted soil is about 1 2 times higher than that of the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng eyenubo et al.: assessment of some heavy metal pollution on soil via e-waste dumping activities and unpolluted soil in abraka, delta state, nigeria. azojete,16(4):741-750. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 746 control in depths 0 – 10 cm and 10 – 20 cm and there is no significant difference in depth 20 – 30 cm. the mean and median values of cr across the depths (tables 1 and 2) of both soils varied significantly from each other. this implies that the datasets were not normally distributed. the decrease with increase in depths corroborate with the findings of oladunni et al. (2013). the value on both sites were 10 – 30 times lower than the optimal and action values of dutch (100.00 and 380.00 mg/kg). this implies that the content of cr in the e-waste is minimal to generate much of its concentrations in the soil. therefore, there is no cause for alarm since the levels of cr are low. statistically, there was no significant difference between the concentration of both site across the depths (t = 0.222, p = 1.440). concentrations of cr in this study were low when compared to those of jadhav et al. (2017). the concentration of cr at both sites varied from 6.55 – 10.19 mg/kg and 5.66 – 6.75 mg/kg respectively. this is an indication that the e-waste has contributed some levels of contaminants to the soil. these values were low when compared to those reported by sampson et al. (2012) (21.60 mg/kg)and higher than those reported by benedicta et al, (2017) (3.03, 2.28, and2,36 mg/kg) in similar studies. cr is a component of floppy disc and magnetic tape (jinhui et al., 2011). cr has been reported to cause skin rashes, kidney and liver damages and carcinogenic effects in human (adaramodu et al., 2012). cr (vi) compounds irritate the eyes, skin and mucous membrane (oladunni et al., 2013). 3.1.2 antimony antimony showed not much difference in concentrations on both soils across depths indicating that the e-waste has not contributed contaminants to the soil. the non much difference observed in mean and median (tables 1 and 2) for sb across depths, shows that the datasets were normally distributed. the mean concentration of sb on both soil across depths were lower than optimal and action values of dutch (3.00 and 15.00 mg/kg) respectively (khadijal, 2016). statistically, there was no significant difference on both sites across depths (t = 0.038, p = 0.020). this implies that the probability of e-waste contributing contaminants of sb(0.02 0.04 mg/kg) to the soil is minimal. sb concentration on both soils were far lower when compared to those reported by jinhui and pixing (2011) (9.90, 7.20, 9.10, 1,100 mg/kg) at different site. sb is known to be toxic to blood, kidney, lungs, nervous system, liver and the mucous membranes through ingestion or inhalation (iarc, 2015). 3.1.3 manganese manganese displayed high concentration at depths 0 10 cm and 10 – 20 cm (78.15 and 68.74 mg/kg) (table 1) on both sites. the data showed significant difference across depths and sites (78.15, 51.16, 41.98 mg/kg and 53.70, 68.74,50.51 mg/kg) respectively. these concentrations are low when compared to the value reported by jinhui and pixing (2011) (300.00 mg/kg) and higher than those reported by brigden et al. (2005) (< 2.00 mg/kg). also, the mean concentration is relatively close to the findings of wu et al. (2008) (85.5 mg/kg). contaminant of mn on the polluted soil only occurred at depth 0 – 10 cm. the mean and median values (tables 1 and 2) for polluted soil were not close to each other across depths. this signifies that the datasets are not normally distributed, which also proves that the datasets were log transferred. while in the control soil, the mean and median values (tables 1 and 2) were close. this implies that the datasets were normally distributed. the concentration of mn on both sites were below the recommended standard of level that demand attention and intervention (1,500.00 and 2,500.00 mg/kg) (sampson et al, 2012). statistically, there is much difference on both site and across depths (t = 0.969, p = 25.42). this signifies that the probability of mn contaminating the soil via the e-waste dump is high. mn is found in batteries (jinhui et al., 2011). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):741-750. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 747 3.1.4 iron iron displayed high concentrations across depths on both sites ranging from 420.43 – 1095.60 mg/kg for polluted soil and 118.32 – 128.44 mg/kg for control soil. these values are high when compared to those reported by adaramodu et al. (2012) (108.00 and103.30 mg/kg). the high concentration of fe on both soils might be ascribed to the presence of the e-waste and other anthropogenic activities. the highest concentration was observed at depth 0 – 10 cm for both soils. there is much difference between the mean and median values across depths. this proves that the datasets were not normally distributed on both sites. as such, the datasets were log transferred. statistically, there is much difference between the datasets across depths and site (t = 0.092, p = 71, 15). this implies that the probability of contamination of fe by the e-waste is very high. this might also be due to high percentage of iron present in them, such as 20.47% of fe in desktop computer (adaramodu et al., 2012).long term exposure by inhaling iron oxide fumes or dust can lead to a problem of benign pneumoconiosis, called siderosis that can be detected as an x-ray change (adaramodu et al. (2012). 3.1.5 arsenic there is not much difference between the concentrations of as across depths and sites. this implies that the e-waste has not contributed contaminant to the soil. the closeness of the mean and median values on both sites shows that the datasets are normally distributed. statistically, there were not much different across depths and sites (t = 0.037, p = 0.020). this signifies that the probability of as contamination by the e-waste on the soil is minimal. all the values of as (0.02 0.05 mg/kg) for both soils are lower than the optimal and action values of dutch (29.00 and 55.00 mg/kg). arsenic concentrations are lower than the value reported by jinhui and pixing (2011) (26.03 mg/kg) and those of brigden et al. (2005) (< 200 mg/kg), but corroborated with the findings of benedicta et al (2017) (0.04-3.67 mg/kg). arsenic is found in light emitting diodes (furlani et al., 2009, jinhui et al., 2011). long term exposure of as can lead to acute poison and injurious to human health (jadhav et al., 2017). arsenic also exhibit toxicity symptoms in plant, such as inhibition of seed germination, decrease in plant height, reduction in root growth, lower fruit and grain yields and even death can occur (salman et al., 2019). arsenic associated with the human solid food chain at the contamination of the products and fodder (salman et al., 2019). figures 2, 3, 4 and 5 present the contamination factors profile and the degree of contamination for both polluted and unpolluted soils across the depths. figure 2 : contamination factors profile of the metals under study on the polluted soil. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng eyenubo et al.: assessment of some heavy metal pollution on soil via e-waste dumping activities and unpolluted soil in abraka, delta state, nigeria. azojete,16(4):741-750. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 748 figure 3 : contamination factors profile of the metals under study on the unpolluted soil. figure 4 : degrees of contamination of different depths on polluted soil. figure 5 : degrees of contamination of different depths on unpolluted soil. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):741-750. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 749 the calculated contamination factors profile in figure 2 (polluted soil), display that at depths 10 – 20 cm and 20 – 30 cm, co shows moderate contamination since its values fell into the categories of 1 < cf ≤ 3 and at depth 0 – 10 cm, it displayed low contamination since its values fell into the categories of cf < 1. cr, sb, mn, fe and as shows low contamination, figure 3 (unpolluted soil) also followed the same trend. the calculated degree of contamination plot in figures 4 and 5 displayed low degree of contamination since all the values fell into the categories of cdeg < 8. the highest calculated degree of contamination was observed in depth 10 – 20 cm (1.00) and 20 – 30 cm (1.31) for polluted and unpolluted soil respectively. this might be due to the penetrating ability of the metals in the soils. 4.0 conclusion e-waste is generally known to cause environmental pollution with serious health problems as a result of the chemical constituents associated with them. the results of this study showed that the e-waste contributed co, cr, mn, and fe to the soil across depths, except in depth 20 – 30 cm for co, which indicates that e-waste dumping can generate toxicity risk to human with long term exposure, and there was no evidence of contamination of sb and as on the soil. however, the concentration of co, cr, mn and fe are still below the optimal and action level of dutch. it was also observed that the datasets of some of the metals across depths were normally distributed, since there is a relative closeness between the mean and the median values, while some other were not, as there is no relative closeness between the mean and median values. the results from the calculated contamination factors and degree of contamination showed low contamination for some metals and moderate contamination for others. in fact, environmental pollution by heavy metals through e-waste dumping generates hazards to human, animals and even plants development, via bioaccumulation and biomagnifications as animals occasionally graze on grasses around the area. the dumping of ewaste, especially by the electrical and electronics work men around their premises has the capability to pollute the environment. therefore, it should be monitored and prevented to save the immediate environment from pollution. references abedin, mj., cottep-howells, j. and meharg, aa. 2002. arsenic uptake and accumulation in rice (oryza sativa l.) irrigated with contaminated water. plant soil, 240 : 311 – 319. adaramodu, aa., osuntogun, ao. and ehi-eromosele, co. 2012. heavy metals concentration of surface dust present in e-waste components : the westminister electronic market, lagos case study. resources and environment, 2 (2) : 9 – 13. benedicta, yf., emmanuel, a., dzidzo, y. and frank, n. 2017. heavy metals concentration and distribution in soil and vegetation at korle lagoon area in accra, ghana. cogent environmental science, 3: 1 – 114. brigden, k., labunska, i., santillo, o. and allosopp, m. 2005. recycling of electronic waste in china and india workplace and environmental contamination. the greenpeace research laboratories, department of biological science, university of exeter, exeter ex4 4ps, uk. colombia department of public health and environment (cdphe), 2008. fact sheet : evaluation of onsite surface soil exposure by recreational users at standard mine – gunnison county, colorado. the colombia cooperative program for environmental health assessment (ccpeha), colombia. deng, wj., zheng, js., bi, xh., fu, jm. and wong, mh. 2007. distribution of pbdes in air particles from an electronic waste recycling site compared with guangzhou and hong kong , south china. environmental international, 33 : 1063 – 1069. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng eyenubo et al.: assessment of some heavy metal pollution on soil via e-waste dumping activities and unpolluted soil in abraka, delta state, nigeria. azojete,16(4):741-750. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eyenokero2013@gmail.com 750 furlani g., moscardini, e., pagnanelli, f., ferella, f., veglio, f. and toro, l. 2009. recovery of manganese from zinc alkaline batteries by reductive acid leaching using carbohydrate as reductant. hydrometallurgy, 99 : 115 – 118. lindsey, a., torre, msph., freddic, b. rebecca, l., siegei, mph., jacques, l-t. and joannie, j. dum. (2015). international agency for research on cancer. world health organization, ca: a cancer journal for clinicians, 63(2): 87 – 108. jadhav, dc., thakur, ts., patil, sn. and ingle, st. 2017. heavy metals contamination of surface soil from e-waste recycling sites of informal sector in mumbai urban. international journal of engineering science and composting, 8 (7) : 14526 – 14530. jahan, i., hoque, s., ullah, sm. and kibria, m g. 2003. effects of arsenic on some growth parameters of rice plant. dhaka university journal of biological science, 12 : 71 – 77. jinhui, l., huabo, d. and pixing, s. 2011. heavy metals contamination of surface soil in electronic waste dismantling area : site investigation and source – apportionment analysis. waste management and research, 29 (7) : 727 – 738. khadijah, ai. 2016. environmental risk assessment for an informal e-waste recycling site in lagos state, nigeria. ph.d thesis middlesex university research repository at htt//:eprints.mdx.ac.uk/22233/ oladunni, bo., tejumade, a. and otolorin, ao.(2013).heavy metals contamination of water, soil, and plants around an electronic waste dumpsite. pollution journal of environmental studies, 22(5): 1431 – 1439. proust, d., fontaine, c. and dauger, n. 2013. impact of weathering and clay mineralogy on heavy metals sorption in sludge-amended soils. catena, 101 :188 – 196. richard, ao., john, b. and stephen, o. 2013. assessment of soil contamination through ewaste recycling activities in tema community one. environmental and pollution, 2(2) : 66 – 70. salman, as., salah, am. z., el-monster, ms, and mahmaud, aah. 2019. soil characterization and heavy metals pollution assessment in orabi farm, el obour, egypt. bulletin of the nation research center, 43(42) : 1 – 13. salman, as., zeid, sa., seleem, em. and abdel-hfiz, ma. 2016. assessment of soil pollution with heavy metals in orabi farms, el-obour city, egypt. in the 54th annual scientific meeting at the egyptian mineral resource authority. gse https//doi.org/10,13140/rg.22.2957089286. sampson, ma. , francis, g., ofosu, it., kwame, a. and kuranchie – mebsah, h. 2012. assessing the heavy metal contaminant of surface dust from waste electrical electronic equipment (ewaste) recycling site in accra ghana. research journal of environmental and earth science, 4 (5) : 605 s– 611. scheutz, c., mosback, h. and kjeldsen, p. 2004. attenuation of methane and volatile organic compound in landfill soil covers. journal of environmental quality, 33 : 61 – 71. taylor, sr. and mclennan, sm. 1985. the continental crust: its composition and evolution. an examination of geochemical record preserved in sedimentary rocks. blackwell science, oxford, 312. vats, mc. and singh, sk. 2014. e-waste characteristic and its disposal. international journal of ecological science and environmental engineering, 1(2): 49 – 61. wu, bv., chen, yc., middendorf, a., gu, x. and zhong, hw. 2008. assessment of toxicity potential of metallic elements in discarded electronic: a case study of mobile phones in china. journal of environmental science, 20: 1403-1408 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):815-826 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 815 socio-economic characteristics of residents in correlation to groundwater source in ikenne local government area, ogun state, nigeria a. a. adewunmi1 and o. p. akinpelu2* 1gateway (ict) polytechnic saapade, remo north, ogun state, nigeria 2department of urban and regional planning, bells university of technology, ota, nigeria *corresponding author's email address: opakinpelu@bellsuniversity.edu.ng article information submitted 18august, 2023 revised 3sept, 2023 accepted 10 sept, 2023 keywords: correlates groundwater residents socio-economic characteristics water sources abstract the study examines the residents’ socio-economic characteristics as correlates of groundwater source in ikenne local government area, ogun state, nigeria. the objectives addressed in this study are analysis of the socio-economic characteristics of the residents; sources of groundwater; and relationship between residents’ socio-economic attributes and groundwater source in the study area. a total of two hundred and seventytwo (272) respondents across all the six political wards of iperu and ilisan, were administered using questionnaires. data collected were analysed using frequency distribution, percentage, anova (it is used to establish if there is significance different between variable), correlation and regression. the study revealed that there is no significant difference in socioeconomic background of the residents (p > 0.05) except for educational attainment. it was found that correlation exists between groundwater source and marital status, education, income and occupation with exception of gender. regression results established that 82 % of variability in groundwater source is predicted by residents’ socioeconomic characteristics. it could be concluded that socioeconomic background of the residents significantly influences their source of groundwater. it is therefore imperative that governments at all levels need to come up with policies and programmes that will enhance peoples’ socioeconomic status, thereby enhancing their ability to provide an improved water source. 1.0 introduction water is one of the essentials of life, needed by all categories of people irrespective of their socioeconomic background. water by its nature is transparent, tasteless, odourless, and colourless liquid, which is the main constituent of earth’s hydrosphere and the fluids of most living organisms. however, the sources of water vary across the globe. the sources are classified into two which are surface and ground-water (okeola et al., 2010) it is on record that nigeria water capacity for surface and groundwater running to billion cubic metres (federal ministry of water resources and rural development, 2011). according to nickson et al. (2005) groundwater is the most reliable and most extensive storage of freshwater on earth which is used by one-third of the entire world’s population for drinking purposes. earlier work of hill (2004) reported that more than one quarter of the world population depends on groundwater for drinking and other basic needs. okelola et. al. (2010) further noted that water from borehole is more reliable for human consumption compared to the one from well. http://www.azojete.com.ng/ mailto:%20jonas.onah.pg.65348@unn.edu.ng mailto:%20jonas.onah.pg.65348@unn.edu.ng mailto:%20jonas.onah.pg.65348@unn.edu.ng galley proof arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):815-826. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 816 it is projected that by the year 2050, more than half of the world’s population will live under moderate water stress, with 80 % of these located in developing regions (schlosser et al., 2014). record shows that of global population using improved drinking water sources stood at 91 % in 2015, while 785 million people still lacked basic water services in 2017 (un, 2019). as defined by world health organization, an improved drinking water is a water source that by nature of its construction adequately protects the water from outside contamination such as public stand pipe, borehole, protected dug well, protected spring (who, 2012). it is observed that inaccessibility to improved water source has resulted to an increase in consumption of contaminated or polluted water (who, 2012; ologbushere et al., 2016; beshiru et al., 2018) with potential detriment to public health. groundwater occupies the entire underground soil layer with about 30.1 % of the global fresh water and that many people have been satisfying their water need through the exploitation of groundwater for various uses (ocheri et al., 2014). as a result, people depend mostly on groundwater resources due to the fact that it is less contaminated and useful for all purposes. nevertheless, overdependence results in too much pressure on the existing groundwater resources. piscopo (2001) identified certain factors that contribute to the decline in groundwater quality and its reduction, which are drawing of water for industrial and agricultural activities as a result of increase in population and low rejuvenation. access to improved water source enhances peoples’ healthy living. to a large extent, accessibility to improved water source might be influenced by peoples’ socioeconomic status. this assertion is corroborated by morakinyo et al. (2015). they established that there is a positive relationship between the educational attainment of the household head and the likelihood of having access to improved drinking water sources. in addition, findings of shewayinet et al. (2021) showed that educational status and source of income of the household head significantly determine the type of water source to be used. it further stated that accessibility to improved water source was 86.2 % increased for government employed compared to agriculture income household. abubakah (2019) in his research work showed that factors associated with improved household water sources included place of residence, education, wealth status, ethnicity, gender, access to electricity and water collection time. a study conducted in eswatini, south africa, found that rich households have better access to resources and therefore have the better financial capacity to afford access to improved water sources (irianti et al., 2016). it is believed that inadequate public water supply is a general problem in most urban areas in nigeria. this might be responsible for why most urban dwellers device convenient means of water source through groundwater, such as well and boreholes. though there are studies on groundwater source (shewayinet et al., 2021; abubakah 2019; irianti et al., 2016), however, study that have investigated socioeconomic characteristics as a predictor of residents groundwater source is scanty in literature. in view of the foregoing, the study examined the residents’ socio-economic characteristics as determinants of groundwater source in ikenne local government area, ogun state, nigeria. this is with a view to establish whether there is a relationship between socioeconomic attributes of residents and groundwater sources; and to determine percentage contribution of the socioeconomic background to variability in groundwater source in the study area. 2. materials and methods ikenne, one of the twenty local government areas in ogun state, nigeria, is geographically located on longitude 60o51‟57‟n or 6.86580 and latitude 30o42‟55‟e or 3.71520 (figure 1a and 1b). ikenne local government area (lga) has its headquarters seated in ikenne with about 144 square kilometers in size. the local government area, is bounded in the west by obafemi owode local government area, in the south by sagamu local government area, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com galley proof adewunmi and akinpelu: socio-economic characteristics of residents in correlation to groundwater source in ikenne local government area, ogun state, nigeria. azojete, 19(4):815-826. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 817 in the east by odogbolu local government area and in the north by remo north local government area. being suburban, it consists of four (4) major towns. these are iperu, ilishan/irolu, ogere, and ikenne township. the climate and geographical location of the local government area is known to support several economic activities such as agriculture, industrial and commercial activities. the sources of water supply to the people of ikenne lga include pipe-borne water, borehole, and deep well. the local government is located along the transitional forest zone of southern nigeria and guinea savannah of the country. there are some rivers that exist in the study area like uren river at ikenne and ogun river at ogere. the local government area has major road bypassing between iperu and ogere town and also between ikenne and ilisan town. these towns are also interlinked or connected together with distributor road. the major occupation of the people in the study area is farming and trading. this is due to the favourable rainforest weather. their engagement in farming activities is as a result of the good nature of soil which supports agriculture at both subsistence and mechanized levels. figure 1a: ogun state in the context of nigeria source: department of surveying and geoinformatics, ilaro (2022). http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com galley proof arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):815-826. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 818 figure 1b: ikenne local government in the context of ogun state source: department of surveying and geoinformatics, ilaro 2022. the research used primary and secondary data. the primary data were sourced from the field through administration of closed-ended questionnaire to the residents, while secondary data were obtained from the data that have been already collected and readily available, including census data and maps. the questionnaire was based on socio-economic attributes of the residents as well as information about groundwater sources. in the administration of the questionnaire to the target respondents, random and systematic sampling techniques were employed. for the household survey, samples were selected using the sample size determination equation of cochran (1977) presented as equation 1. the study used a single proportion formula, 95 % confidence interval, the marginal error of 5 %, and the non-response rate of 10 %, total population of 6,813. 𝑛 = z2(1 − p) d2(n − 1) + z2p(1 − p) (1) where, z = 95 % confidence limit (z-value at α = 0.05 is 1.96); n = number of houses in iperu and ilisan town = 6813; p = 0.5; 1-p = 0.5; d = marginal error or degree of accuracy = 0.05; n = 272. out of a total number of 272 sample size distributed among the six (6) political wards only 165 questionnaires were retrieved. percentage, frequency distribution, anova, (analysis of variance), correlation and regression were used to analyze the socioeconomic attributes of the residents and groundwater sources. thus, regression equation is expressed as: y = b0 +ϰ1 + ϰ2 +ϰ3 + ϰ4+ ϰ5 (2) where; y = groundwater source b0 = constant ϰ1 = gender ϰ2 = marital status ϰ3 = education ϰ4 = income ϰ5 = occupation file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com galley proof adewunmi and akinpelu: socio-economic characteristics of residents in correlation to groundwater source in ikenne local government area, ogun state, nigeria. azojete, 19(4):815-826. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 819 3. results and discussion table 1 presents the socioeconomic background of the residents across different wards of the study area. data used in this study were obtained from field survey conducted in 2022, unless otherwise stated. 3.1 socioeconomic characteristic of residents findings on socioeconomic characteristics such as gender, marital status, educational status, average income and occupation of the respondents are presented below. table 1: socio-economic characteristics of the residents parameter iperu ward 1 n (%) iperu ward ii n (%) iperu wardiii n (%) ilisan ward i n (%) ilisan ward ii n (%) ilisan/irolu ward iii n (%) total n (%) gender male 31(75.6) 17 (53.1) 14 (66.7) 15 (57.7) 15 (57.7) 13 (68.4) 105 (63.6) female 10 (24.4) 15 (46.9) 7 (33.3) 11 (42.3) 11 (42.3) 6 (31.6) 60 (36.4) marital status single 8 (19.5) 4 (12.5) 2 (9.5) 3 (11.5) 3 (11.5) 3(15.8) 23 (13.9) married 31 (75.6) 25 (78.7) 15 (71.4) 22 (84.6) 19 (73.1) 15(78.9) 127 (77.0) widow/(ed) 2 (4.9) 3 (9.4) 3 (14.3) 0 (0.0) 4 (15.4) 1 (5.3) 13 (7.9) separated 0 (0.0) 0 (0.0) 1 (4.8) 1 (3.8) 0 (0.0) 0 (0.0) 2 (1.2) educational status illiterate 1 (2.4) 14 (43.8) 4 (19.0) 1 (3.8) 3 (11.5) 11(57.9) 34(20.6) primary 1 (2.4) 3 (9.4) 0 (0.0) 1 (0.0) 0 (0.0) 0 (0.0) 4 (2.4) secondary 13 (31.7) 4 (12.5) 5 (23.8) 5 (30.8) 3 (11.5) 1(5.3) 34(20.6) nd/nce 16 (39.0) 3 (9.4) 5 (23.8) 6 (23.1) 3 (11.5) 3(15.8) 36 (21.8) hnd/bsc 9 (22.0) 2 (6.2) 6 (28.6) 8(30.8) 13 (50.0) 3(15.8) 41(24.9) pgd 1 (2.4) 6 (18.8) 1 (4.8) 3 (11.5) 2 (7.7) 0 (0.0) 14 (8.5) others 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 2 (7.7) 0 (0.0) 2 (1.2) income <n30,000 9 (22.0) 6 (18.8) 9 (42.9) 5 (19.2) 5 (19.2) 5 (26.3) 39 (23.7) 30000-59999 6 (14.6) 17 (53.1) 5 (23.8) 6 (23.1) 6 (23.1) 8 (42.1) 48 (29.1) 60000-89999 8 (19.5) 2 (6.3) 3 (14.3) 3 (11.5) 3 (11.5) 4 (21.1) 23 (13.9) 90000-119999 13 (31.7) 5 (15.6) 2 (9.5) 7 (26.9) 8 (30.8) 2 (10.5) 37 (22,4) >119999 5 (12.2) 2 (6.2) 2 (9.5) 5 (19.2) 4 (15.4) 0 (0.0) 18 (10.9) occupation farming 2 (4.9) 8 (25.0) 2 (9.5) 0 (0.0) 1 (3.8) 4 (21.1) 17 (10.3) trading 19 (46.3) 10 (31.2) 7 (33.3) 11 (42.3) 6 (23.1) 6 (31.6) 59 (35.8) civil servant 11 (26.8) 9 (28.1) 6 (28.6) 5 (19.2) 14 (53.8) 6 (31.6) 51 (30.9) artisan 6 (14.6) 5 (15.6) 2 (9.5) 5 (19.2) 2 (7.7) 1 (5.3) 21 (12.7) professional 1 (2.4) 0 (0.0) 1 (4.8) 4 (15.4) 0 (0.0) 2 (10.5) 8 (4.8) others 2 (4.9) 0 (0.0) 3 (14.3) 1 (3.8) 3 (11.5) 0 (0.0) 9 (5.5) total 41 (24.8 32 (19.4) 21 (12.7) 26 (15.8) 26 (15.8) 19 (11.5) 165 (100) overall findings on the gender of the respondents show that the proportion of male was higher than their female counterparts. while male accounted for 63.6 %, female recorded 36.4 %. on the basis of each ward, the results from iperu ward i reveal that male constituted 75.6%, while female was 24.4 %. the proportion of male and female in iperu ward ii was 53.1 % and 46.9 % respectively. it was found that the percentage of male to female in iperu ward iii was 66.7 % and 33.3% respectively. the same proportion of male and female was recorded in ilisan ward i and ward ii. while male accounted 57.7 %, female constituted 42.3 %. in ilisan-irolu ward iii the percentage of male and female was 68.4 % and 31.6 % respectively. it could be inferred that both gender was well represented; however, the proportion of male was a little bit more than their female counterparts. the anova analysis shows that statistically significant difference does not exist between genders of http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com galley proof arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):815-826. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 820 respondents across the wards, as f value is 1.021 at p > 0.05. although the anova, result does not show a significant different, however, there is a wide margin between the overall proportion of female to male. it may be deduced that male is more responsive to female regarding the issue of groundwater source in the study area. the analysis of the marital status of the respondents is presented in table 1. it was found in iperu ward i that single, married, and widow constituted 19.5 %, 75.6 % and 4.9 % respectively. findings from pieris ward ii show that 12.5 % was single, 78.1 % was married, while widow or widower accounted for 9.4 %. similarly, married recorded the highest percentage (71.4 %) in iperu ward iii. single widow/widower and separated constituted 9.5 %, 14.3 %and 4.8 % respectively. furthermore, the respective percentage of single married, and separated in ilisan ward i are 11.5 %, 84.6 % and 3.8 %. nothing was recorded for widow or widower. it was found that single accounted for 11.5 %, married constituted 73.1 % and widow or widower recorded 15.4 % in ilisan ward ii. like other wards, married respondents accounted for highest (78.9 %) in ilisan-irolu ward iii. the proportions of other marital status are 15.8 %, 5.3 % for single and widow/ widower respectively. aggregately, married respondents have the highest percentage (77 %). single constituted 15.8 %, while widow or widower accounted for 7.9 %, separated has the least percentage (1.2 %). anova results show that there is no statistically significant difference in the marital status of the respondents across sampled wards as f value of the computed anova is 0.302 at p > 0.05. in aggregate, findings on educational status of the respondents reveal that those that had tertiary education such as national diploma or national certificate in education, higher national diploma or university degree and post-graduate degree constituted the highest (55.2 %). other educational status is no formal education (20.6 %), primary education (2.4 %) and secondary education (20.6 %). other educational attainments accounted for 1.2 %. the computed anova (f = 5.899 and p < 0.05) established that there is a statistical significant difference in the educational status of the respondents across the surveyed wards. expectedly, wards having respondents with high educational attainment supposed to be more concerned with issue of good quality drinking water. this has been earlier posited by (abubakah, 2019) that the educational status of a person to a large extent affects his/her standard of living, level of exposure and attitude. the information on the income distribution showed that majority earned above the minimum wage (₦30,000) in nigeria. the percentage of respondents earning above minimum wage was 76.3 %. those who earned below were 23.7 %. however, the computed anova established that there is no significant difference in the income distribution of respondents across sampled wards with f = 2.412 and p > 0.05. the result implies that most of the respondents are middle income earners. the result presented showed that 35.8 % of respondents engaged in trading and 30.9 % worked in civil service. while those that engaged in farming represented 10.3 %; artisans (welder, furniture, mechanics, and others) constituted 12.7 %. the percentage of professionals was 4.8 %, while others who engaged in other occupations recorded 5.5 %. however, there is no statistical significant difference in the occupational status of the respondents across the surveyed wards with anova results of f = 2.548 and p > 0.05. it implies that there is a level of commonality in the occupational distribution of the respondents across the surveyed wards. 3.2 sources of groundwater findings on sources of groundwater in the study area show that most (70.3 %) of the respondents sourced water from borehole (table 2). however, those who sourced water from dug well are 22.4%, while only 2.4% sourced water from both dug well and borehole. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com galley proof adewunmi and akinpelu: socio-economic characteristics of residents in correlation to groundwater source in ikenne local government area, ogun state, nigeria. azojete, 19(4):815-826. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 821 table 2: respondents’ ground-water source ward source of ground water total (%) well (%) borehole (%) well & borehole (%) iperu ward i 3 (7.3) 37 (90.2) 1 (2.4) 41 (100) iperu ward ii 12 (37.5) 18 (56.2) 2 (6.2) 32 (100) iperu ward iii 3 (14.3) 17 (81.0) 1 (4.8) 21 (100) ilisan ward iv 8 (30.8) 12 (46.2) 6 (23.1) 26 (100) ilisan ward v 2 (7.7) 23 (88.5) 1 (3.8) 26 (100) ilisan/iroluward vi 9 (47.4) 9 (47.4) 1 (5.3) 19 (100) total 37 (22.4) 116 (70.3) 12 (7.3) 165 (100) the results revealed that residents in the study area relied more on water obtained from borehole, probably because of the fact that the source is considered to be more reliable than dug well. although, nickson et al. (2005) asserted that groundwater is the most reliable and most extensive storage of fresh-water on earth which is used by one-third of the entire world’s population for drinking purposes. however, okelola et al. (2010) further noted that water from borehole is more reliable for human consumption compared to the one from well. 3.3 respondents’ proximity to groundwater it was found that majority (78.2 %) of the respondents were close to the source of groundwater, while 21.8 % was far from the source of groundwater. the findings indicate that groundwater; especially borehole is more accessible to the respondents in the study (table 3). table 3: nearness of water source to respondents ward closeness of water source total (%) yes (%) no (%) iperu ward i 40 (97.6) 1 (2.4) 41 (100) iperu ward ii 17 (53.1) 15 (46.9) 32 (100) iperu ward iii 17 (81.0) 4 (19.0) 21 (100) ilisan ward iv 22 (84.6) 4 (7.6) 26 (100) ilisan ward v 23 (88.5) 3 (11.5) 26 (100) ilisan/irolu ward vi 10 (52.6) 9 (47.4) 19 (100) total 129 (78.2) 34 (21.8) 165 (100) it could be deduced that the distribution of boreholes in the study area is fairly even. even distribution of utility such as boreholes tends to enhance accessibility. studies have shown that lack of access to improved water source has resulted to an increase in consumption of contaminated or polluted water (who, 2012; ologbushere et al. 2016; beshiru et al. 2018) with potential detriment to public health. 3.4 uses of groundwater the predominant use of groundwater as found from the study is domestic purpose, such as cooking, washing and drinking (table 4). the proportion of respondents that used groundwater for domestic purpose accounted for 92.7 % out of the total. as shown in the table, the percentage of the respondents that used groundwater for industrial purpose constituted 2.9 %, whereas those that used it for other purposes such as farming accounted for 4.9 %. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com galley proof arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):815-826. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 822 table 4: ground-water usage ward uses of ground water total (%) domestic (%) industrial (%) others (%) iperu ward i 39 (95.1) 2 (4.9) 0 (0.0) 41 (100) iperu ward ii 31 (96.9) 0 (0.0) 1 (3.1) 32 (100) iperu ward iii 19 (90.5) 0 (0.0) 2 (9.5) 21 (100) ilisan ward iv 22 (84.6) 2 (7.7) 2 (7.7) 26 (100) ilisanward v 25 (96.2) 0 (0.0) 1 (3.8) 26 (100) ilisan/irolu ward vi 17 (89.5) 2 (10.5) 0 (0.0) 19 (100) total 153 (92.7) 4 (2.4) 8 (4.9) 165 (100) the findings reveal that the respondents relied more on groundwater to meet their daily domestic water needs. earlier study by hill (2004) found that more than one quarter of the world population depends on groundwater for drinking and other basic needs. 3.5 correlation and regression analyses of respondents’ groundwater source and socioeconomic characteristics the results of correlation analysis presented in table 5 show that there is no relationship between the gender of the respondents and their source of groundwater (r = -0.058). it implies that gender is not a determinant of where respondents source for their groundwater. the result of analysis on groundwater and marital status shows that significant relationship exists between the two variables (r = 0.514). this means that respondents with a spouse or partner are more concerned about where they source for their groundwater than a home with no spouse or partner. table 5: correlation analysis of respondents’ groundwater source and socioeconomic attribute parameter groundwater source gender marital status education income occupation groundwater source 1.000 gender -0.058 1.000 marital status 0.514 -0.005 1.000 education 0.670 -0.025 0.549 1.000 income 0.557 -0.060 0.636 0.811 1.000 occupation 0.604 -0.013 0.588 0.846 0.837 1.000 correlation analysis between groundwater source and occupation reveal that a relationship exists between the two variables (r = 0.604). this implies that residents with better occupation can afford to source for groundwater that is reliable and/or of better quality. the study found a relationship between educational status and groundwater source. this is corroborated by the work of morakinyo et al. (2015), where they found that positive relationship exists between educational attainment of household and access to improved drinking water sources. it was also established in the study that income correlates positively with groundwater source. this is in agreement with the study of shewayine et al. (2021). they also observed in their work that there is a connection between income and household source of water. on the other hand, the regression analysis was done on five (5) variables that were correlated with groundwater source. when gender was input as a predictor of groundwater source, which is considered as a simple correlation between groundwater source and gender, the value of r obtained is 0.058. the value of r2 is 0.3364, which shows that gender can account for 33 % of the variation in groundwater source. this means that 66.4 % of the variation in groundwater remains unaccounted for (table 6). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com galley proof adewunmi and akinpelu: socio-economic characteristics of residents in correlation to groundwater source in ikenne local government area, ogun state, nigeria. azojete, 19(4):815-826. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 823 table 6: predictors of groundwater source model r r square adjusted r square std. error of the estimate change statistics r square change f change df1 df2 sig. f change 1 .058a .336 -.003 .61793 .003 .545 1 163 .462 2 .702b .493 .477 .44642 .489 38.327 4 159 .000 a. predictors: (constant), gender b. predictors (constant), gender, marital status, education, income, occupation c. dependent variable: water source however, when the other four predictors are included (marital status, education, income and occupation), this value increases to .493 or 49.3% of the variance in groundwater source, which is significant with f value of 38.327 and p < 0.005. if gender account for 33%, then marital status, education, income and occupation must account for an additional 49%, which means that addition of the four predictors increase the ability of the model to predict the residents’ variation in groundwater source. the five variables analysed can be used to predict up to 82% of residents’ groundwater source in the study area. however, there is 18% of the variation in groundwater not accounted for. this might be subject of further study. the study conducted by abubakah (2019) found that education, gender and wealth status among others were determinants of improved household water source. this is in line with the outcome of current findings that residents’ socioeconomic background contributes significantly to their source of groundwater. 4. conclusion the finding of the study showed that residents depended more on borehole as a source of groundwater. also, regression analysis established that socio economic characteristics of the residents are strong factors in predicting residents’ groundwater source. hence, governments and corporate organisations should give priority to borehole drilling, especially in areas where people rely more on well water as part of their social responsibilities. in the provision of boreholes more attention is expected to be given to wards where residents were either lowor medium-income earners. the fact that potable water is important for healthy living and the need for people to have access to it as recognised by united nations sustainable development goals (no. 6), thus, water sources that is reliable should be made more accessible to people. therefore, the study recommends that governments at all levels should embark on drilling of boreholes such that it will be easily accessible to people. it is equally important for governments and corporate organisations to embark on awareness campaigns on the need for people to desist from sourcing for water from unreliable sources because of inherent health problems that can lead to diseases and even death. references abubakah, ir. 2019. factors influencing household access to drinking water in nigeria. utilities policy, 58: 40-51. agbadi, pe., darkwah, pl. and kenney, ac. 2019. a multilevel analysis of regressors of access to improved drinking water and sanitation facilities in ghana.journal of environmental and public health, 20: 11-23 akpabio, ib, ati, of, and iniobon, ea. 2013. water for cities in nigeria: the governance dimension. mediterranean journal of social sciences, 40 (4): 297-309. ashraf, ma., maah, mj., yusoff, i. and mehmood, k. 2010. effects of polluted water irrigation on environment and health of people in jamber, district kasur, pakistan. international journal of basic & applied sciences, 10 (3): 37-57. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com galley proof arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):815-826. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 824 bos, r., alves d., latorre, c., macleod, n., payen, g., roaf, v. and rouse, m. 2016. manual on the human rights to safe drinking water and sanitation for practitioners. london, uk: iwa publishing london, www.iwapublishing.com beshiru, a., okareh, ot., chigor, vn. and igbinosa, eo. 2018. assessment of water quality of rivers that serve as water sources for drinking and domestic functions in rural and preurban communities in edo north, nigeria. environmental monitoring and assessment, 190: 387-398. calow, rc., alan, mm., alan, ln. and nick, rs. 2011. groundwater security and drought in africa. linking availability, access and demand, groundwater, the groundwater association journal, 48 (2): 246-256. calixto, oj. and anaya, jm. 2014. socio-economic status: the relationship with health and autoimmune diseases. autoimmunity reviews, 13(6); 641-654. chapra, sc. 1997. surface water quality modelling, mcgrow-hill, new york, 844-856 cochran, wg. 1977. sampling technique. 3rd ed. john wiley & sons. new york david, sg. and thomas, os. 2011. the environmental impact of groundwater exploitation in african grassland. examples and a case study from kalahari region. science direct, department of geography, university of sheffield, united kingdom, s102tn, http://books.google.co.ke/books, pp. 225-235 dickerson, dl., penick, je., dawkins, kr. and van, sm. 2007. groundwater in science education. journal of science teacher education, 18 (1): 45-61. efunshile, am., ezeanosike, o., nwangwu, cc., konig, b., jokelainen, p. and robertson, lj. 2019. apparent overuse of antibiotics in the management of watery diarrhoea in children in abakaliki, nigeria. bmc infectious diseases, 19: 275. https://doi.org/10.1186/s12879-0193899-1 federal ministry of water resources and rural development, 2011. www.waterresources.gov.ng galobardes, bm., shaw, da., lawlor, jw., lynch, jp. and smith, gd. 2006. indicators of socioeconomic position (part 1). journal of epidemiology & community health, 60 (1): 7–12. henry, gj. and heinke, gw. 2005. environmental science and engineering, second edition prentice-hall of india private limited, new delhi, pp. 33-45. hemmig, c. 2015. what development? poverty and the struggle to survive in the fuuta tooro region of southern mauritania, the ohio state university, united states of america. hill, mk. 2004. understanding environmental pollution, 2nd ed. cambridge university press, united kingdom. hounslow, a. 2018. water quality data: analysis and interpretation; crc press: boca raton, fl, usa, new york, washington. www.crcpress.com irianti, s. and prasetyoputra, p. 2007. analysis of the 2007 indonesia family life survey. cogent medicine, 3 (1): 115-143. sasimartoyo, tp. 2007. determinants of household drinking –water source in indonesia: analysis of the 2007 indonesia family life survey. cogent medicine, 3 (1): 192-195. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com http://www.iwapublishing.com/ https://doi.org/10.1186/s12879-019-3899-1 https://doi.org/10.1186/s12879-019-3899-1 http://www.crcpress.com/ galley proof adewunmi and akinpelu: socio-economic characteristics of residents in correlation to groundwater source in ikenne local government area, ogun state, nigeria. azojete, 19(4):815-826. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 825 kausar, s., maann, aa., zafar, i., ali, t. and kanwal, a. 2009. household characteristic affecting drinking water quality and human health. pakistan journal of agriculturalsciences,46 (3): 192-195. morakinyo, om., adebowale, sa. and oloruntoba, eo. 2015. wealth status and sex differential of household head: implication for source of drinking water in nigeria. archives of public health, 73(1): 58-73. nickson, rt., mcarthur, jm., shrestha, b., kyaw-nyint, to. and lowry, d. 2005. arsenic and other drinking water quality issues, muzaffargarh district, pakistan. applied geochemistry, 20: 55–68. https://doi.org/10.1016/j.apgeochem.2004.06.004 ocheri, m., odoma, l. and umar, n. 2014. groundwater quality in nigerian urban areas: a review. global journal of science and frontier research, 14(3): 1-9. okeola, fo., kolawole, od. and ameen, om. 2010. comparative study of physic-chemical parameters of water from a river and its surrounding wells for possible interactive effect. advances in environmental biology, 4(3): 336-344. ologbushere, oa., aluyi, hsa., ogofure, ag., beshiru, a. and omeje, fi. 2016. physicochemical and microbiological profile of bacterial and fungal isolates of ikpoba river in benin city: public health implications. african journal of environmental science and technology, 10(3): 67–76. olugbamila, ob., adeyinka, sa., odunsi, om., olowoyo, sa., isola, ol. and adanlawo, td. 2020. community participation in the provision of environmental sanitation infrastructure in akure, nigeria environmental & socio-economic studies, 8(3): 48-59. orewole, mo., mkainde, ow., adekalu, k. and shittu, ka. 2007. chemical examination of piped water supply of ile –ife in south west nigeria. iran journal of environmental health science and engineering, 4(1): 51-56. pawari, m.j. and gavande, sm. 2015. assessment of water quality parameters: a review, international journal of science and research (ijsr), 4(7): 85-97. piscopo, g. 2001. groundwater vulnerability map, explanatory notes, castelreagh catchment, nsw. department of land and water conservation, australia, found at: http://www.dlwc.nsw.gov.au/care/water/roundwater/reports/pdfs/castlereagh_map_no tes.pdf schlosser, a., strzepek, k. and gao, x. and fant, c., blanc, e., paltsev, s., jacoby, h., reilly, j. and gueneau. a. 2014. the future of global waters: an integrated assessment, earth’s future, 2(8): 341-361. smith, jh., mill, t., mabey, pc., bomberger, tw., chou, dg. and herdry, w. 1997. laboratory protocols for evaluating the fate of organic chemicals in air and water. us environmental protection agency, athens ga epa 600/3-82-0220. unicef and world health organization 2012. progress on drinking water and sanitation, unicef and who, new york, ny, usa, https://sdgs.un.org/ united nations 2019. the sustainable development goals report, united nations< new york, ny, usa, http://sdgs.u.org/ http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com https://doi.org/10.1016/j.apgeochem.2004.06.004 http://www.dlwc.nsw.gov.au/care/water/roundwater/reports/pdfs/castlereagh_map_no%20tes.pdf http://www.dlwc.nsw.gov.au/care/water/roundwater/reports/pdfs/castlereagh_map_no%20tes.pdf https://sdgs.un.org/ http://sdgs.u.org/ galley proof arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):815-826. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: opakinpelu@bellsuniversity.edu.ng 826 world bank 2019. the world bank eswatini water supply and sanitation access project (p166697): project information document (pid), world bank, washington dc, usa. http://www.worldbank.org/projects world health organization 2012. diarrhoeal diseases. who, geneva. switzerland http://www.who.int/vaccine_research/documents/diarrhoealdiseases20091122.pdf world health organization and united nations children’s fund 2017. progress on drinking water and sanitation: 2017 update and sdg baselines, world health organization and united nations children’s fund, geneva, switzerland. http://apps.who.int/iris/handle/10665/258617 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com http://www.worldbank.org/projects http://www.who.int/vaccine_research/documents/diarrhoealdiseases20091122.pdf arid zone journal of engineering, technology & environment azojete december 2021. vol. 17(4):481-494 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 481 original research article applications of various types of circuit breakers in electrical power systems: a review p. i. obi*, c. s. ezeonye and e. a. amako department of electrical & electronic engineering, michael okpara university of agriculture umudike, abia state, nigeria. *corresponding author’s email address: patndyobi@gmail.com 1.0 introduction circuit breaker is one of the major power system components in electric power transmission and distribution. a good circuit breaker must be capable of clearing and isolating faulted sections of the power circuit rapidly and clearly (balan et al., 2016). the research on circuit breaker is never ending due to its significance in power system circuits. circuit breaker is a mechanical device that have the potential of interrupting fault currents by splitting separable contacts and reclosing it after faults clearance, in addition performs the work of a switch. its purpose is to open and close the network to prevent the effects of fault and to connect/disconnect components of the electrical grid. it can be utilized manually during line maintenance while it is operated automatically during fault on the line (anderson, 1999; khan, 2008; umran, 2016; obi et al., 2021). under healthy operating conditions, the fixed and movable contacts of the breakers stay closed and will not automatically operate until unhealthy operating conditions occur on the system. during unhealthy (fault) conditions, the relay senses the fault and sends a tripping signal to the circuit breaker for opening of the faulted section. the circuit breaker tripping coils get energized after receiving this fault signal and the movable contacts are tugged apart by some mechanism, thereby opening the circuit on which it protects. when the circuit breaker contacts are tugged apart under conditions of fault, an electric arc is struck between them. the highest value of current that can be interrupted by a circuit breaker without any harm to the system is known as interrupting or rupturing current. the circuit breaker rupturing current sustain until the discharge halts. during healthy operating conditions article information abstract this paper presents a review on the applications of various types of circuit breakers (cb) used in electric power transmission and distribution. circuit breakers are majorly classified under direct current (dc) or alternating current (ac) system. it shows that the most suitable way of classifying circuit breakers is on the level of voltage rating which is broadly grouped under direct current (dc) or alternating current (ac) circuit breakers. however, reviewed literatures did not clearly distinguish the respective applications of the different types of circuit breakers as applied to dc and ac power network. the dc circuit breakers which comprises of mechanical, solid-state and hybrid breakers are mostly applied in domestic and industrial applications that employ the use of direct current (dc) especially in high voltage direct current (hvdc) network system for the protection of electrical devices. ac circuit breakers are grouped in high voltage and low voltage forms. the low voltage cb comprises of miniature and molded case circuit breakers used majorly in domestic and commercial installations. the high voltage circuit breakers are further subdivided into oil and oil-less forms. the oil-less cb is made up air, vacuum and sulphur hexafluoride (sf6) circuit breakers. these high voltage circuit breakers are majorly applied in high voltage and extra high voltage transmission systems for protection of power system equipment and electrical machines. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 july, 2021 revised 6 sept., 2021 accepted 10 sept., 2021 keywords: oil circuit breaker (ocb) air circuit breaker (acb) sulphur hexafluoride (sf6) circuit breaker vacuum circuit breaker (vcb) low voltage circuit breakers (lvcb) file:///c:/users/user/desktop/azojete/azojete%20archive/upload/vol%2017%20no%204/patndyobi@gmail.com arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):481-494. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 482 the contacts are in closed position, whereas during unhealthy conditions the breaker contacts move to interrupt the current flow that give rise to an electric arc between the contacts. this arc generated during the separation of the circuit breaker contacts produces tremendous heat that can result to system damage or to the circuit breaker itself as well as delaying the process of current interruption. the ratings of circuit breakers are in mega volt-amp (mva), and heavyduty circuit breakers can break-in some thousand amperes of high short circuit currents (mehta and mehta, 2008; bansal, 2019). the main functions of circuit breakers in power circuit are to sustain fault current without distortion due to magnetic forces under fault conditions, to switch load currents, to break fault currents as well as operating current. they are employed in the power system to shield it from any unwanted fault by opening or breaking the circuit to interrupt the fault current. they are rated in terms of the number of poles, rated frequency, rated making capacity, rated voltage and current, short-term rating, and operating duty (hewitson et al., 2004; wadhwa, 2012; alharbi and habiballah, 2020). some authors have worked on the circuit breakers and its applications to the operation of power system. in rao and gajjar (2008), mayr arc model with steady time parameter and cooling power is applied to develop sf6 breaker model in (pscad). it is observed from their results that for the effective interruption of an electric arc, the location of fault should be within the critical length, cooling power should be optimal for the given fault vicinity and the presence of the capacitances across the circuit breaker is required. in jing and bing (2014), the characteristics of magnetic instantaneous acting trip in normally low voltage molded case circuit breakers (mccb) are analyzed using finite element method. the simulation result demonstrates that mccb has good prospect in optimizing the design and protection performance. gao et al. (2017) compared dc semiconductor circuit breaker and sulphur hexafluoride (sf6) circuit breaker with transverse magnetic field (tmf) for dc transmission. their results showed that semiconductor breakers have fast breaking speed, while semiconductor switches may be connected in series and parallel with the high voltage circuit breakers. different types of circuit breakers and their applications were reviewed by goh et al. (2017) which include sulphur hexafluoride (sf6), oil, vacuum, air, and dc breakers which made up of solid-state dc and hybrid dc breaker. chen and ke (2018) discussed modeling and simulation circuit breaker operated on high voltage system with the aid of power system computer aided (pscad). from their results, the current and voltage when the circuit breaker cuts current flow in different positions are primarily harmonious as based on the instituted model of the circuit breaker. liang et al. (2018) investigated on a new synthetic test of direct current (dc) vacuum circuit breaker. they analyzed the breaking process of dc circuit breaker, the basic principle of ac synthetic test and parameters analysis, and also presented a new synthetic test circuit topology of the breaker. al mashakbeh (2019) presented a survey on the importance of electrical circuit protection devices which showed that most industries use circuit breakers and fuses as the electrical circuit protection devices for protecting their circuits from different hazardous conditions. fatigue assessment and ductile multi-body dynamic analysis of 550 kv high voltage circuit breaker was performed by kim (2019) to predict fatigue life of the circuit breaker. sedhuraman et al. (2019) evaluated the performance of smart intelligent circuit breaker (sicb). their results showed that sicb can reduce and rectify the pre-fault by itself without human interface. basic classification of different types of circuit breaker in power system transmission and distribution are reviewed by alharbi and habiballah (2020). they classified them based on their operation, voltage level and packaging, and this helps in protecting power system equipment and devices from dangerous fault current. yang et al. (2020) presented the technical growth, mainly the topology, test technology, and technology of protection and control of high obi et al: applications of various types of circuit breakers in electrical power systems: a review. azojete, 17(4):481-494. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 483 voltage direct current (hvdc) circuit breaker and their applications in voltage source converter high voltage direct current (vsc-hvdc) transmission project. shah et al. (2020) presented simulation of hybrid high voltage direct current (hvdc) circuit breaker with superconducting fault current limiter (sfcl) for fault current limiting with the aid of matlab software. from their given results, the current limiting by super-conducting fault current limiter (sfcl) particularly repressed the dc fault current and notably reduced the current interruption stress for superconducting dc circuit breaker components. from the reviewed literatures, it is seen that the review of different types of circuit breakers as applied to dc and ac power networks were lacking in their analysis. as a result, different types of circuit breakers were categorized under dc and ac networks. their current carrying capacities and voltage levels as well as their applications to power system network are also noted down. 2. materials 2.1 classifications of circuit breakers used in electrical power transmission and distribution. there are various classes of circuit breakers as applied to power system. they are broadly classified as dc and ac circuit breakers which are based on the type of current they operate on in the power network. in ac circuit breakers, they are classified based on the level of operating voltage, by the location of installation, by means of interruption and by its external design. as based on the level of voltage operation, circuit breakers are classified as low voltage circuit breakers with operating voltage up to 1 kv and high voltage circuit breakers with operating voltage beyond 1 kv. the high voltage circuit breakers are subdivided into circuit breakers with operating voltage of 70 kv and below, and those with operating voltage of 132 kv and above. all high voltage circuit breakers are categorized in two main categories which are oil and oilless circuit breakers (gupta, 2015). as based on location of installation, circuit breakers can be classified as outdoor and indoor circuit breakers. the major distinction between the two is on the enclosures, casing, and the place of installation. the indoor type circuit breakers are specified to be installed in protected enclosures such as in buildings or protected casing for protection against weather conditions. while the outdoor type circuit breakers do not demand any shielding, protection or casing. they have stronger enclosure arrangements as compared to the indoor type (wadhwa, 2012). as based on the means of interruption of fault current on the line, circuit breakers can be classified as oil, air-break, air-blast, vacuum, and sulphur hexafluoride (sf6) circuit breaker (alharbi and habiballah, 2020). as based on the design of external structure, circuit breakers can be classified as dead tank and live tank circuit breakers. these are also found to be types of outdoor circuit breakers. the live tank circuit breakers have its enclosures and interrupters mounted above the ground level, while the dead tank circuit breakers have its enclosures and interrupters mounted on the ground (choonhapran, 2007). 2.2 types of ac circuit breakers used in electrical power transmission and their applications there are different categories of circuit breakers used in the transmission and distribution of electrical power. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):481-494. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 484 2.3 low voltage circuit breakers these types of circuit breakers are widely applied in domestic settings as well as in industrial and commercial applications. they include molded case circuit breaker (mccb) and miniature circuit breaker (mcb) (pierre and jean-jacques, 2009; norazizah and noramalina, 2019). 2.3.1 miniature circuit breaker (mcb) the mcbs as shown in figure 1 are mostly applied for domestic and commercial installations, with operating voltage between 220 and 400 v and current range from 6 amps to 63 amps. the current to interrupt cannot be higher than 100 amp and the interruption characteristics are not usually adjustable. generally, they are provided with thermal or magneto-thermal devices and the housing cannot be opened to develop any maintenance of the device (lucius, 2016). figure 1: miniature circuit breaker (jw tech, 2017) 2.3.2 molded case circuit breaker (mccb) the mccb as shown in figure 2 is used in distribution of electric power. it is designed basically to protect electrical circuits and equipment that operates on low voltage below 600 v. it can interrupt currents up to 2500 amp. additionally, this device allows to adjust the interruption current. the operational principle is also thermal or magneto-thermal and the components are located inside an insulating molded case. these devices are designed in order not to be opened for maintenance, so the contacts cannot be replaced. all mccbs are fast enough to restrict the quantity of the prospective current let-through, and some are fast enough to be designated as current-limiting circuit breakers. they can be used in heavy duty applications such as welding machines, protecting generators, protecting motors, protecting feeders and protecting capacitor banks (das, 2012; aio, 2013). figure 2: molded case circuit breaker (global sustainable energy solutions, 2017) obi et al: applications of various types of circuit breakers in electrical power systems: a review. azojete, 17(4):481-494. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 485 2.4 high voltage circuit breakers high voltage circuit breakers are specified and designed to interrupt current flow at natural current zero and hold out against the pressure and tension bring about by dielectric on the procedure of interruption. they are applied in high voltage and extra-high voltage transmission systems. they are extremely classified as oil and oil-less circuit breakers. the oil circuit breakers are subdivided into minimum or low oil circuit breakers and bulk oil circuit breakers. the oil-less circuit breakers are sub-categorized as air-break, air blast, vacuum, and sulphur hexafluoride (sf6) circuit breaker (suwanasri et al., 2013; umran, 2016; obi et al., 2021). 2.4.1 oil circuit breaker (ocb) oil circuit breakers are the category of high voltage circuit breakers used in transmission of electrical energy which make use of oil for the extinguishing of arc during the separation of the breaker contact. they consist of minimum or low oil circuit breakers and bulk oil circuit breakers. low oil circuit breakers operate with minimum quantity of oil which inhibit the interrupting unit in an insulating chamber at the live potential, and sometimes refer to as the live tank circuit breakers due to the oil tank is insulated from the ground. while the bulk oil circuit breakers uses large amount of oil as quenching medium and also for insulating media between earth parts of the breaker and current-carrying contacts, and occasionally designated as dead tank circuit breakers due to the tank is held at earth potential. the contact separation is done under oil which serves as an insulation between the live parts due to its high dielectric strength as shown in figure 3. as the contact is separated underneath the insulating oil, an arc is struck between them. the quenching of an electric arc during contact separation is made possible by two processes. firstly, the hydrogen gasoline has excessive conductivity of heat and cools the electric arc, hence supporting the de-ionization of the medium between the contacts. secondly, the gasoline sets up agitation in the oil and compels it into the space between contacts, thus removing the arcing products from the path of an arc which leads to extinguishing of arc and the circuit current is interrupted. the ratings of oil circuit breakers range from 25 mva at 2.5 kv to 5000 mva at 230 kv while they are applied for voltage range of 33 kv to 220 kv and breaking capacities of 1500 mva to 7500 mva. the merits of oil as a medium for arc quenching are: it has the ability to cool and flow into the space after current zero and electric arc goes out, assimilation of energy by breakdown of oil, oil presents a cooling surface, while the demerits are the high-value of oil maintenance, reduction of dielectric strength of the oil due to the pollution by carbon particles and high in flammability of the oil (hewitson et al., 2004; mehta and mehta, 2008; alharbi and habiballah, 2020). figure 3: oil circuit breaker (bansal, 2019) arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):481-494. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 486 2.4.2 air-break circuit breaker the air-break circuit breaker is fitted in a chamber that surrounds the contacts which is known as arc chute as shown in figure 4. it uses air at atmospheric pressure as a means of interrupting the fault current, mostly used in low voltage applications with the high interrupting current. they are applied on the system that operates on the range of 400 v to 12 kv and rupturing capacities of 500 mva (gupta, 2015). figure 4: air-break circuit breaker (mehta and mehta, 2008) 2.4.3 air-blast circuit breaker this type of circuit breaker as shown in figure 5 is applied when the system operating voltage is 132 kv and above. they make use of compressed air at pressure of 20 – 30 kg/cm2 as a means of arc extinguishing during the separation of breaker contacts. they have the following merits: elimination of fire hazard, the regular expenses for oil replacement are avoided, the fault current to be interrupted are independent due to the energy required for the extinction of an electric arc is gotten from high air pressure, short arcing time, consistent breaking time, chemical stability of air, small in size and suitability for repeated operation. their demerits are: current chopping and restriking voltage, along with high-level noise during the operation and maintenance of the air compressor plant, arc extinguishing properties of the air are inferior, and regular maintenance of the compressor plant which gives the air-blast is required. air blast circuit breakers are categorized into cross blast, radial blast and axial blast. figure 5 shows axial blast type of air circuit breaker. air-blast circuit breakers are applied in low voltage as well as high voltage systems. it is also used for protection of transformers, capacitors, and generators (bansal, 2019). obi et al: applications of various types of circuit breakers in electrical power systems: a review. azojete, 17(4):481-494. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 487 figure 5: air-blast circuit breaker (goh et al., 2017) 2.4.4 vacuum circuit breaker the dielectric strength of vacuum is very much higher than other interrupting mediums thereby it makes use of the higher dielectric strength of the vacuum for arc extinction and the rate of dielectric recovery of vacuum is much faster than that of air. the contact separation and movement is very small, on the order of millimetres instead of centimetres, which makes the role of these breakers and their potential of extinction of an arc very fast. the movable and fixed contacts are set up inside an inalterably shut vacuum interrupter as shown in figure 6. the process and method of the arc quenching is coordinated by a metal surface phenomenon during parting of their contacts. in other words, the arc is not quenched by the medium of interruption however via the use of metal vapour. the vacuum arc can only be cooled down via the usage of a magnetic field which can move the arc over the contact surfaces. the capabilities of vacuum circuit breakers for fault-current interruption are similar to sf6 breakers. they are available in the medium range of voltage up to about 35 kv and at 25 kv single phase (50 kv equivalent) as dual bottle assemblies for electric traction. vacuum switches as load-break switches comprising of a series of group of vacuum bottles are obtainable up to 245 kv. these breakers are less bulky, it has high dielectric strength, it requires less power for control operation, more efficient, release of low arc energy, negligible maintenance, low-value, very reliable, compact, and longer life. however, it requires high level technology for the fabricating vacuum interrupters which is costly and also requires supplementary surge suppressor in parallel with each phase for interruption of small magnetizing currents. they are generally applied in capacitor switching, shunt reactor switching, transformer switching and line dropping (choonhapran, 2007; khan, 2008). arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):481-494. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 488 figure 6: vacuum circuit breaker (gupta, 2015) 2.4.5 sulphur hexafluoride (sf6) circuit breaker sf6 breakers were developed in the 1960s and quickly set off as the favoured choice for wide areas of high and medium voltage applications. they are made up of single pressure type and double pressure type sf6 cbs. the contacts of the breaker are opened by the flow of highpressure sf6 gas and an electric arc is struck between them as shown in figure 7. the conducting free electrons in the electric arc are quickly apprehended by the means of gas to form moderately motionless negative ions. this loss of conducting electrons in the arc rapidly builds up sufficient and adequate insulation strength to quench the arc. the dielectric strength of sf6 at atmospheric pressure is roughly equal to that of air at the pressure of 10 atm. temperatures in the order of 30000 kelvin (k) are expected to be encountered in arcs in sf6 and these are, well beyond the detachment temperature of the gas (about 2000 k); nevertheless, nearly all the decomposition products are electronegative so that the dielectric strength of the gas recovers quickly after the arc has been quenched. filters are made available to ensure the decomposition products are harmless and only a chunk of fluorine reacts with metallic parts of the breaker. the advantages of sf6 cbs includes: sf6 gas cbs can control all known switching phenomena, they have a high degree of reliability, it is highly electronegative, sf6 gas cbs require minimum maintenance, arc reignition is minimized due to the chemical properties of sf6, contact detachment in sf6 gas cbs is least due to dielectric strength provided by the high-pressure sf6, the closely packed design of sf6 gas cbs significantly minimizes the space demands and costs of building installation, and the lowerand medium-current ratings of sf6 gas cbs are very economically satisfied by the modular design. while the demerits of sf6 cbs are the high-value of the sf6 gas used in the circuit breakers, sf6 has to be reconditioned after every operation and the high pressure of sf6 gas will absorb all the conducting free electrons which leads to extinction of the arc. sf6 circuit breakers comprises single-interrupter sf6 cb which is applied up to 220 kv, two-interrupter sf6 cb which is applied up to 400 kv and four-interrupter sf6 cb which is applied up to 715 kv (weedy et al., 2012; turan, 2014). obi et al: applications of various types of circuit breakers in electrical power systems: a review. azojete, 17(4):481-494. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 489 figure 7: sulphur hexafluoride circuit breaker (wadhwa, 2012) 2.5 types of dc circuit breakers used in dc power network the direct current circuit breaker (dccb) is the key piece of equipment used in high voltage direct current (hvdc) network system for the protection of electrical devices that operate with direct current. (siemen, 2017; stanley, 2018). the dccb comprises solid-state, mechanical and hybrid breakers. the hybrid dc circuit breaker is the combination of solid-state and mechanical circuit breakers (atmadji and sloot, 1998; meyer et al., 2005; yao et al., 2019; zheng et al., 2019). the hvdc circuit breaker operates based on commutation principle, giving artificial current zeros. the dc circuit breakers have not commonly been used in hvdc network system because of its high cost, complex nature and redundancy (rao, 2013). the dc waveform of the breakers does not have natural current zero-crossing point, so the dc arc is more difficult to extinguish than the ac arc (grieshaber, 2010; ieee standards association, 2010). therefore, in designing a hvdc circuit breaker, formation of artificial current zero, obviating of restrikes and dissipation of stored energy, are the few issues that have to be solved for maximum optimization and reliable operation and interruption of short circuit current (shrishti et al., 2019). the creation of artificial current-zero is the major problem experienced in extinguishing of arc in dc circuit breakers. this can be successfully achieved by: i. connecting a series resonant l-c circuit across the main contact of a conventional circuit breaker as shown in figure 8. in this process, the main current is interrupted indicating discharge of capacitor c through inductance l and setting up of oscillatory current by the main contact m and supplementary contact s1, hence, artificial current zeros are produced and the circuit breaker main contact m is opened at a current zero. arid zone journal of engineering, technology and environment, december, 2021; vol. 17(4):481-494. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 490 figure 8: hvdc circuit breaker with series resonant l-c (norum, 2016) ii. diverting the main current id to the capacitor c which is initially uncharged as shown in figure 9. in the process of diverting the main current id to the capacitor c, the breadth of current to be interrupted by the breaker reduces. when the main cb contact m opens, id is detracted to the capacitor c, thereby reducing the current to be interrupted by the main contact m of the circuit breaker. figure 9: hvdc circuit breaker with non-linear resistance (zheng et al., 2019) the self-excited oscillation mechanical dccb utilizes the negative resistance attribute of a dc arc, to allow the lc oscillation arm and the main current arm to conduct self-excited oscillation to give rise to the current zero-crossing points. hence, the creation of the oscillating current is dependent on the arc properties and if interruption time is unduly lengthy, the short circuit current is hard to interrupt. these type of circuit breakers are widely applied in high-voltage dc power transmission, uninterrupted power supply (ups), energy intensive industries, renewable energies and energy storage, railway transportation and ships (kevin, 2007; ieee standards association, 2010; xiang et al., 2014; gupta, 2015; xiang et al., 2017; secheron, 2020; yang et al., 2020,). 2.6 differences in alternating current (ac) and direct current (dc) circuit breaker applications alternating current (ac) circuit breaker cannot be interchangeably used or applied in direct current (dc) circuits for some workable basis revealed in this review; alternating current (ac) circuit breakers need additional insulation than direct current (dc) circuit breakers. insulation material in circuit breaker is of utmost importance in circuit breaker efficient operation (csanyi, 2014; kong et al., 2016). in ac circuits, current and voltage intersect the zero after every half cycle because of the frequency, magnitude and direction change at time interval. in dc circuits zero cross is m id + s1 it l s2 – r c m c r id non linear resistor obi et al: applications of various types of circuit breakers in electrical power systems: a review. azojete, 17(4):481-494. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 491 unfeasible in view of the fact that neither the current nor voltage has frequency since they are constant, hence dc melts circuit breaker contacts faster (chan, 2015; xiang et al., 2017). direct current (dc) arc is stronger than alternating current (ac) arc because of the steady state status of the electrons that create the arc consequent upon breaking a dc circuit via a circuit breaker. in ac circuit, the applied voltage and current change direction and magnitude thereby relaxing flow of electrons hence, weaker arc is created (huo et al., 2017). 3. conclusion on the review of applications of different categories of circuit breakers, it is observed that the most suitable way for classifying circuit breakers is on the level of voltage rating which is broadly grouped under dc or ac circuit breakers. it is noted that in the operation of dc circuit breakers, artificial current zero is created by connecting a series resonant circuit with inductor and capacitor across the main contact of a cb and by diverting the main current to the capacitor so that the breadth of current to be interrupted becomes smaller, since there is absence of current zero on dc waveform. the dc circuit breakers are mostly seen in domestic and industrial applications that operate with direct current (dc) and contains additional arc extinguishing measures, while ac circuit breakers are mostly used in low voltage, high voltage and extra high voltage transmission and distribution system for the protection of electrical machines, transformers, capacitors, generators, switching of loads in industrial and commercial settings, and in railway electrifications. the ac and dc circuit breakers cannot be interchangeably applied as they are differently used in ac and dc network respectively. reference aio, ai. 2013. modelization and analysis of the electric arc in low voltage circuit breakers. phd thesis, universidad del país vasco euskal herriko unibertsitatea, bilbao. al mashakbeh, as. 2019. importance of electrical circuits protection devices: a survey study. international journal of computer applications, 178(37): 13-18. alharbi, k. and habiballah, i. 2020. review on circuit breakers. international journal of engineering research & technology (ijert), 9(11): 277-279. anderson, pm. 1999. power system protection. john wiley & sons, inc., new york. atmadji, ams and sloot, jgj. 1998. hybrid switching: a review of current literature. proceedings of the 2nd international conference on energy management and power delivery (empd '98), singapore, 01 – 03 march 1998, 2: 683–688. balan, h., neam, l., buzdugan, mi., varodi and pop, e. 2016. fault current limiter with solidstate circuit breakers. iop conference series: materials science and engineering, 144: 1-9. bansal, r. 2019. power system protection in smart grid environment. crc press, boca raton, new york. chan, l. 2015. dc circuit breaker theory and uses you never know. https://linkadin.com accessed on 28 june, 2021. chen, t. and ke, h. 2018. modeling and simulation of high voltage circuit breaker based on pscad. advances in computer science research, 65: 155–159. choonhapran, p. 2007. applications of high voltage circuit-breakers and development of aging models. phd thesis, darmstadt university of technology, darmstadt. https://linkadin.com/ arid zone journal of engineering, technology and environment, december, 2021; 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vol. 17(4):481-494. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 494 international journal of greater mekong subregion academic and research network, 7(2013): 41-46. turan, g. 2014. electrical power transmission system engineering analysis and design. 3rd edition. crc press, boca raton, new york. umran, hm. 2016. a three-phase test circuit design for high voltage circuit breaker based on modeling. journal for natural and engineering research and studies, 4(7): 39-51. wadhwa, cl. 2012. electrical power system. 6th edition. new academic science ltd., kent, united kingdom. weedy, bm., cory, bj., jenkins, n., ekanayake, jb. and strbac, g. 2012. electric power systems. 5th edition. john wiley & sons ltd, west sussex, united kingdom. xiang, w., hua, y., wen, j., yao, m. and li, n. 2014. research on fast solid state dc breaker based on a natural current zero-crossing point. journal of modern power systems and clean energy, 2(1): 30–38. xiang, x., chai, j. and sun, x. 2017. a no-arc dc circuit breaker based on zero-current interruption. iop conference series: materials science and engineering, 199: 1-7. yang, y., ren, m., cao, j., liu, w., zhan, x. and zhao, c. 2020. hvdc circuit breaker development and applications in vsc-hvdc transmission project. iop conference series: earth and environmental science, 453: 1-8. yao, f., zhao, w., wang, j. and li, z. 2019. arc extinction of dc side low-voltage breaker of charging device for battery pack in power plant based on insulated-gate bipolar transistor module series technology. journal of engineering, 2019(16): 2312-2317. zheng, x., huangqing, x. and yuzhe, x. 2019. two basic ways to realise dc circuit breakers. journal of engineering of the institution of engineering and technology, 16: 3098-3105 arid zone journal of engineering, technology & environment azojete september 2020. vol. 16(3):569-578 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 569 original research article comparative study of durability and microstructure properties of concrete made with different grades of nigerian portland limestone cement c. a. fapohunda*, b. i. famodimu, b. c. adigo and a. s. jeje department of civil engineering, federal university, oye-ekiti, nigeria *corresponding author’s email address: christopher.fapohunda@fuoye.edu.ng 1.0 introduction concrete industry in nigeria has witnessed a large turn-out of research papers on the portland limestone cement concrete. however, most of these works focus on either strength comparative analysis, or strength development investigations of concrete made from the available grades of cement (adewole et al., 2015; joel and mbapuun, 2016). other studies such as ezeokonkwo and anyanechi (2015) and olonode et al. (2015) focused their attention on ascertaining the quality of cement grades. the available grades of cement in nigeria are grades 32.5 and 42. 5 (in the classes of n, representing ordinary early strength; r, representing high early strength, and s, representing standard strength). literatures documenting research works on durability characteristics and microstructures of concrete produced with portland limestone cement are scarce. it is true that until recently, developments in cement and concrete technology have concentrated on achieving higher strengths on the assumption that strong concrete is durable (neville, 2011). it is now known that, for many conditions of exposure of concrete structures, both strength and durability have to be considered explicitly at the design stage. however, according to hilal (2016), in order to achieve desirable strength and good durability requirements to prevent concrete deterioration, reducing the capillary porosity and a substantial reduction in the total porosity as well as reduction gel porosity are necessary. this leads to changes in the c-s-h structure, from porous to more crystalline phase. it is established that the microstructure of concrete (cementitious paste, pore structure, and interfacial transition zone between the cement paste and the aggregate) has a significant role in affecting the strength of concrete. its effect on the durability of concrete is also overwhelming. this is because microstructure describes the porosity, permeability, and pore size distribution article information abstract it is now becoming apparent that concrete should not only be strong but must also be durable. it is also believed that understanding the microstructure of the concrete will help produce strong and durable concrete, and thus enhance innovativeness in concrete application. this paper compares the durability performance and microstructure development of concrete produced with portland limestone cement (plc) grades 32.5r and 42.5r. the durability investigation was accomplished through coefficient of water absorption and sorptivity measurements. the scanning electron microscopy (sem) was used to investigate the microstructure of the concrete samples. the results show that concrete produced with cement grade 42.5r showed higher durability potential than the ones produced with grade 32.5r using 28 days curing period. similarly, it was also observed that concrete specimens produced with 32.5r and with water/cement ratio of 0.40 have better durability index at the later dayscuring of 90 days in comparison to grade 42.5r concrete specimens. it can be concluded that concrete produced using grade 42.5r cement has potential for better durability performance in relation to concrete produced with 32.5r. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 april., 2020 revised 11 july, 2020 accepted 20 july, 2020 keywords: durability, microstructure, portland limestone cement, sorptivity, water absorption http://www.azojete.com.ng fapohunda et al.: comparative study of durability and microstructure properties of concrete made with different grades of nigerian portland limestone cement . azojete,16(3):569-578. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 570 of concrete. thus, when durability of concrete is considered, the quality of concrete within the context of low permeability comes into the play. this is because, with the exception of mechanical damage, all the adverse influences on durability involve the transport of fluids through the concrete. thus, durability of concrete is closely interwoven with the microstructure of concrete. proper understanding of this, is therefore, necessary to provide design engineers with a greater knowledge of concrete behaviour, so that they can optimise the use of the material aspects of concrete in their design. this is more so, when sustainability and environmental issues are becoming important in structural concrete design and construction. understanding the microstructure will enable innovativeness in the utilization of unfit, or weak material, as complimentary material. while researchers in nigeria have given prominence to the study of mechanical properties of concrete produced with nigerian portland limestone cement, little attention has been given to its durability and microstructure characteristics. thus, the aim of this investigation is to carry out comparative evaluation of concrete made with cement grades 32.5 r and 42.5 r in relation to durability and microstructure. specifically, microstructural examinations using scanning electron microscopy (sem) and water-based durability investigations on concrete samples would be conducted. the choice of water-based assessment of durability characteristics is informed by the observation made by the institution of civil engineers (ice, 2019) that water could be responsible for deterioration in buildings and other infrastructures. 2.0 materials and method 2.1 materials and mix proportions the following materials were used; cement, fine aggregate, coarse aggregate, and water. the cement used was portland limestone cement (plc) classified as cem ii by nis 444-1 (2014). two graces of cement, namely, 32.5 r and 42.5 r, being the only ones available in the nigeria market were used. river sand was used as the fine aggregate. the sand was obtained from river fuoye, a river flowing adjacent to the ikole-ekiti campus of federal university, oye-ekiti, nigeria. the sand was dried and all contaminants removed. the portion of the materials which passes through sieve size 4.75 mm but retained in sieve size 2.36 mm was collected and stored. an active quarry in ikole town, where the engineering faculty of the university is situated, served as the source of the coarse aggregate. in accordance to the stipulations of bs 8110 (1997), the maximum aggregate size was limited to 20 mm. portable water, from the university borehole, was used for this investigation. the concrete mix design method adopted by bs en 206 (2013), in combination with the recommendations by the council for the regulation of engineering in nigeria coren (2017), were used to obtain the mix design. the slump loss of between 30 – 60 mm for a target mean 28-day cube compressive strength for 25 n/mm2 was adopted for this investigation. the mix proportion is presented in table 1. table 1: mix proportion for the investigation grade w/c ratio mix designation cement (kg/m3) sand (kg/m3) gravel (kg/m3) water (kg/m3) 32.5 0.4 m14 343 686 1372 137 0.5 m15 343 686 1372 172 0.6 m16 343 686 1372 206 42.5 0.4 m24 343 686 1372 137 0.5 m25 343 686 1372 172 0.6 m26 343 686 1372 206 concrete ingredients were batched by weight, thoroughly mixed, and cast into cube moulds (100 x 100 x 100 mm). the cube specimens were demoulded after 24 hours and moist cured http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 569-578. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 571 until the day of testing at 28 and 90 days of curing. the specimens for microscopic investigation were taking from the crushed 28-day samples. 2.2 experimental investigations 2.2.1 characterization of materials in order to characterize the naturally-occurring materials used for this investigation, some preliminary investigation was done to determine some of their properties. physical properties like: specific gravity, moisture content, water absorption, dry density, bulk density and sieve analysis, were carried out on the aggregates. no preliminary investigation was performed on the cement used. this is because the seal of the standard organization of nigeria was conspicuously displayed on the cement bags that were bought in the open market for this investigation. this was considered a sufficient proof that it has been manufactured to conform to nis 444-1 (2014). 2.2.2 durability investigation the durability assessment of the concrete samples was accomplished through two tests, namely: (i) coefficient of water absorption test and (ii) sorptivity test. 2.2.2.1 coefficient of water absorption test a measure suggested by powers (1983), in which coefficient of water absorption is considered as a measure of permeability of water was used for this investigation. this test measures the rate of up take of water by dry concrete samples in a period of 1 hour. concrete cube specimens with dimensions 100 x100 x 100 mm were used for this test. the specimens were cured and tested at 28 and 90 days. the concrete specimens were preconditioned by drying in an oven at 105o c for three days until constant weight was reached and then allowed to cool in a sealed container for three days. since it is necessary that water flows in one direction only in this test, the other sides of the concrete samples were coated silicone sealant. then the samples were kept partially immersed to a depth of 5 mm at one end in a vertical position, while the rest of the sides were kept exposed to the laboratory air. this configuration to assess the rate of water absorption is shown in figure 1. figure 1: set up for the measurement of coefficient of water absorption and sorptivity of concrete specimens (adaptation from ganesan et al., 2008). the quantity of water absorbed during the first 60 min by the concrete samples was calculated. coefficient of water absorption values of concrete specimens after 28 and 90 days of moisture curing were determined using the equation 1 as suggested by ganesan et al., 2008. �� � � � � �� � � � (1) 2.2.2.2 sorptivity test according to neville (2011), sorptivity is a material property which characterizes the tendency of a porous material to absorb and transmit water by capillarity. for the sorptivity test, the configuration, cube specimens and sample preparation used for coefficient of absorption as file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda et al.: comparative study of durability and microstructure properties of concrete made with different grades of nigerian portland limestone cement . azojete,16(3):569-578. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 572 shown in figure 1, were also used. the difference is that, in this case, the tests were conducted at selected times 0, 2, 4, 8, 10, 20, 30, 60, 90 and 120 minutes. at the selected times, the samples were removed from the water, excess water blotted off with a damp paper towel and then the sample was weighed. the samples were then replaced in the water for the selected time period. then the gain in mass per unit area over the density of water was plotted versus the square root of the elapsed time. the cumulative water absorption (per unit area of the inflow surface) is believed to increase as the square root of elapsed time (t). the slope of the line of best fit of these points was taken as the sorptivity value. the sorptivity values of blended concrete specimens after 28 and 90 days of moisture curing were calculated by the following formula (equation 2) suggested by stanish et al. (1997). � � � �� (2) 2.2.3 microstructural investigations in order to carry out microstructural investigation of the concrete samples, a jeol scanning electron microscopy (sem) equipment with energy dispersive spectrometry capabilities shown in figure 2, was used. the equipment model comes with energy dispersive spectrometer (edx), and allows high resolution identification of elements and compounds present in prepared 2-d cross-sections of aggregate samples to be obtained. the sem studies were conducted on broken samples of concrete samples cured for 28 days in order to investigate their morphological structures. the samples were collected from the innermost core of the concrete cubes after crushing. each of the samples are then prepared into appropriate size that fit into the specimen chamber of the sem equipment. samples were then freeze-dried, cut and polished and examined on the backscattered electron (bse) mode of the sem equipment. the range of scale used in sem analysis was 5μm with the resolution of x 10000. figure 2: the sem equipment used for microstructural investigation of samples 3.0 results and discussion 3.1 materials characterization some of the properties of the aggregates are shown in table 2. table 2: some physical properties of the aggregates sand gravel specific gravity 2.63 2.67 bulk density (kg/m3) 1666.67 1641.67 water absorption (%) 2.00 2.00 moisture content (%) 0.00 0.00 coefficient of curvature (cc) 0.88 0.98 coefficient of uniformity (cu) 3.00 2.43 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 569-578. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 573 it was observed that the specific gravities of the sand and gravel are in the range of 2.63 and 2.67 respectively. specific gravities of natural aggregate according to gambhir (2013) should be between 2.5 and 2.8. thus, both the sand and gravel used in this investigation can be considered as natural aggregate. additionally, the densities of the aggregate ranged from 1280 to 1920 kg/m3; for water absorption, it is 0 to 8% and the moisture content is 0 – 2% for sand and 0 10% for gravel. all these vales obtained for density, water absorption and the moisture content of both the sand and gravel fell between the ranges used in normal concrete (aci, 1999). also, the coefficient of curvature for both are close to 1, thus indicating that both are well-graded, while the coefficient of uniformity of less than or equal to 4 recorded for both sand and gravel suggest that both are uniformly graded (iowa, 2020). overall conclusion of all of these is that the materials are good for concrete production. 3.2 coefficient of water absorption the results of the coefficient of water absorption are presented in table 3. table 3: coefficient of water absorption for the concrete specimens water/cement ratios ka (m2/s) x 10-8 28 days 90 days 32.5r 42.5r 32.5r 42.5r 0.40 5.2 x 10-9 2.01 x 10-10 2.5 x 10-9 3.73 x 10-9 0.50 7.72 x 10-9 7.72 x 10-10 1.9 x 10-9 2.78 x 10-10 0.60 7.72 x 10-9 2.78 x 10-10 4.9 x 10-9 1.51 x 10-10 at 28 days, the values of coefficient of water absorption obtained for cement grade of 42.5r were lower than that of grade 32.5r at all the water/cement ratios. since coefficient of water absorption is a measure of permeability, it can be said that concrete specimens produced with cement grade of 42.5r are less permeable in comparison to concrete produced with cement grade 32.5r. this can be due to the fact that, at the early ages, more c-s-h gel are produced by concrete with cement grade 42.5r, which has a densifying effect. however, at 90 days curing period, concrete specimens produced with grade 32.5r cement displayed low permeability at water/cement ratio of 0.40 than that of concrete produced with grade 42.5r cement. at the water/cement ratios of 0.50 and 0.60, the concrete specimens produced with grade 42.5r cement have smaller values of coefficient of water absorption, hence low permeability. furthermore, it can be seen from table 3 that the observed values of coefficient of water absorption reduced with curing age. this suggested that prolonged curing of concrete samples resulted in more production of c-s-h gel with pore-refining effects leading to reduction in permeable voids. 3.3 sorptivity sorptivity test measures the rate of absorption of water by capillary suction of unsaturated concrete placed in contact with water; no head of water exists (hall, 1989; dias, 2000 and neville, 2011). the results of the sorptivity investigation are presented in table 4. table 4: sorptivity for the concrete specimens (10-2 mm/s1/2) water/cement ratio 28 days 90 days 32.5r 42.5r 32.5r 42.5r 0.40 0.048 0.097 0.073 0.058 0.50 0.034 0.026 0.032 0.018 0.60 0.032 0.022 0.031 0.015 at 28 days of curing, with the exception of concrete samples with water/cement ratio of 0.40, the values rate of absorption of water obtained for grade 42.5 r specimens were lower than that of grade 32.5 specimens. also, the values of the rate of absorption of water reduced with water/cement ratio for all the concrete specimens. this is ostensibly due to higher water file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda et al.: comparative study of durability and microstructure properties of concrete made with different grades of nigerian portland limestone cement . azojete,16(3):569-578. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 574 content in concrete samples at higher water/cement ratios. at 90 days of curing, the values of the rate of water absorption for concrete samples produced with grade 42.5r were lower than that produced with grade 32.5 r specimens at all the water/cement ratios. furthermore, the sorptivity values at 90 days reduced with water/cement ratios for all the specimens, due to higher water content at higher water/cement ratios. it also ought to be observed that sorpitivy at 90 days were lower than sorptivity values at 28 days for all the specimens. it is known that prolong curing results in the densification of the concrete matrix, thus inhibiting the rate of water absorption by the specimens. 3.4 microstructure of concrete specimens the scanning electron microscopy (sem) images of the concrete specimens at 28 days of curing are shown in figure 3. microstructure is usually explained in terms of distribution of pores, sizes of pores and interconnectivity of the pores. figure 3 shows the images of the microstructure of concrete produced with cement grades 32.5 r and 42.5r at the same water/cement ratio. it could be observed that the microstructure of concrete produced with grade 32.5r at 0.40 water/cement ratio consisted of big pores or voids in comparison to grade 42.5r concrete. this suggests that concrete produced with grade 32.5r are likely to be porous and less durable than concrete produced with grade 42.5r. this observation is consistent with the results of permeability measured through the rate of water absorption test as presented in table 3. this pattern can also be observed in the images of the microstructure of concrete samples produced with water/cement ratio of 0.50 for both grades of cement. in particular, the very large pores, from the images of concrete produced with grade 32.5r cement is very glaring. there is also an evidence in the microstructure of weak interfacial zone (itz) between the vicinity of aggregate and the hydrated products. this itz is the weakest region in concrete due to its higher porosity resulting from the poor packing of cement particles (mehta and monteiro, 2006). although, the images of concrete samples produced with grade 42.5 r cement and with water/cement ratio of 0.60, showed a microstructure consisting of large pores, there is evidence that the pores are not connected. figure 4 showed the edx spectrum of the samples from which the elemental counts presented in table 5 was extracted for clarity. silicates and calcium are the constituents of the strength-forming products of hydration. their counts, through the edx spectrum and the ratio of calcium to silicate are strength indicator. from table 5, the ratio � � for concrete produced with 32.5r grade of cement increase marginally with increase in water/cement ratio. however, for concrete produced with grade 42.5r cement, the ratio increases with water/cement ratio. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 569-578. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 575 figure 3: the sem micrograph of the concrete samples at 28 days of curing file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda et al.: comparative study of durability and microstructure properties of concrete made with different grades of nigerian portland limestone cement . azojete,16(3):569-578. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 576 figure 4: edx spectrum of the concrete samples at 28-day curing table 5: the c/s ratio of the mixes concrete mix mix designation ca (c) si (s) � � 32.5 m04 40.60 15.45 2.63 m05 35.50 25.50 1.39 m06 41.60 15.65 2.66 42.5 m04 40.50 23.50 1.72 m05 43.50 20.50 2.12 m06 44.50 20.50 2.17 according to nazari et al. (2011), increasing ratio means increasing strength-forming activities. this conclusion is consistent with the results of sorptivity presented in table 4. 4. conclusions and recommendations 4.1 conclusions from the analysis of the results of this investigation, the following conclusions can be made. the values of coefficient of water absorption obtained for concrete specimens produced with grade 42.5 r are lower than specimens produced with cement grade 32.5 r at 28-day curing. at 90 days curing age, concrete specimens produced with grade 32. 5r cement had lower coefficient of water absorption at lower water/cement ratio of 0.40. the microstructure of concrete produced with 32.5r are more porous than those produced with grade 42.5r cement at 28-day curing . 4.2 recommendations the concrete specimens produced with cement grade 32.5r resulted in low durability, especially at the structural age of 28 days curing. since both of them are available in the nigeria market and both are equally widely used, the need to improve the durability performance of concrete made with grade 32.5r cannot be overemphasized. the use of highly reactive pozzolans like rice husk ash, that abounds in nigeria (joel, 2010, oyekan and kamiyo, 2011 and abalaka, 2013), should be given consideration by incorporating it into concrete mix with cement grade 32.5r. incorporating pozzolans in the concrete with 32.5r cement grade, according to büyüköztürk and lau (2020) will improve the concrete durability performance by strengthening the hydrated cement paste through the adding of mineral additives. this will help in generating a crystalline c-s-h gel with lower gel porosity, compared to a conventional amorphous c-s-h gel. reduction in the porosity of the paste, which translate to low permeability and improved durability, will result. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, september, 2020; vol. 16(3) 569-578. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 577 references aci. 1999. aggregates for concrete. aci education bulletin – e1-99, american concrete institute, american concrete institute, farmington hills, michigan. abalaka, ae. 2013. strength and some durability properties of concrete containing rice husk ash produced in a charcoal incinerator at low specific surface. international journal of concrete structures and materials, 7(4): 287–293. adewole, kk. ajagbe, wo. and arasi, ia. 2015. determination of appropriate mix ratios for concrete grades using nigerian portland-limestone grades 32.5 and 42.5. leonardo electronic journal of practices and technologies, 14(2): 79 88. bs en 206. 2013. concrete specifications, performance, production and conformity. british standard institution, london. büyüköztürk, o. and lau, d. 2020. high performance concrete: fundamentals and application. cambridge: department of civil and environmental engineering, massachusetts institute of technology. http://ankara.imo.org.tr/resimler/ekutuphane/pdf/3146.pdf (assessed 04 02 – 2020) coren, 2017. concrete mix designer manual. council for the regulation of engineering in nigeria. first edition. special publication no. coren/2017/016/rc. dias, wps. 2000. reduction of concrete sorptivity with age through carbonation. cement and concrete research, 30(8): 1255–1261. ezeokonkwo, ju. and anyanechi, cn. 2015. assessment of quality of cement in nigerian market and the controversy of building collapse. journal of scientific and engineering research, 2(1): 22-27. ganesan, k., rajagopal, k. and thangavel, k. 2008. rice husk ash blended cement: assessment of optimal level of replacement for strength and permeability properties of concrete. construction and building materials, 22 (8): 1675 – 1683. hall c. 1989. water sorptivity of mortars and concretes: a review. magazine of concrete research, 41(1): 51–61. hilal, aa. 2016. microstructure of concrete. intech open, intech ltd, london https://www.intechopen.com/books/high-performance-concrete-technology-andapplications/microstructure-of-concrete. doi:10.5772/6457.4 ice. 2019. the role of water in structural failure. https://www.icevirtuallibrary.com/page/icenews/cfp-foen-012020?_ccct=io22p%7ed6je74goti1luej1iai_rm0uwxcicboamvwc0ixd04axxpv4blddpx gosx (accessed 12 – 12 – 2019). iowa, 2020. class notes: c.c. swan, university of iowa: lecture 2: grain size distributions and soil particle characteristics. available online at : http://user.engineering.uiowa.edu/~swan/courses/53030/notes/gsd.pdf. assessed 10 january, 2020. joel, m. 2010. a review of partial replacement of cement with some agro wastes. nigerian journal of technology, 29(2): 12 – 20. joel, m. and mbapuun, id. 2016. comparative analysis of the properties of concrete produced with portland limestone cement (plc) grade 32.5n and 42.5r for use in rigid pavement work. global journal of engineering research, 15: 17 25. mehta, pk. and monteiro, pj. 2006. concrete: microstructure, properties and materials. 3rd ed. london: mcgraw-hill. doi: 10.1036/0071462899. http://ankara.imo.org.tr/resimler/ekutuphane/pdf/3146.pdf https://www.intechopen.com/books/high-performance-concrete-technology-and-applications/microstructure-of-concrete https://www.intechopen.com/books/high-performance-concrete-technology-and-applications/microstructure-of-concrete https://www.icevirtuallibrary.com/page/ice-news/cfp-foen-01-2020?_ccct=io22p%7ed6je74goti1luej1iai_rm0uwxcicboamvwc0ixd04axxpv4blddpxgosx https://www.icevirtuallibrary.com/page/ice-news/cfp-foen-01-2020?_ccct=io22p%7ed6je74goti1luej1iai_rm0uwxcicboamvwc0ixd04axxpv4blddpxgosx https://www.icevirtuallibrary.com/page/ice-news/cfp-foen-01-2020?_ccct=io22p%7ed6je74goti1luej1iai_rm0uwxcicboamvwc0ixd04axxpv4blddpxgosx https://www.icevirtuallibrary.com/page/ice-news/cfp-foen-01-2020?_ccct=io22p%7ed6je74goti1luej1iai_rm0uwxcicboamvwc0ixd04axxpv4blddpxgosx http://user.engineering.uiowa.edu/~swan/courses/53030/notes/gsd.pdf.%20assessed%2010 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng fapohunda et al.: comparative study of durability and microstructure properties of concrete made with different grades of nigerian portland limestone cement . azojete,16(3):569-578. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: christopher.fapohunda@fuoye.edu.ng 578 olonade, ka., jaji, mb., rasaki, sa. and ojo, ba. 2015. comparative quality evaluation of cement brands used in south west nigeria. academy journal of science and engineering, 9(1): 53 – 63. oyekan, gl. and kamiyo, om. 2011. a study on the engineering properties of sandcrete blocks produced with rice husk ash blended cement. journal of engineering and technology research, 3(3): 88-98. powers, tc. 1968. properties of fresh concrete. john wiley and sons, new york. stanish, kd., hooton, rd. and thomas, mda. 1997. testing the chloride penetration resistance of concrete: a literature review, fhwa contract dtfh61 1997. department of civil engineering, university of toronto, toronto, 19 – 22. http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):573-584 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 573 original research article technology awareness of artificial intelligence (ai) application for public procurement process in nigeria m. a. yamusa1,2*, h. s. lawal2, m. abdullahi1,2 and z. h. ishaq3 1public procurement research centre, ahmadu bello university zaria, kaduna, nigeria. 2department of quantity surveying, ahmadu bello university, zaria, kaduna, nigeria 3department of building, ahmadu bello university, zaria, kaduna, nigeria *corresponding author’s email address: yamusajf@yahoo.com 1.0 introduction the public procurement process of acquiring goods, works and services has been noted to be suffering from inefficiencies such as corruption, absence of transparency, faulty procedures, and dysfunctional bureaucratic ties (yap et al., 1994). this led to several calls for transition from the manual paper-based approach to a digitised method (expert group meeting report; egmr, 2011). the transition came along with numerous positive feedbacks. these include reduced procurement expenses, expanded aptitude as well as transparency, abridged corruption and enhanced accountability (egmr, 2011; eteg, 2012). several efforts have been made to transit from the manual paper-based procurement method towards digitising the procurement approach. this started with the development of one-way article information abstract the public procurement process of acquiring goods, works and services has been observed to be suffering from inefficiencies in the forms of corruption cases, absence of transparency, faulty procedures, and dysfunctional bureaucratic ties. in nigeria, it was discovered that the public procurement process has the potential of reaping the benefits of artificial intelligence (ai). however, the level of awareness of the public procurement practitioners of the significance of incorporating ai in procurement is yet to be studied. this study assessed the awareness of artificial intelligence application for public procurement processes in nigeria. data was collected using questionnaire survey. the questionnaire was distributed to public procurement practitioners with at least 5 years of experience in procurement. data was analysed using mean, standard deviation, and relative importance index. analysis of variance and independent t-test was then used to ascertain the level of awareness of the respondents based on their attributes. the study discovered information about artificial intelligence is quite vast as the parameter ‘i have heard about ai’ got the highest ranking with mean score of 3.63 and rii of 72.58%, while ‘i use ai for procurement processes’ to be the lowest ranking attribute with mean score of 1.50 and rii of 30.00% meaning even though information is available, the usage of ai for procurement is quite low. additionally, the results show that while ai is a popular concept within procurement organisations, majority of the procurement practitioners have little knowledge of its application in public procurement. the research recommends that, public procurement organisations should develop the capacity of their employees on the utilisation of ai in procurement process. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 may, 2023 revised 12 july, 2023 accepted 20 july, 2023 keywords: public procurement artificial intelligence awareness process nigeria http://www.azojete.com.ng/ mailto:yamusajf@yahoo.com mailto:yamusajf@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):573-584. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 574 information systems that digitise only tender advertisement. this was followed with more encompassing systems which were developed to digitise the entire front-end and back-end procedures of the procurement system (betts et al., 2006). studies were carried out to address different aspects of the systems development. they include design and implementation (lai et al., 2007); interoperability and integration across manifold platforms (noor et al., 2003); legal and security requirements (du et al., 2004a.b; betts et al., 2006); and tender evaluation through decision support system (padumansa and rehan, 2009; noor and man, 2010; and noor and mohemmad, 2010); and e-tendering research in africa (adebiyi et al., 2010; muchiri et al., 2015; and afolabi et al., 2017). more recently, artificial intelligence (ai) is being used to automate procurement processes. this is because the procurement lifecycle generates tonnes of data, and ai is heavily reliant on data. studies have been conducted where ai has been applied to different procurement processes including analysis of spend (domingos et al., 2016), prequalification and selection of contractor/supplier (khosrowshahi, 1999; lam et al., 2000; lam et al., 2001; elazouni, 2006; and zhang et al., 2016), evaluation and classification of tender (kim, et al., 2018; ovsyanniko and domashova, 2020) as well as in contract management (hassan and le, 2020). in nigeria, several efforts have been made to digitise the public procurement lifecycle (adebiyi et al., 2010; afolabi et al., 2017; and abdullahi et al., 2022, 2020, 2019). yamusa et al. (2020) found that the public procurement process in nigeria has the potential of reaping the benefits of ai. this was further confirmed by studies who modelled requirements and developed machine learning models for a web-based e-procurement system for nigerian public procuring entities (abdullahi et al., 2024; yamusa et al., 2023). however, the level of awareness of the public procurement practitioners of the significance of incorporating ai in the conduct of their daily procurement tasks is yet to be studied. it is important to establish whether public procurement users are aware of how to use ai in various public procurement processes. hence, this study aims to determine the level of awareness of procurement practitioners of using ai for procurement processes. this study will reveal to public procuring entities the benefits of ai methods in carrying out procurement processes effectively. 2.0 methodology a quantitative research approach was adopted for this study, where questionnaire survey was used. thirteen statements regarding awareness level of ai are established (basaif et al., 2020) and used in designing the questionnaire for data collection. the questionnaire was distributed purposively to public procurement practitioner with at least 5 years of experience involved in the procurement of goods, works and services. a likert scale (5-point) was adopted for gauging the variables of the questionnaire where 1 represents “totally disagree” and 5 represents “totally agree”. the sample size was determined using the krejcie and morgan (1970)’s formula in equation 1: 𝑆 = 𝑍2𝑁𝑃(1−𝑃) 𝑑2(𝑁−1)+𝑋2𝑃(1−𝑃) (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:yamusajf@yahoo.com yamusa et al: technology awareness of artificial intelligence (ai) application for public procurement process in nigeria. azojete, 19(3):573584. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 575 where: s = required sample size x2 = table of value of chi-square for 1 degree of freedom at the desired confidence level (3.841) n = the population size p = the population proportion (assumed to be 0.50) d = degree of accuracy expressed as a proportion (0.05) a minimum sample size of 186 was determined. the questionnaires were sent via online using emails and social media platforms. 62 valid responses amounting to approximately 32% of the total distributed were retrieved and found to be adequate for analysis. this is because moser and kalton (1979) noted that amount of feedback is fitting as it yields a return percentage of 30-40%. data collected was analysed using spss (statistical package for the social sciences) version 23 (ibm). firstly, the frequencies, measures of central tendency (the mean), measurements of dispersion based on the mean (standard deviation), and relative important index (rii) were determined. the rii was used in ranking the variables according to the retrieved responses to the level of awareness on ai. the rii was calculated using the field (2013) formula in equation 2: 𝑅𝐼𝐼 = σ𝑊 𝐴∗𝑁 (2) where: rii = relative important index w = the weight of each factor as obtained by the respondents (1 to 5). a = the highest weight (5 in this questionnaire). n = the overall number of respondents. the rii has a range of 0 to 1, where 0 was not included, and the variables are presented with the highest on top and the lowest at the bottom. the natural value of rii was determined and the total average rii of the awareness attributes/statements was compared against the neutral rii to make decision on the level of awareness of the practitioners. total average rii of the awareness attributes ≥ the neutral rii implies high awareness while total average rii of awareness variables < the neutral rii implies low awareness. this method can be found in similar studies by enhassi et al. (2019) and basaif et al. (2020). inferential statistical analysis using analysis of variance (anova) (for attributes with three groups) and independent t-test (for attributes with two groups) was further conducted to ascertain the level of awareness of the respondents based on their various attributes. http://www.azojete.com.ng/ mailto:yamusajf@yahoo.com mailto:yamusajf@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):573-584. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 576 3.0 results and discussion 3.1 demographic information of respondents table 1 presents us with demographic information of the respondents of this study. table 1: respondents' profile attributes classification frequency percentage years of existence of procuring entity 1-5 years 12 19.4 6-10 years 12 19.4 11-15 years 26 41.8 above 15 years 12 19.4 annual turnover of pe 50-250 million 14 22.6 501-750 million 16 25.8 above 750 million 32 51.6 gender female 12 19.4 male 50 80.6 academic qualification bachelor 22 35.5 masters 32 51.6 others 8 12.9 rank operational management level 14 22.6 middle management level 30 48.4 senior/strategic management 18 29 years of experience at least 5 years 30 48.4 6-10 years 14 22.6 11-15 years 12 19.4 above 15 years 4 6.4 bpp conversion status no 14 22.6 yes 48 77.4 other relevant certification no 12 19.4 yes 50 80.6 status of certification fellow 8 12.9 corporate member 24 38.7 probationer member 4 6.4 other 25 41.9 source: authors’ analysis (2022) the result shows that, 41.8% of the pe have been in existence for about 11-15 years and 19.4 have been in existence for over 15 years hence, 61.2% of the procurement entities have been in existence for over 10 years which adds credibility to the findings of this study. additionally, it was discovered that the pes are engaged in procurement activities with 51.6% having an annual file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:yamusajf@yahoo.com yamusa et al: technology awareness of artificial intelligence (ai) application for public procurement process in nigeria. azojete, 19(3):573584. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 577 turnover above 750 million naira and 25. 8% having an annual turnover of 500 to 700 million naira. results received from the respondents show that male respondents constitute 80.6% whereas the female was only at 19.4% which shows that the number of male procurement officers far outweighs that of female officers. interestingly, 87.1% of the respondents are having a bachelor or master’s degree hence, majority of procurement officers are graduates. middle level managers made up 48.4% of the respondents while strategic managers made 29% of the respondents, this implies that people with the desired information about procurement administration make majority of the respondents. which is further buttressed by the finding that 51.6% of the respondents have an experience above 5 years. also, 77.4% have attended the conversion training offered by the bureau of public procurement. however, 80.6% of the respondents hold other relevant certification, where 38.7% of them are corporate members and 12.9% of them are fellows. these qualifications and level of experience in terms of years, education and conversion training helped in shaping the level of accuracy of this study. 3.2 level of awareness of the public procurement practitioners of using ai for procurement processes this section assesses the level of awareness of ai by public procurement practitioners in nigeria. the established set of 13 statements presented in the questionnaire were used in assessing the respondents’ level of awareness of using ai for procurement processes. means, standard deviations, rii, were used to analyse the data and results are presented in table 2. table 2: awareness of the public procurement practitioners of using ai for procurement processes attributes/statements mean sd rii (%) rank i have heard about ai 3.63 1.462 72.58 1 i think ai can help and add value to my daily work 3.44 1.500 68.71 2 i have knowledge about the concept of ai technology 3.35 1.380 67.10 3 i think ai will be a useful tool for procurement processes 3.11 1.404 62.26 4 i know that ai technology is important for carrying out procurement processes in the nigerian construction industry 3.05 1.431 60.97 5 i have read some research and studies about ai 2.95 1.498 59.03 6 i have knowledge on how to use ai technology tools 2.34 1.070 46.77 7 i practice ai in my job 1.94 1.158 38.71 8 people within my organisation are talking about using ai for procurement processes 1.74 .626 34.84 9 i have attended training on ai 1.69 .781 33.87 10 my organisation provides formal training on ai including follow-up programs 1.65 .726 32.90 11 i have taken some courses about ai 1.60 .664 31.94 12 i use ai for procurement processes 1.50 .671 30.00 13 total average 2.46 49.21 http://www.azojete.com.ng/ mailto:yamusajf@yahoo.com mailto:yamusajf@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):573-584. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 578 source: authors’ analysis (2022) from table 2, according to the mean score and relative importance index (rii) of the awareness attributes, ‘i have heard about ai, i think ai can help and add value to my daily work and i have knowledge about the concept of ai technology are the top three attributes with mean score of 3.64, 3.44, 3.35 and rii of 72.58, 68.71 and 67.1 respectively. the study also discovered that the factors with lowest mean score and rii are my organisation provides formal training on ai including follow up, i have taken some courses about ai and i use ai for procurement processes with low mean scores of 1.65, 1.60, 1.5 and low rii of 32.9, 31.94 and 30.00 respectively. this means that despite the fact that most procurement officers are aware of ai and its potential to make their work better, they receive very low support on training from their organisation and also do not make personal efforts to learn about ai hence, they barely use it in procurement process. the overall average mean scores of the 13 statements used to assess the respondents’ level of awareness of ai in procurement process is 2.46 which implies that the awareness of artificial intelligence in procurement is low, this is further buttressed by the average relative importance index of 49.21 which is below the neutral rii of 60 the result agrees with basaif et al. (2022) who found that, the awareness of ai is low in the malaysian construction industry. moreso, there is lack of knowledge of the application of ai among practitioners (basaif et al., 2020). 3.3 awareness of the public procurement practitioners of using ai for procurement processes based on the respondents’ attributes this section assesses the differences in the level of awareness in the use of ai by public procurement practitioners in nigeria based on their demographic classifications. the anova test was used to check if there is significance difference in the level of awareness of the procurement officers based on years of existence of the procurement entity, annual turnover of the procurement entity, academic qualification, rank and years of experience and status of certification. from table 3, it can be seen that the attribute years of existence showed no significant difference in the respondents’ awareness of ‘i have taken some courses about ai’, ‘i have attended training on ai’ and ‘people within my organisation are talking about using ai for procurement processes’. for the other 10 factors, the result shows statistical significant difference in the awareness of the respondents as the significance level is less than 0.05. based on the annual turnover of pe, six factors, including ‘i have knowledge about the concept of ai technology’, ‘i have read some research and studies about ai’, ‘i have taken some courses about ai’, ‘i have heard about ai’, ‘i think ai can help and add value to my daily work’ and ‘my organisation provides formal training on ai including follow-up programs’ reveal statistical significance difference in the level of awareness of the respondents. the remaining 7 factors have no statistical significant difference. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:yamusajf@yahoo.com yamusa et al: technology awareness of artificial intelligence (ai) application for public procurement process in nigeria. azojete, 19(3):573584. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 579 table 3: awareness of the public procurement practitioners using the respondents’ attributes attributes/statements years of existence of pe annual turnover of pe academic qualification rank years of experience bpp conversion status status of certification sig. (.05) i have knowledge about the concept of ai technology 0.000 0.001 0.000 0.031 0.007 0.506 .584 i have read some research and studies about ai 0.000 0.000 0.001 0.481 0.703 0.004 .000 i have taken some courses about ai 0.061 0.022 0.000 0.029 0.000 0.001 .025 i have knowledge on how to use ai technology tools 0.008 0.161 0.004 0.003 0.095 0.044 .000 i know that ai technology is important for carrying out procurement processes in the nigerian construction industry 0.000 0.233 0.001 0.608 0.225 0.012 .000 i have heard about ai 0.000 0.003 0.004 0.101 0.631 0.020 .000 i have attended training on ai 0.064 0.983 0.002 0.056 0.017 0.002 .208 i practice ai in my job 0.037 0.961 0.168 0.045 0.857 0.000 .185 i think ai can help and add value to my daily work 0.000 0.009 0.000 0.718 0.294 0.161 .000 my organisation provides formal training on ai including follow-up programs 0.038 0.010 0.004 0.067 0.000 0.000 .114 i use ai for procurement processes 0.000 0.339 0.146 0.146 0.632 0.502 .004 people within my organisation are talking about using ai for procurement processes 0.086 0.191 0.044 0.007 0.340 0.946 .000 i think ai will be a useful tool for procurement processes 0.000 0.793 0.017 0.000 0.135 0.896 .028 source: authors’ analysis (2022) respondents’ academic qualification affects their level of awareness. this is obvious as eleven factors have been found to be significantly different. only ‘i practice ai in my job’ and ‘i use ai http://www.azojete.com.ng/ mailto:yamusajf@yahoo.com mailto:yamusajf@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):573-584. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 580 for procurement processes’ have shown no statistical significant difference in the level of awareness of the respondents. based on the rank of the respondents, 6 factors which include ‘i have knowledge about the concept of ai technology’, ‘i have taken some courses about ai’, ‘i have knowledge on how to use ai technology tools’, ‘i practice ai in my job’, ‘people within my organisation are talking about using ai for procurement processes’ and ‘i think ai will be a useful tool for procurement processes’ have been found to reveal statistical significance difference. the other factors have a significance level greater than 0.05. the years of experience of the respondents has shown little effect on the level awareness of the respondents with only four have statistically significantly different. ‘i have knowledge about the concept of ai technology’, ‘i have taken some courses about ai’, ‘i have attended training on ai’ and ‘my organisation provides formal training on ai including follow-up programs’ have a significant level less than 0.05. the rest of the nine factors have a significance level above 0.05. the bpp conversion status of the respondents has shown a significant level of impact on the awareness of the respondents on the use of ai in public procurement process. five factors including ‘i have knowledge about the concept of ai technology’, ‘i think ai can help and add value to my daily work’, ‘i use ai for procurement processes’, ‘people within my organisation are talking about using ai for procurement processes’ and ‘i think ai will be a useful tool for procurement processes’ have a significance level greater than 0.05. this indicates that there is no significant difference in the respondents’ awareness of these factors. however, there is high significance level of awareness by the respondents on the remaining eight factors with a significance level less than 0.05. ‘i have knowledge about the concept of ai technology’, ‘i have attended training on ai’, ‘i practice ai in my job’ and ‘my organisation provides formal training on ai including follow-up programs’ have shown no statistical significant difference with a significance level higher than 0.05 for the status of certification attribute. the remaining nine factors have a significance level lower than 0.05. this shows that the awareness of the respondents in these factors are statistically significantly different. 4.0 conclusion the result of the study indicates that most procurement officers have heard about ai, they believe ai can add value to their daily work and have knowledge about the concept of ai however procurement officers barely attend any training on ai, this is further buttressed by the finding of this study that indicates that organisations hardly provide formal training on ai also, procurement officers barely take courses on ai and its usage for procurement processes is very low. the study discovered that there is significant difference in the respondents level of awareness of artificial intelligence based on their years of existence, academic qualification, bpp conversion, status of certification, annual turnover and rank. on the contrary, the study found out that file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:yamusajf@yahoo.com yamusa et al: technology awareness of artificial intelligence (ai) application for public procurement process in nigeria. azojete, 19(3):573584. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusajf@yahoo.com 581 there was no significance difference on the awareness level based on years of experience of the respondents. the research concludes that the level of awareness of application of artificial intelligence in public procurement is low owing to the overall low mean score of 2.46 and a 49.21 score of relative importance., the analysis of variance also shows that there is a significant difference in the awareness level of application of ai in public procurement based on the difference in demographics of the procurement officers. the study recommends that, public procurement organisations as well as the government should demonstrate commitment to develop the capacity of their employees on the utilisation of ai in procurement process. emphasis should be paid on the newly established public procurement organisations. also, special attention should be given to public procurement professionals with low academic qualification and status of certification, as well as professionals with no bpp conversion. disclosure statement no potential conflict of interest was reported by the authors. acknowledgement this study was carried out under the public procurement research centre of ahmadu bello university, zaria. references abdullahi, b., ibrahim, ym., ibrahim, ad. and bala, k. 2022. development of web-based etendering system for nigerian public procuring entities. international journal of construction management, 22(2): 278-291 doi: 10.1080/15623599.2019.1620492. abdullahi, b., ibrahim, ym., ibrahim, ad. and bala, k. 2020. development of e-tendering evaluation system for nigerian public sector. journal of engineering, design, and technology, 18(1): 122-149. https://doi.org/10.1108/jedt-012019-0004 abdullahi, b., ibrahim, ym., ibrahim, ad. and bala, k. 2019. developing a web-based tender evaluation system based on fuzzy multi-attributes group decision making for nigerian public sector tendering. international journal of computer and information engineering, 13(7): 357361. abdullahi, b., ibrahim, ym., ibrahim, ad., bala, k., ibrahim y. & yamusa, ma. 2024. development of machine learning models for categorization of nigerian government’s procurement spending to unspsc procurement taxonomy. international journal of procurement management (ijpm), 19(1): 106-121. adebiyi, aa., ayo, ck. and adebiyi mo. 2010. development of electronic government procurement (e-gp) system for nigeria public sector. international journal of electrical and computer sciences ijecs-ijens, 10(6): 74-84. http://www.azojete.com.ng/ mailto:yamusajf@yahoo.com mailto:yamusajf@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; 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(ed). proceedings of the fifth nigerian institute of quantity surveyors research conference (recon5) held in minna, nigeria, 9-10 november 2020, 273-285. yamusa, ma., ibrahim, ym., abdullahi, m., ahmadu, ha., abdullahi, b., ibrahim, ad., bala, k., & aminu, a. 2023. developing requirement model for a web-based e-procurement system in nigeria. international journal of electronic governance (ijeg), 15(3): 234-254. yap, c., soh, c. and raman, k. 1994. effect of government incentive on computerization in small businesses. european journal of information system, 3(3), 191. zhang, r., jingfei, l., wu, s. and meng, d. 2016. learning to select supplier portfolios for service supply chain, plos one, 11(5): 1-19 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:yamusajf@yahoo.com arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):707-720 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 707 original research article moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions k. o. oriola1, j. b. hussein2*, m. o. oke3 and r. d. isiaka1 1departement agricultural engineering, ladoke akintola university of technology, ogbomoso, oyo state, nigeria 2department of food science and technology, modibbo adama university, yola, adamawa state, nigeria 3department of food engineering, ladoke akintola university of technology, ogbomoso, oyo state, nigeria. *corresponding author’s email address: jbhussein01@mau.edu.ng 1.0 introduction winged bean (psophocarpus tetragonolobus (l.) seeds are tropical crops listed as underexploited legumes, notwithstanding their high yield potential and nutritional value compared with soybean (vatanparast et al., 2016; adegboyega et al., 2019). winged bean is a crop with several uses; it can be grown as a pulse, root, and tuber crop. every part of the plant contains distinct nutritional constituents. the leaves and pods are rich sources of vitamins, minerals, and fibre; the seeds are high in protein, while the tubers are rich sources of carbohydrates (wong et al., 2015; vatanparast et al., 2016; adegboyega et al., 2019). the winged bean seed contains high dietary protein due to its amino-acid contents, considerable protein bioavailability, and low anti-nutritional factors (wan mohtar et al., 2014). depending on the accessions and agro-climatic conditions, the seeds have a high range of crude protein (28.43-36.6%), crude fat (13.87-19.01%), ash (4.55-4.98), and carbohydrate (18.43-37.82), as reported by adegboyega et al. (2019). the seeds also contained a high proportion of phosphorus, calcium, magnesium, zinc, sodium, and copper (lepcha et al., 2017). because article information abstract the thermal properties of three winged bean seed accessions (entry 4 tropical psophocarpus tetragonolobus (tpt) 6, entry ii tropical psophocarpus tetragonolobus (tpt) 30, and entry 12 tropical psophocarpus tetragonolobus (tpt) 32) at 5, 10, 15, 20, and 25% moisture contents and 30, 40, and 50 ᵒc temperatures were determined with the kd2 pro thermal analyzer. the results showed that the thermal properties of the seed accessions were moisture-temperature dependent. entry ii tpt 30 had the highest specific heat capacity (1.37-2.59 kj.kg-1k-1), while entry 4 tpt 6 had the highest thermal conductivity (0.17-0.60 w.m-1k-1) and thermal diffusivity (0.19-0.77 x 10-7 m2.s-1) as the temperature and moisture increased. a second-order polynomial model described the relationship between the moisture, temperature, and the three thermal properties studied. respective high correlation coefficients (r2 ≥ 0.9126, 0.9872, and 0.9801 for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32 accessions, respectively) indicated their ability to simulate these parameters within the moisture-temperature domain studied. the winged bean seeds' thermal properties will be used to guide design decisions for the creation of agricultural machinery, thermal processes, and equipment required for storage, drying, heating, and cooling. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 january, 2022 revised 22 june, 2022 accepted 24 june, 2022 keywords: thermal conductivity thermal diffusivity specific heat capacity moisture content winged bean seed accessions http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):707-720 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 708 most parts of the plant are edible at all stages of its life cycle, coupled with its exceptional nutritional quality, it was taken as a promising candidate for food and nutrient security in protein-deficient areas of the world (lepcha et al., 2017). notwithstanding the great potential of winged bean seeds, prolonged cooking times significantly limit their utilization. sambudi and buckle (1991) reported that the seeds are the essential part; unfortunately, they are the least used product because they are difficult to cook and require a long cooking time for their tenderization. some winged bean seed accessions have harsh seed coats, making water absorption difficult, while most of them have differing degrees of impermeability to water (sambudi and buckle, 1991). ojo and adeomowaye (2015) also reported certain anti-nutritional compounds such as enzyme inhibitors, hemagglutinins, cyanogens, phytic acid, apart from prolonging cooking time. oligosaccharides, saponins, and tannins are other factors preventing the efficient utilization of leguminous crops. thus, the need for intensive heat for cooking wing bean seeds and cracking processes. the thermal properties are essential in various handling and processing operations involving heat and mass transfer (oriola et al., 2021). therefore, studying the thermal properties of wing bean seeds is imperative especially for those accessions that have proved promising. knowledge of the thermal properties of food and agricultural products is essential for quantifying some unit operations like cooling, heating, drying, pasteurization during postharvest handling and storage processes and designing processing systems. thermal properties of agricultural products commonly determined are specific heat, thermal conductivity, and thermal diffusivity. the property needed in the estimation of the amount of energy required to change the temperature of a given mass of product by 1oc is called specific heat, while thermal conductivity and thermal diffusivity are involved in the assessment of the rate of heat transfer for efficient process and equipment design (yang et al., 2002; mahapatra et al., 2013). the measure of the ability of a material to conduct heat through it is known as its thermal conductivity. in contrast, the material’s inertia, that is, the ability of a material to conduct heat relative to the heat stored per unit volume, is thermal diffusivity. thermal conductivities are used for modelling thermal processes such as chilling, freezing, and drying, as such models allow for process optimization to improve quality and efficiency (carson, 2017). on the other hand, the thermal diffusivity explains the heating rate (the heat penetration and temperature distribution) of grains stored in steel silos, mainly in the grain layers closest to the metal sheet, where convective currents of air are responsible for the migration of moisture and heat (pohndorf et al., 2017). these thermal properties are important parameters to know in designing equipment or its part and, in a computer simulation, to analyze, optimize, and control the temperature during the elaboration, storage, transportation, and commercialization of foods. research results have shown that the thermal properties of food and agricultural materials are temperature and moisture dependent (oriola et al., 2016; oriola et al., 2021). also, there is much research on the thermal properties of nuts or seeds such as pumpkin seeds (kocabiyik et al., 2009), peanut pods (bitra et al., 2010), roselle seeds (bamgboye and adejumo, 2010), baobab fruits (adekunle et al., 2013), cowpea flour (mahapatra et al., 2013), red lentil seeds (gharibzahedi et al., 2013), cooked locust bean (oriola et al., 2016), bambara groundnuts file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng oriola et al: moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions. azojete, 18(4):707-720. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 709 (abioye et al., 2016), soybean (pohndorf et al., 2017), and jack bean seeds (adeyanju et al., 2019; oriola et al., 2020). literature search revealed that research on moisture content and temperature effects on the specific heat, thermal conductivity, and diffusivity of winged bean seeds are sparse. the aim of this study was to investigate how temperature and moisture content affected the thermal characteristics of three accessions of winged bean seeds. 2. materials and methods 2.1. samples collection mature winged bean seed (entry 4 tropical psophocarpus tetragonolobus (tpt) 6, entry ii tropical psophocarpus tetragonolobus (tpt) 30, and entry 12 tropical psophocarpus tetragonolobus (tpt) 32) accessions were obtained from the genetic resources unit of the international institute of tropical agriculture (iita) ibadan, oyo state, nigeria. the seeds were manually winnowed to remove all the extraneous materials. these have been identified among the ten most promising winged bean seed accessions by the iita. 2.2. determination of moisture content the initial moisture content of the winged bean seed accession was determined as described by aoac (2010) and adopted by oriola et al. (2016). five (5 g) of the sample was weighted with a digital electronic weighing scale (gf-6000and, japan) of 0.01 g accuracy. the sample was then dry in an electric oven (dhg9101.isa, uk) at 103 ᵒc for 48 hours. after drying, the per cent moisture content in the sample was determined using the expression in equation 1. 𝑀𝐶𝑤𝑏 = 𝑊𝑚 𝑊𝑤 × 100 (1) where; mcwb = winged bean seed moisture content (% wet basis) wm = weight of moisture (g) ww = weight of the wet sample (g) the winged bean seed (100 g each) were also conditioned to five different moisture contents of 5, 10, 15, 20, and 25 % (wet basis) after determining the initial moisture content using an oahm 60 digital moisture analyzer (md7822 model) as described by aoac (2010) and adopted by oriola et al. (2016). next, the moisture content of each sample was increased or decreased to the required moisture contents by using either equation 1 or 2 as appropriate. after that, the samples were poured into polyethene bags, sealed tightly, and conditioned in a refrigerator for 24 h to equilibrate the moisture contents. 𝑄 = 𝑊𝑖 (𝑋𝑓−𝑋𝑖) 100−𝑋𝑓 (2) where: q = mass of water added wi = mass of winged bean seed xf = final moisture content of the winged bean seed xi = initial moisture content of the winged bean seed http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):707-720 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 710 2.3. determination of thermal properties the decagon kd2 pro thermal analyzer that employs the transient line heat source method was used to determine the specific heat capacity (cp), thermal conductivity (k), and thermal diffusivity (α) simultaneously, as described by oriola (2014) and oriola et al. (2016). the sample holder was loaded with a known quantity of the already conditioned winged bean seeds, and the sh-1 probe gang was selected and inserted through the lid of the sample holder. the reading time of 2 minutes was set for computing the thermal properties determined at an average room temperature of 30ᵒc at each moisture level. the reading displayed on the screen was taken and recorded at an error value of 0.001. after that, the needle of the sh-1 probe of the thermal analyzer rested for 15 minutes to equilibrate to the surrounding temperature before the next experiment as recommended by the manufacturer. the experiments were replicated five times at each moisture level. a thermostatic water bath (dk-2000-isl) was used to raise the temperature of the samples to 40 and 50ᵒc, respectively, before the above experimental procedures were then repeated at these temperatures for each winged bean seed accessions. 2.4. statistical analysis the data collected were analyzed with spss® version 20 (statistical package for social sciences, usa). the duncan’s multiple range test was used to determine the significant difference between the means, and the differences were significant at p< 0.05. microsoft excel spreadsheet software version 2013 was used to do all the experimental calculations. regression analyses of the experimental data were analyzed with the stat-ease design expert 11.1.2.0 software. 3. results and discussion 3.1. specific heat capacity (cp) of the three winged bean seed accessions results of the specific heat capacity of the winged bean seed accessions were presented in table 1. in these seeds moisture ranged, the cp values were observed to increase steadily with an increase in moisture content of the samples for each of the three winged bean accessions, irrespective of temperature. this increase in the cp with increasing moisture content could be due to the high specific heat of water compared to the dry material, making the water occupy the void spaces faster at lower moisture contents. the cp values were lower than those reported for pumpkin seeds (2.53 to 3.13 kj.kg-1k-1) by kocabiyik et al. (2009) and peanut pod (2.1 to 3.3 kj.kg-1k-1) by bitra et al. (2010). however, they were slightly higher than cooked locust bean seeds (1.38 to 1.94 kj.kg-1k-1) and jack bean seeds (1.38 to 1.89 kj.kg-1k-1) reported by oriola et al. (2016) and adeyanju et al. (2019), respectively. the high cp values obtained for the three winged bean seed accessions translates to winged bean seed requiring thousands of joules to increase or lower the heat energy by 1 ᵒc. table 1: specific heat capacities of three winged bean seed accessions temperature (oc) moisture contents (%) entry 4 tpt 6 (kj/kgk) entry ii tpt 30 (kj/kgk) entry 12 tpt 32 (kj/kgk) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng oriola et al: moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions. azojete, 18(4):707-720. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 711 5 1.44 ± 0.16c 1.72 ± 0.03bcde 1.67 ± 0.07cde 10 1.65 ± 0.10bc 1.93 ± 0.18bc 1.84 ± 0.10c 30 15 1.73 ± 0.16bc 2.09 ± 0.05b 2.26 ± 0.22b 20 2.40 ± 0.17a 2.48 ± 0.14a 2.37 ± 0.11ab 25 2.42 ± 0.03a 2.59 ± 0.13a 2.63 ± 0.07a 5 1.53 ± 0.01c 1.36 ± 0.03e 1.47 ± 0.12e 10 1.64 ± 0.10bc 1.61 ± 0.11cde 1.49 ± 0.10de 40 15 1.76 ± 0.10bc 1.67 ± 0.13bcde 1.60 ± 0.03cde 20 2.52 ± 0.17a 1.95 ± 0.13bc 1.63 ± 0.13cde 25 2.53 ± 0.15a 2.08 ± 0.21b 1.82 ± 0.07cd 5 1.38 ± 0.02c 1.37 ± 0.28e 1.34 ± 0.09e 10 1.42 ± 0.16c 1.46 ± 0.10de 1.54 ± 0.03cde 50 15 1.52 ± 0.13c 1.55 ± 0.04cde 1.59 ± 0.03cde 20 1.52 ± 0.18c 1.72 ± 0.06bcde 1.62 ± 0.03cde 25 2.00 ± 0.18b 1.88 ± 0.14bcd 1.66 ± 0.16cde means within the same column at each temperature with different superscripts are significantly different (p<0.05) figure 1 represents the surface plot showing the interactions between the temperature, moisture, and cp of the winged bean seed accessions. as observed from the plots, the cp increased linearly as the moisture content increased at a low temperature of 30 oc for the three accessions. the linearly increasing trend in cp with moisture content correlates with work done by other researchers for other agricultural products such as; bart-plange et al. (2012) for cashew kernel, mahapatra et al. (2013) for cowpea, isa et al. (2014) for melon seeds, abioye et al. (2016) for bambara groundnut, oriola et al. (2016) for cooked locust bean seeds and matouk et al. (2018) for faba bean seeds. at a lower temperature (30 ᵒc), the percentage increases of the cp with moisture increase were higher than those at higher temperatures (50 ᵒc) for the three accessions. this suggests that low heat energy would be needed to change the temperature of the bean seed accessions during heating processes. however, other studies have reported decreasing trends with moisture content, such as; bamgboye and adejumo (2010) for roselle seeds and adeyanju et al. (2019) for jack bean seeds. this shows that the food materials to be processed would determine the type of heat processing it needs to be subjected to. thus, these results of cp could help analyze the heat energy required for each stage of the processing and optimization of winged bean seeds. this will, in turn, reduce the heating duration to the barest minimum, which could help in nutrients retention and energy savings. http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):707-720 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 712 figure 1: effects of moisture and temperature on specific heat capacities of winged bean seed accessions several regression equations were fitted to determine the model that best describes the relationship between temperature, moisture content, and cp of the studied winged bean seed accessions. second-order polynomial models gave the highest coefficient of determination (r2) value of 0.9126, 0.9877, and 0.9886 for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32, respectively (table 2). this implies that these 2nd order polynomial equations obtained could best fit the relationships between temperature, moisture, and the cp of the winged bean seed accessions studied. the model f-values of 10.43, 60.04, and 64.92 for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32, respectively (table 3), implied that the models were significant. the analysis of variance p-values less than 0.05 indicated that the temperature, moisture contents and the combined temperature and moisture content were significant with the cp of the entry ii tpt 30 and entry 12 tpt 32 accessions. however, effects of combined temperature and moisture content were not significant (p > 0.05) with the cp of the entry 4 tpt 6 accession. table 2: polynomial regression model equations for three winged bean seed accessions accessions equations r2 𝐶𝑝 = 1.930 − 0.221𝑥1 + 0.576𝑥2 − 0.137𝑥1𝑥2 − 0.256𝑥1 2 + 0.126𝑥2 2 − 0.171𝑥1 2𝑥2 + 0.081𝑥1𝑥2 2 + 0.016𝑥1 2𝑥2 2 0.9126 entry 4 tpt 6 𝑘 = 0.330 + 0.136𝑥1 + 0.068𝑥2 + 0.040𝑥1𝑥2 + 0.010𝑥1 2 + 0.011𝑥2 2 + 0.008𝑥1 2𝑥2 + 0.011𝑥1𝑥2 2 0.9862 𝛼 = 0.572 + 0.073𝑥1 − 0.226𝑥2 − 0.125𝑥1𝑥2 − 0.047𝑥1 2 − 0.044𝑥2 2 + 0.255𝑥1 2𝑥2 + 0.036𝑥1𝑥2 2 0.9567 𝐶𝑝 = 1.740 − 0.297𝑥1 + 0.356𝑥2 − 0.101𝑥1𝑥2 + 0.124𝑥1 2 − 0.006𝑥2 2 + 0.001𝑥1 2𝑥2 + 0.027𝑥1𝑥2 2 + 0.041𝑥1 2𝑥2 2 0.9877 entry ii tpt 30 𝑘 = 0.409 + 0.131𝑥1 + 0.152𝑥2 + 0.007𝑥1𝑥2 − 0.095𝑥1 2 + 0.022𝑥2 2 − 0.097𝑥1 2𝑥2 + 0.007𝑥1𝑥2 2 0.9872 𝛼 = 0.369 + 0.133𝑥1 − 0.164𝑥2 + 0.004𝑥1𝑥2 − 0.049𝑥1 2 + 0.074𝑥2 2 + 0.098𝑥1 2𝑥2 − 0.011𝑥1𝑥2 2 − 0.9880 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng oriola et al: moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions. azojete, 18(4):707-720. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 713 0.049𝑥1 2𝑥2 2 𝐶𝑝 = 1.560 − 0.287𝑥1 + 0.168𝑥2 − 0.173𝑥1𝑥2 + 0.321𝑥1 2 + 0.074𝑥2 2 + 0.149𝑥1 2𝑥2 − 0.030𝑥1𝑥2 2 − 0.141𝑥1 2𝑥2 2 0.9886 entry 12 tpt 32 𝑘 = 0.395 + 0.110𝑥1 + 0.154𝑥2 + 0.014𝑥1𝑥2 − 0.079𝑥1 2 + 0.007𝑥2 2 − 0.078𝑥1 2𝑥2 − 0.006𝑥1𝑥2 2 0.9801 𝛼 = 0.322 + 0.227𝑥1 + 0.054𝑥2 + 0.085𝑥1𝑥2 + 0.101𝑥1 2 + 0.009𝑥2 2 + 0.107𝑥1 2𝑥2 + 0.024𝑥1𝑥2 2 + 0.027𝑥1 2𝑥2 2 0.9959 where; x1 = temperature x2 = moisture content table 3: analysis of variance for effect of temperature and moisture content on the specific heat capacities of three winged bean seed accessions 3.2. thermal conductivity (κ) of three winged bean seed accessions results of the thermal conductivity of the three winged bean seed accessions at different moisture contents and temperatures are as presented in table 4. like the cp, the κ of the three winged bean seed accessions were observed to increase with an increase in the moisture content irrespective of the samples temperature. but, unlike the cp, the κ was observed to increase with the temperature for the three seed accessions. the values of thermal conductivities obtained in this study were slightly higher than 0.11 to 0.28 w.m-1k-1 reported for borage seeds (yang et al., 2002), 0.113 to 0.135 w.m-1k-1 for pumpkin seeds (kocabiyik et al., 2009), and 0.19 to 0.24 w.m-1k-1 for red lentil seeds (gharibzahedi et al., 2013). however, it falls within the same ranged of 0.57 to 0.61 w.m-1k-1 for egusi melon (isa et al., 2014), 0.25 to 0.31 w.m-1k-1 for bambara groundnut (abioye et al., 2016), and 0.21 to 0.41 w.m-1k-1 for jack bean seeds (oriola et al., 2020) within the same moisture contents studied. these values obtained are also within the range of 0.02 to 0.62 w.m-1k-1 for unfrozen food products, as carson (2017) reported. the high value of the thermal http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 714 conductivity obtained for these winged bean seed accessions indicated better heat conductors. table 4: thermal conductivities of three winged bean seed accessions temperature (oc) moisture contents (%) entry 4 tpt 6 (w/mk) entry ii tpt 30 (w/mk) entry 12 tpt 32 (w/mk) 5 0.17 ± 0.02g 0.14 ± 0.04h 0.15 ± 0.02i 10 0.18 ± 0.02fg 0.17 ± 0.02gh 0.18 ± 0.05hi 30 15 0.21 ± 0.02fg 0.19 ± 0.04gh 0.21 ± 0.10ghi 20 0.22 ± 0.04efg 0.21 ± 0.04fgh 0.25 ± 0.02fgh 25 0.24 ± 0.03def 0.24 ± 0.02fg 0.27 ± 0.05efg 5 0.28 ± 0.03cde 0.28 ± 0.04f 0.26 ± 0.11efgh 10 0.29 ± 0.05cd 0.36 ± 0.04e 0.33 ± 0.07def 40 15 0.32 ± 0.02c 0.39 ± 0.03de 0.34 ± 0.02de 20 0.39 ± 0.02b 0.46 ± 0.05bcd 0.50 ± 0.04ab 25 0.40 ± 0.02b 0.61 ± 0.06a 0.56 ± 0.07a 5 0.39 ± 0.05b 0.41 ± 0.03de 0.33 ± 0.08def 10 0.42 ± 0.04b 0.42 ± 0.03de 0.38 ± 0.02cd 50 15 0.45 ± 0.04b 0.44 ± 0.02cd 0.44 ± 0.04bc 20 0.58 ± 0.06a 0.51 ± 0.03bc 0.47 ± 0.06b 25 0.60 ± 0.02a 0.52 ± 0.04b 0.51 ± 0.07ab means within the same column at each temperature with different superscripts are significantly different (p<0.05) figure 2 represents the surface plot showing the interactions between the temperature, moisture, and the thermal conductivity of the winged bean seed accessions. the thermal conductivity of the winged bean seed accessions increased with moisture contents in a linear (reduced cubic) positive relationship following a second-order polynomial equation. the increase in the thermal conductivity with moisture content in linear relationship obtained in this study agreed with other researchers such as singh and goswami (2000) for cumin seed, yang et al. (2002) for borage seeds, aviara et al. (2008) for shea nut kernel, kurozawa et al. (2008) for cashew nut and apple, kocabiyik et al. (2009) for pumpkin seeds and gharibzahedi et al. (2013) for red lentil seeds. however, a nonlinear relationship was reported by oriola (2014) for cassava roots and oriola et al. (2020) for jack bean seeds. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng oriola et al: moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 715 these differences in the thermal conductivity may be attributed to the variation in seed size, porosity of sample bulk, and seed chemical compositions of each seed accession (for example, oil and protein contents) (gharibzahedi et al., 2010). figure 2: effects of moisture and temperature on thermal conductivities of winged bean seed accessions a polynomial function that best described the effects of temperature and moisture content on the thermal conductivity of the three winged bean accessions was investigated. secondorder polynomial models give the best fit resulting in an r2 value of 0.9862, 0.9872, and 0.9801 was obtained for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32 accessions, respectively (table 2). this implies that these 2nd order polynomial equations best fit the relationships between temperature, moisture, and the κ of the winged bean seed accessions studied. the model f-values of 71.53, 77.08, and 49.30 for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32, respectively (table 5), implied that the models were significant. the analysis of variance p-values less than 0.05 indicated that the temperature, moisture contents and the combined temperature and moisture content were significant with the κ of the entry 4 tpt 6 accession. however, the effects of combined temperature and moisture content were not significant (p > 0.05) with the κ of the entry ii tpt 30 and entry 12 tpt 32 accessions. table 5: analysis of variance for effect of temperature and moisture content on the thermal conductivity of three winged bean seed accessions http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 716 3.3. thermal diffusivity of three winged bean seed accessions results of the thermal diffusivity of the three winged bean seed accessions at different moisture contents and temperatures are as presented in table 6. the entry 4 tpt 6 accession was observed to have the highest thermal diffusivity values while entry 12 tpt 32 and entry ii tpt 30 accessions followed, respectively, as the temperature and moisture increased. these values obtained are less than 1.0 and agreed with the thermal diffusivity values published for some other foods in the literature, such as; cumin seeds by singh and goswami (2000), pumpkin seed by kocabiyik et al. (2009), peanut pod and kernel by bitra et al. (2010), doum palm fruits by aremu and fadele (2010), soybean grains by pohndorf et al. (2017), and jack bean seeds by oriola et al. (2020). table 6: thermal diffusivities of three winged bean seed accessions temperatur e (oc) moisture contents (%) entry 4 tpt 6 (m2/s) x 10-7 entry ii tpt 30 (m2/s) x 10-7 entry 12 tpt 32 (m2/s) x 10-7 5 0.19 ± 0.01c 0.31 ± 0.02def 0.13 ± 0.04g 10 0.41 ± 0.11abc 0.20 ± 0.08fg 0.16 ± 0.06g 30 15 0.45 ± 0.17abc 0.19 ± 0.04fg 0.21 ± 0.02fg 20 0.46 ± 0.16abc 0.19 ± 0.01fg 0.22 ± 0.02fg 25 0.55 ± 0.10abc 0.14 ± 0.01g 0.29 ± 0.02ef 5 0.77 ± 0.07a 0.61 ± 0.04a 0.28 ± 0.05ef 10 0.66 ± 0.12ab 0.46 ± 0.06bc 0.29 ± 0.02ef 40 15 0.53 ± 0.07abc 0.38 ± 0.03cde 0.32 ± 0.03ef 20 0.51 ± 0.17abc 0.30 ± 0.02def 0.36 ± 0.06de 25 0.28 ± 0.09bc 0.28 ± 0.03ef 0.38 ± 0.04de 5 0.68 ± 0.16ab 0.52 ± 0.05ab 0.45 ± 0.03d 10 0.65 ± 0.10ab 0.51 ± 0.05ab 0.58 ± 0.04c 50 15 0.61 ± 0.10ab 0.44 ± 0.03bc 0.62 ± 0.02c 20 0.53 ± 0.14abc 0.42 ± 0.06bcd 0.79 ± 0.04b 25 0.50 ± 0.15abc 0.41 ± 0.05bcd 0.96 ± 0.05a means within the same column at each temperature with different superscripts are significantly different (p<0.05) figure 3 represents the surface plot showing the interactions between the three winged bean seed accessions‘ temperature, moisture, and thermal diffusivity. it was observed that the thermal diffusivity of samples of the entry 4 tpt 6 and entry 12 tpt 32 generally increased with an increase in moisture content at 30ᵒc while those of entry ii tpt 30 declined with an increase in moisture at the same temperature. also, at temperatures of 40 and 50ᵒc, the diffusivity of the seed of entry 4 tpt 6 generally decreased with increased moisture content. the thermal diffusivity of the seeds of the entry ii tpt 30 generally reduced with an increase in moisture content irrespective of the sample temperature. however, seeds of the entry 12 tpt 32 were observed to increase with both increases in file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng oriola et al: moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 717 temperature and moisture. abioye et al. (2016) reported an increase in the thermal diffusivity with a rise in bambara groundnut moisture content. in contrast, adekunle et al. (2013) reported increased in thermal diffusivity with temperature increase for baobab fruit pulp powder. figure 3: effects of moisture and temperature dependent on thermal diffusivities of winged bean seed accessions a polynomial function that shows the simultaneously dependent temperature and moisture content on the thermal diffusivities was investigated to correlate experimental data. the best fit resulting in an r2 value of 0.9567, 0.9880, and 0.9959 was obtained for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32 accessions, respectively (table 2). this implies that these 2nd order polynomial equations obtained could best fit the relationships between temperature, moisture, and the thermal diffusivity of the winged bean seed accessions studied. the model f-values of 22.10, 61.87, and 182.61 for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32, respectively (table 7), implied that the models are significant. the analysis of variance p-values less than 0.05 indicated that the temperature, moisture contents and the combined temperature and moisture content were significant with the thermal diffusivity of the entry 4 tpt 6 and entry 12 tpt 32 accessions. however, the effects of combined temperature and moisture content were not significant (p > 0.05) with the thermal diffusivity of the entry ii tpt 30 accession. table 7: analysis of variance for effect of temperature and moisture content on the thermal diffusivity of three winged bean seed accessions http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 718 4. conclusions the influence of moisture and temperature on the thermal properties of winged bean seed accessions revealed that: i. the cp and thermal conductivity generally increased with increased moisture content for the three winged bean seed accessions. in contrast, the thermal diffusivity decreased with increased moisture content at elevated temperatures (40 and 50 ᵒc). ii. second-order polynomial models best described the relationship between the studied thermal properties and the temperature and moisture content. the regression equations (r2 ≥ 0.9126, 0.9872, and 0.9801 for entry 4 tpt 6, entry ii tpt 30, and entry 12 tpt 32 accessions, respectively) obtained in this study provide a reasonable estimate simulating the thermal properties of the winged bean seeds within the moisture-temperature range studied. iii. the analysis of variance (anova) showed that moisture and temperature have a significant (p < 0.05) effect on the thermal properties of the winged bean seeds. iv. these thermal properties of the winged bean seeds examined will help design considerations for the fabrication of agricultural machines, thermal processes, and equipment needed for storage, drying, heating, and cooling. v. the recommended use of the winged bean seeds' thermal qualities will enable the development of agricultural machinery, thermal systems, and apparatus for heating, cooling, drying, and storing. references abioye, ao., adekunle, aa. and agbasi-ebere, v. 2016. some moisture-dependent physical and thermal properties of bambara groundnut. iosr journal of environmental science, toxicology and food technology, 10(10): 65-74. adegboyega, tt., abberton, mt., abdelgadir, ah., dianda, m., maziya-dixon, b., oyatomi, oa., ofodile, s. and babalola, oo. 2019. nutrient and antinutrient composition of winged bean (psophocarpus tetragonolobus (l.) dc.) seeds and tubers. journal of food quality, article id 3075208. https://doi.org/10.1155/2019/3075208. adekunle, aa., shittu, ta., abioye, ao., adeyanju, ja. and osanaiye, fg. 2013. physical and thermal properties of baobab fruit pulp powder. international journal of engineering research and applications, 3(3): 925-928. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng oriola et al: moisture and temperature influence on thermal properties of winged bean (psophocarpus tetragonolobus) seed accessions. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 719 adeyanju, ja., adekunle, aa., abioye, ao., ogunlakin, go., olajire, as. and fashina, oz. 2019. determination of moisture-dependent physical and thermal properties of jack bean (canavalia ensiformis) related to design of processing machines. nigerian food journal, 37(1), 106-116. aoac. 2010. official methods of analysis of association of official analytical chemists (18th ed.). washington d.c aremu, ak. and fadele, ok. 2010. moisture dependence thermal properties of doum palm fruit (hyphaene thebaica). journal of emerging trends in engineering and applied sciences, 1(2): 199–204. aviara, na., haque, ma. and ogunjimi, lao. 2008. thermal properties of guna seeds. international agrophysics, 22: 291-297. bamgboye, ai. and adejumo, o.i. 2010. thermal properties of roselle seed. international agrophysics, 24: 85-87. bart-plange, a., addo, a., kumi, f. and piegu, ak. 2012. some moisture dependent thermal properties of cashew kernel (anarcardium occidentale l.) australian journal of agricultural engineering, 3(2): 65-69. bitra, vsp., banu, s., ramkrishna, p., narender, g. and womac, ar. 2010. moisture dependent thermal properties of peanut pods, kernels and shell. journal of food engineering, 106: 503-512. carson, jk. 2017. use of simple thermal conductivity models to assess the reliability of measured thermal conductivity data. international journal of refrigeration, 74: 458-464. gharibzahedi, smt., etemad, v., mirarab-razi, j. and foshat, m. 2010. study on some engineering attributes of pine nut (pinus pinea) to the design of processing equipment. research in agricultural engineering, 56(3): 99-106. gharibzahedi, smt., ghahderijani, m. and lajevardi, zs. 2013. specific heat, thermal conductivity and thermal diffusivity of red lentil seed as a function of moisture content. journal of food processing and preservation, 38(4): 1807-1811. isa, j., oladele, so. and akinlade, es. 2014. the effect of moisture content on thermal properties of some selected species of egusi melon (colocynthis citrillus l.). international journal of emerging technology and advanced engineering, 4(4): 580-586. kocabiyik, h., kayisoglu, b. ans tezer, d. 2009. effect of moisture content on thermal properties of pumpkin seed. international journal of food properties, 12(2): 277-285. kurozawa, lw., park, kj. and azonbel, pm. 2008. thermal conductivity and thermal diffusivity of papaya (carica papaya l.) and cashew apple (anacardium occidentale l.). brazilian journal of food technology, 11: 78-85. lepcha, p., egan, an., doyle, jj. and sathyanarayana, n. 2017. a review on current status and future prospects of winged bean (psophocarpus tetragonolobus) in tropical agriculture. plant foods for human nutrition, 17: 225-235. mahapatra, ak., melton, sl. and isang, em. 2013. effect of moisture content on thermal properties of cowpea flours. agricultural engineering international: cigr journal, 15(2): 251-255. http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jbhussein01@mau.edu.ng 720 matouk, am., el-kholy, mm., tharwat, a. and shamala, sf. 2018. thermal properties of some legume seeds. journal of soil sciences and agricultural engineering, 9(7): 261-267. ojo, ma. and ade-omowaye, bio. 2015. some functional and physical properties of selected underutilised hard-to-cook legumes in nigeria. american journal of food science and nutrition, 2(5): 73-81. oriola, ko. (2014). effects of ageing and moisture content on thermal properties of cassava roots using response surface methodology. international journal of applied agricultural and apicultural research, 10(1&2): 54-63. oriola, ko., hussein, jb., oke, mo. and ajetunmobi, a. 2020. description and evaluation of physical and moisture dependent thermal properties of jack bean seeds (canavalia ensiformis) journal of food processing and preservation, e15166. https://doi.org/10.1111/jfpp.15166. oriola, ko., hussein, jb., oke, mo. and ajetunmobi, a. 2021. influence of moisture and temperature on the thermal properties of jack bean seeds (canavalia ensiformis). food and feed research, 48(2): 165-174. oriola, ko., oke, mo., hussein, jb. and adebesin, kt. 2016. thermal properties of cooked locust bean (parkia biglobosa) seeds as affected by temperature-moisture interactions. nigerian journal of horticultural science, 21(2016): 48-56. pohndorf, rs., rocha, jc., lindemann, i., peres, wb., oliveira, m. and elias, mc. 2017. physical properties and effective thermal diffusivity of soybean grains as a function of moisture content and broken kernels. journal of food process and engineering, e12626. https://doi.org/10.1111/jfpe.12626. sambudi, h. and buckle, ka. 1991. characteristics of winged bean (psophocarpus tetragonolobus) seeds during soaking and boiling. journal of the science food and agriculture, 57(4): 585-595. singh, kk. and goswami, tk. 2000. thermal properties of cumin seed. journal of food engineering, 45: 181-187. vatanparast, m., shetty, p., chopra, r., doyle, jj., sathyanarayana, n. and egan, an. 2016. transcriptome sequencing and marker development in winged bean (psophocarpus tetragonolobus l.). scientific reports, 6(1) https://doi.org/10.1038/srep29070. wan mohtar, wa., hamid, aa., abd-aziz, s., muhamad, sk. and saari, n. 2014. preparation of bioactive peptides with high angiotensin converting enzyme inhibitory activity from winged bean [psophocarpus tetragonolobus (l.) dc.] seed. journal of food science and technology, 51(12): 3658-3668. wong, qn., massawe, f. and mayes, s. 2015. improving winged bean (psophocarpus tetragonolobus) productivity: an analysis of the determinants of productivity. acta horticulturae, 1102: 83-88. yang, w., sokhansanj, s., tang, j. and winter, p. 2002. determination of thermal conductivity, specific heat, and thermal diffusivity of borage seeds. biosystems engineering, 82(2):169-176. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng 1 arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):751-760 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 741 original research article influence of antimony micro-alloy addition on the mechanical properties of carbidic austempered ductile iron (cadi) a. aliu1, a. a. barnabas1, a. m. rufai2 and s. o. okpo3 1department of material and metallurgical engineering, nigerian army university biu, borno state, nigeria 2department of mechanical engineering, nigerian army university biu, borno state, nigeria 3department of chemical engineering, delta state university, delta state, nigeria. *corresponding author’s email address: ayubaihima2020@gmail.com article information abstract in this research work, the influence of antimony micro-alloy addition on the hardness property, impact energy and wear resistance of carbidic austempered ductile iron (cadi) was investigated. rod-shaped samples were produced using a sand casting technique to investigate the influence of antimony micro-quantities on the microstructural modification of the high manganese content (cadi). selected mechanical properties of the product (cadi) have been tested. rod-shaped samples were produced using a sand casting technique to investigate the influence of antimony micro-quantities on the microstructural modification of the high manganese content (cadi). selected mechanical properties of the product (cadi) have been tested. rod-like shape samples were produced by sand casting technique used for evaluating the influence of micro quantities of antimony on the microstructural modification of high manganese content carbidic austempered ductile iron (cadi) with respect to the selected me 7chanical properties. six compositions of carbidic ductile iron (cdi) with varying antimony content ranging from 0.096 % to 0.480 wt. % were produced, having equivalent carbon of hyper-eutectic composition (4.43). these samples were heated to austenitic temperature of 910ºc and subjected to austempering temperature, 300ºc for period of 1-3 hours. microstructural examination of the samples was carried out to study the matrix and reinforcing phases present. the abrasion wear resistance was evaluated in accordance with the astm g 65 standard. the results show that; the obtained wear resistance values ranging from 2.35e8 to 3.29 e9 with respect to unmodified cadi (taken as reference material) the results show that the wear resistance values ranging from 2.35e8 and 3.29 e9 with respect to cadi sample without antimony addition taken as reference material, rockwell hardness values obtained ranging from 28.6 – 55 hrc and impact toughness values ranges from 46.5 – 53 j for the developed cadi. micrographs obtain revealed that chunky graphite, blocky carbides and pearlite phases were seen in the as-cast sample without antimony addition while the samples with varying addition of antimony element showed spiky graphite, granular carbide and more pearlite phases. however, after subjecting the samples to austempering processes, the pearlite phase transformed to ausferritic structure, while submitted 19 april, 2022 revised 30 september, 2022 accepted 6 october, 2022 keywords: carbidic ductile iron micro-alloy microstructure carbides antimony http://www.azojete.com.ng/ mailto:ayubaihima2020@gmail.com mailto:ayubaihima2020@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):751-760 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 752 1.0 introduction cadi is a material well known for its ability to survive different wear mechanisms such as rolling contact fatigue, adhesion and abrasion (magalh˜aes and seabra, 1998). it is well known of the ability of cadi to do well when it is subjected under different wear mechanisms such as rolling contact fatigue, adhesion and abrasion. austempered ductile iron (adi) act in diverse ways under abrasive conditions, based on tribo-system (low or high stress abrasion) involved in the process. selection of proper heat treatment parameters couldtranslate to good performance of this material in service (dommarco et al., 2001). cadi, is a type of cast iron having carbides intentionally introduced in an ausferritic matrix. from metallurgical point of view, the presence of carbides in cadi is expected to promote an increase in the abrasion wear resistance, while compromising its impact toughness value. available research revealed that the presence of carbides in cadi is expected to promote an increase in the abrasion wear resistance, while compromising its impact toughness value. in addition, there is the need to control the microstructure of cadi in order to obtain an optimum balance between abrasion resistance and impact toughness. one of the methods used in obtaining a microstructure of as-cast carbides in cast iron is to lower is to low the quantity of graphitizing elements (silicon) in the cast iron, to facilitate precipitation of ledeburitic carbides during its solidification. the above may be combined with a second option of putting a chill in the mould which promotes high undercooling. a third option is adding alloying elements (chromium, molybdenum or titanium) that are carbides stabilising in the melt (hayrynen, and brandenberg, 2003) which greatly narrows the interval between stable and metastable eutectic temperatures and promote total or partial solidification according to the metastable diagram gundlach et al., 1985). it must be noted that an under cooling also affects the size and count of the solidification units, and thereby causing micro segregation. the lower the cooling rate, the greater the micro segregation effect, increasing the possibility of carbide precipitation at the last to freeze zones, and resulting to formation of alloyed carbides (lacaze et al., 2003). the size and composition of carbides can vary, from typical unalloyed ledeburitic to thin plate shaped high-alloyed carbides, based on the chemical composition and cooling rate of the material (nastac and stefanescu, 1997; zhao and liu, 2001). caldera et al. (2005) reported that ledeburitic carbides produced either via controlling of cooling rate or the silicon level (non-alloyed carbides) have a high propensity to dissolve during the austenitizing stage and are not as stable as alloyed carbides. therefore, the objective of this work is to produce cadis of varying micro-alloy addition of antimony (sb) and identify its microstructural characteristics and evaluate some mechanical properties, such as their hardness values, abrasion resistance and the impact toughness. 2. materials and methods 2.1 experimental procedures 2.1.1 preparation of sample the charged materials used in this work were sourced from a metal casting company. indirect electric arc furnace of capacity 3 kg was used for melting of the charged materials. locally sourced grey cast iron scraps were used as charge materials. the carbide and graphite structure remained unaltered. the produced cadi is found to be useful for agricultural implements production. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ayubaihima2020@gmail.com aliu et al: influence of antimony micro-alloy addition on the mechanical properties of carbidic austempered ductile iron (cadi). azojete, 18(4):751-760. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 753 all the melts were nodulized with fe-si-mg (9 wt. % mg) and inoculated with fesi (75 wt. % si). calculated amounts of ferro-chrome, ferro-nickel, ferro-manganese, 99% purity copper, and antimony powder were added in the expected quantities after charge calculation was done. six alloys of carbidic ductile iron were cast, with 0 wt. % sb, 0.096 wt. % sb, 0.192 wt. % sb, 0.288 wt. % sb, 0.384 wt. % sb and 0.480 wt. % sb content. the dimension of each sample cast is 20 mm by 20 mm by 200 mm. the rods were cut longitudinal into 20 mm by 30 mm long for the microstructural characterization, 10 mm thick by 50 mm long for impact and 20 mm x 40 mm for wear test samples. the six cast alloys were then heat-treated by heating them to austenitizing temperature of 910oc and held for 1 hour in a heat treatment furnace followed by an austempering step in an equal mixture of sodium nitrate and potassium nitrate salt bath at temperature 300 oc at austempering time of 1-3 hours. 2.2 chemical and microstructural examination the elemental compositions of the produced alloys were determined by means of a spark emission optic spectrometer (spectro-pro maxx-lmm06) produced in usa by spectro ametek with a dv6 excitation source. the microstructures of the produced alloys were accessed using light reflected optical metallurgical microscope (axio-observer a1m manufactured in usa by cit nelian) complimented with fesem scanning electron microscope manufactured in china by i-crim with an edx module, for the purpose of analyzing the influence of antimony element on the matrix and carbide formation of the produced samples. metallographic preparation of the samples for microscopy examination was achieved using standard techniques for cutting, grinding and polishing, etching the polished samples with 2 wt.% nital before viewing the prepared samples under microscope (khanna, 2009) 2.3 mechanical tests 2.3.1 wear test the abrasive wears resistance of the samples was measured using rotopol-v tribometer manufactured by rtech with model number mft-5000. the wear test which was done was based on the taber method. wear test that was carried out was based on taber’s method. this was done by attaching sample to a rotating horizontal disk of 25 cm radius and pressure of a specified load was applied according to friedrich et al. (2009). the samples used were of dimensions, 15mm diameter by 40 mm long. the grit of emery paper used was 220, and revolution of 150 rpm for5 minutes. the weight of the samples in each case was measured before and after each test with a 4 decimal places analytical electronic weighing scale with accuracy of 0.01 mg. after running through a fixed distance, the samples were removed, cleaned with acetone, dried, and weighed to determine the weight loss due to wear and the weight loss was converted to volume loss by using the material density measured, wear rate and wear resistance respectively. wear rate was measured using the equations wear rate = 𝑊𝑣 𝐷 (1) where; wv = wear volume (m3) d = slide distance (m) where: slide distance d = 2𝜋𝑅𝑑 60𝑡 (2) and r = revolution = 150rpm d = diameter of the rotating disc used (m) http://www.azojete.com.ng/ mailto:ayubaihima2020@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):751-760 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 754 wear resistance is 1 wear rate (3) wear resistance = inverse of wear rate obtained grit used is p 220 rough, revolution (r) is 150 rpm, d is the diameter of the rotating disc used. 2.3.2 impact test impact toughness tests was carried out on the produced cadi. the alloyed cadi and the heat-treated samples were carried out under the astm e 23 standard using charpy method in which the samples were machined to square cross-section of 10 mm by 10 mm and 55 mm long, notched at the midpoint. the specimen was placed each in a vice as a beam fixed at two ends. the pendulum of 65 kg weight was raised, on releasing the hammer, the sample was hit behind its v-notch. the energy absorbed was read from the dial scale mounted on the machine. 2.3.3 hardness test the hardness test for both as-cast and after heat treatment was conducted using digital rockwell hardness tester on scale c, in accordance with astm e18-08 (standard test method for rockwell hardness of metallic materials). the minor load used for this test was 10 kg while the major load was 150 kg. the sample was placed on the anvil. the minor load was applied by moving the screw jack up until the specimen came in contact with the indenter. the hardness value was then displayed on the machine. four points hardness values were measured and average of the four measurements was taken. 3. results and discussion 3.1 chemical and microstructural characterization table 1 shows the chemical composition of the produced samples. it shows an approximately hyper eutectic composition (carbon equivalent, c.e of 4.43). there is no dissolution of carbide observed in the microstructure of the cadi after heat treating the cdis (caldera et al., 2005) this could be due to the high thermodynamic stability of alloyed carbides created by the high chromium content of the alloys. figures 1 stands for as-cast microstructures of the cdis which consist of chunky graphite nodules, blocky carbide and pearlite phases while figures 2, 3, 4, 5, 6, 8, 9, 10, 11 and 12 represent the austempered samples which compose of spiky graphite nodules, granular carbides and ausferritic matrix. from the micrographs obtained, the presence of antimony promoted pearlite formation of the alloy and causes improvement in the nodularity of the graphite nodule and increases hardness of the metallic matrix of the produced alloys (patil et al., 2014) while the chromium assisted in the formation of alloyed carbide. after austempering, it was observed that the blocky and granular carbides were still retained in the structure, spiky graphite nodule was still present but no pearlite phase was observed, rather ausferritic matrix was observed. the carbide was stable during the austenitizing stage of the austempering, this is in conformity with (patil et al., 2014). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ayubaihima2020@gmail.com aliu et al: influence of antimony micro-alloy addition on the mechanical properties of carbidic austempered ductile iron (cadi). azojete, 18(4):751-760. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 755 table 1: chemical composition of the produced samples no sample fe c si mn cr ni cu mg sb s p c.e 1 c(ctrl) 89.39 3.62 2.42 0.58 2.6 0.60 0.69 0.06 0.004 0.040 4.43 2 a 89.33 3.62 2.40 0.57 2.61 0.61 0.65 0.07 0.096 0.005 0.041 4.43 3 b 89.24 3.62 2.41 0.57 2.62 0.62 0.61 0.07 0.192 0.005 0.042 4.44 4 c 89.19 3.63 2.40 0.56 2.60 0.60 0.62 0.07 0.288 0.005 0.042 4.44 5 d 89.10 3.62 2.41 0.56 2.63 0.61 0.62 0.06 0.384 0.005 0.040 4.44 6 e 88.97 3.62 2.40 0.58 2.62 0.60 0.63 0.06 0.480 0.004 0.041 4.43 figure 1: 0 % wt. sb figure 2: 0.12 %wt. sb at 300 oc figure 3: 0.24 % wt. sb at 300 oc figure 4: 0.34 % wt. sb at 300 oc figure 5: 0.41 % wt. sb at 300 oc figure 6: 0.48 % wt. sb at 300 oc figure 7: 0 % wt. sb figure 8: 0.12 % wt. sb at 300 oc figure 9: 0.24 % wt. sb at 300 oc chunky graphite pearlite blocky carbide 100µm carbide ausferrite graphite 100µm graphite ausferrite less blocky carbide 100µm ausferrite granular carbide spiky graphite 100µm spiky graphite granular carbide ausferrite 100µm granular carbide spiky graphite ausferrite 100µm blocky carbide pearlite graphite ausferrite cellulose carbide graphite graphite carbide ausferrite http://www.azojete.com.ng/ mailto:ayubaihima2020@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):751-760 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 756 figure 10: 0.34 % wt. sb at 300 oc figure 11: 0.41 % wt. sb at 300 oc figure 12: 0.48 % wt.sb at 300 oc the result shows no dissolution of carbide observed in the microstructure of the cadi after heat treating the cdis (caldera, 2005). this could be due to the high thermodynamic stability of alloyed carbides created by the high chromium content of the alloys. from the micrographs obtained, the presence of antimony promoted pearlite formation of the alloy and causes improvement in the nodularity of the graphite nodule and increases hardness of the metallic matrix of the produced alloys (diao et al., 2011), while the chromium assisted in the formation of alloyed carbide. after austempering, it was observed that the blocky and granular carbides were still retained in the structure, spiky graphite nodule was still present but no pearlite phase was observed, rather ausferritic matrix was observed. the carbide was stable during the austenitizing stage of the austempering, this is in conformity with patil et al. (2014). 3.2 mechanical test 3.2.1 hardness test the rockwell hardness value obtained for the control sample was 38hrc, while the highest hardness value of 52.5hrc was obtained gotten for the sample with 0.288 wt.% antimony, austempered at temperature of 300 oc for 3 hours. it was observed that there was an increase in the hardness values of the samples as the antimony content increased. this could have been caused by the promotion of pearlite phase in the alloys that was by the antimony element present in the produced cadi (diao et al., 2011). a change in hardness values of the alloys with antimony content could be attributed to the variation in volume fraction of carbide and their sizes. addition of more antimony into the cdi increases the volume fraction of the carbides which were smaller in size. such variations can strengthen the material by impending dislocation movement more effectively. however, when the added antimony goes beyond certain amount (0.384 wt. % sb), the hardness starts to decrease which is corresponding to the decrease in the volume fraction of carbides as observed in the present case. finer carbides were found to be more effective to strengthen carbidic austempered ductile iron than coarse carbides. a change in hardness values of the alloys (figure 13) with antimony content could be attributed to the variation in volume fraction of carbide and their size. addition of antimony element in the cdi increases the volume fraction of the carbides which were smaller in size. such variations can strengthen the material by blocking dislocation movement more effectively. however, when the added antimony element goes beyond certain amount (0.384 wt. % sb), the hardness starts to decrease, corresponding to the decrease in the volume fraction of carbides as observed in the present case. finer carbides were found to be more effective to strengthen carbidic austempered ductile iron than coarse carbides. granular carbide ausferrite graphite granular carbide ausferrite graphite graphite granular carbide ausferrite file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ayubaihima2020@gmail.com aliu et al: influence of antimony micro-alloy addition on the mechanical properties of carbidic austempered ductile iron (cadi). azojete, 18(4):751-760. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 757 figure 13: variation of the hardness values of the cast samples with wt%sb for 1 hour austempering time for an austempering temperature of 300oc 3.2.2 wear test the wear test was conducted in accordance with astm g-99 standard. the highest wear resistance value (figures 14) was obtained in sample containing 0.34% sb austempered at 300oc for 3hour which has wear resistance of 3.74e9 which is the optimum value for both wear and hardness properties of the samples. weight loss was found to be as a result of the chromium content, critical content of antimony, carbon equivalent, austempering heat treatment parameters and microstructure matrix. the wear loss obtained was generally lower than the one obtained in previous research (patil et al., 2014). the wear resistance of the samples was found to increase with increase in antimony content, which is probably because of significant role which antimony element played by increasing the nucleation rate and inhibiting the deterioration of graphite nodules (diao et al., 2011). hardness to large extent determines the abrasion resistance of carbidic austempered ductile and the changes in the wear rate were mainly affected by the carbide content. the hard carbides may have played main role in raising hardness and resisting abrasion under low contact stresses (giacchi et al., 2007). the abrasion wear resistance of this many-phases antimony modified cadi was influenced by hardness, shape, size, volume fraction and distribution of hard second phases (carbides) and properties of the matrix (gahr, 1998). it is worth noting that the hardest sample did not show minimum wear rate, indicating that other factors (such as toughness) also have effect on the abrasion wear rate of this cast iron. the existence of fine granular carbides was seen to be of merit in terms of toughness than the ones of blocky carbide. the granular carbide suppresses micro-cracking more effectively due to its lower stress concentration. the added antimony promoted the formation of granular carbide but reduced the volume fraction of carbides. ausferrite matrix in the produced material have also played a great role in the increasing the abrasion resistance of the cadi as obtained. http://www.azojete.com.ng/ mailto:ayubaihima2020@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):751-760 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 758 figure 14a: variation of the wear resistance values of the cast samples with wt%sb for 1 hour austempering time for an austempering temperature of 3000c figure 14b: variation of the wear resistance values of the cast samples with wt%sb for 2 hours austempering time for an austempering temperature of 3000c figure 14c: variation of the wear resistance values of the cast samples with wt%sb for 3 hours austempering time for an austempering temperature of 3000c file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ayubaihima2020@gmail.com aliu et al: influence of antimony micro-alloy addition on the mechanical properties of carbidic austempered ductile iron (cadi). azojete, 18(4):751-760. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 759 3.2.3. impact test the results of the impact toughness (j) versus antimony content in all the material variants studied are shown in figure 15. figure 15: variation of the impact toughness values of the cast samples with wt%sb for 1hour austempering time for an austempering temperature of 300oc from the impact toughness results obtained, there is marginal increase in the impact energy as the antimony content and austempering time increase from 1 to 3hours. this indicates that increase in antimony content led to increase in impact toughness as a result of modification of the matrix phase of the produced carbidic ductile iron and the refinement of the graphite nodules (diao et al., 2011). increase in austempering time also translates to increase in impact energy. this could be as result of the increase in the ausferrite in the matrix of the samples. granular carbide as earlier said is of advantage in terms of toughness and resistance to fatigue crack propagation when compared to coarse carbide. the eutectic carbide crystallizes at the γ-liquid phase boundary. the added antimony element may have preferentially stayed at the interface between γ – phase and carbides and hence discouraging the continuous growth of eutectic carbide. it also decreases the surface tension of the melt, thereby, encouraging the granular growth and stabilizing the granular interface (sun et al., 2012). 4. conclusion the produced carbides were stable alloyed carbides. antimony element added was found to have assisted in changing the graphite nodule from chunky to spiky structure. this helped in getting better mechanical properties. the presence of granular carbides in the microstructure as a result of micro amount of antimony helped in increasing the hardness, wear resistance, and impact toughness of the produced alloy. increase in the antimony content led to more granular carbides, the impact toughness of the alloys was improved. the highest wear resistance was obtained at 0.288 wt. % antimony content. the hardness results were not consistent with the wear resistance results. the best sample obtained is the carbidic austempered ductile iron with antimony critical content of 0.288 wt. %. the analysis of the hardness, wear tests and the impact toughness results showed that the alloy with 0.384% sb (0.384 300 -1hr) have a good balance between hardness, wear resistance and impact toughness, under the current experimental conditions. these material variants have shown an important improvement in abrasion resistance with respect to the cadi variants, while at the same time show good impact toughness and hardness. this confirms that the produced cadi is found to be useful for agricultural implements production. http://www.azojete.com.ng/ mailto:ayubaihima2020@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):751-760 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayubaihima2020@gmail.com 760 references al-rubaie, ks, 2000. equivalent hardness concept and two body abrasion of iron -base alloys. wear, 243: 92 – 100. caldera, m., rivera, g., boeri, r. and sikora, j. 2005. precipitation and dissolution of carbides in low alloy ductile iron plates of varied thickness, materials science technology, 10(21): 1187-1191. diao, xg., ning, zl., cao, fy., ren, sz. and sun, jf. 2011. effects of antimony addition and section size on formation of chunky graphite in ductile iron. materials science and technology, 4(27): 834-838. dommarco, r., galarreta, i., ortiz, h., david, p. and maglieri, g. 2001. the use of ductile iron for wheel loader bucket tips. international journal on the science and technology of friction, lubrication and wear, 249: 101–108. gundlach, rb., janowak, jf., bechet, s. and rohrig, k. 1985. on the problems with carbide formation in gray cast iron. proceedings of the materials research society symposium held on 15-18 april, in san francisco, california, usa., 34: 251-261. hayrynen, kl. and brandenberg, kr. 2003. carbidic austempered ductile iron (cadi) the new wear material. transactions of the american foundry society, 111: 845–850. giacchi, jv., martínez, ra., martínez gamba, mr. and dommarco, rc. 2007. abrasion and impact properties of partially chilled gray iron. wear, 262(3–4): 282-291. gahr, zkh. 1998. wear by hard particles. tribology international, 31(10): 587-596 khanna, op. 2009. materials science and metallurgy. dhanpat rail publication limited, new delhi, 1-17. lacaze, j., camacho, t. and bak, c., 2003. microsegregation in mottled spheroidal graphite cast iron. international journal of cast metal resources, 16: 167–172. magalh˜aes, l. and seabra, j. 1998. wear and scuffing of austempered ductile iron gears. international journal on the science and technology of friction, lubrication and wear, 215: 237–246. nastac, l. and stefanescu, dm. 1997. modeling of the stable – to metastable structural transition in cast iron. advance materials resources, 4 – 5: 469 – 478. patil, sa., pathak, su, and likhite, a. 2014. development and wear analysis of carbidic austempered ductile iron. international journal of innovative research in science, engineering and technology, 3(2): 9652-9657. sun, x., wang, y., li, dy. and wang, g. 2013. modification of carbidic austempered ductile iron with nano ceria for improved mechanical properties and abrasive wear resistance. wear, 301(1–2): 116-121. zhao h. and liu, b. 2001. modeling of stable and metastable eutectic transformation of spheroidal graphite iron casting. isij international, 41: 986 – 991 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ayubaihima2020@gmail.com https://www.sciencedirect.com/science/article/abs/pii/s0043164806002043#! https://www.sciencedirect.com/science/article/abs/pii/s0043164806002043#! https://www.sciencedirect.com/science/article/abs/pii/s0043164806002043#! https://www.sciencedirect.com/science/article/abs/pii/s0043164806002043#! https://www.sciencedirect.com/journal/wear/vol/262/issue/3 https://www.sciencedirect.com/journal/wear https://www.sciencedirect.com/journal/wear/vol/301/issue/1 arid zone journal of engineering, technology & environment azojete march 2021. vol. 17(1):27-34 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 27 original research article nutritional and quality assessment of some irrigated wheat genotypes in nigeria f. abubakar1* and a. zigla2 1lake chad research institute, maiduguri, borno state, nigeria. 2 national agency for food drug administration and control, maiduguri, borno state, nigeria. *corresponding author’s email address: fatidupli@yahoo.com 1.0 introduction wheat (triticum aestavum l.) is unique among cereals, because it contains gluten which has the characteristic of being elastic when mixed with water and retains the gas developed during dough fermentation (makwai et al., 2013). quality wheat flour is of prime importance to the baking industry, which depends largely on the amount of protein and quality of gluten. wheat flour with large amount of protein and high quality gluten is used for normal bread, whereas that with lower amount of protein is mostly used for confectionary or cakes (caballero et al., 2007). wheat varieties exhibit different protein qualities and quantities, influenced mainly by environmental factors, and the quality of the protein is mainly a heritable characteristic (bordes et al., 2008).the annual global wheat production of about 620 million tons is mostly traded from developed temperate countries, to the high wheat-consuming developing countries (bordes et al., 2008). the consumption of bread has increased considerably due to population increase, urbanization, the changing preference for convenient foods particularly snacks and increased wealth in nigeria and other tropical countries (andrae and beckman. 1985: seibel, 2006; shittu et al., 2007; odedeji and adeleke, 2010; malomo et al., 2011). wheat production by these high wheat-consuming developing tropical countries is very low, thus they almost solely rely on other developed temperate countries to supply their requirements through imports (edema et al., 2005; abdelghafor et al., 2010). data in 2010 indicates that import bill for african countries amounted to us$ 12.5 billion. nigeria requires 3.7 million tons of wheat grain per year, but presently produces only 250,000 metric tons (3.2% self-sufficiency), and thus is the world’s largest importer of usa hard red and white winter wheat, with total imports into nigeria during 1999-2010 reaching us$6,792,934,000, and since 2005 the annual value was us$4.0billion (ohinmain, 2014). the current value is about n632 article information abstract the aim of this study is to evaluate the nutritional and end-use qualities of some advanced irrigated nigerian grown wheat genotypes which was developed and produced by lake chad research institute, maiduguri, borno state of nigeria. standard methods were used to determine the physical, milling, proximate, baking, sensory, functional, rheological and textural qualities of the nigerian grown wheat. the result showed that grain physical characteristics of the eleven irrigated wheat genotypes were statistically significant. flour extraction differed significantly from 66.1-79.6% in the irrigated wheat genotypes. three irrigated genotypes namely, florkwa-2, soonot 5, and hubara-3 had the highest flour extraction rate with flour yield above 75%. proximate flour quality indicated significantly higher protein content in hubara (15.2%), pastor-2 (15.8%), kauz (16.2%), soonot-5 (15.8%), while katila-17 had higher carbohydrate (73.2 %) than hubara-1. the results for dough and bread functional and textural qualities further showed that attila-7, katilla17, angi-2 and soonot-5 were superior to the other genotypes, and comparable to the standard imported flour. however, bread sensory evaluation gave the standard flour higher score rating. therefore, the nutritional and end use quality indicated that nigerian grown wheat had properties suitable for bread production. the wheat genotypes namely soonot 5 and attila-7, among the other irrigated genotypes used in this study, were rated higher in bread baking quality and were even comparable to the standard imported flour which indicated that nigerian grown wheat can be used to produce bread © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 march, 2020 revised 3 october, 2020 accepted 14 october, 2020 keywords: nigerian wheat physical proximate baking quality and bread abubakar and zigla: nutritional and quality assessment of some irrigated wheat genotypes in nigeria. azojete, 17(1):27-34 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 28 billion indicating the growing dependence on wheat which needs to be curtailed. there is therefore the need to encourage local wheat production and to develop improved nigerian grown varieties through biotechnology and agronomic practices in order to reduce the cost of importation expenses and to be more self-reliant. the production of locally grown wheat will lead to increase self-sufficiency, employment generation and increase in income through production, processing and value addition. bread and allied products are the major forms in which cereal grains particularly wheat is consumed worldwide and therefore, they occupy an important position in the diets of many people, (kent-jones and amos, 1967). the acceptability of these products depends on their quality, which affects their final composition of the flour, recipe and the baking procedures, (maga 1975). baking quality is a criterion used to determine the quality and suitability of wheat. the baking quality depends on types of wheat uses and processing conditions. strong (hard) wheat are considered of the higher quality and suitable for bread making, where most of cakes made from soft wheat flour. baking quality is determined by the rheological properties of wheat flour (ktenioudaki et al., 2010). the rheological property of wheat flour is essential because it determines other physical characteristics such as dough (baking) volume and sensory attributes (muller, 1975). bread production accounts for about 75% of the total wheat flour usage while confectioneries account for about 25%, (ohinmain, 2014). about 6.2 billion loaves of bread are supplied into the nigerian market annually from over 20,000 bakeries, estimated at about n105 trillion per annum (ohinmain, 2014). the federal government of nigeria had tried to find ways of reducing importation through policies and regulations over the years, such as substitution of wheat with cassava (butt et al., 2011; ohinmain, 2014). there had been previous attempts to boost the production of wheat in the country, in order to reduce the dependency on wheat importation, and recently the agricultural transformation agenda (ata) of the federal government and african development bank (afdb) and the sponsored support to agricultural research and development to strategic crops (sard-sc) wheat project. however, success of these drives hinges mainly on the development and release of high yielding and good quality wheat varieties. several, irrigated wheat genotypes had been identified and are currently at prerelease-advanced stage. nutritional and baking quality tests are mandatory requirements for the release of varieties in nigeria so as to encourage the production and consumption of nigerian grown wheat. the aim of this study is to assess the end-use qualities of some advanced irrigated wheat genotypes, and to identify and release those that possess good physical, milling, proximate, baking, sensory, functional, rheological and textural qualities. 2. materials and methods eleven locally grown wheat genotypes were evaluated for grain, flour and bread baking qualities using standard procedures. the imported wheat flour (hard red winter) was obtained from golden penny company, nigeria as a control. the physical characteristics of wheat grains which includes, grain weight, kernel length and thickness were determined using standard methods (williams et al., 1986). flour extraction was performed by brabender quadrumat senior mill (german model brabender ohg d47055 duisburg, type 880200) at lake chad research institute, maiduguri. the wet and dry gluten were determined by hand washing method for wet gluten and kept in hot air oven (gallenkamp bs oven 250, size 2, germany) set at 100°c to dry for 24 h for dry gluten. the methods described by aacc (1973), and aoac (2000) were followed to determine the moisture, crude fat, crude protein and ash contents in the different genotypes. carbohydrate was determined by difference (egan et al., 1981). bread baking quality was done using straight dough, single mixing and fermentation process and resulting loaves were evaluated in terms of the volume, weight, crust and crumb characteristics sensory quality (consumer acceptability) of the bread samples was done using a panel of 25 trained persons and a 9-point hedonic scale (where 1 = extremely unacceptable and 9 = extremely acceptable) was used, (iwe, 2010). attributes evaluated include bread appearance, crust color, crumb color, texture, taste, chewability, flavour and overall acceptability. keeping quality of packaged bread samples were evaluated on samples kept at ambient conditions for 5days, with microbiology and physical evaluations (weight, moisture, texture) were done at the start and end of the storage period. resulting data were analyzed using analysis of variance (anova) and mean separation was done using least significant difference (lsd) test, at 5% level of probability (p<0.05), (duncan, 1955). arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):27-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 29 3. results and discussion 3.1 physical characteristics of eleven genotypes of irrigated wheat table 1 show the results on grain physical characteristics of the fourteen irrigated wheat genotypes. the irrigated wheat genotypes did not differ significantly (p>0.05) with respect to grain physical characteristics (table 1). grain physical characteristics correlates very well with flour yield and quality as reported by various workers, pena, (1995); nkama and bijik (2001); dziki and laskowski, (2005); nuttall et al., (2017). the result for the physical properties of the irrigated wheat grains is shown in table 1. the 1000 grain weight indicated that there were significant differences among samples. it observed that the values ranged from 33.46-38.88g with florkwa-2 having the highest value while pastor-2 had the lowest grain weight of 33.46g. the grain length indicated that there were significant differences among samples which ranged from 5.96-6.47mm with hubara-2 having the highest value of 6.47mm while pastor-2 had the lowest length. the grain volume indicated that there were significant differences among samples as the grain volume ranged from 27.24 to 31.13mm3 with katilla-17 having the highest value of 31.13mm3 while soonot-5 had the lowest volume. grain thickness indicated that there were also significant differences among samples which indicated that the thickness width ranged from 3.06mm with soonot-5 having the lowest thickness while angi-2 had the highest thickness value. the grain density indicated that there were significant differences among samples and these values ranged from 1.20-1.31g/ml with atilla-7 having the lowest density value while soonot-5 had the highest value for density with 1.20g/ml. as the result indicates, the values are within the range reported by workers for various physical properties of wheat varieties, (pomeranz, 1971 and kent, 1983). table 1. physical characteristics of eleven genotypes of irrigated wheat genotype length thickness l000-grain weight (g) 1000-kernel volume (mm3) kernel density attila-7 6.18 c 3.61a 34.30i 28.54 e 1.20e hubara-1 6.18c 3.59 a 35.52 h 28.56e 1.24d pastor-1 6.26bc 3.56a 36.07f 28.57e 1.26c pastor-2 5.97d 3.59a 33.46 j 27.58f 1.21e angi-2 6.31b 3.63a 38.16b 30.25c 1.26c kauz’s’ 6.28bc 3.25b 37.28e 30.16c 1.24d hubara-2 6.47a 3.30b 37.96c 30.15c 1.26c florkwa -2 6.18c 3.22b 38.88a 30.64b 1.26c katila-17 6.28bc 3.25b 38.78a 31.13a 1.24d hubara-3 6.20bc 3.27b 37.57d 29.26d 1.28b soonot5 6.28bc 3.06c 35.75g 27.24g 1.31a values are means of duplicate determinations and values with different superscript along the columns are significantly different (p<0.05) 3.2 proximate composition of eleven genotypes of irrigated wheat the irrigated wheat genotypes expressed significant (p<0.05) differences in flour proximate quality. the result of proximate composition is as shown in table 2 and the results were within the range reported by various workers, pomeranz, (1971); kent, (1984), nkama, (1995); dziki and laskowski, (2005); and anon, (1982). the result of the crude protein ranged from 11.35% 10.45%. kattilla-17 had the highest protein content while kauz had the lowest protein content. the protein content was significantly higher in hubara-1 (15.40%), kauz’s’ (16.35%), and soonot 5 (15.85%). the quality of wheat flour for breadmaking is generally evaluated by the amount of protein and quality of gluten; and wheat is unique among cereals, because it contains gluten which has the characteristic of being elastic when mixed with water and retains the gas developed during dough fermentation (khatkar et al., 1995). the moisture content ranged from 9.35-11.65% with atilla-7 having the least moisture content while angui-2 had the highest abubakar and zigla: nutritional and quality assessment of some irrigated wheat genotypes in nigeria. azojete, 17(1):27-34 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 30 moisture content. the crude fibre ranged from 2.90% for kauz’s’ to 3.10% for angui1. the ash content ranged from 1.25% for hubara1 and katila7 to 1.55% for pastor. the fat content ranged from 1.00% for hubara-2 to hubara1 with 1.30% while carbohydrate content ranged from 67.60% for hubara-1 to 72.75% for katila-l7 (table 2). table 2 proximate composition of eleven genotypes of irrigated wheat genotype moisture protein fibre fat ash carbohydrate attila-7 9.35g 14.65d 2.95ab 1.25ab 1.50a 70.30 c hubara-1 11.20b 15.40c 3.05ab 1.30 a 1.45ab 67.60i pastor-1 11.37b 13.45g 3.10a 1.25ab 1.50a 69.33ef pastor-2 10.50d 15.65bc 2.95ab 1.30a 1.55a 68.05hi angi-2 11.65a 13.75f 3.10a 1.17abc 1.46a 68.86fg kauz’s’ 9.70f 16.41a 2.90b 1.15abc 1.30bc 68.53gh hubara-2 10.70c 14.45de 3.05ab 1.00c 1.25c 69.55de florkwa -2 10.20e 12.60h 2.95ab 1.00c 1.45ab 71.80b katila-17 10.50d 11.35i 3.00ab 1.15abc 1.25c 72.75a hubara-3 10.10e 14.30e 3.10a 1.10bc 1.30bc 70.10cd soonot5 10.65cd 15.85b 3.00ab 1.20ab 1.45ab 67.85i values are means of duplicate determinations and values with different superscript along the columns are significantly different (p<0.05) 3.3 flour extraction, wet and dry gluten eleven genotypes of irrigated wheat the result for flour extraction, wet and dry gluten fourteen genotypes of irrigated wheat is shown in table 3. similar results have also been reported by aluko, et al., (1990); bijik (2001); and nkama et al. (1998). the result of flour extraction for the irrigated genotypes indicated that there are significant differences among the wheat samples. this could be attributed to the difference in the genetic characteristics and physical quality of each grain and therefore, some wheat grains have higher floury endosperm than other wheat grains. the result of the flour extraction ranged from 66.25% for angui-2 to 78.55% for reyna 28. (table 3). florkwa-2, soonot-5, hubara-3, and angui-2 are among the irrigated wheat with flour yield above 75% and were the best performing genotypes on the field. these fall within the standard range of flour yield reported by li and posner, (1987); li and posner, (1989). milling is very important in wheat processing, and hard and soft wheat with high protein content (>11%) are preferred in wetmilling to co-produce vital gluten and starch (khatkar et al., 1995; tronsmo et al., 2003). the flour yield and flour properties are strongly related to wheat kernel properties, especially to the kernel colour, vitreousness, mass, shape, test weight, density, size and size uniformity are taken into consideration during wheat milling value evaluation (dendy and dobraszczyk, 2001;abdulvahit, 2004; bordes et al., 2008). the wet and dry gluten contents differed significantly among irrigated genotypes. the wet gluten ranged from 18.60% for pastor2 to 46.40% for angui2 while the dry gluten content ranged from 10.05% for angui2 to 14.70% for florkwa-2 with angi-2, florkwa-2 and hubara-3 having higher gluten content than the other genotypes (table 3). as the result indicates, the values are within the range reported by workers for various wheat varieties, (pomeranz, 1971 and kent, 1983) and also that nigerian wheat can be comparable to imported wheat. arid zone journal of engineering, technology and environment, march, 2021; vol. 17(1):27-34. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 31 table 3: flour extraction, wet and dry gluten of the eleven genotypes of irrigated wheat genotype flour extraction (%) wet gluten (%) dry gluten (%) attila-7 69.40bcd 36.15a 12.35ab hubara-1 67.30cd 32.05ab 10.10b pastor-1 73.65abcd 33.00ab 10.70ab pastor-2 73.45abcd 18.60b 10.11b angi-2 66.25d 46.40a 10.05b kauz’s’ 72.70abcd 40.05a 12.80ab hubara-2 71.30abcd 41.40a 13.35ab florkwa -2 78.55a 45.35a 14.70a katila-17 72.57abcd 43.15a 13.80ab hubara-3 76.69ab 46.10a 14.60a soonot5 76.25abc 33.03ab 10.60ab values are means of duplicate determinations and values with different superscript along the columns are significantly different (p<0.05) 3.4 bread sensory evaluation table 4 showed the sensory evaluation of the bread samples from the irrigated wheat and the control. attributes evaluated include bread appearance, crust color, crumb color, texture, taste, chewability, flavor and overall acceptability. although the result indicates significant differences among the samples (p<0.05), the values were closely ranged, and the bread samples were all accepted by the panels for all parameters determined. the appearance ranged from 6.70 for soonot-5 cettia to 820 for the control. the crust colour ranged from 6.15 for atilla-7 to 8.20 for the control. the crumb colour ranged from 6.60 atilla-7 to 8.2 for the control. the taste ranged from 6.95 for angi-2 to 8.40 for the control. the texture ranged from 6.30 for angi2 to 7.95 for the control. the chewability values ranged from 6.60 for angi-2 to 8.25 for the control. the flavor ranged from 6.60 atilla7 to 8.10 for the control. the overall acceptability ranged from 7.10 for angi to 8.35 for the control sample. the bread produced from the commercial wheat flour has shown to have better qualities than the nigerian grown wheat, and this could be attributed to additives in commercial flour that was not added to the locally grown nigerian wheat test genotypes. notwithstanding, the results shows that nigerian grown wheat can perform well as the imported wheat in terms of bread quality. table 4: bread sensory evaluation using 9-point hedonic scale of the eleven genotypes of irrigated wheat flour and the control flour samples appearance/ loaf shape crust colour crumb colour taste texture chewability flavor overall acceptability attila-7 7.10bc 6.15h 6.60c 7.00c 7.10bc 7.00cd 6.60d 7.35bc hubara-1 7.20bc 6.85cdefg 7.05bc 7.40b 7.00bc 6.90de 7.20b 7.20c pastor-1 7.05bc 6.70defg 7.05bc 7.15bc 6.60de 6.95cde 7.05bc 7.30bc pastor-2 6.95bc 6.65efg 7.05bc 7.25bc 6.55de 7.00cd 6.90bcd 7.30bc angi-2 7.10bc 7.00bcdef 7.10bc 6.95c 6.30e 6.60e 7.20b 7.70b kauz’s’ 7.20bc 7.30b 7.00bc 7.20bc 6.75cd 7.05bcd 6.80bcd 7.20c hubara-2 7.25b 7.05bcde 7.20b 6.95c 7.20b 7.40b 7.20b 7.15c florkwa -2 7.25b 6.50gh 6.65c 7.05c 7.25b 6.90de 7.15bc 7.10c katila-17 7.00bc 6.60fg 6.80bc 7.00c 7.15b 7.30bc 6.85bcd 7.35bc hubara-3 7.20bc 7.25bc 6.80bc 6.95c 7.15b 7.00cd 6.75cd 7.25bc soonot-5 6.70c 7.10bcd 6.65c 7.20bc 7.10bc 7.05bcd 7.15bc 7.10c control sample 8.20a 8.20a 8.20a 8.40a 7.95a 8.25a 8.10a 8.35a abubakar and zigla: nutritional and quality assessment of some irrigated wheat genotypes in nigeria. azojete, 17(1):27-34 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 32 values are means of duplicate determinations and values with different superscript along the columns are significantly different (p<0.05) 4. conclusion this study has shown that wheat can be grown in nigeria under irrigated conditions in some northern parts of the country. the sensory evaluation indicated that the bread produced from the nigerian grown wheat performed well along with the control, but the control sample had a higher rating than the nigerian grown wheat. this could be attributed to the improved processing conditions of the larger commercial mills and probably due to the addition of additives for the control sample which resulted in bread with higher characteristics. despite these factors, it could be observed that the nigerian wheat compared favourably with the imported wheat and can be used to produce baked products especially bread and other wheat products with improved processing technologies similar to the foreign wheat. therefore, it nigerian grown wheat should be patronized by both millers and individuals to reduce the importation of wheat into the country acknowledgement the authors wish to appreciate the the collaborations of ‘support to agricultural research for development of strategic crops’ (sard-sc) wheat project , african development bank, (afdb), federal government of nigeria, lake chad research institute, maiduguri, and federal institute for rawmaterial research, oshodi (firro), lagos. references aaac. 1973, 2000. american association of analytical chemist. u.s.a, washington dc. aacc. 1973. official methods of analysis. 14th chemists, st. paul.mn. usa .aacc .inc. abdeighafor, rf., mustafa, ai., ibrahim, amh. and krishnan, pg. 2010. quality of bread from composite flour of sorghum and hard white wheat. advanced journal of food science and technology, 3: 9-15. abdulvahit s. 2004. wet milling of wheat flour: industrial processes and small-scale test methods. lebensm.wiss, technologie. 37: 499-105. aluko, re., olugbeu, lb., orakwe, fc. and dunmade, vb. 1990. baking quality of nigerian wheat. in; 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(valencia, ja., salako, ea., ikwelle, mc., aminukano, m., abubakar, iu., miko, s. and jayyum j. eds). lcri, iar and unimaid, maiduguri. nkama, i., iliyas, a. and jato, a. 1995. studies on the preparation and nutrient composition of kunun gyada a traditional nigerian groundnut cereal-based weaning food. food nutrition bulletin, 16: 238 240. nuttall, jg., o’leary, gj., panozzo, jf., walker, ck., barlow, km. and fitzgerald, gj. 2017. models of grain quality in wheat-a review. field crops research, 202: 136-145. odedeji, jo. and adeleke, ro. 2010. pasting characteristics of wheat and sweet potato flour blends. pakistan journal of nutrition, 9(6): 555 557. ohinmain, ei. 2014. the prospects and challenges of composite flour for bread production in nigeria. global journal of human-social science, 14(3): 43-52. pena, rj. 1995. quality improvement of wheat and triticale. in: wheat breeding at cimmyt: commemorating 50 years of research in mexico for global wheat improvement. wheat special report abubakar and zigla: nutritional and quality assessment of some irrigated wheat genotypes in nigeria. azojete, 17(1):27-34 issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: fatidupli@yahoo.com 34 no. 29. mexico, d.f., cimmyt. rajaram, s. and hatel, gp. and popper, l (eds). verlagagrimedia, pp. 193-198. pomeranz, y. 1971. wheat chemistry and technology. american association of cereal chemists inc., st. paul, minnesota. shittu, ta., raji, ao. and sanni, lo. 2007. bread from composite cassava-wheat flour: 1. effect of baking time and temperature on some physical properties of bread loaf. food research international, 40: 280 290. tronsmo, km., faergestad, em., schofield, jd. and magnus, s. 2003. wheat protein quality in relation to baking performance evaluated by the chorleywood bread process and a hearth bread baking test. cereal science, 38: 205–215. williams, p., el-haramein, fj., nakkoul, h. and rihawi, s. 1986. crop quality evaluation methods and guidelines, publishers. icarda, syria, pp. 1-31. arid zone journal of engineering, technology & environment azojete december 2020. vol. 16(4):773-784 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 773 original research article performance evaluation of solar oven using kapokwool as insulation material a. t. abdulrahim1*, s. abdulkareem2, m. haruna1, a. s. abdulraheem1, f. a. oluwole1, g. m. ngala1 and u. a. mukhtar1 1department of mechanical engineering, university of maiduguri, p.m.b. 1069 maiduguri, nigeria 2department of mechanical engineering, university of ilorin, p.m.b. 1515, ilorin, nigeria *corresponding author’s email address: engrabdulrahimat@gmail.com 1.0 introduction the use of solar thermal devices such as solar box oven and solar brick oven are on in the increase because they offered no fuel cost, environmentally friendly, easily operable among other advantages. the basic concept of solar oven is simply to trap and store solar energy inside a box. the box’s upper side is covered by a transparent material and well-insulated with a reflector at the top which could be used to boosts the incident energy and also functions as an outer cover when the oven is not in use (sayigh, 1977; suharta, 1994; mukherjee and chakrabarti, 2004). the challenges of producing reliable and competitively economic solar box for household purposes have led to intense research work in all areas of improving component parts of a solar box cooker (suharta et al., 1998; abdulrahim et al., 2015; maina et al., 2016; qandil et al., 2018). solar box oven is among common devices which utilize insulation for lagging. thermal insulations play a major role in the design and production of energy efficient process, devices and systems because of their ability to retards heat transfer by acting as barriers in the path of heat flow. previous solar box cookers have used cotton, saw dust, and fibre-glass as insulation materials (suharta et al., 1998; abdulrahim et al., 2015; adewole et al., 2015; maina et al., 2016; adewumi et al., 2019). cotton is widely used in cloth making and, in the hospital, while saw dust is used in stove for cooking as well as in making furniture products which could reduce their availability. fibre-glass is a synthetic fiber with high toxin ratings and usually imported into article information abstract solar ovens are among common devices which utilize insulation materials because of their ability to retards heat transfer by acting as barriers in the path of heat flow. previous solar box cookers have used cotton, saw dust, and fibre-glass as insulation materials but none has used kapok wool despite its potential. this study is aimed at the performance evaluation of solar oven using kapok wool as the insulation material. the solar box oven designed is of the size 59 x 56 x 36cm dimensions made of plywood, with an aperture area of 3304cm2 double glass cover and an oven’s floor area of 1225cm2 made of aluminum. kapok wool was used to line the oven’s walls and floor serving as insulator. the solar box oven was tested at the university of maiduguri, borno state, nigeria. it was tested without load to determine its stagnation temperature and to check its endurance under stagnation conditions. similarly, a water boiling test was conducted to cook rice and beans. the results show that maximum stagnation temperature was 165.1°c and maximum overall daily thermal efficiency of 19.44% was achieved on a clear day test without reflector. the field test of the solar oven demonstrated its ability to cook rice and beans well with 1 kg of rice cooked under 2 hours, while 1 kg of beans was cooked under 1 hour 45 minutes on the same day. this performance demonstrated the suitability of kapok wool as insulation material for solar ovens. © 2020 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 july, 2019 revised 26 october, 2020 accepted 8 november, 2020. keywords: solar oven insulation materials kapok wool stagnation temperature efficiency mailto:engrabdulrahimat@gmail.com http://www.azojete.com.ng abdulrahim et al: performance evaluation of solar oven using kapok wool as insulation material. azojete,16(4):773-784. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 774 the country. natural fibers which have low to zero toxin ratings, easy to reuse and dispose with significant health benefits have been recognized as possible alternative. possible material for replacing these insulation materials was conceived, and the locally available insulating materials that have been considered in this study is kapok wool. kapok is a natural polymer and it is a unicellular fibres like cotton with a thermal conductivity of 0.035wm-1k-1 (ayugi, 2011). voumbo et al. (2010) study shows that the kapok's conductivity dregs between 0.03 and 0.04 w/m.ºk for density between 5 and 40 kg/m3, and taking into account year average diffusivity of 17.1x10g7 m2/s, they concluded that kapok is a good heat insulator. typical analyses indicate that kapok fibers comprises of 64% cellulose ((c6h10o5)n), 13% lignin and 23% pentosan (chalarrekij et al., 2011). besides these constituents, they also contain wax cutin on the fiber surface which makes them water repellent (chalarrekij et al., 2011). purnawati et al. (2018) described kapok fibers as having a hollow structure with a thin fiber wall and a large lumen filled with air which led to low fiber density, and that hydrophobic properties are associated with the wax content of the fiber surface. meiwu et al. (2010) and mwaikambo (2006) stated that kapok was the lightest fiber in the world. studies have also confirmed that kapok fibers have excellent thermal and acoustic insulating properties, high buoyancy, and good absorbency for oil and other non-polar liquids distinguishing kapok from most other cellulosic fibers (wang et al., 2012; lim and huang, 2007; zheng et al., 2015). purnawati et al. (2018) have explained that there are three types of weight/mass loss during thermal degradation: water removal (drying), organic matter release (devolatilization), and bonded-carbon oxidation (slow combustion). in thermal degradation, the first aspect is water desorption in the temperature range of 29.9°c‒65.1°c for kapok fiber and it is endothermic. the second and third peaks are exothermic, and they occurred at 322.8°c and 444.1°c respectively for kapok fiber. the third peak expressed the final decomposition of cellulose as well as lignin degradation. gaan et al. (2009) also identified three stages of cellulose thermal decomposition. the first stage occurred at a temperature of 100°c and represented the release of water. the second stage, at a temperature of 360°c, was identified as a rapid dehydration and decarboxylation reaction that produced combustible gases such as aldehydes, ketones and ethers. the third stage, at 400°c, was classified as the second stage of decomposition and charcoal formation. lignin degradation occurred at a temperature of 250°c‒500°c because of its high stability which made it difficult to decompose (poletto et al., 2012). while a great deal has been published about solar box ovens or solar box cookers that use other materials as insulators, there is hardly any mention of one using kapok wool as insulator. the reason is not that kapok wool is not a good insulator, but they are unexplored. hence, this study would conduct a performance evaluation of solar oven using kapok wool as an insulation material. 2. materials and method 2.1 materials the design concept adopted for the solar oven following suharta et al. (1998). the constructed solar box oven consisted of four components, namely box made of wood, absorber plate made of aluminum sheet which was painted black at its upper surface and kapok wool was used as the insulator. the solar box oven is of the size 59 x 56 x 36cm dimensions with an aperture area of 3304cm2 and absorber plate made of aluminum sheet of 0.4mm thick with an oven’s floor area of 1225cm2, while its total surface area was 5134.6 cm2 and a height of 19cm as shown in figure 1. kapok wool was used to line the oven’s walls and floor. kapok pod was obtained at the university of maiduguri, maiduguri, nigeria from kapok trees (figure 2a). the http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):773-784. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 775 kapok wool was removed from its pod and hand picking of the kapok seed in the kapok wool was done and the kapok wool was then brushed to remove other unwanted particles (figure 2b). figure 1: exploded view of solar box oven. (a) (b) figure 2: kapok source and processing: (a) kapok pod; (b) kapok wool, seed, exocarp and other unwanted particles the top view of the solar box oven is shown in figure 3a. the kapok wool of average thickness of 100mm was put at the sides of the absorber plate and kapok wool of thickness 40mm at the bottom of the absorber plate. kapok wool was also put inside the solar box oven entrance cover to serve as insulation material as shown in figure 3b, c, d. a total mass of 2.026 kg of kapok wool was used to cover a total volume of 0.0469 m3. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: performance evaluation of solar oven using kapok wool as insulation material. azojete,16(4):773-784. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 776 (a) top view of solar box oven (b) bottom view of solar box oven (c ) solar box filed kapok insulator (d) solar box’s door cover filled with kapok figure 3: solar box oven stuffed with kapok wool as insulation (a, b, c and d) thermometer data recorder (3 channels, model: mtm-380sd, accuracy 0.1°c) was used to monitor the temperature profiles in the oven’s floor (absorber plate) and water temperature. the solar power meter (model: spm-1116sd, accuracy 0.1w/m2) was used for measuring solar insolation while aerometer (model: abh-4224, accuracy 0.1m/s) was used to measure the wind speed and ambient temperature. 2.2 method the solar box oven as shown in figure 4 was tested at the entrepreneurship centre, university of maiduguri, borno state nigeria without a load to determine its stagnation temperature and to check the oven endurance under stagnation conditions. water boiling test and cooking of rice and beans was also carried out using the solar oven. the solar oven is preheated for 30 minutes using solar energy to remove vapor inside the oven which can limit the rate of the cooking performance. then, the loading test was done by placing the cylindrical pot covered with a lid filled with 1 litre of water inside the solar box oven. and for cooking food, the food items were put inside the cylindrical pot covered with a lid filled with water inside the solar box oven. thermometer data recorder (3 channels, model: mtm-380sd, accuracy 0.1°c) was used to monitor the temperature profiles in the oven’s floor (absorber plate) and water temperature. the solar insolation was measured using solar power meter (model: spm1116sd, accuracy 0.1w/m2) while the wind speed and ambient temperature (t4) were measured using aerometer (model: abh-4224, accuracy 0.1m/s). figure 4 shows the solar box oven under test. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):773-784. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 777 figure 4: solar box oven under test performance tests were repeated on the same solar oven, and the performance evaluation carried out were: i. stagnation temperature, and ii. solar box oven efficiency. the overall thermal efficiency of the solar box oven is expressed mathematically by khalifa et al. (2005) and olwi et al. (1993) as reported in el-sebaii and ibrahim (2005) as: ƞu = mwcw iavac ∆t ∆t (1) where ƞu represents the overall thermal efficiency of the solar box oven, mw mass of water (kg), cw specific heat capacity of water (j/kg°c), ∆t temperature difference between the maximum of the cooking fluid and the ambient air temperature, ac the aperture area (m2) of the oven, ∆t time required to achieve the maximum temperature of the cooking fluid, iav the average solar radiation intensity (w/m2) during time interval ∆t. 3.0 results and discussion 3.1 preliminary test the results of the stagnation test of the solar oven at no load is shown in figure 5, and the maximum temperature attained was 148.3oc at 13:00 hours (1:00pm). this is due to the fact that on a clear sunshine the solar energy increase to a maximum at solar noon and the solar collector received this energy and its distribution within the solar box is a function of time. maximum wind speed recorded was 1.7m/s which has not exceeded 2.5m/s for which the data shall be discarded if such value lasted for more than 10 minutes (asae s580.1, 2013). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: performance evaluation of solar oven using kapok wool as insulation material. azojete,16(4):773-784. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 778 figure 5: stagnation test of solar oven at no-load at university of maiduguri, maiduguri, nigeria. the results of 1 litre of water boiling test using the solar oven is shown in figure 6. the water temperature reached a maximum of 99.8°c at 12:00 noon. this could be regarded as the boiling temperature of the water, and since most food can be fully cooked at the temperature range of 60 90°c the solar oven performance is good and suitable for cooking. the overall daily efficiency of the solar oven (ƞ) was calculated using equation (1) to be 11.6% where mw = 1kg, cw = 4220 j/(kg.k), ac=0.3304m2, iav = 857.28w/m2, ∆t=55.86°c, and ∆t=7200s. figure 6: solar box oven water boiling test (1 litre of water) at university of maiduguri, maiduguri, nigeria. tables 1 and 2 show the results obtained when the solar oven was used to cook 1 kg of rice and beans each where cooking times, oven plate temperatures and ambient conditions of temperature and solar insolation were noted. rice was cooked under 2 hours after placed inside the oven, and beans was cooked under 1 hour and 45 minutes after placed inside the oven. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):773-784. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 779 table 1: cooking test using rice as food item time (s) oven plate temperature tp (°c) ambient temperature ta (°c) solar insolation i (w/m2) wind speed v (m/s) 9:30 72.2 39.0 912.5 0.5 9:45 79.4 41.2 924.5 0.2 10:00 86.8 40.6 937.6 0.1 10:15 93.8 40.1 930.6 0.0 10:30 100.4 40.8 952.5 0.0 10:45 106.6 41.9 948.0 0.0 11:00 108.5 43.1 943.4 0.0 11:15 114.4 42.5 948.8 0.0 11:30 119.2 43.2 961.5 0.0 rice cooked as at 11:30 am table 2: cooking test using beans as food item time (s) oven temperature tp (°c) ambient temperature ta (°c) solar insolation i (w/m2) wind speed v (m/s) 12:00 106.7 46.0 925.1 0.1 12:15 104.9 46.9 930.3 0.0 12:30 109.0 47.3 932.0 0.0 12:45 114.0 43.9 961.5 0.0 1:00 117.0 46.3 949.7 0.0 1:15 119.2 46.8 941.5 0.0 1:30 119.2 45.8 935.2 0.0 1:45 118.8 49.0 970.6 0.0 beans cooked as at 1:45 pm 3.2 stagnation temperature tests during the repeated tests carried, temperatures of the absorber plate of the oven during the day having fluctuating insolation is shown in figure 7. the plots of oven plate temperature (tp), ambient temperature (ta) and solar insolation (ir) indicate that the solar insolation recorded a minimum of 409.5 w/m2 at 10:15 am and a maximum of 963.6 w/m2 at 11:10am. the maximum absorber plate temperature obtained was 151.1°c recorded at 12:55pm, the temperature between the absorber plate and the ambient temperatures was 109.1°c at 12:55pm, while the maximum ambient air temperature is 44.3°c. maximum wind speed recorded was 1.9m/s which has not exceeded 2.5m/s for which the data shall be discarded if such value lasted for more than 10 minutes (asae s580.1, 2013). these results have demonstrated the suitability of the solar oven for heating water and cooking even during fluctuated weather condition. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: performance evaluation of solar oven using kapok wool as insulation material. azojete,16(4):773-784. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 780 figure 7: stagnation test (fluctuation insolation) at university of maiduguri, maiduguri, nigeria. (tp = oven plate temperature, ta = ambient temperature, ir = solar insolation). also, the temperature distribution inside the oven during clear weather day (14/04/2020) is shown in figure 8. the plots of tp, ta, and ir indicate that the solar insolation (ir) reached a maximum of 1056 w/m2 at 11.35am while the maximum absorber plate temperature (tp) attained was 165.1°c at 12:10pm and maximum ambient temperature (ta) recorded was 46.3°c at 13:05pm. the temperature between the oven plate and the ambient temperature was 123.7°c at 12:10pm. figure 8: stagnation test (clear weather condition) at university of maiduguri, maiduguri, nigeria. (tp = oven plate temperature, ta = ambient temperature, ir = solar insolation). the oven reached a maximum temperature of 151.1°c on the day of fluctuating insolation, and a maximum oven temperature of 165.1°c on the clear weather day. the temperature attained on a clear weather day is higher than the corresponding temperature on fluctuating insolation day by 14°c. this is because at any moment clouds intercept the sun, it decreases the energy to a low value due to the diffuse sky radiation (sayigh, 1977). earlier studies have reported difference levels of solar ovens (cookers) performances with respect to stagnation temperatures attained. these include, suharta et al. (1998) who reported that one of their http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):773-784. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 781 solar ovens with reflector reached 183°c while another one attained a temperature of 202°c. and adewumi et al. (2019) also reported that their solar cooker with no reflector attained a temperature of 69.8°c while the one with four reflectors attained a temperature of 175°c. in the case of adewole et al. (2015), the stagnation temperature attained by their solar cooker with reflectors was 76°c. though there are those solar ovens with higher stagnation temperatures than that of the present study as reported, it could be observed that such solar cookers were installed with reflectors which boosts the incident energy thereby increasing the heat energy available to the absorber plate. the maximum stagnation temperature of 165.1°c attained in this study could cook most foods fully because temperature range of 60-90°c is required to cook any food (folaranmi, 2013), and the oven endurance under stagnation conditions has also been confirmed. 3.3 start cook time suharta et al. (1998) defined a ‘start cook point’ as time for a standard load of 1.2 l of water to reach 80°c. since water has a higher specific heat than any food, it provides the heaviest load for the performance test. the boiling test results are presented in figure 6. the temperature of the water heated in the oven reached 80°c at 10:31am. the performance was quite similar to the performance of the one reported by suharta et al. (1998) in which the solar oven attained 80°c at 10:25am though his own uses one reflector. it has been reported by suharta et al. (1998) that users can generally start cooking 1 h before the ‘start cook point’, and for this oven, at 9:31am. figure 9: boiling test on a clear weather condition at university of maiduguri, maiduguri, nigeria. (tw = water temperature, tp = oven plate temperature, ta = ambient temperature, ir = solar insolation). the results of 1.2kg of water boiling test using the solar oven on 15th april, 2020 is shown in figure 9. the water temperature reached a maximum of 99.6°c at 11:25am. the overall daily efficiency of the solar oven (ƞ) was calculated using equation (1) to be 9.6% where mw=1.2kg, cw = 4220 j/(kg.k), ac = 0.3304m2, iav= 971.22w/m2, ∆t=58.6°c, and ∆t = 9600s. the results of 2.643kg of water boiling test using the solar oven on 16th april, 2020 is shown in figure 10. the water temperature reached a maximum of 99.6°c at 1:00pm. the overall daily efficiency of the solar oven (ƞ) was calculated using equation (1) to be 18.8% where mw = 2.643kg, cw = 4220 j/(kg.k), ac = 0.3304m2, iav=1031.52w/m2, ∆t = 55.22°c, and ∆t = 9600s. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: performance evaluation of solar oven using kapok wool as insulation material. azojete,16(4):773-784. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 782 figure 10: boiling test of 2.643 litres of water on clear weather condition at university of maiduguri, maiduguri, nigeria. (tw = water temperature, tp = oven plate temperature, ta = ambient temperature, ir= solar insolation) the results of 2.313kg of water boiling test using the solar oven on 17th april, 2020 is shown in figure 11. the water temperature reached a maximum of 99.1°c at 12:10pm. the overall daily efficiency of the solar oven (ƞ) was calculated using equation (1) to be 19.44% where mw = 2.312kg, cw = 4220 j/(kg.k), ac = 0.3304m2, iav=1076.14w/m2, ∆t=55.26°c, and ∆t = 7800s. figure 11: water boiling test of 2.313kg of water on a clear weather condition at university of maiduguri, maiduguri, nigeria. the maximum overall daily efficiency obtained during the various tests carried out was 19.44% and it is an indication of good performance and better heat retention ability of the cooker since the solar oven is without reflector. though solar thermal efficiency of 33% have been reported by adewole et al. (2015) based on performance of a reflected solar box cooker implemented in ile-ife, nigeria, adewumi et al. (2019) reported the performance of solar cookers tested at ilorin, nigeria and confirmed that the efficiency of the solar cookers increases with increase number of reflectors from 18.72% (no reflector) to 72.22% (four reflectors). all these reported cases above used reflectors, so if one or more reflectors are introduced to the solar oven in this study, there will be increase in thermal efficiency. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2020; vol. 16(4):773-784. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 783 4.0 conclusion the use of loose kapok wool as insulation material in solar oven has been evaluated in this study. the results based on the performance evaluation carried out in maiduguri, nigeria show that it can serve as a good insulator. the use of kapok wool has ensured insulation and increases oven temperature. the maximum stagnation temperatures obtained were 151.1°c on day of fluctuating insolation and 165.1°c on clear weather day. maximum overall daily thermal efficiency of 19.44% was obtained on a clear day test without reflector. the field test of the solar oven has also demonstrated its ability to cook rice and beans well. for example, 1 kg rice was cooked between 9:30 and 11:30am while 1 kg beans cooked between 12:00 noon and 1:45pm. the solar oven performance has demonstrated the suitability of kapok wool as insulation material for solar ovens and it is here by recommended for use for this purpose. acknowledgements the authors would like to acknowledge the tetfund through the ibr research grant no. tetfund/dess/unimaid/maiduguri/rp/vol.ii at university of maiduguri, maiduguri, nigeria for providing financial support for the study. references. abdulrahim, at., oumarou, mb., rufus, oc., mbaya, il. and sunday, oo. 2015. development of an automated tracker for the enhancement of energy availability in a solar box oven. the international journal of engineering and science (ijes), 4(5): 12 18. adewole, bz., popoola, ot. and asere, aa. 2015. thermal performance of a reflected based solar box cooker implemented in ile-ife, nigeria. international journal of energy engineering, 5(5): 95-101. adewuni, sd., abdulrahim, at., adeleke, aa., ikubanni, pp. and agboola, oo. 2019. performance evaluation of solar cooker made from locally sourced materials. international journal of mechanical and production engineering research and development (ijmperd), 9(2): 299-310. aguyi, g. 2011. thermal properties of selected materials for thermal insulations in uganda. department of physics, makerere university, makerere. asae s580.1, 2013. testing and reporting solar cooker performance. american society of agricultural and biological engineers, asabe standard, usa. ashby, mf. and jones, drh. 1998. engineering materials 2: an introduction to microstructures, processing and design. butterworth – heinemann, oxford, uk. chaiarrekij, s., apirakchaisskul, a., suvarnakich, k. and kiatkamjornwong, s. 2011. characteristics of kapok fibre as a potential pulp source for paper making. bioresources 7(1): 475-488. el-sebaii, aa., and ibrahim, a. 2005. experimental testing of a box-type solar cooker using the standard procedure of cooking power. renewable energy, 30:1861-1871. folaranmi, j. 2013. performance evaluation of double glazed type solar oven with reflector. journal of renewable energy, 2013, article id 184352 | https://doi.org/10.1155/2013/184352, 1-8. gaan, s., rupper, p. and salimova, v. 2009. thermal decomposition and burning behavior of cellulose treated with ethyl ester phosphoramides: effect of alkyl substituent on nitrogen atom. polymer degradation and stability, 4(7): 1025–1134. lim, t.t. and huang, x. 2007. evaluation of kapok (ceiba pentandra (l.) gaertn.) as a natural hollow hydrophobic–oleophilic fibrous sorbent for oil spill cleanup. chemosphere, 66: 955–963. https://doi.org/10.1155/2013/184352 file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdulrahim et al: performance evaluation of solar oven using kapok wool as insulation material. azojete,16(4):773-784. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrabdulrahimat@gmail.com 784 maina, mb., ngala, gm. and abdulrahim, at. 2016. design, fabrication and performance evaluation of solar brick oven. international journal of engineering research and technology, 5(1): 179-182. meiwu, s., hong, x., and weidong, y. 2010. the fine structure of the kapok fiber. textile research journal, 80(2): 159–165. mukherjee, d. and chakrabarti, s. 2004. fundamental of renewable energy systems. new age international publishers, new delhi, india. mwaikambo, l.y. 2006. review of the history, properties, and application of plant fibres. african journal of science and technology, 7: 120–133. poletto, m., zattera, a.j., forte, m. and santana, r. 2012. thermal decomposition of wood: influence of wood components and cellulose crystallite size. bioresource technology, 109: 148–153. purnawati r., febrianto, f., wistara, nj., nikmatin. s., hidayat, w., lee, sh. and kim, nh. 2018. physical and chemical properties of kapok (ceiba pentandra) and balsa (ochroma pyramidale) fibers. journal of korean wood science and technology, 46(4): 393-401. qandil, a., al-younis, s., saleh, a. and hasson, m. 2018. experimental study of the performance of a box solar cooker. international journal of scientific & engineering research, 9(4): 769-773. sayigh, aam. 1977. solar energy engineering. academic press, newyork. suharta, h. 1994. oven matahari (solar oven). prospeknya dalam mangatasi masalah lingkungan dan kelangkaan energi untuk memasak. prosiding simposium fisika jakarta, pskkr batan, jakarta, 179-187. suharta, h., abdullah, a. and sayigh, aam. 1998. the solar oven: development and fieldtesting of user-made designs in indonesia. solar energy, 64 (4-6): 121-132. voumbo, ml., wereme, a., gaye, s., adj, m. and sissoko, g. 2010. characterization of the thermophysical properties of kapok. research journal of applied sciences, engineering and technology, 2(2): 143-148. wang, j., zheng, y. and wang, a. 2012. super hydrophobic kapok fiber oil-absorbent: preparation and high oil absorbency. chemical engineering journal, 213: 1– 7. zheng, y., wang, j., zhu, y. and wang, a. 2015. research and application of kapok fiber as an absorbing material: a mini review. journal of environmental science, 27: 21–32 http://www.azojete.com.ng arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):331-340 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 331 original research article prediction of infant size at birth using principal components based artificial neural network u. usman1, s. suleiman2*, a. b. muhammad3 and m. b. ibrahim4 1department of statistics, usmanu danfodiyo university, sokoto, nigeria 2department of statistics, federal university, dutsin-ma, katsina state, nigeria 3department of computer science, usmanu danfodiyo university, sokoto, nigeria 4department of statistics, usmanu danfodiyo university, sokoto, nigeria *corresponding author’s email address: macostamkd@gmail.com 1.0 introduction birth size is one of the important predictors of a child’s mental development, future physical growth, and survival. it is one of the major risk factors for child morbidity and mortality (onubogu et al., 2017). as reported by the world health organization (who), low birth weight (lbw) is defined as an infant birth weight of less than 2,500g (who, 2011). children in this category are considered to have a greater risk of neonatal, post-neonatal death, and morbidity (dahlui et al., 2016). children born underweight also tend to have cognitive disabilities and a lower intelligent quotient (iq), affecting their performance in school and their job opportunities as adults. previous studies have also linked infant mortality with parents’ socioeconomic status (unicef, 2004). more than 20 million infants worldwide, representing 15.5 per cent of all births are born with low birth weight, 95.6 percent of them in developing countries (unicef, 2004). the level of low birth weight in developing countries (16.5 percent) is more than double the level in developed article information abstract birth size plays a major role in child’s mental development, future physical growth, and survival. the average length of full-term babies at birth is 20 in. (51 cm), although the normal range is 46 cm (18 in.) to 56 cm (22 in.). in the first month, babies typically grow 4 cm (1.5 in.) to 5 cm (2 in.). principal component analysis (pca) is a dimension-reduction tool that can be used to reduce a large set of variables to a small set that still contains most of the information in the large set. in neural networks multicollinearity may increase difficulties in data processing; too much feature inputs will also cause the time-consuming training process, prevent the constringency of the training work, and may eventually affect the network performance. this research investigates the effect of some parents’ socioeconomic status on the sizes of infants at birth in zamfara state. several factors have been identified to have effect on the sizes of infant at birth which is part of major public health challenges in developing countries like nigeria. previous studies considered only some maternal factors responsible for the infant sizes at birth. this current study explored the parents’ socioeconomic status and environmental factors that contributes to the status of the infant sizes at birth using factor and neural network analysis. the analysis was carried out using data collected from federal medical centre, gusau and ahmad sani yariman bakura specialist hospital gusau, zamfara state to explore the association between the afore mentioned factors. multicollinearity results indicated that there is significant correlations among independent variables, factor analysis through principal extraction methods reduced the original 14 correlated variables in to five uncorrelated factors. however, artificial neural network performs better in the presence of multicollinearity as it produces lower mean square error (mse). it also had a better classification accuracy of 83.5% as compared to 65.9% for gender of the baby . © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 28 february, 2023 revised 5 april, 2023 accepted 6 april, 2023 keywords: factor analysis artificial neural network prediction infant multicollinearity http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com mailto:%20sundayjayd@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):331-340. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 332 regions,7 percent (unicef, 2004). birth weight is a strong indicator not only of a birth mother's health and nutritional status but also a newborn's chances for survival, growth, long-term health and psychosocial development (unicef, 2008). a low birth weight (less than 2,500 grams) raises grave health risks for children (unicef, 2008). babies who are undernourished in the womb face a greatly increased risk of dying during their early months and years (unicef, 2008). the effect of low birth weight on infant mortality is not only additive but also interactive. the magnitude of the contribution of low birth weight to infant mortality is higher in developing countries given that the survival of such infants is dependent on environmental sanitation, effective post-natal nutrition and rehabilitation, and the availability of medical care. low birth weight is a public health problem all over the world and is connected with a lot of health challenges and even deaths (isiugo-abanihe and oke, 2011). fetal growth is usually evaluated using birth weight. however, the use of other measurements like the head and length, arm and chest circumferences may be very important in the prediction of long-term health and development results (neggers et al., 1995). artificial neural networks (anns) is a machine learning technique widely used for forecasting model in numerous disciplines which include economic, finance, business, engineering, science, health, foreign exchange among others (suleiman and sani, 2020). anns are powerful tools for modeling. they can learn and identify correlated patterns between input datasets and corresponding target values. once trained, anns can be used to predict the outcome of new independent input data (suleiman et al.,2019). the anns learn these approximate relationships on the basis of actual inputs and outputs. therefore, they are generally more accurate as compared to the relationships based on assumptions (suleiman et al., 2016a; suleiman et al., 2016b). neural networks are semi-parametric non-linear models, which are able to approximate any reasonable function (gulumbe et al., 2016). neural network is a non-parametric method that can be used in the medical field to classify subjects based on input variables into sick or healthy subjects. classification and prediction of the patient's condition based on risk factors are an application of artificial neural networks (gulumbe et al., 2019) principal component analysis (pca) is a dimension-reduction tool that can be used to reduce a large set of variables to a small set that still contains most of the information in the large set. it is a mathematical procedure that transforms a number of (possibly) correlated variables into a (smaller) number of uncorrelated variables called principal components. pca is one of the most popular methods used for variable reduction, which can overcome the disturbance of the multicollinearity of the risk factors and has been used in social sciences, health service, and health sciences (suleiman and badamasi, 2019). the aim of this paper was to investigate parent’s socioeconomic status influence on infants’ birth sizes (weight, height, head circumference, gender of the baby and gestational weeks) in gusau, zamfara state. taiwo et al., (2018) investigated the association between birth measurements and maternal factors in predicting the birth size of infants in osogbo, osun state using canonical correlation analysis (cca) and multiple linear regressions (mlr). the study shows that, maternal factors could be used predict the eventual birth weight of an infant. in this research, five infants’ anthropometric indicators and five parents’ socio economic indicators were respectively used as file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com usman et al: prediction of infant size at birth using principal components based artificial neural network. azojete, 19(2):331-340. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 333 dependent and independent variables. the result revealed that most of the women were educated but almost half of them fall into the category with low living standard index (47%). findings in this study suggest cca to be a better method for assessing the effects of the maternal factors on infant size at birth than usual multivariate techniques like multiple linear regressions. affi et al. (2019) used canonical correlation to examine the relationship between neonatal anthropometric indicators and maternal socio-demographic factors. the neonatal anthropometric indicators were considered as dependent (y) variables whiles maternal sociodemographic factors were considered as independent variables (x). the outcome of the canonical correlation analysis showed that the total shared variance between the two set of variables stood at 69.8%, which indicates a significant relationship between neonatal anthropometric indicators and maternal socio-demographic factors. 1. methodology in this study, secondary source of data was employed, pregnant women socio-economic records gathered from federal medical gusau were analyzed using multivariate techniques of factor analysis based on principal components extraction method and ann. ann was built based on the complete data and factor analysis transformed data. 1.1 data collection data on parents’ socio-economic status and infants’ anthropometric indicators consisting of 546 pregnant women who delivered at federal medical centre, gusau and ahmad sani yariman bakura specialist hospital, gusau zamfara state between january 2017 and december 2018 were considered in this research. three hundred and eighty two (382) pregnant women records constituting 70% of cases were randomly selected for training the proposed neural network model and the 30% (164) pregnant women records were utilized for testing the model. fourteen (14) independent variables used in this research were maternal age (ma),body mass index (bmi), gravida (gr), nutrition habits (nh), mother’s education (mse), father’s education (fse), antenatal care visits (anc), gestational age (ga), maternal weight gain in pregnancy (mwgp),mother's working status (msws),father’s income level (fil),mode of delivery (md), birth order (bo), residence (r) and mother’s supplement usage(mssu). outcome variables are the birth sizes (weight, height, head circumference and mid-upper arm circumference) of the baby were used as dependent variables. table 1 describes how the independent variables were measured. it has indicated that all 14 independent variables were used as categorical. table 1: definitions of independent variables. s/n variable category 1 category 2 category 3 category 4 1 maternal age (ma), 16-25yrs=1 26-35yrs=2 35yr+=3 2 body mass index (bmi), <18.5=1 18.5-25.0=2 >25.0-30=3 >30=4 3 gravida (gr), 1 2 3 4 4 nutrition habits (nh) regular =1 irregular =2 5 mother’s education (mse), no education=1 primary education=2 secondary education=3 high school education=4 6 father’s education (fse) no education=1 primary =2 secondary education =3 high school education =4 7 antenatal care visits (ancv), 0-2=1 3-5=2 6-8=3 >8=4 http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):331-340. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 334 8 maternal weight gain in pregnancy (mwgp) 5-11= 1 >11 = 2 9 mother's working status (msws), working = 1 not working =2 10 father’s income level (fil), <n 18,000 = 1 >n 18,000 = 2 11 mode of delivery (md) normal =1 c-section=2 12 mother’s supplement usage (mssu). yes = 1 no = 2 13 birth order (bo) 1 2-3 4-5 6+ 14 residence rural = 1 urban = 2 2.2 variance inflation factor a variance inflation factor is a tool to help identify the degree of multicollinearity. canonical multicollinearity exists when there is a linear relationship, or correlation, between one and more of the independent variables or inputs. multicollinearity creates a problem in the accuracy of traditional model because all the inputs influenced each other. therefore, they are not actually independent, and it is difficult to test how much the combination of the independent variables affects the dependent variable, or outcome, within the model. while multicollinearity does not reduce a model's overall predictive power, it can produce estimates of the regression coefficients that are not statistically significant (suleiman & badamasi, 2019). in a sense, it can be thought of as a kind of double-counting in the model. variance inflation factor is calculated using the following formula: 𝑉𝐼𝐹𝑖 = 1 1−𝑅𝑖 2 (1) where: r2 i is the coefficient of determination of the regression equation. 2.3 mathematical computation of factor analysis multiple factors are based on the premise that a large number of questionnaire items could be reduced to only a few dimensions. the multiple factor approach emphasized the goal of extracting a maximum amount of variance from a correlation. the factor analysis describes the covariance relationship among many variables in terms of few underlying, but unobservable, random quantities called factors. factors analysis believes that the variables can be grouped by their correlations (suleiman et al., 2019). consider the general factor model 𝑋𝑝×1 = 𝜇𝑝×1 + 𝐿𝑝×𝑚𝑓𝑝×1 + ∑𝑝×1 (2) 𝑋𝑝×1 is the vector of the p correlated variables 𝜇𝑝×1 is the mean vector of the p correlated variables ∑𝑝×1 is the variance covariance matrix of the p correlated variables. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com https://en.wikipedia.org/wiki/coefficient_of_determination usman et al: prediction of infant size at birth using principal components based artificial neural network. azojete, 19(2):331-340. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 335 the regression coefficient (the partial slopes) for all of these multiple regressions are called 𝑖𝑡ℎvariable and the 𝑗𝑡ℎfactor, which could be collected in a matrix as shown below 𝐿 = ( 𝑙11 ⋯ 𝑙15 ⋮ ⋱ ⋮ 𝑙141 ⋯ 𝑙14×5 ) (3) 2.4 the neural network model a neural network is a simplified model of how human brain processes information. it works by simulating a large number of interconnected processing units that resemble abstract versions of neurons (suleiman and gulumbe, 2018). the processing units are arranged in layers. there are typically three parts in a neural network: an input layer, with units representing the input fields; one or more hidden layers; and an output layer, with a unit or units representing the target field(s). the units are connected with varying connection strengths (or weights). input data are presented to the first layer, and values are propagated from each neuron to every neuron in the next layer. eventually, a result is delivered from the output layer (ding et al., 2010). the network learns by examining individual records, generating a prediction for each record, and making adjustments to the weights whenever it makes an incorrect prediction. this process is repeated many times, and the network continues to improve its predictions until one or more of the stopping criteria have been met (ding et al., 2010). initially, all weights are random, and the answers that come out of the net are probably not closer to the correct known values. the network learns through training. , and the answers it gives are compared to the known outcomes. information from this comparison is passed back through the network, gradually changing the weights. as training progresses, the network becomes increasingly accurate in replicating the known outcomes. once trained, the network can be applied to future cases where the outcome is unknown (ding et al., 2010). neural networks are simple models of the way the nervous system operates. the basic units are neurons, which are typically organized into layers, as shown in the following figure 1. figure 1: a neural network with four inputs and one hidden layer with three hidden neurons (ding et al., 2010) http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):331-340. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 336 this is known as a multilayer feed-forward network, where each layer of nodes receives inputs from the previous layers. the outputs of the nodes in one layer are inputs to the next layer. the inputs to each node are combined using a weighted linear combination. the result is then modified by a nonlinear function before being output (ding et al., 2010). for example, the inputs into hidden neuron in figure 1 above are combined linearly to give 𝒁𝒋 = 𝒃𝒋 + ∑ 𝒘𝒊𝒋𝑿𝒊 𝟒 𝒊=𝟏 (3) 𝑍𝑗 are the neural network outputs 𝑏𝑗 are the neural network biases or intercepts 𝑤𝑖𝑗 are the neural network weights 𝑋𝑖 are the neural network inputs the parameters b1, b2, b3 and w1, 1, …, w4, 3 are “learned” from the data. the values of the weights are often restricted to prevent them from becoming too large. the parameter that restricts the weights is known as the “decay parameter,” and is often set to be equal to 0.1. 2.5 factor analysis artificial neural network (fa-ann) algorithm factor analysis (fa) was used to reduce the dimensionality of the original data. then these lowdimensional data was considered as the input of the anns, which gives way for the new algorithm based on fa referred to as fa-bp algorithm (ding et al., 2010). the fa-bp algorithm is summarized in figure 2 below: records of 546 pregnant women were collected from fmc gusau, 70% (382) were utilized for training the network and 30 % (164) were used for testing the network. figure 2: fa-ann algorithm collect the original data apply fa on the original design ann structure based on extracted principal factors select suitable samples, decide nn parameters for training use the trained fa-ann to predict file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com usman et al: prediction of infant size at birth using principal components based artificial neural network. azojete, 19(2):331-340. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 337 3. results and discussion table 1 indicates that there are moderate correlations among the variables since the variance inflation factor for all the variables ranges from 1 to 5. multicollinearity existing among the variables was removed using the factor analysis through principal components extraction technique. table 1: collinearity statistics variables collinearity statistics tolerance variance inflation factor maternal age 0.592 1.689 mothers education 0.534 1.874 fathers income 0.886 1.129 ancv 0.826 1.211 mssu 0.524 1.910 gravida 0.399 2.505 birth order 0.845 1.184 weight gain 0.591 1.693 body mass index 0.342 2.923 fathers education 0.983 1.018 msws 0.972 1.029 residence 0.846 1.183 mod 0.918 1.089 nutritional habit 0.976 1.025 table 2 presents kaiser meyer olkin (kmo) and bartlett’s test conducted to measure the appropriateness of the data for factor analysis. the result of kmo indicates that sampling is adequate since the coefficient is approximately 0.5. bartlett’s test also indicated that the correlations among the variables is significant. thus, factor analysis is suitable for the data reduction. table 2: kaiser meyer olkin (kmo) and bartlett’s test kaiser-meyer-olkin measure of sampling adequacy. .467 bartlett's test of sphericity approx. chi-square 1338.635 df 91 sig. .000 http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):331-340. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 338 table 3 shows the eigenvalues and total variance explained. principal component analysis extraction method for factor analysis was employed in this study. before extraction, the data consists of fourteen linear components. after extraction and rotation, the data was reduced to five distinct linear components with eigenvalue > 1. the five factors are extracted accounted for a combined 56% of the total variance. it is suggested that the proportion of the total variance explained by the retained factors should be at least 50%. the result shows that 56% common variance shared by eleven variables can be accounted by five factors. table 3: eigenvalues and total variance explained component initial eigenvalues extraction sums of squared loadings total % of variance cumulative % total % of variance cumulative % 1 2.417 17.263 17.263 2.417 17.263 17.263 2 1.831 13.080 30.343 1.831 13.080 30.343 3 1.386 9.903 40.246 1.386 9.903 40.246 4 1.102 7.869 48.116 1.102 7.869 48.116 5 1.078 7.697 55.813 1.078 7.697 55.813 6 .983 7.023 62.836 7 .950 6.783 69.619 8 .892 6.372 75.991 9 .832 5.944 81.935 10 .782 5.582 87.517 11 .696 4.971 92.488 12 .558 3.988 96.476 13 .326 2.329 98.805 14 .167 1.195 100.000 tables 4 and 5 present results for the original model ann model and transformed fa-ann model. ann model gives smaller prediction errors for all the scale dependent variables. similarly, ann model gives higher prediction percent for the categorical variable gender of the baby. these results are consistent with the results of (suleiman and badamasi, 2019; chan et al., 2022; obite et al., 2020) but contradicts the results of ding et al., (2010). table 4: neural network root mean square error (rmse) for the continuous dependent variables dependent variables ann fa-ann height .043 .676 weight .247 .576 hcfr .016 .452 gweeks .233 .335 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com usman et al: prediction of infant size at birth using principal components based artificial neural network. azojete, 19(2):331-340. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 339 table 5: neutral network classification performance for gender of baby model observed predicted male female percent correct ann male 90 10 90.0% female 17 47 85.8% overall percent 65.2% 34.8% 83.5% fa-ann male 67 40 62.6% female 16 41 71.9% overall percent 50.6% 49.4% 65.9% 4. conclusion this study investigated the effect parent’s socio-economic status influence on infants’ birth sizes (weight, height, head circumference, gender of the baby and gestational weeks). variance inflation factor was used to establish the presence of multicollinearity among parents’ socioeconomic status influence. factor analysis was found to be appropriate approach to reduce the data set in to uncorrelated factors using principal components extraction method. principal component analysis of parents’ socio-economic status affecting birth sizes reveals 56% of the variation account by the first five principal components. the ann model had a smaller rmse when the original 14 correlated variables were used. therefore, this indicated that ann performance is not affected by the presence of multicollinearity. it is, therefore, recommended that ann should be used when there is multicollinearity in the data set and in further research variants of back propagation algorithms can be used to train the model. reference affi, op., lartey, nl., angkyiire, d. and oppong i. 2019. canonical correlation analysis of neonatal anthropometric indicators and maternal socio -demographic factors. international journal of scientific & technology research, 8(7): 93-97. chan, jyl., leow, smh., bea, kt., cheng, wk., phoong, sw., hong, zw. and chen, yl. 2022. mitigating the multicollinearity problem and its machine learning approach: a review. mathematics, 10, 1283. https://doi.org/10.3390/math10081283. dahlui, m., azahar, n., oche, om. and aziz, na. 2016. risk factors for low birth weight in nigeria: evidence from the 2013 nigeria demographic and health survey. global health action, 9(1): 34-39. doi:10.3402/gha.v9.28822. ding, s., jia, w., xu, x. and zhou, h. 2010. neural networks algorithm based on factor analysis. conference: advances in neural networks. proceedings of 7th international symposium on neural networks, june 6-9, shanghai, china, part i, 319-324. gulumbe, su., suleiman, s., asare, bk. and abubakar, m. 2016. forecasting volatility of nigerian crude price using non-linear auto-regressive with exogenous (narx) inputs model. imperial journal of interdisciplinary research (ijir), 2(5): 434-442. gulumbe, su., suleiman, s., badamasi s., yusuf, at. and usman, u. 2019. predicting diabetes mellitus using artificial neural network through a simulation study. machine learning research, 4(2):33-38. doi: 10.11648/j.mlr.20190402.12 http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com https://doi.org/10.3390/math10081283 arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):331-340. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: macostamkd@gmail.com 340 isiugo-abanihe, u. and oke, o. 2011. maternal and environmental factors influencing infant birth weight in ibadan, nigeria. african population studies, 25(2): 11-19. obite, cp., olewuezi, np., ugwuanyim, gu. and bartholomew, dc. 2020. multicollinearity effect in regression analysis: a feed forward artificial neural network approach. asian journal of probability and statistics, 6(1):22-33. doi: 10.9734/ajpas/2020/v6i130151 onubogu, cu., egbuonu, i., ugochukwu, ef., nwabueze, as. and ugochukwu, o. 2017. the influence of maternal anthropometric characteristics on the birth size of term singleton southeast nigerian newborn infants. nigerian journal of clinical practice, 20: 852. suleiman, s. and badamasi, s. 2019. effect of multicollinearity in predicting diabetes mellitus using statistical neural network. european journal of advances in engineering and technology, 6(6):30-38. suleiman, s. and gulumbe, su. 2018. application of back propagation gradient based neural network training algorithms to volatility forecasting. edited proceedings of 2nd international conference professional statisticians society of nigeria, 2: 273-282. suleiman s., gulumbe, su., asare, bk. and abubakar, m. 2016a.comparative study of backpropagation algorithms in forecasting volatility of crude oil price in nigeria. science journal of applied mathematics and statistics, 4(3): 88-96, doi: 10.11648/j.sjams.20160403.11 suleiman, s., gulumbe, su., asare, bk. and abubakar, m. 2016b.training dynamic neural networks for forecasting naira/dollar exchange returns volatility in nigeria. american journal of management science and engineering, 1(1): 8-14, doi: 10.11648/j.ajmse.20160101.12 suleiman, s., lawal, a., usman, u., gulumbe, su. and muhammad, ab. 2019. student’s academic performance prediction using factor analysis based neural network. international journal of data science and analysis, 5(4): 61-66.10.11648/j.ijdsa.20190504.12 suleiman, s. and sani, m. 2020. application of arima and artificial neural networks models for daily cumulative confirmed covid-19 prediction in nigeria. equity journal of science and technology, 7(2):83 – 90. taiwo, ao., bolanle, so. and kehinde, ab. 2018. evaluation of maternal factors on infant’s birth size using canonical correlation analysis in osogbo, osun state. noun journal of physical and life sciences, 2(1): 67-83. unicef, 2004. the state of world’s children 2004. girls’ education and the promise of education for all. 2004. 111. unicef, 2008. the state of world’s children 2008. the most comprehensive analysis of global trends affecting children, 106-113. who, 2011. world health statistics 2011. 20 avenue appia, 1211 geneva 27, switzerland: who press, world health organization file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):93-106 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 93 effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria d.u. onyishi1 and v.e. oweh2 1department of electrical and electronics, federal university of petroleum resources, effurun, delta state, nigeria 2department of computer engineering, delta state polytechnic, otefe oghara. delta state, nigeria *corresponding author's email address: owehvictor12@gmail.com article information submitted 11 july, 2023 revised 2 september, 2023 accepted 9 sept., 2023 keywords: path loss gsm propagation models log-normal abstract the impact of path loss has significant implications for the pricing strategies adopted by mobile communication companies. accurate determination of path loss is crucial for effectively planning and operating high-capacity networks that deliver reliable services. although previous researchers have devised various system designs, these models cannot be universally applied across all environments. the ongoing signal deterioration due to urbanization and industrialization presents a challenge to network capacity. this study aims to develop an average path loss system specifically tailored for the planning of worldwide system for mobile communication networks in the vicinity of the federal university of petroleum resources effurun (fupre) and its surrounding areas. the methodology employed involves instrumentation and measurement techniques. distances in meters are measured using a digital wheel meter, while a handheld android device equipped with g-mon pro software captures data including reference signal strength indicator (rssi), latitude, and longitude during driving tests conducted along predefined routes. the collected data were subjected to regression analysis. the results indicated that the exponent path loss value (n) is 3.07, suggesting a cellular radio network environment typical of a metropolitan area. the root mean square error (rmse) of 4.91 db falls within an acceptable range for the reference measurement environment in the region. the average network models demonstrated greater precision than all other models, producing outputs with a smaller margin of error. therefore, providers of gsm network infrastructure can leverage this practical model, based on the log-normal shadowing principle, to enhance and optimize their services in the fupre area and its surroundings. 1.0 introduction path loss is the decrease in electromagnetic wave power density as it propagates through space, caused by various phenomena like diffraction, reflection, and absorption. the signal received from the base station weakens as the distance from the transceiver system to the mobile station increases (ibhaze et al., 2017). the disparity between the power from the source and the power received is termed path loss. the performance of cellular network depends on the propagation model deployed during planning stage. due to the complex and diverse nature of the radio propagation environment, the power of a propagation signal fluctuates with respect to time and space. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 94 path loss is a critical factor that impacts the quality of service in mobile communication systems. accurately assessing path loss is essential for designing and operating reliable networks. to achieve precise estimation, different propagation models have been formulated. afolayan et al. (2017), their studied reviewed that propagation prediction is vital tool for gsm networks planning. it determines factors like base trans-receive stations location, coverage area, frequency assignment, and interference management, ensuring reliable and strong signal connections between transceivers and mobile devices. path loss, which can curtail signal range and lead to interference, has a major impact on the capacity of a mobile network, ultimately affecting its overall performance (rana et al., 2014). long term evolution (lte) is a standard for high-speed data connectivity in cellular networks, providing faster data transfer speeds compared to 3g networks (imoize et al., 2019). path loss can be determined using theoretical models, modeling software, empirical models, or field observations. the best approaches used typically combined field measurements with principally beneficial models. poor path loss planning, which generally results from disregarding urbanization and relying on methods that don't incorporate actual field measurements, limits the capacity of wireless lte networks. this study aims to implement a path loss model from four existing gsm network providers which includes mtn, globacom, 9mobile, and airtel within fupre and its environs to build an average network model specifically for this environment. in addition, this research examined some specific parameters such as exponent path loss, shadowing factor, measured path loss, and root mean square error (rmse) that can use create practical average network model using accurate field measurement data. likewise, our research strives to create highly accurate and computationally effective models. the use of log distance and log-normal shadowing modelling can be used in determining the said parameters mentioned above and emphasis will be laid equally on considering the effects and relationship of distance on measured path loss, predicted path loss, network capacity and average path loss. ifesinachi et al. (2021), had shown that a practical model for path loss propagation specifically for an lte network in onitsha, nigeria. measurement data from various locations in the city was collected to developed the model. the study found an exponent path loss is 3.5 and shadowing factors of 8.7 db. comparing the model with existing ones, it demonstrated superior accuracy in forecasting path loss in the onitsha region. ikechukwu (2020), similarly emphasizes the significance of bandwidth and signal power in lte wireless communication. the study identifies limitations due to government restrictions on bandwidth and low-powered devices. to overcome these constraints, the study proposes implementing channel coding and equalization techniques. by employing these strategies, wireless lte communication capacities can be enhanced, improving performance and overall system capability. in the research conducted by faruk et al. (2019), to evaluate the effectiveness of a path loss concept using empirical data, geospatial data and heuristic data for path loss estimates in urban environments the model accurately predicted signal strength within the limit of 1500 meters but showed reduced accuracy beyond that range. the study identified terrain, building file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria. azojete, 20(1):93-106. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 95 materials, and vegetation as factors influencing path loss. the results indicate that the inclusion of geospatial information has the potential to enhance the precision and efficiency of path loss model. according to benmus et al. (2016), who carried out a study aimed at creating a practical model utilizing synthetic neural systems (sns) for the purpose of forecasting the deterioration of signal strength across varying frequencies in tripoli. the objective was to assess the accuracy of sns in path loss prediction and compare it with existing models. the findings revealed that the sns model outperformed existing models, achieving high correlation coefficients of 0.93 for the training dataset and 0.99 for the testing dataset. based on these results, the study came to the conclusion that sns is a useful tool for predicting route loss in mobile phone networks. armoogum et al. (2015) investigated the influence of topography on loss of path in yola, nigeria's village and city regions. radio frequency measurements were taken, revealing that topography had a weighty influence on signal attenuation. in city areas, buildings and structures were the main contributors to path loss, while in village areas, vegetation and terrain played a decisive role. the study emphasizes the prominence of understanding the influence of topography on path loss for effective network development and optimization. according to adeyemi et al. (2014), examined the effects of path loss on lowlands and mountainous areas of bida, niger state. the analysis showed that areas with obstacles like hills and mountains had higher path loss. these obstacles obstruct or reflect the signal, leading to reduced signal strength, coverage, and lower network capacity. in contrast, valley areas with flat terrain had lower path loss as the signal travelled more easily. austins et al. (2014) also conducted work on utilizing traffic engineering to enhance lte network capacity in dense urban areas. they proposed an algorithm that can increase network capacity by up to 20% and is robust to changes in traffic load and cell configuration. the algorithm was executed with minimal modifications to existing lte networks, offering a practical solution for improving capacity in urban settings. capacity. berkeley et al (2012) conducted a study to enhance lte network capacity through interference management and resource allocation. proposed techniques like interference cancellation and advanced signal processing algorithms to mitigate interference and enhance network performance. dynamic resource allocation based on real-time network conditions was employed to fulfil the needs of high-speed users, resulting in increased network capacity by dynamically shared frequencies maximizing reuse while minimizing clashes as users and base station adjust power to maintain good signal while minimize interference and overall capacity of lte is boosted. 2.0 materials and methods the research methodology employed in this investigation involved the application of instrumentation and measurement techniques. the investigation was conducted in the neighbourhood of the federal university of petroleum resources effurun and its surrounding areas. two test handsets equipped with g-mon pro software on an android device were used. similarly, a digital wheel meter attached to a car for measuring the distance covered from the base transceiver station was used. the received signal strength indicator (rssi) measurements http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 96 were acquired from lte base trans-receive stations of gsm service providers located along designated routes such as ugbomro road, dsc expressway, dsc roundabout, okuokoko, federal junction, and fupre. these service providers included mtn, globacom, 9mobile, and airtel, utilizing frequencies ranging from 800mhz to 2600mhz and transmitter power levels of 40, 40, 35, and 38 watts respectively (shoewu et al.,2014). the antennas were mounted on steel towers with an average height of 42 meters, and their spatial separation was measured horizontally. the field experimental data consisted of the rssi values were collected up to a distance of 1500 meters. figure 1 also showed an illustration of the measurement sites. in the end, the gathered data was subjected to regression analysis, which is a robust statistical method employed to assess the correlation between the desired independent variables. the measurement of received signal strength indicator (rssi) over a specific distance at the respective service providers and their angular displacement as shown in table 1. the intention was to verify the signal strength received by various users in relationship with different service providers in the said location. figure 1: google map of the measurement area. available online @www.mdpi.com/journal/map 2.1 mathematical modelling of log distance and log-normal shadowing model of path loss 2.1.1 estimating path loss using a log-distance concept by incorporating variables such as distance and environmental conditions, the model utilizes the logarithmic decay with distance to make predictions about signal strength. the exponent path loss (n) represents the specific path loss characteristic for varying distances between the transmitter and receiver. the concept is represented by equation according to (murdock et al., 2013).         += 0 0 log10)()( d d ndldl i pip (1) where file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria. azojete, 20(1):93-106. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 97 d0 is the initial distance, di is the variable distance from initial point n exponent path loss lp(d0) is the path loss measured, lp(di) is the path loss predicted. the exponent path loss (n) is a constant derived empirically and is influenced by the characteristics of the propagation environment. it is determined using equation (1) and can be mathematically represented as follows.           − = 0 10 0 log10 )()( d d dldl n i pip (2) the exponent path loss can be statistically determined using linear regression analysis, equation (2) which represents the summation of the mean square error in this context.           − =   = = 0 101 01 log10 )()( d d dldl n ini i pip ni i (3) where the term lp(di) represents path loss predicted, lp(d0) represents path loss measured and ni is the number of measured data or sample points. the expression, lp(di) − lp(d0), is an error term with respect to n, and the sum of the mean squared error, e(n), is expressed as =)(ne  = ni i 1  20 )()( dldl pip − (4) the optimal value of the exponent path loss (n), which minimizes the mean square error (mse), is obtained by setting the derivative of equation (4) to zero and solving for n. 0 )( =   n ne (5) 2.1.2 log-normal shadowing concept of path loss the model predicts signal attenuation for mobile communication, considering random shadowing effects from obstacles. it assumes a log-normal distribution for received signal power, indicating signal strength fluctuations with shadowing factors (σρ). the model is represented by equation (hata,1980). +        += 0 0 log10)()( d d ndldl i pp (6) where lp(d) path loss is derived from the log-normal shadowing concept. σρ is the shadowing factor the equation provided above establishes the derived model when the value is accurately measured. the shadowing factor (σρ) is also expressed as (hata,1980).   ni dldl opip 2 )()(( − =  (7) http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 98 where ni = sum of measured statistics points. lp(d0) is the measured path loss, lp(di) is the predicted path loss 2.1.3 the concept of data analysis data collection for the study started 100 meters from the primary transmitter station, followed by a 100-meter drive along the designated route. this process was repeated twice daily for three months. average of rssi values were recorded. to ensure accuracy, the test car maintained a constant speed of 20 km/h, with a highest speed of 30 km/h to consider the doppler effect (shoewu et al., 2014). 2.1.4 power transmitted pt for each the networks power transmitted pt for mtn = 40 watts. power received in rssi is pr(dbm) = 41 dbm. do = 100 metres di =100 metres power transmitted in dbm is expressed as       mw wattsinpower 1 .. log10 (8) (i). power transmitted pt for mtn = 40 watts pt = 40 watts, in decibel milliwatts (dbm)       −3101 40 log10 x = 46.02 dbm (ii). power received in rssi in is pr(dbm) = 41 dbm       = 10 log rssi antipr (9) pr = 10-4.1 = 7.94 x 10-5 2.1.5 measured path loss = lp(do) ( )       = r t op p p dl log10 (10) ( )       = −51094.7 02.46 log10 x dl mtnop = 58 db 2.1.6 the predicted path loss 𝑳𝒑(𝒅𝒊) value can be obtained recalled equation (1) from section 2.1.1         += 0 0 log10)()( d d ndldl i pip for lp(d0) = 58 db , do = 100 metres di =100 metres =)( ip dl 58 db for lp(d0) = 58 db ,do = 100 metres, di =200 metres =)( ip dl 58 +3.01n file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria. azojete, 20(1):93-106. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 99 2.1.7 determination of exponent path loss (n) the optimal value of n, which minimizes the  20 )()( dldl pip − , can be resolve by setting the derivative to zero and solving for n utilizing the values from table 2. substituting into equation (6), we obtain the derivative as follows: =)(ne  = ni i 1  20 )()( dldl pip − = 1138.151 n2 – 7813.12n + 13797 𝜕𝑒(𝑛) 𝜕𝑛 = 0 2(1138.151) n – 7831.12=0 hence, 2276.302n – 7831.12 = 0 therefore, 44.3 302.2276 12.7831 ==n the value of exponent path loss n, mtn network is 3.44 now, setting the same conditions as applied to mtn in table 2, the value of exponent path loss in other networks can be calculated for globacom, 9mobile, airtel and average network are 3.12,3.06,3.00 and 3.08 respectively. 2.1.8 the shadowing factor 𝝈𝝆 (db) the shadowing factor, which indicates location variability, is calculated as the range of values around a mean value. by substituting the values of n and mean error deviation square from table 2 into equation (7), the following result is obtained.   ni dldl opip 2 )()(( − =  for mtn network, where n = 3.44 and ni = 15 = [ 1138.151 n2 – 7813.12n + 13797 15 ] 1 2 =[ 1138.151 x 3.442 – 7813.12 x 3.44 + 13797 15 ] 1/2 = 5.09 db. the process of measuring and computing the shadowing factor(σρ) for mtn was replicated for other chosen network service providers. by utilizing equation (7) and referencing table 2, the resulting values for globacom, 9mobile, airtel, and average network, under the same conditions, were 4.53 db, 4.88 db, 5.60 db, and 5.13 db, respectively. therefore, by substituting the values for lp(do), n, and σρ specific to the mtn network into equation (6), we obtain the log-normal shadowing empirical model tailored for the federal http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 100 university of petroleum resources (fupre) and its surrounding areas. +        += 0 0 log10)()( d d ndldl i pp ( )db d d dl i p 09.5log)44.3(1058)( 0 +        += (11) by substituting various parameters values into equation (6), the log-normal shadowing model for each network was modified as follows: ( ) ( )db d d dl i globacomp 53.4log12.31062)( 0 +        += (12) ( ) ( )db d d dl i mobilep 88.4log06.31060)( 0 9 +        += (13) ( ) ( )db d d dl i airtelp 0.6.5log00.31066)( 0 +        += (14) ( ) ( )db d d dl i averagep 13.5log07.31062)( 0 +        += (15) 3. results and discussion the experimental results obtained from measurement taken from various service providers in the field. the measured results were tested in log-normal shadowing concept of path loss for mtn, globacom, 9mobile and airtel which yielded average network shown in table 1 according to equations (3), (4) and shadowing factor in equations (6), (7) respectively. table 1 results clearly evaluate all others service providers parameters such rssi and angular displacement of all available base stations in order to create highly accurate and computationally effective models. this indicated that the log-normal shadowing concept result are in consonance with the information handling service measured data. table 1 the values of rssi for sites measured field measured rssi average rssi angulur displacement s/n distan ce meters rssi (dbm) mtn rssi (dbm) globac om rssi (dbm) 9mobile rssi (dbm) airtel rssi (dbm) average network latitude (degree) longitude (degree) 1 100 -41 -45 -43 -49 45 5.54984 5.82589 2 200 -47 -49 -46 -52 -49 5.54964 5.82589 3 300 -52 -54 -50 -55 53 5.56314 5.81879 4 400 -55 -54 -53 -59 -55 5.56431 5.81989 5 500 -58 -62 -56 -63 60 5.56435 5.8201 6 600 -61 -65 -59 -66 63 5.56472 5.8216 7 700 -64 -68 -62 -69 66 5.56547 5.82516 8 800 -68 -72 -65 -73 70 5.56661 5.82698 9 900 -71 -74 -69 -76 73 5.56778 5.82366 10 1000 -75 -76 -71 -78 75 5.56836 5.83051 11 1100 -81 -79 -74 -81 79 5.56807 5.83398 12 1200 -83 -82 -76 -84 81 5.56983 5.83409 13 1300 -85 -84 -79 -87 84 5.57167 5.83404 14 1400 -86 -87 -81 -89 86 5.57404 5.83672 15 1500 -87 -92 -85 -95 90 5.57187 5.83972 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria. azojete, 20(1):93-106. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 101 again, when the measured results in table 2 where are the evaluated, the measured path loss, the predicated path loss, mean error deviation and mean error deviation square were obtained. it was also realized that the exponent path loss and shadowing factor is in agreement with the information handling service measured data. table 2: measured path loss, predicted path loss and mean square error for mtn s/n dist. (metre) rssi (dbm) mtn measured path loss 𝐿𝑝(do) predicted path loss 𝐿𝑝(𝑑𝑖) mean error deviation [lp(di)-lp(d0)] mean error deviation square [lp(di) lp(d0)]2 1 100 -41 58 58 0 0 2 200 -47 64 58+ 3.01n 3.01n 6 9.0601n2 – 36.12n + 36 3 300 -52 69 58 + 4.77n 4.77n 11 22.7529n2 –104.94n + 121 4 400 -55 72 58 + 6.02n 6.02n 14 36.240n2 168.56n + 196 5 500 -58 75 58 + 6.99n 6.99n 17 48.860n2 – 237.66n + 289 6 600 -61 78 58 + 7.78n 7.78n 20 60.528 n2 – 311.20n + 400 7 700 -64 81 58 + 8.45n 8.45n -23 71.402 n2 – 388.70n + 529 8 800 -68 85 58 + 9.03n 9.03n 27 81.540 n2 – 487.62n + 729 9 900 -71 88 58 + 9.54n 9.54n 30 91.011 n2 – 572.40n + 900 10 1000 -75 92 58 + 10.0n 10.0n 34 100 n2 – 680.0n + 1156 11 1100 -81 98 58 +10.41n 10.41n 40 108.368n2–832.80n +1600 12 1200 -83 100 58 + 10.75n 10.75n 42 115.56 n2 – 903.0n + 1764 13 1300 -85 102 58 + 11.14n 11.1n 44 123.21 n2 – 976.8n + 1936 14 1400 -86 103 58 + 11.46n 11.46n 45 131.10 n2 – 1031.4n + 2025 15 1500 -87 104 58 + 11.76n 11.76n 46 138.06 n2 –1081.92n+ 2116 ∑ 1138.151 n2 – 7813.12n + 13797 therefore, equations (11), (12), (13), (14) and (15) were employed to generate the data presented in table 3 given below. the table demonstrates the established path losses at several distances from 100 meters from the base station to 1500 meters for a network capacity covered area in the examined regions and allowing a comparison of mean path losses for each network as presented below. table 3: established path losses derived from the proposed modified model. s/n distance in (m) path loss in (db) mtn network path loss in (db) globacom network path loss in (db) 9mobile network path loss in (db) airtel network path loss in (db) average network 1 100 63.09 66.53 64.88 71.60 67.13 2 200 73.44 75.92 74.09 80.63 76.37 3 300 79.50 81.41 79.47 85.91 81.77 4 400 83.80 85.31 83.30 89.66 85.61 5 500 87.13 88.33 86.26 92.56 88.58 6 600 89.85 90.80 88.69 94.94 91.01 7 700 92.16 92.89 90.74 96.95 93.07 8 800 94.15 94.70 92.51 98.69 94.85 9 900 95.91 96.30 94.07 100.22 96.42 10 1000 97.46 97.73 95.48 101.60 97.83 11 1100 98.91 99.02 96.74 102.84 99.10 12 1200 100.21 100.20 97.90 103.97 100.26 13 1300 101.40 101.28 98.96 105.01 101.32 14 1400 102.31 102.28 99.95 105.98 102.31 15 1500 103.64 103.02 100.86 106.88 103.23 mean 90.86 91.72 89.59 95.82 91.52 http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 102 these values obtained as a result operating similar conditions maintained for different networks, namely mtn, globacom, 9mobile, airtel, and average network, the results is presented in table 4 shown below. table 4: different values of the exponent path loss, shadowing factor, lp(do), rmse s/n parameters mtn globacom 9mobile airtel average network 1 n 3.44 3.12 3.06 3.00 3.07 2 𝜎𝜌 (db) 5.09 4.53 4.88 5.60 5.13 3 lp(do)(db) 58.0 62.0 60.0 66.0 62.0 4 rmse(db) 5.15 4.41 4.89 5.65 4.91 figure 2 shows the typical established path loss experienced by gsm operators. the airtel network exhibits the highest path loss compared to mtn, globacom, 9mobile, and average networks, with values of 4.96 db, 4.09 db, 6.23 db, and 4.29 db respectively. the figure also demonstrates a strong correlation connecting the average network model and other networks. therefore, the average network model is positioned centrally, avoiding overspill path loss, and strikes a balance between underestimating and overestimating path loss. considering these factors, it can enhance signal strength, expand coverage area, reduce interference, and increase network capacity. figure 2: the path losses of all typical networks figure 3 demonstrates the measured path losses at a distance of 500 meters for different network providers. the measured path losses are as follows: 75 db for mtn, 75 db for 9mobile, 77 db for average, 79 db for globacom, and 80 db for airtel. this suggests that mtn has the smallest observed path loss, whereas airtel exhibits the highest path loss. the mtn network offers a substantially better capacity while the airtel network only delivers the bare minimum. the graph suggests that the average network has a moderate network capacity due to its central location. figure 3: depicts the relationship between measured path loss in (db) and distance(m) 90.86 91.72 89.59 95.82 91.52 86 88 90 92 94 96 98 average developed path loss in (db) mtn globacom 9mobile airtel average network file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria. azojete, 20(1):93-106. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 103 the expected path loss estimates for several networks at a measurement distance of 1000 meters are shown in figure 4. the values for 9mobile, mtn, average, globacom, and airtel are recorded as 92db, 93db, 94db, 94db, and 97db, respectively. the graph clearly demonstrates that network capacity falls as expected path loss rises. conversely, the graph portrays that the average network demonstrates relatively reduced predicted path loss and accommodates more users in the network. figure 4: displays the predicted route losses in (db) plotted against distance (m). at 500-meter distance away (figure 5) from the starting point, the 9mobile network exhibits a favourable performance factor of 86.26 db, while the airtel network experiences the highest degradation factor of 92.56 db. this indicates that the 9mobile network can accommodate more customers than the airtel network. the results indicate that path loss varies among the different gsm operators and increases at different rates over the measured distance. additionally, the graph shows that the mtn and airtel networks tend to overestimate their path losses, while 9mobile and globacom networks underestimate theirs. there is no significant path loss in the average network., allowing for moderate user capacity without exceeding its limits. this also highlights the improvement in service quality and increased network capacity as credited to the average network. figure 5: illustrates the system capacity models in terms of db versus distance in meters. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 104 figure 6: average measured path loss in (db) figure 7: average predicted path loss in (db) 4. conclusion in this study, an average network model derived from four existing gsm networks operating at 2600 mhz within the federal university of petroleum resources, effurun, delta state was introduced. these networks include mtn, glo, airtel, and 9mobile. the proposed models were developed using the log-normal shadowing model, based on data collected from various locations within the specified area. the resulting path loss models are as follows: the analysis revealed that among the four gsm network models considered, the average network model provided the best fit for the selected locations. specifically, the predicted path loss for the average network was 85.60 db, while mtn, glo, 9mobile, and airtel networks recorded path loss values of 84.60 db, 86.43 db, 83.53 db, and 88.73 db, respectively. furthermore, the average network model exhibited a moderate root mean square error and shadowing factor compared to any of the standard network path loss models examined. when applied within the university environment and its surrounding areas, this model has the potential to reduce path loss, thereby addressing the frequent network fluctuations experienced by subscribers in the region. 85.67 87.2 84.72 90.06 86.46 82 83 84 85 86 87 88 89 90 91 average measured path loss in (db) average measured path loss in (db) mtn globacom 9mobile airtel average network 84.6 86.13 83.53 88.73 85.6 80 82 84 86 88 90 average predicted path loss in (db) average predicted path loss in (db) mtn globacom 9mobile airtel average network file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: effects of pathloss on capacity of wireless lte network in fupre, effurun, nigeria. azojete, 20(1):93-106. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 105 references adebayo, tl. and edeko, fo. 2006. characterizations of analysis of path loss at 1.8ghz: a case investigation of benin city. research journal of applied sciences, 41(04): 23 – 34. adeyemi, a. and adu, o. 2014. an evaluation of viability of a variety of path loss designs for lte network panning. world congress on engineering, london u.k., july 6-8, 23(1): 150 161. afoayan, j., obot, a. and simeon, o. 2017. prediction path loss model for macrocellular settings in cities. nigerian journal of technology, 30(1): 120 – 131. armoogum, ot. and konyeha, sr. 2015. models of wave propagation for the development of mobile communication systems, gaas munich, 3(2): 23 -31. benmus, ta., abboud, r. and shatter, ms. 2016. neutral network at 1000, 1600, and 2100 mhz bands: method to simulate path loss propagation for the greater tripoli area in sciences and technology of control system and computer engineering 16th international conference, held in jaipur, india on december 15th -16th, 3(12):793-798. enyi1, vs., val, ue., ugwu, fc. and chidubem, co. 2021. path loss model predictions for different gsm networks in the university of nigeria, nsukka campus environment for estimation of propagation loss. international journal of advanced research in computer and communication engineering, 10(8): 108 – 115. faruk, n., popoola, si., surajudeen-bakinde, nt. and oloyede o. 2019. an experimental study of geospatial, empirical, and heuristic models for path loss estimates in urban environments. ieee access, 7: 77293 77307. hata, m. 1980. propagation loss empirical approach for land mobile radio services. journal of vehicular technology, ieee, 29(3): 317-325. ibhaze, ae., imoize, al., ajose, so., john, sn., ndujiuba, cu. and idachaba, fe. 2017. a model of empirical propagation for path loss prediction at 2100 mhz in a metropolis setting. journal of technologies and science in india, 10(5): 1-9. ifesinachi, eo., idigo, ve., ohaneme, co. and obioma, pc. 2021. implementation of an empirical model for path loss propagation in an lte network in onitsha, journal of engineering and applied sciences, 19(1): 23 – 34. imoize, al., ibhaze, ae., nwosu, po. and ajose, so. 2019. finding a 4g lte network's bestfit propagation models in lagos, nigeria's. engineering journal of the west indies, 3(12): 4452. murdock, jn., junior, rw., and daniels, rc. 2013. millimeter wave wireless communications. prentice hall. rana, sb., pardeep, p. and parveen k. 2014. modified formulation of algorithms for path loss broadcasting applications. international journal of recent technology and engineering, 23(03): 56 – 63. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):93-106. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: owehvictor12@gmail.com 106 rahman, m., imran, k. and mohammed, t. 2020. a survey of algorithms for path loss wireless communication systems. international journal of electronics and telecommunications, 24(04): 56 – 63. shoewu, o. and edeko, fo. 2014. investigating signal attenuation in cluster-based gsm base stations in the area of lagos, publication on electrical and computer engineering systems in the international transactions, 2(1):28 – 33. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):793-806 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 793 hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria y. abdulganiyu1*, b. s. oresajo1, m. abdulkarim1, o. a. phillips1, h. ibrahim1, t. a. abdulfatah1, h. yakubu1, h. zainab1, m. sadiya1, a. nasiru1 and i. mahmud2 1department of geology, federal university birnin kebbi, kebbi state, nigeria 2department of geology, federal university dutsinma, katsina state, nigeria *corresponding author's email address: charger.ca34@gmail.com article information submitted 30 march, 2023 revised 3 sept, 2023 accepted 9 sept, 2023 keywords: water type physico-chemical heavy metal nemerow’s pollution index contamination abstract a hydro-chemical investigation of drinking water sources in birnin kebbi old town and its environs, in northwestern nigeria, was carried out to determine the potability and suitability of the groundwater for domestic and agricultural uses. twenty-three water samples were collected from these communities, and their physical and chemical parameters, such as electrical conductivity, total dissolved solids, ph, and temperature, were evaluated. both the chemical and heavy metal analyses were conducted at the multi-user laboratory, usmanu danfodiyo university, sokoto. the results obtained indicated that physical parameters like tds and ec and chemical parameters like mg2+, ca2+ and hco3 2are high, while cr2+, fe2+, ni, and pb2+ have values that are below the nsdwq recommended limits. while na2+, cu2+, cl-, and no3 have values far below the nsdwq set limit, the schoeller and piper diagrams show the dominant water type in the study area to be ca-mg-hco3. however, the gibbs plot shows the dominant source of the water to be the precipitation domain due to the dissolution of carbonate rocks, while the wilcox diagram shows that all the water samples in the study area have low salinity. application of nemerow’s pollution index method shows that the majority of the sampling locations displayed high npi values, especially for ni2+ and pb2+. the npi ni2+ values for eleven (11) out of twenty-three samples, making up 47.83%, have npi values that range from 7.53 to 90.01, making them unsuitable for drinking purposes. the npi values for pb2+ for six (6) samples, making up about 26.09%, have high npi values that range from 36.37 to 172.56, depicting a high level of pollution 1.0 introduction groundwater is a valuable resource in the vast, thickly populated, semi-arid and arid areas of kebbi state, northwestern nigeria, and where it is available, it is unreliable. because improved water supply is one of the essentials for a healthy lifestyle, it is constrained by uncontrolled anthropogenic activities (chen, et al. 2016; chitsazan et al., 2019), flow of pollution from upland to lowland, too much use of fertilizers, pesticides in agriculture (joarder et al., 2008) and to some extent by natural conditions (zadawa and omran, 2018). since surface and groundwater quality has become an important water resources issue due to rapid population increase and unplanned urbanization. pollution index become a powerful tool for processing, analyzing, and conveying raw environmental information to decision makers, and the public (caeiro et al., 2005). highly toxic elements, including mercury, lead, arsenic, cadmium and nickel have been established as dangerous surface and groundwater pollutants which pose great health risks, especially in rural communities that directly utilize these resources (burke, 2016). boreholes and dug wells are used to abstract groundwater in addition to water from the river dukkul, which passes through most of the study area (figure 1). notable earlier workers on the hydrogeology of the study area include raeburn and tattam (1930), du preez and barber (1965), anderson and ogilbee (1973), adelana et al. (2003), alagbe (2006), and kwaya et al. (2020) and oteze (1976, 1991). oteze (1976) indicated that the kalambaina aquifer, which is http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com mailto:%20charger.ca34@gmail.com mailto:%20charger.ca34@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 794 shallow and cavernous, is readily subjected to pollution from human and animal wastes. but wali et al. (2020) concluded that both illo and gwandu formations display significant differences in their physicochemical parameters of water quality and mineral facies of rock weathering this work is to employ hydrochemistry and nemerow pollution index (npi) to determine the suitability of the surface and groundwater in the study area for domestic and agricultural uses. this study employed hydrochemistry to determine the suitability of surface and groundwater in the study area, while the nemerow pollution index (npi) is to determine the heavy metal pollution status of the surface and groundwater in the study area. 2. materials and methods 2.1 study area the research was carried out within birnin kebbi old town and several other villages, which form part of the birnin kebbi sheet 49, northwestern nigeria. the study area is part of gwandu formation and is accessible through birnin kebbi dukkul road, birnin kebbi -zauro, badariya kola road with several foot paths and untared roads. the relief of the study area consists of flat-topped hills with ironstone capping which is dominated by gullies which serves as drainage to some of the surrounding villages. generally, the hills are less than 150 feet high, but the relief between the stream valley floor (fadama) and the hill tops reaches 300 feet. south and east of the sokoto basin, crystalline rocks form a dissected upland surrounded by isolated steep sided hills (anderson and ogilbee, 1973). the study area is drained by river dukku and its tributaries which provide extensive floodplains for farming activities as shown in (fig 1) flowing northwest direction. the study area is located within the semi-arid zone of northwestern nigeria, with two distinct seasons characterized with rainy and dry conditions. these are characterized by a short period of rainfall that really exceeds 5 months with a yearly average precipitation of about 600 mm. the rainfall is erratic with longer dry season that lasted from october to april, characterized by high temperature, low humidity with high evapotranspiration which can exceed 2,500 mm/year. vegetation is the savannah-type and is characterized by sparse shrub and short feathery grasses, which forms a complete ground cover during the wet season only. the study area is part of the nigerian sector of the iullemmeden basin in north-western nigeria which is underlain by a sequence of semi-consolidated sedimentary rocks ranging in age from cretaceous to tertiary and consisting mostly of interbedded sand, clay, and limestone. the stratigraphy of the basin is made up of the taloka, dukamaje, wurno, dange, kalambaina, gamba and gwandu formations. the sediments were deposited during four main phases: 1. the illo and gundumi formations are composed of grits and clays, which were deposited unconformably on the pre-cambrian basement. 2. the maastrichtian rima group rests unconformably on the illo and gundumi formations. the group consists of mudstones and friable sandstones (taloka and wurno formations), separated by the fossiliferous dukamaje formation. 3. the paleocene sokoto group consists of the dange and gamba formations (mainly shale) and is separated by the calcareous kalambaina formation. 4. the post-paleocene continental terminal, which is the gwandu formation, occurs as tabular hills or low hummocks over the dip slope of the paleocene formation. the study area is predominantly of the gwandu formation. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abdulganiyu et al: hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria. azojete, 19(4):793806. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 795 2.2 data collection and analysis twenty-three groundwater and surface water samples taken from dug wells, tube wells, rivers, and boreholes were collected from different communities within the study area and subjected to hydrogeochemical analyses to determine the different physicochemical parameters present in the water samples. the apha (1999) criteria were followed for sampling, handling and analysis. electrical conductivity (ec), total dissolved solids (tds), ph, and temperature were measured in the field using a hand-held portable digital 3-in-1 conductivity metre and a ph metre, respectively. the samples were stored at a very low temperature of < 4oc and transported to the multi-user laboratory of usmanu danfodiyo university, sokoto, where they were processed and analyzed for major and minor cations, anions, and oxides using an atomic absorption spectrometer (aas). nemerow pollution index (npi) was used to determine the pollution level since ground and surface water quality has become an important water resources issue due to rapid increase of population and unplanned urbanization. sample points with their respective coordinates are displayed in table 1. twenty-three samples were collected in all, with groundwater (14) taken from dug wells, tube wells and boreholes, while nine (9) surface water samples were collected from the river dukkul in the study area (figure 1 and figure 2) in different communities within the study area (table 1a). the apha (1999) criteria were followed for sampling, handling and analysis. prior to the sampling, the containers were rinse with water from which the samples were to be collected; in order to get representative samples, direct from the aquifer. water was pumped out or bailout using a water drawer from the different groundwater sources for at least 10 – 15 minutes. two samples were collected from each of the sampling points, in one sample from which the cations were to be analyzed and few drops of 1.1 molar hno3 was added to reduce the precipitation of some metals by reducing the ph of the water to 2. physical parameters of electrical conductivity (ec), total dissolved solids (tds) ph, and temperature were measured in-situ at the sampling points using a handheld 3-in-1 conductivity and ph meters, respectively. samples were stored at a very low temperature of 4o c. the samples were taken to the multiuser laboratory of usmanu danfodiyo university, sokoto, where they were processed and analyzed for major and minor cations, anions, and oxides using an atomic absorption spectrometer (aas model aa 6300 shimadzu japan). the piper and schoeller plots were employed for the samples to know the water types and the level of contamination and relative concentration of the anions and cations in the study area. while the wilcox diagram and gibbs plots were used to know the level of salinity and to define the source of the chemical species in the analyzed water samples in the study area. statistical analyses were used to evaluate the heavy metals and the physical parameters measured in the study area using ibm spss 2.1 model software statistical package. nemerow pollution index (npi) was used to determine the pollution level since ground and surface water quality has become an important water resources issue due to rapid increase of population and unplanned urbanization. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 796 figure 1: drainage map of the study area. table 1: community drinking water source analyzed samples with coordinates. sample number names of location with their coordinates drinking water source 1 takalau n 12° 28' 12'' e 4° 11' 16'' borehole 2 takalau n 12° 28' 08'' e 4° 11' 19'' well 3 takalau n 12°28' 11'' e 4° 11' 29'' well ii 4 water works n 12° 28' 53'' e 4° 12' 2'' river dukul 5 gamagira n 12° 27' 57'' e 4° 11' 30'' borehole 6 malala quarters n 12° 28' 16.8'' e 4° 11' 13.1'' borehole 7 fadama ii n 12° 28' 46.5'' e 4° 11' 22.7'' river dukul 8 fadama ii n 12° 28' 46.5' e 4° 11' 22.7'' river dukul 9 tarasa i n 12° 28' 42'' e 4° 10' 23'' well 10 dutsen idi n 12° 28' 01'' e 4° 11' 24'' borehole 11 tungar buzu n 12° 29' 40'' e 4° 16' 23'' well 12 tungar buzu n 12° 29' 57'' e 4° 16' 15'' river dukul 13 tarasa ii n 12° 28' 33'' e 4° 9' 46'' river dukul 14 unguwar jodu n 12° 26' 7.8'' e 4° 7' 36.3'' well 15 tarasa iii n 12° 28' 36'' e 4° 10' 10.7'' river dukul 16 gamagira(dangaladima) n 12° 28' 11'' e 4° 11' 24'' borehole 17 tarasa n 12° 28' 44'' e 4° 9' 34'' tube well 18 gwadangwaji n 12° 28' 31.1'' e 4° 13' 53.7'' bore hole 19 water works ii n 12° 28' 53'' e 4° 12' 2'' river dukul 20 tarasa iv n 12° 26' 56'' e 4° 10' 31'' borehole 21 takalau n 12° 28' 11'' e 4° 11' 24'' borehole 22 tarasa v n 12° 28' 44'' e 4° 9' 41'' river dukul 23 tarasa n 12° 28' 44'' e 4° 9' 41'' river dukul table 1b: equation used for pollution indices computation for water samples collected from study area. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abdulganiyu et al: hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria. azojete, 19(4):793806. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 797 3. results and discussion the results of the physical parameters measured in the study area are presented in table 2. for the 23 surface and groundwater samples analyzed, the measured temperature ranged between 33.3 and 34.2oc. ph values ranged between 0.27 (sample l16a from dangaladima) and 7.32 (sample 4a from the waterworks). the ph of the water in this study indicated weakly acidic to slightly alkaline water because the former samples were from a borehole located 4 m from a pit latrine, while the latter were from near the waterworks, where dry season farming with excessive fertilizers occurs. the ec measured ranges between 70 and 9692, while the tds fluctuates between 35 and 5501. the variation observed in these physical parameters is due to uncontrolled anthropogenic activities in the study area, mainly agricultural activities and improper waste disposal. however, most of the physical parameters measured values fall within the acceptable limit of who (2011), as given in table 2. the geological map of the study area is displayed in figure 2. the results of the major elements and oxides measured for the samples table 3, which was used in plotting the piper diagram, schoeller plot, gibbs diagram, and wilcox diagrams the piper diagram was used to classify the hydro-chemical facies of the groundwater according to the dominant ions analyzed in the samples. the dominant water type in the study area is camg-hco3. figure 4 3, which can be attributed to the presence of ca2+, mg2+, and hco32-, which are dissolved in the water from the breakdown and dissolution of carbonate rock, mainly limestone, which occurs in the area. however, the results of heavy metals measured for samples in the study area are shown in table 4 and table 5 display summary of physical parameters and heavy metals measured in the study area. figure 2: a. generalized geological map of the nigerian sector of iullemmeden basin (sokoto basin) showing the study area (red). b. geological map of the study area. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 798 table 2: physical parameters for the water samples measured in the field sample number ec tds ph temperature (℃) 1a 936 469 6.34 34.2 2a 590 295 5.46 33.7 3a 1638 819 6.76 34.2 4a 114 57 7.32 33.4 5a 916 458 6.94 33.3 6a 3562 1781 1.63 34.2 7a 112 56 6.09 33.5 8a 114 57 6.59 34.2 9a 114 57 7.01 33.8 10a 1244 622.4 0.59 34.2 11b 90 45 4.14 33.8 12b 112 56 6.2 33.7 13a 114 57 6.55 33.8 14a 92 46 6.36 34 15a 114 57 6.81 34.2 16a 1506 5501 0.27 33.8 17a 416 217 5.46 33.8 18a 192 96 5.19 33.8 19a 9692 4846 0.85 33.9 20b 070 035 3.52 34 21a 312 156 5.47 33.7 22a 134 67 5.51 33.7 l 23 90 45 6.08 33.8 average 968.4348 691.1043 5.093043 33.85652 maximum 9692 5501 7.32 34.2 minimum 70 35 0.27 33.3 table 3: major elements and oxides measured in the laboratory. sample number mg/l ca mg/l mg mg/l k mg/l na mg/l p mg/l co3 mg/l hco3 mg/l cl mg/l nh4 mg/l no3 1a 166 194.4** 20** 6.7 0.19 nil 72 0.6 0.4 2.0 2a 102 87.6 5.2 3.8 0.19 nil 60 1.1 0.4 1.2 3a 268** 67.2 26 20 0.20 nil 92 0.7 0.8 2.4 4a 84 74.4 0.7 0.8 0.22 nil 52 1.6 0.4 1.4 5b 64 79.2 7.4 8.3 0.21 0.2 124** 1.9 0.6 1.8 6a 112 100.8 2.4 3.3 0.20 nil 64 0.7 0.4 1.0 7b 46 76.8 0.8 0.9 0.22 nil 64 2.6 0.6 1.4 8b 72 54.0 0.7 0.9 0.22 nil 80 2.1 0.4 1.2 9a 108 51.6 0.7 0.9 0.23 nil 96 1.2 0.8 1.6 10a 68 109.2 2.2 2.5 0.19 0.2 76 0.6 0.4 1.0 11b 74 73.2 0.6 0.6 0.19 nil 84 0.6 0.4 1.0 12b 286** 5.04 0.6 0.8 0.21 nil 104** 1.7 0.4 1.4 13a 56 56.4 0.7 1.0 0.22 nil 112 1.4 0.4 1.4 14a 90 51.6 1.9 0.9 0.19 nil 68 0.5 0.4 1.0 15a 68 78.0 0.7 1.0 0.21 nil 52 1.9 0.8 1.8 16a 286** 135.6 5.8 8.3 0.19 nil 136** 0.5 0.4 1.0 17a 134 126.0 2.6 3.9 0.19 nil 92 0.7 0.6 1.4 18a 72 78.0 0.8 1.7 0.19 nil 108 0.7 0.4 1.4 19a 114 100.8 0.7 1.5 0.20 0.2 148** 3.2 0.4 2.2 20b 96 62.4 0.6 0.8 0.19 nil 76 0.6 0.8 1.4 21a 84 73.2 7.0 1.3 0.19 nil 96 1.0 0.4 1.2 22a 66 62.4 0.7 1.1 0.21 0.2 64 2.2 1.0 3.4 23 52 78.0 1.7 0.9 0.19 0.2 108** 0.8 0.6 3.0 maximum 286 194.4 26 20 0.23 0.2 148 3.2 1.0 3.4 minimum 46 5.04 0.6 0.6 0.19 0.2 52 0.5 0.4 1.0 average 111.652 81.558 3.935 3.126 0.2017 0.2 88.174 1.257 0.5304 1.5913 who 2011 200 150 12 50 120 100 250 50 nswqs 2007 200 250 50 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abdulganiyu et al: hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria. azojete, 19(4):793806. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 799 figure 3: type classification for water samples from the study area using the piper trilinear diagram (back and hanshaw 1965). a = calcium type, b = sodium or potassium type, c = magnesium type, d = no dominant type, e = bicarbonate type, f = chloride type, g = sulphate type, h = no dominant type i = ca+mg type, j = hco3 +co3 type, k= na+k type, l = cl+so4 type m = ca(mg) hco3 type, n = ca(mg) cl so4 type, o = na(k) hco3 type, p = na(k) cl(so4) type. the piper and schoeller plots for the samples indicate the dominance of ca+mg-hco3 water in the study area. the level of contamination and relative concentration of the anions and cations in the study area indicate shallow fresh groundwater that is slightly hard. the water is associated with limestone underlining the area and carbonate hardness from recent precipitation occurring at shallow depths below the surface. ca+mg-hco3 is formed from the dissolution of carbonate minerals, most likely from the kalambaina limestone in the study area. figure 4: schoeller plot showing level of contamination in the analysed water sample. the gibbs plots (figures 5a and b) were used to interpret and define the source of the chemical species in the analyzed groundwater samples. this plot demarcated three domains for the anions and cations, which are the precipitation, rock, and evaporation domains. the ca mg na k cl hco3 no3 parameters 0.0 0.1 1.0 10.0 100.0 co nc en tra tio n ( me q/l ) schoeller plot aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa gggggg gggggg gggggg gggggg gggggg gggggg gggggg kkkkkk kkkkkk kkkkkk kkkkkk kkkkkk kkkkkk kkkkkk oooooo oooooo oooooo oooooo oooooo oooooo oooooo dddddd dddddd dddddd dddddd dddddd dddddd dddddd hhhhhh hhhhhh hhhhhh hhhhhh hhhhhh hhhhhh hhhhhh llllll llllll llllll llllll llllll llllll llllll pppppp pppppp pppppp pppppp pppppp pppppp pppppp qqqqqq qqqqqq qqqqqq qqqqqq qqqqqq qqqqqq qqqqqq rrrrrr rrrrrr rrrrrr rrrrrr rrrrrr rrrrrr rrrrrr ssssss ssssss ssssss ssssss ssssss ssssss ssssss eeeeee eeeeee eeeeee eeeeee eeeeee eeeeee eeeeee tttttt tttttt tttttt tttttt tttttt tttttt tttttt uuuuuu uuuuuu uuuuuu uuuuuu uuuuuu uuuuuu uuuuuu wwwwww wwwwww wwwwww wwwwww wwwwww wwwwww wwwwww xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx iiiiii iiiiii iiiiii iiiiii iiiiii iiiiii iiiiii mmmmmm mmmmmm mmmmmm mmmmmm mmmmmm mmmmmm mmmmmm bbbbbb bbbbbb bbbbbb bbbbbb bbbbbb bbbbbb bbbbbb ffffff ffffff ffffff ffffff ffffff ffffff ffffff jjjjjj jjjjjj jjjjjj jjjjjj jjjjjj jjjjjj jjjjjj nnnnnn nnnnnn nnnnnn nnnnnn nnnnnn nnnnnn nnnnnn cccccc cccccc cccccc cccccc cccccc cccccc cccccc legendlegend a 1 e 2 i 3 m 4 b 5 f 6 j 7 n 8 c 9 g 10 k 11 o 12 d 13 h 14 l 15 p 16 q 17 r 18 s 19 t 20 u 21 w 22 x 23 http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 800 dominance origin for both cations and anions in the analyzed water sample is precipitation dominance, with a few samples falling in the precipitation domain and evaporation domain. figure 5a and b: controlling mechanisms for groundwater quality in the study area (after gibbs, 1970). the wilcox diagram (figure 6) shows the level of salinity of water samples in the study area which is generally ranging from low to very high salinity hazard especially in samples 5 and 6. figure 6: wilcox diagramfor all the samples in the study area. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abdulganiyu et al: hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria. azojete, 19(4):793806. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 801 table 4: heavy metals measured in the surface and groundwater sample number cr fe cu pb ni 1a bdl bdl bdl bdl 1.8001 1b -0.7450 -1.8240 0.2544 -0.1175 bdl 2a -0.2941 0.0147 0.2786 -0.1992 bdl 2b bdl bdl bdl bdl 1.6278 3b -0.3993 0.0624 0.3149 -0.1447 1.7722 4b 0.6376 0.1908 0.2871 -0.0448 1.7221 5a 0.7621 0.3156 0.2386 -0.1175 1.7555 6b 0.7256 0.3230 0.3137 -0.2173 0.1505 7 0.6333 0.3266 0.3246 -0.0312 bdl 8a 0.5775 0.3670 0.4191 0.4772 bdl 9b 0.6634 0.3817 0.6068 1.1445 bdl 10b 0.6720 0.4257 0.2701 -8.5337 bdl 11a 0.5839 0.4514 0.2737 -9.7639 0.3009 12a 2.6063 0.3450 0.3924 0.4137 0.4124 13b -0.1589 0.3413 0.3537 0.5771 0.5629 14b 0.3134 0.4074 0.3174 1.7256 0.5629 15b 0.3564 0.9322 0.3089 -45.2956 0.5517 16a 0.9489 1.5598 -0.2798 -18.7022 0.6075 17b 0.7492 0.7230 0.2968 -33.8270 -0.1672 18b 0.4487 -4.3455 0.2750 -45.1039 -0.0279 19b 0.4830 -2.8002 0.2750 -20.3727 0.0724 20b -0.4165 0.4367 0.3331 -45.2945 0.3009 21b 0.5088 -36.7001 0.2980 -29.5198 0.2285 22b 0.7729 -0.4844 0.3125 -45.2945 -0.3177 23 0.5925 -2.5066 0.3089 0.3637 0.3511 average 0.459824 -1.81264 0.292957 -12.0451 0.7196 table 5: summary of physical parameters and heavy metals measured in the study area. the results of the heavy metals displayed in table 4 reveal average values for cr2+ 0.459824, fe2+-1.81264, cu2+0.292957, pb2+-12.0451, and ni2+ 0.3009, respectively. these values were compared to the who (2011) standard in table 5, which shows that all fall within the acceptable limit permissible for human consumption. evaluated physical and chemical parameters revealed that water resources reveal the presence of mg2+ which indicates the hardness of the water. this could be due to the presence of alkaline earth metals such as magnesium, which remarkably influence the chemistry of the water at the location. ca2+ in twenty out of the twenty-three water analyzed samples comply with the who (2007) and nsdwq (2007; 2015) standards, with the exception of samples from location 3b, which have 268 mg/l, while locations 12b and 16a have 286 mg/l, respectively. the presence of ca2+ indicates the hardness of the water, which could be due to the presence of alkaline earth parameter minimum maximum mean std. deviation variance kurtosis who (2011) cr -.7450 2.6063 .4409 .6371575 .406 4.904 50 fe -36.7001 1.5598 -1.6423 7.4203392 55.061 23.262 300 cu -.2798 .607 .2709 .1616117 .026 5.710 2000 pb -45.2956 1.72 11.9151 17.7880 316.414 -.419 3000 ni -.3177 1.80 .4907 .6785633 .460 -.069 70 ec 70.0000 9692.00 1317.37 74 2638.7740 6963128.2 56 7.506 1000 tds 35.0000 5501.00 883.500 1 1705.7613 2909621.7 11 3.939 500 ph .270000 7.32 5.1821 2.14828 4.615 .697 6.5-8.5 temp 33.30000 34.20 33.8702 .2606 .068 -.394 30-32 http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 802 metals such as calcium, which remarkably influence the chemistry of the water in the location. all the major oxides analyzed for all twenty-three samples fall within the who (2007) and nsdwq (2007; 2015) standards except for hco3 2-. the hco3 2for sixteen of the twentythree samples is in tandem with the who (2007) and nsdwq (2007; 2015) standards, except for samples from seven locations: 5b 124 (mg/l), 12b 104 (mg/l), 13a 112 (mg/l), 16a 136 (mg/l), and 18a 108.(mg/l), 19a 148 (mg/l), and 23 108 (mg/l), respectively. the high values of ca2+, mg2+ and hco3 2recorded in the samples could result from the breakdown and dissolution of carbonate rock, mainly limestone, which occurs in the study area. the contaminants may have migrated through tectonic and sedimentary structures, which serve as conduit pipes for rapid transmission to the groundwater system in the study area. low-salinity ca-mg-hco3 water is the most common type in the research area. nemerow pollution index was used to evaluate the water quality of the study area. npi value exceeding 1.0 indicate the presence of impurity in water and hence require some treatment before being used. other interpretations of the nemerow pollution index are shown in table 6 while the result from nemerow pollution index is displayed in table 7. table 6: standard and classes of computed pollution used in this study pollution index standard /class standard source nemerow pollution index (npi) ni< 1 no pollution adopted from liu et al., (2015a) 1 ≤ 𝑁𝐼 < 2.5 light pollution 2.5 ≤ 𝑁𝐼 < 7 moderate pollution ni ≥ 7 heavy pollution table 7: below is nemerow’s pollution index for water quality showing the level of contamination in the water samples nemerow's pollution index [water quality index) npi values of various sampling locations parameters nsdwq, 2015 location 1 location 2 location 3 location 4 location 5 location 6 ph 8.5 0.75 0.64 0.80 0.86 0.82 0.19 tds 500 0.94 0.59 1.64 0.11 0.92 3.56 e.c 1000 0.94 0.59 1.64 0.11 0.92 3.56 mg2+ 20 9.72 4.38 3.36 3.72 3.96 5.04 na+ 200 0.03 0.02 0.10 0.00 0.04 0.02 cr2+ 0.05 0.00 0.00 0.00 12.75 15.24 14.51 fe2+ 0.3 0.00 0.05 0.21 0.64 1.05 1.08 cu2+ 1 0.25 0.28 0.31 0.29 0.24 0.31 ni 0.02 90.01 81.39 88.61 86.11 87.78 7.53 pb2+ 0.01 0.00 0.00 0.00 0.00 0.00 0.00 cl 250 0.00 0.00 0.00 0.01 0.01 0.00 no3 50 0.04 0.02 0.05 0.03 0.04 0.02 location 7 location 8 location 9 location 10 location 11 location 12 location 13 0.72 0.78 0.82 0.07 0.49 0.73 0.77 0.11 0.11 0.11 1.24 0.09 0.11 0.11 0.11 0.11 0.11 1.24 0.09 0.11 0.11 3.84 2.70 2.58 5.46 3.66 0.25 2.82 0.00 0.00 0.00 0.01 0.00 0.00 0.01 12.67 11.55 13.27 13.44 11.68 52.13 0.00 1.09 1.22 1.27 1.42 1.50 1.15 1.14 0.32 0.42 0.61 0.27 0.27 0.39 0.35 0.00 0.00 0.00 0.00 15.05 20.62 28.15 0.00 47.72 114.45 0.00 0.00 41.37 57.71 0.01 0.01 0.00 0.00 0.00 0.01 0.01 0.03 0.02 0.03 0.02 0.02 0.03 0.03 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abdulganiyu et al: hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria. azojete, 19(4):793806. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 803 location 14 location 15 location 16 location 17 location 18 location 19 location 20 location 21 location 22 location 23 0.75 0.80 0.03 0.64 0.61 0.10 0.41 0.64 0.65 0.72 0.09 0.11 11.00 0.43 0.19 9.69 0.07 0.31 0.13 0.09 0.09 0.11 1.51 0.42 0.19 9.69 0.07 0.31 0.13 0.09 2.58 3.90 6.78 6.30 3.90 5.04 3.12 3.66 3.12 3.90 0.00 0.01 0.04 0.02 0.01 0.01 0.00 0.01 0.01 0.00 6.27 7.13 18.98 14.98 8.97 9.66 0.00 10.18 15.46 11.85 1.36 3.11 5.20 2.41 0.00 0.00 1.46 0.00 0.00 0.00 0.32 0.31 0.00 0.30 0.28 0.28 0.33 0.30 0.31 0.31 28.15 27.59 30.38 0.00 0.00 3.62 15.05 11.43 0.00 17.56 172.56 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 36.37 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.00 0.02 0.04 0.02 0.03 0.03 0.04 0.03 0.02 0.07 0.06 values > or = 1 indicates presence of pollution in the water sample however, the ph npi value varies from 0.03 to 0.86 in all sampling stations that fall within the permissible npi range. table 6. the tds npi value varies, but all fall within the permissible limit except in sampling locations l3 = 1.64, l6 = 3.56, l10 = 1.24, l16 = 11.0, and l19 = 9.69, respectively. the ec npi value falls within the permissible range except for l3 = 1.64, l6 = 3.56, l10 = 11.24, l16 = 1.51, and l19 = 9.69. the npi value for mg2+ for only sample l12 falls within the permissible limit, with others ranging from 2.58 to 9.72. the ec npi value falls within the permissible range except for l3 = 1.64, l6 = 3.56, l10 = 11.24, l16 = 1.51, and l19 = 9.69. the npi values for na+ all fall within the permissible range. the cr2+ value for l 1, l2, l3, and l13 all fall within the permissible range, but other samples range from 6.27 to 52.13, which fall outside the npi range. the fe2+ ranges l1, l2, l3, l4, l18, l19, l21, l22, and l23 all fall within the npi range, but other sampling locations indicate a range of 1.05 to 5.20, which is unsuitable for drinking purposes. the cu2+npi for all samples is within the npi range. the ni npi value for samples l7, l8, l9, l10, l17, l18, and l22 is within the npi range, but others range from 7.53 to 90.01, making them unsuitable for drinking purposes. the values for pb2+ all fall within the permissible npi range except for l8, l9, l12, l13, l14, and l23, which indicate pollution. the cl and no3 exhibit values below the npi range of 1. 4.0 conclusion the hydro-chemical study of the twenty-three water samples from drinking water sources in birnin kebbi old town and its environs was conducted to determine the pollution and contamination status. results revealed surface and groundwater with concentrations of ph, na2+, cu2+, cland no3 and higher concentrations of tds and ec, which are above the nsdwq (2015) set limits. the results also show that the cations na2+ and cu ions from the locations have values less than the maximum limit recommended by nsdwq (2015), while mg2+ and fe2+ have higher values with lower values for trace elements like cr2+, ni, and pb2+. also, the anions analyzed, cland no3 ion have concentrations within the limits of nsdwq (2015) recommended for drinking water. the dominance of the ca2+mg2+-hco3 facie over the other two types can be related to the geology and other geochemical processes that operate within the aquifers in the area. however, application of nemerow’s pollution index shows that the majority of the sampling locations displayed high npi values, especially for ni2+ and pb2+. the npi ni2+ values for eleven (11) out of twenty-three samples, making up 47.83%, have npi values that range from 7.53 to 90.01, making them unsuitable for drinking purposes. the npi values for pb2+ for six (6) samples, making up about 26.09%, have high npi values that range from 36.37 to 172.56, depicting a high level of pollution. the nemerow pollution index for evaluating the water quality, shows some pollutants have concentrations that are above standards. the people in the study area directly rely on the available surface and groundwater http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 804 for drinking and domestic use from boreholes, river and open wells without any treatment. however, if the water is to be consumed for these purposes, proper treatment is necessary to avoid adding to the already existing health issues that affect not only older people but also children and younger people. better management of water systems is needed for water supplies for agricultural and domestic uses in the study area. references alagbe, sa. 2006. preliminary evaluation of hydrochemistry of the kalambaina formation, sokoto basin. nigeria environmental geology, 51: 39–45 doi 10.1007/s00254-006-0302-5 anderson, hr. and ogilbee, w. 1965. exploratory drilling for ground water in western sokoto province, nigeria, with particular· reference to artesian aquifers in the gwandu formation: united state geological survey open-file report, p. 98. apha, 1999. standard methods for the examination of water and wastewater, 20thedn. american public health association, washington dc. black, w. and handshaw, bb. 1965. chemical geohydrology in: advance in hydroscience, academic press, new york, pp. 11 – 49. born, sm., yanggen, da. and zaporozec, a. 1987.a guide to groundwater quality planning and management for local governments. wisconsin geological and natural history survey, madison, special report 9:91 burke, f., hamza, s., naseem, s., huda, sn., azam, m. and khan, i. 2016. impact of cadmium polluted groundwater on human health: winder, balochistan: sage open. 6 (1), p1-8 doi: 10.1177/2158244016634409. caerio, s., costa, mh., ramos, tb., fernandes, f., silveira, n., coimbra, a., mederios, g. and painho, m. 2005. assessing heavy metal contamination in sado estuary sediment: an index analysis approach ecological indicators, 5(2): 151-169. chen, m., qin, x., zeng, g. and li, j. 2016. impacts of human activity modes and climate on heavy metal “spread” in groundwater are biased. chemosphere, 152:439–445. chitsazan, m., aghazadeh, n., mirzaee, y. and golestan, y. 2019. hydrochemical characteristics and the impact of anthropogenic activity on groundwater quality in suburban area of urmia city, iran. environment, development and sustainability, 21(1):331–351. davis, sn. and dewiest, rjm. 1966. hydrogeology, john wiley and sons, inc., hoboken, p.463. gibbs, rj. 1970. mechanisms controlling world water chemistry. science, 170: 1088-1090. doi.org/10.1126/science.170.3962.1088 joarder, mam., raihan, f., alam, jb. and hasanuzzaman, s. 2008. regression analysis of ground water quality data of sunamganj district, bangladesh. international journal of environmental research, 2(3): 291. kogbe, ca. 1972. preliminary study of the geology of the nigerian sector of the iullemmeden basin. (dessauvagie tfj. and whiteman, aj. (eds)). african geology, lbadan, university press, nigeria, pp.219–228. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abdulganiyu et al: hydrochemistry of surface and groundwater in parts of birnin kebbi northwestern nigeria. azojete, 19(4):793806. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 805 kogbe, ca. 1972. preliminary study of the geology of the nigerian sector of the iullemmeden basin. (dessauvagie tfj. and whiteman, aj. (eds)). african geology. lbadan, university press, nigeria, pp.219–228. kogbe, ca. 1976. paleogeographic history of nigeria from albian times. geology of nigeria (ca. kogbe(ed.)), elizabethan publishing, lagos nigeria. kogbe, ca. 1979. geology of the south-eastern (sokoto) sector of the lullemmeden basin department of geology, ahmadu bello university zaria bulletin, 32:142. kwaya, my., hamidu, h., abdullahi, im., yelwa, na., abdulganiyu, y., kana, am., ibrahim, ha. and grema, hm. 2020. irrigation and drinking groundwater quality indices of gada community and environs, semi-arid region, sokoto basin, northwestern nigeria. nigerian journal of science, 54(1): 85-103. liu, s., zhang, y., bi, s., zhang, x., li, x., lin, m. and hu, g. 2015. heavy metals distribution and environmental quality assessment for sediments off the southern coast of the shandong peninsula china, marine pollution bulletin, 100(1): 483-488. nigerian standard for drinking water quality, 2015. nigerian standard for drinking water quality nsdwq nigerian industrial standard, lagos, 554:1-14. obaje, ng. 2009. geology and mineral resources of nigeria. springer dordrecht heidelberg london. oteze, ge. 1989. the hydrogeology of northwestern nigeria. (ca. kogbe (eds.)), geology of nigeria. rock view publ. co. jos, 455-472. petters, sw. 1978.maastrichtian-paleocene foraminifera from northwestern nigeria and their paleogeography. acta paleontological polonica, 23:131-152. piper, am. 1944. a graphic procedure in the geochemical interpretation of water analyses: american geophysics union transactions, 25:914-923. raeburn, c. and tattam, cm. 1930. a preliminary note on the sedimentary rocks of sokoto province: nigeria geological survey bulletin, 13: 57-60. unicef2008. unicef hand book on water quality. united nations children’s fund, new york, pp. 1-191. accessed from: https://www.unicef.org/french/wash/files/wq_handbook_final_signed. wali, su., alias, n. and harun, sb. 2020. hydro-geochemical evaluation and mechanisms controlling groundwater in different geologic environments, western sokoto basin, northwestern nigeria, sn applied sciences, 2:1808 https://doi.org/10.1007/s42452-020 03589-y world health report. 2007. a safer future: global public health security in the 21st century emergency preparedness adgo, health security preparedness (hsp) editors: world health organization, pp. 72. world health organization. 2011. guidelines for drinking-water quality. first addendum to 3rd edition, geneva.,1:515. (https://weatherspark.com/y/51486/average-weather-in-sokotonigeria-year-round. 2016. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com https://www.unicef.org/french/wash/files/wq_handbook_final_signed https://www.unicef.org/french/wash/files/wq_handbook_final_signed https://doi.org/10.1007/s42452-020 https://weatherspark.com/y/51486/average-weather-in-sokoto-nigeria-year-round.%202016 https://weatherspark.com/y/51486/average-weather-in-sokoto-nigeria-year-round.%202016 arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):793-806. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: charger.ca34@gmail.com 806 zadawa, an. and omran, a. 2018. climate change and water security issues in africa: introducing partnership procurement for sustainable water projects in nigeria, pp 127–134. https ://doi. org/10.1007/978-981-10-7748-7_6 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):23-32 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 23 original research article validation of wet chemistry method as alternative to gas chromatography for biogas methane content determination t. h. ibrahim*1,2, e. betiku2,3, b. o. solomon2, j. o. oyedele1, g. o. olaifa1, a. a. adekunle1 1bioresources development centre, national biotechnology development agency, ogbomoso, nigeria. 2biochemical engineering lab., department of chemical engineering, obafemi awolowo university, ile-ife, nigeria. 3department of biological sciences, florida agricultural & mechanical university, tallahassee, florida 32307, usa. *corresponding author’s email address: taiwib098@gmail.com 1.0 introduction anaerobic digestion technology has the potential for simultaneous waste treatment and the generation of biogas, a renewable energy source (del real and lopez-lopez, 2012; kafle and chen, 2015). biogas is a mix of many gases, mainly methane (50-75%) and carbon dioxide (25-45)% with other components such as hydrogen sulphide, nitrogen, ammonia, oxygen and water vapour, usually present in small amounts of 1-5% (al seadi et al., 2013). methane is the component responsible for the calorific quality of biogas and if less than 50%, the biogas will not burn (siles et al., 2011). as a result, monitoring the percentage of methane in biogas that is being produced during anaerobic digestion provide vital information on biogas quality, possible uses awe et al., (2017) and the overall article information abstract anaerobic digestion technology has the potential for simultaneous waste treatment and biogas generation. its rate of dissemination and adoption in most developing countries has however, slowed down for many years partly due to inadequate research facilities such as advanced gas measuring equipment, and associated cost of analyses. this study, therefore, tested and validated the use of classical wet chemistry analysis method (cwcam) as a readily accessible and cheaper alternative to gas chromatographic method (gcm), for determining the proportion of methane (ch4) in produced biogas. biogas samples were simultaneously collected every week in 5 ml and 20 ml hypodermic syringes, from a digester in which cassava vinasse (cv) was being codigested with poultry droppings (pd), using ruminal fluids of cattle (rfc) as inoculum. while samples in 5ml syringes were analyzed using the gcm, the 20 ml samples were analyzed using the cwcam, to determine the percentage of methane in the biogas samples collected each week. the corresponding volumes, corrected to standard temperature and pressure (stp) condition was then calculated. the results from both analytical methods were statistically analyzed and compared using the data analysis tool in microsoft office excel. the difference in results from the two methods ranged from -3 to +2.9% with cwcam giving slightly higher values of methane percentage. overall, a relatively high coefficient of determination (r2 = 0.9728) and low standard error (se = 1.4) of the regression equation between the two sets of results indicate that the two methods may be used interchangeably. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 may, 2022 revised 25 august, 2022 accepted 30 august, 2022 keywords: anaerobic digestion gas chromatography linear regression validation wet chemistry http://www.azojete.com.ng/ mailto:taiwib098@gmail.com mailto:taiwib098@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):23-32. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 24 digestion processes and is, therefore, very necessary in biogas research. gas chromatograph (gc) equipped with either a thermal conductivity or flame ionization detector and using either hydrogen or helium as the carrier gas, is the most widely used analytical method for this purpose (subbarao et al., 2013; adepoju et al., 2016; canepa et al., 2017; dubrovskis and plume, 2017). in developing countries, biogas technology can support energy supply decentralization such that rural communities can produce biogas to meet their energy needs (ray et al., 2016). it can be used for cooking, lighting, crop drying, pumping water for irrigation, direct heating, running internal combustion engines and electric power generation applications (rafiee et al., 2021). also, indoor air pollution (iap) which is a serious health risk especially to women and children in the rural areas, is prevented by using biogas as cooking fuel instead of fuel wood, kerosene and charcoal (abadi et al., 2017). despite the numerous applications of biogas (machunga-disu and machunga-disu, 2012; ray et al., 2016; awe et al., 2017), the dissemination and adoption of its production technology in most developing countries has been very slow for many reasons, chief among which is the lack of necessary research facilities due to poor funding (mukumba et al., 2016; patinvoh and taherzadeh, 2019). therefore, considering the significance of methane quantification in biogas research, limited access to such research facilities as the advanced gas measuring equipment like gc has prompted many researchers to investigate more affordable alternative tools/methods such as low cost self-assembled gas analyzers yang et al., (2019) and classical wet chemistry analytical methods (beck, 1994; raposo et al., 2011). the latter appears to be readily accessible especially to researchers in the rural areas as it only requires simple laboratory skills of volumetric analysis and measurements anozie and adeboye, (2009) while the former require skills in instrumentation. in an international inter-laboratory study to investigate the performances of different biochemical methane potential (bmp) protocols, raposo et al. (2011) reported that one laboratory reliably measured methane volume directly after removing carbon dioxide (co2) by flushing the biogas through a naoh solution. abdelhadi (2008) however, went further in another study, to compare the results of biogas methane quantification using gc and the co2 absorption-volumetric analysis method with a view to test the precision of the latter as an alternative method that can be used to determine the proportion of methane in biogas samples produced in laboratories with limited access to advanced analytical equipment. although the outcomes showed that the two sets of results were comparable, the alternative method was not validated. method validation is required to provide scientific evidence that the alternative analytical method is reliable and consistent before it can be used in routine analysis (belouafa et al., 2017). linear regression is one of the most established and common tool used for this purpose (twomey and kroll, 2008). the objective of this work therefore, was to compare and statistically determine the relationship and association between two alternative analytical methods of gcm and cwcam, using linear regression analysis. this was with a view to validating the latter as a reliable, readily accessible and cheaper biogas analysis method that can stimulate biogas research especially in laboratories with no access to gc or other advanced gas measuring devices. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:taiwib098@gmail.com auwal et al: validation of wet chemistry method as alternative to gas chromatography for biogas methane content determination. azojete, 19(1):13-32. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 25 2. materials and methods 2.1 materials the sources, collection and pretreatments of cv, pd and rfc used in this study have been described in a previous work (ibrahim et al., 2021a). the digester system used was a modified floating drum model and is shown in figure 1. digestion takes place in the black-painted cylindrical reactor tank while the produced biogas flows into the attached piping assembly (that had been partly filled with acidified saline solution). it exerts pressure on, and displaces a quantity of the saline solution that is equivalent to its own volume into the adjacent tubes. temperature and pressure inside the reactor were measured directly with the aid of a mercury-in-glass thermometer (0-100 oc) and a pressure gauge (0-5 bar), respectively attached to the top of the tank. all reagents used in the study were of analytical grade. figure 1: 15 l capacity digester system 2.2 methods 2.2.1 digester operation and monitoring a cv and pd mix in the percentage ratio of 62.5:37.5 was loaded into the reactor tank of the digester, with a pre-degassed rfc as the inoculum (that was 25% of the total digester contents). this was obtained from the work of ibrahim et al. (2021b) as the optimum mixing ratio for biogas production from cv. the system was operated in batch mode for a period of 10 weeks, at mesophilic temperatures. while ph and temperatures were daily monitored (fleck et al., 2017), biogas sample collection/measurement was carried out weekly according to lami and chimdessa (2016) and dahunsi et al. (2018). scum formation on slurry surface was prevented by gently shaking the digester for 1 min twice daily (ghatak and ghatak, 2018) and ph was controlled with the addition of a 0.05 m potassium phosphate buffer (lei et al., 2010). http://www.azojete.com.ng/ mailto:taiwib098@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):23-32. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 26 2.2.2 biogas methane content determination biogas samples were simultaneously collected every week in 5 ml and 20 ml hypodermic syringes, via the membrane-plugged end of the pipe on top of the reactor, by slightly opening the connecting one-way valve. meanwhile, the actual volume of biogas (vbiogas) produced each week was calculated from equation (1) where ‘h’ is the height of the displaced acidified saline solution and ‘a’ is the cross-sectional area of the tube. 𝑉𝑏𝑖𝑜𝑔𝑎𝑠 = ℎ (1) the 5ml syringe samples were analyzed in a gc (model hp5890) with an attached hayesep q column of dimension 13m x 0.5 m x 0.25 µm and a flame ionization detector. its operation was according to the method used by alfa et al. (2014). on the other hand, the biogas samples in the 20 ml syringe were analyzed for methane content by absorbing its co2 component in an alkaline solution and measuring the remaining gas volume, as described by anozie et al. (2005) and pham et al. (2013). about 15 ml of biogas sample in a 20 ml hypodermic syringe that was fitted with flexible hose (the syringe was initially filled with water and then emptied to reduce air contamination) and the free end of the tube was dipped into a 5 m naoh solution. while excess gas was pushed out to have 7.5 ml gas sample (v1) left in the syringe, approximately 7.5 ml of naoh solution was drawn in with the end of the tube still submerged in the solution. the syringe was shaken for 30 s and pointed downwards as excess liquid was pushed out so that syringe plunger level reaches 7.5 ml. the small volume of liquid that was left in the syringe (v2) equals the volume of co2 absorbed. methane volume percent (z) was then calculated using equation (2) while its actual volume was obtained from equation (3), with the assumption that biogas components other than methane and co2 were only present in negligible amounts (hafner et al., 2020). during the adjustment of naoh solution level in the syringe, the biogas pressure (po) would have been equal to the atmospheric pressure (p) and so, the volume of methane at stp was calculated using the ideal gas law (equation (4)), for standardization. 𝑧% = 1 − ( 𝑉2 𝑉1 ) (2) 𝑉𝐶𝐻4 =𝑧𝐶𝐻4 ∗ 𝑉𝑏𝑖𝑜𝑔𝑎𝑠 (3) 𝑉 = 𝑉𝑜∗𝑇 𝑇𝑜 (4) where, v= gas volume at stp (ml); vo = measured gas volume at room temperature (ml); t = standard temperature (273 k); to= room temperature in kelvin; 𝑉𝑏𝑖𝑜𝑔𝑎𝑠is the volume of biogas measured in the displacement unit; 𝑉𝐶𝐻4 is the volume of methane in the biogas 2.2.3 statistical analysis of experimental data in this study, method of linear regression analysis as described by leite and de oliveira (2006) was applied to the output data (values of percentage of methane in biogas file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:taiwib098@gmail.com auwal et al: validation of wet chemistry method as alternative to gas chromatography for biogas methane content determination. azojete, 19(1):13-32. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 27 samples) from gcm and cwcam, with the aid of the data analysis tool in microsoft excel. the relationship between the two methods and the validity of cwcam were then assessed at 95% confidence level, using indices such as the coefficient of determination (r2), standard error and the p-value. 3. results and discussion 3.1 digester performance and stability the temperature profiles of digesting slurry for 10 weeks of anaerobic digestion are shown in table 1. it shows that the average values of the morning and evening temperatures inside the digester naturally stayed within the mesophilic range of 25 to 34.6oc respectively. overall, the average daily temperature was estimated to be about 31 oc. even though, the loaded substrates-mix was conditioned to a ph of 7.2. figure 2: ph profiles of the digesting slurry figure 2 shows general fluctuations in ph within a range of ±2.1 during the retention period. this was due to the periodic accumulation of volatile fatty acids (vfa) and subsequent consumption by the methanogens (macias-corral et al., 2008). highest ph drop was recorded at the start of digestion as the easily digestible fraction of organic table 1: temperature profiles of the digesting slurry weeks temperature (oc) morning evening 1 23.9 37.3 2 24.8 37.2 3 24.2 34.6 4 25.3 35.3 5 26.4 33.5 6 28.2 36.3 7 26.5 33.4 8 26.2 32.8 9 22.6 34.2 10 24.7 33.1 average 25.28 34.77 http://www.azojete.com.ng/ mailto:taiwib098@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):23-32. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 28 matter was hydrolyzed and converted into vfa at the hydrolysis/acidogenesis stage (lin et al., 2021). however, ph control efforts (addition of 1m naoh and/or 1m h2so4 as required) prevented digester failure and ensured biogas production throughout (lei et al., 2010). 3.2 biogas production and its methane content figure 3 shows the daily production profiles of biogas, methane and carbon dioxide for the 10 week figure 3: biogas, methane and carbon dioxide production profiles based on cwcam digestion period. it was observed that after experiencing an initial lag phase, biogas production steadily increased from 139.5 ml in the first week to a maximum weekly production of 267 ml (which also corresponded with the highest methane volume) in the 5th week. afterwards, it began to decrease steadily to 33.5 ml in the 10th week. the biggest drop in biogas production was observed to be 58% between the 8th and the 9th week. the steady decrease in production could be attributable to depletion of nutrients required for microbial activities (baltrėnas et al., 2018). it was also observed that ph was generally alkaline from the 5th week and so, the drop in production could not have been due to imbalance between the hydrolysis/acidogenesis and the methanogenic phases of the digestion processes (lin et al., 2021). similar trends were also observed with the methane and co2 production profiles. digester stability and performance at any point during digestion was gauged by the quality of biogas being produced vis-à-vis its methane content and this is depicted in figure 4. it shows that the best quality biogas had 72.8% methane and 27.2% co2 contents, obtained in the 6th week of digestion. this could be because the average temperature and ph at this time was respectively 31 oc and 7.8, in agreement with the report of babaei and shayegan (2019) which stated that the optimum condition for methanogenesis was 3134 oc and 7.6-8 ph. although, biogas production drastically dropped to 33.5 ml in the 10th week, digester stability remained good as indicated by the quality of produced biogas at 62.4% methane content. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:taiwib098@gmail.com auwal et al: validation of wet chemistry method as alternative to gas chromatography for biogas methane content determination. azojete, 19(1):13-32. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 29 figure 4: methane and carbon dioxide contents in produced biogas (analysis based on cwcam) 3.3 comparison between the gcm and cwcam results for biogas analysis results of the gcm and cwcam performed to determine the percentage of methane in biogas samples collected during the anaerobic codiggestion of cv with pd are graphically shown in figure 5. both methods show that methane content generally increased with time but began to decline after about 6 or 7 weeks. also, the values of methane percentage obtained from the cwcam appear to be slightly higher than values from gcm with the highest variation being about 2.9%. this phenomenon could be attributed to the inability of the alkali solution to remove water, h2s and other trace components (al seadi et al., 2013), along with co2 from the biogas. the closeness of the 2 datasets is clearly seen in the graph. figure 6 is the plot of the regression equation (equation (5)). it shows the linear relationship between the two analytical methods with a very high coefficient of determination (r2 = 0.9728) and a low standard error (se) of 1.40, which indicate that the two methods may be used interchangeably. at a p value of 1.5*e-7, the regression equation is statistically very significant (p << 0.05). 𝑌 = 0.9061𝑋 + 6.1782 (5) figure 5: comparisons between the gcm and cwcam results for % methane determination. figure 6: correlation between the gcm and cwcam results of % methane determination 4. conclusion results from this work established that an accuracy that is comparable to that from gas chromatographic method of biogas analysis for methane content determination, can be achieved with the use of classical wet chemistry method. this indicate that the cwcam 45 50 55 60 65 70 75 0 1 2 3 4 5 6 7 8 9 10 % m e th an e in b io ga s weeks gcm (y), % cwcam (x), % http://www.azojete.com.ng/ mailto:taiwib098@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):23-32. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 30 can be reliably used by researchers who have little or no access to modern gas measuring devices especially in the rural areas of developing countries. list of abbreviations bmp biochemical methane potential ch4 methane co2 carbon dioxide cv cassava vinasse cwcam classical wet chemistry analysis method gcm gas chromatographic method iap indoor air pollution pd poultry dopping rfc ruminal fluid of cattle stp standard temperature and pressure r2 coefficient of determibation vfa volatile fatty acids references abadi, n., gebrehiwot, k., techane, a. and nerea, h. 2017. links between biogas technology adoption and health status of households in rural tigray, northern ethiopia. energy policy, 101: 284-292. abdel-hadi, ma. 2008. a simple apparatus for biogas quality determination. misr journal of agricultural engineering, 25: 1055-1066. adepoju, tf., olatunbosun, be. and olawale, o. 2016. statistical analysis of biogas production from co-digestion of cornstalk with goat dung using a one-factor design. chemistry research journal, 1: 1-10. al seadi, t., dominik, r., heinz, p., michael, k., tobias, f., silke, v. and rainer, j. 2013. biomass resources for biogas production, in: al seadi, t. 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(ed.), biogas, intech, rijeka, croatia, pp. 91-112. dubrovskis, v. and plume, i. 2017. methane production from stillage, 16th international scientific conference of engineering for rural development, latvia university of life sciences and technology, jelgava, pp. 24-26. fleck, l., tavares, mhf., eyng, e., andrade, madmd. and frare, lm. 2017. optimization of anaerobic treatment of cassava processing wastewater. journal of the brazilian association of agricultural engineering, 37: 574-590. ghatak, md.and ghatak, a. 2018. artificial neural network model to predict behavior of biogas production curve from mixed lignocellulosic co-substrates. fuel 232, 178–189. hafner, s.d., richards, b.k., astals, s., holliger, c., koch, k., weinrich, s., 2020. calculation of methane production from gravimetric measurements, standard bmp methods. https://www.dbfz.de/en/bmp. accessed on july 15, 2022. ibrahim, th., betiku, e., oyedele, jo., olaifa, go. and solomon, bo. 2021a. comparative performances of cow dung vs. poultry droppings as co-substrates and sewage sludge vs. cattle ruminal fluids as inoculums, in the anaerobic co digestion of cassava vinasse for biogas production, 2nd annual international conference of the biotechnology society of nigeria, bsn-sw chapter, institute of agricultural research and training (i.a.r.&t.), ibadan, p. 37. ibrahim, th., betiku, e., solomon, bo. and oyedele, jo. 2021b. mathematical modelling and parametric optimization of biomethane production with response surface methodology (rsm): a case of cassava vinasse from a bioethanol distillery, in: almoruf, ofw., akinjide, aa., mutiu, ka.and adegboyega, be. (eds.), 51st annual international conference, nigerian society of chemical engineers (nsche), lagos, nigeria, pp. 241-248. kafle, gk. and chen, l. 2015. comparison on batch anaerobic digestion of five different livestock manures and prediction of biochemical methane potential (bmp) using different statistical models. waste management, 1-11. lami, m. and chimdessa, m. 2016. biogas production from co-digestion of poultry manure and orange peel through thermochemical pre-treatments in batch fermentation. http://www.azojete.com.ng/ mailto:taiwib098@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):23-32. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: taiwib098@gmail.com 32 international journal of environment, agriculture and biotechnology (ijeab), 1: 0777-0795. lei, z., chen, j., zhang, z. and sugiura, n. 2010. methane production from rice straw with acclimated anaerobic sludge: effect of phosphate supplementation. bioresource technology, 101: 4343–4348. leite, hg. and de oliveira, fht. 2006. statistical procedure to test identity between analytical methods. communications in soil science and plant analysis, 33: 7-8, 1105-1118. lin, c-y., chai, ws., lay, c-h., chen, c-c., lee, c-y. and show, pl. 2021. optimization of hydrolysis-acidogenesis phase of swine manure for biogas production using two-stage anaerobic fermentation. processes, 9: 1324. machunga-disu, ll. and machunga-disu, z. 2012. sustainable management of natural resources and the need for revenue transparency, subsidy reform and full deregulation: the transformation from fossil fuel to green energy, green deal nigeria, abuja, nigeria. macias-corral, m., samani, z., hanson, a., smith, g., funk, p., yu, h. and longworth, j. 2008. anaerobic digestion of municipal solid waste and agricultural waste and the effect of co-digestion with dairy cow manure. bioresource technology, 99: 8288-8293. mukumba, p., makaka, g. and mamphweli, s. 2016. biogas technology in south africa: problems, challenges and solutions. international journal of sustainable energy and environmental research, 5: 58-69. patinvoh, rj. and taherzadeh, mj. 2019. challenges of biogas implementation in developing countries. current opinion in environmental science & health, 1-22. pham, ch., triolo, jm., cu, ttt., pedersen, l. and sommer, sg. 2013. validation and recommendation of methods to measure biogas production potential of animal manure. asian australasian journal of animal science, 26: 864-873. rafiee, a., khalilpour, kr., prest, j. and skryabin, i. 2021. biogas as an energy vector. biomass and bioenergy, 144: 10593-10595. raposo, f., fernández-cegrí, v., de la rubia, ma., borja, r., béline, f., cavinato, c. and de wilde, v. 2011. biochemical methane potential (bmp) of solid organic substrates: evaluation of anaerobic biodegradability using data from an international inter-laboratory study. journal of chemical technology & biotechnology, 86: 1088-1098. ray, n., mohanty, m. and mohanty, r. 2016. biogas compression and storage system for cooking applications in rural households. international journal of renewable energy research, 6: 593-598. siles, ja., garcia-garcia, i., martin, a. and martin, ma. 2011. integrated ozonation and biomethanization treatments of vinasse derived from ethanol manufacturing. journal of hazardous materials, 188: 247-253. twomey, pj. and kroll, mh. 2008. how to use linear regression and correlation in quantitative method comparison studies. international journal of clinical practice, 62: 529–538. yang, s., liu, y., wu, n., zhang, y., svoronos, s. and pullammanappallil, p. 2019. low-cost, arduino-based, portable device for measurement of methane composition in biogas. renewable energy, 138: 224-229. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:taiwib098@gmail.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):341-354 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 341 original research article probabilistic assessment of a typical reinforced concrete girder under critical loading a. a. shuaibu, m. ashiru, a. suleiman*, a. u. isah, h. s. otuoze, a. i. muhammed and b. h. s. amartey department of civil engineering, ahmadu bello university, zaria, kaduna state, nigeria *corresponding author’s email address: abdulsuleiman@abu.edu.ng 1.0 introduction bridges constitute a significant portion of the transportation network of which an efficient and well-planned transportation infrastructure has significant impact on the socioeconomic and social development of any nation. for land transport, road transport in particular, highway bridges constitute a vital, critical and challenging component which make movement between two or more places or regions efficient (mahboubi and kioumarsi 2021). however, highway bridges in most parts of the world including developing countries are subjected to continuously increasing traffic from heavy truck-loads (ajagbe et al., 2012), and exposure to harsh environments (val et al., 2000). they likewise impair due to operating conditions, natural hazards, and other forms of physical attacks (ren et al., 2021) as well as deteriorate due to ageing. to salvage bridges to serve their structural and functional performance (lounis, 2004), a high proportion of highway bridges have been categorized as structurally deficient and functionally obsolete (frangopol and liu, 2007). therefore, it is pertinent to allocate adequate resources for their maintenance, rehabilitation and possible replacement with time (val et al., 2000). nevertheless, the high cost of bridge maintenance, rehabilitation and renewal can seldom be accommodated by transport authorities saddled with such responsibilities. therefore, transport authorities in many countries article information abstract reinforced concrete bridges are continuously subjected to increased traffic load and exposed to harsh environments causing bridge members to deteriorate, thus, affecting their durability, safety and performance. this work aims at a probabilistic assessment of a reinforced concrete bridge girder under critical loading considering the flexural and shear failure modes of the bridge. a limit state function for the failure modes was generated and, the stochastic variables and statistical parameters were determined. additionally, the safety indices for each failure mode were determined using first order reliability method (form) procedure. mathematical models were developed and the uncertainties in structural resistance, applied loading as well as structural components were included using the probabilistic method. a computer program in fortran language was developed and deployed for the reliability analysis of the bridge girder to ascertain the level of safety using first-order reliability method. the results revealed that the safety index for shear and flexural failure mode decreases as the span is increased. for concrete strength of 30 n/mm2 and a depth of 1000 mm, the safety index for shear and flexural failure reduced from 4.5 to 2.0 and 10.7 to 3.37 respectively as the span increases from 10 m to 19 m. this indicates that the shear and flexural failure modes are sensitive to increase in span. in order to obtain a minimum safety target of 3.8, it is recommended that the depth of the beam should not be less than 1200 mm while the span should not exceed 16 m, and concrete grade should not be less than 35 n/mm3. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 february, 2023 revised 5 april, 2023 accepted 6 april, 2023 keywords: reliability uncertainties bridge girder shear and flexure safety index http://www.azojete.com.ng/ mailto:abdulsuleiman@abu.edu.ng abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):341-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 342 including developing countries have taken measures to create a number of bridge management programs (liu and frangopol, 2006). a variety of maintenance optimization including simple economic frameworks to complicated markovian decision processes has been employed in different bridge management systems (lounis and zoubir, 2006). an effective and reliable bridge management system relies on the presence of an effective optimization algorithm and a reliable model for performance prediction. an effective bridge management system involves taking competent decisions regarding bridges grounded on available data on resistance, loading, adverse environmental impact and possible results of bridge malfunctioning (holicky et al., 2010). however, the material properties of bridges, its loading history together with mechanical and environmental conditions amongst others (frangopol et al., 2008) are uncertain parameters which lead to developing reliability based approach to evaluate existing bridges. probabilistic assessment, a measure of reliability of a system is a procedure to determine the probability that a system does not reach a defined limit state under a specified reference duration. probabilistic assessment of structures can be regarded as a rational measure of performance since it is a function of uncertainties related to loads and load carrying capacity (czarnecki and nowak, 2006). over time, an increasing trend of reliability has been observed in the design and assessment of bridges (zona et al., 2010; osumeje et al., 2016; steel and sorensen, 2014; frangopol et al., 2008; cheng 2014). first order reliability method (form) (melchers and beck 2018; nikolaidis et al., 2004; gong and zhou 2017) is an effective approach in appraising the reliability of engineering systems. its utility and precision have been ascertained in many use cases (low and tang 2007). form has been used in reliability analysis in various bridge components and its loading (akgül and frangopol 2004; cheng and li 2009; li et al., 2013; okeil et al., 2013; osumeje et al., 2016). however, failure modes of bridge girder under critical loading have been neglected. therefore, this work aim at the probabilistic assessment of a reinforced concrete bridge girder subjected to critical loading. this will be achieved by generating limit state function for the failure modes, identifying stochastic variables with their statistical parameters, and finally determining safety index for each failure mode using the (form). 2. materials and method 2.1 estimating parameters for reliability of bridge girder according to nowak et al. (2022), loads acting on a highway bridges consist of dead loads; live or traffic induced static and dynamic loads; load due to environmental factors including temperature, wind, snow and seismic actions; and other forms of loads like collision and braking loads. in formulating the reliability function, the components from loads are treated as random variables with their variation described by a cumulative distribution function (cdf), a mean value, and a coefficient of variation. however, in this study, the load combination used for the highway bridge is limited to dead load and dynamic load which are obtained using influence line for a loaded sino truck (osumeje et al., 2016). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng shuaibu et al: probabilistic assessment of a typical reinforced concrete girder under critical loading. azojete, 19(2):341-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 343 2.2 the bridge model the bridge model used in this research was a simply supported with deck of 13.0 m span situated in an exposed setting. the bridge section is composed of an open cross section of precast reinforced concrete longitudinal beam constantly spaced at 2060 mm between each other. the precast longitudinal beams upper flange is well coupled to an in-situ deck slab of 200 mm depth cast on a precast concrete slab formwork of 50 mm thick, giving a total of 250 mm depth of slab. the bridge substructure and superstructure are connected using bearing pads. in-situ reinforced concrete piles connected with pile caps is used as the bridge foundation. length of 11.0 m was adopted as the span of bridge with a carriageway of 7.2 m and a walkway of 1.5 m at the two ends of the bridge. 2.3 material properties materials used in the design are specified in accordance with british standards institution (2004). the class of concrete is c40/50 whereas steel reinforcement is s500. the concrete used in the design has a unit weight of 25 kn/m3; the unit weight of asphalt concrete is 22 kn/m3; and weight of parapet wall was 0.5 kn/m all in accordance with the mentioned code. 2.4 limit state evaluation limit state refers to a situation of a probable failure of a structure after which it stops to achieve its design purpose reasonably both in the area of safety and serviceability. according to ayyub and mccuen (2016), the capacity of a structural member to resist failure relies on not just the strength of the member but also the various load composition acting on the structural member. measuring the risk of failure due to variety of load application on a structural member generates stresses and moments which causes engineers and related professionals to evaluate the safety and reliability of structural members. reliability based assessment method is a probabilistic method that involves loads and strengths of structural members’ sections and material properties characterized with their identified and hypothesized formulations, expressed in relations to their formulation types, averages and variances melchers and beck (2018). in general, the resistant of a structural member is required to surpass the applied load to avoid failure and, in this case, the reliability analysis is used as a tool to evaluate the effect of uncertainties in structural design. herein, the reduction in strength of a reinforced concrete structural member as a result of shear and flexure is considered with their limit state functions formulated. similar to the study conducted by (osumeje et al., 2016), these limit state function were analyzed by means of first order reliability method. 2.6 live load from moving vehicles and location of resultant load on bridge 2.6.1 total live load self-weight of vehicle (semi-articulated truck) = 18 tones = 180 kn. maximum carrying capacity of semi-trailer truck =1200 bags of cement, where each bag weight 50 kg. load carried by semi-trailer = 1200 x 50 kg = 60000 kg = 600 kn total live load = 180 + 600 = 780 kn http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):341-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 344 figure 1 shows load distribution on a 6-axles sinotruck according to (eurocode 1, 2003). from the figure, the 780 kn total live load is distributed to the axles in accordance to the eurocode. from the figure, qk1 = 150 kn, qk2 = 120 kn, and qk3 = 90 kn were adopted according to the code. figure 1: load distribution on 6-axles (sinotruck) according to eurocode 2.6.2 resultant position of load from figure 1, the location of the resultant force fr can be obtained as follows; 𝐹𝑅 = 3𝑄𝑘1 + 2𝑄𝑘2 + 𝑄𝑘3 = 780 𝑘𝑁 (1) where 𝑄𝑘1 = 150𝑘𝑁, 𝑄𝑘2 = 120𝑘𝑁, 𝑎𝑛𝑑 𝑄𝑘3 = 90𝑘𝑁 taking moment about point b in the figure, ∑𝑀𝐵 = 0 (2) (𝐹𝑅 · 𝑥′) − [120(3.2 + 4.55) + 150(11.4 + 12.75 + 14.1)] = 0 (3) (780 · 𝑥′) = 5737.5 + 930 𝑥′ = 8.55 𝑚 therefore, the resultant force acts at a distance of 8.55 m away from point b. 2.7 limit state function for shear in interior beam self-weight of asphalt = 𝐴𝑎𝑠𝑝ℎ 𝑥 𝛾𝑎𝑠𝑝ℎ = 2.27 𝑘𝑁/𝑚 self-weight of slab = 𝐴𝑠𝑙𝑎𝑏 𝑥 𝛾𝑐 = 12.88 𝑘𝑁/𝑚 self-weight of girder = 𝐴𝑔 𝑥 𝛾𝑐 = 13.00 𝑘𝑁/𝑚 where 𝛾𝑎𝑠𝑝ℎ and 𝛾𝑐 represents the unit weight of asphalt and concrete respectively and 𝐴𝑎𝑠𝑝ℎ, 𝐴𝑠𝑙𝑎𝑏, and 𝐴𝑔 represents the areas of asphalt, slab and girder respectively. 𝐺𝑘 = (2.27 + 12.88 + 13.00) 𝑥 1.35 = 38 𝑘𝑁/𝑚 (4) where 𝐺𝑘 is the dead load. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng shuaibu et al: probabilistic assessment of a typical reinforced concrete girder under critical loading. azojete, 19(2):341-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 345 2.7.1 shear of dead load the shear force equation for the dead load is given by equation 5 𝑣𝑑𝑙 = 𝐺𝑘𝑙 2 = 38 𝑥 𝐿 2 = 38 𝑥 13 2 = 247 𝑘𝑁 (5) 𝑣𝑑𝑙 is the shear force and l is the span of girder. 2.7.2 load from traffic lane load from traffic lane (𝑞𝑘𝑛) is given by 𝑞𝑘𝑛 = 336( 1 𝐿 )0.67 (𝑝𝑒𝑟 𝑛𝑎𝑡𝑖𝑜𝑛𝑎𝑙 𝑙𝑎𝑛𝑒) (6) adjustment factor for the lane is given by 𝛼2: 𝛼2 = 0.264𝑏𝐿 = 0.274 𝑥 3.6 = 0.986. (7) therefore, lane load per unit length is now given by; 𝑞𝑘 = 𝑞𝑘𝑛 𝑥 𝛼2 3.6 (8) 2.7.3 critical shear for live load vll for span l = 10.0 m, the critical shear for live load is given by the expression; 𝑉𝐿𝐿 = 𝑄𝑘1(3𝐿−4.05)+ 𝑄𝑘2(𝐿−9.55) 𝐿 + 𝑞𝑘𝐿 2 (9) for span l = 13.0 m, critical shear force for live load is given by; 𝑉𝐿𝐿 = 𝑄𝑘1(3𝐿−4.05)+ 𝑄𝑘2(2𝐿−20.45) 𝐿 + 𝑞𝑘𝐿 2 (10) likewise, for l > 13.0 m; 𝑉𝐿𝐿 = 𝑄𝑘1(3𝐿−4.05)+ 𝑄𝑘2(2𝐿−20.45)+ 𝑄𝑘3(𝐿−14.1) 𝐿 + 𝑞𝑘𝐿 2 (11) the applied shear stress 𝑉𝑎𝑝𝑝𝑙𝑖𝑒𝑑 is given by; 𝑉𝑎𝑝𝑝𝑙𝑖𝑒𝑑 = [ 𝑉𝑑𝑙+ 𝑉𝐿𝐿 𝑏𝑑 ] (12) 𝑉𝑑𝑙 is the shear force from dead load, 𝑏 and 𝑑 are the width and depth of girder. hence, the limit state function is given by; 𝐺(𝑥1) = 0.138𝑓𝑐𝑘 (1 − 𝑓𝑐𝑘 250 ) − 𝑉𝑎𝑝𝑝𝑙𝑖𝑒𝑑 (13) where, 𝑓𝑐𝑘 is the characteristic strength of concrete. in obtaining the critical shear for the live load, load model 1 (lm1), which according to eurocode 2 is placed with point load over the support is as shown in figure 2. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):341-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 346 figure 2: arrangement of load model 1 for critical shear 2.8 limit state function for flexure in interior beam 2.8.1 resultant moment due to dead load the resultant moment ((𝑀𝑑𝑙) due to the effect of dead load is given by the expression; 𝑀𝑑𝑙 = 𝐺𝑘𝐿2 8 = 38𝐿2 8 (14) 2.8.2 resultant moment due to live load here, the resultant moment (𝑀𝐿𝐿) due to live load is given by the expression; 𝑀𝐿𝐿 = [𝑀𝑄𝑘 + 𝑀𝑞𝑘] (15) where 𝑀𝑞𝑘 = 𝑞𝑘𝐿2 8 , (16) 𝐴𝑦 = 1 𝐿 (𝐹𝑅) [ 𝐿 2 − (𝑥′ − 𝑥)], (17) 𝑀𝑄𝑘 = 𝐴𝑦 [ 𝐿 2 − 𝑥] − 4.05 (𝑄𝑘1), and (18) 𝑀𝑎𝑝𝑝𝑙𝑖𝑒𝑑 = 𝑀𝑑𝑙 + 𝑀𝑙𝑙 therefore, the limit state function is given by; 𝐺(𝑥2) = 0.167𝑓𝑐𝑘𝑏𝑑2 − 𝑀𝑎𝑝𝑝𝑙𝑖𝑒𝑑 (19) to obtain 𝑀𝑄𝑘 from lm1, the maximum bending moment occurs at the location where one of the tandem axles is applied at a distance from the mid-point of the beam equal to half of that between the aforesaid axle and the resultant of the moving load train as shown in figure 3. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng shuaibu et al: probabilistic assessment of a typical reinforced concrete girder under critical loading. azojete, 19(2):341-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 347 figure 3: arrangement of maximum bending of load model 1 from the above equations, 𝐺(𝑥1) is the expression for failure model one under shear occurring in the beam, 𝐺(𝑥2) is that for failure model two under flexure occurring in the deck beam, 𝑓𝑦𝑘 is the strength of steel, 𝑓𝑐𝑘 is strength of concrete, 𝐴𝑠𝑡 is area of steel reinforcement, 𝑏 is the width of section, and 𝑑 is the effective depth. table 1 shows the stochastic parameters generated for the limit state function in the program. table 1. stochastic parameters for limit state function (osumeje et al. 2016) s/no design variables notation unit variable type mean coefficient of variation 1 traffic load 𝑤𝑄 normal 1.0 0.05 2 concrete compressive strength 𝑓𝑐𝑘 n/mm2 lognormal 40 0.15 3 in-situ slab thickness ℎ mm normal 250 0.05 4 effective depth 𝑑 mm normal 219 0.05 5 width of beam 𝑏 mm normal 400 0.05 6 beam height ℎ mm normal 1300 0.05 7 effective depth 𝑑 mm normal 1237 0.05 3.results and discussion 3.1 effect of span length variation on the safety index under flexure condition this section analyzes the impact of varying span of bridge girder on the safety index under the condition of flexure. figures 4 to 7 are plots showing the relationship between safety indices and span of beams at various depth in the girder under the region of flexure. from figures 4 to 7, it can be observed that as the span of girders increases, the safety index decreases in each of the varied beam depth. from figure 4, which is for concrete strength of 30 n/mm2, it can be observed that for the 1000 mm depth of beam, the safety index for flexural failure was found to reduce drastically from 20.70 to 3.37 as the span increases from 10 m to 19 m. this situation is similar with other plots of different concrete strength. this is because the applied moment which is a function of span, increases with span and therefore reduces the resistance of the section to flexural failure (ibrahim 2014). to remedy this situation, suitable section with increased depth and reduced span should be selected. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):341-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 348 figure 4: flexural safety index vs beam span for various beam depth for 30 n/mm2 characteristic strength of concrete figure 5, shows the plot of the relationship between safety index and span of beams at various depth in the girder under the region of flexure for 35 n/mm2 characteristics strength of concrete. from the figure, it can be observed that as the span of girders increases, the safety index decreases in each beam depth. this is because the moment acting on a member is a function of span. likewise, it can be seen that the higher the depth of girder, the higher the safety index. figure 5: flexural safety index vs beam span for various beam depth for 35 n/mm2 characteristic strength of concrete figure 6, shows the relationship between safety index and span of beams at various depth in the girder under the region of flexure for 40 n/mm2 characteristics strength of concrete. similarly, from the figure, it can be observed that as the span of girders increases, the safety index decreases in each beam depth. this is because the moment acting on a member is a function of span. likewise, it can be seen that the higher the depth of girder, the higher the safety index. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng shuaibu et al: probabilistic assessment of a typical reinforced concrete girder under critical loading. azojete, 19(2):341-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 349 figure 6: flexural safety index vs beam span for various beam depth for 40 n/mm2 characteristic strength of concrete figure 7, depicts the relationship between safety index and span of beams at various depth in the girder under the region of flexure for 50 n/mm2 characteristics strength of concrete. similarly, from the figure, it can be observed that as the span of girders increases, the safety index decreases in each beam depth. this is because the moment acting on a member is a function of span. likewise, it can be seen that the higher the depth of girder, the higher the safety index. figure 7: flexural safety index vs beam span for various beam depth for 50 n/mm2 characteristic strength of concrete 3.2 effect of span length variation on the safety index under shear stress condition in this section, the effects of varying span of the bridge girder on the safety index with reference to shear stress are analyzed. figures 8 to 11 shows the relationship existing between safety index and span of beams for different of girder under shear. figure 8 shows the results for concrete strength of 30 n/mm2, and for 1000 mm depth of beam. it can be seen that the safety index for shear failure reduce drastically from 4.50 to 2.0 as the span increases. this condition is similar for other concrete strength. this situation clearly indicates that the longer the span, the lower the resistance of the member to shear and likewise, the larger the section, the more the resistance of the member to shear aguwa (2013). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):341-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 350 figure 8: shear safety index vs beam span for various beam depth for 30 n/mm2 characteristic strength of concrete figure 9 shows the relationship between safety index and span of beams for different sizes of girder under shear for 35n/mm2 characteristic strength of concrete. it can be seen for each depth of girder that the safety index reduces as the span increases. this is because shear for increases with span on structural members. furthermore, taking a constant span, the safety index is observed to increase with the depth of the girder. this indicates that the longer the span, the lower the resistance of the member to shear. likewise, the larger the section, the more the resistance of the member to shear. figure 9: shear safety index vs beam span for various beam depth for 35 n/mm2 characteristic strength of concrete similarly, figure 10 depicts the relationship between safety index and span of beams for different sizes of girder under shear for 40 n/mm2 characteristic strength of concrete. it can be seen for each depth of girder that the safety index reduces as the span increases. this is because shear for increases with span on structural members. furthermore, taking a constant span, the safety index is observed to increase with the depth of the girder. this indicates that the longer the span, the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng shuaibu et al: probabilistic assessment of a typical reinforced concrete girder under critical loading. azojete, 19(2):341-354. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 351 lower the resistance of the member to shear. likewise, the larger the section, the more the resistance of the member to shear. figure 10: shear safety index vs beam span for various beam depth for 40 n/mm2 characteristic strength of concrete likewise, figure 11 depicts the relationship between safety index and span of beams for different sizes of girder under shear for 50 n/mm2 characteristic strength of concrete. it can be seen for each depth of girder that the safety index reduces as the span increases. this is because shear for increases with span on structural members. furthermore, taking a constant span, the safety index is observed to increase with the depth of the girder. this indicates that the longer the span, the lower the resistance of the member to shear. likewise, the larger the section, the more the resistance of the member to shear. figure 11: shear safety index vs beam span for various beam depth for 50 n/mm2 characteristic strength of concrete http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):341-354. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 352 4. conclusion this research carried out a deterministic and stochastic analysis on a reinforced concrete bridge girder under critical loading considering flexural and shear failure modes of the bridge. a limit state function for the shear and flexure failure modes was generated according to eurocode 2 for critical load model. influence line analysis was used to obtain the critical bending moments and shear forces. flexural and shear failure modes were determined using a safety index of 3.8. a minimum safety index of 2.11 was obtained for shear failure mode of the bridge whereas 3.37 was obtained as a minimum safety index for flexural failure mode of the bridge. in reinforced concrete girder, the shear failure mode is usually sudden with brittle nature. therefore, shear failure is more critical than flexural failure which is ductile. this is in agreement with the finding of eskenati and pour (2015). the analysis carried out evaluated the effect of some basic parameters for materials and loads in for the designing if reinforced concrete bridge girder under critical loading. the analysis showed that concrete grade, traffic load, and the section parameters of the girder have significant effect on the safety index of the bridge. therefore, to increase the reliability of the girders; the design parameters should be selected systematically through a reliability-based approach. from the analysis carried out, it showed that the safety index for the shear and flexural failure mode reduces as the span increases. for instance, for concrete strength of 30 n/mm2 and a depth of 1000 mm, the safety index for shear failure was found to reduce from 4.5 to 2.0 as the span is increased from 10 m to 18.5 m. similar trend also occurred with other concrete strength. likewise, for flexural failure mode, the safety index reduced from 10.70 to 3.37 as the span is increased from 10 m to 19 m for concrete strength of 30 n/mm2. also, similar trend was also obtained for other concrete strength. from this study to obtain a minimum safety index of 3.8 was obtained. therefore, the depth of beam should be at least 1200 mm and span should not exceed 16 m. the concrete grade should not be less than 35 n/mm2. also, it is suggested that s reliability-based approach should be incorporated into eurocode 2 design criteria for reinforced concrete strictures to accommodate uncertainties in structural design parameters. references aguwa, ji.. 2013. 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(ed.)). butterworth-heinemann publishers. kidlington, oxfordshire, uk. okeil, am., belarbi, a. and kuchma, da. 2013. reliability assessment of frp-strengthened concrete bridge girders in shear. journal of composites for construction, 17: 91-100. osumeje, ut., ocholi, a., kaura, jm. and abdulhamid, ao. 2016. effect of uncertainty on the fatigue reliability of reinforced concrete bridge deck under high stress loads. nigerian journal of technology, 35: 510-518. ren, j., song, j. and ellingwood, br. 2021. reliability assessment framework of deteriorating reinforced concrete bridges subjected to earthquake and pier scour. engineering structures, 239: 112363. steel, k. and sorensen, ad. 2014. reliability analysis of a circular bridge pier subject to intentional vehicular impact. second international conference on vulnerability and risk analysis and management (icvram) and the sixth international symposium on uncertainty, modeling, and analysis (isuma) 13-16 july, liverpool, uk., pp. 2702-2709. val, dv., stewart, mg. and melchers, re. 2000. life‐cycle performance of rc bridges: probabilistic approach. computer‐aided civil and infrastructure engineering, 15: 14-25. zona, a., barbato, m., dall’asta, a. and dezi, l. 2010. probabilistic analysis for design assessment of continuous steel–concrete composite girders. journal of constructional steel research, 66: 897-905. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):465-472 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 465 strength characteristics of microbial induced calcite precipitate/cement stabilized laterite blocks s. abdullahi, b. h. s. amartey*, j. m. kaura and y. d. amartey department of civil engineering, ahmadu bello university, zaria. *corresponding author's email address: bilkisuhs@yahoo.com article information submitted 20 november, 2023 revised 22 february, 2024 accepted 25 february, 2024 keywords: bacillus coagulans compressive strength laterite block cement bio calcination abstract this paper assesses the strength characteristics of microbial induced calcite precipitate/cement stabilized laterite blocks. to achieve this, the compressive strength of unmodified lateritic soil blocks, bacillus coagulans calcite precipitate modified lateritic soil blocks, cement modified lateritic soil blocks as well as the combined effects of the bacillus coagulans calcite precipitate and 5% cement stabilized lateritic soil blocks were determined. bacillus coagulans bacteria was used as the bio calcination agent and ordinary portland cement as the stabilizer. the b. coagulans was mixed at various concentrations using the mcfarland standard and cement was replaced at 5% to 20% replacement levels after which the crushing strengths were determined considering various curing ages. the compressive strength increased at the various curing ages ranging from 0.9 n/mm2 to 2.0 n/mm2 at 7 days, 1.3 n/mm2 to 2.1 n/mm2 at 14 days, 1.5 n/mm2 to 2.15 n/mm2 at 21 days and 1.65 n/mm2 to 2.5 n/mm2 at 28 days for all the stabilized blocks with varying concentrations of b. coagulans suspension. the compressive strength of the cement stabilized laterite blocks increased with an increase in percentage of cement replacement, and also with increasing b. coagulans suspension density for stabilized microbial induced calcite precipitate (micp) laterite blocks. the 5% cement stabilized micp laterite blocks performed better than cement stabilized laterite blocks with 20% cement replacement. the optimum concentration was achieved at bacillus coagulans suspension of 2.4 x 109 cell/ml and 5% cement replacement at 28 days curing age with compressive strength value of 4.2 n/mm2. based on the study conducted, it is recommended that for production of laterite blocks, a quantity of 5% cement replacement for stabilization of laterite may be used in addition to bacillus coagulans to produce stronger laterite blocks. 1.0 introduction there was a general survey by various african governments which found that slums and squatter settlements are steadily growing at alarming rates in cities of the african countries. in most cases, this growing phenomenon is an outcome of failed policies, poor governance, inappropriate planning regulations, unresponsive financial systems, strong pressure of ruralurban migration and lack of political will to reverse the situation amicably. the dominance of slums in urban areas adds to the toll on the people already burdened deeply by abject poverty and constrains the enormous potential for human development that urban life offers (freire, 2006; shome, 2023). mud houses are found in large numbers around most of these slums in rural and urban parts of nigeria and indeed all over africa. they are the commonest dwelling places for low-income earners in the continent. unfortunately, they are easily destroyed by the perennial floods that accompany the seasonal rains each year. the need to switch over from plain mud houses to houses built with stabilized lateritic oils becomes imperative as the federal http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):465-472. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 466 government of nigeria recently announced a plan “to do away with mud houses in a not-toodistant future” (ndubaba and malgwi, 2016). it goes to show that research on better alternative materials that will meet the requirements of strength, economy and durability is important. there have been many recent researches to look into the different ways in which laterites can be stabilized to produce stronger, durable and more economical mud blocks. most of such researches have looked into the use of cement as a stabilizer in laterite for blocks production (dahiru et al., 2016; ndubaba and malgwi, 2016; chambua et al., 2021; tiboti et al., 2021; wahab et al., 2021; and ewa et al., 2022) and most of these studies concluded that cement stabilized laterites produced a stronger and more durable blocks. however, the use of cement as the major stabilizer in lateritic soil for block productions also has some disadvantages in terms of cost, green house effects, etc. the emission of greenhouse gases (co2) is one of the major causes of global warming which also causes climate change. according to suhendro (2014), 8 to 10 percent of the world’s total greenhouse gases emissions come from cement manufacturing. the introduction of supplementary cleaner cementitious material in stabilizing laterite for the production of blocks will go a long way into addressing this issue. one of such supplementary cementitious material is the microbially induced calcite precipitation (micp). micp has been identified to be environmentally sustainable and viable for increasing the strength properties of soils (kim and youn, 2016). bacteria is a common microorganism found everywhere from soil, lakes, water dams etc. siddique and chahal (2011), states that there are approximately 40 million bacterial cells in lg of soil and a million bacterial cells in a millimeter of fresh water. there are approximately five nonillions (5x 1030) of bacteria on earth. the bacteria species discovered by scientist from various places all around the world barely scratch the surface as there are constantly new discovery being made. in nature, some bacterial species have the tendency to deposit calcium carbonate (caco3), a phenomenon called bio cementation. these depositions can prove to be a promising binder for the protection and consolidation of construction materials. historical structures can be preserved by using the bacterial remediation technique (ramachandran et al., 2001). application of bio cementation has been investigated by various researchers in order to increase the durability of cementitious materials and restoration of buildings (iqbal et al., 2021) bacterially induced mineralization has recently emerged as a method for protecting and consolidating decayed construction materials (jroundi et al., 2021). in nature, building and remediation of structures with local materials occurs without any requirement of extreme energy usage. the technology of using microbes for calcium carbonate deposition or microbial concrete, called as microbial induced calcium carbonate precipitation (micp) can be used for solving various durability issues of construction materials. microorganisms are abundant in nature, which paves the way for massive production of bacterial calcium carbonate crystals/calcite/concrete. as the microorganisms can penetrate and reproduce themselves in soil or any such environments, there is no need to disturb the ground or environment unlike that of cement (makul et al., 2022). in view of this, this study investigated the compressive strength characteristic and effectiveness of using cement and microbial induced calcite precipitation (micp) as stabilizers in laterite blocks. 2. materials and methods 2.1 materials the materials used for this study were; laterite, ordinary portland cement (opc) and bacteria (bacillus coagulans), 2.1.1 laterite the soil sample used in this research was collected from a borrow pit located at shika, giwa local government area of kaduna state (latitude 11018’0” n and 7027’0” e) as shown in figure 1 using method of disturbed sampling. the soil sample was taken at a depth of 0.7m after file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdullahi et al: strength characteristics of microbial induced calcite precipitate/cement stabilized laterite blocks. azojete, 20(2):465472. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 467 removing the top soil. part of the soil collected was wrapped in sealed polythene bag to avoid loss of moisture and transported in a sack to the soil laboratory for moisture content determination. the soil specimens were then air-dried before pulverizing to achieve particles passing sieve no.4 (4.76mm aperture). figure 1: map view of soil sampling point 2.1.2 cement portland limestone cement (plc) (dangote block master, grade: 42.5r) was used for this research. 2.1.3 the microorganisms the urease (ure) positive bacteria used in this research was bacillus coagulans. american type culture collection (atcc) classified the microorganism as atcc 8038 (atcc, 2013). it is a rod-shaped gram positive incubated in a water bath shaker (lab-line, model 3540) operated at 200 rpm. cell concentrations were determined by viable cell counting on tris±ye plates. 2.1.4 cementation reagent the cementation reagent (c. reagent) used contains 3g of nutrient broth, 20g of urea, 10g of nh4c1, 2.12g of nahco3 and 2.8g cac12 per liter of distilled water in accordance with that described by stocks-fischer (stocks-fischer et al., 1999). 2.1.5 water potable water supplied by ahmadu bello university, zaria water works and obtained from the taps in the civil engineering laboratory of ahmadu bello university, zaria was used for the experiments. 2.2 methods there are many methods to reduce a soil’s susceptibility to weakening by water. these fall in to the following broad categories: i) protecting the wall from exposure to water, ii) reducing the permeability of the wall by increasing the soil density, iii) making the soil water-repellant by the addition of a water proofing agent and iv) providing a secondary cementitioustype strength mechanism which is largely unaffected by water. 2.2.1 mix proportions for cement, b. coagulans, c. reagent, laterite and water three different mix proportions were used in this study. in the first mix, laterite was mixed with cement at 0%, 5%, 10%, 15% and 20% replacement and water at optimum moisture content of the laterite. in the second mix proportion, laterite was also mixed with b. coagulans http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):465-472. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 468 and cementitious reagent (25% b. coagulans and 75% cementitious reagent) at optimum moisture content with b. coagulans and cementitious reagent replacing water in the mix. in the third mix proportion, laterite was first mixed at 5% cement content and then with b. coagulans and cementitious reagent (25% b. coagulans and 75% cementitious reagent) at optimum moisture content with b. coagulans replacing water in the mix. it is shown in table 1. 1. the b. coagulans concentrations were varied at 0,1.5e+08, 6.0e+08, 1.2e+09, 1.8e+09 and 2.4e+09 cell/ml suspension densities. 2. the optimum moisture content of the soil obtained during the british standard light compaction was 10.4% at a maximum dry density of 1.99mg/m3. figure 2 presents the pictorial view of the mixing process of the stabilizers with the lateritetic soil. table 1: mix proportion for cement, b. coagulans, c. reagent and water in laterite first mix (laterite, cement and water) mix materials quantity (kg) laterite cement b. coagulans c. reagent water 0% cement 5.0300 0 0 0 0.57 5% cement 4.7785 0.2515 0 0 0.57 10% cement 4.5270 0.5030 0 0 0.57 15% cement 4.2755 0.7545 0 0 0.57 20% cement 4.0240 1.0060 0 0 0.57 second mix (laterite, bacillus coagulans and cementitious reagent laterite cement b.coagulans c. reagent water 0.00e+00 5.0300 0 0 0 0 1.50e+08 5.0300 0 0.131 0.393 0 6.00e+08 5.0300 0 0.131 0.393 0 1.20e+09 5.0300 0 0.131 0.393 0 1.80e+09 5.0300 0 0.131 0.393 0 2.40e+09 5.0300 0 0.131 0.393 0 third mix (laterite, bacillus coagulans, cementitious reagent and 5% cement laterite cement b. coagulans c. reagent water 0.00e+00 4.7785 0.2515 0.124 0.373 0 1.50e+08 4.7785 0.2515 0.124 0.373 0 6.00e+08 4.7785 0.2515 0.124 0.373 0 1.20e+09 4.7785 0.2515 0.124 0.373 0 1.80e+09 4.7785 0.2515 0.124 0.373 0 2.40e+09 4.7785 0.2515 0.124 0.373 0 figure 2: practical aspect of the mixing process file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdullahi et al: strength characteristics of microbial induced calcite precipitate/cement stabilized laterite blocks. azojete, 20(2):465472. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 469 2.2.2 moulding of laterite blocks after mixing, the blend was compressed to fill the 230 x 110 x 100 mm moulds at the maximum dry density of the laterites to obtain solid blocks as presented in figure 3. figure 3: pictorial presentation of the laterite block moulding work 2.2.3 compressive strength of the lateritic moulded solid blocks the compressive strength test on the molded blocks was conducted according to bs en 12390-3, (2002). solid blocks were molded and three samples for each mix was tested for an average for each curing regime (7 days, 14 days, 21 days and 28 days) using the avery-denison universal testing machine. 3. results and discussion 3.1 effect of b. coagulans on compressive strength the 7th, 14th, 21st and 28th days curing mean compressive strength values of compressed laterite blocks stabilized with b. coagulans at 1.5 x 108/ml, 6.0 x 108/ml, 1.2 x 109/ml, 1.8 x 109/ml and 2.4 x 109/ml bacillus coagulans concentration are presented in figure 4. figure 4: variation of compressive strength with b. coagulans from the trend in figure 4, the compressive strength is seen to increase with increase in suspension density of bacillus coagulans (i.e. from 0.9 n/mm2 for the natural laterite blocks to 2.0 n/mm2 for 2.4 x 109 cell/ml bacillus coagulans induced laterite blocks after 28days curing), the compressive strength is also seen to be lower after 7, 14 and 21 days and increase sporadically at 28 days curing. this poor initial compressive strength could be due to the fact that the time was too short to allow for reaction to take place in the laterite. 0.5 1 1.5 2 2.5 3 0.00e+00 1.50e+08 6.00e+08 1.20e+09 1.80e+09 2.40e+09 c o m p re ss iv e s tr e n gt h (n /m m 2 ) b. coagulans suspension density (cell/ml) days 7 days 14 days 21 28 days http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):465-472. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 470 3.2 effect of cement on compressive strength the 7th, 14th, 21st and 28th curing days mean compressive strength values of compressed soil blocks stabilized with portland cement at 5%, 10%, 15% and 20% replacement are shown in figure 5. figure 5: variation of compressive strength with cement from the trend in figure 5, the compressive strength is seen to increase with curing age. also, the compressive strength is seen to increase with increase in the cement replacement up to a peak compressive strength of 3.7 n/mm2 from 0.9 n/mm2 for the unstabilized laterite blocks after 28 days curing. this value is greater than the 2.0 n/mm2 reported by gonzalez-lopez et al., 2017 and taallah and guettala, 2016. 3.3 effect of 5% cement with various b. coagulans concentrations on the compressive strength of laterite blocks the 7th, 14th, 21st and 28th curing days mean compressive strength values of compressed soil blocks stabilized with b. coagulans at 1.5 x 108/ml, 6.0 x 108/ml, 1.2 x 109/ml, 1.8 x 109/ml and 2.4 x 109/ml bacillus coagulans concentration and 5% cement are shown in figure 6. figure 6: variation of compressive strength with b. coagulans and 5% cement from the trend in figure 6, the compressive strength is seen to increase with curing age. also, the compressive strength of the blocks is seen to increase from 0.9 n/mm2 for the unstabilized 0.5 1 1.5 2 2.5 3 3.5 4 0 5 10 15 20 c o m p re ss iv e s tr e n gt h n /m m 2 ) percentage of cement (%) 7 days days 14 days 21 28 days 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0.00e+00 1.50e+08 6.00e+08 1.20e+09 1.80e+09 2.40e+09 c o m p re ss iv e s tr e n gt h ( n /m m 2 ) b. coagulans suspension density (cell/ml) 7 days 14 days days 21 28 days file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdullahi et al: strength characteristics of microbial induced calcite precipitate/cement stabilized laterite blocks. azojete, 20(2):465472. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 471 soil blocks to a peak compressive value of 4.2 n/mm2 for 5% cement stabilized laterite blocks at 2.4 x 109 cell/ml b. coagulans suspension density after 28 days curing. 4. conclusion based on the results presented, the following can be concluded; i. the compressive strength increased with curing age for all the stabilized blocks with an average 28th day compressive strength of greater than 2.5 n/mm2. ii. the compressive strength of the cement stabilized laterite blocks increased with increase in cement replacement. iii. the compressive strength increased with increasing b. coagulans suspension density for stabilized micp laterite blocks. iv. 5% cement stabilized micp laterite blocks performed better than cement stabilized laterite blocks at 20% cement replacement. iv. the optimum concentration of bacillus coagulans suspension of 2.4 x 109 cell/ml and 5% cement at 28 days curing age, the compressive strength value of 4.2 n/mm2 was achieved. references atcc 2013. american type culture collection p.o box 1549 manassas, va 20108 usa. http://www.atcc.org bs en 12390-3:2002, 2002. testing hardened concrete. compressive strength of test specimens: british standard institute, 3: 3-18. chambua, st., jande, yac. and machunda, rl. 2021. strength and durability properties of concrete containing pumice and scoria as supplementary cementitious material. advances in materials science and engineering, 1(1): 1–13. https://doi.org/10.1155/2021/5578870. dahiru, d., mamman, m. and usman, j. 2016. comparative study of the compressive strength of cement laterite brick produced with rice husk ash and wood ash as partial replacement of cement, atbu journal of environmental technology, 9(1): 72-85. ewa, de., ukpata, jo., egbe, ea. and akeke, ga. 2022. physical properties of sandcrete laterite blocks. international journal of mechanical and civil engineering, 5(1): 1-9. doi:10.52589/ijmce-3u4hby35. freire, m. 2006. urban planning challenges in developing countries. international congress on human development, madrid, 1: 1-14. gonzalez-lopez, jr., juarez-alvarado, ca., ayub-francis, b. and mendoza-rangel, jm. 2017. compaction effect on the compressive strength and durability of stabilized earth blocks. construction and building materials, 163(2018): 179-188. iqbal, dm., wong, ls. and kong, sy. 2021. bio-cementation in construction materials: a review. materials, 14(9): 21-75. https://doi.org/10.3390/ma14092175. jroundi, f., gonzalez-munzo, mt. and rodriquez-navaro, c. 2021. protection and consolidation of stone heritage by bacterial cabonatogenesis. microorganisms in the deterioration and preservation of cultural heritage, 1: 281-299. kim, g. and youn, h. 2016. microbially induced calcite precipitation employing environmental isolates. materials, 9: 468. https://doi.org/10.3390/ma9060468. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com https://doi.org/10.1155/2021/5578870 https://doi.org/10.3390/ma14092175 https://doi.org/10.3390/ma9060468 arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):465-472. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 472 makul, n., fediuk, r. and szelag, m. 2022. advanced interactions of cement-based materials with microorganisms: a review and future prospective. journal of building engineering, 45: 103458. ndububa, ee. and malgwi, yi. 2016. strength improvement of mud houses through stabilization of the lateritic materials. the international journal of engineering and sciences (ijes), 5(9): 56-60. ramachandran, sk., ramakrishnan, v. and bang, ss. 2001. remediation of concrete using microorganisms. aci materials journal, 98 (1): 3–9. https://doi.org/10.14359/10154. shome, p. 2023. blueprint for addressing poverty and inequality. in the creation of poverty and inequality in indis, bristol university press., 1: 259-294. siddique, r. and chahal, nk. 2011. effect of ureolytic bacteria on concrete properties. construction and building materials, 25(10): 3791-3801. stocks-fischer, s., galinat, jk. and bang, ss. 1999. microbiological precipitation of caco3. soil biology and biochemstry, 31(11): 1563–1571. doi: https://doi.org/10.1016/s00380717(99)00082-6. suhendro, b. 2014. toward green concrete for better sustainable environment. procedia engineering, 95: 305-320. taallah, b. and guettala, a. 2016. the mechanical and physical properties of compressed earth blocks stabilized with lime and filled with untreated and alkali-treated date palm fibre. construction and building materials, 104: 52-62. tiboti, p., niyomukiza, jb., kiwanukal, m., mbujje, jw., baigal, j. and hadudu, af. 2021. optimizing laterite cement blocks in the construction of masonry using quarry dust. iop conference series: earth and environmental science, 802(1): 1-8. wahab, na., roshan, mj., rashid, asa., hezmi, ma., jusoh, sn., norsyahariati, nd. and tamassoki, s. 2021. strength and durability of cement treated lateritic soil. sustainability, l 13(11): 1-23., https:// doi.org/10.3390/su13116430. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):437-446 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 437 original research article effects of varying transmitter half power angle in visible light communication s. f. kolawole1* and m. hamza2 1department of electrical and electronics engineering, nigeria defence academy, kaduna. 2department of electrical and electronics engineering, kaduna polytechnic, kaduna. *corresponding author’s email address: sfkolawole@nda.edu.ng 1.0 introduction visible light communication (vlc) is a new paradigm that could revolutionize the future of wireless communication (rehman et al., 2019). vlc is expected to address the tension between continuously increased demand of capacity and currently limited supply of radio-frequency spectrum resource (hu et al., 2021). there is a gradual extension towards the visible light portion of the electromagnetic (em) spectrum which can be utilized for communication in order to complement existing radio frequency (rf) communication. more than 70% of communication originates from indoor as shown by previous studies (ergul et al., 2015). with vlc expected to have its best application in indoor scenarios, it will form an integral part of the next generation wireless communication system. article information abstract visible light communication (vlc) involves sending and receiving information using light as carrier to transmit the information from sender to receiver. one of the most important parameters of a transmitter in a vlc system is the semi angle at half power which is also referred to as the transmitter half power angle. varying it could affect the amount of light or optical power received at the receiver and depending on the configuration of the transmitters. this can lead to loss of some part of received power. this work investigates how such variation in half power angle can affect average received power by considering separate transmitter arrangements/configuration that can be adopted for vlc based on same number of these transmitters. six separate arrangements of six transmitters were considered in a line of sight (los) indoor vlc scenario. the results were achieved by varying the half power angle between a minimum of 10° and a maximum of 80°. the result showed that different levels of received power were attained at different half power angles for each different transmitter configuration. for instance at a low angle of 10^o, the third configuration had an average received power of 2.8139mw while fourth configuration had an average received power of 2.6700mw which implies the third configuration has a better performance. at a high angle of 80°, average received power for third configuration was 1.2207mw and it was 1.0672mw for the fourth configuration showing that the third configuration still performs better. the third configuration generally outperformed all the other ones. the fifth configuration had a good average received (2.8120mw) at low angle of 10^0 but it gradually became poorer (1.1782mw) at higher angles of up to 80° in comparison to other configurations which indicates this configuration does not perform well at higher half power angles. the findings of the work signified that changing the transmitter configuration can cater for power losses that maybe encountered as a result of varying the transmitter half power angle in a vlc system without giving up so much on uniformity of distribution of the light. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 april, 2023 revised 11 july, 2023 accepted 20 july, 2023 keywords: average power half power angle led transmitters transmitter configuration vlc http://www.azojete.com.ng/ mailto:sfkolawole@nda.edu.ng mailto:sfkolawole@nda.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):437-446. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 438 vlc contains huge communication capacity and activates a new spectrum resource entirely which is the biggest value of this technology (albayati, 2019). vlc refers to the communication technology which utilizes the visible light source (usually led) as a signal transmitter, free space as a transmission medium, and the appropriate photodetector (pd) as a signal receiving component (lee, 2011). the light source will serve a dual usage of illumination and communication which further makes vlc attractive. vlc technology is useful mainly due to superior capacity of transmission and information rate, no health hazards and low power utilization (jha et al., 2017). these advantages and many more, makes vlc a suitable candidate to form an integral part of communication systems in the near future. this work seeks to look into how average received power can be affected by the type of arrangement of transmitters and also variation in the transmitter half power angle in vlc. previous studies have looked into transmitter configuration, received power distribution, average received power, effects of changing transmitter/receiver parameters and so on. khalifeh et al., (2019) investigated the effect of leds position for an indoor environment on the performance of a vlc system where the authors improved the distribution of received power and peak power by first reconfiguring their 4 led arrangement and then adding another led to take care of drawbacks. similarly, mahfouz et al., (2018) did a study where they compared between a proposed arrangement of 16 leds and two other 16 leds arrangement in terms of a number of communication parameters. they also checked out the effect of varying the transmitter half power angle from 20° to 70° on the received power of their proposed model. from the results, it was deduced that increasing the half power angle reduces the received power and vice versa. a research was conducted by gismalla and abdullah, (2019) on optimization of received power and snr where they proposed a novel indoor attocells network configuration using 5 leds in order to improve coverage against 1 and 4 led placement. they also investigated effects of altering transmitter half power angle on optical received power where their proposed model was observed to be poorer at very low angles but outperformed the 4 led model at higher angles. in verma and pandey, (2022), researchers looked into the impact of led half power angle and configurations of transmitters on the distribution pattern of power received in indoor vlc. they considered a varying number of transmitters configuration from 2 × 2 up to 9 × 9 array, they also performed optimization to find suitable half power angle. their findings indicated that 200 half power angle when used with a differential optical receiver has a good power level with less noise at a good uniformity and is optimal for the 9 × 9 array configuration from the reviewed literatures, it is obvious that both transmitter configuration and transmitter half power angle affect received power distribution. hence, it is important to consider them jointly in order to have a comparative basis whereby an optimal arrangement of transmitters that has best received power performance can be found relative to the half power angle. therefore, this work will investigate jointly the effect of varying the half power angle and changing the transmitter configuration, considering equal number of transmitters (6 leds) to see the effect on average received power and observe the one with the best performance. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sfkolawole@nda.edu.ng kolawole and hamza: effects of varying transmitter half power angle in visible light communication. azojete, 19(3):437-446. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 439 2. materials and methods the emission pattern of the transmitters follows lambertian model and the lambertian radiant intensity 𝑅(𝜙) is given as (shaaban and faruque, 2020); 𝑅(𝜙) = (𝑚𝑙+1) 2𝜋 𝑐𝑜𝑠𝑚𝑙 (𝜙) (1) where 𝑚𝑙 is the lambert’s mode number and 𝜙 (degrees) is the angle of irradiance from led. the relationship between 𝑚𝑙 and transmitter half power angle φ1 2⁄ (degrees) is; 𝑚𝑙 = − ln(2) ln(cos φ1 2⁄ ) (2) the receiver is modeled as a physical area, 𝐴𝑎 (m 2) collecting light at an angle of incidence, 𝜓 (degrees) which gives rise to effective communication area 𝐴𝑐 (m2) with a field of view (fov) 𝜓𝑐 . 𝐴𝑐 ( 𝜓) = { 𝐴𝑎 cos𝜓 𝑓𝑜𝑟 0 ≤ 𝜓 ≤ 𝜓𝑐 0 , 𝑓𝑜𝑟 𝜓 > 𝜓𝑐 (3) for the communication link, only the line of sight component is considered for less complexity since it offers the strongest contribution to received power at the receiver. the geometry for such a link is given in figure 1, the led is the transmitter and the photodetector (pd) is the receiver. figure 1: line of sight (los) link geometry for vlc (li et al., 2018) the channel dc gain 𝐻𝑙𝑜𝑠(𝑂) of the los link is given as (vatansever and m. brandt-pearce, 2017); 𝐻𝑙𝑜𝑠(𝑂) = { (𝑚𝑙+1) 2𝜋𝑑2 𝐴𝑎𝑐𝑜𝑠𝑚𝑙(𝜙) 𝑐𝑜𝑠(𝜓), 𝑓𝑜𝑟 0 ≤ 𝜓 ≤ 𝜓𝑐 0 , 𝑒𝑙𝑠𝑒𝑤ℎ𝑒𝑟𝑒 (4) where 𝑑 is distance between transmitter and receiver. if optical concentrator 𝐺(𝜓) and optical filter 𝑇(𝜓) are employed, then 𝐻𝑙𝑜𝑠(𝑂) is defined by; http://www.azojete.com.ng/ mailto:sfkolawole@nda.edu.ng mailto:sfkolawole@nda.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):437-446. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 440 𝐻𝑙𝑜𝑠(𝑂) = { (𝑚𝑙+1) 2𝜋𝑑2 𝐴𝑎𝑐𝑜𝑠𝑚𝑙(𝜙)𝑇(𝜓)𝐺(𝜓)𝑐𝑜𝑠(𝜓), 𝑓𝑜𝑟 0 ≤ 𝜓 ≤ 𝜓𝑐 0 , 𝑒𝑙𝑠𝑒𝑤ℎ𝑒𝑟𝑒 (5) the received power 𝑃𝑟 (mw) is given by 𝑃𝑟 = 𝑃𝑡𝑜𝑡𝑎𝑙𝐻𝑙𝑜𝑠(0) (6) where 𝑃𝑡𝑜𝑡𝑎𝑙 is transmitted power in mw and for the 6 led sources, it is written as 𝑃𝑟 = ∑ 𝑃𝑡𝑜𝑡𝑎𝑙 6 𝑖=1 𝐻𝑙𝑜𝑠(0) (7) the average received power is 𝑃𝑎 = ∑ 𝑃𝑟 625 𝑛=1 625 (8) where 𝑛 is individual receiving point in the receiving plane. a standard iso specified office size dimension of 𝐿𝑥 × 𝐿𝑦 × 𝐿𝑧 = 5𝑚 × 5𝑚 × 3𝑚 was considered as the communication environment. six different arrangement of 6 leds were selected for this work. all the arrangements are given in figure 2. the half power angle φ1 2⁄ was varied in steps of 10° from 10° to 80°. this was done for all the transmitter arrangements and separate results were obtained for different φ1 2⁄ and for different transmitter arrangement. a receiving plane is formed in simulation to serve as the receiver with 625 different receiving points selected for less computation time. figure 2: led transmitter configuration on the ceiling in (𝑥, 𝑦) coordinate format for six leds (a) first configuration (b) second configuration (c) third configuration (d) fourth configuration (e) fifth configuration (f) sixth configuration (a) (e) (d) (c) (b) (f) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sfkolawole@nda.edu.ng kolawole and hamza: effects of varying transmitter half power angle in visible light communication. azojete, 19(3):437-446. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 441 3. results and discussion the results of this work are presented in figures 3 to5 and table 2. the results were obtained through a simulation on matlab r2018a version. the simulation parameters are given in table 1. table 1: simulation parameters 1. transmitted power 20mw 2. receiver fov 70° 3. room size 5𝑚 × 5𝑚 × 3𝑚 4. receiver height 0.85𝑚 5. number of leds per lighting source 50 × 50 6. area of detector 0.0001𝑚2 7. gain of optical filter 1 the communication environment was chosen based on iso (international organization for standardization) specification for office size which is 5𝑚 × 5𝑚 × 3𝑚. the transmitted power per led in a lighting source is 20mw and the array per source is 50 × 50. the receiver is placed at a table top height of 0.85m with fov 70°. the parameters were chosen to achieve enough brightness for all considered configurations without exceeding iso limits for illumination of an office size environment which is 300-1000 lx (ding et al., 2012). figure 3 shows the received power distribution for configuration 1 to configuration 6 respectively. this was done with the half power angle at the minimum selected value of 10°. it can be seen from all the figures that the received power distribution is not uniform, most of the power is in receiver locations around the areas directly under the different transmitters. table 2 summarizes the results and it is clear from the table that configuration 3 has the highest average received power at 2.8139mw while configuration 4 has the lowest average received power at 2.6700mw. (a) (b) (c) http://www.azojete.com.ng/ mailto:sfkolawole@nda.edu.ng mailto:sfkolawole@nda.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):437-446. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 442 figure 3: received power distribution at half power angle of 100 (a) first configuration (b)second configuration (c) third configuration (d) fourth configuration (e) fifth configuration (f)sixth configuration table 2: average received power 𝑃𝑎 in mw for the six different configurations at the varying transmitter half power angles from 10° to 80° 10° 20° 30° 40° 50° 60° 70° 80° 1st 2.7645 2.4760 2.1695 1.8763 1.6286 1.4337 1.2813 1.1552 2nd 2.8119 2.5619 2.1894 2.8703 1.6162 1.4204 1.2687 1.1436 3rd 2.8139 2.6326 2.3160 1.9993 1.7308 1.5201 1.3560 1.2207 4th 2.6700 2.2431 1.9459 1.6945 1.4826 1.3133 1.1792 1.0672 5th 2.8120 2.5874 2.2432 1.9265 1.6668 1.4647 1.3077 1.1782 6th 2.7636 2.4902 2.2402 1.9657 1.7152 1.5125 1.3523 1.2192 in figure 4, simulation results for the received power in all receiver locations when the half power angle is at the maximum selected value of 80° are shown. the figures clearly depict in this case that the received power is much more uniform than the 10° half power angle. the configuration with highest average received power is configuration 3 with 1.2207mw and the one with lowest average received power is configuration 4 with 1.0672mw. it can be deduced that the uniformity improves with wider transmitter half power angle since the light is able to spread to more portions of the indoor space. table 2 summarizes all the results of average received for several half power angles as we progressed in steps of 10° from 10° to 80° for the individual configurations. however, it is noteworthy that each time the half power angle increases which in turn improves the distribution uniformity, the average received power tends to decrease for all transmitter configurations. hence, there is an inverse proportion between half power angle and average received power, a direct proportion between half power angle and distribution uniformity and an inverse proportion between distribution uniformity and average received power. table 2 clearly shows this trend for the half power angle against average received power, for all the transmitter configurations. it is also obvious from table 2 and figure 5 that reconfiguring the transmitter arrangement can affect these deductions. (d) (e) (f) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sfkolawole@nda.edu.ng kolawole and hamza: effects of varying transmitter half power angle in visible light communication. azojete, 19(3):437-446. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 443 figure 4: received power distribution at half power angle of 800 (a) first configuration (b)second configuration (c) third configuration (d) fourth configuration (e) fifth configuration (f)sixth configuration the image in figure 5 shows a graphical representation of the performance of each configuration against others, in terms of average received power vs half power angle. the plot was obtained using data from simulations as tabulated in table 2. it can be seen that the 4th configuration has the worst performance out of all the configurations with average received power at all half power angles that is less than that of the other configurations. this is also clearly observed from table 2. the 3rd configuration has the best performance out of all configurations at all values of half power angles and should be considered for improved average power performance if it is the parameter of interest in a given vlc system of 6 transmitters. however, for the other configurations as seen from figure 5, some started out with a good performance with respect to others at lower half power angles like the 5th configuration but the performance dropped at higher half power angles with respect to some of the other configurations. a configuration like the 6th configuration started out poorly at lower half power angles but drastically improved to have the second best result out of all the other configuration as the half power angles began to grow. this clearly indicates the combined effect of transmitter configuration and half power angle on performance of vlc in terms average received power in a receiving plane which can aid design of vlc systems that may be based on 6 transmitters. (a) (f) (e) (d) (b) (c) http://www.azojete.com.ng/ mailto:sfkolawole@nda.edu.ng mailto:sfkolawole@nda.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):437-446. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 444 figure 5: average received power performance comparison between the six different configurations the findings have clearly identified the importance of choosing the right transmitter configuration at the right transmitter half power angle in order to achieve a good power spread within the communication environment. from this work and in respect of the 6 chosen transmitter configurations for the simulations, the 3rd configuration clearly outperforms the remaining 5 configurations by having the highest average received power at both the lowest and highest half power angles which is 2.8139 mw at 10° and 1.2207 mw at 80° respectively. the 3rd configuration also performed better at all the remaining angles in between as seen from table 2. 4. conclusion this work was carried out to look into how varying the transmitter half power angle alongside the chosen configuration of transmitter can affect received power at the receiver of indoor vlc system. the results obtained showed that out of the six selected configurations, the 4th configuration had the worst average received power performance while the 3rd configuration had the best average received power performance out of all the selected configurations and should therefore be adopted against the other configurations discussed in this work from the point of view of average received power. the results of this work have also generally shown that the quality of communication in vlc is affected by how the transmitters are arranged to emit the light to the receiving plane and also the angle at which they do that. hence, this consideration should always be taken into account in designing vlc systems physical links. in further researches, an optimal arrangement and half power angle for maintaining high average received power and distribution uniformity can be investigated. different number of transmitters can also be considered to see the performance and the trend of different arrangements against each other in terms of various communication parameters. the non-line of sight link can also be taken into account in future researches. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sfkolawole@nda.edu.ng kolawole and hamza: effects of varying transmitter half power angle in visible light communication. azojete, 19(3):437-446. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 445 references albayati, s. 2019. an overview of visible light communication systems. international journal of computer science and mobile computing, 8(6):51-56. https://ijcsmc.com/docs/papers/june2019/v8i6201910.pdf ding, j., huang, z. and ji, y. 2012. evolutionary algorithm-based uniform received power and illumination rendering for indoor visible light communication. journal of the optical society of america, 29(6): 971-979. doi: 10.1364/josaa.29.000971 ergul, o., dinc, e. and akan, ob. 2015. communicate to illuminate: state-of-the-art and research challenges for visible light communications. physical communication, 17(6): 72-85. https://doi.org/10.1016/j.phycom.2015.08.003 gismalla, msm. and abdullah, mfl. 2019. optimization of received power and snr for an indoor attocells network in visible light communication. journal of communications, 14(1): 64-69. http://dx.doi.org/10.12720/jcm.14.1.64-69 hu, f., chen, s., zhang, y., li, g., zou, p., zhang, j., shen, c., zhang, x., hu, j., zhang, j., he, z., yu, s., jiang, f. and chi, n. 2021. high-speed visible light communication systems based on sisubstrate leds with multiple superlattice interlayers. photonix, 2(16): 1-18. https://doi.org/10.1186/s43074-021-00039-9 jha, pk., mishra, n. and kumar, ds. 2017. challenges and potentials for visible light communications: state of the art. aip (american institute of physics) publishing, 1849(1). http://dx.doi.org/10.1063/1.4984154 khalifeh, af., alfasfous, n., theodory, r., giha, s. and darabkh, ka. 2019. on the effect of light emitting diodes positions on the performance of an indoor visible light communication system. ieee conference of russian young researchers in electrical and electronic engineering (eiconrus), saint petersburg and moscow, russia, 28-31 january, 2019, 10-14. https://dx.doi.org/10.1109/eiconrus.2019.8656890 lee, cg. 2011. visible light communication, advanced trends in wireless communications. intechopen, 327-338. http://dx.doi.org/10.5772/16034 li, x., zhang, r. and hanzo, l. 2018. optimization of visible-light optical wireless systems: network-centric versus user-centric designs. ieee communications surveys & tutorials, 20(3):1878-1904. https://dx.doi.org/10.1109/comst.2018.2813433 mahfouz, ne., fayed, ha., abudel aziz, a. and aly, mh. 2018. improved light uniformity and snr employing new led distribution pattern for indoor applications in vlc system. optical and quantum electronics, 50(9): 1-18. https://doi.org/10.1007/s11082-018-1618-6 rehman, su., ullah, s., chong, phj., yongchareon, s. and komosny, d. 2019. visible light communication: a system perspective—overview and challenges. sensors, 19(5):1153: 1-22. https://doi.org/10.3390/s19051153 http://www.azojete.com.ng/ mailto:sfkolawole@nda.edu.ng mailto:sfkolawole@nda.edu.ng https://ijcsmc.com/docs/papers/june2019/v8i6201910.pdf https://doi.org/10.1186/s43074-021-00039-9 https://doi.org/10.1109/comst.2018.2813433 https://doi.org/10.3390/s19051153 arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):437-446. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sfkolawole@nda.edu.ng 446 shaaban, r. and faruque, s. 2020. optimized leds positions for channel analysis performance of an intra-vehicle visible light communication system. ieee radio and wireless symposium (rws), san antonio, tx, usa, 26-29 january, 2020, 302-305. https://dx.doi.org/10.1109/rws45077.2020.9050056 vatansever, z. and m brandt-pearce, m. 2017. visible light positioning with diffusing lamps using an extended kalman filter. ieee wireless communications and networking conference (wcnc), san francisco, ca, usa, 19-22 march, 2017, 1-6. https://dx.doi.org/10.1109/wcnc.2017.7925652 verma, a. and pandey, a. 2022. optimization of transmitter semi angle and ambient noise cancellation for indoor visible light communications. gmsarn international journal, 17(1:40-45. http://gmsarnjournal.com/home/wp-content/uploads/2022/05/vol17no1-6.pdf file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sfkolawole@nda.edu.ng https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=web&cd=&ved=0camqw7ajahckewii3d_u-vz9ahuaaaaahqaaaaaqaw&url=http%3a%2f%2fgmsarnjournal.com%2fhome%2fwp-content%2fuploads%2f2022%2f05%2fvol17no1-6.pdf&psig=aovvaw0ywzdyu-vmboh8n0jgtxdq&ust=1680030104583416 cigr ejournal style and format guidelines arid zone journal of engineering, technology & environment azojete cigr section vi special issue: innovation & technologies for sustainable agricultural production & food sufficiency azojete, december, 2018. vol. 14(sp.i4): 237-246 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s email: adeyadey_77@yahoo.com 237 original research article determination of water productivity of cassava in ibadan, south western nigeria a. m. aderemi*1, t. a. ewemoje2, j. o. adedipe1, i. o. oyewo1 and l. a. balogun3 1. agricultural technology department, federal college of forestry ibadan. 2.department of agricultural and environmental engineering, university of ibadan, ibadan, oyo state. 3.department of agricultural and bio environmental engineering, oyo state college of agriculture and technology, igboora, oyo state. article information received: october, 2018 accepted: december, 2018 keywords: water productivity cassava effective rainfall cropwat rainfall data nigeria abstract the response of yields to the actual water (effective rainfall) used by cassava, was the main area of study of this project. a twenty data point (20 years) was processed using cropwat 8.0 model using fixed percentage (80%) method, the model was used to run the 20 years daily rainfall data collected from nimet (nigeria meteorological agency) oyo state from 1994 to 2013 (20 years) while the cassava yield was collected from faostat website. the rainfall pattern for the annual period of cultivation for cassava was determined through the planting and dates of the crop. the results of the annual water productivity values show that there was a very low water productivity of 0.9kg/m3 in 2012 while 2013 recorded the highest water productivity of 2.2 kg/m3. the early planting of cassava after rainfall started in the month of march which contributed to the high yield recorded in 2010, 2011 and 2013. the poor performance of cassava in 2012 could be due to the following; the variety used, the soil type, the plant’s age at harvest, and the rainfall intensity and distribution during that particular year. the trend of the results was used to determine the alternative cost of water if the farm would be fully irrigated. it was gathered that 7000 litres of untreated water would be supplied to any farthest location at ₦ 12,000. therefore, the cost was determined based on the yield and the water used annually. . © 2018 faculty of engineering, university of maiduguri, nigeria. all rights reserved http://www.azojete.com.ng aderemi et al.: determination of water productivity of cassava in ibadan, south western nigeria. azojete, 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: adeyadey_77@yahoo.com 238 1.0 introduction cassava (manihot esculenta) is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. cassava is the third largest source of food carbohydrates in the tropics, after rice and maize, (fao, 1995). cassava is a major staple food in the developing world, providing a basic diet for over half a billion people. it is one of the most drought-tolerant crops, capable of growing on marginal soils. nigeria is the world's largest producer of cassava, while thailand is the largest exporter of dried cassava. cassava is important source of food in the tropics. the cassava plant gives the third highest yield of carbohydrates per cultivated area among crop plants, after sugarcane and sugar beets. it plays a particularly important role in agriculture in developing countries, especially in sub-saharan africa, because it does well on poor soils and with low rainfall. water is the most common liquid on our planet, essential to all life forms and it is also important for crop need. the need of water is increasing sharply throughout the world which is one of the most burning issues of current time. fresh water resources are depleting due to global climatic changes, rash use of surface water, and misuse of ground water and fast increasing industrial pollution. world need for food and crop demand is increasing day by day because of rapid increase in population. (bastiaanssen et al., 2000). as competition for increasingly scarce water resources intensifies, irrigation is under growing pressure to produce “more crops from fewer drops” and to reduce its negative environmental impacts, including soil salinization and nitrate contamination of drinking water. greater use of water-saving precision technologies, such as drip and micro-irrigation, will make an important contribution to sustainable intensification. irrigation water requirements are particularly abundant in the works under several surfaces, crop water requirements, crop yield and evapotranspiration as influenced by water accessibility, crop water modeling and irrigation scheduling techniques. then this consistent data and evapo-transpiration (eto) through cropwat model can be utilized to estimate the contribution of rainfall towards crop water requirement to determine that how much irrigation is required to enhance the productivity. cropwat is one of the models extensively used in the field of water management throughout the world. it is an application software used for irrigation planning and management. it facilitates the estimation of the crop evapotranspiration, irrigation schedule, crop water requirement and yield reduction under varying weather conditions (fao, 2000). rainfall determines the potential of any region in term of crops to be produced, farming system to be adopted, the nature and sequence of farming operations to be followed and to achieve higher agricultural productivity. the objectives of this study were therefore to estimate the effective rainfall using cropwat 8.0 model, evaluate the crop water productivity of cassava on annual basis https://en.wikipedia.org/wiki/agriculture https://en.wikipedia.org/wiki/tropical https://en.wikipedia.org/wiki/subtropical https://en.wikipedia.org/wiki/starch https://en.wikipedia.org/wiki/tuberous_root https://en.wikipedia.org/wiki/carbohydrate https://en.wikipedia.org/wiki/rice https://en.wikipedia.org/wiki/maize https://en.wikipedia.org/wiki/carbohydrates https://en.wikipedia.org/wiki/sugarcane https://en.wikipedia.org/wiki/sugar_beet http://www.azojete.com.ng mailto:adeyadey_77@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 239 for the period of twenty (20) years and calculate the cost of alternative water used for cassava production for the entire period of twenty years on annual basis. among the models, cropwat has been the most widely used for estimation of evapotranspiration and crop water requirement. since there are few weather stations in the study areas, data required for the penman-monteith method has normally been extrapolated from representative weather stations nearby. the weather data available for this study will be processed using cropwat to estimate evapotranspiration and crop water requirement. 2.0 materials and methods the study was carried out using ibadan (nigeria) as a case study area. ibadan lies approximately between latitude 7039i n and longitude 30 90i e of nigeria and altitude 238m above the sea level (google earth). the area lies within the southwest savannah zone of nigeria. the average length of the dry season is about 121-151 days (october to march) during which little or no precipitation occurs. means daily air temperatures (minimum and maximum) range between 23.60c and 33.20c. the wind speed ranges from 50.3 km/day in december to 735 km/day in april, with a north eastern to south western wind direction dominating from november through april. the soil is a medium loam, which has developed on deeply weathered pre-cambrian basement complex rocks but overlain by aeolian drift of varying thickness (ogunwole, 2000). 2.1 climatic data the climatic data used for this work were obtained from the data files of ibadan over a period of twenty years (1994-2013) from the nigerian meteorological agency (nimet) and was imputed into cropwat-8.0 for windows. the weather data are being generated from the automatic weather station of the agency (nimet), which relatively records accurate climatic data of its environments. 2.2 cassava yield data the cassava yield data used for this study for the period of twenty years (1994-2013) was obtained from food and agriculture organization statistics (faostat, 2015). the data was calculated per hectare on annual basis. 2.3 determination of reference crop evapotranspiration the reference evapotranspiration (eto) represents the potential evaporation of a wellwatered grass crop. the water needs of other crops are directly linked to this climate parameter (mohammed, 2009). in order to calculate reference evapotranspiration (eto), the respective climate data should be collected from the nearest and the most representative meteorological stations. several institutes and agencies may keep climatic records such as the irrigation department, the file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderemi et al.: determination of water productivity of cassava in ibadan, south western nigeria. azojete, 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: adeyadey_77@yahoo.com 240 meteorological service or nearby agricultural research stations and may provide information on climatic stations inside or in its vicinity (allen et al., 1998). for this work, the data have been obtained from both the automatic weather station of nimet and faostat. daily climatic data of the year 1994-2013 were used. the climatic data used is rainfall data and the second data used was the cassava yield data. although several methods exist to determine eto, the penman-monteith method has been recommended as the appropriate combination method with the climatic data; temperature, sunshine, humidity, windspeed, (fao, 1998). the fao penman-monteith method to estimate eto is expressed as;      2 2 34.01 273 900408.0 u eeu t gr eto asn        (1) where: eto = reference evapotranspiration (mm day-1) rn = net radiation at the crop surface (mj m-2 day-1) g = soil heat flux density (mj m-2 day-1) t = mean daily air temperature at 2 m height (oc) µ2 = wind speed at 2 m height (ms-1) es = saturation vapour pressure (kpa) ea = actual vapour pressure (kpa) δ = slope vapour pressure curve (kpa oc-1 ) = psychrometric constant (kpa oc-1) for this project, the united states department of agriculture, soil conservation service method on cropwat-8 was used to determine the effective rainfall on monthly basis which accumulated to annual effective rainfall. the usda, scs method for calculation of effective rainfall is described in a fao publication (dastane, 1978). the method is implemented in models for planning and management of irrigation as the cropwat model, where the usda, scs method is the default method for calculation of effective rainfall among other four methods (marica, 2013). 2.4 determination of cassava crop water productivity water productivity is more directly linked to overall ambitions in water-scarce or watercostly situations than in systems which are supplied with plentiful, low value water. wp is most meaningful as an indicator as water resources become increasingly scarce. assessment may be required for the whole system or parts of it, defined in time and space with the formula below, consumedorusedwater producealagriculturwp  (2) http://www.azojete.com.ng mailto:adeyadey_77@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 241 in this project, the annual agricultural yield or benefit of cassava was obtained from the faostat for the period of twenty years (1994-2013) on yearly basis and the rainfall data obtained from nimet was processed to determine the amount of water required by the plant at that particular period of time or water used or consumed. with the equation 2 above, the annual water productivity was calculated for the specified period of time. due to the water productivity calculated, it was easy to predict the amount of water that will be needed in the cassava production annually. 2.5 cost of water applied economics of water contributes towards improved allocations of water and the costs of water used and also the full social benefits of the goods and services that water provides. in this study, the cost of the quantity of water used was determined by considering the cost of water supply by the water tankers from the oyo state water corporation, eleyele, ibadan. it was discovered that the price for which the water is delivered depends on the distance. therefore, for the farthest location supply of 7,000 litres of untreated water, the cooperation charges ₦12,000. with this knowledge, the quantity of water used annually from 1994 to 2013 was calculated annually. this also helps to predict and have the foreknowledge of the amount of money to be spent on irrigation or supply of water if the cassava production is on the large scale, particularly for exportation. 3.0 results and discussion table1 below shows the rainfall pattern based on the planting and harvesting dates of cassava for the period of 20 years. from the rainfall pattern it was seen that it took nine (9) months for the cassava to germinate, some were assumed planted early while some were planted late based on the daily rainfall data obtained. figures1, 2 and 3 below shows effective rainfall versus cassava yield; water productivity and cost of alternative water for irrigation respectively. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderemi et al.: determination of water productivity of cassava in ibadan, south western nigeria. azojete, 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: adeyadey_77@yahoo.com 242 table 1: rainfall pattern during cassava cultivation period year mar apr may june july aug sept oct nov dec jan total rainfall (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) 1994 88.9 301.2 63.6 164.0 67.0 211.5 246.6 19.5 0.0 1,162.3 1995 127.8 81.3 146.7 129.9 220.7 260.1 139.3 213.1 20.2 1,339.1 1996 122.1 188.3 231.4 116.9 161.4 226.5 84.9 0.0 0.4 1,131.9 1997 141.9 104.7 154.1 63.6 98.8 151.7 170.5 1.6 9.0 895.9 1998 126.9 198.5 259.5 114.2 177.3 80.3 263.4 0.0 0.0 1,220.1 1999 189.8 226.9 230.3 162.7 149.5 154.9 24.4 0.0 19.0 1,157.5 2000 112.6 104.0 149.8 183.6 241.0 144.2 19.6 0.0 18.8 973.6 2001 145.9 194.2 93.5 52.1 229.1 63.0 1.9 0.2 1.0 780.9 2002 79.4 116.6 189.3 180.3 168.9 62.6 254.4 74.1 0.0 1,125.6 2003 101.0 129.4 203.7 205.7 107.6 283.8 153.8 39.9 0.0 1,224.9 2004 55.0 181.4 223.6 100.6 136.5 142.0 228.5 0.7 0.0 1,068.3 2005 123.0 111.1 165.2 152.4 92.5 352.7 160.6 3.7 0.0 1,161.2 2006 67.1 107.6 167.1 98.8 104.9 148.8 188.0 256.1 4.9 1,143.3 2007 65.9 176.6 229.4 133.3 356.6 178.4 168.8 71.5 10.8 1,391.3 2008 98.7 64.9 204.3 283.5 161.9 199.7 92.9 0.0 24.7 1,130.6 2009 104.4 130.8 146.7 229.4 74.3 111.5 117.8 2.1 0.0 917.0 2010 131.6 70.8 204.4 167.4 107.1 205.7 256.5 240.5 101.4 1,485.4 2011 38.6 36.2 68.6 143.3 140.5 308.1 244.6 163.6 0.6 1,144.1 2012 38.4 214.6 221.1 145.5 87.7 104.4 190.3 182.5 15.7 1,200.2 2013 37.3 67.2 105.2 124.5 126.4 10.6 128.5 163.7 29.8 793.2 figure 1: effective rainfall versus cassava yield. 3.1 water productivity the figure 2 below shows the trend of water productivity across the years (1994 2013). total rainfall values was computed from the weather station for a period of twenty (20) years in order to estimate the amount of rainfall that was recorded on yearly basis. also to know the trend of rainfall that was recorded for 20 years. effective rainfall was computed from cropwat 8.0 using fixed percentage (80%) method. from the data collected, maximum rainfall was recorded in the 17th year (march 7 – november 12) with a value of http://www.azojete.com.ng mailto:adeyadey_77@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 243 1485.4mm, while the minimum value was recorded in the 8th year (may 10 – january 10) with a value of 780.9mm. effective rainfall was computed in order to know the amount of water in terms of rainfall that is available for the crop (cassava). the maximum and minimum values for effective rainfall were 1037.1mm and 577.8mm respectively. table 2: water productivity table between 1994-2013 (20 years) total effective cassava effective effective water year planting harvesting rainfall rainfall yield rainfall rainfall prod. date date (mm) (mm) (kg/ha) (mm3/ha) (m3) (kg/m3) 1994 april 20th dec. 23rd 1162.3 777.4 10592.8 7774000 7774 1.362593 1995 mar. 15th nov. 17th 1339.1 949.6 10667.1 9496000 9496 1.123326 1996 april 20th dec. 22nd 1131.9 808.5 10664.6 8085000 8085 1.31906 1997 april 5th dec. 10th 895.9 702.6 11881.8 7026000 7026 1.691119 1998 april 15th dec. 20th 1220.1 829.2 10746.1 8292000 8292 1.29596 1999 may 5th jan. 10th 1157.5 814.6 9599.8 8146000 8146 1.178468 2000 may 10th jan. 17th 973.6 718.8 9700 7188000 7188 1.349471 2001 may 9th jan. 10th 780.9 577.8 9601.2 5778000 5778 1.661682 2002 april 25th dec. 27th 1125.6 819.8 9901.3 8198000 8198 1.20777 2003 april 15th dec. 20th 1224.9 858.4 10402.3 8584000 8584 1.211824 2004 april 22th dec. 28th 1068.3 769 11001.1 7690000 7690 1.430572 2005 april 16th dec. 21th 1161.2 789 10990.2 7890000 7890 1.392928 2006 april 18th dec. 27th 1143.3 842.2 12000.3 8422000 8422 1.424875 2007 april 16th dec. 17th 1391.3 921 11202.6 9210000 9210 1.216352 2008 april 15th dec. 20th 1130.6 790.8 11800.4 7908000 7908 1.49221 2009 april 19th dec. 11th 917 702.6 11767.9 7026000 7026 1.674907 2010 march 7th nov. 12th 1485.4 1037.1 12215.5 10371000 10371 1.177852 2011 march 27th nov. 30th 1144.1 776.8 11210.8 7768000 7768 1.443203 2012 march 30th nov. 27th 1200.2 870.7 7958.5 8707000 8707 0.914035 2013 march 26th nov. 30th 793.2 644.8 13947.4 6448000 6448 2.163058 figure 2: water productivity file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderemi et al.: determination of water productivity of cassava in ibadan, south western nigeria. azojete, 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: adeyadey_77@yahoo.com 244 3.2 cost of alternative water table 3: annual water cost cassava effective effective cost of water year yield rainfall rainfall used (kg/ha) (m3) (litre) (₦) 1994 10592.8 7774 7774000 13324636 1995 10667.1 9496 9496000 16276144 1996 10664.6 8085 8085000 13857690 1997 11881.8 7026 7026000 12042564 1998 10746.1 8292 8292000 14212488 1999 9599.8 8146 8146000 13962244 2000 9700.0 7188 7188000 12320232 2001 9601.2 5778 5778000 9903492 2002 9901.3 8198 8198000 14051372 2003 10402.3 8584 8584000 14712976 2004 11001.1 7690 7690000 13180660 2005 10990.2 7890 7890000 13523460 2006 12000.3 8422 8422000 14435308 2007 11202.6 9210 9210000 15785940 2008 11800.4 7908 7908000 13554312 2009 11767.9 7026 7026000 12042564 2010 12215.5 10371 10371000 17775894 2011 11210.8 7768 7768000 13314352 2012 7958.5 8707 8707000 14923798 2013 13947.4 6448 6448000 11051872 figure 3: cost of water the maximum yield of cassava in kg/ha was recorded to be 13,947.40 as at the 20th year (2013) which was planted on the 26th of march and harvested on the 30th of november, with an effective rainfall of 644.8mm. based on the trend of data collected, it shows that the maximum yield was recorded when we observed low rainfall which can be linked to the cost of water that can be used in replacement for effective rainfall (irrigation). http://www.azojete.com.ng mailto:adeyadey_77@yahoo.com arid zone journal of engineering, technology and environment, december, 2018; vol. 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 245 from the figure above, the cost of water used in replace of rainfall on yearly basis (i.e. 1994 – 2013). the maximum cost of water used was observed on year 17 (2010) with the maximum price of 17,775,894. the minimum cost of water used was observed on year 8 (2001) with the minimum price of 9,903,492. these costs are important to determine so that it could be valued along with the main cost of cassava like in the determination of virtual water. this is applicable mostly in countries like israel where water is very scarce. when cassava is produced, the value of the cost of water used for the production is added to the selling price in case of export. similar thing should be employed here so as to attach value to our water. planting early in the rainy season will generally produce the highest yields as shown in table 2. all the cassava planted early in the month of march in the 1995, 2010, 2011 and 2013 had a better yield compare to others except in some few occasions and this was due to the fact that the plants have adequate soil moisture during the most critical part of their growth cycle. however, research has shown that yields can vary according to the variety used, the soil type, the plant’s age at harvest, and the rainfall intensity and distribution during any particular year. one or more of the aforementioned factors could be responsible for the low yield in 2012. 4.0 conclusion and recommendation based on the yield shown above, effective rainfall and water productivity observed to be maximum in the 20th year (2013), the cost of water was calculated to be ₦11,051,872 in which the costs is low compare to other years. this amount can be used to purchase water need for cultivation of cassava in dry season when irrigation is needed in order to obtain maximum yield. the cost of water used can also be used to calculate the concept of virtual water. it is strongly recommended that other parameters like sunshine hour, temperature etc, should also be put into consideration in determining the water productivity for the production of cassava as this will shed more light on the crop yield to water use relationship. since the effective rainfall was determined using cropwat 8.0 model, it is advised to use other models rainfall data for this study. it is as well recommended that federal government parastatals and research institutes should be willing to assist in researches by their willingness to release data and useful materials to assist in further research works. references allen, rg., pereira, ls., raes, d. and smith, m. 1998. crop evapotranspiration; guidelines for computing crop water requirements. fao, irrigation and drainage paper no.56. rome, italy. pp 300. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng aderemi et al.: determination of water productivity of cassava in ibadan, south western nigeria. azojete, 14(sp.i4): 237-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author ‘s: email: adeyadey_77@yahoo.com 246 bastiaanssen, wgm., david, jm. and ian, wm. 2000. remote sensing for irrigated agriculture: examples from research and possible applications, agriculture water management, 46:137-155. dastane, ng. 1978. effective rainfall in irrigated agriculture; irrigation and drainage paper 25; food and agriculture organisation: rome, italy. food and agriculture organization (fao) 2000. cropwat, a computer program for irrigation planning and management. author; smith, m. irrigation and drainage paper 256; pp 340-570. food and agriculture organization of the united nations (fao) 1995. "dimensions of need: an atlas of food and agriculture" marica, a. 2013. short description of the cropwat model. http://agrometcost.bo.ibimet.cnr.it/fileadmin/cost718/repository/cropwat.pdf. (april 15, 2013) mohammed n. 2009. simulation of maize crop under irrigated and rainfed conditions with cropwat. arpn journal of agricultural and biological science. vol. 3: no. 2. pp 200-241. ogunwole, 2000. a critical evaluation of traits of improving yields in water-limited environments. arpn journal of agricultural and biological science vol. 4; pp 107-149. http://www.fao.org/docrep/u8480e/u8480e01.htm http://www.fao.org/docrep/u8480e/u8480e01.htm http://agrometcost http://www.azojete.com.ng mailto:adeyadey_77@yahoo.com 1.0introduction cassava (manihot esculenta) is extensively cultiva cassava is a major staple food in the developing w water is the most common liquid on our planet, ess as competition for increasingly scarce water resou irrigation water requirements are particularly abu among the models, cropwat has been the most widely 2.0materials and methods the study was carried out using ibadan (nigeria) a 2.1 climatic data the climatic data used for this work were obtained 2.2 cassava yield data the cassava yield data used for this study for the 2.3 determination of reference crop evapotranspir the reference evapotranspiration (eto) represents in order to calculate reference evapotranspiration for this work, the data have been obtained from bo although several methods exist to determine eto, t the fao penman-monteith method to estimate eto is (1) where: eto = reference evapotranspiration (mm day-1) rn = net radiation at the crop surface (mj m-2 day g = soil heat flux density (mj m-2 day-1) t = mean daily air temperature at 2 m height (oc) µ2 = wind speed at 2 m height (ms-1) es = saturation vapour pressure (kpa) ea = actual vapour pressure (kpa) δ = slope vapour pressure curve (kpa oc-1 ) = psychrometric constant (kpa oc-1) for this project, the united states department of 2.4 determination of cassava crop water productiv water productivity is more directly linked to over in this project, the annual agricultural yield or 2.5 cost of water applied economics of water contributes towards improved al in this study, the cost of the quantity of water u 3.0results and discussion table1 below shows the rainfall pattern based on t figures1, 2 and 3 below shows effective rainfall v table 1: rainfall pattern during cassava cultivati year mar apr may june july aug sept oct nov dec jan total rainfall (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) 1994 88.9 301.2 63.6 164.0 67.0 211.5 246.6 19.5 0.0 1,162.3 1995 127.8 81.3 146.7 129.9 220.7 260.1 139.3 213.1 20.2 1,339.1 1996 122.1 188.3 231.4 116.9 161.4 226.5 84.9 0.0 0.4 1,131.9 1997 141.9 104.7 154.1 63.6 98.8 151.7 170.5 1.6 9.0 895.9 1998 126.9 198.5 259.5 114.2 177.3 80.3 263.4 0.0 0.0 1,220.1 1999 189.8 226.9 230.3 162.7 149.5 154.9 24.4 0.0 19.0 1,157.5 2000 112.6 104.0 149.8 183.6 241.0 144.2 19.6 0.0 18.8 973.6 2001 145.9 194.2 93.5 52.1 229.1 63.0 1.9 0.2 1.0 780.9 2002 79.4 116.6 189.3 180.3 168.9 62.6 254.4 74.1 0.0 1,125.6 2003 101.0 129.4 203.7 205.7 107.6 283.8 153.8 39.9 0.0 1,224.9 2004 55.0 181.4 223.6 100.6 136.5 142.0 228.5 0.7 0.0 1,068.3 2005 123.0 111.1 165.2 152.4 92.5 352.7 160.6 3.7 0.0 1,161.2 2006 67.1 107.6 167.1 98.8 104.9 148.8 188.0 256.1 4.9 1,143.3 2007 65.9 176.6 229.4 133.3 356.6 178.4 168.8 71.5 10.8 1,391.3 2008 98.7 64.9 204.3 283.5 161.9 199.7 92.9 0.0 24.7 1,130.6 2009 104.4 130.8 146.7 229.4 74.3 111.5 117.8 2.1 0.0 917.0 2010 131.6 70.8 204.4 167.4 107.1 205.7 256.5 240.5 101.4 1,485.4 2011 38.6 36.2 68.6 143.3 140.5 308.1 244.6 163.6 0.6 1,144.1 2012 38.4 214.6 221.1 145.5 87.7 104.4 190.3 182.5 15.7 1,200.2 2013 37.3 67.2 105.2 124.5 126.4 10.6 128.5 163.7 29.8 793.2 figure 1: effective rainfall versus cassava yield. 3.1water productivity the figure 2 below shows the trend of water produc total rainfall values was computed from the weathe table 2: water productivity table between 1994-20       total effective cassava effective effective water year planting harvesting rainfall rainfall yield rainfall rainfall prod.   date date (mm) (mm) (kg/ha) (mm3/ha) (m3) (kg/m3) 1994 april 20th dec. 23rd 1162.3 777.4 10592.8 7774000 7774 1.362593 1995 mar. 15th nov. 17th 1339.1 949.6 10667.1 9496000 9496 1.123326 1996 april 20th dec. 22nd 1131.9 808.5 10664.6 8085000 8085 1.31906 1997 april 5th dec. 10th 895.9 702.6 11881.8 7026000 7026 1.691119 1998 april 15th dec. 20th 1220.1 829.2 10746.1 8292000 8292 1.29596 1999 may 5th jan. 10th 1157.5 814.6 9599.8 8146000 8146 1.178468 2000 may 10th jan. 17th 973.6 718.8 9700 7188000 7188 1.349471 2001 may 9th jan. 10th 780.9 577.8 9601.2 5778000 5778 1.661682 2002 april 25th dec. 27th 1125.6 819.8 9901.3 8198000 8198 1.20777 2003 april 15th dec. 20th 1224.9 858.4 10402.3 8584000 8584 1.211824 2004 april 22th dec. 28th 1068.3 769 11001.1 7690000 7690 1.430572 2005 april 16th dec. 21th 1161.2 789 10990.2 7890000 7890 1.392928 2006 april 18th dec. 27th 1143.3 842.2 12000.3 8422000 8422 1.424875 2007 april 16th dec. 17th 1391.3 921 11202.6 9210000 9210 1.216352 2008 april 15th dec. 20th 1130.6 790.8 11800.4 7908000 7908 1.49221 2009 april 19th dec. 11th 917 702.6 11767.9 7026000 7026 1.674907 2010 march 7th nov. 12th 1485.4 1037.1 12215.5 10371000 10371 1.177852 2011 march 27th nov. 30th 1144.1 776.8 11210.8 7768000 7768 1.443203 2012 march 30th nov. 27th 1200.2 870.7 7958.5 8707000 8707 0.914035 2013 march 26th nov. 30th 793.2 644.8 13947.4 6448000 6448 2.163058 figure 2: water productivity 3.2 cost of alternative water table 3: annual water cost   cassava effective effective cost of water year yield rainfall rainfall used   (kg/ha) (m3) (litre) (₦) 1994 10592.8 7774 7774000 13324636 1995 10667.1 9496 9496000 16276144 1996 10664.6 8085 8085000 13857690 1997 11881.8 7026 7026000 12042564 1998 10746.1 8292 8292000 14212488 1999 9599.8 8146 8146000 13962244 2000 9700.0 7188 7188000 12320232 2001 9601.2 5778 5778000 9903492 2002 9901.3 8198 8198000 14051372 2003 10402.3 8584 8584000 14712976 2004 11001.1 7690 7690000 13180660 2005 10990.2 7890 7890000 13523460 2006 12000.3 8422 8422000 14435308 2007 11202.6 9210 9210000 15785940 2008 11800.4 7908 7908000 13554312 2009 11767.9 7026 7026000 12042564 2010 12215.5 10371 10371000 17775894 2011 11210.8 7768 7768000 13314352 2012 7958.5 8707 8707000 14923798 2013 13947.4 6448 6448000 11051872 figure 3: cost of water the maximum yield of cassava in kg/ha was recorded from the figure above, the cost of water used in r these costs are important to determine so that it however, research has shown that yields can vary a 4.0conclusion and recommendation based on the yield shown above, effective rainfall it is strongly recommended that other parameters l it is as well recommended that federal government references allen, rg., pereira, ls., raes, d. and smith, m. 1 bastiaanssen, wgm., david, jm. and ian, wm. 2000. dastane, ng. 1978. effective rainfall in irrigated food and agriculture organization (fao) 2000. crop food and agriculture organization of the united na marica, a. 2013. short description of the cropwat mohammed n. 2009. simulation of maize crop under i ogunwole, 2000. a critical evaluation of traits of arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):847-864 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 847 reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria o. j. airen* and b. j. o. mujakperuo department of physics, faculty of physical sciences, university of benin, nigeria *corresponding author's email address: osariere.airen@uniben.edu article information submitted 29 june, 2023 revised 15 august, 2023 accepted 23 august, 2023 keywords: well log recovery factor petrophysical porosity and permeability abstract the calculation of hydrocarbon volume in place of sapele deep field in the niger delta, nigeria was done by the integration of seismic and well logs data using the petrel software. on average, the entire field has a hydrocarbon pore volume of 90,341.68, stoiip value of 1,156,970,604.11 bbcf/bbstb and an ultimate recovery value of 951,966,117.95 mmcf/mmstb with a primary recovery factor of 0.81 (81%). petrophysical evaluation reveals that the field on average, has a gross thickness of 268.60m (886.38 ft), net sand thickness of 6.67 m (22.01 ft), porosity value of 0.21 (21%), permeability of 1493.14 md, shale volume of 0.16, net-to-gross value of 0.51 and water saturation (sw) of 0.43 (43%). the combination of well log neutron and density log reveals that the study area is made up of both single and double-phase reservoirs 1.0 introduction virtually all the petroleum in the niger delta is found in paralic sands. the hydrocarbons are trapped in rollover anticlines or against growth faults, especially along footwall (figure 1). minor stratigraphic traps also occur in some fields due to lateral facies changes or in association with clay-filled channels (orife and avbovbo, 1981). the niger delta is comprised of five offlapping siliciclastic sedimentation cycles. these cycles or depobelts as they are more typically called, grade 250 kilometers southwestward over the oceanic crust that underlies the gulf of guinea (stacher, 1995). the depobelts are defined by synsedimentary fault trends that formed in response to different rates of subsidence and sediment supply (doust and omatsola, 1990). as the delta prograded, when local subsidence diminished greatly, the focus of sediment deposition was forced to shift seaward, forming a new depobelt. each depobelt is a separate unit that corresponds to a break in regional dip of the delta and is bounded landward by growth faults and seaward by large counter-regional faults or the growth fault of the next depobelt seaward (evamy et al., 1978). five major depobelts are generally recognized, each with its sedimentation, deformation, and petroleum history (nyantakyi et al., 2013). http://www.azojete.com.ng/ mailto:%20osariere.airen@uniben.edu mailto:%20osariere.airen@uniben.edu mailto:%20osariere.airen@uniben.edu arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 848 figure 1: examples of niger delta oil filed structures and associated trapping styles (stacher, 1995) reservoir hydrocarbon volumetric analysis is a technique that employs geological observations and information to estimate original fluids-in-place. it is often referred to as a "static method” as it primarily sources its data from core samples, wireline logs, and geological maps. volumetric calculations are typically used prior to production to estimate reserves, and after considerable production to determine the efficiency of recovery, the area extent of the reservoir, and as a basis for advanced studies such as reservoir simulations (airen and mujakperuo, 2023a). the niger delta basin to date is the most prolific and economic sedimentary basin in nigeria by the virtue of the impact size petroleum accumulations, discovered and produced as well as the spatial distribution of the petroleum resources to the onshore, continental shelf through deepwater terrains (airen and mujakperuo, 2023b). classic integrated geological studies have shown that several different depobelts are abound in the niger delta basin. reservoir characterization is the concatenation of all relevant information that is required to describe a reservoir in terms of its ability to store and produce hydrocarbons. this entails knowing the complete reservoir architecture, including the internal and external geometry, its model with the distribution of reservoir properties, and understanding the fluid flow within the reservoir. such information helps improve production rates, rejuvenate oil fields, predict future reservoir performance, minimize cost expenditure, and help managements of oil companies to draw up accurate financial models. according to halderson and damsleth (1993), the principal goal of reservoir characterization is to outsmart nature to obtain higher recoveries with fewer wells in better positions at minimum cost through optimization. the oil and gas industry is a technology-driven industry, our ability to locate and extract hydrocarbons from beneath the ground surface is tied directly to the evolution of technologies, concepts, and interpretative sciences. these technologies are seismic-based methods for imaging features beneath the ground’s surface, advances in well logging techniques, improvements in the ability to drill in deep water beyond the continental shelf, the advent of horizontal drilling, micropaleontology, biostratigraphy, to name a few. reservoir’s characterization has evolved over the past 20 years, from a simple engineering evaluation to multidisciplinary teams of geologists, geophysicists, petrophysicists, and petroleum engineers working together. the integration of these various disciplines has changed our perception of the characteristics of oil and gas reservoirs. whereas it used to be commonly perceived that oil and gas reservoirs were relatively simple geologic features, the reality is that they are quite complex, and they can be subdivided into architectural elements or compartments on the basis of several structural and stratigraphic features. part of the misconception comes from the fact that one cannot see a reservoir, because it is beneath ground level in the subsurface. slatt (1998), has claimed that in rocky mountain basins, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 849 compartmentalized reservoirs are the rule, rather than the exception. with the increased flow of information into the public domain concerning reservoirs worldwide, this claim appears to be valid beyond the rockies. thus, in the initial through final stages of characterization, investigators should assume that the field will be compartmentalized and segmented, even at scales too small to recognize by normal subsurface technologies. by integrating the various disciplines mentioned above, it is possible to accurately quantify the characterization process. often, the most limiting factor to a proper reservoir characterization is time. for a variety of reasons, the integrated team may not have sufficient time to complete the required work before drilling or other production steps are initiated (i.e., the cart is placed before the horse). sapele field is a large, mature field that is further subdivided into two fields (sapele shallow and sapele deep) due to its structural complexity. sapele shallow as the name implies, is made up of shallow reservoirs with heavy oil as its hydrocarbon content, while sapele deep is made up of heavily compartmentalized reservoirs with gas and light oil as its hydrocarbon content. the field is in the northwestern part of the niger delta, which has been actively producing for over 3 decades and for the past few years, has been experiencing production decline and sometimes failed wells. thus, there is a need to approach the study area with an improved reservoir characterization for a better understanding of the geologic complexities of the field, to improve hydrocarbon recovery from existing oil and gas reservoirs of the study area. 2. materials and methods the study area was formerly owned and operated by shell petroleum development company plc for over 3 decades and over time, reservoir hydrocarbon production declined as the field turned to a matured field. at this point, shell lost investment interest in the field and so decided to sell it off to seplat in 2010 to increase her (shell) focus in nigeria offshore and deep-water fields. this investigation is borne out of the fact that the study area has been synonymous with poor reservoir performance. hence, wells are constantly serviced to burst production. this led to carrying out the evaluation of the subsurface geology of the study area using 3d seismic, well logs, biostratigraphy, and pressure volume temperature (pvt) data, to acquire a better understanding of the subsurface structural geometry, stratigraphy, petrophysical parameters, depositional environment, age and type of hydrocarbon contained in the reservoirs. this information will help in maximizing hydrocarbon recovery from the reservoirs by ensuring a consistent reservoir description which helps in optimal well placement and other exploration decisions. the sapele deep field is the distal portion of sapele field of oml 41 (figure 2), located in the northwestern (greater ughelli depobelt) part of the niger delta (figure 3). http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 850 figure 2: base map of oil wells in the study area (using petrel) figure 3: location map of niger delta depobelts, showing the study area (reijers et al., 2011) the materials used while carrying out this research work are a suit of subsurface data which includes, 3d seismic cube, and well logs data provided across the fields. petrel®2016 (schlumberger software) was used in the interpretation of the data. these subsurface data belong to seplat petroleum development company plc and were released under the approval of the department of petroleum resources (dpr), 2.1 petrophysical parameters composite well log data (gamma ray, resistivity, density and neutron logs) were used for the petrophysical evaluation of the reservoirs. 2.2 hydrocarbon pore volume (hcpv) before hydrocarbon migration and accumulation took place, the reservoir rock was saturated with water. the displacement of water by hydrocarbon is never complete and therefore hydrocarbon-bearing formations always contain water. equation 1 was used to deduce the hcpv of the reservoirs. 𝐻𝐶𝑃𝑉 = 𝐴 × 𝐻 × ф × ntg × (1 − 𝑆𝑤) (ilavalgan, 2018) (1) where: a = hydrocarbon-bearing area of the reservoir h = gross thickness ф = porosity ntg = net to gross thickness ratio (1-sw) = 1-water saturation (hydrocarbon saturation) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 851 2.3 stock tank oil initially in place (stoiip) stoiip is the total amount of crude oil present in a hydrocarbon reservoir before the commencement of any production in equivalent volume that the oil will occupy when it is stocked in a storage tank. in mathematical terms, stoiip can be expressed using equation 2. 𝑆𝑇𝑂𝐼𝐼𝑃 = 7758 x a x h x ф x (1−sw) 𝐵𝑜𝑖 (amigun and bakare, 2013) (2) where: 7758 = acre-feet conversion for oil a = area in acres h = net pay thickness in feet ф = porosity sw = water saturation boi = oil formation volume factor. 2.4 stock tank gas initially in place (stgiip) the stgiip can be delineated by using static geologic data to determine the volume of the pore space of the reservoir. once the volume of the pore space is estimated, then the gas formation volume factor (bgi) can be used to estimate the stgiip, as seen in equation 3. 𝑆𝑇𝐺𝐼𝐼𝑃 = 43560 x a x h x ф x (1−sw) 𝐵𝑔𝑖 (chidozie, 2017) (3) where: 43560 = acre-feet conversion for gas a = area in acres h = net pay thickness in feet ф = porosity sw = water saturation bgi = gas formation volume factor. 2.5 recovery factor oil recovery factor (rf) is the most significant parameter for all exploration and development (e&p) companies mainly during the early reservoir life, because several investment decisions are based on the amount of hydrocarbon, which could be obtained from the target asset with the available techniques and operational practices. the empirical relation used to calculate the hydrocarbon recovery factor of the study area water-drive reservoirs using five factors that affect the oil recovery in sandstone reservoirs as shown in equation 4 is obtained from wiener et al, 2010. rf = 0.114 + 0.272logk + 0.256sw 0.136log m0 -1.538ф 0.0003h (anthony and aurelius, 2012). (4) where: rf = recovery factor k = permeability (md) sw = water saturation mo = oil viscosity (cp) ф = porosity however, ultimate recovery factor can be obtained by multiplying stock tank oil initially in place (stoiip) by recovery factor (rf). ultimate recovery (ur) = stoiip x rf (glover, 2016) (5) http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 852 3. results and discussion 3.1 well 01 analysis figure 4 shows well 01 penetrated three reservoirs (b, c and d) out of the thirteen reservoirs present in the field. figure 4: well log signature of well 01 from 2970.8 m to 3323.2 m (using petrel®2016). 3.1.1 petrophysical summary of well 01 reservoirs table 1 revealed that well 01 reservoirs has an average gross thickness of 66.42 m (219.19 ft), shale volume of 0.14, net sand thickness of 7.90 m (26.07 ft), porosity of 0.21, permeability of 1458.6 md and a water saturation of 0.38 (38%). from the above-mentioned petrophysical values, well 01 reservoirs possess very good to excellent petrophysical properties which agrees with rider (1986). table 1: petrophysical summary of well 01 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐺𝑟𝑜𝑠𝑠 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (𝑚) 𝑉𝑠ℎ 𝑁𝑒𝑡 𝑆𝑎𝑛𝑑 (𝑚) φ 𝐸𝑓𝑓𝛷 𝐾 (𝑚𝐷) 𝐹 𝑁𝑇𝐺 𝑆𝑤𝑖𝑟𝑟 𝑆𝑤 𝑆ℎ b 56.55 0.10 13.34 0.24 0.22 1703.45 25.98 0.71 0.11 0.12 0.88 c 70.91 0.20 5.92 0.18 0.10 1168.22 43.80 0.33 0.15 0.30 0.70 d 71.80 0.10 4.45 0.20 0.20 1504.20 42.50 0.31 0.15 0.73 0.27 average 66.42 0.14 7.90 0.21 0.18 1458.60 37.43 0.50 0.14 0.14 0.62 vsh = volume of shale swirr = irreducible water saturation ntg = net-to-gross ratio 3.1.2 reservoir volumetric analysis of well 01 the net sand thickness, porosity values and water saturation values as revealed in the various reservoir petrophysical table, field area extent of 16515.73, 7758 acre-feet conversion constant for oil reservoirs and 1.20 oil formation volume factor were used in delineating well 01 reservoir volumetrics. as shown in table 2, well 01 has an average stoiip of 448,153,428.39 million stock tank barrels (mmstb) of oil and an ultimate recovery of 287,469,260.17 mmstb with a recovery factor of 0.71 (71%). the following volumetric analysis have proven that well 01 is economically viable with ultimate recoverable hydrocarbon given by; average primary recovery reserve = 𝑈𝑅 × 𝐵𝑎𝑟𝑟𝑒𝑙 𝑒𝑠𝑡𝑖𝑚𝑎𝑡𝑒 = 287,469,260.17 × 50 = $14,373,463,008.50 at $50 per barrel. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 853 table 2: hydrocarbon volumetric summary of well 01 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 b 460,777.50 992,727,349.80 0.61 605,286,712 c 162,547.60 262,828,523.50 0.71 185,861,293 d 68,727.34 88,904,411.88 0.80 71,259,776 average 134,032.73 448,153,428.39 0.71 287,469,260.17 average primary recovery reserve @usd50.00/b = 287,469,260.17 x 50 = $14,373,463,008.50 3.2 well 06 analysis well 06 penetrated seven reservoirs (b, c, d, e, f, g and h) out of the thirteen reservoir sands present in the field (figures 5a and b). reservoir “b” was delineated with well tops at a depth of 2999.53 m (9898.45 ft) as the top of the reservoir and 3036.85 m (10021.61 ft) as the base. reservoir “c” was delineated at a top depth of 3073.37 m (10142.12 ft) and a base of 3144.04 m (10375.33 ft). reservoir “d” was delineated at 3163.90 m (10440.87 ft) as top and base at 3239.33 m (10689.79 ft) as revealed by the well tops marker. reservoir “e” was deciphered with well tops at a depth of 3444.99 m (11368.47 ft) as the top of the reservoir and 3460.87 m (11420.87 ft) as the base. reservoir “f” was delineated at a top depth of 3554.56 m (11730.05 ft) and a base of 3602.21 m (11887.29 ft). figure 5a: well log signature of well 06 from 2979.3 m to 3535 m (using petrel®2016). http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 854 figure 5b: well log signature of well 06 from 3302.4 m to 3800 m (using petrel®2016). 3.2.1 petrophysical summary of well 06 reservoirs the data presented in table 3, indicates that well 06 reservoirs on average, have a gross thickness of 47.47 m (156.65 ft), shale volume of 0.15, net sand thickness of 6.94 m (22.90 ft), porosity of 0.20, permeability of 1416.23 md and a water saturation of 0.47 (47%). based on this, we can infer that well 06 reservoirs retain a very good to excellent petrophysical properties. table 3: petrophysical summary of well 06 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐺𝑟𝑜𝑠𝑠 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (𝑚) 𝑉𝑠ℎ 𝑁𝑒𝑡 𝑆𝑎𝑛𝑑 (𝑚) φ 𝐸𝑓𝑓𝛷 𝐾 (𝑚𝐷) 𝐹 𝑁𝑇𝐺 𝑆𝑤𝑖𝑟𝑟 𝑆𝑤 𝑆ℎ b 37.32 0.110 9.250 0.22 0.20 1605.600 18.47 0.50 0.10 0.40 0.60 c 70.67 0.080 5.346 0.24 0.22 1836.270 14.76 0.38 0.09 0.40 0.60 d 75.43 0.270 5.520 0.23 0.18 1720.130 21.98 0.44 0.10 0.50 0.50 e 18.00 0.060 16.060 0.22 0.20 1552.000 17.26 0.89 0.09 0.30 0.70 f 47.65 0.200 1.630 0.19 0.16 1305.260 21.79 0.17 0.10 0.40 0.60 g 28.00 0.065 8.790 0.17 0.16 1038.150 30.16 0.63 0.12 0.40 0.60 h 55.24 0.250 2.000 0.15 0.12 856.220 46.82 0.07 0.15 0.90 0.10 average 47.47 0.150 6.940 0.20 0.18 1416.233 24.46 0.44 0.11 0.47 0.53 3.2.2 hydrocarbon volumetric summary of well 06 reservoirs as revealed in table 4, well 06 has an average stoiip of 311,672,938.26 mmcf/mmstb and an ultimate recovery of 215,892,954.64 mmcf/mmstb with a recovery factor of 0.73 (73%). hence, the volumetric evaluation has shown that well 06 is economically viable with an average ultimate hydrocarbon recuperation of $10,794,647,732 at $50 per barrel (table 5). table 4: hydrocarbon volumetric summary of well 06 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 b 130,875.400 423,054,840.70 0.70 297,542,719 c 223,770.000 289,334,627.90 0.67 195,221,567 d 139,025.500 205,780,865.20 0.73 150,360,992 e 134,796.300 871,458,088.60 0.67 581,555,355 f 53,039.130 68,748,305.52 0.72 49,320,481 g 96,101.800 310,649,065.60 0.73 226,370,129 h 3,924.137 12,684,774.30 0.86 10,879,439 average 111,647.500 311,672,938.26 0.73 215,892,954.640 average primary recovery reserve @usd50.00/b = 215,892,954.64 x 50 = $10,794,647,732 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 855 3.3 well 17 analysis this well intercepted eight reservoirs (b, c, d, e, f, g, h, and i) out of the thirteen reservoir sands present in the field (figures 6a and b) and ranges in depth from 2967.2 m (9791.76 ft) to 3630 m (11979 ft). well 17 is made up of three single-phase gas reservoirs, three singlephase oil reservoir and two double-phase reservoirs (gas/oil). figure 6a: well log signature of well 17 from 2967.2 m to 3332.5 m (using petrel®2016). figure 6b: well log signature of well 17 from 3307 m to 3630 m (using petrel®2016). 3.3.1 petrophysical summary of well 17 reservoirs the cumulative petrophysical summary as shown in table 5, indicates that well 17 reservoirs on average, have a gross thickness of 36.30 m (119.79 ft), shale volume of 0.13, net sand thickness of 6.36 m (20.99 ft), porosity of 0.21, permeability of 1479.46 md and a water saturation of 0.47 (47%). however, using seplat shale volume cut-off of 0.35 and water saturation cut-off of 0.60 for sapele deep, it means the reservoirs in well 17 are very good with sound petrophysical properties except for reservoir “d” which has a water saturation of 0.73 that is far above the cut-off. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 856 table 5: petrophysical summary of well 17 3.3.2 hydrocarbon volumetric summary of well 17 reservoirs from table 6, we can deduce that well 17 reservoirs on average, have stoiip of 1,416,052,696.66 bbcf/bbstb and ultimate recovery of 1,207,418,779.00 bbcf/bbstb with a recovery factor of 0.84 (84%). therefore, the volumetric appraisal has revealed that well 17 is economically feasible with an average ultimate hydrocarbon recovery of $60,370,938,950.00 at $50 per barrel (as shown in figure 7). table 6: hydrocarbon volumetric summary of well 17 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 b 69,470.17 449,124,617.97 0.84 376,943,761.59 c 34,308.96 1,245,415,192.60 0.88 1,092,270,920.04 d 180,928.30 1,169,701,335.12 0.78 916,858,367.00 e 265,007.90 1,713,275,786.40 0.75 1,280,708,943.82 f 15,712.70 101,582,585.32 0.83 84,386,561.35 g 9,772.50 117,906,349.62 0.9 106,633,125.45 h 161,911.10 5,877,372,394.42 0.89 5,224,743,203.92 i 18,017.72 654,043,311.84 0.88 576,805,348.85 average 94,391.17 1,416,052,696.66 0.84 1,207,418,779.00 average ultimate recovery @ usd50.00/b = 1,207,418,779.00 x 50 = $60,370,938,950.00 3.4 well 18 analysis as indicated in figures 7a and b, well 18 penetrated the thirteen reservoirs (b, c, d, e, f, g, h, i, j, k, l, m, and n) present in the field and ranges in depth from 3001 (9,903.30) m to 3720 m (12,276 ft). reservoirs in this well are all single-phase reservoirs, the first reservoir is a single-phase oil reservoir, while the remaining twelve reservoirs are single phase gas reservoirs. 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐺𝑟𝑜𝑠𝑠 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (𝑚) 𝑉𝑠ℎ 𝑁𝑒𝑡 𝑆𝑎𝑛𝑑 (𝑚) φ 𝐸𝑓𝑓𝛷 𝐾 (𝑚𝐷) 𝐹 𝑁𝑇𝐺 𝑆𝑤𝑖𝑟𝑟 𝑆𝑤 𝑆ℎ b 18.99 0.15 13.39 0.20 0.18 1393.54 31.86 0.71 0.13 0.53 0.47 c 9.50 0.20 6.32 0.24 0.19 1866.85 15.52 0.67 0.09 0.59 0.41 d 70.67 0.12 4.96 0.23 0.21 1740.15 16.29 0.35 0.09 0.42 0.58 e 83.68 0.08 7.44 0.24 0.22 1796.77 14.92 0.36 0.09 0.31 0.69 f 3.86 0.14 2.99 0.19 0.17 1313.13 21.94 0.77 0.10 0.51 0.49 g 5.99 0.11 5.58 0.19 0.17 1219.23 24.15 0.93 0.11 0.68 0.32 h 75.46 0.11 8.90 0.19 0.18 1309.58 22.69 0.35 0.11 0.43 0.57 i 22.23 0.13 1.32 0.18 0.16 1196.42 26.90 0.12 0.11 0.31 0.69 average 36.30 0.13 6.36 0.21 0.19 1479.46 21.78 0.53 0.10 0.47 0.53 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 857 figure 7a: well log signature of well 18 from 3001 m to 3498.6 m (using petrel®2016) figure 7b: well log signature of well 18 from 3406 m to 3720m (using petrel®2016) 3.4.1 petrophysical summary of well 18 reservoirs the amassed petrophysical data of all well 18 reservoirs (table 7), stipulates that the reservoirs on average, have a gross thickness of 23.43 m (77.32 ft), net sand thickness of 6.67 m (22.01 ft), shale volume of 0.15, porosity of 0.21, permeability of 1466.46 md, a water saturation of 0.49 (49%) and a net to gross ratio of 0.44. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 858 table 7: petrophysical summary of well 18 reservoirs 3.4.2 hydrocarbon volumetric summary of well 18 reservoirs well 18 reservoirs on average, have stoiip of 2,179,663,023.41 bbcf/bbstb and ultimate recovery of 1,900,314,137.78 bbcf/bbstb with a recovery factor of 0.88 (88%) as seen in table 8. based on this evaluation, we can infer that well 18 is a profitable well with ultimate hydrocarbon recovery of $95,015,706,889.00@ $50 per barrel (as shown in figure 9). table 8: hydrocarbon volumetric summary of well 18 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 b 109,982.09 711,034,225.00 0.82 581,252,233.80 c 28,211.01 1,024,059,713.58 0.89 909,473,063.96 d 54,477.67 1,977,539,249.65 0.85 1,681,505,242.87 e 180,028.47 6,535,033,417.00 0.83 5,449,505,257.14 f 161,209.55 5,851,906,540.98 0.93 5,435,426,001.34 g 5,333.91 193,620,737.08 0.91 176,785,534.04 h 19,462.90 706,503,356.47 0.94 666,894,234.90 i 118,729.48 4,309,880,002.15 0.81 3,507,480,421.16 j 39,395.09 1,430,041,931.79 0.88 1,253,979,402.07 k 8,480.22 307,832,149.52 0.92 284,706,530.18 l 4,856.37 176,286,210.60 0.88 155,580,742.91 m 2,408.62 87,432,733.87 0.92 80,103,809.11 n 138,414.57 5,024,449,036.69 0.90 4,521,391,317.72 average 66,999.23 2,179,663,023.41 0.88 1,900,314,137.78 average ultimate recovery @usd50.00/b = 1,900,314,137.78 x 50 = $95,015,706,889.00 3.5 well 19 analysis this well intercept twelve reservoirs (b, c, d, e, f, g, h, i, j, k, l, and m) out of thirteen reservoirs present in the field and ranges in depth from 30021.72 (9,971.68 ft) m to 3761.55 m (12,413.12 ft). this well contains both single and double-phase reservoirs, it has four singlephase gas reservoirs, four double-phase (gas/oil) reservoirs and four single-phase oil reservoirs (figures 8a, b and c). 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐺𝑟𝑜𝑠𝑠 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (𝑚) 𝑉𝑠ℎ 𝑁𝑒𝑡 𝑆𝑎𝑛𝑑 (𝑚) φ 𝐸𝑓𝑓𝛷 𝐾 (𝑚𝐷) 𝐹 𝑁𝑇𝐺 𝑆𝑤𝑖𝑟𝑟 𝑆𝑤 𝑆ℎ b 25.52 0.12 19.29 0.22 0.19 1537.19 21.88 0.76 0.10 0.51 0.49 c 38.48 0.27 5.59 0.23 0.19 1766.02 24.47 0.15 0.11 0.61 0.39 d 23.94 0.09 3.91 0.21 0.19 1508.27 18.55 0.33 0.10 0.40 0.60 e 95.41 0.19 5.71 0.22 0.19 1587.88 21.35 0.36 0.10 0.34 0.66 f 24.73 0.16 14.84 0.21 0.18 1437.18 21.63 0.56 0.10 0.68 0.32 g 2.99 0.23 1.13 0.17 0.13 1108.54 27.28 0.37 0.12 0.50 0.50 h 14.55 0.09 6.24 0.21 0.19 1496.69 18.27 0.43 0.10 0.73 0.27 i 14.95 0.06 12.77 0.23 0.22 1678.61 15.89 0.85 0.09 0.25 0.75 j 7.38 0.06 6.26 0.23 0.21 1660.53 16.35 0.85 0.09 0.49 0.51 k 14.15 0.24 1.94 0.19 0.16 1308.81 24.91 0.14 0.11 0.59 0.41 l 8.37 0.20 0.75 0.18 0.14 1146.87 25.64 0.09 0.11 0.33 0.67 m 2.60 0.22 0.45 0.18 0.14 1131.80 26.49 0.05 0.12 0.44 0.56 n 31.50 0.08 7.80 0.23 0.21 1695.56 17.01 0.74 0.09 0.52 0.48 average 23.43 0.15 6.67 0.21 0.18 1466.46 21.52 0.44 0.10 0.49 0.51 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 859 figure 8a: well log signature of well 19 from 2982 m to 3299.74 m (using petrel®2016). figure 8b: well log signature of well 19 from 3240.63 m to 3558.3m (using petrel®2016). figure 8c: well log signature of well 19 from 3499.20 m to 3761.55m (using petrel®2016). 3.5.1 petrophysical summary of well 19 reservoirs the collective petrophysical data of well 19 reservoirs (table 9), specifies that the reservoirs on average, have a gross thickness of 25.37 m (83.72 ft), net sand thickness of 6.50 m (21.45 ft), shale volume of 0.16, porosity of 0.20, permeability of 1368.95 md, water saturation of 0.45 (49%) and a net to gross ratio of 0.58. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 860 table 9: petrophysical summary of well 19 reservoirs 3.5.2 hydrocarbon volumetric summary of well 19 reservoirs from table 10, well 19 reservoirs on average, have stoiip of 975,022,010.30 mmcf/mmstb and ultimate recovery of 805,469,155.46 mmcf/mmstb with a recovery factor of 0.84 (84%). based on these findings, we can imply that well 19 is a lucrative well with ultimate hydrocarbon retrieval of $40,273,457,773.00@ $50 per barrel (table 10). table 10: hydrocarbon volumetric summary of well 19 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 b 137,931.09 5,006,898,440.22 0.81 4,046,189,387.65 c 38,476.50 1,396,696,795.20 0.90 1,250,055,140.49 d 33,976.06 1,233,330,863.21 0.78 967,107,639.73 e 85,203.44 550,840,228.01 0.85 468,546,846.22 f 163,449.46 1,056,700,762.75 0.84 883,350,186.12 g 6,029.53 218,871,939.30 0.88 191,956,210.72 h 29,824.68 192,816,581.54 0.85 163,804,758.53 i 135,412.31 875,440,554.05 0.80 699,238,970.40 j 14,290.50 92,388,110.04 0.91 83,763,861.04 k 9,203.70 59,501,893.85 0.80 47,783,682.51 l 58,703.66 379,519,169.26 0.85 322,112,636.71 m 98,570.58 637,258,786.15 0.85 541,720,545.34 average 67,589.29 975,022,010.30 0.84 805,469,155.46 average ultimate recovery @usd50.00/b = 805,469,155.46 x 50 = $40,273,457,773.00 3.6 well 27 analysis well 27 comprises of both single and double-phase reservoirs, it has six single phase gas reservoirs, two double-phase (gas/oil) reservoirs and three single-phase oil reservoirs (figures 9a and b). this well intercepted eleven reservoirs (b, c, d, e, f, g, h, i, j, k, and l) out of thirteen existing reservoirs in the field and ranges in depth from 3008.31 (9,927.42 ft) m to 3468.55 m (11,446.22 ft). 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐺𝑟𝑜𝑠𝑠 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (𝑚) 𝑉𝑠ℎ 𝑁𝑒𝑡 𝑆𝑎𝑛𝑑 (𝑚) φ 𝐸𝑓𝑓𝛷 𝐾 (𝑚𝐷) 𝐹 𝑁𝑇𝐺 𝑆𝑤𝑖𝑟𝑟 𝑆𝑤 𝑆ℎ b 18.25 0.05 15.64 0.25 0.24 1908.34 14.37 0.86 0.09 0.34 0.66 c 14.47 0.30 7.80 0.21 0.17 1435.37 33.67 0.54 0.13 0.56 0.44 d 7.34 0.06 3.23 0.25 0.24 2003.82 12.74 0.44 0.08 0.24 0.76 e 50.92 0.15 4.34 0.21 0.18 1439.96 20.61 0.34 0.10 0.56 0.44 f 80.57 0.30 5.08 0.21 0.15 1503.9 20.08 0.38 0.10 0.53 0.47 g 1.56 0.09 0.95 0.21 0.19 1424.71 19.26 0.61 0.10 0.43 0.57 h 6.45 0.07 6.06 0.18 0.17 1210.39 24.25 0.94 0.11 0.51 0.49 i 43.84 0.06 9.85 0.2 0.19 1364.01 20.93 0.45 0.10 0.37 0.63 j 11.35 0.44 5.18 0.17 0.11 1047.68 33.18 0.46 0.13 0.70 0.30 k 2.00 0.09 1.37 0.18 0.17 1183.17 24.6 0.69 0.11 0.32 0.68 l 12.66 0.14 11.71 0.16 0.14 981.73 36.68 0.92 0.14 0.42 0.58 m 54.97 0.13 6.81 0.15 0.13 924.36 35.91 0.37 0.13 0.42 0.58 average 25.37 0.16 6.50 0.20 0.17 1368.95 24.69 0.58 0.11 0.45 0.55 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 861 figure 9a: well log signature of well 27 from 2977.60 m to 3251.10 m (using petrel®2016). figure 9b: well log signature of well 27 from 3232 m to 3506.10 m (using petrel®2016). 3.6.1 petrophysical summary of well 27 reservoirs the combined petrophysical result of well 27 reservoirs as reveal in table 11, states that the reservoirs on average, have a gross thickness of 16.44 m (54.25 ft), net sand thickness of 5.65 m (18.64 ft), shale volume of 0.23, porosity value of 0.23, permeability value of 1769.15 md, water saturation of 0.42 (42%) and a net to gross ratio of 0.58. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 862 table 11: petrophysical summary of well 27 reservoirs 3.6.2 hydrocarbon volumetric summary of well 27 reservoirs well 27 reservoirs on average as seen in table 12, have stoiip of 1,611,259,527.64 bbcf/bbstb and ultimate recovery of 1,295,232,420.62 bbcf/bbstb with a recovery factor of 0.83 (83%). based on these findings, we can infer that well 27 is a sound well with an ultimate hydrocarbon recovery of $64,761,621,031.23@ $50 per barrel (as shown in table 13) table 12: hydrocarbon volumetric summary of well 27 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 b 23,394.13 151,243,036.72 0.87 131,777,322.86 c 64,854.89 2,354,232,365.68 0.83 1,962,510,700.66 d 57,347.69 2,081,721,111.59 0.72 1,492,876,526.56 e 43,617.20 1,583,304,362.06 0.82 1,303,896,962.98 f 20,772.27 134,292,726.40 0.92 123,217,879.21 g 129,374.55 4,696,295,986.84 0.78 3,648,951,631.26 h 224,579.39 1,451,905,742.82 0.82 1,184,750,933.69 i 33,992.73 1,233,935,971.89 0.88 1,082,937,524.18 j 15,734.23 101,721,807.63 0.79 80,486,930.68 k 23,381.23 151,159,626.98 0.83 125,641,375.72 l 104,243.58 3,784,042,065.47 0.82 3,110,508,839.07 average 67,390.17 1,611,259,527.64 0.83 1,295,232,420.62 average ultimate recovery @usd50.00/b = 805,469,155.46 x 50 = $64,761,621,031.23 table 13: cumulative average volumetric of sapele deep 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐻𝐶𝑃𝑉 𝑆𝑇𝑂𝐼𝐼𝑃 𝑅𝐹 𝑈𝑅 well 01 134,032.73 448,153,428.39 0.71 287,469,260.17 well 06 111,647.50 311,672,938.26 0.73 215,892,954.64 well 17 94,391.17 1,416,052,696.66 0.84 1,207,418,779.00 well 18 66,999.23 2,179,663,023.41 0.88 1,900,314,137.78 well 19 67,589.29 975,022,010.30 0.84 805,469,155.46 well 27 67,390.17 1,611,259,527.64 0.83 1,295,232,420.62 average 90,341.68 1,156,970,604.11 0.81 951,966,117.95 average ultimate recovery reserve @usd50.00/b = 951,966,117.95 x 50 = $47,598,305,897.50 4. conclusion the entire sapele deep field has an average hydrocarbon pore volume of 90,341.68, stoiip value of 1,156,970,604.11 bbcf/bbstb and an ultimate recovery value of 951,966,117.95 mmcf/mmstb with primary recovery factor of 0.81 (81%). the high recovery factor in this 𝑅𝑒𝑠𝑒𝑟𝑣𝑜𝑖𝑟𝑠 𝐺𝑟𝑜𝑠𝑠 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (𝑚) 𝑉𝑠ℎ 𝑁𝑒𝑡 𝑆𝑎𝑛𝑑 (𝑚) φ 𝐸𝑓𝑓𝛷 𝐾 (𝑚𝐷) 𝐹 𝑁𝑇𝐺 𝑆𝑤𝑖𝑟𝑟 𝑆𝑤 𝑆ℎ b 6.27 0.25 5.11 0.20 0.16 1393.83 27.77 0.81 0.12 0.59 0.41 c 6.86 0.46 5.5 0.27 0.20 2232.58 23.12 0.80 0.11 0.47 0.53 d 12.24 0.09 3.97 0.31 0.28 2782.08 8.73 0.32 0.07 0.13 0.87 e 26.58 0.06 5.11 0.26 0.24 2056.56 12.66 0.19 0.08 0.39 0.61 f 9.71 0.45 6.34 0.18 0.12 1146.23 37.38 0.65 0.14 0.78 0.22 g 4.03 0.05 4.01 0.26 0.24 2037.52 12.82 0.99 0.08 0.14 0.86 h 71.8 0.25 8.51 0.23 0.18 1703.77 18.2 0.47 0.09 0.47 0.53 i 17.61 0.35 5.97 0.23 0.17 1768.04 16.32 0.34 0.09 0.55 0.45 j 4.93 0.26 2.13 0.21 0.16 1511.37 17.88 0.43 0.09 0.36 0.64 k 6.57 0.14 4.29 0.19 0.16 1244.96 24.41 0.65 0.11 0.47 0.53 l 14.19 0.15 11.19 0.22 0.19 1583.68 17.25 0.75 0.09 0.22 0.78 average 16.44 0.23 5.65 0.23 0.19 1769.15 19.69 0.58 0.10 0.42 0.58 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com airen and mujakperuo: reservoir hydrocarbon volumetric analysis of sapele deep field, niger delta, southern nigeria. azojete, 19(4):847-864. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 863 field is due to the presence of gas and appreciable water drives which has contributed to the high primary recovery factor. considering fluctuation in oil price, an average oil price of usd50.00 per barrel will generate on average, $47,598,305,897.50 billion from a primary production of 951,966,117.95 mmcf/mmstb in the field. thus, sapele deep field is an economically viable field. 5. acknowledgment the authors acknowledge seplat energy plc for the data used for this study. references airen, oj. and mujakperuo, bjo. 2023a. petrophysical appraisal of sapele deep field, niger delta, southern nigeria. nigerian journal of environmental sciences and technology, 7(2): 253-268. airen, oj. and mujakperuo, bjo. 2023b. evaluation of petrophysical properties of the sapele shallow field, niger delta area, southern nigeria. journal of applied science and environmental management, 27(7): 1451-1458. amigun, jo. and bakare, no. 2013. reservoir evaluation of danna field niger delta using petrophysical analysis and 3d seismic interpretation. petroleum and coal, 55(2): 119-127. anthony, aa. and aurelius, oo. 2012. reservoir characterization and structural interpretation of seismic profile: a case study of z-field, niger delta, nigeria. petroleum and coal, 55(1): 37-43. chidozie, ipd. 2017. hydrocarbon prospectively in the eastern coastal swamp depo-belt of the niger delta basin stratigraphic framework and structural styles. springer briefs in earth sciences. doi 10.1007/978-3-319-44627-1_2. doust, h. and omatsola, e. 1990. niger delta, in, edwards, j. d., and santogrossi, p.a., eds., divergent/passive margin basins, aapg memoir 48: tulsa, american association of petroleum geologists, 239-248. evamy, bd., haremboure, j., kamerling, p., knaap, wa., molloy, fa. and rowlands, ph. 1978. hydrocarbon habitat of tertiary niger delta. american association of petroleum geologists bulletin, 62: 1–39. glover p. 2016. petrophysics msc course notes, university of leeds, institute of geophysics and tectonics (igt), 32. halderson, hh. and damsleth, e. 1993. challenges in reservoir characterization. amer. assoc. pet. geol. bull., 77: 541–551. ilavalagan, ps. 2018. determination of movable hydrocarbon by geology department of petroleum engineering, amet university, chennai, tamil nadu, india. https://www.researchgate.net/publication/326646007. nyantakyi, ek., hu, ws., borkloe, jk., qin, g. and han, mc. 2013. structural and stratigraphic mapping of delta field, agbada formation, offshore niger delta, nigeria. american journal of engineering research (ajer), 2(11): 204-215. orife, jm. and avbovbo, aa. 1981. stratigraphic and unconformity traps in the niger delta (abs.): aapg bulletin, 65: 967. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com https://www.researchgate.net/institution/university_of_leeds https://www.researchgate.net/institution/university_of_leeds/department/institute_of_geophysics_and_tectonics_igt https://www.researchgate.net/institution/university_of_leeds/department/institute_of_geophysics_and_tectonics_igt arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):847-864. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: osariere.airen@uniben.edu 864 reijers, tra. 2011. stratigraphy and sedimentology of the niger delta. geologos, 17(3), 133– 162. doi:10.2478/v10118-011-0008-3. rider, m. 1986. the geological interpretation of well logs. blackie, glasgow, 151-165. slatt, rm. 1998. compartmentalized reservoirs – the exception or the rule? in: r.m. slatt (ed.), compartmentalized reservoirs in rocky mountain basins, rocky mtn. assoc.geol., 5-7. stacher, p. 1995. present understanding of the niger delta hydrocarbon habitat, in oti, m. n. and postma, g., (eds). geology of deltas: rotterdam, a.a. balkema, 257-267 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):83-92 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 83 impact of soil compaction and mulching on growth and yield of cowpea in ile-ife, nigeria o. b. adeboye*, s. o. odediran, a. p. adeboye, o. k. adekalu department of agricultural and environmental engineering, obafemi awolowo university, ile-ife, nigeria *corresponding author's email address: adeboyeob@oauife.edu.ng article information submitted 15 oct., 2023 revised 2 february, 2024 accepted 16 february, 2024 keywords: compaction cowpea mulch tractor passes yield abstract agricultural vehicle traffic is one of the principal factors responsible for the compaction of surface and subsurface horizons of soil under field conditions. to control this, a field experiment was conducted to examine the response of tractor wheel passes and mulching on the growth and yield of cowpeas. a tillage model can simulate the effect of different components that contribute to the formation of yields and can facilitate the design of alternative agricultural systems. high bulk density was obtained using the core sampler method within the ploughed layer and the active portion of the crop root zone (10-30 cm), while there were increasing trends in bulk density from planting to crop maturity. a model to predict the crop yield as a function of the degree of compaction and extent of mulching was developed. the model summary was significant at a 5 % probability level (p < 0.005). moreover, interactions between compaction and mulching on cowpea yield showed that the least (0.21 tha-1) and highest (0.51 tha-1) cowpea grain yield occurred at the point when treatment was 4 tractor passes and no mulch and 0 passes with 60 kg mulch, respectively. mulch with no compaction performed better in growth and yields as well as yield-related parameters compared to compaction only without mulch. this gives the best soil management practice that will result in good growth and maximum productivity of cowpeas. 1.0 introduction cowpea has been cultivated and domesticated in africa for centuries. it is now grown worldwide, especially in the tropics. it is a warm-season crop that can be produced in semiarid regions and dry savannahs. it adapts better to sandy soils and dry conditions than soybeans (tjai, 2010). the largest producers of cowpea are nigeria, niger, brazil, haiti, india, myanmar, sri lanka, australia, and the united states (tjai, 2010). in addition to their health-related benefits, beans are considerably cheaper than rice or any other dietary fibre type (ayenlere et al., 2012). it is a good food security item as it mixes well with another recipe (muoneke et al., 2012). cowpea is commonly cultivated as a nutritious and highly palatable source of food in the southern united states, the middle east, africa, asia, and throughout the tropics and subtropics. the seeds of cowpeas have been reported to contain 24 % crude protein, 53 % carbohydrates, and 2 % fat (fao, 2012). cowpea fixes atmosphere nitrogen through symbiosis with nodule bacteria (shiringani and shimeles, 2011). it is an extremely resilient crop cultivated under some of the most extreme agricultural conditions in the world (muoneke et al., 2012). http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):83-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 84 the advent of mechanized and intensive agriculture with its associated soil compaction problems, during the past decades, led to a sharp interest in wheel traffic and soil compaction. the level of tractor utilization in food production in nigeria is a much-debated subject. there is little doubt of the economic and ecological damage of soil compaction to society (graves et al., 2015). the use of agricultural machinery on farms has increased steadily. for example, wheel loads of combine harvesters have increased by about 65 % between the years 1989 and 2009 (schjonning et al., 2015). consequently, the mechanical stresses exerted by today’s machinery may exceed the strength of many arable soils (hornand fleige, 2003; schjonning et al., 2015; zink et al., 2010). it is reasonable to assume that the increase in agricultural machinery loads has exacerbated the extent and severity of soil compaction. compaction is estimated to affect between 25 and 45 % of agricultural land (brus and van den akker, 2018; graves et al., 2015; schjonning et al., 2015). soil compaction may increase flooding incidence and severity (alaoui et al., 2018), and trigger soil erosion (horn et al., 2017), declining water quality through increased nutrient and pesticide leaching (jarvis, 2007), and increase greenhouse gas emissions (ball, 2013). crops and soils can react to the same or different levels of compaction differently. thus, there is a need to assess the impact of compaction under a particular environment and determine the best combination of agronomic and tillage practices that will result in optimum growth and land productivity of cowpeas. therefore, the objective of the study was to develop a model for predicting the impacts of soil compaction and mulching on the yields of cowpeas under sub-humid conditions. 2. materials and methods 2.1 study area the experiment was carried out at the teaching and research farm, obafemi awolowo university, ile-ife, nigeria. the study location is between latitude of 7o26’n-7o33’n and longitude of 4o30’e-4o35’e. the temperature of the study area ranged between 14 and 38ºc from september to december. there were two distinct seasons in the study area, the rainy season which begins in march and ends in october, and the dry season which lasts for the rest of the year (adekalu and osunbitan, 2006). 2.2 experimental procedure the treatments consisted of 0, 2, and 4 tractor-traffic tyre passes imposed on the soil before planting (table 1). a massey ferguson (mf 375e) 2-wheel drive tractor with a rear tyre dimension of 0.44 x 0.70 m, a weight of 43.30 kn, and a resulting ground pressure of 240 kpa was used for the compaction of soil. forward tractor speed was kept constant at 6 km/h for all the treatments. the treatments were arranged in a randomized complete block design in a uniform field of sandy loam soil. the seasonal rainfall was 535 mm while maximum and minimum air temperatures were 32.1 and 29.1oc respectively. the sunshine hour was 6 hrs during the cropping season. the land was ploughed and harrowed after one week. the layout was marked using tape, pegs, and ropes. spacing between plots was 1.5 m and planting spacing was 50 x 75 cm. the areas/plots to be compacted were covered completely with the wheeling at an average soil moisture content of 11.05 % using the gravimetric method and bulk density of 1.09 g/cm3. cowpea (it81d-994) seeds were planted manually on the 16th of september, 2015 at a soil depth of 5 cm in an 8 x 4 m area of each plot by placing three seeds in a hole. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: impact of soil compaction and mulching on growth and yield of cowpea in ile-ife, nigeria. azojete, 20(1):83-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 85 table 1: description of experimental treatments treatment label description control 60m0p 30m0p 0m2p 30m2p 60m2p 0m4p 30m4p 60m4p 0 kg mulch and zero tractor pass 60 kg mulch and zero tractor pass 30 kg mulch and zero tractor pass 0 kg mulch and two tractor passes 30 kg mulch and two tractor passes 60 kg mulch and two tractor passes 0 kg mulch and four tractor passes 30 kg mulch and four tractor passes 60 kg mulch and four tractor passes the experiment consisted of 9 treatments and was replicated three times (figure 1). the seedlings were thinned to one stand per hole 10 days after planting (dap). mulch was applied on the soil surface 14 dap. the experimental area was weeded using a local hoe regularly until maturity. the weight of mulch was 30 and 60 kg, and 0 kg mulch at 8 t/ha served as the control. the area of each plot was 32 m2. ten plants were selected from each plot and tagged for observations at intervals of one week. the established plants were counted at twenty-eight days after planting. the number of leaves on the tagged plants was counted and averages were determined for each treatment. the stem girth of the tagged plants was measured at 5ch above the soil surface using digital vernier callipers. a measuring tape was used to measure the plant height from the soil surface to the apex of the tagged plants. the root lengths of the ten tagged plants per plot were measured as the length from the base of the shoot to the tip of the root of each plant using a ruler till harvest (90 days after planting). at maturity, pods were harvested manually, sun-dried for one week, and shelled. the dry pods and grain yields were weighed using an electric balance. the number of pods per plant, pod length, number of seeds per pod, and dry grain yields were measured. the average numbers of pods and grains per treatment were determined from the tagged. figure 1: experimental layout for treatments 2.3 soil properties the soil samples were analyzed for physical and chemical properties such as bulk density and textural class using standard methods (table 2). the upper 20 cm was characterized by sandy loam, while the lower 20 -30 cm was sandy clay loam. the electrical conductivity of soil was determined in the filtrate of the water extract using a conductivity meter. the bulk density was lower in the upper 20 cm than in the lower 20 to 30 cm. soil ph in the upper 30 cm is adequate for the cultivation of cowpea. the cation exchange capacity of the soil was higher in the upper 20 cm than in the lower 20 to 30 cm. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):83-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 86 table 2: physical and chemical properties of the soil soil depth (cm) 0-10 10-20 20-30 ph cacl2 5.2 5.1 5.05 ec (ms/cm) 0.11 0.14 0.14 bulk density (g/cm3) 0.98 1.20 1.48 p (ppm) 54.24 38.50 39.47 sand % 75 75 77 silt (%) 10 10 8 clay (%) 15 15 15 ca2+(cmol/kg) 47.64 47.43 47.47 mg2+(cmol/kg) 6.14 5.98 5.84 na2+(cmol/kg) 1.15 1.26 1.20 k+(cmol/kg) 0.51 0.26 0.1 2.4 statistical analysis data obtained were analyzed using response surface methodology rsm (design expert 7.0) dx7 mfc application, stat. ease inc., file version 7.0.1.0 using central composite design (ccd); test of significance of treatments and their interactions was determined at 5 % significant level. the fractional design points were used to generate the experimental runs and predicted values. the graphs of treatments and their interactions with the yields and growth of cowpeas were plotted. the experimental procedures were repeated twice. 3. results and discussion 3.1 effect of compaction and mulching on yield the effect of the varying levels of compaction and different mulch applications on the yields of cowpeas is shown in 3d format (figures 2 and 3). the 4 and 0 tractor passes with 0 kg and 60 kg of mulch produced 0.21 and 0.51 t/ha of cowpea respectively. this implies that yield decreases with an increase in compaction but increases with mulch (p < 0.05). the model relating yield, compaction, and mulching (equation 1) is significant (p < 0.05) and with an r2 of 0.99 which indicates a good degree of reliability. this means that the sample variation of 99 % for cowpea yields is attributed to compaction and mulching. this is above the recommended lower limit of gan and yao (2008) that for the good fit of a model, at least r2 of 0.80 is required. the adjusted determination coefficient (adj. r2) was 0.98 supporting the high significance of the model. y = +2.04 +7.70 * c -0.27 * m -0.31 * c * m +6.13 * c2 + 0.020 * m2 (1) where: y is cowpea yield (t/ha); compaction (c) and mulching (m). equation 1 can be used in the determination of cowpea yield under varying conditions of the stipulated factors of compaction and mulching treatments. figure 2: response surface plots showing interactive effects of mulching and compaction on yield design-expert® software yield t/ha x1 = a: compaction kpa x2 = b: mulching kg 0 240 480 720 960 0 15 30 45 60 0.21 0.295 0.38 0.465 0.55 y ie ld t/ ha a: compaction kpa b: mulching kg file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: impact of soil compaction and mulching on growth and yield of cowpea in ile-ife, nigeria. azojete, 20(1):83-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 87 figure 3: soil compaction and mulching treatments on cowpea grain yield 3.2. effect of compaction and mulching on the number of leaves of cowpea the 0 kg mulch and 0 tractor pass (control) had an average of 19 leaves at 14 dap to 65 leaves at 77 dap, compared to 4 tractor passes and 0 kg mulch which had 6 leaves from 14 dap to 39 leaves at 77 dap. there was an increase in the number of leaves with mulch but a decrease in the number of leaves with an increase in compaction (figure 4). this could be attributed to an increase in moisture contents which resulted in higher evapotranspiration. with higher compaction, interstices in the soil which accommodate water have been blocked and water which is essential for cellular activities and canopy formation has been reduced substantially. the response surface plot of mulching, compaction, and number of leaves is shown in figure 5. figure 4: effect of compaction and mulching on cowpea number of leaves. 0 0.1 0.2 0.3 0.4 0.5 0.6 y ie ld (t h a -1 ) treatment 0 10 20 30 40 50 60 70 n u m b er o f le a f treatment 2wap 3wap 4wap 5wap 6wap 7wap 8wap 9wap 10wap 11wap http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):83-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 88 figure 5: response surface plots showing interactive effects of mulching and compaction number of leaves 3.3. effect of compaction and mulching on root length the application of 60 kg mulch with no tractor pass produced the highest root length of 7.2 cm at 2 wap and 29.1 cm at 12 wap, while 4 passes and no mulch produced the lowest root length of 5 cm at 2 wap and 14 cm at 12 wap (figures 6 and 7). mulching conserves moisture, reduces soil temperature, and retards weed growth and competition. compaction-induced productivity losses are primarily a consequence of impeded root system expansion (bengough et al., 2011; valentine et al., 2012). figure 6: effects of compaction and mulching on cowpea root length design-expert® software factor coding: actual number of leaves design points above predicted value design points below predicted value 66 39 x1 = a: compaction x2 = b: mulching 0.00 6.00 12.00 18.00 24.00 30.00 36.00 42.00 48.00 54.00 60.00 0.00 35.00 70.00 105.00 140.00 30 40 50 60 70 n u m b e r o f l e a v e s a: compaction b: mulching 0 5 10 15 20 25 30 35 r o o t l en g th (c m ) treatment 2wap 3wap 4wap 5wap 6wap 7wap 8wap 9wap 10wap 11wap 12wap file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: impact of soil compaction and mulching on growth and yield of cowpea in ile-ife, nigeria. azojete, 20(1):83-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 89 figure 7: response surface plots showing interactive effects of mulching and compaction on root length 3.4 effect of compaction and mulching on plant height the effect of compaction and mulch treatments on plant height is shown in figure 8, the result shows that the average plant height varied from 65 cm at 0 tractor passes and 0 mulch to 35 cm at 4 passes and 30 kg mulch. the control had a plant height of 19 cm at 14 dap and 65 cm at 77 dap, followed by the 0 pass and 60 kg mulch application of 18 cm height at 14 dap and 63 cm at 77 dap. the 4 passes and 30 kg mulch had the lowest mean of 35 cm at 77 dap. the low height could be attributed to high compaction which lowered the rate of interflow in the soil interstices. figure 8: effects of compaction and mulching on cowpea plant height. design-expert® software factor coding: actual root length design points above predicted value design points below predicted value 29.6 14 x1 = a: compaction x2 = b: mulching 0.00 6.00 12.00 18.00 24.00 30.00 36.00 42.00 48.00 54.00 60.00 0.00 35.00 70.00 105.00 140.00 10 15 20 25 30 r o o t l e n g t h a: compaction b: mulching 0 10 20 30 40 50 60 70 control 0p 60m 0p 30m 2p 0m 2p 30m 2p 60m 4p 0m 4p 30m 4p 60m p la n t h ei g h t (c m ) treatment 2wap 3wap 4wap 5wap 6wap 7wap 8wap 9wap 10wap 11wap http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):83-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 90 figure 9: response surface plots showing interactive effects of mulching and compaction on plant height. 3.5 moisture content and bulk density of experimental plots the soil bulk densities are presented in table 3. the tractor passes on the plots affected the bulk densities, in proportion to the number of passes and amount of mulch applied. the higher the number of passes, the higher the bulk density as expected. the higher the amount of mulch, the higher the moisture content of the soil. the higher number of passes slightly reduced the moisture contents. compaction significantly affected the parameters. bulk density increased while soil moisture content reduced with an increased number of tractor passes. these results agreed with dauda and samari (2002) where high moisture contents decreased with the number of tractor passes. mulch treatments alone produced high ranges of soil moisture contents over compaction. however, higher soil bulk density due to compaction could be attributed to the effects of tractor-wheel traffic and implement passes and lower macro-porosity and evaporation rate (agbede, 2006). the highest moisture status of no pass and 60 kg mulch could be adduced to the minimum soil disturbance with little exposure of the soil surface to the atmosphere and consequent reduction in water evaporation, therefore conserving soil temperatures and the available water in the soil (agele et al., 2000). table 3. soil moisture contents and bulk densities of the plots 21dap 42 dap 63 dap 84 dap treatment moisture contents (%) bulk density (g/cm3) moisture contents (%) bulk density (g/cm3) moisture contents (%) bulk density (g/cm3) moisture contents (%) bulk density (g/cm3) 0p 0m 12.15 1.17 17.56 1.11 12.04 1.31 7.72 1.13 0p 60m 13.13 1.13 18.52 0.88 12.10 1.36 8.51 1.32 2p 30m 11.14 1.12 16.45 1.12 10.86 1.13 6.22 1.39 4p 0m 8.03 1.12 13. 69 1.08 8. 68 0.92 7.00 1.71 4p 30m 8.68 1.39 13.09 0.93 9.95 0.95 5.39 1.12 2p 60m 12.26 1.34 16.29 0.97 11.79 1.13 6.24 1.73 2p 0m 10.08 1.18 15.37 1.05 10.03 0.97 6.20 1.42 4p 60m 9.27 1.28 14.74 1.55 10.90 0.87 6.37 1.73 0p 30m 12.49 1.31 17.71 1.06 12.82 1.31 6.82 1.11 dap – days after planting design-expert® software factor coding: actual plant height design points above predicted value design points below predicted value 63.46 34.12 x1 = a: compaction x2 = b: mulching 0.00 6.00 12.00 18.00 24.00 30.00 36.00 42.00 48.00 54.00 60.00 0.00 35.00 70.00 105.00 140.00 30 40 50 60 70 p l a n t h e ig h t a: compaction b: mulching file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adeboye et al: impact of soil compaction and mulching on growth and yield of cowpea in ile-ife, nigeria. azojete, 20(1):83-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 91 4. conclusion this study shows the negative effects of multiple tractor wheel passes (twp) on cowpea growth and soil properties. increases in tractor wheel passes from 0, 2, and 4 tractor passes increased the bulk density of soil but reduced the grain yield. multiple tractor wheel passes and amendments with mulching affected soil physical properties and conserved soil moisture. mulch treatments produced better growth parameters and yields of cowpeas. compaction of the soil by multiple tractor tyre passes affected the growth parameters and yields of cowpea. the application of 60 kg mulch increased grain yields compared to the zero passes and zero mulch application. this could be attributed to high mulch which conserves moisture and helps root growth. thus, farmers should reduce compaction as much as possible to get high yields of cowpea. research on cost-benefit analysis in cowpea production under different soil management techniques vis-a-vis different planting seasons should be conducted to ascertain the most reliable and effective practice that could be recommended for farmers in the cropping seasons. there is a need to determine the long-term effects of compaction operations on soil properties, crop growth parameters, dry biomass and crop yield. references adekalu, ko., olorunfemi, ia., and osunbitan ja. 2006. grass mulching effect on infiltration, surface runoff, and soil loss of three agricultural soils in nigeria. bioresource technology, 98: 912-917. agbede, tm. 2006. effect of tillage on soil properties and yam yield on an alfisol in southwestern nigeria. soil tillage research, 86(1):1-8. agele, so. 2000. effect of animal manure and npk fertilizer on simulated erosion and maize yield. journal of environmental education, 19(2): 131-138. alaoui, a., rogger, m., peth, s. and bloschl, g. 2018. does soil compaction increase floods? a review. journal of hydrology, 557: 631–642. ayenlere, ae., mohammed, ab., dutse, f., abdullahi, m. and mohammed-lawal, a. 2012. an assessment of the economics of maize-cowpea cropping system in the ogun area of kwara state, nigeria biological and environmental sciences journal for the tropics, 9 (1): 39-43. ball, bc. 2013. soil structure and greenhouse gas emissions: a synthesis of 20 years of experimentation. european journal of soil science, 64(3): 357–373. bengough, ag., mckenzie, bm., hallett, pd. and valentine, ta. 2011.root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits. journal of experimental botany, 62: 59–68. brus, dj. and vanden akker, jjh. 2018. how serious a problem is subsoil compaction in the netherlands? a survey based on probability sampling. soil, 4(1):37–45. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):83-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 92 dauda, a. and samari a. 2002. cowpea yield response to soil compaction under traffic on a sandy loam soil in the semi-arid region of northern nigeria. soil tillage research, 68:17-22. food and agriculture organization (fao) statistical databases, 2012. ‘faostat: agriculture data. rome, italy. http://faostat.fao.org/site, accessed 9th december 2015. gan, he. and yao, xd. 2008. optimization of formulation of soy-cakes baked in infrared microwave combination oven by response surface method. journal of food science and technology, 61(2):153 – 163. graves, ar., morris, j., deeks, lk., rickson, rj., kibblewhite, mg., harris, ja., farewell, ts. and truckle, i. 2015. the total costs of soil degradation in england and wales. ecological economics, 119, 399-413. horn, r. and fleige, h. 2003. a method for assessing the impact of load on mechanical stability and on physical properties of soils. soil tillage research, 73(1&2), 89–99. horn, r., fleige, h., zimmermann, i. and peng, x. 2017. soil physical compaction and erosion as a threat to food production and human health. in: singh, b.r., mclaughlin, mj and brevik, ec. (eds.), the nexus of soils, plants, animals and human health. schweizerbart science publisher, stuttgart, pp.42–49 muoneke, co., ndukwe, om., umana, pe., okpara, da. and asawalam, do. 2012. productivity of vegetables cowpea (vigna unguiculatal. walp) and maize (zea mays l.) intercropping system as influenced by component density in a tropical zone of southeastern nigeria. international journal of agricultural research and development, 15 (1):835-847. reminson, su., bello, b. and okunarin, t. 1980. the effects of different spacing and phosphorus application on the growth and yield of cowpea. ife journal of agriculture, 2: 67 – 73. schjønning, p., van den akker, jjh., keller, t., greve, mh., lamandé, m., simojoki, a., stettler, m., arvidsson, j. and breuningmadsen, h. 2015. driver pressure stateimpact-response (dpsir) analysis and risk assessment for soil compaction– a european perspective. advances in agronomy,133: 183–237. shiringani, rp. and shimeles, ha. 2011. yield response and stability among cowpea genotypes at three planting dates and test environments. african journal of agricultural resources, 6(4): 32593263. thomas jefferson agricultural institute (tjai). 2010. cowpea: a versatile legume for hot, dry conditions. thomas jefferson agricultural institute, columbia, mo. https://www.jeffersoninstitute.org/pubs/cowpea (accessed 6th october 2023) valentine, ta., hallett, pd., binnie, k., young, mw., squire, gr., hawes, c. and bengough, ga. 2012. soil strength and macropore volume limit root elongation rates in many uk agricultural soils. annals of botany, 110 (2): 259–270. zink, a., fleige, h., and horn, r. 2010. load risks of subsoil compaction and depths of stress propagation in arable luvisols. soil science society of america journal,74(5): 1733-1742 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):827-836 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 827 assessment of air quality of service stations in a built-up area: a case study of lagos metropolis a. s. shote1*, s. a. aasa1,2 and a. i. musa1 1department of mechanical engineering, olabisi onabanjo university, ago-iwoye, ogun state, nigeria 2department of mechanical and aeronautical engineering, university of pretoria, south africa *corresponding author's email address: shote.adeola@oouagoiwoye.edu.ng article information submitted 24 august, 2023 revised 13 oct, 2023 accepted 15 oct, 2023 keywords: emission air quality index carbon monoxide carbon iv oxide service station abstract emissions emanating from commercial facilities in high dense area are subject of concern as more people are being hospitalised or suffering from long term exposure to poor air quality. thus, there is the need to conduct assessment of air quality and other hazardous emissions in some commercial facilities. this paper presents the air quality index, formaldehyde and environmental emissions emanating from four service stations in lagos metropolis. four different filling stations were strategically selected from dense localities and monitored for about 8hrs per day for 30 days. the level of air qualities is assessed respectively for these locations. the data is time-averaged over the period of the data acquisition, and the results are presented. the air quality index for all the service stations were found to be below the recommended threshold by the world health organization (who) guidelines. the co, co2 and hcho emissions have similar pattern with respect to all locations monitored. further analyses of emissions from different stations revealed that there is significant difference in service station b (ss b) from service station d (ss d) for co2 emissions at 95% confidence as pvalue (0.04) is less than 0.05. a proportion of 51% of co2 can be accounted for by the emission variability in the service stations. however, there is no significant difference in the other emissions patterns at 95% confidence as pvalue is greater than 0.05 (pvalue >0.05) for aqi, co, hcho and tvoc emissions. in general, the emissions within the selected built-up areas were found not to sufficiently harm service station workers for short term exposure. 1.0 introduction in recent time, there are various reports of environmental concerns on public health emanating most especially from air pollution ( xiao et al., 2020, parajuli et al., 2016, sonibare et al., 2010, heracleous and michael, 2019, azumaa et al., 2020, tan et al., 2021). air pollution is one of the leading menaces that are wrecking weighty atmospheric hazards on our ecosystem and human health. human activities seem to be a major cause of releasing numerous lifethreatening compounds into the environment. these emissions, in large quantities, are directly responsible for the lowering air quality of the respective environment. the potential associated hazards with the downstream sector of the petroleum value chain are often overlooked most especially in the cities where effect or the havoc of continuous emission could be swiftly felt. various researchers ( zhang et al., 2021, xiao et al., 2020, marc-andre et al., 2007, parajuli et al., 2016, kassomenos et al., 2006, sonibare et al., 2010, heracleous and michael, 2019, azumaa et al., 2020, tan et al., 2021) have conducted emission assessments of road traffic, industrial activities, commercial activities as well as secondary pollutants. some dangerous pollutants (pm10, carbon monoxide (co) and oxides of nitrogen) are identified by muir et al., (2006). http://www.azojete.com.ng/ mailto:%20jonas.onah.pg.65348@unn.edu.ng mailto:%20shote.adeola@oouagoiwoye.edu.ng mailto:%20shote.adeola@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):827-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 828 long term exposure to some of these pollutants can pose a risk of lung cancer, respiratory diseases, arteriosclerosis, as well as heart rate variability (lelieveld et al., 2015, brook et al., 2017, zivin and neidell, 2018, darbre, 2018). co is a poisonous gas emitted from incomplete combustion of hydrocarbons. once it is taken up by the body system, co diffuses into plasma and passes across the red blood cell membrane. it then enters the red blood cell cytoplasm where it is united with haemoglobin to form carboxyhemoglobin (cohb). the affinity of the red blood cells for co is 210 – 300 times greater than for oxygen (fang et al., 2006). this will prevent tissue respiration and the organism may eventually die of oxygen starvation. despite the growing trends of studies on atmospheric pollution, the long term health effects of air pollution remain largely unknown due to the fact that the blanket control of the harm is insufficient, and the combined effect of several contaminants is frequently eclipsed by the severe contributions of primary contaminants (lelieveld et al., 2015; kelly and fussell, 2011). the global burden of death reiterated that, air pollution killed 4.9 million people worldwide in 2017 (stanaway et al., 2018). air pollution constitutes a major public health issue in both developed and developing countries. according to (nguyen and kim, 2006), about 2.7 million people die annually as a result of air pollution all over the world. as a direct consequence of swiftly growing industrialization across the entire planet, the quality of air around us keeps dropping. this is undoubtedly undesirable, as it has both short and long terms effects on the life expectancy most especially in developing and under developed countries. the air quality index, or sometimes called air pollution index, is a unified index that summarizes the concentrations of various pollutants in a single index. the pollutants are then categorized to determine the efficiency of dissemination discharge and utilization in different regions (plaia and ruggieri, 2010). this helps in the reliable comparison of air quality patterns over time and space, as well as the prediction and possible caveat of air pollution (mirabelli et al., 2020). a number of aqis based on various sub-indicators and calculation methodologies have been developed by researchers depending on local air quality scenarios as well as national standards to account for changes in air quality and management requirements among countries (kanchan et al., 2015). however, it is really difficult to use existing aqis for local or regional comparison due to their weak comparability and cross-applicability. therefore, most regions and territories need to generate their own data and determine the possible effect on life. it should be noted that most aqis used by some regions and countries are currently based on a single major pollutant rather than the overall air quality (perlmutt et al., 2017) which may significantly underestimate the impact of numerous contaminants. hence, the need to develop data for various regions within nigeria on the safety compliance with standard methods or practices is imperative. very recently, the commercial activities of service stations in lagos metropolis are becoming a threat to the environment and the people staying within that environment as some regulations or the available regulations are perceived to be violated by the various stakeholders that are involved for the commercial dispensing of hydrocarbons. in some cases, there is serious oil spillage that ultimately affect the immediate environment. the safety of the fuel dispensing environment is also a subject of concern. in the past, filling stations are usually located on the outskirt of the cities because of the perceived danger of fuel to life, however, filling stations are becoming features of residential areas now. some of the filling stations have also extended their operations to include sales of cooking gas, lube bay, shopping malls, gas cylinders, and vehicle servicing. clusters of service stations in residential areas are source of concerns for residents in some areas. the close proximity to residential structures is one of the main issues causing fatal destructions which are usually experienced in accident situation. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: assessment of air quality of service stations in a built-up area: a case study of lagos metropolis. azojete, 19(4):827836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 829 furthermore, there are growing numbers of illegal filling stations in lagos and these numbers could increase significantly in the coming years if regulations and enforcement are not put in place. the activities of legal and the illegal filling stations could negatively affect the air quality around residential areas. these issues have necessitated this research as serious concern is growing among lagos residents on the possible implication on health and safety. some highly built up areas where the environmental menace seems dominant are selected for this research to ascertain the effect of the commercial activities of service stations in the area. commercially dense areas were chosen for this study because of the huge potential effect on large number of people and the subsequent over stretching of the health facilities. this study presents the air quality assessment around four service stations in lagos metropolis. each service station was randomly selected from east, north, west, and south of lagos metropolis. 2. materials and methods 2.1 study area lagos state (with latitude 6.5227on, and longitude 3.6218oe) is located in the south western part of nigeria and is regarded as one of the top ten fastest growing urban areas of the world (diop et al., 2014, un-habitat, 2006). the approximate size of lagos is 1,171.3km2 with water occupying about 172km2 as shown in figure 1. it is mainly bothered in the north by ogun state and in the south by atlantic ocean. it is the economic and financial hub of africa with huge urban agglomeration of residents (city-population, 2015). it is the largest metropolitan city in africa with numerous intrinsic challenges associated with its unfolding evolution. city of lagos is also known for many commercial activities like petroleum related businesses, industrialization among others. some of the key metros of the study area are shown in figure 1 with the various service stations locations where data were logged. figure 1: map of lagos metropolis (6.5227on, 3.6218oe) 2.2 data acquisition process four filling stations were selected in strategic positions in lagos metropolis due large number of people engaging in hydrocarbon related commercial activities on a daily basis. common emissions were chosen for this research. co, co2 and formaldehyde hcho were monitored for four months with the aid of air analyzer (model number, b09288j77j; pallipartners, china). all these emissions co, co2 and formaldehyde hcho were selected based on prevalence, relevance to air quality assessment and immediate health implication. for instance, co is a very common atmospheric pollutant whereas co2 is a greenhouse gas responsible for global warming; climate change and the duo are primarily associated with hydrocarbons. carbon monoxide is known to be toxic and can cause cardiovascular problems even at low concentration. it is therefore important in assessing co level to determine the air quality. however, co2 level is crucial for the understanding of impact of human activities on the immediate environment. again, choosing formaldehyde (hcho) along with co and co2 as it is also associated with structures, vehicular emissions. it can also cause respiratory irritation, and has the propensity for carcinogenicity. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):827-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 830 meteorological parameters (temperature, precipitation, humidity and wind speed) were also obtained for the four locations. the four filling stations were selected based on the main four regional areas of lagos (figure 1). the selected filling stations were chosen on the basis of high commercial activities and perceived environmental threat. the selected service stations are designated as -1, -2, -3 and -4 respectively. service station-1, -2, -3 and -4 are located on the western (6.4183on, 2.8301oe), eastern (6.4569on, 3.8859oe), southern (6.4281on, 3.4219oe) and northern (6.6194on, 3.5105oe) parts of lagos state respectively. all the four service stations have an average fuel dispense stands of about 6 numbers. four locations are measured away from each of the dispenser packs at about 3m in all the four cardinal directions. the locations are also designated south, east, west and north. these data were monitored over three periods of the day during the dry season of the year: (a) two hours in the morning; (b) two hours in the afternoon; and (c) two hours in the evening. the emissions were measured monitored at the nose level of an average height of attendants at the various selected stations to determine the likelihood of the level of risk that the attendants are exposed to during the working hours in the various service stations. baseline data were obtained from all the filling stations before the scheduled daily monitoring. the baseline data are taken outside the territory of each of the filling stations. these locations are chosen strategically to calibrate the gas analyzer and are free from hydrocarbon emissions. the various data obtained were time-averaged to obtain single data for each location at respective filling station. the data were further processed according to navidi (2021) by employing analysis of means or variance (anova) and compared with the available standards locally and internationally. equation 1 (shihab, 2023) are used to obtain the air quality index data according to geometric mean method with aqi range from 0 -125+. the uncertainty in the experimental data for all the emissions is less than 5%. this was obtained using the magnitude of the bias and the precision uncertainties in the measurements. l lh lclh i cc ccii aqi + − −− = )( ))(( (1) where ih is the index break point corresponding to ch; il is the index break point corresponding cl; cc is the pollutant concentration; cl is the concentration breakpoint that is ≤ cc, and ch is the concentration breakpoint that is ≥ cc. 3. results and discussion 3.1 meteorological air quality averaged meteorological parameters like the temperature, wind speed, humidity and precipitation are monitored and presented in table 1. it also provides the essential background meteorological information which has direct implications on activities relating to discharge of hydrocarbons into the neighbourhood. the table basically indicates the usual or expected values for a normal environment that is safe for anyone to stay while performing his or her daily routine task. meteorological air quality index gives indication or insight to how dangerous the air around is, as it tracks the smog level, exhaust, dust as well as other pollutants. table 1: mean meteorological values meteorological parameter measurement value temperature 30oc precipitation 0% wind speed 13km/h humidity 84% air density 1.03 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: assessment of air quality of service stations in a built-up area: a case study of lagos metropolis. azojete, 19(4):827836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 831 3.2 air quality index the air quality is obtained in-situ from the emission analyzer equipment by using equation 1. the data for the air quality index is presented in figure 2. averaged data (av) and the error gap in the data for all the filling stations are also presented in figure 2. in figure 2, the abscissa denotes the various locations (‘n’ for north, ‘w’ for west, ‘e’ for east, ‘s’ for south) along the horizontal direction while the ordinate represents the measured aqi. on the legend, ‘ss’ implies service (filling) station and letters ‘a to d’ just in front of ss represents the various stations monitored. for all the plots, break point for the air quality are clearly not exceeded as all of the data fall below it and are within the desirable region for the air quality of the filling stations monitored. this shows that all the filling stations are world health organization compliant. the guidelines of who are intended to serve as a reference for various governments in setting air quality targets and implementing measures to reduce exposure to malicious air pollutants. air quality index value above the break point line is considered ‘moderate’ in terms of its effect on the health of individual over a long period of time. magnification (figure 2) of the line plots of the various service stations shows that there are clear variations in the relationship between all the aqi data presented for all the four locations. there is a gradual increase in the aqi as shown in the averaged data (av) from all the four service stations. this could be attributed to the direction of wind which is apparently from north-west to south-east. the difference in the aqi can be seen with station-c having the lowest values all through the four locations. further analyses were carried out to determine whether there is significant difference in the aqi for all the four stations. the results revealed that pvalue is greater than 0.05 at 95% confidence. this shows that there is no significant difference in the emissions as a result of different locations of the filling station. this implies that analyzing data from one of the filling stations monitored in lagos metropolis suffices for the air quality in any of the four locations. figure 2: air quality index in four different locations 0 10 20 30 40 50 60 a ir q u a li ty i n d e x( a q i) spot ss a ss b ss c ss d _av d e si ra b le r e g io n f o r a q i break point for aqi n sew 0 0.5 1 1.5 2 2.5 a ir q u al it y in d ex (a q i) spot ss a ss b ss c ss d _av n w e s http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):827-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 832 3.3 co and co2 emissions the emissions of co and co2 were measured in parts per million (ppm). the patterns of the emissions seem similar to each other. figures 3 and 4, show that there is increase in co and co2 emissions from the north-west to the south-east for all the service stations monitored. this could be attributed to the direction of the wind. the wind direction seems to play a role on the concentration of the co and co2 emissions in all the service stations. further analysis on whether there is disparity in the respective emissions (co and co2) as a result of difference in locations reveals that at 90% confidence, there is no significant difference as a result of change in location within all the filling stations respectively. that means monitoring one of the four filling stations in lagos metropolis is sufficient to obtain reasonable information. however, figure 4 revealed that at 95% confidence, there is significant difference in co2 emissions in service station b when compared with that of service station d as pvalue (0.04) < 0.05. the emission variability of over 50% of co2 can be accounted for by the two reference service stations -b and -d. the study showed that the threshold for co emissions is not exceeded. this suggests that long term exposure to co/co2 due to the commercial activities involving hydrocarbons may not necessarily affect or harm the attendants. figure 3: carbon monoxide emissions (ppm) from four different service stations figure 4: carbon dioxide emissions (ppm) from four different service stations 3.4 emission of formaldehyde the emission pattern of formaldehyde is presented in figure 5 for all the stations monitored. it was observed that, the northern locations of all the service stations monitored showed value lower than that of the other three locations. this might also be due to the direction of the wind. however, since pvalue exceeds 0.05, there is no discernable difference in the emission pattern at 95% confidence regarding the location change for any of the four filling stations. 0 2 4 6 8 10 c o e m is si o n ( p p m ) spot ss a ss b ss c ss d _av n w e s who out door level 250 350 450 550 650 c o 2 em is si o n ( p p m ) spot ss a ss b ss c ss d _av n w e s file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: assessment of air quality of service stations in a built-up area: a case study of lagos metropolis. azojete, 19(4):827836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 833 3.5 comparative evaluation of all the emissions table 2 shows the ground average for all the emissions within the four service station locations. the values for co, aqi, and hcoc conform to standard. the average of all the emissions per location is presented in figure 6. the results show that the emission patterns are all similar throughout the period of the investigations. for co emission, comparison of individual filling stations to that of the ground averaged emission revealed that all the emissions are close in magnitude that of the ground averaged value with only service station b slightly having lesser ground averaged emission value. however, service station a has marginal increase in the co, hcho and tvoc compared to other locations. this could be attributed to the convectional current of the wind. figure 5: formaldehyde (hcho) emissions (mg/m3) table 2: averaged value of the emissions at all the four locations emissions ground averaged value tvoc (mg/m3) 0.006 aqi 1.512 co (ppm) 2.188 co2 (ppm) 452.6 hcho (mg/m3) 0.003 0 0.001 0.002 0.003 0.004 0.005 h c h o e m is si o n ( m g /m 3 ) spot ss a ss b ss c ss d _av n w e s 0 2 4 3.25 2 2 1.5 co emissions (ppm) st at io n s ss a ss b ss d ss c 0 200 400 600 499.5 368.75 433.75 508.25 co2 emissions (ppm) st at io n s ss a ss b ss d ss c http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):827-836. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 834 figure 6: comparison of means for all the emissions and air quality index (a) co, (b) co2, (d) hcho and (d) tvoc (e) aqi 4. conclusions it is very important to acquired and analyse the prevailing air quality characteristics at various locations within lagos metropolis so that it can form and improve government legislation on the location and localization of industries within lagos sphere. every company dealing with hydrocarbons cited within the residential area is expected to follow a certain standard because of the health issues or the possible damage or long-term havoc as a result of prolonged exposure to such gaseous chemicals. the data here will certainly help the various stakeholders including the investors and the government to properly regulate the activities of these companies. the most prominent lethal emissions are assessed and monitored in service stations in lagos state, in this research at four different locations. the data obtained are subjected to analysis of variance. the following conclusions are hereby arrived at: • the aqi conform to standard in all the four filling stations. about 20% in the aqi variability in the service stations can be accounted for. co and co2 need to be watched and possibly attenuated as they are more lethal compared to others. • at 90% confidence, there is no difference in all the emissions with respect to all the four locations. therefore, difference in locations is not significantly affecting the emission patterns. it suffices that emissions data for a location away from the nozzle points are sufficient for all the other data from the other similar equi-distance locations from the reference nozzle point. • there is significant difference in ss b from ss d for co2 emissions at 95% confidence as pvalue (0.04) is less than 0.05. about 51% of co2 can be accounted for by the emission variability in the service stations. however, there is no significant difference with respect to other service stations combination (pvalue > 0.05). 0 0.002 0.004 0.006 0.00475 0.0025 0.003 0.00275 hcho emissions (mg/m3) st at io n s ss a ss b ss d ss c 0 0.01 0.02 0.03 0.025 0 0 0 tvoc emissions (mg/m3) st at io n s ss a ss b ss d ss c 0 1 2 1.5 1.5 1.3 1.75 aqi st at io n s ss a ss b ss d ss c file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: assessment of air quality of service stations in a built-up area: a case study of lagos metropolis. azojete, 19(4):827836. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 835 it is recommended that service stations in highly populated cities like lagos are expected to do routing environmental assessment, at least annually, to determine and control the unforeseeable environmental consequences that may emanate from increase in the volume of their commercial activities. governments are encouraged to legislate on this and make it a bylaw in the interest of conservation of our biodiversity. • the data thus presented will also complement the available data in the literature. reference azumaa, k., jinnob, h., tanaka-kagawa, t. and sakai, s. 2020. risk assessment concepts and approaches for indoor air chemicals in japan. international journal of hygiene and environmental health, 225: 113470. brook, rd., newby, de. and rajagopalan, s. 2017. the global threat of outdoor ambient air pollution to cardiovascular health: time for intervention. jama cardiology, 2: 353–4. city-population. 2015. metro lagos (nigeria): local government area, retrieved 16th oct., 2021. darbre, pd. 2018. overview of air pollution and endocrine disorders. international journal of. geneneral medicine, 11: 191–207. diop, s., barusseau, jp. and descamps, c. 2014. the land and ocean 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engrkachalla@unimaid.edu.ng 427 original research article evaluation of concrete strength with scarified road waste material k. mohammed1* and z. mustapha2 1department of civil and water resources engineering, university maiduguri, maiduguri, borno state, nigeria 2department of civil engineering, modibbo adama university of technology, yola, adamawa state, nigeria *corresponding author’s email address: engrkachalla@unimaid.edu.ng 1.0 introduction concrete plays a major role in any infrastructural development and aggregate is one of the basic constituents constituting about 75% of its total volume (eze et al., 2018). the high and increasing cost of these materials has greatly hindered the development of shelter and other infrastructural facilities in developing countries especially nigeria. there arises the need for engineering consideration of the use of cheaper and locally available waste materials to meet desired need, thus paving way to an overall reduction in construction cost while maintaining sustainable development goals (olutoge, 2010). several methods were employed to minimize constructional waste to ensure maximum utilization of scarce resources and curtail the ever challenging effect of constructional waste such as the scarified wearing course layer of pavement. this scarified surface contains greater percentage of the ever dwindling aggregates. aggregates utilization in concrete production stand at about one billion tons per year and this has led to several environmental challenges that included depleting securable sand deposits and an associated price increase in the material (ezeagu and agusi, 2018). the rapid extraction of sand from the river beds causes problems like erosion, lowering of the water table, sinking article information abstract the rising construction materials cost, dwindling materials availability and environmental challenges couple with the serious effect of construction waste have caused a serious concern in the construction industry. most of the time, repairs of failed road pavements result in generation of scarified road material wastes (srmw) and these are usually dumped by the roadsides thus causing environmental issues. these srmws could be useful if recycled in the production of concrete but their composition remains a question. hence, this study seeks to investigate the suitability of srmw in the production of concrete if used as fine aggregate. the fine aggregate content in nominal concrete mix was altered with srmw that ranged between 0 – 40 % at an increment of 10%. similarly, the srmw was used as an additive in normal concrete mix. the casted concrete cubes of 150 x 150 x 150mm size were tested for strength on 7, 14, 21 and 28 days periods. the experimental results showed that the use of scarified road waste material in lieu of fine aggregates in concrete mixes yielded some promising characteristics. the study revealed that it can be useful in the production of light weight concrete within an optimum range of 10% replacement. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 march, 2022 revised 8 may, 2022 accepted 10 may, 2022 keywords: constructional waste scarified pavement concrete aggregate characteristics strength http://www.azojete.com.ng/ mailto:engrkachalla@unimaid.edu.ng mailto:engrkachalla@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):427-434. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 428 of bridge piers, change in river courses leading to floods, deepening of the river beds, loss of vegetation on the bank of rivers, and so on. over the years, scientists in the construction and building industry have been conducting research on the utilization of waste products in concrete. some of the waste products that have been studied include fly ash, rice husk, saw dust, and discarded tires, plastic, glass rock, steel slugs, stone dust and ceramic (shankar and ali, 1992; sahu et al., 2003; rao and andal, 2002). while it was known that each waste product has its specific effect on properties of both fresh and hard concrete, the use of such product in producing concrete not only makes it economical but also solves some of the current waste disposal problems (reddy, 2010). nowadays, societies are facing the challenges of how best to use the wastes emanating within the environment and that includes the constructional wastes. waste recycling means continual use of the resources that have already been used (de beir et al., 2010). primarily, the effort is aimed at the maximum possible saving of raw material resources, fuels and energy demands, reduction of waste volume and environmental sustainability (cimpan, 2016). additionally, material recycling contributes to environment conservation by reducing greenhouse emission (jagannadha, 2015). consequently, the increasing volume of road deterioration in recent years has forced society to re-use the generated deteriorated waste (jagannadha, 2015). due to this, there has been a natural increase in the use of recycled material in civil engineering (leite et al., 2011). in road construction, recycled material is most often used in base construction layers and in concrete production, it can serve as a substitute for natural aggregate (wu, 2012). scarified road material waste (srmw) is a waste from a deteriorated pavement that is normally dumped by the road site to fallow or used as fill material in some cases. while it was known that this material can be used as constituent material in concrete production, its appropriate categorization in terms of strength class suitability still remains a challenge if used as substitute materials in concrete. hence, this study seeks to investigate the behavioural performance of srmw in concrete medium. 2. materials and method the materials used for this study included fine aggregate (river sand), srmw samples, coarse aggregate and ordinary portland cement and were all obtained within maiduguri, borno state, nigeria. the srmw which was obtained at a dump site near an ongoing road construction work was further crushed manually and segregated using sieve 4.75mm aperture size. subsequent retained particles on the sieve were re-crushed and sieved to yield finer materials for the concreting work that was used to replace some portion of the natural occurring sand under normal concrete mix. the aggregates in this concrete production were clean and wellgraded according to literature requirements (bs 882, 1992). the tests were conducted in accordance with the methods outlined in the bs codes. the stepwise procedures followed in conducting the tests are outlined below: i. specific gravity test was carried out in accordance with the procedure outlined in bs en 1377-2 (1990). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engrkachalla@unimaid.edu.ng mohammed and mustapha: evaluation of concrete strength with scarified road waste material. azojete, 18(3):427434. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 429 ii. particle size distribution analysis test was carried out in accordance with the procedure outlined in bs 812-103 (1985). iii. aggregate water moisture content test was conducted in accordance with the procedure outlined in bs 812-109 (1990). iv. bulk density test was carried out in accordance with the procedure outlined in bs 8122 (1975). v. slump test was carried out on the fresh concrete in accordance with the procedure outlined in bs 1881-102 (1983). furthermore, the concreting moulds were cleaned and oiled before each casting. a total of ninety (90) concrete cubes of 150mm x150mm x 150mm were produced with a nominal mix ratio of 1:3:6 and w/c ratio of 0.55. de-moulding of the cubes was done 24 h after casting. the casted cubes were then transferred into the curing tank. the cubes were removed from the curing tank at the end of the curing periods and subsequently crushed after 5 h air-drying. additionally, concrete cubes with srwm were also produces in-which the fine aggregates component replacement ranges from 10% to 50% and as 10 and 20% additives (10a and 20a). the cured samples were tested at 7, 14, 21 and 28 days for compressive strength in accordance with bs 1881-116 (1983) requirements. 3. results and discussions the specific gravity test result showed that the sand, srmw and gravel used had the value of 2.85, 2.56 and 2.66 respectively and this is in agreement with other literature findings (neville and brooks, 2002). hence, this result was satisfactory; otherwise, the concrete constituent will float over the water surface in the mix (bs 812-112, 1990). moreover, the moisture contents of sand, srmw and gavel, were found to be 4.23%, 28.58% and 1.54% respectively as shown in table 1. bulk density of aggregate (sand, srmw and gravel) for both loose and compacted samples is also shown in table 1. this indicates that the use of srwm in concrete production will require lesser amount of water despite the low bulk density in comparison with other aggregates. table 1: physical properties of aggregates property sand srmw gravel specific gravity 2.85 2.56 2.66 moisture content 4.23% 28.58% 1.54% bulk density 𝜌 (g/cm3) loose compacted loose compacted loose compacted 0.74 0.85 0.08 0.12 0.81 0.89 table 2 shows the slump for the various srwm replacement from normal up to 40% replacement. the slump value increases with increasing srwm content with about 10 mm change from 0 – 40% swrm replacement. interestingly, the slump values are within the workable range because the minima and maxima values were between 30mm to 50mm. http://www.azojete.com.ng/ mailto:engrkachalla@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):427-434. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 430 table 2: slump test for the concrete % srwm w/c ratio height of concrete before removal of mould (mm) height of concrete after removal of mould (mm) slump (mm) 0 10 20 30 40 10a 20a 0.5 0.5 0.5 0.5 0.5 0.5 0.5 300 300 300 300 300 300 300 270 265 262 260 257 256 250 30 35 38 40 43 44 50 the result of the sieve analysis (particle size distribution curve) for of sand, srmw and coarse aggregate respectively are presented in figures 1, 2 and 3 respectively. the curves indicated that the srmw sample is well-graded fine aggregate, and this is in accordance with aashto (1995) classification of soil system which describes fine aggregate as material that passes a 0.075 (no 200) sieve and coarse aggregate as materials pass 75mm sieve and are retained on 20mm. figure 1: particlesize distribution curve for the sand 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 0.0001 0.001 0.01 0.1 1 10 100 p er ce n ta g e p as si n g particle size in mm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engrkachalla@unimaid.edu.ng mohammed and mustapha: evaluation of concrete strength with scarified road waste material. azojete, 18(3):427434. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 431 figure 2: particle-size distribution curve of the srmw figure 3: particle-size distribution curve of the coarse aggregate table 3 presents the concrete compressive strength for the respective range between 7 – 28 days period. the effect of replacement of fine aggregate with srmw on concrete compressive strengths is shown with figure 4. it can be observed that the compressive strength of the concrete decreased with increasing srmw content because the maximum target mean strength at 28 days was 24.17 mpa and the minimum value of 6.6 mpa at 40% swrm. however, despite the decreasing strength, addition of 10% (10a) admixture had the potential to increase the concrete strength even at the 10% swrm. the investigation revealed that replacing fine aggregates beyond 10% is not advisable because of the decreasing strength behaviour with further addition of swrm. on the alternative, the use of swrm will be effective under low strength concrete, 10.4 mpa which can further be increased to 11.4 mpa 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 0.0001 0.001 0.01 0.1 1 10 100 p er ce n ta g e p as si in g particle size in mm 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 0.0001 0.001 0.01 0.1 1 10 100 p er ce n ta g e p as si n g particle size in mm http://www.azojete.com.ng/ mailto:engrkachalla@unimaid.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):427-434. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 432 with additional additives at 28 days. this type of concrete is equivalent to grade 7 concrete that has a value of 7n/mm2 specified for plain concrete as recommended in bs-8110-1 (1997). table 3: compressive strength (mpa) of concrete at varying percentages of srmw in concrete figure 4: characteristics strengths behaviour 4. conclusions to address problem of constructional waste and optimum utilization of the scarce resources especially fine aggregates in the production of concrete, this study found that the use of scarified road waste material in lieu of fine aggregate yielded some prominent results that included the addition of 10% (10a) admixture had the potential to increase the concrete strength at the maximum 10% swrm value. this waste material use can be in an optimum value of 10% and is generally suitable for light weight concrete. references aashto provisional standards. 1995. american association of state highway and transportation officials, washington d. c. 0 5 10 15 20 25 30 7 days 14 days 21 days 28 days c o m p re ss iv e s tr e n gt h ( m p a) curing period (days) 0 10 20 30 40 10 adm 20 adm s/no. srwm content (%) concrete strength (n/mm2) 7 days 14 days 21 days 28 days 1. 0 14.5 18.2 22.48 24.17 2. 10 6.2 6.7 8.9 10.4 3. 20 6.4 7.0 7.2 8.5 4. 30 5.0 6.5 6.7 6.8 5. 40 5.5 5.7 6.2 6.6 6. 10 admixture 7.1 8.2 10.2 11.4 7. 20 admixture 6.8 8.3 9.0 9.6 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engrkachalla@unimaid.edu.ng mohammed and mustapha: evaluation of concrete strength with scarified road waste material. azojete, 18(3):427434. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 433 bs-en 1377-2. 1990. methods of test for soils for civil engineering purposes. london: british standard institution. bs 812-2. 1975. testing aggregates methods for determination of physical properties. bs-812-103-1.1985. sieve tests. methods for determination of particle size distribution. london: british standard institution. bs-812-109. 1990. testing concrete. methods for determination of moisture content. british standard institution. london, uk bs-812-112. 1990. testing aggregates. methods for determination of aggregate impact value (aiv). british standard institution. london, uk bs-882. 1992. specifications of aggregates for natural sources for concrete. british standard institution. london, uk bs-1881-102. 1983. testing concrete. method for determination of slump. british standard institution london, uk. bs 1881-116. 1983. method for determination of compressive strength of concrete cubes, british standard institution. london, uk bs-8110-1. 1997. the structural use of concrete. london: british standard institution. london, uk cimpan, c., maul, a., wenzel, h. and pretz, t. 2016. techno-economic assessment of central sorting at material recovery facilities – the case of lightweight packaging waste. journal of cleaner production, 112(5): 4387–4397 https://doi.org/10.1016/j.jclepro.2015.09.011 de beir, j., fodha, m. and magris, f. 2010: life cycle of products and cycles. macroeconomic dynamics, 14(3): 212–230. ezeagu, ca. and agusi, ms. 2018. effects of the total and partial replacement of sharp sand with quarry dust on concrete. journal of advance research in construction and urban architecture, 3: 1-6. eze, oo., aguwa, ji. and auta, sm. 2018. effects of partial replacement of river sand with stone dust in concrete production. 1st international civil engineering conference (icec), department of civil engineering, federal university of technology, minna. nigeria. 7th – 9 th november 2018, pp 284 -293. jagannadha, rk. 2015. suitability of recycled aggregate in fibre reinforced high strength concrete for sustainability. journal of structural engineering, 42: 264–272. leite, fdc., motta, rds., vasconcelos, kl. and bernucci, l. 2011. laboratory evaluation of recycled construction and demolition waste for pavements. construction and building materials, 25(6): 2972–2979. https://doi.org/10.1016/j.conbuildmat.2010.11.105 neville, am. and brooks, jj. 2010. concrete technology, longman publisher, singapore, pp. 2185. http://www.azojete.com.ng/ mailto:engrkachalla@unimaid.edu.ng https://doi.org/10.1016/j.jclepro.2015.09.011 https://doi.org/10.1016/j.conbuildmat.2010.11.105 arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):427-434. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engrkachalla@unimaid.edu.ng 434 olutoge, fa. 2010. investigations on sawdust and palm kernel shells as aggregate replacement. journal of engineering and applied sciences, 5(4): 7-13. rao, gt. and andal, t. 1996. a study of behavior of concrete with stone sand replacing river sand. national conference on alternate construction materials in civil engineering. harmipur, india., pp. 196-201. reddy, mv. 2010. investigations on stone dust and ceramic scrap as aggregate replacement. international journal of civil and structural engineering, 1(3): 661666. sahu, ak., kumar, s. and sachin, ak. 2003. crushed stone waste as fine aggregate for concrete. the indian concrete journal, 77(1): 845-861. shankar, nb. and ali, md. 1992. engineering properties of rock flour. proceedings of the national conference on cement and building materials from industrial waste. may 7-9 1992, hyderabad, india., pp. 167-192. wu, m., wen, h., balasingam, m. and manahiloh, k. 2012. influence of recycled asphalt pavement content on air void distribution, permeability, and modulus of base layer. transportation research record, 2267(1): 65–71. https://doi.org/10.3141/2267-08 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engrkachalla@unimaid.edu.ng https://doi.org/10.3141/2267-08 arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):267-280 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 267 original research article modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool a. e. ikpe1 and i. b. owunna2 1department of mechanical engineering, akwa ibom state polytechnic, ikot osurua, ikot ekpene, nigeria, p.m.b. 1200 2department of mechanical engineering, university of benin, benin city, nigeria, p.m.b. 1154. *corresponding author’s email address: aniekan.ikpe@eng.uniben.edu 1.0 introduction internal combustion (ic) engines consist of various types which may include; two stroke, four stroke and six stroke engine. four stroke petrol engine finds its application in mechanical components such as cars, airplanes, motorcycles etc. (akpobi and oboh, 2007). in four stroke ic engines, reciprocating motion of the piston is converted into rotary motion of the crankshaft via a connecting rod (georgiev, 2011). the combustion of air-fuel mixture in internal combustion engine occurs in the combustion chamber of the engine where mechanical work is achieved (ikpe et al., 2016a; ikpe et al., 2016b). the heat generated in the process reacts with the mixture inside the cylinder to form a hot in-cylinder pressurize gases that cause reciprocating movement of the piston to be translated into rotating motion of the crankshaft (soda, 2013; ikpe and owunna, 2020). the working principles of four stroke ic engine mostly occur in four stages namely: 1st article information abstract the trends in internal combustion engine (ice) cycle is gradually changing due to the quest for optimum performance, efficiency and zero emission level which are often achieved through a series of experimental procedures. to reduce the huge experimental cost, time and resources, matlab 2018b was employed in the modelling and simulation process of a four stroke internal combustion renault engine (mercedes-benz 250se) w108 model. the displaced volume was 4.65x10-4 mm3 (4.65x10-7 cm3) while the minimum volume occupied by the charge was 0.5x10-4 mm3 (5x10-8). moreover, the maximum velocity occurred at a crank angle of 72º, having a value of 19.65 m/s while the minimum velocity occurred at a crank angle of 288º with a value of -19.65 m/s. however, maximum cylinder pressure of 28 bar was observed at crank angle of 20º, followed by gradual decline up to 0.2 bar at subsequent crank angles of 100, 200, 300º. the results showed that maximum peak pressure between simulated data and experimental data were 5347 and 5320 kpa, while maximum spark pressure in cylinder before combustion between simulated data and experimental data were 1849 and 1730 kpa. in addition, highest crank angle at maximum pressure for simulated and experimental data were 30 and 22º. it has been established that developing mathematical models to simulate ic engine operation cycles can help offset the cost, time and resources required for experimental set up, testing and data acquisition from the engine. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 11 october, 2021 revised 7 march, 2022 accepted 16 march, 2022 keywords: modelling ic engine four stroke internal combustion performance simulation http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 268 stroke (suction stroke), 2nd stroke (compression stroke), 3rd stroke (power stroke) and 4th stroke (exhaust stroke). during the first stroke, the inlet valve opens due to cranking and pure air is drawn into the cylinder through the inlet valve and piston moves from top dead center (tdc) to bottom dead center (bdc) while the exhaust valve is closed. for the second stroke, the piston moves from bottom dead center (bdc) to top dead center (tdc). at this stage, both the inlet and exhaust valves are closed and the air drawn into the cylinder during suction stroke is compressed as the piston ascends. the compression ratio which varies from 14:1-22:1 occurs under high temperature and pressure ranging from 30-45kg/cm2 and 650-800oc. as the ascending piston approaches the end of the tdc, liquid hydrocarbon fuel is sprayed into the combustion chamber which ignites and combusts with the compressed air. both valves remain closed and the piston moves from tdc to bdc in the 3rd stroke, as the hot product of combustion consisting mainly of carbon ii oxide and nitrogen in the compressed air expands and forces the piston downward (palanivendhan et al., 2016). this causes the cylinder pressure to fall from its maximum (47-55 kg/cm2) to minimum (about 3.5-5 kg/cm2) near towards the end of the stroke. during this stroke, power is gained by the engine for mechanical work. in the 4th stroke, the exhaust valve opens while the piston travels upwards and the exhaust gases are swept out via the open valve by the piston traveling upward the cylinder. several studies have been carried out by different researchers in recent times to investigate the performance of ic engines in different areas of application. partel and rathod (2013) studied the performance of high-speed supercharger in four stroke internal combustion engine and found that, 30-35% increase in brake mean effective pressure (bmep) is achievable with supercharged engines compared to naturally aspirated engines. it was also found that the engine power increases with increase in supercharge pressure. davis et al. (2015) experimentally investigated the performance parameters (break specific fuel consumption (bsfc), total fuel consumption (tfc), break thermal efficiency and mechanical efficiency of a single cylinder four stroke spark ignition engine by preheating the intake air using a thermocouple module. while the mechanical efficiency was observed to increase from 17.7920.12% at part load condition, the bsfc and tfc were found to decrease with preheated air from 0.981-0.877 kg/kwhr at full load and from 0.430-0.380 kg/hr at full load condition, indicating a reduction in fuel consumption. karabulut and ersoy (2012) investigated the vibration aspect of a two-cylinder four-stroke internal combustion engine and found the flywheel moment of inertia as the major component to be minimized in order to reduce the angular speed fluctuation of the crankshaft. the in-cylinder gas pressure and the piston mass were also found to be the major factors responsible for the rotational and translational vibration of the engine. the findings also revealed that the vertical vibrations of the engine could be minimized by means of subjecting the crankshaft to counter weight. islam et al. (2016) employed k-e turbulent model in ansys fluent software in modelling and simulating spark ignition premixed combustion via variations in pressure, temperature, velocity file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu ikpe and owunna: modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool. azojete, 18(2):267-280. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 269 and swirl ratio in four stroke single cylinder. at 1500 rpm crank angle rotational speed using gasoline as fuel, the maximum pressure after compression of air-fuel mixture was 1.3 mpa. the maximum temperature as a result of expansion was 710 k while approximately 490 w brake power was achieved. iliev and hadjiev (2012) investigated the effects of engine speed on the performance of fourstroke direct injection gasoline engine using computational fluid dynamics (cfds). the results showed highest cylinder pressure of 57.76 bars at engine speed of 3000 rpm and lowest cylinder pressure of 45.1 bars at engine speed of 1000 rpm. in addition, highest pumping mean effective pressure (mep) of 0.0357 bar at 1000 rpm engine speed and minimum of 1.7497 bar at 6000 rpm where obtained. however, highest brake power of 63.76 kw at 4500 rpm and indicator power of 77.09 kw at 4500 rpm speed were obtained for the four-stroke port injection gasoline engine modelling. the working principles of internal combustion engine over the years have improved significantly due to several reforms and developments incorporated by experts in automotive industries. however, automobile industries are continuously driven by the cravings for effective performance, better fuel efficiency and less emissions (ikpe et al., 2021), which are mostly determined by experimental methods. although numerical methods are also employed to determine the performance of an ic engine as stated in the aforementioned literature, it is possible that validating the numerical with experimental results could yield more accurate and useful data for further studies in this area. hence, matlab (matrix laboratory) software which is a numerical modelling tool, was employed in modelling the performance characteristics of four stroke internal combustion renault engine cycle. it is a programming tool that is designed for easy, simple as well as complex calculation and analysis, and its versatility in solving numerically related problems cuts across several field of studies. 2. materials and methods the experimental data was collected from a renault production engine (mercedes-benz 250se) w108 model at different engine speeds and inlet pressures. the data includes pspark, ppeak and θpeak pressure. the geometric parameters of the engine were entered into matlab 2018b software to predict the pressure and other performance characteristics of the engine. the geometric data of the engine according to (ayub et al., 2015) are presented in table 1. the angle of spark firing and burning duration angle were not explicitly known but their approximate values were obtained from the investigation by kuo (1996) who also used this experimental data for comparison. table 1: geometric parameters of mercedes-benz 250se renault engine number of cylinders 6 number of valves per cylinder 2 displacement (cc) 2500 bore x stroke (mm) 82 x 78.8 compression ratio 9.8:1 ratio of connecting rod length to crank radius 3.2 http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 270 intake valve open before tdc (degree) 11o intake valve close after bdc (degree) 53o maximum valve lift (mm) 8 inlet valve diameter (mm) 41.2 matlab software was used for modeling and simulation of the four (4) stroke ic engine model. matlab codes were written to provide access to matrix and data structures provided by the linpack (linear system package) and eispack (eigen system package) projects. matlab is a high-performance language which is capable of performing technical computing. it combines visualization, computation and programming environment. the matlab software provides a modern programming language environment as well as complex data structures containing inbuilt editing and debugging tools. matlab software also support oop (object oriented programming). the simulation of the ic engine model was done with matlab 2018b software. the model is a four stroke internal combustion engine with an in-line configuration. the engine is naturally aspirated with 6 cylinders, and uses petrol as fuel. the engine features a single overhead camshaft, 2 valves per cylinder. data employed for the simulation is presented in table 2, and was obtained from a technical report on renault production engine (mercedes-benz 250se) w108 model (ayub et al., 2015). table 2: data employed for the simulation parameters value intake manifold pressure (kpa) 101325 specific heat ratio 1.4 cylinder temperature during intake(k) 300 engine speed(rpm) 3000 range of θs -30o to +30o with respect to tdc range of θb 30o to 120o heating value of gasoline 44000kj/kg air to fuel ratio 14.6/1 2.1. matlab codes for the ic engine modelling the codes used in the experiment were generated by considering the processes that makes up the full engine. for a four stroke engine, four processes were involved; namely: intake stroke, compression stroke, power stroke and exhaust stroke. developing mathematical models to simulate the ic engine helped in testing certain parameters of the engine rather than performing an experimental set up to see the effects of such parameters on the engine. the mathematical model does not give accurate or perfect results but is helpful in speeding up the engine development process before producing a real prototype. the ic engine modelling and simulation in this study was divided into two categories namely: the first was fluid-dynamic based model and the second was a thermodynamic-based model. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu ikpe and owunna: modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool. azojete, 18(2):267-280. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 271 fluid-dynamic based model which is also called the multidimensional model because its formation is primarily due to the conservation of mass and the state variables of the engine at certain locations in the engine. that is, these variables are independent of time (time independent variables) and are tied to space variables, of which the governing equations are more or less ordinary differential equations or partial differential equations. the thermodynamic-based models are function of time or crank angle and this model is based on the laws of thermodynamics. in these models, the first law of thermodynamics was applied to the cylinder and the charge in it. the system is treated as an open system during the intake and the exhaust stroke while the compression and power stroke was treated as a close system. the thermodynamic model used in this case was zero-dimensional because it only depends on time or crank angle. the resulting equations from this model are ordinary differential equations instead of partial differential equations. in the engine models developed in this study, the combustion model was simulated according to weibe’s function. however, the geometry and flame propagation were not considered. 2.2 modelling of the ic engine strokes the intake stroke of the four stroke engine is modelled as a one dimensional isentropic flow through a restriction, the restriction being the poppet valve of the engine. the equation governing this process is given by equation 1. 𝑑𝑚 𝑑𝜃 = 𝐶𝐷𝐴𝑅𝑃𝑂 6𝑁(𝑅𝑇𝑂)0.5 ( 𝑃𝑇 𝑃𝑂 ) 1 𝑘 { 2𝑘 𝑘−1 (1 − ( 𝑃𝑇 𝑃𝑂 ) 𝑘 𝑘−1 )} 0.5 (1) where, 𝐴𝑅 is the reference area given by equation 2, 𝑃𝑇 is the cylinder pressure, 𝐿𝑣 is the valve lift, 𝐶𝐷 is the discharge coefficient, 𝑃𝑂 and 𝑇𝑂 are the intake manifold pressure and temperature respectively. 𝐴𝑅 = 𝜋𝐷𝑣𝐿𝑣 (2) the above differential equation was then solved using the inbuilt matlab differential equation solver, which is the code45 that solves differential equation based of the runge kutta fourth order differential equation. after solving the equation, the pressure for the intake model was computed using the equation 3. 𝑃𝑖𝑛𝑡𝑎𝑘𝑒 = 𝑚𝑅𝑇 𝑣 + (𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑢𝑒 𝑡𝑜 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 𝑣𝑜𝑙𝑢𝑚𝑒) (3) the mass, m is gotten by solving the differential equation above while t is the cylinder temperature and v being the volume at various crank angle. the flow chart for the intake model is presented in figure 1. http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 272 figure 1: flow chart for the intake process the drag coefficient is given by the correlation in equation 4, the valve lift is given by equation 5 while the crank angle is given by equation 6. 𝐶𝐷 = 107.78 ( 𝐿𝑣 𝐷𝑣 ) 4 − 77.204 ( 𝐿𝑣 𝐷𝑣 ) 3 + 14.1 ( 𝐿𝑣 𝐷𝑣 ) 2 − 1.01 ( 𝐿𝑣 𝐷𝑣 ) 1 + 0.6687 (4) 𝐿𝑣 = 𝐿𝑣𝑚𝑎𝑥(1+𝑐𝑜𝑠(∅)) 2 (5) ∅ = 𝜋(𝐼𝑉𝑂−𝐼𝑉𝐶+2𝜃+540) 𝐼𝑉𝑂−𝐼𝑉𝐶+180 (6) where: 𝐿𝑉 is the valve lift function, 𝐿𝑣𝑚𝑎𝑥 is the maximum valve lift, 𝜃 is the crank angle, ivo is the inlet valve open angle before top dead center, ivc is the inlet valve close angle after bottom dead center. for our work, it was assumed that the intake starts at 0o and end at 180o. 2.3. modelling the compression and the expansion process the compression and expansion process was modelled according to equation 7. 𝑑𝑝 𝑑𝜃 = −𝑘 𝑝 𝑣 𝑑𝑣 𝑑𝜃 + (𝑘 − 1) 𝑄𝑇 𝑣 𝑑𝑥 𝑑𝜃 − 𝑘 𝑐 𝑤 (7) this differential equation is solved to yield the pressure as a function of crank angle, where 𝑄𝑇 is the heat supplied from the combusted fuel, c is the blow-by constant, w is angular velocity. the temperature for this process can also be calculated using equation 8. 𝑑𝑇 𝑑𝑄 = 𝑇(𝑘 − 1) [( 1 𝑝𝑣 ) ( 𝑑𝑄 𝑑𝜃 ) − ( 1 𝑣 ) ( 𝑑𝑣 𝑑𝜃 )] (8) this differential equation is solved to yield the temperature as a function of crank angle. the exhaust process was simply modelled as a constant pressure process. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu ikpe and owunna: modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool. azojete, 18(2):267-280. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 273 3. results and discussion experimental and simulated results obtained from the four stroke ic engine are presented in this section. table 3 shows the experimental results obtained from the four stroke renault engine. similarly, the results obtained from running the code in matlab environment for the four stroke engine are presented in figures 2-10. table 3: experimental result obtained from four strokes renault engine cases n(rpm) pinlet spark advance θs burn duration θb ppeak θpeakpressure pspark 1. 2000 63.7 -18 71 3050 16 atdc 890 2. 2000 102.2 -10 65 3780 22 atdc 1730 3. 4000 45 -27 75 2720 11 atdc 546 4. 4000 100.2 -23 78 5320 20 atdc 1420 figure 2 shows the plot of volume occupied by the charge in the cylinder vs the crank angle. the results clearly show that the plot follows a sinusoidal path, having a maximum volume at 180o or (180 + 360n) where n can be 0, 1, 2... and minimum value at 0o or (360n) where n can be 0, 1, 2, 3… the maximum volume occupied by the charge is also known as the displacement volume. interestingly, the displaced volume is 4.65x10-4 mm3 (4.65x10-7 cm3) while the minimum volume occupied by the charge is 0.5x10-4 mm3 (5x10-8). this volume is also known as the clearance volume which indicates the volume remaining above the piston of an ic engine when it reaches top dead center (tdc). the variation in volume of the charge also allows for variation in the density of the charge. with the minimum density occurring at the bdc and the maximum density occurring at the tdc during the compression stroke. the change in the density of the charge is part of what causes the pressure to rise during the compression stroke. as the piston moves upward to compress the charge, it squeezes the charge to occupy a small space which invariably increases the density which in turn increases pressure and temperature (owunna and ikpe, 2021). the density of the charge should be carefully monitored so that auto ignition temperature will not be reached during compression of the charge to clearance volume. the auto ignition temperature of the charge (fuel-air mixture) varies from 520k to 553k. figure 2: plot of volume occupied by charge in cylinder against crank angle http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 274 figure 3 shows the piston velocity vs crank angle for a rotating speed of 4000 rpm of the crank shaft. it can be observed that the maximum positive velocity occurs at a crank angle of 72o or corresponding crank angle (72 + 360n). moreover, the maximum negative velocity occurs at a position of 288o or corresponding crank angle (288 + 360n). the position of zero velocity occurs at turning points of crank angle 0o or multiples of 180o. careful observation shows that from bdc, the piston accelerates from the bottom of the cylinder upwards till it reaches a maximum velocity of 19.65 m/s at a position of 72o. still moving upwards, the piston now decelerates from 19.65 m/s to zero velocity at 180o, which is the bdc of the engine. the same process is repeated as the piston travels upward the cylinder (from the bdc to the tdc). air-fuel charge is introduced into the cylinder as the piston travels from tdc to bdc. as a result of the piston movement from tdc to bdc, the in-cylinder pressure is reduced to a value in the range of atmospheric pressure (760 mm hg) (eastop and mcconkey, 1993). as the piston approaches the bottom of the cylinder, air is channeled through the carburettor, of which a metered amount of fuel is added to the air. the inlet valve closes at this point, but this only occur when the piston has traveled midway along the return stroke. the higher the piston velocity, the higher the output power delivered by the piston. furthermore, the higher the stroke ratio, the lower the piston velocity and the lower the stroke ratio, the higher the piston velocity at the same crankshaft speed figure 3: plots of piston velocity against crank angle figure 4 shows the plot of pressure of the charge against crank angle. this plot vital in ic engine application as it helps auto mechanics to know the pressure distribution in the cylinder, position of maximum pressure. considering different piston crank angles, mahmound and ahmed (2017) in similar study plotted an ic engine cylinder pressure against crank angle, and the plot maintained almost the same trend as that obtained in this study. this implies that at crank angle of 0 degree, the piston traveled from bdc to tdc where it attended a peak pressure of 29 bar. in this case, the air-fuel mixture available when the piston is at the bottom of the cylinder is compressed as file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu ikpe and owunna: modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool. azojete, 18(2):267-280. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 275 the piston travels upward towards tdc. in addition, figure 4 indicates that engine pressure reduces as the crank angle increases. this implies that at increasing crank angles, available space in the cylinder decreases, and the amount of air-fuel mixture compressed by the engine is proportional to the available space. figure 4: plot of cylinder pressure against crank angle figure 5 represent the plot of pressure against volume occupied by the charge. the pressure volume diagram shows each of the process, here, the straight line at the base represent the exhaust process. this is because during the modelling, assumption was made that the exhaust phase is a constant pressure process. the area enclosed by the pressure volume diagram represent the work output delivered by the engine during one complete thermodynamic cycle. figure 5: plot of cylinder pressure against pressure volume figure 6 shows the cumulative work against the crank angle. this is crucial as it helps determine how much work is spent on compressing the charge, how much work is produced by the expansion process and the useful work made available to the crankshaft. with this, careful optimization can be done in order to optimize the useful power and reduce the power consumed in compressing the charge. the broken line plot represents the amount of heat loss to the environment. it can be seen that significant heat loss commenced during temperature rise and a jump in the heat loss occurred immediately the combustion process started occurring. the heat loss to the environment is one of the major inefficiencies in internal combustion engines. http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 276 figure 6: plot of cumulative work and heat loss against crank angle figure 7 shows the experimental and simulated cylinder gas peak pressure. it was observed that the cylinder pressure increased as the combustion of in-cylinder air-fuel mixture occurred. this correlate with the findings of challen and baranescu (2003). on the other hand, in-cylinder pressure changes with crank angle due to cylinder volume change, heat transfer to chamber walls, flow in and out of crevice regions and leakages (semin et al., 2010). the cylinder gas peak pressure occurred inside the cylinder and were computed during combustion in four crank angles cases of 10o, 20o, 30o, and 40o. the results indicates that maximum peak cylinder gas pressured occurred at the lowest crank angle degree and vice versa. therefore, maximum experimental peak cylinder gas pressured of 5320 kpa and maximum simulated peak cylinder gas pressured of 5347 kpa occurred at the lowest crank angle of 10o. this agrees with the findings of kuo (1996) who studied cylinder pressure in a spark-ignition engine. figure 7: peak pressure between simulated data and experimental data crank angle = 30o crank angle = 20o crank angle = 40o crank angle = 10o experimental data 3050 3780 2720 5320 simulated data 3287 4745 2734 5347 3050 3780 2720 5320 3287 4745 2734 5347 0 1000 2000 3000 4000 5000 6000 cylind er gas peak press ure (kpa) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu ikpe and owunna: modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool. azojete, 18(2):267-280. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 277 figure 8 presents the experimental and simulated cylinder spark pressure results. spark plug is connected to high voltage generated by coil or magneto. as current flows from the coil, voltage is developed between the central and outside electrodes. initially, current cannot flow because the air-fuel mix gases in the plug gab serves as an insulator. as soon as the voltage exceeds the dielectric strength of the gases, the gases becomes ionized. the ionize gas becomes a conductor and allows current to flow across the gab. the resultant heat and pressure force the gases to react and produce fire ball in the spark gab as the gases burn on their own. therefore, maximum experimental cylinder spark pressure of 1730 kpa and maximum simulated cylinder spark pressure of 1849 kpa occurring at maximum spark voltage of 18000 v is required for proper engine firing. this indicated that spark pressure increased as the spark voltage also increased. hence, the supply of higher results in a hotter and longer spark duration. figure 8: spark pressure in cylinder before combustion for simulated and experimental data figure 9 shows a comparison of experimental and simulated results for heat flow rate to cylinder liner at different crank angles. crank angle is the measure of the position of an engine’s crankshaft in relation to the piston as it travels along the cylinder walls. it is observed that heat flow rate to cylinder walls is maximum in the combustion stroke at crank angle between 0-180o with a maximum value of 250 w for the simulated result and 160 w for the experimental result. this is more likely the stroke and crank angle where the cylinder accommodates the highest heat rate as a result of air-fuel mixture combustion. the combustion stroke (also known as power or expansion stroke) is the third phase in ic engine cycle where the ignited air-fuel mixture expands and pushes the piston downwards. the force created by this expansion is responsible for the engine’s power (ikpe and owunna, 2021). after combustion stroke, the heat flow rate to cylinder walls reduced from a maximum value of 250-160 w for simulated and experimental result. also, the heat flow rate to cylinder walls reduced from a maximum value of 160-155 w for simulated and experimental result at crank angle between 180-360o in the exhaust stroke. the result showed that heat flow rate from the combustion chamber is higher in the combustion stroke than the exhaust stroke. this is because the hot gasses exiting the combustion chamber is extremely hot (600-1000oc), but gradually cools as it passes through the exhaust stroke or when exposed to atmospheric air. spark voltage = 14000 v spark voltage = 18000 v spark voltage = 12000 v spark voltage = 16000 v experimental data 890 1730 546 1420 simulated data 917 1849 490.4 1384 890 1730 546 1420 917 1849 490.4 1384 0 200 400 600 800 1000 1200 1400 1600 1800 2000 sp ar k p re ss u re (k p a) experimental data simulated data http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 278 figure 9: heat flow rate to cylinder liner at different crank angles figure 10 shows the average percentage error between the simulated and experimental data. accuracy of the matlab model is optimum, as the average percentage error for peak pressure and spark pressure is well below 10%. the angle of crank where peak pressure occurs showed a significant difference with percentage error of about 34.3%. discrepancy between results from the matlab model and the experimental finding is as a result of the assumptions that were made. in this case, the effect of valve lift, ram effect, and exhaust valve timing were neglected in the model. heat transfer from cylinder walls and the chemical kinetics of combustion reactions were not computed in the model. figure 10: average percentage error between the simulated and experimental data 4. conclusion in this study, the performance characteristics of a four stroke internal combustion renault engine cycle was successfully modeled using 2018b matlab simulation tool. the codes were written where simulations were run for one cycle of the engine using matlab. the model can be seen as accurate because, the average percentage error for the peak pressure (8.6%) and the spark pressure (5.57%) were below 10%. the angle of crank where peak pressure occurred indicates compression stroke combustion stroke intake stroke exhaust stroke experimental data crank angle = -180-0o crank angle = 0-180o crank angle = 360-540o crank angle = 180-360o simulated data crank angle = -180-0o crank angle = 0-180o crank angle = 360-540o crank angle = 180-360o 120 160 60 155 200 250 150 160 -50 0 50 100 150 200 250 300 he at flo w rat e to cyl ind er lin er .6 8 5. 3 4.2 0 5 10 15 20 25 30 35 40 peak pressure spark pressure angle of max pressure a ve ra ge p er ce n ta ge e rr o r (% ) peak pressure spark pressure angle of max pressure 57 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu ikpe and owunna: modelling the performance characteristics of four stroke internal combustion renault engine cycle using matlab simulation tool. azojete, 18(2):267-280. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 279 considerable difference from the result, with percentage error of about 34.2%. discrepancy between the simulated and experimental result may be due to cylinder pressure measurement. references akpobi, ja. and oboh, p. 2007. internal combustion engine: a computerized design approach. advanced material research, 18-19: 423-433. ayub, a., ayub, o. and khan, sa. 2015. mathematical modeling of in-cylinder process in a four stroke spark ignition engine using matlab. muhammad ali jinnah university, islamabad. challen, b. and baranescu, r. 2003. diesel engine reference book, second edition. elsevier, oxford, uk. davis, v., shafee, sm. and baskar, p. 2015. performance analysis of four stroke si engine with preheated intake air. international journal of chemical science, 13(3): 1277-1284. eastop, t.d and mcconkey, a 1993. applied thermodynamics for engineering technologies. fifth edition, pearson education limited. georgiev, rp. 2011 design of four-cylinder internal combustion engine. public university of navarra, project and engineering department, pamplona, spain. iliev, s. and hadjiev, k. 2012. analysis of engine speed effect on the four-stroke gdi engine performance. proceedings in manufacturing systems, 7(4): 229-234. ikpe ae., owunna, i., ebunilo, po. and ikpe, e. (2016a) material selection for high pressure (hp) compressor blade of an aircraft engine. international journal of advanced materials research, 2(4): 59-65. ikpe ae., owunna, i., ebunilo, po. and ikpe, e. 2016b. material selection for high pressure (hp) turbine blade of conventional turbojet engines. american journal of mechanical and industrial engineering, 1(1): 1-9. ikpe, ae and owunna, ib. 2020. a 3d modelling of the in-cylinder combustion dynamics of two stroke internal combustion engine in its service condition. nigerian journal of technology, 39(1): 161-172. ikpe, ae., owunna, ib. and john, po. 2021 port flow simulation and in-cylinder swirl motion characteristic effects in internal combustion engine duty cycle. applications of modelling and simulation, 5: 102-114. ikpe ae and owunna ib. 2021 simulation of mass and pressure dynamics of in-cylinder charges at variable valve lift clearance in four stroke spark ignition engine. advances in engineering design technology, 3: 115-131. islam, a., sohail, mu., ali, sm., hassan, a. and kalvin, r. 2016 simulation of four stroke internal combustion engine. international journal of scientific and engineering research, 7(2): 1212-1219. http://www.azojete.com.ng/ mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):267-280. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aniekan.ikpe@eng.uniben.edu 280 karabulut, h. and ersoy, h. 2012. dynamic behavior of a two-cylinder four-stroke internal combustion engine. gazi university journal of science, 25(2): 519-532. kuo, ps. 1996. cylinder pressure in a spark-ignition engine: a computational model. journal of undergraduate science, 3: 141-145. mahmound, am. and ahmed, ya. 2017. investigation of spark plug ignition engine mathematical model using matlab (gui). advances in natural and applied sciences, 11(11): 36-50. owunna, ib. and ikpe, ae. 2021. comparative analysis of four stroke and six stroke internal combustion renault engine efficiency using matlab simulation tool. nigerian journal of engineering, 28(3): 62-69. palanivendhan, m., modi, h. and bansal, g. 2016. five stroke internal combustion engine. international journal of control theory and applications, 9(13): 5855-5862. partel, p. and rathod, pp. 2013. performance analysis of four stroke internal combustion engine with supercharger-review study. international journal of emerging technology and advanced engineering, 3(2): 162-169. semin, o., ismail, ar. and nugroho, tf. 2010. experimental and computational of engine cylinder pressure investigation on the port injection dedicated cng engine development. journal of applied sciences, 10(2): 107-115. soda, m. 2013. numerical investigation of internal combustion engine related flow. kth mechanics, se-100 44 stockholm, royal institute of technology, sweden file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:aniekan.ikpe@eng.uniben.edu arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):235-246 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 235 original research article evaluation of the impacts of boko haram activities on the patronage of yankari game reserve, bauchi state, nigeria c. ukah*, t. f. adeniyi and c. u. okonkwo department of environmental management, nnamdi azikiwe university, awka, anambra state, nigeria. *corresponding author’s email address: nomsostainless@gmail.com 1.0 introduction tourism sector has a great potential to distribute wealth and promotes regional development, creates a high multiplier effect and generates varying consumption of goods and services. globally, tourism plays an essential role in the growth and economic expansion of any country. tourism helps in the generation of foreign exchange and serves as source of income to local people who reside within the tourism environs. tourism is one of the largest sectors in the world. it is also one of the first to be affected by terrorist attacks (caroline, 2015). tourism is a multifaceted activity that encourages the movement of people to reside in destinations outside their usual place of habitation. according to cook (2011), tourism is a brief movement of people to target areas outside their usual places of works and abode; the activities carried out, during their stay in the place of destinations and facilities therein takes care of their needs. as a result, the whole tourism industry entails the act of traveling, staying in the hotel, transiting and provision of security, warmth and general peaceful environment. curiously, while tourism is cited as one of the world’s largest industry (world travel and tourism council, 2016), it could be one of the most fragile industry that is highly vulnerable to the repercussions of the ongoing terrorist threat. terrorism has been a topic of concern in global politics and peace. terrorism is the illegal form of hostility conducted to accumulate ransom, bring down a government, obtain the release of the hostages, ensure the total breakdown of article information abstract this study examined the temporal pattern of tourists’ patronage at yankari game reserve before and after the emergence of boko haram between 2000 and 2019. data for this study were obtained from both primary and secondary sources. the primary data were gotten through the administration of structured questionnaire. the result indicated that 90.0% of the tourists alleged that bombings and suicide attack carried out respectively by the boko haram sect made them not to visit the reserve in about five years. in addition, 72.5.0% affirmed that stories and news feeds of massacre orchestrated by boko haram have reduced their rate of patronage of the tourist site. t-test was employed to test the hypothesis. findings revealed that there is a significant difference (t = 6.010, p<0.05) in the temporal pattern of tourist patronage before and after the emergence of boko haram insurgency. the study has shown that boko haram activities have affected tourist patronage of yankari game reserve. it is recommended that the nigerian government should strategize on how to put an end to the boko haram crisis in the northeastern part of the country which could lead to increases in tourist patronage of yankari game reserve. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 january, 2023 revised 3 march, 2023 accepted 6 march, 2023 keywords: boko haram tourism terrorism patronage yankari game reserve bauchi state http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):235-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 236 economic activities or penalize the non-believers of religion and much more (ball et al., 2013). terrorist activities in chad, niger and cameroon, have been impacting negatively on the security, socio-political and economic situations in the region (joseph, 2016). the terrorists reportedly targeted these countries for attacks in retaliation for their participation in the regional joint task force and for their audacity to support nigeria’s efforts in quelling the insurgency (enobi and johnson-rokosu, 2016). according to serge eric epoune, a spokesman for cameroon’s ministry of tourism, noted that people do visit tourist sites in their thousands, but that number has dwindled because people fear for their lives. it has therefore jeopardized cameroon’s financial revenues. the economy of lake chad basin has been adversely affected by the boko haram insurgency (joseph, 2016). mukesh and priyanka (2014) opined that despite the economic strength of tourism, terrorism and political turmoil present major challenges to the industry. terrorist activities have significant effect on international tourism of a country and are also the largest economic factor in the equation between terror and foreign tourism. this implies that terrorism, no doubt, has an effect on the flow of foreign exchange into a country as a result of its impact on international tourism. the increase in terrorist activity is causing a decline in foreign direct investment in that country. nigeria is not an exception because it has numerous tourist sites that have remained important and unique for sightseeing over the years. one great example of the tourist sites is the yankari game reserve. insurgency in the northeast of nigeria was waged by the boko haram group. bintube (2015) noted that boko haram is an insurgent islamic group known as jama’atul ahalul sunna waljama’a lidda a’ wati wal jihadi (jaswal jihad). the persistent increase in the extent of the despicable activities of the insurgent boko haram sect in the northeastern part of nigeria since 2009 has had unpleasant humanitarian consequences for the region (imasuen, 2015). businesses and life in the communities wrecked by the insurgency have been typically horrible and marked by violence. since the beginning of the terrorist activities, the northeastern states have been completely devoid of civil normalcy as there is evidence of displacement in population, a refugee catastrophe, inadequate medical facilities and loss of livelihoods. the sect usually carries out irregular hit-and-run attacks, and according to nnamdi et al. (2015), the insurgents develop new brutal tactics of bombing, targeted shooting, ensnaring and cutting the throats of victims. the islamic group usually attacks “security operatives, christians, traditional leaders, politicians, schoolchildren and teachers, islamic scholars, public servants, traders and lately, anyone who is not a member” (nnamdi et al., 2015). these operations resulting in mass deaths have attracted international outcry and condemnation. nwolise (2009) conceptualizes security to involve the deployment and use of military resources by society to support its values when faced with threats and challenges from both internal and external sources. richmond (2012) saw the contemporary perspective of security as a change from the centric state to a people-centric approach, where the human population is regarded as a reference for security. he promotes efforts to counteract threats to human security by improving the effects of poverty, unemployment, armed conflicts and human rights violation on the population. the relationship between tourism and security revolves around concepts relating to the nature of tourism-related security incidents and crises; concepts relating to the impact of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng ukah et al: evaluation of the impacts of boko haram activities on the patronage of yankari game reserve, bauchi state, nigeria. azojete, 19(2):235-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 237 security incidents and crises on the tourism industry, the tourists and host communities; and concepts relating to the short, medium and long-term reactions of all tourism stakeholders to existing and potential security incidents and crises (pizam and mansfeld, 1996 as cited in boulal, 2017). as regards the potential impact on tourism, pizam and mansfeld (1996) identified crimerelated incidents, terrorism, war and civil/political unrest as safety incidents that could have a negative impact on the host communities, the tourism industry and the tourists. they observed that the impact of security incidents on tourism, tourists and host communities is directly correlated with the severity of the incidents. the number of security incidents within a given period of time as well as their frequency determines how serious the effects could be on tourism growth. a high recurrence of safety occurrences causes changes in the reservation and cancellation behaviour of tourists, selective spatial behaviour in the affected destination and other tourism demand characteristics (hall et al., 2004; mathew and fada, 2014). the link between tourism and terrorism is indisputable in the present era as a result of the strength of the industry and the reality that tourists’ destination sites are ultimate targets for rebel attacks intended to cause huge amounts of social and economic disorder. many countries in africa have the prospective of becoming the foremost traveler destination on earth with the demand rising at 10.1% yearly as estimated by the world travel and tourism council (wttc). soergel (2016) reported that matthias fekl, france’s minister of state for foreign trade, promotion of tourism and french nationals abroad, told french media that the nation had seen a 10 per cent drop in international travelers’ overnight stays during the first half of 2016 compared with the same period a year earlier. a sensational illustration of tourism being harmed by a single event was an attack in tunisia on 26 june, 2015 at the tourist resort of port el kantaoui, about 10 kilometers north of the city of sousse, where a gunman killed 38 tourists on the beach, 30 of whom were british (british broadcasting corporation, 2016). the insecurity in the northeast within which bauchi state falls, calls for an investigation into the effect the activities of boko haram have on the level of patronage of the yankari game reserve. the aim of this study is to assess the effects of boko haram activities on the patronage of yankari game reserve with the objectives to examine tourists’ perception on the effect of boko haram activities on patronage as well as assessing the staff’s perception on the effect of boko haram activities on patronage of yankari game reserve. a null hypothesis which stated that there is no significant difference in the temporal pattern of tourist patronage before and after the emergence of boko haram was also tested. the area chosen for this study is justifiable because it is situated in the northeastern part of nigeria where the activities of boko haram have been on the increase since 2009. moreover, this study deals on a topical issue that is of global concern in the sense that most countries of the world have experienced or are experiencing terrorists’ activities in one form or the other. the paper is organized as follows, section 1 contains the introduction, section ii contain the study area, section iii contains the methodology, section iv contains the results and discussion of findings, section v contains the conclusion and recommendations, while section vi contains the references. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):235-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 238 2. materials and methods 2.1 study area yankari game reserve can be found in south-central bauchi state in the northeastern nigeria (figure 1). it covers an area of about 2,244 square kilometers (866 sq mi). the entire park lies on the kerri development, of tertiary age, which is made up of sandstone, silt stones, kaolinites and grits. under this lies the gombe formation, of cretaceous age, made up of sandstones, silt stones, and ironstones. the valleys of the gaji, yashi and yuli rivers are loaded up with alluvium of later age. sandy loams and clayey soils of riverine alluvium happen in the valley of the gaji yashi and yuli rivers. east of the gaji valley is a 5–7 km wide band of extremely unfortunate sandy soils that aid a shrub savanna formation. it is likewise an area of moving slopes, mostly between 200m and 400m. kariyo hill is the most elevated point at 640m. in the dry season, bigger natural life in the recreation area relies upon the gaji river and its tributaries for survival (abdullahi et al., 2009). annual rainfall in the park is between 900mm and 1,000mm ((abdullahi et al., 2009). yankari game reserve is nigeria’s biggest game reserve which boasts of a wide variety of plant and animal species. yankari is within the sudan savannah vegetation zone with diverse flora and fauna, a historic site and infrastructural facilities. yankari game reserve is one of the few places where eco tourists are guaranteed to see diverse and varied wildlife species at most times of the year, in this way yankari is the chief nature travel industry destination in nigeria and plays a critical role in the development and promotion of tourism and ecotourism in particular in nigeria. yankari is home to several natural warm water springs and its location in the heartland of the west african savanna makes it remarkable for sightseers and holidaymakers to see wildlife in its natural habitat. in 1956, the reserve was chosen for a game reserve and in 1962, the yankari game reserve was officially launched for public sightseeing. it is in fact one of the leading ecoconservation sites in nigeria and one of the top emergent and admired eco-tourism target tourism locations in west africa (umar et al., 2015). the recreation area’s principle entrance is at mainamaji village, about 29 km from dindima. it is situated within the duguri, pali and gwana districts of alkaleri lga, bauchi state. this lga has a populace of 208,202 involving an absolute land area of 7,457.78 square kilometres (ogunjinmi et al., 2008). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng https://en.wikipedia.org/wiki/alkaleri https://en.wikipedia.org/wiki/local_government_areas_in_nigeria https://en.wikipedia.org/wiki/bauchi_state ukah et al: evaluation of the impacts of boko haram activities on the patronage of yankari game reserve, bauchi state, nigeria. azojete, 19(2):235-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 239 figure 1: map of bauchi state showing alkaleri l.g.a and yankari game reserve 2.2 methods data for this study were obtained from primary and secondary sources. the sets of primary data were sourced through the administration of structured questionnaires to respondents. the questionnaire contained questions on the level of patronage before and after the emergence of boko haram among others. the secondary data includes data on the temporal distribution of tourist patronage between 2000 to 2009and after the emergence of boko haram (2010 to 2019). this data was collected from the record office in yankari game reserve as well as other available published data sources. specifically, a t-test was employed to test the hypothesis. for the questionnaire administration, one hundred and eighty-two persons were sampled (142 staff and 40 tourists). the questionnaire administration was carried out within five days as staff come to work on routine. as such, repeated visits were made to the area to cover a good number of staff and tourists. all copies of the questionnaire were administered and returned with the help of three research assistants. 3.0 results and discussion the result showed that male tourists constituted 62.5% of the total tourists, while females were 37.5% at the time of the survey. this implies that even in the midst of fear and uncertainty, men take more risk than the women. however, quite a number of the tourists who patronized the game reserve during the persistent boko haram activities were males while females constituted a smaller percentage. similarly, staff gender indicated that 78.2% were males, while 21.8% were females. the high number of male staff may not be unconnected with the nature of the reserve 0 25 50 km http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):235-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 240 as well as the religious belief of the people which prohibits women to work in certain places tagged as unholy. another reason might be that men being the stronger vessel must always provide for their families. the results also showed that none of the tourists was below the age of 18 years, 12.5% were between the ages of 18 – 27 years; 45.0% were between the ages of 28 – 37years, while 42.5% were above 38 years. this age bracket is however significant as young adults tend to explore many areas or tourism sites. the curiosity to see certain phenomenon of interest makes many young tourists to explore sites irrespective of their security challenges. this can be likened to the situation reported here where despite the security challenges in the northeast, tourists still make visits to the game reserve. for the staff of the game reserve, the results showed that 14.1% were within the ages of 18 – 27 years; 45.1% were within the ages of 28 – 37 years, while 40.8% were above 38 years. the information shown here implies that majority of the staff fall within the ages of 28 years and above. the educational qualification of tourists and staff of the game reserve varies ranging from no formal education to tertiary education. the result indicated that majority (52.5%) of the respondents had masters and phd, this was followed by respondents with ond/hnd/bsc (30.0%) followed by respondents with primary education (10.0%), while only a few (7.5%) had secondary education. on the side of staff, the results indicated that majority (30.3%) of the staff had ond/hnd/bsc (first degrees in different disciplines), 23.2% had secondary education, 25.4% had primary education, and 7.7% had master’s degrees while 13.4% have no formal education. this result suggested that most of the respondents were knowledgeable enough to understand and give responses pertaining the issue of insecurity in yankari game reserve. 3.1 tourist’s perception on the effect of boko haram activities on patronage the result shows that tourists have varied perceptions on the activities of boko haram insurgents which have impacted negatively on the game reserve. from the result, 47.5% opined that they were first discouraged from making trip to the game reserve due to the increasing kidnapping in the region. the kidnapping in the area as at that time was high and this actually put fears in the mind of tourists which affected their choice of destination to the reserve. the result also indicated that 90.0% of the tourists alleged that bombings and suicide attacks carried out respectively by the boko haram sect made them not to visit the reserve in about five years especially from 2010 to 2015 hence, as noted by the tourists, these two operations (bombings and suicide attacks) carried out by the islamic sect affected their visit to the game reserve during that period especially from 2010 to 2015. in addition, 72.5.0% affirmed that stories and news feeds of massacre orchestrated by boko haram have reduced their rate of patronage of the tourist site. as noted above, the stories of massacre carried by boko haram are reported in international newspapers and published online as well as different social media platforms made tourists to have bad feelings concerning nigeria and this affected their destination to the site. from the result also, 55.0% of the tourists alleged that the deplorable infrastructures such as roads and electricity affected their choice of destination to the game reserve. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng ukah et al: evaluation of the impacts of boko haram activities on the patronage of yankari game reserve, bauchi state, nigeria. azojete, 19(2):235-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 241 the overall percentage response indicates that a good number of the respondents (92.3%) affirmed that the aforementioned activities carried out by boko haram actually affected their desire to visit the game reserve in recent years. similarly, chothia (2012) noted that boko haram islamic sect have caused massive destruction through series of bombings, bloodbath, suicides and major damage of infrastructural facilities and these have negative impact on foreign arrivals. this means that these activities have direct and indirect impacts on tourists’ patronage to the reserve. the findings above was justified by butler (1980) when he argued that a momentous proportion of tourists to a given tourist site decreases as a result of social conflicts or increased level of insecurity. however, in the past seven years, the patronage level of the once highly visited game reserve in west africa has dwindled as a result of the increase in terrorism orchestrated by the activities of boko haram. these activities characterized by bombing, suicide attacks, kidnapping, massacres and destruction of infrastructure (eme and ibietan, 2012; bintube, 2015) have put fear in the hearts of tourists and this has effects on their resolve to choose the area as a tourist location cum tourist arrival. compared to other business sectors, tourism is the most uncovered business sector vulnerable to social conflicts (krol et al., 2000). tribe (2010) stated that social conflicts could have an effect on tourism in terms of inadequate business approach, redundancy in employment, inadequate infrastructure and destruction of properties. in a similar manner, butler (1980) noted that a significant number of tourists to a given tourist site may decrease as a result of social conflicts. the operations of boko haram in the northeastern region have had a spillover effect on tourism activities in bauchi state. this is because the waves of violence, carnage and destruction of infrastructure have dissuaded tourists from choosing the yankari game reserve as their destination. the patronage level of the game reserve is seriously affected because no tourist will visit a destination that is unsecured and characterized by suicide attacks, bombings and kidnappings. the reduction in the number of tourists visiting the game reserve as a result of the happenings in the northeast has negatively impacted on the revenue of this tourist site in particular and bauchi state in general. this is so because tourists are forced to cancel their bookings and appointments including room reservations as a result of the threats of boko haram (suleiman, 2011). 3.2 years of service or employment the result showed that 7.7% had been employed in the reserve for 1 – 3 years, 26.8% had been working in the reserve for 4 6yrs, 21.1%% had been working in the reserve for 7 – 10yrs; 26.8% had been working for 11 – 13yrs, while 17.6% had been staff of the game reserve for more than 13years. this information indicated that most of the staff interviewed have been working in the game reserve for more than 3yrs, which implies that they have adequate knowledge on tourists’ patronage to the game reserve. since they have been working long and even during the peak of the boko haram activities, they would be able to give precise and detailed information on how the activities have impacted or affected tourists’ visits to the reserve. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):235-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 242 3.3 staff’s perception on the effect of boko haram activities on patronage like the tourists, the staff of the yankari game reserve has varied discernment concerning the effects of boko haram activities on tourists’ patronage. the result shows that 91.5% of the respondents affirmed that they have worked in the game reserve for years now and have not experienced boko haram activities while 8.4% refuted the claim. this implies that there has never been any form of boko haram activity in yankari game reserve. similarly, all the respondents alleged that tourists’ level of patronage to the game reserve was high before the emergence of boko haram and have drastically fallen since the emergence of boko haram insurgence. nevertheless, the result implies that tourists’ level of patronage has considerably declined since the emergence of boko haram insurgency. on the other hand, the result indicated that 52.8% were of the opinion that tourist’s low patronage to the game reserve has affected the staff of the game reserve psychologically, economically and emotionally, while 47.2% held a contrary viewpoint as they believed that tourist low patronage has nothing to do with them psychological, economically and emotionally. furthermore, 65.5% of the respondents held the opinion that tourists’ patronage has no effect on flora and fauna composition of the game reserve while 34.5% of the respondents had different opinion as to that regards. 3.4 hypothesis ho: there is no significant difference in the temporal pattern of tourist patronage before and after the emergence of boko haram. the t-test result in table 1 showed that the probability value of 0.000 is less than a 5% (0.05) significance level; based on this result, the null hypothesis is rejected and the alternate accepted. it therefore shows that there is a significant difference in the temporal pattern of tourist patronage before and after the emergence of boko haram (t = 6.010, p<0.05). this means that tourist patronage in the two time periods differs significantly. a look at the mean values further shows that patronage level was higher before the emergence of boko haram but declined immediately after the emergence of boko haram. table 1: t-test result of temporal pattern of tourist patronage to yankari game reserve before and after the emergence of boko haram temporal scale n mean sd t-cal sig (2-tailed) before boko haram 10 34645.86 7029.08 6.010* 0.000 after boko haram 10 14672.00 5283.44 *difference between means is significant at 5% alpha level; df =20 it is clear that terrorism is major challenge that has affected the rate of tourism patronage in nigeria. this is in agreement with the findings of deemua and ogujiofor (2013), who stressed that any tourist destination with a record of terrorist attacks has a reduced number of visitors due to the fear of being attacked. it was further stressed that the tourism industry is susceptible to shocks such as terror attacks or the incidence of infectious disease which shape the risk perception of the destination countries. some countries recover quickly from terrorist attacks while others do not. this is backed up by the study carried out by pizam and fleischer (2002) when the authors stress that significant effects of terrorism on tourism usually occur with a bit file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng ukah et al: evaluation of the impacts of boko haram activities on the patronage of yankari game reserve, bauchi state, nigeria. azojete, 19(2):235-246. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 243 of a time delay within three to nine months following an attack and vary in length of time. they also found that certain countries recover relatively quickly from terror attacks if they are not followed by additional attacks. repeated terror attacks, however, can result in a lasting decline in tourist demand or wipe it out entirely. similarly, nnamdi et al. (2015) assert that the various activities of boko haram have damaged properties and lives have been destroyed, banks and business burgled, and police stations and infrastructure damaged. this concurs with the findings of this study which asserts that in the past seven years, the patronage level of the once highly visited game reserve in west africa has dwindled as a result of the increased terrorist activities orchestrated by boko haram. these activities characterized by bombings, suicide attacks, kidnappings, massacres and destruction of infrastructure (eme and ibietan, 2012; bintube, 2015) have put fear in the mind of tourists and this has effects on their resolve to choose the area as a tourist location cum tourist arrival. the persistent insecurity risk posed by the boko haram sect has greatly affected the growth of tourism in the yankari game reserve as a result of gross insecurity. the killings and abduction of people have also worsened the situation in the area, thereby affecting tourist patronage. boko haram terrorism has resulted in a drastic reduction in economic investment in the region. in the wake of the crisis in the country, many international agencies and countries began to issue travel warnings to their citizens about the dangers involved in visiting and doing business in some parts of the country (joseph, 2016). the government of the united states fired the first shot of warning to its citizens about the risks of going to nigeria. this situation has had grave consequences for the economic development of the country, as the insurgency has further damaged nigeria’s profile as a desirable destination for investment, travel, tourism, scholarship and migration. conclusion this study evaluated the temporal pattern of tourists’ patronage at yankari game reserve before and after the emergence of boko haram between 2000 and 2019. data for this study were obtained from both primary and secondary sources. the primary data were gotten through the administration of structured questionnaire. the hypothesis which stated that there is no significant difference in the temporal pattern of tourist patronage before and after the emergence of boko haram was tested using the independent samples test. the result revealed that there is a significant difference (t = 6.010, p<0.05) in the temporal pattern of tourist patronage before and after the emergence of the boko haram insurgency. the study has shown that boko haram activities have effects on tourist patronage of yankari game reserve. each of the activities carried out by boko haram has exerted a great influence on tourists’ decision to visit the game reserve in the past 7 years. this study recommends that the nigerian government should improve on security. as a matter of fact, security in and out airports and tourism sites in the northeast (yankari game reserve) should be beefed. for the yankari game reserve, the state government should make the necessary effort to secure all the territorial boundaries of the reserve and ensure strict screening of tourists to the reserve. in addition, the government should strategize on how to put an end http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):235-246. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nomsostainless@gmail.com 244 to the boko haram crisis which will in turn lead to an increase in tourist patronage of the northeast, especially yankari game reserve. the government should also devise means of convincing investors and business organizations to invest in the area by promising them maximum security. moreover, the management of the game reserve can increase patronage by making the reserve more attractive and fun to be at. more state-of-the-art facilities should be constructed to meet the demands and needs of the tourists. references abudullahi, mb., sanusi, ss., abdul, sd. and sawa, fbj. 2009. an assessment of the herbaceous species vegetation of yankari game reserve, bauchi, nigeria. american-eurasian journal of agriculture and environmental science, 6: 20-25. ball, d., geringer, j., mcnett, j., and minor, m. 2013. international business: the challenge of global competition (13th ed.). new york, ny: mcgraw-hill. bintube, m. 2015. boko haram phenomenon: genesis and development in north eastern region nigeria. international journal of sociology and anthropology research, 1 (1):1-22. boulal, s. 2017. the impact of terrorism on the economic sustainable tourism development of the island of crete. athens journal of tourism, 4(4), 35 – 354. https://doi.org/10.30958/ajt.4.4.4 british broadcasting corporation. 2016. tunisia attack: what happened, bbc news, online, 1.2.2017 [available online at: http://www.bbc.com/news/world-africa-33304897] butler, rw. 1980. the concept of the tourist area life-cycle of evolution: implications for management of resources. canadian geographer, 24 (1): 5-12. caroline, d. 2015. terrorized tourists: a study of the impact of terrorism on tourism. honors thesis paper 317. university of southern mississippi, mississippi. chothia, f. 2012. who are nigerians boko haram islamists? available at: http://www.bbc.co.uk/news/world-africa-13809501 cook, d. 2011. the rise of boko haram in nigeria. combating terrorism centre. 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[available at: http://www.wttc.org/-/media/files/reports/special-and-periodic-report/tourism-as-a-driver-ofpeace--full-report-copyrighted.pdf] file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng http://www.wttc.org/-/media/files/reports/special-and-periodic-report/tourism-as-a-driver-of-peace--full-reporthttp://www.wttc.org/-/media/files/reports/special-and-periodic-report/tourism-as-a-driver-of-peace--full-report arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):659-668 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 659 original research article reduction of colour from indigo dye-rich wastewater by electro-coagulation using iron (fe) and aluminum (al) electrodes a. a. badejo*, f. c. nkeshita, o. j. adelasoye and o. p. adeyanju civil engineering department, federal university of agriculture, abeokuta, ogun state, nigeria *corresponding author’s email address: badejoaa@funaab.edu.ng 1.0 introduction adire is an integral part of the egba culture in abeokuta, ogun state, nigeria. the use of this traditional ‘tie and dye’ has crept into offices and schools where most schools within and outside abeokuta uses it as friday and occasional wears. textile industries are water intensive and dye-rich effluent discharges from the adire manufacture flow into surface and groundwater, causing pollution. conventional textile dyeing used between 120 and 180 litres of water for every 1 kg of fabrics to be dyed (karthik and rathinamoorthy, 2015). the color of dye lowers the dissolved oxygen level in rivers and streams by inhibiting sunlight penetration, thus, destroying aquatic life (durotoye et al., 2018; elango et al., 2017; forgacs et al., 2004; kaur et al., 2010; robinson et al., 2001). additionally, effluent from adire textile industry also causes environmental problems which can affect human life (rajendran, 2018). article information abstract indigo dyes are important substances in the adire textile industry which are not environmentally friendly because they produce colored effluent. this study evaluated the performance of a batch-scale electrocoagulation (ec) technique for indigo dye-rich wastewater treatment. a pilot-scale ec unit using iron (fe) and aluminum (al) electrodes, having a mono-polar parallel arrangement with a constant inter-electrode distance of 10 mm was developed. the fe anode and al cathode had effective areas of 16.50 and 22.75 cm2 respectively. the impact of ph, sodium chloride (nacl), and electrolysis time on ec performance was assessed by calculating the color reduction. a three-factor three-level box benkhen design with three center points was used to generate fifteen experimental runs using nacl, ph, and electrolysis time as independent variables and color removal efficiency as the response variable. a regression analysis was performed after the results of the experimental data were fitted to a full quadratic model resulting in the generation of regression coefficients. the model was inversely transformed and modified to make it significant. the results show that the optimum ph and nacl concentration were 3 and 4 g/l respectively with electrolysis time of 35 minutes. under these optimum conditions, the percentage of colour removal was 32.78% with a predicted value of 80%. an r2 value of 83.45% was obtained and anova verified that the accuracy of the proposed polynomial model is acceptable. therefore, it is noteworthy that an ec technique could be used in reducing color from indigo dye-rich wastewater in textile industry. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 march, 2022 revised 25 may, 2022 accepted 30 may, 2022 keywords: colour dye-rich wastewater electro-coagulation iron aluminum http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng badejoaa@funaab.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):659-668 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 660 these make the treatment of dye-rich wastewater of necessity to protect public health and the environment. to treat the effluent generated, several methods have been adopted in the treatment of dyerich wastewater to reduce or eliminate the associated environmental and ecosystem problems. these include physico-chemical, chemical, advanced oxidation, microbiological, enzymatic decomposition and electrochemical methods such as: adsorption with inorganic and organic supports, coagulation by aluminum, lime, or iron salts, ion exchange and filtration, subsurface flow constructed wetlands, wet electrolytic oxidation and ec (badejo et al., 2012; carlos et al., 2009; forgacs et al., (2004); martínez-huitl and brillas, 2009; robinson et al., (2001); dai et al., 2006). ec treatment technique is the most widely accepted because of its cost efficiency and relatively high removal capacity and low sludge generation (bharath et al., 2018). ec is the process of dissolution, coagulation and flocculation in the presence of electricity (moussa et al., 2017). according to martínez-huitle and brillas (2009), ec technique combines coagulation, floatation and electrochemistry for water treatment, it provides an alternative to the use of polymers and polyelectrolyte coagulants for breaking stable emulsions and suspensions. ec and coagulation/flocculation works on the same principle by removing pollutants through destabilizing the repulsive forces that keeps the pollutants suspended in water. neutralizing the repulsive forces brings about the formation of flocs that can be easily removed after sedimentation. the coagulants in the ec technique are generated by electrolytic oxidation as against the use of chemical coagulants in the coagulation/flocculation process. it is also efficient in treating oily water and has wide applications as compared to other wastewater treatment methods (abbass et al., 2018). ec has been used for various wastewater treatments such as municipal and industrial (including textile, tanneries, pulp and paper, oily and food processing industry) wastewater (islam, 2019). bazrafshan et al., (2013) observed that the technology removed approximately 98% of cod, bod, tss and bacterial indicators on diary wastewater. ec can also be employed in conjunction with the conventional method of dye-rich wastewater treatment. furthermore, zailani et al. (2018) reported that aluminum electrode had higher removal efficiencies than iron electrodes in stabilized leachate treatment. similarly, manilal et al. (2017) and nasrullah et al. (2012) found aluminum to be the superior iron and steel in sewage treatment while eyvaz et al. (2009) found alternating pulse current to be superior to direct current for pollution removal in disperse dyes. photo-fenton and ec processes were integrated in removing organic and inorganic pollutants from industrial effluent in dye-rich wastewater treatment by módenes et al. (2012). ec has also been combined with electro-oxidation techniques and ozone processes in the treatment of highly coloured and polluted industrial wastewater (barrera-díaz et al., 2003; bernalmartínez et al., 2010). also, response surface methodology (rsm) a collection of mathematical and statistical techniques was adopted. rsm is useful for developing the empirical model building, improving and optimizing processes parameter; it is also used for finding the interaction of several affecting factors (azargohar and dalai, 2005). similarly, rsm uses quantitative data from the related experiment to determine regression model and optimize an output variable which is influenced by several input variables (behera et al., 2018). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng badejo et al: reduction of colour from indigo dye-rich wastewater by electro-coagulation using iron (fe) and aluminum (al) electrodes. azojete, 18(4):659-668. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 661 the technological advancement in man’s activities brought about by industrial revolution has resulted in effluents from industries channeled without proper treatment. there is therefore, the need for a wastewater recycling technique to avoid scarcity of clean water. this study focused on optimizing the ec process using fe and al electrodes having mono-polar parallel arrangement for colour removal in indigo dye-rich wastewater with the rsm. 2. materials and methods indigo dye-rich wastewater was obtained from a local adire market at asero, abeokuta ogun state, nigeria. the ph, conductivity, total dissolved solids, dissolved oxygen, temperature and color were measured using standard methods (apha, 2005), before and after the experiment to determine the treatment efficiency of the ec process. all experiments were conducted in triplicate. using rsm, experiment was run 15 times using box-behnken design. the total volume of raw dye waste-water used was 22.5 litres, with 1.5 litres per run. 2.1 experimental set-up the reactor was made of transparent cylindrical plastic container (230 x 160 x 110 mm) with an effluent tap. mono-polar parallel arrangement was obtained with two fe (30 x 80 x 1 mm) and two al (50 x 50 x 0.5 mm) electrodes connected in parallel (10 mm distance apart) and circuit completed with two 12 volts battery connected in series to supply power to the whole set-up with a stirrer to achieve uniform mixing (figure 1). multi-meters were placed at strategic position to measure the input voltage and current. distilled water was used for washing the electrodes after each run while h2so4 and naoh solutions were used for adjusting the ph of the solution. figure 1: experimental setup based on rsm, 15 runs of experiment were performed using the box-behnken design (bbd). the bbd has 3 levels (-1, 0 and +1) for the design matrix to observe the effect of the treatment parameters (ph, nacl and electrolysis time) on colour removal efficiency by the ec process. the significance and adequacy of the predicted model was determined by anova. the http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):659-668 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 662 statistical significance was verified by the f-test which uses f-value that describes the variation in the mean of the data. the accuracy of the fitted polynomial model was determined by the coefficient of r2. the model was transformed according to the diagnostic information obtained from the former model. the ph, nacl and electrolytic time were kept in the range of 3 10, 0 4 mg/l and 10 60 minutes respectively in this experiment. the coded and actual values of the variables of the design of experiments for the overall ec optimization are shown in table 1. for a typical run, 1.5 l of the raw wastewater was poured into the reactor after all the initial tests. the initial ph was adjusted using h2so4 and naoh solutions to reach the desired values for each run. the effluent collected at each run was allowed to settle before the final test is done. after each run, the electrodes and the reactor were washed with distilled water to avoid errors as residues on treated wastewater from the former run may affect the characteristics of the next run thereby leading to false results. after the electrocoagulation reaction is completed, the wastewater was left to naturally precipitate for 30 minutes for the removal of flocs formed during the process, and the various analyses were carried out with the supernatant. design expert 11.0 software was used to investigate the effect of chosen treatment/operating parameters in the ec process of the dye by optimizing experimental conditions in the rsm category. the response surface plot was carried out to check the influence of three operating parameters on colour removal. table 1: variables and their levels factor independent process variable (unit) coded levels of variables -1 0 +1 x1 electrical conductively ec (mg/l) 0 2 4 x2 ph 3 7 11 x3 electrolysis time (mins) 10 35 60 the influence of the process variables was evaluated by the color removal efficiency of the process. the center points were used to evaluate the experimental error and the replicability of data. the rsm provides that it is possible to indicate independent process variables quantitatively with equation 1: 𝑦 = 𝐹(𝑥1, 𝑥2, 𝑥3, … , 𝑥𝑛) ± 𝜀 (1) where: y is the response (efficiency of colour removal), f is the response function, ɛ is the experimental error, and x1, x2, x3, …, xn are independent variables. 3. results and discussion the results obtained from this study show good correlation between actual and predicted responses as shown in table 2. the experimental inputs for the various factors in each of the 15 runs with their corresponding colour removal response as shown in table 2 for both the experimental and predicted values confirmed the reliability of the model. the inverse transformation has been applied on both the experimental and predicted values respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng badejo et al: reduction of colour from indigo dye-rich wastewater by electro-coagulation using iron (fe) and aluminum (al) electrodes. azojete, 18(4):659-668. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 663 table 2: colour removal responses of dye-rich wastewater for experimental and predicted values 3.1 model fitting the box-cox plot indicated that the current power of the model (yλ) was 1 (figure 2). this represented no transformation of the actual response data (y1). the area bounded by the red line indicated the 95% confidence interval (ci) beyond which the model was not significant. the ‘power’ at the green line (-1) that is, the inverse transformation was used since it falls within the 95% ci. the green line is often called the minimum model residual. figure 2: box-cox plot for electrocoagulation data design-expert® software color current transform: none current lambda = 1 best lambda = -1.01 ci for lambda: (-2.25, 0.38) recommended transform: inverse (lambda = -1) lambda l n (r e si d u a ls s ) box-cox plot for power transforms 4 5 6 7 8 9 -3 -2 -1 0 1 2 3 5.14167 run run independent variables colour response values (%) nacl concentration (ec) (g/l) ph electrolysis time (mins) experimental predicted 1 4 3 35 0.0305 0.0398 2 4 11 35 0.0329 0.0608 3 2 7 35 0.1592 0.0909 4 0 7 10 0.2653 0.2486 5 2 3 60 0.2252 0.2221 6 0 11 35 0.1206 0.1420 7 0 3 35 0.1057 0.1211 8 2 7 35 0.0458 0.0909 9 0 7 60 0.1379 0.1473 10 4 7 60 0.1712 0.1804 11 2 11 10 0.2193 0.2300 12 2 11 60 0.1209 0.1055 13 4 7 10 0.0700 0.0530 14 2 7 35 0.1416 0.0909 15 2 3 10 0.0486 0.0716 http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):659-668 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 664 3.2 model reduction and transformation the new model still did not attain significance until the quadratic model was reduced. the model’s f-valve of 4.74 and the p-value of 0.0369 indicated the employed model is significant, there is only a 3.69% chance that the f-value occur due to noise. the model was modified by the removal of the a2 quadratic co-efficient in-order to make the model fit properly. the high p-values 0.5018, 0.6717, 0.8846 and 0.3068 for factors b, c, ab and b2 respectively indicated that they were not significant to the model. however, only factors ab and b2 were eliminated in order to improve the quality of the regression model. furthermore, the lack of fit f-value of 0.9244 is not significant relative to the pure error, and this demonstrated that the model successfully fits. that is, it approximately predicted the effect of the factors on the treatment process. therefore, the model for predicting the colour removal using the ec process includes a set of coefficients and uncoded factors as shown in eqn. 2. 𝑌𝐶𝑜𝑙𝑜𝑢𝑟 −1 = 0.0772 − 0.0576 𝐴 + 0.0484 𝐵 − 0.0045 𝐶 + 0.0011 𝐴𝐶 − 0.0007 𝐵𝐶 + 0.0001 𝐶2 (2) 3.3 effect of operating parameters the response surface plot obtained from the combined effects of the 3 operating parameters: nacl concentration, electrolyte time and ph on colour removal is shown in figure 3. (a) (b) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng badejo et al: reduction of colour from indigo dye-rich wastewater by electro-coagulation using iron (fe) and aluminum (al) electrodes. azojete, 18(4):659-668. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 665 (c) figure 3: three-dimensional surfaces for colour removal efficiencies: (a) ec vs. initial ph at electrolysis time 35 min (b) initial ph vs. electrolysis time at ec 2g/l, and (c) ec vs electrolysis time at initial ph 7. 3.3.1 effect of nacl concentration and the initial ph it could be observed from figure 3a that there was no noticeable colour removal at constant electrolysis time of 35 minutes until nacl was added. the removal efficiency increased up to about 20% as the nacl concentration increased. this was as a result of the increase in current density as the solution conductivity increased (naje et al., 2017). higher removal efficiency was obtained at lower (acidic) ph (<3) as the model predicts a maximum removal of 80% at a ph of 3 and a nacl concentration of 4 mg/l. 3.3.2 effect of initial ph and electrolysis time the 3-d interaction between the initial ph and the electrolysis time at a constant nacl concentration of 2 mg/l is shown in figure 3b. at 60 mins electrolysis time, the plot is linear as the ph moves from the acidic medium up to the alkaline. the best colour removal efficiency predicted by the response surface plot for this combination is about 36%. the optimum parameters are ph of 3 at 20 mins electrolysis time. 3.3.3 effect of nacl concentration and electrolysis time figure 3c shows 3-d interaction between the nacl concentration and the electrolysis time at the constant initial ph of 7. the effect of increasing the nacl concentration on the color removal efficiency was more than that of increasing the electrolysis. from anova, it was observed that factor c is not significant to the model. this therefore, explains the little effect that the electrolysis time have on the process. the best removal efficiency predicted by the plot for this combination is also about 36% with optimum nacl concentration of 4 g/l and electrolysis time of 20 mins. 3.4 optimizing the treatment process the optimum conditions were obtained by taking the top summit point of the various response surface plots (figure 2). the response surface model gives a predicted maximum colour removal rate of 80% at an optimum initial ph of 3 and nacl concentration of 4 mg/l http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):659-668 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 666 during 35 mins electrolysis time. the predicted value is very far from the experimentally observed value of 32.4%. this is largely due to the variation and constant degradation in the current supplied by the battery. it could also be partly due to the purity of the metals used as electrodes. 4. conclusion this study investigated the performance of ec technique for decolorization of indigo-dye wastewater in a laboratory pilot-scale batch study. the findings of this study revealed that the ph of the medium and electrolyte concentration were the most influential parameters than the electrolysis time in colour removal through electrocoagulation. acidic ph of 3 and increased concentrations of nacl will produce higher colour removal. electro-coagulation technique could be used in reducing color from indigo dye-rich wastewater in textile industry. references abbas, sh. and ali, wh. 2018. electrocoagulation technique used to treat wastewater: a review. american journal of engineering research, 7(10): 74-88. apha-awwa-wef, 2005. standard methods of examination of water and wastewater, 21st ed. american public health association, washington, d.c.usa. azargohar, r. and dalai, ak. 2005. production of activated carbon from luscar char: experimental and modeling studies. microporous and mesoporous materials, 85(3): 219–225. badejo, aa., coker, oa. and oyedele, vo. 2012. subsurface flow constructed wetlands system vegetated with phragmites karka in the treatment of dye-rich wastewater. journal of natural science, engineering and technology, 11(2): 87-93. barrera-díaz, c., ureña-nuñez, f., campos, e., palomar-pardavé, m. and romero-romo, m. 2003. a combined electrochemical-irradiation treatment of highly colored and polluted industrial wastewater, radiation physics and chemistry, 67: 657–663. bazrafshan, e., moein, h., mostafapour, kf. and nakhaie, s. 2012. application of electrocoagulation process for dairy wastewater treatment. journal of chemistry, 2013: 1– 8. behera, sk., meena, h., chakraborty, s. and meikap, bc. 2018. application of response surface methodology (rsm) for optimization of leaching parameters for ash reduction from low-grade coal. international journal of mining science and technology, 28(4): 621–629. bernal-martínez, la., barrera-díaz, c., solís-morelos c. and natividad, r. 2010 synergy of electrochemical and ozonation processes in industrial wastewater treatment. chemical engineering journal, 165: 71–77. bharath, m., krishna, bm. and manoj kumar, b. 2018. a review of electrocoagulation process for wastewater treatment. international journal of chemical technology research, 11(3): 289-302. carlos, a., martı´nez-huitle, l. and brillas, e. 2009. decontamination of wastewaters containing synthetic organic dyes by electrochemical methods: a general review. applied catalysis b: environmental, 87(3 4): 105–145. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng badejo et al: reduction of colour from indigo dye-rich wastewater by electro-coagulation using iron (fe) and aluminum (al) electrodes. azojete, 18(4):659-668. issn 1596-2644; 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vol. 18(4):659-668 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: badejoaa@funaab.edu.ng 668 nasrullah, m., ab wahid, z. and yahaya, mf. 2012. sewage water treatment by electrocoagulation process. international journal of civil engineering and geo-environmental, 3: 41-45. rajendran, s. 2018. study on the physico-chemical parameters of dye industry effluents from industrial estate vatva, ahmedabad. international journal of advance research in computer science and management, 5: 1706–1710. robinson t., mcmullan, g., marchant, r. and nigam, p. 2001. remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative. bioresources technology 77: 247–255. zailani, l., amdan, n. and zin, n. 2018. removal efficiency of electrocoagulation treatment using aluminum electrode for stabilized leachate. iop conference series: earth and environmental science, 140: 12049 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/badejoaa@funaab.edu.ng arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):1-8 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 1 mechanomyographic amplitude tracks muscle mechanical responses during nmes-evoked torque production m. o. ibitoye1* and n. a. hamzaid2 1department of biomedical engineering, faculty of engineering and technology, university of ilorin, p.m.b 1515, ilorin 24003, kwara state, nigeria 2department of biomedical engineering, faculty of engineering, university of malaya, kuala lumpur 50603, malaysia *corresponding author's email address: ibitoye.mo@unilorin.edu.ng article information submitted 18 nov., 2023 revised 29 january, 2024 accepted 5 february, 2024 keywords: electrical stimulation muscle force mechanomyography accelerometer motor unit recruitment abstract this study investigates the pattern of relationship between mechanomyographic (mmg) signal amplitude and neuromuscular electrical stimulation (nmes)-evoked muscle contractions in healthy volunteers. recent evidence has suggested that nmes-evoked muscle contractions enhance motor ability for physical performance in healthy individuals, maintain muscle health, and offset secondary complications of inactivity in persons with neurological conditions. however, the traditional nmes operation is inefficient, thus making the nmes outcomes less than optimal. responsible for this is the lack of mechanical responses of muscle from the electrically-evoked limb during nmes-evoked contractions. this study investigated the use of a muscle contraction signal (mechanomyography, mmg) generated during nmes-evoked contractions in healthy knee extensors in tracking the muscle mechanical responses during nmes-evoked force production. six healthy males underwent nmes-evoked submaximalto-maximal isometric contractions, in random order, of their knee extensors at 30deg and 90deg knee angles on an isokinetic dynamometer. the mmg signal was acquired through an accelerometer sensor affixed to the rectus femoris (rf) muscle belly. paired samples t-tests was used to compare the relationship between the two knee angles (90deg and 30deg) tested. results show that the mechanomyographic amplitude (mmg-rms) increased with increase in torque production and stimulation intensity up to 50 ma and 60 ma at knee flexion angles of 90deg and 30deg, respectively, before the appearance of plateau-like contractions—an indication of fusion of contracting muscle fibre at maximal contraction level. although there were knee angle differences in the pattern of relationship between mmg and stimulation intensity, the effect was only statistically significant (p ≤ 0.05) for the torque versus stimulation intensity plot. these results suggest that mmgrms tracks motor unit recruitment strategy that might be responsible for muscle force/joint torque modulation during electrically stimulated contractions. the mmg signals may, therefore, have a clear application as an indicator of muscle force in areas where muscle force is needed and impractical to measure 1.0 introduction although healthy volunteers, athletes (micke et al., 2023) and non-athletes (yoo et al., 2023), have demonstrated improved muscle strength and joint torque production following neuromuscular electrical stimulation (nmes)-evoked contractions (filipovic et al., 2012), the open-loop mode of operation of commercially available nmes systems precludes the optimal application of the technology for routine clinical practices (gil-castillo et al., 2020; keller et al., 2002). alternatively, mostly through simulation studies, the closed-loop controlled of nmes http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 2 systems promise to automate the modulation of stimulation parameters for optimal outcomes (gil-castillo et al., 2020). however, for effective and efficient implementation, a closed-loop system requires reliable feedback from the controlled limb (jensen et al., 2002). practically, the information on the muscle force production which is required, in real-time, to automate the operation of such nmes systems (peckham and knutson, 2005) is difficult and may be impossible to measure directly for this application (li et al., 2018). the inability of the conventional muscle function assessment modalities to non-invasively measure the mechanical responses (force, fatigue, or joint position) sequel to the motor control of muscle contractions (motor units (mu) recruitment and firing rates) suggests the need for a complementary alternative (ibitoye et al., 2014). muscle mechanomyography (mmg), due to a low frequency of muscle dimensional changes (cè et al., 2022; orizio, 1993), has been established as a reliable measure of muscle surface oscillation during nmes-evoked muscle contractions (brandenberger et al., 2023; orizio et al., 1997). impetus from the earlier work of orizio et al. (1997) and that of gobbo et al. (2006), have also suggested a good relationship between muscle contractile properties and mmg parameters during nmes-evoked contractions. apart from the ease of attachment of mmg sensors onto the skin surface, mmg measurements are immune from stimulation artefact and represent the summation of the activities of active motor units—useful to estimate the neural activation level and the associated muscle force modulation (beck et al., 2004). however, the probable nonlinear relationship between the nmes-evoked contractions and the generated muscle force/joint torque (rabischong and chavet, 1997) as well as with the mmg amplitude features (due to the muscle fibre fusion at a high contraction intensity level) (orizio et al., 2003) warrants that the mmg signal be continuously reassessed during clinically relevant muscle tasks. this may provide insight into the possibility of mmg signal deployment to interpret physiological phenomena underlying nmes-evoked muscle force production. earlier, windhorst et al. (1986) suggested that there is a reduction in the “mechanical effect of mu activation” during stimulated contractions in cat medial gastrocnemius muscle. in humans, orizio et al. (2003), tracked the suggested pattern with mmg signal during sustained voluntary contractions of biceps brachii muscle. these authors recommended the application of mmg for improved identification of muscle activity during nmes-stimulated contractions. previously, in our laboratory, we have identified a “strong relationship between mmg signals and torque during nmes-induced contractions” in spinal cord injury survivors (ibitoye et al., 2016). using a machine learning method, we have also estimated knee torque from mmg signals (and other relevant input parameters) in comparison to the torques generated from the isokinetic dynamometer (ibitoye et al., 2016). to our knowledge, no analysis of the mmg amplitude (mmg-root mean square (mmg-rms)) only at different levels of nmes-evoked isometric contractions and at different knee angles has been examined to evaluate muscle mechanical responses using traditional statistical methods. the objective of this study was to examine whether the mmg signal amplitude could track the mechanical responses of the knee extensors during nmes-evoked contractions for force/torque production. additionally, the study also sought to investigate if there are statistically significant effects of knee angle on the mmg signal amplitude relationship with the incremental nmes-evoked muscle contractions. 2. methodology 2.1 study participant the university of malaya medical ethics committee (approval no: 1003.14 (1)) approved the experimental procedure performed in this study. the schematic representation of the experimental setup is as presented in figure 1. six healthy male participants [mean (sd) age, 23.2 (1.3) years; height, 173.0 (0.1) cm; body mass, 72.2 (5.2) kg] volunteered for this study. all study participants consented to participate in the experiment. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ibitoye and hamzaid: mechanomyographic amplitude tracks muscle mechanical responses during nmes-evoked torque production. azojete, 20(1):1-8. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 3 figure 1. schematic of the experimental setup on an isokinetic dynamometer with “a”, and “b” representing the cathode and anode electrode, respectively of the nms. “c” stands for the accelerometer sensor (to acquire mmg signals). 2.2 experimental procedure following initial familiarization sessions to habituate the participants to the nmes-evoked muscle contractions of moderate-vigorous intensity, they were safely secured, during the experiment, to an isokinetic dynamometer (biodex medical system (system 4), shirley, ny, usa) using a rigid “restraining straps” over the pelvis, trunk and the thigh to reduce body movement during testing in accordance with the standard practice (brown and weir, 2001) (figure 1). this procedure was necessary to prevent participants’ voluntary contributions to the muscle contractions and joint movements as much as practically possible. for electrical stimulus contractions, electrical pulses (“square-wave pulses” at 30 hz frequency and pulse duration of 400 μs, of increasing current amplitude from 20 ma to 80 ma) was imposed for 4 secs to allow sufficient contraction duration for data collection (orizio et al., 1992). nmes pulses were administered via a computer-controlled neurostimulator (rehastimtm, hasomed gmbh, germany) through 9×15 cm2 electrically-conductive and selfadhesive electrodes (hasomed gmbh, germany) on the quadriceps muscle of each participant’s dominant leg (adams et al., 1993) (figure 1). this method was used in this study because a similar stimulation pattern has been previously recommended (babault et al., 2001) stimulated contractions without premature muscle fatigue. 2.3 measurements 2.3.1 incremental peak torque as described earlier, following the administration of a series of randomly ordered nmes-evoked submaximal isometric muscle actions delivered using stimulation current from 20ma to 80ma in 10ma increments (seven different levels of stimulation intensities) for 4 secs (ibitoye et al., 2016), joint torques were produced. the nmes-evoked torque productions were obtained from the isokinetic dynamometer on which the participants were safely secured. to prevent voluntary effort by the participants during testing, there was no visual feedback displayed by the dynamometer to the participants. this was in addition to the instructions given to the participants not to contribute or prevent nmes-evoked muscle contractions through any voluntary effort. this was because the experiment was only meant to assess the torque production by nmes. in each trial, the value of the highest nmes-evoked torque was used as the neurostimulation-evoked peak torque (pt). from the pts’ values, percentages of submaximal torque levels were subsequently calculated for analysis. in order to minimize http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 4 potential muscle fatigue, a recovery duration of 10-min was allowed after each trial before the next. 2.3.1 mechanomyographic signal while the generated torques were being measured by the isokinetic dynamometer (figure 1), mmg signals were simultaneously being collected from the rectus femoris (rf) muscle of the quadriceps with an accelerometer sensor (sonostics bps-ii vmg transducer used in biopac mp150 environment) affixed using an adhesive tape (barry, 1991). the attachment of the accelerometer sensor was directly onto the belly of rf muscle. this was meant to obtain the maximum muscle contraction though surface oscillation of the muscle (barry, 1991). rf was selected for investigation because it is functionally relevant and a major contributor to the common actions of daily activity, such as standing—where it is considered to be near isometric contraction during knee extension (antonelli et al., 2009). 2.3.3 signal processing the acquired mmg signals (sampling rate: 2 khz) were band-pass filtered digitally (20-200 hz). the signals were amplified and stored through acqknowledge data acquisition and analysis software (mp150, biopac systems, santa barbara, ca, inc.) for further analysis using programs written in the labview programming software environment (version 12.0, national instruments, austin, tx, usa) (ibitoye et al., 2016). from the mmg and torque signals, the 2secs segment was selected (the middle position where maximum muscle recruitment might have occurred). this segment selection was based on the standard procedure (orizio et al., 1992). thereafter, the mmg-rms was extracted for further analysis. to account for any potential inter-individual variability (due to muscle composition-related factors during submaximal electrical stimulus-evoked contractions in each participant), the mmg-rms and pt for the highest stimulation intensity were used to normalize their respective values at submaximal levels. this procedure is common in related studies (beck et al., 2005; keller et al., 2018). 2.3.4 statistical analysis the comparison between the two knee angles tested (90deg and 30deg) on mmg-rms or pt versus stimulation intensity data, at each stimulation intensity level, was examined using paired samples t-tests. microsoft office excel 2013 (microsoft, redmond, wa, usa) and spss (ibm spss for windows version 20, ny, usa) were used for the statistical analysis. statistical significant (i.e., p ≤ 0.05) was assumed for comparison between knee angles at each stimulation intensity level. 3. results and discussion figure 2 presents the plots of normalized nmes-evoked peak torque versus stimulation intensity (a) and normalized mmg-rms versus stimulation intensity (b) at 90deg and 30deg knee angles. the statistical analysis results of the data presented was also indicated on figure 2 where the paired samples t-tests was used to statistically compared the relationship between the two knee angles tested. the peak torque was significantly different between the tested knee angles at particular lower and higher stimulation intensities (p<0.05, (figure 2 a)) but the mmg-rms between the tested angles was found with no significant difference (figure 2 b). specifically, in figure 2, the significant increase in the pt at 90deg over 30deg knee angle at (a) for 70 ma and 80 ma reflected as a decline in the mmg amplitude in (b). on (b), at 60 ma to 80 ma, the higher the torque production the lower the mmg amplitude. this is suggestive of muscle mechanical response during high stimulation intensity where muscle stiffness could lead to a decline in mmg amplitude (beck et al., 2005). 3.1 torque response, mmg response versus stimulation intensity the results presented in figure 2 based on the two knee angles investigated, revealed that at low stimulation intensities (from 20-50 ma), isometric torque production increased with file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ibitoye and hamzaid: mechanomyographic amplitude tracks muscle mechanical responses during nmes-evoked torque production. azojete, 20(1):1-8. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 5 reduction in the knee flexion angle, but increased with increasing knee flexion angle from 50 80 ma (figure 2 (a)). this pattern was also mirrored by the mmg versus stimulation intensity plot (figure 2 (b)) up to 40 ma, except for the appearance of a plateau-like response of mmgrms at 60 ma. specifically, at 90deg knee angle, the mmg amplitude increased up to 50 ma stimulation intensity, and declined thereafter up to the stimulation intensity of 80 ma while at 30deg knee angle, the mmg amplitude increased up to 60 ma stimulation intensity before plateauing up to the stimulation intensity of 80 ma. it can be proposed that, although not statistically significant at stimulation contraction levels, the different patterns of the mmg amplitude versus stimulation intensity were due to knee flexion angle differences in muscle stiffness and intramuscular fluid pressure as earlier suggested (ebersole et al., 1999; orizio et al., 2003). the mmg (figure 2) decline at high stimulation intensity has been suggested to be due to the “fusion of motor unit twitches” (beck et al., 2004; orizio et al., 2003) and it is thought to be as a result of the high level of muscle/ intramuscular stiffness. this is attributable to the profound indication of muscle mechanical response to high stimulation intensity/twitches (orizio et al., 2003). essentially, the results obtained in this study has established a relationship between mmg amplitude (rms) and muscle mechanical responses (pt) during low and high stimulation intensity for nmes-elicited muscle force production in healthy volunteers. 3.2 knee angles and mmg response although the knee angle did not have statistically significant effects on the pattern of response of mmg amplitude and stimulation intensity levels, from 50 ma to 80 ma the decline in mmg amplitude to high contraction intensity tended to be more pronounced and appeared earlier in 90-degree knee angle (figure 2 (b)). this may suggest that the higher the torque production the higher the tendency for muscle stiffness which affects the muscle dimensional changes as reflected by a decline in mmg amplitude. figure 2. plots of normalized nmes-evoked peak torque versus stimulation intensity (a) and normalized mmg-rms versus stimulation intensity (b) at 90deg and 30deg knee angles. *p ≤ 0.05 for comparison between knee angles at each stimulation intensity level. data are presented as mean±se; n=6. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 6 therefore, there seem to be knee angle effects on the contracting mu mechanical characteristics which could explain the mu activation pattern during nmes-evoked muscle contractions at different joint angles. moreover, the extent of muscle stiffness observed from 50 ma may be due to the possibility of firing a greater quantity of fast twitch motor units in the rectus femoris. this explanation is in accordance with that of barry (1991) during the stimulated contractions of the abductor pollicis brevis muscle. 4. conclusion mmg amplitude (rms) relationship with the incremental nmes-evoked torque production of knee extensors has been investigated to study whether mmg-rms might be used to track the muscle mechanical responses (pt). it has been identified that based on its sensitivity to the incremental stimulation amplitude and torque production, the mmg signals may be deployed to interpret physiological phenomena underlying nmes-evoked torque production. the use of mmg-rms to track incremental knee torque production will be an interesting tool for clinicians and other allied health professionals who could not afford to use the expensive isokinetic dynamometer—conventionally required to measure muscle force via joint torque. also, these results may have implications in using mmg-rms as a force/torque sensor for application in advanced prostheses in individuals with prosthetic support but without neurological lesions. in the future, a larger number of test participants will be recruited for a better interpretation of the mmg response to nmes-evoked toque production in both the healthy and denervated muscles. acknowledgment this research study was supported by “hir grant number: um.c/625/1/hir/mohe/eng/39”. we are grateful to the experimental participants for their time and cooperation. references adams, gr., harris, rt., woodard, d. and dudley, ga. 1993. mapping of electrical muscle stimulation using mri. journal of applied physiology, 74(2): 532-537. antonelli, mg., beomonte zobel, p. and giacomin, j. 2009. use of mmg signals for the control of powered orthotic devices: development of a rectus femoris measurement protocol. assistive technology, 21(1): 1-12. babault, n., pousson, m., ballay, y. and van hoecke, j. 2001. activation of human quadriceps femoris during isometric, concentric, and eccentric contractions. journal of applied physiology, 91(6): 2628-2634. barry, dt. 1991. vibrations and sounds from evoked muscle twitches. electromyography and clinical neurophysiology, 32(1-2): 35-40. beck, tw., housh, tj., cramer, jt., weir, jp., johnson, go., coburn, jw., malek, mh. and mielke, m. 2005. mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review. biomedical engineering online, 4(1): 67. https://doi.org/10.1186/1475-925x-4-67 beck, tw., housh, tj., johnson, go., weir, jp., cramer, jt., coburn, jw. and malek, mh. 2004. mechanomyographic amplitude and mean power frequency versus torque relationships during isokinetic and isometric muscle actions of the biceps brachii. journal of electromyography and kinesiology, 14(5): 555-564. https://doi.org/http://dx.doi.org/10.1016/j.jelekin.2004.03.001 brandenberger, kj., rawdon, cl., armstrong, e., lonowski, j. and cooper, ld. 2023. a nonvolitional skeletal muscle endurance test measures functional changes associated with impaired blood flow. journal of rehabilitation and assistive technologies engineering, 10: 1-12, 20556683231164339. https://doi.org/10.1177/20556683231164339 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ibitoye and hamzaid: mechanomyographic amplitude tracks muscle mechanical responses during nmes-evoked torque production. azojete, 20(1):1-8. issn 1596-2490; 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vol. 20(1):1-8. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 8 meta-analysis. european journal of sport science, 23(8): 1570-1580. https://doi.org/10.1080/17461391.2022.2107437 orizio, c. 1993. muscle sound: bases for the introduction of a mechanomyographic signal in muscle studies. critical reviews in biomedical engineering, 21(3): 201-243. http://europepmc.org/abstract/med/8243092 orizio, c., esposito, f., paganotti, i., marino, l., rossi, b. and veicsteinas, a. 1997. electricallyelicited surface mechanomyogram in myotonic dystrophy [journal article]. the italian journal of neurological sciences, 18(4): 185-190. https://doi.org/10.1007/bf02080462 orizio, c., gobbo, m., diemont, b., esposito, f. and veicsteinas, a. 2003. the surface mechanomyogram as a tool to describe the influence of fatigue on biceps brachii motor unit activation strategy. historical basis and novel evidence. european journal of applied physiology, 90(3-4): 326-336. https://doi.org/10.1007/s00421-003-0924-1 orizio, c., solomonow, m., baratta, r. and veicsteinas, a. 1992. influence of motor units recruitment and firing rate on the soundmyogram and emg characteristics in cat gastrocnemius. journal of electromyography and kinesiology, 2(4): 232-241. peckham, ph. and knutson, js. 2005. functional electrical stimulation for neuromuscular applications. annual review of biomedical engineering, 7(1): 327-360. https://doi.org/10.1146/annurev.bioeng.6.040803.140103 rabischong, e. and chavet, p. 1997. regression-based indices of fatigue in paraplegics' electrically stimulated quadriceps. medical engineering & physics, 19(8): 749-754. https://doi.org/http://dx.doi.org/10.1016/s1350-4533(97)00038-6 windhorst, u., christakos, cn., koehler, w., hamm, tm., enoka, rm. and stuart, dg. 1986. amplitude reduction of motor unit twitches during repetitive activation is accompanied by relative increase of hyperpolarizing membrane potential trajectories in homonymous αmotoneurons. brain research, 398(1): 181-184. https://doi.org/http://dx.doi.org/10.1016/00068993(86)91266-7 yoo, h-j., park, s., oh, s., kang, m., seo, y., kim, bg. and lee, s-h. 2023. effects of electrical muscle stimulation on core muscle activation and physical performance in non-athletic adults: a randomized controlled trial. medicine, 102(4): e32765. https://doi.org/10.1097/md.0000000000032765 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):219-234 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 219 original research article inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory a. m. epemu and b. e. nyong-bassey department of electrical and electronic engineering, federal university of petroleum resources effurun, nigeria. *corresponding author’s email address: epemu.ayebatonye@fupre.edu.ng 1.0 introduction winding function theory (wft) is a widely used method for calculating inductances in various types of machines, considering factors such as configurations, eccentricities, and airgap lengths as presented by faiz and tabatabaei (2002). it has been successfully applied in studies on synchronous and asynchronous machines, variable speed doubly-fed reluctance machines, and induction machines with spatial harmonics and rotor bar skewing as seen in liang et al. (1991) and gojko et al. (1999). to address specific challenges, a modified version of wft called modified winding function theory (mwft) was proposed. mwft enables the modelling of airgap eccentricity in synchronous machines, providing accurate results as presented by al-nuaim and toliyat (1998). researchers have combined wft with direct phase quantities to analyze synchronous generators under internal faults, effectively considering asymmetries and spatial harmonics in jiang et al. (1999). additionally, a global method based on wft was developed for simulating faulty induction machines, including stator and rotor faults, as well as airgap eccentricities. this method can also be extended to synchronous machines as presented by houdouin et al. (2003). mwft has been employed to model synchronous generators with dynamic eccentricity, yielding results consistent with finite element analysis (fea) by faiz and tabatabaei, (2002) and tabatabaei et al. (2004). obe (2009) proposed a direct numerical procedure based on wft to accurately calculate inductances in synchronous reluctance machines, incorporating actual geometry and article information abstract this study evaluates the inductance characteristics of synchronous reluctance motors (synrms) with concentrated and distributed windings. two methods based on winding function theory (wft) are used: the sinusoidal method and the actual winding function method. the actual winding function method, which considers spatial harmonics and actual geometry, is found to be more accurate. the study reveals that the distributed winding synrm has a higher saliency ratio (2.10) compared to the concentrated winding synrm (1.58), indicating better performance. these findings contribute to our understanding of synrm inductance and can guide improvements in motor design and performance. the study also suggests avenues for developing more precise inductance calculation methods for synrms, enabling optimized motor performance. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 10 october, 2022 revised 3 march, 2023 accepted 6 march, 2023 keywords: winding function theory synchronous reluctance motor concentrated winding distributed winding saliency ratio http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 220 winding placements. this approach has also been applied to cage-less synchronous reluctance machines, considering stator windings and cross-coupling effects in obe et al. (2009). furthermore, obe (2010) extended the application of wft to calculate torque and inductances in axially laminated synchronous reluctance machines, considering saturation effects, rotor lamination insulations, and stator slots. the full-order model based on wft showed better agreement with fea compared to the sinusoidal model. the performance of synchronous reluctance machines is influenced by inductance values along the direct and quadrature axes, impacting torque capability and the saliency ratio (spargo, 2016). the present study aims to calculate inductances for concentrated and distributed winding synchronous reluctance motor models using both the sinusoidal and actual winding function methods. the d-axis and q-axis inductances will be comparatively analyzed to determine the model with superior performance. in summary, this study aims to contribute to the understanding of inductance characteristics in synchronous reluctance motors with concentrated and distributed windings. by utilizing wftbased methods, the study provides a comprehensive numerical comparison of inductances, facilitating the design and optimization of motor performance. 2.0 materials and methods 2.1 modified winding function theory for machines with salient pole rotor in conventional winding function theory, the air gap function is assumed to be composed of only even harmonics. figure 1 presents a machine with two-pole winding residing within the air gap. the winding function theory was amended in this section to include machine geometries with salient poles, this will be termed the modified winding function theory. figure 1: an ideal machine with a salient pole rotor. according to lipo (2012), by applying ampere’s law, the line integral is taken along the path of the conductor 1-2-3-4-1 as shown in equation (1), going along the path around the conductor in figure 1, and the total mmf is calculated as seen in equation (2). h dl j ds =   (1) 12 23 34 41 ( )n i+ + + =m m m m (2) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 221 the mmf drops are equivalent to the turns function ( )n  multiplied by the current, i in the winding. as with the case of the conventional winding function theory, linear iron is assumed to have high relative permeability; thus, mmf drops in the stator and rotor iron are negligible and ignored. the turns function will account for the changing mmf throughout the machine, as in the case of the cylindrical rotor, while the inverse air gap function will be used to account for the changing air gap thickness. the magnetic field intensity ( )h  can be evaluated to form equation (3) if ( )m can be assigned to be the mmf of the inner stator surface to the rotor pole, and the entire surface can now be taken to be at the same magnetic potential. 2 1 0 ( ) ( ) 0g d    − = m (3) from the assumptions in (3), the value of the mmf can be given as follows:   2 2 1 1 12 34 0 0 (0) ( ) ( ) ( ) ( )g d n g i d        − −+ = m m (4) to find the right term in equation (4), assuming the left term is equal to zero; 2 1 1 12 0 2 (0) ( ) ( ) ( )g n g i d      − −= m (5) 2 1 12 1 0 1 (0) ( ) ( ) 2 ( ) n g i d g       − − = m (6) 12 34(0) ( )n i+ =m m (7) 12 34(0) ( ) ( )n i + =m m (8) 2 1 34 1 0 1 ( ) ( ) ( ) ( ) 2 ( ) n n g i d i g         − −    = −    m (9) 2 1 1 0 1 ( ) ( ) ( ) 2 ( ) m n g i d g        − − =  (10) ( ) ( ) ( )m n m  = − (11) note that equation (11) is known as the modified winding function, which shows that a new average value ( )m  will be subtracted from the turns function ( )n  . http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 222 if two windings a and b with radius r and stack length l, new inductance values can be gotten using the modified winding function theory as shown in equation (12), for self or magnetizing inductance and equation (13) for mutual inductance. 2 10 0 ( ) ( )aa aa a a a rl l n m g d i g     −= =  (12) 2 10 0 ( ) ( )ab ab a b b rl l n m g d i g     −= =  (13) note that the flux linkage aa is the flux in winding a, due to its current, and the flux linkage ab is due to the current in winding b, it should also be noted that these equations employ a product of winding functions and turns functions. since the inverse air gap function 1( )g − contains even harmonics for conventional wft and when the winding functions are expressed in odd harmonics, a new equivalent mutual inductance will be given as presented in equation (14) 2 10 0 ( ) ( )ab a b rl l m m g d g     −=  (14) while that of self or magnetizing inductance will be given as seen in equation (15) 2 2 10 0 ( )( )aa a rl l m g d g     −=  (15) for synchronous reluctance machines, where the reference position for the angle , is chosen as the axis on phase a, r is defined as the point of symmetry on one of the two-pole faces relative to the axis of phase a, the magnetizing inductance for phase a, is given in equation (16): 2 2 1 0 0 ( ) ( , )aa a rl rl n g d      −=  (16) the inverse air gap function dependency on the rotor position was explicitly shown in equation (16). since 2 ( )an  is a constant equal to 2 4 tn where tn is the total number of turns per pole per phase, equation (16) can now be written as presented in (17) 22 1 0 0 ( , ) 4 t aa r n l rl g d     −  =      (17) the formula for the calculation of mutual inductance for a synchronous reluctance machine is quite more complicated than that of self-inductance. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 223 2 1 0 0 ( ) ( ) ( , )ab a b rl rl n n g d       −=  (18) as shown in equation (18), the product of the turns function in winding a and the winding function of winding b is used to multiply the inverse air gap function r . note the inverse air gap function is plotted for an arbitrary value 0 2r   . 2.2 machine description a three-phase synchronous reluctance machine with a traditional dumbbell salient pole rotor, having a p number of poles and three-phase windings ‘abc’ will be modelled using analytical expressions representing the air gap and the windings. the number of poles p is the same as the number of poles on the rotor (figure 2), with dimensions presented in table 1. d-axis q-axis g1 a+ ab+ bc+ cd-axis figure 2: three-phase four-pole synchronous reluctance machine table 1. machine dimensions of the synrm extrapolated from obe, (2009) machine dimensions values stator outer radius 105.2mm stator inner radius 67.99mm rotor radius 67.69mm effective stack length 160.22 airgap length at pole face, g1 0.4mm airgap length between poles, g2 21.3mm stator slot depth 18mm ratio of pole arc to pole pitch 2/3 number of pole pairs 2 winding connection y number of winding layers 1 distributed winding concentrated winding number of slots 36 12 number of turns 32 96 stator slot pitch 10° 30° http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 224 the study considered two machine models: (a) a proposed 12-slot full-pitch single-layer concentrated winding and (b) a proposed 36-slot full-pitch single-layer distributed winding, with dimensions shown in table 1. figure 3 depicts the winding clock diagrams. a traditional dumbbell rotor with damper windings was used. figure 3: winding clock diagrams of (a) concentrated winding synrm (b) distributed winding synrm 2.3 stator winding function the determination of machine inductances is crucial as it defines the behaviour of the synrm since it influences the reluctance torque of the synrm, using the expression for the calculation of stator self and mutual inductances presented in equations (17) and (18). using fourier series, the winding expression of an arbitrary phase a, of an m-phase machine with pp pole pairs can be written as 1,3,5,... 4 2 ( ) cos ( )t wn a p n p p n k n p n p n mp       = = − (19) where, k= 0, 1,2, for phases a, b, and c respectively, showing the phase shift of the various phases, nt is the number of turns per pole per phase, pp is the number of pole pairs, n is the harmonic order, m is the number of phases,  is the stator circumferential position and kwn is the winding factor for the nth harmonic as seen in obe (2010). according to obe and binder (2011), for the actual winding function model, the stator winding expression an of an arbitrary phase a, at the kth data point is shown in equation (20). 1 ( ) ( ) ( ) n a k a a n k n k n k n == −  (20) where, ( )an k is the turns function. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 225 2.4 airgap winding function the airgap expression in equations (17) and (18) is dependent on the nature of the rotor geometry. as stated earlier, the rotor used in this machine is the traditional dumbbell rotor. in the sinusoidal model, the air gap will be modelled using the fourier series as presented in equation (21) 1 2 1 2 1 1 2 1 ( , ) ( ) ( ) sin cos 2 ( )r c c c p r n g k g k g g k g g n p n n         = = + − + −  − (21) where 1g and 2g are the airgap at the pole face and between poles,  is the pole arc to pole pitch ratio, ck is the carter coefficient, accounting for slot openings, r is the angular position of the rotor and  is the stator circumferential position. the actual airgap of the synchronous reluctance machine having a traditional dumbbell rotor, with all harmonics included was modelled the same way as presented in obe (2009). 2.5 rotor cage winding function the stator-to-rotor mutual inductances were determined using equation (18), but the rotor cage winding expression in the rotor reference frame will be used. the fundamental (sinusoidal d-q) components of the d-axis and q-axis rotor winding expression derived from lipo (2012), are shown in equations (22) and (23) 𝑁𝑑𝑟(𝜑, 𝜃𝑟) = 2 𝜋 [𝑛𝑚 + 2sin2 𝛾 2 − sin(𝑛𝑚𝛾)cos(𝑛𝑝𝛾) sin𝛾 ] sin𝜉 (22) 𝑁𝑞𝑟(𝜑, 𝜃𝑟) = 8 𝜋 [𝑛𝑚 − cos(𝛾 𝑛𝑏−1 2 )sin(𝑛𝑚𝛾) sin𝛾 ] sin2 𝛾 2 cos𝜉 (23) where 𝑛𝑚 = 1 2(𝑛𝑏 − 2)⁄ , 𝑛𝑝 = 1 2(𝑛𝑏 + 2)⁄ , nb is the number of rotor bars per pole, γ is an angle known as the rotor slot span and 𝜉 = (𝜑 − 𝜃𝑟). the actual rotor winding expression is presented in equations (24) and (25) as seen in (lipo, 2017) 𝑁𝑑𝑟(𝜙) = 4 𝜋 sin2 ( 𝛾 2 ) + 4 𝜋 sin2 ( 3𝛾 2 ) + 4 𝜋 sin2 ( 5𝛾 2 ) (24) 𝑁𝑞𝑟(𝜙) = 4 𝜋 [cos 𝛾 2 − cos 3𝛾 2 ] 2 + 4 𝜋 [cos 3𝛾 2 − cos 5𝛾 2 ] 2 (25) 2.6 inductance calculation the stator winding functions, the rotor cage winding functions and the airgap functions were used in calculating the stator self and mutual inductances, and also the stator to rotor mutual inductances as presented in equations (17) and (18). the sinusoidal winding function model was used in the combination of sinusoidal winding expression as shown in equation (19), and the airgap function as corrected by carter’s factors http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 226 considering only the second harmonic as shown in equation (21). the actual winding function model used winding expressions from equations (20) and (21) with the inclusion of spatial harmonics. inductance calculations using equations (17) and (18) were achieved using trapezoidal numerical integration in matlab. in the evaluation of equations (17) and (18), the stator slots are held constant and the rotor is moved from 0 to 2π radians. to calculate stator to rotor winding inductances, the rotor winding function is shifted alongside the rotor for each computation point. the stator phase a self-inductance and the phase a and phase b mutual inductance can also be expressed as seen in equations (26) and (27) 1 2 cos 2asas ls rl l l l = + − (26) 1 2 1 cos 2 2 3 asbs rl l l     = − − −    (27) as stated in krause et al. (2013), the magnetizing dand q-axis inductances were given in equations (28) and (29) ( )1 2 3 2 mql l l= − (28) ( )1 2 3 2 mdl l l= + (29) the inductances evaluated along the direct and quadrature axis are presented in equations (30) and (31). d ls mdl l l= + (30) q ls mql l l= + (31) 3. results and discussion the section focuses on the results of the procedural calculation of the inductances of both machine models. since the modelling was done in parts, that is modelling stator windings, rotor windings and the air gap, using the sinusoidal and the actual models it is ideal to show the various results before inductance calculations. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 227 figure 4: phase a winding function of a 36-slot distributed stator winding showing the actual, sinusoidal and the harmonic spectrum the phase a actual (including mmf harmonics) and sinusoidal winding function of the distributed winding configuration, and the harmonic spectra are shown in figure 4. the winding function plot was achieved using equations (19) and (20). figure 5: phase a winding function of a 12-slot concentrated stator winding showing the actual, sinusoidal and the harmonic spectrum the phase a actual (including mmf harmonics) and sinusoidal winding function of the concentrated winding configuration, and the harmonic spectra are shown in figure 5. the winding function plot was also achieved using equations (19) and (20). the concentrated winding configuration was seen to have more mmf harmonics than the distributed winding. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 228 figure 6: inverse airgap function for actual and the sinusoidal considering only the second harmonic the inverse airgap functions for the sinusoidal and the actual model of a synchronous reluctance machine having a 4-pole traditional dumbbell rotor, using the airgap dimensions as seen in table 1 are presented in figure 6. the sinusoidal plot was derived from equation (21), while the actual was done considering the airgap length at the pole face and the interpolar airgap. figure 7: fundamental components of d-axis cage winding expression, showing the actual and the sinusoidal using equations (22) and (24), the d-axis cage winding functions were derived as presented in figure 7. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 229 figure 8: fundamental components of q-axis cage winding expression, showing the actual and sinusoidal while using equations (23) and (25), the q-axis cage winding functions were derived as presented in figure 8. figure 9: self-inductance of distributed stator windings, for phase a the actual and sinusoidal self-inductance of the distributed winding model is presented in figure 9. the plots were achieved using trapezoidal numerical integration of equations (17) and (18) in matlab. figure 10: self-inductance of concentrated stator windings, for phase a http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 230 the actual and sinusoidal self-inductance of the concentrated winding model is presented in figure 10. the plots were also achieved using trapezoidal numerical integration of equations (17) and (18) in matlab. figure 11: mutual inductance between distributed stator winding, for phase a and phase b the actual and sinusoidal mutual inductance for phase a and phase b of the distributed winding model is presented in figure 11. the plots were calculated using trapezoidal numerical integration of equations (17) and (18) in matlab. figure 12: mutual inductance between concentrated stator winding, for phase a and phase b the actual and sinusoidal mutual inductance for phase a and phase b of the concentrated winding model is presented in figure 12 derived from the trapezoidal numerical integration of equations (17) and (18) in matlab. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 231 figure 13: mutual inductance between distributed stator winding, of phase a and d-axis winding in figure 13, the actual and sinusoidal stator to rotor mutual-inductances of the distributed stator winding phase a and the rotor d-axis winding were presented. the plots were calculated using trapezoidal numerical integration of equations (22) and (24) in matlab. figure 14: mutual inductance between distributed stator winding, of phase a and q-axis winding in figure 14, the actual and sinusoidal stator to rotor mutual-inductances of the distributed stator winding phase a and the rotor d-axis winding were presented. the plots were calculated using trapezoidal numerical integration of equations (23) and (25) in matlab. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 232 figure 15: mutual inductance between concentrated stator winding, of phase a and d-axis winding figure 15 shows the actual and sinusoidal stator to rotor mutual-inductances of the concentrated stator winding phase a and the rotor d-axis winding. the plots were calculated using also the trapezoidal numerical integration of equations (22) and (24) in matlab. figure 16: mutual inductance between concentrated stator winding, of phase a and q-axis winding in figure 16, the actual and sinusoidal stator to rotor mutual-inductances of the concentrated stator winding phase a and the rotor d-axis winding were presented. the plots were calculated using trapezoidal numerical integration of equations (23) and (25) in matlab. the magnetizing d-axis and q-axis inductances of the distributed and concentrated winding synrm models were calculated from the self-inductance plots in figures 9 and 10 and the results are shown in table 2. the inductance coefficients l1 and l2 in equations (26) and (27) were derived file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng epemu and nyong-bassey: inductance calculation of concentrated and distributed winding synchronous reluctance motor using modified winding function theory. azojete, 19(2):219-234. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 233 from the self-inductance plots and used to calculate the magnetizing d-axis and q-axis inductances using equations (28) and (29). the direct and quadrature axis inductance were later calculated using equations (30) and (31). the calculated results are presented in table 2 for comparison. table 2. calculated values of dand q-axis inductances, saliency ratio and torque index winding calculated (sinusoidal) calculated (actual) d-axis inductance (ld) q-axis inductance (lq) saliency ratio (ld/lq) torque index (ld-lq) d-axis inductance (ld) d-axis inductance (lq) saliency ratio (ld/lq) torque index (ld-lq) distributed 404.48 mh 131.01 mh 3.09 273.47 350.18 mh 167.18 mh 2.10 183.0 concentrated 449.18 mh 145.18 mh 3.09 304.0 366.28 mh 232.38 mh 1.58 133.9 from table 2, the calculated sinusoidal saliency ratios are the same and the torque indexes were close compared to the actual saliency ratios and torque indexes. the actual saliency ratios were ideal as the distributed winding topology will have a better saliency ratio when compared to that of the concentrated winding. the reason for the better saliency is mainly because of the presence of harmonics in the concentrated windings. 4. conclusion this paper presented a numerical study comparing the inductances of concentrated and distributed winding synchronous reluctance motors (synrms) using two winding function theorybased methods. the actual winding function theory, which accounted for slot opening effects and spatial winding harmonics, was found to be more accurate than the sinusoidal method. the study revealed that the distributed winding topology outperformed the concentrated winding topology, showing a better saliency ratio and torque index. these findings have significant implications for synrm design and optimization. references al-nuaim, na. and toliyat, ha. 1998. a novel method for modelling dynamic air -gap eccentricity in synchronous machines based on modified winding function theory. ieee transactions on energy conversion, 13(2): 156–162. faiz, j. and tabatabaei, i. 2002. extension of winding function theory for nonuniform air gap in electric machinery. ieee transactions on magnetics, 38(6): 3654–3657. gojko, jm., momir, dd. and aleksandar, ob. 1999. skew and linear rise of mmf across slot modelling winding function approach. ieee transactions on energy conversion, 14(3): 315–320. houdouin, g., barakat, g., dakyo, b. and destobbeleer, e. 2003. a winding function theory-based global method for the simulation of faulty induction machines. in proceedings of the ieee international electric machines and drives conference, madison, wi, usa, 1–4 june 2003; no. 1, 297–303. jiang, h., aggarwal, r., weller, g., ball, s. and denning, l. 1999. a new approach to synchronous generator internal fault simulation using combined winding function theory and direct phase quantities. 9th international conference on electrical machines and drives, canterbury, uk, 0301 september 1999. no.468, 105–111. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):219-234. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: epemu.ayebatonye@fupre.edu.ng 234 krause, pc., wasynczuk, o., sudhoff, sd. and pekarek, sd. 2013. analysis of electric machinery and drive systems. wiley, hoboken, new jersey. liang, f., xu, l. and lipo, ta. 1991. dq analysis of a variable speed doubly ac excited reluctance motor. electric machines & power systems, 19(2): 125-138. lipo, ta. 2012. analysis of synchronous machines. taylor & francis group, llc, boca raton, florida. lipo, ta. 2017. introduction to ac machine design. wiley, hoboken, new jersey. obe, es. 2009. direct computation of ac machine inductances based on winding function theory. energy conversion and management, 50(3): 539–542. obe, es. 2010. calculation of inductances and torque of an axially laminated synchronous reluctance motor. iet electric power applications, 4(9): 783-792. obe, es, and binder, a. 2011. direct-phase-variable model of a synchronous reluctance motor including all slot and winding harmonics. energy conversion and management, 52: 284–291. obe, es., nnadi, db., and eke, j. 2009. inductances and airgap flux density of a synchronous reluctance machine using the actual machine geometry. nse technical transactions, 44(1): 29– 40. spargo, cm. 2016. synchronous reluctance technology part-ii. magnews, durham research online, 44(2): 1–6. tabatabaei, i., faiz, j., and lesani, h. 2004. modelling and simulation of a salient-pole synchronous generator using modified winding function theory. ieee transactions on magnetics, 40(3): 1550–1555. toliyat, ha., rahimian, mm., and lipo, ta. 1991. dq modelling of 5 phase reluctance machines including third harmonic ieee conference record of the 1991 ieee industry applications society annual meeting dearborn, mi, usa, 28 september 4 october 1991, 231-237. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology & environment azojete june 2022. vol. 18(2):197-208 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 197 original research article an independent framework for off-grid hybrid renewable energy design using optimal foraging algorithm (ofa) m. m. muhammad1*, j. usman1, i. mustapha1, m. u. m. bakura1 and a. t. salawudeen2 1department of electrical and electronics engineering, university of maiduguri, maiduguri, nigeria 2department of electrical and electronic engineering, university of jos, jos, nigeria *corresponding author’s email address: engr.massa@gmail.com 1.0 introduction electricity is requisite for socio-economic development of every society. unfortunately, subsaharan africa is challenged with different electrification problem. one of the popular technologies which have been widely adopted to improve the electrical energy demand has been based on renewable energy resources especially in remote areas where power generated cannot be supplied to such communities due to difficulties in the transmission and distribution systems (njoh et al., 2019). renewable energy generation have identified solution to these problems and as an effective source of energy in such areas. the off-grid mode of energy generation does not article information abstract the rapidly increase in electrical energy demand from residential, commercial and industrial sectors is one of the major challenge in power system, especially in the current period of high oil prices, steadily reducing energy sources and increased concerns about environmental pollution. renewable energy is considered as one of the solution to this increase in power demand. the conventional method of power system cannot meet the power demand for many reasons such as environmental effects, location of the consumer, price of fuel and others. this paper presents the design of an off-grid hybrid renewable energy system (hres) for electrification of a typical remote area. the designed hybrid system consists of three different configurations of pv/battery, wind/battery and pv/wind/battery systems. the system components are modelled and the objective function is designed as a function of total annualized cost of the system subject to some constraints binding the decision variables. the total annual cost is formulated as a function of annual capital cost and annual maintenance cost of the system subject to some operational constraints. in order to determine the optimal number of the decision variables that would satisfy the load demand in the most cost effect manner, optimal foraging optimization (ofa) algorithm was used. finally, a simulation experiment shows that the total annual cost obtained by each algorithm for the pv/battery system is $9,340.42 or n3,876,274.30, $9,446.77 or n3,920,409.55 and $10,076.34 or n4,181,681.1 for ofa, ga and pso respectively. for the wind/battery configuration, the total annual cost obtained by ofa, ga and pso are $17,508.20 or n7,265,903, $12,493.27 or n 5,184,707.05 and $16,535.93 or n6,862,410.95 respectively. similarly, the pv/wind/battery configuration showed that the ofa, ga and pso obtained an annualized cost of $15,926.07 or n6,609,319.05, $18,167.09 or n7,539,342.35 and $16,535.93 or n6,862,410,95 respectively. from the results obtained by ofa are compared with that of genetic algorithm (ga) and particle swarm optimization (pso) algorithm. results showed that all the algorithm can efficiently size the hybrid system with ofa obtaining the most economical design. therefore, for economically and efficiently electrification of a remote area in abuja using an off-grid hybrid renewable energy system, ga optimization algorithm is recommended for wind/battery system and ofa optimization algorithm is recommended for pv/wind/battery system. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 august, 2021 revised 21 october, 2021 accepted 30 october, 2021 keywords: optimal foraging algorithm (ofa) stand-alone hybrid energy system optimal sizing total annual cost micro-grid http://www.azojete.com.ng/ mailto:engr.massa@gmail.com mailto:engr.massa@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):197-208. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 198 require complex interconnections of power systems generation equipment like the main grid. one of the major challenges which have hinder harnessing renewable energy to full capacity is the weather conditions. the total dependency of wind and solar energy on weather and climatic conditions has been a major drawback in total harvesting their energy to full capacity (ogunjuyigbe et al., 2016) . the energy generated from the individual sources may not be sufficient for a considerable amount of time. to address these challenges several researches have proposed hybridizing different renewable energy sources to compensate for energy shortage that arise from individual sources. to efficiently and economically utilize the hybrid energy systems, a proper sizing mechanism is important (ogunjuyigbe et al., 2019). several studies related to the optimal sizing of stand-alone hybrid energy systems have been conducted in the literature. dong et al. (2016) reported an improved ant colony optimization (aco) algorithm for optimizing a multi-objective stand-alone hybrid pv/wind/battery/hydrogen system with major focus on reliability and economy of supply. the loss of power supply and total annual cost were modelled as a dual objective function which the aco was used to minimize. an optimized hybrid renewable energy system of pv/wind/battery for electrification of a remote area in iran using particle swarm optimization technique was proposed in (askarzadeh, 2015).the particles of pso probe the search space to minimize the life cycle cost (lcc), at the same time maintaining a reliable system. in (kanase-patil et al., 2010) lingo software was used to analyzed integrated renewable energy systems for off-grid rural electrification of remote area in india. the optimal system cost, reliability and cost of energy were evaluated for four different renewable energy technologies which include biomass, micro hydro, solar and wind. in maleki et al. (2014), a discrete harmony search (dhs) optimization algorithm was used to optimally size an off-grid of pv/wind/diesel system with battery storage. for performance evaluation, the results of dhs are compared with results found by a discrete simulated annealing (dsa) algorithm. the proposed methods minimize the total annual cost (ct) of the off-grid system effectively. although various aspects of hres system have been studied, useful and interesting model and efficient optimization tool for optimal sizing is still a major challenge for researchers. in this regard, this paper presents an efficient sizing technique for optimal sizing of off grid hybrid renewable energy system using optimal foraging algorithm (ofa). the hres model is designed to incorporate photovoltaic system, wind energy and energy storage. different configurations including pv/battery, wind/battery and pv/wind/battery were considered to analyze the effectiveness of ofa in solving the hres problem. each configuration of hres system is optimization considering total annualize cost as a metric. for performance evaluation the results of ofa are compared with that of found by particle swarm optimization and genetic algorithm. the outline of this paper is organized as follows: the modelling of the hybrid energy system is given in section 2. section 3 presents the hybrid renewable energy optimization problem formulation. section 4, present the optimal foraging algorithm (ofa). section 5 gives the simulation results. finally, a conclusion for this work is stated in section 6. 2. materials and methods the hybrid energy system is made up of photovoltaic modules and wind turbines (wts) as renewable energy sources and battery bank for excessing energy storage. the battery bank helps to maintain constant power supply when the power generated by the renewable energy sources is less than the power demand. if the power generated by the renewable energy sources is higher than the load demand, then excess energy is stored in the battery bank. the schematic representation of the hybrid renewable energy system is shown in figure 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engr.massa@gmail.com muhammad et al: an independent framework for off-grid hybrid renewable energy design using optimal foraging algorithm (ofa). azojete, 18(2):197-208. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 199 figure 1. schematic description of the pv/wind/battery based hybrid system (gil mena et al., 2021). 2.1 modelling a brief modelling of the hybrid system which consist of pv modules, the wind turbines, the battery storage as being used in the algorithm is as presented. 2.1.1 photovoltaic system the output power of every pv system (𝑃𝑃𝑉) at time step t can be calculated from the solar radiation using: ( ) ( )pv pvp t i t a    (1) where i is the solar radiation (w/m2), a symbolizes the area of pv (m2) and ƞ𝑃𝑉 is the efficiency of the pv’s modules. it is assumed that the pv panels is embedded with maximum power point tracking (mppt) system. 2.1.2 wind turbine low speed winds usually don’t have sufficient power to subdue friction of the wind turbine. therefore, at wind speed less than the cut-in wind speed (𝑉𝑐𝑖) no power is generated. with increase in velocity greater than the cut-in wind speed, the power generated by the wind turbine generator rises as the cube of wind speed. as the wind speed increase continuously, up to the rated value say (𝑉𝑟), the generator produces as much power it is designed for say (𝑃𝑟) in kw. at a certain level, when the wind speed is so high it becomes a threat to the wind turbine. at this wind speed, named the cut-out wind speed (𝑉𝑐𝑜), the wind turbine needs to be shut down to prevent it from damaging (maleki et al., 2016). hence, the output power is zero. mathematically, this behavior can be expressed as follows: 𝑃𝑊𝑇(𝑡) = { 0 𝑃𝑟 𝑃𝑟 𝑣3(𝑡)−𝑉𝑐𝑖 3 𝑉𝑟 3−𝑉𝑐𝑖 3 𝑣(𝑡) ≤ 𝑉𝑐𝑖 𝑜𝑟 𝑣(𝑡) ≥ 𝑉𝑐𝑜 𝑉𝑐𝑖 < 𝑣(𝑡) < 𝑉𝑟 𝑉𝑟 < 𝑣(𝑡) < 𝑉𝑐𝑜 (2) http://www.azojete.com.ng/ mailto:engr.massa@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):197-208. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 200 where 𝑣(𝑡) is the wind speed in m/s at time t. the rated power of the wind turbine generator (𝑃𝑟) is defined as a function of the air density (𝜌𝑎 ), the swept rotor area occupied by the rotating wind turbine blades (𝐴𝑤 ), the power coefficient (𝐶𝑝) and the wind turbine generator efficiency (ƞ𝑔) as follows: 31 2 r a w p g rp a c v       (3) 2.1.4 battery the battery is used to store the excess generated power by the renewable resources and also cut power mismatch between generation and load demand. state of charge (𝑆𝑂𝐶) of battery in accordance with productivity and consumption period can be obtained when the total output power of the hybrid system is greater than the load demand, 𝑒𝑃𝑉(𝑡) + 𝑒𝑊𝑇(𝑡) > 𝐸𝐿𝑜𝑎𝑑(𝑡), the charge quantity of the battery at time t can be written as (maleki et al., 2014): ( ) ( ) ( 1) (1 ) [ (t) ( )) ]load bc inv e t ebat t ebat t epv ewt t           (4) where 𝑒𝐵𝑎𝑡(𝑡) and 𝑒𝐵𝑎𝑡(𝑡 − 1) are the charge quantities of the battery bank at time 𝑡 and 𝑡 − 1, σ is the hourly self-discharge rate, ƞ𝐼𝑛𝑣 is the inverter efficiency, 𝐸𝐿𝑜𝑎𝑑(𝑡) is the load demand for a particular hour and ƞ𝐵𝐶 is the charge efficiency of the battery bank. when the total output power of hybrid system is less than the load demand, 𝑒𝑃𝑉(𝑡) + 𝑒𝑊𝑇(𝑡) < 𝐸𝐿𝑜𝑎𝑑(𝑡), the battery bank is in discharging state. the charge quantity of the battery at time t can be obtained as: ( ) ( ) ( 1) (1 ) ( ) ( ))load inv e t ebat t ebat t epv t ewt t              (5) where ƞ𝐵𝐷 is the discharging efficiency of the battery bank which ranges from 0-100%. in this research, the value is assumed to be 100%. 2.1.5 load profile the load profile defines the requirements of power supply from the off-grid pv/wind hybrid energy system. the hourly load profile for a residential building collected through questioner (figure 2). the study of the load profile reveal that the households wake up in the morning to prepare for business, work and school (more electricity is needed to prepare for hot showers and breakfast). people then leave for business, work and school typically at 7:00hr and close by 18:00hr on weekdays. at around this time, most households switch on lighting points, fans, prepare for dinner and watch tv up to around 22:00hr before bed time. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engr.massa@gmail.com muhammad et al: an independent framework for off-grid hybrid renewable energy design using optimal foraging algorithm (ofa). azojete, 18(2):197-208. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 201 figure 2. hourly load profile 3. problem formulation 3.1 objective function the optimization problem is to minimize the total annual cost ( )tac of system. the tac consists of annual capital cost ( )acc and annual maintenance cost ( )amc . to optimally size the stand-alone hybrid energy system, the following cost function is minimized using optimal foraging algorithm (ofa). (kellogg et al., 1998). ac amtac c c  (6) capital cost take place at the starting of a project while maintenance cost take place during project life. to transform the initial capital cost to the annual capital cost, the capital recovery factor (𝐶𝑅𝐹) is expressed by equation (7). (belfkira et al., 2014). (1 ) (1 ) 1 n n i i crf i     (7) where, 𝑛 denotes the life span of the system and 𝑖 is the interest rate. the duration of the proposed hybrid energy system is assigned to be 20 years. some of the hybrid system components is expected to be changed during the project’s lifetime. the lifetime of a battery is assumed to be 5 years. using single payment present worth factor, we have (eltamaly et al., 2016): 0,5,10,15 1 (1 ) bat bat k k c p i     (8) where 𝐶𝐵𝑎𝑡 is the present worth of battery and 𝑃𝐵𝑎𝑡 is the battery price. similarly, the duration of converters is assumed to be 10 years. we can calculate the converter cost as 0,10 1 (1 ) conv conv k k c p i     (9) where 𝐶𝐶𝑜𝑛𝑣/𝐼𝑛𝑣 is the present worth of converter/inverter components and 𝑃𝐶𝑜𝑛𝑣/𝐼𝑛𝑣 is converter/inverter price. http://www.azojete.com.ng/ mailto:engr.massa@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):197-208. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 202 thus, the total annual capital and maintenance cost are obtained by equations (10) and (11) relatively. ac pv wt bat convc crf npv c nwt c nbat c nconv c           (10) where 𝑛𝑃𝑉 is the number of pv panels, 𝐶𝑃𝑉 is unit cost of pv panel, 𝑛𝑊𝑇 is the number of wind turbines, 𝐶𝑊𝑇 is the unit cost of wind turbine, 𝑛𝐵𝑎𝑡 is the number of batteries and 𝑛𝐶𝑜𝑛𝑣 is the number of converter/inverter systems. am pv mtn pv wt mtn wtc c n c n     (11) where 𝐶𝑃𝑉−𝑀𝑡𝑛 and 𝐶𝑊𝑇−𝑀𝑡𝑛 are the annual maintenance cost of pv panel and wind turbine respectively. the maintenance costs of battery and converter/inverter systems are ignored. 3.2 constraints for the stand-alone pv/wind/storage energy system, the following decision variable constraints should be satisfied: min max ,npv npv npv npv integer   (12) min max ,nwt nwt nwt nwt integer   (13) min max ,nbat nbat nbat nbat integer   (14) where 𝑛𝑃𝑉𝑚𝑎𝑥, 𝑛𝑊𝑇𝑚𝑎𝑥 and 𝑛𝐵𝑎𝑡𝑚𝑎𝑥 are the upper bound of the pv panels, wind turbines and batteries respectively. then, 𝑛𝑃𝑉𝑚𝑖𝑛, 𝑛𝑊𝑇𝑚𝑖𝑛 and 𝑛𝐵𝑎𝑡𝑚𝑖𝑛 are the lower bound of pv panels, wind turbines and batteries respectively. moreover, at any time, the quantity of charge in the battery bank should satisfy: min max( ) ( ) ( )ebat t ebat t ebat t  the maximum charge quantity of the battery bank 𝑒𝐵𝑎𝑡𝑚𝑎𝑥 takes the value of nominal capacity of battery bank (𝑆𝐵𝑎𝑡𝑡) and the minimum charge quantity of the battery bank 𝐸𝑚𝑖𝑛 is obtained by maximum depth of discharge (𝐷𝑂𝐷). min (1 ) battebat dod s   (15) 4. optimal foraging algorithm (ofa) the ofa is a metaheuristic algorithm developed from the idea of optimal foraging theory (oft). optimal foraging theory is a concept that described the dietary patterns of biology organisms towards food (salawudeen et al., 2018, mu'azu et al., 2018) . when a biological organism searches for food, three important questions must be considered. these questions are: i. where is best suitable to search for food? ii. at what point/time should a new source of food be searched? and iii. what kind of food sources should be exploited? organisms employ these three rules to maximize the net energy acquired during foraging process. this concept was used to develop the ofa by zhu and zhang. (ahmed t s et al., 2020) and (zhu et al., 2017). in ofa, individual foragers select areas to forage using a certain rule. after foraging a new search space, the individual foragers decide whether the food energy in this area is beneficial or not. other foragers are attracted to the new area if the food energy is valuable thus increasing the diversification of the algorithm. now, assume there are n individual foragers in a group foraging in d-dimensional search space. the initial positions of the foragers ,1 ,2 ,[ , ,..., ]t t t t i i i n dx x x x can be generated as (zhang et al., 2017, zhu et al., 2017 and salawudeen et al., 2021): file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engr.massa@gmail.com muhammad et al: an independent framework for off-grid hybrid renewable energy design using optimal foraging algorithm (ofa). azojete, 18(2):197-208. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 203  1 t l u l i i i ix x r x x    (16) the objective function of this initial position is computed as  ( ) min ( ), , 1,2,3,...,t l t u i x r i i if x f x r x x x i d     (17) where r is the constrain space, l ix and u ix are the lower and upper bound values, 1r is a random number generated within the range of 0 and 1. as the foragers in ofa iterate during the optimization process, the best foragers in the group forage using 1 2 3( ) ( )t t t t t t i i i worst i worstx x k r x x k r x x          (18) the remaining individual in the foraging group forage using 1 3 5( ) ( )t t t t t t i i random i random ix x k r x x k r x x          (19) where k is defined as max/k t t , t is the current iterations, tmax is the maximum iteration number, r2, r3, r4 and r5 are all randomly generated number. in ofa, the position of foragers obtained after t iterations is regarded as unprofitable position, and the corresponding fitness is regarded as unprofitable fitness ( t jf ). similarly, the positions of foragers after iteration t+1 is regarded profitable prey location and the corresponding fitness can be represented as 1t jf  . based on this information, the positions of current foragers are updated if the following equation is satisfied (eltamaly et al., 2016) and (zhang et al., 2017). 1 1 11 ( 1) t t t i j j t i f f tt           (20) where  is a random number. if the above equation (22) is not satisfied the previous position of the foragers are retained 5. results and discussion this section discourses the results of the hybrid renewable energy system obtained by the optimal foraging algorithm in comparison with genetic algorithm and particle swarm optimization. the hybrid system design was implemented in matlab r2020b simulation platform. as input, the model employed data of wind speed and solar irradiance measured in in abuja, nigeria (latitude: 9.08200 n, longitude: 8.67530 e). the hybrid resources component parameters have been given in table 1. the parameter settings of the ofa, ga and pso are as follows. ofa: 𝑘 = 𝑖𝑡𝑒𝑟/𝑖𝑡𝑒𝑟𝑚𝑎𝑥 𝑁 = 50, 𝑖𝑡𝑒𝑟𝑚𝑎𝑥 = 30,000, pso: 𝑁 = 50, 𝑐1 = 2, 𝑐2 = 2, 𝜔 = 1, 𝑖𝑡𝑒𝑟𝑚𝑎𝑥 = 300,000; ga: 𝑁 = 50, 𝑖𝑡𝑒𝑟𝑚𝑎𝑥 = 300,00. the lower and upper bounds of the decision variables were set to 0 and 300 respectively. at the initial stage, it is assumed that the battery is charged at 30% of its nominal capacity. the average (avg), best (best) and standard deviation (std) performed over 30 independent runs are summarized in table 2. http://www.azojete.com.ng/ mailto:engr.massa@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):197-208. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 204 table 1: component parameters parameters value parameters value parameters value i n pv panel rated power a ƞpv cpv cpv-mtn life span power conv/inv rated power inv /conv invp life span 5% 20years 260 w 1.656m2 15.7% 585 $ 21 $ 20 years 3 kw 95% 2000 $ 10years diesel generator pdr cdiesel cdiesel-mtn life span pfuel wind turbine rated power (pr) civ cov rv wtc cwt-mtn life span 1.9 kw 1713.15$ 0.2 $/h 8760 h 1.24 $/l 1 kw 2.5 m s 13m s 11m s 2313$ 40$ 20 years battery voltage sbatt ƞbc ƞbd pbatt dod σ life span 12 v 2.4kwh 85% 100% 170 $ 0.8 0.0002 5 years table 2. the mean, standard deviation, best and worst performances of the algorithms hres index algorithms ofa ga pso pv/wind/battery pv/battery wind/battery average rank final rank mean std best worst rank mean std best worst rank mean std best worst rank 17,957.19 2,601.833 15,926.07 21,765.71 1 10,601.46 1,274.94 9,340,42.00 11,223.17 1 18,527.51 1,492.00 17,508.20 19,759.55 3 2.5 1 18,720.07 543.67 18,167.09 19,331.17 3 10,601.46 1224.256 9,446.77 10,601.46 2 13,527.51 705.512 12,493.27 13,527.51 1 3 2 17,549.15 1,066.27 16,535.93 18,948.22 2 10,178.25 102.47 10,076.34 10,319.43 3 17,745.15 933.5633 16,535.93 18,075.15 2 3.5 3 the breakdown of the statistical results obtained by the algorithms on each sizing component is presented in table 2. from this table, the algorithms are ranked based on the best results obtained for each configuration. it can be observed that the ofa obtained the best final rank with a rank of 1. whereas the ga and pso obtained a rank of 2 and 3 respectively. this shows that, for the hybrid system design in this paper, the ofa appears to be the suitable algorithm for obtaining the most economical system. this further justifies the acceptability of the algorithms in solving the hres problem, the characteristics of the algorithms were generated. the superimposed convergence graph of the algorithms on each hybrid system configuration is given in figure 3, figure 4 and figure 5 for pv/battery, wind/battery and pv/wind/battery, respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engr.massa@gmail.com muhammad et al: an independent framework for off-grid hybrid renewable energy design using optimal foraging algorithm (ofa). azojete, 18(2):197-208. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 205 it is seen from tables 3-5, that economically the pv/battery configuration obtained the best annualized cost for supplying the load demand. the total annual cost obtained by each algorithm for the pv/battery system is $9,340,42, $9,446.77 and $10,076.34 for ofa, ga and pso respectively. for the wind/battery configuration, the total annual cost obtained by ofa, ga and pso are $17,508.20, $12,493.27 and $16,535.93 respectively. similarly, the pv/wind/battery configuration showed that the ofa, ga and pso obtained an annualized cost of $15,926.07, $18,167.09 and $16,535.93 respectively. the optimal size of the hybrid resources obtained by the ofa are as follows. pv/batter: npv = 102, nbat = 35, wind/battery: nwt = 101, nbat = 99 and pv/wind/battery: npv = 125, nwt = 18, nbat = 115. the cost of other components has also been given in the table. table 3. summary of the best results obtained for pv/battery system hres ofa ga pso npv nwt nbatt nconv/inv pv cost ($) wt cost ($) battery cost ($) conv/inv cost ($) total annual cost ($) 102 - 35 4 6,930.07 - 1,374.00 1,036.04 9,340,42 66 - 100 4 4,484.17 - 3,926.57 1,036.04 9,446.77 77 - 97 4 5,231.52 - 3,808.78 1,036.04 10,076.34 table 4. summary of the best results obtained for wind/battery system hres ofa ga pso npv nwt nbatt nconv/inv pv cost ($) wt cost ($) battery cost ($) conv/inv cost ($) total annual cost ($) - 101 99 3 - 11,988.00 4,673.20 847.51 17,508.20 - 77 115 3 - 6,941.67 4,515.56 1,036.04 12,493.27 - 75 102 3 - 6,761.37 4,005.10 1,036.04 11,802.51 table 5. summary of the best results obtained for pv/wind/battery system hres ofa ga pso npv nwt nbatt nconv/inv pv cost ($) wt cost ($) battery cost ($) conv/inv cost ($) total annual cost ($) 125 18 115 5 8,492.74 1,622.73 4,515.56 1,295.05 15,926.07 25 140 65 5 1,698.55 12,621.23 2,552.27 1,295.05 18,167.09 39 107 75 5 2,649.73 9,646.22 2,944.93 1,295.05 16,535.93 http://www.azojete.com.ng/ mailto:engr.massa@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):197-208. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 206 figure 3: convergence on pv/battery configuration figure 4: convergence on wind/battery configuration figure 5: convergence on pv/wind/battery configuration from the convergence plots given in figures 3 to 5, it can be observed that the ofa converges faster in wind/battery and pv/wind battery configurations. for the pv/battery configuration, only ga has a better convergence over ofa. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engr.massa@gmail.com muhammad et al: an independent framework for off-grid hybrid renewable energy design using optimal foraging algorithm (ofa). azojete, 18(2):197-208. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 207 6. conclusion this paper presents an off-grid hybrid renewable energy system for electrification of a remote area in abuja, nigeria. the hybrid system was formulated into an optimization problem where the annualized cost serves as the objective function to be minimized. the optimization problem was solved using optimal foraging optimization algorithm and results was compared with genetic algorithm and particle swarm optimization. results analysis showed that the optimal foraging algorithm obtain the best result in terms of the objective function cost and convergence analysis. references askarzadeh, a. and dos santos coelho, l. (2015. a novel framework for optimization of a grid independent hybrid renewable energy system: a case study of iran. solar energy, 112: 383-396. belfkira, r., nichita, c., reghem, p. and barakat, g. 2008. modeling and optimal sizing of hybrid renewable energy system. proceedings of the 13th international power electronics and motion control conference., 1-3 september 2008, poznan, poland, pp. 1834-1839. dong, w., li, y. and xiang, j. 2016. optimal sizing of a stand-alone hybrid power system based on battery/hydrogen with an improved ant colony optimization. energies, 9(10): 785. eltamaly, am., mohamed, ma. and alolah, ai. 2016. a novel smart grid theory for optimal sizing of hybrid renewable energy systems. solar energy, 124: 26-38. gil mena, aj., bouakkaz, a. and haddad, s. 2021. online load-scheduling strategy and sizing optimization for a stand-alone hybrid system. journal of energy engineering, 147(1): 04020078. kanase-patil, a., saini, r. and sharma, m. 2010. integrated renewable energy systems for off grid rural electrification of remote area. renewable energy, 35(6): 1342-1349. kellogg, w., nehrir, m., venkataramanan, g. and gerez, v. 1998. generation unit sizing and cost analysis for stand-alone wind, photovoltaic, and hybrid wind/pv systems. ieee transactions on energy conversion, 13(1): 70-75. maleki, a. and askarzadeh, a. 2014. optimal sizing of a pv/wind/diesel system with battery storage for electrification to an off-grid remote region: a case study of rafsanjan, iran. sustainable energy technologies and assessments, 7: 147-153. maleki, a., khajeh, mg. and ameri, m. 2016. optimal sizing of a grid independent hybrid renewable energy system incorporating resource uncertainty, and load uncertainty. international journal of electrical power & energy systems, 83: 514-524. njoh, aj., etta, s., ngyah-etchutambe, ib., enomah, le., tabrey, ht. and essia, u. 2019. opportunities and challenges to rural renewable energy projects in africa: lessons from the esaghem village, cameroon solar electrification project. renewable energy, 131, 1013-1021. ogunjuyigbe, a., ayodele, t. and akinola, o. 2016. optimal allocation and sizing of pv/wind/split diesel/battery hybrid energy system for minimizing life cycle cost, carbon emission and dump energy of remote residential building. applied energy, 171: 153-171. salawudeen, a., mu’azu, m., sha’aban, y. and adedokun, e. 2018. on the development of a novel smell agent optimization (sao) for optimization problems. proceedings of the 2nd international conference on information and communication technology and its applications (icta 2018), held on 5-6 september at minna, nigeria., pp. 287-297. http://www.azojete.com.ng/ mailto:engr.massa@gmail.com arid zone journal of engineering, technology and environment, june, 2022; vol. 18(2):197-208. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.massa@gmail.com 208 salawudeen, at., mu’azu, mb., yusuf, a. and adedokun, ae. 2021. a novel smell agent optimization (sao): an extensive cec study and engineering application. knowledge-based systems, 107486. salawudeen, at., mu’azu, mb., yusuf, a. and adedokun, ea. 2018. from smell phenomenon to smell agent optimization (sao): a feasibility study. proceedings of icget held on 2-4 may, at abuja, nigeria., pp 8. yu, j., ryu, j-h. and lee, i-b. 2019. a stochastic optimization approach to the design and operation planning of a hybrid renewable energy system. applied energy, 247: 212-220. zhang, w-b. and zhu, g-y. 2017. drilling path optimization by optimal foraging algorithm. ieee transactions on industrial informatics, 14(7): 2847-2856. zhu, g-y. and zhang, w-b. 2017. optimal foraging algorithm for global optimization. applied soft computing, 51: 294-313. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:engr.massa@gmail.com arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):357-376 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 345 original research article geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, north-central, nigeria o. a. omali* and j. t. arogundade department of earth sciences, kogi state university anyigba, nigeria *corresponding author’s email address: omaliaurelius@yahoo.com 1.0 introduction the importance of water as a basic resource for human activities cannot be over-emphasized. it is needed for cooking, washing, cleaning, construction activities, manufacturing etc. the qualitative and quantitative assessments of its sources are therefore necessary to ensure its availability in the study area. lokoja has witnessed an upsurge in human and infrastructural growth since it became the capital of kogi state in 1991. the demand for potable water supply for various needs has grown significantly. the state water board is currently supplying about 2.7 million gallons of water per day to lokoja and its environs as against the 10 million gallons needed per day (omali, 2012). successive governments in kogi state, the united nation children emergency fund (unicef), water and environmental sanitation (wes) and private developers have provided a number of boreholes to augment the water supply in the area. the major source of water for domestic and industrial uses in the study area is groundwater. the methods of exploration are grouped into surface geological, subsurface geological, surface geophysical and subsurface geophysical methods. the techniques of water resources evaluation require an understanding of the concept of groundwater yield, the quantity and quality of article information abstract this research is aimed at delineating the groundwater potential in lokoja and environs using dar zarrouk parameters. the study area is part of the basement complex of south-western nigeria and the lokoja sub-basin of the middle niger sedimentary basin, on area coverage of about 400km2. thirty-five (35) vertical electric soundings (ves) using schlumberger array method with the aid of abem signal averaging system (sas) terrameter were used for the data acquisition. the result of the interpretation shows four geo-electric layers. the resistivity soundings results revealed that about 4 curve types were identified in the study area namely aa, ha, a and h type with the lithologic layers varying from 3 to 4 and consisting of varying resistivity and thicknesses across each ves point. the geo-electric sections revealed that the major aquifer systems in the study area are weathered basement and weathered/fractured basement. the longitudinal conductance computed that range from 0.00904951 to 0.7814713 ω-1indicates that the aquifers in the area have poor to moderate protective capacity whereas transverse resistance that range from 24.5841 to 7290.15ω indicates very low groundwater development class. hydraulic conductivity with a range of 0.36757m/day to 56.86754m/day and transmissivity values with a range of 4.4548 to 917.273m2 /day indicate very low to moderate aquifer capable of sustaining moderate communities. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 april, 2021 revised 28 april, 2022 accepted 30 april, 2022 keywords: hydraulic conductivity transmissivity vertical electrical sounding transverse resistance longitudinal conductance http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 358 groundwater in the hydrogeological environment. the method of exploitation of groundwater involves the drilling and installation of pumps and piezometers and abstraction of water from the subsurface. the concept of dar zarrouk parameters can be used to assess the groundwater potential of an aquifer, such that, when the thickness and resistivity of subsurface layer are known, its transverse resistance and longitudinal conductance can be estimated (egbai and iserhienemekeme, 2015; bello et al., 2019). according to egbai and iserhien-emekeme (2015) and bello et al. (2019), the concept of dar zarrouk parameters can be used to assess the groundwater potential of an aquifer, such that, when the thickness and resistivity of subsurface layer are known, its transverse resistance and longitudinal conductance can be estimated. over the years, the dar zarrouk parameters primarily derived from layer resistivity and thickness, have proven to be important in understanding the spatial distribution of aquifer’s hydraulic parameters, assessment of contaminated landfills and subsurface investigation of engineering structures (udoinyang and igoekwu, 2012; okiongbo and oborie, 2015) which can be obtained from surface geo-electric soundings, have proven to be important in understanding the spatial distribution of aquifer hydraulic parameters. dar zarrouk parameters of an aquifer including transverse resistance, reflection coefficient and coefficient of anisotropy can be established with resistivity measurement of an aquifer (heigold et al., 1979; nwosu et al., 2014; kwame et al., 2019). nwosu et al. (2014) derived analytical relations between aquifer transmissivity and transverse resistance. in the same vein, kwami et al. (2019) were able to delineate groundwater potential zones in gombe and its environs using dar zarrouk parameters. there are several water boreholes in lokoja metropolis and environs. however, majority of these boreholes are not functioning as expected due to low yield and poor maintenance. there are several boreholes scattered throughout the lokoja metropolis and environs however, majority of these boreholes are not functioning as expected due to low yield and poor maintenance. some of the physical properties of an aquifer such as hydraulic conductivity and transmissivity that control the flow and yield of groundwater can be adequately estimated using dar zarrouk parameters (bello et al., 2019). the aim of this work therefore, is to use dar zarrouk parameters to assess the groundwater potential of the aquifers and ascertain aquifers of good yield and productivity in the basement complex rock of lokoja metropolis. 1. study area the area is located between latitudes 7o 441 3311n and 7o 521n and longitudes 6o 381 611e and 60 481e. it lies on part of the basement complex of south-western nigeria and the lokoja subbasin of the middle niger sedimentary basin, on area coverage of about 400 km2 as shown in figure 1. the major settlements in the area include lokoja, adankolo, lokongoma, kabawa, ganaja, zangodaji, sarkin noma and felele. the study area is accessible through a trunk “a” road from abuja to lokoja and okene to lokoja and a trunk “b” road from ajaokuta to lokoja. it is also accessible by ferry via the river niger from shintaku. the area is populated by several ethnic groups and it is thus very typical of the middle belt region of nigeria. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 359 figure 1: map of nigeria showing lokoja, the study area 2.1 geology and hydrogeology of the study area the study area falls into two geological domains, viz, the basement complex of south-western nigeria and the lokoja sub-basin of the mid niger-basin. the north-western, western and south-western parts of the study area are predominantly covered by migmatite, whereas the northern part is composed of biotite hornblende gneiss. in addition, the south and southeastern part are dominated by undifferentiated older granite, mainly porphyroblastic granite, granite gneiss with porphyroblastic gneiss while the south also composed of outcrops of fine grained biotite granite. the central portion of the area is made of feldspathic sandstone and siltone. however, thick alluvium deposits trend from the northeast to south of the area along the benue and niger drainage system (figure 2). the study area falls into two geological domains, viz, the basement complex of south-western nigeria and the lokoja sub-basin of the mid niger-basin (abimbola, 1997; akande et al., 2005). the north-western, western and south-western parts of the study area are predominantly covered by migmatite, whereas the northern part is composed of biotite hornblende gneiss. in addition, the south and southeastern part are dominated by undifferentiated older granite, mainly porphyroblastic granite, granite gneiss with porphyroblastic gneiss while the south also composed of outcrops of fine grained biotite granite as shown in figure 2, the central portion of the area is made of feldspathic sandstone and siltone. however, thick alluvium deposits trend from the northeast to south of the area along the benue and niger drainage system (udenzi and osazuwa, 2004). hydrogeologically, the area is drained by river benue and river niger in addition to the meme river, which is a tributary of river niger. groundwater in the study area is recharged by these drainage systems and from meteoric water during rainfall. prolific aquifers are sourced from weathering of the basement rocks and fractures of the rock (omali, 2014). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 360 figure 2: (a) generalized geological map of lokoja area (omada et al., 2015) (b) detailed geological map of the study area (omali, 2014) 3. materials and methods a total of thirty-five (35) vertical electrical soundings (ves) were carried out in this study. terrameter sas 300c was used to carry out the resistivity measurement in the field. schlumberger configuration was adopted with maximum half-current electrode spread (ab/2) of 60m while the half potential electrode separation (mn/2) was maintained between 0.5m and 7.5m. the ves curves were quantitatively interpreted by partial curve matching and computer iteration techniques, using resound, a computer programme based on linear filter theory (zohdy, 1989). the principle of the resistivity method is that electric current is passed into the ground through two outer electrodes, and the resultant potential difference is measured across two inner electrodes that are arranged in a straight line, symmetrically about a centre point the potential difference to the current ratio is displayed by the terrameter as resistance. a geometric factor in meters (m) is calculated as a function of the electrode spacing. the resistance readings obtained from the terrameter is multiplied by this factor to give an apparent resistivity value. the electrode spacing is progressively increased, keeping the centre point of the electrode array fixed. the electrical resistivity survey was carried out to determine aquifer types. 3.1 hydraulic parameters the term dar zarrouk parameters has been used to describe the relationship between the longitudinal unit conductance and transverse resistance. longitudinal conductance (si) =∑ ℎ𝑖/ϼ𝑖𝑖=1 (1) hi = layer thickness measured in meters (m) pi= aquifer resistivity in measured in ohms meter (ῳm) transverse resistance (r) = ∑ ℎ𝑖 ϼ𝑖𝑖=1 (2) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 361 the longitudinal conductance (si) in equation (1) is a measure of the impermeability of a rock layer (billing, 1972; mbonu et al., 1991). transmissivity (tr) = k.hi (3) tr is measured in meter square per day (m2day) k is the hydraulic conductivity measured in metes per day (m/day) hi is the layer thickness of the aquifer measured in meters (m) hydraulic conductivity (k) = 386.40rrw -0.93283 (4) rrw is the layer resistivity measured in ohms meter an n-layer dz curve is composed of n branches, each of which terminates at a point whose coordinates, lm and pm, represent the thickness and resistivity of a fictitious layer that replaces all the overlying layers. according to eqns. (3) and (4), the coordinates of any given point on a dz curve are a function of the thicknesses and resistivity of layers that exist above a given depth, d, but they are not related to the thicknesses and resistivity of layers beneath that depth. in contrast, on a ves (vertical electrical sounding) curve, the coordinates of a given point are calculated from an integral expression (stefanesco et al., 1930) that involves all the thicknesses and resistivity in the section, and, therefore, they are not related to particular depth. the longitudinal conductance (s) is a measure of the impermeability of a rock layer (billing, 1972). electrical anisotropy is a measure of stratified rock which is generally more conductive in the parallel plane than in the perpendicular plane (malick et al., 1973; cihan et al., 2014). for a sequence of horizontal, homogeneous and isotropic layers of resistivity ℯ1 and thickness hi. eqs. (v) and (vi) defined the dar zarrouk parameters (longitudinal conductance s and transverse resistance tr) as follows: equation 1, 2, 3 and 4 are only true for a sequence of horizontal, homogeneous and isotropic layers of resistivity ℯ1 and thickness hi (malick et al., 1973; cihan et al., (2014) and kwami et al., 2019). the methods discussed above were employed to generate vertical electrical sounding data. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 362 4. results the results of the analyses are as presented in tables 1-9 and figures 3-6 table 1: vertical electrical sounding data ves no. location coordinates layer no. resistivity(ohm-m) thickness (m) inferred layer remark 1 ganaja bh1 n 070 4433” e0060 44’ 33” 1 161.45 1.09 topsoil (clay/laterite 2 17.87 10.83 weathered basement(aquifer) aquiferous unit 3 5721.11 competent basement 2 500 unit (bh1) n 070 44’ 56.6" e0060 44’ 24.7” 1 538.83 1.07 topsoil (clay/laterite 2 83.19 12.07 weathered basement(aquifer) aquiferous unit 3 6928.32 competent basement 3 500 unit (bh2) n 070 45’ 24.7” e060 44’ 24.7” 1 190.66 2.76 topsoil (clay/laterite 2 48.35 8.89 weathered basement(aquifer) aquiferous unit 3 1230.23 competent basement 4 200 unit (bh1) n 070 45’ 33.1" e060 44’ 21.1” 1 648.47 2.9 topsoil (clay/laterite 2 18.35 14.34 weathered basement(aquifer) aquiferous unit 3 1298.98 competent basement 5 200 unit (bh2) n 070 45’ 48” e060 44’ 15.5” 1 485 3.87 topsoil (clay/laterite 2 15.57 12.23 weathered basement(aquifer) aquiferous unit 3 7724.31 competent basement 6 phase i (bh1) n 070 47’ 24.7” e 060 43’ 22.3” 1 20 8 topsoil (clay/laterite 2 41.5 7.5 clay/laterite 3 277.6 3.7 weathered basement(aquifer) aquiferous unit 4 491.89 competent basement 7 phase i (bh2) n 070 47’ 29.3” e 060 43’ 33” 1 75 14 topsoil (clay/laterite 2 166.23 3.6 weathered basement(aquifer) aquiferous unit 3 260.4 competent basement 8 phase ii (bh1) n 070 48’ 4.7” e060 41’ 55.2” 1 111.99 3.09 topsoil (clay/laterite 2 6.81 3.61 weathered basement(aquifer) aquiferous unit file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 363 ves no. location coordinates layer no. resistivity(ohm-m) thickness (m) inferred layer remark 3 1109.59 competent basement 9 phase ii (bh2) n 070 47’ 44.3” e 060 42’ 18.6” 1 1092.09 3.25 topsoil (clay/laterite 2 50.44 12.51 weathered basement(aquifer) aquiferous unit 3 4432.72 competent basement 10 otokiti estate (bh) n 070 48’ 18.5” e 060 41’ 7” 1 25.92 2.86 topsoil (clay/laterite 2 7.8 16.13 weathered basement aquiferous unit 3 330.45 competent basement 11 army barrack (bh) n 070 48’ 9.4” e060 40’ 34.5” 1 157.61 9.62 topsoil (clay/laterite 2 55.61 12.54 weathered basement(aquifer) aquiferous unit 3 819.94 competent basement 12 roja table water (bh 1) n 070 48’32.6” e060 38’41.3” 1 144.33 0.6 topsoil (clay/laterite 2 8.48 3.39 weathered basement(aquifer) aquiferous unit 3 2875.1 competent basement 13 zangodaji (bh 2) n 070 48’ 40.6” e 060 38’ 26.1” 1 58 6 topsoil (clay/laterite 2 100.65 7 clay/laterite 3 750.04 5 weathered basement(aquifer) aquiferous unit 4 1930.2 _ competent basement 14 adankolo (bh 1) n 070 47’ 15.6” e 060 44’ 16” 1 79.4 10 topsoil (clay/laterite 2 99.35 4 clay/laterite 3 317.5 3 weathered basement(aquifer) aquiferous unit 4 521.93 competent basement 15 adankolo (bh 2) n 070 47’23.5” e060 44’ 28.6” 1 664 7.8 topsoil (clay/laterite 2 66.84 8.8 clay/laterite 3 316.62 5.7 weathered basement(aquifer aquiferous unit 4 505.53 competent basement 16 adankolo (bh 3) n 070 47’ 21.6” e 060 44’ 17.5” 1 39.7 11.8 topsoil (clay/laterite 2 79.86 6.14 weathered basement(aquifer) aquiferous unit 3 507.56 competent basement 17 adankolo (bh 4) n 070 47’ 33.9” e 060 44’ 29.9” 1 372 15 topsoil (clay/laterite 2 389.49 3.3 clay/laterite 3 469.4 6.7 weathered basement (aquifer) aquiferous unit 4 690.3 competent basement http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 364 ves no. location coordinates layer no. resistivity(ohm-m) thickness (m) inferred layer remark 4 690.3 competent basement 18 marine road (bh) n 070 48’ 7.1” e060 44’ 54.4” 1 79.4 10 topsoil (clay/laterite) 2 198.2 13.5 weathered basement(aquifer) aquiferous unit 3 409.16 competent basement 19 kenwo hotel (hdw) n 070 47’ 50” e060 43’ 55.9” 1 99.35 7.5 weathered basement 2 123 12.2 weathered basement(aquifer) aquiferous unit 3 1734.9 15.7 fractured basement aquiferous unit 4 678 competent basement 20 kasuwa hotel (bh) n 070 48’ 28.9” 1 317.5 3.7 weathered/fractured basement e 060 44’ 55.5” 2 311.2 19 weathered basement(aquifer) aquiferous unit 3 1212.5 11.6 fractured layer aquiferous unit 4 1456 competent basement 21 graj(gra) (hdw) n 070 48’ 24.5” e 060 43’ 44.5” 1 521.93 4.6 topsoil/clay/laterite 2 233.14 5.7 weathered basement(aquifer) aquiferous unit 3 895.8 competent basement 22 new layout (hdw) n 070 48’ 37.8” e 060 44’ 12.7” 1 49.3 1.04 topsoil (clay/laterite) 2 253.7 3.59 clay/laterite 3 547.2 12.03 weathered basement(aquifer) aquiferous unit 4 780.2 competent basement 23 new layout (hdw 2) n 070 48’ 37.2” e 060 44’ 32.8” 1 23 2.1 topsoil (clay/laterite) 2 179.3 3.7 clay/laterite 3 234.1 9.6 weathered basement(aquifer) aquiferous unit 4 1267.8 competent basement 24 megiri (hdw ) n 070 48’ 45.1” e 060 44’ 42.1” 1 56.9 1.8 topsoil (clay/laterite) 2 89.1 3.37 clay/laterite 3 135.7 10.6 weathered basement(aquifer) aquiferous unit 4 230 competent basement 25 kabawa (hdw) n 070 49’ 8.5” e060 44’ 54.7” 1 112.7 2.4 topsoil (clay/laterite) 2 65.8 6.2 clay/laterite 3 124.7 11.8 weathered basement(aquifer) aquiferous unit 4 569.2 competent basement 26 sarkinnoma (hdw) n 070 50’ 31.3” e060 44’ 50” 1 354 7.01 topsoil (clay/laterite) 2 213 13.09 weathered basement(aquifer) aquiferous unit 3 678 competent basement file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 365 ves no. location coordinates layer no. resistivity(ohm-m) thickness (m) inferred layer remark 27 felele (hdw 1) n 070 51’ 6.2” e060 43’ 31.7” 1 301 2.03 topsoil (clay/laterite) 2 226.1 11.2 weathered basement(aquifer) aquiferous unit 3 429.5 competent basement 28 felele (hdw 2) n 070 51’ 15.8” e 060 43’ 21.8” 1 29.4 5.6 topsoil (clay/laterite) 2 79.5 9.17 weathered basement (aquifer) aquiferous unit 3 96.1 competent basement 29 felele (hdw 3) n 070 51’ 6.6” e060 43’24.5” 1 45.8 3.6 topsoil (clay/laterite) 2 67.23 13.6 clay/laterite 3 156.9 7.9 weathered basement(aquifer) aquiferous unit 4 1273.1 competent basement 30 behind secretariat (hdw) n 070 45’ 47” e 060 43’ 32.8” 1 564.6 13 tosoil 2 234.67 10.4 clay/laterite 3 1472.4 12.4 weathered basement (aquifer) aquiferous unit 4 96.1 competent basement 31 lgea primary school zango 1 n 070 50’ 56” e060 45 34" 1 45.8 14.6 topsoil (clay/laterite) 2 76.8 17.9 weathered basement (aquifer) aquiferous unit 3 1076 competent basement 32 lgea primary school zango 2 n 070 48’ 37.2” e060 41’ 21” 1 18.8 12.8 topsoil (clay/laterite 2 26.8 9.4 weathered basement (aquifer) aquiferous unit 3 79 competent basement 33 lgea primary school zango 3 n 070 47’ 30.2” e060 44’ 32.8 1 29 8.9 topsoil (clay/laterite 2 45 24.8 weathered basement (aquifer) aquiferous unit 3 86 competent basement 34 mami market n 070 46’ 41” e060 51’ 26” 1 41 9.4 topsoil (clay/laterite 2 42 12.6 weathered basement (aquifer) aquiferous unit 3 53 competent basement 35 model nurs. and prim. sch. aneibo quarters n 070 46’ 35” e 060 48’ 05” 1 123 5.7 topsoil (clay/laterite 2 12 8.9 weathered basement (aquifer) aquiferous unit 3 201 competent basement http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 366 table 2: dar zarrouuk parameters the aquifer protective rating (protection against contamination) of any aquifer can be established using table 3 below (oladapo and akintorinwa, 2007). ves no. location layer resistivity(rr w) layer thickness (h) aquifer conductivity (σ) longitudinal conductance (s) transverse resistance (r) hydraulic conductivity (k) m/day transmissivity (tr)m2/day) 1 ganaja bh1 17.87 10.83 0.05624296 0.60604364 193.53 26.24325 284.21 2 500 unit (bh1) 83.19 12.07 0.01202067 0.14508955 1076.53 6.250823 75.447 3 500 unit (bh2) 48.35 8.89 0.02068252 0.18386763 429.8 10.37 92.189 4 200 unit (bh1) 18.35 14.34 0.05449591 0.78147138 256.29 25.60232 367.137 5 200 unit (bh2) 15.57 12.23 0.06422607 0.78548491 190.42 29.84245 364.973 6 phase i (bh1) 277.6 3.7 0.0036023 0.01332853 1027.12 2.03115 7.5152 7 phase i (bh2) 166.23 3.6 0.00601576 0.02165674 598.43 3.27712 11.797 8 phase ii (bh1) 6.81 3.61 0.14684287 0.5301028 24.5841 64.54349 233 9 phase ii (bh2) 50.44 12.51 0.01982553 0.24801744 631 9.96867 124.708 10 otokiti estate (bh) 7.8 16.13 0.12820512 2.06794872 125.81 56.86754 917.273 11 army barracks (bh) 55.61 12.54 0.01798237 0.22549901 697.35 9.10135 114.13 30 behind secretariat (hdw) 226.1 11.2 0.00442282 0.0495356 2531.3 2.45965 27.548 31 lgea primary school zango 1 124.4 12.1 0.0080385 0.0923406 1505.24 2.60048 23.7623 32 lgea primary school zango 2 167 8.9 0.005988 0.1287423 1504.1 1.48076 15.3225 33 lgea primary school zango 3 76.9 13.3 0.0130039 0.2244317 1027.39 2.56871 34.3067 34 mami market 205.6 13.9 0.0048638 0.0872312 2796.16 3.24587 12.4326 35 model nurs. and prim. sch. aneibo quarters 157.1 11.34 0.006365 0.11439123 1781.5 1.84089 69.0012 3.45855 27.3225 7290.15 6.52105 59.798 29 felele (hdw 3) 156.9 7.9 0.00637349 0.05035054 1239.5 28 felele (hdw 2) 79.5 9.17 0.01257862 0.11534591 27 felele (hdw 1) 226.1 11.2 0.00442282 0.0495356 2531.3 2.45965 27.548 26 sarkinnoma (hdw) 213 13.08 0.00469483 0.06140845 2786.04 2.60048 34.0142 300.267 5.86317 19.7588 25 kabawa (hdw) 124.7 11.8 0.00801924 0.0946271 1471.46 24 megiri (hdw ) 89.1 3.37 0.00112233 0,0378227 4.28499 50.5628 23 new layout (hdw 2) 234.1 9.6 0.00427168 0.0410081 2247.4 2.38115 22.859 22 new layout (hdw) 547.2 12.03 0.00182749 0.0219846 6582.82 1.07848 12.9741 1328.9 2.3903 13.6247 21 graj(gra) (hdw) 198.2 13.5 0.00504541 0.068113 2675.7 20 kasuwa hotel (bh) 233.14 5.7 0.00428926 0.02444883 2.78118 37.5459 19 kenwo hotel (hdw) 1212.5 11.6 0.00082474 0.00956701 14065 0.51343 5.9557 18 marine road (bh) 1734.9 15.7 0.0005764 0.00904951 27237.9 0.36757 5.7708 490.34 6.49362 39.8708 17 adankolo (bh 4) 469.4 6.7 0.00213937 0.01427354 3144.98 16 adankolo (bh 3) 79.86 6.14 0.01252191 0.07688454 1.24434 8.337 15 adankolo (bh 2) 316.62 5.7 0.00315836 0.01800379 1804.73 1.79663 10.24 14 adankolo (bh 1) 317.5 3 0.0031496 0.00944882 952.5 1.79198 5.3759 28.75 52.60192 178.32 13 zangodaji (bh 2) 750.04 10 0.00133326 0.01333262 7500 12 roja table water (bh 1) 8.48 3.39 0.11792452 0.39976415 0.80365 8.0365 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 367 table 3: rating of protective capacity of aquifers (after oladapo and akintorinwa, 2007). according to offodile (1983), the aquifers in the study area were classified in terms of their yielding capacity using transmissivity. this is as shown in table 4. table 4: aquifer classification based on transmissivity values (offodile, 1983). table 5 shows the protective capacity of the aquifers within study area obtained using their longitudinal conductance longitudinal conductance (ω—1) protective capacity rating >10 excellence 5–10 very good 0.7–4.9 good 0.2–0.69 moderate 0.1–0.19 weak 0.1 poor transmissivity (m 2 /day) classification of well >500 high potentials 50–500 moderate potential 5–50 low potential 0.5–5 very low potential <0.5 negligible potential http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 368 table 5: longitudinal conductance and protective capacity of the study area figure 3 is one of the geo-sections (station 16) obtained from the vertical electrical sounding carried out in the study area. it is one the station where three (3) geo-electric layers were encountered during the study. protective capacity rating 30 behind secretariat (hdw) 0.0070633 poor 31 lgea primary school zango 1 0.09234012 poor 32 lgea primary school zango 2 0.1287434 poor 33 lgea primary school zango 3 0.2241145 weak 34 mami market 0..087234 poor 35 model nurs. and prim. sch. aneibo quarters 0.1143912 poor ves no. locations longitudinal conductance (s) 1 ganaja bh1 0.60604364 4 200 unit (bh1) 0.78147138 good 5 200 unit (bh2) 0.78548491 good moderate 2 500 unit (bh1) 0.14508955 weak 3 500 unit (bh2) 0.18386763 weak 8 phase ii (bh1) 0.5301028 moderate 9 phase ii (bh2) 0.24801744 moderate 6 phase i (bh1) 0.01332853 poor 7 phase i (bh2) 0.02165674 poor 12 roja table water (bh 1) 0.39976415 moderate 13 zangodaji (bh 2) 0.01333262 poor 10 otokiti estate (bh) 2.06794872 good 11 army barracks (bh) 0.22549901 moderate 16 adankolo (bh 3) 0.07688454 poor 17 adankolo (bh 4) 0.01427354 poor 14 adankolo (bh 1) 0.00944882 poor 15 adankolo (bh 2) 0.01800379 poor 20 kasuwa hotel (bh) 0.02444883 poor 21 graj(gra) (hdw) 0.068113 poor 18 marine road (bh) 0.00904951 poor 19 kenwo hotel (hdw) 0.00956701 poor 24 megiri (hdw ) 0,0378227 poor 25 kabawa (hdw) 0.0946271 poor 22 new layout (hdw) 0.0219846 poor 23 new layout (hdw 2) 0.0410081 poor 28 felele (hdw 2) 0.11534591 poor 29 felele (hdw 3) 0.05035054 weak 26 sarkinnoma (hdw) 0.06140845 poor 27 felele (hdw 1) 0.0495356 poor file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 369 figure 3: geo-electric section of station 16 in the study area. table 6: vertical electrical sounding station 16 (3 layers) depth(m) thickness(m) resistivity(ohm-m) inferred lithology 0-11.8 11.8 39.70 laterite 11.8-17.94 6.14 79.86 weathered basement >18 507.56 basement figure 4 is one of the geo-sections (station 17) obtained from the vertical electrical sounding carried out in the study area. it is one the station where four (4) geo-electric layers were encountered during the study. figure 4: geo-electric section of station 17 in the study area weathered basement ves 16 0 11.8 17.9 laterite competent basement weathered basement (aquiferous unit) competent basement ves 17 0 15 18.3 25 laterite clay http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 370 table 7: vertical electrical sounding station 17 (4 layers) depth (m) thickness(m) resistivity(ohm-m) inferred lithology 0-15 15 372 laterite 15-18.3 18.3 389.49 clay 18.3-25 >26 25 469.4 908.80 weathered basement competent basement table 8 shows the hydraulic conductivity of the aquifers in the study area, obtained using the layer resistivity. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 371 table 8: hydraulic conductivity of the aquifers in the study area ves no. locations hydraulic conductivity (k) m/day 1 ganaja bh1 26.24325 2 500 unit (bh1) 6.250823 3 500 unit (bh2) 10.37 4 200 unit (bh1) 25.60232 5 200 unit (bh2) 29.84245 6 phase i (bh1) 2.03115 7 phase i (bh2) 3.27712 8 phase ii (bh1) 64.54349 9 phase ii (bh2) 9.96867 10 otokiti estate (bh) 56.86754 30 behind secretariat (hdw) 0.42835 31 lgea primary school zango 1 2.60048 32 lgea primary school zango 2 1.48076 33 lgea primary school zango 3 2.56871 34 mami market 3.24587 35 model nurs. and prim. sch. aneibo quarters 1.84089 29 felele (hdw 3) 3.45855 27 felele (hdw 1) 2.45965 28 felele (hdw 2) 6.52105 25 kabawa (hdw) 4.28499 26 sarkinnoma (hdw) 2.60048 23 new layout (hdw 2) 2.38115 24 megiri (hdw ) 5.86317 21 graj(gra) (hdw) 2.78118 22 new layout (hdw) 1.07848 19 kenwo hotel (hdw) 0.51343 20 kasuwa hotel (bh) 2.3903 17 adankolo (bh 4) 1.24434 18 marine road (bh) 0.36757 15 adankolo (bh 2) 1.79663 16 adankolo (bh 3) 6.49362 13 zangodaji (bh 2) 0.80365 14 adankolo (bh 1) 1.79198 11 army barracks (bh) 9.10135 12 roja table water (bh 1) 52.60192 http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 372 table 9 shows the aquifer potential of the aquifers in the study area using transmissivity data obtained. table 9: aquifer potential of the aquifers in the study area 1 ganaja bh1 moderate 2 500 unit (bh1) moderate 3 500 unit (bh2) moderate 4 200 unit (bh1) moderate 5 200 unit (bh2) moderate 6 phase i (bh1) very low 7 phase i (bh2) low 8 phase ii (bh1) moderate 9 phase ii (bh2) moderate 10 otokiti estate (bh) high 27.548 59.798 27.3225 30 behind secretariat (hdw) 4.4548 31 lgea primary school zango 1 23.7623 32 lgea primary school zango 2 15.3225 33 lgea primary school zango 3 34.3067 34 mami market 12.4326 35 model nurs. and prim. sch. aneibo quarters 69.0012 low low low moderate low moderate low low low 29 felele (hdw 3) 27 felele (hdw 1) 28 felele (hdw 2) 25 kabawa (hdw) 50.5628 moderate 26 sarkinnoma (hdw) 34.0142 low 23 new layout (hdw 2) 22.859 low 24 megiri (hdw ) 19.7588 low 21 graj(gra) (hdw) 37.5459 low 22 new layout (hdw) 12.9741 low 19 kenwo hotel (hdw) 5.9557 low 20 kasuwa hotel (bh) 13.6247 low 17 adankolo (bh 4) 8.337 low 18 marine road (bh) 5.7708 low 15 adankolo (bh 2) 10.24 low 16 adankolo (bh 3) 39.8708 low 13 zangodaji (bh 2) 8.0365 low 14 adankolo (bh 1) 5.3759 low moderate 12 roja table water (bh 1) 178.32 moderate 11.797 233 124.708 917.273 11 army barracks (bh) 114.13 284.21 75.447 92.189 367.137 364.973 7.5152 ves no. locations transmissivity (tr)m2/day) aquifer potential file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 373 figure 5. map of the study area showing variation in hydraulic conductivity figure 6. map of the study area showing variation in transmissivity discussion from the result of the vertical electrical sounding (table 1), two types of aquifer were delineated, namely; the weathered basement aquifer and weathered/fractured aquifer. the weathered basement aquifer was shown by ves 1 to 18, 21, 22 to 35 while weathered/fractured aquifer was revealed by ves stations 19 and 20. thirteen (13) out of the thirty five (35) ves curves revealed a 4–layer geo-electric model (ves 6, 13 to 15, 17, 19, 20, 22 to 25, 29 &30) and the characteristic geo-electric signatures are aaand hatype curves, while the remaining twenty two (22) indicated a 3–layer geo-electric model and the characteristic geo-electric signatures are hand a–type curves. the a – type curve represents a subsurface condition in which there is an increase in resistivity values from the topsoil to the bedrock (ρ1< ρ2< ρ3). the h – type curve represents a subsurface whereby the resistivity of the first layer is greater than the second layer while the resistivity of the second layer is less than the third layer (ρ1> ρ2< ρ3). the aa – type curve represents a subsurface which is composed of four layers in which there is an increase in resistivity from the first layer to the competent basement (ρ1< ρ2< ρ3< ρ4). the ha – type curve shows a subsurface in which the resistivity of the first layer is greater than the second layer while the second layer is less than the third layer and the resistivity of the third layer is less than the fourth layer (ρ1> ρ2< ρ3< ρ4). the topsoil generally comprises clay and laterite and constitutes the zone of aeration (phreatic zone). this zone contributes to groundwater development as it serves as a conduit through which meteoric water infiltrates the subsurface to form groundwater (table 1). the weathered basement aquifer in the study area formed the second layer for the 3–layer formations. the depth of the layer ranges from 3.0m to 16.13m and the thickness ranges from 3.1m to 6.14m. the resistivity is of the range of 6.81ωm to 166.23ωm (tables 1 and 2). for the four layer formations, the weathered layer aquifer forms the third layer. the depth of the layer varies from 18m to 25m, while the thickness ranges from 5m to 6.7m with a resistivity range of 316.62ωm – 750.20ωm. the groundwater yield of this aquifer type is determined by the degree of shaliness of the weathered zone. low yield is encountered when the aquifer unit is clayey. this is because clay is not permeable to allow the flow of water. sources of clay in lokoja can http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 374 be attributed to weathering of feldspar of the lokoja formation and the basement rocks in the area. the weathered/fractured aquifer forms the third layer in the four-layer geo-electric model. the depth of the layer ranges from 17m – 9.2m, a thickness range of between 3m and 3.7m and a resistivity varying from 277.6ωm – 317.5ωm (table 1 and 2). this zone underlies the weathered zone directly. the groundwater yield from this aquifer type could be high if the density of the fractures in the fractured column is high. the fresh basement complex forms the last layer in the geo-electric section. the resistivity values of the competent basement for both aquifers vary from 33.45ωm – 7724.31ωm. the layer resistivity of the aquifers together with the thickness of the layer as shown in table 2 were used to compute the various dar zarrouk parameters as shown in table 2. the rating of the aquifer protective capacity according to oladapo and akintorinwa, 2007 is shown in table 3. this rating was used as standard for the data obtained from the study area. the classification of aquifers based on their discharge ability/yielding ability according to offodile, 1983 is shown in table 4. this classification was used as standard for the data obtained from the study area. the longitudinal conductance was used to evaluate the protective capacity of the aquifers in the study according to oladapo and akintorinwa, 2007. the longitudinal conductance ranges from 0.00915ῳ to 2.063ῳ with an average of 1.068ῳ (table 5). the results show that most of the aquifers in the area have poor to moderate protective capacity. this is an indication that most of the aquifers in the study area are adequately protected. wells located in this area are therefore susceptible to surface contamination because of the proximity of the aquifer to the surface. tables 6 and 7 show the geo-electric properties of some of the aquifers (location 16 and 17). the results were obtained from vertical electrical sounding (ves) done with the aid of abem terrameter using schlumberger array. the hydraulic conductivity obtained ranges from 0.36757m/day to 56.86725m/day with a mean value of 21.34m/day (table 8). the results show that the aquifers have low to moderate yielding potentials. the spatial distribution of hydraulic conductivity across the study area (figure 4) that the southern part of the study has good yield that the northern area. the transmissivity of the aquifer in the area ranges from 4.4543m2 to 912.273m2/day with a mean value of 213.34m2/day. this was used to compute the aquifer potential of the study area as shown in table 9. the spatial distribution of transmissivity across the study area shows poor to moderate potentials (figure 5) the transverse resistance obtained ranges from 28.75ῳm2 to 7290ῳm2 with an average value of 1120 ῳm2 this result indicates very low groundwater development class (ezeh, 2012). the spatial distribution as shown in figure 6 indicate that the northeastern part of the study have the least groundwater development. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com omali and arogundade: geophysical mapping of aquifer potential zones using hydraulic parameters in lokoja and environs, northcentral, nigeria. azojete, 18(3):345-376. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 375 4. conclusion the result of the vertical electrical sounding two types of aquifer was delineated, namely; the weathered basement aquifer and weathered/fractured aquifer. thirteen (13) out of the thirtyfive (35) ves curves revealed a 4–layer geo-electric model and the characteristic geo-electric signatures are aaand hatype curves, while the remaining twenty-two (22) indicated a 3– layer geo-electric model and the characteristic geo-electric signatures are hand a–type curves. the results obtained revealed that the aquifers within the study area have poor to moderate protective capacity and very low to moderate yielding/discharge potentials. the resistivity soundings results revealed that about 4 curve types were identified in the study area namely aa, ha, a and h type with the lithologic layers varying from four 3 to 4 consisting of varying resistivity and thicknesses across each ves point. the geo-electric sections revealed that the major aquifer systems in the study area are weathered basement and weathered/fractured basement. the longitudinal conductance computed indicates that the aquifers in the area have poor to moderate protective capacity whereas transverse resistance indicates very low ground water development class. hydraulic conductivity and transmissivity values indicate very low to moderate aquifer potentials. references bello, r., balogun, ao. and nwosu, um. 2019 evaluation of dar zarrouk parameters of parts of federal university of petroleum resources, effurun, nigeria. journal of applied sciences and environmental. management, 23(9): 1709-1715. billing, mp. 1972. structural geology. in: eaglewood cliffr. n., third ed. prentice-hall. 1972.. cihan, a., zhou, q., birkholzer, j. and kraemer, s. 2014. flow in horizontally anisotropic multilayered aquifer systems with leaky well sand aquitards. water resources research, 50: 741–747. egbai, jc. and iserhien-emekeme, re. 2015. aquifer transmissivity dar zarrouk parameters and groundwater flow direction in abudu, edo state, nigeria. international journal of science and environmental technology, 4(3): 628-640. ezeh, cc. 2012. hydro geophysical studies for the delineation of potential groundwater zones in enugu state, nigeria. international research journal of geology and mining, 2 (5): 103–112. heigold, pc. gilkeson, rh. cartwright, k. and reed, pc. 1979. aquifer transmissivity from surficial electrical methods. ground water, 17(4): 338–345. kwami, ia., ishaku, jm., bello, am., yusuf, a. and mukkafa, s. 2018. assessment of water quality index for the groundwater in gombe and environs, north-east nigeria. iosr journal of applied geology and geophysics, 6(5): 29–37. kwami, ia., ishaku, jm., bello, am., yusuf, a. and mukkafa, s. 2019. delineation of aquifer potential zones using hydraulic parameters in gombe and environs, north-east nigeria. heliyon, 5(7): e01927. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):357-376. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: omaliaurelius@yahoo.com 376 malick, sb., bhattacharya, dc. and nag, sk. 1973. behaviour of fractures in hard rocks – a study by surface geology and radial ves methods. geoexploration, 1: 529–556. mbonu, ddc., ebeniro, jo., ofoegbu, co. and ekine, as. 1991. geoelectrical sounding for the determination of aquifer characteristics in parts of the umuahia area of nigeria. geophysics, 56(5): 284 – 291. nwosu, li., nwankwo, cn. and ekine, as. 2014. delineating aquifer systems using darzarouk parameters determined from surface geo-electric survey: case study of okigwe district, southeastern nigeria. british journal of applied science and technology, 4(34): 4751–4770. offodile, mi. 1983. the occurrence and exploitation of groundwater in nigeria basement complex. journal of mining and geology, 20(3): 131–146. okiongbo, ks. and oborie, e. 2015. investigation of relationships between geoelectric and hydraulic parameters in a quaternary alluvial aquifer in yenagoa, southern nigeria. ife journal of science, 17(1): 163-172. oladapo, mi. and akintorinwa, oj. 2007. hydro geophysical study if ogbese southwest, nigeria. global journal of pure and applied sciences, 13(1): 55–61. omali, ao. 2014. hydrogeophysical investigation for groundwater in lokoja metropolis, kogi state, central nigeria. journal of geography and geology, 6(1): 81-95. stefanesco, ss., schlumberger, c. and schlumberger, m. 1930. sur la distribution electrique potentielle autor d'une prix de terre ponctuelle dansun terrain a couche horizontales, homogenes et isotrope: jour. physique et le radium, 11(1): 132–140. todd, kd. 1980. groundwater hydrology, third ed. john wiley and sons, new york, pp. 636. udoinyang, ie. and igboekwe, mu. 2012. aquifer transmissivity, dar zarrouk parameters and the direction of flow of suspended particulate mattee in boreholes in mouau and the kwa ibo river umudike-nigeria. green journal of physical science, 2(3): 70-78. zohdy, aar. 1989. a new method for the automatic interpretation of schlumberger and wenner sounding curve. geophysics, 54: 245 – 253 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/omaliaurelius@yahoo.com arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):733-746 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 733 assessment of arsenic in groundwater in monguno, borno state, nigeria i. m. umar1*, b. m. sheriff2 and b. b. muhammad3 1school of architecture, building and civil engineering, loughborough university, london, uk. 2department of geology, university of maiduguri, maiduguri, borno state, nigeria. 3department of civil & water resources engineering, university of maiduguri, maiduguri, borno state *corresponding author's email address: engr.ibraheem1@gmail.com article information submitted 30 july, 2023 revised 3 sept, 2023 accepted 10 sept, 2023 keywords: arsenic groundwater drinking water health risk monguno abstract arsenic contamination poses a severe health threat in the semi-arid region of north-eastern nigeria, particularly in monguno town, borno state. this study rigorously evaluated groundwater arsenic concentrations in 102 samples from various boreholes across upper, middle, and lower aquifers of the chad formation, utilizing the palintest digital arsenator test kit. to ensure precision, each water sample underwent analysis twice, totaling 204 tested and analyzed samples. furthermore, the geographical coordinates of the 102 boreholes were meticulously mapped using qgis (quantum geographic information system), providing a visual representation and analysis of the arsenic presence. findings revealed that only 3 samples met the who recommended threshold, 56 fell within the 10-50 µg/l range, signifying a low risk, while 43 samples exceeded 50 µg/l, breaching safety limits. prolonged exposure to high arsenic levels can lead to severe health implications. a comprehensive human health risk assessment considered parameters such as average daily dose (add), hazard quotient (hq), and cancer risk (cr). notably, for 43 water sources with arsenic concentrations exceeding 50 µg/l, hazard quotient (hq) values ranged from 1.2 to 5.3, indicating potential health risks. these elevated values underscore potential carcinogenic and non-carcinogenic hazards in monguno. a direct linear relationship was observed between hq and arsenic concentrations across all samples, reinforcing the correlation. despite the absence of specific reference values for monguno, the analogous trend in north central nigeria reinforces this observation. urgent collaborative efforts are imperative for intervention and remediation, emphasizing the need for cooperation between government agencies, non-governmental organizations, research institutions, and the local community. continuous research and monitoring are vital to understanding arsenic sources and distribution, ensuring the long-term effectiveness of remediation measures, and securing safe drinking water access for the community 1.0 introduction water is a vital prerequisite for the sustenance of life, yet its consumption is subject to both quantitative and qualitative constraints. consequently, inhabitants of a specific locality may encounter water scarcity and health-related hazards stemming from the ingestion of contaminated water. globally, the uneven distribution of freshwater resources and population densities has created significant challenges in ensuring access to safe water for millions of people. throughout history, individuals residing in arid and semiarid regions have strived to secure access to water that is conducive to maintaining a healthy lifestyle. the issue of http://www.azojete.com.ng/ engr.ibraheem1@gmail.com engr.ibraheem1@gmail.com engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):733-746. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 734 insufficient clean water is further exacerbated by the contamination of freshwater sources with various toxic pollutants (qu et al., 2019). aquifers are acknowledged as essential assets that underpin the predominant provision of potable water and essential socio-economic and ecological activities across africa (gaye and tindimugaya, 2019). the utilization of groundwater is integral to the foundational aspects of planning for climate-resilient water supply, particularly in areas susceptible to drought (howard et al., 2016; pavelic et al., 2012). in the context of nigeria, groundwater constitutes the primary potable water supply for more than 75% of the populace. specifically, in monguno, the use of groundwater is at the peak demand and the main aquifer employed for water extraction is predominantly associated with the geological formation of the lake chad basin. according to barber and jones (1960), the chad formation can be divided into three aquiferous zones: upper, middle, and lower aquifers. the upper aquifer is mostly unconfined and semi-confined, while the middle and lower aquifers are confined. the middle aquifer is primarily composed of fine to mediumgrained sand, interbedded with silty and clayey layers, at a depth of approximately 250 meters with an average thickness of about 50 meters. the lower aquifer, found in areas such as maiduguri, gudumbali, kukawa, and monguno, varies in depth from 250 meters to 500 meters, depending on the local geology, as depicted in figure 1. figure 1: cross-section of the chad formation (after barber and jones, 1960) arsenic contamination of groundwater represents a significant global health challenge, as evidenced by numerous studies (neil et al., 2018; wei et al., 2018; shakoor et al., 2019). the severity of this issue is underscored by the exposure of over 200 million individuals worldwide to arsenic-contaminated groundwater exceeding 10 pg/l, primarily through the consumption of drinking water (naujokas et al., 2013; shahid et al., 2018; shakoor et al., 2018; singh et al., 2018). consequently, the contamination of groundwater with arsenic poses significant health risks, leading to arsenic poisoning on a global scale for millions of people (bhowmick et al., 2018; cao et al., 2018; gonzalez-martinez et al., 2018). contamination of groundwater with arsenic (as) can arise from both natural and anthropogenic sources. natural occurrences may result from the dissolution of minerals containing arsenic at deeper levels of groundwater, as documented in various studies (nath et al., 2018; neil et al., 2018; saunders et al., 2018). arsenic (as) is a naturally occurring trace element found in various rocks and sediments. its release into groundwater depends on factors such as the chemical form of arsenic, the geochemical conditions in the aquifer, and file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com umar et al: assessment of arsenic in groundwater in monguno, borno state, nigeria. azojete, 19(4):733-746. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 735 biogeochemical processes. additionally, human activities, including mining and various industrial applications such as animal feed, wood preservation, and pesticide use, can contribute to the release of arsenic into groundwater. arsenic poses a significant concern in drinking-water supplies due to its toxicity at low levels and its classification as a known carcinogen. in 2001, the united states environmental protection agency (usepa) lowered the permissible limit of arsenic in public water supplies from 50 µg/l to 10 µg/l, highlighting the importance of monitoring and addressing arsenic contamination in groundwater. recently, a myriad of studies conducted in diverse regions of nigeria has brought attention to an increased susceptibility to arsenic-contaminated groundwater. despite the absence of published findings on arsenic-polluted groundwater in monguno, nigeria this absence does not confer assurance regarding the potability of drinking water, nor does it negate the potential for arsenic contamination. one noteworthy investigation by orosun (2021) delved into the assessment of arsenic and associated health risks arising from mining activities in select areas of north-central nigeria. this comprehensive study involved the meticulous collection of 306 samples of soil, water, and guinea corn, subjected to analysis through atomic absorption spectrometry. the discerned outcomes unveiled variable concentrations of arsenic, frequently exceeding permissible consumption limits, thereby substantiating the presence of pollution. furthermore, the study underscored a pronounced likelihood of non-cancerous health effects attributable to arsenic in drinking water sourced from mining-affected areas. in another study focusing on arsenic pollution, ezeabasili et al. (2014) scrutinized the pollution status of surface and subsurface water in onitsha town, anambra state, nigeria. their investigation disclosed arsenic concentrations in boreholes spanning from 0 mg/l to 1.2507 mg/l. alarming exceedances of the world health organization (who) standard of 0.01 mg/l were noted in water sourced from rivers, with a concurrent 87.8% of boreholes proximal to these water bodies surpassing the stipulated who threshold. notably, the study pinpointed sources of arsenic in onitsha, including refuse dumps, industrial effluents, and sewage. recognizing arsenic as the most toxic metal on earth's surface, the study underscored the imperative of stringent monitoring of its production and the necessity for effluent treatment before discharge into the environment. in the monguno local government area (lga) of borno state, ensuring access to high-quality potable water is a significant concern. during the wash (water, sanitations and hygiene) cluster meeting on november 8, 2022, it was reported that water quality tests in monguno town identified elevated arsenic levels in numerous boreholes, prompting the need for further investigation. the presentation underscored the urgency of detailed assessments due to the health implications of arsenic (meeting discussion, november 8, 2022). consequently, a thorough examination of boreholes in monguno and its surroundings for arsenic concentrations is imperative. this assessment will establish a baseline, enabling researchers and policymakers to formulate effective, sustainable solutions for the provision of safe drinking water in the region. despite the extensive water sampling efforts conducted by various wash partners in monguno, nigeria, and the recognized global health risks associated with arsenic-contaminated groundwater, there is a notable absence of comprehensive assessments of arsenic levels and potential sources in different regions of the state, particularly in monguno. hence, it is crucial to evaluate the arsenic concentrations in groundwater from various sources in monguno. this study was therefore undertaken with the aim of determining the arsenic content in the groundwater of all identified boreholes in monguno, while also assessing the potential health hazards associated with the consumption of this groundwater. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):733-746. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 736 2. materials and methods 2.1 study area the study area, monguno town, is geographically located at 12°41′0″n 13°36′0″e and borders marte, mafa, nganzai, guzamala, and kukawa at the fringes of lake chad. it covers an area of 1,913 km2 and had a population of 109,851 according to the 2006 census. figure 2 illustrates the study area map, specifically highlighting the discerned water locations within the towns of monguno, kumalia, and kaguram. the hydrology of the borno basin comprises atmospheric, surface, and groundwater systems. the region's rainfall intensity is influenced by the climate and other natural factors. research by offodile (1993) and nicolas (2013) indicated that the rainfall intensity gradually decreases from the southern to the northern part of the chad basin (offodile, 1993). schoeneich (1998) presents a rainfall distribution map of nigeria, placing the chad basin area within the sahel climatic zone with an isohyet of 600 mm/a. the chad formation aquifers typically receive recharge from rainfall through infiltration for the upper aquifer, whereas the middle and lower zone aquifers mainly recharge within their outcrop areas. figure 2: map of the study area in monguno local government area, borno state, nigeria. socio-economically, the majority of the population in monguno is engaged in fishing, farming, and livestock grazing. however, due to the impact of insurgency in recent years, these activities have been limited. with the improved security situation in monguno town, farming activities have gradually resumed. 2.2 water sampling, preservation and storage groundwater samples used for drinking purposes by the local inhabitants were collected from a total of 102 boreholes across the three zones of the lake chad basin aquifer: upper, lower, and middle aquifer. the geographical coordinates of the 102 boreholes were acquired through global positioning system (gps) technology. data accumulated during the research project were subsequently archived within qgis, a geographical information system (gis), serving as a visual database to facilitate the graphical representation and analysis of information. the data collection process was coordinated in collaboration with wash implementing partners responsible for managing the water points in monguno lga. the comprehensive sampling file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com umar et al: assessment of arsenic in groundwater in monguno, borno state, nigeria. azojete, 19(4):733-746. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 737 initiative spanned a duration of 13 consecutive days, commencing with the meticulous collection of data and extending through subsequent stages of analysis. water samples were collected from every operational borehole identified in monguno. prior to the sampling activity, a survey form (on kobo) was administered to gather detailed information about each borehole, including its management, depth, and geographical location (figure 3). figure 3: map of monguno town showing the concentration of arsenic in groundwater. each of the groundwater samples was collected in two whirl pak water sample bags that are well labeled per groundwater sample. the samples were exclusively allocated for arsenic content analysis and were carefully stored post-intake under controlled environmental conditions in a dedicated cooler in monguno, nigeria. this storage practice, although not necessitated by microbial concerns, adhered to recommended guidelines to ensure optimal sample preservation for accurate results. the samples were tested immediately the following day of the sample intake which was driven by the necessity to mitigate any potential alterations in sample integrity over time, thereby safeguarding the precision of the arsenic content analysis results. in addition, unlike microbial tests, the time difference between testing and analysis has no significant impact on the outcome of arsenic tests. 2.3 laboratory analysis of arsenic the laboratory analysis of the groundwater samples was conducted using the palintest digital arsenator test kit pt981, palintest halma company, united kingdom (uk). the arsenator test kit follows a series of three steps to determine the arsenic concentration in the water samples: i. loading the tri-filter arsenic trap (bung device): the arsenator toolkit, featuring the h2s removal filter, red filter paper, and black filter, was meticulously loaded into the arsenator using forceps. activation involved inserting the preloaded black filter into the arsenator for 3 seconds. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):733-746. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 738 ii. sample preparation: at this stage, a 50 ml water sample, marked on the container, was poured into a conical flask. a1 reagent and a2 sachet powder were added, and the flask was sealed promptly with a bung. iii. arsenic measurement and color comparison: after 20 minutes, the black paper slide was introduced, displaying arsenic concentration on the digital meter in µg/l. results above the digital arsenator's detection limit (100 µg/l) prompted consideration of the dilution factor. cross-verification was performed using the color comparator, capable of measuring arsenic concentrations up to 500 µg/l. to ensure precision and accuracy each water sample underwent the specified analysis steps twice, resulting in a total of 204 tested and analyzed samples. the laboratory at the initiative for reconstruction and resettlement (irr) meticulously adhered to the iso 17025:2017 guidelines, ensuring compliance with standards for testing laboratory competence, encompassing aspects such as equipment calibration, quality control procedures, and personnel competence. additionally, strict adherence to the palintest arsenator test kit manufacturer's guidelines was maintained, covering instrument calibration, maintenance, and usage instructions to guarantee the accurate functioning of the test kit. in instances where arsenic concentrations exceeded the digital arsenator's detection limit, a scientifically derived dilution factor was calculated, following established principles and laboratory protocols. furthermore, cross-verification was conducted using a color comparator, aligning with recognized colorimetric techniques for arsenic analysis, thereby corroborating results obtained from the digital arsenator. 2.4 human health risk assessment in order to evaluate the potential impact of arsenic on human health across the 102 water samples, various parameters including the average daily dose (add), hazard quotient (hq), and cancer risk assessment have been computed. i. average daily dose (add): the estimation of add for arsenic through drinking water was conducted utilizing equation (1): add = 𝐶∗𝐼𝑅∗𝐸𝐹∗𝐸𝐷 𝐴𝑇∗𝐵𝑊 (1) in this equation, c denotes the concentration of arsenic in groundwater at averaged for all the 102 water samples in monguno, ir represents the daily ingestion rate of groundwater, ed specifies the exposure duration, ef indicates exposure frequency, bw is the body weight, and at signifies the average life expectancy. ii. calculation of hazard quotient (hq) the hq for arsenic in groundwater at the 102 water points was determined according to the (us-epa 2005) guidelines using equation (2): hq = 𝐴𝐷𝐷 𝑅𝑓𝐷 (2) here, rfd represents the oral reference dose for arsenic (0.3 µg kg⁻¹ day⁻¹) (usepa 2005). an hq value below 1 is considered indicative of safety. iii. cancer risk (cr) assessment the estimation of cr followed the usepa 2005 guidelines, as expressed in equation (3): cr = add x csf (3) here, csf denotes the cancer slope factor for arsenic (1.5 mg kg⁻¹ day⁻¹). this comprehensive assessment provides valuable insights into the potential health risks associated with arsenic exposure through drinking water in different water sources in monguno. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com umar et al: assessment of arsenic in groundwater in monguno, borno state, nigeria. azojete, 19(4):733-746. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 739 3. results and discussion 3.1 arsenic concentration in water samples the analysis of the groundwater samples revealed significant variations in the arsenic concentration across the study area. out of the total 102 samples collected, the results indicate that only 3 samples obtained from shallow wells equipped with hand pumps and deep boreholes, reaching depths of approximately 400 meters, had arsenic concentrations below the permissible limit of safe drinking water, which is set at 10 µg/l by both the world health organization (who) and the national standard for drinking water quality (nsdwq). additionally, 56 samples exhibited arsenic concentrations falling within the range of 10 to 50 µg/l. while this concentration level is deemed acceptable with low risk, it is essential to continue monitoring and managing these water sources to prevent potential future increases in arsenic levels. (table 1, figure 4) however, the most concerning finding was that 43 samples showed arsenic concentrations exceeding 50 µg/l (as depicted in figure 4). these levels surpass the permissible limits for drinking water established by both who and nsdwq. prolonged exposure to such high levels of arsenic can lead to various health implications and pose significant risks to the local population. figure 4: distribution of arsenic concentrations in groundwater samples these results underscore the urgent need for intervention and remediation measures to address the presence of elevated arsenic concentrations in the groundwater of the study area. access to safe drinking water is vital for the well-being of the community, and immediate action is required to mitigate the health risks associated with arsenic contamination. table 1: laboratory results of arsenic concentration (µg/l) in groundwater from 102 borehole in monguno sample id number arsenic value -1st sample (µg/l) arsenic value – 2nd sample (µg/l) average value (µg/l) borehole-1 18 18 18 borehole-2 98 100 99 borehole-3 28 28 28 borehole-4 15 17 16 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):733-746. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 740 borehole-5 28 30 29 borehole-6 11 11 11 borehole-7 25 25 25 borehole-8 24 26 25 borehole-9 17 19 18 borehole-10 17 21 19 borehole-11 25 27 26 borehole-12 21 19 20 borehole-13 24 22 23 borehole-14 22 24 23 borehole-15 19 21 20 borehole-16 22 18 20 borehole-17 17 19 18 borehole-18 248 252 250 borehole-19 149 151 150 borehole-20 22 24 23 borehole-21 9 11 10 borehole-22 26 28 27 borehole-23 31 29 30 borehole-24 9 11 10 borehole-25 97 99 98 borehole-26 360 360 360 borehole-27 211 209 210 borehole-28 189 191 190 borehole-29 15 17 16 borehole-30 490 490 490 borehole-31 86 88 87 borehole-32 151 149 150 borehole-33 63 61 62 borehole-34 24 26 25 borehole-35 20 22 21 borehole-36 48 46 47 borehole-37 88 86 87 borehole-38 121 119 120 borehole-39 221 219 220 borehole-40 410 410 410 borehole-41 11 9 10 borehole-42 7 9 8 borehole-43 15 17 16 borehole-44 34 32 33 borehole-45 28 30 29 borehole-46 20 22 21 borehole-47 41 41 41 borehole-48 26 28 27 borehole-49 29 27 28 borehole-50 89 89 89 borehole-51 15 17 16 borehole-52 43 47 45 borehole-53 17 19 18 borehole-54 48 50 49 borehole-55 13 15 14 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com umar et al: assessment of arsenic in groundwater in monguno, borno state, nigeria. azojete, 19(4):733-746. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 741 borehole-56 65 65 65 borehole-57 54 56 55 borehole-58 21 23 22 borehole-59 81 83 82 borehole-60 59 61 60 borehole-61 150 150 150 borehole-62 79 83 81 borehole-63 125 125 125 borehole-64 135 137 136 borehole-65 39 41 40 borehole-66 97 99 98 borehole-67 44 46 45 borehole-68 38 40 39 borehole-69 91 93 92 borehole-70 93 91 92 borehole-71 12 16 14 borehole-72 49 51 50 borehole-73 13 15 14 borehole-74 82 84 83 borehole-75 89 91 90 borehole-76 67 71 69 borehole-77 94 92 93 borehole-78 300 300 300 borehole-79 22 24 23 borehole-80 52 48 50 borehole-81 230 230 230 borehole-82 81 79 80 borehole-83 90 90 90 borehole-84 290 290 290 borehole-85 13 11 12 borehole-86 54 56 55 borehole-87 79 81 80 borehole-88 9 13 11 borehole-89 6 4 5 borehole-90 29 31 30 borehole-91 37 39 38 borehole-92 37 37 37 borehole-93 29 31 30 borehole-94 22 20 21 borehole-95 110 110 110 borehole-96 31 29 30 borehole-97 68 70 69 borehole-98 0 0 0 borehole-99 26 26 26 borehole-100 97 95 96 borehole-101 78 80 79 borehole-102 390 390 390 average arsenic concentration 76 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):733-746. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 742 the findings from the current investigation reveal that the average arsenic (as) concentration across all water samples was 76 µg/l (refer to table 1 and fig. 4). the lowest observed arsenic concentration was 0 µg/l in only one borehole, whereas the highest recorded level of arsenic reached 490 µg/l. the assessment of arsenic concentrations in groundwater samples from monguno town reveals a concerning scenario with potential implications for public health and access to safe drinking water. a significant proportion of the sampled groundwater sources (42.2 %) were found to be contaminated with elevated levels of arsenic, exceeding the permissible limits set by who and nsdwq. this indicates a widespread contamination issue within the study area, posing serious health risks to the local population, including skin lesions, respiratory issues, cardiovascular diseases, and an increased risk of cancer. arsenic exposures may play a role in increasing prostate cancer risk (yang, 2022). while a limited number of samples (2.9 %) had arsenic concentrations below the permissible limit, the majority of samples (54.9 %) fell within the acceptable range of 10 to 50 µg/l, with low immediate health risks. however, continuous exposure to even lower levels of arsenic over time can still lead to health issues, emphasizing the need for ongoing monitoring and management. the geographical distribution of arsenic concentrations, as shown in figure 2, is dispersed within the study area, suggesting that contamination is not solely based on geography. nevertheless, boreholes drawing water from the lower aquifer appear to be more susceptible to elevated arsenic concentrations. this observation points to the role of geological factors and aquifer characteristics in arsenic mobilization and its impact on water quality. haun (2020) on conducted a study on groundwater pollution risk assessment in unsaturated and saturated aquifer and found that the second semi-confined aquifer, or lower aquifer, was predominantly ranked as relatively low (30.29%) and mediate (38.17%) in contamination risk, indicating it is generally less susceptible to pollution compared to the upper aquifer. 3.2 assessment of human health risk any detected arsenic concentration exceeding 10 µg/l in water samples holds the potential for adverse human impacts, as emphasized by the world health organization (who, 2011). furthermore, a specific human health risk assessment has been meticulously conducted within the framework of this study, aligning with the concerns raised by health and environmental organizations, as well as regulatory authorities at local, regional, and global levels, pertaining to environmental toxicology, food security, and health risks (shah et al., 2020). the study, as outlined in table 2, employs calculated risk assessment parameters to investigate the potential transfer of arsenic from water to humans, aiming to predict conceivable health hazards among the local inhabitants of monguno. table 2: add, hq and cr values for 102 water sources in monguno. range of arsenic concentration (µg/l) number of boreholes add (mg/kg/day) hq cr 0-9 3 0.0001487 0.4957 0.000223 10-50 56 0.0002938 0.9793 0.0004407 51-100 25 0.0003614 1.2047 0.0005421 101-200 8 0.001263 4.2101 0.001895 >200 10 0.001576 5.2533 0.002364 the add values exhibit a range of 0.0001 to 0.001 mg.kg-1day-1 across 102 water samples in monguno (refer to table 4). notably, the maximum add occurs in 10 water samples with arsenic concentrations surpassing 200 µg/l. these samples also exhibit the highest hq value at 5.2533, signifying an elevated risk corresponding to increased arsenic concentration. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com umar et al: assessment of arsenic in groundwater in monguno, borno state, nigeria. azojete, 19(4):733-746. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 743 the mean arsenic levels in water samples follow an ascending order concomitant with a rise in arsenic content, irrespective of the varying number of boreholes per arsenic level. specifically, for 9 µg/l arsenic in 3 boreholes, the mean value is as minimal as 0.000233. in contrast, for arsenic content ranging from 10 to 50 µg/l across 56 boreholes, the mean value escalates to 0.0004407. meanwhile, samples from the 10 boreholes with the highest arsenic concentrations exhibit a proportional increase in potential cr value, reaching 0.002364. this trend is consistently mirrored in the add and hq values across all 102 sites, as detailed in table 2. the elevated values of add, hq, and cr in certain monguno groundwater samples suggest potential carcinogenic and non-carcinogenic health hazards within the local community. while specific reference values for monguno are absent, the analogous trend in north central nigeria reinforces this observation. notably, the hazard indices (hi) calculated for the well waters consistently exceed the acceptable range of 1.00e-6 to 1.00e-4, indicating heightened health hazards and cancer risks (orosun, 2021). figure 5: model for representing the hazard quotient for concentration of arsenic in monguno a linear model depicting the hazard quotient per arsenic sample for all 102 samples is presented in figure 5. the graph reveals a clear linear relationship, allowing for the extrapolation of known arsenic levels within the monguno geographical location. the congruent findings in this study align with the observations made by etim (2017), who identified a linear relationship in hazard indices, add, hq, and hi across 210 groundwater samples collected from 35 shallow wells. the assessment of arsenic concentrations in groundwater samples from monguno town reveals a concerning scenario with potential implications for public health and access to safe drinking water. a significant proportion of the sampled groundwater sources (42.2 %) were found to be contaminated with elevated levels of arsenic, exceeding the permissible limits set by who and nsdwq. this indicates a widespread contamination issue within the study area, posing serious health risks to the local population, including skin lesions, respiratory issues, cardiovascular diseases, and an increased risk of cancer. arsenic exposures may play a role in increasing prostate cancer risk (yang, 2022). 0 1 2 3 4 5 6 0 50 100 150 200 250 h az ar d q u o ti e n t (h q ) average arsenic presence in 102 water sample (ug/l) hazard quotient per arsenic presence in water sample hazard quotient (hq) linear (hazard quotient (hq)) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):733-746. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: engr.ibraheem1@gmail.com 744 4. conclusion and recommendations the results of this research highlight a critical water quality issue in monguno town, borno state, nigeria, with a significant number of groundwater samples showing elevated arsenic concentrations, posing potential health risks to the local population. urgent measures are needed to address this pressing concern and ensure access to safe drinking water for the community. out of the 102 groundwater samples collected, 43 samples exhibited arsenic concentrations above the permissible limits set by both the world health organization (who) and the national standard for drinking water quality (nsdwq). prolonged exposure to arsenic-contaminated water can lead to serious health implications, making it imperative to take immediate action to safeguard public health. while some samples (3 out of 102) fell within safe limits, and others (56 out of 102) were within an acceptable range with low risk, continued monitoring and effective management of these sources are essential to prevent potential future increases in arsenic levels. collaboration between government agencies, non-governmental organizations, research institutions, and the local community is vital to formulate and implement comprehensive remediation plans. additionally, continued research and monitoring efforts are necessary to better understand the sources and distribution of arsenic in groundwater and to assess the long-term effectiveness of remediation measures. references barber, wm. and jones, dr. 1960. geology and hydrology of maiduguri borno province. records of geological survey, maiduguri, bulletin 34. bhowmick, s., pramanik, s., singh, p., mondal, p., chatterjee, d. and nriagu, j. 2018. arsenic in groundwater of west bengal, india: a review of human health risks and assessment of possible intervention options. science of the total environment, 612: 148-169. cao, h., xie, x., wang, y., pi, k., li, j., zhan, h. and liu, p. 2018. predicting the risk of groundwater arsenic contamination in drinking water wells. journal of hydrology, 560: 318325. etim, eu. 2017. occurrence and distribution of arsenic, antimony and selenium in shallow groundwater systems of ibadan metropolis, southwestern nigerian. journal of health and pollution, 7(13): 32–41. https://doi.org/10.5696/2156-9614-7-13.32 ezeabasili, acc., anike, ol., okoro, bu. and u-dominic, cm. 2014. arsenic pollution of surface and subsurface water in onitsha, nigeria. african journal of environmental science and technology, 8(9): 491-497. gaye, cb. and tindimugaya, c. 2019. review: challenges and opportunities for sustainable groundwater management in africa. hydrogeological journal, 27: 1099–1110. https://doi.org/ 10.1007/s10040-018-1892-1. gonzalez-martinez, f., sanchez-rodas, d., caceres, dd., martinez, mf., quinones, la. and johnson-restrepo, b. 2018. arsenic exposure, profiles of urinary arsenic species, and polymorphism effects of glutathione-s-transferase and metallothioneins. chemosphere, 212: 927-936. howard, g., calow, r., macdonald, a., bartram, j., 2016. climate change and water and sanitation: likely impacts and emerging trends for action. annual review of environmental resources, 41: 253–276. huan, h., hu, l., yang, y., jia, y., lian, x., ma, x., jiang, y. and xi, b. 2020. groundwater nitrate pollution risk assessment of the groundwater source field based on the integrated numerical file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com umar et al: assessment of arsenic in groundwater in monguno, borno state, nigeria. azojete, 19(4):733-746. issn 1596-2490; 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epa/630/p-03/001f; risk assessment forum. washington, dc, usa. wash cluster meeting, 2022. water quality test discussion: higher arsenic concentrations in monguno town boreholes. borno state, nigeria. wei, b., yu, j., kong, c., li, h., yang, l., xia, y. and wu, k. 2018. a follow-up study of the development of skin lesions associated with arsenic exposure duration. environmental geochemistry and health, 40: 2729-2738. world health organization. 2011. guidelines for drinking-water quality (4th ed.). world health organization. page 314. isbn: 978-92-4-154995-0. yang, y., mcdonald, ac., wang, x., pan, y. and wang, m. 2022. arsenic exposures and prostate cancer risk: a multilevel meta-analysis. journal of trace elements in medicine and biology, 72: 126992. https://doi.org/10.1016/j.jtemb.2022.126992 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com https://doi.org/10.1007/s10653-019-00306-6 arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):555-574 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 555 original research article effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars g. i. agbara* and b. babagana department of food science and technology, university of maiduguri, nigeria *corresponding author’s email address: giagbara@unimaid.edu.ng 1.0 introduction bread is a spongy, yeasted baked dough of worldwide acceptance and its consumption although is reported to be on the decline in developed economies (dewettinck et al., 2008), article information abstract studies involving the use of composite flour for baked goods are unending for reasons such as high quest for functional foods, unsustainable wheat import and nutritional enhancement of baked goods. in this study, cassava flour (cf) was differently treated: roasted (cr), fermented (cf), oven dried (co) and sundried (cs) before separately blended with flours from de-braned, hammer milled nigerian wheat varieties, norman (wn) and atilla (wa) in the ratio of 75:25. the blends (8) were used to bake breads. refined commercial wheat flour bread was the control. the breads and the flour blends were evaluated for physical, chemical and sensory qualities using standard procedures. results revealed that the blends had higher ash (0.57-1.31%) and carbohydrate (76.69-81.03%), lower moisture (8.27-10.30%), protein (6.91-10.10%) and crude fat (1.28-2.45%) and desirable higher water and oil absorption capacities (0.85-1.30mg/g) and (1.16-1.40g/g) respectively. there were improvements in the swelling power (6.91-10.10g/g) and solubility (4.00-7.00%) due to cf addition. the ash, protein, and fibre of the treated breads were higher, while the carbohydrate and fat were lower than in the wheat bread. specific loaf volume (slv) of wheat bread (2.58ml/g) and bread with oven dried cf (2.61ml/g) were higher; others had lower slv not significantly different from each other (p>0.05). there were significant increase(p<0.5) in the mineral contents of the composite bread, more in the bread with sun and oven dried cf. the least amounts were recorded in the breads containing fermented cf for obvious reasons. as for wheat flour and the flour blends, they varied respectively: k 84.04-140.56, ca 20.29-38.79, mg 17 51-32.32, fe 2.26-4.91 and zn 1.40-2.59 (mg/100g) greater in the blends. as for the breads, significant variations were k 157.36-296.29, ca 22.61-60.94, mg 32.78-70.54, fe 2.98-7.47, and zn 1.56-7.47 (mg/100g) lower in wheat bread and bread containing fermented cf. wheat bread had superior sensory attributes followed by bread with oven-dried cf but the bread with fermented cf had the poorest sensory ranking. the composite bread had better nutritive value and poorer sensory properties, demanding the use of flavour enhancing agents in order to mask the unpleasant fermented taste and aroma. addition of dry heat treated cf to wheat flour (25:75) produced bread with overall quality comparable to wheat bread. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 august, 2022 revised 7 november, 2022 accepted 8 november, 2022 keywords: cassava flour fermentation dry heat treatment nigerian wheat cultivars wheat-cassava bread minerals http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 556 who incidentally are situated in the wheat belt of the world. rising urbanization, income enhancement and adoption of western styled diet, bread like many others foods has become an important staple, a food security item in the lives of urban dwellers in developing countries, supplying vital nourishment through provision of dietary energy, protein, minerals, vitamins and non-nutrients bioactive compounds (dewttinck et al., 2008). the unsustainability of the production of affordable nourishing bread from costly imported wheat motivated fao (1970) to initiate research on composite flour technology, a concept that has taken root and expanded to include baked and unbaked foods. the technological challenge has always been how to overcome the effects of gluten dilution on addition of non-wheat to wheat flour at higher level of replacement which in turn lower bread volume and alter bread texture. wheat grain contains 8-15% protein, 75-80% of the total is endosperm protein. there are two types of this protein: gliadins and glutenin (shewry, 2002), these two during dough formation constitute the gluten, a visco-elastic material with both nutritional and functional properties, and responsible for retaining leavening gases during fermentation and baking, and also provides structural frame to baked goods. cassava flour on the other hand contains approximately 80-90% starch, <5% protein, <1.5% fat among other constituents (montagnac et al., 2009; oladunmoye et al., 2010). availability of high quality cassava flours from improved cassava varieties in nigeria has made the formulation of wheat-cassava composite flours a commercial reality which continued to attract further investigations (eleazu et al., 2014; oladunmoye et al., 2014; aondoaver et al.,2021). however, the problem of bread volume depression remained the subject of many studies with varying outcomes. the study is currently being refocused from the evaluation of gluten quality and quantity to modifying the properties of non-wheat starch to accommodate greater than 10% wheat flour replacement. it was reported that higher than 10% substitution was said to have impaired bread volume and texture (eriksson et al., 2014). recent studies by olurin et al. (2021) demonstrated that among processing variables, cassava level significantly impact wheat-cassava loaf specific volume. it was also observed that 10% addition was found to be the optimum (eriksson et al., 2014). nindjin et al. (2011) concluded that cassava starch had better bread making power than cassava flour because of lower fibre content, the same authors reported that up to 30% starch inclusion yielded bread not different from the wheat bread. additionally, squenza et al. (2021) concurred that cassava starch is better than cassava flour, that 20% cassava flour reduced bread volume. starch can be modified through physical, chemical, and biological processes to suit end-use requirements. eduardo et al. (2013) reported that bread with roasted cf had significant higher volume unaffected by pectin and cassava level unlike bread with fermented or sun dried cf. iwe et al., (2015), miyazaki et al., (2006) and dudu et al., (2020), applied modified cassava starch as partial replacement of wheat flour and reported better bread quality which was not different from wheat bread. heat treatment alters starch microstructure. furthermore, senanayake et al., (2013) reported moist heat treatment of sweet potato starch increases its gelatinization temperature, enzymic susceptibility, swelling volume, and changes its x-ray diffraction pattern, in addition to enhancement of solubility index and swelling power. enzymes such as amylases, proteases, xylanases etc. are used as bread improvers for better bread making performance through enhanced aeration. among oxidants, ascorbic acid tops the list as bread improver, a powerful reducing agent that reinforces disulphide bonds of gluten network of weak flour for greater bread volume. therefore, idowu et al. (2017) applied specific improvers to enhance air incorporation in wheat-cassava bread, and observed 10% cassava bread had the best slv and noted that soy flour addition had bread volume depressing effect. pasqualone et al. (2010) on the other hand, utilized aerating property of egg white to produce acceptable wheat-cassava file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 557 bread. aristizabel galvis et al. (2017) observed that more than 20% cassava flour inclusion requires addition of additives to the formulation for greater bread quality. but contrarily, lagnika et al. (2019) reported 20% cassava flour was the best level and noted that water and oil absorption capacities increased while swelling power decreased on partial replacement of wheat flour with cassava flour. erikkson et al. (2014) reported 13.4g/g swelling power for wheat flour against 8.75g/g for cf indicating greater associate force within cf starch granules than in wf. however, agbara et al. (2020) reported that water absorption capacities of different brands of wheat flours sold in nigerian markets were enhanced on blending with either cf or sweet potato flour and concluded that greater flour water absorption was responsible for reduced bread volume and heavier weight in composite breads. dry heat application causes starch dextrinization, which leads to increased solubility and decreased swelling power, and in some cases residual water availability leads to initial gelatinization prior to dextrinization. heat application leads to amylose chains interaction or their binding to lipids, a process that alters starch functionality (hover, 1994). fermentation on the other hand changes starch microstructure, causes perforation of granules due to the action of microorganisms and their enzymes (oyeyinka and kayitesi, 2020) leading to the production of lactic acids and other flavour enhancing substances (demiate et al., 2000). numfor et al. (1995) observed that average starch granule diameter, solubility and swelling power were depressed after fermentation. in the present study differently treated cassava flours were blended with debranned, undegermed flours from two nigerian grown wheat cultivars (norman and atilla), the effects of the treatments on the quality of wheat-cassava bread were evaluated with reference to bread produced from commercial wheat flour. 2. materials and methods 2.1 material procurement and preparation 2.1.1 collection of raw materials nigerian wheat cultivars (norman and attila) were obtained from the lake chad research institute (lcri). cassava roots and commercial wheat flour (premium wheat flour, irs flour mills, lagos nigeria) and other baking ingredients were sourced from gamboru market, maiduguri, borno state nigeria. 2.1.2 preparation of wheat flour the wheat cultivars, norman and atilla were sorted, tempered, debranned, sun-dried and milled into flour. the flours were sieved through 0.250mm and stored in an airtight plastic jars to prevent moisture re-absorption (figure1) wheat ↓ sorting ↓ debranning ↓ sun-drying ↓ milling ↓ sieving ↓ wheat flour figure 1: flow chart for wheat flour production http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 558 2.1.3 preparation of cassava flour (fermented) the cassava roots were sorted washed, peeled, sliced, rinsed and soaked in water for 72 h for fermentation to take place. the water was changed every 24 h. the fermented cassava slices were further sun-dried for 3 days and milled into flour. the flour obtained was sieved (0.250 mm) and stored in an airtight plastic jar and left at room temperature. 2.1.4 preparation of cassava flour (roasted) the cassava roots were sorted, washed, peeled, sliced, rinsed, air dried and toasted at high temperature (150-180°c) in a pan using gas cooker for 15-20 min in order to gelatinize starch. the roasted cassava slices were further sun-dried for 48 h and milled into flour. the flour obtained was sieved with 0.250mm mesh and stored in an airtight plastic ja 2.1.5 preparation of cassava flour (oven-dried) fresh cassava roots were sorted, washed, peeled, sliced, rinsed, and oven dried at 80°c for 10 h. the oven-dried cassava slices were further air-dried for 3 days and then milled. the flour obtained was sieved through 0.250mm sieve and stored in an airtight plastic jars. 2.1.6 preparation of cassava flour (sun-dried) fresh cassava roots were sorted, washed, peeled, sliced, rinsed and sun-dried for 72 h. the sun-dried cassava slices were milled into flour and sieved. the flour obtained was stored in an airtight container and left at room temperature. the flowchart are combined and shown in figure 2 cassava roots sorting washing peeling slicing rinsing soaking [72h] toasting [150°c, 20min] oven drying [10h] sundrying sun drying air drying air drying milling milling milling milling sieving sieving [0.3mm screen] sieving sieving fermented cf roasted cf oven-dried cf sun dried cf figure 2: process flow chart for production of differently treated cassava flours (cf) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 559 2.2 blend formulation flour blends were produced in the following ratio; 75% wheat flour and 25% cassava flour. the formulations were: i) wncf (norman-fermented cassava flour, cf) ii) wncr (normanroasted cf) iii) wnco (norman-oven dried cf) iv) wncs (norman-sun dried cf) v) wacf (atilla-fermented cassava cf) vi) wacr (atilla-roasted cf) vii) waco (atilla-oven dried cf) viii) wacs (atilla-sun dried cf) ix) w100% (commercial wheat flour). cf, cr, co, cs: fermented, toasted, oven-dried, sun-dried cassava flours. each blend was thoroughly mixed in a kitchen mixer and packaged for analysis and bread making. 2.3.1 determination of functional properties of blends and wheat flour bulk density, water and oil absorption capacities, swelling power and solubility were determined as shown below. 2.3.2 bulk density (bd) the sample was filled into a 50ml cylinder up to 10ml mark; the cylinder was tapped gently on a laboratory bench to fill the air spaces within the flour in the cylinder (murphy et al., 2005). bd is equivalent to flour weight divided by flour volume 2.3.3 water absorption capacity (wac) and oil absorption capacity (oac) wac and oac were determined by modified method of niba et al. (2001). one gram (1g) weight was suspended into 5ml of distilled water for wac and another one gram (1g) suspended into 5ml of peanut oil in a centrifugal tube. the slurry was shaken on a flat form tube rocker for 20 min at room temperature and centrifuged at 3000 rpm for 15 min. the supernatant was decanted and the tube inverted over tissue paper to allow the adhering drop of water or oil escape and later the tube was reweighed. wac/oac = (wt. of sediment-wt of sample)÷(sample wt)…….. (1) 2.3.4 swelling power and solubility the swelling powers of flours were determined based on a modified method of leach et al. (1959) with modification: 0.5g of sample was placed into a pre-weighed centrifuge tube. 10ml of distilled water was then added and stirred. the mixture was placed on a water bath thermostatically controlled at 80°c with continuous stirring for 30 min. it was cooled to room temperature and centrifuged at 1500rpm for 15 min. the supernatant was poured into a preweighed crucible and then placed in an oven to evaporate. the solid residue left behind in the crucible expressed as a percentage of the weight of sample was % solubility. the weight of the sediment in the tube expressed as a percentage of sample weight was the swelling power. 2.4.1 bread recipe for bread production the recipe used for bread production is as shown below on 100% flour basis. flour =100g, sugar = 7g, salt =1g, yeast =1.4g, fat = 7g, warm water = 60-70ml. 2.4.2 bread making procedure the aacc (2000) straight dough method (10-10b) was slightly modified to prepare the various breads. dry ingredients were initially mixed in a mixer (mc-b100 crown star, china), later sugar (small portion) and yeast earlier dissolved in warm water were added and mixed and finally the shortening was robbed in and kneaded into smooth elastic-like dough, covered and allowed to ferment 90 min. after the first fermentation the dough was cut into roughly equal sizes and weighed, shaped and placed into greased bread pans and proofed for another 60 min in a fermentation cabinet. (80-85% r.h, 30±2°c). the proofed dough pieces were baked at 180-200°c for 30 min in a gas oven. after baking, the loaves of bread were allowed to cool to ambient temperature. http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 560 2.4.3 determination of physical properties of bread 2.4.4 bread weight the weight of cooled bread was determined by weighing each loaf of bread on an electronic weighing balance to the nearest tenth of a gram. 2.4.5 bread volume the volume of bread was determined by modification of rapeseed displacement method. (millet seed displacement method) (aacc, 2000). a loaf of bread was placed in containers of known volume, unoccupied spaces filled with filled with millet seeds to the brim. subtracting the volume occupied by the millet seeds from the total volume of the container was regarded as volume occupied by a loaf of bread. 2.4.6 specific loaf volume the specific loaf volume (slv) was obtained by dividing loaf volume by loaf weight (aacc, 2000). 2.5 determination of proximate composition of the flours and the bread moisture, crude protein, crude fat, crude fibre, total ash, was determined using the established procedures of aoac (2005). carbohydrate contents were obtained by 'difference'. 2.5.1 determination of moisture content the moisture content was determined by drying 2 g of the sample in at 150°c for 1 h. weight loss expressed as the percentage of the initial weight was regarded as % moisture content. 2.5.2 ash content ash content was determined by incinerating 5g of each sample in a muffle furnace at 550°c for 5 h, the grey ash were cooled in a desiccator to avoid absorption of moisture and weighed after to obtain ash content. 2.5.3 crude fiber about 5g (wo) of sample was weighed into a 500ml erlenmeyer flask and 100ml of tca digestion reagent was added. the samples were then boiled for 40 min counting from the start of the boiling. the flasks were removed from the heaters, cooled (30 min) then filtered through a whatman no. 4. the residues were washed with hot water stirred once with a spatula and transferred to a porcelain dish. the samples were dried overnight at 105°c. after drying, samples were cooled in desiccators and each weighed as w1. the samples were burnt in a muffle furnace at 500 °c for 6 h, allowed to cool and re-weighed as w2. % crude fiber = w1− w2÷(wo) ×100……..equation (2) where wo → dry weight of food sample, w1 → weight of crucible + fiber + ash, w2 → weight of crucible + ash (2) 2.5.4 fat content the soxhlet extraction method was used for the determination of the fat content of the samples. about 5g of each sample was weighed and the weight of the flat bottom flask taken with the extractors mounted on them. the thimbles were held half way into the extractors with the weighed samples. extractions were carried out using petroleum ether (boiling point 40-60°c). the thimbles were plugged with cotton wool. at the completion of extraction, the solvents were removed by evaporation on water bath and the remaining part in each flask was dried at 800c for 30min in the oven to dry the fat. the flasks were cooled in a desiccator, and reweighed to obtain the wright of fat expressed in percentage. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 561 2.5.5 protein content the micro kjeldhal method was used to determine crude protein content of the samples. about 0.2g of each sample was placed into digestion flask, 10g of catalyst (copper sulfate and sodium sulfate, 5:1) and 25ml concentrated sulfuric acid were added to each digestion flask the flasks were placed into the digestion block in the fume cupboard and heated until frothing ceased giving clear and light blue green coloration. the mixtures were then allowed to cool and diluted with distilled water (total, 250ml). distillation apparatus were connected and 10ml of the samples poured into separate receivers of distillation apparatus. also 10ml of 40% sodium hydroxide (naoh) was added. the released ammonia was absorbed by boric acid which was then titrated with 0.02m of hydrochloric acid until green color change to purple. percentage of nitrogen in the sample was calculated using the formula below % nitrogen = (t˗˗b) × normality of acid ×14.008 ÷ (weight of sample × 1000) x 100 (3) where b= blank titer value, t = actual titer value, % protein = %n x 6.25 2.6 determination of mineral composition of the blends and bread the minerals (potassium, calcium, magnesium, zinc, and iron) were determined according to the established procedures of aoac (2005) using the ashes obtained during the ash determination process. 2.7 evaluation of sensory properties of bread twenty (20) panelists s consisting of 9 males and 11 females evaluated the breads based on shape, crust color, aroma, crump sponginess, mouth feel, taste, and acceptability on a 9-point hedonic scale where 9 is like extremely, 5 neither like nor dislike and 1 equivalent to dislike extremely. (ihekoronye and ngoddy, 1985). coded samples were randomly presented to the panelists during a two sessions of 10 judges each. warm water was provided for mouth gargling. 2.8 statistical analysis data (functional, chemical, sensory properties) were subjected to analysis of variance. means were separated using duncan's multiple range test and significance set at 5% probability (p<0.05) 3. results and discussion 3.1 functional properties of wheat and differently processed cassava composite flours table 1 reveals the bulk density of the flours ranged between 0.62g/ml (wacf) and wncf and 0.68g/ml for w100, wnco, and wacr indicating fermented cassava flour had lower density or higher porosity due to presence of coarser flour particles. lower density may correlates positively with lower calorific value, usually finer starchy stuff presents higher density. the blends containing oven or roasted cassava flour (cf) had relatively higher bulk density (0.650.68) indicating higher dry matter or greater nutritive value or presence of finer flour particles. bulk density has greater influence on dispersibility, wettability and other hydration properties of blends as in wet processing apart from its influence on handling and storage. bulk density is generally influenced by flour density and its granulation characteristics which determines the packaging requirements and material handling (adebowale et al., 2012). the water absorption capacities (0.85-1.30g/g), oil absorption capacities (1.16-1.40ml/g), swelling capacities (6.7110.10g/g), and water solubilities (4.00-7.00%) with the following grand mean 1.10g/g, 1.27g/g, 7.61g/g, and 4.58%. these values are not far from the values reported by aondoaver et al., (2021) for wheat-cassava (90:10) flour. agbara et al. (2020) reported water absorption capacities of 1.31-2.00ml/g for different brands of wheat flours sold in nigerian markets and http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 562 their blends with either 20% cassava or 20% sweet potato flour. lagnika et al., (2019) had earlier observed an increase in wac & oac and decrease in swelling power on replacing 20% wheat flour with cf. the blends had greater water absorption than the wheat flour and among the blends, more in those containing oven and sun-dried cf. flour water absorption capacity is determined by the presence of hydrophilic groups of proteins and carbohydrates that are able to form hydrogen bonds with water molecules (singh, 2001). wac gives general idea of flour suitability in aqueous food formulations, dough handling and machinability as commercial bulk fermentation (okerie, et al., 1988). the blends had higher oil absorption capacity (oac) than the control, a desirable quality for better bread texture and flavour. again blends containing atilla flour blended with either roasted or oven dried cassava flour had greater oac. swelling capacity is under the influence of many factors such as temperature, starch granule type, ratio of amylose to amylopectin. the blends had greater swelling powers (sp) (6.71-10.10) than the wheat flour (6.71g/g), the variation between them was not wide as indicated by the coefficient of variation of 0.533%, however blends with fermented cassava flour had the highest sp (wacf 10.1g/g and wacf 7.98g/g). the control had higher fat contents than others, and might be responsible for reduced swelling. water solubility of the blends (4.00-7.00%) was low and the control had the least, with minimal variations between the observed values. polymers such as starch and protein form a colloidal solution with water. however, flours naturally contain free sugars, amino acids and shorter chain polypeptides and amylose leached out during heating. starch dextrinization as a result of dry heat application might lead to increased flour water solubility, therefore, blends containing dry heat treated cf blended with norman had slightly greater solubility. the solubility of flour is influenced by such factors such as flour composition, particle size, temperature, ph, and processing and storage conditions (mirhosseini and amid, 2013). swelling capacity is said to be a combined effect of protein and starch content in flour (woolfe, 1992). swelling capacity is also related to ratio of amylose to amylopectin of the starch (adebowale et al., 2005). lower amylose content is equivalent to higher flour swelling power. oladunmoye et al. (2014) reported greater amylose in wheat starch (28.19%) than in cassava starch (19.49%), against 25.53% reported by ojo et al. (2017) for cassava starch. the bottom line is higher bulk density, water and oil absorption capacities, swelling power, and solubility are desirable properties for flours used for baked goods especially bread making. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 563 table 1: functional properties of flour blends produced from nigerian wheat (norman and atilla) with differently treated cassava and control sample bd (g/ml) wac(g/g) oac(g/g) sp(g/g) slb (%) w wnco waco wncr wacr wncs wacs wncf wacf 0.68±0.00a 0.68±0.0058a 0.67±0.0115a 0.65±0.0100b 0.68±0.0058a 0.65±0.0115b 0.63±0.0115c 0.63±0.0100c 0.62±0.0058c 0.85±0.05d 1.12±0.01c 1.30±0.10a 1.21±0.10ab 1.29±0.10a 1.11±0.00cd 1.07±0.20cd 1.12±0.02c 0.97±0.10d 1.11±0.03c 1.13±0.10c 1.34±0.10a 1.11±0.10c 1.35±0.10a 1.22±0.10b 1.26±0.10b 1.24±0.10b 1.24±0.10b 6.71±0.01d 7.16±0.03c 7.33±0.03ab 7.12±0.01c 7.20±0.1ab 7.31±0.01ab 7.51±0.01b 10.1±0.05e 7.98±0.01a 4.00±0.00d 6.00±0.20b 5.00±1.00c 7.00±0.50a 5.00±0.00d 4.00±0.30d 5.00±1.00c 6.00±0.00e 5.00±1.00c cv% 1.34 4.58 4.17 0.533 13.45 data are means ± sem. (n=3) means with the same superscript in a column are not significantly different (p>0.05). w: 100% commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn &wa 75:25. bd:bulk density, wac & oac: water & oil absorption capacity, sp:swelling power, slb: solubility. 3.2 proximate composition of the composite flours produced from differently treated cassava flours blended with atilla and norman (wheat cultivars) flours table 2 shows that the wheat (w) flour had higher moisture, protein, crude lipid and lower ash and carbohydrate. moisture, ash, protein, crude lipid, and carbohydrate contents of the flour blends varied significantly (p<0.05) from 8.27%-10.30%, 0.57-1.31%, 7.49-9.20%, 1.281.24% and 76.69-81.03% respectively. among the blends those containing sun-dried cf had slightly higher moisture while those with toasted and oven dried cfs had the least. effective flour storage demands moisture contents less than 14% (ahmed, 2015). additionally, effective packaging and low temperature storage. the ash contents of wheat-fermented cf blends were lower than in other blends but greater than the ash content of the commercial wheat flour (0.67%) and greater ash were located in wheat-sundried cf blends (wncs 1.15% and wacs 1.13%. leaching that occurred during fermentation/soaking was responsible for the lower ash contents of blends containing fermented cf. ash represents the inorganic material component and the extent of its presence is determined by flour extraction rate. protein content of the control (w) was higher (9.20%) and decreased in the blends, and among the blends it was higher in wheat-sundried cf and lower in blends containing roasted and fermented cfs (wacfn7.49%, wncf 7.75, waco 7.63% and wncr 7.51%). agume et al. (2017) similarly reported that soaking and roasting of soybeans decreased total protein of soy flour by 23%. crude lipids were lower in the blends (1.28 and 1.76%), highest in the control(w) (2.45%). lower fat and protein cf dilutes the level of the same in wheat flour whenever blended together. cassava flour contains less than 1-3% protein and less than 1.5% fat (montagnac et al., 2009). cf addition to wheat flour for bread making is primarily to obtain affordable bread with good physical and sensory characteristics, not necessarily for nutrient value enhancement, however there were enhancement of the ash and possibly the dietary fibre contents of the blends although it was not measured. cf has a dietary fibre content of 4% against 1.5% in the fresh tuber (montagnac et al., 2009). ibidapo et al. (2019) did not observe any meaningful differences in the proximate compositions of the flours of four nigerian grown wheat cultivars, the following range of values were obtained: protein 15-16%, fat 0.88-1.3%, fibre<3.5%, ash<1.0% and carbohydrate 69-73%. http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 564 table 2: proximate composition (%) of norman and atilla wheat cultivars blended with differently treated cassava flours (75:25) sample moisture total ash crude protein crude lipid cho w wnco waco wncr wacr wncs wacs wncf wacf 10.30±0.05a 8.78±0.09c 8.27±0.03d 8.30±0.02d 8.28±0.02d 9.91±0.02b 9.50±0.00b 8.76±0.01c 8.97±0.02c 0.65±0.06d 1.31±0.03a 0.96±0.03c 0.98±0.00c 1.00±0.01c 1.15±0.02b 1.13±0.03b 0.69±0.01d 0.57±0.01e 9.20±0.04a 8.43±0.06b 7.63±0.11c 7.51±0.03c 7.69±0.03c 9.06±0.04a 8.63±0.17b 7.75±0.01c 7.49±0.02d 2.45±0.00a 1.64±0.02c 1.51±0.12d 1.28±0.06e 1.63±0.01c 1.65±0.01c 1.49±0.29d 1.76±0.01b 1.37±0.02e 76.69±0.09d 78.63±0.16c 80.68±0.28ab 80.95±0.06a 80.51±0.08ab 77.05±0.09d 78.14±0.43c 80.37±0.03b 81.03±0.06a cv% 0.4087 2.83 0.9146 6.49 0.2387 data are means ± sem.(n=3) means with the same superscript in a column are not significantly different (p>0.05).w: commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn &wa 75:25 3.3 proximate compositions (%) of bread produced from nigerian wheat cultivars (norman and atilla) blended with differently treated cassava flours (75:25) significant variations (p<0.05) were observed in the proximate composition of the breads (table 3). bread moisture reflects baking time and temperature, nature of ingredients used in formulation and also proofing time. bread moisture varied from 21.14% (wacf) to 30.18% (wnco). formulations containing oven-dried and roasted cf had higher moisture especially those blended with norman wheat flour. bread moisture has implications on its tenderness, storage stability and stalling tendency. high moisture content has been associated with short shelf life of composite bread as it encourages microbial proliferation that leads to bread quality deterioration (eleazu et al., 2014) but reduces rate of stalling and greater tenderness on the other hand. wheat bread had lower moisture as similarly reported by ndungu et al. (2015) and pasqualone et al.(2010). crude lipid content of the breads were enhanced in some, but in others fat contents of the composite breads were lower than recorded for the wheat bread, the values varied from 7.19% (wacr) to 10.86% (wacf), least in the bread containing roasted or oven dried cassava. but an increase in oil has been reported in the flours of some seeds after roasting (agume et al.,2017). the difference in the fat contents of the breads must have originated either from the wheat cultivars since cassava is a poor source of fat and moreover equal amounts of fat were used in the formulations. with reference to table 2, atilla tends to contain slightly higher fat than norman, the two wheat cultivars were equally treated during milling. the dietary fiber contents of the breads (0.57-1.21%) were in majority of the cases higher in the treated breads and which originated from the added cassava flours, breads with fermented cassava and wheat bread had the least level of fibre. norman wheat flour proved to be fibre richer than atilla flour or it could be the effect of dry heat treatment the cassava roots received. both soluble and insoluble fiber are now recognized to be beneficial to humans, breads like most processed foods from refined cereal or root tuber flours are not good sources of dietary fibre needed for the well-being of modern man that cherish convenient foods and ready-to-cook refined cereals. the higher carbohydrate content of the wheat bread (49%) indicates higher dietary energy, the amount was not significantly different(p>0.05) from the amounts recorded for bread with fermented cf (47.70-47.94%) and the lower amounts were recorded in the breads that contained roasted, oven dried or file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 565 sundried cf. eleazu et al. (2014) reported carbohydrate content of 42.91-47.09% for cassava breads. addition of differently treated cfs to wheat flour enhanced the ash contents, greater than 1.12% observed in the control, and ranged from 1.18% to 1.81% in the composite flour breads. breads with fermented cf had lower ash contents as observed in wnco (1.18%). blending increased the ash contents of the resulting blends but more in breads due to added yeast, salt and water used in formulations. ash indicates the inorganic component of biological material, flour extraction rate determines its colour and ash content. although higher ash content is beneficial to human nutrition, however sensory attributes of the breads could be impaired if overly high amounts of ash is present, and perhaps accompanied by higher presence of antinutrients. the protein content of the breads varied from the lowest recorded for atillafermented cf bread (10.78%) to 15-41% (norman-oven dried cf) bread. breads with oven or roasted cf had higher protein, perhaps due to higher dry matter content of dry heat treated cf. flours from nigerian wheat cultivars used in the study had higher level of protein and fat than the commercial wheat flour used as the control. ibidapo et al. (2018) had earlier made similar observation and observed insignificant difference in the nutritional value of four nigerian grown wheat cultivars. higher amounts of fat was recorded in breads containing fermented and sundried cf, and in wheat bread. atilla breads had higher amounts of fat than norman. the bottom line is bread containing heat treated cf have greater, ash, protein, moisture, and lower fat, fibre and carbohydrate. table 3: proximate compositions (%) of bread produced from nigerian wheat cultivars (norman and atilla) blended with differently treated cassava flours (75:25) sample moisture total ash crude protein crude lipid crude fiber cho w wnco waco wncr wacr wncs wacs wncf wacf 22.46±0.18d 30.81±0.61a 29.47±0.14b 30.49±0.47a 30.38±0.22a 27.22±0.26c 23.70±0.02d 28.23±0.10b 21.14±0.16d 1.12±0.08d 1.18±0.01d 1.49±0.02b 1.81±0.01a 1.76±0.03a 1.73±0.02a 1.56±0.03b 1.26±0.04c 1.45±0.02b 11.45±0.09d 15.41±0.30a 14.73±0.07b 15.24±0.24a 15.19±0.11a 13.89±0.14c 12.09±0.01d 14.40±0.05b 10.78±0.08cd 10.10±0.13b 8.25±0.06d 9.29±0.06c 7.19±0.10cd 7.73±0.05d 9.36±0.05c 10.62±0.12a 8.06±0.13d 10.86±0.06a 0.67±0.01c 1.21±0.07a 0.95±0.03b 0.97±0.01b 0.88±0.03b 1.18±003a 1.11±0.02ab 0.67±0.01c 0.57±0.02d 49.00±0.43a 44.73±0.66b 42.39±0.26d 45.50±0.70b 44.71±0.32b 43.32±0.22c 44.39±0.39b 47.78±0.45a 47.94±0.36a cv% 1.10 2.34 1.09 0.9905 3.17 0.9820 data are means ± sem.(n=3) means with the same superscript in a column are not significantly different (p>0.05).w: commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn &wa 75:25 http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 566 3.4 physical properties of bread produced from the blends of nigerian wheat cultivars (norman and atila) and differently treated cassava flours as shown in table 4, bread weight (429-456g), volumes (1010-1170ml) and specific volumes (2.25-2.68) were comparable indicating little variation between the values obtained. wheat bread had the least weight and therefore responsible for the highest specific volume but bread containing oven dried cf blended with norman (wnco) had the highest bread volume (1170ml) significantly not different from the volume of wheat bread (1150ml). others had absolute bread volumes less than these two (wnco and w100%). breads containing norman had greater volumes than those containing atilla, perhaps norman is a stronger wheat and able to do well with dry heat treated cf. agbara et al. (2020) reported 2.16-2.48 ml/g slv for 20% cassava or 20% sweet potato bread and slv of 2.55-3.28ml/g for bread made from different wheat flour brands sold in nigerian markets which are similar to slv obtained in the present study. expectedly, higher slv was recorded for wheat bread as equally reported by padqualone et al.,2010; menon et al.,2015; agbara et al.,2020). higher water absorption capacity of the blends (agbara et al., 2020) or higher particle size of cf (lagnika et al.,2019) and fibre content of cf (agbara et al.,2020) than obtain in wheat flour might be responsible for the bread volume depression and not necessarily gluten dilution, and this calls for use of cf of finer granulation therefore lower fibre content for cf inclusion greater than 10%. erikkson et al. (2014) observed that cf from three varieties of cassava had greater swelling power, solubility and water binding capacity than wheat flour. but lagnika et al. (2019) reported greater water absorption for wheat flour than cf; varietal differences and location might be responsible for this disparity. bread volumes and specific volumes for bread with sundried and fermented cf performed poorly despite the fact that they had lower water absorption. chisenga et al. (2020) reported a lower specific loaf volume (slv) of 1.5-2.5 g/ml for wheat-cassava bread against higher slv reported by erikkson et al.(2014). aristizabal et al. (2017) recommended addition of improvers if the added cf is greater than 20%. idowu et al. (2015) reported greater slv (3.14-3.57ml/g) for 10% cassava bread treated with improvers. fermented cassava flour had comparable bread volume depressing effect like theheat treated cf; dextrinization of cassava starch molecule occurred as a result of dry heat application and caused reduction of its swelling power but increased its water absorption due to higher dry matter content. however, bread volume enhancing effect of dry heat treated cf was not significantly different from that of wheat flour or the effect could have originated from greater bread making power of norman than atilla as observed in this study. table 4 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 567 table 4: physical properties of bread produced from the blends of nigerian wheat cultivars (norman and atila) and differently treated cassava flours sample specific loaf volume (ml/g) loaf volume (ml) bread weight (g) w (100%) wnco waco wncr wacr wncs wacs wncf wacf 2.68±0.10a 2.61±0.11a 2.29±.009a 2.39±0.08b 2.25±0.03b 2.31±0.03b 2.37±0.07b 2.37±0.08b 2.25±0.02b 1150±9.21a 1170±9.20a 1030±9.10c 1090±5.30b 1010±7.41c 1035±7.50c 1060±5.81b 1060±5.07b 1010±4.98c 429±2.08c 448±3.10b 450±5.13a 456±5.25a 449±5.10a 448±2.11b 447±3.00b 447±3.02b 451±5.12a cv% 0.06 7.06 3.76 data are means ± sem.(n=3) means with the same superscript in a column are not significantly different (p>0.05).w: commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn & wa 75:25. 3.5 mineral compositions (mg/100g) of flour blends produced from nigerian wheat (norman and atilla) cultivars blended with differently treated cassava flours (75:25) the mineral contents of the commercial wheat flour (w) and the wheat-cassava flour blends are presented in table 5. atilla-fermented cassava flour had the least concentration of the investigated elements (k, ca, mg, fe and zn) as a result of leaching and the mineral content of the refined wheat flour and those of norman-fermented cassava flour were not significantly different (p>0.05). norman-oven dried cf (wnco) had the greatest concentration of these elements and the next were blends containing sun-dried cf. norman appeared to have greater mineral content than atilla as revealed by higher mineral content of norman containing blends. since dry heat exposure increases the dry matter content of a product, therefore all the samples containing dry heat treated cf had higher mineral content than blends containing fermented cf. refined wheat flour unless fortified after milling, gets depleted of essential macroand micronutrients including non-nutrient bioactive compounds due repetitive grinding and sifting. according to lopez et al. (2003), 80% of the total amount of minerals is concentrated in the aleurone layer of wheat pericarp (bran), which is removed during milling while only 20% minerals are present in endosperm. hussein et al. (2013) similarly reported lower levels of elements in wheat flour milled in a quadrumat junior mill than in barley and corn flours ground whole. the order of dominance of the elements in the various blends was k>ca>mg>fe>zn and the range recorded for each investigated element in the blends were: k 84.96-140.56 > ca 17.62-38.79 > mg 14.69-32.32 > fe 2.23-4.91 > zn 1.172.5mg/100g. the values recorded for refined wheat flour in this study were within the wide ranges reported by araujo et al. (2015) for mineral content of commercial wheat flours sold in brazilian cities. but emmanuel-ikpeme et al. (2012) and hussein et al.(2013) reported slightly higher mineral contents in the respective wheat flours that served as control in their various, however values reported by oluwalana et al. (2012) for both the wheat flour and wheat-sweet potato bread were lower than the concentrations of the same elements obtained in this study. http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 568 table 5: mineral compositions (mg/100g) of flour blends produced from nigerian wheat (norman and atilla) cultivars blended with differently treated cassava flours (75:25) sample k ca mg fe zn w (100%) wnco waco wncr wacr wncs wacs wncf wacf 84.04±2.05d 140.56±3.43a 100.77±0.50cd 105.89±2.58c 107.47±2.62c 119.22±1.20b 121.36±2.96b 84.96±2.07d 68.08±0.69d 20.29±0.21d 38.79±0.39a 29.36±0.72c 30.25±0.74c 29.66±0.30c 35.27±0.86b 34.67±0.85b 20.51±0.21d 17.62±0.43e 17.51±0.43d 32.32±0.33a 24.47±0.60c 25.21±0.62c 25.59±0.62c 28.39±0.29b 28.89±0.70b 17.70±0.43d 14.69±0.36e 2.66±0.65d 4.91±0.50a 3.72±0.91c 3.83±0.93c 3.75±0.38c 4.31±0.44b 4.39±1.07b 2.69±0.66d 2.23±0.54e 1.40±0.03c 2.59±0.03a 1.89±0.02b 1.68±0.58b 1.98±0.02b 2.27±0.02a 2.23±0.02a 1.42±0.03c 1.17±0.03d cv% 2.15 2.03 2.12 1.97 10.54 data are means ± sem.(n=3) means with the same superscript in a column are not significantly different (p>0.05). w: commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn &wa 75:25 3.6 mineral contents of breads produced form the blends of nigerian wheat cultivars with differently treated cassava flours (75:25) significant enhancements of the mineral contents of the composite breads were the outcome of blending wheat flour with differently processed cf (table 6). wheat bread and breads containing fermented cf had the least concentration of k, ca, mg, zn and fe and in most cases were not significantly different (p>0.05) from the concentration of the same element in the refined wheat flour used as the control, and higher levels of concentration of these minerals were observed in breads containing roasted and sundried cf. leaching during soaking/fermentation was responsible for the lower contents of minerals in bread containing fermented cf. sun drying had little negative impact on the mineral contents of the cassava flour than roasting, oven drying and fermentation therefore breads containing sundried cf contained the highest levels o investigated elements closely followed by bread containing roasted and oven dried cf perhaps due to higher dry matter than fermented cf. the order of dominance followed the same trend noticed earlier in the composite flours (table 6). higher nutritive value is one of the outcomes of the application of composite flour in bread making. separate or combined inclusion of quinoa, chickpea or spirulina flour is responsible enhanced mineral content of shammy bread reported by el-said et al. (2021), in another study, okereke et al. (2021) enhanced the mineral content of wheat-root tuber native or modified starches with the addition of moringa oleifera seed flour. observed increased in the minerals in the present work must have originated from the flours of two wheat cultivars that were not commercially milled therefore retained higher level of nutrients, and the additional effect of added cassava flours. oluwalana et al (2012) similarly observed greater enhancement in the mineral content of wheat-sweet potato bread than in the wheat bread. winiarskar-meczan and kviecien (2011) reported the following mean levels of minerals contained in various bread types consumed in lublin, portland: 12.22, 56.2, 362.5, 110.4, 308.4, file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 569 2.7, 1.9, 0.4, 2.1 (mg/100g) for ca, mg, na, k, p, fe, zn, cu, mn respectively, these values are lower than the levels of minerals obtained in this study, perhaps due to lower dry matter (56.94-62.20%) of the reported breads in question. processing conditions, prevailing soil characteristics, location and cultivar of crop are among the factors influencing mineral content of food products. table 6: mineral compositions (mg/100g) of composite bread produced from the blend of nigerian wheat norman and atilla blened with differently treated cassava sample k ca mg zn fe w 157.36±8.71c 22.61± 1.61f 32.78± 1.82e 1.56± 0.13c 2.98± 2.47f wnco 271.10±7.31b 45.43± 0.28d 62.34± 0.47c 3.02± 0.01b 5.78± 0.36c waco 225.59±2.64 43.50± 1.50d 54.78± 1.70d 2.80± 0.01b 5.53± 1.90d wncr 271.26±5.55b 54.59 ±1.02b 64.58± 1.32bc 3.64± 0.06a 6.93± 1.30b wacr 269.55±3.90b 51.94± 1.26c 64.17± 0.92bc 3.46± 0.08a 6.59± 1.60bc wncs 296.29±2.94a 60.94± 1.73a 70.54± 0.70a 3.92± 0.04a 7.47± 0.82a wacs 280.52±3.20a 53.89± 0.27b 66.79± 0.76b 3.47± 0.10a 6.84 ±0.35b wncf 170.99± 7.56b 25.73± 0.56e 35.62± 1.57e 1.77± 0.10c 3.39 ±1.90e wacf 149.92± 2.87c 25.45± 0.26e 32.33± 1.82e 1.69 ±0.02c 3.23± 0.34e cv% 4.96 0.94 1.23 0.06 1.22 data are means ± sem. (n=3) means with the same superscript in a column are not significantly different (p>0.05). w: commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn &wa 75:25 3.7 sensory characteristics of bread produced from the blends of nigerian wheat cultivars (norman and atilla) and differently treated cassava flours (table 7) 3.7.1 shape denatured protein along with gelatinized starch granules is responsible for the structural framework of bread and other baked goods. addition of differently processed cassava flour (cf) at 25% level was sufficiently enough to dilute the gluten level, therefore the control had the best shape (8.07) on a 9-point hedonic scale, followed by the bread containing oven dried (wnco 7.53 and waco 7.33.) and sun dried cassava. bread containing roasted cf had the poorest shapes wacr 6.20 and wacr 6.40 indicating the adverse effects of incorporating fully pre-gelatinized starch on bread shape. 3.7.2 crust colour crust defines the extent of browning, which is determined by temperature and time of baking and availability of sugar substrates for browning reactions. generally, crust colour of the various bread was generally low, the oven dried (7.67) and sundried (7.15) had better crust colour scores that were not significantly different from wheat bread. bread with fermented cf had the poorest crust colour because not sufficiently browned because of reduced sugar availability for browning. 3.7.3 aroma generally, aroma of the various bread were equally high but the fermented cassava aroma caused lower aroma scores for bread with fermented cf (wncf 7.07 and 6.93 wacf), wheat bread, oven dried, roasted and sundried breads had greater aroma scores. unpleasant aroma and colour can develop during fermentation or during sun drying of cf no matter the length of time involved, which in turn might affect the bread aroma or colour negatively. on the other hand roasting introduces pleasant aroma to foods but uncontrolled roasting process http://www.azojete.com.ng/ file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 570 impairs both aroma and appearance of roasted foods. bread containing atilla appeared to have higher aroma scores. aroma scores of the 100% wheat was not significantly different from aroma of breads containing roasted cf 3.7.4 mouth feel this occurs as a result of the impression conveyed to the tactile receptors in bucal activity concerning the smoothness, coarseness, oiliness, dryness etc. of the food. mouth feel scores varied from 8.53 for the wheat bread and decreased progressively in the composite breads to 6.40 (wncf), meaning the wheat bread had better smooth passage in the mouth than the treated breads. others with high mouth feel scores were: wnco 7.40, wncs 7.40, wacf 7.27 and waco 7.00. difference in flour granulation decides both texture and mouth feel of the breads among others parameters. 3.7.5 taste taste score of 100% wheat (8.40) was significantly higher than those of composite bread just like any other bread attribute under investigation here. bread taste is determined by presence of simple sugars, bread ph or acidity as well as salt and other bread ingredients in the formulation. bread with fermented cf with reduced ph had the poorest taste (wncf 7.00 and wacf 6.20) followed by sun-dried cf (wncs 7.07 and wacs 6.93), the taste was influenced by fermented odour. in fact addition of differently cf altered the taste profile of the wheat breads, cf itself has bland taste and excellent white colour, and the treatments were responsible for the lower taste scores of composite breads. 3.7.6 overall acceptability the overall acceptability was significantly greater in the wheat bread followed by bread containing oven dried cf and other breads containing atilla, least acceptability scores were recorded for bread with fermented cf. human taste buds usually resists the introduction of novel or modified foods and this resistance usually gives way with time due to sensitization both physical and physiological. table 7: sensory characteristics of bread produced from the blends of nigerian wheat cultivar (norman and atila) and differently treated cassava flours sample shape crust color aroma crumb structure mouthfeel taste overall acceptability w wnco waco wncr wacr wncs wacs wncf wacf 8.07±3.09a 7.53±2.81a 7.33±2.88b 6.20±2.86d 6.40±2.59d 7.27±3.09b 6.60±2.80d 6.27±2.83d 7.07±2.91c 7.60±2.92a 7.67±2.35a 6.73±2.75b 6.33±2.72 7.00±2.36ab 6.80±2.78b 7.15±3.10a 6.07±3.15d 6.55±3.10c 7.73±2.68a 6.53±3.03d 7.13±2.08c 7.27±2.76c 7.60±2.76a 7.33±2.45b 7.47±2.25b 7.07±3.12c 6.93±2.79d 8.33±2.35a 7.93±2.39a 6.67±3.02c 6.93±3.62c 6.80±3.14c 7.13±2.92b 7.00±2.69b 6.60±2.84 7.20±2.52b 8.53±2.41a 7.40±2.55b 7.00±2.65c 6.60±3.44d 6.87±3.20c 6.93±3.09c 7.40±3.80b 6.40±3.16 7.27±2.88b 8.40±2.59a 7.47±2.60b 7.00±2.89c 6.73±2.67d 7.20±3.54b 7.07±2.53c 6.93±.2.53d 7.00±2.85c 6.20±3.01e 8.80±1.80a 7.40±2.15b 7.80±2.82b 6..73±2.67d 7.20±3.34c 7.07±2.53c 6.93±2.53c 6.20±3.01e 6.60±2.80d cv% 3.14% 3.10% 2.78% 2.82% 3.13% 2.94% 2.73% data are means ± sem.(n=3) means with the same superscript in a column are not significantly different (p>0.05). w: commercial wheat flour, wn: norman, wa: atilla, co, cr, cs, cf are oven-dried, toasted, sun-dried, fermented cassava flours respectively blended with wn &wa 75:25. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng agbara and babagana: effects of differently treated cassava flours blended with bambara groundnut flour on the bread making potential of two nigerian wheat cultivars. azojete, 18(4):555-574. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 571 4. conclusion norman performed better than atilla with dry heated cassava flour in terms of bread volume and flavour. however, depressed bread volume in the treated breads was observed and this is a recurring and yet to overcome challenge in the application of composite flour for bread making. but the truth is oven dried, roasted and sun-dried cassava flours blended with any of these wheat varieties produced acceptable bread with higher nutritive value and comparable bread volume with respect to wheat bread. however, bread containing fermented cf required additional flavour enhancing agents to mask unpleasant fermented odor and taste. moreover, fermented cassava flour had poorer functional properties inimical to bread dough formation, and mineral leaching during soaking further depleted mineral contents of the blends and breads containing fermented cassava flour (cf). the bottom line: pretreatment of cassava flour or its starch provides better functionality and satisfaction of end use requirements, and dry heat pretreated cf provides better performance in bread making. references aacc 2000. approved methods of analysis. association of american cereal chemists, 10th ed., aacc international, st.paul, mn. adebowale, ar., adegoke,m.t, sanni, s.a. adegunwa m.o. 2012. functional properties and biscuit making potential of sorghum-wheat flour composite. american journal of food technology, 7(6):372-379. adebowale, ya., adeyemi, a. and oshodi, aa 2005. physicochemical and functional properties of winged bean flour and isolate compared with soy isolate. journal of food science, 53: 450-454. agbara, gi., ishira, i., kassum, la. and lawan, hk. 2020. evaluation of bread making performance of some wheat flour brands available in nigerian markets as affected by cassava or sweet potato flour inclusion. journal of food technology research, 7(2): 144-153. agume, asn., njintang, ny. and mbofung, cmf. 2017. effects of soaking and roasting on the physiochemical properties and pasting properties of soy flour. foods, 6(2):12. doi:10.3390/foids6020013 ahmed, msh. 2015.effect of storage temperature and periods on some characteristics of wheat flour quality 06(12): 1148-1159, 19.4236/fns.2015.612120. aoac 2005. official method of analysis of aoac international, 18thed association of official analytical chemists international, maryland, usa. aondoaver, as., praise, aj., omolola, aj. and oshiapi, ip. 2021. physical and micro structural properties of composite cassava-wheat, produced from blends of wheat and low post harvest physiological deterioration cassava flours. american journal food science and technology, 9(4):142-148, doi:10.12691/ajfst-9-4-5. araujo, r., macedoo, sm., korn, mdga., pimental, mf., bruns, re. and ferreira, slc. 2008. mineral composition of wheat flour consumed in brazilian cities. journal of the brasilian chemical society, 19(5): 935-942; 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vol. 18(4):555-574. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: giagbara@unimaid.edu.ng 574 ojo, mo., ariahu, cc. and chinnma, ec. 2017 proximate functional and pasting properties of cassava starch and mushroom (pleurotus pulmonarius) flour blends. american journal of food science and technology, 5(1):11-18. doi: 10.1269/ajfst.5.13 okereke, go., igbabul, bd. and ikya, jk. 2021. evaluation of bread made from wheat flour, modified white yam/trifolliate yam/sweet potato starches and moringa oleifera seed flour blends. international journal of food science and nutrition, 6(2): 107-109. okerie, bo. and bello, ab. 1988. physicochemical and functional properties of winged bean flour and isolate compared with soy isolate. journal of food science, 53: 450-454. oladunmoye, oo., aworh, oc., maziya-dixon, b., erukainure, ol. and elemo, g. 2014. chemical and functional properties of cassava starch, durum wheat semolina flour and their blends. food science and nutrition, 2(2):132-138. doi: 10.1002/fsn3.83. oladunmoye, oo., akinoso, r. and olapafe, aa. 2010. evaluation of some physical-chemical properties of wheat, cassava, maize, and cowpea flours for bread making. journal of food quality 33: 693-708. doi: 10.1111/j.1745-4557.2010.00351.x olurin, to., dudu, oe., olaniyan, am. and ogunmoyela, o. 2021 effect of optimizing process variables on the quality characteristics of cassava-wheat composite bread. journal of agriculture and food sciences, 19:1-7. doi:10.4314/jafs.v19i1. oluwalana, b., malomo, sa. and ogbodogbo, eo. 2012. quality assessment of flour and bread from sweet potato wheat composite flour blends. international journal of biological and chemical sciences, 6(1): 65-76. oyeyinka, sa. and kayitesi, e. 2020. effect of fermentation time on physiochemical properties of starch extracted from cassava root. food bioscience,33:100485 https://doi.org/10.1016/j.fbio.2019.100485. pasqualone, a., caponio, f., summo, c., paradiso, vm., bottega, g. and pagani, ma. 2010. gluten-free bread making trials from cassava (manihot esculenta crantz) flour and sensory evaluation of the final product. international journal of food properties, 13(3):562-573. doi:10.1080/10942910802713173 senansyake, s., gunaratne, a., ranaweera, kds. and bamunuarachachi, a. 2013. effect of heat moisture treatment conditions on swelling power and water solubility index of different cultivars of sweet potato (ipomoea batatas lam.) starch. international scholarly research notices, 2013, article id502457, https://doi.org/10.1155/2014/502457. shewry, pr. 2009. wheat: journal of experimental botany, 60:1537-1553. singh, u. 2001. functional properties of grain legumes flours. journal of food science and technology, 38: 191-198. sguenza, t., gallego, ac. and gomez, m. 2021. can cassava improve the quality of gluten free breads? lwt-food science and technology, 149: 91-97 https://doi.org/10.1016/let.2021.111923 winiarska-mieczan, a.and kwiecien, m. 2011. evaluation of the mineral composition of bread stuff and frequency of its consumption. acta scientiarum polonorum. technologia alimentaria, 10(4):487-495. woolfe, j. 1992. sweet potato: an untapped food resource, xv+643pp cambridge: cambridge university press file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology and environment. august, 2016; vol. 12:94-102 copyright © faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng development of wind operated passive evaporative cooling structures for storage of tomatoes m. o. sunmonu 1 *, ogbonnaya chukwu 2 and ron haff 3 ( 1 department of food engineering, university of ilorin, ilorin, nigeria 2 department of agricultural and bioresource engineering, federal university of technology, minna, nigeria 3 us department of agriculture, agriculture research service, western regional research centre, albany, ca., usa) corresponding author’s email address: sholams2000@yahoo.co.uk abstract a wind operated passive evaporative cooler was developed. two cooling chambers were made with clay container (cylindrical and square shapes). these two containers were separately inserted inside bigger clay pot interspaced with clay soil of 7 cm (to form pot-in-pot and wall-in wall) with the outside structure wrapped with jute sack. the soil and the jute sacks were wetted with salt solution. five blades were constructed inside the cooling chambers with aluminium material which were connected with a shaft to a vane located on a wooden cover outside the cooling chamber. the vanes (made of aluminium) were to be powered by the wind which in turn rotates the blades inside the cooling chamber. the total volume of 40500cm 3 and storage capacity of 31500cm 3 were recorded for the square structures while total volume of 31792.5cm 3 and storage capacity of 24727.5cm 3 were recorded for the cylindrical structures. during the test period, the average temperatures of 27.07 o c, 27.09 o c and 33.6 o c were obtained for the pot-in-pot (cylindrical), wall-in-wall (square) and the ambient respectively. the average relative humidity of 92.27%, 91.99% and 69.41% were obtained for the pot-inpot (cylindrical), wall-in-wall (square) and the ambient respectively. the average minimum and maximum wind speed recorded for the month of october was 2.5m/s and 2.6m/s respectively keywords: wind, evaporative, passive, fruits, tomatoes, cylindrical, square, aluminium 1. introduction fruits in their natural and fresh form are highly perishable. once ripe, either before or after harvest, tends to deteriorate. in order to extend their shelf life, they need to be properly stored. proper storage means controlling both the temperature and relative humidity of the storage environment (susan and durward, 1995). owing to lack of information on appropriate post harvest storage techniques, it is estimated that about 20-30% of total fruits are lost after harvesting (kader, 1987). about 23% of most perishable fruits and vegetables are lost during their journey through the agricultural food chain due to spoilage, physiological decay, water loss, and mechanical damage (fao, 2011 ; stuart, 2009).. these losses have been estimated at about 40 to 50% in the tropics (fao, 1995). renewable energy flows involve natural phenomena such as sunlight, wind, tides and geothermal heat, which are renewable (naturally replenished) (iea, 2002). as wind turbines and wind vanes depend on power from wind to function effectively, wind energy can as well be used to drive fans in evaporative cooling structures so that the conditioned air and space air can be evenly distributed in the storage chamber. the wind energy can be used to remedy the fluctuations or near-absence of electricity supply in this part of the country (medugu and malgwi, 2005). however, because refrigerator is rather complex, energy intensive and expensive to purchase and maintain, its application for fresh perishable crops storage is thus not feasible under the prevailing sunmonu et al.: development of wind operated passive evaporative cooling structures for storage of tomatoes. azojete, 12:94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 95 socio-economic status of the rural remote areas. this therefore necessitates the need to develop an alternative, inexpensive, an easy to operate and maintain cooling system that does not need electricity for preserving the various types of fruits and vegetables produced by several small scale farmers. consequently, in developing countries, there is an interest in simple low cost alternatives, many of which depends on evaporative cooling which is simple and does not require any external supply (fao, 1994) evaporative cooler works on the principle of cooling resulting from evaporation of water from the surface (fao, 1995). the cooling achieved by this device also results in high relative humidity of the air in the cooling chamber from which the evaporation takes place relative to the ambient air. the atmosphere in the chamber therefore becomes more conducive for fruits and vegetables storage (nspri, 1990). the aim of this study was to improve fruits and vegetable storability by developing a wind operated passive evaporative cooling structures for the storage of fruits. 2. materials and methods 2.1 design calculations 2.1.1 capacity of the square cooling chamber each cooling chamber had a length of 45 cm, breadth of 30 cm and height of 45 cm so the volume of each cooling chamber was calculated from the relation: the length of the shaft from the top of the cooling chamber to where the blades were attached was 10 cm, meaning the chamber can be filled with fruit up to this length from the bottom of the cooling chamber. actual capacity for fruit storage was 31500 cm 3 assuming a tomato radius of 3 cm, volume of one tomato fruit is calculated from the relation: (2) the square box design should be able to hold approximately; 31500/ 113.04 number of tomatoes totaling up to 279 fruits. 2.1.2 capacity of the cylindrical cooling chamber each cylindrical cooling chamber has a diameter of 30 cm and length of 45 cm so the volume of each cooling chamber is calculated from the relation; (3) where: r and h is the radius and height of the cooling chamber respectively volume = 31792.5cm 3 the length of the shaft from the top of the cooling chamber to where the blades were attached was 10cm, meaning the chamber was filled with fruit up to this length from the bottom of the cooling chamber. actual capacity for fruit storage = 24727.5 cm 3 arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 96 from equation 2 above, volume of tomato was calculated as 113.04 cm 3 . therefore cylindrical design should be able to hold approximately 24727.5/ 113.04 number of tomatoes totaling up to 218 fruits. 2.1.3 design for fan blade velocity the longitude, latitude and altitude of gidan kwano (minna, niger state, nigeria) is 6.26 o e, 879’, 9.02 o n, 056’ and 256.4m respectively. using high a sensitivity global positioning system, the minimum and maximum wind speeds of 2.5m/s and 2.6m/s respectively were recorded in the month of october (since the wind speed is highest in the month of october to drive the vanes) when the experiment was carried out. however, an average speed of 2.55m/s was adopted for this design. the vanes on top of the cooling chambers will rotate with the speed of the wind. the higher the wind speed, the more the vanes rotate. hence, the blades in the cooling chamber will rotate and circulate air radially and evenly on the stored tomatoes. taking the radius to be 1.5m, the blade rotation was found to be 12 rpm and the angular velocity was 1.699 rad/s. with this conversion, the rotation of the vanes (rad/s) was compared with the wind velocity (also in radians/seconds). the tip speed is the speed of the wind because it gives an idea of how much power is generated by the wind. the fan was made of five blades and it was made to rotate with the speed of the wind to move the air radially. the blades were attached by means of a screw to the long shaft (about 10 cm) that connects to the vanes as shown in figures 1 and 2. 2.1.4 amount of air moved in one revolution the air flow rate was calculated using the expression given by tony (2001) and maxwell et al. (2012 as ( ) ( ) (5) where: q is volumetric flow rate (m 3 /s), d is diameter (m), l is length (m). q was obtained as 104.49 cm 3 /s. 2.1.5 distance travelled in one second let the average number of revolutions per minute of the fan be rpm. dividing this by 60 yielded the fan’s revolution per seconds (rps). multiplying the rps by the circumference (π r) gave the meters travelled in one second by the blade. n was obtained as 54 rps, where n is the distance travelled per second (m/s). sunmonu et al.: development of wind operated passive evaporative cooling structures for storage of tomatoes. azojete, 12:94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 97 figure 1: exploded and isometric views of cylindrical wind operated evaporative cooling structure arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 98 figure 2: exploded and isometric view of square wind operated evaporative cooling structure sunmonu et al.: development of wind operated passive evaporative cooling structures for storage of tomatoes. azojete, 12:94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 99 2.1.6 power in the wind for known swept area of the blades and the wind speed, the theoretical power available in the wind was calculated from the relation given by tony (2001) and maxwell et al. (2012) as: (6) where: p is the wind power, (watt), is the air or wind density= 1.293kg/m 3 , a is swept area of the impeller fan obtained as 7.065m 2 , v is the wind speed, (m/s). p was obtained as 29.7w. the power in the wind using maximum and minimum wind speed of 2.5m/s and 2.6m/s were 28.55 w and 30.88 w respectively. 2.1.7 fan pressure fan pressure was calculated from the relation due to tony (2001) and maxwell et al. (2012): (7) where: , q is the discharge (m³/s). when fan pressure was 0.05685n/m 2 , 0.05465n/m 2 and 0.05911n/m 2 , the wind power was 29.70watts, 28.55 watts and 30.88 watts respectively. 2.2 description of the passive evaporative cooler and its principle of operation two cooling chambers were made with clay container (round and rectangular shapes). these two containers were separately inserted inside a bigger clay pot interspaced with clay soil of 7 cm(to form pot-in-pot and wall-in wall) as shown in figures1 and 2 with the outside structure wrapped with jute sack. the soil and the jute sacks were constantly wetted with salt solution (nacl) at interval of between 2 to 4 hours depending on the rate of evaporation to keep the soil in moist condition. the salt solution was used to reduce the growth of microorganisms present in the soil. fan with five blades were constructed inside the cooling chambers with aluminium material which were connected with a shaft to a vane located on a wooden cover outside the cooling chamber. the vanes (made of aluminium) were powered by the wind. 2.3 collection of fresh fruits the experiment was carried out at federal university of technology gidankwano campus in minna, niger state, nigeria and the matured green samples of tomatoes (globe varieties) were sourced from garatu market. about 280 and 220 pieces of tomatoes were used for the square and cylindrical structure respectively as calculated above. the mature green samples of tomatoes were stored inside the two types of passive evaporative cooling structures for a period of 16 days. 2.4 testing the performance of the evaporative cooling system 2.4.1 determination of temperature and relative humidity the temperature and relative humidity of stored tomatoes in the two structures were taken daily using a digital thermometer and a relative humidity measuring instrument at 8.00am, 12 noon and 6.00pm and their average taken and compared with the average ambient temperature. the wind operated passive evaporative cooling structures were tested with mature green tomato fruits for a period of sixteen days. arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 100 3. results and discussion the storage chambers for the two structures recorded lower temperature when compared with the ambient. the temperature and relative humidity in the storage structures as well as the ambient is as presented in figures 3 and 4 below. the temperatures in the evaporative coolers were lower than that obtained for the ambient for stored tomatoes while the relative humidity was observed to be higher. this may be attributed to the cooling effect of the evaporative cooler. the results showed a temperature reduction of between 5 o c 6 o c against the ambient and an increase in relative humidity of between 15-17% against the ambient for both structures for stored tomatoes. this is in line with the temperature reduction of up to 10 o c and increase in relative humidity of the air from 40% of the ambient to 92% of the storage chamber reported by dzivama et al. (2006). reduction in temperature in the structures was enhanced by wetting the jute sacks and evaporation of water from soil around the structures. this agreed with the findings of thompson (1988). also reduction in the temperature may be as a result of the shade provided for the evaporative cooling structures as well as the wooden covers (roy and khudiya, 1986). this is also in line with the temperature reduction of between 8 o c to 12.5 o c reported by babarinsa (2006). also, higher values of relative humidity of above 90% were noticed in the structures as a result of higher volumes of water applied at interval on the surface of the soil. the higher value may also be attributed to the higher saturation efficiency of the jute sack (dzivama et al., 2006). the higher relative humidity is in line with the 82% to 100% result obtained by babarinsa (2006). figure 3: variation in temperature inside the cooling structures for stored tomatoes (cylindrical structure) sunmonu et al.: development of wind operated passive evaporative cooling structures for storage of tomatoes. azojete, 12:94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 101 figure 4: variation in relative humidity inside the cooling structures for stored tomatoes (square structure) 4. conclusion this research focused on the development of wind operated passive evaporative cooling structures for the storage of fruits. the following conclusions were drawn from the research: 1. the average temperature recorded in the cooling chambers was lower than that of the ambient when used to store fresh tomatoes. 2. also higher relative humidity was recorded in the structure compared with the ambient. the higher value of relative humidity recorded is an indication of the effectiveness of the evaporative cooling structures. this tends to lower the temperature in the cooling structures and thus extends the shelf life of the stored vegetables. 3. the use of square structures is also recommended if higher numbers of produce (vegetables) is to be stored since it has a higher storage capacity compared with the cylindrical structures. references babarinsa, fa. 2006. performance evaluation of an evaporative cooling structures for fruits and vegetables in the tropics. agricultural mechanization in asia, africa and latin america (ama), 37(4): 60-65. dzivama, au., igbeka, jc. and audu, i. 2006. performance efficiency of an active evaporative cooling system for the storage of fruits and vegetables in semi arid environment. agricultural mechanization in asia, africa and latin america (ama): 37 (4): 36-41. arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 94-102. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 102 fao. 1994. fats and oils in human nutrition; report of a joint fao/who expert consultation. fao food and nutrition paper 57, fao. rome. fao. 1995. small scale postharvest handling practicesa manual for horticultural crops, 3 rd edition. food and agricultural organization of the united nations, rome. fao. 2011. global food losses and waste: extent, causes and prevention. food and agricultural organization of the united nations, rome, pp. 37. iea. 2002. iea renewable energy working party. renewable energy into the mainstream. pp. 9. published by world energy outlook. www.worldenergyoutlook.org/media/weowebsite/20081994/weo2002 kader, aa. 1987. postharvest biology and technology research on deciduous tree fruits. recent trends and future outlook. in: proceedings of the summerland research station, commemorative symposium (april 27-28, 1987). agriculture canada, summerland, b.c. canada. pp. 96-105. manwell, jf., mcgowan, jg. and rogers, al. 2012. wind energy explained: theory, design and application. chichester, west sussex, uk: john wiley & sons ltd. pp. 92–96. isbn 9780470015001. medugu, dw. and malgwi, di. 2005. a study of wind energy potentials: remedy for fluctuations of electric power in mubi, adamawa state, nigeria. nigerian journal of physics, 17: 40-45. nspri. 1990. storing your products advisory booklet, no 4. nigeria stored products and research institute, ilorin, nigeria. roy, sk. and khurdiya, d. 1986. studies on evaporative cooled zero energy input cool chambers for the storage of horticultural produce. india food packer, 40 (6): 26-31. stuart, t. 2009. waste uncovering the global food scandal. penguin books: london, isbn: 978-0141-03634-2. susan, ds. and durward s. 1995. g95-1264 storing fresh fruits and vegetables. historical materials from university of nebraska, lincoln extension. retrieved online from http://digitalcommons.unl.edu/extensionhist/1042/ retrieved on 1/1/1995. thompson, ak. 1998. controlled atmosphere storage of fruits and vegetables. cab international publisher, london. pp. 11-12. tony, b. 2001. wind energy handbook. john wiley and sons isbn 04714 89972 pp. 65. http://www.worldenergyoutlook.org/media/weowebsite/2008http://www.worldenergyoutlook.org/media/weowebsite/2008https://en.wikipedia.org/wiki/international_standard_book_number https://en.wikipedia.org/wiki/special:booksources/9780470015001 http://digitalcommons.unl.edu/extensionhist/1042/ https://en.wikipedia.org/wiki/special:booksources/0471489972 availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 60-65 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng development of a water air-conditioner for the semi arid region of nigeria aji i. s1, balami a.a.2 and abdulrahim a. t.1 abstract the harsh weather condition experienced in maiduguri between the months of february and june of most years has been a problem to the populace. buying conventional air-conditioners to ameliorate this problem is difficult for the ordinary people in maiduguri. in an attempt to lower the temperature of an average 16m2 room, an electrically operated water supply cooling system was designed, constructed and tested and was found to make the room conducive for human comfort. guard sponge was selected and used out of the existing sponges because it has been found to reduce the ambient temperature better than others. weather conditions of maiduguri for the past fifteen years and the unreliability of electricity supply were put into consideration in the design of the water air conditioner. the machine was able to reduce the temperature of an average room (16 m2) by 28% over a period of 42 minutes. the efficiency of the water air-conditioner with respect to the conventional unit is 60%. seventy five per cent the machine parts were sourced locally, this is to make its production cheap and more affordable to low income earners. 1. introduction the natural process of lowering air temperature is by adding moisture (dossat, 1990). by controlling humidity, cleanliness and even distribution of air in a room, the comfort requirement of the occupant of the conditioned space can be met. air conditioning has its origin in the fundamental works done by robert boyle, carnot and others in the 17th century and towards the beginning of the 18th century. during the last twenty years, several developments have taken place in the area of cooling and air conditioning. earlier works that contributed tremendously in the development of cooling and air-conditioning include those of chinnappa in india and australia, robinson in france and berger in thailand (bridgman, 1941). presently, several types of air conditioning processes and systems are available throughout the world. in nigeria, the common systems used are the central air conditioning, split and window units for both homes and offices (abdulrahim and liman, 2002; gisilambe and yahaya, 2002). due to the harsh weather conditions experienced in nigeria and coupled with the high cost of purchasing a conventional air-conditioning unit, the desire for a conducive atmosphere is becoming illusive to low income earners. this paper presents the development of a water air-conditioner for use in the semi-arid regions and mainly concerns cooling and humidification of the surrounding air in an average room. 1 department of mechanical engineering, university of maiduguri 2 department of agricultural engineering, federal university of technology. minna, http://www.azojete.com.ng/ azojete vol. 5 2007 61 2. materials and methods 2.1 design considerations and machine components the materials for constructing the machine were chosen on the basis of their availability, properties and economic consideration. the machine was designed for a room size of 16 m2 and can be operated using dual voltage (12 vdc and 22 vac). the various physical and mechanical properties of the materials used, namely service life of part, cost and availability of the material and ease of construction, were considered in the design of the air-conditioner (holowenko et-al; 1961). the air-conditioner consists of axial flow fan of 160 mm diameter, 10.33 w electric motor, fan shaft of 5 mm diameter, frame, housing, guard sponge, 2-liter water reservoir and feeder pipe of 3 mm diameter. 2.2 construction and principles of operation the frame of the air-conditioner, which holds all its components, was made from 19 mm angle iron and it was sprayed with aluminium paint to prevent corrosion. it was drilled at 100 mm intervals to enable fixing of the plastic cover, which was made from 2 mm thick plastic sheet. a 300 mm diameter hole was cut on the front and rear sides to enable fixing of the air-distributor and allow for passage of in-coming air respectively. a 2 litre pvc gallon was used as the reservoir. the feeder pipe (pvc), which is light in weight and rust-resistant, connects the water reservoir and the pump in-let. the outlet side of the pump was also connected to another pvc pipe with holes drilled at intervals of 10 mm and runs through the entire length of the sponge (300 mm). this is to allow for trickling of water on the sponge. the guard sponge with a dimension of 500 x 300 x 50 mm that provides space for heat transfer was placed at the edge of the back cover inside an aluminium wire mesh brazed on the main frame. the plastic fan was fixed to the frame with the size of fan blade commensurate to the diameter of the air distributor. the overall dimension of the water air-conditioner is 500 x 435 x 195 mm. the complete assembly of the water air-conditioner is as shown in figure 1. development of a water air-conditioner for the semiarid region of nigeria 62 (a) (b) key: 1. fan motor 4. central switch 7. handle 2. fan blade 5. fan switch 8. air distributor 3. eectric pump 6. pump switch 9. water reservoir 10. p.v.c. pipe figure 1: semi-sectional (a) and isometric (b) views of the air-conditioner 2.3 operational principle the principle of evaporative cooling (eastop and mcconkey, 1999) was employed for the effective working of the water air-conditioner. the pump draws water from the reservoir through the pipe which is connected to the reservoir and sends it through its outlet to the drilled pipe that allows trickling of water unto the sponge. as the sponge gets soaked, the fan sucks air from outside through the sponge and subsequently forces it to the air distributor. the heat transfer process is as shown in equations 1 – 4 below. q = qin – qout 1 qin = ma(ha1+ 1hv1)+ma( 2- 1)hf 2 qout = ma(ha2+ 2hv2) 3 thus, q = ma(ha1+ 1hv1)+ma( 2- 1)hf ma(ha2+ 2hv2) 4 where; q = heat transferred during the process, qin = enthalpy of air stream coming in qout = enthalpy of air stream going out azojete vol. 5 2007 63 ma = mass of dry air in the mixture, ha = enthalpy of dry air per unit mass of dry air,  = moisture content hv = specific enthalpy of water vapour hf = specific enthalpy of free air. 2.4 performance evaluation the performance evaluation of the air-conditioner was out in maiduguri, which lies on latitude 11o51 n and longitude 13o51 e. the weather in the area of study is very dry between the months of march and june, with annual rainfall of less than 500 mm and very low humidity (about 15% for most months). in the hot season the temperature may be as high as 44oc. (mmc, 1998). 2.4.1 determination of the rate of discharge of cooling water this is the volume of water that is completely drained out of the reservoir in a unit time. this can be the water drained out of the reservoir by the action of the pump and onto the sponge by the action of gravity. the rate of discharge of the cooling water is the determining factor of the frequency and time of refilling the reservoir. for the rate of discharge to be determined, the following parameters should be known; i. cross-sectional area of the pipe ii. velocity of the water iii. time taken for the water to drain. thus the rate of discharge is given by (ned and carlos, 1987); d = av 5 where, d = rate of discharge in m3/s, a = cross-sectional area in m2, v = velocity of the water in m/s the most suitable method of finding the discharge rate is by experiment. the discharge time was determined by filling the reservoir with water and opening the control valve of ‘full flow” and measuring the time taken using a stop watch. for this design, the time observed for water to completely drain out of the reservoir was four hours. development of a water air-conditioner for the semiarid region of nigeria 64 2.4.2 efficiency of the air-conditioner the efficiency of the air-conditioner was determined using equation 6 below. 1 21 t tt r   where; r = efficiency of the machine t1 = temperature of the hot and dry space t2 = temperature of the conditioned space 4. results and discussion table 1: reduction of the ambient temperature using the water air-conditioner initial room temperature (oc) final room temperature (oc) rate of cooling (oc/min) humidity (%) time (min) efficiency (%) 40 27 13 60 47 32.5 43 29 14 57 41 32.6 37 30 7 50 37 18.9 table 2: reduction of the ambient temperature using the conventional air-conditioner initial room temperature (oc) final room temperature( oc) rate of cooling (oc/min) humidity (%) time (min) efficiency (%) 40 15 15 60 20 62.5 43 17 16 57 23 60.5 45 18 27 50 24 60.0 table 1 shows the reduction of ambient temperature using the water air-conditioner and table 2 shows that of the conventional unit. when the water air-conditioner was operated for 42 minutes at ambient temperature and humidity of 43oc and 57% respectively, the temperature of the room was observed to fall by 15oc. in the case of the conventional unit, it was operated at the same ambient conditions and the temperature of the room was observed to have fallen by 25oc in only azojete vol. 5 2007 65 22 minutes. the longer time taken in the case of the water air-conditioner might be due to the improper sealing of the air-conditioner housing and the presence of the whole unit being in the room under observation. this might have increased the humidity of the ambient space. power requirement of the water air-conditioner is much lower than that of the conventional unit. despite all these, the water air-conditioner cooling rate was 59% compared to that of the conventional unit. 4. conclusion and recommendations the ambient temperature and humidity obtainable with the water air-conditioner can provide the desired comfort in an average 16 m2 room in a semi arid environment. the water air conditioner developed was able to lower the temperature by about 15oc using the principle of evaporative cooling. guard sponge was selected and used because of its availability and ability to reduce the temperature of the air passing through it better than others. compared to the conventional units that cost between n45,000.00 and n150,000.00, the water air conditioner is cheaper with a unit costing only about n6,000.000 to produce. references abdulrahim, a.t and b.s liman (2002). a survey of technical condition of air-conditioning systems in maiduguri metropolis. faculty of engineering seminar series. university of maidguri. vol. 2, no1, pp24-29. bridgman, p.w. (1941). the nature of thermodynamics. harward university press. dossat, r.j. (1990). principles of refrigeration, 2nd edition, wiley eastop, t.d and a. mcconkey (1999). applied thermodynamics for engineering technologists. fifth edition, pearson education publishers (singapore), delhi gisilambe, a.m and s.j. yahaya (2002). human adjustment to the dry season of the sudano sahelian environment. a case study of maiduguri metropolis. arid zone journal of engineering, technology and environment. vol. 2, pp 54-64 holowenko, r.a.; g.h. laughlin and s. h. allen. (1961). theory and problems of machine. mcgraw-hill inc., new york. mmc (1998). maximum and minimum temperatures over the last 15 years. maiduguri metropolitan council meteorological center. ned, h.c. h and e. carlos (1987). fundamentals of hydraulic engineering system. 2nd edition, prentice-hall, inc. new jersey, pp 54 arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):837-846 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 837 impact of acid leaching on upgrading indigenous lowgrade chromite ore for iron and steel plant development k. ayinla1,3*, a. a. baba1, r. t. oyewumi-musa2, b. c. tripathy3, g. a. anafi4, r. k. dwari3 1department of industrial chemistry, university of ilorin, p.m.b. 1515, ilorin-240003, nigeria. 2department of chemical and geological sciences, al-hikmah university, ilorin, p.m.b. 1501, nigeria. 3csir institute of minerals and materials technology, bhubaneswar-751013, india. 4department of science laboratory technology, kwara state polytechnic, ilorin, nigeria *corresponding author's email address: ayinla.ik@unilorin.edu.ng article information submitted 11 may, 2023 revised 27 sept, 2023 accepted 19 oct, 2023 keywords: aluminium chromite evaluation iron kinetics purification abstract low-grade chromite concentrate from the tunga kaduka benue trough region of north-eastern nigeria is contaminated with iron and aluminium impurities. to transform it into useful material, such impuririties must be removed for it to be useful for the production of special steel and ferrochrome alloys. consequently, in this study, a nigerian chromite was treated by hydrochloric acid (hcl) solution. the influence of leaching duration, acid concentration, reaction temperature, and particle size on the extent of impurities dissolution was determined. from the results obtained, the dissolution of iron and aluminium increases with increasing leaching time, hcl concentration, reaction temperature, and decreasing particle size. under these conditions, the highest recovery of iron and aluminium was obtained to be 95.54 and 82.51%, respectively. the dissolution kinetics of iron and aluminium was evaluated by shrinking core models. the finding reveals that diffusion through the fluid was the leaching kinetics rate-controlling step of iron and aluminium. the activation energy was found to be 25.33 kj/mol for iron and 18.42 kj/mol for aluminium. the residual samples at optimal conditions as analyzed by x-ray powder diffraction and scanning electron microscopy were found to 1.0 introduction while chromium is naturally present in many ores, its economically viable form is chromite. chromite ore is inert and insoluble in water and some mineral acids while in spinel form (muthy et al., 2011). the spinel is the main mineral phase of the chromite ore with a composition of ab2o4, where the divalent cation a can be fe2+ or mg2+, and the trivalent cation b can be fe3+, cr3+, or al3+(atalay and ozhayoghu, 1989; atalay and ozhayoghu, 1989). consequently, the composition made chromite ore a complex mineral with an admixture of magnesium, iron, aluminium, and chromium in varying proportions depending on the deposit. iron can be replaced by magnesium and similarly, chromium by ferric iron or aluminium in the spinel structure to improves cr:fe ratio in chromite (kamolpomwijit et al., 2007). this is a factor that would determine chromite quality for various industrial applications. the major commercial chromite ore and concentrates-producing countries are south africa, zimbabwe, india, and kazakhstan. these countries represent 90% of world production as a whole and nigeria and others cover the remaining 10% (kamari et al., 2001). south africa has reserves of about 3.1 billion tonnes, making the country a leading producer of chromite. this is followed by zimbabwe with reserves of about 140 million tonnes and resources of 1 billion http://www.azojete.com.ng/ mailto:%20jonas.onah.pg.65348@unn.edu.ng mailto:%20shote.adeola@oouagoiwoye.edu.ng mailto:%20shote.adeola@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):837-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 838 tonnes (morimoto et al., 1989; cicek et al.,1998; cicek et al.,2000; ji, 2012). nigeria’s output is from podiform bodies on the benue trough of the zamfara state with reserves put at 65 million tonnes and further resources of 97 million tonnes which are yet to be mined for further industrial applications (abubakre et al., 2007). pure metallic chromium is difficult to produce because it is readily contaminated by many other elements. therefore, a large quantity of raw chromite ore needs to be mined and beneficiated in various chrome ore beneficiation plants throughout the world to cater for the customized needs of various ferroalloy plant industries (zhang et al., 1989). the main purpose of the beneficiating process is to render the ore concentrate physically and chemically suitable for subsequent treatments which depend on the mineral characteristics of the ore deposits, gangue mineral assemblage, and the degree of dissemination of constituent minerals (tinjum et al., 2008; wazne et al., 2008; meegado et al., 1996; atalay et al., 1981). to cater for a possible menace that can be posed by the tailing disposal process, many alternate methods have been proposed. the research works carried out by amer and ibrahim (1986) on hydrometallurgical processing of low-grade chromite ore from barramiya, egypt, by oxidative leaching in an autoclave reveals that, at a short processing time of 25 minutes, 90% of chromium in the form of chromate was achieved in only one leaching stage. in addition, some early papers examine the liquid-phase oxidation (lpo) procedure in treating chromite ore tailings utilizing molten naoh-nano3 medium or highly concentrated koh-kno3 aqueous solution under oxidative circumstances with air, oxygen, or nitrate as the oxidant. (banerjee et al., 2005; hundley et al., 1985; kashiwase et al., 1974). the yield of chromium extraction in this technique has completely addressed the aforementioned threat of tailing disposal with zero waste. it is critical to design an eco-friendly and low energy cost beneficiation mechanism for treating nigerian origin chromite ore in order to serve as an alternative to other beneficiation processes revealed by literature and to solve the problem associated with energy consumption and equipment requirements for successful gravity separation and flotation process. the goal of this study is to look into the effect of various parameters on the kinetics of chromite ore dissolution in hcl solution. this aims to examine the dissolution mechanism and develop an empirical equation linking the rate constant of ore leaching to particle size, system temperature, and hcl concentration for the purpose of scaling up and process design for the iron and steel industries. 2.0 materials and methods 2.1 materials the chromite sample used in this study was sourced from tunga kaduka (12°06′30″n 5°56′00″e), anka local government of zamfara state, north-western nigeria. the ore was crushed and pulverized into fine particles with the aid of a laboratory crusher and mill; and sieved into four different particle sizes ˂ 78 µm, 110 µm, 218 µm, and 358 µm using the astm standard sieves. hydrochloric acid used was of analytical grade. all the solutions with specified concentrations were prepared with distilled water. 2.2 mechanical activation of chromite a twin-bowl insmart planetary ball mill (model pbm-07) with an overall capacity of 500 ml and a useful capacity of 250 ml was used for mechanical activation work on the chromite ore. this was carried out at 300 r/min using 10 mm diameter stainless steel balls keeping the ballto-powder mass ratio at 10:1. milling was carried out for the duration of 1 h (kamari et al., 1999). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: impact of acid leaching on upgrading indigenous low-grade chromite ore for iron and steel plant development. azojete, 19(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 839 2.3 experimental procedures the leaching experiments were performed in a glass 250-ml flask equipped with a magnetic stirrer using an agitation speed of 200 rpm and a reflux condenser to prevent evaporation loss, which was bathed in a water bath. chromite (2 g) was reacted with different concentrations of hydrochloric acid (0.1–2.0 mol/l), with different hydrochloric acid/chromite mass ratios (3:1–7:1 ml/g), different leaching times (15–120 min), and different leaching temperatures (28, 30, 40, 60 and 80 °c). after the acid leaching, the mixture was filtered through 0.5-μm pore size white filter paper using a pressure filtration unit and washed to separate the leached residue and the solution. the mg2+, fe3+, and al3+ contents in the solutions were determined using atomic absorption spectroscopy (aas) and a flame photometer. the residue at optimal conditions was analyzed by x-ray fluorescence (xrf), scanning electron micrograph (sem), and x-ray diffraction (kamari et al.,2001). 3.0 results and discussion 3.1 ore characterization the x-ray patterns of the milled ore at two different particle sizes (75 µm and 210 µm) are illustrated in figure 1. figure 1: xrd spectra of raw grounded and harmer mill chromite ore to size (a) 210 µm (b) 75 µm. the xrd pattern of the 210 µm sample (figure 1(a)) indicates that the ore is primarily comprised of chromite (fecr2o3) {jcpds no. 32-2007}, hematite (fe2o3) {jcpds no. 21 0034}, and alumina (al2o3) {jcpds no. 011338} phases. however, after 60 minutes of high energy milling (figure 1(b)), the corresponding phases of quartz (sio2), ilmenite), rutile (tio2), and bixbyite (mn2o3) were slightly broadened and their intensity decreased due to the refinement of crystalline grains and the accumulation of lattice distortion caused by ball impact and collision. (than et al., 1970; xu et al., 2005). the elemental composition by eds of raw chromite ore is presented in fig. 2. the chemical composition of the raw chromite powder examined by edxrf gave 38.34% cr, 33.80% fe, 19.70% al, 13.84% si, 3.69% mg, 0.14% mn, and 0.55% ti by weight. also, the eds spectrum (figure 2) was in support of edxrf revealing cr2o3 (20.3%), fe2o3 (6.39%), sio2 (4.13%), and al2o3 (6.67%) as major constituents present in the studied ore. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):837-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 840 figure 2: eds diffractogram of raw chromite powder from the sem result (figure 3a), a distinct light grey region (a) and dark grey region (b) denote the presence of manganese and ferro silicate compounds while figure 3b&c indicate distinctive textural features in the raw ore. figure 3: the microstructural morphology of the chromite powder (a) sem image (b) photomicrograph at 310 µm (scale: 2/100 nm 4x) (c) photomicrograph at 78 µm (scale: 2/100 nm 4x) the black cuboids’ mineral phase (1) is attributed to chromite (fecr2o4), complemented with the large coal brown region (2) which is attributed to thermally stable alumina and manganese oxide, indicating bixbyite (mn2o3). also, an admixture of iron and other trace impurities in the form of haematite (fe2o3) is present in the brownish region marked as (3) while the predominant associated gauges are identified as siliceous compound (sio2) can be found underneath (vandar et al., 1994; zanello and raspi, 1977). 3.2 extraction results 3.2.1 effect of leaching time based on the mineralogical analysis results, the effect of leaching time was first investigated and the details are summarized in figure 4. figure 4: influence of leaching time on fe and al dissolution from chromite ore file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: impact of acid leaching on upgrading indigenous low-grade chromite ore for iron and steel plant development. azojete, 19(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 841 as shown in figure 4, the effect of the reaction time on the leaching efficiency of fe and al atacid concentration of 0.5 mol/l, and 55°c.the leaching efficiency of fe and al into solution increases as leaching time increases. this could be related to the creation of water-soluble al and fe chlorides. when the leaching time was 1 h, the leaching efficiency of fe and al was observed to be less than55%. similarly, when the time was extended to 1.5 h, the leaching efficiency of fe and al further increased to 60%; and more than 68% of fe and al can be leached out after 2 h. also, figure 3 shows that the dissolution rates of fe and al are very close and reach an apparent steady-state within 2 h. therefore, 2 h was agreed to be the optimum duration for the leaching of fe and al. 3.2.2 effect of hcl concentration the effect of acid concentrations on the leaching are shown in figure 5. figure 5: influence of hydrochloric acid concentration on fe and al dissolution from chromite ore it can be seen that the acid concentration has a significant impact on the leaching efficiency of fe and al, whose leaching efficiency was raised from 35 to 85% and 30 to 74% when the acid concentration of hcl was varied from 1.0 mol/l to 2.0 mol/l respectively. this is due to the acid concentration effect on increasing the h+ activity that results in further dissolution of al and fe impurity (sun et al., 2007). the leaching efficiency reached the maximum value at the acid concentration of 1.5 mol/l. the reason for this may be due to the chromite structure collapsing at this concentration or fe2+ and al3+ species blocking h+ diffusion (wang et al., 2008). 3.2.3 effect of leaching temperature figure 6 shows the effect of reaction temperatures on the leaching efficiency of fe and al at a hydrochloric acid concentration of 1.5mol/l, time of 2 h and hydrochloric acid-to-chromite ratio of 4 ml/g. as expected, the leaching efficiency of fe and al increases with rising temperatures and the leaching efficiency of fe and al was up to 95.8% and 84.9% at 80 °c. however, the temperatures that continue to rise is advantageous to the formation of jarosite because of the presence of fe, which could lead to a poor leaching efficiency of al (ayinla et al., 2019). in addition, al may also be incorporated into the leached residue as a result of the precipitation of alunite and therefore cause a fall in the purity of silica gel (baba et al., 2013). thus, the optimized condition of the leaching temperature is 80 °c. figure 6: influence of leaching temperature on fe and al dissolution from chromite ore http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):837-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 842 3.2.4 effect of particle size the influence of particle size (78-358µm) was also tested. a particle size value corresponds to 100% of the particles below that size. the results showed that the particle size affected the iron and aluminium extractions (figure 7) figure 7: influence of leaching particle diameter on fe and al dissolution from chromite ore figure 7 shows that the amounts of extracted iron and aluminium increased when the particle size decreased. in the range of 358-78 µm, these trends became steeper because of the effect of increased specific surface area. the results showed that grinding was beneficial to extractions of the metal values because more grinding increased the iron and aluminium extractions. however, this technique has technical and economic restrictions. when the chromite ore samples were ground to 78 µm, the extracted iron and aluminium were about 95% and 89%, respectively. 3.3 kinetics analysis the reactions occurring during the leaching process are typically heterogeneous (ekmekyapar et al., 2012) and the relevant kinetics follow the shrinking core model which was described by lid-dell in detail (liddell, 2005). the following expressions can be used to describe the leaching process kinetics (levenspiel, 1999; meegoda, 1999): for diffusion control through the fluid film: 1 − (1 − α)2/3 = kt (1) for solid product diffusion control: 1 − 3(1 − α)2/3 + 2(1 − α) = kt (2) for surface chemical reaction control: 1 − (1 − α)1/3 = kt (3) where αis the fractional conversion of iron and aluminium, t is the reaction time (min) and k is the apparent rate constant(min−1). the overall rate of dissolution is controlled by the slowest of these sequential steps. values of eqs. (1) – (2) versus the reaction time were plotted to determine the kinetic parameters and leaching rate controlling step comparing the r2 values to ascertain the most fitted. the results are shown in table 1. table 1: apparent rate constant (k) for kinetic models and correlation coefficient values temperature °c diffusion through the product layer surface chemical reaction k(min-1) r2 k(min-1) r2 28 0.0029 0.9823 0.0011 0.7625 30 0.0027 0.9866 0.0016 0.8854 iron 40 0.0035 0.9913 0.0020 0.8812 60 0.0045 0.9813 0.0025 0.7895 80 0.0046 0.9925 0.0028 0.8814 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: impact of acid leaching on upgrading indigenous low-grade chromite ore for iron and steel plant development. azojete, 19(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 843 28 0.0020 0.9856 0.0010 0.7120 30 0.0025 0.9830 0.0014 0.8812 aluminium 40 0.0030 0.9825 0.0019 0.8945 60 0.0035 0.9914 0.0022 0.8350 80 0.0038 0.9923 0.0025 0.8912 it is obvious from table 1 that the highest r2 values were obtained for the diffusion through the product layer. additionally, in leaching processes, the dissolution ratio directly depends on the activation energy, which can be calculated based on the arrhenius equation (k = a × e−ea/r×t). based on the arrhenius activation energy theory, the arrhenius equation was plotted as ln (k) vs. (1/t) for each temperature and the activation energies were calculated from the slopes of straight lines (figure 8a &b). figure 8: plot of lnk versus 1/t for activation energy calculation: (a) graph for iron removal (b) graph for aluminium removal where the slope is −ea/r. the values of activation energies (ea) and frequency factors (a, min1) calculated from arrhenius plot are 25.33 kj/mol for iron and 18.42 kj/mol for aluminium. it has been previously stated that the typical activation energy for a chemically controlled process is greater than 40 kj/mol, while the activation energy of a diffusion-controlled process is usually below 40 kj/mol (ekmekyapar et al., 2012). from the results obtained, it can be concluded that the leaching process of iron and aluminium from low-grade chromite ore of nigerian origin using hydrochloric acid is controlled by the diffusion process. consequently, the equations representing the kinetics of the leaching process of iron and aluminium can be expressed according to eqs. (7) and (8), respectively. 1−3(1 −α)2/3 + 2(1 − α) = 0.7272 × e−28.35/8.314t × t (4) 1 − 3(1 − α)2/3 + 2(1 − α) = 0.9686 × e−13.92/8.314t × t (5) 3.4 residue analysis xrf analysis was used for the elemental analysis of chromite ore concentrate after leaching (table 2). the amount of fe and al drastically decreases which gives rise to an increase in the value of cr in the chromite ore (54.46 %). an unexpected increase in si and ti content was also observed during the leaching process. this could be due to un-dissolve silica-containing minerals which are insoluble in the acidic solution. table 2: xrf analysis result of chromite or before and after acid leaching elemental composition before leaching (%) after leaching (%) cr 38.34 59.22 fe 33.80 5.76 al 19.20 6.40 si 13.84 23.07 http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):837-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 844 mg 3.69 3.31 mn 0.14 1.19 ti 0.55 1.07 the morphologies of the leaching residues obtained under optimum conditions were analyzed by using the xrd method (figure 9a-c). figure 9: xrd spectra of leach residues at optimum conditions (a) at 30 min (b) 60 min(c) 120 min in the diffractogram of leached residue (figure 9c)), the presence of phases cr2o3 and mgcro4 are indicated. the presence of un-reacted sio2 could not be identified in the diffractogram, which may be due to the smaller amount compared with the other phases or their peak intensity might be reduced due to the formation of new phases with somehow bigger grain sizes. however, other peaks as indicated by the xrd pattern of the final acid leaching residue comprised of tio2 and fetio3 phases which did not react during acid leaching. to examine the microstructure of the partially reacted chromite ore, the cross-section of the leaching residue was polished and examined using sem. the sem of acid-leached residue after drying along with water-washed residues after drying are shown figure 10a-b. figure 10: sem images of leached residues at optimum leaching conditions it is observed that smooth and nearly cubical grains (figure 3(a)) of milled chromite ore are completely transformed into porous and nodular clusters of particles after leaching (figure 10(a)). during the water treatment of the leached residues, excess acid is removed along with water-soluble titanates/ferrates causing the agglomerated form to collapse and particles become mostly free (figure 10(b)). final acid leaching residue mostly contains unreacted chromite, silica and rutile which were not converted during acid leaching. 4.0 conclusions in this study, acid leaching of nigerian chromite ore by hydrochloric acid for purification of low-grade chromite ore as potential raw material for the production of special steel and ferrochrome alloys. in the range of studied parameters, the most suitable conditions for the leaching process of iron and aluminium attained at temperature 80◦c, 1.5 m hcl, l/s ratio = 20 g/l and 78 µm particle size dissolution. under these conditions, it was found that iron file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com shote et al: impact of acid leaching on upgrading indigenous low-grade chromite ore for iron and steel plant development. azojete, 19(4):837-846. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 845 leaching recovery of 95.54 % with a aluminium leaching recovery of 82.51% could be obtained. the dissolution kinetics of iron and aluminium support diffusion as the rate-controlling step. the activation energies were determined to be 25.33 and 13.42 kj/mol for the leaching of iron and aluminium, respectively. the residue evaluation was carried out using xrf, xrd and sem respectively, the obtained result clearly showed the presence of cr2o3, mgcro4 and sio2 as the major mineral phase. references abubakre, ok., muriana, ra. and nwokike, pn. 2007. characterization and beneficiation of anka chromite ore using magnetic separation process. journal of minerals & materials characterization & engineering, 6 (2): 143–150. amer, m. and ibrahim, ia. 1996. leaching of a low-grade egyptian chromite ore. hydrometallurgy, 43 (1–3): 307–316. atalay, mu., ozbayoglu, g. and dogan, mz. 1989. mechanism of collector adsorption in chromite flotation. in: aytekin, y. (ed.), proceedings of ii international mineral processing symposium, izmir, turkey, pp. 441–449. atalay, u. and ozbayoglu, g. 1992. beneficiation and agglomeration of chromite–its application in turkey. mineral processing and extractive metallurgy review, 9:185–194. ayinla, ik., baba, aa., padhy, sk., adio, o., odeleye, ka. and tripathy, bc. 2019. synthesis and characterization of pure silica powder from a k-feldspar silicate ore for industrial value addition. faculty science university ankara series b, 61 (1-2): 69-87. baba, aa., ayinla, ik., adekola, fa., bale, rb., ghosh, mk., alabi, agf., sheik, ar. and folorunso, io. 2013. hydrometallurgical application for treating a nigerian chalcopyrite ore in chloride medium: part i. dissolution kinetics assessment. international journal of minerals; metallurgy and materials, 20(11): 1-8. banerjee, th., sengupta, ak., gundewar, ts. and amanullah, cs. 2005. proposed modified process flow-sheet for augmenting the throughput capacity of chrome ore beneficiation plant of m/s tisco, sukinda, orissa. in: international conference on mineral processing technology mpt2005., (12-16 december, 2005), bombay, 623–631. cicek, t., cocen, i. and birlik, m. 2000. applicability of multi-gravity separation to kop chromite concentration plant. in: mineral processing on the verge of the 21th century, (12-16 november 2000) balkema, rotterdam. proceedings of 8th international mineral processing symposium, antalya, 87–92. cicek, t., cocen, i. and samani, s. 1998. gravimetric concentration of fine chromite tailings. in: innovations in mineral and coal processing, balkema, rotterdam. proceedings of 7th international mineral processing symposium, istanbul (10-14, december, 1998), pp. 731–736. ekmekyapar, a., aktas¸ e., künkül a. and demirkıran, n. 2012. investigation of leaching kinetics of copper from malachite ore in ammonium nitrate solutions. metallutgical material transaction b, 43:764–72. hundley, gl., nilsen, dn. and siemens, re. 1985. extraction of chromium from domestic chromite by alkali fusion. u.s. bureau of mines, report of investigations, ri8977. u.s. bureau of mines, pittsburg, u.s. ji, z. 2012 preparation of trivalent chromium compounds from chromite by acid-leaching technique. inorganic chemistry indices., 44:1–5. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):837-846. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ayinla.ik@unilorin.edu.ng 846 kamolpornwijit, w., meegoda, jn. and hu, z. 2007. characterization of chromite ore processing residue practical periodic hazard. toxic radioactive waste management., 11: 234–23. kanari, n., gaballah, i. and allain e. 1999. a study of chromite carbochlorination kinetics. metallurgical material transaction. 30:577–587. kanari, n., gaballah, i. and allain, e. 2001. kinetics of oxychlorination of chromite. i. effect of temperature. 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sadiqwaziri@unimaid.edu.ng 343 efficacy of sugarcane bagasse and rice husk adsorbent for treatment of heavy metals from petroleum refinery effluent s. a. waziri1*, m. mustapha2 1department civil and water resources engineering, university of maiduguri, nigeria. 2department of agricultural and environmental resources engineering, university of maiduguri, nigeria *corresponding author's email address: sadiqwaziri@unimaid.edu.ng article information submitted 16 december, 2022 revised 27 january, 2023 accepted 3 february, 2023 keywords: heavy metal sugarcane bagasse oil refinery rice husk abstract heavy metals are being extremely released into the environment due to poor was management resulting from industrialization and urbanization. discharging wastewater contaminated with heavy metals poses a significant risk to human health and the surrounding ecosystem. heavy metals are characterized by their non-biodegradable nature and potential carcinogenic properties. activated carbons (acs), which are carbon-based nano-porous adsorbents, are widely utilized in the removal of heavy metals because of their extensive surface area. in this study, active carbon materials were prepared using rice husk and sugarcane precursor by applying physical-chemical activation methods. to examine the sequestering of heavy metals (cadmium, chromium, copper, lead, nickel, and zinc) in a refinery effluent, a batch adsorption technique was adopted, and the process parameter were investigated at different temperatures and impregnation ratio. scanning electron microscope (sem) and fourier-transform infrared spectroscopy (ftir) were used to determine the surface morphology and functional group while x-ray diffraction analysis (xrd) was used for the study of the crystallographic property of the activated carbon adsorbent. both rice husk and bagasse showed promising capacity for multiple adsorption of heavy metals. freundlich and langmuir's models were applied to study the sorption behavior. although, process parameters play a vital role in the activation of the adsorbent, rice husk, and sugar bagasse have a strong potential for heavy metal adsorption. the hierarchy of performance effectiveness of rice husk was cr>pb>cu>cd>zn>ni according to the langmuir model with chromium (cr) having the highest performance with a coefficient of correlation r2 of 0.9512 and the least nickel (ni) having r2 of 0.6156. while sugarcane bagasse fitted well to the freundlich model with the efficacy of removal in the order pb>cu>cd>ni>cr>zn with lead (pb) having the highest efficacy of removal with r2 of 0.957 and the least was zinc (zn) with r2 of 0.211 respectively. 1.0 introduction the persistent contamination of water and the environment by heavy metals in a dynamic proportion presents a significant concern. the emergence of these metals from myriad technological and anthropogenic genesis into aquatic systems poses a substantial threat to the well-being and sustainability of various forms of life. heavy metals are the most common pollutants present in industrial effluents. their discharge into the environment causes serious environmental problems. among the hazardous heavy metals, lead, cadmium and copper have received much attention due to their harmful, carcinogenic, and non-biodegradable (duan et al., 2020) and toxic effects at low concentrations (aboli et al., 2020). in drinking water, http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):343-356. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 344 concentrations of 0.005 mg/l for pb (ii), 0.001 mg/l for cd (ii) and 0.1 mg/l for cu (ii) can cause illness in humans and can even be fatal (bohli et al., 2015). these ions have damaging effects on humans as they can penetrate via soil or water (waziri et al., 2016). lead is released bodies from various industries including oil refineries(meitei and prasad, 2013), plastic, paint, cable, steel, and dyes. nickel is another toxic heavy metal ion heavily used in industries such as mining, oil industry and plating, it poses a potential threat for diseases such as lung and bone cancer while acute nickel poisoning causes headache, nausea, weakness, dry coughs, and pain in the chest (fu and wang, 2011) a demanding research trend in environmental science and technology is the improvement of water pollution control and aquatic purification. the demand for efficient, convenient, and cost-effective technology for decontaminating groundwater and surface water without endangering public health remains critical (luo et al., 2016). several researchers in the past decades have shown interest in treating heavy metal ions from effluent before their eventual discharge into natural streams and other water bodies (deng et al., 2011). interestingly, there are many methods used for wastewater treatment which include membrane and biological processes, sedimentation, floatation, coagulation, lime precipitation, ion exchange, and electrochemical methods (gupta, 2015). these methods have been applied for metal ions removal from effluents with some of the techniques having their pros and cons since incomplete metal removal, generates toxic sludge, has high cost, and continuous input of chemicals (kaur et al., 2016). for instance, in the electrochemical process, most of the metal ions are possible to be removed but it has high operational and capital cost (anglada et al., 2009) in chemical precipitation, there is the advantage of low cost but it has high sludge quantity thereby creating disposal problems. similarly, flocculation and coagulation have the advantage of less sludge generation but it has a high cost of chemical consumption (guimarães et al., 2016), ions exchange offers the benefit of regeneration of material but it is limited by its high cost implication (kaur et al., 2016). however, the most economical, effective, and efficient method of metal ions removal from wastewater is adsorption (kulbir et al., 2018). the readily employed sorbent is activated carbon but it has a high cost and needs chelating agents (for metal-containing effluents) to improve its performance, hence exacerbating the cost (singh and waziri, 2019). due to the cost of activated carbon, a more cost-effective and reliable adsorption treatment method is usually applied (chew et al., 2023). the world produces a large amount of agricultural waste discarded indiscriminately every year, resulting in a huge waste of resources. the rational application of agricultural waste can not only reduce environmental pressure, but also create economic value, so it is necessary to develop new ways of recycling agricultural waste (sadh et al., 2018). agricultural waste refers to the waste generated from agricultural production, livestock breeding, agricultural and sideline products processing, and life activities of rural residents, mainly including residues in farmland and orchard, livestock manure, and residues in agricultural and side-line products and domestic waste. these wastes not only contain 65% to 90% carbon, hydrogen, and oxygen, but also are rich in nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, as well as trace elements. it is essential to pay attention to the extensive use of agricultural waste for sustainable development. agricultural waste is usually the first choice to prepare biomassderived activated carbon, attributing to its high specific surface area, high stability, excellent adsorption properties, simple production process and low price (wang et al., 2023). the major byproduct of the rice milling industry is the rice husk. it contains a large amount of lignocellulosic biomass and ash. the ash is about 99 percent silica. millions of tons of rice are produced annually by developing countries. rice plant is about 20 percent rice husk which constitutes a huge disposal challenge as the volume increases annually (dhaliwal et al., 2011; kalderis et al., 2008). about 80% of the sugar produced is obtained from sugar cane making it the second largest crop. the extracted juice is adopted as the primary source of sucrose, while the fermented juice has been used for the manufacture of bio-ethanol (bian et al., 2013). consequently, it has been faced with the challenge of a large fibrous byproduct, bagasse, which is about 30% of the entire plant (ijaola et al., 2014). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com waziri et al efficacy of sugarcane bagasse and rice husk adsorbent for treatment of heavy metals from petroleum refinery effluent. azojete, 20(2):343-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 345 in this paper, koh and naoh treated rice husk and sugarcane bagasse activated carbon are respectively produce for treatment of heavy metals from refinery effluent. batch adsorption studies was carried out and effect of temperature and impregnation ratio on ac yield, removal efficiency and the treatment mechanisms were studied. 2.0 materials and methods 2.1 materials rice husk and sugarcane bagasse were the precursors utilized for the activated carbon production. they were obtained from open market (street vendors) in barara-ambala, haryana, india. waste water sample was obtained from indian oil and petroleum company ltd. (iocl), panipat, haryana, india. potassium hydroxide (koh), sodium hydroxide (naoh) and other chemicals were used analytical reagent (ar) grade. 2.2 methods 2.2.1 preparation of activated carbon the materials was collected, sun dried, crushed and grinded manually using pestle and mortar into fine powder, the samples was further sieved through 1.0 to1.5 mm sieve size to obtain a uniform precursor of about 500 g was weighed and then placed in a muffle furnace and then carbonized. the precursor was then pyrolyzed at 300 400°c for 1 hour, distillate formed while carbonization was collected to prevent air pollution. the pyrolyzed precursor (charcoal or char) was allowed to cool prior to transferring into a crucible. it was thereafter grounded into powder by using pestle and mortar and sieved through of 0.150mm sieve-size to get uniform particles. precursor of about 100 g potassium hydroxide koh (rice husk) and sodium hydroxide naoh (bagasse) (owabor and iyaomolere, 2013). 100g was transferred into a beaker mixed with 50% zncl2, 1n naoh, 1n koh, at different impregnation ratio (1.0, 1.5, 2.0) until thoroughly mixed. thereafter, the paste was then poured into a container, dried at 105°c overnight and thereafter placed into the muffle furnace and heated at different temperatures of 500℃, 550℃ and 600℃ for 1 hour to enhance the surface area of the sample and make it a better adsorbent. after it has cooled, it was then washed with mineral free water and the residual filtrate was ensured neutral ph. further, it was oven-dried at 105°c overnight. subsequently the adsorbent was stored in an airtight polyethylene bag and later used (kannan and veemaraj, 2009) 2.2.2 yield activated carbon (ac) yield was computed on chemical-free nature basis and is regarded as an indication of the process accuracy of the activation. yield is represented as percentage weight of activated carbon by weight of dried adsorbent. (yield (%) = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑐𝑡𝑖𝑣𝑎𝑡𝑒𝑑 𝑐𝑎𝑟𝑏𝑜𝑛 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑟𝑎𝑤 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 𝑥 100 (1) 2.2.3 bulk density a 25 ml glass cylinder filled to a particular volume with powder ac was placed in oven overnight at 80°c. the vessel was then compacted. bulk density is expressed as gml-1: (𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑑𝑟𝑦 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 (𝑔)) (𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑃𝑎𝑐𝑘𝑒𝑑 𝑑𝑟𝑦 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙𝑠 (𝑚𝑙)) 𝑥 100 (2) 2.2.4 microscopy the surface morphology of the prepared adsorbents was studied using scanning electron microscope (jeo-jsm-5910, jeol ltd., japan). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):343-356. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 346 2.2.5 iodine number iodine number (in) can be used to determine the relative porosity of the activated carbon. it is micro pore indication of the ac (up to 2 nm). astm d4607-94 method was used in this study. iodine number can be defined as the milligrams of iodine adsorbed by 1.0 g of carbon when the iodine concentration of the filtrate is 0.02 n (0.02 mol. /l). 2.2.6 chemical oxygen demand (cod) an indirect method that is usually employed for expressing the amount of organic content in waste water is chemical oxygen demand. it is an important water quality indicator, expressed in milligrams per liter (mg/l) which shows mass of oxygen consumed per liter of solution. the experiment was done according is: 3025 (part 58) – reaffirmed 2006. 2.2.7 total dissolved and suspended solids materials which are totally dissolved in water are termed as total dissolved solids. it can be filtered. it can also be defined as remaining part of solids after evaporation of filterable sample. while suspended solids are ones which cannot be dissolved as well as filtered. it is carried out according to is: 3025 (part 16 & 17). 2.3 batch equilibrium studies basically the test was conducted on rice husk and sugarcane bagasse to compare their effectiveness in the treatment of oil refinery wastewater. a known quantity of each adsorbent (1g) was transferred into erlenmeyer flasks of volume 250 ml, containing 100 ml of domestic effluent thereafter put in a shaking incubator at 120rpm for 3hrs at 25℃. batch adsorption studies were conducted by adding certain amount of activated carbon (rice husk and sugarcane bagasse) 1g into 250 ml erlenmeyer flasks containing 100 ml of different impregnation ratio and temperature. the conical flasks then were placed in a shaking incubator at 120 rpm for 3 h. there after the effluent was filtered with a filter paper and the residual filtrate was analyzed. the amount of sorption at time t and the percentage removal were calculated according to previous study (fathy et al., 2012). 2.4 adsorption models the capacity of adsorbent to treat heavy metal pollution up to a certain level is studied with the help of adsorption model. when there is a contact for a particular time between the carbon sorbent and the pollutant, a stage is arrived when the maximum amount of pollutant is adsorbed and the remainder is known. in an equilibrium conditions for any given process, the mass balance equation employed for the calculation of the materials adsorbed is given as eqn (3). 𝑋 𝑀 = (𝐶𝑜 − 𝐶𝑒) 𝑉 𝑀 (3) where x/m (is milligram of pollutant by gram adsorbent) is the mass of contaminant by the mass of adsorbent, co is the initial concentration of pollutant, ce is the pollutant concentration after equilibrium, v is the volume of solution to which the adsorbent mass is applied, and m is adsorbent mass. langmuir or freundlich models has been used for the study of many mechanism (selvaraju & bakar, 2017). langmuir isotherm is represented by eqn (4). 𝑋 𝑀 = 𝐾𝐿𝐶𝑒 1+𝑎𝐿𝐶𝑒 (4) where kl and al are model’s constants. linear regression is used for the determination of kl and al values. the linear equation for langmuir model is given by eqn (5): file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com waziri et al efficacy of sugarcane bagasse and rice husk adsorbent for treatment of heavy metals from petroleum refinery effluent. azojete, 20(2):343-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 347 1 𝑋 𝑀 = 1 𝐾𝐿𝐶𝑒 + 𝑎𝐿 ⁄ 𝐾𝐿 (5) the general freundlich equation is: 𝑋 𝑀 = 1 𝐾𝑙𝐶𝑒 + 𝑎𝐿 𝐾𝑙 (6) linear equation for freundlich model is given by: ln 𝑋 𝑀 = ln 𝐾𝐹 + 1 𝑛 ln 𝐶𝑒 (7) where n and kf are affinity and adsorption capacity, respectively. langmuir and freundlich models are employed batch adsorption systems where equilibrium is provided enough time between the pollutant in solution and the pollutant adsorbed. in this way most of the contaminants are trapped on the carbon sorbent. 3.0 results and discussion the activated carbon was produced successfully, however, analysis of the data and tests conducted comprising adsorption process by batch method and sample analysis before and after adsorption in the wastewater stream are discussed below. the properties of the activated carbon produced have been checked by various methods to understand the intrinsic qualities of the precursor towards heavy metals removal as presented in table 1. the different heavy metal content of the oil refinery effluent use in this study is presented in table 2. table 1. activated carbon characterization s/n parameters rice husk sugarcane bagasse 1 bulk density (g/cm3) 0.400 0.333 2 yield (%) 77.10 84.44 3 in (mg/g) 1312 1128 4 ash content (%) 22.90 15.56 5 moisture content (%) <1 <1 6 particle size (µm) >150 >150 table 2. heavy metals in oil refinery effluent. s/n parameter value 1 cadmium 0.015 2 chromium 0.210 3 copper 0.740 4 lead 0.030 5 nickel 0.304 6 zinc 1.130 the wastewater treatment for various heavy metals at temperature of 600℃ with various impregnation ratios using rice husk and sugarcane bagasse activated carbon are given in the table 3. the various impregnation ratios 1, 1.5 and 2 of the rice husk activated carbon is denoted as rh 1, rh 1.5 and rh 2 respectively. similarly, for sugarcane bagasse activated carbon it is denoted as sb 1, sb 1.5 and sb 2. accordingly, the corresponding activated carbon produced at temperature of 550℃ is presented in table 4 and that produced at 550℃ is provided in table 5. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):343-356. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 348 table 3. heavy metal effluent characteristics after treatment (600℃) rice husk sugarcane bagasse s/n parameter rh 1 rh 1.5 rh 2 sb 1 sb 1.5 sb 2 1 cadmium (cd) 0.0009 0.0003 0.00015 0.0012 0.0007 0.00 2 chromium (cr) 0.0315 0.0252 0.0210 0.0399 0.0294 0.021 3 copper (cu) 0.074 0.052 0.030 0.089 0.067 0.044 4 lead (pb) 0.0027 0.0012 0.0003 0.0015 0.0006 0.00 5 nickel (ni) 0.058 0.043 0.031 0.055 0.040 0.031 6 zinc (zn) 0.147 0.113 0.091 0.102 0.079 0.045 table 4. heavy metal effluent characteristics after treatment (550℃) rice husk sugarcane bagasse s/n parameters rh 1 rh 1.5 rh 2 sb 1 sb 1.5 sb 2 1 cadmium (cd) 0.0021 0.0017 0.00075 0.0023 0.0018 0.0014 2 chromium (cr) 0.0462 0.0420 0.0357 0.0525 0.0462 0.0357 3 copper (cu) 0.148 0.104 0.089 0.133 0.118 0.096 4 lead (pb) 0.0045 0.0039 0.0030 0.0030 0.0027 0.0018 5 nickel (ni) 0.097 0.091 0.076 0.082 0.067 0.058 6 zinc (zn) 0.237 0.192 0.124 0.226 0.181 0.136 table 5. heavy metal effluent characteristics after treatment (500℃) rice husk sugarcane bagasse s/n parameter rh 1 rh 1.5 rh 2 sb 1 sb 1.5 sb 2 1 cadmium (cd) 0.0021 0.0017 0.00075 0.0023 0.0018 0.0014 2 chromium (cr) 0.0462 0.0420 0.0357 0.0525 0.0462 0.0357 3 copper (cu) 0.148 0.104 0.089 0.133 0.118 0.096 4 lead (pb) 0.0045 0.0039 0.0030 0.0030 0.0027 0.0018 5 nickel (ni) 0.097 0.091 0.076 0.082 0.067 0.058 6 zinc (zn) 0.237 0.192 0.124 0.226 0.181 0.136 3.1 temperature effect on yield of activated carbon. the overall efficiency of activated carbon production process can be determined by two important parameters, these are: carbonization and activation temperature. many researchers have studied the effect of activation temperatures on yield. thomas et al. studied the adsorption koh and h3po4 impregnated jack fruit ac for removal of ni in aqueous solution and showed that as the carbonization temperature increases the yield decreases. conversely as the impregnation ratio increases the yield of the ac increases (thomas et al., 2017). owabor and iyaomelere (2013) evaluated the influence of salt treatment on the structure of pyrolyzed periwinkle shell and reported that as the temperature increase the yield of the ac decreases while the increase in impregnation ratio increase the yield up to a certain optimum level after which further increase in ir led to the decrease in the yield of the ac. the effect of temperature on rice husk ac is presented in figure 1a, it shows that as the temperature increases the yield decrease. at temperatures 500℃, 550℃ and 600℃ for ir 1, the corresponding yield are 91.11, 90.58 and 88.64 while for ir 1.5 is 89.49, 88.72 and 85.58 and ir 2 recorded 87.78, 87.1 and 84.53 respective. furthermore, the effect of temperature on the yield of bagasse shown in figure 1b follows similar pattern, the yield at temperature of 500℃, 550℃ and 600℃ for ir 1 is 90.13, 89.76 and 86.32, and ir 1.5 is 88.47, 87.33 and 84.29 while ir 2 is 87.88, 86.19 and 83.54 respectively. this phenomena is due to volatilization of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com waziri et al efficacy of sugarcane bagasse and rice husk adsorbent for treatment of heavy metals from petroleum refinery effluent. azojete, 20(2):343-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 349 carbon burn off as the temperature increases. similar results has been reported by others scholar. njewa et al. (2022) studied the synthesis and characterization of activated carbons prepared from agro-wastes by chemical activation and observed that the increase in temperature decrease the yield in the actinvarted carbon. zakaria et al. (2021) reported on effect of impregnation ratio and activation temperature on the yield and adsorption performance of mangrove based activated carbon. they observed that as the temperature is increase 300℃ to 500℃ the yield decreased from 45% to 38%. a b figure 1 (a) temperature effect on yield of rice husk (b) temperature effect on yield of sugarcane . 3.2 impregnation ratio effect on yield of activated carbon the weight ratio between the precursor material and the activation agent is known as the impregnation ratio. the effectiveness and efficiency of the chemical activation process are largely dependent on this ratio. researchers have identified impregnation ratio is one of the most important factors that affects the activation mechanism and the qualities of the activated material (yahya et al., 2015). the effect of impregnation on the yield of the rice husk and sugarcane bagasse is presented in figure 2a and figure 2b. a b figure 2 (a) impregnation ratio effect on yield of rice husk (b) impregnation ratio effect on yield of sugarcane rice husk activated carbon produced varied in behavior to other activated carbons. in this case the rhac yield decrease with increase in impregnation ratio. however, the difference between the ratios are very minimal, this can be as result of pore formation. the yield performance as depicted in table 2(a), shows that for impregnation ratio one (ir 1) the corresponding yield for carbonization temperatures of 500℃, 550℃ and 600℃ are 91.11%, 90.58% and 88.64%. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):343-356. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 350 while for ir 1.5, the yield is 89.39% at 500℃, 88.72% at 550℃ and 85.58% 600. for the final carbonization temperature of 600℃ the yield are 87.78%, 87.1% and 84.53% for ir 1, ir 1.5 and ir 2 respectively. similarly, the yield of sugarcane bagasse activated carbon reduced with increased impregnation ratio as shown in table 2(b) which can mainly be due to evolution of volatile material. for ir 1, ir 1.5 and ir 2, the yield are respectively 90.13%, 88.47% and 87.88% at temperature of 500℃, and at the same for 550℃, the yield are 89.75%, 87.33% and 86.19%. similarly for 600℃ the yield for ir 1, ir 1.5 and ir 2 are 86.32%, 84.29% and 83.54%. 3.3 morphology of adsorbent the surface morphology of the activated carbon was examined using a scanning electron microscope (sem) at x3000, x4000, x5000 and x10,000 magnifications. this is to enable detail and compressive assessment of the precursor at the various magnifications. the morphology of the rice husk activated carbon was determined using a scanning electron microscope. sem images shown in fig 3(a-d) provides detailed information and reactions that took place on the surface of the activated carbon microstructure (dada et al., 2022). it can be seen from the images obtained, the rhac surface having heterogeneous and irregular, which also contains undulating layer of outer covering that is referred to as the vascular bundle structure containing sio2 (wazir et al., 2020) as reveled in figure 3(a) and (b). at higher magnification as shown in figure 3(c) and (d) rough and coarse surfaces with different cracks and crevices can be observed which reveal the presence of developed pores that emerge as a of the physical and chemical activation (el nemr et al., 2022). these highly developed pore structure is having imperative effect on the process of adsorption and to affirm the presence of meso and macro-pores which are potential site for the sorption and transportation of metal ions in aqueous solution (dada et al., 2022). figure 3: sem images for rice husk carbon (a) magnification x3000 (b) magnification x4000 (c) magnification x5000 (d) magnification x10,000 similarly, the sem sugarcane bagasse activated carbon shown in figure 4(a-d) comprises relatively smooth surface with cravices that have emerge as result of the activation process. during the thermal activation and preparation of the adsorbent, volatile organic compounds are evolved, this gives rise to the pore network of the sugarcane bagasse. other literatures have reported identical result. raut et al. (2023) studied the synthesis and characterization of a b c d file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com waziri et al efficacy of sugarcane bagasse and rice husk adsorbent for treatment of heavy metals from petroleum refinery effluent. azojete, 20(2):343-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 351 raw bagasse, and activated carbon using chemical additive where the developed pore are visibly relative not equal (raut et al., 2023). figure 4: sem images for sugarcane bagasse activated carbon (a) magnification x3000 (b) magnification x4000 (c) magnification x5000 (d) magnification x10,000 3.4 x-ray diffraction spectroscopy (xrd) in order to determine the level of amorphous nature or crystallinity of an activated carbon, xray diffraction becomes indispensable. the x-ray diffractometer ultima iv, rigaku (japan) was used for the study working at a current of 40 ma and voltage of 40 kv. the variation of the diffraction angle (2θ) ranges between 10o to 80o. x-ray scattering is an analytical method that reveals details about the crystallographic structure, chemical makeup, and physical characteristics of materials. it operates by assessing the intensity of x-rays that are deflected by a sample, taking into account the angles of incidence and scattering, as well as polarization and the wavelength or energy of the x-rays (raut et al., 2023). the xrd diffractogram of rice husk and sugarcane bagasse are shown in figure 4(a) and figure 4(b). a b figure 5: xrd spectra (a) rice husk activated carbon (b) sugarcane bagasse activated carbon the xrd diffractogram obtained from rice husk activated carbon as shown from fig. 5(a), displaying irregular pattern with two sharp peaks observed around 2θ=21o, 2θ=25o and 2θ=36o which are indication of the presence of a microcrystalline cellulose. choi et al. (2018) have 0 500 1000 1500 2000 0 20 40 60 80 100 in te n si ty a .u 2θ degree 0 1000 2000 3000 0 20 40 60 80 100 in te n si ty a .u 2θ degree b d c a http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):343-356. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 352 reported similar findings in structural characterization of cellulose obtained from extraction wastes of graviola (annona muricata) leaves. however, the rest of the diffractogram does not show any visible peak, this posits the adsorbent as an amorphous in nature there by making a better adsorbent due to large surface area and pore volume (abdul khalil et al., 2013; gurung et al., 2023). the sugarcane bagasse activated carbon was tested for its crystallinity as represented by the diffractogram pattern shown in figure 4(b). it can be seen from the spectra that there exist sharp peaks at 2θ=11o, 2θ=22o and 2θ=25o, and also between 2θ=30o 40o. this signifies that the spectra constitute the presence of ordered arrangement of atom and hence microcrystalline arrangement (namasivayam and kavitha, 2006). although, the well-defined arrangement giving insight as crystalline structure apparently collapses across the diffractogram showing the formation of an amorphous properties of the sugarcane bagasse activated carbon. 4.1 heavy metals adsorption in the adsorption isotherm, the amount of adsorbate that can be absorbed by the adsorbent is a function of the adsorbate concentration and temperature. the characteristics of the adsorbate include solubility, molecular structure, molecular weight, polarity, and hydrocarbon saturation. the equation that is often used to describe experimental isotherm data was developed by freundlich, langmuir, and others (budhiary and sumantri, 2021). the langmuir adsorption isotherm is based on monolayer, uniform, and finite adsorption site assumptions, therefore a saturation value is reached beyond which no further adsorption takes place. it also assumes that there is no interaction between the molecules adsorbed on neighbouring sites (belhachemi and addoun, 2011). the langmuir equation which is valid for monolayer adsorption onto a surface with a finite number of identical sites is given by equation (2) above. freundlich isotherm is an empirical equation for multilayer, heterogeneous adsorption sites. the freundlich equation is given by equation (4). simultaneous adsorption of heavy metals in petroleum refinery effluent using rice husk activated carbon. the obtained data was examined by the r2 coefficient derived from the linear plots of the isotherm models presented in figure 6 for rice husk and figure 7 for sugarcane bagasse. 0 1 2 3 4 0 1 2 3 4 5 c e m g /l c e /q e m g /l c d c r c u p b n i z n r 2 = 0 .7 9 6 9 (c d ) r 2 = 0 .9 5 1 2 (c r) r 2 = 0 .8 2 2 (c u ) r 2 = 0 .9 0 3 9 (p b ) r 2 = 0 .6 1 5 6 (n i) r 2 = 0 .7 5 8 7 (z n ) 0 2 4 6 8 1 0 -8 -6 -4 -2 0 ln c e ln q e c d c r c u p b n i z n r 2 = 0 .8 5 4 1 (c d ) r 2 = 0 .5 9 0 1 (c r) r 2 = 0 .8 7 4 2 (c u ) r 2 = 0 .9 5 7 (p b ) r 2 = 0 .8 1 (n i) r 2 = 0 .2 1 1 3 (z n ) figure 6: heavy metal adsorption of rice husk activated carbon. figure 7: heavy metal adsorption of sugarcane bagasse activated carbon the findings in table 6, shows that the simultaneous adsorption of heavy metals from petroleum refinery is fitted well for both langmuir and freundlich models. cadmium recorded r2 0.7969 and 0.8343 for langmuir and freundlich isotherms, chromium has 0.9512 and 0.936, copper exhibited an r2 of 0.822 and 0.8093 while lead manifested 0.9039 and 0.6156, and lastly zinc revealed 0.7586 and 0.6726 respectively. this shows that the adsorption of the heavy metals on the surface of the rice husk activated carbon is consistent (denga et al., 2023). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com waziri et al efficacy of sugarcane bagasse and rice husk adsorbent for treatment of heavy metals from petroleum refinery effluent. azojete, 20(2):343-356. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 353 furthermore, the separation factor kl, which was used to assess the favorability of the adsorption, is less than 1, indicating good adsorption of the heavy metals (mashile et al., 2020) table 6: adsorption isotherm models and their constant for rice husk activated carbon langmuir freundlich heavy metals r2 qmax kl r2 kf n cadmium 0.7969 3.147 -0.7516 0.8343 242.7 0.01193 chromium 0.9512 4.646 -0.8632 0.936 145.4 0.01801 copper 0.822 3.568 -0.9687 0.8093 89.64 0.01283 lead 0.9039 3.527 -0.798 0.9099 213.7 0.01593 nickel 0.6156 3.887 -1.585 0.6259 81.77 0.00896 zinc 0.7586 3.75 -1.028 0.6726 73.02 0.00803 on the other hand, the concurrent adsorption of heavy metals using sugarcane bagasse activated carbon is presented in figure 7. the obtained values were also analyzed based on the r2 coefficient obtained in the langmuir and freundlich models as revealed in table 7. the r2 coefficient for cadmium ion obtained from langmuir and freundlich models are 0.8676 and 0.8541, chromium 0.5696 and 0.5901, copper 0.8733 and 0.8742, and lead 0.9378 and 0.957. the other metal ions are nickel which recorded r2 coefficient of 0.7949 and 0.81, and zinc having 0.2005 and 0.2113 for langmuir and freundlich isotherm respectively. analogous to the rice husk adsorbent, sugarcane bagasse performs well in the tested models, although it fits well with the freundlich adsorption model as shown in table 7. table 7: adsorption isotherm models and their constants for sugarcane bagasse activated carbon langmuir freundlich heavy metals r2 qmax kl r2 kf n cadmium 0.8676 3.44 -0.7769 0.8541 156.1 0.01314 chromium 0.5696 4.654 -0.8573 0.5901 152.4 0.00404 copper 0.8733 2.989 -1.281 0.8742 64.11 0.0128 lead 0.9378 3.276 -0.5961 0.957 287.8 0.01419 nickel 0.7949 4.249 -1.125 0.81 106.2 0.01456 zinc 0.2005 3.156 -0.941 0.2113 75.3 -0.00872 4.0 conclusion the simultaneous adsorption of six heavy metals usually found in refinery wastewater using rice husk and sugarcane bagasse was studied. the experimental data obtained for rice husk shows competitive adsorption and is fitted to both langmuir and freundlich models. the order of strength of the sorption was cr>pb>cu>cd>zn>ni. the data obtained for sugarcane bagasse fitted well into the freundlich model, the order of adsorption preference was pb>cu>cd>ni>cr>zn. the investigated process parameter reveals that the impregnation ratio and temperature affect the sorption capacities of activated carbon. rice husk and sugarcane bagasse as shown from the batch experiment conducted can be effectively used for the treatment of heavy metal from refinery and other industrial effluents. references abdul khalil, hps., jawaid, m., firoozian, p., rashid, u., islam, a. and akil, hm. 2013. activated carbon from various agricultural wastes by chemical activation with koh: preparation and characterization. journal of biobased materials and bioenergy, 7(6): 708–714. https://doi.org/10.1166/jbmb.2013.1379 aboli, e., jafari, d. and esmaeili, h. 2020. heavy metal ions (lead, cobalt, and nickel) biosorption from aqueous solution onto activated carbon prepared from citrus limetta leaves. carbon http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; 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e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sadiqwaziri@unimaid.edu.ng 357 https://doi.org/10.1016/j.rinma.2021.100183 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com 1optimum paste temperature for oil extraction usig iar motorised kneader arid zone journal of engineering, technology and environment. october, 2008; vol.6, 67-73 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng optimum paste temperature for oil extraction using iar motorised kneader gyuse, e.t. 1 and yiljep, y.d.2 abstract an experiment to determine optimum paste temperature for oil extraction using the institute for agricultural research (iar) motorised kneader was conducted at the agricultural engineering department of ahmadu bello university zaria, in 2002. some 20 kg of groundnut paste from the manipinta variety (locally known as kampala) with 55% oil content at 5 6% moisture content was used for the experiment. the paste was divided into five equal replicates (of 4kg each) for use with motorised kneader. results show that iar motorized kneader enhanced extraction efficiency at low values of paste temperatures. optimum extraction efficiencies of 88.31 – 98.55% were obtained at paste temperature of 23.50 – 25.00oc, corresponding to atmospheric and added water temperatures of between 15.75 – 23.09 and 22.00 – 26.00oc, respectively. it is therefore recommended that groundnut paste at elevated temperature be allowed to cool to about 24.50oc before kneading. the optimum extraction efficiency of the kneader was realized at room temperature during the harmattan season. 1. introduction groundnut is a source of highly nutritious food for both humans and livestock. the uses to which the crop is put are many, and its importance is steadily increasing. as human food, the kernel is consumed raw, salted or roasted and is used in various forms of confectionary; the oil is excellent for margarine manufacturer (ker et al., 1957 as cited by ola, 2000). oil processing is a lucrative business due to the enormous demand for oil, both for domestic and industrial uses (pirie, 1975). moreover, in some parts of africa such as nigeria and ghana, oil extraction and marketing have become a source of income to many people. extraction of vegetable oils from the oil-bearing materials dates back many ages. it was developed in china and india probably much earlier than in other parts of the world. whereas the old chinese oil processes used in remote villages of manchuria were driven by manpower, in india, the primitive village ghanis was driven by bullocks and in their absence by manpower (parek, 1964). according to adeeko and ajibola (1990), groundnut oil extraction is affected by factors such as paste temperature, speed of the oil extraction machine, temperature of water used, atmospheric temperature, machine processing time, feed rate, amount of water used, particle size of oil seeds and moisture content of oil seed. head et al. (1995) stated that higher processing temperatures improve oil flow by reducing the viscosity of the oil. according to them, small-scale expeller minimizes the 1department of agric. engineering and technology, samaru college of agriculture, ahmadu bello university, zaria. nigeria 2agricultural engineering & irrigation programme, national agricultural extension and research liaison services, ahmadu bello university, zaria. nigeria. http://www.azojete.com.ng/ optimum paste temperature for oil extraction using iar motorised kneader 68 need for pre-treatment by using a relatively fast worm shaft speed which shears the oil seed as it passes through the expeller and produces frictional heat within the expeller barrel. this assists oil expulsion by raising the temperature of the oil seed. however, even when using a small-scale expeller, heating and/or steaming the oil seed before expelling will assist oil extraction. heat treatment is essential for some seeds with low fibre content such as groundnut; they must be heated and moisturized before expelling or the machine will produce an oil paste of oil and cake. with the oil press machines, head et al. (1995) stated that until the barrel reaches the operating temperatures, a large amount of sediment ‘foots’ might be produced with the oil. hui (1996) reported that in oil pressing plants, the seed is subjected to extreme heat and pressure and oil is mechanically forced out from the oil cell. according to unifem (1993), in traditional oil extraction, the paste is heated first, and then with water the mixture is stirred and allowed to boil. after boiling, the mixture is allowed to cool, during which time the oil gathers at the top and is scooped off. extraction efficiency with this method is about 40%. williams (1966) established that solvent extraction of oil from oil seeds generally involves washing out of the oil from the ground seed by means of a hot (or raised temperature) solvent and its subsequent evaporation in order to recover the dissolved oil. the extraction meal is freed from solvent by heating and finally by steaming and the remaining traces are distilled from the meal until the latter is completely freed from any smell of solvent. the objective of this study was to determine water and paste temperatures that produce the highest oil yield from iar motorized paste kneader. 2. materials and methods 2.1. the kneader description the iar kneader is a motorized kneader powered by an electric motor. the top of kneader chamber through which the oil material is fed is 355 mm in diameter while the bottom is 190 mm in diameter. the height of the kneading (bucket) chamber is 570 mm, and that of the finger-like kneading mechanism is 320 mm. the height of the shaft holding the fingers is 690 mm. the clearance between the bottom of the kneading chamber and the lower end of the kneading fingers is 10 mm, while that between the walls of the chamber and the fingers is 20 mm. the fingers are inclined at angle of 30o to the shaft. principle of operation the kneader expresses oil from groundnut paste by using a metal with a power driven finger-like shaft fixed to a metal frame. with the iar kneader, little or no heat is developed in the course of kneading since the extraction chamber is an open bucket. oil extraction is accomplished by kneading. the groundnut paste is fed into the mortar, and as the power driven finger-like shaft rotates, it stirs the paste and coagulates it when azojete vol. 6 2008 69 warm water is added. the oil released is collected through a 30 mm diameter pipe at the bottom of the mortar. 2.2 data collection manipinta (locally known as kampala) was the available groundnut variety at the time of this experiment. it was obtained at the samaru market in zaria, kaduna state, nigeria. its oil content is 55% at 5 – 6% moisture content. the groundnut was ground at agricultural engineering department of ahmadu bello university, zaria with a pepper grinding machine and the kneading experiment was carried out in the same department. twenty kilograms of the groundnut paste was divided into five equal parts and the kneading machine was used on the five samples. factors such as speed of kneading fingers, feed rate, time of kneading and water used in kneading were assumed constant. ambient temperatures, that of the paste before kneading, water temperature were measured using a dry bulb thermometer. oil yield and water used were measured using a measuring cylinder, whereas machine extraction efficiency was calculated using the equation 1 below. eff = %100) 2 1 ( x w w 1 where eff = oil extraction efficiency (%) w1 = weight of oil extracted (kg) w2 = weight of paste kneaded (kg) 3. results and discussion data collected from the use of the kneader are presented in table 1. it can be seen from the table that the extraction efficiency of the kneader decreased with increasing paste temperatures. at lowest temperatures of paste (31.50oc), water (28.00oc) and atmosphere (28.50oc), the kneader extraction efficiency was 50.20%. the extraction efficiency decreased to 41.13% at higher temperatures of 32.95oc, 28.90oc and 31.60oc of paste, water and the ambient surrounding, respectively. table 1: data collected from the use of the kneader sample tp * (oc) tw (oc) ta (oc) we (kg) wf (kg) eff (%) t (min) a 31.50 28.00 28.50 1.20 1.10 50.20 27.00 b 31.80 28.20 29.40 1.15 1.05 47.99 27.20 c 32.50 28.60 30.50 1.20 1.00 45.70 24.06 d 32.95 28.90 31.60 1.10 0.90 41.13 28.00 e 32.98 29.10 32.10 1.10 0.95 43.42 26.25 mean 32.34 28.56 30.42 45.69 st. dev 0.67 0.46 1.50 3.59 *tp – temperature of paste, tw – temperature of water, ta – ambient temperature, we – weight of extracted oil, wf of oil after frying, eff. – extraction efficiency, t – oil frying time optimum paste temperature for oil extraction using iar motorised kneader 70 figure 1 shows that elevated temperatures of paste decreased the extraction efficiency of the kneading machine. at about 0oc of paste temperatures, the kneader did not function properly since the paste tended to block up. the operational and optimum paste temperature is between 23.50 and 25oc. this range corresponds to the kneader extraction efficiency range of 88.31 – 98.55%. y = -165.58ln(x) + 621.29 r 2 = 0.9216 0 10 20 30 40 50 60 31 31.5 32 32.5 33 33.5 34 paste temperature (oc) m a c h in e e x tr a c ti o n e ff ic ie n c y ( % ) figure 1: machine extraction efficiency versus paste temperature elevated ambient temperatures decreases the kneader extraction efficiency and vice versa (figure 2). ambient temperature affects paste temperatures and eventually kneader extraction efficiency. temperatures of water used in kneading also inversely affected paste temperatures and the kneader extraction efficiency. increasing the water temperatures above 35oc decreased the efficiency (figure 3). azojete vol. 6 2008 71 y = -68.488ln(x) + 279.51 r 2 = 0.8871 0 10 20 30 40 50 60 28 29 30 31 32 33 atmospheric temperature ( o c) m ac h in e e x tr ac ti o n e ff ic ie n cy ( % ) figure 2: machine extraction efficiency versus atmospheric temperature y = -205.53ln(x) + 734.61 r 2 = 0.8566 0 10 20 30 40 50 60 27.5 28 28.5 29 29.5 water temperature ( o c) m ac h in e e x tr ac ti o n e ff ic ie n cy ( % ) figure 3: machine extraction efficiency versus water temperature paste and water temperatures vary with ambient temperatures provided no external heat is applied. figure 4 shows that temperatures of water and paste increase with increase in ambient temperature and vice versa. when optimum paste temperature tp is between 23.5 and 25°c (figure 1), the atmospheric temperature (ta) can be estimated from equation 2, and when optimum water temperature tw is between 22 and 26°c (figure 3) the atmospheric temperature (ta) can be estimated from equation 3: optimum paste temperature for oil extraction using iar motorised kneader 72 y = 13.456ln(x) 13.595 r 2 = 0.9788 y = 9.3153ln(x) 3.2436 r 2 = 0.9934 27 28 29 30 31 32 33 34 28 29 30 31 32 33 atmospheric temperature ( o c) p a st e & w a te r t e m p e ra tu re s ( o c ) past temp. water temp figure 4: water and paste temperatures versus atmospheric temperature ta = ep(+13.595/13.456 2 ta = ewt+3.2436/9.3153 3 adding warm water (at 26oc) at ambient temperature decreases paste temperature as shown in figure 5, and this is favourable for oil extraction. tp = 41.036ln(tw) 105.2 r 2 = 0.9761 31.4 31.6 31.8 32 32.2 32.4 32.6 32.8 33 33.2 27.5 28 28.5 29 29.5 water temperature ( o c) p a st e t e m p e ra tu re ( o c ) figure 5: water temperatures versus paste temperature azojete vol. 6 2008 73 4. conclusion it was observed that at reduced temperatures of paste, the motorized kneader extraction efficiency was enhanced. with the kneader optimum extraction efficiency is 88.31 – 98.55%, the corresponding paste, water and ambient temperatures were in the ranges of: 23.5 – 25°c, 22 – 26°c and 15.75 – 23.09°c respectively. this means that groundnut paste brought from the mill at elevated temperatures should be allowed to cool before kneading, which is in line with the recommendation of unifem (1993) for traditional oil 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(1975). food protein sources. cambridge university press cambridge london new york melbourne. 1st ed. pp. 19. unifem (1993). united nations development fund for women. oil processing intermediate technology publications, no. 2. williams, k.a. (1966). oils, fats and fatty foods, 4th ed. j & a churchill ltd, 104 gloucester place london w. 1 pp 190 -195. arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):693-706 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 693 original research article application of image analysis in food grain quality inspection and evaluation during bulk storage n. a. aviara1*, a. a. adesanya2, i. j. iyilade2 e. o. olorunsola2 and s. k. oyeniyi2 1department of agricultural and environmental resources engineering, university of maiduguri, maiduguri, nigeria 2department of agricultural and environmental engineering, university of ibadan, ibadan, nigeria. *corresponding author’s email address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 1.0 introduction increase in consumer’s taste and awareness has led to the need of thorough quality inspection of food products. food borne illnesses caused by food borne pathogens have been a major concern since they have led to the death of many people globally. these are some of the reasons why enhanced monitoring is required in grain bulk storage (brosnan et al., 2004). over the years, grain bulk storage quality inspection has been performed manually by quality assurance officers with little or no precision. quality itself is said to be the conglomeration of all the elements that make food product acceptable to the consumer (shewfelt et al., 2000). during bulk storage, grain quality is a function of soundness and admixtures, collection point, mills and terminals, cleaning, storage temperature and moisture content (sinha and muir 1973). the basis of quality assessment is also with attributes such as appearance, smell, texture and flavour frequently examined by human inspectors. human inspection of grain quality in bulk storage has been found to be tedious, time consuming and inaccurate. neethirajan et al. (2007) corroborated the above by noting that manual article information abstract with increased expectations for high quality food products and safety standards, the need for accurate, fast and objective quality determination of moisture, purity, germination and pathogen free food products and grains during bulk storage continues to grow. this paper reviews the application of image analysis in food grain quality inspection and discusses the potential of the technology for application in grain quality monitoring and evaluation during bulk storage. image analysis procedure and physical properties of the grain bulk were also discussed. image analysis is an automated alternative to manual inspection with less processing time and more accurate results. human inspection has been found wanting due the bias judgment and results. image analysis of food grains during bulk storage can only get better with its diverse applications in varietal identification, distinctness, uniformity and stability (dus) testing, detection of insects and foreign bodies within the grain bulk and the detection of hot spot in the bin to mention a few. in nigeria, image analysis will be a great tool in terms of grain quality preservation in national grain reserves (ngrs), providing seeds for farmers for the next planting season and reviving the grain reserves in nigeria to boost gainful employment of citizens. an automated grain reserves using image analysis is possible in nigeria only if appropriate government policies and funding can throw its full weight behind the innovation. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 march, 2022 revised 12 may, 2022 accepted 15 may, 2022 keywords: image analysis machine vision computer vision grain quality evaluation bulk storage http://www.azojete.com.ng/ mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 694 inspection, sieving, cracking-xoatation and berlese funnels being used at present to detect insects in grain handling facilities are not only inefficient but also time consuming. the need for fast and accurate measuring instruments cannot be over emphasized. one of the techniques that can be applied in the functioning of such equipment is the image analysis procedure. for real time image capturing and processing, the computer vision technique has commanded rapt attention for research and application for more than four decades. the application of this technique has found relevance in engineering fields such as robotics, industrial image processing, food processing and other fields. some of the advantages of computer vision includes quickness, non-destructive evaluation possibilities, easy procedures for application, large output per unit time. application of computer vision to food processing fields evolved first in 1989 for grain quality inspection (zayas et al., 1989). principal areas of application of computer vision technology in food industry include quality evaluation of food grains, fruits, vegetables and processed foods such as chips, cheese and pizza. the technique has also been found useful for determination insect infestation in grains and blemishes in fruits and vegetables (mahendran et al., 2011). computer vision is a broad area of research and a comprehensive definition is difficult to distil, a generally accepted definition of computer vision is ‘the analysis of images to extract data for controlling a process or activity’ (mahendran et al., 2011; relf, 2004). this paper examines the potentials of image analysis procedure for application in food grain quality inspection and evaluation during bulk storage. 2. image analysis procedure as highlighted by gujjar and siddappa (2013), the procedure for application of image analysis in food grain quality evaluation during bulk storage of samples is shown in figure 1. figure 1: procedure for food grain image acquisition, identification and processing source: gujjar and siddappa (2013). 2.1 steps involved in image analysis steps involved in image analysis according to siddagangappa and kulkarni (2014) include the following: image acquisition, preprocessing image, filtering image, binarization and image segmentation. 2.1.1 image acquisition the images are acquired with a colour digital camera or using sensor to capture images of grain samples. in order to obtain a good image, proper illumination must be provided and kept a fixed distance between the camera and the grain samples. the environment has to be controlled to improve the data collection with sample being plain background. the grains are spread on a blue sheet randomly, such that they are not in contact with other grains. the images should be captured and stored in jpeg format automatically (siddagangappa and kulkarni, 2014, chitra et al., 2016). food grain image image enhancement image segmentation classification decision feature selection and extraction neutral network file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com aviara et al: application of image analysis in food grain quality inspection and evaluation during bulk storage. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 695 2.1.2 preprocessing of image this is one of the steps for enhancement of quality of the captured image.gaussian filter for image smoothering is normally used and grayscale image is binarized after use of threshold method to eliminate background noise (siddagangappa and kulkarni, 2014, chitra et al., 2016 ). 2.1.3 filtering image the images of grains in storage are often corrupted due to the variation in illumination, intensity or may have poor contrast and cannot be used directly. filtering aids in transformation of the intensity values to reveal certain image characteristics. the original and filtered images of samples of cowpea are shown in figure 2 (a and b), respectively (siddagangappa and kulkarni, 2014). (a) (b) figure 2: original image (a) and filtered image (b) of white cowpea source: siddagangappa and kulkarni (2014). 2.1.4 binarization binarization of an image is a process representing an image using only two different pixel values. it can be performed by classifying a grayscale image into two groups of pixels based on certain threshold gray value. the pixel values greater than or equal tio the threshold is set to a particular gray value and those below the threshold to another gray value. the quality of the binary image is much dependent on how appropriately the threshold for binarization are chosen (visen et al., 2004). an example of binarization can be given as follows: if f(x,y) ˃ t then f(x,y) = 0 else f(x,y) = 255 (1) where: t is a threshold value and x and y are co-ordinates. 2.1.5 image segmentation segmentation accuracy determines to a large extent, the eventual success or failure of computerized analysis procedures. segmentation basicly includes edge detection. appropriate image segmentation for white cowpea is shown in figure 3. threshold is also one of the approaches of segmentation. the other approach is region oriented segmentation also known as watershed segmentation. after enhancement of image, the edges of the object in binary image have to be detected using canny and sobel detector (mask). edge detection using sobel detector results in more accuracy than using canny edge detector (siddagangappa and kulkarni, 2014, chitra et al., 2016). http://www.azojete.com.ng/ mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 696 figure 3: image of white cowpea after segmentation source: siddagangappa and kulkarni (2014). 2.2 feature extraction. 2.2.1 colour feature extractions according to gujjar and siddappa (2013), alogrithms can be developed using matlab 7.0 programming language to extract colour features of individual grains. from red (r), green (g), and blue (b) colour bands of an image, hue (h), saturation (s), intensity (i) can be calculated using equations (2 – 4) 1 = 1 3 (𝑅 + 𝐺 + 𝐵) (2) 𝑆 = 1−3(𝑚𝑖𝑛(𝑅,𝐺,𝐵)) (𝑅+𝐺+𝐵) (3) 𝐻 = cos−1{((𝑅−𝐺)+(𝑅−𝐺))} 1 2 {(𝑅−𝐺)2+(𝑅−𝐺)(𝐺−𝐵)} 1 2 (4) the mean values of i, s and h, as well as their minimum and maximum values can be calculated for an image after segmentation, thereby enabling nine colour features to be extracted. 2.2.2 morphological feature extraction algorithms developed in windows environment using matlab 7.0 programming language can be used to extract morphological features of individual grains following the procedure described by gujjar and siddappa (2013). the following morphological features can be extracted from images of individual grains as shown in figure 4. area: the algorithm can calculate the number of pixels inside, and include the seed boundary (mm²/pixel). length: this can be taken as the length of the rectangle bounding the seed. width: it is the width of the rectangle bounding the seed. major axis length: this can be taken as the distance between the end points of the longest line that could be drawn through the seed. the major axis end points can be found by computing the pixel distance between every combination of border pixels in the seed boundary. minor axis length: this is the distance between the end points of the longest line that could be drawn through the seed while maintaining perpendicularity with the major axis. aspect ratio, k1: this is the ratio of the minor axis to the major axis. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com aviara et al: application of image analysis in food grain quality inspection and evaluation during bulk storage. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 697 rectangular aspect ratio, k2: this is the ratio of the intermediate axis or width to the major axis or length. figure 4: images of white cowpea seeds after morphological operations source: siddagangappa and kulkarni (2014). 2.2.3 textural feature extraction algorithms can be developed in windows environment using matlab 7.0 programming language to extract textural features of individual grain images (gujjar and siddappa, 2013, chitra et al., 2016). 3. related works on image analysis application computer vision can function as an inspection approach for grain quality evaluation. it stands as an automated, non-destructive and cost-effective technique to accomplish these requirements. computer vision has been successfully adopted for the quality analysis of meat, fish, pizza, cheese, and bread. likewise, grain quality and characteristics have been examined by this technique. xiang (1997) worked on colour image analysis for cereal grain classification. he differentiated images of individual kernels and bulk grain samples for five grain types in canada. neethirajan and jayas (2007) developed sensors for grain storage. this is to mitigate grain loss due to deterioration during storage. shah and khan (2014) investigated imaging techniques for the detection of grain deterioration due to pests (insects and fungi) during storage. lai et al. (1986) suggested some pattern recognition techniques for identifying and classifying cereal grains. this method yielded 100% accurate prediction for the samples used in the study. the pattern obtained was selected out of a great number of possible ones. the grains considered here were corn, wheat, soyabean and sorghum. zayas et al. (1989) illustrated the use of image analysis to discriminate between wheat and nonwheat components in a grain sample. they presented two methods, multivariate discriminate and a structural prototype method for pattern recognition. the main concern in this method was the misclassification of irregularly shaped stones as wheat. the limitation in the proposed method was the requirement to manually orient the kernels. visen et al. (2004) proposed algorithms to acquire and process color images of bulk grain samples of five grain types, namely oats, barley, rye, wheat, and durum wheat. the developed algorithms were used to extract over 150 color and textural features. a back propagation neural network-based classifier was developed to identify the unknown grain types. the color and textural features were presented to the neural network for training purposes. the trained network was then used to identify the unknown grain types. classification accuracies of over 98% were obtained for all grain types. huang et al. (2004) proposed a method of identification based on bayes decision theory to classify rice variety using color features and shape features with 88.3% accuracy. majumdar and jayas (2000) developed http://www.azojete.com.ng/ mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 698 classification models by combining two or three features sets (morphological, color, textural) to classify individual kernels of canada western red spring (cwrs). anami et al. (2005) developed a neural network approach to classify single kernel of different grains like wheat, maize, groundnut, redgram, green gram and black gram based on color, area covered, height and width. the minimum and maximum classification accuracies were 80% and 90% respectively. sanjivini et al. (2010) using this approach, performed texture and morphologically based retrieval on a couple of food grain images. image warping and image analysis approach were applied. normalization of food grain images was employed and elimination of the effects of orientation using image warping technique with proper scaling was achieved. the images were properly enhanced to reduce noise and blurring. the approach was tested on sufficient number of food grain images of rice based on intensity, position and orientation. a digital image analysis algorithm based on color, morphological and textural features was developed to identify the six varieties of rice grains which were widely planted in the chhattisgarh region of india. the accuracy of the results was between 80% and 90%. in this case, pre-processing and segmentation process was found to be tedious. savakar, (2012) illustrated an algorithm for recognition and classification of similar looking grain images using artificial neural networks and that showed that accuracy of 7884% was achieved by using either individual color or texture feature, and accuracy of 8590% was seen when both features were combined. kaur and singh (2013) proposed a machine algorithm to grade rice grains into premium, grade a, grade b and grade c, respectively, using multi-class svm. maximum variance method was applied to extract the rice kernels from background, after the chalk had been extracted from rice. the percentage of head rice, broken rice and brewers in rice samples were determined using ten geometric features. multi-class svm classified the rice kernel by examining the shape, chalkiness and percentage of broken (head rice, broken and brewers) kernels. the svm classified accurately to more than 86%. based on the results, it was concluded that the system was enough to use for classifying and grading the different varieties of rice grains based on their interior and exterior quality. mebatsion et al. (2013) proposed a method for the classification of cereal grains, namely; barley, rye, oats and wheat (canada western amber durum (cwad) and canada western red spring (cwrs)). this was performed using morphological and color features. the combined model defined by morphological and color features achieved a classification accuracy of 98.5% for barley, 99.97% for cwrs, 99.93% for oat, and 100% for rye and cwad. pabamalie and premaratne, (2010) focused on providing a better approach for identification of rice quality by using neural network and image processing concepts. here a back propagation neural network with two hidden layers was developed for the quality classification. thirty-one texture and color features that have been extracted from rice images were used for discriminate analysis. here foreign matters, type of admixture and brown grain content were the three parameters considered for sample preparation. tests on the system for the training and test sets showed accuracy between 68 and 94% for the four grades. lukas and stejskal (2003) applied computer based image analysis to the estimation of area of sticky trap occupied or contaminated by pests and used the results to differentiate between heavy and weak contaminators. venkatesh et al. (2015) developed a simple and easytooperate automatic sorting system based on digital image processing for defect detection and sorting of grains, fruits and vegetables. the sorting operation was based on the features extracted from the images by different image processing techniques. the quality of fruits vegetables and grains used were color, firmness and bruises, since these formed the relevant sorting parameters for classifying the agro-products in terms of ripeness, decaying and growth defects respectively. results showed that the products were successfully sorted. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com aviara et al: application of image analysis in food grain quality inspection and evaluation during bulk storage. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 699 4. potential applications of image analysis during bulk storage the following areas of application of image analysis due to varma et al. (2013) and gowda et al. (2013) can be adapted for grain quality inspection and evaluation during bulk storage:  distinctness, uniformity and stability (dus) testing;  varietal identification;  moisture  sorting and grading;  detection of foreign bodies in grains;  detection of insect infestation inside grain kernel;  detection of hot spots in grain bin. 4.1 distinctness, uniformity and stability (dus) testing one of the applications of image analysis is testing for distinctness, uniformity and stability (dus). new varieties are compared to create differences (distinctness) from existing varieties before they are given official recognition. the goal is to identify consistent differences in respect of one or more characters between existing and potential new varieties. the physical and visual traits of the seed are potential characters. manually, differences in appearance can be assessed by measurement or subjective scoring. measurement can be used for simple size and shape measurements, such as lengths and their ratios while subjective scoring is used for more subtle differences that would be more difficult or cumbersome to measure (varma et al., 2013). the disadvantage of this method is that it is tedious to do and subject to inconsistency between observers and over time. there have been a number of attempts to use image analysis to assess seed appearance. these have ranged from straightforward use of colour meters (mcmichael, 1994) to the use of image analysis to extract shape features (keefe et al., 1988). the development of nondestructive methods for the evaluation of cereal grain varieties has important implications for the food processing industry. 4.2 varietal identification seed identification processes by manual means by technicians is slow, prone to error and subjective and give results which may be difficult to quantify for both economic and technological purposes. therefore, it is important economically and technically to implement repeatable and quick automated methods to identify and classify seeds. seed varieties provide necessary options to growers, processors and consumers (varma et al., 2013). variety identification is also important for plant breeders and geneticists. visual assessments made using color, size, shape and texture are easily achieved, but the results possess questionable integrity. reliable visual evaluation needs experience and expertise (varma et al., 2013). an objective method will help in reducing the subjective nature of this visual assessment. automatic systems can be based on seed images, from which the characteristics for the classification, such as size, shape, colour and texture, can be obtained quickly (kapadia et al., 2017, tanwar et al., 2018). digital image analysis offers an objective and quantitative method for estimation of morphological parameters (varma et al., 2013). smykalova et al. (2013) carried out the phenotypic evaluation of flax seeds using image analysis and reported that the discrimination of variety, locality and stability of fax seeds was possible with the technique, zhang et al. (2018) used digital image analysis to carry out the phenotyping of seeds and seedlings, while ansari et al. (2021) inspected the varietal purity of paddy grains using machine vision and multivariate analysis. other studies that explored the use of image analysis in varietal difference detection include vijaya geetha et al. (2011) http://www.azojete.com.ng/ mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 700 (mustard), saini et al. (2014), vresak et al. (2016) and grillo et al. (2017) (wheat), aznan et al. (2017) and pratibha et al. (2017) (rice), and tu et al, (2021) (maize). 4.3 moisture according to hellevang (1995), grain moisture content affects economic returns because it affects the quantity of grains, grain storability and grain marketability. change in grain moisture content results to changes its weight. this change in weight is also called shrink (hellevang, 1995). the importance of moisture content as a factor in grain quality deterioration cannot be overemphasized. it controls the development of bacteria, mites, fungi and insects that are responsible for the spoilage of grains in storage. due to this, it is necessary to bring all food grains to safe moisture content before storage (gowda et al., 2013). however, this safe moisture content is related to the required storage time because the lesser the moisture content of the grain, the lesser the insect activity and the respiration rate of the grain. insect infestation tends to increase in moisture content above 10% up to a certain limit. generally, insect activity is rapid at relative humidity exceeding 75%. one of the most remarkable features about the storage insect pests is that some of them can live in products having moisture content less than 10% (sashidhar et al., 1992). with the use of image analysis, the effects of moisture content on insect activity in bulk storage can be detected and monitored. bora et al. (2018) used image processing analysis to track colour changes in apple and determine the product moisture content at different stages of the drying process. mohd ramli et al. (2021) used voxel weighting from radio tomography images to determine the moisture content of rice. 4.4 sorting and grading grading and sorting is essential for seed classification, separating the good seed from the bad ones and also seeds of different physical properties. a number of techniques for seed quality evaluation and sorting are based on the detection of various physical properties of seeds (varma et al., 2013). the declining cost and increasing speed and capability of computer hardware of image processing and its integration with controlled environmental condition systems have made computer vision more attractive for use in automatic inspection of crop seeds in storage. new algorithms and hardware architectures have been developed, and the availability of appropriate image analysis software tools suggests that the use of machine vision systems is becoming convenient during seed bulk storage (varma et al., 2013). for example, kapadia et al. (2017) noted that han et al. (1996) utilized frequency domain image analysis in detecting stress cracks in corn kernels. a fast fourier transform algorithm was applied to the pre-processed images and the transformation results were condensed into seed feature signatures representing position or orientation invariant morphological features. stress cracks are internal fissures that can be observed in kernels by x-ray inspection (kapadia et al., 2017). chaugule and mali (2014) evaluated texture and shape using neural network and applied this to the classification of four paddy varieties. the most suitable features for the accurate classifications of the features of the four varieties were identified. the most satisfactory results were delivered by the shape feature and texture feature sets. raj and swaminarayan (2015) reviewed the application of image processing in the grading of agricultural products and noted that the technique along with classification algorithms yielded very good results. han et al. (2014) graded wheat grains using digital image processing techniques, dessai and rao (2017) graded rice grains using image analysis and artificial neural network (ann) and jitanan and chimlek (2019) graded soya beans in terms of quality using image processing and machine learning. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com aviara et al: application of image analysis in food grain quality inspection and evaluation during bulk storage. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 701 4.5 detection of foreign bodies in grains foreign bodies may be defined as any unwanted substances (dirt, stone, dead insects, rat excreta etc.) which are present in desired product (food grains). the high demand and expectations of consumer to get pure product free from these foreign materials have made food industry to invest on machineries for processing and inspection to ensure a good quality product for consumers (gowda et al., 2013). several conventional methods like visual inspection which is time consuming, laborious and physical separation methods such as sieving, elutriation, sedimentation, screening, filtering, and gravity separation and advanced devices like metal detectors, x-ray machines and optical sensors have been employed, but it was found that distinguishing foreign materials and the product depends on the response of the energy spectrum between the product and foreign body, hence there is no any device which can detect these type of contaminants regardless of size, shape and type (vadivambal and jayas, 2010). meinlschmidt and margner, (2003) developed a thermal imaging setup to detect foreign materials like rotten nuts, hard shells, and stones in hazelnuts which are continuous moving over a belt conveyor. using three image processing techniques (histogram analysis, texture analysis) an object-oriented algorithms for grains and online thermal imaging were developed. gujjar and siddappa (2014) used artificial neural network (ann) and image segmentation to detect foreign bodies in grain samples with success rate that was appreciable. jiang et al. (2018) combined image preprocessing and threshold segmentation algorithm with terahertz time domain spectroscopy reflection imaging to detect foreign bodies embedded in bulk wheat grains and the technology proved a useful tool. ghatkamble (2021) used the machine vision system to automatically determine the amount of the foreign bodies present in rice grains. this system was found to be helpful to farmers in the sowing of the seeds and marketing of the rice grains. digital image analysis algorithms were developed using machine learning techniques in matlab and python programming language to determine the foreign bodies present in the rice grain samples applying the neural network method. the foreign bodies in the rice grain image samples were determined based on the color, texture and morphological features. all three features mentioned above were supplied to the neural network for training purpose and the trained network was later used to identify the foreign bodies in the grains. salam et al. (2022) used image processing and different classification algorithms to detect foreign materials in chickpea mixtures with the ann giving overall superior accuracy of results over the svm and lda. 4.6 detection of insect infestation inside grain kernel it is easier and better to prevent an insect infestation than to treat an established infestation. therefore, the on time detection and tracing insect infestation in stored grains play a vital role in order to take necessary action for insect control. the general methods for this purpose preferred are:  determination of co2 production method which is not appropriate for high moisture grains (more than15%) since the co2 produced by the grains and other microorganisms will interact with the results.  ninhydrin reaction with amino acids of grain which is an destructive method  floatation method which is not suitable for cryptolestes spp.  acoustic method which cannot detect eggs and pupae of insect.  the x-ray method, which cannot detect larval development. however, all these methods are standardised by the international standards organisation (iso) to find the hidden infestation in cereals and pulses methods have few limitations in applications. http://www.azojete.com.ng/ mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):693-706 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 702 other method still being used are insect traps for small scale stored grains and berlese funnels method which is time consuming and cannot be used for all types of insect species (cfia, 2008). however, neethirajan et al. (2007) and shah and khan (2014) noted that the acoustic technique (possibly imaging), near-infrared hyperspectral imaging and soft x-rays showed potentials for application in the accurate detection of internal infestations of stored grains. digital images of the scanned object are normally analyzed for various spectral and spatial features using statistical techniques that yield high classifications accuracies. 4.7 detection of hot spots in grain bin hot spots in grain bin are high temperature areas which are created by respiration of fungi, insect or the stored grains itself. it initiates the spoilage of grains. reasons for hotspot development are:  loading of high moisture grains over dry grain inside storage bin;  entry of water through leaks and holes;  moisture migration within grain bulk due to respiration of insect or grain  moisture rising through cracked floor. hot spots, originating from either fungal or insect activity, may develop during the late fall, particularly in non-aerated grains. wilkins (1983) affirmed that that heating by fungi was initiated during the dry season primarily by the activity of low temperature penicillium species growing in a 4-month old grain pocket of -5°c to +8°c and 18.5% to 21.8 % moisture content. white and muir (2001) suggested that grain bulk in storage structures should be inspected at least once in week at a depth of less than 0.5m interval to detect the hot spots. the common methods of temperature measurement are carried out by using large numbers of thermocouples, thermometers, thermistors, resistant temperature detectors installed at various locations of bin. the short comings of these instruments are that they will measure the temperature only at specific points if the instruments are in contact with the object. therefore, to accomplish this large number of temperatures, sensing devices should be installed throughout the grain bulk. in case the storage bin is too large, it would become even more complicated to find hot spots using these devices which measures temperature only at specific points. therefore, image analysis is an exceptional alternate method which can sense the temperature distribution across a specific area of interest by capturing a thermal image using infrared camera without making contact with grain sample. manickavasagan et al. (2006) reported that thermal imaging while giving good results may not be used as an independent method to monitor the grain temperature in a silo. however, gowda and alagusundaram (2013) reviewed the application of thermal imaging in grain storage and noted that the technique would be an appropriate tool for protecting stored grains by its use in measuring temperatures in storage bins to detect hotspots, and wang et al. (2021) presented cloud imaging as a technique that possesses great potential for application in this field. 5. conclusion image analysis, with its ability to emulate human intelligence in handling visuals ingrain bulk storage, is an important technology that finds many applications in modern seed varietal identification and quality control. it is already an extremely powerful and will continue to improve, following developments in computing technology along with the sensory and central processing elements. in the context of grain bulk storage, image analysis techniques are capable of coping with the variability and therefore have potential for wide-ranging applications. development in image acquisition, pattern recognition and decision making as well as improvements in software and hardware technologies will help to improve the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com aviara et al: application of image analysis in food grain quality inspection and evaluation during bulk storage. azojete, 18(4):693-706. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 703 system. the technology has the ability to create more jobs in nigerian economy through the establishment of automated grain reserves, which would enhance food security and produce high quality grains. the challenges to this technology include lack of appropriate government policies, funding, technical expertise and the ease of accepting the technology. references anami, bs., savakar, dg., aziz makandar, a. and unki, ph. 2005. a neural network model for classification of bulk grain samples based on color and texture. proceedings of international conference on cognition and recognition, held at mandya, india, on 22 and 23 december, 2005., pp. 359-368. ansari, n., ratri, ss., jahan, a. and ashik-e-rabbani, m. 2021. inspection of paddy seed varietal purity using machine vision and multivariate analysis. journal of agriculture and food research, 3: 100109. aznan, aa., rusland, r., rukunudin, ih., azizan, fa. and hashim, ay. 2017. rice seed varieties identification based on extracted colour features using image processing and artificial neural network (ann). international journal on advanced science, engineering and information technology, 7(6): 2220-2225. bora, gc., pathak, r., ahmadi, m. and mistry, p. 2018. image processing analysis to track colour changes in apple and correlate to moisture content in drying stages. food quality and safety, 2: 105-110. brewbaker, jl. 2003. corn production in the tropics. the hawaii experience. college of tropical agriculture and human resources, university of hawaii at manoa. cfia. 2008. inspection procedure pi-003: detecting and identifying small organisms associated with grains and field crops. canadian food inspection agency, ottawa. changule a. and mali, sn. 2014. evaluation of texture and shape features for classification of four paddy varieties. journal of engineering, 2914, art. id617263: 1-8. chitra, hsh., suguna, s. and sujatha, sn. 2016. a survey on image analysis techniques in agricultural products. indian journal of science and technology, 9(12): 1-13. dessai, s. and rao, ap. 2017. seed quality analysis using image processing and ann. international journal of trend in scientific research and development, 1(4): 698-702. ghatkamble, r. 2021. identification and classification of foreign bodies from rice grains using digital image processing. in: tuba, m., akashe, s., joshi, a. 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8(63): 1-14 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndubisi.aviara@unimaid.edu.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):295-304 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 295 effect of harrowing depth, speed and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state s. n. eni-ikeh department of mechanical engineering, michael okpara university of agriculture, umudike, abia state, nigeria *corresponding author's email address: eni-ikeh.stella@mouau.edu.ng article information submitted 12 january, 2024 revised 22 february, 2024 accepted 25 february, 2024 keywords: fuel consumption clayloam harrow farmers abia state abstract this research was conducted to study the effect of harrowing depth, speed and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state to aid farmers to examine and choose the right harrowing implement based on the soil type for an effective and munificent production. the operational speed, effective working width and cutting depth were taken as factors for the study of the fuel consumption rate. the results revealed that the highest fuel consumption rate of 7.5l/ha was noted when the harrow worked at the cutting depth of 10 cm and a speed of 6 km·h–1 and width of 180cm (when working at full width) while the lowest fuel consumption rate of 6.5l/ha was achieved at a speed of 6 km·h–1, working width of 120cm and a cutting depth of 5 cm. the quadratic model was significant for the response (p < 0.05). the results indicated that the coefficient of determination (r2) was 0.98, which specified the high correlation among the factors. the predicted r² (0.97) was consistent with the adjusted r² of 0.95. the adequacy precision of 31.000 showed a suitable indicator and that the model could navigate the design space. the optimization process with the optimal operating factor of operational speed of 6.15 km/hr, working width of 180cm and tillage depth of 30cm and the optimum fuel consumption rate and the desirability of 7.17 l/ha and 0.697 were respectively obtained. 1.0 introduction agricultural machinery including tractor is considered as one of the most important aspects for operating most agricultural operations and duties (bell, 2016). adewoyin and ajav (2013) reported that agricultural productions were significantly improved since tractors have been used for agricultural operations. the tractor can be described as a power source in the agricultural fields to operate a variety of implements (yahya, 2016). several agricultural operations are required for different purposes, namely, harrowing, seeding, cultivating, and spraying. different operations also need special equipment. bell (2016) reported that tine harrow, disc, chisel, rotary, and subsoiler harrows are used as main implements for secondary tillage operation. tillage can be defined as the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning (gatea, 2013). tillage can be classified as primary and secondary tillage. it is normally conducted when the soil is wet enough to allow plowing and strong enough to give reasonable levels of traction. this can be immediately after the crop http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):295-304. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 296 harvest or at the beginning of the next wet season. primary tillage consists of cutting, breaking, returning, and popularizing soil by implements (ahaneku et al.2019). (gatea, 2013) posited that primary tillage operation is used for several objectives. first, it is for cutting soil and seedbed preparation. second, it is to destroy activities and breeding of insects and pests. thirdly, it is to control weeds and fertile soil by converting crop residues. finally, it is to reduce water and wind erosion also to increase soil aeration and the infiltration rate. the greatest amounts of fuel are consumed by tine harrow, disc, and chisel harrows, (khadr, 2018; stajnko et al., 2019) the amount of fuel consumption by tractor engines during tillage operation depends on several factors including harrowing depth, operational speed, etc (godwin, 2017). there is a liner correlation between the amounts of fuel consumption and harrowing depth, due to increasing soil resistance and volume of soil. similarly, moitzi et al. (2016) observed that the amount of fuel consumption increased significantly when the harrowing depth increased. rashidi et al. (2013) reported that the correlation between depth of harrowing and performance of tractor is non-linear because the mass of soil per cutting unit increases and a higher power is required to pull and operate the implements. in other words, greater amount of power requires if depth of harrowing will increase. for the same purpose, moeinfar et al. (2014) used a chisel harrow for secondary tillage at three levels of harrowing depth and reported that the higher level of depth had the greatest influence on increasing draft force. therefore, the greatest power should be applied to operate primary tillage implements at a deeper level. rashidi et al. (2013) studied effects of tractor forward speed, depth of harrowing, and soil moisture content on the performance of tractor in clay soil texture and have discovered that the performance of tractor significantly increased when tractor forward speed increased. similarly, hunt (2001) indicated that the tine harrow requires higher power because it pulverizes soil to the higher level. furthermore, all functions of secondary tillage cannot be achieved by other types of harrow compared to the tine harrow. increase in agricultural mechanization in the country has caused varied imports of implements and sizes of tractors though they have not been based on data on power requirement that is matched to our soils and field conditions. even after buying these machineries, at farm level implements are paired to tractors without considering the power output from the tractor and power demand by implements. farm machinery managers, farmers, consultants and policy makers need to rely on power requirements and performance data while selecting tillage implements for tillage operation. availability of tillage implement power requirements for different soils and conditions, and performance data is important for efficient farm machinery management. therefore, there is need to upgrade the tillage implements for selection and matching of tractors for local soils and conditions that would help farmers and mangers to match tractors and implements carrying out tests for different soils and soil conditions with common tillage implements. the objective of this study is to determine the effect of harrow depth, speed of operation and effective cutting width on fuel consumption rate and field efficiency of a tine harrow. the tillage of soil with minimum energy consumption can be achieved by breaking the bonds between soil aggregates with tensile deformations. values of machine capacities are applied in scheduling field operations, its power units and labor as well as to determine implement and file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com eni-ikeh: effect of harrowing depth, speed and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state. azojete, 20(1):295-304. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 297 machine operating costs. different machines have different field efficiencies, though depending upon the system of operations, soil type conditions and the system of management. this condition improves field efficiency but it is not, of course, a desirable operating condition. the proposed implement includes a tine harrow. thus, the destruction of a pre-stressed soil formation due to tensile stresses caused by the mutual arrangement of working elements and the interconnection of machine operation modes contributes to the reduction of energy consumption. 2.0 materials and method 2.1 study area the study was conducted in ikwuano l.g.a of abia state nigeria, with a population of about 3,920,208 million. it is located within latitude 50 201 and 50 301 n, of equator and longitude 70 401 and 70 501 e of the greenwich meridian and characterized by sub-humid eco-climate. (25003000) mm per annum, average annual temperature of 270c and relative humidity range of 8090% in the wet season (nrcri, 2016). dry season start in november and ends in march while rainy season lasts from april to october. the inhabitants of ikwuano are predominantly farmers. the l.g.a comprises six agricultural zones (ariam, umuariaga, amaoba, amaimeand amawom and oboro). 2.2 experimental site the experiment was performed at michael okpara university of agriculture, umudike, farm site. michael okpara university of agriculture, umudike is located in ikwuano lga of abia state, the soil texture of the site is a sandy loam with 65% sand, 19% clay, and 16% silt. the total area of the site is 1800 m2 with 100 m length and 30 m width. tractor forward speeds will be determined by selecting a particular gear that will give the desired speed. the meter rule will be placed from the bottom to the surface of the harrowed land to measure harrowing depth, time will be determined with stop watch setting at zero before each operation. topping up the tank method of determining the quantity of fuel used will be adopted in the determination of tractor fuel consumption. 2 . 3 specifications of tractor and implement used for the test. a massey ferguson tractor of model mf430e and capacity 55.2 kw, with 3point hitch systems was used for the test. this tractor was selected for the study because it recorded the highest pulverizing efficiency with the tillage implements as compared to tractors that are mostly used in southeast nigeria for field operations (oduma and oluka, 2017). the hitched implements studied is tine harrow, the same operator was used to operate the machine throughout the test with three replications of each operation to ensure minimal variation in the operation skill and style throughout the study (oduma et al., 2018). 2.4 determination of soil physical some soil physical characteristics such as moisture contents, bulk density, soil structure, texture, porosity, that influence machinery performances, were determined using the method adopted by oduma et al. (2019). 2.5 experimental procedure the field tests were conducted using the methods adopted by (oduma et al. 2019) in which the harrowing operations were generally performed longitudinally at selected, width, forward http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):295-304. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 298 speeds and cutting depth. the area worked and the corresponding time taken to complete the area were noted; and the fuel consumption rate was determined as stated below. 2.6 fuel consumption the fuel consumption was evaluated as adopted by oduma et al. (2018). fc = 𝐴𝑚𝑜𝑢𝑛𝑡𝑜𝑓𝑙𝑖𝑡𝑟𝑒𝑢𝑠𝑒𝑑 𝑇𝑜𝑡𝑎𝑙𝑘𝑖𝑙𝑜𝑚𝑒𝑡𝑒𝑟𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 (1) 2.7 experimental design the experimental design adopted in the research work was a three level – three factor full factorial design. the experiment consists of three factors which were varied at three levels of tillage depths which include 5, 8, 10 cm, three levels of effective working widths of 60, 120 and 180 cm and three levels forward speeds (6, 7, and 8 km/hr). central composite response design which gives 17 test runs was performed for each sample using equation 2 (umani et al., 2019). n = 2k + 2k + nc (2) where, n = number of test runs, k = experimental factors and nc = centre point in order to obtain the desired data, the range of values of every one of the 3 factors (k) was evaluated (table 1). working width, operational speed and tillage depth were adopted as independent factors for the energy requirement and field efficiency of the plough. the response selected was the drawbar power, kw. four repetitions of the center points were adopted in order to predict a well and concise approximation of errors; and the field experiments were conducted in randomized form. table 1: actual values, codes and levels of the test variables for design of experiments factors symbols codes and levels -1 0 1 working width (m) tillage depth (cm) operational speed (km/hr) a b c 60 5 6 120 8 7 180 10 8 3.11 response surface methodology (rsm) the design expert of version 11.0 was employed to design the experiment, analyze data obtained, optimize the practical factors and produce models for the estimation of the draft force and drawbar power of the disc plough. the quadratic, cubic, linear and two factorial interaction (2f1) models were designated to analyze the draft force and drawbar power of the implement; and the models were fixed to the generated experimental data. data obtained were analyzed using the response surface methodology (rsm) to fit the quadratic polynomial equation gotten from the design expert software as expressed in equation (3) according to chih et al. (2012). ү = β0 + ∑ 𝛽𝑖𝑋𝑖2 𝑖=1 + ∑ 𝛽𝑖𝑖𝑋𝑖22 𝑖=1 + ∑ ∑ 𝛽𝑖𝑗𝑋𝑖𝑋𝑗2 𝑗=𝑖+1 2 𝑖=1 (3) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com eni-ikeh: effect of harrowing depth, speed and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state. azojete, 20(1):295-304. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 299 where: ү = response; β0 = constant term; ∑ 𝛽𝑖2 𝑖=1 = summation of coefficient of linear terms; ∑ 𝛽𝑖𝑖2 𝑖=1 = summation of quadratic terms; ∑ ∑ 𝛽𝑖𝑗2 𝑗=𝑖+1 2 𝑖=1 = summation of coefficient of interaction terms; 𝑋𝑖𝑋𝑗 = independent variables. also, the multiple regressions were adopted to fit the coefficient of the polynomial model to enable the response variables be correlated with the independent variables. the reliability of fit of the model, the discrete and interaction effect of the tillage parameters (effective working width, operational speed and depth of tillage) on the responses (energy requirement and field efficiency) of the implement were evaluated using analysis of variance (anova). data attained were also subjected to statistical analysis to obtain the effects of the effective working width, operational speed and tilling depth and their interactions on the drawbar power of the implement at ∝ = 0.05 using minitab 17.0. 3.0 results and discussion 3.1 fuel consumption rate (energy consumption) of harrow table 2 showed the randomized design layout of three levels –three factors full factorial composite design of experiment with actual and predicted values of energy requirements of tine harrow. the harrowing operation which was performed at selected operational speeds, working width and harrowing depths, at average soil moisture content of 12.5% and the results of the energy requirement of the disc harrow were shown in table 2. results revealed that, the tine harrow operation requires the range of 6.5 – 7.5 lha-1 of fuel for tilling depth between 10 – 30 cm operated under speed range from 6 – 8km/hr and cutting width varying from 60 – 180 cm. table 2: randomized design layoutof three levels –three factors full factorial composite design of experiment with actual and predicted values of energy requirements of tine harrow run order coded factors actual factors energy requirements a b c harrowing depth (cm) effective working width (cm) operational speed (km/hr) actual values of fuel consumption rate l/ha predicted values of fuel consumption rate l/ha 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 -1 1 -1 0 0 0 0 1 0 1 0 1 0 -1 -1 0 0 0 1 1 1 0 0 1 1 0 0 1 0 1 1 0 0 0 -1 0 0 1 0 0 1 0 0 -1 -1 1 -1 0 1 0 0 5 10 10 5 5 10 8 10 8 5 8 10 10 8 8 8 5 60 180 60 120 120 120 120 180 120 180 120 180 120 60 60 120 120 7 7 7 6 6 6 7 6 8 8 8 6 6 6 7 6 7 7.0 7.0 7.0 6.5 6.5 7.0 7.0 7.5 7.0 7.5 6.5 7.0 7.0 7.0 7.0 7.0 7.0 7.48 7.35 7.65 7.28 6.96 7.85 7.29 7.85 7.49 7.50 7.28 7.63 7.49 7.64 7.83 7.49 7.53 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):295-304. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 300 figure 1 shows the response surface diagram of operational speeds, working width and cutting depth against the fuel consumption rate showing the relationship among the factors (operational speed, width and harrowing depth) and the response (fuel consumption rate). the result shows that the fuel consumption rate increases with tillage depth and that the resultant impact of increasing the tillage as from 30cm depth on fuel consumption rate is higher than the resultant impact observed in increasing the operational speed. fig. 1. response surface plot of tillage depth of the tine harrow and operational speed against fuel consumption table 3: anova for selected factorial model for fuel consumption rate source sum of squares df mean square f-value p-value model 2.86 8 0.3575 107.25 < 0.0001 significant a-speed 2.48 2 1.24 372.33 < 0.0001 b-depth 0.1356 2 0.0678 20.33 < 0.0001 ab 0.2422 4 0.0606 18.17 < 0.0001 pure error 0.0600 18 0.0033 cor total 2.92 26 table 3 presents the anova for selected factorial model for fuel consumption rate. the model f-value of 107.25 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case a, b, ab are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. table 4: fit statistics for fuel consumption rate std. dev. 0.0577 r² 0.9795 mean 7.10 adjusted r² 0.9703 c.v. % 0.8132 predicted r² 0.9538 adequacy precision 31.0000 table 4 show the fit statistics for fuel consumption rate. the predicted r² of 0.9538 is in reasonable agreement with the adjusted r² of 0.9703; i.e. the difference is less than 0.2. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com eni-ikeh: effect of harrowing depth, speed and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state. azojete, 20(1):295-304. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 301 adequacy precision measures the signal to noise ratio. a ratio greater than 4 is desirable. your ratio of 31.000 indicates an adequate signal. this model can be used to navigate the design space. 3.2 model assessment of energy requirements (fuel consumption rate) of tine harrow the energy requirement of the disc harrow in clay-loam soil is dependent on the results displaying significant difference of the factors (tillage parameters). the contributions, effects, coefficient of model terms, lack of-fit test and significance of the factors and their interactions on the fuel consumption rate were examined according to fakayode et al. (2016) and umani et al. (2019). from the statistical analysis conducted, a quadratic model equation was suggested for the evaluation of fuel consumption of the disc harrow as displayed in table 5. the developed model though existed insignificant as recorded in table 6 for the response (p ˃ 0.05) implies that the model term could not be noted at 95 % level of significant. the model developed to estimate the energy requirement (fuel consumption rate) with respect to the independent variables or functional operating parameters (operational speed, effective working width and cutting depth) is as expressed in equation 4. fc = 5.0d + 7.0s + 10.0d + 7.0s +10.0d + 6.0s +5.0d + 6.0s +5.0d + 6.0s + 10.0d + 7.0s + 8.0d + 6.0s + 10.0d + 8.0s + 8.0d + 8.0s + 5.0d + 8.0s + 8.0d + 6.0d + 8.0s + 6.0d + 10.0s + 7.0d + 8.0s + 8.0d + 7.0s (4) where: fc = fuel consumption rate, l/ha; d = harrowing depth, cm; s = operational speed, km/hr the p-value of the model term is 0.1479 (table 6) which is above 𝛼level of 0.05 and suggests that the model is insignificant, in other words, the functional or operating parameters have insignificant effects on the fuel consumption rate of the implement except the depth of cut in which the p-value is 0.0347which is lower than the chosen 𝛼level of 0.05. thus, depth of cut has major influence on the fuel intake/consumption rate of disc plough as compared to the operational speed and working width of the machine. this is consistence with the findings of kareem and sven (2019) and ajav and adewoyin (2012). p-values less than 0.0500 indicate model terms are significant. in this case a, c² are significant model terms. the equation in terms of actual factors can be used to make predictions about the response for given levels of each factor. here, the levels should be specified in the original units for each factor. this equation should not be used to determine the relative impact of each factor because the coefficients are scaled to accommodate the units of each factor and the intercept is not at the center of the design space. table 5: anova of model summery statistics tine harrow source sum of squares df mean square f-value p-value mean vs total 833.00 1 833.00 linear vs mean 0.5625 3 0.1875 1.70 0.2169 2fi vs linear 0.3125 3 0.1042 0.9259 0.4634 quadratic vs 2fi 0.6125 3 0.2042 2.79 0.1192 suggested cubic vs quadratic 0.3125 3 0.1042 2.08 0.2451 aliased residual 0.2000 4 0.0500 total 835.00 17 49.12 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):295-304. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 302 table 6: anova of response surface model for fuel consumption rate. source sum of squares df mean square f-value p-value model 1.49 9 0.1653 2.26 0.1479 not significant a-tillage depth 0.5000 1 0.5000 6.83 0.0347 b-width 0.0312 1 0.0312 0.4268 0.5344 c-speed 0.0313 1 0.0313 0.4268 0.5344 ab 0.2500 1 0.2500 3.41 0.1071 ac 0.0000 1 0.0000 0.0000 1.0000 bc 0.0625 1 0.0625 0.8537 0.3863 a² 0.0007 1 0.0007 0.0090 0.9271 b² 0.0796 1 0.0796 1.09 0.3317 c² 0.5533 1 0.5533 7.56 0.0285 residual 0.5125 7 0.0732 lack of fit 0.3125 3 0.1042 2.08 0.2451 not significant pure error 0.2000 4 0.0500 cor total 2.00 16 3.2 model validation of energy requirements of the harrow the results of the validation of the developed model equation for energy requirements are presented in table 6. the results revealed that the model is significant with coefficient of determination, r2 of 0.6238, which shows good relationships among the independent variables. it is an indication that the response model (fuel consumption rate) could describe 62.38% of the overall changeability in the response. the simulation of the model equation obtained indicated that the fuel consumption rate (energy requirements) is in the trial array. a negative predicted r² of -1.7663 implies that the overall mean may be a better predictor of the response than the current model according to kothari (2014). adequacy precision measures the signal to noise ratio. a ratio greater than 4 is desirable. the ratio of 6.0455 indicates an adequate signal. this model can be used to navigate the design space. table 6 model summary statistics/validation of model term std. dev. 0.2706 r² 0.6238 mean 7.00 adjusted r² 0.5143 c.v. % 3.87 predicted r² -1.7663 adeq precision 6.0455 3.3 optimization of the energy requirements of tine harrow the optimization of the functional parameter; operating speed, working width and tillage depth of tine harrow on clay-loam soil was conducted using response surface methodology (rsm) in other to minimize the fuel consumption rate (energy requirement). fig 2 shows the curve of the optimization process with the optimal operating factor of operational speed of 6.15 km/hr, working width of 180cm and tillage depth of 30cm. the optimum fuel consumption rate and the desirability of 7.17 l/ha and 0.697 were respectively obtained. the optimum depth as shown by the result of optimization is in line with the specification of adewoyin and ajav (2013). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com eni-ikeh: effect of harrowing depth, speed and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state. azojete, 20(1):295-304. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 303 figure 2 optimization curve of the fuel consumption rate of a tine harrow 4.0 conclusion the study was carried out to obtain data on the effect of harrowing depth, speed of operation and effective cutting width on fuel consumption rate of a tine harrow on clay loam soil in abia state, under field conditions in south-east agro-ecological region of nigeria for suitable selection, operation and matching of the implement. from the findings in the research work, the following conclusions can be made about the study: results obtained in this study will aid in proper selection, management and operation of the farm machinery based on soil type/condition and operational speed for better performance. finally, owing to differences in soil type/conditions among different agricultural areas; it is therefore recommended that studies of this kind should be carried out in every agricultural zone to provide data on machine/implement performances based on soil types for increased production. references ahaneku, ie. 2019. simple and cost-effective method for fuel consumption measurements of agricultural machinery. agronomy research, 10: 97-107. ajav, ea. and adewoyin, ao. 2012. effect of ploughing depth and speed on tractor fuel consumption in a sandy-loam soil of oyo state-nigeria. journal of agricultural engineering and technology, 20(2):1 – 10. bell, b. 2016. farm machinery. 4th ed. farming press books and videos miller freeman professional ltd., united kingdom. chih, wt., lee, it. and chung, hw. 2012. optimization of multiple responses using data envelopment analysis and response methodology, tamkang. journal of science and engineering. 13(2), 197-203. fakayode, oa., ajav, ea. and akinoso, a. 2016. effect of processing factors on the quality of mechanically expressed moringa (moringa oliefera) oil: a response surface approach. journal of food process engineering, 40(4): e12518. gatea, aa. 2013. influence of tillage pattern and forward speed of the tractor in the efficiency tillage. international journal of agricultural science research, 3(4): 109-119. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):295-304. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 304 godwin, rj. 2017. a review of the effect of implement geometry on soil failure and implement forces. soil tillage research, 97(2): 331-340. hunt, d. 2011. farm power and machinery management. lowa state university press, usa. kareem, ik. and sven, p. 2019. effect of ploughing depth, tractor forward speed, and plough types on the fuel consumption and tractor performance. polytechnic journal, 9(1): 43-49, doi: 10.25156/ptj. v9n1y2019.pp43-49. khadr, ka. 2018. effect of some primary tillage implement on soil pulverization and specific energy. journal of agricultural engineering, 25(3): 731-745. kothari, cr. 2014. research methodology. methods and techniques. second revised. edition. new age international publishers. new delhi., pp. 140 – 145. moeinfar, a., mousavi-seyedi, sr. and kalantari, d. 2014. influence of tillage depth, penetration angle and forward speed on the soil/ thin-blade interaction force. agricultural engineering international, the cigr journal, 16(1): 69-74. moitzi, g., szalay, t., schüller, m., wagentrist, h., refenner, k., weingartmann, h., liebhard, p., boxberger, j. and gronauer, a. 2013. effects of tillage systems and mechanization on work time, fuel and energy consumption for cereal cropping in austria. agricultural engineering international journal, 15: 94–101. oduma, o. and oluka, si. 2017. performance characteristics of agricultural field machineries in southeast nigeria. journal of experimental research, 5(1): 57–71. oduma, o., oluka, si. and eze, pc. 2018. effect of soil physical properties on performance of agricultural field machinery in south eastern nigeria. agricultural engineering international: cigr journal, 20(1): 25-31. oduma, o., oluka, si., edeh, jc. and ehiomogue, p. 2019. development of empirical regression equations for predicting the performances of disc plough and harrow in clay-loam soil. agricultural engineering international: cigr journal, 21(3): 18-25. rashidi, m. 2013. effect of soil moisture content, tillage depth and operation speed on draft force of tine harrow plow. middle east journal of scientific research, 16(2): 245-249. umani, kc., fakayode, oa., ituen, euu. and okokon, fb. 2019. development and testing of an automated contact plate unit for a cassava grater. computers and electronics in agriculture, 157: 530–540. yahya, h. 2016. effect of a new combined implement for reducing secondary tillage operation. international journal of agriculture and biology, 8(6): 724-727. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):297-308 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 289 original research article effect of wild-vine powder (wvp) as admixture in compressed lateritic earth blocks (cleb) s. y. ismail* and a. aboshio department of civil engineering, bayero university kano, kano, nigeria *corresponding author’s email address: yunusasani@gmail.com 1.0 introduction housing is generally recounted as one of the fundamental needs of humans, and its possession is one of the maximum cherished cultural acquisitions. unfortunately, due to the huge populace of poor citizens, many nigerians are unable to afford their own houses. due to the high and continuously increasing cost of construction materials, they have been unable to get ownership of a house. as a result, it has become critical to identify methods of reducing costs of building construction (raheem et al., 2012). the study conducted by usman, (2015), shows that sandcrete blocks, though widely used in nigeria, are more expensive when compared to the cost of blocks made from other materials. commercially available ones are also known to be, often times, low in compressive strength and less durable and thus mostly used as non-structural materials in buildings. hence the quest for alternative blocks from other materials to which laterites has found wide application in this regard (ghoumari, 1989). the compressed stabilized earth blocks, made from laterites, are known to be low-cost building material owing to the aboundance of the soil material used in its production. laterite earth blocks are known to have good potential of mitigating some of the aforementioned challenges associated with sandcrete blocks and possibly reverse the shelter-demand backlog in communities and nations of the world (taallah and guettala, 2016). article information abstract in this paper, the effect of wild-vine powder on strength and durability properties of compressed lateritic earth blocks was evaluated through series of laboratory experiments. the wild-vine powder (wvp) used was obtained by crushing roots of wild-vine into smaller particles and then grinding into powder. it was thereafter subjected to chemical composition analysis using standard procedure. the wvp was added to the mixes of the laterite soils at varying percentages of 0, 2, 4, 6, 8, and 10% respectively by weight of the laterite required for the compressed lateritic earth blocks. the mixes were cast in steel fabricated mould of dimension (230mm x 120mm x 100mm) compressed using utm machine and demoulded using a locally fabricated mould. the samples were thereafter air-dried and subjected to uniaxial compression tests to establish their compressive strength, alongside durability tests to determine their resistance to abrasion and water absorption. the results showed that wvp predominantly contain calcium oxide (44.6%) and potassium oxide (36.1%). the addition of wvp up to 6% in compressed lateritic earth blocks (cleb) improves the compressive strength, resistance to abrasion, and water absorption for stabilized cleb-block. the addition of wvp in laterite up to 10% is adequate as it gives compressive strength of 2.21n/mm2 greater than 2n/mm2 specified by nbrri, 2016, and thus recommended for use in building of low-cost earthen buildings. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 23 november, 2021 revised 16 september, 2022 accepted 5 april, 2023 keywords: wild-vine ash compressed lateritic earth blocks (cleb) abrasion http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com mailto:chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):297-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 298 compressed laterite earth blocks (cleb) are specialized laterite blocks that are produced when earth (laterite) is blended homogeneously with a stabilizing agent, such as cement or lime, and then compressed into block moulds. owing to its excellent properties and potential, the use of the compressed stabilized earth has been of growing in the provision of low-cost houses of good strength and improved comfort which are appealing parameters as society progresses in the production of eco-friendly or green buildings. building with earth (which is an inexpensive material) is cost-effective because of its local availability and abundance in many surroundings. a few analyses have been carried out on the cost-benefit and improved comfort of using earth blocks in building construction. satprem, (2010) by comparing the cost of a wall made with cleb and a wall made from fired bricks in india affirms the position of the cost-effectiveness of the compressed earthen blocks. another comparison of compressed earth block, concrete block, and adobe for a thermal test by the biology department of southwest texas junior college (2014), shows that the internal temperature of compressed earth block becomes lower than the adobe and concrete block which offers cleb advantage, to not only cost but also reduced internal temperature, over the other materials considered in the study. nevertheless, due to its high water absorption rate when exposed to water, the use of laterite has suffered some set-back in its utilization for building construction due to the high maintenance cost associated with this effect. excessive water intake of laterite blocks leads to the deterioration of the construction material within a short period, leaving its surfaces soft which in turn contributes to early cracking in walls where they are used (harpers 2011). laterite soil has also been ranked as one of the historical building materials and its use has already made history in most countries in africa, especially in nigeria. ella (2003) reported that in most rural parts of northern nigeria, majority of residential houses are built with mud. the walls and dome-shaped roofs of these houses are normally rendered periodically with suitable mud renders such as “farinbirji” (clayey lateritic soil), “jarkasa” (fine red soil) and the likes mixed with straw, horse, or cow dung. but because these materials do not stand the effects of harsh weather conditions, it becomes necessary to incorporate some other materials known as rendering admixtures to improve their performance. some of these admixtures include: 1. “makuba” (powdered locust bean pod); 2. “katsi” (dye residue): a by-product of indigo dyeing. it improves the strength of the laso plaster. 3. “gabaruwa”: it is obtained from the fruits of the acacia tree. 4. “gashinjima”: goat hair mixed with the grease of previously soaked skins gives the plaster waterproofing qualities 5. “dafara”: a gumlike material obtained from the root of a wild vine (cissus populnea) also called dafara, serves as a binder. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com ismail and aboshio: effect of wild-vine powder (wvp) as admixture in compressed lateritic earth blocks (cleb). azojete, 19(2):297308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 299 the wild vine (cissuspopulnea) is a parasitic plant that belongs to the family amplidaceae (vitaceae). it is readily found in most forest areas of tropical nigeria especially the middle belt area and other african countries like senegal, sudan, uganda, and abyssinia (irvine, 2011). the wild-vine is commonly known as ‘urookoho’ by the idomas, igbo, and igala tribes of nigeria, ‘dafara’ in kano and zaria, ‘latutuwa’ in katsina by hausas of the indicated towns of northern nigeria (irvine, 2011). extract from the roots of wild-vine plants has been pragmatically used in the rendering of mud-based structures as admixtures, similar to the use of makuba (powder locust bean pod) (ella, 2003), katsi (dye residue), gabaruwa (from the fruits of the acacia tree) which have been widely reported to improve on the stability of the soil materials (ella, 2003). it is against this background that this study seeks to evaluate the effect of wild-vine powder (wvp) as an admixture in compressed lateritic earth blocks (cleb) with a viewto improve the strength, and durability of cleb as well as to minimize the cost of materials used for building and block production. 2. materials and methods 2.1 materials the materials used in this research include; wild vine powder (wvp), lateritic soil, and water. the roots of the wild vine were collected from wild vine plants (figure 1) in falgore forest in doguwa local government area of kano state. the laterite soil sample was collected from janguza borrow pit with the gps utm coordinates latitude 11.970894 and longitude 8.376062. the water used in this research was clean portable water obtained from civil engineering laboratory, bayero university, kano 2.2 experimental methods 2.2.1 assessment of material properties the oxide composition of wild vine powder (wvp) was carried out by astm c114 (2018) standard at the laboratory of the national steel raw materials exploration agency, kaduna state using x2 ranger model xrf equipment made by bruker equipment. the roots of the wild vine (figure 2) were cut vertically to expose the inner part for easy drying. they were dried in the open air under the sun on a clean and dust-free surface (figure 3) to ensure faster grinding of the roots. thereafter, the roots were crushed into smaller particles using pestle and mortar and then ground into powder (figure 4). the samples were air-dried for seven days in a cool, dry place. after drying, grinding was performed using a punner and a hammer to break the lumps present in the soil. the sample was sieved through a 6 mm sieve size. an atterberg limit was carried out to determine the plastic limit, liquid limit, and plasticity index based on bs 1377 -2 (1990). the test provides a method for measuring the soil’s plasticity and is also useful in soil classification. http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):297-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 300 figure 1: wild vine plants with white stem figure 2: roots of wild vine plant figure 3: wild vine powder after drying figure 4: wild vine powder (wvp) 2.2.2 production of compressed lateritic earth bricks the production process of cleb comprised the batching, mixing, and casting. the materials used for the production of lateritic blocks were measured by weight and stabilized with addition of 0, 2, 4, 6, 8, and 10 % of the wvp measured by weight of the lateritic soil. the stabilized soil was mixed uniformly with a gradually increasing amount of water equivalent to the optimum moisture content of the soil. a handful of the moist soil, compressed firmly with the palm to form a lump was allowed to drop from an approximate height of 1.10 m on a hard and flat surface. this process was repeated for the gradual increasing moisture until the soil lump breaks into 4 5 parts. at this stage, the optimum moisture content is attained. the mixing procedure was repeated for all other mixes. this mixing procedure adopted was from the national building code (2006) and this was also employed by raheem et al. (2012). the casting procedure is similar to that used by raheem et al. (2012). prior to casting, a mould and demoulder were designed and drawn as shown in figure 5 before taking to the technology incubation centre, kano for fabrication. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com ismail and aboshio: effect of wild-vine powder (wvp) as admixture in compressed lateritic earth blocks (cleb). azojete, 19(2):297308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 301 figure 5: mould, demoulder and its parts a steel fabricated mould (230 mm x 120 mm x 100 mm) was cleaned neatly to remove dirt or impurities and oiled to enhance the demoulding of the blocks. the wet mixture was filled into the mould in 3 layers, with each layer being compacted with 35 blows of 4.5 kg rammer. the soil was compressed using hsm36 model cussons made universal testing machine at loading rate of 0.4 kn/s until 20 kn force is reached as shown in figure 6. this helps to remove the entire void trapped in the earth brick figure 7 is isometric drawing of utm machine, with the , mold, and base plate set up. figure 6: compressing cleb using utm machine figure 7: isometric drawing of utm http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):297-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 302 lastly, the brick was gently and carefully demoulded using the demoulder shown in figure 8. here the compressed earth block in the mould was removed from the ut machine and placed in its compactment in the frame of the fabricated demoulder. thereafter, with the aid of the ejection lever, efforts were applied, manually, at the free-end of the lever to push the sample out of the mould as shown in figure 8. figure 8: demoulding lateritic earth block using the demoulder designed and fabricated by the author identification marks were inscribed on the compressed earth bricks to allow easy reference. the bricks were allowed to dry for 7 days in the open air as shown in figure 9. figure 9: lateritic earth blocks in an open-air for drying 2.2.3 compressive strength compressive strength tests were carried out to determine the load-bearing capacities of the blocks as shown in figure 10. the bricks were taken to the laboratory two hours before the test to normalize the temperature and to ensure that the surfaces of the bricks were free of moisturerelatively dry. the weight of each brick was measured and then compressed using hsm36 model cussons made universal testing machine loading rate of 0.4 kn/s until the brick is crushed (showing visible cracks) as can be seen in figure 10. the maximum crushing force was recorded. the compressive strength was computed by dividing the crushing force by the sectional area of the blocks. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com ismail and aboshio: effect of wild-vine powder (wvp) as admixture in compressed lateritic earth blocks (cleb). azojete, 19(2):297308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 303 figure 10: crushing of lateritic earth block 2.2.4 durability of the compressed lateritic earth bricks the durability test conducted on the compressed lateritic earth bricks is the water absorption and abrasion tests. 2.2.4.1 water absorption the water absorption test was conducted in accordance with bs 1881-122 (2011) standards using the complete immersion test method. three dried blocks were randomly selected from each group of the specified wvp content and weighed on a balance. these blocks were then immersed completely in water for 30 minutes, after which they were removed and weighed again. the percentages of water absorbed by the blocks were estimated as follows: wa =(ws-wd)/wd 100 (1) where: wa= percentage moisture absorption ws = weight of soaked block wd = weight of dry block 2.2.4.2 abrasion resistance the abrasion was carried out as described by raheemet al. (2012) using the scratching method. air-dried brick was weighed and then placed on a smooth and firm surface. the surfaces of the brick were subjected to wire brushing in a back-and-front motion for 50 strokes. where one back and front motion is considered as a single stroke. after being brushed, the bricks were weighed again to determine the number of particles lost. this procedure was repeated for all the bricks produced with various wvp contents. the percentage of weight loss obtained was taken as the abrasion resistance capacities of the bricks. http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):297-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 304 3. results and discussion 3.1 geotechnical properties of lateritic soil table 1 presents the results of geotechnical properties of laterite soil obtained from the janguza borrow pit. the results show liquid limit, plastic limit, plasticity index, linear shrinkage, moisture content, dry unit weight, cohesion, and friction angle. the soil based on a unified soil classification system (uscs) is classified as sl (clay of low to medium plasticity.) table 1: summary of geotechnical properties of the laterite atterberg and shear-box tests results natural moisture content (%) 7.4 liquid limit (%) 39 plastic limit (%) 20 plasticity index (%) 19 linear shrinkage (%) 8 moisture content (%) 14.8 dry unit weight ϒ (kn/m3) 17.46 cohesion c (kn/m2) 21.7 friction angle ɸ (deg) 35.4 3.2 compressive strength of lateritic earth bricks the behaviour of compressive strength of lateritic earth bricks as presented in figure 11 shows that the compressive strength increases with the increase of wvp of up to 6%. however, beyond the 6 % addition of wvp, the compressive strength of the lateritic earth bricks decreases. the increase in compressive strength with the addition of wvp up to 6% may be due to the presence of fibrous material contained in the wvp in form of fibres (see plate 4) which increased its structural integrity; this observation is similar to the findings of the experimental work reported by mostafa and uddin (2016) on experimental analysis of compressed earth block (ceb) with banana fibre resisting flexural and compressive forces, and the gummy properties of the root of wild vine which act as a binder. the increase in compressive strength could be due to stabilizing agent (wvp) which binds the soil particles together and then reduces the pores space in the brick. the decrease in compressive strength beyond 6% could be due to saturation of wvp in the mix. in addition, the results show that the addition of wvp at all the percentages, ranging from 2% up to 10% content in the wvpbricks, satisfied the minimum 28days compressive strength of 2n/mm2stipulated by nigerian building and road research institute (nbrri, 2016) for blocks. the compressive strength of cleb decreased beyond 6% addition of wvp, this could be due to the saturation of wvp in the mix. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com ismail and aboshio: effect of wild-vine powder (wvp) as admixture in compressed lateritic earth blocks (cleb). azojete, 19(2):297308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 305 figure 11: effect of wvp on compressive strength of lateritic earth blocks 3.3 abrasion test on lateritic earth brick the results of the abrasion test presented in figure 12 shows that the rate at which wvp stabilized brick resist abrasion increases with an increase in the percentage of wvp content. the increase in abrasion resistance could be attributed due to the stabilizing ability of wvp which binds the soil particles together. figure 12: effect of wvp on abrasion resistance of lateritic earth bricks 3.4 water absorption the effects of the water absorption capacity of lateritic earth brick stabilized with wvp are presented in figure 13. the figure shows that the water absorption decreases with an increase in the percentage of wvp content. this could be a result of the reduction of pores space as the stabilizing agent (wvp) increases. however, at 0% wvp, the bricks disintegrate leaving spread lateritic soil particles in the water. the water absorption of lateritic earth brick with up to 4% of wvp content is above the maximum limit specified by the nigerian industrial standard (2004). figures 14 and 15 show the visual nature of the un-stabilized and stabilized earth blocks after the water absorption test. 0 0.5 1 1.5 2 2.5 3 3.5 4 0 2 4 6 8 10 a ve ra ge c o m p re ss iv e st re n gt h ( n /m m 2 ) wvp (%) 0 0.5 1 1.5 2 2.5 3 3.5 0 2 4 6 8 10 a b ra si o n ( % ) wvp (%) http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):297-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 306 figure 13 effect of wvp on the water absorption of lateritic earth block as compared with the standard of 10% figure 14: unstabilized cleb figure 15: stabilized cleb plate 13 and plate 14 show lateritic earth block removed from water tank. 3.5 effect of wvp on average weight and density of cleb the dry mass and density of wvp-stabilized cleb are presented in table 2. 0 5 10 15 20 25 0 2 4 6 8 10 w at e r a b so rb ti o n ( % ) wvp (%) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com ismail and aboshio: effect of wild-vine powder (wvp) as admixture in compressed lateritic earth blocks (cleb). azojete, 19(2):297308. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 307 table 2: effect of wvp on average weight and density of cleb content of av. dry mass of av. density of wvp % cleb (kg) cleb (kg/m3) 0 5.02 1889.01 2 4.76 1791.14 4 4.54 1708.02 6 4.28 1609.06 8 4.00 1504.26 10 3.71 1393.15 the densities of the bricks presented, range from 1889.01kg/m3 for unstabilized cleb to 1393.15kg/m3 for 10% wvp-stabilized cleb, these values obtained fall within the ranges of 1200kg/m3 2400kg/m3 specified by shestoperov (1983), as the density of special masonry. in addition, debouncha and hashim (2011) reported that the dry density of most compressed stabilized bricks could vary between 1300kg/m3-2400kg/m3. the introduction of wvp brought about a sharp decline in the value of the densities, with the highest content of wvp (10%) producing the least density of 1393.15kg/m3, this could be due to saturation of wvp in the mix. the densities of stabilized-cleb decrease with an addition of wvp in all the percentages, which shows that the density of wvp-cleb was lower than that of the unstabilized blocks. this is possible because the fibres reduce the compact and dense nature of the blocks as the fibres are less dense, this is consistent with the research reported by danso (2017) who reported his findings on the properties of coconut, oil palm, and bagasse fibres as potential building materials. 4. conclusions base on the results of this study, the following conclusions were drawn. the wild-vine powder is predominantly composed of calcium oxide (44.6%) and potassium oxide (36.1%). the addition of wvp in the compressed lateritic earth blocks (cleb) improves its compressive strength and resistance to abrasion when a 6% addition of wvp is used. the water absorption of cleb decreases with an increase in percentages of wvp stabilizers. the recommended optimum dosage for wvp in lateritic earth blocks is 6% by weight of laterite. references astm c114 2018.standard test methods for chemical analysis of hydraulic cement. american society for testing and materials, west conshohocken, usa. retrieved from www.astm.org. biology department of southwest texas college, 2004.thermal change on three blocks material. department of southwest texas junior college. retrieve from www.indianetzone.com british standards bs 1881-122, 2011.testing concrete. part 122: method for determination of water. british standard institution, london www.bsigroup.com. published: july 2011. bs 1377, part 2 1990.methods of test for soils for civil engineering purposes. british standard institution, london., www.bsigroup.com. published: august 2016. http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):297-308. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yunusasani@gmail.com 308 danso, h. 2017. properties of coconut, oil palm, and bagasse fibres as potential building materials. procedia engineering, 200: 1-9. deboucha, s. and hashim, r. 2011. a review on bricks and stabilized compressed earth blocks. scientific research and essay, 6(3): 499-506. ella, ob. 2003. effect of katsi (dye residue) on the performance characteristics of mud renders. the nigerian academic forum, a multidisciplinary journal, 4(2):48-54. ghoumari, f. 1989. materiaunen terre crue compactee: amelioration de sa durability a i’eau. these de doctorat. insa de lyon, france. irvine, fr. 2011. woody plants of ghana with special reference to their uses. london: oxford university press, 486–487. harper, d. 2011.alternative methods of stabilization for unfired mud bricks. engineers without borders. newcastle university. retrieved from www.newterritories.com mostafa, m., and uddin, n. 2016.experimental analysis of compressed earth block (ceb) with banana fibers resisting flexural and compressive forces. case studies in construction materials, 5: 53-63. nis 87, 2004.nis 87. 2004. nigerian industrial standard: standard for sancrete blocks. standard organization of nigeria, lagos, nigeria. nbrri 2016. nigerian building and road research institute: industrial standard for blocks production, nbrri interlocking blockmaking machine. nbrri newsletter, 1(1): 15-17. raheem, aa., falala, oo. and adeyeye, jk. 2012. production and testing of lateritic interlocking blocks. journal of construction in developing countries,17(1)2: 3348. satprem, m. 2010. compressed stabilized earth block and stabilized earth technique. auroville earth institute, auroville, tamil nadu, india. retrieved from http://www.earthauroville.com/compressed-earth-blocks-en.php shestoperov, sv. 1983. road and building materials. 1st edition, mir publishers, moscow. taallah, b. and guettala, a. 2016. the mechanical and physical properties of compressed earth block stabilized with lime and filled with untreated and alkali-treated date palm fibers. construction and building materials, 104: 52-62. usman. nd. 2015. an assessment of the potential of life cycle management system on project performance in the building industry in abuja, nigeria. ph.d. thesis, kenyatta university, nairobi, kenya file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):13-22 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 13 original research article evaluation of the influence of ground wastes glass on mechanical properties of high performance concrete a. m. auwal*, m. o. a. mtallib, m. t. abdulwahab and a. mohammed department of civil engineering, bayero university kano nigeria. *corresponding author’s email address: abuiyal1@gmail.com 1.0 introduction concrete is the most used construction material due to its satisfying performance in strength requirements and its ability to be moulded into a variety of shapes and sizes. nowadays, the higher demand for housing and infrastructure, accompanied by recent developments in civil engineering facilities, such as high-rise structures, offshore platforms, tunnels, highway pavement, hydropower structures and long-span bridges associated with long term poor performance and poor consolidation of conventional concrete (cc) especially in congested reinforcement led to accelerated research for the development of concrete which would score on all the aspects of strength, workability, durability, affordability. thus, to overcome the aforementioned shortcomings associated with cc, high performance concrete (hpc) was introduced due to its technical and economic advantages of high strength, high early strength, high modulus of elasticity, high durability and long life in severe environments, resistance to chemical attack, article information abstract the construction industry is largely reliant on the use of cement-based products. every tonne of ordinary portland cement (opc) emits equivalent amount of co2 into the atmosphere, contributing to increased raw material consumptions and environmental concerns. in this regard, the use of waste materials that can be blended with opc as partial or full replacement to reduce the environmental impacts is strongly desirable. this research was experimentally carried out to evaluate the influence of ground waste glass (gwg) as a partial replacement of cement in high performance concrete (hpc). a grade 50 hpc was designed based on aci 211.1-91. various experiments were carried out to determine the mechanical properties of the hpc. tests include specific gravity of constituent materials, sieve analysis of gwg and aggregates, slump flow of fresh hpc, compressive, splitting tensile and flexural strengths of hardened hpc were carried out. the chemical composition analysis of gwg was conducted using x-ray fluorescence (xrf) analytical method. hpc cubes, cylinders and beams were cast, cured and tested at curing ages of 3, 7, 28, 56 and 90 days using 0, 5, 10 15, 20 and 25 percentage replacement levels. the optimum compressive strength of 57.44 n/mm2 was obtained at 10% cement replacement after 28 days of curing age. the slump test result shows that the workability of the hpc decreased as the gwg content increases. generally, the strengths of hpc reduced as the percentage of gwg replacement increased beyond 10% but increases with curing age. therefore, 10% is the optimum replacement level of gwg for cement in hpc. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 nov., 2021 revised 28 may, 2022 accepted 30 july, 2022 keywords: high performance concrete ground waste glass workability compressive strength splitting tensile strength flexural strength http://www.azojete.com.ng/ mailto:abuiyal1@gmail.com mailto:abuiyal1@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):13-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 14 toughness and impact resistance, ease of placement, compaction without segregation (mehta and aitcin, 1990; aitcin and neville, 1993; bickley and mitchell, 2001). the constituent materials used for the production of hpc are the same as those for cc except that hpc has higher cement content about 450-550kg/m3, silica fume or any other supplementary cementitious materials and always a superplasticizer (neville and brooks, 2010). the higher cement content could produce substantial heat of hydration in the concrete due to reaction between cement and water, lead to cracking. furthermore, the higher cement content will necessitate the production of more cement, which will led to global warming and climate change due to the emissions of green-house gases like co2 to the atmosphere. the international energy agency (iea) in the year 2020 reports that the cement industry emits 2.4 billion tons of co2 corresponding to 7% of total global emissions. the practice of incorporating the industrial waste materials has gained tremendous attention in research to develop greener and sustainable building materials. in nigeria, 4% of the solid wastes generated are glass micheal et al., (2014) which is disposed in the form of glass bottles from beverage factories and glass sheets from ceramics industries. glass disposal in landfill could have significant negative effects on the environment because it is non-biodegradable. therefore, recycling the waste glass as supplementary cement materials into concrete production could be a viable solution not only to the pollution problem, but also to the problem of the high cost of building materials. the american concrete institute (aci committee 363, (1998)) defines hpc as concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely when using conventional constituents and normal mixing, placing and curing practices. hpc enhances the service life of the structure and suffers less damage which would reduce overall costs. hpc consist of all ingredients of cc with chemical and mineral admixtures. chemical admixtures, usually a superplasticiser which reduces the water content, thereby reducing the porosity within the hydrated cement paste (bharatkumar et al., 2001) and supplementary cementitious materials generally called mineral admixtures and or pozzolana. the pozzolana was introduced to reduce the cost, overcome the adverse effects of opc and utilize wastes. also, the use of pozzolana improves/modifies fresh and hardens properties of concrete as well as microstructure of the concrete matrix resulting in stronger and durable concrete. this is due to the reaction between the amorphous silica of the pozzolana and calcium hydroxide during the cement hydration. glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological and decorative usage. glass is an immensely versatile material used every day in numerous applications. it is produced in many forms such as container glass, flat glass, and bulb glass. glass is an inert material that could be recycled and used many times without changing its chemical property (shayan and xu, 2004). it is an amorphous material with high silica content, so it is reasonable to expect fine glass powder to be used as pozzolana and/or partial replacement of cement in concrete. this is also a higher value choice than the use of glass as aggregate, not only because it makes full use of its physical and chemical properties, but also because cement is more expensive than aggregate, thus offering more economic and environmental advantages. several researches show that, at a higher age, gwg with 15% to 20% of cement replacement provides compressive strengths exceeding those of control concrete (lalitha et al., 2017, kumarappan, 2013, nassar and soroushian, 2011). however, a study by rashed (2014) showed that previous studies with glass addition were not conclusive file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abuiyal1@gmail.com auwal et al: evaluation of the influence of ground wastes glass on mechanical properties of high performance concrete. azojete, 19(1):13-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 15 considering workability and strength. in this research, we tried to evaluate the influence of gwg as partial replacement opc in the production of hpc. 2. materials and methods 2.1 materials grade 42.5 opc, manufactured in nigeria by bua group, was used it was obtained from a major dealer along gwarzo road, kano state, nigeria. the coarse aggregate is a crushed granite rock of nominal size of 20 mm obtained from monkey rock quarry, kanonigeria. the fine aggregates used is naturally occurring clean river sand obtained from challawa river, kano. potable tap water at civil engineering laboratory of bayero university, kano was used for mixing and curing of specimens. conplast sp 342 ms, which is a chloride free super-plasticising admixture based on selected sulfonated naphthalene polymer was also used. gwg was prepared from transparent soda-lime glass waste. broken waste glasses were collected from disposal sites at kofar-ruwa market, kano-nigeria. the samples were cleaned, given time to dry and crushed into smaller pieces using a mortar and pestle. the crushed waste glasses were ground to a fine powder using a model 2a corn milling machine manufactured by nildeep talavia, india, then sieved through a 75µm bs sieve. the x-ray fluorescence (xrf) analysis of opc and gwg was conducted using a model ftir-8400s manufactured by shimadzu, japan, at spectral laboratory services, kaduna-nigeria. 2.2 methods to achieve the objectives of this study, hpc grade 50 was designed based on aci 211.1 (1991). six (6) mixes as shown in table 1 were used, g-00 is the control mix and g-05, g-10, g-15, g-20 and g-25 are mixes containing gwg at replacement levels of opc by weight at 5, 10, 15, 20, and 25%, respectively. the mixes were used for the determination of the slump flow in accordance with bs en 12350-2 (2000). the test for compressive, splitting tensile and flexural strengths of gwg-hpc was carried out in accordance with bs en 12390-2 (2009), bs en 12390-6 (2009) and bs en 12390-5 (2009) respectively. the specimens were prepared and cured for 3, 7, 28, 56 and 90 days, all tests were conducted for three replicates and averages were evaluated. table 1. grade 50 hpc mix proportions per cu.m. mix mark cement (kg/m3) gwg (kg/m3) fine aggr. (kg/m3) coarse aggr. (kg/m3) water (kg/m3) superplasticizer (kg/m3) g-00 539.5 0 631.16 979.34 205 6.5 g-05 512.525 26.975 631.16 979.34 205 6.5 g-10 485.55 53.95 631.16 979.34 205 6.5 g-15 458.575 80.925 631.16 979.34 205 6.5 g-20 431.6 107.9 631.16 979.34 205 6.5 g-25 404.625 134.875 631.16 979.34 205 6.5 http://www.azojete.com.ng/ mailto:abuiyal1@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):13-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 16 3. results and discussion 3.1 physical and chemical analysis of the constituents materials the specific gravities and fineness moduli of constituent materials a presented in table 2, while the oxides composition of the opc and gwg are presented in table 3. the particle size distribution of gwg, fine and coarse aggregates are presented in figure 1. table 2. specific gravities of constituents materials table 3. chemical composition of opc (bua brand) and gwg oxides opc composition (%) bs en 197-1 (2000) gwg composition (%) astm c618 (2008) sio2 10.773 the sum of reactive cao and sio2 shall be at least 50%. the ratio of cao to that of sio2 shall be at least 2%. mgo ≤ 5%. cl ≤ 0.1 %. so3 ≤ 4.0%. loi ≤ 5%. 72.697 the sum of reactive sio2, al2o3 and fe2o3 shall be at least 70%. the reactive sio2 shall not be less than 25% the cao shall be less than 10%. so3 ≤ 4% loi ≤ 10%. al2o3 1.702 1.257 fe2o3 2.877 0.352 cao 60.773 4.696 mgo 0 1.890 zno 0.004 0.001 mno 0.04 0.110 so3 0 0.000 tio2 0.066 0.041 cr2o3 0.012 0.011 cl 0 0.000 loi 6.424 3.221 the result indicates that the opc has a combined cao and sio2 of 71.546% which is above the minimum recommended value of 50%. the individual oxides of so3 and mgo are all within the limits recommended in bs en 197-1 (2000) for opc. thus, the opc used can be said to be of sound quality in terms of chemical composition and satisfied the standard requirements. the chemical composition of gwg indicates a combined sio2, al2o3 and fe2o3 content of 74.306%, which is slightly above the minimum value of 70% recommended in astm c618 (2008) for a good pozzolana and would therefore be a reactive pozzolana. the magnesium oxide content was 0.0% which satisfied the required maximum value of 4%. calcium oxides content of 4.696% which satisfied the required value of not more than 10%, loss on ignition (loi) value of 3.221% which is within the acceptable value of 10% and so3 content of 0% which is also within the maximum content of 4%. this shows that gwg is a good pozzolanic material which satisfied the recommended limit given in bs en 197-1 (2000) and astm c618 (2008). the result is consistent with the findings of shao et al. (2000); shi and wu (2005); chen et al. (2006) and taha and nounu, (2008) on conventional concrete made with gwg. sample opc gwg fa ca sp specific gravity 3.16 2.58 2.63 2.70 1.19 fineness modulus 2.8 6.62 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abuiyal1@gmail.com auwal et al: evaluation of the influence of ground wastes glass on mechanical properties of high performance concrete. azojete, 19(1):13-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 17 the particle size distribution of gwg, fine and coarse aggregates were presented in figure 1. as indicated, the fine aggregate falls in grading zone 2 based on bs 882 (1992) grading limits for fine aggregates. this shows that there is more medium sand than fine and coarse sand. it is cohesive and well-graded, which is desirable for making hpc. also, in figure 1, the curve indicates that coarse aggregates have dominant particle sizes of 14 mm and 10 mm. this shows that the aggregate size is within the specified limits of a maximum of 20 mm as suggested by shetty (2012) for use in hpc. gwg has grain sizes ranging from 1.75 to 75µm. this implies that the gwg could be used as pozzolana in concrete based on bs en 206-1 (2000). figure 1. particle size distribution chart of gwg, fine and coarse aggregates 3.2 slump flow of gwg-hpc the slump flow result is presented in figure 2; it can be seen that the slump flow value gradually reduces with increasing levels of gwg. the reduction in workability could be due to the high reactivity and higher surface area of gwg when compared to opc. it may also be due to the increase in water demand due to increase in gwg content leading to the increase in surface area of glass particles and the number of angular shaped glass particles in the mix resulting in lesser fluidity consistent with the findings of ferraris et al. (2001) and shekhawat and aggarwal (2014). 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 10 100 p a s s in g ( % ) sieve metric size (mm) fine aggregate coarse aggregate zone ii upper limit zone ii lower limit gwg http://www.azojete.com.ng/ mailto:abuiyal1@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):13-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 18 figure 2. slump flow gwg-hpc similar trends in the slump flow values were reported by metwally (2007); vandhiyan et al. (2013); and afif et al. (2017). all the samples examined satisfied the requirement of bs en 206-9 (2010) for slump flow value of 550-850mm. 3.3 effects of gwg on strength of hpc the compressive strength of gwg-hpc is shown in figure 3. the result shows an improvement in compressive strength with increase in gwg at 5% and 10% and starts to reduce gradually at 15%, 20% and 25% opc replacement level. the reason behind the improvement is due to the pozzolanic reaction of gwg. ground waste glass being highly reactive, it reacts with calcium hydroxide (ca(oh)2) (a by-product of cement hydration) in the presence of water to produce calcium silicate hydrates (c-s-h). the decrease in compressive strength beyond 10% gwg content. in this case, the amount of silica available in the hydrated cement matrix is probably too high and the amount of produced c-s-h is most likely insufficient to reacts with all the available silica and as result of that, the dilution effect of opc and weaker formation of c-s-h gel due the pozzolanic reaction takes over and the strength starts to decrease. the observation is consistent with earlier works by ogork and auwal (2016). figure 3. compressive strength of gwg-hpc. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 0 10 20 30 40 50 60 70 80 90 100 c o m p re ss iv e s tr e n gt h ( n /m m 2 ) curing age (days) 0% gwg 5% gwg 10% gwg file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abuiyal1@gmail.com auwal et al: evaluation of the influence of ground wastes glass on mechanical properties of high performance concrete. azojete, 19(1):13-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 19 the results also, shows an improvement in compressive strength with increase in curing period at all replacement levels. the improvement in compressive strength with increase in curing age could be due to micro filling ability and pozzolanic activity of gwg. the smaller particle size of gwg can fill the micro voids within the opc particles. this observation is in agreement with earlier studies of ogork and uche (2014) and lalitha et al. (2017) who worked on groundnut husk ash (gha), corn cob ash (cca) and gwg respectively. thus, it can be concluded that 10% is the optimum level for replacement of cement with gwg. the optimum dosage is in agreement with kumarappan (2013) and lalitha et al. (2017) who worked with glass powder as partial replacement of opc. thus, it can be concluded that 10% is the optimum level for replacement of cement with gwg. the splitting tensile and flexural strengths of gwg-hpc follow a similar pattern to compressive strength, as shown in figures 4 and 5. figure 4. splitting tensile strength development of gwg-hpc the result reveals a gain in splitting tensile and flexural strengths with increases in gwg at 5% and 10%, then gradually drops at 15%, 20%, and 25% opc replacement levels. there was also an improvement in splitting tensile and flexural strengths as the curing age increases. the improvement could be due to micro filling ability and pozzolanic activity of gwg. the smaller particle size of gwg can fill the micro voids within the opc particles. this observation is consistent with the findings of ogork and auwal (2016) using corn cob ash as supplementary cementitious material (scm). 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 10 20 30 40 50 60 70 80 90 100 sp lit ti n g te n si le s tr e n gt h ( n /m m 2 ) curing age (days) 0% gwg 5% gwg 10% gwg 15% gwg 20% gwg 25% gwg http://www.azojete.com.ng/ mailto:abuiyal1@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):13-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 20 figure 5. flexural strength of gwg-hpc 4. conclusion the following conclusions are drawn from the study: i. the soda-lime gwg is suitable material for use as a pozzolana since it satisfied the requirement for such material by having a combined (sio2 + al2o3 + fe2o3) of more than 70%. ii. the workability of hpc reduces as percentage of gwg increases. therefore, more water is required to make the mixes more workable. iii. the strengths of concrete can be improved by the replacement of cement with gwg of adequate replacement level. iv. the optimum replacement level of gwg for cement in hpc is 10%. references aci committee 211.1-91 2002. standard practice for selecting proportions for normal, heavyweight, and mass concrete: american concrete institute, farmington hills, mi, usa. aci committee 363, 1998. guide to quality control and testing of high-strength concrete, american concrete institute, farmington hills, mi, 1-18. afif, r., nabil, e. and sherzad, ii. 2017. effect of glass powder on the compression strength and the workability of concrete. civil and environmental engineering research article, cogent engineering, 4: 1-12. aitcin, pc. and neville, am. 1993. high performance concrete. demystified, concrete international, 15(1): 21-26. american society for testing and materials (astm), c618. 2008. specification for coal fly ash and raw or calcined natural pozzolanas for use as mineral admixtures in ordinary portland cement concrete. annual book of astm standards, west conshecken, usa. bickley, ja. and mitchell, d. 2001. a state-of-the-art review of high-performance concrete structures built in canada: 1990-2000, cement association of canada, ottawa, ontario, 1-122. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 10 20 30 40 50 60 70 80 90 100 fl e xu ra l s tr e n gt h ( n /m m 2 ) curing age (days) 0% gwg 5% gwg 10% gwg 15% gwg 20% gwg 25% gwg file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abuiyal1@gmail.com auwal et al: evaluation of the influence of ground wastes glass on mechanical properties of high performance concrete. azojete, 19(1):13-22. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 21 bharatkumar, bh., narayan, r., raghuprasad, bk. and ramachandramurthy, ds. 2001. mix proportioning of high-performance concrete. cement concrete composites, 23: 71– 80. bs 882, part 2, 1992. grading limits for fine aggregates. british standard institution, london. bs en 12350-8, 2000, testing fresh concrete, self-compacting concrete – slump flow test. british standard institution, london. bs en 12390-2, 2000, testing hardened concrete, compressive strength of test specimens. british standard institution, london. bs en 12390-5, 2000, testing hardened concrete, flexural strength of test specimens. british standard institution, london. bs en 12390-6, 2000, testing hardened concrete, tensile splitting strength of test specimens. british standard institution, london. bs en 197-1, 2000, composition, specification and conformity criteria for common cements. british standard institution, london. chen, ch., huang, r., wu, jk. and yang, cc. 2006. waste e-glass particles used in cementitious mixtures, cement and concrete research, 36(3): 449-456. ferraris, cf., obla, kh. and hill, r. 2001. the influence of mineral admixtures on the rheology of cement paste and concrete. cement and concrete research, 31(2): 245255. international energy agency (iea), 2020. energy technology perspective, retrieve at https:/www.iea.org/reports/energy-technology-perspective-2020, iea publications, paris, 1-400. kumarappan, n. 2013. partial replacement of cement in concrete using waste glass. international journal of engineering research and technology (ijert), 2(10): 18801883. lalitha, s., alaguraj, m. and divyapriya, c. 2017. experimental study on use of waste glass powder as partial replacement to cement in concrete. international journal of engineering sciences & research technology, 6(10): 26-31. mehta, kp. and aitcin, pcc. 1990. principles underlying production of high-performance concrete. journal of cement, concrete and aggregates, 12(2): 70-78. metwally, im. 2007. investigations on the performance of concrete made with blended finely milled waste glass. advanced structural engineering, 10(1): 47–53. michael, sa., ronke, ga., esther, ds., akinwale, oc., olufiropo, sa., michael, af., colin, ab. and hammond, f.n. 2014. municipal solid waste management and the role of waste pickers in nigeria. international journal of education and research, 2(3): 1-12. nassar, rud. and soroushian, p. 2011. field investigation of concrete incorporating milled waste glass. journal of solid waste technology and management, 37(4): 307319. neville, am. and brooks, jj. 2010. concrete technology, pearson education ltd, 2nd edition, new delhi, india. http://www.azojete.com.ng/ mailto:abuiyal1@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):13-22. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abuiyal1@gmail.com 22 ogork, en. and auwal, am. 2016. mechanical properties of self-compacting concrete made with corn-cob ash. book of proceedings of the 15th annual international conference, (nimacon 2016), 21st – 25th november, 2016, ahmadu bello university, zaria, 379-383. ogork, en. and uche, oau. 2014. effect of particle size of groundnut husk ash (gha) in cement paste and mortar, international journal on research and innovation trends in computing and communication, 2(9): 2764-2769. rashad, am. 2014. recycled waste glass as fine aggregate replacement in cementitious materials based on portland cement. construction and building materials, 72: 340-357. shao, y. lefort, t. moras, s. and rodriguez, d. 2000. studies on concrete containing ground waste glass. cement and concrete research, 30(1): 91-100. shayan, a. and xu, a. 2004. value-added utilisation of waste glass in concrete. cement and concrete research, 34(1): 81-89. shekhawat, bs. and aggarwal, b. 2014. utilisation of waste glass powder in concrete – a literature review. international journal of innovative research in science, engineering and technology, 3(7): 14822-14826. shetty, ms. 2012. concrete technology, theory and practice, s. chand and company ltd., seventh edition, ramnagar, new delhi, india. shi, c. and wu, y. 2005. mixture proportioning and properties of self-consolidating lightweight concrete, containing glass powder. aci materials journal, 102(5): 355-363. taha, b. and nounu, g. 2008. properties of concrete contain mixed colour waste recycled glass as sand and cement replacement. construction and building materials, 22(5): 713-720. vandhiyan, r., ramkumar, k. and ramya, r. 2013. experimental study on replacement of cement by glass powder. international journal of engineering research and technology, 2(5): 234-238 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abuiyal1@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):71-82 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 71 technological capability of selected palm oil mills in nigeria k. owolarafe1, b. s. ogunsina1, s. o. obayopo2, t. a. morakinyo3, g. o. binuyo4*, v. o. okorie5, o. b. falana1, i. a. owolabi1, g. a, badmus6 and i. o. olaoye7 1department of agricultural and environmental engineering, obafemi awolowo university, ile-ife, nigeria 2department of mechanical engineering, obafemi awolowo university, ile-ife, nigeria 3department of food science and technology, obafemi awolowo university, ile-ife, nigeria 4african institute for science, policy and innovation, obafemi awolowo university, ile-ife, nigeria 5department of agricultural extension and rural development, obafemi awolowo university, ile-ife, nigeria 6nigerian institute for oil palm research (nifor), benin city, nigeria 7department of agricultural and civil engineering, first technical university, ibadan *corresponding author's email address: gbinuyo@oauife.edu.ng article information submitted 16 june, 2023 revised 31 july, 2023 accepted 5 august, 2023 keywords: special palm oil fresh fruit bunches oil mill capacity oil production technologies abstract an assessment of the technological capability of some modern palm oil mills in selected states of nigeria (viz: edo, ogun, ondo and osun states) for production of special palm oil was carried out in this study. information regarding the year of establishment of the mills, ownership of the mills, available facilities, production capacity and status of the mills (among others) were collected from the staffs of the mills. it was observed that governmentowned mills (okitipupa and nigerian institute for oil palm research with capacities of 24 and 6 tons/hr, respectively) were in dilapidated condition and not functioning due to lack of proper maintenance. the mills had resulted into the utilization of intermediate technologies that can barely produce special palm oil and hence the huge investment in the mills has been wasted. in contrast, privately-owned mills (okomu, jb and royal farm with capacities of 45, 8 and 3 tons/hr, respectively) which were also visited were functional. two of them (okomu and jb) were observed to have state of the art technologies for production of special palm oil and adopted well-arranged routine maintenance of the mills’ facilities. the study recommended that the existing public mills should be revived through public-private partnership system while privately-owned small-scale mills can be organized into groups such that they can acquire modern facilities for production of special palm oil. it is also recommended that there should be appropriate linkage between the mills and research institutes for sustainability. 1.0 introduction nigeria lost her position as a leading country in the global palm oil market since the last three decades, because the quantity and quality of her exportable palm oil is declining unabatedly. indonesia, malaysia and thailand are presently ranked by the world trade organization as the world’s top producers of palm oil (fao, 2021). in the last two decades, palm oil and special palm oil (spo) were missing in nigeria’s export list; whereas, indonesia, malaysia and thailand exported substantial quantities within that same period (adjei-nsiah et al, 2012). owolarafe et al. (2019) established that nigeria now imports palm oil and spo (which is a major raw http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 72 material for some local industries) to meet domestic demand. these importations deplete foreign reserves, negate terms of trade, and increase manufacturing costs and unemployment rate. the decline in the country’s palm oil production is largely attributed to old age of plantations, small land area dedicated to new plantations, limited extension service system for oil palm farmers and lack of appropriate oil palm fruit processing technology among smallholder processors (fao, 2002; elekwachi et al., 2012). nigeria’s human resource, climatic and edaphic conditions favour oil palm production; there are about fourteen states with suitable conditions for cultivation of oil palm (owolarafe et al., 2019). lack of appropriate oil palm fruit processing technology among small and medium scale processors, who occupy a major position in the palm oil industry, is perhaps the most critical problem (owolarafe and oni 2011; owolarafe, 2015; morakinyo and bamgboye, 2016). while the problems associated with the age of oil palm plantations and agricultural policies and extension services are being addressed by the government, non-governmental organizations and other actors in the industry (fao, 2002; elekwachi et al., 2012), the challenge of appropriate oil palm fruit processing technology for small and medium processors in nigeria has rarely been given needful attention, inspiring little or no hope in many cases (owolarafe and oni, 2011; badmus et al., 2019). owing to low processing capacity of the plants and extraction efficiency barely up to 70%, substantial quantities of freshly harvested oil palm fruits accumulate beyond 24 hours, deteriorate and eventually get wasted along the processing line. in many cases, the palm oil quality gets grossly impaired. in addition, the extant technologies among small and medium scale processors can hardly produce spo which is in high demand by the large-scale food and allied processing industries because it contains <3% of free fatty acid and <1% moisture. the continued importation of spo by local industries has turned it into a very expensive product. consequently, many local industries with limited funding for spo importation go bankrupt and lay off workers within a very short time or use technical palm oil (tpo) as a substitute to produce substandard products which can hardly compete in the global market. this also magnifies the cutthroat competition between domestic and industrial users of palm oil. the corollaries of these factors are that local industries that are dependent on spo have high workers’ downtime and employees’ turnover, operation is epileptic and many of them evade taxes to reduce production cost, thereby depleting earnings. there are few mills having the capacity for production of special palm oil in nigeria and as result, the output is grossly inadequate to meet the demand for the product in the country. in a study, an analysis of spo requirement of four sampled food industries in the country indicates demand gap of about 94,860 mt (elekwachi et al., 2012). according to the united states department of agriculture (2021), the supply gap for palm oil would increase in subsequent years if appropriate technologies are not put in place to increase the cultivation and processing of palm oil. previous studies (owolarafe et al., 2002; salako et al., 2014; morakinyo and bamgboye, 2016; badmus et al., 2019), have enabled small and mediumscale oil palm fruit processors to improve on their traditional processing methods, culminating in improved efficiency and higher product quality. however, the improved methods could not produce spo; and there is dearth of information about the existing appropriate technology addressing the challenges for spo production by these categories of processors. in an effort to find appropriate technology for the small and medium-scale processors who occupy 80% of the actors in the industry, there is the need to ascertain the current level of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng owolarafe et al: technological capability of selected palm oil mills in nigeria. azojete, 20(1):71-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 73 technology adopted by the large-scale mills and the improved small and medium-scale mills such that the upgrading of the latter can be facilitated. this study aims at appraising the level of technologies adopted by some mills in the palm fruits processing value chain in nigeria with special focus on the production of special palm oil. 2 materials and methods palm oil processing mills in edo, ogun osun and ondo states were purposively selected due to the high volume of palm oil production (owolarafe, 2015). these include nifor and okomu oil company mills in edo state, jb farms nigeria limited in ogun state, royal farms in osun state, okitipupa oil company in ondo state. information regarding the operations of the selected mills was obtained through structured interviews of mill managers, operators, and administrative staff. the visits were executed at intervals within three months to gather relevant information which includes year of establishment of the mills, ownership of the mills, available facilities, production capacity and status of the mills among others. this is based on the findings from literature that over 70% of palm oil production in nigeria comes from the selected study areas (udosen and ugboya, 2013). 3 results and discussion 3.1 an overview of the mills. table 1 shows some features regarding functionality of the mills. the parameters considered include year of establishment of the mills, ownership of the mills, installed capacity, sources of parts and services, current status of the mills and ability to produce special palm oil. the results show that the palm oil industry in nigeria falls under private and public ownership and it is characterized by different categories of processors who produce locally or internationally marketable products. nifor is a public firm in edo state, established in 1939 with a mandate to frontier research on oil palm and produce special palm oil. the institute has also developed some cost-effective processing machines to produce palm oil for small and medium-scale processors. table 1 features of the palm oil production facilities studied features mill names nifor mill okomu oil company jb farm nigeria limited royal farm okitipupa oil company location (state) edo edo ogun osun ondo ownership public private private private public capacity of plant (tons/hr) 6 45 8 1 24 year of establishment 1939 1976 1985 2017 1976 source of parts and services imported imported imported local imported current status of mill defunct functional functional functional defunct ability to produce spo no yes yes no no http://www.azojete.com.ng/ gbinuyo@oauife.edu.ng%20 arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 74 however, nifor has extended its mandate to research focusing on coconut palm, shea tree, raphia palm, and date palm. the okitipupa oil company situated in okitipupa, ondo state has over 30,000 acres of oil palm trees in 10 locations in the state. as a public firm, the company was established in 1976 to produce special palm oil to meet local and international demand. on the 17th of may, 1976, okitipupa oil palm plc was formed as a limited liability company to take over the okitipupa oil palm project from the nigeria joint agency limited. the corporation was taken over by the government in 1980 and did not see the light of the 21st century. the company is now operated as a fragment of the installation made in 1976. there were, however, ongoing efforts to resuscitate the project in another location where it was gathered that new sets of equipment were being installed. the okomu oil company located in edo state is a large-scale, private-owned oil mill fed by about 19,000 ha of oil palm plantation. the okomu oil palm company was established in 1976 as a federal government pilot project to rehabilitate palm oil production in nigeria. at inception, the pilot project covered 15,580 hectares, out of which 12,500 hectares could be planted with oil palm trees. it was incorporated in 1979 as a limited liability company. the okomu oil company is now majorly owned by a belgian company with a 62.69% controlling stake in the company’s 953.9 million ordinary shares. no other shareholder owns more than 5% of the company. okomu oil company is famous for producing a high volume of special palm oil for international and local markets. the plant processes up to 45 tonnes per hour of ffb in a fully mechanized and automated process. also, the plant derives ffb from her oil palm plantation, which seats over 5,000 hectares of land. the company has repeatedly shown the relevance of palm oil and has its stock listed on the nigeria stock exchange. apart from the success story it has in the palm oil industry, the company has produced about 7,341 tonnes of dry rubber and employed 4,528 of direct and indirect labour, contributing significantly to nigeria’s economy (okomu, 2020). the jb farm nigeria limited is a privately-owned oil mill, located in ogun state. the company was established in 1985 and deals in the establishment of commercial oil palm plantations and palm oil production. the firm collaborated with desmet ballestra, which yielded the installation of the refineries in the years 2014 and 2021. the company is rapidly developing and expanding its scope. also, in the small-scale and private ownership category, royal farms, established in 2017 at osun state, is one of the processing centres in the state, whose mandate is to produce special palm oil for industrial application. it has a 1 ton/hr capacity processing mill supplying some towns around osu and ile-ife neighbourhood. although the mill is expanding yearly, presently, the company cannot meet the local demand for technical palm oil and expect to expand its production capacity. currently, the company is supplied from 200 acres of young oil palm plantation. 3.2 technologies, capacity, maintenance, and source of parts and services at the mills nifor has a mechanized palm oil mill which is referred to as a large-scale plant and a mediumscale plants. it also produces palm oil using the traditional method. the large-scale plants, which produced and stored 7000 metric tonnes of spo stopped production in the first quarter of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng owolarafe et al: technological capability of selected palm oil mills in nigeria. azojete, 20(1):71-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 75 2020 due to poor maintenance of the facility and unavailable imported spare parts. however, the small-scale production facility is functional, and it is supported by the traditional production method. the process obtainable in nifor produces technical palm oil (tpo), which has a high level of free fatty acid. the institute was known for the production of spo in large quantities before the facility was grounded (figure1). the unit operations installed includes spikelet cleaner, biomass-fired sterilizer, digester screw press, and clarifier. the level of technology application in nifor was found to promote the emission of greenhouse gases as air emission from the biomass-fired sterilizer forms cloud of smoke. similarly, the effluent from the clarifier was exposed in an open pit. according to ohimain et al. (2013), emissions from biomass in a small-holders mill are significantly higher than emissions from fossil fuels. (a) (b) (c) figure 1. abandoned facilities (a) sterilizer (b) stripper (c) digester screw press nifor, in collaboration with the food and agriculture organization of the united nations (fao) and united nations development programme (undp), developed a semi-mechanized integrated small-scale processing equipment (sspe), which later improved considerably since its initial introduction. the new model had increasingly high extraction efficiency and required less labour input. these include the nifor large, with a throughput capacity of 0.5 1.0 tonnes (fresh fruit bunch/ hour (ffb/hr), the nifor medium, with a throughput capacity of 0.25 0.5 tonnes ffb/hr, and the nifor mini, with a throughput capacity of 0.1 0.25 tonnes ffb/hr. the sspe consists of the unit machines required in palm fruit processing. the units are combined to form a system that would convert an ffb to spo in a singular operation. a miniboiler supplies steam to three vertical sterilizers. the two top sterilizers are loaded at once and processed such that the digester receives sterilized ffb and processes continuously. the process of filling the sterilizers continues; to ensure that ffbs are cooked at every instance. the digester further processes the fruit and empty the products into the screw press. the oil is collected in a crude form and processed in a clarifier. in the last production line, the fibers and the nuts are separated as by-products and are manually conveyed to where they would be utilized as biomass for firing the boiler. the fruit sterilizer of the first model was optimized by introducing a tilting system. the sterilizer could accommodate more threshed fruits and would tilt at an angle of 90 degrees to empty the cooked fruits into the digester. conversely, due to the lack of financial support and poor maintenance of the facilities, nifor couldn’t finish the development of the system to commercial status. http://www.azojete.com.ng/ gbinuyo@oauife.edu.ng%20 arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 76 in the current production system, after harvesting the palm fruit bunches from the farm, the ffbs are shipped to the local oil plant and split into two using an axe; to enhance the separation of the fruits from the calyces. palm fruits are removed manually from the bunches. the loosed fruits are transported to the cleaning machine manually. the cleaned fruits are weighed to glimpse the volume of the palm oil to be produced. also, it enhances the evaluation of the efficiency of the machines after converting the cleaned fruits to palm oil. the fruits are subjected to heat by cooking in a sterilizer, and the process takes 1 hour to soften the fruits. after that, sterilized fruits are loaded into the horizontal digester cum mono screw-press for the mechanical oil expression of the oils in the digested fruits. finally, to enhance the quality of the oil, the extracted oil is further processed in a clarifier, which separates the oil from sludge and dries the oil to the expected moisture content. the flow process of the current system adopted by the small-scale processing equipment unit (sspe)of the institute is shown in figure 2 this system cannot produce spo. quartering of bunch on cutting platform fresh fruit bunch fruit striping using a motorized striper sterilization of fruit in a sterilizer fruit digestion and oil extraction with a digester-screw press oil clarification in a clarifier nutfibre separation using a nut-fibre separator figure 2: flow chart of process line adopted by the sspe unit of nifor file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng owolarafe et al: technological capability of selected palm oil mills in nigeria. azojete, 20(1):71-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 77 the okitipupa oil company operated an imported facility mill capacity of 24 tons of ffb/hr that has been abandoned. all the sets of equipment were already in a complete state of disrepair as at the time of this report. the reasons adduced for these were prolonged lack of maintenance emanating from inconsistency in government policies as it related to the company, and lack of imported spare parts. the popular productive mill has resulted in very small-scale production which cannot support the large expanse of plantations in the company. oil milling activities in the mill generate a lot of untreated waste which is exposed to the environment. okomu oil mill, on the other hand, processes 45 tons/hr capacity of ffbs with all the sets of equipment, accessories, and spares imported. the facilities available in okomu oil mill include an ffb splitter, tilting sterilizer (figure 3a), 45 tonnes capacity steam boiler, conveyor, ffb stripper (figure 3b), twine shaft digester screw press, clarifier, centrifuge pumps, and 7000 tonnes capacity spo storage tank (figure 3c). once ffb arrives from the farm, they are weighed and transported to the ffb cage and conveyed with the conveyor chain to the splitter. the splitter has spines to punch holes in the bunches to enhance humidification during sterilization. the products go to the tilting sterilizer, which cooks the fruits at a temperature greater than 100℃ and a pressure of 3 bar supplied from a 45 tonnes capacity steam boiler (powered by the shredded fibers; a waste product of the plant). the tilting sterilizer is equipped with a hydraulic system that empties the ffb into a hopper leading to a conveyor. the conveyor transports the cooked ffb to a stripper or thresher, separating the fruits from the bunches. the fruits are conveyed into a vertical digester for maceration, then discharged into the twin-cam screw-press by gravity for extraction of the palm oil. (a) (b) (c) figure 3. functioning facilities (a) tilting sterilizer (b) stripper (c) spo storage tank another essential process in the purification of crude palm oil is the centrifugation of the oil. the extracted oil flows to the centrifuge machine, and oil is separated from the sludge. in the absence of this process, about 8-10% of oil production will be lost to the sludge and other waste from the oil extraction process. before the oil clarification process, some fully stripped bunches with trapped oil are further pressed to extract the oil. one by-product (fibers) is transported to the field and used as mulch to retain water in the soil and prevent the rapid growth of weeds in the nurseries. the last production stage is converting the palm nuts into, palm kernel oil (pko) and palm kernel cake (pkc) used as animal feed because of its high protein content. http://www.azojete.com.ng/ gbinuyo@oauife.edu.ng%20 arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 78 the available storage tanks have about 7000 tonnes capacity to store spo. the company is expanding its storage capacity during the time of the report. the proposed new storage tanks would have the capacity to store up to 15,000 tonnes of spo. the usual practice is to sell the spo (pure olein) in trucks to the industrial market. however, about 15% of the total production is sold to the local market in a 1-liter bottle. despite the high volume of production of palm oil at the okomu oil mill, there is a vast market gap to meet up the local market demand for the spo. the facility is operated 24 hours a day to prevent frequent cleaning of the machines. however, routine maintenances are done at designated times to prevent downtime and wear of machine components. all the parts of the machines are imported, and a break or wear of the parts can lead to great loss except there is a spare part already sourced from the international market. the flow process operated in the mill is shown in figure 4. the jb farm nigeria limited possesses two medium-scale mills (refineries and fractional plants) which process 8 tonnes of ffbs per hour equivalent to 200 tonnes per day (figure 3). from raw materials (ffbs) to palm oil production processes, the processing machines available are sterilizer, stripper, digester screw press, clarifier (purification and drying of oil), and spo storage tank. other material flow processes include nut and fibre separation, nut conditioning and cracking, cracked mixture separation, and kernel drying and storage for the kernel line. the dried kernels are crushed for the extraction of crude palm kernel oil. the boiler is fuelled by biomass (fibre and shell) to produce superheated steam, used to generate electricity through a turbine generator. the lower pressure steam from the turbine is supplied to the sterilizer and clarifier to enhance the palm oil production technique. the installations have mechanical handling systems (bucket and screw conveyors, pumps and pipelines) and operate continuously, depending on the availability of ffbs. above all, the farm has a cost-effective effluent treatment system that prevents environmental pollution caused by sludge. in some mills, such systems are not provided because of their cost implication. the flowchart of the process adopted by okomu and jb farm as modern method is shown in figure 5. at royal farm, the production line is a setup of the nifor sspe, which consists of units of palm fruit stripper, sterilizer, digester-screw press, and clarifier. as shown in plate 4, the operation of the mill still simulates the typical traditional method of oil extraction, which is inefficient (owolarafe and oni, 2011). however, there is a trace of adoption of modern technology even though they are not functional yet because of the limited supply of ffbs. 3.3 current status of the mill the technology at the nifor mill is already obsolete, and the nifor sspe currently in operation cannot produce spo since fruits must be fermented before being processed. fermentation of fruits increases the free fatty acid (ffa) present in palm oil after processing (adjei-nsiah et al., 2012). the bunch stripper available was not in use because facilities to sterilize whole bunches were not available. however, the digestion and oil extraction systems are efficient. nifor oil mill continued technical palm oil production using traditional methods. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng owolarafe et al: technological capability of selected palm oil mills in nigeria. azojete, 20(1):71-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 79 figure 5: flow chat of the complete ffb refining and fractionation plant operation adopted by okomu mill and jb farm figure 6: jb farms functioning palm fruit processing plant http://www.azojete.com.ng/ gbinuyo@oauife.edu.ng%20 arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 80 figure 6: royal farm mill at okomu company complete automation of the processing of fresh fruit bunches into special palm oil is adopted and still working well. fresh fruit bunches are conveyed to bunch sterilizer, the sterilized bunches are subjected to agitation in a stripper to strip the fruits which are subsequently sent to a digester for thorough digestion. the fruit mash flows under gravity into a screw press which separates the crude palm oil from fibres and nuts, the crude palm oil is transported to a clarifier that purifies and dries the palm oil, a centrifuge pumps that removes impurity such as sludge, and finally to a 7000 tonnes capacity spo storage tank. the mill sells the spo (pure olein) in trucks to the industrial market. conversely, about 15% of the total production is sold to the local market in a 1-liter bottle, the rest is exported (owolarafe, et al., 2002). thus, the company cannot support the huge demand for spo by local industries unlike okomu oil company, jb farm nigeria limited is a medium-scale palm oil production with the potentials to increase its capacity. as stated earlier, the oil mill has installed a plant in a bid to increase the number of fresh fruit bunches processed per day and to produce special palm oil to close the demand gap of spo by the industry. similarly, royal farm in its current state operates as a small-scale mill due to its small supply of ffb. however, the company is planning to install a medium-scale locally made facility to boost special palm oil production in osun state. 3.4 projections for future development for the production of adequate highquality palm oil for domestic and industrial applications. the machines required to produce special palm oil include a conveyance system, steam boiler, sterilizer, stripper, digester screw press, clarifier, centrifuge, and storage system (salako et al., 2014; morakinyo and bamgboye, 2019). the complete set of the processing unit is usually imported by the existing largescale mills in nigeria. among these large-scale mills, it is evident that only the privately-owned are functioning effectively and efficiently. the public mills having one problem or the other are either moribund or performing far below installed capacity. some small and medium-scale mills are however coming up with local content, notable in this study is the jb firm with about 8 tons /hr capacity mill. this provides an insight on the development of appropriate mills for production of spo in the country. since there is huge market for spo (elekwachi et al., 2012: owolarafe, 2015), there arise the need to have a plan to support small and medium-scale processors in acquisition of modern facilities capable of producing spo. local fabricators should also be supported with adequate training to improve file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng owolarafe et al: technological capability of selected palm oil mills in nigeria. azojete, 20(1):71-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 81 the situation in the fabrication of sets of equipment for production of spo. considering the capital requirement for establishment of plant for production of spo, small scale processors may have to be organized into clusters to have central mills with capacity of about 5 -10 tons/hr which will be in form of public-private partnership as recommended by owolarafe and oni (2011). input for such mills will have to be in kind such that they can thrive and be sustained. it is expected that, more than four million participants/actors in the palm oil industry will be productive in line with the new focus of producing spo and serve the food and agro-allied industries appropriately 4 conclusion an appraisal of selected palm oil mills carried out in this study indicates that privately-owned mills function effectively and efficiently more than the public mills at all the scales of production considered. the public-owned mills which initially had imported facilities for production of spo had gone moribund due to lack of proper maintenance particularly procurement of spare parts. in contrast, the private mills are able to source their parts due to proper management mechanism geared towards profit-making for the mills. though functional large and medium scale mills visited are expanding, they are unable to produce enough spo to meet the demand from food and agro-allied industries. however, for the fact that the medium one is able to source the spare parts and services within the country raises the hope for local capacity building in that respect. in order to achieve enough spo production, public-private partnership of existing public mills should be encouraged. furthermore, small processors should also be organized to pool resources together such that they can procure modern facilities for production of spo with support in form of loan from the government. linkage between research institutes and the upcoming mills should also be established to foster local content development for sustainability of the mills. these efforts are likely to address shortage of special palm oil for the use of food and agro-allied industries in nigeria. acknowledgement the authors are grateful to the tertiary education trust fund (tetfund), nigeria, for providing the financial support for the study. the contributions of the staffs of the mills visited vz: nifor, okomu, okitipupa, jb farms and royal farms are hereby acknowledged. source of funding the study was carried out under the tetfund national research fund (nrf) project titled “development of appropriate agro-processing technologies for production of special palm oil for industrial applications in nigeria” with grant code: tetfund/dr&d/ce/nrf/cc/10/vol.1 references adjei-nsiah, s., zu, ak. and nimoh, f. 2012. technological and financial assessment of smallscale palm oil production in kwaebibrem district, ghana. journal of agricultural science, 4(7): 111-120 badmus, ga., owolarafe, ok., osunleke, as., ajadi, so and ajayi, oa 2019. mathematical modelling of digester-screw press process for expression of oil from oil palm fruit. ife journal of science, 21(3): 193-211. http://www.azojete.com.ng/ gbinuyo@oauife.edu.ng%20 arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):71-82. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbinuyo@oauife.edu.ng 82 elekwachi, j., owolarafe, ok., fadare, so. and adu, a 2012. palm oil scoping study. a report submitted to the partnership initiatives in the niger delta (pind), yenagoa. food and agriculture organization (fao) 2021. statistical yearbook, world food, and agriculture. fao, rome, italy. https://reliefweb.int/report/world/fao-statistical-yearbook2021-world-food-and agriculture?gclid=cj0kcqjw8qmhbhclarisanatbodgcthbdrjfdecfg4ufnbl65vny2xs7jt 2trtgzjyzv74s1oosdnewaascwealw_wcb access on 2september, 2022 morakinyo, ta. and bamgboye, ai. 2019. assessment of indigenous technology of oil palm fruits processing in southern nigeria. american journal of chemistry and materials science, 6 (1):1-9. morakinyo, ta. and bamgboye, ai. 2016. performance characterization and optimization of a synchronized medium-scale of oil palm fruits processing mill. journal of food process engineering, 40(5): 1-9., doi: 10 1111/jpe/12523. hoboken, ohimain, ei., izah, sc. and abah, so. 2013. air quality impacts of smallholder oil palm processing in nigeria. journal of environmental protection, 4(8): 83-98. owolarafe, ok., faborode, mo. and ajibola, oo. 2002. comparative evaluation of digesterscrew press and hand-operated hydraulic press for oil palm fruit processing. journal of food engineering, 52: 249 255. owolarafe, ok. and oni, oa. 2011. modern mill technology and centralized processing system, an alternative for improving performance of palm oil mills in abia state, nigeria. technology in society, 33: 12-22. owolarafe, ok., ogunsina, bs. obayopo, so., morakinyo, ta., binuyo, go., okorie, vo., badmus, ga. and olaoye, io. 2019. development of appropriate agro-processing technologies for production of special palm oil for industrial applications in nigeria. tetfund/dr&d/ce/nrf/cc/10/vol.1, tertiary education trust fund, abuja, nigeria. owolarafe, ok. 2015. building a paradise in nigeria-the r & d option for small and medium scale agro-allied industries. the 282nd inaugural lecture series of obafemi awolowo university, ile-ife, presented on 22nd december, 2015, obafemi awolwo university press ltd, ile-ife., pp. 12 15. salako, ya., owolarafe, ok. and anozie, an. 2014. performance evaluation of a small-scale palm fruit biomass-fired boiler. agricultural engineering international, the cigr journal, 16 (4): 51-55 united states department of agriculture 2021. which country produced the most palm oil? retrieved from https://www.statista.com/chart/23097/amount-of-palm-oil-produced-inselected-countries/ accessed on 27 february, 2021 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://www.statista.com/chart/23097/amount-of-palm-oil-produced-in-selected-countries/ https://www.statista.com/chart/23097/amount-of-palm-oil-produced-in-selected-countries/ arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):369-374 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 369 comparative analysis of cutting fluids developed from groundnut oil and used engine oil for machining operation m. a. abba-aji, m. i. ishaq and i. halliru department of mechanical engineering, university of maiduguri, p.m. b 1069, maiduguri, nigeria *corresponding author's email address: birma4real2004@yahoo.com article information submitted 23 october, 2023 revised 4 may, 2024 accepted 10 may, 2024 keywords: cutting fluid viscosity emulsifying wax liquid paraffin potassium dichromate ph abstract this research concentrates on the development of cutting fluid from spent engine oil used in motor vehicles (used engine oil) and groundnut oil, for the purpose of cooling the heat generated in the cutting zone during metal work. cutting fluid are widely used in machining process such as turning, milling, grinding and forming manufacturing process. four different soluble oil were developed using locally sourced material and applied as cutting fluids for turning operation in a lathe machine. sample a comprises groundnut oil, emulsifying wax, potassium dichromate, 2-aphtol, sulphur, soap. sample b comprises groundnut oil, liquid paraffin, potassium dichromate, 2-naphtol, sulphur, soap. sample c comprises of used engine oil, emulsifying wax, potassium dichromate, 2-naphtol, sulphur, soap. sample d comprises of used engine oil, liquid paraffin, potassium dichromate, 2-naphtol, sulphur soap. determination of temperature, viscosity, ph values and percentage of free fatty acid (%ffa) were conducted on these samples. viscosity and ph values of the samples were measured using brookfield synchro-electric viscometer and ph meter, respectively. a straight-turning operation was carried out on a bar (workpiece) of 4mm diameter, using a lathe machine at a feed rate of 2 mm/min at a turning speed ranging from 58 to 370rpm. using dry cutting, the cutting zone generated a temperature of 73°c. when applying the developed cutting fluids directly at the tool tip-work piece point of contact, determination of their ability to dissipate heat away from the cutting zone, using a thermocouple was conducted. it was observed that the turning operation conducted with sample d serving as cutting fluid (with a cutting zone temperature of 17.0°c and viscosity of 0.365) dissipated more heat (56°c) away from the cutting zone when compared to samples a, b and c, having temperature and viscosity of 32°c, 28°c, 20°c and 0.02, 0.235, 0.155 nsm-2 respectively. sample d has the lowest ph value of 3.78 making it more acidic and susceptible to corrosion. in conclusion, all the samples can be used for cutting fluid. 1.0 introduction metalworking operation involves generation of heat due to friction between the tool and the work piece. the surrounding air alone is rather a poor coolant for metalworking operations because the rate of heat transfer is low. ambient-air cooling is adequate for light metalworking processes such as metal cutting with periods of rest in between them (tschätsch and reichelt, 2009). however, for heavy metalworking operations, more heat is produced which cannot be removed by mere ambient air. it is not reasonable to introduce long idle periods into the cycle time to allow the air-cooling of the tool when the heat removal can instead be accomplished with a flood of liquid, which can keep up with the heat generation (osha, 1999). the primary http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):369-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 370 functions of cutting fluid are: to cool the cutting tool, workpiece and chips; to reduce friction at the contact surface; and to reduce adhesion of the cutting tool and workpiece or chips at the contact surfaces (ávila and abrão, 2001). moreover, the cutting fluid flushes away chips from the cutting zone and protects the workpiece and tool from excessive heat (nwadinobi1 and okoli, 2018). thus, in machining operations the use of cutting fluid is inescapable. this incessant need prompts the desire to explore a new type of cutting fluid from cheap locally available materials. tang et al. (2021) conducted a review on biological-stability of water based cutting fluids. in their research, cutting fluids were classified in accordance with their compositions into oil-based and water-based cutting fluids. it was reported that oil-based cutting fluid has high biological stability but insufficient cooling performance. in order to address this limitation, the present research looks at alternative cutting fluid from used engine oil (recycled spent engine oil that is used in motor vehicle) and groundnut oil. four different types of cutting fluids will be developed based on the additives, hence, a comparative analysis will be carried out to measure the performance of the newly developed cutting fluids. 2.0 materials and method 2.1 materials the cutting fluid was prepared from used engine oil, groundnut oil, emulsifying wax, soap, potassium dichromate, 2-naphtol and sulphur. four different samples were made, samples a, b, c, d. the percentage of oil (used engine oil and groundnut oil) is 90% by volumes of the prepared cutting fluid (akii, 2001). the rest of the constituents (emulsifying wax, soap, potassium dichromate, 2-naphtol and sulphur) take the remaining 10%. in preparing a sample of cutting fluid, 1350 cm3 of mineral oil was used. according to nwadinobi and okoli (2018), the constituents of the cutting fluids with their respective mass are presented in table 1. table 1: mass of cutting fluids constituents sample cutting fluids constituents quantity in grams (g) a emulsifying wax groundnut oil potassium dichromate 2-naphthol sulphur soap 102.15 1.35 1.00 1.00 0.67 120.15 b groundnut oil paraffin liquid potassium dichromate 2-naphthol sulphur soap 1.35 120.15 1.00 1.00 0.67 120.15 c used engine oil emulsifying wax potassium dichromate 2-naphtol sulphur soap 1.35 120.15 1.00 1.00 0.67 120.15 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abba-aji et al: comparative analysis of cutting fluids developed from groundnut oil and used engine oil for machining operation. azojete, 20(2):369-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 371 d used engine oil liquid paraffin potassium dichromate 2-naphtol sulphur soap 1.35 120.15 1.00 1.00 0.67 120.15 in addition to the materials above, in accordance with the work of rasak et al. (2022), ethanol was used to dissolve the 2-naphtol and then water, to dissolve potassium dichromate, and soap. also, a high-speed steel cutting tool and a bar of a circular cross-section of 0.02 mm diameter were used. 2.2 methods the materials were weighed as required, 1.35g of used engine oil (table 1) was poured into a beaker together with the emulsifying wax. with a stirrer in place and a thermometer clamped into the beaker, its content was heated on a kerosene stove. when the wax had totally melted at about 70 °c, the content of the beaker was thoroughly stirred for 20 minutes as prescribed by nwadinobi and okoli (2018) and the heating was stopped. at this temperature, its encounter with water and other similar liquids gives a frying sound. sequentially, one after the other, dissolved potassium dichromate and 2-naptol were poured into the beaker when the temperature of its content was about 60 °c or less potassium dichromate dissolves readily in water and 2-napthol in ethanol. thorough stirring was done for each of the additions, a required quantity of sulphur powder was then added regarding the variations of 0.02%, 0.05%, 0.07% and 4% and a final stirring was done to obtain an oil blend for the respective variations. in agreement with the work of rasak et al. (2022), the emulsion was formed by pouring the soap solution into the oil, and not the other way around to form the required emulsion and viscosity. this was done at room temperature, by pouring the soap into the beaker of measured oil; stirring was done gently until a thorough mixture was obtained. 2.2.1 weighing the weighing was done using a high precision chemical balance (electronic precision chemical balance model adoi) with a capacity of 3000g and 0.1g sensitivity. each of the materials was weighed separately in its respective percentage in grams. 2.2.2 performance test methods the major test parameter used to investigate the performance of each of the developed cutting fluids was temperature, the determinant being a measure of the ability of the cutting tool to conduct heat away from the work zone during the machining operation. in addition, the acidity and viscosity of the developed cutting fluids were also determined. 2.2.3 temperature measurement astm e618-07 was used to evaluate the ability of each sample fluid to conduct heat away from the work zone, a bar of circular cross-section (0.04 m in diameter) was mounted on a threejaw chuck of a lathe machine, and a straight straight-turning operation was carried out on the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):369-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 372 bar using a feed rate of 2 mm/min for five minutes while applying the cutting fluid directly at the tool tip-work piece point of contact. the tool used was one with a positive rake; a new one was used for another sample, but with the same original tool tip ground configuration. the cutting speed was varied from 58 rpm to 370 (nwadinobi and okoli, 2018). the cutting fluid was applied with the aid of a coolant delivery system built into the lathe machine. a temperature indicator (thermocouple) made of copper and constantine wire was used to measure the temperature right at the point where the tooltip made contact with the workpiece during chip removal. the reference junction of the thermocouple was always kept at 0 °c by constant monitoring and the addition of ice at 0 °c to the junction. the temperature reading at this point (which was read from the thermocouple as electric voltage) was noted and recorded and the procedure was repeated for all samples at the specific cutting speeds. the ph value, a measure of hydrogen concentration in the fluid, was obtained by using a phmeter using a buffer solution of ph 7.0. the ph value was displayed on a digital device. according to sui’i et al, (2023), the acidic value was calculated from equation 1; 𝐹𝐹𝐴 % = 𝑚𝑙 𝑜𝑓 𝑎𝑙𝑘𝑎𝑙𝑖 ×𝑁×10 10(𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑔) (1) where, 𝐹𝐹𝐴 % = 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝑓𝑟𝑒𝑒 𝑓𝑎𝑡𝑡𝑦 𝑎𝑐𝑖𝑑 n = normality of alkali ml of alkali = 165 ml samples b, c, d and e have the mi values 28 ml, 47 ml, 19 ml and 278 ml respectively. therefore, the ph values are shown in table 2. 3.0 results and discussion from the results obtained, dry cutting has the highest temperature value of 73. using sample d cutting fluid, having a cutting zone temperature of 17oc from table 2, heat dissipated from the zone was 56oc. table 2: sample properties s/no. sample viscosity ph value measured temperature °c at cutting speed of 53-180 rpm measured temperature °c at cutting speed of 180-373 rpm percentage of free fatty acid (ffa%) 1. a 0.020 08.54 20 32 13.65 2. b 0.235 07.03 16 28 5.572 3. c 0.155 10.24 9.0 20 9.353 4. 5. 6. d e f 0.365 0.026 7.54 7.05 6.0 8.0 24 17.0 19.0 26 3.780 55.72 table 2 shows the properties and behaviour of the samples under different working conditions. it could be observed that samples a, b, c and d which are mineral oil with emulsifying wax, mineral oil with liquid paraffin and the control cutting fluid respectively; had the ability to conduct away heat from the work zone at a lower cutting speed below (180 rpm). however, at cutting speeds greater than 180 rpm, sample d outweighed other samples in temperature lowering at the work zone. this result agrees with the work of nwadinobi1 and okoli (2018). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abba-aji et al: comparative analysis of cutting fluids developed from groundnut oil and used engine oil for machining operation. azojete, 20(2):369-374. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 373 thus, it is fair to say that sample b had the same wettability at lower cutting speed. but its better perceived thermal stability due to its higher viscosity at higher temperatures due to the raised cutting speed, this may have accounted for the higher stability of sample d to cool the work zone than every other sample. though it would have been a reasonable conclusion to exalt sample d over every other sample at this stage, it nonetheless has a higher viscosity than all other samples. this has some implications; it will not be able to penetrate rapidly to the tool chip interphase where maximum working temperature does occur (rasak et al., 2022). also, a fluid with a higher ability to conduct heat away from the work zone will promote the softening effect of the workpiece material caused by the heat, with this the metal keeps its resistance at higher levels than when a cutting fluid with a lower cooling ability is used (rasak et al., 2022). the acid value of the oil gives a measure of how corrosive the cutting fluid developed from it could be to the workpiece, especially if it is mild steel. the very low acid values of samples b, c, and d put them forward ahead of others for use in machining operations involving mild steel. the high acid value of sample d may have been responsible for its highest translucent nature above other samples. a high acid value promotes emulsification with higher corrosion tendencies. 4. conclusion on the basis of the experiments carried out on the various samples of oils the following conclusions are made: (i) all the samples can be used as cutting fluid because their performances show that they can remove heat during machining operation. (ii) the ph values of samples a, b, and c which are 13.65, 5.572, and 9.353 respectively, have the least tendency to corrode the work piece (mild steel) compared to sample d 3.781. (iii) sample d removed heat (56oc) away from the cutting zone more than the other samples under the same conditions. reference akii, ao. 2001. introduction to manufacturing technology. ambik publishers, university press, ibadan. astm e618-07. 2018. standard test method for evaluating metals using an automatic screws/bars. astm international. ávila, rf. and abrão, am. 2001. the effect of cutting fluids on the machining of hardened aisi 4340 steels. journal of materials processing technology, (119)1: 21-26. kazeem, ra., fadare, da., ikumapayi, om., azeez, tm. and adediran, aa. 2022. development of bio-cutting fluid (cirtulus lanatus) and its performance assessment on the machining of aisi 1520 using taguchi technique and grey relational analysis. biointerface research in applied chemistry. platinum open access journal, 12(4): 5324-5346. lizhi, t., zhang, y., li, c., zhou, z., nie, x., chen, y., cao, h., liu, b., zhang, n., said, z., debnath, s., jamil, m., ali, hm. and sharma, s. 2022. biological stability of water-based cutting fluids: progress and application. chinese journal of mechanical engineering, 35(1): 1-24. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):369-374. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 374 nwadinobi1, cp. and okoli, ju. 2018. development of cutting fluid from spent engine oil. nigerian journal of technology (nijotech), 37(4): 950 – 956. osha. 1999. metalworking fluids: safety and health best practices manual. salt lake city: u.s. department of labor, occupational safety and health administration. https://www.osha.gov/metalworking-fluids/manual accessed: 10th december, 2021. sui’i, m., sumamaryah, e., anggraeni, fd., suprihana, s., mustika, m. and utomo, y. 2023. modification of free fatty acid test for food products containing fat and organic acid. journal of food research, 7(6): 229-234. tschätsch, h. and reichelt, a. 2009. cutting fluids (coolants and lubricants). chapter in: applied machining technology. 349-352. springer, berlin, heidelberg. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):45-62 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 45 investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site 1a. l. ndagiman, 2d. r. suleiman* and 3i. sulaiman* 1,2department of chemical engineering, the federal polytechnic bida, nigeria. 3department of mechanical engineering, the federal polytechnic bida, nigeria *corresponding author's email address: skishk2009@gmail.com article information submitted 5 oct., 2023 revised 2 february, 2024 accepted 9 february, 2024 keywords: characterization energy generation gasification process greenhouse gases incineration waste-to-energy conversion abstract waste management has become a pressing global issue, with an increasing focus on sustainable solutions that not only mitigate environmental concerns but also harness valuable resources. solid waste in various dump sites in bida, nigeria, present a significant environmental challenge, posing health risks to the community while emitting harmful greenhouse gases. characterisation of kutufani solid waste was carried out. the proximate and ultimate analysis of the waste samples were carried out. results showed that 29.7 % of the waste to be composed of various types of plastic materials. other categories of the waste is composed of paper, agricultural waste and textile materials. the proximate analysis of the waste was conducted and the highest moisture content of 6.36 % and volatile matter 43.16 % were obtained. the ultimate analysis results showed nitrogen and sulphur content to be within safe limits. the combined calorific values obtained were 25,771 kj/kg (hhv) and 18,841 kj/kg (lhv). the waste is suitable for conversion to energy with gasification or incineration process. 1.0 introduction energy plays an important role in meeting the needs of residential, industrial, transport, agricultural and other sectors of economy. an estimated 93 percent of africa’s economically viable hydropower potential remains unexploited (eberhard et al., 2011). much of that is located in the democratic republic of congo, ethiopia, cameroon, angola, madagascar, gabon, mozambique, and nigeria (eberhard et al., 2011). many african nations have everyday electricity blackouts. according to data from the world bank, only a small number of nations on the continent can claim to have 100% access to electricity, including egypt and tunisia, while a few others come close, including mauritius, cape verde, and gabon (amauakwa-mensah and surry, 2022). some of the larger economies, such as south africa and ghana, provide the vast majority of their people with power, but they are still not yet at 100% and power cuts remain a problem (amauakwa-mensah and surry, 2022). in addition to hydropower, fossil fuels have long been used as the primary source of energy. however, their use results in the production of acid rain-inducing pollutants like so2 and nox as well as greenhouse gases like co2. globally, the supply of fossil fuels is running out while use is rising (sarakikya and kiplagat, 2015). according to sarakikya and kiplagat (2015), oil finds peaked around 1960 and have since considerably decreased. in fact, a moment will come when http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 46 production will begin to drop while extraction costs would rise. world energy consumption doubled between 1970 and 2000, and it is expected to double again between now and 2050. global consumption of coal increased by 5.4% in 2011, to 3.72 billion tons of oil equivalent, while natural gas use grew by 2.2% to 2.91 billion tons of oil equivalent (sarakikya and kiplagat, 2015). due to the depletion of fossil fuels and environmental concerns, it is increasingly a priority to meet energy demands through the use of innovative alternatives and renewable energy sources. municipal solid waste (msw) is a byproduct of human activities that, if an effective management system is not implemented, may cause environmental damage and put human health in danger (ibikunle et al., 2019). however, the increase in msw generations can be taken as an opportunity for power generation in domestic or industrial use, when the msw is seen as a raw material. for instance, barely 20 to 30% of the 32 million tons of solid municipal waste produced in nigeria each year by its 196 million residents is collected. in lagos, nigeria's commercial hub, 21 million people produce more than 10,000 tons of msw per day at a rate of 0.5 kg/capita/day, while more than 730,412 people in onitsha generate 370,706 tons annually (ibikunle et al. 2019). data currently available indicate a rise of msw globally, which is undoubtedly attributable to population expansion, however managing msw is very challenging (alao et al., 2022) solid waste management has emerged as one of the greatest challenges facing state and local government environmental protection agencies in nigeria. the volume of solid waste being generated continues to increase at a faster rate than the ability of the agencies to improve on the financial and technical resources needed to parallel this growth (alao et al., 2022). viewing msw as a resource (rather than waste that needs to be managed) for energy generation in the waste-to-energy initiative will better aid the efficient management of the msw generated across the country. waste-to-energy (wte) includes processes such as incineration, gasification, and pyrolysis that thermally treat solid waste and directly recover energy in the form of electricity and/or heat (alao et al., 2022; oyedepo, 2012). it also includes bio-chemical processes such as landfill gas recovery, anaerobic digestion that converts the chemical energy in solid waste to yield products of high energy value example methane (aneni, 2018). a direct conversion of the waste to an energy source, which shortens the time of treatment, the ability to treat toxic materials, and the ability to control emissions from point sources make thermal treatment methods with energy recovery options very popular. the advantages include the potential to significantly reduce waste quantities, recover minerals and chemicals, and destroy contaminants. their use is anticipated to improve quality of life because it can reduce harmful waste dumping, preventing environmental pollution and land degradation; reduce fossil fuel use and greenhouse gas emissions; offset methane that could be released from open landfills; prevent harmful health effects from exposed waste burning; and stop the spread of infectious diseases via parasitic agents (aneni, 2018). certain studies have carried out a community-level assessment of the wte potential that could be derived from msw for selected localities and states in nigeria. daura et al. (2014) determined and analysed the characteristics and composition of municipal solid waste in kano metropolis. ibikunle et al. (2019) estimated the power generation capacity from municipal solid wastes in ilorin metropolis, north-central, nigeria. the study determined the amount of msw produced annually and the amount produced per person each day in the nigerian kwara state capital of ilorin. the number of daily combustible waste fractions that could be employed for power generation as well as the fractions' proximate and final analyses were calculated. the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 47 study was designed to determine the steam power plant's capacity to produce electricity from the available combustible waste fractions. the university of nigeria, enugu's solid waste composition and treatment potential were estimated by nwoke et al. (2022). based on a student population of 36000 and a weekly generation of 4821.1kg, the study found that the estimated waste generation rate for the university campus was 0.019kg/capita/day from the four sources evaluated. only a small part, or 7.16% of created garbage, which cannot be composted or recycled, will be transferred to landfill. of the waste generated, 28.35% is biodegradable and 64.49% is recyclable (nwoke et al.,2022). olatunji et al. (2019) estimated the combustion enthalpy of msw for the purpose of energy recovery. abba et al. (2019) estimated the potential of msw in yola; the study estimated that 685.69 tons of methane was generated from msw between a decade (20042014). this study therefore presents a community-level assessment of the wte potential in nigeria. studies have been reported on the effects of indiscriminate waste dumping, types of waste generated in bida and even proposing mathematical model for optimal msw disposal in the town (yahaya and yahaya, 2022). however, limited research has been done on the energy content of its msw. this research further investigates the potential of msw as an alternative source of energy and a possible waste management solution, taking landfill sites of kutufani bida, niger state as study area. the findings of this study are anticipated to contribute significantly to the broader discourse on sustainable waste management and renewable energy generation. moreover, it underscores the importance of recognizing landfills as not merely a problem but as a potential solution to the global challenges of waste disposal, energy generation, and environmental protection. as the world strives to achieve sustainable development goals, this research endeavours to exemplify how a holistic approach to waste management can lead to a brighter, cleaner, and more energy-abundant future for urban communities like bida. 2 materials and methods 2.1 study area bida is located in the central part of nigeria, within niger state. it lies approximately 120 kilometres west of the state capital, minna and approximately 200 kilometres west of nigeria's capital city, abuja. the geographical coordinates of bida are approximately latitude 9.0707° n and longitude 6.0086° e (mohammed et al., 2021). figure 1 shows niger state relative to nigeria in a map and bida relative to niger state as given by ajiboye et al. (2023). the terrain in and around bida is relatively flat, with some undulating areas (mohammed et al., 2021). niger state, in general, is characterized by a mixture of savannah grasslands and wooded areas. the location experiences a tropical climate, typical of the west african region. it has a rainy season that usually occurs from may to september, with the highest rainfall occurring in july and august. the dry season extends from october to april. temperatures in bida are relatively high round the year, with the hottest months typically being march and april (adedibu et al., 2022). it is not directly situated on a major river, but it is in close proximity to the niger river, one of nigeria's largest rivers, which flows to the south of the town. the vegetation in and around bida is characterized by savannah grasslands, with scattered trees and shrubs. this type of vegetation is typical of the nigerian interior (mohammed et al., 2021). in september 2021, the population of bida was estimated to be around 190,000 people (ajiboye et al., 2023). overall, bida, niger state, is a region with a rich cultural heritage, http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 48 predominantly agricultural economy, and a unique blend of traditional and modern influences (ajiboye et al., 2023). it is an essential part of niger state's cultural and economic landscape. figure 1: map of bida in the context of niger state in the nigerian map (source: ajiboye et al., 2023) kutufani is a district within bida town. it can be accessed off banwuya road and is situated west of the old/etswafura market. a dumpsite is located between about 25 houses as depicted in figure 2. a. b. figure 2: a. satellite view of kutufani dump site (source: google maps), b. kutufani dump site (source: site survey) the dumpsite had been evacuated before but has already accumulated to an enormous size. the volume of the waste dump was determined by sectioning the dump to basic shapes a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 49 triangle of size 600 m by 420 by 400 m and apex of 400 m, and a rectangle of 200 by 100 m. the height was estimated to be 3 m using a tape measure on site. hence, the volume of the waste study site is 312,000 m3. 2.2 population assessment of kutufani about 60 compounds have close proximity to the waste dump site with no alternative dump site; hence it is assumed waste is generated by the residents. saidu et al. (2022) estimated population of direct people generating refuse in the area to be 1,600. equation 1 is used to predict the population of kutufani over a 20 year period, from 2022 (rominiyi and adaramola, 2020). (1) where: is the projected population for a specified year, is the population of the base year which is 2022 in the present situation, t is the base year in consideration, r is the growth rate used for the projection, and n is the time interval between projections. saidu et al. (2022) studied the trend of waste generation in bida and estimated a 0.46 kg/person/day as the average daily generation rate of solid waste. the future waste generation is determined using equation 2 as given by suryati et al. (2021). (2) where: is the rate of waste generated in %, is the weight or volume of generated waste in kg and is the number of waste producer. saidu et al. (2022) gave the growth rate of bida to be 3.87 %; this is adopted for equation 1. 2.3 sample collection according to suggestions by adeboye et al. (2022), the dumpsite was separated into six sections and samples were collected from each section over a three-weeks period. as per recommendations from gukop et al. (2021) that recurrent sample selection and analysis would best give a more accurate representative data, the recurrent waste samples were selected for further analysis. the sample was characterised using the astm d523 method for measuring the composition of unprocessed msw garbage (astmd-5231-92, 2022). over the course of three weeks, representative msw samples were gathered and then homogenized. each slice yielded a sample that could weigh up to 10 kg. the collected msw samples were divided into four equal sections, two of which were rejected, and the process was repeated until only a sizable portion, weighing about 1 kg, was left. all six of the sections of the dumpsite chosen locations underwent this process. the waste streams were divided into various waste fractions during the characterisation phase. due to their regular occurrence in waste streams and combustibility, the most prevalent waste components among the various waste fractions defined were taken into account for energy content studies. following that, the waste sample was manually sorted. the trash sample's organic component was then the topic of additional experimental research. the samples were weighed using a digital weighing scale with a capacity of 2 kg and a spring scale with a capacity of 25 kg. the procedure for gathering and sorting the samples also involved the use of garbage bags, hand shovels, and bin bags. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 50 2.4 proximate analysis proximate analysis can be defined as a technique to measure the chemical properties of a compound based on four particular elements: moisture content, volatile matter, ash content and fixed carbon (nunes et al., 2018; soares et al., 2019). 2.4.1 determination of moisture content the determination of moisture content is a crucial step in proximate analysis, which is commonly performed to assess the composition of a sample, typically in coal, biomass, and other organic materials. american standard testing methods (astm) d3173 was employed for determining municipal solid waste (msw) sample (adeboye et al., 2022; nwoke et al., 2020; rominiyi and adaramola, 2020). the required sample to be analyse was pulverised in a thomas willey mill, model ed-5 milling machine to appropriate sizes and a representative sample of the material to be analysed was obtained. an empty moisture tin/container was weighed and its mass recorded. 2 g of the sample was placed into the moisture tin/container and the combined weight recorded. subsequently the sample was placed in a drying oven set (searchtech instruments: dhg-9101-2sa) at 105°c for 2 hours. after drying, the container was taken out from the oven and placed in a container in a desiccator to cool to room temperature. equation 3 was used to determine the moisture of the sample (%) (ibikunle et al., 2022; adeboye et al., 2022). (3) where: is the mass (g) of empty crucible, is the mass(g) of crucible + test-sample, is the mass (g) of empty crucible + test-sample after heating, is the moisture content. for each sample, triplicate samples were analyzed for moisture content determination. 2.4.2 determination of volatile matter content the volatile matter is the condition of the material at which when heated in the absence of air under prescribed condition, liberated as gases and vapours (elehinafe et al., 2019). the astm standard astm d3175-11, which outlines the procedure for determining the volatile matter content of solid fuels was used to determine the volatile matter content (neto et al., 2023; ahmed et al., 2017; ndecky et al., 2022). the sample was finely ground to a particle size of 0.212 mm (no. 70 sieve). the finely ground sample is dried to constant weight and anhydrous calcium chloride was prepared as the desiccant to be used. a clean, dry crucible is weighed to the nearest 0.1 mg and 2 g of the dried finely ground sample is placed into the crucible. the weight of the crucible with the sample is taken subsequently the crucible with the sample is placed in a carbolite sheffield muffle furnace preheated to 950 ± 25°c and kept in the furnace for a minimum of 7 minutes or until the sample stops visibly evolving volatile matter. the volatile matter content (vm) is determined using equation 4 (alexio da silva et al., 2021; ibikunle et al., 2022; durogbitan, 2019). (4) where: vm is the volatile matter content in percent, is the mass (g) of empty crucible, is the mass(g) of crucible + test-sample before heating and is the mass (g) of empty crucible + test-sample after heating. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 51 2.4.3 determination of ash content ash content is an essential parameter in proximate analysis to determine the amount of inorganic residue present in a sample after complete combustion. astm d3174 is used to determine the ash content in this study (zakariya et al., 2020; ondachi et al., 2023; ibikunle et al., 2018). a clean dry crucible is weighed and recorded and 2 g of sample is added to the crucible. the crucible with the sample is then placed in the muffle furnace preheated to 550 °c. the sample was ignited in the crucible at this temperature for at least 4 hours and a constant weight is obtained (when the weight of the crucible and ash no longer changed significantly). the furnace temperature was stable throughout the ignition process. the crucible was removed and allowed to cool in a desiccator to prevent moisture absorption. once the crucible was at room temperature, it was weighed again and noted. the residue left after determining the volatile matter was used as the fresh sample for the ash content determination. the ash content was determined using equation 5 (ibikunle et al., 2022; durogbitan, 2019; ibikunle et al., 2018). (5) where: is the weight of the empty crucible (g), is the weight of the crucible + the test sample before heating (g) and is the weight of the empty crucible + the residue (g). 2.4.4 determination of fixed carbon fixed carbon represents the carbon content that remains after volatile matter has been driven off. this determination is typically performed using the astm d3172-13 standard method (ibikunle et al., 2018). the experimental method depicted by the astm d3172-13 starts with the same procedures used to determine the moisture content, volatile matter and ash content respectively. the fixed amount of carbon left behind was then calculated by deducting the percentage amount of ash, moisture, and volatile matter from 100, as given in equation 6 (ibikunle et al., 2018; ondachi et al., 2023). fixed carbon = 100 – (% mc + % vm + % ash content) (6) where, mc is the moisture content and vm is the volatile matter in %. 2.5 ultimate analysis ultimate analysis of municipal solid waste (msw) involves determining the composition of the waste in terms of its major components, such as carbon, hydrogen, nitrogen, sulphur and oxygen. astm d5231-92(2016) standard test method for determination of the composition of unprocessed municipal solid waste was employed for the study. a representative sample of kutufani solid waste from the dump site was collected. the collected sample was well-mixed to capture the variability in waste composition. the large non-combustible items like metals, glass, and stones were taken out and homogenized by thoroughly mixing it to ensure a representative subsample can be taken. the composite sample was then dried in an oven at a temperature of 105 °c to 110 °c until it reached a constant weight. this step is crucial to remove moisture content. the procedure continued with sample combustion following the astm standard: astm d3176-89(2017) standard practice for ultimate analysis of coal and coke. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 52 2.5.1 carbon and hydrogen analysis standard test method for determination of carbon, hydrogen, and nitrogen in analysis samples of coal (astm d5373-16) was used to analyse the carbon in the sample. for carbon and hydrogen analysis the representative sample of 10 mg was weighed and placed into a combustion furnace. the sample was heated to a high temperature (around 1000 °c) in the presence of oxygen for carbon analysis. the amount of carbon dioxide (co2) and water vapour (h2o) produced during combustion was measured (vasileiadou et al., 2023). 2.5.2 sulphur analysis using the standard test method astm standard: astm d4239-19 the sample was weighed put into a crucible and loaded into the tube furnace combustion system. the sample was also heated to a high temperature (about 1000 °c) in the presence of oxygen. the sulphur in the sample is converted to sulphur dioxide (so2) during combustion. the generated so2 gas is collected and passed through a sulphur dioxide detector to quantify sulphur content (vasileiadou et al., 2023; ubuoh et al., 2021). 2.5.3 nitrogen analysis nitrogen content is estimated using kjeldahl's method as outlined by ondachi et al. (2023). estimating nitrogen content in msw using kjeldahl's method involves a series of chemical reactions and titrations. the msw sample was weighed and accurately measured and recorded (w). the weighed sample is transferred into the digestion flask and concentrated sulfuric acid (h2so4) was added to the sample in the digestion flask. the amount of acid used was ensured to be sufficient to digest all the organic matter. ondachi et al. (2023) suggested 2 to 3 times the weight of the sample. a stopper is placed on the digestion flask while heat is applied using a cooking gas setup. the digestion flask is heated gently until the mixture turns clear or slightly brownish. this process is called digestion and can take several hours. no fume was allowed to escape from the flask. after digestion, the flask was cooled for a few minutes and the contents of the digestion flask transferred into the distillation flask. the distillation apparatus was setup with the receiving flask in place. a few drops of a ph indicator (methyl red) were added to the contents of the distillation flask and heat was applied to the distillation flask, which caused ammonia (nh3) to be released from the digested sample. this ammonia gas was collected by condensation in a known volume of hydrochloric acid (hcl) solution in the receiving flask. the acid was sufficient to ensure complete neutralization of ammonia. lastly titration of the collected ammonia solution in the receiving flask was done with a standardized solution of sodium hydroxide (naoh). the naoh solution was slowly added until the ph reached a stable endpoint as indicated by a colour change in the ph indicator. the volume (v) of the naoh solution used for titration was recorded. the nitrogen content in the sample was calculated using the equation 7 (ondachi et al., 2023). /kg (7) where, n is the normality of the titrant (naoh or hcl), v is the volume of titrant used (ml), m is the molar mass of nitrogen (14.007 g/mol) and w is the weight of the sample (g). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 53 2.5.4 oxygen analysis the oxygen content is simply determined using equation 8. oxygen (%) = 100 (carbon (%) + hydrogen (%) + nitrogen (%) + sulphur (%)) (8) 2.6 calorific value determination the experiment used combustible msw that was prepared in accordance with astm d2013 standards for sample preparation for calorific value estimation. after separating combustibles from non-combustibles, a 100 g sample was obtained. to calculate the moisture contents, they were baked for 24 hours at a temperature of 105 °c. in order to achieve complete combustion in the bomb calorimeter experiments, the dried samples were size decreased using a milling machine and sorted using a 1 mm sieve at the national cereal research institute (ncri), badeggi, niger state, nigeria (nwoke et al., 2020). the calorific values of the device were determined by testing two duplicates of each type of waste. the samples were burned in an enclosed space with only pure oxygen, and the energy released was measured as an increase in the temperature of the bomb and its surroundings (adeleke et al., 2021; nwoke et al., 2020). the experiment employed an oxygen bomb calorimeter model at8-obca. 1g of solid materials were compressed into pellets before being dropped into the bomb’s metallic cup. the test material was fed through with a 10-cm-long fuse wire. the sample is heated more intensely by the fuse wire, which also served as a solid support to hold the sample in place while handling the bomb before it detonated (adeleke et al., 2021; nwoke et al., 2020). caloric value was calculated using equation 9 (adeleke et al., 2021; nwoke et al., 2020). (9) where, q is the calorific value in joules or calories, m is the mass of the sample in g, c is the heat capacity of the calorimeter in , δt is the temperature change in c and is the mass of the ignition source in g. 3 results and discussion 3.1 population prediction the data generated for the population and waste predictions for kutufani is presented in table 1. table 1: population prediction of kutufani s/n year population of kutufani waste generation rate total waste generated (metric ton/day) 1. 2022 1,600 0.47 0.752 2. 2027 1,631 0.48 0.783 3. 2032 1,663 0.49 0.815 4. 2037 1,696 0.50 0.848 5. 2042 1,729 0.51 0.882 6. 2047 1,762 0.52 0.916 7. 2052 1,797 0.53 0.952 figure 3 indicates that there is going to be a steady rise in the waste generation of the dump site with the rate of growth. table 1 projects population growth and waste generation in kutufani from 2022 to 2052, showing a gradual population increase from 1,600 to 1,797 individuals and a corresponding rise in the waste generation rate per person per day from 0.47 to 0.53 metric tons. consequently, http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 54 the total daily waste output is expected to grow from 0.752 to 0.952 metric tons as depicted in figure 3. this data highlights the need for significant enhancements in waste management strategies and infrastructure to accommodate the increasing waste output as the population expands. the projections suggest that kutufani will face heightened demand for efficient waste collection, recycling, and disposal services. as waste volumes grow, the environmental impacts are likely to intensify, necessitating the adoption of sustainable practices such as improved waste minimization and energy recovery techniques. local authorities will need to consider these trends carefully to ensure that infrastructure and policy developments are adequately planned to meet the escalating needs for waste management, aiming to mitigate environmental consequences and support sustainable growth. figure 3: waste generation prediction for kutufani waste dump site 3.2 solid waste composition the composition of municipal solid waste at the dumpsite is shown in table 2. the detailed analysis of waste categories over the three-week study highlights significant variations and trends crucial for developing effective waste management strategies. nylon exhibited the most dramatic fluctuations, increasing from 6.42% to 16.45%, suggesting potential seasonal influences or variable consumer behaviour that could be targeted in waste reduction initiatives. in contrast, agric waste and textile materials demonstrated relatively stable but significant contributions to the waste stream, indicating their suitability for consistent recycling or composting programs. lower, yet consistent contributors like bones and wood, although less impactful overall, still offer opportunities for specialized recycling efforts, such as bone meal production or wood chipping for biofuel. plastics, despite slight variations, remained a highvolume category throughout the study, underscoring the ongoing need for robust plastic waste management and recycling measures. this analysis suggests that understanding both the variability and the average impact of each waste category can guide tailored and effective strategies for waste reduction and recycling, ultimately enhancing sustainability in waste management practices. 2022 2027 2032 2037 2042 2047 2052 population of kutufani 1,600 1,631 1,663 1,696 1,729 1,762 1,797 total waste generated (metric ton/day) 0.752 0.783 0.815 0.848 0.882 0.916 0.952 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1,500 1,550 1,600 1,650 1,700 1,750 1,800 1,850 to ta w as te g en er at ed ( m et ri c to n /d ay ) years k u tu fa n i p o p u la ti o n file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 55 table 2: waste characterisation for kutufani dumpsite s/n waste category weight (%) in the time of study in week average (%) 1 2 3 1. textile materials 10.22 11.85 10.95 11.01 2. nylon 6.42 12.1 16.45 11.66 3. paper 13.41 10.31 10.88 11.53 4. agric waste 15.41 14.25 13.54 14.4 5. rubbers 6.19 6.32 5.04 5.85 6. toiletries 9.21 10.54 8.69 9.48 7. plastics 20.5 16.51 17.1 18.04 8. bones 5.01 4.22 4.69 4.64 9. wood 5.49 3.45 5.42 4.79 10. glass and ceramics 8.14 10.45 7.24 8.61 ahmed (2019) stated that there is a mild significant difference between fresh waste collected and waste that has aged in the dump site. one of the differences are often the absence of food waste which is evident in the results of the physical characterisation in table 2. results presented by the study conducted by ahmed (2019) also show the absence of food, this is because of natural deterioration. an earlier study carried out by saidu et al. (2022) analysing fresh waste collected from houses in the area shows above 40 % food waste. figure 4 shows the graphical representation for the waste sample characterised from the dumpsite. figure 4: waste characterisation from figure 4, plastic has the highest percentage while agricultural waste was the second highest. the percentage of agricultural waste shows that residents of the area are farmers as inferred by mohammed et al. (2021). the large proportion of waste items, including plastic, paper, and other recyclable materials, is a sign that material reuse and recycling are not wellpracticed in the area, however, the absence of metal waste is an indication of some form of recycling being practised (adeboye et al., 2022). currently, the area recycles only metallic materials. the low to no percentage composition of metals in the research region is due to scavengers moving with large magnets collecting metallic debris for recycling before reaching the dumpsite and even within the site. 11.01 11.66 11.53 14.4 5.85 9.48 18.04 4.64 4.79 8.61 0 5 10 15 20 nylon agric waste toiletries bones glass and ceramics w as te c at e go ri e s physical waste characterisation average (%) http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 56 3.3 proximate analysis the proximate analysis yielded the results presented in table 3. agricultural waste was discovered to contain the highest moisture content of the solid waste sample analysed; it was found to be 6.36 %. the moisture content indicates the amount of water present in the waste. a high moisture content can affect the waste's calorific value and its suitability for incineration. but even though this is the case, it does not mean the sample with lowest moisture content automatically becomes valuable during incineration, like glass and ceramics (0.12 in table 3) in the case of samples studied here. the sample with highest volatile matter content of the waste sample was toiletries with a value of 43.16 %. volatile matter consists of organic compounds that can be released as gases during combustion. this parameter is crucial for assessing the waste's potential for energy recovery through incineration. adeboye et al. (2022) explained that the volatile matter content influences the rate at which a solid fuel burnout and a high percentage of volatile matter indicates that a solid fuel contains large amount of useful gases such as methane which can be released easily when such material is subjected to a heating regime. the volatile matter for kutufani samples has generally high volatile matter values which is promising for the energy recovery potential of the dump site. table 3: proximate analysis results for kutufani dump site s/n sample description moisture content (%) ash content (%) volatile matter content (%) fixed carbon (%) 1. textile materials 5.40 1.50 36.06 57.04 2. nylon 4.02 0.06 36.01 59.04 3. paper 5.62 0.04 34.06 60.28 4. agric waste 6.36 0.92 36.14 56.58 5. rubbers 3.72 0.16 36.02 60.10 6. toiletries 2.01 0.13 43.16 54.70 7. plastics 3.84 0.43 38.41 57.32 8. bones 2.11 1.50 33.19 63.20 9. wood 4.32 1.52 33.10 61.06 10. glass and ceramics 0.12 0.04 32.51 67.33 11. combined samples 4.46 1.66 29.57 64.31 the fixed carbon content was determined to be at a range of 67.33 to 54.7 %, which is a good indication of the wastes sample’s combustibility. fixed carbon represents the non-volatile, solid components of the waste, primarily composed of carbon and minerals. it is an essential parameter for assessing the waste's combustibility (adeboye et al., 2022; ibikunle et al., 2022). ash consists of the inorganic materials that remain after combustion. it is an indicator of the waste's mineral content and plays a role in determining its disposal method. the highest ash content of the samples studied was determined to be 1.52 % (wood) which is relatively low and is within the range 0.49–12.58 %, which is said to indicate lower quantity of salt, heavy metal and chlorine and other organic pollutants thereby making the management of the msw easier and also advantageous to the environment (adeboye et al., 2022; anshar et al., 2014). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 57 the moisture content can reduce the energy potential of the waste and make it less suitable for incineration. proper moisture management may be required to improve its combustibility. the relatively low results obtained for the moisture content of the samples is as a result of taking samples during the dry seasons. although there are indications that high moisture content in samples can aid in the production of methane in case of organic waste management (adeboye et al., 2022). the remaining parameters studied like the volatile matter, fixed carbon and ash content all indicate the suitability of kutufani solid waste to have potential as a fuel source for energy recovery through incineration or gasification, have excellent combustibility and suitability for landfilling. 3.4 ultimate analysis the ultimate analysis of solid waste involves determining the elemental composition, which typically includes carbon (c), hydrogen (h), nitrogen (n), sulphur (s) and oxygen (o). this analysis was conducted using a combination of analytical techniques, such as elemental analysis and bomb calorimetry. the results of the ultimate analysis are given in table 4. the carbon content in solid waste is a crucial parameter for estimating energy content, as it is the primary source of energy during combustion. the percentage of carbon in solid waste typically ranges from 20 to 50%. a higher carbon content indicates a higher energy potential for waste-to-energy conversion processes (jabeen et al., 2022). table 4: ultimate analysis results for kutufani dump site s/n sample description carbon (%) hydrogen (%) sulphur (%) nitrogen (%) oxygen (%) 1. textile materials 62.00 5.60 0.00 0.39 32.01 2. nylon 56.10 6.10 0.01 0.15 37.64 3. paper 56.30 6.00 0.01 0.20 37.09 4. agric waste 53.78 4.90 1.20 0.28 39.84 5. rubbers 55.24 6.00 0.01 0.13 38.46 6. toiletries 40.68 5.70 0.06 0.26 34.66 7. plastics 37.77 6.10 0.22 0.12 31.33 8. bones 41.91 6.40 1.32 0.13 34.06 9. wood 44.90 5.40 1.00 0.08 38.42 10. glass and ceramics 28.33 4.17 0.00 0.04 32.46 11. combined samples 59.12 5.30 1.08 0.28 34.22 the results indicate glass and ceramics with lowest carbon value 28.33 %. hydrogen is another important element that contributes to the energy content of solid waste. it combines with oxygen during combustion to produce water vapor (h2o), releasing additional heat. the hydrogen content in solid waste is usually in the range of 2 to 10% (abdel-shafy and mansour, 2018; jabeen et al., 2022). the highest value of hydrogen from table 4 is determined to be 6.40 and the lowest 4.17 % within the range that will increase heat during energy recovery. nitrogen and sulphur contents were determined to be 0.39% and 1.32% respectively which are both within acceptable limits indicating that the effect of air pollution as a result of the emission of oxides of these elements http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):45-62. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 58 will be reduced. nitrogen content in solid waste is significant because it can lead to the formation of nitrogen oxides during combustion, which are harmful pollutants. nitrogen content in solid waste typically varies between 1 and 5% (abdel-shafy and mansour, 2018; jabeen et al., 2022). sulphur on the other hand is a potentially problematic element in solid waste, as it can lead to the formation of sulphur dioxide (so2) during combustion, contributing to air pollution. sulphur content in solid waste is typically low, ranging from 0.1% to 2%. oxygen (o) content: oxygen content is an essential parameter to consider when estimating energy content, as it affects the stoichiometry of combustion reactions. oxygen content varies widely but is usually between 20 and 40% (abdel-shafy and mansour, 2018; jabeen et al., 2022). the highest oxygen content was determined to be 39.84 %. 3.5 solid waste calorific value the calorific value analysis of solid waste is essential for estimating its energy content, which plays a crucial role in waste-to-energy conversion processes such as incineration and gasification (adeboye et al., 2022). the results obtained from the calorific value analysis of a representative sample of kutufani solid waste is given in table 5. table 5: calorific value results for kutufani solid waste materials s/n sample description lhv (kj/kg) hhv (kj/kg) 1. textile materials 13,362 17,476 2. nylon 17,820 18,566 3. paper 12,782 14,085 4. agric waste 11,338 15,668 5. rubbers 18,163 22,197 6. toiletries 12,752 14,085 7. plastics 23,708 33,712 8. bones 12,970 14,770 9. wood 14,600 16,580 10. glass and ceramics 14,210 14,353 11. combined samples 18,841 25,771 due to the larger percentage of moisture, organic, and mineral components in the trash, the calorific values of msw waste fractions are typically lower for developing nations like nigeria than for industrialized countries (adeboye et al., 2022). msw's heating value depends on its elemental composition and nearby analyses. for the plastic samples that were examined, the highest values for higher heating value (hhv) and lower heating value (lhv) were found to be 33,712 kj/kg and 23,708 kj/kg, respectively. the combined sample calorific values are 25,771 kj/kg (hhv) and 18,841 kj/kg (lhv) which is in accordance with literature (durogbitan, 2019). according to adeboye et al. (2022), solid wastes must have a calorific value of 7.5 to 17 mj/kg in order to qualify as a fuel source. this is encouraging because even the lowest values discovered for the samples are greater than expected, making kutufani solid waste a potential candidate for energy recovery and a good source of fuel. nevertheless, it has a lower calorific value than coal, which ranges between 37 and 40 mj/k (benedict et al., 2022). practically speaking, this means that a kilogram of coal produces around twice as much energy as the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng ndagiman et al: investigating the energy potential and quantification of bida waste landfill: a case study of kutufani dump site. azojete, 20(1):45-62. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: skishk2009@gmail.com 59 same amount of msw's organic fraction. although this fraction has a lower heating value than coal, which means it produces less power per unit mass, it is nevertheless used and is considered a renewable energy source because it is cost-free and has the added benefit of utilizing waste. 4. conclusion in the pursuit of effective and sustainable waste management strategies, the comprehensive municipal solid waste (msw) assessment study for kutufani dump site has undertaken a multidimensional approach. the study has successfully predicted population growth for kutufani over a 30-year period along with waste generation rate for the predicted period. this prediction serves as a critical reference point for estimating future waste generation rates. proximate analysis reveal solid waste maximum moisture content of about 6.36 % and volatile matter of 43.16 % making it suitable for energy recovery through incineration or gasification. the harmful pollutant released during the ultimate analysis are within safe levels for nitrogen at 0.39 % and sulphur at 1.32 %. the plastic samples examined, recorded 33,712 kj/kg as the higher heating value (hhv) and 23,708 kj/kg as lower heating value (lhv). these values are within limits for kutufani solid waste to be considered as fuel. the combined sample calorific values are 25,771 kj/kg (hhv) and 18,841 kj/kg (lhv) which is in accordance with literature. in conclusion, our msw assessment study has not only provided a comprehensive understanding of waste generation but has also laid the groundwork for informed decisionmaking in waste management and renewable energy utilization. acknowledgements the authors especially are extremely grateful to tertiary education trust fund (tetfund), nigeria. this work has been possible with the financial support of tertiary education trust fund (tetfund) under the institution-based research (ibr) intervention (tetf/dr&d/poly/bida/ibr/2022/vol.ii/3). references abba, ah., babagana, um., atiku, aa. and burmamu, br. 2019. evaluation of energy potentials from municipal solid waste: a case study of yola, nigeria. futy journal of the environment, 13(1): 36-46. abdel-shafy, h. and mansour, msm. 2018. solid waste issue: sources, composition, disposal, recycling, and valorization. egyptian journal of petroleum, 27(2): 1275-1290. adeboye, bs., idris, mo., adedeji, wo., adefajo, aa., oyewusi, tf. and adelekun, a. 2022. characterization and energy potential of municipal solid waste in osogbo metropolis. cleaner waste systems, 2(20): 1-6. adedibu, pa., opeyemi, aa., lawrence, aj., paul, ji. and oguntoye, e. 2022. savanna biomes in nigeria: indicator species and plant adaptation strategies. scienceopen, 12(4): 1-23. adeleke, oa., akinlabi, sa., jen, tc. and dunmade. i. 2021. evaluation and prediction of energy content of municipal solid waste: a review. iop conference series: materials science and engineering, 11(07): 1-19. ahmed, mi., rizman, zi., rasat, msm., alauddin, zaz., soid, snm., aziz, msa., mohamed, m., amini, mhm. and amin, mfm. 2017. the effect of torrefaction on oil palm empty fruit bunch http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2024; 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comprehensive experimental study of municipal solid waste (msw) as solid biofuel and as composite solid fuel in blends with lignite: quality characteristics, environmental impact, modeling, and energy cover. energy, ecology and environment, 8(3): 211–240. yahaya, aa. and yahaya, ta. 2022. mathematical model for optimal solid waste management and disposal in bida metropolis, niger state, nigeria. the review of contemporary scientific and academic studies, 2(7): 1-5. zakariya, ia., fazhil, na., izhar, tnt., zaaba, sk. and jamaluddin, nf. 2020. municipal solid waste characterisation and quantification as a measure towards effective solid waste management in universiti malaysia perlis. iop conference series: earth and environmental science, 616 (20): 1-6. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):203-210 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 203 original research article model for prediction of some mechanical properties of ductile cast iron austempered in jatropha curcas seed oil a. terngu, o. f. agboola and d. k. garba department of mechanical engineering, nigerian defence academy kaduna *corresponding author’s email address: takor@nda.edu.ng 1.0 introduction improvements in properties of metals can be achieved by controlling composition and by further processing in mechanical working and heat treatment. the heat treatment principle governs the procedures required to obtain particular microstructure in a given metal to achieve these properties to suit desirable working conditions (aachary and venugopalan, 2000). the importance of heat treatment lies in its ability to control a metal’s structure-sensitive properties. austempering heat treatment is a proven way of obtaining the desired microstructure for improved mechanical properties such as increased strength, toughness, wear resistance, hardness and fatigue strength in ductile iron components (adewuyi and afonja, 2002). it is an isothermal heat treatment process in which, depending on the applied austempering conditions, an attractive combination of mechanical properties of austempered ductile iron may be produced (alp et al., 2005). in many applications, this renders the austempered ductile iron a valuable and an economical substitute for high strength steels (asm, 1996). the important microstructural features of austempered ductile iron are the morphology of the ferrite, the volume fraction of retained austenite, the carbon content in retained austenite, and the presence or absence of carbide in austenite or ferrite. a mixture of bainitic ferrite retained austenite, and graphite nodules, are the most desirable combination of phases in the cast iron. thus, the mechanical properties of austempered ductile iron may be related to three microstructural variables: bainite morphology, austenite volume fraction and the formation of martensite (asm, 1996). austempered ductile iron components, competes article information abstract austempering heat treatment is a proven way of obtaining the desired microstructure for improved mechanical properties. it is an isothermal heat treatment process in which an attractive combination of mechanical properties of austempered ductile iron (adi) may be produced. in this paper, a statistical model for the determination of some mechanical properties was developed. the ductile cast iron was annealed after which it was austennitized at 850 and 950 °c. after the austenitizing process, it was then austempered in hot jatropha seed oil. the developed prediction model was then utilized to assess the tensile strength and hardness of the adi. the result of the austempering process showed appreciable improvement in tensile and hardness values measured. optimum values of tensile and hardness were 962 kn/mm2 and 405 bhn respectively. values of 961.4n/mm2 and 340.1bhn were obtained using the developed model. it can therefore be concluded that, the closeness in the values obtained from the experimental measurement and the prediction model is an indication of the effectiveness of the developed model. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 december, 2022 revised 18 march, 2023 accepted 24 march, 2023 keywords: austempering, austempered ductile iron (adi) prediction model tensile strength hardness value http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng takor@nda.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):203-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 204 favorably with steel forgings, especially for heavy-duty parts where reliability is paramount. it is used to upgrade from standard ductile irons, and as a substitute for manganese steel and nickelhard materials. aid is particularly cost-effective when strength is required: tensile and yield values are twice those of standard ductile iron; fatigue strength is 50 % higher. austempered ductile iron can replace aluminum with its high strength-to-weight ratio when reduced section sizes are the requirement. adi castings are increasingly displacing steel forgings and castings, welded fabrications and carburized steel, due to superior performance. because of its equivalent strength, nearly 80 % of all cast and forged steels can be replaced with some grade of adi (ayman and megahead, 2008). an adi component will be 10 % lighter than steel for a given shape. adi is three times stronger than the best cast or forged aluminum and weighs only 2.5 times as much. because it is twice as stiff, an adequately designed adi part can replace aluminum at a weight saving. adi's dynamic properties exceed those of forged, cast and microalloyed steels. unlike aluminum, adi's endurance limit remains nearly constant after tens of millions of cycles. the presence of graphite in the adi matrix improves noise damping, for quieter and smoother running components. adi's abrasion resistance exceeds that of conventionally processed steels and irons at a lower 'bulk' hardness level. unlike carburized steel, which loses wear resistance as the carburized layer is removed, adi improves in service. wear resistance is superior to steel at any hardness level, making it ideal for earth moving and high abrasion applications (metals handbook, 1981). austempering is mainly carried out in a nitrate/nitrite salt bath, due to its advantages compared to other hot baths like lead, mineral oils and polymer solutions. however, in recent years attention has been given to vegetable oils by many researchers. a study on quenching properties of sunflower, coconut oil, palm, and groundnut oils by (canale et al., 2005) compared the quench severities obtained with petroleum oil. they reported that vegetable oils performed better than mineral oils in a decreasing order: sunflower oil > coconut oil > palm oil > groundnut oil. sani (2008) investigated the potentials of using hot shear butter and groundnut oils as austempering quenchants for steels and cast iron. his findings indicated that these oils could be used to austemper medium carbon steel and ductile iron. a recent study by isah (2011) evaluated kahaya senegalensis (mahogany) seed oil as quenching medium in austempering of ductile iron. he reported that the kahaya senegalensis seed oil is an effective austempering quenchant for ductile iron. these breakthroughs could eliminate the need for a molten salt bath which has its attendant side effects such as high energy consumption, increased capital equipment cost, and the hazards the workers are exposed to when using molten salt bath. jatropha curcas seed oil was utilized as austempering medium in this research work. a prediction model was then designed to predict some of the mechanical properties of the austempered cast iron produced from the austempering process. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng akor et al: model for prediction of some mechanical properties of ductile cast iron austempered in jatropha curcas seed oil. azojete, 19(2):203-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 205 2.0 materials and methods: 2.1 materials the raw materials used for this investigation were high-purity sorrel pig iron obtained from metallurgical research institute jos, and ferroalloys of magnesium, silicon, manganese and cast iron to produce ductile iron. 2.2 equipment the equipment used in casting and production of test samples and mechanical tests include a 250kg rotary furnace at nasir foundries, jos; nobertherm electric furnace, electric oven, lathe, milling machine, pensky martens flash point tester and wolpet impact testing machine were accessed at the laboratories of the mechanical engineering department, nigerian defence academy, kaduna. metal analyzer at the research and development laboratories of defence industries corporation of nigeria (dicon) kaduna was also used in analyzing some of the metallic materials. jatropha oil used for austempering was produced at narit zaria. 2.3 methods 2.3.1 production of ductile iron samples charges consisted of 50 kg pig iron with composition c=4.17%, si=1.66%, mn=0.19%, s=0.01%) and a nodularizing alloy. the 25mm diameter nodularizing alloy had chemical composition (si=45.5%, mg= 5.85% ca=1.08%,). a sandwich treatment technique was used. the ferrosilicon alloy was placed on a pocked in the bottom of an open heated ladle and covered with scrap in this technique. the melt was poured on the other side of the ladle to react with the magnesium alloy effectively. the melt was then cast into ‘y’ blocks. the pouring temperature was 1380 oc (metals hand book, 1992). the ductile iron produced had the chemical composition: c = 3.42%, si = 3.1%, mn = 0.21%, cr = 0.02%, p = 0.11% and ni = 0.00004% 2.4. production of jatropha seed oil dry jatropha seeds were collected from rafin sewa gora village of zango lga, kaduna state. the seeds were manually shelled and dried inside the house to prevent exposure to direct sun rays. they were then taken to national research institute for chemical technology (narict) zaria, nigeria for oil extraction. the cold pressed method was employed to extract oil from the seeds. the mechanically extracted jatropha oil was used in its crude form for austempering ductile iron without further processing. the chemical composition of the jatropha seed oil produced is as follows: flash point = 8.43; acid value = 4.22; free fatty acid = 210; saponification value = 62.12mgkoh; peroxide value meg/kg = 88.15; iodine value g/100g = 40; viscosity at 38 0c mm2/sec = 249 respectively. test samples were machined from the nodular cast iron. these were subjected to annealing heat treatment after which jatropha seed oil was used for the austempering. 2.5 mechanical properties determination. two methods were utilized to determine the mechanical properties of the austempered ductile cast iron; the specimens were physically subjected to mechanical testing and then the developed model. in the experimental testing, the universal testing machine was used. each of the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):203-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 206 machined samples were fixed in-between the two jaws of the machine and subjected to tensile loading till failure. readings of extension and load where taken in at intervals. 2.6 development of the prediction model as described earlier in this study, the ductile iron structures where enhanced by austenitizing and austempering at selected temperature levels and times. data was collected from the ductile iron smaples by running each condition as indicated in tables 1 and 2 to study the factors influencing the austempering process. table 1: test factors for austempering process of ductile iron. factors low level high level austenitizing temperature (tϕ) 800 °c 950 °c austempering temperature (tϵ) 250 °c 300 °c austempering time (tϵ ) 1 hr 5 hr in this regard, statistical design and development of a mathematical model for the austempered ductile iron was carried out. a total of 8 runs were performed on the samples, factors of interest and response variables were identified, and appropriate levels for each variable were determined. a complete factorial design was used to test every combination of the factor levels. mathematical symbols (and +) called “coded factor levels” representing lows and highs (actual) levels were randomly used as shown in table 2 6 in order to set off any lurking variables (stankova, 2015). table 2: factorial design of austempering process of ductile iron showing the combination of chosen factors experiment number austenitizing temperature (tϕ) austempering temperature (tϵ) austempering time (tϵ ) 1 -1 -1 -1 tϕ +1 -1 -1 tϵ -1 +1 1 tϕ +1 +1 -1 tϵ -1 -1 +1 tϵ tϵ +1 -1 +1 tϕ tϵ -1 +1 +1 tϕ tϵ tϵ +1 +1 +1 the response data (tensile strength and hardness values) from running all the combinations of the chosen factors, each at two levels, were combined. a linear mathematical model equation to predict a given response was developed. the model will be derived from the response function expressed according to stankova (2015) as: y = β0 + β1 tϕ+β2tϵ + β3 tϕ tϵ + β4 tϵ + β5 tϵ tϵ + β6 tϕ tϵ + β7 tϕ tϵ tϵ (1) where y = the predicted mechanical properties (tensile strength and hardness) β0 = the intercept β1 to β7 = the model coefficient for the input factor tϕ = austenitization temperature (ductile iron and steel samples) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng akor et al: model for prediction of some mechanical properties of ductile cast iron austempered in jatropha curcas seed oil. azojete, 19(2):203-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 207 tϵ = austempering temperature and tϵ = austempering time 3.0 results and discussion 3.1 experimental measurements the result of the experimental measurement for the tensile strength and hardness test are shown in tables 3 and 4 respectively. table 3: tensile strength of the austempered ductile iron tensile strength (n/mm2) austenitised at 950 °c austempering temperature 250 °c austempering tempreture 300 °c time(hrs) jatropha jatropha 1 726 668 2 770 690 3 822 740 4 839 814 5 962 840 austenitised at 850 °c 1 847 683 2 931 790 3 892 764 4 840 745 5 820 730 table 4: hardness strength of the austempered ductile iron hardness (bhn austenitised at 950 °c austempering temperature 250 °c austempering tempreture 300 °c time (hrs) jatropha jatropha 1 331 227 2 325 297 3 346 275 4 305 291 5 340 265 austenitised at 850 °c 1 287.6 254 2 302.1 279.5 3 291.4 264.1 4 297.8 239.5 5 288 220 3.2 tensile strength and hardness the responses measured from running all the combinations of chosen factors at two levels are shown in table 5. the factors had impact on the responses obtained. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):203-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 208 table 5: complete matrix including interactions with effects calculated for austempered ductile iron run no main effects interaction effect response tϵ tϕ tϵ tϕtϵ tϵtϵ tϕtϵ tϕtϵtϵ tsj hvj 1 + + + 847 287.6 2 + + + 683 235.4 3 + + + 726 331 4 + + + 668 297 5 + + + 820 288 6 + + + 730 220 7 + + + 962 340 8 + + + + + + + 840 265 784.5 283 effect tsj -108.5 29 107 18.5 2.5 97 -34.5 effecthvj -57.3 50.5 -9.5 2.8 -14.2 -2 -6.3 where: tsj = tensile strength values for samples austempered in jatropha oil. hvj= hardness values for samples austempered in jatroph oil. 3.3 discussion the combination of low levels of austempering temperature, austenitizing temperature and time, produced austempered ductile iron of tensile strength value as high as 847 n/mm2 for jatropha oil. a lower tensile strength values of 840 n/mm2 for jatropha oil at the combination of high austempering temperature, high austenitizing temperature and time. the highest tensile strength values of 962 n/mm2 were achieved at a combination of low austempering temperature with high austenitizing temperature and time. it means a low level of austempering temperature would increase tensile strength. the developed mathematical model equation for the prediction of the tensile strength values with the fitted factors of temperatures and time in coded form for jatropha seed oil is expressed as: t.s =784.5+14.5tϕ -54tϵ+9.3tϕtϵ+ 53.5 tϵ +1.3tϵtϵ + 48.5 tϕtϵ -17tϕtϵtϵ (2) where: tϕ = austenitizing temperature (ductile iron samples) tϵ = austempering temperature and tϵ = austempering time in all the equations. the value for the intercept of 784.5 represents the average of all the tensile strength values obtained after 8 runs of the test (actual responses). by substituting the values of the main and interactions effects in coded form in equation (1) for any experimental condition using jatropha seed oil as austempering medium, the tensile strength values for the austempering process of ductile iron were calculated. the predicted values for tensile strength were determined by putting the code factor levels into the coded model in equation (2). the effect of tϵ, tϵ and tϕtϵ caused bigger effect on the predicted tensile strength values than other effects. these are in the magnitude of -108.5, 107 and 97 for samples austempered. the comparison of actual and predicted tensile strength of the adi is presented in table 6. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng akor et al: model for prediction of some mechanical properties of ductile cast iron austempered in jatropha curcas seed oil. azojete, 19(2):203-210. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 209 table 6: actual and the predicted tensile strength values table 6 compares the predicted values of tensile strength values with the responses obtained under different experimental conditions. the predicted values are very close to the actual values obtained from the experiment utilizing jatropha. the reliability of the model equations predicted well with the studied austempered ductile iron. responses have been ascertained within the selected temperatures and time. 3.4 prediction of the hardness of austempered ductile iron a similar statistical design and mathematical model were developed to predict the hardness of the ductile iron austempered in jatropha oil. the responses obtained for hardness values depended on austenitization temperature, austempering temperature and time. combining a low level of austempering temperature with high austenitizing temperature and austempering time produced the highest hardness of 405bhn for the samples austempered in jatropha seed oil. high levels of austempering temperature and time and low levels of austenitizing temperature produced the most negligible hardness value of 220 bhn. this suggests that high a level of austempering temperature and low levels of austenitizing temperature contribute greatly to the decrease in hardness value. the developed mathematical model equation for the prediction of hardness value (hv) with the fitted factors of temperature and time in coded form for samples austempered in jatropha seed oil can be expressed as: h.v =283 + 25.3tϕ – 28.7tϵ + 1.4tϕtϵ 4.8 tϵ -7.1tϵtϵ tϕtϵ 3.2tϕtϵtϵ (3) table 7 presents the predicted hardness values compared with the actual values of responses obtained under different experimental conditions. the predicted values obtained by applying equation (3) are found to be very close to the actual values obtained. table 7: actual and predicted hardness values of adi at different conditions hardness values (bhn) of adi jatropha seed oil quenchant run no actual predicted r1 287 287.7 r2 235.4 235.3 r3 331 331.1 r4 297 297.1 r5 288 287.9 r6 220 219.9 r7 340 340.1 r8 265 264.9 tensile strength values (n/mm2) of adi jatropha seed oil quenchant run no actual predicted r1 847 849.5 r2 683 683.4 r3 726 726 r4 668 668 r5 820 820 r6 730 730 r7 962 961.4 r8 840 840.6 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):203-210. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: takor@nda.edu.ng 210 4. conclusions from the results and analysis of the results obtained, the following conclusions could be drawn. (i) jatropha, seed oil was able to cause the formation of ‘ausferrite’ and ‘bainite’ structures at 250°c in the ductile cast iron specimens. (ii) there was an appreciable improvement in the mechanical properties of ductile iron when austempered in jatropha seed oil. the as-cast tensile strength, yield strength and hardness values of 560 n/mm2; 266 bhn which increased to optimum values of 1039n/mm2 and 405 bhn for samples austempered in the jatropha seed oil. (iii) the developed statistical model for predicting the tensile and hardness values for the austempered ductile iron compared well with the values obtained using the experimental method of determining mechanical properties. references aachary, j. and venugopalan, d. 2000 microstructural development and austempering kinetics of ductile iron during thermomechanical processing. metallurgical and materials transaction, 31(a): 25752585. adewuyi, bo. and afonja, aa. 2002. austempered ductile iron, a viable to steel. nigerian journal of engineering and management, 1(1): 6-13. alp, t. wazzan, aa. and yilmaz, f. 2005. microstructure property relationships in cast irons. the arabian journal for science and engineering, 2 (b): 163-175. american society metals (asm) 1996. specialty hand book, cast iron. 1st edition, (davis, jr. (ed.)). asm international, ohio, pp. 356-392. ayman, h. and megahed, mm. 2008. fracture toughness characterization of austempered ductile iron produced using both conventional austempering processes. materials and design, 3: 1866-1877. canale, lcf., fernandes, mr., agustinho, scm., totten, ge. and farah, af. 2005. oxidation of vegetable oils and its impact on quenching performance. international journal of materials and product technology, 24(1-4): 101-125. isah, la. 2011. evaluation of khaya senegalensis (mahogany) seed oil as quenching medium in austempering process of ductile iron. ph.d thesis. department of metallurgical and materials engineering, ahmadu bello university, zaria, nigeria. metals handbook, 1992. heat treating of ductile irons. 9th edition, ohio, american society of metals metal park, usa., 15: 358-488. sani, s. 2008. potentials of using some vegetable oils as quenchants for austempering of steel and cast irons. ph.d thesis. department of metallurgical and materials engineering, ahmadu bell university, zaria, nigeria. stankova, k. 2015. probability and statistics for engineers and scientists. prentice hall india ltd india. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/takor@nda.edu.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2008; vol.6, 22-28 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng computer hazard: a potential impediment to the growth of information and communication technology (ict) in nigeria abdulfattah, a.a.1 rakiya, a.m.2 and abdulfattah, b.m.3 abstract the well-orchestrated new millennium (year 2000) problem in computer-based economy has gone without any noticeable negative imprint as envisaged, and computer users have had sigh of relief. with information and communication technology (ict) still dictating pace in many sectors, the number of computer users is on the increase with full readiness to exploit all possible gains of this information age. in this paper, the authors bring into limelight health implication of the increase in computer application as a result of electromagnetic radiation from the monitor coupled with the attitude of computer users in nigeria and the negative influence it could have on the application of ict facilities in the country if not quickly tackled. 1. introduction it is axiomatic that every adventure has both positive and negative effects. the combined effort of electronic engineers and computer scientists that brings about programmable computer machines is yet to exhaust applauds when telecommunication was added to it thereby producing information and communication technology (ict). these three distinct fields have collectively under the term ict revolutionize our life’s and will continue to do so for at least half a century to come. information and communication technology (ict) has essentially modified the telecommunication industries resulting in what is known as value added network services (vans) which are market driven services operated in the same capacities of existing public telephone switched network (ptsn) or public telephone data network (psdn) infrastructures. some of the products of vans are cellular telephony and internet. the ict revolution has also led to the development of many computer application softwares such as internet explorer and netscape navigator for browsing, and microsoft outlook and netscape composer for mailing, and numerous other application softwares and programming languages developed to take advantage of the increasing capability of the computer hardware as a whole and microprocessors in particular. the list is seemingly endless and achievement is tremendous. however, the relative ease with which the year 2000 (y2k) problem was tackled may not be applicable in the case of problem that will result from emission of electromagnetic radiation by the computer monitor, which is the focus of this paper. it shall discuss in this paper the principle of electromagnetic emission by the computer monitors and their effects on the computer operator/user. 1 department of computer engineering, university of maiduguri, nigeria 2 computer science department, federal polytechnic, bauchi. nigeria 3 electrical engineering department, city university of new york, usa http://www.azojete.com.ng/ azojete vol. 6 2008 23 2. computer popularity oguntoye (1996) noted: “as to be expected, computer-based technology has begun to dominate the domains of even domestic and office items such as cars, copiers, washing machines, telephone systems and the various media of information”. also the federal government of nigeria declared in her ‘national policy on education’ that: “in recognition of the prominent role of information and communication technology in advancing knowledge and skills necessary for effective functioning in the modern world, there is urgent need to integrate information and communication technology into education in nigeria” (frn, 2004). more so, with the application of ict to many developmental concerns (ndukwe, et al, 2006) and increase in the number of tertiary institutions offering computer based courses like computer science, information technology and computer engineering together with emergence of applications such as multi-media capacity, internet connectivity and computer networking, computer popularity is on the increase and it is rapidly replacing electronic gadgets in homes. in this regard microsoft (2007) said: “as online computer systems become more popular, televisions and computers are increasingly integrated. such technologies combine the capabilities of personal computers, television, dvd players, and in some cases telephones, and greatly expand the kinds of services that can be provided. for example, computer-like hard drives in set-top recorders automatically store a tv program as it is being received so that the consumer can pause live tv, replay a scene, or skip ahead. for programs that consumers want to record for future viewing, a hard drive makes it possible to store a number of shows. some set-top devices offer internet access through a dial-up modem or broadband connection. others allow the consumer to browse the world wide web on their tv screen. when a device has a hard drive and a broadband connection, consumers may be able to download a specific program, opening the way for true video on demand. consumers may eventually need only one system or device, known as an information appliance, which they could use for entertainment, communication, shopping, and banking in the convenience of their home”. again, since the usefulness of computer surpasses those of domestic electronic devices both in terms of fun and learning, it suggests that man-machine rapport will increase in terms of time and proximity. furthermore, based on cost consideration, the type of monitor expected to be in wider use in nigeria is the cathode ray tube (crt). again, with the availability of object-oriented programming languages, many people with computers will be attracted to the world of programming via these simplified programming softwares. likewise, the number of applications software users had geometrically increased because of impact of ict on the society, and many children are glued to the monitor for games and educational purposes. 3. computer monitor and electromagnetic radiation of the three types of monitors available, the crt is more popular owing to factors such as cost and being first in existence. however, the liquid crystal display (lcd) type is gaining popularity because of its lightweight and portability, while the plasma screen has size to its advantage, nonetheless it cannot compete well with crt in use due to high cost and fragility. data collected in the two tertiary institutions and business centres mentioned above computer hazard: a potential impediment to the growth of ict in nigeria 24 confirmed our observation that most monitors in the tertiary institutions meant for learning purposes are crt high emission (vertically and horizontally curved surface) types, though gradually been replaced with low emission (horizontally curved but vertically flat) types and all the ones in use by the business centres are crt high emission types. in terms of technique, the crt monitor is the same with domestic crt television. it is made up of vacuum tube with electron gun at one end and a convex surface screen coated with phosphorous at the inner end. when heated the electron gun emits stream of high-speed electrons that are attracted to the screen end by an electric field created inside the tube. while the electrons move the focus controls, and the deflection coil steers the beam to a specific point on the phosphorous screen. the phosphorous glows when struck by the beam presenting fluorescence-like illumination. the level of brightness depends on the amount of beam striking the screen at a particular time. the agent of attraction in the vacuum tube is the electric field created by about 35 kv anode voltage (scott, 1995; geoffrey, 1971). the electric field is radiated electromagnetically to the outer surface of the tube with the tube material as the medium. the quantity of the electromagnetic emission on the surface of the tube is governed by equations 1-3 (wilhelm, 1982):      3.......... 2........ 1........ // // //    jxx oz jxx oy jxx oz eeiiand eehh eeee       where zyz iandhe ,, are electric field, magnetic field and current density at the surface of the tube while oe , oh and oi are the equivalent of the same parameter at the inner surface.  is the area of curvature of the tube surface (a factor that makes the tube high or low emission type) and  is the depth of penetration or skin depth which is usually a function of frequency expressed as     4 1 2 1    f  where  is conductivity of the material, f is the frequency, and  is permeability however, on getting out of the tube surface, air is encountered as another medium, meaning that from the source to the computer user three media are passed, namely: the vacuum, the tube material, and the air. out of the three media only two have effect on the electromagnetic emission since the vacuum medium does not affect the signal in anyway. the tube material is the medium of the electromagnetic emission from the inner side of the tube to its surface while air acts as the medium from the surface of the monitor to any point u in the vicinity. from the above explanation the magnitude of electric field at the surface of the monitor, and the magnitude at any point u in the vicinity could be expressed by equation 5. azojete vol. 6 2008 25  5//  jxx zu eeee  from these expressions, it is seen that the magnitude of the electromagnetic emission decreases exponentially with distance and that only about thirty seven percent escapes to the surface, hence at a certain point its effect diminishes (scott, 1995). the diminishing effect accounts for reason why no alarm has been raised in the case of television for viewers usually sit at some distance away from it unlike the case of computer machine where the operator/user is required to sit closer to it for most of the time. to compute the magnitude of electromagnetic emission at any point s (monitor surface) or u (user), we need to determine the electric field strength using equation 6 (simon et al., 1965; gordon, 1992).    6 4 1 2    nc r e o o   from equation 6, we can determine oe , having known the charge (θ), permittivity of free space ( o ) and radius (r) of the hypothetical spherical surface. hence equation 1 can be used for determining the electric field at the tube surface while magnetic field and current density can be computed using equations 2 and 3 respectively. each of the above expressions requires physical measurement to determine the minimum distance between the computer user and the monitor. however, a rough estimate can be made based on an empirical evaluation. 4. types of electromagnetic radiation there are two types of electromagnetic emissions as applied to computer monitor: these are extremely low frequency (elf) and very low frequency (vlf). they consist of radio frequencies below that used for normal broadcasting. these two emissions come in two forms-electric and magnetic – and the elf magnetic emission is the worse of the two. from equation 6, we can see that the smaller the frequency the higher the depth of penetration and from equations 1 and 2, the higher the electric or magnetic radiation especially when  is less than  . 5. effect of elf and vlf on the body although elf magnetic emissions are more threatening, nevertheless both of them interact with the natural electric activities of the body cells but in varying degrees. scott (1995) says: ‘another trend in green monitor designed is to minimize the user’s exposure to potentially harmful electromagnetic fields. several medical studies indicate that these electromagnetic emissions may cause health problems, such as miscarriages, birth computer hazard: a potential impediment to the growth of ict in nigeria 26 defects and cancer. time risk may be low, but if you spend a third of your day (or more) in front of a computer monitor, that risk is increased’. the reason is that the emissions interact with the electrical activities of the human body, especially new tissues. apart from this, there is a less hazardous one called “screen glare”. screen glare causes eye strain and victims soon resort to use of lens to provide visual aid (scott 1995). 6. data collection as part of the data collection technique, questionnaire were issued within the federal polytechnic bauchi, abubakar tafawa balewa university, bauchi, private computer training institutions/schools and the ‘business centres’ within bauchi metropolis to know computer users’ knowledge of the effects of electromagnetic emission and the preventive techniques available. the responses were analyzed together with the laboratory measurement taken and solutions to these effects are proffered. 7. results and data analyses the analysis of data collected within elite class of abubakar tafawa balewa university, bauchi and federal polytechnic, bauchi shows that 50% of the respondents are unaware of any hazard that may result from close association with computer machine. about 80% of those that are aware of computer hazard can only name one of such hazards, which is sight defect, and this forms 40% of total respondents. only 30% know how to prevent the hazard. none of the respondents knows of the other problems as stated in section 5. above. in fact, 65% of the respondents are not aware that radiation is more pronounced at the sides and back of the crt monitor. our observations of the sitting arrangements in most of the offices and business centres visited corroborate the peoples lack of knowledge of more electromagnetic radiations at the side and back of the crt monitor, because seats are not more than 0.3 0.6m away from the back of the monitors. physical measurements in computer laboratories show that an average eye can see normal front at about 2.4m away from the monitor and that the computer keyboard and mouse cable can go up to 1.6m on the average. furthermore, all the business centres and training schools visited use only high emission curve screen crt monitors with only 10 percent of the offices visited in the two institutions mentioned above use lcd monitors. 8. challenges and fall-out of hazard the information above shows that people are grossly uninformed of numerous health hazards associated with frequent contact with the computer machines even though these hazards are totally preventable. the challenges here are three, namely: (i) how to increase awareness of the hazard among the populace, (ii) its implications, and (iii) suggest ways of preventing such occurrence. these challenges are crucial owing to the fact that should one or more member of a family or business organizations contact any of the hazards, the superstitious belief that computer is a “witch” will be made stronger resulting in the following: azojete vol. 6 2008 27 i. number of computer users at homes, offices and industries will decline. ii. large sums of money will be needed by individual and organizations on medical treatment and/ or litigation. iii. it will have adverse effect on economy. iv. information transfer and acquisition would become poor. v. technological retrogression will set in because the existing infrastructure would have to be replaced, that is, do away with computers, and in the alternative government and private organization would have to invest largely on computer friendliness and anti-superstitious belief campaign. 9. guidelines for prevention i. go for low-emission crt or flat screen tft monitors or lcd monitors. ii. stay at least 0.9m away from the sides and back of the crt monitors. iii. use anti-glare screen on your computer for it cuts elf and vlf thereby reducing these hazards including eye strain. iv. spend less than eight hours daily with crt monitors except low-emission type. it is recommended that these guidelines be complied with always. 9. conclusion and recommendations with the present level of computer literacy in particular and application of ict in general in nigeria, multi-media computers are gradually replacing domestic electronic appliances. the number of people with access to computer has increased and man-machine interaction has also increased. this created both economic and social positive effects plus a host of others. the economic effects are; family economic planning, research, word and data processing, desktop publishing on both commercial and non-commercial bases together with application of computer in educational instructions. on the social aspects, the use of internets has increase social interaction, exchange of idea, information transmission, availability of computer games for recreational purposes and cultural identity. the following recommendations regarding computer hazard can be made: i. government should intensify campaign at enlightening the populace on the dangers of using curve-screen high emission crt monitors and of sitting close to it. ii. government should publicize the guidelines above as a preventive measure. iii. government should enforce compliance with the guidelines in all governmental offices and industries through appropriate agencies. iv. enact law to punish offenders v. organizations should be encouraged to use low-emission crt or lcd monitors through subsidy or interest-free loan to purchase such monitors. computer hazard: a potential impediment to the growth of ict in nigeria 28 references edward, h. (1997). electrical technology, (5th ed), new york, longman incorporation. federal republic of nigeria, (2004). national policy on education, 4th ed, yaba-lagos, nerdc press. geoffrey, h. h. (1971). colour television theory, england, mcgraw-hill book company. gordon, l. (1992). introduction to fields and circuits, new york, oxford university press. herbert, p. n. jr. (1991). introductory electromagnetic, canada, john wiley. microsoft, (2007). computer and internet integration. in microsoft encarta, student edition microsoft corporation. ndukwe, e., casal, c. r., nnoli-edozien, n., ike, o. f. (eds.). (2006). ict for development: the challenges of meeting the millennium development goals in africa, abuja – nigeria, nigerian communications commission. oguntoye, f.a. (1996). computer education in nigeria: an appraisal, abeokuta, bookworm, p. 40. scott, m. (1995). upgrading and repairing pc’s (5th ed), indianapolis, que corporation. simon, r. (1965). fields and waves in communication electronics, new york, john willey. wihelm, r. (1982). electromagnetic compatibility in radio engineering, poland, elsevier scientific pub. arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):271-288 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 271 original research article development and performance evaluation of a motorized tigernut oil extraction machine p. a. omale1*, a. k. aremu2, m. o. omobowale2 1department of agricultural and environmental engineering, joseph sarwuan tarka university, makurdi, benue state, nigeria. 2department of agricultural and environmental engineering, university of ibadan, ibadan, oyo state, nigeria *corresponding author’s email address: omale.paul@uam.edu.ng 1.0 introduction the extraction of oil from oil seeds and nuts such as cotton, soyabean, olive, corn, mustard seed, palm tree, coconut, carrot, groundnut, sunflower seed, rapeseed, sesame, castor seed etc. across the globe is a common practice and have played a significant part in human diet as source of fat and oil (aremu and ogunlade, 2016, akomaye and fehintola, 2019). the oil extracted from these oil seeds and nuts are applied in different areas and for different purposes such as food nutrients, cosmetics, medications, biodiesel, paints (samaila and chukwu, 2014, omale and omobowale, 2018, yusuf, 2018). the extensive range of applications for vegetable oil and the high demand in society attract researchers to explore and uncover new oil seeds. bamgboye and adejumo (2011) emphasized the vital role of oil extraction in oil seed processing, highlighting its significance in terms of quality and quantity. they also noted that extraction methods include chemical, mechanical, and traditional approaches. various extraction methods have different oil yield which can be improved upon by optimizing the extraction conditions (divine and anuanwen, 2020, naquib and faisal, 2020). article information abstract tiger nut is a common nut in africa which contains 24.5% oil. the extraction of this oil has been a major challenge to developing countries as most oil is locally extracted because of high cost of importation of oil expellers. a motorized tiger nut oil extracting machine was designed and fabricated consisting of four sections namely feeding, extraction, heating and power sections using available local materials, and was evaluated and optimized. the oil yield (oy), operational rate (or), extraction efficiency (ee), throughput capacity (tc) and extraction loss (el) of the machine were determined as affected by barrel temperatures (bt) of 30°c, 45°c, 60°c range, screw speeds (ss) of 60 rpm, 75 rpm, 90 rpm range., 0.5 mm, 1 mm, 1.5 mm range of choke clearance (cc) of the machine and yellow/brown varieties of tiger nut. the optimum er, ee, oy, el and tc values of 9.93 kg/hr., 89.02%, 23.78%, 1 kg/hr. and 50.06 kg/hr. were achieved at 60°c barrel temperature, 60 rpm and 0.5 mm choke clearance while the lowest values gotten at 30°c barrel temperature, 90 rpm and 1.5 mm choke clearance were 6.33 kg/hr., 52.40%, 13.90%, 0.33 kg/hr. and 33.96 kg/hr. respectively. analysis of variance revealed that barrel temperature, screw speed, choke clearance and variety have significant effects on all the machine parameters evaluated at p<0.05 except for the el. the evaluation results revealed that the brown tiger nut has more oil than the yellow tiger nut and that the developed machine is deemed efficient for small scale tiger nut oil production. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 february, 2023 revised 5 march, 2023 accepted 6 march, 2023 keywords: development extraction efficiency tiger nut oil http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 272 africa is reported to have produced several oil seeds, with oil palm, groundnut, soybeans, and cotton topping the list as observed by boadi et al. (2022) where many other oil seeds and nuts have not been utilized such as tiger nut are in abundance. yet, the demand of vegetable oil in africa (especially nigeria) is more than its supply as such, causes constant increase in the price of available vegetable oil. tiger-nut (cyperus esculentus l) is a grass like root plant that is rich in nutrients needed by both human and animal. it is cultivated in many african countries including northern nigeria (omale et al., 2020). tiger nut has 24.5% oil (zhen-shan et al., 2022). it has different varieties and have different names by different ethnic groups. it is generally known in nigeria as “aya” in hausa, “ofio” in yoruba, “akiausa” in igbo and “shoho” (awulu et al., 2018 and omale et al., 2020). itcontains golden brown oil which is consumable compared to several other vegetable oil because of its nutritional quality (yali et al., 2022, ezebor et al., 2005). however, the manual process of extracting the oil from tiger nuts is time-consuming and labor-intensive. bamgboye and adejumo (2007) and olayanju et al. (2006) found that the traditional extraction method is widely used in africa due to expensive imports of oil expeller and screw press, resulting in slow, tedious, timeconsuming, and demotivating oil extraction processes. in an effort to improve efficiency and increase production, the development and performance evaluation of a motorized tiger nut oil extraction machine was undertaken. this machine is expected to revolutionize the tiger nut oil extraction industry, offering faster and more efficient oil extraction potential. 2 methodology 2.1 design conception the developed tiger nut oil extraction machine has five main components: the feeding, extraction, power, heating, and the frame components. the feeding section is made up of stainless-steel hopper, while the extraction section has a screw shaft, barrel, barrel guide, cake collector, oil collector, and choke. the power section has an electric motor, gear box, belt, and pulleys. the heating section has a heating element, temperature sensor, and control panel, and the frame supports the other parts. plate 1 shows the pictorial view of the machine while figures 1, 2, and 3 show the machine's isometric drawing, exploded drawing, and orthographic drawing, respectively. 2.2 design consideration the utmost consideration was given to the tiger nut's engineering properties, availability, durability, strength, corrosion resistance, and safety of construction materials, as well as overall cost. 2.3 design of machine components 2.3.1 design of the hopper the hopper was made with a stainless-steel material. the passing hole of the hopper was designed to be sizeable enough to avoid choking of the materials using a mass flow pattern as described by khurmi and gupta (2008). the volume of the hopper was calculated using equation 1: file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 273 𝑉 = 1 3 × ℎ × (𝑎2 + 𝑏2 + 𝑎𝑏) (1) where: v = volume, h = height of the hopper, a = length of the larger base, b = length of the smaller base 2.3.2 belt drive design a rubber v-belt was used to transmit power from the prime mover to the screw shaft by means of pulleys. 2.3.3 selection of the pulleys of the machine the diameters of the pulleys were selected considering the speeds (in revolutions per minute) to be transmitted between the electric motor and the screw (worm) shaft. the diameters of the pulleys were calculated using equation 2 as given by khurmi and gupta (2008): 𝑁1𝐷1 = 𝑁2𝐷2 (2) where: n1 = speed of the electric motor (rpm), n2= speed of the screw shaft, (rpm), d1= diameter of the electric motor pulley (mm), d2= pulley diameter of screw shaft 2.3.3.1 distance between pulley centre the distance between pulley centre was calculated from equation 3 (cleghorn and nikolai, 2015). 𝑋 = 𝐶2 + ((𝑅1 + 𝑅2) − (2𝑅1𝑅2cos ɵ))0.5 (3) where: x is the distance between the centers of the pulleys, c is the distance between the axes of the pulleys, r1 and r2 are the radii of the two pulleys, and theta is the angle between the belts as they wrap around the pulleys. 2.3.4 belt length according to shigley et al. (2011), the length of an open belt drive is given by. belt length (l) = 2x + π 2 (d1 + d2 ) + (d2−d1)2 4x (4) where: x = distance between pulleys centre (mm), d1= driver (electric motor) pulley diameter (mm), d2 = driven (screw shaft) pulley diameter (mm). 2.3.5 design of the screw shaft of the oil extraction machine the screw shaft is the major oil extraction part of the tiger nut oil extraction machine and acted upon by the material weight, pulley, and screw flights. when in use, the screw shaft conveys, press and squeeze the biomaterial for oil extraction. 2.3.5.1 diameter of the worm shaft to safeguard against bending and tensional stresses, the shaft diameter was estimated from equation 5 (callister et al., (2018; khurmi and gupta, 2008; adesoji et al., 2012). http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 274 ds 3 = 16t 0.27πδ0 (5) where: ds = diameter of the screw shaft, t = torque transmitted by the shaft (nm) and δ0 = yield stress for stainless steel (n/mm2). 2.3.5.2 estimation of the pitches of the decreasing pitch screw conveyor the inlet velocity of raw material (v) was estimated from equation 6 (jones and kocher, 1995). v = ps × π 4 (𝐷2 − 𝑑2)n 4dl (6) where: v = inlet velocity (mm/s), ps = screw pitch (mm), d = outside diameter of screw (mm), d = inside diameter of screw (mm), l = length of the screw shaft (mm), n = shaft speed (rpm). 2.3.5.3 the screw winding length the screw winding length (l) was estimated applying pythagoras rule as the square root of the sum of squares of the circumference (c) of the shaft diameter and the screw pitch (ps) (omote and mwangi, 2012) as given in equation 7. l = √c2 − ps 2 (7) the circumference of the shaft diameter = πd (mm) 2.3.5.4 axes of flight screw distance axes of flight screw distance was estimated applying the relation shown in equation 8 (fadeyibi et al., 2016). a ds ≤ √2 2 (8) where: a = flight axis distance (mm), ds = barrel diameter (mm). 2.3.5.5 maximum flight height maximum flight height (channel depth) (hmax) was estimated following the equation reported by fadeyibi et al. (2016) as. hmax = ds − a (9) where: hmax = maximum height of flight (mm), ds = barrel diameter (mm), a = flight axis distance (mm) 2.3.5.6 helix angle (pitch angle) the helix angle (angle of pitch) at the barrel surface (α), which is associated to lead, and diameter was estimated applying equation 10 (fadeyibi et al., 2016). file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 275 α = tan−1 ( p πds ) (10) where: α = helix angle (o), p = mean screw pitch (lead) (mm), ds = barrel diameter (mm). 2.3.6 pressurized cone (choke) the choke was conical in shape and made of stainless-steel material which was attached to the shaft at the end of the screw flight to effectively pressurize the tiger nut. the linear movement of the worm shaft was controlled by adjustable nuts that estimate the extraction ratio. the weight of the choke was calculated from equations 11 and 12 (hannah and hillier, 1999). weight of choke = density × (volume of cone – volume of bore) (11) w = ρ × ( 1 3 π(r2 + r2 + rr)h − πr2h) (12) where: w = weight of choke (kg), ρ = density of stainless steel (kg/m3), r = bigger radius of conical choke (mm), r = smaller radius of conical choke (h) = height of conical choke (mm). 2.3.7 press cage (barrel) design the press cage (barrel) was designed to have a large hole for feeding oil bearing material. this feeding hole was machined at the beginning of the screw shaft where the screw pitch was maximum. on the mid zone, the barrel has an oil outlet sieve. the inner diameter of the press cage was determined from equation 13 (olaniyan, 2010). di = d + 2c (13) where: di = inner diameter of the press cage, d = screw shaft diameter (mm), c = clearance between the internal wall of press cage and screw thread (mm). the outer diameter of the press cage was estimated using equation 14 (olaniyan, 2010). di = 0.95 d0 (14) where: d0 = outer diameter of the press cage in mm. the thickness (t) of the press cage was determined from equation 15 (olaniyan, 2010). t = d0 − di (15) 2.3.8 screw press power requirement the design of the tiger nut oil extraction machine considered the entire areas where power is needed such as power to overcome the inertia of the screw shaft, power to drive and convey the tiger nut through the entire length of the press, power to effectively press and squeeze out entrapped oil from the tiger nut and power compensation for friction and heat losses during operation. 2,982 watts power was designed for to run the developed machine. http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 276 2.3.9 design of machine frame the frame was designed to avoid failure of the beam by bending and the column by buckling by considering the entire weight of components and constructed with mild steel material. 2.4 machine description the isometric drawing, pictorial view, exploded views and orthographic projections of the machine assembly are presented in figures 1 to 4. figure 1: isometric drawing of the tiger nut oil extraction machine figure 2: pictorial view of the machine figure 3: exploded drawing of a motorized tiger nut oil extracting machine file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 277 figure 4: orthographic drawing of a motorized tiger nut oil extracting machine 3 performance evaluation the developed machine’s throughput capacity, extraction rate, oil yield, extraction efficiency and extraction loss as affected by different machine parameters such as choke clearances (0.5mm, 1mm and 1.5mm), shaft speeds (60rpm, 75rpm and 90rpm), barrel temperature (30°c, 45°c and 60°c) and variety (brown and yellow) were evaluated by operating the machine at different speeds, choke clearances and barrel temperatures respectively for tiger nut oil extraction. 3.1 determination of the throughput capacity this is the machine's capability in terms of quantity of tiger nut it processes per unit time. it was quantified using the relationship according to adesoji et al. (2012) given in equation 16: or = wfs t (16) where: or = rate of operation (kg/hr), wfs = weight of fed sample (kg), t = operation time (hr). 3.2 determination of the extraction rate extraction rate is the weight of oil that the machine could bring out per unit time (adesoji et al., 2012) and this was calculated applying equation 17. er = wo t (17) where: er = extraction rate (kg/hr), wo = weight of oil extract (kg), t = operation time (hr). http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 278 3.3 determination of the oil yield the extraction oil yield was expressed as the percentage fraction of the mass of extracted oil to the mass of pressed tiger nut sample. tiger nut oil yield was calculated using the equation 18 stated by olaniyan and oje (2011) and adesoji et al. (2012) as: oy = 100 woe woe+wrc (18) where: oy = oil yield (%), woe = weight of oil extracted (kg), wrc = weight of residual cake (kg). 3.4 estimation of extraction efficiency the extraction efficiency of the machine was evaluated by expressing the oil extracted as a percentage of the total oil content of the tiger nut samples. this was calculated using equation 19 (olaniyan and oje, 2011; adesoji et al., 2012). oe = 100 woe xwfs (19) where: oe = extraction efficiency (%), woe = weight of oil extracted (kg), wfs = weight of fed sample (kg) and x = oil content of tiger nut in decimal. 3.5 determination of extraction loss extraction loss is the fraction of the unrecovered sample to the fed sample. this was estimated according to olaniyan and oje (2011) and adesoji et al., (2012) using equation 20: el = 100[wfs− (woe+wrc)] wfs (20) where: el = extraction loss (%), wfs = weight of fed sample (kg), woe = weight of oil extracted (kg), wrc = weight of residual cake (kg). 4 results and discussion 4.1 extraction rate the oil extraction rate of the brown tiger nut ranged from 6.3312 9.9300 (kg/hr) while that of the yellow tiger nut ranged from 6.4708 -9.4070 (kg/hr) as shown in figure 5. it was observed that the least extraction rate for the brown tiger nut was achieved when the machine was set to 30°c barrel temperature, speed of 90 rpm and choke clearance of 1.5mm and that of yellow tiger nut was gotten at 60°c barrel temperature, 90 rpm and 1.5 mm choke clearance. the highest extraction rate for both the brown and yellow tiger nut were obtained at 45°c barrel temperature, 60 rpm speed and 0.5 mm choke clearance. analysis of variance revealed that tiger nut variety, barrel temperature, screw speed and choke clearance all have significant effects on the extraction rate of the developed machine at p < 0.05. the extraction rate was observed to increase as the choke clearance decreases and the speed and barrel temperature increases respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 279 figure 5: extraction rate results of the machine 4.2 extraction efficiency the extraction efficiency of brown tiger nut was found to be between 53.6616% and 90.22778% while that of yellow tiger nut was between 52.3990% and 89.0152% (figure 6). it was observed that the lowest extraction efficiency for brown tiger nut was obtained at 60°c barrel temperature, 90 rpm speed, and 1.5mm choke clearance, and for yellow tiger nut it was also obtained at 60°c barrel temperature, 90 rpm speed, and 1.5mm choke clearance. the highest extraction efficiency for both brown and yellow tiger nut was obtained at 45°c barrel temperature, 60 rpm speed, and 0.5mm choke clearance, respectively. analysis showed that the tiger nut variety, barrel temperature, screw speed, and choke clearance all have a significant impact on the extraction efficiency (p < 0.05) as shown on table 1. the efficiency was found to decrease as choke clearance and speed decreased and as barrel temperature increased. 0 2 4 6 8 10 12 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 60 rpm 75 rpm 90 rpm 60 rpm 75 rpm 90 rpm 60 rpm 75 rpm 90 rpm 30°c 45°c 60°c ex tr ac ti o n r at e (k g/ h r) barrel temperature (°c) brown tiger nut yellow tiger nut http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 280 figure 6: extraction efficiency of the machine 0 10 20 30 40 50 60 70 80 90 100 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 60 rpm 75 rpm 90 rpm 60 rpm 75 rpm 90 rpm 60 rpm 75 rpm 90 rpm 30°c 45°c 60°c ex tr ac ti o n e ff ic ie n cy ( % ) barrel temperature (°c) brown tiger nut yellow tiger nut file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 281 table 1: anova result of the machine evaluation tests of between-subjects effects source dependent variable type iii sum of squares df mean square f sig. variety weight of cake .012 1 .012 107.884 <.001 weight of oil .011 1 .011 93.593 <.001 operation time 7.697e-5 1 7.697e-5 49.330 <.001 extraction rate .846 1 .846 6.203 .014 extraction efficiency 391.670 1 391.670 93.593 <.001 oil yield 27.945 1 27.945 99.619 <.001 extraction loss .020 1 .020 .286 .594 throughput capacity 43.736 1 43.736 32.209 <.001 barrel temperature weight of cake .008 2 .004 37.324 <.001 weight of oil .010 2 .005 44.228 <.001 operation time .001 2 .000 254.714 <.001 extraction rate 5.468 2 2.734 20.046 <.001 extraction efficiency 370.170 2 185.085 44.228 <.001 oil yield 24.875 2 12.438 44.339 <.001 extraction loss .668 2 .334 4.770 .010 throughput capacity 569.860 2 284.930 209.833 <.001 screw speed weight of cake .104 2 .052 485.451 <.001 weight of oil .103 2 .051 439.513 <.001 operation time 7.421e-5 2 3.711e-5 23.780 <.001 extraction rate 34.523 2 17.262 126.558 <.001 extraction efficiency 3678.586 2 1839.293 439.513 <.001 oil yield 260.172 2 130.086 463.744 <.001 extraction loss .334 2 .167 2.389 .097 throughput capacity 52.439 2 26.220 19.309 <.001 choke clearance weight of cake .308 2 .154 1440.226 <.001 weight of oil .305 2 .152 1305.339 <.001 operation time .002 2 .001 488.747 <.001 extraction rate 28.153 2 14.077 103.206 <.001 extraction efficiency 10925.269 2 5462.634 1305.339 <.001 oil yield 773.140 2 386.570 1378.083 <.001 extraction loss .049 2 .025 .352 .704 throughput capacity 1205.484 2 602.742 443.882 <.001 error weight of cake .012 108 .000 weight of oil .013 108 .000 operation time .000 108 1.560e-6 extraction rate 14.730 108 .136 extraction efficiency 451.963 108 4.185 oil yield 30.295 108 .281 extraction loss 7.560 108 .070 throughput capacity 146.652 108 1.358 a. r squared = .977 (adjusted r squared = .965) b. r squared = .974 (adjusted r squared = .962) c. r squared = .955 (adjusted r squared = .933) d. r squared = .893 (adjusted r squared = .841) http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 282 4.3 oil yield the oil yield of brown tiger nuts ranged from 14.2615% to 24.033%, while the yield of yellow tiger nuts ranged from 13.9028% to 23.6181%, as shown in figure 7. it was noted that the lowest oil yields for both types of tiger nuts were obtained when the machine was set at 60°c barrel temperature, a speed of 90 rpm, and a choke clearance of 1.5mm. the highest oil yield for brown tiger nuts was obtained at 45°c barrel temperature, 90 rpm speed, and 0.5mm choke clearance, and for yellow tiger nuts, it was obtained at 45°c barrel temperature, 60 rpm speed, and 0.5mm choke clearance. an analysis of variance revealed that the tiger nut variety, barrel temperature, screw speed, and choke clearance all significantly impacted the oil yield of the machine, with p < 0.05. this aligns with the findings reported by aremu and ogunlade (2016) in their study of african oil bean seeds. the oil yield decreases as the choke clearance and speed increases but increases as the barrel temperature increases and this is because increased choke clearance and speed in an oil extraction machine reduce oil yield due to limited contact time, hindering efficient extraction. conversely, higher barrel temperature improves oil yield by enhancing fluidity, reducing viscosity, and increasing solubility and separation, facilitating oil extraction. e. r squared = .974 (adjusted r squared = .962) f. r squared = .976 (adjusted r squared = .964) g. r squared = .321 (adjusted r squared = -.012) h. r squared = .949 (adjusted r squared = .924) file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 283 figure 7: oil yield of the machine 4.4 extraction loss the extraction loss of brown tiger nuts varied from 0.5 to 1 kg/hr, while that of yellow tiger nuts ranged from 0 to 0.8333 kg/hr, as depicted in table 2. it was noted that the lowest extraction loss for brown tiger nuts was achieved with a machine set at 30°c barrel temperature, 90 rpm speed, and choke clearance of 1.5mm, 1mm, and 0.5mm. for yellow tiger nuts, the lowest extraction loss was obtained at 60°c barrel temperature, 90 rpm speed, and 1.5mm choke clearance. the highest extraction loss for brown tiger nuts was achieved at 45°c barrel temperature, 90 rpm speed, and 1.5mm choke clearance, while the highest extraction loss for yellow tiger nuts was obtained at 45°c barrel temperature, 90 rpm speed, and 1.5mm choke clearance. analysis showed that the factors of tiger nut variety, barrel temperature, screw speed, and choke clearance all had no significant impact (p < 0.05) on the extraction loss of the machine. the extraction loss increased as the barrel temperature, speed, and choke clearance increased, which is in line with the findings reported by ishola et al. (2022). 0 5 10 15 20 25 30 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 0 .5 m m 1 m m 1 .5 m m 60 rpm 75 rpm 90 rpm 60 rpm 75 rpm 90 rpm 60 rpm 75 rpm 90 rpm 30°c 45°c 60°c o il yi el d ( % ) barrel temperature (°c) brown tiger nut yellow tiger nut http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 284 table 2: results of the extraction loss of the machine 4.5 throughput capacity table 3 shows the throughput capacity of the developed machine to extract tiger nut oil varied between 33.9683 and 49.3333 kg/hr for brown tiger nuts and 36.7424 to 50.0580 kg/hr for yellow tiger nuts. the lowest processing throughput capacity for both types of tiger nuts was observed when the machine was set at a barrel temperature of 30°c, a speed of 60 rpm, and a choke clearance of 0.5 mm. the highest extraction throughput capacity for both brown and yellow tiger nuts was achieved at a barrel temperature of 60°c, a speed of 75 rpm, and a choke clearance of 1.5 mm. the analysis further showed that variety of tiger nut, barrel temperature, screw speed, and choke clearance significantly impacted the processing throughput capacity of the machine. in addition, an increase in choke clearance, barrel temperature, and speed leading to an increase in throughput capacity. brown tigernut yellow tigernut barrel temp. (°c) speed (rpm) choke clearance (mm) extraction loss (kg/hr) std. deviation extraction loss (kg/hr) std. deviation 30 60 0.5a .6667 .28868 .6667 .28868 1a .6667 .28868 .5000 .00000 1.5a .5000 .00000 .5000 .00000 75 0.5 .8333 .28868 .6667 .28868 1 .5000 .50000 .6667 .28868 1.5 .6667 .28868 .6667 .28868 90 0.5 .6000 .17321 .5000 .00000 1 .3333 .28868 .6667 .28868 1.5 .6667 .28868 .5000 .00000 45 60 0.5 .3333 .28868 .6667 .28868 1 .3333 .28868 .5000 .00000 1.5 .6667 .28868 .5000 .00000 75 0.5 .6667 .28868 .6667 .28868 1 .8333 .28868 .5000 .00000 1.5 .6667 .28868 .5000 .00000 90 0.5 .6667 .28868 .5000 .00000 1 .5000 .00000 .6667 .28868 1.5 .5000 .50000 .6667 .28868 60 60 0.5 1.1667 .28868 .5000 .00000 1 .8333 .28868 .8333 .28868 1.5 .6667 .28868 .6667 .28868 75 0.5 .6667 .28868 .6667 .28868 1 .6667 .28868 .6667 .28868 1.5 1.0000 .00000 .8333 .28868 90 0.5 .6667 .28868 .8333 .28868 1 .6667 .28868 .6667 .28868 1.5 .6667 .28868 .5000 .00000 file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 285 table 3: results of the throughput capacity of the machine 5 conclusion a motorized tiger nut oil extraction machine was developed and evaluated to provide an economic means of processing oil from tiger nuts. the main aim of developing the machine is to provide the most economical means for processing oil from tiger nut. the machine achieved optimum extraction parameters at 45°c barrel temperature, 60rpm speed, and 0.5 choke clearance, resulting in a throughput capacity of 9.9kg/hr, 90.23% extraction efficiency, 24.032% oil yield, and 1kg/hr extraction loss. lower values were obtained at 30°c barrel temperature, 90rpm speed, and 1.5 choke clearance. analysis of variance revealed that barrel temperature, screw speed, choke clearance and variety have significant impacts on all the machine evaluated parameters at p≤0.05 except for the extraction loss. it is confirmed that the brown tiger nut has more oil than the yellow tiger nut and the developed machine is efficient for small scale tiger nut oil production. brown tigernut yellow tigernut variety barrel temp. (°c) speed (rpm) choke clearance (mm) throughput capacity (kg/hr) std. deviation throughput capacity (kg/hr) std. deviation 30a 60a 0.5a 33.9683 .54986 36.7424 .65608 1b 42.8936 1.53289 41.8719 .85323 1.5c 46.1538 .00000 46.7692 1.06588 75a 0.5 34.6218 .58220 37.9032 .69841 1 38.7366 1.25022 45.0142 .98692 1.5 34.3044 .98053 45.5840 .98692 90b 0.5 36.7424 .65608 38.7097 .00000 1 40.9195 .79635 40.0297 1.33506 1.5 39.5699 .74497 44.4444 .00000 45b 60 0.5 37.5244 1.17321 38.7366 1.25022 1 42.8936 1.53289 42.3645 .85323 1.5 45.0142 .98692 41.8719 .85323 75 0.5 37.9032 .69841 38.7366 1.25022 1 40.4598 .79635 45.0142 .98692 1.5 43.3862 .91643 50.0580 2.08756 90 0.5 38.7366 1.25022 39.5699 .74497 1 46.1994 1.77822 45.0142 .98692 1.5 48.6667 1.15470 50.0580 2.08756 60c 60 0.5 40.9195 .79635 40.0297 1.33506 1 42.3645 .85323 45.5840 .98692 1.5 48.6667 1.15470 47.3846 1.06588 75 0.5 44.4851 1.64873 40.0297 1.33506 1 44.4851 1.64873 43.9153 .91643 1.5 49.3333 1.15470 46.1994 1.77822 90 0.5 44.4851 1.64873 42.8936 1.53289 1 48.0513 1.92359 45.0142 .98692 1.5 46.7692 1.06588 46.7692 1.06588 http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 286 acknowledgement i wish to acknowledge the tertiary education trust fund nigeria for sponsoring my phd studies at the university of ibadan from which this research work emanated. reference adesoji, mo., kamaldeen, ay., adebayo, lw. and kunle, oa. 2012. design, development and testing of a screw press expeller for palm kernel and soybean oil extraction. post-harvest, food and process engineering. international conference of agricultural engineering-cigr-ag. eng. 2012: agriculture and engineering for a healthier life, valencia, spain, 8-12 july 2012. 1748 pp. akomaye, am. and fehintola, uc. 2019. physicochemical properties of hura crepitans and pycnanthus angollensis seed oils and their possible. scholars bulletin, scholars middle east publishers, dubai, united arab emirates. pp 184-187. aremu, ak. and ogunlade, ca. 2016. effect of operating parameters on mechanical oil expression from african oil bean seed. global journal of science frontier research: d agriculture and veterinary, 16(1): 18-26. boadi, p. gyimah ft. and aryeetey, r. 2022. descriptive analysis of changes in ghana's food availability and food safety information between 2010 and 2020. african journal of food, agriculture, nutrition & development, 22(2): 19624-19657. awulu, jo., omale, pa. and omadachi, jo. 2018. characterization of tiger nut oil extracted using mechanical and chemical methods. journal of science and multidisciplinary research, 10(2): 13-25 bamgboye, ai. and adejumo, ao. 2007. development of a sunflower oil expeller. agricultural engineering international: the cigr ejournal. manuscript ee 06 015. vol ix. bamgboye, ai. and adejumo, ao. 2011. effects of processing parameters of roselle seed on its oil yield. international journal of agricultural and biological engineering, 4(1): 82-86. callister jr., wd. and rethwisch, dg. 2018. materials science and engineering: an introduction. john wiley & sons, inc, hoboken, new jersey, usa. 992 pages. cleghorn, wl. and nikolai, d. 2015. mechanics of machines. oxford university press. oxford, england. divine, nb. and anuanwen, fc. 2020. optimization methods for the extraction of vegetable oils: a review. processes, 8(2): 209. ezebor, f., igwe, cc., owolabi, fat. and okoh, so. 2005. comparison of the physico-chemical characteristics, oxidative and hydrolytic stabilities of oil and fat of cyperus esculentus l. and butyrospermum parkii (shea nut) from middle-belt states of nigeria. nigerian food journal, 23: 33-39. file:///c:/user/downloads/azojete143/www.azojete.com.ng omale et al: development and performance evaluation of a motorized tigernut oil extraction machine. azojete, 19(2):271-288. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 287 fadeyibi a., osunde, zd., agidi, g. and egwim, ec. 2016. design of single screw extruder for homogenizing bulk solids. agricultural engineering international: cigr journal, 18(4): 222-231. hannah, j. and hillier, m.j. 1999. applied mechanics, third edition. pearson education limited, harlow, england., 445 pp. ishola, ta., busari, ra. and oyebanji, ai. 2022. effect of operating parameters on decortication of jatropha curcas fruits. journal of applied sciences and environmental management, 26 (1): 115-120. jones, dd. and kocher, mf. 1995. auger design for uniform unloading of granular material: i. rectangular cross-section containers. transactions of the american society of agricultural engineers (asae), 38(4): 1157-1162. khurmi, rs and gupta, jk. 2008. a textbook of machine design, 14th edition, new delhi: eurasia publishing house (pvt) ltd., pp. 500. naquib, mc. and faisal, m. 2020. development and performance evaluation of an optimized screw type domestic oil expeller. proceedings of the 5th na international conference on industrial engineering and operations management, detroit, michigan, usa, august 10 14, pp. 1730-1740. olaniyan, am. 2010. development of a manually operated expeller for groundnut oil extraction in rural nigerian communities. asia-pacific journal of rural development, 20(1): 185 201. olaniyan, am. and oje, k. 2011. development of model equations for selecting optimum parameters for dry process of shea butter extraction. journal of cereals and oilseeds, 2(4): 4756. olayanju, t., akinoso, r. and oresanya, m. 2006. effect of worm shaft speed, moisture content and variety on oil recovery from expelled beniseed. agricultural engineering international: cigr e-journal, manuscript fp06 008, 8: 1-7. omale, pa. and omobowale, mo. 2018. mechanical properties of tigernut (cyperus esculentus) as influenced by moisture content. proceedings of xii cigr section vi technical symposium, 22-25 october, ibadan, nigeria., pp. 12-27. omale, pa., iyidiobu, bn. and ibu, ej. 2020. effect of drying temperature on the nutritional quality of tiger nut (cyperus esculentus). international journal of engineering applied sciences and technology, 4(9): 399-403. omote, mg. and mwangi, d. 2012. jatropha oil pressing machine. bachelor of science thesis, department of mechanical and manufacturing engineering, faculty of engineering, university of nairobi, 84 pp. samaila, rs. and chukwu, o. 2014. melon seeds oil expeller. journal of agricultural engineering and technology (jaet), 22 (2): 13-25. http://www.azojete.com.ng/ mailto:%20omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):271-288. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: omale.paul@uam.edu.ng 288 shigley, je., mischke, cr. and budynas, rg. 2011. mechanical engineering design (9th ed.). mcgraw-hill. new york, united states. yali, y., xiaoyu, l., tiehua, z., changhui, z., shiyao, g., yiling, p. and feng, g. 2022. tiger nut (cyperus esculentus l.): nutrition, processing, function and applications. foods, 11(4): 601. https://doi.org/10.3390%2ffoods11040601 yusuf, ak. 2018. a review of methods used for seed oil extraction. international journal of sciences and research, 7(12): 233-223. zhen-shan, z., hui-jie, j., xiao-dan, l., yu-lan, l., an-chi, w., wen-xue, z., 2022. effect of drying methods on the quality of tiger nuts (cyperus esculentus l.) and its oil. food science and technology (lwt), 167: 113827. file:///c:/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):453-468 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 453 original research article implementation of numerical integration using field programmable gate arrays and microcontrollers: a review m. adamu1*, a. i. audu2, c. u. ngene2 1department of computer science, college of education and legal studies, nguru, nigeria 2department of computer engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: msmajemusa4@gmail.com 1.0 introduction the study of how to find the numeric values of an integral function at a given set of independent variables is known as numerical integration. a classic numerical analysis task is to find a square with the same area as the area under a curve. the purpose of numerical integration is to obtain an approximate solution to a definite integral (khalil, 2015). situations arise in which the analytical method developed so far cannot be used to evaluate some definite integrals (abdel-raouf et al., 2014). when analytical methods fail, we typically turn to numerical operations, which are normally carried out on a calculator or computer. these approaches do not give exact values for the definite integrals, but they do give plausible estimates (khalil, 2015). configurable computing, which adapts hardware resources to meet article information abstract majority of numerical integration algorithms are written in software and require a long time to initialize and generate results. there is a gradual shift from software-based designs to (field programmable gate arrays (fpga)-based designs because they are versatile devices that are increasingly being used as real-time hardware targets in industries. fpgas are utilized in real-time measurement and control, signal processing, and digital communication, among other applications, because they are inexpensive real-time reconfigurable devices. because of the high increase in the volume of data used in designs and the large data dependencies in complex computations, researchers are motivated to highlight the need for a shift from the software based implementation of numerical integration to hardware-based fpgas implementations that are much quicker, more efficient, and more reliable. in this paper, different numerical integration implementations are studied, their strategies discussed, findings assessed and recommendations drawn to enable the suggestion of a better way of improving them. a tabular summary of the review is provided to enhance the understanding of the findings of the review and recommendations for each of the implementations. based on the review, it can be deduced that fpgas implementations are faster than software based implementations in c++ and matlab. it is also evident from the review that architectural designs like pipelining and parallelism when employed on fpgas greatly improve the throughput of designs and models which significantly reduce data dependencies. it is recommended that fpga implementation should be employed in the development of numerical integration algorithms due to their low cost, power consumption, small size, and high speed. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 january, 2022 revised 3 april, 2022 accepted 6 april, 2022 keywords: numerical integration field programmable gate array fpga microprocessors http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com file:///c:/users/hp/appdata/roaming/microsoft/word/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 454 specific hardware designs, has recently been shown to improve performance for a variety of computationally intensive applications (wang and ziavras, 2003). the desire to design and implement definite integrals on hardware devices that are portable, fast, and accurate in computation, is an active area of research. various attempts have been made in the literature to develop definite integral solution systems using approaches that are distinct from each other. the attempts made to implement definite integrals in hardware have largely focused on microcontrollers, which are devices that operate sequentially. recent attention has been focused on the idea of implementing definite integral systems on field programmable gate arrays (fpgas) (razak et al., 2017). because of the high increase in the volume of data used in designs and the large data dependencies in complex computations, researchers are motivated to highlight the need for a shift from the software-based implementation of numerical integration to hardware-based fpgas implementations that are much quicker, more efficient reliable, and reconfigurable. they also have the additional feature of circuit design optimization by packages like vhdl. software-based numerical integration implementations are dominant, and with the large increase in the volume of data for processing and the large dependencies on data during computations and processing, there is an urgent need for a shift to hardware-based designs (fpga implementations) for better performance (razak et al., 2017). studies on fpga and microcontroller-based numerical integration are examined one by one in order to identify research gaps that will benefit and strengthen the numerical integration research trend. the goal of the review is to raise awareness among researchers about the need to enhance research in numerical integration by identifying gaps and encouraging the gradual shift from software-based numerical integration towards fpga-based numerical integration so as to take advantage of the exceptional capabilities of the fpgas, which include speed and precision, re-configurability, circuit optimization, parallelism, low power consumption, and, finally, the ability to reduce design latency by improving the overall processing time of a complex operation (razak et al., 2017). the paper is organized into five sections. section one of the paper introduces the paper by presenting a background to the study, motivation, state of numerical integration and the goal of the study is to highlight the need for a shift from microcontroller-based to fpga-based implementations. section two presents a review of related literature. section three examines and discusses different research on microcontroller and fpga-based numerical integration implementations. section four presents a tabular summary of the review of the different implementations of numerical integration. conclusions are drawn in section five, and references are listed at the end. 2. review of related literature the review of related literature begins with an explanation of the concepts of fpgas and microcontrollers, followed by research works on numerical integration. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 455 2.1 field programmable gate arrays (fpgas) an fpga (field programmable gate array) is a semiconductor in which the circuitry can be customized. this allows you to describe exactly which wire (signal) leads where and what operation should be applied to that signal. the quantity of really concurrent instruction executions is not limited by the number of physical cores it has, whereas a traditional processor is limited by its physical capabilities (cong et al., 2018). you can define your own instructions (sub-circuits) using an fpga, which might potentially boost computational speed. because of their speed and low energy consumption, fpgas can outperform microcontroller cpus in numerical workloads. fpgas are also well-known for their high-throughput, lowlatency signal processing capabilities in applications such as real-time audio, video, and data stream processing (elizabeth, 2022). 2.2 microcontroller a microcontroller (mcu for microcontroller unit) is a miniature computer built on a single mos integrated circuit (ic) chip. a microcontroller is a computer that has one or more cpus (processor cores), memory, and programmable input and output peripherals. a microcontroller is related to, but less sophisticated than, a system on a chip in modern terms (soc). a microcontroller may be one of the components of a soc, but it is frequently combined with advanced peripherals such as a graphics processing unit (gpu), a wi-fi module, or one or more coprocessors (raghunathan, 2021). automobile engine control systems, implantable medical devices, remote controls, office equipment, appliances, power tools, toys, and other embedded systems all employ microcontrollers. they make it cost-effective to digitally control even more devices and processes by decreasing the size and cost compared to a system that uses a separate microprocessor (papoutsidakis et al., 2017). 2.3 literature on numerical integration in the study of jandja et al. (2018), the five columns rule in solving definite integration by parts through transformation of integral limits, offers an alternative method for solving definite integration by parts. a function f(x), which is continuous on the closed interval [a, b], serves as the starting point for the definition of the definite integral. the given interval is divided into "n" subintervals, which, while not required, can be assumed to have equal lengths (x). an arbitrary domain value, x i, is chosen in each subinterval, and its subsequent function value, f(xi), is determined. the product of each function value times the corresponding subinterval length is determined, and these “n” products are added to determine their sum (cliffsnotes, 2022). it solves integrals using a tabular integration by parts algorithm with integral limit transformations. the results showed that after transformation, the part-by-part integration formula takes on a new form. the final solutions obtained by this method and the standard technique in calculus textbooks were discovered to be identical. the authors devised the fivecolumn rule to shorten the traditional methods' lengthy procedures (jandja et al., 2018). the following is how each column works: the first column alternates the positive and negative signs, the second column is f(x), and the third column is g'(x), and then its integral lies below it, the fourth column is the lower limit (x = a) and upper limit (x = b), and the fifth column is the transformation of integral limits, i.e. the lower double limit u(a)v(a) and upper double limit u(b)v(b), and the sixth column is the transformation of integral limits (jandja et al., 2018). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com https://history-computer.com/author/elizabeth-milne/ arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 456 yu (2016) investigates two types of definite integrals in his paper "a study of definite integrals using parseval's identity." the fundamental conclusion regarding the summability of the fourier series of a function is known as parseval's identity, after marc-antoine parseval. it is a generalized pythagorean theorem for inner-product spaces from a geometric perspective (which can have an uncountable infinity of basis vectors) (provenzi, 2021). the infinite series expressions of the two types of definite integrals were determined using parseval's identity. for practical calculations, two instances were used. the study's research technique was to uncover solutions using hand computations and then validate them using maple. the research method enables the detection of calculation errors as well as the modification of original thinking paths. when compared to the one obtained by maple, parseval's identity method produced good results. it further stated that maple offers advice and guidance on problemsolving techniques (yu, 2016). gonzalez et al. (2010) provided a new heuristic method for evaluating definite integrals in their paper "definite integrals via the method of brackets." the method of brackets is a technique for evaluating definite integrals over the half-line that was created in the context of evaluating integrals derived from feynman diagrams. a limited set of operating rules are used in this method to turn the integral into a bracket series. this bracket series is evaluated by a second, condensed set of rules, which yields the output as a regular series (gonzalez et al., 2020). despite the fact that the method is heuristic and lacks a rigorous explanation, the researchers believe it is a powerful method of integration. working with and generating results of definite integrals is relatively simple. in methods developed for the evaluation of feynman diagrams, evaluating a definite integral is reduced to solving a linear system of equations with method of brackets and origin. the study described the operating rules and provided various examples to demonstrate the method. the bracket technique simplifies the evaluation of a large class of definite integrals to the solution of a linear system of equations, with the main principle being that any parameter ‘a’ is assigned a bracket. the study presents a powerful approach of integration that is simple to use (gonzalez et al., 2010). an algorithmic way to find definite single and double integrals using simpson's rule has been proposed (selvakumar, 2017). one of the numerical techniques used to calculate the definite integral is simpson's rule. typically, we employ the calculus fundamental theorem to get the definite integral, which requires us to use antiderivative integration techniques. finding the antiderivative of an integral, for example in scientific experiments where the function must be ascertained from the observed values, can occasionally be challenging. therefore, in such circumstances, numerical approaches are utilized to approximate the integral (byjus, 2022). engineers and scientists will benefit from this study since it will make it easier to calculate definite integrals with less calculation time (run time) and storage space. the work highlighted a need to develop a simpson approach that is distinct from the classic simpson method used in literature to solve ordinary differential equations numerically. numerical experiments were conducted after the invention of the new simpson approach to demonstrate the algorithm's validity (selvakumar, 2017). yu (2014) investigated three types of definite integrals in his research, "evaluating some types of definite integrals" using parseval's theorem, infinite series representations of these definite file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 457 integrals were produced, and some examples were presented for practical computations. the work additionally used maple to calculate estimated values of definite integrals in order to verify the results obtained through the application of parseval's theorem to the research findings. according to the findings, the theorem has a wide range of applications and can be used to solve a variety of complex situations (yu, 2014). 3. research in numerical integration numerical integration algorithms were analyzed to establish the nature of the numerical integration method used, as well as the results and recommendations derived from the study. this will allow for the identification of areas where more work is required to strengthen and reposition the development of robust software models and reconfigurable hardware-based solvers with small size, high speed, high accuracy, power efficiency, and low resource utilization to benefit a wide range of complex applications, due to the increasing volume of process data and data dependencies in designs. 3.1 high speed numerical integration using fpga in their study, razak et al. (2017) used fpga to construct four numerical integration algorithms on hardware. the four hardware-based numerical integration methods are left riemann sum (lrs), middle riemann sum (mrs), right riemann sum (rrs) and trapezoidal sum (ts). using the target chip altera cyclone iv fpgas, system performance is assessed in terms of resource usage, clock latency, execution time, power consumption, and computational error. cyclone iv devices are perfect for low cost, small-form-factor applications in the wireless, wireline, broadcast, industrial, consumer, and communications industries because they offer power and cost savings without losing performance, as well as a low cost integrated transceiver option (altera corporation, 2014). the customizable logic block (clb) matrix at the center of field programmable gate arrays (fpgas), a semiconductor device, is coupled by programmable interconnects. after production, fpgas can be reprogrammed to meet specific application or feature needs. fpgas are distinguished from application specific integrated circuits (asics), which are made especially for particular design tasks, by this property. although one-time programmable (otp) fpgas are available, sram-based fpgas, which can be updated as the design changes, are more common (xilinx, 2022). the results of the study indicated that mrs and ts are more precise and error-free. when compared to other types of calculation, fpga computations are the fastest, followed by c++ and matlab computations (razak et al., 2017). 3.2 pipelined fpga implementation of numerical integration of the hodgkinhuxley model in the study of osorio (2016), the hodgkin-huxley model is utilized to describe the onset and propagation of action potentials in neurons' axons. the model consists of a set of nonlinear differential equations that may be solved numerically for a given set of parameters. action potentials in neurons' axons start and spread according to the hodgkin-huxley model. differential evolution techniques frequently work in tandem with numerical integration. double-precision floating-point arithmetic can be used to implement complex functions in modern fpgas with competitive performance and cost (osorio, 2016). a mathematical model that describes the initiation and spread of action potentials in neurons is the hodgkin-huxley http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 458 model, often known as the conductance-based model. an approximate representation of the electrical properties of excitable cells, such as neurons and muscle cells is provided by a set of nonlinear differential equations. it is a dynamical system in continuous time. in order to understand the ionic mechanisms behind the start and spread of action potentials in the squid giant axon, alan hodgkin and andrew huxley developed the model in 1952 (stiles and gray, 2022). the best set of empirical parameters is what optimization aims to achieve. iterations or generations in differential evolution may number in the thousands or millions. for the following generation, new solutions that outperform the prior generation are kept. those who fail the test are eliminated (osorio, 2016). in this case, numerical integration on an fpga was utilized to offer the best parameters at a specific point in order to build a model. according to the findings, fpga-based pipelines improve model speed despite significant data dependencies, lowering latency and increasing throughput. the researchers proposed design efforts that will give a higher performance gap between a hardware implementation and a comparable software implementation due to large data dependencies. they also stated that complex architectures can be mapped on fpgas since they are large enough. large pipelines are required for complex computational models, which can be shared by multiple instances of the optimization algorithm running at the same time. deeper pipelines and higher clock frequencies will necessitate the use of more segment adders and multipliers in future designs (osorio, 2016). 3.3 a hardware intensive approach for efficient implementation of numerical integration for fpga platforms in their research, khursid and mir (2014) employed a one-to-one link between integration algorithms and universal fir filters. the trapezoidal rule for numerical integration was implemented in this study by translating the integrating algorithm onto fir structures. the integration algorithm is implemented using this relationship to produce a structure. however, critical route delays in such systems are common, limiting sampling/throughput rates. concurrency was used at several points throughout the procedure to tackle the problem. independently, the effects of pipelined and parallel structures on speed and power metrics were investigated (khursid and mir, 2014). fpgas enable rapid prototyping of application specific integrated circuit (asic) at low to medium production volumes. because the designimplement-test-debug cycle may take only hours rather than months as with asic, design modifications will be easier. fpgas also have intrinsic advantages such as low power consumption, low cost, ease of modification, real-time processing, and large capacity. furthermore, fpga is distinguished by its flexibility as a result of the predesigned configurable logic blocks (clb) that is used in industrial applications that match the aimed requirements, and the parallel structure that makes it suitable for high-speed applications; it also outperforms microprocessors. furthermore, fpga clock rates are in the hundreds of megahertz range (mhz) (abdelaty et al., 2020). performance can be greatly improved by architectural modifications like pipelining and parallel processing in models, according to a study. the dynamic power dissipation is drastically decreased when all of the structures are run at the same nominal frequency. system tweaks can be used to create low-power designs (khursid and mir, 2014). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 459 3.4 implementation of fractional order integrator/differentiator on field programmable gate array using the grunwald–letnikov concept, rana et al. (2016) proposed a systematic technique for hardware implementation of the basic operators of fractional calculus (fractional integrator and derivative) using a field programmable gate array (fpga) in the labview environment. the fractional order integrator and derivative of sinusoid and square waveform signals were simulated, and hardware implementation results were provided. in system modeling, fractional order calculus has been discovered to be useful. when compared to integer order modeling, fractional calculus modeling is substantially more accurate. the strong match between the simulated and experimental results demonstrated the fpga device's suitability for fractional order control and signal processing applications (rana et al., 2016). a fractional-order integrator, also known as a fractional integrator, is a type of integrator that determines the fractional-order integral or derivative of an input, also known as a differintegral. the parameter of differentiation or integration is a real or complex one. the fractional integrator is helpful in fractional-order control when the output of the control system depends on the history of the system being controlled (krishna, 2011). a toolkit developed transforms labview code into vhdl (very high-speed integrated circuits hardware description language) for fpga processing. the paper recommends future studies to integrate fractional operators with the hardware processes for fractional order control or signal processing applications to enhanced performance (rana et al., 2016). 3.5 solution of definite integrals using functional link artificial neural networks changdar and bhattacharjee (2019) described a method for solving definite integrals using feedforward artificial neural networks in their paper "solution of definite integrals using functional link artificial neural networks." the major goal was to develop a new method based on neural networks that could be used to solve definite integrals in a more efficient and unique way than existing approaches. the integrand was approximated by training the neural network weights using a neural network model based on flann architecture. when compared to other current approaches, the solved examples show that the procedure is effective and practicable in all circumstances. by reducing a well-constructed error function, the definite integrals were solved (changdar and bhattacharjee, 2019). the results showed that the procedure is effective and precise when compared to existing traditional numerical approaches, and that it is well-suited for applications that need the integration of higher order polynomials. although it takes time to set up and acquire results, the research effort provided a fast and reliable technique to integrate higher order polynomials using a robust algorithm. the process needs to be sped up, and the portability of the method and solver also needs to be addressed. this will enable quick and on-the-spot answers to definite integral problems. 3.6 high precision computing of definite integrals with .net framework c# and x-mpir high precision computing of definite integrals with.net framework c# and x-mpir is a study by dzhambov (2014) that is part of a series of publications chronicling the progress of building tools for high precision computations in this environment. an application for realizing arbitrary precision functions and numerical algorithms in a given context, created with the http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 460 most up-to-date state-of-the-art library. the main goal of the research project is to create powerful, mutually supportive computational instruments for dealing with non-trivial problems in a given environment. the program solves infinite integrals with an arbitrary real integer a, or (a,∞). it employs a text form function expression that can include algebraic operations and functions. the application was written in c# with the goal of being as portable as possible (dzhambov, 2014). there is need of hastening the results generation procedure. this can be achieved by implementing it on hardware (fpga) using hardware description language such as vhdl (abdelaty et al., 2020). the researchers also proposed opportunities for further advancement in a variety of approaches, including the use of contemporary processors' multicore architecture for parallel computing. because similar software products are generally built using unix-like systems with specialized hardware, and therefore, wider audience would be interested. 3.7 chaotic firefly algorithm for solving definite integral in their paper "chaotic firefly algorithm for solving definite integral," abdel-raouf et al. (2014) created a firefly algorithm with chaos (ifch) for calculating definite integrals. the improved firefly algorithm with chaos (ifch) solves the problem of concurrent numerical integration calculations in sciences and engineering while also giving adaptive segmentation points. the firefly algorithm is the most recent addition to the swarm intelligence metaheuristics for optimization problems family. the results of the ifch algorithm were compared to those of the monte carlo method, trapezoidal rule, simpson's rule, and midpoint rule. when compared to exact values, the researchers discovered that the ifch algorithm outputs were quite close to the exact values of the specified functions under consideration. this approach has numerous applications and can easily solve a variety of difficult problems (abdel-raouf et al., 2014). 3.8 a chaotic bat algorithm for solving definite integral by combining the bat algorithm with chaos, khalil (2015) improved the bat algorithm for estimating the numerical value of definite integrals. the algorithm is capable of overcoming the problem that older algorithms have with non-uniform segmentation spots. several simulation examples show that the technique can converge to the best solution with excellent accuracy and a high convergence rate. ibach solves the problem of concurrent numerical integration and adaptive segmentation. the bat algorithm's superior performance can be attributed to its search capacity (khalil, 2015). when implemented on hardware (fpga) using hardware description languages such as vhdl, the algorithm is improved due to the parallelism and pipelining inherent in fpga (abdelaty et al., 2020). 3.9 the efficient implementation of numerical integration for fpga platforms the research of hemavathi and ravichanda (2015) is focused on numerical strategies for computing approximation solutions to infinite integrals. these are software-oriented strategies. the researchers believe that a hardware-oriented solution that assesses performance in terms of speed and area is required. integral implementations have long critical path delays, which limit throughput rates. this has been mitigated by architectural changes file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 461 that allowed the structure to run at higher throughput rates while using less space. the trapezoidal rule is used to implement pipelining structures, fine grain pipelined structures, and parallel structures. the method used in this study is mapping the trapezoidal rule onto the fir structure. at the system level, pipelining and parallel processing have been utilized to manage concurrencies (hemavathi and ravichanda, 2015). according to the study, the greater the number of parallel structures, the better the throughput and error rates of the models. further research into architectural changes such as pipelining and parallel processing is recommended to significantly improve performance. 3.10 quick implementation of definite integrals computation with very high precision dzhambov (2017) discussed how to use parallel calculations with two perspective quadrature algorithms in a specific context, namely the.net framework. comparative experiments show that using specific tools from the environment, it is possible to perform effective computations with extremely high precision. this paper describes a portion of the research done to create a tool library for arbitrary precision calculations. the main goal is to demonstrate that tools for solving non-trivial problems with high precision computations can be implemented in a real-world setting, such as desktop computers. it is successful because of the following factors: 1) appropriate quadrature schemes 2) optimization of basic program instruments for high precision computations, and 3) effective implementation of fundamental mathematical functions (dzhambov, 2017). 3.11 numerical simulations and fpga implementations of fractional-order systems based on product integration rules. product integration (pi) rules are well-known numerical algorithms for solving integer and, more recently, fractional order differential equations. the pi rules used to solve fractionalorder systems (fos) have high memory reliance, making their hardware implementation complex and resource-intensive. abdelaty et al. (2020) modified utilized versions of the pi rules to enable digital implementations in their study "numerical simulations and fpga implementations of fractional-order systems based on product integration rules." the predict-evaluate-correct-evaluate (pece) and pi rectangle rules were investigated. fpga implementations of the three pi rules were created using xilinx ise 14.7 on artix 7 kit. the improved throughput for pi rectangular was 128.8 mbits/sec, 129.12 mbits/sec for pi trapezoidal, and 1280 mbits/sec for fractional-order pece (abdelaty et al., 2020). 3.12 strategies for choosing an appropriate numerical method for fpga-based hil yushkova (2021) did research on "strategies for choosing an acceptable numerical method for fpga-based hardware-in-the-loop (hil)" to improve the results of hil techniques by combining field-programmable gate arrays (fpgas), which allow for faster and more accurate real-time simulations. the selection of right numerical approach for implementation is one of the implementation issues. four widely used numerical methods were evaluated for hil performance: first order forward euler, second order adams-bashforth, second order runge-kutta, and fourth order runge-kutta. the simplest methods achieved the best overall http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 462 performance (1st order forward euler and 2nd order adams-bashforth), even though rungekutta methods achieved the highest accuracy when accuracy limiting constraints in real-world environments are considered (yushkova, 2021). 3.13 accelerating interference-based qos analysis of vehicular ad hoc networks for bsm safety applications: parallel numerical solutions and simulations zhao et al. (2021) considered the context of more practical vehicular communication environment: bsm broadcast, asynchronous timing between hidden terminals, nakagami channel fading, and non-homogeneous poisson process vehicle distribution in their study "accelerating interference-based quantity of service (qos) analysis of vehicular ad hoc networks for (broadcasting basic safety message) bsm safety applications: parallel numerical solutions and simulations." the computational complexity of numerical solutions for quantity of service (qos) and capacity metrics is so high that the computation time is unacceptably long. the metrics were evaluated using a combination of numerical integration and a parallel technique. for speeding up the computational process, the monte carlo integration and mpi (message passing interface) methods were used, and the analysis of qos measures was validated (zhao et al., 2021). 4. comparative analysis of different implementations of numerical integral solver numerical integration algorithms are studied and their strengths, weaknesses, and application strategies are deduced and presented in tables 1-3. appropriate recommendations are drawn from each of the algorithms studied to suggest areas that can be improved in order to enhance research in numerical integration. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 463 table 1: fpga-based numerical integral solver implementation summary s/n title stregnth weaknesses application strategy recommendation 1 high speed numerical integration using fpga (razak et al., 2017) able to successfully established that fpga perform better than software based models multiple algorithms: fpgas and software basedmodels. advantages and disadvantages discussed and the choice left open. fpgas and software based designs. mrs, rrs, lrs, tp, c++ and matlab. the choice of an algorithm for a specific usage is determined by type of work to be done. indicated that fpgas implementations are faster than software and hence recommended improvement by using floating points. 2 pipelined fpga implementation of numerical integration of the hodgkin-huxley model (osorio, 2016). use of fpga to reduce data dependencies and increase model performance peculiar application of fpga and numerical integration to a specific model fpga and hodgkin-huxley model numerical integration method the design needs to be generalized or extended to capture more numerical integration methods not just that of hodgkin-huxley model. 3 a hardware intensive approach for efficient implementation of numerical integration for fpga platforms (khursid and mir, 2014). eliminate critical route delays in models using numerical integration not a generalized model design. meant to improve performance of a specific design. fpga implementation using one-to-one relation with fir filter. concurrency can be achieved through pipelined and parallel structures in models. 4 implementation of fractional order integrator/differentiator on field programmable gate array (rena et al. 2016). accurate performance achieved through fpga implementation application of fpga and numerical integration for fractional order control and signal processing applications. fpga in labview environment for fractional order control and signal processing. the researchers recommend future studies integrating the developed fractional operators with the hardware processes. 5 the efficient implementation of numerical integration for fpga platforms (hemarathi and ravichanda, 2015). the design is able to discover that the bigger the number of parallel structures, the better the models' throughput. restricted to the calculation of numerical integration of infinite integrals. fpga implementation, mapping trapezoidal rule onto the fir structure to implement pipelining structures, fine grain pipelined structures, and parallel structures. recommended architectural adjustments such as pipelining and parallel processing to significantly enhance performance. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 464 6 numerical simulations and fpga implementations of fractional-order systems based on product integration rules (abdelaty et al., 2020). improved throughput achieved with the implementations in the model and a reduced memory reliance. specific application of fpga to pi rules used to solve fractional-order systems (fos) used of fpga implementations of fractionalorder systems based on product integration rules recommend modified use of versions of the pi rules to enable digital implementations on fpgas to improve throughput. 7 strategies for choosing an appropriate numerical method for fpga-based hil (yushkova, 2021). achieved performance improvement in runge– kutta,1st order forward euler and 2nd order adams– bashforth numerical methods. restricted to research on strategies for choosing an acceptable numerical method for fpga-based hardware-in-theloop (hil). used fpgabased hardwarein-the-loop (hil) using four numerical integration methods (first order forward euler, second order adams– bashforth, second order runge– kutta, and fourth order runge– kutta.) runge–kutta methods get the highest accuracy among the numerical methods while the 1st order forward euler and 2nd order adams– bashforth have high cost performance indexes. table 2: neural network-based artificial intelligence (ai) numerical integral solver implementation summary s/n title stregnth weaknesses application strategy recommendation 1 chaotic firefly algorithm for solving definite integral (abdel-raouf et al., 2014) has a good convergence rate, precision, robustness and accuracy. initialization delays and takes time to generate results. solves definite integral using improved firefly algorithm with chaos (ifch) can be greatly improved if implemented on fpga using appropriate toolkits. 2 a chaotic bat algorithm for solving definite integral (khalid, 2015) overcome problem of non-uniform segmentation spots in other models. able to converge to the best solution with excellent accuracy and high convergence rate. software based design and takes time to initialize and generate results. solves definite integral using improved bat algorithm with chaos. can be greatly improved if implemented on fpga using appropriate toolkits. 3 solution of definite integrals using functional link artificial neural networks (changdar and bhattacharjee, 2019) efficient, effective and precise, with a well-constructed error function takes time to initialized and generate results used functional link artificial neural networks to perform numerical integration can be greatly improved if implemented on fpga using appropriate toolkits. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 465 table 3: software-based numerical integral solver implementation summary s/n title stregnth weaknesses application strategy recommendation 1 high precision computing of definite integrals with .net framework c# and x-mpir (dzhambov, 2014) powerful, mutually supportive computational instruments for double exponential transformation the approach is for a specific problem. definite integration with .net framework c# and x-mpir. a software based design. initialization delays can be reduced or eliminated by fpga implementation using appropriate toolkits. it can be extended to include more class of definite integrals. 2 quick implementation of definite integrals computation with very high precision (dhambov, 2017) perform effective computations with extremely high accuracy using specific tools of an environment. design for a specific environment. initialization delays and takes time to generate results. used parallel calculations with two perspective quadrature algorithms in a specific context, namely the.net framework can be greatly improved if implemented on fpga using appropriate toolkits 3 accelerating interference-based qos analysis of vehicular ad hoc networks for bsm safety applications: parallel numerical solutions and simulations (zhoa et al., 2021) numerical integration and a parallel techniques were used to reduce computation time delay. restricted to computational complexity of numerical solutions for quantity of service. used monte carlo integration and mpi (message passing interface) numerical integration and parallel techniques can reduce latency in deigns if employed. 5. conclusion this study was able to review different types of numerical integration techniques implemented in software and field programmable gate array (fpga). it is evident from the review that pipelining and parallel processing were the major techniques employed to achieve speed and accuracy, both in software-based and fpga-based numerical integral solvers. numerical integration on fpga-based hardware is becoming more common as researchers devote more time and resources to maximizing the capabilities of fpgas. the ability of fpgas to operate at higher speeds while incorporating numerous pipelining and parallel processing with a high degree of accuracy, low power, and minimum resource utilization has made them the choice of most industries and researchers. the software-based algorithms are the conventional numerical integration approaches that operate sequentially (programmes that follow sequence of instructions). different researchers found out that such algorithms require improvement in terms of power consumption, speed, latency, throughput, accuracy, size reduction, and resource utilization. numerical integrators developed on fpgas are shown to employ pipelining and parallel processing to greatly speed up complex processes. the research trend in numerical integrals needs to tap into these functionalities coupled with the re-configurability of the fpgas. hence, fpga implementation should be employed in the development of numerical integration algorithms due to their low cost, power consumption, small size, and high speed. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 466 references abdel-raouf, o., abdel-baset, m. and el-henawy, i. 2014. chaotic firefly algorithm for solving definite integral. international journal of information technology and computer science, 6(6): 19–24. altera corporation. 2013. cyclone iv fpga device family overview. cyclone iv device handbook, (1). retrieved from https://www.digikey.com/en/datasheets/intel-fpgasaltera/intelfpgasaltera-cyclone4-handbook accessed on 2/9/2022. abdelaty, am., roshdy, m., said, la. and radwan, ag., 2020. numerical simulations and fpga implementations of fractional-order systems based on product integration rules. ieee access, 8:102093-102105. byjus. 2022. simpson rule. retrieved from https://byjus.com/maths/simpsons-rule/ accessed on 2/9/2022 changdar, s. and bhattacharjee, s. 2019. solution of definite integrals using functional link artificial neural networks. retrieved from http://arxiv.org/abs/1904.09656, 2019 accessed on 12/12/2021. cliffsnotes. 2022. definite integral. retrieved from https://www.cliffsnotes.com/studyguides/calculus/calculus/integration/definite-integrals accessed on 2/9/2022. cong, j., liu, b., neuendorffer, s., noguera, j., vissers, k. and zhang, z. 2011. high-level synthesis for fpgas: from prototyping to deployment. ieee transactions on computeraided design of integrated circuits and systems, 30(4): 473-491. dzhambov, v. 2014. high precision computing of definite integrals with .net framework c# and x-mpir. cybernetics and information technologies, 14(1): 172–182. dzhambov, v. 2017. quick implementation of definite integrals computation with very high precision. journal of information technologies and control, 3: 20-24., doi: 10.1515/itc-20170030. gonzalez, i. and moll, vh. 2010. definite integrals by the method of brackets. part 1. advances in applied mathematics, 45(1): 50–73. gonzalez, i., jiu, l. and moll, vh. 2020. an extension of the method of brackets, part 2, open mathematics, 18(1): 983-995. retrieved from https://doi.org/10/1515/math-2020-0062 accessed on 2/9/22022. elizabeth, m. 2022. what is fpga and how does it work? retrieved from https://historycomputer.com/fpga-field-programmable-gate-array/ accessed on 10/02/2022. jandja, m. and mohammad, l. 2018. the five columns rule in solving definite integration by parts through transformation of integral limits. journal of physics: conference series 1028, file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com https://www.digikey.com/en/datasheets/intel-fpgasaltera/intel-fpgasaltera-cyclone4-handbook%20accessed%20on%202/9/2022 https://www.digikey.com/en/datasheets/intel-fpgasaltera/intel-fpgasaltera-cyclone4-handbook%20accessed%20on%202/9/2022 http://arxiv.org/abs/1904.09656 adamu et al: implementation of numerical integration using field programmable gate arrays and microcontrollers: a review. azojete, 18(3):453-468. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 467 2nd international conference on statistics, mathematics, teaching and research, 9-10 october, makassar, indonesia, 012109: 1-7. hemavathi, h. and ravichandra, v. 2015. the efficient implementation of numerical integration for fpga platforms. international journal of ethics in engineering & management education, 2(7): 34-38. khalil, aw. 2015. chaotic bat algorithm for solving definite integral. international journal of computers and technology, 14(4): 5592-5598. khurshid, b., and mir, rn. 2014. a hardware intensive approach for efficient implementation of numerical integration for fpga platforms. 27th international conference on vlsi design and 13th international conference on embedded systems, 312-317. krishna, bt. 2011. studies on fractional order differentiators and integrators: a survey of signal processing, 91(3): 386-426. millenium circuits limited. 2022. field programmable gate arrays (fpga) vs. microcontroller – what’s the difference? retrieved from https://www.mclpcb.com/blog/fpgavs-microcontroller/ accessed on 2/9/ 2022. osorio, rr. 2016. pipelined fpga implementation of numerical integration of the hodgkinhuxley model. ieee 27th international conference on application-specific systems, architectures and processors (asap), 202-206. papoutsidakis, m., tanwar, r., chatzopoulos, a. and tseles, d. 2017. custom made embedded automation systems for smart homes-part 2: the implementation. international journal of engineering, applied science and technology, 2(5): 16-19. provenzi, e. 2021. from euclidean to hilbert spaces: introduction to functional analysis and its applications. new york, john wiley and sons. razak, fna., talip, msa., yakub, mfm., khairudin, asm., izam, tftmn. and zaman, fhk. 2017. high speed numerical integration algorithm using fpga. journal of fundamental and applied sciences, 9(4): 131-144. raghunathan, kr. 2021. history of microcontrollers: first 50 years. ieee microcontrollers, 41(6): 97-104. rana, kps., kumar, v., mittra, n. and pramanik, n. 2016. implementation of fractional order integrator/differentiator on field programmable gate array. alexandria engineering journal, 55 (2): 1765-1773. stiles, pj. and gray, cg. 2021. improved hodgkin–huxley type model for neural action potentials. european biophysics journal, 50(6): 819-828. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):453-468. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: msmajemusa4@gmail.com 468 wang, x. and ziavras, sg. 2003. parallel lu factorization of sparse matrices on fpga‐based configurable computing engines. concurrency and computation: practice and experience, 16(4): 319-343. xilinx 2022. field programmable gate array (fpga), https://www.xilinx.com/products/ silicon-devices/fpga/ what-is-an-fpga.html accessed 2nd september, 2022. yu, c. 2014. evaluating some types of definite integrals. american journal of software engineering, 2(1): 13-15., doi: 10.12691/ajse-2-1-3. yu, c. 2016. a study of definite integrals using parseval ’ s identity. international journal of scientific research in computer science, engineering and information technology, 1(2): 28– 35. yushkova, m., sanchez, a. and de castro, a. 2021. strategies for choosing an appropriate numerical method for fpga-based hil. international journal of electrical power and energy systems, 132: 107186. zhao, j., zhou, h., wang, y., lu, h., li, z. and ma, x. 2021. accelerating interference-based qos analysis of vehicular ad hoc networks for bsm safety applications: parallel numerical solutions and simulations. vehits, 600-610 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/msmajemusa4@gmail.com arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):427-434 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 427 effects of orientation on the properties of fan palm fibre reinforced sheet o. a. adeleke1, b. yinusa2,3*, m. a. azeez2 and a. g. arisoyin2 1department of civil engineering, university of ilorin, nigeria 2department of agricultural and bio-environmental engineering, federal college of agriculture, akure, nigeria 3department of agricultural and environmental engineering, university of ibadan (research scholar) *corresponding author's email address: yinusa_babatunde@yahoo.com article information submitted 24 november, 2023 revised 19 february, 2024 accepted 25 february, 2024 keywords: orientation fan palm fibre rsm compressive strength flexural strength abstract in this research, the effect of orientation of the strength of fan palm fibre reinforced sheets was investigated. the material used was fan palm fibre whose length varies from 0.8 to 1.7m with an average bulk density of 1.133g/cm3, specific gravity of 0.46 and moisture content (mc) of 7.40%. and the mould used was a wooden mould of 300×300×9 mm. the fibre was soaked in both water and cement slurry for 24 hours and 7 days. soil sieve analysis was carried out using astm standard and curing was done for 28 days. the percentage of fibre in the sampled reinforce sheet was between 1-3% at various orientations (0, 30, 60° and 2d). the properties examined were water absorption (wa), compressive strength (cs) and flexural strength (fs). data analysis was done using response surface methodology (rsm). the results showed that the reinforced sheets with long fibre of 1, 2 and 3% have wa of 5.76, 3.72 and 5.05% respectively. while those with short fibre of 1, 2 and 3% have 6.87, 7.36 and 7.75% respectively. the cs of the reinforced sheets of 1, 2 and 3% fibre at 0, 30, and 600 orientations were 6.9568, 8.0779, 7.2330; 3.2870, 6.6764, 7.355; and 3.0592, 5.3215, 3.9090 n/mm2 respectively and the fs results were also observed. the cs and fs of reinforced sheets at 00 and 300 fibre orientations seems to be the best. 1.0 introduction over the years steel has been the dominating material used as reinforcement in concrete and mortar in the construction industries. since then the cost of steel has continued to rise, this has led to increase in the cost of production of structural members. asbestos cement sheet was introduced as an alternative to corrugated sheet because it does not suffer atmospheric corrosion and it is also cheaper. but asbestos was discredited in 1970s because of its extreme fineness; tiny asbestos fibres are easily suspended in the atmosphere and prolonged inhalation of these fibres results into a form of pneumoconiosis known as asbestosis which also increases the incidence of cancer of the lungs encyclopedia americana (1829). two decades ago, asbestos was the major source of reinforcement in the fibre cement industries but as a result of the adverse effect, it was replaced with many other fibres, from glass, steel, synthetics and natural fibres. fan palm is the tallest indigenous plant that is abundant and characterizes all types of savannah. the wood is moderately heavy and brown with black fibre (mcholam, 2001). it can tolerate high temperature and resists decay for at least 25 years. its length varies over a wide range of 5-90 cm with cross sectional area of 4.368 mm2 (okeola, 1989). fan palm has a surface area of 163.27 and 80.25 mm2 for the fruits and seeds respectively (yalcin and ayse, 2016). african fan palm has a typical diameter of 40-50 cm as opined by tropical plants (2024). osibodu (1986) observed that a single strand of fan palm fibre has a modulus of elasticity of 14.44 n and that ultimate tensile strength of 280.3 n/mm2. okeola (1989) researched on the pull-out strength of matrix or the anchorage bond between the fan palm fibres and the cement http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):427-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 428 paste and was calculated to be 1.92 n/mm2. more so, the flexural strength of fan palm fibre of 2.15 n/mm2 was reported by okeola (1989). the arrangement of fibres in a matrix has been proved (bryan, 1986) that it affects the crack opening and propagation, and substantially improve the material toughness and when the fibres are not aligned in the direction of the principal tensile strain, fracture increases. orientation is very important in design of composite materials because of anisotropy’s effect. based on this premises, this paper looked at the effect of orientation on the strength of fan palm fibre reinforced sheets. 2.0 materials and methods 2.1 sample materials fan palm fibre was used to make the reinforce sheets. it has a length of 0.8-1.7 m it is as shown in figure 1. fan palm was bought from sabo market ilorin, kwara state, nigeria. and it was transported to the workshop where it was treated and the fibres were removed by beating and scraping. figure 1: fan palm trees 2.2 mechanical and physical properties of fan palm a. bulk density the average bulk density of fan palm was 1.133 g/cm3. the bulk density was determined using astm standard. b. specific gravity the specific gravity was determined using equation (1). and is the ratio of the fibre in the sun (air) to the weight of water occupying the equal volume of that fibre. an average specific gravity of 0.46 was observed. specific grav. = (1) c. moisture content moisture content of the sample material was determined using oven-drying method and as given by paes 219, (2004) as given in equation (2): mcwb = 𝑊1−𝑊2 𝑊2 × 100 (2) where, mcwb = moisture content, %; w1 = initial mass of the sample, g; w2 = final mass of the sample, g. water absorption (w.a): water absorption was determined using equation 3. w.a = × 100, % (3) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adeleke et al: effects of orientation on the properties of fan palm fibre reinforced sheet. azojete, 20(2):427-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 429 where, weight of saturated samples = ws (g); weight of oven dry samples = wo (g) 2.3 grain size analysis the sample sand was dried in the oven-drying machine for 24 hours and sand was weighed and recorded along with the sizes of the sieves as the aperture decreases in size. the sample was shaken using sieve shaker for few minutes, and then each sieve was weighed and recorded with the retained sand. the percentage passing and retained was calculated based on the total weight of the sample. the result was showed in tables 1 and 2 and the weight (wt) of the sharp sand used was 1000 g. table 1: grain size analysis sieve size, mm wt of empty sieve wt of sieve + retained sand (g) wt of retained sand (g) 4 554 557 3 3.35 454 468 14 2.36 480 490 10 1 522 583 61 0.5 498 737 234 0.4 491 593 102 0.25 470 846 376 0.063 302 462 160 pan 275 310 35 table 2: grain size analysis sieve size, mm % passing % retained cumulated % retained 4 94.4 0.3 0.3 3.35 98.3 1.4 1.7 2.36 97.3 1 2.7 1 91.2 6.1 8.8 0.5 67.3 23.9 32.7 0.4 57.1 10.2 42.9 0.25 19.5 37.6 80.5 0.063 3.5 16 96.5 pan 0 3.5 100 2.4 preparation of constituent materials and production of fan palm fibre reinforced composite a. defibering the removal of fibres was done manually with the aid of knife, cutlass and club. the fibre were scraped and brushed thoroughly and carefully to remove all the deleterious lignin content which will affect the interfacial bond between the fibres and the matrix. b. mix proportion the ratio of cement to sand is 1:2 and the water cement ratio is 0.5, the fibre content used ranges from 1 percent to 3 percent by weight of the cement. c. mixing and casting the quantities of each material used were first weigh using weighing balances. the cement and the sand were mixed on a flat board using hand trowel, the mortar was thoroughly mixed as water was added proportionally to satisfaction. wooden moulds of 300 x 300 x 9 mm (figure 2) were used for the casting. the moulds were lubricated to enhance easy removal set composites from the moulds. about one third of the overall depth of the mould was compacted http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):427-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 430 with the mortar serving as the cover before the fibres were arranged at different angles. the fibres were covered and compacted again to prevent voids and honey combs. the cubs were made using mould 40 x 40 x 40 mm containing varied percentages of short fibres ranging from 1-3 % both the cubes and the flat sheets were removed from the mould after 24 hours. figure 2: moulds and arrangement of fibre (the figure was taking with black and white camera) d. orientation orientations of the fibres were 00,300, 600 and 2d which is the discontinuous fibres or short fibres. the control experiment was without fibre and fibre orientation e. curing curing is the process of hydration in which a concrete composite gained strength. curing was done by immersing the composites in water for 28 days after which they were kept to dry, getting them ready for testing. the flexural and compressive strengths were determined using universal testing machine (testometric) at university of ilorin. 3.0 results and discussion the mean compressive strength of 6.9568, 8.0778 and 7.2330 n/mm2 at 1 % fibre content were obtained for the fan palm fibre reinforced sheets at fibre orientations of 00, 300 and 600 respectively as showed in table 3. while 3.2870, 6.6764 and 7.355 n/mm2; 3.0592, 5.3215 and 3.9090 n/mm2 where obtained at 2 and 3% fibre content respectively (table 3). more so, the mean flexural strength of 8.58, 7.84 and 7.23 n/mm2 at 1% fibre content were obtained for the fan palm fibre reinforced sheets at fibre orientations of 00, 300 and 600 respectively as showed in table 4. while 3.29, 5.42 and 7.12 n/mm2; 1.67, 2.59 and 1.96 n/mm2 where obtained at 2 and 3 % fibre content respectively (table 4). table 5 showed that fan palm fibre reinforced sheets with long fibre of 1, 2 and 3 % have water absorption of 5.76, 3.72 and 5.05 % respectively. while those with short fibre of 1, 2 and 3 % have 6.87, 7.36 and 7.75 % respectively. 3.1 the effect of orientation and fibre percentage on compressive strength of fan palm fibre reinforced sheet. the mean compressive strength obtained varies from 6.9568 to 8.0778 n/mm2 from different fibre orientations as showed in table 3, which were higher than those values obtained by anaidhuno et al. (2017) and this variation may be due to crops’ properties because different fibres were used. the effects of fibre orientations and percentage of fibre were significant on compressive and flexural strength (p < 0.05) as shown in table 6 because the compressive strength increases with increase in fibre orientation but decreases with increase in percentage of fibre in the fan palm fibre reinforcement sheets and this was depicted in the response surface plot of the relationship as shown in figure 3. more so, the model that gave the best fit was a linear relationship as shown in equation (4). however, the goodness of fit for the model was file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adeleke et al: effects of orientation on the properties of fan palm fibre reinforced sheet. azojete, 20(2):427-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 431 expressed by the coefficient of determination (r2) of 0.7177, which suggest that, the model could explain 71.77 % of the variability in the response and the model satisfies lack of fit test. 3.2 the effect of orientation and fibre percentage on flexural strength of fan palm fibre reinforced sheet table 4 showed the average flexural strength of fan palm fibre reinforced sheets at different orientation degrees and the values were more than 2.15 n/mm2 reported by okeola (1989). and this difference may be due to fibre orientation considered during this research which was reported in okeola (1989). however, the result shows that, flexural strength decreases with in decrease in fibre percentage but increases with increase in degree of orientation of fibre in the sheets as is shown in figure 4, and the relationship was significant (p < 0.05) as it is shown in table 7 and the model that gives the best fit is a linear model. the goodness of fit for the model was expressed by the coefficient of determination (r2 = 0.8720). however, equation (5) presented the interaction between flexural strength, orientation of fibre and fibre percentage (amount). 3.3 the effect of orientation and fibre percentage on water absorption of fan palm fibre reinforced sheet. the mean water absorption of the reinforced sheets ranges from 3.72 to 7.75%. this was higher than 66.50 and 63.2% reported for coir and palm kernel (gram, 1983). the little variation could be due to adequate strength properties embedded in the fibre orientation, which could be related to the mechanical and physical properties of fan palm fibre. however, the water absorption decreases with increase in fibre percentage but increases with increase in degree of orientation of fibre in the fan palm fibre reinforced sheets. the mathematical expression in equation (6) shows that a relationship occurs between the water absorption, fibre orientation and percentage of fibre. however, the effects of fibre orientation and percentage of fibre on water absorption is not significant (p > 0.05) (table 8) and the model that gives the best fit is a linear relationship. the coefficient of determination r2 was found to be 0.4445, indicating that the relationship between the three variables (predictors and response) is weak as is shown in figure 5. table 3: the average compressive strength at different orientation of fibre arrangement fibre orientation mean compressive strength @ 1% fibre mean compressive strength @ 2% fibre mean compressive strength @ 3% fibre 00 6.9568 3.2870 3.0592 300 8.0778 6.6764 5.3215 600 7.2330 7.355 3.9090 mathematical models 1. compressive strength = 0.029*orientation -1.66*fibre + 8.22431 (r2 = 71.77%) (4) 2. flexural = 0.0153*orientation 2.9050* fibre + 10.4261 (r2 = 87.20 %) (5) 3. water absorption = 0.41011* orientation 8.78375*fibre + 62.10558 (6) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):427-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 432 table 4: the average flexural strength at different orientation of fibre arrangement fire orientatio n mean flexural strength @ 1% fibre mean flexural strength @ 2% fibre mean flexural strength @ 3% fibre 00 8.58 3.29 1.67 300 7.84 5.42 2.59 600 7.23 7.12 1.96 table 5: the average water absorption at different orientation of fibre arrangement sample of long fibre % of fibre % of absorption a 1 5.76 b 2 3.72 c 3 5.05 sample of short fibre % of fibre % of absorption a 1 6.87 b 2 7.36 c 3 7.75 table 6: anova on the effect of orientation and fibre percentage on compressive strength of fan palm fibre reinforced sheet source ss df ms f-value p > f remark model 21.09 2 10.54 7.63 0.0225 *sig a 4.50 1 4.50 3.25 0.1214 b 16.59 1 16.59 12.00 0.0134 resid. 8.30 6 1.38 cor t. 29.39 8 *significant @ p < 0.05 table 7: anova on the effect of orientation and fibre percentage on flexural strength of fan palm fibre reinforced sheet. source ss df ms f p > f remark model 51.91 2 25.96 20.44 0.0021 *sig a 1.28 1 1.28 1.01 0.354 b 50.63 1 50.63 39.86 0.0007 residual 7.62 6 1.27 cor t. 59.53 8 *significant @ p < 0.05 table 8: anova on the effect of orientation and fibre percentage on water absorption of fan palm fibre reinforced sheet source ss df ms f p > f remark model 1828.18 2 914.09 2.0 0.229 *not sig. a 1210.94 1 1210.9 2.6 0.164 b 617.23 1 617.23 1.3 0.297 residual 2283.25 5 456.65 cor total 4111.43 7 not significant @ p < 0.05 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adeleke et al: effects of orientation on the properties of fan palm fibre reinforced sheet. azojete, 20(2):427-434. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 433 figure. 3: surface response plot of factors on compressive strength figure 4: trend of flexural strength due to fibre orientation and percentage in reinforced sheets figure 5: trend of water absorption due to fibre orientation and percentage in reinforced sheets 4. conclusion from this study, three properties of the reinforced sheets (water absorption, flexural strength and compressive strength) were examined. and the followings were concluded; http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):427-434. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yinusa_babatunde@yahoo.com 434 1. the effects of fibre orientation and percentage of fibre on water absorption is not significant at p < 0.05. and water absorption decreases with increase in fibre percentage but increases with increase in degrees of orientation of fibre in fan palm fibre reinforced sheets 2. flexural strength decreases with in decrease in fibre percentage but increases with increase in degrees of orientation of fibre in the sheets and the relationship was significant at p < 0.05. 3. the effects of fibre orientations and percentage of fibre were significant on compressive at p < 0.05 and compressive strength increases with increase in fibre orientation but decreases with increase in percentage of fibre in the fan palm fibre reinforcement sheets. 4. more so, the compressive and flexural strength of the reinforced sheets at 00 and 300 fibre orientations seems to be the best. it is therefore, recommended that fibre reinforced sheets should be made using 0° and 30° fibre orientation. 5. acknowledgement we want to appreciate god and our colleagues who have made this research work a success. thank you all. references anaidhuno, up., edelugo, so. and nwobi-okoye, cc. 2017. evaluation of the mechanical properties and simulation of sisal/jute hybrid polymer composite failure in automobile chassis panel. international organization of scientific research, 7(9): 56-64. bryan, h. 1986. engineering composite materials. institute of materials, london., pp. 65-67. gram, he. 1983. durability of natural fibres in concrete. report no. 1, swedish cement and concrete research institute, stockholm, pp. 255. mcholam, a. 2001. agro forest data base, vol 2. publication of world agro-forest center, nairobi, kenya., p. 2. montgomery, dc. 2005. design and analysis of experiments: response surface method and designs. new jersey: john wiley and sons, pp. 167. okeola, og. 1989. property of fan palm fibre reinforced cements composite, b.eng. project, civil engineering department, university of ilorin, pp 5-14. yalcin, c. and ayse g. 2016. dimensional specific physical properties of fan palm fruits, seeds and seed coats. international agrophysics, 30(3): 301-309. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):741-750 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 741 original research article modification, fabrication and performance evaluation of insulated box for post-harvest handling of fish s. a. atanda, a. o. anifowoshe*, m. o. oladeinde, q. a. olumoh, i. o. udefi and p. o. pessu nigerian stored products research institute, yaba, lagos. *corresponding author’s email address: olajuwonakeem22@gmail.com 1.0 introduction in fish industries, the high perishability of products makes them spoil almost immediately once harvested, if not properly handled, transported and stored (akinete et al., 2007; agbon et al., 2002). nigerians are large consumers of fish and it has remained one of the main products consumed in terms of animal protein (pessu et al., 2016). a major concern is the waste occurring in most distribution chain that not only bring loss of income to fishermen and fish traders, but also contribute to food insecurity (tsado et al., 2012; towers, 2011). in order to reduce these losses, fresh fish storage time is extended by avoiding damage and bruises by chilling with ice as soon as possible both on board and at the shore (obodai et al., 2009). transportation of the harvested fish to the market or processing centers with the fish and ice in the same container becomes necessary because ice is used as chilling substance to keep the temperature of fish lower than ambient temperature. in order to reduce the melting of ice, an insulated box was desired (sormin et al., 2016). insulated boxes are made of an insulating material that is best packed between two layers of durable, waterproof, non-absorbent plastics. a good insulator will maintain the inner temperature of the insulated box for a long time. article information abstract in order to address the challenges associated with postharvest handling of fresh fish, nigerian stored products research institute (nspri) developed an insulated transportation mechanism named ice fish box™ which has a capacity of 18 kg of fish and ice. however, capacity and ease of movement was encountered in the developed box leading to modification using a smaller box (inner box) of dimension 495 mm×340 mm× 340 mm fitted into a bigger box of dimension 540 mm×360 mm× 360 mm and a trolley on wheels using human muscle power for ease of movement. the construction was carried out using standard procedures and all materials used were sourced locally. results of its performance tests indicated that the modified box can carry approximately 60 kg of fish and ice at full load and the trolley can carry load of up to 120 kg of stacked boxes and swerves easily at angle 45º. it is expected that these modifications would allow for more storage of fish and ease movement on all terrains as handlers mostly women find it almost difficult in moving the earlier designed insulated box around. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 19 april, 2022 revised 30 september, 2022 accepted 6 october, 2022 keywords: ice fish box manual modified handlers transportation tires http://www.azojete.com.ng/ mailto:olajuwonakeem22@gmail.com mailto:olajuwonakeem22@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):741-750 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 742 nigerian stored products research institute (nspri) developed a technology for transportation, storage and distribution of fresh fish in 2014. it was a portable, semi-air-tight lagged-coolant system with an effective cooling capacity due to uniform coldness distribution within the box. the developed box was insulated/lagged with polyurethane material placed in between two boxes of different dimensions with 490 mm x 290 mm x 200mm and 470 mm x 280 mm x 190 mm respectively and has a capacity of 18 kg when fully loaded. additionally, the developed box has hole drilled at the center of it and a flexible pipe was connected to it which serves as drainage for melted ice and slime. a study by pessu et al. (2016) showed that the 18 kg capacity box preserved clarias gariepinus l and oreochromis niloticus l. for 36 hours and 42 hours respectively. the key parameter assessments were found to be within the acceptable limit. however, it was found that the hole in the insulated box was not effective enough and this directly aid speedy defrosting of ice as well as soaking of fish in the box. in addition, the capacity of the box compared to quantity of fish that was available for transportation was low. in the year 2018, feedbacks received from most users of the developed box and recommendation by ishola et al. (2015), necessitated the idea of modifying the design. therefore, the aim of this study was to modify the insulated box by increasing its holding capacity, rechanneling the drainage hole to increase outflow of melted ice and also to design and fabricate a trolley for easy carriage of the developed box with suitable materials. 2.0 materials and methods 2.1 design and fabrication protocol the design and fabrication was based on the need for increased capacity, ease of movement and better drainage over the previous design. this modification was carried out in 2019 at nspri lagos zonal office. all materials used were sourced from mushin, oyingbo and lagos island lagos state. these includes plastic boxes, isocyanate, resin, mild steel angle rods (0.5mm), steel flat bars (0.5mm), round galvanized steel pipe (0.5 mm), swivel and static caster solid tires (10 cm dia), plastic board (3mm thick), glue, rivets. the modified box comprised of smaller plastic box (495 mm ×340 mm ×340 mm) fitted within a bigger plastic box (540 mm×360 mm ×360 mm) with a holding volume of 60 l and the space between the boxes was filled with polyurethane. equal volume of liquid resin and isocyanate (1 l) was mixed and was transferred within 20 seconds of mixing into space between the boxes. mechanical agitation was ensured for even spread of the mixture resulting in a solid mass of polyurethane as the insulating material in such a way that insulator was 22 mm wall to wall. extruded polyurethane was scrapped followed by riveting a plastic board to serve as cover for the space left by the inner box to the outer box. the lid of the box was insulated with polyurethane of 10 mm thickness and covered using plastic board. subsequently, a hole was drilled at one side of the box with an affixed flexible pipe (2 mm in diameter) at an angle of 5o to promote faster flow of wastewater. figures 1 and 2 illustrated the earlier design and the new design respectively while figure 3 shows the flow chart of the process involved in producing an insulated box. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:olajuwonakeem22@gmail.com atanda et al: modification, fabrication and performance evaluation of insulated box for post-harvest handling of fish. azojete, 18(4):741-750. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 743 figure 1. illustration of the earlier design showing the drainage at the center of the box. figure 2. illustration of the modified design showing the drainage at the center of the box. figure 3. flow chart showing process followed to producing an insulated box. box in box 50l in 60l • container formation of insulator in-between the boxes, by introduction of resin and isocyanate • resin and isocyanate drainage hole • drilling insulating the box lid and other finishing insulated box http://www.azojete.com.ng/ mailto:olajuwonakeem22@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):741-750 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 744 2.2 trolley design 2.2.1 design principles-human factor push forces and other human capacities and limitations were put into consideration and assumptions are made as a design guide. these included weight of the trolley (trolley should be 15% of the gross weight of the expected load), frame supporting the caster wheel must not bend to allow the wheel to swivel easily and the handle of the trolley to be held by a mover for easy of movement of the trolley. (iso 11228, 2003,2005) in a stepwise manner, the length and width of the box the trolley is to carry was measured to have the required dimensions and clearance for calculating other parameters for the frame. designing of frame main goal is to minimize its weight, maximize its strength and rigidity while maintaining a high-level comfort. having got the required dimension, the thickness of the angle bar is required. also, caster wheel of diameter 200 mm was chosen which is as described in trolley design guide to accommodate larger weight. 2.2.2 design criteria fundamentally, factor of safety of the trolley must be defined and must be respected always for the frame. the maximum allowed stress, 𝑠𝑎𝑑𝑚, was calculated considering the material’s yield stress,𝑠𝑒, and the trolley safety factor (carlos, 2018). 𝑠𝑎𝑑𝑚 = 𝑠𝑒 𝑛 , where 𝑛 = 𝑓𝑎𝑐𝑡𝑜𝑟 𝑜𝑓 𝑠𝑎𝑓𝑒𝑡𝑦 (1) however, assumed good factor of safety ranges between 2 and 4 and the framing material which is astm a36 mild steel has yield stress of 36300 psi. 𝜎𝑎𝑑𝑚 = 36300 3 = 9075𝑝𝑠𝑖 ~ 62.57 𝑁 𝑚𝑚2 (2) 2.2.3 design calculations the design calculations are based on kaustubh et al. (2015) and shubham et al. (2018) work. the frame length as measured was 520 mm and width 365 mm which is to directly carry a box when fully loaded with fish and ice of total weight w = 80𝐾𝑔 ~ 784.5n which is radially a downward force that causes the frame to bend, hence we find the thickness of the angle bar used for the frame. figures 4, 5 and 6 show the load diagram, shearing force diagram and bending moment calculation respectively used for the design. figure 4. load diagram load (f)= 80𝑘𝑔 ~ 784.5𝑁 (3) 𝑅𝐴and 𝑅𝐵 = vertical reaction at and b respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:olajuwonakeem22@gmail.com atanda et al: modification, fabrication and performance evaluation of insulated box for post-harvest handling of fish. azojete, 18(4):741-750. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 745 to determine the support reaction taking moment at a, 𝑀𝐴 = 0 therefore, (784.5 ∗ 50.8) + (784.5 ∗ 314.2) − (𝑅𝐵 ∗ 365) = 0 (4) 286342.5 365 = 𝑅𝐵 = 784.5 summation of all vertical forces was 0. i.e 𝑌 = 0 𝑅𝐴 + 𝑅𝐵 = 1569 (5) 𝑅𝐴 = 784.5 load on the wheels, 𝑅𝐴1 = 𝑅𝐴2 = 𝑅𝐴 2 = 784.5 2 = 392.25𝑁 (6) for the fixed tires. 𝑅𝐵 = 784.5𝑁 figure 5. shear force diagram shearing force calculation shear force (sf) at a = 784.5 sf at 𝐶 = 784.5 − 784.5 = 0 sf at 𝐷 = 784.5 − 784.5 − 784.5 = −784.5 sf at 𝐵 = 0 bending moment calculation 𝑀𝐴 = 0 𝑀𝐶 = 784.5 ∗ 50.8 = 39852.6𝑁𝑚𝑚 𝑀𝐷 = (784.5 ∗ 314.2) − 784.5 ∗ 263.4 = 39852.6𝑁𝑚𝑚 𝑀𝐵 = 0 figure 6. bending moment diagram http://www.azojete.com.ng/ mailto:olajuwonakeem22@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):741-750 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 746 maximum bending moment, m = 39852.6𝑁𝑚𝑚 sectional modulus for square pipe or tube was assumed 𝑍 = 𝑏4 − ℎ4 6𝑏 (7) = 50.84 − ℎ4 304.8 and 𝑍 = 𝑀 𝑠𝑎𝑑𝑚 = 637.64𝑚𝑚3 (8) therefore, 194352.67 = 50.84 − ℎ4 now, ℎ4 = 50.84 − 194352.67 = 6465350.1396 then, ℎ = √6465350.1396 4 = 50.42𝑚𝑚 wall thickness of angle, 𝑡 = 𝑏 − ℎ 2 (9) = 50.8 − 50.42 2 = 0.2𝑚𝑚 standard value for angle thickness of 0.5 mm gauge was used for this work. 2.2.4 design layout the layout is a three-wheeled which can be used as suited for in the two configurations of three wheeled vehicle (delta and tadpole configurations). the design outline of trolley is shown in figure 7. figure 7. design outline of the trolley 2.3 performance test 2.3.1 drainage testing the drainage of the modified insulated box was tested with known amount of water poured in the box and the time taken for complete draining of the water was noted and compared to the earlier design. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:olajuwonakeem22@gmail.com atanda et al: modification, fabrication and performance evaluation of insulated box for post-harvest handling of fish. azojete, 18(4):741-750. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 747 2.3.2 no load and capacity testing no load test was carried out as described by ishola et al. (2015), ice blocks were purchased at abule oja, lagos state and transported to nspri lagos zonal office fish processing center. measured quantity of crushed ice were introduced into the modified insulated box and immediately transferred outside the fish processing center. ambient temperature and relative humidity were recorded using digital data logger and the capacity of the modified insulated box was determined. 3. results and discussion 3.1 modified box the modified box holds approximately 60 kg of ice as compared to the earlier design that can take approximately 18 kg of ice. also, it was observed that the draining efficiency of the modified box was better than the earlier design; 5 l of water poured in the modified box took 23 min 42 sec to drain completely compared to 50 min 25 sec observed in the earlier design with retention of 850 ml of water. this was due to change in the position of the drain spot of the modified box and slanting of the box in contrast to the earlier box in which drip hole was located in the middle of the box and elevated. 3.2 no load test in order to test the insulating capacity of the modified box, the box was put through a noload test experiment using crushed ice. 59 kg of crushed ice was introduced and placed in the open at the fish processing center nspri lagos office at an ambient temperature of 28.8 ºc and 74.6 % relative humidity. the ice melted completely at 96 hours in which amount of ice after 24 hours of sampling was carried out. figure 10 represents no load test parameters including temperature, relative humidity and quantity of ice that remained in a 24hour sampling period while figure 11 shows the box fully loaded with crushed ice. figure 10. no load test parameters. figure 11. no load test (fully loaded box with ice) 28.6 28.8 28.7 28.9 29.1 75 78 85 79 74 58 38 19 6 0.2 0 2 4 4 8 7 2 9 6 period (hours) temperature (oc) relative humidity (%) amount of ice (kg) http://www.azojete.com.ng/ mailto:olajuwonakeem22@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):741-750 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 748 3.3 trolley total weight of the trolley was found to be approximately 7.4 kg which is in line with trolley design recommendation that states that trolley should be around 15% of the total weight it was meant to carry according to designing trolleys guide. consideration as to where the trolley will be used was noted which is riverine area as obtained from observations report from responders of the earlier fish box preceding this newly fabricated box. taking this into consideration, the trolley was painted with an anti-corrosion paint which is to serve as protection for the trolley skeleton. the trolley and loaded stacked boxes are shown in figure 12. figure 12. actual views of the (a) trolley and (b) loaded modified insulated boxes stacked on the trolley. 4. conclusion this study was carried out to modify the insulated fish box by increasing its holding capacity, rechanneling the drainage hole to improve the area of water letting out system and also to design and fabricate a trolley for easy carriage. as shown in the results, the drainage of the modified insulated box performed better compared to the earlier design and the box can take approximately 60 𝐾𝑔 of ice block as compared to the earlier design which takes 18 𝐾𝑔. also, the introduction of trolley and a swivel wheel for easy movement and steering over different terrains will boost productivity (as minimal energy is required). there will be an improvement in post-harvest handling of fresh fish leading to reduction in loss and increase earnings in the value chain. conclusively, the study has successfully achieved all its objectives and therefore adoptable for any fish boxes to be produced. declaration there is no conflict of interest and authors agreed to publish the manuscript acknowledgement funding for this research was provided by the management of nigeria stored products research institute ilorin, kwara state. our appreciation goes to miss okonkwo, e.u. who her noble experience towards implementation and completion of the research. also, messrs., alausa m.a, dibia, i. oyibojaboh, c.o. and members of perishable crop research department nspri zonal office lagos efforts are highly appreciated. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:olajuwonakeem22@gmail.com atanda et al: modification, fabrication and performance evaluation of insulated box for post-harvest handling of fish. azojete, 18(4):741-750. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 749 references agbon, ao., ezeri, gno., ikenwiewe, bn., alegbleye, no. and akomolade, dt. 2002. a comparative study of different storage methods on the shelf life of smoked current fish. journal of aquatic science, 17(2): 134-136. ajayi, ao., benson, ob., johnson, om. and agboola, aa. 2021. willingness to use ice-fish box by fresh fish by value-chain actors in lagos state, nigeria. proceedings of the annual conference of the agricultural extension society of nigeria. twenty-sixth annual conference held at federal university of agriculture, abeokuta, nigeria on 26-29 april 2021. theme: redefining agricultural extension practice to cope with emergencies, pp: 77-83. https://dx.doi.org/10.4314/jae.v26i1.10s akinneye, jo., ambee, i. and arannilewa, st. 2007. effect of drying methods on the nutritional composition of three species of (bonga sp., sardinella sp. and heterotis niloticus) journal of fisheries international, 2(1): 99-103. benson, ob., ambee i., oluwatoyin, a., bunmi, o. and solagbade, a. 2018. gender roles in fisheries post-harvesting activities in catch-locations within coastal areas of lagos state nigeria. journal of agricultural extension and rural development, 10(12): 245-250. carlos, efp. 2018. development and mechanical design of a tricycle. instituto superior técnico, universidade de lisboa, portugal. pp: 1-10. ishola dt., isiaka aa., awagu ef. and olayemi ff. 2015. the performance evaluation on the effectiveness of nspri’s ice-fish box. iosr journal of agriculture and veterinary science, 8(2): 107-111. iso 11228-1. 2003. international organization for standardization. international standard iso 11228-1. ergonomics – part 1: lifting and carrying. 1st ed. geneva. iso 11228-2. 2005. international organization for standardization. international standard iso 11228-2. ergonomics manual handling – part 2: pushing and pulling. 1st ed. geneva. kaustubh, vw. and wankhadeb, na. 2015. design and analysis of transfer trolley for material handling. international journal of innovative and emerging research in engineering, 2(1): 166170. kumolu-johnson, ca. and ndimele, pe. 2011. a review on post-harvest losses in artisanal fisheries of some african countries. journal of fisheries and aquatic science, 6(4): 365-378. obodai, ea., muhammad, ba., obodai ga. and opoku, e. 2009. effect of fuel wood on the quality of smoked freshwater fish species sold in tamale central market, norther region, ghana. ethiopian journal of environmental studies and management, 2(2): 27-35 patwegar, aa., prathamesh, b., renuka, c., varsha, s., satappa, z. and avinash, m. 2019. design and fabrication of material handling trolley. international research journal of engineering and technology, 6(3): 2397-2400. pessu, po., atanda, sa., agboola, aa., adeniyi, bm., nwanade, cf, and benson, ob. 2016. biochemical and lipid oxidation changes in clarias gariepinus (burchell 1822) stored in fish ice box. journal of agricultural research, 1(2): 1-6 raja, b., dolok, s., fredy, p. and nicolas, k. 2016. the effect of cool box insulator type on the temperature characteristics and quality of decapterus russelly (rüppell, 1830) during http://www.azojete.com.ng/ mailto:olajuwonakeem22@gmail.com https://dx.doi.org/10.4314/jae.v26i1.10s arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):741-750 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: olajuwonakeem22@gmail.com 750 chilling preservation. aquatic procedia, 7: 195 – 200. https://dx.doi.org/10.1016/j.aqpro.2016.07.027 shubham, ss., sagar, dp. and prof. shailendra rz. 2018. design and fabrication of easy handling trolley. international research journal of engineering and technology, 5(5): 1690-1694. tsado, jh., adeniji, ma., ojo, ma., adebayo, co. and abdulazzeez, r. 2012. perception of women knowledge on the nutritive value of fish in kaduna north local government area of kaduna state, nigeria. journal of agriculture and social research, 12(1): 162-169 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:olajuwonakeem22@gmail.com https://dx.doi.org/10.1016/j.aqpro.2016.07.027 arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):781-792 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 781 mathematical modeling of field recital of harrow in clay – loam soil in south eastern nigeria c. g. okeke1 and o. oduma2* 1department of agricultural & bioresources engineering, enugu state university of science and technology, enugu, nigeria. 2department of agricultural and bioresources engineering, michael okpara university of agriculture, umudike, abia state, nigeria *corresponding author's email address: odumaoke@gmail.com article information submitted 9 aug, 2023 revised 6 sept, 2023 accepted 10 sept, 2023 keywords: clay-loam disc harrow depth efficiency speed working width abstract this research was carried out to model and optimize the efficiency of disc harrow on clay-loam soil in south – east nigeria to assist farmers scrutinize and select appropriate harrowing implement reliant on soil type for efficacious and magnificent production. the harrowing operation was conducted at selected effective working widths, operational speeds and cutting depths using 2-gangs tandem disc harrow. the experimental design adopted in the research was a three level – three factor full factorial design. the experiment consists of three factors which were varied at three levels of harrowing depths which include 10, 20, 30 cm; three levels of effective working widths of 60, 120 and 180 cm and three levels of operational speeds (6, 7 and 8 km/hr). central composite response design which gives 17 test runs was performed for each sample. the results found that the highest field efficiency of 98.50% was obtained when the harrow was operated at the pulverizing depth of 20cm under operational speed of 7 kmh-1 and working width of 120 cm. the quadratic model equation was statistically significant (p ˂ 0.05) for the prediction of the field efficiency. additionally, the results show that the coefficient of determination; r2 for the field efficiency was 0.9139, which indicated adequate correlations among the factors. the predicted r² of 0.7695 was reliable with the adjusted r² of 0.8031 which identified excellent interactions between the factors (effective working width, operational speeds and harrowing depths). the adequacy precision (10.3749) obtained indicated seemly indicator and that the model could navigate the design space. the optimum field efficiency and the desirability of 96.66% and 0.697 were respectively attained at optimum depth of 30 cm, working width of 180 cm and speed of 6.16 kmh-1. therefore, farm operators can henceforth, evaluate and select the harrow implements using the developed model 1.0 introduction tillage is the preparative phase of seedbed (crop planting environments) which is the crucial period in plant growth, development and yield. it is the paramount and utmost essential farming operation in most agricultural areas that oversees the success of the agricultural period. the success of plant growth and yield production hinge on quality of mechanical manipulation of the soil in piercing and pulverizing the soil to produce proper environment for plant development; to guarantee regular growth of plant, in a manner that will permit roots access to air, nutrients and moisture. it is therefore imperative to scrutinize the effect of tillage depth, operational speed and working width of the various tillage implements and to relate it with the performance capabilities of farm implements during execution of task for proper http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com mailto:odumaoke@gmail.com mailto:odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):781-792. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 782 selection of the suitable tillage apparatus based on soil type or situation for better agricultural production at reduced cost (boydas and turgut, 2017). selecting the appropriate tools to match certain soil types or condition is an essential guide in lessening the energy loss, cost of work, mechanical breakdown, and to maintain the soil fertility as well as decreasing the detrimental effect of soil structure like compaction (coates and thacker,2001). accordingly, cost of using machineries has to be rationally economical, consistent and should have least energy requirements (udo and akubuo, 2000). additionally, tillage depth, working width, soil type, speed, soil conditions and operator’s skillfulness affect performance and energy consumption rate (bukhari and balock, 1982). therefore, contrivance size and working depth and/or speed ought to suit the machine size to upsurge its working proficiencies (collins et al., 1998). it is noteworthy that the best agricultural processes can be attained by sufficient knowledge of performance characteristics, dynamic utilization and management of tractors and the coupled tools (oduma and oluka, 2019). skillful machine applications and management needs accurate performance records as well as general energy demands of diverse equipment to undertake an indicated job and to attain a steady mechanization arrangement by matching the capabilities of different agronomic devices. again, discrepancy in environmental soil states desires the accounts of the energy and performance features of the tractor coupled tools. for that reason, anazodo et al. (1983) upheld that due to divergences within ecological soil locations, records of performance of equipment under different soil kinds are very vital for choice of the contrivances. the current costly agronomic tools necessitate upgraded process alongside with appropriate utilization of resources and reduction of effective costs so as to increase production and to upsurge revenues. the foremost expenses of each agribusiness system are contrivance/equipment cost. increasing the proficiencies at minimized energy intake rate of machines may cause a significant drop in production expenditures. a good farmer goes to appositely exploit every single farm input with the intention of curtailing cost (yohanna et al., 2010). agricultural mechanization tools are recurrently imported to nigeria to help varied farm mechanization resolutions of the government (oluka, 2000). right now, importation cost of farm machineries is excessive owing to the depression in value of nigerian currency, and to muddle through within such poor fiscal status quo, farm operators ought to be farsighted in selecting and acquiring farm equipment. as a result, it is imperative that operators and owners of agricultural machines should be conversant with the technique with which their equipment handle any given task, as well as the easiness in which it does the job to ensure minimum wastage of time and energy. substantial amount of cash is expended by agriculturalists annually in energy supply, operation charge, maintenance and management of farming equipment. indecorous selection or unsuitable matching of machines most times causes great energy and power loss. statistics on the performance of harrow will effortlessly resolve the strain of farmers, and assist in enhancing and increasing their outputs as they make proper selection of tools that would match their soil situations. development of mathematical model (through studying the effect of tillage depth, operational speed and effective working width on the field efficiency of harrow) is vital and stress-free means of assisting farmers at all levels in appraising, envisaging and/or predicting the credible performance capabilities of harrowing equipment for apposite selection of the implement in view of the soil type and/ or situations before acquiring and engaging the mechanism to work. therefore, the aim of this study is to develop a mathematical model by examining the effect of tillage depth, speed of operation and effective working width on the field efficiency of disc harrow in clay-loam soil, which will help farmers in southeast nigeria and other areas with similar soil type/conditions in assessing/predicting the performance and selecting the tillage implement to reduce cost, lessen energy loss, and improve agricultural productivity. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com okeke and oduma: mathematical modeling of field recital of harrow in clay – loam soil in south eastern nigeria. azojete, 19(4):781-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 783 2. materials and methods 2.1 research farm the research was conducted at the experimental farm of michael okpara university of agriculture, umudike (05o 25′n/ 7o 34′e), abia state, nigeria, figure 1. the climatic state in the farm is characterized by an average temperature of 27°c, annual rainfall varying from 2250 to 2500mm and average relative humidity of 75%, distinctive of tropical rain forest areas (amanze et al., 2020). clay-loam is appropriate for arable farming. the research area has average soil bulk density of 1.68 g/cm3, porosity of 37.40%, moisture content varying from 12.35% to 18.90% (w.b) and granular in structure (oduma et al., 2021). figure 1: map of the study area (source: kelechi et al., 2019) 2.2 tractor and harrow used for the research the tractor (massey ferguson) of model mf430e with capacity of 55.2kw and 3point hitch mechanism and a disc harrow with operating units of 2-gang tandem discs was obtained from works department, michael okpara university of agriculture and used for the study. 2.3 field test procedure the harrowing operation was conducted at selected effective working widths of 60, 120 and 180 cm and cutting depths of 10, 20 and 30 cm using 2-gangs tandem disc harrow. the area harrowed and the equivalent time taken to till the area was recorded according to oduma and oluka (2019). 2.4 experimental design the experimental design adopted in the research work was a three level – three factor full factorial design. the experiment consists of three factors which were varied at three levels, namely: the harrowing depths which include 10, 20, 30 cm; the effective working widths of 60, 120 and 180 cm and three levels of operational speeds (6, 7 and 8 km/hr). central composite response design which gives 17 test runs was performed for each sample using equation 3 according to umani et al. (2019) and oduma et al. (2022) n = 2k + 2k + nc (1) where, n = number of test runs, k = experimental factors and nc = centre point in order to obtain the desired data, the range of values of every one of the three factors (k) was evaluated (table 1). effective working width, operational speed and harrowing depth were adopted as independent factors for the energy requirement assessment of the harrow. the response selected was the fuel consumption rate (l/ha) of the harrow. four repetitions of the http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):781-792. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 784 center points were adopted in order to predict a well and concise approximation of errors; and the field experiments were conducted in randomized form (oduma et al., 2021). table 1: actual values, codes and levels of the test variables for design of experiments factors symbols codes and levels -1 0 1 effective harrowing width (cm) depth of cut (cm) operational speed (km/hr) a b c 60 10 6 120 20 7 180 30 8 2.5 calculation of actual field efficiency the actual field efficiency was evaluated using equation 1 proposed by kepner, (1982) as adopted by oduma et al. (2022). ɛf = 100𝑇𝑝 𝑇𝑡 (2) where: ɛf = field efficiency, %; tp = productive time, h; tt = total working time, h. tt = tp + ti (3) td = idle or delay time, h 2.6 statistical analysis the design expert of version 11.0 was used in the experimental design, analyzing the data obtained, optimizing the functional parameters and to generate model equations for the estimation of the energy requirement (fuel intake rate) of the disc harrow. the quadratic, cubic, linear and two factorial interaction (2f1) models were selected and used to analyze the fuel consumption rate of the implement; and the models were fitted to the generated experimental data. data generated was analyzed applying the response surface methodology to fit the quadratic polynomial equation obtained from the design expert software version 11.0 expressed in equation (4) according to chih et al. (2012). ү = β0 + ∑ 𝛽𝑖𝑋𝑖2 𝑖=1 + ∑ 𝛽𝑖𝑖𝑋𝑖22 𝑖=1 + ∑ ∑ 𝛽𝑖𝑗𝑋𝑖𝑋𝑗2 𝑗=𝑖+1 2 𝑖=1 (4) where, ү = response; β0 = constant term; ∑ 𝛽𝑖2 𝑖=1 = summation of coefficient of linear terms; ∑ 𝛽𝑖𝑖2 𝑖=1 = summation of quadratic terms; ∑ ∑ 𝛽𝑖𝑗2 𝑗=𝑖+1 2 𝑖=1 = summation of coefficient of interaction terms; 𝑋𝑖𝑋𝑗 = independent variables. furthermore, the multiple regressions were equally employed in fitting the coefficient of the polynomial model so that the response variable may be correlated with the independent variables. the consistency of fit of the model, the individual and interaction effect of the tillage parameters (harrowing width, operational speed and depth of cut) on the response (fuel consumption rate) of the implement were calculated by means of anova. again, the results were also analyzed statistically to ascertain the effects of the factors and their interactions on the total fuel consumption rate at ∝ = 0.05 via minitab 17.0. 2.8 model validation and optimization procedure the model equations developed from the study were validated by comparing the results obtained from the experiment (actual values) with the results of the model equation developed (predicted values) by simple simulation. the coefficient of determination, r2 was also used to indicate the adequacy of the model. the value of r2 nearer to +1 indicates high file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com okeke and oduma: mathematical modeling of field recital of harrow in clay – loam soil in south eastern nigeria. azojete, 19(4):781-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 785 degree of correlation between the dependent and independent variables (kothari, 2013). optimization of the practical factors of disc harrow on clay loam soil was done by means of design expert in response surface methodology (rsm) to determine the optimum field efficiency. 3. results and discussion 3.1 harrow operation the process of harrowing operation was conducted at selected working width, operational speeds and harrowing depths, at soil moisture content varying from 12.5 – 18.90 % and the results of the field efficiency of the disc harrow were presented in table 2. this table presents the relations between the trial factors (working width, operational speeds and harrowing depths) with the field efficiency of the harrow. the values of actual field efficiencies achieved in the course of the tillage operation vary from 91.70 – 98.50% for the range of operational speed (6 – 8 kmh-1), harrowing depth between 10 – 30cm and working width range from 60 – 180 cm. the results found that the highest field efficiency of 98.50% was obtained when the harrow was operated at the cutting depth of 20cm under operational speed of 7 kmh-1 and working width of 120 cm; while the least field efficiency of 91.70 % was achieved at cutting depth of 30cm under working width of 180 cm and operational speed of 7 kmh-1. it was frequently discovered that at different operational speeds and effective working width, the field efficiencies increase with the increase in harrowing depth and increases to peak point of 98.50% at operational speed of 7 kmh-1 and at depth of 20cm under effective working width of 120 cm. the field efficiency of the implement decreases by 6.15% when harrowing at depth of 10 cm and 3.05% at depth of 30 cm irrespective of the effective width of cut and operational speed. this is in line with the observations of oduma et al. (2022) and sale et al. (2013). table 2: randomized design layout of three levels –three factors full factorial composite design of experiment with actual and predicted values of energy requirements of disc harrow run order coded factors actual factors field efficiency, % a b c harrowing depth (cm) effective working width (cm) operational speed (km/hr) actual values of field efficiency predicted values of field efficiency 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 -1 1 -1 0 0 0 0 1 0 1 0 1 0 -1 -1 0 0 0 1 1 -1 0 0 1 1 0 0 -1 0 1 -1 0 0 0 -1 0 0 1 0 0 1 0 0 -1 -1 1 -1 0 1 0 0 20 30 30 10 20 20 30 30 20 20 10 20 30 10 20 20 20 60 180 60 120 120 120 120 180 120 180 120 180 120 60 60 120 120 6 7 7 8 7 7 8 7 7 6 6 8 6 7 8 7 7 97.83 91.70 92.20 95.90 95.90 98.50 97.10 95.90 95.80 96.90 97.80 95.50 98.11 97.50 97.50 95.60 97.88 91.51 86.47 86.40 81.29 86.51 86.51 81.43 86.47 86.51 91.59 91.64 81.54 91.50 86.55 81.45 86.51 86.51 figure 2 is the response surface plot of harrowing depth, effective working width and operational speed against field efficiency of disc harrow showing the relationship between the factors and the response. it was observed that the highest field efficiency of 98.50% was noticed http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):781-792. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 786 at speed of 7 kmh-1 at harrowing depth of 20 cm and effective working width of 120 cm. the highest field efficiency achieved at operational speed of 7 kmh-1 is slightly higher than the operational speed of plough and was attributed to the lower tractive and draft force associated with secondary tillage operation after the soil has been acted upon by the plough (primary tillage implement) which is related with low working speed enabling the implement to pierce deep and collapse the resistance force offered by the soil to implement penetration thereby creating an adequate environmental condition for plant root to penetrate deep into the soil as observed by sale et al. (2013). figure 2: response surface plot of harrowing depth, effective working width and operational speed against field efficiency of disc harrow. 3.2 effects of tillage factors (speed, effective working width and tillage depth) on field efficiency of disc harrow the values of actual field efficiency attained during the harrowing operation ranged from 91.70 to 98.50% for the range of operational speed, effective working width and tillage depth of the discs harrow. these field efficiencies are within the range of efficiency of 90 – 77% as recommended by hunt (2013) for harrowing at speed range of 6 – 10 kmh-1. it was commonly practical that at different operational speeds and effective working width, the actual field efficiency increases with the increase in tillage depth and increases to a maximum point of 98.50% at operational speed of 7 kmh-1 and tillage depth of 20cm under effective working width of 120 cm. the actual field efficiency of the implement decreases by 6.15% when harrowing at depth of 10 cm and 3.05% at depth of 30 cm irrespective of the effective width of cut and operational speed. the maximum field efficiency (98.50%) was achieved at a slightly higher forward speed (7 kmh-1) as compared to ploughing operation, and is in line with the observation of chandrashekar and jayant (2018) in their studies on performance evaluation of vertical rotary plough wherein the maximum field efficiency of the plough (88.09 %) was noted at a very low operating speed of 2 km h−1. the highest field efficiency attained at higher working speed of 7 kmh-1 might be due to somewhat lower tractive and draft force associated with higher working speed of harrow as compared to plough, enabling the implement to shatter and break the lump/clod of the soil after ploughing, thus creating a suitable environmental condition/seedbed for plant root to penetrate deep into the soil as detected by sale et al. (2013). additionally, the range of predicted field efficiency (81.29 – 91.64%) obtained (table 2) is within the experimental range and somewhat higher than the range of field efficiency of 72.90 – 78.80% gotten by sale et al. (2013) in their study of performance of selected tillage implements and may be ascribed to variation in soil conditions. the results obtained from this study postulate that the tillage depth and operational speed have boundless effect on the field efficiency of tillage implement than the effective working width. hence, the depth of tillage ought to be determined depending on the root length of crop in other to enhance the field efficiency of disc harrow as indicated by oduma et al. (2022) and chandrashekar and jayant (2018). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com okeke and oduma: mathematical modeling of field recital of harrow in clay – loam soil in south eastern nigeria. azojete, 19(4):781-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 787 3.3 statistical analysis of results the analysis of the effects of tillage factors (operational speed, effective working widths and harrowing depth) on the field efficiency of the harrow is presented in the anova results for field efficiency in table 3. the results showed that the field efficiency was significantly (p ≤ 0.05) affected by the interaction of tillage depth and operational speed and increases with the increase in cutting depth as noted by ajav and adewoyin (2012) in their study of the influence of forward speed and tillage depth on draft of tillage implements in sandy loam soil. the field efficiency was also significantly (p ≤ 0.05) affected by the interaction of tillage depth and effective working width of the harrow. the field efficiency decreases with the increase in speed of operation which may be ascribed to high drawbar pull associated with high working speed (sachin et al., 2013). thus, the p-value for interaction of the operational speed and tillage depth; and interaction of tillage depth and working width are 0.0515and 0.0003 respectively. it then infers that the mean field efficiency differs for the different interactions of tillage depths, effective working widths and operational speeds. table 3: analysis of variance for field efficiency source sum of squares df mean square f-value p-value a-tillage depth 0.0595 1 0.0595 0.0818 0.7831 b-width 1.35 1 1.35 1.86 0.2148 c-speed 1.64 1 1.64 2.25 0.1771 ab 31.98 1 31.98 43.97 0.0003 ac 4.00 1 4.00 5.50 0.0515 bc 1.42 1 1.42 1.95 0.2056 pure error 4.70 4 1.17 total 59.10 16 3.4 model assessment of disc harrow efficiency the field efficiency of the disc harrow in clay -loam soil depends on the results illuminating the significant difference for combination of the speed, effective working width and cutting depth of the harrow. the model coefficient, effect, contribution, test of lack of-fit and the significance of the factors and their interactions on the field efficiency were evaluated according to umani et al. (2019), oduma et al. (2022) and hensh et al. (2022). a quadratic model was significant for the response (table 4), thus, p ˂ 0.05; indicating that the significant model term was achieved at 95% significance level. the quadratic model equation obtained to predict the field efficiency in regard to the independent variables or operating factors (speed, effective working width and harrowing depth) is as stated in equation 5. fe = 128.30 – 0.89a – 0.15b – 24.52c + 0.005ab + 0.1ac + 0.10bc – 0.01a2 0.0001b2 + 1.56c2 (5) where fe = field efficiency, %; a = harrowing depth of the disc harrow, cm; b = effective working width of the disc harrow, cm; c = operational speed, kmh-1 the quadratic model as acquired in this research work is in accordance with the findings of oduma et al. (2019) in the study of the development of empirical regression equations for predicting the performances of disc plough and harrow in clay-loam soil. the p-value (0.0055) of the model as presented in table 5 is less than the designated 𝛼level of 0.05 indicating that the model is significant. thus, the interactions of the operating factors (speed, effective working width and harrowing depth) have significant effects on the field efficiency of the implement. hence, the model term p-values of 0.0003, 0.0515 and 0.0072 which are less than http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):781-792. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 788 the selected 𝛼level of 0.05 stipulate that the model terms are significant. thus, ab (interaction of a-harrowing depth and b-effective working width), ac (interaction of aharrowing depth and c-operational speed) and c² are significant model terms as displayed in table 5. this result agrees with the report indicated by chandrashekar and jayant (2018). nevertheless, it is not statistically consistent with the results of (oduma et al. (2022) in the research of performance of tractor and tillage implements in clay soil wherein the p–value of the field efficiency attained is 0.00 at p ≤ 0.05 and could be credited to the variances in the soil and/or ecological/environmental conditions of diverse study regions as indicated by saeed et al. (2017). finally, the lack of fit f-value of 0.1114 (table 5) implies that the lack of fit is not significant relative to the pure error. however, there is a 94.89% chance that a lack of fit f-value this large could occur due to noise. non-significant lack of fit according to oduma et al. (2022) is good since the model is required to fit. table 4: anova of model summery statistics source sequential p-value lack of fit pvalue adjusted r² predicted r² linear 0.8698 0.0712 -0.1672 -0.9071 2fi 0.0094 0.2649 0.4950 -0.2972 quadratic 0.0219 0.9489 0.8031 0.7695 suggested cubic 0.9489 0.6820 aliased table 5: anova of response surface quadratic model for field efficiency of disc harrow source sum of squares df mean square f-value p-value model 54.01 9 6.00 8.25 0.0055* a-tillage depth 0.0595 1 0.0595 0.0818 0.7831ns b-width 1.35 1 1.35 1.86 0.2148ns c-speed 1.64 1 1.64 2.25 0.1771ns ab 31.98 1 31.98 43.97 0.0003* ac 4.00 1 4.00 5.50 0.0515* bc 1.42 1 1.42 1.95 0.2056ns a² 3.50 1 3.50 4.81 0.0643 b² 0.5663 1 0.5663 0.7786 0.4068ns c² 10.19 1 10.19 14.01 0.0072* residual 5.09 7 0.7273 lack of fit 0.3927 3 0.1309 0.1114 0.9489ns pure error 4.70 4 1.17 cor total 59.10 16 *significant; ns= not significant 3.5 validation of the model results of the validation of the model equation are shown in table 6. the results show that the model is significant. the coefficient of determination, r2 (0.9139) shows good alliances amid the independent variables, which means that the response model can elucidate 91.39 % of the full changeability in the response (fakayode et al., 2016; oduma et al., 2022)]. table 2 shows the simulation results of the quadratic model achieved in the study which indicated that the field efficiency falls within the experimental array. the predicted r² (0.7695) is reliable with the adjusted r² of 0.8031 (table 6); thus, the difference is less than 0.2 indicating that the trial data fitted very well, as posited by bako et al. (2021). the adjusted r2 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com okeke and oduma: mathematical modeling of field recital of harrow in clay – loam soil in south eastern nigeria. azojete, 19(4):781-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 789 obtained is compatible with the r2 (0.9615) as obtained by kothari (2014). the adequacy precision (10.375) ratio obtained is greater than 4 is appropriate, indicating an acceptable signal and that the model equation might be espoused to navigate the design space. table 6: coefficient of determination, r² for validation of model term 3.6 optimum field efficiency of disc plough: optimization of the practical factors (harrowing depth, effective working width and operational speed) of disc harrow on clay loam soil was done by means of design expert in rsm to determine the optimum field efficiency. the curve (figure 3) presents the optimization process with the optimal operational factors of harrowing depth of 30 cm, effective working width of 180 cm (which is the full width of disc harrow) and operational speed of 6.16 kmh-1. thus, the optimum field efficiency and the desirability of 96.66% and 0.697 were respectively attained. the optimum harrowing depth as shown in the result of the optimization is in accordance with the findings of chandrashekar and jayant (2018) which vary from 20 – 30 cm due to the disparity in the length of roots of crop penetration for improved yield as pertinent in different crops. however, the optimum speed (1.94ms-1) obtained by oduma et al. (2020) is lower than the optimum speed obtained in this study. this could be as a result of dissimilarities in the soil environments exclusively the moisture contents of the diverse study regions as indicated by anazodo (1983) and olatunji (2011). figure 3: optimization curve of field efficiency of disc harrow in clay – loam soil 4. conclusions the modeling of the field performance of disc harrow on clay-loam soil in south-east nigeria was conducted. in the course of the harrowing process, it was detected that the peak field efficiency was noted when the harrow was engaged at depth of 20cm with the working width of 120 cm and speed of 7 kmh-1 while the lowest field efficiency of 91.70 % was recorded at depth of 30cm, working width of 180 cm and operational speed of 7 kmh-1. the statistical analyses carried out, showed that the quadratic model was recommended for the prediction of the field efficiency of the disc harrow. the developed model and the coefficients were statistically significant. the predicted and the adjusted r2 values were resolutely reliable. hence, the experimental values were appropriate with the coefficient of std. dev. 0.8528 r² 0.9139 mean 96.19 adjusted r² 0.8031 c.v. % 0.8867 predicted r² 0.7695 adeq precision 10.3749 http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):781-792. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 790 determination (r2 = 0.9139) postulating exceptional correlations amid the independent variables. the generated model will aid the farmers in assessing the performance of the contrivance for appropriate selection and assignation to task. the optimum efficiency and the desirability of 96.66% and 0.697 were respectively attained at optimal tillage depth of 30 cm, operational speed of 6.16 kmh-1 and effective working width of 180 cm. due to dissimilarities in agro-ecological field situations and soil types in different regions, it is therefore recommended that research of this kind should be conducted in every agricultural zone to obtain models for assessing the performance of tillage implements for decision on machine selection based on soil characteristics for increased production, to minimize production costs, reduce loss/wastage of energy, time and waste of agricultural products references ajav, ea. and adewoyin, ao. 2012. effect of ploughing depth and speed on tractor fuel consumption in a sandy-loam soil of oyo state-nigeria. journal of agricultural engineering and technology, 20 (2): 1 – 10. amanze, nn., oduma, o. and orji, fn. 2020. physical characteristics of soils at demonstration farm of michael okpara university of agriculture, umudike. umudike journal of engineering and technology (ujet), 6(2): 97 – 103. anazodo, ug n. 1983. survey and comperative analysis of farm machinery management system in nigeria. proceedings of nigerian society of agricultural engineering, 7: 59-73. bako, t., mamai, ea. and istifanus, ab. 2021. determination of the effects of tillage on the productivity of a sandy loam soil using soil productivity models. research in agricultural engineering, 67: 108–115. boydas, mg. and turgut, n. 2007. effect of tillage implements and operating speeds on soil physical properties and wheat emergence. turkish journal of agriculture and forestry, 31: 399-412. bukhari, sb, and balock, jm. 1982. fuel consumption of tillage implements. agricultural mechanization in asia, africa and latin america (ama), 11(3): 20-22. chandrashekar, k. and jayant, s. 2018. studies on performance evaluation of vertical rotary plough. international journal of current microbiology and applied sciences, 7(12): 1431-1447. chih, wt., lee, it. and chung, hw. 2012. optimization of multiple responses using data envelopment analysis and response methodology, tamkang. journal of science and engineering, 13(2): 197-203. coates, we. and thacker, gw. 2001. reduced tillage systems for arizona cotton growers. college of agriculture and life sciences, university of arizona. http://cals.arizona.edu/crops/equipment/.html; webmaster:jsjones@aq.arizona.edu. collins, ne., williams, th. and kemble, lj. 1998. energy requirements for grain production system. agricultural mechanization in asia, africa and latin america (ama), 19 (4): 9-14. fakayode, oa., ajav, ea. and akinoso, r. 2016. effect of processing factors on the quality of mechanically expressed moringa (moringa oliefera) oil: a response surface approach. journal of food process engineering, 40(4): 1-12. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com http://cals.arizona.edu/crops/equipment/.html okeke and oduma: mathematical modeling of field recital of harrow in clay – loam soil in south eastern nigeria. azojete, 19(4):781-792. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 791 hensh, s., chattopadhyay, ps. and das k. 2022. drawbar performance of a power tiller on a sandy loam soil of the nadia district of west bengal. research in agricultural engineering, 68: 41–46. hunt, d. 2013. farm power and machinery management. 10th edition. scientific international congress on agricultural engineering, dublin, 3:1703-1709. kelechi, mu., nwankwo, iu, itaman, vo. and ihemeje, eo. 2019: a comparative study of microbes associated with earphones used among university students of michael okpara university of agriculture umudike, abia state, nigeria. acta scientific microbiology, 2(4):2-7. kepner, ra., bainer, r. and barger, el. 1982. principles of farm machinery, avi publishing company inc. westport. kothari, cr. 2014. research methodology. methods and techniques. second revised edition. new age international publishers. new delhi. 140 – 145. oduma, o., ehiomogue, p., okeke, cg., orji, nf., ugwu, ec., umunna, mf. and obieogu, kn. 2022. modeling and optimization of energy requirements of disc plough operation on loamy-sand soil in south-east nigeria using response surface methodology. scientific africa, 17: 1-8. doi: https://doi.org/10.1016/j.sciaf.2022.e01325. 17: 1 -8. oduma, o., okeke, cg., onyeka, fc. and edu, cn. 2021. penetration characteristics of some selected tractor-hitched tillage implements in agro-ecological soils of south-east nigeria. futo journal series (futojnls), 7(1): 37 – 46. oduma, o., okeke, cg., eje, be., inekwe, g. and nnadi, dc. 2020. simple regression relationships for assessing the performances of selected tillage implements in south-east, nigeria. scientific journal of agricultural engineering, university of belgrade, 1: 51 – 64. oduma, o., oluka, si., edeh, jc. and ehiomogue, p. 2019. development of empirical regression equations for predicting the performances of disc plough and harrow in clay-loam soil. agricultural engineering international journal, 21(3): 18–25. oduma, o. and oluka, si. 2019. effects of soil type on power and energy requirements of some selected agricultural field machinery in south – east nigeria. journal of agricultural engineering, university of belgrade, sebia, 3: 69 – 77. olatunji, om. 2011. evaluation of plough disc performance on sandy loam soil at different soil moisture levels. research journal of applied sciences, engineering and technology 3(3): 179-184. oluka, si. 2000. costs of tractor ownership under different management systems in nigeria. nigeria journal of technology (nijotech), 19 (1): 15-28. sachin, vw., pravin pj. and babasaheb, sg. 2013. influence of forward speed and tillage depth on draft of primary tillage implements in sandy loam soil. international agricultural engineering journal, 22(3): 26-30. saeed, r., mohammad, a. and javad, j. 2017. performance of tractor and tillage implements in clay soil. journal of the saudi society of agricultural sciences, 16: 154 -162. sale, sn., gwarzor, ma., felix, og. and idris, si. 2013. performance evaluation of some selected tillage implements. proceeding of the niae, 34:71-77. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com https://doi.org/10.1016/j.sciaf.2022.e01325.%2017 arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):781-792. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: odumaoke@gmail.com 792 udo, du. and akubuo, co. 2000. fuel consumption in tillage operations for sandy loam soil. proceedings of the niae, 74-83. umani, kc., fakayode, oa., ituen, euu. and okokon, fb. 2019. development and testing of an automated contact plate unit for a cassava grater. computer and electronics in agriculture, 157530-540. https:/doi.org/101016/j.compag.2019.01.028. yohanna, jk., fulani, au. and aka’ama, w. 2010. a survey of mechanization problems of the small scale (peasant) farmers in the middle belt of nigeria. journal of agricultural science, 3(2): 262–266. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):295-304 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 305 performance evaluation of a hybrid solar-wind power system for heipang community load demand i. b. maren1*, a. b. adisa2, h. dandakouta3 and r. i. ejilah3 1department of mechanical engineering, university of jos, plateau state, nigeria 2department of mechanical and production engineering, abubakar tafawa balewa university, bauchi state, nigeria 3department of automobile engineering abubakar tafawa balewa university, bauchi state, nigeria. *corresponding author's email address: mareni@unijos.edu.ng article information submitted 27 september, 2023 revised 26 december, 2023 accepted 25 february, 2024 keywords: load sharing strategy (lss) hybrid system simulation capacity factor design abstract the electricity generation capacity of nigeria, which is predominately fossil-based and unsustainable, is far below the energy needs of its growing population and industrial demand. there is a need therefore to increase the level of renewable energy in the energy mix to reduce the adverse effect of fossil fuels on the environment and enhance access to electricity. assessing the performance of renewable energy systems in a location is a prerequisite for embarking on the technology. in this paper, 10-year average minimum solar radiation and wind speed data of the heipang community of barkin-ladi lga of plateau state and load sharing strategy design approach were used to design a hybrid solar wind power system to meet the load demand of the heipang community. matlab codes were written to simulate the designed hybrid solar-wind power system to assess its performance over the year against the given load demand profile using one-year hourly global solar radiation, wind speed, and ambient temperature data. results show that for a load demand of 158.32 kw and a daily energy demand of 710.59 kwh/day, with two-day autonomy, it will require 283 units of 300w capacity solar panels, 2 units of 50 kw rated capacity wind turbine at 42m high and 90 units of 48v, 350ah deep cycle batteries to meet the load demand. the capacity factors of solar, wind, and hybrid solar-wind power systems are 18%, 23%, and 21% respectively indicating high renewable energy resource potentials. the performances result also show slight complementarity between solar and wind power generation, thereby requiring battery backup to supplement the deficit http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 306 1.0 introduction nigeria has been relying on fossil fuels to run its economy. these resources are finite and have adverse effects on the environment. it is therefore important to look for alternative sources that will meet the increasing energy demand while minimizing the negative environmental impacts oyedepo (2012). renewable energy resources such as solar and wind energies are promising in terms of power generation and are being considered as alternatives to fossil fuels due to their availability and topological advantages in local power generation and environmental friendliness (hassan et al. 2023). renewable energy options are unpredictable in nature, and weather dependent and their variation may not match with the time distribution demand, therefore hybrid solar wind power systems with battery backup will attenuate their fluctuations significantly. this study presents an evaluation of the performance of a designed and simulated hybrid solar-wind power system in the heipang community (kpang, tapo, and tatu) of barkin-ladi lga of plateau state based on the solar and wind energy resources potentials and the load demand of the community. this will provide information to government and non-governmental agencies for possible intervention in the community. many recent works have been carried out on the factors that influence the performance of solar and wind power systems. dhass et al. (2020) studied the effect of temperature on internal parameters of various photovoltaic (pv) cell materials with results showing that temperature affects the performance of solar cells with gaas and a-si having major and minor deviations in performance. the study on the impacts of temperature and irradiance on polycrystalline silicon solar cell parameters using a metaheuristic technique was done by fébba et al. (2018). the results of the study showed that the shunt and series resistance were more affected by the increasing temperature than by increasing irradiance, with a linear increase and decrease for series and shunt resistance, respectively. similarly, the effect of light intensity and temperature on the performance parameters of monocrystalline and polycrystalline silicon solar devices was conducted (amin and al-maghrabi, 2018). the experimental results showed that all electrical parameters of the solar cells such as maximum output power, open circuit voltage, short circuit current, and fill factor are affected by temperature variation and solar cell performance decreases with increase in temperature due to increase in carrier recombination rates. guda and aliyu (2015) developed a mathematical model for the photovoltaic array based on the equivalent electrical circuit of the solar cell. results obtained competed favorably with those obtained through the use of the manufacturers’ datasheet and they were considered to be more accurate because they represented the actual field performance of the pv array. ma et al. (2019) developed a mathematical model for solar photovoltaic modules. the developed model accurately produced characteristic curves for different pv modules and the validation of the model through comparison with measured curves achieved good agreement. beniysa et al. (2019) used newton raphson's numerical method to develop a photovoltaic module model. the accuracy of the modeling was evaluated by comparing the modeled peak power to the reported experimental one provided by each photovoltaic module manufacturer which gave good agreement. nacar et al. (2021) proposed a sixparameter single-diode model for photovoltaic modules to improve accuracy in estimating the electrical behavior of the modules using particle swarm optimization and metaheuristic algorithms. the proposed model was tested and shown to predict the current voltage (i-v) curve with high accuracy. site-specific wind turbine power curve or estimation of its power output was developed by dongre and pateriya, (2019). different statistical methods based on empirical power curves were employed using techniques such as smoothing splines and polynomial regressions. the results showed file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 307 that smoothing splines gave outstanding performance over all the other methods. seo et al. (2019) developed a wind turbine power curve using the maximum likelihood estimation (mle) method. the obtained logistic function closely follows the measured wind turbine powers. teyabeen et al. (2018) carried out a comparative study of nine wind turbine power curves models based on manufacturers’ power curve data. the accuracy of the models wasere evaluated using statistical criteria such as normalized root mean square error (nrmse) and correlation coefficient. the power-coefficientbased model showed the most favorable efficiency. dongre and pateriya (2019) used statistical methods such as polynomial, splines and smoothing splines techniques to develop a site-specific power curve of a wind turbine to estimate its power output. the approach estimated the wind turbine power output accurately. saha et al. (2023) carried out a simulation and modeling of a hybrid solar-wind power system in a matlab/simulink environment using the maximum power point tracking (mppt) method. the hybrid solar-wind systems provided reliable power and the mppt enhanced energy outcome in varying conditions. bangura et al. (2023) carried out a study on the modeling and simulation of a hybrid solar-wind energy system consisting of a photovoltaic cell and a wind turbine driven by a permanent magnet synchronous generator (pmsg). the proposed system achieved stable power flow under different weather conditions. holmukhe et al. (2022) carried out a study on a hybrid solar-wind power system using matlab software to validate the system's reliability and economic feasibility. results showed that the hybrid power system was more reliable and economically feasible than a solar or wind power system alone. naggarapu et al. (2023) carried out battery modeling and performance analysis of time-varying load using matlab/simulink tool to estimate the state of charge (soc) of autonomous vehicles. the proposed model achieved a root mean square error (rmse) value of 0.1 and a widely acceptable soc. sawant et al. (2023) studied the role of battery energy storage in enhancing the reliability of wind-integrated power systems using the sequential monte carlo simulation (smcs) approach. results of the study showed that battery energy storage enhanced the reliability of wind-integrated power systems and the proposed operational strategy improved system reliability. degla et al. (2022) carried out a study on how to improve the lithium‐ion battery model for photovoltaic applications based on comparative analysis and experimental tests. results showed that the nernst model accurately predicted battery voltage with near-zero error. shabani et al. (2021) carried out a study on the techno-economic impacts of battery performance models on the optimal design of a grid-connected pv system using a non-dominated sorting genetic algorithm. results showed that battery models with accurate performance predictions give more efficient system optimization and a complex battery model gives a higher self-sufficiency ratio and lower life cycle cost. ahammad and shahidul (2014) used a sharing strategy to design a hybrid solar-wind power system for given load demand using the energy resources of khulna and chittagong in bangladesh. using different load scenarios, results show that a minimum unit cost of energy of $0.11/kwh was achieved in khulna using average load and maximum solar radiation and wind speed. the performance of a hybrid solar-wind power system is greatly influenced by the stochastic solar and wind energy resources of the location of operation. (amirsaman et al. 2014). many research works have been done on the design, simulation, and optimization of hybrid solar-wind power systems for different locations as highlighted in the literature reviewed, and to the best of the researchers’ knowledge, little information appears to exist on the design of hybrid solar-wind power system using load sharing strategy and its performance in heipang community. as highlighted in rehman et al. (2020) resource potentials play a key role in the economics of the hybrid solar-wind power system and since the resources vary from location to location, it will be relevant to look at the performance http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 308 of hybrid solar-wind power systems in heipang community to provide relevant information to investors and policy makers. 2. materials and methods 2.1 materials the area at which this study was undertaken is in barkin-ladi l.g.a of plateau state, nigeria, and is located between longitudes 8o 50’ e and 8o 59’ e and between latitudes 9o 34’ n and 9o 42’ n (land and survey, 2018). the geomorphology of heipang can be generally classified as plain land hence giving it the vantage position for the location of the airport. the data used for the design and simulation of the hybrid solar-wind power system were 2018 hourly solar radiation, ambient temperature, and wind speed of heipang community in barkin-ladi lga measured at 10m height, obtained from the nigerian meteorological agency office in abuja. the estimated hourly load demand profile for a typical day in of heipang community, not connected to the grid (kpang, tapo, and tatu), was obtained from the field survey by means of a structured questionnaire and interview of the inhabitants of the community. matlab and excel software were the tools used for analysis. 2.2 design of hybrid solar-wind power system 2.2.1 design considerations the design of the hybrid solar wind power system entails the sizing of the power generating systems to meet the load demand of the community that are not connected to the grid. the two renewable energy resources considered in this design were solar and wind energies. the daily estimated load demand of the community under study was assumed to be constant throughout the year for simulation purpose. 2.2.2 design concept the design of the hybrid solar-wind power system for heipang community is based on the percentage load sharing strategy approach (ahmmad and shahidul, 2014). the load was shared between solar and wind power generating systems. 2.2.3 solar and wind energy potentials of site the available solar energy potential per unit surface area of solar module in heipang community was determined using a power output model for photovoltaic generator developed by hybrid optimization of multiple electric renewables (homer, 2016) using equations 1 to 3. (1) (2) (3) where, 𝑃𝑃𝑉 is power generated by solar system at time (kw), 𝑁𝑃𝑉 is number of photovoltaic modules, 𝑌𝑝𝑣 is rated capacity of the solar module, 𝑓𝑝𝑣 is photovoltaic derating factor, 𝐺𝑇 is solar radiation normal to inclined plane (w/m2), 𝐺𝑇,𝑁𝑂𝐶𝑇 is solar radiation at nominal operating solar cell (w/m2), file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 309 𝐺𝑇,𝑆𝑇𝐶 is incident solar radiation at standard test condition (w/m2), 𝛼𝑝 is temperature coefficient of power, 𝑇𝑐 is solar cell temperature (oc), 𝜂𝑚𝑝,𝑆𝑇𝐶 is maximum power point efficiency under standard test (%), 𝐴𝑝𝑣 is surface area of the solar module (m2), 𝑇𝑎 is ambient temperature of location of study (oc), 𝑇𝑐,𝑁𝑂𝐶𝑇 is nominal operating solar cell temperature (oc), 𝑇𝑎,𝑁𝑂𝐶𝑇 is ambient temperature at nominal operating temperature (oc), 𝜏𝛼 is solar transmittance-absorptance factor of solar module cover. the available wind energy potential per unit surface area of wind turbine system in heipang community was determined using equations 4 and 5. (4) where, 𝑣 is wind speed at hub height (m/s), 𝑣𝑜 is wind turbine cut-out wind speed (m/s), 𝐻𝑊𝑇 is wind turbine hub height (m), 𝐻0 is reference height for measuring wind speed (m), 𝛼1 is power law exponent. the best fit power output model for the wind turbine selected (fd21-50) as determined by means of least square method in the course of this research (maren et al., 2022) is given as: (5) 2.2.4 load sharing strategy of the solar-wind power system according to equations 1 and 5, the power generated by the photovoltaic module per unit area is and power generated by wind turbine per unit area is respectively. thus, the load shared by the solar power generation system and the wind power generation system of the proposed hybrid system are given by the equations 6 and 7 respectively. load shared to the photovoltaic module of the hybrid system was determined using equation 6 is (ahammad and shahidul, 2014): 𝑃𝑠ℎ = 𝑃𝑝𝑣𝑎 𝑃𝑝𝑣𝑎+𝑃𝑤𝑡𝑎 × 𝑃 (6) where: p is the total load of appliances of heipang community not connected to the grid (kpang, tapo and tatu) in kw., 𝑃𝑝𝑣𝑎 is power generated by photovoltaic per unit area (kw/m2), 𝑃𝑤𝑡𝑎 is power generated by wind turbine per unit area (w/m2). load shared to the wind turbine of the hybrid system is (ahammad and shahidul, 2014): 𝑃𝑤ℎ = 𝑃𝑤𝑡𝑎 𝑃𝑝𝑣𝑎+𝑃𝑤𝑡𝑎 × 𝑃 (7) http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 310 where: p is the total load of appliances of heipang community not connected to the grid (kpang, tapo and tatu) in kw., 𝑃𝑝𝑣𝑎 is power generated by photovoltaic per unit area (kw/m2), 𝑃𝑤𝑡𝑎 is power generated by wind turbine per unit area (w/m2). 2.2.5 sizing and selection of photovoltaic module the power from the photovoltaic module should be able to meet the percentage of load allotted to it based on the solar potential in the site. if the load allotted to the photovoltaic system is shp , then the number of photovoltaic modules required to serve the load is: 𝑁𝑃𝑉 = 𝑃𝑠ℎ 𝑃𝑟𝑠 (8) where: 𝑃𝑠ℎ is solar power system load share (kw), 𝑃𝑟𝑠 is power rating of the selected photovoltaic module (kw). the photovoltaic module randomly selected for this research work was the won300 monocrystalline model (wuxi technology, 2019). the solar panel was selected because of its relatively higher efficiency when it was tested and compared with other monocrystalline solar panels available in market (noa testing inspection technology. 2018). 2.2.6 sizing and selection of wind turbine from equation 7 the load allotted to the wind turbine system is whp , thus, the number of wind turbines required to serve the load is: 𝑁𝑊𝑇 = 𝑃𝑤ℎ 𝑃𝑟𝑤 (9) where: 𝑃𝑠ℎ is solar power system load share (kw), 𝑃𝑟𝑤 is power rating of the selected wind turbine (kw) the wind turbines selected for the design was fd21-50 model (ghrepower, 2020). it was selected because of its high-power output performances in heipang wind speed regime as analyzed in the course of this research. battery was used to store excess energy or supply when there was energy deficit. battery life was affected by its depth of discharge. deep cycle batteries discharge 50-80% of their capacity (izdin.hlal et al., 2019). the battery capacity required to supply the full load demand was determined using equation 10 (tharani and dahiya, 2018). (10) where: 𝐸𝐿 is electrical load (kw), 𝑆𝐷 is battery day of autonomy (day), 𝜂𝑏𝑎𝑡 is efficiency of battery (%) the number of batteries in parallel was computed using equation 11: (11) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 311 where: 𝐶𝑤ℎis capacity of battery (wh), 𝐶𝑎ℎ is ampere-hour rating of the selected battery (ah), 𝑉𝐵 is nominal voltage of the selected battery (v). the number of batteries in series was obtained by equation 12: (12) where: 𝑉𝑠𝑦𝑠𝑡𝑒𝑚 is hybrid solar-wind power system voltage (v), 𝑉𝐵 is nominal voltage of the selected battery (v). the storage battery selected for the design was hoppecke 24 opzvsolar.power 3500 48v.this type of battery can be effectively used in sectors applicable with high charging and discharging operation such as in solar and other off-grid applications (europe solarstore, 2023). 2.2.7 sizing and selection of inverter the dc/ac converter, also known as inverter was used to convert dc signal from the battery to ac signal to supply to load. inverter power )(tpinv was determined using the corresponding load power requirements, as follows (ghenai et al., 2020): (13) where: 𝑃𝑙𝑜𝑎𝑑(𝑡) is power consumed by the load at hour t (kw), 𝜂𝐼𝑁𝑉 is inverter efficiency (%) sku-ato-ogi-200kw inverter was selected for this study (inverter.com, 2021). 2.3 simulation of hybrid solar-wind power system matlab programme codes were written to simulate the designed system to determine the performance indices such as: hourly power generated by solar and wind energy conversion systems, loss of power supply probability, battery state of charge and the capacity factors of the renewable energy system, using equations 1 to 29. equations 14 to 20 were used to convert solar radiation normal to the horizontal to that normal to the inclined plane corresponding to the plane of the photovoltaic (duffie et al., 2020). (i) angle of declination given as: (14) where: 𝑛𝑑 is number of the days in a year (ii) the hourly extraterrestrial solar radiation is the radiation beyond the atmosphere and is computed from the expression: (15) where: 𝐺𝑠𝑐 is solar constant 1367 (w/m2), 𝑛𝑑 is number of the days in a year, 𝛿 is angle of declination (degree), 𝜙 is latitude of the location (degree), 𝜔 is hour angle (degree).  http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 312 (iii) the clearness index relates the measured global radiation in the atmosphere to the extraterrestrial radiation and is computed from the expression: (16) where: 𝐺𝑚 is measured daily global solar radiation on horizontal surface (w/m2), 𝐺𝐸 is hourly extraterrestrial solar radiation (w/m2). (iv) the diffuse component of the total solar radiation is computed from: (17) where: 𝐺𝑚 is measured daily global solar radiation on horizontal surface (w/m2), 𝐾𝑇 is clearness index (v) the beam radiation on a horizontal plane can be computed from the relation: (18) 𝐺𝑚 is measured daily global solar radiation on horizontal surface (w/m2), 𝐺𝑑 is diffuse solar radiation (w/m2) (vi) the ratio of flux of beam radiation on an inclined surface to that on the horizontal surface is computed from: (19) where: 𝐺𝑠𝑐 is solar constant 1367 (w/m2), 𝑛𝑑 is number of the days in a year, 𝛿 is angle of declination (degree), 𝜙 is latitude of the location (degree), 𝜔 is hour angle (degree), �́� is inclined angle of solar panel to the horizontal plane (degree) (vii) the solar radiation normal to inclined angle equal to the solar panel inclination to horizontal plane or latitude of the location is estimated from: (20) where: 𝐺𝑏 is beam radiation on a horizontal plane (w/m2), 𝐺𝑑 is diffuse solar radiation (w/m2), 𝐺𝑚 is measured daily global solar radiation on horizontal surface (w/m2), 𝑅𝑏 is ratio of beam radiation on an inclined surface to that on the horizontal surface, 𝜌𝑔 is diffuse reflectance of the surroundings, �́� is inclined angle of solar panel to the horizontal plane (degree). 2.3.1 wind power output model the wind power output model used for the simulation of the designed system was computed using equations 4 and 5. the matlab codes uses equation 4 to convert the wind speed measured at 10m height at the weather station to the height of the wind turbine hub, which was used as input in equations 5. br file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 313 2.3.2 solar power output model model-1: homer model for solar power output developed by hybrid optimization of multiple electric renewables (homer) given in equation 1 to 3 was used in the simulation. model-2: using the solar radiation available on the tilted surface, the ambient temperature and the manufacturers data of the pv modules as model inputs, the power output of the pv generator, pvp was calculated using equation 21 and 22 which was also used in the simulation (zhou, 2007). (21) (22) where: 𝑁𝑃𝑉 is number of photovoltaic modules, 𝑣𝑜𝑐 is normalized value of the open circuit voltage to the thermal voltage (v), 𝑅𝑠 is photovoltaic module series resistance (ω), 𝑉𝑜𝑐 is open-circuit voltage of the photovoltaic module under standard test condition (v), 𝐼𝑠𝑐 is short-circuit current of the photovoltaic module under standard test condition (a), 𝐼𝑠𝑐𝑜 is short-circuit current of the photovoltaic module under the standard solar radiation, go (a), 𝑉𝑜𝑐𝑜 is open-circuit voltage of the photovoltaic module under the standard solar radiation go (v), 𝛽 is photovoltaic module technology specific-related dimensionless coefficient, 𝐺𝑜 is standard solar radiation 1000w/m2, 𝐺𝑇 is solar radiation normal to inclined plane (w/m2), 𝑇𝑜-is temperature of the photovoltaic module at standard condition 25oc (oc), 𝑇𝑐 is solar cell temperature (oc), 𝛾 is exponent considering all the non-linear temperature-voltage effect, 𝛼 is factor responsible for all the non-linear effects that the photovoltaic depends on, 𝑇𝑎 is ambient temperature of location of study (oc), 𝑇𝑐,𝑁𝑂𝐶𝑇 is nominal operating solar cell temperature (oc), 𝑇𝑎,𝑁𝑂𝐶𝑇 is ambient temperature at nominal operating temperature (oc), 𝐺𝑇,𝑁𝑂𝐶𝑇 is solar radiation at nominal operating solar cell (w/m2), 𝑇𝑎 is ambient temperature of location of study (oc) however, the five parameters ( in the model equation 21 were determined from the solar panel parameters measured by solar or flash simulator at the noa testing and inspection technology ltd, building 26, no. 2777, east jinxiu road, shanghai, china (noa testing inspection technology. 2018). 2.3.3 battery capacity model the initial storage capacity of the battery is computed as (tharani and dahiya, 2018): (23) where: 𝐶𝑏𝑎𝑡(𝑡 − 1) is battery bank capacity at hour (t-1) (wh), 𝐸𝐿 is electrical load (kw), 𝑆𝐷 is battery day of autonomy (day), 𝜂𝑏𝑎𝑡 is efficiency of battery (%), 𝐷𝑂𝐷 is depth of discharge (%). in case when the battery capacity reaches a maximum value, , the control system stops charging process. during the charging process, when the total output of pv module and wind generators is greater than the load demand, the available battery bank capacity at hour t can be determined as (izdin.hlal et al., 2019): (24) http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 314 on the other hand, the battery discharges when the load demand is greater than the available energy generated. thus, the capacity of the battery bank at any time t in hour can be expressed as (izdin.hlal et al., 2019): 𝐶𝑏𝑎𝑡(𝑡) = 𝐶𝑏𝑎𝑡(𝑡 − 1). (1 − 𝑠) − ( 𝑃𝑙𝑜𝑎𝑑(𝑡) ?𝑖𝑛𝑣 − (𝑃𝑃𝑉(𝑡) + 𝑃𝑊𝑇(𝑡))) 𝜂𝑏𝑎𝑡𝐷?𝑏𝑎𝑡𝐷 (25) where: 𝐶𝑏𝑎𝑡(𝑡 − 1) is battery bank capacity at hour (t-1) (wh), 𝜎 is self-discharge rate of the battery bank, 𝑃𝑃𝑉(𝑡) is power generated by solar system at time t (kw), 𝑃𝑊𝑇(𝑡) is power generated by wind turbine at time t (kw), 𝑃𝑙𝑜𝑎𝑑(𝑡) is power consumed by the load at hour t (kw), 𝜂𝑖𝑛𝑣 is inverter efficiency (%), 𝜂𝑏𝑎𝑡𝐶 is battery efficiency during charging process (%), 𝜂𝑏𝑎𝑡𝐷 is battery efficiency during discharging process (%). charging constraint discharging constraint (26) where: 𝐶𝑏𝑎𝑡 𝑚𝑖𝑛 is minimum capacity of battery (wh), 𝐷𝑂𝐷 is depth of discharge (%) =50%, 𝐶𝑏𝑎𝑡𝑚𝑎𝑥. is maximum capacity of battery = 1,512𝑘𝑊ℎ 2.3.4 energy management strategy of hybrid solar wind power system the role of control strategy management in hybrid solar-wind power system is very important in system operation. this is because a proper control system increases system efficiency, the power availability, the amount of power generated and the life span of the battery system while decreasing the number of deficit hours and the amount of dumped load of the system (sigarchian et al., 2014). the proposed energy management of the hybrid solar-wind power system is summarized as follows: case 1 if and then satisfy the load and charge the battery with the surplus power. case 2 if and then stop charging the battery, satisfy the load. excess power is dumped. case 3 if and then satisfy the load by discharging the battery to cover the deficit in load power file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 315 case 4 if and then stop battery discharging. there is power deficit. where: , is the total power generated by solar and wind power systems, , is the load demand of heipang community, , is the battery state of charge in time , , is the maximum state of charge of battery, , is the battery depth of discharge at time , , is the maximum depth of discharge of battery. figure 1: energy management strategy flow chart of hybrid solar-wind power system http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 316 2.3.5 hybrid solar wind power system total energy generation the total annual energy generation by the hybrid solar wind power system is computed as follows: (27) where: 𝑃ℎ(𝑡) is hybrid solar-wind power generated at time (t) (kw), 𝑃𝑝𝑣(𝑡) is power generated by solar system at time t (kw), 𝑃𝑤𝑡(𝑡) is power generated by wind turbine at time t (kw), 𝛥𝑡 is time step used for simulation (hr). 2.3.6 capacity factor of hybrid solar-wind power system the ratio of the actual power generated to the power it would have generated if operating at its rated capacity in one year is the capacity factor of a power system. the capacity factor of the hybrid (solarwind) power system was determined from (center for sustainable systems, 2023): (28) where: 𝑃ℎ(𝑡) is hybrid solar-wind power generated at time (t) (kw), 𝑃𝑃𝑉(𝑡) is power generated by solar system at time t (kw), 𝑃𝑊𝑇(𝑡) is power generated by wind turbine at time t (kw), 𝑃𝐻𝑦𝑏𝑟𝑖𝑑 is hybrid solar-wind power generated (kw), 𝑇 is operation time (8760) of hybrid solar wind power system (hr), 𝜂𝑖𝑛𝑣 is inverter efficiency (%), 2.3.7 total available energy generation for load demand the total energy, generated by the wind turbine and pv generator at hour to meet a demand at hour is calculated as follows: i.e., energy generated by solar and wind plus the energy stored in battery. (29) 𝐶𝑏𝑎𝑡(𝑡 − 1) is battery bank capacity at hour (t-1) (wh), 𝑃𝑃𝑉(𝑡) is power generated by solar system at time t (kw), 𝑃𝑊𝑇(𝑡) is power generated by wind turbine at time t (kw), 𝛥𝑡 is time step used for simulation (hr), 𝐶𝑏𝑎𝑡 𝑚𝑖𝑛 is minimum capacity of battery (wh), 𝜂𝑖𝑛𝑣 is inverter efficiency ( %). 3. results and discussion 3.1 designed hybrid solar-wind power system based on the load sharing strategy design approach, 283 units of 300w capacity solar panels, 2units of 50 kw rated capacity wind turbine at 42m high and 90 units of 48v, 350ah deep cycle battery will be required to meet the estimated load demand of 158.32 kw and a daily energy demand of 710.59 kwh/day, with two days autonomy (figure 2). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 317 figure 2: diagram of the designed hybrid solar-wind power system 3.2 simulation of hybrid solar-wind power system 3.2.1 solar power output figure 3 (a, b, c and d) shows the plot of the power output of photovoltaic system against time for different hours of the day and different days of the year under consideration. there is a correlation between the simulation results of the solar power output of the photovoltaic system using solar power model 1 developed by (homer, 2016) as given by equation 1 and solar model 2 developed by (zhou, 2007) as given by equation 21. the results show a high level of correlation value of 0.9998, between solar power models 1 and 2 and can thus be used interchangeably. the solar power generated corresponds to the intensity of the incident solar radiation, which increases from morning hours (7: 00 am) when the solar intensity is low and peaks up around afternoon hours, when there is no cloud and declines as the sun sets in the evening. similarly, the models correlate throughout the seasons of the year depending on the diurnal and seasonal variation of the solar radiation in the location of study. the plots also show a close superimposition of the solar power models thereby substantiating the high correlation between the models. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 318 figure 3: plots of power output pf photovoltaic system against time 3.2.2 solar and wind power output figure 4 (a, b, c and d) presents the plots of the solar and wind power generated against time for different months of the year under review, with solar and wind energy penetration of 48%, 52% in march, 40%, 60% in june, 30%, 70% in september and 42% and 58% in december respectively. as shown in the figures, wind power yield is relatively more stochastic than solar and cannot provide stable power supply if used alone. based on the simulation of the hybrid solar wind power system, annual performance assessment of the system shows that the solar power system has a capacity factor of 18%, higher than that in cirata, indonesia which 15% (febrian et al., 2023). wind power system has a capacity factor of 23% which is over 20%, lower than that in usa which ranges from 21% to 52% and averages 35% (center for sustainable systems, 2023) and the hybrid solar wind power system having capacity factor of 21%. this is an indicator of high solar and wind energy potentials in heipang community. the plot also shows some level of complementarity between the solar and wind energy generation as wind energy is generated in the night hours when there is no sunshine. the complementarity is measured by the coefficient of correlation which gives a value 0.24. if the coefficient of correlation is 1, the two renewable sources vary in the same way and when it is -1, they vary in opposite way which shows good complementarity. in figure 4b, there is complementarity for hours between 6:00 pm of the first day to 8:00 am the next day and between 6:00 pm of the second day to 8:00 am the third day. similarly, in figure 4c, the solar and the energy show good complementarity between the 15 to 30 hours. however, in the late hours of the third day there is power deficit to meet the load and that is where the battery backup role comes to play. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 319 figure 4: plots of solar and wind power generated and load demand against time 3.2.3 hybrid solar-wind power generated, load demand and state of charge of battery of system figure 5 (a, b, c and d) shows a three-day plot of hybrid solar-wind power, battery stored energy and load demand over hours of the days for different months of the year under review. the designed system is based on 2 days autonomy, meaning the battery can supply power for two consecutive days when there is no power generation by either solar, wind or both power systems which is the minimum requirement for solar wind power system design (adeoye et al., 2022), (broomfield designers, 2017). based on the simulation plot the energy in the battery meets the load demand of the haipang community. as shown in the figures, the battery complements the power deficit of the hybrid solarwind power system, thereby meeting the load demand of heipang community. in extreme cases where the battery fails to meet the load demand, there will be power deficit. this problem can be solved http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):305-324. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 320 figure 5: plot of hybrid solar-wind power generated, battery energy and load demand against time figure 6 (a, b, c, d and e) shows the annual simulation plot of solar-wind power, and load demand, battery soc in kwh, deficit load, dump load and battery soc in % against time. based on the simulation results shown in figures 6a 6b, 6c, 6d and 6e, the hybrid system has an annual load deficit of -2676.81kw and an excess load of 117, 676.89kw as generated by the solar-wind power system as obtained. the battery state of charge depends on the energy generated and the load demand at any time. in figure 6b the plot trend shows the soc of the battery is high enough to meet the load demand except between 1000 and 2000 hours point and between 4000 to 7000 hours where the soc drops to minimum soc (socmin) which results to power deficit as shown in figure 6c. figure 6d shows dump load plot with the excess power generated corresponding with when there is high energy generation by the hybrid solar-wind power system. the question that comes to mind is why the deficit when there is excess power generated? this is because renewable energy generation is stochastic in nature so the energy generated may not occur corresponding to the load demand. thus, sometimes there will be moments of excess generation when the load is at its lowest or deficit when the load demand is at its peak when there is no power generation by the hybrid system. backup battery reduces the dump load as excess power is stored in the battery after meeting the load demand. one of the ways to reduce the excess or deficit power generation is by optimal design of the hybrid solar-wind power system. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com maren et al: performance evaluation of a hybrid solar-wind power system for heipang community load demand. azojete, 20(1):305-324. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 321 figure 6: plot of annual simulation of (a) solar-wind power and load demand (b) battery soc in kwh (c) deficit load (d) dump load and (e) battery soc in % against time. 4. conclusion a hybrid solar-wind power system was designed to meet the load demand of haipang community not connected to the grid. for a load demand of 158.32 kw and a daily energy demand of 710.59 kwh/day, with two-day autonomy, the system capacity to meet the load demand comprise of 283 units of 300w solar panels, 2 units of 50 kw rated capacity wind turbine at 42m high and 90 units of 48v, 350ah deep cycle batteries. simulation result of the system shows that the designed system meets the load demand of the community with an annual excess power generation of 128,394.02kw and a deficit of 2676.81kw. the capacity factor of the hybrid solar-wind power system is 21% which compete favorably with solar generation in other countries such as indonesia which is 15%. this shows that it is feasible to design a hybrid solar-wind power system to meet the load of heaipang community. there is slight complementarity between solar and wind power generation, the battery backup system enhances the efficient performance of the hybrid solar-wind power system and reduce energy deficit and dump load. optimal design of the hybrid solar-wind power system will further reduce the excess and deficit power of the system. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng corresponding author’s e-mail address: mareni@unijos.edu.ng 322 references adeoye, o., cofie, p. and abood, s. 2022. pv solar battery sizing autonomy for residential applications photovoltaic solar battery sizing autonomy for residential applications. american society for engineering education, 5: 1-8. ahammad, m. and shahidul, ik. 2014. design strategy for aan off-grid solar-wind hybrid power system. 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drive for greater efficiency is necessary to increase the amount of electricity generated per watt of installed pv capacity and so reduce the unit cost of the electricity. when simulations related to the behavior of system are accessible and reliable (abdulkadir et al. 2012) it reduces time dedicated to discrimination and investigations, therefore, there exists a strong connection between applied sciences and mathematics addressed by numerical models applied to the simulation of systems of real world. just as the fossil fuel-based energy industry relies on exploration and article information abstract measurement and modeling of broadband and spectral terrestrial solar radiation is important for the evaluation and deployment of solar renewable energy systems. this paper focuses on optimizing the performance of 200w solar module taking into consideration the local climatic conditions of bauchi locality. the uncertainty in life cycle savings for solar thermal and photovoltaic (pv) systems as linearly correlated with uncertainty in solar resource data. these uncertainties paved way for the need to conduct a critical assessment of the resource. assessment of the solar resource for these technologies rely upon measured data, where available. in this paper, we present the development of mathematical model of photovoltaic solar cells based on their detailed single diode equivalent circuit representation. pertinent simulation models for pv solar module both for an ideal weather situation and for taking into consideration the effects of microclimatic conditions that prevail in bauchi as evaluated and compared with benchmarks available. the complete model of the pv system was implemented using matlab/simulink platform. the standard characteristic curves for the 200w solar panel are as presented. the simulation of the ideal pv system made use of standard test conditions (stc) to facilitate comparison with the existing benchmark results in the literature. the analysis of the characteristics performance curves returned an average voc = 42.9v and isc = 4.21a. the simulation results further revealed that the power delivered by the 200w monocrystalline solar module of 144.3w @620w/m2, 35ºc as recorded for bauchi under all climatic conditions as evaluated. the benchmark values obtained in the laboratory are voc = 45.5v, isc = 5.92a and 200-w under the standard test condition (stc) conditions of cell temperature 25ºc, solar irradiance of 1000w/m2 and air mass (am) of 1.5. the average conversion efficiency and fill factor as evaluated are 0.77 and 16% respectively. this result agrees with the benchmark of module efficiency of >15.66% recorded at stc. the results conclusively reveal that the microclimate of a locality essentially affects the performances of solar pv systems deployed to each location on the globe. therefore, utilization of these parameters is essential for consideration in the design of solar systems in all localities. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 13 july, 2021 revised 24 november, 2021 accepted 2 december, 2021 keywords: characteristic curves terrestrial solar radiation technologies mathematical modeling microclimate parameters pv systems http://www.azojete.com.ng/ mailto:kunduli@yahoo.com mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 98 proven reserves for discovery and economic support of energy markets, the renewable energy sector depends upon the assessment of resources for planning and selling their energy production technology. for solar-based renewable energy technologies such as solar thermal or photovoltaic conversion systems, the basic resource or fuel available is the sunshine. research have shown that uncertainty in life cycle savings for solar thermal and photovoltaic (pv) systems has linear correlation with uncertainty in solar resource data (zainab et al. 2020). assessment of the solar resource for these technologies rely upon measured data, where available. however, the sparse distribution in space, and particularly over time, of measured solar data leads to the use of modeled solar radiation as the basis for many engineering and economic decisions. measured and modeled solar radiation have attendant uncertainties. most solar radiation models rely on measured data for their development or validation, and often the uncertainty or accuracy of that measured data is unknown. this paper presents the performance of the 200w solar panel using modeling and evaluation of results arising from it. the modeling of pv cell for the most part involves the approximation of the non-linear i-v curve. many researchers utilized circuit-based approach to characterize the pv cell of which the simplest model is the current source in corresponding to a diode. investigation of the improvement of a technique for the mathematical modeling of the pv cell is important to satisfy the numerical i-v equation with the experimental remarkable points of the i-v curve of the practical solar cell (guda, 2012). to describe a specific photovoltaic cell, it is appropriate to decide the current-voltage (i-v) and power-voltage (p-v) characteristic curves of the array for all operating field conditions. this is significant because the performance characteristic of the pv cell’s building block regularly published in the manufacturer’s datasheet depends on ideal standard test condition (stc) that may not be achievable anywhere on the planet (guda, 2012; jayashri and harish, 2013). subsequently, the need to conduct the mathematical modeling to characterize the system and restrict the model to track down the optimal performance of the pv cell/module at prevailing conditions found in a specific area. tarak et al. (2012) introduced matlab/simulink model to mimic the solar cell at different boundary conditions while (gupta et al. 2017) introduced the advancement of a matlab/simulink model for the solar pv cell, module and array. (guda and aliyu, 2015; jayashri and harish 2013) additionally recreated the attributes of pv module for acquiring the exhibition of a reference pv array. mansur and richard (1989) reported that knowledge of the characteristic of photovoltaic (pv) panel is a prerequisite for designing and dimensioning a pv electricity power supply system. these were the reason for the development of pv panel models useful for electrical applications. (abdulwahab, 2014; rahim and mehrdad, 2018) presented modeling and simulation for the pv cells, modules, and array, and building of blocks based on matlab / simulink programming package. the aim of this paper is to develop a model based on the equivalent single diode circuit using matlab/simulink resources to generate the characteristic curves of the solar pv system under investigation, extract the computed key output parameters such as vpv, ipv and ppv. other objectives include evaluation of performance of the pv electricity generator by comparing the output power when the operating temperature is calculated and measured respectively, determination of the module conversion efficiency, the fill factor (ff) and compare the results with the benchmark values (efficiency >15.66% and 0.7 – 0.8 ff) of the module technology under investigation. 2. materials and method in this section, the materials deployed, and methods used in achieving the objectives of this work are presented. it guides the paper in the proper sequence into its logical conclusion. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:kunduli@yahoo.com mustapha et al: performance evaluation of 200w solar photovoltaic panel considering bauchi microclimatic conditions. azojete, 18(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 99 2.1 description of the experimental test rig the ground data used was from the archives of the experimental test rig and car database all in the department of electrical and electronics engineering, atbu, bauchi, nigeria. the key data measuring equipment installed at the stations are; kipp & zonen pyranometer, wind monitor (05103-l) (medugu and ogbaka, 2017), data logger (cr 1000), are all found at campbellsci, (2021). the data parameters for the study are as presented in table 1. bauchi is located at lat. n10º 16’ 48.1”, lon. e 9º 47’ 23” and alt. 627m. the electrical characteristics of the installed 200w solar module are as presented in table 2 to serve as part of the inputs parameters to the pv model for simulation to determine the power output for the microclimate in consideration. data measured for the year 2019 from the experimental test bed installed at the research hut of the faculty of engineering, abubakar tafawa balewa university (atbu) bauchi and that obtained from the meteorological station installed by center for atmospheric research (car) at the department of electrical and electronics engineering, atbu bauchi described above for the comparative performance analysis. table 1: meteorological data description table 2: electrical characteristics of 200w solar module @stc (african energy, 2014) 2.2 methods 2.2.1 temperature dependent electrical efficiency of pv module the most common model for calculating cell temperature (tc) is given by eqn. (1), (de rosa et al. 2015; mboumbow and njomo 2013; xue gui et al. 2011). 𝑇𝐶 = 𝑇𝑟𝑒𝑓 + (𝑁𝑂𝐶𝑇 − 20𝑂𝐶) 𝜙 800 (1) where; tref is the reference ambient temperature, noct is the nominal operating cell temperature, 𝜙 solar irradiance at that instance. module technology (simono) values nominal output (pmax) [ wpk ] 200 voltage at pmax ( vmp) [v ] 37.77 current at pmax (imp) [a] 5.29 open circuit voltage (voc) [v] 45.25 short circuit current (isc) [a] 5.92 power tolerance +/3% maximum system voltage dc 1000v cell efficiency >18. >18.3% -165 module efficiency >15.66% table 1: meteorological data description s/n. parameter unit 1. solar irradiance w/m2 2. ambient temperature (0c) 3. air temperature (0c) 4. relative humidity % 5. wind speed m/s 6. wind direction degrees 7. barometric pressure bars 8. cell temperature (0c) http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 100 the correlation between temperature rise and the decline of pv efficiency (η) as presented in eqn. (2) (adeel et al. 2019; tao et al. 2018). 𝜂 = 𝜂𝑟𝑒𝑓[1 − 𝛽𝑟𝑒𝑓(𝑇𝐶 − 𝑇𝑟𝑒𝑓) + 𝛾𝐿𝑜𝑔10𝜙(𝑡)] (2) where; ηref, is the reference pv efficiency, βref is the temperature coefficient of pv efficiency (0.5%/°c); tc and tref represents the real pv temperature and the reference temperature at the standard test condition respectively (stc) in °c and γ is the solar radiation coefficient. ϕ is a material property, having values of about 0.004/k and 0.12/k respectively, for crystalline silicon modules, the latter part, however, is usually taken as zero and eqn. (2) reduces to eqn. (3) (adeel et al. 2019; tao et al. 2018). 𝜂 = 𝜂𝑟𝑒𝑓[1 − 𝛽𝑟𝑒𝑓(𝑇𝐶 − 𝑇𝑟𝑒𝑓)] (3) the effect of temperature on the electrical efficiency of a pv cell/module is determined by using the fundamental equation of power (pm) as in eqn (4) (adeel et al. 2019). 𝑃𝑚 = 𝐼𝑚𝑉𝑚 = (𝐹𝐹)𝐼𝑆𝐶𝑉𝑂𝐶 (4) where; ff is fill factor, isc is short circuit current, voc is open circuit voltage and subscript m refers to the maximum power point in the modules i-v curve. both the open circuit voltage and the fill factor decrease substantially with temperature (as the thermally excited electrons begin to dominate the electrical properties of the semi-conductor), while short-circuit current increases, but only slightly. 2.2.2 characteristic of solar cell the analysis of the characteristics of the solar cell is resolved by using the equivalent electrical circuit model of the pv cell depicted in figure 1. it is a one-diode model, also known as the 5-parameter circuit. the most commonly used one diode model of figure 1 can model the cell. the parameters in the circuit are; diode current (id), photo generated current (isc), shunt current (ish), shunt resistance (rsh), series resistance (rs), output current (i) and output voltage (v). the ideal photovoltaic module consists of a single diode connected in parallel with a light generated current source (isc) (abdulkadir et al. 2012). figure 1: equivalent one diode model of solar cell applying kirchhoff’s current law, the output current (i) is given by eqn. (5), (harrag and messalt, 2017) 𝐼 = 𝐼sc − 𝐼𝐷 − 𝐼sh (5) isc (photo-generated current) is also called il (light current) which refers to direct current generated by photovoltaic effect, whereas i is the output current of the cell. the light current depends on both irradiance and temperature and measured at some reference conditions eqn. (6), adeel et al. (2019). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:kunduli@yahoo.com mustapha et al: performance evaluation of 200w solar photovoltaic panel considering bauchi microclimatic conditions. azojete, 18(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 101 𝐼𝑆𝐶 = [𝐼𝑆𝐶𝑟𝑒𝑓 + 𝐾𝑖(𝑇𝑘 + 𝑇𝑟𝑒𝑓)] = 𝜎 1000⁄ (6) from shockley’s diode equation eqn. (7) (santiago, 2018). 𝐼𝐷 = 𝐼𝑂 [𝑒𝑥𝑝 { (𝑉+𝐼𝑅𝑆) 𝑛𝑉1 } − 1] (7) where; 𝑉1 = 𝑘𝑇 𝑞 (nguyen and nguyen, 2015) (8) applying ohm’s law the shunt current; 𝐼𝑆𝐻 = 𝑉+𝐼𝑅𝑆 𝑅𝑆𝐻 (9) substitute eqn. (6), (7), and (8) in eqn. (5) and re-arranging them gives the output current in eqn. (9) in the form of eqn. (10). 𝐼 = 𝐼𝑆𝐶 − 𝐼𝑂 [𝑒𝑥𝑝 { 𝑞(𝑉𝑃𝑉+𝐼𝑃𝐻𝑅𝑆) 𝑁𝑆𝐴𝑘𝑇 } − 𝑉𝑃𝑉 + { 𝐼𝑃𝐻𝑅𝑆 𝑅𝑆𝐻 }] (10) where i(a) is pv cell current, isc is the photo-generated current in (a) or short circuit current, io is the diode saturation current (a), q is the electron charge (1.602 x 10-19 c.), vpv photovoltaic open circuit voltage in (volts), iph is the photo current (a), rs is the series resistance in ohms, ns is the number of series cells, a is the diode ideality factor, k is boltzmanns constant (1.38 x 10-23 joules per kelvin, t is the cell temperature in kelvin and rsh is the shunt resistance in ohms. 2.2.3 performance of photovoltaic panel (afr 200) the performance of the pv cell is determined at three (3) key points on the characteristic curve. five (5) eqns. are required to find the five unknown parameters in eqn. (13). manufacturer’s data sheet provides cell voltage and current at three (3) key points at m, a and s depicted in figure 2. figure 2: pv characteristics curve illustrating key points of performance 𝐼𝑆𝐶 = 𝐼𝐷 − 𝑉𝐷 𝑅𝑆𝐻 − 𝐼𝑃𝑉 = 0 (11) 𝐼𝑅𝑆 = 𝐼𝑆𝐶𝑟𝑒𝑓 [𝑒𝑥𝑝 ( 𝑞𝑉𝑂𝐶 𝑁𝑆𝑘𝐴𝑇 ) − 1] (12) 𝐼𝑂 = 𝐼𝑃𝑉 [( 𝑇 𝑇𝑟𝑒𝑓 ) 3 𝑒 𝑞𝐶𝑔 𝐴𝑘 ⁄ × ( 1 𝑇𝑟𝑒𝑓 − 1 𝑇 )] (13) 𝐼𝑃𝑉 = 𝑁𝑃𝐼𝑆𝐶 − 𝑁𝑆𝐼𝑂 [𝑒𝑥𝑝 { 𝑞(𝑉𝑃𝑉 + 𝐼𝑃𝐻𝑅𝑆) 𝑁𝑆𝐴𝑘𝑇 } − 1] − 𝑉𝑃𝑉 + { 𝐼𝑃𝐻𝑅𝑆 𝑅𝑆𝐻 } (14) the parameters that need to be defined before solving eqn. (14) are rsh, rs, a, iph and io. these parameters are specific to every different commercial pv module and calculated from the product data sheet values http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 102 tested at standard test condition (stc) or reference point, 1kw/m2 solar irradiation, 25oc cell temperatures and air mass (am)1.5 (iec, 2008). knowing the parameters, solar radiation data and the cell temperature, the electricity generated by the solar cell can be determined. to solve the four non-linear equations with four unknowns, matlab codes as written and simulink blocks constructed to calculate the ipv, vpv and ppv using figure 3. the solar irradiance and the calculated cell temperature (tc) and or measured cell temperature as imputed to the simulink model for the p-v characteristic curves and i-v characteristic curves; upon appropriate matlab, command is given. eqns. (6), (7), (11), (12), (13) and (14) imbedded in sub blocks within the simulink model solves for the required unknowns. this method eliminates the long iteration associated in the newton raphson method used by (guda and aliyu, 2015) for solving the unknown equations derived, represented here in equations (11), (12), (13) and (14). data filter pro, origin 50, and matlab computing software as utilized to process the data. the algorithmic flowchart for the implementation of the simulation is as in figure 4. figure 3: pv model simulator ppv ipv vpv pv power i-v char vpv workspace-vpv ppv workspace-ppv ipv workspace-ipv vpv product pv power pv current vin inso temp vout ipv pv modulesimulik model temperature operating temp insolation irradiance file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:kunduli@yahoo.com mustapha et al: performance evaluation of 200w solar photovoltaic panel considering bauchi microclimatic conditions. azojete, 18(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 103 figure 4: algorithmic flowchart for pv model simulation 3.0 results and discussion 3.1 characterization of measured data the various results for the performance evaluation of the 200w solar pv panel obtained in this paper are as presented and subsequently discussed. firstly, is the determination of the power output of the 200w panel at prevailing weather conditions of bauchi. secondly, the fill factor and module efficiency are determined. the characterized seasonal average test bed data presented in table 3 and that for center for atmospheric research (car) data obtained from the archives of electrical and electronics engineering department in table 4. the seasons comprised of harmattan spanning through october, november, december and january; clear sky spanning through february, march, april and may while cloudy spans through june, july, august and september for the year 2019 these seasonal average solar irradiance and cell temperature are the inputs to the matlab simulink model to generate the characteristic curves to determine the performance parameters comprising of open circuit voltage (voc), short circuit current (isc), and power output of the 200w solar module using the characterized data presented in tables 3 and 4. secondly, open circuit voltage (voc), short circuit current (isc), voltage at maximum power point (vmmp), current at maximum power point (impp) and power at maximum power point (pmpp) using data characterized in table 3 for varying temperature between 25oc and 75oc keeping solar irradiance constant for the respective seasons. http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 104 table 3: summary of statistical characterizations of measured test rig data for bauchi measured parameters statistical information micro-climatic seasons harmattan cloudy clear sunny solar irradiance (w/m2) maximum 761 723 758 average 653 563 646 minimum 348 341 347 temperature (oc) maximum 41 35 48 average 38 33 44 minimum 30 31 35 table 4: summary of statistical characterizations of measured car met data for bauchi measured parameters statistical information micro-climatic seasons harmattan cloudy clear sunny solar irradiance (w/m2) maximum 484 628 724.5 average 448 412 608 minimum 425.4 120 381 temperature (ºc) maximum 30 27 35 average 27 26 33 minimum 24 24.9 30 3.2 analysis of characteristic curves the family of seasonal characteristic i-v curves of the 200w solar module installed at the test rig for the three seasons are as presented in figures. 5 (a, b, & c) and 6 (a, b, & c) when the cell temperature was measured directly from the underside of the module and when the cell temperature was calculated using eqn. (1) respectively. figures. 7 (a, b & c) presents the corresponding family of p-v curves when the cell temperature was measured and similarly, figures. 8 (a, b & c) are p-v curves when the cell temperature was calculated using eqn. (1). the characteristics in the figures clearly depicts the variations in the respective seasons; during each season the power output is dependent both on solar irradiance and temperature changes. the effect is noticeable during the cloudy season because of cloud cover at that period. during the harmattan however, the variation is small due to hazy conditions. the clear sunny period shows a remarkable performance due to the clearness of the sky during that period. the current and voltage deduced from them are isc = 4.4a, voc = 43.5v during harmattan season; isc = 4.6a, voc = 42v during the clear sunny season and isc = 3.64a, voc = 43.2v during the cloudy season. the average power generated for the year was 144.3w. similarly, when the data obtained from car station was used, the cell temperature was calculated using eqn. (1), the corresponding values of the current and voltage deduced from this family of curves are isc = 2.72a, voc = 43.4v during harmattan season; isc = 3.93a, voc = 43.3v during the clear sunny season and isc = 2.47a, voc = 43.3v. the average power generated for the year was 104.2w. these results showed correlating values when compared to the benchmark values of isc = 5.9a, voc = 45.5v, and 200w obtained at stc (25oc, 1000w/m2 and am of 1.5). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:kunduli@yahoo.com mustapha et al: performance evaluation of 200w solar photovoltaic panel considering bauchi microclimatic conditions. azojete, 18(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 105 (a) harmattan season (b) clear sunny season (c) cloudy season figure 5: seasonal average i-v characteristics curve using test rig data for bauchi (a) harmatttan season (b) clear sunny season (c) cloudy season figure 6: seasonal average i-v characteristics curve using car data for bauchi (a) harmatttan season (b) clear sunny season (c) cloudy season figure 7: seasonal average p-v characteristic curve using test bed data for bauchi (a) harmatttan season (b) clear sunny season (c) cloudy season figure 8: seasonal average p-v characteristic curve using car data for bauchi table 5 summarizes the performance indices of the 200w solar panel investigated. it can be seen that the average values of short circuit current (isc), open circuit voltages (voc) and power at maximum power point (pmpp) for the three scenarios are correlating and within the benchmark of the manufacturers results. table 5: performance analysis of the 200w solar module performance indicator measured temperature calculated temperature laboratory obtained values (@stc) short circuit current (a) 4.2 3.04 5.9 open circuit voltage (v) 42.9 43.3 45.5 power at max. power point (w) 144.3 104.2 200 http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 106 where; test rig or experimental rig in column 1; refers to the results computed when the cell temperature of the solar panel was measured directly at the underside of the surface of the panel on the other hand car column 2; refers to the results computed when the cell temperature was calculated at prevailing bauchi microclimate conditions using eqn. (1). these results are now compared and tallied with the values obtained by the manufacturer at standard test condition (stc) defined in the methods as obtained in the laboratory presented in column three and it is the benchmark to which the performance is validated. figure. 9. (a, b & c) are family of characteristic curves generated at an interval of 5ºc rise in cell temperature starting from 25ºc to 75ºc. the curves as generated facilitates to investigate the temperature effects on the performance efficiency and the fill factor of the solar module at the prevailing weather conditions of bauchi. the determined key performance indicators as compared to the benchmark values from manufacturer’s data sheet. fill factor and conversion efficiency are performance parameters of pv cells that are dependent on the cell temperature and irradiation prevailing at a location. the fill factor is dependent on the thermally excited electrons, as the temperature begin to rise it dominates the electrical properties of the semi-conductor. the correlation between temperature rise and the decline of pv efficiency as presented in eqn. (3) was the basis for this evaluation, hence, the use of the curves to extract key evaluation parameters. (a) harmattan season (b) clear sunny season (c) cloudy season figure 9: family of i-v & p-v characteristic curves as a function of temperature for bauchi tables 6 presents the conversion efficiency and the fill factor for the 200w solar module under investigation. the trend revealed that; as the temperature begins to rises, the value of the conversion efficiency drops progressively to 13.6% across all the season. similarly, the fill factor follows in the same trends to about 0.77 as the temperature rises to 75ºc. the overall result gives an average efficiency of 16% and fill factor of 0.77. the performance of the 200w module investigated for the whole year is satisfactory. this result is in the neighborhood of the benchmark of >15.66% presented by the manufacturers data sheet at stc. it can as well be seen that as the fill factor approaches unity the conversion efficiency improves and hence, the performance of the pv module. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:kunduli@yahoo.com mustapha et al: performance evaluation of 200w solar photovoltaic panel considering bauchi microclimatic conditions. azojete, 18(1):97-108. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 107 table 6: temperature effects on the conversion efficiency and fill factor for the 200w solar module in the three climatic seasons temperature (ºc) micro-climatic variant harmattan cloudy clear sunny fill factor conversion efficiency (%) fill factor conversion efficiency (%) fill factor conversion efficiency (%) 25 0.800 16.9 0.744 16.9 0.886 16.9 30 0.767 16.7 0.797 16.7 0.859 16.7 35 0.756 16.3 0.805 16.3 0.817 16.3 40 0.747 16.0 0.812 16.0 0.718 16.0 45 0.794 15.7 0.801 15.7 0.757 15.7 50 0.779 15.3 0.773 15.3 0.779 15.3 55 0.765 15.0 0.749 15.0 0.747 15.0 60 0.744 14.6 0.727 14.6 0.732 14.6 65 0.730 14.3 0.725 14.3 0.769 14.3 70 0.724 13.9 0.768 13.9 0.777 13.9 75 0.744 13.6 0.784 13.6 0.787 13.6 4. conclusion the mathematical model of the solar pv system for the determination of performance parameters as implemented in this paper was successful. the 200w module i-v and p-v characteristics performance curves analysis conducted returned an average open circuit voltage of 42.9v and short circuit current of 4.21a, under all climatic conditions in bauchi. this result is in agreement with the benchmark values obtained in the laboratory of voc = 45.5v, isc. = 5.9a and 200w at stp conditions (25ºc, 1000w/m2 and am of 1.5). the simulation results further revealed that the power delivered by the 200w monocrystalline solar module of 144.3w @620.6w/m2, 35ºc is within the benchmark obtained at stp in the manufacturer’s data sheet. the evaluated conversion efficiency of 16% and fill factor of 0.77 are within the benchmark values of >15.66% efficiency and 50% to 82% fill factor range for silicon solar cells respectively. finally, the key results presented here have conclusively exhibited the performance of the solar module investigated. acknowledgement the results presented in this paper rely on trodan data collected and managed by the centre for atmospheric research, national space research and development agency, federal ministry of science and technology, anyigba, nigeria. we thank the centre for atmospheric research and their partners for promoting high standards of atmospheric observatory practice as well as the federal government of nigeria for continuous funding of the nigerian space program (www.carnasrda.com). references abdulkadir, m. samosir, as. and yatim, ahm. 2012. modeling and simulation based approach of photovoltaic system in simulink model. arpn journal of engineering and applied sciences, 7(5): 616-623. abdulwahhab, om. 2014. improvement of the matlab/simulink photovoltaic system simulator based on a two-diode model. international journal of soft computing and engineering (ijsce), 4(1): 117-122. adeel, s., kashif, m. and faizan, r. 2019. the efficiency of solar pv system. proceedings of 2nd international multi-disciplinary conference 19-20 december 2016, gujrat. https://www.researchgate.net/ pp.1-7. african, e. 2014. photovoltaic module afr200 www.africanenergy.com (2014 ed., pp. 1). st. david, arizona, usa 85630. www.africanenergy.com http://www.azojete.com.ng/ mailto:kunduli@yahoo.com http://www.carnasrda.com/ https://www.researchgate.net/publication/334277230 http://www.africanenergy.com/ http://www.africanenergy.com/ arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):97-108. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kunduli@yahoo.com 108 de rosa, m., romano, g., rossi, c., scarpa, f. and tagliafico l. 2015. a dynamic thermal model for hybrid photovoltaic panels. energy procedia, 81: 345 – 353. firth, sk., lomas, kj. and rees, sj. 2010. a simple model of pv system performance and its use in fault detection. solar energy, 84: 624–635. guda, ha. 2012. improved modeling and simulation of a stand-alone experimental photovoltaic array for different climatic conditions of bauchi locality. phd thesis, abubakar tafawa balewa university, bauchi, nigeria. guda, ha. and aliyu, uo. 2015. photovoltaic array conversion efficiency and fill factor performances under varying intensity of solar irradiance. international journal of engineering and technology, 5(6): 329334. gupta, n., garg, r. and kumar, p. 2017. sensitivity and reliability models of a pv system connected to grid. renewable and sustainable energy reviews, 69: 188–196. harrag, a. and messalti, s. 2017. three, five and seven pv model parameters extraction using pso. international conference on technologies and materials for renewable energy, environment and sustainability, tmrees17, 21-24 april 2017, beirut lebanon. energy procedia, 119: 767–774. jayashri, v. and harish, kk. 2013. mathematical modeling and experimental validation of performance characteristics of solar 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kc. and kaushik, p. 2014. effects of ambient temperature and wind speed on performance of monocrystalline solar photovoltaic module in tripura, india. journal of solar energy, 2014: 1-5. doi: 10.1155/2014/817078 tao, m., jiaxin, z. and zhenpeng, l. 2018. mathematical modelling and sensitivity analysis of solar photovoltaic panel integrated with phase change. material applied energy, 228: 1147–1158. tarak, s., mounir, b., adel, g. and ahmed, m. 2012. matlab/simulink based modelling of solar photovoltaic cell. international journal of renewable energy research, 2(2): 213-218. xue-gui, z., zhi-hong, f., xing-ming, l. and xin-li, l. 2011. sensitivity analysis and more accurate solution of photovoltaic solar cell parameters. solar energy, 85: 393–403. zainab, u., joseph, t., henry, a. and charles, n. 2020. a critical appraisal of pv systems performance. a review. building, 10 (11): 192, www.mdpi.com/journal/buildings file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:kunduli@yahoo.com http://www.mdpi.com/journal/buildings arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):607-622 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 607 original research article partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control i. j. udom department of agricultural engineering, akwa ibom state university, ikot akpaden, nigeria *corresponding author’s email address: ikpeudom@aksu.edu.ng 1.0 introduction intensive piggeries constitute point sources of nutrient loaded waste waters which is the primary cause of algal bloom in the akwa ibom state university (aksu) tributary of the obio akpa river. reduction of the nutrient concentrations in the wastewater to required standard for discharge to land and surface water is necessary (mariet et al., 2013). one economical way to do this is to optimize the efficiency of agricultural wastewater treatment technologies to cope with the continuous intensification of waste generation and pollution of land and water resources particularly in developing countries (adeyi et al., 2014). according to schilling (2021) the best economical approach to decrease wastewater nutrient and sediment loads to streams and rivers is to create wetlands along water courses to intercept and process approaching wastewater loads. article information abstract piggery wastewater management is an environmental concern due to the risk of nutrient pollution on surface and groundwaters. in surface and subsurface flow constructed wetlands, nutrient removal show inconsistency, and the contributions of their various partitions remain unclear; making the optimization of constructed wetlands (cw) systems difficult. pennisetum clandestinum plants and sediment in constructed wetlands play important roles in nutrient polishing and reduction but their capacities have not been partitioned. an experimental constructed horizontal sub-surface flow wetland (hssfw) planted with pennisetum clandestinum was fed from a piggery wastewater source at akwa ibom state university (aksu). samples of piggery wastewater were collected before and after each six respective days of detention in the wetlands. nutrient mass balances and effluent qualities of the partitions were evaluated based on world health organization (who) and nigeria environmental standards regulation enforcement agency (nesrea) benchmarks. nitrogen detention by sediment, plant uptake, denitrification and water column partitions in planted hssfcw varied between 4.32-18.3, 8.7140.3, 6.6-17.4 and 24-80.37% respectively, while the unplanted hssfcw nitrogen detention varied between 5.3-24.3, 6.3-16, 59.788.4% respectively. phosphorus detention in planted hssfcw varied between 7.2-45.2, 3.5-28.6 and 26.2-89.3% for sediment, plant and water column concentrations respectively, while the unplanted hssfcw phosphorus equilibrium between sediment and water column fluctuated between 9.8-55.6% and 44.490.2% respectively. nesrea benchmarks was generally attained in three days. the result outlined the importance of plant uptake and sediment storage as major nutrient removal pathways in wastewater polishing and improving pollution control. increasing the proficiency of these compartments would also improve removal efficiency and reduce nutrient impact on land and water. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 may, 2023 revised 25 july, 2023 accepted 30 july, 2023 keywords: nutrient partitioning pollution piggery wastewater constructed wetland nitrogen phosphorus http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/hp/desktop/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 608 constructed wetland (cw) treatment of agricultural wastewater has been proven (wetzel, 2001) as a technology that substitute centralized physical infrastructures with lower cost community scale systems, environmental sustainability and efficiency in removing nutrient from agricultural waste waters (ghrabi et al., 2011; waly et al., 2022). the ability of cw to treat piggery wastewater for discharge to land and surface water in the study area was demonstrated by udom et al. (2018). however, the ability of cw to remove nitrogen and phosphorus varies (udom et al., 2023) and an understanding of the removal mechanisms is necessary to explain the role each of the cw compartments play in the nutrient recycling and removal (kurzbaum et al., 2012). this is important following the observation of el-sheikh et al. (2010) and kurzbaum et al. (2012) admitting that the difficulty of optimizing cw systems could be abated by addressing observed inconsistencies in nutrient removal and vagueness in the contributions of the various partitions in nutrient cycling 2. materials and methods 2.1 study area the study was carried out at the obio akpa river watershed on the campus of the akwa ibom state university. the location of obio akpa is shown in figure 1. figure 1: site map of obio akpa source (https://goo.gl/maps obio akpa campus is located between longitudes 070˚ 3” e and 070 3” e and latitude 04o 45” n and 04o 55” n in the humid tropics. the minimum and maximum temperatures range between 1827oc and 24ᵒc-36oc respectively. relative humidity ranges between 55-86%. rainfall has a bimodal distribution lasting from april to october with a short break in august. average rainfall values range from 2050 to 2450 mm (udom et al., 2018) 2.2 wetland design three concrete horizontal subsurface flow (hssf) wetland basins sized 7 m x 1.75 m x 0.60 m and lined with a 2.5 mm thick polythene soil liner were constructed within akwa ibom state university, obio akpa campus, in immediacy with the piggery building for the experimental purpose. both the wastewater inlet and outlet sections of the wetland basins were filled up to 0.60 m depth with 30 mm crushed granite rock extending one meter from the walls into the treatment area. the wetland basin was filled up to 0.60 m depth with the coarse floodplain soil. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 609 two of the wetland cells were then planted with pennisetum clandestinum (pc) and the control (c) was not planted. thereafter, the wetland was left for three months to stabilize before delivery of wastewater (kostel, 2019). 2.3 operating method the inflow rates of the secondary effluent in the three cells were constant at 9.6 m3/day. the water levels were maintained at 10 cm just below the surface of the treatment cells. each cell was sampled daily from days 1–6. the flow of 3 m3/day was delivered by gravity flow through a system of pipes to each of the cw treatment cells. the area, porosity and theoretical hydraulic retention time hrt estimated by kostel (2019) as: 𝐻𝑅𝑇 = 𝐿𝑊 𝑦𝑛 𝑄 = 𝑤𝑒𝑡𝑙𝑎𝑛𝑑 𝑣𝑜𝑙𝑢𝑚𝑒 (𝑉) ∑ 𝑖𝑛𝑓𝑙𝑜𝑤𝑠 (𝑄) (1) where, l = length of the wetland cell (m); w = width of the wetland cell (m); y = depth of water in the wetland cell (m), n = porosity or the space available for water to flow through the wetland (a percent expressed as a decimal) ; 𝑄 = 𝐴𝑦𝑝 = average flow rate through the wetland (m3/d); a (m2) is the mean surface area of the system; v (m3) is the system volume; y (m) is the flow depth; p is the porosity, which is the existing space for the water to flow through the media, roots and other solids in the hssf system. 2.4 wastewater sampling seven-months data of secondary piggery wastewater taken twice monthly, were collected before and after six days’ detention in the wetland. the collection points were at the inlet to the wetland (0 m), the middle of the wetland (3.5 m) and at the outflow point (7.0 m) of each unit cell. clean, labelled one-liter plastic bottles duly washed with detergent, rinsed and dried were used for wastewater collection. the bottles were then rinsed with effluent water samples three times before filling with water samples. the effluent samples were collected by tipping the outflow pipe for the wastewater to spill into a container after recording the rise of wastewater in the pipe which indicates the depth of effluent wastewater in the wetland basin for every sampling regime and retention time. to assess the changes in nitrogen and phosphorus contained in the sediments, samples were collected from 0.25 cm and 0.50 cm depths using hand trowel since soil auger was not appropriate in order not to damage the liner on the cw floor. the samples were properly labelled and submitted to the laboratory for analysis. samples from the sampling depths were mixed, ground to pass through a 40 mesh sieve, wet digested and analyzed for tn and tp using a 3-aa3 auto analyzer (bran-luebbe, inc., germany). this was done at the beginning and at the end of the sampling period. the difference between the initial and final nutrient values explained the amount of nutrient retained in the interval. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 610 plants (above and below ground) were tested destructively to appraise plant nutrient uptake from the soil in the beginning and at the end of the experimental period. each entire plant was harvested, washed and rinsed with pure water and blotted with absorbent paper. it was easy to uproot whole plants because the roots only proliferated in the shallow depth above the plastic liner. the harvested plants were oven dried at 80 oc for a minimum of 48 hours until constant weight was achieved (ademoroti, 1996).). all dried plant samples were powdered separately in a micro plant grinding machine to less than 1 mm, wet digested and analyzed for total nitrogen and phosphorus using spectrophotometric method according to ademoroti (1996). 2.5 nitrogen removal mass balance nutrient mass balances evaluated by computing the nutrient content of the various compartments in the wetland system before and after the retention time were compared with the nigerian standard (nesrea, 2009). the complete equations of the various sinks involved in the nutrient transformations are stated in the following equations. 𝑁𝑖𝑛𝑓𝑙𝑢𝑒𝑛𝑡 = 𝐶𝑖 𝑉𝑖 𝐴 (2) where, 𝑁𝑖𝑛𝑓𝑙𝑢𝑒𝑛𝑡 = influent nitrogen (mg/l.); ci = influent nitrogen concentration (mg/l) vi = volume of the influent fed to the wetland (m3/d); a = constructed wetland area (m2) 𝑁𝑖𝑛𝑝𝑢𝑡 = 𝑁𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 + 𝑁𝑝𝑙𝑎𝑛𝑡 + 𝑁𝑚𝑒𝑑𝑖𝑎 + 𝑁𝑜𝑡ℎ𝑒𝑟𝑠 (3) where, 𝑁𝑖𝑛𝑝𝑢𝑡 = total nitrogen input to the wetland system (mg/l) 𝑁𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 = nitrogen content in effluent (mg) 𝑁𝑝𝑙𝑎𝑛𝑡 = nitrogen content in plant biomass (mg.) 𝑁𝑚𝑒𝑑𝑖𝑎 = nitrogen in wetland media (mg) 𝑁𝑜𝑡ℎ𝑒𝑟𝑠 = nitrogen loss from wetland by other processes (mg) 𝑁𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 = 𝐶𝑒𝑉𝑒 𝐴 (4) where, ce = effluent nitrogen concentrations (mg/l); ve = volume of the influent (litres) a = constructed wetland area (m2) 𝑁𝑝𝑙𝑎𝑛𝑡 = 𝑀𝑓𝑖𝑛𝑎𝑙𝑁𝑓𝑖𝑛𝑎𝑙 − 𝑀𝑖𝑛𝑖𝑡𝑖𝑎𝑙𝑁𝑖𝑛𝑖𝑡𝑖𝑎𝑙 (5) where, mfinal = average dry biomass per wetland at the end of the study period (mg) minitial = average dry biomass per wetland at the beginning of the study period (mg) ninitial = average n concentration in plants as percentage of dry weight at the beginning of the study period (mg/l). nfinal = average n concentration in plants as percentage of dry weight at the end of the study period (mg/l). 𝑁𝑚𝑒𝑑𝑖𝑎 = 𝑊𝑚𝑒𝑑𝑖𝑎 × 𝑁𝑚𝑒𝑑𝑖𝑎 𝑎𝑡 𝑡ℎ𝑒 𝑒𝑛𝑑 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑎𝑟𝑒𝑎 𝑎𝑛𝑑 𝑑𝑎𝑦𝑠 𝑜𝑓 𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (6) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 611 where, wmedia = dry mass of the media (mg) nmedia = mean n concentration in the wetland media (mg) 𝑁𝑜𝑡ℎ𝑒𝑟𝑠 = 𝑁𝑖𝑛𝑝𝑢𝑡 − [𝑁𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 + 𝑁𝑝𝑙𝑎𝑛𝑡 + 𝑁𝑚𝑒𝑑𝑖𝑎 ] (7) other losses involve the uptake by micro biota (bacteria, fungi, algae), dead leaves loss, denitrification, and ammonia volatilization. 2.6 phosphorus removal mass balance phosphorus mass balances calculated by computing the values of each of the compartments concentrations (udom, 2018) are shown in equations 8 13 below 𝑃𝑖𝑛𝑓𝑙𝑢𝑒𝑛𝑡 = 𝐶𝑖 𝑉𝑖 𝐴 (8) where, ci = influent concentration (mg/l). vi = volume of the influent fed to the wetland (litres) a = constructed wetland area (m2). 𝑃𝑖𝑛𝑝𝑢𝑡 = 𝑃𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 + 𝑃𝑝𝑙𝑎𝑛𝑡 + 𝑃𝑚𝑒𝑑𝑖𝑎 + 𝑃𝑜𝑡ℎ𝑒𝑟𝑠 (9) 𝑃𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 = 𝐶𝑒𝑉𝑒 (10) where, ce = effluent concentrations (mg/l); ve = volume of the influent (litres) 𝑃𝑝𝑙𝑎𝑛𝑡 = 𝑀𝑓𝑖𝑛𝑎𝑙𝑃𝑓𝑖𝑛𝑎𝑙 − 𝑀𝑖𝑛𝑖𝑡𝑖𝑎𝑙𝑃𝑖𝑛𝑖𝑡𝑖𝑎𝑙 (11) where, mfinal = average dry biomass per wetland at the end (mg/m2) minitial = average dry biomass per wetland at the beginning (mg/m2) pinitial = average p concentration in plants as percentage of dry weight at beginning (mg/l) pfinal = average p concentration in plants as percentage of dry weight at the end (mg/l) 𝑃𝑚𝑒𝑑𝑖𝑎 = 𝑉𝑚𝑒𝑑𝑖𝑎 × 𝜌𝑚𝑒𝑑𝑖𝑎 (12) where, wmedia = dry mass of the media (mg) 𝜌𝑚𝑒𝑑𝑖𝑎 = density of the dry mass of the media (mg/l) pmedia = mean p concentration in the wetland media (mg/l) 𝑃𝑜𝑡ℎ𝑒𝑟 = 𝑃𝑖𝑛𝑝𝑢𝑡 − (𝑃𝑒𝑓𝑓𝑙𝑢𝑒𝑛𝑡 + 𝑃𝑝𝑙𝑎𝑛𝑡 + 𝑃𝑚𝑒𝑑𝑖𝑎 ) (13) 2.7 analysis wetland treatment performance was evaluated in terms of reduction in concentration of targeted nutrients. nutrient retention was calculated as the difference between input and output of n and p concentrations transport and presented in percent as changes in specific retention. differences between compartments means evaluated by a one-way analysis of variance (anova) was used to determine the significant differences in variations of nitrogen and phosphorus concentrations in the cw compartments. 3. results and discussion the study evaluated nutrient uptake by plants, retention in the wetland sediment, water column and the effluent. the difference between the wastewater input and output and accumulation http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 612 accounted for other losses (denitrification). phosphorus removal model included uptake by plants, retention in water column and sediment. nutrient distribution in the constructed wetland (cw) compartments after six hydraulic retention days are shown in tables 1 – 4. 3.1 nitrogen distributions table 1 show that nitrogen concentration in planted wetland was partitioned among sediment, plants, water column and others specifically denitrification. the distribution of nitrogen in the planted wetland compartments for detention times ranging from one to six days are shown. table 1: mean nitrogen concentrations in planted cells wetland compartment pollutants concentrations (mgl-1) 0 hdt 1 hdt 2 hdt 3 hdt 4 hdt 5 hdt 6 hdt inflow 28.02 sediment 1.21±0.111 2.50±0.229 4.53±0.412 4.97±0.458 4.82±0.443 5.12±0.460 plants 2.44±0.219 5.57±0.514 9.63±4.374 9.775±0.629 10.90±1.627 11.30±0.337 water column 22.52±2.62 15.86±1.457 8.87±0.815 8.63±0.789 8.12±0.743 6.73±0.615 others* 1.85±0.173 4.09±0.376 4.99±0.458 4.90±.0.448 4.18±.382 4.87±0.448 hdt = hydraulic detention time (days) *denitrification the distribution of nutrients among the wetland compartments progressively reduced the pollutant concentration in the water column as the compartments continue to strip off nutrients from the water column. after one day retention, the sediment compartment of the planted cw absorbed 1.21 ± 0.11mg/l (4.32%) of the inflow nitrogen. from the second to the sixth day, nitrogen storage in sediment increased to 2.5 ± 0.21 mg/l (8.92%), 4.53 ±.41 mg/l (16.17%), 4.97 mg/l (17.74%), and 5.12 ±0.46 mg/l (18.27%). sediment deposition in wetlands benefits downstream water quality by retaining nitrogen that is sorbed to the sediments retained. this can have an important cumulative effect on water quality at the watershed scale. plants storage also increased with number of days that wastewater was detained in the wetland. after initial value of 2.44±0.22 mg/l (2.44%), plants uptake increased to 5.57±0.51mg/l (19.88%), 6.63±4.37mg/l (34.37%), 9.75±0.63(34.37%), 10.26±1.63m/l(35.69%) and 10.72±0.34mg/l(4.32%). other losses, principally volatilization, increased from 1.85±0.17mg/l (6.60%) in first day of detention to 4.87±0.45mg/l (17.38%) at six days after wastewater detention. the water column concentration of 28.02mg/l nitrogen received from the piggery facility changed markedly in the long run, losing 76% of its concentration to the wetland compartment and finally delivered 6.73±0.62mg/l effluent after six days of retention in the cw. the absorption of the nitrogen by the wetland media was the main path for nitrogen reduction in the water column, while denitrification played a complementary role both at the sediment-water boundary and in the overlying water (shen, 2020.) table 2 shows how the nitrogen concentration in non-planted wetland was partitioned among sediment, water column and others specifically denitrification. the distribution of the concentrations in the non-planted wetland compartments reflects the effect of detention for times ranging from one to six days file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 613 table 2: mean nitrogen concentrations in non-planted cells pollutants concentrations (mgl-1) 0 hdt 1 hdt 2 hdt 3 hdt 4 hdt 5 hdt 6 hdt inflow 28.02 sediment 1.49±0.137 3.06±0.285 5.03±0.458 6.51±0.596 7.20±00.661 6.81±0.662 water column 24.78±2.272 20.87±1.915 18.00±1.650 17.56±1.609 17.59±1.614 16.93±1.548 others* 1.78±0.164 3.89±0.358 4.99±0.463 4.95±0.453 4.37±0.401 4.66±0.428 hdt = hydraulic detention time (days). in the non-planted cw cells, (table 2 column 3), nitrogen retention in the sediment increased from 1.49±0.14mg/l (5.22%) at 1hdt to 3.06±0.29 (28.77), 5.03±0.46mg/l (17.95%), 6.51±0.60mg/l (23.23%), 7.2±0.66 (25.70%) and 6.81±0.62mg/l (24.3%) at six days of retention respectively. cw water column concentration changed correspondingly from 24.78 ±2.27 mg/l to 20.87±1.92mg/l, 18.0±1.65mg/l, 17.56±1.61mg/l, 17.59±1.61 and 16.93±1.55mg/l respectively, after six days of retention in the cw. other loses accounted for 6.35%, 13.88%, 17.81%, 17.67%, 15.60% and 16.63% for one to six days of retention respectively. nitrogen retention in sediment provides the process sites for reduction of nitrogen concentrations in cw. as particulates accumulate and settle on the wetland floor with their nitrogen loads from decomposed materials, they are used by microorganisms and plants (if available). if the rate of consumption is less than the rate of accumulation, there will be net increase in nitrogen retention in the cw sediment (lee et al., 2009). 3.1.1 sediment figures 2 and 3 shows nitrogen concentrations in cw compartments for planted and unplanted wetland conditions. figure 2: nitrogen concentrations in planted wetland cells figure 3: nitrogen concentrations in nonplanted cells 0 10 20 30 0 hdt1 hdt2 hdt3 hdt4 hdt5 hdt6 hdt sediment plants water column others 0 10 20 30 0 hdt1 hdt2 hdt3 hdt4 hdt5 hdt6 hdt sediment water column others http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 614 wetland soils constitute the single largest pool of n in wetland environments and the quantity of n amassed in cw soils is contingent on the balance between allochthonous import and particulate export. nitrogen partitioning to intact sediment is chiefly by adsorption, absorption, or precipitation (thompson and goyne, 2012). sorptive concentration is the most significant influence on the accumulation of nutrients in wetland sediment. figure 2 shows nitrogen concentration variations in the sediment. nitrogen concentration in the sediment gradually built up linearly from 1hdt up to 3hdt followed by a near constant increase up to 6hdt. at the introduction of the wastewater, the increase in the nitrogen concentration resulted in an increase in the amount of sediment sorbed by the wetland sediment. increased absorption of nitrogen by the sediment continued to drive the strip-off of nitrogen from the wastewater (the rising limb of figure 2) towards nonlinearity. at higher concentrations, a maximum sorption plateau was reached at 3hdt after which subsequent (availability of nitrogen) increases in nitrogen concentration do not result in further sorption of nitrogen to the wetland sediment. this is the case in figure 2 from 3hdt to 6hdt. this equilibrium condition continued until there was a change in any of the conditions in the wetland such as physicochemical and physical properties, properties of the pollutants, or environmental factors such as temperature and wetland moisture fluctuations. sediment retained 4.32% of available nitrogen concentration within 1hdt, 8.9%, 16.1%, 17.7%, 17.2% and 18.3% in 2,3,4,5 and 6 hdt respectively. a study by el-sheikh et al. (2010) recorded initial increase in holding of pollutants in treatment bed followed by a decrease with distance along the bed. in the present study, there was an increase of 4.6% retention between 1 and 2 hdt, 7.2% between 2 and 3 hdt, 1.6% between 3 and 4 hdt, 0.4% between 4 and 5 hdt and finally 1.1% between 5 and 6 hdt. the work of xu et al. (2016) showed that an hdt of 12 h, gave an average total nitrogen (tn) removal efficiency of 91% and 41% when hdt increased to 24 h. there is an indication here of an optimal hdt and capacity beyond which efficiency increases negatively and storage capacity fluctuates. 3.1.2 plants plants perform various key roles in constructed wetlands in wastewater treatment. nutrient uptake by wetland plants contributes to the wetland removal process. wetland plants require nutrients for growth and reproduction, and take up nutrients primarily through their root system (vymazal, 2011). as hssfcws do not efficiently remove nitrogen due to the low oxygenation of the filtration bed and thus low nitrification, plant uptake may be responsible for the removal of reasonable amount of nitrogen (vymazal, 2020). nitrogen accumulation in the entire plant compartment is shown in figure 2. at the onset (1hdt), the plant stored 8.71% of incoming nitrogen load. the amount of nitrogen stored by the plant compartment increased up to 40.3% in 6hdt. a rapid uptake in the first three hdts was followed by a gradual accumulation of nitrogen in the plant compartment. plant nutrient file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 615 concentrations are the highest in the beginning of the growing season and decrease gradually throughout the growing season as plants mature and senesce. plants can only store finite amounts of nutrient at a particular time no matter the abundance in the water column. according to (vymazal, 2020)., nutrient standing stocks in wetland macrophytes are usually limited and do not increase linearly with available nutrients. the increase in nutrient concentration in the water column will not cause an increase of nutrient concentrations in the biomass but can result in higher above ground biomass. generally, the removal of nitrogen in hssfcws is usually low or medium and the percentage of nitrogen removed by plant uptake increases with decreasing inflow load. (vymazal, 2020)., observed that in combination with low inflow loadings, the amount of nitrogen removed through above ground biomass harvesting in constructed wetlands treating municipal wastewater amounted to 62% of removed nitrogen. these results have a slight dissimilarity to a certain range as n removal transformations may be affected by plant species, media, wastewater type, retention times, loading rates, environmental climate (vymazal, 2020). these results revealed that plants can actually play an important direct role in nutrients removal in lightly loaded systems. 3.1.3 water column cw water column serves as temporary storage for incoming wastewater to the wetland basin before distribution to other compartments for processing and retention. the trend of nitrogen variation in wastewater column in both the planted and unplanted cw are shown in figures 2 and 3. beyond 3hdt, the concentration line of nitrogen in the unplanted cw appeared to be parallel to the sediment line indicating water column equilibrium with the sediment whereas that of the planted wetland continued to show a decrease in concentration. nitrogen storage in water column varied from 80.37% in 1hdt to 56.60, 31.7, 29.9, 29.0 and 24.0% in 2,3,4,5, and 6 hdt respectively in the planted cw. in the unplanted cw, the water column held more nutrient in concentration compared to the planted cw. in the 1hdt, the unplanted cw held 10.10% more nitrogen in storage than the planted cw. from 2hdt to 6hdt, the unplanted cw held 22.54, 40.47, 40.83, 40.35 and 44.45% more nitrogen in storage than the planted wetland. this difference explains the role of the wetland plant in the cw nitrogen storage. a study by wetzel (2001) showed that wastewater quality in the water column is not static but fluctuates with dynamic processes in the wetland sinks that extract pollutants from the wastewater either by direct assimilation or physiologically mediated alteration of absorption sites on sediment and plants. the quality of wastewater column at the end of the hdt is the excess of the saturation of the sinks (temporary capacities) or interim extractions of nutrients by the wetland sinks. the residual wastewater is left behind in the wetland basin after the effluent is discharged or collected. as nutrients are added to the water column, the equilibrium is temporarily shifted and will rapidly return to the steady state as the nutrients are taken up by the various fractions of the solid phase. thus, after reestablishment of equilibrium, there would be more nutrient in the system but not necessarily in the water column. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 616 the main n removal pathway in the planted (figure 2) and unplanted (figure 4) wetlands had differences in nutrient storage in this present study. differences recorded in storage in sediment compartment include 28%, 22.4%, 11.04%, 31%, 49% and 33% for 1 hdt to 6 hdt respectively. similarly, differences in water column include 10%, 31.6%, 102%, 103%, 116.6% and 151.6% respectively for 1 hdt to 6 hdt. loses due to denitrification decreased in the unplanted wetland from 1 hdt (-3.7%), 2 hdt (-4.9%), to 3 hdt (0%), increased from 4 hdt to 5 hdt (1.02% to 4.54%) and decreased again to -4.3%. although the anova values of 𝑝 ≅ 1 𝑎𝑡 0.05 probability level for both the planted and non-planted hssfcws suggested that there was no difference between the compartments. the per cent differences obtained in this study indicates that plant uptake and sediment storage might be the key factors in wetland n removal. the rapidly declining n removal efficiency with increasing loading rates as seen in figure 3 may be because of limits on the rate of denitrification, nitrification, oxygen availability, or nh3 or no3 diffusion. 3.2 phosphorus distribution table 3: phosphorus concentrations in planted cells pollutants concentrations (mgl-1) 0 hdt 1 hdt 2 hdt 3 hdt 4 hdt 5 hdt 6 hdt inflow 10.42 sediment 0.76±0.071 2.03±0.183 4.36±0.403 4.49±0.412 4.63±0.420 4.71±0.432 plants 0.36±0.036 1.08±0.101 1.46±0.137 1.63±0.147 2.52±.230 2.98±0.275 water column 9.30±0.851 7.31±0.668 4.58±.422 4.30±0.376 3.27±0.301 2.73±0.249 phosphorus concentration in the planted cws varied through detention days with progressive increments in retention in the various compartments except the water column which concentration was decreasing. phosphorus in the sediment sink progressively increased from 0.76±0.07mg/l (7.29%) after the first day of detention to 2.03±0.60 (19.48%), 4.36±0.40 (41,84%), 4.49±0.41 (43.09%), 4.63±0.42 (44.43%), and 4.71±0.43 (45.20%) respectively, after the sixth day of detention. the wetland plants extracted phosphorus from the water column pool of nutrients. plants phosphorus content progressively increased from 0.36±0.04 (3.45%) after one day to 1.08±0.10 (10.36%), 1.48±0.14 (14.2%), 1.63±0.15 (15.64%), 2.52±0.23 (24.18%) and 2.98±0.28 (28.60%) mg/l respectively from day two to six. there was continuous reduction of phosphorus concentration in the water column from 9.30±0.851 (89.25%), 7.31±0.668 (70.15%), 4.58±.422 (43.95%), 4.30±0.376 (41.27%), 3.27±0.301 (31.38) to 2.73±0.249 (26.20%) concentration from one to six days respectively. sedimentation follows once phosphorus attached to particles and aggregates in wastewater arrive a cw and, as the velocity of the water is reduced, the phosphorus particle can settle on the bottom. as reported by braskerud (2002), sedimentation of particulate phosphorus is the main retention process in small cw in receipt of wastewater rich in suspended matter. one more file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 617 factor affecting the retention capacity is residence time. the longer time wastewater stays in a cw, the more phosphorus can be removed and retained through the different mechanisms in table 3. the different compartments also will have the opportunity to take their full available supply from the pool. increased phosphorus demand associated with plant and microorganism growth will deplete the water column phosphorus concentration to satisfy these needs if incoming supply is less than storage. table 4: phosphorus concentrations in non-planted cells pollutants concentrations (mgl-1) 0 hdt 1 hdt 2 hdt 3 hdt 4 hdt 5 hdt 6 hdt inflow 10.42 sediment 1.02±0.092 2.18±0.199 5.63±0.514 5.68±0.520 5.68±0.520 5.79±0.306 water column 9.40±4.585 8.24±0.753 4.79±0.439 4.74±0.432 4.74±0.432 4.48±0.453 the non-planted cw sediment sink phosphorus retention increased from 1.02±0.09 (9.79%) to 2.18±0.20 (20.92%), 5.63±0.51 (54.03%), 5.68±0.52 (54.51%) and 5.79±0.31 (55.57%) at the end of six days. the water column concentration gradually decreased from 9.40±4.59 (90.21%) to 8.24±0.75 (79.08%), 4.79±0.44 (45.97%), 4.74±0.43 (45.49%) and 4.48±0.45 (42.99) mg/l at the end of six days respectively. this is due to stripping of nutrients from the water column by the sediment to fill its empty sites and thus establish equilibrium within the cw system. as nutrients are added to the water column, the equilibrium is temporarily shifted and will rapidly return to the steady state as the nutrients are taken up by the sediment. thus, after reestablishment of equilibrium, there would be more nutrient in the system but not necessarily in the water column (braskerud, 2002). figure 4: phosphorus concentrations in planted cells figure 5: phosphorus concentrations in non-planted cells in figures 4 and 5 show the trend of p storage in cw compartments. maximum p retention capacity of soil/sediment was generally reached following saturation of all sorption sites. sorption of p onto cw sediment and uptake by plants increased rapidly and initially as phosphorus that was stripped-off the water column was stored in the sediment and up taken by plants. after 0 2 4 6 8 10 12 0 hdt1 hdt2 hdt3 hdt4 hdt5 hdt6 hdt source/sinks sediment 0 2 4 6 8 10 12 0 hdt1 hdt2 hdt3 hdt4 hdt5 hdt6 hdt sediment water column http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 618 3hdt, phosphorus storage in both sediment and plants reduced with sediment storage tending towards equilibrium and plant storage showing only minimal increase perhaps in response to plant growth. zurayk et al. (1997) observed that p removal in the soil-based systems is rapid, and an equilibrium value may be reached beyond which no further removal is possible or negligible. baldovi et al. (2020) deduced from phosphorus removal studies in a pilot scale free water surface constructed wetland that increasing the detention time of wastewater in the system will allow for more time for plant uptake of p, possibly resulting in higher removal rates. in the unplanted cw, incoming phosphorus stream supplied sediment storage up to the 3hdt when both the water column and sediment storage were in balance. the non-significant difference (p=0.05) between the planted and non-planted wetlands suggest no difference between the compartments, but the per cent differences obtained in this study indicate that sediment storage might be the key factors in wetland p removal. hence, there is indication that from 1hdt to 3hdt, the increase is linear and from 4hdt to 6hdt, the increase is nearly constant. the main removal pathway in p was accumulation is the sediment. 3.3 nutrient balances with hdts over the range of the hdts, there were disparities in the concentration of nutrients in the wetland compartments. the accrual of concentration of nutrients in the compartments increased with increase in hdts except for the water column which reduced as nutrients remained extracted toward the compartments. in figure 2, the linearity of water column retention of nutrients approached a balance after 3hdt to a much less rate of decrease determined by the growing plant compartment. this trend was also observed in the non-planted cells (figure 3). although the capacities of the “others” compartment for nitrogen appeared to have been satisfied after 3hdt, the major exchange of nutrient remained between the sediment and water column as the balance between them keep shifting probably due to changes in environmental conditions particularly temperature. obviously, higher hdts improve the quality of the effluent by allowing more interaction time for nutrient removal processes in hssfcw compartments to be maximized. in this study, nitrogen and phosphorus levels required by the nigerian standard for wastewater quality for discharge to land and surface water was met in the 3hdt and subsequent increases in the hdts resulted in marginal increases in nutrient removal. these increases, particularly for nitrogen, could be attributed to increased removal of no3 associated with denitrification predominant in planted hssfcws. 3.3.1 nitrogen balance figures 6 and 7 summarized the percentage of nitrogen detentions in the entire compartments in the planted and unplanted cws. plant uptake process was the major removal route of nitrogen from the water phase, accounting for 34.4% of the inflow nitrogen load, followed by retention in wetland water column (31.7%), denitrification (others) process accounted for 17.8% and lastly, sediment retention in wetland accounted for 16.1% all in the 3hdt. saunders and kalff (2001) identified denitrification as more operative than nitrogen sedimentation in inhibiting nitrogen from being transferred downstream. plants escalate nitrogen retention through vegetative uptake file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 619 and offer favorable conditions for sedimentation and denitrification by increasing the supply of potentially limiting organic carbon and nitrate to denitrifying bacteria. figure 6: nitrogen removal in planted wetland figure 7: nitrogen removal in non-planted wetland in the non-planted cws, the water column continuously held the nutrient in dynamic storage as high as 64.2% in 3hdt. sediment retained 18% nitrogen while others (specifically denitrification) accounted for 17.8%. the amount removed by denitrification was the same with that of the planted wetland. this observation suggests non-fluctuation in temperature since denitrification is affected by temperature. szogi et al. (2003) and hunt et al. (1997) observed that cw media adsorption and plant uptake are significant components of cw n cycling when they receive relatively low loading of n resulting in very significant denitrification occurring in the constructed wetland. 3.3.2 phosphorus balance figures 8 and 9 illustrate the trends in phosphorus removal in both planted and unplanted wetlands. figure 8: phosphorus removal in planted wetland figure 9: phosphorus removal in nonplanted wetland phosphorus detention in water column of planted wetland was 44%. plant uptake contributed 14.20 % and detention in the wetland sediment contributed 41.8%. phosphorus retention in water column of unplanted wetland was 54% and retention in wetland sediment was 46% respectively. sediment plants water column others sediment water column others 17.8% sediment water column 44% plants sedimentwater column http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):607-622. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ikpeudom@aksu.edu.ng 620 besides chemical adsorption by ligand exchange, the physical adsorption becomes operational as the chemical adsorption sites approach saturation at higher equilibrium concentrations of phosphorus in the water column. the chemical and physical adsorption of phosphate onto the surface of soil minerals is a rapid process. slower reactions continue to remove phosphorus from the water column for periods of from several days to several months. adsorption by wetland sediment is not necessarily a permanent sink for wastewater p; it is at least partially reversible. a reduction in the phosphorus concentration in the water column in contact with the sediment, by plant uptake or by flushing or dilution with low phosphorus water, will release some p into solution. the wetland sediment functions to some extent as a " phosphorus buffer" in regulating the concentration of phosphate in solution. soils that adsorb p the least readily typically release p the most easily. it is not known how long a wetland can continue to remove p from wastewater. it is known that if sufficient p is added, the p adsorption capacity of a wetland soil can be saturated. in addition to becoming saturated and losing the capacity to retain any more phosphorus, a wetland soil can release some of the p that it has previously absorbed if the p concentration in the water in contact with the soil is reduced (dunne et al., 2005). 4. conclusion nitrogen and phosphorus removal in cw involves a complex of physical, chemical and biological processes. the mechanisms that remove these nutrients include: sorption on wetland sediments, storage in plants biomass, and denitrification. based on this study, nutrient retention in compartments of hssf constructed wetland with and without pennisetum clandestinum treating piggery wastewater in southern nigeria varied. n removal by sediment, plant uptake, denitrification and water column concentration in planted cw varied between 4.32-18.3, 8.7140.3, 6.6-17.4 and 80.37-24.0% respectively. in the unplanted cw, nitrogen detention among the sediment, denitrification and water column compartments varied between 5.3-24.3, 6.3-16, 88.459.7% respectively. similarly, phosphorus detention in planted cw compartments varied between 7.2-45.2, 3.5-28.6 and 89.3-26.2% for sediment, plant and water column concentration respectively for 1-6hdt. in the unplanted cw, phosphorus detention equilibrium between sediment and water column shifted between 9.8-55.6% and 90.2-44.4% in the sediment and water column respectively. by considering the 3hdt which quality conformed with the nigerian standard for discharge to land and surface water, plants, denitrification and sediment in the planted cw detained 34.4, 17.8 and 16.1% of nitrogen respectively and 14.2 and 41.8% of phosphorus in the plant and sediment compartments respectively. the result obtained in this study indicate that plant uptake and sediment storage contributed more than other compartments in n and p removal in the hssf wetlands treating piggery wastewater. improving these partitions could also improve removal efficiency at shorter hdt and reduce the pollution on land and water resources. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng udom: partitioning nutrients cycling in a constructed subsurface wetland treating piggery wastewater for pollution control. azojete, 19(3):607-622. issn 1596-2490; 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abunada, z., mickovski, sb. and thomson, c. 2022. constructed wetland for sustainable and low-cost wastewater treatment: land and water law review, 11: 1388. https:// doi.org/10.3390/land11091388. wetzel, rg. 2001. fundamental processes within natural and constructed wetlands ecosystems: short term versus long term. water science and technology, 44(11-12):1—8. xu, x., wu, z., dong, y., zhou, z. and xiong, z. 2016. effects of nitrogen and biochar amendment on soil methane concentration profiles and diffusion in a rice-wheat annual rotation system. scientific reports, 6: 38688. doi: 10.1038/srep38688 yang, jy., huffman, t., drury, cf., yang, xm., jong, rde and campbell, ca. 2012. estimating changes of residual soil nitrogen in chernozemic soils in canada. canadian journal of soil science, 92(3): 98-112. zurayk, r., nimah, m., geha, y. and rizk, c. 1997 phosphorus retention in the soil matrix of constructed wetlands. communications in soil science and plant analysis, 28(6-8):521-535 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/ikpeudom@aksu.edu.ng tel:385 tel:121578 https://www.sciencedirect.com/science/article/abs/pii/s0304389419315328 tel:10.2136 tel:2003.1943 https://cdnsciencepub.com/doi/10.4141/cjss2010-037#pill-con1 https://cdnsciencepub.com/doi/10.4141/cjss2010-037#pill-con2 https://cdnsciencepub.com/doi/10.4141/cjss2010-037#pill-con3 https://cdnsciencepub.com/doi/10.4141/cjss2010-037#pill-con4 https://cdnsciencepub.com/doi/10.4141/cjss2010-037#pill-con5 tel:6-8 tel:521-535 arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):355-366 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 341 original research article chemical constituents of solvent extracted bitter kola nut oil and its benefcial health properties w. a. adebayo department of food science and technology, obafemi awolowo university, ile-ife, nigeria *corresponding author’s email address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 1.0 introduction nuts and seed are nutrient dense foods with complex matrices rich in unsaturated fatty acids (60 – 98%), high quality protein, fiber, minerals (iron, potassium, magnesium, calcium, phosphorus and selenium), and other bioactive compounds such as tocopherols, phytosterols, and phenotic compounds (nzekwe et al., 2015). prominent nuts and seeds are groundnut, almonds, cashew nuts, cotton seeds, palm kernels, pecans, sesame seeds, soybean seed, sunflower seeds and walnuts. they have been widely utilized in various food formulation and development due to their nutritional and health benefits (gonzalez-perez and arellano, 2009). vegetable oils extracted from nut and seeds are important ingredients in the food, agro-allied and chemical industries. prominent vegetable oils are palm oil, soybean oil, canola oil, and sunflower oil which contribute more than 70% of the global vegetable oils consumption (kojima et al., 2016). the world major exporting countries in vegetable oils are indonesia, malaysia, and argentina while leading importers being india, china and eu (kojima et al., 2016). global demand for vegetable oils is greatly affected by the exponential increase in the world’s population, rising awareness of the health benefits of the unsaturated fatty acids present in the vegetable oils and increased industrial usage (kojima et al., 2016). recent advances in technology increases global utilization of vegetable oils therefore put pressure on conventional nut and seeds. therefore, there is dire need to explore non-conventional nuts and seeds. one of the non-convectional nuts and seeds is bitter kola (garcinia kola). bitter kola is a species of dicotyledonous flowering plant in the malphighiales plantae order and clusiaceae family (manourova et al., 2019). it is a perennial crop growing in the forest, distributed throughout west and central africa where its favorable climatic conditions article information abstract this study investigated chemical composition and biological activity of bitter kola oil. solvent extraction was done using soxhlet extraction method and the chemical composition of the oil was investigated using standard procedures. the oil yield of bitter kola nut oil was 2.480%. the color was deep brown. the chemical composition of the oil showed 58 different chemical compounds of which 40 are reported to have biological activity. 23.1% of the chemical composition of bitter kola oil obtained was made up of fatty acids. the fatty acid compositions of the oil showed saturated and unsaturated components that ranged from 0.59 – 10.10% and 0.72 – 4.13%, respectively. some of the saturated components of bitter kola nut oil include palmitic; lauric; myristic; pentadecanoic and stearic fatty acids while the unsaturated components were oleic; linoleic and hydnocarpic fatty acids. in conclusion, this study showed that bitter kola oil comprises of many biologically active compounds which could be used could beuse in food formulation, pharmaceutical and chemical industries. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 december, 2022 revised 27 february, 2023 accepted 6 april, 2023 keywords: chemical constituents solvent extraction bitter kola oil beneficial health http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):355-366. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 356 are met (iwu, 1993). in nigeria, bitter kola is primarily cultivated in southern states such as ekiti, osun, oyo, ogun, ondo, edo and delta. bitter kola stem and leaves have been employed over the centuries to treat different ailments but the most valued products of bitter kola are from its nuts, which possess anti-microbial, anti-diabetic and anti-inflammatory properties (okoye et al., 2014). eleyinmi et al. (2006) documented that bitter kola nut comprises of crude protein (39.52 g/kg), lipid extract (43.25 g/kg), ash (11.42 g/kg), crude fiber (114.02 g/kg), and a carbon: nitrogen ratio of 57.88. despite enormous benefits of bitter kola vegetable oil, it is still classified as an underutilized nut. therefore, there is need to investigate its chemical and biological properties as this will provide scientific data that will promote possible utilization of bitter kola vegetable oil for both domestic and industrial usage. 2. materials and methods 2.1 source of materials mature bitter kola nut was obtained from teaching and research farm, obafemi awolowo university, ile-ife, nigeria. all chemicals needed for this work were of analytical (sigma chemical (st. louis, mo, usa and fisher scientific, oakville, on, canada) grades. 2.2 sample preparation about 5 kg of matured bitter kola nut was sorted and washed with potable water to remove foreign particles attached to the nuts. the cleaned bitter kola nut was decorticated, dried in a hot-air oven (afos mini kiln, hull, england) and milled with a laboratory milling machine (retsch gmbh and co., haan, germany). the milled bitter kola nut was then subjected into solvent extraction process using n-hexane (analytical grade) as extraction solvents. milled bitter kola nut (1.00 kg) was measured and weighed into the extraction thimble of known weight. the loaded thimble was then placed in a soxhlet apparatus. the extraction solvent (5 l) was measured into the round bottom flask for each extraction process. then, the temperature of the heating mantle was set to 50 ˚c. as the temperature of the solvent increased, as a result of heat convection, solvent began to vaporize and vapor formed then passed through the thimble and began to condense due to the cooling effect of the water flowing in and out of the soxhlet extractor setup. this continuous process of heating and cooling was carried out until considerable amount of bitter kola oil was extracted after 8 h. at the end of the experiment, the thimble was removed from the soxhlet extractor set-up and the rest of the solvent in the apparatus was recovered. subsequently, a simple distillation process was carried out on the miscella in order to separate bitter kola oil from the solvent (figure 1). then, the extracted oil was labeled accordingly. 2.3 determination of moisture content the moisture content was determined using the oven drying method. 10 g of decorticated bitter kola nut sample were placed inside a moisture can. the sample was then dried in a uniscope laboratory oven set at the temperature of 105 ˚c for 3 h till no change in mass was observed. after drying, the sample was placed inside a dessicator and allowed to cool to room temperature. then, the sample was weighed and the values were recorded. the moisture content of the bitter kola nuts was then expressed as percentage moisture content (wet basis) using equation 1: file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng adebayo: chemical constituents of solvent extracted bitter kola nut oil and its benefcial health properties. azojete, 19(2):355-366. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 357 𝑀𝐶(𝑤.𝑏) = 𝑀b − 𝑀c 𝑀b − 𝑀a × 100% (1) where: m.c (w.b) = moisture content (wet basis); ma= weight of moisture can; mb = weight of moisture can plus sample weight before drying and; mc = weight of moisture can plus sample weight after drying. bitter kola nuts solvent crude extracted bitter kola oil figure 1: a flow chart showing solvent extraction of bitter kola oil 2.4 determination of oil yield solvent extracted bitter kola oil was transferred to a beaker, and then it was heated in a water bath for 2 h, in order to completely evaporate the solvent from it. at the end of the heating process, the volume of the recovered bitter kola oil was measured and expressed as percentage oil yield, using equation 2: 𝑂𝑌% = 𝑊0 𝑊𝑆 × 100 (2) where: oy = oil yield, %; ws = weight of milled bitter kola nut used, g w0 = weight of extracted bitter kola oil, g sorting washing decorticating drying milling soxhlet extractor (n-hexane) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):355-366. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 358 2.5 color the color of the extracted bitter kola oil was determined by physical observation. 2.6 determination of chemical composition of solvent extracted bitter kola oil the chemical components of bitter kola oil such as alkanes, alkenes, alcohols and aromatic hydrocarbons were evaluated using aoac (2002) methods. first, the oil sample was pre-treated with a process of methylation, following which it was subjected to gc-ms (gas chromatography mass spectrometry (model gl – 15a, schimadzu corporation, kyoto, japan) analysis. the column temperature of the gc-ms was programmed between 60 ˚c and 300 ˚c. 2.7 fatty acid profile the fatty acid profile of solvent extracted bitter kola oil was determined by using gas chromatography as a separation method. fatty acids (fas) were determined by means of indirect method, which involves their conversion to corresponding methyl esters (fatty acid methyl esters; fames) due to their reaction with trimethylsufonium hydroxide solution. individual fatty acids were then quantified by means of two distinct methods. firstly, quantification was based on the received peak area, following which the results were normalized without correction factor. secondly, quantification was based on the external calibration curve (aocs, 2009). 2.8 statistical analysis values obtained after all analyses were taken as data, which were then analyzed inferentially with the aid of statistical tools such as mean, analysis of variance (anova), and tukey test (p < 0.05). 3. results and discussion the initial moisture content of the bitter kola nut was 49.67% (w.b) (table 1). the initial moisture content value obtained is lower than 60.48 and 71.9% reported by odebunmi et al. (2009) and onyekwelu et al. (2015), respectively but higher than 15.20% documented by adeyeye et al. (2017). this wide range of moisture content obtained from various studies could be due to different levels of maturity of bitter kola nut samples, loss of moisture during transportation and storage and different farming practices. the high moisture content value (49.67%, w.b) obtained shows that the nut is susceptible to moisture-dependent deterioration. also, it shows that bitter kola nut has poor keeping quality unless it is subjected to drying. table 1: physico-chemical properties of bitter kola oil properties hexso initial moisture content oil yield (%) 49.67% (w.b) 2.480 physical observation (colour) deep brown hexso = n-hexane solvent extracted bitter kola oil the percentage oil yield value of bitter kola nut obtained was 2.48% (table 1). the oil yield value obtained is higher than 2.09% documented by olatunde et al. (2021) but lower than 8.5% reported by ordu et al. (2018). these disparities in values of oil yield are attributed to different levels of maturity of bitter kola nut samples and different handling and storage practices. the oil yeild obtained was lower when compared with oil yield of conventional nuts and seeds such as file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng adebayo: chemical constituents of solvent extracted bitter kola nut oil and its benefcial health properties. azojete, 19(2):355-366. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 359 groundnut (40 – 50%), palm kernel (39.53%), sesame (44.80%), rapeseed (40.00%), sunflower (25.50%) and canola (40.00%) (pahl, 2008; dim, 2013; chauchan et al., 2016; sitepu et al., 2021). color of bitter kola nut oil by physical observation is deep brown (table1). similar observation was documented by adeyeye et al. (2017). however, ordu et al. (2018) reported reddish-brown while olatunde et al. (2021) reported light yellow. these disparities in color of bitter kola oil may be attributed to different levels of maturity of bitter kola nut samples, loss of moisture during transportation and storage, different types of growing soil, different farming practices and different methods of extraction. the color of bitter kola oil is affected by constituents of the nut such as tannins, saponins, terpenoids and flavonoids (adeyeye et al. 2017). color is an important parameter used as an indication of adulteration of oils (lira et al., 2020). the chemical composition of bitter kola nut oil is presented in table 2. fifty-eight (58) different chemical compounds are obtained over 68 peaks, using gas chromatographymass spectrometry analysis method (gc-ms). table 2: chemical composition of bitter kola nut oil peak no compound rt %peak area 1 .beta.-myrcene 5.734 0.22 2 heptane, 3-(chloromethyl)5.919 0.08 3 heptane, 3-(chloromethyl)5.970 0.17 4 benzoic acid 8.123 0.85 5 1-dodecene 8.242 0.17 6 dodecane 8.377 0.85 7 geraniol 8.875 0.12 8 1-tridecene 10.559 0.62 9 tetradecane 10.686 2.69 10 phenol,3,5-bis(1,1-dimethylethyl) 11.689 3.89 11 11-(2-cyclopenten-1-yl)undecanoic acid, (+) (hydnocarpic acid) 11.883 0.72 12 dodecanoic acid (lauric acid) 12.289 0.59 13 1-hexadecanol 12.641 1.08 14 hexadecane 12.756 3.96 15 2-bromo-4,6-di-tert-butylphenol 12.807 0.71 16 1-octadecanesulphonyl chloride 13.554 0.16 17 tetradecanoic acid (myristic acid) 14.166 1.24 18 1-nonadecene 14.507 1.04 19 heneicosane 14.607 4.01 20 pentadecanoic acid (pentadecylic acid) 15.011 0.60 21 7,9-di-tert-butyl-1-oxaspiro (4,5) deca-6,9diene-2,8-dione 15.344 0.17 22 1-octadecanesulphonyl chloride 15.429 0.44 23 malonic acid, 2-chloropropyl pentadecyl ester 15.461 0.31 24 hexadecanoic acid, methyl ester 15.527 0.51 25 dibutyl phthalate 15.667 4.06 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):355-366. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 360 26 n-hexadecanoic acid (palmitic acid) 15.955 10.10 27 m-cymene,5-tert-butyl 16.033 1.63 28 n-nonadecanol-1 16.201 1.94 29 eicosane 16.290 3.45 30 1,6,10,14-hexadecatetraen-3-ol,3,7,11,15tetramethyl-(e,e) 16.417 0.72 31 kaur-16-ene 16.781 0.22 32 n-heptadecanol-1 16.875 0.50 33 9-octadecenoic acid, methyl ester, (e)16.999 0.23 34 octadecane,1-chloro17.233 0.64 35 9,12-octadecadienoic acid (z,z) (linoleic acid) 17.408 3.92 36 9-octadecenoic acid, (e)(oleic acid) 17.490 4.13 37 octadecanoic acid (stearic acid) 17.698 1.80 38 trans-geranylgeraniol 17.875 0.87 39 1-hydroxy-1,7-dimethyl-4-isopropyl-2,7cyclodecadiene 17.951 0.38 40 9-hexadecenoic acid, octadecyl ester, (z)18.068 1.10 41 heneicosane 18.167 1.84 42 1,1,6-trimethyl-3-methylene-2-(3,6,9,13tetramethyl-6-thenye-10,14-dimethylenepentadec-4-enyl) cyclohexane 18.490 0.75 43 17-pentatriacontene 19.376 0.63 44 9-octadecenamide, (z) 19.455 1.44 45 [1,1’-biphenyl]-2,3’-diol,3,4’,5,6’-tetrakis (1,1dimethylethyl 19.540 0.81 46 behenic alcohol 20.029 0.27 47 eicosane 20.108 1.01 48 phosphoric acid, tris (2-ethylhexyl) ester 20.587 1.33 49 trichloroacetic acid, undecyl ester 20.791 1.09 50 eicosane 20.994 0.77 51 bis (2-ethylhexyl) phthalate 21.121 5.09 52 1h-pyrazole-5-carboxamide,3-cyclopropyl-n(3,5-dimethyltricyclo [3.3.1.1(3,7)] dec-1-yl)1-methyl 21.542 0.22 53 2-methylhexacosane 21.807 0.68 54 oleoyl chloride 21.252 1.48 55 behenic alcohol 21.433 1.04 56 eicosane 22.575 0.85 57 methoxy-thc 22.620 0.42 58 9-octadecenamide, (z)22.906 0.37 59 decanedioic acid, bis (2-ethylhexyl) ester 23.177 0.75 60 eicosane 23.313 0.29 61 squalene 23.433 7.11 62 1-heptacosanol 23.955 4.10 63 octadecane,3-ethyl-5-(2-ethylbutyl)24.056 1.78 64 trans-geranylgeraniol 24.165 0.51 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng adebayo: chemical constituents of solvent extracted bitter kola nut oil and its benefcial health properties. azojete, 19(2):355-366. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 361 65 1-(2,5-bis-methosymethoxy-phenyl)-3,7,11trimethyl-dodeca-2,6,10-triene 24.240 0.66 66 oct-5-en-2-ol, 8-(1,4,4a,5,6,7,8,8a-octahydro2,5,5,8a-tetramethylnaphth-1-yl)-6-methyl 24.587 1.71 67 purine-2,6-dione,1,3-dimethyl-7-(2-oxo-2phenylethyl)-8-(piperidin-1-yl)-3,7-dihydro 24.697 1.35 68 ethyl trans-4a, cis-4b,trans-8a,cis-10aperhydro-trans-2,4a,8a-trimethyl-8oxophenanthrene-2-carbothiolate 24.864 0.78 rt: retention time the compound with the highest concentration is n-hexadecanoic acid (palmitic acid) (10.10%), a saturated fatty acid with reported anti-inflammatory, anti-oxidant and anti-microbial biological activities (abubakar and majinda, 2016). other identified compounds with relatively high concentrations were: squalene (7.11%), eicosane (6.37%), heneicosane (5.85%), bis(2 ethylhexyl)phthalate (5.09%), 9-octadecenoic acid (4.13%), 1-heptacosanol (4.10%), dibutyl phthalate (4.06%), hexadecane (3.96%), 9-12-octadecadienoic acid(z,z) (linoleic acid) (3.92%), phenol, 3,5-bis(1,1-dimethylethyl) (3.89%), and tetradecane (2.69%); while the compound with the least concentration is geraniol (0.12%), a fatty alcohol with reported anti-microbial, antidiabetic, anti-inflammatory, anti-oxidant, cardio-protective, anti-depressant and insecticidal biological activities (lira et al., 2020). total percentage of fatty acids obtained is 23.10%. this includes saturated fatty acids (14.33%): palmitic acid, c16:0 (10.10%); lauric acid, c12:0 (0.59%); myristic acid, c14:0 (1.24%); pentadecanoic acid, c15:0 (0.60%) and stearic acid, c18:0 (1.80%). palmitic acid (10.10%) is the prominent saturated fatty acid, a fatty acid with anti-microbial, antiinflammatory and anti-oxidant properties used in food production, soap production, skincare, cosmetics and other industries (abubakar and majinda, 2016) while lauric acid (0.59%), a fatty acid with anti-microbial and anti-viral activities (lira et al., 2020), has the least concentration among the saturated fatty acids although adeyeye et al. (2017) documented higher concentration of total saturated fatty acids (25.74%), with lower percentage of palmitic acid (5.50%) and higher percentage of lauric acid (2.57%). total percentage of unsaturated fatty acids is 8.77% which includes: hydnocarpic acid, c16:1 (0.72%), linoleic acid, c18:2 (3.92%) and oleic acid, c18:1. the unsaturated fatty acid with the highest concentration is oleic acid (4.13%), a monounsaturated fatty acid with antimicrobial activity, cholesterol lowering capacity and reported health benefits (lira et al., 2020), while the least concentration of unsaturated fatty acids is hydnocarpic acid (0.72%); another monounsaturated fatty acid with anti-oxidant properties which is traditionally used to treat leprosy (lira et al., 2020). although, adeyeye et al. (2017) documented a higher concentration of total unsaturated fatty acids (74.26%), with higher percentage of oleic acid (24.23%). also, total percentages of mono-unsaturated and polyunsaturated fatty acids were 4.85 and 3.92%, respectively. the ratios of poly-unsaturated fatty acid to total saturated fatty acid (p/s) and oleic to linoleic are 0.27 and 1.05, respectively. although, adeyeye et al. (2017) reported higher p/s ratio (1.91) and lower oleic/linoleic rato of 0.57; which indicates that bitter kola oil they obtained was not as stable and suitable for frying compared to the oil obtained in this study. these differences in fatty acid profile could be as a http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):355-366. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 362 result of different levels of maturity of bitter kola nut samples, loss of moisture during transportation and storage, different types of growing soil and different farming practices. the biological activities of chemical compound of bitter kola oil are presented in table 3. forty (40) chemical compounds found in bitter kola oil are reported to have biological activities such as anti-oxidant, anti-inflammatory, anti-microbial, anti-fungal, anti-diabetic, anti-cancer, antituberculosis, anti-depressant, cardio-protective, anti-septic, anti-viral, anti-aging, antituberculosis, anti-epileptic, anti-cytotoxic, psychoactive and insecticidal activity. the anti microbial effect of bitter kola oil may be attributed to the long aliphatic chains and fatty acid ester in it, which have been reported to build up in the cell membrane and mitochondria of a cell, thus resulting in disruption of the cell integrity and the death of the cell (belakhdar et al., 2015). table 3: biological activities of compounds in bitter kola nut oil peak no compound %peak area class of compound biological activity 1 .beta.-myrcene 0.22 acyclic alkene anti-oxidant, anti-aging, anti-inflammatory 4 benzoic acid 0.85 aromatic hydrocarbon anti-microbial 5 1-dodecene 0.17 acyclic alkene anti-bacterial 6 dodecane 0.85 acyclic alkane anti-oxidant 7 geraniol 0.12 terpene alcohol anti-microbial, antidiabetic, antiinflammatory, antioxidant, cardioprotective, antidepressant, insecticidal 8 1-tridecene 0.62 acyclic alkene pheromone and allomone properties 9 tetradecane 2.69 acyclic alkane anti-microbial, antituberculosis 10 phenol,3,5-bis(1,1dimethylethyl) 3.89 aromatic hydrocarbon anti-oxidant 11 11-(2-cyclopenten-1yl)undecanoic acid, (+) (hydnocarpic acid) 0.72 fatty acid anti-oxidant 12 dodecanoic acid (lauric acid) 0.59 fatty acid anti-microbial 13 1-hexadecanol 1.08 fatty alcohol anti-microbial and antioxidant 14 hexadecane 3.96 acyclic alkane anti-microbial and antioxidant 17 tetradecanoic acid (myristic acid) 1.24 fatty acid larvicidal and repellent activity 18 1-nonadecene 1.04 acyclic hydrocarbon anti-fungal 19 and 41 heneicosane 5.85 alkane anti-microbial file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng adebayo: chemical constituents of solvent extracted bitter kola nut oil and its benefcial health properties. azojete, 19(2):355-366. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 363 20 pentadecanoic acid (pentadecylic acid) 0.60 fatty acid anti-microbial 24 hexadecanoic acid, methyl ester 0.51 fatty acid ester anti-microbial 25 dibutyl phthalate 4.06 phthalate ester anti-microbial 26 n-hexadecanoic acid (palmitic acid) 10.10 fatty acid anti-inflammatory, antioxidant, anti-microbial 28 n-nonadecanol-1 1.94 fatty alcohol anti-bacterial 29, 47, 50,56 and 60 eicosane 6.37 acyclic alkane anti-microbial 32 n-heptadecanol-1 0.50 fatty alcohol anti-bacterial 33 9-octadecenoic acid, methyl ester, (e) 0.23 fatty acid methyl ester anti-microbial 35 9,12-octadecadienoic acid (z,z) (linoleic acid) 3.92 fatty acid anti-oxidant activity 36 9-octadecenoic acid, (e) (oleic acid) 4.13 fatty acid anti-microbial 37 octadecanoic acid (stearic acid) 1.80 fatty acid anti-oxidant activity 59 decanedioic acid, bis (2ethylhexyl)ester 0.75 fatty acid ester anti-microbial 61 squalene 7.11 aromatic hydrocarbon anti-oxidant and anticardiovascular disease 62 1-heptacosanol 4.10 fatty alcohol anti-microbial, antioxidant 63 octadecane,3-ethyl-5-(2ethylbutyl) 1.78 acyclic alkane anti-microbial the biologically active compounds with relatively high concentration are n-hexadecanoic acid (palmitic acid) (10.10%), which has reported anti-inflammatory, antioxidant and anti-microbial properties (abubakar and majinda, 2016); eicosane (6.37), heneicosane (5.85%), dibutyl phthalate (4.06%) and hexadecane (3.96%) which have reported anti-microbial activity (usha et al., 2015; ahsan et al., 2017; kim, 2020). although, there is dearth of information on the biological activity of kaur-16-ene, its derivatives have been reported to have anti-inflammatory activity (chavan et al., 2010). hexadenoic acid methyl ester, 9-octadecenoic acid methyl ester and 9,12octadecadienoic acid were also documented by fapohunda et al. (2017) although, they occurred in higher concentrations of 4.08, 12.42 and 5.04% respectively. these differences in chemical composition of bitter kola nut oil could be as a result of different levels of maturity of bitter kola nut samples, loss of moisture during transportation and storage, different types of growing soil and different farming practices. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):355-366. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 364 4. conclusion this study shows the chemical composition and biological activity of bitter kola nut oil. chemical compounds such as n-hexadecanoic acid (palmitic acid), eicosane heneicosane, dibutyl phthalate and hexadecane which occur in relatively high concentration have notable anti-inflammatory, anti-oxidant and anti-microbial properties. also, other compounds such as 1-dodecene, nnonadecanol and n-heptadecanol-1 have anti-bacterial activity. behenic alcohol has anti-viral activity, squalene has anti-cancer activity and geraniol, which has the lowest concentration, has anti-depressant, cardio-protective and anti-diabetic activity. based on the favorable reported biological activities of the components of bitter kola nut oil, the oil can find its application in food formulation, pharmaceutical and chemical industries subject to further clarification. references abubakar, m. and majinda, r. 2016. gc-ms analysis and preliminary antimicrobial activity of albizia adianthifolia (schumach) and pterocarpus angolensis (dc). medicines, 3 (1): 3 – 12. adeyeye, a., ayodele, o. and akinnuoye, g. 2017. comparative study of the proximate and fatty acid profiles of cola nitida, cola acuminata and garcinia kola. american journal of food science and nutrition, 4 (6): 80 – 84. ahsan, t., chen, j., zhao, x., irfan, m. and wu, y. 2017. extraction and identification of bioactive compounds (eicosane and dibutyl phthalate) produced by streptomyces strain kx852460 for the biological control of rhizoctonia solani ag-3 strain kx852461 to control target spot disease in tobacco leaf. amb express, (7): 54 – 62 aoac international. 2002. official methods of analysis of aoac international. aoac international, gaithersburg, maryland. aocs. 2009. official methods and recommended practices of the aocs. aocs press, urbana, illinois. belakhdar, g., benjouad, a. and abdennebi, e. 2015. determination of some bioactive chemical constituents from thesium humile vahl. journal of materials and environmental science, 6 (10): 2778 – 2783. chauchan, r., ahmad, i., khan, y., tamboli, e. and ahmad, s. 2016. characterization of arachis hypogaea l. oil obtained from different extraction techniques and in vitro antioxidant potential of supercritical fluid extraction extract. drug development and therapy, 7: 87 – 91. chavan, m., kolhe, d., wakte, p. and shinde, d. 2012. analgesic and anti-inflammatory activity of kaur-16-en-19-en-19-oic acid from annona reticula l. bark. phytotherapy research, 26 (2): 273 – 279. dim, p. 2013. extraction and characterization of oil from sesame seed. research journal of pharmaceutical, biological and chemical sciences, 4 (2): 752 – 757. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng adebayo: chemical constituents of solvent extracted bitter kola nut oil and its benefcial health properties. azojete, 19(2):355-366. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 365 eleyinmi, a., bressler, d., amoo, i., sporns, p. and oshodi, a. 2006. chemical composition of bitter cola (garcinia kola) seed and hulls. polish journal of food and nutrition sciences, 15, 395 – 400. fapohunda, s., awoyinka, a., oluchi, o., adaramola, b., jegede, d., adewumi, a., aleshinloye, a. and onigbinde, a. 2017. evaluation of the nutraceutical potential of garcinia kola seed oil. journal of pharmacognosy and phytochemistry, 6 (5):1894 – 1901. gonzalez-perez, s. and arellano, j. 2009. handbook of hydrocolloids. second edition. woodhead publishing limited, cambridge. iwu, mm. 1993. handbook of african medicinal plants. first edition. crc press, london: 183 – 184. kim, b., kim, h., jin, c., kang, s., kim, j., jeon, y., park, k., lee, i. and han, a. 2020. composition and antioxidant activities of volatile organic compounds in radiation-bred coreopsis cultivars. plants, 9 (6): 717 – 726. kojima, y., parcell, j. and cain, j. 2016. a global demand analysis of vegetable oils for food and industrial use: a cross-country panel data analysis with spatial econometrics. agricultural and applied economics association annual meeting, boston, massachusetts, july 31 – august 2 lira, m., andrade junior, f., moraes, g., macena, g., oliveira pereira, f. and lima, i. 2020. antimicrobial activity of geraniol: and integrative review. journal of essential oil research, 32 (3):187 – 197. maňourová, a., leuner, o., tchoundjeu, z., van damme, p., verner, v., pribyl, o. and lojka, b. 2019. medicinal potential, utilization and domestication status of bitter kola (garcinia kola heckel) in west and central africa. forests,10 (2): 124 – 143. nzekwe, u., ajuziogu, g., njoku, e., okafor, g., sani, m., onyeke, c., onyeonagu, c., ohaneje, a. and eze, c. 2015. nutritional food content of seed and effects of five different growing media on the seed germination and seedling growth of afzelia africana sm caesalpiniaceae. african journal of biotechnology, 15 (11): 384 – 391. odebunmi, e., oluwaniyi, o., awolola, g. and adediji, o. 2009. proximate and nutritional composition of kola nut (cola nitida), bitter cola (garcinia cola) and alligator pepper (afromomum melegueta). african journal of biotechnology, 8: 300 – 310. okoye t., uzor p., onyeto c. and okereke e. 2014 safe african medicinal plants for clinical studies. in: toxicological survey of african medicinal plants: kuete, v., ed. elsevier, waltham. olatunde, o., tian, d., yong, j. and lu, c. 2021. chemical compositions of the essential oil extracted from the seeds of garcinia kola and its biological activities. biomedical and pharmacology journal, 14 (2): 607 – 621. onyekwelu, j., oyewale, o., stimm, b. and mosandl, r. 2015. antioxidant, nutritional and antinutritional composition of garcinia kola and chrysophyllum albidum from rainforest ecosystem of ondo state, nigeria. journal of forestry research, 26: 417 – 424. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):355-366. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adebayoadewale@ymail.com, adebayow@oauife.edu.ng 366 ordu, j., sunday, b. and okafo, s. 2018. evaluation of the activity of garcinia kola seed oil and honey on skin cream foundation. the pharma innovation journal, 7 (5): 675 – 681. pahl, g. 2008. biodiesel: growing a new energy economy. chelsea green publishing company, vermont. 45 – 200. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/adebayoadewale@ymail.com,%20adebayow@oauife.edu.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2008; vol.6, 1-9 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng a technical assessment of water supply quality and distribution in three local government areas of lagos state, nigeria ogedengbe, k. and ilupeju, s.a.1 abstract the study was carried out to assess the technical problems associated with the sources, quality and quantity of drinking water supplies in agege, ifako/ijaiye and alimosho local government areas (lgas) of lagos state, nigeria. it was also conducted to find out the extent of water contaminations, from various sources, being consumed by residents of the lgas studied and also to proffer solutions to reduce their effects. households participation was involved it was revealed that about 35% of respondents use borehole, 25% obtained water from communal taps and 16% from well water. individual house tap accounted for 11%, 9% from water vendors and 4% of the respondents employed water tankers. chlorination was the most employed treatment technique while few others boil water before drinking. an average of 50 litres was the water use per capita. 50-100 meters was obtained as the average distance between respondents’ residence and water sources. the survey showed that some of these sources were sited near soakaways, some co-existing with tombs, dirty drains and water logged environment. twelve water samples were examined for analysis on chemical and biological properties. results obtained however showed that all chemical properties analyzed are within recommended standards for drinking water. salmonella spp. was also not detected in any of the samples. 1. introduction despite huge amount of money that was invested in water supply during the united nations international drinking water supply and sanitation decade (idwssd, 1981-1990), over 2.4 billion people still do not have access to good quality water. it is also estimated that over 3 million children die each year of dehydration from diarrhoea caused mostly by unhygienic environmental conditions (unicef, 2000). governments of most developing countries try to provide conventional water supply system for both rural and urban dwellers. however, there are traces of evidence that most rural dwellers still lack good quality and adequate supply of this infrastructure, which result in outbreak of water borne diseases (mnase et al., 2001). some urban centres in nigeria are also without regular supply of pipe-borne water in which case alternative sources are sought to alleviate poor water supply condition. boreholes, roof catchment system, shallow dug-wells, springs, streams and water vendors are some of other sources of water enjoyed by those dwellers. to meet required water demand in homes, storage is used to ensure continuous supply at all times (mnase et al., 2001). despite all efforts by governmental and non-governmental organizations in nigeria to make life worth living, some areas still lack major amenities for proper daily activities’ needs. these areas are tagged poor urban, rural urban or sub-urban (mnase et al., 2001). 1 agricultural and environmental engineering department, faculty of technology, university of ibadan. nigeria. http://www.azojete.com.ng/ a technical assessment of water supply quality in three local government areas of lagos state, nigeria 2 a study was carried out in agege, ifako/ijaiye and alimosho lgas to assess the drinking water quality. the three lgas where this study was carried out exhibit two characteristics, namely: (i) sub-urban features such as high population density, poor housing, inadequate water supply, poor sewage and drainage facility and irregular clearance of garbage. some houses are temporary structures, often built from range of materials such as iron sheet, mud blocks, woods and sometimes cement blocks. their living pattern is surely different from those in the urban areas who are characterized with a concentration of people who depend totally on incomes derived from non-agricultural pursuits. (ii) poor urban features that is exposed to a lot of social dangers emanating from poor environment and inadequate supply of good water. these dangers include poor health, bad roads which are as a result of continuous erosion since most areas do not have proper drainage plan execution. others include drudgery due to long period of fetching water and probably inappropriate means of transportation (mnase et al., 2001). a pre-study survey was conducted on selected few health centres and medical homes in the three lgas. the record for the year 2001 revealed that there were about 500 reported cases of water related diseases. typhoid was found to be so common among the reported cases. the objectives of this study were: (1) to investigate the sources and uses of water supply and the distribution network in the selected local government areas (lgas); (2) to investigate technical problems associated with supply in the three lgas; (3) to recommend appropriate solutions based on the investigations. 2. materials and method agege, alimosho and ifako/ijaiye were chosen for the study; out of which orile-agege, okooba, agbado-casso, abule-egba, alakuko, akowonjo, iju-ishaga, ekoro, and idimu were chosen to carry our household investigations. the study was conducted from three different perspectives: the first was an investigation on several sources of water available in the study areas including the three water works that were supposed to be supplying water to these areas which were visited. they were: (1) iju major water works (ijw), situated at ifako-ijaiye lga. (2) agege mini water works (amw), in agege lga, (3) idimu micro water works (iw), in alimosho lga. investigations carried out on them include; the sources of water, water treatment procedure, quality of water pumped out to dwellers, quantity produced by each water works and finally problems associated with distribution of treated water. other sources of water supply studies were selected boreholes and wells, streams and rivers within the areas. the second perspective was administering questionnaires. in this, about 300 copies of the questionnaires were distributed throughout the study areas. it was distributed at 100 copies per lga. to achieve this, houses were sampled within location for data collection. azojete vol. 6 2008 3 in addition, informal interviews, personal observations were also used to determine hygienic behaviour and to assess general environmental sanitation conditions. the last perspective of the study was conducted as a laboratory analysis on some water samples collected from the three major sources in all the locations. samples were randomly taken from communal taps, boreholes and wells. these wells are those highly fetched by dwellers. four water samples were taken in each lga and compared with the existing standards. the samples were collected in very clean plastic bottles which were thoroughly washed and rinsed with distilled water. each bottle measured approximately 100ml. the ph values were measured the day the samples were collected so as to ensure accurate results. parameters sought from water analysis included, ph, total dissolved solids (tds), hardness, sodium (na), potassium (k), calcium (ca), lead (pb), cadmium (cd), iron (fe), chloride (cl), manganese (mn), total count plate, coliform total and salmonella spp. 3. results and discussion 3.1 public water supply the results of investigation in water treatment plants which supply water to the study areas revealed that three water works are situated in these areas which supply water to various parts of the state. they are: (i) iju water works (ijw) which is also the main treatment plant that supplies water to all areas of lagos state and it is the second largest throughout the state after adiyan major water works which is not part of the study in this paper. ijw supplies about 160.325 million litres/day. (ii) agege mini water works (amw) and, (iii) adimu micro water works (im). the sources of water for the water works and their capacities are found in table 1. table 1: sources and quantity of water supplied by each water scheme plant sources of water capacity ijw iju/ogun river 160.325 million litres/day amw underground 9.4625 million litres/day imw underground 3.785 million litres/day iju water scheme has two intake channels; ogun intake 1 and ogun intake 2. intake 1 pumps from five outlets: three at 1105 m3/h each and the other two at 1130 m3/h. intake 2 has 3 outlets each at 2240 m3/h. water treatment techniques for the water works are as shown in table 2. table 2: treatment techniques employed in each water scheme plant treatment technique ijw sedimentation, filtration, liming, chlorination amw aeration, filtration, disinfection (chlorination) imw aeration, filtration, disinfection (chlorination) a technical assessment of water supply quality in three local government areas of lagos state, nigeria 4 from table 1, ijw produces 160 million litres of water per day, out of which about 20% is supplied to the study areas per day. total supply of water to study areas is then; 20% of ijw + amw daily production + imw daily production. this is about 42.3125 million litres/day. from 1991 census by the national population commission and from wendell cox consultant (2001), the population figures obtained for agege, alimosho and ifako/ijaiye were 417,966, 430,890 and 328,397 respectively. with a projected increase of 20% for every five years (npc, 1996), the projected population of the three lga combined was 1,733,342. this gives a per capita consumption of 26.14 litres/head/day. the recommended per capita consumption for developing countries is 100 litres/head/day (umoh, 1984). therefore, the quantity of water supplied to these lga (26.14litres/head/day) is very small. this is responsible for the inhabitants seeking other sources of water supply. as a result of high turbidity level in water from ogun river, it was discovered from treatment laboratory at iju water works that it required a lot of treatment input and techniques. clarification was done to remove colour. this was achieved by addition of alum as water passes through the plant flash mixer. water with high turbidity easily coagulates small flux to bigger flux that settle down easily. filtration came next as water passed through sets of graded sand, then liming, to reduce acidity and aggressiveness that could result from addition of alum. at this stage a ph level of 6.8 to 8.2 was achieved as recommended by who (1984). finally, chlorination was introduced to remove contaminations in the water. a chlorine residual content of about 0.4mg/l was allowed to maintain a good level of disinfection as water passed through pipes to various consumers. amw and imw have a number of tube wells popularly called boreholes. information pertaining to this showed that the two plants were initiated to boost water produced by adiyan and iju water works which are the major water schemes in the state. it was expressed that supply from the two stations was erratic since water comes from a constant aquifer and continuous tapping of underground water from the source were suspected to have led to reduction in the water level. the underground water which characteristics depended on soil properties was observed to be cleaner than surface water. with information given at both schemes, the major treatments carried out were aeration and disinfection. water was pumped from wells into reservoirs, where it was oxidized. oxidized fe was then filtered out by compartmentalized filters. the water was then chlorinated and supplied to the mains from ijw. 3.2 questionnaire and interview seven sources of water supply to households in the study areas were considered for this survey work. these are given in table 3. out of all sources studied, borehole was the most employed, followed by communal tap, then well. rainwater was generally accepted and used but it did not form a regular source because of its seasonality. about 66.7% of the respondents were female, meaning that women are more involved in water supply activities than men irrespective of age. this same trend was reported by sangodoyin (1993). however, a number of respondents that used a particular source could not be ascertained because a single person or household was engaged in two or more sources of water for different purposes. there were cases of individuals who used tap water for drinking and well water for other domestic purposes. azojete vol. 6 2008 5 table 3: number of respondents using different sources of water in the three lgas sources lgas agege ifako/ijaiye alimosho borehole 31 41 32 communal tap 26 22 27 well 18 12 18 individual tap 11 13 9 vendor 9 8 10 tanker 5 4 4 rain water result of water used per head showed that about 90% of the respondents used less than 100 litres of watrer. about 11.7% use between 10-20 litres, 34.3% use between 20-50 litres of water (table 4). this did not meet up with who standard. the average per capita consumption of water per day for unsophisticated society is 100 litres and up to 500 litres for industrialized society or where irrigated agriculture is practiced (umoh, 1984). table 4: quantity of water used per person per day quantity (litres) sample population percentage ( %) <10 9 3 10-20 35 11.7 20-50 103 34.3 50-100 123 41 >100 30 10 data pertaining to distance from source of water to respondents houses revealed 53% of respondents live between 50-500 metres from their major sources of water (table 5), though about 35% live within a radius of 50 metres from the source of water but the erratic nature of supplies led to less consumption per day due to multiple and costly attempts of fetching water (i.e by families, and water vendors). table 5: distance from water sources distance (metres) no. of respondents percentage (%) 0-50 106 35.3 50-100 147 49 100-500 43 14.3 >500 4 1.4 respondents showed a low treatment attitude to procured water. only two treatment techniques out of five studied were recorded. boiling was carried out by 12 respondents while chlorination was practiced by 21, most of which have residential or personal wells. this is shown in table 6. the table also shows that 33 respondents out of a sample population of 300 do treat water before consumption. the use of buckets and drums was a technical assessment of water supply quality in three local government areas of lagos state, nigeria 6 found to be moderately high and common among respondents as shown in table 7. storage facilities and water use could be linked with economic or financial status of respondents. storage and overhead tanks were used by respondents who use motorized boreholes or wells and sometimes individual taps. table 6: treatment techniques practiced treatment method no. of respondents heating 12 adding of alum settling chlorination 21 filtration table 7: storage facilities being used by respondents storage item no. of respondents storage tanks 22 drums 105 kegs 78 buckets 121 overhead tanks 18 3.3 water quality tests the chemical and biological properties of the water samples collected from the three lgas are shown in tables 8, 9 and 10. it was found that they were within the 1984 recommended who standards. all the samples did not contain cadmium. the average value of the ph was 6.8 in ifako/ijaiye and 6.9 in agege and alimosho. except for potassium, the contents of all the parameters measured were higher in the borehole water samples than in the tap water samples. for the potassium, the mean value was 4mg/l as against 6mg/l in the tap water samples as shown in tables 8 to 10. boreholes in agege and alimosho had the highest ph values. borehole water in ifako was the only sample that indicated presence of cadmium (0.01/mg/l) which lies within safe recommended standard for drinking. well samples indicated highest content of tested parameters out of all sources surveyed. it has a reasonably high concentration of calcium, manganese, lead and hardness. the result in the tables indicate that it is the most unsafe of all the analyzed samples though the values obtained still lie within recommended drinking water standards. azojete vol. 6 2008 7 table 8: result of water test in agege lga parameter tap agg1 agg2 well sodium (mg/l) 82 105 110 102 pastassium (mg/l) 6 4 4.0 4 calcium (mg/l) 3 10 9.0 18 lead (mg/l) 01 0.03 0.03 0.03 cadmium (mg/l) nd nd nd 0.01 hardness (mg.l) 200 350 360 380 ph 6.9 7.5 7.8 7.4 iron (mg/l) 0.10 0.19 0.21 0.18 chloride (mg/) 260 320 320 480 total dissolved solids (tds) 26 28 30 31 manganese (mg/l) 0.48 0.52 0.61 0.72 total plate count (100 cfu/ml) 5.00 8.00 8.00 10.00 coliform total nil nil 0.02 0.03 salmonella spp. nil nil nil nil agg1 and agg2 are the two borehole water samples taken in agege lga. nd = not detected. table 9: result of water test in ifako/ijaiye lga parameters tap ifj1 ifj2 well sodium (mg/l) 80 96 104 110 potassium (mg/l) 6 3 4 5 calcium (mg/l) 3 16 16 22 lead (mg/l) 0.01 0.01 0.02 0.03 cadmium (mg/l) nd 0.01 0.01 nd hardness (mg/l) 205 300 360 390 ph 6.8 7.2 7.4 7.5 iron (mg/l) 0.1 0.15 0.18 0.19 chloride (mg/l) 264 450 420 430 total dissolved solids (tds) 25 30 29 28 manganese (mg/l) 0.47 25 0.27 0.4 total plate count (100 cfu/ml) 5.0 10 7 30 coliform total nil nil nil nil salmonella spp. nil nil nil nil ifji and ifj2 are the two borehole water samples taken in ifako/ijaiye lga nd = not detected. a technical assessment of water supply quality in three local government areas of lagos state, nigeria 8 table 10: result of water test in alimosho lga parameters tap ifj1 ifj2 well sodium (mg/l) 82 93 92 90 potassium (mg/l) 6 4 4 5 calcium (mg/l) 4 12 18 16 lead (mg/l) 0.01 0.02 0.01 0.02 cadmium (mg/l) nd nd nd nd hardness (mg/l) 198 240 260 300 ph 6.9 7.9 7.8 7.8 iron (mg/l) 0.1 0.15 0.12 0.19 chloride (mg/l) 264 450 470 470 total dissolved solids (tds) 26 27 28 32 manganese (mg/l) 0.48 0.55 0.58 0.6 total plate count (100 cfu/ml) 5 20 10 28 coliform total nil nil nil 0.05 salmonella spp. nil nil nil nil akm1 and akm2 are the two borehole water samples in alimosho lga nd = not detected. results in the tables further reveal that there were lower ph values in the tap water compared to wells. this was traced to their sodium content where it was discovered that there was a direct variation between the two parameters. an increase in the quantity of sodium in each sample directly indicates an increase in ph. a progressive rise in calcium from tap water to boreholes and well water was also traced to treatment of public water. calcium content in tap water was 3mg/l in agege and ifako/ijaiye and 4mg/l in alimosho samples. it was 9mg/l and 22mg/l in boreholes and wells respectively. this was also due to the presence of manganese in the samples. as reported by nyc dep (2002), presence of iron in water does not necessarily mean that it is unfit for drinking; it is also present in various foods and drinks. though a small rise in iron content was noticed in untreated water samples, the level of iron concentration obtained does not pose a threat to humans if used for consumption. total coliform counts show presence of coliform in borehole 2 and well samples in alimosho as shown in table 10, while total plate content were higher in well water than in other sources. possible sources of infections the results of the assessment show that all samples of water from the various sources in the study area did not signify any harmful level of contaminations. the question is how do people contract some of the water borne infections noticed in the pre-study survey? interactions with respondents show that water is sometimes drawn from wells with dirty containers, sometimes the containers are tied with muddy ropes. some individuals were also seen collecting water from burst pipes. they arranged this by digging under burst pipes for easy access to collect the water. these methods of obtaining water rather than the qualities of the water may be responsible for the contamination of the water leading to infection. azojete vol. 6 2008 9 4. conclusions facilities available to lagos state water corporation (lswc) can produce higher quantity of water than provided during the study period if all water plants work. this will reduce the hectic effort of getting safe water. at least agege and alimosho lgas services would improve if idimu plant and agege mini plant work at their maximum capacities. from the results of tested samples, it was observed that all the samples that represent major sources of water for consumption are fit for human consumption. water from lswc has the least chemical and bacteriological contents which means it is the safest source among the samples tested. results from the household interviews indicate that majority of the respondents do not treat the water from other sources adequately before use and therefore, mass education in this regard is necessary for the people in the three lgas studied. references kaminsky, p; p. amato, m. fielder, a. lawton, m. lois, r. molloy, and m.shah (1996). the water project; environmental studies project on bergen, county. www. bergen. org/aast/project/es/ws. mnase, g.; m. mulenga and b. fawcett (2001). linking urban sanitation ageges with poor community needs in southern africa. a study of zambia, zimbabwe and south africa. dfid knowledge and research project r7124, university of southampton. nyc dep (2002). new york city department of environmental protection www.nyc.gov/html/wastesup. html. drinking water supply and quality report. sangodoyin, a.y. (1993). women’s role in rural water supply and development, trends and expectations in nigeria. the environmentalist, vol. 13, no. 4, pp. 255-261. umoh, p.u. (1984). a legal perspective on water resources and environmental development policy in nigeria. precedent in nigeria court. fourth dimension publishing /co. ltd. nigeria. unicef (2000) global water supply and sanitation assessment 2000 report for united nations children fund. wendel cox consultant (2001). www. demographia com/db-lagos htm. who (1984). world health organization: guidelines for drinking water quality. vol. 1. who, geneva. arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):585-598 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 585 original research article modular cryogenic energy storage system: simulation and technoeconomic analysis z. m. sarkinbaka1,2, a. g. salihu2,3*, a. s. grema2, a. l. yaumi2 1chemical engineering department, federal university wukari, taraba state, nigeria 2chemical engineering department, university of maiduguri, maiduguri, nigeria 3chemical engineering department, american university of nigeria, yola, nigeria *corresponding author’s email address: asgirei@unimaid.edu.ng 1.0 introduction sustaining economic growth while at the same time decreasing the usage of fossil fuels for environmental safety is a global challenge. several efforts are being made, mainly in two aspects: to reduce energy consumption by improving energy efficiency and to explore clean and sustainable renewable energy sources (wang et al., 2017). renewable energy sources are being discovered and quickly developed. however, the high-level of penetration of renewable energy in the grid causes serious problems with power grid stability and reliability due to the intermittency and volatility of renewable energy. suitable solutions are urgently needed and energy storage is known as one of the most promising technologies for addressing the difficulties (xu et al., 2015). the increasing penetration of renewable energy has led electrical energy storage systems to play a key role in balancing and increasing the efficiency of the grid. liquid air energy storage (laes) is a promising technology, mainly proposed for large-scale applications, that uses article information abstract sustaining economic growth while reducing reliance on fossil fuels for environmental protection is a global challenge. efforts are made to decrease energy utilization by enhancing energy efficiency and discovering clean renewable energy sources. cryogenic energy storage (ces) is a grid-scale energy system where electricity is stored in the form of liquefied gas. it is regarded as a solution because it allows for increased electricity generation while also providing economic benefits by avoiding costly operational consequences. the ces was modeled and simulated in aspen hysy v8.8 using three system confirmations: standalone adiabatic, waste heat integration, and combustion integration. unlike in the conventional ces, dowtherm-q was used as the thermal fluid due to its thermal stability, non-corrosiveness, and high temperature resistance. the results indicated that the higher the adiabatic efficiency of the turbine, the greater the power generated; also, increasing the turbine inlet temperature enhanced the performance of the system configuration by lowering the pressure and increasing the power of the turbine. the economic analysis revealed that the waste heat-based system has both the lowest operating cost, capital cost, utility cost, and higher energy savings. waste heat integration produces the most power (653.70 kw) and saves the most energy (69.58%), with lower capital costs, operating costs, and utility costs due to the increased adiabatic efficiency of the turbine. it implies that ces with waste heat integration is economically more promising compared to adiabatic standalone and the integration of combustion. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 april, 2023 revised 7 june, 2023 accepted 10 june, 2023 keywords: cryogenic energy storage system standalone adiabatic waste heat integration integration of combustion aspen hysys http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 586 cryogen (liquid air) as an energy vector. the use of liquid air as a storage medium allows a high energy density to be reached and overcomes the problem related to geological restrictions (borri et al., 2020). an essential characteristic of electricity is that electrical energy cannot be stored directly. therefore, the supply of electricity must be continuously balanced with the demand for it. the constant balancing of supply and demand has important operational and cost implications. for instance, adequate generating capacity needs to exist to supply the highest level of demand, even though the last increment of capacity will only be needed infrequently and for short periods. also, the inability to store electricity requires that reserve generating capacity, either in the form of spinning or non-spinning reserves, be maintained to account for changes in the amount of load or the unplanned loss of an operating generator (nderitu, 2013). although it is not possible to store energy in the form of electricity, it is possible to convert electrical energy into an alternative form that can be stored. the stored energy can then be converted back to electricity whenever it is desired. there are a wide variety of possible forms in which energy can be stored. common examples include chemical energy (batteries), kinetic energy (flywheels or compressed air), gravitational potential energy (pumped hydroelectric), and energy in the form of electrical (capacitors) and magnetic fields. from the standpoint of the electrical system, these energy storage methods act as loads while energy is being stored (while charging a battery) and as sources of electricity when the energy is returned to the system (while discharging a battery) (preckel, 2013). grid-scale energy storage (es) systems are widely regarded as a solution to the problems caused by the rapid transition to higher shares of electricity generation from highly intermittent renewable energy sources (steinmann, 2016). apart from ensuring the security of supply, es is supposed to introduce economic benefits by providing balancing services and avoiding costly operational inferences. cryogenics-based energy storage (ces) is the only grid-scale es technology without geographical constraints and a potential positive environmental impact. cryogenics-based energy storage (ces) is a thermoelectric bulk energy storage technology that stores electricity in the form of a liquefied gas at cryogenic temperatures (hamdy et al., 2019). cryogenic energy storage systems have the potential to provide a cost-effective and efficient method for storing large amounts of energy. however, developing an energy storage system capable of meeting global energy demand is a global challenge. in nigeria, like in any other developing or developed country, a real-time increase in energy demand poses a risk to energy supply. ces provides an alternative solution to energy demand, but it is not widely used due to a lack of thorough understanding of its economic viability. the outcome of this analysis will provide valuable information for the development and implementation of cryogenic energy storage systems. hence the objective of the present study is to model and simulate a cryogenic energy storage system using aspen hysys involving multiple design configurations, implement parameter sensitivity analysis for the specified configurations, implement an economic strategy file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng sarkinbaka et al: modular cryogenic energy storage system: simulation and techno-economic analysis. azojete, 19(3):585-598. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 587 for the selected system configuration, compare their performances and determine the best configuration. 2.0 materials and methods 2.1 materials some of the materials used in this study include: ▪ aspen hysys v8.8 ▪ air ▪ perfluoropropane c3f8 ▪ methanol (𝐶𝐻3oh) ▪ dtrm-q 2.2 methods a summary of the procedure conducted from modelling and simulation, parameter sensitivity analysis, and economic analysis, is shown in figure 1. s figure 1: description of the process flow diagram for the research process modelling and simulation of the ces system parameter sensitivity analysis economic strategy component selection aspen process economic analyzer temperature, pressure. adiabatic efficiency and power. thermodynamic package (peng robinson) utility cost operating cost (opex) capital cost (capex) feed stream specification flow sheet development reaction specification http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 588 the actual functioning of the turbomachinery was presumed to operate with adiabatic efficiencies, and the values were selected based on the information found in the literature, as indicated in table 1. table 1: assumed adiabatic efficiencies for turbomachinery. adiabatic efficiencies value compressors 0.85 cold expander 0.84 cryogenic pump 0.75 turbines 0.90 source: (li, 2011; li et al., 2014; sciacovelli et al., 2017). table 2 shows the stream values used for the simulation of the three system configurations of the ces system. table 2: stream values for the states indicated in the flow sheets in figures 2, 3 and 4 (hamdy, 2019). streams variables adiabatic waste heat combustion 1 �̇� t p kg/s °c bar 198.3 15.0 1.0 198.3 15.0 1.0 198.3 15.0 1.0 7 �̇� t p kg/s °c bar 198.3 18.0 180.0 198.3 18.0 180.0 198.3 18.0 180.0 8 �̇� t p kg/s °c bar 123.8 18.0 180.0 65.5 18.0 180.0 65.5 18.0 180.0 12 �̇� t p kg/s °c bar 59.4 -193.2 1.1 105.7 -193.2 1.1 105.7 -193.2 1.1 19 �̇� t p kg/s °c bar 1187.0 194.0 150.0 211.4 450.0 151.0 105.7 194.0 1.1 23 �̇� t p kg/s °c bar 118.7 194 12.2 211.4 450.0 12.2 211.4 734.0 80.0 ng1 �̇� t p kg/s °c bar 211.4 718.2 8.8 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng sarkinbaka et al: modular cryogenic energy storage system: simulation and techno-economic analysis. azojete, 19(3):585-598. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 589 2.3 process flow description of the cryogenic energy storage system configurations as presented in figures 2-4, the inlet air to the compression process is modeled with the ambient temperature at 15 °c, the ambient pressure at 1.0 bar, molar fraction of 0.79 for nitrogen and 0.21 for oxygen according to the international standard atmosphere (hamdy, 2019). in all systems, the inlet air to the compressor has a mass flow rate of 198.3 kg/s, which is compressed to a pressure of 180 bar in a three-stage compression process to regulate the air temperature so that the output air has a lower temperature with inter-cooling of 18–20 °c. thermal fluid (dowtherm-q with 303 kg/s, 6 bar and 360 °c) is used as a heat storage medium to recover and store the heat of compression (hamdy et al., 2019). the high-pressure air is further cooled and expanded until the dew point is reached. the slightly sub cooled liquid air is stored in a simple cryogenic insulated storage vessel at near ambient pressure (1.1 bar) and a temperature of 194 °c. for cold storage, the refrigerant r218 was found to recover the high-grade cold because it is neither toxic nor flammable (li, 2011; yokomizo, 2005). for improving the low-grade cold temperature, methanol is more appropriate as its boiling point is higher than the ambient temperature. the recovered cold is supplied to the first cold box to increase the portion of liquefied air in the liquefaction process of the subsequent charging process. the high-pressure air is superheated and expanded in four gas turbine stages, and power is generated as shown in figure 2. figure 3 shows the ces system with waste heat integration similar to that of figure 2, except for the additional heat rate 𝑄𝑖𝑛 that is supplied to the heat storage (hs). figure 4 did not have hs, and the four-stage reheaters are replaced with a combustion chamber in which fuel is burned to supply extra heat, which increased the temperature of the high-pressure gas before the expansion process. stand-alone adiabatic cryogenic energy storage (aces) system is designed to store and release energy using cryogenic fluids like liquid air. two important modes of operation for aces systems are waste heat integration and integration of combustion. their applications, as well as their differences as shown in figure 3 and 4. figure 2: flow sheet of the stand-alone adiabatic ces system (case a) http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 590 waste heat integration in aces systems involves capturing and utilizing waste heat generated during the charging and discharging cycles of the system. this helps improve overall energy efficiency by making use of wasted energy. during charging, waste heat can be captured and stored, typically in a thermal energy storage (hs) system. during discharging, the stored heat is used to enhance the system's output. waste heat integration focuses on capturing and reusing heat within the aces system to improve its efficiency without involving external combustion processes as shown in figure 3. figure 3: flow sheet of the waste heat integration (case b) figure 4 shows the integration of combustion in aces systems involves using an external heat source, often a combustion process, to boost the system's energy output. this is particularly useful when additional power is required beyond what can be achieved with the stored cryogenic fluid alone. during the discharging phase, an external heat source, natural gas combustion is used to vaporize the cryogenic fluid, rapidly expanding it and driving a turbine for power generation. integration of combustion relies on external combustion processes to augment the energy output of the aces system. it's a way to provide an extra power boost when needed. figure 4: integration of combustion (case c) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng sarkinbaka et al: modular cryogenic energy storage system: simulation and techno-economic analysis. azojete, 19(3):585-598. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 591 2.4 economic analysis the economic analysis was carried out by a cost estimating software called aspen process economic analyzer, which is integrated in the hysys, and generates capital cost (capex) estimates, operating cost (opex) estimates, as well as investment cash flow curves to evaluate the lifecycle economic impact of process decisions during conceptual design with the aspen process economic analyzer. 3.0 results and discussion 3.1 the results and discussion of the sensitivity analysis for case a, b and c figure 5 shows the sensitivity analysis result of the three parameters where the adiabatic efficiency, as an independent variable, affected the two dependent variables, that is, power and delta t. it is clearly seen that increases in adiabatic efficiency result in increased power output, while higher temperature differences lead to reduced adiabatic efficiency and subsequently lower power output. these relationships highlight the importance of optimizing the adiabatic efficiency of the system to maximize power generation. figure 5: a graph of sensitivity analysis for the case a as shown in figure 6(a), an increase in adiabatic efficiency affected the turbine by increasing its power and decreasing the temperature. this case noticeably shows that the power of the turbine increases with an increase in adiabatic efficiency and reduces with increases in delta-t. figure 6(b) presents the relationship between the two dependent variables, which are temperature changes and power. the power of the turbine increased as the temperature decreased. generally, the increase in adiabatic efficiency allows the turbine to convert more energy into useful work and reduces the temperature drop across the turbine, resulted in increased power output. http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 592 (a) sensitivity analysis of the case b with power, adiabatic efficiency, and delta-t (a) sensitivity analysis of the case b with delta-t and power figure 6: a graph of sensitivity analysis for the case b figure 7(a) indicates the variation of the adiabatic efficiency as an independent variable with deltat and power as independent variables. in the sensitivity analysis of case c, the power of the turbine increases with an increase in adiabatic efficiency. additionally, an increase in temperature decreases (delta-t) resulted in a decrease in adiabatic efficiency, again leading to a decrease in turbine power, as seen in figure 7(b). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng sarkinbaka et al: modular cryogenic energy storage system: simulation and techno-economic analysis. azojete, 19(3):585-598. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 593 . (a) sensitivity analysis of the case c with delta-t, adiabatic efficiency and power. (b) sensitivity analysis of the two dependent variables figure 7: a graph sensitivity analysis of the case c the chart in figure 8 represented the overall performances of the ces system that involved the turbine power of three design configurations at constant adiabatic efficiency. case a had 354.98kw of power produced. case b had an optimum power of 653.750kw and case c had a turbine power of 651.71kw. http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 594 figure 8: a chart showing power generated for the three cases of system configurations. the responses obtained from the sensitivity analysis in figure 9 showed that as the turbine inlet pressure decreased, the inlet temperature increased. this elevated temperature, along with the subsequent higher enthalpy drop across the turbine, leads to an increase in the power generated by the turbine. figure 9: chart showing the relationship between pressure, temperature and power for the case a the influence of turbine inlet temperature is illustrated in figure 10. the result shows that there is a significant increase in electricity efficiencies with a large decrease in the pressure and an increase in the turbine inlet temperature (tit). however, the net power output only increases with a decrease in turbine inlet pressure. increasing the turbine inlet temperature is a very effective way to enhance the performance of the system configuration in terms of power generation. in this system, a decrease in the turbine inlet pressure increased both the turbine inlet temperature and the power generated by the turbine, because as the temperature increases, 0 20 40 60 80 100 0 100 200 300 400 500 600 700 case a case b case c ef fi ci en cy v al u es o f tu rb in e p o w er turbine power(kw) adiabatic efficiency (%) 0 100 200 300 400 500 600 700 t1 t2 t3 t4 parameters t u rb in ee power (kw) inlet temperature (°c) inlet pressure (kpa) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng sarkinbaka et al: modular cryogenic energy storage system: simulation and techno-economic analysis. azojete, 19(3):585-598. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 595 the molecules will get energetically further apart from each other, and the attraction between the molecules will decrease and eventually the pressure will decrease, leading to high power output. figure 10: chart showing a relationship between pressure, temperature and power for case b the behavior of the parameters described in figure 11 are attributed to the integration of combustion system and turbine. therefore, decreases in the inlet pressure, it causes a decrease in turbine inlet temperature but leads to an increase in turbine power. this behavior is a result of the interplay between pressure, temperature, and power in the gas turbine system. figure 11: chart showing a relationship between pressure, temperature and power for case c 3.2 the results and discussion of the economic analysis for case a, b and c the economic analysis was conducted using aspen economic analyzer in aspen hysys, for the ces systems configurations in terms of capital cost, operating cost and utility cost at the same desired rate of return. the plot in figure 12 showed that case b is more economical with the 0 200 400 600 800 1000 1200 t1 t2 t3 t4 parameters tu rb in e power (kw) inlet temperature (°c) inlet pressure (kpa) 0 100 200 300 400 500 600 700 800 pressure (kpa) temperature (°c) power (kw) values p ar am et er s t2 t1 http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 596 lowest total capital cost, total operating cost and the total utility cost compared to case a and case c at the same minimum level of acceptable compensation for the investment’s level of risk. figure 12: graph for the total capital cost, total operating cost, total utilities cost and desired rate of return for the three cases figure 13(a) shows case b, where the integrated systems with waste heat recovery are more economical with a higher positive energy savings of 1.257e9 kj/h. compared to the negative energy savings of a standalone adiabatic system with -129,200,000.00 kj/h and the integration of a combustion system with -283,200,000.00 kj/h. as shown in figure 13(b), the case b systems reached energy savings efficiencies of 69.58%. the energy destruction in the charging process of the two cases a and b dominated with a share of 74.35 and 134.66 % of the energy destroyed in the overall system, respectively. the energy losses are caused almost entirely by the thermal energy emitted from the heat storage to the environment after the discharge process. the effects of cold storage and heat storage were found to be significant to the overall performance of the overall system. (a) energy saving at the same desired rate of return 0 20000000 40000000 60000000 total capital cost [usd] total operating cost [usd/year] total utilities cost [usd/year] desired rate of return [percent/'year] v al u es paramererscase a case b case c -5e+08 0 500000000 1e+09 1.5e+09 case a case b case c en er gy s av in g axis title desired rate of return [percent/'year] energy saving [kj/h] file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng sarkinbaka et al: modular cryogenic energy storage system: simulation and techno-economic analysis. azojete, 19(3):585-598. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 597 (b) percentage of actual of the three cases figure 13: energy saving and percentage of actual of the systems configurations. (a) energy saving at the same desired rate of return. (b) percentage of actual of the three cases 4.0 conclusion a successful modelling and simulation of the cryogenic energy storage system using three design configurations was carried out. the sensitivity analysis indicates that adiabatic efficiency, temperature, pressure, and power influence the operations of each configuration. it indicated that adiabatic efficiency had significantly increased by 90-100 %. it also showed that the lower the pressure, the higher the temperature, and the more power generated. the economic analysis revealed that the waste heat integration system has the lowest operating cost, capital cost, utility cost and higher energy savings compared to the other two system configurations. waste heat integration was found to be only beneficial to turbine power generation and resulted in energy savings of 69.58%. the integrated systems reach significantly lower capital costs, operating costs and utility costs due to the increased adiabatic efficiency. the ces system with waste heat integration achieved the highest power of 653.70 kw. the adiabatic standalone ces systems and the system with combustion integration reached low power at the discharge phase of 354.98kw and 651.71 kw, respectively. it is recommended that parameter optimization be carried out on the primary system case b, to achieve the best design which include maximizing the round-trip efficiency and minimizing the costs. references borri, e., tafone, a., zsembinszki, g., comodi, g., romagnoli, a. and cabeza, lf. 2020. recent trends on liquid air energy storage: a bibliometric analysis. applied sciences switzerland, 10(8): 1–19, https://doi.org/10.3390/app10082773. hamdy, s. 2019. cryogenic energy storage systems: an exergy-based evaluation and optimization. m.sc dissertation. university of leeds. hamdy, s., morosuk, t. and tsatsaronis, g. 2019. exergetic and economic assessment of integrated cryogenic energy storage systems. cryogenics, 99: 39–50, https://doi.org/10.1016/j.cryogenics.2019.02.009. hamdy, s., moser, f., morosuk, t. and tsatsaronis, g. 2019. exergy-based and economic -74.35 69.58 -134.66 -150 -100 -50 0 50 100 case a case b case c percentage c as es http://www.azojete.com.ng/ mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):585-598. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asgirei@unimaid.edu.ng 598 evaluation of liquefaction processes for cryogenics energy storage. energies, 12(493): 1–18, https://doi.org/10.3390/en12030493. li, y. 2011. cryogen based energy storage : process modelling and optimisation. phd thesis. university of leeds. li, y., cao, h., wang, s., jin, y., li, d., wang, x. and ding, y. 2014. load shifting of nuclear power plants using cryogenic energy storage technology. applied energy, 113: 1710–1716, https://doi.org/10.1016/j.apenergy.2013.08.077. nderitu, d. and preckel, pv. 2013. lucart to try out pm, 16(44): 1-3. sciacovelli, a., vecchi, a. and ding, y. 2017. liquid air energy storage ( laes ) with packed bed cold thermal storage – from component to system level performance through dynamic modelling. applied energy, 190: 84–98, https://doi.org/10.1016/j.apenergy.2016.12.118. steinmann, w. 2016. thermo-mechanical concepts for bulk energy storage. renewable and sustainable energy reviews, 75: 205-219,https://doi.org/10.1016/j.rser.2016.10.065. wang, j., lu, k., ma, l., wang, j., li, j., wang, d., miao, s. and dooner m. 2017. technology development. energies, 10(7): 991. https://doi.org/10.3390/en10070991. xu, f., jin, s., zhong, h., wu, d., yang, x., chen, x., wei, h., fu, r. and jiang, d. 2015. electrochemically active, crystalline, mesoporous covalent organic frameworks on carbon nanotubes for synergistic lithium-ion battery energy storage. scientific reports, 5: 1–6, https://doi.org/10.1038/srep08225. yokomizo, o. 2005. united states patent, 2(12): 610-612. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:asgirei@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):143-152 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 143 original research article sizing analysis of hybrid energy supply for buildings integrated with battery storage u. a. mukhtar*, m. shuwa, and a. b. muhammad department of mechanical engineering, university of maiduguri, p.m.b 1069, maiduguri nigeria *corresponding author’s email address: umuktara@yahoo.co.uk 1.0 introduction the demand for energy and its sustainability is one of the major challenges confronting the energy sector in the world. the energy demand is predicted to be enormous and requires sustainable measures for its supply. the entire world is experiencing continuous increase in population, modernization and industrial development and these have led to higher energy demand general use of available energy sources and the application of appropriate technology will enable demand for energy to be met. over the past decades, most of the energy production were based on the combustion of fossil fuels accounting for more than 80% of the total energy generation worldwide (iea, 2017). the continuous increase in the price of the fossil fuel is one of the major concerns that make the application of the energy unattractive nowadays. the awareness for the depleting characteristics of fossil fuel at long run has been stressed by many researchers and its applications are responsible for the release of harmful substances to the environment (negi and mathew, 2014; krishna and kumar, 2015; raza et al., 2022). many policies have been formulated around the world with a view of increasing the share of renewable energy and reduction in emissions as part of the response to the climate change (mathiesen et al., 2011; blazquez, et al., 2018; raza et al., 2022) which has severe negative impacts to the environment. the drawbacks associated with the use of the conventional energy has push so many stake holders and researchers towards the utilization of an alternative energy sources to provide heat and power for homes and industrial article information abstract one of the limitations in the application of renewable energy sources is the intermittency and variability in its supply. this characteristic has attracted many researchers and stakeholders to focus on the application of different types of hybrid energy technologies with storage systems to improve in the efficiency of the supply and dispatch ability of the system. the application of hybrid energy technology to generate heat and electricity is very popular nowadays and sustainable in the supply of energy for on-grid and off-grid services. the sizing of the hybrid energy supply is paramount to saving energy and meeting the energy demand at all time. this research work involves an analysis for sizing hybrid energy supply integrated with battery storage to meet the energy demand for 3-bedroom, office, sports and school building. merit modelling tool was applied for the demand and supply matching and analysis of the various chunks of technologies of pv, wt, chp and generator were carried out based on the suitability to achieve the best matching. the results show that hybrid systems with output capacities of 2.96 mwh, 203.15 mwh, 1.38 mwh and 2.14 mwh were used to meet the energy demands of 3-bedroom, office, sports and school buildings. the office building energy sizing was achieved with a match rate of about 90% with no energy deficit. however, surplus energy of 34.2mwh was recorded. the 3-bedroom, sports and school energy sizing were achieved with less than 1mwh of energy surplus or deficit and a matching rate of about 60%. for future study, the performance of the identified energy technologies can be verified using an integrated building performance simulation tool to ascertain its feasibility. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 august, 2022 revised 24 november, 2022 accepted 27 november, 2023 keywords: battery storage energy supply hybrid energy system sizing analysis http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk umuktara@yahoo.co.uk arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):143-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 144 applications. the continuous application of renewable energy technology to provide heat and electricity can serve as an effective solution leading to reducing the inter dependency on the conventional energy sources (nguyen et al., 2019). the application of the renewable energy source for heat and power generation has been demonstrated by many researchers as the most sustainable energy source which has less negative effect on the health and nature (negi and mathew, 2014; quaschning, 2016). one of the advantages of the renewable energy system (res) is that the system can be developed as stand-alone or on-grid and can be located close to consumers. this decreases the transmission and transformation loses depending on the type of the res applied. the res is associated with high initial cost that leads to higher price of energy. however, the overall cost of the system greatly overweighs the increasing cost of fossil fuels, operation and maintenance cost and the cost of releasing harmful substances into the atmosphere. the major problem that limits the use of the renewable energy sources is its variability and intermittency nature (mathiesen et al., 2011; yaqoot et al., 2016; bahramara et al., 2016). several efforts have been used to meet the energy demand utilizing the application of different types of hybrid renewable energy systems. for example, solar energy is obtainable in day-light, variation in wind speed also has great effect on the output of the system. hybrid combination of these energy sources promises for a greater system performance and reliability towards overcoming the intermittency and variability character. the intermittency in the solar radiation and wind speed variation have been mitigated by the application of hybrid renewable energy systems integrated with storage facility to improve the efficiency of the system and the dispatch ability. olatomiwa et al. (2016) discussed on how to overcome the variability and intermittency nature of the renewable energy sources by the integration of a hybrid renewable energy systems with energy storage systems (ess). the ess applied to hybrid energy technologies includes batteries, compressed air energy storage, flywheel, fuel cell, magnetic energy storage, superconductor, thermal energy storage systems etc. (negi and mathew, 2014; zohuri, 2018). renewable energy sources such as solar, wind, biomass, tidal, fuel cells, geothermal etc. are usually combined to form a hybrid system that is more reliable and free from environmental pollution. hybrid energy technology involved the combination of two or more renewable energy sources, or renewables and conventional energy along with ess in order to guarantee the reliability in the energy supply (elhadidy and shahid, 2000; mahesh and sandhu, 2015; zohuri, 2018) with an equipment that control the power (nema et al., 2009). the benefit for the use of a hybrid energy system (hes) is targeted towards its reliability of supply as the system combines two or more energy sources which is an added advantage for energy storage in the combined strength of the systems. the energy storage facility supplements for the output in case of a reduction in strength in one of the resources due to climatic variations to improve in the dispatch ability of the system. stand-alone systems with one energy source are less adaptable to fluctuations in load. the fluctuation condition may lead to system collapse when it experiences a large variation in the load (negi and mathew, 2014). most configurations of hes are commonly based on the solar and wind energy sources. hybrid configurations may also consist of biomassconcentrated solar power (csp), coal/gas-csp, photovoltaic (pv)-fuel cell, pv/geothermal, windbiodiesel, wind-tidal systems etc. integrated with an ess (negi and mathew, 2014; zohuri, 2018). the hes with more than two energy sources generate greater electrical output and are more reliable. however, these types of hes are sometimes limited with the availability of the different energy sources at the same area and are usually associated with high capital, operation and maintenance cost. figure 1 shows the schematic diagram of distributed energy generation. the hybrid energy output is supplemented by the storage systems that are all connected to the electrical control devices for grid and off-grid energy supply. the selection for any of the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk mukhtar et al: sizing analysis of hybrid energy supply for buildings integrated with battery storage. azojete, 19(1):143-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 145 combinations of the hes strictly depend on many factors such as the weather condition of the area, energy demand, availability of space and building location (yang et al., 2007). the sizing of the energy systems plays an important role in the selection criteria. analysis must be carried out in order to select for the optimum combination for a hes. the designs of the components and configurations of the hes can be optimized to make for flexibility in operation with a view in selection of the system configuration based on performance requirement and economy. for example, the sizing of the hes requires the best matching technologies that meet the requirement of building energy demand at all times. optimal sizing of the hes can greatly promote penetration of the system and improve the technical and economic performance of the energy supply to buildings (deshmukh and deshmukh, 2008). in the present study, hybrid energy supply sizing analysis was conducted for building integrated with battery storage. the sizing approach is strategically based on the analysis of matching hybrid energy supply. this involved the matching of several chunks of technologies of hybrid energy with battery storage system to meet the energy demands of buildings. the battery storage was applied to mitigate the hybrid energy supply. the main importance of the battery storage system is to store excess energy for later use in the case of a variation in the supply of power or when no renewable energy source is recorded. figure 1: schematic diagram for a hybrid distributed energy generation 2. materials and methods the sizing of the hes is one of the major issues that are affecting the hybrid energy supply to meet building energy demand. optimal sizing of the hes gives rise to a better performance of the system, energy and cost saving (anoune et al., 2018a). several methods of sizing hybrid systems have been studied by many researchers (rouhani et al., 2013; upadhyay and sharma, 2014; koubaaa et al., 2021). the deterministic and stochastic approach use the meteorological data for the yearly average monthly data and the data for the worst months of solar radiation and wind speed (luna-rubio et al., 2012; anoune et al., 2018b). this sizing methodologies, usually lead to the oversizing of system components due to the uncertainty in the availability of solar radiation and wind speed either for both cases of the average monthly and worst month data (luna-rubio et al., 2012). iterative sizing method is based on the total cost involving for example number of pv and wind turbine (wt) units. this is unlike the analytic method which utilise a computational method that describe the size of the hes as a function of its feasibility (upadhyay and sharma, 2014). a graphical construction method for sizing a stand-alone pv-wind hybrid system has been http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):143-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 146 presented (markvart, 1996). the sizing approach was based on meeting the energy demand in relation to the average solar radiation and wind speed required for the energy supply by the system. clarke et al. (2013) presented a study on sizing hybrid energy schemes and the generation of a simulation input model for performance appraisal specifically for low energy communities. the study outlined the procedures for sizing of the hes and how to generate initial input models considering the capacity levels of each technology to achieve a successful demand and supply matching. most of the methodologies applied in sizing the hes are centred on the analysis of the various components and the overall configuration of the system, cost and performance approach. the present work involved application of the procedure outlined in the work of clarke et al. (2013) where the sizing methodology is based on the analysis of hybrid energy supply schemes. hybrid technologies of interest with different capacities are selected for example pv, wind turbine, generator, chp systems chunked to meet energy demand of buildings. however, the present work put into practice, the procedure outlined for sizing the hybrid energy supply, to meet building’s energy demand. simulation was conducted using merit software for the sizing analysis. this was achieved through matching of several chunks of technologies of hybrid energy supply with battery storage system. data for energy demand; totality of energy requirement in a building in mwh, for different building types involving 3-bedroom dwelling, sports center, office and school were used in the analysis. the buildings were all located in glasgow, uk on latitude 55.5 and longitude -4.15 with the average weather condition of the area applied. most importantly, the wind speed and solar radiation at the particular period were used in the merit tool for the pv and wt to obtain the power output. in this analysis, hybrid system required for a particular building, for example sports center (pv, wt and battery) was chunked into t capacities of 100w, 500w, 30 kwe, and 50 kwe. multiple batteries of capacities 50ah@12v, 80ah@12v and 120ah@12v connected in either parallel or series were integrated to meet the energy demand for the various buildings. the distributed energy system is sized by using dual-mode inverter system that connects ac and dc buses to control the load requirement. a block diagram description is illustrated in figure 2. because of the intermittency in solar radiation and wind speed, battery systems are employed in connection to the inverter of the hybrid system to store electrical energy for later use. figure 2: block diagram of the distributed energy resources for hybrid system combination file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk mukhtar et al: sizing analysis of hybrid energy supply for buildings integrated with battery storage. azojete, 19(1):143-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 147 the battery charge state is ascertained at different time when discharged to meet load requirement. detailed analysis of battery state of charge for pv, wt and biomass hybrid system has been described (sawle et al., 2018). the battery capacity is dependent on the load requirement during a particular period. the battery storage capacity (bsc) is obtained using equation 1 where dod is the battery allowable depth of discharge, el is the daily load energy of the battery, ad is autonomy days that indicate the expected number of days for battery load supply, ɳiv is inverter efficiency and ɳ𝐵is the battery efficiency (ismail et al., 2013). 𝐵𝑆𝐶 = (𝐸𝐿 × 𝐴𝐷) ɳiv × ɳ𝐵 × 𝐷𝑂𝐷 (1) in calculating the wt power output, several factors are considered. factors such as the ambient temperature and terrain of the area, the altitude that defined the turbine position from the base level, season of the year and wind speed are important in determining the performance of the wt system. wind gradient, which often defined the performance of the wt system, depends on these factors. the power output of the wt system was calculated using equation 2 where pwt is the power produced by the turbine system (kw), prw is the wind rated power (kw), vr the nominal speed of the turbine system (m/s), v is the wind speed (m/s), vci is the cut in speed (m/s) and vco is the cut out speed (m/s) (sawle et al., 2018). 𝑃𝑊𝑇 = { 0 𝑉 ≤ 𝑉𝐶𝐼 𝑜𝑟 𝑉 ≥ 𝑉𝐶𝑂 𝑃𝑅𝑊 ( 𝑉− 𝑉𝐶𝐼 𝑉𝑅− 𝑉𝐶𝐼 ) 𝑉𝐶𝐼 < 𝑉 < 𝑣 𝑃𝑅𝑊 𝑉𝑅 ≤ 𝑉 ≤ 𝑉𝐶𝑂 (2) the power output of pv system is explicitly dependent on the amount of solar radiation through the roof area defined by the number of panels of the pv system applied. the power generated by the pv system is directly proportional to the solar radiation. other factors that affect the performance of the system includes angle of inclination, cell temperature, weather condition and geographical location. the power output of the pv panel was calculated at time t, by applying the equation 3 where ppv is the pv system peak power generation (kw), prs, is the rated power of the pv panel (kw), r is radiation factor, rcr, is the certain radiation at 150 w/m2 and rsrs is the standard solar radiation at 1000 w/m2 (sawle et al., 2018; jamshidi and askarzadehj, 2019). 𝑃𝑃𝑉 = { 𝑃𝑅𝑆 ( 𝑅2 𝑅𝑆𝑅𝑆 𝑅𝐶𝑅 ) 0 ≤ 𝑅 < 𝑅𝐶𝑅 𝑃𝑅𝑆 ( 𝑅 𝑅𝑆𝑅𝑆 ) 𝑅𝐶𝑅 ≤ 𝑅 < 𝑅𝑆𝑅𝑆 𝑃𝑅𝑆 𝑅𝑆𝑅𝑆 ≤ 𝑅 (3) in chp system, the scale of power output is determined by the amount of fuel consumption of the system. this is in totally of the fuel used for the generation of electricity and the fuel used for auxiliary heating. the electrical output generation is obtained by multiplying the power output of the chp system with number of dark hours (pearce, 2009). the main advantage of the chp system is to provide a complete backup to the pv or wt output in order to maintain a constant load, during an intermittent condition of solar radiation or wind speed. the chp system was designed to correlate between demand and supply load in order to maximize the chp fuel efficiency and improve system maintenance (nosrat and pearce, 2011). the hybrid system is designed to use a variable speed diesel generator in order to meet the electrical load requirement at various scales of power output. this is so important in that the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):143-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 148 diesel generator can provide load at different power output in case of deficit in the power supply by other energy systems. the main function of the generator is to balance the hybrid power source in case when the battery is depleted to its allowable depth. the generator is conditioned to operate also as a back up to the intermittent nature in the supply load of pv and wt systems. the generator rated power is proportional to the system fuel consumption hence the scale of the actual power output of the system can be determined (jamshidi and askarzadeh, 2019). 3. results and discussion figures 3-6 show the power demand and supply profiles of the 3-bedroom, sports, office and school buildings in glasgow. several chunks of hybrid technologies were analysed using merit software for demand and supply matching. hybrid capacities of pv, wt, chp and generator systems with consideration to the various building requirement were applied with battery storage for the analysis. the surplus energy need to be stored by an efficient storage system in order to meet the energy demand. the results for the hybrid energy sizing analysis of the various building types were obtained from the simulation conducted using the merit tool. the results obtained are presented in table 1. figure 3: power demand and supply matching profiles for 3-bedroom flat building figure 4: power demand and supply matching profiles for office building file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk mukhtar et al: sizing analysis of hybrid energy supply for buildings integrated with battery storage. azojete, 19(1):143-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 149 figure 5: power demand and supply matching profiles for sports building figure 6: power demand and supply matching profiles for school building table 1: analysis of the buildings’ energy demand and hybrid energy supply technologies building types hybrid combinations match rate (%) correlation coefficient total demand (mwh) total supply (mwh) energy surplus (mwh) energy deficit (mwh) 3-bed pv, wt, generator and battery 66.66 0.48 2.11 2.96 0.851 0.0005 office pv, wt, chp and battery 89.61 1.00 164.92 203.15 38.220 0 sports pv, wt and battery 55.85 0.35 0.82 1.38 0.545 0.014 school pv, wt and battery 57.79 0.22 2.11 2.14 0.666 0.647 the hybrid systems of 3-bedroom, office, sports and school supplied energy of 2.96 mwh, 203.15 mwh, 1.38 mwh and 2.14 mwh respectively to meet the energy demands of the buildings. it can be observed from table 1 that the hybrid supply for the 3-bedroom, office and sports buildings have sufficiently met the buildings energy demand with almost no deficit in the demand side. however, the office building recorded unusable energy supply of 38.22 mwh. this indicated that the hybrid energy supply for the office building was not well sized due to the surplus energy. the surplus energy is accounted when energy is not used or during period of high wind speed and solar radiation. the hybrid system capital and operation cost should be higher for the office and 3-bedroom buildings, due to the use of fossil fuel for the auxiliary energy generation and the cost of the emission of harmful substance into the environment. the analysis for the office sizing would have to be considered first before the 3-bedroom flat with a view of eliminating the auxiliary application utilising high cost of fossil fuel. this is in contrast to the school building that have the same energy demand as in the case of the 3-bedroom flat. however, their hybrid energy supply capacities are different. emphasis should be given to the sizing of the energy supply http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):143-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 150 schemes, in their capacities for the chunks of the pv, wt and battery storage systems in order to achieve the best match. 4. conclusion in this paper, hybrid energy supply sizing analysis was conducted using merit modeling tool for demand and supply matching through chunks of capacities of pv, wind, chp and generator integrated with a battery storage to meet the energy demands of 3-bedroom, office, sports and school buildings. the results showed that excess energy was recorded with higher percentage of matching rate for the office compared to the other buildings. however, no energy deficit was recorded in the 3-bedroom, office and sports buildings. the surplus energy recorded in the hybrid supply for the school building can balance up the deficit energy, when an efficient battery storage system is employed. the result analysis indicated that the sizing of the hybrid energy supply for the 3-bedroom, sports and school buildings was successfully achieved. however, there is the need to resize the hybrid energy supply for the office building, in order to avoid excess energy supply to the building. references anoune, k., laknizi, a., bouya, m., astito, a. and abdellah, ab. 2018a. sizing a pv-wind based hybrid system using deterministic approach. energy conversion and management, 169: 137-148. anoune, k., bouya, m., astito, a. and abdellah, ab. 2018b. sizing methods and optimization techniques for pv-wind based hybrid renewable energy system: a review. renewable and sustainable energy reviews, 93: 652-673. bahramara, s., moghaddam, mp. and haghifam, mr. 2016. optimal planning of hybrid renewable energy systems using homer: a review. renewable and sustainable energy reviews, 62: 609620. blazquez, j., fuentes-bracamontes, r., bollino, c.a. and nezamuddin, n., 2018. the renewable energy policy paradox. renewable and sustainable energy reviews, 82(1):1-5. clarke, ja., hand, j., hong, j., kelly, n., picco, m., samuel, a. and svehla, k. 2013. low energy communities: the automatic sizing of hybrid renewable energy schemes and the generation of a simulation input model for performance appraisal. in 13th building simulation conference, bs2013 held 25 – 28 august, 2013, chambery, france deshmukh, mk. and deshmukh, ss. 2008. modeling of hybrid renewable energy systems. renewable and sustainable energy reviews, 12(1): 235-249. elhadidy, ma. and shaahid, sm. 2000. parametric study of hybrid (wind+ solar+ diesel) power generating systems. renewable energy, 21(2): 129-139. iea. 2017. key world energy statistics. international energy agency, paris https://www.iea.org/publications/freepublications/publication/keyworld2017.pdf accessed on 05 february, 2019. ismail, ms., moghavvemi, m. and mahlia, tmi. 2013. techno-economic analysis of an optimized photovoltaic and diesel generator hybrid power system for remote houses in a tropical climate. energy conversion and management, (69): 163-173. jamshidi, m. and askarzadeh, a. 2019. techno-economic analysis and size optimization of an offgrid hybrid photovoltaic, fuel cell and diesel generator system. sustainable cities and society, 44: 310-320. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk https://www.iea.org/publications/freepublications/publication/keyworld2017.pdf mukhtar et al: sizing analysis of hybrid energy supply for buildings integrated with battery storage. azojete, 19(1):143-152. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 151 koubaa, z., elleuch, ma. and frikha, a. 2021. a new approach for sizing a hybrid energy system for the power plant. proceedings of the international conference on decision aid sciences and application (dasa), ieee virtual conference, 7-8 december, pp. 1050-1055. krishna, ks. and kumar, ks. 2015. a review on hybrid renewable energy systems. renewable and sustainable energy reviews, 52: 907-916. luna-rubio, r., trejo-perea, m., vargas-vázquez, d. and ríos-moreno, gj. 2012. optimal sizing of renewable hybrids energy systems: a review of methodologies. solar energy, 86(4): 1077-1088. mahesh, a. and sandhu, ks. 2015. hybrid wind/photovoltaic energy system developments: critical review and findings. renewable and sustainable energy reviews, 52: 1135-1147. markvart, t. 1996. sizing of hybrid photovoltaic-wind energy systems. solar energy, 57(4): 277281. mathiesen, bv., lund, h. and karlsson, k. 2011. renewable energy system, climate mitigation and economic growth. applied energy, 88(2): 488-501. negi, s. and mathew, l. 2014. hybrid renewable energy system: a review. international journal of electronic and electrical engineering, 7(5): 535-542. nema, p., nema, rk. and rangnekar, s. 2009. a current and future state of art development of hybrid energy system using wind and pv-solar: a review. renewable and sustainable energy reviews, 13(8): 2096-2103. nosrat, a. and pearce, jm. 2011. dispatch strategy and model for hybrid photovoltaic and trigeneration power systems. applied energy, 88(9): 3270-3276. nguyen, kh. and kakinaka, m. 2019. renewable energy consumption, carbon emissions, and development stages: some evidence from panel co-integration analysis. renewable energy, 132: 1049-1057. olatomiwa l, mekhilef s, ismail ms, moghavvemi m. 2016. energy management strategies in hybrid renewable energy systems: a review. renewable and sustainable energy reviews. 62: 821-35. pearce, jm. 2009. expanding photovoltaic penetration with residential distributed generation from hybrid solar photovoltaic and combined heat and power systems. energy, 34(11): 1947-1954. quaschning, v. 2016. understanding renewable energy systems. routledge. raza, ma., khatri, kl., haque, miu., shahid, m., rafique, k. and waseer, t.a. 2022. holistic and scientific approach to the development of sustainable energy policy framework for energy security in pakistan. energy reports, 8: 4282-4302. rouhani, a., kord, h. and mehrabi, m., 2013. a comprehensive method for optimum sizing of hybrid energy systems using intelligence evolutionary algorithms. indian journal of science and technology, 6(6): 4702-4712. sawle, y., gupta, sc. and bohre, ak. 2018. a novel methodology for scrutiny of autonomous hybrid renewable energy system. international journal of energy research, 42(2): 570-586. upadhyay, s. and sharma, mp. 2014. a review on configurations, control and sizing methodologies of hybrid energy systems. renewable and sustainable energy reviews, 38: 47-63. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):143-152. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: umuktara@yahoo.co.uk 152 yang, h., lu, l. and zhou, w. 2007. a novel optimization sizing model for hybrid solar-wind power generation system. solar energy, 81(1): 76-84. yaqoot, m., diwan, p. and kandpal, tc. 2016. review of barriers to the dissemination of decentralized renewable energy systems. renewable and sustainable energy reviews, 58: 477490. zohuri, b. 2018. hybrid renewable energy systems. in hybrid energy systems: 1-38. springer, cham file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/umuktara@yahoo.co.uk arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):493-504 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 493 original research article development of a fuzzy logic controller (flc) for a chicken feather plucking machine s. a. alim1*, i. a. abdullateef2 and k. o. shobowale3 1department of mechanical engineering, ahmadu bello university, zaria, nigeria 2department of electrical & electronic engineering, university of ilorin, ilorin, nigeria 3department of mechatronics engineering, air force institute of technology, kaduna, nigeria. *corresponding author’s email address: moaj1st@yahoo.com 1.0 introduction feathers are epidermal growths or flat appendages that form a unique exterior covering, or plumage, on dinosaurs, birds, some non-avian (non-bird) and possibly other archosauromorphs. they are regarded as the most complicated skin structures observed in vertebrates (prum and brush, 2002; prum and brush, 2003). they aid in thermal insulation, flight, and waterproofing. in addition, the associated coloration helps them look pretty, communicate and offer some form of protection (pettingill, 1970; smith, 2020). after slaughtering the chickens, there is the need to remove the feathers from the skin so as to be able to cut the animal into smaller pieces. this would enable the removal of the inedible parts while preparing the edible parts for consumption. the traditional method of manually plucking the feathers is commonly practiced in nigeria for domestic and commercial uses. researchers have developed different types plucking machines which vary in dimensions and orientation. for both manual and machine plucking, the chicken must have undergone scalding. scalding is done article information abstract feathers are epidermal growths or flat appendages that form a unique exterior covering, or plumage, on (avian) birds, some non-avian and possibly other archosauromorphs. they are regarded as the most complicated skin structures observed in vertebrates. the traditional method of manually plucking the feathers with the hand is still the common practice in nigeria for both private and commercial use. for both manual and machine plucking, the chicken must have undergone scalding. in an attempt to add some form of intelligence to the design of the mechanical chicken feather plucking machines, a fuzzy logic controller (flc) is developed for this system. compared to conventional control techniques, flc has been best applied in complex ill-defined problems, which can be controlled by an efficient human operator without knowledge of their underlying dynamics. in the design of the flc, two input parameters were considered namely scalding temperature and weight of the chicken. while the output parameters considered were the rotating speed and rotating time of the plucker. nine rules were developed to effect the control process. for a chicken of 2.0kg weight and temperature of 80°c, the rotating speed and plucking time are 402rpm and 20.3secs. it shows the proof of concept that the chicken feather plucking process can be automated. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 29 march, 2023 revised 15 july, 2023 accepted 20 july, 2023 keywords: chicken feather weight of chicken scalding temperature speed of rotating disc rotating time fuzzy logic controller http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com moaj1st@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):493-504. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 494 to reduce the feather retention force (frf) on the chicken. local breed of chicken, cockrels, layers, broilers and noilers are the major categories of chickens that are reared and consumed in nigeria. of these four categories, broilers have the least feather retention force, while the local breed have the highest feather retention force. scalding is the process of immersing the birds in warm water to loosen the feathers. in a small plant, scalding (i.e., placing the carcass in and removing it from a scalding tank) is performed manually, but in large plants it is done in a continuous manner whereby the birds are subjected to a single or multistage scalding bath(s) while suspended from a moving shackle line (berry, 2017; barbut, 2004; irshad and arun, 2013; barbut, 2016). the water can be heated by oil, gas, electricity, alternatively, vertical cabinets utilizing hot-water sprays or steam can also be used (irshad and arun, 2013). interestingly, there are various scalding schemes, where selection of one over the other depends on the following; the degree of difficulty in removing the feathers (frf), the chilling method that is to follow (water or air), and the age of the bird (barbut, 2004; irshad and arun, 2013; barbut, 2016). higher scalding temperatures are better for loosening feathers from their follicles, but hard scalding is also the harshest on the skin. the outer layer of the skin, epidermis, becomes loose and is removed during the plucking operation. the removal of the epidermis can result in discoloration of the skin if it is dehydrated during subsequent air chilling (irshad and arun, 2013). the objective of this study is to replace the manual and mechanical process of feather plucking with an intelligent based system through fuzzy logic controller. the scald temperature and time profile depend mainly on the desired final market carcass/part skin color, the age and weight of the broilers, kill-line speed, and the number and type of scald tanks (buhr, walker, bourassa, caudill, kiepper and zhuang, 2016). adequate agitation of the scald water and uniform application temperature are essential to ensure good feather removal (barbut, 2004; barbut, 2016). the methods of scalding are: 1. soft scalding/semi scalding/slack scalding method is a process that leaves the epidermal layer intact but still allows a relatively easy feather removal. it is commonly used for young broilers and young turkeys (berry, 2017; barbut, 2004; energy solution centre, 2007; irshad and arun, 2013; barbut, 2016). birds slaughtered for display should be scalded in this way to improve their appearance, this is because water that is too hot will cause the outer layer of skin to loosen or be lost (berry, 2017; barbut, 2004; irshad and arun, 2013; buhr, walker, bourassa, caudill, kiepper and zhuang, 2014). the suggested temperature-time combinations for soft scalding are as seen in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com ajibola et al: development of a fuzzy logic controller (flc) for a chicken feather plucking machine. azojete, 19(3):493-504. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 495 table 1: suggested scalding parameters for soft scalding s/n author(s) scalding temperature scalding time 1 nunes, 2011 55°c 120 -180 secs 2 energy solution centre, 2007 51.1 – 54.4 oc 45 secs 3 mountney and parkhurst, 2001 50 – 51 °c 210 secs 4 irshad and arun, 2013 50 51 oc 60 – 180 secs 5 barbut, 2004 50 53 oc 60 – 180 secs 6 berry, 2017 51.7 – 54.4 oc 30 60 secs 7 buhr et al. 2014 51 54 °c 120 210 secs 8 barbut, 2016 50–53 °c 60 180 secs 2. sub scalding/medium scalding method is used for mature birds. the epidermal layer is broken down by this time–temperature combination, and the feathers are usually much easier to remove (berry, 2017; energy solution centre, 2007; irshad and arun, 2013; barbut, 2016). for home processing, this method of scalding is recommended (berry, 2017). the suggested temperaturetime combinations for medium scalding are as seen in table 2. table 2: suggested scalding parameters for medium scalding s/n author(s) year scalding temperature scalding time 1 irshad and arun, 2013 54 58 oc 60 120 secs 2 energy solution centre 2007 53.9 – 57.8 oc 60 120 secs 60 – 62.8 oc 15 30 secs 3 barbut, 2004 54 58 oc 60 120 secs 4 berry 2017 58.9 60 oc 30 75 secs 5 buhr et al 2016 54 58°c 60 120 secs 60 63°c 15 30 secs 6 barbut 2016 54 – 58 °c 60 – 120 secs 3. hard scalding/full scalding method is the fastest and eliminates pinfeathers, but the carcasses tend to dry out and have a less desirable appearance. it is easier to remove the feathers from carcasses scalded at these temperature ranges than from those scalded at lower temperature, but the flesh of such poultry is doughy and lifeless, as such the skin becomes discolored soon after processing (berry, 2017; barbut, 2004; energy solution centre, 2007; irshad and arun, 2013; buhr et al., 2014). because the skin removes, the use of hard scalding for chickens is limited in some markets (energy solution centre, 2007). hard scalding has been the most common scalding method in the us poultry industry and is desirable for products with retained skin that are to be batter coated (irshad and arun, 2013; buhr et al., 2014). waterfowls such as geese, ducks and swans, may be scalded at this temperature (or higher temperature) because it is the only appropriate method of releasing their feathers (they have higher frf). also, the skin does not discolor as readily as do other species of poultry (berry, 2017; barbut, 2004; energy solution centre, 2007; irshad and arun, 2013; barbut, 2016). hard http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):493-504. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 496 scalding raises the temperature of the bird’s tissues and minimize the growth of bacteria and defeathering should be performed within 90 seconds of scalding (energy solution centre, 2007). the suggested temperature-time combinations for hard scalding are as seen in table 3. table 3: suggested scalding parameters for hard scalding s/n author(s) year scalding temperature scalding time 1 irshad and arun 2013 56 60oc 45 90 secs 2 energy solution centre 2007 71.1 oc 10 secs 3 nunes 2011 57°c 120 secs 4 mountney and parkhurst 2001 56 – 58 °c 120 150 secs 5 barbut 2004 60 °c 45 90 secs 6 berry 2017 60 – 65.6 oc 7 buhr et al 2014 60 – 66 °c 45 90 secs 8 barbut 2016 60 – 63 °c 45 – 90 secs hotter or longer scalding may be better for defeathering and salmonella control. this leads to over scalding which increases the toughness of cooked chicken and turkey breast meat. a toohigh scald temperature also causes a potential carcass yield loss attributed to subcutaneous fat (lipid) liquefaction (buhr et al., 2014). 2.1 manual scalding and manual defeathering manual scalding is the process of immersing of slaughtered bird in a hot water container and using fingers to pluck the feathers. manual scalding is practiced at home and in some small facilities. the dead bird is immersed in 60-65.6oc (140-150°f) water for about one minute. in most cases, an open tank is used that can accommodate one to ten birds, and the water is kept hot by a burner located in the bottom of the tank. the water is replaced and the tank cleaned once every shift or day (energy solution centre, 2007). figure 1 shows the process of manual scalding and manual defeathering. the manual scalding process as can be seen, the water is heated with an electric cooker and the carcass to be scalded is immersed in the water that is still being heated. figure 1: manual scalding and manual defeathering file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com ajibola et al: development of a fuzzy logic controller (flc) for a chicken feather plucking machine. azojete, 19(3):493-504. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 497 the chicken is removed from the scalding tank and the person can be seen plucking the feathers manually. this process takes between 2 and 5 minutes depending on how fast the plucker is. birds should be plucked immediately after scalding. if mechanical pluckers are used, they should be adjusted for the size birds being plucked. mechanical pluckers make the job much faster. carcasses that are to be exhibited should be plucked by hand being sure that all pinfeathers are removed, and that there is no damage to the skin. this procedure requires a good deal of time if done correctly. rubbing the feathers from the skin is frequently more effective than a picking motion (berry, 2017). figure 2 shows a fully feathered live chicken which is what is available before the slaughtering and scalding processes are done. and a fully defeathered carcass which is what is obtained after the series of processing. figure 2: a fully feathered live chicken/ fully defeathered bird 2.0 methodology in order to achieve the plucking process, the scalded chicken was lowered into the vertically assembled feather plucking machine (figure 3). this is a galvanized steel drum lined internally with rubber fingers subjected into a rotary motion by the transmitted torque from an electric motor. the carcass was rubbed with the rubber fingers and the feathers were thereby plucked continuously until the bird is completely defeathered (adetola et al., 2012). it also shows a summary of the defeathering process. it starts from scalding the carcass, the mechanical scalding is done and the chicken is picked out after the defeathering is done. figure 3: mechanical chicken feather plucking machine (farmsquare, 2021) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):493-504. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 498 in an attempt to add some form of intelligence to the design of the mechanical chicken feather plucking machines, a fuzzy logic controller (flc) is developed for this system. compared to conventional control techniques, flc has been best applied in complex ill-defined problems, which can be controlled by an efficient human operator without knowledge of their underlying dynamics. in the design of the flc, two input parameters were considered namely scalding temperature and weight of the chicken. while the output parameters considered were the rotating speed and rotating time of the plucker. the parameters are as discussed below. scalding temperature: the scalding temperature plays the major role in the efficient plucking of chicken feathers whether manually or by a machine. in fact, the percentage reduction in feather retention force (frf) ranges from 18% to 81% after about 2.5 minutes, 56oc scalding (abubakar et al., 2019). as such, the system is designed to have a temperature range from 50 – 100oc, because most of the scalding done at home and by the local butchers in nigeria who are the main target of this work is between 75 – 90oc usually at a lower retention time of less than 2 minutes. this position is also supported by the work of adetola et al. 2012. the membership functions used are as seen in figure 4. figure 4: membership functions of the scalding temperature weight of the chicken: the age of a chicken in weeks has a relation to its weight. due to this, weight is taken as an input parameter. the weight of the chicken has relationship with the body size parameters such as neck length, back length, kneel length, wing length, breast width, thigh length and shank length. the weight usually requested for by eateries is between 1.5-2.0kg after plucking. this informed the selection of 1.2 – 4.7kg as the weight of the chicken. some people usually prefer large bird having a weight of around 4kg. the membership function is as seen below in figure 5. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com ajibola et al: development of a fuzzy logic controller (flc) for a chicken feather plucking machine. azojete, 19(3):493-504. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 499 figure 5: membership functions of the weight of the chicken drum rotating speed: one of the two output parameters of the plucker is the rotating speed of the rotating disc of the plucker/drum. the rotating disc is the only rotating part of the machine, mounted on the motor and has some plucking fingers (rubber studs) on it. accordingly, the work of mady and obia (2018), the rotating speed ranging from 240-560rpm. this is the range adopted in this work for the universe of discourse of the rotating disc. the membership functions are as seen in figure 6. figure 6: membership functions of the drum rotating speed plucking time: the second output parameters selected is plucking time. this was done in order to ensure that the machine does not work endlessly, the outer skin of the carcass does not peel off and that time is conserved as time is money in this regard. the more chickens that is processed translates into finance for the operator of the machine. accordingly, the work of mady and obia http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):493-504. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 500 (2018), they used three different scalding times of 30, 60 and 90 seconds. as such, 7 – 90 secs were selected as the plucking time. the membership function of the plucking time is in figure 7. figure 7: membership functions of the plucking time 3.1 operating principle of the proposed system the chicken feather plucker would be designed to take two 2kg birds at a time. a pressure sensitive plate would be used at the bottom of the rotating drum. this would double as the weight sensor. a temperature sensor would be installed to measure the instantaneous temperature of the carcass. these two sensors would get the inputs for the microcontroller to process and send actuation message to the motor and the timer. the timer connected to the motor controls the time of operation of the motor. the motor controls the speed of rotation of the plucker. at the end of the rotation, the carcass(es) can be removed for further processing. the block diagram of the proposed flc chicken defeathering machine is as seen in figure 8. figure 8: block diagram of the proposed flc chicken defeathering machine defeathered chicken defeathering drum sensing of weight and temperature fis determines the drum rotating speed and plucking time actuator then effects the flc determined output parameters slaughtered chicken file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com ajibola et al: development of a fuzzy logic controller (flc) for a chicken feather plucking machine. azojete, 19(3):493-504. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 501 rule base 1. if (weight of the chicken is light) and (temperature of the chicken is soft scalding) then (speed of the plucker is high) and (plucking time is long) 2. if (weight of the chicken is medium) and (temperature of the chicken is soft scalding) then (speed of the plucker is medium) and (plucking time is long) 3. if (weight of the chicken is heavy) and (temperature of the chicken is soft scalding) then (speed of the plucker is high) and (plucking time is medium) 4. if (weight of the chicken is light) and (temperature of the chicken is medium scalding) then (speed of the plucker is low) and (plucking time is medium) 5. if (weight of the chicken is light) and (temperature of the chicken is hard scalding) then (speed of the plucker is low) and (plucking time is small) 6. if (weight of the chicken is medium) and (temperature of the chicken is medium scalding) then (speed of the plucker is medium) and (plucking time is small) 7. if (weight of the chicken is medium) and (temperature of the chicken is hard scalding) then (speed of the plucker is high) and (plucking time is small) 8, if (weight of the chicken is heavy) and (temperature of the chicken is medium scalding) then (speed of the plucker is medium) and (plucking time is long) 9. if (weight of the chicken is heavy) and (temperature of the chicken is hard scaling) then (speed of the plucker is low) and (plucking is medium) 3.0 results and discussion the developed flc system was simulated using fispro and the results are as presented. figures 9 and 10 show the interaction between weight of chicken vs rotating speed and weight of chicken vs plucking time respectively. it can be seen that as the weight increases, the plucking speed increases up to about 520rpm for a chicken with weight of about 2.25kg. the plucking speed remain relatively up to a weight of about 2.25kg. after this, the rotating speed drops gradually until it gets to zero. similarly, as the weight of the chicken increases, the plucking time rises up to about 1.3kg weight, then remains relatively constant at about 19sesc up to about 3.2kg weight. the rule base used is based on expert knowledge obtained from literature and this basically affected the output obtained from the simulation results. however, the validation of these results guides to know whether to modify the rule base as the performance of the flc in giving desired output is tied to the rule base. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):493-504. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 502 figure 9: weight of chicken vs rotating speed figure 10: weight of chicken vs plucking time figure 11: scalding temperature vs rotating speed figure 12: scalding temperature vs plucking time file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com ajibola et al: development of a fuzzy logic controller (flc) for a chicken feather plucking machine. azojete, 19(3):493-504. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 503 figures 11 and 12 show the interaction between scalding temperature vs rotating speed and scalding temperature vs plucking time respectively. as the scalding temperature increases, the rotating speed experiences a sharp rise to about 400rpm. then rises until the speed is at about 520rpm for 70oc scalding temperature. the speed stays relatively stable at this point till it fall back to zero. furthermore, the plucking time has a rapid rise to about 80secs, before falling to about 19secs. the information obtained from the literature with regards to the range of rotating speed was not much, however assumptions were made to get the linguistic hedges (low, medium and high) which eventually formed out universe of discourse. when a validation of the simulation results is conducted, proper modifications can be made to the rule base. for a two input two output system that is designed, assuming that the weight of the chicken is 1.5kg and the scalding temperature is 80oc then the rotating speed and the plucking time are 278rpm and 18.6sec. the input (1.5kg and 80oc are crisp input, the fuzzified by the flc and the fuzzy output is computed. the fuzzy output is then deffuzzified using centre of area method to obtain the output (278rpm and 18.6 seconds).1.5kg weight of chicken would have a 1.0 membership function on light weight, while 80oc would also have 1.0 membership function on high temperature. these fuzzified input would then trigger some of the rules in the rule base and the corresponding output are computed. the implication of this is that if a chicken weighing 1.5kg scalded at a temperature of 80oc, the plucking machine would rotate at a speed of 278rpm for 18.6 seconds. conclusion the simulation studies were clear indicating that the chicken feather plucking process could be automated. as a result of cost, most of the consumers go for chicken usually not more than 2.0kg and the scalding temperature is usually very hot water assumed to be around 80oc. as such, for a chicken of 1.5kg weight and the scalding temperature is 80oc then the rotating speed and the plucking time are 278rpm and 18.6sec. it is evident that the system has a potential to be integrated into a small-scale slaughterhouse to reduce the plucking time, reduce waiting time of customers and increase the earning of the owners of the slaughter houses. references abubakar, m., zakariyah, a. and usman, a. 2019. design, construction and performance evaluation of chicken defeathering machine. arid zone journal of engineering, technology and environment (azojete), 15(3): 702-713. adetola, so., onawumi, as. and lucas, eb. 2012. investigation into mechanized de-feathering process and optimal scalding temperature of exotic and local birds in southwestern nigeria. transnational journal of science and technology, 2(3): 87-96. barbut, s. 2004. slaughter-line operation | poultry. in devine, c. and dikeman, m. (eds), encyclopedia of meat sciences, first edition, pp.1255-1261, elsevier ltd, amsterdam, the netherlands. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):493-504. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: moaj1st@yahoo.com 504 barbut, s. 2016. poultry: processing. in caballero, b., finglas, p.m. and toldrá, f. (eds.) encyclopedia of food and health, pp. 458-463, elsevier ltd, amsterdam, the netherlands. berry, jg. 2017. home processing of poultry, oklahoma cooperative extension service. http://osufacts.okstate.edu accessed on 1 april, 2023. buhr, rj., walker, j., bourassa, dv., caudill, ab., kiepper, bh. and zhuang, h. 2014. impact of broiler processing scalding and chilling profiles on carcass and breast meat yield. poultry science, 93(6): 1534-1541. energy solution centre (2007). food processing technologies. energy solution center, washington, usa. http://foodtechinfo.com/foodpro/index_gas_technologies/scalding_-_poultry/ accessed on 1 april, 2023 farmsquare. 2021. defeathering plucking machine for poultry birds. farmsquare, nigeria. https://farmsquare.ng/shop/equipment-planting-materials/livestock-equipments/defeatheringmachine-for-poultry-birds-electric-powered/ accessed on 1 april, 2023. irshad, a. and arun, ts. 2013. scalding and its significance in livestock slaughter and wholesome meat production. international journal of livestock research, 3(2): 45-53. mady, maa. and obaia, ar. 2018. manufacture and performance valuation of poultry plucker suitable for small farms, misr journal agricultural engineering, 35 (2): 407 – 422. mountney, gj. and parkhurst, cr. 2001. slaughtering and defeathering. in: text book of poultry product technology, third edition. haworth food products press, new york, usa. pp. 172-179. nunes, f. 2011. scalding and plucking for optimum carcass quality and yield. poultry world, doetinchem, netherlands. https://www.poultryworld.net/the-industry-andmarkets/processing/scalding-and-plucking-for-optimum-carcass-quality-and-yield/ accessed on 1 april, 2023. pettingill, o.s.j. 1970. ornithology in laboratory and field. fourth edition. burgess publishing company, north carolina., u.s.a., pp. 29–58. prum, ro. and brush ah. 2002. the evolutionary origin and diversification of feathers. the quarterly review of biology, 77 (3): 261–295. doi:10.1086/341993. prum, ro. and brush, ah. 2003. which came first, the feather or the bird? scientific american. 288 (3): 84–93. bibcode:2003sciam.288c..84p. doi:10.1038/scientificamerican0303-84. smith, k. 2020. chicken feather structure. backyard chicken coops, brisbane, australia. https://www.backyardchickencoops.com.au/blogs/learning-centre/featherstructure#:~:text=feathers%20are%20a%20feature%20that,do%20serve%20other%20important %20purposes.&text=there%20are%20four%20main%20types,feathers%2c%20semiplumes%2c% 20and%20filoplumes accessed on 1 april, 2023 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/moaj1st@yahoo.com http://osufacts.okstate.edu/ http://foodtechinfo.com/foodpro/index_gas_technologies/scalding_-_poultry/ arid zone journal of engineering, technology and environment. august, 2016; vol. 12:83-93 copyright © faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng development and performance evaluation of a re-circulatory vegetable moisturizer m. o. sunmonu 1 *, m. m. odewole 1 , o. i. obajemihi 1 and a.t. ayodeji 2 ( 1 department of food engineering, university of ilorin, nigeria 2 department of agricultural and biosystems engineering, university of ilorin, nigeria) *corresponding author’s e-mail address: sholams2000@yahoo.co.uk tel.: +2348050745127 abstract a re-circulatory vegetable moisturizer for preventing wilting in vegetables was developed and its performance evaluation carried out. freshly harvested amaranthus vegetables were used for the experiments. the temperature and relative humidity were monitored daily. the vitamin a of this produce was determined at intervals of two days for 9 days. the effects of the storage parameters (temperature and relative humidity) on the nutritional value of the produce were determined using statistical analysis of variance (anova). further analysis by duncan’s new multiple range test (dnmrt) was carried out to compare the means. the vegetable moisturizer was evaluated by comparing the change in nutritional (vitamin a) of amaranthus vegetable with hand wetting system and no wetting condition. the results showed that the moisturizer had higher mean vitamin a content (4.93mg/100g)compared to the mean vitamin a content of the manual wetting (4.88mg/100g) and no wetting condition (4.57mg/100g). the sensory characteristics showed that the moisturizer was more desirable when compared to the manual wetting and no wetting condition after nine days. it was concluded that the moisturizer preserved the nutritional and sensory characteristics (texture and colour) better than the manual and no wetting condition as a result of lower temperature, higher relative humidity and better water draining of the moisturizer. keywords: moisturizer, vegetable, nutrition, amaranthus, storage 1. introduction vegetables are the fresh and edible portions of herbaceous plants. they are important food and highly beneficial for the maintenance of health and prevention of diseases. they contain valuable food ingredients which can be successfully utilized to build up and repair the body. they are valued mainly for their high carbohydrate, vitamin and mineral contents. vitamins are organic molecules required in trace amounts for normal development, which cannot be synthesized in sufficient quantity by the organism and must be obtained from the diet. the 14 vitamins known today are vitamin a, b complex [b1, b2, b3, b5, b6, b9, biotin, choline and b12) and vitamins c, d, e and k. the vitamins present in vegetables make an important contribution to human nutrition, as they have specific functions in normal body performance. the vitamin content of vegetables shows a wide variation among species (salunkhe et al., 1991). differences within cultivars occur, as well as between different batches of the same cultivar grown under different environmental and orchard conditions (rodriguez-amaya, 2001).vegetables are rich and comparatively cheaper source of vitamins. consumption of these items provides taste, palatability, increases appetite and provides fibre for digestion and to prevent constipation. postharvest handling of vegetables is the process involved in storing, preserving and transportation of vegetables after harvest. it begins where production ends. quality cannot be improved after harvest, only maintained; therefore it is important to harvest vegetables at the proper stage and size and at peak quality. mailto:sholams2000@yahoo.co.uk sunmonu et al.: development and performance evaluation of a re-circulatory vegetable moisturizer. azojete, 12:83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 84 leafy vegetables are mostly water (>90%) and have the propensity to lose water through transpiration. water loss is the main cause of weight loss (loss in saleable weight) and wilting (acedo, 2010). a loss of 5-10% of fresh weight would make leafy vegetables to appear wilted and become unusable (kanlayanarat, 2007). water loss also induces degradation of nutritional components (e.g. vitamin c loss) and imposes stress (i.e. water stress) that increases respiration and ethylene production (acedo, 2010).water loss is one of the most visible changes in vegetables, often being the factor that limits marketing life (ben-yehoshua and rodov 2003; shamaila, 2005). due to the too much drudgery involved in constant wetting of leafy vegetables manually by green grocers in markets, there is need to develop a re-circulatory vegetable moisturizer to prevent water loss and wilting of vegetables during postharvest handling and to compare the difference in the nutritional content (vitamin a) of amaranthus vegetable that is exposed to this moisturizing system, manual wetting condition and ambient condition. 2. materials and methods 2.1 design consideration and computation the criteria considered in the design of the vegetable moisturizer included the capacity of tank, availability of materials used for construction at affordable price, minimal maintenance cost and simplicity of the design so that its use could be extended to the general public and finally, the efficient use of water to reduce wastage by making the systems a recyclable type. 2.1.1 design of components of moisturizer 2.1.1.1 capacity of storage tank given as (1) with and 2.1.1.2 flow velocity (2) area of pipe, (3) diameter of main pipe diameter of delivery pipe 2.1.2 pump power capacity pump power requirement was calculated using the expression given by phocaides (2000) as (4) q is flow rate in l/s, e1 is the pump efficiency which is approximately 0.5 and e2 is the driving efficiency is approximately 0.7 for electric motors. a 0.5hp pump would be used so that additional head can be produced at the different outlet pipes. arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 85 2.1.3 pressure at the outlet for the head at the outlets pipe on each shower, h = 0.5x 75x 0.5x0.7/0.5 = 26.25m. actual total head = total head loss + head at outlets. head at outlets , average head on one outlet= 20.23/ 6 = 3.37m pressure at outlet = 3.37x 9.81 x 1000 pressure from the shower holes = (5) number of holes on shower cap= 166 and average diameter of hole = 0.1cm average area of hole= = 7.9 x 10 -7 m 2 . the average values of parameters used in the machine design are presented in table 1. table 1: summary of the parameters used in the development of the vegetable moisturizer parameters measurements units _____________________________________________________________________________________________ capacity of storage tank 0.048 m 3 area of the pipe 5.1 x 10 -4 m 2 velocity of flow 0.98 m/s area of delivery pipe 1.27 x 10 -4 m 2 velocity of flow of delivery pipe 3.94 m/s velocity of discharge 0.66 m/s pump capacity 0.11 hp pressure at outlet 33059 n/m 2 pressure from the shower holes 192 n/m 2 _____________________________________________________________________________ 2.2 description of vegetable moisturizing system the re-circulatory vegetable moisturizer consists of a tank, pump, pipes and shower system. the pipe is made from polyvinyl chloride, while body of the vegetable moisturizer is made from stainless steel. the tank capacity is 0.048m 3 while the pump horse power is ½ hp. 2.2.1 working principle of the equipment water is pump from the re-circulatory tank through the piping system and it is discharged through the shower system on the vegetables which are placed on top of a wire mesh which separates the vegetable from the storage tank. the pressure of the water is controlled by a valve place at the discharge part of sunmonu et al.: development and performance evaluation of a re-circulatory vegetable moisturizer. azojete, 12:83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 86 the pump. the water is being recycled through the pump and the whole process repeats itself. the photographic presentation of the moisturizer is shown in figure 1, while its assembly drawing showing the components with part list is a presented in figure 2. figure 1: picture of vegetable moisturizer 2.3 performance evaluation of vegetable moisturizer three storage systems (vegetable moisturizer, manual wetting system and no wetting system-as control) were set up for testing for vitamin a for nine days. the water in the moisturizer is to be replaced every three days. about 500 g of amaranthus vegetable was kept in the vegetable moisturizer and the other two systems.the vegetable moisturizer was used to wet the vegetble three times a day and manual wetting was also done three times.wet-bulb and drybulb temperature in the three sysyems were taken using a wet and dry bulb thermometer in the morning and the evening for the nine days of the experiment.vitamin a content of amaranthus vegetables were taken in the three systems with three replicates on the second, fifth, seventh and nineth days.the three different storage systems moisturizer system, manual hand wetting system and the control (no wetting) were labelled a,b and c respectively.each storage systems had three different replicate of vegtable for accuracy of values.the method used in the determination of the vitamin a content of the amaranthus vegetables was a titrimetric method offerred by aoac (1995). 3. results and discussion figure 3 shows the variations in the temperatures and relative humidity of amaranthus vegetables in the three different storage media.. the results suggest that temperature variations within moisturizer system and manual hand wetting seem to be relatively the same on the average. slightly higher temperatures values were observed in control method (no wetting). relative humidity on the other hand appears to be slightly lower in control method (no wetting) compared to moisturizer system and arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 87 manual hand wetting while moisturizer system and manual hand wetting appears to record relative the same relative humidity on the average. tan and considine (2006) noted that moisture present in vegetables increases the relative humidity in storage system. this can be a reason for higher relative humidity in the moisturizer (83.11%) and manual hand wetting system (84.89%). figure 2: vegetable moisturizer assembly ( vegetable water sprinkler) sunmonu et al.: development and performance evaluation of a re-circulatory vegetable moisturizer. azojete, 12:83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 88 figure 3: variations in temperature ( o c) and relative humidity (%) within storage type the analysis of variance (table 2) shows that temperature variations within storage types were significant at 10% level of significance however, variations in relative humidity within storage types were not significant. this shows that temperature changes within storage type depend onto a large extent the storage systems used. this was as a result of different water level present in the different storage systems as discussed earlier (mittal et al., 2006). but relative humidity variations do not depend on storage system (moisturizer system, manual hand wetting and control systems). since the three systems were exposed to the same ventilations (room), the vapour pressure change should almost be the constant (bachmann and earles, 2000). to determine the differences in variations temperature along the levels of the storage conditions, the new duncan’s multiple range test (ndmrt) was conducted (table 3). the result of the comparison among the levels of storage conditions shows that control method has the highest temperature variations. moisturizer system and manual hand wetting shows the same temperature variations. the high temperature variation of the control shows that the temperature depends on the ambient temperature of the room but the moisturizer and the manual method depend on the temperature of the water used in wetting. relative 28.56 28.47 29.56 83.11 84.89 80.33 0 10 20 30 40 50 60 70 80 90 sprinkler system manual hand wetting control method sprinkler system manual hand wetting control method temperature relative humidity te m p e ra tu re (o c )/ r e la ti ve h u m id it y( % ) arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 89 humidity observed in all levels of the storage type as reported by bachmann and earles (2000) due to the fact of same room condition. table 4 compares vitamins a content of the stored vegetables along storage type and it revealed that vitamin a content of the stored vegetables in all storage types are different from each other’s irrespective of the storage days. figure 4 graphically illustrates the vitamin a content and it shows that the vitamin a content in the moisturizer system and manual hand wetting system is higher compared to the control (no wetting system). anjum et al. (2008) emphasized that storing vegetables at room temperature gradually decreases beta-carotene (vitamin a) content which is the reason for reduction in vitamin a of the control method. the moisturizer system and the manual hand wetting retained a higher vitamin a which was 4.93mg/100g and 4.88mg/100grespectively because of the water present which causes evaporative cooling and thereby reducing temperature (mittal et al., 2010). from table 4, it is also seen that there is decrease in the content of vitamin a as storage progresses. table 2: analysis of variance (anova) of the effect of temperature ( o c) and relative humidity (%) on storage type sum of squares df mean square f sig. temperature storage types between st 13.083 2 6.542 3.030 0.057* within st 110.125 51 2.159 total 123.208 53 relative humidity storage types between st 189.778 2 94.889 1.703 0.192 within st 2841.556 51 55.717 total 3031.333 53 *significant ststorage type table 3: new duncan’s multiple range test (ndmrt) of the variations in temperature ( o c) and relative humidity (%) on the storage type main factor storage type average value temperature ( o c) moisturizer system 28.56a manual hand wetting 28.47a control method 29.56b relative humidity (%) moisturizer system 83.11a manual hand wetting 84.89a control method 80.33a means with the same alphabet are not significantly different from each other sunmonu et al.: development and performance evaluation of a re-circulatory vegetable moisturizer. azojete, 12:83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 90 table 4: effect of storage type on vitamin a content (mg/100g) of amaranthus vegetable storage factors vitamin mean std. d minimum maximum s to ra g e co n d it io n moisturizer system vitamin a 4.93 0.08 4.85 5.10 manual wetting vitamin a 4.88 0.15 4.65 5.15 control method vitamin a 4.57 0.18 4.40 4.90 figure 4: effect of storage type on vitamin a content (mg/100g) of amaranthus from table 5, it can be seen that as the day goes by there is decrease in the content of vitamin a. one major reason is that betacarotene (vitamin a) is rapidly oxidized when exposed to light and oxygen (howard et al., 1999). the analysis of variance result of the effect of storage type, and storage days on vitamin a is presented on table 6. it can be observed that storage type and storage days had significant effect on vitamin a at 5% level of significance. this implies that vitamins a content of stored vegetables differs significantly across the storage type and storage days. it can be concluded that the variation or discrepancies observed in vitamin a were due to the different storage type used and storage days. the storage type affected the variation in vitamin a content because the different storage types have different temperature which implies different vitamin a content. this agrees with azevedo and rodriguez-amaya (2005) that concluded that higher temperatures increase the biosynthesis of vitamin a (carotenoids) which results in loss of vitamin a. table 7 shows the comparisons between the different levels of storage type, storage days using the new duncan multiple range test (ndmrt) and it shows that vitamin a content of the vegetables stored in moisturizer system and manual hand wetting were statistically the same on the average but were significantly 4.93 4.88 4.57 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 sprinkler system manual hand wetting control method v it am in a ( m g/ 1 0 0 g) storage type arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 91 higher than the vitamin a contents of vegetables stored in control method. this agrees with kader (2002) that high temperature is a major cause of postharvest loss in nutritional content which was a reason for lower vitamin a content (higher temperature). the mean value of vitamin a content of stored vegetable differs significantly across storage day 2 and day 9 respectively while for day 5 and day 7 the mean value of vitamin a content remain the same. this implies that, depending the storage type, the average vitamin a contents of stored vegetables of (day 2) (day 5and 7), (day 9) are statistically different due to the degradation of vitamin a along storage days(cardoso and lucia et al., 2009). table 5: effect of storage days on vitamin a content (mg/100g) of amaranthus vegetable storage factors vitamin mean std. d minimum maximum s to ra g e d ay s 2nd day vitamin a 4.97 0.13 4.80 5.15 5th day vitamin a 4.80 0.20 4.50 5.10 7th day vitamin a 4.74 0.21 4.45 4.95 9th day vitamin a 4.67 0.20 4.40 4.90 table 6: analysis of variance (anova) on the effect of storage type and storage days on vitamin a content (mg/100g) of stored amaranthus vegetable source sum of squares df mean square f sig. st 0.902 2 0.451 71.41 0.001* sd 0.441 3 0.147 23.30 0.001* st * sd 0.098 6 0.016 2.58 0.045* error 0.152 24 0.006 total 1.593 35 *significant at 5% ststorage type sdstorage days table 7: new duncan’s multiple range test (ndmrt) to compare the different levels of storage type and storage days on the vitamin a content (mg/100g) of amaranthus vegetable main factor level vitamin a (mg/100g) storage type moisturizer system 4.93a manual hand wetting 4.88a control method 4.57b storage days day 2 4.97a day 5 4.80b day 7 4.74b day 9 4.67c means with the same alphabet are not significantly different from each other sunmonu et al.: development and performance evaluation of a re-circulatory vegetable moisturizer. azojete, 12:83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 92 table7 also shows the comparisons between the different levels of storage type, storage days using the new duncan multiple range test (ndmrt). from table 7it can be seen that vitamin a content of the vegetables stored in moisturizer system and manual hand wetting were statistically the same on the average but were significantly higher than the vitamin a contents of vegetables stored in control method. this agrees with kader (2002) that high temperature is a major cause of postharvest loss in nutritional content which was a reason for lower vitamin a content (higher temperature). the mean value of vitamin a content of stored vegetable differs significantly across storage day 2 and day 9 respectively while for day 5 and day 7 the mean value of vitamin a content remain the same. this implies that depending the storage type, the average vitamin a contents of stored vegetables of day 2, days 5and 7, day 9 are statistically different due to the degradation of vitamin a along storage days (cardoso and lucia et al., 2009). 4. conclusion a vegetable moisturizer was developed to reduce water loss in vegetables during postharvest storage. the difference in nutritional content (vitamin a) of amaranthus vegetable that is exposed to this moisturizing system, manual wetting condition and exposed to ambient condition (no wetting) was compared. the following can be concluded 1. the vegetable moisturizer was able to reduce drudgery encountered in manual wetting of vegetables 2. the vegetable moisturizer was more efficient in reducing water loss and thereby preserving the sensory properties better as well as retaining higher value of vitamin a in the system. 3. the percentage vitamin a loss in the moisturizer (4%) was lower when compared to the manual hand wetting (6%) and the no wetting condition (12%). references acedo, al. 2010. postharvest technology for leafy vegetables.avrdc-adb postharvest projects reta 6208/6376.avrdc publication no. 10.avrdc the world vegetable centre, shanhua, tainan, taiwan, pp. 67. anjum, f., kham,ba.,noreen, n., masood,t. and faisal, s. 2008. effect of boiling and storage on betacarotene content of different vegetables. pakistan journal of life and social sciences, 6(1): 6367. aoac. 1995.official methods of analysis.association of official analytical chemists, 16th edition, vol. 2. arlington, va, usa. azevedo, ch. and rodriguezamaya, db. 2005. caroteniod composition of kale as influenced by maturity, season and minimal processing. journal of the science of food and agriculture, 85(4): 591597. bachmann, j. and earles, r. 2000. postharvest handling of fruits and vegetables. appropriate technology transfer for rural areas horticulture technical note. fayetteville, nc, usa, pp. 19. arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 83-93. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 93 ben-yehoshua, s. and rodov, v. 2003. transpiration and water stress. postharvest physiology and pathology of vegetables. new york: marcel dekker new york, ny, usa, pp 111-159. cardoso, ps., lucia, cm., stringheta, pc., charles, jb. and pinheirosant ana, hm. 2009. carotene and pro-vitamin a content of vegetables sold in vicosa, brazil during spring and winter, brazilian journal of pharmaceutical sciences, 45: 527–537. howard, la., wong, ad., perry, ak. and klein, bp. 1999. betacarotene and ascorbic acid retention in fresh and processed vegetable, journal of food science, 64: 929 – 936. kader, aa. 2002. quality parameters of fresh cut fruits and vegetables products. in fresh-cut fruits and vegetables. lamikanra o., ed, science, technology and market, crc press, boca raton, florida, pp. 11-20. kanlayanarat s. 2007. postharvest technologies for fresh leafy vegetables in thailand. paper presented during the reta 6376 workshop on best practices in postharvest management of leafy vegetables in gms countries, hanoi, vietnam. mittal, a., kataria, t., das, gk. and chatteree, sg. 2006. evaporative cooling of water in a small vessel under varying ambient humidity, international journal of green energy, 3: 347-368. phocaides, a. 2000. technical handbook on pressurized irrigation techniques. food and agriculture organization of the united nations rome, 2000. rodriguez-amaya, db. 2001. a guide to carotenoid analysis in foods. ilsi press, international life sciences institute, one thomas circle, n.w. washington, dc, usa. salunkhe, dk., bolin, hr. and reddy, nr. 1991. storage, processing, and nutritional quality of fruits and vegetables. volume i. fresh fruits and vegetables. crc press, boston, ma, usa. shamaila, m. 2005. water and its relation to fresh produce. produce degradation: pathways and prevention. boca raton, fl: taylor and francis, florida, pp 267-291. tan, sc. and considine, m., 2006. storage conditions for fresh fruits and vegetables. department of agriculture and food. government of western australia, kensington, pp. 145. arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 1-12 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng evaluation of solar chimney power plant in semi-arid region of nigeria ngala, g.m 1* ., oumarou, m.b 1 ., muhammad, a.b 1 . and shuwa, m 2 . ( 1 department of mechanical engineering, university of maiduguri, borno state, nigeria 2 center for entrepreneurial and enterprise development, university of maiduguri, borno state, nigeria.) *corresponding author’s e-mail address: garba.ngala68@gmail.com abstract solar chimney power plant (scpp) is a renewable energy facility that converts the potential energy in the sun into kinetic energy and subsequently into electrical energy. the problem of global warming and electricity generation/distribution in nigeria cannot be over emphasized; however with the vast land in the semi arid region and the potentials of the above technology, high prospects exist for solar chimney as it is a decentralized form of power generation. the aim of this paper was to theoretically evaluate the performance of the solar chimney power plant in semi-arid region of nigeria, and estimate the amount of electrical energy that can possibly be generated. a mathematical model was used to estimate the amount of power generated, and determine the relationship between various meteorological and physical factors to the power produced. a solar chimney power plant with collector diameter of 700 m and chimney height of 700 m can produce up to 3000 mw of electricity. keywords: solar chimney power plant, semi-arid region, power generation, nigeria nomenclature ach chimney cross-sectional area (m 2 ) acoll collector area (m 2 ) cp specific heat capacity (kj kg1 k1 ) fr collector heat removal factor f' collector efficiency factor f'' collector flow factor g gravitational acceleration (m s2 ) q solar radiation (w m2 ) hch chimney height (m) . m mass flow rate (kg s1 ) ptot useful energy contained in the airflow (kw) pt,m maximum mechanical power taken up by the turbine(kw) pout electric output from the solar chimney (kw) . q heat gain of air in the collector (kw) ta ambient temperature (k) tfm mean air temperature (k) tin inlet air temperature (k) tout outlet air temperature (k) tpm mean plate temperature (k) vch air velocity at the chimney inlet (m s1 )  effective absorption coefficient of the collector  heat loss coefficient (w m2 k1 ) mailto:garba.ngala68@gmail.com ngala et al.: evaluation of solar chimney power plant in semi-arid region of nigeria. azojete, 11: 1-12 2  tot total efficiency  ch chimney efficiency  coll collector efficiency  t turbine efficiency  air air density (kg m3 ) ∆p pressure difference produced between chimney base and the surroundings (pa) ∆t temperature rise between collector inflow and outflow 1. introduction the solar energy flux reaching the earth’s surface represents a few thousand times the current use of primary energy by humans. the potential of this resource is massive and makes solar energy an essential component of renewable energy portfolio aimed at reducing the global emissions of greenhouse gases into the atmosphere. however, the current use of this energy resource represents less than 1% of the total electricity production from renewable sources (gcep, 2006). only about 35% of nigerians have access to electricity compared with 95% in egypt and 75% in south africa. on the overall, energy consumption in africa is less than 5% of the global use. though 13% of the world’s populations and 10% of the world crude oil-reserves are in africa, about 85% of the people in africa still live in rural areas without access to electricity. nigeria, the most populous country in africa is herself facing an irony of sort; being the sixth largest world producer of crude oil, but yet facing very serious energy crisis for many decades (ngala et al., 2006). at present, the government is committed to finding a long-term solution to this crisis through the renewable energy master plan (remp) with a target of increasing the present 5,000 mw to 16,000 mw by this year 2015 (ecn, 2007). the solar chimney power facility has the potential to become a valuable technology for renewable energy production, especially in countries with abundant solar radiation and large unused flat land. solar chimney power plant, designed to produce electric power on a large scale, utilizes solar radiation to create air which drives the generator connected to turbines to produce electric power (larbi et al., 2010). the idea of solar chimney dates back to 1903 when isidoro cabanyes, a spanish artillery colonel wrote his book on solar chimney. this was followed up by prof. bernard dubos who in 1926 proposed to the french academy of sciences the construction of a solar aero-electric power plant in north africa with its solar chimney on the slope of a high mountain (marco, 2010). the first experimental prototype built was in manzanares, spain. it worked for 7 years thus proving the efficiency and reliability of this novel technology. the chimney height was 194.6 m and the collector had a radius of 122 m (schlaich et al., 2005). a solar chimney power plant consists of a central chimney, surrounded by a solar collector that consists of a transparent canopy or roof supported a few meters above ground level, as shown in figure 1. a turbine driving a generator is located at the base of the chimney. solar radiation passing through the canopy strikes the ground below it from where heat is transferred to the arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 1-12 3 adjacent air by means of convection. due to buoyancy, the heated air flows towards the centre of the collector and then up the chimney where it drives the turbine. figure 1: solar chimney power plant schematic (koonsrisuk and chitsomboon, 2009) fundamental investigation of energy balance, design criteria and cost analysis of the prototype was conducted by haaf et al. (1983). the following year, the same authors reported preliminary test results of the solar chimney power plant. krisst demonstrated a ‘‘backyard-type’’ device with a power output of 10 w in west hartford, connecticut, usa. kulunk produced a microscale electric power plant of 0.14w in izmit, turkey (ming et al., 2006). many attempts have been made to evaluate the performance of solar chimney power plants in some parts of the world theoretically. dai et al. (2003) concluded that a solar chimney power plant in northwestern regions of china was able to produce 110–190 kw of electric power with a chimney height of 200 m and diameter of 10 m, and with a collector cover of 196,270 m 2 . frederick and reccab (2006) studied the potential of solar chimney power plant applications in rural areas. nizetic et al. (2008) analyzed the potential for electric energy production in mediterranean countries and estimated the quantity and price of the electric energy produced. larbi et al. (2010) presented the performance analysis of a solar chimney power plant expected to provide the remote villages located in algerian southwestern region with electric power. zhou et al. (2010) developed a simple mathematical model based on energy balance to analyze the performance of solar chimney power plants in qinghai-tibet plateau. sangi (2012) presented performance evaluation of solar chimney power plants in iran. the semi-arid region of northern nigeria is endowed with an average solar radiation and sunshine hours of 7 kw/m 2 /day and 9 hours respectively (ngala et al., 2013). to this should be added the fact that semi-arid regions are characterized by annual rain falls of 125 to 500 mm and ngala et al.: evaluation of solar chimney power plant in semi-arid region of nigeria. azojete, 11: 1-12 4 average daily temperatures of 40-45 o c (sfsa 2007), which corresponds to the mesophilic temperature range, and are endued with enormous unused flat land. these conditions together make the semi-arid region and maiduguri in particular very suitable for citing large scale solar chimney power plant. however the aim of this paper is to evaluate the performance of solar chimney in the semi-arid region of nigeria. 2. solar chimney power plant (scpp) a scpp consists of a solar hot air collector, a solar chimney and a turbine with generator. this unique combination accomplishes the task of converting solar radiation into electrical power. the solar-to-electric conversion involves two intermediate stages. in the first stage, conversion of solar energy into thermal energy is accomplished in the collector by means of the greenhouse effect. in the second stage, the chimney converts the generated thermal energy into kinetic and ultimately into electric energy by using a combination of a turbine and generator. figure 2 provides an overall view of a typical solar chimney system. in its simplest form, the collector is a glass or plastic film cover stretched horizontally and raised above the ground. this covering serves as a trap for re-radiation from the ground. it transmits the shorter wavelength solar radiation but blocks the longer wavelength radiation emitted by the ground. as a result, the ground under the cover heats up, which, in turn, heats the air flowing radially above it. a flat collector of this kind can convert a significant amount of the irradiated solar energy into heat. the soil surface under the collector cover is convenient energy storage medium. during the day, a part of the incoming solar radiation is absorbed by the ground and is later released during the night. this mechanism is capable of providing a continuous supply of power all year round. the characteristics of the scpp includes: (1) low operation cost. (2) cooling water is not required. (3) construction technology is familiar, and materials are abundant and cheap. (4) soil under the collector can act as natural energy storage system. (5) both direct and diffuse solar radiations can be utilized for solar-thermal conversion. (6) the scpp energy conversion efficiency is lower than other renewable energy power systems, but can be improved by increasing its dimension (asnaghi and ladjevardi, 2012). 3. mathematical expression of solar chimney power plant performance parameters factors affecting the performance of scpp fall into two categories: the meteorological conditions and the structural parameters. the meteorological conditions include solar radiation, ambient temperature and wind speed. structural parameters include the chimney height, the collector radius, chimney diameter, properties of the collector material and sand under the collector, as well as collector inlet gap. also important for power generation are the wind turbine and the controlling system of the plant. detailed analysis of heat transfer and fluid flow inside the solar chimney could be processed with computational fluid dynamics software (gannon and backstrom, 2000; backstrom and gannon, 2000). here, a simple method is reported, which takes into account solar collection, useful work and electric power output of the turbine, and is expected to evaluate the performance of the solar chimney power plant. arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 1-12 5 3.1 total efficiency total efficiency ηtot is determined here as a product of the individual component efficiencies: ηtot = ηc.ηch.ηt (1) ηc is the efficiency of the collector, in other words, the effectiveness with which solar radiation is converted into heat, ηch is the efficiency of the chimney and describes the effectiveness with which the quantity of heat delivered by the collector is converted into flow energy, ηt stands for the efficiency of the wind turbine generator (sangi, 2012). 3.2 solar collector a solar chimney collector converts available solar radiation q on the collector surface ac into heat output. collector efficiency ηc can be expressed as a ratio of the heat output of the collector as heated air  q divided by the product of solar radiation q (measured in w m −2 ) times the area of the collector ac. qa q c c   (2) heat output  q at the outflow from the collector under steady conditions can then be expressed as a product of the mass flow ̇, the specific heat capacity of the air cp and the temperature difference between collector inflow and outflow (tout − tin):  inoutp ttcmq   (3) where chchair avm   (4) substituting equation (4) into (3) and then (3) into (2) gives collector efficiency as   qa ttcav c inoutpchchair c     (5) the ground which is covered by glass or other transparent materials, acts as a heat absorption layer. the periphery of the solar air collector is open to the atmosphere, and its central part is connected with the base of the solar chimney. the energy balance equation is given as,   )( agmcc ttaqaq    (6) substituting in equation (2) q tt ingm c )(     (7) equating equation (5) and (7) ngala et al.: evaluation of solar chimney power plant in semi-arid region of nigeria. azojete, 11: 1-12 6    inoutpchair cingmc ch ttca attqa v      (8) this simple balance equation is independent of collector roof height because friction losses and ground storage in the collector are neglected. to evaluate collector performance, it is necessary to know the mean fluid (tfm) and mean ground temperature (tgm) (sangi, 2012), which could be estimated by the method recommended by duffie and beckman (1991).   cr r ingm af fq tt    1 (9)   cr infm af fq tt ''1   (10) where the collector heat removal factor (fr) can be expressed as                        p c c p r mc fa a cm f ' exp1   (11) also the collector flow factor ( ''f ) is defined as the ratio of collector heat removal factor (fr) to collector efficiency factor ( 'f ). ' '' f f f r (12) the mean fluid temperature is eventually required to solve the model, which could be found from the arithmetic mean of the inlet temperature and the mean ground temperature. 2 gmin fm tt t   (13) 3.3 solar chimney the chimney itself is the plant’s actual thermal engine. it is a pressure tube with low friction loss (like a hydro power station pressure tube or pen stock) because of its favorable surface-volume ratio. the updraft velocity of the air is approximately proportional to the air temperature rise (δt) in the collector and to the chimney height. in a multi-megawatt scpp the collector raises the air temperature by about 30 to 35 k. this induces an updraft velocity in the chimney of (only) about 15 m/s at nominal electric output, as most of the available pressure potential is used by the turbine(s) and therefore does not accelerate the air. it is thus possible to enter into an operating solar chimney power plant for maintenance without danger from high air velocities. hence the chimney efficiency is expressed as ratio of the output power to the solar heat gains. ap chtot ch tc gh q p    (14) arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 1-12 7 this simplified representation explains one of the basic characteristics of the solar chimney, which is that the chimney efficiency is fundamentally dependent only on chimney height (schlaich et al., 2005 and sangi, 2012). flow speed and temperature rise in the collector do not come into it. thus the power contained in the flow from eqn. (14) can be expressed as follows with the aid of eqns. (3) and (4):  inoutchchair a ch chtot ttav t gh qp    (15) a pressure difference δp is produced between chimney base (collector outflow) and the surroundings: a chair t t ghp    (16) 3.4. turbine the wind turbine generator fitted at the base of the chimney converts free convection flow into rotational energy. turbines in a solar chimney do not work with staged velocity as a free running wind energy converter, but as a cased pressure-staged wind turbo generator, in which similar to a hydroelectric power station, static pressure is converted to rotational energy using a cased turbine. the mechanical power taken up by the turbine is given by the following expression; qap cchctm  3 2  (17) this equation can further be expressed as qa tc gh p c ap ch ctm  3 2  (18) if ptm is multiplied by ηt which contains both blade transmission and generator efficiency, this produces the electrical power from the solar chimney to the grid, qa tc gh p c ap ch ctout  3 2  (19) it is recognized that the electrical output of the solar chimney is proportional to hchac, i.e. to the volume included within the chimney height and the collector area. thus, the same output can be achieved with different combinations of chimney height and collector diameter (schlaich et al., 2005 and sangi, 2012). there is no physically optimum size. optimal dimensions can be determined only by including the cost of the individual components (collector, chimney, mechanical components) at a particular site. ngala et al.: evaluation of solar chimney power plant in semi-arid region of nigeria. azojete, 11: 1-12 8 4. results and discussion the mathematical expressions developed for the plant performance indicators were computed using some parameters that are given in table 1. figure 2 shows the effect of solar radiation on power output and figure 3 shows the effect of collector radius on the generated power at a constant insolation of 800 w/ m 2 . the effect of chimney height on plant performance is shown in figure 4. it can be noted that the power production increases with the increase in the chimney height and solar radiation. the relationship of both chimney height and solar radiation with power produced is linear, while the relationship between collector radius and power produced is non linear as shown in figures 2, 3 and 4 respectively. figure 5 shows the profile of solar radiation and temperature at the site of interest and figure 6 is the monthly average daily solar radiation in six locations of the semi-arid region. table 1: technical data used in the analysis of solar chimney power plant performance. parameters value parameters value chimney height 700 m collector efficiency (ηc) 0.65 chimney diameter 10 m solar radiation (q) 800 w/m 2 collector diameter 700 m ambient temperature 35 o c turbine efficiency (ηt) 0.8 distance from ground to collector cover 2.5 m figure 2: effect of solar radiation on solar chimney power plant power output 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 500 1000 1500 p o w e r (w x1 0 9 ) solar rad. (w/m2) arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 1-12 9 figure 3: effect of plant collector radius on power output for a constant insolation of 800 w/m 2 figure 4: effect of chimney height on power output for insolation of 800 w/m 2 figure 5: solar radiation and temperature profile for 8 th of april, 2012 in maiduguri 0 2 4 6 8 10 12 14 16 18 0 50 100 150 200 250 300 350 p o w e r (w x1 0 9 ) roof radius (m) 0 0.5 1 1.5 2 2.5 3 3.5 4 0 200 400 600 800 p o w e r (w x1 0 9 ) chimney height (m) 0 10 20 30 40 50 60 0 200 400 600 800 1000 1200 te m p .( o c ) so la r r ad .( w /m 2 ) time solar radiation temp ngala et al.: evaluation of solar chimney power plant in semi-arid region of nigeria. azojete, 11: 1-12 10 figure 6: monthly average daily solar radiation in six locations. (fadere, 2009) 5. conclusion the intention of this study which was to evaluate the performance of solar chimney power plants in semi-arid regions of nigeria theoretically and to estimate the quantity of the produced electric power has been achieved. mathematical models based on the energy balance were used to estimate the power output of solar chimneys as well as examine the effect of various ambient conditions and structural dimensions on the power output. a solar chimney power plant with 700 m chimney height and 700 m collector diameter is capable of producing monthly average 3000 mw electric power over a year. the capacity of power generation is dependent on ambient conditions and structural dimensions such as solar irradiation, ambient temperature, chimney height and collector diameter. the power generation capacity increased with the increase in solar chimney height and solar collector area. also, the higher the solar radiation is, the greater the power generation. references asnaghi, a. and ladjevardi, sm. 2012. solar chimney power plant performance in iran. renewable and sustainable energy reviews, 16: 3383– 3390. backstrom, twv and gannon, aj. 2000. compressible flow through solar power plant chimneys. asme, journal of solar energy engineering, 122:138–145. dai, yj., huang, hb. and wang, nrz. 2003. case study of solar chimney power plants in north-western regions of china. renewable energy, 28:1295–1304. duffie, ja. and beckman, wa. 1991. solar engineering of thermal processes. new york: wiley interscience. 3.5 4 4.5 5 5.5 6 6.5 7 so la r ra d ia ti o n ( kw /m 2 /d ay ) monthly solar radiation in six locations azare kaduna kano katsina maiduguri sokoto arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 1-12 11 ecn. 2007. renewable energy master plan, energy commission of nigeria, federal ministry of energy resources, nigeria. fadere, da. 2009. modelling of solar energy potential in nigeria using an artificial neural network model. applied energy, 86: 1410-1422. frederick, no. and reccab, moj. 2006. the potential of solar chimney for application in rural areas of developing countries. fuel, 85: 2561–2566. gannon, aj. and backstrom, twv. 2000. solar chimney cycle analysis with system loss and solar collector performance. asme, journal of solar energy engineering, 122: 133–137. gcep. 2006. energy assessment analysis summer, an assessment of solar energy conversion technologies and research opportunities. stanford university. koonsrisuk, a. and chitsomboon, t. 2009. accuracy of theoretical models in the prediction of solar chimney performance, journal of solar energy, 83: 1764–1771. larbi, s., bouhdjar, a. and chergui, t. 2010. performance analysis of a solar chimney power plant in the southwestern region of algeria. renewable and sustainable energy reviews, 14: 470–477. marco, adsb. 2010. solar chimney power plants –developments and advancements. solar energy, rd. rugescu (ed.), pp. 432. intech, croatia, downloaded from sciyo.com on 24/09/2014. ming, t., liu, w. and xu, g. 2006. analytical and numerical investigation of the solar chimney power plant systems. international journal of energy research.30: 861–873. ngala, gm., abdulrahim, at. and usman, ml. 2006. developments in bioethanol fuel production, use and its potential as an alternative fuel in developing countries, university of maiduguri, faculty of engineering seminar series, 4(1): 11-19. ngala, gm., sulaiman, at. and garba, i. 2013. review of solar chimney power technology and its potential in semi-arid regions of nigeria. international journal of modern engineering research, 3(3): 1283-1289. nizetic, s., ninic, n., and klarin, b. 2008. analysis and feasibility of implementing solar chimney power plants in the mediterranean region. energy, 33: 1680–1690. sangi, r. 2012. performance evaluation of solar chimney power plants in iran. renewable and sustainable energy reviews, 16: 704-710. ngala et al.: evaluation of solar chimney power plant in semi-arid region of nigeria. azojete, 11: 1-12 12 schlaich, j., bergermann, r., schiel, w. and weinrebe, g. 2005. design of commercial solar updraft tower systems-utilization of solar induced convective flows for power generation. asme journal of solar energy engineering, 127: 117–124. sfsa. 2007. sustainable innovation in agriculture: a background to the sahel and the semiarid region. syngenta foundation for sustainable agriculture. helika limited, uk zhou, xp., wang, f., fan, j. and ochieng, rm. 2010. performance of solar chimney power plant in qinghai-tibet plateau. renewable and sustainable energy reviews, 14: 2249–2255. availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 76-84 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng development of a model for optimum saturation efficiency of an evaporative cooling system dzivama, a. u.1 and j. c. igbeka2 abstract the performance efficiency of an evaporative cooling system (fan and pad) under varied levels of parameters (water flow rate, pad thickness and air velocity) was evaluated using a 3-factor statistical design. a response equation was developed and was used to obtain the optimum levels of the parameters required for optimal operation of the evaporative cooling system. simulation result of the response equation indicated that for optimum operation of the evaporative cooling system, a water flow rate of 4.4l/min, pad thickness of 47mm and air velocity of 1.6m/s was required. simulated saturation efficiency of 70.4 % was obtained with these values while the measured was 84.6 % at water flow rate of 4.5l/min, pad thickness of 60mm and air velocity of 2.3m/s. 1. introduction an evaporative cooling system (fan and pad) essentially consists of a storage chamber (where the produce is stored), pad-end (where evaporation of water and consequently humidification and cooling of the air take place simultaneously), exhaust fan which draws the humidified and cooled air into the storage chamber and water circulation components (pump) which circulates the water on to the pad and keep the pad continuously moist. the performance efficiency of an evaporative cooling system in terms of its saturation efficiency is dependent among other things, the water flow rate required to keep the pad moist, the pad thickness through which the air has to travel before entering the storage chamber and the velocity of air passing through the pad. various research works have been carried out on the effects of these parameters on the saturation efficiency of an evaporative cooling system. the saturation efficiency under these parameters generally increases initially with increase in the levels of the parameters and then either remains constant or decline slightly at higher levels of the parameters (wiersma, 1983; thakur and dhingra, 1983; fao/sida, 1986; dzivama, 2000; and dzivama and igbeka, 2001). in order to set standards for the operation of the evaporative cooling system, this work was carried out to develop a model equation for the selection of the combination levels of the parameters for optimal performance of an evaporative cooler. this would enable the calculation of saturation efficiency of the cooler within the ranges tested. 2. materials and methods an active evaporative cooler earlier constructed and tested under varied levels of water flow rate (wr), pad thickness (pt) and air velocity (av) (dzivama, 2000) was used for this study. the cooler consists of a pad-end of dimensions 1000 x 15000mm made of local sponge, a storage cabin of dimensions 1000 x 1300 x 15000 mm made of plywood and internally insulated with 50mm polystyrene, a suction fan of 20w power rating and water pump with a discharge capacity of 7.5l/min and power rating of 150 w. figure 1 shows the schematic diagram of the cooler 1department of agricultural & environmental resources engineering, university of maiduguri, nigeria (email: audzivama@yahoo.com) 2department of agricultural engineering, university of ibadan, nigeria http://www.azojete.com.ng/ mailto:audzivama@yahoo.com azojete vol. 5 2007 77 water pump collector figure 1: schematic diagram of the evaporative cooler pad cabinet fan return pipe overhead tank control valve tray the study involved interactive effects of water flow rate, pad thickness and air velocity on the saturation efficiency of the cooler. three levels of wr (3.5, 4.5 and 5 l/min), three levels of pt (30, 60 and 90mm) and five levels of av (0.8, 1.3, 1.8, 2.3, and 2.8 m/s) were used. the choice of these levels of parameters was based on available information (thakur, 1983; fao/sida, 1986, walker and hellickson, 1983; brooker et al., 1992) and factors related to the physical properties of the local sponge for use as pad (dzivama et al. 1999). the parameters were combined in a split-split plot design experiment, which is best suited for a three – factor experiment (gomez and gomez, 1983). the water flow rate was considered as the main plot, the pad thickness as the subplot and the air velocity as the sub-subplot. the design layout of the experiment is shown in table 1. each level of selected water flow rate was randomly assigned a level of pad thickness and air velocity. the evaporative cooler was then operated and the change in temperature and relative humidity inside the storage chamber was measured with a hygroskop gt-lhygrometer. readings were taken at 10 minutes interval until steady state conditions were reached. each test was conducted in three replicates and the average at the steady state conditions were calculated and recorded for each setting. the saturation efficiency of the cooler was calculated from equation 1 as suggested by harris (1987): development of a model for optimum saturation efficiency of an evaporative cooling system 78 es = 100 )()( )()( x tt tt wbdbo dbidbo   1 where: se = saturation efficiency, % to (db) = outdoor dry bulb temperature, oc ti (db) = storage chamber dry bulb temperature, oc t (wb) = outdoor wet bulb temperature of the region, oc; for maiduguri t = 18.5, oc (maiduguri meteorological station, 1996) table 1: experimental layout (split-split plot design) wr, l/min pt, mm air velocity, m/s av1 av2 av3 av4 av5 wr1 pt1 pt2 pt3 wr1pt1av1 wr1pt2av1 wr1pt3av1 wr1pt1av2 wr1pt2av2 wr1pt3av2 wr1pt1av3 wr1pt2av3 wr1pt3av3 wr1pt1av4 wr1pt2av4 wr1pt3av4 wr1pt1av5 wr1pt2av5 wr1pt3av5 wr2 pt1 pt2 pt3 wr2pt1av1 wr2pt2av1 wr2pt3av1 wr2pt1av2 wr2pt2av2 wr2pt3av2 wr2pt1av3 wr2pt2av3 wr2pt3av3 wr2pt1av4 wr2pt2av4 wr2pt3av4 wr2pt1av5 wr2pt2av5 wr2pt3av5 wr3 pt1 pt2 pt3 wr3pt1av1 wr3pt2av1 wr3pt3av1 wr3pt1av2 wr3pt2av2 wr3pt3av2 wr3pt1av3 wr3pt2av3 wr3pt3av3 wr3pt1av4 wr3pt2av4 wr3pt3av4 wr3pt1av5 wr3pt2av5 wr3pt3av5 analysis of variance (anova) analysis of variance was used to examine the variation in the results of the performance efficiency of the cooler obtained under the experimental variables and their interactions. microstat statistical software with split-split plot program was used for the analysis table 2 shows an outline for the. table 2: outline of the anova source of variation df ss ms f – factor p – factor main plot analysis replication 2 main plot factor (a) 2 errors (a) 4 sub-plot analysis sub-plot factor (b) 2 a x b 4 error (b) 12 sub-subplot analysis sub-subplot factor (c) 4 a x c 8 b x c 8 a x b x c 16 total 134 azojete vol. 5 2007 79 optimization technique regression analysis was used to describe the relationship between the independent variables (water flow rate, pad thickness and air velocity) and the saturation efficiency of the cooler (dependent variable). according to gomez and gomez (1983), the relationship between independent variables is multi non-linear when: 1. at least one of the independent variables exhibits a non-linear relationship with the dependent variable; 2. at least two independent variables interact with each other; and 3. both 1 and 2 cases occur simultaneously. it was found out earlier (dzivama, 2000) that the relationship is non-linear. as a result a method of multiple non-linear regression as described by ott (1977) and babatunde (1997), was used to derive the response equation given by equation 2. y = bo + b1x1 + b2x2 + b3x1 2 + b4x2 2 + b5x1x2 + b6x2 2x1 + b7x1 2x2 + b8x1 2x2 2 2 where bo, b1 …b8 are constants. equation 2 was adopted and modified to take care of the 3 – factor factorial design experiment in this study. the possible response equation based on the modified form of equation 2 of a multiple regression is expressed as: y = bo + b1x1 + b2x2 + b3x3 + b4x1 2 + b5x2 2 + b6x3 2 + b7x1x2 + b8x1x3 + b9x2 2x3 + b10x1x2x 3 where: y = the saturation efficiency (se) of the cooler, % x1 = water flow rate (wr), l/min x2 = pad thickness (pt), mm x3 = air velocity (av), m/s the response equation was determined by the inverse of the 135 x 9 matrix, y = bx as presented below: y1 = x11 x21 x31 x11 2 x21 2 x31 2 x11x21 x11x31 x21x31………… b0 y2 = x12 x22 x32 x12 2 x22 2 x32 2 x12x22 x12x32 x22x32…………...b1 ... ... yn = x1n x2n x3n x1n 2 x2n 2 x3n2 x1nx2n x1nx3n x2nx3n…………..bn x’x was computed and the vector of the totals given by x’y. then the inverse of the design matrix (x’x)-1 was computed and multiplied by the vector of the totals (x’x)x-1y to get the coefficient b0, b1…bn however, it was not possible to obtain an inverse of the matrix 135 x 9 and therefore the factors which were not significant in the result of the analysis of variance were identified and dropped in the calculations. the combinations wr x pt x av was not significant in the result of the development of a model for optimum saturation efficiency of an evaporative cooling system 80 analysis of variance and it was not used. the extreme values of the co-ordinates, se (wr, pt, and av) were obtained by solving the partial differential equation (equations 4 6) as in stephenson (1975). r e dw ds = b1 + b4wr +b7pt +b8av = 0 4 t e dp ds = b2 + b5pt +b7wr +b9av = 0 5 v e da ds = b3 + b6av +b8wr +b9pt = 0 6 thus, we have three simultaneous equations which were solved to obtain the extreme values of the co-ordinates se (wr, pt, and av). the nature of the extreme values is given by the signs of the second differentials of se (wr), se (pt) and se (av). the function is maximum when the second differential is negative and minimum when it is positive at the values; wr, pt, and av given by the solutions of the simultaneous equations. minitab software was used in analyzing the matrix. 3. results and discussions 3.1. saturation efficiency of the cooler the results of the saturation efficiency calculated from the measurements using equation 1 is presented in table 3. table 3: saturation efficiency, % (calculated from the cooler temperature) wr, l/min pt, mm air velocity, m/s 0.8 1.3 1.8 2.3 2.8 3.5 30 60 90 48.7 61.5 56.4 56.4 66.7 61.5 57.4 69.2 65.6 55.4 68.7 66.7 54.9 68.7 66.7 4.5 30 60 90 64.1 76.9 69.2 70.8 82.1 79.5 74.4 84.6 82.1 74.4 84.6 84.1 76.9 84.6 83.1 5 30 60 90 53.3 66.7 64.7 62.6 72.8 69.2 64.1 79.5 76.9 65.1 82.1 80.1 66.7 84.6 82.6 the result in table 3 shows that the saturation efficiency of the evaporative cooling system increased initially with the levels of the parameters and then either remained constant or slightly declined. this could be attributed to the fact that, at low water flow rate, pad thickness and air velocity, the water could only partially wet the pad and therefore, less available water to be evaporated and thus less cooling. with less pad thickness, the distance of travel for the air inside the pad is less and thus the contact time between the air and water is less and this means less amount of water is evaporated. at low air velocity, the air moves in a streamline and therefore only evaporates the water within its path. at high levels of the parameters, the saturation efficiency increased and this could be due to the fact that: (i) the water flow rate was enough to sufficiently moisten the pad; azojete vol. 5 2007 81 (ii) (ii) the pad was thick enough so that the distance of air travel within the pad was long enough for the air-water time to effect good evaporation; and (iii) (iii) at high air velocity, turbulence could have been developed within the pad to evaporate more water from the pad. however, at much higher levels of the parameters, the saturation efficiency either remained constant or slightly declined. this could be due to excess water blocking the pore spaces within the pad and thus impeding air flow through the pad. also, air moving at higher velocity might push out the water from the pad in droplets instead of evaporating the water as evidenced by the presence of water droplets inside the cooler during the experiment at these levels of the parameters. from table 3, the optimum operating condition of the cooler was observed to be at water flow rate of 4.5 l/min, pad thickness of 60 mm and air velocity of 2.3 m/s, with a performance efficiency of 84.6 %. this could be explained by the fact that at pt2 (60 mm) and wr2 (4.5 l/min), the pad was sufficiently moist to allow more evaporation, but without excessive flow of water to block the pore spaces within the pad for the air movement. furthermore, at av of 2.3 m/s, the velocity was fairly high but because of the fairly large pad thickness of 60 mm, the air – water contact time was increased. this allowed for an increase in heat and mass transfer, thus an increase in efficiency. for a region with very low outdoor relative humidity and high temperature, it is possible to obtain saturation efficiency in the cooler approaching 85 % (rusten, 1985). thus, the 84.6 % performance efficiency obtained in the cooler in maiduguri with an average ambient condition of 38 oc and 15 % temperature and relative humidity respectively, and a wet bulb depression of 18.5 oc compared to 21.5oc of the evaporative cooler, is considered efficient. 3.2 analysis of variance the result for the analysis of variance is presented in table 4. the result showed that all the main factors (wr, pt, av) and their interactions (wr x pt, wr x av, and pt x av) were significant at 5 %. however, the combined effect of wr x pt x av was not significant at 5 %. this result confirmed the observations earlier discussed that the performance efficiency was found to increase with increase in all the levels of the parameters up to a certain level and then it either remained constant or declined slightly. table 4: results of the analysis of variance source of variation ss df ms f sig. of f main effects 3864.80 8 1733.10 435.21 0.00 wr 6649.17 2 3324.59 834.86 0.00 pt 4317.89 2 2158.95 542.15 0.00 av 2897.74 4 724.44 181.92 0.00 2 way interactions 708.85 20 35.44 8.90 0.00 wr x pt 338.12 4 84.53 21.23 0.00 wr x av 249.30 8 31.16 7.83 0.00 pt x av 121.44 8 15.18 3.81 0.00 3 – way interactions 97.86 16 6.12 1.54 0.00 wr x pt x av 97.86 16 6.12 1.54 0.00 explained 14671.51 44 333.44 83.73 0.00 development of a model for optimum saturation efficiency of an evaporative cooling system 82 3.3 the response equation the resulting equation obtained from equation 3 is given as: se = 7.9 – 0.013wr + 22.2av + 0.27 wr 2 – 0.008pt 2 6.2av2 + 0.067wrpt + 1.07wrav 0.029ptav , (r 2 = 0.95) 7 the critical values and the nature of the coordinates of the parameters obtained by solving the simultaneous equations 4, 5, and 6 for the optimum operation of the cooler are presented in table 5. table 5: critical values of the parameters for optimum performance efficiency parameter values nature of coordinates water flow rate 4.4 l/min maximum pad thickness 47 mm minimum air velocity 1.6 m/s maximum the saturation efficiency obtained by substituting the optimum measured values in table 3 and the critical values in table 5 are presented in table 6. table 6: saturation efficiency, % (obtained by the predicted and measured values parameter values predicted optimum level measured optimum level water flow rate (l/min) 4.4 4.5 pad thickness (mm) 47 60 air velocity (m/s) 1.6 2.3 saturation efficiency (%) 70.42 84.6 the saturation efficiency obtained by using the predicted values was slightly less than the one obtained by the measured values. this could be due to the fact that some combination levels of wr x pt x av that were found insignificant and difficult to substitute in the solution of the 135 x 9 matrix were dropped. this equation gave the optimal values of the parameters for efficient operation of the evaporative cooler, which could not have been measured experimentally. it also enabled the calculation of the saturation efficiency given some independent variables within the range tested and not necessarily those tested. 3.4 contribution of the parameters and their interactions the contributions of the variables and their interactions are summarized and presented in table 7. the result showed that the water flow rate contributed the most to the saturation efficiency of the cooler, followed by the pad thickness and then the air velocity. this could be explained from the fact that water is required for evaporation to take place and there must be a medium (pad) to provide the water for the evaporation. air velocity is required to blow away the saturated air from the vicinity to allow more evaporation to take place. azojete vol. 5 2007 83 table 7: contribution of the parameters and their interactions source df seqss wr 1 4097.9 pt 1 2406.4 av 1 2322.9 wr2 1 2237.9 pt2 1 1599.3 av2 1 566.3 wr x pt 1 203.8 wr x av 1 141.4 pt x av 1 45.2 wr x pt x av 1 35.1 4. conclusion the results of the experiment and the analysis showed the interactive effect of the parameters and their levels on the saturation efficiency of evaporative cooling system. optimum combination levels of wr, pt and av of 4.4 l/min, 47 mm and 1.6 m/s respectively were obtained by the analysis compared to wr, pt and av of 4.5 l/min, 60 mm and 2.3 m/s respectively obtained experimentally. the model allows for the calculation of the saturation efficiency of the cooler at levels not necessarily measured. references babatunde, o. o. (1997). development of a model equation for selecting disc and tilt angles of disc plough for optimal operation. proceeding of istro symposium on tillage research and agricultural development in sub-saharan aqgfrica at ncam idofan, ilorin october 21st to 24th, 1997: 169-178 brooker, d.b., f.w. bakker-arkema and w.h. carl (1992). drying of cereal grains. avi pub. co. inc., west port, connecticut, usa. dzivama, a. u. (2000). performance evaluation of an active evaporative cooling system (fan and pad) for the storage of fruits and vegetables: mango (mangifera indica), banana (musa sapientum), and tomatoe (lycopersicum esculentum). phd thesis. university of ibadan, nigeria dzivama, a. u. and j. c. igbeka, (2001). mathematical model of the process involved at the pad end in an evaporative cooling system. university of maiduguri, faculty seminar series, 1(1)p57-70 dzivama, a. u.; u. b. bindir, and f. o. aboaba, (1999). evaluation of pad materials in construction of active evaporative cooler for storage of fruits and vegetables in arid environments. agricultural mechanization in asia, africa an latin america, vol. 30 no. 3. fao/sida (1986). farm structures in tropical climates. edited by lennat, bengson and whitaker. fao/sida, rome. gomez, k.a. and a.a. gomez (1983). statistical procedures for agricultural research. an international ricecust book. a willey interscience publication, new york. harris, n.c. (1987). modern air conditioning practice, 3rd edition, mcgraw-hill book co., new york. development of a model for optimum saturation efficiency of an evaporative cooling system 84 maiduguri meterological station (1996). maiduguri weather station, federal ministry of aviation, maiduguri, zonal office of an evaporative cooler, res. j., punjab university, 20(3):345-352. ott, l. (1977). an introduction to statistical methods and data analysis. duxbury press, massachusetts. rusten, e. (1985). understanding evaporative cooling. vita technical paper. stephenson, g. (1975). mathematical methods for science students. 2nd ed. longman group ltd. lond. pp. 168 -174 thakur, b.c. and d.p. dhingra (1983). parameters influencing the saturation efficiency walker,j. n. and m. a. hellickson (1983). ventilation of agricultural structures. asae monograph 6th series. pub. asae michigan, usa. wiersma, f. (1983). evaporative cooling. in ventilation of agricultural structures, an american society of agricultural engineers monograph 6th series, michigan, usa arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):289-296 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 289 original research article impacts of climate change on the yeild of some selected root crops in enugu state, south eastern nigeria l. c. orakwe1, a. c. okoro1, c. p. nwachukwu1*, e. i. ugwu2 1department of agricultural and bio-resources engineering, nnamdi azikiwe university, awka, nigeria 2department of agricultural and bio-resources engineering, university of nigeria, nsukka, nigeria *corresponding author’s email address: chykearcade@yahoo.com 1.0 introduction climate change is one of the most serious environmental threats facing mankind worldwide. it affects agriculture in several ways, including its direct impact on food production. climate change, which is attributable to the natural climate cycle and human activities, has adversely affected agricultural productivity in africa (ziervogel et al., 2006). in nigeria, agriculture is the main source of food and employer of labour, employing about 60-70 per cent of the population (mayong et al., 2005). it is a significant sector of the economy and the source of raw materials used in the processing industries as well as a source of foreign exchange earnings for the country (mohammed-lawal and atte, 2006). there are a number of hallenges which have militated against self-sufficient food production and agricultural development in nigeria, despite its huge agricultural potentials and opportunities (fao et al., 2019). unsteady temperature and rainfall pattern could be due to effects of climatic change in the area and according to arnell, (1992) climatic variability could result in changes in rainfall distribution. the study further shows that change in climatic factors have significant effect article information abstract climate change variability has posed a huge threat on the yield of root crops in southeastern nigeria. studies were carried out to assess the effect of climate change on some selected root crops in enugu state. climatic and root crop yield data were collected for twenty years (20years) each from nigerian meteorological agency (nimet), abuja, and agricultural development programme (adp) under the ministry of agriculture, enugu state respectively. data collected were statistically analyzed using anova. the anova result shows that significant difference (p<0.05) were observed in annual temperature and mean values of annual rainfall and minimum temperature. crop yields of cocoyam, yam and cassava were also significantly different at p<0.05. the highest mean annual rainfall was observed in 2006, annual temperature was also significant at p<0.05 in 2015. most significant values (p<0.05) for cocoyam yield was recorded in 2016. the regression of combined climatic factors and crop yields from 2001 to 2020 showed that coefficient of determination (r2) recorded for cocoyam and yam yield as 0.59 and 0.34 respectively, cassava recorded a very poor correlation of 0.09. the multiple correlation coefficient (r) shows that there was high correlation (r = 0.769) between cocoyam yield and climatic factors, and a moderate correlation (r=0.584) for yam yield and climatic factors. single correlation between climatic factors and crop yield showed that moderate correlations were recorded for cocoyam yield and mean annual sunshine hour (r = 0.441) and cocoyam yield with annual temperature (0.450). it is recommended to use up to 30 years crop yield data for future studies. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 october, 2022 revised 8 march, 2023 accepted 12 march, 2023 keywords: climate change annual temperature annual rainfall crop yield and root crops http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com mailto:chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):289-296. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 290 on agricultural productivity. fao (2004) estimated 25% loss of cereals, 37% loss of root and tubers and 53% loss of fruits in developing world as a result of factors ranging from weather conditions, production practices to harvesting, handling to processing. it is projected that crop yield in africa may fall by 10-20% by 2050 or even up to 50% due to climate change (fao, 2006). given the above statistics, climate change has indeed become a global issue. it is very likely that climate change problem can aggravate conditions that can slow the pace of progress along sustainable development pathways. addressing sustainable development challenges in agricultural sector is, therefore, of paramount importance to nigeria especially in southeast where agriculture is largely rain-fed. root crop farming system which is cassava and yam-based (dixon et al., 2001) is one of the food and agricultural systems that is under threat by climate change despite its importance in nigeria’s food basket especially in the derived savannah ecological zone. for example, food products from cassava followed closely by yams are the predominant food crops consumed by both urban and rural households in southeast zone and which also serve as major sources of income; in fact, when compared to other arable crops, cassava ranks topmost as regards potential to generate cash income for farmers (nweke et al., 1997). in nigeria, agboola and ojeleye (2007), examined the impact of climate change in ibadan nigeria. the study adopted both primary and secondary sources of data. for the secondary source of data, time series data covering 30 years were collected on climatic variables and the analysis was done with bivariate chi-square and anova supported by graphical illustrations. the study revealed that farmers have experienced reduced crop yield on food crop production due to reduction in rainfall and relative humidity as well as increase temperature. eragha et al (2014) in their study found that temperature had a significantly negative influence on crop yield, while rainfall was found to have a significantly positive effect on crop yield. the technique of analysis was done with the error correction technique. the data coverage was 1970-2009. the study used variables like crop output, temperature and rainfall as well as carbon emission. similarly, carbon emission was found to have a significantly negative impact on crop production in nigeria. this paper is targeted at examining the impact of climate change on the yield of some selected root crops production in enugu state. 2. materials and methods 2.1. study area description enugu state is located on the northwestern fringe of southeastern nigeria between latitudes 6°30n and 7°10n and longitudes 6°35e and 7°30°e, 200 meters above sea level. figure 1 shows the map of enugu state. the estimated population of enugu state is about 4,1671 million people (npc, 2007). the land area is approximately 16,727 square km. the soil type is mostly hydromorphic, which is heavy and composed of silt and clay file:///c:/user/downloads/azojete143/www.azojete.com.ng orakwe et al: impacts of climate change on the yeild of some selected root crops in enugu state, south eastern nigeria. azojete, 19(2):289-296. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 291 figure 1: map of enugu state 2.2 methodology 2.2.1 data collection data on temperature, rainfall volume, relative humidity and sunshine duration ranging from 2000 to 2020 were collected from nigerian meteorological agency, abuja (nimet). the data for crop yield were sourced from agricultural development programme, enugu state. 2.2.2 data analysis the data was subjected to statistical analysis using the genstat statistical package. regression and correlation analysis were conducted to establish a relationship between the climatic data and the yield of some selected root crops in enugu state. 3. results and discussion 3.1. effect of climatic factors on some vegetable crops yield table 1 shows the effect of climatic factors (mean annual rainfall, sunshine hour, average minimum temperature and annual range of temperature) on crop yields (cassava, yam and cocoyam) from 2001 to 2020. the results in table 1 shows that significant differences (p<0.05) were observed in mean values of the climatic data (annual rainfall, minimum temperature and annual temperature) and on crop yield (cassava, yam and cocoyam yield) from 2001 to 2020. the highest rainfall amount was http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):289-296. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 292 observed in 2006, while the least was in 2001. average minimum temperature recorded most significant values in the year 2016 and 2017. table 1: mean annual variability of selected climatic factors and cassava, yam and cocoyam outputs year rainfall (mm) sunshine max. temp. (oc) min. temp. (oc) temp. range (oc) cassava (kg/ha) yam (kg/ha) cocoyam (kg/ha) 2001 139.77j 5.31 32.44 22.53bcd 9.91abc 11.13cde 11.04d 5.55c 2002 143.39gh 5.48 32.64 22.94bcd 9.70abc 11.26bcde 11.13d 5.55c 2003 157.58f 5.28 32.95 23.23bcd 9.72abc 11.28bcde 11.22cd 5.73c 2004 149.18g 5.16 32.20 22.56bcd 9.64abc 10.67def 11.34cd 5.72c 2005 141.45ij 5.52 32.70 22.29bcd 10.41ab 12.15bcd 11.36cd 5.62c 2006 201.22a 5.31 32.04 22.29bcd 9.75abc 12.36bcd 11.46cd 5.19c 2007 159.27ef 5.38 32.09 23.17bcd 8.94bc 12.36bcd 11.52cd 6.09c 2008 147.38gh 5.75 32.71 22.18bcd 10.53ab 13.11b 11.76abc 6.29c 2009 147.48gh 5.28 32.54 23.28bc 9.25abc 13.07b 11.85abc 6.36c 2010 140.58ij 5.81 32.77 23.97b 8.20cd 13.07b 26.37a 9.48ab 2011 144.11hi 5.40 32.20 22.15bcd 10.05abc 12.77bc 26.48a 9.44b 2012 178.14b 5.47 32.19 21.90cd 10.05abc 12.77bc 28.45a 9.60ab 2013 161.76ef 5.54 32.04 21.25d 10.81ab 18.78a 13.14ab 5.67c 2014 160.55ef 5.58 32.07 21.25d 10.75ab 1.25g 13.66b 5.38c 2015 167.41d 5.61 32.23 21.64cd 11.09a 1.22g 13.47b 5.65c 2016 159.03ef 5.56 32.53 32.53a 0.00e 9.41ef 12.02abc 11.32a 2017 172.61c 5.55 33.08 33.08a 0.00e 9.43ef 11.86abc 9.55ab 2018 159.21ef 5.55 32.58 22.79bcd 9.79abc 9.43ef 11.93abc 9.55ab 2019 162.08e 5.56 32.88 23.19bcd 9.69abc 9.25f 12.25abc 9.06b 2020 157.73f 5.40 30.13 23.26bcd 6.74d 9.07f 12.58abc 8.59b sem 1.90 0.11 0.13 0.42 0.41 0.51 0.69 0.28 abcdefghij means within the rows with different superscripts differ significantly (p<0.05); sem standard error of the mean 3.2. relationship between climatic factors and the yield of some root crops table 2 shows the regression and correlation of combined climatic factors and yields from 2001 through 2020. the regression equations were significant for predicting yam yield and cocoyam yield but not significant for predicting cassava yield. this result was supported by the better coefficient of determination (r2) recorded for cocoyam yield (59.10%) and yam output (34.10%) and the poor r2 recorded for cassava yield prediction (9.70%). the coefficient of determination measures the reliability of the regression equation and as such, the prediction of cocoyam yield with combined climatic factors was most reliable whereas, the prediction of cassava yield with climatic factors was least reliable. the multiple correlation coefficient(r) shows that there was high and strong positive association(r-0.769) between cocoyam yield and climatic factors. in other words, an increase or decrease in cocoyam output was associated with an increase or decrease in the amount of climate factors. very moderate positive correlation (r-0.584) was also recorded for yam yield and climatic factors implying that an increase in the values of the climatic factors. this result is in agreement with the work of chikezie et al. 2015. the result of this work concurred with the findings of ishaya, et al. (2014) which observed that tuber crops such as yam file:///c:/user/downloads/azojete143/www.azojete.com.ng orakwe et al: impacts of climate change on the yeild of some selected root crops in enugu state, south eastern nigeria. azojete, 19(2):289-296. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 293 and cassava and sweet potatoes may not be negatively impacted by climate variability. a poor association was recorded between cassava yield and climate factors (r-0.311). the poor association implies that the yield of the cassava crop was not really strongly dependent on the amount of the climatic factors. table 2: regression and correlation of combined climate factors on crop yields from year 2001 through 2020 regression equations a r2 % sem r sig 1. cassava output = -32.514-0.016(mar)+2.191(mas)+ 3.580(mamxt)-2.574(mamnt)-2.442(atr) -32.51 9.70 3.89 0.311 ns 2. yam output = -47.968+0.027(mar)+11.804(mas)+ 10.641(mamxt)-10.952(mamnt)-10.602(atr) -47.97 34.10 4.52 0.584 *** 3. cocoyam output = 4.849+0.003(mar)+3.705(mas)+ 1.999(mamxt)-2.172(mamnt)-2.528(atr) -4.85 59.10 1.43 0.769 *** marmean annual rainfall; mas-mean annual sunshine; mamxt-mean annual maximum temperature; mamnt-mean annual minimum temperature; atrannual temperature range. ***, **, * = significance at 1%, 5%, 10% table 3 shows the regression and correlation of individual climatic factors and yields from 2001 through 2020. the regression equations were significant for predicting cocoyam yield but not significant for predicting yam and cassava yield. the regression equations 2 to 5 are significant in the prediction of cocoyam yield. equation 2 shows that mean annual sunshine hour (mash) can predict output with a coefficient of determination (r2) of 19.40% which though is not appreciably high. the value of 19.40% shows that mean annual sunshine hour (mash) accounts for about 19.40% of the variability in cocoyam yield. similarly, equation 3 shows that mean annual maximum temperature (mamxt) can singly predict cocoyam yield significantly with a coefficient of determination (r2) of 11.2%. equation 4 shows that mean annual minimum temperature (mamnt) can singly predict cocoyam yield significantly with a coefficient of determination (r2) of 38.30%. equation 5 shows that mean annual temperature range (atr) can singly predict cocoyam yield significantly with a coefficient of determination (r2) of 20.30%. very moderate positive correlations (r = 0.441, r = 0.450) were recorded for the association between cocoyam yield with mean annual sunshine hour (mash) and cocoyam yield with annual temperature range (atr) respectively. the correlation coefficient of 0.441, and 0.450 shows a moderate association between cocoyam yield with mash and atr respectively. thus, an increase in cocoyam yield was moderately associated with an increase in mash and atr. low positive correlation (r = 0.331) was recorded cocoyam yield with mean maximum temperature (mmt). high positive correlation (r = 0.619) was recorded for the association between cocoyam yield and mean annual minimum temperature http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):289-296. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 294 (mamt). thus, an increase in cocoyam yield was highly associated with an increase in mean annual minimum temperature. table 3: regression of individual climatic factors on crop yields from year 2001 through 2020 regression equations a r2 % sem r sig cassava 1. cassava output = 5.745-0.032(mar) 15.745 1.40 3.92 0.119 ns 2. cassava output = 6.087+0.841(mas) 6.087 3.20 3.89 0.179 ns 3. cassava output = -17.167+0.861(mamxt) -17.167 5.10 3.85 0.227 ns 4. cassava output = 10.883-0.008(mamnt) 10.883 0.00 3.95 0.007 ns 5. cassava output = 9.499+0.136(atr) 9.499 1.20 3.92 0.111 ns yam 1. yam output = 17.396-0.021(mar) 17.396 0.30 5.36 0.057 ns 2. yam output = 6.958+1.313(mas) 6.958 4.20 5.25 0.206 ns 3. yam output = -4.575+0.579(mamxt) -4.575 1.30 5.33 0.112 ns 4. yam output = 17.658-0.149(mamnt) 17.658 0.80 5.34 0.092 ns 5. yam output = 12.111+0.232(atr) 12.111 1.90 5.31 0.140 ns cocoyam 1. cocoyam output = 5.877+0.009(mar) 5.877 0.40 2.15 0.060 ns 2. cocoyam output = 1.077+1.131(mash) 1.077 19.40 1.94 0.441 ** 3. cocoyam output = -15.221+0.695(mamxt) -15.221 11.20 2.03 0.335 ** 4. cocoyam output = -2.223+0.403(mamnt) -2.223 38.30 1.69 0.619 *** 5. cocoyam output = 9.904-0.301(atr) 9.904 20.30 1.93 0.450 *** marmean annual rainfall; mas-mean annual sunshine; mamxt-mean annual maximum temperature; mamnt-mean annual minimum temperature; atrannual temperature range, ns-non significant 4. conclusion it was obvious that variation in climate change can affect the yield of some selected tuber crops. rainfall was highest for the 20 years under study in 2006, while annual range in temperature was highest in 2015. cassava, yam and cocoyam were highest in 2013 while, yam was highest in 2010, 2011 and 2012 and cocoyam is highest in 2016. the regression equation for the crop yield with climatic factor showed that mean annual sunshine hour (mash), mean annual maximum temperature (mamxt) mean annual minimum temperature (mamnt) and mean annual temperature range (atr) with low coefficients of determination (r2) can singly predict cocoyam yield. very moderate positive correlations were recorded for the association between cocoyam yield with mean annual sunshine hour (mash) and cocoyam yield with annual temperature range (atr) respectively. a low positive correlation was recorded cocoyam yield with mean maximum temperature (mmt) while a high positive correlation was recorded for the association between cocoyam yield and mean annual minimum temperature (mamt). thus, an increase in cocoyam yield was highly associated with an increase in all these climatic factors, mash, atr mmt and mamt. file:///c:/user/downloads/azojete143/www.azojete.com.ng orakwe et al: impacts of climate change on the yeild of some selected root crops in enugu state, south eastern nigeria. azojete, 19(2):289-296. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 295 it is recommended that more data on crop yield should be kept at enugu adp office of the ministry of agriculture enugu state to enable the use of more data up to 30 years and above. references agboola, t. and ojeleye, d. 2007. climate change and food production in ibadan. nigeria afi crop science conference proceedings, 8: 1423-1433. arnell, nw. 1992. impacts of climatic change on river flow regimes in the uk. water and environmental management, 6: 432-442. chikezie, c., ibekwe, uc., ohajianya, do., orebiyi, js., ehirim, nc., henri-ukoha, a., nwaiwu, iuo., ajah, ea., essien, ua., anthony, g. and oshaji, io. 2015. effect of climate change on food crop production in southeast, nigeria: a co-integration model approach. international journal of weather, climate change and conservation research, 2(1):47-56. dixon, j., gulliver, a. and gibbon, d. 2001. farming systems and poverty: improving farmers’ livelihoods in a changing world. experimental agriculture, 39: 109-110. eregha, pb., babatolu, js. and akinnubi, rt. 2014. climate change and crop production in nigeria: an error correction modelling approach. international journal of energy and policy, 4: 297-311. fao 2004. the world food summit five years later: mobilizing the political will and resources to banish world hunger. rome: fao. fao 2006. the state of food insecurity in the world. rome. fao, ifad, unicef, wfp and who. 2019. the state of food security and nutrition in the world, 2019. safeguarding against economic slowdowns and downturns. rome: fao. ishaya, s., hassan, sm. and james, se. 2014. post-adaptation vulnerability of ceareals to rainfall and temperature variability in the federal capital territory of nigeria. ethiopian journal of environmental studies & management 7(5):532547, 2014issn:19980507doi:http://dx.doi.org/10.4314/ejesm.v7i5.7. manyong, vm., ikpi, a., olayemi, jk., yusuf, sa., omonoma, bt., okoruwa, v. and idachaba, fs. 2005. agriculture in nigeria: identifying opportunities for increased commercialization and investment in usaid/iita/ui project report ibadan, nigeria.159. mohammed-lawal, a. and atte, oa. 2006. an analysis of agricultural production in nigeria. african journal of general agriculture, 2(1): 1-6. nweke, fi., ugwu, bo., dixon, ago., asadu, cla. and ajobo, o. 1997. cassava 290 production in nigeria: a function of farmer access to market and to improved production and processing technologies. cosca working paper no. 21. collaborative study of cassava in africa, international institute for tropical agriculture, iita, ibadan, nigeria. ziervogel, g., nyong, b., osman, c., conde, sc. and dowing, t. 2006. climate variability and change: implications for household food security. assessment of impacts and adaptations for http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):289-296. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: chykearcade@yahoo.com 296 climate change (aiacc) working paper no. 20, january 2006. the aiacc project office, international start secretariat, washington dc, usa file:///c:/user/downloads/azojete143/www.azojete.com.ng arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 119-129 www.azojete.com.ng published by the faculty of engineering, university of maiduguri, nigeria. development and performance evaluation of fluted pumpkin seed dehulling machine odewole, m.m1*., adesoye, o.a2., oyeniyi, s.k3. and isiaka, a.o4. 1(department of food and bioprocess engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria 2department of mechanical engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria 3department of agricultural and environmental engineering, faculty of technology, university of ibadan, ibadan, nigeria 4 department of agricultural and biosystems engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria) *corresponding author’s e-mail address: odewole2005@yahoo.com abstract a machine for dehulling fluted pumpkin seed (telfairia occidentalis) was developed. the main objective of developing the machine was to provide a better substitute to traditional methods of dehulling the seed which contains edible oil of high medicinal and nutritional values. traditional methods are full of drudgery, slow, injury prone and would lead to low and poor outputs in terms of quantity and quality of dehulled products. the machine is made of five major parts: the feed hopper (for holding the seeds to be dehulled before getting into the dehulling chamber), dehulling chamber (the part of the machine that impacts forces on seeds thereby causing fractures and opening of seeds coats for the delivery of the oily kernels), discharge unit (exit for oily kernels and seed coats after dehulling), the frame (for structural support and stability of all parts of the machine) and electric motor (power source of the machine).the development process involved design of major components (shaft diameter (20 mm), machine velocity (7.59 m/s), power requirement (3hp single phase electric motor) and structural support of 45𝑚𝑚 × 45𝑚𝑚 × 3𝑚𝑚mild steel angle iron), selection of construction materials and fabrication. ansys r14.5 machine design computer software was used to design the shaft and structural support; while other components were designed with conventional design method of using design equations. the machine works on the principle of centrifugal and impact forces. performance evaluation was carried out after fabrication and 87.26%, 2.83g/s, 8.9% and 3.84%were obtained for dehulling efficiency, throughput capacity, percentage partially dehulled and percentage undehulled respectively. keywords: fluted pumpkin seed, development, cracking efficiency, throughput capacity, working principle. 1.introduction fluted pumpkin (telfairia occidentalis) plant is a tropical vine grown in west africa as a leafy vegetable and for its edible seeds. the common names for the plant are fluted gourd, fluted pumpkin, and ugu (badifu et al., 1995). it belongs to the family curcubitaceae and has a simple, dark green veined leaf that is18cm wide and 35cm long (esquinas-alcazar and gulick, 1983). the plant has the widest diversity in terms of variation in pod and seed colour, seed and plant vigour, anthocyanin content of leaves and petioles or shoots and leaf size (ipgri, 1999). seeds of fluted pumpkin are enclosed inside the pods of the plant (figure 1), odewole et al., (2015a) reported the description of the pod and other useful information. odewole et al., (2015b) reported that the oily kernels of fluted pumpkin seeds contain vitamin e, vitamin a, zinc and http://www.azojete.com.ng/ odewole2005@yahoo.com odewole et al: development and performance evaluation of fluted pumpkin seed dehulling machine. azojete, 11: 119-129 120 essential fatty acid. the oil is also good for maintaining healthy blood vessels, nerves and tissues and can be used to treat prostrate and bladder problems in man. odewole et al., (2015a) reported some mechanical properties of three varieties of fluted pumpkin seeds necessary for the design of cracking machine. (a) (b) figure 1: fluted pumpkin pods (a) and seeds (b) source: odewole et al., (2015b) dehulling (as applicable to this type of seed)is the formation of fractures on the outer surface of seed coat through the application of force with the overall aim of recovering some needed materials after cracking. this action will cause division of materials into different components. some of the forces that are used to achieve this action include centrifugal, impact, compression, attrition or their combinations (odewole and ajibade 2015). dehulling is necessary in processing of some agricultural materials in order to be able to utilize them fully or rather to remove some unwanted material. to be able to get the oily kernels in fluted seeds and utilize its oil for other useful purposes, dehulling is one of the important postharvest operations that must be done. however, the traditional method of dehulling seeds is full of drudgery, slow, injury prone, unhygienic, and normally leads to low and poor outputs in terms of quantity and quality of product. therefore, the objectives of this work were to develop a mechanical dehulling machine and carry out its performance evaluation in terms of dehulling efficiency, throughput capacity, percentage partially dehulled and percentage undehulled. 2. materials and methods 2.1. design considerations in designing the fluted pumpkin seed dehulling machine, the following factors were considered: force to dehull the seed with minimum damage to the kernel (determined to be 53.5 n by odewole et al., 2015a), power requirement and structural stability of the machine. 2.2. shaft design the horizontal shaft of the machine was designed with ansys (2010) r14.5 version of machine design software. figure 2 shows the free body diagram of the designed shaft. points a and b are fixed to the frame of the machine. point c is the force acting (6.87 n) on the shaft from the electric motor, while forces on points d (10.85n) and f( 10.00n) are due to the action of the arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 119-129 www.azojete.com.ng published by the faculty of engineering, university of maiduguri, nigeria. 121 roller bearings on the shaft. the force on point e (27.72 n) is the value for the three plates on thick plates of the shaft and that of seeds to be cracked. the shear force and bending moment diagrams from the ansys software are shown in figure 3. the maximum shear force of 20.54 n (0.3 m of the shaft’s full length) occurred at point e. maximum bending moment of 1.85 nm occurred at point d (0.45 m of the shaft’s full length). after using different specifications of solid cylindrical mild steel metal, the design that gave safely carried all the specified loads was 20 mm solid cylindrical mild steel. figure 2: free body diagram of designed shaft figure 3: shear force and bending moment diagram of shaft http://www.azojete.com.ng/ odewole et al: development and performance evaluation of fluted pumpkin seed dehulling machine. azojete, 11: 119-129 122 2.3. pulley design all the designs in this section were according to the procedures given in odewole and ajibade (2015). 𝑁1𝐷1 = 𝑁2𝐷2 (1) assumed diameter of electric motor pulley, d1=100 mm; diameter of the dehuller’s pulley = d2; speed of electric motor (medium) n2=1450 rpm, assumed speed of the dehuller = 900 rpm; using equation (1), d2 =161.11 mm 2.4. power required for operating the machine power = 𝑃𝑓 + 𝑃𝑚 + 𝑃𝑝 + 𝑃𝑐(2) where, 𝑃𝑓 =power to overcome inertia. 𝑃𝑚 = power to rotate moving parts. 𝑃𝑝 =power to convey seeds to be cracked. 𝑃𝑐 = power to crack seeds 𝑃𝑓 = 𝑊 × 𝑉(3) 𝑉 = 𝜋𝐷2𝑁2 60 = 7.59𝑚/𝑠 where: v = driven shaft speed. 𝑊 = 𝑊𝐷 + 𝑊𝑇 + 𝑊𝑆 + 𝑊𝑃(4) where, 𝑊 =total weight, 𝑊𝐷 =weight of plates on the shaft, 𝑊𝑇 =weight of thread 𝑊𝑃 =weight of the driven pulley, 𝑊 𝑤𝑎𝑠 𝑎𝑠𝑠𝑢𝑚𝑒𝑑 𝑡𝑜 𝑏𝑒 73.56 𝑁, 𝑃𝑓 = 558.32 𝑊 𝑃𝑓 since the power to overcome inertia will also rotate the moving part 𝑃𝑝 = 𝑊𝑆𝑂𝑇 × 𝑉 (5) where: 𝑊𝑆𝑂𝑇 = weight of seed on the blades, 𝑃𝑝 = 189.75 𝑊 𝑃𝑐 = 𝑇𝐹𝐶 × 𝑉(6) where:𝑇𝐹𝐶(dehulling force from utm) = 53.5𝑁 (odewole et al., 2015b), therefore, 𝑃𝑐 = 406.07 𝑊 total power = 558.32 + 558.32 + 189.75 + 406.07 = 1712.46 𝑊 power to operate the machine = total power assumed efficiency⁄ (7) 1712.46 0.80 = 2140.56 w = 2.141 kw = 2.82 hp a single phase electric motor of approximately 3 hp was considered safe for the machine. 2.5. design of structural support (frame) the ansys r14.5 was also used to design the frame that will safely withstand all the loads on the machine. figures 4 and 5 show the mesh, static structural equivalent strain, stress and deformation analyses of the frame. the nodes (points where lines met) were where strain, stress and deformation analyses were individually carried out for proper design of the frame. from the arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 119-129 www.azojete.com.ng published by the faculty of engineering, university of maiduguri, nigeria. 123 colour code on the scales on figures 6,7 and 8, the maximum strain (deep green), stress (deep green) and deformation (red) that can occur on the frame were 3.26 × 10−6𝑚/𝑚 , 6.40 × 105 𝑁 𝑚2⁄ and 6.55 m respectively. the dimension of angle iron that safely carried all loads and shocks was 45𝑚𝑚 × 45𝑚𝑚 × 3𝑚𝑚 mild steel. (a) (b) figure 4: mesh (a) and strain (b) analysis of machine tool frame (a) (b) figure 5: stress (a) and deformation (b) analysis of machine tool frame 2.6. machine fabrication figure 6 shows the pumpkin seed dehulling machine after fabrication and assembly. mild steel sheet was used to fabricate all the parts of the machine. for the structural support (frame), mild steel angle iron with dimension 45𝑚𝑚 × 45𝑚𝑚 × 3𝑚𝑚 was used all through; and mild steel sheet of thickness 3 mm was used for the hopper and the discharge unit, 5 mm mild steel was http://www.azojete.com.ng/ odewole et al: development and performance evaluation of fluted pumpkin seed dehulling machine. azojete, 11: 119-129 124 used for the dehulling chamber. all the dimensions were marked out, cut, turned, welded and assembled according to designed specifications. figure 6: fabricated dehulling machine 2.7. machine description and working principle figure 7 shows the orthographic projection of the fluted pumpkin dehuller. the machine is divided into five major parts namely: the feed hopper, dehulling chamber, discharge unit for the mixture of oily kernels and seed coats(chaffs), the frame and source of power (3 hp single phase electric motor). the hopper is conical in shape and it is on a pipe and placed on top of the dehulling chamber casing. the dehulling chamber has cylindrical cross section and consists of an internal horizontal solid shaft (20 mm) with three blades attached to it at 120º to each other. driven pulley which takes power needed for dehulling from the electric motor via v-belt linkage and driving pulley of the electric motor is attached to one end of the shaft. at a short distance from the driven pulley, a roller bearing around the shaft is attached to the dehulling chamber and another roller bearing close to the other end of the shaft is used to hold the shaft to the dehulling chamber. all components of the machine are rigidly attached to the structural frame of the machine made of 45𝑚𝑚 × 45𝑚𝑚 × 3𝑚𝑚 mild steel angle iron. arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 119-129 www.azojete.com.ng published by the faculty of engineering, university of maiduguri, nigeria. 125 figure 7: orthographic projection of dehuller the machine works on the principle of centrifugal force and impact force. when the seeds get into the dehulling chamber via the hopper, they are rotated vigorously (centrifugal force action) and hit against the hard surface (impact force action) of the dehulling chamber. the two actions would lead to formation of fractures that would later cause splitting of seeds for the liberation of the needed oily kernels. after dehulling, all materials (kernels, escaped whole seeds, partially dehulled seeds, seed coats) inside the dehulling chamber are discharged via the outlet; and separation of discharged materials into various components would be done manually. it is advisable to allow the machine to run empty for about 30 s before loading it with seeds to be dehulled. this action is a safety precaution that will not cause the starting current of the electric motor to increase; failure to do so might subject the electric motor to serious damage. the part list of the machine is shown in figure 8. http://www.azojete.com.ng/ odewole et al: development and performance evaluation of fluted pumpkin seed dehulling machine. azojete, 11: 119-129 126 figure 8: exploded view of the dehuller showing working components and part list 2.8. performance evaluation of the machine the performance evaluation of the fabricated machine in terms of dehulling efficiency, throughput capacity, percentage partially dehulled and percentage undehulled was carried out. fluted pumpkin pods of 13 weeks old (minimum harvesting age) were procured at national horticultural research institute (nihort), ibadan, nigeria. the pods were broken manually for the recovery of seeds needed for the dehulling operation. the seeds were cleaned and fed into the machine via the hopper. the total mass of fluted pumpkin seed loaded into the machine was 900 g. fifteen (15) runs were carried out on the machine; for each run, 60 g of fluted pumpkin were fed into the machine and the time taken to complete the dehulling was obtained using a stop watch (nocam android). after dehulling, collected samples were grouped into various components (kernel, partially dehulled, shells and escaped whole seeds).the performance indices in terms of dehulling efficiency and throughput capacity are as stated and evaluated below: dehulling efficiency (%) = 𝑀𝐼−(𝑀𝑃+𝑀𝐸) 𝑀𝐼 × 100% (odewole and ajibade 2015) (8) throughput capacity tc(g/s) = 3.6𝑀𝐶 𝑡 (ghafari et al.,2011) (9) 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑛𝑔𝑒 𝑝𝑎𝑟𝑡𝑖𝑎𝑙𝑙𝑦 𝑑𝑒ℎ𝑢𝑙𝑙𝑒𝑑 = 𝑀𝑃 𝑀𝐶 × 100 (10) arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 119-129 www.azojete.com.ng published by the faculty of engineering, university of maiduguri, nigeria. 127 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑛𝑔𝑒 𝑢𝑛𝑑𝑒ℎ𝑢𝑙𝑙𝑒𝑑 = 𝑀𝐸 𝑀𝐶 × 100 (11) where: mc = mi = mass of sample before dehulling (900 g), t = time used in dehulling (1150 s), mp is mass of partially dehulled (80.1g), me is mass of undehulled seeds (34.60g). 3. results and discussion table 1 shows the results of the machine performance evaluation and figure 9 shows (a) the partially dehulled seeds and (b) the kernels after dehulling. from table 1, it can be seen that out of the total mass of 900 g of fluted pumpkin seeds loaded into the machine for performance evaluation, 402.86g of kernels, 80.1 g of partially dehulled seeds, 252g of shells, 34.6 g of escaped whole seeds (undehulled) and 115.84g of waste were obtained and the total time for dehulling all the 900g fed into the machine was 1150s (19.2mins). the lowest and highest times of operations were 57s and 91s respectively. the mean values of kernel, partially dehulled seed, seed coat, undehulled seeds, wasted seeds and time of operation obtained were 26.80g, 5.34g, 16.80g, 2.31g, 7.69g and 76.67 seconds respectively. the results above means that from 60 g of whole (undehulled) seeds used per run of the performance evaluation operation, 26.80 g, 5.34 g, 16.80 g, 2.31 g, 7.69 g of kernel, partially dehulled seed, seed coat, undehulled seeds, wasted seeds would be obtained respectively at mean time dehulling time of 76.67 seconds . table 1: data obtained from dehulling machine performance evaluation s/n kernel (g) partially dehulled seed (g) seed coat (g) undehulled seed(g) waste (g) time (s) 1 32.3 6.7 14.2 5.9 78 2 31.4 4.9 14-3 8.2 87 3 24.5 2.2 17.3 2.1 10.4 86 4 25.9 5.3 16.7 8.5 87 5 25.7 9.6 18.2 11.7 57 6 25.3 1.7 19.6 6.7 3.6 77 7 26.4 3.6 15.2 7.7 6.5 75 8 28.2 11.8 13.8 4.3 3.1 66 9 22.8 1.7 16.7 10.1 84 10 26.3 2.8 17.0 8.1 12.2 79 11 26.2 2.3 19.3 12.6 89 12 24.1 7.4 19.6 10.1 63 13 23.5 6.2 19.1 5.7 6.8 91 14 30.6 6.7 14.7 6.3 67 15 29.4 7.2 16.3 5.4 64 total 402.6 80.1 252 34.6 115.4 1150 mean 26.80 5.34 16.80 2.31 7.69 76.67 the machine’s dehulling efficiency; the throughput capacity, percentage partially dehulled and percentage undehulled were evaluated to be 87.26%, 2.82 g/s 8.90% and 3.84% respectively. alonge and idung (2015) got 88% cracking efficiency and 916 seeds/h for bush mango seeds. odewole and ajibade (2015) got cracking efficiency of 96.65% and throughput capacity of http://www.azojete.com.ng/ odewole et al: development and performance evaluation of fluted pumpkin seed dehulling machine. azojete, 11: 119-129 128 510 g/min for thevetia nut. ologunagba, (2012) got cracking efficiency and throughput capacity of 75.11% and 426 kg/h for palm nut respectively. oyebanji et al.,(2012) got cracking efficiency of 50.83% and 71.3% cracking efficiencies for centrifugal and impact palm nut cracker respectively. the closeness in values of performance indices in some cases could be due to the fact that some seeds have similar characteristics to fluted pumpkin seed used in this work in terms of their engineering properties; while wide difference in values could be due to method of cracking used, type and variety of seeds used, moisture contents of seeds during cracking, deficiency in design, fabrication and operation of cracking machine, and human factor in terms of lack of/inadequate technical know-how in operating properly designed and fabricated cracking machines for their intended purposes. mohsenin, (1986) reported that the output of agricultural and processing machines depends on engineering properties of materials to be introduced into the machine. also, results from oyebanji et al., (2012) showed that methods of cracking in terms of principle of operation can cause differences in the outputs of machine. furthermore, ologunagba et al., (2010) got different values of machine performances in terms throughput capacity, separating efficiency and quality performance efficiency for palm nut and fibre separator when machine factors (tilt angle of machine) and crop factor (moisture content of palm nut) and moisture were used. (a) (b) figure 9: (a) partially dehulled seed and (b) kernels (after dehulling) 4. conclusions a fluted pumpkin seed dehulling machine was developed and tested. the performance indices of the machine in terms of dehulling efficiency, throughput capacity, percentage partially dehulled and percentage undehulled were estimated to be 87.26%, 2.82g/s, 8.90% and 3.84% respectively. these values obtained from the performance indices are appreciable enough. hence, the use of the machine will eliminate the drudgery attached to the traditional method and increase the recovery of kernels from the seed for oil extraction processes. it is therefore recommended that effect of different speeds of the machine and some crop factors on the performance indices of the machine should be done. also, winnowing unit should be incorporated into future designs. arid zone journal of engineering, technology and environment. august, 2015; vol. 11: 119-129 www.azojete.com.ng published by the faculty of engineering, university of maiduguri, nigeria. 129 references alonge, af and idung, m. 2015. development of a bush mango (irvingiagabo-nensis) nutcracker. agricultural engineering international: cigr journal: 17(2):191-199. ansys incorporated 2010. user’s guide, south pointe 275 technology drive canonsburg pa 15317; usa. badifu, gi., akpapunan, ma. and mgbemere, vm. 1995. the fate of beta-carotene in processed leaves of fluted pumpkin, a popular vegetable in nigerian diet. plant foods for human nutrition: 48: 141-147. esquinas-alcazar, jt. and gulick, pj. 1983. genetic resources of curcubitaceae. international board of plant genetic resources, rome, 4: 67-70. ghafari, a, chegini, gr., khazaei, j. and vahdati, k. 2011.design, construction and performance evaluation of the walnut cracking machine. international journal of nuts and related science: 2(1): 11-16. ipgri 1999.the biodiversity of traditional leafy vegetables. published by ipgri, rome (1999) eds. chweya, j. a. and eyzaguirre p.b. pp 1-18. mohsenin, nn. 1986. physical properties of plant and animal materials. 2nd edition. gordon and breach science publishers, new york. odewole, mm. and ajibade, ro. 2015. fabrication and performance evaluation of thevatia nut cracking cachine. nigerian journal of technological development (njtd): 12(1): 12-17. odewole, mm., adesoye, oa. and shadare, oa. 2015a. determination of some mechanical properties of ugu seed (telfairia occidentalis) in relation to the design of cracking machine. science, technology and arts research (star) journal: 4(3):187-194. odewole, mm., sunmonu, mo., obajemihi, oi. and owolabi te. 2015b. extraction of oil from fluted pumpkin seed (telfairia occidentalis) by solvent extraction method. annals of food science and technology (afst), 16(2): 372-378. available on: www.afst.valahia.ro ologunagba, fo. 2012. design and evaluation of a horizontal-shaft palm nut cracking machine. journal of engineering and applied sciences: 4: 80-86. ologunagba, fo., olutayo, a. and ale, mo. 2010. development of a palm nut and fibre separator. arpn journal of engineering and applied sciences, 5(12): 10-15. available at www.arpnjournals.com oyebanji, ja., oyedepo, so. and adekeye, t. 2012. performance evaluation of two palm kernel nut cracker machines. proceedings of international conference on clean technology and engineering management (iccem): 211-223. http://www.azojete.com.ng/ http://www.afst.valahia.ro/ http://www.arpnjournals.com/ arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):173-186 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 173 development of a generic on-line departmental e-library using the iterative design approach p. o. olabisi*, o. a. ogunkanmi and h. i. abdullahi computer engineering department, bells university of technology, ota, nigeria *corresponding author's email address: niyiolabisi@gmail.com article information submitted 11 july, 2023 revised 28 october, 2023 accepted 3 nov., 2023 keywords: content management e-resources digital library library automation system waterfall model. abstract this work was based on the development of a departmental digital library that is generic in nature as can be adopted by departments of any specialisation. it aimed at providing easy access to textbooks, lecture materials, past questions, project reports, research theses, published articles, current innovations in the field of study of the department, and various online resources to facilitate academic excellence, efficient delivery of information and advance research activities. a generic iterative and incremental software design approach deployed and a well-structured database directory for managing e-resources was designed. the implementation took the two dimensions of the front-end client-side which involved designing both the user interface and user experience while considering factors such as accessibility, readability and usability and the back-end server-side operations which involved creating a connection between the front-end and the server and managing the database. html, css and java script were employed in programming the front-end while the back-end server side was programmed with php, mysql, and a content management system. with e-resources uploaded into the cloud and results of tests conducted on the website showed average time to complete an e-resource search and download is 16.2 seconds, result of the readability test is 8.2 and the result of the accessibility test is 79 aggregated from the results of four different accessibility testers. the generic departmental e-library was developed with website designed to provide easy of online accessibility to students and staff of the department. 1.0 introduction the information technology revolution has greatly transformed and enhanced the human existence and activities, making life much easier in many areas. numerous technologies and tools have been developed and deployed as a result of the fast shift in the usage of information technology. a library as a collection of information resources accessible to authorised individuals preserved such resources in either physical (hard copies) or digital form (soft copies), or both. going historical lane, libraries have been a form of gateway to accessing information, knowledge, and recreation (alarape and edet, 2017). access to books used to be majorly confined to the library building, but advancements in technology, now make it possible to access information resources through online means right at the users’ comfort. information resources in digital form are accessed using electronic infrastructures, providing a paradigm shift from what we are used to online access to information resources (igbo et al., 2022). the utilisation of modern technology has become vital for rapid and effective information storage, retrieval and exchange, as well as for offering superior services to users (odunola et http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 174 al., 2018). ordinarily, any library plays the role of supporting, facilitating and expanding the frontiers of knowledge in both formal and informal education. the digital library interfaces library and information science with computer and communication technologies. it is an offshoot of the electronic libraries with the addition of online network access made available to users to be able to remotely access the contents of the library in electronic form. several key elements of the digital library are mentioned in (hiremath et al., 2019). the digital library (dl) platforms provide varieties of digital contents to users, like: managing courseware that enable the provision of documents in different formats, assigning access to contents based on types of users, emphasizing content sharing, and allowing for interactivity (abraham, et al., 2020; anyim, 2017). building a digital library involve activities like acquisition and management of collections, content dissemination and online service provision (rathee and kaushik, 2019; sejane, 2017). the digital library has greatly enhanced library management system to be more dependable, efficient, remote and simple to use. figure 1 shows a collection of resources and services required in a digital library (ahmmod, 2016). locally stored digital content can have remote access through computer networks. organisers of e-libraries make use of the catalogue to categorize, classify, and search for books and periodicals. a virtual library is a digital space in which resources are stored and organized. additionally, it may mean a location where books can be read using computers and mobile devices connected to the internet. some virtual libraries are operated on free access, while some requires membership registration. types of digital library discussed in (henry, 2021) include virtual, automated, hybrid and open libraries, and examples of major internationally operated digital library are the world digital library and the project gutenberg, which provide free online access to millions of e-books and other e-resources. figure 1: components and services of a digital library. some of the benefits of developing a generic departmental digital library are that it: creates some relief for the central institutional library system. provides opportunity for repository of specialized e-resources. encourages distributed digitalized repository system of e-resources and library resources, as we have in distributed database (ddb) system used in e-learning. such ddb system maximizes local processing of data, placing it closer to where it is required thereby enabling high level of digital library (dl) digital resources technological infrastructure experience & expertise dl services digital objects: texts, graphics, images, audio, video, artefacts, computer programmes, catalogues, etc. computing, storage, networks, communication, web portals, multimedia, etc. knowledge, skills, competencies of practitioners to operate, manage and maintain dl systems. integrated access, online retrieval, online delivery, inter-library loan, resource sharing, training, etc. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng olabisi et al: development of a generic on-line departmental e-library using the iterative design approach. azojete, 20(1):173-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 175 data security and availability, and efficient use of each cpu capacity in each location through parallel data processing (husam, 2020). reduces possibilities of high down-time of web links and access to library e-resources. brings library resources digitally closer to the students on departmental basis thereby increasing usability of these resources. provides better management and preservation of research outputs of the department. saves time in searching for intellectual resources. provides round the clock 24/7 access to relevant departmental and other academic resources to students of the department. guarantees possibilities of finding solutions to academic problems and issues without need to seek for appointments with faculty members, except when it becomes very crucial. the objectives that were set out for implementation in this study are to: implement open-source e-resources management software that will effectively serve the academic needs of the students of the department. source for relevant and adequate e-resources for the e-library. create a secure access and authentication system that gives access to only the students and staff of the department. design a well-structured database directory for the e-resources. launch the e-library on the internet by creating a dedicated website for it. the computerized system for managing library operations offers a complete solution for reducing physical work, simplifying the manual method, and reducing costs and stress among other benefits (thirunavukkarasu et al., 2023). for proper administration of an e-library, a search automation is created and built into the system with the use of a software program such as: cascading style sheets (css), hypertext pre-processor (php), hypertext mark-up language (html), or mysql database. this is done with the v-model software development process adopted in this work (adebesin, 2015; abdulrazzaq and mustafa, 2017). an e-library, unlike conventional libraries, organizes and manages collection of resources of knowledge electronically and virtually makes them available to users in digital format via computer network links particularly through the internet. users access the services with the use of a computer or any network connection devices and an internet connection (pyrounakis et al., 2014). several research efforts have been made on the digitalization of libraries, digital preservations and repositories of institutional knowledge resources. also, a number of digital system model plans have been developed for effective safeguarding of university library resources (pyrounakis et al., 2014; md monirul et al., 2022). roy et al. (2018) developed a library management system that has several features which include user login and an administrator login that enables the administrator to control the entire system. it was aimed at creating a computerized system to manage all of the library's daily operations including software requirement specification (srs) and had the objectives of increasing control and performance, cutting cost, saving time, creating online notice board option and providing materials for lectures. naveed et al. (2021) in their work gave recommendations for improving the library management system in lahore as follows: http://www.azojete.com.ng/ niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 176 libraries should give regular practical training to working library staff to help improve their professional capabilities particularly on library management system automation and customizing skills to meet unique needs. widely used and publicly accessible lims (access-based) software should be adopted as the standard application for data exchange throughout lahore's libraries after its renovation. foreign software producers should provide low-cost software to poor nations, allowing developing-country libraries to more effectively use foreign software. modules such as a mobile app should be connected with pakistani libraries' library management systems. each library should have its budget to guarantee effective software management. an assessment of online interfaces for library management software systems was conducted by (shailendra and namrata, 2011). they indicated that today's libraries have challenges of implementing cutting-edge technology, in preserving of resources and providing access to those resources at the face of shrinking finances, more competition, and increasing demand for more user-friendly services. hussain, (2020) mentioned some of the popular cutting-edge technologies adopted in library services to satisfy the users’ needs as: big data, virtual reality, augmented reality, artificial intelligence, block-chain technology, internet of things, library mobile apps, 3d printers, drones, robots, digital interface for printed books, user-focused interfaces and application, driverless cars, library maker-space, learning management system (lms), and easy video creations. jha (2023) made extensive discussion of the application of block-chain technology in the modern library. oyetola et al. (2023) noted that global practices are being changed by new technologies such that traditional ways of doing things are giving way to new skills, and information delivery in libraries is experiencing integration and use of artificial intelligence (ai) of robotics, chatbots, use of ai in teaching, learning and research, and so on. subaveerapandiyan (2023) made an extensive review of employing ai in digital libraries operations like ai chatbots, intelligent libraries, robots, and some other ai applications and how these can revolutionize library operations like retrieval of information, automating routine tasks, streamlining cataloguing, classification and recommendation processes, personalizing interaction with users, and provision of some other innovative services. hussain (2022) wrote about augmented reality (ar) as a new technology which is used to make accessing library information easy and in very short time as it organizes this information in sequential order. the challenges of digital library were mentioned by sharma and chauhan (2019) and perdana and prasojo (2020) to include: knowledge and resource management, technological constraints, preservation of resources, inadequate finance and infrastructure, software issues, security problems, lack of expertise, service approaches, and intellectual property rights. in the digital library initiatives of the library of congress, ten different challenges categorized under building the resources, interoperability, intellectual property, providing effective access and sustaining the resources were listed. it was noted that technological solutions are not always available to these challenges, but new ways of thinking and ideas sharing may help in resolving some of them. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng olabisi et al: development of a generic on-line departmental e-library using the iterative design approach. azojete, 20(1):173-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 177 the challenges of digital libraries in nigeria were particularly discussed by igboechesi and dang (2019) to include, among others: traditional bureaucracies, meritocracy and mediocrity, librarians’ indifference, inadequate infrastructure/financial challenge and network and connectivity. with the ever-changing landscape of information technology, libraries must increasingly focus on considerations of the total cost of ownership, as they must choose the greatest, most future-proof items for it investments and growth. information retrieval among massive amounts of information in digital library systems has also sparked a couple of research efforts like that carried out by al-juboori (2014). then coming the challenges of utilization and users’ satisfaction with the provisions of e-library resource could be dissatisfaction with the type and quantity of the collection of books and other e-resources, displays and menus that may not be easily understood, and so. features that determine the level of functionalities of an e-library being web-based are noted as: user friendly interface, usability, operative links, accessibility, extensibility, interoperability, reliability, maintainability, response time, scalability, and security (abdulrazzaq and mustafa, 2017). 2.0 methodology 2.1 the iterative and incremental approach the iterative and incremental approach is one of the generic software design processes used when developing software from algorithms for specific applications. it divides the process of creating software into smaller steps. each step is called iteration, and each iteration contains processes of planning, designing, development, and testing phases. the iterative approach, in contrast to the waterfall approach, develops elements one at a time, delivering a usable product after each iteration and enhancing functionality as it moves from iteration to iteration. the iterative approach counters the requirement bloating limitation of the waterfall model and also combines the benefits of prototyping and the waterfall models. the key phases of the generic iterative and incremental model are discussed in the following subsections. 2.1.1 planning and analysis this is the first step in the iterative method. here the developer meets with the business owner, stakeholder, or client to discuss the requirements. 2.1.2 design the design phase was embarked upon after obtaining the iteration requirements. since this stage is expected to deliver the best results to the client with less cost, the design was an appropriate one. it therefore requires that the design is either an entirely original specification or an expansion of an existing one. 2.1.3 implementation in this process, the developer puts the chosen design into practice using a chosen coding technique. while writing the code, the software engineer and developer perform unit test at each phase of the process. 2.1.4 testing after implementing the code, then testing is carried out to find bugs in the code, and before they are addressed by the developer if no bugs are found. the developer can create new test http://www.azojete.com.ng/ niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 178 cases or use a previous one created with thorough testing carried out to avoid any error affecting the software's specification. there are 3 types of testing activities in the testing phase. these are: unit testing: involves the testing of individual units of codes, integration testing: involves verifying the units of code function when integrated, and user acceptance testing: is used in determining whether or not the systems met the user requirements for that iteration. 2.1.5 evaluation and review in this stage of the iteration, the entire project is examined to ensure it meets all the client’s requirements that have been established at the time. the client is given the project to review and if completely satisfied, the cycle is ended else the adjustments or feedback made by the client is incorporated into the planning phase of the next iteration. 2.2 system methodology workflow the system shown in figure 2 depicts the methodology workflow. a website was created in the name of the department and accessed through the domain name. then, its homepage was loaded; the homepage contains links to the login portal for 3 different types of individuals, which are the staff and students of the department, and the administrator of the e-library website. the flowchart shows a decision tree to determine if the visitor is already registered on the e-library and the next steps that should be taken by the visitor. it also shows the activities the administrator should perform to view, edit, add or delete books and other eresources, and users. 2.3 materials requirement the software used for the design of the e-library system are listed as follows: i. operating system: microsoft windows 7, 8, 10 sp1 professional edition (64 bits) and later editions., mac or unix os. for this work, the windows 10 operating system was used. ii. mysql database software: was used to build the e-resources database. the minimum hardware requirements are intel® coretm 2 duo, 4gb, web access and peripherals. table 1: acquired and uploaded e-resources. s/n category subject number 1 e-books mathematics 80 electronics 136 tutorials 234 computer 400 2 articles electronic/computer fields 272 3 past questions various subjects 95 4 lecture notes various subjects 65 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng olabisi et al: development of a generic on-line departmental e-library using the iterative design approach. azojete, 20(1):173-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 179 figure 2: flowchart of system methodology 2.4 catalogue tree a detailed cataloguing process shown in figure 3 was developed based on areas in which available materials would be harnessed to assist students in their studies. the catalogue majored on core specialization areas that make up computer engineering, which are electronics engineering, computer programming and mathematics. materials in the major subject areas of these specializations that are listed in the catalogue include: past questions, lecture materials/notes, published articles in areas relevant to programme, memos of important concern to the students and e-books in various subjects/courses taught in the programme at different levels of study. the catalogue process was implemented to enable students search for relevant e-resources in an optimized, less-clumsy manner while saving search time. students can easily locate an item from the digital library’s catalogue depending on their preferred method of access. it could function as subject, author, or title catalogue depending on the student’s preference due to the filtering and sorting technique implemented. the process for developing the catalogue which is displayed on the website page for users of the e-library to help ease their search for relevant e-resource at the shortest time, involves the following tasks: an excel spreadsheet was used to construct a catalogue with the fields mentioned above. the spreadsheet was linked to the sql database (so it can be retrieved via url) the worksheet was updated as new e-resources get added and the cataloguing process progressed. start home page staff login login end 1. view profile 2. edit profile 3. view users 4. add books 5. view books 6. view books report 7. issued books student login admin login register register staff login page student login page admin login page 1. view profile 2. edit profile 3. search for books 4. request for books 1. view profile 2. edit profile 3. search for books 4. request for books log out login login http://www.azojete.com.ng/ niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 180 the excel spreadsheet was used to create a retrieval system search field. the database was configured using the url for the spreadsheet. the hyper-text markup language (html) as the standard markup language for documents designed to be displayed in a web browser was used to write codes which was pasted into the catalogue website so that students can access the catalogue and use it for effective searching of materials (e-resources) they require from the site. figure 3: catalogue tree for e-library resources. e-resources e-books memos articles past questions lecture notes 100 level digital electronics 200 level 300 level 500 level 400 level electronics mathematics schaum’s series computer analog electronics micro electronics integrated circuits opto-electronics power electronics embedded system audio electronics telecomms nano electronics bio-electronics computer architecture c programming data structure computer architecture artificial intelligence computer algorithms computer networking computer graphics & visualisation expert systems robotics machine learning neural network natural language programming fuzzy logic rendering geometry modeling animation & simulation virtual reality scientific visualisation computer data mining graph theory & combinatories operating systems gpu programming database packages file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng olabisi et al: development of a generic on-line departmental e-library using the iterative design approach. azojete, 20(1):173-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 181 2.5 acquisition of e-resources while setting up the e-library system, materials such as e-books, past questions and solutions, journals articles, handouts and lecture materials, college lectures of previous years, and so on, were acquired from academic members of staff, the school library, the internet and the college of engineering of the institution. past questions and some hard copy lecture notes were scanned using android and flatbed scanners, while softcopy of lecture materials, past questions and marking guides/solutions were obtained from academic staff. copyright issues where necessary for certain e-resources, particularly for materials that are not published open access (oa), were being handled by the university’s central library. this is inclusive of handling the issue of subscription to relevant non-open access journals from where articles would be downloaded. implementation of the well-defined and structured catalogue includes filtering and sorting technique implemented with the main entry for each e-resource material. this is made up of: book title, author, publisher, year of publication, category and language. evaluating this elibrary development, a case of electronics and computer subject related e-resources was embarked upon resulting in acquiring materials listed in table 1. these were acquired, categorized and uploaded unto the e-library site for a test-run. table 1: worksheet for cataloging 2.6 measuring users’ satisfaction there are various methods used in reporting the satisfaction of users of an e-library. these include: end-user computing satisfaction (ecs) and importance performance analysis (ipa). from any of these methods, the customer satisfaction index (csi) can be calculated to obtain the overall user satisfaction (simon and ogom, 2015; hamzah et al., 2022). users’ satisfaction to a large scale can also be rated using usability testing, discussed in subsection 2.7.3.2 and used to determine user’s satisfaction index for this work. 2.7 methods for administering the webpage the e-resources uploaded to the site at start-up are stated in table 2. table 2: e-resources uploaded at the onset. http://www.azojete.com.ng/ niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 182 2.7.1 users’ registration and book search users of the e-library, which are students and staff of the department, are meant to register on the e-library website. figures 4 to 7 show the e-resources uploading page, the e-resources collection page, the users’ registration page and a search engine usage page, respectively. to have access to the e-resources after registration, users login to the site, then search for materials they so needed. figure 4: membership registration figure 5: search engine figure 6: uploading page screenshot figure 7: e-resources collection 2.7.2 analysis of the database management system the e-library database management system was implemented and tested using the following parameters: 2.7.2.1 efficiency testing the implementation of a digital library system makes books transaction (uploading new materials and accessing them) easier for the department of computer engineering students and staff. 2.7.2.2 reliability the system’s membership registration, validation, books transaction, generation of the report, and search engine were accurately performed. 2.7.2.3 usability the system is a user-friendly environment that makes it easy for the students and staff of the department to perform tasks more effectively by rating how usable or satisfying the e-library platform has been. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng olabisi et al: development of a generic on-line departmental e-library using the iterative design approach. azojete, 20(1):173-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 183 2.7.2.4 readability testing the readability test was carried out by using the automated software webfx that evaluated the website by applying multiple readability formulas. most readability tests hope to achieve readability scores that fall in the range of content that can be easily understood by fifth graders. hence, the readability score for the e-library should be measured with respect to its target audience, which are the department’s students and staff. 3. results and discussion tables 3 and 4 show the results of the e-resources of e-books and past questions that were loaded into the database for use by students of the department of computer engineering. it is expected that over time, with further administrative efforts, the number of e-resources would be increased. table 5 gives the result of the usability test conducted for five participants with the use of the hallway test. the average time to complete a task of accessing the site, searching for required e-resource and obtaining it is 16.2 seconds with the task completion rate of 100 % for each participant without any error. table 3: e-book classes loaded in the database. s/n e-books type/subject no. of e-books 1 mathematics 80 2 electronics 136 3 schaum’s series 234 4 computer 400 table 4: result of past question e-resources in the database. level session 2020/2021 2021/2022 2022/2023 100 15 15 18 200 18 20 24 300 17 21 22 400 9 8 10 500 16 19 20 table 5: result of the usability test. parameter participant1 participant2 participant3 participant4 participant5 avg average time to complete task (in seconds) 17 15 13 23 13 16.2 task completion rate 100% 100% 100% 100% 100% 100% number of errors 0 0 0 0 0 0 shown in figure 8 is the result of the readability test. this test result shows that the site has an average reading ease of about 8.2 of 100 and should be easily understood by 17 to 18-yearolds. it shows a generally low readability score, which is understandable to the target audience and acceptable for now. shown in figure 9 is the result of the accessibility test carried out with the use of four different automated software tools, namely: audioeye, wave, axe and html_codesniffer. each tool gave individual total number of tests, as well as failures encountered. what is shown in figure http://www.azojete.com.ng/ niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 184 9 is the average test score of 79 for the four test tools. this result shows that the e-library website is largely compliant with accessibility guidelines. figure 8. result of readability test figure 9. result of accessibility test 4. conclusion the aim to develop a generic departmental digital library that will be accessible to its students and staff to obtain e-resources was achieved. e-resources in major subject areas of computer engineering were loaded from the backend of the content management system using the catalogue tree into the e-library website in the cloud to ensure smooth and easy management. the verified process helps to restricted access to the e-library. algorithms for more advance search engine, fascinating web crawler for e-library systems and automatic users’ registering and authentication will enhance future works. references abdulrazzaq, mb. and mustafa, om. 2017. designing and implementing of an online library management system. science journal of university of zakho, 5(3): 278-284. abraham, p., kuriakose, s. and salim, am. 2020. role of digital libraries in library and information science education: a study among lis students of mg university, kottayam. library philosophy and practice (e-journal). libraries at university of nebraska-lincoln. https://digitalcommons.unl.edu/libphilprac/4476 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng olabisi et al: development of a generic on-line departmental e-library using the iterative design approach. azojete, 20(1):173-186. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 185 adebayo, oa., ahmed, yo. and adeniran, t. 2018. the role of ict in provision of library services: a panacea for sustainable development in nigeria. library philosophy and practice (e-journal) 1951: 1-12. http://digitalcommons.unl.edu/libphilprac/1951 adebesin, tt. 2015. library management system. a project report submitted to the department of computer science, federal university, oye-ekiti in october 2015. ahmmod, s. 2015. report on digital library system. submitted to syed mustafizur rahman chowdhury, northern university bangladesh. 14 december-2015. al-juboori, afma. 2014. design and implementation of an e-library search system. international journal of innovation and applied studies. 7(4): 1322. alarape, ma. and edet, sn. 2017. a web-based e-library system for tertiary institutions. international journal of applied information systems (ijais) 12(2): 17-22. anyim, wo. 2018. e-library resources and services: improvement and innovation of access and retrieval for effective research activities in university e-libraries in kogi state nigeria. library philosophy and practice (e-journal). 1647. https://digitalcommons.unl.edu/libphilprac/1647 hamzah, ml., hultari, la., purwati, aa. and nazaruddin, n. 2022. analysis of e-library based on level of user satisfaction using eucs and ipa methods. journal of applied engineering and technological science. 4(1): 599-610. henry, kj. 2021 the emergence and challenges of digital library. international journal of advancement in education, management, science and technology. 4(3): 50-54. hiremath, s., lalasangi, s. and acharya, s. 2019. role of digital libraries in e-learning. ip indian journal of library science and information technology. 4(2): 61-62. http://doi.org/10.18231/j.ijlsit.2019.017 hussain a. 2018. cutting edge: technology's impact on library services. igi global. doi: 10.4018/978-1-7998-1482-5.ch002: 16 – 27. igbo, hu., ibegbulam, ij., asogwa, be., and imo, nt. 2022. provision of digital information resources in nigerian university libraries. information research, 27(3): 936. retrieved from http://informationr.net/ir/27-3/paper936.html (archived by the internet archive at https://bit.ly/3eu2rl1) https://doi.org/10.47989/irpaper936 igboechesi, gb. and dang, tl. 2019. challenges of digital library in nigeria: an overview of the university of jos, nigeria. pioneering concepts in strategic management & entrepreneurship edited by s. n. banerjee. published by exceller open, www.excelleropen.com 7-16. islam, m., islam, n., munshi, nu and haider, ms.. 2022. an effective digital safeguarding system in university libraries: a model plan. wuhan university. published by elsevier ltd. data and information management 6: 100007. https://doi.org/10.1016/j.dim.2022.100007. jha, sk. 2023. application of blockchain technology in libraries and information centers services. library hi tech news. https://doi.org/10.1108/lhtn-02-2023-0020. accessed 10 february, 2023. khalifa, has. 2020. trends in designing databases for e-learning systems. albahit journal of applied sciences. 1(1): 16-21. http://www.azojete.com.ng/ niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):173-186. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: niyiolabisi@gmail.com 186 library of congress. 2023 challenges to building an effective digital library. https://memory.loc.gov/ammem/dli2/html/cbedl.html. downloaded october 28, 2022. masiye, ss. 2019. design and development of an electronic library management system for mufulira skills training institute. the international journal of multi-disciplinary research. www.ijmdr.net` naveed, m., siddique, n. and adil, hm. 2021. measuring the status of library management systems: a case of higher education institutions in lahore. library philosophy and practice (e-journal: 20-21. oyetola, s o., oladokun, bd., maxwell, ce. and akor, so. 2023. artificial intelligence in the library: gauging the potential application and implications for contemporary library services in nigeria. data & metadata 2: 36. doi: 10.56294/dm202336 perdana, ia. and prasojo, ld. 2020. digital library practice in university: advantages, challenges, and its position. advances in social science, education and humanities research. published by atlantis press sarl. 401: 44-48. pyrounakis, g., nikolaidou, m., and hatzopoulos, m. 2014. building digital collections using open source digital repository software: a comparative study. international journal of digital library systems. 4(1): 10–24. https://doi.org/10.4018/ ijdls.2014010102. rathee, s. and kaushik, s. 2019. steps and planning in setting up digital libraries and repositories. journal of advancements in library sciences. 6(2): 72-76. roy, a., mridha, a., paul, d. dutta, j., mondal, s. and giri, s. 2018. e-library management system. a project report for the bachelor of computer application, gandhinagar institute of technology, india. https://www.studypool.com/documents/27333301/design-engineeringproject-e-library-management-system-report-. accessed on 12 february, 2023. sejane l. 2017. access to and use of electronic information resources in the academic libraries of the lesotho library consortium. a phd thesis of the university of kwazulunatal, pietermaritzburg, south africa. https://ukzn-dspace.ukzn.ac.za/bitstream/handle/10413/14345/sejane_lefuma_2017.pdf?sequence=1&isallowed=y shailendra, k. and rai, n, 2011. web interface in library management software systems. desidoc journal of library & information technology 31(4): 271-272. sharma, vk. and chauhan, sk. 2019. digital library challenges and opportunities: an overview. library philosophy and practice (e-journal). 3725.. libraries at university of nebraska-lincoln. https://digitalcommons.unl.edu/libphilprac/3725. simon, br. and ogom, oj. 2015. evaluation of the extent of utilization of electronic library resources and services by undergraduate students in university of calabar library, calabar, nigeria. education journal. 4(2): 82-89. doi: 10.11648/j.edu.20150402.15 subaveerapandiyan, a. 2023. application of artificial intelligence (ai) in libraries and its impact on library operations review. library philosophy and practice (e-journal). 7828. libraries at university of nebraska-lincoln. https://digitalcommons.unl.edu/libphilprac/7828 thirunavukkarasu, m., sravvani, kn. and durga, l. 2023. e-library management system using web programming. international journal of engineering research & technology (ijert), 12(4): 389-391. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2008; vol.6, 60 -65 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng comparative performance of a locally developed votex rice fan thresher dauda, s.m.. 1 and a.u. dzivama2 abstract the efforts to discover and make optimal and effective use of locally developed rice thresher as substitute for imported rice threshers form the focus of this paper. a locally developed rice thresher was compared with an imported votex rice fan from holland. the study was based on threshing efficiency, cleaning efficiency, total grain losses, grain recovery range, capacity utilization and threshing intensity. three popular rice varieties, faro 51, faro 29 and faro 21 were used to evaluate the performances of the threshers. the results showed that, the local thresher had 98.01%, 99.32%, 4.78%, 95.22%, 54.67% and 0.029 kwkg-1, as: threshing efficiency, cleaning efficiency, total grain loss, grain recovery range, and capacity utilization and threshing intensity respectively. whereas the imported votex rice fan thresher had 98%, 95.77%, 8.72%, 91.28%, 76.97% and0.0037 kwkg-1 as threshing efficiency, cleaning efficiency, total grain loss, grain recovery range, capacity utilization and threshing intensity respectively. thus the local thresher compared favorably with the imported thresher and can be used as substituted thereby conserving nigeria’s foreign exchange. 1. introduction rice is one of the most important crops grown in nigeria (dauda et al, 1999). it is the sixth major crop in terms of cultivable area after sorghum, maize, cowpea, cassava and yam. it is the only crop which is grown nationwide and in all agro-ecological zones from sahel to the coastal swamps. it is estimated that 4.1 million hectares of land could be put into cultivation. in 1999, the rice area harvested in nigeria was 2.1 million hectares a ten-fold increase compared to the average for the 1960s (210,000 ha). compared with the other food crops, the recent increase in rice area is unrivalled, implying a structural shift towards rice production in the nigerian (misari et al, 2001). the current emphasis on energy conservation and utilization in many countries prompted agricultural policy makers to reset priorities in agriculture. consequently, policy makers in nigeria focus interest on the production and processing of rice. agriculture is one of the fields where nigeria heavily relied on imported technology especially in areas of machinery and equipment (bashir and daudu, 2003). these machinery have not made any appreciable impact on increased food production due to several problems, among which is the regular breakdown of these machinery. experience has shown that a number of these machinery and equipment breakdown as early as few days after commissioning due to lack of adaptability, ignorance, abuse or misuse (yisa, 1997). imported equipment can be sophisticated to justify better output but more maintenance will be required (priel; 1974). the more sophisticated the equipment, the better it is expected to perform, but it becomes counter productive if such sophisticated equipment is imported into an underdeveloped country with inadequate maintenance capability, technology or lack of 1department of agric. engineering federal university of technology, minna. nigeria 2 department of agric & environmental resources engineering, university of maiduguri, nigeria. audzivama@yahoo.com http://www.azojete.com.ng/ mailto:audzivama@yahoo.com azojete vol. 6 2008 61 knowledge of the vital equipment characteristics-maintainability and reliability (imonigie, 2003). in contrast with the locally manufactured machines, the imported machines are usually more prone to maintenance problems since they are designed and manufactured with the parts/components under different environmental and operating conditions. the progressive technological change in the equipment-exporting countries (usually developed countries) inevitably leads to rapid equipment obsolescence in developing countries. this further poses problems to the maintenance personnel who always battle to adapt or adjust to the change (imonigie, 2003). dauda and adgidzi (2002) and (dauda and adgidzi (2003), reported on the development of an indigenous rice thresher in nigeria, and also their performances. the locally developed rice thresher has a hopper, transmission unit, cleaning unit, straw and grain outlets and a supporting frame. the method of feeding is the throw-in type, in which, rice heads are feed into the hopper and fall in by gravity. the inventory of imported rice threshers by make in niger state, nigeria was reported by chukwu (2002), which shows that the most common is votex rice fan thresher (representing 62.79% of total number available). the performance evaluation of the votex rice fan thresher has been reported (chukwu, 2001). votex rice fan thresher is an imported rice thresher (plate 1). it was developed and built at the university of wageningen-holland and had undergone intensive evaluation in countries like indonesia, nigeria, mali, philippines, sierra leone and vietnam, during which the thresher was perfected (volgelenzang, 1982). the votex rice fan thresher is a portable thresher for small farms and easily carried by four people to the field. the design of the threshing drum, which also have a cleaning function and a long concave arrangement covering about 1500 of the drum circumference make it possible for the votex rice fan thresher to handle very long (up to 100cm straw length). it also has only one moving part which is the cross flow threshing drum. the objective of this work was to evaluate the performances of the national cereals research institute, badeggi, nigeria locally developed rice thresher (plate 2) compared with an imported votex rice fan from holland. plate 1 – votex rice fan thresher plate 2 – locally developed rice thresher comparative analyses of locally developed and imported votex rice thresher 62 2. materials and method three popular rice varieties, faro 51, faro 29 and faro 21 were harvested from national cereals research institute, badeggi research field; they represent the conventionally known grain sizes (long, medium and short) grown by farmers in nigeria. tests were carried out on both the locally developed and the imported votex ricefan threshers at 556 rpm cylinder speed, 14% rice moisture content and 1:1.22 grain/straw ratio to obtain the total losses, threshing efficiency, cleaning efficiency, input and output capacities, grain recovering range (grr), capacity utilization (cu), threshing index (tix) and threshing intensity (tin) in accordance with the draft nigeria standard test code for grain threshers (ncam, 1990). the threshed materials were collected at the grain outlet, cleaned and weighed. the unthreshed materials were separated from straw and weighed after hand threshing and cleaning. the tex was carried in replicates and the average were calculated and recorded as the values of the parameters determined the results for both threshers were presented and compared. (a) determination of total losses (lt) 1.....100(%) x gt qu pu  2.....100(%) x gt gc pc  3.....100(%) x gt gl pl  4.....100(%) x gt gs ps  5.....(%) pspcplpult  where, pu = percentage of unthreshed grain, % qu = quantity of unthreshed grain obtainable from straws, kg gt = total grain received at grain outlet, kg pc = percentage of cracked and broken grain, % qc = quantity of cracked and broken grain from grain outlet, kg pl = percentage of clean grain, % ql = quantity of clean grain obtained at straw outlet, kg ps = percentage of sieve loss, % qa = clean grain at sieve overflow + sieve underflow + stuck grain, kg (b) determination of efficiencies threshing efficiency (te): a bundle each weighing 10kg of unthreshed rice was fed into each of the machines and timed using a stop watch. this is the ratio of total weight of grain threshed to the total weight of grains fed into the thresher expressed as a percentage. it is also the difference between 100% and the percentage of unthreshed grain as (equation 6). 6.....100(%) pute  azojete vol. 6 2008 63 cleaning efficiency (ce): the clean grain that pass through the cleaning unit was collected at the grain outlet and weighed and also the unclean grain was as well weighed and the ratio as percentage taken. the ratio of the weight of clean grain that pass through the cleaning unit to the total weight of grains at the outlet of the grain retainer expressed as a percentage (equation 7). where, gc = clean grain received at grain outlet, kg (c) determination of input and output capacities. to determine the input capacity for each test, a known weight of rice bundle was fed at a time. the threshing time for each test was recorded by a stop watch. similarly, to determine the output capacity, the weight of threshed grain received at specified grain outlet per unit time was taken and recorded. (d) grain recovery range (grr) 8.....100 ptgrr  (e) capacity utilization (cu) 9.....100x ic qc cu  (f) threshing index (tix) 10.....)(decimaltexcuxgrrtix  (g) threshing intensity (tin) 11..... oc fc tin  where pt = percentage total losses, % oc = output capacity, kg ic = input capacity, kg fc = power consumed by thresher, kw 3. results and discussion the results presented in table 1 show the overall mean performances for both locally developed and imported votex rice fan threshers under the same treatment. the mean values for threshing efficiencies for both threshers were obtained to be 98%. as shown in the table, 7.....100(%) x gt gc ce comparative analyses of locally developed and imported votex rice thresher 64 the cleaning efficiency for the local rice thresher was higher (99.32%) as compared to the imported votex rice fan which was obtained to be 95.77%. the trend reversed for the capacity utilization with a 54.67% for the local thresher compared to 76.97% for the imported votex fan thresher. the lower capacity utilization may be attributed to the local thresher still being in its prototype stage. similarly, the local thresher recorded a lower threshing index of 51.00% compared to the imported votex fan thresher with 65.00%. this also may be attributed to lack of perfection of the local thresher when compared to the imported thresher, which took many years to perfect the mean value of cumulative total losses was lower for the local rice thresher at 4.7% compared to 8.72% for the imported votex rice fan. this is possible with the local thresher having a good sieve arrangement design. table 1: result of performance evaluation of locally developed rice thresher and imported votex ricefan locally developed rice thresher imported votex ricefan faro 51 faro 29 faro 21 mean faro 51 faro 29 faro 21 mean unthreshed grain (%) 1.99 1.98 2.00 1.99 1.99 2.01 2.00 2 cracked & broken grain (%) 0 0 0 0 2.95 3.08 3.23 3.1 sieve loss (%) 2.77 2.78 2.82 2.79 1.43 1.51 1.54 1.49 blown loss (%) 0 0 0 0 2.12 2.13 2.15 2.13 total loss (%) 4.76 4.76 4.82 4.78 8.71 8.71 8.74 8.72 threshing efficiency (%) 98.10 98.00 97.98 98.01 98 98 98 98 cleaning efficiency (%) 99.40 99.32 99.22 99.32 95.79 95.76 95.76 95.77 input capacity (kghr-1 ) 490 490 490 490 1300 1300 1300 1300 output capacity (kghr-1 ) 267.9 267.9 267.9 267.9 1026.44 1026.44 1026.44 1026.44 grain recovery range (%) 95.43 95.27 94.97 95.22 91.60 91.25 91 91.28 capacity utilization (%) 54.68 54.67 54.66 54.67 76.99 76.97 76.96 76.97 threshing index (%) 51.00 51.00 51.0 51.0 65 65 65 65 threshing intensity (kwkg-1) 0.029 0.029 0.029 0.029 0.0037 0.0037 0.0037 0.0037 4. conclusions based on the results of the performance indices of both local and imported votex rice fan, the local performs credibly as the foreign with a tendency of performing better with little further modification. this measure is bound to reduce the foreign exchange expenditure on the importation of rice threshers and to encourage local manufacturers and research institution in the adoption and production of this locally developed rice thresher, this will help in improving the production and processing of rice locally in nigeria. references a.o.a.c. (1984). official method of analysis 14th edition. association of official analytical chemists, washington d.c. andeh, w.b. (1992). nigerian indigenous technology, university press, ibadan bashir, i.m. and j.o. daudu (2003), problems associated with the maintenance of fully imported technologies. a case study of agricultural machinery and equipment in azojete vol. 6 2008 65 kaduna state, nigeria. nigeria journal of engineering and appropriate technology1 (1) pp 59-62. chukwu, o. (2001). performance evaluation of votex rice fan threshers. paper presented at the 1st international conference of the nigerian institution of agricultural engineers (niae) held at nike lake resort hotel enugu 10th-14th september, 2001. chukwu, o. (2002). performance evaluation of locally manufactured rice threshers in niger state. proceedings of 4th annual engineering conference, school of engineering and engineering technology, federal university of technology, minna. pp 23-30. dauda s.m., misari s.m., dzivama a.u. and agidi g. (1999). performance evaluation of local rice parboiling techniques in borno state. proceedings of the nigerian institution of agricultural engineering 21, pp 125-130. dauda s.m. and adgidzi d. (2002). development of indigenous rice thresher in nigeria. arid zone journal of engineering, technology and environment 2, pp 1-9. dauda s.m. and adgidzi d. (2003). performance evaluation of a locally developed rice thresher. nigerian journal of engineering and appropriate technology 1 (1) pp 5255. imonigie, p.s. (2003). problem associated with maintenance of imported machines. nigerian journal of engineering and appropriate technology 1 (2) pp 67-71 misari s.m., ukwungwu m.n. and imolehin e.d. (2001). accelerated development and production of quality rice in nigeria. paper presented at the 2nd meeting of the national executive committee of rice farmers’ association of nigeria, gwagwalada 28th february, 2001. ncam (1990). test code for power maize shellers. draft nigerian industrial standard. prepared by the national center for agric. mech., ilorin, nigeria. 18pp. priel v.z. (1974). systematic maintenance organization. macdonald and evans ltd. london. vogelenzang andelst (1982). votex rice fan thresher manufacturer, b.v. holland. yisa m.g. (1997). agricultural mechanization, how far? and what next? paper presented at nse quarterly dinner in minna, niger state, nigeria. arid zone journal of engineering, technology & environment azojete september 2021. vol. 17(3):389-402 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 389 original research article strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature c. h. salihu1*, a. e. abalaka2, r. a. lafiya-araga3, b. j. olawuyi2, i. kariim4 1department of building, school of environmental sciences, modibbo adama university of technology yola, adamawa state, nigeria. 2department of building, school of environmental technology, federal university of technology minna, niger state, nigeria. 3department of chemistry, school of physical sciences, federal university of technology minna, niger state, nigeria. 4department of chemical engineering, school of engineering and engineering technology, federal university of technology minna, niger state nigeria *corresponding author’s email address: changliab@gmail.com article information abstract geopolymer concrete has been gaining extensive attention in recent years due to its numerous advantages over ordinary portland cement concrete in terms of reduced carbon footprint, improved mechanical strength, durability as well as chemical resistance. however, production of geopolymer concrete is usually affected by several factors such as the synthesis temperature, nature of the source material and the type of alkaline activator used. for these materials to have wider application within the nigerian construction industry, there is a need to synthesize the concrete at ambient temperature and to examine the suitability of native alkaleri kaolin to produce geopolymer concrete. the study presents the strength and microstructural properties of metakaolin geopolymer concrete synthesized at ambient temperature. alkaleri calcined kaolin from bauchi state nigeria was used as the main geopolymer precursor with sodium hydroxide and sodium silicate as the alkaline activating agent. the geopolymer concrete was prepared with silicon/aluminium ratio of 2.0 and 2.5 (geopolymer concrete m1 and m2 respectively) and cured for 3, 7, 14, 28, and 90 days at ambient condition (average temperature of 26°c and average relative humidity of 61± 15%). fourier transform infra-red, x-ray diffraction, thermo-gravimetric analysis, scanning electron microscopy as well as compressive strength and split tensile strength test were conducted on the geopolymer concrete at appropriate curing age to examine their microstructure and strength properties. the fourier transform infra-red revealed that there was an immediate geopolymeric reaction between the metakaolin and the alkali activator. the x-ray diffraction showed that the raw metakaolin sample and both geopolymer concrete m1 and m2 were amorphous in nature; while the geopolymer concrete m2 (silicon/aluminium ratio of 2.5) exhibited good dissolution of the kaolinite which resulted in a more compact and stable structure in comparison with geopolymer concrete m1 (silicon/aluminium ratio of 2.0). this was also confirmed by the scanning electron microscopic images of the geopolymer concretes. the thermogravimetric analysis revealed that both geopolymer concrete m1 and m2 were thermally stable at 300°c and at 800°c, only the organic phase of the geopolymer decomposed. the strength properties (compressive and tensile strength) of geopolymer concrete m1 and m2 increased with increase in the curing age, and geopolymer concrete m2 displayed slightly higher strength in all the curing ages as compared with the geopolymer concrete m1. this implies that the higher the silicon/aluminium ratio, the higher the mechanical strength of the geopolymer. both the geopolymer concrete samples attained a compressive strength that can be acceptable for structural use as normal strength concrete grade c20/25 as specified in the requirement of bs en 2061 2000 at 28 days curing. © 2021 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 27 march, 2021 revised 21 may, 2021 accepted 28 may, 2021 keywords: kaolin geopolymerization ambient temperature silicon/aluminium ratio strength properties arid zone journal of engineering, technology and environment, june, 2021; vol. 17(2):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 390 1.0 introduction concrete has gained universal recognition as the most utilized man-made construction material. consequently, the global consumption of concrete which is estimated to be about 10 billion tons yearly, is believed to rise exponentially primarily been driven by urbanization, industrialization as well as economic growth and expansion taking place around the world (thapa and waldmann, 2018). making cement for concrete involves heating pulverized limestone and clay to a temperature reaching 1450°c. they chemically interact to form the cementitious compounds in portland cement. the limestone or calcium carbonate (caco3) is broken down to carbon dioxide gas and calcium oxide when heated to extreme temperatures (naqi and jang, 2019). the calcination of the limestone as well as the use of fossil fuels for the heating process releases carbon dioxide into the atmosphere, contributing to global warming. the emissions by cement manufacturing process contributes about 5-7% to the global carbon dioxide emission, estimating it to one tone of carbon dioxide been released to the atmosphere when one tone of ordinary portland cement is manufactured (das et al., 2018; andrew, 2018). also, about 1.5 to 1.8 tons of limestone and 0.4 tons of clay are needed to produce every ton of portland cement (british geological survey, 2005). therefore, the production of portland cement is an extremely resource and energy intensive process. the increased use of cement in concrete causing environmental concerns in terms of emission of carbon dioxide during cement manufacture has brought pressure on the scientists and engineers to research on other alternative supplementary materials in order to reduce cement consumption in the construction industry. in that regard, geopolymer cements have been proposed in recent years by researchers (lateef et al., 2016; shabarish et al., 2018 and liang et al., 2016) as a greener and more sustainable alternative to opc and also to address the environmental problems related to the disposal of industrial waste and by-products while reducing costs. consequently, geopolymerization became popular and geopolymer binders such as fly ash (fa), granulated blast furnace slag (gbfs), metakaolin (mk) and silica fumes (sf) which are termed alumina-silicate materials were adopted and considered more ecologically friendly alternative to ordinary portland cement as their production does not involve limestone calcinations. geopolymer binders or cements are used together with aggregates and an alkaline activating solution through a process called geopolymerization to produce geopolymer concretes. geopolymer concrete (gpc) have been proven by research (al-shathr, 2016; neupane et al. 2018) to have superior advantages than ordinary portland cement concrete. such advantages include but not limited to high early strength, exceptionally high thermal and chemical stability and improved durability that makes this type of concrete acceptable for construction work. however, geo-polymerization of alumina-silicate materials is affected by several factors which include the synthesis temperature, actual chemical composition of the source material, its particle size distribution, the type of alkaline activator used and the curing temperature (lateef et al., 2016). in recent times, investigations have centred on the mechanical, microstructural and durability properties of geopolymer concrete (diaz-loya et al. 2011; bashir et al., 2017; fernandezsalihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 382 jimenez et al., 2006). on factors that affect the geopolymerization, barbosa et al. (2000) specified on the nature of source material, that geopolymers made from calcined source materials, such as mk, fa, and gbfs yield higher compressive strength when compared to those synthesized from non-calcined materials, such as kaolin clay. xu and van deventer (2000), carried out a study on 15 different natural alumina-silicate materials and reported that alumina-silicates with increased rate of dissolution after polymerisation attained higher compressive strength. the authors concluded that the chemical composition of the aluminasilicate materials such as the percentage of calcium oxide (cao), potassium oxide (k2o) as well as the molar ratio of silicon/aluminium (si/al) in the source material, the type of alkaline activator and the molar ratio of (si/al) in the alkaline solution during dissolution had significant effect on the compressive strength of the gpc. according to khale and chaudhary (2007) the si/al ratio of the source material substantially affected the compressive strength of the resulting geo-polymeric products, which increased almost linearly with the si/al ratio of geopolymer precursors. a similar conclusion was also pointed out in the study conducted by he et al. (2011) on mk and red mud – fa gpc to evaluate the effect of the source materials on the strength and microstructural properties. correspondingly, in another study, najet et al. (2013) found that the si/al ratio of geopolymer precursor has a significant effect on the mechanical properties and the microstructure of the resulting geo-polymeric products. the authors suggested that more effort should be made to investigate the effects of compositions of alumina-silicate materials from different origin and geopolymers induced under some reaction conditions such as low temperature synthesis (rovnanik, (2010). some studies (duxson et al., 2007; kong et al., 2007) carried out on the geopolymeric synthesis of mk to produce gpc revealed that the chemical composition of mk, synthesis and curing temperature significantly affect the final properties of a geo-polymeric product as well as recommend the need to research on locally available mk to understand the extent of reactivity when influenced by different experimental parameters such as si/al and ambient temperature synthesis. based on these, nigeria as a developing country has a competitive advantage in the development of this sustainable construction material, because of the large deposit of kaolin scattered in different part of the country. therefore, the study focuses on a developing field that utilizes cheap and abundant alumina-silicate materials such as kaolin from alkaleri in bauchi state, nigeria to make gpc at ambient temperature aimed at examining the strength and microstructural properties with respect to the curing ages of the gpc. this is to identify what variable works best for the indigenous kaolin at the nigerian climatic condition. 2.0 materials and methods 2.1 kaolin the kaolin clay which is off-white in color and in powdered form was purchased from local miners at pali district of alkaleri local government area, bauchi state, nigeria. the kaolin sample was calcined in a laboratory furnace at a temperature of 700°c for 3hours to form mk. the metakaolin obtained was sieved in a 75µm sieve and its chemical composition was examined by way of x-ray fluorescence, which was done at nigerian geological survey agency kaduna, following the method outlined by usman et al. (2020). arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 383 2.2 alkaline solution 12m of sodium hydroxide solution and sodium silicate solution containing 30.2% sio2, 22.8% na2o and 47% water of crystallization were used as the alkali activator to induce the geopolymerization process. the alkaline activating solution was prepared 24 hours prior to the mixing of concrete (kamarudin et al., 2011). 2.3 aggregate aggregate mostly provide volume stability to concrete and improves its durability. aggregate which forms 75-80% of the volume of concrete is classified as fine and coarse aggregate (neville 2000). sharp river sand was used as fine aggregate because of its lower silt and clay content which can adversely affect the strength of the concrete. it was prepared at saturated surface dry condition following the procedure as outlined in astm c128. while crushed granite was used as the coarse aggregate. the coarse aggregates were kept at saturated surface dry condition by soaking in water for 24 hours and surface drying it with a dry towel until all surfaces were dry before experimentation. 2.4 experimental procedures for metakaolin (mk) geopolymer concrete (gpc), a total number of fifty (50) 100 x 100 x 100mm concrete cubes as one of the specified size by astm c39/c39m-03 (for compressive strength tests) and thirty (30) 150mmꝋ x 300mm concrete cylinders as specified by astm c496/c496m-17 (for split tensile tests) were casted. the experiment was designed for twentyfive (25) cubes, that is (5 cubes for each curing age) and fifteen (15) cylinders (3 cylinders for each curing age) for each si/al ratio gpcm1 (si/al: 2.0), gpc m2(si/al: 2.5). the astm standard stipulated a minimum of three specimens for an average strength value at a particular curing age, hence the selection of five (5) number of specimens for compressive strength test and three number of specimens for tensile strength test at each curing age. the curing ages considered for the study were 3, 7, 14, 28and 90-days. tables 1, 2, and 3 gives details of number of cubes cast, material composition, specimen number and ratios adopted for the gpc samples. table 1: number of cubes for curing age/si/al ratio curing age no. of cubes for compressive strength test gpcm1(si/al: 2.0) gpcm2(si/al: 2.5) no of cylinders for tensile strength test gpc m1 gpc m2 3 3 3 3 3 3 3 3 3 3 15 15 3 7 14 28 90 total 5 5 5 5 5 5 5 5 5 5 25 25 table 2: volume of materials for geopolymer concrete specimen si/al ratio mk (kg) fine aggregate (kg) coarse aggregate (kg) naoh (kg) na2sio3 (kg) water (kg) gpc m1 2.0 1.87 2.52 5.90 0.41 0.53 0.65 gpc m2 2.5 1.87 2.52 5.90 0.26 0.68 0.65 salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 384 table 3: ratios of materials for geopolymer concrete specimen si/al na2sio3/naoh sio2/na2o concentration of naoh (mol/l) h2o/mk gpc m1 2.0 1.3 2.4 12 0.35 gpc m2 2.5 2.6 2.4 12 0.35 2.4.1 geopolymer concrete production. for the purpose of this study/research, mk gpc was prepared at si/al ratios of 2.0 and 2.5, cured at ambient temperature for 3, 7, 14, 28 and 90 days. the experiment adopted the separate mixing method as reported by rattanasak and chindaprasirt (2009). the alkaline activating solution was prepared 24 hours prior to the time of mixing the concrete. this was done by dissolving 480g of sodium hydroxide pellets in one liter of water and allowed to cool down to room temperature. the sodium silicate solution was weighed based on the si/al ratio and added to the sodium hydroxide solution (usman et al., 2020). predetermined quantity of dry mk powder for each si/al ratio and the alkaline solution (table 2) were poured into the concrete mixer and the precise quantity of water according to the water/cement ratio was also added. these materials were mixed for 20 minutes and the fresh geopolymer matrix was poured into 50mm cubic steel molds which were used to examine the microstructure after geopolymerization. the required measure of fine and coarse aggregates (table 2) was poured into the geopolymer paste and the mixing continued for another 20 minutes. the fresh gpc obtained was then transferred into 100mm cubic steel molds for compressive strength test and 150mm ɵ x 300mm cylindrical steel molds for tensile strength test. curing of the geopolymer specimens was done in a laboratory ambient environment for 3, 7, 14, 28 and 90 days. the average temperature of the laboratory as at the time of curing was 26.6°c. the relative humidity was 62% at 3and 7-days curing, 31% at 14 and 28 days curing and 22% at 90 days curing age. during curing, all specimens were covered with a plastic film to prevent quick drying of the concrete specimens. 2.4.2 microstructural characterization of geopolymer fourier transform infra-red (ftir), xray diffraction (xrd), thermo-gravimetric analysis (tga) and scanning electron microscopy (sem), were the key tools used in this study for investigating the composition, microstructure, chemical elements and the thermal properties of the constituent materials used in the experiment and the geopolymer produced. 2.4.2.1 attenuated total reflectance – fourier transform infra-red (atr-ftir) fourier transform-infrared (ftir) spectroscopy was used to characterize and identify the geopolymerization by means of transmitting the infra-red radiation directly through the sample. this was done at national research institute for chemical technology (narict) zaria kaduna state, nigeria. the specimens were ground to powder and small amount of potassium bromide (kbr) was added to each sample and they were placed in a mould. cold press machine was used to press the mould which contains the geopolymer powder and potassium bromide (kbr) at 6 ton for 3 minutes to form pellets for examination. shimadzu ftir 8400s fourier infra-red spectrometer (u.s.a) was used to evaluate the functional group of the sample. ftir absorption spectra were arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 385 recorded in the range of 400 – 4000cm-1 using a spectral resolution of 2 cm-1. the spectrum of each sample represents an average of 32 scans (mousa 2013). 2.4.2.2 x-ray diffraction (xrd) x-ray diffraction on mk and resulting geopolymers was done to give more details about the microstructure and chemical composition of the gpc. following the procedure reported by soleimani et al. (2012), the gpc specimens were grounded into powder and scanned with cukα radiation having generator voltage of 45 kv and tube current of 40ma. the diffractive patterns of the mk and gpc were gotten at 1° per 3.5 minutes over an interval of 2θ = 5° 80° and steps of 2θ = 0.02°. the procedure was performed at the nigerian geological survey agency in kaduna, nigeria using empyrean xrd diffractometer by p-analytical b.v (netherlands). 2.4.2.3 thermal gravimetric analysis (tga) thermal gravimetric analysis is a method of thermal analysis in which changes in weight of a sample is measured as a function of temperature or time in a controlled atmosphere. tga was carried out at step-b laboratory of federal university of technology, minna using tga 4000 manufactured by perkinelmer (netherlands). 13.836 mg of gpc m1 and 16.367 mg of gpc m2 in powdered form were scanned (heated) from 50oc to 900oc at 10oc /min in a nitrogen environment at a flow rate of 20 ml/min (rosas et al., 2014) 2.4.2.4 scanning electron microscopy (sem) scanning electron microscopy (sem) was carried out at chemical engineering department of ahmadu bello university, zaria on the impact fractured surfaces of the different compositions of the geopolymer. the concrete specimens were cut into thin sections and coated with gold before transferring to the sample holder for imaging using jeol-6400 model scanning electron microscope (kamarudin et al., 2011). the images were captured at 5mm working distance with the accelerating voltage of 15kv. the emission current was 10µa which was adjusted from time to time. 2.4.2.5.1 strength properties of geopolymer concrete compressive strength and split tensile strength tests were performed on the gpc to examine their mechanical properties at different si/al ratio (2.0 and 2.5) and at different curing ages considered (3, 7, 14, 28 and 90 days). compressive strength test of the geopolymer specimens was performed according to the specifications of astm c39/c39m-03. specimens for the compressive strength test were crushed using the compression testing machine (10kn) mode_jys2000a at the building department laboratory, fut minna. an average crushing load of 5 specimens was obtained for each of the curing age and the compressive strength (n/mm2) was calculated by dividing the maximum crushing load (n) by the area of the concrete cubes (mm2). salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 386 split tensile strength test was carried out on the gpc sample at the appropriate curing age using the modified form of astm c496/c496m-17. the concrete cylinders were crushed using the universal testing machine utm3000 (30kn) at the building department laboratory, fut minna. for better comparison of result and to obtain an average tensile load, 3 samples were tested for each curing age. the tensile strength was found by dividing the maximum crushing load by the cross-sectional area of the cylinder. (1) 3.0 results and discussion 3.1 chemical composition of metakaolin table 4 present the oxides found in metakaolin, having al2o3 and sio2 as the major oxides and traces of other oxides. as seen on the percentages of the major oxides, the metakaolin has si/al ratio of 1.65 making it adequate for geopolymerization (kim, 2012). table 4: chemical composition of metakaolin oxides al2o3 sio2 so3 k2o cao tio v2o5 cr2o3 mno fe2o3 mass (%) 34.30 54.70 0.771 0.385 3.87 0.17 0.054 0.01 2.02 oxides ga2o3 zno iro2 re2o7 eu2o3 l.o.i nio yb2o3 cuo mass (%) 0.041 0.01 0.07 0.13 0.084 3.30 0.006 0.040 0.016 source: xrf result from nigerian geological survey agency kaduna 3.2 sieve analysis of fine and coarse aggregate the results of the sieve analysis for the fine and coarse aggregate are shown on the grain size distribution curve (figure 1). figure 1: grain size distribution curve of fine and coarse aggregate coefficient of uniformity (cu) and coefficient of curvature (cc) of fine aggregate coefficient of uniformity (cu) = 2.96 coefficient of curvature (cc) = 0.95 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 c u m u la ti ve p as si n g (% ) sieve size (mm) fine aggregate coarse aggregate arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 387 classification of sand = uniformly graded or poorly graded since it did not meet the criteria cu ≥ 6 for well graded soil and 1<cc<3 for coefficient of curvature coefficient of uniformity (cu) and coefficient of curvature (cc) of coarse aggregate coefficient of uniformity (cu) = 1.37 coefficient of curvature (cc) = 0.95 classification of coarse aggregate = uniformly graded or poorly graded since it did not meet the criteria cu ≥ 4 for well graded gravel and 1<cc<3 for coefficient of curvature. the grain distribution curve of fine and coarse aggregate shows that they are both uniformly graded. this means that most of the aggregate particles (both fine and coarse) are in a very narrow size range or are approximately the same size (malewar et al., 2017; pawar et al., 2016). the use of uniformly graded aggregate entrapped more voids within the concrete mass which could increase its permeability and subsequently reduce the mechanical strength. good compaction of the fresh concrete was done to mitigate the effect of using the uniformly graded aggregate. 3.3 microstructural properties of gpc 3.2.1fourier transform infra-red of gpc figure 2 and 3 presents the ftir spectra of mk, gpc m1 and m2 at all the curing ages considered. salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 388 figure 2: ftir spectra of (a)mk, gpc m1 at (b)3 days, (c)7 days (d)14 days, (e)28 days curing and (f)90 days curing ages arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 389 figure 3: ftir spectral of (a)mk, gpc m2 at (b)3 days, (c)7 days (d)14 days, (e)28 days (f)90 day curing ages the ftir spectrum of kaolin calcined at 700°c for 3 hours is presented in figure 2a. the spectrum is characterized by series of vibration bands, indicating si-o bending vibration at about 450 cm-1, 4-co-ordinate vibration of al(iv)-o at 917 cm-1 and si-o-al vibration at 775 cm-1. the broad band in the region of 3413 cm-1 and 1642 cm-1 are general characteristic bands salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 390 showing o-h and h-o-h groups from weakly bound water molecules and absorbed atmospheric water (soleiman et al., 2012). figure 2 and 3 show the ftir spectra of gpc m1 and gpc m2 respectively, cured at 3, 7, 14, 28 and 90 days. after the geopolymerization, the following changes were noted: there was a major disruption of the al environment as indicated by the reduction of the band at 775 cm-1, corresponding to si-o-al vibration at 3 days and its subsequent disappearance from the 7-days curing age in both gpc m1 and gpc m2. this confirms an immediate reaction between the mk and the alkaline solution. evidence of shift was seen in the characteristic band at 1028 cm-1 relating to the si-o asymmetric stretching towards lower wave numbers after the geopolymerization. the shifts to lower wave numbers became prominent in gpc m1 (si/al:2.0) at 14, 28 and 90 days. however, for gpc m2 (si/al: 2.5), the shift was seen to have occurred from 3 days and subsequently, 7, 14, 28 and 90 days. soleimani et al. (2012) suggested that this shift indicates the formation of new structure different from the mk. the authors inferred that the large shift towards lower wave numbers is an evidence of geopolymerization that occurred with the partial replacement of sio4 tetrahedral by alo4 tetrahedral, resulting in a change and reorganization in the local chemical environment of si-o bond. the 4-co-ordinate vibration of al(iv)-o at 917 cm-1 present in the mk sample and gpc m1 was seen to have disappeared as the si/al ratio was increased to 2.5 as shown in figure 3. this is an indication of the displacement of al in the mk by si forming si-o-si-o-al bonds, accounting for the increase in the mechanical strength of gpc m2. the number of bands in the range of 400-600 cm-1 in the ftir spectra of gpc increased considerably for gpc m2 at 3, 7, 14, 28 and 90 days while the increase in the number of bands in that region for gpc m1 was evident from 14 days. this indicates that the geopolymer sample with the higher si/al ratio is more suitable for geopolymerization and the rate of strength gain seems to increase with curing age. the characteristic bands at 3413 cm-1 and 1642 cm-1 corresponding to the presence of absorbed water and weakly bound water molecules (nasab et al., 2014) was seen to have increased in intensity in the geopolymer samples cured at 3 and 7 days, owing to the presence of additional water that was employed during the casting of the gpc. there was a decrease in the intensities of this bands at later curing ages of 14, 28 and 90 days in both gpc m1 and gpc m2, indicating that the geopolymer samples became drier. an absorption band at 1405 cm-1 related to na2co3 (claudio et al., 2013) was present in all the spectra of the geopolymer samples. the existence of this peak could be related to unreacted naoh, which was carbonated by the co2 in the atmosphere. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 391 3.2.2 x-ray diffraction (x-ray) figure 4 and 5 shows the x-ray diffractive patterns of the mk and the gpc at different curing ages. k: kaolinite, mu: muscovite, z: zeolite, i: illite, q: quartz. figure 4: x-ray diffraction patterns of (a)mk , gpc m1 at (b) 3 days, (c) 7 days, (d) 14 days, (e) 28 days and (f) 90 days curing ages k: kaolinite, mu: muscovite, z: zeolite, i: illite, q: quartz. figure 5: x-ray diffraction patterns of (a) mk, gpc m2 at (b) 3 days, (c) 7 days, (d) 14 days, (e) 28 days and (f) 90 days curing ages amorphous phases such as calcined silica and alumina were identified in the mk by the x-ray diffraction which were indicated by the presence of large halo peaks centered on 2θ = 20o – 30o. the x-ray diffraction (xrd) patterns presented sharp peaks at 2θ = 12°, 2θ = 25° and 2θ = 27°, as seen in figure 4a, detailing the presence of muscovite, kaolinite and quartz respectively. salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 392 the major features of the x-ray diffraction patterns of gpc m1 cured at different ages (figure 4b, c, d, e and f) are sharp peaks centered at approximately 12° indicating muscovite, 25° signifying kaolinite, 27° representing quartz and trace amount of illite at 35°62°, which is a characteristic reflection of amorphous geopolymer (guo et al., 2010). there was incomplete geopolymerization reaction as seen on the diffraction peak revealing the presence of kaolinite which was not properly dissolved by the alkaline activating solution. in the geopolymerisation process, the mk particles are dissolved by the alkali solution (nasab et al., 2014), indicating that the lower si/al ratio (2.0) accounted for the incomplete dissolution of the kaolinite. crystalline phases in the parent material such as quartz did not take part in the polymerization at the si/al: 2.0 as can be seen in the patterns since there was no reduction in the intensities of the peaks after the geopolymerization reaction. this agrees with the current understanding that amorphous phases in raw materials are more reactive and more involved in geopolymerization reactions (zhang et al., 2010). for the gpc m2, the xray diffraction patterns at the curing ages of 3, 7, 14, 28 and 90 days (figures 5b, c, d, e and f) were characterized by sharp peaks at 2θ = 12°, 25° and 27°, indicating the presence of muscovite, kaolinite and quartz in the gpc sample respectively as observed earlier in gpc m1. trace amount of illite was also detected at 2θ = 38°62°. the peaks relative to kaolinites decreased as the si/al ratio increased to 2.5 which indicate that with higher amount of sodium silicate, most of the kaolinite dissolved and contributed to the geopolymerization. in addition, the intensity of peaks relative to muscovite and illite that appeared in the diffractogram of gpc m1 decreased as the si/al ratio increased to 2.5. this shows that as the concentration of silicon increases there was further dissolution of muscovite and illite present in the mk sample which also contributed in the geopolymerization process, thereby resulting to more orderly and stable phases in their spectra as compared to the one with lower si/al ratio. 3.2.3 thermo-gravimetric analysis (tga) figures 6 and 7 present the thermo-gravimetric analysis (tga) and derivative thermogravimetric (dtg) curves of the gpc m1 and gpc m2. table 5 further summarise the result of tga of the gpc samples. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 393 figure 6: thermogravimetric and derivative thermogravimetric analysis of gpc m1 (si/al: 2.0) figure 7: thermogravimetric and derivative thermogravimetric analysis of gpc m2 (si/al: 2.5) salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 394 table 5: thermo-gravimetric analysis (tga) of gpc sample peak degradation temperature, tp (oc) t5% (oc) onset temperature (°c) degradation temperature range (oc) moisture content (%) gpc m1 413.00 492.62 365.49 355.68 577.36 305.70-439.14 439.14-685.25 3.48 gpc m2 373.25 496.33 318.13 325.70 576.09 288.70-432.33 432.33-681.67 3.26 thermo-gravimetric analysis was performed on the gpc specimens to compare their thermal behavior after curing for 90 days at ambient conditions. the weight loss of gpc m1 started at approximately 30°c with maximum weight loss temperature at approximately 98.9°c and was completed at approximately 300°c. this loss of weight can be attributed to the removal of water molecules absorbed (up to approximately 100°c) or differently linked (up to approximately 200°c, free water in the pores of the concrete; at higher temperatures, structural water and bound water in the nanopores) to the silicate molecules (duxson et al., 2007; rosas et al., 2014). the overall weight loss was 3.478% and geopolymer material residue of 96.522% remained. after the loss of water in the concrete sample, the tga curve showed degradation of the composition at two points. the concrete specimen was thermally stable up to about 300°c. at 305.70°c, the first degradation started which ended at 439.14°c, resulting in a weight loss of 2.728%. the second degradation process started at the temperature at which the first degradation stopped and was completed at 685.25°c recording a weight loss of about 3.571%. the two degradation steps can be attributed to the combustion of the dispersed organic phase. there was a total weight loss of 9.777%, leaving combustion residue of 90.222% at 800°c. the temperature at which 5% of the concrete sample would have degraded (t5) was 365.49°c. the gpc m2 losses its water molecules at the temperature range of 30-150°c with maximum weight loss temperature of approximately 126.35°c and weight loss of about 3.264%. two degradation points were also identified on the tga/dtg curve (figure 7), the first starting at 288.73°c and stopped at 432.33°c losing about 3.57% of its weight. the second degradation process started at 432.33°c and ended at 681.67°c with a weight loss of about 3.463%. the overall weight loss is 10.297% and the geopolymer material residue of 89.703% remained at 800°c. at 318.13°c, 5% of the concrete degraded. the thermo-gravimetric analysis revealed that both gpc m1 and m2 are thermally stable up to 300°c and the thermal treatment up to 800°c resulted in a complete removal of the organic phase from the composition. 3.2.4 scanning electron microscopy (sem) of geopolymer concrete scanning electron micrographs of the gpcs studied exhibit significant change in the microstructure with variation of si/al ratio. in all the cases, (figure 8 a, b, c and d) there is evidence of strict adhesion between the components of the gpcs. the change in the microstructure appears more between the impact fractured surfaces of gpc m1 (figure 8b) and gpc m2 (figure 8d). arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 395 sem of gpc m1 (figure 8b) identified components of the concrete such as the granite and portions of un-dissolved mk and aggregate. the surfaces of the aggregate upon impact were cleaner in this composition which revealed that there was no proper bonding between the aggregate and the mk matrix. the sem image also showed a scarcely compact and porous structure. this could be due to the incomplete dissolution of the mk powder by the alkaline activating solution as identified by the x-ray difractograms, thereby forming a weaker bond (si-o-al) between the geopolymer binder paste and the aggregate (fine and coarse). figure 8: (a, b, c and d): morphological features of gpc m1 (a and b) and gpc m2 (c and d) at 90days curing. the sem image of gpc m2 (figure 8d) shows a better interaction between the aggregate and the mk matrix as the aggregate were seen to be well embedded within the matrix and portions of the matrix were still attached to the aggregate upon impact fracture. this revealed that the composition with si/al ratio 2.5 (gpc m2) resulted in the development of stronger bond between the components of the concrete. as was observed in the x-ray diffraction patterns of the gpcs, there was a proper dissolution of the mk powder which interacted well with the aggregate to produce a homogenous hybrid material, thus, contributing to the increase in the salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 396 mechanical strength of the gpc. such observation agrees well the conclusion that the higher the si/al ratio, the higher the degree of dissolution; and the higher the degree of reaction, the higher the compressive strength of the gpc (alvarez-ayuso et al., 2008). 3.4 strength properties of geopolymer concrete results of the strength properties (compressive and tensile) conducted on the gpcs are presented in figures 9 and 10. figure 9: compressive strength of gpc figure 10: split tensile strength of geopolymer concrete 0.51 1.33 1.99 2.54 2.9 0.62 1.44 2.23 2.69 2.93 0 0.5 1 1.5 2 2.5 3 3.5 3 7 14 28 90 sp lit t e n si le s tr e n gt h ( n /m m 2 ) curing age (days) gpc m1 gpc m2 3.73 10.5 15.36 24.6 30.16 4.71 11.88 16.48 28.16 31.78 0 5 10 15 20 25 30 35 3 7 14 28 90 c o m p re ss iv e s tr e n gt h ( n /m m 2 ) curing age (days) gpc m1 gpc m2 arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 397 3.3.1 compressive strength of geopolymer concrete 3.3.1.1 effect of curing age figure 9 represents the compressive strength of gpc m1 and gpc m2. the compressive strength of 3.73 n/mm2 and 4.71 n/mm2 were recorded at 3 days by the gpcm1 and m2. the strength of gpc m1 appreciated to 10.50 n/mm2 at 7days indicating 181.5% increase on the strength at 3days. on the other hand, gpc m2 attained a strength of 11.88 n/mm2 representing 152.2% increase. the prompt strength gain at 7 days could be as a result of the shift of the si-o vibration bands to lower wave numbers which confirmed geopolymerization reaction by the ftir. physical observation found that the gpc samples have expelled most of its water of hydration making it appear more drier than when observed at 3 days. this could also result to the rapid strength development at this age. as the curing duration increased, a proportionate improvement in the compressive strength was also observed. at 14 days curing age, the compressive strength reached 15.36n/mm2 and 16.48n/mm2 representing 46.3% and 38.7% increase in strength for both gpcs m1 and m2 respectively. after the 28-day curing the compressive strength was characterized by further increase of 60.1% for gpc m1 and 70.9% for gpc m2. the compressive strengths of the gpc at 28 days curing age falls under grade c20/25 which is considered as normal strength concrete in accordance with the specification of bs en 206-1 2000 (concrete, specification and performance). the code states that the compressive strength of concrete is denoted by concrete strength classes, which relate to the characteristic cube strength (fck) determined at 28 days. it is taken that at 28 days 75-85% of the strength of concrete has been attained. at 90 days, the increase in strength of both gpc m1 and m2 was not significant. the maximum strength of 30.16n/mm2 was attained for m1 (si/al: 2.0) and 31.78n/mm2 for gpc m2 (si/al: 2.5) representing 22.6% and 12.9% increase in strength respectively. the increase in the compressive strength of the specimens at longer curing age suggests that the transient nature of geopolymerization extends into longer period and that the development is dependent on the si/al ratio (mousa, 2013). 3.3.1.2 effect of silicon/aluminium ratio gpc m2 was observed to have attained higher compressive strength than gpc m1 at all the curing ages considered. at 3 days the compressive strength of gpc m2 (si/al: 2.5) increased by 26.3% from the gpc m1 (si/al: 2.0). at 7, 14, 28and 90-days curing ages, the gpcs m2 were characterized by 13.1%, 7.3%, 14.5% and 5.4% increase in the compressive strength respectively from the gpc m1. the formation of si-o-si-o-al bond at the expense of si-o-al bonds confirmed by the ftir and the higher rate of dissolution of the mk by the alkali activating solution at higher ratio as indicated by the xrd might have improve the compressive strength of gpcm2. this indicates that at higher si/al ratio, the strength properties of geopolymers increases, in so doing, making the structure more stable (kim 2012). salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: changliab@gmail.com 398 3.3.2 split tensile strength of geopolymer concrete 3.3.2.1 effect of curing age figure 10 represents the tensile strength of gpc m1 and m2. as in the case of the compressive strength, at 3-days curing age the split tensile strength of both gpc m1 and m2 (0.51 n/mm2 and 0.62 n/mm2 respectively), were relatively low owing to the presence of water in the concrete samples. appreciable split tensile strength development started at the 7-days in which the gpc m1 reached strength of 1.33n/mm2 equivalent to 160.8% increase in the split tensile strength from the 3 days curing age. at that same age, the gpc m2 attained strength of 1.44n/mm2 representing 134.3% increase. it was evident that there was a gradual appreciation of strength for both gpc m1 and gpc m2 at 14, 28 and 90 days curing age representing 49.6%, 28.1% and 13.7% increase in split tensile strength for gpc m1 respectively and 54.9%, 20.6% and 11.4% increase for gpc m2. 3.3.2.2 effect of silicon/aluminium ratio the result of the split tensile test of the gpc m2 showed higher split tensile strength than that of gpc m1. at curing age of 3, 7, 14, 28 and 90 days the split tensile strength of gpc m2 was represented by 21.6%, 8.3%, 12.0%, 5.5% and 1.0% increase in split tensile strength from gpc m1 respectively. it can therefore be concluded that the si/al ratio has a significant effect on the split tensile strength of gpc. the increase in si/al ratio is directly proportional to the increase in the split tensile strength. 4.0 conclusion the ftir analysis showed that geopolymerization has occurred by the disappearance of the sio-al vibration band at 775 cm-1 in all the samples of the gpc. the shift of the characteristic band at 1028 cm-1 relating to the si-o asymmetric stretching towards lower wave numbers which indicates the formation of new structure different from the mk also confirms geopolymerization. increase in the si/al ratio led to the displacement of al by si thereby forming more si-o-si-o-al bonds resulting to the increase in the mechanical strength of the gpc m2 as confirmed by the xrd and the compressive strength test. the xrd revealed that both the gpc m1 and m2 are amorphous in nature and as the si/al ratio increased, there was higher rate of dissolution of the mk by the alkaline activating solution and improvement in the stability of the structure, as supported by the sem images of the geopolymer specimens. the gpc is thermally stable up to 300°c as detected by the tga and can withstand temperature of 800°c as only the organic phases in the concrete degraded at that temperature. the sem of the gpc m1 showed a scarcely compact and porous structure due to the incomplete dissolution of the mk at that ratio. but the sem of gpc m2 revealed a firm adhesion with stronger interaction between the components of the concrete. arid zone journal of engineering, technology and environment, september, 2021; vol. 17(3):389-402. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: gukopn@unijos.edu.ng 399 the gpc synthesized from alkaleri kaolin at ambient temperature exhibited good mechanical properties (compressive and split tensile strengths) acceptable for use as normal strength concrete (concrete grade c20/25 as specified in the requirement of bs en 206-1 2000). the strengths improved with increase in the si/al ratio and the curing ages of the concrete. the study recommends that with the limited understanding of the microstructural behavior and thermal properties of the gpc more experiments such as the magic angle spinning-nuclear magnetic resonance (mas-nmr), energy-dispersive x-ray spectroscopy (edxs) and differential scanning calorimetry (dsc) should be carried out to provide better comprehension on the nature of the material in order that it may find different applications within the nigerian construction industry. references al-shathr, b., al-attar, t. and hasan, z. 2016. effect of curing system on metakaolin based geopolymer concrete. journal of babylon university: engineering sciences, 24(3): 569-576. alvarez-ayuso, e., querol, x., plana, f., alastuey, a., moreno, n., izquierdo, m., … barra, m. 2008. environmental, physical and structural characterisation of geopolymer matrixes synthesised from coal (co-) combustion fly ashes. journal of hazardous materials, 154: 175183. andrew, rm. 2018. global co2 emissions from cement production. earth system science data. 10: 195-217. barbosa, vff., mackenzie, kjd. and thaumaturgo, c. 2000. synthesis and characterization of materials based on inorganic polymers of alumina and silica: sodium polysialate polymers. international journal of inorganic materials, 2 (4): 309-317. bashir, i., kapoor, k. and sood, h. 2017. an experimental investigation on the mechanical properties of geopolymer concrete. international journal of latest research in science and technology, 6(3): 33-36. british geological survey: mineral profile 2005. cement raw materials. natural environmental research council, office of the deputy prime minister. claudio, f., francesco, c., giuseppina, r., domenico, a., costantino, m., alberto, b., … gaetano, m. 2013. application-oriented chemical optimization of a metakaolin based geopolymer. journal of materials, 6 (5): 1920-1939. das, sk., mishra, j. and mustakim, sm. 2018. an overview of current research trends in geopolymer concrete. international research journal of engineering and technology (irjet) 05(11): 376-381. diaz-loya, ie., allouche, en., and vaidya, s. 2011. mechanical properties of fly-ash based geopolymer concrete. aci materials journal, 108(3): 300-306. duxson, p., lukey, gc., mallicoat, sw., kriven, wm. and van deventer, jsj. 2007. effect of alkali and si/al ratio on the development of mechanical properties of metakaolin-based geopolymers. colloids and surfaces a: physicochemical engineering aspects, 292 (1): 8-20. salihu et al.: strength properties and microstructural characterization of metakaolin geopolymer concrete synthsized at ambient temperature. azojete, 17(3):389-402. issn 1596-2490; 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standardization, 20-21 http://www.astm.org/ arid zone journal of engineering, technology and environment. august, 2016; vol. 12:74-82 copyright © faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng optimization of some mineral contents of dried osmo-pretreated green bell pepper (capsicum annuum) using response surface methodology m. m. odewole 1 *, m. o. sunmonu 1 , s. k. oyeniyi 3 , o. adeyinka-ajiboye 2 and z. o. ayodimeji 2 ( 1 department of food engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria. 2 department of agricultural and biosystems engineering, faculty of engineering and technology, university of ilorin, ilorin, nigeria. 3 department of agricultural and environmental engineering, faculty of technology, university of ibadan, ibadan, nigeria) *corresponding author’s e-mail address: odewole2005@yahoo.com, tel.: +234 805 0453 697 abstract a study to optimize three mineral contents (magnesium, potassium and manganese) of dried osmo-pretreated green bell pepper was done using response surface methodology (rsm). five levels of osmotic solution concentration (a) (5% (w/w), 10% (w/w), 15% (w/w), 20% (w/w) and 25% (w/w)) of common salt and osmotic process durations (b) (60 min, 90 min, 120 min, 150 min and 180 min) were considered. after osmotic dehydration, all pre-treated and some control (unpre-treated) samples were dried at a constant temperature of 50˚c in a fabricated cabinet dryer. rsm under central composite design in design expert 8.0.3 computer software package was used to design the experiment, analyse data, optimize the process and present all results with 2-dimesional and 3-dimensional plots. from results obtained, optimized combinations were selected on the basis of their desirability values which were 0.931, 0.432 and 1.00 for magnesium, potassium and manganese respectively. from the desirability values on the response surface plots, the optimum (maximum) value of magnesium was found to be 29.18 mg/100g at osmotic process duration of 180 min and osmotic solution concentration of 25% (w/w); for potassium, the optimized value was 46.13 mg/100g at osmotic process duration of 60 min and osmotic solution concentration of 5% (w/w); while the optimized value for manganese was 10.96 mg/100g at osmotic process duration of 150 min and osmotic solution concentration of 15% (w/w). dried pre-treated products had values closer to fresh samples than control (dried unpre-treated) samples for all the three mineral contents considered. keywords: green bell pepper, optimization, response surface methodology (rsm), osmotic dehydration, drying. 1. introduction bell peppers (capsicum annuum), also known as sweet peppers are plump, bell-shaped vegetables featuring either three or four lobes. they come in various colours such as green, red, yellow, purple, white and even rainbow between stages of ripening (steve, 2009). according to gmf (2010), bell peppers are not 'hot' because the primary substance that controls "hotness" in peppers called capsaicin is found in very small amount in them. green bell pepper contains vitamin a and vitamin c which are rich in lycopene and has been proven to prevent cancer (vengaiah and pandey, 2006). some of the other nutritional contents of green bell pepper are: vitamin b (b1, b2, b3 and b5), vitamin k, vitamin e, fiber, calories (lowest nutrient) and others. green pepper assists in digestion and has been proven to cure cold, cataracts, rheumatism and diabetes (gmf, 2010 and vengaiah and pandey, 2006). some minerals like magnesium, manganese and potassium are very beneficial to human health and are also present in green bell pepper. magnesium contains enzymes that aid metabolism of calcium by converting sugar to energy and protein synthesis in the body, and according to fao (2002), deficiency of magnesium could cause nervousness, heart spasm and calcium depletion to human health. potassium helps to regulate body waste balance system and normalises heart rhythms thereby stimulating the kidney functions and mailto:odewole2005@yahoo.com odewole et al.: optimization of some mineral contents of dried osmo-pretreated green bell pepper (capsicum annuum) using reponse surface methodology. azojete, 12:74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 75 reducing the risk of high blood pressure (salmonson, 2013). manganese is an antioxidant and also helps in the stabilization of human blood sugar (gmf, 2010). pre-treating vegetables helps it keep its natural colour and kills off enzymes that can cause food spoilage (presvervingvegetables, 2001). osmotic dehydration is a pre-treatment method for partial dehydration of water-rich foods, such as fruits and vegetables, by immersing them in hypertonic solution of sugar and/or salt. heat may not be applied during osmotic dehydration hence it offers higher retention of initial food characteristics, such as colour, aroma, nutritional constituents, and flavour compounds (sunjka and raghava, 2004). some factors that influence osmotic dehydration include osmotic solution concentration, osmotic process duration, osmotic solution temperature, type of osmotic agent, ratio of product to osmotic solution, agitation of solution during osmotic dehydration (chavan and amarowicz, 2012) and physiology of the food material to be pre-treated. drying is an old method of preserving food. it is a simultaneous heat and mass transfer process that involves the transfer of heat to provide the necessary latent heat of vaporization and movement of water or water vapour through the food material and then away from it to effect separation of water from it. drying removes water from foods for two reasons; to prevent (or inhibit) micro-organisms and hence preserve the food, and to reduce the weight and bulkiness of food for cheaper transport and storage. dried foods can be stored for long periods without deterioration and according to earle and earle (2004), the principal reason for this is that the microorganisms which cause food spoilage and decay are unable to grow and multiply in the absence of sufficient water. optimization is simply the process of finding input variables (process conditions) that would give the maximum or minimum values of desired output. linear programming and sequential technique, differential calculus, and simultaneous technique are some of the methods of optimization. the need to execute research tasks easily within the shortest possible time with greater accuracy and precision is required in recent times. for this reason, optimization tools with various methods in form of software packages for computer systems are now available; example of such method is rsm which is available in design expert software package. rsm was used to optimize osmotic dehydration process and drying of carrot by (singh et al., 2006) in sodium chloride solution and drying temeperature of 65˚c. the optimum conditions obtained were 11% salt concentration, 30˚c osmotic solution temperature and process duration of 120 min. green bell pepper contains some minerals like magnesium, potassium and manganese that are highly beneficial to human health. this important fruit crop is usually faced with the problem of short shelf life when freshly harvested. in odewole and olaniyan (2016), ten (10) days was reported as the maximum period in which the crop can retain its maximum nutritional contents in refrigerated storage. the implication of this is that, the availability of the crop in areas where refrigerated storage of the freshly harvested crop can not be easily achieved may be imposibble. osmotic dehydration coupled with hot air drying in a specialized mechanical dryer is one of the promising ways of curtailing the aforementioned problems. therefore, the objective of the study was to establish osmotic dehydration conditions that will optimize some mineral contents (magnesium, potassium and manganese) of dried osmo-pretreated green bell pepper with with the use of rsm in design expert (version 8.0.3) computer software package. arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 76 2. materials and methods 2.1. experimental equipment and materials the following equipment and materials were used for the study: laboratory oven (genlab, model n53 cf, england), a fabricated cabinet dryer, electronic weighing balance (ohaus cl series, model cl 201, china), stop watch (nokia x2-01), desiccator, containers for osmotic dehydration pre-treatment, stainless steel tray and knife, foil paper, spatula and hand gloves. common salt, distil water, fresh green bell pepper. 2.2. experimental design five levels of osmotic solution concentrations (a) of common salt (5% (w/w), 10% (w/w), 15% (w/w), 20% (w/w) and 25% (w/w)) and five levels of osmotic process duration (b) (60 min, 90 min, 120 min, 150 min and 180 min) were substituted into the experimental design interface of design expert 8.0.3 version under rsm of central composite design. the result gave an experimental table with various combinations of a and b that were used for conducting the osmotic dehydration pre-treatment process. 2.3. experimental procedure fresh green bell peppers (figure 1) mostly of bell boy variety were procured from a food stuff market in ilorin, kwara state, nigeria. they were deseeded (figure 2) and sliced to 3 mm longitudinally and 100 g of sliced pepper was introduced into the osmotic solution concentrations for each pre-treatment combination at average ambient temperature of 28 ˚c. at the end of the pre-treatment, a non-uniform mass of not greater than 82 g was achieved. for the drying operation, 75 g of pre-treated product was introduced into the dryer for each pre-treatment combination. the temperature of 50 ˚c was maintained throughout the period of drying. the drying temperature of 50˚c was chosen based on what odewole and olaniyan (2016) reported that the best temperature range for drying fruits and vegetables is 35˚c to 75˚c. after drying (that is, when samples in the dryer attained almost constant weight and the texture properly turned crispy, and at approximately four hours of drying), all the dried samples were arranged inside the desiccator and were later taken for nutritional analysis. the experiment was carried out in the laboratory of food and bioprocess engineering department, university of ilorin, ilorin, nigeria. figure 1: fresh samples of whole figure 2: green bell pepper after deseeding green bell pepper 2.4. output parameters magnesium, potassium and manganese of dried osmo-pretreated products were determined according to aoac (2002) procedures. odewole et al.: optimization of some mineral contents of dried osmo-pretreated green bell pepper (capsicum annuum) using reponse surface methodology. azojete, 12:74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 77 2.5. data analysis all the output data obtained for magnesium, potassium and manganese were introduced back into the experimental table earlier designed with design expert computer software package. the data were analysed following the stipulated procedures of the software for rsm in order to get the 3-dimensional (3-d) plots and 2 dimensional (2-d) contour plots that relate the two process conditions ( a and b) with each of the output parameter (mineral contents) and desirability values for optimum process conditions. 3. results and discussion 3.1 optimized mineral contents this section presents the results and discussion of the optimization process. for the three outputs considered (magnesium, potassium and manganese), the higher their values in the dried product, the better the product; because of their excellent importance in human body as earlier mentioned. hence, the goal of the optimization process for the three outputs was to maximize them in the dried osmopretreated product. 3.1.1 magnesium (mg/100g) figures 2a and 2b show the desirability value (always between 0 and 1) of optimum process conditions for magnesium in form of 2-d and 3-d plots respectively. also, figure 2c shows the optimum value of magnesium with respect to process conditions a and b. the desirability value is 0.931 for optimized (maximized) value of magnesium. this desirability value shown in small rectangular and square boxes on figures 2a and 2b is the closest to 1 and is the best combinations that enabled the goal of the optimization of getting maximum value of magnesium to be achieved. the location of desirability value of 0.931 from figures 2a and 2b on figure 2c indicate that the optimum value of magnesium of the dried osmo-pretreated green bell pepper is about 29.18 mg/100g with osmotic process duration of 180 min and osmotic solution concentration of 25% (w/w). the control sample of green bell pepper that was not pretreated contained 19.63mg/100g of magnesium after drying, and fresh sample of green bell pepper contained 30.03mg/100g magnesium which is almost the same as the amount present in dried osmodehydrated green bell pepper. hence, this is a confirmation that osmotic dehydration helps to retain nutrients in food. this is in agreement with results obtained by odewole et al., (2015), sunjka and raghava (2004) and odewole and olaniyan (2015) for osmotic dehydration and drying of different food materials. figure 2a: 2-d plot showing desirabilty value of optimum process conditions for magnesium arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 78 figure 2b: 3-d plot showing desirabilty value of optimum process conditions for magnesium figure 2c: 3-d plot for optimum value of magnesium (mg/100g) 3.1.2 potassium (mg/100g) figures 3a and 3b show the desirability value of optimum process conditions for potassium. also, figure 3c shows the optimum value of potassium with respect to process conditions a and b. the desirability value is 0.432 for optimized (maximized) value of potassium. from figure 3c, the optimum value of potassium is 46.13mg/100g with 60 min osmotic process duration and 5% (w/w) osmotic solution concentration. fresh sample of green bell pepper used for this study contained 47.40mg/100g of potassium while the control sample that was just dried without osmotic dehydration pre-treatment had 36.18mg/100g of potassium. the amount of potassium present after osmotic dehydration (46 mg/100g) is very close to the amount in the fresh sample and considerably higher than the amount present in the odewole et al.: optimization of some mineral contents of dried osmo-pretreated green bell pepper (capsicum annuum) using reponse surface methodology. azojete, 12:74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 79 dried unpre-treated control sample. this means, osmotic dehydration led to quality retention of green bell pepper after drying. figure 3a: 2-d plot showing desirabilty value of optimum process conditions for potassium figure 3b: 3-d plot showing desirabilty value of optimum process conditions for potassium arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 80 figure 3c: 3-d plot for optimum value of potassium (mg/100g) 3.1.3 manganese (mg/100g) the desirability value of optimum process conditions for manganese is shown in figures 4a and 4b. also, figure 4c shows the optimum value of manganese with respect to process conditions a and b. the desirability value is 1.00 for optimized (maximized) value of manganese. from figure 4c, the optimum value of manganese is 10.96 mg/100g with 150 min osmotic process duration and 15% (w/w) osmotic solution concentration. the amount of manganese present in dried untreated (control) sample of green bell pepper (7.23 mg/100g) is low compared to the amount present in fresh samples of green bell pepper (11.40 mg/100g). this result further confirmed the report of singh et al., (2006) and pokharkar and prasad, (1998) that osmotic dehydration used to improve quality of products. figure 4a: 2-d plot showing desirabilty value of optimum process conditions for manganese odewole et al.: optimization of some mineral contents of dried osmo-pretreated green bell pepper (capsicum annuum) using reponse surface methodology. azojete, 12:74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 81 figure 4b: 2-d plot showing desirabilty value of optimum process conditions for manganese figure 4c: 3-d plot for optimum value of manganese 4. conclusion in conclusion, different combinations of osmotic solution concentration and osmotic process duration gave the optimum values of magnesium, potassium and manganese of dried osmo-pretreated green bell pepper (capsicum annuum).the optimized combinations were selected on the basis of their desirability values which were 0.931, 0.432 and 1.00 for magnesium, potassium and manganese respectively. from the desirability values on the response surface plots, the optimum value of magnesium was found to be 29.18 mg/100g at osmotic process duration of 180 min and osmotic solution concentration of 25% (w/w); for potassium, the optimum value was 46.13 mg/100g at osmotic process duration of 60 min and osmotic solution concentration of 5% (w/w); while for manganese it was 10.96 mg/100g at osmotic process duration of 150 min and osmotic solution concentration of 15% (w/w). dried pre-treated products had nutrients values closer to fresh samples than control (dried unpre-treated) samples for all arid zone journal of engineering, technology and environment, august, 2016; vol. 12: 74-82. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 82 the three nutrients considered. this further confirmed osmotic dehydration as a quality improving pretreatment method for food materials after drying. references aoac. 2002. official methods of analysis. association of official analytical chemists, washington d.c. chavan, ud. and amarowicz, r. 2012. osmotic dehydration process for preservation of fruits and vegetables. journal of food research: 1(2): 202-209. earle, rl. and earle, md. 2004. unit operation in food processing. published by the new zealand institute of food science and technology. http://www.nzifst.org.nz/unitoperations/ fao, 2002. agriculture and consumer protection: human vitamins and mineral requirements – a report of joint fao/who expert consultation. bangkok, thailand. gmf. 2010. bell peppers world healthiest foods. george metaljan foundation). whfoods.org. retrieved in december, 2004. odewole, mm. and olaniyan, a.m. 2016. effect of osmotic dehydration pretreatments on drying rate and post-drying quality attributes of red bell pepper (capsicum annuum). agricultural engineering international, cigr journal: 18(1): 226-235. odewole, mm. and olaniyan, am. 2015. empirical modelling of drying rate and qualities of red bell pepper. lambert academic publishing, saarbrucken, germany: 1-161. odewole, mm., ayodimeji, zo. and alabi, kp. 2015. post-storage qualities of pre-treated dried red bell pepper. ukrainian food journal: 4(4): 605-618. pokharkar, sm. and prasad, s. 1998. mass transfer during osmotic dehydration of banana slices. journal food sci. technol: 35(4): 336-338. preserving vegetables, 2001. natural organic pretreatments: http://www.preservingyourharvest.com/naturalpre-treatments.html. retrieved on december 14, 2014. salmonson, r. 2013. minerals and your body: academic.emporia.edu. retrieved on august 12, 2016. singh, b., panesar, b., nanda, v., gupta, a. and kenedy, j. 2006. application of response surface methodology for the osmotic dehydration of carrots. journal of food engineering: 29: 592-614. steve, a. 2009. how to grow sweet peppers. http://www.harvesttotable.com/category/plant/ retrieved on december 27, 2014. sunjka, p. and raghava, g. 2004. assessment of pretreatment methods and osmotic dehydration for cranberries. canadian biosystems engineering/le génie des biosystèmes au canada, 46. vengaiah, pc. and pandey, jp. 2006. dehydration kinetics of sweet pepper (capsicum annuum l.) www.aseanfoodinfo/articles/11018495.pdf . retrieved on 15 april 2013. http://www.nzifst.org.nz/unitoperations/ http://www.preservingyourharvest.com/naturalpre-treatments.html http://www.harvesttotable.com/category/plant/ http://www.aseanfoodinfo/articles/11018495.pdf arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):417-426 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 417 wind energy assessment in auchi, nigeria using weibull distribution and nasa data i. seidu1, s. salisu1, a. a. masud2, u. musa1, d. m. almustapha3 and i. k. musa3 department of electrical engineering, ahmadu bello university, zaria. 2department of electrical engineering, jubail industry college, saudi arabia. 3department of electronics and communication engineering, ahmadu bello university, zaria. *corresponding author's email address: oyarebu209@gmail.com article information submitted 10 january, 2024 revised 18 february, 2024 accepted 25 february, 2024 keywords: wind energy potential weibull distribution pdf rmse wind speed abstract the advancements in wind energy farms in the developed world have significantly reduced the cost of wind energy turbine systems, making them more competitive and contributing to a reduction in global warming, which has a widespread impact on the global population. this study evaluates the wind energy potential of auchi, a community in edo state, nigeria, using the weibull distribution function. wind speed data from nasa spanning an 11-year period (2012-2022) at a height of 10 m is utilized, and statistical methods are employed to estimate the weibull parameters (scale and shape), which are then used to calculate the wind power density and the probability density function which was validated using root mean square error (rmse) and coefficient of determination r2. the results indicate that auchi possesses favorable wind conditions for power generation, with an average wind speed of 6.07 m/s and an average power density of 153.64 w/m². additionally, the study examines the influence of surface roughness and height on wind speed and power density, highlighting the potential for harnessing wind energy for electrification purposes in auchi, thereby offering a solution to nigeria’s energy challenges. 1.0 introduction the increasing global demand for energy, along with concerns about climate change from fossil fuel emissions, necessitates a shift to sustainable power generation (akdağ and dinler, 2009). wind energy, as a renewable and environmentally friendly source, stands out amidst this backdrop. unlike fossil fuels, wind energy offers a perpetually renewable option for power generation (mudasiru et al., 2018). renewable energy sources (res), including wind, geothermal, hydroelectric, and solar energy, present varied options with differing viability based on geographical context. developing nations, particularly those with limited access to nonrenewable resources, are significantly impacted by the global energy crisis, prompting the adoption of alternative energy sources (mohammadi et al., 2016). in nigeria, unreliable electrical power supply has hindered socioeconomic progress and increased air pollution. government efforts have seen limited success, necessitating an independent power supply (amadi, 2018). renewable technologies, like wind turbines (wt), offer a solution due to their independence from traditional sources and unlimited renewability (khan et al., 2018). despite extensive global research on wind energy potential, studies specific to the auchi community in southern nigeria are lacking. this study aims to fill this gap by analyzing wind energy potential in auchi, edo state, nigeria from 2012 to 2022, using weibull distribution http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):417-426. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 418 functions. the objective is to assess its appropriateness for an independent wind turbine power supply system that is free of carbon emissions 2.0 materials and method statistical methods, particularly the weibull distribution, were employed to assess wind energy potential at selected sites, aiming to estimate wind power. this approach, known for its precision and simplicity, surpasses alternative methods such as gaussian, beta, gamma, poisson, rayleigh, normal, and lognormal distributions (amadi, 2018). the statistical analysis is based on wind data collected over 11 years (2012-2022) at a height of 10 m, obtained from the official website of the national aeronautics and space administration (nasa). 2.1 theory of weibull and its parameters for wind energy assessment to comprehensively assess the potential of wind power at a specific location, it is necessary to conduct a statistical analysis of the recorded data on wind speeds, depicting the frequency distribution influenced by factors like location, climate, terrain, and surface profiles (mohammadi et al., 2016). selecting a distribution function depends on data characteristics such as discreteness, symmetry, and skewness. for continuous data, the weibull distribution is particularly suitable, excelling in modeling wind speed distribution, even with infrequent extreme values (adedipe et al., 2018). the weibull distribution relies on scale (c) and shape (k) parameters (sedzro et al., 2022). according to iec 61400-12, it is advisable to utilize the weibull function with two parameters for accurately approximating recorded wind speed data. it adapts to the distribution shape by adjusting its parameters, offering reliable outcomes (ma et al, 2022). to account for wind's inherent unpredictability, statistical approaches based on probability distribution functions are critical for assessing wind energy potential at a specific height. equation (1) and (2) depict the weibull probability density function (pdf), represented as f(v), and the cumulative distribution function (cdf), denoted as f(v) [1]. 𝑓(𝑣) = 𝑘 𝑐 (∀)𝑘−1 × exp[−(∀)𝑘] (1) 𝐹(𝑣) = 1 − exp[−(∀)𝑘] (2) in (3), v corresponds to wind speed, k is a parameter without units, and c possesses the same dimensions as v. by assigning a value of 2 to k, the distribution function undergoes a transformation into the rayleigh distribution function. the expressions for the values of k and c are given in equations (6) and (7), respectively. ∀ = 𝑣 𝑐 (3) the average monthly wind speed and the standard deviation (s.d) of the collected data, both expressed in m/s, were calculated from the wind data , also in m/s, using (4) and (5), respectively (mudasiru et al, 2018). 𝑉𝑚𝑒𝑎𝑛 = 1 𝑛 ∑ 𝑉𝑖 𝑛 𝑖=1 (4) s. d = [ 1 n−1 ∑ (vi − vmean)2n i=1 ] 1 2⁄ (5) in this context, n represents the number of observed monthly wind speed data points. 𝑘 = ( 𝑆.𝐷 𝑣 )−1.086 , (1 ≤ 𝑘 ≤ 10) (6) c = v ℶ(1+ 1 k ) (7) where ℶ(x) is gamma function of expressed in (8). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com seidu et al: wind energy assessment in auchi, nigeria using weibull distribution and nasa data. azojete, 20(2):417-426. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 419 ℶ(𝑥) = ∫ 𝑡𝑥−1exp (−𝑡)𝑑𝑡 ∞ 0 (8) according to (1), the calculated mean wind speed, determined using the weibull parameters, is approximated using (9), derived from (7). 𝑣𝑎 = 𝑐ℶ (1 + 1 𝑘 ) (9) in order to assess the effectiveness of the weibull distribution model in estimating wind speeds concerning acquired meteorological data,it is common to analyze the root mean square error (rmse), coefficient of determination (𝑅2), and relative error (re) (aziz et al., 2023). however, for our study, we will specifically focus on the rmse and r2 metrics, as described in equations (10) (teimouriane et al., 2022) and (11) (mohammadi et al., 2016). rmse = [ 1 n ∑ (yi − xj) 2n i=1 ] 1 2⁄ (10) 𝑅2 = 1 − ∑ (𝑦𝑖−𝑥𝑗) 2𝑛 𝑖=1 ∑ (𝑦𝑖−𝑦𝑚)2𝑛 𝑖=1 (11) r2, also known as the coefficient of determination, is the statistic that assesses the goodnessof-fit of a regression model, indicating the portion of dependent variable variation explained by the independent variable(s) (abou et al., 2023). it is a value that ranges from 0 to 1, with 0 indicating that the independent variable(s) have no explanatory power, and 1 indicating a perfect fit where the independent variable(s) can explain all of the variance in the dependent variable (zambak et al., 2023). rmse quantifies the average disparity between predicted and actual values in a dataset, making it a widely employed metric for evaluating the accuracy and suitability of regression models (teimourian et al., 2022). where𝑦𝑚 , represents the mean frequency, 𝑦𝑖 , corresponds to the observed frequency, and 𝑥𝑗 pertains to the estimated frequency of wind speed. 2.2. site and data description this study centers on auchi, a community in edo state, nigeria, located at approximately 7.0669° n latitude and 6.2748° e longitude. monthly wind speed data for energy assessment over 11 years (2012 to 2022) were obtained from nasa and measured at a height of 10 m. 2.3 vertical wind speed profile modelling wind speed exhibits vertical variability, gradually increasing with altitude until reaching a maximum value at a specific height. establishing the wind speed at the wind turbine's hub height is essential. this relationship is described by a power law, as shown in (12) (adedipe et al., 2018). v2 = v1 × ( h2 h1 )α (12) in this context, the estimated wind speed 𝑉2 at the desired practical height 𝐻2, is derived from the measured wind speed 𝑉1 at a known height 𝐻1 by accounting for the influence of surface roughness coefficient α on the wind profile. its value varies with factors like height, time, season, terrain, wind speed, and temperature, calculated using (13) (aljeddani et al., 2023). α = 0.37−0.088lnv1 1−0.088ln ( h1 10 ) (13) 2.4 wind power density prediction wind power potential at a site (14) is determined by analyzing the average wind speed swept by the rotor blades (akdağ and dinler, 2009). p(v) = a×ρ×vmean 3 2 (14) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):417-426. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 420 here, ρ (1.225 kg/m³) denotes air density, considering variations with factors like air pressure, temperature and altitude. the rotor blade swept area a in m². wind power density, calculated using the formula in (15) with the weibull pdf (parvin et al., 2023), represents wind power per unit area. p(v) = p(v) a = ℶ×c3×ρ( 3 k +1) 2 (15) the general sequence of stages in the assessment process for potential power evaluation is shown in figure 1. start import wind speed data fit weibull model evaluate weibull performnace prepare and clean data error output model statistical variation tabulate and print weibull performance (mean wind speed and wind speed power density) figure 1: methodology flow chart 3. results and discussion in 2015, the highest average wind speed was recorded, while 2013 had a moderate mean speed. notably, october and november showed the lowest mean speeds at 3.94 m/s and 4.62 m/s, respectively, which corresponds to the findings of (ogbeide et al., 2018) while january, february, and december exhibited high mean speeds at 10.59 m/s, 9.45 m/s, and 8.04 m/s. the surface roughness coefficients obtained using (13) for each year are listed in table 1. table 1. surface roughness coefficient value year 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 𝛼 0.212 0.208 0.218 0.203 0.209 0.216 0.210 0.217 0.207 0.217 0.213 𝑉𝑚𝑒𝑎𝑛 6.049 6.332 5.642 6.636 6.263 5.748 6.172 5.704 6.400 5.716 5.940 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com seidu et al: wind energy assessment in auchi, nigeria using weibull distribution and nasa data. azojete, 20(2):417-426. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 421 3.1 parameters of the weibull distribution and density function table 2 presents the weibull parameters c and k, power density (p), and the error measure rmse and for wind speed data collected at 10 m for 11 years. table 2. annual performance metrics for the weibull distribution year (m/s) k c (m/s) p(w) 𝐑𝟐 rmse 2012 6.049 8.5164 6.3490 149.3785 1.00000 0.251 2013 6.332 4.9512 6.8597 175.8379 1.00000 0.168 2014 5.642 9.1577 5.9634 124.3886 1.00000 0.258 2015 6.636 4.3593 7.2240 202.416 1.00000 0.164 2016 6.263 6.2782 6.7209 170.1381 0.99999 0.237 2017 5.748 10.4829 6.0298 131.5783 0.99991 0.252 2018 6.172 8.8483 6.5346 162.8481 1.00000 0.172 2019 5.704 4.7162 6.2051 128.5687 1.00000 0.496 2020 6.400 5.5440 6.9074 181.5927 1.00000 0.300 2021 5.716 7.6065 6.0688 129.3591 1.00000 0.184 2022 5.940 5.8440 6.4074 145.8137 1.00000 0.260 3.2 wind speed variation the data for the eleven-year period, showing the average monthly wind speed at a 10-meter height, indicates that october and november exhibited the lowest mean wind speeds throughout the given years, whereas december to march displayed the highest mean wind speeds on average. these fluctuations can be ascribed to the shifts between the dry season and harmattan season, along with the transition from the hot season to the rainy season. during the intermediate periods, the mean wind speed remains relatively moderate. figure 2 – 12 shows the mean monthly speed obtained from nasa. figure 2: wind speed data 2012 figure 3: wind speed data 2013 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):417-426. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 422 figure 4: wind speed data 2014 figure 5: wind speed data 2015 figure 6: wind speed data 2016 figure 7: wind speed data 2017 figure 8: wind speed data 2018 figure 9: wind speed data 2019 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com seidu et al: wind energy assessment in auchi, nigeria using weibull distribution and nasa data. azojete, 20(2):417-426. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 423 figure 10: wind speed data 2020 figure 11: wind speed data 2021 figure 12: wind speed data 2022 the weibull scale parameter (c) ranges from 5.9634 m/s to 7.2240 m/s, c tends to be smaller than k for wind speed data, with k ranging from 4.9512 to 10.4829. the annual power density varies from 124.3886 w/m² to 181.5927 w/m², as illustrated in figure 13 for each year. figure 13: annual weibull probability density function http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):417-426. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 424 the highest peak wind speed was observed in 2018, which was closely followed by 2014, both exhibiting more focused distributions. in contrast, 2022 and 2020 show lower and broader distributions, indicating fewer instances of high wind speeds. meanwhile, 2016 falls in between, signifying a transitional phase. the wind speed distribution in this study best fits within the 3 m/s to 7 m/s interval. figure 14 illustrates the cumulative probability distribution of the weibull function for wind speed data at a 10 m height from 2012 to 2022. figure 14: annual weibull wind speed probability distribution by setting a wind speed threshold of 3.5 m/s, the frequency spans from 0% to 5%. raising the threshold to 5 m/s expands the range to 10% to 30%. at 7 m/s, the frequency extends from 60% to 96%, and at 10 m/s, it sharply concentrates around 98%. based on the cumulative probability, it is indicated that at a wind speed of approximately 3.5 m/s, there exists a potential to generate a substantial amount of wind energy, ranging from 10% to 30%, from the wind farm, varying by year. moreover, an escalation in wind speed will result in an increase in the harvestable wind energy. this is in agreement with the findings of (abdulkarim et al., 2017) and (gaddafi et al., 2017). 3.3 wind speed power density figure 15 depicts wind speed data over eleven years (2012 to 2022), highlighting variations in annual wind speed power density at both 10 m and 100 m height levels based on annual averages. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com seidu et al: wind energy assessment in auchi, nigeria using weibull distribution and nasa data. azojete, 20(2):417-426. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: oyarebu209@gmail.com 425 figure 15: annual wind speed power density at 10 m and 100 m, november and may had the lowest power density (61.8324 w/m², 82.2259 w/m²) and (293.1663 w/m², 325.2405 w/m²), respectively. february and august recorded the highest power density at 10 m (208.5994 w/m², 202.6488 w/m²) and at 100 m (899.5688 w/m², 852.6808 w/m²) for february and july. power density at 100 m is about four times higher than at 10 m, representing average monthly values. 4. conclusion the study assessed the wind energy potential in auchi community in edo state, utilizing the weibull distribution function and nasa wind speed data from 2012 to 2022. results indicate that auchi experiences moderate and consistent wind speeds (ranging from 5.642 m/s to 6.636 m/s) that increase with altitude, indicating favorable conditions for wind energy generation and electrification. additionally, the analysis explored the influence of seasonal fluctuations and surface roughness on wind speed distribution and power density. these findings augment the existing body of knowledge on wind energy assessment in nigeria and offer valuable insights for prospective wind farm projects in the area. nevertheless, further investigation is necessary to evaluate the economic viability and environmental ramifications of implementing wind turbines in auchi, alongside determining optimal design and 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economics and policy, 13(2): 427-432. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):387-402 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 387 original research article assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process d. o. akuboh1*, m. saidu1, a. s. abdulkareem2 and a. o. busari1 1department of civil engineering, federal university of technology, minna, nigeria 2department of chemical engineering, federal university of technology, minna, nigeria *corresponding author’s email address: dominicakuboh@yahoo.com 1.0 introduction water is a basic need required by plants and animals especially human being. developing countries are faced with the challenge of potable water supply due to inadequate funding. the cost of water treatment is increasing and the quality of river water is not stable due to suspended and colloidal particle load caused by land development and high storm runoff during the rainy seasons. during the rainy season the turbidity level increases thereby increasing the cost of water treatment. this could affect the quality of drinking water being supplied to consumers. therefore, it is of important to find a natural alternative for water coagulant to treat the turbidity. these alternatives to chemical coagulants are referred to as nature-based solutions for water (wwdr, 2018). nature-based solutions for water may be employed to address water availability, improved water quality and reduce risks associated with water related disasters and climate change (wwdr, 2018). globally, the amount of resources available to meet human needs is limited. safe drinking water is essential to the health and wellbeing of a community, and water from all sources must have some form of purification before consumption (arnoldson et al., 2008, muhammad et al., 2015). article information abstract globally, chemical coagulants such as alum are employed in water treatment during coagulation and flocculation process to improve drinking water quality. this process has an effect on human health. this research was carried out to assess the potentials of a plant-based coagulant (cyperus esculentus pulp) as substitute for alum or as coagulation aids. the water sample from river gorao along minna-bida road in niger state were obtained in line with the standard laboratory procedures of the american public health association (apha) for the evaluation of the efficacy of the two coagulants (plant-based coagulant – cyperus esculentus) and aluminium sulphate (alum). jar test was done for some turbidity range. the results showed turbidity and colour removal efficiencies of 80.47% and 55.37% respectively. the water quality index (wqi) shows that cyperus esculentus produces good quality water (grade b) with wqi of 44.5. recommendations arising from this study includes that further investigation should be carried out on other potential plant-based coagulants. yellow variety of cyperus esculentus should be investigated for its coagulation potentials and the use of cyperus esculentus as coagulant is recommended as coagulant aid for reduction of turbidity in water. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 january, 2021 revised 30 march, 2022 accepted 6 april, 2022 keywords: alum colour cyperus esculentus turbidity water quality http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com mailto:dominicakuboh@yahoo.com mailto:omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):387-402. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 388 drinking water treatment involves a number of combined processes based on the quality of the water source such as turbidity, amount of microbial load present, others may include cost and availability of chemicals in achieving desired level of treatment (muhammad et al., 2015). conventional methods used for purification of water include coagulation, sedimentation, filtration, aeration and disinfection. in drinking water treatment, the coagulation process is used to destabilize suspended particles and to react with organic materials in the raw water. proper coagulation is essential for good filtration performance and for disinfection by product (dbp). common coagulants are aluminium sulphate, ferric chloride, poly-aluminium chlorides and synthetic polymers. the use of coagulants such as alum is one of the commonest methods employed which reduce the repulsive force between particulate matter, encouraging particle collision and floc formation (muhammad et al., 2015). similarly, in wastewater treatment, coagulation has been practiced with the intention of removing colloidal impurities causing turbidity in the water (saharudin and nithyanandam, 2014). aluminium and iron coagulants are the most commonly used for the treatment of wastewater. however, when aluminium is used as a coagulant in wastewater treatment, it could have adverse effect on human health such as intestinal constipation, loss of memory, convulsions, abdominal colic’s, loss of energy and learning difficulties (sulaiman et al., 2017). therefore, nowadays great attention is given to the improvement and implementation of natural coagulants in wastewater treatment too. natural coagulants can be extracted from animals, microorganisms and also from natural plants origin (saharudin and nithyanandam, 2014). turbid water that is murky or cloudy in appearance caused by impurities imparts an unpleasant taste to the water and thus has become the impetus behind the need for water treatment (choy et al., 2015). such colloidal particles generally contain fine particles that are difficult to settle by gravity and are usually negatively charged (kim et al., 2001). throughout flocculation, the size of the flocs will continue to grow until they reach the steady-state floc size distribution. muhammad et al. (2015) conducted a study on water melon for water treatment and recommended that more natural sources should be investigated for potential coagulation abilities. similarly, sulaiman et al. (2017), carried out a study on moringa oleifera for water treatment and concluded that moringa oleifera seed extract is a potential source for water treatment due to its efficiency. some plant-based coagulants have been investigated by various authors till date. moringa oleifera seeds extracts were investigated by ogunlela and famakinwa (2016, amagloh and benang (2009), oria-usifo (2014 and sulaiman et al. (2009). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 similarly, citrullus lanatus (water melon) seeds extracts was investigated by muhammad et al. (2015) and phoenix dactylifera (date palm) seed extracts was investigated by saleem et al. (2019) and al-sameraiy (2012). additionally, many other plant-based coagulants comprising habiscus esculentus, jatropha curcas, ceratonia siligua (locust bean), hylocereus undatus (dragon fruit), mangifera indica (mango), pisum sativum (pea), tamerindous indica (tamarind), zea may (corn) and vigna unguiculata (cowpae) were investigated by saleem et al. (2019). vigna unguiculate was also investigated by choy et al. (2015). muhammad et al. (2015) concluded their research on the use of water melon as a potential coagulant for water treatment by recommending that more natural sources should be investigated for potential coagulation abilities. naturally occurring coagulants are usually presumed safe for human health (ogunlela and famakinwa, 2016). the above narratives justify the reason why we are investigating the potential of tiger nuts (cyperus esculentus) pulp in comparison with alum in this study. a number of studies have pointed out that the introduction of natural coagulants and adsorbents as a substitute for metal salts may ease the problems associated with chemical coagulants. using natural coagulants instead of aluminium salts might give advantages, such as lower cost of water production, less sludge production and ready availability of reagents. there are also disadvantages such as increased concentration of nutrients and chemical oxygen demand (cod) in the treated water due to the organic nature of this type of coagulants (muhammad et al., 2015). from the foregoing, the development of natural, environmentally-friendly/biodegradable, renewable, cost-effective, easy to use and alternative sources of water treatment by recycling and re-use of organic wastes especially for use in rural areas and developing countries can therefore not be over-emphasized. classification of tiger nut extracted from the review work of bamishaiye and bamishiaye (2011) and oyedele et al. (2015) reveals that tiger nut (cyperus esculentus) is a grass-like tuber plant and an annual/perennial plant. it is mainly available in the north and thrives in a few southern regions in nigeria in areas synonymous to the sudan and guinea savannah. it is available in black, brown and yellow specie. its uses include human consumption, livestock fees and erosion control. its native name in hausa language is ‘aya’ and it belongs to the family of cyperaceae. its chemical composition includes sodium, calcium, potassium magnesium, iron, zinc and traces of copper while it’s nutrient constituents includes moisture, lipid, fibre, protein, ash, starch, reducing sugar and total sugar. the aim of the study is to determine the potential of using tiger-nuts (cyperus esculentus) pulp as coagulant in water treatment. 2. materials and methods 2.1 materials procurement and instrumentation the materials used for the study includes tiger nut (cyperus esculentus) – dried brown variety with origin from jibiya in katina state, nigeria and aluminium sulphate (alum) obtained from the lower usuma dam water treatment plant in abuja, distilled water and raw water from river goroa obtained from gorao river along minna-bida road, niger state, nigeria. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):387-402. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 390 laboratory reagents employed were as specified by the standard method for the examination of water and wastewater by the american public health association (apha). they include hydrocholoric acid, methyl orange indicator, calcium oxide, sodium hydroxide. sulphate, hr nitrate, nitrite and phosphate pillets. equipment used includes flocculator (stuart sw6), conductivity meter (jenway 4520), cod reactor (hach), magnetic stirrer (stir), spectrophotometer (hach, dr 5000), calorimeter (hach dr/890), turbidity meter, dissolved oxygen metre, ph meter, digital weighing balance and burner. others include laboratory equipment such as titration apparatus, beakers, conical flasks, measuring cylinder, spatula, grinding machine, pestle and mortar, two (2) 150ml and eighteen (18) 75ml plastic bottles for water samples. 2.2. methods 2.2.1. raw water sample, coagulants sample collection and experimental procedure the raw water sample was collected from river goroa, minna-bida road, where local gold mining occurs. all standard procedures for sample collection, storage, transportation and preservation stipulated by apha were observed. tiger nuts (cyperus esculentus) were obtained from some traders in jibiya market, katsina state. alum and cyperus esculentus coagulant solutions were prepared using 10g/100ml of distilled water and added to the water samples at various doses during the jar test to determine its effect on flocculation and sedimentation as well as coagulant optimum dose. the above process was repeated using a combination of alum and plant-based materials as coagulants aid. the raw water sample was tested before and after treatment. thereafter, physical, chemical and bacteriological characteristics were conducted in accordance with the procedures of the american public health association (apha), american water works association (awwa) and the world environment federation (wef) standard for the examination of water and wastewater. jar tests were conducted to determine optimum or effective dosage of a coagulant to be applied in treatment of the raw water. in this case, alum was replaced by prepared tiger nut wastes respectively to determine the optimum dose. a stuart flocculator equipped with a six (6) number of paddles for rapid and slow mixing is used. a turbidimeter is used for turbidity measurements in the process after a given settling time. 100ml of the raw water were measured in six number 100ml beakers each and the paddles inserted in each. the flocculator was switched on at a speed of 250rpm for 3 minutes for rapid mixing. after 3 minutes, the speed was reduced to 25rpm for slow missing and this continued for 17 minutes for coagulation/flocculation. 30 minutes settling time was allowed before the residual turbidity and other water quality parameters were measured. the raw water and coagulated water samples are presented in figure 1 (a) and (b) for clarity. figure 2 shows the nature of cyperus esculentus plant, fruit, seed and seed power to be used as coagulant aid. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 figure 1(a): raw water samples figure 1(b): coagulated water samples a. alum crystal b. tiger nut plant c. tiger nut tuber (brown variety) d. tiger nut pulp (grinded) figure 2: alum crystal, tiger nut plant, tuber and prepared bio-coagulant. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):387-402. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 392 2.2.2. preparation of coagulant solutions a. alum coagulant solution alum was sourced from the lower usuma water treatment plant store, abuja and subsequently broken down into crystals and crushed in the laboratory into smooth powdered form. 10g of the powdered alum was measured on the weighing scale and mixed with 100ml distilled water and stirred properly with the aid of electric magnetic stirrer in the laboratory. b. cyperus esculentus pulp as coagulant solution dried cyperus esculentus (brown variety) were sourced from jibiya in katsina state, nigeria and subsequently used in production of milk. the waste generated from the extraction of milk was then sun properly sun-dried, ground and sieved using the least available domestic sieve. 10g of the powdered cyperus esculentus pulp was measured on the weighing scale and mixed with 100ml distilled water and stirred properly by the aid of electric magnetic stirrer in the laboratory. figures 3 and 4 show the research flow charts and the one for the preparation of the bio-coagulant. figure 5 shows the flocculator used for the experiment. source for water sample, chemical and plant-based coagulants i.e. alum, date palm seeds and tiger nut pulp water sample transportation laboratory measurement of raw water quality parameters prepare and process plantbased coagulant i.e. tiger nut pulp process alum crystals by pounding into powdered form conduct jar test using alum solution as coagulant conduct jar tests using plant-based coagulant i.e. tiger nut pulp (cyperus esculentus) measure water quality parameters of optimum jars for each coagulant with lowest turbidity and colour combination in the laboratory repeat jar test with mix of alum + plant-based coagulant in proportions of 80:20, 60:40, 40:60 and 20:80 percent respectively compute turbidity and colour removal efficiencies and water quality index (wqi) of raw water and all optimum jars compare results and classify water treated by the various coagulant sources according to their wqi figure 3: research flow chart file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 dried tiger nut (cyperus esculentus) – brown variety sorting soaking grinding filter through white cloth using water milk rap residue in the white cloth and place load to remove water sun-dry residue (pulp figure 4: flow diagram for preparation of cyperus esculentus bio-coagulant figure 5: jar test equipment (flocculator) 2.2.3. water quality tests the quality of the raw water/wastewater is tested before and after treatment with the optimum dose obtained from the jar test (after filtration) for its physico-chemical and bacteriological parameters in line with the apha examination of water and wastewater guidelines and compared with native or who (2012) water quality standards for conformity or otherwise. some of the physico-chemical water quality parameters investigated includes ph, turbidity, colour, electrical conductivity, total dissolved solids (tds), aluminium, iron, lead, calcium, magnesium, manganese, sulphate, chloride, nitrate, nitrite, chromium, hardness, alkalinity, biochemical oxygen demand (bod), chemical oxygen demand (cod) and dissolved oxygen (do). http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):387-402. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 394 2.2.5 methods for determination of water quality parameters. the methods for the determination of water quality parameters in the laboratory are as stipulated by the american public health association handbook for the examination of water and wastewater. 2.2.6. method for water quality index determination the weighted arithmetic water quality index was employed in the determination of the water quality indices for the raw water, chemical and plant-based coagulated water samples. weighted arithmetic water quality index method classified the water quality according to the degree of purity by using the most commonly measured water quality variables. the method has been widely used by various scientists and the calculation of wqi was made by using the following equation wqi = ∑qiwi wi (1) the quality rating scale (qi) for each parameter is calculated by using this expression: qi = 100(vi−vo) (si−vo) (2) where, is estimated concentration of ith parameter in the analysed water is the ideal value of this parameter in pure water = 0 (except ph =7.0 and do = 14.6 mg/l) is recommended standard value of ith parameter the unit weight (wi) for each water quality parameter is calculated by using the following formula: wi = 𝐾 𝑆𝑖 (3) where, = proportionality constant and can also be calculated by using the following equation. (4) k is equal to unity (armah et al, 2012). 3. results and discussion the results obtained from the laboratory investigation of the raw and treated water samples using alum and cyperus esculentus are compared with who (2012) guidelines for drinking file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 water quality in this section. the results were further analysed to ascertain the efficiencies of turbidity and colour removal for the three coagulants. table 1 below shows the inherent average raw water parameters. table 1: average raw water quality parameters note: all measurements requiring measuring devices were repeated at least three times. 3.1. coagulated water using alum two jar tests were conducted using alum as coagulant in 2020 and 2021 respectively. the jar test results using alum solution as coagulant in 2020 and 2021with floc formation time of less than a minute were achieved. the results of jar tests carried out using alum solution as coagulant in 2020 and 2021 were well documented with floc formation time of majorly less than a minute. the computation of turbidity and colour removal efficiencies are presented in tables 2-5. table 2: trial turbidity removal efficiency for 100% alum 2020 s/no. parameter chemical notation unit average conc. maximum limit (who) maximum limit (nsdwq) 25th feb., 2020 19th march, 2021 1 colour colour pt.co 405 1383 894 15 15 2 odour odour unobjectionable unobjectionable 3 taste taste unobjectionable unobjectionable 4 temperature t o c 27.7 27.8 27.75 ambient 5 turbidity tur. ntu 50 192 121 5 5 6 ph ph 7.22 7.05 7.135 6.5 8.5 6.5 8.5 7 electrical conductivity ec µs/cm 286 222 254 250 1000 8 total dissolved solid (tds) tds mg/l 251 144 197.5 1000 500 9 aluminium al mg/l 22.4 32.4 27.4 0.2 0.1 10 alkalinity mg/l 106 106 120 11 bod bod5 mg/l 102 1.9 51.95 6 2 12 dissolved oxygen do mg/l 5.5 7 6.25 5 7.5 13 chloride cl mg/l 24.9 31.9 28.4 250 250 14 calcium ca mg/l 32.1 30 31.05 75 75 15 magnesium mg mg/l 17.1 22 19.55 50 0.2 16 manganese mn mg/l 1.2 1.2 0.1 to 0.5 0.4 17 chromium cr mg/l 0.08 0.05 0.065 0.1 0.05 18 cod cod mg/l 4 11.00 7.5 10 1000 19 copper cu mg/l 0.016 0.86 0.438 1 to 2 20 zinc zn mg/l 0 0 2 5 21 iron fe mg/l 3.11 1.62 2.365 0.3 0.3 22 lead pb mg/l 0.001 0.003 0.002 0.01 0.01 23 sodium na mg/l 40 40 200 200 24 potasium k mg/l 14 14 25 sulphate so4 mg/l 7 7.00 7 250 100 26 flouride f mg/l 0.7 0 0.35 1.5 1.5 27 nitrite no2 mg/l 0.139 0.091 0.115 3 0.2 28 nitrate no3 mg/l 7.46 12.5 9.98 50 0.2 29 hardness mg/l 120 60 200 150 30 phosphate po4 3mg/l 0.26 31 total coliform count tcc mpn 84 1530 807 0 10 32 e-coli (faecal coliform) e-coli cfu/100ml 14 645 329.5 0 0 a. physical parameters b. chemical parameters c. bacteriological parameters concentration jar alum dose (mg/l)initial turbidity (to) (ntu) final turbidity (tf) turbidity removal efficiency te = (to tf)/to *100 1 10 121.00 2.74 97.74 2 20 121.00 2.30 98.10 3 30 121.00 2.67 97.79 4 40 121.00 2.73 97.74 5 50 121.00 3.17 97.38 6 60 121.00 2.74 97.74 average te 97.75 http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):387-402. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 396 table 3: turbidity removal efficiency for 100% alum 2021 average turbidity removal efficiency for alum = (97.75 + 94.92)/2 = 96.34 table 4: trial colour removal efficiency for 100% alum 2020 br – below range table 5: colour removal efficiency for 100% alum 2021 average colour removal efficiency for alum = (99.18 + 83.82)/2 = 91.50 3.2. coagulated water using 100% cyperus esculentus jar test was conducted using ceperus esculentus pulp solution as coagulant. the computation of turbidity and colour removal efficiencies arising from the results of the jar test are presented in tables 6 and 7. table 6: turbidity removal efficiency using 100% cyperus esculentus turbidity removal efficiency ratio = te(cyperus esculentus/te(alum) x 100 = (80.47/96.34) x 100 = 83.53% jar alum dose (mg/l)initial turbidity (to) (ntu) final turbidity (tf) turbidity removal efficiency te = (to tf)/to *100 1 10 121.00 4.95 95.91 2 20 121.00 5.41 95.53 3 30 121.00 5.78 95.22 4 40 121.00 6.64 94.51 5 50 121.00 7.16 94.08 6 60 121.00 6.91 94.29 average te 94.92 jar alum dose (mg/l)initial colour (co) (pt. co) final colour (cf) colour removal efficiency ce = (co -cf)/co *100 1 10 894.00 1.00 99.89 2 20 894.00 br 3 30 894.00 br 4 40 894.00 br 5 50 894.00 15.00 98.32 6 60 894.00 6.00 99.33 average ce 99.18 jar alum dose (mg/l)initial colour (co) (pt. co) final colour (cf) colour removal efficiency te = (co cf)/co *100 1 10 894.00 215.00 75.95 2 20 894.00 154.00 82.77 3 30 894.00 65.00 92.73 4 40 894.00 br 5 50 894.00 br 6 60 894.00 br average cf 83.82 jar cyperus esculentus initial turbidity (to) (ntu) final turbidity (tf) turbidity removal efficiency te = (to tf)/to *100 1 10 121.00 31.90 73.64 2 20 121.00 20.80 82.81 3 30 121.00 22.80 81.16 4 40 121.00 23.80 80.33 5 50 121.00 20.20 83.31 6 60 121.00 22.30 81.57 average te 80.47 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 table 7: colour removal efficiency using 100% cyperus esculentus colour removal efficiency ratio = ce(cyperus esculentus)/ce(alum) x 100 = (55.37/91.50) x 100 = 60.50% 3.3. combination of alum and plant-based coagulants 3.3.1 coagulated water test results – combination of alum and cyperus esculentus as coagulation aid in varying percentages. jar test was conducted at the optimum cyperus esculentus coagulant dose of 50 mg/l and a lower dose of 40 mg/l for the purpose of comparison using a combination of alum and cyperus esculentus as coagulant using alum: cyperus esculentus ratio of 80%:20%, 60%:40%, 40%:60% and 20%:80% respectively. this step was predicated on the fact that the turbidity and colour removal efficiencies of cyperus esculentus even though close to that of alum did not exceed it. it was clear that 80% alum and 20% cyperus esculentus coagulant produced the optimum jar with turbidity of 6.40 ntu and colour of 71 pt.co at a temperature of 28.0oc. 3.4. summary of results for turbidity and colour removal efficiencies and optimum dose and combination of the plant-based coagulants with alum the summary of the turbidity and colour removal efficiencies as well as the optimum dose and percentage coagulant combination with alum are presented in tables 8 and 9 below. table 8: summary of turbidity, colour removal efficiencies, optimum dose and proportion of coagulant combination with alum. note: averages of te and ce for alum are 96.34% and 91.50% respectively. alum is 20% more efficient in turbidity removal and 65% more efficient in colour removal than cyperus esculentus coagulant from the results of the study. jar cyperus esculentus dose initial colour (co) (pt. co) final colour (cf) colour removal efficiency ce = (co cf)/co *100 1 10 894.00 508.00 43.18 2 20 894.00 388.00 56.60 3 30 894.00 392.00 56.15 4 40 894.00 403.00 54.92 5 50 894.00 344.00 61.52 6 60 894.00 359.00 59.84 average cf 55.37 turbidity removal efficiency colour removal efficiency optimum proportion in combination with alum optimum combined coagulant dose te (%) ce (%) alum/nature-based coagulant d(%) 1 alum 94.92 97.75 83.82 99.18 n/a n/a n/a n/a 2 cyperus esculentus 80.47 55.37 1.20 1.65 80/20 50 s/no coagulant te(alum average)/te ce(alum average)/ce http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com corresponding author’s e-mail address: dominicakuboh@yahoo.com 398 table 9: consolidated experimental results 2020 2021 100% 80% alum + 20% c.e@ 40mg/l 80% alum + 20% c.e@50mg/l 1 colour colour pt.co 15 1,383.00 br 154 154 344 105 71 2 odour odour non-objectionable non-objectionable non-objectionable non-objectionable non-objectionable non-objectionable non-objectionable 3 taste taste non-objectionable non-objectionable non-objectionable non-objectionable non-objectionable non-objectionable non-objectionable 4 temperature t o c 27.80 27.70 27.80 27.75 29.60 28.30 28.00 5 turbidity tur. ntu 5 192.00 50.00 192.00 121.00 20.20 7.15 6.40 6 ph ph 6.5 8.5 7.05 7.22 7.05 7.14 7.40 7.20 7.20 7 electrical conductivity ec µs/cm 250 222.00 286.00 222.00 254.00 241.00 249.00 253.00 8 total dissolved solid tds mg/l 1000 144.00 251.00 144.00 197.50 144.40 147.30 140.30 9 aluminium al mg/l 0.2 32.40 1.4 1.4 1.40 1.4 1.5 1.4 10 alkalinity mg/l 120 106.00 106 106 106 94 86 84 11 bod bod5 mg/l 6 1.90 0.80 0.80 0.80 0.40 1.20 1.00 12 dissolved oxygen do mg/l 5 7.00 8.00 8.00 8.00 8.00 7.20 8.80 13 chloride cl mg/l 250 31.90 35.80 21.80 28.80 18.00 18.00 18.00 14 calcium ca mg/l 75 30.00 35.30 24.00 29.65 25.60 17.60 25.60 15 magnesium mg mg/l 50 22.00 10.20 10.90 10.55 25.90 30.20 26.30 16 manganese mn mg/l 0.1 to 0.5 1.20 2.50 1.60 2.05 0.90 0.40 0.30 17 chromium cr mg/l 0.1 0.05 0.01 0.01(br) 0.00 0.00 0.00 0.00 18 cod cod mg/l 10 11.00 0.00 0.00 0.00 0.00 0.00 0.00 19 copper cu mg/l 1 to 2 0.86 0.004 0.004 0.004 0.008 0.009 0.003 20 zinc zn mg/l 2 0.00 21 iron fe mg/l 0.3 1.62 0.07 0.07 0.07 0.27 0.05 0.11 22 lead pb mg/l 0.01 0.003 0.003 0.003 0.003 0.001 0.001 0.001 23 sulphate so4 mg/l 250 7.00 66.00 21.00 43.50 3.00 14.00 15.00 24 flouride f mg/l 1.5 0.00 25 nitrite no2 mg/l 3 0.091 0.005 0.008 0.0065 0.009 0.002 0.002 (br) 26 nitrate no3 mg/l 50 12.50 0.20 0.80 0.50 4.40 1.60 1.30 27 hardness mg/l 200 120.00 182.00 96.00 139.00 90.00 96.00 96.00 28 phosphate po4 3mg/l 0.26 0.32 0.39 0.355 4.00 0.62 0.14 29 total coliform count tcc mpn 0 1530.00 0.00 46.00 46.00 58.00 146.00 74.00 30 e-coli (faecal coliform) e-coli cfu/100m 0 645.00 0.00 12.00 12.00 24.00 46.00 34.00 c. bacteriological parameters b. chemical paramaters/cations cyperus esculentus (c.e) coagulation a. physical parameters coagulant s/no. parameter chemical notation unit maximum limit (who) raw water alum coagulation average for alum mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 3.5. water quality index determination and coagulated water classification weighted arithmetic water quality index was employed in the determination of the water quality indices after the use of all coagulants in this research. initial computations of wqi and the summary of the computations is tabulated in table 10 and 11. table 10: computation of wqi for raw water table 11: consolidated results for water quality index and water quality classification for the coagulants/coagulant mix used 3.6 discussion of results 3.6.1 colour the initial average water colour in table 1 was 1383 pt-co. while the least colour out of the coagulants combination used from tables 2 to 5 stands at 71pt.co using 100% alum and 20% cyperus esculentus coagulant at 50mg/l. the w.h.o and nsdwq acceptable maximum standard for drinking water is 15pt-co (table 1). this indicates that the alum-cyperus esculentus combination in the above proportion reduced the initial average colour of the raw water 19.479 times (1,948%) to 71pt.co. though, above the w.h.o guideline and nsdwq by 56 pt.co., raw water sample standard permissible level as per who guidelines ideal value unit weight (wi) quality rating qi vi si vo (1/si) ((vi vo)/(si vo))*100 1 calcium ca mg/l 31.05 75 0.00 0.0133 41.40 0.55 2 magnesium mg mg/l 19.55 50 0.00 0.0200 39.10 0.78 3 manganese mn mg/l 1.20 0.5 0.00 2.00 240.00 480.00 4 chromium cr mg/l 0.07 0.1 0.00 10.00 65.00 650.00 5 iron fe mg/l 2.365 0.3 0.00 3.33 788.33 2,627.78 6 lead pb mg/l 0.002 0.01 0.00 100.00 20.00 2,000.00 7 chloride cl mg/l 28.40 250 0.00 0.00 11.36 0.05 8 sulphate so4 mg/l 7.00 250 0.00 0.00 2.80 0.01 9 nitrate no3 mg/l 9.98 10 0.00 0.1000 99.80 9.98 10 nitrite no2 mg/l 0.115 3 0.00 0.33 3.83 1.28 11 dissolved oxygen do mg/l 6.25 5 14.60 0.20 86.98 17.40 12 biochemical oxygen demand bod5 mg/l 51.95 6 0.00 0.17 865.83 144.31 13 chemical oxygen demand cod mg/l 7.50 10 0.00 0.10 75.00 7.50 14 turbidity tur. ntu 121.00 5 0.00 0.20 2,420.00 484.00 15 colour pt-co 894.00 15 0.00 0.07 5,960.00 397.33 16 total alkalinity mg/l 106.00 120 0.00 0.01 88.33 0.74 17 total hardness th mg/l 9.98 200 0.00 0.01 4.99 0.02 18 ph ph 7.14 8.5 7.00 0.12 9.00 1.06 19 total dissolved solids tds mg/l 197.50 1000 0.00 0.00 19.75 0.02 20 electrical conductivity ec µs/cm 254.00 250 0.00 0.00 101.60 0.41 21 aluminium al mg/l 32.40 0.2 0.00 5.00 16,200.00 81,000.00 ʃwi = 121.68 ʃqiwi = 87,823.21 wqi = ʃqiwi/ʃwi 721.77 grade e: unsuitable for drinking purpose parameters/no notation unit qi*wi s/no description of coagulant/coagulant mix wqi water quality classification wq interpretation as per wawqi 1 raw water 721.77 grade e unsuitable for drinking purpose 2 100% alum 68.21 grade c poor water quality 3 100% cyperus esculentus 44.54 grade b good water quality 4 80% alum + 20% cyperus esculentus 39.61 grade b good water quality http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):377-386. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 402 the processes of filtration and disinfection is expected to improve the colour in a conventional water treatment facility. 3.6.2 turbidity the initial raw water turbidity was 192ntu from table 1 while the least turbidity out of the coagulants used from tables 2 to 5 stands at 6.40 ntu using 80% alum and 20% cyperus esculentus at 50mg/l coagulant dose at 50 ntu. the w.h.o and nsdwq acceptable maximum standard for drinking water is 5 ntu (table 1). this indicates that the cyperus esculentus reduced the initial turbidity of the raw water 30 times (3,000%) to 6.40 ntu. though slightly above the w.h.o guidelines and nsdwq by 1.40 ntu, the processes of filtration and disinfection is expected to bring the turbidity value within acceptable range in a conventional water treatment facility. the floc appearance and settling time using alum were mainly more than and less than a minute in both jar tests performed in 2020 and 2021 respectively from observation. however, using 100% cyperus esculentus, the floc appearance and settling time was mainly less than a minute. 3.7. water quality index and water quality classification the computation of water quality index as exemplified on table 10 and summarised in table 11 shows that 100% cyperus esculentus and 80% alum + 20% cyperus esculentus at 50mg/l produces grade b (good water quality) with wqi values of 44.54 and 39.61 respectively. the raw water was established to have a water quality index of 721.77, grade e and unsuitable for drinking purposes. the potency of 100% cyperus esculentus as in optimum combination with alum as a plant-based coagulant aid was therefore evidently validated by this result. 4.0 conclusion the conclusions arising from this research are drawn as follows: in the work reported, the physical parameters before and after the jar tests, including the resultant analysis of cyperus esculentus pulp shows that it has the potentials to serve as biocoagulant. while cyperus esculentus recorded turbidity and colour removal efficiencies of 80.45% and 55.37%. comparatively, the turbidity and colour removal efficiencies of alum from the research was 97.75% and 99.18% respectively. this implies that alum is more effective than cyperus esculentus coagulant but the turbidity removal efficiency of cyperus esculentus coagulant is more than 80% which is also good. finally, a combination of alum and cyperus esculentus coagulant reveals that the optimum dose of 50mg/l suffices for 80% alum and 20% cyperus eculentus as coagulants. cyperus esculentus coagulant functions optimally and effectively in combination with alum rather than when acting alone. therefore, cyperus esculentus have the capacity to limit the use of alum coagulant by at least 20%. the recommendations arising from this study are as follows: 1. further investigation should be carried out on other potential plant-based coagulants to improve access to clean water for people living in rural areas. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com akuboh et al.: assessing the potentials of a plant-based coagulant (cyperus esculentus pulp) as alternative to alum in conventional water treatment process. azojete, 18(3):387-402. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 401 2. investigation of the potential of yellow variety of tiger nut (cyperus esculentus) as a coagulant in water treatment should be conducted. 3. cyperus esculentus alone has the potential to substantially reduce turbidity and improve overall water quality and its use as a plant-based coagulant aid and partial alternative to alum is recommended. references al.sameraiy, m. 2012. a novel water treatment approach for turbidity removal using date seeds and pollen sheath. journal of water resource and protection, 04(02):79 – 82., doi:10.4236/jwarp.2012.42010 amagloh, fk. and benang, a. 2009. effectiveness of moringa oleifera seed as coagulant for water purification. african journal of agricultural research, 4(1): 119-123. armah, fa., luginaah, i. and ason, b. 2012. water quality index in the tarkwa gold mining area in ghana. the journal of transdisciplinary environmental studies, 11(2): 115. arnoldsson, e., bergman, m., matsinhe, n. and persson, km. 2008.assessment of drinking water treatment using moringa oleifera natural coagulant. vatten 64:137–150. bakare, bf. 2016. an investigation of moringa oleifera seed extract as a natural coagulant in water treatment. proceedings of the world congress on engineering and computer science 2016, october 19 – 21, 2016, san francisco, usa., vol ii., pp. 1-4. bamishaiye, ei. and bamishaiye, om. 2011. tiger nut: as a plant, its derivatives and benefits. african journal of food, agriculture, nutrition and development, 11(5): 5157 – 5170. choy, sy., prasad, km., wu, ty. and ramanan, rn. 2015. a review on common vegetables and legumes as promising plant-based natural coagulants in water clarification. international journal of environmental science and technology, 12(1): 367-390. hdra. 2002. moringa oleifera: a multi-purpose tree. hdra the organic organisation. coventry, uk. kim, sh., moon, bh. and lee, hi. 2001. effects of ph and dosage on pollutant removal and floc structure during coagulation. micro-chem journal, 68:197-203. muhammad, im., abdulsalam, s., abdulkarim, a. and bello, aa. 2015. water melon seed as a potential coagulant for water treatment. global journal of researches in engineering: c chemical engineering, 15(1): 17-23. ogunlela, ao. and famakinwa, jo. 2016. the use of moringa oleifera seed powder for treating recirculatory aquaculture system (ras) discharge. the international journal of science and technology, 4(9): 77 81. oria-usifo, ee., anyata, bu. and ekenta, eo. 2014. use of moringa oleifera seed extracts as alternative natural material for water purification. journal of engineering and applied sciences, 10: 41 – 53. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com http://dx.doi.org/10.4236/jwarp.2012.42010 arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):377-386. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: dominicakuboh@yahoo.com 402 saleem, m., sami, aj. and bachmann, rt. 2020. characterisation and coagulant activity screening of fractionated water-soluble seed proteins from moringa oleifera, materials today: proceedings, https://doi.org/10.1016/j.matpr.2020.03.700, pp. 1-4. sulaiman, m., zhigila, da., mohammed, k., umar, dm., aliyu, b. and manna, fa. 2017. moringa oleifera seed as alternative natural coagulant for potential application in water treatment: a review. journal of advanced review on scientific research, 30(1): 1-11. saharudin, nfa. and nithyanandam, r. 2014. wastewater treatment by using natural coagulant. chemical engineering department, school of engineering, taylor’s university, malaysia. 2nd eureka 2014. who 2012. guidelines for drinking-water quality, fourth edition. world health organization, geneva, switzerland. wwdr. 2018. nature based solutions for water. world water development report, world water assessment programme of unesco financially supported by the government of italy. pp. 24 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dominicakuboh@yahoo.com https://doi.org/10.1016/j.matpr.2020.03.700 arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):493-516 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 493 original research article framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel d. e. salla1*, y. g. musa-haddary2, b. a. kolo2 and y. j. gandu2 1department of quantity surveying, bayero university, kano, nigeria 2department of quantity surveying, ahmadu bello university, zaria, nigeria *corresponding author’s email address: edsalla.qs@buk.edu.ng 1.0 introduction contractor selection decision support systems (cs-dss) are computer-based information systems that are designed to enhance the selection of contractors. these systems become attractive when they align with specific requirement for their use (zhang et al., 2017). however, the acceptance of dsss is a recognized antecedence to their adoption (momani et al., 2017; momani et al., 2018). although cs-dsss abound as readily available prescription from many construction management research, they are generally ignored by the target endusers in the midst of growing pressures on public procurement personnel to use them (bpp, 2011b; ppa, 2007). the neglect of dsss in the face of their obvious relevance, requires a article information abstract laboratory-based designs of contractor selection decision support systems (cs-dsss) are common in construction management research. however, target end-users like the public procurement entities do not usually make use of these ubiquitous technologies in practice, in spite of their enormous potentials. the absence of reliable framework for investigating technology adoption in public procurement has continued to impede the possibilities of investigating the acceptance of such technologies. the present study aims at developing a framework for investigating cs-dss acceptance for the smallest decision making unit in public procurement. the structure of a novel theoretical technopsychological framework for investigating cs-dss acceptance in nigerian public procurement is presented in this paper through the lens of an extended innovation diffusion theory technology acceptance model (idt-tam). from an individual level remit (micro-level), a strategic review of literature was followed by a delphi survey of carefully selected 18-number procurement experts in nigeria. the study shows that the prescriptions of cs-dsss by researchers can be supported by a foresight on the end-user behavioral intension to use such technologies. operationalization of the framework with empirical data can model the acceptance behavior of procurement personnel on cs-dsss before they are adopted at the organizational or strategic level for enhanced contractor selection in public procurement. the emerging framework is recommended for designers of cs-dss for articulating the antecedent behavior of public procurement personnel. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 dec., 2022 revised 11 april, 2022 accepted 20 april, 2022 keywords: contractor selection public procurement contractor selection technology technology acceptance framework http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 494 forward-looking proposition for their use, relying on relevant technology acceptance model(s) (al-rahmi et al., 2018; cheung and vogel, 2013). some studies have posited that the adoption of technology in public procurement is influenced by political and economic factors, in addition to government’s strategic decision to introduce the technology (de clerck and demeulemeester, 2016; henriksen and mahnke, 2005). available technology acceptance models do not sufficiently contain factors that recognize the perculiarity of the contractor selection task in public procurement. for instance, the public procurement field is neither a mandatory nor a voluntary field. the end-user’s preference to the driving systems in contractor selection technologies will influence their intension to use them (el-gazzar et al, 2016; venkatesh et al., 2003). therefore, relevant factors in a framework will serve as suitable structure to aid the prediction of use for a contractor selection decision support system (cs-dss) (davis and venkatesh, 1996; venkatesh and davis, 2000; venkatesh et al., 2003). such frameworks are, however, lacking in extant literature, hence, the justification for this paper. in order to design acceptance framework for dsss, the inclusion of domain-specific factors for public procurement such as the subjectivity in decision making during contractor selection (bobar et al., 2015; plebankiewicz and kubek, 2015), socio-technical factors (bana e costaa, correa et al., 2002) and the heterogeneous group effect (liu et al., 2014; liu et al., 2017) have become necessary. these factors combine in disproportionate manner to influence the adoption of technology generally and their acceptance at the individual level. the articulation of these factors will engender the understanding of target end-user, the absence of which may lead to a needless underutilization of information system resource when it is introduced for enhancing contractor selection in public procurement (durodolu, 2016). a novel cs-dss acceptance framework will enhance the prediction of contractor selection decision support systems acceptance in public procurement. available technology acceptance frameworks in literature lack relevance for the nigerian public procurement environment which is neither a mandatory or a voluntary field for the use of technology in contractor selection (lai, 2017). 1.2 research in contractor selection techniques research on contractor selection techniques have been prescriptive on methods, techniques and processes, generally designing potent technologies for enhanced selection (holt, 2010). the contractor selection process has a strategic implication for achieving better quality, reducing transaction costs, and enhancing shorter lead times (alptekin et al., 2017; singh and tiong, 2005). research on contractor selection is presented in research clusters in figure 1. these research clusters influence the design of system architecture for contractor selection technology. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 495 figure 1: clusters in contractor selection research 2. relevance of technology acceptance frameworks the continuous development of technology for contractor selection attracts investigation on their acceptance by understanding end-user preferences (maguire and brid, 2017). as a customer foresight enquiry for system vendors, prediction is a prior study for developing relevant measures to guide procurement manager in facilitating the adoption of cs-dss in public procurement and their acceptance by public procurement personnel. system consumers’ purchase intention, antecedents and moderators are necessary (chen and huang, 2016; schweitzer et al., 2019), to promote engaged scholarship by promoting the development of acceptable contractor-selection decision-support systems (närman et al., 2012). other anticipated benefits of this research include: enrichment of cs-dss feedback loop (kayande et al., 2009), guide in the design of training interventions for procurement personnel on use of technology for contractor selection (dainty et al., 2005; mahamadu et al., 2018; roodhooft and abbeele, 2008), while understanding the aec procurement personnel as target end-users of cs-dsss. the adoption of technology encompasses strategic, organizational, group as well as the individual level influences, in addition to technological factors as shown in several studies (alharthi et al., 2014; shimizu et al., 2006). this focuses on the micro-level (individual) behavioral of public procurement personnel towards contractor selection technology (cs-dss). 2.1 concept of innovation and technology contractor selection techniques have attracted the application of several innovations in the past. innovation and technology are correlated with human requirements (legris et al., 2003; schweber and harty, 2010). organizations and countries alike have modified lifestyles, continually recording experiences on the ease of handling real problems through the application of technology (group et al., 2002; semaan and salem, 2017). through the application of less efforts and reduction in manual computation, complex tasks are easier handled with associated savings on time and other resources (mohemad et al., 2010). when such technologies are novel, they are simply described, especially by new users as innovations. technology has tremendously impacted on public procurement (baldus and hatton, 2019). few public procuring entities have struggled to implement and effectively utilize electronic systems to track and manage business processes and strategic planning. most of the relevant http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 496 information on contracts, terms, and conditions, and aspects of procurement engagements are contained in hard copy (paper files and pdf copies of agreements) (bpp, 2011). the digitization of the procurement processes has witnessed many obstacles to mine the data and utilize analytic systems to conduct analysis for insight generation. adoption models will continue to be relevant in investigating technology acceptance. in environments where decision making is extremely disorderly, it is necessary for teams to prepare to confront, inquire, and encourage the forecast on the acceptance of such technology (cheung and vogel, 2013; tran et al., 2011). 2.2 technology acceptance and technology adoption research on contractor selection have prescribed technologies as panaceas for contractor selection problem (semaan and salem, 2017). extant information system and innovation adoption literature have focused on decision-making at organizational level, where the investigations are concerned with factors that drive organizational adoption of such technologies (papadonikolaki, 2018; phillips-wren and mckniff, 2016; tran et al., 2011). individual employee-level acceptance studies have been generally neglected (brandon-jones and kauppi, 2018). in public procurement, the adoption of technology must recognize the organizational strata, with the procurement personnel as the smallest decision making unit as the target end-user of such technology. the efficacy of known technology adoption frameworks for assessing cs-dss acceptance in public procurement is reduced. the inadequacy of sole models and theories; model for pc utilization (mpcu), theory of planned action (tpa), theory of planned behavior (tpb) (tran et al., 2011), theory of reasoned behavior (trb), the unified theory of acceptance and use of technology (utaut), technology adoption model (tam) and diffusion of innovation (doi) (lee et al., 2018), technology organization environment (toe) (tran et al., 2011); and agent-based model (nnaj et al., 2019) have been observed in literature. previously, researchers have extended existing models or integrated them in a bid to enhance their explanatory powers to investigate technology acceptance or adoption in a wide spectra of fields (al-rahmi et al., 2018; kalamatianou and malamateniou, 2017; liu et al., 2018; rana and dwivedi, 2015). the frameworks are contingent upon investigating technology acceptance in construction generally (yap et al., 2019) and public procurement in particular (adam et al., 2016). 2.2.1 technology acceptance model (tam) social and behavioral psychology, ict, and consumer marketing literature have used several fragmented theories regarding acceptance behavior for many years; tpb, tra, tam, doi, model of pc utilization (mpcu) (davis et al., 2017), motivational model (mm) (nnaj et al., 2019), combined tam and tpb (c-tam-tpb) (taylor and todd, 1995) to predict consumers' acceptance behavior. these models have evolved in a bit to assess technology acceptance in several fields. table 1 presents common theories in technology acceptance, which has formed reliable artifacts for modelling end-user acceptance of technology. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 497 table 1: technology/innovation adoption theories level theory principle in the theory sources individual level theories ttf task requirement dishaw and strong (1999) task functionality individual performance actual tool use tri optimism (parasuraman and colby, 2015; shonhe, 2019; yusif et al., 2020) innovativeness discomfort security tam perceived usefulness davis (1989) davis et al. (1989) perceived ease of use utaut performance expectancy venkatesh et al. (2003) exertion anticipation social impact facilitating conditions tpb attitude toward the behavior ajzen (1985,1991, 2002) subjective norms behavioral control sct attitude trybus et al. (2016) tra attitude towards behavior fishbein and ajzen (1975) intention subjective norms firm level theories doi individual characteristics rogers (1995) internal characteristics of the organization external characteristics of the organization institutional theory attitude towards behavior scott and christensen (1995), scott (2001) intention subjective norms toe technology context tornatzky and fleischer (1990) organization context environment context source: adapted from (ali, 2016) 2.3 categorization of factors that influence technology acceptance in public procurement this study merged seemingly isolated research domains to guide in investigating the acceptance of technology in public procurement, especially with the considerations on contractor selection technology; contractor selection, decision support systems, public procurement and technology acceptance. thus, investigation on technology adoption in public procurement took cognizance of the affected areas. a cross-domain feature of this research http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 498 is presented in figure 2, showing the convergence of the seemingly distinct, yet related knowledge domains. figure 2: study features investigations on the adoption or acceptance of technology for contractor selection in public procurement is a hydra-headed concept, because of the challenge of situating such a research in seemingly distinct bodies of knowledge (halbesleben and wheeler, 2008). although, a typical research should follow recognized pedagogical principle, there is the need to review some codified bodies of knowledge for; contractor selection, contractor selection technology cs-dss, public procurement as well as technology adoption/acceptance. the consideration of these concepts are necessary in determining relevant factors that will influence the adoption or acceptance of technology. figure 4 is a flow chart for the strategic review of literature adopted for this study. three hundred and eleven articles had relevant contents for the seemingly distinct knowledge areas; contractor selection, contractor selection technology cs-dss, public procurement and technology adoption/acceptance figure 3 shows the category of factors that influence technology adoption in public organizations as demonstrated in previous studies (ali, 2016). artifact compatibility complexity leadership support policy requirement enterprise architecture knowledge and skill of personnel institutional readiness nature and culture of procuring entity intention to adopt cs-dss policy concerns complexity to projects figure 3: all-level factors that affect technology adoption in public procurement file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 499 3. methodology this research adopted a qualitative method, informed by a research paradigm which forms a framework as comprising commonly-held agreement about a subject and a structure of what direction researches are undertaken as demonstrated in simmons et al. (2013). the present study is designed to develop a framework for predicting acceptance of contractor selection technology cs-dss in public procurement. the methodology was logically and systematically aligned to augment the absence of a framework for predicting the acceptance of technology in public procurement for enhanced contractor selection (adam et al., 2017). a sequential methodology started from a strategic review of extant literature on seemingly distinct body of knowledge; contractor selection, decision support systems, public procurement and technology acceptance. their convergence presented a pool of motivators of technology acceptance in public procurement which were subjected to a delphi survey of experts in the public procurement field. figure 3 is the flow chart of the methodology adopted. the factors with high agreement by the experts were analyzed using spss version 24 and the results were presented by descriptive statistical analysis, on the basis of which a framework for investigating technology acceptance in public procurement was designed figure 3: methodology output  general factors that influence technology adoption  develop technology acceptance framework for individual level (public procurement personnel) contractor selection delphi survey factors that influence technology adoption (domain-specific), qualitative analysis (nvivo) studies on dss / cs-dss attributes / theoretical framework (general factors) public procurement stage i literature review (preparatory stage) stage ii in-depth review of literature (exploration of literature) stage iii in-depth review of literature theories on technology adoption output prior researches previous paradigm design science of dss in-depth review of literature (exploration of literature) output in-depth review of literature (strategic exploration of literature) http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 500 3.1 philosophical position a deductive relativist explanatory research position, hinged on a philosophical paradigm that is grounded in theory was adopted in this study. from the philosophy, the acceptance behavior of public procurement personnel is studied by assessing the factors that influence technology acceptance by procurement personnel. this study adopted a triangulation by sequential mixed method, verifying the importance of factors that influence technology acceptance amongst public procurement personnel. 3.2 delphi survey the preliminary stage of the delphi survey (okoli and pawlowski, 2004) was based on established set of criteria for the identification and inclusion of relevant public procurement stakeholders as shown in table 2. table 2: criteria and scoring for inclusion of experts on delphi survey expert's description scoring criteria for experts in public procurement allotted points total allotted point a. academics (a). first or second author in academic article on public procurement in nigeria 6 (b) first, second or third author on an academic article related to procurement 5 (c) first or second author on any academic article on contractor selection 5 (d) first or second author on academic article on information system/it studies 5 (d) first or second author on academic publication on eprocurement 5 (e) first or second author on academic publication on technology adoption 5 (f) first or second author on academic publication on organizational behavior 3 33 b. public procurement manager (a) has minimum bsc./hnd in any of aec or engineering, management, economics, business administration, computer sciences or information technology, or economics 5 (b) more than 10 years of experience as built-environment professionals, registered with professional body 5 (c) 3–5 years of professional experience in public procurement 5 (d) 1–3 years of professional experience in the regulation and policy on public procurement 5 (e) more than 5 year experience as member of technical evaluation committee for public procurement of works and related goods and services 5 (f) a minimum 25 years in nigerian federal civil service 4 (f) more than 5 years of professional experience in the planning, implementation, regulation, or development of public procurement laws 4 33 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 501 source: adapted with modifications from tabish and jha (2018) 3.2 new factors that will influence cs-dss adoption in public procurement the qualitative data was collected through with open-ended question to accept the emergence of new factors that motivate cs-dss adoption. responses from two (2) experts suggested new factors which were further reviewed. raw string data from the experts’ responses were exported to an nvivo software program for qualitative data analysis. subsequently, analytical techniques checked the factor clusters to form single modified variants. the analytical order followed: a. coding: suggested motivators by the participants were coded. b. cluster analysis (ca): ca analytical technique was applied to cluster nodes by word similarity. from general review of clusters, secondary nodes denote factors recommended by experts and their primary nodes. the nodes show the most appropriate new factor to which the secondary nodes were synthesized and defined. a primary node represents one suggested factor, suggested by the public procurement experts. c. the nvivo created the primary nodes and the secondary nodes. the secondary nodes were re-assigned to the primary nodes d. recommended factors were matched with the existing factors. the new factors were coded differently but fit in content with existing factors. e. frequencies of responses were computed as percentages of all the 18 experts in the delphi survey with the aid of spss version 24. 4 analysis, results and discussion 4.1 pilot study pilot to ensure: completeness, redundancy, operationality, mutual independence of preferences, double identification and size was carried out to ensure that the list of variables are not more than necessary or duplicated. the result is presented in table 3 c. consultant in procurement of public construction works (a) more than 10 years active professional membership in aec professional bodies 10 (b) 5–10 years of professional experience consultancy services in planning, implementation or management of procurement on construction projects/public works 10 (c) have mba., ma., msc. or ph.d. in any of aec or engineering, management, economics, business administration, computer sciences or information technology, or economics 6 (d) has presented 2-3 non-academic articles/conference papers on public procurement or information system or technology application in procurement, dss, contractor selection 5 (e) participated in policy review on information technology or public procurement 2 34 http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 502 table 3: importance of factors that influence technology adoption (delphi-round 1) factor response rate (percent %) rank itam1 perceived usefulness 100.00% 1 fitr1 attitude towards behavior 96.88% 2 iutau1 performance expectancy 96.88% 3 itam2 perceived ease of use 95.31% 4 iutau2 exertion anticipation 93.75% 5 iutau3 social impact 92.19% 6 itra3 subjective norms 92.19% 7 itra1 attitude towards behavior 90.63% 8 ftoe1 technology context 89.06% 9 itra2 intention 75.00% 10 iutau4 facilitating conditions 75.00% 11 gpsy2 social (social norms and self-image) 73.44% 12 ittf2 individual performance 56.25% 13 itra3 subjective norms 52.00% 14 gtrt1 clarity 51.00% 15 gpsy1 personality (exploration behavior) 50.75% 16 gtrt3 comprehensiveness 50.76% 17 gpsy3 cognitive (risk perception) 50.35% 18 gtrt2 logical structure 48.00% 19 itra3 subjective norms 47.99% 20 gtrt4 applicability in public sector tendering 46.11% 21 ittf1 task requirement 43.21% 22 key: codes starting with ‘i’ are individual level constructs source: delphi survey (2022) procurement experts (delphi survey respondents) identified additional factors that they believed will influence the adoption of cs-dss in public procurement. the factors are: legal requirement, system architecture, and increase in volume of data, transparency and security. 4.2 new factors that will influence cs-dss adoption in public procurement the qualitative data collected through the open-ended question to accept new factors to be included in cs-dss adoption query were identified. the responses from two (2) experts who suggested new factors were reviewed. raw string data from the experts’ responses were exported to an nvivo software program for qualitative data analysis. subsequently, analytical techniques are used to check factor clusters to form single modified variants or ensembleenabled factors reasonably with the existing factors. the analytical order followed: f. coding: suggested motivators by the participants were individually coded. g. cluster analysis (ca): ca analytical technique was applied to cluster the nodes by word similarity through meta-synthetic measure. from the general review of cluster analysis, the secondary nodes represent the factors recommended by experts and their primary nodes, which present the most appropriate new factor to which the secondary nodes can be synthesized and identified. therefore, a primary node represents one suggested factor derived from the suggestions from the public procurement experts. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 503 h. application of nvivo created the primary nodes and the secondary nodes. the secondary nodes were carefully assigned to the primary nodes i. subsequently, recommended factor were matched with the existing factors manually. the new factors included were phrased differently but fit with the content of existing factors. j. frequencies of responses were computed as percentages of all the 18 experts in the delphi survey. 4.3 delphi questionnaire survey (round 2) round 2 developed a well-rounded questionnaire from round 1 questionnaire. the questionnaire of round 2 contains all factors in questionnaire 1, rephrased from the round 1 feedback for each factor in addition to the modified factor; ‘system architecture (sa)’. all the factors were reviewed for completeness and appropriateness for application in the list. the review was necessary to encourage experts to rate each criterion in 1-9 interval scale. three factors related to motivation to adopt contractor selection dss were added at this stage, as shown in table 4. table 4 criteria included in round 2 by experts s/no factors that influence technology adoption in public procurement 1 system architecture: the system architecture of the dss addresses all the concerns in contractor selection literature; selection criteria, selection technique, multi-criteria decision making method and procurement route etc. 2 increase in volume of data: contractor selection is increasingly requiring the consideration of large data. 3 transparency: cs-dss provides an open and transparent process for contractor selection source: delphi survey (2022) 4.4. analysis of data (delphi round 2) the respondents in round 2 were asked to rate the importance of factors using 1-9 scale. descriptive statistical analysis was applied to describe the central tendency of data in relation to ‘mean’, descriptive statistical analysis was performed using spss, version 24. table 5 shows the round 2 of the delphi survey. table 5: delphi round 2 result of factor importance factor response rate (as a percentage) group mean standard deviation rank itam1 perceived usefulness 97.20% 8.56 1.118 1 fitr1 attitude towards behavior 96.88% 8.49 1.125 2 iutau1 performance expectancy 96.88% 8.47 1.164 3 itam2 perceived ease of use 95.31% 8.42 1.105 4 avev2 system architecture 93.75% 8.41 1.340 5 avev5 security 92.19% 8.32 0.941 6 itra3 subjective norms 92.19% 8.28 1.503 7 itra1 attitude towards behavior 90.63% 8.11 1.155 8 ftoe1 technology context 89.06% 8.09 1.307 9 http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 504 gtrt1 clarity 75.00% 8.03 1.223 10 iutau4 facilitating conditions 75.00% 8.01 1.598 11 gpsy2 social (social norms and self-image) 73.44% 7.94 1.365 12 ittf2 individual performance 56.25% 7.75 1.587 13 itra3 subjective norms 52.00% 7.74 1.460 14 avev3 increase in volume of data 51.00% 7.71 1.674 15 gpsy1 personality (exploration behavior) 50.75% 7.70 1.302 16 gtrt3 comprehensiveness 50.76% 7.29 1.298 17 avev4 transparency 50.35% 7.17 1.350 18 gtrt2 logical structure 48.00% 6.66 1.322 19 itra3 subjective norms 47.99% 6.43 1.294 20 gtrt4 applicability in public sector tendering 46.11% 6.12 1.266 21 ittf1 task requirement 43.21% 6.05 1.239 22 iutau2 exertion anticipation 43.20% 5.58 1.211 23 itra2 intention 43.19% 5.56 1.183 24 gpsy3 cognitive (risk perception) 43.17% 5.54 1.155 25 iutau3 social impact 43.10% 5.52 1.127 26 source: delphi survey (2022) system architecture (sa) was added by the procurement experts in the first round of the survey, it had a contrasting response of 93.75%. the results for system architecture (sa) in the second round at its first introduction implies that it is adjudged to be a very important factor that will influence the acceptance of cs-dss in public procurement. 4.4.1 reliability scale reliability of round 2 was verified by a conducting cronbach’s alpha test for the interval scale measurement on 1-9 scale. cronbach’s alpha is 0.921 for the round 2 responses measured 1-7 scale as presented in table 6. table 6: reliability statistics for round 2 survey cronbach’s alpha cronbach’s alpha based on standardized items no. of items 0.921 0.920 26 4.4.3 non-parametric kendall’s w test (consensus amongst public procurement experts) the non-parametric kendall’s w test (kendall’s coefficient of concordance) is used to measure group consensus. w is always between 0 and 1 (presented as 0 showing ‘no disagreement’ while 1 portrays a perfect agreement. intermediate values indicate lesser or greater agreement. with the aid of spss, non-parametric kendall’s w test was carried out as presented in table 7. table 7: kendall’s w test result test statistics n 18 kendall’s w (kendall's coefficient of concordance) 0.312 asymptomatic significance 0.000 from table 7 the kendall’s coefficient of concordance, w is 0.312 at p = 0.000. this signifies that from the delphi enquiry, value of w is significant with p = 0.000. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 505 4.5. round 3 of delphi questionnaire survey 4.5.1. analysis of data (round 3 survey) a descriptive statistical analysis of the third round of the delphi survey data is presented in table 8 table 8: result for round 3 (n=18) factor group mean standard deviation rank itam1 perceived usefulness 8.68 0.718 1 fitr1 attitude towards behavior 8.19 0.677 2 itra1 attitude towards behavior 8.07 0.785 3 itam2 perceived ease of use 8.02 0.893 4 avev2 system architecture 8.01 0.687 5 fdoi4 trialbility 8.00 0.745 6 gtrt3 comprehensiveness 6.80 0.680 7 gtrt2 logical structure 6.70 0.840 8 ftoe1 technology context 6.50 0.943 9 gtrt1 clarity 5.80 0.883 10 iutau4 facilitating conditions 5.70 0.756 11 gpsy2 social (social norms and self-image) 5.60 0.650 12 ittf2 individual performance 5.30 0.680 13 itra3 subjective norms 4.80 0.598 14 avev3 increase in volume of data 4.75 1.022 15 gpsy1 personality (exploration behavior) 4.55 1.062 16 avev5 security 4.45 0.760 17 iutau1 performance expectancy 4.40 0.820 18 itra3 subjective norms 4.30 0.670 19 itra3 subjective norms 4.25 1.020 20 gtrt4 applicability in public sector tendering 4.18 1.001 21 ittf1 task requirement 4.17 0.657 22 iutau2 exertion anticipation 4.09 0.820 23 itra2 intention 3.89 0.811 24 gpsy3 cognitive (risk perception) 3.82 1.015 25 iutau3 social impact 3.69 1.010 26 4.6. reliability test outcome scale reliability of round 3 was tested by cronbach’s alpha test for the interval scale measurement on 1-9 scale. as presented in table 9, cronbach’s alpha is 0.807, indicating stronger stability of responses in round 3, table 9: reliability statistics for round 3 cronbach’s alpha cronbach’s alpha based on standardized items number of items 0.807 0.810 16 source: delphi survey (2022) http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 506 4.6.1 measure of consensusnon-parametric kendall’s w test kendall’s w coefficient of concordance is applied in measuring the group consensus. subsequently, non-parametric kendall’s w test was carried out using spss version 3 and result is presented in table 10. table 10: kendall’s w test result test statistics n 16 kendall’s w (kendall's coefficient of concordance) 0.264 assymp. significance 0.000 kendall’s coefficient of concordance w is 0.264, significant at p =.000. as supported in the report for round 2, where w is significant at p =.000, there was fair consensus among the experts. the experts in round 3 demonstrated a reasonable agreement with each other, determining the importance of factors with value of w =.264 significant at p=0.000. with the increased consensus from round 2 to round 3 indicates greater agreement and increased consensus, showing no further inclusion of new factor(s). 4.7. comparison of rounds 2 and 3 delphi rounds and the final numbers of participants are presented in table 11. round 3 and prior round 2 show slight differences in the rankings of the factors. table 11: summary of round 2 and 3 survey round 3 round 2 factor group mean rank group mean rank itam1 perceived usefulness 8.68 1 8.56 1 fitr1 attitude towards behavior 8.19 2 8.47 2 itra1 perceived enjoyment 8.07 3 8.47 3 itam2 perceived ease of use 8.02 4 8.42 4 avev1 system architecture 8.01 5 8.41 5 fdoi4 trialbility 8.00 6 8.32 9 gtrt3 complexity 6.80 7 8.28 8 gtrt2 logical structure 6.70 8 8.11 7 ftoe1 technology context 6.50 9 8.09 6 gtrt1 clarity 5.80 10 8.03 10 iutau4 facilitating conditions 5.70 11 8.01 12 gpsy2 social (social norms and selfimage) 5.60 12 7.94 11 ittf2 individual performance 5.30 13 7.75 14 itra3 subjective norms 4.80 14 7.74 13 avev3 increase in volume of data 4.75 15 7.71 18 gpsy1 personality (exploration behavior) 4.55 16 7.70 16 avev5 security 4.45 17 7.29 17 iutau1 performance expectancy 4.40 18 7.17 18 itra3 subjective knowledge 4.30 19 6.66 19 itra3 subjective norms 4.25 20 6.43 20 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 507 gtrt4 applicability in public sector tendering 4.18 21 6.12 21 ittf1 task requirement 4.17 22 6.05 22 iutau2 exertion anticipation 4.09 23 5.58 23 itra2 intention 3.89 24 5.56 24 gpsy3 cognitive (risk perception) 3.82 25 5.54 25 iutau3 social impact 3.69 26 5.52 26 kendall’s w 0.264 0.312 cronbach alpha (α) 0.807 0.921 delphi survey (2022) based on the consensus of procurement experts, the individual level variables were carefully selected. these guarded in the compatibility check with existing models for the design of an acceptance framework for contractor selection decision support system in public procurement. the variables are presented in table 12. the factors had high agreement, with mean scores between 7 and 8. table 12: individual level factors with highest agreement by procurement experts rank factor high agreement band 1 perceived usefulness high agreement factors (mean score 7-8) 2 attitude towards behavior 3 perceived enjoyment 4 perceived ease of use 5 system architecture 6 trialbility 7 complexity factors that influence the acceptance of cs-dss in public procurement and their kendall w status from three rounds of delphi survey are shown in table 13. each factor showed their descriptions as presented in the survey instrument. table 13: delphi study findings (factors and agreement weights) factor description kendall’s w itam1 perceived usefulness cs-dss is useful in contractor selection > 0.75 fitr1 attitude towards behavior a good cs-dss should meet my expectations on major concerns in contractor selection > 0.75 itra1 perceived enjoyment cs-dss will have better advantage in application compared to current manual approach > 0.75 itam2 perceived ease of use cs-dss will be easy to use > 0.75 avev2 system architecture the system architecture of cs-dss must address all concern in contractor selection > 0.75 http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 508 fdoi4 trialbility the cs-dss should be open to trial > 0.75 gtrt3 compatibility the cs-dss should be compatible with existing structure > 0.75 source: delphi survey, 2022 figure 6 presents requisite features of a cs-dss acceptance framework, which informs the design of a novel technology acceptance framework for investigating public procurement personnel, as agreed by carefully selected public procurement experts in nigeria. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 509 perception on technology characteristics tam technology context idt domain-specific system architecture ds key: ds = domain-specific; extension 1…n = additional variable three rounds delphi survey enhanced the assessment of 23 factors that influence adoption of cs-dss and the agreement weightings for carefully selected group of 18 public procurement experts in nigeria. relevant factors for influencing the adoption of technology in public procurement shows the support for a theoretical framework that includes technical as well as psychological factors for investigating acceptance behavior as considered to be most relevant in public procurement were determined. 4.8 framework for the acceptance of cs-dss in public procurement the technology acceptance models as identified in literature are associated with considerable number of factors that influence the adoption and/or acceptance of technology. modelling of behavioral intension of public procurement personnel towards contractor selection decision intention to adopt cs-dss perceived ease of use extension 1…n observability relative advantage complexity selection criteria selection techniques trialability perceived compatibility perceived ease of usability procurement route multi-criteria decision making figure 6: theoretical framework for cs-dss acceptance http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):493-516. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 510 support systems require the inclusion of relevant variables that influence the acceptance of behavior of personnel. the most relevant factors were included through predetermination of factors and the consideration of their associated weights. hypotheses are proposed on the arrows, indicating the kind of relationship between variables. preparatory to the modelling of causality, figure 7 shows a relationship between the acceptance behavior and other dependent variables, on the basis of which meaningful enquiries can be made on the public procurement personnel. figure 7: extended integrated idt-tam framework for cs-dss acceptance 5. conclusion this study builds up a theoretical framework that requires operationalization with the aid of empirical data to achieve an important objective of investigating the acceptance behavior of public procurement personnel towards contractor selection technology in nigerian public procuring entities. there are many technology acceptance theories in literature. these include; technology acceptance model (tam), theory of reasoned action (tra), innovation diffusion theory (idt), technology organization environment (toe), theory of planned behavior (tpb), unified theory of acceptance and use of technology (utaut), model for pc utilization (mpcu), task technology fit (ttf), motivation model (mm), technology readiness index (tri). with the aid of agreement from a team of 18 experts in public procurement, a suitable framework; integrated innovation diffusion theory and technology acceptance framework (idt-tam) for assessing cs-dss acceptance in public procurement was designed. the main factors for investigating technology acceptance are technology characteristics which include compatibility, complexity, trialbility, perceived enjoyment and technological context (system architecture) was included in addition to psychological factors of perceived ease of use and perceived usefulness. according to the procurement experts, these factor are very relevant for modelling acceptance behavior on contractor selection decision support systems amongst public procurement personnel. such antecedent behavior is a valuable information for system vendors in proffering technologies that are needed for file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng salla et al: framework for investigating contractor selection decision support systems’ (cs-dss) acceptance by public procurement personnel. azojete, 18(3):493-516. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edsalla.qs@buk.edu.ng 511 enhanced contractor selection. the system vendors can rely on the framework developed in this study to investigate acceptance behavior of procurement personnel towards contractor selection support systems to enhance the potentials of acceptance. the study builds up a theoretical framework that requires operationalization with the aid of empirical data to achieve an important objective of investigating the acceptance behavior of public procurement personnel towards contractor selection technology in nigerian public procurement entities. antecedent behaviors are valuable information for system vendors to proffer acceptable solution for enhanced contractor selection. references adam, f., csaki, c., prier, e., bufacchi, v. and prier, e. 2016. ethical decision making and decision support systems in public procurement a theoretical discussion. supply chain forum: an international journal, 13(3): 70–80. addo-duah, p., westcott, t., mason, j., booth, c. and mahamadu, a. 2014. developing capability of public sector procurement in ghana: an assessment of the road subsector client. construction research congress, 2053–2060. al-harthi, aas., soetanto, r. and edum-fotwe, ft. 2014. revisiting client roles and capabilities in construction procurement. in international conference on construction in a changing world cib w92 procurement systems, sri lanka, p. 12. al-rahmi, wm., yahaya, n., aldraiweesh, aa., alamri, mm., aljarboa, na., alturki, u. and aljeraiwi, aa. 2018. integrating technology acceptance model with innovation diffusion theory: an empirical investigation on students’ intention to use e-learning systems. ieee access., doi.10.1109/access.2019.2899368 ali, omsh. 2016. the perceived benefits of cloud computing technology for regional municipal government and barriers to adoption. university of southern queensland, unisq toowoomba, 487-535west st., darling heights qld 4350, australia. alptekin, o. and alptekin, n. 2017. analysis of criteria influencing contractor selection using topsis method. in iop conference series: materials science and engineering, 245(6): 062003. baldus, bj. and hatton, l. 2019. u.s chief procurement officers’ perspectives on public procurement. journal of purchasing and supply management, 26(1): 1–7. bana e costaa, ca., correa, ec., de corted, j. and vansnick, j. 2002. facilitating bid evaluation in public call for tenders: a socio-technical approach. the international journal of management sciences, 30: 227–242. basole, rc. 2006. modeling and analysis of complex technology adoption decision: an investigation in the domain of mobile ict. georgia institute of technology, north ave. nw, atlanta, ga 30332, georgia, usa. bobar, v., mandić, k., delibašić, b. and suknović, m. 2015. an integrated fuzzy approach to bidder selection in public procurement: serbian government case study. acta polytechnica hungarica, 12(2): 193–211. bpp. procurement procedures manual for public procurement in nigeria 2011. federal http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, september, 2022; 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adeyeye, 2016; ojinnaka et al., 2016; dankwa and liu, 2017; raihan and saini, 2017; badje et al., 2018; bello et al., 2020; article information abstract this study aimed to prepare and evaluate the quality characteristics of biscuits produced from wheat, maize and cashew nut flour blends. the flours were processed and blended using different proportions of eight (8) formulations with whole wheat flour as a control. the proximate composition of the flour blends, physical properties and sensory evaluation of the biscuits produced were determined using the standard analytical techniques. the data obtained were statistically analyzed using analysis of variance (anova). the results show that moisture, ash, fat, protein and carbohydrate of the flours used for the blends ranged from 5.43-10.12 %, 1.7429.51, 9.34-26.56 and 34.48-77.25% respectively. also, the moisture, ash, protein, fat, fibre carbohydrate and energy values of the biscuit ranged from 2.90 -3.92%, 0.99 1.57%, 11.19 14.59%, 16.24 20.30%, 0.97 4.85%, 56.04 66.96% and 457.68 470.80 kcal/100g respectively. however, with an increase in maize flour (mf), a significant increase in fibre contents was observed while moisture content decreased drastically. additionally, the protein, fat and energy contents of supplemented samples were found to be higher than the control but decreased with an increase in maize flour levels. the weight, length, width, thickness and spread ratio of the biscuit samples differed significantly (p<0.05) ranging from 15.25 17.36g, 51.70 53.03mm, 50.54 52.36mm, 9.57 11.27mm and 4.48 5.47mm respectively. the spread ratio and overall acceptability of biscuit samples decreased with the increased level of maize flour although the sensory evaluation showed that most values obtained are closer to the control. this shows that the acceptance level of the biscuits samples was higher except for sample wmc 8 ( sample produced from wheat, maize and cashew nut flour at the ratio of 20:70:10). in conclusion, the production of biscuits supplemented with cashew nuts and maize flour increased protein, energy contents and taste, which could be used to address protein-energy malnutrition prevalence. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 5 april, 2023 revised 14 june, 2023 accepted 18 june, 2023 keywords: biscuits cashew nut flour maize flour proximate composition overall acceptability http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):461-476. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 462 babiker et al., 2021). hence, supplementing wheat flour with suitable health-promoting plant materials can improve the overall acceptability and nutritional quality of biscuits (swieca et al., 2017; klunklin and savage 2018). wheat (triticum spp.) is the principal cereal for baked products, popular and unique among cereals due to its gluten protein (dhanavath and prasada, 2017). it is a common cereal grain that is widely grown and consumed in different parts of the world in different forms such as bread, biscuits, pasta and other products (nadeem et al., 2010). wheat flour contains 60.01 73.67% carbohydrate, 11.37 16.77% protein, 0.77 1.41% fat, 0.64 0.77% ash, 1.07 3.50% fibre (ibidapo et al., 2019) with considerable proportions of vitamins (thiamine and other bvitamins) and minerals (topping, 2007). with the rise in the market price of wheat, especially in regions where wheat does not thrive because of importation cost, efforts are being focused on the innovation of suitable flours from local plant sources such as cereals, legumes, roots, tubers, nuts and others that are readily available (dotsey, 2009). maize (zea mays) is one of the cereal grains and a member of the gramineae family. maize has a multitude of uses and ranks second to wheat among the world’s cereal crops in terms of production (abdulrahaman and kolawole, 2006). the estimated annual production of maize is about 5.6 million tonnes (carr et al., 2021). in nigeria, maize has been rated the second-grown food crop with a total production of 9,180,270 tonnes (fao, 2014). however, maize is used for food, feed and fuel. maize grain has great nutritional value and can be used as raw material for manufacturing many industrial products (afzal et al., 2009). based on the nutritional value, maize flour contains 53.99 62.99% carbohydrate, 12.32 – 13.50% protein, 12.90 – 14.20% fat, 0.90 – 1.04% ash, 1.05 – 6.74% fibre and considerable proportions of minerals (oladapo et al., 2017; sule et al., 2014). cashew (anacardiumoccidentale linn.) belonging to the family anacardiaceae and is an extremely hardy tree that grows on poor soil under various climatic conditions. the nut is the most important product (lima and daurte, 2006). however, cashew nut is a good source of protein and oil, containing nutritionally unsaturated fatty acids and earning a huge amount of foreign exchange through its kernel and cashew nut shell liquid (cnsl) (adepoju et al., 2019) according to adepoju et al. (2019), cashew nut flour contains 5.73 – 5.90% moisture, 22.05 – 23.97% protein, 40.16 – 42.13% fat, 3.12 – 3.49% ash, 2.01 – 2.30% fibre and 22.39 26.72% carbohydrate. despite the importance of these local agricultural products, information regarding their incorporation in many food formulations is limited. therefore, this study was aimed at evaluating the proximate composition, physical and sensory properties of biscuits produced from cashew nut, maize and wheat flour blends. 2.0 materials and methods wheat flour (triticum spp.), maize flour (zea mays), roasted cashew nut (anacardiumoccidentale linn.), simas margarine (pt satimivomas pratama, indonesia), salt and sugar (dangote nigeria plc., lagos), baking powder, eggs and powdered milk (peak brand) were purchased from maiduguri monday market. the baking of the biscuit was carried out at food processing laboratory of the department of food science and technology university of maiduguri. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com mshelia et al: production and evaluation of the physiochemical and sensory property of biscuits from wheat-maize-cashewnut flour blends. azojete, 19(3):461-476. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 463 2.1 preparation of wheat, maize and roasted cashew nut flour 2.1.1 processing of wheat into flour the whole wheat flour (wf) was processed into flour following the method described by ndife et al. (2014) with slight modification by sun drying instead of oven drying. the grains was cleaned by sorting out contaminants such as stones, sticks, leaves and any foreign object, washed, sun-dried and was then milled using an attrition mill, sieved and packaged until further use 2.1.2 processing of maize into flour the maize flour (mf) was processed following the method described by obinna-echem and robinson (2019). the grains were sorted to remove foreign matters, winnowed and milled into flour using an attrition mill (globe p44 shanghai china), sieved, packaged and stored. 2.1.3 processing of cashew nuts the preparation of cashew nut (cf) was carried out according to the method described by ojinnaka and ogubulom, (2013) with slight modifications where no soaking in water was involved and was roasted for 20 min (not 15 min). the nut was cleaned (dry cleaning) and sorted to remove foreign materials and unwholesome nuts. it was then roasted for 20 min using an open pan method. shelling of the nut was done by using a wooden hammer. the nuts were dried (oven drying method). next, the nuts were ground into flour using a blender. 2.2 experimental design and flour formulation for the production of biscuit samples to produce biscuits from wheat-maize-cashew nut flour blends, a 33 factorial design was used to evaluate the physiochemical and sensory properties of the biscuits. table i. depicts the formulation of the flour blends for the production of biscuits using wheat, maize flour and cashew nuts where the wheat flour with maize flour and cashew nuts. table i. formulation of flour blends for biscuit production sample wheat flour (%) maize flour (%) cashew nut flour (%) wmc 1 100 0 0 wmc 2 80 10 10 wmc 3 70 20 10 wmc 4 60 30 10 wmc 5 50 40 10 wmc 6 40 50 10 wmc 7 30 60 10 wmc 8 20 70 10 2.3 production of biscuits preparation of biscuits was carried out as previously described by srivatava et al. (2012) where 70g of butter was creamed with sugar (30g) in a bowl until a uniform mixture was achieved. a large beaten egg (1 piece), formulated flour (300g), powdered milk (10g), baking powder (5 http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):461-476. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 464 g), salt (a pinch) and vanilla flavour (5 g) were all added gradually to the initial mixture until a uniform dough was achieved as shown in figure 1. the resulting dough was put on a lightly floured board and flattened with a wooden rolling pin to about ¼ inch thickness. the flattened dough was cut into circular shapes using a biscuit cutter and arranged on a greased tray and baked in an oven at a temperature of about 120℃ for 15 min. the biscuits were then removed from the oven allowed to cool on a rack and then packaged in a cellophane bag for further analysis. the same method was applied to the biscuit made from all the formulated flour samples figure 1. preparation of biscuits. 2.4 determination of proximate composition the proximate composition of the flour blends and the biscuit samples were determined following the methods described by aoac (2005). all the samples were analyzed for moisture, crude protein, crude fats, ash and fibre contents. however, the carbohydrate content was determined by difference as calculated using equation1. % cho=100 (% moisture + % fat + %protein + %ash + %fibre) (1) where; cho = carbohydrate 2.5 determination of caloric value the caloric value (kcal) of the biscuits sample was determined according to the method described by marero et al. (1998) applying factors 4, 9, and 4 to the percentage of protein, lipid, and carbohydrate, respectively as shown in equation ii. caloric value (kcal) = (4 x % cho) + (4 x % protein) + (9 x % fat) (2) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com mshelia et al: production and evaluation of the physiochemical and sensory property of biscuits from wheat-maize-cashewnut flour blends. azojete, 19(3):461-476. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 465 2.6 determination of the physical properties of biscuits 2.6.1 the weight the weight of the biscuits was determined according to the method described by ayo et al. (2007) where the biscuits were weighed using an electronic balance (precision of 0.01g) immediately after cooling. 2.6.2 the size (width and thickness) the width (w) (mm) and thickness (t) (mm) of the biscuits samples were measured using the digital vernier 150mm with an accuracy of 0.01 mm (adeyeye, 2016). 2.6.3 the spread ratio the spread ratio was determined according to the method described by kaur et al. (2017). the spread ratio was calculated using equation iii below. spread ratio = width thickness (3) 2.7 sensory evaluation the baked biscuit was given out to ten untrained panellists for sensory evaluation. the biscuit samples produced from wheat, maize and cashew nut flour at different ratios were labelled as wf 1, wmc 2, wmc 3, wmc 4, wmc 5, wmc 6, wmc 7 and wmc 8 as shown in table 1 ten (10) questionnaires were distributed to the panellists. they were asked to evaluate the eight products on colour, taste, texture, aroma and overall acceptability using a 9-point hedonic scale as follows: 9like extremely,8like very much, 7like moderately, 6like slightly,5 moderately,4dislike slightly, 3dislike moderately, 2dislike much, 1dislike extremely. 2.8 statistical analysis all experiments were performed in triplicate, and the data generated were analysed using analysis of variance (anova) where the separation of means using duncan multiple range test using statistical package for social science 23 version (spss). 3. results and discussion 3.1 proximate composition of the flour blends table 2 shows the proximate composition of various flours used for the production of biscuits. there was a significant difference between the moisture, ash, protein, fat and carbohydrate content of the flours. the moisture content of the flour samples ranged from 5.43 10.12%. sample wf had a higher moisture content as compared to other samples while sample cf had the least. ash content ranged from 0.79 3.02%, cf had the highest ash content however, the total amount of minerals in food is represented by the ash content (bilge et al., 2016). the fat content of the flour significantly varied ranging from 1.74 29.51% where cf had the highest fat content. the ratio of saturated, monosaturated and polysaturated is 1:2:1 in cashew nut fat and is good which promotes the absorption of fat-soluble vitamins hence, it is very important in diets and therefore a good source of edible oil (akinhanmi et al., 2008). subsequently, protein is very important in a diet however, the protein content of cashew nuts was http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):461-476. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 466 significantly higher which could be compared to that of soybeans, cowpeas and melon seeds as previously reported by hussain et al. (2008). subsequently, the energy value of the flour ranged from 365.06-509.75. among all the flour samples used for biscuit production, the protein, fat and ash content of cf was significantly higher than all the samples. this is in agreement with a previous study reported by aremu et al. (2006) on the proximate composition of cashew nut flour. according to emelike et al. (2015), the high protein content of cashew nut flour makes it suitable to be incorporated in the formulation of composite flour for snack production. this shows that the daily dietary needs of the individual could be reached by consuming a moderate amount of cashew nuts. table 2. proximate composition of the flour used for the blends data are mean±sd (n=3). mean values bearing similar superscripts are not significantly different (p< 0.05). 3.2 proximate composition of biscuits. the proximate compositions of the biscuits produced from cashew nut, wheat and maize flour are shown in table 3. supplementing wheat flour with 10% cashew nut and varying levels of maize flour significantly (p<0.05) affected the moisture, protein, fat, ash, fibre, carbohydrate contents and energy value of the biscuits. moisture content played a vital role on the shelf life of biscuits. in this study, the moisture content of the biscuit samples ranged from 2.90 3.92% and varied significantly (p<0.05) from each other. sample wf 1 (3.92%) which is the control sample had the highest value while sample wmc 8 (2.90%) had the least moisture content. however, the increased supplementation of wheat flour with maize flour caused a significant (p < 0.05) decrease in the moisture content of the biscuits. this is similar to a previous study reported by raihan and sanni (2017) which shows that the supplementation of wheat flour with other flour (maize and cashew nut flour) decreased the moisture content of the biscuits. furthermore, elevated moisture content of about 14% may lead to microbial deterioration, loss of nutritional quality and a decrease in the shelf life of food products (dabel et al., 2016). in this study, the moisture content of the biscuits obtained is within the acceptable range (˂10%) which will improve the shelf life of the biscuits (ayo et al., 2007). the ash content of the biscuit samples varies significantly (p < 0.05) and ranged from 0.99 – 1.57%. the ash content of sample wmc 8 was significantly higher (1.57%) as compared to all the samples produced. however, the control sample (wf 1) had the lowest ash content. hence, it has been observed that an increase in maize flour has led to a significant increase in the ash content of the biscuit samples. this could be due to the higher ash content in maize as compared to wheat. flour moisture (%) ash (%) protein (%) fat (%) carbohydrate (%) energy (kcal/100 g) wf 10.12± 0.03a 0.79± 0.01c 11.72± 0.04b 1.74± 0.04c 75.63± 0.12a 365.06 mf 9.35 ± 0.23b 0.85± 0.12b 9.34± 0.07c 3.21± 0.34b 77.25± 0.05a 375.28 cf 5.43 ± 0.06c 4.02± 0.03a 26.56± 0.05a 29.51± 0.03a 34.48± 0.03b 509.75 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com mshelia et al: production and evaluation of the physiochemical and sensory property of biscuits from wheat-maize-cashewnut flour blends. azojete, 19(3):461-476. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 467 according to ikuomola et al. (2017), the content of non-organic compounds containing mineral constituents indicates the amount of ash content in food. nevertheless, the crude protein of the biscuits ranged from 11.19 – 14.59% whereas the crude protein content of sample wmc 2 (14.59%) was significantly higher than all the samples. however, sample wf 1 which is the control sample had the lowest crude protein content (11.19%). it has been observed that the addition of various flour blends (varying level of maize and cashew nut flour) lead to an increase in the crude protein content of the biscuits. this is expected because cashew nut paste has appreciable crude protein compared to wheat and maize flour. therefore, the addition of cashew nut paste to any cereal-based snacks could balance the overall amino acid and help to overcome protein malnutrition in developing countries. nevertheless, the fat content of the biscuit samples ranged from 16.24 – 20.30% and differed significantly (p<0.05) from each other. the fat content of sample wmc 3 (20.30%) was significantly higher as compared to all the samples produced. however, sample wf 1 (control sample) had the lowest fat content. this finding is similar to a previous study on biscuits produced from wheat, maize, almond and coconut flour, which shows that the control sample (wheat only) had the lowest fat content (makinde et al., 2018). also, bello et al. (2020) reported a similar trend of fat content although the biscuits were produced from wheat, unripe plantain and fluted pumpkin seed. according to ojinnaka et al. (2013), the fat content has a significant effect on the keeping quality of food products. excess fat content may lead to rancidity and unpleasant odour in food (vieira et al., 2015). the fibre content of the biscuit samples differed significantly (p < 0.05) from each other and ranged from 0.97 – 4.85%. sample wmc 8 (4.85%) recorded the highest value whereas sample wmc 2 (2.87%) obtained the least fibre content. values obtained for the fibre content in this study were above the acceptable levels (1.6 2.8%) in food as reported by fao/who, 1971. the fibre contains insoluble materials which can reduce constipation by increasing bowel movement. the carbohydrate content of the biscuit samples ranged from 56.04 – 68.27%. http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):461-476. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 468 table 3. proximate composition of biscuit samples produced from different flour blends data are mean±sd (n=3). mean values bearing similar superscripts are not significantly different (p< 0.05). wf 1= 100% wf (control); wmc 2= 80% wf: 10%mf :10% cf; wmc 3= 70% wf : 20%mf :10% cf; wmc 4= 60% wf: 30%mf :10% cf wmc 5= 50% wf : 40%mf :10% cf; wmc 6= 40% wf : 50%mf :10% cf; wmc 7= 30% wf : 60%mf :10% cf; wmc 8= 20% wf : 80%mf :10% cf. where; wf= wholewheat flour, mf = maize flour, cf = cashew nut flour sample moisture (%) ash (%) protein (%) fat (%) fibre (%) carbohydrate (%) energy (kcal/100 g) wf 1 3.92 ± 0.03a 0.99 ± 0.01c 11.19 ± 0.03c 16.24 ± 0.04c 3.97 ± 0.02d 66.96± 0.02a 458.76 ± 0.32d wmc 2 3.65 ± 0.03a 1.05 ± 0.02bc 14.59 ± 0.02a 20.21 ± 0.04a 2.87 ± 0.03c 57.63 ± 0.03c 470.77 ± 0.29b wmc 3 3.50 ± 0.06a 1.15 ± 0.03bc 14.56 ± 0.03a 20.30 ± 0.03a 3.45 ± 0.03b 57.04 ± 0.03c 468.68 ± 0.31c wmc 4 3.37 ± 0.03ad 1.23 ± 0.01b 14.53 ± 0.02a 20.06 ± 0.04ab 3.89 ± 0.02b 56.92 ± 0.02d 466.25 ± 0.35c wmc 5 3.27 ± 0.04ab 1.31 ± 0.03b 14.48 ± 0.03a 19.96 ± 0.03b 4.14 ± 0.03ab 56.84 ± 0.03d 464.92 ± 0.27c wmc 6 3.12 ± 0.04b 1.42 ± 0.03b 13.40 ± 0.04b 19.81 ± 0.03b 4.37 ± 0.04a 57.88 ± 0.03c 483.41 ± 0.25a wmc 7 3.05 ± 0.02b 1.54 ± 0.02a 13.33 ± 0.03b 19.55 ± 0.05b 4.62 ± 0.05a 57.91 ± 0.04c 458.03 ± 0.14d wmc 8 2.90 ± 0.02c 1.57 ± 0.02a 13.24 ± 0.04b 19.38 ± 0.02bc 4.85 ± 0.03a 58.06 ± 0.03b 459.62 ± 0.18d file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com mshelia et al: production and evaluation of the physiochemical and sensory property of biscuits from wheat-maize-cashewnut flour blends. azojete, 19(3):461-476. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 469 however, the carbohydrate content of sample wf 1 (66.69%) was significantly higher as compared to all the samples. sample wmc 4 (56.84%) had the least carbohydrate content. the range of carbohydrate content obtained in this study falls within the reported carbohydrate content of cookies ranges of between 54.70 – 73.02g/100g (raihan and saini 2017; ashraf et al., 2018; bello et al., 2020). in this study, it has been observed that the carbohydrate content of the biscuit samples decreased with the supplementation of 10% cashew nut and varying levels of maize flour. this corroborates with the previous studies on the production of biscuits using composite flour where a relative decrease in carbohydrate content of biscuits was observed with the addition of oat, sorghum and amaranth flour (raihan and saini, 2017). again, the increment of germinated fluted pumpkin levels in cookies (bello et al., 2020), also, a decrease in carbohydrate content of cookies and bread samples were observed with the increment of cashew-apple residue to wheat flour (ebere et al., 2015) and cashew flour to wheat flour (badje et al., 2018). the energy value of the biscuit samples ranged from 457.68 – 470.80 kcal/100g and differed significantly (p<0.05) from each other. the energy value of sample wmc 2 (470.80 kcal/100g) was significantly higher compared to other samples, while sample wf 1 (457.68 kcal/100g) had the lowest energy value. according to protonotariou et al. (2016), biscuits contain over 400 calories per 100 g which is in agreement with the range obtained in this study. this is also in agreement with a previous study reported by adeyeye, (2016) where the energy value falls within the range of 378 – 489kcal/100g. also, a similar trend of energy value was reported by giwa and ikujenlola, (2010). 3.3 physical properties of biscuits. table 4 shows the physical properties of biscuits produced from wheat-maize-cashew nut flour blends. the weight of the biscuits ranged from 15.25 – 17.36g. a significant difference (p<0.05) exists between the physical parameters of biscuit samples. the weight of sample wmc 8 was significantly higher as compared to all the biscuit samples produced while sample wmc 2 (15.25g) had the least weight. the weight of the biscuit sample increased with the increase of maize flour. http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):461-476. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 470 table 4. physical properties of biscuit samples produced from different flour blends sample weight (g) width (mm) thickness (mm) spread ratio wf 1 16.19 ± 0.03d 52.36 ± 0.04a 9.57 ± 0.02h 5.47 ± 0.02a wmc 2 15.25 ± 0.05h 51.88 ± 0.03b 10.48 ± 0.03g 4.95 ± 0.02b wmc 3 15.60 ± 0.06g 51.73 ± 0.05c 10.75 ± 0.04f 4.81 ± 0.01c wmc 4 15.92 ± 0.05f 51.53 ± 0.04d 10.84 ± 0.03e 4.75 ± 0.01d wmc 5 16.08 ± 0.04e 51.37 ± 0.03e 10.95 ± 0.02d 4.70 ± 0.01e wmc 6 16.42 ± 0.04c 51.19 ± 0.05f 11.03 ± 0.02c 4.64 ± 0.01f wmc 7 17.03 ± 0.03b 50.83 ± 0.05g 11.12 ± 0.01b 4.57 ± 0.01g wmc 8 17.36 ± 0.03a 50.54 ± 0.06h 11.27 ± 0.02a 4.48 ± 0.01h data are mean±sd (n=3). mean values bearing similar superscripts are not significantly different (p< 0.05). wf 1= 100% wf (control); wmc 2 = 80% wf : 10%mf :10% cf; wmc 3 = 70% wf : 20%mf :10% cf; wmc 4 = 60% wf : 30%mf :10% cf wmc 5 = 50% wf : 40%mf :10% cf; wmc 6 = 40% wf : 50%mf :10% cf; wmc 7 = 30% wf : 60%mf :10% cf; wmc 8 = 20% wf : 80%mf :10% cf where; wf= wheat flour, mf = maize flour, cf = cashew nut flour file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com mshelia et al: production and evaluation of the physiochemical and sensory property of biscuits from wheat-maize-cashewnut flour blends. azojete, 19(3):461-476. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 471 furthermore, the results show a significant difference (p<0.05) in the width of the biscuit which ranged from 50.54 – 52.36mm. however, sample wf 1 had the highest width while sample wmc 8 had the least width. in this study, the width of the sample increased with an increase in the supplementation of wheat flour with maize flour. spread ratio values of the biscuit samples decreased with an increase in maize flour. the spread ratio of the biscuits ranged from 4.48 – 5.47 whereas sample wmc 8 had the least spread ratio. gaines (1990) showed that the spread ratio determines the quality of the flour which depends on the values of the thickness and diameter/width of the product. this is in agreement with a previous study that reported the addition of cashew-apple fibre to wheat flour which increased the weight and height while a decrease in the diameter and spread ratio of cookie samples was observed (ebere et al., 2015). subsequently, adeyeye, (2016) also reported that the supplementation of wheat flour with sorghum flour decreased the width and spread ratio of cookies. however, the author also reported that the thickness and weight of the cookies decreased with the addition of sorghum flour. furthermore, raihan and saini (2017) also observed a decrease in diameter, spread ratio and an increase in thickness of biscuits when oat, sorghum and amaranth composite flour was added to wheat flour. this could be attributed to the water binding power, internal structure, the particle size of the flours and their capacity to compact (belorio et al., 2019). 3.4 sensory evaluation of the biscuit samples. the sensory properties of the biscuits are shown in table 5. in this study, supplementation of 10% cashew nut flour and varying levels of maize flour to wheat flour significantly affected (p<0.05) the texture, taste and overall acceptability of prepared biscuit samples. there was a significant difference (p>0.05) in the aroma and colour of the prepared biscuit samples. table 5. sensory evaluation of biscuits produced from different flour blends sample colour taste aroma texture overall acceptability wf 1 7.80 ± 0.92a 7.20 ± 1.48ab 6.30 ± 1.57a 7.70 ± 1.25a 8.40 ± 0.84a wmc 2 6.70 ± 1.70a 8.00 ± 1.05a 7.80 ± 1.23a 7.50 ± 1.43ab 7.30 ± 0.67ab wmc 3 6.30 ± 1.49a 7.00 ± 1.15ab 6.70 ± 1.25a 7.10 ± 1.10abc 7.10 ± 0.74ab wmc 4 6.40 ± 1.51a 6.60 ± 1.07ab 6.70 ± 0.82a 7.00 ± 1.05abc 6.90 ± 1.73ab wmc 5 6.20 ± 1.75a 6.50 ± 1.35ab 6.40 ± 1.65a 6.70 ± 0.97abc 6.70 ± 1.34ab wmc 6 6.00 ± 1.94a 6.40 ± 1.65ab 6.20 ± 1.48a 6.50 ± 1.08abc 6.70 ± 1.42ab wmc 7 6.00 ± 1.70a 5.90 ± 2.08b 6.20 ± 0.90a 6.00 ± 1.15bc 6.30 ± 1.74ab wmc 8 5.40 ± 1.78a 5.70 ± 1.70b 5.80 ± 1.62a 5.50 ± 1.35c 5.70 ± 1.16b http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):461-476. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 472 data are mean±sd (n=3). mean values bearing similar superscripts are not significantly different (p< 0.05). wf 1= 100% wf (control); wmc 2= 80% wf : 10%mf :10% cf; wmc 3= 70% wf : 20%mf :10% cf; wmc 4= 60% wf : 30%mf :10% cf wmc 5= 50% wf : 40%mf :10% cf; wmc 6= 40% wf : 50%mf :10% cf; wmc 7= 30% wf : 60%mf :10% cf; wmc 8= 20% wf : 80%mf :10% c the colour mean scores of the biscuit samples ranged from 5.40 7.80. considering the colour, sample wf 1 had the highest score while sample wmc 8 obtained the least score. generally, the biscuits produced from wheat flour supplemented with cashew nut flour and various levels of maize flour had a darker colour than the control biscuits. this is in agreement with the previous study who reported an increase in dark colour with the level of supplementation which could be due to the protein content which is adequate for maillard reaction to take place and are very common and desirable in baked products (ikuomola et al., 2017). regarding the texture, sample wf 1 was significantly higher (p>0.05) than all the samples while sample wmc 8 had the lowest score which ranged from 5.50 – 7.70. it has also been observed that the texture of the biscuit decreases with an increase in the supplementation of wheat flour with maize flour. the taste scores of the biscuit samples ranged from 5.70 – 8.00, however, sample wmc 2 recorded the highest and differed significantly (p<0.05) from all the samples while sample wmc 8 had the least taste score. the aroma of the biscuit samples ranged from 5.80 – 7.80. furthermore, a significant difference (p<0.05) existed between the aroma of the biscuits where sample wmc 2 recorded the highest while sample wmc 8 had the least score. among all the biscuit samples produced, the overall acceptability score of the biscuit samples ranged from 5.70 – 8.40. sample wf 1 was significantly higher as compared to all the samples while sample wmc 8 had the least overall acceptability score. the lower acceptable scores of the biscuits supplemented with maize and cashew nut flour could be due to the dark colouration. in this study, although the biscuit supplemented with 10% cashew nut flour and 10% maize flour (wmc 2) had a higher aroma and taste score compared to the control biscuits sample, however, it is not the most acceptable sample. the sensory evaluation showed that although there was a significant (p< 0.05) increase in the proximate composition of the biscuit samples, the overall acceptability of biscuit samples decreased with increasing levels of maize flour. 4. conclusion in conclusion, the study showed that acceptable biscuits from the blends of cashew nut, wheat and maize flour with improved nutritional quality and high dietary fibre content could be produced. the results from this study showed that supplementation of 10% cashew nut and varying levels of maize (10, 20, 30, 40, 50, 60 and 70%) flour to wheat flour increased the nutritional values of biscuit samples produced. it is clear that such effort might lead to increased utilization of cashew nuts flour and the production of cashew nuts will be encouraged. furthermore, the high protein content in cashew nut flour incorporated biscuits could be used to address the problem of prevalence of protein-energy malnutrition in many communities. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com mshelia et al: production and evaluation of the physiochemical and sensory property of biscuits from wheat-maize-cashewnut flour blends. azojete, 19(3):461-476. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 473 moreover, the high level of dietary fibre of the biscuits would be beneficiary to the health of consumers. biscuits produced from wheat supplemented with maize and cashew nut flour will help reduce the country's dependency on the importation of wheat grain. references abdulrahaman, aa. and kolawole, om. 2006. traditional preparations and uses of maize in nigeria. ethnobotanical leaflets, 10: 219-227. adepoju, ab., coker, oj. and adetula, oa. 2019. effects of processing methods on the proximate and physicochemical properties of flour and oil of cashew nut. nigerian journal of nutritional sciences, 40: 87-90. adeyeye, sao. 2016. assessment of quality and sensory properties of sorghum–wheat flour cookies. cogent food and agriculture, 2: 1-10. afzal, m., nasir, z., bashir, mh. and khan, bs. 2009. analysis of list plant resistance in some genotypes of maize against chilo partellus (swinhoe) (pyralidae: lepidoptera). pakistan journal of botany, 41: 421-428 akinhanmi, tf., atasie, vn. and akintokun, po. 2008. chemical composition and physicochemical properties of cashew nut (anacardium occidentale) oil and cashew nut shell liquid. journal of agricultural, food and environmental sciences, 2: 1-10. aoac. 2005. official methods of analysis of aoac international. 18th ed. gaithersburg (md): aoac international. available: http://www.eoma.aoac.org. accessed 10 july 2022 aremu, mo., olonisakin, a., bako, da., and madu, pc. 2006. compositional studies and physicochemical characteristics of cashew nut (anarcadium occidentale) flour. pakistan journal of nutrition, 5: 328-333. ashraf, u., bandral, jd., sood, m., sofi, s., rafiq, s. and sharma, s. 2018. effect of replacement of wheat flour with apricot powder on nutritional and sensory quality of nutcrackers. the pharma innovation journal, 7: 695-701. ayo, ja., ayo, va., nkama, i. and adeworie, r. 2007.physicochemical, invitro digestibility and organoleptic evaluation of acha-wheat biscuit supplemented with soybean flour. nigerian food journal, 25: 15-17. babiker, ee., ozcanb, mm., ghafoora, k., al juhaimia, f., ahmeda, iam. and almusallama, ia. 2021. bioactive compounds, nutritional and sensory properties of cookies prepared with wheat and tiger nut flour. food chemistry, 349: 1-8. badje, ds., soro, d., yeo, ma. and koffi, ek. 2018. physico-chemical, functional and sensory properties of composite bread prepared from wheat and defatted cashew (anacardiumoccidentale l.) kernel flour. international journal of environmental and agriculture research, 4: 88-98. belorio, m., sahagún, m. and gómez, m. 2019. influence of flour particle size distribution on the quality of maize gluten-free cookies. foods, 8: 3. http://www.azojete.com.ng/ mailto:ladi.peter05@gmail.com mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; 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vol. 19(3):461-476. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 476 ojinnaka, mc. and agubolum, fu. 2013. nutritional and sensory properties of cashew nut wheat based cookies. american journal of food and nutrition, 3: 127-134. ojinnaka mc., ihemeje, a. and ugorji co. 2016. quality evaluation of cookies produced from african breadfruit, wheat and pigeon pea flour blends. agriculture and biology journal of north america, 3: 101-106. oladapo as., adepeju, ab., akinyele, aa. and adepeju, dm. 2017. the proximate, functional and anti-nutritional properties of three selected varieties of maize (yellow, white and pop corn) flour. international journal of scientific engineering and science, 1: 23-26. protonotariou, s., batzaki, c., yanniotis, s. and mandala, i. 2016. effect of jet milled whole wheat flour in biscuits properties. lwt food science and technology, 74: 106-113. raihan, m. and saini, cs. 2017. evaluation of various properties of composite flour from oats, sorghum, amaranth and wheat flour and production of cookies thereof. international food research journal, 24: 2278-2284. świeca, m., gawlik-dziki, u., dziki, d. and baraniak, b. 2017. wheat bread enriched with green coffee – in vitro bioaccessibility and bioavailability of phenolics and antioxidant activity. food chemistry, 221: 1451-1457. srivastava, s., genitha, tr. and yadav, v. 2012. preparation and quality evaluation of flour and biscuit from sweet potato. journal of food processing and technology, 3: 1-5. sule, ei., umoh, vj., whong, cmz., abdullahi, io. and alabi, o. 2014. chemical and nutritional value of maize and maize products obtained from selected markets in kaduna state, nigeria. african journal of food science and technology, 5: 100-104. topping, d. 2007. cereal complex carbohydrates and their contribution to human health. journal of cereal science, 46: 220-229. vieira, sa., mcclements, dj. and decker ea. 2015. challenges of utilizing healthy fats in foods. advances in nutrition, 6: 309s-317s. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ladi.peter05@gmail.com arid zone journal of engineering, technology and environment, august, 2017; vol. 13(4):502-512 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 502 development and performance evaluation of a poultry waste management technique using gravity sand filter *t. d. akpenpuun 1 , k. a. adeniran 2 , b. a. akinyemi 3 and o. o. ologun 4 ( 124 department of agricultural and biosystems engineering, university of ilorin, ilorin, nigeria) ( 3 department of agricultural and biosystems engineering, landmark university, omu-aran, kwara state) *corresponding author’s e-mail address: akpenpuun.td@unilorin.edu.ng abstract the research aimed at developing and evaluating a poultry waste management technique using gravity sand filter. poultry waste slurry prepared in a mixing tank was intermittently applied uniformly to the surface of a filter bed using a spreader as dosing technique. two different types of configurations were designed for the filter bed. single media bed consisted of 150mm depth of silica sand with average particle diameter of 0.5mm. dual media bed consisted of 100mm depth of granulated charcoal with average particle diameter of 1.0mm and 50mm of silica sand with average particle diameter of 0.5mm. design considerations important to achieving this level of treatment include; pretreatment, media characteristics, hydraulic and organic loading rates and filter dosing techniques. each sand filter configuration was operated daily for a period of 12days. the following data were collected on a daily basis: volume of effluents (mm 3 ), hydraulic residence time (hours), unit filter run volume (m 3 /m 2 ), filtration rate or filtration velocity (mm/hr). head loss on the filter was calculated using carmen-kozeny equation for uniform sand bed. laboratory investigations showed that effluent from the filter had biological oxygen demand (bod5), total suspended solids (tss), total dissolved solids (tds), and turbidity range between1.98 – 12.08 mg/l, 20.75 – 30.20 mg/l, 29.40 – 34.40 mg/l and 5.10 – 6.20 ntu. keywords: poultry, waste, filtration, technique, management, poultrywaste, gravity sand filter, filtration technique 1. introduction poultry production forms an important aspect of livestock sub-sector in nigeria and is considered to be the largest livestock group estimated to be about 4.2 million, consisting mainly of chickens, ducks, guinea fowls, turkeys, pigeons and ostriches (npc, 2006). poultry litter is a mixture of bedding material and poultry manure arising from the housing of poultry and with dry matter content not less than 55% (onisanwa, 2014). poultry industries produce large quantities of waste in solid and liquid form. poultry solid waste consists of bedding materials, excreta (manure), feed, feathers, hatchery waste (empty shells, infertile eggs, dead embryos and late hatchlings), shells, sludge, abattoir waste (offals, blood, feathers and condemned carcases) and mortality (onisanwa, 2014). poultry waste is usually a combination of poultry bird faeces, urine, sawdust and remnants of animal feeds, drugs and pesticides (adedayo, 2012). poultry raised for commercial purpose could produce a large amount of manure, which unlike the manure of free ranged or pastured animals is a collectable resource. poultry manure contains high phosphorus which has a positive effect on the growth and productivity of crops. it is also effective when combined with mineral phosphorus fertiliser for farm use (moreki and keaikitse, 2013). dead birds and hatchery waste are high in protein and contain substantial amounts of calcium and phosphorus due to high levels of mineral supplements in the diet. the approximated percentages of nutrient intake excreted by poultry are: nitrogen (65.5%), phosphorus (68.5%) and potassium (83.5%), elements for soil fertility and increased crop production (olumayowa and abiodun, 2011). poultry meat and eggs provide affordable and quality food products that are consumed worldwide. advances in knowledge and technology over recent decades favour the growth and arid zone journal of engineering, technology and environment, august, 2017; vol. 13(4):502-512 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 503 intensification of poultry production in developing countries where there are increasing human populations. however, poultry is a potential hazard that can result in pollution of surface and ground water and the emission of large quantities of unpleasant and provocative odour (greenhouse gases) (moreki and chiripasi., 2011). one aspect of poultry operations that has not kept pace with the increase in the intensity of poultry production is waste management. the production of poultry products results in hatchery wastes, manure, litter, and on-farm mortalities all which are high in protein and contain substantial amounts of calcium and phosphorus due to the high levels of mineral supplements in the poultry diet. the processing of poultry results in additional waste materials, including offal (feathers, entrails, and organs of slaughtered birds), processing wastewater and bio-solids. most of these by-products can provide valuable organic and inorganic materials if managed and recycled properly, regardless of flock size (moore and chiripasi, 2011). poultry waste disposal employed by poultry operators are selling, burying, flushing, rendering, incinerating, compositing, livestock feeding and soil fertilising. other waste disposal methods include conversion of poultry waste to source of energy and treatment of water contaminated with heavy metal (moore and chiripasi, 2011). recent studies have provided evidence of environmental, social and economic contributions of waste utilisation for urban food production. however, a major problem to contend with remains how waste can best be managed for healthy food production with minimal negative health implications (nahn and nahm, 2004). in lieu of this, concern for soil, water and air quality is the key to selecting a successful waste management plan and technique. this concern for an appropriate poultry waste management technique necessitated this study aimed at developing and evaluating a poultry waste management technique using gravity sand filter. 2. materials and methods 2.1 description of structural components the poultry waste management mechanism consisted of plastic slurry tank, plastic filter tank (sand and gravel and sand and charcoal), pipes and under-drains, manual control valves, spreaders, and effluent tank. shown in figures 1, 2 and 3 are the experiment setup, manifolds and spreader of the treatment plant. figure 1: sand filter treatment figure 2: manifolds with lateral pipes figure 3: spreader for poultry waste the slurry tank was a cylindrical plastic drum. the slurry tank was connected to the filter tank, placed below the slurry tank, by a discharge outlet positioned at 5cm from the bottom of the filter tank to enable flow by gravity. this connection was made using 2 inches diameter pvc pipe. a akpenpuun et al.: development and performance evaluation of a poultry waste management technique using gravity sand filter azojete, 13(4):502-512. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 504 control valve was installed 30 cm from the slurry tank in order to control flow. the filter tank was also cylindrical in shape and made of plastic material but it was of bigger size or volume compare to that of slurry tank. in the filter tank, there was a layer of a sand filter bed. sand filter bed is a range of grain sizes for the base soil or soils to satisfy filtration requirements. a screen or spreader was provided at the top cover of the filter tank in order to spread or discharge the flow of slurry uniformly throughout the filter cross section. at the bottom of the filter tank, was an underdrain system. it had a common header pipe going down the middle of the filter with a series of lateral pipes extending from the header. 2.2 performance tests and evaluation poultry waste (boiler waste) was obtained from rask integrated farm, ilorin, and mixed thoroughly with 100 liters of water to prepare the slurry in a slurry tank. the slurry was discharged from the slurry tank through a discharge outlet into the filter tank at a height of 120 mm above the filter bed surface. a control valve was installed on the outlet of the filter tank to control effluent flow. the effluent was collected in a measuring cylinder positioned 30cm below the filter tank. the volume of the discharged effluent was recorded 3 times daily at an interval of 1 hour for each of the configurations throughout the period of the experiment. the effluent was analysis to determine the strength of the effluent. a. single media (configuration a) this was made up of silica sand (average particle size diameter of 0.5mm and depth 150mm) and silica gravel (average particle size diameter of 5 – 50mm and depth 130mm) as shown in fig. 4. figure 4: configuration a b. dual media (configuration b) this was made up of silica sand (average particle size diameter of 0.5mm and depth 50mm), coal (average particle size of 1.0mm and depth 100mm) and silica gravel (average particle size diameter of 5 – 50mm and depth 130mm) as shown in figure 5. figure 5: configuration b arid zone journal of engineering, technology and environment, august, 2017; vol. 13(4):502-512 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 505 2.3 measurement of parameters the slurry was filtered for a period of 12 days using two configurations of gravity sand filter namely: single media (configuration a) and dual media (configuration b). samples obtained from configuration a and b were coded a1 – a12 and b1 – b12, respectively. during filtration, the effluent volume, filtration velocity and head loss were measured daily for each configuration. also, the dissolved oxygen in the effluent was determined in accordance with iso 5815-1 (2003) and iso 5814 (2012) for each configuration in order to evaluate the biochemical oxygen demand (bod5). other water quality parameters such as total suspended solids (tss) and total dissolved solids (tds) were also determined in accordance with iso 7027-1 (2016), while turbidity of the effluent was determined in accordance with iso 7027-1, 2016. the study investigated and evaluated the effect of time of operation on the bod5, tss, tds, turbidity, filtration rate and head loss in each of the gravity sand filter configurations. 2.4 data and analysis descriptive statistics and one-way analysis of variance (anova) were performed using statistical package for social sciences (spss). the tukey hsd test was used to further compare the means of the treatment parameters. 3 results and discussion tables 1 and 2 present the daily operating records for single and dual media filter configurations a and b, respectively, operating for the period of 12 days. they present the number of hours operated, unit filter run volume, filtration rate and head loss for the single media filter configuration on daily basis. table 1: daily operating records for single media filter (configuration a) sample no time & date hours of operation ufrv (mm3/mm2) filtration rate(mm/hr) head loss (mm) start stop a1 26/05/2016 26/05/2016 2:55 166.70 57.15 31.00 13:45 16:40 a2 27/05/2016 27/05/2016 6:05 165.55 52.27 34.30 08:20 11:30 a3 28/05/2016 28/05/2016 9:25 163.89 49.17 37.70 14:20 17:40 a4 29/05/2016 29/05/2016 13:00 162.22 45.27 41.40 08:55 12:30 a5 30/05/2016 30/05/2016 16:45 160.00 42.67 45.20 09:00 12:45 a6 31/05/2016 31/05/2016 20:35 156.67 40.87 48.40 08:25 12:15 a7 01/06/2016 01/06/2016 24:35 152.77 38.19 51.80 8:55 12:55 a8 02/06/2016 02/06/2016 28:45 148.88 35.73 54.00 13:25 17:35 a9 03/06/2016 03/06/2016 33:10 144.44 32.70 57.30 09:05 13:30 a10 04/06/2016 04/06/2016 37:50 138.89 29.76 62.30 08:40 13:20 a11 05/06/2016 05/06/2016 42:45 133.33 27.12 66.20 13:05 18:00 a12 06/06/2016 06/06/2016 48:00 126.67 24.13 72.40 12:20 17:35 akpenpuun et al.: development and performance evaluation of a poultry waste management technique using gravity sand filter azojete, 13(4):502-512. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 506 table 2: daily operating records for dual media filter (configuration b) sample no time & date hours of operation ufrv (mm3/mm2) filtration rate(mm/hr) head loss (mm) start stop b1 18/06/2016 18/06/2016 2:35 166.70 64.53 43.60 12:20 14:55 b2 19/06/2016 19/06/2016 5:17 165.55 61.32 41.40 13:48 16:30 b3 20/06/2016 20/06/2016 8:07 163.89 57.84 39.10 09:34 12:24 b4 21/06/2016 21/06/2016 11:05 162.22 54.68 37.00 10:02 13:00 b5 22/06/2016 22/06/2016 14:13 160.00 51.06 34.50 11:46 14:54 b6 23/06/2016 23/06/2016 17:33 156.67 47.00 31.70 12:05 15:25 b7 24/06/2016 24/06/2016 21:08 152.77 42.63 28.80 14:30 18:05 b8 25/06 25/06 24:58 148.88 38.84 26.20 13:09 16:59 b9 26/06 26/06 2858 144.44 36.11 24.40 08:42 12:42 b10 27/06/2016 27/06/2016 33:13 138.89 32.68 22.10 14:05 16:20 b11 28/06/2016 28/06/2016 37:33 133.33 30.77 20.80 11:50 16:10 b12 29/06/2016 29/06/2016 42:03 126.67 28.15 19.00 12:20 16:50 table 3 shows the effluent quality through configuration a and configuration b, respectively. the analysis of variance result in table 5 shows that the p-value corresponding to f statistics is less than 0.05, suggesting that the effect of configuration on the head loss of sand filter, effect of configuration on the bod of effluent and effect of configuration on the tds of effluent were significantly different. on the other hand, the effect of configuration on the filtration rate of sand filter, tss of effluent and turbidity of effluent corresponding to the f statistic of one-way anova were greater than 0.05 respectively, suggesting that the treatments were statistically insignificant. shown in tables 4 and 6 are configuration b effluent quality and tukey hsd test result for the effects of treatments on the effluent. arid zone journal of engineering, technology and environment, august, 2017; vol. 13(4):502-512 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 507 table 3: configuration a effluent quality for single media sand filter sample number do0 (mg/l) do5(mg/l) bod5 (mg/l) tss (mg/l) tds (mg/l) ts(mg/l) turbidity (ntu) a1 122.20 118.02 4.18 21.84 30.96 52.80 5.25 a2 118.80 112.68 6.12 21.45 31.95 53.40 5.30 a3 116.20 110.00 6.20 24.20 30.20 54.40 5.40 a4 113.10 105.90 7.20 24.70 29.80 54.50 5.45 a5 112.00 104.62 7.38 25.20 30.60 55.80 5.60 a6 105.60 98.16 7.44 22.80 33.50 56.30 5.70 a7 100.80 92.98 7.82 25.80 30.60 56.40 5.80 a8 96.00 86.02 9.98 23.20 33.70 56.90 5.90 a9 92.80 82.66 10.14 23.40 34.40 57.80 6.00 a10 88.20 77.64 10.56 28.90 31.60 60.50 6.10 a11 78.40 67.58 10.82 29.80 30.80 60.60 6.15 a12 73.60 61.52 12.08 30.20 31.50 61.70 6.20 control 139.80 125.48 14.32 46.80 52.10 98.90 9.80 table 4: configuration b effluent quality for dual media sand filter sample number do0 (mg/l) do5 (mg/l) bod5 (mg/l) tss (mg/l) tds (mg/l) ts (mg/l) turbidity (ntu) b1 123.66 121.68 1.98 20.75 29.4 50.15 5.1 b2 117.14 113.32 3.82 20.35 30.35 50.7 5.2 b3 115.5 116.6 3.9 23 28.7 51.7 5.25 b4 112.34 107.48 4.86 23.47 28.38 51.75 5.3 b5 112.24 107.22 5.02 23.92 29.08 53 5.4 b6 105.7 100.62 5.08 21.66 31.84 53.5 5.45 b7 103.82 95.38 5.44 24.5 29.05 53.55 5.5 b8 97.56 90.06 7.5 22.04 32.01 54.05 5.55 b9 95.92 88.26 7.66 22.22 32.68 54.9 5.6 b10 92.66 84.6 8.06 27.46 30.04 57.5 5.7 b11 79.6 71.3 8.3 28.28 29.27 57.55 5.8 b12 74.7 65.2 9.5 28.69 29.91 58.6 5.9 control 143.62 131.1 12.52 44.4 49.5 93.9 9.6 table 5: anova for the effects of treatments on the effluent treatments fstatistic fcritical p-value effect of configuration on the filtration rate 1.59 4.30 0.22 effect of configuration on the head loss of sand filter 19.02 4.30 *0.01 effect of configuration on the bod of effluent 5.29 4.30 *0.01 effect of configuration on the tds of effluent 7.13 4.30 *0.01 effect of configuration on the tss of effluent 0.28 4.30 0.60 effect of configuration on the turbidity of effluent 4.58 4.30 *0.04 *significant at 5%, df1 = 1, df2 = 22 akpenpuun et al.: development and performance evaluation of a poultry waste management technique using gravity sand filter azojete, 13(4):502-512. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 508 table 6: tukey hsd test result for the effects of treatments on the effluent treatments tukey hsd qstatistics tukey hsd p-value tukey hsd inference effect of configuration on the head loss of sand filter 6.1682 0.001 ** p<0.01 effect of configuration on the bod of effluent samples 3.6117 0.018 * p<0.05 effect of configuration on the tds of effluent samples 3.78 0.014 * p<0.05 effect of configuration on the turbidity of effluent 3.03 0.040 * p<0.05 shown in figure 8 is the relationship between tss and hydraulic residence time. the figure shows that the removal of tss concentrations was similar for both configurations, so design factors such as pretreatment, maximum water depth, and filter area apparently have little effect on particle removal. it was observed that tss removal dropped at about 28 hours after treatment was started, but increased as the experiment proceeded. there is similarity in the trend of observation with the work of moreki and keaikitse (2013) who reported that tds and tss removal from selected poultry operations around gaborone fluctuated as the treatment proceeded. figure 8: relationship between tss effluent quality and hydraulic residence time the trend for tds removal in both treatment configurations is shown in figure 9. the removal of tds is similar to that observed for tss and is statistically not significant for both configurations. similarly, tds removal was not a function of time, indicating that the accumulation of material on and within the filter had little impact on particle removal. moreki, et. al., (2011) report a similar trend in the fluctuation of tss and tds during treatment. 0 5 10 15 20 25 30 35 0 6 :0 5 1 3 :0 0 2 0 :3 5 2 8 :4 5 :0 0 3 7 :5 0 :0 0 4 8 :0 0 :0 0 to ta l s u sp e n d e d s o lid s (m g/ l) time (hours ) configuration a configuration b arid zone journal of engineering, technology and environment, august, 2017; vol. 13(4):502-512 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 509 figure 10: relationship between tds and hydraulic residence time figure 10 shows the relationship between effluent quality in terms of bod and detention. it can be observed from figure 10 that filter configuration a recorded higher removal values of bod throughout the detention time than configuration b. the highest value of bod removal recorded for configuration b was 9.81 mg/l. removal of bod in configuration b was much more significant than the bod removal in configuration a. grant et. al., 2008 who used both configurations in the treatment of broiler droppings recorded a similar trend. figure 10: relationship between bod and hydraulic residence time figure 11 shows the extent of turbidity in both configurations. the observation that turbidity removal and hydraulic residence time. the removal of turbidity increased with the hydraulic residence time. early in the life of the filter a substantial amount of turbidity was removed by deep bed filtration process. configuration a recorded higher removal of turbidity than configuration b. however, the differences in turbidity removal by both configurations was not significant. 0 5 10 15 20 25 30 35 40 0 2 :5 5 0 6 :0 5 0 9 :2 5 1 3 :0 0 1 6 :4 5 2 0 :3 5 2 4 :3 5 :0 0 2 8 :4 5 :0 0 3 3 :1 0 :0 0 3 7 :5 0 :0 0 4 2 :4 5 :0 0 4 8 :0 0 :0 0 to ta l d is so lv e d s o lid s (m g/ l) time since first sample (hours ) configuration a configuration b 0 2 4 6 8 10 12 14 0 6 :0 5 1 3 :0 0 2 0 :3 5 2 8 :4 5 :0 0 3 7 :5 0 :0 0 4 8 :0 0 :0 0 b io ch e m ic al o xy ge n d e m an d ( m g/ l) time (hours ) configuration a configuration b akpenpuun et al.: development and performance evaluation of a poultry waste management technique using gravity sand filter azojete, 13(4):502-512. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 510 figure 11: relationship between turbidity and hydraulic residence time the filtration rate and hydraulic residence time is shown in figure 12. the filtration rate performance for both configurations decreased with hydraulic residence time. figure 12 shows that filtration rate reduces as the filter ages due to the filter clogs. it can be observed that at the beginning of the experiment configuration a and configuration b had filtration rates of 65.30 and 58.5 mm/hr, respectively. the steady reduction in the filtration rate observed is similar to the steady drop in filtration rate reported by grant et. al., 2008. figure 12: relationship between filtration rate and hydraulic residence time head loss is a function of time, indicating that the accumulation of material on and within the filter had little impact on the clogging or ripening of the sand filter. figure 13 shows that head loss in both configurations is statistically significant. pretreatment reduces the total sediment load to the filter by about 65-70%, but may not reduce the head loss in the filter since much of this sediment likely is fairly coarse, which would result in little loss of permeability if it accumulated on the surface of the filter. this was also corroborated by adene et. al., 2006. 0 1 2 3 4 5 6 7 0 6 :0 5 1 3 :0 0 2 0 :3 5 2 8 :4 5 :0 0 3 7 :5 0 :0 0 4 8 :0 0 :0 0 t u rb id it y (n tu ) time since first sample (hours ) configuration a configuration b arid zone journal of engineering, technology and environment, august, 2017; vol. 13(4):502-512 issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 511 figure 13: relationship between head loss and hydraulic residence time 4 conclusion from the study, the following conclusion were drawn: (i) configuration b operated on higher filtration rate with an average filtration rate of 45.50mm/hr compared to configuration a operating at an average filtration rate of 39.60mm/hr, during the 12days operating period. (ii) head loss in configuration b is lower than that of configuration a. this infers that configuration a clogs or ripens faster and backwashing would be required more often than that of configuration b. (iii) configuration b produces better effluent quality with percentage bod removal 53%, percentage tss removal 50%, tds removal 42% and turbidity removal of 45% compared to configuration b producing effluent quality with percentage bod removal of 42%, tss removal of 46%, tds removal of 40% and turbidity removal of 40%. the sand filter could, therefore, be said to be effective in the treatment of poultry waste. references adedayo v. 2012. poultry waste management techniques in urban agriculture and its implications: a case of metropolitan lagos, nigeria. asian journal of agricultural science vol. 4 no. 4: 258-263 moreki, jc. and sc. chiripasi. 2011 poultry waste management in botswana: a review. online journal of animal and feed research. vol. 1 no. 6: 285-292. moreki, jc and keaikitse t. 2013. poultry waste management practices in selected poultry operations around gaborone, international journal of current microbiology, botswana. vol. 2 no. 7: 240-248 nahm, kh. and nahm, b.a. 2004. poultry production and waste management. republic of korea, yu han publishing. isbn 89-7722-623-6. onisanwa, id. 2014. the impact of health on economic growth in nigeria. journal of economics and sustainable development. vol. 5 no.19:159 – 166 olumayowa, o., and abiodun, oo. 2011. profit efficiency and waste management in poultry farming: the case of egba division, ogun state, nigeria. int. j. poult. sci. vol. 10 no. 2:137 142. 0 20 40 60 80 0 6 :0 5 1 3 :0 0 2 0 :3 5 2 8 :4 5 :0 0 3 7 :5 0 :0 0 4 8 :0 0 :0 0h e ad lo ss ( m m ) time since first sample (hours ) configuration a configuration b akpenpuun et al.: development and performance evaluation of a poultry waste management technique using gravity sand filter azojete, 13(4):502-512. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 512 charles, mw. 2008. poultry waste management in developing countries, utilisation of poultry waste. north carolina state university, department of poultry science, raleigh nc, united states of america. grant, s., and marshalleck, a. 2008. ‘energy production and pollution mitigation from broilers houses on apoultry farm in jamaica and pennsylvania. ‘international journal for service learning in engineering. vol. 3 no. 1:41-42. npc 2006. national population commission. bulletins on population census figures. international organization for standardization iso 5815-1 2003. water quality: determination of biochemical oxygen demand after n days (bodn): part 1: dilution and seeding method with allylthiourea addition. https://goo.gl/h8xxey. date accessed: 11th jan. 2017. international organization for standardization iso 5814 2012. water quality: determination of dissolved oxygen electrochemical probe method. https://goo.gl/yaqoow. date accessed: 11th jan. 2017. international organization for standardization, iso 6060: 1989. water quality: determination of the chemical oxygen demand. https://goo.gl/st8pjo. date accessed: 11th jan. 2017. international organization for standardization, is 3025 2009. (part 21): method of sampling and test (physical and chemical) for water and wastewater, part 21: hardness (second revision). https://goo.gl/q88jcl. date accessed: 11th jan. 2017. international organization for standardization, iso 7027-1, 2016. water quality-determination of turbidity: part 1: quantitative methods. https://goo.gl/2lufds. date accessed: 11th jan. 2017. https://goo.gl/h8xxey https://goo.gl/yaqoow https://goo.gl/st8pjo https://goo.gl/q88jcl https://goo.gl/2lufds arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):575-586 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: edirin.omoze@uniben.edu 575 original research article artificial neural network (ann) pathloss prediction model for lte network for microcells in an urban environment e. l. omoze* and j. o. emagbetere department of electrical and electronic engineering, university of benin *corresponding author’s email address: edirin.omoze@uniben.edu 1.0 introduction the demand trend for mobile communication services has shown that as population increases coupled with technological advancement, the demand for mobile communication services increases (bi et al., 2001). the mobile communication technology has advanced from first generation (1g) to (4g) in nigeria. the brand name for the fourth generation of mobile wireless cellular communication standard is long term evolution (lte). lte, a successor to both 2g and 3g developed by the 3rd generation partnership project (3gpp) committee to improve universal mobile telecommunications services (umts) communication standard is a highly flexible radio interface. the demand for telecommunication services necessitates the need for proper planning of cellular networks. the performance of cellular networks depends on the propagation model deployed during planning stage. due to the complex and diverse nature of the radio propagation environment, the power of a propagating signal fluctuates with respect to time and space. thus, a model that will work best is that which is developed using propagation data gotten from that environment. the use of empirical and deterministic models for deployment of mobile networks presents a compromise between accuracy and simplicity (ojo et al., 2021). example of empirical models in literature are the okumura-hata model, walfisch ikegami model, stanford university interim model, egli model and cost 231 hata model (zhang et al., 2019 and jo et al., 2020). article information abstract one of the challenges faced by telecommunication service providers is capacity. the capacity of a cell depends on the model used in planning the cell during deployment stage. this paper presents artificial neural network (ann) pathloss prediction model for long term evolution (lte) network for microcells in benin city, edo state, nigeria. received signal strength data collected with respect to distance, mobile station antenna height and base station antenna height was used to create a data base with pathloss estimated from the measured data. a feature variable consisting of 80% of measurement data collected was used to train a 432-1 multilevel perceptron artificial neural network with pathloss as the label using python language on scientific python development environment interface (spyder). the result of the 20% test data shows that artificial neural network is suitable for predicting pathloss in benin city. this is as a result of root mean square error (rmse) values and mean absolute error values of 0.59𝑑𝐵 and 0.42𝑑𝐵 obtained respectively which are less than the 6𝑑𝐵 error value allowed for network planning. it is recommended that the result of the study be adopted in designing or expanding lte network capacity in the areas studied in this work. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 9 september, 2021 revised 28 october, 2021 accepted 5 november, 2021 keywords: pathloss artificial neural network (ann) received signal strength root mean square error (rmse) long term evolution (lte) http://www.azojete.com.ng/ file:///c:/users/i3/downloads/edirin.omoze@uniben.edu mailto:edirin.omoze@uniben.edu arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):575-586. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gedirin.omoze@uniben.edu 576 although the empirical models are simple to use because of the few parameters needed to predict the path loss in a given environment, they provide unsatisfactory results when applied to a more general radio propagation environment since they are mostly site specific (zhang et al., 2019 and jo et al., 2020). deterministic models are more accurate but quite complex to develop and lack computational accuracy with an example being the ray tracing method. in order to develop models that can predict pathloss with high accuracy and computationally efficient, researchers in recent times have looked into machine learning based path loss prediction models. a lot of researchers have contributed knowledge in the area of developing pathloss models for cellular network planning. while some have develop models for different mobile network technologies, others have simulated cellular networks at different frequencies. shoewu et al. (2019) presented the result on a study conducted in wetland and dry land areas in lagos state, nigeria using received signal strength data collected with tems investigation software installed on mobile phone via drive test for 4g cellular networks. their result show that existing empirical model such as ecc-33 model, cost 231 hata model, free space model, okumura model and davidson-hata model are not suitable for pathloss prediction in lagos. sulyman et al. (2014), sree vardhan et al. (2016), ubaidillah et al. (2020) and atanasoy et al. (2017) also carried out propagation studies on different locations. sharma et al. (2018) presented a report on optimization of propagation pathloss model in 4g wireless communication system was presented. the authors in this study carried out data collection at 1800mhz in india and compared their result with predictions made by cost-231 hata, egli, walfich-bertoni, ecc-33 and sui models with pathloss values obtained from the measured field strength data. the authors reported that cost231 hata, is best model based on the closest agreement to the measured path loss exponent. thus, the cost 231 hata model was optimized. among the various studies reviewed, it is worthy of note that propagation models are environment specific and existing empirical models are mostly not suitable for use in planning cellular networks in environment where the terrain characteristics is not similar with that in which the model is built for. in wireless communication, pathloss prediction is treated as a supervised learning task with the received signal strength, distance between the mobile station and the base station, mobile station antenna height and base station antenna height as the feature variables and the path loss values as the label. artificial neural network (ann) is a one of the artificial intelligence algorithms that can be used in developing pathloss models based on data collected in a typical radio propagation environment and trained with it (eichie et al., 2017). the flexibility of ann to learn from a given data set without being explicitly programmed can be seen from researches in recent times. an artificial neural network (ann) is a learning algorithm whose design is inspired by the behavior of neurons in the human brain. an ann is based on a collection of connected units or nodes called artificial neurons. a neuron is the fundamental processing element of a neural network. each neuron transmits its output via a connection of weights like the synapses in a biological neural network to another neuron in the next layer. weights are assigned to a neuron based on its relative importance against other inputs. shown in figure 1 is the structure of an artificial neuron. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng omoze and emagbetere: artificial neural network (ann) pathloss prediction model for lte network for microcells in an urban environment. azojete, 18(4):575-586. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edirin.omoze@uniben.edu 577 a neural network consists of several layers. the outer most layers that receive the input to the network are called the input layers. the next layer is called the hidden layer. this layer does further processing of the signal and passes it to the output layer. shown in figure 1 is the structure of an artificial neuron with weights and bias. figure 1: analysis of a single neuron with weights and bias a neuron (𝑎 ) is presented in figure 1 with a vectorial input = [𝑥1, 𝑥2, … , 𝑥𝑛] . these inputs are multiplied with weights 𝑊 = [𝑤𝑗1, 𝑤𝑗2, … , 𝑤𝑗𝑛] alongside the summation of a bias term to produce a weighted sum as in equation (1). 𝑂𝑗 = ∑ 𝑥𝑖𝑤𝑗𝑖 + 𝑏𝑛 𝑖,𝑗=1 (1) the weighted sum in equation (1) is fed into a non-linear mapping function 𝑓 called the activation function which produces a scalar output 𝑎1,𝑛 as in equation (2) [11]. 𝑎1,𝑛 = 𝑓(∑ (𝑥𝑖𝑤𝑗𝑖) 𝑛 𝑖,𝑗=1 + 𝑏) (2) the ann learning is obtained by updating the weights along the mlp artificial neural network in consecutive iterations of feed forward and back-propagation procedures with the matrix of neurons in the hidden layer as in equation (3). 𝑧𝑛 (𝑙) = 𝑓(𝑎𝑛 (𝑙)) = [𝑓(𝑎1,𝑛 (𝑙)), 𝑓(𝑎2,𝑛 (𝑙)), 𝑓(𝑎3,𝑛 (𝑙)), … , 𝑓(𝑎𝑘,𝑛 (𝑙))] 𝑇 (3) where 𝑎𝑛 (𝑙) = { 𝑤(𝑙,𝑛). 𝑋𝑛 𝑓𝑜𝑟 𝑙 = 1 𝑤(𝑙,𝑛). 𝑧𝑛 (𝐿−1) 𝑓𝑜𝑟 2…𝐿 − 1 for m features, the weight matrix for layer 𝑙 = 1 and for layers 𝑙 = 2,3, … , 𝐿 − 1 associated with 𝑋𝑛=[𝑥1,𝑛, 𝑥2,𝑛 , … , 𝑥𝐷,𝑛] are given by 𝑤(1,𝑛) = [ 𝑤1,1 (1,𝑛) 𝑤1,2 (1,𝑛) 𝑤2,1 (1,𝑛) 𝑤2,2 (1,𝑛) ⋯ 𝑤1,𝑚 (1,𝑛) 𝑤2,𝑚 (1,𝑛) ⋮ ⋱ ⋮ 𝑤𝑘,1 (1,𝑛) 𝑤𝑘,2 (1,𝑛) ⋯ 𝑤𝑘,𝑚 (1,𝑛) ] and http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/edirin.omoze@uniben.edu arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):575-586. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gedirin.omoze@uniben.edu 578 𝑤(𝑙.𝑛) = [ 𝑤1,1 (𝑙,𝑛) 𝑤1,2 (𝑙,𝑛) 𝑤2,1 (𝑙,𝑛) 𝑤2,2 (𝑙,𝑛) ⋯ 𝑤1,𝑚 (𝑙,𝑛) 𝑤2,𝑚 (𝑙,𝑛) ⋮ ⋱ ⋮ 𝑤𝑘,1 (𝑙,𝑛) 𝑤𝑘,2 (𝑙,𝑛) ⋯ 𝑤𝑘,𝑚 (𝑙,𝑛) ] using equation 3, the feed forward computation of figure 1 is performed as given in equation 4 as; 𝑧𝑛 (𝐿−1) = 𝑓 (𝑤(𝐿−1,𝑛). 𝑓 (𝑤𝐿−2,𝑛 . 𝑓 (… 𝑤2,𝑛 . 𝑓(𝑤(1,𝑛). 𝑋𝑛)))) (4) the prediction value 𝑦𝑝 from the final layer of the feedforward procedure is a linear output of 𝑧𝑛 (𝐿−1) and 𝑤(𝐿.𝑛) as in equation (5). 𝑦𝑝 (𝐿) = 𝑤(𝐿.𝑛). 𝑧𝑛 (𝐿−1) (5) where: 𝑤(𝐿.𝑛) = [𝑤1,1 (𝐿), 𝑤1,2 (𝐿), 𝑤1,3 (𝐿), … , 𝑤1,𝑘 (𝐿)] f: is the activation function from one neuron to another 𝑋𝑛: represents the nth column of the 𝑚 × 𝑛 elmatrix in the input layer 𝑎𝑛 (𝑙): represents the output of neuron 𝑎 in layer 𝑙 𝑦𝑝: is the output of the neural network 2. materials and method this section presents the description of the study area as well as materials and method adopted in this work which includes the data measurement setup, data acquisition process, data pre-processing and model development. 2.1 description of study area edo state is one of the 36 states in nigeria. it lies on latitude 6°30'n and 6º00'e. the state is in the south geopolitical zone of nigeria, bounded by kogi state to the north east, anambra state to the east, delta state to the south and ondo state to the west with a total land area of 17.802km2 as shown in figure 2. edo state has 18 local government areas with benin city as the state capital and the largest urban centre. nifor is one of rural communities in edo state. for the purpose of this study, benin city will be referred to as location 1 and nifor location 2. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng omoze and emagbetere: artificial neural network (ann) pathloss prediction model for lte network for microcells in an urban environment. azojete, 18(4):575-586. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edirin.omoze@uniben.edu 579 figure 2: map of nigeria showing location of edo state (https://www.guardian.ng/news accessed 10th july, 2020) 2.2 measurement set-up and data collection in order to develop suitable model for lte cellular network situated in benin city, benin city was divided into ten sub locations which reflect the major areas of the city. this is because of the large number of base stations in benin city. an experimental set up was designed and implemented to measure and record received signal strength data from one of the mobile network providers. the base station transmits signals using sectorial antennas spaced at 120° apart with antenna heights ranging from 32 to 38 meters. the measurement set-up consists of base stations, an acer smart phone, a global positioning system and a personal computer as shown in figure 3. figure 3: received signal strength measurement set up http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/edirin.omoze@uniben.edu https://www.guardian.ng/news arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):575-586. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gedirin.omoze@uniben.edu 580 2.2.1 measurement campaign in order to study the network from subscribers’ point of view, a network cell info lite software installed on an acer phone was used to collect rss data at intervals of 50m away from the base station during a download from the network. the measured data were transferred to the laptop through a universal serial bus (usb) interface. in addition, a handheld gps (garmin gps 76cs) receiver was used to obtain the spatial coordinates of the measuring points in degrees. rss collected was used to calculate the pathloss of the transmitted signals. (omoze, 2021). 2.3 data pre-processing data pre-processing is an important step in preparing data set for ann algorithm to enhance performance of the learning algorithm. the step taken to pre-process the field data collected in this work is feature normalization. 2.3.1 feature normalization normalization is a data pre-processing step in which the data collected are rescaled to lie between 0 and 1. this is necessary to avoid weight appropriation bias. in this work, the normalization technique used is the standard scaler technique presented in equation (6). �̅�𝑖 = 𝑥𝑖−�̅� 𝜎 (6) where �̅�𝑖 is the standardized of 𝑥𝑖 , �̅� is the expected value of the feature given denoted as e(𝑥); 𝐸(𝑥) = �̅� = 1 𝑛 ∑ 𝑥𝑖 𝑛 𝑖=1 (7) and 𝜎 is the standard deviation of a feature given as ; 𝜎 = √ 1 𝑛 ∑ (𝑥𝑖 − �̅�)2𝑛 𝑖=1 (8) where the subscript 𝑖 denotes the sample number and n the number of samples. feature scaling is done on the features of the dataset using the standardscaler module imported from sklearn library using the fit transform command on the feature. 2.4 model development in order to develop model with high accuracy and generalization ability, the rss data collected with respect to distance (𝑑), base station antenna height ℎ𝑡𝑥 and mobile station antenna height ℎ𝑟𝑥 was divided into 80% training data set and 20% test data set using the stratified shuffle split technique in the scientific python development environment software (spyder). figure 4 is the flow chart of model development adopted in this study. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng omoze and emagbetere: artificial neural network (ann) pathloss prediction model for lte network for microcells in an urban environment. azojete, 18(4):575-586. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edirin.omoze@uniben.edu 581 figure 4: flow chart of model development adopted in this study 2.4.1 artificial neural network (ann) training in this work, a 4-32-1 multi-level perceptron neural network was used to train the training data set. the input to the network is a feature matrix of distance (𝑑)𝑚, received signal strength values (𝑅𝑆𝑆)(𝑑𝐵𝑚) , base station antenna height (ℎ𝑡𝑥)𝑚 and mobile station antenna height (ℎ𝑟𝑥)𝑚 while the output is the pathloss values (𝑃𝐿)𝑑𝐵. where pathloss (𝑃𝐿) is given in equation (9). 𝑃𝐿(𝑑𝐵) = 𝑃𝑡𝑥(𝑑𝐵𝑚) − 𝑃𝑟(𝑑𝐵𝑚) (9) where 𝑃𝑡𝑥 is the transmitted power by the base station antenna and 𝑃𝑟 is the measured power (rss). figure 5 shows the artificial neural network architecture used in this work. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/edirin.omoze@uniben.edu arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):575-586. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gedirin.omoze@uniben.edu 582 figure 5: block diagram of a mlp-artificial neural network with 4 features the hidden layer activation function is the rectified linear unit (relu) as presented in equation (10) while the output layer activation function is the linear activation function as given in equation (11). 𝑓(𝑥) = { 𝑥 𝑥 > 0 0 𝑥 ≤ 0 (10) 𝑓(𝑥) = 𝑎𝑥 (11) where 𝑎 = 1 2.4.2 cross validation cross validation (cv) is a process that provides continuous monitoring of the generalization performance of the model over the learning process. cv requires splitting the data into 2–3 non-overlapping subsets: the training set which is used for parameter learning, the validation set on which the prediction error is used to approximate the generalization error, and the test set on which the prediction error is used to approximate the unbiased generalization error after the learning is completed. in this work, early stopping technique was adopted. to utilise early stopping, 10% of the training set was used as a validation set with a patience of 10 and the validation mean square error was monitored during the training process. 2.5 model validation the validation of the developed model is a vital aspect of the modeling process; essential to its evaluation are the values of the goodness of fit indices obtained from the analysis of the given model. in this section, the artificial neural network model is validated to ascertain its suitability for the data collected in the environment investigated. the root mean square of errors (rmse) and mean absolute error (mae) are computed using equation (12) and equation (13) and are used to evaluate the goodness of fit of the developed model. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng omoze and emagbetere: artificial neural network (ann) pathloss prediction model for lte network for microcells in an urban environment. azojete, 18(4):575-586. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edirin.omoze@uniben.edu 583 rmse=√ 1 𝑛 ∑ (𝑦𝑖 − 𝑦𝑝(𝑖)) 2𝑛 𝑖=1 (12) 𝑀𝐴𝐸(𝑦𝑖, 𝑦𝑝) = 1 𝑛 ∑ |𝑦𝑖 − 𝑦𝑝(𝑖)| 𝑛 𝑖=1 (13) where 𝑦𝑖 is the pathloss estimated from the measured received signal strength data and 𝑦𝑝(𝑖) is the pathloss predicted using the developed artificial neural network model. by computing equations (12) and (13), rmse and mae error values of 0.59𝑑𝐵 and 0.42𝑑𝐵 respectively. 3. results and discussion this section presents the results obtained from training received signal strength data collected in real time from lte (4g) mobile networks in benin city. because of the problem of overfitting, the data collected for the 10 zones were merged and used to train the artificial neural network. table 1 shows descriptive statistics of the data collected in this study. table 1: table of descriptive statistics of data collected for lte (4g) cellular network index 𝑑 𝑅𝑆𝑆 𝐻𝑟𝑥 𝐻𝑡𝑥 𝑃𝐿 count 294 294 294 294 294 mean 309.18 -77.33 1.5 35.22 107.83 std 178.69 7.16 0 2.86 7.16 min 50 -96 1.5 30 92.17 25% 150 -82.86 1.5 34 102.74 50% 300 -78.19 1.5 36 108.19 75% 450 -72.74 1.5 36 112.86 max 800 -62.17 1.5 40 126 it presents received signal strength data collected from 294 sample points for a maximum cell radius of 800m with average rss value of -77.33dbm. the average base station antenna height at this location for the 700mhz network was 35.22m with 126dbm pathloss value obtained at the cell edge. it is clear that the 700mhz cells in location 2 are micro cells. from literature, pathloss prediction for mobile communication systems is often treated as a supervised learning problem, thus the data collected for this investigation was divided into feature dataframe and target dataframe using dataframe indexing techniques in the scientific python development environment. in order to develop models with high generalization ability on unseen samples, the 80% training data was trained using a 4-32-1 multi-layer perceptron feedforward neural network built using the keras functional api on tensorflow backend and learning was done by back propagating the errors. the input to the neural network is the normalized values of the feature dataframe with the distance, received signal strength, mobile station antenna height and base station antenna height as feature variables. in the neural network architecture perspective, three key factors are considered, the type of activation function, the number of hidden layers and the number of hidden nodes on each layers. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/edirin.omoze@uniben.edu arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):575-586. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gedirin.omoze@uniben.edu 584 in order to avoid overfitting of the training dataset, dropout regularization technique was adopted in the hidden layer with a dropout probability of 0.3. since the aim of training is to predict real value number as the pathloss, the output layer is made up of a single neuron with the linear activation function. the artificial neural network model was compiled using the adams optimizer with the mean square error as the loss function. training was done using a batch size of 32 for dataset for 100 epochs. figure 6 shows a comparative analysis of prediction made using artificial neural network (ann) and pathloss values obtained from measured data with respect to distance while figure 7 shows training history of artificial neural network for 100 epochs. figure 6: plot of measured pathloss and pathloss predicted using artificial neural network figure 7: performance curve of trained neural network history for pathloss prediction for 700mhz network at location 2. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng omoze and emagbetere: artificial neural network (ann) pathloss prediction model for lte network for microcells in an urban environment. azojete, 18(4):575-586. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edirin.omoze@uniben.edu 585 3.1. discussion the artificial neural network model was compiled using the adams optimizer with the mean square error as the loss function. training was done using a batch size of 32 for dataset for 100 epochs. figure 6 is a plot of pathloss measured with respect to distance. this plot shows that pathloss increases with respect to distance. it also shows that artificial neural network was able to learn and predict the behaviour of the network. figure 7 is a plot of performance curve of trained neural network history for pathloss prediction for 700mhz network. here, the network was trained for 100 epochs. at 0 epoch, the network had not learnt the variation in the measured data thus the high loss, mean absolute error and mean square error values. as the number of epoch increases, the network learns more about the data set and this can be seen in the lower high loss, mean absolute error and mean square error values obtained at 70 epoch. the plot also shows that at 70 epoch, the network has fully learnt the variation in the data set presented. 4. conclusion this study presents ann pathloss model development for lte network in an urban environment. using received signal strength data measured with respect to base station antenna height, mobile station antenna height and distance from the base station, pathloss was estimated. a feature matrix consisting of 4× 240 elements was used to train a 4-32-1 multilevel perceptron artificial neural network with pathloss values as the label. the hidden layer activation function is the rectified linear unit activation function while the activation function for the output layer is the linear activation function. by performing cross validation with a validation set of 10%, ann training was achieve at the 74th epoch with a mean square error value of 0.0058dbm and a validation mean square error value of 0.00086dbm. the result obtained from this study shows that artificial neural network with rmse and mae values of 0.59𝑑𝐵 and 0.42 𝑑𝐵 respectively were obtained when compared with pathloss estimated from the measured data. this shows that the developed artificial neural network algorithm will provide good of lte networks if deployed during design stage in the benin city. references atanasov, ph. and kiss'ovski, zh. 2017. optimization of path loss models based on signal level measurements in 4g lte network in sofia. bulgarian journal of physics, 44(02): 145154. bi, q., zysman, gl. and menkes, h. 2001. wireless mobile communications at the start of the 21st century. ieee communications magazine, 39(1): 110-116. doi:10.1109/35.8943 eichie, jo., oyedum, od., ajewole, mo. and aibinu, am. 2017. comparative analysis of basic models and artificial neural network based model for path loss prediction. progress in electromagnetic research, 61: 133-146. jo, h., park, c., lee, e., choi, hk. and park, j. 2020. path loss prediction based on machine learning techniques: principal component analysis, artificial neural network, and gaussian process. sensors, 20: 1927., doi:10.3390/s20071927. available online www.mdpi.com/journal/sensors. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/edirin.omoze@uniben.edu arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):575-586. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gedirin.omoze@uniben.edu 586 ojo, s., imoize, a. and alienyi, d. 2021. radial basis function neural network path loss prediction model for lte networks in multi-transmitter signal propagation environments. international journal of communication systems, 34 (03): e4680, doi:10.1002/dac.4680. omoze, el. 2021. radio signal characterization of cellular networks and machine learning based path loss model development. phd thesis, department of electrical and electronics engineering, faculty of engineering, university of benin. sharma, pk., sharma, d. and sai, tv. 2018. optimization of propagation path loss model in 4g wireless communication systems. proceedings of the second international conference on inventive systems and control (icisc 2018), 19-20 january, coimbatore, india: 12451248, doi:10.1109/icisc.2018.8399004 shoewu, o., akinyemi, la. and oborkhale, l. 2019. modelling path loss in mobile communication 4g network system for dryland and wetland terrains. proceedings of southern africa telecommunication networks and applications conference (satnac), 14 september, fairmont resort, ballito, kwazulu-natal, south africa: 44-49. sree vardhan, c., venkat ratnam, d., bhargyasree, n. and hema dattu, a. 2014. analysis of path loss models of 4g femtocells. proceedings of the eleventh international conference on wireless and optical communications networks (wocn), 11-14 september, vijawada, andhra pradesh, india: 1-6, doi: 10.1109/wocn.2014.6923071 sulyman, ai., nassar, at., samimi, mk., maccartney, gr., rappaport, ts. and alsanie, a. 2014. radio propagation path loss models for 5g cellular networks in the 28 ghz and 38 ghz millimeter-wave bands. ieee communications magazine, 52(09): 78-86. ubaidillah, a., ulum, m. and pramono, s. 2020. planning of path loss in large scale signal propagation model at 5g network by using linear regression methods. journal of physics: conference series, 1569(3): 032080. zhang, y., wen, j., yang, g., he z. and wang, j. 2019. path loss prediction based on machine learning: principle, method, and data expansion. applied sciences, 09: 1908, doi:10.3390/app9091908. available online @www.mdpi.com/journal/appl file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng file:///c:/users/hp/appdata/roaming/microsoft/word/giagbara@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):561-572 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 561 original research article delignification trends in pretreatment of musa paradisiaca pseudo-stem and the production of bioethanol f. k. owofadeju, t. e. kolajo* and o. a. onibudo department of wood products engineering, university of ibadan, ibadan, nigeria *corresponding author’s email address: tolukolajo@yahoo.com 1.0 introduction biomass utilization in the production of bioenergy provides an alternative to the use of fossil fuels and, as a result, reduces greenhouse gas emissions and restoring ecosystem balance (ben iwo et al., 2016). biomass for bioenergy also alleviates concerns about the depletion of nonrenewable petroleum resources used in the production of fuels, chemicals, and other bio-products. a rational approach to the use of agricultural and forestry residues has also been necessary. first generation biofuels were created by fermenting the sugar found in grain starches like corn, sorghum, cassava, and barley as well as the sugar in sugar cane and beets (alalwan et al., 2019; dahman et al., 2019) as evidenced by the world's top two producers of ethanol, united states and brazil, which use corn and sugarcane respectively to produce about three-quarters of the world's ethanol (yesmin et al., 2020; fu et al., 2022). this has led to competition between the economies of food and energy. second generation biofuels investigate the hydrolysis and fermentation of lignocellulose carbohydrates (baruah et al., 2018; garba 2021) using feedstocks article information abstract this study was conducted to assess the potential of pre-treated musa paradisiaca pseudostem as an alternative source of raw material for ethanol production. the pseudo-stem was pre-treated with naoh and naoh-aq at varying time and liquor concentrations using a digester. cellulose yield (cy) was determined gravimetrically, residual klason lignin (rkl) was evaluated in accordance with tappi t236 standards and the effect of the pre-treatment variables were examined. acid hydrolysis using dilute solutions of hcl and h2so4 followed pre-treatment, while fermentation was achieved by the addition of an active yeast strain (saccharomyces cerevisae). the ethanol produced was distilled, qualitative analysis was conducted using the fourier transform infrared spectroscopy (ftir) and other standard methods. there was a general decrease in cy and rkl with increasing pulping time and alkali charge, using both naoh and naoh-aq. cy ranged from 2.4 – 4.2g and 3.2 5.0g while rkl ranged from 2.46%-3.9% and 1.94-3.00% for both naoh and naoh-aq pre-treatments respectively. however, there was significant difference between the effects of liquor concentration and time on cy at p=0.05. the addition of 0.1% anthraquinone to soda pulping liquor significantly increased cy and decreased rkl. the difference in glucose yields between the two dilute acid hydrolyses was not significant. various qualitative tests on bio-ethanol showed traits very similar to the laboratory grade ethanol while ftir confirmed the presence of ethanol. it is therefore proven that naoh and naoh-aq are suitable pretreatment methods in the production of bioethanol from musa paradisiaca. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 26 may, 2023 revised 12 july, 2023 accepted 20 july, 2023 keywords: dilute acid hydrolysis anthraquinone pretreatment bioethanol delignification http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com tolukolajo@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):561-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 562 such as corn stalks, rice stalks, plantain pseudo-stems, banana pseudo-stems, poplar and willow trees, grasses such as hemp and switchgrass, capable of producing two rounds of harvests per year continuously without the need for replanting, and biomass found in municipal wastes (useia, 2022). the plantain pseudo-stem has been identified as a biomass that can be used for a variety of purposes, including bioethanol production (ahmad and danish, 2018). it is the leftover plantain bunch material that has been harvested and allowed to rot. this feedstock is cheap, plentiful, and renewable. the presence of lignin between and within the cell-wall of cellulose microfibrils, which results in recalcitrance during hydrolysis, makes it, like other biomass feedstocks, difficult to process. to hydrolyze and ferment lignocellulose sugars into ethanol, lignin must be eliminated (islam et al., 2019). the optimization of ethanol production processes from lignocellulosic biomass is regarded as important research from both an industrial and a scientific standpoint (ramaraj and unpaprom, 2019). one of the primary reason bioethanol has struggled to compete favorably with fossil fuels is the lack of a commercially viable manufacturing cost. this begins with the selection of appropriate pretreatment methods to overcome lignin's recalcitrance. the presence of lignin in lignocelluloses has hampered bioethanol production (zhao and zhao, 2018). for the purpose of removing lignin from the cellulose matrix, a number of pretreatment procedures have been investigated, including diluted acid pretreatment (li et al., 2016; thomas et al, 2017; liu et al., 2018), ultrasound pretreatment (ivetic et al., 2017; luzzi et al., 2017), ionic liquids (liu et al., 2016; raj et al., 2018), since biomass differs in morphology, chemical composition, and structure, a suitable, appropriate, and commercially viable pretreatment method for each specific biomass is required. in this study, plantain pseudo-stems were pre-treated with soda (naoh) and soda/anthraquinone (naoh-aq) before being hydrolyzed and fermented to produce bioethanol. the pretreatment variables' effects on cellulose yield and residual lignin were investigated and a t-test was conducted to ascertain the significant levels of the differences. 2.0 materials and methods 2.1 collection and preparation pseudo stems from a mini-plantation was harvested at the university of ibadan in nigeria, located at latitude 7.440n and longitude 3.900e. the pseudo-stems were collected, and the leaf was identified in the university of ibadan's herbarium as belonging to the plantae kingdom, musaceae family, musa genus and paradisiaca species. for easier pulping, the stems were cut into 3-5 cm chips. 2.2 pretreatment dissolution and serial dilutions of sodium hydroxide pellets with de-ionized water were used to prepare the naoh pulping liquor while 0.1% anthraquinone were combined with sodium hydroxide to create naoh-aq liquor. the samples were pretreated in a 6-liter chemical reactor file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com owofadeju et al: delignification trends in pretreatment of musa paradisiaca pseudo-stem and the production of bioethanol. azojete, 19(3):561-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 563 built for low temperature biomass pretreatments (kolajo and onilude, 2016). the biomass to liquor ratio was 1 to 15 w/v while a temperature of 120°c, was maintained throughout the pulping experiment as adopted by kolajo (2021). pulping duration was varied (30, 45 and 60 minutes) at 10-, 12-, and 14% alkali concentrations. the resulting cellulose substrate was washed with distilled water before being refined in a lab refiner for a minute and then put through a 0.1mm sieve. the pulp yield was measured gravimetrically following electronic oven drying to a constant weight. 2.3 dilute acid hydrolyses separately, 0.5g of cellulose substrate was mixed with 50 ml of 0.2m hcl and h2so4 in accordance with camargo et al. (2019). the reaction was run at 25°c for two hours. the reaction was stopped by neutralizing the acid while additionally changing the ph by adding 25ml of concentrated potassium hydroxide solution. the resulting glucose mixture was filtered to remove impurities and then fermented. 2.4 fermentation and distillation fermentation was performed at 37oc. the experiment was conducted in a dnp-9052-1a thermostat incubator. a 500ml glucose solution made from hcl and h2so4 hydrolyzed cellulose substrates was mixed with 1.0g of an active yeast strain (saccharomyces cerevisiae). the yeast was mixed evenly, the mixture was labeled, and it was placed in the incubator for 48 hours (kolajo, 2021). the resulting ethanol was distilled at 78oc using a simple batch distillation method according to astm d86. 2.5 qualitative tests for the qualitative analysis, the ftir device (buck scientific infrared spectrometer m350) was used (gallignani et al., 1994; conklin et al., 2014). a buck scientific infrared spectrometer with the model number m530 was used to gather the infrared (ir) spectra of the solutions over a 500–4000 cm–1 range. the absorbed radiation was transformed into rotational and/or vibrational energy by the sample molecules. the resulting signal, which was displayed as a spectrum at the detector typically ranges from 400 to 4000 cm-1, representing the molecular fingerprint of the sample. the samples were compared to the pure ethanol's infrared spectra, which were obtained. the astm d7795-12 standard was also used for chemical tests (acidity and alkalinity) as well as physical tests (density, boiling point, odor, and color). 3.0 results and discussion 3.1 cellulose yield of pretreated plantain pseudo-stem the highest yield obtained for the plantain pseudo-stem using only naoh and naoh-aq pretreatments was 4.2g at 10% concentration and 30 minutes, and 5.1g at 10% concentration and 30 minutes. tables 1 and 2 show that the yield for both naoh and naoh-aq pulping was in the range of 2.4 4.2g and 3.2 5.0g, respectively. the cellulose yield difference between naoh and naoh-aq pulping is significant at p-value of 0.05, indicating that the addition of aq to naoh pretreatment significantly yielded a higher cellulose volume for hydrolysis, as also reported by khristova et al. (2006) and lois-correa (2012). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):561-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 564 3.2 residual klason lignin (rkl) of pretreated plantain pseudo-stem for the naoh and naoh-aq pulping of the samples, the rkl of the pre-treated biomass ranged from 2.46 to 3.9% and 1.94 to 3%, respectively (tables 1 and 2). for the naoh and naoh-aq pulping of the samples, the pretreatment with the lowest rkl was 2.46 and 1.94%; this indicates an average of over 60% lignin removal in both schedules. however, according to xu et al. (2011), the amount of rkl is within the range that permits cellulose hydrolysis. the results of the analysis of variance reveal a significant difference between the rkl values of pulping with naoh and naoh-aq. table 1: pretreatment variables and pulp yields using naoh conc. (%) time (mins) yield (g) kappa no. rkl 10 30 4.27 ± 0.06 30.17 3.900 10 45 4.03 ± 0.15 29.00 3.770 10 60 3.17 ± 0.15 21.10 2.743 12 30 3.80 ± 0.10 26.10 3.393 12 45 3.67 ± 0.21 21.40 2.782 12 60 3.07 ± 0.06 18.90 2.457 14 30 3.47 ± 0.15 23.40 3.042 14 45 2.70 ± 0.10 20.10 2.623 14 60 2.47 ± 0.06 18.90 2.457 table 2: pretreatment variables and pulp yields using naoh-aq conc. (%) time (mins) yield (g) kappa no. rkl 10 30 5.13 ± 0.15 23.10 3.003 10 45 4.93 ± 0.12 22.20 2.886 10 60 4.37 ± 0.06 19.20 2.496 12 30 4.53 ± 0.06 22.20 2.886 12 45 4.37 ± 0.15 18.90 2.457 12 60 4.00 ± 0.10 15.90 2.067 14 30 3.83 ± 0.15 19.20 2.496 14 45 3.57 ± 0.06 16.50 2.145 14 60 3.234 ± 0.15 14.90 1.937 3.3 effect of pretreatment on cellulose yield and rkl 3.3.1 effect of pretreatment time on cellulose yield the effects of pretreatment time on the yield of pre-treated plantain pseudo-stem for naoh and naoh-aq are depicted in figures 1 and 2. as the cooking time and alkali concentration increased, the cellulose yield decreased. kolajo and onilude (2019) speculate that this drop-in yield may be caused by the biomass's extractives and other non-fibrous components dissolving. as a pseudo-stem, there are a number of other cell types present besides cellulose fibres (patel file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com owofadeju et al: delignification trends in pretreatment of musa paradisiaca pseudo-stem and the production of bioethanol. azojete, 19(3):561-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 565 and patel, 2022; kolajo et al., 2023) which are likely to be dissolved by the cooking liquor. the yield from the pretreatment may be impacted as the carbohydrate content of the biomass dissolves over time. 10% 12% 14% 0 1 2 3 4 5 liquor concentration y ie ld ( g ) 30 mins 45 mins 60 mins figure. 1: the effect of pretreatment time on cellulose yield using naoh 10% 12% 14% 0 2 4 6 liquor concentration y ie ld ( g ) 30 mins 45 mins 60 mins figure 2: the effect of pretreatment time on cellulose yield using naoh-aq 3.3.2 effect of liquor concentration on cellulose yield an increase in alkali charge resulted in a decrease in the cellulose yield obtained from pretreatment at constant temperature and pretreatment duration. this pattern can be seen in the pulping of the plantain pseudo-stem with naoh and naoh-aq (figures 1 and 2). the increase in alkali charge indicated by the graphs may be the cause of this. because the alkali affects both the lignin and carbohydrate components of the pseudo stem, an increase in alkali charge led to a corresponding decrease in yields. these observations correlate with other findings in http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):561-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 566 literature (jie et al., 2022, kolajo 2021) who reported that total pulp yield is decreased as active alkali charge is increased. 3.3.3 effect of time and liquor concentration on rkl figures 3 and 4 show how rkl is impacted by both time and alcohol concentration. as the time was extended, the lignin content further decreased, resulting in a lower kappa number and rkl. a rapid decrease in rkl was observed between 45 to 60 minutes of pretreatment at 10% concentration in contrast to 12 and 14% alkaline charges. this trend was similar in both naoh and naoh-aq pretreatments. this may be attributed to the dissolution of the non-fibrous components of the biomass first, before delignification. this then implies that pulping at 10% alkali charge will require a longer duration for delignification to occur. however, rkl across the liquor concentrations also decreased as the time was increased, indicating lignin dissolution. figure 3: effect of time and naoh concentration on rkl of plantain pseudo-stem 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 r k l time (mins) conc 10 conc 12 conc 14 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com owofadeju et al: delignification trends in pretreatment of musa paradisiaca pseudo-stem and the production of bioethanol. azojete, 19(3):561-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 567 figure 4: effect of time and naoh-aq concentration on rkl of plantain pseudo-stem 3.4 qualitative tests the bioethanol produced is a clear, colorless liquid that boiled between 79 and 82oc. the tested density varied from 0.83g/ml to 0.85g/ml. after distillation at between 80 and 82oc, there was complete miscibility with water and no residue was left behind. the ph ranged from 7.5 to 8.0. the test results supported the presence of ethanol as reported by suleiman et al. (2017) and kolajo (2021) when compared to laboratory grade ethanol (analar® chemicals). 3.5 fourier transform infrared spectroscopy analysis (ftir) the results of the ftir analysis of the bioethanol made from plantain stem biomass are shown in table 3. the vibrational frequencies for (o-h), (c-h), and (c-o) for sample a, as depicted in figure 5, were noted at 3467 cm-1, 2780 cm-1, and 1209 cm-1, respectively. figure 6 illustrates the vibrational frequencies for (o-h), (c-h), and (c-o) for sample b at 3189 cm-1, 2775 cm-1, and 1072 cm-1. table 3. the infrared spectra of bioethanol obtained from plantain pseudo stem (𝒄𝒎−𝟏) sample code acids o-h c-h c-o a hcl 3467 2780 1209 b h2so4 3189 2775 1072 all produced bioethanol spectra from the hydrolysis of both hydrochloric and sulphuric acids contained bands in the 3189–3467 cm-1 range for the hydroxyl functional group (oh) (forough et al., 2013). while the stretching vibrations of (c-o) were responsible for the absorbance peaks around 1072–1209 cm-1, the stretching vibrations of (c-h) were responsible for the absorbance peaks at 2775–2780 cm-1. the samples' similar bands served as proof that they were all bioethanol samples. numerous functional groups, including hydroxyl (oh stretch), methyl (ch3 stretch), 0 0.5 1 1.5 2 2.5 3 3.5 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 r k l time (mins) conc 10 conc 12 conc 14 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):561-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 568 and alkane (ch2 stretch), are present in bioethanol. the infrared spectra of bioethanol show transmittance and a peak corresponding to a functional group. these functional groups can also be seen in the spectra of pure ethanol (ogidi, 2020). in the (o-h) stretching region between 3000 cm-1 and 3600 cm-1 are reported to have distinct broad bands in the infrared spectra of pure ethanol and blends, according to corsetti et al. (2015). additional ethanol-specific traits can be found in the fingerprint region. figure 5: ftir for hydrolyzed substrate using hcl figure 6: ftir for hydrolyzed substrate using h2so4 1000200030004000 wavenumbers 0 50 100 p er ce n t t ra n sm it ta n ce 3 8 5 9 .2 0 3 4 6 7 .2 0 3 1 9 4 .4 0 2 7 7 6 .8 0 2 3 6 4 .8 0 2 0 2 3 .2 0 1 6 7 6 .8 0 1 2 0 9 .6 0 1 0 2 9 .6 0 7 4 1 .6 0 1000200030004000 wavenumbers 3 8 5 0 .4 0 3 1 8 8 .8 0 2 7 7 5 .2 0 2 3 5 3 .6 0 1 8 3 9 .2 0 1 0 7 2 .0 0 7 0 8 .0 0 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com owofadeju et al: delignification trends in pretreatment of musa paradisiaca pseudo-stem and the production of bioethanol. azojete, 19(3):561-572. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 569 3.6 conclusion there is a general decrease in cellulose yield and residual klason lignin as pretreatment time and concentration increased in both soda and soda anthraquinone pulping processes. this trend also confirmed that lignin condensation did not occur. cellulose yield is increased significantly with the addition of 0.1% anthraquinone to soda pulping liquor with a higher decrease in residual klason lignin. there was sufficient delignification as confirmed by the subsequent hydrolysis and fermentation into ethanol. the properties of bioethanol produced compared well with laboratory grade ethanol. this has established that plantain pseudo-stem wastes can be utilized for bioethanol production using low temperature and cost-effective pretreatments that can be explored for biomass having similar morphology. funding: no financial support was received for this research. competing interests: the authors have no competing interests to declare. credit authorship contribution: owofadeju f.k.: experimentation, supervision, funding; 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vol. 19(3):561-572. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tolukolajo@yahoo.com 572 thomas va., donohoe bs., li m., pu y., ragauskas aj., kumar r., nguyen ty., cai cm. and wyman ce. 2017. adding tetrahydrofuran to dilute acid pretreatment provides new insights into substrate changes that greatly enhance biomass deconstruction by clostridium thermocellum and fungal enzymes. biotechnology biofuel, 10:252. united states energy information administration. 2022. “biofuels explained: ethanol” washington dc. retrieved nov. 23, 2022 from https://www.eia.gov/energyexplained/biofuels/ethanol.php xu, j., wang, j., sharma-shivappa rr. and cheng, jj. 2011. enzymatic hydrolysis of switchgrass and coastal bermuda grass pretreated with different chemical methods. bioresources, 6(3): 29903003. yang, j., gao, c., yang, x., su, y., shi, s. and han, l. 2022. effect of combined wet alkaline mechanical pretreatment on enzymatic hydrolysis of corn stover and its mechanism. biotechnology biofuels bioproducts, 15: 31. doi: 10.1186/s13068-022-02130-0 yesmina, mn., azada, mak., kamruzzamanb, m. and uddinb, mn. 2020. bioethanol production from corn, pumpkin and carrot of bangladesh as renewable source using yeast saccharomyces cerevisiae. acta chemica malaysia (acmy), 4(02): 45-54. doi: 10.2478/acmy-2020-0008 zhao, h, and zhao, s. 2018. bamboo and rattan announcing the genome atlas of bamboo and rattan (gabr) project: promoting research in evolution and in economically and ecologically beneficial plants. giggascience, 6:1-7 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/tolukolajo@yahoo.com https://www.eia.gov/energyexplained/biofuels/ethanol.php arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):391-400 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 391 original research article assessment of pahs in borehole water from the vicinity of the delta steel company, warri, delta state, nigeria o. v. peretomode, o. b. eyenubo department of science laboratory technology, delta state university, abraka, nigeria *corresponding author’s email address: obipere@gmail.com 1.0 introduction environmental pollution has long been a topic of discussion globally as a result of its impact on humans and the environment (wang et al., 2019). this is because, as a result of urbanization and industrialization, there has been an increase in the exploration and exploitation of natural resources, which has resulted in the release of several organic pollutants such as polycyclic aromatic hydrocarbons (pahs), which are found in coal, wood, gasoline, volcanic activities, and the burning of wastes in the environment (halek, et al., 2006; maliszewska-kordybach, et al., 2009) (mojiri et al., 2019) (shariatifar, et al., 2021) (roudbari, et al., 2021). in addition to being released into the atmosphere by incomplete burning of crude oil, wood, coal gas, and other organic substances, which are globally widespread and present in various ecosystems, pah pollutants are a problem (masih et al., 2008) (okoli et al., 2011, grand-clement et al., 2017, adeniji et al., 2019). abolfazi and elahe (2008), vidal et al. (2011), and karyab et al. (2013) highlighted that harmful substances from road run-off, oil spills, and leaching from creosote-impregnated wood typically cause water sources to become contaminated. other authors (wakeham, et al., 1980; hostettler, et al., 1999; chimezie & c, 2006; adekunle, et al., 2017; okedere & elehinafe, 2022) have reported the pollution of pahs in wastewater, seawater, surface water and ground water. article information abstract water contamination due to industrialization is a major problem affecting the environment and all life. this work evaluates the existence of polycyclic aromatic hydrocarbons (pah) in borehole water from delta steel company in warri, delta state. the water sample was analysed in accordance with the us environmental protection agency (epa) using a gas chromatography-mass spectrometer (gc-ms). the concentration of σ16 pah in water from the sampling site shows that the concentration was in the range of 23.78 – 125.9 mg/l. the study further shows that groundwater in the area was polluted with both light and heavy pah concentrations. the light pah concentrations were about 43.8%, ranging from 26.4 mg/l and 50.04 mg/l. whereas the heavy pah concentrations were about 56.2%, ranging from 23.78 mg/l and 125.9 mg/l, with benzo (a) pyrene at 0.0001 mg/l and 0.002 mg/l for all other pahs that exceed the world health organization permissible limit of 0.002 mg/l. heavy pahs were dominant, with benzo(a)fluoranthene accounting for the highest concentration in the samples. the fourfivering pahs were the dominant group of pahs in the study. this observation was attributed to the prolonged industrial practices in the area. therefore, this study recommends that, for health and safety, the water be subjected to major treatment before consumption. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 december, 2022 revised 3 february, 2023 accepted 5 may, 2023 keywords: water pollution petroleum waste domestic use water quality http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):391-400. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 392 furthermore, pahs are believed to be endocrine disruptive compounds (ed) capable of suppressing the immune system, and human exposure to pahs has been related to a number of disorders including cancer, heart disease, and asthma (londono, et al., 2015; sharifiarab, et al., 2022). according to vishi et al. (2005), pahs are aromatic hydrocarbons that include two or more benzene rings in various structural configurations. heavy pahs are defined as having more than four rings and are more stable than light pahs, according to li et al. (2016). light pahs, on the other hand, are those with three rings or fewer. studies (purcaro, et al., 2013; duedahl-olesen, et al., 2015), have shown that there are over a hundred of these (pahs) in nature. however, 16 of them have been suggested as priorities by the us environmental protection agency (us epa) for monitoring in food and environmental matrices due to their toxicity and prevalence (ergonul & sanchez, 2013; iwegbue, et al., 2021). the prevalent discovery of pahs in sources of water like saltwater, groundwater, and river water is due to rising human activity as well as inappropriate and unregulated waste disposal. furthermore, due to the high levels of pah, many of these water sources have been deemed dangerous for human consumption (lee & shin, 2010). this has led to the shortage of portable water which is generally a global problem (wang, et al., 2019) in most coastal settlements, underground water pumped from aquifers provides the main source of fresh water for both drinking and other household uses, especially in dsc, warri in delta state. this source of water is prone to contamination by pahs, which can migrate a long distance from their point of emission (iwegbue, et al., 2021). recent complaints of perfumed and crude oil-tainted water, as well as residents' observations of crude oil films on the top of water taken from public boreholes, served as the basis for this study. nonetheless, there has been no study of pah on these boreholes to date, which makes it important in terms of health consideration, given the proximity of the residence to the steel company. determining the pah concentration in borehole water obtained from dsc in warri, delta state, nigeria, is the goal of this study. 2. materials and methods 2.1 description of study area the research area in dsc, warri, delta state, which is situated in the oil region of southern nigeria, is seen in figure 1. it shares boundaries with sapele, udu and uwvie. the latitude and longitude of warri are at 5.544230, 5.760269 respectively. it has residents of over 311,970 people (npc, 2006). hence, the large population and commercialization especially due to petroleum activities in the study area makes it possible for the alteration of the natural constituent of the natural environment. the locations, source, and coordinates of the water samples that were obtained in dsc, warri, are displayed in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com peretomode and eyenubo: assessment of pahs in borehole water from the vicinity of the delta steel company, warri, delta state, nigeria. azojete, 19(2):391-400. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 393 figure 1: the sampling area is depicted on a map of nigeria that includes warri, delta state (esinulo, et al., 2016). table 1: description of water samples collected from dsc metropolis sample location source longitude latitude ekete waterside borehole 5.492909 5.821895 ekete waterside borehole 5.495130 5.818762 ekete waterside borehole 5.495386 5.814213 ekete waterside borehole 5.500314 5.810617 ekete waterside borehole 5.505750 5.825264 igbogidi borehole 5.510931 5.823070 ekete waterside borehole 5.511643 5.834042 ekete waterside borehole 5.501483 5.835471 ekete inland borehole 5.495082 5.793469 ekete inland borehole 5.493253 5.795970 ekete inland borehole 5.496860 5.799696 ekete waterside borehole 5.495031 5.807402 dsc high asagba borehole 5.618943 7.167605 dsc high borehole 5.619943 7.166605 2.2 sample collection 14 boreholes at dsc, warri, delta state, nigeria were used to collect a total of 42 water samples (in triplicate). 1l brown glass bottles with no air bubbles were used to collect the samples. the bottles were thoroughly washed before the samples were collected for analysis to prevent contamination. 2.3 extraction of pahs from samples for the analysis of semiand non-volatile organics, the united states environmental protection agency (usepa) method 3510 for aqueous matrix was utilized (usepa, 2016). after filtration, a 100mg/l sample water was put in a 2l glass separation funnel. 30mg/l of the saturated sodium chloride (nacl) was then added and thoroughly mixed. 100mg/l of dichloromethane (ch2cl2) was then added as an extraction solvent and properly mixed. the mixed sample was given a few minutes to settle before the dichloromethane (ch2cl2) extract was taken. the organic layer was placed over anhydrous magnesium sulphate and dried together after the extraction procedure http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):391-400. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 394 was repeated with 100ml of dichloromethane. after being concentrated using a 2ml rotary vacuum evaporator, the sample extract was cleaned up. 2.4 pah evaluation using gc-ms after being carefully packed in a 10 ml polypropylene cartridge column and activating 1g of silica gel at 130 oc for 10 hours, the cartridge was conditioned with 6 ml of dichloromethane (ch2cl2). a column was loaded with the concentrated cartridge, and the extract was collected using a pearshaped flask that was positioned underneath the column. following rotary evaporator drying of the entire filtrate concentration at 38 oc, the column was eluted with 10mg/l dichloromethane (ch2cl2). the residue was next diluted in 1 ml of methanol and placed in a 2 ml standard vial before being quantified using a gc while helium was flowing at a rate of 1.4 ml/min. 2.5 statistical analysis experimental data obtained were analysed using microsoft excel 360 to evaluate the mean standard deviation and percentage. 3. results and discussion table 1 displays the findings of the water samples tested by dsc, warri, for pah content. the presence of all 16 pahs in varying quantities in the water samples drawn from the borehole attests to how prevalent the contaminants are (wang, et al., 2018). since there is currently no limit in place for nigeria, this study was conducted using who guidelines (onydinma, et al., 2021). the concentrations of all samples, regardless of the sampling point, were generally above the who permissible limit. the highest mean result from the sample site was benzo(b)fluoranthene at 125.9 mg/l, followed by indeno(1,2,3-cd)pryene at 96.76 mg/l. given that fossil fuels have been shown to be present in rainwater, these contaminants may have originated there (who, 1998; kim, et al., 2011). benzo(g,h,i)pyrene and benzo(k)fluoranthene were among those that also displayed high mean values, with 74.68 and 91.44 mg/l, respectively. according to pan et al. (2005), benzo(k)fluoranthene is a harmful contaminant that is apparently becoming more prevalent in water sources. anthracene and benzo(g,h,i)pyrene had mean values of 24.22 and 26.4mg/l, respectively, whereas chrysene had the lowest mean value at a mean concentration of 23.78 mg/l. studies have shown that chrysene is one of the most insistent pahs in water linked to improper fuel combustion and is difficult to remove (wang, et al., 2013; dimante, et al., 2017). from the results, the greatest mean value was for the 5r pah homologue, which was followed by the 6r homologue with values of 51.55 and 32.75 respectively. whereas, 4r homologue had the lowest mean value at 25.33. there was a 0.12 to 0.63ppm variation in the mean pah content. this contrasts with wang et al.'s works from 2021, which had a pah content of 0.0003ppm. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com peretomode and eyenubo: assessment of pahs in borehole water from the vicinity of the delta steel company, warri, delta state, nigeria. azojete, 19(2):391-400. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 395 table 1. concentrations of pahs from borehole water sample name amount ppm concentration (mg/l) who permissible limit (mg/l) napthalene 0.15 29.3 0.002 acenapthylene 0.24 47.94 0.002 acenapthene 0.25 50.04 0.002 phenanthrene 0.18 36.64 0.002 fluorene 0.16 31.7 0.002 fluoranthene 0.23 45.32 0.002 anthracene 0.13 26.4 0.002 pyrene 0.27 53.1 0.002 benz (a) anthracene 0.14 27.08 0.002 chrysene 0.12 23.78 0.002 benzo (k) fluoroanthene 0.46 91.44 0.002 benzo (b) fluoranthene 0.63 125.9 0.002 indeno (1,2,3-cd) pyrene 0.48 96.76 0.002 benzo(a)pyrene 0.17 34.3 0.0001 dibenz (a,h) anthracene 0.37 74.76 0.002 benzo (g,h,i) perylene 0.12 24.22 0.002 table 2 shows the different pah homologues present in the water sample analyzed from the borehole in dsc warri. the result shows 16 pah were observed to be present in the 2-, 3-, 4, 5-, and 6-ring homologues. the 2-ring pah (napthalene, acenapthylene, and acenapthene) was detected to be 15.6% in the water sample at varying concentrations between 29.3 and 50.04mg/l. poor handling of petroleum products may be related to the presence of naphthalene. it is one of the oil spill-derived petrogenic pahs with a low molecular weight (sun, et al., 2016). the 3-ring pahs fluorene, anthracene, phenanthrene, which is regarded as a tracer for vehicular emissions (sun, et al., 2016), and fluoranthene were detected to be 17.11% in the water sample at varying concentrations of 26.4 and 36.64mg/l. the 4-ring pah (pyrene, benz(a)anthracene, and chrysene) was detected to be 10.9% in the water sample, with varying concentrations between 2.90 and 6.49mg/l. the 5-ring pahs benzo(a)pyrene), (benzo(k)fluoranthene, benz(b)fluoranthene, and dibenz(a,h)anthracene were detected to be 42.96% in the water sample, with varying concentrations between 34.3 and 125.9mg/l. the 6-ring pah (benzo(g,h,i)pyrene, indeno(1,2,3-cd)pyrene) was detected to be 12.09% in the water sample, with varying concentrations between 24.22 and 96.76mg/l. it was found that the pah concentrations were higher than those found in the studies of badawy & enababy (2010). however, the percentage distribution of pah 43.8% belongs to 2and 3-ring pahs (figure 2). this is an indication that 56.2% are heavy pahs which are steadier and are extra toxic (lawal, 2017). scoggins et al. (2007) also reported a similar domination of heavy pah concentration. the poorly treated industrial effluent from the nearby area may have contributed to the high mean concentration of pahs found in the groundwater sample, which may have caused petroleum contamination of the groundwater aquifer. the pah concentration from the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):391-400. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obipere@gmail.com 396 result is consistent with the works of okoli et al. (2011), where the pollution of the water was attributed to the incessant release of refinery effluents into the creeks bordering the coastal settlement. table 2: percentage distribution of pah homologue in dsc sample site warri figure 2: ring size variation of pahs in dsc sample site warri 4. conclusion this study assessed the presence of pahs in some boreholes at dsc warri. there were 16 different pahs found in the sample, which included naphtalene, fluorene, pyrene, and benzo(a)pyrene. the samples contained 16 distinct pahs, including naphtalene, fluorene, pyrene, and benzo(a)pyrene. this included typical two-ringed and six-ringed pahs from the various homologues. with the exception of 0.001 mg/l for benzo(a)pyrene, the presence of these pah chemicals in this investigation was found to be higher than the who permitted limit of 0.002 mg/l for drinking water. as a result, this finding raises concerns for public health because it could pah homologue name percentage % 2rings (2r) napthalene 3.58 acenapthylene 5.86 acenapthene 6.11 3rings(3r) fluorene 3.87 anthracene 4.48 phenanthrene 3.22 fluoranthene 5.54 4rings (4r) pyrene 6.49 benz(a)anthracene 2.90 chrysene 3.31 5rings (5r) benzo(k)fluoranthene 11.17 benzo(b)fluoranthene 15.38 dibenz(a, h,)anthracene 11.82 benzo(a)pyrene 4.19 6rings (6r) benzo(g,h,i)pyrene 9.13 indeno(1,2,3 – cd)pyrene 2.96 0 5 10 15 20 25 30 35 40 45 2rings (2r) 3rings (3r) 4rings (4r) 5rings (5r) 6rings (6r) % d is tr ib u ti o n pah homologue file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/obipere@gmail.com peretomode and eyenubo: assessment of pahs in borehole water from the vicinity of the delta steel company, warri, delta state, nigeria. azojete, 19(2):391-400. issn 1596-2490; 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hossain and shiblee, 2017). this is to determine optimally, which of the generating units should run at any point in time as well as the power generated by the gas, hydro and thermal plants so that the total cost is minimized. minimizing the total cost in this optimization problem is subject of many control and operational constraints and can be obtained using different optimization methods that include lagrangian relaxation and benders decomposition-based methods, mixed-integer and dynamic programming among others (farhat and el-hawary, 2009; kovalev et al., 2011). these are however conventional optimization methods which use gradients for the search of optimum values. evolutionary optimization methods have become an alternative to conventional optimization techniques for solving real world problems having non-convexity, article information abstract in a grid or part of a grid operated by a single service provider with various types of power plants, the total load demand on the grid can be serviced by the plants’ outputs in such a way that a minimum cost of energy is spent to generate this total demanded load thereby maximizing profit for the service providers without placing exorbitant tariff on customers. this paper considered how this can be archived in the nigerdelta region of nigeria (as a case study). we assumed that the power generated by the plants in the region is also consumed by the region. using the lagrnge multiplier optimization method in our analysis and for a total power demand/generation of 2170 mw, a total of 752,435 × 104cal/hr of fuel will be burnt. but with the system of running cost minimization developed in this paper, only about 575,521 × 104cal/hr of fuel was burnt in generating that same quantity of power demanded resulting in a net savings of 176,914 × 104 cal/hr. this is equivalent to 2.057 × 103 kwh; with energy sold at ₦48/kwh in nigeria, a total of ninety-eight thousand, seven hundred and thirty-six naira (₦98,736.00) only will be saved each hour resulting in a net savings of eight hundred and sixty-four million, nine hundred and twenty-seven thousand, three hundred and sixty naira (₦864,927,360.00) only per annum. this is, therefore, recommended for implementation in running nigeria’s power system. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 6 april, 2022 revised 13 june, 2022 accepted 20 june, 2022 keywords: optimization energy cost savings and profitability grid plant’s capacity http://www.azojete.com.ng/ mailto:patndyobi@gmail.com mailto:patndyobi@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 670 non-differentiability and discontinuity. in this way, evolutionary methods have been successfully applied to power system problems as well. though, the evolutionary methods have been suitable for power system problems, the premature convergence and stagnation they exhibit poise a problem when using them directly (attaviriyanupap, et al., 2002). a hybrid algorithm combines the conventional and evolutionary optimization techniques for solving power system problems; it can be used for solving the problems having non-convexity and non-smoothness in the function space. this hybrid optimization technique solves problems with multi objectives (jafari et al., 2019; lei et al., 2020; panda et al., 2020). a cost-based approach has also been used to determine the optimal operational strategy that yields a minimum operating cost. the optimal operational strategy is achieved through the estimation of the hourly generated power, the amount of thermal power recovered from the one type of power plant in the grid e.g fuel cell power plants (fcpp) to satisfy the thermal load, the amount of power trade with the local grid, and the amount of by-products (hydrogen) that can be generated from the plant type which is useful to the society (el-sharkh et al., 2006). as such, the cost-based optimization is archived by minimizing the objective function (of) as given in equation (1) 𝑂𝐹 = 𝑀𝑖𝑛 (∑ 𝐶𝑜𝑠𝑡𝑖 − ∑ 𝐼𝑛𝑐𝑜𝑚𝑒𝑖𝑖𝑖 ) (1) where ∑ 𝐶𝑜𝑠𝑡𝑖𝑖 is the sum all the cost i, of production (in ₦ or any other currency), ∑ 𝑖𝑛𝑐𝑜𝑚𝑒𝑖𝑖 sum of all i source of income (in ₦ or any other currency). however, in grids (like nigeria’s) where none of the plant’s by-product can be a source of income, such method cannot be adopted. power systems operate as a grid (obi et al., 2017) with several power generating plants that include hydropower plants, steam and gas turbine power plants (among others). suppose the generation and transmission stages of such grid is ran by a single service provider, then the service provider can maximize profit by reducing the cost of production which include generating power and getting the power generated to load centers to the barest minimum (obi and offor, 2012). reduction of production cost can come from the following (avalos, 2008): 1. reduction of salaries of technical and non-technical staffs. 2. reduction of losses along the power lines (before the generated power gets to the consumers so that there will be more power at the load centers). 3. economic combination of various power plants on the grid to feed the total grid demand (based on their respective running cost). in this research, the item 3 option given above shall be investigated and we shall assume that the power plants feed only loads in the nigeria regions under study which are the south – south and south – east regions of nigeria. also, we shall assume that the total load demand is less than the total power the various plant combinations can generate. at the moment, there are nine (9) functional power plants in the region and their functional generating capacities are given in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com obi et al: optimal load scheduling of power plants in a grid considering the plant’s capacity and line losses. azojete, 18(4):669-682. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 671 table 1: list of power plants in the region of nigeria under analysis power station location type capacity status aba power station aba combined cycle gas turbine (more of steam) 340 mw operational (260mw) afam i – v power station afam combined cycle gas turbine (more of steam) 726 mw partially operational (313mw) afam vi power station afam combined cycle gas turbine (more of gas) 624 mw operational (600mw) alaoji power station(nipp) aba combined cycle gas turbine (more of steam) 1074 mw partially operational (250mw) okpai power station okpai combined cycle gas turbine (more of gas) 480 mw operational (470mw) omoku power station omoku combined cycle gas turbine (more of steam) 450 mw operational (340mw) sapele power station sapele gas-fired steam turbine and simple cycle gas turbine (more of steam) 1020 mw partially operational (335 mw) sapele power station(nipp) sapele combined cycle gas turbine (more of gas) 450 mw operational (420mw) delta ughelli power station ughelli combined cycle gas turbine (more of gas) 900 mw partially operational (360 mw) source: (nigerian agip oil company, 2003; nigerian agip oil company and rivers state government, 2003; shell petroleum development company, 2003; geometric power limited, 2005; shell petroleum development company, 2005; federal government of nigeria national integrated power project, 2012; transnational corporation of nigeria plc, 2012; niger delta power holding company and federal government of nigeria, 2013; eurafric power limited, 2014; oputa, 2015). they are all combined circle power plants generating power from gas and steam respectively. the heat from the gas turbine section is used to heat up water to steam and eventually used to drive another turbine. the more of steam combined circle plant generate more power with the steam driven alternator than the gas. the combined operation of the power plants in table 1 was carried out without considering the various plant’s limit or capacity (oputa, 2015; oputa et al., 2019). the authors optimized the power plant’s operations by using only the respective plant’s incremental fuel cost without considering their limit and power line losses. 2. materials and methods in this paper, we developed mathematical models showing the relationship between the power generated by the various power plants in the grid and the cost of fuel burnt to generate such power. we shall then use programs in matlab to solve the models developed as they are complex models that will be difficult to solve manually. the method of equal incremental fuel cost for all power plants in the region under analysis was employed. hence, we assumed that all 9 plants run with equal incremental fuel cost. we however did not consider the effect of the by-product of each plant to the environment. http://www.azojete.com.ng/ mailto:patndyobi@gmail.com http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/aba,_abia http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam&action=edit&redlink=1 http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam&action=edit&redlink=1 http://en.wikipedia.org/wiki/combined_cycle_gas_turbine http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/national_integrated_power_project http://en.wikipedia.org/wiki/abia_state http://en.wikipedia.org/wiki/combined_cycle_gas_turbine http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai&action=edit&redlink=1 http://en.wikipedia.org/wiki/combined_cycle_gas_turbine http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/omoku http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/sapele http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/national_integrated_power_project http://en.wikipedia.org/wiki/sapele http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/ughelli http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 672 if a quantity of fuel burns for one hour liberating an energy 𝑓𝑖 (in calorie) to generate a particular power output, 𝑃𝐺𝑖 (in mw) in that one hour, the relationship between the quantity of fuel burnt and power generated is given as (gupta, 2009; bommirani and thenmalar, 2013). 𝑓𝑖 = 𝑎𝑖 + 𝑏𝑖𝑃𝐺𝑖 + 𝑐𝑖𝑃𝐺𝑖 2 (2) 𝑎𝑖 (𝐶𝑎𝑙), 𝑏𝑖 (𝐶𝑎𝑙/𝑀𝑤), 𝑎𝑛𝑑 𝑐𝑖 (𝐶𝑎𝑙/𝑀𝑊2) are constants of the ith power plant. for n plants in the system (nine (9) in this case), the total fuel burnt by all the (9) plants is 𝐹𝑇 = ∑ (9 𝑖=1 𝑎𝑖 + 𝑏𝑖𝑃𝐺𝑖 + 𝑐𝑖𝑃𝐺𝑖 2 ) (3) reducing the cost of generating the total power generated by all the plants can be archived by minimizing equation (3); this equation is thus the operating function (of). the minimization of the of is subject to some factors (constraints). these include: 1. real power balance: real power in supply, 𝑃𝐺𝑖 must be equal to real power in demand, 𝑃𝐷 (plus real power losses, 𝑃𝐿). − ∑ 𝑃𝐺𝑖 + 𝑃𝐷 + ∑ 𝑃𝐿 = 09 𝑖=1 (4) 2. spare capacity constraint: some load predictions at load centers are inaccurate; there are also sudden changes in load demand as well as inadvertent losses of schedule generation in the nigeria power system. the spare capacity constraint can be used to account for these and more. this ensures that the total generation available at any time should be in excess of total anticipated load demand and total system loss by an amount not less than a specific minimum, called the spare capacity, 𝑃𝑆𝑃 (bogdan et al., 2007; jinchao et al., 2012). ∑ 𝑃𝐺𝑖 9 𝑖=1 = ∑ 𝑃𝐿 + 𝑃𝑆𝑃 + 𝑃𝐷 (5) pl is calculated in its simplest quadratic for as 𝑃𝐿 = ∑ ∑ 𝑃𝐺𝑖𝐵𝑖𝑗𝑃𝐺𝑗 9 𝑗=1 9 𝑖=1 (6) where, 𝐵𝑖𝑗 are the loss coefficients connecting the ith and jth buses of the transmission network. it can also be calculated by a more general formula containing a linear and constant term as shown in equation (7), this is known as the kron’s loss formula (saadat, 1999). 𝑃𝐿 = ∑ ∑ 𝑃𝐺𝑖𝐵𝑖𝑗𝑃𝐺𝑗 + ∑ 𝐵0𝑖𝑃𝐺𝑖 + 𝐵00 𝑛 𝑖=1 9 𝑗=1 9 𝑖=1 (7) generation capacity constraint: in carrying out the optimization of the of, the generating capacity of each plant must not be exceeded. hence, 𝑃𝐺𝑖 𝑛𝑖𝑚 ≤ 𝑃𝐺𝑖 ≤ 𝑃𝐺𝑖 𝑚𝑎𝑥 (8) 3. grid capacity constraint: for secure operation, the actual transmission capacity must be restricted by its upper limit as 𝑆𝑖𝑖(𝑃𝐺𝑖) ≤ 𝑆𝑙𝑖 𝑚𝑎𝑥 . 𝑖 = 1, 𝑏2, … , 𝑛𝑙 (9) where nl is the number of transmission lines; sli is the electric power flow of the ith transmission line which is influenced by the pgi; and 𝑆𝑙𝑖 𝑚𝑎𝑥 is the upper limit of the ith transmission line (gupta, 2009). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com obi et al: optimal load scheduling of power plants in a grid considering the plant’s capacity and line losses. azojete, 18(4):669-682. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 673 4. minimum emission of pollutant from fossil-fuel et constraint: the minimization of the of should also ensure that the environment is not over polluted with bye-products of the respective plant’s operations. hence, the of must be minimized in such a way that et is minimum (obi et al., 2017). 𝑀𝑖𝑛𝐸𝑡 = ∑ 𝐸𝑖(𝑃𝐺𝑖)𝑁𝑐 𝑖=1 (10) or 𝑀𝑖𝑛𝐸𝑡 = ∑ (𝛼𝑖𝑃𝐺𝑖 2 + 𝛽𝑖𝑃𝐺𝑖 + 𝛾𝑖 + 𝜉𝑖𝑒𝑥𝑝(𝜏𝑖𝑃𝐺𝑖))𝑁𝑐 𝑖=1 (11) where αi, βi, γi, ζi, and 𝜏i, are coefficients of the ith generator’s emission characteristics, 𝑁𝑐 is the number of power plant in the grid. our task is therefore to minimize equation (3) subject to equations (4) to (10). however, we shall not consider the effect of emission of pollutant from fossil-fuel and the grid capacity constant. hence, we shall minimize the of as shown in equation (3) subject to constrains as shown in equations (5), (6) and (8) alone. hence, we are to minimize the total cost fuel burnt 𝐹𝑇 = ∑ (9 𝑖=1 𝑎𝑖 + 𝑏𝑖𝑃𝐺𝑖 + 𝑐𝑖𝑃𝐺𝑖 2 ) subject to (i) − ∑ 𝑃𝐺𝑖 + 𝑃𝐷 + ∑ 𝑃𝐿 = 09 𝑖=1 (ii) ∑ 𝑃𝐺𝑖 9 𝑖=1 = ∑ 𝑃𝐿 + 𝑃𝑆𝑃 + ∑ 𝑃𝐷𝑖 9 𝑖=1 (iii) 𝑃𝐺𝑖 𝑛𝑖𝑚 ≤ 𝑃𝐺𝑖 ≤ 𝑃𝐺𝑖 𝑚𝑎𝑥 again, we can also neglect the spare capacity in the constrain in (i) above. by combining the of and constrains functions and applying lagrange multiplier (ℒ) (saadat, 1999). ℒ = 𝐹𝑇 + 𝜆 ((𝑃𝐷 + ∑ 𝑃𝐿 − ∑ 𝑃𝐺𝑖 9 𝑖=1 ) + ∑ µ𝑖(max)(𝑃𝐺𝑖 − 𝑃𝐺𝑖(𝑚𝑎𝑥))9 𝑖=1 ) + ∑ µ𝑖(min)(𝑃𝐺𝑖 −9 𝑖=1 𝑃𝐺𝑖(𝑚𝑖𝑛)) (12) where µ𝑖(max) = 0 when 𝑃𝐺𝑖 < 𝑃𝐺𝑖(𝑚𝑎𝑥) and µ𝑖(min) = 0 when 𝑃𝐺𝑖 > 𝑃𝐺𝑖(𝑚𝑖𝑛). thus, if the constraint is not violated, its associate µ variable is zero and the corresponding term in equation (12) does not exist. equation (12) is minimum at 𝜕ℒ 𝜕𝑃𝑖 = 0 (13) 𝜕ℒ 𝜕𝜆 = 0 (14) 𝜕ℒ 𝜕µ𝑖(𝑚𝑎𝑥) = 𝑃𝐺𝑖 − 𝑃𝐺𝑖(𝑚𝑎𝑥) = 0 (15) 𝜕ℒ 𝜕µ𝑖(𝑚𝑖𝑛) = 𝑃𝐺𝑖 − 𝑃𝐺𝑖(𝑚𝑖𝑛) = 0 (16) the solution of the equation (12) is therefore given as 𝑑𝑓𝑖 𝑑𝑃𝐺𝑖 + 𝜆 𝜕𝑃𝐿 𝜕𝑃𝐺𝑖 = 𝜆 (17) from equation (7), 𝜕𝑃𝐿 𝜕𝑃𝐺𝑖 = 2 ∑ 𝐵𝑖𝑗𝑃𝐺𝑗 + 𝐵0𝑖 9 𝑗=1 (18) http://www.azojete.com.ng/ mailto:patndyobi@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 674 putting (15) and (2) into (14), (14) can be rewrite as 𝑏𝑖𝑃𝐺𝑖 + 2𝑐𝑖𝑃𝐺𝑖 + 2 ∑ 𝐵𝑖𝑗𝑃𝐺𝑗 + 𝐵0𝑖 9 𝑗=1 = 𝜆 (19) or ( 𝑐𝑖 𝜆 + 𝐵𝑖𝑖) 𝑃𝐺𝑖 + ∑ 𝐵𝑖𝑗𝑃𝐺𝑗 9 𝑗=1 𝑗≠𝑖 = 1 2 (1 − 𝐵0𝑖 − 𝑏𝑖 𝜆 ) (20) the optimal dispatch for an estimated 𝜆1 by solving equation (20) using iterative process by gradient method. 𝑃𝐺𝑖 and its value at the kth iteration is given as (saadat, 1999) 𝑃𝐺𝑖 𝑘 = 𝜆𝑘(1−𝐵0𝑖)−𝑏𝑖−2𝜆𝑘 ∑ 𝐵𝑖𝑗𝑗≠𝑖 𝑃𝐺𝑗 𝑘 2(𝑐𝑖+𝜆𝑘𝐵𝑖𝑖) (21) total power generated must be equal to the total power demanded and total power lost. ∑ 𝑃𝑖 = 𝑃𝐷 + 𝑃𝐿 9 𝑖=1 (22) implementing equation (21) in (22), 𝑓𝜆𝑘 = 𝑃𝐷 + 𝑃𝐿 𝑘 (23) where 𝑓𝜆𝑘 = ∑ 𝑃𝐺𝑖 𝑘 = 𝜆𝑘(1−𝐵0𝑖)−𝑏𝑖−2𝜆𝑘 ∑ 𝐵𝑖𝑗𝑗≠𝑖 𝑃𝐺𝑗 𝑘 2(𝑐𝑖+𝜆𝑘𝐵𝑖𝑖) 9 𝑖=1 (24) using taylor series on the rhs of (21) 𝑓𝜆𝑘 + ( 𝑑𝑓𝜆 𝑑𝜆 ) 𝑘 ∆𝜆𝑘 = 𝑃𝐷 + 𝑃𝐿 𝑘 (25) ∆𝜆𝑘 = ∆𝑃𝑘 ( 𝑑𝑓𝜆 𝑑𝜆 ) 𝑘 = ∆𝑃𝑘 ∑( 𝜕𝑃𝐺𝑖 𝜕𝜆 ) 𝑘 (26) where ∑ ( 𝜕𝑃𝐺𝑖 𝜕𝜆 ) 𝑘 9 𝑖=1 = ∑ 𝑐𝑖(1−𝐵0𝑖)+𝐵𝑖𝑖𝑏𝑖−2𝜆𝑘 ∑ 𝐵𝑖𝑗𝑗≠𝑖 𝑃𝐺𝑗 𝑘 2(𝑐𝑖+𝜆𝑘𝐵𝑖𝑖) 2 9 𝑖=1 (27) note that for any iteration, ∆𝑃𝑘 = 𝑃𝐷 + 𝑃𝐿 𝑘 − ∑ 𝑃𝐺𝑖 𝑘9 𝑖=1 (28) the iterative process is continued until ∆𝑃𝑘 is less than a specific accuracy limit. using the simplest/approximate loss formula 𝑃𝐿 = ∑ 𝐵𝑖𝑖𝑃𝐺𝑖 29 𝑖=1 (29) using equation (29), the common incremental fuel cost of all power plants 𝜆 as 𝐵𝑖𝑗 = 𝐵00 = 0. then equations (21) and (27) respectively becomes 𝑃𝐺𝑖 𝑘 = 𝜆𝑘−𝑏𝑖 2(𝑐𝑖+𝜆𝑘𝐵𝑖𝑖) (30) ∑ ( 𝜕𝑃𝐺𝑖 𝜕𝜆 ) 𝑘 9 𝑖=1 = ∑ 𝑐𝑖+𝐵𝑖𝑖𝑏𝑖 2(𝑐𝑖+𝜆𝑘𝐵𝑖𝑖) 2 9 𝑖=1 (31) equations (28) to (31) were used to analyze the system. 3. results and discussion data collected from respective power plants’ data books show the energy or fuel burnt in generating a corresponding amount of power (oputa, 2015) and they are given in table 2. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com obi et al: optimal load scheduling of power plants in a grid considering the plant’s capacity and line losses. azojete, 18(4):669-682. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 675 table 2: fuel burnt/power generation characteristics of each plant power station energy (fuel) burnt/hour [(cal) × 104/ℎ𝑟] plant output power (mw) power station energy (fuel) burnt/hour [(cal) × 104/ ℎ𝑟] plant output power (mw) aba power station 2.3 0 delta – 5.1 0 9,200 80 ughelli power 102,000 300 11,430 90 station 105,385 305 13,900 100 115,845 320 16,600 110 134,385 345 afam i – v power station 3.1 0 sapele power 3.2 0 22,500 150 (station nipp) 147,200 400 28,560 170 150,865 405 35,345 190 158,330 415 42,840 210 161,360 419 afam vi power station 2.8 0 sapele power 4.0 0 254,000 500 station 8,725 80 285,145 530 13,505 100 295,925 540 15,140 106 329,460 570 19,330 120 alaoji power station (nipp) 4.2 0 omoku 2.1 0 36,725 180 power 8,885 80 40,857 190 station 14,810 105 45,205 200 18,200 117 47,462 205 21,580 128 okpai power station 3.3 0 163,200 400 175,548 415 195,350 438 219,950 465 source: (nigerian agip oil company, 2003; nigerian agip oil company and rivers state government, 2003; shell petroleum development company, 2003; geometric power limited, 2005; shell petroleum development company, 2005; federal government of nigeria national integrated power project, 2012; transnational corporation of nigeria plc, 2012; niger delta power holding company and federal government of nigeria, 2013; eurafric power limited, 2014). the quantity of energy (or quantity of fuel burnt) by each plant when generating power is given in table 2. from the table, the values of the plant constantai, bi, ci for each plant can be calculated and their approximate values are given in table 3. the data in table 2 were used to obtain the fuel cost – power equation any particular plant. for example, using the figures in the blue highlighted values of aba power station, 92,000kcal/hr generated 80mwin that 1 hour. hence, 92000 = 𝑎 + 𝑏(80) + 𝑐(80)2. also, 139,000 = 𝑎 + 𝑏(100) + 𝑐(100)2 http://www.azojete.com.ng/ mailto:patndyobi@gmail.com http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/national_integrated_power_project http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 676 having some 3 set of equations for a particular plant, ‘a’, ‘b’ and ‘c’ for that plant were obtained and presented in table 3. table 3: energy equations for various power plants in the region (a function of their power generated) power station a b c fuel eqn aba power station 2.3 19 1.2 2.3 + 19𝑃𝐺 + 1.2𝑃𝐺 2 afam i – v power station 3.1 15 0.9 3.1 + 15𝑃𝐺 + 0.9𝑃𝐺 2 afam vi power station 2.8 8 1 2.8 + 8𝑃𝐺 + 𝑃𝐺 2 alaoji power station(nipp) 4.2 6 1.1 4.2 + 6𝑃𝐺 + 1.1𝑃𝐺 2 okpai power station 3.3 8 1 3.3 + 8𝑃𝐺 + 𝑃𝐺 2 omoku power station 2.1 15 1.2 2.1 + 15𝑃𝐺 + 1.2𝑃𝐺 2 sapele power station 4 5 1.3 4 + 5𝑃𝐺 + 1.3𝑃𝐺 2 sapele power station(nipp) 3.2 8 0.9 3.2 + 8𝑃𝐺 + 0.9𝑃𝐺 2 delta ughelli power station 5.1 10 1.1 5.1 + 10𝑃𝐺 + 1.1𝑃𝐺 2 the minimum power to be generated by each individual power plant without economically running at a loss is given in table 4. table 4: minimum power to be generated without economic loss power station minimum power generation (mw) plant operational capacity (mw) aba power station 20 260 afam i – v power station 38 313 afam vi power station 58 600 alaoji power station(nipp) 22 250 okpai power station 55 470 omoku power station 45 340 sapele power station 40 335 sapele power station(nipp) 55 420 delta-ughelli power station 38 360 source: (nigerian agip oil company, 2003; nigerian agip oil company and rivers state government, 2003; shell petroleum development company, 2003; geometric power limited, 2005; shell petroleum development company, 2005; federal government of nigeria national integrated power project, 2012; transnational corporation of nigeria plc, 2012; niger delta power holding company and federal government of nigeria, 2013; eurafric power limited, 2014). the minimum power that a particular power plant must be generating to keep the said plant in the system is got from the fact that most plant in the system are combined cycle power plants. thus, it comprises of more than one unit and some unit’s operation depend on the operations of some other units. from tables 3 and 4, the respective incremental fuel cost and the plant’s limits are given in table 5: file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 obi et al: optimal load scheduling of power plants in a grid considering the plant’s capacity and line losses. azojete, 18(4):669-682. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 677 table 5: incremental fuel cost model of various power plant in the region s/n power station incremental 𝜆 plant’s limit 1 aba power station [19 + 2.4𝑃𝐺] 20 ≤ 𝑃𝐺 ≤ 260 2 afam i – v power station [15 + 1.8𝑃𝐺] 38 ≤ 𝑃𝐺 ≤ 313 3 afam vi power station [8 + 2𝑃𝐺] 58 ≤ 𝑃𝐺 ≤ 600 4 alaoji power station(nipp) [6 + 2.2𝑃𝐺] 22 ≤ 𝑃𝐺 ≤ 250 5 okpai power station [3.3 + 2𝑃𝐺]𝐿5 55 ≤ 𝑃𝐺 ≤ 470 6 omoku power station [15 + 2.4𝑃𝐺] 45 ≤ 𝑃𝐺 ≤ 340 7 sapele power station [5 + 2.6𝑃𝐺] 40 ≤ 𝑃𝐺 ≤ 335 8 sapele power station(nipp) [8 + 1.8𝑃𝐺]𝐿8 55 ≤ 𝑃𝐺 ≤ 420 9 delta-ughelli power station [10 + 2.2𝑃𝐺] 38 ≤ 𝑃𝐺 ≤ 360 taking a case where the 9 power plants generate a total power of 2,170 mw at a particular time from table 2; we calculated the approximate lost coefficient of the system as given in table 6 and they are specified in per unit on a 1,000 mwa base. table 6: lost coefficient of the system under analysis line coefficient value (× 10−6𝑀𝑊−1 line coefficient value (× 10−6𝑀𝑊−1) 𝐵11 1.46 𝐵22 2.17 𝐵33 1.15 𝐵44 1.73 𝐵55 2.22 𝐵66 2.68 𝐵77 1.99 𝐵88 2.73 𝐵99 1.68 then the simplest power loss for the system as given in equation (29); 𝑃𝐿 = 0.0146 ( 𝑃𝐺1 100 ) 2 + 0.0217 ( 𝑃𝐺2 100 ) 2 + 0.0115 ( 𝑃𝐺3 100 ) 2 + 0.0173 ( 𝑃𝐺4 100 ) 2 + 0.0222 ( 𝑃𝐺5 100 ) 2 + 0.0268 ( 𝑃𝐺6 100 ) 2 + 0.0199 ( 𝑃𝐺7 100 ) 2 + 0.0273 ( 𝑃𝐺8 100 ) 2 + 0.0168 ( 𝑃𝐺9 100 ) 2 (32) starting with 𝜆1 as 400.0, the values for 𝑃𝐺1 1 , 𝑃𝐺2 1 , … . , 𝑃𝐺9 1 from equation (30), and 𝑃𝐿 from equation (32) were computed by a program developed in matlab and the results are as presented in table 7 in mw (where 𝑃𝐺1 1 , 𝑃𝐺2 1 , … . , 𝑃𝐺9 1 are in the order as presented in the table 5 listing the power plants, i.e 𝑃𝐺1 1 power generated by aba power station, 𝑃𝐺2 1 is the power generated from afam i – v power station and so on) table 7: power plant generating power after 1st iteration plant generation value (mw) plant generation value (mw) plant generation value (mw) 𝑃𝐺1 1 158.6728 𝑃𝐺2 1 213.6828 𝑃𝐺3 1 195.9099 𝑃𝐺4 1 178.9783 𝑃𝐺5 1 195.8261 𝑃𝐺6 1 160.2735 𝑃𝐺7 1 151.8301 𝑃𝐺8 1 217.5139 𝑃𝐺9 1 177.1645 𝑃𝐿 1 0.7215 http://www.azojete.com.ng/ mailto:patndyobi@gmail.com http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 678 total power 2,170 mw real power difference from the 1st iteration is therefore ∆𝑃1 = 2170 − ∑ 𝑃𝐺𝑖 19 𝑖=1 − 𝑃𝐿 1 = 511.6009 from equation (31), ∑ ( 𝜕𝑃𝐺𝑖 𝜕𝜆 ) 1 9 𝑖=1 = 4.1157 ∆𝜆1 = 511.6009 4.1157 = 124.305 𝜆2 = 𝜆1 + 124.305 = 524.305 repeating the process for the second iteration (using 𝜆2 = 524.305 ) gives the results displayed in table 8 table 8: power plant generating power after 2nd iteration plant generation value (mw) plant generation value (mw) plant generation value (mw) 𝑃𝐺1 2 210.4095 𝑃𝐺2 2 283.5900 𝑃𝐺3 2 257.9969 𝑃𝐺4 2 235.3991 𝑃𝐺5 2 258.8524 𝑃𝐺6 2 211.9622 𝑃𝐺7 2 199.6725 𝑃𝐺8 2 287.3723 𝑃𝐺9 2 234.5880 𝑃𝐿 1 0.8632 real power difference from the 2nd iteration is therefore ∆𝑃2 = 2170 − ∑ 𝑃𝐺𝑖 29 𝑖=1 − 𝑃𝐿 2 = −4.8632 again, from equation (31), ∑ ( 𝜕𝑃𝐺𝑖 𝜕𝜆 ) 2 9 𝑖=1 = 4.0081 ∆𝜆2 = −4.8632 4.0081 = −1.2113 𝜆3 = 𝜆2 − 1.2113 = 523.0937 repeating the process for the third iteration (using 𝜆3 = 523.0937) gives the results displayed in table 9 table 9: power plant generating power after 3rd iteration plant generation value (mw) plant generation value (mw) plant generation value (mw) 𝑃𝐺1 3 209.9055 𝑃𝐺2 3 282.6187 𝑃𝐺3 3 257.3920 𝑃𝐺4 3 234.8494 𝑃𝐺5 3 258.2481 𝑃𝐺6 3 211.4587 𝑃𝐺7 3 199.1074 𝑃𝐺8 3 286.7098 𝑃𝐺9 3 233.6382 𝑃𝐿 3 0.8461 this iterative process continues until the 6th and 7th iterations. ∆𝑃6 = 2170 − ∑ 𝑃𝐺𝑖 39 𝑖=1 − 𝑃𝐿 6 = −0.4036 again, from equation (31), ∑ ( 𝜕𝑃𝐺𝑖 𝜕𝜆 ) 6 9 𝑖=1 = 3.7465 ∆𝜆6 = −0.4036 3.7465 = −0.1077 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com obi et al: optimal load scheduling of power plants in a grid considering the plant’s capacity and line losses. azojete, 18(4):669-682. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 679 𝜆7 = 𝜆6 − 0.1077 = 518.7254 𝑎𝑠 𝜆6 = 518.8331 the 7th iteration gives results presented on table 10: table 10: power plant generating power after 7th iteration plant generation value (mw) plant generation value (mw) plant generation value (mw) 𝑃𝐺1 7 209.1435 𝑃𝐺2 7 282.1315 𝑃𝐺3 7 256.124 𝑃𝐺4 7 234.3539 𝑃𝐺5 7 257.8456 𝑃𝐺6 7 211.2426 𝑃𝐺7 7 198.5624 𝑃𝐺8 7 286.1638 𝑃𝐺9 7 233.5374 𝑃𝐿 7 0.7653 ∆𝑃7 = 2170 − ∑ 𝑃𝐺𝑖 39 𝑖=1 − 𝑃𝐿 7 = −0.3815 we settle for the results on table 9 as our final iterative results since the difference is below 4 kw (and 4 𝑘𝑊 ≪ 1270 𝑀𝑊). the total fuel consumption worth of the total power plants to generate the 2170 mw (including losses) at normal generation and for optimum power generation are given in equations (33) and (34) respectively. 𝐹𝑇𝑛 = 𝑓1(80) + 𝑓2(150) + 𝑓3(500) + 𝑓4(180) + 𝑓5(400) + 𝑓6(80) + 𝑓7(80) + 𝑓8(400) + 𝑓9(300)(33) 𝐹𝑇𝑒𝑑 = 𝑓1(209.1435) + 𝑓2(282.1315) + 𝑓3(256.624) + 𝑓4(234.3539) + 𝑓5(257.8456) + 𝑓6(211.2426) + 𝑓7(198.5624) + 𝑓8(286.1638) + 𝑓9(233.5374) (34) the power generated by the various plants and fuel/energy burnt per hour when the total generation is shared as highlighted in table 2 and when shared with the plants running on equal incremental fuel cost is contained in results of equations (33) and (34) are presented in table 11. table 11: comparing sharing of 2,170 mw by the various plants in grid power stations with unequal incremental fuel cost with equal incremental fuel cost fuel burnt per hour [× 104cal/hr ] plant output power [mw] fuel burnt per hour [× 104cal/hr] plant output power [mw] aba power station 9,200 80 56,413 209.1435 afam iv-v power station 22,500 150 75,299 282.1315 afam vi power station 254,000 500 67,860 256.124 alaoji power station (nipp) 36,725 180 61,772 234.3539 okpai power station 163,200 400 67,976 257.8456 omoku power station 8,885 80 56,667 211.2426 sapele power station 8,725 80 52,252 198.5624 sapele power station (nipp) 147,200 400 75,471 286.1638 delta-ughelli power station 102,000 300 61,811 233.5374 total 752,435 2170 575,521 2169.6185 http://www.azojete.com.ng/ mailto:patndyobi@gmail.com http://en.wikipedia.org/w/index.php?title=aba_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_iv-v_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=afam_vi_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=alaoji_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/national_integrated_power_project http://en.wikipedia.org/w/index.php?title=okpai_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=omoku_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=sapele_power_station&action=edit&redlink=1 http://en.wikipedia.org/wiki/national_integrated_power_project http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 http://en.wikipedia.org/w/index.php?title=delta_-_ughelli_power_station&action=edit&redlink=1 arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 680 with a total power of 2,170 mw generated by all nine (9) generating units in the region to service the power demand and losses along the power lines, the energy burnt by each plant and the total energy burnt by all the 9 power plants in every hour are presented in table 10. using a case where the plant’s individual generation as highlighted on table 2 equals 2170 mw, their individual fuel burnt are shown in table 10 and the total fuel burnt by all nine (9) plants in the generation of this power, is 752,435 × 104 𝐶𝑎𝑙/ℎ𝑟. however, when the plants ran with the same incremental fuel cost, the power generated by each plant changed. more generating responsibilities were given to those plants whose generation costs are relatively lower. for example, afam iv-v and aba power stations (a more of steam combine circle plants) were given more generating responsibilities as they are relatively cheaper generating with them than most other plants on the grid. hence, their generations were increased from 150 mw to 282.1315 mw and from 80 mw to 209.1435 mw respectively. however, the same total power generation of approximately 2170 mw was achieved (precisely 2169.6185 mw). the energy used by the individual plant and the total energy used by all nine (9) plants to generate that same total of 2,170 mw power each hour as presented in table 10 is 575,521 × 104 𝐶𝑎𝑙/ℎ𝑟 . this implies that a total of 176,914 × 104 𝐶𝑎𝑙 (or 7.407 × 109 𝐽𝑜𝑢𝑙𝑒𝑠 ) of energy is saved each hour. this value converted to kwh gives 2.057 × 103 𝑘𝑊ℎ as the energy saved each hour. with energy sold at forty-eight naira only per kilowatt-hour (₦48/kwh) in nigeria, a total of ninety-eight thousand, seven hundred and thirtysix naira (₦98,736.00) only will be saved each hour. this means that a total of eight hundred and sixty-four million, nine hundred and twenty-seven thousand, three hundred and sixty naira (₦864,927,360.00) only will be saved per annum. 4. conclusion this paper showed how the total running cost of different power generating plants in a grid feeding a fixed load can be achieved. this was done by giving more generation task to those power plants whose cost of generating power is relatively low (provided their generation capacity is not exceeded). with this, the same quantity of total power is generated with a relatively lower cost; this can be regarded as comparative cost advantage in power generation cost. as seen from the studies, a total of over eight hundred million (₦800,000,000:00) naira was saved annually when all power plants in the region analyzed were ran with this method (equal incremental fuel cost) over when the load was shared arbitrarily by the plants. this saved money can be used to build more power plants, expand transmission capacities or used for other capital projects in the country. therefore, optimized combination of power plant running is highly recommended in running the nigerian power system. references attaviriyanupap, p., kita, h., tanaka, e. and hasegawa, j. 2002. a hybrid ep and sqp for dynamic economic dispatch with non-smooth fuel cost function. ieee transaction on power systems, 17(2): 411-416. avalos, mjr. 2008. analysis and application of optimization techniques to power system security and market. phd thesis, department of electrical and computer engineering university of waterloo, canada. bogdan, z., cehil, m. and kopjar, d. 2007. power system optimization. energy, 32: 955-960. bommirani, b. and thenmalar, k. 2013. optimization techniques for the economic dispatch in power system operation. international journal of information technology, 2(1): 475-482. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com obi et al: optimal load scheduling of power plants in a grid considering the plant’s capacity and line losses. azojete, 18(4):669-682. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 681 el-sharkh, my., tanrioven, m., rahman, a. and alam, ms. 2006. a study of cost-optimized operation of a grid-parallel pem fuel cell power plant. ieee transactions on power systems, 21(3): 1104-1114. eurafric power limited. 2014. 1020mw 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n. and yunna, w. 2012. a parallel adaptive particle swarm optimization algorithm for economic/environmental power dispatch. mathematical problems in engineering, 2012: 1-15. kovalev, gf., lebedeva, lm. and krupeniov, ds. 2011. models and methods for estimation and optimization of electric power system reliability. reliability: theory & applications, 12(2): 92-105. lei, g., song, h. and rodriguez, d. 2020. power generation cost minimization of the gridconnected hybrid renewable energy system through optimal sizing using the modified seagull optimization technique. energy reports, 6: 3365-3376. niger delta power holding company (ndphc) and federal government of nigeria. 2013. national integrated power project (nipp), 1,072mw combined cycle gas turbine power plant data book, alaoji, abia state. nigerian agip oil company (n.a.o.c). 2003. national integrated power project (nipp), 490mw okpai combined cycle power plant data book, kwalle, delta state. nigerian agip oil company (n.a.o.c) and rivers state government. 2003. national integrated power project (nipp) omoku 600mw combined cycle power plant data book, omoku, rivers state. obi, pi., iloh, jpi., ulasi, aj. and emeghara, mc. 2017. decentralized power supply improvement in africa economics: a case study of nigeria. proceedings of the 3rd international conference on engineering adaptation and policy reforms (ijeapr, 2017), uli, nigeria, 17 – 18 may 2017, pp. 9-17. obi, pi. and offor, kj. 2012. power flow and contingency assessment of the existing 330kv nigeria power grid to cope with the proposed increase in power generation 2014. international journal of engineering research and technology (ijert), 1(4): 1-9. http://www.azojete.com.ng/ mailto:patndyobi@gmail.com http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine http://en.wikipedia.org/wiki/simple_cycle_combustion_turbine arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):669-682 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: patndyobi@gmail.com 682 oputa, o. 2015. running cost minimization of an electric power sector. international journal of engineering and computer science, 4(7): 13169-13175. oputa, o., obi, pi., okeke, o. and anyaka, bo. 2019. an optimized combination of power plants running in a grid. proceedings of the 1st nieee nsukka chapter conference on engineering and management technology in the 3rd industrial revolution, nsukka, nigeria, 28 – 30 november 2019, pp. 26-36. panda, a., mishra, u., ming-lang, t. and ali, mh. 2020. hybrid power systems with emission minimization: multi-objective optimal operation. journal of cleaner production, 268: 153-160. saadat, h. 1999. power system analysis. 3rd edition, mcgraw – hill company, new york. shell petroleum development company (s.p.d.c). 2003. afam i – v combined cycle gas turbine 750mw power plant data book, afam, rivers state. shell petroleum development company (s.p.d.c). 2005. afam vi combined cycle gas turbine 750mw power plant data book, afam, rivers state. transnational corporation of nigeria plc, transcorp’s power subsidiary, transcorp ughelli power limited ughelli. 2012. general electric 900mw gas-fired thermal power plant data book, ughelli, delta state. wood, aj., wollenberg, bf. and sheble, gb. 2013. power generation operation and control, 3rd edition, john wiley & sons, inc, new york, usa file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:patndyobi@gmail.com arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):71-84 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 71 original research article corrosion of aluminium metal in food environments and its associated health risk issues: a review t. n. guma* and m. m. maikudi department of mechanical engineering, faculty of engineering and technology, nigerian defence academy, kaduna, nigeria *corresponding author’s email address: tnguma@nda.edu.ng 1.0 introduction corrosion is an inevitable natural process that attacks an engineering-serviceable material, especially metal, by its interaction with the environment, resulting in deterioration of its cherished properties and service attributes (guma et al, 2017., inan-eroglu et al, 2019). material corrosion occurs to various degrees wherever an environment other than a vacuum exists. corrosive environments include all natural and synthetic gases and liquids and chemicals, soils, all living and dead animal bodies and waste products from them, bacteria and viruses and other microorganisms, plants and extracts from them, all kinds of food, etc. all environments are corrosive to different metals in various ways or levels. material corrosion directly or indirectly affects us in all spheres of our human activities. metallic article information abstract a material for use in contact with food must have adequate strength and integrity to avoid its accidental fracture and leaching of pernicious substances into the food due to corrosion or abrasion of the material. this review covers the basics of aluminium metal and its corrosion in foodhandling usage and the associated health-risk issues of its particle intake by human food consumers, as well as current research on the topic. the review findings show that aluminium metal has outstanding advantages in food handling in terms of low cost, wide availability, light weight, ability to heat and cool fast, high temperature tolerance, good corrosion resistance, and perennial shiny appearance in unpolluted natural environments. its other advantage is excellent formability into designed kitchenware shapes. on the other hand, the findings show that aluminium metal has lower strength and hardness integrity. it is also leachable with lower health-safety level for food-handling usage compared to many other food-grade metals such as stainless steel. furthermore, daily intake of aluminium substances above 10 mg per kilogram by an individual is risky to their health. the other findings are that food environments with high chloride, acidity, and alkalinity contents can cause greater corrosion of aluminium metal to leach its particles into food, with a higher chance of intaking the particles into the human body system than other food environments. finally, the findings show that only appropriately alloyed and adequately coated aluminium of sufficient strength should be used in contact with food. the information from the review is meant to serve as a consolidated current literature position on corrosion in the use of aluminium metal for food handling and associated health-risk issues for safe-guarding or a way forward by researchers and stakeholders that need background information for making the metal safer for food handling © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 august, 2022 revised 2 october, 2022 accepted 10 october, 2022 keywords: aluminium metal food-handling usage corrosion inevitability food consumers health-risks background information research progress http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng tnguma@nda.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):71-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 72 corrosion has a massive technological and economic cost, as well as implications for environmental and personal safety (guma et al, 2017., inan-eroglu et al, 2019). food processing is one of the largest industries in the world since everyone out of the over seven billion humans on earth eats daily (salas et al., 2012). corrosion in food environments is therefore a significant problem because it can lead to many equipment failures with costly downtime and the potential to impact food safety and quality. according to reports from the national association of corrosion engineers over the last few decades, the total direct cost of corrosion to the food industry has been estimated to be more than $2.1 billion per year (guma and sukuntuni, 2019., montanari, 2015). the cost includes costs of food machinery, cutlery and utensils, commercial and restaurant equipment and appliances, cans, use of corrosion inhibitors and other preventive methods, and improvement research (bryan, 2021). metals and alloys can be used in contact with food in processing equipment and containers, household utensils, and foils for wrapping food. metals and alloys used in food environments are usually covered with protective surface coatings but can inevitably be decoated by corrosion or abrasion with the release or leaching of metallic substances into food. leached substances can endanger human health if their total content in food exceeds the health-safe guideline value, or if they cause an unacceptable change in the composition of the food or deterioration of its organoleptic properties (guma and sukuntuni, 2019., montanari and montanari, 2015). according to the food and drug administration (fda) authorities, a material for use in contact with food must meet several conditions for food safety, such as by (guma and sukuntuni, 2019., noemie et al, 2022): i. not allowing deleterious substances to migrate into food or impart odours, colours, and tastes to it. ii. being durable, corrosion-resistant, and non-absorbing. iii. having sufficient weight and thickness and strength to withstand repeated washing and forces. iv. being well finished with smooth and easily cleanable surface. v. being resistant to pitting, crazing, scratching, chipping, scoring, distortion, and decomposition. all the above conditions can be anticipated and fulfilled except material corrosion, because the level of environmental corrosivity and material degradation rates vary randomly at different locations and can in many cases be unpredictable and not adequately counteracted. there are therefore established guidelines defined by food and feedstuff laws on the use of metals and alloys in contact with food and feedstuffs with regards to corrosion and toxicology (council of europe’s policy, 2002., alabi and adeoluwa, 2020., sambathkumar et al, 2023). of the food-grade metals, there has been notable concern about the use of aluminium due to the toxicological effects of its ions in the human body system. because of toxicity issues associated with aluminium metal, not all its types are used for food processing or handling. aluminium substances that are naturally found in food or water are known to be strongly and stably bound to benign substances or elements and less absorbable into the human body, so they present much lower health risks to humans when taken into their bodies with food compared to corroded or abraded aluminium ions, which are free and highly unstable radicals (alzubaidy et al., 2011., alabi and adeoluwa, 2020., sambathkumar et al, 2023). the problem with even food-grade aluminium metal is that it can undergo erosion, crevice, pitting, filiform, cavitation, exfoliation, inter-granular, galvanic, and micro-biologically influenced corrosion, etc., and leach healthrisky substances into food due to a lack of awareness of the need for its corrosion prevention or proper control in many food environments (guma and sukuntuni, 2019., stahl et al., 2017., alabi and adeoluwa, 2020., sambathkumar et al, 2023). the aim of this paper is to present a consolidated basic current literature position on the corrosion of aluminium metal with regard to the use of the metal for food handling and its associated healthrisk issues. the objective is to provide readily available basic facts for safe-guarding or a way forward for researchers and stakeholders that need the background information for making the metal safer for food handling. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng guma and maikudi: corrosion of aluminium metal in food environments and its associated health risk issues: a review. azojete, 19(1):71-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 73 information presented in this review paper was sourced from various relevant books, scholarly journals, and organizational activities. the sourced information was integrated and fined-tuned using our experiences as professionals and academics in the field for easy reading and understanding by people for safety awareness or research purposes. 2. the corrosion issues with the use of aluminium metal for food handling 2.1 aluminium as a food-handling material the common metals for food handling include cast iron, grade 304 and 316 stainless steels, aluminium, and copper (nordic council, 2015., zunko and turk, 2022). however, the bulk of food-grade materials are stainless steel at the top of the scale and aluminium, but any material can be used if it is covered with a protective coating that can withstand corrosion aggressiveness in food handling applications. compared to aluminium, stainless steel is significantly stronger, harder, and less likely to affect the flavour or texture of food due to its neutral chemical makeup (zunko and turk, 2022). on the other hand, aluminium can affect the way food tastes if it comes in contact with the metal’s surface for an extended period of time. not only this, aluminium can change the appearance of food, and this does not bode well for restaurants and chefs. although stainless steel is used more than aluminium for equipment, utensils, and cutleries for food matters, aluminium has advantages as a food contact material because it is light in weight, low cost, rust resistant, and is prized in cookware for the speed with which it heats and cools compared to stainless steel. like steel, the aluminium used to make cookware and utensils or build food equipment is alloyed with other elements to the requisite level to meet strength, hardness, durability, and health-safety requirements for food-handling. this is because pure aluminium per se exhibits good corrosion resistance but has poor mechanical properties and a low food safety level, so it must be alloyed with other suitable elements to meet food handling requirements. the main alloy elements used to impart these properties are manganese, silicon, iron, and copper (council of europe’s policy, 2002., nordic council, 2015., stahl et al, 2017., rahimzadeh et al, 2022., weidenhamer et al, 2022). the percentages present in each of those elements determine the aluminium grade's physical properties. aluminium pots, plates, pans, and spoons are commonly used in our kitchens in homes, restaurants, and hotels for food preparation or service. aluminium foil and soda cans are also used in the cooking industry. formal inquiries with the use of aluminium metal for food handling are its greater softness, ability to tolerate less abuse, inability to be much stressed before fracture, and intake of its ions in the human body system above acceptable levels causes liver toxicity and leads to alzheimer’s disease and other degenerative symptoms compared to the other commonly known metals used for food handling such as stainless steel (bryan, 2021). it is prohibited to use objects in contact with foodstuffs that do not meet the requirements of regulation (ec) no. 1935/2004 in accordance with section 31 of the german food and feedstuffs law, 2005 (guma & sukuntuni, 2019). pure aluminium and some aluminium alloys contain elements in quantities and/or numbers that negate health safety levels, so use of aluminium in the food industry is guided by rules as to what the content of each aluminium alloy should be for applications. there are maximum tolerances laid down according to regulation en 602:2007 of european standards in connection with the use of aluminium in the food industry. stipulated maximum contents of various allowable elements in aluminium alloys for food industry applications are shown in table 1 (guma & sukuntuni, 2019). table 1: the maximum content of various allowable elements in aluminium alloys for food industry applications element si fe cu mn mg cr ni zn zi ti others max. content by mass [%] 13.5 2 0.6 4 11 0.35 3 0.25 0.3 0.3 0.15 *source: guma and sukuntuni, 2019 for example, al 6061 alloy with percentage elemental weight composition of: 96.85 aluminium, 0.9 magnesium, 0.7 silicon, 0.6 iron, 0.3 copper, 0.25 chromium, 0.20 zinc, 0.10 titanium, 0.05 http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng https://pubmed.ncbi.nlm.nih.gov/?term=rahimzadeh%20mr%5bauthor%5d https://pubmed.ncbi.nlm.nih.gov/?term=weidenhamer+jd&cauthor_id=35100934 arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):71-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 74 manganese, and 0.05 others within the specified ranges given in table 1, is a commonly used food aluminium alloy (guma and sukuntuni, 2019). 2.2 corrosion and status of aluminium as a food-grade material it is important that abrasion and corrosion problems be taken into consideration when using any material in contact with food so as to prevent deterioration of the material and leaching of its particles into food. among the food-grade metals, aluminium and stainless steel are notable for their generally high corrosion resistance (nordic council, 2015., inan-eroglu et al, 2019). pure aluminium has very good corrosion resistance in most unpolluted environments, such as the atmospheric environment. this is primarily attributed to the ability of aluminium metal to spontaneously form a thin oxide layer on its surface, which effectively prevents further oxidation of the metal. the oxide layer is impermeable and strongly adheres to the aluminium body, in contrast to oxide layers on many other metals. if the formed oxide layer is damaged by mechanical action, it repairs itself immediately (asm, 1999., inan-eroglu et al, 2019). the formed oxide layer is the fundamental reason for aluminium’s good corrosion resistance. the oxide layer is stable in environments with ph in the range of 4–9. aluminium can, however, corrode greatly in highly alkaline and acidic environments with ph values outside the 4–9 range (asm, 1999., al-rudaini and al-saadie, 2021). in food preparation environments, many cleaning and sanitation agents, including alkaline, acidic, oxidizing, and reducing chemicals, are employed to remove bacteria, scale, fouling, and corrosive biological and mineral deposits on equipment and utensils and cutleries, to ensure a high hygiene level (ellis, 2021., salas et al, 2012). these cleaning and sanitation agents can, however, cause various levels of material corrosion, including aluminium equipment and kitchenware. water is also a great agent of aluminium corrosion and is widely used for food processing. extensive use of high-pressure water and steam is the leading cause of aluminium corrosion in food processing facilities. this is due to the ability of high-pressure water and steam to cause erosion corrosion of aluminium, often in combination with the other different corrosive agents comprising alkaline, acidic, oxidizing, and reducing chemicals for cleaning purposes (ellis, 2021., salas et al, 2012). some food products with highly acidic contents, such as citric fruit juices, tomatoes, cabbage, jams, soft fruits, pickled vegetables, and dressings, as well as alkaline foods or ingredients, and foodstuffs with much added salts, are also inherently corrosive to aluminium metal (ellis, 2021., salas et al, 2012). the ph ranges of different food categories in the food industry as a measure of their corrosivity extent to metals, including aluminium, are shown in table 2. table 2: ph ranges of different food categories as measures of their corrosivity levels food category ph range vegetables 3.0-6.0 fruits 2.0-5.0 bakery 5.0-6,5 meat 6.0-7.0 fish 5.5-6.0 dairy 5.0-6.5 beverages 2.0-5.5 *source: salas et al, 2012 the food processing environment is indeed a complex composition consisting of various levels of alkaline such as caustic soda (naoh), alkali phosphates (na3po4), sodium carbonate (na2co3) and file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng guma and maikudi: corrosion of aluminium metal in food environments and its associated health risk issues: a review. azojete, 19(1):71-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 75 bicarbonate (nahco3); acids such as phosphoric, citric, and sulfamic acids; and oxidizers such as chlorine, nitric acid, ozone, hypochlorite, hydrogen peroxide (h2o2), which can be very corrosive to aluminium and other metals. if aluminium utensils are coated with protective coatings such as teflon, there is no leaching of aluminium during cooking as long as the coating is intact. aluminium can accumulate much more in foods stored or cooked in uncoated aluminium pans than in coated cookware (ellis, 2021; salas et al., 2012). the amounts of aluminium that accumulate in foods during preparation depend on the ph of the foods, the length of cooking periods, and the types of utensils. ingested aluminium can accumulate in the brain, bones, and liver and cause some diseases like, encephalopathy, as well as bone and other disorders (ellis, 2021). 2.3 some current researches on the food environment corrosion of aluminium metal and the associated health risks a review of some recent researches pertaining to food corrosion of aluminium has been made as follows: jimenez and kane (1994) described aluminium as one of the most common materials with alloy elements added to improve its physical and chemical properties for food packaging. they discovered that applying coating materials or plastic laminates to aluminium containers and flexible foil packages improves their end-of-life performance. they demanded thorough compatibility testing with the specific product to be used as a requirement for the final selection of packaging and extensively discussed test results on the interactions of various foods and beverages with aluminium containers. they reviewed the electrochemical action of foods wrapped with aluminium foil and placed in contact with other metallic objects. their conclusion was that aluminium and its salts have a harmless effect when ingested with foods that have been exposed to the metal (jimenez and kane, 1994). the possibility of foods interacting with non-coated aluminium was modelled by piergiovanni et al. (1990), using corrosion behaviour results from an aluminium household foil under different conditions of acidity, temperature of the contacting phase, and dissolved oxygen. they kept the aluminium foil in contact with acetic acid solutions whose ph values ranged from 2.5 to 3.5 and dissolved oxygen concentrations ranged from 0 to 8 ppm, under various temperature conditions of 0.3 to 50°c and contact durations of 24 to 120 hrs. they detected corrosion and found that all the three variable factors had an influence on its rate and, consequently, the extent of the interaction; but ph and temperature had greater effects on the rate since their relationships with the rate were exponential in nature. they also found a linear relationship with a minor accelerating effect between corrosion rate and dissolved oxygen. by applying the arrhenius equation, they evaluated the thermal sensitivity of the phenomenon with respect to the different variable factors. they showed that the activation energies varied within 31-635 and 88-471j/mol, giving an indication of higher thermal sensitivity at the lower ph values and higher dissolved oxygen amounts (piergiovanni et al.,1990). a method of estimating aluminium leaching from aluminium cookware in some meat extracts and liquid milk was investigated by al-juhaimam (2010), using four kinds of aluminium cookware from four countries chosen from the local market. he used extracts of boiled lamb, chicken, and fish to make 10–50% (w/v) concentrations. in addition, he diluted fresh liquid milk and long-life milk to make 10– 50% (v/v) concentrations. he applied weight loss, atomic absorption, and polarization methods, and surface study to the methods. his estimated aluminium intake per person from weight loss in 30% meat extract and milk ranged from 8.16 to 12.75 mg/h, with fish extract having the highest leaching and chicken extract having the lowest leaching. atomic absorption gave comparable results to those of weight loss. comparing the results of his study with the provisional weekly intake of aluminium approved by the fda/who showed that aluminium leaching from aluminium cookware might add high doses of aluminium into the diet (al juhaimam, 2010). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):71-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 76 al-zubaidy et al. (2011), studied the effects of ph, salinity, and temperature on aluminium cookware leaching during food preparation. they noted that intake of aluminium by humans portends hazards, and the subject had been under study for some years and had attracted significant attention from the media as it is believed that the intake enhances or causes diseases like the well-known alzheimer's disease. in the study, the effects of ph, salinity, and temperature of egyptian and indian aluminium cookware were measured during food preparation using tap water and drinking water. they used the weight loss method to study aluminium leaching into different food solutions. they also used environmental scanning electron microscopy to study the morphology of the cookware samples before and after exposing them to the different food solutions and applied the arrhenius equation to find activation energies. they found that cookware aluminium was very sensitive to low and high ph as the corrosion rate increased in an alkaline environment. they also observed that corrosion rates decreased with drinking water compared to tap water, and increasing salt concentration increased the corrosion rate up to a certain value, after which a decrease was observed to reach a plateau of constant corrosion rate. they attributed this behaviour to the combination of high conductivity and oxygen solubility of the solutions (al zubaidy et al., 2011). mohammad et al. (2011), studied the effect of aluminium leaching from cookware on food. they observed that the intake of aluminium from utensils had been of growing concern for the health of the community. in their study, they investigated the leaching of aluminium from aluminium utensils in different food solutions. they chose two available aluminium utensils of different origins from the local market. they used minced meat with drinking water and tap water for the study. they also used two other techniques of analysis: weight loss measurement and inductively coupled plasma-mass spectrometry, for the study. they found that their results showed little variation between the whole meat and meat extract solution. they chose the meat extract solution for all experimental work and examined different solutions starting from water, different concentrations of meat extract, and a 40% meat extract solution with tomato juice, citric acid, and table salt. they found that the results of the two measurements were almost consistent. they found that the amount of aluminium leaching was high in the cooking solutions using all the above additives. they observed that, according to the world health organization (who), their obtained values could be considered unacceptable in relation to their limitations, indicating a high risk to the consuming community (mohammad et al., 2011). a study on the corrosion behaviour of wrought aluminium alloy under domestic food cooking conditions was conducted by adeosun et al. (2012), using the gravimetric method. they subjected flat, cold-rolled and annealed sheets of wrought aluminium alloy to solutions of capsicum annuum, l. esculentum, allium cepa, and their blends under heating and cooling conditions in still air, a refrigerator, and left some in the open still atmosphere. the results of their study showed that corrosion occurred within the 288-hour test period in the test environments. they also found that there was severe degradation within the first 70-hour period of the tests when coupons were heated and cooled, and unheated coupons showed low corrosion propensity. their micro-structural analysis showed the presence of corrosion pits on coupon surfaces with second phase particles sandwiched in α-aluminium matrix. immersed coupons in the blended media showed a higher number of pits on the surface. they attributed rapid corrosion of wrought aluminium alloy in capsicum annuum, l. esculentum, and allium cepa media to the presence of corrosion-aggressive elements such as allicin, diallyl-disulphide, and allyl-propyl disulphide present in the corrosion media (adeosun et al., 2012). odularu et al. (2013), carried out a comparative study on leaching from aluminium, clay, stainless steel, and steel cooking pots through the absorption of aluminium by rice boiled in distilled water in a variety of containers, such as old and new aluminium pots, clay receptacles, stainless steel pots, and steel pots. they took 10 g of rice as a representative sample and used colorimetric analysis of classical methods to determine the concentration of aluminium. they used a control for aluminium of 350 ±130 μg/g. they found that new aluminium pots had a concentration of 126 ± 64 μg/g, old steel file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng guma and maikudi: corrosion of aluminium metal in food environments and its associated health risk issues: a review. azojete, 19(1):71-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 77 utensils had 186.83 ± 75.18 μg/g, new steel pots had 241.00 ± 200 μg/g, old aluminium pots had 314 ± 128 μg/g, new clay pots had 132 ± 68 μg/g, old clay pots ± 137 μg/g, new stainless-steel utensils had 289.00 ± 75.155 μg/g. they detected aluminium leaching in all forms of new and old cooking utensils, but the leaching was below and within the control concentration range. they also found that old aluminium pots had the highest concentration of leaching while new steel pots had the least leaching of aluminium. they concluded from their study that the aluminium contamination of the tested foods was insufficient to constitute a health risk (odularu et al., 2013). rahem (2014), studied the effects of citric acid in tomato paste and sodium chloride (nacl) as cooking salt on the corrosion behaviour of kitchenware aluminium by electrochemical technique under different cooking temperatures of 30, 50, and 70oc and different paste solutions of 1, 3, and 5% with and without the addition of 1%-nacl. he found that an increase in paste concentration increased current density, the addition of nacl increased current density more rapidly than without addition, and an increase in temperature had a strong effect on the corrosion behaviour of the aluminium (rahem, 2014). jabeen et al. (2016), conducted a study to identify the correlation between food and aluminium intoxication through leaching. they opined that ingestion is the main route of aluminium exposure to the human body. they therefore deem it necessary to identify the aluminium levels in the human body leached out from aluminium wares and aluminium foil. they baked pieces of chicken and red meat with different types of solutions containing tomato juice, fresh yogurt, salt, and vinegar in different combinations. from there, they wrapped them in aluminium foil in different combinations, marinated them in aluminium pans, and tested them for the ph and weight of the pieces and foil. they found that citric acid, in combination with lactic acid, was the source of elevated levels of aluminium in food items, especially raw beef. they also found that citric acid with tomato juice had the highest aluminium accumulation rate of 292.25 mg/kg in beef than other solutions, while the chicken leaching rate was 209.52 mg/kg with the combination of yogurt and lemon juice. they concluded that once aluminium exceeds the acceptable limit from the daily ingestion of food cooked in these pots, coupled with other sources from the environment, this environmental factor may contribute to an increase in neurodegenerative diseases. the aim of their research study was to detect the leaching of aluminium levels from aluminium foil in different food solutions, as it is becoming a common practice (jabeen et al., 2016). juhaiman (2016), studied curcumin extract as a green inhibitor of leaching from aluminium cookware at quasi-cooking conditions. he successfully used curcumin aqueous extract as a green corrosion inhibitor at quasi-cooking conditions at 90°c to inhibit leaching from aluminium cookware in solutions containing vegetables or meat. he bought the cookware from the market from four countries and cut them to make the aluminium samples. he chose six types of vegetables and three kinds of meat and used each type of vegetable and meat to prepare 30% w/v aqueous solutions. he used three methods: the gravimetric method, atomic absorption, and fourier transform infrared spectroscopy. he applied the gravimetric method to determine the leaching rate and the corrosion inhibition efficiency with and without nacl; and also investigated the effect of curcumin concentration, tab water, immersion time, and alloying elements. he found good consistency between gravimetric and atomic absorption methods. he also found that adsorption of curcumin on the aluminium surface was in accordance with langmuir isotherm and calculated and discussed the values of the adsorption constant (kads) and the free energy of adsorption (gads). his fourier integral transform spectrum indicated that curcumin coordinated with al3+, resulting in the formation of an al3+-curcumin complex on the metal surface; and using a small amount of curcumin decreased leaching from aluminium cookware into food by 60%-80% depending on the food type (juhaiman, 2016). aluminium leaching from aluminium-only foil and baking paper-aluminium foil into baked meat was determined by inan-eroglu et al. (2018). they cooked mutton, beef, and chicken breast and drumstick http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):71-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 78 in the oven using the two foil types at 150, 200, and 250°c temperatures for 60, 40, and 20 minutes, respectively, and determined the aluminium content in the meat by icps-ms. they discovered that increasing the fat content of the meat, increasing the cooking temperature and time, and decreasing the ph increased leaching from aluminium-only foil rather than baking paper-aluminium foil. they concluded their studies by recommending further studies on the effects of foil types on aluminium leaching into food under different conditions (inan-eroglu et al., 2018). guma and durami (2019), reaffirmed that the outstanding demerits of aluminium as a food-grade metal are its low tensile strength and impact tolerance, with greater liability to break compared to other common food-grade metals. they pointed out that aluminium can corrode appreciably in alkaline environments of ph higher than 9 with aggravation in its strength and that frequent intake of its substances along with food into the human body due to corrosion or abrasion can be health-risky. they observed that aluminium containers were in use for preparing and serving various menus from the general nigerian diet to about 1000 cadets on a daily basis at the nigerian defence academy (nda) cadets’ mess (canteen). they also noted that the menus and various ingredients used to make them amidst the general mess environment were inevitable in corroding the containers. they used accelerated corrosion tests to find out whether some of the commonly prepared and served menu items at the mess, such as eba, fried rice, egusi soup, tomato stew, alayafu vegetable dressings, and their possible different combination admixtures in any alkaline environment of ph greater than 9, had severe corrosion effects on the tensile strength of the containers. they procedurally produced and prepared 64 astm standard tensile samples of aluminium 6063, as a commonly used food-grade alloy for such containers. they then subjected 62 samples in pairs to alkaline treatments that mimicked the alkaline environment and corrosivity extremity of each menu sample to the containers. then, they tested the samples for their ultimate tensile strengths (uts) and collated and reported the results as the respective average pair values. their analysis of the reported results relative to those of the control sample pair showed negligibly small tensile strength reductions of 0.00027% to 0.00135%. their further analysis of the results using literature facts understandably indicted that the menu samples amidst the mess environment have negligible effects on corrosion and tensile strength of the containers and the health of the cadets (guma and durami, 2019). guma and sukuntuni (2019), discussed the health risks that can be associated with daily intake of aluminium substances above prescribed amounts into the human body system, as well as its low strength and impact resistance as a food-contact material, which makes it unable to take much force without breaking. they described corrosion as a severe, typical degrading process that worsens the effects of using aluminium metal as a food contact material. they reaffirmed that aluminium can corrode appreciably in acidic media with a ph of less than 4. the purpose of their research was to experimentally understand the corrosivity extents of some nigerian menu items, such as akamu, lemon juice, okro soup, pounded yam, and beans, amidst any unusual acidic environments to aluminium cookware and utensils used to prepare or serve food on a daily basis to more than 900 cadets at the cadets' mess of the nigerian defence academy. they also assessed the effects of the menu items on the impact strengths of the cookware and utensils. they procured and ascertained the al 6061 aluminium alloy as a commonly used metal for cookware and utensils and used it to produce 60 astm impact specimens. after procedurally cleaning the specimens to a similar surface finish, they used 5 specimen pairs for control and 25 other pairs each soaked for 28 days in the prepared menu samples separately sequentially homogenized with 0, 2, 4, 8, and 10% by weight of concentrated phosphoric acid (h3p04) under ambient laboratory conditions. after the soaking, they removed and tested the specimens for their impact strengths. their analysis of their collated test data revealed that the strength of the specimens in the menu media decreased as the h3p04 treatment of the media increased. they found that the lemon fruit juice medium treated with 10% by weight of h3po4 caused the comparatively highest but negligible impact strength reduction of 0.031% only relative to the control (un-soaked) specimen’s impact strength value. they came to the conclusion file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng guma and maikudi: corrosion of aluminium metal in food environments and its associated health risk issues: a review. azojete, 19(1):71-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 79 that the menu samples amidst any acidic environmental conditions of the mess have negligible effects on corrosion and impact strength of aluminium cookware and utensils as used there (guma and sukuntuni, 2019). guma and aliyu (2021), noted that sufficient hardness is a necessary quality of every cookware material to prevent its leaching of harmful particles into food due to corrosion and/or abrasion, but aluminium metal is less hard with health concerns compared to the majority of other cookware metals. they reaffirmed that chloride media play an important role in the corrosion and hardness reduction of the metal. they experimentally investigated the corrosion, hardness integrity, and food safety level of aluminium cookware under the food chloride environmental exposures at a canteen. their investigation stemmed from a desire to understand the extent to which some commonly prepared and served nigerian foods, named amala, moimoin, ogbono (irvingia gabonensis) soup, sweet potatoes (ipomoea batatas), and boiled beef, can cause corrosion and affect the hardness integrity and food safety level of aluminium cookware as used at the mess under various chloride environmental exposure conditions. they procedurally produced hardness coupons from unused aluminium cookware and soaked them for 30 days in the separate menu media, which were each prepared, characterized by ph and chloride content, and progressively homogenized with 0–1200ppm of nacl to accelerate the chloride corrosivity of the menus and their exposure environments to different degrees. after the soaking, they removed and measured the vickers micro-hardness values of the coupons. their analysis of the hardness measurements showed that the nacl additions to the test media minutely decreased the coupons’ hardness values by only 0.000667 to 0.023 percent, which presupposed a negligible deterioration in the hardness of the utensils themselves. their x-ray fluorescence analysis of ogbono soup test medium, which caused the comparatively highest hardness reduction of 0.023%, revealed undetected aluminium content that could be negligibly much less than 0.03% by weight in the medium and less than the food and drug administration (fda) authority of the usa's 10 mg maximum aluminium substances per kilogramme of daily food intake stipulation, with a negligible chance of any health risk to the soup consumers (guma and aliyu, 2021). fatunsin et al. 2022, investigated the effect of ph on the leaching of potentially toxic metals from different types of used cooking pots. they noted that humans are exposed to potentially toxic metals through many routes. they also noted that cooking foods in cookware that is prone to material leaching can be an exposure route to the potentially toxic metals. in their study, they assessed the effect of ph on the leaching of some potentially toxic metals from used cooking pots into deionized water. they prepared a series of deionized waters with a ph of 3 to 7. they brought each pot of water to a boil in clay, non-stick, stainless steel, cast aluminium, pressed aluminium, and glass pots, respectively. they determined the potentially toxic metals leached from each sample pot by inductively coupling a plasma-optical emission spectrophotometer of the agilent nu7m technologies 700 series. they found that the deionized water from the aluminium cast pot and non-stick pot had the highest concentrations of aluminium at 2273 μg/l and zinc at 24.39 μg/l. they also found that the clay pot had the highest concentrations of chromium and nickel, at 7.27 and 22.63 μg/l respectively. from the stainless steel pot, they found the highest concentration of iron to be 237 μg/l and lead to be 24.39 μg/l. however, they found no potentially toxic metals in the deionized water from the glass pot. the results from their study showed that more leaching of potentially dangerous metals into deionized water occurred at lower ph values of 3 to 5 than at neutral ph for almost all the pots. they therefore concluded that cooking acidic foods in pots except when glass pots are used, should be avoided. the results of their study therefore revealed the health implications associated with using metal pots for cooking slightly acidic foods, as metals can be easily leached from the pots into the foods (fatunsin et al., 2022). 3. remedies so far used to mitigate effects of aluminium metal corrosion in food environments http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):71-84. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 80 the deterioration of the mechanical properties of aluminium metal as an excellent material coupled with its toxicological effects of corrosion leaching in food has created a need for remediating its use for food handling. the common feasible remedies for the problem include: i. use of only the correct aluminium grade, such as aa 6061, and aa 6063 aluminium, for the manufacture of cookware, food utensils, and food processing machinery in accordance with reputable authorities on the subject such as the german food and feedstuffs law, 2005 (montanari, 2015., guma and sukuntuni, 2019) ii. production of all aluminium equipment, cookware, utensils, and other facilities that are used for food handling with highly smooth and cleanable surface finishing and regular geometrical patterns to minimize corrosion (ellis, 2021., montanari, 2015., gupta et al, 2019). iii. protecting the surfaces of aluminium facilities that must be used for food handling by coating the surfaces to a thickness of 50-100 μm with a suitable material that should be hard-anodized (ellis, 2021., montanari, 2015., gupta et al, 2019). iv. avoiding contact of food-handling aluminium facilities with acids or using the facilities for cooking acidic foods such as simmering tomato sauce (ellis, 2021., montanari, 2015., gupta et al, 2019). v. using only suitable soft materials to clean food-handling aluminium facilities such as cookware, utensils, equipment, etc, and taking precautions to preserve the protective anodized coating layer on them. avoiding prevalent cleaning practices involving the use of corrosive fluids and hard or metallic scrub which leads to erosion of the protective coating. that is, only materials that are not harmful or corrosive should be used for cleaning aluminium cookware, utensils, packages, and other food-handling facilities (eliss, 2021; montanari, 2015., gupta et al, 2019). vi. complying to the manufacturers’ instructions that aluminium cookware, utensils, packages, and other food-handling facilities should never be rubbed with hard or metallic scrub (montanari, 2015., gupta et al, 2019). 4. conclusion a literature review on the food-handling usage of aluminium metal, as well as issues of its corrosion leaching into food and associated health-risk to food consumers, has been presented as a consolidated basic current literature position on the subject for the renewal of public awareness, and for researchers and stakeholders who need the information to better the metal for the usage. the review critically shows that aluminium is the foremost food-grade metal due to its many outstanding advantages and extensive use in the food industry in various forms such as utensils, food processing equipment, food containers, foils for wrapping food, and bottles. however, a critical concern from the bulk of the reviewed literature is that daily intake of aluminium metal by humans above a permissible level can be detrimental to their health, and the quantity of its intake can be enhanced by the extent to which the metal dissolves and leaches into food; as determined by the extent of its corrosion in contact with particular food environments. the review has also shown that only certified and standardly coated aluminium alloys must be used in contact with food. however, increased acidity, alkalinity, or chloride content of foods or food environments can even corrode the certified and standardly coated food-grade aluminium alloys and cause leaching into food. much conducted research for a better understanding of the corrosion leaching of aluminium into food and ways of counteracting its leaching in different food environments has been found in the literature, but the utopian solution to the problem is still to be found. further research on alloy modifications of aluminium to utopian or better strength and corrosion resistance levels in all environments appears to be the foreseen way out of the problem. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/tnguma@nda.edu.ng guma and maikudi: corrosion of aluminium metal in food environments and its associated health risk issues: a review. azojete, 19(1):71-84. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: tnguma@nda.edu.ng 81 references alabi, oa. and adeoluwa, ym. 2020. production, usage and potential public health effects of aluminium cookware: a review. annals of science and 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https://doi.org/10.1007/s00501-022-01267 arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):885-896 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 885 analysis of rainfall trend in benin and warri cities of southern nigeria c. c. emeka-chris department of agricultural and bioresources engineering, michael okpara university of agriculture, umudike, nigeria *corresponding author's email address: cemekachris1@gmail.com article information submitted 18 april, 2023 revised 23 july, 2023 accepted 25 july, 2023 keywords: analysis rainfall trends south, southern nigeria abstract in this study the trends and patterns in the rainfall of benin and warri cities in southern nigeria were examined. rainfall data (1983-2014) for benin and warri cities were used. the mean, standard deviation, coefficient of skewness, coefficient of kurtosis, coefficient of variation and standardized anomaly index were used as statistical tools to analyze the data and establish the distribution of rainfall in these cities. spss 17 and minitab 16 were used to analyse the data the data obtained. the result of the trend analysis revealed that the year 2005 recorded the lowest annual rainfall of 229.10mm and 1925.8mm for benin and warri respectively. the years 2008 and 2011 recorded the highest rainfall of 4489.8mm and 3068.70mm for warri and benin respectively. the mean annual rainfall for the study period was 2162.46mm. the annual rainfall trend indicated a progressive increase in the annual rainfall during the period of study. the implications are that 2011 and 2008 recorded the highest rainfall event, including heavy rainfall, that can lead to flooding for benin and warri respectively while 2005 recorded the lowest rainfall events that can lead to drier year, potentially affecting crop yield in both cities. it is recommended that water resources managers should make adequate arrangement on how to prevent flooding by designing and constructing water carrying structures, including adequate urban and regional planning 1.0 introduction due to the detrimental impacts on natural and human systems caused by climate variability and change, it has become a topical issue. agriculture, forestry, and fisheries activities are the most affected by climate variability and change (fao 2012). crop productions are influenced significantly by variability in rainfall characteristics (nyong, 2008). the emission of excess greenhouse gases has generally been accepted to cause climate change (falaiye et al., 2021). intense flooding, severe and more frequent droughts, increase in wildfires, and heat waves in various parts of the world have been caused by climate change (shiru et al., 2019). studies and reports on climate change and variability are on the increase due to its considerable impact on hydrometeorological variables, namely rainfall, temperature and evaporation (wen et al., 2017, zhang et al., 2003; scalzitti and kochanski, 2016 and xu et al., 2016. the most important component is rainfall and its variability are related to flood and drought. this affects the supply of water for agricultural purposes and socio-economic development (wang et al., 2014). the overflowing of the normal confines of stream or other bodies of water that can result from storm surge, melting of glacier or heavy rainfall over areas that are habitually dry is defined as flooding (zbigniew et al., 2013). the impact of climate change is becoming more pronounced worldwide with consequences of climatic hazard such as severe storms, floods, heat waves and droughts (umuteme and http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):885-896. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 886 orusi, 2012). the niger delta, region of nigeria is recorded as the largest single area subjected to annual flooding in the country (olanrewaju et al., 2017). this is because it is a flat low-lying swampy area of alluvial deposition across which the tributaries of the niger meander (agbonkhese et al., 2014). as a result of the large inter-annual rainfall variability which often results in climatic and environmental hazard, there is dire need to study rainfall trends in the areas as a result of recent socio-economic developments such as urbanization, industrialization and over population (joshua and ekwe, 2013). furthermore, it is important to analyze rainfall trends and their applicability to various aspects of economic activity. for instance, rainfall regime has strong effect on agriculture, air traffic and other means of communication. rainfall is effective for plant growth and thus influences the efficiency of water for agricultural purposes. rainfall trends (variations) are of great interest to climatologists as well as agriculturists due to the important role of moisture in agriculture. therefore, it is very important that rainfall trends (variations) and patterns of the cities of study be investigated to recognize the exact impact of rainfall on economic growth and development. also, almost every farmer is interested in what the expected rainfall would be, more than any other climatic element as it determines the success or failure of crops. the objective of this work was to analyze the rainfall trends and patterns in benin and warri cities in southern nigeria. the parameters addressed were the examination of annual variability of rainfall depths of the selected locations in southern nigeria. 2. materials and method 2.1 description of the study area 2.1.1 location, climate and vegetation benin city is the capital of former bendel state and now edo state. it comprises of three major local government areas of the state, namely oredo, egbor and ikpoba okha. it has an area of about 1125km2it is located between latitude 06o 191 0011n and longitude 5o341 0011e and has an average elevation of 77.8m above sea level (figure 1 the soil consists of sedimentary formation of the miocene-pleistocene-age known as the benin formation (odemerho, 1988). the current population of benin city is 13, 875,786 (as of 12/27/2023) and is projected to surpass 30 million people in 2030 according to united nation’s data (source: world population prospects, 2022 revision warri city is in the south-western part of the niger delta in delta state, nigeria. warri city is located at latitude 5o 311 711 north and longitude 5o 441 5311 east and has an elevation of 6m above the sea level (figure 2). warri has a population of 3,600,000 according to 1991 population census. it is directly underlained by a quaternary formation, the somebreiro-warri deltaic plain sand consisting of fine and coarse–grained unconsolidated sediments of sand, peats, and gravel (obafemi et al., 22012; abotutu and ojeh, 2013). benin and warri cities are located in the humid forest belt of nigeria with rainfalls that begin in march or april and ends in october or november, while the dry season is from december to february. these cities experience double maxima rainfalls with a dry little spell in august referred to as ‘august break’. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng emeka-chris: analysis of rainfall trend in benin and warri cities of southern nigeria. azojete, 19(4):885-896. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 887 figure 1: map of edo showing benin city figure 2: map of delta state showing warri city 2.2 data collection the relevant data used for the study are monthly rainfall data of the study areas (benin and warri). these data are amount of monthly and annual rainfall depths recorded in these study areas from 1983-2014 using automatic rain gauges by nigerian meteorological agency (nimet) in oshodi, lagos state. at nimet station, observation is made at fixed hours, namely 0000(midnight), 0600 (6am), 1200 (noon) and 1800 (6pm) greenwich mean time. additional observations are made at other time between the four main times often hourly or at three hours interval. this procedure is in line with world meteorological organization (wmo, 2008). daily rainfall measurements were taken by nimet meteorologist using rain gauges. the data covered a period of thirty-two years from 1983-2014. these data are monthly rainfall records from 1983 to 2014. the parameter used here is the annual rainfall depths or amounts recorded in millimeter by rain gauges. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):885-896. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 888 the data were collected in an electronic format to enable effective analysis in microsoft excel version 2010. 2.3 data analysis in analyzing the required data, descriptive statistical tools were used. these include determination of the mean annual rainfall depths, standard deviation of the yearly rainfall depths, coefficient of skewness of annual rainfall depths, coefficient of variation, standard anomaly index of the annual rainfall depths and graphical plots for each city. these are mainly plots of standard anomaly index over time and trend line plots of annual rainfall over time (i.e. years the rainfall amount were recorded). 2.3.1 mean yearly (annual) rainfall this is a measure of central tendency. mathematically, it is denoted as �̅� and computed as: 𝑛 �̅� = ∑ 𝑥𝑖 𝑖 = 1 (1) 𝑛 where �̅� = mean yearly rainfall, depth measured in mm 𝑥𝑖 = yearly rainfall values (mm) n = total number of observations. 2.3.2 yearly rainfall depth standard deviation this is a measure of dispersion. the standard deviation measured the absolute dispersion for variability. the greater the standard deviation, the greater will be the magnitude of the deviation of the yearly rainfall values from the mean yearly rainfall for the periods. a small standard deviation means a high degree of uniformity of the yearly rainfall values. computationally, it is denoted as 𝜎 and given by 𝜎 = √ 𝑛 ∑ 𝑖=1 (𝑥𝑖−𝑋)2 𝑛−1 (2) where: 𝑥𝑖= annual rainfall for the year 𝑋 = mean annual rainfall n = total number of observations 𝜎 = standard deviation 2.3.3 standard coefficient of skewness to measure the co-efficient of skewness, the karl pearson’s co-efficient of skewness method was used, which is based upon the difference between mean and mode. the difference value is divided by the standard deviation to give the relative measure. this is obtained using the formula: coefficient of skewness = 𝑀𝑒𝑎𝑛−𝑀𝑜𝑑𝑒 𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛 (3) when, skew > 0: right skewed distribution that is most values are concentrated on left of the mean with extreme values to the right. skew < 0: left skewed distribution that is most values are concentrated on the right of the mean, with extreme values to the left. skew = 0: mean = mode = median; and distribution is symmetrical. 2.3.4 standard coefficient of kurtosis it refers to the degree of flatness or peakness of the distribution of rainfall data (depth) when a distribution is normal or symmetrical, the co-efficient of kurtosis is equal to 3. when it is more than 3, it is more peaked than the normal and when it is less than 3, it is less peaked than the normal. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng emeka-chris: analysis of rainfall trend in benin and warri cities of southern nigeria. azojete, 19(4):885-896. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 889 mathematically, kurt (x) = 4 𝜎4 (4) where 4 = fourth moment about the mean 𝜎 = standard deviation 2.3.5 coefficient of variation in determining the coefficient of variation, the following were done: (a) the annual rainfall data (depths) for the area of studies were collected from nimet office in oshodi, lagos state (b) the mean(average) of the annual rainfall depth were calculated using formula in equation 1 above (c) then the standard deviation of the annual rainfall data for the areas of studies calculated using the formula in equation 2 (d) the result of the standard deviation (𝜎) is divided by the mean ( 𝑋̅̅ ̅̅ ) (f) the result in ‘d’ is multiplied by 100 to express the coefficient of variation as a percent mathematically (gupta, 2011), coefficient of variation, c. v = 𝜎 �̅� 𝑥 100 (5) where 𝜎 = yearly rainfall standard deviation �̅� = mean annual rainfall 2.3.6 standardized anomaly index (s.a.i) it is used in the analysis of rainfall variability. it is given as sai (z-scores) = 𝑥𝑖−�̅� 𝜎 , i= 1, 2, …0. (6) where, 𝑥𝑖= yearly observations �̅�= mean annual rainfall depth 𝜎 = yearly rainfall standard deviation. 2.3.7 graphical plots graphical plots were used to plot annual rainfall data (depths) against time(years) and standard rainfall anomaly index values against time (years). statistical tools, mainly spss 17 and minitab 16 were used in rainfall depth trend analysis and in the graphical representation. 3. results and discussion 3.1 descriptive statistics of the annual rainfall the results of the descriptive statistics of the annual rainfall are shown in tables 1 to 2. the annual variations in the rainfall during the thirty-two years (1983-2014) studied are presented in table 1. it is evident that some years recorded higher values of the rainfall values than others. it was observed for benin that 2011 recorded the highest rainfall value of 3068.7mm, while 2005 recorded the lowest rainfall value of 229.1mm. also, for warri, it was observed that 2008 recorded the highest rainfall value 4489.8mm, while 2005 recorded the lowest rainfall value of 1925.8mm. these results for both benin and warri revealed that there were variations in the annual rainfall depths. the variations in rainfall depths (both seasonal and spatial) to a greater extent have effects on agricultural activities as most farmers depend on favourable weather condition to commence their agricultural activities and this plays a crucial role in determining agricultural yields (audu et al., 2012). it also has effect on other human activities. the year http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):885-896. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 890 2005 recorded lowest rainfall depth for both benin and warri. the implication is that 2005 was driest year and suggests low agricultural production/ crop yield. the mean, maximum and minimum annual rainfall amount (depth in millimeters) from 1983 to 2014 as shown in table 2 for benin were 2,162.46mm, 3,068.70mm and 229.10mm, respectively. maximum and minimum annual rainfalls were recorded in the years 2011 and 2005, respectively. the rainfall distribution was found to be highly skewed with a skewness coefficient of -1.16. this negative skewness coefficient suggests that there may be a higher frequency of above –average values. it may indicate that extreme or heavy rainfall events are more prevalent in the dataset, potentially influencing long-term trends and variability. understanding this implication of negative skewness, it is crucial in making informed decisions related to various applications such as agricultural, urban planning and environmental management. the kurtosis value was 4.13, so the distribution of annual rainfall depth had heavier tails and it was noted to be a leptokurtic distribution. benin’s annual rainfall distribution had coefficient of variation of 24.72%, which indicated the variability of the annual rainfall depths relative to the mean. a cv of 24.7% indicates a moderate level of variability in annual rainfall depths. it suggests that the annual rainfall depths have a notable amount of fluctuation relative to the mean, which can impact the reliability of rainfall patterns over time. higher annual rainfall variability may increase the risk of extreme weather events, such as floods and this will influence decision making in agricultural planning, water resource management and infrastructure design. table 1: annual series of rainfall from 1983 to 2014 year benin annual rainfall depth (mm) warri annual rainfall depth (mm) 1983 1657.9 2522.6 1984 1225.6 2741.4 1985 1557.7 2958.8 1986 1313.2 2887.1 1987 2419.2 2147.3 1988 2007.3 2442.6 1989 1939.8 2636.4 1990 2588.4 2567.7 1991 2439.2 2952.9 1992 2026.9 2944.5 1993 1899.1 2976.9 1994 2595.3 2870.7 1995 2677.9 3449.4 1996 2507 2592.1 1997 2082.8 2906.2 1998 2204.4 2537.3 1999 2164 3127.6 2000 2257.7 2879.9 2001 2424.3 2400.2 2002 2422.2 3307.4 2003 1860.1 2359.9 2004 2239.8 3138.5 2005 229.1 1925.8 2006 2183.9 2547.3 2007 1904.6 2642.4 2008 2727.7 4489.8 2009 2417.3 2656.1 2010 2663 2896.7 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng emeka-chris: analysis of rainfall trend in benin and warri cities of southern nigeria. azojete, 19(4):885-896. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 891 2011 3068.7 3179.5 2012 2568.9 3089.5 2013 2530.4 2307.6 2014 2395.3 2108.5 table.2: descriptive statistics of annual rainfall for each study station. no of years minimum annual rainfall depth (mm) maximum annual rainfall depth (mm) mean annual rainfall depth (mm) std dev of annual rainfall depth (mm) skewness of annual rainfall depth (mm) kurtosis of annual rainfall depth (mm) cv of annual rainfall depth benin rainfall (mm) 32 229.1 3068.7 2162.46 534.52 -1.61 4.13 24.72 warri rainfall (mm) 32 1925.8 4489.8 2787.21 464.16 1.31 4.45 16.65 the mean, maximum and minimum annual rainfall depths from 1983 to 2014 for warri were 2,787.2mm, 4, 489.80mm and 1, 925.80mm, respectively. warri had positively skewed rainfall distribution, with skewness coefficient of 1.31. a positive skewness of 1.31 in annual rainfall trend means that there is a longer tail on the right side of the annual rainfall depth distribution, and the majority of the data points are concentrated on the left side. these suggests that there are more occurrences of lower rainfall amounts compared to higher rainfall amounts. this may impact water resource management, leading to potential challenges in ensuring an adequate water supply for agricultural, industrial and domestic use the agricultural implication is that it can lead to a higher frequency of drier years compared to wetter years, potentially affecting crop yields and overall agricultural productivity. its kurtosis value was 4.45. this showed that the annual rainfall depths of the city had leptokurtic distribution. a leptokurtic distribution suggests an increase in extreme rainfall events, including heavy rainfall conditions. this is important for infrastructure planning, etc. disaster preparedness and climate change adaptation warri experienced steady annual rainfall above 2100mm except for the year 2005 with annual rainfall value of 1, 925.8mm. however, this observation is different from the work of olanrewaju et al. (2017), which revealed that in warri, the year 2013 had the lowest total rainfall. the differences in observations can be due to differences in years of rainfall data analyzed and computational errors. 3.2 standardized anomaly index the variation of the standardized anomaly index for benin with year is shown in figure 3 figure 3: standardized anomaly index for annual total rainfall at benin sa i years 1983-2014 http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):885-896. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 892 between 1983 and 2000, benin experienced belowaverage longterm rainfall, with 6 periods of positive anomaly index indicating low annual rainfall. the 6 respites of positive anomaly index above average means between 1983-2000, there were only 6 years that the annual rainfalls depths were above average rainfall depth. there are 18 years between 19832000 and since only 6 years recorded rainfall depth above average rainfall, then 1983-2000 recorded 12 years of low rainfall distribution. this result is in line with the findings of akinsanola and ogunjobi (2014), who reported that there was decreasing amount of rainfall in benin within the study period of 1983-2000. after 2000 there was above long-term averages of annual rainfall during the period spanning 2001 to 2014, with 4 respites of negative anomaly index below average. the implication is that between 2001 and 2014, there were more years of extreme rainfall events above average rainfall, including heavy rainfall than can lead to flooding. this can hamper growth of crops, lead to soil erosion etc. the highest positive annual rainfall anomaly index above average was recorded in 2011, while the lowest negative annual rainfall anomaly index below average was recorded in 2005. the implications are that 2011 recorded the highest rainfall event, including heavy rainfall, that can lead to flooding while 2005 recorded the lowest rainfall events that can lead to drier year, potentially affecting crop yields. the standardized rainfall anomalies index (sai) was used to establish the dry and wet years in the city for the period of study. the result revealed twelve dry years out of the thirty-two years period considered and twenty wet years on the negative and positive sides of the graph respectively. the positive sai values indicate wetterthan – average years, while negative sai values indicate drierthanaverage years. sai values above 0 are indicative of wet years, while sai values below 0 are indicative of dry years. the established threshold here is 0(zero). the line corresponding to zero is the base line which signifies the average rainfall of thirty-two years the plots of the standardized rainfall anomaly index against time (years) for warri are shown in figure 4. figure 4: standardized anomaly index for annual total rainfall at warri from figure 4, it can be seen that warri experienced below long-term averages annual rainfall during the period spanning 1983 to 1995 with 7 respites of positive anomaly index above average years. the implication is that between 1983-1995, warri recorded more years of low rainfall that can lead to drier years, which will impact on agricultural production and domestic water need -3 -2 -1 0 1 2 3 4 sa i years 1983-2014 sai warri file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng emeka-chris: analysis of rainfall trend in benin and warri cities of southern nigeria. azojete, 19(4):885-896. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 893 this result is in line with the findings of akinsanola and ogunjobi (2014) who reported that there was decrease in the amount of rainfall in warri within this period of study (1983-1995). from 1996, warri experienced alternate negative anomaly index below average and positive anomaly index above average until 2014. the result revealed 16 dry years and 16 wet years on the negative and positive sides of the plot respectively for the thirty-two years period considered. the highest positive anomaly index above average was recorded in 2008. this trend may suggest a shift a wetter climate regime. implications of highest positive anomaly index above average involve heightened risks of excessive rainfall, flooding, soil erosion and potential impacts on infrastructure, land use and water quality. such conditions can also affect aquatic ecosystems, leading to changes in stream flow and water quality (ipcc, 2007). the lowest negative index below average was recorded in 2005. this trend indicates a prolonged period of drierthan – normal conditions. implications of negative anomaly index below average are increased risk of drought conditions, water scarcity and potential impacts on agricultural productivity, water resources and ecosystems health. 3.3 trend plots of annual rainfall the trend of annual rainfall with index (time in years) for benin city is shown in figure 5 figure 5: trend plot of annual rainfall depths against index (time in years) in benin from figure 5 it is evident that the year 2005 recorded the lowest annual rainfall of 229.10mm, while the year 2011 recorded the highest rainfall of 3068.70mm. the implications of lowest annual rainfall of 229.1mm are increased risk of drought conditions, water scarcity and potential impacts on agricultural productivity, water resources and ecosystems health. implications of highest rainfall of 3068.70mm is that the condition will translate to soil erosion as well as flooding. the effects of these conditions are low agricultural production, destruction of infrastructure as well as health hazard. i the mean annual rainfall for the study period was 2162.46mm. years 1983, 1984, 1985, 1986, 1988, 1989, 1992, 1993 1997, 2003, 2005 and 2007 experienced annual rainfall below the mean value, while the years 1987,1990, 1991, 1994, 1995, 1996, 1998, 1999, 2000, 2001, 2002, 2004, 2006, 2008, 2009, 2010, 2011, 2012 and 2013 experienced annual rainfall above the mean value. the trend line fluctuated from index 1 at annual rainfall of 1657.9mm until index 5 when it suddenly increased to 2419.2mm. then the trend line decreased below mean annual rainfall of 2162. 46mm between index 6 to 7. thereafter, there was increase in trend line above mean annual rainfall from index 8 to 32, with few decreases in trend line above mean annual rainfall at indices 10, 11 15, 21, 23 and 25 respectively. from the graph, there is a progressive increase in the annual rainfall depths during the period in the study area. 200 600 1000 1400 1800 2200 2600 3000 3400 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 a m o u n t o f r ai n fa ll (m m ) index series1 http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):885-896. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 894 this is in agreement with the work of ihimekpen et al. (2018) and floyd et al. (2016) which indicated that rainfall data from benin city showed statistically significant evidence of an increasing trend. the effect is that there is possibility of flood occurrence with time and so water resources managers should make adequate arrangement on how to prevent the flood by designing/constructing water carrying structures, including adequate and regional planning the trend of annual rainfall depth for warri city is shown in figure 6. figure 6: trend plot of annual rainfall depth against index/ time (years) in warri from figure 6, it is evident that the year 2005 recorded the lowest annual rainfall of 1925.8, while the year 2008 recorded the highest rainfall of 4489.80mm. the mean annual rainfall for the study period is 2787.21mm. a mean annual rainfall of 2787.21mm indicates abundant water supply, sustainable ecosystem support and agricultural potential. however, it also necessitates careful water management and preparedness for extreme events to ensure the well-being of both natural and human systems. it has become an annual environmental problem during every rainy season. umuteme and orusi (2012) reported that in july 2012 over 300 people were render homeless in warri due to an early morning rain that lasted for several hours. according to efe and mogborukor (2010), the 4th – 6th august 2002 flood in warri which resulted from rainfall submerged several houses, workshops in the metropolis. it reoccurred in the following years leading to the destruction of properties worth over 3.6 million of naira and rendering over 3,250 people homeless. years 1983, 1984, 1987, 1988, 1989, 1990, 1996, 1998, 2001, 2003, 2005, 2006, 2007, 2009, 2013 and 2014 experienced annual rainfall below the mean value, while the years 1985, 1986,1991, 1992, 1993, 1994, 1995, 1997, 1999, 2000, 2002, 2004, 2008, 2010, 2011 and 2012 experienced annual rainfall above the mean value. the trend line increased from 2522.6mm at index 1 until index 5 at 2147.3mm where it decreased below mean annual rainfall up to index 8 at 2567.7mm. thereafter, it increased above mean annual rainfall up to index 30, with few decreases below annual rainfall at indices of 13, 14, 16, 19, 21, 23, 24, 25, 27, 31 and 32 respectively. 4. conclusion the study examined the rainfall trends and patterns in two southern cities (benin and warri) of nigeria for the period 1983-2014. it was observed that these two cities showed fluctuations in trend of annual rainfall depths. the results clearly show a variable rainfall pattern over the years in all the cities studied, making it challenging to predict rainfall for upcoming seasons. it was generally observed that the climate of the region indicates a rainfall characterized by alternating wet and dry periods, and that the beginning of rainfall is becoming earlier which implies possible longer rainy season in the area. rainfall depths are climatic variables which 2000 2500 3000 3500 4000 4500 5000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 a m o u n t o f r ai n fa ll (m m ) index/ time ( years) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng emeka-chris: analysis of rainfall trend in benin and warri cities of southern nigeria. azojete, 19(4):885-896. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 895 influence human well-being, plant growth and crops production. the variation in rainfall patterns results to unfavourable growing conditions. from the outcome of this study, it is recommended that: 1.efficient use of agricultural land should drive the focus of water resources development. this requires a strong government policy for harnessing and managing water resources. 2. models that rely on anticipated reductions in rainfall, such as drainage systems and dams should be reassessed to prevent potential flooding in these cities. references abotutu, a. and ojeh n. 2013. structural properties of dwelling and thermal comfort in tropical cities: evidences from warri, nigeria. international journal of science and technology, 2(2): 67-98. agbonkhese, o., agbonkhese, g., aka, o., joe-abaya, j., ocholi, m. and adekunle, a. 2014. flood menace in nigeria: impacts, remedial and management strategies. civil and environmental research, 6(4): 32 – 40. available on line at www.iiste.org. akinsanola, aa. and ogunjobi, ko. 2014. analysis of rainfall and temperature variability over nigeria. global journal of human-social science (b) geography, geo-sciences, environmental disaster management, 14 (3): 10-28. audu, ho., binbol, nl., ekanem, em,, felix, i. and bamayi, ea. 2012. effect of climate change on lenght growing season in uyo, akwa ibom state, nigeria. international journal of applied research and technology, 1(6): 289-294. efe, i. and mogborukor, a. 2010. flood hazards in warri, a third world city. nigeria. journal of social and management sciences. 5(2): 83-93. falaiye, oa., olaitan, ag. and nwabachili, sc. 2021. parametric analysis of rainfall variability over some selected locations in nigeria. international journal of climate research, 5(1): 3548. doi:10.18488/journal.112.2021.51.35.48 floyd, ac., oikpor, r. and ekene, b. 2016. an assessment of climate change in benin city, edo state. futy journal of the environment,10(1): 1-8. fao 2012. the state of food insecurity in the world. economic growth is necessary but of sufficient to accelerate reduction of hunger and malnutrition. fao, rome gupta, sp. 2011. statistical methods. sultan chand & sons, new delhi. ipcc 2007. climate change impacts, adaptation and vulnerability, contribution of working group ii to the fourth assessment. report of the intergovernmental panel on climate change assessment, summary for policy makers. cambridge university press, new york. http://www.icpp.ch/pdf/assessment joshua, jk. and ekwe, mc. 2013. indigenous mitigation and adaption strategy in drought and environmental changes in nigeria section of lake chad basin. international journal of applied research and studies (ijars), (5):1-14. nyong, ao. 2008. climate change, agriculture and trade: implications for sustainable development. international centre for trade and sustainable development http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng http://www.icpp.ch/pdf/assessment arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):885-896. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 896 (ictsd), http://www.agritrade.org/events documents/paper-anthony. nyong barcelona 08.pdf. agrit mat precipitation measurements. obafemi, a., etudoyin, s. and akinbosola, m. 2012. public perception of environmental pollution in warri, nigeria. journal of applied science, environment and management, 16(3): 233-240. odemerho, fo. (1988). benin city: a case study of urban flood problems. in sada, p.o. and odemerho, fo. (eds). environmental issues and management in nigerian development, evans brothers, ibadan. olanrewaju, r., ekiotuasinhan, b. and akpan, g. 2017. analysis of rainfall pattern and flood incidences in warri metropolis, nigeria. geography and environment sustainability, 10(4): 8397. doi: 10.2405/2071-1988-2017-10-4-83-97 scalzitti, j., strong, c. and kochanski, a. 2016. climate change impact on the roles of temperature and precipitation in western us snowpack variability. geophysical research letters,43: 5361-5369., https://doi.org/10.1002/2016gl068798. shiru, ms., shahid, s., chung, es., alias, n. and scherer, l. 2019. a mcdm-based framework for selection of general circulation models and projection of spatio-temporal rainfall changes: a case study of nigeria. atmospheric research, 225: 1-16., https://doi.org/10.1016/j.atmosres.2019.03.033. umuteme, b. and orusi, k. 2012. flood rendered hundreds homeless in warri. frontiers news, wed 18th, july 2012. wang, r., chen, j., chen, x. and wang, y. 2017. variability of precipitation extremes and dryness/wetness over the southeast coastal region of china, 1960–2014. international journal of climatology, 37: 4656-4669., https://doi.org/10.1002/joc.5113. wen, x., wu, x. and gao, m. 2017. spatio-temporal variability of temperature and precipitation in gansu province (northwest china) during 1951–2015. atmospheric research, 197: 132-149., https://doi.org/10.1016/j.atmosres.2017.07.001. xu, y., wang, l., wu, g. li, q. and song, s. 2016. spatial and temporal trends of reference crop evapotranspiration and its influential variables in yangtze river delta, eastern china. theoretical and applied climatology, 130: 1–14. zbigniew, w., kundzewice, sk., sonia, is., john, h., newille, n. and pascal, p. 2013. flood risk and climate change: global and regional perspective. hydrological science journal, 59(1): 1 28. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://doi.org/10.1002/2016gl068798 https://doi.org/10.1016/j.atmosres.2019.03.033 https://doi.org/10.1002/joc.5113 arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):215-230 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 215 a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework v. o. nkeleme*1, e. u. udo2, c.k. okoro2, l. i. oborkhale2, k. o. odo2 1department of electrical/electronic engineering, federal polytechnic mubi adamawa state 2department of electrical/electronic engineering, michael okpara university of agriculture umudike, abia state *corresponding author's email address: victornkeleme@gmail.com article information submitted 18 december, 2023 revised 16 february, 2024 accepted 20 february, 2024 keywords: carrier aggregation hetnet rssf-hda mif-hda conv-hda abstract mobile user equipment can benefit from increased bandwidth and radio coverage of various access technologies through carrier aggregation and integration of heterogeneous networks. however, because of the mobility of user equipment, these technologies have increased the frequency of handoff scenarios, which results in low throughput and a high outage probability. in order to enable users to move between cells without losing connections, handover is an essential part of mobility management. however, no lone access mechanism can provide seamless and delay-free seamless interaction. as a result, the development of a suitable handover decision algorithm is necessary to ensure excellent service continuity and dependable user equipment access to the network at any location and at any moment. to confirm if various handover choice algorithms are effective in preventing communication failures and enhancing system performance. this research produced a mathematical model for the real-time spectrum selection framework and handover decision algorithm (rssf-hda). additionally, mathematical models were extracted for comparison between the multi-influenced handover decision algorithm (mif-hda) and the conventional handover decision algorithm (conv-hda). a statistical comparative study was carried out using data from mtn drive-test readings at the low-cost housing estate located in abesan, ipaja, lagos. according to statistical analysis results, the real-time spectrum selection framework and handover decision algorithm enhance system performance in terms of cell edge spectral efficiency, and user throughput when compared with multi-influenced handover algorithm and mtn field readings. for cell edge spectral efficiency at an average speed of 80km/s, rssf-hda gave a value of 1.52 bits/hertz compared to mif-hda and mtn field readings with values of 1.37bits/hertz and 1.33bits/hertz respectively. for user throughput, inferred that there is no significant difference in readings of system throughput from the mtn field readings, mif-hda, and simulated rssf-hda which were 31%, 33%, and 34% respectively. 1.0 introduction recent years have seen a rise in research and development aimed at enhancing coverage and capacity to deliver high data rates to user equipment (ues) at an affordable rate. as a result, cellular networks have seen significant evolutionary improvement as well as new inventions and research initiatives (hachemi et al., 2022, sudhamani et al., 2023). the physical layer advancements of contemporary networks are moving in the direction of network efficiency. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 216 therefore, previous study suggest that systems based on the architecture of dense heterogeneous networks (het-nets) and increased utilization of radio spectrum through carrier aggregation techniques be used as solutions (wahidin et al., 2022, hashemi, and farrokhi, 2020). thus, these two technological advances serve as the cornerstone for network densification, with the inclusion of ca as a crucial functionality in the 3rd generation partnership project (3gpp) release 10 marking a major step towards the development of long term evolution advanced (lte-a)(satapathy and mahapatro, 2022). it is anticipated that the addition of ca technology in lte-a's release 10 (rel.10) and later releases will enable high data rates and increase system capacity.(goyal and kumar, 2020). this implies that a muchanticipated aspect of lte-a is the expansion of transmission bandwidth. lte-advanced (long term evolution) has carrier aggregation (ca) as one of its primary background characteristics. a maximum bandwidth of 100mhz would be available to customers with ca. there are three possible system bandwidth configurations: contiguous, noncontiguous, and inter-band noncontiguous (lin et al., 2014). for long time evolution (lte) carriers, the bandwidth of these component carriers (ccs) can vary greatly, from 1.4mhz to 20mhz. additionally, propagation properties vary throughout different ccs. for instance, ccs in the 800mhz spectrum have different propagation characteristics than component carriers in the 2.4ghz band (ohmann et al., 2014). however, a new handover situation brought about by the introduction of ca technology allows ccs operating in the same sector and enodeb to undertake handovers, potentially redefining primary component carriers (pccs). throughput degradation increases as a result of the higher handover chance. as long as the serving pcc provides the ues with an adequate amount of rss, the handover situation here translates into a successful handover decision (hod). in essence, handover is evaluated when a voice call is in progress and heading toward the current enodeb (i.e., from a source to a target enodeb). this instance involves a ue reporting signal measurements to the serving enodeb from the neighboring enodeb. the measurement report from the ue at the source enodeb is used to make the handover decision. on the other hand, in a ca-based system, the source and the target enodebs may be ccs of the same or separate enodebs because of numerous ccs. making decisions with such a signal measurement report (mr) is not completed quickly. consequently, it increases the likelihood of throughput deterioration, user outage probability, and handover failure, particularly for high-velocity user equipment (alhammadi, et al., 2023, bastidas-puga et al., 2019). the primary goal of handover is to keep the connection active as the subcarrier passes through the source enodeb's coverage region and approaches the target enodeb. providing services that meet consumer needs is one of the main objectives of communication in cellular networks (khan and han, 2015). however, an effective handover decision algorithm improves continuous connectivity, but the network's performance is still insufficiently enhanced. as such, investigating the hod algorithm is innovative as it may effectively manage the main responsibilities in cellular networks by raising the quality of services and concurrently managing the network's resources, in addition to offering encouragement for conducting this kind of research. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 217 conventional handover algorithms are applicable in heterogeneous networks and exhibit simple moderate handover with an inaccurate high percentage of unwanted handovers. multiinfluenced factor handover algorithms are applied in coordinated carrier aggregation, the decision-making process integrates rss, bandwidth, speed, handover situation, and sinr to accomplish seamless mobility and apply to indoor scenarios. finally, the rssf-hda utilizes coordinated carrier aggregation. system performance is improved by using spectrum sensing, which lowers the likelihood of outages, call dropouts, and handover ping-pong. only two (2) carrier component was considered the statement of problem thus implies that there are increased in the frequency of handoff which led to low throughput and high outage probability. in order to make sensitive decisions about handover when implementing heterogeneous networks (hetnet) and ca in lte-a systems, the objective of this study is to utilize a user mobility broadband spectrum aggregation in lteadvance heterogeneous to mitigate these quality-of-service indices 2.0 materials and method the serving enodeb made handover decision based on the measurement report (mr) received from the served ue. a list of the signal levels of nearby cells is contained in mr, and depending on the hod algorithm in use, it can also provide additional information. an algorithm for a handover decision can be implemented in multiple ways. it can generally be divided into the following categories: i. conventional handover decision algorithms (conv hda) ii. multi-influenced handover decision algorithms (mif-hda) iii. real-time spectrum selection framework and handover decision algorithm (rssfhda) the conventional handover choice algorithm, known as the rss-based strategy, used rss as the primary criterion to initiate handover (abdullah & zukarnain, 2017). here, the handover is enabled as a result of comparing the signal intensities of nearby enodebs. the rss-based approach was improved by using the rss threshold (hysteresis) (kunarak & suleesathira, 2020) and by combining it with the user's distance (mahardhika et al., 2015), sinr (khattab et al, 2023), and iinr (choi et al., 2021). a threshold is established and implemented in relation to signal strength in order to reduce the ping-pong effects. if the new enodeb rss is more than the threshold and the current enodeb rss is less than the threshold, the handover is initiated. however, the rss-based approach for assessing the attributes and quality of services is straightforward in theory and straightforward to apply. however, route loss in the wireless medium caused the rss signal to vary, which lead to ping pong, throughput degradation, and needless handovers. additionally, threshold rss had disadvantages such as high call drop and handover delay. however, recent research has shown that incorporating ca and hetnets technologies maked handover decisions more difficult. the rss-based criterion is insufficient for a decision-making process in hetnet using the ca approach. concurrently, in a coordinated carrier aggregation deployment scenario, mif decision-making criteria was examined (capez et al, 2022). several factors that affected the decision-making http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 218 process were employed by mif. even if the simulation's result indicated that ping pong had decreased, the outcome is not ideal when hetnet is taken into account in ca. the handoff delay and service disruption time are decreased by the multi-criteria algorithm. consequently, during handover, this reduced packet loss and increased throughput (alhabo & zhang, 2020). as a result, in future mif-hda research, the selected criteria guaranteed that the level of decision-making accuracy is maintained. rss, mobility, application, and bandwidth are some of the primary factors that are either useror network-related. although every previous work in hetnets and ca was built on a separate set of criteria, it is still uncertain which set of characteristics results in the best handover procedure. therefore, a new method known as the multi-criteria handover decision algorithm was presented for effective handover decision-making when ca and hetnet are taken into consideration in an lte-a system to determine the appropriate parameters for a successful handover process(abdulazeez-ahmed et al., 2020a). a novel handover decision algorithm called real-time spectrum selection framework and handover decision algorithm (rssf-hda) was proposed, and its proposed handover performance for an lte-a system was compared with two other hoda (mif-hda and convhda) (nkeleme et al., 2023). according to the results of the simulation analysis, rssf-hda was more effective than the current hda deployment in enabling wider bandwidth and greater se. the metrics of rssf-hda spectral efficiency (se) are higher than those of the other hda considered in the research, rising from 1.35 bps/hz/cell at mobile speeds of 20 kmph to 1.87 bps/hz/cell at 120 kmph. 2.1 simulation of mif-hda and rssf-hda carrier aggregation based handover technique in heterogenous network. abdulazeez-ahmed et al., (2020) provided an effective multi-influence handover decision method that took into account the mobile parameter (load and ue distance) as well as the network parameter (radio resources and network architecture) while making decisions. to construct lte-a heterogeneous network topologies, the algorithm was implemented as a multicell system using a system-level simulator from the matlab toolbox. many built-in libraries and capabilities in matlab enabled the conversion of c and c++ code into matlab programs. additionally, it raised the likelihood of new technology, allowed the required data manipulation, and fortifies the security of emerging technologies (nkeleme et al., 2023). pcc is often used for data transfer between the ue and the enodeb as well as information sharing for control signals. pcc was utilized for the random-access mechanism and scc allocation in addition it served as a conduit for data transfer. numerous handover decision algorithms have been developed in response to the ca concept's handover decision issues in lte-a and next-generation systems, but none of them have produced the desired results, especially for hetnet's carrier aggregation deployment scenario (cads). consequently, abdulazeez-ahmed et al., ( 2020) developed an effective multi-influenced handover decision algorithm that used mobile parameters like load and ue distance as well as network parameters like radio resources and network architecture as input for decision-making. the third generation partnership project (3gpp)-standardized cell range expansion (cre) power regulation mechanism ( wu, et al,. 2020) was used in this study file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 219 as a virtual bias applied to the real ue received power (abdulazeez-ahmed et al., 2020). the handover choices were conducted adaptively based on the following criteria. in an lte-advanced uplink and downlink system level simulator, nkeleme et al., (2023) presented a workable ca strategy that made use of two ccs in the same bands (het-nets cads) utilizing the multi-taper ofdma sensing of reference signal received power estimator (mto-rsrpe) technique. a global rendition algorithm was created to achieve the real-time spectrum selection framework's goal. this algorithm served as the foundation for the implementation of the new rssf-hda program flowchart, the resource allocation, parameters, and threshold values are given in nkeleme et al., (2023). 2.2 system model and simulation configuration for mif-hda and rssf-hda the standard (nkeleme et al., 2023) was utilized in the creation of the radio frequency system model scenario. 30 mobile user devices (ues) were uniformly distributed at random to serving and target cell sites during each transmission time interval (tti). the ues' directional motions was determined at random with a set speed during the design process, which comprises a variety of mobile speed scenarios (5, 25, 40, 70, 100, and 130 km/h). all users' mobility movements were taken into consideration within the first 32 cells, which are close to the center cell. an illustration of the deployed scenario's clustered enodebs is shown in figure 1. during the simulation, each user will suffer interference from six separate enodebs, which are regarded as the stations that generate these signals. the frequency reuse factor (frf) was set to one. the performance findings for the rssf-hda, mif-hda, and the starting point conventional handover decision algorithm (conv-hda) were displayed. results for cell edge spectral efficiency, average successful handover, and user throughput was analyzed based on the utilization of hard handover at different mobile speeds. as a result, figure 1 displays the hetnets cads architecture. carrier aggregation enables the deployment of more ues in macro and micro cells, as the topological architecture illustrates. six (6) neighbors surrounded each of the sixty-one (61) enodeb that were taken into consideration. figure 1: an illustration of the deployed scenario's clustered enodebs (nkeleme et al., 2023) subsequently, as seen in figure 1, seven (7) enodebs create a single cluster. furthermore, every enodeb was segmented into three sectors and encompasses an approximate radial http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 220 distance (r) of 500 meters. ultimately, a radius of about 5r was established for the mobility area of the mobile stations, also known as user equipment (ues) (shown as a blue circle). 2.3 curve fitting process and decomposing of simulations in order to extract significant patterns and relationships from datasets, curve fitting is a key procedure in data analysis. this study highlights the capabilities and versatility of the rssf hda system by breaking down the stages involved in the curve fitting process. the generated data is saved in an a.mat file, where the independent and dependent variables (observations) were represented by corresponding variables. to ensure a smooth integration of the data into the curve fitting tool, matlab's `read` function was utilized to import the data into an appropriate format. the curve fitting tool was accessed via the matlab apps tab or programmatically via the 'cftool' command. its dynamic and user-friendly interface made effective curve fitting possible. the tool allowed to select multiple curve fitting models, alter parameters, and view the fitting process in real-time. 2.4 mathematical models of performance indicators 2.4.1 spectral efficiency the average bits per second per hz (bps/hz) that may be transferred over a radio link channel and accurately received at the receiver side is referred to as spectral efficiency. mathematically, the user's spectral efficiency are expressed by adding up the entire throughput that is successfully received by the user at a given moment and dividing it by the whole user's channel bandwidth. the equation used in this thesis is expressed as follows: 𝑆𝐸 = 𝑁𝑠𝑦𝑚𝑏𝑜𝑙𝑝𝑒𝑟𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟∗log(𝐴𝑀𝐶)∗𝐶𝑅 𝑠𝑢𝑏𝑓𝑟𝑎𝑚𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛∗𝐵𝑊 (1) se is the cell edge spectral efficiency in bps/hz 𝑁𝑠𝑦𝑚𝑏𝑜𝑙𝑝𝑒𝑟𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟 is the number of symbols per subcarrier in bps amc is adaptive modulation and coding cr is cognitive radio value bw is bandwidth in hertz the decomposed models for the spectral efficiency variance with reference to the reviewed literature are expressed as follows: conv-hda 𝑆𝐸𝑐𝑑𝑓 = 125.7(𝑆𝐸)2−266𝑆𝐸+124.3 (𝑆𝐸)3−127.8(𝑆𝐸)2+ 179.8𝑆𝐸+31.38 (2) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency se is the cell edge spectral efficiency in bps/hz 𝑆𝐸𝑐𝑑𝑓 = 403.3(𝑆𝐸𝐴𝑣)2−1140𝑆𝐸𝐴𝑣+806.1 (𝑆𝐸𝐴𝑣)3+1253(𝑆𝐸𝐴𝑣)2−4066 𝑆𝐸𝐴𝑣+3319 (3) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 221 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency in bps/hz 𝑆𝐸𝐴𝑣 = −0.00004048(𝑆)2 + 0.009475𝑆 + 1.237 (4) where 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency. s is mobile speed in km/hour mif-hda 𝑆𝐸𝑐𝑑𝑓 = 42.45(𝑆𝐸)2−37.88𝑆𝐸−25.29 (𝑆𝐸)3−30.39(𝑆𝐸)2−49.39𝑆𝐸+154.3 (5) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency se is the cell edge spectral efficiency in bps/hz 𝑆𝐸𝑐𝑑𝑓 = 0.04822(𝑆𝐸𝐴𝑣)2−0.1279𝑆𝐸𝐴𝑣+0.08481 (𝑆𝐸𝐴𝑣)3−4.738(𝑆𝐸𝐴𝑣)2+ 7.448𝑆𝐸𝐴𝑣−3.876 (6) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency in bps/hz 𝑆𝐸𝐴𝑣 = −0.00004424(𝑆)2 + 0.01022𝑆 + 1.224 (7) where 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency. s is mobile speed in km/hour rssf-hda 𝑆𝐸𝑐𝑑𝑓 = 283.8(𝑆𝐸)2−573.1𝑆𝐸+234.6 𝑥3−312.1(𝑆𝐸)2+ 576.8𝑆𝐸−73.28 (8) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency se is the cell edge spectral efficiency in bps/hz 𝑆𝐸𝑐𝑑𝑓 = 143.6(𝑆𝐸𝐴𝑣)2−356.9𝑆𝐸𝐴𝑣+219.8 (𝑆𝐸𝐴𝑣)3+2219(𝑆𝐸𝐴𝑣)2−8020𝑆𝐸𝐴𝑣+7286 (9) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency in bps/hz 𝑆𝐸𝐴𝑣 = −0.00004322(𝑆)2 + 0.009998𝑆 + 1.335 (10) where 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency. s is mobile speed in km/hour 2.4.2 throughput the third generation partnership project (3gpp) group has established five categories of service performance metrics, comprising network availability, accessibility, retainability, mobility, and integrity. in all radio access technologies, user throughput is a crucial measure for assessing the integrity of data services (buenestado et al., 2014). the throughput with respect to the bite rate adopted in this thesis is expressed mathematically as follows: 𝐵𝑖𝑡 𝑅𝑎𝑡𝑒 = 𝑁𝑅𝐵∗𝑁𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟𝑝𝑒𝑟𝑅𝐵∗𝑁𝑠𝑙𝑜𝑡𝑝𝑒𝑟𝑠𝑢𝑏𝑓𝑟𝑎𝑚𝑒∗𝑁𝑠𝑦𝑚𝑏𝑜𝑙𝑝𝑒𝑟𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟∗log(𝐴𝑀𝐶)∗𝐶𝑅 𝑠𝑢𝑏𝑓𝑟𝑎𝑚𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (11) where: 𝐴𝑀𝐶=selected adaptive modulation scheme, 𝐶𝑅 = selected code rate http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 222 the decomposed model for conv-hda (khan, and han, 2015) and the multi-influence hda ( abdullah, and zukarnain, 2017) with respect to the user throughput is expressed as follows: conv-hda 𝑇𝐻𝑐𝑑𝑓 = 8487𝑇𝐻2−4046𝑇𝐻+484 𝑇𝐻3+12900𝑇𝐻2−7480 𝑇𝐻+1159 (12) mif-hda 𝑇𝐻𝑐𝑑𝑓 = 9811𝑇𝐻2−4623𝑇𝐻+545.4 𝑇𝐻3+12090𝑇𝐻2−6694𝑇𝐻+1018 (13) the result obtained from the simulation is expressed as follows: rssf-hda 𝑇𝐻𝑐𝑑𝑓 = 6748𝑇𝐻2−3183𝑇𝐻+376.6 𝑇𝐻3+9803𝑇𝐻2−5831 𝑇𝐻+953.7 (14) where 𝑇𝐻𝑐𝑑𝑓 is the cumulative distribution function of user throughput th is the user throughput in mbps 2.5 field measurements for lte-a in order to offer service to user units, the lte-a network used advanced base stations (enodebs and enbs) to cover the whole cell. it also utilized the same transmit power level, modulation mechanism, and antenna layouts ( zhang et al., 2020). wireless channel parameters in lte-a systems control the downlink quality between the enodeb and the user equipment (ue). the channel quality indicator (cqi) used in the lte-a network expresses the wireless channel's condition. typically, the sinr value based on reference signal received power (rsrp) and reference signal received quality (rsrq) represented the cqi established by the user unit (rsrq). the modulation technique, transfer block size (tbs), and coding rate of the data transmission are chosen in accordance with the user unit's cqi value that is transmitted to the enodeb, because of this, throughput and cqi value were directly related. to determine the impact of sinr, rsrp, and rsrq channel characteristics on the throughput value in the lteadvance network, this study employed tems software to collect field data from lsdpc lowcost housing estate, abesan, ipaja lagos locations. the drive test was conducted for 15 months (september 2022 to nov 2023) as shown in table 1. 2.6 method of field data computation using regression analysis the data obtained from the drive test was analyzed using various statistical tools such as regression analysis, which is a mathematical equation, that shows the connection between a few independent factors and a dependent variable. the dependent variable y and the independent variable x in the basic linear regression model are specified as follows. 𝑌𝑖 = 𝛽𝑜 + 𝛽1𝑋𝑖 +∈𝑖 𝑖 = 1,2, … , 𝑛 (15) where: 𝛽 is the regression coefficient n is the size of the data, ∈𝑖 represents the error term two or more independent variables are used to express the dependent variable (k). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 223 𝑌𝑖 = 𝛽𝑜 + 𝛽1𝑋𝑖1 + 𝛽12𝑋𝑖2 + ⋯ , +𝛽𝑘𝑋𝑖𝑘 + ∈𝑖 𝑖 = 1,2, … , 𝑛 (16) according to information obtained from mtn lagos, the algorithms used are similar to multiinfluenced handover decision algorithms. this provides a strong foundation for the comparison, as seen in table 3. 3.0 results and discussion a drive test was conducted in abesan estate ipaja lagos from the month of september 2022 to november 2023, a summary of the readings obtained are shown in table 1. table 1: monthly average field drive-test values in abesan estate ipaja lagos state (sept 2022 to nov 2023) s/n date total pdcp dl throughput serving cell rs sinr (db) serving cell rsrp (dbm) serving cell rsrq (db) 1 sept 2022 60528.76 11.97 -64.00 -16.79 2 oct 2022 73187.50 20.83 -87.45 -14.12 3 nov 2022 36445.00 17.16 -84.42 -12.46 4 dec 2022 19778.75 14.24 -93.97 -13.78 5 jan 2023 33452.65 10.13 -91.01 -15.73 6 feb 2023 31344.65 11.10 -78.09 -16.5 7 march 2023 39708.55 11.80 -70.00 -14.89 8 april 2023 30896.15 19.79 -75.19 -13.19 9 may 2023 36348.25 17.22 -78.80 -17.89 10 june 2023 50672.00 13.89 -78.50 -15.60 11 july 2023 33364.25 15.39 -78.09 -15.80 12 aug 2023 22520.20 21.29 -88.90 -15.60 13 sep 2023 32464.15 21.89 -66.00 -13.65 14 oct 2023 36324.35 14.30 -77.80 -12.93 15 nov 2023 33160.15 20.70 -90.80 -13.65 the cumulative density function cell edge spectral efficiency was plotted against the cell edge spectral efficiency for the three hda as shown in figure 2. this is to determine its degree of positive variation. figure 2 shows that rssf-hda has the best cell edge spectral efficiency, meaning greater data rates near the cell's edge. mif-hda follows closely behind, providing competitive performance, but conv-hda lags, indicating data rate limits at the cell edge. at 1.4bps/hz, values of 0.12, 0.32, and -0.08 was calculated for conv-hda, mif-hda, and rssfhda, respectively. at 1.5bps/hz, the values for conv-hda, mif-hda, and rssf-hda was 0.50, 0.90, and 0.16, respectively. the high performance of rssf-hda at the cell edge as shown in figure 2 may be helpful in circumstances requiring high-quality connections on the edges of network coverage http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 224 figure 2: cdf cell edge spectral efficiency over cell edge spectral efficiency the simulated data plot of the cumulative density function of spectral efficiency over average spectral efficiency is shown in figure 3. this further shows that the rssf-hda has a consistent spectrum efficiency and performance. in comparison, mif-hda is somewhat sensitive to network conditions, whereas rssf-hda marginally exceeds mif-hda in terms of responding to changing conditions. this shows that rssf-hda may provide better performance in dynamic situations. figure 3 further illustrates the comparable values of 1.5bps/hz cell edge spectral efficiency, to produce values of 0.85, 0.50 and 0.15 for conv-hda, mif-hda, and rssf-had, respectively figure 3: cdf spectral efficiency over average spectral efficiency this further demonstrates that the rssf-hda has a consistent spectrum efficiency and performance. in comparison, mif-hda is somewhat sensitive to network conditions, whereas rssf-hda marginally exceeds mif-hda in terms of responding to changing conditions, showing that rssf-hda provides better performance in dynamic situations. the plot of the average ue spectral efficiency over all mobile speeds for each handover decision algorithm is presented in figure 4 in relation to the obtained simulation data. figure 4 compares the average se of the ue at various mobile speeds using the deployed rssf-hda. generally, it appears from the results (figure 4) that the average se rises as ue speed rises. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 225 the outcomes shows that the proposed rssf-hda surpasses its counterparts for the speeds under consideration. rssf-hda significantly outperforms the other hodas in improving the average se. conv-hda, mif-hda, and rssf-hda algorithms produced values of 1.72, 1.75, and 1.86, respectively, at 80 km/hr. figure 4: ue’s average spectral efficiency over all the mobile speeds it further indicates that the rssf-hda has the best average spectral efficiency, demonstrating efficient data transmission resource utilization. mif-hda follows closely but falls just short of rssf-hda's performance. conv-hda performs similarly to mif-hda, meaning that it is a solid overall performer but not the greatest. figure 5(a) displays the model plots of user cdf throughput over user throughput in relation to the acquired simulation data. from figure 5(a) it is shown that at 0.34mbps, the conv-hda, mif-hda, and rssf-hda algorithms generated corresponding values of 0.83, 0.77, and 0.70, respectively. rssf-hda achieves the highest user throughput, showcasing efficient data transfer capabilities. mif-hda closely follows, offering competitive performance. conv-hda aligns with mif-hda, indicating reliable data transfer efficiency. the decision between these models may depend on specific network requirements and priorities. rssf-hda excels in data transfer efficiency, but mif-hda and conv-hda remain strong contenders for a balance of performance and adaptability. the user throughput of rssf-hda and the other two handover algorithms is shown in figure 5 for all ue speeds. in comparison to conv-hda and mif-hda, rssf-hda outperforms both in terms of throughput for the user. in comparison to conv-hda and mif-hda, rssf-hda generally achieves a throughput of 34% while other algorithms have 33% as shown in figure 5 (b). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 226 figure 5: throughput; (a) user throughput (b) percentage throughput the comparative assessment of mif-hda, and rssf-hda algorithms from mtn lte-a network drive test readings is illustrated in table 2. the spectral efficiency and system throughput are the key performance indices consider. table 2: comparative assessment of mif-hda, and rssf-hda algorithms from mtn ltea network drive test readings s/n kpi for seamless transmission graduation (point of measurements reading from fieldwork mifhda reading simulation rssf_hda 1 cell edge spectral efficiency taken @40km/h, 80km/hr, and 120km/hr presented as a, b, and c respectively) a) 1.23 bits/hertz 1.47 1.62 b) 1.35 1.56 1.68 c) 1.42 1.76 1.88 average cell edge spectral efficiency (bps/hz) 1.33 1.37 1.52 2 system throughput (taken @ 0.2mbps, 0.25mbps, and 0.3mbps presented as a, b, and c respectively) a) 0.32 0.35 0.70 b) 0.65 0.88 0.75 c) 0.85 0.96 0.92 average percentage throughput 31% 33% 34% (a) (b) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 227 note i. all readings taken on the assumption of a zeros take off (time series reading) ii. the average readings are based on several readings from the simulation with the exception of the field measurement which is the average of the three points of measurement the graphical anova expression for table 2 when considering cell edge spectral efficiency at 40km/hr 80km/hr. and 120km/hr is shown in figure 6 the anova test result (figure 6) submits that the readings from fieldwork, mif-hda, and rssf-hda vary substantially (f= 7.258, p=0.025<0.05) from each other. the mean±std result shows that the reading from simulated rssf-hda (1.73±0.136bits) is higher in comparison with the readings from mif-hda (1.60±0.148bits) and those from fieldwork (1.33±0.096bits). the homogeneity of variance test of the compared groups (levene (l-stat.) = 0.448, p=0.659>0.05) ascertained that the variances are homogeneous (i.e., equal); therefore, the data series is fit for the application of parametric statistical tools. in the case of figure 6, the variance in mean varies substantially from each other. the readings from simulations are higher than those from mif-hda and those from fieldwork. figure. 6: comparative result of readings from fieldwork, mif-hda, and reading from simulated rssf-hda of cell edge spectral efficiency taken @40km/h, 80km/hr, and 120km/hr respectively the result (figure. 6) shows that readings from fieldwork lie between 0.61±0.268; readings from mif-hda lie between 0.73±0.332, while readings from simulated rssf-hda lie between 0.79±0.115. the fisher’s estimate with an f-statistic value of 0.404 and associated probability value of 0.685>0.05 indicates that the variations were not significantly high. however, it was inferred that there is no significant difference in readings of system throughput from the fieldwork, mif-hda, and simulated rssf-hda. the anova test result was confirmed meaningful and accurate by levene’s test (levene’s stat. = 1.963, p=0.221>0.05); thereby, mean±std = 1.33±0.096 mean±std = 1.60±0.148 mean±std = 1.73±0.136 levene’s stat. = 0.448, p=0.659>0.05 f-stat. = 7.258, p=0.025<0.05 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 228 confirming the homogeneity of the variances in the data series which is one of the key assumptions of a data series for anova test. the graphical anova expression for table 2 when considering system throughput at 0.2mbps, 0.25mbps, and 0.3mbps is shown in figure 7 figure. 7: comparative result of readings from fieldwork, mif-had, and reading from simulated rssf-hda of system throughput taken 0.2mbs, 0.25mbs, and 0.3mbs respectively the result (figure. 7) shows that readings from fieldwork lie between 0.61±0.268; readings from mif-hda lie between 0.73±0.332, while readings from simulated rssf-hda lie between 0.79±0.115. the fisher’s estimate with an f-statistic value of 0.404 and associated probability value of 0.685>0.05 indicates that the variations were not significantly high. however, it was inferred that there is no significant difference in readings of system throughput from the fieldwork, mif-hda, and simulated rssf-hda. the anova test result was confirmed meaningful and accurate by levene’s test (levene’s stat. = 1.963, p=0.221>0.05); thereby, confirming the homogeneity of the variances in the data series which is one of the key assumptions of a data series for anova test. 4.0 conclusion voice and multimedia services are in extremely high demand on cellular networks. due to its limited capacity, the current macro cellular network is unable to fully satisfy this demand. additionally, adding several macro-base stations to increase capacity and expand coverage is quite expensive. along with this, there are problems with urban space restrictions. to improve the coverage, capacity, and data rate in lte-a, numerous strategies have been proposed. the deployment of heterogeneous networks is one of the most economical techniques. lte-a hetnet significantly boosts wireless cellular networks' capacity and performance. with hetnets, you may employ a variety of cell sizes, including femtocells, macrocells, picocells, microcells, and relays, to enhance capacity and improve coverage. hetnet is the most effective, affordable, and scalable method for increasing the capacity of current and future wireless networks. the ues receive a solid network connection and an improved user experience as a result. however, if hetnet deployment is poorly managed, it frequently results in increased handover for ues. in this research, the rssf-hda, a novel handover decision algorithm, was mean±std = 0.61±0.268 mean±std = 0.73±0.332 mean±std = 0.79±0.115 levene’s stat. = 1.963, p=0.221>0.05 f-stat. = 0.404, p=0.685>0.05 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):215-230. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 229 proposed as a better option when compared with mif-hda and the field data obtained from the drive test. the research further presents a statical comparison of the field drive test readings, the mif-hda, and the rssf-hda reading to establish the existing relationship between the various cell edge spectral efficiency readings and to further establish the best algorithm under consideration for seamless handover. the outcome of this comparison suggests that rssf-hda has better quality of service (qos) parameters when compared with the mtn real-time drive-test values and the mif-hda algorithm. therefore, it is recommended that the rssf-hda should be adopted by mtn nigeria for better quality of service. acknowledgment the researchers are grateful to the tertiary education trust fund (tetfund) for their crucial assistance in supporting this research work. their kind financing has enabled us to pursue creative research projects that expand knowledge in our profession. the tetfund's dedication to investing in research and development supports not only individual researchers like our own, but also academic quality and growth across disciplines. we are grateful to tetfund for its commitment to fostering research activities in tertiary institutions, and also, we are delighted to have received their funding. their assistance has been critical in ensuring the effective completion of our research project, and we optimistic about the beneficial influence it will have on my academic aspirations and the wider scholarly community references abdulazeez-ahmed, m., nordin, nk., sali, ab. and hashim, f. 2020. multi-criteria handover decision for heterogeneous networks: carrier aggregation deployment scenario. international journal of computer networks and communications, 12(4): 41–54. https://doi.org/10.5121/ijcnc.2020.12403 abdullah, rm. and zukarnain, za. 2017. enhanced handover decision algorithm in heterogeneous wireless network. sensors17(7): 1626. https://doi.org/10.3390/s17071626 alhammadi, a., hassan, wh., el-saleh, aa., shayea, i., mohamad, h. and saad, wk. 2023. intelligent coordinated self-optimizing handover scheme for 4g/5g heterogeneous networks. ict express, 9(2): 276-281. bastidas-puga, er., andrade, ág., galaviz, g. and covarrubias, dh. 2019. handover based on a predictive approach of signal-to-interference-plus-noise ratio for heterogeneous cellular networks. iet communications, 13(6): 672–678. https://doi.org/10.1049/iet-com.2018.5126 buenestado, v., ruiz-aviles, jm., toril, m., luna-ramirez, s. and mendo, a. 2014. analysis of throughput performance statistics for benchmarking lte networks. ieee communications letters, 18(9): 1607–1610. https://doi.org/10.1109/lcomm.2014.2337876 capez, gm., henn, s., fraire, ja. and garello, r. 2022. sparse satellite constellation design for global and regional direct-to-satellite iot services. ieee transactions on aerospace and electronic systems, 58(5): 3786-3801. choi, hh., kim, h., na, jh. and lee, h. 2021. non-orthogonal multiple access-based handover for throughput enhancement. ieee transactions on vehicular technology, 70(11): 12278–12282. https://doi.org/10.1109/tvt.2021.3117785 hachemi, mh., mohammed, s., irid, h., benchehima, m., hadjila, m., mohammed, o., bir, b. and djir, e. 2022. pedestrian mobility management for heterogeneous networks. indonesian journal http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):215-230. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 230 of electrical engineering and computer science, 28(3): 1530–1540. https://doi.org/10.11591/ijeecs.v28.i3.pp1530-1540 hashemi, sa. and farrokhi, h. 2020. mobility robustness optimization and load balancing in self-organized cellular networks: towards cognitive network management. journal of intelligent & fuzzy systems, 38(3): 3285-3300. khan, m. and han, k. 2015. a vertical handover management scheme based on decision modelling in heterogeneous wireless networks. iete technical review, 32(6): 402-412. khattab, o., murad k. and basil a.2023. designing a vertical handover algorithm for securityconstrained applications. journal of applied sciences, 13(4): 2166-2169. kunarak, s. and suleesathira, r. 2020. multi-criteria vertical handoff decision algorithm for overlaid heterogeneous mobile ip networks. journal of the franklin institute, 357(10): 6321– 6351. https://doi.org/10.1016/j.jfranklin.2020.03.025 lin, x., andrews, jg. and ghosh, a. 2014. spectrum sharing for device-to-device communication in cellular networks. ieee transactions on wireless communications, 13(12): 6727–6740. https://doi.org/10.1109/twc.2014.2360202 mahardhika, g., ismail, m. and nordin, r. 2015. vertical handover decision algorithm using multicriteria metrics in heterogeneous wireless network. journal of computer networks and communications, 20(5): article id 539750 | https://doi.org/10.1155/2015/539750 nkeleme, vo., oborkhale, li. and sani, g. 2023. adaptive real-time spectrum selection framework and handover decision algorithm (rssf-hda) for heterogeneous networks. nigerian journal of technology, 42(2): 264–272. https://doi.org/10.4314/njt.v42i2.15 ohmann, d., simsek, m. and fettweis, gp. (2014). achieving high availability in wireless networks by an optimal number of rayleigh-fading links. ieee workshops, gc wkshps 20(14): 1402–1407. https://doi.org/10.1109/glocomw.2014.7063630 satapathy, p. and mahapatro, j. 2022. an efficient multicriteria-based vertical handover decisionmaking algorithm for heterogeneous networks. transactions on emerging telecommunications technologies, 33(4): e4409. https://doi.org/10.1002/ett.4409 sudhamani, c., roslee, m., tiang, jj. and rehman, au. 2023. a survey on 5g coverage improvement techniques: issues and future challenges. sensors , 23(4): 2356. https://doi.org/10.3390/s23042356 wahidin, ph. and christiary, y. 2022. the evaluation of the throughput performance of an lte-advanced urban area network with the inter-band non-contiguous carrier aggregation method. journal of hunan university natural sciences, 49(8): 209–217. https://doi.org/10.55463/issn.1674-2974.49.8.25. wu, h., wei, z., hou, y., zhang, n. and tao, x. 2020. cell-edge user offloading via flying uav in non-uniform heterogeneous cellular networks. ieee transactions on wireless communications, 19(4): 2411-2426. zhang, j., björnson, e., matthaiou, m., ng, dwk., yang, h. and love, dj. 2020. prospective multiple antenna technologies for beyond 5g. ieee journal on selected areas in communications, 38(8): 1637-1660. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):729-740 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 729 original research article evaluation of pyrolyzed oil palm frond in the adsorption of residual phenolic compounds in facultatively treated palm oil mill effluent a. a. lawal1*, a. u. dzivama1, n. a. aviara1, m. a. hassan2, m. r. zakaria2, y. shirai3 1department of agricultural and environmental resources engineering, faculty of engineering, university of maiduguri, maiduguri, borno state, nigeria 2department of bioprocess technology, faculty of biotechnology and biomolecular sciences, universiti putra malaysia, 43400 upm serdang, selangor, malaysia 3department of biological functions and engineering, graduate school of life science and systems engineering, kyushu institute of technology, 2-4 hibikino, wakamatsu-ku, kitakyushu, fukuoka 808-0196, japan. *corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 1.0 introduction palm oil mill effluent (pome) is an aqueous mixture of organic acids, phenolic compounds, and particulate matter derived from palm oil fruit and cell wall fragments. the concentration of the organic matter in pome is expressed in chemical oxygen demand (cod), which ranges between 16,000 and 100,000 mg/l, and when compared to domestic sewage it is 2 folds more polluting (alhaji et al., 2016; wu et al., 2010). a series of biological degradation processes such as anaerobic, facultative and aerobic treatment systems are typically employed to reduce the concentration of the organic matter in pome before discharge to surface water (hassan and article information abstract aerobic digestion is the final stage of biological treatment systems employed for treating palm oil mill effluent (pome). the presence of phenolic compounds in pome inhibits the performance of aerobic microbes. to mitigate the inhibitory effect, removing phenolic compounds at the early stage of aerobic treatment could be a workable solution. in this study, the performance of biochar from oil palm frond (opf-bc) prepared using steam pyrolysis was investigated for the efficient removal of phenolic compounds. adsorption kinetics and equilibrium tests were performed to assess the time required to reach adsorption equilibrium and uptake capacity for phenol, catechol and gallic acid spiked in water and facultatively treated pome. adsorption of the phenols onto opf-bc attained equilibrium within 2 h irrespective of the water matrix. in the water maximum adsorption capacities of 38.7, 28.2 and 26.2 mg/g were obtained for phenol, catechol, and gallic acid, respectively. the presence of background organic matter in facultatively treated pome reduced the adsorption capacities by 3-folds. the simplified equivalent background model estimated dosage to achieve 80% removal ranged between 14.4 and 18.8 g/l. the opf-bc demonstrated efficient phenolic compounds removal performance, making it a promising and economical adsorbent for the hybrid adsorption-aerobic treatment system. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 march, 2022 revised 5 july, 2022 accepted 10 july, 2022 keywords: biochar phenolic compounds palm oil mill effluent adsorption capacity http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):729-740 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 730 abd-aziz, 2012). nevertheless, this treatment is ineffective for the complete removal of cod mainly due to the inhibitory effect of a high concentration of phenolic compounds on microorganisms (chantho et al., 2016; muñoz-palazon et al., 2019), the bio-recalcitrant nature of phenolic compounds at low concentrations (hussein et al., 2001), and microbial degradation of organic acids into micropollutants such as phenolic compounds (ghosh et al., 2007; max et al., 2012). incomplete degradation of cod may indirectly lead to the discharge of treated pome with a substantial amount of organic micropollutants into the aquatic environment. in an effort to reduce the concentration of cod in pome to a safe discharge limit, numerous advanced treatment techniques have been investigated, mainly focusing on the feasibility of upgrading the conventional biological treatment system (bashir et al., 2019; othman et al., 2014; tan et al., 2014). accordingly, identifying a technically and economically feasible treatment technique that can be integrated into the conventional biological treatment system is gaining tremendous research attention. based on these criteria, the adsorption technique is generally considered to be a preferred option due to its simplicity of operation, nongeneration of toxic pollutants, efficient removal of recalcitrant and organic compounds, and cost-effectiveness (de gisi et al., 2016). adsorptive removal of contaminants by adsorbents, mainly with activated carbon, has been widely used for wastewater treatment. though activated carbon is considered the most effective adsorbent due to its higher surface area, the activation of its precursor and regeneration after use are associated with excessive energy consumption, and its precursor, which is mostly coal, is non-renewable. accordingly, applying low-cost adsorbents for wastewater treatment has been the main research focus in recent years. biochar derived from oil palm frond is an environmentally friendly and low-cost adsorbent produced from a renewable bioresource. nevertheless, little attention is given to the adsorption of micropollutants on biochar derived from oil palm fronds (opf-bc). in addition, limited studies are focusing on the removal of phenolic compounds from facultatively treated pome. therefore, the objective of this study was to evaluate the effectiveness of opf-bc in adsorbing phenol, catechol, and gallic acid from facultatively treated pome. 1. materials and methods 1.1 materials oil palm fronds were harvested in january 2021 from the oil palm plantation of universiti putra malaysia in selangor, malaysia. the fronds were cut into approximately 5 cm and dried in an oven (memmert, germany) for about 48 h at 100 °c. the dry fronds were stored at room temperature in an airtight plastic bag before biochar production (figure 1). effluent from facultatively treated pome was collected in february 2021 from felda palm oil mill, pasoh. the wastewater sample collected was filtered to remove suspended solids using whatman’s filter (0.45 μm) (figure 1). the initial contents of 1001.57 ± 51.4 mg/l for cod, 42.19 ± 0.62 mg/l for total phenolic compounds, and 8.47 ± 0.03 for solution ph were recorded. subsample from the filtered facultatively treated pome was diluted to 1:1 with ultrapure water (arium mini lab water system). a mm phosphate-buffered ultrapure water with 8.0 ±0.2 was prepared by dissolving the required amounts of k2hpo4 and kh2po4 in a known quantity of ultrapure water. phenol, catechol and gallic acid used in this study as adsorbates were selected based on their residual concentration in facultatively treated pome. all chemicals used were of analytical grade. sodium carbonate, dipotassium phosphate, monopotassium phosphate and folin-ciocalceau phenol reagent were purchased from merck, gallic acid was purchased from r & m, while phenol and catechol were purchased from scharlau and tci respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng lawal et al: evaluation of pyrolyzed oil palm frond in the adsorption of residual phenolic compounds in facultatively treated palm oil mill effluent. azojete, 18(4):729-740. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 731 figure 1. feedstocks: (a) oil palm fronds, (b) facultatively treated pome 1.2 methods 1.2.1 production of biochar the opf-bc was produced by steam pyrolysis in a locally fabricated steam carbonization system. a detailed description of the system was described elsewhere (lawal et al., 2020a; lawal et al., 2020b). the dry oil palm fronds weighing about 250 g were loaded into a reactor and placed in the vertical tubular furnace of the carbonization unit. about 100% saturated steam was allowed to flow at 200 cm3/min into the furnace to remove air in the reactor and to maintain a steam atmosphere during pyrolysis. the dry frond sample was heated to 600 ± 5 oc at a 10 oc/min heating rate and held for 2 h and finally cooled to room temperature. 1.2.2 adsorption kinetic test adsorption kinetic experiments were carried out by adding a fixed dose (4 g/l) of opf-bc into 100 ml of water matrix of a known concentration of a phenolic compound contained in a 250 ml erlenmeyer flask. the erlenmeyer flask was covered with aluminium foil and transferred into a shaker incubator (tech-lab tsi-285, malaysia) and shaken at 150 rpm and in a controlled temperature atmosphere of 30 °c. about 10 to 12 samples of approximately 1 ml were collected at different time points from the mixture and analyzed for residual concentration. 1.2.3 equilibrium isotherm test a bottle point experiment with variable biochar doses (1 to 50 g/l) was also used to evaluate the adsorption capacity of phenol, catechol, and gallic acid spiked in phosphate-buffered ultrapure water onto opf-bc. the effect of background organic matter on the adsorption of individual phenolic compounds spiked in samples of the facultatively treated pome water matrix was also investigated. for each water matrix, a 25 ml sample was added to a known amount of opf-bc in a 60 ml glass bottle vial and sealed with a rubber stopper. glass vials without opf-bc are designated as control. the sealed vials were vigorously shaken by hand and transferred into a shaker incubator (tech-lab tsi-285, malaysia) and shaken at 150 rpm for 2 h at 30 °c. after equilibrium was attained, the water matrix from each vessel was filtered through a 0.22 μm syringe filter to remove the added opf-bc and analyzed for residual concentrations of an adsorbate. both kinetic and equilibrium isotherm experiments were repeated three times under similar conditions, and average values with their standard deviations were reported. 1.3 analysis 1.3.1 water matrices concentrations of phenol, catechol and gallic acid in the filtered water matrices were quantified using the modified folin-ciocalceau method (ergül et al., 2009). herein, 500 μl of http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):729-740 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 732 folin-ciocalceau phenol reagent diluted 1:3 with ultrapure water was added to a 100 μl water matrix. after 5 minutes, 500 μl sodium carbonate solution (2000 mg/l) was added and the mixture was allowed for the reaction to complete for 30 minutes at room temperature. absorbance was measured by a uv-vis spectrophotometer (genesys 20, thermofisher scientific, us) at the wavelength of 725 nm for gallic acid and total phenolic compounds and 760 nm for phenol and catechol against blank. the measured absorbance was used to calculate the concentration of an analyte based on its calibrated curve developed using 10 concentration points spread over the concentration range of 5 to 50 mg/l. the coefficient of determination of the curves was > 0.998. the concentration of cod in facultatively treated pome was determined based on apha (american public health association) standard method 8000. this involved adding 2 ml of filtered water matrix into a cod vial (20 to 1500 mg/l) and heated to 150 °c in a hach reactor (hach, usa) for 2 h. after cooling, cod concentration was measured using the hach dr 2800 spectrophotometer (hach, germany). 1.4 modeling data obtained from the equilibrium isotherm experiments in phosphate-buffered ultrapure water were simulated using the freundlich model 𝑞𝑒 = 𝐾𝐹(𝐶𝑒) 𝑛 (1) where qe (mg/l) is the solid-phase concentration of adsorbate at equilibrium, ce (mg/l) is the aqueous-phase concentration of adsorbate, and kf [(mg/g)(mg/l)n] and n are freundlich parameters for capacity affinity and linearity respectively. in a situation where the isotherm shifts of different adsorbates on an adsorbent are relatively non-parallel (n values varied significantly), the concentration-specific distribution ratio expressed as 𝐾𝑐𝑠𝑑 = 𝑞𝑒 𝐶𝑒 , (2) is more appropriate for affinity comparison than kf (lattao et al., 2014). since the freundlich model can not adequately predict the competitive adsorption process, the simplified equivalent background compound model (sebcm) was found to be suitable to describe the adsorption of a target compound in the presence of a higher concentration of background organic matter in the wastewaters (qi et al., 2007). the sebcm relates the residual concentrations of the targeted compound to the adsorbent dose in a 2-parameter model: 𝑙𝑛 ( 𝐶1,0 𝐶1 − 1) = 1 𝑛1 𝑙𝑛 𝑚𝐴 𝑉 − 𝑙𝑛𝐴 (3) where c1,0 and c1 are the initial and equilibrium concentrations of adsorbate, n1 is the freundlich linearity parameter, ma mass of adsorbent, v volume of solution and a equation parameter. the parameters n1 and a obtained by fitting experimental data in eq. (3) are important parameters required in eq. (4) to determine the adsorbent dose necessary for the removal of a certain percentage of target adsorbate (bonvin et al., 2016; qi et al., 2007): 𝑚𝐴 𝑉 = 𝐴 1 𝑛1 ( 𝐶1,0 𝐶1 − 1) 1 𝑛1 (4) 2. results and discussion 2.1 adsorption kinetics adsorption kinetic test was carried out to estimate the time required to reach equilibrium. the experimental results showed that adsorption of phenol, catechol and gallic acid in the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng lawal et al: evaluation of pyrolyzed oil palm frond in the adsorption of residual phenolic compounds in facultatively treated palm oil mill effluent. azojete, 18(4):729-740. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 733 phosphate-buffered ultrapure water and facultatively treated pome onto opf-bc attained equilibrium within 2 h (figure 2). in phosphate-buffered ultrapure water, phenol recorded the highest initial percentage removal of 80% and attained closed to adsorption equilibrium after 40 min, followed by catechol, with a similar trend but at a slightly lower percentage removal of 77%, and a higher adsorption equilibrium time of 90 min. gallic acid exhibited the lowest initial percentage removal of 68% and reached adsorption equilibrium after 2 h. however, in facultatively treated pome, the percentage removal was drastically reduced to 46% for phenol, 55% for catechol, and 33% for gallic acid. the adsorption equilibrium for phenol was delayed to 90 min, while that for gallic acid was achieved in only 60 min, indicating possible adsorption competition and/or interference from background organic matters in the facultatively treated pome. these results are in agreement with previous studies showing an equilibrium time of less than 2 h for phenol and catechol (alam et al., 2009; vunain et al., 2018). early and fast removal of phenolic compounds during aerobic treatment is an operational requirement that can benefit the entire treatment process by reducing the inhibitory effect of the phenolics on microorganisms and reducing bio-recalcitrant micropollutants. figure 2. adsorption kinetics of opf-bc at 4 g/l dosages for phenol (□, ■), catechol (∆, ▲) and gallic acid (○, ●) spiked in (a) phosphate-buffered ultrapure water and (b) facultatively treated pome. 2.2 adsorption isotherm 2.2.1 adsorption equilibrium in water the isotherms for the adsorption of phenol, catechol, and gallic acid from phosphate-buffered ultrapure water onto opf-bc are presented in figure 3a, and their respective freundlich parameters are listed in table 1. it can be seen from figure 3a, that the isotherms of phenol and catechol are quite similar, both showing a pore-filling mechanism at low carbon dosage. the isotherm trend for gallic acid differed considerably. its adsorption capacity at both high and low biochar dosages decreased by more than half that of phenol and catechol indicating low opf-bc affinity for gallic acid. the maximum experimental adsorption capacities of 38.7, 28.2, and 26.2 mg/g were obtained for phenol, catechol, and gallic acid, respectively. the values of the n parameter are highly nonlinear (<0.5) indicating a predominantly adsorption/porefilling mechanism. the estimated capacity parameter of freundlich, kf will not provide a reliable basis for comparison among the phenolic compounds due to the relative non-parallel shift of the isotherms (unequal n values of the adsorbates). for a reliable comparison of estimated capacity parameters, kcsd values calculated at three different specific liquid-phase 0 20 40 60 80 100 0 50 100 150 r em o v al e ff ic ie n cy ( % ) time (min) (a) 0 20 40 60 80 100 0 50 100 150 r em o v al e ff ic ie n cy ( % ) time (min) (b) http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):729-740 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 734 concentrations were evaluated (figure 3b). at low concentration, opf-bc showed high affinity for the phenols in the decreasing order of catechol > phenol > gallic acid. as liquidphase concentration increased, the affinity of opf-bc for the phenolic compounds decreased indicating near saturation of its adsorption sites. figure 3. (a) adsorption isotherms for phenol (□), catechol (∆) and gallic acid (○) in phosphate-buffered ultrapure water, and (b) their respective concentration-specific distribution coefficient at 10, 25 and 40 mg/l. table 1. freundlich parameters and coefficient of determination for phenol, catechol, and gallic acid adsorption onto opf-bc. adsorbate freundlich parameters kf n r2 phenol 6.333 0.3921 0.9356 catechol 8.447 0.2779 0.9999 gallic acid 3.9231 0.4937 0.4207 2.2.2 adsorption equilibrium in facultatively treated pome to study the effect of background organic matter on the adsorption capacity of phenolic compounds on opf-bc, the adsorption isotherms for phenol, catechol, and gallic acid were determined in phosphate-buffered ultrapure water containing no organic compounds and in facultatively treated pome, containing background organic matter (figure 4). for adsorption of the phenolics in facultatively treated pome approximately three-fold lower adsorption capacities were observed for phenol, catechol, and gallic acid, reflecting the negative effect of competing for organic matter. it is widely known that background organic matter in wastewater affects the adsorption of target micropollutants on porous carbon materials via direct competition for adsorption sites or size exclusion effect or both (bonvin et al., 2016; zoschke et al., 2011). in comparison, opf-bc was able to adsorb approximately 1 and 3 mg/g more of catechol than phenol and gallic acid across all dosages respectively in the presence of background organic matter (figure 3d). due to their small size and molecular weight, phenol and catechol competed favourably well with other micropollutants in facultatively treated pome for adsorption sites located in the micropore region of opf-bc as compared to gallic acid. 1 10 100 1 10 100 q e (m g /g ) ce (mg/l) (a) 0 0.5 1 1.5 2 phn cat ga k cs d (l /g ) (b) 10 mg/l 25 mg/l file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng lawal et al: evaluation of pyrolyzed oil palm frond in the adsorption of residual phenolic compounds in facultatively treated palm oil mill effluent. azojete, 18(4):729-740. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 735 figure 4. comparison between adsorption isotherms of (a) phenol, (b) catechol, (c) gallic acid (d) group isotherms in phosphate-buffered ultrapure water (empty symbols) and facultatively treated pome (filled symbols). 2.3 effect of background organic matter on removal efficiency of phenolic compound the dependence of the removal efficiency of phenol, catechol and gallic acid from phosphatebuffered ultrapure water and facultatively treated pome water matrices on opf-bc dosage ranging from 0.4 to 10 g/l is presented in figure 5a. at the same biochar dosage, an opf-bc dose of 6 g/l was required to remove more than 97% phenol and catechol, and 84% gallic acid from phosphate-buffered ultrapure water, whereas the presence of background organic matter in facultatively treated pome drastically reduced their removal efficiency to 63%, 67%, and 44%, respectively. the percentage removal of cod in facultatively treated pome was comparatively lower than that of phenolic compounds (figure 5b). to compare the effect of background organic matter on the removal efficiency of opf-bc for the phenolic compounds, their removals were examined in both the facultatively treated pome and its half-diluted sample at three biochar doses. figure 6 shows the competitive effect of increasing cod concentration on the removal efficiency of the phenols at three different doses of opf-bc. for all doses of opf-bc, an increase in cod concentration reduced the removal efficiency of the phenolic compounds. this is in line with the findings of bonvin et al. (2016) on the removal of micropollutants in varying concentrations of background organic matter. dilution reduces the concentration of background organic matters which compete for adsorption sites or block pores and thus reflecting an increase in available adsorption sites. alternatively, increasing adsorbent dosage is expected to reduce the difference between removal efficiencies 1 10 100 1 10 100 q e (m g /g ) ce (mg/l) (a) 1 10 100 1 10 100 q e (m g /g ) ce (mg/l) (b) 1 10 100 1 10 100 q e (m g /g ) ce (mg/l) (c) 1 10 100 1 10 100 q e (m g /g ) ce (mg/l) (d) http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):729-740 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 736 of adsorbate in wastewater with different concentrations of background organic matter because of the additional adsorption sites provided. this trend was observed with the removal of catechol where the difference in its removal efficiency in facultatively treated pome and half-diluted facultatively treated pome decreased at high dosage (figure 6c). however, this is not the case with gallic acid where the difference in removal efficiency increases at high dosage indicating its low affinity for opf-bc. figure 5. comparison of the dependence of removal efficiency on opf-bc dose: (a) among phenol (□, ■), catechol (∆,▲) and gallic acid (○, ●) spiked in phosphate-buffered ultrapure water and facultatively treated pome, (b) among phenol, catechol and gallic acid spiked in facultatively treated pome and its cod (ж) content. figure 6. effect of cod concentration on the removal efficiency of phenol, catechol and gallic acid at: (a) opf-bc dose (1 g/l); (b) opf-bc dose (5 g/l); and (c) opf-bc dose (10 g/l). 0 20 40 60 80 100 120 0 5 10 15 r em o v al e ff ic ie n cy ( % ) biochar dose (g/l) (a) 0 20 40 60 80 100 120 0 5 10 15 r em o v al e ff ic ie n cy ( % ) biochar dose (g/l) (b) 0 100 phenol catechol gallic acid r em o v al e ff ic ie n cy ( % ) (a) 0 mg cod/l 501.79 mg cod/l 1003.57 mg cod/l 0 200 phenol catechol gallic acid r em o v al e ff ic ie n cy ( % ) (b) 0 mg cod/l 501.79 mg cod/l 1003.57 mg cod/l 0 200 phenol catechol gallic acid r em o v al e ff ic ie n cy ( % ) (c) 0 mg cod/l 501.79 mg cod/l 1003.57 mg cod/l file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng lawal et al: evaluation of pyrolyzed oil palm frond in the adsorption of residual phenolic compounds in facultatively treated palm oil mill effluent. azojete, 18(4):729-740. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 737 2.4 biochar dose for efficient removal of phenolic compound in facultatively treated pome to accurately estimate the quantity of opf-bc dose required for efficient removal of the phenolic compounds spiked in facultatively treated pome, sebcm was first employed to simulate the relative removal of experimental data (figure 7). the removal plots predicted by sebcm fit well with the experimental data as shown in figure 7, indicating the validity of extending the application of sebcm for wastewater containing a high concentration level of background organic matter. the parameters obtained from fitting the experimental data were then utilized to quantitatively estimate the opf-bc dose required for 80% removal using eq. (4), and the results are presented in table 2. the opf-bc dose required to remove 80% ranges from 14 to 19 g/l with an average dose of 15.87 g/l to remove all compounds combined. though the estimated quantity of opf-bc seems large (14 -19 g/l) compared to activated carbon doses (15 21 mg/l) reported for the 80% removal of benzotriazole, mecoprop, and sulfamethoxazole from wastewater (altmann et al., 2014; bonvin et al., 2016), the performances of the adsorbents are comparable considering the concentration levels of the respective target pollutants and background organic matter. in this study, concentration levels are three-fold larger (mg/l against μg/l), corresponding to the three-fold higher dosage. the result indicates that efficient removal of phenolic compounds to below inhibitory level can be achieved with a low opf-bc dose and this underscores the possibility of the practical application of the adsorption process in large scale aerobic treatment system. figure 7. (a) group plots of experimental data for the relative removal of phenol, catechol and gallic acid in facultatively treated pome, and sebcm simulation of relative removal of (b) phenol, (c) catechol and (d) gallic acid in facultatively treated pome. 10 30 50 70 90 110 0 5 10 15 r el at iv e re m o v al , c /c 0 (% ) biochar dose (mg/l) (a) 20 40 60 80 100 0 5 10 15 r el at iv e re m o v al , c /c 0 (% ) biochar dose (mg/l) (b) sebcm regr. line 10 30 50 70 90 110 0 5 10 15 r el at iv e re m o v al , c /c 0 (% ) biochar dose (g/l) (c) sebcm regr. line 0 20 40 60 80 100 0 20 40 60 r el at iv e re m o v al , c /c 0 (% ) biochar dose (g/l) (d) sebcm regr. line http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):729-740 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakar.lawal@unimaid.edu.ng 738 table 3. sebcm parameters and goodness of fit for phenol, catechol and gallic acid, and their estimated 80% removal. adsorbate sebcm parameter estimated opf-bc dose for 80% removal (g/l) a n1 r2 phenol 8.6478 1.3298 0.9434 14.36 catechol 6.0761 1.4199 0.9603 14.48 gallic acid 62.35 1.717 0.969 18.81 3. conclusion the fast adsorption kinetics of opf-bc for phenolic compounds will prevent the initial inhibition effect on the aerobic microbes, which will lead to a potential reduction of hydraulic retention time of the aerobic process. for instance, an aerobic process usually takes 2 to 10 days to degrade phenolic compounds, whereas complete removal will be achieved within 2 h using opf-bc. therefore, the initial removal of phenolic compounds using opf-bc during aerobic treatment will benefit the entire process in terms of reducing the time for treatment. another benefit arising from adsorbing more than 43% cod in facultatively treated pome will be a plus to the primary objective of removing phenolic compounds. the removal of close to half the concentration of cod in facultatively treated pome reduces the organic loading during aerobic treatment, which could translate to a reduction in the size of the aerobic tanks. acknowledgement this research was funded by the fundamental research grant scheme – malaysia research star award [grant number: frgs-mrsa/1/2018/stg07/upm/01/1]. the authors would like to express their profound appreciation to universiti putra malaysia, kyushu institute of technology and the university of maiduguri consult for their additional support. references abd waft, ns., lau, hln., loh, sk., abdul aziz, a., ab rahman, z. and may, cy. 2017. activated carbon from oil palm biomass as potential adsorbent for palm oil mill effluent treatment. journal of oil palm research, 29: 278–290. alam, mdz., ameem, es., muyibi, sa. and kabbashi, na. 2009. the factors affecting the performance of activated carbon prepared from oil palm empty fruit bunches for adsorption of phenol. chemical engineering journal, 155: 191–198. alhaji, mh., sanaullah, k., lim, sf., khan, a., hipolito, cn., abdullah, mo., bhawani, sa. and jamil, t. 2016. photocatalytic treatment technology for palm oil mill effluent (pome) – a review. process safety and environmental protection 102: 673–686. altmann, j., ruhl, a.s., zietzschmann, f. and jekel, m. 2014. direct comparison of ozonation and adsorption onto powdered activated carbon for micropollutant removal in advanced wastewater treatment. water research 55: 185–193. antal, mj. and grønli, m., 2003. the art, science, and technology of charcoal production. industrial & engineering chemistry research 42: 1619–1640. bashir, mjk., lim, jh., abu amr, ss., wong, lp. and sim, yl. 2019. post treatment of palm oil mill effluent using electro-coagulation-peroxidation (ecp) technique. journal of cleaner production 208: 716–727. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng lawal et al: evaluation of pyrolyzed oil palm frond in the adsorption of residual phenolic compounds in facultatively treated palm oil mill effluent. azojete, 18(4):729-740. issn 1596-2644; 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(eds.), materials science and engineering of carbon: characterization. elsevier inc., oxford, pp. 227–247. othman, mr., hassan, ma., shirai, y., baharuddin, as., ali, aam. and idris, j. 2014. treatment of effluents from palm oil mill process to achieve river water quality for reuse as recycled water in a zero-emission system. journal of cleaner production 67: 58–61. qi, s., schideman, l., mariñas, bj., snoeyink, vl. and campos, c. 2007. simplification of the iast for activated carbon adsorption of trace organic compounds from natural water. water research 41: 440–448. som, am., wang, z. and al-tabbaa, a. 2012. palm frond biochar production and characterisation. earth and environmental science transactions of the royal society of edinburgh 103: 39–50. sun, l., wan, s. and luo, w., 2013. biochars prepared from anaerobic digestion residue, palm bark, and eucalyptus for adsorption of cationic methylene blue dye: characterization, equilibrium, and kinetic studies. bioresource technology 140: 406–413. tan, yh., goh, ps., lai, gs., lau, wj. and ismai, af. 2014. treatment of aerobic treated palm oil mill effluent (at-pome) by using tio2 photocatalytic process. jurnal teknologi (sciences & engineering) 70: 61–63. thangalazhy-gopakumar, s., al-nadheri, wma., jegarajan, d., sahu, jn., mubarak, nm. and nizamuddin, s. 2015. utilization of palm oil sludge through pyrolysis for bio-oil and bio-char production. bioresource technology 178: 65–69. vunain, e., houndedjihou, d., monjerezi, m., muleja, aa. and kodom, b. 2018. adsorption, kinetics and equilibrium studies on removal of catechol and resorcinol from aqueous solution using low-cost activated carbon prepared from sunflower (helianthus annuus) seed hull residues. water, air, & soil pollution 229: 366. wu, ty., mohammad, aw., jahim, jmd. and anuar, n. 2010. pollution control technologies for the treatment of palm oil mill effluent (pome) through end-of-pipe processes. journal of environmental management 91: 1467–1490. zoschke, k., engel, c., börnick, h. and worch, e. 2011. adsorption of geosmin and 2methylisoborneol onto powdered activated carbon at non-equilibrium conditions: influence of nom and process modelling. water research 45: 4544–4550 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):129-142 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 121 original research article effect of moisture content on some physical properties of red kidney bean (phaseolus vulgaris l.) seed grown in north eastern nigeria n. a. aviara and r. a. ma’aji department of agricultural and environmental recourses engineering, faculty of engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: ndubisi.aviara@unimaid.edu.ng, nddyaviara@yahoo.com 1.0 introduction beans are members of the fabaceae family, which includes legumes. they are economically and nutritionally important food crops that are cultivated and consumed worldwide, (sneh et al., 2020). legumes are of leguminosae plant family, and they constitute one of the world's most important groups of plants; second only to cereals in providing food crops for world agriculture. they represent an important source of dietary protein for large segment of the human population and domestic animals. pulses as listed by the food and agricultural organization (fao), including french, navy, pinto, field, haricot, china, marrow frijoles, snap, string, wax, black and white kidney beans are the most widely produced and consumed food legumes in asia, south america, latin america and africa, where they serve as good sources of protein with good nutritional and functional properties (mundi, 2012). the kidney bean is a variety of the common bean (p. vulgaris l.), so named because of its kidneylike shape and its color. the optimum moisture content of the seeds for their harvesting, shelling and storage ranges between 12 and 14%. the color of kidney beans ranges all the way from very light red to very dark, or almost purple. ‘hard seed’ is a term reserved for those seeds that take up water slowly or not at all during soaking because of a relatively impermeable seed coat. ‘hard seeds’ are often found after storage of dried beans in an atmosphere of very low humidity. a small percentage of hard seeds may be expected in kidney beans held under such conditions. these beans generally do not soak up completely and may remain undesirably article information abstract this study was aimed at determining some physical properties of red kidney bean seed as a function of moisture content. in the moisture range of 6.84-15.74% (d.b), seed length, width and thickness increased from 11.4-16.83mm, 6.2-8.87mm and 4.3-5.16mm, and arithmetic and geometric diameters increased from 8.6-10.29mm and from 8.3-9.14mm, respectively. in the above moisture range, one thousand seed weight, seed surface area, true density, and porosity increased linearly, while sphericity increased logarithmically, and angle of repose increased as a polynomial of the second order with moisture content. bulk density decreased with increase in moisture content in the above moisture range. static coefficient of friction on all the structural surfaces applied increased logarithmically with moisture content, and kinetic coefficient of friction on the surface all increased linearly with moisture content except on fiber glass where the increase was polynomial of the second order. static and kinetic coefficients of friction were highest on hessian bag material and lowest on fiber glass. regression models that could be used to express the relationship between the physical properties and moisture content, with high coefficients of determination, were established. the data obtained in this study would be applicable in the design of red kidney bean seed handling and storage facilities. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 dec., 2022 revised 21 february, 2023 accepted 18 february, 2023 keywords: red kidney beans phaseolus vulgaris l. physical properties angle of repose static coefficient of friction kinetic coefficient of friction design parameters nigeria http://www.azojete.com.ng/ mailto:nddyaviara@yahoo.com ndubisi.aviara@unimaid.edu.ng nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):129-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 130 hard, even after canning (susan, 2016). the crop lacks biological nitrogen fixation due to poor nodulation. therefore, it needs good amount of nitrogen of about 100 to 125 kg/ha. this crop also requires 60 to 70 kg of p205/ha and adding potassium hardly affects the yield. figure 1a and b show the red kidney bean pods and seeds, respectively. figure 1: (a) red kidney bean seeds pods, (b) red kidney bean seeds to harvest the beans requires uprooting and pulling the entire bean plant out of the soil and hanging it upside down in a dark, dry, and warm spot for a few days (or in some cases weeks) to cure the beans. once the plants become dried and hardened completely, the pods are plucked from the bean plant and arranged on a wooden rack or solid platform. the harvested pods are then allowed in to dry in sun for 3 to 4 days after which they are shelled to obtain the seeds using bullocks or with sticks and or sickles. seed bins are used to store the clean red kidney bean seeds (singh and chandra, 2020). the ever-increasing functional and utilization requirements of agricultural products together with the complexity of modern technology for their production, processing and storage necessitate better knowledge of their engineering properties so that machines, processes and handling operations can be designed for maximum efficiency and highest quality of end products. for instance, the application of physical properties such as shape which is an important parameter for stress distribution in materials under load is important in developing sizing and grading machines and for analytical prediction of drying behavior. the properties may be moisture dependent and this can affect the adjustment and performance of the agro-processing equipment. a range of moisture contents of the seed usually exist within which optimum performance is achieved therefore, the effect of moisture content on the physical properties of agricultural grains and seeds, is of important consideration in the design of the handling, processing and storage equipment (aviara et al., 1999). the aim of this study is to investigate the effect of moisture content on the physical properties of red kidney bean (phaseolus vulgaris l.) seed. the properties addressed are axial dimensions (length, width and thickness), surface area of the seed 1000 seed weight, particle/true density, bulk density, angle of repose, porosity, sphericity, arithmetic mean diameter and geometric mean diameter at different moisture contents, as well as coefficients of static and kinetic friction of the seed on different structural surfaces and moisture levels. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nddyaviara@yahoo.com aviara and ma’aji: effect of moisture content on some physical properties of red kidney bean (phaseolus vulgaris l.) seed grown in north eastern nigeria. azojete, 19(1):129-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 131 2. materials and method the bulk quantity of red kidney beans used in this study was obtained from a local market in jalingo, taraba state. the seeds were brought to the laboratory and cleaned manually to remove all foreign and other fine materials as well as damaged seeds. the bulk seeds were divided into five batches, four of the batches were conditioned to raise their moisture content to different moisture levels using the addition of calculated amount of water method according to tamirat (2012). the remaining batch was used for experiment at the market storage moisture level. after conditioning, the seeds were stored in separate polyethylene bags which were sealed and kept in a refrigerator for 24 hours to enable the moisture to be uniformly distributed throughout the seeds. after the attainment of uniform seed moisture content, the bags were stored at room temperature. the market storage moisture of the seeds the four higher moisture levels obtained after the conditioning operation were determined by oven drying at 105°c for 8 hours, as recommended for proteinous crops by aviara et al. (1999). this was carried out in three replicates and the average values were recorded. the axial dimensions of the seeds, namely: the length (l), width (w), and the thickness (t) were measured using the method of ndukwu (2009). this involved counting of 100 seeds selected randomly from the bulk material and using micrometer screw gauge of 0.01mm accuracy to measure the different dimensions of each of the seeds. this method was preferred due to simplicity, accuracy and availability of material. the arithmetic mean diameter was determined using equation (1) (mohsenin, 1986). twenty (20) seeds were used for the determination of this parameter. the average values were recorded and used in the analysis. 𝐴𝑚 = 𝐿+𝑊+𝑇 3 (1) where: am = arithmetic mean diameter (mm), l = length (mm), w= width (mm), t = thickness (mm). geometric mean diameter was determined using equation (2) (joshi et al., 1993). 𝐷𝑔 = (𝐿𝑊𝑇) 1 3⁄ (2) where: dg = geometric mean diameter (mm) the sphericity was determined using equation (3) (aviara et al., 1999). 𝜑 = 𝐷𝑔 𝐿 (3) where: 𝜑 = sphericity the one thousand seed weight of the seeds was determined using the method of aviara et al. (2014). this involved counting 1000 seeds at each moisture level and pouring them dockage free into a container of a known weight, then weighing the seeds and the container using a digital electronic balance of approximately 0.001g reading accuracy. the weight of the container was subtracted from weight of the 1000 seeds + container to obtain the weight of the 1000 seeds. this experiment was replicated three times and the average value recorded. the surface area of the seed was measured using the method of aviara et al. (1999). this involved carefully wrapping the seeds with a foil paper, and cutting of the excess paper, then unwrapping the papers and spreading them carefully on a graph sheet and tracing the boundary http://www.azojete.com.ng/ mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):129-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 132 formed using a pencil. the surface area of the seeds was then determined by counting the number of square boxes the traced boundary covered on the graph. this was repeated for all the four other moisture levels and at 20 trials each. the true or particle density of the seeds was determined using the standard liquid displacement method as reported by aviara et al. (2005). in this experiment, water was used as the liquid. the samples were coated with thin layer of epoxy resin, weighed individually on an electronic weighing balance and tied with a thread before immersing them individually into a 10ml cylinder containing a known volume of water and the volume of water displaced in the cylinder was noted and taken in order to obtain the volume of the seed. twenty trials were carried out at each moisture level. true density was calculated from the obtained values using equation (4): 𝜌𝑡 = 𝑀 𝑉𝑓−𝑉𝑖 (4) where: ρt = true density (g/cm3), m = mass of individual seed (g), vi = initial volume of water in the cylinder (ml), vf = final volume of water in the cylinder after submergence of seed (ml). the bulk density was determined using the aoac method as reported by aviara et al, (1999). this method was used for accuracy and better understanding. samples were poured from a height of 15cm into a 500ml cylinder of known mass. the sample was weighed on the balance and weight of the seeds was calculated by subtracting the mass of the cylinder alone from the final mass of seeds and cylinder, while the volume of the cylinder was taken to be the volume occupied by the seeds. three trials were carried out with their average calculated for each of the moisture levels. the bulk density was then determined using the expression in equation (5): 𝜌𝑏 = 𝑀𝑠 𝑉𝑠 (5) where: ρb = bulk density (g/cm3), ms = mass of seeds (g), vs = volume of seeds (cm3). the porosity of red kidney beans was determined using the formula (singh and chandra, 2014): (6) where: 𝜀 = porosity (%), pb = bulk density (kg/m3), ρt = true density (kg/m3) in determining the angle of repose, the cylindrical pipe method was used as reported by zewdu and solomon (2007) and aviara et al. (2014). a topless and bottomless cylinder was filled with seeds and slowly raised on a surface to leave the seeds piling to form a cone. the diameter of the cone was measured using a meter rule in order to obtain the radius and the height of the cone was also measured using a meter rule and these were used to calculate the angle of repose. equation (7) due to aviara et al. (2017) was applied to determine the angle of repose. (7) where: θ = angle of repose in degrees (°), h = height of piled seeds (mm), r = radius of base of cone formed by seeds (mm). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nddyaviara@yahoo.com aviara and ma’aji: effect of moisture content on some physical properties of red kidney bean (phaseolus vulgaris l.) seed grown in north eastern nigeria. azojete, 19(1):129-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 133 the static coefficient of friction was evaluated on plywood structural surface with wood gain parallel to direction of movement and plywood with wood grain perpendicular to the direction of movement. other structural surfaces used were hessian bag material and fiber glass. the incline plane method as described by dutta et al. (1988) and aviara et al. (1999) was applied. this involved placing of an open ended box (150mm x 150mm x 150mm) on an adjustable tilting surface which was formed with structural surface. the box was filled with seed and the structural surface with the box and its content on top was gradually raised using a screw device until the box started to slide down. the angle of tilt was read from a graduated scale and the tangent of the angle was taken as the static coefficient of friction. this was done for four samples of different moisture content. for the kinetic coefficient of friction, the open-ended box used in determining the static coefficient of friction was placed on a horizontal surface. plywood with wood grain parallel to the direction of movement and plywood with wood grain perpendicular to the direction of movement were employed (aviara et al., 2013). the box was filled with seeds. it was connected by means of a string, parallel to the surface and passed over a pulley to a pan hanging from it. weights were placed in the pan until the box and it content moved uniformly when given a gentle push. the kinetic coefficient of friction of product on a given structure surface was calculated using equation (8) (aviara et al., 2013). 𝜆 = 𝑊𝑝+𝑊𝑚 𝑊𝑏+𝑊𝑠 (8) where: λ is the kinetic coefficient of friction of seed on a structural surface, wp is the weight of pan (kg), wm is weight placed in the pan to move the box and content (kg), wb is weight of the box (kg) and ws weight of sample (kg). measurements were replicated five times at each moisture level with different samples. the average value at each moisture level was plotted against moisture content. the relationship existing between the properties and seed moisture content was determined using regression analysis. 3. results and discussion 3.1 seed moisture content and axial dimensions the initial (market storage) moisture content of red kidney beans seed was found to be 6.84% (d.b), the four other moisture level obtained after conditioning the seeds were 7.5, 10, 12, and 15.74%, respectively. the investigations were carried out at the above moisture levels to determine the effect of moisture content on the physical properties of red kidney beans. the mean values of the axial dimensions of the red kidney bean seed at different moisture contents are presented in table 1. all three axial dimensions namely length, width and thickness increased with increase in moisture content. the average diameters also increased with increase moisture content as axial dimensions. the arithmetic and geometric mean diameter ranged from 8.6 to 10.284 mm and 8.3 to 9.137 mm as the moisture content increased from 6.84 to 15.74% db, respectively. the values of dimensions of a single red kidney bean were higher than those for lentils, cotton seeds, sweet corn and pea, respectively. http://www.azojete.com.ng/ mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):129-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 134 table 1: axial dimensions of red kidney bean seed at different moisture contents 3.2 sphericity the variation of sphericity of red kidney beans with moisture content is presented in figure 2. the figure shows that the sphericity of the seed increased logarithmically from 0.546 to 0.689 as the moisture content increased from 6.84% to 15.74% (db). the relationship existing between sphericity and moisture content can be expressed with equation (9): 𝜑 = 42.387 + 9.572ln (m), r2 = 0.9721 (9) where 𝜑 = sphericity. the sphericity of red kidney bean shows that the seed is not perfectly spheroidal in shape. figure 2: effect of moisture content on sphericity of red kidney beans 3.3 one thousand seed weight the variation of one thousand seed weight (m1000) is presented in figure 3. from the figure, it can be seen that the m1000 of red kidney beans increased linearly from 3.3 to 4.1 kg when the moisture content increased from 6.84 – 15.74 % d.b. increase of 47.3% in the one thousand grain mass was recorded within the above moisture range. the relationship between one thousand seed weight and moisture content can be represented with the following regression equation: m1000 = 2.8059 +0.0885m, r2 = 0.9325 (10) 59 60 61 62 63 64 65 66 67 68 69 70 5 7 9 11 13 15 17 sp h e ri ci ty , % moisture content, % db moisture content d.b% axial dimension (mm) average dimension (mm) length, l width, w thickness, t arithmetic mean, da geometric, mean, dg 6.84 11.4 6.2 4.3 8.6 8.3 7.5 11.5 6.5 4.5 8.9 8.2 10 16.75 8.64 4.96 10.12 8.93 12 16.45 8.44 5.21 10.2 9.01 15.74 16.83 8.87 5.16 10.29 9.14 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nddyaviara@yahoo.com aviara and ma’aji: effect of moisture content on some physical properties of red kidney bean (phaseolus vulgaris l.) seed grown in north eastern nigeria. azojete, 19(1):129-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 135 where: m1000 = one thousand seed weight (kg), m = moisture content (% db), r2 = coefficient of determination. red kidney bean has a relatively big grain size, compared with other commonly grown legume crops. figure 3: effect of moisture content on one thousand seed weight of red kidney beans 3.4 surface area of seeds the variation of the surface area of red kidney with moisture content, % db of bean grains, is shown in figure 4. surface area of the bean grains increased linearly from 7.4-7.7mm² in the moisture range of 6.84-15.74 (d.b). the regression equation that adequately expressed the relationship existing between surface area and seed grain moisture content is presented as equation (11). as = 7.1942 + 0.0322m, r2= 0.9922 (11) where: as = seed surface area (cm2). figure 4: effect of moisture content on surface area of red kidney beans 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 5 7 9 11 13 15 17 o n e t h o u sa n d s e e d w e ig h t, k g moisture content, % db 7.35 7.4 7.45 7.5 7.55 7.6 7.65 7.7 7.75 5 7 9 11 13 15 17 su rf ac e a re a, c m 2 moisture content, % db http://www.azojete.com.ng/ mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):129-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 136 3.5 bulk density the bulk density of red kidney beans decreased from 679.14 to 563.04 kg/m³ when the moisture content increased from 6.84-15.74% db, (figure 5). the decrease in bulk density with increase in moisture contents indicates that the increase in volume due to moisture gain in the sample is greater than the accompanying increase in the mass of the bulk seeds. bulk density (ρb) was found to decrease linearly with the moisture content and the relationship existing between them was represented by equation (12). ρb = 775 12.592m, r2= 0.9699 (12) where: ρb = bulk density (kg/m3). figure 5: effect of moisture content on bulk density of red kidney beans 3.6. true density the variation of true density with moisture content is presented in figure 6. true density increased from 1128-1290 kg/m3 as the moisture content of red kidney bean seed increased from 6.84-15.74% (db). the increase of true density with increase in moisture content may have been due to higher rate of increase of mass of the individual seed than the rate of increase of the volume. the relationship between true density and moisture content was found linear and can be represented by the following regression equation. ρt = 1042.8 + 15.703m, r2 = 0.9879 (13) where: ρt = true density (kg/m3) figure 6: effect of moisture content on true density of red kidney beans 500 550 600 650 700 5 10 15 20 b u lk d e n si ty , k g/ m 3 moisture content, % db 1100 1150 1200 1250 1300 5 7 9 11 13 15 17 tr u e d e n si ty , k g/ m 3 moisture content, % db file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nddyaviara@yahoo.com aviara and ma’aji: effect of moisture content on some physical properties of red kidney bean (phaseolus vulgaris l.) seed grown in north eastern nigeria. azojete, 19(1):129-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 137 3.7 porosity porosity was evaluated using mean values of bulk density and true density of red kidney beans and found to increase with increase in moisture content, as shown in figure 7. from the figure, porosity was found to increase linearly from 39.79 to 56.38 % in the moisture range of 6.8415.74% (db). the relationship between porosity and moisture content could be adequately expressed with equation (14). ɛ = 28.113+1.8824m, r2 = 0.9279 (14) where: ɛ = porosity (%). figure 7: effect of moisture content on porosity of red kidney beans 3.8 angle of repose the variation of angle of repose of red kidney bean seed with moisture content is shown in figure 8. from this figure, it was observed that the angle of repose increased from 25.1 to 29.4o as the moisture content increased from 6.84 to 15.74% (db). the increase in angle of repose with moisture content was found to be polynomial of the second order. the relationship existing between angle of repose and moisture content can be expressed using the equation (15). θ = 14.512 + 1.9628m – 0.0647m2, r2 = 0.9825 (15) where θ = angle of repose (degree). figure 8: effect of moisture content on angle of repose of red kidney beans 30 35 40 45 50 55 60 5 7 9 11 13 15 17 p o ro si ty , % moisture content, % db 24 25 26 27 28 29 30 5 7 9 11 13 15 17 a n gl e o f re p o se , d e gr e e moisture content, % db http://www.azojete.com.ng/ mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):129-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 138 3.9 static coefficient of friction the static coefficient of friction of red kidney bean seed obtained experimentally at different moisture contents in the range of 6.84– 15.74% (db) on four structural surfaces are presented in figure 9. the figure shows that the static coefficient of friction of red kidney beans increased with increase in moisture content and varied according to the surface. static coefficient of friction was maximized on hessian bag material (0.403-0.530) followed by plywood with wood grain perpendicular to the direction of movement (0.390-0.540), followed by plywood with wood grain parallel to the direction of movement (0.341-0.500) and was minimum on fibre glass (0.295-0.400). the relationship existing between static coefficient of friction and moisture content was found to be logarithmic on all the structural surfaces employed and it can be expressed for the different structural surfaces using equations (16) to (19), respectively. µh = 0.0889 + 0.1695ln(m), r2 = 0.9754 (16) µpp = 0.0634 + 0.1713ln(m), r2 = 0.9841 (17) µpl = 0.0041 + 0.17744ln(m), r2 = 0.9731 (18) µfg = 0.0872 + 0.1138ln(m), r2 = 0.9557 (19) where: µh is the static coefficient of friction of red kidney beans on hessian bag material, µpp is coefficient of static friction on plywood with wood grains perpendicular to the direction of movement, µpl is coefficient on plywood with wood grains parallel to the direction of movement, and µfg is coefficient on fiber glass. this property is very useful in the design of silos, bins, and storage container for seeds. figure 9: effect of moisture content on static coefficient of friction of red kidney beans seed on different structural surfaces 3.10 kinetic coefficient of friction the variation of kinetic coefficient of friction of red kidney beans with moisture content on four structural surfaces is presented in figure 10. the kinetic coefficient of friction increased linearly with increase in moisture content in the range of 6.84 – 15.74% (db). it is observed that the kinetic coefficient of friction was highest against hessian bag (0.599-0.651) followed by plywood with wood grains perpendicular to the direction of movement (0.50-0.526) then plywood with wood grains parallel to the direction of movement and lowest on fibre glass (0.201-0.422). the relationships existing between the kinetic coefficient of friction and moisture content of the seed on hessian bag material, plywood with wood grains perpendicular to the direction of movement and plywood with wood grains parallel to the direction of movement were linear, 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 5 10 15 20 st at ic c o e ff ic ie n t o f fr ic ti o n moisture content, % db hessian bag matls ply wood with grains perpendicular plywood with grains parallel file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nddyaviara@yahoo.com aviara and ma’aji: effect of moisture content on some physical properties of red kidney bean (phaseolus vulgaris l.) seed grown in north eastern nigeria. azojete, 19(1):129-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 139 while the relationship on fiber glass was a polynomial of the second order. these relationships were expressed using the regression equations (20) to (23). λh = 0.5671 + 0.0053m, r2 = 0.9697 (20) λpp = 0.4953 + 0.0017m, r2 = 0.7509 (21) λpl = 0.3671 + 0.0138m, r2 = 0.9918 (22) λfg = -0.4621+ 0.1376m – 0.0052m2, r2 = 0.99 (23) where: λ is kinetic coefficient of friction. the kinetic coefficient of friction is needed before the power requirement for continued flow of granular or unconsolidated materials can be estimated. figure 10: effect of moisture content of kinetic coefficient of friction of red kidney bean seed on different structural surfaces 4. conclusions the physical properties of red kidney bean seed determined at five moisture levels yielded important data that will be useful in machine designs for planting, processing, packaging and storing of the products and showed significant differences at all moisture levels. in the moisture range of 6.84 15.74% (d.b) for red kidney seeds, the investigations on the physical properties revealed the following; (i) the major (length), intermediate (width) and minor (thickness) dimensions of the seed increased from 11.4 16.83, 6.2 8.87 and 4.3 5.16 mm, respectively. arithmetic and geometric diameters increased from 8.6-10.29 mm and from 8.3-9.14 mm, respectively. (ii) sphericity increased with increase in moisture content from 0.601 to 0.684. (iii) one thousand seed weight increased from 3.3 4.22 kg. (iv) true density increased from 1129-1290 kg/m3, while bulk density decreased from 679.14 – 563.04 kg/m3. (v) surface area and porosity increased from 7.4 – 7.7 cm2, and from 39.8-56.7%, respectively. (vi) angle of response increased from 25.1 29.44 and both static and kinetic coefficients of friction increased linearly with moisture content and varied with structural surface. references 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 5 10 15 20 k in e ti c co e ff ic ie n t o f fr ic ti o n moisture content, % db hessian bag matl plywood with grain perpendicular plywood with grains parallel fiber glass http://www.azojete.com.ng/ mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):129-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nddyaviara@yahoo.com 140 aviara, na., gwandzang, mi. and haque, ma. 1999. physical properties of guna seeds. journal of agricultural engineering research, 73:105-111. aviara, na., ibrahim, eb. and onuoha, ln. 2014. physical properties of brachystegia eurycoma as affected by moisture content. international journal of agricultural and biological engineering, 7(1): 84-93. aviara, na., kawuyo, ua. and okolo, dc. 2017. physical properties of two acha varieties as a function of moisture content. arid zone journal of engineering, technology and environment, 13(5): 555-566. aviara, na., oluwole, fa. and haque, ma. 2005. effect of moisture content on some physical properties of sheanut (butyrospernum paradoxum). international agrophysics, 19:193-198. aviara, na., pwanzadom, p. and abbas, t. 2013. moisture dependent physical properties of moringa oleifera seed relevant in bulk handling and mechanical processing. industrial crops and products, 42(1): 96-104. dutta, sk., nema, vk. and bhadwaj, rk. (1988). physical properties of gram. journal of agricultural engineering research, 39: 269-275. joshi, dc., das, sk. and mukherjee, rk. 1993. physical properties of pumpkin seed. journal of agricultural engineering research, 54:219-229. mohsenin, nn. 1986. physical properties of plant and animal materials, 2nd ed. gordon and breach science publishers, new york, pp 889. ndukwu, mc. 2009. determination of selected physical properties of brachystegia eurycoma seeds. research in agricultural engineering, 55(4): 1-7. singh, y. and chandra, s. 2014. evaluation of physical properties of kidney beans (phaseolus vulgaris). food science research journal, 5: 125-129. 10.15740/has/fsrj/5.2/125-129. singh, y. and chandra, s. 2020. study to assess physical properties of different types of kidney beans (phaseolus vulgaris). journal of pharmacognosy and phytochemistry, 9(2): 2455-2459. sneh, p., sanju, bd., kawaljit, ss., maninder, k. and sukhvinder, sp. 2020. kidney bean (phaseolus vulgaris) starch: a review. legume science, 2020: e52. https://doi.org/10.1002/leg3.52 mundi, s. 2012. structural and functional characterization of red kidney bean (phaseolus vulgaris) proteins and enzymatic protein hydrolysates, food and nutritional sciences university of manitoba winnipeg, manitoba canada susan, f. 2016. a complete course in canning and related process. a volume in woodhead publishing series in food science, technology and nutrition, (3): 512-540 zewdu, a. and solomon, w. 2008. moisture dependent physical properties of grass pea (lathyrus sativus l.) seeds. agricultural engineering international. the cigr ejournal. manuscript fp 06 027. vol. x file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nddyaviara@yahoo.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):25-44 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 25 effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria e. nwaokolo and a. gbenga-ilori* department of electrical and electronics engineering, university of lagos, akoka, lagos, nigeria *corresponding author's email address: gbengailori@unilag.edu.ng article information submitted 18 sept., 2023 revised 15 december, 2023 accepted 3 january, 2024 keywords: attenuation reflection test building loss propagation dielectric properties abstract dielectric properties determine how buildings attenuate communication signals. it is therefore an important factor in the propagation of signals. while building loss is an important parameter in link planning, it is often poorly characterized, and the data relating to the effect of building materials on propagation is either unavailable or poorly represented. in this paper, scattering parameters of typical urban buildings in nigeria are measured to determine signal penetration loss for the frequency range of 800mhz to 3.2ghz. building materials tested include reinforced concrete slabs, hollow sandcrete blocks, and prefabricated reinforced concrete slabs. the finishing of these materials ranged from burn bricks, rough paint, smooth paint, smooth wall tiles, smooth glassy tiles, to hardwood. the measurements were carried out using the oblique free-space measurement method. the dielectric properties of tested building materials were derived using the new noniterative conversion method. model equations that can predict scattering parameters and dielectric properties of a building given the test frequency and thickness of the building were also derived. comparative analysis of the derived model with actual measurements showed an rmse value ranging from 0.0192 to 0.2188. results showed that the frequency of propagation, the thickness of the material under test (building wall), and building finishing affect the dielectric properties and contribute to the signal attenuation experienced in buildings. it was also seen that concrete structures had higher permittivity values hence they had difficulty with microwave signal penetration. sandcrete blocks are therefore recommended for building walls in urban areas. 1.0 introduction microwave communication is ubiquitous in our everyday lives. it is the backbone for mobile communication, wi-fi connectivity, and the internet of things (iot) (chen et al., 2023). good mobile communication service is dependent on numerous factors including the type of building material, path loss, and interference (huaman et al., 2020; oladimeji et al., 2022; gómez-pérez et al., 2017; akobundu and gbenga-ilori, 2019). in deploying mobile communication networks in nigeria, telecommunication companies rely on available data on signal path loss within the vicinity of deployment. in many cases, losses due to buildings are neglected. though many communication devices are mobile and can be used outdoors, with the advent of iot, there is an increasing number of communication devices used indoors hence the importance of capturing factors that lead to building losses in communication networks. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 26 a few researchers have considered the impact of buildings on different communication systems. in the work done by ferreira et al. (2017), the authors showed that the materials and dimensions used for building walls can result in the attenuation of microwave signals in radio wave communication. the authors analyzed building materials commonly used in southern europe. in the work of zhekov et al. (2018), authors studied the loss introduced into radio wave communication by multiple building structures like brick, cavity and solid concrete block, and plasterboard walls; tile and slate roofs; and ten types of modern windows. the uk office of communications, in rudd et al. (2014), studied the impact of increased use of energy-efficient construction practices on building entry loss in communication systems. this study measured the building losses of several properties with a range of different construction materials in the uk, including foil-backed plasterboard and metallized double glazing. asp et al. (2014) examined increased levels of outdoor-indoor attenuation in modern energy-efficient buildings and their impact on mobile cellular networks. comparative studies of attenuation from such buildings and older buildings were done. the paper also evaluated the use of a dedicated aperture installed in building materials for achieving increased indoor signal coverage. in reducing the impact of building materials on signal loss in communications systems, authors have considered different solutions. zhang and lim (2020) used the uniform theory of diffraction (utd) where buildings are considered to be flat-surfaced and the ray tracing method was utilized to include diffraction effects on buildings. ng et al. (2022) presented an empirical analysis of the em wave propagation through composite building materials. the study proposed the use of composite building materials enhanced with different volumetric fractions of iron (iii) oxide (fe2o3) inclusions as a reddish‐brown colouring admixture in modern‐day concrete, as a means of improving signal penetration in buildings. in most of the literature reviewed, empirical analyses were done on foreign buildings and there is a need to test local nigerian building materials to have accurate data on the level of attenuation. danladi et al. (2015) investigated gsm signal strength variation in and around mud buildings with rusted corrugated iron sheet roof materials mostly used in the rural areas of nigeria. their results showed that the indoor rss was lower than that of the outdoor consequently contributing to the attenuation of gsm signals. elechi et al. (2018) and elechi and otasowie (2015) took measurements of gsm signal strength in buildings made of mud, sandcrete, and alucoboard to determine the signal penetration loss. the measurement results indicated that the building with alucoboard wall cladding had the maximum signal penetration loss, while the sandcrete buildings with unrusted corrugated iron sheet roofs had the minimum signal penetration loss. in this paper, authors considered reinforced concrete slabs, hollow sandcrete blocks, and prefabricated reinforced concrete slabs materials commonly used in buildings located in urban areas of nigeria. the finishing of these materials ranged from burn bricks, rough paint, smooth paint, smooth wall tiles, smooth glassy tiles, and hardwood. the goal was to conduct a reflection test which can be used to determine the scattering parameters (s-parameters) of buildings in the microwave frequency range of 800mhz to 3.2ghz and use these results to compute the dielectric properties of the building materials tested in order to quantify the building losses experienced due to the attenuation of communication signals. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 27 1. materials and method this work aimed to determine the dielectric properties of typical buildings in urban areas of nigeria and use these parameters to estimate microwave signal attenuation losses from these buildings. to achieve this, reflection test measurements were first conducted to derive the sparameters using the free space method (fsm), and the data obtained was used to compute the dielectric properties and attenuation losses of the buildings considered, and develop a predictive model using machine learning. the location of the fsm test was the main campus of the university of lagos, lagos, nigeria, as the area provided access to several building materials commonly used in urban areas in the country. 1.1 materials the materials used for the fsm measurement set-up were mainly the vector network analyzer (vna), antennas, and transmission line as shown in figure 1. the transmit and receive antennas had to be in far field of each other and the material under test (mut). the space between these two antennas can be considered as a two-port network whose behavior is characterized by s-parameters which are used to extract the dielectric properties of buildings. figure 1: fsm measurement set-up the mut tested were selected by examining the buildings to find out typical walls that satisfy the following requirements: 1) mut contains the same construction material throughout the test plane, 2) distance between the wall and the closest obstacle put the test antennas in far field of the mut, and 3) mut has a completely flat wall surface, with no curves or undulations. the building material under test and for which the measurements were done have dielectric properties. the buildings used were categorized based on age and composite material for erecting the building. for reinforced concrete structures, a structure of 50 years postcompletion is considered old but for sandcrete hollow-block structure, a 35-year postcompletion structure is considered old according to the nigerian building code (nbc, 2006). the major building materials used for the structures on the campus of the university of lagos are reinforced concrete slabs and hollow sandcrete blocks. port 1 port 2 receive antenna transmit antenna transmission line http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 28 1.2 free space method (fsm) measurement the free space method (fsm) (sivakumar et al., 2022) was used to carry out the reflection tests used to determine the s-parameters. the type of fsm used was the oblique angle system in which both transmitting and receiving antennas were at oblique angles to the measuring plane (shi et al., 2019). the fsm method is most suitable when the mut has a high temperature, cannot be destroyed under test, has a large flat solid plane, and is large enough to contain the entire beam width of the antenna. in the oblique incidence method, the propagating antenna and receiving antenna are both on the same plane, equidistant from the mut, and are inclined to the mut at an oblique angle. for this measurement, the wave emanating from the transmit antenna was incident on the mut and reflected to the receiving antenna which was inclined at an angle equal to that of the transmit antenna and was equidistant from the centre of the mut as was the transmit antenna. using this method, the scattering parameters, forward reflection coefficient (𝑆11) and forward transmission coefficient (𝑆21), were obtained after testing each mut considered. figure 2 describes the step used for the fsm test. figure 2: fsm test and measurement steps the far-field distance between the transmit and receive antennas is determined using equation (1) (guo et al., 2019): input test frequency range and number of points compute the theoretical angle of inclination of the antenna set-up and start the vna position the antennas at mut and use laser-light on the antennas to ensure they align with the mid-point of test width on the wall take measurements (ensuring far-field criteria is met) and mark positions for the antennas calibrate the vna with the calibration kit measure s-parameters and save data to the vna’s memory more test locations? save result file for further analysis stop move to next location yes no file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 29 𝑑 > 2𝐷2𝑓 𝐶 (1) where 𝑑 is the distance between the antenna and mut in metres, 𝐷 represents the largest dimension of the antenna plane perpendicular to the direction of radiated waves in metres, c is the speed of light which is 3.0 × 108 𝑚/𝑠, and 𝑓 is the test frequency used for the measurement which was between 800 𝑀𝐻𝑧 and 3.2 𝐺𝐻𝑧. given that the dimension of the antenna 𝐷 used in this work was 287.4 𝑚𝑚, the far-field distance d was computed for the 800 𝑀𝐻𝑧 and 3.2 𝐺𝐻𝑧 frequencies as shown in equations (2) and (3) respectively: 𝑑 > 0.4405 𝑚, (800 mhz) (2) 𝑑 > 1.7621 𝑚, (3.2 ghz) (3) the antennas were mounted on a moveable wooden pole and positioned perpendicular to the base. the base was fabricated with a knife-edge ending to allow measurements at an angular inclination of the antennas. as stated earlier, the materials under test (mut) were either reinforced concrete or sandcrete hollow blocks. in total, eighteen (18) locations were used in ten (10) buildings for our measurements and these buildings were labelled b1 to b10. the building tests were also conducted indoors and outdoors. five buildings made out of sandcrete hollow blocks were used as mut and tested in nine (9) locations consisting of indoor and outdoor. the buildings were labelled b3 (point 1) and (point 2), b4, b7, b8, and b9. the average age of the sandcrete block buildings tested was 11 years old and therefore classified as new buildings according to the nigerian building code (nbc, 2006). two outdoor tests were carried out on building b3. no indoor tests were carried out because no suitable mut was found for the test. the mut at b3 point 1 (pt. 1) was a smooth painted wall while the mut at b3 point 2 (pt. 2) had smooth wall tiles as the finishing. two tests were carried out on building b4, and they were done both indoors and outdoors. the building had a smooth-painted wall finish. one outdoor test was carried out on building b7. the building had a smooth-painted wall finish. two tests were carried out on building b8, conducted both indoors and outdoors. the outdoor wall of the building used as the mut had burnt-brick tiles as the finishing while the indoor mut had a smooth-painted wall finishing. two tests were carried out both indoor and outdoor on building b9. the building had a smooth-painted wall finish. five buildings made out of reinforced concrete structures were tested in nine (9) locations. the buildings were labelled b1, b2, b5, b6, and b10. the average age of the buildings tested was forty-nine (49) years old which classifies all of them as old buildings according to the nigerian building code (nbc, 2006). building b1 test location had a burned brick finish on it. the finishing material of building b2 was rough-painted walls. building b5 had smooth glassy wall tiles finish while building b6 had a rough wall paint finish for both indoor and outdoor. building b10 had a smooth-painted wall finish. the scattering parameters 𝑆11 and 𝑆21 determined from the process described in figure 2 were then used to determine the dielectric properties of the mut by subjecting the test result to the new non-iterative algorithm (luukkonen et al., 2011). this algorithm relies on a system of equations to compute the permeability and permittivity. these dielectric parameters were used http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 30 to determine the level to which the mut attenuates communication signals. the frequency used for the measurement test was in the range of 800mhz and 3.2ghz, since most telecommunication 3g, 4g, and wi-fi frequency signals are within this band. 2.3 computation of dielectric parameters of buildings the goal was to use the measured s11 and s21 parameters to determine the permittivity and permeability of the buildings using the new non-iterative method (kharkovsky, 2002). the parameters and steps needed for the new non-iterative method are shown in figure 3. figure 3: steps for the new non-iterative method (kharkovsky, 2002) equations (4) to (12) are the system of equations that make up the new non-iterative conversion model to convert our measured s parameters into dielectric properties of the mut. given the s parameters, a computational ratio p (kharkovsky, 2002) can be defined to simplify the process: 𝑃 = 𝑆11 2 − 𝑆21 2 + 1 2𝑆11 . (4) the reflection coefficient γ is: γ = 𝑃 ± √(𝑃2 − 1) , (5) while the transmission coefficient t is: 𝑇 = 𝑆11 + 𝑆21 − γ 1 − γ(𝑆11 + 𝑆21) . (6) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 31 a parameter λ can also be defined in terms of the transmission coefficient such that: 1 λ2 ∶= − ( 1 2𝜋𝑑′ 𝑙𝑛 ( 1 𝑇 )) 2 (7) where 𝑑′ is the thickness of the material being measured (kharkovsky, 2002). the wavelength of propagation in an empty cell 𝜆𝑜𝑔 in metres is: 𝜆𝑜𝑔 = 1 √ 1 𝜆0 2 − 1 𝜆𝑐 2 (8) where 𝜆0 is the free-space wavelength in metres and 𝜆𝑐 is the cut-off wavelength in metres. the effective permeability of the material (h/m) is given as (kharkovsky, 2002): 𝜇𝑒𝑓𝑓 = 𝜆𝑜𝑔 λ ( 1 + γ 1 − γ ), (9) and the effective permittivity of the material (f/m) is given as: 휀𝑒𝑓𝑓 = 𝜆𝑜𝑔 λ ( 1 − γ 1 + γ ). (10) the permeability of the material (h/m) is (kharkovsky, 2002): 𝜇 = 𝜇𝑒𝑓𝑓 = 𝜆𝑜𝑔 λ ( 1 + γ 1 − γ ), (11) while the permittivity of the material (f/m) is given as: 휀 = ((1 − 𝜆0 2 𝜆𝑐 2 ) × 휀𝑒𝑓𝑓) + (( 𝜆0 2 𝜆𝑐 2 ) ÷ 𝜇𝑒𝑓𝑓). (12) matlab was used for the computation of the metrics used to determine the permittivity ( ), and permeability (  ) of the buildings measured. the attenuation constant for each test location was later computed from the dielectric parameters using equation (13), (pozar, 2011). the attenuation constant shows the degree to which a signal degrades as it traverses the building. 𝛼 = 𝜔√ 𝜇휀 2 {√1 + 𝜎2 𝜔2𝜇2 − 1} (13) where 𝛼 is the attenuation constant of the wave in nepers/metre as it propagates through a medium,  is the conductivity value of the mut in s/m, and  is the angular frequency of the em wave in rads/s. the loss tangent 𝛿 is given in equation (14): http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://en.wikipedia.org/wiki/loss_angle arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 32 tan 𝛿 = 휀" 휀′ = 𝜎 𝜔휀′ (14) where 휀" is the imaginary part of the permittivity which connotes how much energy radiated is dissipated by the material while 휀′ is the real part of the permittivity which connotes how much electric energy is absorbed or stored in the material. by comparing equations (13) and (14), the 𝛼 in nepers/m could be re-written as: 𝛼 = 𝜔√ 𝜇휀′ 2 {√1 + ( 휀" 𝜇 ) 2 − 1} (15) the attenuation constant can also be written in db/m which is more relatable by using the conversion metric shown in equation (16): 𝛼 (𝑑𝐵/𝑚) = 8.86 × 𝛼 (𝑁𝑒𝑝𝑒𝑟𝑠/𝑚). (16) the attenuation factor in this work was measured for 1800mhz and 2600 mhz as these were the frequencies used by network operators in all locations tested. 2.4 predictive model a predictive model was developed in this paper with machine learning using linear regression techniques to achieve two main objectives: to • establish a statistical relationship between the input and output variables to obtain a general characteristic equation with minimal error values using measurements taken, and • predict new observations with minimal errors using the equation set that makes up the model. the model was developed using python to simulate the linear regression techniques shown in equation (17): 𝑧𝑗 = 𝛽0 + 𝛽1𝜔𝑗 + 𝛽2𝜂𝑗 + 𝑒𝑗 (17) where jz is the dependent variable, 𝜔 and 𝜂 are the independent variables, 0 is the constant or intercept, 1 is the slope or coefficient of  , 2 is the slope or coefficient of  , e is the error term, and j is numbers 1,2,3,4…n. the python libraries imported to develop the model include numpy, cmath, pandas, and matplotlib. equation (18) shows that the dependent variable has both the real and imaginary parts: 𝑧𝑗 = 𝑥𝑗 + 𝑖𝑦𝑗 (18) where x and y are the values of the complex numbers of the dependent variable 𝑧𝑗 . therefore 0 0 0 1 1 1 2 2 2 i i i        = + = + = + (19) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 33 to minimize the errors in equation (17), the minimization problem in equation (20) is solved: 𝑎𝑟𝑔 𝑚𝑖𝑛 𝛽0, 𝛽1, 𝛽2 ∑ ‖𝑧𝑗 − (�̂�𝑜 + �̂�1𝜔𝑗 + 𝛽2𝜂𝑗)‖ 2𝑛 𝑗=1 = 𝑎𝑟𝑔 𝑚𝑖𝑛 𝛽0, 𝛽1, 𝛽2 ∑ (𝑧�̅� − (�̂�𝑜 ̅̅ ̅ + �̂�1 ̅̅ ̅𝜔𝑗 + 𝛽2𝜂𝑗))𝑛 𝑗=1 (𝑧𝑗 − (𝛽0 + 𝛽1𝜔𝑗 + 𝛽2𝜂𝑗)) (20) equation (20) is principally used to perform the regression on the model using the uploaded dataset. comparing equations (17) and (20), the value of error can be minimized and 0 1 2, ,    can be obtained as they are the parameters for which the error values are minimum. ‖𝑧‖2 = 𝑧𝑧̅ (21) �̂� = (𝑋∗𝑋)−1𝑋∗𝑧 (22) 𝑋∗ = �̅�𝑇 (23) the dataset was made up of mainly complex numbers. in organizing the data, the dataset was segmented into four parts: data from reinforced concrete blocks (indoor), data from reinforced concrete blocks (outdoor), data from sandcrete blocks (indoor), and data from sandcrete blocks (outdoor). the input variables were the thickness of mut, building type (concrete or sandcrete), and measurement environment (indoor or outdoor). the output variables were s11, s21,  , and  . the prepared model was trained using the dataset and  -values were computed to produce a general equation that can be used to make predictions. a general equation was obtained from the model which was used to accurately predict s11, s21,  , and  when input variables are provided. in preparing the model, the input parameters selected are the test frequency and the thickness of the wall or mut. hence equation (17) can be rewritten as equation (24): 𝑧𝑗 = 𝛽0 + 𝛽1𝑓𝑟𝑒𝑞𝑗 + 𝛽2𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠𝑗 + 𝑒𝑗 (24) by training the model, the best values for 0 , 1 , 2 , and e were obtained to give a general equation for making output predictions. sixteen sets of values 0 , 1 , 2 , and the error e were obtained and were used to predict the corresponding output value: �̂� = [𝛽0 𝛽1𝛽2]𝑇[1 𝜔 𝜂] (25) where  represents the test frequency and  represents the thickness of the mut. the system of 16 equations constitutes the model and can be used to predict the s11, s21,  , and  values of a mut which could be made of concrete or sandcrete blocks, and could be an outdoor or indoor mut. to quantify the deviation of the predicted value from the actual measured value, the root mean square error (rmse) computation was done using equation (26). rmse values were computed for each of the 16 characteristic equations and this produced 16-rmse values. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 34 𝑅𝑀𝑆𝐸 = √∑ |𝑧𝑖|2𝑁 𝑖=1 𝑁 (26) in testing the suitability of the model, the rmse values were normalized using equation (27). 𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 𝑅𝑀𝑆𝐸 = 𝑅𝑀𝑆𝐸 max 𝑣𝑎𝑙𝑢𝑒 − min 𝑣𝑎𝑙𝑢𝑒 (27) where the max value is the highest value of the dataset, and the min value is the lowest value of the dataset. some of the max value and min value used for rmse normalization were complex numbers, hence equation (28) was used to obtain the absolute values. 𝑧 = 𝑥 + 𝑦𝑖 (28) |𝑧| = √(𝑥 + 𝑦𝑖)(𝑥 − 𝑦𝑖) (29) when data is normalized it ranges from 0 to 1. the closer the normalized data is to zero, the better the model is at making accurate predictions. 3. results and discussion this section presents the results and analysis of the models used. as stated earlier, the materials under test (mut) were either reinforced concrete or sandcrete hollow blocks. in total, eighteen (18) locations were used in our measurements and these muts were labelled b1 to b10. figures 4, 5, 6 and 7 show the dielectric properties measured outdoors for all the buildings while figures 8, 9, 10 and 11 show the dielectric properties measured indoors for all the buildings. figure 4: dielectric plots for buildings outdoor permittivity real (_′) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 35 figure 5: dielectric plots for buildings outdoor permeability real (_′) figure 6: dielectric plots for buildings – outdoor permittivity img (_′′) figure 7: dielectric plots for buildings – outdoor permeability img (_′′) http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 36 figure 8: dielectric plots for buildings – indoor permittivity real (휀′) figure 9: dielectric plots for buildings indoor permittivity img (휀′′) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 37 figure 10: dielectric plots for buildings indoor permeability real (𝜇′) figure 11: dielectric plots for buildings indoor permeability img (𝜇′′) 3.1 results for sandcrete block structures results for the five buildings made out of sandcrete hollow blocks tested in nine (9) locations are presented in this section. the buildings include b3 (point 1), b3 (point 2), b4, b7, b8, and b9. 3.1.1 building b3 -point 1 and point 2 (outdoor) results of the dielectric properties for building b3 show a difference between the permittivity value range of 3.0245 – 3.0377 for building b3 (pt. 1) and the permittivity value range of 3.1153 – 3.2428 for building b3 (pt. 2) as shown in figure 4. this was due to slight variations in the thickness of mut and the finishing of the buildings. the permittivity range for b3 (pt. 1) was between 3.0196 to 3.0377 and for b3 (pt. 2) between 3.11535 to 3.2428 as shown in figure 4, while permeability values for b3 (pt. 1) range is 1.0042 1.0231 and for b3 (pt. 2) is 1.0502 1.0387 as shown in figure 5. the loss tangents are shown in figures 6 and 7. with these permittivity and permeability results, the attenuation constants related to the use of microwave signal reception within this building were quantified in db/m for 1800 mhz and 2600mhz frequencies as shown in table 1. it can be deduced from table 1 that higher propagation frequencies experienced higher attenuation losses given the same mut. in building b3, microwave signals from telecommunication base transceiver stations (bts) experienced attenuation losses of between 3.2887 to 4.78 db/m depending on the propagation frequency used. table 1: computed building attenuation losses at b3 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) b3 point1 1800 3.0032 -1.7408i 1.0128 3.2887 2600 3.05001.6857i 1.0186 4.5279 b3 point2 1800 3.15751.7912i 1.0460 3.4142 2600 3.21381.7526i 1.0410 4.7800 http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 38 3.1.2 building b4 (outdoor and indoor) results for building b4 show that the outdoor permittivity value was between 3.1371 and 3.2711 as shown in figure 4, while the indoor permittivity value had a range of 3.0522 to 3.1921 as shown in figure 8. the main factor for the difference was the variation in the thickness of the outdoor and indoor walls. the attenuation constant which is an indication of the losses associated with the microwave communication in the building was computed and results are shown in table 2. in this building, microwave signals from telecommunication base transceiver stations (bts) experienced attenuation losses of between 3.3176 and 4.7056 db/m depending on the propagation frequency used. table 2: computed attenuation losses at b4 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 3.1868 1.7691i 1.0907 3.3176 2600 3.23271.7366i 1.0862 4.6504 indoor 1800 3.1085 1.7655i 1.0325 3.3608 2600 3.1618 1.7282i 1.0276 4.7056 3.1.3 building b7 (outdoor) one outdoor test was carried out on building b7. the permittivity value range for building b7 was between 3.2074 and 3.3093 as shown in figure 4. it was deduced that permittivity increases with frequency. table 3 shows that attenuation losses experienced in this building ranged between 3.4664 and 4.8888 db/m depending on the propagation frequency used. figures 4 to 7 show the dielectric properties for measurements taken outdoors. table 3: computed attenuation losses at b7 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 3.28081.8014i 1.0664 3.4664 2600 3.29601.7903i 1.0650 4.8888 3.1.4 building b8 (outdoor and indoor) two tests were carried out on this building, conducted both indoors and outdoors. it was noticed that the indoor test carried out produced the lowest measured permittivity value of 2.9344 as shown in figure 8. this was a result of the finishing and also the thickness of the wall which was also the smallest value measured at 0.1922 metres. the outdoor permittivity value ranged from 3.3883 to 3.4784 as shown in figure 4, while the indoor permittivity value ranged from 2.9344 to 3.0051 as shown in figure 8. the attenuation loss value range was between 2.6570 and 4.4824 db/m as shown in table 4. table 4: computed attenuation losses at b8 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) indoor 1800 2.9891 1.4569i 1.0817 2.6570 2600 2.9990 1.4346i 1.0864 3.6999 outdoor 1800 3.4573 1.7354i 1.2100 3.2170 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 39 2600 3.4700 1.7094i 1.2160 4.4824 3.1.5 building b9 (outdoor and indoor) results from tests on building b9 showed a difference between the outdoor permittivity value with a range of 3.1371 to 3.2711 as shown in figure 4 and the indoor permittivity value with a range of 3.0522 to 3.1921 as shown in figure 8. this was mainly due to variations in the thickness of the outdoor and indoor walls. the attenuation loss value range was between 2.8019 and 3.9828 db/m as shown in table 5. table 5: computed attenuation losses at b9 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) indoor 1800 3.2785 1.6196i 1.2533 2.8738 2600 3.3326 1.5697i 1.2473 3.9828 outdoor 1800 2.9776 1.4991i 1.0259 2.8019 2600 3.0416 1.4408i 1.0200 3.8621 from the results shown in tables 1 to 5, it can be concluded that the highest permittivity value of 3.47835 was recorded during the outdoor testing of building b8. this value was recorded as a result of two main factors; the thickness of the wall and the burn-brick tiles finishing which added to the measured permittivity value. the values of complex permittivity computed agree with published values (vilovic et al., 2008). there were some scenarios in which the computed values exceeded the known published values, and this was due to the difference in thickness of mut encountered in our testing over those used in published works, as well as the difference in finishing used in the buildings tested. the values of loss tangent computed and shown in figures 6,7, 10 and 11 agree with that of published scientific works. the loss tangent values were less than 1, and in a few scenarios, the values were close to 1. from computed dielectric values and attenuation constants, the sandcrete hollow block muts can be considered lossy dielectrics and will offer some opposition to communication signals due to the high level of attenuation. the range of the attenuation loss recorded was between 2.6570 db and 4.888 db depending on the microwave frequency. 3.2 results for concrete structures presentation of results for the five buildings made out of reinforced concrete structures are presented in this section. nine (9) locations were tested indoors and outdoors and these buildings were labelled b1, b2, b5, b6, and b10. 3.2.1 building b1 (outdoor) building b1 had only one test done outdoors. the permittivity value of the mut was determined to be between 5.682 and 5.8247 as shown in figure 4. the range of the attenuation loss was between 4.6912 and 6.4946 db/m as shown in table 6. this value connotes that communication signals would experience high losses as they penetrate the building walls. the thickness of the mut measured was 0.2465 m, a good part of the perimeter walls of the http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 40 building exceeds this value. a higher attenuation level was therefore experienced in some locations of the building. table 6: computed attenuation losses for b1 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 5.9613 + 1.8575i 1.1249 4.6912 2600 5.8927 + 1.8447i 1.1455 6.4946 3.2.2 building b2 (outdoor and indoor) for building b2, the difference between the permittivity value of 5.32511 measured outdoors and the value of 5.16218 measured indoors was not very significant as shown in figures 4 and 8, and this was a departure from the trend. this resulted due to a slight difference between the thickness of the outdoor wall (0.2535 m) and the thickness of the indoor wall (0.2015 m). furthermore, the rough-painted walls were the same and therefore presented almost the same test conditions in both scenarios. the attenuation loss value range was between 3.9939 and 6.1939 db/m as shown in table 7. table 7: computed attenuation losses for b2 3.2.3 building b5 (outdoor and indoor) the outdoor wall for building b5 had the thickest wall dimension of 0.2940 m among all the concrete walls measured and it also had a smooth glassy wall tiles finish. these factors combined to make the building produce the highest permittivity value of 6.85039 as shown in figure 4. the attenuation losses for both indoor and outdoor are shown in table 8. table 8: computed attenuation losses for b5 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 6.3265 + 2.3355i 1.3629 5.5204 2600 6.4588+ 2.2061i 1.3476 7.4969 indoor 1800 5.5919 + 1.8696i 1.2145 4.4012 2600 5.7009 + 1.7464i 1.2024 5.9027 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 5.5935 + 1.8754i 1.2915 4.2818 2600 5.5290 + 1.8652i 1.2081 6.1939 indoor 1800 5.1807 + 1.2801i 1.4387 3.9939 2600 5.2718+ 1.8878i 1.2219 6.0867 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 41 3.2.4 building b6 (outdoor and indoor) building b6 test location had a rough wall paint finish for both indoors and outdoors. the outdoor mut had a thickness of 0.2828 metres, a slightly higher value than that of b2 which was 0.2535 m. the permittivity value of the test location at a frequency of 800 mhz was 5.7545, a higher value than the 5.3281 obtained in the outdoor testing of building b2 at the same frequency as shown in figure 4. it was deduced that a slight increase in the thickness of mut can significantly influence the permittivity values. the attenuation losses computed at different propagation frequencies are shown in table 9. table 9: computed attenuation losses for b6 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 5.7266 + 2.1570i 1.2043 5.1603 2600 5.8366 + 2.0531i 1.1926 7.0503 indoor 1800 5.2927 + 1.7535i 1.2559 3.9492 2600 5.3180+ 1.7274i 1.2528 5.5245 3.2.5 building b10 (outdoor and indoor) results for building b10 showed a difference between the outdoor permittivity value ranging from 5.3613 to 5.4728 as shown in figure 4, and the indoor permittivity value ranging from 5.1630 to 5.2041 as shown in figure 8. this was due to variations in the thickness of the outdoor and indoor walls. the attenuation loss value ranged between 4.2189 and 5.6948 db/m as shown in table 10. these values connote that communication signals would experience high losses as they penetrate the building walls. table 10. computed attenuation losses for b10 test location propagation frequency (mhz) permittivity permeability attenuation constant (db/m) outdoor 1800 5.4360 + 1.9682i 1.3505 4.3321 2600 5.4353 + 1.8661i 1.3584 5.7942 indoor 1800 5.1249 + 1.8012i 1.1243 4.2189 2600 5.2308 + 1.6929i 1.1138 5.6948 in summary, the permeability values obtained when testing the concrete buildings ranged from 1.12044 to 1.689166 as shown in figure 10. permeability values should be as close as possible to 1, which is the approximate relative permeability of most non-metals. a few of the values obtained were between 1 and 2. this is a drawback of the new non-iterative method used for permittivity and permeability extraction. this method produces better permittivity results but introduces slight errors when computing permeability values. the method was however adopted since accuracy in permittivity values is paramount for this work. from the data obtained, the outdoor measurement of the b5 building yielded the highest permittivity value of 6.85039 due to wall thickness and building finishing. these values showed that a large amount of microwave energy can be absorbed and stored in the walls of the building tested. the values of the computed loss tangent agree with that of the published scientific work of stavrou et al. (2003). the loss tangent values obtained for reinforced concrete muts are significantly lesser http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 42 than the values obtained for the sandcrete buildings. it was deduced that the muts tested for reinforced concrete have more lossy dielectric properties and will offer more obstruction to communication signals than the sandcrete block buildings from the range of attenuation. in the above-mentioned buildings, the underlining building material used was reinforced concrete with high permittivity values of up to 6.85039. this connotes that the walls of the buildings absorb much of the signal. these buildings also have their internal walls made of reinforced concrete and this further attenuates communication signals. the use of repeaters can significantly improve the communication signal indices for these buildings (fata and aboulila, 2017). in addition, adopting 5g telecommunication can provide better indoor communication, since it has a more compact base station that can be deployed much closer to the indoor user equipment. figures 12 and 13 show plots comparing the predicted 𝑆21 and 휀 using the model described in this paper and actual measured values. analysis of the reliability of this model was carried out under error analysis. for each data set, errors between predicted and measured values were determined using the rmse. results show that the least rmse value was 0.00778376, and this was obtained from the prediction of the s21 parameters for indoor sandcrete hollow blocks. the highest rmse value was 0.218891, and it was obtained from the prediction of the permittivity for an outdoor reinforced concrete slab. to test the suitability of the model, the rmse values were normalized. the highest normalized value obtained for any wall type was 0.300973105. in general, the values obtained were closer to 0 than to 1, hence indicating that the predictive model was good and reliable. figure 12: plot of predicted and actual figure 13: plot of predicted and actual s_21 versus frequency complex permittivity versus frequency. 4. conclusion the study in this paper was undertaken to determine the microwave signal attenuation factor of common building materials in urban areas of nigeria. measurements of the s-parameters were first taken and the data obtained was used to compute the dielectric properties of the buildings after which a predictive model using machine learning was developed. the model was able to predict, with very minimal error, the permittivity, permeability, and s-parameters when known information such as test frequency, and underlining building materials was provided. the model produced a minimum rmse of 0.007784 when predicting the s11 values of indoor walls of sandcrete buildings, while it produced a maximum rmse value of 0.21889 when predicting the permeability of outdoor concrete walls. results from this work showed that the frequency, thickness of the mut (building wall), and building finishing impact the dielectric properties of the buildings. it was also observed that concrete structures produced higher file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nwaokolo and gbenga-ilori: effect of dielectric properties of building structural materials on attenuation of microwave signals in urban areas of nigeria. azojete, 20(1):25-44. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 43 permittivity values hence the mut shows decreased susceptibility to microwave signal penetration. though this work was limited to the microwave frequency band up to 3.2 ghz, future work can be directed at measuring a wider bandwidth of up to 40 ghz so as to accurately determine how the dielectric properties of the buildings would impact 5g communication. it is recommended that the use of sandcrete blocks for building walls should be encouraged as this offers improved dielectric properties and reduced attenuation of microwave signals. furthermore, when spaces are to be carved out from open areas, especially in buildings made from concrete, effort should be made to use materials with better dielectric properties like plywood, and pvc and reduce the use of materials like aluminium and glass which have higher permittivity values. references akobundu, gc. and gbenga-ilori, ao. 2019. gps anti-jamming technique using smart antenna systems. arid zone journal of engineering, technology and environment, 15(1): 1-16. asp, a., sydorov, y., keskikastari, m., valkama, m. and niemela, j. 2014. impact of modern construction materials on radio signal propagation: practical measurements and network planning aspects. in 2014 ieee 79th vehicular technology conference, 18th to 21st may 2014, seoul, korea., 79: 1-7. chen, w., lin, x., lee, j., toskala, a., sun, s., chiasserini, cf. and liu, l. 2023. 5g-advanced toward 6g: past, present, and future. ieee journal on selected areas in communications, 41(6): 1592-1619. danladi, ta., ahmed, m. and nyitamen, ds. 2015. investigation of building penetration loss for gsm signals into selected building structures in kaduna. iosr journal of electronics and communication engineering, 10(4): 56 60. elechi, p., edeko, f. and egwaile, j. 2018. relative permittivity based model for gsm signal loss in buildings. journal of electrical engineering, electronics, control and computer science, 4(2): 19-26. elechi, p. and otasowie, po. 2015. determination of gsm signal penetration loss in some selected buildings in rivers state, nigeria. nigerian journal of technology, 34(3): 609-615. fata, aa. and aboulila, mm. 2017. in-building solutions using distributed antenna system based on fractal array. in 2017 progress in electromagnetics research symposium spring (piers), 22nd to 25th may 2017, st. petersburg, russia., 984-987. ferreira, d., caldeirinha, rf., fernandes, tr. and cuinas, i. 2017. hollow clay brick wall propagation analysis and modified brick design for enhanced wi-fi coverage. ieee transactions on antennas and propagation, 66(1): 331-339. gómez-pérez, p., crego-garcía, m., cuiñas, i. and caldeirinha, rf. 2017. modeling and inferring the attenuation induced by vegetation barriers at 2g/3g/4g cellular bands using artificial neural networks. measurement, 98: 262-275. guo, qy. and wong, h. 2019. a millimeter-wave fabry–pérot cavity antenna using fresnel zone plate integrated prs. ieee transactions on antennas and propagation, 68(1): 564-568. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):25-44. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gbengailori@unilag.edu.ng 44 huaman, jr., postigo-malaga, m., yanyachi, p. and chilo, j. 2020. measurements of 3g and 4g signal attenuation in adobe buildings structures. in 2020 ieee international instrumentation and measurement technology conference (i2mtc), 30th june 2020, dubrovnik, croatia: 1-6. kharkovsky, sn., akay, mf., hasar, uc. and atis, cd. 2002. measurement and monitoring of microwave reflection and transmission properties of cement-based specimens. ieee transactions on instrumentation and measurement, 51(6): 1210-1218. luukkonen, o., maslovski, si. and tretyakov, sa. 2011. a stepwise nicolson–ross–weir based material parameter extraction method. ieee antennas and wireless propagation letters, 10: 1295-1298. nbc, 2006. national building code. fed. repub. niger. national building code, ministry of housing and urban development: 1 – 476. ng, jp., sum, yl., soong, bh., maier, m. and monteiro, pj. 2022. electromagnetic wave propagation through composite building materials in urban environments at mid‐band 5g frequencies. iet microwaves, antennas and propagation, 16(10): 627-638. oladimeji, tt., kumar, p. and oyie, no. 2022. propagation path loss prediction modelling in enclosed environments for 5g networks: a review. heliyon, 8(11): 1-16. pozar, dm. 2011. microwave engineering. hoboken, nj: john wiley & sons. rudd, r., craig, k., ganley, m. and hartless, r. 2014. building materials and propagation. office of communications (ofcom) final report. london, uk: 2604. shi, d., wang, c. and gao, y. 2019. a new permittivity measurement method for walls in indoor scenes. ieee transactions on antennas and propagation, 67(4): 2118-2129. sivakumar, r., lee, y., azemi, s.n., ahmad, z., soh, p. and you, k. 2022. a free space material measurement system for microwave materials at kuband. in 2022 ieee international rf and microwave conference (rfm), 19th – 21st, december 2022, kuala lumpur, malaysia: 1-4. stavrou, s. and saunders, sr. 2003, march. review of constitutive parameters of building materials. in twelfth international conference on antennas and propagation, 2003 (icap 2003). (conf. publ. no. 491), 31st march to 3rd april, 2003, exeter, uk: 211-215. vilovic, i., nad, r., sipus, z. and burum, n. 2008, september. a non-destructive approach for extracting the complex dielectric constant of the walls in building. in 2008 50th elmar international symposium, 10th to 12th september 2008, zadar, croatia, (2): 609-612. zhang, y. and lim, sy. 2020. an investigation into the diffraction effects of building façade for propagation modelling. progress in electromagnetics research, 97: 25-34. zhekov, ss., nazneen, z., franek, o. and pedersen, gf. 2018. measurement of attenuation by building structures in cellular network bands. ieee antennas and wireless propagation letters, 17(12): 2260-2263. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):865-870 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 865 chemical composition ananlysis of coconut shell powder and ash for composite reinforcement m. a. abba-aji, e. s. ameh and m. shuwa department of mechanical engineering, university of maiduguri, p.m.b 1069, maiduguri, nigeria *corresponding author's email address: birma4real2004@yahoo.com article information submitted 15 march, 2023 revised 9 oct, 2023 accepted 16 oct, 2023 keywords: composite reinforcement infra-red coconut shell powder abstract the use of natural resources which are environmentally friendly to replace the conventional composites materials had been the interest of many researchers lately. beside the use of natural fibres as reinforcement in polymer matrix composites, the use of fillers made from natural sources such as coconut shell, corn cobs, palm kernel shell, rice husk, has been confirmed to be potential material that can offer some good properties to satisfy the requirements needed for some engineering applications. in this study, the potential of coconut shell powder and coconut shell ash were investigated. fourier transform infra-red spectroscope was used to determine the chemical compositions of the samples. the results obtained revealed that coconut shell powder and coconut shell ash demonstrated comparable chemical properties to the conventional composites. the presence of some basic elements which are required to produce reinforcement materials with high strength, durability, light weight and corrosion resistance were confirmed. the results obtained revealed that coconut shell powder and coconut shell ash could be used as composites and other polymer matrix that are required for engineering applications 1.0 introduction coconut shell powder used for reinforcement consist of lignin and pentosanes. it has recently gained lots of attention and acceptance as composite reinforcement in a wide variety of applications in the aerospace, construction and manufacturing industries. recent investigations show that some special characteristics such as light weight, specific stiffness, strength, uniform quality, good resistance to water, resistance to heat and fungal attack and the ability to create new surface finish (obiukum et al., 2016). coconut shell powder are used in applications such as a filler in the manufacture of thermostat moulding powders like bakelite, synthetic resin glues or phenol formaldehyde, mosquito coils, incense sticks, plywood, laminating boards and as lost circulation materials in oil well drilling, (sumatilal and jigar, 2018). inadequate disposal of coconut shell after consumption of the fruit has tremendously aggravated the problem of solid waste management in nigeria. this menace constitutes serious health challenges to both human and the environment. harnessing the huge economic potential of coconut shell crop to obtain products such as coconut shell ash, coconut shell powder and activated charcoal which is highly essential in our mining, foundry and manufacturing industries has not been accorded full priority, hence there is the need for the continuous research on how best to harness this crop fully in order to eliminate or reduce the hazards associated with the present mode of its disposal. coconut shell powder is a form of reinforcement used in a wide variety of applications, such as solid woods for domestic uses, production of furniture, as partial replacement for cement in construction activities, (obiukkwu et al., 2016). coconut shell particles are also used in http://www.azojete.com.ng/ mailto:%20birma4real2004@yahoo.com mailto:%20birma4real2004@yahoo.com mailto:%20birma4real2004@yahoo.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):865-870. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 866 solving drilling problems in the oil industries, they are also used as active carbon which is considered extremely effective for the removal of impurities in waste water, as fillers to improve mechanical properties of composites, synthetic glues and for medicinal purposes, (salman, 2015).these among other uses have helped in reducing the indiscriminate disposal of the coconut shell after consumption of the fruit and the problem associated with its poor disposal. coconut shell powder which is usually sourced from local miller is a light brown material which has a bulk density of 0.7gcm-3 with varying thicknesses between 2-8mm and an approximate density value of 1.60g/cm3 (leman et al., 2017). coconut shell powder exhibits admirable properties such as low cost, renewable, high specific strength to weight ratio, low density, less abrasion to machine and it is environmentally friendly. 2. materials and methods 2.1 materials and equipment the materials used were un-carbonised coconut shell powder and coconut shell ash. the major equipment used in the study include; mallet, furnace and weigh balance. machineries such as the ftir spectrometer, hammer mill and automatic vibratory sieve were employed. 2.2. methods 2.2.1 crushing process the coconut shells was obtained from damaturu central market located at abasha ward in damaturu, local government area of yobe state, nigeria. it was broken into pieces using sledge hammer in the mechanical engineering department of federal polytechnic damaturu, yobe state and was later pounded in a local mortal to reduce the particle size. thereafter the broken pieces were grounded to powder with the aid of a hammer mill, and sieved using an automatic vibratory sieving machine with different mesh sizes to obtain a fine powdery product. in this study, three different samples of mesh sizes 0.45mm, 0.15mm and 0.9mm were collected and labelled respectively for the experimental analysis which was carried out at the multi-user laboratory of the chemistry department at ahmadu bello university zaria, nigeria to determine the chemical and elemental characteristics of the product with the aid of an infrared transform spectrometer. mallet was employed to reduce the sizes of the coconut shell into smaller pieces, before it was taken to the hammer mill shown in figure 1 for further crushing and grinding operation. this very important equipment was used to crush the coconut shell aggregates into suitable fine flour by repeated blows for use as specimen in the study. figure 1: hammer mill figure 2: automatic vibratory sieve file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abba-aji et al: chemical composition ananlysis of coconut shell powder and ash for composite reinforcement. azojete, 19(4):865870. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 867 2.2.2. sieving process. the coconut shell particles were sieved to obtain coconut shell powder with the aid of an automatic vibratory sieving machine. this process lasted for about 2 hours and the samples with the required particle sizes were collected and labelled according to the mesh size. the automatic vibratory was used to characterize the coconut shell powder into finely divided substance as required for this study.it consist of different meshes as shown in figure 2. this powder is usually obtained from coconut shell which is free from contamination. the coir pit is broken into small pieces and crushed with the aid of a hammer mill or as pounding machine and later fed into a pulverizing machine to produce a powdery substance. the powder obtained from the pulveriser are then fed into a cyclone and the parallel product is collected in a bag filter and subsequently fed into a vibrating sieving machine and packed according to mesh size requirements. 2.2.3. weighing process this process was carried out to obtain the required weight of the individual samples. 3 kg was used for this study to ensure uniformity. the three samples were labelled accordingly and later packaged in an airtight plastic container before it was taken to the laboratory for the test. the electric weigh balance that was used to weigh each of the sample sizes used for the study is shown below . figure 3: automatic weigh balance. 2.2.4. ash process the process used to obtain the ash was by burning coconut shells in an open domestic stove in an operation which lasted for 3 hours. the resultant ash product which was grey in colour was subsequently taken to the laboratory to also determine its chemical and elemental characteristics in order to compare its result with the result obtained from the result of the analysis done on the coconut shell powder. this equipment was used to burn the coconut shell in an open environment to obtain the ash which was used as the second specimen in this research work. (udhayasankar and karthikeyan, 2015) the sieves sizes ranged from 355-63μm. the coconut shell powders retained in the pan below 70μm, were used for the analysis, in line with the work of bello et al. (2015). http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):865-870. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 868 figure 4: local cooking stove figure 5: coconut shell ash 2.2.5. fourier transform infrared (ftir) test the ftir spectroscopy is an established technique for quality control when evaluating industrially manufactured material. a change in the characteristics pattern of absorption bands usually indicates a change in the composition of the material or the presence of contaminants. this technique is usually used for analysing the chemical composition of smaller particles, typically 10-50 microns. coconut shell is located in between the coconut flesh and coconut husk. this shell is naturally created to protect the inner part of the coconut. the coconut shells were broken into pieces and grounded into powdery form which was used as the first sample. coconut ash is a grey powdery substance which is usually obtained by burning coconut shell powder in a furnace which is regulated at a certain temperature. figure1 presents a sample of the coconut shell ash. the fourier transform infrared (ftir) spectrometer figure 6 is an instrument which acquires broadband near infra-red (nir) to far infra-red (fir) spectra. unlike dispersive instruments such as grating monochromatic or spectrograph, ftir spectrometers collect all wavelengths simultaneously. the ftir instruments send infrared radiation of about10, 000 to 10 cm-1 through a sample, with some radiation absorbed and some transmitted. the absorbed radiation is converted into rotational and or vibrational energy by sample molecules. the resulting signal at the detector presents as a spectrum, typically from 4000cm-1 to 400cm-1, representing a molecular fingerprint of the sample making the ftir analysis a great tool for chemical identification. (abdulkadir et al., 2016) figure 6: schematic diagram of ftir spectrometer f510 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com abba-aji et al: chemical composition ananlysis of coconut shell powder and ash for composite reinforcement. azojete, 19(4):865870. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 869 3. results and discussion 3.1 chemical composition of coconut shell powder table 1 presents the result chemical composition of coconut shell powder obtained from ftir test. table 1 chemical composition of coconut shell powder sn compound full name concentration 1 wax(g) 5 2 c carbon 11. 00% 3 k2o potassium oxide 1.36% 4 sio2 silicon dioxide 0.89% 5 cl chlorine 0.89% 6 fe2o3 iron(ii) oxide 0.45% 7 mgo magnesium oxide 0.42% 9 na2o sodium oxide 0.31% 10 cao calcium oxide 0.26% 11 moo3 molybdenum (vi) oxide 0.19% 12 s sulphur 0<lld 13 al aluminium 0<lld 14 p phosphorous 0<lld the result of the chemical composition of coconut shell powder obtained by concentration are, wax 5% this accounts for the reason why it is being used for maturing of coils, creams, air purifiers. the presence of 11% carbon and 0.89% silicon dioxide make coconut shell powder and coconut shell ash to offer significant stability in terms of insulation, thereby making it suitable for manufacturing of electronic chips and in the aerospace industries. potassium oxide at 1.36 % carbon, iron (ii) oxide 0.45%, magnesium oxide 0.42%, sodium oxide 0.31%, calcium oxide 0.26 %, molybdenum (vi) oxide 0.19%, sulphur and phosphorus having 0 concentration less than the lower level detection (lld). the composition of aluminium in this composition, (0<lld), accounts for good ductility, softness, corrosion resistance and high electrical conductivity of coconut shell powder and coconut shell ash made products such as foils and cables. potassium oxide equips csp with high thermal conductivity property making it suitable for glass, optic and ceramic production. the sodium oxide in csp makes it a suitable material that can replace conventional composites in the manufacture of ceramics because it makes csp to offer a great density to weight advantage. finally, the presence of sodium dioxide in csp makes it suitable for the partial replacement of cement in construction activities because it does not react with other composites material. 3.1.1 chemical composition of coconut shell ash the result of the ftir experiment conducted on coconut shell ash which was obtained by burning coconut shell in a local cooking stove to determine the composition is presented in table 2; table 2: chemical composition of coconut shell ash s/no 1 2 3 4 5 6 7 8 9 10 oxide content sio2 al 2o3 fe2o3 cao mgo mno na2o p2 o 5 k2o so3 percentage (%) 33.61 24.31 16.12 4.861 1.790 0.891 0.901 0.311 0.741 0.861 from the result presented in table 2, the coconut shell ash contains metals such as silica, potassium, zinc, calcium, and silicon iron which are crucial in order to mix with other materials to offer great thermal conductivity, excellent density to weight ratio, high resistance to corrosion, thermal stability, great flexural strength, durability, and the ease with which it can formed into complex shapes. these results are in agreement with the work of abba-aji et al. (2019). this has made it a potential material for most engineering applications such as additives, http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):865-870. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 870 filler, water purification, energy generation, activated carbon and as reinforcements and for fabrication of aluminium matrix composite for the automobile industry. 4. conclusion the analysis of the ftir experiment was successfully conducted on coconut shell powder and coconut shell ash. the chemical compositions of the coconut shell ash revealed the presence of sio2, al2o3 and cao. this offer some essential properties making it suitable for automobile and other engineering applications. coconut shell powder consists of sodium dioxide and other elements presented in the results making it suitable for reinforcement and other applications. from the results, it is clear that both coconut shell ash and powder could be used as composite materials. the development and use of this product has the potential to gradually replace the convectional composites which are fast depleting should it be given adequate attention. also, if these natural fibres are adequately utilized, it will help in reducing the problem of environmental pollution while increasing the market value of coconut waste from the study conducted on chemical composition of coconut shell powder and coconut shell ash using ftir method, the following are the recommendation. 1. adequate attention should be given to the utilization of coconut shell-based products and other agricultural based waste as this will open up new avenues for both academicians and industrialist to design a sustainable module for the future of natural fibres, 2. more studies should be carried on other natural fibres so as to explore further on the development of composite materials. references abba-aji ma., abu, jo., lawal, sa. and abubakre, ko. 2019. development of automobile piston from aluminium alloy and coconut shell ash as additive. nigeria journal of engineering science and technology research, 5(2): 72-79. abdulkadir, i., ubam s., salihum, aa. and almustapha, mn. 2016. a rapid method of crude oil analysis using ft-ir spectroscopy. nigerian journal of basic and applied sciences, 24 (1): 47-55. bello, sa., hassan, sb., agunsoye, jo., zebase, mg. and raheem, i a. 2015. synthesis of uncarbonised coconut shell nanoparticles: characterisation and particle size determination. tribology industry, 37(2): 257-263. leman, as., shahibab, s., senin, ms., shamsudeen, s., anak, na., moh’d, ss., kalid, fs., azshar, at. and razak, nh. 2017. durability of coconut shell powder (csp) concrete, iop series; journal of material science and engineering, remedy publications ltd, 27(1): 16-18. obiukum, oo., uchechukwu, mn. and nwaogwugwu, mc. 2016. study on the properties of coconut shell powder reinforced high density polyethylene composites; federal university of technology owerri multidisciplinary journal, futojnls publications, 2(2): 43-55. salman, z. 2015. energy potential of coconut biomass, the journal of physical chemistry, 63(6): 79-81. sumatilal, s. and jigar, m. 2018. a comprehensive review of coconut shell powder composite; preparation, processing and characterization, journal of thermoplastics composites and materials, 16(8): 48-51. udhayasankar, r. and karthikeyan, b. 2015. a review on coconut shell reinforced composites international journal of chemical technology and research, 8(11): 624-637. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com https://www.ajol.info/index.php/njbas arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):473-482 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 473 investigation of the properties of concrete made with flyash and dry waste okra powder y. rahmat1, a. s. abdulazeez2*, i. gambo3, i. audu4, a. a. isah5 1,3,4department of building, abubakar tafawa balewa university bauchi, nigeria 2department of building, university of abuja, fct, nigeria 5works and services department, federal college of education, okene, kogi state, nigeria *corresponding author's email address: deenlegit@gmail.com article information submitted 27 december, 2023 revised 13 february, 2024 accepted 25 february, 2024 keywords: chemical composition compressive strength density dry waste okra powder flexural strength fly-ash split tensile strength abstract concrete is the most utilized construction material globally, with the issues of global warming, overburden and over-dependence on cement leads to the research into alternative materials in the production of concrete, which would not only reduce the usage of cement but also improve the performance of concrete product. the research investigates the effect of fly ash (fa) and dry waste okra powder (dwop) on the strength performance of concrete. concrete mix of 1:2.43:2.85 with water cement ratio of 0.5 was used. 10% by weight of cement was replaced by fly-ash, and dry waste okra powder was added at 0.25% to 1% at 0.25% interval as admixture. the parameters investigated are, chemical composition, setting time, workability, chemical composition of fly-ash and dry waste okra powder, density, compressive strength, flexural strength and split tensile strength. the results showed that fly-ash is a good pozzolan with combined sio2, al2o3 and fe2o3 to equal 89.04%. the use of dry waste okra powder increases the setting time of cement/fa-dwop paste and also resulted in the increase in workability of the concrete as the percentage admixture increases. the result showed that fly-ash ash has a pozzolanic effect and dwop has an admixture effect on concrete properties by considering the strength activity index, higher compressive strength, higher flexural and splitting strength than control concrete for fly-ash blended admixture concrete at 0.5% and 0.75% up-to 1% admixture content. from this result, it can be concluded that fa as partial replacement material is a good pozzolanic material and dwop is suitable as admixture material in concrete production. 1.0 introduction concrete is the most utilized and acceptable construction material in the world. the concrete industry, due to its complexity, nature and sheer size, has a considerable impact on the environment. concrete itself is inherently environmentally friendly but materials used its production are not friendly due to process of sourcing and producing them, portland cement (pc) which is a major component in concrete production is not environmentally friendly. according to lappiatt and ahmad (2004) in agboola, (2020) that concrete industries throughout the world annually produces concrete around 12 billion tons and utilizes portland cement estimate around 1.6 billion tons. which means on an average, approximately 1 ton of concrete is produced each year for every human being in the world. there is a concern to the large usage of concrete and cement and there is need for more understanding on how to improve concrete properties. the amount of co2 produced from the usage of concrete is directly proportional to the amount of cement used in the concrete mix (agboola, et al., 2020). of all the pollutants in the cement manufacturing industry, co2 gas emission is the most http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):473-482. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 474 prevalent. according to mahasenan, et al. (2003) 900 kg of co2 is emitted for the manufacturing of every ton of cement. pc is under discussion currently, not only because it is cost intensive in application but also for its effect on environmental during manufacturing. the problems of pollution and other properties of concrete have led to research on cement alternative that will partially or completely replace cement in the construction industry (agboola, et al., 2021). the current trend is to reduce the amount of portland cement used in the production of concrete with supplementary cementitious material (scm) which is affordable and available to improve desirable properties of concrete. one of the best strategies to make the construction industry more compatible with the requirements of sustainable development would be to utilize concrete as much as possible, but with the least amount of portland cement in any way possible. one of such strategy is the usage of byproducts of industrial process that are classified as pozzolan which possesses excellent cementitious properties such as, fly ash, ground granulated blast furnace slag, and condensed silica fume. the other strategy to improve the environmental friendliness of the concrete industry is the large-scale utilization of waste products which are classified as pozzolan or supplementary cementitious material such as waste glass powder (agboola, et al., 2020); construction debris, waste papers, saw dust waste from wood, dredged material, recycled carpets, and tires. according to mohammad (2010) cement is one of the essential ingredients of concrete that both contributes to the construction industries and environmental problem. however, the production of cement emits carbon dioxide to the surroundings which result to environmental pollutions. the american society for testing and material (astm c125-06) defined pozzolan as a siliceous or siliceous-aluminous material, which in itself possesses little or no cementitious value but which will, in finely divided form and at normal temperature and in the presence of moisture chemically react with calcium hydroxide to form compounds that contain cementitious properties. pozzolan can be used to replace cement in concrete to improve strength and durability properties (agboola, et al., 2019). shetty (2009) pozzolan can be classified into two namely, natural or artificial pozzolan. natural pozzolans include clay and shales, opaline cherts, diatomaceous earth, volcanic ash and pumicites, artificial pozzolans include fly ash, blast furnace slag, silica fume, rice husk ash, and metakaolin. fly ash, as one of the classifications of artificial pozzolans, is not environmentally friendly, but economical and accessible. fly ash is a fine powder which is an industrial waste which a product of burning of coal in electric generation power plants. fly ash is a pozzolanic material that contains aluminous and siliceous materials that forms cement in the presence of water. fly ash forms a compound similar to cement in the presence of lime and water. fly ash can be classified as class f and class c according to astm c618 (gourav and reddy, 2014). according to yazici and sahan, (2012), fly ash is one of the potential materials in reducing the use of cement in construction as it possesses similar binding ability when blended with cement while containing little to no hazardous chemical substances, making it a more viable and environmentally friendly supplementary material. also, with the utilization of fly ash in concrete and with the requirements to boost the pozzolanic activity of fly ash in an attempt to improve the performance in concrete, okra waste powder was introduced into concrete mix. however, okra powder is an admixture which has a potential for improving the properties in concrete. as part of these efforts, karandikar et al. (2014) researched on aqueous okra powder and the result showed that the aqueous okra possessed ca2+ ions of cement paste which aid hydration rate in concrete. however, this led to the consideration of okra powder as an alternative to synthetic admixture. synthetic admixture contributes largely to the emission of toxic substance into the atmosphere, although can be used as additive to cement in concrete. asif, et al. (2019) conducted a study on aqueous okra with silica fume on concrete and found out that pectin which is a major compound present in okra extract showed more calcium than silica fume in file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rahmat et al: investigation of the properties of concrete made with fly-ash and dry waste okra powder. azojete, 20(2):473-482. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 475 concrete. it is on the premises that indigenous material such as okra plant, which is very cheap, it is abundant and readily available, it is encouraged not only for cooking purpose but also for other positive uses such as in concrete production. the okra plant is planted in many cities in nigeria. okra is a traditionally cultivated rain-fed crop which is sensitive to mild winters. little changes in weather affect the crops and this leads it to bioactive waste littered around, which is not utilize for any purpose but causes environment hazards. however, compared to the other parts of the world, the amount of fruitful works done on the use of bio-based admixtures in concrete productions in nigeria is limited. huge amounts of okra vegetable are wasted every year with little attention given to exploit its usage as a source of mineral admixture. this prompted the research to explore the locally available materials to improve on the performance of concrete in construction. concrete strength is majorly deemed to be one of the most important properties that need to be satisfied for any concrete. strength of concrete is the single property that is most valued by designers and quality control engineers which can be defined as the ability to resist stress without failure which manifest by the appearance of cracks. this study however, investigate the properties of concrete made with fly ash and dry waste okra powder. 2.0 materials and methods all materials used for the laboratory experiment were procured from the immediate environment. the relevant standards were used in the process of conducting the experiments. 2.1 materials the materials for the laboratory experiment included, coarse aggregate fine aggregate, cement, fly ash, dried waste okra powder (abelmoschus esculentus (l.)) and water. coarse aggregate was obtained from a quarry site within bauchi metropolis. the fine aggregate was obtained from yelwa river-flow in bauchi state. the ordinary portland cement is the brand of dangote of grade 42.5 which was procured from vendors within bauchi metropolis. the dried waste okra powder was obtained within bayara in bauchi local government area of bauchi state from local farmers. the particle sizes of fine aggregate were those passing through sieve with aperture size of 2.36 mm but retained on sieves of 150µm.it was confirmed to be free from dust and free from deleterious substances. the coarse aggregates used in this study were granite with particle size range between 5 mm and 20 mm. the dried waste okra powder (dwop) was milled to fine powder, and was stored in a cool place. portable water which was fresh, colorless, odorless and free of organic matter was used in these experiments. for the purpose of this investigation, a mix ratio of 1:2.43:2.85 by weight of cement, sand and gravel, and water cement ratio of 0.50 was used. the cement in the mix was partially replaced with fly ash at interval of 10%, and dried waste okra powder was added at 0.25%, 0.5%, 0.75% and 1%. the concrete with 0% pozzolanic replacement and admixture served as the control. 2.2 methods 2.2 chemical test on fly ash in order to determine the chemical constituents of fly-ash, samples were taken and subjected to analysis at ashaka cement factory in gombe state, nigeria. 2.3 setting times tests setting times tests the setting times (initial and final) were carried out in accordance with bs en 196-3 (1995), using the vicat probe and the vicat needle apparatus. the cement content of the paste was tested of 100% cement, then partially replaced at 10% fly-ash without admixture, and percentage dosage of dry waste okra powder (dwop) was added to 10%fa at 0.25%, 0.5%, 0.75%, 1%. the paste without pozzolana and dwop served as the control. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):473-482. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 476 2.3 strength activity index of cement the strength activity indices of cement-fly ash were evaluated according to astm c311. the control mortars were prepared according to the recipe provided in astm c311. cubes were prepared for compressive strength testing. for the mixture with the fly ash as partial cement replacement, test mixture was prepared with constant water and sand volume fraction, and a 20 % replacement by volume of cement with fly ash. the compressive strength test was carried out in accordance with astm c109. a 1:3 cement sand mix with water cement ratio of 0.5 was used to prepare 50 x 50 x 50mm prism specimens to determine the compressive strength of the cement mortar, cured at 7 and 28 days. 2.4 workability test the slump test was carried out in accordance with the provisions of bs en 12350: part 2 (2000). the replacement was done at 10% with fly-ash, other concrete mix include percentage dosage of dry waste okra powder was at 0%, 0.25%, 0.5%, 0.75%, 1% at 10% fly ash as cement replacement. the slurry sample without fa serves as the control. compacting factor test was conducted in accordance with (bs 1881-102, 1983). 2.5 density test this was carried out prior to crushing of the concrete specimen. at the end of each curing period, the concrete specimens were weighed using an electric weighing machine balance. density is calculated as mass of concrete specimen in (kg) divided by volume of concrete cube (m3) and expressed in kg/m3. 2.6 compressive strength cubes of size 100mm x 100mm x 100mm were cast for each mix and left in room temperature for 24 hours before demolding and cured in water until testing at 7 days to 90 days. compressive strength was determined in accordance with bs en 12390-3 (2009), 100mm cubes have been used for the investigation and the nominal size of the coarse aggregate used in this study does not exceed 20mm. 2.7 flexural strength flexural strength of pervious concrete specimens was determined by a point load test on beam specimens of size 100 mm x 100 mm x 500 mm, and in accordance with bs en 12390-3 (2009), three numbers of specimens for each set were tested at 28, 56 and 90 days of normal curing. the samples were tested in universal testing machine (utm) of capacity 1000kn. flexural strength of the specimen is expressed as the modules of rupture. flexural strength was computed using equation 1. (1) where fis the maximum load in (kn) lis the average measured length in (mm) dis the average measured diameter in (mm) the tensile splitting strength is expressed to the nearest 0.05 mpa. 2.8 split tensile strength test of concrete in the determination of tensile strength of concrete, the procedures as in accordance with bs en 12390-3 (2009) was followed. the split tensile strength fct in n/mm2 was computed using the equation 2. fct = 2𝐹 p x l x d (2) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rahmat et al: investigation of the properties of concrete made with fly-ash and dry waste okra powder. azojete, 20(2):473-482. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 477 where: f is the maximum load in (kn) l is the average measured length in (mm) d is the average measured diameter in (mm) 3. result and discussion 3.1 chemical composition of fly-ash table 1 shows the chemical composition of fly ash determined using a xrf technique. the result obtained in this study is in consistent and comparable with astm c618 requirement, which shows that (sio2+al2o3 + fe2o3) minimum requirement for a standard pozzolana is 70%. however, the findings of this shows that (sio2+al2o3 + fe2o3 is equal to 89.04% and this met the minimum requirement for a pozzolana. therefore, fly-ash sample is expected to show pozzolanic behavior in cementitious system. minor compounds such as tio2, p2o5, mgo, mno, so3, na2o, cao, are also found in fly-ash sample under consideration in minute quantity. table 1: chemical composition of fly-ash sample fa silicon oxide sio2 58.56 aluminium oxide al2o3 23.31 iron trioxide fe2o3 7.17 calcium oxide cao 3.36 potassium oxide k2o 0.16 sodium oxide na2o 0.14 sulphur trioxide so3 0.03 phosphorus pentoxidep2o5 0.82 magnesium oxide mgo 1.61 manganese oxide mno 0.03 titanium oxide tio2 0.08 loss of ignition loi 1.26 3.2 setting time test figure 1 shows setting time and consistency of portland cement/fly ash-dry waste okra powder paste. it was discovered that the higher the amount of okra powder in the paste, the higher the time required for the paste to set. the observed setting time and consistency behavior corresponds and in consistent with finding of agboola et al. (2020) which observed that setting time increases with the addition of pozzolana. figure 1: setting time test of fa-dwop paste 0 50 100 150 200 250 300 350 0% 10%fa 0.25% 0.5% 0.75% 1% s e tt in g t im e ( m in ) admixture content initial setting time final setting time http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):473-482. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 478 3.3 strength activity index the result for the strength activity index of cement mortar is presented in table 2. the result shows an increasing trend of strength at 7 days and 28 days respectively for both control mortar and mortar produced with fly ash as partial replacement of cement. the result also shows that, at both 7and 28-days curing age, the strength activity index of 20% fly ash cement mortar meet the minimum requirement specified by astm c311, that the strength activity index of pozzolana must meet 75% of the control strength at 7 and 28 days. this indicates that fly ash is a good pozzolana and can be used to replace cement in concrete production. table 2: strength activity of cement-fly ash compressive strength (n/mm2) strength activity index % rha 7 days 7 days 28 days 0% control 24.0 33.5 100 100 20% fly ash 19.6 29.3 81.7 87.5 3.4 workability the slump test results are presented in figure 2. the slump value increases with increase ratio of dry waste okra powder content. from the values for the six mixes, on the degree of workability for slump test, 0.25% to 1% addition with dry waste okra powder falls within high slump (50 -100) which is a category of high degree workability, while 0% control concrete and 10% fly-ash falls with medium slump (25–50) which is a low degree workability according to neville and brooks (2010). the workability increases with the addition of dwop in concrete. for the compacting factor test, the degree of workability ranges from low to medium, which falls within the range specified by bs 812 and neville and brooks (2010). mixes with 0%, 10%fa, 0.25%, 0.50%, 0.75% dwop, has compacting value of 0.93, 0.93, 0.93, 0.92, and 0.92 respectively, which shows higher workability while 1% dwop admixture with 0.90 shows low workability as presented in figure 3. figure 2: slump test of fa-dwop paste figure 3: compacting factor test of fadwop paste 3.4 density of concrete the results of the density test are shown in figure 4, for opc/fa-dwop concrete samples cured in normal water and weighed at 7, 14, 28, 56 and 90 curing days. the density of concrete cube samples varies from 2450 kg/m3 to 2560 kg/m3 and it increase with increase curing periods. concrete with 0.75% dried waste okra powder present higher density than all other percentage addition of admixture beyond 28days of curing. the density of concrete increase as the percentage admixture increases up-to 0.75%. concrete samples with density higher than 2600kg/m² are called higher density concrete samples (kazjonovs et al., 2010), values obtained exceeded the 2400 kg/m3 at 28days hydration period expected for a normal weight concrete. 0 20 40 60 80 sl u m p v al u e ( m m ) admixture content 0.88 0.89 0.9 0.91 0.92 0.93 0.94 c o m p ac ti n g fa ct o r (r at io ) admixture content file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rahmat et al: investigation of the properties of concrete made with fly-ash and dry waste okra powder. azojete, 20(2):473-482. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 479 this indicates that concrete produced with fly ash and okra powder replacement shows dense concrete and possesses quality for greater durability of concrete. figure 4: density of fa-dwop concrete 3.5 compressive strength of concrete figure 5 presents compressive strength of opc/fa-dwop concrete specimens cured in water, and crushed at 7, 14, 28, 56 and 90days hydration periods. concrete samples with 0% replacement has high strength index at early days of strength test at 7days to 28days but encountered loss in strength as compared to concrete with 10% fly-ash as cement replacement and other admixture addition percentage level. concrete specimens with 0% admixture achieved 28.9 n/mm² while 10%fa achieved 28.4 n/mm² and 0.25%, 0.50%, 0.75%, and 1.0% fa-dwop achieved 28.5 n/mm², 28.6 n/mm², and 28.9 n/mm², and 28.5 n/mm² at 28 days respectively. control concrete has high strength as compared to all other admixture content mix at 28days. at 56-day curing age, concrete specimens with 0% control concrete achieved 29.5 n/mm² while 10%fa achieved 29.9 n/mm² and 0.25%, 0.50%, 0.75%, and 1.0% fa-dwop achieved 30.5 n/mm², 30.8 n/mm², 31.6 n/mm², and 31.2 n/mm². this shows 6.65% strength increase of 0.75%fa-dwop concrete as compared to control concrete. at 90day curing age, 0% control concrete specimens achieved 30.4 n/mm² while 10%fa achieved 31.2 n/mm² and 0.25%, 0.50%, 0.75%, and 1.0% fa-dwop achieved 31.5 n/mm², 32.4 n/mm², 31.8 n/mm², and 31.2 n/mm². this shows 6.17% strength increase of 0.75%fa-dwop concrete as compared to control concrete. the result is in line with the study of agboola (2020) who stated that pozzolanic material influences strength and durability properties of concrete at later stages. the increase in strength might be as a result of admixture and pozzolanic material present in the concrete mix. presence of pozzolanic materials enhance the strength of concrete (duggal, (2008); aci 201.2r (2001)). pozzolanic material can be used as a partial replacement of cement in concrete due to the high silica present in it and its ability to react with calcium in cement in the presence of water to form a compound with calcium hydrate silicate (csh). the result shows 0.75% admixture has high strength beyond all other percentage admixture and the control concrete at higher curing age. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 28days 56days 90daysd en si ty o f c o n cr et e in ( kg /m 3 ) admixture contents 0% 10%fa 0.25% 0.5% 0.75% 1% http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):473-482. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 480 figure 5: compressive strength test of fa-dwop concrete 3.6 flexural strength of concrete figure 6 shows the flexural strength of opc/fa-dwop specimen cured in water and tested at 28, 56and 90-days curing ages. 0% control concrete specimens achieved 4.63 n/mm² while 10%fa achieved 4.43 n/mm² and 0.25%, 0.50%, 0.75% and 1.0% percentage admixture achieved is 4.43 n/mm², 4.51 n/mm², 4.61 n/mm² and 4.53 n/mm² at 28 days. at 56 days curing age, concrete specimens with 0% control concrete achieved 5.11 n/mm² while 10%fa achieved 4.97 n/mm² and 0.25%, 0.50%, 0.75% and 1.0% percentage admixture achieved 5.18 n/mm², 5.27 n/mm², 5.43 n/mm² and 5.11 n/mm². this represents 3.04% increase in flexural strength of 0.75% fa-dwop concrete as compared to control concrete. at 90 days curing age, concrete specimens with 0% control concrete achieved 5.43 n/mm² while 10%fa achieved 5.51 n/mm² and 0.25%, 0.50%, 0.75% and 1.0% percentage admixture achieved 5.51 n/mm², 5.55 n/mm², 5.57 n/mm² and 5.54 n/mm². this represents 2.51% increase in flexural strength of 0.75% fa-dwop concrete as compared to control concrete. the increase in strength of concrete produced could be as a result of the type of admixture and pozzolana used in the production of the concrete. however, the flexural strength increases with increase in curing days. concrete produced with fly ash and dry waste okra powder gives higher flexural strength as it creates good bond, excellent filler and admixture between the concrete constituents. figure 6: flexural strength test of fadwop concrete figure 7: split tensile strength of fadwop concrete 3.7 split tensile strength of concrete figure 7 shows the split tensile strength of opc/fa-dwop specimen cured in water and tested at 28, 56and 90-days curing ages. 0% control concrete specimens achieved 3.21 n/mm² while 10%fa achieved 3.15 n/mm² and 0.25%, 0.50%, 0.75% and 1.0% percentage admixture achieved is 3.15 n/mm², 3.16 n/mm², 3.19 n/mm² and 3.12 n/mm² at 28 days, control concrete has highest strength at 28 days of curing. at 56 days curing age, concrete specimens with 0% 0 5 10 15 20 25 30 35 7days 14days 28days 56days 90days c o m p re ss iv e s tr e n gt h o f c o n cr e te in ( n /m m 2 ) hydration periods 0% 10%fa 0.25% 0.5% 0.75% 1% 0 1 2 3 4 5 6 28days 56days 90days fl e xu ra l s tr e n gt h o f c o n cr e te in ( n /m m 2 ) hydration periods 0% 10%fa 0.25% 0.5% 0.75% 1% 0 1 2 3 4 5 28days 56days 90days sp lit t e n si le s tr e n gt h o f c o n cr e te in ( n /m m 2 ) hydration periods 0% 10%fa 0.25% 0.5% 0.75% 1% file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rahmat et al: investigation of the properties of concrete made with fly-ash and dry waste okra powder. azojete, 20(2):473-482. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 481 control concrete achieved 3.49 n/mm² while 10%fa achieved 3.53 n/mm² and 0.25%, 0.50%, 0.75% and 1.0% percentage admixture achieved 3.55 n/mm², 3.61 n/mm², 3.68 n/mm² and 3.56 n/mm². this represents 5.16% increase in flexural strength of 0.75% fa-dwop concrete as compared to control concrete. at 90 days curing age, concrete specimens with 0% control concrete achieved 3.62 n/mm² while 10%fa achieved 3.65 n/mm² and 0.25%, 0.50%, 0.75% and 1.0% percentage admixture achieved 3.71 n/mm², 3.74 n/mm², 3.81 n/mm² and 3.74 n/mm². this represents 4.99% increase in split tensile strength of 0.75% fa-dwop concrete as compared to control concrete. the increase in strength of concrete produced could be as a result of the type of admixture and pozzolana used in the production of the concrete. however, the split tensile strength increases with increase in curing days. concrete produced with fly ash and dry waste okra powder gives higher tensile strength as it creates good bond, excellent filler and admixture between the concrete constituents. 4. conclusion and recommendations the results of pozzolanic property and the oxide composition of fly-ash showed that it is a good pozzolana with essential constituent which include 58.56% sio2, 23.31%, al2o3 and 7.17% fe2o3 content summing up-to to 89.04%. concrete of structural and mass concrete purposes can be produced by incorporating two types of waste materials, namely dry waste okra powder and fly-ash as admixture and cement replacement respectively. the use of locally available material as building material will also solve the problem of environmental impact. in addition, production of every ton of fly-ash concrete results in the reduction of each ton of co2 emission from cement production, and save the environment significantly by reducing green-house gas and particulate production. the fly-ash-blended cements and paste with dwop as admixture have higher setting time than 100% cement paste; hence, they are most applicable where low rate of heat development is required such as in mass concreting. this indicated that fly-ashblended cement is good as low heat cement. control concrete, 10% fly ash concrete and pozzolanic concrete containing 0.25% dwop have low workability as compared to concrete containing higher dwop content. to improve workability, 0.5% up-to 1% dwop should be used in the concrete mix. the compressive strength of concrete ranges from 28.4 to 28.9 mpa (at 28 days), and the strength of concrete increase as the curing days increases. fly-ash can be used up to 10% to replace cement for structural concrete in order to improve its compressive strength. the optimum dwop content is 0.75% considering concrete compressive strength at 90 days. dwop up to 1% can be used for structural concrete purposes due to its high strength index. dry waste okra powder as admixture is compatible with blended cement. strength development of dwop modified fly-ash blended concrete of 0.75% exceeded the control samples by 6.65% and 6.17% at 56days, 90days at respectively. it is recommended that further tests be conducted to determine the water absorption capacity, permeability, shrinkage resistance, fire resistance, durability on concrete and mortars made with dry waste okra powder and fly-ash blended cement, also using a different mix and altering water cement ratio is also recommended. test should also be conducted to determine the effects of fly-ash blended cement and dry waste okra powder as admixture on the mechanical properties of concrete for longer curing duration beyond 90 days. references agboola, sa., amina, os., simdima, gg. and solomon, wp. 2021. effect of volcanic ash as partial replacement of cement in concrete subject to aggressive chemical environment. international journal of engineering applied sciences and technology, 6(5): 100 – 108., doi:10.33564/ijeast.2021.v06i05.012. agboola, sa., mamman, ai., tapgun, j. and bappah, h. 2020. strength performance of concrete produced with volcanic ash as partial replacement of cement. international journal of engineering research & technology, 9(3): 372 -378. doi:10.13140/rg.2.2.13367.68002. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):473-482. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: deenlegit@gmail.com 482 agboola, sa. (2019. durability properties of composite waste glass powder and volcanic ash concrete exposed to aggressive chemical environment. m.sc. thesis, department of building, faculty of environmental technology, abubakar tafawa balewa university, bauchi, nigeria. american society for testing and material 2006. standard terminology relating to concrete and concrete aggregates. american society for testing and material, west conshohocken, no c125. usa. american concrete institute 1999. aggregates for concrete. aci committee 201 2r01, american concrete institute, farmington hills, michigan, usa, 1-41. asif k., chandresha, sp. and parikh, kb. 2019. strength and durability study of high strength concrete incorporating aqueous extract of okra as a bio-admixture along with silica fume. journal of emerging technologies and innovative research, 6(4): 2349-5162. british standards institution, 1983. bs 1881-102: testing concrete. method for determination of slump. bsi. http://shop.bsigroup.com/en/productdetail/?pid=00 0000000000048831 duggal, sk. 2008. building materials. new age international publishers, new delhi, india. 142300. gupta, b l. and gupta, a. 2012. concrete technology. ak jain for standard publishers, new delhi, india. gourav, k. and reddy, vbv. 2014. characteristics of compacted fly ash bricks and fly ash brick masonry. journal of structural engineering (india), 41(2): 144–157. kazjonovs, j., bajare, d. and korjakins, a. 2010. designing of high-density concrete by using steel treatment waste. modern building materials. structure and techniques international conference. may 19-21, 2010. vilnius, lithuania, pp. 138-142. karandikar, mv., sarase, sb., lele, pg. and khadaikar, sa. 2014. use of natural bio-polymers for improved mortar and concrete properties of cement – a review. indian concrete journal, 88(7): 84–109. mahasena, n., smith, s. and humphreys, k. 2003. the cement industry and global climate change: current and potential future cement industry co2 emissions. green house gas control technologies6th international conference, 2: 995-1000. mohammad, nf. 2010. performance of concrete by using pulverized fuel ash (pfa) as cement replacement material. b. sc project, department of civil engineering and earth resources, university of malaysia pahang. shetty, ms. 2009. concrete technology; theory and practice. s chad and company, new delhi, india, 174-418. yazici, s. and sahan, h. 2012. effect of fly ash fineness on the mechanical properties of concrete. indian academy sciences journal, 337(3): 389-403. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):247-256 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 247 original research article development of a manually operated sleeve puller kit for reciprocating type engine m. a. abba-aji, m. shuwa and v. m. dagala department of mechanical engineering, university of maiduguri, p.m .b 1069, maiduguri, nigeria. *corresponding author’s email address: birma4real2004@yahoo.com 1.0 introduction sleeve puller is bond to removal of piston liners of various kinds, particularly, to apparatus for removing the piston liners of internal combustion engines. during the active life of various engines, the pistons are constantly reciprocating up and down the cylinder and eventually the cylinder liner becomes scored, out of round, or so worn that compression is adversely affected and therefore, it becomes necessary to remove the cylinder liner and either replace the liner and the rings of the piston or grind and lap the bore of the cylinder liner and place oversized rings on the piston (sarvana, 2017). in the past, many researchers made some efforts to provide tools for removing sleeves of various kinds from internal combustion engines. however, in most of these prior art structures, it has been necessary to remove the piston before the mechanism for removing the cylinder could be attached (krishnamoorthi et al., 2017). due to space limitations, in most cases it has been necessary to remove the crank shaft from the engine before the piston could be removed. therefore, the entire mechanism has to be disassembled before removing the cylinder liners (krishnamoorthi et al., 2017). article information abstract this work describes design and construction of manually operated sleeve puller kit for removal of piston liners. piston cylinder sleeves which are firmly fixed in the engine block of many reciprocating engines are normally removed for the purpose of repairs, maintenance and replacement, and is difficult to remove by hammering; hence the need for a puller. to demonstrate the workability of the design, a cylinder sleeve of 100kva generator was constructed. the components for the device were: frame, screw and base, constructed from grey cast iron, unalloyed free cutting steel and copper alloy materials respectively. the components were constructed using cutting, drilling, rolling and arc welding machine operations. the sleeve puller was tested on a 100kva parkins generator. the cost of producing the device was n9, 150:00, which was effective compared to similar devices in the market that cost within the range of n15, 000 to n20, 000. from the performance test results obtained, the maximum torque to raise the required load was determined to be 452.898 × 103 n-mm and shear stress of the screw as 23.697mpa which was less than the strength of free cutting steel (56mpa). buckling criterion was 371.09kn>75kn, transverse shear at the root and body area of the screw are 8.768<19mpa and 10.484mpa<56mpa. a piston sleeve puller was successfully developed. a hydraulic or electrically operated can further be investigate. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 december, 2022 revised 6 march, 2023 accepted 6 march, 2023 keywords: shear stress torque grey-cast iron screw sleeves http://www.azojete.com.ng/ mailto:birma4real2004@yahoo.com mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):247-256. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 248 the present research concentrates on the design and construction of a cost effective sleeve puller kit, for removable of internal combustion engine cylinder sleeves or liners for the purpose of repairs and maintenance. the work is limited to a sleeves diameter of 100mm to 150mm. 2. methodology 2.1 materials selection and design of machine components the device comprises of three components; the frame, screw and the base. frame: the material selected for the frame was fg200 (graphite flakes grey-cast iron with tensile strength of 200n/mm) which is in agreement with the work of sarvana, (2017). the material has precipitate of carbon as ‘graphite flakes which is soft in nature, and improves ability to resist compression load. screw: the material for the screw was ‘unalloyed free cutting steel’ with composition of 0.25% carbon, 1.2% manganese, 0.14% sulphur. it has tensile strength of 56n/mm2 with 10% elongation. sulphur gives resistance to wear and 0.25% carbon gives it sufficient strength to compensate weakness in roots also easy in cutting due to manganese, this is in line with the work of anand et al. (2015). base: to ease replacement due to wear, either screw or the base material has to be soft, as screw is costlier than the base, phosphor bronze is the ideal material for the base, which is a copper alloy having 0.2% of phosphor which increase tensile strength. ultimate tensile strength for this according to khurmi and gupta, (2012) is 19mpa, coefficient of friction is 0.1, with bearing pressure of 10mpa. 2.2 methods 2.2.1 design analysis the following considerations were made during the design: a. the form and shape of the device is produced in a simplified manner. b. the stresses and load bearing capacity. c. the device efficiency, economy and availability of materials d. the safety and durability of the device to be produced e. single thread screw was assumed for the design. f. the screw is considered to be long coulomb 2.2.1 screw design: according to khurmi and gupta (2012), for unalloyed cutting steel, assuming core diameter = dc, length = l = 360mm, syc = syt = yield strength = 1193.5 mpa compressive strength (σc) is given as: 𝜎𝑐 = 1193.5 5 ⁄ = 238.7𝑀𝑃𝑎 𝜎 = 𝑊 𝜋 4 ⁄ × (𝑑𝑐 2) (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng abba-aji et al: development of a manually operated sleeve puller kit for reciprocating type engine. azojete, 19(2):247-256. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 249 238.7 = 75000 𝜋 4 ⁄ × (𝑑𝑐 2) 𝑑𝑐 = 20𝑚𝑚 let d = nominal diameter corresponding to the cylinder bore diameter, p = pitch, dr = root diameter, dm = mean diameter, l = lead screw, fos = factor of safety: d = 55mm, p = 9mm, according to khurmi and gupta (2012), dr = 55 – 9 = 46mm>30mm and 𝑑𝑚 = 𝑑 − 0.5𝑝 = 55 − 4.5 = 50.5𝑚𝑚 assuming screw has single start threads l = p = 9mm according to khurmi and gupta (2012), helix angle is obtained using the relation: 𝑡𝑎𝑛 ∝ = 𝑙 𝜋 × 𝑑𝑚 ⁄ (𝑟𝑎𝑑) (2) = 9 𝜋 × 50.5 ⁄ , ∝ = 3.2460 𝑟𝑎𝑑 coefficient of friction between screw and base, μ = o.1, considering bad lubricating conditions, assume μ = 0.18, according to khurmi and gupta (2012), the thread angle ø is obtained from the relation: 𝑡𝑎𝑛∅ = 𝜇 = 0.18 ∅ = 10.2039 > 3.0346 torque required to raise the load according to khurmi and gupta (2012) is calculated as: 𝑇 = 𝑊 ( 𝑑𝑚 2⁄ ) tan ∅ + 𝛼 (𝑁𝑚𝑚) (3) = 75 × 103 × (50.5 2⁄ ) tan 10.2039 + 3.246 𝑇 = 452.898 × 103𝑁𝑚𝑚 according to khurmi and gupta (2012), number of cross section of screw is subjected to addition of frame friction torque and base torque. 𝜏𝑡𝑒𝑛 = 16𝑇 𝜋 × 𝑑𝑟 3⁄ (𝑀𝑃𝑎) (4) = 16 × 452.898 𝜋 × 463⁄ 𝜏𝑡𝑒𝑛 = 23.697𝑀𝑃𝑎 𝜏𝑝𝑒𝑟𝑚 = 56𝑀𝑃𝑎 > 23.69𝑀𝑃𝑎 http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):247-256. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 250 the maximum tensile strength of free cutting steel (56mpa) is greater than the tensional shear stress of the screw. therefore, according to khurmi and gupta (2012), the screw is safe in tensional shear stress. according to khurmi and gupta (2012), using buckling criterion, when load was raised, the screw acted as coulomb, and there were chances of buckling or crushing, therefore, it must be decided whether the coulomb was long or short. since one end of the screw was fixed and other was free, the end fixity coefficient was 0.52, and the young modulus 207, 000mpa. border line between short and long coulomb was; 𝑠𝑦𝑡 2⁄ = 𝜂 × 𝜋2 × 𝐸 1 𝑘⁄ 2⁄ (5) 560 2⁄ = 0.25 × 𝜋2 × 2007000 1 𝑘⁄ 2⁄ 1 𝑘⁄ = 42.709 the length of the screw has to be greater than the length of the cylinder (360mm) in order to remove the liner, therefore, as reported by khurmi and gupta (2012), the length of screw considered is 550mm 𝐾 = √𝐼 𝐴 ⁄ (𝑚𝑚) (6) i = inertia, k = radius of gyration, a = cross sectional area 𝐼 = 𝜋 4⁄ × 𝑑𝑟 4 𝑚𝑚4 (7) = 219.786 × 103𝑚𝑚4 𝐴 = 1661.9925𝑚𝑚2 𝐾 = 11.5 𝑚𝑚 according to khurmi and gupta (2012), 𝑆𝑙𝑒𝑛𝑒𝑟𝑑𝑒𝑠𝑠 𝑟𝑎𝑡𝑖𝑜 𝑙 𝐾⁄ = 550 11.5⁄ slenderness ratio is more than critical slenderness ratio, therefore, screw is considered as long coulomb, hence using euler’s formula; 𝑃𝑐𝑟 = 𝜋2 × 𝐸 × 𝐼 (1 𝑘⁄ )2 ⁄ (𝐾𝑁) (8) = 0.25 × 207000 × 𝜋2 × 1661.9025 47.8262⁄ = 371.09 > 75𝐾𝑁 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng abba-aji et al: development of a manually operated sleeve puller kit for reciprocating type engine. azojete, 19(2):247-256. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 251 2.2.2 base design: according to khurmi and gupta (2012), the permissible bearing pressure between steel screw and bronze base is 10mpa, number of threads required given: pb = bearing pressure (mpa) w = load applied (n) z = required number of threads 𝑃𝑏 = 𝑊 𝜋 4(𝑑2 − 𝑑𝑟 2) × 𝑧 (𝑀𝑃𝑎)⁄⁄ (9) 10 = 75 × 103 𝜋 4(552 − 462) × 𝑧⁄⁄ where 𝑧 = 10.50 ≈ 11 𝐻 = 𝑍 × 𝑃 = 11 × 9 𝐻 = 100𝑚𝑚 transverse shear stress at root of threads is given as; 𝜏 = 𝑊 𝜋 × 𝑑𝑟 × 𝑡 × 𝑍⁄ (𝑀𝑃𝑎) (10) where: w = axial load on the screw (n) t = torque (n.m) dr = root diameter of the screw (m) z = number of engaged threads 𝜏 = 75 × 103 𝜋 × 55 × 4.5 × 11⁄ 𝜏 = 8.768𝑀𝑃𝑎 < 19𝑀𝑃𝑎 the ultimate tensile strength (19mpa) is greater than the transverse shear stress at root of threads, therefore, base is safe in transverse shear at the root (khurmi and gupta, 2012). transverse shear stress at threads in screw is given by; 𝜏 = 𝑊 𝜋 × 𝑑 × 𝑡 × 𝑍⁄ (𝑀𝑃𝑎) (11) 𝜏 = 75 × 103 𝜋 × 46 × 4.5 × 11⁄ = 10.48𝑀𝑃𝑎 < 56𝑀𝑃𝑎 the tensile strength of free cutting steel (56mpa) is greater than the transverse shear stress at threads in the screw, making it safe in transverse shear stress at screw (khurmi and gupta, 2012). 𝜎𝑡 = 𝑊 𝜋 4⁄ × 𝐷𝑜 2 − 𝐷𝑖 2⁄ (12) where di and do are the inner and outer diameter respectively, http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):247-256. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 252 112 = 75 × 103 𝜋 4⁄ × 𝐷𝑜 2 − 552⁄ 𝐷𝑜 = 65𝑚𝑚 by empirical relations 𝐷𝑜 ′ = 1.3 × 𝐷𝑜 = 1.3 × 65 = 85𝑚𝑚 the width of coulomb, considering shear failure, 𝜏 = 𝑊 𝜋 × 𝐷𝑜 × 𝑇⁄ (13) 19 = 75 × 103 𝜋 × 65 × 𝑇⁄ 𝑇 = 20𝑚𝑚 2.2.3 component construction and assembly the construction of three main parts of the device; frame, screw and base are described. frame: a 5mm thick u-channel cast iron was used in the construction. hacksaw was used for cutting and drilling machine was used to drill the hall, which was threaded using tap and wrench to accommodate the screw. the pieces were joint using electric arc welding (figure 1). figure1: sleeve puller frame screw: threads were produced using cutting and rolling operations. the shank of the blank design for cut threading was full-sized from the fillet under the head to the end of the bolt. measuring tape was used to measure the required size, and hack saw was used for cutting. the bolt blank was mounted on a lathe machine in order to produce the thread (figure 2). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng abba-aji et al: development of a manually operated sleeve puller kit for reciprocating type engine. azojete, 19(2):247-256. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 253 figure 2: the screw base: the base was made at the machine shop by using the cylinder sleeve measurements. the most important measurement was the outside diameter, it must be as close as possible to the block size and tight fit (figure 3). the required hole was drilled at the centre of the base using a drilling machine and then threaded using tap and wrench (khurmi and gupta, 2012). figure 3 assembled sleeve puller (isometric view) the efficiency of the device was calculated using the relation 𝜂 = 𝑤𝑜𝑟𝑘 𝑖𝑛𝑝𝑢𝑡 𝑤𝑜𝑟𝑘 𝑜𝑢𝑡𝑝𝑢𝑡⁄ × 100 (14) 𝑤ℎ𝑒𝑟𝑒; 𝑤𝑜𝑟𝑘 𝑖𝑛𝑝𝑢𝑡 = 𝑒𝑓𝑓𝑜𝑟𝑡 × 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑚𝑜𝑣𝑒𝑑 𝑤𝑜𝑟𝑘 𝑜𝑢𝑡 𝑝𝑢𝑡 = 𝑙𝑜𝑎𝑑 × 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑚𝑜𝑣𝑒𝑑 (mohammed, 2021) 3.1 bills of engineering measurements and evaluation the production cost is evaluated based on market prices of materials, the overhead and labour cost which is presented under section 3.1.1. 3.1.1 analysis of bill of engineering measurements the material cost depends on the market prices, given in table 1, as mc = n 6, 100.00 http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):247-256. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 254 table 1: prices of materials s/no material size amount (n) 1 flat bar 750 x 100 x 10 2, 500.00 2 blank bolt 600 x 30 2, 000.00 3 flat plate 200 x 200 x 15 1, 000.00 4 electrode gauge 12 6, 000.00 5 total 6, 100.00 direct labour cost was assumed to be 40% of the material cost from table 1, that is, 𝐷𝐿𝐶 = 40 100⁄ × 6100 = 𝑁 2440.00 overhead cost was assumed to be 10% of the material cost; 𝑂𝐻𝐶 = 10 100⁄ × 6100 = 𝑁 6100.00 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝐶𝑜𝑠𝑡 𝐶𝑃 = 610 + 2440 + 6100 = 𝑁 9150.00 from the market survey conducted so far, the price of similar device ranges from n15, 000 to n20, 000. this indicates the cost effectiveness of the present device. 3. results and discussion the shear stresses and the buckling in screw were determined from the performance test carried out and compared with the maximum as shown in table 2. table 2: performance test evaluation tensional shear stress (mpa) the screw in buckling (kn) transverse shear stress at root (mpa) transverse shear area on the screw (mpa) 23.69 75 8.769 10.488 maximum tensional shear stress (mpa) maximum buckling in screw (kn) maximum transverse shear stress at root (mpa) maximum transverse shear area on the screw (mpa) 56 371.09 19 56 the performance test was carried out where iron sleeves provided a wear resistant surface for the piston rings supported by surrounding block. the iron sleeves have the same coefficient of expansion as the block, about 0.0015 to 0.002 of interference to be removed. the sleeve puller was firmly fixed on engine block and removal was successful, as shown in figure 4. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng abba-aji et al: development of a manually operated sleeve puller kit for reciprocating type engine. azojete, 19(2):247-256. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 255 figure 4: a piston removal using sleeve puller the frame was placed at the top of the engine block to provide the necessary support to remove sleeves. a threaded rod (screw) was inserted through the centre of the frame at the top where a nut was attached (figure 1). the sleeve was removed manually. a flange (the base) was attached to the sleeve at the bottom of the threaded rod (screw). when the rod was turned in clockwise direction, the sleeve was then removed successfully. the torque required to raise the load was calculated using equation 3 as 452.898 x 103 n-mm and the shear stresses experienced by the screw and the base were calculated as the tensional shear stress of the screw as presented in table 1, was 56mpa>23.69mpa , hence the screw was safe in tensional shear stress. the buckling criterion was 371.09kn>75kn, hence the screw was safe in buckling. the transverse shear stress at the root of threads in base was 8.768mpa<19mpa, making the base safe in transverse shear stress at root. the transverse shear area on screw body was safe in transverse shear stress at screw. conclusion the sleeve puller was successfully constructed, using the specified design considerations, from locally sourced materials. the sleeve puller was tested on a 100kva parkins generator. the performance test was carried out where iron sleeves provided a wear-resistant surface for the piston rings, which were supported by surrounding block. the iron sleeves have the same coefficient of expansion as the block, so typically required about 0.0015 to 0.002 of interference to be removed. the sleeve puller was firmly fixed on engine block and removal was carried out successfully. the sleeve puller is an easy way of removing piston sleeves. the cost of the device, n9, 150:00, was effective when compared to similar devices in the market that range from n15, 000 to n20, 000 according to survey. it can be modified hydraulically or electrically to reduce effort applied on pulling. it can also be modified to serve dual purposes as a puller and presser. references anand kumar, m., prasad rao, aa. and narayana rao, h. 2015. design analysis of dry cylinder liners used in diesel engines. international journal of science engineering and advance technology, 9(3): 518-526. http://www.azojete.com.ng/ mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):247-256. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 256 khurmi, rs. and gupta, jk. 2012. a textbook of machine design. eirasia publishing house (pvt) ltd. new delhi. krishnamoorthi, t., prem kumar, k., velliyagiri, j., vengatesh, j. and murugesane g. 2017. removal of dry type liner from the engine block by using hydraulic operation. international journal of engineering research and technology, 7(5): 39-46. mohammed, lk. 2021, design, construction and performance evaluation of hydraulic cylinder liner puller. international journal of information, engineering and technology, 11(4): 105-109 sarvana kumar, a. 2017. design and fabrication of hydraulic cylinder liner puller. international journal of mechanical engineering technology, 8(8): 1601-1607 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):747-758 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 733 maximum power point tracking in partial shaded photovoltaic system using smell agent optimization algorithm r. o. amusat1, s. shodiya2, y. h. ngadda1 and d. i. malgwi1 1department of physics, university of maiduguri, borno nigeria 2department of mechanical engineering, university of maiduguri, borno nigeria *corresponding author's email address: amusatramoni@gmail.com article information submitted 27 aug, 2023 revised 9 oct, 2023 accepted 11 oct, 2023 keywords: pv array maximum power point tracking partial shading conditions and booster converter abstract with partial shading conditions, it is essential to acquire maximum power point at which the photovoltaic systems (pv) operate effectively despite the variation in the cell temperature and incident angle of sunlight rays on the panels. this study explores the use of a smell agent optimization (sao) algorithm for maximum power point tracking (mppt) in partial shaded pv systems. the proposed mppt system is composed of a pv model, a dc-dc converter model and a control part. the smell agent algorithm (saa) was adopted in the control part of the mppt system to implement the optimization algorithm using four different shading patterns (sps) and to calculate the optimal switching duty cycle of the dc-dc converter. the effectiveness of the proposed system was verified using simulations in the matlab/simulink environment. the sao respectively track maximum values for power, voltage and current as 845.8476 w, 211.7308 v, 3.99492 a while the maximum values for power, voltage and current for perturb and observe (p and o) are 845.0465 w, 211.6305 v, 3.993028 a respectively during sp1. the results showed that the sao algorithm has excellent tracking results in terms of convergence speed, accuracy, power extracted stability, and dynamic response in reaching the optimum point. 1.0 introduction solar energy is the pathway to an environmentally friendly future energy. every single day, the sun generates far greater quantities of energy than we require for our daily activities. this allows researchers to create models that can predict the future prospects of renewable energy (amusat et al., 2020). using renewable energy (solar energy) to generate electric power has an advantage over other traditional power source of energy owing to its ability to transform directly into electrical energy using the photovoltaic (pv) solar cells. a photovoltaic system is made of semiconducting materials that convert incident photon into electric energy with its conducting qualities adjusted by changing the type and amount of impurities added to the initial semiconducting substance. solar cells or photovoltaic cells can be combined together to make panels or modules. large photovoltaic arrays can be created by grouping panels’ together (amusat et al., 2020). a solar panel (with numerous cells connected in series and/or parallel) or a set of panels is commonly referred to as an array (surya and babu, 2012). many efforts have been made in the field of modeling and simulation of diode-based photovoltaic cells but, tracking of the maximum power point at which solar panel operates effectively, incorporating a shading parameter into the conventional pv-array model that will account for varying degrees of shading across individual cells of a given pv-module are the http://www.azojete.com.ng/ mailto:amusatramoni@gmail.com mailto:amusatramoni@gmail.com mailto:amusatramoni@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):747-758. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 748 major concern (claude and nazih, 2015). maximum power point trackers are devices that maximize the output power of photovoltaic systems for different ambient conditions and maintain the operation of pvs at their maximum power points (derbeli et al., 2021). many studies on mppt techniques have been conducted (claude and nazih, 2015). the mppt techniques: the perturbed and observation (p and o) and climbing hill (h and c) techniques are widely used due to their ease of implementation and low sensor requirements (attou et al., 2014; parween, 2019; jiang et al., 2017; srushti and uttam 2013; lokanadham and vijaya, 2012). the incremental conductance algorithms compare pv array incremental and instantaneous conductance which track a pv system’s maximum power point and transfer high pv energy to the load (william and ramesh, 2013; hsieh et al., 2013; rajaram and sharma, 2015). short circuit current (isc) and open circuit voltage (voc) can be used to determine the mpp current (impp) and mpp voltage (vmpp) (hadji et al., 2013; subudhi and pradhan, 2012). the main disadvantage of this mppt is the uncertainty that exists in this tracking approach, as demonstrated by the approximate relationship of isc to impp and voc to vmpp. also, most research does not consider the effect of partial shading (psc) on the pv system when determining the mppt. research on pv maximum power point tracking has been conducted in recent years and the effect of partial shading has been considered. researchers discovered that conventional methods have been very poor in tracking the performance with many of them failing to track the true mpp under partial shading of pv arrays. (nur and chee, 2014). as a result of the shortcomings of traditional mppt algorithms, many research studies have used artificial intelligence (ai) techniques to address the stated limitations. such as fuzzy logic controller (flc) and neural network (nn) (seyedmahmoudiana et al., 2016; ramana and jena, 2015; lalam and kalpana, 2013; zaki et al., 2012; younis et al., 2012). the flc which is based on rational data interpretation can find means of retrieving the maximum power under partially shaded and rapidly varying atmospheric conditions. even though these techniques are efficient when dealing with the nonlinear characteristic i v curves, they require a significant amount of computation. flc, for example, deals with operations such as fuzzification, rulebased storage, inference mechanisms, and defuzzification. the enormous amount of data needed for training is a major constraint for nn. more so, since the operational conditions of the pv system change continuously, mppt must respond instantaneously to changes in irradiance and temperature. therefore, low -cost processors cannot be employed in such a system. their tracking efficiencies are affected by high control circuit complexity and large data processors for training the system. there are new mppt algorithms, inspired by nature and biological structure that were developed to track pv array output power. among these are particle swarm optimization and grasshopper optimization algorithms (sadegh et al., 2022; mansoor et al., 2020; saxena et al., 2018; saremi et al., 2017; kashif et al., 2012; miyatake et al., 2011; chen et al., 2010). some bio-inspired optimizations were introduced to tackle the limitations of conventional techniques based on the literature review. but, handling the most extreme environmental changes such as changing irradiance and pscs, require an improvement in the aspects of computational burden, precision and accuracy of the result, ease and the convergence of the implementation. therefore, efforts are made nonstop to look for more current algorithms with good performance. the sao, which has not been exploit in pv is a current introduced meta-heuristic algorithm, recognized for its robust characteristics in tackling different optimization problems mentioned above. in this study, sao was explored in tracking the maximum power point of the pv system under partial shading conditions. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com amusat et al: maximum power point tracking in partial shaded photovoltaic system using smell agent optimization algorithm. azojete, 19(4):747-758. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 749 2 materials and method 2.1 materials the materials used for this study are the solar panel of model tala power solar systems tp250mbz with specification shown in table 1, booster converter of the specification shown in table 2, sensors, mppt controller and four different sps of solar irradiance at constant cell temperature of 25oc as shown in figure 3 table 1. key specification of tala power solar systems pv array model tp250mbz type polycrystalline silicon (156mm×156mm) model tala power solar systems tp250mbz cell type polycrystalline silicon maximum power pmp [w] 249 open circuit voltage voc [v] 36.8 short circuit current isc [a] 8.83 maximum voltage vmp [v] 30 maximum current imp [a] 8.3 temperature coefficient of voc [%/deg. c] -0.33 temperature coefficient of isc [%/deg. c] 0.063805 diode ideality factor 0.94812 diode saturated current io [a] 1.0132e-10 shunt resistance rsh [ω] 314.7646 series resistance rsh [ω] 0.2914 light generated current il [a] 8.8382 number of cell ncell 60 table 2. specification of the booster symbol parameters values l inductance 1.1478 x 10-3 cin input capacitance 10 μf co output capacitance 0.467 x 10-3 r load resistance 53 ω 2.2 method figure 1 is the schematic diagram of the proposed system. an intelligent control technique based on sao algorithm for mppt during unexpected changes in atmospheric conditions was used. the algorithm in the system is used to track the maximum operating point of the solar panel. the sao is a new meta-heuristic algorithm based on the evaporation of smell molecules in the form of gas and the perception capability of a smell agent. the mathematical model of the sao consists of three modessniffing, trailing and random modes (salawudeen et al., 2021). this is used to update the duty cycle a dc – dc converter, there by tracking the global maximum point while updating the position and velocity continuously as shown in figure 1. this in turn gives a signal to boost the converter that maintains the operating voltage of the maximum operating point irrespective of the solar irradiance and temperature. to evaluate the performance of the algorithms, the proposed sao-based mppt method is implemented on a dc-dc boost converter and its performance was compared with that of the p and o algorithm using matlab simulink environment. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):747-758. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 750 figure 1: schematic diagram of the proposed pv system (adopted: attou et al., 2014). 2.2.1 mathematical modeling of pv cell photovoltaic cell models have long been a means of describing photovoltaic cell behavior. the most commonly used model for predicting energy production in photovoltaic cell is the single diode lumped circuit model (dominique et al., 2013). the performance of photovoltaic systems, vis a-vis, the output current/voltage curve (i-v curve) and power/voltage (p-v curve) are studied using an equivalent circuit model. this equivalent circuit consists of a current source with two resistors, one connected in parallel and the other in series. based on these electronic components, equations (1-5) were used for the photovoltaic systems (jobeda and simon, 2018). figure 2 shows an equivalent circuit of a photovoltaic with one diode. figure 2: equivalent circuit of a photovoltaic with one diode (adopted: jieming et al., 2013). the mathematical equations of pv from used in the program are shown in equations (1) to (5) (jobeda and simon, 2018). the module ipv (photon current) under the different environmental conditions are related as eq. (1): 𝐼𝑝𝑣(𝑇, 𝑆) = [𝐼𝑠𝑐 + 𝐾𝑖(𝑇𝑟 − 𝑇𝑜) ∗ ( 𝑆 1000 )] (1) the terms in equation (1) are: ki is the photon current temperature coefficient; s is solar irradiance (watt/meter square), tr is the cell reference temperature in degree (kelvin), isc short-circuit current (ampere), to is the cell operating temperature (kelvin) which is 25oc at stc file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com amusat et al: maximum power point tracking in partial shaded photovoltaic system using smell agent optimization algorithm. azojete, 19(4):747-758. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 751 the reverse saturated current at standard testing condition is expressed as eq. (2): 𝐼𝑟𝑠 = 𝐼𝑠𝑐 [𝑒𝑥𝑝 ( 𝑞𝑉𝑜𝑐 𝑁𝑠𝐴𝐾𝑇) − 1] (2) the diode saturated current varies as a cubic function of the temperature and 𝐼𝑜 can be expressed as eq. (3): 𝐼𝑜 = 𝐼𝑟𝑠 ( 𝑇𝑜 𝑇𝑟 ) 3 𝑒𝑥𝑝 [ 𝑞 ∗ 𝐸𝑔𝑜 𝐴𝐾 ( 1 𝑇𝑟 − 1 𝑇𝑜 )] (3) in order to assure the parameters required on the consumers, a photovoltaic system has to be made a sufficient number of pv cells interconnected in series or parallel usually called module of array. then the photon current can be expressed as eq. (4): ipv = np ∗ iph − np ∗ i0 [exp ( qvpv nsakt ) − 1 ] (4) where np and ns are the number of pv cells connected in parallel and series respectively iph is photocurrent (ampere). the output power of the pv at any given point as eq. (5): 𝑃 = ipv ∗ vpv (5) 2.2.2 mathematical model of the smell agent sao algorithm is a meta-heuristic algorithm that mimics the process of smell perception (muhammad et al., 2023; salawudeen et al., 2021). sao is classified into 3 modes; these include: 2.2.2.1 sniffing mode the total number of molecules evaporating from the smell source is used in modeling the smell agent algorithm. each member of the total population is assigned a vector position using eq. (6) (salawudeen et al., 2021): ,1 ,2 ,[ , ,... ]t t t t i q q q nx x x x= , (6) where i=1,2, 3…, n and q is the population of the smell molecule a molecule is said to obey newton’s first law of motion (uniform velocity) as it evaporates and moves toward the direction of the smell. the rate of displacement of the smell molecule is denoted by v using eq. (7): ,1 ,2 ,[v , v ,..., v ]t t t t i q q q nv = , (7) where i=1,2, 3…, n the equation (7) offers an appropriate velocity for molecule in the proposed sao. since the movement of smell molecules is non-uniform in six-dimensional coordinates, then, velocity is obtained as in eq. (8): 𝑉(𝑢.𝑣.𝑤) = ∆𝑋(𝑥.𝑦.𝑧) ∆𝑡 (8) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):747-758. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 752 where, ∆𝑋(𝑥.𝑦.𝑧) is the change in the displacement, x,y,z are the displacement coordinates ∆𝑡 is the time interval and 𝑉(𝑢.𝑣.𝑤) is the velocity in the u,v,w coordinates. using equation (8) the initial position of the smell molecule relative to the cartesian coordinate can be represented by eq. (9): 𝑋(𝑥,𝑦,𝑧) (𝑡+1) = 𝑉(𝑥,𝑦,𝑧) (𝑡) ∆𝑡 + 𝑋(𝑥,𝑦,𝑧) (𝑡) (9) if ∆𝑡 = 1 and the iteration increases continuously until all the iterations get exhausted. then, the initial position of the smell molecule relative to the cartesian coordinate can be represented as in eq. (10): 𝑋(𝑗) (𝑡+1) = 𝑉(𝑢,𝑣,𝑤) (𝑡) + 𝑋(𝑥,𝑦,𝑧) (𝑡+1) (10) as the gas molecule moves in different directions, its velocity can be expressed from the static pressure of the gas as eq. (11): 𝑉 = √ 3𝐾𝑇 𝑚 (11) the velocity of the smell molecule from equation (7) is updated as indicated in eq. (12) 𝑉(𝑡) (𝑡+1) = 𝑉(𝑖) (𝑡) + 𝑟𝑜√ 3𝐾𝑇 𝑚 (12) where, 𝑉(𝑡) (𝑡+1) is the updated velocity, 𝑉(𝑖) (𝑡) is the previous velocity, k is boltzmann’s constant, t is the temperature of the environment of the smell molecules, m is the mass of the molecules and 𝑟𝑜 is the random number. thus, the updated position of the agent of the smell molecules is given as in eq. (13): 𝑋𝑡 (𝑡+1) = 𝑋𝑖 𝑡 + (𝑉(𝑖) (𝑡) + 𝑟𝑜√ 3𝐾𝑇 𝑚 ) (13) where, 𝑋(𝑖) (𝑡) is the previous position of the molecule 2.2.2.2 trailing mode this is the movement of the agent continuously toward the region with the highest concentration until the molecule with the overall best is found. this depends on the strength of the olfaction (olf) of the agent (muhammad et al., 2023; salawudeen et al., 2018). the movement is done through eq. (14): 𝑋𝑡 (𝑡+1) = 𝑋𝑖 (𝑡) + 𝑟1𝑜𝑙𝑓(𝑋𝑎𝑔𝑒𝑛𝑡 (𝑡) − 𝑋𝑖 (𝑡) ) − 𝑟2𝑜𝑙𝑓(𝑋𝑤𝑜𝑟𝑠𝑡 (𝑡) − 𝑋𝑖 (𝑡) ) (14) 𝑟1and𝑟2 are random numbers generated at different intervals, 𝑋𝑎𝑔𝑒𝑚𝑡 (𝑡) and 𝑋𝑤𝑜𝑟𝑠𝑡 (𝑡) are the fitness of the present position of the agent and the position with the worst smell fitness respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com amusat et al: maximum power point tracking in partial shaded photovoltaic system using smell agent optimization algorithm. azojete, 19(4):747-758. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 753 2.2.2.3 random mode if there is variation in the intensity of the smell molecule from one point to another over a certain period, the agent may be trapped by local minima resulting in failure in subsequent trailing, then, the agent will execute random mode in searching for the smell molecule source. the random mode is described as in eq. (15): 𝑋𝑖 𝑡+1 = 𝑋𝑖 𝑡 + 𝑟3𝑆𝑀 (15) where, sm is a constant indicating the step movement, and 𝑟3 is a random number that stochastically penalizes the value of the step movement (muhammad et al., 2023; salawudeen et al., 2018). 2.2.3 partial shading condition the psc has a greater impact on reducing the power generated by solar systems, and this depends upon the shading pattern, the number of bypass diodes, and the solar system arrangement. the partially shaded pv module functions as a load and not as a source of power. this is known as the hot-spot effect, and if the heat produced exceeds a certain threshold, it leads to disintegration and damages the cell, resulting in an open circuit (al-wesabi et al., 2020).to safeguard against such a hazardous scenario, the bypass diode is installed in the pv system, as shown in figure 3.the bypass diodes will remain in the reverse cut-off state if the photovoltaic panels are subjected to normal conditions. in the event the pv modules are exposed to the psc, the bypass diode conducts to form a short circuit; thereby preventing it from getting reversed by the reverse leakage current and enhancing the whole output power. to examine the efficiency of these algorithms, the 4s configuration (figure 3) was employed in the simulation. this is a well-known configuration for the pv system which consists of four series connected pv modules and has four different power peaks under pscs. the four different shading patterns (sps) used in this model correspond to these radiations pattern 1( 1000, 950,900,850 w/m2), pattern 2 (950,900,850,800 w/m2), pattern 3 (900,850,800,750 w/m2) and pattern 4 (850,800,750,700 w/m2). each of the four elements of irradiance in each pattern corresponds to the irradiance falling on the pvs. pattern 1 pattern 2 pattern 3 pattern 4 figure 3: pv patterns for partial shading conditions (adopted: sadegh et al.,2022) 900 w/m2 ipv + vpv pv 3 pv 2 850 w/m2 950 w/m2 pv 1 1000 w/m2 pv 4 850 w/m2 ipv + vpv pv 3 pv 2 800 w/m2 900w/m2 pv 1 950 w/m2 pv 4 800 w/m2 ipv + vpv pv 3 pv 2 750 w/m2 850 w/m2 pv 1 900 w/m2 pv 4 750 w/m2 ipv + vpv pv 3 pv 2 700 w/m2 800 w/m2 pv 1 850 w/m2 pv 4 bypass diode http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):747-758. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 754 3. results and discussion the results for the pv system under a temperature of t _ 25 °c and different shading patterns of power for sao and p and o algorithms are shown in table 3.these results are for transition from pattern 1 to pattern 4 and consist of several local maximum power points (lmpps) and only one global maximum power point (gmpp) under pscs. as shown in table 4, sao tracks maximum values for power as 845.8476 w while the maximum values for p and o as 845.0465 w during sp1. the performance of sao and p and o algorithms in four patterns have been compared in table 4which shows that all algorithms succeed in tracking gmpp but the convergence speed of sao is higher, its efficiency is slightly improved and has less tracking energy losses compared to p and o mppt algorithms. table 3: shading patterns (sp1, sp2, sp3 and sp4) for maximum power of sao and p and o techniques in watt (w) s/n pattern 1 sao p and o pattern 2 sao p and o pattern 3 sao p and o pattern 4 sao p and o 1 0 0 0 0 0 0 0 0 2 688.2668 826.0345 675.2183 772.7223 650.2169 720.7421 593.3545 659.3255 3 628.2921 845.0079 731.9725 794.727 709.6505 744.1879 670.7713 693.1686 4 756.3685 845.0458 764.4782 794.7547 735.3934 744.241 685.2611 693.2556 5 818.0000 845.0452 783.9713 794.7576 741.5228 744.2793 692.9182 693.2257 6 842.2819 845.0456 792.309 794.7556 741.9805 744.244 691.2745 693.2411 7 842.4592 845.0455 792.4423 794.7553 742.1281 744.2403 691.4015 693.2564 8 790.5823 845.0453 776.2829 794.7576 742.6341 744.2794 692.1432 693.2261 9 843.3691 845.0453 793.2386 794.7575 742.7758 744.2463 691.9284 693.2404 10 843.5959 845.0456 793.4373 794.7568 742.9336 744.2439 692.0617 693.2556 11 844.1987 845.0457 793.9608 794.7558 743.3733 744.2789 692.4209 693.2273 12 844.3433 845.0457 794.0848 794.7557 743.4716 744.2441 692.5025 693.2416 13 842.0566 845.0458 793.9811 794.7552 743.6923 744.2435 693.1189 693.2557 14 845.1664 845.0452 794.7898 794.7571 744.0636 744.2436 692.9823 693.226 15 845.5824 845.0452 795.1522 794.7576 744.351 744.2796 693.2221 693.2404 16 845.6837 845.0452 795.242 794.7574 744.418 744.2465 693.2805 693.2544 17 845.7514 845.0452 795.2922 794.7574 744.4675 744.244 693.3165 693.2259 18 845.7999 845.0461 795.3297 794.7555 744.5033 744.2779 693.3434 693.2419 19 845.295 845.0463 795.0421 794.7559 744.5278 744.2446 693.3761 693.2562 20 845.8476 845.0463 795.3871 794.7551 744.5419 744.2419 693.3672 693.2281 21 845.6934 845.0465 794.9709 794.7548 744.5614 744.2765 693.3928 693.2421 table 4: comparative analysis of sao and p and o techniques in 4 sp configuration pattern target power (w) sao tracking power (w) p and o tracking power (w) 1 923.1130 845.8476 845.0465 2 874.3670 795.3871 794.7575 3 825.4070 744.5614 744.2796 4 776.2320 693.3928 693.2564 figures (4-7) are the detailed simulations of results for the pv system under different shading patterns. the power curves for sao and p and o algorithms have been shown in figure (4-7) for a transition from pattern 1 to pattern 4. figure 4 shows the power curve for both sao and p and o corresponding to the partial shading conditions of pattern (1000, 950,900,850 w/m2), in this case, sao and p and o respectively track 845.8476 w and 845.0465w as the gmpp and several lmpps as depicted in table 3. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com amusat et al: maximum power point tracking in partial shaded photovoltaic system using smell agent optimization algorithm. azojete, 19(4):747-758. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 755 figure 4: output power curve of sao and p and o models for pattern 1 at 25oc figure 5 shows the power curve for both sao and p and o corresponding to the partial shading conditions of pattern (950,900,850,800) w/m2. the sao and p and o respectively track 795.3871 w and 794.7576 w as the gmpp and several lmpps as depicted in table 3. the two algorithms track the gmpp but the sao has a higher value under the same tracking time and partial shading condition as shown in table 4. figure 5: output power curve of sao and p and o models for pattern 2 at 25oc figure 6 shows the power curve of the sao and p and o, this corresponds to the partial shading conditions of the pattern (900,850,800,750 w/m2). the sao and p and o respectively track 744.5614 w and 744.2796 w as the gmpp and several lmpps as depicted in table 3. in respective of their tracking efficiency. the sao has a higher value under the same tracking time and partial shading conditions as shown in table 4 figure 6: output power curve of sao and p and o models for pattern 3 at 25oc figure 7 shows the power curve corresponding to the partial shading conditions of pattern the (850,800,750,700 w/m2) of both sao and p and o, in this case, sao and p and o respectively track 693.3928 w and 693.2564 w as the gmpp and several lmpps as depicted 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 100 200 300 400 500 600 700 800 900 time (seconds) p o w e r (w a tt s ) sao p and o 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 100 200 300 400 500 600 700 800 time (seconds) p o w e r (w a tt s ) smo p and o 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 100 200 300 400 500 600 700 800 time (seconds) p o w e r (w a tt s ) sao p and o http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):747-758. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: amusatramoni@gmail.com 756 in table 3. though both algorithms track the gmpp, the sao has a higher value under the same tracking time and partial shading conditions as shown in table 4. figure 7: output power curve of sao and p and o models for pattern 4 at 25oc 4. conclusion the mppt based on smell agent optimization was developed using matlab/simulink environment. this was used to track maximum power under partial shading conditions. the power curves of the shaded pv array have several local peaks and a single maximum power. the effectiveness of the proposed method was determined by comparing its results with conventional techniques (p and o). both algorithms' responses were observed under various conditions, and the results show that the proposed algorithm has excellent tracking results in terms of convergence speed, accuracy, power extracted stability, and dynamic response in reaching the optimum point. references al-wesabi, i., shafik, mb., min, d., mohammad, as., zhijian, f., ahmed, ga., tariq, a., ayman, m. and al-rassas. 2020. pv maximum power-point tracking using modified particle swarm optimization under partial shading conditions. chinese journal of electrical engineering, 6(4): 107-121. amusat, ro., shodiya, s. and ngadda, yh. 2020. preassessment model of solar photovoltaic module using user-friendly matlab program. journal of science technology and education, 8(4): 132-139. amusat, ro., shodiya s. and ngadda yh. 2020. mathematical modeling of maximum power of solar photovoltaic systems and regression analysis for field test conditions. nigeria journal of engineering science and technology research, 6(1): 104 111. attou, a., massoum, a. and saidi, m. 2014. photovoltaic power control using mppt and boost converter. balkan journal of electrical & computer engineering, 2(1): 23-27 chen, lr., tsai, ch., lin, yl., lai, ys. 2010. a biological swarm chasing algorithm for tracking the pv maximum power point. ieee transactions on energy conversion, 25: 484–493. claude, zb. and nazih, m. 2015. a general review on photovoltaic, modeling, simulation and economic study to build 100 mw power plant in lebanon. british journal of applied science and technology, 11(2): 1-21. derbeli, m., napole, c., barambones, o., sanchez, j., calvo, i., fernández-bustamante, p. maximum power point tracking techniques for photovoltaic panel: a review and experimental applications. energies 2021, 14, 7806: 1-31 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 100 200 300 400 500 600 700 time (seconds) p o w e r (w a tt s ) sao p and o file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com amusat et al: maximum power point tracking in partial shaded photovoltaic system using smell agent optimization algorithm. azojete, 19(4):747-758. issn 1596-2490; 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26-34. williamm, ic. and ramesh, r. 2013. comparative study of p&o and inc mppt algorithms. american journal of engineering research (ajer), 2(12): 402-408. younis, ma., khatib, t., najeeb, m. and ariffin, am. 2012. an improved maximum power point tracking controller for pv systems using artificial neural network, przeglad elektrotechniczny, 88 (3):116-121. zaki, am., amer, si. and mostafa, m. 2012. maximum power point tracking for pv system using advanced neural networks technique. international journal of emerging technology and advanced engineering, 2(12): 58 -63. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%204/engr.ibraheem1@gmail.com arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):611-622 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 611 original research article composition and biochemical methane potential from different typha components n. a. sale1*, r. a. kohn2, a. sale3, u. s. mohammed3 and i. b. dalha3 1national agricultural extension and research liaison service, ahmadu bello university, zaria, kaduna state, nigeria 2animal and avian science department, university of maryland college park, md, 20742, usa 3department of agricultural and bio-resource engineering, ahmadu bello university, zaria, kaduna state, nigeria *corresponding author’s email address: nuraalhajisale@yahoo.com 1.0 introduction invasive species are recognized as one of the main causes of erosion of global biodiversity. they represent one of the major environmental challenges of the 21st century (uicn, 2004). many countries have studied the problem but have not found an ideal solution (obiri, 2011). indeed, when invasive species become well established in the environment, the control article information abstract invasive species are recognized as one of the main causes of erosion of global biodiversity which represent one of the major environmental challenges of the 21st century. typha is among the fifth most invasive species in west africa, nigeria included. presently in hadejia valley wetlands of nigeria, typha grass has been perceived as a threat to the surrounding communities. although some research efforts have shown it can be used as a resource material for renewable energy or animal feed, its use has not yet become a commercial practice. this study investigates compositional characteristic using in vitro digestibility and biogas production from different typha botanical fractions using anaerobic digestion inoculated with rumen microorganisms. treatments considered were single plant components as well as combinations. the results show that spike (seed) had the highest soluble crude protein and the leaves had the highest energy content (cellulose and hemicellulose). the leaf and stem at full maturity had a lignin content of 18-20%. rhizome and stem contained higher ash content while root had greater total volatile solid. the spike yielded the most biogas (457 ml/g) at 60 days retention period. the root component yielded the least gas (259 ml/g) over the same period. the seed pod produced the most methane gas per weight of vs (255 ml/gvs). blending leaf and stem or root and rhizome increased the volume of biogas generated (399 ml/g and 442 ml/g respectively) while a combination of all components of the plant decreased the volume of gas (388 ml/g – 289 ml/g). the combination of the root and the rhizome produced a higher volume of methane (254 ml/g) than either component by itself (root with 160 ml/g while rhizome 226 ml/g). different typha components has different compositional characteristic which influence the activity of anaerobic microorganism and affect the volume and quality of biogas produced. rumen microorganisms digest typha component and spike gives the highest gas volume per grams of typha biomass while rood produce the least volume. combination of different typha component affect the volume of gas generation defending of which component of plants were mixed. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 26 july, 2021 revised 16 may, 2022 accepted 20 may, 2022 keywords: composition cattails biogas production components typha methane http://www.azojete.com.ng/ mailto:nuraalhajisale@yahoo.com mailto:nuraalhajisale@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):611-622. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 612 becomes nearly impossible and requires considerable financial and human investment. for example on a continental scale, the united nations environment program (unep) estimated that alien invasive species cost the global economy $1.4 trillion annually (obiri, 2011). in nigeria, the annual cost estimated for invasive species is about $50 million (kasulo, 2000). typha is among the fifth most invasive species in west africa (noba et al., 2017). the grass is commonly called “cattail” and the family is represented worldwide by the genus typha. the weed is a perennial aquatic herbaceous plant with a world-wide distribution in freshwater habitats. it is an erect perennial that can grow to two or three meters in height (bender and bender, 2018). the typha family has a higher growth rate than any other aquatic plant and the family is characterized by having rhizomes, extensive fleshy stems, and tall leaf blades (yakubu, 2015). an abundance of wind-dispersed seeds that allow typha to colonize wetlands across a great distance, and its rapid growth rate and large stature enable aggressive colony propagation. it is especially aggressive where water nutrient levels are elevated from agriculture. over recent decades, the distribution and abundance of typha in wetland ecosystems around the world has caused great concern particularly in africa. in sub-saharan africa, the grass is a menace to the optimal use of channels, rivers, and agricultural lands. mshandete (2009) reported that typha infestation in tanzania lake jipe river was 65-80% of 30 km2. it was estimated to contain 193.3 tons of fresh typha, which is equivalent to 42.46 tons of dry material. a similar report from senegal showed that there was 3.05 million tons of fresh typha material (approximately 520,000 tons in dry form) in the left bank of delta area (diouf et al., 2015). in the dakar area, typha covered 12,058 hectares with 800 tons of fresh material. another report from nigeria estimated that typha infestation in the hadejia valley irrigation scheme alone contained 600,000 tons of fresh biomass (naerls, 2020). this aquatic weed threatens the economic activity, health, and welfare of many communities including the hadejia valley irrigation schemes in northern nigeria. for example in marma channel and nguru lake in hadejia valley the invasion was more severe with over 35,000 hectares of potential farming and grazing lands having been taken over by the typha grass. typha infestation has also contributed to the desiccation of burum gana channels where about 60% of dry season irrigation farms have been affected (babagana et al., 2018). these situations increase the poverty level of communities around the wetlands and also often lead to conflicts among farmers (babagana et al., 2018). the average income of fish catch per fishermen has been reduced from about $8 per day to less than $3 per day (sabo et al., 2010). indirectly, this weed decreases the productivity of rice and other related crops (sabo et al., 2016; salako et al., 2016) wherever it exists. ahmed et al. (2017) and goes (2004) established that the obstructions of canals and water infrastructure caused by typha have increased the risk of flooding in farmlands. ringim et al. (2015) investigated the implication of invasive typha plants on biodiversity in hadejia-nguru wetlands. the authors recommended the overall holistic utilization of the grasses as it had negative impacts on the community around them. in the past, most of the effort spent was on eradication and destruction of the grass without direct economic use. because of its nature, it regenerates fast and re-establishes within a short time. these conventional methods of controlling the grass consume time, labor, and cost. therefore, recent efforts have been made to find alternative methods of typha management so that the threats posed by the grass will be converted to opportunities. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nuraalhajisale@yahoo.com sale et al: composition and biochemical methane potential from different typha components. azojete, 18(4):611-622. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 613 typha has been considered as a renewable energy source and a feedstock for livestock (gijzen et al., 1988; hu and yu, 2005). although this weed is high in lignin, the literature shows it can be degraded by fiber-degrading microorganisms to produce biogas (thanacoses et al., 2003). weimer and kohn (2016) used ruminant microbes for rapid lignocellulose degradation and short-chain fatty acid production for conversion to methane sale et al. (2019) reported the adaptation of rumen microorganisms to typha biomass. mshandete (2009) demonstrated the use of cockroach gut microorganisms with different typha botanical fractions for improved biogas production. adeneran and onothoja (2017) investigated biogas production from constructed wetland (typha grass, water hyacinth, and cyperus papyrus). diouf et al. (2015) studied the fermentability of typha domengensis with rumen content and compared the gas production potential with other biomass. similarly, hu and yu (2005) studied the anaerobic digestion of typha by rumen culture from small ruminant animals. however, the effects of different typha components such as leaves, stalk, root and different combination using rumen fluid from a cow has not been reported. therefore, the present study investigates compositional characteristic and biochemical methane potential of typha biomass from different plants components inoculated with rumen microorganisms. 2.0 materials and methods 2.1 sample collection typha latifolia was obtained from a pond at the university of maryland, united states. this species is similar to the one in hadejia-nguru wetland northern nigeria (yakubu, 2015). therefore, it is assumed to have similar characteristics. the mature plant was harvested at 16% dry matter (dm). the plant was separated into different components (spike, leaf, stem, root, and rhizome) as shown in figure 1. samples were chopped with an electric 15-amp shredder and sun-dried to a dry matter content of 93, 91, 91, 92, and 90% for spike, leaf, stem, root, and rhizome respectively. the second plate in figure 1 similarly shows the dried typha. the samples were then ground with a wiley mill through a 1-mm screen. figure 1: different components of typha are shown as wet, dry, and chopped forms. 2.2 rumen fluid in this study, all procedures including the use of animals were approved by an international animal care and use committee at the university of maryland. rumen fluid was collected anaerobically before daily feeding from a fistulated non-lactating holstein cow fed a timothy hay-based ration. immediately, the rumen fluid was moved to the laboratory and transferred to a blender under co2. after blending, rumen fluid was squeezed through four layers of cheesecloth and then glass wool, into an air-free flask under co2 (figures 2). dried typha wet typha http://www.azojete.com.ng/ mailto:nuraalhajisale@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):611-622. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 614 figure 2: collection of the rumen fluid and filtration of fibers 2.3 reducing media media were prepared using the method of kohn and kim (2015) to minimize the adjustment period. the medium contained water (400 ml/l, micromineral (0.1 ml/l), digested casein (2 g/l), macromineral (200 ml/l), iv buffer (200 ml/l), rumen fluid (200 ml/l) and resazurin (1 ml/l). it was bubbled with co2 while bringing to boil and subsequently cooling. the ph was measured at 39°c and adjusted using naoh or hcl to 6.8. 2.3 analytical methods 2.3.2 dry matter content (dm) the dry matter content was determined by the method adopted from kohn and kim (2015) drying in a kostertm crop forage tester for an hour and weighing with an electronic balance before and after drying at 15 minute interval. the dry matter content was calculated using the equation below. 𝐷𝑟𝑦 𝑚𝑎𝑡𝑡𝑒𝑟 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 = 𝐹𝑖𝑛𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡−𝑃𝑎𝑛 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡−𝑝𝑎𝑛 x 100 (1) 2.4 experimental method 2.4.1 experimental factors and treatment total volume of gas and methane production were determined for the whole-plant, different vegetative part (spike, leaf, stem, root and rhizome), and the combinations of all components as similarly reported by mshandete (2009). a total of eight treatments were considered. the treatments were: spike, leaf, stem, leaf and stem, root, rhizome, root and rhizome, and the whole plant (spike, leaf, stem, root, and rhizome). the combinations of leaf and stem or root and rhizome were 50:50 ratios by weight while the whole plant came out in 20:20:20:20:20 ratio by weight for spike, leaf, stem, root, and rhizome accordingly. the experiment focus on biochemical methane potential from different plants component and no control was considered. 2.4.2 experimental set up each anaerobic digester was developed using a 1,000ml flask fitted with a 2-hole rubber stopper. each stopper had glass tubing attached to luer-lock connectors and valves for sampling. a 1-l mylar gas collection balloon was attached to a valve on each of the flasks figure 3 showed diagram of the experimental setup. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nuraalhajisale@yahoo.com sale et al: composition and biochemical methane potential from different typha components. azojete, 18(4):611-622. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 615 a total volume of 330 ml media and sample was prepared with 30 g at 90% dry mater content of typha biomass and 300 ml of media. the mixture has a total solid content of 2% with organic loading rate of 1g/30 ml. after mixing the samples, carbon dioxide was used to purge the air since it’s heavier than air and can easily replace it. next, the digesters were moved to a thermostatically water bath in a hood at a temperature between 35 40oc with water volume in the bath maintained to replace evaporation. feeding of the material into the digester was done in three phase’s at 10 g each. the first feeding was the initial seeding of the digester. the second feeding was done after ten days while the third was carried out after twenty-three days of the first feeding. volumes of gas produced from the typha degradations were measured three times a week with a 100 ml glass syringe. balloons were used to collect the generated gas over time and then the syringes were used to measure the accumulated gas in the balloons. the ph was tested using the ph meter and a piece of litmus paper at certain intervals. this is to monitor and maintain the ph at 6.5-7.5 by adding naoh or hcl as the case may be. methane, co2, and other gasses were analyzed by wet chemistry method which is simple, cheap and affordable. the method involved the use of alkaline base (naoh, or koh) that absorbed co2 and h2s leaving the ch4 and some water vapour. the method is an alternative to the used of gc and other biogas analysers especially in places where that equipment were not available (pham et al., 2013). for this research 50 ml of collected biogas were injected into a bicarbonate/sodium hydroxide solution into a sealed wheaton bottle with a glass syringe. the bottle was shakes for 5 minutes and the sample absorbed the co2 and other gasses such as h2s while the methane pushed back the syringe and the volume is read from the graduated syringe. the experiment used completely randomized design (crd) with eight treatments and repeated three times (8x3=24). the treatments were t1= whole plant; t2 = spike; t3 = leaf; t4 = stem; t5 = leaf and stem; t6 = root; t7 rhizome; t8 = root and rhizome. biogas and methane volume were measured as an indicator of the performance of each treatment. data collected were analysed using statistical analysis software (sas, version 20). figure 3: schematic arrangement of an experimental treatment. 3 results and discussion 3.1 fiber component of typha at different maturity levels table 1 shows the compositional properties of the typha latifolia at different maturity levels. these records were established to guide the selection of material at appropriate growth stages and provide necessary information to improve the digestibility of typha biomass in anaerobic conditions. the maximum crude protein of 9.9 and 9.8% was observed in a leaf when the plant http://www.azojete.com.ng/ mailto:nuraalhajisale@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):611-622. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 616 was at a tender age (0.5 m height) and senescence seed. however, the minimum crude protein of 2.1 and 2.3 % was recorded when the plant was at the second maturity up to the senescence stages. the result did not agree with mshandete (2009) that reported the maximum crude protein of 29.19% from a combination of root and rhizome while the minimum (10.63%) from a combination of stem and leaf. this was due to the combination of different typha botanical fractions and the present study analysed the typha plant at different growth stages. the highest soluble crude protein was obtained in the early bloom of the seed while the lowest soluble protein was recorded in the stem at the second stage of maturity. neutral detergent fiber (ndf) varied from 68.2 to 79.2% while the maximum was observed in the early bloom leaf. the minimum detergent fiber (ndf) was recorded at 0.5 m leaf. the acid detergent fiber (adf) ranged from 34 to 60% with the maximum recorded in the senescence leaf and minimum found in the early bloomed seed. this indicates more fiber concentrate in the mature leaf than any part of the plant. the results obtained are within the range reported by hu and yu (2005) and nuntiya et al. (2009). the authors obtained the ndf to be 64% and adf 42% the lignin was found to increase with an increase in maturity but it varies slightly within the plant components. the maximum lignin obtained was in the senescence leaf, and the minimum was found from the stem at 0.5 m height plant; the range for the lignin was recorded at 11.5 to 21%. hu and yu (2005) reported the maximum lignin of 10.5% while nuntiya et al. (2009) reported the maximum lignin of 8.86%. the lignin content obtained from this research was higher than what was reported by hu and yu (2005), and nuntiya et al. (2009), this could be due to the age of the plants considered. the implication of this result is that as the plant mature it developed resistant to digestibility under conventional method of anaerobic digestion due to higher lignin content. a higher carbon to nitrogen ratio was also observed within the range of 34 to162. the stem produced a higher ratio at all growth stages. this revealed that if single stem component is use the microorganisms will have nitrogen deficiency which inhibits methane production. mshandete (2009) reported the minimum and maximum carbon to nitrogen ratios of 12 and 23, respectively from typha domingensis. early bloom seed, senescence seed and stem have minimum ash content (5.05, 5.92, 5.97%, respectively) while stem at first maturity growth stage showed the maximum (10.74%). mshandete (2009) obtained the maximum ash at root components (27.68%) and the minimum (8.84%) with the stem. these indicate that different growth stages, components, and typha species affect the fiber composition. these have an influence of the activity of anaerobic microorganism and affect the biogas and methane volume. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nuraalhajisale@yahoo.com sale et al: composition and biochemical methane potential from different typha components. azojete, 18(4):611-622. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 617 table 1: compositions of typha at different stages of maturity dm= dry matter; cp= crude protein; scp = soluble crude protein; ndf= neutral detergent fiber; adf= acid detergent fiber; c/n= carbon to nitrogen ratio; and ash =ash content. 3.2 proximate properties of the typha components typha components contained 80 to 90% water before air drying (sale et al., 2018). the total solids of the plants before drying ranged from 8 to 11% as reported by sale et al. (2018). such a high amount of moisture was a challenge in the process of using the plant as feedstock for biogas production. furthermore, the plant anatomy is such that it conserves the moisture during drying as each stem is wrapped with concentric layers of tissue. however, sale et al. (2018) reported that typha could be air dried once the tissue was disrupted by slicing or chopping. the root and the stem were found to have the highest total solid at (> 10%) while the rhizome and the spike had the lowest solid concentration at (< 8%). the maximum volatile solid was observed in a spike at 92% and in the leaf at 90%. however, the minimum value was recorded with the stem and the rhizome components. the ash content from different botanical fractions ranged from 8 to12%. as expected, the higher the volatile solids the more digestible the material while the higher total solid indicates higher energy content. therefore, this data suggests the spike might have a higher gas potential than any part of the plant component on a wet basis. the rhizome and the stem components had the highest ash content at > 12%. the spike showed the lowest value of ash at < 8%. interestingly, it was observed that as the ash content increased, the volatile solid decreased as shown in table 2. plant maturity dm % cp scp ndf adf lignin c/n ash -% of dm - 0.5 m stem 0.102 5.4 1.5 75.3 49.5 11.5 64.51 10.74 0.5 m leaf 0.181 9.9 2.9 68.2 49 12.1 34.99 8.63 1 m stem 0.23 2.1 0.4 74.0 46.7 12.3 161.82 7.71 1 m leaf 0.242 5.2 1.8 72.2 49.5 12.8 66.01 8.3 1.5 m stem 0.14 4 1.2 75.7 49.1 11.8 84.77 8.19 1.5 m leaf 0.187 7.5 2 69.6 52 11.7 46.46 8.17 early bloom stem 0.094 2.3 0.7 72.7 48.1 13.4 151.58 7.71 early bloom leaf 0.135 5.7 1.7 79.2 50.4 13.7 60.12 7.52 early bloom seed 0.149 9.8 4.8 75.1 33.6 12.1 34.69 5.05 senescence stem 0.386 2.3 0.8 75.9 57.9 18.2 148.02 5.97 senescence leaf 0.198 3.1 1.1 78.5 60.4 20.8 105.69 7.06 senescence seed 0.138 9.8 4.6 73.7 40 12.0 34.47 5.92 http://www.azojete.com.ng/ mailto:nuraalhajisale@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):611-622. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 618 table 2. proximate properties of the typha components plant components ts (%) vs (%) ash (%) rhizome 7.84 87.67 12.33 root 10.78 88.89 11.11 stem 10.78 87.72 12.28 leaf 8.91 90.44 9.56 spike 6.93 92.37 7.63 whole plant 10.68 88.79 11.21 ts = total solid. vs= volatile solid. ash= ash content 3.3 gas productions per volatile solid (vs) figure 4 show gas production per volatile solid obtained the highest gas was obtained using the single botanical fractions of the spike at 455 ml/g vs. the lowest value was recorded with the root component at 292 ml/g vs. the records obtained might be due to lower fiber content found in the spike and higher volatile solid as against any other parts of the plant. the root contained a lot of ash which could have affected the volatile solid. when the plant components were blended, the composition of root and rhizome produced the highest gas per volatile solid at 442 ml/g vs. the whole plant produced less than the combinations of the leaf and the stem at 313 ml/g vs as shown in figure 4. getahu et al. (2014) obtained gas production from different wastes to be 0.15, 0.17, and 0.08 m3/kg vs fruit, food, and paper respectively. the authors conclude that paper waste produces the least gas. figure 4: gas productions per gram of volatile solid for single plant components and combinations 3.4 methane yield from different vegetative parts of the plant figure 5a indicates the methane yield obtained from the different typha botanical fractions. the maximum methane yield was obtained for the treatment with only a spike (255 ml/g of biomass at sixty (60) days retention time). the lowest yield was observed from the root (161ml/g of biomass over the same period). one of the possible reasons might be due to the higher soluble crude protein content in the seed which enhances the growth and development of methanogen that are responsible for methane production. another reason was oil content in the seed which has higher potential methane content. leaf has the second-highest volume of methane generation (231 ml/g) over the same retention period. this is because leaf has a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nuraalhajisale@yahoo.com sale et al: composition and biochemical methane potential from different typha components. azojete, 18(4):611-622. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 619 lower carbon to nitrogen ratio before the plant mature (0.5-1.5m height) a good carbon to nitrogen ratio enhances methanogen development and thereby increases the activity of microorganisms. higher cellulose and hemicellulose were also obtained from the leaf as indicated in table 1. biogas generation from typha grass has a little number of publications around the world. the available literature indicates that only one similar study was conducted by mshandete (2009). therefore, the comparison was not much. however, the result obtained was not in agreement with mshandete (2009) that obtained the maximum yield of methane using single leaf botanical fractions and minimum with the spike. one of the reasons might be due to the difference in inoculant source and typha species used. mshandete used inoculant from cockroach gut microbial source with typha domingensis while the present study used rumen microbes with typha latifolia. figure 5a. methane yield from 30 g of different typha components figure 5 b show methane yield from the combination of different typha components. a combination of the root and rhizome produces the highest yield of methane (254 ml/g). this is due to higher carbohydrate content from the two components and higher total volatile solid from the root. similarly, the lignin content from these two components was not much therefore, the components were easily degraded and produce higher gas yield. also, the combination of these two components might produce a good balance of micro and other trace elements for the growth and activities of microorganisms. the combination of whole plant components produced the lowest methane volume (202 ml/g), which might be due to the production of inhibitory substance to some microorganisms. these inhibited the process and therefore led to a decrease in volume generation. the blending of the leaf and stem was the second after the root and rhizome with the gas yield of 206 ml/g figure 5b shown. however, a similar result from combination of different typha component was obtained by mshandete (2009). the author obtained the maximum methane generation from the combination of root and rhizome (75 ml/gvs) at 30% total solids. series1 0 2000 4000 6000 8000 root stem leaf rhizome spike m et h an e vo lu m e (m l) typha components http://www.azojete.com.ng/ mailto:nuraalhajisale@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):611-622. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 620 figure 5b. methane yield from 30 g blended typha components 4. conclusions typha compositional characteristics at different maturity and the effect of the different components for methane production has been evaluated. plant growth stages affect the compositianal characteristic which has an influence of the activity and growth of microorganisms that digest the plant and produce biogas. seed (spike) had higher soluble crude protein (4.8%) which gives it a higher potential for methane production. leaf had the highest energy content (cellulose and hemicellulose) (78%). lignin is one of the limiting factors in the anaerobic digestion of lignocellulosic material obtained to increase as the plant`s maturity increases. this affect the digestibility of the plant under conventional method and therefore some preteatment is needed to improve biodigestion process. rumen microorganisms improve digestion of typha component despite the higher lignin content. root and stem have the maximum total solid among all the different components tested (10.78%). the spike had the highest volume of gas per gram of volatile solid at 455 ml/g vs and the highest methane generation (255 ml/g). gas production increased with the composition of the leaf and the stem or the root and rhizome compared to single component production. the combinations of the entire parts of the plant decreased the cumulative volume of gas compared to a composition of only the stem and the leaf or that of the root and the rhizome. however, a combination of the root and rhizome increased the methane concentration compared to other combinations. conflict of interest the authors have no conflicts of interest acknowledgments we appreciate the contributions of our colleagues at the national agricultural extension and research liaison services (naerls) (prof. m. k. othman, engr. a. o. lawal, engr. aminu fagge, engr. t. o. olanrawaju, and a. a. wahab) and the polytechnical university of madrid (evar iglesias and fernando escribano). we also thank the transforming irrigation water management in nigeria (triming) under the federal ministry of water resources of nigeria for funding the research under the world bank assisted project. series1 0 2000 4000 6000 8000 whole plant leaf & stem root & rhizome m et h an e vo lu m e (m l) typha combinations file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nuraalhajisale@yahoo.com sale et al: composition and biochemical methane potential from different typha components. azojete, 18(4):611-622. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nuraalhajisale@yahoo.com 621 funding the research was funded by the world bank under the federal ministry of water resources of nigeria. references adeniran, ea. and onothoja, ub. 2017. the potentials of production of biogas from constructed wetland macrophytes. african journal of biotechnology, 16(33): 1724–1732. http://doi.org/10.5897/ajb2017.16052 ahmed, sd., sampson, ka., adjei, ka., deinmodei, m. and ameso, vc. 2017. preliminary investigations of flooding problems and the occurrence of kidney disease around hadejianguru wetlands, nigeria, and the need for an ecohydrology solutions. ecohydrology and hydrobiology, 18(2):212-224. babagana, m., adamu, a., usman, dd., amma, ha., ado, g., yakubu, m. and zungum, iu. 2018. characteristics and socio economic activities of local communities living along the nguru wetlands, yobe state, nigeria. international journal of contemporary, research and review, 9(6): 20224-20239. bender, da. and bender ae. 2018. a dictionary of food and nutrition, third edition. new york: oxford reference collection. oxford university press. diouf, i., demba, s., cheikh, d., bienvenu, s. and mouhamadou, ds. 2015. study of the fermentescibilty of typha domingensis in mode mesophilic. american scientific research journal for engineering, technology, and sciences (asrjets), 16(1):126-136. retrieved from http://asrjetsjournal.org/ getahu, t., mulat g., argaw a., tom van, g. and bart, vb. 2014. potential of biogas production from municipal solid waste in a tropical climate. environmental monitoring and assessment, 186:4637-4646, available@ doi 10.1007/s10661-014-3727-4. gijzen, hj., zwart, kb., verhagen, fjm. and vogels, gd. 1988. high-rate two-phase process for anaerobic degradation of cellulose employing rumen microorganisms for an efficient acidogenesis. biotechnology and bioengineering, 31: 418 – 425. goes, bjm. 2004. effects of river regulations on aquatic macrophyte growth and floods in the hadejia-nguru wetlands and flow in the yobe river, northern nigeria; implications for future water management. river research and applications, 18 (1): 81-95. hu, zh. and yu, hq. 2005. anaerobic digestion of cattail by rumen cultures. waste management, 26(11):1222–1228. http://doi.org/10.1016/j.wasman.2005.08.003 kasulo, v. 2000.the impact of invasive species in africa lakes: the economics of biological invasions. edward elgar publishing, massachusetts usa, pp. 183. available https://doi.org/10.4337/9781781008645 kohn, ra. and kim, s. 2015. using the second law of thermodynamics for enrichment and isolation of microorganisms to produce fuel alcohols or hydro carbon. journal of theoretical biology, 382:356-362 mshandete, am. 2009. anaerobic digestions of cattail weeds to produce methane using american cockroach gut microorganisms. arpn journal of agricultural and biological science, 4 (1): 45-57 http://www.azojete.com.ng/ mailto:nuraalhajisale@yahoo.com http://doi.org/10.5897/ajb2017.16052 http://asrjetsjournal.org/ http://doi.org/10.1016/j.wasman.2005.08.003 https://doi.org/10.4337/9781781008645 arid zone journal of engineering, technology and environment, december, 2022; 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of hadejia nguru wetland system nigeria. environmental and natural resource journal, 14 (2): 44-59 sale, na., kohn, ra., lawal, ao., fagge, aa. and idris, si. 2019. adaptation of rumen microorganisms to typha biomass for enhancement of biogas generation. proceedings for the 40th annual general meeting and 20th international conference for nigerian institution of agricultural engineers, 16-20th september 2019, omu-aran, pp. 1223-1228?? -?? sale, na., ratiff, snl., iyiola, t. and kohn, ra. 2018. cattail drying process for animal feed. proceedings of animal science association of nigeria and nigerian institute of animal science 7th asan-nias joint annual meeting, 9th -13th september, ilorin, 23: 602-605. thanakoses, pa., black, s. and. holtzapple, mt. 2003. fermentation of corn stover to carboxylic acids. biotechnology and bioengineering, 83: 191-200 national agricultural extension and research liaison services (naerls) 2018. second quarter report, typha management, and economic use, submitted to transforming irrigation water management in nigeria (triming). a study conducted in hadejia valley irrigation scheme. pp 2-10. uicn 2004. prevention and management of invasive alien species: implementation of cooperation in west africa, proceedings of a regional workshop, accra ghana, pp: 117. weimer, pj. and kohn, ra. 2016. impacts of ruminant microorganisms on the production of fuels: how can we intercede from the outside? applied microbiology and biotechnololgy journal, 100: 3389–3398 yakubu, ba. 2015. studies on the ecology and control of typha spp. in hadejia-nguru wetlands, nigeria. phd dissertation in botany submitted to ahmadu bello university, zaria, pp. 6-8. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nuraalhajisale@yahoo.com arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):517-526 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 517 original research article analytical determination of queueing system performance for sustainable economic development p. b. anyin1*, and a. a. etika2 1*department of civil engineering, university of calabar, calabar, nigeria 2department of civil engineering, cross river university of technology, calabar, nigeria *corresponding author’s email address: profpeteranyin@unical.edu.ng 1.0 introduction with the 5% annual rate of urbanization, the united nation projected that half of the world population would live in urban areas at the end of 2020 (united nation, 2016). it is predicted that by the year 2050, approximately 64% of the developing world and 86% of the developed world would be urbanized. that is equivalent to approximately 3 billion urbanites by 2050, much of which will occur in africa and asia (united nation population fund 2012). notably, it is also found time past by united nation that nearly all global population growth from 2017 to 2030 will be absorbed by cities, about 1.1 billion new urbanites over 13 years. urbanization creates enormous social, economic and environmental changes such as traffic queue, congestion and delay especially in intracity transportation services. this traffic congestion in traffic service delivering points creates queue, hence queue and time lost ought to be studied. the term ”queue” can be defined as a waiting line especially of persons or vehicles (customers) in a file or line waiting for services where one or more customers are called upon at a time to be served based on accessible service units known as servers. queueing theory has its origins in a research that established models to describe the copenhagen telephone exchange (chen, 2021). the ideas have since seen applications in telecommunication, traffic engineering article information abstract the increase in land travel demand over the years which poses a challenge in managing the high influx of people and goods into urban centres and cities such as abuja, calabar, lagos, kano, and kaduna, nigeria has led to queues in security check points. this study determines a mathematical model for analysing queueing system performance measures using the data obtained from kugbo check-point, abuja keffi highway. the service time data and system settings are used to choose the m/m/1 queueing mathematical model for a single server queueing system. according to the study, an average queue includes 3751 cars and takes 1 hour and 11 minutes to complete. an hourly queueing graph showed that on the busiest days, queue length and waiting time rose. based on the busiest days (mondays), an hourly queueing graph revealed that customer queueing length and waiting time is at its highest in the morning hours from 7am to 11am, and then from 4pm to 7pm. for effective and economical system management, this length of time spent on queue should be taken into account, also artificial intelligent simulation models like netsim, simevent in matlab models are recommended for comparative studies. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 dec., 2022 revised 24 april, 2022 accepted 30 april, 2022 keywords: urbanization mathematical model queueing system performance measures waiting line http://www.azojete.com.ng/ mailto:profpeteranyin@unical.edu.ng mailto:profpeteranyin@unical.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):517-526. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 518 and computing and particularly in industrial engineering, design of factories, shops, offices and hospitals, as well as in project management. it is employed in transportation facility to ensure quality control. with this knowledge, it is possible to rationalize the decision making process, with respect to waiting lines. from a qualitative one, thereby improving the chances of deciding correctly (agner, 1909). service pattern – series called’ “service discipline” where identical servers are accessed through two or more channels rendering the same services; and queueing rule refers to as queue discipline which include; first-in-first-out (fifo) meaning, who comes in first leaves earlier, last-in-first-out (lifo) meaning, who comes in later leaves earlier. random order of service (ros) which means random selection of customers. shortest processing time first (sptf) meaning, customers with shortest service processing time will receive service first and longest processing time first (lptf) meaning, ros opposite. a priority queue is that in which arrivals are classified into groups based on criterion (adeke, 2015; borgs et al., 2012; penttinen, 2008; daigle, 2005; sethi et al., 2020, kleinrock, 1975). queueing process is basically presented as shown in figure 1, where arrivals enter the system, they join a queue, wait for services and then proceed into the service facility to be served after which they depart out of the system. figure 1: schematic of queueing process (adeke, 2015) following the increasing demand for land travel over the years, its poses a challenge in managing high inflow of vehicles into cities, which result into queue in the security check-in system which leads to prolong waiting time (biliyamin and abosede, 2012). the check-in process requires vehicles to join queues for security check using scanners, which could lead to congestions and tension on the road if not properly managed. queueing studies is aimed at using queueing parameters such as; inter-arrival, pattern of service, service rate, busy and idle times of server and number of service units, to examine performance characteristics of system service, and other parameters of interest called “performance characteristics”, this is used for determining the efficiency and capacity management strategy for the system (zukerman, 2018). the performance characteristics is pivotal for every queueing studies. the performance of queueing system is influenced by system configuration and service protocol which is significant to system management in decision making (adeke, 2015, varma and maguluri, 2022). following the 5% annual growth in travel demand, it can be related that the future of every checkpoint, bus stops, and other related bottlenecks are at risk. queue affects customers’ value of time (vot), and it forces them to renounce more productive and rewarding way of using time and to renege promises. this study attempts to determine queueing system performance characteristics (waiting time, queue length) using mathematical models. to justify the goal of this research, the daily growth in land traffic response and terrible increase in security checkpoints make it necessary to create a model to anticipate the future of vehicle performance in various checkpoints. arrivals queue service departure file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:profpeteranyin@unical.edu.ng anyin and etika: analytical determination of queueing system performance for sustainable economic development. azojete, 18(3):517-526. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 519 2. material and methods 2.1 probability and distribution function consider the case where the inter-arrival and service times are independent and exponentially distributed (memoryless). therefore, the arrival process follows a poisson process with parameter 𝜆 and service times are assumed to be iid and exponentially distributed with parameter 𝜇 , and are independent of the arrival process. queueing entities are random variables; when we say that random variable x takes value x, this means that x represents a certain outcome of an experiment which is an event, so {x = x} is an event. therefore, we may assign probabilities to all possible values of the random variable. therefore the function denoted 𝑃𝑋(𝑥) = 𝑃(𝑋 = 𝑥) is called probability function. the cumulative distribution function of random variable 𝑋 is defined for all 𝑋 ∈ 𝑅 (r being the set of all real numbers), is defined as; 𝐹𝑋(𝑥) = 𝑃(𝑋 ≤ 𝑥) accordingly, the complementary distribution function �̅�𝑋(𝑥) is defined by; �̅�𝑋(𝑥) = 𝑃(𝑋 > 𝑥) consequently, for any random variable, for every 𝑋 ∈ 𝑅, 𝐹(𝑥) + �̅�(𝑥) = 1. this relation is termed a reversible process. then 𝑌 = 𝑔(𝑋) is also a random variable. in this case, if 𝑃𝑋(𝑥) is the probability function of 𝑋 then the probability function of 𝑌 is; 𝑃𝑌(𝑦) = ∑ 𝑃𝑋(𝑥) 𝑥;𝑔(𝑥)=𝑦 a poisson random variable with parameter λ has the following probability function: 𝑃(𝑋 = 𝑖) = 𝑒−λ λ𝑖 𝑖! 𝑖 = 0, 1, 2, 3, . . . . to compute the values of 𝑃(𝑋 = 𝑖), it may be convenient to use the recursion 𝑃(𝑋 = 𝑖 + 1) = λ 𝑖+1 𝑃(𝑋 = 𝑖) 𝑃(𝑋 = 0) = 𝑒−λ (1) the importance of the poisson random variable lies in its property to approximate the binomial random variable in case when n is very large and p is very small so that np is not too large and not too small. for convenient we will consider a sequence of binomial random variables xn, n = 1, 2, . . . with parameters (𝑛, 𝑝) where 𝜆 = 𝑛𝑝, or 𝑝 = 𝜆/𝑛. then the probability function lim 𝑛→∞ 𝑃(𝑋𝑛 = 𝑘) is a poisson probability function with parameter λ. to prove this we write: lim 𝑛→∞ 𝑃(𝑋𝑛 = 𝑘) = lim n→∞ ( 𝑛 𝑘 ) 𝑃𝑘(1 − 𝑝)𝑛−𝑘 substituting 𝑝 = 𝜆/𝑛, we obtain lim 𝑛→∞ 𝑃(𝑋𝑛 = 𝑘) = lim n→∞ 𝑛! (𝑛 − 𝑘)! 𝑘! ( λ 𝑛 ) 𝑘 (1 − λ 𝑛 ) 𝑛−𝑘 now notice that lim 𝑛→∞ (1 − λ 𝑛 ) 𝑛 = 𝑒−λ lim 𝑛→∞ (1 − λ 𝑛 ) −𝑘 = 1 and lim 𝑛→∞ 𝑛! (𝑛−𝑘)!𝑛𝑘 = 1 http://www.azojete.com.ng/ mailto:profpeteranyin@unical.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):517-526. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 520 therefore, lim 𝑛→∞ 𝑃(𝑋𝑛 = 𝑘) = λ𝑘𝑒−λ 𝑘! (2) 𝑓(𝑥) = {𝑋 ≤ 𝑥} = {𝜆𝑒−𝜆𝑥 𝑥 ≥ 0 0 𝑥 < 0 the cumulative distribution function (cdf) is given as 𝐹(𝑥) = 𝑃{𝑋 ≤ 𝑥} = {1 − 𝑒−𝜆𝑥 𝑥 ≥ 0 0 𝑥 < 0 the general relationship between these functions is; 𝑓(𝑥) = 𝑑𝐹(𝑥) 𝑑𝑥 (3) equation (3) is according to zukerman (2018). 2.2 utilization utilization is an important measure for queueing systems performance, denoted by ρ. it is the average proportion of time a server is busy. in most scenarios a server pays for its time regardless of whether it is busy or not. normally, the time that transmission capacity is not used is time during which money is spent but no revenue is earned. it is, therefore, important to design systems that will maintain high utilization (zukerman, 2018). if you have two identical servers and one is busy 0.4 of the time and the other 0.6. then the utilization is 0.5. we always have that 0 ≤ ρ ≤ 1. if we consider an m/m/∞ queue (poisson arrivals, exponentially distributed service times and infinite servers) and the arrival rate is finite, the utilization is zero because the mean number of busy servers is finite and the mean number of idle servers is infinite, therefore queue won’t build up. in scenarios where m/m/1 queue is considering the utilization equation would be ρ>0 (zukerman, 2018). therefore utilization equation ρ = λ 𝜇 (4) this expression is called traffic intensity or utilization equation. figure 3 presents a system of queueing with vehicular arrival rate, 𝜆 and service rate as 𝜇 in a sequence of arrival, in a single server customer flow describing a utilization factor. figure 3: flow diagram for m/m/1 model (daniel, 1995). 2.3 little’s formula the fundamental queueing formula 𝐿 = 𝑋𝑊 (little's law) states that “the time-average queue length (number in the system) l is equal to the product of the arrival rate x and the customer-average waiting time (time spent in the system) w”. this formula is valid in great generality, and defined by little (1961). this is an important queueing mathematical theory result that applies to m/m/1 queue (and to the other systems) is called little’s formula. it can also be expressed as; 𝐸[𝑄] = 𝜆𝐸[𝐷] (5) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:profpeteranyin@unical.edu.ng anyin and etika: analytical determination of queueing system performance for sustainable economic development. azojete, 18(3):517-526. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 521 where 𝐸[𝑄] and 𝐸[𝐷] are the representative of the stationary mean queue-size and the delay mean (system waiting time) from the moment it arrives until the culmination of the service, respectively (zukerman, 2018). this is graphically displayed in figure 2. figure 2: cumulative fluid model (adeke 2015) from the graphical proof of little’s formula for the case of m/m/1. consider a stable m/m/1 queue that starts at time t=0, for a null queue. let 𝐴(𝑡) be the number of arrivals up to time t, and let 𝐷(𝑡) be the number of departure up to time t. the queue-size (number in the system) at time t is denoted 𝑄(𝑡) and is given by 𝑄(𝑡) = 𝐴(𝑡) − 𝐷(𝑡), 𝑡 ≥ 0 (6) let 𝐿 be an arbitrarily long period of time. then the mean queue-size 𝐸[𝑄] is given by 𝐸[𝑄] = 1 𝐿 ∫ 𝑄(𝑡)𝑑𝑡 𝐿 0 (7) also notice that ∫ 𝑄(𝑡)𝑑𝑡 = ∑ 𝑊𝑖 𝐴(𝐿) 𝑖=1 𝐿 0 where 𝑊𝑖 represent the time spent in the system by the 𝑖𝑡ℎ customer. (since l is arbitrarily large, the may have been large number of events during [0, l] where our stable m/m/1 becomes empty, so 𝐴(𝐿) = 𝐷(𝐿).) therefore, 1 𝐿 ∫ 𝑄(𝑡)𝑑𝑡 = 1 𝐿 ∑ 𝑊𝑖 𝐴(𝐿) 𝑖=1 𝐿 0 and realizing that 𝜆 = 𝐴(𝐿)/𝐿 and 𝐸[𝐷] = 1 𝐴(𝐿) ∑ 𝑊𝑖 𝐴(𝐿) 𝑖=1 (8) 𝐸[𝑄] = 1 𝐿 ∫ 𝑄(𝑡)𝑑𝑡 𝐿 0 = 𝐴(𝐿) 𝐿 1 𝐴(𝐿) ∑ 𝑊𝑖 𝐴(𝐿) 𝑖=1 = 𝜆𝐸[𝐷]. considering the number `of customers in the systems, denoted by 𝑁𝑠. where 𝑁𝑠 can only take the values of zero or more, 𝐸[𝑄] = 𝜆𝐸[𝐷]. 𝐸[𝑁𝑠] = 𝜆𝐸[𝐷]. where 𝐸[𝐷] = 1/𝜇; 𝐸[𝑁𝑠] = 𝜆(1/𝜇) http://www.azojete.com.ng/ mailto:profpeteranyin@unical.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):517-526. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 522 𝐸[𝑁𝑠] = 𝜆 𝜇 the conventional notations in queueing theory for k-server queue is represented by equation (4). since queue process is a stochastic process that obeys birth and death process. in m/m/1 we consider a case where the arrival process follows poisons process with parameter 𝜆 and service times are assumed to be independently identically distributed with parameter µ and is independent of the arrival (zukerman, 2018). assuming m/m/1 queue capacity starts from 𝑗, the first entity will pass through state n, for a period of time 𝜆 (𝜆 =0, because no queue). then it moves to state 𝑗 + 1. the total time the entity stays in the system is also exponentially distributed and is independent of any arrival = µ. the second entity enters state 𝑗 and wait until the first entity is done with service. after the second entity spends the total time of 𝜆 + µ, it will move to state 𝑗 + 1 with probability 𝜆 𝜆+µ and to state 𝑗 − 1 with probability µ 𝜆+µ . we write that; 𝜋𝑗+1(𝜆 + µ) = 𝜋𝑗(µ) 𝜋𝑗+1µ = 𝜋𝑗𝜆 for i = 0, 1, 2, 3 from equation 6, 𝜌 = 𝜆 𝜇 𝜋𝑗+1 = 𝜋𝑗 𝜌 since the utilization equation from j to j+1 is 𝜌, the opposite will be 𝜋0= 1 – 𝜌 𝜋1 = 𝜋0 𝜌 𝜋1 = 𝜌(1 𝜌) summing the states we obtain; 𝐸[𝑄] = ∑ 𝑖𝜋𝑖 ∞ 𝑖=0 . 𝐸[𝑄] = 𝜌 1 – 𝜌 . according to zukerman (2018), queue length, 𝐿 = 𝜌 1 – 𝜌 (9) 2.4 data source traffic count data were collected at kugbo checkpoints. the daily vehicular demand was 45000 units and hourly vehicular demand was 3698 units. figure 4 below presents the traffic situation in kugbo checkpoint. figure 4: traffic situation in kugbo checkpoint showing the presence of queue file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:profpeteranyin@unical.edu.ng anyin and etika: analytical determination of queueing system performance for sustainable economic development. azojete, 18(3):517-526. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 523 2.5 data collection traffic count data were collected using a pneumatic sensor traffic dictator connected to a computer, which reads the fluid pressure from the vehicles. the data collected are the arrival time and the service time. 2.6 data processing the arrival rate was computed using equation (12) and service rate was determined using equation (13). easyfit statistical application was used to determine the frequency distribution that the arrival time and service rate followed. 2.7 assumptions the following assumptions were applicable to scenarios considered for the study.  arrivals are discrete and assumed to follow poisons distribution and the system assumes exponentially distributed service time.  the system assumes a steady state with utilization factor or traffic intensity ⍴𝑡 < 1.  the scenario operates using fifo and non-pre-emptive queueing rules  the queue server is assumed to be one  there is inspection and rejected interjecting arrivals in the system. 2.6 basic analysis following adeke (2018), for the estimation of the parameters, the period of heavy operation was assumed from the day with the busiest traffic shown in table 3, to be the peak period of this analysis; that is a non-stop inflow and continues service situation spanning from 06:00 am to 06:00 pm. inter-arrival time,(sec/veh) = 12∗60∗60(𝑠𝑒𝑐) 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐴𝑟𝑟𝑖𝑣𝑎𝑙 𝐷𝑒𝑚𝑎𝑛𝑑 (veh𝑠) (10) service time, (sec/veh) = 12∗60∗60 (𝑠𝑒𝑐) 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑑𝑎𝑖𝑙𝑦 𝐷𝑒𝑝𝑎𝑟𝑡𝑢𝑟𝑒 (veh𝑠) (11) arrival rate, 𝜆 (veh/sec) = 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐴𝑟𝑟𝑖𝑣𝑎𝑙 𝐷𝑒𝑚𝑎𝑛𝑑 (veh𝑠) 12∗60∗60 (𝑠𝑒𝑐) (12) service rate, µ (vehs/sec) = 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑑𝑎𝑖𝑙𝑦 𝐷𝑒𝑝𝑎𝑟𝑡𝑢𝑟𝑒 (veh𝑠) 12∗60∗60 (𝑠𝑒𝑐) (13) summary of the equations utilized in the analysis is presented in table 1. table 1: summary of performance estimation formulae performance parameters formulae utilisation factor 𝜌 = 𝜆 𝜇 average waiting time in system 𝑊𝑞 = 1 𝜇(1−𝜌 ) average queue length 𝐿𝑞 = 𝑊𝜆 = 𝜌 1 – 𝜌 source: zukerman (2018) http://www.azojete.com.ng/ mailto:profpeteranyin@unical.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):517-526. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 524 4. results and discussion 4.1 vehicular demands the daily and hourly vehicular travel demands for the kugbo check point are presented in table 2. this shows that the volume flow rate of vehicles at this check point is large. table 2: vehicular travel demand for kugbo, checkpoints 4.2 queue system performance the waiting time and queue length of customers determined using little’s formula and the performance indicators for kugbo checkpoint, are presented in table 3. table 3: daily vehicular performance measures days totalarrival (veh) arrival rate (vehs/sec) service rate (veh/sec) traffic intensity (unit) average waiting time(sec) queue length (veh) monday 42443 0.9825 0.9985 0.9840 3818 3751 tuesday 39598 0.8950 0.9985 0.89635 84 75 wednesday 38069 0.8612 0.9985 0.8625 46 39 thursday 36862 0.8008 0.9985 0.8020 20 16 friday 39378 0.8555 0.9985 0.8868 62 56 saturday 34996 0.6965 0.9985 0.6975 7 5 sunday 34760 0.6169 0.9985 0.6179 4 3 table 3 shows the service rate for all days, and assumed to be the same for all days, the traffic intensity (utilization factor), waiting time and queue length of various days was estimated. monday has the highest traffic intensity, waiting time and queue length followed by tuesday, friday and wednesday, sunday has the least queueing effect. these performance characteristics are dependent on the arrival rate, the higher the arrival rate the higher the performance characteristics. from the traffic utilization factors, this show that monday has the busiest traffic as well as the longest queue length of 3751 vehicles and waiting for 3818 seconds in other words 64 minutes, a whole lot of time to waste. this signals a problem to motorists plying this route. it is practically impossible to have every hour on monday very busy. table 4 displays the evidence of cumulative hourly queue distribution on monday. the arrival of vehicles at the checkpoint are different depending on the hour of arrival and the service rate is assumed a constant at 3594 hourly service time taken on average, finally the cumulative queue shows the difference between the arrival and service describing the utilization factor where by, the negative sign indicates no queue while otherwise queue. table 4: vehicular hourly cumulative arrival and departure november 2017 time(h) 7 8 9 10 11 12 13 14 15 16 17 18 arrival 1855 12213 18527 22291 24740 28456 31708 34083 36020 37270 39526 38833 service 3594 7193 10841 14318 18018 21706 25304 28905 32497 36018 39606 39526 cum. queue -1739 5020 7686 7973 6722 6750 6404 5178 3523 1252 -80 -693 s/n checkpoints estimated daily arrivals (vehicles/day) estimated hourly arrivals (vehicles/hour) 1 kugbo 44379 3698 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:profpeteranyin@unical.edu.ng anyin and etika: analytical determination of queueing system performance for sustainable economic development. azojete, 18(3):517-526. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 525 the bar differences between the constant and the rising arrival indicate the queued vehicles. at the last column of 18 hour of the day, the service rate rose higher than the arrival rate indicating the reconciliation period, where the queue dissipates. consequently, the idle period in the system is indicated with a negative sign which denotes under-utilization. it is seen that between 7am to 3pm the queue builds up and collapsed by 4pm, but the peak of it is by 8 to 10am. therefore, the waiting line becomes infinite around its peak hours. every hour has her traffic situation at a constant service rate, and this is demonstrated in figure 5 which shows that the hourly queue condition is dependent on the rate of arrival. figure 5: hourly arrival and service graph following the information in figure 5, the waiting line is over 7830 vehicles which is equivalent to 7970 seconds, 2 h and 13 mins. therefore, within this time customer are delayed for quite an unbearable time. this can be related to customer’s feelings and reaction to services delivered lately which neutralizes potential happiness of the service delivered. this study is relevant to urban settlers in decision making for optimum service delivery. 5. conclusion the queueing system performance characteristics were determined using mathematical models and it was found that; an average queue length of 3751 vehicles and, 1h and 11mins waiting time. also the customers suffer more queue on mondays. judging from the busiest day an hourly queue chart proved that the queue length and waiting time of customers is at its peak in morning hours from 7am to 11 am and subsequently from 4pm to 7pm. `looking at this, commuters could be late for jobs, truckers could incur additional charges and business travellers can loss their transaction. for effective and economical system management, this length of time spent on queue should be taken into account. other artificial intelligent simulation models like netsim, simevent in matlab models are recommended for comparative studies. http://www.azojete.com.ng/ mailto:profpeteranyin@unical.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):517-526. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 526 reference adeke, pt., 2018. modelling of queueing process at airport check-in system: a case study of manchester and leeds-bradford airports. nigerian journal of technology (nijotech), 37(1): 35 – 43. adeke, pt. 2015. mathematical modelling of priority queues. m.sc. dissertation, university of leeds. uk., accessed: 24th october, 2017. agner, ke. 1909. the theory of probabilities and telephone conversation. nyt tidsskrift for matematik, b. 20; 33 – 39. biliyamin, ab. and abosede, ba. 2012. effects of congestion and travel time variability along abuja -keffi corridor in nigeria. global journal of researches in engineering civil and structural engineering. 12(3): 63 – 87. borgs, c., chayes, jt., doroudi, s., harchol-balter, m. and xu, k. 2012. pricing and queueing. performance evaluation review, 40(3): 71–73. chen, x. 2021. public restrooms and queueing. major papers, 170., m.sc. thesis, university of wndsor, canada. https://scholar.uwindsor.ca/major-papers/170/ daigle, jn. 2005. queueing theory with applications to packet telecommunication, springer science and business media, new york. daniel, a. 1995. introduction to queue theory: notation, single queue and littles result. ece/cs 441: computer system analysis. university of leeds, uk. gupta, n. and garg, r. 2012. a view of queue analysis with customer behaviour, balking and reneging. proceedings of the national conference on trends and advances in mechanical engineering, ymca, university of science and technology, faridabad, haryana, oct 19-20, 2012, pp: 906 – 910. harchol-balter, m. 2012. multi-server queueing systems with multiple priorities. queueing systems: theory and applications journal (questa), 51(3-4): 331 – 360. little, jdc. 1961. a proof of the queueing formula: l = λw. operations research, 9: 383– 387. kleinrock, l. 1975. queueing systems, volume 1: theory, new yrk: wiley – interscience, john wiley and sons. penttinen, a., 2008. introduction to teletraffic theory. chapter 8 – queueing systems, lecture notes: s-38.145., date retrieved; 20 october, 2017. sethi, r., jain, m., meena, rk. and garg, d. 2020. cost optimization and anfis computing of an unreliable m/m/1 queueing system with customers’ impatience under n-policy. international journal of applied and computational mathematics, 6(2): 51.1-14. varma, sm. and maguluri, st. 2022. a heavy traffic theory of two-sided queues. acm sigmetrics performance evaluation review, 49(3): 43-44. zukerman, m. 2000. introduction to queueing theory and stochastic teletraffic models. city university of hong kong. hong kong., pp. 303 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:profpeteranyin@unical.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):447-460 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 447 original research article the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system e. u. udo, o. a. nwaorgu, k. o. odo* and n. d. kanu department of electrical and electronic engineering, michael okpara university of agriculture, umudike, abia state. *corresponding author’s email address: kayceebby@yahoo.co.uk 1.0 introduction satellite communications are essentially used for providing communication links between different areas on the earth by receiving information from a transmitting earth station. satellite communications play an important role globally in the telecommunications system. about 3,000 satellites are orbiting the earth relaying continuous and discrete information bearing data, video and audio from one location to another in the world. satellite based communication networks at high frequencies are rapidly expanding. these high frequency operations have enabled a large number of available applications and services including communications, navigation, telemedicine, remote sensing, network sensors distribution and access to internet without the use of wires. however, high frequency applications can generally result to large transmission problems because of atmospheric attenuations (harb et al., 2012). satellite communications that operate at high frequencies beyond 10 ghz are expected to deliver a wider bandwidth and a higher data rate for multimedia and broadband services. however, such systems have to cope with strong atmospheric impairments, mainly due to rain. this particular impairment is even worse in the tropical regions, which are mostly characterized by heavy article information abstract this paper presents the effects of atmospheric attenuations on c, ku and ka microwave frequency bands. the atmospheric attenuations such as cloud, rain, oxygen and water vapour have a much significant effect on the transmitting and receiving of signals over satellite communication especially in locations prone to rainfall. this paper analyzed the effects of atmospheric attenuation on satellite communications in selected location in the city of aba. the rainfall, cloud and gas data were measured and collected from the nigerian meteorological agency for a period of three months using simulink model to determine the frequency bands within the areas affected by bad weather condition. the method employed the use of matlab and international telecommunication union radiocommunication sector (itu-r) prediction model which include the fuzzy logic system to improve the received signal on satellite communication. the results obtained shows that for the exceedance time of 0.01, the attenuation values recorded during the rainfall at elevation angles of 100, 200, 300 and 400 are 14.0440, 17.84080, 25.32430, 13.45070, 17.67230, 24.05440, 14.37360, 18.35890, 26.18720, 13.12440, 16.62090, 23.31440, 12.70280, 16.03920 and 22.36270 while for the exceedance time of 1.00, the attenuation values recorded are 0.639130, 0.88553, 1.41930, 0.605330, 0.834540, 1.32490, 0.62090, 0.91320, 1.48480, 0.585040, 0.804960, 1.26970, 0.560440, 0.767250 and 1.2080 respectively. therefore, the work reported here showed that the effects of satellite connection which suffers from poor signal quality due to atmospheric disturbances in the study area was minimized. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 2 march, 2023 revised 2 may, 2023 accepted 7 may, 2023 keywords: atmospheric attenuation rain attenuation fuzzy logic satellite communication http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 448 precipitation. in this case, deep signal fading due to rain will definitely affect the quality of analogue transmissions and increase the error rate of digital transmissions, (idrissa et al, 2016). a satellite functions most effectively if the transmissions are directed to a desired area. when the desired area of coverage is focused, the emissions do not move away from the designated area and it minimizes the interference to the other systems. without a functioning communication link, most satellites are rendered useless. to ensure a proper satellite to ground link, one has to make estimations of the signal attenuation because of the distance to the satellite, atmospheric distortions and other system specific losses. an important aspect is noise originating in the system components and from general background radiation ((vangli, 2010). the effect of atmosphere is a primary issue when designing satellite-to-earth links operating at frequencies beyond 10 ghz. droplets of rain absorb and scatter radio waves, leading to signal attenuation and decrease in the system reliability and availability. it also causes one of the major fundamental problems on the communication satellite links performance, resulting to large variations in the signal power at the receiver end. (osahenvemwen and omoriguwa, 2017). however, satellite services using 10ghz frequencies and above are influenced by different propagation impairments like attenuation caused by rain, cloud and ice depolarization (osahenvemwen and omoriguwa, 2013). interestingly, there are some basic effects of propagation abnormalities which affect the communication satellite systems performance. in a satellite communication, weather losses result from degradation of the satellite signals by hydrometers as they cross the earth’s atmosphere. some of the losses encountered by satellite communication systems are rain, cloud and gas attenuations. when higher frequencies are transmitted and received under heavy attenuations, signal degradation which is proportional to the intensity of propagation abnormalities occurs. the radio frequency in ka band offers three advantages for satellite communication over the low frequencies of c and ku bands in terms of spectrum availability, reduced interference potential and reduced equipment size. satellite signals inevitably confront propagation impairments during signal transmissions between the satellite and earth stations. the ka band is more susceptible to tropospheric impairments than lower frequencies which can degrade service quality. rain, ice, fog, gas, clouds and moist air affect communication links in different ways. if estimation of such impairments can be done, proper mitigation techniques can be implemented to improve the quality of service (sujimol et al., 2015). attenuation caused by rain, cloud and gas are primary sources of impairment to information propagation at millimeter and microwave wavebands. these impairments become particularly severe at higher frequencies, especially beyond ku-band. therefore, it is very difficult to maximally utilize satellite based network resources which are affected by weather attenuations (singh et al., 2017). ishag et al., (2015) carried out a design and implementation of attenuation due to rain control and reduce simulation modules in matlab simulator in order to investigate the ku band signal file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk udo et al: the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system. azojete, 19(3):447-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 449 efficiency under the rain attenuation effect. the results showed that the horizontally polarized signal was more attenuated by the rain than the circularly and vertically polarized signal. ajewole et al., (2017) investigated rain effects on the performance of ku-band satellite signals in akure, nigeria. comparison of the predicted rain induced attenuation estimated by applying the measured data was conducted with some chosen rain attenuation models like itu-r, garcia and moupfouma. the results showed that the time series of rainfall during a typical rainy event is the reception pattern at ku-band. this is an indication that there is a very strong relationship between the reduction of the satellite signals and the rate of rainfall recorded. however, they did not consider worst cases of rain rates above 120mm/hr that could help to improve the efficiency of the results. osahenvemwen and omorogiuwa, (2017) described in a study that attenuation increases as rainfall rate increases and the vertical polarized signal offers less rain attenuation than the horizontal polarized signal at ku and ka bands. furthermore, odo et al., (2021) conducted a comparative analysis of rain attenuation models in satellite links and discovered that rain attenuation is a major source of impairment to signal propagation at microwave and millimeter wavebands. also, rain attenuation causes a distorting effect on signal quality at higher frequencies leading to digital transmission errors. the knowledge of rain attenuation and its performance was essential in order to optimize system capacity. the authors used itu-r, dah and ajayi models for estimating rain attenuation. therefore our research focused on the effects of performance improvement of satellite communication over atmospheric attenuations on c, ku and ka frequency bands for proper implementation of the attenuation model in the satellite communication and the selection of the frequency band that best suite transmission. 2. materials and methods the materials used in this study include coaxial cable, rain gauge, stopwatch, compass, radiosonde, parabolic reflector antenna, matlab/simulink and pc. data was obtained from the nigerian meteorological agency for a period of three months and analyzed in matlab/simulink. the models were implemented based on the international telecommunication union radio wave sector recommendations considered to be suitable for satellite communications (itu-r 2017). the general satellite system model contains three main components, viz; earth stations, satellites and the links between the channels. the channel and receiver models were created using matlab/simulink. the city of aba in abia state of nigeria was chosen as a study area to investigate satellite attenuation and how atmospheric condition affects satellite communication with different bands in the area. atmospheric condition of these areas such as rainfall rate, rain height above sea level, and liquid water content of rain drops, temperature and relative humidity were taken into consideration. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 450 the effect of raindrops was determined at higher transmission frequencies, especially above 10 – 250 ghz. the effects of how other atmospheric phenomena such as clouds, water vapour and oxygen causes signal attenuation was discovered. 2.1 mathematical modeling of the rain attenuation model the rain attenuation model shown in figure 1 was implemented based on the modified itu-r prediction model. the model includes the fuzzy logic inference system which acts as a decision scheme to select and adjust the satellite connection to most bands that favors certain weather impairment within the selected location. the initialization includes values for earth station position parameters of latitude and altitude above sea level, rain parameters such as rain rate, rain height and percentage of exceeding time 𝑝 and transmitter parameters of frequency f, elevation angle 𝜃 and polarization angle 𝜏. the developed simulink model performs two procedures simultaneously. the first method starts by obtaining the frequency-dependent rain damping empirical values before calculating the rainspecific coefficients 𝑟 and 휀 as shown in equations (1) and (2). 𝑟 = 𝑟𝐻 + 𝑟𝑉 +(𝑟𝐻−𝑟𝑉)𝐶𝑜𝑠 2𝜃𝐶𝑜𝑠2𝜏 2 (1) 휀 = 𝑟𝐻𝜀ℎ+𝑟𝑣𝜀𝑣+(𝑟𝐻𝜀𝐻−𝑟𝑣𝜀𝑣)𝑐𝑜𝑠 2𝜃 cos(2𝜏) 2𝑘 (2) the rain-specific attenuation (the rain attenuation per 1 km) is then calculated using equation (3) dependent on the actual measured precipitation rate (at p = 0.01%) 𝛿𝑅𝑎𝑖𝑛 = 휀(𝑅0.01) 𝑘 (3) this value will be applied in the second method to identify the effective path length as well as to predict the overall rain attenuation. the horizontal reduction factor (𝑟𝐻) for 0.01% at the time can be calculated using equation (4). 𝑟𝐻 = 1 1+0.78√ 𝑃𝐻𝛿𝑅 𝑓 −0.38(1−𝑒−2𝑃𝐻) (4) where ph is the horizontal projection which depends on the slant path length and the elevation angle as shown in equation (5). 𝑃𝐻 = 𝑆𝐿 cos 𝜃 (5) the slant path length depends on the vertical height from the earth station to the rain height as well as on 𝜃, as shown in equation (6). 𝑆𝐿 = { 𝐻𝑅−𝐻𝑠 sin𝜃 𝑓𝑜𝑟 𝜃 ≥ 5° 2(𝐻𝑅−𝐻𝑠) √𝑠𝑖𝑛2𝜃+ 2(𝐻𝑅−𝐻𝑠) 𝐸𝑅 +sin𝜃 𝑓𝑜𝑟𝜃 ≥ 5° (6) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk udo et al: the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system. azojete, 19(3):447-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 451 where 𝐻𝑅 𝑎𝑛𝑑 𝐻𝑠 are the rain and earth station heights above sea level and 𝐸𝑅 is the earth radius. the vertical change factor (𝑉𝐹) can be calculated at 0.01% of the time using equations (7) to (8). 𝜔 = tan−1 ( 𝐻𝑅−𝐻𝑠 𝑃𝐻𝑟𝐻 ) (7) 𝑅𝐿 = { 𝑃𝐻𝑟𝐻 cos𝜃 𝑓𝑜𝑟 𝜔 > 𝜃 𝐻𝑅−𝐻𝑠 sin𝜃 𝑓𝑜𝑟𝜔 ≥ 5° (8) 𝑉𝐹 = 1 1+√sin𝜃[31(1−𝑒 𝜃 1−𝑥) √𝑅𝐿𝛿𝑅 𝑓2 −0.45] (9) where 𝑥 depends on the latitude (𝜑) of the earth station. the effective path length can be obtained using equation (10), whereas the total rain attenuation at 0.01% of time (𝐴0.01) can be calculated using equation (11) (fiebig et al., 2004). 𝐸𝐿 = 𝑅𝐿𝑉𝐹 (10) 𝐴0.01 = 𝐸𝐿𝛿𝑅 (11) consequently, the predicted rain attenuation at any percentage of time (𝑝) can be calculated using equations (12) and (13). { 0 𝑖𝑓 𝑝 ≥ 1% 𝑜𝑟 |𝜑| ≥ 36° −0.005(|𝜑| − 36) 𝑖𝑓 𝑝 < 1% 𝑎𝑛𝑑 |𝜑| < 36° 𝑎𝑛𝑑 𝜃 ≥ −0.005(|𝜑| − 36) + 1.8 − 4.25𝑠𝑖𝑛𝜃 𝑜𝑡ℎ𝑒𝑟𝑤𝑖𝑠𝑒 25° (12) 𝐴𝑟𝑎𝑖𝑛 = 𝐴0.01 ( 𝑝 0.01 ) −[0.655+0.033 ln(𝑝)−0.045𝑙𝑛(𝐴0.01)−𝛽(1−𝑝)𝑠𝑖𝑛𝜃] (13) 2.2 mathematical modeling of the cloud attenuation the amount of liquid water content contained in the cloud is also responsible for absorption and scattering of electromagnetic energy especially for frequencies above 10 ghz but with less intensity than that of rain. cloud attenuation in addition to the transmission parameters (signal frequency, elevation angle) rests on the cloud parameters such as average height and thickness, total columnar content of liquid water and temperature (singh et al., 2017). however, the cloud specific attenuation coefficient can be calculated using equation (14). 𝛿𝑐𝑙𝑜𝑢𝑑 = 0.819𝑓 𝑒"[1−( 2+𝑒′ 𝑒" ) 2 ] (14) the cloud attenuation at any probability depends on the liquid water content that can be obtained from radiometric measurements for the selected regions as shown in equation (15). 𝐴𝑐𝑙𝑜𝑢𝑑 = 𝛿𝑐𝑙𝑜𝑢𝑑 ( 𝐿𝑊𝐶 𝑠𝑖𝑛𝜃 ) (15) (itu-2002). figure 1 describes the block diagram of the cloud attenuation process used to calculate liquid water content and temperature. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 452 figure 1: cloud attenuation model 2.3 water vapor and oxygen attenuations models the effective water vapour path length is based on the assumption of an exponential atmosphere to describe the relation between water vapour density and altitude. the water vapour specific attenuation in (db/km) can be calculated as shown in equation (16). 𝛿𝑤 = 𝑓 2𝑟𝑇 2.5𝜌[𝑠1 + 𝑠3 + 𝑠4 + 𝑠5 + 𝑠6 + 𝑠7 + 𝑠8 + 𝑠9] × 10 −4 (16) the total gas attenuation 𝐴𝐺𝑎𝑠𝑒𝑠 for oxygen and water vapour attenuations can be predicted using equation (17). 𝐴𝐺𝑎𝑠𝑒𝑠 = 𝐴𝑜+𝐴𝑊 𝑠𝑖𝑛𝜃 = 𝛾𝑂𝐿𝑂+𝛾𝑊𝐿𝑊 𝑠𝑖𝑛𝜃 (17) (al-samawi et al., 2022). 2.4 simulink implementation of the rain attenuation model the rain attenuation model used in this paper is obtained from the itu-r standard rain attenuation. the simulink used for the rain attenuation model was attached directly to the fuzzy logic decision making for selection of parameter. the simulink implementation of the rain attenuation model is shown in figure 2. initialization principal relaxation frequency calculation secondary relaxation frequency calculation complex dielectric permittivity calculation cloud specific attenuation calculation cloud attenuation calculation cloud lwc cloud 𝜃 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk udo et al: the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system. azojete, 19(3):447-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 453 figure 2: simulink implementation of the satellite communication system with attenuation model 3. results and discussion the percentage of exceedance time for rain attenuation was tabulated from 0.01 to 1.00 for various elevation angles of 10, 20, 30, 40 and 50 degrees for c, ku and ka bands. table 1 shows the rain attenuation values at various frequency bands for different elevation angle. the results revealed that, the higher the elevation angle, the lower the attenuation and therefore the higher the values of eb/no. i𝑡 was also observed that, bad weather attenuates satellite transmission to a large extent in the study area. this is because during heavy rainfall, bad channel quality imposes serious problems to the users of the satellite network. this leads to communication link outage at lower elevation angles θ. the elevation angle depends on the 𝐸𝑏/𝑁𝑜 along with the transmission bit rate and bandwidth. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 456 table 1: rain attenuation values at c, ku and ka bands at different elevation angles @ elevation angle =10 degree @ elevation angle =20 degree @ elevation angle =30 degree @ elevation angle =40 degree @ elevation angle =50 degree percentage of exceedance time c ku ka c ku ka c ku ka c ku ka c ku ka 0.01 14.0440 17.84080 25.32430 13.45070 17.67230 24.05440 14.37360 18.35890 26.18720 13.12440 16.62090 23.31440 12.70280 16.03920 22.36270 0.020 12.45470 16.050 22.9940 11.94060 15.29210 21.80480 12.8050 16.48620 23.80840 11.64880 14.87390 21.1110 11.26180 14.33560 20.22430 0.030 11.46380 14.8060 21.41860 10.98610 14.12870 20.28690 11.78530 15.25440 22.18190 10.70510 13.73480 19.6290 10.34250 13.22810 18.78860 0.040 10.73580 13.90920 20.23080 10.28250 13.26930 19.14760 11.04110 14.34170 20.9690 10.01590 12.89440 18.51830 9.67210 12.41240 17.71490 0.050 10.16450 13.20490 19.28180 9.73090 12.59120 18.2390 10.45670 13.61980 19.99290 9.4760 12.23180 17.63330 9.14740 11.79510 16.86040 0.060 9.69650 12.62480 18.49390 9.27940 12.03320 17.48550 9.97750 13.02480 19.18190 9.03430 11.68680 16.90 8.71840 11.24170 16.15310 0.070 9.30140 12.13310 17.8820 8.89860 11.56060 16.84340 9.5730 12.52040 18.48970 8.66190 11.22560 16.27550 8.35690 10.79510 15.55130 0.080 8.96080 11.70760 17.23740 8.57830 11.15190 16.28530 9.22390 12.08360 17.88720 8.3410 10.82670 15.7330 8.04550 10.40910 15.02870 0.090 8.66180 11.33340 16.72090 8.28240 10.79260 15.79260 8.91770 11.69930 17.35480 8.05970 10.47630 15.25410 7.77270 9.76820 14.56770 0.010 8.39630 11 16.25910 8.02680 10.47270 15.35230 8.65540 11.35690 16.87850 7.80990 10.16430 14.82640 7.53030 7.84510 14.15610 0.020 6.71150 8.86710 13.26730 6.40720 8.42490 12.50490 6.9170 9.1640 13.78870 6.22870 8.17330 12.06340 5.9990 6.79200 11.50140 0.030 5.79450 7.69340 11.59350 5.52720 7.30690 10.91590 5.97510 7.95560 12.05740 5.37060 7.08120 10.52380 5.16910 6.08550 10.02510 0.040 5.18160 6.90380 10.45640 4.93970 6.55280 9.83790 5.34510 7.1420 10.880 4.7980 6.34790 9.48030 4.61590 5.56290 9.02560 0.050 4.72950 6.31850 9.60760 4.50670 5.99430 9.03410 4.88020 6.53860 10.050 4.37620 5.80520 8.70260 4.20850 5.15320 8.28140 0.060 4.37570 5.85880 8.93710 4.1680 5.55590 8.39970 4.51620 6.06450 9.30550 4.04640 5.37930 8.08920 3.89020 4.81900 7.69470 0.070 4.08760 5.48340 8.38720 3.89240 5.19180 7.87970 4.21970 5.67720 8.73520 3.77810 5.03190 7.58650 3.63140 4.53870 7.21430 0.080 3.84640 5.16820 7.92560 3.66170 4.89790 7.44160 3.97140 5.35180 8.25420 3.55360 4.74030 7.16320 3.41480 4.29860 6.80990 0.090 3.640 4.89780 7.52470 3.46440 4.64040 7.06480 3.75890 5.07270 7.84020 3.36160 4.49050 6.79930 3.22970 4.08940 6.46230 0.10 3.46040 4.66210 7.17590 3.29270 4.41460 6.73550 3.57390 4.82930 7.47810 3.19470 4.27280 6.48130 3.06880 3.83300 6.15870 0.20 2.39480 3.25380 5.06960 2.27560 3.06740 4.74990 2.47560 3.37380 5.28930 2.20590 2.97470 4.56570 2.11660 2.84350 4.33220 0.30 1.86050 2.54030 3.98630 1.76640 2.4040 3.73110 1.92530 2.63560 4.16190 1.71150 2.31910 3.58410 1.64110 2.21520 3.39790 0.40 1.5190 2.08140 3.28260 1.44140 1.96550 3.07020 1.57170 2.16030 3.42890 1.39610 1.89820 2.94790 1.3380 1.81220 2.79310 0.50 1.27570 1.7520 2.77410 1.20950 1.65370 2.5930 1.31980 1.81910 2.89880 1.17110 1.59660 2.48890 1.1220 1.52370 2.35710 0.60 1.08970 1.5050 2.38350 1.03320 1.41570 2.22690 1.12180 1.55830 2.49140 1.020 1.36650 1.85590 0.957960 1.30360 2.02290 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk udo et al: the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system. azojete, 19(3):447-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 455 0.70 0.947740 1.3050 2.07150 0.893530 1.22660 1.93460 0.976160 1.3510 2.16580 0.864850 1.18370 1.85560 0.828120 1.12900 1.75640 0.80 0.822940 1.13170 1.81540 0.779780 1.07220 1.69490 0.852270 1.040 1.89850 0.754620 1.03450 1.62560 0.722420 0.986420 1.53800 0.90 0.72330 1.090 1.60120 0.68520 0.943460 1.49440 0.749190 0.920330 1.67480 0.662990 0.910150 1.43310 0.634570 0.867670 1.35550 1.00 0.639130 0.88553 1.41930 0.605330 0.834540 1.32490 0.62090 0.91320 1.48480 0.585040 0.804960 1.26970 0.560440 0.767250 1.2080 continuation of rain attenuation values at c, ku and ka bands at different elevation angles http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 456 figures 3 to 7 showed that the higher the percentage of exceedance time, the lower the attenuation. similarly, for the given elevation angle of rainy weather events, the higher the attenuation, the lower the elevation angle, the higher the rain 𝐸𝑏/𝑁𝑜. it means that the increase in attenuation at lower elevation angle will affect the signal-to-noise ratio in satellite communication. figure 3: graph of percentage of time (%) against signal − to − noise ratio (eb/no) for c, ku and ka frequency bands at 10o elevation angle the graph of 𝐸𝑏/𝑁𝑜 with rainfall events for c, ku and ka frequency bands at 10 o elevation angle is shown in figure 3. it is observed that the values of 𝐸𝑏/𝑁𝑜 at 0.1 percentage of exceedance time are 4 db, 5 db and 7.5 db respectively. it is an indication that an increase in the percentage of exceedance will lower the attenuation. figure 4: graph of percentage of time against signal − to − noise ratio for c, ku and ka frequency bands at 20o elevation angle the graph of 𝐸𝑏/𝑁𝑜 with rainfall events for c, ku and ka frequency bands at 20 o elevation angle is shown in figure 4. it is observed that the values of 𝐸𝑏/𝑁𝑜 at 0.1 percentage of exceedance time are 3 db, 4.5 db and 7 db respectively. this indicates that an increase in the percentage of exceedance will lower the attenuation. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 5 10 15 20 25 30 @ elev. angle= 10 degrees percentage of time (%) e b /n o ( d b ) 10 20 30 40 50 60 c band ku band ka band 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 5 10 15 20 25 percentage of time (%) e b /n o ( d b ) @ elev. angle= 20 degrees c band ku band ka band 10 20 30 40 50 60 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk udo et al: the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system. azojete, 19(3):447-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 457 figure 5: graph of percentage of time against signal-to-noise ratio for c, ku and ka frequency bands at 30o elevation angle the graph of 𝐸𝑏/𝑁𝑜 with rainfall events for c, ku and ka frequency bands at 30 o elevation angle is shown in figure 5. it is seen that the values of 𝐸𝑏/𝑁𝑜 at 0.1 percentage of exceedance time are 4 db, 5 db and 8 db respectively. it is an indication that an increase in the percentage of exceedance will lower the attenuation. figure 6: graph of percentage of time against signal-to-noise ratio for c, ku and ka frequency bands at 40o elevation angle the graph of 𝐸𝑏/𝑁𝑜 with rainfall events for c, ku and ka frequency bands at 40 o elevation angle is shown in figure 6. it is seen that the values of 𝐸𝑏/𝑁𝑜 at 0.1 percentage of exceedance time are 3 db, 4.5 db and 6 db respectively. it indicates that an increase in the percentage of exceedance will lower the attenuation. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 5 10 15 20 25 30 @ elev. angle= 30 degrees percentage of time (%) e b /n o ( d b ) 10 20 30 40 50 60 c band ku band ka band 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 5 10 15 20 25 @ elev. angle= 40 degrees percentage of time (%) e b /n o ( d b ) 10 20 30 40 50 60 c band ku band ka band http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 458 figure 7: graph of percentage of time against signal-to-noise ratio for c, ku and ka frequency bands at 50o elevation angle the graph of 𝐸𝑏/𝑁𝑜 with rainfall events for c, ku and ka frequency bands at 50 o elevation angle is shown in figure 7. it is observed that the values of 𝐸𝑏/𝑁𝑜 at 0.1 percentage of exceedance time are 3 db, 4 db and 6 db respectively. it is an indication that an increase in the percentage of exceedance will lower the attenuation. 3.1 gas attenuation the significant amount of dry air and water vapour attenuation appears at specific regions across the frequency spectrum. across the asynchronous transfer mode of the selected locations in aba and the total correlated gases attenuation at various relative humidity’s are shown in figure 8. the gas attenuation was seen to increase as frequency increases from 250 ghz for a significant increase in relative humidity of the gases. the specific gas attenuation started at frequencies above 100 ghz due to the effect of oxygen before the attenuation level went down. the effect appeared again at frequencies above 210, 310 and 410 ghz during selection by the fuzzy logic inference system. this effect occurs due to water vapour attenuation and to select the best frequency using fuzzy logic band at the expense of weather with varying relative humidity. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 5 10 15 20 25 @ elev. angle= 50 degrees percentage of time (%) e b /n o ( d b ) 10 20 30 40 50 60 c band ku band ka band file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk udo et al: the effects of atmospheric attenuations on c, ku and ka frequency bands on satellite communication system. azojete, 19(3):447-460. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 459 figure 8: gas attenuation at various relative humidity 4. conclusion this paper presented the effects of atmospheric impairments and its attenuation effects to the satellite signal quality in terms of performance evaluation and assessments concerning various effective atmospheric and transmission parameters during dynamic weather conditions. the models for cloud, gas and rain attenuation were developed based on itu-r standard and these models were implemented using matlab/simulink. the gases attenuation at fixed 50% relative humility reached higher level at approximately 415 ghz. the relative humidity is directly proportional to the amount of signal power attenuation due to the water vapour particles in space, and the total gases attenuation. however, the location such as ogbor hill and umungansi in the study area usually suffer from higher relative humility which indicates increased gas attenuation in the location, so proper implementation of the attenuation model in the satellite communication will help initiate the selection of the frequency band that best suite transmission. the plots of attenuation against the percentage of exceedance time decreases at various rainfall events of c, ku and ka frequency bands at 10℃, 20℃, 30℃, 40℃ and 50℃ and these indicates that an increase in the percentage of exceedance lowers the attenuation signal. references abubakar, i., lam, hy. and din, j. 2016. implementation of adaptive coding and modulation for satellite communication links in heavy rain region: an operator’s perspective. arpn journal of engineering and applied sciences, 11 (12): 7858-7861. al-saegh, am., sali, a., ismail, a. and mandeep, js. 2014. analysis and modeling of the cloud impairments of satellite-to-land mobile channel at ku and ka bands. 7th advanced satellite multimedia systems conference and the 13th signal processing for space communications workshop, 436–441. doi.org/10.1109/asms-spsc.2014.6934579 0 50 100 150 200 250 300 350 400 10^-2 10^-1 10^0 10^1 10^2 frequency (ghz) s p e c if ic a tt e n u a ti o n (d b /k m ) relative humudity=10 relative humudity=20 relative humudity=50 relative humudity=70 10 20 30 40 50 60 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk arid zone journal of engineering, technology and environment, sept., 2023; vol. 19(3):447-460. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: kayceebby@yahoo.co.uk 460 ajewole, mo., durodola, om. and ojo, js. 2017. performance of ku-band satellite signals received during rainy condition in two low latitude tropical locations of nigeria. adamawa state university journal of scientific research, 1(5): 1-17. harb, k., yu, fr. and abdul-jauwad, s. 2012. performance evolution in satellite communication networks along markovian channel prediction. journal of wireless networking and communications, 2(5): 143-157. fiebig, u., sigliar, r., heder, b. and csurgai, l. 2004. comparison of rain attenuation models of satellite communication channels based on measured point rain intensity. international conference on telecommunications and computer networks, 1: 837843. itu, 2002. “handbook on satellite communications,” 3rd edition, wiley, new york. jang, js. 1997. a course in fuzzy systems and control. prentice hall, upper saddle river, new jersey, pp 424. itu-r, 2017. propagation data and prediction methods required for the design of earth-space telecommunication systems. itu radiocommunication assembly, jeneva, 1-28. itu-r p.618-13. odo, ko., okoro, ck., iroegbu, c. and ogbonnaya, ij. 2021. comparative analysis of rain attenuation models in satellite links. journal of engineering and applied sciences, 19(1): 494 – 505. osahenvemwen, oa. and omorogiuwa, o. 2013. effect of rain on satellite communication networks in nigeria: case study of warri town, journal of nigeria association of mathematical physics, 25(2): 107-114. (http://nampjournals.org/abstracts/vol25abstract.pdf) osahenvemwen, oa. and omorogiuwa, o. 2017. rain attenuation analysis from system operating at ka and ku frequency bands. american journal of advanced research, 1: 7-12. singh, h., kumar, r., bonev, b. and petkov, p. 2017. cloud attenuation issues in satellite communications at millimeter frequency bands-state of art. international journal of scientific and engineering research, 8(7): 858–862. sujimol, mr., acharya, r., singh, g. and gupta, rk. 2015. rain attenuation using ka and ku band frequency beacons at delhi earth station. indian journal of radio and space physics, 44: 45-50 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/kayceebby@yahoo.co.uk http://nampjournals.org/abstracts/vol25abstract.pdf 4 corresponding author's email address: deenlegit@gmail.com 749 arid zone journal of engineering, technology & environment original research article performance of concrete using metakaolin as cement partial replacement material s. a. agboola1*, k. a. abbas1, a. k. musa1, m. o. shabi1, a. a. abdulwaheed2, and a. zakari3 1department of building, university of abuja, fct, nigeria 2department of surveying and geo-informatics, university of abuja, fct, nigeria 3department of architecture, university of abuja, fct, nigeria *corresponding author’s email address: deenlegit@gmail.com article information abstract concrete, due to its versatility and ready availability, continues to be of great importance around the world, and with the increasing need for shelter, the force pulled by construction activity brought about the high demand for construction materials and a devastating effect on the environment due to the activities from the raw materials needed in the production of cement and concrete. this research investigates the effect of metakaolin as a partial replacement of cement for concrete production. cement was partially replaced by metakaolin at 5%, 10%, 15%, 20%, 25% and 30%. a constant water/binder ratio of 0.50 was used. the parameters investigated include the chemical composition of metakaolin, setting time, workability, density, compressive strength, splittensile strength, and flexural strength. the results showed that metakaolin is a good pozzolan with combined sio2, al2o3 and fe2o3 to equal 92.89%. the results from the test show that the inclusion of metakaolin increased the setting time of cementmetakaolin paste and resulted in the workability reduction of concrete as partial cement replacement with metakaolin increases. this research reveals that partial cement replacement with 0% and 10% mtk in concrete both gave an average compressive strength of 28.9 n/mm2, at 28 days. meanwhile, the highest value for compressive strength obtained at 90 days is 34.8 n/mm2, which was at 10% replacement with mtk. the result shows that metakaolin (mtk) has a pozzolanic effect, considering the strength activity index and improved compressive strength, split tensile strength and flexural strength of concrete. the optimum cement replacement was 10% metakaolin, which performed better than the control concrete. at later stages of curing, 15% also shows promising results. when metakaolin is calcined, it is expected to undergo pozzolanic reactions with cement hydrates, forming secondary calcium silicate hydrate (c–s–h), which aids strength development. it can be concluded that metakaolin is a suitable material for partial replacement of cement up to 10%. thus, using mtk as a partial replacement for cement in concrete at a lower replacement volume will reduce cement usage, production costs, and environmental pollution from cement production. submitted 20 february, 2024 revised 08 june, 2024 accepted 24 june, 2024 keywords: chemical composition compressive strength density flexural strength metakaolin © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction concrete, due to its versatility and ready availability, continues to be of great importance around the world, and with the increasing need for shelter, the force pulled by construction activity brought about the high demand for construction materials and a devastating effect on the environment due to the activities from the raw materials needed in the production of cement and concrete. according to harley (2007), the construction industry uses more than twice the amount of concrete compared to all other building materials combined, such as wood, steel, plastic, and aluminium. this is because of the availability of its constituents, as well as its adaptability, flexibility, strength, durability, impermeability, etc. it is a composite material used to construct buildings, industries and infrastructures. concrete is composed of cement, aggregate, and water, and the azojete december 2024. vol.20(4):749-759 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:deenlegit@gmail.com mailto:deenlegit@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 750 addition of admixture and additives to alter and modify its properties. concrete is second to water as the most utilized material and substance worldwide. according to shoubi et al. (2013), it was estimated that the global concrete industries produce about 12 billion tons of concrete annually and use about 1.6 billion tons of portland cement. the high demand for concrete requires a large amount of cement to develop its strength. thus, approximately 1 ton of concrete is produced yearly for every human globally. there is a need for a more concerted approach to producing concrete and an understanding of the need to improve its properties. the amount of co2 produced in concrete is directly proportional to the cement used in the concrete mix. 900 kg of co2 is produced to manufacture each cement ton (gao et al., 2015). opc is currently being discussed not only due to its cost but also because of its environmental impact during manufacturing. the current trend is to reduce the amount of cement in concrete by using pozzolana and other supplementary cementitious materials to enhance concrete performance. the american society for testing and materials (astm) defined pozzolan as a siliceous or siliceous-aluminous material. this material does not have much cementitious value on its own, but in the presence of moisture, when finely divided, it reacts with calcium hydroxide at ordinary temperatures to form compounds with cementitious properties. shetty (2009) classified pozzolans as either natural or artificial pozzolan. natural pozzolans include materials such as clay, shales, opaline cherts, diatomaceous earth, volcanic ash, volcanic tuffs, and pumicites; artificial pozzolans consist of silica fume, fly ash, rice husk ash, and metakaolin (agboola et al., 2020a). metakaolin, a kaolin product, is one of the classifications of artificial pozzolans and is an area of study for this research. it is available in abundance, economical and easily accessible. the use of metakaolin is one of the potential means of generating affordable binders for concrete production. it effectively converts naturally occurring material that has not been exploited for decades to wealth. metakaolin is one type of calcined clay from the calcination of kaolin clay. metakaolin differs from other artificial pozzolans in that it is not a waste product resulting from an industrial byproduct, nor is it completely natural. it originated from kaolinite clay mineral and is processed for different applications, including cementitious material products. metakaolin is mainly produced by a heat treatment called kaolin clay calcination within 6000 to 8000c. the treatment process of calcination is essential for the production of highly reactive pozzolanic material, as the water is driven off from the kaolinite clay, and the material structure collapses, resulting in an amorphous alumino-silicate form referred to as metakaolin or metakaolinite. according to agboola et al., (2024), using pozzolan to replace opc in concrete lowers heat development during hardening and improves the durability of the final concrete structures. it also improves the performance of concrete mix and reduces the cost of concrete production when introduced into concrete. however, the most important single property of concrete is strength because the primary aim of structural design is that the structural elements must resist or carry the load imposed on them. strength is an essential property for consideration because it is related to several other properties that are more difficult to measure directly. a simple strength test can indicate such properties as durability. however, this study tends to assess the strength property of concrete produced with metakaolin. 2. materials and methods 2.1 materials the materials for the laboratory experiment included coarse aggregate, fine aggregate, cement, metakaolin and water. coarse aggregate was received from a quarry site within the bauchi metropolis. the fine aggregate was obtained from the yelwa river flow in bauchi state. the ordinary portland cement is the dangote of grade 42.5 brand, which was procured from vendors within the bauchi metropolis and conforms to bs en 196-1 (2016). kaolin used for this research was obtained in sufficient quantity from the alkaleri local government area of bauchi state. the particle sizes of fine aggregate were those passing through sieves with an aperture size of 2.36 mm but retained on sieves of 150µm. it was confirmed to be free from dust and harmful substances and conform to bs 882 (1992). the coarse aggregates used in this study were granite with a particle size range between 5 mm and 20 mm, which conforms to 882 (1992). the kaolin was ground using a stone crusher and mortar, while the pestle was ground into fine powder. mtk was then fired (calcined) in the laboratory at a controlled temperature of 700oc in a kiln furnace; the resulting metakaolin was allowed to cool at room temperature. after cooling, it was sieved through a 15 µm sieve. these experiments used portable water that was clean, colourless, odourless, and free of organic matter. this investigation used a mix ratio of 1:2:4 by weight of cement, sand, and gravel and a water-cement ratio of 0.50. the cement in the mix was partially replaced with metakaolin at intervals of 5% to 30%. the concrete with 0% metakaolin served as the control. http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 751 2.2 methods 2.2.1 chemical composition of metakaolin to determine the chemical constituents of metakaolin (mtk), samples were taken and subjected to analysis at sodexmines nigeria limited plateau state, nigeria, using the edxrf method. the machine used to carry out this test was minipal 4 energy dispersive x-ray fluorescence. significant, minor oxides and losses on ignition (loi) were measured and recorded. 2.2.2 setting times tests the setting times (initial and final) were carried out per bs en 196-3 (1995) using the vicat probe and the vicat needle apparatus. the paste's cement content was partially replaced with metakaolin (mtk) at different cement replacement levels of 5 30% at an interval of 5%. the cement pastes without metakaolin served as the control. to achieve consistency, 300g of cement was weighed, and 25% of the weight of the cement sample, which is 75 g, was measured for water. to achieve consistency, 1% of the measured water was continuously added until consistency was achieved. consistency was determined using equation 1. consistency = 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑐𝑒𝑚𝑒𝑛𝑡 𝑐𝑒𝑚𝑒𝑛𝑡 𝑠𝑎𝑚𝑝𝑙𝑒 𝑥 100% (1) 2.2.3 strength activity index of cement the strength activity indices of cement and metakaolin were evaluated according to astm c311. the control mortars were prepared according to the recipe provided in astm c311. for the mixture with the metakaolin as partial cement replacement, a test mixture was prepared with constant water and sand volume fraction and a 20% replacement by volume of cement with metakaolin. the compressive strength test was carried out per astm c109. a 1:3 cement sand mix with water cement ratio of 0.5 was used to prepare 50 x 50 x 50mm prism specimens to determine the compressive strength of the cement mortar, cured at 7 and 28 days. 2.2.4 workability test slump test was carried out per bs en 12350: part 2 (2000). the replacement was done at 5% up to 30% cement with metakaolin. the slurry sample without mtk serves as the control. the compacting factor test was conducted per (bs 1881-102, 1983). 2.2.5 density test this was carried out prior to the crushing of the concrete specimen. at the end of each curing period, the concrete specimens were weighed using an electric weighing machine balance. density is calculated as the mass of the concrete specimen in (kg) divided by the volume of the concrete cube (m3) and expressed in kg/m3. density tests were conducted on 100x100x100mm cube specimens at 7, 14, 28, 56 and 90 days per bs en 12390-7 (2000). 2.2.6 compressive strength test of concrete the compressive strength tests were conducted per bs en 12390-3 (2009). cube specimens of 100 x 100 x 100mm were prepared. all the cubes’ specimens were cured by total immersion in water and were removed from the moulds after 24 hours of casting until the testing age. they were allowed to drip off and be at a saturated surface dry condition before being tested for strength. concrete specimens were tested at curing ages of 7, 14, 28, 56 and 90 days. the cement was replaced with metakaolin at 5% to 30% at 5% intervals. 2.2.7 split tensile strength test in assessing the split tensile strength (fct) of concrete samples with metakaolin (mtk) as a partial replacement of cement, the splitting tensile strength was conducted on 100 x 300mm concrete cylinder specimens per the provision of bs en 12390-6 (2009). the splitting strengths were determined at a 120 kn/min loading rate until failure on a 600 kn avery denison universal testing machine (avdtm). the splitting test was calculated using equation 2. http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 752 fct = 2f π×l×d (2) where; f is the maximum load in (kn), l is the average measured length in (mm) d is the average measured diameter in (mm) the tensile splitting strength is expressed to the nearest 0.05 mpa. 2.2.8 flexural strength the flexural strength of concrete specimens was determined by a point load test on beam specimens of size 100 mm x 100 mm x 500 mm, and in accordance with bs 1881:116 (1983), three numbers of specimens for each set were tested at 7, 14, 28, 56 and 90 days. these specimens were tested in a universal testing machine (utm) of capacity 1000kn. flexural strength was computed using equation 3. flexural strength= fs = pl 𝑏𝑑2 (3) where, b = measured width in “mm” of the specimen d = measured depth in “mm” of the specimen l = length in “mm” of the span on which the specimen was supported p = maximum load in “kg” applied to the specimen 2.3 quantities of concrete constituents table 1 presents the quantities of concrete constituent used. table 1: quantities of concrete constituents at various replacement of cement with mtk sample (%) cement mtk ca fa water (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) control (0%) 420 0.0 1079 661 210 5% 399 21 1079 661 210 10% 378 42 1079 661 210 15% 357 63 1079 661 210 20% 336 84 1079 661 210 25% 315 105 1079 661 210 30% 294 126 1079 661 210 3. results and discussions 3.1 chemical composition of metakaolin table 2 shows the chemical composition of metakaolin determined using an xrf technique. the result obtained in this study is consistent and comparable with the astm c618 requirement, which shows that the (sio2+al2o3 + fe2o3) minimum requirement for a standard pozzolana is 70%. according to astm standards, the maximum limit for so3, loss on ignition (loi), and moisture content are 4%, 10% and 3%, respectively. the so3, loi and moisture content of metakaolin were 0.02%, 1.62% and 0.11%, respectively, below the acceptable maximum limit. therefore, the metakaolin sample is expected to show pozzolanic behaviour in the http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 753 cementitious systems. the consumption of calcium and hydrate (ch) in the process caused the formation of calcium silicate hydrate (csh) and stratlingite (c2ash8). minor compounds such as tio2, mgo, mno, so3, na2o, and cao are also found in metakaolin samples under consideration. however, the amounts of individual components of the minor compounds were not more than 0.7%. table 2: chemical composition of metakaolin constituent mtk (%) silicon oxide (sio2) 48.92 aluminium oxide (al2o3) 43.46 iron oxide (fe2o3) 0.51 calcium oxide (cao) 0.62 potassium oxide (k2o) 0.16 sodium oxide (na2o) 0.21 sulphur trioxide (so3) 0.02 magnesium oxide (mgo) 0.11 manganese oxide (mno) 0.03 titanium oxide (tio2) 0.56 loss of ignition (loi) 1.62 3.2 setting time test figures 1 and 2 show the setting time and consistency of portland cement and metakaolin paste. it was discovered that the higher the amount of mtk in the binary paste, the higher the time required for the pc/mtk paste to be set. the increase in setting times may be due to the high content of k2o in the ash, which may have reacted with water to produce caustic potassium hydroxide that absorbs the water available for the hydration of cement, as reported by kosmatka et al., (2002). however, the setting times for all percentage replacement of cement with metakaolin are within specification for portland cement, which is a minimum of 45 minutes for the initial setting time and 375 minutes for the final setting time (astm c150-15, 2015). the increased setting times of metakaolin paste means that metakaolin can be used as a set retarder in concrete to be transported over a long distance. the consistency of the paste increased because of the particle interference effect, so a large amount of water is needed to properly wet a higher percentage of metakaolin in the mix to produce cement gel, as the cement is more soluble than the metakaolin. the observed setting time and consistency behaviour correspond and are consistent with the findings of agboola et al. (2020b), who observed that setting time increases with the addition of pozzolana. http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 754 figure 1: setting time of mtk-cement paste figure 2: consistency of mtk-cement paste 3.3 strength activity index the result for the strength activity index of cement mortar is presented in table 3. the result shows an increasing strength trend at 7 and 28 days, respectively, for both control mortar and mortar produced with metakaolin as partial cement replacement. the result also shows that, at both 7and 28-day curing age, the strength activity index of 20% mtk-cement mortar meets the minimum requirement specified by astm c311, that the strength activity index of pozzolana must meet 75% of the control strength at 7 and 28 days. this indicates that metakaolin is a good pozzolana and can replace cement in concrete production. table 3: strength activity of cement-mtk compressive strength (n/mm2) strength activity index % mtk 7 days 28 days 0% control 24.0 33.5 100 100 20% mtk 19.9 29.2 82.9 87.2 as per bs en 196-1 (en, 2005), a constant water-to-binder ratio (0.5) was maintained to prepare a concrete mix for the workability test. 0% metakaolin concrete has higher workability compared to other percentage replacement levels of cement, as shown in figure 3. from the values for the seven mixes, on the degree of workability for the slump test, 0% to 20% falls within high slump (50 -100), which is a category of high degree workability, 25% and 30% percentage cement replacement with metakaolin falls with medium slump (25–50) which is a low degree workability according to neville and brooks (2010). the slump value decreases with the increase in the metakaolin in the concrete mix. concrete produced with metakaolin has less slump value, which may be due to the nature of the surface texture, the chemical composition of the pozzolana and the absorption capacity of metakaolin. for the compacting factor test, the degree of workability ranges from low to medium, which falls within the range specified by bs 812 and neville and brooks (2010). mixes with 0% 25%, with compacting values of 0.94, 0.94, 0.93, 0.92, 0.92 and 0.91, respectively, shows medium workability, while 30% with 0.90 shows low workability, as presented in figure 4. 0 50 100 150 200 250 300 350 0% 5% 10% 15% 20% 25% 30% s et ti n g t im e (m in ) metakaolin contents initial setting time final setting time 25 26 27 28 29 30 31 32 33 0% 5% 10% 15% 20% 25% 30% c o n si st en cy ( % ) metakaolin contents http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 755 figure 3: slump test of mtk concrete figure 4: compacting factor for mtk concrete 3.5 density of concrete figure 5 presents the density of concrete produced with metakaolin as a partial replacement of cement and replaced at 5% to 30% by weight of cement. the result shows the effect at various curing ages from 7 to 90 days. the density of metakaolin-cement concrete and control concrete ranges from 2430 to 2560 kg/m3. at early stages, say 7 to 28 days, concrete produced with metakaolin has reduced density as compared to the control concrete, while beyond 28 days, concrete produced with 5% and 10% percentage replacement of cement with metakaolin has higher density as compared with the control concrete. considering the lowest value of density reported in this study, it is higher than the density of conventional concrete of 2400 kg/m3, according to (kazjonovs et al., 2010) and comparable to the reported value of earlier investigators (agboola et al., 2020), for pozzolanic concretes. figure 5: density of concrete produced with metakaolin 3.6 compressive strength of metakaolin concrete compressive strengths with percentage of metakaolin in concrete mix at different curing ages are given in figure 6. in this study, mtk was used to partially replace cement in concretes at levels of 5%, 10%, 15%, 20%, 25%, and 30%, with water cement ratio of 0.5 at 7 days, 14 days, 28 days, 56 days and 90 days respectively. the control concrete and 10% cement have the same strength index and present high strength compared to other percentage cement replacement levels at 28 days of curing age. 10% replacement is higher than control and design strength beyond 28 days. this may be due to the hydration of cement with metakaolin. the high strength in 10% cement replacement may be due to the mtk behaving as a filler that decelerates the cement hydration process. this deceleration process of the hydration generates a large amount of calcium hydroxide at later curing ages to react with the active silica and aluminate phases of the metakaolin to produce secondary 0 10 20 30 40 50 60 70 80 0% 5% 10% 15% 20% 25% 30% s lu m p ( m m ) metakaolin content slump 0.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0% 5% 10% 15% 20% 25% 30% c o m p ac ti n g f ac to r metakaolin content compacting factor 2350 2400 2450 2500 2550 2600 7days 14days 28days 56days 90days d en si ty o f c o n cr et e in ( k g /m 3 ) hydration period 0% 5% 10% 15% 20% 25% 30% http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 756 calcium aluminosilicate hydrates, which later enhances strength performance in concrete (mark et al., 2016). however, a further increase in metakaolin content shows a decrease in compressive strength compared to control concrete. in addition, the reduction in compressive strength of concrete with higher cement replacement levels may be due to the saturation of the cement mix with k2o, which forms a composite that alters and limits the formation of calcium silicate hydrates from cement hydration. mtk can be used up to 10% to replace cement for concrete production since the results showed that concrete tends to gain more strength over a more extended period beyond 28 days of curing age which is in agreement (olutoge et al., 2012). figure 6: compressive strength of concrete produced with metakaolin 3.7 split tensile strength of metakaolin concrete figure 7 shows the split tensile strength of concrete produced with metakaolin at 5% to 30% replacement level. the split tensile strength of concrete attained is in the range of 2.08 to 2.48 mpa and 2.63 to 3.26 mpa at 7 and 28 days, respectively. the result shows that the split tensile strength of concrete increases as curing age increases. the control concrete is stronger than other percentage cement replacement levels at earlier curing age. at later curing stages beyond 28 days, 5% and 10% are stronger than the control concrete. the high strength observed in 5% and 10% cement replacement may be due to the mtk behaving as an excellent filler and makes good bonding between the aggregates and paste of the concrete. it is observed that the replacement of cement with metakaolin, up to 15%, has only a marginal reduction in splitting strength. figure 7: split tensile strength of concrete produced with metakaolin 3.8 flexural strength of metakaolin concrete figure 8 shows the flexural strength of concrete produced with metakaolin at a replacement level of 5% to 30%. the flexural strength of concrete attained ranges from 3.69 to 4.37 mpa and 3.91 to 4.65 mpa at 7 and 28 days, respectively. the result shows that the flexural strength of concrete increases as curing ages increases. the control concrete is stronger than other percentage cement replacement levels at 7 and 28 days of curing age. at later curing stages, 5% and 10% are stronger than the control concrete. the high strength observed in 5% and 10% cement replacement may be due to the mtk behaving as an excellent filler and makes good 0 5 10 15 20 25 30 35 40 7days 14days 28days 56days 90days c o m p re ss iv e s tr en g th o f c o n cr et e in ( n /m m 2 ) hydration periods 0% 5% 10% 15% 20% 25% 30% 0 1 2 3 4 5 7days 14days 28days 56days 90days s p li t t en si le s tr en g th o f c o n cr et e in ( n /m m 2 ) hydration periods 0% 5% 10% 15% 20% 25% 30% http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 757 bonding between the aggregates and paste of the concrete. it is observed that the replacement of cement with metakaolin, up to 15%, has only a marginal reduction in the flexural strength. figure 8: flexural strength of concrete produced with metakaolin 3.9 effect of metakaolin as a pozzolan on the strength of concrete the study presents the percentage of cement replacement in concrete with mtk, which was replaced at 5% to 30% of cement weight. the results show the effect at various curing ages from 7 to 90 days. at early stages, up to 28 days, concrete produced with mtk has reduced density compared to the control concrete. the same trend was observed for compressive, split tensile, and flexural strength. the strength of concrete drops as the percentage of mtk increases. as the curing age increases beyond 28 days, concrete produced with 5% and 10% mtk has increase in strength beyond the control up to 90 days of curing age. this shows that the pozzolanic reaction progresses later in curing, and continued cement-mtk hydration will result in more compact concrete samples and higher strength. at earlier ages, there was little or no pozzolanic reaction as strength and density did not indicate any significant influence on the concrete samples, but at later stages, the impact of mtk as a pozzolana was observed. the effect of mtk on the density of concrete shows that as the density of concrete increases, the compressive strength of concrete also increases. 4. conclusion the results of the pozzolanic property and the oxide composition of metakaolin showed that it is a good pozzolana with essential constituents, which include 48.92% sio2, 43.46% al2o3 and 0.51% fe2o3 content, summing up to 92.89%. the presence of mineral constituents such as silica, alumina and ferrite oxides in mtk showed a promising potential for a pozzolana. utilizing locally available materials is an option to reduce the cost of production of building materials. using locally available materials as building materials will also solve the environmental impact problem. in addition, producing every ton of metakaolin concrete reduces each ton of co2 emission from cement production and saves the environment significantly by reducing greenhouse gas and particulate emissions. the mtk-blended cements have a higher setting time than the control; hence, they are most applicable where a low rate of heat development is required, such as in mass concreting. this indicated that mtk-blended cement is as good as low-heat cement. concrete made using metakaolin to replace cement partially can be used for construction works involving long hauling distances due to its increased final setting time. the optimum mtk content is 10%, considering the compressive strength of concrete at 90 days. metakaolin up to 20% can be used for mass concrete production. it is recommended that further tests be conducted to determine the permeability, shrinkage resistance, fire resistance, and durability of concrete and mortars made with metakaolin as cement replacements. admixtures may be added to improve performance; using a different mix and altering the water-cement ratio is also recommended. the test should 0 1 2 3 4 5 6 7days 14days 28days 56days 90days f le x u ra l s tr en g th o f c o n cr et e in ( n /m m 2 ) hydration period 0% 5% 10% 15% 20% 25% 30% http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):749-759. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deenlegit@gmail.com 758 also be conducted to determine the effects of metakaolin on the mechanical properties of concrete for a longer curing duration beyond 90 days. references agboola, sa., aliyu, aa., abbas, ki., akewusola, ra., musa, ak. and shabi, mo. 2024. experimental investigation of the durability properties of concrete produced with metakaolin as partial replacement of cement, 8(2): 149 – 162. agboola, sa., mamman, ai., musa, ak. and bappah, h. 2020a. effect of waste glass powder as a pozzolanic material in concrete production. international journal of engineering research and technology (ijert), 9(2): 589 – 594. 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engineering and renewable energy, chittagong, bangladesh (id-063), 22–24. kazjonovs, j., bajare, d. and korjakins, a. 2010. designing of high-density concrete by using steel treatment waste. paper presented on modern building materials, structure and techniques international conference may 19-21, 2010., vilnius, lithuania, 138-142. kosmatka, sh., kerkhoff, b. and panarese, wc. 2002. design and control of concrete mixtures, 14th edition, portland cement association, stokie. mark, b., gawu, sky., adjaottor, aa. and john, sa. 2016. early and late strength characterization of portland cement containing calcined low-grade kaolin clay. journal of engineering, 1: 1-5. neville, am. and brooks, jj. 2010. concrete technology. 2nd edition. long man group united kingdom limited, 30–269. olutoge, fa., quadri, ha. and olafusi, os. 2012. investigation of the strength properties of palm kernel shell ash concrete. etasr-engineering technology and applied sciences research, 2(6): 315-319. shetty, ms. 2009. concrete technology theory and practice. s chad and company, new delhi, india, 174– 418. shoubi, mv., barough, as. and amirsolemani, o. 2013. assessment of the roles of various cement replacements in achieving the sustainable and high-performance concrete. inte http://www.azojete.com.ng/ mailto:deenlegit@gmail.com arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):597-610 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 597 original research article simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics t. o. onah1, o. m. egwuagu1, r. e. ozioko1, s. chukwujindu1, a. m. nwankwo*2, i. a. nnaji1, c. c. aka2 1department of mechanical and production engineering, enugu state university of science and technology, enugu, enugu state, nigeria 2department of mechanical engineering, caritas university, amorji-nike, emene enugu, enugu state, nigeria *corresponding author’s email address: zubbymike@gmail.com 1.0 introduction in biomedical applications, computational fluid dynamics (cfd) is used in designing and analyzing medical device, which helps with the visualization of fluid flows for detection of particular problem, and providing insight into patterns within flow field. as such u.s. food and drug administration (fda) have designed a computational inter laboratory study (with 28 independent groups) to validate cfd techniques and produce experimental parameters to support cfd verification and validation (huang, 2018). ansys was used to simulate prediction models for blood fluid flow transition for fda which is one out of numerous techniques of solving numerical problems of navier stokes equations (nse), which has found its needs in the fluid dynamics area of biomedical engineering (bernsdorf et al., 2008, jain et al., 2017, sun and mun, 2008, and jain, 2020) article information abstract computational fluid dynamics (cfd)anasys 2020r1 was used for the analysis of food and drug administration (fda) benchmark study for biomedical flow transition. an idealized medical device is presented within this study and the cfd predictions of pressure and velocity are compared against experimental measurements of pressure and velocity. the fluid flow transition considered for reynold numbers(s) 500, 2000, and 6500 with turbulent fluid flow modelslaminar, k-omega, k-omega sst and k-epsilon based on throat reynolds number reth. 500, 2000 and 6500. mesh independence k-omega sst model used at 0.0008, 0.0004 and 0.0002 element sizes showed good matched velocity of 5.9m/sec. this converged at 0.0002, which is 2% of total pressure drop. axial velocity at centreline for reth 500, 2000 and 6500 at line x =0, showed maximum difference of 77.4% velocity centerline at 0.08m and 19% wall pressure at -0.09m sudden expansion laminar region of re = 500. besides, 65.6% and 17.2% obtained at transition re =2000, showed good agreement between cfd simulations and experimental measurements, at turbulent region re = 6500, all models were in good agreement at 49.6% velocity centerline and 8.10% pressure drop in laminar region. also, downstream of the simulation of reth =6500, other models disappeared which demonstrated k-epsilon model is best at higher reynolds region. the result revealed negligible pressure gradient at the center line of the wall pressure, and dropped at the normalization point of the experimental pressure data range of 0 to -120n/m2 and balanced at the throat reynolds number of reth = 500. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 june, 2022 revised 22 july, 2022 accepted 25 july, 2022 keywords: computational fluid dynamics (cfd) after sudden expansion axial velocity models simulation http://www.azojete.com.ng/ mailto:zubbymike@gmail.com mailto:zubbymike@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):597-610. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 598 this technique represents and handles complex anatomical geometries with ease and also enables simulations on massively parallel computing architectures (jain et al., 2017). works of jain (2020), zhang et al. (2008), jain et al. (2017) have been applied in lattice boltzmann’s method (lbm) for complex transitional flows of anatomical geometries and was found to be efficient and effective. however, effort has not been made to appraise its effectiveness in fda nozzle benchmark area. it is overbearing, to discover suitability of benchmark using methods without application (white and chong, 2011). lbm application to fda nozzle benchmark was only for laminar cases. previous works done on computation transition flow using lbm by jain (2020), jain et al. (2017) was for moderate reynolds number. therefore, there is need to evaluate simple lbm scheme, without employing complex collision synthetic models at turbulence inflow, to accurately predict benchmarked fda result, focus should be on the reynold number categories of transition and turbulent flow regimes of ranges 2000 and 6500. comparative analysis was for velocities, shear stresses, pressures and jet breakdown location with simulations. u.s. food and drug administration created an initiative to establish cfd simulation as a regulatory tool for medical scheme. stewart et al. (2012) worked on two ‘benchmark ‘flow models with specific parameters which they tested for accurate provision of experimental datasets. experimental results are a useful basis for validating accuracy of cfd simulation and assessing its capacity in development and improvement of medical device. this disquisition focuses on nozzle benchmark model and compares experimental measurement of pressure and velocity provided by particle image velocimetry (piv) testing and compares it against cfd results. the ideal medical device made up of four sections: inlet tube, gradualchange section, tube throat and outlet tube. inlet tube and outlet tube have diameter of 0.012m, throat has a diameter of 0.004m. the cone-shaped “gradual-change” section connects the inlet with throat and has a length of 0.22685m, nozzle has a length of 0.04m. the flow will enter through inlet and then experience a gradual convergence and go through the narrow nozzle throat before it increases at expansion region and flows through the outlet tube. the outlet length is 30 times size of the diameter, 0.36m, which gives enough space for fluid flow full development. the inlet length is calculated using equation 1 (stewart et al., 2012): 𝐿𝑒 = 4.4𝐷 𝑅𝑒 1 6 (1) where: le is inlet length in (mm), d is diameter in (mm) and re is reynolds number the numerical methodology employed were based on laminar, (stewart et al., 2012), where flow rate and tube throat reynolds number is 500, near transition and turbulent tube throat reynolds number is 2000 and 6500, used for determination of free stream velocities that allowed calculating first layer height y+ (stewart et al., 2012) cfd is a valuable tool for characterizing velocity, pressure, and shear stress in flow fields by numerical techniques. over 50 years, cfd application have extended in the areas of airfoil and automobile for observing any kind of flow around them to improvement and assessment of blood contacting medical devices (burgreen et al., 2001 and marsden et al., 2014). the advantages of cfd in designing medical device includes; it provides insight in performance without costly prototypes, providing data assessment at critical regions and predicting difficult measuring quantities which influence blood damage (raben et al., 2016, fraser et al., 2012). although u.s. food and drug administration have nothad cfd simulation on blood contacting medical device, heart valves international standard does (iso 5840-2, 2015 and iso 5840-3, 2013). iso 14708-5 (2010) recognizes implantable circulatory support device experimental validation with cfd simulation for flow fields characterization in and around these devices, and assess potentials of hemolytic and thrombogenic. however, nsai (2012) for iso 14708file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com nnaji et al: simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics. azojete, 18(4):597-610. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 599 5 and iso 5840-2 (2015) standards indicate that cfd usage be limited to design stage which is more appropriate for evaluating relative changes than assessing absolute quantities in design (iso 14708 5, 2010). cfd does not predict value of blood damage but predicts solutions to complex fluid flows, hence the focus on transitional flow regime of reynolds number 2000 and 6500. physical quantities of velocities, shear stresses, pressures and jet breakdown location are compared with simulations. evaluating other benchmark devices using computational studies requires fda-specified test conditions. particle image velocimetry (piv), and hemolysis testing results from the first study on the nozzle model which previously has been disseminated through a series of publications (stewart et al., 2012, stewart et al., 2013 and hariharan et al., 2011). this study aims at evaluating the fda benchmarks for velocity analysis after sudden expansion using the blood pump model performance of 2daxisymmetric model based on simulation models 2. materials and methods the idealized medical device is made up of four sections: the inlet tube, the gradual-change section, the nozzle throat and the outlet tube. the inlet and outlet tube have a diameter of 0.012m, the throat has a diameter of 0.004m. the cone-shaped “gradual-change” section connects the inlet with the throat and has a length of 0.22685m, the nozzle throat has a length of 0.04m. the methods are, the flow enters the system through the inlet and experience a gradual convergence as it goes through the throat before it increases at the sudden expansion side and flows through the outlet tube. the length of the outlet is 30 times the size of the tube diameter, and this gives enough space for the full development of the flow. the benchmark nozzle model geometry was used as standard, ansys fluent simulation software. the three flow regimes reynolds number values were, for the laminar (re=500), transition (re = 2000), and turbulent (re = 6500). the fluid flow model in turbulence used were: the kw model, k-w sst model, spalat allmaras model, transition sst model, laminar model, k-e model and reynolds stress model. the y plus values were for k-e and reynolds stress models and the rest of the models has y plus values as was given by the equation 1 above. equations 2 to 5 were used for calculations. the velocities were calculated using the reynolds equation and the wall distance was calculated using equations 3 to 5. 𝐿𝑒 = 4.4𝐷 𝑅𝑒 1 6 (2) 𝑅𝑒 = 𝜌𝑈𝑓𝑟𝑒𝑒𝑠𝑡𝑟𝑒𝑎𝑚𝐿𝑏𝑜𝑢𝑛𝑑𝑎𝑟𝑦 𝑙𝑎𝑦𝑒𝑟 𝜇 (3) 𝐶𝑓 = (2𝑙𝑜𝑔10(𝑅𝑒𝑥) − 0.65)−2.3 𝑓𝑜𝑟 𝑅𝑒𝑥 < 109 (4) 𝜏𝑤 = 𝐶𝑓 . 1 2 𝜌𝑈𝑓𝑟𝑒𝑒𝑠𝑡𝑟𝑒𝑎𝑚 2 𝑈∗ = √ 𝜏𝑤 𝜌 (4)𝑦 = 𝑦+𝜇 𝜌𝑢∗ (5) where: re is reynolds number, cf is the coefficient of friction u* is the freestream velocity and 𝜏𝑤 is the wall shear stress. le is the inlet length in (mm), d is the diameter of tube (mm), re is the reynolds numbers, cf is the coefficient of friction, 𝜏𝑤, 𝑎𝑛𝑑 𝑈 𝑖𝑠 𝑡ℎ𝑒 𝑓𝑟𝑒𝑒𝑠𝑡𝑟𝑒𝑎𝑚, is the wall shear stress, and 𝑈 is the freestream, 𝜌 is the density of the fluid (𝑘𝑔/𝑚3), l is the boundary layer conditions. http://www.azojete.com.ng/ mailto:zubbymike@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):597-610. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 600 3. results 3.1 velocities and wall distances table 1 shows the boundary conditions used for the models, which have the flow rate, inlet and throat reynolds numbers, and inlet and free stream velocities. table 1: flow boundary conditions in the nozzle model flow rate (m3/s) inlet re throat re inlet velocity u0 freestream velocity 5.21×106 167 500 0.0461 ms-1 0.4143 m/s 2.08×105 667 2000 0.1842 ms-1 1.6572 m/s 6.77×105 2167 6500 0.5985 ms-1 5.3859 m/s table 2 shows the calculated wall distances according to flow conditions of the various reynolds numbers, when y+ is 1 and 30 table 2: wall distance according to flow conditions re =500 re=2000 re=6500 wall distance (m) (when y+ =1) 6.8×10-5 m 2.2×10-5 m 8.1×10-6 m wall distance (m) (when+=30) 2.0×10-3 m 6.6 × 10-4 m 2.4 × 10-4m the description of nozzle benchmark model design of a 2d-axisymmetric axial nozzle model geometry inlet length of 0.23m and out length of 0.36m, throat 0.04m (figure 1), were created in solid work and imported in the ansys work bench 2020r1, with incompressible fluid blood. figure 1: geometry of 2d axisymmetric axial nozzle model then cfd fluent solver edge sizing of table 3 default growth rate used by pre-processor to generate meshes and figures 2, 3 and 4 for each of 0.0008m, 0.0004m and 0.0002m element sizes, respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com javascript:void(0) nnaji et al: simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics. azojete, 18(4):597-610. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 601 table 3: edge sizing details figure 2: mesh of element size 0.0008 figure 3: mesh of element size 0.0004 http://www.azojete.com.ng/ mailto:zubbymike@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):597-610. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 602 figure 4: mesh of element size 0.0002 the next which is set-up was used for the initialization and running calculation for 10000 iterations (figures 5, 6 and 7). the accuracy of the numerical solution presented within this study is contingent on the accurateness of the mesh structure and boundary conditions as specified in table 1. mesh convergence is an important part of ensuring that a solution is valid. by monitoring the residual rms error and ensuring that variables (such as the pressure drop) do not significantly change with the refinement of the mesh. table 4 shows information about the mesh sizes used when trying to solving the flow problem. table 4: mesh information element size (m) nodes elements pressure drop (pa) 0.0008 13421 12647 21907 0.0004 34610 33169 21512 0.0002 112291 109651 21111 the k-𝜔 sst model was chosen for the mesh independence study and the reynolds number was chosen to be 6500 with an inlet velocity of 0.5985 ms-1. the convergence criteria were set to 1x10-3 and a convergence tolerance of 10-7 was reached during the hybrid initialization. the residuals were given 1000 iterations to converge and although most of the plots converge around the 10-7 and show very good agreement the continuity plot plateaus at around 1.1 x103 for all the meshes. figures 5, 6 and 7, thus illustrate the scaled residuals plot at different element sizes. 0.0008 takes 200 iterations to reach a steady-state whereas the other meshes reach a steady-state somewhere around the 150th iteration which is an indication of a higher degree of accuracy. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com nnaji et al: simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics. azojete, 18(4):597-610. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 603 figure 5: simulation iteration of scaled residual value for 0.0004 mesh figure 6: simulation iteration of scaled residual value for 0.0004 mesh figure 7: simulation iteration of scaled residual value for 0.0002 mesh figures 2, 3 and 4 show that the lower the element size, the higher the number of nodes and element number with decrease in pressure. figures 5, 6, and 7 show the scaled residual values of the three element sizes, with average 200 number of iterations handles by the ansys before convergence. the pressure and velocity contours of each element sizes are shown in figures 8 9, 10, 11, 12, and 13, respectively. it shows that the velocity component of element size 0.0008 slowed down at 5.6m/s which is different from the velocities at same point of 0.0004 and 0.0002 http://www.azojete.com.ng/ mailto:zubbymike@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):597-610. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 604 element sizes. however, velocities at 0.0004 and 0.0002 element sizes started at 6.6m/s and 6.59m/s with 0.01% difference and agreed at velocity 5.9m/s. based on the inference, 0.0004 element size was now chosen as a mesh independence for subsequent analysis and simulation for determination of axial velocity at centreline, wall pressure and axial velocity at different points using k-epsilon, laminar, k-omega and k -omega-sst models. these effects of these models were studied at before and after the sudden expansion exchange of 0.02m as studied by onah et al. (2022). figure 8: pressure contour of 0.0008 element size figure 9: velocity contours of 0.0008 element size figure 10: pressure contour of 0.0004 element file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com nnaji et al: simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics. azojete, 18(4):597-610. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 605 figure 11: velocity contours of 0.0004 element size figure 12: pressure contour of 0.0002 element size figure 13: velocity contours of 0.0002 element size figure 14 shows the mesh independence plot for the simulation, velocity against y+. the axial velocity shows 0.016 meters after the sudden expansion. the velocity magnitude at 0.004 and 0.0002 are the same which shows the convergence of the solution. http://www.azojete.com.ng/ mailto:zubbymike@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):597-610. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 606 figure 14: mesh independence determination tables 5, 6 and 7 were respectively, generated from simulation showing the results of flow rate and throat and inlet reynolds numbers. showing the reynolds numbers and inlet velocities, and mesh data. table 5: different flow rate throat and inlet reynolds numbers flow rate (m3/s) throat reynolds number inlet reynolds number 5.21 x 106 500 167 2.08 x 105 2000 667 6.77 x 105 6500 2167 table 6: reynolds number and inlet velocities re inlet velocity (m/s) 6500 0.5985 2000 0.1842 500 0.04613 table 7: no of elements, nodes, element sizes and pressure drops no of elements nodes element size pressure drop(pa) 16401 17181 0.0008 23132.2 39862 41274 0.0004 21747.4 118394 120986 0.0002 21006.8 4. results the results of axial velocity at the throat with reynolds numbers 500 and 6500 after sudden expansion were discussed. comparative study of axial velocity models at throat reynolds number reth. = 500, after sudden expansion at line cut for various y = 0.088m 0.024m and 0.08m with experimental data is of stewart et al. (2012) presented in figure 15 as file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com nnaji et al: simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics. azojete, 18(4):597-610. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 607 figure 15: axial velocity at reth = 500, after sudden expansion at line cut for various y = 0.088m, 0.024m and 0.08m figures 15 d, e and f show the plots after sudden expansion for simulations of axial velocities reth = 500, y= 0.008, 0.024, and 0.08. the simulation showed poor match with k-epsilon and k-omega sst, but laminar and k-omega matched with the experimental data at 16d and 16e. but at 16f, all showed deviation from the experimental data. this mismatch is due to participant choice of laminar model for lower reth for jets delivering after sudden expansion to be at laminar region from upstream to downstream before sudden expansion. thus, komega sst and k-epsilon are possibly to be applied in area with higher reynolds number. the line amongst the jet and recirculated zone signifies unaffected instability, but noticeable interruption at reth = 500 in our experiments was observed. undoubtedly, at this low reth, simple turbulence models ought not to be used. the models comparative study of axial velocity at reth. = 6500, after sudden expansion at line cut for various y = 0.008m, 0.024m, and 0.08m. figure 16 shows the analysis of the throat reynolds number 6500 axial velocity after sudden expansion. http://www.azojete.com.ng/ mailto:zubbymike@gmail.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):597-610. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 608 figure 16: axial velocity at reth. = 6500, after sudden expansion at line cut for various y = 0.008m, 0.024m, and 0.08m from the result in figure 16 d, e, and f, it can be seen that the experimental data at the point of downstream of the sudden expansion has 95% confident interval with k-epsilon followed by k-omega sst. this proves the fact that from upstream before sudden expansion the fluid flow regime is confirmed. therefore, at higher reynolds number, k-omega and laminar departed downwards beyond downstream than experimental and disappeared. this reveals that laminar and k-omega models are better for lower reynolds number of reth = 500, while k-omega sst is meant for near transition of reth = 2000, and k-epsilon is best for a higher reynolds turbulent region of reth = 6500. thus, the study shows that rans is particularly good for estimating transitional and turbulent flow but failed to estimate the wall pressure and axial velocity of laminar fluid flow. furthermore, the estimation of the flow regime after the sudden expansion had a poor agreement with the experimental results. to establish cfd as a regulatory tool for medical devices its predictive capabilities for laminar flow regimes and divergent sections within a medical device need to be enhanced. lastly, mesh refinements need to be considered as a potential solution for capturing flow patterns more accurately. table 8 shows the percentage error associated with the wall pressure at the inlet for the three flow regimes. this showed that at the laminar regime the wall pressure is more and decreases with an increase in the reynolds number. table 8: percentage of error for wall pressure at inlet (-0.09m) flow conditions maximum difference at -0.09m laminar flow (re =500) 19.0% transitional flow (re=2000) 17.2% turbulent flow (re=6500) 8.10% file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com nnaji et al: simulation analysis of benchmark axial velocity after sudden expansion using computational fluid dynamics. azojete, 18(4):597-610. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: zubbymike@gmail.com 609 5. conclusion a 2d axisymmetric axial nozzle model geometry was created in solid works and imported to ansys work bench 2020r1 for simulation. four simulation models were employed based on throat reynolds numbers reth =500, 2000, and 6500. mesh independence was determined using k-omega sst for 0.0008, 0.0004, and 0.0002 element sizes. however, 0.0004 element size was chosen for subsequent simulation for axial velocity at centerline, wall pressure and axial velocity at different determinations. the result at line x=0 for reth = 500, 2000, and 6500 showed maximum difference of 77.4% for the velocity at centerline at 0.08m and 19% for the wall pressure at -0.09m sudden expansion at the region of laminar regime of re = 500. besides, 65.6% and 17.2% were obtained at transition of re = 2000, with good agreement between the cfd simulation and the experimental measurements. meanwhile, at turbulent regime of re = 6500, all the simulation models were in good agreement at 49.6% velocity centerline and 8.10% pressure drop, except in laminar region. downstream of the simulation of reth = 6500, other models disappeared which demonstrated k-epsilon best for higher reynolds number. along wall pressure, negligible axial pressure gradient at centerline with drop in normalization point of experimental data from 0 to -120/m2 counterbalanced at reth = 500 was observed. this evaluation confirms the possibility of cfd simulation in analsying nozzle benchmarks of 2d axisymmetric model for blood pumps. references bernsdorf, j., harrisson, se., smith, sm., lawford, pv. and hose, dr. 2008. applying the lattice boltzman technique to biofluids: a novel approach to simulate blood coagulation. computation mathematics application, 55(7): 1408 1414. doi:https://doi.org/10.1016/j.camwa.2007.08.007 burgreen, gw., antaki, zj. and wu, zj. 2001. holmes: computational fluid dynamics as a development tool for rotary blood pump. artificial organs, 25(5): 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file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:zubbymike@gmail.com arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):435-452 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 435 original research article effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions e. w. gadzama1*, a. o. eberemu2*, t. s. ijimdiya2 and k. j. osinubi2 1department of civil engineering, modibbo adama university, yola, adamawa state, nigeria 2*department of civil engineering and africa centre of excellence on new pedagogies in engineering education, ahmadu bello university, zaria, nigeria 2department of civil engineering, ahmadu bello university, zaria, kaduna state, nigeria *corresponding author’s email address: gadzymo@yahoo.com article information abstract naturally, not all soils readily meet specifications for engineering use. therefore, improvement of soil engineering properties is one of the main concerns of a civil engineer. this paper evaluates the strength characteristics of a deficient lateritic soil classified as an a-4(3) using the american association of state highway and transportation officials (aashto) classification system and cl using the unified soil classification system (uscs) after improvement, using microbial induced calcite precipitation (micp) technique. the soil sample was obtained from a site in abagana, in anambra state. it was treated with varying suspension densities up to 2.40 x 109 cells/ml of sporosarcina pasteurii (s. pasteurii) a non-pathogenic microorganism cultured from the soil, under sterilized and unsterilized condition. the treated soil was compacted using the british standard light (standard proctor) compactive effort at the moulding water content range of -2 to +4% optimum moisture content (omc). the compacted soil specimens were then permeated a cementitious reagent containing 20 g of urea, 10 g of nh4cl, 3 g of nutrient broth, 2.8 g of cacl2 and 2.12 g of nahco3 per litre of deionized water to aid the microbial induced calcite precipitation (micp) process in three circles with 2/3rd pore volume. the atterberg limits results showed a better improvement in the sterilized than the unsterilized specimens. similarly, the unconfined compressive strength generally recorded higher results in the unsterilized specimens. highest unconfined compressive strength (ucs) results were recorded at s. pasteurii suspension densities of 1.20 x 109 /ml and 1.80 x 109 /ml for the unsterilized and sterilized specimens respectively. microstructural analysis using x-ray diffraction performed on precipitates derived through the interaction of s. pasteurii and the cementitious reagent confirmed calcite as the dominant composition of the precipitate, analysis using the scanning electron microscopy (sem) on the micp treated soil depicts presence of calcite precipitate and bio-cementation on the surface morphology of the treated soil grains. it was concluded that there are other species of microorganisms that augmented the micp processes in the unsterilized specimens resulting to higher ucs values in the study. 1.20 x 109 /ml s. pasteurii suspension density was recommended as the optimal mix for the treatment of the unsterilized soil. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 31 january, 2022 revised 29 march, 2022 accepted 6 april, 2022 keywords: sustainability micp s. pasteurii compaction sterilized unsterilized http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com file:///c:/users/engr%20e%20w%20gadzama/downloads/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 436 1.0 introduction the improvement of soil engineering properties is one of the major tasks of a civil engineer (sotoudehfar et al., 2016; tang et al., 2020). it is noteworthy that not all soils formed will readily meet specification for engineering use (jayanthi and singh, 2016). for over a century, several procedures of soil improvement such as application of lime, cement, bitumen, chemical additives such as sodium silicate, lignin and chemical grouting etc. have been established and being used in several engineering projects. although most of these methods of soil/ground improvement currently in use satisfy their engineering requirements, they have been reported to be environmentally unfriendly. the demand for, innovative and sustainable techniques of ground improvement have generally compelled researchers to look for novel and more sustainable ways of satisfying society’s demand. this has led to the discovery of a multidisciplinary study between geotechnical engineers and microbiologist known as microbially induced calcite precipitate (micp). this discovery has provided engineers with the idea to consider soil not only as engineering materials but also as an ecosystem (mujah et al., 2017). dejong et al. (2013) reported that, micp technique has shown some superior results of applications in geotechnical engineering. this could be done beneath existing structures without being an obstruction to the structures, enabling the improvement over longer distances. therefore, the discovery of micp processes of improving the engineering properties of soil in the last two decades should not be seen to have only disproved the longterm misconception of the conventional geotechnical engineering, but also as one of the manifestations of interdisciplinary approaches to fit in ideas and techniques from other disciplines to advance innovative solutions to complex problems to geotechnical engineering problems (kavazanjian and karatas, 2008; dejong et al., 2013). micp method of soil improvement has attracted an intensive research interest globally, which is novel as well as promising and sustainable, it is cost effective, non-disruptive in-situ ground improvement to a lot of geotechnical problems (mujah et al., 2017; 2021; burdalski and gomez, 2020; choi et al., 2020; wani and mir, 2020; cui et al., 2021; gowthaman et al., 2021 and osinubi et al., 2021a). for effective micp process using ureolysis, the presence of a urease enzyme secreting bacteria is vital (bachmeier et al., 2002). during micp process, there are two major reactions that may occur individually or simultaneously: when strength improvement is the target, biocementation should be considered. according to mujah et al. (2017), this discovery of micp has provided engineers with the idea to consider soil not only as a construction material but also as an ecosystem. calcite (caco3) is essential for effective micp, it is also product of a two-stage chemical reaction resulting from micp process, (see equations. (1) and (2) which is responsible for improving the soil properties through biocementation and bioclogging. 𝐶𝑂(𝑁𝐻2)2+2𝐻2o→ 2𝑁𝐻4++𝐶𝑂3 2− (1) 𝐶𝑎2++𝐶𝑂3 2− → 𝐶𝑎𝐶𝑂3↓ (2) in equation (1), urea is hydrolyzed by the urease positive bacteria breaking it into ammonium and carbonate, while in equation (2) the product of the hydrolyzed urea, in the presence of calcium source yields to calcite as a precipitate. dejong et al. (2013) considered soil as a living ecosystem which offers the potential for innovative and sustainable solutions to several geotechnical problems which was further file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 437 buttressed by osinubi et al. (2019); osinubi et al. (2021b); mohammadizadeh et al. (2020); nafisi et al. (2020); hoang et al. (2020); lai et al. (2021) and wang et al. (2021). the objective of this study was to evaluate the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions, treated with an ureolytic microorganism and cementation reagent. the organism was locally isolated from the lateritic soil. 2. materials and methods 2.1 materials 2.1.1 soil sample type lateritic soil with pore throat that allowed the free mobility of the microorganisms when in compacted form was used in the study. it was obtained from abagana (latitude 6o10’15” n and longitude 6o58’10” e), in njikoka local government area, anambra state, nigeria. the method of disturbed sampling was adopted during the sample collection at depths between 0.3 m and 3.0 m. 2.1.2 bacteria the species of bacteria used in this research is s. pasteurii commonly found in soil, the urease positive bacteria is rod-shaped, spore-forming and gram-positive, was cultured from the lateritic soil sample in the department of microbiology, modibbo adama university, adamawa state. 2.1.3 cementitious reagent the cementitious reagent reported in several studies (e.g., stocks-fischer et al., 1999; venkata et al., 2016; tirkolaei and bilsel, 2017; osinubi et al., 2019; 2021a&b) was used. it is composed of 20 g urea, 10 g nh4cl, 3 g nutrient broth, 2.8 g cacl2 and 2.12 g nahco3 per litre of deionized water. 3 g/l of nutrient broth was added to the cementation reagent as the most viable amount for survival of bacteria (sharma and ramkrishnan, 2016). 2.2 methods 2.2.1 bacteria culture/growth medium the identification of the bacteria was carried out using the biochemical method (conventional procedure) according to cheesbrough, (2006). bacteria were cultured in an ammonium-yeast extract media described in mortensen et al. (2011) and feng et al. (2014). the bacteria s. pasteurii was isolated from soil, inoculated on media containing the following: 20g yeast extract, 10g ammonium chloride, 2g urea 0.1g nickel per litre of de-ionized water, naoh was used to adjust the ph of the media to 9.0. the media was poured in an aliquot amount of 10ml per culture bottle corked with foil paper, autoclaved at 121oc per 1.1kg pressure for a period of 15 min. 1g each of the soil samples were inoculated on each of the culture bottle and incubated at 370c for 24-48hours to aid proper isolation, identification and characterization of s. pasteurii as an isolated urease producing organisms. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 438 2.2.2 determination of bacteria suspension density the density of bacteria cell was varied in stepped s. pasteurii suspension of mcfarland standard 0.5, 2, 4, 6 and 8, which is equivalent to 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 /ml and 2.40 x 109 cells/ml, respectively. the maximum volume of microorganisms mixed with the soil was one-third (1/3) of the pore volume as recommended by rowshanbakht et al. (2016). 2.2.3 test tube experiments to characterize calcite precipitate 3ml of s. pasteurii for suspension densities of 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml, were mixed with 7ml of the cementation reagent in three cycles at six hours interval, this was allowed to remain in the laboratory for 24 hours at a temperature range of 24±20 c, the precipitate resulting from their reactions was filtered through a filter paper, the solids retained on the filter paper was oven dried at a temperature of 1050c and was kept for characterization using xrd test. the composition of the precipitate was determined using x-ray diffraction (xrd) empyrean model (manufactured by malvern panalytical netherlands). the precipitate was grounded into a fine powder using the sample preparation block and compressed in the flat sample holder to create a flat, smooth surface that was later fixed on the sample stage in the xrd cabinet which determined the average bulk composition. 2.2.4 sample preparation: 3000g of the pulverized air-dried soil sample passing through bs no.4 sieve (4.76 mm) was thoroughly mixed at moulding water contents between -2 % and +4 % relative to omc each containing 1/3 of its pore volume representing each s. pasteurii suspension densities. specimens were cured for 12 hours in sealed polythene bags in the laboratory at 24 ± 20c temperature for hydration and distribution of the microorganisms within the soil before compaction. this was followed with the permeation of the compacted specimens with the cementation reagent in three circles with 2/3 of their pore volume each under gravity within 24 hours to initiate the micp process. 2.2.5 index properties the determination of the natural moisture content, specific gravity, and particle size distribution were in accordance with procedures outlined in bs 1377: 1990. 2.2.5.1 atterberg limits determination soil samples passing through bs no. 40 sieve (425 µm) was used for atterberg limits tests which consist of liquid limit, plastic limit and plasticity index. the samples were treated with varying densities of s. pasteurii at the optimum moisture content (omc) of the soil for british standard light (bsl) compactive effort and then treated with the cementation reagent in three cycles each with 2/3 pore volume within a 24-hour period. the treated soil samples were airdried at room temperature before conducting the tests in accordance with the procedure outlined in bs 1377: 1990. 2.2.5.2 compaction experiments compaction was carried out in accordance with the method outlined in bs 1377, (1990) to obtain the omc. compaction was done using the bsl compactive effort (standard proctor). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 439 2.2.5.3 sterilization of soil 10,000 g of the air dried soil sample was measured into a stainless steel bucket with cover, which was put into an oven set at a temperature of 120oc. the sample was allowed to remain in the oven for three hours, after which it was allowed to cool down to room temperature, the above procedure was repeated three times to ensure that spore forming organisms are properly sterilized. similar procedures are discribed in trevors, (1996); mahmood et al. (2014) and yan et al. (2019). this was repeated until the required quantity of soil sample needed for the test was realized. 2.2.5.4 unconfined compressive strength (ucs) the treated specimens were cured in the moulds for 24 hours before they were extruded. the extruded specimens were further cured for 24 hours in the laboratory at a temperature of 24 ± 2oc and then sealed in polyethene bags for another 24 hours. it was then crushed to failure using the ucs machine model number 24-9150/01 ele international, united kingdom at a regulated strain of 0.02 %/min. specimens tested had an average height to diameter ratio of 2:1. crushing of specimens was carried out in triplicates with the average result obtained used in accordance with guidelines specified in bs 1377 (1990). 2.2.5.5 calcite content (acid washing method) 5 g of the treated soil was mixed with 20 ml of 2-m hydrochloric acid (hcl) to dissolve calcium carbonate on the treated specimens. all the solution and insoluble soil solid were washed with distilled water on filter paper having a coarse pore size in a no. 200 sieve for 10 minutes in order to remove all soluble calcium from the soil particles. the solid particles retained on the sieve were oven-dried at a temperature of 105o c for 24 hours and weighed. the difference between the mass of the originally treated soil sample (a) and the washed soil sample (b) was the mass of calcite. the calcite content (cc) was computed using equation (3) as reported in soon, et al. (2014) and choi, et al. (2017). 𝐶𝐶 = 100 − 𝐵 𝐴 𝑥100 % (3) 2.2.6 microanalysis microanalysis using scanning electron microscopy (sem) phenom world pro g6 desktop thermo fisher scientific, netherland, was conducted on both natural and s. pasteurii treated lateritic soil to investigate the changes in morphological features due to the formation and distribution of calcite bonds on the inter particle surface in the micro-structure of the soil. specimens of lateritic soil optimally treated with s. pasteurii were used in the study. the test was performed using phenom world pro desktop sem equipped with a software tool that could automate data collection and duplicate analysis. the specimen was positioned in an electrically powered tilt and rotating specimen holder which was regulated by a dedicated motion regulator which initiates an infinite 360o rotation with a pseudo-eucentric tilting adjusted focus oscillating from 10o to 45o, which allows the creation of exact size and information from micro and nano fibre samples (phenom world, 2017). similar procedure was reported by osinubi et al. (2020). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 440 3.0 results and discussion 3.1 test tube experiments to characterize calcite precipitate figure 1 shows the microstructural analysis using x-ray diffraction on the precipitates derived through the test tube experiment described in section 2.2.3, i.e. the interaction between s. pasteurii and the cementitious reagent. the result confirmed calcite as the dominant composition of the precipitate with few impurities of quartz and actinolite, which was earlier reported by konhauser, (2006) to be among the most cations frequently associated with biogenic minerals. the xrd spectra presented in this study agrees with the report by carmona et al. (2016). figure 1: x-ray diffraction of precipitate obtained from test tube experiment 3.2 index properties table 1 summarizes the index properties of the natural lateritic soil. the particle passing bs sieve no. 200 is 36.0%, with silt and clay contents of approximately 22 % and 14 %, respectively. the liquid and plastic limits recorded were 44.0 and 21.6%, respectively; while the plasticity index was 22.5%. based on the results, the soil is classified as a-4(3) using the american association of states highways and transportation officials (aashto, 1986) classification system and cl using the astm-unified soil classification system (uscs-astm, 1992). the omc and the maximum dry density are 15.3 % and 1.83 mg/m3 respectively. the x-ray diffraction test showed kaolinite as the dominant clay mineral. table 1: physical properties of the natural soil property natural moisture content (%) 11.3 percentage passing no. 200 sieve (wet sieve) 36.0 liquid limit (%) 44 plastic limit (%) 21.6 plasticity index (%) 22.5 cec(meq/100 g) 5.50 specific gravity 2.62 aashto classification a – 4(3) uscs sc colour reddish brown dominant clay mineral kaolinite file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 441 3.3 x-ray diffraction of natural soil. table 2 shows the oxide composition of the natural soil. it could be observed that the highest oxide composition recorded by the soil is silicon, followed by aluminium and iron respectively. the silicasesquioxide ratio {sio2/(al2o3 + fe2o3)} recorded is 1.64, according to okeke et al. (2016), a soil is said to be lateritic, if it has a silica-sesquioxide ratio value between 1.33 and 2.0, while any value higher than 2.0 is indicative of non-lateritic soil. table 2: oxide composition of the natural lateritic soil oxide sio2 al2o3 cao tio2 v2o5 cr2o3 fe2o3 mno cuo zro2 loi total concentration (%) 56.5 19.00 0.33 2.89 0.061 0.051 15.41 0.075 0.056 0.290 4.54 99.20 3.4 atterberg limits 3.4.1 liquid limit the variation of liquid limit (ll) with s. pasteurii suspension densities for sterilized and unsterilized samples is shown in figure 2. it was observed that the ll for the unsterilized specimen (llus) recorded higher values compared to the natural ll, the values recorded are: 44%, 49.5%, 49.0%, 50.5%, 49.5% and 49.5% for 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml of s. pasteurii suspension densities, unlike the unsterilized specimens, there was a steady decrease in the liquid limit for sterilized specimens (lls) values with increase in s. pasteurii suspension densities, the values recorded are 45.5%, 41.6%, 39.3%, 40.1%, 40.1% and 40.4% for 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml of s. pasteurii suspension densities with the lowest value of 39.3% recorded at 6.0 x 108 cells/ml s. pasteurii suspension density. it was further observed that the sterilized specimen recorded a lower ll values than the unsterilized specimen, which suggest that the existence of organisms in the specimens may have played a vital role for observed trend of results. similar results were reported by yosodian et al. (2012) and liu et al. (2020). figure 2: variation of liquid limits with s. pasteurii suspension density for lateritic soil under sterilized and unsterilized condition 3.4.2 plastic limit figure 3 shows the effect of different micp treatment for different s. pasteurii suspension densities on the plastic limit (pl) for sterilized and unsterilized specimens, it was observed 38 40 42 44 46 48 50 52 0 . 0 e + 0 0 6 . 0 e + 0 8 1 . 2 e + 0 9 1 . 8 e + 0 9 2 . 4 e + 0 9 m o is tu re c o n te n t (% ) sporosarcina pasteurii suspension density (cells/ml) llus lls http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 442 that there was a drastic decrease in the pl values from 21.55% for natural to 14.82% at 1.50 x 108 cells/ml s. pasteurii suspension density, which could entirely be due to decrease in co2 in the sterilized soil specimen which is a major ingredient for microbial reaction in micp processes. another reason could be due to the participatory role by other bacterial species, which later continued to increase with not only s. pasteurii suspension densities all through the reactions 15.29%, 15.65%, 16.27% and 17.37% at 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml, s. pasteurii suspension densities for unsterilized specimen. on the other hand, the sterilized specimens recorded a continuous decrease in the pl values from 22.75% for natural to 20.61% at 6.0 x 108 cells/ml, after which it increased to 21.02% and then decreased steadily to 19.30% at 2.40 x 109 cells/ml s. pasteurii suspension density. when improvement in engineering properties is the target, an increase in the pl of the treatment is desirable since it will result to decrease in the plasticity index of the soil, which is an indication of improvement in the engineering properties of the soil, this have been observed in the sterilized compared to unsterilized specimens elsewhere (osinubi et al., 2019; hafez et al., 2019). figure 3: variation of plastic limits with s. pasteurii suspension density for lateritic soil under sterilized and unsterilized condition 3.4.3 plasticity index figure 4 shows the effect of s. pasteurii suspension densities on the plasticity indices (pi) for the sterilized and unsterilized specimens. it was observed that the unsterilized specimens recorded higher pi compared to sterilized specimen, generally there was an increase in the pi values in the unsterilized specimens upon micp treatment. the following values were recorded for unsterilized specimens: 22.45%, 34.68%, 33.71%, 34.85%, 33.23% and 32.13% for 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml, s. pasteurii suspension densities, while for sterilized specimens, there was a steady decrease in the pi values from 22.45% for the natural to 18.65% which is the lowest pi value at 6.0 x 108 cells/ml s. pasteurii suspension density, thereafter it steadily increased to 19.08%, 20.28% and 21.11% at 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml, s. pasteurii suspension densities for sterilized specimens. the increase in pi values for both unsterilized and the sterilized specimens could be linked to the secretion of exopolymeric substance as a result of the interaction between the microbes and the soil during the micp processes. these findings are consistent with those reported by moravej et al. (2018); osinubi, et al. (2019), but did not agree with the findings reported by neupane (2016). the results presented suggest that the sterilized specimens recorded more improvement in the engineering properties of the lateritic soil through the decrease pi. 14 16 18 20 22 24 0 . 0 e + 0 0 6 . 0 e + 0 8 1 . 2 e + 0 9 1 . 8 e + 0 9 2 . 4 e + 0 9 m o is tu re c o n te n t (% ) s. pasteurii suspension density (cells/ml) plus pls file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 443 figure 4: variation of plasticity index with s. pasteurii suspension density for lateritic soil under sterilized and unsterilized condition 3.5 distribution of calcite content figure 5 shows the precipitation characteristics of calcite content with compacted soil column depth. it could be observed that the amount of calcite precipitate recorded in the unsterilized specimen were generally higher than those recorded in the sterilized specimens with the highest calcite content of 10% and 7% recorded respectively at the top of both compacted soil columns, this could be linked with the roles played by other urease positive bacteria that may be present in the unsterilized specimens (hafez et al., 2019). it was also observed that the calcite precipitate distribution pattern was not uniform in both soil columns, this could be due to the urease activities of the microorganisms did not equal or balance the flow of the cementation, which may have resulted into the non-uniform formation of calcite precipitate similar to findings by shahin (2017) who reported that it is difficult to obtain a homogenous cementation in micp due to imbalance in the flow of microorganisms and the cementation reagent within the pore space of soils. this the results presented suggest that there could be other species of microorganisms present in the unsterilized specimen which were destroyed in the sterilized specimen which would have contributed to additional ureolytic activities of s. pasteurii used in this study, this may have given an edge to the unsterilized over the sterilized specimens in the formation of more calcite specimen. the calcite precipitate distribution pattern for the sterilized specimen is similar to those obtained by shahin (2017) in a sand column containing 10% of fines. figure 5: distribution of calcite content with soil column depth for lateritic soil under sterilized and unsterilized condition 17 22 27 32 37 0 . 0 e + 0 0 6 . 0 e + 0 8 1 . 2 e + 0 9 1 . 8 e + 0 9 2 . 4 e + 0 9m o is tu re c o n te n t (% ) s. pasteurii suspension density (cells/ml) pius pis 2.0 4.0 6.0 8.0 10.0 12.0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 c al ci te c o n te n t (% ) soil column depth (mm) cc unster at 1.20e+09/ml cc ster at 1.80e+09/ml http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 444 3.6 effect of moulding water content on the unconfined compressive strength of lateritic soil under sterilized and unsterilized condition. figures 6a-f illustrates the variation of unconfined compressive strength (ucs) of lateritic soil under sterilized and unsterilized condition with moulding water content. peak ucs values were observed in the unsterilized specimens at moulding content of 13.3%, which is equivalent to 2 % dry of omc the peak ucs values recorded were: 659.00kn/m2, 1372.69 kn/m2, 2095.49 kn/m2, 2232.28 kn/m2, 1869.54 kn/m2 and 1796.44 kn/m2, for 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells /ml of s. pasteurii suspension densities. comparing the above results with those recorded for sterilized specimens, peak ucs values are: 691.95 kn/m2, 1530.53 kn/m2, 1371.33 kn/m2, 1516.35 kn/m2, 1881.09 kn/m2 and 1644.54 kn/m2, for 0, 1.50 x 108, 6.0 x 108, 1.20 x 109, 1.80 x 109 and 2.40 x 109 cells/ml of s. pasteurii suspension densities. it was observed that the highest ucs value of 2232.28 kn/m2 was recorded at 1.20 x 109 cells/ml s. pasteurii suspension density for unsterilized specimens while lesser ucs value of 1881.09 kn/m2 was recorded as the peak value for the sterilized specimens although higher population of microorganisms were used (1.80 x 109 cells/ml s. pasteurii suspension density). the higher results recorded for the unsterilized as against the sterilized specimens might be due to the presence of other species of urease positive organisms in the unsterilized soil, another reason is that in unsterilized specimens, the co2 which is an important ingredient in calcite formation was affected, as it will have been decreased through sterilization. these may have contributed positively in the micp process that eventually added to the ureolytic activities of s. pasteurii used in the study, causing more calcite precipitation thereby increasing the ucs values more than the sterilized specimens. although it is not a standard practice in engineering to sterilize soils before use, the ucs results recorded in this study has demonstrated that other species of microorganisms might have played a vital role in the improvement of soil properties during micp processes. the results obtained for unsterilized specimens in this study have established that higher soil strength can be attained at lower moulding water content which agrees with the findings earlier reported by cheng et al. (2013; 2017); mujah et al. (2017; 2021) and shahin (2017). 300 400 500 600 700 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 u n co n fi n ed c o m p re ss iv e st re n gt h (k n /m 2 ) moulding water content (%) a 0.0e+00 cells/ml unsterilized 0.0e+00 cells/ml sterilized file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 445 100 500 900 1300 1700 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 u n co n fi n ed c o m p re ss iv e st re n gt h (k n /m 2 ) moulding water content (%) b 1.50e+08 cells/ml unsterilized 1.50e+08 cells/ml sterilized 0 400 800 1200 1600 2000 2400 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 u n co n fi n ed c o m p re ss iv e st re n gt h (k n /m 2 ) moulding water content (%) c 6.0e+08 cells/ml unsterilized 6.0e+08 cells/ml sterilized 0 400 800 1200 1600 2000 2400 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 u n co n fi n ed c o m p re ss iv e st re n gt h ( kn /m 2 ) moulding water content (%) d 1.20e+09 cells/ml unsterilized 1.20e+09 cells/ml sterilized http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 446 figure 6: variation of unconfined compressive strength with moulding water content for lateritic soil under sterilized and unsterilized condition, (a) natural soil, (b) 1.50x108, (c) 6.0 x108, (d) 1.20x109, (e) 1.80x109 and (f) 2.40x109/ml s. pasteurii suspension densities 3.7 scanning electron microscopy figures 7 a-c shows the scanning electron micrograph of the natural, the unsterilized and the sterilized treated soils, in the natural soil (figure 7a), there are pores/voids that are observed with no calcite precipitate, which eventually decreased as observed in figure 7b unsterilized treated soil due to calcite precipitates around the soil particles, comparing the micrographs of the sterilized with the unsterilized soils, the quantities of calcite precipitate in the unsterilized specimen was more pronounced than those in the sterilized soil as could be observed in figures 7b and c. this suggests that there are other species of ureolytic microorganisms that have immensely contributed in the precipitation of more calcite in the unsterilized. from the sem results presented, it is clear that the micp treatment of an a-4(3) lateritic soil using ureolysis resulted into formation of higher quantity of calcite precipitates in the unsterilized than the sterilized specimen. 100 500 900 1300 1700 2100 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 u n co n fi n ed c o m p re ss iv e st re n gt h ( kn /m 2 ) moulding water content (%) e 1.80e+09 cells/ml unsterilized 1.80e+09 cells/ml sterilized 100 500 900 1300 1700 2100 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 u n co n fi n ed c o m p re ss iv e st re n gt h ( kn /m 2 ) moulding water content (%) f 2.40e+09 cells/ml unsterilized 2.40e+09 cells/ml sterilized file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 447 figure 7: micrograph at x1000 magnification: (a) natural soil, (b) unsterilized soil treated with 1.20 x 109cells/ml suspension density at -2% omc, (c) sterilized soil treated with 1.80 x 109 cells/ml suspension density at omc figure 8 shows the scanning electron micrograph of the natural and the treated soil for atterberg limits tests. figure 8a is for the natural soil, hair cracks and voids could be observed as indicated by the arrows, which disappeared mainly due to bio-cementation and bio clogging after the treatment with s. pastuerri and the cementitious reagent (figure 8b). the result presented has demonstrated the effectiveness of bio-cementation and bio clogging in micp process as reported in the literature. figure 8: micrograph at x1000 magnification of samples for atterberg limits: (a) natural soil, (b) unsterilized soil treated with 1.20 x 109cells/ml suspension density at -2% omc 4. conclusions in this study, the sterilized specimens recorded more improvement in the engineering properties of the lateritic soil through the decrease in pi values of the treated soil. this work has demonstrated that higher unconfined compressive strength for the treated soil can be obtained at lower degree of saturation, this finding is challenging the widely belief that biocemented soils need to be treated under full saturated conditions. although soils are not normally sterilized before use in engineering practice, the ucs values recorded were favorably higher in unsterilized specimens compared to the sterilized, it has also been established that bio-cementation is the method to adopt for strength gain in micp. it has also been demonstrated that other species of microorganisms present in the soil contribute in the micp improvement of the engineering properties of soil. the sem analysis presented, have also http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):435-452. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gadzymo@yahoo.com 448 demonstrated that the micp treatment of an a-4(3) lateritic soil using ureolysis resulted into formation of higher quantity of calcite precipitates in the unsterilized than the sterilized specimen. the optimum mix of 1.20 x 109 /ml s. pasteurii suspension density is recommended for the treatment of an a-4(3) lateritic soil which can be used in lightly trafficked road. references aashto 1986. standard specifications for transport materials and methods of sampling and testing. 14th edition, american association of state highway and transport officials (aashto), washington, d.c 1-59. astm, 1992. annual book of astm standards, 4(8), philadephia. bachmeier, kl., williams, ae., warmington, jr. and bang, ss. 2002. urease activity in microbiologically-induced calcite precipitation. journal of biotechnology, 93: 171-181. bs 1377: 1990. method of testing soils for civil engineering purpose. british standard institute, bsi, london. burdalski, rj. and gomez, mg. 2020. investigating the effect of microbial activity and chemical concentrations on the mineralogy and morphology of ureolytic bio-cementation, proceedings of the american society of civil engineers, geo-congress held in minneapolis, minnesota 25–28, february 2020. gsp no. 320: 83-95. carmona, jpsf., oliveira, pjv. and lemos, ljl. 2016. biostabilization of a sandy soil using enzymatic calcium carbonate precipitation. advances in transportation geotechnics 3. proceedings of the 3rd international conference on transportation geotechnics held in vila flor cultural centre guimaraes, portugal 4-7, september 2016. ictg proceedings no. 143: 1301-1308. cheesbrough, m. 2006. district laboratory practice in tropical countries part 2, second edition. cambridge university press, new york. cheng, l., cord-ruwisch, r. and shahin ma. 2013. cementation of sand soil by microbially induced calcite precipitation at various saturation degrees. canadian geotechnical journal 50: 81–90. cheng, l., shahin, ma. and cord-ruwisch, r. 2017. surface percolation for soil improvement by bio-cementation utilizing in situ enriched indigenous aerobic and anaerobic ureolytic soil microorganisms. geomicrobiology journal, 34(6): 546-556. choi, s., park, s., wu, s. and chu, j. 2017. methods for calcium carbonate content measurement of biocemented soils. asce, journal of material of civil engineering, 29(11): 1 -4. choi, sg., chang, i., lee, m., lee, jh., han, jt. and kwon, th. 2020. review on geotechnical engineering properties of sands treated by microbially induced calcium carbonate precipitation (micp) and biopolymers. construction and building materials, 246: 1-14. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/gadzymo@yahoo.com gadzama et al: effect of bio-cementation on the strength characteristics of compacted lateritic soil under sterilized and unsterilized conditions. azojete, 18(3):435-452. issn 1596-2644; 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(2020) should be introduced to eliminate this sort of drawbacks. it consists of links that lies inside the arrangement with symmetricallyspaced holes arranged on the solid cylindrical disc. the number of the links is between three and or nine. as the number of the links was increased, the smoother the operation became. today, due to unavailability of resources, it is imperative using the resources available at hand for the purpose intended. generally, the problem with gear transmission is that, the production of gears is complex processes that requires more time and a great deal of precision is also required for mass production. another major problem of gear drive transmission is that, it causes backless error leading to jamming and becomes more noisy compared to other drives because of pitch mismatch. ranjbarkohan (2011) and kumar (2015) system loaded with l-pins at 012o of the tubular disc. the pins are made up of the stainless steel (x6cr17). the gearless mechanism produced has an improved efficiency of 94.8% as compared to that of kumar (2015) with 92.1% article information abstract gearless transmission is an elbow mechanism that transmits power with little losses. the system is mainly used to reduce the usage of complex gears likewise the wearing conditions of the gears that requires high cost of repairs and or maintenance. therefore, exploration into this study lead to rejuvenate ideas through which power was transmitted using different mechanism by replacing a bevel gear with an elbow mechanism for transmitting the power between the two shafts at 90°. the mechanism hubs were fixed at both ends of the shafts through which power was transferred. the sizes of the pins and links were measured, likewise the holes were drilled precisely. in this study, three elbows were connected radially at an angle of 120° to the center of the axis. the transmission was made cost-effective and efficient with the average efficiency of 94.8% and a complete freedom of interchangeability whereby the total cost of production was #76,000. of this arrangement, the mechanism has effective and minimum amount of power (10.18nm) at the handle needed for a complete revolution. it’s a simple working principle, smooth with an effective and lesser power needed to propel it. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 december, 2022 revised 18 march, 2023 accepted 24 march, 2023 keywords: gearless transmission power losses efficiency cost http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com victordagala@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):193-202. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 194 performed through a study on a multi angular gearless drive and also that of htway et al. (2019), somraj and sallesh (2017) with 3, 5 7 and 9 odd pins respectively. barot and patel (2020) designed a gearless mechanism to transmit power at different angles between 0-180o of the shafts and analyzed in comparative expression analysis level (creo5) for checking the feasibility of the transmission system. it showed the speed ratio of the shaft 1:1 during operation and indicated a maximum displacement at the elbow links same with that of chakradhar et al. (2019) loaded with 3 numbers of l-pins. 1.1 application of the gearless transmission system the gearless transmission has the wider application as an extension for a socket wrench. here, the design made it easy and faster in automotive and other mechanical industries where direct access to bolt and screws are often limited. however, there are conceivable applications for this technology that extend into various arenas to mention but a few; i. it could invariably be used for gang drilling. ii. the elbow system could be used for periscope in submarine. iii. lubrication pump for computerized numerical control (cnc) lathe. iv. used in vehicles (go-carts). 1.2 principle of operation of gearless transmission system a common form of gearless transmission system is normally an angle located shaft that is transmitted from the driving shaft via the rods to the driven shaft bent to fit the angles between the shafts. the shafts need to be spaced equally around the circle at openings and are free to slip in and out during shafts rotation. the drive (figure 1a) is predominantly suitable and quiet for high-speed operation though its recommendation but only for light duty operations (katharine et al., 2013). for an improved gearless transmission system as shown in figure 1b, it has the power to replace both bevel and crown gears with greater efficiency unlike that of micah et al. (2021) for power transmission with a little change. the system could serve as an innovative idea which could be of great benefit to the society at a larger scale. the mechanism shows a deceptive turn by the action of one rod during revolutions. figure 1b shows the replica of figure 1a where the driving shaft ‘a’ is revolved and the driven shaft ‘b’ also rotates but in counter clockwise. as the shaft ‘a’ turns through half revolution, rod ‘c’ slides out of both shafts ‘a’ and ‘b’ respectively at the first half revolution. at the remaining half of the revolution, rod ‘c’ slides inwards until it reaches the inner most position. therefore, all rods are successively sliding inwards and outwards. as this illustration shows a right angle transmission, the drive could be applied also to shafts located at midway the angles between 0° and 90 °. during construction of the transmission system, holes of the given rods are located accurately at the same position in each shaft, and the holes are equally spaced in radial and circumferential directions. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com dagala et al: improved gearless transmission system. azojete, 19(2):193-202. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 195 figure 1a: gearless transmission shaft figure 1b: improved gearless transmission system 2. materials and methods 2.1 design considerations ✓ holes in each cylinder must be equally spaced for equal rotation. ✓ angle between holes = 120o to avoid overlap ✓ no. of rods = 3 based on the requirement of the system ✓ the greater the number of rods, the smoother the operation and higher the efficiency according to somraj and sallesh (2017) ✓ 3-8 rods feasible for greater efficiency ✓ end of the cylinders have the input and output shaft fitted with screws to prevent abnormal shift of the pins ✓ each shaft is supported on bearings for easy rotation. ✓ main assembly is mounted on a frame for support. 2.2 materials selection the choice of materials for engineering purposes depends on the following factors: 1. availability of the materials for specific purpose. 2. suitability of the materials for the specific purpose. 3. the cost of materials for the intended purpose. 4. physical and chemical properties of the material 5. mechanical properties of the material. 6. corrosion resistivity of the material 2.3 mechanism component operations 2.3.1 supporting frame the supporting frame is often a structural system that supports other components of the physical construction that limits the construction extent and gives it strength and shape. the shaft is the bar or rod used in the construction of the mechanism for transmitting the power. ball bearing are fixed at the terminals of the shaft to allow easy rotation of the shaft in order to prevent the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):193-202. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 196 wearing of the shaft terminals. while the bolts are fasteners that consist of the threaded linings holes and pitches and nuts are used for fastening or tightening parts. 2.4 design calculations. this is to determine the parameters of the components parts of the improved gearless transmission system 2. 4.1 design of the handle in determining the parameter of the handle of the improved gearless transmission system, power of the handle =1/7 horse power (hp) (1) but, 1 horse power (hp) = 746 watt = 746 × 1 7⁄ = 106.57 𝑁𝑚/𝑠 revolution per minute of the handle (speed) 𝑁 = 100 𝑟𝑝𝑚 from equation 1, power of the handle (p) = 106.57 watt. 𝑃 = 2 𝜋𝑁 𝑇 60 (2) where, n = speed of the shaft in rpm t = torque transmitted from equation 2, 106.57 = 2𝜋×100×𝑇 60 t = 10.18 𝑁𝑚 t = 1018 𝑁𝑚𝑚. 2.4.2 shaft design parameter from equation 2, transmitted torque t = 1018 nmm 𝑇𝑚𝑎𝑥 = 1018 × 1.25 = 1272 𝑁𝑚𝑚 as the shaft in figure 2 is imperiled to pure torsional stress, 𝑇𝑚𝑎𝑥 = 𝜋 × 𝑓𝑠 × 𝑑3 16 (3) 1272 = 𝜋 × 40 × 𝑑3 16 d = 5.5𝑚𝑚 figure 2: shaft of the improved gearless transmission file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com dagala et al: improved gearless transmission system. azojete, 19(2):193-202. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 197 the maximum bending moment (𝑀𝑡) of the transmission shaft is give as, 𝑀𝑡 = 𝑊×𝐿2 4 (4) where w is the shaft weight which is equal to 13.23n and l is the length of the shaft 350mm therefore, mt= 405184.4 𝑁𝑚𝑚, bending stress of the shaft (𝜎), 𝜎 = 32𝑀𝑡 × 𝑑 3 (5) σ = 202.6n/mm2 tensional shear stress (𝜏) of the shaft, 𝜏 = 16𝑀𝑡 𝜋𝑑3 (6) τ= 16×405184.4 π×20 3 = 257.94𝑁/𝑚𝑚² 2.4.3 hub design parameter from figure 2 with an internal radius (ro)10mm, outer radius (ro) 40mm with a length of 30mm; density of the mild steel = 7860 kg/m3 volume of the hub = (ro 2 − ri 2) × length (7) vol. of hub = (402 – 102) × 30 = 141371.7𝑚𝑚3 = 1.41 × 10−4𝑚3 mass of hub = density of mild steel × volume of hub = 7860 × 1.41 × 10−4 = 1.11 kg weight of hub = 𝑚 × 𝑔 (8) weight of hub = 1.11 × 9.81 = 10.9n evaluating the bending stress of the hub, it becomes; σ𝑏 = 𝑊×𝐷𝑖 2 𝐷𝑜 2−𝐷𝑖 2 (9) where 𝐷𝑖 and 𝐷𝑜 are the inner and outer diameter of the hub, while w is the weight of the hub σ𝑏 = 10.9×202 802−202 = 72.66𝑁/𝑚𝑚 the improved gearless transmission system is presented in figure 3. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):193-202. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 198 figure 3: hub of the improved gearless transmission 2.4.4 elbow rod design parameter from figure 3, tmax was transmitted to the elbow links in figure 4, therefore, it is divided by 3, because of the three rotational axis which gives 1272/3 = 424nmm. that is the diameter of the elbow link obtained by dividing the torque on equal shaft with dimensions 150mm length and 10mm width. therefore, 𝑇𝑚𝑎𝑥/3= 1272 /3= 424 𝑁𝑚𝑚 if 𝑇 = × 𝑓𝑠 × 𝑑3 16 (10) where fs is maximum, shear stress = 40n/mm now d as the diameter = 7.17 𝑚𝑚. figure 4: elbow link of the improved gearless transmission 2.5 construction of the improved gearless transmission mechanism (principles) the gearless transmission mechanism as a system that transmits motion between the driving and the driven shafts at any fixed angle. the mechanism contains a variety of pins and rods that are bent at the right angle. the number of pins were between 3 and 8 because the greater the number of the pins, the smoother and higher the efficiency. the pins sided inside the holes and created a pair of sliders. in this mechanism, the 3 holes were drilled on the circumference of the circle called a pitch at 120 to each other from the middle of the cylinder. the end of the cylinders was file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com dagala et al: improved gearless transmission system. azojete, 19(2):193-202. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 199 fitted with an input and output shaft with the aid of keys and each shaft was supported on a bearing house consisted of a ball bearing. the main assembly was mounted on a mild-steel frame as shown in figure 1. 2.6 construction of the improved gearless transmission hub construction of the hub was done by the use of lathe and drilling machine. during the construction, the following operations were used. 1. marking 2. cutting 3. hole drilling 4. turning 5. facing 2.7 procedure for machining of the improved gearless transmission hub i. a mild steel of length and diameter more than 30mm and 80mm respectively was used. ii. facing operation was done at both ends to make the piece of length 30mm. iii. turning operation was done on lathe to make the piece to 80mm diameter. iv. the pitch circle diameter of 20mm was marked. v. three points on the circle at angle difference of 120o were mark vi. drilling of holes of 9mm diameter was done at the above marked points. vii. drilling of a blind hole of 9mm diameter was done at the center of the length of the hub to a depth of 20 mm. viii. hand tapping of 8 mm was done in the blind hole. 2.8 construction of the improved gearless transmission shaft operating done for machining of shaft was “facing” 2.9 procedure for machining of the improved gearless transmission shaft 1. a piece of diameter 20mm and length greater than 350mm was used. 2. facing was done to reduce the length to 350mm. 3. turning operation was not done as we got the shaft having diameter exactly 20mm. 4. external thread of pitch 2mm was made at one end of the shaft. 2.10 construction of the improved gearless transmission pins construction of pins was done on the lathe using open hearth and bench vice (bending machine). 2.11 procedure of making the improved gearless transmission pins 1. a rod of length greater than 300mm and diameter 8mm was used. 2. facing operation was used to reduce the length of the rod to 300mm. 3. the rods were heated, at their centre on the open hearth at a high temperature so that the stress exceeded the yield stress of the mild steel. 4. the rods were bent at 90o on the bench vice (bending machine) in order to obtain the pin rods. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):193-202. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 200 2.12 construction of the improved gearless transmission frame construction of the frame was done by cutting and welding operation. 2.13 simulation of the improved gearless transmission system static structural analysis of the system was observed in order to determine the total deformation of the elbow rod, hub and the shaft at 100rpm. 2.14 performance evaluation of the mechanism (efficiency test) the efficiency of any mechanism shows the performance of the mechanism. the efficiency of any system is defined as the ratio of the output to that of the input. for this gearless transmission system, the mechanical efficiency was calculated using equation 11 𝜂 = 𝑁𝑜 𝑁𝑖 (11) where: η = mechanical efficiency of the gearless transmission, no= speed of the shaft at the output in rpm, ni= speed of the shaft at the input in rpm . the performance evaluation of the improved gearless transmission system was conducted using equation 11 and different input shaft speeds. 3. results and discussion the performance of the improved gearless transmission system is presented in table 2. table 2: performance evaluation of the improved gearless transmission system table 2 shows the experimental efficiencies of the improved gearless transmission system. therefore, the average efficiency of the system is as follows: 𝜂𝑎𝑣 = (95 + 92 + 93 + 97 + 96 + 96)/6 = 94.8% thus, the average efficiency of the improved gearless transmission system is 94.8%. the efficiency of the system could be increased by following ways: 1) proper lubrication of the pins and hub 2) lubrication oil of suitable viscosity should be taken. 3) by reducing the weight of the mechanism through proper designing. 4) finished surface after grinding to reduce the friction between the hub and pins. the system was found worthy of implementation. base on the frictional cases and the system vibration, there was little reduction in the speed due to the power reduction which could be modified as research continues and the average efficiency of the improved gearless transmission system obtained is 94.8% greater than the existing gearless transmission systems found in s/no. no ni η 1 100 95 0.95 2 100 92 0.92 3 100 93 0.93 4 100 97 0.97 5 100 96 0.96 6 100 96 0.96 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com dagala et al: improved gearless transmission system. azojete, 19(2):193-202. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 201 literature. with the help of solid work analysis, after applying all the boundary conditions given in the existing design parameters, all were included in the simexpress module. in solid work analysis, it works on the finite element method (fem). simexpress statistical analysis used to conclude the result to determine the efficiency and design analysis. 4. conclusion from the data obtained, it is confirmed that the system worked perfectly well with the minor human error or deficiencies compared to the existing modules. the system as evaluated shows improved simple transmission mechanism associated with numerous benefits. it is fairly light in weight, easy to design, easy to manufacture and economically viable both at the time of manufacturing and at running time with minor drawbacks such as inability to transmit velocity ratios other than 1:1, inability to transmit higher torques which could be improved for various uses in the real world such as; i. for low power transmission between perpendicular shafts ii. static applications where 1:1 velocity ratio is to be transmitted iii. low-duty vehicles which are not subjected to shocks and vibrations like the cricket matches for transporting drinks. the gearless transmission system shown in figure 5 has the power to replace both bevel and crown gears with greater efficiency unlike that of micah et al. (2021) for power transmission with a little change. therefore, the system could serve as an innovative idea which could be of great benefit to the society at a larger scale. references barot, rp. and patel, dm. 2019. design and analysis of multi-angular gearless transmission system. trend in mechanical and biomedical design: selection from the proceedings of icmechd, 533-541. chakradhar, u., muniteja, k., charanteja, k., lokesh e., tulasi ram ch., ajay,t. and karthik, i. 2018. a review on review of gearless transmission through elbow mechanism. international journal of research in engineering science and management, 2(11): 470-471. htway, z., kline, mm., lin, n. and myint, km. 2019. stress analysis and simulation of gearless transmission mechanism. university research journal of science, engineering and engineering education (urjsee), 1: 110 – 113. kumar, ak. 2015. gearless power transmission for skew shafts (asrrs mechanism). international. journal of advanced science and technology, 79(3): 61-72. micah, p., hariram, v., seralathan, ps. and godwin, j. (2021). design and numerical analysis of gearless transmission used in small wind turbine. trends in mechanical and biomedical design. iop conference series: material science and engineering, 872: 1-8. doi: 10.1088/1757899x/872/1/012096 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):193-202. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victordagala@yahoo.com 202 ranjbarkohan, mrm. 2011. kinematic and kinetic analysis of slidercrank mechanism in otto linear four cylinder z24 engine. journal of mechanical engineering research, 3(3): 85-95. somraj, r. and sailesh, b. 2017. design and fabrication of gearless power transmission for skew shafts. international research journal of engineering and technology (irjet), 4(04); 1018-1023. khan, as. and pandey, g. 2021. design fabrication of gearless transmission using elbow mechanism. international research journal of engineering and technology (irjet), 8(5): 27382743. patel, m., parikh, d., parmar, p. and patel, s. 2019. gearless power transmission. international journal of mechanical engineering and technology, 10(7): 235-241. pinghua, ju., zi, c., yan r. and xiao, b. 2020. assembly quality control point judgment method in motion mechanism on plsr. china mechanical engineering 31(13): 1562 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/victordagala@yahoo.com arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):163-174 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 163 original research article fabrication and evaluation of an affordable infant radiant warmer for use in limited resource settings m. o. ibitoye*, y. k. ahmed, a. b. saad and t. m. ajibola department of biomedical engineering, faculty of engineering and technology, university of ilorin, nigeria *corresponding author’s email address: ibitoye.mo@unilorin.edu.ng 1.0 introduction neonatal hypothermia is believed to be a global health challenge (beletew et al., 2020) as approximately 40% of the global incidences of neonatal mortality are due to hypothermia (lawn et al., 2014). hypothermia is an abnormal and unsafe drop in body temperature (≤ 36.5oc) (who, 1997; mohamed et al., 2021). literature evidence (lawn et al., 2005) suggests that up to 99% of infant mortality incidences are in limited resource settings. one reason for this may be due to the fact that up to 85% of infants in these environments are often exposed to cold stress (lunze et al., 2013) without efficient means of prevention. in addition, underweight infants (weight less than 2.5 kg), which account for 20 million annual infant deliveries (world health organization, 2016), are most vulnerable to morbidity due to less body fat that often leads to thermoregulation challenges (nahimana et al., 2018). as the economic growth in terms of gross domestic product (gdp) per capita reduces infant mortality (nishiyama, 2011), most developing countries are unable to meet the minimum threshold for healthcare financing, and “basic neonatal care technologies are inadequate” (maynard et al., 2015). therefore, with between 2% to 10% of gdp budgeted for healthcare in most developing countries as against the minimum of 15% recommended by the african union for developing economies (organisation of africa unity, 2001), mothers are left with the only option of the affordable or traditional methods of keeping their babies warm. unfortunately, the available inexpensive and or traditional methods to article information abstract the challenges of thermoregulation due to hypothermia, which is believed to underlie high infant morbidity and mortality rate, is common with underweight or preterm infants especially those from limited resource settings. available devices in the market to check hypothermia are expensive, especially for most countries with between 2% to 10% of gdp on the healthcare budget. affordable thermoregulation realization for infants is therefore of significant clinical importance in these settings. the aim of this study was to design and fabricate an affordable ($110) and clinically useful radiant warmer to facilitate hypothermia treatment. the radiant warmer was fabricated with an overhead radiant heater for heat radiation targeted at infants laid in a clinically comfortable foam mattress in a bassinet. a portable fan was placed above the heating element to facilitate downward heat flow. a biocompatible temperature sensor was also placed on the bassinet to monitor the infant’s body temperature. the warmer incorporated an arduino-based pid temperature microcontroller to regulate the temperature of the heating element. the warmer, with castor wheels to aid the device’s mobility, has a strong and durable galvanized pipe stand capable of supporting the device. the device performance indicated an acceptable physiological heating temperature range of 36 °c 36.5 °c within 20 min of warm-up and up to 36.7 °c in 30 min of use. therefore, the device can be adjudged potentially useful in facilitating thermoregulation in infants by providing suitable thermal support. with these results and the potential of the device to reduce infant mortality rates and promote their growth, it is hereby recommended that the device may be fully deployed for clinical application. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 august, 2022 revised 7 november, 2022 accepted 10 november, 2022 keywords: radiant warmer thermoregulation underweight infants hypothermia limited resource settings http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng file:///c:/users/user/downloads/ibitoye.mo@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):163-174. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 164 promote thermoregulation such as kangaroo mother care may be inefficient especially when the infant is ill and need constant clinical monitoring (ahmed et al., 2011; nahimana et al., 2018). furthermore, the mother may be ill or too busy to provide adequate thermoregulation supports through this method (gupta et al., 2015; nahimana et al., 2018). for this reason and better infants’ thermal stability, the challenges of thermoregulation are believed to be significantly addressed by a radiant warmer (boundy et al., 2016). this is also due to the fact that incubators are too expensive for limited resource settings (maynard et al., 2015) and may readily impair infants’ thermal environment (chaseling et al., 2016). specifically, a radiant warmer uses a controlled heating element to keep infants healthily warm, promote thermoregulation and facilitate easy access to the infants, especially while under observation (bell, 1983), stability after birth, and during surgical procedures (knobel-dail, 2014). another important strength of this “open care system” is the ability to facilitate the regulation of heat loss and metabolic rate (bell, 1983) while promoting the infants’ neurodevelopment (nahimana et al., 2018) and keeping them in good clinical condition. radiant warmers also provide the required source of heat energy and reduce conductive heat losses by providing a warm environment surrounding the infants. research interventions toward facilitating easy access to this device, therefore, hold huge benefits for urgent neonatal care technologies through the reduction of infant morbidity and mortality rates. previously, researchers have developed some viable alternatives for this purpose. however, cost (especially due to running and spare part costs) and the issue of maintainability have prevented the success of these efforts in low resources settings. to overcome the highlighted challenges with available options, we sought to design and construct an affordable radiant warmer that could be easily maintained and used in limited resource settings to improve neonatal care through the facilitation of thermoregulation. this device was designed to address the shortage of clinical-grade radiant warmers in limited resource settings while keeping its cost affordable and its use simple even for inexperienced caregivers. 2. materials and methods 2.1 system design and block diagram the design is modularized into different segments that interconnect and work together as a whole to provide regulated warmth for neonates. the block diagram of this arrangement is shown in figure 1. the heater control unit consists mainly of the rotary encoder and the arduino board. there is also a ceramic insulated heater placed above the infant bassinet (where the infant is placed). the power supply unit powers the heater control circuit, the heater, the display unit, and the temperature sensor. figure 1: system block diagram design considerations and assumptions were based on the fact that infants, especially those that are underweight need thermal supports for survival. the device’s is well above 1 metres from the ground to the infant bassinet to present dusty air from reaching the infant. it is assumed that the ambient temperature will not impair the temperature to be gained by the infant during device’s operation. the interface between the infant and the device (foam mattress inside the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng ibitoye et al: c. azojete, 19(1):163-174. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 165 bassinet) is biocompatible. the device is designed in such a way that the infant will be accessible and clearly visible by the care givers. other considerations and assumption for safe operation of the device has been discussed further under system description. 2.2 materials compliance with the safety standard based on the target infant population and consideration for the cost-effectiveness is the major design and material selection considerations in this study. these factors influenced the technology deployed and the material used in this study. material availability within our environment, or those that can be seamlessly ordered within the country or from abroad, at an affordable cost was also prioritised once they are durable and able to support the required technical specifications. in table 1, we have presented the materials selected and the justification for their selection. the materials listed in table 1 are locally available within the country or can be ordered from abroad seamlessly. table 1: material selections and their justification: s/n materials warmer modules justification 1. galvanized pipes, nuts and bolts hardware locally sourced, durable, and resistant to corrosion and cracking especially for the environment for the purpose to serve. 2. microcontroller board (arduino mega 2560) hardware and software capable of creating interactive objects, interfacing multiple sensors, sensing, and effective temperature regulation. 3. ac 220v 750w ceramic insulated heater hardware portable, compatible for the purpose, and very high melting point. 4. transparent plastic sheet acrylic board hardware low weight, good impact strength, transparent, and safe for infants. 5. portable infant bassinet hardware portable, cheap, durable, easy access to the infant, and safe for use. 6. thin film transistor and liquid crystal display module for arduino board hardware cheap, portable, good response time, and visible from far a distance 7. triac hardware requires a single fuse for protection, power control 8. humidity and temperature sensor (dht22) hardware small size, cheap, fast in operation, high accuracy and reliability. 9. buzzer & light emitting diode (led) hardware affordable, light and sound indicator in one sensor—portable. 10. 120w 30v transformer for power unit hardware good capacity and high efficiency 11. portable ac fan hardware affordable and efficient 12. silicone sealant hardware minimal waste, rapid drying, water resistance, transparent 13. k type thermocouple + max6675 board hardware efficient, wide temperature range (0– 1024 oc), ability to digitize temperature, and no self-heating issue. 14. bridge rectifier hardware provides dc voltage (0-15 v) and efficiently 15. opto-isolator hardware complete electrical isolation between input and output and promote safety inexpensively. 16. buck converter power supply hardware step down capability and filtering with few external components. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):163-174. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 166 17. pvc pipe hardware easy installation and proper cable enclosure. 18. rotary encoder hardware reliable, accurate, high resolution, and compact size 19. power cable hardware high reliability 20. castor wheels hardware ease of movement of the whole device and durability 21. plastic case box and lid hardware portable, lightweight, resistive 22. blue and white spray paint + gloss varnish hardware protects and resists dirt retention, nontacky, improves surface durability 2.3 system description the device was made with safety considerations specifically to accommodate tender neonates and infants. the radiant warmer was kept within the “physiologically accepted range” of 36 °c 36.5 °c, based on international standards (world health organization, 1997). this temperature range was attained in 20 min after the heater was switched on and was maintained for up to 2 hours (table 3). the heat generated by the heater was controlled by a control knob (rotary encoder) with the use of proportional integral derivative (pid) controller in the arduino board. the warmer was built in such a way that cleaning and disinfection could be done easily especially, the infant’s mattress. this was made possible by the materials used for these components of the warmer. appropriate safety arrangements for this device included the alarm and visual indication of the infant’s skin temperature. due to the nature of the heater used, the warm-up time was ≤ 20 min and this could be considered appropriate and acceptable as available for most proprietary warmers (bell, 1983) and as recommended by united nations children's fund (unicef) (unicef, 2018) that similar warm-up time is appropriate for infants suffering from hypothermia. the radiant warmer consists of three different modules that were constructed in three stages: (i) hardware module (ii) software module, and (iii) integration of the hardware and software modules to form a complete system. the structure/ frame of the device consists of galvanized pipes and other metallic materials joined together by welding. this network was thereafter painted and varnished to produce a quality gloss finish. the total height of the device stands at over 2 meters with the distance between the heater and the bassinet being at approximately 1 meter. following the device’s design, its isometric and orthographic views were developed and are shown in figure 2, with figure 3 representing the various parts of the radiant warmer. figure 2: isometric and orthographic views of the radiant warmer with measurements made in mm. a: side view; b: plan view and c: isometric view. the detail information about the component of the designed radiant warmer could be found in figure 3 and complemented by the information in figure 4. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng ibitoye et al: c. azojete, 19(1):163-174. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 167 figure 3: various parts of the radiant warmer figure 4 presents the complete radiant warmer which consists of the mounted heater, acrylic panel and bassinet while the control panel, and the device’s frame are mounted to stand on castor wheels to facilitate mobility. the design, development, and testing of the device were carried out in a laboratory setting. the pid control system was used to regulate the heating element. figure 4: the complete radiant warmer 2.4 mode of operation and performance evaluation to demonstrate the device’s performance for objective evaluation the following procedures were taken. the time taken to warm up the infant’s compartment as pre-set was identified and reported. the following steps were thereafter taken to put the radiant warmer into use: (i) the external surfaces of the warmer were disinfected to prevent infection transmission using antiseptic solution; (ii) the room temperature was checked to ensure that the initial set http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):163-174. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 168 temperature was normal and to ensure that no other source of heat could move towards the warmer; (iii) the infant mattress was pre-warm for easy habituation for the infant and in order not to expose the infant to a sudden cold environment; (iv) infant placement into the bassinet prior to the attachment of the humidity and temperature sensors with a biocompatible selfadhesive tape; (v) thereafter, the temperature as indicated on the lcd display was modulated by the rotary encoder to set, adjust and keep the temperature within physiologically acceptable range; (vi) the infant position was manually and frequently changed (as necessary) to ensure an even temperature distribution; (v) after use, the infant was carefully removed with the infant wrapper and the device was disinfected before subsequent use. as mentioned earlier, the ambient temperature in the infant’s compartment was kept within the “physiologically accepted range” (36 °c – 36.5 °c), based on international standards (world health organization, 1997). with the use of an arduino mega 2560 (arduino, scarmagno, italy), that serves to perform all the instructions and commands of the device, the infant’s temperature could be modulated from the initial temperature to 36.5°c for hypothermic neonates. this temperature could be maintained with the use of an embedded pid controller which uses a control loop feedback or process variable that senses the output of the heater and feed it back so that the system can make adjustments accordingly to monitor where the output should be. the constant set temperature used was 36.4°c which is within the range recommended by the world health organization (world health organization, 1997). apart from the versatility of the pid controller as an excellent component for the protection of the infant by controlling the heat that flows towards the bassinet where the infant is located, an alarm system was also incorporated to indicate when there is a problem with either the heater output, power or the temperature sensor. this arrangement is meant to prevent any kind of compromise on the infant as an additional safety feature. specifically, the alarm buzzer was designed to be activated once there is an abnormal situation, and continuous noise indicates that the device is due for maintenance. an emergency power switch was also put in place in case of an emergency stop which is designed to completely deactivates the functionality of the warmer. instructions to the users will include procedures to perform basic and regular electrical safety checks to reduce the risks of damage to the device and avoid overloading and electrical surges, and other abnormal situations may also affect the users and the infants. as an additional instruction to ensure the safety and uninterrupted operation of the device, there is a need to avoid human error by not placing any accessories directly over the infant’s compartment and not placing items on top of the heater except for the mounted fan. the special user instructions will include the need to properly sterilize the device before and after every each use so far the infant is placed inside the infant’s compartment. this will include the need to ensure that the warmer is not positioned or used near flammable anaesthetics or other clinical items that are flammable. all the infants connecting tubes or cables must be inspected before and after moving the device and before use. 3. results and discussion 3.1 results infant compartment temperatures were taken at intervals as shown in table 2 to observe the heater’s response with time under the control of a rotatory encoder. the results’ readings were obtained considering the time spent to heat up the infant’s compartment and to observe the duration for which the infant’s compartment can be kept within the allowable temperature range (and in order to be in thermal equilibrium). within two hours of testing, table 2 presents the results obtained. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng ibitoye et al: c. azojete, 19(1):163-174. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 169 table 2: infant’s compartment temperature at different times s/n time spent/ (minutes) heater temperature/ (°c) measured infant compartment temperature/ (°c) expected infant compartment temperature (°c) 1. 10 133 34.3 36.4 2. 20 146 36.3 36.4 3. 30 150 36.7 36.4 4. 60 147 36.4 36.4 5. 120 145 36.3 36.4 a t-test to compare the measured infant compartment temperature and expected infant compartment temperature using stata 14.2 software (statacorp llc texas, usa) gave a p-value of 0.7969. the p-value indicated no observed difference in the measured and expected results. hence, the device worked efficiently. a correlation table of relationship between parameters is shown in table 3. figure 5: variation of heater and infant compartment temperature with time figure 5 presents the variation of heater and infant compartment temperature with time. it shows that the measure and the expected temperature has a strong correlation. table 3: relationship between variables using correlation time heater measured expected time 1.0000 heater 0.3120 1.0000 measured 0.4088 0.9918 1.0000 expected it can be seen from the table 3 that measured infant compartment temperature strongly correlates with the heater temperature. this shows that the measured temperature is being controlled by the heater temperature. electrical safety testing of the device’s components was carried out based on the global standard (“iec60601-1”) to prevent both internal and external electrical damage and safety of the users (grodt, 2018). specifically, the following test and results were carried out to ensure the electrical safety of the device which is arguably the most important test. an insulation resistance test was conducted to measure the total resistance of the device’s insulation by applying a high voltage of 700 v (grodt, 2018). the value of resistance for the radiant warmer (i.e., with heating element) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):163-174. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 170 (weithöner) after the insulation resistance test was 1.1 mω, which fell within the safety range of the iec standard (grodt, 2018). earth continuity test was also carried out by measuring the resistance between the device’s metal body and the ground pin (i.e., the terminal in the control circuit board that connects the body of the device to the circuit earth/ ground terminal). following this test, the value obtained was 0.5 ω. the test was carried out at a higher current (35 a) (embe, 2019) so that the ground bond test of the circuit maintains safe voltages before the circuit breaker trips in emergency situations. this step was essential to serve as an additional protection to prevent injury which may be due to electric shock in the developed radiant warmer. another important test performed was the leakage current test (weithöner). this test was conducted to measure the undesirable leakage current that may flow across the device. the limit leakage current recorded was 95 µa, which was less than 100 µa according to the iec standard (jonsson and stegmayr, 2000; zion, 2022). thereafter, physical condition checks were also performed on the device. this included the functional test to ensure the infant’s compartment would not collapse during movement or due to the infant weight or external load placed on it. specifically, this test was performed through the placement of a load of up to 20 kg (in gradual increments from 2 20kg) on the device’s bassinet. the device was rigorously dragged and moved across the laboratory to test the durability of its stand and welded joints. an abrasion test was also conducted on the device to ensure that its wheels would not tear if dragged along rough surfaces. the wheels were tested against bumps, abrasive surfaces, and floors which it may typically encounter when in use in low resource settings. these surfaces were made up of cement concrete, sheet vinyl, or tile floors. the direction of wheel rolling was reversed and tested to ensure that it could withstand deformation, wear, or physical failure. before switching on the radiant warmer to a set point, the ambient airflow velocity was measured which was ≤ 0.3m/sec using a portable anemometer and this was adjudged a good level since we intended to minimize the heat loss. the alarm levels and functions were also tested to ensure that they were loud enough for the clinical staff or operator but were quiet enough in order not to impair the infant’s hearing. with the alarms turned on, after measuring the audio level from inside the infant’s compartment, the sound pressure, using the decibel x app (skypaw co., ltd, hanoi, vietnam) (capriolo et al., 2022), was recorded at 72 db while the sound pressure recorded 3 meters away from the radiant warmer was 58 db. according to the who (etienne krug et al., 2015) and the centers for disease control and prevention of the usa (cdc, 2022), these values are below the harmful range for the general population but slightly beyond the recommended level only for the “preterm or very low birth weight infants” (almadhoob and ohlsson, 2020). however, the values can be considered safe especially since the exposure time is very short and only necessary when the temperature is out of the threshold. table 4 also presents the analysis of the cost for the selected materials in this study. based on the market survey, the cost of production of this device at usd 110 is under 10% of some commercialized and standard radiant warmers. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng ibitoye et al: c. azojete, 19(1):163-174. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 171 table 4: cost analysis of the radiant warmer s/n item quantity unit price (₦) total price (₦) 1. galvanized pipes and other metallic materials 2 5000 10000 3. arduino mega 2560 1 3500 3500 4. alternating current insulated heater 1 3000 3000 5. transparent plastic sheet acrylic board 1 4000 4000 6. portable infant bassinet 1 1500 1500 7. thin film transistor liquid crystal display module 1 1700 1700 8. triac 1 500 500 9. humidity and temperature sensor 1 400 400 10. buzzer 1 200 200 11. 120 w transformer 1 5000 5000 12. portable direct current fan 1 2500 2500 13. silicone sealant 1 1400 1400 14. k type thermocouple + max6675 board 1 700 700 15. bridge rectifier 1 350 350 16. opto-isolator 2 300 600 17. buck converter 1 300 300 18. trucking pvc pipe 1 500 500 19. rotary encoder 1 700 700 20. power cable 1 1000 1000 21. nuts and bolts 10 50 500 22. castor wheels 4 500 2000 23. plastic case box and lid 1 2000 2000 24. blue and white spray paint + gloss varnish 1 3000 3000 25. heat sink 1 300 300 26. connecting wires 5 300 1500 27. jumper wires 5 200 1000 28 switch 1 350 350 29. resistors(pack) 1 100 100 miscellaneous 5,000 grand total 53,600 = ~ usd 110 3.2 discussion it is well known (world health organization, 1997; trevisanuto et al., 2018; mohamed et al., 2021) that body heat regulation in infants is less efficient and this condition is worse in preterm, low birth weight, and/or sick infants (world health organization, 1997). this low-cost device is specifically designed to reduce infant mortality, especially in low-resource settings. with this device, infants requiring urgent thermoregulation assistance within a reasonable budget in these settings could be facilitated. one of the major advantages of this locally fabricated radiant warmer is the ease of use (no ambiguous instructions and steps for operation). operators of the device can quickly understand and master the uncomplicated process involved due to the simple control system used in its design and implementation. the structure of the device was also made to promote portability due to the use of strong and lightweight materials which helps in the ease of its movement from one location to another. the fast warm-up time as well as uniform heating of the infant’s compartment also prove to save time and minimize unwanted heat leakages. table 2 presents an acceptable heater’s temperature response with time. the apparent thermal stability pattern shown in table 2 after 20 min of warm-up time is in agreement with the range of temperature for which a radiant warmer should be during usage (whiteside, 1978; unicef, 2018). therefore, the design has demonstrated an encouraging response for clinical deployment. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):163-174. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 172 for example, no statistical significant observed difference was found between the measured infant’s compartment temperature and expected infant’s compartment temperature. unlike the design proposed by thavaraj et al. (2017), this present device is simpler to use and costs a significantly lower amount of capital for production. warneford (2018) developed a prototype of a “neonate warming blanket”. while the author’s work represented a good attempt at thermoregulation facilitation, in its current state, the prototype lacks some vital elements of a radiant warmer, and information on some important components and the device’s assembly were not presented. also, chandrasekaran et al. (2021) developed a disposable cardboard incubator for thermoregulation promotion. the system maintained the set temperature reliably (chandrasekaran et al., 2021), however, the device is fragile and its durability and maintainability including cleaning are questionable. generally, proposals on the development of radiant warmers that incorporate and report control systems, especially for temperature distribution appear uncommon in the literature. thus, the radiant warmer designed, fabricated, and presented in this study has proven to be a viable alternative when compared to both the available prototypes, in terms of functionality, and commercially available options, in terms of affordability. this is because the cost of the radiant warmer reported in this study was also considerably lower compared to those previously designed and commercialized as our proposed device is specifically targeted for use in low-resource settings. our approach to making the device affordable was based on the use of local source of materials and fabrication compared to other devices which are majorly made up of imported materials. furthermore, over simplicity of some alternatives without a power supply for operation make such options lack flexibility and control and, therefore, may not be useful to the population of infants targeted in the current study. this may pose a significant limitation for such devices’ deployment in rural settings. 4. conclusion the device developed in this study can specifically be used in limited resource settings to promote thermoregulation for needy patients. the device has the potential to improve neonatal care and reduce mortality rate and prevent complications due to hypothermia, especially in limited resource settings where pediatricians and those specialising in neonatology are grossly inadequate. the device has demonstrated a good performance with a good response of the heater within the time range from 10 min to 2 hours of usage. considering the estimated cost of device production of $ 110, the device could be adjudged suitable and affordable for use in limited resource settings. other alternative sources of power may be considered in the future to enable the deployment of this device to villages where constant electricity supply is a challenge. also, additional facilities and optional accessories in the proprietary alternative warmers such as the integration of an oxygen blender and suction module will be incorporated in the future. with this, a preventable cause of infant mortality such as hypothermia could be checked with the affordable technology presented in this study, especially for vulnerable populations. reference ahmed, s., mitra, sn., chowdhury, amr., camacho, ll., winikoff, b. and sloan, nl. 2011. community kangaroo mother care: implementation and potential for neonatal survival and health in very low-income settings. journal of perinatology, 31(5): 361-367. doi: 10.1038/jp.2010.131. almadhoob, a. and ohlsson, a. 2020. sound reduction management in the neonatal intensive care unit for preterm or very low birth weight infants. cochrane database of systematic reviews, (1): cd010333. doi: 10.1002/14651858.cd010333.pub3. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng ibitoye et al: c. azojete, 19(1):163-174. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 173 beletew, b., mengesha, a., wudu, m. and abate, m. 2020. prevalence of neonatal hypothermia and its associated factors in east africa: a systematic review and meta-analysis. bmc pediatrics, 20(148):114. doi: 10.1186/s12887-020-02024-w. bell, ef. 1983. infant incubators and radiant warmers. early human development, 8(3): 351-375. doi: https://doi.org/10.1016/0378-3782(83)90018-x. boundy, eo., dastjerdi, r., spiegelman, d., fawzi, ww., missmer, sa., lieberman, e., kajeepeta, s., wall, s. and chan, gj. 2016. kangaroo mother care and neonatal outcomes: a meta-analysis. pediatrics, 137(1): e20152238. doi: 10.1542/peds.2015-2238 capriolo, c., viscardi, rm., broderick, ka., nassebeh, s., kochan, m., solanki, ns. and leung, jc. 2022. assessment of neonatal intensive care unit sound exposure using a smartphone application. american journal of perinatology, 39(02):189-194. doi: 10.1055/s-0040-1714679. cdc. 2022. what noises cause hearing loss? 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where? why? the lancet, 365(9462): 891-900. doi: https://doi.org/10.1016/s0140-6736(05)71048-5. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng https://doi.org/10.1016/0378-3782(83)90018-x https://www.cdc.gov/nceh/hearing_loss/what_noises_cause_hearing_loss.html https://doi.org/10.1016/j.eclinm.2020.100664 https://www.ebme.co.uk/articles/electrical-safety-testing-in-accordance-with-iec-62353/ground-bond-testing https://www.ebme.co.uk/articles/electrical-safety-testing-in-accordance-with-iec-62353/ground-bond-testing https://doi.org/10.1046/j.1525-1594.2000.06557.x https://doi.org/10.2147/rrn.s52377 https://doi.org/10.1016/s0140-6736(14)60496-7 https://doi.org/10.1016/s0140-6736(14)60496-7 https://doi.org/10.1016/s0140-6736(05)71048-5 arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):163-174. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibitoye.mo@unilorin.edu.ng 174 lunze, k., bloom, de., jamison, dt. and hamer, dh. 2013. the global burden of neonatal hypothermia: systematic review of a major challenge for newborn survival. bmc medicine, 11(1): 24. doi: 10.1186/1741-7015-11-24. maynard, kr., causey, l., kawaza, k., dube, q., lufesi, n., maria oden,z., richards-kortum, rr. and molyneux, em. 2015. new technologies for essential newborn care in under-resourced areas: what is needed and how to deliver it. paediatrics and international child health, 35(3): 192-205. doi: 10.1179/2046905515y.0000000034. mohamed, soo., s. m. i. ahmed, smi., r. j. y. khidir, rjy., m. t. h. a. shaheen, mtha., m. h. m. adam, mhn., b. a. y. ibrahim, bay., e. o. a. elmahdi, eoa. and a. s. m. farah asm . 2021. outcomes of neonatal hypothermia among very low birth weight infants: a meta-analysis. maternal health, neonatology and perinatology, 7(14): 1-9. doi: 10.1186/s40748-021-00134-6. nahimana, e., may, l., gadgil, a., rapp, v., magge, h., kubwimana, m., nshimyiryo, a., kateera, f., feldman, ha., nkikabahizi, f., sayinzoga, f. and hansen, a. 2018. a low cost, re-usable electricityfree infant warmer: evaluation of safety, effectiveness and feasibility. public health action, 8(4): 211217. doi: 10.5588/pha.18.0031. nishiyama, a. 2011. economic growth and infant mortality in developing countries. the european journal of development research, 23(4): 630-647. doi: 10.1057/ejdr.2011.17 organisation of africa unity. 2001. abuja declaration on hiv/aids, tuberculosis and other related infectious diseases, african union, abuja, federal republic of nigeria. thavaraj, v., ramji, s., sastry, o. and sharma, n. 2017. solar powered baby/infant radiant warmer installed in neonatal intensive care unit in a tertiary care hospital. journal of clinical neonatology, 6(1): 15-18. doi: 10.4103/2249-4847.199760. trevisanuto, d., testoni, d. and de almeida, mfb. 2018. maintaining normothermia: why and how? seminars in fetal and neonatal medicine, 23(5): 333-339. https://doi.org/10.1016/j.siny.2018.03.009. unicef. 2018. warmer system,newborn,radiant,w/access, new york, united states. warneford, m. 2018. design and implementation of a neonatal warming blanket with temperature regulation functionality, flinders university, flinders university, australia, weithöner, f. electrical safety testing. http://www.frankshospitalworkshop.com/electronics/training_course_electrical_safety_testing.html (accessed 11/11/2022 2022). whiteside, d. 1978. proper use of radiant warmers. the american journal of nursing, 78(10): 1694–1996. who. 1997. thermal protection of the newborn : a practical guide. p 68. who. world health organization. 1997. thermal protection of the newborn: a practical guide, world health organization, geneva. world health organization. 2016. care of the preterm and/or low-birth-weight newborn. geveva: world health organization zion, j. 2022. electrical safety: standards and basic testing. https://www.flukebiomedical.com/blog/electrical-safety-standards-basic-testing fluke, us (accessed 11/11/2022 2022). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/ibitoye.mo@unilorin.edu.ng https://doi.org/10.1016/j.siny.2018.03.009 https://www.flukebiomedical.com/blog/electrical-safety-standards-basic-testing arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):403-416 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 403 generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria c. c. emeka-chris department of agricultural and bioresources engineering, michael okpara university of agriculture, umudike, nigeria *corresponding author's email address: cemekachris1@gmail.com article information submitted 8 may, 2024 revised 27 may, 2024 accepted 30 may, 2024 keywords: rainfall intensity duration frequency model gumbel distribution abstract inadequate meteorological data poses a significant challenge for engineers in accurately designing, operating, and planning water resources, particularly against extreme rainfall events. this study focuses on generating intensity duration frequency (idf) models for port harcourt city in south nigeria. daily rainfall data spanning thirty-two years (1983-2014) were collected from the nigeria meteorological agency (nimet) oshodi, lagos state. the annual maximum series method was employed to select datasets for rainfall analysis. two statistical distributions, gumbel and log pearson type iii, were utilized to calculate observed rainfall intensity values at durations of 10, 15, 20, 30, 60, 120, 180, 240, 300, and 360 minutes, considering return periods of 2, 5, 10, 20, 50, and 100 years. non-linear regression analysis using microsoft excel's optimization technique solver wizard was performed to derive parameters for the idf models for each duration and return period. metrics such as chi-square (χ2), coefficient of determination (r2), and root mean square error (rmse) were analyzed in order to assess the performance of the models. for the gumbel distribution, r2 values ranged from 0.76 to 1.00, with rmse from 0.20 to 11.73. the log pearson type iii distribution showed perfect r2of 1 and rmse ranging from 0.23 to 9.68, indicating superior performance in terms of r2 and rmse. while there were no significant differences among the predicted intensities of various idf models, the log pearson type iii model is recommended for predicting rainfall intensities in port harcourt due to its superior performance metrics. these idf models serve as valuable tools for engineers and hydrologists in estimating stormwater runoff, designing drainage systems, managing reservoirs, and planning water resources development to mitigate flooding and its impacts. moreover, they can enhance the teaching of land drainage courses for engineering students, providing practical demonstrations and improving their understanding of the subject matter. 1.0 introduction precipitation is an important component in the hydrologic cycle. brian et al. (2006) posited that rainfall frequency analyses are desirable in the development plus designing of different water resources schemes, this includes storm sewers, culverts, and other hydraulic structures. a lifethreatening precipitation happening endangers the quality of water, annihilation of assets, loss of lives due to flooding and pollution (brian et al., 2006). according to panel et al. (2016) the valuation of dangerous precipitation is a vital issue in hydrologic risk investigation and design. additionally, they noted that the assessment of rainfall excesses as embodied in the intensity duration-frequency (idf) relationship has been the main objective of applied and theoretical hydrology. similarly, elsebaie (2012) noted that rainfall intensity-duration-frequency curves are http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 404 graphical demonstrations of the quantity of rainwater that falls within a specified period of time in catchment areas. prodanovic and simonovic, (2007) suggested, that to design flood protection structures involving hydrologic flows, rainfall events statistics (that is, in relations to intensity, duration, and period of return) are required. additionally, elsebaie (2012) noted that, graphically the measure of precipitation that falls within a catchment range in a specified period of time are denoted by rainfall – intensity duration-frequency (idf) curves. he added that, idf curves are an important tool for the engineers when designing urban drainage works. according to (koutsoyiannis, 2003) the idf relationship is a mathematical connection between the precipitation intensity i, the duration d, and the return period t. in addition, al-dokhayel (1986) accomplished a research on the estimation of rainfall depth duration frequency (ddf) relationships intended for qasim region in kingdom of saudi arabia (ksa) on different return periods, by the use of two continuous probability distributions, namely, gumbel distribution and log pearson type iii (lpt iii) distributions. he found that, between the two distributions under study, the lpt iii distribution technique provided greater precipitation estimations with lesser standard errors. similarly, david et al. (2019) noted that the institution of idf relationships commenced in the nineteen thirties, subsequently many sets of connections have been lumped together globally. consequently, elsebaie (2012) posited that the establishment of the idf was formally on the basis of frequency investigation of precipitation at a particular station observed throughout a long period, normally the annual maximum of the series (ams) or adequately high values greater than threshold. according to akpan and okoro (2013), nwaogazie and duru (2002) and nwoke and okoro (2012) developed rainfall intensity frequency models based on statistical method of least squares. in nigeria, current studies on rainfall idf development have been done in southern nigeria, with little information made available about rainfall intensities in particular for short durations. the insufficient accessible idf curves for selected parts of the country are very costly and plotting of the curves was done manually. hence, this method of developing idf curves manually is prone to error. the broad objective of this research was to generate intensity duration – frequency (idf) curves and models for estimating the precipitation intensities for port harcourt city, using two statistical methods, that is gumbel distribution and log pearson type 111 distribution. 2. materials and method 2.1 description of the study area the area studied is port harcourt city. the city is the capital and largest city of rivers state, in nigeria. it is the fifth most populous city in nigeria after lagos, kano, ibadan and benin (statista, 2021 and world population review.com, 2021). it lies along the bonny river and is located in the oil rich niger delta at latitude 04o451to 04o 601n and longitude 06o 501e to 08o 0107oe (figure 1). it is located 64 kilometres from the atlantic ocean and situated 15.0 metres above sea level. port harcourt experiences rainy season from march to october and receives 2293.6mm of rainfall per year (abah et al., 2019). only the months of november to february truly qualify as dry season months in the city and the so-called dry season are not free from occasional rainfall. port harcourt has three hydrovegetation zones such as beach ridge, salt water and fresh water. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com emeka-chris: generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria. azojete, 20(2):403-416. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 405 figure 1: map of port harcourt city local government area and its environs source: abah et al. (2019) 2.2 data collection the required data in this research are the precipitation depths for smaller durations namely, 5, 10, 15, 20, 30, 60, 120, 180, 240, 300 and 360 minutes. precipitation data were collected from nigeria meteorological agency lagos, nigeria. thirty-two years span of records was used for the studied location between 1983-2014. 2.3 development of idf curves two common frequency analysis techniques were used in the development of the relationship between rainfall intensity, storm duration, and return periods from rainfall data for the region under study. these techniques are the gumbel distribution and the lpt iii distribution. 2.3.1 gumbel theory of distribution gumbel assumption methodology was adopted to perform the flood probability studies. in addition, elsebaie (2012) noted that this is because the method of the analysis is widely accepted for idf analysis owing to its appropriateness for modeling maxima. the gumbel methodology determines the 2, 5, 10, 25, 50 and 100 year return intervals for each duration period and hence requires several calculations. the frequency precipitation for duration with a definite return period is expressed by the following formula pt = pave + ks (1) where, k =gumbel frequency factor given by: k = √6 π [0.5772 + 𝐼𝑛[𝐼𝑛 [ 𝑇 𝑇−1 (8)]]] (2) where, pave = the average of the maximum precipitation corresponding to a specific duration. in utilizing gumbel’s distribution, the arithmetic average (pave) in equation (3) was used: pave = 1 𝑛 ∑ pn i=1 i (3) where, pi = the individual extreme value of rainfall and n is the number of events or years of record. the standard deviation, s of p data was calculated using equation (4) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 406 s = [ 1 𝑛−1 ∑ (𝑃𝑖 − 𝑃𝑎𝑣𝑒𝑛 𝑖=1 )22 1 ] (4) the frequency factor (k), which is a function of the return period and sample size, was multiplied by the standard deviation to give the departure of a desired return period rainfall from the average. then the rainfall intensities, i (mm/h) for return period t were obtained from: it = 𝑃𝑇 𝑇𝑑 (5) where, td is duration in hours, pt is frequency precipitation values and it is intensities for different durations. from the raw data, the maximum precipitation (p) and the statistical variables (average and standard deviation) for each of the duration 0.25hr, 0.5hr, 1hr, 2hr, 4hr, and 6hr) were computed. 2.3.2 log pearson type iii the log pearson type iii probability model was utilized in the calculation of the precipitation intensity at different precipitation durations and return periods to form the historic idf curves for the designated localities. logarithmically transformed data was used in determination of the mean and the standard deviation. the simplified expression for this latter distribution is given as: p* = log (pi) (6) p*t = p*ave + kt s (7) p*ave = 1 𝑛 ∑ 𝑃 ∗𝑛 𝑖=1 (8) s* = [ 1 𝑛−1 ∑ (p ∗ − 𝑛 𝑖=1 p*ave)21/2 ] (9) where, p*t is frequency precipitation and p*ave is the average of the maximum precipitation corresponding to a specific duration based on the logarithmically transformed pi values; i.e. p* of equation (6). kt is the pearson frequency factor which depends on return period (t) and skewness coefficient (cs). the skewness coefficient (cs) is required to compute the frequency factor for this distribution. the skewness coefficients were computed using equation (1) as suggested by (burke and burke, 2008). 𝐶𝑠 = 𝑛 ∑ (𝑃∗𝑖−𝑃𝑎𝑣𝑒 𝑛𝑖 𝑖 )³ (𝑛−1)(𝑛−2)(𝑆∗)³ (10) the computed frequency precipitation p*t values and intensities (it) for six different durations and six return periods using lpt iii methodology. 2.4 intensity-duration –frequency (idf) model development the intensity-duration-frequency (idf) formulae are the empirical equations demonstrating a correlation between the variables. several commonly used idf equations relating the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com emeka-chris: generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria. azojete, 20(2):403-416. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 407 rainfall intensities, the frequencies, and durations are available in literature (burke and burke, 2008; nhat et al., 2006 and mohammad, 2016). the commonly used idf equations is sherman equation, which is given as: i = 𝑎𝑇𝑏 (𝑡+𝑑)𝑐 (11) where, i = intensity of rainfall in mm/hr; t = duration of rainfall in minutes; t = return period of rainfall in years; a, b, c, and d, are the regional idf parameters to be determined. equation (11) which is the most general form of idf equation has been used to develop the idf equations by optimization method. 2.4.1 application of excel solver optimization technique to estimate idf parameters the excel solver methods are mainly the generalized reduced gradient (grg solver) for optimization of nonlinear equations and the linear programming solver (lp solver) for linear equations. due to the fact that idf equations are nonlinear, the grg solver was used in this work to get the optimum of the parameters for the models. 2.4.2 calibration of the sherman (1932) model sherman (1932) model as given in equation (14) was calibrated using grg solver optimization method to obtain optimum values for the regional parameters namely a, b, c, and d for the models. thus, the objective function becomes: min sse = ∑ (iobs −iest)2n i=1 (12) where, iobs is observed intensity corresponding to any duration and iest is estimated intensity corresponding to any duration. solving equation (12) produces the optimum values for the parameters a, b, c, and d achieved through an iterative process that produces the least squared error. 2.5 model performance analysis the performance of the intensity duration frequency (idf) models given by gumbel distribution and log pearson type 111 distribution (lpt 111) were evaluated by obtaining empirical data from the models and then goodness of fit test, correlation coefficient, and root mean square error (rmse) analysis were carried out. to determine the best-fit distribution, the observed distributions were fitted to the theoretical distribution by comparing the frequencies observed in the data to the expected frequencies of the theoretical distribution. a goodness-of-fit test between observed and expected frequencies is based on the chi-square quantity, which is expressed as: χ2 = σk i= (𝑂𝑖−𝐸𝑖)2 𝐸𝑖 (13) where, χ2 = random variable whose sampling distribution is approximated very closely by the chisquare distribution. oi and ei = observed and expected frequencies for the ith class interval in the histogram. k = the number of class intervals. mohammad (2016) provided programmable formulae to obtain the coefficient of http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 408 determination (r2 ) and root mean square error (rmse) as follows: r2 = ∑ (𝐼𝑜𝑏𝑠−𝐼𝑎𝑣𝑔)2−∑ (𝐼𝑜𝑏𝑠−𝐼𝑝𝑟𝑒𝑑)2𝑛 𝑖=1 𝑛 𝑖=1 ∑ (𝐼𝑜𝑏𝑠−𝐼𝑎𝑣𝑔)2𝑛 𝑖=1 (14) rmse = √ 1 𝑁 ∑ (𝐼𝑖 − 𝐼∗)2𝑁 𝑖=1 (15) the theoretical description of correlation coefficient (cc) is as given in equation (16) cc = ∑ ( (𝐼𝑜𝑏𝑠−𝐼𝑎𝑣𝑔𝑜𝑏𝑠)( 𝐼𝑝𝑟𝑒𝑑− 𝐼𝑎𝑣𝑔𝑝𝑟𝑒𝑑 ) √∑ (𝐼𝑜𝑏𝑠−𝐼𝑎𝑣𝑔 𝑜𝑏𝑠) 2 +𝑁 𝑖=1 ∑ (𝐼𝑝𝑟𝑒𝑑−𝐼𝑎𝑣𝑔 𝑝𝑟𝑒𝑑) 2𝑁 𝑖=1 𝑁 𝑖=1 (16) where, iobs is the observed precipitation intensity of ith event, ipred is the predicted precipitation intensity of the ith event, iavg obs is the average observed precipitation intensity and iavg pred is the average of predicted precipitation intensity. 3. results and discussion 3.1 intensity duration frequency idf curves by gumbel and log pearson type (lpt) 111 methods for port harcourt. the results of the intensity durationfrequency curves by gumbel and log pearson type methods for port harcourt city are shown in figures 2 and 3, respectively. figure 2: idf curves by gumbel method at port-harcourt figure 3.1b: idf curves by lpt iii method at port-harcourt 1 10 100 1000 1 10 100 1000 in te n si ty ( m m /h r) duration (min) 2-years 5-years 10-years 25-years 50-years 100-years 1 10 100 1000 1 10 100 1000 in te n si ty ( m m /h r) duration (min) 2-years 5-years 10-years 25-years 50-years 100-years file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com emeka-chris: generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria. azojete, 20(2):403-416. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 409 figures 2 and 3 show results of the idf curves obtained by gumbel and lpt 111 methods for the region. according to the idf curves rainfall estimates are increasing with increase in the return period and the rainfall intensities decrease with rainfall durations in all return periods. the trends of the results from the two methods have good consistency. the idf curves proved the basic principle in hydrology that high intensity rainfalls had shorter durations. it also showed that rainfall intensities increase with return periods. this is in line with findings of similar research carried out by ogbozige (2021), mohammed et al. (2021), majeed et al. (2021), agarwal et al. (2021), al-wagdany (2020) and gratein et al. (2019). 3.2 rainfall intensity duration frequency models and their parameter values the parameter values used in deriving the gumbel and log pearson type iii models, including the models for port harcourt region is shown in table 1. table 1: parameters values used in deriving models for rainfall intensity at port harcourt city. s/no. location distribution parameters models a b c d 1. port harcourt gumbel 135 1.72 0.83 46.35 𝐼 = 135𝑇𝑟 1.72 (𝑡 + 46.35)0.83 log pearson type iii 140 1.23 0.73 30.33 𝐼 = 140𝑇𝑟 1.23 (𝑡 + 30.33)0.73 the gumbel and log pearson type 111 models, including the parameter values used in deriving the models for the region studied are shown in table 1. the parameter values used in deriving the models are a, b, c and d. parameters b (1.72), c (0.83), and d (46.35) values using gumbel distribution are higher than values obtained using log pearson type 111 method for port harcourt region. 3.3 model performance/validation for port harcourt idf models the results of the computed indicators of goodness of fit between gumbel and log pearson type iii models, namely chi square (χ2), root mean square error (rmse), correlation coefficient (r) and coefficient of determination (r2) are given in tables 2a and 3, respectively. tables 2 and 3 show the model performance / validation of idf model obtained for port harcourt region using gumbel and log pearson type iii distributions respectively. table 2: model performance/ validation for port harcourt idf model obtained by gumbel method duration (min) location distribution model validation 10 15 20 30 60 120 180 240 300 360 port-harcourt gumbel χ2 0.98 2.69 0.96 7.49 4.10 1.05 0.27 0.25 0.01 0.50 rmse 4.68 7.59 4.28 11.73 7.82 3.00 1.34 1.20 0.20 1.43 r 1.00 1.00 1.00 0.99 0.87 0.98 0.99 1.00 1.00 1.00 r2 1.00 1.00 1.00 0.98 0.76 0.97 0.99 1.00 1.00 1.00 pvalue 0.96 0.75 0.97 0.19 0.54 0.96 1.00 1.00 1.00 0.99 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 410 table 3: model performance/validation for port harcourt idf model obtained by log pearson type 111 method tables 2 and 3 show the model performance / validation of idf model obtained for port harcourt region using gumbel and log pearson type 111 distributions respectively. goodness of fit tests was used to choose the best statistical distribution among those techniques. as can be seen in tables 2 and 3, most of the data fit both gumbel and log pearson type 111 distributions at 5% level of significance. however, the data at 30minutes and 60minutes durations do not give good fit using gumbel distribution for port harcourt region. also, the data for 15 minutes and 30 minutes durations do not give good fit using log pearson type 111 distribution for port harcourt. the correlation coefficient (r) and coefficient of determination (r2) obtained from the fitted idf models adopting gumbel distribution are high and ranged from 0.97 to 1.00 except at 60 minutes duration with r as 0.87 and r2 as 0.76, respectively. however, the correlation coefficient and coefficient of determination obtained from the fitted idf model adopting log pearson type 111 distribution have perfect value of 1. the values of root mean square errors (rmse) obtained are lower for durations from 30minutes to 360 minutes using log pearson type 111, except for durations of 300minutes when compared to gumbel distribution. the results show the goodness of fit of the formulae to estimate the rainfall intensities of the region of study, especially for higher durations and frequencies of 2 to 100 years. 3.4 comparison of observed and predicted rainfall intensities the results of the predicted rainfall intensities for different durations and return periods are shown in table 4 and 5. also some selected index values of predicted intensities for comparison of short, medium and higher durations are shown in table 6. location distribution model validation duration (min) 10 15 20 30 60 120 180 240 300 360 port-harcourt log pearson type iii χ2 2.60 4.29 2.23 4.17 0.42 0.39 0.03 0.10 0.01 0.10 rmse 7.86 9.68 6.70 8.58 2.35 1.86 0.45 0.78 0.23 0.67 r 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 r2 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 p-value 0.76 0.51 0.82 0.52 0.99 1.00 1.00 1.00 1.00 1.00 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com emeka-chris: generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria. azojete, 20(2):403-416. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 411 table 4: predicted intensity-duration frequencies for different return periods by gumbel method at port-harcourt return period (years) 2 5 10 25 50 100 duration (min) observed predicted observed predicted observed predicted observed predicted observed predicted observed predicted 10 86.382 83.96554981 110.701 106.8743 126.84 122.0707 147.192 141.1825201 162.282 155.5011 177.294 174.8547 15 74.664 78.78027513 94.128 99.97962 107.044 114.0438 123.328 131.7165551 135.408 144.9406 147.42 156.6058 20 71.565 74.22266278 90.215 93.96795 102.591 107.0701 118.02 123.5249021 129.774 135.8244 141.282 142.618 30 72.624 66.57923988 91.556 83.98306 104.12 95.53717 119.964 110.0404577 131.712 120.8618 143.398 122.3677 60 50.865 51.07672082 64.083 64.07358 72.856 72.71203 83.919 83.56395718 92.122 91.6294 70.341 89.48134 120 32.678 35.17853278 41.195 44.05725 46.847 49.96015 53.975 57.40454873 59.26 62.90963 64.517 62.30258 180 25.935 27.01030311 32.693 33.89063 37.178 38.46038 42.833 44.24513759 47.027 48.50819 51.199 49.64461 240 22.938 22.00838133 28.616 27.689 32.384 31.45697 37.136 36.24202741 40.659 39.75916 44.164 42.05611 300 18.895 18.61875859 23.734 23.49087 26.945 26.71826 30.995 30.82797277 33.998 33.84244 36.985 36.90138 360 17.29 16.16426144 21.795 20.45039 24.784 23.28608 28.555 26.90547973 31.35 29.55577 34.131 33.12582 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 412 table 5: predicted intensity-duration frequencies for different return periods by lpt iii method at port-harcourt return period (years) 2 5 10 25 50 100 duration (min) observed predicted observed predicted observed predicted observed predicted observed predicted observed predicted 10 93.82 88.7856 118.928 112.5219 135.293 128.0203 156.419 148.055 171.905 162.92524 187.623 177.5798 15 75.344 81.5423 95.512 103.3653 108.656 117.5917 125.62 135.944 138.052 149.13244 150.68 163.0634 20 71.213 75.5563 90.273 95.78784 102.697 108.9643 118.73 125.936 130.483 137.84965 142.414 151.0655 30 71.784 66.2023 90.998 83.93016 103.522 95.46815 119.682 110.3 129.428 120.41026 143.558 132.3153 60 50.816 49.3025 64.269 62.46537 73.114 71.04943 84.333 82.0608 92.683 89.409988 101.158 98.44184 120 32.657 33.9709 41.397 42.96677 47.095 48.8773 54.447 56.4645 59.837 61.708828 65.309 67.7292 180 26.175 26.568 33.18 33.55299 37.747 38.17439 43.639 44.1175 47.96 48.416597 52.345 52.9129 240 21.525 22.1083 27.286 27.88576 31.041 31.73105 35.887 36.6852 39.44 40.416534 43.047 43.99422 300 19.321 19.0897 23.935 24.05273 27.229 27.37287 31.48 31.6576 34.596 34.998441 37.76 37.96152 360 17.252 16.893 21.87 21.26524 24.88 24.20328 28.764 28.0007 31.612 31.050985 34.502 33.57369 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com emeka-chris: generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria. azojete, 20(2):403-416. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 413 the rainfall intensity of any duration and return period is predicted by the aid of the developed idf models. the factors that enhance the distribution of the observed and predicted rainfall intensities are duration and return period. observed and predicted rainfall intensities were compared as way of verification of the developed models. for the studied location in tables 4 and 5, it was noted that rainfall intensity decreases with increasing durations and for a given duration the higher return period yielded corresponding higher intensity values. from table 5, the highest predicted intensity values were given by log pearson type 111. table 6: comparison of selected index values of predicted intensities (mm/hr) for short, medium and higher durations method station 10min duration 60min duration 300 min duration 100-year return period 100-year return period 100-year return period gumbel log pearson type 111 port harcourt port harcourt 174.85 177.58 89.48 98.44 36.9 37.96 table 6 shows the comparative predicted intensities by gumbel and log pearson type111 models for short, medium and higher durations. in table 4 at 10 minutes duration and 100year return period, the predicted intensities by gumbel model was 174.85mm/hr. the predicted intensities at the same 10minutes duration and 100-year return period by log pearson type 111 was 177.58mm/hr. also, for 60minutes duration and 100-year return period, the predicted intensities by gumbel was 89.48mm/hr. while at the same 60minutes duration and 100-year return period, the predicted intensities by log pearson type 111 was 98.44mm/hr. finally, at 300minutes duration and 100 years return period, the predicted intensities by gumbel was 36.90mm/hr. while at the same 300minutes duration and 100-year return period, the predicted intensities by log pearson type 111 was 37.96mm/hr. the predicted intensities values given in tables 3.4 establishes the consistent superiority of log pearson type 111 model over gumbel model in predicting higher intensity values at short, medium and higher durations in the studied location. this observation was also established in the works for port harcourt, ikeja and lahore city idf models by nwaogazie et al. (2019); david and nwaogazie (2020) and ahmed and ali (2016) respectively. 3.5: comparison of idf curves obtained with published idf curves the comparison of idf curves obtained with published idf curves by mbajiorgu and okonkwo (2010) is shown in table 7. table 7: comparison of mbajiorgu and okonkwo (2010) estimated intensities with intensities predicted by gumbel distribution. method station 10-yr 15min 2-yr, 30mins 5-yr, 1hr 25-yr, 1hr 100yr,6hr mbajiorgu and okonkwo port harcourt 122.4 71.6 62.8 82.5 34.4 gumbel distribution port harcourt 114.0 66.6 64.1 83.6 33.1 mbajiorgu and okonkwo (2010) used the gumbel method to develop idf curves for some selected locations in nigeria. port harcourt is common to his work, so comparison was made using results of predicted intensities developed by gumbel distribution models for port harcourt. table 7 shows the intensities estimated by mbajiorgu and okonkwo (2010) using gumbel method and predicted intensities from this work by gumbel distribution model. from the table, the intensities predicted by gumbel distribution models for the selected location of study are lower than those of mbajiorgu and okonkwo (2010) at both shorter and higher rainfall durations. this could be as a result of differences in number of years of records of data http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 414 collected. mbajiorgu and okonkwo (2010) did not exactly specify the number of years of rainfall data used; rather the work stated that the length of available records used varies from 22 to 30 years. in this study, 33 years of daily rainfall data was used. also, according to david and nwaogazie (2020)) at times values of rainfall recorded at some stations may be incorrectly observed. however, the differences are not statistically significant at 5% level of significance. it was also noted that for a given return period, intensities decrease as duration increases. this is in line with what mbajiorgu and okonkwo (2010) obtained as shown in table 7. storms of 10-years return period and 15minutes duration gave the highest intensities than storms of 100years return period and 6 hours duration. therefore, models developed by gumbel and log pearson type 111 distributions are in agreement with probability distribution function (pdf) theory which shows higher intensities occurring at shorter duration and lower intensities at longer duration. 4. conclusion this work shows the procedure for the development of rainfall intensity duration frequency models for port harcourt in south -south nigeria. in this study, idf models were developed for studied location. these models are guides for estimating the rainfall intensities for any specific return period at different durations. the highest intensity occurs at return periods of 100 years with durations of 10minutes (0.15hr), while the lowest intensity occurs at return period of 2 years with durations of 360minutes (6.0hr). 5. engineering implications of findings the idf models developed will serve as tools for the engineers and hydrologists in estimating storm water runoff from a watershed for the design of drainage systems, reservoir management and planning of water resources development. this will mitigate flooding and its consequences. also, the findings when applied as demonstration tools in teaching land drainage courses to engineering students, will enhance their understanding and appreciation of the course. references abah, ae., woken, gn. and sounyo, ii. 2019. fasciola infection in goats slaughtered from port harcourt metropolis rivers state, nigeria. international journal of health, 5(11): 76-80 doi:10.14202/ijoh.2019.76-80. www.onehealthjournal.org/vol.5/11.pdf agarwal, s., kumar, s. and singh, u. k. 2021: intensity duration frequency curve generation using historical and futre downscaled rainfall data. indian journal of ecology, 48(1): 275-280 akpan, su. and okoro, bc. 2013.developing rainfall intensityduration-frequency models for calabar city, south-south nigeria. american journal of engineering (ajer), 2(6): 19-24. al-dokhayel, aa. 1986. regional rainfall frequency analysis for qasim, b. sc. project, civil engineering department, king saud university, riaydh. al-wagdany, as. 2020.intensity duration frequency curve derivation for different rain guage records. journal of king saud university science, 32: 34213431 ahmed, r. and ali, s. 2016. modelling of intensity-duration-frequency curves for lahore city using frequency analysis. wit transactions on ecology and the environment, 210:725-733. brian, h., zelinka, c., castello, c. and curtis, d. 2006. spatial analysis of storms using gis. onerain inc., 9267 greenback lane, orangevale, p. 1. burke, cb. and burke, tt. 2008. storm drainage manual. indiana ltap. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com emeka-chris: generation of rainfall intensity-duration frequency models for port harcourt city in southsouth ngeria. azojete, 20(2):403-416. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 415 david, ao., nwaogazie, il. and agunwamba, jc. 2019. modelling rainfall intensity by optimization technique in abeokuta, south-west, nigeria. journal of engineering and report, 6(4): 1-10 david, ao. and nwaogazie, il. 2020. optimization technique in rainfallintensity duration –frequency modelling for ikeja, south-west, nigeria. nigerian journal of technology (nijotech), 39(4):1276-1285 david, ao., nwaogazie, il., opafola, ot., babalola, aa. and lawal, ns. 2019. rainfall intensityduration-frequency models for ibadan using optimization technique. uniosun journal of engineering and environmental sciences, 2(2): 47-52. doi:10.36108/ujees/0202.20.0270 elsebaie, ih. 2012: developing rainfall intensity frequency relationship for two regions in saudi arabia. journal of king saudi universityengineering sciences, 24: 131-140 gratein, t., kundwa, mj., bakunzibake, p., bunani, p. and habyarimana, jl. 2019. development of rainfall intensity duration frequency (idf) curves for hydraulic design aspects. journal of ecology and natural resources, 3(2): 1-14. koutsoyiannis, d. 2003. on the appropriateness of the gumbel distribution for modeling extreme rainfall, in: proceedings of the esf lesc exploratory workshop, hydrological risk: recent forecasting, assessment of the impacts of landuse and climate changes. european science foundation, national research council of italy, university of bologna, bologna. mbajiorgu, cc. and okonkwo, gi. 2010. rainfall intensity – duration – frequency analyses for south eastern nigeria. agricultural engineering international: the cigr journal, 12(1): 22-30. majeed, ar., nile, bk. and albaidhani, jh. 2021. selection of suitable precipitation duration frequency (pdf) model and build of intensity duration frequency (idf) curves for rainfall in najaf city, iraq. journal of physics conference series, 1973(1): 012184., doi:10.1088/17426596/1973/012184 mohammad, z. 2016. application of optimization techniques to estimate intensity duration frequency (idf). water and energy international, pp. 63-72. www.indianjournals.com mohammed, a., azumi, sd., modibbo, aa. and adami, aa. 2021. development of rainfall intensity duration frequency (idf) curves for design of hydraulic structures in kano state, nigeria. platform, a. journal of engineering, 5(2): 10-22. nhat, lm., tachikawa, y. and takara, k. 2006. establishment of intensityduration-frequency curves for precipitation in the monsoon area of vietnam. annals of disaster prevention research institute, kyoto university, kyoto, japan., no 49 b. nwaogazie, il. and duru, o. 2002. developing rainfallintensity-duration-frequency models for port harcourt city. nigerian society of engineers technical transaction, 37(2): 19-32. nwaogazie, il., masi, gs., ricardo, ze. and edward, g. 2019. probability and non-probability rainfall intensity-duration-frequency modeling for port harcourt metropolis, nigeria. international journal of hydrology, 3(1): 66-75. nwoke, hu. and okoro, bc. 2012. rainfall intensityfrequency regime for warri, southsouth nigeria. journal of new clues in sciences, 2: 42-49. ogbozige. fj. 2021. development of intensity –duration –frequency (idf) models http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com http://www.indianjournals.com/ arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):403-416. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cemekachris1@gmail.com 416 for manually operated rain guage catchment: a case study of port harcourt metropolis using 50 years rainfall data. tanzanian journal of engineering and technology, 40(2): 33-44. prodanovic, p. and simonovic, sp. 2007. development of rainfall intensity duration frequency curves for the city of london under the changing climate. water resources report, london. sherman, cw. 1932. frequency and intensity of excessive rainfall at boston, massachusetts. transactions, asce, 95: 951-960. statistica. 2021. port harcourt, location, facts and population. retrieved 4th march, 2024. worldpopulationreview.com 2021. population of cities in nigeria (2021). retrieved 20th february 2024. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):523-534 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 523 design, construction and performance evaluation of a mucuna bean seed cracker p. j. etim department of agricultural engineering, akwa ibom state university, ikot akpaden, akwa ibom state, nigeria *corresponding author's email address: promiseetim@aksu.edu.ng article information submitted 26 december, 2023 revised 4 march, 2024 accepted 10 march, 2024 keywords: mucuna bean seed moisture content seed cracking cracking machine cracking efficiency abstract a cracking machine was developed for mucuna bean seed. design considerations and calculations were made using relevant equations and data from some engineering properties of the seed. a 2 hp electric motor running at a speed of 1400 rpm was used to transmit power to the gear mechanism. the cracker was fabricated using locally available materials to promote the possibility of replacing damaged parts. the performance of the machine was evaluated at various moisture levels since traditional post-harvest processing of the seed is moisturedependent. the feed rate of the machine decreased as the moisture level increased. a significant decrease of 17.31 % was observed across the various moisture levels tested as the feed rate of the machine decreased from 8.01 to 6.59 kg/hr. at a moisture content level of 5.31 % (dry basis), the throughput capacity of the machine was obtained as 12.02 kg/hr, while between 9.14 to 11.52 % moisture content, it decreased by 3.5 %. the efficiency of cracking of the seed increased from 56.6 to 66.1 % as moisture content increased from 5.31 to 18.38 % (dry basis). the percentage of seed breakage also increased with moisture level. the seeds were observed to crack more efficiently when moisture was reduced. an average of 500 seeds were cracked within an hour, as against a minimum of 48 hours that would have been spent if the seeds were to be soaked in water before manual cracking. 1.0 introduction mucuna bean seed is a tropical tree crop widely available in africa and asia. it is harvested and consumed as food and used in the production of traditional medicine for treatment of kidneyrelated diseases, blood purification, expulsion of excessive gases, expelling of worms, menstrual cycle balance and blood pressure stabilization. the seed is harvested, processed, and utilized as a soap thickener, taste modifier and spice for confectionaries. after harvesting, the seeds are usually soaked in warm water for a period of two to four days, for effective moisture penetration and softening, before they can be manually cracked and utilized. the cumbersome process of traditionally processing the seed has resulted in increased loss of interest in processing and use of the oil seed, despite its huge nutritional and medical prospects. a machine for cracking the seed was considered for development based on values of some engineering properties of the seed obtained and established machine design equations (alonge and etim, 2017). the machine was designed to evaluate the efficiency of cracking the seed in variation to moisture content since moisture plays a vital role in the traditional method of cracking the seed. agricultural products can either be cracked in wet or dry form, depending on specific function (antia et al., 2014). mahmoud and elkaoud (2019) also highlighted the relevance of engineering properties of agricultural products in the design of processing machines. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):523-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 524 many authors have developed machines for cracking of different products such as dika nut (owolarafe et al., 2013), palm nut (ibikunle et al., 2018) and basreng (ripitani et al., 2022) etc. a decorticating machine for delonix regia was developed to advance the course for research into the huge nutritional and medicinal benefits of the seed (ojolo et al., 2019). preliminary studies revealed that the force required to break the pod was 1360 n. the power rating was 6 kw, and the seed recovery efficiency was 98.4 %, while the throughput capacity was obtained as 56.4 kg/hr. an almond kernel extraction machine was designed, and a compression test machine was used to determine the force required to crack the seed (marey et al., 2017). the compressive force measured, was instrumental to the design of the cracker as it gave the maximum permissible load. oduma et al. (2016) designed a hand-fed motorized machine for slicing oil beans. some of the factors considered were the physical and mechanical properties of the seed; mechanical properties of the construction materials; machinability of construction materials, availability of materials and cost. a shelling machine was developed for groundnut (alonge et al., 2016; alonge et al., 2017). the incorporation of a separation unit into the system increased the efficiency of the machine. hussain et al. (2018) developed a cracking machine for walnuts. relevant equations were used to design the frame, hopper, shaft, belt length, safe stress of the belt, and power required by the machine for operation. a cracking machine for cashew nuts was developed (ojolo and ogunsina, 2007). the percentage of whole kernels produced and the capacity of the machine were estimated as 66.60 % and 18.3 kg/hr respectively. a shelling machine was designed and developed for cashew nuts (ojolo et al., 2009). the throughput capacity, shelling efficiency and whole kernel recovery were obtained as 15.57 kg/hr, 95 % and 70 % respectively. a review of shelling, threshing, dehulling and decortication machines for agricultural products was done to highlight new frontiers in the development of processing machines (aremu and fadele, 2018). a thevetia nutcracker was developed and the optimum cracking efficiency and throughput capacity were evaluated as 96.65 % and 8.5 kg/hr (odewole and ajibade, 2015). sharifian et al. (2008) developed a walnut cracking machine based on some information from the mechanical properties of the fruit. the maximum cracking force and power required were 797 n and 1.99 watts respectively. in designing the cracker, they reported that the cracking efficiency of the machine is a function of the moisture content of the nut. a similar trend was reported for a palm kernel briquetting machine (onyenwoke and simonyan, 2013). properties influencing the cracking and separation of palm nuts were studied (olaoye and adekande, 2018). moisture content had a significant effect on the performance of the machine. a dual-purpose palm nutcracker was developed and tested for performance at various moisture levels (bamboye and sadiku, 2003). the machine gave output capacities of 90.4 kg/hr for motorized and 19.8 kg/hr for the manually operated cracker. ibrahim et al. (2016) in examining the performance of a shea nut sheller observed that the feed rate of the machine reportedly varied with the moisture content. this agrees with the assertion by some authors that the moisture content of the product affects the performance of machines meant for processing (aremu et al., 2015; sanusi et al., 2019; busari et al., 2019; ndukwu et al., 2019). khairy et al. (2015) highlighted the need to have fair knowledge of the moisture content of an agricultural product before designing its processing machine. fadele and aremu (2016) developed a shelling machine for moringa oliefera seed. they reported that as the moisture level of the seed increased from 8.43 to 34.59 % (wet basis), the maximum machine capacity and efficiency of shelling and overall efficiency were obtained as 5.39 kg/hr, 86% and 57.98 % respectively. the selection of materials for construction for most of the machines was based on durability, suitability, strength, availability, and cost. the development file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com etim: design, construction and performance evaluation of a mucuna bean seed cracker. azojete, 20(2):523-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 525 of a suitable technology is key to addressing challenges limiting the efficient post-harvest processing of agricultural products (ritanti et al., 2022). moisture also plays a critical role in the post-harvest processing of the seed since it is usually soaked in warm water for days as shown in figure 1, before it could be manually cracked. this study aimed to put a novel idea into the works by developing a machine for the cracking of mucuna bean seed, evaluating its performance, and investigating the effect of moisture content on the cracking of the seed. figure 1: mucuna bean seed soaked in water for manual cracking 2. materials and methods 2.1 design considerations some physical and mechanical properties of the seed were considered in designing the hopper and discharge chute of the machine. the force required to crack the seed under static load was obtained through a compression test using a universal testing machine (utm – instron 3382, 100 kn floor model) at the central engineering workshop of akwa ibom state university, nigeria. the force required to break the seed on its major and minor axes were 1,500 and 250 n respectively. the cracker was fabricated using locally available materials to promote the possibility of replacing damaged parts with locally available ones in the market. the total cost of producing the machine was one hundred and fifty thousand naira, equivalent of $ 200. 2.2 description of the machine the cracker was made of two rotating drums, sprockets, a belt, a pulley, and a gear mechanism. the gear mechanism served as an intermediary between the power transmission system and the drive mechanism. one of the drums was attached to a shaft and was rotational, while the other was stationary. the rotating drum had splines attached around its surface. fifty per cent of the major diameter of the seed was used as the thickness of each spline. the drums were mounted in such a way that enabled them to rub against each other when rotating. the essence of employing the gear mechanism was to ensure control of the speed of the rotating drum, and to limit impact when the two drums come in contact, thus mitigating against opportunity for increased damage to the seeds. power was transmitted from the electric motor to the gear mechanism by a v-belt arrangement. the transmission between the gear train and the rotating shaft was aided by a chain drive. the main frame was made of mild steel. exploded and orthographic views of the machine are shown in figures 1, 2 and 3. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):523-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 526 figure 1: exploded view of the machine legend: a hopper i gear b rotating drum cover j ankle bar c metal sheet k electric motor d air duct l driving pulley e stationary drum m belt f coupling flange n driven pulley g discharge outlet o driving drum h sprocket p shaft figure 2: side view of the machine (from 1st angle) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com etim: design, construction and performance evaluation of a mucuna bean seed cracker. azojete, 20(2):523-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 527 figure 3: side view of the machine (from 3rd angle) 2.3 design analysis 2.3.1 shaft design torque transmitted by the shaft (t) and the diameter (d) of the drive shaft were obtained using the equations (1) and (2) respectively as developed by khurmi and gupta (2018): 𝑇 = 60𝑃 2𝜋𝑁 (1) 𝑑3 = ( 16𝑇 𝜋𝜏 ) (2) the maximum permissible stress shear stress ( was taken as 42 mpa (mega pascal). the diameter of the shaft (d) was obtained as 15 mm (millimetre) and π = 3.142. 2.3.2 belt design the length of the belt 𝐿 = 𝜋(𝐷1+ 𝐷2) 2 + 2𝑥 + (𝐷1−𝐷2)2 4𝑥 (3) d1 is the diameter of the bigger pulley, given as 80 mm, while d2 is the diameter of the smaller pulley, given as 76 mm, while 𝑥 is the centre distance between the two pulleys (270 mm). the length of the belt was obtained as 786 mm. the angle of contact of the belt and pulley was derived from the equation below (khurmi and gupta, 2018). 𝜃 = (180 − 2𝛼) 𝜋 180 rad (4) where, 𝑆𝑖𝑛𝛼 = 𝑟1−𝑟2 𝑥 (5) the angle was obtained as 3.13 rad. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):523-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 528 tensions on the tight side (t1) and slack side (t2) of the belt t1 were obtained by use of the equation 6 (khurmi and gupta, 2018). 𝑃 = (𝑇1 − 𝑇2)𝑣 (6) 2.3 log( 𝑇1 𝑇2 ) = 𝜇𝜃 (7) where, v = velocity of the belt (m/s), 𝜃 = angle of wrap (°) and n = coefficient of friction between belt and pulley. 2.3.3 chain design the rotation speed of the smaller sprocket (ns) was determined using equation 8: 𝑁𝑏 𝑁𝑠 = 𝐷𝐵 𝐷𝑠 = 𝐺. 𝑅. (8) nb was the rotation speed of the smaller sprocket (1400 rpm) and the gear ratio was taken as 3:1. the rotation speed of the larger sprocket (ns)was obtained as 491.3 rpm. the velocity ratio was obtained as 3. computing the larger sprocket teeth number was done using equation 9: 𝑇2 = 𝑇1 ( 𝑁𝑏 𝑁𝑠 ) = 𝐺. 𝑅. (gear ratio) (9) the number of teeth (t1) for a velocity ratio of 3 for a roller chain was as specified is 25 (khurmi and gupta, 2018). a value of 75 was obtained as the number of teeth of the larger sprocket. the design power (pd) was obtained from the relation below (khurmi and gupta, 2018). 𝑃𝑑 = 𝑅𝑎𝑡𝑒𝑑𝑃𝑜𝑤𝑒𝑟, 𝑃 × 𝑆𝑒𝑟𝑣𝑖𝑐𝑒𝐹𝑎𝑐𝑡𝑜𝑟, 𝐾𝑠 (10) the service factor was computed as the production of various factors (k1, k2 and k3). where k1 was the load factor, taken as 1.25 because the expected load was with mild shock; k2 = lubrication factor, taken as 1, because of routine lubrication of the chain mechanism. k3 = rating factor, taken as 1, because the machine was assumed to be used for a maximum of eight hours per day. ks =k1 x k2 x k3 = 1.25 x 1 x 1 = 1.25 the design power was obtained as 1.87 kw. the choice of the chain was made with reference to the standard table established by the amse code for chain drives. the speed of the bigger sprocket (1400 mm) was constant with a no. 6 chain at 2.73 kw (relatively higher than the design power given as 1.875 kw). thus a no. 6 chain with strands was used to transmit the required power. the pitch of the chain, p1 was obtained as 9.525 mm with reference to the standard table (khurmi and gupta, 2018). the roller diameter, d, was given as 6.35 mm. the minimum width of the roller, w, was obtained as 5.72 mm. the pitch diameter of the smaller sprocket, d, was obtained from equation 11 and 12. 𝑑1 = 𝑝𝑐𝑜𝑠𝑒𝑐 ( 180 𝑇1 ) (11) 𝑑2 = 𝑝𝑐𝑜𝑠𝑒𝑐 ( 180 𝑇2 ) (12) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com etim: design, construction and performance evaluation of a mucuna bean seed cracker. azojete, 20(2):523-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 529 where t1 and t2 are number of teeth on the smaller and bigger sprocket respectively. the pitch line velocity of the smaller sprocket, v1, was obtained from the expression below. 𝑉 = 𝑛𝐷1𝑁1 60 (13) the pitch line velocity was obtained as 5.87 m/s the load on the chain was obtained using equation 14. 𝑤 = 𝑅𝑎𝑡𝑒𝑑𝑃𝑜𝑤𝑒𝑟 𝑃𝑖𝑡𝑐ℎ𝑙𝑖𝑛𝑒𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (14) the load on the chain was obtained as 226.58 n. the factor of safety was obtained using equation 15. 𝐹𝑠 = 𝑊𝑏 𝑊 (15) the value obtained for the safety factor (39) was more than the value specified for a 1400 rpm driven roller chain (khurmi and gupta, 2018). the minimum centre distance between the smaller and bigger sprockets was assumed to be 30 times the pitch. the centre distance between the sprockets was obtained as 285 mm. to accommodate the initial slag, the value of the centre distance was reduced by 5 mm. the number of chain links was obtained from the equation 16 (khurmi and gupta, 2018): 𝐾 = (𝑇1+ 𝑇2) 2 + 2𝑥 𝑃 + (𝑇2−𝑇1)2 2𝜋 × 𝑝 𝑥 (16) the number of chain links was obtained as 54.7. the length of the chain was computed using equation 17: 𝐿 = 𝐾𝑃 (17) where, k, was the chain linkage and p, was the pitch diameter. the length was obtained as 58.7 mm. 2.4 moisture content (m.c.) of the product used for evaluating the performance of the machine: the moisture content (% dry basis) of the seed used for performance evaluation of the machine was obtained using equation 18. 𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒𝐶𝑜𝑛𝑡𝑒𝑛𝑡(𝑀. 𝐶. ) = (𝑤1− 𝑤2) 𝑤2 (% dry basis) (18) w1 was the initial weight of the seed and w2 was the final weight of the seed after drying. 2.5 performance evaluation of the machine the feed rate of the product to the machine, throughput capacity of the machine, cracking efficiency and percentage of seed breakage were evaluated using equations 19, 20, 21 and 22 respectively. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):523-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 530 2.5.1 feed rate: the feed rate of the seed in the machine was calculated using equation 19. 𝐹𝑟 = 𝑊𝑡 𝑇𝑐 (kg/hr) (19) wt was the weight of the seed that filled the hopper (kg) and tc was the time taken to empty the whole seed into the cracking chamber (hr) 2.5.2 throughput capacity: throughput capacity of the machine was calculated used equation 20. 𝐶𝑡 = 𝑊𝑡 𝑇𝑑 (kg/hr) (20) td was the total time taken by the cracked mixture to level the discharge outlet (hr). 2.5.3 efficiency of cracking: the efficiency of cracking was determined using equation 21. 𝐸𝑐 = ( 𝑊𝑡− 𝑊𝑛. 𝑊𝑡 ) × 100% (21) wn was the weight of partially cracked and un-cracked mucuna seeds (kg) 2.5.4 percentage of seed breakage (pbk): the percentage of seed breakage was calculated using equation 22. 𝑃𝑏𝑘 = ( 𝐶𝑑 𝐶𝑑+ 𝐶𝑢 ) × 100% (22) cd was the weight of cracked and damaged seed (kg) and cu weight of cracked and undamaged seed (kg) 3.0 results and discussion 3.1 performance testing the machine was tested at various moisture levels and the results obtained are presented in table 1. table 1: performance evaluation of the machine moisture content dry basis (%) feed rate (kg/hr) throughput capacity ( kg/hr) efficiency of cracking (%) percentage of seed breakage (%) 5.31 8.01 12.02 56.60 60.34 9.14 7.52 11.29 60.19 63.33 11.52 7.26 10.89 61.80 64.20 14.53 7.01 10.51 62.76 66.82 16.31 6.67 10.00 64.1 67.4 18.38 6.59 9.88 66.1 69.60 from the results obtained, the feed rate of the machine decreased as the moisture content of the seed increased. at the various moisture levels, a decrease of 17.31 % was recorded as the feed rate of the machine decreased from 8.01 to 6.59 kg/hr. this was responsible for the easy flow of the seed when loaded on the hopper. a mathematical relationship linking the two variables was established in equation 23. 𝐹𝑟 = 8.561 − 0.11𝑚 (𝑅2 = 0.987) (23) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com etim: design, construction and performance evaluation of a mucuna bean seed cracker. azojete, 20(2):523-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 531 the throughput capacity also decreased with increasing moisture levels. at a moisture level 5.31 % (dry basis), the throughput capacity of the machine was obtained as 12.02 kg/hr, while between 9.14 to 11.52 % (dry basis), it decreased by 3.5 %. the throughput capacity decreased from 10.51 to 9.88 kg/hr as moisture content increased from 14.53 to 18.31% (dry basis). the efficiency of cracking of the seed increased with increasing moisture content. the result obtained ranged from 56.6 to 66.1 % as moisture level increased from 5.13 to 18.38 %. the range of value was slightly less than what was obtained for a cashew nutcracker (ojolo et al., 2009) and a walnut cracker (antia et al., 2014). it was however higher than what was obtained (alonge et al., 2016) for a bambara groundnut sheller (7.5 kg/hr). it was observed that the seeds tend to crack more efficiently when dried than wet owing to loss of moisture. the increased amount of moisture toughens the seed initially, though it gets softened after a minimum of two days. a relationship between moisture content and throughput capacity was obtained as in figure 4. the high coefficient of correlation obtained in equation 24, shows a strong relationship between moisture content and the throughput capacity. 𝐶𝑡ℎ = − 0.166𝑚 + 12.85 (𝑅2 = 0.988) (24) figure 4: relationship between moisture content and throughput capacity and feed rate the percentage of seed breakage showed a positive correlation with moisture level. this was evident in the high 𝑅2 value obtained from a mathematical relationship established for the two factors as presented in equation 25. some cracked samples of the seeds and pods are shown in figure 4. 𝐸𝑠𝑏𝑟 = 0.680𝑚 + 56.75 (𝑅2 = 0.982) (25) plate 2: cracked mucuna bean seeds with pods the percentage of seed breakage increased with moisture content. at the various moisture levels tested, a variation of 13.3 % was recorded. the efficiency of the machine to crack the 6 7 8 9 10 11 12 13 14 4 8 12 16 20 p er fo rm a n ce i n d ic a to r moisture content (% dry basis) throughput capacity (kg/hr) feed rate (kg/hr) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):523-534. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 532 seed was higher as the product moisture level increased. the values ranged from 56.6 to 66.1 % as captured in figure 5. a mathematical relationship linking the moisture level of the seed and the cracking efficiency of the machine was established in equation 26. 𝐸𝑐 = 0.672𝑚 + 53.49 (𝑅2 = 0.976) (26) figure 5: relationship between moisture content and percentage of seed breakage and cracking efficiency the range of values obtained was lower than what was obtained for a cashew nutcracker (ojolo and ogunsina, 2007), but higher than what was reported for a shelling machine of moringa oleifera seed (fadele and aremu, 2016). the seeds were observed to have cracked more efficiently when moisture was reduced. an average of 500 seeds were cracked within an hour, as against a minimum of 48 hours that would have been spent on the same quantity if the seeds were to be soaked in warm water and cracked manually as confirmed by local food processors in the study area. 4. conclusion the economic potential of mucuna bean seed is enormous and the development of machines for its processing is of huge significance. this research was an attempt to develop a cracking machine that would limit the time taken to manually crack the seed. the machine was tested for efficiency at various moisture levels of the seed ranging from 5.31% to 18.38% (dry basis). the efficiency was highest (66.10%) at a moisture content of 18.38%, indicating the seed will crack more efficiently if its moisture content is increased (dry basis). the feed rate and throughput capacity of the machine decreased as the moisture level of the seed increased. the percentage of seed breakage increased from 60.34 to 69.60 % within the tested moisture levels. the cracker is recommended for low-income farmers, who need available technology to enable easy processing of the seed, against the conventional manual method which involves soaking in water for days. further development and optimization of the bean cracker should be considered to cover a range of speed (rpm) and other factors, to improve the capacity and efficiency of the machine. acknowledgments the author acknowledges all academic and technical staff of the department of agricultural engineering, akwa ibom state university, ikot akpaden, and that of the department of agricultural and food engineering, university of uyo, uyo, both in nigeria, for their contribution towards the success of the research. conflict of interest the author wishes to state that there is no competing interest associated with the publication of the findings from the study. 55 60 65 70 75 4 8 12 16 20 p er fo rm a n ce i n d ic a to r moisture content (% dry basis) percentage of seed breakage (%) efficiency of cracking (%) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com etim: design, construction and performance evaluation of a mucuna bean seed cracker. azojete, 20(2):523-534. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: promiseetim@aksu.edu.ng 533 funding this study did not receive a grant from any individual, group, or agency. references alonge, af., and etim, pj. 2017. effect of moisture content on some physical properties of mucuna bean seed. acta hort., 1152: 149-158. https://doi.org/10.17660/actahortic.2017.1152.21. alonge, af., bassey, e., esua, oj. and onwude, di. 2016. development and preliminary testing of a bambara groundnut sheller. international journal food research, 23: 7-13. alonge, af., ossom, is. and bassey, e. 2017. design modification and performance testing of a bambara groundnut sheller. chemical engineering transaction, 58: 367-372. https://doi.org/10.3303/cet1758062. antia, oo., olusunde, w. and offiong, a. 2014. determination of optimum moisture content of palm nut cracking for efficient production of whole kernel. nigerian journal of technological development, 11(2): 27-30. aremu, a., adeniyi, ao. and fadele, ok. 2015. development and performance of a jatropa shelling machine based on seed moisture content. journal of biosystems engineering, 40(2): 137-144. doi: 10.5307/jbe.2015.40.2.137 aremu, ka., and fadele, ok. 2018. a review of shelling, threshing, dehulling and 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ogunlana, r and jimoh, ar. 2019. effect of moisture content and machine speed on the performance evaluation of an existing motorized groundnut decorticator. an international peer review e-3 journal of sciences and technology, 8 (3): 199205. sharifian, f., didar, ar.and derafshi, mh. 2015. design of a walnut cracking machine based on acquired mechanical properties. 10th international congress on mechanization and energy in agriculture, antalya, 18: 14-17. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com https://doi.org/10.1016/j.sciaf.2019.e00174 http://dx.doi.org/10.4314/njtd.v12i1.3 https://www.researchgate.net/deref/http%3a%2f%2fdx.doi.org%2f10.1108%2f17260531011062528?_sg%5b0%5d=x4k39mtl8dzt4c5wlertz3zcrfkgsxrjsjt4usab9lue6fh4sfeixko-nc77mclxgln66n3klxa923-qglrdyay_la.amfvx4z2tyx3qffkc9zzfxy46g_wyntlenbzs2t4md8kprqe7_vzodjp_y_nb6ibg4_i2lgz7v4szcwuq6iyyg https://doi.org/10.1002/eng2.12058 arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):601-618 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 601 development of a palm nut cracker with spinning disc shell separator b. o. lukman*, s. o. oyegbile, o. m. adeshina, e. owoo, and k. o. oriola department of agricultural engineering, ladoke akintola university of technology, ogbomosho, nigeria *corresponding author's email address: bolukman35@gmail.com article information submitted 20 september, 2023 revised 3 january, 2024 accepted 10 january, 2024 keywords: palm nut cracking separation spinning disc kernel purity shell purity abstract this paper presents the design and evaluation of a palm nut cracker with a spinning disc separator. the machine has five units namely: the hopper, the cracking chamber, the separating unit made of a vibrating screen and a spinning disc, the collectors, and the drive unit. the machine was designed and fabricated using locally sourced materials, and it was tested and evaluated at two operating speeds (480 and 660rpm) with palm nuts at three moisture contents of 5, 10, and 12%, respectively. the kernelshell mixture was separated using the spinning disc made of three different materials; mild steel, plywood, and jute fiber. at a constant feed rate of 50 nuts per second, the cracking unit achieved a maximum cracking efficiency of 94.52%, while the throughput capacity was 8.05 kg/hr at 660 rpm for nuts with a moisture content of 10%. the spinning disc constructed of mild steel had the highest separation efficiency of 69.2% and kernel purity of 90.69% for cracked mixture with 12% moisture content at 60 rpm. 1.0 introduction oil palm (elaeis guinensis) is a plant that originated in africa. it belongs to the genus elaeis, subfamily cocoideae and family palmae. the fruits are oval and have three layers; the outer epicarp or exocarp, middle mesocarp; a breakable endocarp called the shell. these fruits are usually harvested and processed for oil, fiber, and nuts (fao, 2009). oil palm fruit produces two distinct oils, namely; palm oil and palm kernel oil, and are obtained from the mesocarp and the inner endosperm (palm kernel), which are enclosed in the hard endocarp (palm nut), respectively (koya et al., 2004). there are four cultivars of oil palm namely: microcaria, dura, tenera, and pisifera. dura and tenera cultivars are of commercial value and are referred to as thick-shelled and thin-shelled varieties, respectively. figure 1 shows types and structure of oil palm fruit. palm oil can be processed into soap, detergents, cosmetics, and innumerable products, and it also finds use in the oleochemical and food industry. broken shells, fibers, and empty bunches obtained after processing oil palm fruit are used as fuel. broken shells are also used as aggregate in concrete and road construction (oriola et al., 2021; raheem et al., 2021; kareem et al., 2022). figure 2 shows the flowchart of the various uses of oil palm products. http://www.azojete.com.ng/ mailto:%20efegabs@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 602 figure 1: types and structure of oil palm fruit ((edet et al., 2022)) figure 2: flowchart of the uses of oil palm by-product nut cracking occurs when the material breaks without separation (alade et al., 2020). cracking palm nuts to release whole and clean kernels with little or no objectionable damage is a vital process that determines the quality of the kernel. the age-long traditional cracking method has remained the most familiar method of extracting the kernel from the hard endocarp. this is achieved by hitting or smashing the nut between two stones using impact force to expose the kernel therein, the kernels are subsequently handpicked from the broken shell-kernel mixture. this method is labor-intensive, crude, time-consuming, and less productive. the maximum amount of kernel that can be obtained in a day per worker using this method was reported to be 50 kg (udo et al., 2015). mechanical crackers can be classified as modern mechanical crackers and indigenous mechanical crackers (adebayo, 2004; udo et al., 2015). modern mechanical crackers such as ripple mills (and their modified designs, such as rolek nutcracker) are imported to nigeria, while the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 603 indigenous mechanical crackers are designed using locally sourced materials. ripple mill, and its modified designs have a large capacity ranging from 3 to 20 tons/hr (rohaya et al., 2006). they are made of two essential components; the rotor and the stator. the rotor is the rotating part of the machine, while the stator is the stationary part. the machine cracks nuts by subjecting them to centrifugal force with the aid of the rotating rotor and then pressing them against the stator. these crackers are costly and require frequent maintenance as most parts are worn out easily (rohaya et al., 2006). indigenous mechanical crackers are classified as hammer-impact, roller, and centrifugal crackers, which can further be classified into vertical and horizontal shaft centrifugal crackers (oyebanji et al., 2012). the roller cracker uses two rollers that rotate in opposite directions. however, low efficiency has been reported for this machine because the clearance between the rollers cannot be varied (adebayo, 2004; adejugbe et al., 2017). the hammer impact cracker uses hardened metal to crack by impact. however, it has low efficiency as high kernel breakage is observed. centrifugal cracker breaks the palm nuts by hurling it against a stationary hard wall subjecting the nuts to shock. this cracker has been reported to have some setbacks, such as the high uncracked nut percentage and kernel breakage percentage, when necessary, factors like speed, moisture content, and palm nut size are not taken into consideration (koya, 2006). indigenous crackers are inexpensive and require low maintenance compared to their modern counterpart. over the years, researchers have developed different indigenous palm nutcrackers, but humble success has been recorded. most researchers reported high throughput capacity, which is expected as crackers are driven at high speed but at the expense of whole kernel production (alade et al., 2020). a mixture of kernels and broken shells (of varying shapes and sizes) is produced after the cracking process (agu et al., 2017). the kernels are traditionally separated from the shell by handpicking the kernel from the cracked mixture (whole kernel and the broken shell). this approach is characterized by low efficiency and output. there are two types of palm kernelshell separators: dry and wet separators (akusu et al., 2017). these used the physical properties of the content of the cracked mixture (such as specific gravity, size, shape, coefficient of friction, terminal velocity, and drag coefficient) to effect separation. the dry separator did not require any liquid medium. however, the wet separator does. the dry method of separation is more efficient than its wet counterpart (akusu et al., 2017). wet separators include a hydro-cyclone, clay water bath, and salt-water bath using density difference as the basis for separation. this approach had little success due to the close density of the kernel and shell (koya, and faborode, 2006; udo et al., 2015). some of the dry separation techniques include systems utilizing vibrating and reciprocating screens, rotating screens, vibrating and reciprocating inclined planes, rotary separators, and indented cylinders. some researchers also developed machines in which cracking and separation operations occur sequentially; the cracker and separator are built together, and the separator separates mainly based on differences in the shape and size of the kernel and shell mixture. various researchers have developed different dry separators. however, a five-stage winnowing system designed by halim et al., (2009) recorded better separation efficiency. the system has five different columns, and each column has peculiar parameters; no two columns were designed with the same parameters, including air speed and flow rate, column head, feed ratio. each column has a cyclone, a duct, and a blower. it was designed to collect shells at columns 1 and 4, kernels at columns 2 and 3 while collecting mixture of both kernel and shell at column 5. this winnowing system is expensive and cannot be afforded by small-scale farmers (onyekachi and nwankwojike, 2020). a theoretical model for separating this mixture using spinning disc was developed by (koya and faborode, 2006), but no machine has been designed based on this theory. hence, the need to develop a lowspeed operated yet efficient palm nutcracker with a dry separator (spinning disc) for adoption by small-scale palm kernel oil processors. this study was aimed at designing and evaluating the http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 604 performance of a low-speed palm nutcracker with a spinning disc as the separator based on koya and faborode’s theory 2. materials and methods 2.1 description of the machine the machine is made of five units with several components; the hopper, the cracking unit, the separating unit (the pre-cleaner and the spinning disc), the collector, and the drive unit (figure 3). figure 4 shows the exploded view of the machine. 2.1.1. the hopper the hopper was made in the shape of half of a square pyramid frustum with the dimensions 300 mm × 240 mm × 157 mm as obtained from design calculation to ensure a feed rate of 1 kg/s. it was inclined horizontally to ensure the nuts flow freely into the cracking chamber. a small rectangular slider was provided at the interface between the hopper and the cracking chamber. this was considered necessary to protect the operator from flying splinters/fragments resulting from the chattering of the nuts during the cracking process. 2.1.2. the cracking chamber the cracking chamber was divided into two parts; the upper trapezoidal shape with the dimension of 250 mm × 150 mm × 100 mm and the lower rectangular shape with the dimension of 350 mm × 250 mm × 250 mm as obtained from the design calculation to achieve a minimum 20 kg/h throughput capacity. this cracking chamber has a rotating shaft onto which four hammers are mounted using a system of vertically arranged three discs of the same dimension (90 mm diameter and 6 mm thick) with four equally spaced hangers (along the circumference of the discs) for suspending the hammers. these hammers have dimensions of 95 mm × 40 mm × 10 mm. the bottom part of the chamber is provided with a concave screen drilled with a 15 mm bit. the cracking is achieved by the impact force exerted on the nut by these hammers against the wall of the cracking chamber. the outlet was located below the cracking section. it has an opening of 180 mm by 100 mm 2.1.3. separating unit this consists of two different parts, namely, the vibrating flat screen (pre-cleaner) and the spinning disc i. vibrating screen (pre-cleaner) the cracked nuts from the cracking chamber are discharged onto the pre-cleaner. this was made of mild steel and has a length of 1200 mm, a width of 350 mm and 200 mm at the top and bottom, respectively, and a height of 30 mm. it was divided into three sections with varying aperture sizes: 5 mm, 10 mm, and 12 mm, which cover 300 mm, 550 mm, and 350 mm lengths of the screen, respectively. it is inclined slightly less than the repose angle of the dura variety of palm kernel nut. this unit was mounted on the supporting frame. it was subjected to vibration-induced as the machine operates, causing fragmented shells and fibers to be removed from the mixture through the section with a 5 mm aperture section. in contrast, broken shells with some broken kernels are removed through the other two sections of the screen as the mixture's constituents slide down the plane toward the spinning disc. ii. spinning disc this is a 10mm thick mild steel disc with a 300mm diameter that spins horizontally. the spinning disc is to be operated at a reduced speed say 60 – 90 rpm (koya and faborode, 2006). hence, it is keyed onto and driven by the shaft of the speed reducer (with a gear ratio of 40: 1) to reduce the speed of this separating unit. the speed reducer is mounted directly on a wooden stool, and below it is a 2 hp single-phase electric motor with a speed of 2400 rpm to drive the system. a v-belt was used to transmit power between the two (the speed reducer and the electric motor). the speed of the spinning disc was varied by changing the pulley size of the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 605 electric motor. the cracked mixture from the vibrating screen falls directly onto this rotating disc near its center. the separation of this unit is based on the differences in sizes and invariably masses of the cracked mixture and differences in external friction of the kernel and shell on the surface of the disc. the disc throws the kernel and shell over different distances based on the mass of each component of the mixture, and the separation is thus effected. the angle at which the disc rotates before the particle drops off is known as the discharge angle. according to (koya and faborode, 2006), there is a significant difference between the discharge angle of the kernel and shell on a rotating disc. this makes the separation of kernel-shell mixture feasible using a spinning disc. theoretical detail can be found in the work of (koya and faborode, 2006). 2.1.4. the collectors these cylindrical units receive whole kernels, broken kernels, and shells separated by the spinning disc. the collectors are two in number. they have the same height (200 mm) but different diameters. the sizes of the collectors were arrived at after several trials; the first one has a smaller diameter of 500 mm, and it receives whole kernel and broken kernel, while the second one with a diameter of 650 mm receives shells. the arrangement of the entire system is such that the spinning disc is situated at the center of the two collectors. the collectors are nearly half the height of the wooden stool on top of which the spinning disc was mounted 2.1.5. the drive unit this consists of the prime mover, namely, the petrol engine, electric motor, pulleys, and belts. the 6.5 hp petrol engine powers the cracking unit while the 2 hp electric motor drives the spinning disc via the speed reducer. the summary of the design calculations, formulas, and values is shown the table 1 figure 3: isometric view of the machine a hopper, b cracking unit, ci vibrating screen (pre-cleaner), cii spinning disc, d – collectors, e—tool frame, f prime mover http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 606 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 607 table 1: summary of design formula and values s/n part design parameter mathematical formula employed source equation number design value 1 hopper volume 1 3⁄ 𝐼𝑛(𝐴1 + 𝐴2)√𝐴1𝐴2 2 free internet help (1) 2.94 x 10-3 m3 2 cracking shaft power 2𝜋𝑁𝑇 60 khurmi and gupta, 2013 (2) 0.97 kw velocity πdn 60 khurmi and gupta, 2013 (3) 13.28 m/s twisting moment √(𝐾𝑚 × 𝑀)2 + (𝐾𝑡 × 𝑇)2 khurmi and gupta, 2013 (4) 79.0 nm bending moment 1 2 (𝑇𝑒 + (𝐾𝑚 × 𝑀) khurmi and gupta, 2013 (5) 276 nm diameter √ 16 × 𝑇𝑒 π × τ 3 khurmi and gupta, 2013 (6) 37 mm 3 hammer weight ?vg khurmi and gupta, 2013 (7) 24.6 n force 2𝑇 𝐷 khurmi and gupta, 2013 (8) 73 n 4 spinning disc shaft power 2𝜋𝑁𝑇 60 khurmi and gupta, 2013 (9) 0.0013 kw twisting moment √(𝐾𝑚 × m + αfd 8 )2 + (𝐾𝑡 × 𝑇)2 khurmi and gupta, 2013 (10) 2.16 nm bending moment 1 2 ( + te) khurmi and gupta, 2013 (11) 1.98 nm diameter √ 16 × 𝑇𝑒 π × τ 3 khurmi and gupta, 2013 (12) 20 mm 5 cracking belt length π (r1 + r2) + 2c + (𝑟1+ 𝑟2)2 𝐶 khurmi and gupta, 2013 (13) 1.21 m 6 speed reducer belt length π (r1 + r2) + 2c + (𝑟1+ 𝑟2)2 𝐶 khurmi and gupta, 2013 (14) 0.67 m 7 vibrating screen capacity 1 2 ((𝑎 + 𝑏)𝐿𝐻) free internet help (15) 1.98 x 10-4 m3 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 608 2.2 sample conditioning the machine was evaluated using nut samples at different moisture levels. the original moisture content of the nut was obtained using the oven-drying method according to american society of agricultural and biological engineers. this was done by placing three different samples with an initial weight of 50 g in the oven, which was taken as mi. the samples were placed in the oven at 120oc temperature until constant moisture content was achieved. then the moisture content of the sample was then calculated using the equation (jaiyeoba et al., 2020); m = 𝑀𝑖−𝑀𝑓 𝑀𝑓 % (16) where: m = moisture content of the sample (dry basis); 𝑀𝑖 = initial weight of the sample (g); 𝑀𝑓= final weight of the sample(g). the initial moisture content of the test sample was calculated to be 5% d.b. in order to explore the performance of the machine at different moisture contents, the initial moisture content was raised to varying moisture contents (10% and 12%). this was done by calculating the weight of water required to raise the samples to the desired moisture contents using the equation 17 (ogunlade and aremu, 2020) and this was added to samples in two different air-tight containers and kept in a refrigerator for 16 h. w = ( 100−𝑀𝑜 100−𝑀𝑖 − 1)× wi (17) where: w = weight of water required to raise the moisture level of the sample (g); wi = weight of the sample to be induced (g); 𝑀𝑜 = original moisture content of the sample (%); 𝑀𝑖 = moisture content to be induced (%) 2.3 experimental procedure the cracking experiment was carried out using 4.5 kg of dura nut, separated into three groups with distinct moisture content: 5%, 10%, and 12%. each group was divided into two sub groups to explore the cracking efficiency at two different machine speeds: 480 and 660rpm. for each treatment (moisture level and speed), the nut was fed into the cracking unit at a constant rate of 50 nuts per second and the experiment was triplicated. the mass of cracked nuts, broken kernel, and whole kernel was recorded for each group, from which the kernel breakage percentage, whole kernel percentage, cracking efficiency, and throughput capacity were estimated. to investigate the effect of spinning disc speed and material on the separation efficiency, the vibrating screen (pre-cleaner) was covered with a metal plate. the spinning disc material used include; mild steel, plywood, and jute, and the disc was operated at three different speeds; 50, 60, and 70 rpm. the experiment was repeated three times for each spinning disc material, and the mass of the kernel (broken and whole) and the mass broken shell received by the collectors were recorded, from which the separation efficiency, kernel purity, and shell purity were estimated. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 609 2.4 performance evaluation the parameters shown in table 2 were used to evaluate the machine's performance. table 2: performance parameters parameter formula term equation number source cracking efficiency 𝐴𝐶 𝐴𝑇 % ac and at denote cracked nut mass and the mass of the nut fed into the machine, respectively. (18) rohaya et al., 2006 kernel breakage 𝐵𝐾 𝐴𝐶 % 𝐵𝐾and ac denote the mass of the broken kernel and cracked nut mass, respectively. (19) rohaya et al., 2006 whole d (unbruised) kernel 𝑈𝐾 𝐴𝐶 % 𝑈𝐾 and ac denote the mass of the unbruised kernel and cracked nut mass, respectively. (20) rohaya et al., 2006 throughput capacity 𝐴𝑇 𝑇 kg/hr at and t denote the mass of the nut fed into the machine and the cracking duration, respectively. (21) rohaya et al., 2006 separation efficiency 𝑆𝑘 𝐴𝑇 % 𝑆𝑘 and 𝐴𝑇 denote the mass of the kernel collected in the kernel collector after separation, the mass of the nut fed into the machine (22) akusu et al., 2017 kernel purity 𝑎 𝑎+𝑏 % a and b denote the mass of recovered kernels in the kernel collector and the mass of recovered shells in the kernel collector, respectively (21) akusu et al., 2017 shell purity 𝑐 𝑐+𝑑 % c and d denote the mass of recovered shells in the shell collector and the mass of recovered kernels in the shell collector, respectively (23) akusu et al., 2017 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 610 2.5 statistical analysis analysis of the variance (anova) of the mean values of the cracking efficiency, separation efficiency, kernel purity and shell purity were carried out to determine the significance level of moisture content, speed, and disc material at p ≤ 0.05 using spss 23 software. 3. results and discussion 3.1 results table 3 shows the mean mass of the cracked nut at different moisture content and operating speed. table 4 shows cracking efficiency, the percentage of kernel breakage, the percentage of the whole kernel, and throughput capacity at different machine operating speeds and kernel nut moisture contents. table 5 shows separation efficiency, and tables 6 and 7 show kernel and shell purity for all spinning disc materials using different moisture content and disc speeds. table 8, 9, 10 and 11 shows anova results of cracking efficiency, separation efficiency, kernel purity and shell purity. table 3: mass of cracked nuts with different moisture content at different operating speed moisture content 5% 10% 12% mean cracking time (s) mean cracked nuts (g) mean cracking time (s) mean cracked nuts (g) mean cracking time (s) mean cracked nuts (g) speed (rpm) 660 62.00±0.05 221.30±0.05 105.70±0.05 236.30±0.05 200.00±0.05 245.10±0.05 480 163.70±0.05 225.00±0.05 168.30±0.05 225.00±0.05 234.00±0.05 220.10±0.05 table 4: evaluation parameters of the cracker moisture content (%) cracking efficiency (%) whole kernel (%) kernel breakage (%) throughput capacity (kg/hr.) 660 rpm 480 rpm 660 rpm 480 rpm 660 rpm 480 rpm 660 rpm 480rpm 5 88.52 90.00 86.50 91.72 13.28 8.28 12.49 4.95 10 94.52 90.00 84.47 88.52 15.53 11.48 8.05 4.81 12 88.04 98.24 85.92 89.17 14.08 10.83 4.41 3.39 table 5: separation efficiency for all spinning disc materials at different moisture content and speed table 6: kernel purity moisture content (%) separation efficiency (%) mild steel plywood jute fiber 50 rpm 60 rpm 70 rpm 50 rpm 60 rpm 70 rpm 50 rpm 60 rpm 70 rpm 5 16.6 55.3 32.5 14.7 48.7 31.0 11.1 45 21.1 10 12.0 60.7 37.4 16.4 56.5 31.7 12.7 37.5 21.7 12 13.1 69.2 42.7 13.1 60.0 42.7 12.7 37.5 30.2 moisture content (%) kernel purity (%) mild steel plywood jute fiber 50 rpm 60 rpm 70 rpm 50 rpm 60 rpm 70 rpm 50 rpm 60 rpm 70 rpm 5 25.90 82.04 47.86 24.26 86.34 50.74 20.94 63.80 41.87 10 24.79 84.19 49.54 34.60 92.47 49.38 34.23 71.70 41.81 12 28.23 90.69 56.78 28.20 87.71 57.16 29.60 61.58 41.25 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 611 table 7: shell purity table 8: anova results of cracking efficiency source sum of squares df mean square f-value significance speed 8.544 2 8.544 0.48 0.527 moisture content 16.55 2 8.276 0.39 0.706 table 9: anova results of separation efficiency source sum of squares df mean square f-value significance moisture content 124.169 2 62.084 0.185 0.833 speed 6730.160 2 3365.080 55.240 0.000 disc material 740.229 2 370.114 1.192 0.321 table 10: anova results of kernel purity source sum of squares df mean square f-value significance moisture content 108.246 2 54.123 0.026 0.974 speed 12510.086 2 2085.0144 28.034 0.000 disc material 1338.7554 2 74.3753 2.47 0.185 table 11: anova results of shell purity source sum of squares df mean square f-value significance moisture content 1053.923 2 526.961 0.663 0.441 speed 6841.846 2 3420.943 6.083 0.001 disc material 2727.590 2 1363.795 3.2 discussion 3.2.1. effect of cracking speed and moisture content on cracking efficiency cracking the samples earlier conditioned to a moisture content of 10% (wb) at 480 and 660 rpm yielded 11.48% kernel breakage with a cracking efficiency of 90% and 15.53% kernel breakage with a cracking efficiency of 94.52%, respectively. the influence of the speed on cracking efficiency is depicted in figure 6 below. this agrees with the findings that cracking efficiency increases as the speed increases (udo et al., 2015; john et al., 2020; olaoye and adekanye, 2018). however, at 5% moisture content and 660 rpm, the machine produced a cracking efficiency of 88.52% and, on average, 13.42% kernel breakage. the machine yielded moderate kernel breakage of 8.28% with a cracking efficiency of 90% at 480 rpm, which is low compared to the one obtained at 660 rpm. also, when the samples at 12% moisture level were cracked at 480 and 660 rpm, 10.83% kernel breakage with a cracking efficiency of 98.24% and 14.08% kernel breakage with a cracking efficiency of 98.04% was obtained, respectively. cracking efficiency at 660 rpm was low compared to 480 rpm for both 5% and 12% moisture content samples, which can be attributed to too low or too high moisture content. similar moisture content (%) shell purity (%) mild steel plywood jute fiber 50 rpm 60 rpm 70 rpm 50 rpm 60 rpm 70 rpm 50 rpm 60 rpm 70 rpm 5 34.81 54.90 76.64 35.79 51.15 75.13 15.25 38.51 61.90 10 45.74 66.67 89.39 55.13 62.40 76.81 31.86 56.60 61.95 12 49.81 96.62 91.83 49.79 68.35 88.23 16.88 52.19 61.32 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 612 results were reported by (morakinyo et al., 2021) obtained optimum performance at 10.2% moisture content with 96% cracking efficiency for dura nuts. kernel breakage percentage was observed to be highest, and whole kernel percentage was observed to be lowest at 10% level, resulting in poor performance of the machine at this moisture level. from table 8, speed and moisture content does not significantly influence cracking efficiency at significance level, p < 0.05. this may be attributed to the fact that the cracking unit was operated at low speeds compared to palm nut crackers designed by different researchers over the years. 3.2.2. effect of moisture content and speed on whole kernel and kernel breakage percentage figures 7-8 show the influence of the moisture content and cracking speed on the percentage of the cracked nut. it can be inferred from figures 7 and 8 that the whole kernel percentage decreases, and the kernel breakage percentage increases with moisture content. the highest whole kernel percentage, 91.72%, and the lowest kernel breakage percentage, 8.28%, were recorded at 480rpm using nuts with 5% moisture content, thus making it the optimum moisture content for nut cracking. in contrast, (olaoye and adekanya, 2018) reported the percentage of the broken kernel to be the highest at 16.1% and the lowest at 9.3%. this value of moisture content is high, which may be due to the fact that it was operated at a very high speed (1200rpm), and thus, the nut must be maintained at high moisture content to be cracked optimally. again, antia et al., 2014 reported 2.5% as the optimum moisture content at which they observed 84.2% cracking efficiency, emphasizing that sufficient drying is needed to ensure whole kernel production. this discrepancy can result from the methodology employed in carrying out an investigation. it was observed that all samples cracked at 660 rpm generally recorded a high percentage of kernel breakage, while lower kernel damage was generally recorded for samples cracked using 480 rpm. however, the reverse is the case for the whole kernel percentage. the results showed that the lowest kernel damage and the highest whole kernel were obtained at 5% moisture content. it is evident from the results that kernel breakage percentage increases and whole kernel percentage decrease with speed. figure 6: cracking efficiency against moisture content figure 7: whole kernel percentage against moisture content 80 85 90 95 100 5% 10% 12% c ra ck in g ef fi ci en cy moisture content 660 rpm 480 rpm 80 85 90 95 5% 10% 12%w h o le k e rn e l moisture content 660 rpm 480 rpm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 613 figure 8: kernel breakage percentage against moisture content 3.2.3. effect of shaft speed and moisture content on the throughput capacity the throughput capacity at different moisture content and operating speeds were investigated. it decreases with moisture content and increases with the operating speed. this is illustrated in figure 9 below. the operating speed and moisture content considerably affect the throughput capacity. the throughput capacity is highest with 5% moisture content and 660rpm and lowest using kernel nuts with 12% moisture content with 12.49 kg/h and 4.41 kg/h, respectively. the throughput capacity is highest at 5% moisture content and lowest at 12% content, corresponding to 4.95 kg/h and 3.39 kg/h, respectively, at 480rpm. (john et al., 2020) reported the same trend; as the cracking speed increased from 800 to 2400 rpm, the throughput capacity increased from 11.56 to 37.00 g/s. however, some researchers said high throughput capacity as their machines were operated at very high speeds; (olaoye and adekanya, 2018) observed maximum (94.5 kg/h) and minimum (82.5 kg/h) throughput capacity at 9.3% and 16.1% moisture content respectively and at a constant speed of 1200rpm. similarly, (jimoh and olukunle, 2013) observed that the throughput capacity increased from 750 to 1200 kg/hr and from 625 to 1270 kg/hr as the moisture content decreased from 12.00% to 9.00% for tenera and dura palm nuts, respectively. furthermore, (morakinyo, 2020) reported the throughput capacity as 180 and 200 kg/hr, 218 and 240 kg/hr, and 230 and 235 kg/hr at 15, 18, and 21 hrs drying time for tenera and dura nuts, respectively that is as moisture content decrease or as the drying time increase the throughput capacity increase. figure 9: throughput capacity against moisture content 3.2.4. separation efficiency figure 10 presents the results of the separation tests conducted with the separating unit of the machine in a graphical form. the bar chart shows that generally, irrespective of the type of surface used, the separation efficiency of the machine was highest at the disc speed of 60 rpm and least at 50 rpm. a similar trend was reported by (antia et al., 2019), the highest separation efficiency of 92% and the lowest separating efficiency were observed at a shaft speed of 1800 rpm with a moisture content 0 5 10 15 20 5% 10% 12%k er n el b re ak ag e moisture content 660 rpm 480 rpm 0 5 10 15 5% 10% 12% th ro u gh p u t ca p ci ty moisture content 660 rpm 480rpm http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 614 of 9.3% and at 600 rpm speed with a moisture content of 16.1%. also, the separation efficiency improved with an increase in the moisture content of the nuts on the two surfaces of mild steel and plywood. similarly, (adewale and olufemi, 2014), observed that moisture content has more influence on separation efficiency than shaft speed. an increase in separation efficiency with moisture content indicates that the mixture's drag coefficient and terminal velocity improved with moisture content on these surfaces. however, this trend was reversed on the disc covered with jute fiber at the same speed of 60rpm, but the separation efficiency was still observed to increase with an increase in moisture content, as seen with the two other surfaces at this same speed of 60rpm. more importantly, the mild steel surface proved the best by consistently giving the highest separation efficiency across the three moisture levels of palm nut used in this study vis a vis at 5%, 10%, and 12% (db). this was followed by the results obtained on plywood, while jute fiber gave the least separation efficiency. table 9 shows statistical results of the two-way analysis of variance of separation efficiency, and it indicated that speed significantly influences the separation while moisture content and disc materials do not at p ≤ 0.05. 0 10 20 30 40 50 60 70 80 50rpm 60rpm 70rpm 50rpm 60rpm 70rpm 50rpm 60rpm 70rpm mild steel plywood jute fiber se p ar at io n e ff ic ie n cy speed 5% moisture content 10% moisture content 12% moisture content file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 615 figure 10: separation efficiency for all spinning disc surfaces at different moisture content and speed 2.3.5. kernel and shell purity table 10 and 11 show the anova results of kernel and shell purity respectively, and it is evident from the tables that speed significantly influence both kernel and shell purity and moisture and disc material do not at p ≤ 0.05. generally, high kernel purity was recorded at 60 rpm followed by 50 rpm and 70 rpm, irrespective of the moisture content and disc material. the highest kernel purity was observed with plywood for a cracked mixture at 10% moisture content at 60 rpm with a value of 92.47%. in comparison, the lowest kernel purity was observed with jute fiber for a cracked mixture at 5% moisture content using 50 rpm with a value of 20.94%. for mild steel and plywood, the shell purity increases with moisture content, and this can be attributed to the fact coefficient of friction of the shell increase with moisture, as reported by (gharibzahedi et al., 2013). this also supports the report of (koya, 2004) that kernel and shell have a high coefficient of friction on jute fiber compared to mild steel and plywood. regardless of the moisture content and disc materials, high shell purity was recorded at 70 rpm followed by 50 rpm and 60 rpm; however, the highest shell purity was observed with mild steel using a cracked mixture of 12% moisture content at 60rpm with a value of 96.62%. the lowest shell purity was obtained for jute fiber at 5% moisture content using 50rpm with a value of 15.25%. other researchers reported similar results, (adejugbe et al., 2017) observed 98% and 98%, while (okoko et al., 2017) reported 97.9% and 95.9% as the optimum kernel and shell purity, respectively. in contrast, (adewale and olufemi, 2014), using a rotary separator, observed low values of 73.12% and 80.16% as the optimum kernel and shell purity, respectively. 4. conclusion palm nut cracker with a spinning disc separator has been successfully designed and evaluated at the department of agricultural engineering, ladoke akintola university of technology. the following are the conclusions; 1) the cracking unit's maximum performance, 94.52% cracking efficiency and 8.05kg/hr throughput capacity, was observed at 660 rpm using kernel nuts with 10% moisture content. 2) the throughput capacity of the machine and kernel breakage increases with speed. 3) the highest separation efficiency was observed with mild steel spinning discs with a value of 69.2% for the cracked mixture at 12% moisture content and at an operating speed of 60 rpm leading to a kernel purity of 90.69% and shell purity of 96.62%. 4) speed significantly influences the separation of the kernel from the shell regardless of the spinning disc material. 5) the speed of 60 rpm gives optimum performance for the spinning disc. the result from the evaluation indicated that this machine could be employed in small-scale palm kernel oil mills where less than 50 kg of palm nut is cracked daily. however, more research is needed to improve the kernel purity of the machine using a spinning disc made of mild steel. references adebayo, aa. 2004. development and performance evaluating of a motorized palm nut cracking machine. proceeding of the annual conference, nigeria institution of agricultural engineers., 26: 326330. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)601-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 616 adejugbe, it., oyegunwa, oa., iliya, dd., aigbogun, jo., oyelami, at. and olusunle, soo. 2017. design and development of an improved palm kernel shelling machine and separator. physical science international journal, 14(3): 1-9. adetan, da., adekoya, lo. and oladejo, ka. 2007. an improved pole-and knife methods of harvesting oil palm. agricultural engineering international: the cigr e-journal manuscript pm 06027, vol. ix. olasumboye, at. and koya, oa. 2014. development of a rotary separator for dry palm kernel and shell mixture. innovative systems design and engineering, 5(7): 32-41 ww.iiste.org. adzimah, sk. and seckley, e. 2009. modification in the design of an already existing palm nut-fiber separator. african journal of environmental science and technology, 3(11): 387-398. morakinyo ta., nwankpa g., olawoye b., taiwo ka., and akanbi ct. 2020. effect of drying variables on the optimum performance of a centrifugal palm nuts cracker using dura cultivar: a response surface methodology approach. journal of agricultural engineering and technology (jaet), 25(2): 72-86 agu, rs., eze, pc. and omeje, cu. 2017. separation of oil palm kernel and shell mixture using soil and palm ash slurries. nigerian journal of technology (nijotech), 36(2): 621 – 627. akinoso, r. and raji, ao. 2011. physical properties of fruit, nut, and kernel for oil palm. international agrophysics, 25: 85 – 88. www.international-agrophysics.org. akubuo, co. and eje, be. 2002. palm kernel and shell separator. biosystems engineering, 81(2): 193 – 199. akusu, om., kiin-kabari, db. and barber, li. 2017. palm kernel separation efficiency and kernel quality from different methods used in some communities in rivers state, nigeria. journal of food technology research, 4(2): 46-53. israel ea., koya oa. and omidiji bv. 2020. development of modified palm – nut cracker. agricultural engineering international journal: cigr journal, 22(1): 202-212. https://www.cigrjournal.org. amoah, jy., aggey, m. and annumu, s. 2007. cracked-mixture sieving rates and efficiencies in smallscale palm nut processing in ghana. ghana journal of science, 47: 69 – 81. antia, o., assian, u. and olosunde, w. 2019. effect of moisture content on palm nut shell fragmentation for effective separation of kernel. international journal of mechanical and civil engineering, 2(1): 48-55. aphale, a., bolander, n., park, j., shaw, l. and wassgren, c. 2003. granular fertilizer particle dynamics on and off a spinner spreader. biosystem engineering, 86(3): 319 – 329, diol: 10.1016/ s1537-5110(03)0062 asabe. 2008. method of moisture measurement. asabe s401.1, agricultural handbook published by american society of agricultural and biological engineers. 360-361. ayhan, ds. 2003. fuel conversion aspects of palm oil and sunflower oil. energy sources, 25: 457– 466. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com lukman et al: development of a palm nut cracker with spinning disc shell separator. azojete, 20(3):601-618. issn 1596-2490; 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vol. 20(3)601-618. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bolukman35@gmail.com 618 koya, oa. and faborode, mo. 2006. separation theory for palm kernel and shell mixture on a spinning disc. biosystems engineering, 95(3): 405 – 412, doi.10.1016/j.biosystemseng.2006.07.005. koya, oa., idowu, a. and faborode, mo. 2004. some palm kernel and shell properties are relevant in nut cracking and product separation. journal of agricultural engineering and technology, 12: 33 – 45. jimoh mo. and olukunle oj. 2013. design of an effective automated machine for quality palm kernel production. iosr journal of mechanical and civil engineering, 6(1): 89-97. ndukwu, mc. and asoegwu, sn. 2010. functional performance of a vertical-shaft centrifugal palm nut cracker. research in agricultural engineering, 56(2): 77–83. nwachukwu, ec. and obasi, u. 2006. development of a palm-kernel/shell separator for rural areas in the imo state of nigeria. discovery and innovation, 18(3): 182 – 190. nwadinobi, cp. 2019. evaluation of soil-water ratio effectiveness in soil-bath wet separation process for kernel recovery. nigerian journal of technology (nijotech), 38(1): 99 – 103. ogunlade, ca. and aremu, ak. 2020. modeling and optimisation of oil recovery and throughput capacity in mechanically expressing oil from african oil bean (pentaclethra macrophylla benth) kernels. journal of food science and technology, 57: 4022–4031. okoko p., akanga a. and umani k. 2017. design, fabrication and testing of a fragmentation unit to enhance palm kernel separation. international journal of agriculture innovations and research, 6(2): 2319-1473. olakanmi, eo. 2004. development and performance testing of a palm kernel cracker. compendium of engineering monographs, 4(1) pp. 11 – 13. olasumboye, at. 2012. development of a rotary separator for the dry palm kernel and shell mixture. m.sc. thesis., department of mechanical engineering, obafemi awolowo university, ile – ife, nigeria. ologunagba, fo. 2012. design and evaluation of a horizontal shaft palm nut cracking. journal of engineering and applied science, 4: 80-86. rohaya, mh., nasrin, ab., choo, ym., ma, an. and ravi, n. 2006. a commercial scale implementation of rolek-tm palm nut cracker: techno-economic viability study for production of shell-free kernel. journal of oil palm research, vol. 17(2): 153 – 167. morakinyo ta. 2020. design, modifications and performance evaluation of a centrifugal impact palm nuts cracker. international journal of engineering applied sciences and technology, 5(4): 466479. morakinyo ta., olawoye b., taiwo ka. and akanbi ct. 2021. modeling of the cracking efficiency of tenera cultivar palm nuts using comparative analysis between artificial neural network and response surface methodology. journal of national academy of agricultural sciences, 11: 267–280. udo, sb., adisa, af., ismaila, so. and adejuyigbe, sb. 2015. development of palm kernel nut cracking machine for rural use. agricultural engineering international journal: cigr journal, 17(4): 379 388., https://www.cigrjournal.org file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2008; vol.6, 3848 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng constituent composition of harmattan dust and its influence on properties of fadama soils in semi-arid region, north east nigeria kundiri, a.m.1, alhassan, a.b.1 and audu, i.2 abstract a study of the soils of the fadama around gashua was carried out to assess the contribution of harmattan dust deposition on their genesis and characteristics. the surface horizons have medium coarse prismatic structure or strongly developed coarse subangular or angular blocky which becomes coarse prismatic with depth. the surface horizons typically have loam to sandy loam textures and low bulk density values (<1.17). the annual addition of the harmattan dust has the potential of improving the nutrient contents of fadama soils. this study shows that harmattan dust is an important soil-forming factor in fadama soil pedogenesis and represents a significant natural process in the fluvial ecosystems. the clay minerals of dust and soil were similar, being dominated by kaolinite and illite, with smaller amounts of vermiculite. it is concluded that harmattan dust contributes significantly to the fertility of fadama soils. 1. introduction ecosystems acquire their soil nutrients from either unconsolidated sediments derived directly from in situ weathering or atmospheric deposition of mineral dust that commonly mixes with the soil and sacrificial deposits. distinction between these two sources is important in understanding the geochemical characteristics of soils and the controls over supply of rock derived nutrients to plants ( wells et al. 1987, vitousek et al. , 1999; wang et al. 2004). the distinction between substrate weathering and mineral-dust inputs can be made by integrating isotopic, mineralogical, textural, and geochemical analyses of soil. the nutrient input by dust may be an important factor for the maintenance of soil fertility. for example, dust geochemistry has been used to evaluate the long-term importance of atmospheric mineral-dust additions to the fertility of tropical forests on old, deeply weathered substrates in the amazon basin (swap et al., 1992; verecchia et al., 1995). similarly, chadwick et al. (1999) have demonstrated the role of atmospheric inputs to ecosystems’ fertility on older hawaiian islands using isotopic and mineralogical approaches. geochemical, isotopic, and mineralogical methods have also been used to identify the presence of aeolian dust in soils and superficial deposits in deserts (shachak and lovette, 1998). this body of work has improved understanding about interrelated aspects of dust content, soil composition and texture, and soil hydrology. nevertheless, little is known about the relative contributions of harmattan dust and bedrock weathering to rock-derived nutrient content of most dry land environments in nigeria. studies on aeolian dust and their influence on soil development in semi arid region of west africa have indicated that the dust plays a significant role in improvement of the fertility of these soils (stoorvogel et al., 1997; stahr and herrmann, 1996). dust characteristics and their 1department of soil science, university of maiduguri, pmb 1069 maiduguri. borno state, nigeria. e-mail: amkundiri@yahoo.com 2 department of agricultural and environmental resources engineering, university of maiduguri, maiduguri. pmb 10690, maiduguri. borno state, nigeria. e-mail: idrissaudu@unimaid.edu.ng http://www.azojete.com.ng/ mailto:amkundiri@yahoo.com mailto:idrissaudu@unimaid.edu.ng azojete vol. 6 2008 39 influence on genesis, texture ad nutrient status of soils have been examined in numerous studies (moberg et al., 1991; mctainsh, 1984). the larger amounts of available phosphorus in the surface horizons as compared with the subsoil could partly be the consequence of the deposition of harmattan dust, which is known to contain up to 10 times the available phosphorus per unit weight of the surface horizons on which it is falling. during the period between november to january each year, dry north easterly surface winds (harmattan) distribute dust in most parts of northern nigeria (moberg et al., 1991; mctainsh, 1984) and sometimes over most parts of the country. the presence of harmattan dust in the soils of north eastern part of the country has not received much attention. there is paucity of research on the extent, composition and contribution of harmattan dust deposition to the fertility of seasonally flooded fadama soils (kundiri, 1995; kundiri et al., 1997). the conclusions by moberg et al. (1991) which highlights the paucity of information on the influence of aeolian processes on soils in northern nigeria serves as a stimulus for the paper. the primary purpose of this paper was to determine the characteristics and constituent composition of the harmattan dust on fadama and also to compare these properties with fadama and nearby upland soils in which they are falling. the paper also attempts to estimate the abundance of far-travelled harmattan dust on the fadama soils as well as the relative importance of harmattan dust in providing potential plant nutrients. 2. materials and method the study was carried out on the alluvial floodplain of the komadugu-yobe which is situated in the semi arid region of nigeria around gashua in yobe state, between latitude 12o-13o n and longitude 10o-11o e. the pattern of the rainy season is such that it starts in june or july, gradually increasing in amount and frequency, reaching a maximum in august and ceasing completely in september/october. the area has more or less flat topography. geologically, the area is composed of recent and sub-recent alluvium. the floodplain area currently has a sparse vegetation cover. the natural vegetation consists mainly of acacias with patchy short grasses. the grass species include cenchrus biflorus, aristida stipoides, schoenfeldia gracilis and chloris prieurii. the soils were described using the terms, scales and codes in soil survey field handbook (hodgson, 1974) and recorded on soil survey and land research centre proforma data recording cards modified to suit fluvial environments (kundiri, 1995). eight representative soil profile pits were dug and the morphological characteristics of each surface horizon were also described. soil samples were collected from the surface horizons and prepared for subsequent laboratory analysis. harmattan dust was also collected on the fadama around gashua using 6 plates placed 1.5 m above the ground during the cool dry season between the months of november and june. the height was selected so that it was sufficient to prevent surface saltation of grains from entering the trap. each plate was 1.5 m2 in area and was screened with fine wire mesh to avoid contamination by birds and insects. the oven-dried weights of the harmattan dust were measured and the samples were ashed at 600 °c for 3 hours to obtain the weight of the constituent composition of harmattan dust and its influence on properties of fadama soils in semiarid region, north east nigeria 40 mineral component. the sample weights were corrected for collector efficiencies, collector diameter, and length of sampling period to estimate the flux of dust. the same laboratory methods used in analyzing the soil samples were also adopted for the analysis of the dust samples. the samples of fadama soil and harmattan dust were analysed for the following physical and chemical properties: particle size distribution by pipette method using hydrogen peroxide to destroy organic matter and 5% sodium hexametaphosphate (calgon) as dispersing agent (bascomb, 1974). the ph was measured in a 1:2.5 soil:water suspension using a ph meter (maff, 1985). the electrical conductivity was determined in a 1:5 soil:water ratio using a conductivity meter (maff,1985). exchangeable cations were determined by extraction with 1m nh40ac (ph 7) solution. exchangeable k+ and na+ were determined by flamephotometry and ca++ and mg++ by spectrophotometry. organic carbon was determined by dichromate wet oxidation method (bascomb, 1974) and total n by kjeldhal digestion (maff, 1985). phosphorus in the samples was extracted with 0.5 m nahc03 (ph 8.5) (olsen et al., 1954). cation exchange capacity was determined by bacl2 saturation and subsequent displacement of the adsorbed saturating cation (rhodes, 1985). the constituent compositions of the particle size fractions were determined using the method described by moberg et al. (1988). the estimates of sand fractions were based on x-ray diffraction of non-oriented samples and microscopy (klute, 1986) while the clay fraction was estimated by using a combination of x-ray diffraction analysis on both oriented and nonoriented samples as well as total elemental analysis and thermogrametric analysis (ramsperger et al., 1998). clay-sized and silt-sized sub-surfaces from the two soil types were analysed to determine whether there were any differences in the clay and silt mineralogy of the surface 0-20 cm and 20-40 cm soil layers as well as the influence of harmattan dust. 3. results and discussion the texture of the fadama soil is closely related to the sediments in which it is formed (table 1). the surface horizons have either strongly developed coarse prismatic structure or moderately developed subangular blocky. analysis of field and laboratory data suggests that the surface horizons of the fadama soils are physically and chemically distinct from the soils of the surrounding uplands (table 2). the surface horizons typically have loam to sandy loam textures and low bulk density values (<1.17 g/cm3). the fadama soils also showed a difference, although less distinct, between the surface 0-20 cm and 20-40 cm layers, where they had considerably higher clay and lower sand content (table 1). at some sites, these soils exhibited distinct bands of 0.5–1.5 cm thickness within the 0-20 cm depth with a distinctive reddish colour (munsell 5yr 3/2) as shown in table 3. azojete vol. 6 2008 41 table 1: particle size analysis of soil samples from gashua fadama surface horizon (0-20cm) sub-surface horizon (20-40cm) upland soil (0-40cm) moisture content {%} 3.2 4.1 2.1 organic matter content (%) 7.1 5.3 4.1 clay (%) 39.1 32.5 23.1 silt (%) 27.7 28.4 20.4 fine sand (%) 23.3 20.3 18.3 coarse sand (%) 9.9 18.8 38.2 table 2: chemical properties of soil samples taken from the fadama at gashua fadama upland harmattan dust surface horizon (0-20 cm) ph 6.40 6.80 6.90 ec ds m-1 7.00 5.80 6.00 moisture content (%) 0.70 0.40 0.30 organic carbon (%) 0.50 0.30 0.60 bulk density kg m-3 1.23 1.37 nitrogen {mg/kg} 0.38 0.21 0.50 phosphorus {mg/kg} 9.50 6.30 10.20 calcium {mg/kg} 7.10 5.10 8.30 potassium {mg/kg} 0.70 0.40 0.90 magnesium {mg/kg} 5.90 2.30 6.20 sodium {mg/kg} 0.60 0.40 0.70 cec{mg/kg} 31.20 28.50 37.90 percent base saturation 63.40 60.71 65.87 sub-surface horizon (20-40 cm) ph 6.80 5.70 ec (ds m-1) 6.40 5.20 moisture content (%) 0.50 0.40 organic carbon (%) 0.30 0.20 bulk density (kg m-3) 1.32 1.34 nitrogen {mg/kg} 0.21 0.11 phosphorus {mg/kg} 7.60 6.30 calcium {mg/kg} 5.30 4.70 potassium {mg/kg} 0.40 0.30 magnesium {mg/kg} 4.70 3.20 sodium {mg/kg} 0.40 0.30 cec{mg/kg} 29.62 25.40 percent base saturation 59.68 54.86 constituent composition of harmattan dust and its influence on properties of fadama soils in semiarid region, north east nigeria 42 table 3: description of soil profile pit pit no 1 horizon depth (cm) texture structure moist matrix colour mottle colour apg 0-13 clay loam moderately developed coarse subangular blocky grayish brown 10yr4/2 many fine and medium clear yellowish brown 10yr5/8 bg1 14-41 clay moderately developed medium prismatic gray 2.5y 5/1 many fine and medium diffused distinct yellowish brown 10yr5/4 bcg 42-47 clay loam moderately developed fine and medium subangular blocky grayish brown 10yr5/2 light grayish brown 2.5y5/2 pale brown 10yr6/3 2cg 48-73 sand apedal single grained pale brown 10yr6/3 many fine and medium prominent brownish ellow 10yr6/8 3cg 74-78 loamy sand very weak medium subangular blocky grayish brown 2.5yr6/1 many fine and medium prominent strong brown 7.5yr4/6 3cg2 79-114 sand apedal single grained pale brown 10yr7/1 common prominent and diffused reddish yellow 7.5yr7/8 azojete vol. 6 2008 43 plot 2 horizon depth texture structure moist matrix colour mottle colour apg 0-20 clay strongly developed coarse prismatic dark grayish brown 2.5y4/2 common fine clear dark gray 5y4/1 bg1 21-50 clay weakly developed coarse subangular blocky gray 2.5y 5/1 common fine diffused yellowish brown 10yr5/6 strong brown 7.5yr5/8 bg2 51-94 clay strongly and moderately developed medium angular and subangular blocky gray 2.5y5/1 common fine distinct diffused strong brown7.5yr5/8 bcg 95-104 sandy clay loam weakly developed medium subangular blocky grayish brown 2.5y5/2 many distinct clear strong brown 7.5yr5/8 2cg 105-107 sandy loam massive with weakly developed coarse subangular blocky in loamy layer pale brown 10yr6/3 many medium and coarse prominent and diffused strong brown 7.5yr5/8 all the surface horizons had higher organic matter contents, ec, and nitrogen and phosphorus concentrations. the major exchangeable cations in these soils are ca and mg, with the amount of exchangeable ca in the 0-20 cm layer of the fadama soils being conspicuously high. the ph of the 0-20 cm layer vary from slightly acidic to neutral soils and harmattan dust. the slightly acidic top soils may be due to the presence of strongly acidic functional groups in organic matter which were dissociated during organic matter mineralization. the electrical conductivity of the soils (table 2) fall within 5.20-7.0 ds/m which is greater than 4.0 ds/m threshold levels for salinity hazards to crops (richards, 1969). the high ec values for fadama and upland soils as well as the harmattan dust suggests that additional increase in salts could have a tendency for salt build up which could have serious implications for sustainable crop production. the total nitrogen content of the soils varies from 0.11 to 0.38%. the moderate levels of nitrogen suggest that continuous cropping on these soils would require adequate fertilizer application. available phosphorus is low in all soils and was rarely above 9.5 ppm in any of the top soils. the larger amounts of available phosphorus in the surface horizons as compared with the subsoil could partly be the consequence of the deposition of harmattan dust, which is known to contain up to 10 times the available phosphorus per unit weight of the surface horizons on constituent composition of harmattan dust and its influence on properties of fadama soils in semiarid region, north east nigeria 44 which it is falling (moberg et al. 1991). from an agronomic point of view, the soils may be defined as high base status soils, since calcium and magnesium are the dominant exchangeable cations. the base saturation in it is above 50%. the relatively high base saturation is one of the noteworthy characteristics of these soils and could partly be responsible for their fairly high productivity under traditional agriculture (tiessen et al., 2003). the cation exchange capacity (cec) of the soils in all units is medium to highland satisfies minimum values of 3 meq/100g suggested by dent and young (1981) as satisfactory for arable cropping. the moderate level of cec in the soils could be explained by the low organic matter content and the fact that clays are mainly kaolinitic, in nature, which is common with soils of north east nigeria (esu, 1989; beavington, 1978). the fadama soils are more fertile than the adjacent upland soils partly because of the annual deposition of sediments and organic matter by the flood water from the yobe river. the surface 0-20 cm and 20-40 cm soil layers of the fadama soils were dominated by quartz, with feldspars, illite, kaolinite, chlorite and interstratified vermiculite, illite, or chlorite all present in reasonable proportions (table 4). however, the amount of these clay minerals had all decreased in the 20-40 cm layer (table 5). this is an indication of the contribution of harmattan dust to the surface of fadama soils. the differences between the 0-20 cm and 20-40 cm soil layers of the fadama soils in texture, structure, and chemistry support the theory that the surface layers are strongly influenced by aeolian-derived material, while the sub-surface horizons are the products of the weathering of the local bedrock. table 4: xrd analysis (%) of soil samples taken from fadama and upland at gashua clay mineral fadama upland surface horizon (0-20 cm) illite 20.0 18.3 kaolinite 18.1 17.2 gibbsite 4.3 3.8 vermiculite 6.2 5.7 chlorite 2.1 2.0 microcline 6.3 5.7 orthocline 9.6 7.7 quarrtz 47 44 sub-surface horizon (20-40 cm) illite 16.3 15.1 kaolinite 14.2 12.6 gibbsite 4.0 3.8 vermiculite 5.7 5.1 chlorite 1.9 1.2 microcline 5.3 4.9 orthocline 7.2 6.3 quarrtz 40.1 39.3 azojete vol. 6 2008 45 this study shows that harmattan dust is an important soil-forming factor in fadama soil pedogenesis and represents a significant natural process in the fluvial ecosystems. however, at this time we have no data on long-term rates of dust influx. the high deposition corresponds more frequently with the harmattan period. sediment within the fine sand range dominated the trapped sediment (table 5). a long-term monitoring program to measure influx rates and the effects of climate is needed to describe more completely the effects of harmattan dust influx in fadama ecosystems. this study reveals that the estimated contributions of dust to soil fertility of the soils on which the dust falls could be remarkable. the content of silts is much higher in the harmattan dust than the soils in which it falls (reynolds et al., 2006). table 5: xrd analysis of dust samples falling on the fadama soils % of components silt 2-20µm 36 clay <2 µm 40 % <2 µm illite 48 kaolinite 37 vermiculite 21 chlorite 5.3 quarrtz 1.8 the samples trapped during periods of high deposition generally comprised of coarser material and contains higher percentage of quartz, suggesting that much of the sediment trapped was locally derived. the role of aeolian dust in ecosystem nutrient dynamics in these semi-arid ecosystems is likely to be significant (drees et al., 1993). phosphorus can co-limit productivity (with n) in semi-arid environments (snyman, 2002), particularly when water availability is high. despite uncertainty regarding the total contribution of dust to surface p, this study shows that this contribution is significant. in both fadama and upland soils, it is likely that aeolian dust inputs represent an important input of p to ecosystems. the more specific roles of these inputs, including their availability to biotic systems, remain unknown. similar approaches reveal the importance of aeolian dust to dryland soil nutrient pools in other geologic settings (stuart, 2001). atmospheric dust input varied during the period of collection as did particle size, being bigger in period of maximum fall. dust deposition rates are highly variable but did not show any distinct seasonal pattern, although slightly higher amounts were recorded in novemberjanuary when maximum deposition occurs. the dry colour of the dust varied from light yellowish brown (10y 6/5) to pale brown (10yr 6/4). the study recorded dust accession rates of (1500 kg/ha), which is higher than the values reported by moberg et al. (1991). but the absolute quantities of sediment trapped were comparable to those reported by previous studies. this can be explained by the proximity of the area to sand dunes around kajimaram, tolotulowa and kaska. any addition of soil material of this order of magnitude would certainly modify the nature of the soil profile. constituent composition of harmattan dust and its influence on properties of fadama soils in semiarid region, north east nigeria 46 however, as found in previous studies around the world, any monitoring of dust accession rates of 1 year or less is probably not representative of long-term dust deposition, since influx rates may vary annually especially when related to variance in climatic conditions (o’hara et al., 2006). the clay minerals of dust and soil comprised of smectite and illite, with smaller amounts of kaolinite (table 4). the dust samples showed higher amount of kaolinite (table 5). 4. conclusions increases in dust deposition generally coincided with increase in wind speed and with samples collected during this period having a higher proportion of coarse particles, suggesting an influx of locally derived material. the nutrient status of harmattan dust is substantially greater than the native soil and may serve as a nutrient renewal vector. harmattan dust had clearly finer particle size distribution than dust collected during local storms, but the angularity and evidence of weathering on dust particles did not distinguish dust from different sources. comparing the dust with adjacent soil samples, a higher clay and organic matter content was found in dust, giving relatively high exchange capacities and available weatherable k, ca, mg and p were slightly higher in dust than in the soils. the ec, cec, and water soluble ions in the dust were distinctly higher than at the soil surface, and dust therefore contributes ions to the soils. the enrichment with nutrients at the soil surface can be partly contributed by dust deposition. this study shows that harmattan dust is an important soil-forming factor in fadama soil pedogenesis and represents a significant natural process in the function of fadama ecosystems. however, at this time we have no data on long-term rates of dust influx. a long-term monitoring program to measure influx rates and the effects of climate is needed to describe more completely the effects of harmattan dust influx in fadama ecosystems. acknowledgments the authors wish to thank the eu for funding this research through an eu funded linkage between the centre for arid zone studies (cazs), university of maiduguri, nigeria, and silsoe college, cranfield university, uk. the interests and support of university of maiduguri and the management of the north east arid zone development programme (neazdp) are highly appreciated. references bascomb, c.l. 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(2003). deposition of harmattan dust and its influence on base saturation of soils in northern ghana. geoderma. verrecchia, e., yair; a.; kidron g.j. and verrecchia, k., (1995). physical properties of the psammophile cryptogamic crust and their consequences to the water regime of sandy soils, north-western negev desert, israel. journ of arid env. 29, 427–437. vitousek, p.m.; kennedy, m.j.; derry, l.a. and chadwick, o.a., (1999). weathering versus atmospheric sources of strontium in ecosys-tems on young volcanic soils. oecologia 121, 255– 259. wang, g., wanquan, t. and mingyuan, d. (2004). flux and composition of wind eroded dust in different landscapes of an arid inland river basin in north western china. journ. of arid env. 58:373-385. wells, s.g.; mcfadden, l.d. and dohrenwend, j.c., (1987). influence of late quaternary climatic changes on geomorphic and pedogenic processes on a desert piedmont, eastern mojave desert, california. quaternary research 27, 130– 146. arid zone journal of engineering, technology & environment azojete march 2022. vol. 18(1):135-142 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 135 original research article design and implementation of a transistorized bi-controlled based utility-connected battery charger for underdeveloped nations z. jagun1, a. okandeji2*, c. eya3, m. olajide4, a. ominike5, and s. ukagu6 1department of computer engineering, olabisi onabanjo university, ogun state, nigeria 2department of electrical and electronic engineering, university of lagos, akoka, lagos, nigeria 3department of electrical engineering, university of nigeria, nsukka, enugu state, nigeria 4department of electrical and electronic engineering, olabisi onabanjo university, ogun state, nigeria 5department of computer science and information technology, petroleum training institute, effurun, delta state, nigeria 6department of electrical and computer engineering, igbinedion university okada, edo state, nigeria *corresponding author’s email address: aokandeji@unilag.edu.ng 1.0 introduction communication and medical industries, navigating devices, transportable poly-media players, cable-less deployed remotes, and movable drilling machine needs rechargeable batteries to boost their working efficiencies (tar and fayed, 2016). apart from the aforementioned fields of life, erratic public power supply in underdeveloped nations generally has forced these nations to utilize rechargeable batteries. the impression is to use the charged batteries to support the continuation of the services in those areas in the absence of grid power supply. there are currently not less than 144 underdeveloped nations globally. the erratic power supply in these countries has triggered the use of rechargeable batteries. however, inappropriate charging and over-discharging of secondary batteries, especially in mechanical and electric workshops, are the main causes of battery damages (esther et al., 2013). additional cause of battery damage in underdeveloped nations is the inability to repair the micro-controller based battery chargers locally due to lack of innovative technical know-how. essentially, underdeveloped nations repair faulty foreign battery chargers by replacing the faulty panel with a new panel. this increases the cost of maintenance, littering the environment, increasing the rate of pollution, and in extreme cases, poses health challenges to the public. the reason is that the majority of the article information abstract this paper presents a transistorized bi-controlled based utility-connected battery charger to address the problem of erratic public power supply in underdeveloped nations. in this study, a utility battery charger was built by the integration of grid power supply, line frequency transformer, power electronic switches, alternating current-direct current bridge converter, regulator, and resistor-inductor-capacitor. the excess-voltage protection and battery monitoring were obtained by the bicontrolled technique. in contrast to other charging systems in underdeveloped nations, the proposed system is very simple, rugged, reliable and cheap to maintain due to simplicity and un-programmed nature of the system. the results showed that the proposed system is craggy and robust to resist voltage stress, highly reliable and relatively free from leakage currents due to the presence of a double controlled scheme using a common point of action and a line frequency transformer. in addition, the system can be used to charge batteries ranging from 50µa and above. the system can be utilized in communication companies, electric vehicles, drilling machines. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 july, 2021 revised 3 december, 2021 accepted 10 december, 2021 keywords: battery charger codeless nations underdeveloped http://www.azojete.com.ng/ mailto:candidus.eya@unn.edu.ng mailto:candidus.eya@unn.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):135-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 136 battery charger repairers in underdeveloped nations do not have the technical expertise about the coded integrated circuit parts in the damaged chargers. secondly, instructions on panel repair are mostly hidden by the manufacturers. the secondary battery charging, on the other hand, needs good controllers to obtain a good state of charge (soc) and a long-lasting life span of the battery (woo et al., 2011). due to their broad working temperature array, stumpy self-discharge, extensive service life and maintenance free operations, lead acid batteries are commonly utilized. secondary batteries can be charged either by renewable or non-renewable power sources. renewable energy such as solar energy from the sun has the problem of decreasing the efficiency of charging batteries due to fluctuations in solar irradiations and varying environmental temperatures (eya and agu, 2015). fossil fuel based charging source is a good option of the battery charging sources due to its relative constant supply, even though it has its own problems of environmental pollutions and oil spillage. utility battery charging systems (ubcs) can be unidirectional or bidirectional converters (yilmaz and krein, 2013., hart, 2011). under unidirectional condition, the ubcs make use of power diodes to rectify alternating current (ac) power to direct current (dc) power but utilizes igbts and mosfets under bidirectional process. utility battery charging systems are often found in telecommunication industrial storage systems, ministry of transportations, electrical home inverter backup systems, hospital battery-based equipment (agu, 2019). there are various approaches in the charging system of a battery. these approaches include steady voltage (sv) or constant voltage (cv), constant current (cc), constant current constant voltage (cccv), and pulse charging (lee at al., 2013, tar and fayed, 2016). the easiest method is the steady voltage charging scheme (lee et al., 2013, copea and podrazhansky, 1999, hua and lin, 2000). the sv charging current depends on the voltage source. the charging current of the battery decreases once the voltage of the battery starts rising. in addition, the current might be excessively rated at the onset charging level if the battery is at a small capacity before charging. the cc method utilizes a steady current to charge the battery so that it can trim down the duration of charging efficiently (hart, 2011). however, this could possibly lead to overcharging and hence, the temperature of the battery could rise rapidly after it is completely charged. the mode of cccv charging is realized by joining both cc and cv charging schemes (hua and lin, 2000, hart, 2011, chen and lai, 2012). at the onset charging phase, the steady current is utilized to charge the battery until it gets to an excessively charged point or an initially defined voltage. this charging type then switches to cv phase to uphold the battery capacity. the merit is that the duration of charging could be drastically minimized. however, a more complicated regulatory circuit is needed, and a holding current could not be practically controlled efficiently. in pulse charging schemes, each charging cycle is engaged in “on” and “off” per frequency for better charging effectiveness (karami et al., 2007, dhar et al., 2001, chen, 2007, eya et al., 2019). however, the systems and their control techniques are complex, possess high power losses, advanced technical know-how, and high maintenance. meanwhile, considering the epileptic state of the economy of underdeveloped countries, low level of technical know-how, poor maintenance practice, intermittent lockdown due to the covid-19 pandemic, and the negative effects of the damaged rechargeable batteries in these nations as well as the complex controls of the aforementioned schemes, this study presents a codeless bicontrolled based utility-connected battery charger for underdeveloped nations. in particular, the objective of this study is to investigate the design of a power circuit and the codeless bi-controlled relay-based battery control scheme. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:candidus.eya@unn.edu.ng jagun et al: design and implementation of a transistorized bi-controlled based utility-connected battery charger for underdeveloped nations. azojete, 18(1):135-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 137 the proposed system possesses a simplified power charging circuit, uncomplicated control circuit, rugged isolated power transformer, transistorized circuit components, and a reliable overvoltage and excess charging protections. therefore, the system can easily be implemented by a user once the circuit configurations are followed unlike other charger systems that are very complicated, coded with several hidden procedures for implementation. furthermore, the proposed system is user friendly in terms of maintenance. accordingly, even under seriously covid-19 pandemic lockdown, it can be locally repaired without removing the entire panel in case of any fault. 2. materials and methods the method adopted in this study is the design-and-implementation scheme. figure 1 consists of a power ac source, step-down transformer, h-bridge, uncontrolled ac-dc converter, filter and charger circuits. the charger circuit is sub-divided into lm317 section, and transistor-transistor coupled circuit. the lm317 part takes care of charging the battery of 12 v with current ranging from 50µa to 2.5a while transistor-transistor coupled circuit charges above 2.5a to 20.5a. 2.1. system component design 2.1.1. transformer design the primary turns 𝑵𝑷 of the transformer is derived as shown in (kirchev et al., 2007) 𝑁1 = 0.694𝑉𝑝 𝑓∅ = 0.694𝑉𝑝 𝑓𝐵𝐴 . (1) the electrical power in the primary side of the transformer is transferred to the secondary side due to magnetic coupling between them. accordingly, 𝒇 = frequency = 50𝐻𝑧, 𝐵 = magnetic flux density and 𝐴 = cross-sectional area of the transformer. the cross-section area of the transformer is given as (kirchev et al., 2007) 𝐴 = 𝐿 × 𝑊, (2) where 𝐿 = 𝑙𝑒𝑛𝑔𝑡ℎ, 𝑎𝑛𝑑 𝑊 = 𝑤𝑖𝑑𝑡ℎ of the transformer. with the aid of the measuring rule, 𝑙 = 5.7𝑐𝑚 = 0.057𝑚, and 𝑤 = 4.2𝑐𝑚 = 0.042𝑚. inserting the values of l and w in equation 2, the cross-section a becomes 2.394 × 10−3𝑚2. given that b = 1.210𝑊𝑏/𝐴 , supply voltage 𝑉𝑝=230v, and f = 50hz, then equation 1 is used to compute the primary coil of the transformer to be 358 turns. the secondary coil number 𝑁2 is obtained by using equation 3 as shown in (kirchev et al., 2007). 𝑁𝑠 = 𝑁𝑝 × 𝑉𝑝 −1 × 𝑉𝑠 (3) from equation 3, 𝑁2 =28 turn. 𝑉𝑠 = secondary voltage of the step-down transformer 2.1.2. single phase ac –dc circuit design the dc output voltage and current of the h-bridge rectifier are expressed as shown in (chen, 2009, charles and sadiku, 2009). 𝑉𝑑𝑐 = 0.637 × 𝑉𝑠√2 (4) 𝐼𝑑𝑐 = 2×𝐼𝑠√2 𝜋 (5) http://www.azojete.com.ng/ mailto:candidus.eya@unn.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):135-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 138 16.2v and 21.6a are realized by inserting the secondary voltage of the transformer vs = 18v and secondary current is = 24a into equation 4. the power output of the ac–dc converter as given in (charles and sadiku, 2009) becomes 𝑃𝑜 = 𝑉𝑑𝑐𝐼𝑑𝑐 (6) 𝑃𝑜 is computed by inserting 16.2v and 21.6a into equation 6 which yielded 349w. under lossless conditions, the power output of the rectifier is equal to the power input to the charger section. hence, the power of the charger can be approximated to be 349w. 2.1.3. lm 317 design circuit the lm 317 section is regulated using equation 7 as in (charles and sadiku, 2009). 𝑉𝑑𝑐 𝑉𝑟𝑒𝑓 − 𝑅3 𝑅4 = 1 (7) 𝑽𝒓𝒆𝒇, 𝑹𝟑 and 𝑹𝟒 are reference voltage and resistances, respectively. r1 and r2 are calculated using the expression in equation 8 and equation 9, respectively, (charles and sadiku, 2009). 𝑅1 = 𝑘𝑉𝑑𝑐 𝐼𝑑𝑐 (8) 𝑅2 = 5𝑅1, (9) where k is the constant (0.7≤ k ≤0.74) 2.1.4. determination of inductance, resistance and capacitance design the inductance of the inductor ls is determined using the expression in equation 10. 𝐿𝑠 = 𝑉𝑑𝑐−𝑉𝑅2−𝑉𝑐2 ∆𝐼𝐿 ∆𝑡⁄ . (10) where 𝑉𝑐2 ,𝑉𝑅2, ∆𝑡 and ∆𝐼𝐿, respectively, represents the voltage across c2, voltage across r2, change in time duration, and current flowing through the inductor the resistances of the resistors 𝑅7 , 𝑅8 and 𝑅9 in figure 2 are, respectively, expressed in equations 13, 14 and 15. 270𝑘𝛺 ≤ 𝑅5 ≤ 300𝑘𝛺 (11) 10𝑘𝛺 ≤ 𝑅6 ≤ 20𝑘𝛺 (12) 9.1𝑘𝛺 ≤ 𝑅7 ≤ 10.2𝑘𝛺 (13) 1𝑘𝛺 ≤ 𝑅8 ≤ 2.2𝑘𝛺 (14) 1.1𝑘𝛺 ≤ 𝑅9 ≤ 2.2𝑘𝛺 (15) 10.2𝑘𝛺 ≤ 𝑅10 = 𝑅11 ≤ 15.2𝑘𝛺 (16) 3.1𝑘𝛺 ≤ 𝑅12 ≤ 4.2𝑘𝛺 (17) 2.1𝑘𝛺 ≤ 𝑅13 = 𝑅14 ≤ 5𝑘𝛺 (18) 5.1𝑘𝛺 ≤ 𝑅15 = 𝑅16 ≤ 10𝑘𝛺 (19) 470µ𝐹 ≤ 𝑐3 ≤ 500µ𝐹 (20) 47µ𝐹 ≤ 𝑐3 = 𝑐4 ≤ 50µ𝐹 (21) the input and output capacitances of the capacitors c1 and c2 are related as shown in equation 22: file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:candidus.eya@unn.edu.ng jagun et al: design and implementation of a transistorized bi-controlled based utility-connected battery charger for underdeveloped nations. azojete, 18(1):135-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 139 𝐶2 = 𝐶1 2 . (22) where c1 is in the range of 𝟐𝟓𝟎µ𝑭 ≤ 𝑪𝟏≤ ≤ 𝟓𝟎𝟎µ𝑭. the proposed circuit diagram shown in figure 1 is made up of di-charging modes, viz: r1-lm317r3-r4 charging mode, and t1-r2-t2-t3-ls charging mode. the dual charging modes do not supply the battery current simultaneously. if the current capacity to charge a battery is greater than what the r1-lm317-r3-r4 charging mode can carry out, it transfers the charging action to t1-r2-t2-t3-ls charging mode to handle. figure 1: proposed circuit diagram 2.2 working principle of the proposed system an isolated 12v biasing voltage is supplied to v1, v2, v3, v4, v5 and v6 points as shown in figure 2. then, current flows from point v3 via r13 to the base terminal of transistor t5. the transistor t5 drives the current from v4 to the base terminal transistor t6 which spontaneously drives the current from point v5 to ground. this action drops zero voltage at the base terminal of transistor t4. then, transistor t7 conducts current from v6 to close the relay switch at normally open (no) point. as soon as the relay is put in the active condition (that connecting the source and load), the system starts charging the battery. the charging of the battery connected to the proposed charger depends on the current drawn by the connected battery to the charging system. if the current drawn by the battery ranges from 50µa to 2.5a, the r1-lm317-r3-r4 charging mode circuit charges that battery but if the current required for charging the battery is more than 2.5a, the internal pass transistor of the lm317 dispels more energy than the allowable limit, and the lm317charger section gets shut down. at this point, the lm317 regulator section is protected against overloads and short-circuits. under the condition of the current being above 2.5a, the voltage-drop across r1 increases and transistors t2 and t3 bypasses the excess battery current lm317 cannot handle, and then the r1-lm317-r3-r4 charging mode takes over the charging process. the circuit components r2, t2 and t3 protect t1 from current above 2.5a and then charge the battery. 2.3 transistorized bi-controlled technique the transistorized bi-controlled technique is shown in figure 2. it consists of two arm sub-circuits joined together with aid of 4071b for controlling the over-voltage conditions in the system. one arm sub-circuit produces vso. the vso is activated to disconnect the ac relay (acrls) from the load line when the ac input voltage is more than 230vrms. the second arm sub-circuit produces vbo. vbo is produced when the battery voltage is more than 14.40v. the second arm sub-circuit of figure 2 shows the circuit diagram for charging and regulating over-charged state of the battery that is, having above 14.4v. as the battery continues to charge, the zener diode http://www.azojete.com.ng/ mailto:candidus.eya@unn.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):135-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 140 zd monitors the level of the battery voltage. once the battery voltage is above 14.4v, zd breaks down and acts as a resistive load. then, current flows from the battery terminal and enters the base terminal of transistor t1. this scenario drives t4 to conduct current from point v3 through r13 to ground. immediately, a zero voltage is placed at the base terminal of t5. then, t5 and t6 stops conducting. subsequently, 12v is placed at the base terminal of t7 through r14 and it blocks t7 from conducting. the resultant effect is that the relay switch rls disconnects and remains open, and the charging action stops. when the zd recovers from the break down effect and the battery voltage becomes less than 14.4v, the charging process repeats itself. by so doing, the battery cannot be excessively charged. r12 r15 r13 r16 r14 v3 v6 vb v5 r c s n o zd2 t4 t5 t6 t7 n c vs d1 d3 d2d4 v1 r8 rx r6r5 + r7 c4 v2 c5 r9 r10 r11 zd1 c3 4071b tl084 v4 pc817 vbo vso figure 2: codeless bi-controlled technique 3. results and discussion the experimental set-up and results are shown in figures 3-6. an un-energized set-up and zero voltage waveform on both analog oscilloscope and digital multimeter are shown in figure 3. the battery, digital multi-meter, and oscilloscopic display is shown in figure 3. it is observed that the level of the battery voltage, as displayed by the digital multi-meter, was 11.7vdc under active operation of the system as well as the commencement of battery charging. figure 3: 11.7 vdc battery voltage from the digital meter with the proposed system figure 4: 12.23vdc battery voltage from digital meter with the proposed system the progressive battery charging is shown from figures 4 to 6. it is observed that figure 4, 5 and 6 recorded 12.23v, 14.36v and 14.40v at time durations of 9:00am, 9:47am and 10:12pm, respectively. finally, the charging of the battery stopped immediately the battery voltage reached 14.40v and that is exactly when there was zener diode break down which is shown in figure 6. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:candidus.eya@unn.edu.ng jagun et al: design and implementation of a transistorized bi-controlled based utility-connected battery charger for underdeveloped nations. azojete, 18(1):135-142. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 141 figure 5: 14.36vdc battery voltage from digital meter with the proposed system figure 6: 14.40vdc battery voltage from digital meter with the proposed system analytically, for the first forty minutes, as shown in figures 4 and 5 the rate at which the battery was charged was very fast. 4. conclusion in this study, a transistorized bi-controlled based utility-connected battery charger for underdeveloped nations was investigated. the proposed system was designed, developed and validated with pictorial displays. the proposed system was observed to be fast with peak charging time of 1hr 12minutes being the time taken to fully charge the battery to 14.40v. the charging of the battery stopped immediately the battery voltage reached 14.40v and this is as a result of the zener diode break down. the charger has a capacity of 349w. the system can be utilized in electric vehicles, storage systems for telecommunication base stations, and home inverter system. a major disadvantage of the proposed system is itsheavy weight, with relative power loss due to the line frequency transformer. minimizing these drawbacks should be the focus of future research. references agu, mu. 2019. principles of power electronics, circuits. university of nigeria nsukka press, nsukka, nigeria. charles, ka., and sadiku, mn. 2009. fundamentals of electric circuits. mcgraw-hill companies. inc. 1221 av. new york, 4th edition. chen, by., and lai, ys. 2012. new digital-controlled technique for battery charger with constant current and voltage control without current feedback. ieee transactions on industrial electronics, 59(3):1545-1553. chen, lr. 2007. a design of an optimal battery pulse charge system by frequency-varied technique. ieee transactions on industrial electronics, 54(1): 398-405. copea, rc., and podrazhansky, y. 1999. the art of battery charging. 14th annual ieee battery conference on applications and advances. 12-15, january. long beach, usa. pp. 233–235. dhar, sk., fetcenko, ma., and ovshinsky, sr. 2001. advanced materials for next generation high energy and power nickel-metal hydride portable batteries. 16th annual battery conference on applications and advances, 1 january, california, usa., pp. 325336. http://www.azojete.com.ng/ mailto:candidus.eya@unn.edu.ng arid zone journal of engineering, technology and environment, march, 2022; vol. 18(1):135-142. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aokandeji@unilag.edu.ng 142 esther, gs., dhivya, ps., and sivaprakasam, t. 2013. solar powered high efficient dual buckconverter for battery charging. international journal of innovative research in electrical electronics instrumentation and control engineering,1: 449-521. eya, cu., and agu, mu. 2015. solar based boost differential inverter. nigerian journal of technology (nijotech), 31 (1): 164-167. eya, cu., ejiogu, ec., agu, mu., and nnadi, db. 2019. transformer-less voltage stabilizer controlled by proportionalplus-integral (pi) controller. mat journal of power electronics and devices, 5(3):42-51. hart, dw. 2011. power electronics. mcgraw-hill companies, inc., new york, ny 10020. hua, cc., and lin, my. 2000. a study of charging control of lead-acid battery for electric vehicles. ieee international symposium on industrial electronics, 1:135-140. karami, h., shamsipur, m., ghasemi, s., and mousavi, mf. 2007. lead-acid bipolar battery assembled with pri. chem fo. positivepasted electrode. journal of power sources, 164(2): 896904. kirchev, a., delaille, a., perrin, m., lemaire, e., and mattera,f., 2007. studies of the pulse charge of lead-acid batteries for pv applications. part ii. impedance of the positive plate revisited+. journal of power sources, 170(2): 495-512. lee, cs., lin hc., and lai, sy. 2013. development of fast large lead acid battery charging system using multi-state strategy. international journal of computer, consumer and control (ij3c), 2(3): 56-65 tar, b., and fayed, a. 2016. an overview of the fundamentals of battery chargers. ieee 59th international midwest symposium on circuits and systems (mwscas), 16-19 october, abu dhabi, uae, pp. 1-4. woo, dg., choe, gy., kim, js., lee, bk., hur, j. and kang, gb. 2011. comparison of integrated battery chargers for plug-in hybrid electric vehicles: topology and control. in: proceedings of the 2011 ieee international electric machines and drives conference, 14-17 may, niagara falls, ontario, canada., pp. 1294–1299. yilmaz, m. and krein, pt. 2013. review of battery charger topologies, charging power levels, and infrastructure for plug-inelectric’ hybrid vehicles. ieee transactions on power electronivs, 28: 2151-2170 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:candidus.eya@unn.edu.ng arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):643-658 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 643 original research article fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea d. a. uzoma1*, d. r. awotunde1, a. i. auwalu1, k. a. abba2, j. b. lucius3, b. t. magaji3, and a. m. oparaeke4 1durable crops research department, nigerian stored products research institute, kano station, kano state, nigeria. 2post-harvest engineering department, nigerian stored products research institute, maiduguri substation, borno state, nigeria. 3department of crop protection, faculty of agriculture, ahmadu bello university, zaria, nigeria. 4department of crop science, faculty of agriculture, forestry and wild-life resources management, university of calabar, nigeria *corresponding author’s email address: uzomaanugwom@yahoo.com 1.0 introduction cowpea (vigna unguiculata (l.) walp) is a popular leguminous crop in africa which is commonly known as beans, ewa (yoruba), agwa (igbo), or wake (hausa) in nigeria. the grain is rich in protein and other micronutrients necessary for healthy living. many societies endowed with cowpea have evolved different ways of utilizing the grain for food and perhaps the reason for the coinage “naman talaka” (poor man’s meat) by hausas of west and article information abstract insect probe traps are effective in detecting grain insects but neglected because it is time consuming and precise method of interpreting the catch have not been adequately specified. interestingly, this is not readily available in nigeria and where available, it is expensive due to foreign exchange rates. therefore, there is need for a locally available and more acceptable insect probe trap for integrated pest management practice during postharvest handling of cowpea. locally sourced materials were used to fabricate a probe trap for monitoring callosobruchus maculatus (coleoptera: chrysomelidae) infesting stored cowpea. the fabricated probe trap was evaluated together with a standard probe trap. treatments were repeated three times, and also tried in three different insect densities (3, 7 and 15 insects per kg respectively) artificially infested into 10 kg cowpea grains contained in plastic storage buckets, and traps were inspected after every 24 hours for five days. the probe trap was also evaluated in 100 kg cowpea sample contained in sack bag to determine the effect of grain volume on the performance of the trap. data collected were subjected to anova and means were separated using student newman keuls test (snk) at 5 % confidence level. the result of total trap catches revealed that the fabricated traps’ mean catch (36.6) was significantly (p ≤ 0.05) higher than the standard probe trap which had lower trap catch mean (12.7) value. thresholds for management decisions were also determined and the fabricated trap was found to be economically profitable (n 936.75 cheaper); hence, objectives of the study were achieved. it is recommended for cowpea handlers in nigeria to use the fabricated insect probe trap because it is effective in monitoring beetles, it is less expensive and also locally available. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 3 march, 2022 revised 9 may, 2022 accepted 10 may, 2022 keywords: fabrication monitoring probe trap cowpea weevil stored cowpea http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 644 central africa (institute for agricultural research policy brief, 2012). rapid progress has been made in production research related to this crop, particularly since the establishment of the grain legume improvement program at international institute for tropical agriculture and the strengthening of the research program for grain legumes in a number of west african agriculture research centres (ajeigbe et al., 2008). nigeria produces more than two million tons (adeola et al., 2011) which represents 58 % of the total world cowpea production annually (peace, 2015). the crop is seen as a major cash crop by central and west african farmers, with an estimated two hundred million (200,000,000) people consuming cowpea on a daily basis (langyintuo et al., 2003). according to langyintuo et al. (2003), at least two hundred and eighty five thousand (285,000) tons of cowpea is shipped among countries in the african region each year. the drive to reduce post harvest loss of crops has been great. this is attributed to increasing world population, which is a threat to future global food security. in view of this, food and agricultural organization has indicated the need to reduce post harvest losses in order to ensure future global food security (fao, 2013). cowpea bruchid, callosobruchus maculatus (f) (coleoptera: chrysomelidae) is a cosmopolitan pest that causes considerable economic damage to dried cowpea and other related stored legumes kingsolver, (2004), and is the main constraint to increased cowpea production and storage (carlos, 2004). similarly, carlos (2004) also stated that unprotected cowpea grains are often completely consumed by bruchids in the first 10 to 12 months of storage. c. maculatus multiplies rapidly in storage, giving rise to a new generation every month in grains at temperature of 30 to 35 oc and 70 to 90 % relative humidity (rh) (fatima et al., 2016). grains attacked by the bruchids losses some weight, nutritional composition, and viability, which makes them unfit for use as food or seed (sarwar, 2015). currently, emphases on the management of pests such as cowpea bruchid rely upon a combination of methods (integrated pest management) which are environmentally friendly to offer effective management (lester, 2006). according to christian and william (2011), inspection during storage is an important component of integrated pest management (ipm) which prevents losses during storage. stored product entomologists have a variety of new monitoring and decision making procedures which changes as grain and grain products move from field to consumers (hagstrum and flinn, 2014). insect probe trap, originally conceived by loschiavo (1975) is a type of pitfall trap which is buried in grains and it catches insects which drop through small pitfall apertures into the trap (anugwom et al., 2017). the device exploits the wandering behavior of the insects which help in timely detection of insects in stored produce leading to timely control (michael and christian, 2012). this trap is a hollow metal plate tube with a series of perforations (holes) all along the sides (anugwom et al., 2017). the top is a cap, and the bottom is a cone-like translucent plastic that screws in place. it is very effective in detecting beetles that move readily in grains and different designs of the insect probe trap have been made. the trap catches depends on the insect population present in samples, i.e. if insect density is low the trap may take longer time to trap insects, which makes its use to be neglected and also underestimated because there is no precise method for interpreting the trap catches (toews and phillips, 2002; flinn et al. 2009 and 2010; cuperus et al., 1990). unless improved probe traps are introduced together with a strategy for their use in commercial grain storage practice, the potential benefits of any new technique will be lost. however, marianne and rebecca (2011) reported that light is an important component in file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 645 the environment of insects, which according to adriana and lars (2001) is due to visual stimuli. light may act as a token stimulus guiding the insect to situations where it may find the optimal requirements for existence arnold et al., (2016), insects’ response to light in most cases is to the intensity of the light (ashfaq et al., 2005). therefore, light lures/repellants can be useful in the practice of ipm, in order to limit the use of toxic insecticides during storage of grains (dadmal and suvarna, 2014). in order to modify this important ipm tool in the form of locally available and more acceptable among grain handlers, some locally sourced material were used to fabricate a probe trap (mbogo, 2013). according to anugwom et al. (2017), ambient/natural light lure can improve the performance of perforated insect probe trap for monitoring c. maculatus infesting stored cowpea. therefore, ambient light source was created on the cap of the newly designed probe trap as cap window to lure insects to the trap. farmers are faced with a lot of problem in monitoring insect pests in stored cowpea. insect specimens collected with probe traps are undamaged and so are good for research purpose. the standard probe trap is used to monitor c. maculatus infestations in stored cowpea but it is not efficient in trapping the insect due to variation in atmospheric conditions, leading to inappropriate management decisions regarding the action threshold. the standard probe traps is also scarcely available in nigerian markets, and are unknown to grain handlers; even where available, it’s expensive due to high rate of foreign exchange. the standard probe trap with 3 mm perforations is specific to c. maculatus which cannot be used for other larger bruchids like callosobruchus subinotatus, infecting cowpea. thus, there is the need for a probe trap that can be used to monitor all insects infecting stored cowpea. furthermore, since the insect probe trap can be fabricated from locally sourced materials, waste can be converted into wealth. the objective of this study was to fabricate a probe trap for monitoring callosobruchus maculatus using locally sourced materials, determine the thresholds for management decisions during postharvest handling of cowpea, and assess the cost benefit of using the locally fabricated probe trap. 2. materials and methods 2.1 research location fabrication and evaluation of the performance of the modified probe trap on c. maculatus infesting stored cowpea was conducted in the entomology laboratory of nigerian stored products research institute (nspri), kano sub-station (coordinate 11o30’n, 8o30’e) nigeria, between march 2016, to october 2016, at average temperatures of 29 ± 3 oc and 52 to 75 % relative humidity. 2.2 trap development 2.2.1. materials for fabrication of probe trap materials used to fabricate the trap included; anvil, bench-vise, work/vise bench, 1 mm plumbing sockets; threaded male, threaded female and plain respectively, plastic cone (cosmetic container), sand paper, scissors, saw-blade, plastic gum, glue gum, screw driver, measuring tape, plastic materials, plastic funnel, hammer, chisel, steel pipe (1 mm), perforated steel plate (from obsolete automobile silencers and heavy duty equipment casings), needle/office pins, knife, iron sponge, wood-ash, soap and water. http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 646 2.2.2. fabrication and assembly perforated steel material obtained from obsolete automobile parts were first de-coupled using chisel, hammer and anvil, and were straightened back into a flat plate, washed with wood-ash, iron sponge, soap and water to remove rusts. a dimension of 12 x 9.5 cm was measured and cut out using a measuring tape, hammer and chisel. the measured plates were then rolled into cylindrical shape using steel pipe, hammer, bench-vise and anvil. funnels of desired shapes and sizes were cut and glued to the threaded male plumbing socket, to make up the trapping chamber (funnel/tunnel). on the other hand, the threaded female socket was fitted to the plastic cone using glue gum to form the reservoir. about 31.84 mm diameter circle marked out from transparent plastic material was glued to the plain socket at depth of 1.7 cm, forming the cap window of the trap (anugwom et al., 2017). the fabricated components of the trap are presented in figure 1. figure 1: uncoupled parts of the fabricated trap coupling was done by fixing the threaded male socket having the funnel with plastic gum to one end of the perforated steel cylinder, while at the other end; the plain socket with transparent plastic (cap) was fixed with gum. after gum had dried, the threaded female socket (receptacle/reservoir) was screwed to the male socket (funnel) on the perforated probe body to complete the coupling procedure. 2.2.3 trap description unlike the standard probe trap, the cap of the newly developed probe trap is lighted to enhance the attraction of insects to the trap. like most other perforated probe traps, the bottom is cone-shaped with an elongated steel cylinder made up of 4 mm diameter perforations to allow the entry of cowpea weevils but precluding the grains. trapped insects will pass through the funnel into a detachable reservoir from where they can be disposed. the trap assembly and modified cap are shown in figures 2 and 3, respectively. figure 2: components of the fabricated insect probe trap reservoir cap window/light source funnel/tunnel 10.5cm cap 30 cm trapping chamber perforated body file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 647 figure 3: modified cap of an insect probe trap for monitoring cowpea beetle the trapping chamber (receptacle/reservoir) is large, making it appear as a tunnel as well as a pit inside, which prevents captured insects from escaping (lochiavo, 1975; neethiraja et al., 2007; anugwom et al., 2017). 2.3. research materials the experimental materials used in evaluating the performance of the modified trap and the standard check trap were: cowpea grains (kananado variety), cowpea bruchids (0 – 24 hours of emergence), moisture analyzer (ohaus mb25®, usa), illuminance meter (konicaminolta® t10, japan), digital probe thermometer (hanna® instruments, usa), digital thermo-hygrometer (bresser® meade instruments europe), digital calliper, freezer (thermocool), kilner jars, weighing scale (camry, nt-100 kg), sack bags, polyethylene bags, ropes, probe traps (standard check and modified/locally made), insect aspirators, insect collection bottles, storage buckets (34 cm depth with 1037.1 mm body diameter), and clock. 2.4. evaluation of light sources illuminance meter (konica-minolta® t10, japan) was used to determine the intensity of light illuminating through the cap of the fabricated probe trap from the ambient and the result was recorded in lux. the average illuminance intensity of the light source within 24 hours period in the laboratory environment was determined to be 14.30 lx. 2.5. procurement and disinfestations of cowpea grains used for the experiment cowpea grains (900 kg) collected in sealed polyethylene bags were bought from dawanau grain market, kano, nigeria and disinfested by freezing at -20oc to -24oc for 72 hours to keep the sample free of insects (judy and karen, 2000; patrick, 2013; anugwom et al., 2017). after three days, the grains in sealed bags were removed from the freezer and left under ambient conditions for 27 hours to prevent condensational effect on the seeds before use. 2.6. determination of moisture content of cowpea grains used determination of moisture content of grain was done before and after the experiment using the moisture meter (ohaus mb 25) according to mettler (2016) to ascertain if the grain moisture level was affected due to artificial infestations or abiotic conditions; and moisture content of cowpea grains used was determined to be 13.9 % before and 14.1 % after the experiment. 2.7. insect culture adults of c. maculatus were collected from an existing pure culture in entomology laboratory of nspri, kano. clean cowpea grains were disinfested using the cold shock method, to exterminate any insect contamination on the grains prior to culturing of the beetles. the stock culture of c. maculatus were raised by paring 50 adults (male and female http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 648 respectively) in each two-liter kilner jar containing 2 kg of disinfected cowpea and numbering five jars to mate and oviposit. the kilner jars (cultures) were covered with netted cover to prevent the bruchids from escaping. the jars were left to stand for about 30 days until adult emergence under prevailing laboratory conditions with temperature ranging from 29oc – 35oc and relative humidity of 52 to 75 %. freshly emerged adult beetles (0 to 24 hours old) were sieved out, with stipulated numbers counted using the aspirator and placed into labeled collection bottles, for artificial infestation. 2.8. trial of the modified trap using 10 kg and 100 kg cowpea sample a total of two treatments were used which include the fabricated probe trap and a standard check probe trap, each treatment was repeated three times, and in three different insect population densities (3 insects per kg, 7 insects per kg and 15 insects per kg) which were tagged; low, medium and high densities respectively and labeled accordingly. the bruchids were artificially infested into a 10 kg weight of cowpea grains contained in plastic storage buckets (34 cm depth and 1037.1 mm body diameter). the modified trap alone was also evaluated on 100 kg weight of cowpea grains contained in sack bags and artificially infested with three different bruchids population densities (as above), and was repeated three times and labeled accordingly. traps were inspected every 24 hours for five days in both trials and data collected were recorded for further use. 2.8.1. barrier control in order to prevent insects from either leaving or entering the samples, barrier was created, while considering the working conditions. the storage bucket covers were re-constructed for easy insertion and removal of the trap from samples without having to open the covers completely during trap use; such a container also ensured the vertical placement of traps as required for its functionality as well as preventing insects crossing samples (anugwom et al., 2017). the buckets were grey in colour, and resistant to passage of ambient light which prevents insects from being disturbed by ambient light or movement of persons/objects. also, samples in sack bags were stacked in vertical position on pallets and tied to the base of traps’ cap with the trap in top/centre position, leaving the cap of the trap above to receive ambient light. 2.8.2. experimental layout all the traps (18) used for the study were coded and labeled base on trap type and population density of the insect infested. insect collection bottles containing the three different insect densities were labeled as: l, m, and h for low, medium and high insect densities respectively. plastic storage buckets as well as sack bags used were also labeled inline with the insect collection bottles “l, m, and h” respectively for easy application of treatments. samples after artificial infestation were arranged in complete randomized design (crd) format on laboratory benches, while on the other hand, 100 kg samples were stacked on pallets in vertical position on the laboratory floor. 2.8.3. use of traps traps were pre-assigned (labeled) to treatment levels, and then arranged on the laboratory bench for easy allocation to cowpea samples and data collection. traps were first inspected for any residual sample or other contaminants, cleaned, screwed and inserted vertically into the grains through the circular window (for 10 kg samples) created on the storage buckets’ file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 649 cover. the traps’ body was inserted vertically into the grain bulk excluding the cap of the traps, at grain depth of 26 cm (modified traps), and 21 cm (standard check probe trap). while in the case of 100 kg sample, traps were inserted leaving the cap above the sack bag and bag was tied to the base of traps’ cap to receive ambient light. 2.8.4. inspection of traps traps were inspected hours directly after every 24 h for 5 days, they were pulled out from the sacks or buckets and gently hit on a hard surface while still in vertical position to ensure trapped insects were in captured position, before un-screwing to inspect. considerations were made in keeping insects in place during inspection of trap catch each day, water was also used to wet trapped insects in the reservoir before they were discharged and counted. traps after inspection each day were cleaned and returned into the grain samples for another run. 2.9. data analysis data collected were subjected to analysis of variance (anova) using the sas (2000) statistical package, version 9.0 and means were separated using the student newman keuls test (snk) at 5 % confidence level. correlation analysis was done to determine the relationship in trap catches between trapping duration and population density, trapping duration and grain volume, and population densities and grain volume. 2.10. cost benefit analysis profitability of fabricating the insect probe trap was measured in terms of gross margin and net profit in order to ascertain the economic effectiveness of fabricating the probe trap locally (firth, 2002). 3. results and discussion 3.1 fabricated trap and its components the newly fabricated probe trap has a transparent cap window as light lure (figure 3), perforated body made of steel from obsolete automobile silencers, and other body parts made from locally sourced plastic materials as shown in figures 4 and 5. improvised plastic materials and other components used in fabricating the trap were of the desired dimension and shape, and as such fitted well. figure 4: locally made probe trap for monitoring c. maculatus infesting stored cowpea the probe body of the trap has a pointed end made from cosmetic containers, beneath which is the trapping chamber made of plastic funnel. the plastic funnel is lengthy, appearing as tunnel inside, and the reservoir which is 12.5 cm deep, is also detachable (figures 5 and 6). http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 650 from the results, the insect probe trap fabricated from locally sourced material was able to trap c. maculatus in stored cowpea. the perforation size chosen could permit entry of c. maculatus (3 mm) and other pulse insects of 4 mm and below in size, while also precluding entry of cowpea grains into the trap (anugwom et al., 2017). which means the trap can be used to detect other pests of cowpea like c. subinotatus which is 4mm in size. the differences between standard and modified traps are presented in table 1. table 1: variations between the modified trap and standard trap trap part standard trap fabricated trap trap body diameter 28.49 mm 31.84 mm general length of trap 22.5 cm 30 cm length of perforated part 12.5 cm 10.5 cm perforation size 3 mm 4 mm length of trapping chamber 8.3 cm 15 cm length of funnel/tunnel 4.3 cm 10 cm size of reservoir 6.8 cm 12.5 cm cap length/design 1.3 cm, no cap window 4.4 cm, with cap window weight of trap 51.5g 154.7g the difference between the funnel/tunnel and trapping chamber of the modified and standard check traps were as presented in figures 5 and 6 respectively. figure 5: the funnel/tunnel of the locally made probe trap figure 6: schematic illustration of fabricated trapping chamber the modified probe trap has an increased trapping chamber (both in size and length) with a cone-like end. it has a long funnel, which enables the discharge of bruchids into the reservoir as required and as well, prevents their escape from the reservoir. the reservoir is large, resembling a pit inside, while the trapping chamber (funnel) is like a tunnel inside, which means the modified trap can carry larger number of insects. because the reservoir was reservoir funnel/tunnel opening file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 651 detachable, and cone-like, it was easier for the traps to be inserted and withdrawn from grains as well as inspection/disposal of trapped insects. the locally fabricated trap was similar to the standard and it is in conformity with the designs described by anugwom et al. (2017). 3.2 daily trap catches the result of daily trap catches presented in table 2, showed that at day one, the locally fabricated trap had the best trap catch mean (21.0) and was significantly higher (p ≤ 0.05) than the standard check traps’ mean catches. the fabricated trap was also the best mean (8.2) on day 2; it was significantly higher than the standard probe trap mean catch (3.2). at day three, the fabricated trap was higher and significantly different from the standard probe trap. on day four and five, the fabricated trap was higher but similar (p ≥ 0.05) to the standard probe trap. table 2: daily trap catches trapping days treatments day 1 day 2 day 3 day 4 day 5 total insect densities high density 25.3a 9.0a 5.2a 3.2a 3.3a 46.0a medium density 8.5b 5.8b 2.0b 1.2b 1.2b 18.7b low density 4.8c 2.3c 1.0b 0.5b 0.5b 9.2c se ± 0.95 0.88 0.74 0.42 0.59 1.35 trap types fabricated 21.0a 8.2a 3.8ab 2.0a 1.6a 36.6a standard 4.8b 3.2c 1.7b 1.2a 1.8a 12.7c se ± 0.78 0.72 0.60 0.34 0.48 1.10 density * trap ** ns ns ns ns ** means with the same letter are not significantly different at 5 % level of significance using snk. trap catches were decreasing as days goes because insect densities were been reduced by the trap on daily bases, which supports findings by toews and phillips (2002). the fabricated probe trap was quick to reduce insect populations from samples because it is readily visible and the insects find it attractive which was in accordance with findings by ashfaq et al. (2005) who reported that insects are attracted to lights. the standard probe trap became similar to the modified trap on the fourth and fifth days because samples containing the standard probe trap had more un-trapped insects during these days compared to the modified probe traps’ samples with most of its insect already trapped, which supports toews and phillips (2002) and michael and christian (2012) who reported that trap catches are affected by insect density and trapping duration. 3.3 day one trap catches at different population density the result of trap catches at different population densities on day one is shown in table 3. the results showed that at high insect population density, the fabricated probe trap had high trap catch mean value (43.0) and significantly (p ≤ 0.05) higher than the standard check traps’ mean catch (7.7). in medium insect density, the fabricated trap was the best mean and significantly different from the standard check probe trap. at low bruchids population density, the locally fabricated trap was the best mean but it was similar (p ≥ 0.05) to the standard probe tr http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 652 table 3: interactive effect of trap type and population density on number of insect catches on day one treatments population densities trap types high medium low fabricated 43.0a 12.7b 7.3c standard 7.7c 4.3c 2.3c se ± 1.35 means with the same letter are not significantly different at 5 % level of significance using snk. the fabricated trap caught relatively higher number of cowpea weevils compared to the standard probe trap on the first day because of modifications (i.e. cap window, perforation size and total size of trap) which was designed to improve the performance of the trap (anugwom et al., 2017). which means that the modified probe trap was improved compared to the standard check probe trap in early detection of c. maculatus in stored cowpea. 3.4 effect of modifications on the fabricated probe traps performance the result of total trap catches presented in table 2 revealed that the fabricated traps’ mean catches (36.6) was significantly (p ≤ 0.05) higher than the standard probe trap which had lower trap catch mean value of 12.7. the fabricated trap was improved in detecting cowpea weevils; this means that introduction of ambient light source was effective in improving the probe trap for early detection of c. maculatus infesting stored cowpea. findings by ashfaq et al. (2005); dadmal and suvarna (2014) and anugwomet al. (2017), described that insects (coleopterans) are attracted to light and this according to adriana and lars (2001); arnold et al. (2016) was due to visual stimuli. 3. 5 evaluation of trap catches at different population densities the result of trap catches at different population density is illustrated in table 4. the result showed that at high insect population density, the fabricated probe trap had high trap catch mean value (71.7) which was significantly different from the standard check probe trap which had the least mean catch (20.3). at medium bruchids population density, the fabricated trap had mean trap catch of 25.3, which was significantly (p ≤ 0.05) higher than the standard check traps’ mean catch (12.0). under low bruchids population density, the fabricated trap had mean catch of 12.7 which was similar (p ≥ 0.05) to the standard check trap which had lower mean catch of 5.7. table 4: interactive effect of trap type and population density on the total number of insects caught by probe traps population densities trap type low medium high fabricated 38 (12.7)d 76 (25.3)b 215 (71.7)a standard 17 (5.7)d 36 (12.0)d 61 (20.3)cd se ± 1.91 note that values in parenthesis are the mean value and means with the same letter are not significantly different at 5 % level of significance using snk. the modified probe trap was improvement upon and at variance with the standard probe trap catches in the highly file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 653 populated treatment. this can be attributed to presence of light which attracted the insects as supported in findings by arnold et al. (2016). this means that the locally fabricated probe trap was improved in detecting cowpea bruchids in stored grains due to introduction of ambient light source 3.6 correlation of trap catches between trapping duration, population density, and volume of grain the results (table 5) showed that the correlation between trapping duration and population density was negative, and the correlation between trapping duration and volume of grain was also negative, while the correlation between population density and volume of grain was positive. which means that irrespective of population density trap catches were affected by trapping duration and it was contrary to the findings by cuperus et al. (1990) who reported that trap catch increased with increase in trapping duration, and this can be attributed to differences in experimental methods used; either because insect densities were been reduced by the modified trap on daily basis (michael and christian, 2012) or the insects were becoming less active with time (kingsolver, 2004) or due to mortality of the bruchids with increase in time (michael and christian, 2012). while on the other hand, result of correlation between population density and volume of grain showed that both variables affected trap catches. this was because insect densities were the same per kilogram of grain used in both weights (10 kg and 100 kg). the result supports toews and phillips (2002) who reported that probe trap catches are affected by insect density, but was at variance with flinn et al. (2010) whose reports showed that because insect densities are greater at the top and centre of grains and decreasing with grain depth due to temperature effects (flinn et al., 2009). probe trap catches are not affected by grain volume. this was because the cowpea weevils trapped were artificially and homogeneously infested in the grain samples. table 5: correlation matrix of trap catches between trapping duration, population density, and volume of grain time pd30l1 pd70m1 pd150h1 pd300l2 pd700m2 pd1500h2 time 1 pd30l1 -0.911** 1 pd70m1 -0.940** 0.988** 1 pd150h1 -0.854** 0.986** 0.949** 1 pd300l2 -0.906** 0.989** 0.972** 0.986** 1 pd700m2 -0.879** 0.978** 0.976** 0.961** 0.985** 1 pd1500h2 -0.995** 0.896** 0.938** 0.824** 0.882** 0.868** 1 pd (population density), l (low), m (medium), h (high), 1 (10 kg experiment), and 2 (100 kg experiment). 3.7 pest populations detected by the fabricated and standard check probe traps the number of bruchids caught by the modified and standard probe traps respectively per day in the different population densities (high, medium and low) was as shown in figure 7. thirteen (13) bruchids was the average number caught by the fabricated trap per day in samples with 15 insects per kilogram of cowpea grains, while the standard caught four (4) bruchids per day. in samples with 7 insects per kilogram of grain, the average number of bruchids caught by the fabricated and standard trap per day was 5 and 2 respectively. also, the average number of bruchids detected by the fabricated probe trap in sample with low http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 654 insect density (3 insects per kg) was 2 per day, while the standard trap caught 1 bruchid per day. figure 7: average trap catches per day (24 hours interval trapping duration) trap catches of 13 bruchids and above by the modified trap at average temperature of 29 ± 3oc and 52 to 75 % relative humidity indicates that cowpea grains sampled had up to 15 bruchids per kilogram of cowpea grain sampled. trap catches between 12 and 5 bruchids means that the grain sampled contained up to 7 bruchids per kilogram, while trap catches between 4 and 2 bruchids shows that there are about 3 bruchids per kilogram of cowpea grain sampled. the result of trap catches by the modified trap in medium insect density according to hagstrum and flinn (2014) revealed that the bruchids population was within the economic threshold (et) or action threshold (at) where integrated pest management actions should be taken to prevent pest population from reaching economic injury level (christian and william, 2011). in addition, hagstrum and flinn (2014) classified a population as above or below an economic threshold (et) when ≥ 5 insects are caught per probe trap. therefore, other population (that is low) with less than 5 bruchids (2 or 1) caught per trap could be sampled again later to determine if the population is increasing for necessary control measures to be initiated (hagstrum and flinn, 2014). on the other hand, the standard trap detected populations below the action threshold (5 insects) in high and medium densities which means the fabricated trap is improved and useful in economic threshold determination of cowpea beetle infesting stored cowpea. from the results, trap catches of 13 bruchids and above under the above mentioned abiotic conditions has reached the economic injury level (eil) and should be fumigated. 3.8 costs and benefits of fabricating the probe trap locally in carrying out the economic implication of fabricating the probe trap locally and cost of importing the standard check probe trap, the following costs and returns (table 6) were considered. most of the tools used can be re-used for other fabrication enterprise so depreciation was, however, not considered in the course of computation. total cost of fabricating 63 units of the modified trap was n 111, 510.00, while the cost of importing 63 units of the standard trap was n 170, 526.00. price per unit of the modified probe trap was n 1 770, while the price per unit standard check trap was n 2 706.75, therefore, the difference in costs between the modified trap and the standard check trap was n 936.75. 0 2 4 6 8 10 12 14 high density medium density low density modified standard population densities trap catches average daily catches file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 655 table 6: cost benefit analysis of locally fabricated probe trap and standard probe trap locally fabricated probe trap standard check probe trap variables qty up (n) tvc (%) qty up(n) tvc (%) coloured materials 5 500 2500 2.24 traps 63 1738.5 109525.5 64.23 iron sponge 10 30 300 0.27 labour 1 25200 25200 22.6 plumbing socket 189 80 15120 13.56 plastic cone 63 50 3150 2.82 perforated plate 1 15500 15500 13.9 plastic funnel 63 50 3150 2.82 plastic gum 4 1200 4800 4.3 sand paper 1 1000 1000 0.9 super glue 48 50 2400 2.15 transparent plastic 1 1890 1890 1.69 transportation 1 5000 5000 4.48 shipping 1 61000 61000 35.77 anvil 1 5000 5000 4.48 bench-vise 1 8000 8000 7.17 chisel 1 500 500 0.45 hammer 1 1500 1500 1.35 knife 1 400 400 0.36 measuring tape 1 700 700 0.63 pins/needles 1 100 100 0.09 plastic ruler 1 50 50 0.04 saw blade 1 350 350 0.31 scissors 2 1200 2400 2.15 screw driver 2 500 1000 0.9 steel pipe 1 1500 1500 1.35 work-bench 1 10000 10000 8.97 total cost 403 (item) n8030 n11150 100 64 (item) n6279 n17056 100 gr n323810 n401524 gm n322690 n384479 rni n1.90 n1.35 where tvc (total variable cost), up (unit price), qty (quantity per material used), % (percentage cost per variable item), gr (gross revenue), gm (gross margin), and rni (return per naira investment). high costs (22.6 %) spent on labour can be attributed to inadequate selection of tools, which increased the amount and price of labour required during fabrication of the modified trap. the plumbing sockets as well as perforated steel plate were the most expensive materials utilized in the fabrication process because while the plumbing sockets were expensive in the local markets, the perforated steel plate was scarcely available. analysis of the costs also showed that the gross revenue (gr) and gross margin (gm) for profit was high in local fabrication of the probe trap than importation of the standard check probe trap, with higher return realized per naira invested compared to importing the standard probe trap. this was because locally sourced materials were utilized in the fabrication of the modified probe trap; therefore, cost of transportation was reduced as well as cost of exchange rates (mbogo, 2013). the results support the findings by mbogo (2013), showing that fabricating the trap locally is more profitable compared to importing the standard probe trap. http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 656 the locally made probe trap was cheap compared to the standard (imported) probe trap because of high cost of shippment of the standard trap. this means that money was saved from fabricating the trap locally; hence, it is profitable to use the locally made probe trap in monitoring bruchids infesting stored cowpea because it does not depend on foreign exchange rates. indeed, fabricating the trap locally provided, in important respect, a model of how the subsidiary of locally fabricated tool can promote the development of the economy in which it is embedded which can be emulated and replicated in all developing markets (mbogo, 2013). 4. conclusions based on the findings, the following conclusions were made: 1. the modified probe trap was fabricated using locally sourced material. 2. the light source (cap window) design and use of 4 mm perforations improved the performance of the modified probe trap. 3. the modified probe trap catches of 13 bruchid and above within 24 hours trapping period, at average temperature of 29 ± 3oc and 52 to 75 % relative humidity means the sample has reached the economic injury level (eil) and should be fumigated. catches between 12 and 5 is within the action threshold (at), control measures must be applied to prevent pest populations from reaching the economic injury level. while catches of 2 or < 5 is below the action threshold (at) and sampling must be done again before a growing brchids population can cause economic losses. 4. the modified probe trap was n 936.75 cheap compared to the standard probe trap and had higher return per naira invested in the fabrication process. references adeola, ss., folorunso, st., gama, en., amodu, my., and owolabi, jo. 2011. productivity and profitability analyses of cowpea production in kaduna state. pelagia research library; advances in applied science research, 2(4): 72 -78. adriana, db. and lars c. 2001. the evolution of color vision in insects. annual review of entomology, 46:471–510. ajeigbe, ha., abdoulaya t. and chikoye d. 2008. legume and cereal seed production for improved crop yields in nigeria. proceedings of the training workshop on production of legume and cereal seeds, 24 january – 10 february, international institute of tropical agriculture, kano station kano, nigeria. 108 pp. anugwom, ud., bamaiyi, lj., magaji, bt., oparaeke, am. and arowora, ka. 2017. effects of different colors of light source on probe trap catch of cow-pea weevil infesting stored cowpea. international journal of biological and environmental engineering, 2(1):1-8. arnold, sej., stevenson, pc. and belmain, sr. 2016. shades of yellow: interactive effects of visual and odour cues in a pest beetle. peerj, 4: e2219; doi 10.7717/peerj.2219. ashfaq m., rashid, ak., ahsan, mk., fahad r. and shahid h. 2005. insect orientation to various colour lights in the agricultural biomes of faisalabad. parkistan entomology, 27 (1): 49 – 52. barak, av., burkholder, we. and faustini, dl. 1990. factors affecting the design of traps for stored-product insects. journal of kansas entomological society, 63: 466 485. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com uzoma et al: fabrication of probe trap for monitoring cowpea weevil infesting stored cowpea. azojete, 18(4):643658. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 657 carlos g. 2004. cowpea: post-harvest operations. inpho-post-harvest compendium; food and agriculture organization of the united nations, rome, italy., pp. 1 70. christian n. and william, gm. 2011. the economic injury level and action threshold in stored-product systems. stewart postharvest review, (8): 1-8. doi: https://doi.org/10.2212/spr.2011.3.3 cuperus gw., fargo, ws., flinn, pw. and hagstrum, dw. 1990. variables affecting capture of stored grain insects in probe traps. journal of the kansas entomological society, 63(4): 486 – 489. dadmal, sm. and suvarna k. 2014. insect faunal diversity collected through light trap at akola vicinity of maharashtra with reference to scarabaeidae of coleopteran. journal of entomology and zoology studies, 2(3): 44 – 48. fatima, ms., amjad u., kamran s., muhammad a., bismillah s., muhammad a., nazeer a., khwaja j., syed r. ali s. and inayat r. 2016. rearing and identification of callosobruchus maculatus (bruchidae: coleoptera) in chickpea. journal of entomology and zoology studies, 4(2): 264-266. firth c. 2002. the use of gross and net margins in the economic analysis of organic farms. in: powell et al. (eds), uk organic research 2002: proceedings of the cor conference, 26-28th march 2002, aberystwyth, pp. 285-288. flinn, pw., opit, gp. and throne, je. 2009. predicting stored grain insect population densities using an electronic probe trap. journal of economic entomology, 102(4): 1696 – 1704. flinn, pw., hagstrum, dw., reed c. and phillips, tw. 2010. insect population dynamics in commercial grain elevators. journal of stored products research, 46: 43 – 47. food and agricultural organisation 2013. save food: global initiative on food losses and waste reduction. fao, rome. available at: http://www.fao.org/save-food/key-findings/en/; retrieved 23-03-2015. hagstrum, dw. and flinn, pw. 2014. modern storedproduct insect pest management. journal of plant protection research, 54(3): 205-210 institute for agricultural research, 2012. policy brief on potentials and constraint on cowpea for food and poverty alleviation, retrievable at www.aatf.africa.org. accessed 7th october, 2016. judy, aj. and karen, av. 2000. control of cowpea weevil, callosobruchus maculatus, using freezing temperatures. horticultural crops research laboratory usda-ars. google library; retrieved 2014-12-19. kingsolver, jm. 2004. handbook of the bruchidae of the united states and canada (insecta; coleoptera). u.s. department of agriculture, technical bulletin 1912, 1: 82-86. langyintuo, a., lowenberg, dj., faye m., lambert d., ibro, g., moussa, b., kergna, a., kushwaha, s. and ntoukam, g. 2003. cowpea supply and demand in west africa. field crops research, 82: 215-231. http://www.azojete.com.ng/ mailto:uzomaanugwom@yahoo.com https://doi.org/10.2212/spr.2011.3.3 http://www.fao.org/save-food/key-findings/en/ http://www.aatf.africa.org/ arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):643-658 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: uzomaanugwom@yahoo.com 658 lester ee. 2006. integrated pest management (ipm): definition, historical development and implementation, and other ipm. pest management science, 62:787-789. loschiavo, sr. 1975. field tests of devices to detect insects in different kinds of grain storages. the canadian entomologist, 107: 385-389. marianne, sc. and rebecca l. 2011. insect vision: ultraviolet, colour, and led light. university of georgia, department of entomology; news letter. pp. 4. available online at www. discoverlife.org. mettler t. 2016. moisture determination with the halogen moisture analyzer. guide to moisture analysis; procedures basic principles, leicester, united kingdom. available at: www.mt.com/moisture. mbogo g. 2013. impact of local sourcing initiatives: a case of nile breweries ltd (sabmiller) sorghum and malting barley programmes. an initiative of nile breweries ltd, jinja, uganda. michael, dt. and christian n. 2012. trapping and interpreting captures of stored grain insects. stored product protection department, kansas state research and extention. www.ksre.ksu.edu. neethirajan s., karunakaran c., jayas, ds., white, ndg. 2007. detection techniques for stored product insects in grain. journal of stored products research, 18: 157-162. patrick k. 2013. preserving our history: freezing infested materials. integrated pest management working group, low temperature treatment fact sheet. available at http://www.museumpests.net/treatment.asp., peace, 2015. cowpea production in nigeria. agronigeria. landmark centre, lagos nigeria. available at www.agronigeria.com.ng/cowpea philips, tw., cogan, pm. and fadamiro, hy. 2000. pheromones; in alternatives to pesticides in stored products ipm. (b.h. subramanyam and d.w. hagstrum, eds)., pp. 273-302. kluwer academic publishers, boston. sarwar, m. 2015. extermination of insect pests (coleoptera: bruchidae) and damage of stored pulses by different methods in market. american journal of marketing research, 1(3): 99-105. toews, md., and phillips, tw. 2002. factors affecting capture of cryptolestes ferrugineus (coleoptera: laemophloeidae) in traps placed in stored wheat. journal of economic entomology, 95(1): 200 – 207 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:uzomaanugwom@yahoo.com http://www.ksre.ksu.edu/ http://www.museumpests.net/treatment.asp http://www.agronigeria.com.ng/cowpea arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):151-160 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 151 development of smart meter for energy billing and power management a. a. raji1* and s. o. oladosu2 1department of electrical and electronics engineering, olabisi onabanjo university, ibogun campus, ibogun, ogun state. 2department of electrical and electronics engineering, d.s. adegbenro i.c.t polytechnic, itori-ewekoro, ogun state. *corresponding author's email address: akeem.raji@oouagoiwoye.edu.ng article information submitted 16 oct., 2023 revised 6 december, 2023 accepted 12 january, 2024 keywords: energy bill energy conservation electronic meters microcontroller power management abstract rising cost of energy tariff in nigeria has brought to the fore the need for energy savings and power management. however, existing prepaid meters in the country are not user friendly. they do not give room for users to track power usage in a bid to observe the impact of load increase on units of energy purchased from utility providers. load profiles like voltage, current and power of connected loads are not displayed on the energy meters making it impossible to conserve energy and manage power. in addition, these meters do not send notifications to consumers on the status of energy subscription. this study therefore developed a single-phase smart energy meter that availed consumers the opportunity of observing load changes on the screen from time to time. it notified customers via short message service (sms) when energy subscription was made and when unit of energy was low. the system consisted of hardware and software parts. the hardware parts composed of power supply unit, sensing unit, display unit, gsm module and energy meter. the software part involved programming atmeg328p microcontroller enshrined on arduino nano board using c# programming language. the system displayed energy worth of 50wh for 4naira on the first recharge. this unit of energy was exhausted after leaving the system for several hours by connecting appliances like electric fan, soldering iron and electric iron. in particular, the system displayed power value of 114.73w when standing fan and two soldering irons were connected to the system. the power of connected load increased to 216w when electric iron was added. in addition, the system displayed unit of energy used and the remaining unit at every point in time. it also sent notifications to consumers through sms to subscribe when energy unit was less than 5wh and stopped working when energy unit was exhausted. it was therefore seen that the system was functional and displayed load profile (power and voltage) changes appropriately. the system is suitable for use in residential buildings, offices and applications where energy management is required. 1.0 introduction in the time past, electricity billing in nigeria was done by officials of the defunct national electricity power authority (nepa) who moved from house to house to take energy readings on installed meters. these readings were used to generate energy bills given to the consumers at the end of the month. in the absence of installed meters, customers were given estimated bills based on assumed energy totals. this system of energy billing is not only time consuming but also tedious as it requires large work force to cover many households. it is prone to errors and a number of households may be left uncovered. this process may be hampered or affected http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):151-160. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 152 by weather conditions. it is also shrouded in secrecy as customers may not be aware of what constitutes energy bill they are expected to pay at the end of the month. with advancement of technology, there came an introduction of electronic prepaid meters where households subscribe to utility providers before they are given access to use the energy (adebisi et al., 2022). though the prepaid meters gve sound alarm when energy unit is low, many consumers are either oblivious of this alarm or do not understand the importance of sound alarm. most often than not, customers wait until they exhaust all the energy units and are disconnected from supply before they make another recharge. in addition, these prepaid meters do not display how energy is consumed and customers may not be able to pinpoint which device is consuming more power, therefore giving no room for energy conservation and management. a number of research works have addressed different aspect of metering problems. for example, sheelasobanarani et al. (2014) simulated prepaid energy metering system on proteus software while rodrey et al. (2007) proposed automatic power meter reading solution that allowed energy providers to monitor energy consumption and produce corresponding bills which were sent to consumers by short message service (sms), electronic mail (e-mail) and postal service. load monitoring and auditing system was developed by adebisi et al. (2022) which informed users of the energy utilized and balance via google mail. customers in places with poor internet facility may not be able to access the google mail to receive updates on energy consumption. an automatic energy metering system for gaining control over consumers load was developed by okokpuji et al. (2020) and bobade et al. (2016). rachananjali et al. (2016) proposed an approach for preventing meter tampering. other research works reported in the literature have focused on implementation of smart energy metering system based on global system for mobile (gsm) communication technology (jain et al., 2012; aniedu et al., 2016; bhat et al., 2017; mortuza et al., 2020; odusami et al., 2019; oyubu and nwabueze, 2015 and egwale and odia, 2016) while gupta et al. (2017) incorporated memory in its gsm based solution. amhenrior et al. (2022) developed a low cost smart prepaid meter which integrated gsm and wireless-fidelity technology. devi et al. (2019) developed an automatic energy meter reading system using raspberry pi and internet of things (iot). ragul et al. (2020) designed and constructed iot based smart energy meter that sent energy readings to the web server. nwagbo et al (2019) developed an arduino based energy meter. sabahat and rajderkar (2019) constructed theft detecting energy meter that cut off users once energy theft was detected. a smart energy metering solution using zigbee and gsm module was developed elsewhere (myilsamy, 2015; revidi et al., 2015 and suresh and mangaleswari, 2016). muhammad et al. (2023) developed energy metering system that sent energy readings to utility providers via sms. in addition, ogidan et al. (2023) developed a gsm based smart energy meter for real time notification of consumers. these research works fail to address how users can monitor load profile changes that will afford them the opportunity of managing the power effectively by providing avenue for energy conservation and energy savings. hence, this work develops smart energy meter that displays energy readings, power consumption of connected loads, units of energy use and balance. it gives notifications via sms to consumers at different time instant to intimate them of when energy subscription is effected, when they are running low on energy subscription and after exhaustion of purchased energy. consumers observe power utilized by connected loads at different time instant. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng raji and oladosu: development of smart meter for energy billing and power management. azojete, 20(1):151-160. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 153 2.0 materials and methods 2.1 system description figure 1 illustrates the basic building units of the system. it consists of power supply unit that transforms alternating current (a.c) source to the direct current (d.c) required to power the system components, sensing unit, gsm module, display unit, relay unit and energy metering unit. a.c source sensing unit (voltage and current sensor) power supply unit control unit (atmeg328p arduino microcontroller) relay driver relay load gsm module customer’s mobile phone display unit figure 1: block diagram of energy metering system 2.1.1 power supply unit this unit provides the required voltage for the components of smart energy meter. figure 2 shows the power supply unit simulated on proteus software. the 220/12v transformer ( )1tr steps down 220v a.c source to 12v a.c which is rectified to d.c form using bridge rectifier circuit 1 4( )d d− with four kbl406 diodes. the ripples in the d.c output waveform are removed by 2200 f capacitor. 7805 and 7812 voltage regulators are utilized to regulate the d.c output voltage to 12v d.c and 5v d.c to power the arduino board and relay unit. figure 2: power supply unit http://www.azojete.com.ng/ akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):151-160. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 154 2.1.2 sensing unit this unit comprises current and voltage sensors. the current sensor determines or measures load current in the energy meter. an acs-712 is utilized as the current sensor because of its non-invasive nature. the current sensor utilizes halleffect technology for its operation. voltage sensor on the other hand measures the supply voltage. figure 3 depicts the circuit diagram of voltage sensor, wherein step down transformer at is utilized to reduce 220v a.c to 12v a.c. in a bid to reduce the voltage to within the operational voltage of arduino microcontroller in the range of 0-5v, a 2.5 d.c offset voltage is added by two 100k resistors. ac input to the arduino 100k 100k 1r 2r 5v+ 3r100k 100k 4r at 220:12 220v 12v220v + − 2.5 .v d c figure 3: voltage sensing circuit 2.1.3 relay unit the relay disconnects the load when the energy unit is zero and energizes the connected load when the customer subscribes or recharges his or her account. a 15a electromechanical relay is used to control the customer’s load. the relay driver interfaces between the relay and arduino microcontroller and is employed to drive the relay to disconnect and reconnect customer’s load. in this work, uln2003 relay driver is utilized. it is made up of seven open collector darlington pairs having common emitter. this implies that, the relay driver has the capability of controlling seven different relays at a time. 2.1.4 control unit the main brain behind the smart energy metering is arduino microcontroller (at mega 328p). data fetching and overall circuit operation is centered on the microcontroller. it fetches the current and voltage values from current and voltage sensor and transforms them into power and energy values using equations (1) and (2) ( ) cospower w iv=  (1) and ( ) cosenergy wh iv t=  (2) in which w stands for watt which is the unit of power, i is the current rating of the load in ampere, v is the a.c power supply voltage in volt and cos is the power factor while t is the time in hour (h) for which the load is in operation. here, 0.8 power factor is employed. in addition, the microcontroller sends signal to the relay to disconnect the load when the energy unit is zero and reconnects when the user recharges. it also communicates with the gsm module for transfer of sms to users at appropriate time most especially when consumers subscribe, or energy unit is less than 5wh and ultimately when customers run out of energy units. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng raji and oladosu: development of smart meter for energy billing and power management. azojete, 20(1):151-160. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 155 2.1.5 gsm module an ultra-compact and wireless sim900 gsm module is used which has a modem that allows it to connect to personal computer (pc) and microcontroller serially. the module utilizes gsm technology for communication with the user with a mobile subscriber identification module (sim), for transferring sms from utility provider to the customers. for the purpose of execution, an airtel (telecom operator in nigeria) sim card is inserted into the gsm module for the transfer of sms. 2.1.6 display unit this unit is utilized to display information concerning energy totals for a given subscription, remaining energy unit or balance, energy and power consumed as well as values of voltage and current of connected load. an 16 2 liquid crystal display (lcd) module is employed to display aforementioned information on the screen. figure 4 illustrates the circuit diagram of the energy meter linking various units of the system. figure 4: circuit diagram of smart energy meter (nwagbo et al., 2019) 2.1.7 system software design the main activity that is carried out here is implementation of equations (3.1) and (3.2) and development of code that controls the activities of the arduino microcontroller board using c# programming language. the basic operation of the system is guided by the flow chart presented in figure 5. http://www.azojete.com.ng/ akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):151-160. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 156 figure 5: flow chart of the operation of smart energy meter 2.1.8 performance test the developed model of the smart energy meter is presented in figure 6 which depicts the external features of the smart meter such as 13a socket for load supply, 5v d.c source and lcd screen while figure 7 illustrates the internal features of the model showing basic components like gsm module, atmeg 328 arduino microcontroller, 220/12v transformer, capacitor, power switch and connecting wires among others. figure 6: external feature of the smart energy meter file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng raji and oladosu: development of smart meter for energy billing and power management. azojete, 20(1):151-160. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 157 figure 7: internal circuitry of the smart energy meter in order to test the operation of the system, an initial energy of 50wh was purchased for 4 naira. figure 8b showed the system under test with standing fan and two soldering irons. (a) (b) (c) figure 8: system under test (a) sms received for energy recharge (b) energy meter with connected load with lcd showing used energy and balance and (c) lcd displaying power, current and voltage values of connected load however, in order to observe load changes and track power increase, a pressing iron was added to the load as shown in figure 9. however, the system was left in operation for a number of hours. (a) (b) figure 9: energy meter under test with connected load and showing increase in power consumption figure 10: system under test (a) energy unit is less than 5wh and (b) sms received http://www.azojete.com.ng/ akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):151-160. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 158 figure 10a showed the system under test with lcd displaying the used energy while figure 10b showed the sms received in such an instance. furthermore, figure 11 illustrated the system in operation when the energy unit is less than 2wh and 1wh. (a) (b) figure 12: system under test with lcd displaying light cut off and recharge figure 11: system under test showing (a) energy unit that is less than 2wh and (b) energy unit that is less than 1wh finally, when energy unit on the system is zero and the purchased energy unit is exhausted, figure 12 showed the lcd displaying zero unit and zero balance and as well informed the customer regarding no balance and request for recharge. 3.0 results and discussion it was observed from the performance test carried out in this work that the system displayed energy unit of 50wh on recharge of 4 naira as indicated in figure 8(a). it was seen that when loads including standing fan and two soldering irons were connected to the system, power value of 114.73w was displayed while the supply voltage of 220v was observed on the system as illustrated in figure 8(c). however, on adding pressing iron to the existing load, the power increased to 216w which was observed in figure 9. the system was left for several hours until the energy unit was less than 5wh as presented in figure 10. furthermore, test revealed also that the system displayed 2wh and 1wh as the unit of the energy was further reduced. this was observed in figure 11. figure 12 showed the lcd screen of the system intimating customers to recharge when the customers exhausted all the energy units earlier purchased. in this case, it was observed that the system stopped working and failed to supply electricity to the connected loads. 4.0 conclusion the existing metering system in nigeria does not provide avenue for consumers to observe instant changes in power utilized as load profile of connected devices is usually not displayed. the meter is also unable to provide notifications either by short message service or electronic mail to intimate consumers of status of energy subscription. it is in this connection that this work developed an alternative means of smart energy metering which monitored customers’ energy usage, determined and displayed the energy and power used by consumers. it sent notifications to users when subscription was made and informed customers via sms whenever customer was running low on energy as well as when customers were out of energy. a number of tests carried out showed that the system was functional and performed to expectation, facilitating sms transfer using gsm module with airtel sim card mobile network. appliances like fan, electric iron and soldering iron were used as candidates for testing the developed file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng raji and oladosu: development of smart meter for energy billing and power management. azojete, 20(1):151-160. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 159 system. the system displayed voltage value of 220v and power value of 114.73w when standing fan and two soldering irons were connected to the system. however, it was seen that the power increased to 216w when pressing iron was added to the system. these loads were left for hours until the energy unit was exhausted. it was seen that the system responded to changes in connected loads appropriately. the meter was efficient in obtaining energy readings and exhibited fast means of transfer of messages from utility provider to the customers. the smart meter is recommended for use in residential buildings, offices and hospitals. references adebisi, oi., adejumobi, ia., mathew, s. and abdusalam, aa. 2022. development of a webbased single-phase load monitoring and auditing system. international journal of electrical and computer engineering (ijece), 12(6): 6785-6795. amhenrior, he., oloma, i. and ikharo, ba. 2022. design and implementation of a gsm and wifi based low cost smart prepaid energy meter. proceedings of 2022 5th information technology for education and development, held in abuja, nigeria, 01-03 november 2022 https:// doi.org.10.1109/ited56637.2022.10051577, accessed on 5th december, 2023. aniedu, an., inyiama, hc., chukwuneke, cj. and asogwa, dc. 2016. smart energy meter for load control using mobile communication technology. international journal of electrical and telecommunication system research, 8(8): 23-28. bhat, s., shetty, kb., reshma, j-d., shetty, s. and rajesh, sr. 2017. gsm based automatic meter reading and billing system. international journal for research trends and innovation, 2(7):2124. bobade, ss., jadhav, vs., mokal, aa. and mahajan, kd. 2016. automatic energy meter billing system with theft detection. international research journal of engineering and technology, 3(4): 237-240. devi, pb., abdul ayyub, mm., raja, ar., kumar, vsv. and vishnu, v. 2019. automatic energy meter reading using raspberry pi and iot. international journal of electronics and communication, special issue icrtcret, 03: 19-22. egwale, jo. and odia, oo. 2016. development of a gsm-based smart energy meter. international journal of electrical and telecommunication system research, 8(8): 8-14. gupta, t., karnal, v., pandey, p. and verma, g. 2017. gsm based design and development of smart energy meter using eeprom, lcd and microcontroller, gyancity. journal of electronics and computer science, 2(1): 49-57. jain, a., kumar, d. and kedia, j. 2012. smart and intelligent gsm based automatic meter reading system. international journal of engineering research and technology, 1(3): 1-6. nwagbo, c., ezekwe, cg. and ituma, c. 2019. design and construction of gsm based prepaid energy meter using arduino. academic research international, 10(31): 33-41 mortuza, mg., ahmed, zu., jaki, h., ahmad, mr., uddin, mj. and kabir, mh. 2020. gsm based automatic energy meter reading and billing system. european journal of engineering research and science, 5(6): 725-730. myilsamy, k. 2015. automated wireless meter reading system for controlling power consumption. international journal of engineering and science (ijes), 70-74. http://www.azojete.com.ng/ akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):151-160. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: akeem.raji@oouagoiwoye.edu.ng 160 muhammad, a., hammed, s., muhammad, n., muhmmad, ss. and faizan, q. 2023. intelligent smart energy meter reading system using global system for mobile communication. intelligent systems and applications, 1:35-47 odusami, m., abayomi alli, o., misra, s., ugbabe, d., ahuja, r. and maskeliunas, r. 2019. an improved sms based metering system.emerging technology in computer engineering: microservices in big data analytics, 192-204. ogidan, ok., temikota, ko. and omale, i. 2023. development of a low cost gsm-based smart energy meter for real time notifications. uniport journal of engineering and scientific research (ujesr), 7(1): 58-69. okokpujie, k., abayomi-alli, a., abayomi-alli, o., odusami, m., okokpujie, p. and akinola, oa. 2020. an automated energy bill metering system based on gsm technology. journal of natural science, engineering and technology, 19(1&2): 25-39. oyubu, ao. and nwabueze, ca. 2015. design and testing of a smart energy metering system based on gsm modem. european journal of engineering and technology, 3(4): 35-42. rachananjali, k., bala krishna, bkk., and narasimha-rao, chn. 2022. automatic energy meter reading for multiple devices employing prepaid alerting system. international journal of health sciences, 6(1): 6844–6853. https://doi.org/10.53730/ijhs.v6ns1.6461, accessed on october 10, 2023. ragul, k., mukul, m., vijay, p. and rajkumar, p. 2020. design and implementation of smart energy meter using iot. international research journal of engineering and technology (irjet), 7(4): 4448-4451 revidi, s., vedachary, m. and reddy, ak. 2015. gsm and zigbee based automatic energy meter reading system with instant billing. international journal of scientific engineering and technology research, 4(55): 11091-11097. rodney tan, hc, lee, ch. and mok, vh. 2007. automatic power meter reading system using gsm network. proceedings of the 8th international power engineering conference (ipec 2007), held at singapore, 03-06 december, 2007, 465-469. sabahat, a. and rajderka, k. 2019. design and implementation of remotely located energy meter monitoring with control and theft detection through gsm. iosr journal of engineering, 9(5):15-20. suresh, g. and mangaleswari, n. 2016. design and implementation of smart energy meter for the smart grid. international journal of advanced research in basic engineering sciences and technology, 3(20): 25-31 sheelasobanarani, k., dineshraja, s., dhanaraj, b., manickan, k. and raja, kk. 2014. an integrated prepaid energy meter using gsm. international journal of industrial electronics and electrical engineering, 2 (5): 5-7. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://doi.org/10.53730/ijhs.v6ns1.6461 arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):581-600 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 581 development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems d. o. awosanya*, a. a. murana, and a. a. olowosulu department of civil engineering. ahmadu bello university, zaria, nigeria *corresponding author's email address: awosanyaolugbenga2015@gmail.com article information submitted 29 march, 2023 revised 19 december, 2023 accepted 23 december, 2023 keywords: traffic analysis axle load spectra traffic classification wim axle load distribution (axle load spectra) axle load quantification factors abstract design traffic is employed in this research to estimate the expected load repetitions for a given axle load spectrum during the pavement life. in changing traffic characterization in mechanistic-empirical (m-e) design procedure, the process does away with the equivalent single axle load (esal) concept and traffic analysis implementation was done by directly using axle load. comparison of predicted number of axle load range repetitions determined by equivalent axle load factor (ealf) and general axle load equivalency factors (gaf), is the main objective. in this study, axle load spectrum by weigh-in-motion (wim) data and parametric standard axle loads which cause equal damage were collected and utilized. determination of the axle load distribution factor (aldf) from the wim data. it is a critical input in the method based on different axle load groups for the estimation of the predicted number of axle load repetitions during the pavement design period. the results that the marked difference on the estimated predicted axle load predictions with the determination of ealf and gaf 63.95% of gaf value for sast. similarly, 10.14% for sadt; 30.24% for tadt and 21.43% for trdt. this indicates the inherited error in the empiricism content in the empirical approach of handling traffic, for the determination of ealf. the estimated traffic prediction value increases as the captured axle load magnitude increased, as a resultant of the type of commodities and goods carried on the roadway pavement. 1.0 introduction the characterization of traffic is one of the significant elements in the analysis and design of pavements (flexible, rigid, and composite), (buch et al., (2009), timm and newcomb (2002) observed that the primary change in traffic analysis when using mechanistic -empirical (m-e) design is the elimination of the load equivalency factors and calculation of equivalent single axle load (esals), and determines the expected number of repetitions of each load during the pavement life directly using axle load spectra. in this approach, the anticipated truck traffic is classified by axle type (steering, single, tandem, and tridem), and within each axle type, the distribution of axle weights is calculated. this is a more precise characterization of truck traffic loads, and it allows for more detailed and nuanced damaged investigations (salama and chatti, 2011). pavement engineering calculations using axle load spectra are generally more complex than those using esals or traffic index (ti) because loading cannot be reduced to one equivalent number. however, the load spectra approach of quantifying traffic loads offers a more practical and realistic representation of traffic loading than using ti or esals (highway design manual, 2012). the load input to (m-e) methods in changing of traffic characterization is in terms of axle load distributions (i.e., load spectra) by axle configuration. this approach is a significant improvement over the aggregate esal-based method described previously, because it allows a http://www.azojete.com.ng/ mailto:%20efegabs@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 582 mechanistic pavement design approach. (papagianakis and massad, 2008). axle load distribution factors (aldf) represent the percentage of the total number of truck axle repetitions within each load interval (which varies with axle type) for each axle type. aldf constitute a major change from the current 1993 aashto pavement design guide that requires only the total number of 18-kip esals as input (kim et al., 2011) in characterizing effects of applied loads of mixed-traffic stream, the combined loading effects of different axle types in the design traffic must be considered when designing a pavement. there are two common approaches by which the combined effects are evaluated: one based on the hypothesis of cumulative damage, and the other by the method of equivalent load. under the hypothesis of cumulative damage, where the design repetitions of load for each axle type is a critical input whereby the total amount of damage caused by the mixed traffic is computed as the sum of damage ratios of all load types. (oguara, 2004, fwa et al., 2006; huang, 2007; and timm and newcomb, 2002) method based on different axle load groups in traffic analysis is when the design is based on a number of axle load groups, as characterized by the aldf, whereby, the predicted number of repetitions for each axle load group during the design period is determined. the procedure for predicting the predicted number of repetitions for each axle load group during the design period is similar to the method based on esal, except that each load group is considered separately. the initial repetitions of each axle type, growth factor, directed distribution factor (ddf), and lane distribution factor (ldf) are determined. these are critical variables required for the computation of repetitions of each axle type for a period of 20 years for a flexible pavement. nigerian empirical mechanistic pavement analysis and design system is a framework for mechanisticempirical pavement design for tropical climate developed by olowosulu, (2005). two major components in nempads that required to be refine, that were (1) traffic data are required in the m-e pavement design procedure. it is expressed in terms of 8, 200 kg (80 kn) equivalent single axle loads (esals)and secondly, simplified procedure for prediction of pavement response in the prediction pavement performance. the focus on changes in traffic characterization is the main interest in this research study, for transition from using equivalency factors to determine the number of equivalent single axle loads (esals) to a push toward using load spectra in nempads. report 1-26 recommended that traffic should be divided into a number of load groups, each with different load magnitudes and configurations and different numbers of load repetitions (huang, 2007). the main objective of this study is to compare the estimated number of repetitions of each axle load range for each axle type during the pavement life using ealf determined from the empirically based approach and determined gaf from the (m-e) methods, respectively, and then to recommend the most accurate and reliable estimated predicted number of load repetitions this is achieving with following objectives:( 1) determination of axle load damage factor with the same traffic composition with either of these pavement design approaches: computation of ealf based on empirical based method and gaf based on (m-e) method. (2) estimation of the expected number of repetitions of each axle load range during the pavement life by either utilizing ealf or gaf. the scope of this study, includes the (1) the collection of traffic information that includes the axle load spectrum by portable wim data and loading on the axle configurations considered in this study, that cause the same amount of damage at the standard axle. the determination of aldf is from the analysis of the traffic data. traffic analysis using the method based on different axle load groups technique has been used to estimate the predicted number of load repetitions. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 583 axle load damage factors were computed on the basis of the pavement design approach. ealf was computed on the basis of handling traffic on empirically based approach and gaf was computed on the basis of handling traffic in (m-e) methods. both axle load damage factors were the critical tools with the aldf were the determined traffic inputs utilized to estimate the predicted number of load repetitions within the two considered approaches respectively, and then compared with each other. the scope of this study, includes the (1) the collection of traffic information that includes the axle load spectrum by portable wim data and loading on the axle configurations considered in this study, that cause the same amount of damage at the standard axle. the determination of aldf is from the analysis of the traffic data. traffic analysis using the method based on different axle load groups technique has been used to estimate the predicted number of load repetitions. axle load damage factors were computed on the basis of the pavement design approach. ealf was computed on the basis of handling traffic on empirically based approach and gaf was computed on the basis of handling traffic in (m-e) methods. both axle load damage factors were the critical tools with the aldf were the determined traffic inputs utilized to estimate the predicted number of load repetitions within the two considered approaches respectively, and then compared with each other. 2. materials and methods. to determine the number of load repetitions of each axle type for a period of 20 years on a flexible pavement, the required transport information and the analysis of the traffic data are utilized in the following considerations: 2.1 input data characterization and axle load spectra this includes truck traffic load data; axle configuration and equivalencies; als records; analysis of als data of the independent axle load surveys; and truck traffic information. 2.1.1 truck traffic load data truck traffic information is used for estimating pavement loading known as axle load spectra, incorporated into the (me) design procedure. this information involves the independent axle load surveys and loads on the axle configurations that cause the same amount of damage as the standard axle 2.1.2 axle configuration and equivalencies the damage due to different axle groups is dependent on the axle spacing, the number of types per axle, the load on the group and the suspension. for design purposes, it is generally appropriate to consider axle groups in terms of the following four types: • single axle with single wheels; (sast); • single wheels single axle with dual wheels; (sadt); • tandem axles both with dual wheels; (tadt); • tridem axles all with dual wheels; (trdt). table 1: axle loads which cause equal damage axle configuration sast sadt tadt trdt load (kn) 53 80 135 181 source: road design part 2pavement, campwo3-102-99; austroads (2004b) and 2012 the standard axle is defined as a defined as a single axle with dual wheels that carries a load of 8.2 tonnes (80kn). loads on the axle configurations given above that cause the same amount of damage as the standard axle are given in table1. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 584 2.1.3 als records according to ahmed and erlingsson, (2015), als is one of the key inputs for m-e design of pavement structures (lu and harvey 2006). swan et al. (2008) have also indicated that the als was one of the most significant factors in the m-e pavement design. in this paper, the axle loads and configurations from wim instruments are usually presented in the form of the als or frequency distribution of the axle load groups of a given axle configuration. therefore, raw wim data must be analyzed to produce the als. this traffic data was captured by a portable weigh-in-motion (wim) system on kaduna zaria roadway with the following details: (i) number of axles; (ii) gross vehicle mass (gvm); and (iii) individual axle weights, recorded in” tons”. the data are grouped into different axle loads for each axle configuration (steering, single, tandem, tridem and quad). usually, the axle load interval or bin width of 10 kn is used to group the axle loads for sast and sadt; bin width of 20kn for tadt and bin width of 30kn for trdt. the frequency for each load group is then calculated to derive the als. 2.1.4 analysis of als data of the independent axle load surveys the independent axle load surveys have become the main source of up-to-date vehicle weight data, as there have no recent data on weighbridge operations is available. the wim data contains vehicle classification and axle group load data. traffic survey conducted as secondary data by (stewart scott international, 2007) on kaduna zaria northbound and zaria kaduna southbound. als data captured on the kaduna –zaria roadway was used for the study. measurements were made on the northbound axis (kaduna-zaria) on 5th march, during the 9.am and 3.00pm (about 6hrs) and similar exercise was conducted on the southbound axis (zaria-kaduna) on 6th of march, 2007. the als for the roadway have been developed which provide the load distribution of steering axles, other single axles, tandem axles and tridem representative als for the roadway. the als for the sites has been developed which provide the load distribution of steering axles, other single axles, tandem axles and tridem axles (awosanya et al., 2021). als data from the independent axle load surveys was used for the study. 2.1.5 truck traffic information truck traffic information adopted from the secondary data of the work of s.s.i (2007) includes: results of independent axle load surveys for kaduna-zaria roadway traffic volume: adt (2006) = 11,000; percent truck =8%: adt (1983) =7402 defaults = ddf = (1.0); ldf (0.5); design period=20yrs 2.2 methods 2.2.1 axle load information from the truck traffic information. axle load information includes axle configurations, average number of axles per truck, and axle load distribution factors. 2.2.1.1 axle configuration axle configuration is defined by the number of axles sharing the same suspension system and the number of tires in each axle. multiple axles involve two, three, or four axles spaced 1.2 to 2.0 meters apart, and are referred to as tandem, triple, or quad, respectively. they are treated differently from single axles because they impose pavement stresses/strains that overlap (papagiannakis and massad, 2008). 2.2.1.2 average number of axles per truck this input represents the average number of axles for each truck class (classes 5 to 13) for each axle type (steering, single, tandem, and tridem).m-e procedure allows for dividing the single axle category into steering single axle (single tire) and other single axle (dual tires). a is the average number of axles per truck, is the ratio between the cumulative number of all the axles from the total weighed trucks and the cumulative vehicle weighed on the roadway, which is computed for each of the axis on the roadway. this variable is as presented in equation 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 585 a= 𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑎𝑙𝑙 𝑡ℎ𝑒 𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑 𝑎𝑥𝑙𝑒 𝑛𝑢𝑚𝑏𝑒𝑟𝑓𝑟𝑜𝑚 𝑡ℎ𝑒 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑑𝑎𝑡𝑎 𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑎𝑙𝑙 𝑡ℎ𝑒 𝑡𝑟𝑢𝑐𝑘𝑠 𝑤𝑒𝑖𝑔ℎ𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑊.𝐼.𝑀 (1) 2.2.1.3 axle load distribution factors the axle load distribution factors (aldf) simply represent the percentage of the total axle applications within each load interval for a specific axle type (steering, single, tandem, and tridem) and vehicle class (classes 5 through 13). a definition of load intervals for each axle type is provided below: single (steering single or other single) – 0-250kn, at 10kn intervals; tandem – 0 to 500kn at 20kn intervals; tridem -0 to 750 kn at 30kn intervals. the percentage (decimal) of axles for each axle load group (the frequency of axle load ranges determined in the aldf), is defined by: pi = number of axles in load range total no.of axles in load range of the bound axis of each roadway. (2) aldf constitute a major change from the current 1993 aashto pavement design guide that requires only the total number of 18-kip esals as input. 2.2.1.4 traffic growth factors adt growth rate was predicted by using the statistically based growth models built on historical trends, whereby, conversion to linear or exponential annual growth rates was employed in which the current process uses one growth rate (adt growth rate) for all truck classes, was determined using equation 3. r = ( tf t0 ) ( 1 yf−yo ) – 1 (3) where: yo is the base year, yf is the future year, to and tf are the corresponding estimates of adt, and r is the estimated exponential growth rate (nchrp 538, 2005) traffic growth factors are the yearly growth rates for each truck class. the growth function can be either linear growth or compound growth. g is the growth factor: one simple way to project the growth factor is to assume a yearly rate of traffic growth and use the average traffic at the start and end of the design period as the design traffic: g= 1 2 [ 1+( 1 + 𝑟) 𝑌] (4) in which r is the growth rate (decimal) per year (huang, 2007) 2.3 axle load damage quantification factors the key parameter needed in the comparison of the predicted of repetitions for each axle load group depends mainly on how the traffic is being handled. in handling the traffic by the empirically based methods, the equivalent axle load factor (ealf) for each axle load group is being determined by the aashto esal equation. however, handling the traffic by the m-e methods, it is useful to define a companion summary measure-a general axle load equivalency factor (gaf) is being employed. the key link in this comparison is that the same developed axle load distribution factor (aldf) is being utilized in both computations, between the empirical methods and m-e methods. the two detail descriptions are presented below: 2.3.1 determination of equivalent axle load factor (ealf) in handling of traffic in empirically based methods, the method of analysis was based on the aashto equivalency factors in which the aashto equations for computing equivalent axle load factor (ealf) for each of the generated axle load ranges for each axle type as contained log ( 𝑊𝑡𝑥 𝑊𝑡18 ) = 4.79log (18+1) 4.79+ http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 586 in the developed axle load distribution factor required in m-e design procedure. the following regression equations based on the results of road tests can be used for determining ealf: = log ( 4.2−𝑃𝑡 4.2−1.5 ) ; 0.4 + 0.082(𝐿𝑥 +𝐿2)3.23 ( 𝑆𝑁+1)5.19 (𝐿2)3.23 (5) where, wtx= the number of x-axle load application at the end of time t,; wt18 = the number of 18kip (80kn) single axle load application to time t, ; lx = the load in kip on one single axle, one set of tandem axles, or one set of tridem axles,; l2 is the axle code = 0 for steering axle; 1 for single axles, 2 for tandem axles, and 3 for tridem axles (huang, 2007).; sn = structural number a function of thickness, modulus of each layer, and drainage condition of base and sub-base.; pt = terminal serviceability – which indicates the pavement conditions to be considered as failures, = the value of when 𝐿𝑋 = 18 and 𝐿2=1, hence, practically, ealf is not very sensitive to pavement thickness and sn equal to 5 may be used for most cases and a pt value of 2.5 can be used (aashto, 1986, 1993 and huang 2007). 2.3.2 determination of general axle equivalency factor (gaf) in handling of traffic in m-e methods, the method of analysis was based on the practical comparison of axle load spectra, through which statistical measures are needed that are related to the concept of pavement damage and are independent of pavement –related variables. general axle load equivalency factors (dahlin1994; aashto1993) can fulfil this need. the (gaf) are defined as: w =𝐿𝑖 =axle load of any type or spacing in pounds (or converted to kn) =load li =carried by axle group type i (kn), from the aldf.: 𝑆𝐿𝑖 = standard load for axle group type,that has a similar unity damage for each axle type:-single axle with single tires: sl=53kn; -single axle with dual tires: sl=80kn=18,000pounds; -tandem group with dual tires: sl=135kn; -tridem group with dual tires: sl=181kn. any changes in gafs can be attributed directly to changes in traffic loads that is the focus of this study for the purpose of improving the pavement performance to be determined by nempads (hajek et al., 2000, austroads 2004b and 2012; moffatt et al., 2014). 2.4 determination of the predicted number of load repetitions. the considered method in this thesis for estimating pavement loading known as axle load spectra for use with the mechanistic-empirical (me) design procedure, whereby method based on different axle load groups is being employed. the procedure for predicting the predicted number of load repetitions for each axle load (for each axle load range) during the design life, is similar to the method based on esal, except that each load group is considered separately. timm and newcomb, (2002) studied the primary difference between how traffic is handled in empirically based methods versus mechanistic-empirical (m-e) methods. in estimating anticipated traffic loading, whereby, the design is based on the axle load spectra, then the initial number of repetitions per day for the ith load group can be computed from ( 𝑛𝑜)𝑖 = ( 𝑃𝑖𝐹𝑖) (𝐴𝐷𝑇)𝑜 (t) (a) (8) ealf = 𝑊𝑡18 𝑊𝑡𝑥 (6) gaf = ( w 18,000 ) 3.8 = ( 𝐿𝑖 𝑆𝐿𝐼 ) 3.8 (7) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 587 in which pi is the percentage (decimal) of axles in the ith load group (the frequency of axle load ranges determined in the aldf), determined according to equation 2 above. the predicted number of load repetitions 𝑛𝑖 for load group i during the design period is 𝑛𝑖 = 365 (𝑛𝑜)𝑖 (g) (d) (l) (y) (9) in which ( 𝑛𝑜)𝑖 is the initial number of repetitions per day for the ith load group, determined above in equation 8, g is the growth factor, d is the directional distribution factor, which is usually assumed to be 0.5 unless the traffic in two directions is different, l is the lane distribution factor which varies with the volume of traffic and the number of lanes, and y is the design period in years. 2.4.1 predicted number of repetitions in empirically based approach. in handling traffic in empirically based approach, ealf was used as a key axle damage factor parameter in calculating the predicted number of repetitions for the empirical approach, using equations 8 and 9. 2.4.2 predicted number of repetitions in mechanistically–empirical methods. in handling traffic in m-e methods, gaf is used as a key axle damage factor variable in calculating the predicted number of repetitions for the empirical approach, using equations 8 and 9. in these methods, empiricism was being eliminated. 2.4.3 comparison of predicted number of axle repetitions determined by ealf and gaf. a comparison between handling traffic in an empirically based methods and the m-e methods can best be illustrated by the same traffic composition and the method based on different axle load groups, with a marked difference of the axle load damage factor computed for each of the same determined axle load ranges in the aldf. in this study, there is a need to compare the value of the predicted number of repetitions of each axle load group during the design period, using empirical and mechanistic-empirical methods. in handling traffic in empirically based approach, ealf was used as a key axle damage factor parameter in calculating the predicted number of repetitions for the empirical approach. in handling traffic in m-e methods, gaf is used as a key axle damage factor variable in calculating the predicted number of repetitions for the (m-e) methods this indicate the impact of empiricism content in the traffic projection in the axle applications and its effect on the elimination of empiricism content in the traffic projection in the axle applications. 3. results and discussion traffic elastic analysis is performed using the method based on different axle load groups. the different variables discussed in the previous section are considered. the investigation of the resulting estimate of predicted number of load repetitions by making comparison its value on the basis of the determination of ealf and gaf. the following sections discuss the outcomes of these results 3.1 average number of axles per truck average number of axles on each of the axis of the roadway as calculated according to equation 1, are presented in table 2. from the analysis of results, obtained axle configuration from the surveyed truck configurations on the kaduna-zaria roadway. the average number of axles on the southbound axis (zaria to kaduna) was 2.66, and on the northbound axis (kaduna to zaria) it was 2.71. the results showed that the truck magnitude and the captured countered axles on the northbound axis are greater in number than the weighed truck number on the southbound axis. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 588 table 2: average number of axles per truck for kaduna-zaria roadway kaduna-zaria roadway southbound axis (sb) northbound axis (nb) axle configurations no of axles counted for each bin no of axles counted for each bin sast 86 99 sadt 68 76 tadt 75 90 trdt 0 3 total number of axles counted for each bin 229 268 total number of trucks counted 86 99 average number of axles per truck 229/86= 2.66 268/99= 2.71 3.2 axle load distribution factor (aldf) axle load distribution factor (aldf) as calculated according to equation 2, are presented in table 3. from the analysis of the results, the cumulative for each of the axle type, of the calculated frequencies is 100%. the frequencies of axle ranges is presented in table 3, with the corresponding axle load ranges for each of the axle configurations. the captured axle load data on the kaduna-zaria roadway. it indicates generally that the captured surveyed and weight of the axles on the northbound (nb) axis are greater in magnitude than the weighted axle in the southbound (sb) axis. the reason behind the differentials was that construction and industrial commodities were carried on the nb axis, whereby, in the sbaxis, agricultural products were carried. the number of axles counted for each bin has the greatest magnitude of axle load magnitude in the nbaxis are higher for sast, tadt, and sadt respectively, than in the sb axis. for trdt, not captured on the sbaxis, but very scanty on the nb axis, and the sample space is very minimum. 3.3 growth factor and annual growth rate. the adt growth rate was calculated according to equation 3, and the growth factor was calculated according to equation 4, and are both presented in table 4. from the analysis of results, obtained traffic volumes adt values for the year 1983 and 2006, for the kaduna-zaria roadway. in percentage terms, the resulting exponential growth rate is 1.74 percent. the use of the obtained growth rate resulted in the growth factor that is 1.21%. the determined growth factor and growth rate were not both affected by the content of empiricism and therefore, had the same impact of the predicted number of axle load repetitions and pavement performance as implemented by timm and newcomb (2002). 3.4 computation of equivalent axle load factor (ealf) the regression equations based on the results of road tests is used for the determination of ealf for the four different axle types observed on the kaduna-zaria roadway. the axle load intervals are determined for each axle types from the result of the secondary data captured on the kaduna-zaria roadway from the work of s.s.i (2007). the determined ealf from the same traffic composition for the four different axle types is presented in table 5. 3.5 computation of gaf. general axle load equivalency factors (gaf) is computed from the same traffic composition using the statistical measures that are needed to the concept of pavement damage and are independent of pavement -related variables. the determined gaf is presented for the kadunazaria roadways in table 6, for the four different axle types on the considered roadway. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 589 table 3: results of the calculated axle load distribution factor (aldf) for the four different axle configurations single axle with single tire (sast) single axle with dual tires (sadt) southbound axis (sb) axis northbound axis (nb) axis southbound axis (sb) axis northbound axis (nb) axis s/n bin count (no of axles counted for each bin) for southbound axis percentage of occurrence (frequency) %for sb-axis count (no of axles counted for each bin) for northbound axis percentage of occurrence (frequency) % for nb-axis s/n bin count (no of axles counted for each bin) for southbound axis percentage of occurrence (frequency) % for sb-axis count (no of axles counted for each bin) for northbound axis percentage of occurrence (frequency) %for nb-axis 1 0 0 0 0 0 1 0 0 0 0 0 2 10 2 2.33 4 4.04 2 10 1 1.47 1 1.32 3 20 3 3.49 3 3.03 3 20 1 1.47 2 2.63 4 30 9 10.47 8 8.08 4 30 8 11.76 6 7.89 5 40 16 18.60 9 9.09 5 40 31 45.59 6 7.89 6 50 39 45.35 18 18.18 6 50 10 14.71 5 6.58 7 60 3 3.49 32 32.32 7 60 2 2.94 0 0 8 70 8 9.30 15 15.15 8 70 1 1.47 2 2.63 9 80 1 1.16 5 5.05 9 80 5 7.35 1 1.32 10 90 0 0 2 2.02 10 90 1 1.47 4 5.26 11 100 2 2.33 0 0 11 100 2 2.94 6 7.89 12 110 2 2.33 2 2.02 12 110 1 1.47 6 7.89 13 120 1 1.16 1 1.01 13 120 1 1.47 11 14.47 14 130 0 0 0 0 14 130 2 2.94 9 11.84 15 140 0 0 0 0 15 140 1 1.47 2 2.63 16 150 0 0 0 0 16 150 0 0 3 3.95 17 160 0 0 0 0 17 160 0 0 5 6.58 18 170 0 0 0 0 18 170 1 1.47 1 1.32 19 180 0 0 0 0 19 180 0 0 1 1.32 20 190 0 0 0 0 20 190 0 0 1 1.32 21 200 0 0 0 0 21 200 0 0 3 3.95 22 210 0 0 0 0 22 210 0 0 1 1.32 23 220 0 0 0 0 23 220 0 0 0 0 24 230 0 0 0 0 24 230 0 0 0 0 25 240 0 0 0 0 25 240 0 0 0 0 26 250 0 0 0 0 26 250 0 0 0 0 total number of axles counted 86 100.00 99 100.00 total number of axles count 68 100.00 76 100.00 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 590 table 3 cont’d: results of the calculated axle load distribution factor (aldf) for the four different axle configurations tandem axle with dual tire (tadt) tridem axle with dual tires (tdt) southbound axis (sb) axis northbound axis (nb) axis southbound axis (sb) axis northbound axis (nb) axis s/n bin count (no of axles counted for each bin) for southbound axis percentage of occurrence (frequency) % for sb-axis count (no of axles counted for each bin) for northbound axis percentage of occurrence (frequency) % for nb-axis s/n bin count (no of axles counted for each bin) for southbound axis percentage of occurrence (frequency) % for sb-axis count (no of axles counted for each bin) for northbound axis percentage of occurrence (frequency) % for nb-axis 1 0 0 0 1 1.11 1 0 0 0 0 0 2 20 4 5.33 1 1.11 2 30 0 0 0 0 3 40 11 14.67 3 3.33 3 60 0 0 0 0 4 60 31 41.33 6 6.67 4 90 0 0 0 0 5 80 13 17.33 4 4.44 5 120 0 0 0 0 6 100 2 2.67 6 6.67 6 150 0 0 0 0 7 120 2 2.67 4 4.44 7 180 0 0 0 0 8 140 1 1.33 2 2.22 8 210 0 0 0 0 9 160 0 0 7 7.78 9 240 0 0 0 0 10 180 0 0 8 8.89 10 270 0 0 2 66.67 11 200 3 4.00 8 8.89 11 300 0 0 0 0 12 220 2 2.67 15 16.67 12 330 0 0 0 0 13 240 2 2.67 11 12.22 13 360 0 0 0 0 14 260 0 0 1 1.11 14 390 0 0 1 33.33 15 280 0 0 6 6.67 15 420 0 0 0 0 16 300 2 2.67 3 3.33 16 450 0 0 0 0 17 320 1 1.33 1 1.11 17 480 0 0 0 0 18 340 1 1.33 1 1.11 18 510 0 0 0 0 19 360 0 0 0 0 19 540 0 0 0 0 20 380 0 0 2 2.22 20 570 0 0 0 0 21 400 0 0 0 0 21 600 0 0 0 0 22 420 0 0 0 0 22 630 0 0 0 0 23 440 0 0 0 0 23 660 0 0 0 0 24 460 0 0 0 0 24 690 0 0 0 0 25 480 0 0 0 0 25 720 0 0 0 0 26 500 0 0 0 0 26 750 0 0 0 0 total number of axles counted 75 100.00 90 100.00 total number of axles count 0 0 3 100.00 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 591 table 4: traffic growth factors future adt future year 11,000.00 2006 base adt base year 7402 1983 growth rate (r) % equation 3 utilized 1.74% design period 20years growth factor (g) equation 4 utilized 1.21% table 5: results of the determined ealf for each axle load range of the axle load spectrum. s/n axle load range for sast (kn) ealf for sast axle load range for sadt (kn) ealf for sadt axle load range for tadt (kn) ealf for tadt axle load range for trdt (kn) ealf for trdt 1 0 0.0000 0 0.0000 0 0 0 0.0000 2 10 0.0001 10 0.0003 20 0.0004 30 0.0004 3 20 0.0013 20 0.0033 40 0.0045 60 0.0054 4 30 0.0089 30 0.0169 60 0.0233 90 0.0271 5 40 0.0352 40 0.0562 80 0.0773 120 0.0865 6 50 0.1024 50 0.1441 100 0.1983 150 0.2096 7 60 0.2452 60 0.3095 120 0.4258 180 0.4217 8 70 0.5132 70 0.5843 140 0.8037 210 0.7478 9 80 0.9728 80 1.000 160 1.3755 240 1.2177 10 90 1.7102 90 1.5871 180 2.1832 270 1.8722 11 100 2.8329 100 2.3764 200 3.2689 300 2.7668 12 110 4.4720 110 3.4024 220 4.6801 330 3.9723 13 120 6.7843 120 4.7068 240 6.4744 360 5.5754 14 130 9.9545 130 6.3417 260 8.7232 390 7.6785 15 140 14.1965 140 8.3709 280 11.5145 420 10.4005 16 150 19.7563 150 10.8707 300 14.9531 450 13.8773 17 160 26.9131 160 13.9303 320 19.1618 480 18.2628 18 170 35.9815 170 17.6516 340 24.2905 510 23.7257 19 180 47.3134 180 22.1493 360 30.4673 540 30.4705 20 190 61.2998 190 27.1493 380 37.8983 570 38.6986 21 200 78.3723 200 33.9998 400 46.7682 600 48.6488 22 210 79.0055 210 41.6493 420 57.2904 630 60.5788 23 220 123.7182 220 50.6698 440 69.6985 660 74.7697 24 230 153.0754 230 61.2458 460 84.2462 690 91.5270 25 240 187.6899 240 73.5770 480 101.2082 720 111.1817 26 250 228.2242 250 87.8790 500 120.8813 750 134.0910 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 592 table 6: determination of the gaf for each load range of the axle load spectrum 3.6 determination of the predicted number of load repetitions using ealf predicted number of axle repetitions utilizing ealf is determined by utilizing the ealf as a primary input using the same traffic composition for the four different axle types in empirical approach with the empiricism contents not eliminated. this is presented between figures 1 and figures 4. figure 1: predicted number of repetitions using ealf for single axle with single tire loads during 20-year design period at kaduna-zaria roadway s/ n axle load range for sast gaf for sast=(axle load range/ 53) ^3.8 axle load range for sadt gaf for sadt=(axle load range/ 80)^3. 8 axle load range for tadt gaf for tadt=(axl e load range/ 80) ^3.8 axle load range for trdt gaf for trdt=(axl e load range/ 80) ^3.8 1 0 0 0 0 2 10 0.0018 10 0.0004 20 0.0007 30 0.0011 3 20 0.0246 20 0.0052 40 0.0098 60 0.0151 4 30 0.1150 30 0.0241 60 0.0459 90 0.0703 5 40 0.3432 40 0.0718 80 0.1369 120 0.2098 6 50 0.8014 50 0.1676 100 0.3197 150 0.4897 7 60 1.6022 60 0.3351 120 0.6392 180 0.9792 8 70 2.8782 70 0.6020 140 1.1482 210 1.7590 9 80 4.7807 80 1.0000 160 1.9072 240 2.9216 10 90 7.4795 90 1.5645 180 2.9838 270 4.5709 11 100 11.1622 100 2.3348 200 4.4529 300 6.8215 12 110 16.0341 110 3.3539 220 6.3964 330 9.7988 13 120 22.3172 120 4.6682 240 8.9030 360 13.6386 14 130 30.2508 130 6.3277 260 12.0679 390 18.4870 15 140 40.0902 140 8.3858 280 15.9931 420 24.5001 16 150 52.1073 150 10.8995 300 20.7870 450 31.8441 17 160 66.5898 160 13.9288 320 26.5645 480 40.6947 18 170 83.8412 170 17.5373 340 33.4466 510 51.2375 19 180 104.1807 180 21.7918 360 41.5605 540 63.6675 20 190 127.9427 190 26.7622 380 51.0398 570 78.1890 21 200 155.4768 200 32.5216 400 62.0240 600 95.0159 22 210 187.1479 210 39.1464 420 74.6585 630 114.3709 23 220 223.3356 220 46.7158 440 89.0947 660 136.4861 24 230 264.4341 230 55.3126 460 105.4900 690 161.6025 25 240 310.8525 240 65.0221 480 124.0076 720 189.9699 26 250 363.0143 250 75.9329 500 144.8164 750 221.8473 table 6 : determination of the gaf for each load range of the axle load spectrum. 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 1 7 0 1 8 0 1 9 0 2 0 0 2 1 0 2 2 0 2 3 0 2 4 0 2 5 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weights (kn) sb nb file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 593 figure 2: predicted number of load repetitions using ealf for single axle with dual tires loads during 20year design period at kaduna-zaria roadway. figure 3: predicted number of load repetitions using ealf for tandem axle with dual tires loads during 20-year design period at kaduna -zaria roadway figure 4: predicted number of load repetitions using ealf for tridem axle with dual tires loads during 20-year design period at kaduna-zaria roadway. 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 1 7 0 1 8 0 1 9 0 2 0 0 2 1 0 2 2 0 2 3 0 2 4 0 2 5 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths (kn) sb 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 0 3 0 0 3 2 0 3 4 0 3 6 0 3 8 0 4 0 0 4 2 0 4 4 0 4 6 0 4 8 0 5 0 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn) sb nb 0 1 2 3 4 5 6 7 8 0 3 0 6 0 9 0 1 2 0 1 5 0 1 8 0 2 1 0 2 4 0 2 7 0 3 0 0 3 3 0 3 6 0 3 9 0 4 2 0 4 5 0 4 8 0 5 1 0 5 4 0 5 7 0 6 0 0 6 3 0 6 6 0 6 9 0 7 2 0 7 5 0lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn) sb nb http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 594 3.7 determination of the predicted number of load repetitions using gaf predicted number of axle repetitions utilizing gaf is determined by utilizing the gaf as a primary input using the same traffic composition for the four different axle types in mechanistic –empirical procedures without the empiricism contents that has been eliminated. this is presented between figures 5 and figures 8. figure 5: predicted number of load repetitions using gaf for single axle with single tires loads during 20year design period at kaduna-zaria roadway figure 6: predicted number of load repetitions using gaf for single axle with dual tires loads during 20-year design period at kaduna -zaria roadway figure 7: predicted number of load repetitions using gaf for tandem axle with dual tires loads during 20-year design period at kaduna-zaria roadway 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 1 7 0 1 8 0 1 9 0 2 0 0 2 1 0 2 2 0 2 3 0 2 4 0 2 5 0lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn ) sb nb 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 1 7 0 1 8 0 1 9 0 2 0 0 2 1 0 2 2 0 2 3 0 2 4 0 2 5 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths (k n) sb nb 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 0 3 0 0 3 2 0 3 4 0 3 6 0 3 8 0 4 0 0 4 2 0 4 4 0 4 6 0 4 8 0 5 0 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn) sb nb file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 595 figure 8: predicted number of load repetitions using gaf for tridem axle with dual tires loads during 20year design period at kaduna -zaria roadway 3.8 comparison of the expected number of repetitions of each axle load group during the pavement life determined by ealf and gaf. comparison of the expected number of repetitions of each load group during the pavement life by traffic analysis, whereby, the results of the determined aldf was utilized and presented in table 3. the axle load ranges obtained and contained in table 3, was used in the determination of ealf using equations 5 and 6, that was presented in table 5, and the same axle load ranges were used in the calculation of gaf using equation 7 and presented in table 6. the differences in the obtained results of ealf and gaf was presented in table 7 for the axle load ranges for each of the different axle configurations. from the traffic analysis, the method based on different axle load groups was used for the determination of the predicted number of load repetitions by using equations 8 and 9, and this is presented between figures 9 and figures 12. the marked difference is determined by using ealf or gaf individually in equation 8 respectively, which is an input of equation 9, and the results were compared. the obtained results indicate the effect of the empiricism content in ealf but that was eliminated in gaf. the projected traffic that was compared was plotted on the four different axle configurations for different axle load ranges was plotted between figure 9andfigure 12. the compared predicted number of repetitions for load group were presented in figure 9 to figure 12. the presentations are presented are as follows: the predicted number of axle load repetitions for the sast is presented in figure 9. similarly, figure 10 is for sadt; figure 11 is for tandem axles with dual tires and figure 12 depicts the trdt. 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 0 3 0 6 0 9 0 1 2 0 1 5 0 1 8 0 2 1 0 2 4 0 2 7 0 3 0 0 3 3 0 3 6 0 3 9 0 4 2 0 4 5 0 4 8 0 5 1 0 5 4 0 5 7 0 6 0 0 6 3 0 6 6 0 6 9 0 7 2 0 7 5 0lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 596 table 7: axle load damage quantification factors comparison of ealf and gaf for sast. comparison of ealf and gaf for sadt. comparison of ealf and gaf for tadt. comparison of ealf and gaf for trdt. s/n axle load range for sast (kn) ealf for sast gaf for sast axle load range for sadt (kn) ealf for sadt gaf for sadr axle load range for tadt (kn) ealf for tadt gaf for tadt axle load range for trdt (kn) ealf for trdt gaf for trdt 1 0 0 0 0 0 0 0 0 0 0 0 0 2 10 0 0 10 0 0 20 0 0 30 0 0 3 20 0.001 0.02 20 0.003 0.01 40 0.005 0.01 60 0.005 0.02 4 30 0.009 0.12 30 0.017 0.02 60 0.023 0.05 90 0.028 0.07 5 40 0.035 0.34 40 0.056 0.07 80 0.077 0.14 120 0.093 0.21 6 50 0.102 0.8 50 0.144 0.17 100 0.198 0.32 150 0.239 0.49 7 60 0.245 1.6 60 0.31 0.34 120 0.426 0.64 180 0.513 0.98 8 70 0.513 2.88 70 0.584 0.6 140 0.804 1.15 210 0.968 1.76 9 80 0.973 4.78 80 1 1 160 1.376 1.91 240 1.658 2.92 10 90 1.71 7.48 90 1.587 1.56 180 2.183 2.98 270 2.631 4.57 11 100 2.833 11.16 100 2.376 2.33 200 3.269 4.45 300 3.939 6.82 12 110 4.472 16.03 110 3.402 3.35 220 4.68 6.4 330 5.64 9.8 13 120 6.784 22.32 120 4.707 4.67 240 6.474 8.9 360 7.807 13.64 14 130 9.954 30.25 130 6.342 6.33 260 8.723 12.07 390 10.512 18.49 15 140 14.197 40.09 140 8.371 8.39 280 11.514 15.99 420 13.875 24.5 16 150 19.76 52.11 150 10.371 10.9 300 14.953 20.79 450 18.019 31.84 17 160 26.913 66.59 160 13.93 13.93 320 19.162 26.56 480 23.091 40.69 18 170 35.982 83.84 170 17.652 17.54 340 24.28 33.45 510 29.259 51.24 19 180 47.313 104.18 180 22.149 21.79 360 30.467 41.56 540 36.714 63.67 20 190 61.3 127.94 190 27.552 26.76 380 37.898 51.04 570 45.669 78.19 21 200 78.372 155.48 200 34 32.52 400 46.768 62.02 600 56.358 95.02 22 210 99.006 187.15 210 41.649 39.15 420 57.29 74.66 630 69.037 114.4 23 220 123.718 223.34 220 50.67 46.72 440 69.698 89.09 660 83.99 136.5 24 230 153.075 264.43 230 61.246 55.31 460 84.246 105.49 690 101.52 161.6 25 240 187.69 310.85 240 73.577 65.02 480 101.208 124.01 720 121.96 190 26 250 228.224 363.01 250 87.879 75.93 500 120.881 144.82 750 145.667 221.9 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 597 figure 9: comparison of the expected number of load repetitions for single axle with single tires loads determined by ealf and gaf during 20year design period at kaduna -zaria roadway. figure 10: comparison of the expected number of load repetitions for single axle with dual tires loads determined by ealf and gaf during 20year design period at kaduna -zaria roadway. figure 11: comparison of the expected number of load repetitions for tandem axle with dual tires loads determined by ealf and gaf during the 20year design period at kaduna zaria roadway. 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 1 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 1 7 0 1 8 0 1 9 0 2 0 0 2 1 0 2 2 0 2 3 0 2 4 0 2 5 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn) sb (e ) sb( m-e) nb ( e) nb (m-e) 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 0 3 0 0 3 2 0 3 4 0 3 6 0 3 8 0 4 0 0 4 2 0 4 4 0 4 6 0 4 8 0 5 0 0 lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths (kn)\ sb ( e ) sb (m-e) n ( e) nb (m-e) 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 1 7 0 1 8 0 1 9 0 2 0 0 2 1 0 2 2 0 2 3 0 2 4 0 2 5 0l o g a r it h m o f p r e d ic t e d n u m b e r o f r e p e t it io n s individual axle weigths (kn) sb ( e ) sb(me) nb ( e) nb(m-e) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 598 figure 12: comparison of the expected number of load repetitions for tridem axle with dual tires loads determined by ealf and gaf during the 20year design period at kaduna zaria roadway. 4. conclusion the following conclusions were drawn from this study: (i) the required traffic loading was characterized for the method based on different axle load groups, whereby, traffic loading was handled in a disaggregate fashion. the load input was in terms of axle load distribution by axle configuration. (ii) traffic loads were handled through a more complicated process called axle load spectra, in which all traffic loads were analyzed based on vehicle class, axle type, and axle load, and therefore, represented, the true distribution of traffic weights carried by the pavement under consideration. the axle load spectrum from the wim data contains no empiricism content, therefore, it relied not on the equivalency factors. (iii) the percentage of the total number of truck axle repetitions within each load interval (which varies with axle type) for each axle type was determined from the axle load spectrum of the wim data, that shows the axle load distribution factors (aldf). aldf constitute a major change from the current 1993 aashto pavement design guide that requires only the total number of 18-kip esals as input. (iv) a unique and rational way of handling volume changes and traffic growth was incorporated in this forecasting process in traffic analysis instead of the traditional approach of growth rate assumption. careful consideration of current and historical traffic trends and the application of engineering was utilized to obtain an accurate prediction of traffic growth. the growth factor calculated was accurate based on the determined growth rate input and its significance influence on the estimated traffic. the growth factors have the same influence both on the load spectra and the same as using esals, because the empiricism content has no significant impact on the estimated traffic. (v) the ealf was determined based on the empirical equations developed from the aasho road test, whereby, the regression equations based on the results of road tests was utilized. however, gaf was calculated for each load range of the axle load spectrum, whereby, the needed statistical measures that are related to the concept of pavement damage and are independent of pavement -related variables. the obtained values from the same traffic composition shows that the biggest different between the aashto ealf and the gaf, for the practical range for each load range of the axle load spectrum. (vi) this finding confirms the comparison of the axle load number of repetitions determined by aashto ealf and the gaf, because its practical range of difference with the same traffic 0 2 4 6 8 10 0 3 0 6 0 9 0 1 2 0 1 5 0 1 8 0 2 1 0 2 4 0 2 7 0 3 0 0 3 3 0 3 6 0 3 9 0 4 2 0 4 5 0 4 8 0 5 1 0 5 4 0 5 7 0 6 0 0 6 3 0 6 6 0 6 9 0 7 2 0 7 5 0lo g a r it h m o f p r ed ic te d n u m b er o f r ep et it io n s individual axle weigths ( kn) sb ( e) sb(m-e) nb ( e ) nb (m-e) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com awosanya et al: development of axle load spectra for integration in traffic characteriaztion for nigerian empirical mechanistic pavement analysis and design systems. azojete, 20(3):581-600. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 599 composition was the same difference in output based on the primary inputs of the different axle load damage factors determined individually. references aashto, 1986. guide for design of pavement structures; american association of state highway and transportation officials, washington, d.c aashto, 1993. guide for design of pavement structures; american association of state highway and transportation officials, washington, dc. priest, al. and timm, dh. 2006. methodology and calibration of fatigue transfer functions for mechanistic-empirical flexible pavement design. report no. ncat report 06-03, national center for asphalt technology, auburn university, alabama olowosulu at. 2005. a framework for mechanistic empirical pavement design for tropical climate. journal of civil engineering, 2005; vol. 5, no. 1: pp. 44-51 austroads, 2004b; austroads pavement design guide’ austroads inc., sydney, australia. austroads 2012, guide to pavement technology: part 2: pavement structural design, agpto2-12, austroads, sydney, nsw dahlin, curtis.1994. the basis for using gross vehicle weight distributions of 5-axle semisto determine the validity of weight data, minnesota department of transportation david, ht. and david en. 2002.traffic forecasting. hot mix asphalt technology-july/august, 2002: pp14-21 hajek, jj. and selezneva, o. 2000. estimating cumulative traffic loads, final report for phase 1, fhwa-rd-00-054, usdot, federal highway administration, washington, dc. highway design manual. 2012: topic 613traffic considerations: california department of transportation. california state highway systems, usa. huang, yh. 2007. pavement analysis and design: prentice-hall, inc., new jersey ioannides, am. 1992. mechanistic performance modeling: a contradiction of terms. a proceedings of the 7th international conference on asphalt pavements, vol.2, nottingham, england: 165-179. michael, am. geoffrey, wj. william, ym. 2014. influence of multiple –axle group loads on mechanistic-design of asphalt pavements.26th arrb conference-research driving efficiency, sydney, new south wales: 1-16. nchrp, 1990. calibrated mechanistic structural analysis procedures for pavement, nchrp 1-26, vol. 1, final report; vol. 2, appendices; university of illinois at urbana-champaign. nchrp report 538. 2005: traffic data collection, analysis, and forecasting for mechanistic pavement design. transportation research board, washington, d.c neeraj buch. syed waqar haider. joel brown, pe. and karim chatti. 2009. characterization of truck traffic in michigan for the new mechanistic empirical pavement design guide. research report rc-1537.east lansing, mi 48824, michigan. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)581-600. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 600 papagiannakis, at. and massad, ea. 2008. pavement design and materials: john wiley sons, inc., hoboken, new jersey. road design standard part 2 pavement: cam pw .03 -102-99. 2003. cambodian ministry of public works and transport. stewart scott international. 2007. a dhv company, interim report: axle load study and review and update of the design standard for federal roads, nigeria. fwa, tf. 2006. the handbook of highway engineering. press taylor & francis group, llc. boca raton. usa. oguara, tm. 2006. highway engineeringpavement design, construction, and maintenance. malthouse press limited, lagos, nigeria. kim, yr. jadoun, fm. hou, t. muthadi, n. 2011. local calibration of the mepdg for flexible pavement design report no. fhwa\nc\2007-07. raleigh, nc 27601. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):413-426 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 403 original research article a resource performance model for efficient distribution of resources to operating system services in factored operating system h. mikailu1, i. agaji2*, b. v. nachamada3 and i. gambo4 1deparment of computer science, nigerian army university, biu, nigeria 2department of computer science, federal university of agriculture makurdi, nigeria 3department of computer science, university of jos, jos, nigeria 4department of computer science and engineering, obafemi awolowo university, ile-ife, nigeria *corresponding author’s email address: ior.agaji@uam.edu.ng 1.0 introduction processor performance is increasing rapidly as the number of cores on the chip increases at each release of a new generation of central processing unit (cpu) and with multicore, cpu is becoming not only faster but more powerful and efficient. the emergence of two families of computing technology (multicore and cloud computing) has the potential to improve the computational system capacity to the average computer user (nafaa, 2015). air force research laboratory (2012) reported that in the future, computer chips with 1,000 to 10,000 cores on one slice of silicon will be produced with the recent technological advancement. the growth in hardware manufacturing technology and the progressing evolution which agrees to moore’s law, could afford computer microprocessor chip with thousands of processor cores on a single microprocessor in the next decade (wentzlaff and agarwal, 2016). the evolution of multicore processors suggest that single-stream article information abstract central processing will be composed of thousands of heterogeneous cores in the near future. the existing systems are difficult to scale, adapt or tackle the heterogeneous nature of the future multicore technology. this study developed a resource performance model for efficient distribution of resources to operating system (os) services. a multiagent based method was used to design the architecture of the model while the unified modeling language and flowchart were used in the detailed design of the proposed model. the model was simulated using java 2 enterprise edition. in simulating the model, four (4) variables were used to determine the processor core capacity. the result of the simulation shows an efficient distribution of 5000 cores to four (4) os services (servers) with each having 1250 fleet of servers. the percentage differences in the four of servers from the minimum are 0.11%, 0.09% and 0.04% respectively. the result shows that the distribution of processor cores to os services is efficient since the differences in total performance function of the fleets of servers were very little. therefore, to maximize the profit that comes with multicore systems, this efficient model is needed for processor cores distribution to os service in a factored operating system. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 23 nov., 2021 revised 7 may, 2022 accepted 15 may, 2022 keywords: factored operating system multicore multi-agent fleets of servers performance function http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng file:///c:/users/user/downloads/ior.agaji@uam.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 414 performance may not get louder in the future. microprocessor manufacturers have resorted to integrating multiple processors onto a single chip (wentzlaff and agarwal, 2016). in respect to the anticipation of exponential increase in a number of cores, the genre has fundamentally changed. the question and the problem now is how to efficiently utilize the abundant resources available, and not how to contend with scarce system resources. there exists a need for the software developers to step up its development technology to produce systems that are scalable and adaptable to the ever-changing hardware environment. furthermore, the future central processors will be composed of thousands of heterogeneous cores, while the design of the existing systems are such that they are not scalable. the benefits that the multicore technology might not be harvested, hence the necessity of this research (nafaa, 2015). factored operating system (fos) is, therefore, designed with this motive, taking scalability and adaptability as the primary design constraints. fos is a new operating system designed for multicore processors and cloud computers. in fos, os services are implemented as independent distributed systems running on different cores from user applications where each service is divided into a fleet or parallel set of collaborating processes that commune using messages. fos aims to design system services that scale from a few to thousands of cores (air force research laboratory, 2012). this study is therefore aimed at developing resource performance model for efficient distribution of resources to os services for a fos to address the inefficiency of the conventional os in utilizing multicore resources. this is allows the resource performance model to compute resource capacity, and efficiently distribute these resources to various os services that will form fleets of independent distributed servers. for a better scalability to be attained, system resources would be employed as many processor cores running simultaneously or as an individual, rapid and potent core for executing a single-threaded and serial part of the application processes. 2. review of relevant literature the international technology roadmap for semiconductors, itrs, (2015) reported that in each new generation of technology, the producers of microprocessors often increment the relative frequency of the processors, which was possible on account of moore’s law. in the early twenty-first century, a physical cap in the form of thermal limits was encountered. by increasing both the number of transistors on a chip and rising the clock speed was not achievable. attempting increased number of transistors on a chip and rising the clock speed induced severe trouble associated with heat dissipation. therefore, microchip producers resolved to go on with moore’s law by yet manufacturing microchips with an increased number of transistors having insignificant frequency increments. hence, the main reason behind the change of viewpoint, from a single core technology to that of multicore systems. borkar (2007) affirmed that moore’s law remains in effect whenever the increment in the number of transistors on integrated circuits is maintained. it has, therefore, become reasonable to anticipate computer systems with thousands of heterogeneous processor file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng mikailu et al: a resource performance model for efficient distribution of resources to operating system services in factored operating system. azojete, 18(3):413-426. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 415 cores in the future. to this end, it becomes critical for operating systems to scale with the new hardware technology. the resources of the upcoming multicore systems should be managed with efficiency other than expected, else it will be improbable for application processes executing on such a platform to take full benefits of the newly available technology. according to laplante and milojicic (2016), the deceleration of processor scaling due to moore’s law resulted in the resurgence research in new types of computing structures, the need arises for rethinking operating systems paradigms. it is envisioned that by 2030 operating systems will be created using a new technology paradigm that would be nearly unrecognizable today. wickizer et al. (2008) and wentzlaff and agarwal (2009) demonstrated that locks may not proffer the wanted scalability sought after by the new technological developments. thus, a study of the factored operating system was incited. their performance differences were made visible depending on core count. two observations were made in this research, they were; (i) with an increase in the number of cores, the lock contention cost factor became the largest, and the synchronization overhead was seen to have consumed most resources. (ii) the total execution time was heightened with more than eight active cores in the benchmark. the research indicated that synchronizing the operating cost induced by locks was the reason for performance declined. thus, if software design remains as it is at present, lock contention will continue to be a big problem to multicore processor systems. schart (2016) identified three fundamental design problems of os for multicore structure: they were locks, sharing of processor cores and cache-coherent shared memory. in this study, the impact of these challenges on scalability and proposed locks avoidance to counter scalability threat was highlighted. this would be achieved via splitting up operating system services onto dedicated cores where processes will request for operating system functionality in a concurrent manner. the work also proposed the splitting up of application and os, so as to avoid sharing of cores with each other, rather, each core will be dedicated to every thread on the system. lastly, instead of cache coherent shared memory, the work proposed message passing to be used for operating system or application communication. the work offered some improvements, but it is not clear, how to structure an os with locks that proffer satisfactory design scalability and load scalability as well. hence, it is sensible to name lock as a challenge because of the technological advancement of multicores. reuther et al. (2017) presented a detailed feature analysis of 15 supercomputing and big data schedulers. for big data workloads, the scheduler latency was the most critical performance characteristic of the scheduler. a theoretical model of the latency of these schedulers was developed and used to design experiments targeted at measuring scheduler latency. detailed benchmarking of four of the most popular schedulers slurm, son of grid engine, mesos, and hadoop yarn were conducted. the model results indicated that scheduler performance could be characterized by two key parameters: the marginal latency of the scheduler ts and a nonlinear exponent αs. for all four schedulers, the utilization of the computing system decreased to less than 10% for computations lasting only a few seconds, while multi-level http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 416 schedulers such as llmapreduce that transparently aggregated short computations could improve utilization for these short computations to >90% for the four schedulers that were tested. thus, conventional supercomputing schedules currently filled the role of managing heterogeneous resources but have inherent scalability limitations. in another study, asmussen et al. (2016) integrated cores and memories into a packetswitched network-on-chip (noc) and equipped each core with a data transfer unit (dtu) as the common hardware component. the only means for the core to communicate with other cores or memories was through the dtu, offering message passing and memory access. controlling the dtu allowed the control of the core and therefore, the software running on the core. os services like file systems and network stacks were provided based on a core-neutral communication protocol between dtus. the work introduced networkon-chip-level isolation, presented the design of microkernel-based os, m3, and the familiar hardware interface, and evaluated the performance of the prototype in comparison to linux. the result showed that without using accelerators, m3 outmatches linux in some application-level benchmarks by more than a factor of five. however, this design decreases system utilization as the processing element (pe) was idle for a specific time, waiting for an incoming message or the completion of a memory transfer. furthermore, clements et al. (2013) introduced a scalable commutativity rule that provides a new approach for software developers to understand and exploit multicore scalability right at the software interface. the work introduced commuter to aid programmers to analyze interface commutativity and test to ensure implementation scales in commutative situations. commuter was applied to 18 posix calls and the results were used to guide the implementation of a new research operating system kernel called sv6. linux scales for 68% of the 13,664 tests generated by commuter for these calls and commuter finds many problems that have been observed to limit application scalability, while on the hand, the sv6 scales for 99% of the tests. thus, using sv6, it was observed that it was practical to achieve a broadly scalable implementation of posix by applying the rule, and that commutativity was also essential to achieving scalability and performance on real hardware. however, it became hard to identify bottlenecks and impractical to fix problems since product testing was done late in the production. rakhee and garg (2014) provided an overview to multicore processors, multicore processor parallelism and performance measurement for multicore central processing units (cpus).and addressed the techniques used to evaluate multicore cpu performance, metrics, factors, benchmark tools used to measure multicore cpu performance. the works were anticipated new approaches in multicore cpu performance analysis as multicore cpu production increases to new levels. baumann et al. (2009) experimented with an advanced micro devices (amd) system with four cpus and each with four processors, making sixteen processors used for the benchmarks. at first processes were devoted to a processor updating the space of a little part of memory, and cache coherence techniques on hardware responded by releasing these modifications to other processor cores. as core counts grew, it was observed that the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng mikailu et al: a resource performance model for efficient distribution of resources to operating system services in factored operating system. azojete, 18(3):413-426. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 417 performance declined, demonstrating inadequate load adaptation. efficiency was noticed to drop by a factor of 40 when achievements between one core and sixteen cores were compared. subsequently, inter-core communication (messaging) was tested and was observed to have performed better. no degradation whatsoever was noticed by the increase in number of cores using a message passing method. where delay was seen is when the focus was not on only on passing a message, but on executing it as well. however, in this circumstance, a linear increase in time was detected, which is attributed to a queuing delay. figure 1 illustrates the core layout in fos. it depicts three applications and operating system server cores. two applications denoted as a0 and a2 enjoy the benefit of user-space cachecoherent shared memory. the operating system servers denoted as s do not utilize cachecoherent shared memory, but interact via messaging. application a1 does not require cachecoherent shared memory. this feature can either be enabled or excluded, depending on the specific requirements of an application. wentzlaff et al. (2011) evaluated fleets within fos and designed and implemented three critical fleets (network stack, page allocation, and file system) and compared with linux. the comparisons showed that fos achieved superior performance and had better scalability than linux for large multicores. with 32 cores, fos page allocator performed 4.5 times better than linux, and fos network stack performed 2.5 times better. additionally, the work demonstrated how fleets could adapt to changing resource demand and the importance of spatial scheduling for excellent performance in multicores. their experiments have demonstrated that this design is appropriate for the multicore design architectures of the future while proffering improved scalability than the existing solutions. the uniqueness of factored operating system design architecture grants operating system the privilege to scale to high core counts without meddling with the application. wentzlaff et al. (2011) experiment concerning the impact of proper spatial scheduling on performance in multicore processor systems used the read-only file system fleet with ‘good’ and ‘bad’ layouts and was executed on a 16-core intel xeon e7340. this machine had a minimal intra-socket communication cost applying user-space messaging, which revealed significant communication heterogeneity between intra-socket and inter-socket communication. the file system fleet consisted of four servers, and the clients’ number increases from one to ten. single file system server resides on each socket in the good layout experiment. the file system component of libfos was self-aware and selected the local file system server for all requests. in the bad layout experiment, all servers resided on a single socket and clients were distributed among remaining sockets. the result of the experiment showed that good layout is uniformly better than the lousy layout in figure 1: cores layout in a fos environment (source: schartl, a1 a0 a1 s s a1 a1 a1 a0 a0 a0 a0 a0 s s a2 a2 a2 a2 figure 1: cores layout in a fos environment (source: schartl, 2016) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 418 performance. for large multicores with hundreds of cores, it was anticipated that communication heterogeneity will increase further. the authors asserted that global structures that achieved symmetric performance, e.g., buses, will not scale to large core counts and new on-chip will expose heterogeneous communication costs. the work maintained that future multicores would feature much more significant heterogeneity and commensurately higher end-to-end performance inequality from spatial scheduling. to improve the system performance through utilizing the exponential increase in transistor hardware, microprocessor industries have reversed to integrating multiple processors onto a single die. some present examples include intel and amd’s quad-core offerings, tilera’s 64-core processor, and an 80-core intel prototype processor. according to major microprocessor manufacturers’ suggestion, the trend of integrating more cores onto a single microprocessor will go on. by inferring the doubling of transistor resources every one and half year, in a short period, over 6000 processor cores on a single microprocessor will be integrated (beckmann, 2010; wentzlaff and agarwal, 2016). efforts have been applied to combat heterogeneity problems of hardware as well as scalability and adaptability, however, conventional supercomputing schedules currently filled the role of managing heterogeneous resources but have inherent scalability limitations. how to structure an os with locks that can proffer satisfactory design scalability and load scalability as well remains a challenge. moreover, some of the proposals design, decreases system utilization as the processing element was idle for a specific time, waiting for an incoming message or the completion of a memory transfer. also, a linear increase in time was detected, which is attributed to a queuing delay (salto and alba, 2015). thus, since caches could be employed to their fullest potency, load scalability can be increased. the new method is to maintain operating system services and application code on different cores, as free cores becomes a commodity. it is, therefore, beneficial that a set of cores be devoted to operating system services only, since the number of cores is in the rise, having observed that processor core sharing inflicts extra costs in terms of cache misses. it is highly believed that this will result in more efficient use of the available hardware when the proposed resource performance model for efficient distribution of resources to os services for a fos is implemented (salto and alba, 2015). 3. methodology the research methodology adopted in this work is the multi-agent oriented software development method. to develop a resource performance model for efficient distribution of resources to operating system (os) services for a factored operating system, a multiagent based method is used to design the architecture of the model. a unified modeling language (uml) and flowchart were used to design the proposed model. the model is simulated using java 2 enterprise edition. in simulating the model, four (4) variables are were to determine the processor core capacity, they are: processor type (pt), processor speed (sp), register size (rs) and cache size (cs). random integer numbers were generated between 1 to 40 to represent the values of the variables, each with an associated weight of 0.4, 0.3, 0.2 and 0.1 respectively. these were used in order of priority to compute and determine file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng mikailu et al: a resource performance model for efficient distribution of resources to operating system services in factored operating system. azojete, 18(3):413-426. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 419 the rank of processor cores capabilities. these processor cores were then logically and efficiently distributed to the four (4) os services using the algorithm proposed for this model to form fleets of independent distributed servers. one advantage of agent-based architectures is that it is relatively easy to extend and expand, as new conditions are discovered or prioritized. the method is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determine the requirements. 3.1 proposed design of the resource performance model the resource performance model computes the capacity resources and distributes it to the os services. this is intended to compute the capacities of processor cores and distributes them to os services (pc security management, file system naming, scheduler and file management). this is to enable the schedulers to allocate resources optimally to the requesting process jobs, having estimated their resource requirements, to attain efficient system throughput. design principles applied in this research are to replaces the traditional os use of time multiplexing in processing with application code via a system call interface with space multiplexing. also, os services are factored into function-specific services and implemented as a parallel independent distributed service. this is because operating system services are divided from user application code and executed on separate cores. moreover, each service is divided into a fleet or parallel set of collaborating servers that interact using messages. the aim is to develop systems that scale from a few to thousands of cores. 3.2 the proposed architecture of resource performance model the architecture of the proposed framework is shown in figure 2. in this framework, a multi-agent method is modeled in the form of a distributed system designed to represents resource performance model as a group of autonomous agents. the resource agent extracts resource core information, computes capacities of the resource cores and distributes these resources to the various operating services to form fleets of servers. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 420 figure 2: the architecture of the resource performance model 3.3 the resource performance model the proposed resource performance model is depicted in figure 3, which shows the activities performed, such as: computing resource capacity and distributing resources to operating system services. the parameters of both the resources r are input into the model. the system begins by extracting the parameters of and rj; where rj represents 1 to n number of resources each with four parameters as well. the computed resources are then distributed to the various operating system services to form fleets of servers. the resource performance sub-model shows that for each 1 to n resource (processor cores) performance function (pf) were computed and the results generated. each of the resource was associated with its performance capacity. the algorithm described the factors that picture the quality of a server processing capability, such as processor type, speed, register and cache size. the server performance was calculated to gauge the processing capability of each server. thus, this was used as performance metrics for optimal servers’ distributions. for the purpose of this study, four processor variables were used, they include; processor type (pt), processor speed (ps), register size (rs) and cache size (cs). therefore, each available server (s) was ranked in accordance with its respective computation capability. the server performance function (pf) is expressed as: 𝑃𝐹(𝑆) = (β1 x pt) + (β2 x ps) + (β3 x rs) + (β4 x cs) (1) where β1, β2, β3 and β4 are the weights of the first to fourth terms respectively, for instance, β1 = 0.4, β2 = 0.3, β3 = 0.2 and β4 = 0.1, this is in descending order of priority. higher pf value for a server means having better performance possibility as opposed to other servers. hence, by applying the ranking method, servers were ranked according to their pf values. if the pf value of a server was high, then the server rank was high as well. resource agent resource1 info. resource2 info. resource 3 info. resource n info. server 1 agent server 2 agent server 3 agent server n agent … update distribute resources fleet of servers collaborative interaction resource pool repository agent file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng mikailu et al: a resource performance model for efficient distribution of resources to operating system services in factored operating system. azojete, 18(3):413-426. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 421 the resource distribution flowchart module in figure 3 depicts resource distribution into various operating system services. it showed 1 to n number of operating system services (e.g. system file naming, file management, scheduling, pc security management and error detection), and 1 to n number of processor cores (resources) to be distributed to the services. resource rj is assigned to service si, where j = 1 to n and i = 1 to m respectively. this algorithm fully distributed resource cores to the operating system services forming fleets of servers. the allocation of resources to operating system services was in sequential order until all the operating system services were allocated a processor core in the first round and also the next. this algorithm addressed the allocation problem pointed out by beckmann (2010) as the current scheduling problem in factored operating system. furthermore, when an additional resource was added to the system at any time, the resource agent followed the same procedure to redistribute the processor cores. figure 3: the flowchart of the proposed model resource rj; j=1to n no yes compute performancefunction(pf) = (β1 x pt) + (β2 x ps) + (β3 x rs) + (β4 x cs) rj = pfj; j=1-m is j < = n? print pfj; j=1-m start get parameter rj; j=1...n end no yes no yes os service(si); i=1to 4 allocate pfj to si is j <= n? j = m 1 is i <= 4&j>0? update repository http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 422 3.4 the sequence diagram of the proposed model figure 4 depicts a unified modelling language (uml) sequence diagram that described agents’ interaction in a manner in which they interacted with each other. the resource agent computes the capacity or performance function of each resource and distributes the resources to the various operating system services. figure 4: the sequence diagram of the proposed model the model was simulated using java-2 enterprise edition. the properties of an array were used as signals that formed the initial data generation to train the model. the array length and the sum values of the array elements were used as the input parameters of the process jobs. a randomly generated data between -1 and 1 were used as input weights for the network. 4 the experiment in the experiment, the processor cores performance capacity was computed and distributed to the os services. this experiment computes the capacities of processor cores and distributes them to the four os services identified in the simulation of the model. in this experiment, 5000 processor cores were used for the simulation purpose. the data input for this experiment include the processor type, processor speed, register size, and cache size which are used as processor core parameters. these parameters were used to determine the capacity of each processor in the simulation. in figure 5, the input page for the experiment is depicted. figure 5: processor computation and distribution input page 5 the result and discussion fleets servers resources resource agent distribute res. to os services compute res. performance get resource parameters file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng mikailu et al: a resource performance model for efficient distribution of resources to operating system services in factored operating system. azojete, 18(3):413-426. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 423 the sample results of the computed and distributed processor cores are shown in tables 1, 2, 3 and 4, along with the total number of 1250 processors for each server. where fma and sch represent the file manager and scheduler respectively. table 1: file manager server table 2: scheduler server file manager fleet of servers information! processor id performance (ghz) fma-1 40.0 fma-56 39.0 fma-57 38.0 fma-120 37.0 fma-121 37.0 fma-122 36.0 fma-249 33.0 fma-250 32.0 fma-395 27.0 fma-1080 6.0 fma-1085 5.0 fma-1142 4.0 fma-1143 4.0 fma-1147 3.0 fma-1148 3.0 fma-1211 2.0 fma-1212 2.0 fma-1213 2.0 fma-1249 1.0 fma-1250 1.0 total capacity 25541.0 scheduler fleet of servers information! processor id performance (ghz) sch-1 40.0 sch-2 40.0 sch-56 39.0 sch-57 38.0 sch -120 37.0 sch -250 32.0 sch -305 31.0 sch -306 30.0 sch -908 12.0 sch -909 12.0 sch -910 11.0 sch -969 10.0 sch -972 9.0 sch -1023 8.0 sch -1029 7.0 sch -1079 6.0 sch -1080 6.0 sch -1085 5.0 sch -1142 4.0 sch -1250 1.0 total capacity 25523.0 http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 424 table 3: system file naming server table 4: pc security manager server system file naming fleet of servers information! processor id performance (ghz) sfn-1 40.0 sfn -121 37.0 sfn -122 36.0 sfn -123 36.0 sfn -184 35.0 sfn -185 34.0 sfn -249 33.0 sfn -785 15.0 sfn -849 14.0 sfn -850 13.0 sfn -851 13.0 sfn -908 12.0 sfn -909 12.0 sfn -910 11.0 sfn -1079 6.0 sfn -1080 6.0 sfn -1085 5.0 sfn -1142 4.0 sfn -1143 4.0 sfn -1147 3.0 sfn -1249 1.0 sfn -1250 1.0 total capacity 25513.0 pc security management fleet of servers information! processor id performance (ghz) psm -1 40.0 psm -2 40.0 psm -56 39.0 psm -57 38.0 psm -120 37.0 psm -122 36.0 psm -123 36.0 psm -783 16.0 psm -784 16.0 psm -785 15.0 psm -849 14.0 psm -969 10.0 psm -970 9.0 psm -971 9.0 psm -972 9.0 psm -1023 8.0 psm -1029 7.0 psm -1079 6.0 psm -1080 6.0 psm -1085 5.0 psm -1142 4.0 psm-1250 1.0 total capacity 25533.0 4.3 discussions tables 1, 2, 3 and 4 constitute the result of processor cores computed and distributed to os services that included file manager, scheduler, system file naming and pc security manager services of the os. the sever capacities were observed to range from 1ghz to 40ghz as performance capacity in the tables. table 1 shows that processor id fma-1, processor id fma-395 and processor id fma-1080 with performance capacity of 40.0ghz, 27.0ghz and 6.0ghz respectively were allocated to the file manager server. the result in table 1 is the file manager server of the os service that consists of 1250 sets of processors allocated to it. this is also observed with the other os services in table 2, the processor id sch-1, processor id sch-972 and processor id sch-1142 with performance capacity of 40.0ghz, 9.0ghz and 4.0ghz respectively were allocated to the scheduler server. the result in table 2 is the file manager server of the os service that consists of 1250 sets of processors allocated to it. in table 3, the processor id sfn-1, processor id sfn-850 and processor id sfn-1250 with performance capacity of 40.0ghz, 13.0ghz and 1.0ghz respectively were allocated to the system file naming server. the result in table 3 is the file manager server of the os service that consists of 1250 sets of processors allocated to it. in table 4, the processor id psm-1, processor id psm-970 and processor id psm-1085 with performance capacity of 40.0ghz, 9.0ghz and 5.0ghz respectively were allocated to the pc security management server. the result in table 2 is the file manager server of the os service that consists of 1250 sets of processors allocated to it. the performance file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng mikailu et al: a resource performance model for efficient distribution of resources to operating system services in factored operating system. azojete, 18(3):413-426. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 425 capacities of these os services were summed, giving a total of 25541.0ghz for file manager, 25513.0ghz for scheduler, 25523.0ghz system file naming and 25533.0ghz for the pc security manager. thus, the framework used these results to aid optimal scheduling of process jobs concerning their resource requirements. it is observed that the resource computation and distribution to various os services were adequately accurate and nearly equal in capacities that can proffer solution to the allocation problem (how many cores should be allocated to each os service) as pointed by (beckmann, 2010). moreover, the result of the simulation shows an efficient distribution of 5000 cores to four (4) os services (servers) with each having 1250 fleet of servers. the percentage differences in the four of servers from the minimum are 0.11%, 0.09% and 0.04% respectively. the result shows that the distribution of processor cores to os services is efficient since the differences in total performance function of the fleets of servers were very little. therefore, to maximize the profit that comes with multicore systems, this efficient model is needed for processor cores distribution to os service in a factored operating system. 5. conclusion this study was embarked upon because the conventional os with a single scheduler is inefficient in multicore resource utilization, particularly with the advancement of multicore hardware technology. the framework has computed resource capacities and efficiently distributed processor cores to the various os services in fos with a negligible difference in capacities. the work enables multiple processes to access scheduling services in parallel, enable simultaneous allocation of processor cores to processes, thereby, utilizing the abundant system’s processor cores. the model surmounts the scalability and adaptability issue that comes with ever growing core counts presented by the advancement in hardware technology. a performance processor core resource was developed to compute resource capacity and then allocated these processor cores to the various fos services. this enables the framework to function in a distributed fashion and also proffered solution of cores allocation to os services which is a major scheduling problem of fos identified by beckmann (2010). to improve on the overall performance throughput of the model, a process job transfers between the processor cores will be implemented in the future. references air force research laboratory 2012. fos: a factored operating system for high assurance and scalability on multicores. massachusetts institute of technology technical report, rome, ny, usa, 27pp. https://pdfs.semanticscholar.org/8257/e7 21b495476132ba49d515fce417e2 bdb991.pdf asmussen, n., volp, m., nothen, b., hartig, h. and fettweis, g. 2016. operating-systems chair and vodafone chair mobile communications systems. m3: a hardware/operating-system codesign to tame heterogeneous manycores. retrieved on 3rd december 2017, from https://os.inf.tudresden.de/papers_ps/asmussen-m3-asplos16. pdf baumann, a., barham, p., dagand, p., harris, t., isaacs, r., peter, s., roscoe, t., schiipbach, a. and singhania, a. 2009. the multi-kernel: a new os architecture for scalable multicore systems. proceedings of the acm sigops 22nd symposium on operating systems principles. 11-14 october, big sky, montana, usa., pp. 1-15. https://www.sigops.org/s/conferences/sosp/2009/papers/baumann-sosp09.pdf http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng https://www.sigops.org/s/conferences/sosp/2009/papers/baumann-sosp09.pdf arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):413-426. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ior.agaji@uam.edu.ng 426 beckmann, n. 2010. distributed naming in a factored operating system. msc. thesis. department of computer science, massachusetts institute of technology, cambridge, massachusetts, u.s.a. https://www.researchgate.net/publication/267718821 borkar, s. 2007. thousand core chips – a technology perspective. proceedings of dac. 4-8 june, san diego, california, usa., pp. 746-749. http://impact.asu.edu/cse520fa08/thousandcore.pdf clements, at., kaashoek, mf., zeldovich, n., morris, rt. and kohler, e. 2013. the scalable commutativity rule: designing scalable software for multicore processors. retrieved on 23rd july 2017, from https://people.csail.mit.edu/nickolai/ papers/clements-sc.pdf laplante, p. and milojicic, d. 2016. rethinking operating systems for rebooted computing. proceedings of the ieee international conference on rebooting computing (icrc). 19-21 october, san diego, 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intelligence xix, pp.103-125. doi:10.1007/978-3-662-49017-4_7 schartl, a. 2016. design challenges of scalable operating systems for manycore architectures. retrieved on 7th april 2017, from http://www4.cs.fau.de/lehre/ws 16/pskvbk/slides/slides-schaertl.pdf the international technology roadmap for semiconductors, 2015. the executive report 2.0. retrieved on 18th february 2017 from https://www.semiconductors.org/wpcontent/uploads/ 2018/06/0_2015-itrs-2.0-executive-report-1.pdf wentzlaff, d. and agarwal, a. 2009. factored operating system (fos): the case for scalable operating system for multicores. newsletter acm sigops operating systems review archive, 43(2): 76-85. doi: 10.1144/1531793.1531805 wentzlaff, d., gruenwald, c., beckmann, n., modzelewski, k., belay, a., kasture, h., youseff, l., miller, j. and agarwal, a. 2011. fleets: scalable services in a factored operation system. computer science and artificial intelligence laboratory technical report, massachusetts institute of technology, cambridge, ma 01239, usa. wentzlaff, d. and agarwal, a. 2016. factored operating systems (fos): the case for a scalable operating system for multicores. retrieved on 6th april 2018, from http://www.slideshare.net/mkindika/factored-operating-systems wickizer, s., chen, h., chen, r., mao, y., kaashoek, f., morris, r., pesterev, a., stein, l., ming wu, m., dai, y., zhang, y. and zhang, z. 2008. corey: an operating system for many cores. proceedings of the 8th usenix symposium on operating systems design and implementation (osdi '08) , san diego, california, (december 2008), 43-57 http://www.usenix.org/events/osdi/tech/full\_papers/boyd-wickizer/boyd\_wickizer.pdf file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/ior.agaji@uam.edu.ng https://www.researchgate.net/publication/267718821 http://impact.asu.edu/cse520fa08/thousandcore.pdf https://ieeexplore.ieee.org/abstract/document/7738695/authors https://arxiv.org/pdf/1705.03102.pdf http://www4.cs.fau.de/lehre/ws%2016/pskvbk/slides/slides-schaertl.pdf http://www4.cs.fau.de/lehre/ws%2016/pskvbk/slides/slides-schaertl.pdf https://www.semiconductors.org/wpcontent/uploads/ http://www.usenix.org/events/osdi/tech/full/_papers/boyd-wickizer/boyd/_wickizer.pdf arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):623-642 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 623 original research article impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete s. o. odeyemi1*, m. s. sholagberu1, r. abdulwahab1, a. a. adedeji2 1department of civil & environmental engineering, kwara state university, malete, nigeria. 2department of civil engineering, university of ilorin, ilorin, nigeria *corresponding author’s email address: samson.odeyemi@kwasu.edu.ng 1.0 introduction since the industrial revolution, global warming has become a big problem for a sustainable future. the upsurge in global warming in the last five (5) decades cannot be overlooked. carbon (iv) oxide (co2) is the main greenhouse gas that leads to global warming. when co2 gets accumulated in the air and traps heat, it consequently leads to an increase in temperature on earth. there are many sources of carbon (iv) oxide emissions, however, burning of fossil fuels and the production activities of manufacturing companies are the chief source of global co2 emissions. cement manufacturing industries produce more than 5% of the world’s co2 emissions (chen and zhang, 2010). studies have shown that about 0.98 tons of co2 equivalent are discharged in the production of one ton of cement clinker (qian et al., 2018). turner and collins (2013) estimated that 1.22 kg of co2 are discharged into the atmosphere for each kilogram of cement produced. hence, it is pertinent to utilize the wasted co2 in the development of strong and low-cost concrete (adeyemi and malachi, 2020). el-hassan (2020) recommended acc as a means of reducing co2 emissions, thus preserving the world. article information abstract there are different methods of curing concrete. these include immersion in water, sprinkling of the concrete samples, curing with sand or sawdust and open-air curing method. however, research on the use of accelerated carbonation curing (acc) method for curing concrete is very scanty. therefore, this study concentrates on determining the impact of acc on the properties of guinea corn husk ash (gcha) blended concrete. materials such as portland limestone cement, guinea corn husk ash (gcha), sand, and granite dust were tested for fineness, coarseness, specific gravity before they were used for producing the concrete. characterizations, such as scanning electronic microscopy (sem), energy dispersive x-ray fluorescence spectrometry (edxrf) and x-ray diffraction (xrd) were performed to investigate the properties of the gcha. the batched concrete was then cured using the acc and water curing (wc) methods. mix ratios of 0%, 5%, and 10% gcha were utilized in obtaining the highest compressive strength. compressive strength for 0%, 5%, 10% incorporation of gcha in concrete for both acc and wc methods of curing at 56th day were found to be 23.3 n/mm2 and 24.5 n/mm2; 19.1 n/mm2 and 21.7 n/mm2; 11.1 n/mm2 and 11.8 n/mm2 respectively. the highest sorptivity values were obtained at 10% replacement of cement with gcha for both acc and wc cured samples. however, the sorptivity values decreased as the curing age increases both for acc and wc cured concrete. this demonstrates that both methods produced durable concrete. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 20 april, 2022 revised 11 june, 2022 accepted 14 june, 2022 keywords: accelerated carbonated curing compressive strength concrete guinea corn husk ash durability http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 624 ahmad et al. (2017) defined carbonation as a process of diffusion where co2 gas in the atmosphere infiltrates concrete and in the presence of water produces carbonic acid. this acid reacts with the ca(oh)2 in concrete to form caco3. the caco3 produced owing to the carbonation process makes the resulting concrete dense, thereby improving its properties. carbonation of cementations materials is accountable for the reduction of ph value which results in the concrete becoming less alkaline. hence the process of carbonation of concrete is sometimes known as neutralization process. there are different methods of curing concrete, which includes; immersion in water, sprinkling of the concrete samples, curing with sand and in some cases sawdust, and open-air curing method (atoyebi et al., 2020; james et al., 2011; odeyemi et al., 2021). nevertheless, research implementing acc for concrete curing is few. for example, kim et al. (2022) considered the effect of carbonation curing on the properties of cement mortar containing appreciable level of belite and exposed to high temperatures. their findings show that heat resistance of cement mortar relative to that of samples cured in water was enhanced by carbonation curing. zhang et al. (2017) carried out a review on carbonation curing of some cement-based materials. though some findings were reported, the review recommended further laboratory and industrial research on the subject matter. in the same vein, research abound on the usage of gcha as a possible partial replacement for cement in concrete (aburime et al., 2020; alkamu et al., 2018; bello et al., 2018; ndububa and yakubu, 2015; odeyemi, anifowose, et al., 2020; odeyemi, atoyebi, et al., 2020). however, these authors adopted the method of immersion in water to cure their concrete samples but none of them considered the use of acc. hence, the current study was designed to determine the impact of acc method on the properties of gcha blended concrete. 2.0 materials and methods 2.1 materials 2.1.1 binder portland limestone cement of dangote brand [grade 42.5r], was adopted in this research because it is the mostly used binder in the area of study. soundness, normal consistency, and fineness test were conducted on the cement before use according to bs en 12620:2002+a1:2008 (2008). 2.1.2 water potable water, free from deleterious materials, was utilized for mixing the concrete used in this research. it was tested for its ph value using portable ph meter (s-903) housed at the department of civil engineering water laboratory, university of ilorin, ilorin, nigeria. 2.1.3 fine aggregate the sharp sand (fine aggregates) adopted for this study was collected from asa river, in ilorin. laboratory tests such as specific gravity and fineness modulus were carried out as stipulated in bs en 933-1 (2012), water absorption and sieve analysis, were conducted on the sharp sand in accordance with bs iso 3310-2 (2013). file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 625 2.1.4 coarse aggregate coarse aggregate (crushed stone) which was locally sourced was utilized in this study. the coarse aggregate was sieved to a minimum particle-size distribution ranging from 4.75 to 10 mm. tests such as specific gravity, aggregate crushing value (acv), and water absorption were conducted on the aggregate in accordance with the standard specified in bs en 12620:2002 a1+2008 (2008). 2.1.5 gcha the guinea corn husk (gch) was sourced from farmlands at alapa and otte, in asa local government area of kwara state. the husk was calcinated at a temperature of 650 ℃ as recommended by bello et al. (2018) using a thermolyne furnace at the foundry and forging workshop, department of mechanical engineering, institute of technology, kwara state polytechnic, ilorin. the resulting ashes from the calcination process were grinded to finer particles using a milling machine before sieving with 75 μm sieve to obtain a uniform size distribution. 2.2 methods 2.2.1 fineness test on portland limestone cement and gcha the cement and gcha used in this study were sieved with no. 9 (90 microns) sieve size to obtain their fineness. an empty pan of a known weight was used to hold one hundred (100) grams of the samples. the weight of the pan with the cement/gcha was determined and recorded. for a period of 15 minutes, the cement was sieved through circular and vertical motions. the weight of the residue on the sieve was recorded. equation 1 was used to calculate the fineness of the samples. 𝐹𝑖𝑛𝑒𝑛𝑒𝑠𝑠 = 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝑆𝑎𝑚𝑝𝑙𝑒 𝑅𝑒 𝑡𝑎𝑖𝑛𝑒𝑑 𝑜𝑛 𝑆𝑖𝑒𝑣𝑒 100 . (1) 2.2.2 fineness modulus test the fineness modulus was determined following the procedure enumerated in bs en 933-1 (2012). the fineness modulus of the samples was found with equation 2 by totaling the percentage of retained aggregates on individual sieves and dividing the outcome by 100. the test sample was dried in an oven at a temperature of 110 ± 5 ℃ before weighing. afterwards, the samples were sieved using a set of bs sieves on an electric sieve shaker. after the sieving process, the weight of the samples on each sieve was taken and recorded. the summation of weight of samples on individual sieves was calculated as a ratio of the total sample weighed. fineness modulus= total cummulative % retained 100 (2) 2.2.3 specific gravity test specific gravity of the sample was conducted in accordance with bs 1377-3:2018+a1:2021 (2018). the samples were painstakingly checked on bs sieves to get rid of deleterious materials. an empty bottle was weighed, and the weight designated as w1. the test sample was inserted into the empty bottle and weighed. the weight of both (i.e., the bottle and sample) was recorded as w2. distilled water was poured into the bottle until it reached a marked point. entrapped air and water bubbles at the surface water were removed by shaking the bottle vigorously. the weight of the bottle, with sample and distilled water was designated as w3. subsequently, the bottle was emptied and kept in an oven. upon removal from the http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 626 oven, distilled water was introduced into the dry bottle to the gauge mark and recorded as w4. equation 3 was then used to calculate the specific gravity. 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 = 𝑊2−𝑊1 (𝑊4−𝑊1)−(𝑊3−𝑊2) . (3) 2.2.4 soundness test this test was conducted as specified by neville (2011). in conducting the test, standard consistency of cement was required. 400g of cement was used for this experiment. paste of cement was well mixed and filled into le-chatelier’s mould. the upper surface of the paste in the mould was cleaned and smoothened before placing a small weight over the cover lid. immediately, the mould was inserted in water whose temperature was 27℃ and left for 24 hours. thereafter, the mould was taken out from water and the distance between the indicator point was measured as reading 1. afterwards, the mould was placed in boiling water for 3 hours. after the stated time, the mould was taken out of the boiling water and made to cool at room temperature. the gap between the indicator points was also recorded as reading 2. equation 4 was adopted in determining the soundness of the cement. 𝑆𝑜𝑢𝑛𝑑𝑛𝑒𝑠𝑠 𝑜𝑓 𝑐𝑒𝑚𝑒𝑛𝑡 = (𝑅𝑒𝑎𝑑𝑖𝑛𝑔 2) – (𝑅𝑒𝑎𝑑𝑖𝑛𝑔 1) (4) 2.2.5 normal consistency for cement the normal consistency of the cement was determined following the procedure specified by odeyemi et al. (2022). 300g of cement was placed on a mixing plate. a crater was formed at the center in which 75ml of water was added. within 30 seconds, the material was turned and thoroughly squeezed with hand for at least one minute. thereafter, it was pasted into a ball and tossed from one hand to the other for about six (6) times while keeping the hands 15 cm apart. then, with the ball in the hollow of one hand, the material was hard-pressed into the mould through its larger end and smoothen off the top with a trowel. the mould was placed with its bigger end on a glass plate and smoothen off at the smaller end. thereafter, the mould resting on the glass plate under the plunger was raced in the vicat apparatus. the scale was then set to zero bringing the end of the plunger in touch with the paste surface and then released. the penetration was noted. the experiment was repeated with trial pastes containing different percentages of water. the volume of water mixed was calculated as a fraction by weight of the dry cement as given by equation 5. 𝑁𝑜𝑟𝑚𝑎𝑙 𝐶𝑜𝑛𝑠𝑖𝑠𝑡𝑒𝑛𝑐𝑦 = 𝑠𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑙𝑢𝑛𝑔𝑒𝑟′𝑠 𝑝𝑒𝑛𝑒𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 1 𝑎𝑛𝑑 2 2 (5) sample 1 = first trial of paste made; sample 2 = second trial of paste made. 2.2.6 setting time test after determining the normal consistency of the sample, 1 mm size square needle was inserted to the lower end of a vicat apparatus and made to get in touch with the top of the paste following the procedure reported in neville (2011). the scale of the apparatus was set to avoid error due to parallax before releasing the needle and noting the penetration. the experiment was repeated until the paste had sufficiently stiffened to prevent the needle from penetrating no further than 5 7mm from the lower end of the mould. the time when this was achieved was recorded as the setting times as shown in equations 6a and 6b. 𝐼𝑆𝑇 = 𝑇2 − 𝑇1 (6a) 𝐹𝑆𝑇 = 𝑇3 − 𝑇1 (6b) file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 627 where ist = initial setting time; fst = final setting time; t1 =time of first initial setting needle penetration; t2 =time of final initial setting needle penetration; t3 =time of final initial setting needle penetration. 2.2.7 water absorption test the water absorption capacity was determined following the procedure used by odeyemi et al. (2022). aggregate of 2 kg was used in this experiment. it was washed and placed in a wire basket. this basket was then submerged in water at 27 ℃. the air entrapped in the basket was taken away from the sample by lifting the basket 25 mm from the bottom of the tank and then allowing it to drop 25 times at the rate of one drop per second. thereafter, the aggregate was kept in water for 24 hours. the basket and aggregate were weighed while kept in water. subsequently, they were taken out of water and dried with an absorbent cloth before weighing. the aggregate was then heated in an oven for 24 hours at to 100 ℃. upon removal from the oven, the aggregate was cooled in an airtight container before weighing. the water absorption (%) was calculated using equation 8. 𝑊𝑎𝑡𝑒𝑟 𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 (%) = (𝑊1 –𝑊2) 𝑊2 𝑥 100 (7) w1 (g) = weight of air-dried aggregate; w2 (g) = weight of oven dry aggregate 2.2.8 sieve analysis test this sieve analysis test was performed on both the fine and coarse aggregates to determine their particle size distribution as recommended by odeyemi et al. (2020). the aggregates were oven dried at 105 ℃. a set of bs sieves was then used for sieving. for the fine aggregate, the size of the sieve ranged from 0.075 mm to 2.36mm with a receiver placed at the bottom of the sieves. for the coarse aggregate, the size of the sieves ranged from 4.76 mm to 31.75 mm with a receiver also placed at the bottom of the sieves. the sieve was thereafter shaken vigorously. the particles of the aggregate were then collected and weighed respectively and used in the computation of their particle size distribution curve. 2.2.9 aggregate crushing value the aggregate crushing value was determined following the procedure in jethro et al. (2013). aggregate in a plate was weighed and the weight designated as w. the samples were then divided into 3 layers. the individual layers were given 25 strokes of a tamping rod before weighing. the weight obtained was recorded as w1. the topmost part of the aggregate was cautiously leveled, and a plunger was fixed to rest horizontally to the surface of the aggregate. care was taken to ensure that the plunger does not jam in the cylinder. thereafter, the aggregate with plunger was inserted into the loading platform of the compression testing machine with a loading capacity of 4 tonnes (t). the aggregate was subjected to the load for 10 minutes. the resulting crushed aggregate was sieved with a 200 mm diameter bs sieve 4.00mm stainless steel mesh and loss of fines was avoided. the portion of the aggregate passing through the 200 mm diameter bs sieve was weighed and recorded as w2. the percentage of weight of fines formed to the weight of total sample in each test was calculated using equation 8. acv = w2 𝑥 100 w1−𝑊 . (8) w2= weight of fraction passing through the appropriate sieve (g); w1𝑊 = weight of surface dry sample (g) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 628 2.2.10 scanning electronic microscopy (sem) the sem analysis was done at the material science and engineering laboratory, kwara state university, malete following the procedure adopted by odeyemi et al. (2022). the aspex 3020 model of the equipment was used to investigate the surface morphological structure of gcha. to test the sample, electrons were fired into the sealed vacuum chamber that holds the sample. the sample was coated in gold using palzer’s sputtering device before introducing it under the microscope. the electron beam was brought to a great precision by an electromagnetic coil. another coil steered the electron beam from one side to another to scan across the sample. the electrons made contact with the surface of the sample before bouncing off it. a detector then records the scattered electrons and converts it to an image. the sem displayed the image of the sample at different magnifications of 250, 500, 750 and 1000 on a mode of 16 kv accelerating voltage. 2.2.11 energy dispersive x-ray fluorescence spectrometry (edxrf) the edxrf analysis was conducted at the centre of excellence, nanotechnology advance material in akure, ondo state, nigeria following the procedure adopted by odeyemi et al. (2022). the skyray edxrf analyser (edx 3600b) was used to determine both the elemental and oxide compositions of the gcha. the equipment was designed to operate at the following specifications: analyzable element ranging from 11𝑁𝑎(𝑠𝑜𝑑𝑖𝑢𝑚) − 92𝑈 (𝑢𝑟𝑎𝑛𝑖𝑢𝑚) ; analyzable element content ranges dynamically from ppmlevel to nearly 100 percent; test time (60sec200 sec with extra 50 sec if vacuum requires); inside dimension of sample chamber of 320mm (diam) x 180 mm (height); maximum voltage of 50kv; dimension of spectrometer 650(w) x 466 (h) x 608 (d) mm. to test the sample, the voltage of the equipment was adjusted to ensure adequate power from the x-ray source. the xrd software package on the computer system connected to the equipment was activated and then initialized using pure silicon standard sample. thereafter, the non-homogeneous sample (gcha) was ground to a finer and standardized size before loading into the xrd sample holder. the run parameters such as step size, end angle, start angle, and speed were selected, and the sample was scanned. the equipment analyzed the samples relative to peak formations with the xrd standard reference manual and then the operation ended. 2.2.12 x-ray diffraction (xrd) on gcha the xrd analysis was done at the centre of excellence, nanotechnology advance material, akure, ondo state (naseni) following the procedure adopted by odeyemi et al. (2022). the equipment, (gbc difftech xrd-mma), with a model number of emma014 and cukα radiation of λ=1.54060 å was utilized. the equipment specifications include maximum power of 3.0 kw, voltage ranging from 0 – 60 kv, ampere ranging from 0 – 80ma, long term stability 0.01 % over 8 hrs. of performance, ripple displays at 0.003% rms. to achieve a high-resolution scanning, the powder stage had a tripod mounted to allow very precise height adjustment. a variable radius ranging from 175 mm to 250 mm (k𝛼1 and k𝛼2 peaks completely separated at 80 deg with cukα) was adopted. the scanning speed with full multi-pass averaging 0.0002º/min to 60º /min. the range of 2θ = 0º to 70º with scanning step size of 0.002º was used to determine the chemical phase and the crystalline structure of the gcha. 2.3 concrete mixing proportion two concrete mixtures having the same mix proportions (1:2:4) containing portland limestone cement (plc) with gcha, fine aggregate and coarse aggregate were considered in this study as shown in table 1. the first combination was prepared with plc as the cementitious material. in the second mixture the guinea corn husk ash and portland file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 629 limestone cement were combined as cementations material. both concrete combinations were prepared with a water-to-cementitious material ratio of 0.5 to achieve a slump height of 100 mm (±20 mm) following the recommendations in odeyemi et al. (2020). after mixing, each of the concrete was divided into equal parts and then cured using acc and water immersion curing method. table 1: weight of constituent materials per cubic meter materials quantity portland cement (kg) 205.71 guinea corn husk ash (5%) 10.28 guinea corn husk ash (10%) 20.56 sharp sand (kg) 411.4 coarse aggregate (granite) (kg) 822.8 water to cementations material 0.5 2.4 set up for acc accelerated carbonation curing (acc) chamber for curing the concrete samples was constructed for this experimental study following the schematic diagram found in assaggaf et al. (2019). a snapshot of the chamber and the orthographic view is shown in figure 1. the total length, width and height were 1.0 m x 1.0 m x 1.0 m while the inner length, width and height of the chamber that could contain 90 cubes were 0.9m by 0.9m by 0.9m, respectively. the inner part was built in three layers so that 30 cubes could be arranged in each layer. galvanized plate of 0.6mm thickness was used for the inner construction to prevent the corrosion of the inner chamber. the outer layer thickness was 0.7mm black plate. ‘fev col pur’ adhesive material was used as a moisture curing polyurethane adhesive, which serve as glue that bond both the outer layer and the inner layer plates together. this material is in form of liquid but when sprayed into the plate it became glue like. there were two valves that regulate the inflow and out flow of co2, one on top of the cylinder gauge and the other at the outlet of chamber. a door was inserted to gain access into the chamber and to mitigate the loss of co2 from the chamber. two holes were drilled through the wall of the chamber. the inlet hole was connected to the co2 cylinder through a hose. a pressure gauge was also connected to the setup to measure the pressure in the acc chamber. the second hole serves as the outlet for flushing out the co2 from the chamber after curing the concrete samples. (a) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 630 (b) figure 1: accelerated carbonation chamber (a) snapshot view (b) orthographic view 2.5 curing process a total of 126 concrete cubes were cast. 18 samples without gcha were used as control samples and 108 contained varying percentages of gcha. 63 samples were cured by immersion in water while the remaining 63 were cured in acc. thereafter, the chamber was tightly closed to avoid any escape of the gas. co2 was allowed to circulate within the chamber for ten (10) hours as was done by assaggaf et al. (2019). samples of the cubes were taken out of the chamber after 10 hours to determine their performance in the compression, durability and shrinkage. the samples cured in water were immersed for a maximum number of 56 days before testing. 2.6 compressive strength test the compressive strength test was carried out following the stipulations in bs en 12390-3 (2019). the cubes were tested at 7, 28, and 56 days after they were cast. for each method of curing, 3 cubes were crushed at each day of testing to obtain the average strength. 2.7 durability test two different tests were adopted in determining the durability of the concrete samples as recommended by fapohunda et al. (2020) viz.: (i) coefficient of water absorption test and (ii) sorptivity test. 2.7.1 coefficient of water absorption test the rate at which the dry concrete samples take up water in one (1) hour was investigated using the method found in fapohunda et al. (2020). the concrete samples had 100 x100 x 100 mm dimensions. the specimens were tested after 56 days of curing. the samples were dried in an oven at 105 ℃ for three (3) days until a stable weight was recorded. subsequently, the samples were left to cool in an air-tight container for another three (3) days. since it was file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 631 required for water to flow in a direction in this test, all sides except one of the concrete samples were coated with silicone sealant. then, the samples were partially immersed in a vertical position to a depth of 5 mm at one end, while the remaining sides were exposed to the ambient air. the volume of water absorbed by the concrete samples in the first 60 minutes was determined. equation 9 was considered in calculating the coefficient of water absorption (𝐾𝑎) for the concrete specimens after 56 days curing. 𝐾𝑎 = [ 𝑄 𝐴 ]2𝑥 1 𝑡 (9) where t =time curing (s), a= area of concrete (m2), q = quantity of water absorbed (m3). 2.7.2 sorptivity test the tests were carried out at selected times ranging from 0 to 120 minutes as stipulated in fapohunda et al. (2020). at the times under consideration, the samples were taken from water and excess water dried off using a damp paper towel before weighing the sample. the samples were then placed back in water until another selected time. the gain in mass per unit area over the density of water was plotted versus the square root of the elapsed time. the cumulative water absorption (per unit area of the inflow surface) is thought to increase as the square root of elapsed time (t), increases. the slope of the line of best fit of these points was taken as the sorptivity value. equation 10 was adopted in determining the sorptivity values of the blended concrete specimens at 7, 28 and 56 days of curing. 𝑖 = 𝑠 √𝑡 . (10) where i = sorptivity (m ⋅ s− 1 2); s = slope, t = elapsed time (s) 2.7.3 shrinkage test on concrete the shrinkage was determined as specified in neville (2011). the initial length of the tested specimens 𝐿𝑜 (𝑚) was determined and recorded. afterwards, the length of the sample at each curing age 𝐿𝑡 (𝑚) was determined and recorded. the same procedure was adopted for the masses of the samples. the drying shrinkage ratio ɻ 𝑠 (𝑚) and mass loss ∆𝑤 (𝑔) were calculated using equations 11a and 11b. the average value of the three specimens tested was recorded as the drying shrinkage value for the sample. ɻ 𝑠 = ( 𝐿𝑜− 𝐿𝑡 280 𝑥 100%). (11a) ∆𝑤 = (𝑤𝑜 − 𝑤𝑡 )𝑥100% (11b) 3.0 results and discussion 3.1 test results for materials 3.1 fineness of cement fineness of cement was found to be 1.5%. this result indicates that the cement is very fine and suitable for concrete formation. 3.2 sieve analysis result for fine aggregates (sharp sand) the fineness modulus from the sieve analysis was 2.8%. this falls within the range (2.2 % 3.2%) for fine aggregates. similar result was obtained by odeyemi et al. (2020) when they determined the properties of the fine aggregate used in the designing of concrete using gcha as an additive. figure 2 confirms the size of the sand particles used in the research as the grain diameter were found to be between 0.080 mm to 2.5 mm with most grains falling in the fine range of particle distribution. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 632 figure 2: grain size distribution for fine aggregate 3.3 sieve analysis result for coarse aggregate (granite) the fine modulus obtained from the sieve analysis was 6.8%. this result falls within the range (5.5%-8.0%) for coarse aggregates. in comparison, the results obtained in this research is quite higher than that obtained by odeyemi et al. (2020) when they determined the grading of granite used for their concrete. this is because the granite used in this research is coarser than that used in the earlier stated literature. figure 6 confirms the size of the granite particles used in the research as the grain diameter were found to between 3.6 mm to 30 mm with most grains falling in the coarse range of particle distribution. figure 3: grain size distribution for coarse aggregate 3.4 specific gravity (s.g.) of cement, sharp sand and granite the s.g. of the cement, sharp sand and granite used in this study was obtained as 3.11, 2.57 and 2.69 respectively. it was observed that the s.g. for cement obtained in this research was similar to that obtained by tijani et al. (2020) while the specific gravity of coarse aggregate was file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 633 the same with that obtained by odeyemi et al. (2020). also, the s.g. for the sharp sand fell in the range (2.5-3.0) stated for natural aggregates by neville (2011). 3.5 normal consistency of portland limestone cement table 2 shows that the result of the normal consistency of cement was found to be 32% (128ml). when the quantity of water in concrete is lower than the standard consistency, the hydration of cement will be hampered. also, if the quantity of water is too much there may be reduction in the strength of the cement. hence, the result suggests that 32% of water (128ml) is required to make a standard consistency cement paste for the research work. table 2: normal consistency of cement percentage of water by wt. of dry cement (%) quantity of water added (ml) gauging time (minutes) penetration (mm) 30 120 4 8 31 124 4 30 32 128 4 35 33 132 4 40 3.6 soundness of cement the soundness of portland limestone cement used in this research was obtained as 1mm. according to bs en 196-3:1995 (1995), soundness for ordinary portland cement must not exceed 10mm. therefore, since the result obtained was 1mm, the result confirms that the cement can still maintain its shape and volume after it gets hardened. 3.7 initial and final setting time of cement the initial settling time was calculated as 1 hour 3 minutes. this indicates the time the cement turns into paste by mixing and begins to lose its plasticity properties. the final setting time was found to be 6 hours and 8 minutes. 3.8 water absorption capacity of sharp sand and granite the water absorption capacity for sharp sand and granite were found to be 1.4% and 0.2 % respectively. this indicates that the sharp sand has larger absorption capacity than the granite. it also indicates that the sharp sand has more pores for absorption and could retain more water than the granite. 3.9 aggregate crushing value for granite the aggregate crushing value was found to be 21.5 %. this indicates that the resistance of the aggregates to failure under an increasing compressive load is high. jethro et al. (2013) obtained a coarse aggregate value of 21.6 % for granite used in their study and concluded that the resistance of granite is highly durable for engineering work and road construction. 3.10 quantity of water the ph of the water used in this study was found to be 7.5. this indicates a neutral ph. if the water was too acidic or basic, it may attack the concrete by dissolving both hydrated and unhydrated cement compounds or even react with the compounds present in the carbonated guinea corn husk ash, thereby causing shrinkage in the concrete. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 634 3.11 xrd analysis of calcined gcha figure 4 illustrates the x-ray diffraction form of the calcined gcha. it confirmed the presence of a crystalline compound in the calcined gcha. the peaks at 2 theta (2θ) angles 20.2008°, 28.2348°, 41.0028°, 43.564°, 54.6025°, and 61.9344° are attributed to the presence of sio2 (quartz) particles. the gcha molecules tend to form a hexagonal crystalline structure. this result is in agreement with what nandanwar et al., (2015) obtained when they carried out the xrd characterization of sio2 particles and obtained an hexagonal shape. figure 4: the xrd pattern of the calcined gcha 3.12 xrf analysis of calcined gcha table 3 shows the oxide composition of gcha. it consists mainly of sio2 (63.1559%), k2o (23.4164%), al2o3 (4.1534%), and fe2o3 (4.6572%). it was discovered that the sum of al2o3, sio2, and fe2o3 gave 71.9665%. this is above the minimum 70% specified for supplementary cementitious materials by astm c618 (standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete, astm international, west conshohocken, pa, 2019, 2019). odeyemi et al. (2020) and ndububa et al. (2015) also obtained similar results. the findings are also in tandem with what was obtained by odeyemi et al. (2022) for bamboo leaf ash (bla). these further confirms that gcha is suitable as a pozzolan in concrete. table 3: the oxide composition of calcined gcha oxide composition (%) mgo 3.3649 al2o3 4.1534 sio2 63.1559 p2o5 2.2621 so3 4.0899 k2o 23.4164 cao 6.9492 tio2 0.0000 v2o5 0.0000 cr2o3 0.0000 mno 0.0187 file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 635 coo 0.0000 fe2o3 4.6572 nio 0.0098 cuo 0.0483 zno 0.2338 as2o3 0.0049 pbo2 0.0559 wo3 0.3297 au2o 0.0000 ag2o 0.0018 rb2o 0.0489 nb2o5 0.0062 moo3 0.3045 cdo 0.000 sno2 0.4802 sb2o3 0.4169 *loi 0.0000 * loss of ignition 3.13 sem analysis of calcined gcha the morphological structure of the calcined gcha at 650 ℃ is revealed in figure 5. figure 5(a-d) are of equivalent width of 15.8 mm at 250-1000 magnification. figure 5(a) shows the image of the gcha at magnification of 250. the structure contains numerous pores of irregular size. a nearer view of the structure in figure 5(b) shows that the gcha at magnification 500 also contains flat-like materials with coarse edges. moreover, at figure 4 (cd), magnifications 750 and 1000 respectively, it was clearly observed that there are discontinuous patterns of arrangement on the gcha image that are well compact. therefore, it was inferred that the gcha calcined at 650℃ is a potential material for the substitution of cement in concrete. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 636 figure 5: sem images of calcined gcha at different magnifications (a) magnification at 250 (b) magnification at 500 (c) magnification at 750 (d) magnification at 1000 3.14 compressive strength of concrete the average compressive strengths for 0%, 5% and 10% gcha inclusion in concrete after being cured by acc and water curing are revealed in figure 6. the tests were conducted on the 7th, 28th and 56th day of curing. for the control experiment for acc, the compressive strength increased from 16.2 n/mm2 at day 7 to 23.3 n/mm2 at day 56. for the wc, the compressive strength increased from 17.6 n/mm2 at day 7 to 24.5 n/mm2 at day 56. for 5% inclusion of gcha in concrete, the compressive strength increased from 12.6 n/mm2 at day 7 to 19.1 n/mm2 at day 56 and from 13.7 n/mm2 at day 7 to 21.7 n/mm2 at day 56 for acc and wc respectively. for 10% inclusion of gcha in concrete, the compressive strength increased from 6.2 n/mm2 at day 7 to 11.1 n/mm2 at day 56 and from 7.9 n/mm2 at day 7 to 11.8 n/mm2 at day 56 for acc and wc respectively. hence, from the graph it could be observed that as the ratio of gcha increases the compressive strength reduced for both acc and wc concrete. these findings are like those published by poongodi et al., (2021). moreover, the acc method of curing produced results that are close to the results obtained using wc. this follows the same trend of results reported by assaggaf et al. (2019). furthermore, the advantage in using acc is that the curing was carried out for only ten (10) hours unlike the immersion method which was done for 56 days. figure 6: compressive strength for concrete samples (a) acc (b) wc (a) 0% gcha (b) 5% gcha and (c) 10 % gcha file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 637 3.15 sorptive behaviour figure 7(a) shows the plot of sorptivity against the percentage replacement of gcha for acc with r-square values of 0.9932, 0.9868, and 0.8322 at 7, 28 and 56 days of curing respectively. the highest value (0.26 mm/𝑚𝑖𝑛0.5) and lowest value (0.09 mm/𝑚𝑖𝑛0.5) value of sorptivity was obtained at the 7th and 56th day for 10 % gcha and 0% gcha respectively. figure 7(b) shows the plot of sorptivity against the percentage replacement of gcha for wc with rsquare values of 0.9423, 1.0000, and 0.8547 at 7, 28 and 56 days of curing respectively. the highest value (0.23 mm/𝑚𝑖𝑛0.5) and lowest (0.08 mm/𝑚𝑖𝑛0.5) value of sorptivity was obtained at the 7th and 56th day at 10 % gcha and 0% gcha for wc respectively. the graph shows the same trends for both acc and wc. the values of sorptivity are less than 0.1 mm/𝑚𝑖𝑛0.5 at 56 days indicating that both curing methods are suitable for concrete development. similar result was obtained by cantero et al. (2021) in a study that involves the use of a recycled concrete. this further validates that acc cured concrete are durable. figure 7: sorptivity for concrete (a) acc (b) wc 3.16 water absorption figure 8(a) expresses the plot of water absorption against the percentage replacement of gcha for acc. the highest value for the water absorption (2.91 𝑚/𝑠2) was obtained for http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 638 10% inclusion of gcha at 56th day of curing. the graph also reveals that as the level of substituting cement with gcha increases the water absorption also increases. this indicates that the total reachable pore volume of the concrete becomes more exposed as the percentage gcha increases. in the same vein, as the number of curing days increases the water absorption also increases. figure 8(b) shows the plot of water absorption against the percentage replacement of gcha for wc. the highest value for the water absorption (2.87 %) was obtained for 0% inclusion of gcha at 56th day of curing. unlike the acc method, the 56th day water absorption result decreased with the surge in the proportion of gcha in the concrete. the results show that the highest value of water absorption occurred in acc method. this high value in water absorption implies that the acc method may not be suitable for concrete members kept in water. figure 8: water absorption (a) acc (b) wc 3.17 shrinkage figure 9(a) reveals the change in shrinkage against the percentage replacement of gcha for acc. the highest value of shrinkage (-153 𝜇𝑚/𝑚) was obtained after 56 days of curing at 10% inclusion of gcha. the correlation coefficient at day 7, 28 and 56 were all greater than 0.9. these findings agree with the result of cantero et al. (2021). a similar trend was observed in figure 9(b) samples cured in wc. the highest value was obtained as -176 𝜇𝑚/𝑚 at day 56 for 10% inclusion of gcha. the correlation coefficient at day 7 and 28 were greater than 0.9. however, that of 56 days decreased slightly. hence, in both acc and wc, the variation in loss of moisture content in the concrete due to hydration of cement and temperature between day 7 and 28 is not as significant when compared to the shrinkage that occurred between day 28 and 56. generally, the shrinkage tends to reduce as the days of curing increases and as the percentage of gcha increases. file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng odeyemi et al: impact of accelerated carbonation curing (acc) on the properties of guinea corn husk ash blended concrete. azojete, 18(4):623-642. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 639 figure 9: shrinkage (a) acc (b) wc conclusion this research studied the impact of acc on the performance of guinea corn husk ash blended concrete and the following conclusions were drawn. (a) the chemical composition of portland limestone cement utilized in the research is within the acceptable range recommended by bs en 12620:2002+a1 (2008) and guinea corn husk ash (gcha) satisfies the requirement for a pozzolan and can be adopted as supplementary cementitious material for concrete production. (b) the method of curing by immersion in water produced the concrete with the highest strength with a strength value of 21.7 n/mm2 this was closely followed by the concrete cured in acc with a strength value of 19.1 n/mm2. (c) both acc and water immersion curing methods produced concrete that are durable. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/samson.odeyemi@kwasu.edu.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):623-642 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: samson.odeyemi@kwasu.edu.ng 640 notation acc – accelerated carbonation curing gcha guinea corn husk ash gch guinea corn husk wc – water curing sem scanning electronic microscopy edxrf energy dispersive x-ray fluorescence spectrometer xrd x-ray diffraction references aburime, pi., ndububa, ee. and kpue, do. 2020. the impact of guinea corn husk ash as an admixture for crack control in concrete. european journal of engineering research and science, 5(10): 1152–1159. https://doi.org/10.24018/ejers.2020.5.10.2171 adeyemi, sa. and malachi, j. 2020. assessment of the ternary 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samson.odeyemi@kwasu.edu.ng 642 architecture, 9(7): 2286–2291. https://doi.org/10.13189/cea.2021.090716 odeyemi, so., anifowose, ma., abdulwahab, r. and oduoye, wo. 2020. mechanical properties of high-performance concrete with guinea corn husk ash as additive. lautech journal of civil and environmental studies, 5: 139–154. https://doi.org/10.36108/laujoces/0202/50(0131) odeyemi, so., atoyebi, od. and ayo, e. 2020. effect of guinea corn husk ash on the mechanical properties of lateritic concrete effect of guinea corn husk ash on the mechanical properties of lateritic concrete. iop conference series: earth and environmental sceince, 1-11. https://doi.org/10.1088/1755-1315/445/1/012034 odeyemi, so., atoyebi, od., kegbeyale, os., anifowose, ma., odeyemi, ot., adeniyi, ag. and orisadare, oa. 2022. mechanical properties and microstructure of high-performance concrete with bamboo leaf ash as additive. cleaner engineering and technology, 6: 1–6. https://doi.org/10.1016/j.clet.2021.100352 poongodi, k., murthi, p., awoyera, po., gobinath, r. and olalusi, ob. 2021. durability properties of self-compacting concrete made with recycled aggregate. silicon, 1: 2727– 2735. qian, x., wang, j., fang, y. and wang, l. 2018. carbon dioxide as an admixture for better performance of opc-based concrete. journal of co2 utilization, 25: 31–38. https://doi.org/10.1016/j.jcou.2018.03.007 standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete, astm international, west conshohocken, pa. 2019. https://doi.org/10.1520/c0618-19 tijani, ma., ajagbe, wc., ganiyu, aa., aremu, as. and ojewole, yn. 2020. strength and absorption of sorghum husk ash sandcrete blocks. premier journal of engineering and applied science, 1(1): 1–7. turner, lk.. and collins, fg. 2013. carbon dioxide equivalent (co2-e) emissions: a comparison between geopolymer and opc cement concrete. construction and building materials, 43: 125–130. https://doi.org/https://doi.org/10.1016/j.conbuildmat.2013.01.023 zhang, d., ghouleh, z. and shao, y. 2017. review on carbonation curing of cement-based materials. journal of co2 utilization, 21: 119–131. https://doi.org/https://doi.org/10.1016/j.jcou.2017.07.003 file:///c:/user/downloads/azojete143/www.azojete.com.ng samson.odeyemi@kwasu.edu.ng https://doi.org/https:/doi.org/10.1016/j.conbuildmat.2013.01.023 https://doi.org/https:/doi.org/10.1016/j.jcou.2017.07.003 arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):161-172 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 161 matlab simevent for traffic queue model p. b. anyin1*, p. b. anyin2, and a. a. murana3 1department of civil engineering, university of calabar, calabar, nigeria 2department of electrical electronics engineering, university of cross river state, nigeria. 3department of civil engineering, ahmadu bello university zaria, nigeria *corresponding author's email address: profpeteranyin@unical.edu.ng article information submitted 2 january, 2024 revised 9 february, 2024 accepted 11 february, 2024 keywords: queueing simulation distributive statistics simulinks abstract the use of matlab (simevent) for network performance measure determination is encouraged by the novel precision that comes with artificial intelligence techniques. however, most efforts in this direction have been undervalued due to distribution assumptions. therefore, a comparative analysis with an analytical method is studied in this work, with service rate distribution determined, using a distributive statassist tool. kendall’s model adopted was m/m/1 for a single server queueing system and was confirmed by the service rate distributive pattern as 1.0 second per customer. estimating the network measures showed analytical and simulation models hourly average queue length of 3,751 vehicles, with 1hr and 11minutes waiting time. the total daily queueing length is 8419vehicles, with 8819secs total waiting time. the utilization factor of 0.984 and the model is found to be 0.9825/1.025/1. from the optimum determination of the analytical model (am) and simulation model (sm) weekly performance measures carried out, the am produced the following average waiting time 3751, 125, 56, 35, 110, 19, and 17, from monday through sunday. in contrast, the sm produced an average waiting time of 3681, 3007, 2789, 2567, 2854, 2467, and 1976 respectively. due to the continuous waiting line output, the sm has proven realistic. therefore, the simulation model coupled with distributive statassist tool is recommended for queueing studies. a comparative study of simulators is recommended for further studies. 1.0 introduction life is full of trade-offs. people must choose how to spend scarce money and time. timesaving and convenience are commonly mentioned by consumers as among the most important motivations for purchasing a service. however, waiting to be served may neutralize potential benefits and negatively affect attitudes toward the quality of service, brand, or product (anyin and etika, 2022; anyin, 2022; delgado, 2016). customers identify waiting in line as frustrating, stressful, and expensive (anyin and etika, 2022). vehicular queue length and queuing duration are an important basis for traffic management departments to establish and implement traffic control measures. the study of vehicular queue length and queuing duration has important practical significance and value in operational research (li et al., 2019; anyin et al., 2023; adeke et al., 2018). with the development of artificial intelligence-based models in scientific research, models like matlab and other commercial simulation tools used for qualitative and quantitative analysis have progressed into qualitative-based management decisions referred to as operational research. as recommended by anyin and etika (2022), a simulation model is http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):161-172. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 162 needed for a more detailed evaluation of any case study in the field. the use of matlab simulink for queue model is not new. however, most efforts in this direction have been undervalued due to service rate distribution assumptions. thus, this study attempts to suggest a better approach to queueing performance characteristics determination using matlab simevent. the basic knowledge of queueing performance characteristics which includes, waiting time and queueing length, can be gained more in anyin and etika (2022). the basic queueing theory may be divided into two mathematical studies: one deals with specific type distributions from which mathematical formulas are derived, while the other deals with classical empirical or hypothesized distributions which are determined through analysis. fundamentally, queueing analysis is used to determine the difference between a queued road segment and how long it would have taken if there were no queueing or congestion (tarabia, 2008, lakshmi and sivakumar, 2013). the goodness of fit (gof) test is used to test if sample data fits a distribution from a certain population (therefore, a population with a normal distribution or one with a weibull distribution). in other words, it tells you if your sample data represents the data you would expect to find in the actual population. the goodness of fit tests commonly used in statistics are the chi-square, kolmogorov-smirnov, anderson-darling, and shipiro-wilk (feine et al., 2018). the chi-square test is the most commonly used goodness of fit test and it is one among many you will find among advanced placement (ap) statistics or elementary statistics. the chi-square can be used for discrete distributions like the binomial and poisson distribution, while the kolmogorov smirnov and andersondarling goodness of fit tests can only be used for continuous and discrete distribution (garfield et al., 2008, piccolino, 1996). chi-square has two potential disadvantages and they are; (a) the test can only be used for data put into classes (bins). if you have nonbonded data you will need to make a frequency table or histogram before performing the test. (b) it requires a sufficient sample size for the chisquare approximation to be valid (feine et al., 2018; piccolino, 1996). there are two types of chi-square tests, the first is the chi-square independence test, which compares two sets of data to see if there is a relationship. the second is the chi-square goodness of fit is to fit one categorical variable to a distribution. both tests use the chi-square statistic and distribution (feine et al., 2018, garfield et al., 2008). the kolmogorov-smirnov test is a test used for the normalization of statistical data. the advantage of this test is that its distribution is not built on assumptions (feine et al., 2018). a sample can be compared to a distribution using a one-sample kolmogorov smirnov (k-s) test or a two-sample k-s test. this test is easily taken using software because critical values need to be calculated for each distribution and finding the table for critical values is not an easy task (feine et al., 2018). depending on the choice fit test, easyfit calculates the goodness of fit statistics for each of the fitted distributions. easyfit is a data analysis and simulation application that allows users to fit probability distributions to sample data, select the best model, and apply the analyzed results to make informed decisions. easyfit gives room automatically rather than manually to fit a large number of distributions to your data and select the best model in a bit of seconds (moura et al., 2010, feine et al., 2018). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng anyin et al: matlab simevent for traffic queue model. azojete, 20(1):161-172. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 163 a model in a general sense, is a small physical or mathematical abstraction of an object or a system. this has found application in many fields of research such as communication, transportation engineering, mathematics, chemistry, and a host of others (schlecht, 2022). we have different types of models, but this research is going to be limited to queueing models. 1.1 queueing theory the queuing process was first expressed by erlang in 1913 to treat congestion problems associated with telephone call exchange at the beginning of the 20th century (fomundam and herrmann, 2007) the term, ”queue” as defined by anyin and etika (2022) as a waiting line especially of persons or vehicles (customers) in a file or line waiting for services where one or more customers are called upon at a time to be served based on available service units known as servers. service pattern – series called’ “service discipline” where identical servers are accessed through two or more channels rendering the same services; and queueing rule refers to queue discipline which includes; first-in-first-out (fifo), last-infirstout (lifo) (anyin et al., 2024). there are different types of models with diverse functionalities, they are as follows; m/m/1, m/g/1, m/m/c, m/m/, g/m/1, g/g/1, g/g/, g/m/c, g/g/c, d/d/1, m/d/1, m/d/c, and m/d/. where m/m/1 stands for poisson arrival distribution and exponential service distribution. 1 represents several servers which is one. g represents general arrivals and general servers. c represents constant service rate, represents infinity server, d for arrival represents deterministic distributive arrival and for service, it represents deterministic service rate (fomundam and herrmann, 2007; meisling 1958; priya et al., 2021). 1.2 simulation models simevents is a matlab event-based toolkit that provides a discrete-event simulation engine and component library containing predefined blocks with different system functionalities such as entity generators, ros and fifo, signal scope, path combiner, set attribute, etc., used for modeling in simulink. one can model event-driven communication between components to analyze and optimize end-to-end latencies, throughput, packet loss, and other performance characteristics. libraries of predefined blocks, such as queues, servers, and switches, enable you to accurately represent your system and customize routing, processing delays, prioritization, and other operations. with simevents one can design distributed control systems, hardware architectures, and sensor and communication networks for aerospace, automotive, and electronics applications. one can also simulate event-driven processes, such as the execution of a mission plan or the stages of a manufacturing process, to determine resource requirements and identify bottlenecks (vilaplana et al., 2014; inacio and antunes, 2008, seo et al., 2019). 2 material and method a simulation model was implemented in the determination of traffic network performance measures. this study was performed on the kugbo checkpoint abuja-keffi highway. kugbo is the name of a town in abuja, located along abuja-keffi highway. it occupies about 121km2. abuja-keffi highway is a road linking keffi, karu, maraba, new-karu, and nyanya, to abuja, with an average travel demand of 42400vehs a day (anyin and etika 2022). figure 1 shows a google map of the kugbo checkpoint spotted in red ink. abuja is a city in the central part of nigeria and the federal capital of nigeria. it is about 1250m (about 4100 ft) above sea level, http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):161-172. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 164 occupying 713 km2 of land area. the city’s average monthly temperature is in the range of 210 350 c (690 – 770 f). the coordinates of abuja is latitude 904’20.1504”n and latitude 7029’28.6872”e. the data collected was processed and is presented in table 1. figure 1: (a) google map picturing kugbo checkpoint (b) traffic situation in kugbo checkpoint. table 1: vehicular hourly arrival rate for november 2017 kugbo checkpoint (anyin and etika 2022). 2.1 data collection the data used in this study was adopted from anyin and etika (2022). the estimated average hourly travel demand measured in the vehicle (vehs) per time revealed that monday had the highest travel demand as seen in table 1. 2.1.1 data distribution data distribution was carried out using easyfit to test the fitness of the distribution. this was done on inter-arrival and service time data. the arrival rate is supposed to follow a definite distribution pattern which is used to analyze its customer’s flow into the system. from the pieces of literature, it is seen that arrivals come either in batches or in singles, and are determined using the easyfit toolkit to detect the distribution pattern it follows. in discrete random variables, there is no chi-square in this case kolmogorov-smirnov test is used to fit the distribution. there are various distribution series that embrace diverse distribution patterns from frechet, cauchy, exponential, constant, deterministic, infinity, poisson, and a host of others. the advantage of having a known distribution span from the analytical model to the simulation model, though its reflection on am is not as obvious as sm. kolmogorov-smirnov was chosen because of its wide range of precision decisions and tolerance. the analytical file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng anyin et al: matlab simevent for traffic queue model. azojete, 20(1):161-172. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 165 model (am) and simulation model (sm) have different input formats; while am requires arrival and service rates; inputs for sm are average inter-arrival time and average service time. the performance of the entity generator and server blocks is determined by the distribution. 2.1.2 simulation model the model used is a matlab r2013a software event predictive engine, called simevents. the simevents model was built using built-in blocks found in the simulink library. blocks used for this model and their functions are as follows; event-based random number – this block is used for setting interarrival time for random events to conform to the selected arrival distribution type which could be exponential (as specified by this study), uniform, and constant. time-based entity generator – the block generates discrete entities representing stochastic arrivals based on the specified intergeneration time from the event-based random number block. intergeneration time is the time lapse between consecutive arrivals in the model. in this model, an exponential distribution type is specified with estimated mean interarrival time as the intergeneration time for each queue type or case based on demands. the initial seed value of each run is set using 5-digit odd numbers to aid the repeatability of the random process when re-entered. set attributes block – it is used for assigning unique attributes or characteristics to discrete arrivals for the sake of identification or classification and priority specifications. path combiner this block assembles entities with different attributes assumed to present the entry buffer area in the system before sorting into various queues using priority block. the precedence is set as equiprobable since all arrivals have equal chances of entering the system before taking a decision. priority block – in this block, the combined entities from the path combiner are sorted out based on set attributes which distinguishes each entity accordingly; the priority option does the categorized sorting. fifo block – this block ensures that entities arriving on the queue willing to proceed to the service facility do so based on the first-in-first-out rule. output switch – it is used for sorting combined entities based on assigned attributes under the ‘set attribute’ block. n-server block – this block allows the assignment of more than one server per queue category. read timer block – it measures the arrival and departure time of entities into the system, hence, two sets of it are used to estimate time spent by entities in the system (sojourn time). entity sink – all departures exit the network through the entity sink block. signal scope – this block displays the output of the simulation process in graphical form (adeke et al., 2019). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):161-172. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 166 these block operations were operated and connected as follows. the event-based random number generator creates a sample of random numbers, according to the distribution pattern of the arrival. the numbers are travel demands and are ordered as shown in table 1. these numbers are converted by time-based entity generators. this generator operation was measured by interarrival time, and the instantaneous event counting scope arrival was used for plotting the service rate. the start timer was sandwiched between the generator and the fifo-queue block (there are many other protocols available) for feeding entities. the fifo queue worked with a single server and serviced the entities that entered. another random number-based block was connected to fifo-queue block, which influenced its service delivery to work by the distribution pattern (exponential order). while the service was going on, the corresponding queue length and waiting time blocks measured the system network characteristics. the utilization factor also was connected to the single server for system efficiency measurement. the flow chart for this experiment is shown in figure 2. this shows the various steps in the queueing process as represented by the simulink model which is characterized by different blocks and system functionalities. figure 2: flowchart of simulation model this simulation model and procedure were repeated for all the scenarios. a single entity generator was used for generating identical entities; average inter-arrival time is entered in the event-based random number block with distribution type specified as poisson distributed arrivals. a fifo queueing block was used to control the service rule and finite capacity of the queue specified as maximum demand in the fifo block. a single server block was used for the scenario. the characteristic equation is, utilization factor (1) expected number of customers in the queue: = 𝜌2 1−𝜌 expected time customers spend in the system: = 1 𝑚µ(1−𝜌) (2) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng anyin et al: matlab simevent for traffic queue model. azojete, 20(1):161-172. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 167 expected time customers spend in the server: = 1 (1−𝜌) (3) expected time customers spend in the queue: = 𝜌 𝑚µ(1−𝜌) (4) where 𝑚 represents the number of servers and µ represents the service rate (anyin and etika 2022). the server determines the model type, this study used the m/m/1 model as explained in section 1.1. the first m is determined by the arrival rate, the second m is determined by the service rate, and the 1 was determined from the average service time distribution pattern. 3 results and discussion this section presents the result of the study and discusses the relation of the outcome and its application and contribution to knowledge. the outcome is particularly the network performance characteristics and its corresponding comparative analysis. this, therefore begins with the arrival characteristics. 3.1 arrival characteristics the arrival time distribution pattern was achieved using the data provided in table 1, where with the aid of easyfit the distribution pattern was determined from kolmogorov-smirnov series to be poisson distribution. the outcome of the test is provided in table 2. table 2: average arrival poisson distribution pattern. the arrival rate is supposed to follow a defined distribution pattern which was used to analyze its customer’s flow into the system. it was seen that arrivals come either in batches or in singles, and are determined using the easyfit toolkit to detect the distribution pattern it follows. kolmogorov-smirnov series was used to check the goodness of fit, and it accounted that poisson distribution ranked first, though, from easyfit discrete distribution, chi-square was not displayed in all the occasions but was displayed in continuous distribution. a kolmogorov-smirnov statistics test showed that; the arrival rate followed the poisson distribution and is accepted as a null hypothesis with 0.22455 at 5 degrees of freedom less than 1, as shown in table 2. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):161-172. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 168 3.2 service characteristics the service rate at the checkpoint was also determined using easyfit statassist application, this application enabled this study to fit data to a distribution. with the distribution pattern, the server simulation equation adopts a defined analysis equation in serving its customers. it finds use in most simulations, precisely in mathlab where with the help of event-basedrandom numbers, distribution patterns are created for simulation. the service rate data is used to determine the service rate pattern. the service time goodness of fit was analyzed using kolmogorov-smirnov. the best fit was exponential. a kolmogorov-smirnov statistics test showed that; the service time followed exponential distribution and was accepted as a null hypothesis with = 0.05959 at 5 degrees of freedom which is less than 0.15755, shown in table 3. the acceptance of exponential distribution at all levels of critical juxtaposes that the service time practicability of this study is stochastic rather than deterministic. a deterministic service rate defines the serviceability of the system to follow a constant proportion. from the graph shown in figure 3, it is seen that the mean of the distribution has a mean service rate of 0.00167/second, and its inverse is 1.0015 second. which can be interpreted as the server serving the event entities at an exponential rate of one customer per second. the serviceability distribution pattern is relatively important to the simulation model (sm) in determining its stochastic service distributions. table 3: average service time goodness of fit result service characteristics figure 3: average service time exponential distribution pattern. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng anyin et al: matlab simevent for traffic queue model. azojete, 20(1):161-172. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 169 3.1 queueing model determination from the number of servers observed from the field, it is discovered that the system has one server, the choice of model is a single server denoted by m/m/1 where, m represents the arrival rate pattern following poisons distribution, m, the service times of all customers are independent and identically distributed random variables (i.i.d) and exponentially distributed. two types of queueing models can be used in this research, single (m/m/1) and dual (m/m/2), so far only m/m/1 has been used, which is determined as 0.9825/1.029/1. 3.3.1 determination of queue system performance measures the average arrival rate for all days is estimated and used respectively across the days shown in table 4. from table 1, monday has the highest hourly travel demand, this corresponds to the queueing outcome found in table 4. these queueing studies provide insight into how queue data are determined graphically. this study is limited to comparative and efficient investigation of simevent-simulinks and easyfit coupling. table 4: performance measures of analytical and simulation model. 3.4 optimum performance of analytical and simulation model 3.4.1 system performance measure the waiting time and queue length of customers are determined using little’s relation and simevent-simulinks, following the mathematical relations provided by anyin and etika (2022). the various performance measures for all days were estimated in an excel spreadsheet for kugbo checkpoint. from table 4, the traffic intensity of both the analytical and simulation models are approximately the same, but the waiting time and queue length are different because the analytical model follows constant proportion and the simulation model follows a discretetime process by using the service rate distribution pattern. the service rate for all days is assumed to be the same and the arrival rate follows a constant proportion in the analytical model, while in the simulation model, the service time cannot be assumed to be the same, because of the provision for distribution input and the fact that arrival is dynamic because of the provision of event-based-random-number block which provides distribution to the system. 3.4.2 waiting time of sm and am from table 4, it is practically impossible to have only mondays very busy, because the analytical model could not estimate the waiting time of other days in the week, but the simulation model could. this could be seen from the unrealistic assumptions that govern the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/akeem.raji@oouagoiwoye.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):161-172. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 170 analytical approach over the simulation approach and its negligence of distribution pattern. therefore, the graphical distribution of the waiting time of the simulation model is chosen and shown in figure 4a. 3.5 system utilization factor it is essential to understand the network system’s occupancy or working period within the experimental duration, as it affects other performance parameters. this is the percentage of time the system functioned out of the available period (12 hours). the analytical and simulation model utilization factors were determined following non-priority system operation based on the fifo rule. results obtained from m/m/1 analytical and simulation models are denoted as am and sm respectively. the utilization factor for am and sm is as shown in figure 4b. figure 4: this consists of (a) the waiting time of the analytical and simulation models. (b) the utilization factor of the an and sm. from the system utilization factors plot evaluated in figure 4b. the sm and am have approximately the same values of 0.9839 and 0.9835 units respectively, this connotes that both models are valid and in agreement with anyin and etika (2022). = 0.28482. it is seen that the mean of the distribution which happened to become the mean 10 minutes arrival is 589.49 veh. this value was adopted for further determination of the secondary parameters. it finds its application in engineering operational management, to provide a hedge to mitigate future hitches. from figure 5 shown below, the simulation model outputs the following network performance measure characteristics, the average waiting lines of 3682vehs and waiting time 3751sec. figure 5: the waiting time of the simulation model (sm). 4 conclusion in this work, an m/m/1 model queueing system with customer interjection and jockeying neglected was extensively studied using matlab simevents. this model was chosen using a distributive statassist tool by analyzing the arrival and service distribution pattern. thus, the queueing model was confirmed to be single server, by service rate distributive pattern of 1.0 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng anyin et al: matlab simevent for traffic queue model. azojete, 20(1):161-172. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 171 second per customer. the optimum performances of both am and sm were achieved. it was found that; the arrival rate followed poisson distribution and the service rate followed exponential distribution in the kolmogorov smirnov series. the model determined was a single server queue model, 0.9825/1.029/1, from the simulation model and analytical model, the system performance measures show the days that customers suffer more queues to be mondays, which gave an average queue length of 3682 vehicles and 3751 seconds waiting time. the utilization factors for am and sm are the same 0.9835, thus validate the sm. from the optimum determination of am and sm performance measures carried out, the am produced the following average waiting time 3751, 125, 56, 35, 110, 19, and 17, while the sm produced average waiting time of 3681, 3007, 2789, 2567, 2854, 2467, and 1976, for mondays through sundays respectively. looking at the sm waiting line which is more empirical because of the distributive nature of the simulation, while for analytical model used for the analysis of the queueing system yielded unrealistic results due to unrealistic assumptions of having an average constant service rate throughout the process. the difference in performance outputs from analytical and simulation models is attributed to the fact that; the simulation model carries out discrete time analysis of the system. a comparative study of other simulation models such as genetic algorithm, python, netsim, and others on the queueing model is recommended. references anyin, pb., anyin, pb. and murana, aa. 2024. matlab simevent for traffic queue assessment in kugbo checkpoint abuja-keffi highway. computational engineering and physical modeling, 2(1):56–66. anyin, pb., ewa, d., etika, a. and anyin, pb. 2024. application of generative adversarial networks (gans) to develop traffic queueing jockey theory on horizontal curves. nigeria journal of technology, 42(4): 478 485, www.nijotech.com. anyin, pb. and etika, aa. 2022. analytical determination of queueing system performance for sustainable economic development. arid zone journal of engineering, technology and environment, 18(3):517–526. anyin, pb., odama, go. and njoku, fc. 2022. performance evaluation of fuzzy logic controller’s certain membership functions for control of slip energy recovery drive for improved power factor. international journal of advances in engineering and management (ijaem), 4(5): 1937 – 1958. adeke, pt., atoo, aa. and zava, ae. 2018. traffic signal design and performance assessment of 4-leg intersections using webster’s model: a case of ‘srs’ and ‘b-division’ intersections in makurdi town. traffic 5(05): 1253 1258. adeke, pt., joel, m. and edeh, j. 2019. simulation of priority queuing at total petrol filling station in makurdi town using simevents toolkit. computational engineering and physical modeling, 2(1): 56–66. priya, bk., kumar, ms., geetha, m., prabhu, j., maheshwari, v., rajendran, s., prasanna, m. and rajendran, p. 2021. queueing network model with jockeying to reduce the waiting time in the airport. international journal of system of systems engineering, 11(3-4): 363–379. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/akeem.raji@oouagoiwoye.edu.ng http://www.nijotech.com/ arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):161-172. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: profpeteranyin@unical.edu.ng 172 delgado, kv., de barros, ln., dias, db. and sanner, s. 2016. real-time dynamic programming for markov decision processes with imprecise probabilities. artificial intelligence, 230: 192-223. garfield, jb. and ben-zvi, d. 2008. developing students' statistical reasoning: connecting research and teaching practice. springer., p. 8., retrieved august 11, 2023. giovanni, g. 2014. queuing theory and telecommunications, volume: networks and applications, 2nd edition. springer, ny, pp. 585-599. inacio, p. and antunes, r. 2008. matwave-an usb electronic prototype for wave signal generation. on 14-16th april 2008 ieee international symposium on consumer electronics, in vilamoura, portugal., pp. 1–4. lakshmi, c. and sivakumar, ai. 2013. application of queueing theory in health care: a literature review. journal of operations research for health care, 2(1): 25-39., https://doi.org/10.1016/j.orhc.2013.03.002. https://www.sciencedirect.com/science/article/pii/s2211692313000039, li, b., yu, z., huang, l. and guo, b. 2019. vehicle departure pattern and queue length prediction at an isolated intersection with automatic vehicle identity detection. iet intelligent transport systems, 13(12): 1804–1813. meisling, t. 1958. discrete-time queuing theory. operations research, 6(1): 96–105. https://doi.org/10.1287/opre.6.1.96. moura, js., fathy, kh., callaway, sd. and stein, ls. 2010. a stochastic optimal control approach for power management in plug-in hybrid electric vehicles. ieee transactions on control systems technology, 19(3):545–555. piccolino, av. 1996. the advanced placement course in statistics: increasing students' options. the mathematics teacher, 89(5): 376–377, doi:10.5951/mt.89.5.0376. schlecht, mt., knorr, m., christoph, p., schmid, sm., huber, r. and weber, hb. 2022. lightfield-driven electronics in the mid-infrared regime: schottky rectification. science advances, 8(22): eabj5014. seo, s., kim, j., muljadi, e., meor-danial, s., worthington, m. and wills, r. 2019. reactive power control to mitigate flicker in a tidal and river hydrokinetic power generation. on 4 08th august, 2019 ieee power & energy society general meeting (pesgm), in atlanta ga, usa, pp. 1–5. tarabia, am. 2008. analysis of two queues in parallel with jockeying and restricted capacities. applied mathematical modelling, 32(5): 802-810. vilaplana, j., solsona, f., teixid´o, i., mateo, j., abella, f. and rius, j. 2014. a queuing theory model for cloud computing. the journal of supercomputing, 69: 492–507. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://doi.org/10.1016/j.orhc.2013.03.002 https://www.sciencedirect.com/science/article/pii/s2211692313000039 https://doi.org/10.1287/opre.6.1.96 arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):807-814 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 807 estimating the collapse point of a transmission line in a developing power systems j. n. onah1*, d. u. onyishi2, c. c. eze3 and g. a. ogbahor4 1,2department of electrical/electronic engineering federal university of petroleum resources, effurun, delta state 1,3, 4department of power engineering, world bank africa center of excellence, university of nigeria, nsukka, enugu state nigeria *corresponding author's email address: jonas.onah.pg.65348@unn.edu.ng article information submitted 5 july, 2023 revised 18 august, 2023 accepted 20 august, 2023 keywords: voltage collapse proximity indicator collapse point maximum power real power transfer abstract the trouble with a developing national grid is compounded by the fact that the power system supplies power to a vast number of loads which is fed by a number of generating units sometimes far from the load centers. variations of loads bring about power losses and corresponding increase in the reactive power requirements of the transmission systems. thus, the paper is aimed at establishing the point of collapse of transmission lines to enable a control system operator to take proactive measures in the event of small/large system disturbances. voltage collapse proximity indicator is exploited to show that the variations in load close to the maximum load require extremely large amounts of reactive power at the sending end in order to support the increase in load. in the work, it was identified that katemkpe-shiroro transmission line is the most critical transmission line contributing immensely for voltage collapse scenarios in nigeria national grid. consequently, it ranked first because it has the highest voltage collapse proximity index. computation involving voltage collapse proximity indicator obtained the collapse point or the knee point as 2.8684. this serves as a criterion that will enable control system expert to take proactive measure before the impending voltage collapse 1.0 introduction nigerian national grid (nng) is a network of electricity transmission lines connecting generating buses to load buses across the entire country (mbah, 2022). the network is designed to operate within certain stability limits. the statutory limit for voltage is 0.95 to 1.05 per unit and that of frequency is 50hz+5 per cent. whenever the grid operates out of these stability ranges there would be a sequence of events accompanying voltage instabilities that bring about voltage collapse. these usually occur whenever transmission lines are stressed beyond their fold or knee point. there is an urgent need to determine the point of collapse of some of the components of the power supply system like the transmission line to enable the power control expert to take proactive measures before the saddle node bifurcation point of the entire system is reached. for the past 36 years, there are a total of 750 scenarios (onah et al., 2018; 2019; 2021,). from the return of democratic rule in nigeria, the country has had worrisome challenges in the power industry. between 1999 and 2014, there were 478 incidents of voltage collapse. the worst case took place between 2003 and 2004 with an average of 52 incidents. from 2015 to date the figure is estimated to be 98 incidences (samuel et al., 2014). uncertainty has trailed the causes of incessant voltage collapse incidences in nigeria national grid (nng). the information relating to the cause of national blackout from september 2021 to june 2022 kept energy users and the utility companies in the dark (tcn, 2022). for close to four decades, nigeria national grid encountered an average of 22 incidences of voltage http://www.azojete.com.ng/ mailto:%20jonas.onah.pg.65348@unn.edu.ng mailto:%20jonas.onah.pg.65348@unn.edu.ng mailto:%20jonas.onah.pg.65348@unn.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):807-814. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 808 collapse per year in the year 2018. it is observed that the figure declined to an average of 20.83 in the year 2022(samuel et al., 2014). recently, mbah (2022) reported that the nigerian national grid encountered seven incidences of partial and total voltage collapse in the year 2022. various factors such as poor transfer capabilities of the transmission lines, outages of transmission lines, insufficient/lack of reactive reserves, generators being far from load centers, among others are responsible for this ugly trend (onah et al., 2018; 2019; 2021). still on a bad note, 15 incidents of voltage collapse in the year 2017 were estimated to cost nigeria 100billion dollars. nigerian manufacturers, small scale businesses and families spent over 3.5 trillion naira per year to power their private generating sets with diesel and petrol. private households spent 1.56 trillion naira which is equivalent to 13.35million dollars during that period (onah et al., 2021). various approaches which look at mechanisms that cause voltage collapses and proximities of voltage collapse near the saddle node bifurcation point have been exploited by experts in voltage stability analysis (onah et al., 2018; 2019,). unfortunately, the approaches are time consuming. according to (reis et al., 2006) l-index and voltage collapse proximity indicator using ieee 14-bus were compared but the approach is complex. the approach uses a class of voltage instabilities that corresponds to static bifurcations of load flow equations. however, minimum singular values of the jacobian matrix and total generated reactive power were calculated as indicators of stability margin, and sensitivity methods were used for reactive support allocation. improvement in stability margin under progressive loading was investigated on a 39-bus test system for different allocations and amounts of reactive support with reactive generation capabilities taken into account but the approach did not look at the degree of compensation. be that as it may, the method is time consuming and less accurate in voltage collapse prediction. again, the fast voltage stability index is based on the power flow through a single line. it is determined by the measurement of voltage and reactive power of the line. a work that used an improved sensitivity technique to rapidly calculate the real power transfer limit of a defined boundary was exploited by hong et al. (1997), but the complexity of the approach is boring. the minimum singular value of the power flow jacobian matrix was used as a static voltage stability index (ekwue et al.,1999). the proposed approach utilizes the sparsity of the power flow jacobian matrix which is complex for a large system. in the work of alvarado et al. (1994), the bifurcation geometry for the study of voltage collapse in electric power systems was given attention. the authors utilized the initial direction in state space of dynamic voltage collapse to compute the right eigenvector of the static power system model. in their view, the normal vector to the bifurcation set in parameter space is a simple function of a left eigenvector but the approach is less accurate in the voltage collapse prediction. tamura et al. (1983) showed optimal multiplied introduced to prevent divergence of power flow for ill conditioned and heavily stressed systems. it was further investigated that there is a relationship between multiple load flow solutions and voltage instability by coming up with multilevel criterion. the criterion comprises three criteria which shows voltage instability but cannot be used independently to show whether the system is stable or not. they are of the view that a system is voltage stable if all the criteria indicate voltage stability otherwise voltage instability. however, their approach cannot estimate the maximum loadability of a transmission line. the new voltage stability index proposed by samuel et al. (2017) and samuel et al. (2019) for voltage collapse prediction may give inaccurate predictions owing to the implicit assumption that the resistances of the lines ought to be ignored when they are high. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com onah et al: estimating the collapse point of a transmission line in a developing power systems. azojete, 19(4):807-814. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 809 mokred et al. (2023) proposed modern voltage stability index for voltage collapse prediction and compared the work with some selected voltage collapse prediction indices. if the authors should take a cursory study of vcpi, they may be shocked with its excellent results and accuracy. the work considered the impedance of the transmission line, the sending and receiving end voltages but the approach is only limited to real power flow along the transmission line. thus, this paper relies on the simplicity, reliability and accuracy of vcpi to fill the missing links found on the above literature. again, the work shows the voltage collapse point of various transmission line of nng. 2. materials and methods the line data and the bus datased in the simulation were collated from transmission company of nigeria, national control center one-line diagram for 45-bus is shown in the matlab/simulink power system analysis tool box (psat) was used to carry out the power flow analysis. vcpi is the index employed to predict voltage collapse of nigeria 330kv power system. the incidences of voltage collapse from 1987 to 2022 were obtained from (onah et al., 2018; 2019; 2021,) and are shown in table 1 (samuel et al., 2014). table 1: voltage collapse incidences on nigeria national grid (nng) from 1987 to 2022 s/n year partial system collapses total system collapses total number of collapses 1 1987 13 20 33 2 1988 8 13 21 3 1989 6 10 16 4 1990 0 14 14 5 1991 1 5 6 6 1992 1 0 0 7 1993 14 5 19 8 1994 4 2 6 9 1995 10 1 11 10 1996 8 2 10 11 1997 13 7 20 12 1998 13 5 18 13 1999 5 4 9 14 2000 6 5 11 15 2001 5 14 19 16 2002 32 9 41 17 2003 39 14 52 18 2004 30 22 52 19 2005 15 21 36 20 2006 10 20 30 21 2007 9 18 27 22 2008 15 25 40 23 2009 20 19 39 24 2010 20 22 42 25 2011 6 13 19 26 2012 8 16 24 27 2013 2 22 24 28 2014 11 2 13 29 2015 2 8 10 30 2016 6 22 28 http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):807-814. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 810 31 2017 not available not available 21 32 2018 11 2 13 33 2019 not available not available 11 34 2020 not available not available 4 35 2021 not available not available 4 36 2022 not available not available 7 total 750 the vcpi index investigates the stability of each line of the system. it is based on the concept of maximum power transferred through a line. the power system is stable if the indicator is less than one, but when the indicator is equal to one or more, the point of voltage collapse is reached. interestingly, this signifies that near maximum load, extremely large amounts of reactive power are required at the sending end to support an increase in load. the vcpi is thus a very sensitive indicator of impending voltage collapse. the advantage of the use of the index lies in the simplicity, reliability and its ability to give a good indication about the critical power a system can maintain before collapse over the whole region and for all cases studied. the voltage collapse proximity indicator can be given in terms of real power as follow (salama and ghariany, 2001). vcpi (p) = pa pamax (1) where: pa is given as the real power flow along the transmission line. pmax is given as the maximum real power that can be transferred along the transmission line. in terms of reactive power, the voltage collapse proximity indicator is given as (salama and ghariany., 2001). vcpi (q) = qa qa(max.) (2) where: qa is given as the reactive power flow along the transmission line and qmax is given as the maximum reactive power that can be transferred along the transmission line. the reak and the reactive power flow in equations (1) and (2) were obtained using load flow analysis. however, the maximum power that can be transferred to the receiving end at any instant is given as: pa(max.) = va 2 z cos ∅ 4cos2∅ ( θ−∅ 2 ) (3) qa(max.) = va 2 z sin ∅ 4cos2∅ ( θ−∅ 2 ) (4) where z is the load impedance, va is the sending end voltage, ∅ is the phase angle given as tan−1( pa pamax ⁄ ), θ is the phase angle got from load flow studies.the maximum real and reactive power were obtained from the results of load flow analysis. the data obtained were used to carry out steady state analysis of the power system. 3. results and discussion the transfer capabilities of the critical lines are shown in figure 2 using vcpi. the worst-case transmission line is katamkpe-shiroro with the voltage collapse proximity indicator of 2.8684. the transmission line is singled out to investigate the effects of real power variation with vcpi. the effect of the variation of real power transfer with vcpi is shown in figure 1. the stability of each of the critical lines of the system was investigated based on the concept of maximum power transfer through a line. the power system is in a stable mode if the indicator is less file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com http://www.sciencedirect.com/science/article/pii/s0196890400000236#%21 http://www.sciencedirect.com/science/article/pii/s0196890400000236#%21 onah et al: estimating the collapse point of a transmission line in a developing power systems. azojete, 19(4):807-814. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 811 than one, but when the indicator is equal to one or more, the point of voltage collapse is encountered. the closer the value of vcpi to zero the more the stability of the transmission lines. this implies that at or near maximum load, extremely large amounts of reactive power are required at the sending end to support an incremental increase in load. thus, vcpi is a very sensitive indicator of impending voltage collapse. the point of voltage collapse was established at the moment the real power transfer got closer to the maximum power transfer capability of the transmission line as can be seen in figure 2. the loadability limit of the transmission line is 2.6p.u. the voltage collapse proximity indicator of the transmission line in figure 2 is approximately 2.8 with the increase in real power flow along the transmission line. the practicability of this model was tested in the 45-bus nigeria national grid. from the simulations, it was found that out of the 53 transmission lines, 17 transmission lines were overloaded. the most critical transmission line ranked first and has vcpi value of 2.8684 as shown in figure 1. in equation 1 as espoused by figure 2, it is observed that with the increase in real power flow along katamkpe-shiroro transmission line, a stage was reached where the maximum load was not able to sustain the load on the transmission line. voltage collapse proximity indicator evaluated the nng and identified areas with very weak transfer capabilities as follow; kainji-b.kebbi (1.4667), egbin-aja (1.2830), kaduna-shiroro (1.1805), kano-kaduna (1.5657), ikeja-benin (1.0877), ajaokuta-benin (1.2683), onitsha-benin (2.0482), onitsha-newhaven(1.5288), akangba-ikeja (1.6667), calabar-ikotekpene (2.0700), benin-ihovo (2.6273), omotosho-benin (1.0035), owerri-alaoji (1.105), katamkpe-shiroro (2.8684), katamkpe-gwagwalada (1.5271), gombe-damaturu (2.5412), and kaduna pq kaduna pv (2.0755) are the transmission lines whose vcpis are very high. the maximum peak in the figure 1 shows katamkpe-shiroro transmission line with vcpi of 2.8684. again, the minimum peak at the same figure 2 shows omotosho-benin transmission line with vcpi of 1.0035. the higher the value of vcpi the closer the transmission line to voltage collapse. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):807-814. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 812 figure 1: voltage collapse proximity indicator of 45-bus nng figure 2: variation of vcpi of katamkpe – shiroro transmission line with real power 4. conclusion a very simple, reliable and accurate index (vcpi) estimated the collapse point of a very weak transmission system in a 45-bus nng. the computation involving the approach identified and ranked areas with very weak transfer capabilities in nng. the vcpi identified weak boundaries with respect to voltage instability. it also assessed the effects of possible small and large power disturbances. since katemkpe-shiroro transmission line was identified as the most critical transmission line contributing immensely for voltage collapse scenarios in the 45-bus of nigeria national grid, it is recommended that control system operators should exploit adequate measures to control the impending system collapse. the approach proved to be effective for a practical 45-bus nng. acknowledgement the authors acknowledge the support received from the africa centre of excellence for sustainable power and energy development (ace-sped) university of nigeria, nsukka which enabled timely completion of this research. 0 0.5 1 1.5 2 2.5 3 3.5 0 10 20 30 40 50 60 v c p i transmission lines branch numbers file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com onah et al: estimating the collapse point of a transmission line in a developing power systems. azojete, 19(4):807-814. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 813 references alvarado, f., dobson, i. and hu, y. 1994. computation of closest bifurcations in power systems. ieee transactions on power systems, 9(2): 918-928. ekwue, ao., wan, hb., cheng, dt. and song, yh. 1999. singular value decomposition method for voltage stability analysis on the national grid system (ngc). electric power systems research journal, 21(3): 425–432. hong, yh., pan ct. and lin ww. 1997. fast calculation of a voltage stability index of power systems. ieee transactions on power systems, 12(4): 1555 – 1560. nigerian electricity regulatory commission (2022). analysis of industry data., https://nerc.gov.ng/index.php/library/industry-statistics, retrieved on 12th april. mokred, s., wang, y. and chen, t. 2023. a novel collapse prediction index for voltage stability analysis and contingency ranking in power system. protection and control of modern power system, (1):7-8. mokred, s., wang, y. and chen, t. 2023. modern voltage stability index for prediction of voltage collapse and estimation of maximum load-ability for weak buses and critical lines identification. international journal of electrical and power energy systems, 8(7): 145-148 onah, jn., jagun, zoo., odin, bo. and okafor, cc. 2021. technical losses reduction on the nigerian national grid. nigerian research journal of engineering and environmental sciences, 6(2): 663-668. onah, jn., jagun, zoo., madueme, tc. and oti, se. 2019. estimating the margin to voltage collapse in a dwindling electric power network. nigerian journal of technology, 38(2): 470 – 475. onah, jn., madueme, tc. and ogbuefi, uc. 2019. estimating the point of collapse of a weak transmission line in a perturbed electric network. proceedings of nieee nsukka chapter conference on engineering and management technology in the third industrial revolution, 15-18th february nsukka (1):123-129 onah, jn., madueme, tc., oti, se., alor, jm., eya cu. and ozioko, oi. 2018. a comparative approach to voltage collapse of nigeria’s power grid. international conference and exhibition on power and telecommunication,8-14th october, port harcout river state (1):1-6. onah, jn., madueme, tc., oti, se. and ogbuefi, uc. 2018. towards voltage stability on the nigerian national grid. proceedings of first international conference, faculty of engineering, university of nigeria, nsukka, enugu state, 25-28th april (1): 267-276. reis, c. and barbosa, fm. 2006. a comparison of voltage stability indices. benalmadena, spain. ieee melcon. 16-19th may, (1): 429-432, doi: 10.1109/melcon.2006.1653269 salama, mm. and ghariany, ef. 2001. estimating the voltage collapse proximity indicator using artificial neural network, energy conversion and management, 42(1): 69-79 samuel, ia., katende, j., daramola, sa. and awelewa, a. 2014. review of system collapse incidences on the 330kv nigerian national grid. international journal of engineering science invention, 3(4): 55-59. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com https://ieeexplore.ieee.org/xpl/recentissue.jsp?punumber=59 https://nerc.gov.ng/index.php/library/industry-statistics http://dx.doi.org/10.1109/melcon.2006.1653269 arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):807-814. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jonas.onah.pg.65348@unn.edu.ng 814 samuel, ia., katende, j., awosope, coa. and awelewa, aa. 2017. prediction of voltage collapse in electrical power system networks using a new voltage stability index. international journal of applied engineering research, 12(4): 190–199. samuel, ia., katende, j., awosope, c., awelewa, a., adekitan, a. and agbetuyi, f. 2019. power system voltage collapse prediction using a new line stability index (nlsi-1): a case study of the 330-kv nigerian national grid. international journal of electrical and computer engineering, 9(3): 512–515. tamura, y., mori, h and iwamoto, s. 1983. relationship between voltage instability and multiple load flow solutions in electric power systems. ieee transactions on power apparatus and systems, 102(5): 1115-1125. mbah, n. 2022. tcn records progress in power grid reforms, four other milestones for 2022. in-house journal of transmission company of nigeria, 36(4): 6-12 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):537-560 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 537 original research article analysis of field characteristics for irrigation system design: a case study u. e. uche1*, l. k. soretire1, i. m. b. omiogbemi1, l. i. iwuoha1 and w. e. aserifa2 1department of mechanical engineering, air force institute of technology, kaduna, nigeria 2department of aerospace engineering, air force institute of technology, kaduna. *corresponding author’s email address: eaumie@gmail.com 1.0 introduction the high cost of development of irrigated agriculture requires justification by assessment of the risks and benefits. in fact, the design of the irrigation scheme itself is dependent on detailed knowledge of soils lying within the irrigation area. hence, a knowledge of the soils within the irrigation area serves as an aid in the location of canals and other irrigation waters, aids in determining the irrigation need, determines the drainage need, controls the overall land leveling need, and limits the size of fields in irrigation projects (albaji et al., 2022). according to gonzález-briones et al. (2018), irrigation is described as "the artificial application of water to the soil for the purpose of supplying the water essential to plant growth" with the following three goals: (i) to make up for soil moisture deficiencies; (ii) to improve the environmental conditions of the soil and crop; and (iii) to apply nutrients and plant protectors. article information abstract the determination of field characteristics is key to the successful installation of irrigation because the water use efficiency depends on the soil infiltration rate, storage capacity, permeability, and plasticity. the shear strength of the soil was also determined for the purpose of construction of water abstraction systems. the applicability of irrigation for paddy rice cultivation in the igwu river basin was assessed as a case study using secondary data from the igwu river world bank rice project and abia state ministry of agriculture. primary data was generated by field and laboratory soil tests. the soil survey and project land classification were based on the united state bureau of reclamation general land classification standard on limiting factors to irrigation. field and laboratory tests were used to generate data on the specific gravity of soil particles and the compaction characteristics to determine the dry, moist, saturated, and buoyant unit weight of the soil. consistency limits, plasticity, shear, and compressive parameters as well as coefficient of permeability, infiltration characteristics and soil storage capacity were also determined. the result showed that the soil profile is well drained to a depth of about 1m and of characteristic agricultural nature, rich in mineral nutrient and having a ph of 6.7. the soil is of good workability, with largely fine to medium texture, characterized by dull orange. (7.5yrs 6/4 dry, brownish black (10yrs 3/2) wet topsoil. the topsoil is made up of sandy loam of weak angular structure, few fibrous roots and, of mixed humous, with few fine and continuous pores. it was further, observed that erosion was minimal because of forest cover and the area holds a high potential for irrigated agriculture. it is therefore the opinion of the authors that the study site is suitable for paddy rice irrigation. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 1 may 2023 revised 14 july 2023 accepted 20 july 2023 keywords: infiltration rate permeability irrigability plasticity workability http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 538 rice may be grown on many types of soil. purseglove (1975) reported that soil from sandy loamy and shallow laterite to heavy clay may be used if there is adequate water either as rainfall or by irrigation. because of water requirements, heavy clay is preferred as a means of holding and preserving water for the plant. the water should not be stagnant but free flowing (appraisal of rice project nigeria, 1974). rice is adapted to acid soils and will thrive well under ph ranges of 4.5 to 7.5 (chapman and carter, 1976). however, the optimum range is a ph of 5.56.5. the purpose of the study is to establish the suitability, and compatibility of the field characteristics of the study site for irrigated paddy rice project as a case study for the design of paddy rice irrigation systems. 2.0 materials and methods 2.1 study area and experimental design the study site (figure 1) is in igbere town which lies at latitude 504’ n and longitude 7032’ e. in bende local government area of abia state of nigeria (ofomata, 1975). figure 1: topographic map of the study site in the study, both historical data and field tests were explored to characterize the field and elicit irrigation design parameters. a completely randomized block design was employed in obtaining test samples. the randomized block design permits the isolation of smaller areas, each homogenous within itself which are known as blocks as shown in figure 2. figure 2: randomized block experimental sampling design. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 539 the study includes a soil survey, irrigability of the project area, determination of specific gravity of soil particles, consistent limit test, coefficient of permeability and infiltration characteristics tests. 2.2 soil survey a survey of the characteristics of the soil in the project area was conducted by the world bank project team during the feasibility stages of the igwu rice scheme within which the study site is contiguous (appraisal of rice project, nigeria, 1974). the information is presented in the result section. further, an augur soil sample from the study site was collected randomly as per figure 2, from different soil depths and analyzed by the soil science department of the university of nigeria to include the physical and chemical properties of the project soils. 2.3 irrigability of the project area the evaluation of the project land for irrigation suitability was carried out with reference to the results of the soil physical and chemical tests conducted. as dent and young (1981) noted, qualitative evaluation is one in which the suitability of land for a purpose or alternative purpose is expressed in qualitative terms only, such as highly suitable, moderately suitable, or marginally suitable. qualitative evaluation is adopted for this work because of little or no information on economic and social-cultural factors which are needed for quantitative appraisal. some of the economic factors include land, labour, and capital input while the socio-cultural elements are land tenure systems and the religious belief attached to the land. in classifying the project land, the usbr general land classification system which sums up the limiting factors – slope, texture, depth of rooting zone, salinity, and flooding risk, has been used (table 2). 2.4 determination of specific gravity of soil particles the specific gravity of material is the ratio of the given weight of a given volume of that material to the weight of an equal volume of water. but the weight of an equal volume of water displaced by solids equals to weight of solids in air minus submerged weight of solids. density bottles together with a stopper were completely dried and weighed (w1). about 5 to 10 gm of oven dried soil were placed in the density bottles. the soil, bottle, and stopper were weighed (w2). distilled water was then added to cover the soil and thoroughly shake to remove air bubbles. more distilled water was added. the stopper fitted and allowed time to settle. after an hour more water was added to fill the density bottle. time was allowed to eliminate air and the water, soil, stopper, and bottle weighed (w3) after the exterior of the bottle had been dried. the bottles were finally thoroughly cleaned, filled with distilled water, stoppered, and reweighed (w4). the specific gravity of the solid soil particles was determined from equation (1) :(smith, 1981). it is dimensionless. gs = w2−w1 (w4−w1)−(w3−w2) (1) where gs = specific gravity w1 = mass of density bottle and stopper (gm) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 540 w2 = mass of density bottle, stopper, and oven dried soil (gm) w3 = mass of density bottle, stopper, oven dried soil and distilled water. (gm) w4 = mass of density bottle, stopper, soil and topped distilled water (gm) 2.5 the proctor compaction test the proctor compaction test (smith, 1981) was carried out to determine the various unit weights, optimum moisture content, void ratio, degree of saturation as well as porosity. the test further enabled the choice of appropriate moisture content for the triaxial test using equation 2. wn = ws×100 = (mco -mcs) (2) mcs (100) where wn = amount of water to be added ws = mass of sample (g) mcs = moisture content of soil (%) mco = optimum moisture content of soil from proctor test (%) the proctor compaction test involves compacting 3 kg of sample in three approximately equal layers by means of 2.5 kg rammer falling through a height of 30 mm above the soil, 25 times for each layer of the soil placed in 1000 cm3 compaction mould. a sample of the compacted soil was taken and its moisture content was determined gravimetrically. the remainder of the soil specimen was broken up and mixed with the remainder of the sample. 60 cm3 increment of water, representing about 20% (twenty percent) of the sample was added after each breaking and mixing, and the above procedure was repeated (smith, 1981). 2.6 consistency limit test the liquid index (li) which relates the natural moisture content of the soil to both the plastic and liquid limits is given by equation 3; (levchich, 1981) li = m−pl pi (3) where li = liquid index (%) m = the natural moisture content of the soil (%) pi = difference between the plastic and liquid limit or (%) plasticity index the liquid limit test involved the initial mixing of a soil passing the no. 425m b5 test sieve and of about 200g minimum weight with distilled water to putty like consistency. the soil was then placed in the casagrande apparatus consisting of a brass cup and leveled off to a depth of 1cm by means of palette knife. after making a groove in the soil the crank of the apparatus was turned to lift and lower the cup until the two sides of the sample closed at the bottom of the groove. the number of blows was recorded. the water content of the soil sample was determined by drying in oven at 105° for 24 hours and weighed. more distilled water was added to the paste and the procedure repeated three more times. a ‘flow curve’ of moisture content (as ordinate) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 541 versus number of blows (as abscise) to a logarithmic scale was plotted (figure 6). the moisture content of the soil sample at the count of 25 blows was determined. for the plastic limit test the same soil sample passing through the same sieve size but of about 15gm was mixed with distilled water on a glass plate to obtain a plastic material and shaped into ball. the soil was rolled between the palms of the hand and the glass plate to form the soil into a thread of about 3mm diameter. it was then reformed into ball, kneeled, and rolled out. the procedure was repeated until cracks appeared at a rolled was determined. this represents the plastic limit of about 24% for the project soil. lastly the linear shrinkage test was conducted by preparing the soil as for the liquid limit test. at a blow of 25, a paste was taken and placed in a brass mould of semicircular cross section and the length noted (14 cm). the sample was air dried, transferred to oven at 105 °c for 24 hours drying after which the length was measured (13 cm) and the linear shrinkage was obtained using equation 4 ls = 1−length after drying initial length (4) where ls = linear shrinkage cm. 2.7 determination of shear parameters the unconsolidated undrained, triaxial compression test was used to determine the shear parameters for soil in the project pump station site involving cohesive strength c and angle of friction ø of the soil. to obtain the cohesive strength g and angle of friction ø a series of mohr circles are drawn (figure 3). a common tangent through them represents the coulomb equation. for any desired width and depth of the strip footing foundation for the pump house the net ultimate bearing capacity of the soil can be determined. the ultimate bearing capacity is the value of the gross loading intensity at which the ground fails in shear. the test consisted of preparing a sample of the soil by extruding three soil samples using tubes from a compaction cylinder, pushing them one after the other into split moulds of known dimension and noting the length and weight of specimen as well as the determination of their moisture content. after necessary adjustment of triaxial machine the samples being surrounded by rubber membranes were placed centrally on the pedestal of the triaxial cell and subjected to compressive stresses one after the other. at the maximum (failure) stress the cell was drained of fluid, dismantled and the rubber membrane removed to observe the failure mode. calculations involved in the triaxial test are as follows: a. actual load: this is necessary because a proving ring is used to measure the load. load = load dial reading x proving ring constant b. area: the area of the specimen normal to its axis at any stage of the test has been computed on the assumption that the specimen deforms as a right-angled cylinder. the area at any strain e is given by equation 5. a = 𝐴 𝐶 1−𝐸 (5) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 542 where e = percentage strain at the stage of the which it is to be determined = 𝐿𝑜−𝐿 𝐿𝑜 lo = original length of specimen (mm) l = final length of specimen at the stage test. (mm) c. compressive strength the principal stress difference 61 63 is determined from compressive strength as given in equation 6 as; 61 63 = axial load a (6) 61 = maximum principal stress n/m2 62 = minimum principal stress n/m2 to obtain the cohesive strength g and angle of friction ø a series of mohr circles are drawn. (figure 3) a common tangent through them represents the coulomb equation. figure 3: mohr circle for principal stress and mohr envelope the shear strength of the soil can be given by equation 8 as; z = c + c tan ø (7) where z = shear strength of the soil c=cohesive strength of soil (point of intersection) ø=angle of friction. for any desired width and depth of the strip footing foundation for the pump house the net ultimate bearing capacity of the soil can be determined from the expression in equation 8 as; qn = cnc + rz (nq 1) + 0.5 rb nr (8) where qn = net ultimate bearing capacity of the soil (kn/m2) nc, nq and nr = bearing capacity factors c = cohesion (kn/m2) r = unit weight of soil (kn/m3) z = foundation depth (m) b = width of foundation (m) from the mohr circle the shear at failure is given by equation 9; zf = ½ (61 63) sin 2 ø (9) for the samples file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 543 (1) zf = ½ (26.3) sin 106 = 12.64 n/cm3 = 126.4 kw/m2 (2) zf = ½ (32.7) sin 109 = 15.46 n/cm2 = 154.59 kw/m2 (3) z = ½ (66.2) sin 106 = 3.82 n/cm2 = 3.17 kw/m2 average shear strength of soil = 154.59 + 126.41 + 318.17 3 = 199.22 kw/m2 = 200 kn/m2 c = 85 kn/m2 ø = 150 2.8 determination of the co-efficient of permeability the test consists of a constant head permeameter cylinder containing a disturbed sample of the soil, through which water was allowed to percolate under a constant head of pressure. the quantity of water q passing through the sample in the time t was collected in the measuring cylinder while manometers tapped into the side of the cylinder gave the loss of head h over a length of sample l. the downward movement of water (vy) is given by equation 20; vy = 𝐼𝑓 𝑛𝑠 (20) where: vy = rate of flow through the soil (cm/s) if = soil permeability (cm/s) n = pore space s = degree of saturation vy = 1.43 × 10−5 0.38 × 0.8 = 4.7 × 10-5 cm/s = 0.169 cm/hr 2.9 determination of infiltration characteristics the test involved the use of concentric cylinders of 30 cm and 60 cm diameters installed about 10cm deep in the soil and the ponding of water in the inner and outer cylinders. the second hand of a wristwatch was used to observe the rate at which water level descended in the inner http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 544 cylinders. after each reading at specified time intervals (table 13) the water surface in the cylinder rings was returned to the original level and the process was repeated. the functional relationship between the cumulative intake f and the time t was determined based on the equation. f = atb + c (21) where f = cumulative intake (mm) t = time water is in contact with the soil a,b.c = constant unique to the soil and hence the intake family to determine the constants a, b and c, the method of average suggested by michael (1978) was used. the results of the analysis are: a = 0.064 b = 1.14 c = 0.2 hence the infiltration rate at any instant t was obtained as follows (equation 22): f = atb + c 𝑑𝐹 𝑑𝑡 = abtb-1 = 1 (22) where i = infiltration rate mm/min. at t = 435min i = 0.064 × 1.14 × (435). 14 = 0.17 mm/min 2.10 soil storage capacity the range of water available to the plant is that between the field capacity (fc) and the wilting point (wp). the readily available moisture which is that portion of the available moisture that is most easily extracted by plants is taken as 75% of the available moisture (israelsen and hansen, 1962). the available moisture is given by equation (23): ma – fc wp (23) where ma = available moisture (%) fc = field capacity (moisture content of the fields soil after drainage has become negligible (%) wp = wilting point (soil water content below which plant growing in that soil remains wilted even when transpiration is nearly eliminated (%) in determining the permanent wilting point a field capacity of 2.3 times the wilting point was assumed considering the silty nature of the field soil (israelsen and hansen, 1962). therefore, the available moisture is given by equation 24. ma = fc 𝐹𝐶 2.3 (24) the field capacity was estimated by weighing after drying in oven, samples scooped at various depths and locations of the field (under cover) two days after thorough wetting. the depth of available moisture was obtained using equation 25: file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 545 da = 𝑀𝑎 𝐴𝑠 𝐷𝑟 100 (25) where da = depth of available moisture in the roof zone as = apparent specific gravity dr = rice rooting depth the unit weights of the soil were obtained by determining the respective densities and multiplying by acceleration due to gravity (g) 2.10.1 the bulk density, sm. of compacted soil at any given moisture content is given by equation 26: sm = 𝑀2−𝑀1 1000 (kg/m3) (26) where m1 = mass of mould in gm m2 = mass of mould + soil (in gm) 2.10.2 the soil dry densities sd in kg/m3 is given by equation 27: sd = 𝑆𝑚 1+𝑚 (27) sm = bulk density in kg/m3 m = moisture content (dry basis). the dry density gives the state or compaction of the soil. 2.10.3 optimum moisture content and maximum dry density. these are obtained by plotting a curve of dry density versus moisture content from which the optimum moisture content and maximum dry density can be read off. figure 4 shows that for all densities except the one which gives optimum moisture content (omc). there are two moisture contents that gave the same density. also using more than 25 blows a greater density can be obtained and the optimum moisture will be less. the porosity (n) of the soil, void ratio, and degree of saturation were determined as follows: (i) porosity is determined from the expression (equation 28 and28) d = gs( 𝑛 100 ) (28) n = 100 (1 − 𝑆𝑑 𝐺𝑠 ) (29) where n = porosity % (ratio of volume and pores to total soil volume) sd = dry bulk density g/cm average dry density of the sample. sd = 1534+1598+1639+155+1525+1458 6 = 1551.5 kg/m3 = 1.5515 g/cm3 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 546 gs = 2.51 therefore porosity n = 100 (1 − 1.55 2.51 ) = 0.38 × 100 = 38% (ii) void ratio this is the quantity expressing the ratio or volume of pores to the volume of solids (equation 30) e = vr vs (30) = 𝑛 1−𝑛 where vr = volume of void vs = volume of solid this index is important because the total soil volume changes with volume change of voids and hence a knowledge of the dynamics of pore due to external load is possible with the information or void ratio. e = 0.38/ (1-0.38). = 0.61 (iii) degree of saturation: this is the ratio of volume of water to volume of voids and it refers to the volume of water present in the total pore volume. s = vw/vv (31) s = degree of saturation vw = volume of water vv = volume of void. it can also be shown that s = 0.154 ×2.51 0.61 × 100 s = 𝑀𝐺𝑆 𝑒 × 100 s = 43.4 (a) determination of saturated density and buoyant density of soil. wn = swn (32) wn = water contained in pores when saturated (kg/m3) sw = density of water kg/m3 n = porosity. wn = 1000 × 0.30 (380 kg/m3) saturated density of soil ss = saturated density kg/m3 sd = dry density ss = 1551.5 + 380 = 1931.5 kg/m3 buoyant density of soil file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 547 sb = ss sw sb = buoyant density kg/m3 sb = 1931.2 -1000 = 931.5 kg/m3 (b) dry unit weight: to obtain the dry unit weights of the soil n/m3, the various dry densities are multiplied by acceleration due to gravity. assuming g =10m/s (i) dry unit weight wd = gsd = 10 × 1551.5 = 15515 n/m3 (ii) bulk moisture unit weight wm = gsm where sm = sd (1 + m) = 1551.5 (1+ .126) = 1746.99 kg/m3 0.126 for moisture content m is obtained from the graph – figure 6 wn = 10 × 1747 = 17470 n/m3 (iv) saturated unit weight ws = ss = 1931.5 × 10 = 19315 n/m3 (iv) buoyant unit weight wb wb = gsd = 10 x 931.5 = 9515 n/m3 ). the available moisture is given by equation 33,34 and 35 respectively. ma = fc wp (33) where ma = available moisture (%) fc = field capacity (moisture content of the fields soil after drainage has become negligible (%) wp = wilting point (soil water content below which plant growing in that soil remain wilted even when transpiration is nearly eliminated (%) in determining the permanent wilting point a field capacity of 2.3 times the wilting point was assumed considering the silty nature of the field soil (israelsen and hansen, 1962). therefore, ma = fc 𝐹𝐶 2.3 (34) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 548 the field capacity was estimated by weighing after drying in oven, samples scooped at various depths and locations of the field (under cover) two days after thorough wetting. a value of 28% for the field capacity was obtained. therefore ma = 28 28 2.3 = 15.83% the depth of available moisture was obtained using: da = 𝑀𝑎 𝐴𝑠 𝐷𝑟 100 (35) where da = depth of available moisture in the roof zone da = 15.83 ×1.5 ×40 100 = 9.498cm = 9.5cm the readily available moisture da is then given as dra = 75 ×9.5 100 = 7.125 cm 3. results and discussion 3.1 soil survey historically, the soil in the project area is generally waterlogged seasonally because of heavy clay dominance and the impervious sub-strata of shales. reyment 1965 the soil is classified under the hydromorphic soils of eastern nigeria. according to the soil survey, which details the soil profile of the igwu rice scheme, the soil is 6.7 ph, well-drained to a depth of around 1 m, and has a typical agricultural nature. the project further described the soil as being of good workability, with largely fine to medium texture, characterized by dull orange. (7.5 yr 6/4 dry, brownish black (10 yr 3/2) wet topsoil. the topsoil is made up of sandy loam of weak angular structure, few fibrous roots and of mixed humous, few fine and continuous pores. in conclusion the report noted that erosion was minimal because of forest cover and the area holds a high potential for irrigated agriculture. the result of the study (table 1) is closely related to the world bank appraisal report of the igwu irrigation scheme (appraisal of rice project, nigeria 1974). the table indicates good soil of sandy loam with high carbon content (.6%) extending over a depth of 34cm. however, the decrease in carbon and nitrogen content down the soil shows a progressive decrease in plant nutrient, thereby limiting the extent of soil removal during leveling. the test further shows that the predominate cation involved in exchange is calcium (6.2) which generally promotes good tilth while sodium is found in lesser amount. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 549 table 1: physical and chemical properties of study site soil mechanical analysis chemical analysis ph 1:2:5 organic matter na/100g/soil d e p th ( cm ) % c la y % s ilt % f in e s an d % c o ar se s an d t e x tu ra l c la ss % g ra ve l in k g so il h 2 o k c l % c % o .m % n c /n n a k c a m g t e 3 a i 3 + h + % b as e s a t c e c s u m m at io n c e c t it ra ti o n p (p p m ) p ( k g/ h a 0 -5 4 1 2 1 0 7 2 6 sa n d y lo am 0 5 .2 0 4 .1 0 0 .6 0 0 .0 3 0 .0 6 9 .7 0 0 .2 9 0 .3 2 6 .2 0 0 .6 0 7 .4 1 1 .2 0 0 .4 0 7 4 .0 0 9 .0 1 1 0 .0 0 2 .0 0 4 .4 8 5 4 -8 6 5 0 9 3 4 7 cl ay 0 .5 0 6 .7 0 5 .6 0 0 .1 5 0 .2 6 0 .0 3 5 .5 0 0 .4 6 0 .4 9 2 5 .3 0 2 .1 0 2 8 .3 5 0 .8 0 4 .8 0 9 7 .8 0 3 3 .9 5 2 9 .0 0 8 .0 0 1 7 .9 2 8 6 -1 7 0 6 0 1 0 2 2 8 cl ay 0 6 .0 0 4 .5 0 0 .1 0 0 .1 7 0 .0 2 4 .3 0 0 .3 9 0 .4 0 2 3 .0 0 1 .7 0 2 5 .5 0 0 .6 0 0 .6 0 9 0 .1 0 2 6 .7 0 2 8 .1 0 4 .0 0 8 .9 6 in classifying the project land, the usbr general land classification system which sums up the limiting factors – slope, texture, depth of rooting zone, salinity, all salinity and flooding risk. table 2 has been used. table 2: land classification of limiting factors. factors and symbol meaning highest class in which classifiable drainage w minor drainage difficulties medium drainage difficulties major drainage difficulties ii iii iv available moisture am moderate – 10% 13% low 6% 10%` very low under 6% ii iii iv salinity s saturated extract conductivity 4-6 mmhos/ cm at 250c saturated extract conductivity 416 mmhos/ cm at 250c saturated extract conductivity over 16 mmhos/ cm at 250c ii iii or iv v or vi alkalinity a na/t = 10 % 15% na/t = 15 % 20% na/t = 20% 30% na/t over 30% ii iii iv v or vi flooding f only exceptional flooding major floods every two or three years, or for short periods each year major floods each year ii iii iv or v depth d deep = 0.75 m 1.5 m moderately deep = 0.25 m 0.75 m ii iii http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 550 shallow = 0.25 m iv or v erosion e medium to slight erosion severe erosion very severe erosion ii iii iv or v slope t 3% 6% 6% 8% 8% 25% over 25% ii iii iv v or vi micro relief m scattered holes and ditches up to 60 cm in depth. more densely distributed deeper holes and ditches ii iii the system employs six capability classes ranging from class 1 to 6 with class 1 having the least limitations and class 6 the greatest limitation. 3.2 irrigability of the project area figure1 in 2.1 shows detailed topographic map of the project site that characterized the field. the field is divided into four land patches by the atayi and iyioma streams. each land unit has a terrain sloping towards the stream bordering it. hence the entire field drains into the stream. the extreme western section of the field is more or less a high land with a general slope of about 6% and ranges in elevation from 102.25 m to 105.66 m. it is, therefore, proposed that this portion of the field be used for the farmstead. the central portion of the field surrounded by both steams is relatively flat and rises about 4m above the surrounding steam beds. presently it is marshy but a mechanical analysis of soil from the area indicated a preponderance of fine sand (table 3). with good drainage, a central location, and an area of about 0.5ha this area is considered suitable for siting the pump station. a shear stress analysis of the underlying soil showed good load bearing capacity. the other portions of the field are gently sloping (0.6 %) and of general sandy loam topsoil to an average depth of 60 cm, well-drained but badly fragmented by the streams. overall, a total land area of 10.15 ha is considered irrigable out of the 16-ha project land. table 3 summarizes the attributes of the study site for irrigation. table 3: project land classification factor considered site attribute possible class drainage medium drainage difficulties iii available moisture 15% i salinity 0.25 mm ho/cm i flooding major flood for short period each year iii depth erosion 0.5m moderately deep iii erosion medium to slight erosion ii slope 0.3 to 6% ii micro-relief scattered to and ditches to 60cm in depth ii an average class of ii is assigned to the project for irrigation purposes. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 551 3.3 compaction test the value obtained as presented in tables 4, 5, 6, plotted in figure 4 and summarized in table 7 could be seen as reasonable for soil of high organic matter and plant mineral content. it should however be noted that it is impossible to obtain complete saturation as per the compaction test as there must be air void in the compacted soil. hence the test should be used as a guide to compaction on site (majumdar 2015) table 4: analysis of data on compaction test location amayi taken by uche uche date: tested by g. okey and uche uche type of mould proctor no of blows 25 25 wt of mould ÷ssoil gm 5937 6040 wt of mould gm 4231 4231 wt of soil mould gm 1706 1809 bulk density kg/m3 1706 1809 w.c. timing 84 55 10 wt. tin ÷wet soil 71.8 63.0 58.8 wt. of tin 15.9 16.0 wt. of water 5.5 4.8 wt. of dry soil 50.4 52.2 moisture content % 10.9 11.4 average mc % 11.2 dry density 1534 table 5: specific gravity test date: 1 2 3 mass of density bottle w1 (g) including stopper 29.1 29 25.2 mass of density bottle + stopper + oven dried soil w2 (g) 71 73.2 61.5 mass of density bottle + stopper + oven dried soil + distilled water w3 (g) 104.4 105.3 97.3 mass of density bottle + stopper + distilled water 79.21 79.07 75.2 specific gravity gs = 2.51 2.47 2.56 the proctor compaction test enabled the choice of appropriate moisture content for the triaxial test. result is as shown in table 6. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 552 table 6: particle site distribution for the pump station site bs sieve size (mm) bs sieve no. weight retained i weight retained ii percent retained percent passing 2.50 0.578 0.60 0.45 0.30 0.15 7 14 25 36 52 72 72 200 passing 200 2.5 35.3 126.1 140.1 140.0 6.3 200.3 1.2 27.7 113.3 1.4 138.4 44 198.0 0.20 3.46 13.19 14.33 15.35 0.59 21.97 15.89 99.80 96.34 83.15 68.82 53.47 52.88 15.89 0 an optimum moisture content of 15.4% at 1640 maximum dry density was obtained (figure. 4) figure 4: proctor soil density curve result of the dry, moist, saturated, and buoyant unit weight test of the soil is shown in table 7. table 7: summary of compaction test results. properties value optimum moisture content maximum dry density porosity void ratio degree of saturation saturated density buoyant density dry unit weight bulk moist unit weight 15.4% 1640 kg/m3 38% 0.61 63. 4% 1931.5 kg/m3 931. 5 kg/m3 15515 n/m3 17470 n/m3 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 553 it should also be noted that climatic condition should be taken into account as well as the ability to accurately control moisture content on site. relative compaction is therefore recommended in using the proctor soil density curve result. 3.4 consistent limit test the design of foundations especially under saturated soil conditions as is often the case in the project area during the high flood season and the selection of irrigation canal lining material are influenced by the atterberg limits: liquid limits (ll), plastic limit (pl) and shrinkage limit (sl) as shown in figure 5. figure 5: soil consistency limit the result of the test is as shown in table 8 which is plotted and read from figure 6 to obtain the liquid limit of 29%, plastic limit of 5% and plastic index of 24%. table 8: determination of the liquid and plastic limits of the soil type of test liquid limit plastic limit test no. 1 2 4 5 moisture content tin no. 51 23 20 4 45 74 199 mass of wet soil + tin w(g) 29.25 20 29.8 33.85 30.25 21.8 33.5 mass of dry soil + tin wd (g) 26.1 26.7 26.5 29.7 27.00 20.8 32.6 mass of tin wt (g) 15.8 15.6 15.5 15.6 15.5 15.4 27.9 mass of water ww = w-wd (g) 3.15 3.3 3.3 4.15 3.25 1.0 0.9 moisture content m %= ww x 100 x ws 30.6 29.7 30.28 29.4 28.3 18.5 19.2 number of blows: n 13 17 29 34 48 5.05 5% http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 554 figure 6: liquid limit test. using the plasticity chart for soil classification shown in figure 7, the project soil falls within the inorganic clay of low plasticity (29, 24) (smith, 1981). figure 7: plasticity chart for soil classification lastly, the linear shrinkage test was conducted with a length of 14cm to obtain 13cm on drying. to obtain 7.14%. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 555 3.5 determination of sheer parameters the result of the coefficient of permeability test (table 9 and 10), indicates that the project soil has a permeability coefficient of the order of 10.4 mm/s. the unconsolidated undrained, triaxial compression test result was used to determine the shear parameters (cohesive strength c and angle of friction ø) of the soil for the project pump station site. length = 7.64 m =764cm net weight of specimen = 167.2gmb = 162.8gm n/c = 12.3% moving ring no = 4582 ring constant = 0.53 diameter 3.8cm time of strain = 1.08 min table 9: triaxial test reading weight/pressure test 1 test 2 test 3 63 = 7 63 = 14 63 = 21 strain dial reading strain % area of specimen (cm2) stress dial reading force (n) 61 -63 (n/cm2) stress dial reading force (n) 61 -63 (n/cm2) stress dial reading force (n) 61 -63 (n/cm2) 30 1 11.46 175 92.8 8.1 21 11.1 1 4 2.12 0.2 60 2 11.57 240 127.2 11 95 50.4 4.4 245 129.9 11.2 90 3 11.7 289 153.2 13.1 186 98.6 8.4 428 226.8 19.4 120 4 11.82 325 172.3 14.6 265 140.5 11.9 583 209 26.1 150 5 11.94 355 188.2 15.8 323 171.2 14.3 710 376.3 31.5 180 6 12.07 382 202.5 18.8 370 196.1 16.3 918 486.5 40.3 210 7 12.2 430 227.9 18.7 414 219.4 18 1020 540.6 44.3 240 8 12.33 480 254.4 20.6 460 243.8 19.8 1034 525.1 42.6 270 9 12.4 508 269.2 21.6 1165 617.5 49.6 300 10 12.6 515 273 21.7 551 295.6 23.5 1235 654.6 52 330 11 12.74 540 286.2 22.5 586 310.6 24.4 1305 691.7 54.3 average shear strength of soil is 199.22 kn/m2 (200 kn/m2). hence for any desired width and depth of strip foundation for the pump house the net ultimate bearing capacity of the soil can be determined. the ultimate bearing capacity is the value of the gross loading intensity at which the ground fails in shear. 3.6 permeability test a permeability test was carried out using a constant head permeameter as detailed by smith (1981). the test indicated a disturbed clay sample permeability coefficient of 1.43 × 10-d mm/s. if the final intake rate (if) of the soil is assumed equal to permeability of the soil at 80% saturation (israelsen and hansen, 1962). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 556 hence it will take about ten days for water to set through the rooting zone of 40cm depth assuming a uniform clay soil down the root depth. but the topsoil test indicated a 54cm deep sandy loam. intermittent water submergence permitting drying of soil during irrigation interval and puddling (wang and hagan, 1981) as proposed for the project will further reduce deep percolation losses. based on the above information a deep percolation loss of 15 per cent of the water applied has been assumed. this enables a plot efficiency of 80% (eighty per cent) to be adopted. in the determination of the co-efficient of permeability the dar ‘cy’ s equation was deployed and the result obtained from the testis as shown in table 10. this result indicates that the project soil has a permeability co-efficient of the order of 10.4 mm/s which if compared with table 11 could be considered of drainage status. table 10: constant head permeameter test qty of water flowing through sample (q) time for flow (t) difference standpipe level (h) difference between tapping points (l) cross sectional area of sample (a) k = 𝑄𝐿 𝐴ℎ𝑡 average (k) (cm3) (min) (cm) (cm) (cm2) (cm/s) (cm/s) 8.5 7.0 9.5 30 30 30 75 60 80 10 10 10 45.36 45.36 45.36 1.39 × 10-5 1.42 × 10-5 1.45 × 10-5 1.43 × 10-5 0.515mm/hr. table 11: permeability by soil types (smith, 1981) table 12 further confirms the behavior of the soil as expected from the textural analysis. it could therefore be considered as slightly pervious. based on table 11, the soil can be grouped under class 1 soil. soil type value of permeability(mm/s) drainage properties gravel 1000 10 good sand 10 – 10-2 good silt (fine/red clay) 10-2 – 10-5 poor clay ➢ 10-5 impervious file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 557 table 12: soil class based on permeability (kinori and mavorach, 1984). class seepage hydraulic5 conductivity (10 cm/s) 1 2 3 4 5 6 7 very slow slow medium slow medium medium guide quick very quick 3 3 – 15 15 – 60 60 – 170 170 – 350 350 – 700 700 3.6 field infiltration measurement of infiltration rate was at three different locations. the result of the first location was ignored due to error. it was therefore not considered in the final estimation. result of the infiltration test of the study site is as shown in table 13. table 13: infiltration test cylinder no 1 cylinder no 2 distance of water surface from reference point infiltration during period distance of water surface from reference point infiltration during period average infiltration rate average accumulated infiltration elapsed time (min) before filling (cm) after filling (cm) depth average rate (cm/uc) accum. in filling (cm) before filling (cm) after filling (cm) depth average rate (cm/uc) accum. in filling cm/hr cm 22 22 5 21.5 22 0.5 6 0.5 21.4 22 0.6 7.2 0.6 6.6 0.6 10 21.4 22 0.6 3.6 1.1 21.6 22 0.4 2.4 1 3 1.1 15 21.2 22 0.8 3.2 1.9 21.4 22 0.6 2.3 1.6 2.8 1.8 25 21.4 22 0.6 1.4 2.5 21.1 22 0.9 2.2 2.5 1.8 2.5 45 21 22 1.1 1.4 3.6 20.7 22 1.3 1.7 3.8 1.6 3.7 60 20.7 22 1.3 1.3 4.9 20.4 22 1.6 1.6 5.4 1.5 5.2 75 20.4 22 1.6 1.3 6.5 20.1 22 1.9 1.5 7.3 1.4 6.9 90 20.2 22 1.8 1.2 8.3 19.8 22 2.2 1.5 9.5 1.4 8.9 110 19.8 22 2.2 1.2 10.5 19.6 22 2.4 1.3 11.9 1.3 11.2 120 19.4 22 2.6 1.3 14.5 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 558 figure 8: plot of accumulated infiltration and infiltration rate against elapsed time from the infiltration rate curve figure 8, a constant infiltration rate of 1.5cm/hr. after 160 min was obtained. using the curves, the functional relationship between the cumulative intake f and the time t was determined to be 0.17 mm/min. it is to be noted however, that the cumulative infiltration curve does not strictly agree with the theoretical plots due probably to error in measurement arising from the crude infiltrometer used for the test and possible lateral water movement from the inner cylinder. finally, it should be borne in mind that ring tests generally overestimate infiltration due to lateral spreading of water applied to a small area only akhil, 2022hence values obtained are subject to field experience of infiltration characteristics over the project life. 3.7 soil storage capacity the range of water available to the plant is that between the field capacity (fc) and the wilting point. the readily available moisture which is that portion of the available moisture that is most easily extracted by plants is taken as 75% of the available moisture (israelsen and hansen, 1962 the apparent specific gravity of 1.5 was estimated from the dry bulk density (table 7) since the two terms have equal numerical value (michael, 1978). the igwu rice scheme with similar site conditions as the study area indicated an average rice rooting depth of 40 cm. if a condition of uniform soil is assumed then depth of available moisture (da) is 9.5cm and readily available moisture is 7.125 cm 4. conclusion successful use of water for irrigation agriculture involves a highly complex undertaking such as engineering planning, design and construction in addition to. agricultural and other supporting activities. this underscores the essence of the analysis of field characteristics aspect of irrigation project at the preliminary design stage. in this study the soil parameters were determined starting file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com uche et al: analysis of field characteristics for irrigation system design: a case study. azojete, 19(3):537-560. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 559 with soil survey (good soil of sandy loam with high carbon content (.6%) extending over a depth of 34cm) and irrigability of the field (an average class of ii, 10.15 out of the 16-ha considered irrigable). the study then proceeded with the determination of the soil compaction strength (17470 n/m3), average shear strength (199.22 kn/m2) and soil consistency test (inorganic clay of low plasticity (29, 24)). the coefficient of permeability of the project soil is 1.43 × 10-4 mm/s with cumulative water intake of 0.17 mm/mi. under the condition of uniform soil depth, the available moisture (da) is 9.5cm and readily available moisture is 7.125 cm. these are the field characteristics that determine the agronomic water needs of the envisaged croprice and therefore the irrigation stream size and subsequent canal hydraulic design. the study, therefore, assessed the field characteristic of igwu river basin as a case study for installation of irrigation system to produce paddy rice. the results of the analysis recommend the study site suitable for paddy rice irrigation on the aspect of field characteristics. reference. akhil ak. 2022. measurement of infiltration rate of soil -ring infiltrometer method, smart service, london. albaji, m., eslamian, s., naseri, aa. and eslamian, f. 2022. handbook of irrigation system selection for semi-arid regions. crc press, boca raton, florida city in florida, usa. appraisal of rice project nigeria, 1974. international bank for reconstruction and development, international development association, https://documents1.worldbank.org/curated/en/842751468096580653/pdf/multi-page.pdf. accessed on 14th january, 2023. chapman, sr and carter, lp. 1976. crop production principles and practices. w. h. freeman and co., san francisco, publishers, proceeding 41:250 – 253. dent, d. and young, a. 1981. soil survey and land evaluation. george allen and unwin publishers london. gonzález-briones, a., castellanos-garzón, ja., mezquita-martín, y., prieto, j., corchado, jm. 2018. a framework for knowledge discovery from wireless sensor networks in rural environments: a crop irrigation systems case study. wireless communications and mobile computing., vol. 2018, issue 2018, pp.1-14, hindawi publishing corporation. israelsen, ow. and hansen, ve. 1962. irrigation principles and practices. 3rd edition, wiley international edition, new york. kinori, b. and mavorach, j. 1984. manual of surface drainage engineering vol. 2, elsevier pub. co., amsterdam. levchich v. 1981, soil mechanics in civil engineering, abic publishers onitsha, nigeria http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com https://documents1.worldbank.org/curated/en/842751468096580653/pdf/multi-page.pdf arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):537-560. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: eaumie@gmail.com 560 majumdar dk. 2015. irrigation water management principles and practice. phi learning private limited, delhi, india. michael, am. 1978. irrigation theory and practice. vikas publishing house, new delhi. p. 801. ofomata, ge. 1975. nigeria in maps: eastern states. ethiope publishing house, benin city. purseglove, jw. 1975. tropical crops monocotyledons, john wiley and sons new york. reyment, ra. 1965. aspects of the geology of nigeria. the stratigraphy of the cretaceous and cenozoic deposits.ibadan university press. 23-73. smith, mj. 1981. soil mechanics longman scientific and technical, civil -general. publisher. england: longman. wang, j. and hagan, r. 1981. irrigated rice production systems: design procedures 1981: 172. https://books.google.com.ng/book wang, j. and hagan, r. (1981). irrigated rice production systems: design procedures 1981: 172. https://books.google.com.ng/book file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/eaumie@gmail.com https://books.google.com.ng/book arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):377-386 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 377 soriginal research article determination of the physico-mechanical properties of three cultivars of cowpea (vigna unguiculata) grain e. o. adanu*1, 3, s. a. iya2, i. t. yakubu2 and h. u. kabri2 1department of agricultural education, federal college of education (technical), gombe, nigeria 2department of agricultural and environmental engineering, modibbo adama university of technology, yola, nigeria 3department of biological and agricultural engineering, universiti putra malaysia, 43400, upm serdang, selangor, malaysia *corresponding author’s email address: emmazone44@gmail.com 1.0 introduction cowpea (vigna unguiculata (l.) walp) is an annual grain legume indigenous to tropical africa but also cultivated in latin america, south eastern asia and southern united states (iita, 2005; da silva et al., 2018; ng and marechal, 1985). africa accounts for over 87% of global cowpea production, with nigeria responsible for 58% of global production (faostat, 2017 as cited in nkomo et al., 2021). in africa, 52% of cultivated cowpea is useful for food, 13% serves animal feed, 10% is utilized for seeds, 9% is used for other purposes, and 16% is wasted (iita, 2009; baysah, 2013). cowpea and other legumes, are responsible for up to 80% of the total protein intake for adults and are wholly the only source of protein for lots of children in west africa (fao, 2015). it is also a vital source of soil fertility improvement through the fixation of nitrogen and is relatively drought-tolerant (nkomo et al., 2021; olajide and ilori, 2017). rapid and accurate determinations of physical attributes are needed in processing agricultural materials (stroshine and hamann, 1995). physico-mechanic and aerodynamic data of agricultural products are necessary for the development of machines required for several operations ranging from harvesting, separation, handling and storage; and the conversion into food, feed and fodder (gursory and guzel, 2010). the size and shape properties of agricultural produce are vital in designing cleaning, grading, conveying equipment, and in thin layer drying (singh and meghwal, 2019). bulk density and true density are used in determining floor space, structural loads, and quality of the product. porosity is useful in determining other properties like thermal conductivity, volume change, or diffusion coefficient (kumar et al., 2018). the study of the article information abstract this study evaluated the physico-mechanical properties of it89kd-288, ife brown, and it98k-573-1-1 varieties of cowpea. the cowpeas were obtained from local farmers in different parts of north eastern nigeria. the crop varieties were identified, sundried and cleaned before testing. the results for length, width, thickness, equivalent diameter, arithmetic diameter, sphericity, surface area, volume, mass, angle of repose, frictional angle, and bulk density were obtained at pre-determined moisture contents. other results for it98k-573-1-1 seed-chaff ratio, pod angle of internal friction, hardness, compressive force in the major, intermediate and minor axes, shear force in the major, intermediate and minor axes are 4.0±0.18, 44.4±1.0o, 1.46±0.0.99 kgf/mm2, 62.0±6.5 n, 38.3±1.6 n, 81.0±11.7 n, 61.0±4.74 n, 45.1±2.4 n, and 76.5±9.8 n respectively. there was significant difference between the physical and gravimetric properties of it89kd-288, ife brown, and it98k-573-1-1 varieties of cowpea. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 30 december, 2021 revised 30 march, 2022 accepted 6 april, 2022 keywords: cowpea physical properties mechanical properties http://www.azojete.com.ng/ emmazone44@gmail.com mailto:omaliaurelius@yahoo.com mailto:omaliaurelius@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):377-386. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 378 engineering properties of agro-produce is useful in the design and simulation of food processes and equipment. the angle of repose and coefficient of friction aided the precise development of the hopper, silos and the conveyor belt. the conveyor belt serves purposes ranging from transportation, loading and unloading, dehulling and packaging (malik and saini, 2016; vashishth et al., 2020). in milling operations, the hardness of grains (soft or hard) determines the particle size distribution in the extracted flour (hrušková and švec, 2009). many studies have been carried out on the properties of cowpea (soyoye et al., 2020; kayode et al., 2018; chukwu et al., 2010), however, only a few went further to observe the pod characteristics as handling begins from the point of harvest (dalha et al., 2018). this study is to determine some engineering properties of three cowpea varieties that are popular in north eastern nigeria. it would offer researchers and agro-processing technologists a tool for furthering development in cowpea processing. 2. materials and methods 2.1 material selection and preparation cowpeas were obtained from cham community in gombe state, ngurore and sangere areas of adamawa state directly from farmers as shown in figure 1. the seeds were taken to the agricultural development programme (adp) office in adamawa state for identification. it was identified as it98k-573-1-1, ife brown and sampea 11 (it89kd-288). after the identification, the seeds were collected, cleaned and sorted for testing. the oven dry method was used to determine its moisture content prior to testing according to asae standards, (2003). figure 1: cowpea varieties commonly grown in parts of north east nigeria. 2.2 physical properties 2.2.1 dimensions and shape sixty whole seeds were selected at random and their corresponding length (l), width (w) and thickness (t) were measured and recorded using a digital vernier calliper having a resolution, reliability and maximum error of 0.01 mm, 0.01 mm and 0.02 mm respectively as found in de araujo et al. (2020). sphericity (%), arithmetic mean diameter (𝐷𝑎)(mm), equivalent diameter (𝐷𝑒)(mm), surface area (s)(mm2) and volume (v)(mm3) were estimated using equations 1, 2, 3, 4, and 5 respectively (stroshine and hamann, 1995; khodobakhshian et al., 2016). sphericity = ( 𝐿𝑊𝑇 𝐿 ) 1 3 (1) 𝐷𝑎 = (𝐿+𝑊+𝑇) 3 (2) 𝐷𝑒 = (𝐿𝑊𝑇) 1 3 (3) 𝑆 = 𝜋𝐷𝑒 2 (4) 𝑉 = 𝜋 6 𝐷𝑒 3 (5) file:///c:/user/downloads/azojete143/www.azojete.com.ng emmazone44@gmail.com adanu et al.: determination of the physico-mechanical properties of three cultivars of cowpea (vigna unguiculata) grain. azojete, 18(3):377-386. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 379 where: l = mean length of the seeds (mm); w = mean width of seeds (mm); and t = mean thickness of the measured seeds (mm). 2.2.2 mass of cowpea seeds the apparatus used were sample container and electric weighing balance. a 1000 whole seed of each variety were selected, placed in a container with known mass; it was weighed and the mass of the container was subtracted from the gross mass. the procedure was repeated 10 times and corresponds with igbozuike and aremu (2009). the average mass of the individual seed is estimated as shown in equation (6) (mohsenin, 1986), mass of seed (g) = total mass number of seeds (6) 2.2.3 bulk density the bulk density is the ratio of the mass sample of the seeds to its total volume. it was determined using procedure outlined by botelho et al. (2021) by filling predetermined container from a constant height. the bulk density (γ) was determined by filling a 100ml beaker with seeds by dropping them from a height of 150mm and the seeds weighed. dropping the seeds from a height of 150mm produces a tapping effect in the container to reproduce the settling effect during storage. the bulk density of the sample was calculated as shown in equation (7). bulk density (γ) = 𝑀 𝑉 (7) where: γ is bulk density of cowpea sample, g/cm3, m is bulk mass of cowpea sample, g, v is bulk volume of cowpea sample, cm3. 2.2.4 angle of repose sample container, metal funnel and meter rule were used. the metal funnel was erected on flat metal surface. a known quantity of cowpea seed was filled into the funnel by means of the sample container. the funnel was lifted gradually from the flat metal surface to allow the seeds flow freely to form a conical shape on the flat surface (togo et al., 2018). the height, h(cm) and length of the base of the conical heap, lb(cm) were measured and the corresponding angle of repose (°) computed following the relationship given by ozguven and kubilay (2004). 𝜃𝑟 = 𝑡𝑎𝑛−1[ 2𝐻 𝐿 ] (8) the procedure was repeated 10 times for each variety and the mean value determined and the values were recorded. similar method was used by togo et al. (2018). 2.2.5 coefficient of static friction the tilting table was used to compute coefficient of static friction. it was determined against plywood. the coefficient of static friction was calculated from equation (9). the procedure was similar to that found in dalha et al. (2018). 𝜇 = 𝑡𝑎𝑛𝜃 (9) where: 𝜇 is the coefficient of static friction and 𝜃 is the angle of tilt of the experiment table. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/emmazone44@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):377-386. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 380 2.3 mechanical properties 2.3.1 compression test the instron universal testing machine at the department of mechanical engineering at the bayero university, kano (buk) was used for performing compression test on the cowpea seeds. a seed of cowpea was placed between the two heads of the compressing device while the upper head is lowered at the rate of 1.25mm/min (chukwu and sunmonu, 2010). reading was immediately taken as displayed by the digital force gauge. ten seeds were observed for each variety and in the three major axis of major, minor, and the intermediate. 2.3.2 shear strength shear strength of the samples were determined using the universal testing machine at the department of mechanical engineering in bayero university, kano. the slots of the tester were screwed to compress the material in-between them. the reading was taken at the instance of the seed crack. this can be observed from the graph and its recordings. similar process was reported by chukwu and sunmonu (2010). 2.3.3 hardness hardness was tested using the rockwell brinell hardness tester according to astm e10-14 test method. the brinnel hardness tester is shown in figure 2. the upper part of the instrument slot was a steel ball indenter with known diameter. it was lowered on the sample with a weighted force (kgf) to create an indentation. the first sound made by the sample when tightly pressed indicates its hardness. the counter reading was taken where the sample was not making a total contact with the tester. the hardness value divided by contact area gives the contact hardness number. 𝐵𝐻𝑁 = 2𝑃 𝜋𝐷(√𝐷2−𝑑2) (10) where: 𝐵𝐻𝑁 is the brinell hardness number (kgf/mm2); 𝑃 is the applied load in (kgf); 𝐷 is the diameter of the indenter (mm); and d the diameter of the indentation (mm). figure 2. the brinnel hardness tester is shown in (a) and the test demonstration (ai). the universal testing machine (b) demonstrating test of a specimen (bi) 2.4 statistical analysis descriptive statistics, analysis of variance (anova) and post hoc testing of mean difference using tukey were computed to test and describe the cowpea varieties. these tests were run with the ibm○r spss○r 26 statistics (ibm corp. ○c copyright ibm corporation 2019) and the microsoft○r office excel○r 2019 software’s for microsoft windows. file:///c:/user/downloads/azojete143/www.azojete.com.ng emmazone44@gmail.com adanu et al.: determination of the physico-mechanical properties of three cultivars of cowpea (vigna unguiculata) grain. azojete, 18(3):377-386. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 381 3. results and discussion 3.1 seed dimensions the table 1 showed the mean dimensions of the three varieties of cowpea tested and the moisture content at which the test was conducted. the dimensions of length, width and thickness for the three varieties of cowpea investigated showed significant difference at (p≤ 0.01). the mean comparisons using the tukey’s hsd test indicated that the it98k-573-1-1, ife brown and it89kd-288 differ significantly with one another. with regards to length, the it89kd-288 is longer while it98k-573-1-1 is the shortest. the it89kd-288 is the widest and thickest of the varieties; while ife brown has the least width and thickness (table 1). the result for length, width and thickness were similar to results obtained by nimesh and sharanagat (2016), and banjpai et al. (2019) for chicken pea and jamun (syzgium cuminii) seeds respectively. the results by hamid et al. (2016) for red and black cowpea were comparatively smaller. sieve apertures among other parameters in the designing process of agricultural machines are selected based on grain dimensions (mohsenin, 1986). table 1. mean and standard deviation results for length, width and thickness of the cowpea varieties variety mc(%) n length(mm) width(mm) thickness(mm) it98k-573-1-1 11.7+0.26 60 8.27+0.21a 7.36+0.20a 5.65+0.16a ife brown 12.0+0.19 60 9.59+0.14b 6.99+0.30b 5.18+0.22b it89kd-288 11.8+0.20 60 11.3+0.11c 8.57+0.17c 6.57+0.02c all the parameters tested were highly significant at p≤0.001 3.2 arithmetic mean diameter (da) and equivalent diameter (de) the results for the computed arithmetic mean and equivalent diameter are shown in table 2 below. the results for arithmetic mean diameter and equivalent diameter for the three varieties observed showed significant difference (p≤ 0.01). further mean comparison revealed that the arithmetic mean diameter for it98k-573-1-1 (mean, m=7.09, standard deviation, sd=0.19), ife brown (m=7.26, sd=0.22), and it89kd-288 (m=8.81, sd=0.12) were all significantly different with one another. for equivalent diameter, it98k-573-1-1 (m=7.00, sd=0.11) significantly differ from it89kd-288 (m=8.60, sd=0.11); while ife brown did not differ with it98k-573-1-1 (m=7.03, sd=0.21). 3.3 volume, surface area and sphericity volume, surface area and sphericity for all the three varieties tested were significantly different (p≤ 0.01). the mean comparison test in table 2 showed that ife brown and it98k-573-1-1 did not differ for volume and surface area. however, all three varieties differ significantly for sphericity (p≤ 0.01). a similar trend was reported by theertha et al. (2014) for black grain; ehiem et al. (2016) for canarium schweinfurthii engl.fruits and yalcin (2006) for cowpea seed. table 2. computed values of shape and size for the three varieties from observed dimensions variety sphericity (%) da (mm) de (mm) sa (mm2) seed vol. (mm3) it98k-573-1-1 82.86±3.2b 7.09±0.19a 7.00±0.11a 154±2.42a 180±2.83a ife brown 73.77±4.0a 7.26±0.22b 7.03±0.21a 155±4.63a 182±5.44a it89kd-288 75.86±2.4c 8.81±0.12c 8.60±0.11b 232±2.97b 333±4.26b 3.4 1000 seed mass the variety of cowpea studied had significant impact on the seed mass, f (2, 27) = 1533619, p=.000. the 1000 seed mass for the three varieties tested showed that every variety is clearly http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/emmazone44@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):377-386. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 382 distinct in terms of mass from another. the variety can be identified based on the mass (table 3). similar result was reported by davies and zibokere (2011) for cowpea seed mass; and by ehiem et al. (2016) for canarium schweinfurthii engl.fruits. table 3. mean and standard deviation results for gravimetric properties of the cowpea varieties variety mc n 1000seed mass (g) angle of repose (°) angle of internal friction (o) bulk density it98k-573-1-1 11.7±0.26a 10 203±6.19a 20.7±3.06a 36.1±4.24a 711.3±9.40a ife brown 12.0±0.19b 10 218±5.22b 19.2±3.15b 34.4±3.11b 740.1±8.11b it89kd-288 11.8±0.20c 10 359±5.25c 19.7±3.04c 35.5±3.24c 695.7±11.2c 3.5 angle of repose and static coefficient of friction the table 3 above showed that the results of the angle of repose for it89kd-288, ife brown and it98k-573-1-1 all differ significantly when compared. the mean angle of repose for all three varieties ranged between 19.2° and 20.7° with it98k-573-1-1 having the larger angle, whereas ife brown has the least. the observed angle of repose values is higher than those reported by hamid et al. (2016) for red and black cowpeas; but lower than what was reported in mirzabe et al. (2021) and bajpai et al. (2019) for arugula and jamun (syzgium cuminii) seeds respectively. materials with low angles are highly flowable and can be transported using gravitational force or a little energy (bhattacharya, 2013; hashemi and al-amoudi, 2018). from the table 3, the mean comparison test for angle internal friction revealed that all the varieties in the study differ significantly. the mean angle of internal friction for it98k-573-1-1, ife brown and it89kd-288 cowpea varieties are 36.1±4.24o, 34.4±3.1o and 35.5±3.24o respectively. davies and zibokere (2011) obtained similar result for some three varieties of cowpea studied. the angle of internal friction is an indication of the minimum positioned angle which will guarantee a continuous flow of materials (mohsenin, 1986). 3.6 bulk density the mean bulk densities for it89kd-288, ife brown and it98k-288 are 695.7 g/cm3, 740.1 g/cm3 and 711.3 g/cm3 in that order. the mean comparison showed that all tested varieties differ significantly from the other. it was observed that larger volumes tend to have lesser bulk densities as can be seen with the it89kd-288. it implies that more can be tightly packed together for small than the larger sized seeds thereby resulting in greater mass per unit volume of space as reported elsewhere by mirzabe et al. (2021) and hamid et al. (2016) for arugula seed, and red and black cowpea respectively. mass, volume and density of agricultural products are vital in designing silos and storage bins, for determining seed purity and maturity evaluation (gustustafson, and kjelgard, 2000 as cited in heidarbeigi et al., 2009). 3.7 some mechanical and gravimetric properties of the it98k-573-1-1 besides the aforementioned properties tested for all three varieties of cowpea in this study, the it98k-573-1-1 was isolated for further testing. the test comprised of seed-chaff ratio, pod angle of friction, compressive force test, shear force test, and hardness test as shown in table 4 below, 3.7.1 seed-chaff ratio and it98k-573-1-1 whole pod angle of internal friction seed-chaff ratio is the comparison by weight of the cowpea grain collected from a representative pod and the chaff of the pod. in the result presented in table 4, the seed-chaff file:///c:/user/downloads/azojete143/www.azojete.com.ng emmazone44@gmail.com adanu et al.: determination of the physico-mechanical properties of three cultivars of cowpea (vigna unguiculata) grain. azojete, 18(3):377-386. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 383 ratio for ten pods tested was 4.0±0.18. this data is useful during threshing, while separating pod from the chaff through different outlets. the result of the angle of internal friction for the pod of cowpea is necessary in threshing, conveying and storage. the result, 44.4o±1.0, means that angular elevation above 44.4o on a plywood will produce sliding of the it98k-573-1-1 cowpea pod. table 4. mechanical properties of it98k-573-1-1 cowpea variety parameter n min. max. mean sd range seed-chaff ratio 10 3.7 4.3 4.0 0.18 0.63 pod angle of friction (o) 10 42.4 46.1 44.4 1.0 3.7 compressive force (n) a-major axis 10 53.0 72. 62.0a 6.5 18.6 b-minor axis 10 35.3 40.2 38.3b 1.6 4.9 c-intermediate 10 57.9 100.1 81.0c 11.7 42.2 shear force (n) a-major axis 10 54.9 69.7 61.0a 4.74 14.7 b-minor axis 10 41.2 48.1 45.1b 2.4 6.9 c-intermediate 10 60.8 92.2 76.5c 9.8 31.4 hardness (kgf/mm2) 10 0.04 3.18 1.455 0.99 3.14 3.7.2 compressive force (it98k-573-1-1) in this study, it was observed that there was a significant difference between the compressive strength of the three geometrical axes, f (2, 27) = 75.80, p<.001, np 2 = .85. post hoc testing using tukey’s hsd revealed that the intermediate axis (m=81.0n, sd=11.7) was significantly different from the other geometric axis. similarly, the minor axis (m=38.3n, sd=1.6) has the least compressive force requirement; while the major axis (m=62.0n, sd=6.5) had the comparatively moderate compressive force requirement as shown in figure 3a. the reason why the minor axis and the major had the least force requirement for compressive deformation is due to the dicot nature of cowpea which enables it to shatter along its axis of dicot separation, perpendicular to the direction of the impacting load. the compression test is similar to nimesh and sharanagat (2016) for chicken pea seed. the findings indicated that the minimum force required to shatter or rupture a cowpea kernel is 38.3n. figure 3. the compressive force (a) and shear force (b) test result for all three dimensions of the it98k-573-1-1 cowpea. it was obtained from graphical plot on the computer screen of the utm machine. it was the point of first failure of the plot. 3.7.1 shear force (it98k-573-1-1) the shear force for it98k-573-1-1 cowpea variety is presented in table 4 for the major, minor and intermediate axis. there was significant difference among the three geometrical axes on http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%203/azojete18no_3firstbatchofpapers/emmazone44@gmail.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):377-386. issn 1596-2644; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: emmazone44@gmail.com 384 the shear strength, f (2, 27) = 59.9, p<0.001, np 2 = 0.82. the mean comparison test revealed significant differences between pairs of geometric axes. the intermediate axis (m=76.5n, sd=9.76) requires the highest shear force, while the minor axis (m=45.1n, sd=2.39) requires the least. from the results as represented in figure 3b, the minimum force required to shear a cowpea kernel is 45.1n. the eta square result showed that the geometric axis of the cowpea is the most important main effect of variance. 3.8 hardness the mean hardness test for the it98k-573-1-1 cowpea was 1.455 kg-f/mm2, and the values ranged from 0.04 to 3.18 kg-f/mm2 for the 10 samples that were randomly tested. this result can be found in table 4. material hardness indicates the degree of resistance of the material to various load applied. chukwu and sunmonu (2010) recorded grain hardness of 7.98±0.03kg and 11.96±3.57kg for the sampea7 and tvx 3236 cowpea varieties respectively. 4. conclusion the physico-mechanical properties of it98k-573-1-1, ife brown and it89kd-288 varieties of cowpea seeds were determined. they were investigated at an average moisture content range of 11.7 and 12.0%wb. it is clear that the physical and gravimetric properties of cowpea can be used to distinguish its varieties. it is proven that the studied properties of cowpea are necessary for the development of cowpea post-harvest equipment. references asae s352.2. 2003. moisture measurement – unground grain and seeds. american society of agricultural engineers. mi49085-9659, usa. 6-89 bajpai, a., kumar, y., singh, h., prabhakar, pk. and meghwal, m. 2020. effect of moisture content on the engineering properties of jamun (syzgium cuminii) seed. journal of food process engineering, 43(2): 1–8. baysah, ns. 2013. assessing the effect of seed quality characteristics on the growth and yield of four cowpea (vigna unguiculata walp) varieties. postgraduate thesis submitted to the college of agriculture and natural resources, kwame nkrumah university of science and technology, kumasi, ghana. botelho, fm., botelho, scc., menezes-junior, jan., souza, ip. and araujo, mji. 2021. physical properties of cowpea grains during drying. international journal of development research, 11(7): 48416-48420. chukwu, o. and sunmonu, mo. 2010. determination of selected engineering properties of cowpea (vigna unguiculata) related to design of processing machines. international journal of engineering and technology, 2(6): 373-378. dalha, ib., yusuf, dd., yunusa, su. and abubakar, m. 2018. determination of physical and mechanical properties of some selected varieties of cowpea. proceedings of the 2018 international conference of the nigerian institution of agricultural engineers held at the federal institute of industrial research, oshodi, lagos, nigeria, 10th – 14th sept. 2018. davies, rm. and zibokere, ds. 2011. effects of moisture content on some physical and mechanical properties of three varieties of cowpea (vigna unguiculata (l) walp). agricultural engineering international: cigr journal, 13(1): 241-250. da silva, ac., santos, dc. and junior, dlt. 2018. cowpea: a strategic legume species for food security and health, intechopen, london, uk. file:///c:/user/downloads/azojete143/www.azojete.com.ng emmazone44@gmail.com adanu et al.: determination of the physico-mechanical properties of three cultivars of cowpea (vigna unguiculata) grain. azojete, 18(3):377-386. issn 1596-2644; 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moisture content, length, width, thickness, size and shape, arithmetic, geometric and equivalent mean diameters, surface area, volume and a thousand weight. others includes; bulk and solid densities, porosity, angle of repose and coefficient of static friction. the fineness modulus, uniformity coefficient, particle size distribution and terminal velocity were determined for both paddy acha and grains. the properties were determined using standard methods at the moisture content of 10.3% (db) in replicates. the results showed that the length, width, thickness, size of grain, flatness index, thousand grain weight, angle of repose, angle of internal friction, bulk and solid densities were 1.58 mm, 0.90 mm, 0.76 mm, 1.58 mm, 1.65, 0.53g, 24.7o, 0.46o, 608.01 kg m-3 and 1131.0 kg m-3 respectively. the terminal velocity, porosity, coefficient of static friction, arithmetic and geometrical mean, equivalent diameters, surface area, volume, fineness modulus (paddy), fineness modulus (grain), particle size distribution (grain), particle size distribution (paddy), uniformity coefficient (grain), uniformity coefficient (paddy) was 3.96 m s-1, 46.24, 0.459, 1.127 mm, 1.859 mm, 1.059 mm, 3.36 mm2, 3.00 mm3, 3.17, 3.00, 0.34, 0.36, 0.63 and 0.60 respectively. thus, the acha (paddy and grains) can be classified as medium size and spherical in shape. in the sieve analysis of the paddy acha, 99.57 % of the paddy was retained on 0.351 mm mesh while 27.27 % and 61.72 % of the grains were retained on the 0.894 and 0.351 mm meshes. this is indicative of more variability in the grains than in the paddy. the properties show that the paddy separates easily and the grains are easily cleaned from contaminants. 1.0 introduction acha is a typical west african cereal crop cultivated in large quantity in nigeria. other large acha cropping and producing countries in west africa guinea are: mali and burkina faso. it was reported that about 587,270 tons of acha were produced on 566,047 hectares in these regions in 2012 (wilma et al., 2018). acha produces rough pods also known as raw or paddy acha (figure 1a), which still have their glume and lemmas after threshing (cruz et al., 2016). the paddy has an oval seed coating with slightly flattened side. the paddy is very small (figure 1a), measuring 1.5 mm in length, 0.9 mm in width and a 1000 weight of 0.5g (satimehin and philip, 2012). hulled acha grains (figure 1b) have a shiny shin pericarp whose colours vary from white through yellow to purple depending on the variety (rose, 2017). http://www.azojete.com.ng/ mailto:dritido@gmail.com mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 706 figure 1: acha, a. greatly magnified 1 mm acha paddy b. grains (source: koréissi, 2015; cruz et al., 2016) chakraverty et al. (2003) identified seed and system parameters as the two broad factors that affect the cleaning of agricultural grains and seeds. the accurate estimation of seed shape is fundamental in the design of pneumatic technology for grain cleaning because it is important for the determination of terminal velocity and drag coefficient used for estimating the reynolds number (cervantes et al., 2016). the seed sizes are classified into three categories namely small, medium and large based on their length (philip, 2011). komar and reimers (1978) stated that the departure of a grain from a spherical shape causes a decrease in its settling or terminal velocity within a fluid; the more non-spherical the particle, the greater the departure from the terminal velocity of a grain of the same weight in a stream of air (carventes et al., 2016). the moisture content of grains is known to alter the shape of the grain. el fawal (2009) reported an increase in seed sphericity with increased moisture content. the 1000-kernel weight is a good indicator of the grain size, which can vary relative to growing conditions and maturity even for the same variety of a given crop when compared with other crops at the same moisture level. the 1000 kernel weight also provide an idea of relative size of the kernel for handling purposes (sablani and ramawamy, 2003). the bulk density gives a good idea of the storage space required for a known quantity of particular grain. bulk density also influences the effective conductivity and other transport properties (philip, 2011). satimehin and philip (2012) recorded a bulk density of 0.607 g m-3 at 10.31% moisture content (db) for acha grains (digitaria exilis) in nigeria. bulk densities of some biomaterials increase linearly with increase in moisture content between 12 and 18% while some decrease linearly with increase in moisture content (sokhansanj and lang, 1996; fraser et al., 1978; irvine et al., 1992; dutta et al., 1988; carman, 1996; bala and woods, 1991; deshpande et al., 1993). satimehin and philip (2012) found the mean kernel density of acha grain to be 1.13 g cm-3 at 10.31% moisture content (db). the porosity of grain is an important parameter that affects the kernel hardness, breakage susceptibility, milling, drying rate, and resistance to fungal development (chang, 1988). stroescu et al. (2019) identified terminal velocity, angle of friction, angle of repose and the coefficient of internal resistance of seeds as properties that enable their separation from a matrix of other materials by pneumatic segregation. the ease with which the particles fall along the tray depends on the tilt or repose angle that is used in designing adjustable inclined cleaning trays in dehulling and cleaning. terminal velocity is an important aerodynamic property of seeds that is necessary for designing pneumatic conveying systems, fluidized bed dryers and cleaning of seeds from foreign materials (ghamari et al., 2011). experimental results have shown that the value of terminal velocity even for the same species of grains fluctuates in a very vast range (kaankuka, 2015 and stroescu et al., 2019). this is because the motion of a grain particle falling freely through air during the separation of undesirable chaff from the grain, is guided by the shape and weight of the grain and the density of the media (air) through which it is falling as well as gravitational pull on the grain (sümer and helvaci, 2008). the greater the difference between values of critical velocities of individual components in a mixture, the better and more efficient its pneumatic separation (panasiewicz et al., 2012). according to file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com owolarafe et al: some physical properties of acha (digitaria exilis) relevant in mechanical dehulling and cleaning. azojete, 19(4):705718. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 707 panasiewicz et al. (2012) the lower the critical velocity is, the lower the density and drag of a particle, which in turn depend on the shape and properties of its surface (such as smooth, coarse, ribbed, mesh, covered with trichomes). khoshtaghaza and mehdizadeh (2006) and refit et al. (2006) found that increasing the mass and moisture content of the kernel results in a linear increase in the terminal velocity. kaankuka et al. (2015) reported terminal velocities of acha, the acha chaff and the velocity of the air required for the cleaning the hulls as 3.96 ms-1, 1.9 ms-1 and 2.5 ms-1 respectively. there are no technologies for the processing of acha because of the dearth of literature on its properties relevant to designing them such as the dehulling and cleaning machine. the properties of acha will help make the design of processing machines easier and more efficient. this study is geared towards generating some engineering data of acha, relevant for designing efficient machines for its postharvest processing operations. thus, the objective of this study is to determine some physical properties of acha relevant to mechanical its dehulling and cleaningient. the objective of this study is to determine the properties of acha relevant to mechanical dehulling and cleaning. 2. materials and methods acha (digitaria exilis) paddy and grains that were used in determining some selected physical properties were bought from jos south local government area of plateau state, nigeria. the properties of paddy acha and grains relevant to mechanical dehulling and cleaning were determined. the properties of paddy acha determined were the moisture content, size, shape,1000-paddy weight, bulk and solid densities, porosity, angle of repose and coefficient of static friction. the properties of paddy acha and grains determined were fineness modulus, particle size distribution, uniformity coefficient and terminal velocity. 2.1 determination of moisture content the moisture content of paddy acha was determined by the oven-dry method. 10 to 15 g of paddy acha was taken from the paddy lot, put into a container and weighed using an electronic digital weighing machine (metler toledo balance) having a sensitivity of 0.01 g. the known weight was oven dried at a temperature of 110c for 18 hours. the weight of the dried sample was taken and the moisture content was obtained using equation 1. 𝑀𝐶(𝑑.𝑏)% = 𝑊𝑤 − 𝑊𝑑 𝑊𝑑 × 100. (1) where: ww is weight of wet paddy acha (g) wd is weight of dry paddy acha (g) 2.2 determination of size the size of paddy acha can be subdivided into length, width and thickness (figure 2). these dimensions were measured using a digital vernier caliper with 0.01mm accuracy and used to determine the size of paddy. some paddy acha were pinched between the thumb and the index finger from the lot onto a plane white surface from which ten (10) samples were randomly selected, measured and the sizes calculated using equations 2, 3, 4 and equation 5 (maduako and hannan, 2004). 𝑑𝑎 = (𝐿+𝑊+𝑇) 3 (2) http://www.azojete.com.ng/ mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 708 𝑑𝑔 = (𝐿 × 𝑊 × 𝑇) 1 3⁄ (3) 𝑑𝑠 = [ 𝐿𝑊 + 𝑊𝑇 + 𝑇𝐿 3 ] 1 2⁄ (4) 𝑑𝑒 = 𝑑𝑎 + 𝑑𝑔 + 𝑑𝑠 3 (5) where: dg is the geometric mean diameter (mm) da is the arithmetic mean diameter (mm) ds is the square mean diameter (mm) de is the equivalent diameter (mm) 𝐿 is the mean length of the seeds (mm) 𝑊 is the mean width of the seeds (mm) 𝑇 is the mean thickness of the seeds (mm) the surface area (sa) was determined using equation 6 (malik et al., 2016) 𝑆𝑎 = 𝜋 × 𝑑𝑔 2 (6) the sphericity (φ) of particle was determined using equation 7. 𝜑 = 𝑑𝑔 𝐿 (7) figure 2: dimensional axes of the acha paddy 2.3 determination of seed shape the seed shape was determined from the flatness index (fi) which measures the relationship between the seed’s dimensions along the three principal axes (cervantes et al., 2016; cerda and garcia-fayos, 2002) to characterize seed shape. the index was determined from equation 8. it ranges from a value of 1 for spheres to values greater than 2 for spindly seeds (cervantes et al., 2016). 𝐹𝐼 = (𝐿+𝑊) 2𝐻 (8) where l is the length and w is the width and h is the height of the seed (mm) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com owolarafe et al: some physical properties of acha (digitaria exilis) relevant in mechanical dehulling and cleaning. azojete, 19(4):705718. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 709 2.4 determination of one thousand weight 1000 grain weight of paddy acha was measured using a mettler xsr electronic balance with accuracy of 0.001g. cleaned paddy acha were carefully counted to 1000 kernel and placed on the weighing pan of the electronic balance and weighed. the procedure was carried out in 5 replicates and the results recorded. 2.5 determination of bulk and solid density a plexi-glass cylindrical container (63.00 mm in height and 64.03 mm in diameter) was filled with paddy acha and weighed on a mettler xsr electronic balance with accuracy of 0.01g. the procedure was repeated five times and the bulk density was calculated from equation 9. 𝜌𝑎𝑏 = 𝑊2 − 𝑊1 𝑉 (9) where: ρab is paddy acha bulk density (kg m-3) 𝑊1 is weight of empty cylindrical container (kg) 𝑊2 is weight of the paddy acha and cylindrical container (kg) 𝑉 is volume of the container (m3) the solid or kernel (true) density refers to the density of an individual unit and is another way of describing density. this may or may not contain internal pores. the solid density was calculated using equation 10 as described by ozturk et al. (2009). 𝜌𝑎𝑡 = ρ𝑤 × 𝐺𝑆𝑃 (10) where: ρat is the true density (kg m-3) ρw is is the density of water (kg m-3) gsp is the specific gravity of the paddy acha (g/g) 2.6 determination of porosity the porosity of seeds depends on bulk density and the true density, and is usually affected by the moisture content of a crop material. the porosity value (ε) which is defined as the fraction of space in the bulk grain not occupied by the grains was calculated from the average values of bulk density and true density using equation 11 (mohsenin, 1986). 𝜀(%) = (1 − 𝜌𝑎𝑏 𝜌𝑎𝑡 ) × 100 (11) where: ε – porosity ρab -bulk density of paddy acha (kg m-3) ρat true (kernel) density of paddy acha (kg m-3) 2.7 determination of angle of repose a double-ended open cylindrical container of 20 cm diameter and 40 cm height was placed on a 100 cm circular plastic plate and filled with acha grains. the cylinder was tapped until a uniform packing was attained and then gently lifted up 20 mm above the surface where the bottom of the container was uncovered. the lifting of the container continued gradually until all the paddy acha formed a conical heap on the plate. the procedure was replicated 5 times http://www.azojete.com.ng/ mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 710 while measuring the heights each time and the angle of repose calculated using equation 12 (waziri and mittal, 1983). 𝑅𝑎 = 𝑡𝑎𝑛−1 ( 2𝐻ℎ 𝐻𝑑 ) (12) where: ra is the angle of repose of the acha paddy acha () hh is the height of the heap of paddy acha (mm) hd is diameter of the plastic plate (mm) 2.8 determination of fineness modulus the fineness modulus of paddy acha and grains was determined in the laboratory according to astm e11(2001) using a gilson shaker (serial no.064438) and golden mettler electronic weighing balance of 0.001g accuracy. one hundred grams (100 g) of paddy acha was weighed in a pan of known weight (24.4g) and placed on 5 sieves stacked sifter with an empty bottom pan. the sieves stack was arranged from the biggest to the smallest from top to bottom: 2.818, 1.201, 0.894, 0.351 and 0.186 mm with a bottom pan that has no mesh/covering and designated as 0. the shaker was manually agitated vigorously for10 min in three replications. the paddy acha retained after the sifting on each screen was weighed and the percentage paddy retained on each designated sieve was calculated. the percentage of paddy acha retained on each screen and the bottom pan was determined from equation 13. the fineness modulus, which is the cumulative percentage of the paddy retained on each sieve and the pan added up and divided by 100 was obtained using equation 14 (karaj and muller, 2010). the procedure was also undertaken for acha grains. r (%) = ( m1−m2 m ) x100 (13) fm = 𝑅 100 (14) where: fm is the fineness modulus r is the percentage grains retained on each sieve (%) m1is mass of each sieve (g) m2 is mass of each sieve + mass of paddy acha or grains retained on the sieve (g) m is the total mass of the paddy acha or grains (g) 2.9 determination of particle size distribution the particle size distribution for the paddy acha and grains were determined. the particle size distribution was calculated using equation 15 (boloni, 1994). 𝑃𝑆𝐷 = 0.135 × (1.366)𝐹𝑀 (15) where psd is the particle size distribution and fm is the fineness modulus 2.10 determination of uniformity coefficient the uniformity coefficient (cu) expresses the dispersion in particle sizes of paddy acha and grains. it is defined as the ratio of d60 to d10 determined from the gradation curve, which is a logarithm plot (figure 3) of the cumulative percent passing of paddy acha or grains on the yaxis and the sieve size opening on the x-axis (keaton, 2018). the cu for paddy and grains were computed using equation 16. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com owolarafe et al: some physical properties of acha (digitaria exilis) relevant in mechanical dehulling and cleaning. azojete, 19(4):705718. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 711 𝐶𝑢 = 𝐷60 𝐷10 (16) where: d60 is paddy acha or grain diameter at which 60% of particles that is finer and 40% of particles that are coarser (mm). d10 is paddy acha or grain diameter at which 10% of particles are finer and 90% of the particles are coarser (mm). figure 3: grain size distribution curve 2.11 determination of terminal velocity the terminal velocity of the paddy acha and grains were calculated from equation 17. 𝑉𝑡 = √ 2𝑊(𝜌𝑝 − 𝜌𝑓) 𝐶𝑑𝐴𝑝𝜌𝑝𝜌𝑓 2 (17) where: vt -terminal velocity (m s-1) cd drag coefficient w weight of grains (kg) ρp density of particle (kg m-3) ρf density of air (kg m-3) 𝐴𝑓 -frontal area, which is equal to 1.088 x 10-6 for paddy acha and grains (m3) (kaankuka et al., 2015) 2.12 determination of coefficient of static friction the coefficient of static friction of paddy acha was determined on a galvanized steel surface using a tilting table. the angle of inclination of the table to the horizontal at which samples started sliding were measured with a protractor attached beside the inclined plane apparatus (maduako and hannan, 2004). measurements were replicated five times and the coefficient of static friction was determined using equation 18. http://www.azojete.com.ng/ mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 712 𝜇 = tan 𝛼 (18) where: 𝜇 = coefficient of static friction 𝛼 = angle of inclination of the table to the horizontal (o) 3. results and discussion the summary of some properties of paddy acha and grain is presented in table 1. the coefficient of static friction was determined to be 0.46 and is similar to the value of 0.456 obtained by philip (2011) but lower than the value of 0.82 reported by bako and bardey (2020). this variation may be due to the difference in the moisture contents of the acha grains used in the different studies as the coefficient of internal resistance of grain have been reported to increase with increases in moisture content (aviara et al., 2017). the terminal velocity was 3.96 m/s for paddy acha and 2.13 for grain. the result is consistent with the values of 3.96 m/s paddy acha and 1.9 m/s for grain reported by kaankuka et al. (2015) and the value of 3.97 m/s for paddy acha reported by bako and bardey (2020). the difference in the terminal velocities of the paddy acha and grain lend them to separation by using appropriate air velocities in conveyor and pneumatic separation and can be applied to the separation of damaged grains from whole grains as well. the length of the paddy acha was 1.58mm. this is consistent with the value of 1.604 mm reported by philip (2011) and 1.84 mm reported by bako and bardey (2020). the width of the paddy acha was 0.9 mm, which is similar to the values of 0.864 and 0.85 reported by philip (2011) and bako and bardey (2020) respectively. the thickness of the paddy acha was 0.76 mm, which compares to 0.796 mm and 0.75 mm reported by philip (2011) and bako and bardey (2020) respectively. the knowledge of the axial dimension of seeds has been used in the determination of the clearance between dehulling cylinders and drums (tokan et al., 2012; solanki et al, 2018; simonya and yiljep, 2008) to minimize damage to grains. the knowledge of the axial dimension of the grain can also be used in the design of indented cylinders for acha grain cleaning. the one thousand grain weight of the paddy acha was 0.53 g. the value is the same as 0.529 g established by philip (2011) but differs from the 0.83 g reported by bako and bardey (2020). the bulk and solid densities were 608.01 kg m-3 and 1131.00 kg m-3 respectively. these values are similar to 606.6 kg/m3 and 1130 kg/m3 for solid and bulk densities respectively reported by philip (2011). bako and bardey (2020) reported solid and bulk densities of 1626.15 kg/m3 and 1092.86 kg/m3 respectively which are different from the results obtained in this study. the porosity was determined to be 46.24 % which is similar to the value of 46.25% reported by philip (2011) but different from 32.52 % reported by bako and bardey (2020). although porosity is reported to have a linear relationship with moisture content (karimi et al., 2009), it is known to decrease with increase in bulk density and this may explain the variation in the porosities reported in these studies. the knowledge of the weight and densities of seed is important in the design of feed hoppers and the size of hopper throats. the ratio of the intergranular void space volume and bulk volume of seeds is the porosity and it is important in pneumatic cleaning as less hulls attached to the kernel are cleaned and can be easily blown off by the impeller air velocity. the angle of repose of the paddy acha was 24.70º which corroborate the value of 24.50º reported by kaankuka et al. (2014). bako and bardey (2020) reported a value of 32.50 ̊. the different values in the different studies may still be due to variation in moisture content as the angle of repose increases linearly with increasing moisture content (bako and bardey, 2020; aviara et al., 2017). the angle of repose is an important determinant in the estimation of forces acting on structures and the design of solid flow structures such as silos, storage bins and the design of free fall devices such as hoppers. it is vital in determining the angles at which chutes are inclined for consistent flow of granular materials. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com owolarafe et al: some physical properties of acha (digitaria exilis) relevant in mechanical dehulling and cleaning. azojete, 19(4):705718. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 713 table 1. properties of paddy acha and grains properties value length (mm) 1.58 width (mm) 0.90 thickness (mm) 0.76 size of grain (mm) 1.58 arithmetic mean dimeter (mm) 1.13 geometric mean diameter (mm) 1.86 square mean diameter (mm) 1.58 equivalent diameter (mm) 1.06 surface area (mm2) 3.36 volume (mm3) 3.36 flatness index 1.63 1000-wieght (g) 0.53 angle of repose (deg) 24.7 bulk density (kg/m3) 608.01 solid density (kg/m3) 1131.00 porosity 46.24 fineness modulus (grain) 3.00 fineness modulus (paddy) 3.17 particle size distribution (grain) 0.35 particle size distribution (paddy) 0.36 uniformity coefficient (grain) 0.63 uniformity coefficient (paddy) 0.60 terminal velocity, paddy (m/s) 3.96 terminal velocity, grain (m/s) 2.13 coefficient of static friction 0.46 table 2 is the sieve analysis for fineness modulus and particle size analysis for paddy acha and grain. the fineness modulus of the grain and paddy were 3.00 and 3.17 respectively while the particle size distribution of the paddy and grain were 0.35 mm and 0.36 mm respectively. in the sieve analysis of the paddy acha, 99.57% of the paddy was retained on 0.351 mm mesh while 27.27% and 61.72% of the grains were retained on the 0.894 and 0.351 mm meshes. this is indicative of more variability in the grains than in the paddy. aviara et al. (2017) investigated the effect of moisture content (5 30% d.b.) on the particle size distribution of two acha varieties (digitaria exilis and iburau) using sieve analysis method and reported that only a little fraction (less than 1.5%) of the grains passed through the 0.425mm mesh. the results of this study agree with that of aviara et al. (2017). particle size distributions of grains have been used in the determination of the grain weight for bins and hopper designs (belay et al., 2009) and is an important factor in feed rate calibration (khurmi and gupta, 2007). http://www.azojete.com.ng/ mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 714 table 2. sieve analysis for fineness modulus and particle size of acha paddy and grain sieve no (size bss, mm) acha type mass of acha retained (g) percentage retained per sieve (%) cumulative percentage retained per sieve (%) percentage finer (%) 6 (2.818) paddy 0 0 0 100 grain 0 0 0 100 14 (1.201) paddy 0.03 0.06 0.06 99.94 grain 0.07 0.96 0.96 99.04 20 (0.894) paddy 0.20 0.37 0.43 99.57 grain 1.9 27.27 28.23 71.77 44 (0.351) paddy 53.73 99.57 100.00 0 grain 4.3 61.72 89.95 10.05 80 (0.186) paddy 0 0 100.00 0 grain 0.6 8.61 98.57 1.44 pan (0) paddy 0 0 100 0 grain 0.1 1.44 100 0 total paddy 53.97 300.49 grain 6.97 317.70 figure 4 is the grain size distribution curve for the paddy acha and grain. the d10, d30 and d60 for paddy acha were 1.0 mm, 0.9 mm and 0.6 mm respectively. the figure also shows that the d10, d30 and d60 for grain were 0.8 mm, 0.7 mm and 0.5 mm respectively. the uniformity coefficient for paddy acha and grain was 0.60 and 0.63 respectively (table 1). the uniformity coefficient expresses the proportion of coarse to fine particles of the acha. a uniformity coefficient greater than 6.0 indicates a densely graded (well graded) material with a considerable range of particle size. a uniformity coefficient of less than 4.0 indicates a uniformly graded (open graded) material with a narrow range of particle size. the uniformity coefficient is useful in designing the clearance between the dehulling cylinder and concave in the dehulling unit of machines. figure 4: grain size distribution curve for paddy and hulled acha file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com owolarafe et al: some physical properties of acha (digitaria exilis) relevant in mechanical dehulling and cleaning. azojete, 19(4):705718. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 715 4. conclusions acha (paddy and grains) can be classified as medium size and spherical in shape. the paddy was more uniformly graded and of finer aggregates than the grains that were of more variability of considerable range between fine and coarse. the gravimetric properties of the paddy acha shows that it separates easily according to its weight and the grains can be easily cleaned from contaminants. the determined properties are recommended for use in designing the size of hopper, diameter of the hopper throat, clearance between the dehulling cylinder and concave, size of openings on the screen in the cleaning unit of dehulling machines and the appropriate velocity of air required for effective cleaning of the grains. references astm c1444-00, 2001. standard test method for measuring angle of repose of free flowing mould powders. american society of testing materials, west conshohoken, pa, usa. aviara, na., kawuyo, ua. and okolo, dc. 2017. physical properties of two acha varieties as a function of moisture content. arid zone journal of engineering, technology and environment, 13(5): 555-566. bako, t. and bardey, ia. 2020. engineering properties of acha (digitaria exilis) grains in relation to the design of grain processing machines. agricultural engineering international: cigr journal, 22 (2):159-170. bala, bk. and woods, jl. 1991. physical and thermal properties of malt. drying technology, 9(4): 1091-1104. belay, g., zemede, a., assefa, k., metaferia, g. and tefera, h. 2009. seed size effect on grain weight and agronomic performance of tef (eragrostis tef (zucc.) trotter). african journal of agricultural research, 4 (9): 836-839 boloni, i. 1994. uniformity of agricultural grind’s grain size distribution. international agrophysics, 8: 197 – 201. carman, k. 1996. some physical properties of lentil seeds. journal of agricultural engineering research, 63(2): 87-92. cerda, a. and garcia-fayos, f. 2002. the influence of seed size and shape on their removal by water erosion, cetena. 48 (4): 293 301 cervantes, e., martins, jj. and saadaoui, e. 2016. updated methods of seed shape analysis. scientifica, 23-33. chakraverty, a., mujum, as., raghavan, gsv. and ramaswamy, h. 2003. handbook of postharvest technology, cereals, fruits, vegetable, teas and spices. marcel dekker inc. new york. chang, cc. 1988. measuring density and porosity using gas pycnometer. cereal chemistry, 65(1): 13-15. cruz, jf., béavogui, f., dramé, d. and diallo, ta. 2016. fonio, an african cereal. cirad. montpellier, france. 154 pp. http://www.azojete.com.ng/ mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 716 deshpande, sd., bal, s. and ojha, tp. 1993. physical properties of soybean. journal of agricultural engineering research, 56: 89-98. dutta, sk., nema, vk. and bhardwaj, rk. 1988. physical properties of gram. journal of agricultural engineering research, 39: 259-268. el fawal, ya. 2009. study on physical and engineering properties from grains of some field crops. misrata journal of agricultural engineering, 26 (4): 1933 – 1951. fraser, bm., verma, ss. and muir, we. 1978. some physical properties of faba beans. journal of agricultural engineering research, 23: 53-57. ghamari, s., rabbani, h. and khazaei, j. 2011. mathematical models for predicting the terminal velocity of chickpea, rice and lentil. world applied science journal, 15 (11): 1557-1561. irvine, da., jayas, ds. and white, ndg. 1992. some physical properties of flaxseed lentil faba beans. canadian agricultural engineering, 34: 075 081. kaankuka, tk. 2015. comparative performance evaluation of an existing and modified acha dehullers. global journal of engineering research, 14: 9-15. kaankuka, tk., itodo, in. and awulu, jo. 2015. design analysis of an existing acha (digitaria exilis) dehulling machine. journal of science and technology, 35 (4): 1-10. kaankuka, tk., itodo, in. and obetta, se. 2014. effect of cylinder type and speed on acha (digitaria exilis) dehulling. international journal of applied engineering and technology, 4 (2): 125-131. karaj, ad. and muller, j. 2010. sieve analysis and graphical interpretation of particle size. jas enterprises. gujarat, india., pp. 210 karimi, m., kheiralipour, k., tabatabaeefar, a., khoubakht, gm., naderi, m. and heidarbeigi, k. 2009. the effect of moisture content on physical properties of wheat. pakistan journal of nutrition, 8 (1): 90-95. keaton, jr. 2018. coefficient of uniformity. in: encyclopedia of engineering geology. amec foster wheeler, los angeles, ca, usa. khoshtaghaza, mh. and mehdizadeh, r. 2006. aerodynamic properties of wheat kernel and straws materials, agricultural engineering international: the cigr ejournal. manuscript ft 05007. vol. viii: 1-10. khurmi, r. and gupta, j. 2007. theory of machines. (8th ed.). eurasia publishing house (pvt) ltd. new delhi. 72-381. komar, pd. and reimers, ce. 1978. grain shape effects on settling rates. journal of geology, 86: 193–209. koréissi, y. 2015. fonio (digitaria exilis) in west africa: towards improving nutrient quality. gvo drukkers & vormgevers b.v. publishers. wageningen, mali., pp. 179. maduako, jn. and hannan, m. 2004. determination of some physical properties of three of groundnut varieties. nigerian journal of technology, 24 (2): 12-18 malik, m., saini, cs. and yildiz, f. 2016. engineering properties of sunflower seed: effect of dehulling and moisture content. cogent food and agriculture, 2(1): 1145783. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com owolarafe et al: some physical properties of acha (digitaria exilis) relevant in mechanical dehulling and cleaning. azojete, 19(4):705718. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 717 mohsenin, nn. 1986. physical properties of plant and animal materials. (2nd edition). gordon & breach science publishers. new york. morita, t. and singh, rp. 1979. physical and thermal properties of shirt-grain rough rice. transaction of the american society of agricultural engineers, 22: 630-636. ozturk, im., kara, ee. and ercisli, s. 2009. physico-chemical grain properties of new common bean cv. ‘elkoca-05. scientific research and essay, 4 (2): 88 – 93. pabis, s. 1967. grain drying in thin layers. presented at the agricultural engineering symposium of national institute of agricultural engineering, silsoe, paper 1/c/4 panasiewicz, m., sobczac, p., mazur, j., zawislak, k. and andrejko, d. 2012. the technique and analysis of the process of separation and cleaning grain materials. journal of food engineering, 109(3): 603-608. philip, tk. 2011. development of an acha (digitaria exilis) dehulling machine. phd thesis, university of agriculture, makurdi, nigeria. philip, tk. and itodo, in. 2012. demographic characteristics, agricultural and technological profile of acha farmers in nigeria. agricultural engineering international: cigr journal, 14(1): 89-93. refit, rv., kamil, w. and skin, fd. 2006. effect of moisture content on the physical properties of soybean. biosystems engineering, 56(4): 123-129. rose, v. 2017. fonio: tasty early maturing cereal for diversified production systems in west africa. biodiversity international, 7(2): 234 241. sablami, ss. and ramaswamy, hs. 2003. physical and thermal properties of cereal grains. in: handbook of postharvest technology: cereals, fruits, vegetables, tea and spices. (eds) chakraverty, aa., mujumdar s., raghavan, gsv and ramaswamy, hs. 17 – 40. satimehin, aa. and philip, tk. 2012. some physical properties of acha as affected by moisture content. postharvest technology and process engineering, 14(4): 233 -240. simonyan, kj. and yiljep, yd. 2008. investigating grain separation and cleaning efficiency distribution of a conventional stationary rasp bar sorghum thresher. agricultural engineering international, 10: 1-13. sokhansanj, s. and lang, w. 1996. prediction of kernel and bulk volume of wheat and canoloa during adsorption and desorption. journal of agricultural engineering research, 63: 129–136. solanki, cd., mridula, sk., aleksha, k. and gupta, rk. 2018. buckwheat dehuller and optimization of dehulling parameters. international journal of current microbiology and applied sciences, 7 (11):1041-1052. stroescu, g., paun, a., bracacescu, c. and olan, m. 2019. streamlining organic seed production technologies for vegetable species by making seed conditioning module. engineering for rural development, 22: 34-38. sumer, m. and helvaci, ps. 2008. solid-state two-phase flow handbook. department of chemical engineering, ege universisty, izmir, turkey. http://www.azojete.com.ng/ mailto:dritido@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):705-718. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: dritido@gmail.com 718 tokan, a., danladi, yb., shekarau, mbe. and dada, sg. 2012. design, fabrication and testing of a fonio dehusking machine. international journal of engineering innovation and research, 1(6): 2277 – 5668. wilma, ss., emeses, bo. and rambo, ek. 2018. prospects and constraints to acha production and processing in bogoro local government area of bachi state: implication to relevant technology transfer. journal of agriculture and veterinary science, 11(7): 58-64. wratten, fd., poole, wd., cheness, jl., bal, s. and ramarao, v. 1969. physical and thermal properties of rough rice. transaction of the american society of agricultural engineers, 12: 801-803. waziri, an and mittal, jp. 1983. design related physical properties of selected agricultural products. agricultural mechanization in africa and latin america, 14:59-62. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:dritido@gmail.com arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):409-422 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 409 original research article kinetics of the valorization of food waste for medium chain carboxylates production; effect of ensiling and inoculum source j. a. undiandeye1*, i. obiora-okafo2 and e. a. idama3 1department of chemical engineering, university of port harcourt, nigeria. 2department of chemical engineering, nnamdi azikiwe university, nigeria. 3department of chemical engineering, modibbo adama university, nigeria *corresponding author’s email address: jerome.undiandeye@uniport.edu.ng 1.0 introduction according to the united nations, as much as 17 % of the global food production is lost between the farm and the consumer’s table (uno 2022), resulting in an estimated economic loss of usd 680 billion (usmani et al. 2021). being a greenhouse gas emitter, food wastes including left-overs from restaurants, homes and hotels, contribute to environmental pollution. since the complete elimination of food waste is impossible, their valorization for the production of biofuels and platform chemicals has become the most attractive method of reducing their impact on the environment. depending on their sources, the composition of food wastes varies greatly, with carbohydrate, protein and oils/lipids being the major component (paritosh et al. 2017). for food waste with a high composition of scraps of vegetables and peels from fruits, valorization by anaerobic digestion (ad) has to be preceded by pretreatment for an enhanced biodegradability (gallipoli et al. 2020) as a result of their lignocellulosic structure. many conventional pretreatment methods are either too expensive or are prone to the formation of inhibitors that often affect downstream processing (amin et al. 2017). one pretreatment process that reduces the drawbacks of conventional pretreatment processes is ensiling. article information abstract higher yields of medium chain carboxylates (mcc) can be obtained from the anaerobic fermentation of complex feedstocks like food waste if pretreatment preceeds fermentation. however, many conventional pretreatment processes produce inhibitors that could affect downstream processing in addition to increasing the cost of the overall process. in this study, ensiling was used as a cost effective and sustainable pretreatment method to instigate the formation of electron donors like lactic acid and ethanol in food waste for mcc production. food waste was ensiled for 120 days and thereafter subjected to batch anaerobic fermentation using two different inocula including leachate and rumen fluid. results show that ensiling degraded the cellulose and hemicellulose component of food waste and converted the water soluble carbohydrate content to lactic acid, acetic acid and ethanol. ensiled substrates had a total mcc yield of 990.44 g/kgvs and 878.68 g/kg vs when leachate and rumen fluid was used as inoculum respectively, while the unensiled food waste had a total mcc yield of 522.80 g/kgvs and 430.88 g/kgvs when leachate and rumen fluid was respectively used as inoculum. in order to predict the mcc production, two kinetic models were used including the first-order model and the modified gompertz model. statistical indicators including the coefficient of determination, r2, the root-mean-square-error and the akaike information criterion show that the first-order model predicted the experimental mcc better than the modified gompertz model. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 18 feb., 2023 revised 25 may, 2023 accepted 30 may, 2023 keywords: anaerobic fermentation chain elongation electron donors kinetic models lignocellulosic biomass http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):409-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 410 ensiling is an anaerobic fermentation process whereby the water-soluble carbohydrate (wsc) component of a system is converted to organic acids that reduce the ph of the system, such that microbial activities is inhibited and the system remains at steady state. the strong acidity of some of the organic acids like lactic acid (pka = 3.86) and butyric acid (pka = 4.82) enhances the hydrolysis of lignocellulosic biomass (cui et al. 2020). although the literature is very rich as far as ensiling for biofuel production is concern, studies on ensiling of food waste is limited, especially for medium chain carboxylates (mcc) production. mcc are carboxylic acids having carbon chain lengths of 6 – 12 with a wide range of application in the field of medicine, agriculture and corrosion prevention (watanabe and tsujino 2022). they can be produced by the fermentation of waste biomass through a process called chain elongation (ce), using electron donors like lactic acid and ethanol in the presence of dedicated microbial communities. the most popular mcc in literature is caproic acid, whose productivity from food waste varies between 0.12 – 16 gcod/l/day depending on the process parameters, inoculum type and feed composition (stamatopoulou et al. 2020). in most of such studies, the addition of ethanol (or lactic acid) as electron donor is required for an improved yield of mcc. however, a life cycle assessment shows that the addition of ethanol to a system for an improved yield of mcc comes with economic and environmental consequences (chen et al. 2017). since ce takes place in the presence of dedicated microbial community, it is necessary to use an inoculum with a high concentration of microbial community that are adapted to the process. so far, the highest yield of mcc have been produced when pure cultures are used (cavalcante et al. 2017). however, when complex feedstocks like food waste are to be used as substrates, cultures containing a large spectra of microorganisms are preferred (groof et al. 2019). in order to improve the understanding of ce processes, kinetic models are required. parameters obtained from such models are often used to control and optimize the yield of a desired product. although kinetic models are common for the fermentation of simple substrates like glucose, models based on complex substrates like food wastes are limited in literature (groof et al. 2019). therefore, the purpose of this study was to (i) investigate the effect of ensiling on the lignocellulosic component of food waste, (ii) investigate the effect of ensiling on mcc production from food waste, (iii) investigate the effect of inoculum source on mcc production from food waste and (iv) carryout a kinetic study on mcc production from food waste. 1. materials and methods 1.1 substrate and inocula the only carbon source used was food waste which was collected from some major restaurants in choba, port harcourt, and consisted mainly of rice, eba, vegetables, meat, fish and bones. the hard bones were removed from the mixture after which the waste was blended using a kitchen blender. the charactersitics of the blended food waste is shown in table 1. two different inocula were used for the anaerobic fermentation including rumen fluid and leachate. the rumen fluid was obtained from freshly slaughtered goats in an abatior in port harcourt. the leachate was generated from food waste as previously described (kefas and undiandeye 2022). the inocula, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jerome.undiandeye@uniport.edu.ng undiandeye et al: kinetics of the valorization of food waste for medium chain carboxylates production; effect of ensiling and inoculum source. azojete, 19(3):409-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 411 whose characteristics are also shown in table 1, were pretreated at 90 °c for 30 minutes to deactivate methanogenes and then stored at 4 °c until required. table 1. mean values (n=3, ± standard deviation) of parameters of substrates and inocula parameter unit food waste leachate rumen fluid total solids % 16.27 ± 2.16 6.75 ± 1.12 2.92 ± 0.15 volatile solids % 13.98 ± 1.95 3.49 ± 0.68 2.11 ± 0.07 ph 4.27 ± 0.28 4.37 ± 0.21 6.94 ± 0.47 wsc g/l 59.19 ± 4.27 nd nd lactic acid g/l 1.25 ± 0.18 nd nd butyric acid g/l 0.15 ± 0.06 nd nd acetic acid g/l 1.02 ± 0.03 nd nd ethanol g/l 0.36 ± 0.07 nd nd cellulose %ts 15.89 ± 2.08 nd nd hemicellulose %ts 6.29 ± 0.15 nd nd lignin %ts 1.76 ± 0.07 nd nd wsc, water soluble carbohydrate; nd, not determined 1.2 silage preparation ensiling was carried out as previously described (undiandeye et al. 2022a). briefly, about 300 g of the grinded food waste were sealed under vacuum in airtight bags and stored at ambient temperature for 120 days. the experiment was setup in triplicates in order to account for experimental variation. 1.3 anaerobic fermentation set-up batch reactors were used for the anaerobic fermentation of food waste before and after ensiling using schott bottles of 500 ml total volume and working volume of 200 ml. each reactor contained 2.7 gvs of substrate, 100 ml of inoculum, and anoxic distilled water to make up the working volume. the initial ph in all reactors was adjusted to 5.5 (± 0.2) using 10 m hcl or 10 m naoh solutions. thereafter, the reactors were sealed using butyl rubber stoppers and alluminium caps and transferred to biological incubators operated at 38 °c and 150 rpm. the fermentation process lasted for 30 days with samples collected for analysis on days 0 (5 hours after start of experiment), 3, 5, 12, 19, 26 and 30. 1.4 analytical methods total solids (ts) and volatile solids (vs) of substrates and inocula were determined as described previously (undiandeye et al. 2022b) and corrected using the equation of weissbach and strubelt (2008) so as to avoid overestimation of the product yield. wsc of food waste was measured using an azura high-performance liquid chromatography (hplc) system (knauer gmbh, germany) equipped with degasser, binary pump system, auto sampler, column oven and refractive index detector (rid) set at 40 °c. ethanol and volatile acid contents were measured by analysis on a 7890a gas chromatograph with a flame ionisation detector (fid) (agilent technologies, usa) as described previously (undiandeye et al. 2023b). the head space gas composition in each bottle was measured by withdrawing 1 ml of gas sample using a syringe and transferred into 20 ml glass vials that had been flushed with argon. measurement was then carried out using gas http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):409-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 412 chromatography equipped with an autosampler in a perkin elmer gc. cellulose, hemicellulose and lignin contents were determine by measuring the neutral detergent fibre (ndf), acid detergent fibre (adf) and acid detergent lignin (adl) of the substrates using the methods described by van soest and wine (2020). the difference between adf and adl was taken as cellulose while hemicellulose was calculated as the difference between ndf and adf. the yield (y) and productivity (p) of each mcfa was calculated using equations 1 and 2 respectively. 𝑌 = 𝑐𝑣 𝑚𝑠 (1) 𝑃 = 𝑐 𝑡 (2) where c = maximum concentration of a given mcc (g/l), v = working volume of reactor (l), ms = mass of added substrate (kg vs), t = time at which maximum c was achieved (d). 1.5 kinetics of mcc production and statistical analysis two kinetic models were used to fit the production of mcc including the first-order model and the modified gompertz model given in equations 3 and 4 respectively. 𝑐𝑡 = 𝑐𝑚𝑎𝑥[1 − exp⁡(−𝑘 × 𝑡)] (3) 𝑐𝑡 = 𝑐𝑚𝑎𝑥𝑒𝑥𝑝 {−𝑒𝑥𝑝 [ 𝑅𝑚𝑎𝑥𝑒 𝑐𝑚𝑎𝑥 (𝜆 − 𝑡) + 1]} (4) where ct = concentration of a carboxylate at any time (g/l), t; cmax = maximum concentration of carboxylic acid (g/l); k = kinetic constant (/d); rmax = maximum rate of carboxylic acid production (g/l/d), λ = lag phase (d). all data were analysed using analysis of variance (anova) in originpro software (originlab corporation, northampton, usa). tukey’s test was used to compare significant difference at 95% confidence level. three statistical parameters including the coefficient of determination (r2), the root-mean-square-error, rmse (equation 5) and the akaike information criterion, aic (equation 6) were used to determine the model that gave a better description of a given mcfa production. 𝑅𝑀𝑆𝐸 = √ 𝑆𝑆 𝑁 (5) 𝐴𝐼𝐶 = 𝑁 × 𝐿𝑁 ( 𝑆𝑆 𝑁 ) + 2𝐶 (6) where n = number of experimental data, ss = sum square of residuals, c = number of parameters in a model. 3 results and discussion 3.1 ensiling characteristics the physico-chemical parameters of ensiled food waste after 120 days is shown in table 2. compared to the food waste before ensiling, there was a significant decrease (p < 0.05) in the concentration of wsc. a decrease in wsc has also been reported during the ensiling of alfalfa (gao et al. 2021) and napiergrass (zhang et al. 2022). the major reason for the reduction of wsc during ensiling is because they are converted to organic acids which are subsequently file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jerome.undiandeye@uniport.edu.ng undiandeye et al: kinetics of the valorization of food waste for medium chain carboxylates production; effect of ensiling and inoculum source. azojete, 19(3):409-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 413 required to maintain the quality of the silage. this explains why substrates with a low wsc content like cattle manure are not suitable for ensiling (franco et al. 2020). conversely to the concentration of wsc, the concentration of lactic and acetic acids increased significantly (p<0.05) after the duration of ensiling. the increase in lactic acid led to a significant reduction (p<0.05) in the ph of the system. a decrease in ph is desired in silages to inhibit microbial activities. one evidence of microbial inhibition in silages is the absence of butyric acid (undiandeye et al. 2022a). butyric acid formation in silages leads to a significant loss in vs. in the present study, a vs loss of 6.65% was observed, which is within acceptable range (steinbrenner et al. 2019). table 2. mean values of physico-chemical parameters of food silage after 120 days parameter unit ensiled food waste total solids % 15.38 ± 1.43 volatile solids % 13.05 ± 0.83 ph 3.19 ± 0.9 wsc g/l 14.04 ± 0.38 lactic acid g/l 18.96 ± 3.04 butyric acid g/l 0 acetic acid g/l 9.26 ± 1.93 ethanol g/l 4.67 ± 0.31 cellulose %ts 12.27 ± 1.84 hemicellulose %ts 2.48 ± 0.09 lignin %ts 1.98 ± 0.16 wsc, water soluble carbohydrate the most degraded lignocellulosic component was hemicellulose (about 61%). ren et al. (2007) have also reported a preferential degradation of hemicellulose relative to cellulose during the ensiling of corn stover due to its less rigid structure. three reasons have been attributed to the degradation of cellulose and hemicellulose during ensiling by ren et al. (2007) and undiandeye et al. (2023a); (i) the availability of hemicellulase and cellulase that are naturally present in food waste, (ii) production of degrading enzymes during ensiling and (iii) hydrolytic effect of the acids produced during ensiling. these lignocellulosic components (hemicellulose and cellulose) are usually degraded to wsc, which are in turn, converted to fermentation products like lactic acid, acetic acid, and ethanol. the degradation of cellulose and hemicellulose is an indication that ensiling disrupted the rigid structure of the substrate, thereby making it less recalcitrant to enzymatic fermentation for mcc production. the perceived increase in lignin content as also shown in table 2 was solely due to the degradation of cellulose and hemicellulose. 3.2 products of anaerobic fermentation 3.2.1 effect of ensiling the fermentation profile of organic acids from food waste before and after ensiling is shown in figure 1. the concentration of mcc was higher from the fermentation of ensiled substrate than from the fermentation of the unensiled food waste, irrespective of the source of inoculum. one http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):409-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 414 reason is because of the higher concentration of lactic acid and ethanol in the silage. in ce processes, lactic acid and ethanol are used as electron donors for the elongation of short chain fatty acids, and their availability often leads to a higher increase in the concentration of mcc (reddy et al. 2018). another reason for the higher concentration of mcc from the ensiled silage could be because of the pretreatment effect that ensiling had on the substrate. the organic acids produced during ensiling hydrolysed the cellulose and hemicellulose components of lignocellulosic biomass to simple sugars (nagle et al. 2020), which were then converted to more electron donors. figure 1. fermentation profile of (a) unensiled substrate with leachate, (b) ensiled substrate with leachate, (c) unensiled substrate with rumen fluid and (d) ensiled substrate with rumen fluid (c4, butyric acid; c6, caproic acid; c7, heptanoic acid; c8, caprylic acid). error bars indicate standard deviation of replicates. 3.2.2 effect of inoculum source the effect of inoculum source on the fermentation products is also shown in figure 1. apart from acetic acid (not shown), caproic acid dominated the fermentation product when leachate was used as inoculum whether the substrate was ensiled or not. the high concentration of 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n ce n tr a tio n ( g /l ) time (day) (a) 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n ce n tr a tio n ( g /l ) time (day) (b) 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n ce n tr a tio n ( g /l ) time (day) (c) 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n ce n tr a tio n ( g /l ) time (day) c4 c6 c7 c8 (d) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jerome.undiandeye@uniport.edu.ng undiandeye et al: kinetics of the valorization of food waste for medium chain carboxylates production; effect of ensiling and inoculum source. azojete, 19(3):409-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 415 caproic acid is an indication that (i) the condition of experiment was favourable for mcc production and (ii) the microbial community in leachate are adapted for chain elongation especially if the leachate is young (saadoun et al. 2021) as was the case in the present study. an important observation when rumen fluid was used as inoculum was that lactic acid and ethanol were not completely used up, and that butyric acid dominated the fermentation profile in the reactors containing ensiled and unensiled substrates. usually, ce is a a type of series reaction where acetic acid is elongated to butyric acid, butyric acid to caproic acid, and so on. since lactic acid and ethanol were not completely used up, it indicates that the lower production of mcc was not as a result of a deficiency in electron donors but probably an indication that the microbial community in the inoculum are less adapted to ce when compared to leachate under the given conditions. for instance, in the fermentation of glycerol, dams et al. (2018) reported a higher concentration of caproic acid than butyric acid while weimer et al. (2015) reported a dominance of butyric acid in the fermentation of switchgrass with rumen fluid as inoculum in both studies. it is therefore possible that the source of substrate and operating conditions can influence the activity of microbial community and the dynamics of mcc production. 3.2.3 ph fluctuation figure 2. variation in ph during the fermentation of (a) unensiled substrate with leachate, (b) ensiled substrate with leachate, (c) unensiled substrate with rumen fluid and (d) ensiled substrate with rumen fluid (error bars indicate standard deviation of replicates). 0 5 10 15 20 25 30 4,4 4,6 4,8 5,0 5,2 5,4 5,6 5,8 6,0 p h time (day) (a) 0 5 10 15 20 25 30 3,5 4,0 4,5 5,0 5,5 6,0 p h time (day) (b) 0 5 10 15 20 25 30 4,4 4,6 4,8 5,0 5,2 5,4 5,6 5,8 6,0 p h time (day) (c) 0 5 10 15 20 25 30 3,5 4,0 4,5 5,0 5,5 6,0 p h time (day) (d) http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):409-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 416 overall, there was a decrease in the ph of all systems untill day 12, after which it stabilized (figure 2). however, the ph in the systems containing unensiled substrate increased slightly on day 0. it is possible that since the unensiled substrates contained limited chain elongators, the first few hours was used for microbial hydrolysis which may have resulted in an initial increase in ph (hirakura et al. 2006). a decrease in ph during anaerobic fermentation has been attributed to the formation of organic acids (weimer et al. 2015), as a result of which the systems with the highest concentration of organic acids had the lowest ph at the end of fermentation time. 3.3 product yield and productivity table 3. mean values (± standard deviation) of yield and productivity of mcc yield (g/kgvs) productivity (g/l/day) substrate c6 c7 c8 c6 c7 c8 uenl 265.44 ± 18.23 100.74 ± 6.17 156.62 ± 11.38 0.12 ± 0.05 0.04 ± 0.00 0.07 ± 0.00 enl 487.50 ± 9.28 194.85 ± 13.48 308.09 ± 23.07 0.22 ± 0.03 0.09 ± 0.00 0.14 ± 0.00 uenr 205.88 ± 17.21 80.15 ± 4.29 144.85 ± 3.27 0.09 ± 0.00 0.04 ± 0.00 0.07 ± 0.00 enr 430.15 ± 24.29 157.35 ± 6.31 291.18 ± 5.73 0.20 ± 0.01 0.07 ± 0.00 0.13 ± 0.00 uenl, unensiled substrate with leachate; enl, ensiled substrate with leachate; uenr, unensiled substrate with rumen fluid; enr, ensiled substrate with rumen fluid; c6, caproic acid; c7, heptanoic acid; c8, caprylic acid. the yield and productivity of mcc from the fermentation of the substrates is shown in table 3. clearly, ensiling and inoculum source significantly (p<0.05) affected the yield of the measured mcc. there was a higher yield of even-numbered mcc like caproic acid (c6) and caprylic acid (c8) compared to odd-numbered mcc like heptanoic acid (c7). indeed, ce is a complex process. besides process parameters like initial ph, temperature and inoculum source, the composition of a substrate can significantly influence ce pathways. for instance, if the ratio of lactic acid to acetic acid content is higher than 3.0, the ce pathway for the formation of odd-numbered mcc may be favoured (wu et al. 2019). therefore, the higher yield of even-numbered mcc compared to that of odd-numbered mcc in the present study could be attributed to an availability of an appropriate lactic to acetic acid ratio (2.05) (tang et al. 2022). 3.4 biogas production methane was not detected in the gas stream throughout the period of fermentation, an indication of the effect of heat-treating the inocula. availability of active methanogenes would have led to the consumption of volatile acids for methane production (dahiya and mohan 2019), thereby resulting to a reduced yield of mcc. the major gas produced during the fermentation process was carbon (iv) oxide, as also reported by several authors (dahiya and mohan 2019; saadoun et al. 2021; tang et al. 2022). hydrogen was a major co-product of the fermentation process, being present in significant quantity, an indication that the process can also be adapted for hydrogen production. other authors have also reported a co-production of hydrogen and carboxylates during the fermentation of anaerobic waste (brodowski et al. 2020) and food watse (regueiramarcos et al. 2023). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jerome.undiandeye@uniport.edu.ng undiandeye et al: kinetics of the valorization of food waste for medium chain carboxylates production; effect of ensiling and inoculum source. azojete, 19(3):409-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 417 3.5 kinetics the first-order model and the modified gompertz model were used to fit the experimental values of mcc produced from the substrates. each of these models gave a reasonably good fit to the experimental data. in order to compare the degree of fitness of the two models to the experimental data, statistical parameters including the coefficient of determination (r2), rootmean-square error (rmse) and the akaike information criterion (aic) were used. as shown in table 4, the production of mcc (c6) was better described by the first-order model as seen from the higher r2 values as well as lower rmse and aic values. the fitness of the first-order model to the experimental data of mcc is shown in figure 3. table 4. model and statistical parameters for evaluation of fitness to experimental c6 production. substrates model parameters uenl enl uenr enr fom cmax 3.63 6.64 2.82 5.87 k 0.16 0.34 0.25 0.07 r2 0.997 0.989 0.993 0.999 rmse 0.006 0.002 0.007 0.003 aic -29.47 -37.29 -19.38 -35.64 mgm cmax 3.69 6.68 2.87 5.91 rmax 0.125 0.226 0.11 0.198 λ 4.07 3.93 4.28 4.16 r2 0.991 0.972 0.985 0.992 rmse 0.017 0.006 0.018 0.007 aic -21.17 -33.23 -11.56 -28.74 fom, first-order model; mgm, modified gompertz model; uenl, unensiled substrates fermented with leachate; enl, ensiled substrate fermented with leachate; uenr, unensiled substrate fermented with rumen fluid; enr, ensiled substrate fermented with rumen fluid (kinetic parameters and their units have their usual meanings as described in equations 4 and 5). kinetic constants are an indication of how fast a product is formed or consumed (fogler 2016). from the first-order model, these constants were seen to vary significantly with respect to ensiling and inoculum source. although fogler (2016) has reported that k depends largely on temperature, recent studies have shown that process parameters like ph, inoculum to substrate ratio, substrate type and inoculum source can significantly affect the values of k (zhu et al. 2017; khadka et al. 2022). in the present study, the higher values of k obtained from the ensiled substrates could be attributed to the availability of the required electron donors at the start of the experiment. kinetic constants between 0.059 and 0.321 /day have been reported in the fermentation of wastewater using anaerobic sludge as inoculum (morais et al. 2019). from the modified gompertz model, maximum rate of caproic acid production was also significantly higher from the ensiled substrates, which is in agreement with the measured data. the lag phase of approximately 4 days for c6 production was similar in all substrates as was also observed during the experiment where no mcc was detected until on day 5. the lag phase for the production of http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):409-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 418 mcc can vary significantly depending on the ph (regueira-marcos et al. 2023) and inoculum used. for instance, if a fermentation broth from a reactor producing mcc is used as inoculum, the lag phase can be negligible (jerome undiandeye, 2023unpublished phd thesis, university of rostock) since such inocula are already adapted to mcc production. using sludge as inoculum, morais et al. (2019) reported a lag phase of about 7 days in the fermentation of swine wastewater. figure 3. fitness of the first-order model to the the measured data of mcc produced from the fermentation of (a) unensiled substrate with leachate, (b) ensiled substrate with leachate, (c) unensiled substrate with rumen fluid and (d) ensiled substrate with rumen fluid. 4. conclusion the use of food waste as a substrate for medium chain carboxylates (mcc) production is one way of achieving the goal of circular economy. the yield of mcc from food waste can be enhanced by ensiling, which is a cost effective, easy and sustainable method of pretreatment of lignocellulosic biomass. ensiling degraded cellulose and hemicellulose contents of food waste as well as converted the water soluble carbohydrate content of food wastes into lactic acid and ethanol that were used for the chain elongation process, thereby enhancing the yield of mcc. 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n c e n tr a ti o n ( g /l ) time (day) c6: measured c6: model c7: measured c7: model c8: measured c8: model (a) 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n c e n tr a ti o n ( g /l ) time (day) (b) 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n c e n tr a ti o n ( g /l ) time (day) (c) 0 5 10 15 20 25 30 0 1 2 3 4 5 6 7 c o n c e n tr a ti o n ( g /l ) time (day) (d) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jerome.undiandeye@uniport.edu.ng undiandeye et al: kinetics of the valorization of food waste for medium chain carboxylates production; effect of ensiling and inoculum source. azojete, 19(3):409-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 419 compared to rumen fluid, leachate is a better inoculum for the production of mcc from food waste. as far as the modeling of the production of mcc is concern, the first-order model is a better model for the understanding and prediction of reactor performance compared to the modified gompertz model. the parameters obtained from the model can, therefore, be used for the process simulation and optimization of biological reactors used in the fermentation of food wastes for mcc production. references amin, fr., khalid, h., zhang, h., rahman, s., zhang, r., liu, g., chen, c. 2017. pretreatment methods of lignocellulosic biomass for anaerobic digestion. amb express, 7(72): 1-12. brodowski, f., duber, a., zagrodnik, r., oleskowicz-popiel, p. 2020. co-production of hydrogen and caproate for an effective bioprocessing of waste. bioresource technology, 318(6): 1-14. cavalcante, w., leitão, rc., gehring, t., angenent, lt., santaella, st. 2017. anaerobic fermentation for n-caproic acid production. a review. process biochemistry, 54: 106–119. chen, ws., strik, d., buisman, cjn., kroeze, c. 2017. production of caproic acid from mixed organic waste. an environmental life cycle perspective. environmental science & technology, 51(12): 7159–7168. cui, x., sun, h., sobhi, m., ju, x., guo, j., dong, r. 2020. butyric acid fermentation during ensiling of wilted maize stover for efficient methane production. acs sustainable chemistry & engineering, 8(17): 6713–6721. dahiya, s., mohan, sv. 2019. selective control of volatile fatty acids production from food waste by regulating biosystem buffering. a comprehensive study. chemical engineering journal, 357: 787–801. dams, ri., viana, mb., guilherme, aa., silva, cm., dos santos, ab., angenent, lt., santaella, st., leitao, rc. 2018. production of medium-chain carboxylic acids by anaerobic fermentation of glycerol using a bioaugmented open culture. biomass and bioenergy, 118: 1–7. fogler, hs. 2016. elements of chemical reaction engineering. 5th edition, prentice hall. franco, rt., buffière, p. bayard, r. 2020. cattle manure for biogas production. does ensiling and wheat straw addition enhance preservation of biomass and methane potential? biofuels, 11(6): 671–682. gallipoli, a., braguglia, cm., gianico, a. montecchio, d., pagliaccia, p. 2020. kitchen waste valorization through a mild-temperature pretreatment to enhance biogas production and fermentability. kinetics study in mesophilic and thermophilic regimen. journal of environmental sciences, 89:167–179. gao, r., wang, b., jia, t., luo, y., yu, z. 2021. effects of different carbohydrate sources on alfalfa silage quality at different ensiling days. agriculture, 11(1): 1-13. groof, v., coma, m., arnot, t., leak, dj., lanham, ab. 2019. medium chain carboxylic acids from complex organic feedstocks by mixed culture fermentation. molecules, 24(3): 1-32. http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; 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effect of ensiling and inoculum source. azojete, 19(3):409-422. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 421 tang, j., pu, y., huang, j., pan, s., wang, xc., hu, y., ngo, hh., li, y., abomohra, a. 2022. caproic acid production through lactate-based chain elongation. effect of lactate-to-acetate ratio and substrate loading. environmental technology & innovation, 28(2): 1-10. undiandeye, j., gallegos, d., lenz, j., nelles, m., stinner, w. 2022a. effect of novel aspergillus and neurospora species-based additive on ensiling parameters and biomethane potential of sugar beet leaves. applied sciences, 12(5): 1-12. undiandeye, j., gallegos, d., sträuber, h., nelles, m., stinner, w. 2022b. ensiling parameters in vertical columns and multiple kinetic models evaluation of biomethane potential of ensiled sugar beet leaves. biofuels, 13(8), 995–1005. undiandeye, j., kiman, s., abubakar, am., dahunsi, so. 2023a. medium chain carboxylates production from cassava wastes pretreated by ensiling. biofuels, bioproducts and biorefining, early view: 1-11. undiandeye, j., kiman, s., kefas, hm., nelles, m., stinner, w. 2023b. ensiling water hyacinth for enhanced biomethane production. effect of co-ensiling with maize straw and eggshell powder as additive. journal of chemical technology & biotechnology, 98(2): 490–497. united nations organization, uno. 2022. stop food loss and waste, for the people, for the planet. https://www.un.org/en/observances/end-food-waste-day.acessed on 1/2/2023. usmani, z., sharma, m., awasthi, ak., sharma, gd., cysneiros, d. nayak, sc., thakur, vk., naidu, r., pandey, a., gupta, vk. 2021. minimizing hazardous impact of food waste in a circular economy advances in resource recovery through green strategies. journal of hazardous materials, 416: 1-15. van soest, pj, wine, rh. 2020. use of detergents in the analysis of fibrous feeds. iv. determination of plant cell-wall constituents. journal of association of official analytical chemists, 50(1): 50–55. watanabe, s., tsujino, s. 2022. applications of medium-chain triglycerides in foods. frontiers in nutrition, 9: 802-805. weimer, pj., nerdahl, m., brandl, dj. 2015. production of medium-chain volatile fatty acids by mixed ruminal microorganisms is enhanced by ethanol in co-culture with clostridium kluyveri. bioresource technology, 175: 97–101. weissbach, f., strubelt, c. 2008. correcting the dry matter content of grass silages as a substrate for biogas production. landtechnik 63(4): 210-211. wu, q., bao, x., guo, w., wang, b., li, y., luo, h., wang, h., ren, n. 2019. medium chain carboxylic acids production from waste biomass. current advances and perspectives. biotechnology advances, 37(5): 599–615. zhang, l., li, x., wang, s., zhao, j., dong, z., zhao, q., xu, y., pan, x., shao, t. 2022. effect of sorbic acid, ethanol, molasses, previously fermented juice and combined additives on ensiling characteristics and nutritive value of napiergrass (pennisetum purpureum) silage. fermentation, 8(10): 1-9. http://www.azojete.com.ng/ mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):409-422. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jerome.undiandeye@uniport.edu.ng 422 zhu, x., zhou, y., wang, y., wu, t., li, x., li, d., tao, y. 2017. production of high-concentration n-caproic acid from lactate through fermentation using a newly isolated ruminococcaceae bacterium cpb6. biotechnology for biofuels, 10(1): 1-12. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:jerome.undiandeye@uniport.edu.ng arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):1-12 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 1 original research article evaluation of the mechanical properties of surface modified ukam fibre reinforced polyester composites g. e. okpanachi1*, a. abugh2, g. b. nyior2 and u. h. suleiman1 1centre for satellite technology development, abuja, nigeria 2department of mechanical engineering, federal university of agriculture, makurdi, nigeria. *corresponding author’s email address: okpanachi1976@gmail.com 1.0 introduction natural fibres which are fibres obtained from plants, animals and mineral resources can be used as substitute for glass fibres in polymer composite materials because of the following advantages; low costs, low density, unlimited availability, biodegradability, renewability and recyclability (okpanachi and ogakwu, 2010) these characteristics makes natural fibres suitable for use as reinforcement for engineering polymer systems (joffe et al., 2003) because natural fibre reinforced composites have comparable specific properties with glass fibre components and specific weight greater than synthetic fibre components (westman et al., 2010). similarly, a matrix reinforced with natural fibres provides an additional benefit because the properties of the plastic are markedly improved (joffe et al., 2003). conversely, the natural fibres possess some disadvantages which results to poor adhesion with the hydrophobic polymer matrix, propensity to coagulate during manufacturing and the tendency to soak up moisture which could affects its effectiveness significantly when used as a component in the reinforcement of polymers (puglia et al., 2005). article information abstract this work evaluated the properties of ukam fibre reinforced polyester composites. the ukam fibres were subjected to different surface treatments including alkaline, saline, permanganate and acetylation. composites were produced at 5%, 10%, 15%, 20% and 25% fiber loadings and its mechanical properties determined. the results found that the most suitable mixture for excellent improvement in mechanical properties was obtained with the 25% fibre and 75% resin. additionally, the results showed improvements in mechanical properties with surface treatments at all fibre loadings. furthermore, it was observed that fibre surface treatment leads to compatibility which resulting in good load transfer between the modified fibre and matrix. whereas acetylation treated composites exhibited the highest values of hardness at all levels of fibre loading, alkaline treated samples exhibited the highest tensile and compressive strengths at all fibre loadings. it is noteworthy that saline treated composites exhibited highest impact and flexural modulus of rupture. interestingly, there was no significant improvement noticed with potassium permanganate treated reinforced fibre composites. therefore, the results clearly showed that alkaline, saline, and acetylation fibre surface treatment methods could be used to produce ukam fibre composites with good mechanical properties for potential engineering applications. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 january, 2022 revised 4 april, 2022 accepted 4 december, 2022 keywords: ukam fibre polyester resin tensile strength hardness value impact strength http://www.azojete.com.ng/ mailto:okpanachi1976@gmail.com mailto:okpanachi1976@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):1-12. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 2 current research trends on fibre reinforcement methods have identified that surface treatments method which involves fibre reinforcement through adhesion and bonding between the fibre surfaces are potentially able to overcome the problem of incompatibility between fibre and matrix reinforced composites (ghali et al., 2011). according to (tserki et al., 2005) several modification processes on the fibrematrix interfacial bonding have been proposed such as hydrophilizing agent coating, plasma modification, corona discharge and flame treatment (molitor et al.,2001) and coupling agent (pickering et al., 2016) these processes modify the membrane surfaces to increase the hydrophilicity, adsorption of molecules, ionic change and biocompatibility etc., without affecting their bulk properties(zhang and zhu, 2000). also surface modification through efficient coupling of the fibre and matrix can be achieved by chemical treatment (chen et al., 2011). in addition, chemical treatment other treatments such as alkaline, silane, acetylation and potassium permanganate can improve the adhesion of the fibre and matrix, reduces the hydrophilic nature of fibres and can be used in modifying the properties of natural fibres. the direct effect of the alkaline surface treatment is seen in the cellulosic fibril which leads to chemical reaction and the extraction of lignin and hemi cellulosic compounds (jahn et al., 2002). as a result of silane treatment, siloxane bridge interlinking the fibre and the resin is created through the establishment of an interfacing region between the matrix and the fibre. this further prevents the fibre swelling into matrix through the formation of hydrocarbon chains (sreekala et al., 2000). the acetylation treatment ensures swelling of the fibre cell wall which prevents absorption of moisture resulting in improved dimensional stability and environmental degradation (bledzki et al., 2008). while potassium permanganate acts as an initiator for grafting and methylcrylate on fibres by triathy et al. (1985) and moharana et al. (1990). although surface treatment of fibres could lead to improve dynamic mechanical analysis of the composites produced (dash et al., 2000) the compatibility of a fibre reinforced polymer composite are greatly affected by interfacial characteristics existing between the reinforcing fibers and the polymer matrix (suardana et al., 2011). it is however, important that the reinforcement and resin used should be compatible with each other r with good adhesion to ensure that stresses are transferred, and thus carried by the fibre. similarly, it can be detrimental if adhesion is beyond the desired requirement because this can make the composite brittle as the excessive adhesion between the fibre and the resin does not allow the growth of cracks along the fibre in an impact situation. according to idrus et al. (2011) increase in fibre loading hardness can be achieved by increasing saw dust content used in the composites however the author further stated that e treated saw dust exhibit better hardness performance compared to raw saw dust at all fibre loading from 10 wt. % 30 wt. % composition. ramires and froilini (2017) has shown that an increase in fibre content used in the composites lead to a significant increase in the impact strength and further research results on fibre properties have also shown that some improved mechanical properties can be achieve by increasing the fibre contents in the composites (ugoamadi, 2011, romanzini et al., 2013). ukam fibres (cochlospermum planchonii) are cellulose based natural fibres that has excellent mechanical properties, low density, abundant and renewable. however, not much work has been done on the surface modification of ukam composites. the work of (okpanachi and ogakwu, 2010) seems to be the only work on surface modification of ukam fibre polyester composites. in their study however only the axial and compressive file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi1976@gmail.com okpanachi et al: evaluation of the mechanical properties of surface modified ukam fibre reinforced polyester composites. azojete, 19(1):1-12. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 3 strength of the composites were determined using alkali solution for surface treatment. the hardness, impact, flexural properties and surface treatment methods including saline, potassium permanganate and acetylation were not considered. it is important that comprehensive treatment procedures and studies be carried out on the composites to allow a better understanding of the micromechanics of these processes on the overall mechanical properties. therefore, the aim of this study is to evaluate the properties of ukam fibre reinforced composites under different surface treatment. 2. materials and methods 2.1 materials the main materials used in this study are: ukam fibres, polyester resin, polyvinyl alcohol (pva) while potassium permanganate (kmno4), acetic acid, silae solution, sodium hydroxide, were used for chemical treatment of the ukam fibres. also, cobalt octane was used to act as accelerator, methyl ethyl ketone peroxide (mekp) (1 % by volume) as catalyst. the modified fibres were used to produce the composites which were then evaluated for mechanical properties including hardness, tensile, compression, impact, and flexural strengths. 2.2 fibre surface treatment 2.2.1 alkali treatment sodium hydroxide solution was used in the alkaline treatment in accordance with liu et al. (2009). the ukam fibres were then soaked in naoh of 5 % concentration at room temperature for 24 hours. to remove any alkali solution sticking to the fibre surface the fibers were washed severally with water which has been neutralized with dilute acetic acid and then washed again with water. 2.2.2 silane treatment silane solution was dissolved in water and used for the silane treatment following valadez et al. (2009). after the treatment process, ukam fibres were immersed in silane dissolved in a water-ethanol mixture for 3 hours. the potential of hydrogen of the solution was 9.0. this contains 60 % ethanol and 40 % water mixed thoroughly which was allowed to stand for an hour. 2.2.3 potassium permanganate (kmno4) treatment 0.5 % of potassium permanganate in acetone was used in soaking the alkali treated fibres for 30 minutes after it has been thoroughly washed with water. distilled water was used in soaking the permanganate fibre for ten minutes in order to catalyse the reaction. furthermore, the fibres were sun dried after it was decanted. 2.2.4 acetylation ukam fibres were soaked in demineralized water for an hour, filtered and then placed in a flask, containing acetylating solution. acetylating solution is made of 250 ml toluene, 125 ml acetic anhydride and a small amount of catalyst perchloric acid (60 %). the temperature for the acetylation process was 60 oc for the period of 1 to 3 hours. after modification, the fibre was washed thoroughly with distilled water until acid free. the treated fibres were sun dried before the manufacturing of the composites. 2.3.2 composites production the ukam fibre composites samples were produced using the hand lay-up method (aly et al., 2010) in a wooden mould and the sample compositions are shown in table 1 http://www.azojete.com.ng/ mailto:okpanachi1976@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):1-12. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 4 table 1: composition of ukam fibre and resin sample ukam fibre (wt%) resin (wt%) 1 5 95 2 10 90 3 15 85 4 20 80 5 25 75 2.4 determination of mechanical properties the process and procedure applied in determining the mechanical properties of the ukam fibre sample are presented as follows: 2.4.1 hardness test hardness test was carried out in accordance with american society for testing and materials d 785 90 using the universal hardness tester indentec, (model 8187.5 lkv). the dimension of the prepared test samples was 30 mm x 30 mm x 30 mm. from the test the hardness strength was determined. 2.4.2 tensile test tensile strength test was conducted using hounsfield tensometer (model no.s/n 8889) according to astm d 638 03 (croccolo et al., 2013). from the test elastic modulus, ultimate tensile strength and percentage elongation were determined. 2.4.3 compression test the test was conducted by following astm – c 109 88 using universal (digital) testing machine. sample specimen dimensions of 30 mm x 30 mm x30 mm were produced for the test. compressive load was applied axially onto the specimen till it ruptured. the compressive strength was determined. 2.4.4 impact test impact test on the composites was carried out in according to astm d 256 – 06a. the specimen dimensions were 60 mm x 12 mm x 5 mm. a pendulum swings are used to break the sample kept in cantilever. impact strength of the composites is determined from the results. 2.4.5 flexural test flexural test was conducted based on astm 790-07 using universal (digital) testing machine. sample dimensions of 100 mm x 10mm x 5 mm were produced for the test. the test sample was placed between rollers and force (using hydraulic handle) was applied until the sample ruptured. the mor and moe were determined. in each case three different samples were tested and the average value obtained. 3.0 results and discussion 3.1 mechanical properties of ukam composites due to fibre loading and surface treatment the experimental results for various samples under different fibre loading and surface treatment are given figure (1-8). in each of the figures, bar charts for different mechanical properties are plotted against different composition of fibre loading. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi1976@gmail.com okpanachi et al: evaluation of the mechanical properties of surface modified ukam fibre reinforced polyester composites. azojete, 19(1):1-12. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 5 3.1.1 hardness figure 1 presents the hardness properties of the composites sample due to fibre loading and surface treatment. in general, hardness was observed to increase with increase in fibre loading for all treatments. figure 1: hardness of composites due to surface treatment and fibre loading additionally, the work reported showed that the addition of natural fibres to a polymer matrix reduce flexibility of the resulting composite thereby increases the stiffness similar what was reported by idrus et al. (2011) where hardness properties of a composite were enhanced as a result of the decrease in flexibility and increase in stiffness of the composites. also further analysis of the results reveals that surface modified composites have better hardness strength to those of untreated fibre composites at all fibre loadings. hardness increased with treatment because treated fibre becomes more hydrophobic with increased interaction between fibre and matrix, which results in increases in strength, stiffness, and interfacial adhesion. generally, the pattern of the increased hardness based on surface treatment followed the order: untreated< saline < kmno4 < alkali < acetylation. acetylation treated composites exhibited highest values of hardness at all levels of fibre loading. this scenario could be linked to better adhesion of the matrix to the fibre brought about by acetylation as reported by (idrus et al., 2011). however, at 20 % fibre loading the pattern changed slightly to: untreated < silane < alkali < kmno4 < acetylation. the discrepancy in the pattern at 20 % fibre loading is caused by pores and voids (pickering et al., 2016). it is observed that when the void fraction values become more pronounced, then the value of hardness decreases. 3.1.2 tensile strength figure 2 indicates the change in the value of the tensile strength in relation to the respective change noticed in the fibre loading and surface treatment. http://www.azojete.com.ng/ mailto:okpanachi1976@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):1-12. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 6 figure 2: tensile strength of composites as a result of fibre surface treatment and loading the results showed increase in tensile strength with increase in fibre reinforced composites was consistently higher than the untreated composites. it is clear from this that treatment enhanced compatibility between the matrix and the fibres, allowing the required transfer of stresses between fibres and matrix with concurrent increase in values of tensile strength. at 5, 10, 15 and 20 % fibre loadings: untreated < kmno4 < acetylation < silane < alkali. the alkali treated samples exhibited the highest increase in tensile strength at all fibre loadings. this is because during alkaline treatment, hemicellulose and lignin are removed, the inter-fibrillar regions are likely to be soft, and that makes the fibrils to align themselves along the direction of tensile loading. pickering et al. (2016) was of the opinion that physical and chemical treatments usually improve the wettability of fibre and thus improve the interfacial strength leading to improvement in mechanical properties as the cellulose structure is totally modified. however, at 25 % fibre loading the order became untreated < acetylation < kmno4 < silane < alkali. the discrepancy could be explained on the basis of chemical bonding which occurs when there are enough chemical groups between the fibre and matrix that can undergo reaction to form bonds between the fibre and matrix. this clearly shows that there was not enough chemical reaction for kmno4 treated fibres at 25 % fibre loading. 3.1.3 modulus of elasticity the modulus of elasticity (moe) increased with increase in ukam fibre loadings for all the treatments (figure 3). figure 3: modulus of elasticity of tensile strength composite as a result of fibre surface treatment and loading 0 0.5 1 1.5 2 2.5 3 5 10 15 20 25 m o d u lu s o f e la st ic it y fibre loading (wt%) alkali silane kmno4 acetylation untreated file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi1976@gmail.com okpanachi et al: evaluation of the mechanical properties of surface modified ukam fibre reinforced polyester composites. azojete, 19(1):1-12. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 7 the increased in moe of the composites with increase in ukam fibres loadings is attributed to the inherent high stiffness strength of the fibres. the sodium hydroxide treated composites gave the highest value of moe (2.7521 mpa) at 25 % fibre loading for same reason as for tensile strength. surface treatment could improve the stiffness of fibers and accelerate the reorganization of fibrils along the direction of tension force after removal of binding materials by treatment (jacob et al., 2004). the moe values at 5, 10, 15, 20 and 25 % ukam fibre loadings for the treatments varied from 1.0218 – 1.5276 mpa, 1.0364 – 1.5531 mpa, 1.1582 – 1.7504 mpa, 1.1801 – 1.8012 mpa and 1.2016 – 1.8342 mpa respectively. also the percentage elongation increased with increase in fibre loading and treatments for similar reasons. figures 3 and 4 respectively present the moe and the percentage elongation of fibre surface treatment at various loadings. figure 4: percentage elongation of composites as a result of fibre surface treatment and loading 3.1.4 impact strength the influence of surface treatment and fibre loading on impact properties is shown in figure 5. it can be noted that for all applied treatments, there was a proportional increase in the impact strength of the composite with respect to increase in the fibre loadings. the results clearly showed that impact energy of reinforced composites was enhanced by four treatments which is in agreement with a study by ramires and frallini (2017). figure 5: impact strength as a result of fibre surface treatment and loading of composites in addition, the results show that silane treated composites impact strength was the highest compared to other treatments, especially at higher fibre loading ratios. at lower 0 5 10 15 20 25 5 10 15 20 25 p e rc e n ta ge e lo n ga ti o n fibre loading (wt%) alkali silane kmno4 acetylation untreated http://www.azojete.com.ng/ mailto:okpanachi1976@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):1-12. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 8 fibre loading ratios, however, the differences were not significant. the results show that the average impact energy of the composites increased by 28.09%, 20.07%, 14.06%, 15.44%, and 22.34% for composites with 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, and 25 wt.%, respectively, over the values obtained for the untreated composites using the same weight fractions. the higher values of impact energy for the treated composites over the untreated composites can be attributed to the improved mechanical interlocking due to rougher surfaces of the treated sisal fibres and improved interfacial bonding. the silane treated composite at 25 % fibre loading had the highest impact strength of 1.65 j. this is for the fact that silane used for treatment of fibre have different functional groups at either ends such that interaction at one end can occur with hydrophilic groups whilst the other end can interact with hydrophobic groups in the matrix to form a bridge between them (pickering et al., 2016). 3.1.5 compressive strength figure 6 presents the compressive strength of the composites due to fibre loading and surface treatment. the result shows an increase in compressive strength with increases in fibre content and treatment. this is because an increase in fibre content increases the micro-packing of fibres in the cured matrix, which causes mechanical compaction of the fibrous ingredients with resultant high compression strength. interestingly, alkali treated composite showed the highest compressive strength values at all fibre loadings, with highest value of 143.03 mpa at 25 % fibre loading. in general, the order of increase in compressive strength with fibre treatments was, alkali > silane > kmno4 > acetylation > untreated. the lowest values of compressive strength exhibited by untreated ukam fibre in the matrix of polyester are that untreated fibres are incompatible with the matrix due to its hydrophilic nature (jacob et al., 2004). the compressive strength values for other treatments at 25 % fibre loading were 94.14, 68.03, and 66.09 mpa for silane, acetylation, and kmno4 when compared with the value of 45.62 for the untreated fibre. figure 6: compressive strength of composites as a result of fibre surface treatment and loading 3.1.6 flexural strength furthermore, the modulus of elasticity of composites as a result of fibre surface treatment and loading due to flexural strength is shown in figure 7. it was revealed that flexural strength increased with increasing fibre loading and treatments for all the composites investigated which is in agreement with the work of romanzini et al. (2013). silane treated file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi1976@gmail.com okpanachi et al: evaluation of the mechanical properties of surface modified ukam fibre reinforced polyester composites. azojete, 19(1):1-12. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 9 composites at 5 – 15 % fibre loadings has the highest values of mor (16-24 mpa). the order of increase in mor with treatments were; at 5 and 10 % fibre loading, silane > kmno4 > alkali > acetylation > untreated, while at 15, 20 and 25 % fibre loadings respectively, were, silane > alkali > kmno4 > acetylation > untreated, kmno4 > silane > alkali > acetylation > untreated and acetylation > silane > alkali >acetylation > kmno4 > untreated. figure 7: modulus of elasticity of composites as a result of fibre surface treatment and loading due to flexural strength from the results obtained acetylation treatment gave the highest value of mor at 25 % fibre loading while the mor values of the composites at 5 % were 7, 16.06, 16.05, 7.99 and 15.94 mpa respectively, for untreated, silane, potassium permanganate, acetylation and alkali treated composites. the values of mor increased to 19.23, 26.77, 27.37, 24.1, 31.78 mpa at 25 wt% ukam fibres addition for untreated fibres, alkali, silane, potassium permanganate, acetylation treatment respectively. acetylation treated ukam fibre composite gave the highest modulus of rupture at 25 % fiber loading, compared with other treated the composites sample. figure 8 presents the effect of surface treatment on moe obtained from flexural strength for both untreated and treated composites. the work reported here shows that the modulus of elasticity of the composite was observed to increase with increasing fibre loading and treatments, and order of increase was thus, silane > kmno4 > acetylation > alkali > untreated at 5 % fibre loading, alkali > silane >kmno4 > acetylation > untreated at 10 % fibre loading. at 15, 20 and 25 % fibre loading the orders were respectively, alkali > silane > acetylation > kmno4 > untreated and acetylation > silane > alkali > kmno4 > untreated. the moe values of the composites at 5 % fiber loading were 519.23, 760 mpa, 671, 603 and 613 mpa for untreated, acetylation, potassium permanganate and silane treatment. these values increased to 1005.58, 1749.5, 1903.22, 1171.79 and 2140.71 mpa at 25 % ukam fibres addition for untreated fibres, alkali, silane, potassium permanganate, acetylation treatment respectively. acetylation treated ukam fibre loading at 25 % composite had the highest value of modulus of elasticity (2140.38 mpa). based on the results the highest increase recorded in both the moe and mor of the composite with increasing fibre loading could be attributed to higher stiffness of the ukam fibres. this shows that addition of ukam fibres has positive effect on flexural strength and flexural modulus of both treated and untreated composite with highest performance http://www.azojete.com.ng/ mailto:okpanachi1976@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):1-12. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 10 recorded at 25 wt%. composition of fibre loading. again, the highest flexural strength recorded can also be attributed to the enhanced interfacial adhesion between polyester resin and ukam fibres and the efficient stress transfer achieved through surface treatment. the results obtained in this study are consistent with other studies (kim et al., 2001, romanzini et al., 2013). figure 8: modulus of rupture of composites as a result of fibre surface treatment and loading 4. conclusion the mechanical properties (hardness, tensile, impact and flexural strengths) of treated ukam fibre reinforced composites have been evaluated and the results presented to show that surface treatment processes improved the mechanical properties of treated fibre reinforced composites. the hardness and tensile strength exhibited in the acetylation and alkali treated composites respectively are higher than those in the other treated composites under all levels of fibre loading. also the modulus of elasticity (moe) and percentage elongation are found to increase with increase in fibre loading for all treatments. references aly, mf., goda, i. and hassan, ga. 2010. experimental investigation of the dynamic characteristics of laminated composite beams. international journal of mechanical and mechatronics, 10: 59-67. bledzki, a., mamun, a., lucka-gabor, m. and gutowski, v. 2008. the effects of acetylation on properties of flax fibre and its polypropylene composites. express polymer letters, 2(6): 413-422. chen, h., miao, m. and ding, x. 2011. chemical treatments of bamboo to modify its moisture absorption and adhesion to vinyl ester resin in humid environment. journal of composite materials, 45(14): 1533-1542. croccolo, d., de agostinis, m. and olmi, g. 2013. experimental characterization and analytical modelling of the mechanical behaviour of fused deposition processed parts made of abs-m30. computational materials science, 79: 506-518. 0 5 10 15 20 25 30 35 5 10 15 20 25 m o d u lu s o f ru p tu re fibre loading(wt%) alkali silane kmno4 acetylation untreated file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi1976@gmail.com okpanachi et al: evaluation of the mechanical properties of surface modified ukam fibre reinforced polyester composites. azojete, 19(1):1-12. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 11 dash, b., rana, a., mishra, h., nayak, s. and tripathy, s. 2000. novel low‐cost jute– polyester composites. iii. weathering and thermal behavior. journal of applied polymer science, 8(9): 1671-1679. ghali, lh., aloui, m., zidi, m., daly, hb., msahli, s. and sakli, f. 2011. effect of chemical modification of luffa cylindrica fibers on the mechanical and hygrothermal behaviours of polyester/luffa composites. bioresources, 6(4): 3836-3849. idrus, mm., hamdan, s., rahman, mr. and islam, ms. 2011.treated tropical wood sawdust-polypropylene polymer composite: mechanical and morphological study. journal of biomaterials and nanobiotechnology, 2(04):435. jacob, m., thomas, s. and varughese, kt. 2004. mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber composites. composites science and technology, 64(7-8): 955-965. jähn, a., schröder, m., füting, m., schenzel, k. and diepenbrock, w. 2002. characterization of alkali treated flax fibres by means of ft raman spectroscopy and environmental scanning electron microscopy. spectrochimica acta part a: molecular and biomolecular spectroscopy, 58(10): 2271-2279. joffe, r., anderson, j. and wallström, l. 2003. strength and adhesion characteristics of elementary flax fibres with different surface treatments. composites part a: applied science and manufacturing, 34(7): 603-612. kim, jk., sham, ml. and wu, j. 2001. nanoscale characterisation of interphase in silane treated glass fibre composites’, composites part a: applied science and manufacturing, 32(5): 607-618. liu, l., yu, j., cheng, l. and qu, w. 2009. mechanical properties of poly (butylene succinate)(pbs) biocomposites reinforced with surface modified jute fibre. composites part a: applied science and manufacturing, 40(5): 669-674. moharana, s., mishra, s. and tripathy, s. 1990. chemical modification of jute fibers. i. permanganate‐initiated graft copolymerization methyl methacrylate onto jute fibers. journal of applied polymer science, 40(3‐4): 345-357. molitor, p., barron, v. and young, t. 2001. surface treatment of titanium for adhesive bonding to polymer composites: a review. international journal of adhesion and adhesives, 21(2): 129-136. okpanachi, ge. and ogakwu, pi. 2010. effects of fibre surafce treatment on the mechanical properties of ukam fibre reinforced polyester composites. journal of engineering and applied sciences, (2): 1-12. pickering, kl., efendy, ma. and le, tm. 2016. a review of recent developments in natural fibre composites and their mechanical performance’, composites part a: applied science and manufacturing, 83: 98-112. puglia, d., biagiotti, j. and kenny, j. 2005. a review on natural fibre-based compositespart ii: application of natural reinforcements in composite materials for automotive industry. journal of natural fibers, 1(3): 23-65. http://www.azojete.com.ng/ mailto:okpanachi1976@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):1-12. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi1976@gmail.com 12 ramires, ec. and frollini, e. 2017.tannin–phenolic resins: synthesis, characterization, and application as matrix in biobased composites reinforced with sisal fibers. composites part b: engineering, 43(7): 2851-2860. romanzini, d., lavoratti, a., ornaghi jr, hl., amico, s. and zattera, aj. 2013. influence of fiber content on the mechanical and dynamic mechanical properties of glass/ramie polymer composites. materials and design, 47: 9-15. sreekala, m., kumaran, m., joseph, s., jacob, m. and thomas, s. 2000. oil palm fibre reinforced phenol formaldehyde composites: influence of fibre surface modifications on the mechanical performance. applied composite materials, 7(5): 295-329. suardana, n., piao, y. and lim, jk. 2011. mechanical properties of hemp fibers and hemp/pp composites: effects of chemical surface treatment. materials physics and mechanics, 11(1): 1-8. tripathy, s., jena, s., misra, s., padhi, n. and singh, b. 1985. a study on graft copolymerization of methyl methacrylate onto jute fiber. journal of applied polymer science, 30(4): 1399-1406. tserki, v., zafeiropoulos, n., simon, f. and panayiotou, c. 2005. a study of the effect of acetylation and propionylation surface treatments on natural fibres’, composites part a: applied science and manufacturing, 36(8): 1110-1118. ugoamadi, c. (2011). factors that improve the impact responses of ukam plant fibre reinforced composite. nigerian journal of technology, 30: 111-117. valadez-gonzalez, a., cervantes-uc, j., olayo, r. and herrera-franco, p. 2009.effect of fiber surface treatment on the fiber–matrix bond strength of natural fiber reinforced composites. composites part b: engineering, 30 (3): 309-320. zhang, z. and zhu, s. 2000. microvoids in unsaturated polyester resins containing poly (vinyl acetate) and composites with calcium carbonate and glass fibers. polymer, 41(10): 3861-3870 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi1976@gmail.com corresponding author’s email address: uaibrahim@unimaid.edu.ng 101 arid zone journal of engineering, technology & environment original research article development of rating curve for river ngadda u. a. ibrahim* p. daniel1 and m. b. gutti 1department of civil and water resources engineering, university of maiduguri, maiduguri, borno state *corresponding author’s email address: uaibrahim@unimaid.edu.ng article information abstract accurate river discharge estimation is critical for sustainable water resource management and infrastructure design, especially in areas where data scarcity is a major concern. this study addresses this issue by developing a rating curve for the ngadda river in borno state, nigeria. the lack of continuous discharge data and reliable rating curves has historically hindered water resource project planning in the region. leveraging stage-discharge rating curves and utilizing an optimization-based technique with excel solver, curve parameters were calibrated to accurately depict the hydraulic relationship between river stage and discharge. the analysis of discharge data at logojeri and maiduguri gauging stations revealed seasonal changes in river flow, emphasizing the importance of continuous monitoring for effective water resource management. correlation analysis between actual and predicted discharge confirmed the reliability of the developed rating curve, while uncertainty analysis revealed insights into potential errors associated with the discharge estimation. the developed rating curve which is for the two specific gauging stations (maiduguri and logojeri), provides a useful tool for converting stage data into discharge values, thereby assisting with water resource planning and decision-making. it is therefore urged for ongoing monitoring efforts and the installation of monitoring tools to modify and improve the developed rating curve's ability to capture the dynamic hydrological behavior of the ngadda river. submitted: 25th july 2024 revised: 5th december 2024 accepted: 3rd february 2025 keywords: flow regime seasonal variation uncertainty analysis water resources management © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction navigating the complex dynamics of water resource management demands precision, yet the scarcity of reliable data often casts a shadow over planning endeavors. in the center of jere and maiduguri where river ngadda is a beacon of hope for many, this challenge is particularly felt. the absence of continuous discharge data and dependable rating curves has long hindered effective water resource project planning in the region. accurate stream flow records are indispensable in hydrologic information systems, water resources management, disaster warning and validation of models at catchment and basin-wide scales. these discharge records are obtained by converting the measurement of the river stage using stage–discharge relationships (negatu et al., 2022). as additional data are collected, the rating curve can be refined to more accurately reflect the relation (alfa et al., 2018).these curves can be simple or complex depending on the flow regime and the characteristics of the cross section and stretch of a river (yang and lee, 2017). river flow is a critical requirement for surface water resources assessment, planning and management(wara et al., 2019).engineering designs and hydrological studies for water supply development projects rely heavily on the accuracy of the river flow data obtained from rating curve (othman et al., 2019).rating curve depends on hydraulic characteristics of the stream channel, flood plain and varies over time at almost every station (hamilton et al., 2019). this study aims to close the gap by developing a new rating curve for river ngadda. with a focus on improving discharge estimation accuracy, our goal is to provide policymakers and stakeholders with an essential tool for making informed decisions about water resource management in maiduguri and its surroundings. we hope to understand the complexity of river ngadda's hydrology by thorough data collecting and analysis as well as the use of an excel solver. by doing so, we want to improve our understanding of its azojete march 2025. vol.21(1):101-107 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:uaibrahim@unimaid.edu.ng mailto:uaibrahim@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):101-107. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 102 flow dynamics while also laying the groundwork for a more resilient and sustainable approach to water resource planning in the region. 2. material and methods 2.1 study area river ngadda stretches along jere and maiduguri in borno state, nigeria. located in the northeastern part and experiences distinct dry and wet seasons (bwala, 2021). river ngaddasituated on latitude 10° 24' 42''n and longitude 13° 42' 10''e (figure 1), originates from the convergence of rivers yedzaram and gombole at sambisa swamp. it flows as river ngadda into alau dam, traversing the maiduguri metropolis and eventually discharging into jere bowl rice scheme (obroh and sambo, 2022).the river plays a vital role in various human activities, including fishing, irrigation for vegetables, brick making and serving as a water source for residences along its banks. people use it as a source of water for washing and animals rely on it for drinking water (abdulhakim et al., 2014). figure 1: map of study area 2.2. data collection the study focuses on maiduguri situated in borno state, nigeria, where river ngadda plays a pivotal role in various activities. the study stems from the pressing issue of insufficient discharge data for the river, prompting a comprehensive approach to data collection and analysis. in this study, a time series of river discharge records was acquired from the chad basin development authority. the dataset’s temporal resolution is a daily time step which constitutes of readings from two key stations and spans from august6, 1977 to march 31, 1978 for logojeri station and that of maiduguri station spans from august1, 1977 to november 30, 1977. the recorded data consisted of stage measurements and corresponding discharge measurements. prior to this analysis, the acquired time series underwent minimal pre-processing where high peaks and lows were critically checked. 2.3 utilization of stage-discharge rating curves the study employed stage-discharge rating curves, treating discharge as a unique function of the stage. the discharge calculation followed a power curve equation ensuring a robust representation of the stage-discharge relationship. the equation provided a quantitative framework to estimate discharge based on observed stage, addressing the central challenge of limited discharge data. the power curve equation is given as: 𝑸 = 𝒄(𝒉 − 𝒂)𝒏 (1) http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):101-107. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 103 where, q represents discharge in cubic meters per second (m3/s), h is the observed stage in meters above sea level, h is the gauge height of zero flow in meters above sea level, and c, h, and n are calibration coefficients crucial for accurately depicting the hydraulic relationship. 2.4 calibration coefficients and excel solver calibration coefficients (c, h, and n) were determined using a trial-and-error procedure, employing randomly assumed values to optimize the calibration process. the excel solver, a powerful optimization tool played a very important role in streamlining this trial-and-error process enhancing efficiency and accuracy in obtaining the calibration coefficients. the use of excel functions facilitated the determination of discharge error by comparing actual discharge with estimated discharge. 3. results and discussion 3.1 fitting of discharge logojeri and maiduguri gauging stations the discharge data at logojeri and maiduguri gauging stations were fitted using trial-and-error, revealing insightful patterns. the rating curve was used to transform the stage measurement into discharge. the analysis of discharge data at logojeri gauging station revealed interesting patterns in the seasonal variation of the river ngadda. the fitted discharge curves, as shown in figures 2 and 3, highlighted a significant decrease in discharge commencing in november. this observation indicates a notable change in the flow regime during this period. the understanding of such variations is crucial for effective water resource management and infrastructure planning, emphasizing the importance of continuous monitoring. this seasonal pattern aligns with typical hydrological cycles but emphasizes the need for comprehensive data to capture and predict variations accurately. the observed discharge trends will help in refining future water resource models and inform decision-making for stakeholders. figure 2: logojeri station discharge calibration figure 3: maiduguri station discharge calibration http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):101-107. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 104 3.2 correlation of dataset correlation analysis between actual and predicted discharge at both logojeri and maiduguri gauging stations provided insights into the reliability of the developed rating curve. the linear relationship observed from august to november suggests a consistent predictive capability of the model during this crucial period. however, further analysis and consideration of other factors affecting discharge, such as precipitation patterns and land use changes, would enhance the robustness of the rating curve for a broader range of conditions. figure 4 visually represents this correlation. figure 4: actual vs predicted discharge for maiduguri and logojeri gauge stations 3.3 stage-discharge rating curve the plotted stage-discharge rating curves (figures 5 and 6) visually represent the culmination of the study's efforts. the relatively linear trend for maiduguri and the fluctuating pattern for logojeri highlight the unique hydraulic characteristics of each gauging station. the developed rating curves provide a valuable tool for transforming readily available stage data into discharge, addressing the historical lack of discharge data for the river ngadda. these curves form a basis for future water resource planning and engineering designs in the region. figure 5: rating curve for maiduguri station figure 6: rating curve for logojeri station http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):101-107. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 105 3.4 uncertainty analysis to assess the confidence level and potential errors, uncertainty analysis was conducted. tables 1 and 2 presents the uncertainty analysis results for logojeri and maiduguri gauge stations. the results provided important statistical characteristics of the discharge data for river ngadda. for logojeri station, the mean values were clustered around zero suggesting a distribution centered at a baseline which reflects the peculiar flow dynamics of the river. the low standard error values indicate a high degree of precision in mean estimates crucial for capturing the nuanced variations in discharge. the median and mode proximity implies symmetry in the distribution aligning with the seasonal patterns of the river's behavior as observed in the study. positive kurtosis and skewness values hint at potential outliers and a right-skewed pattern mirroring the intermittently intense flow events that characterize the river ngadda. the range, minimum and maximum values offer context for the spread and boundaries of the dataset considering the diverse hydraulic conditions encountered during gauge measurements. similarly, for maiduguri station, the statistical patterns echo those of logojeri emphasizing the centered distribution with moderate variability. the low standard error values underscore the precision in mean estimates crucial for understanding the river's complex behavior. positive kurtosis and skewness continue to suggest a right-skewed distribution aligning with the unique hydraulic characteristics of river ngadda. altogether, these statistical measures when contextualized within the specific dynamics of river ngadda enrich our understanding of the discharge data, providing a foundation for robust decision-making in water resource management and infrastructure planning. the calculated confidence intervals provide a range within which the actual discharge is likely to fall. these results serve as a critical component for decisionmakers and water resource managers guiding them in understanding the potential variations and uncertainties associated with the developed rating curve. table 1: uncertainty analysis for logojeri gauge station logojeri confidence interval plus confidence interval minus mean 2.62 × 10-14 mean 1.69 × 10-14 standard error 0.11 standard error 0.10 median -3.41 median -3.22 mode -3.85 mode -3.64 standard deviation 7.17 standard deviation 6.77 sample variance 51.47 sample variance 45.86 kurtosis 4.22 kurtosis 4.22 skewness 2.25 skewness 2.25 range 31.88 range 30.09 minimum -3.85 minimum -3.64 maximum 28.03 maximum 26.45 table 2: uncertainty analysis for maiduguri gauge station maiduguri confidence interval plus confidence interval minus mean -2.17 × 10-14 mean 5.39 × 10-15 standard error 0.12 standard error 0.11 median -3.54 median -3.30 mode -3.54 mode -3.30 standard deviation 7.87 standard deviation 7.35 sample variance 61.94 sample variance 53.97 kurtosis 5.00 kurtosis 5.00 skewness 2.41 skewness 2.41 range 39.35 range 36.73 minimum -3.54 minimum -3.30 maximum 35.81 maximum 33.43 http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):101-107. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 106 4. conclusion the development of the rating curve equation in this study represents a significant stride in addressing the persistent challenge of scarce discharge data for river ngadda. the equation, specifically crafted for logojeri and maiduguri stations, offers a practical solution for transforming readily available stage data into discharge values, providing a valuable resource for water resource management and infrastructure planning. the distinct characteristics observed in the rating curves of maiduguri and logojeri stations contribute nuanced insights into the behavior of river ngadda. maiduguri's rating curve, marked by a linear trend, signifies a consistent discharge pattern, while logojeri's curve exhibits fluctuations, indicative of its unique hydraulic dynamics. these variations underscore the importance of site-specific considerations in developing accurate and reliable rating curves. the study leveraged an optimization-based excel solver for estimating the rating curves, showcasing its efficiency in predicting curve parameters with precision. the application of excel solver not only streamlines the process but also eliminates the need for a time-consuming trial-and-error approach, enhancing the overall robustness of the developed rating curve. quantitative and qualitative assessments of the performance of excel solver underscore its promise as a reliable tool for predicting parameters, further emphasizing its potential utility in similar hydrological studies. the study advocates for the continued utilization of excel solver in advancing the accuracy of rating curves and highlights its role in reducing uncertainties associated with stage-discharge relationships. the research outcomes reinforce the paramount importance of routine activities, including stage-discharge measurements, flood marking, and vegetation density surveying, in ensuring the continuous improvement of rating curves. the seasonally varying discharge patterns observed in river ngadda underscore the necessity for ongoing monitoring to capture dynamic changes in flow regimes and maintain the relevancy of the developed rating curve. as the uncertainties identified in the analysis pave the way for future research, it is imperative to recognize the study's contribution to advancing the understanding of river ngadda's discharge dynamics. the results not only underscore the significance of continuous monitoring but also guide forthcoming research and data collection efforts, aiming to further refine and enhance the accuracy and applicability of the developed rating curve in the dynamic context of river ngadda. the continuation of routine activities for continuous improvement such as stage-discharge measurements, flood marking, and vegetation density surveying. these activities play a foundational role in data collection and contribute to refining and enhancing the confidence of the rating curves over time. continuous, consistent monitoring ensures that the rating curve remains adaptive to changing environmental conditions and reliably represents the river's behavior. the final recommendation advocates for the development and implementation of comprehensive monitoring strategies. these strategies should encompass both routine activities and specialized observations, ensuring a holistic approach to data collection. such comprehensive monitoring strategies adapt to changing environmental conditions and incorporate evolving insights into the river's hydraulic behavior. the aim is to establish a robust and adaptive framework for continuous improvement in understanding river ngadda's discharge dynamics. references abdulhakim, a., toyosi, i., addo, s. and ebenezer, a. 2014. water quality assessment of river ngadda, northeastern nigeria. elixir aquaculture, 76: 28716–28719. alfa, mi., adie, db., ajibike, ma. and mudiare, oj. 2018. development of rating curve for ofu river at oforachi hydrometric station. nigerian journal of technological development, 15(1): 1-14. https://doi.org/10.4314/njtd.v15i1.3 bwala, m. 2021. impact of irrigational runoff on fish biodiversity in river ngadda , maiduguri – borno state. nigerian journal of pure and applied sciences, 34(1): 3981-3988. https://doi.org/10.48198/njpas/20.b04 hamilton, se., watson, m. and pike, rg. 2019. the role of the hydrographer in rating curve development. confluence: journal of watershed science and management, 3(1): 1-15. https://doi.org/10.22230/jwsm.2019v3n1a11 negatu, ta., zimale, fa. and steenhuis, ts. 2022. establishing stage–discharge rating curves in developing countries: lake tana basin, ethiopia. hydrology, 9(1). https://doi.org/10.3390/hydrology9010013 http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com https://doi.org/10.22230/jwsm.2019v3n1a11 arid zone journal of engineering, technology and environment, march 2025; vol.21(1):101-107. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 107 obroh, og. and sambo, g. 2022. flood vulnerability mapping of river ngadda using geospatial and remote sensing techniques maiduguri metropolis, borno state. journal of global ecology and environment, 14(4): 44– 58. https://doi.org/10.56557/jogee/2022/v14i47453 othman, ny., abd saleh, z. and omran, za. 2019. development of stage – distance – discharge relationship and rating curve using least square method. civil engineering journal, 5(9): 1959-1969. https://doi.org/10.28991/cej-2019-03091385 wara, c., thomas, m., mwakurya, s. and katuva, j. 2019. development of river rating curves for simple to complex hydraulic structure based on calibrated hec-ras hydraulic model, in kwale, coastal kenya. journal of water resource and protection, 11(4): 468–490. https://doi.org/10.4236/jwarp.2019.114028. yang, c. and lee, kt. 2017. analysis of flow-sediment rating curve hysteresis based on flow and sediment travel time estimations. international journal of sediment research, 33: 171182.https://doi.org/10.1016/j.ijsrc.2017.10.003. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):587-596 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 587 original research article influences of ph and temperature on the anaerobic fermentation of groundnut shell and cow dung for biogas production p. mamman*, m. saidu, a. busari and s. sadiku department of civil engineering, federal university of technology, minna, niger state, nigeria *corresponding author’s email address: zionpaul212@yahoo.com 1.0 introduction production of waste materials is an undeniable part of human society. the wastes are produced by several sectors including industries, forestry, agriculture and municipalities. the accumulation of waste and the “throw-away philosophy” results in several environmental problems, health issues and safety hazards, and prevent sustainable development in terms of resource recovery and recycling of waste materials (isa et al., 2014). a perspective aimed at promoting greater sustainable development and resource recovery has influenced solid waste management practices, and is gradually becoming implemented through policy guidelines at national levels in a number of industrialized and even developing countries (isa et al., 2014). guidelines and directives to reduce waste generation and promote waste recovery are laid down according to the “waste management hierarchy”, in which waste retention, reuse, recycling and energy recovery are designed to minimize the amount of waste left for final, safe disposal (isa et al., 2004). potentially, all organic waste materials contain some quantities of nutrients essential for the growth and metabolism of anaerobic bacteria in biogas production. again, every biodegradable material will produce biogas but article information abstract the increasing demand, high cost and health implications of using energy derived from hydrocarbon compound have necessitated the continuous search for alternative sources of energy. groundnut shell (gs) and cow dung (cd) as renewable source of energy supply have been proven to be very efficient. this study investigated the influences of operating parameters in anaerobic fermentation of gs and cd in the laboratory scale using the simple locally fabricated digesters labeled a-e of 4,000cm3 working volume. the temperatures were recorded one time daily using a thermometer that was fitted to the digester. the digesters were fed on a batch basis with the slurry of different mix ratio and operated at ambient temperature (28-40°c) for 30days. digester a being the control containing 100% of cd have ph of 7.00 and 7.20 before and after digestion respectively. this shows that the ph values of cow dung was neutral before digestion and slightly alkaline after digestion while digester e containing 100% of groundnut shell also a control have ph of 7.10 and 7.20 respectively before and after digestion. the temperatures in the five digesters fluctuated optimally between 28°c and 40°c which conforms to the mesophilic range. most microorganisms grow best under neutral ph conditions, since other ph values may adversely affect metabolism by altering the chemical equilibrium of enzymatic reactions, or by actually destroying the enzymes. low ph can cause the chain of biological reactions in fermentation to cease. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 january, 2022 revised 26 april, 2022 accepted 30 april, 2022 keywords: biogas production substrate ph temperature groundnut shell cow dung http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com zionpaul212@yahoo.com galley proof arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):587-596. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 588 the quantity and quality of gas produced will vary depending on the feedstock used (ren21, 2017). cattle dung is the most suitable material for biogas plants because of the methane producing bacteria already contained in the stomach of ruminants. the specific gas production, however, is lower and the proportion of methane is around 65% because of prefermentation in the stomach (maramba, 1978). its homogenous consistency is favourable for use in continuous plants as long as it is mixed with equal quantities of water (figure 1). liquid cattle manure, a mixture of dung and urine, requires no extra water. however, the simple animal housing found on most farms in developing countries normally does not allow the collection of all animal excrement. hence, most of the urine with its valuable plant nutrients is lost. the main advantage of animal manure, with respect to continuous digestion, is that it is easy to collect and easy to mix as slurry and load into digesters. figure 1: cow dung sample arachishypogaea(groundnut) is a native of south america but its cultivation is now widespread globally (duke, 1981). it was introduced to the african continent during the colonial era (duke, 1981). groundnut is produced in africa majorly by nigeria, sudan, senegal, chad, ghana, congo and niger (taphee et al., 2014). groundnut pyramids were a success story of the northern nigeria (kano state especially) prior to independence while its farming remains a popular practice in northern nigerian with the fruit pods being put to no usage (taphee et al., 2014). prior to this study, the potentials of groundnut shell (figure 2) in biogas generation in nigeria have been reported in few recent studies (yavini et al., 2014; ibrahim et al., 2016). the objective of this study is to determine the influence of ph and temperature on anaerobic fermentation of groundnut shell and cow dung for biogas production. figure 2: arachishypogaea groundnut shell file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof mamman et al: influences of ph and temperature on the anaerobic fermentation of groundnut shell and cow dung for biogas production. azojete, 18(4):587-596. issn 1596-2644;e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 589 2. materials and methods the waste materials that were used in the study are cow dung and groundnut shell. groundnut shell was collected from a milling station at pati shabakolo, a village in lavun local government area of niger state, nigeria, during the 2019/2020 harvest season. the sample was collected in clean bags and transported to the site of experiments, while cow dung was sourced from federal university of technology, minna farm. the waste materials were manually sorted to remove foreign materials and groundnut shell was sun dried for about fourteen (14) days in order to reduce the moisture content and for ease of handling. groundnut shell was further crushed mechanically using pestle and mortar for size reduction and milled into powdered form and finally sieved with about 1.18μmm sieve tray. 2.1 anaerobic digester set-up and operation a 4,000cm3 plastic container was obtained from kure’s market in minna, niger state, washed and all stains removed. two holes were drilled; one at the centre with about 1.25cm diameter, and the other drilled at the side of the container with a diameter of 1.25cm. a reinforced flexible hose pipe of 100cm was inserted into the hole that was drilled at the centre of the cover. this pipe served as the gas outlet of the bio digester. it is then tight firmly and glued with epoxy resin steel adhesive in order to prevent any form of leakages and was connected to 2000cm3 capacity container which served as the water chamber. the 1.25cm diameter side hole was fitted with ⅜ flexible hose pipe, male and female socket and ½inch plug where the sample was taken for ph (figure 3 and 4). the ph was measured daily using a digital ph meter. the sample to be analyzed were collected into a dry bottle from the digester and then analyzed. the probe of the ph meter was immersed into the samples to be analyzed and the meter was allowed to stabilize before the reading was taken. a hole was drilled at the side of the digester opposite the 1.25cm diameter but of 1.10cm diameter where the thermometer probe was fitted tightly with adhesive gum. the temperature reading was taken between 2pm and 4pm daily throughout the period of the experiment and also the ambient temperature. figure 3: the digester showing the male female socket figure 4: the digester and the gas holder 2.2 biogas digestion assay the slurry combination was formulated to contain about 5% solid content and the bio digester was filled with the slurry to 75% of the digester volume.100% of cow dung and 0% of groundnut shell were mixed with water for digester a.75% of cow dung and 25% of groundnut shell were mixed with water for digester b.50% of cow dung and 50% of http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):587-596. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 590 groundnut shell were mixed with water for digester c.25% of cow dung and 75% of groundnut shell were mixed with water for digester d.0% of cow dung and 100% of groundnut shell were mixed with water for digester e. the slurry was stirred properly to avoid lump, and poured into bio-digester a, b, c, d and e respectively. the digestion was allowed for a period of 30days under ambient temperature (psychrophilic).the ph of the medium was measured daily in order to ensure that the ph value is within the range at which the biogas can be produce. the temperature of the medium was taken 1time daily proximate and ultimate composition of the groundnut shell and cow dung was carried out according to the method of aoac (2010). 2.3 proximate analysis 2.3.1 determination of moisture content (mc) the hot oven air method of association of official analytical chemists (aoac, 2010) would be adopted for this analysis. porcelain crucibles was washed and dried in an oven at 100oc for 30min. these were allowed to cool in the desiccators. about ten (10g) of the substrates were placed into weighed crucibles and placed in an oven at 105oc for 4h. the samples were removed from the oven after this and were cool and weighed. the drying will be resumed and all the crucibles with the samples will be re-weighed until a constant weight is obtained. the percentage moisture was calculated from the loss of weight of the sample using the following formula; %𝑀𝐶 = 𝑊1−𝑊2 𝑊1 × 100 (1) where 𝑊1 = weight of the original sample 𝑊2 = weight of final dried sample 2.3.2 determination of total solids (ts) it is the amount of solid present in the sample after the loss of water molecules present in it. in other words, is refers to as the quantity of the material residue left in the crucible after evaporation of the sample and its subsequent drying in a laboratory oven at 105°c for a period of one hour. two crucibles were properly washed and dried in the laboratory oven at a temperature of 105°c for one hour. the crucibles were stored and cooled in a desiccator until needed. the crucibles were weighed (w2) before use. laboratory oven was switch on and allowed to reach a temperature of 105°c. this temperature was maintained throughout the experiment. substrates were added to the crucibles (w3) and diligently placed in the laboratory oven at a temperature of 105°c. the substrate samples were dried to a constant mass for a period of 1 to 2hours. the crucibles plus substrate residues were allowed to cool in a desiccator to balance temperature. desiccators are designed to provide an environment of standard dryness. desiccator was properly lubricated with grease and this is to prevent moisture from entering the desiccator as the test glassware cools. crucibles plus substrate (material) residue were weighed using electronic precision balance (w1). equation (2) was used to determine the percentage of ts. %𝑇𝑆 = 𝑊1−𝑊2 𝑊3−𝑊2 × 100 (2) %ts = percentage total solid file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof mamman et al: influences of ph and temperature on the anaerobic fermentation of groundnut shell and cow dung for biogas production. azojete, 18(4):587-596. issn 1596-2644;e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 591 w1 = weight of dried crucible + dried residue w2 = weight of crucible w3 = weight of wet sample (substrate) + crucible 2.3.3 determination of volatile solids (vs) the vs is the solid remaining after evaporation or filtration are dried, weighed, and ignited at 600°c. in the determination of vs of the substrates the residues obtained from ts determination were ignited at 600°c for a duration of 30minutes using a muffle furnace. the crucibles and black mass of carbon were allowed to cool partially in air before it was transferred to the desiccator for complete cooling. the samples were weighed once temperature balance is reached (w4) the percentage vs were determined using equation (3). %𝑉𝑆 = 𝑊1−𝑊4 𝑊1−𝑊2 × 100 (3) where, %vs = percentage volatile solid w4 = weight of crucible + weight of residue after ignition 2.4 ultimate analysis the ultimate analysis determines the weight percentage of element present in biomass like carbon, nitrogen, hydrogen, oxygen and sulphur. 2.4.1 determination of carbon content this was determined using the walkey and black method. 10g gs each of the finely ground substrate were weighed into 500ml conical flasks, appendix h. potassium dichromate 10ml) was poured inside the flasks and the mixture was swirled. h2so4 (20ml) were added and the flasks swirled again for 1min in a fume cupboard. these mixtures were allowed to cool for 30min after which 200ml of distilled water, 1g of naf and 1ml of phenylalanine indicator were added. the mixture was then shaken and titrated with ferrous ammonium sulphate solution in a burette. the blank was also treated similarly. the percentage carbon content was calculated using equation (4); %𝐶𝑎𝑟𝑏𝑜𝑛 = 𝐵−𝑇 ×133×0.003×100 𝑊 (4) where; b = blank titre value t = sample titre value c = concentration of fe solution w = weight of waste sample 2.4.2 chemical oxygen demand (cod) chemical oxygen demand (cod) is a measurement commonly used to determine substrate quality. the cod values indicate the amount of oxygen (in milligrams per liter of product) needed to oxidize or stabilize these wastes. biochemical oxygen demand (bod) and chemical oxygen demand (cod) are two different ways to measure how much oxygen the wastewater from a digester will consume when it enters the environment. industries normally focus more on cod and municipalities more on bod removal. efforts must be http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):587-596. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 592 made to reduce these values to protect the environment (nwaigwe and enweremadu, 2015). 2.4.3 determination of nitrogen this was carried out using the micro-kjeldahl method described by pearson, 1976. the method involves estimation of the total nitrogen in the sample and subsequent conversion of the nitrogen to protein with the assumption that all the protein in the samples are present as nitrogen. using a conversion factor of 6.25, the actual percentage of protein in the sample was calculated using equation (5) micro-kjedahl digestion/distillation apparatus and 50ml kjeldahl flasks were utilized in carrying out the analysis. % crude protein = % nitrogen x f (5) where: f = conversion factor (6.25) 2.5 digestions samples (2g) were weighed in kjeldahl flasks appendix 6h j. catalysts such as sodium sulphate and copper sulphate were added in the flasks in the ratio of 3:1. oxidizing agent (conc. h2so4, 15ml) was then added, glass beads were added to prevent bumping during heating. heating was carried out cautiously on a digestion rack under fume cupboard until a greenish clear solution appeared. the digest was allowed to clear for about 30min; it was heated for another 30min and allowed to cool. about 10ml of distilled water was added to avoid caking after which the digest was transferred with several washings into a 25ml volumetric flask and made up to the mark with distilled water. 2.5.1 distillation of the protein a 50ml receiver flask containing 5ml boric acid (methyl red and blue indicator) will be placed under the condenser of the distillation apparatus so that the tip will be 2cm inside the indicator. a 10ml of 40% naoh solution was added to the digested sample in the apparatus through the funnel stop cork. closing the steam by-pass and opening the inlet stop cork on the steam jet arm of the distillation apparatus started off the distillation. the distillate was collected in the conical flask (35ml) with its indicator – methyl red and blue. titration was then carried out using 0.01m hcl to first pink colouration. the percentage of nitrogen and protein was calculated using equation 6 v; %𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 (𝑁) = 𝑇𝑖𝑡𝑟𝑒 ×0.0014×250 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 × 100 (6) 3. results and discussion 3.1 feedstock characterisation the results of the physico-chemical analyses of the substrates prior to anaerobic digestion are shown in tables 1. the result of chemical analyses shows that steam explosion reduces the total solid of gs from 87.90% to 79.42% while the volatile solid was increased from 75.11% to 86.32% as a result of steam explosion pre-treatment. though the nitrogen content of gs increases after steam explosion the carbon content remain barely constant even after steam explosion. carbon to nitrogen ratio is one of factor affecting the anaerobic process; it affects methane yield and production rates. it is often suggested that an optimum c/n ratio should be between 20:1 and 30:1 in table 2 lignocelluloses content of the substrate are: hemicellulose before and after pre-treatment are 34.11% and 40.20% file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof mamman et al: influences of ph and temperature on the anaerobic fermentation of groundnut shell and cow dung for biogas production. azojete, 18(4):587-596. issn 1596-2644;e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 593 respectively, cellulose are 30.50% and 28.80% while lignin before and after pre-treatment are 35.39% 31.00% respectively. hemicellulose consists of several type of sugar unit and sometimes referred to by sugars they contain. hemicellulose is associated with cellulose and contributes to the structural component of the plant (rowell, 2005). cellulose is a main structural component in a plant cell. table 1: characteristics of the substrates properties cowdung groundnutshell pretreated (gs) moisture content (%) 89.50 25..89 81.21 ts (%) 19.60 87.90 79.42 vs (%) 54.01 75.11 86.32 vs/ts ratio 2.76 0.86 1.09 carbon content 42.00 62.02 61.90 nitrogen content 0.38 0.50 0.70 n/c ratio 0.01 0.01 0.01 table 2: lignocellulose content of groundnut shell properties not treated physically pre-treated hemicellulose (%) 40.20 34.11 cellulose (%) 30.50 28.80 lignin (%) 35.39 31.00 3.2 operational parameters the ph for each of the digesters was measured before and after digestion. the daily ambient and digesters temperatures were adequately monitored. 3.2.1 ph of the digesters before and after digestion. figure 5 shows the ph values of the media in all the digesters, and were varied almost in the optimal limits of methanogenic bacteria (ph: 6.1 -7.4), all the digesters showed a general increase in ph with minimal fluctuation. this progressive increase in ph before biogas production could account for steady rate of gas production which is in agreement with the studies carried out previously by ahmadu (2009) and igboro (2011). methanogenic bacteria are very sensitive to ph and do not thrive below a value of 6.0 (karki et al., 2005). most microorganisms grow best under neutral ph conditions, since other ph values may adversely affect metabolism by altering the chemical equilibrium of enzymatic reactions, or by actually destroying the enzymes. the methanogenic group of organisms is the most ph sensitive. low ph can cause the chain of biological reactions in digestion to cease. figure 5: ph of the slurry before and after biogas production 6.4 6.6 6.8 7 7.2 7.4 a b c d e p h digester http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):587-596. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 594 figure 6 shows that digester a being the control containing 100% of cow dung have ph of 7.00 and 7.20 before and after digestion respectively. this shows that the ph values of cow dung was neutral before digestion and slightly alkaline after digestion while digester e containing 100% of groundnut shell also a control have ph of 7.10 and 7.20 respectively before and after digestion. the ph of the digester c containing 50% each of cow dung and groundnut shell increases from day one of the digestion to day 7 of the digestion and toward the end of the digestion, the ph shows slightly alkaline solution. digesters a and e have the highest ph of 7.6 in day five of the digestion and 7.5 in day 30 of the digestion respectively. figure 6: variation of ph of the digesters with time 3.3 digester temperature during biogas production figure 7 shows that the temperatures in the five digesters fluctuated optimally between 28°c and 400c which conforms to the mesophilic range. the temperatures were recorded once daily using a thermometer that was fitted to the digester. the foregoing show that the digesters operated within the mesophilic temperature range; and that it is possible to install digesters that will operate within this range in minna and environs as reported elsewhere (igboro, 2011 and alfa, 2013). since all the digesters were operated simultaneously, the temperature across them were the same as shown in figure 7 figure 7: variation of digesters temperature (oc) with time the study of biogas production from co-digestion of groundnut shell and cow dung was conducted in digesters labeled a-e as shown. biogas production was monitored and measured until biogas production reduced significantly. figure 8 shows the fluctuation in the 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 7.8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 p h f o r n o e x p lo d ed time in days f g h i j 25 26 27 28 29 30 31 32 33 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 t em p er a tu re i n o c fo r n o n ex p lo d ed time in days f g h i j file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof mamman et al: influences of ph and temperature on the anaerobic fermentation of groundnut shell and cow dung for biogas production. azojete, 18(4):587-596. issn 1596-2644;e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 595 quantity of gas produced from each substrate possibly due to variation in the ratio of the substrates. biogas production was very low in the first week of setup in all the digesters. as the feedstock matures over the days, gas production increases. the co-digestion of 25% cd-75% gs, 50% cd-50% gs, and 75% cd-25% gs have their highest gas production around sixteen and twenty-first day of retention period respectively while their least were recorded toward the end of the retention period. also, digester a and e containing 100% each of cd and gs being the control for the pre-treated have their highest biogas production around eighteen and twenty first day of retention period respectively and the least are also seen toward the end of the digestion figure 8: variation of volume of biogas production (cm3) with time 4. conclusion from the results of the study conducted, a 4,000cm3 biogas digester fabricated using locally available materials and tested under the existing weather condition in minna were used for co-digestion of cd and gs. the ph values recorded before and after digestion indicates that the digesters operated well. the temperatures inside the digesters were stable fluctuating around 28°c to 40°c which is within the mesophilic range. now agricultural waste could be an alternative renewable source of energy in the form of biogas. anaerobic digestion of gs and cd increased the cumulative biogas yield. the most important conclusion that can be drawn from this research is that neutral ph affects the quantity of biogas production. also, most microorganisms grow best under neutral ph conditions, since other ph values may adversely affect metabolism by altering the chemical equilibrium of enzymatic reactions, or by actually destroying the enzymes. low ph can cause the chain of biological reactions in digestion to cease. references ahmadu, to. 2009. comparative performance of cow dung and chicken droppings forbiogas production, m.sc. thesis, department of mechanical engineering, ahmadu bello university, zaria. 0 10 20 30 40 50 60 70 80 90 100 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 v o lu m e o f b io g a s p ro d u ct io n ( cm 3 ) time in days steam exploded a steam exploded b steam exploded c steam exploded d steam exploded e non exploded f non exploded g non exploded h non exploded i non exploded j http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com galley proof arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):587-596. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: zionpaul212@yahoo.com 596 alfa, mi. 2014. comparative production and utilization of biogas for cooking, using cow dung, chicken droppings, cymbopogoncitratus (lemon grass). m.sc. thesis, department of water resources and environmental engineering, ahmadu bello university, zaria nigeria. aoac. 2010. official methods of analysis. association of analytical chemists.14th ed. washington, usa. 22209. duke, ja. 1981. handbook of legumes of world economic importance. plenum press, new york. ibrahim, md. and imrana, g. 2016. biogas production from lignocellulosic materials: codigestion of corn cobs, groundnut shell and sheep dung. imperial journal of interdisciplinary research, 2(6): 5-11. igboro, sb. 2011. production of biogas and compost from cow dung in zaria, nigeria. phd dissertation, department of water resources and environmental engineering, ahmadu bello university, zaria nigeria. isa, b., post, j., furedy, c. 2004. solid waste management and recycling; actors, partnerships and policies in hyderabad, india and nairobi, kenya; kluwer academic publishers: dordrecht, london, uk. karak, t., bhagat, rm. and bhattacharyya, p. 2012. municipal solid waste generation, composition, and management: the world scenario. critical reviews in environmental science and technology, 42(15): 1509-1630. karki, ab., shrestha, nj. and bajgain s. 2005. biogas as renewable energysource in nepal: theory and development. nepal, bsp. obtainable on www.snvworld.org koberle, e. 1995. animal manure digestion systems in central europe. in: proceedings of the second biomass conference of the americas, august 21-24, portland, oregon, national renewable energy laboratory (nrel). 23:34 maramba, f. 1978. production and utilization of biogas in rural areas of industrialized and developing countries, schriftenreihe der gtz, no. 97, pg. 63, after; biogas and waste recycling the phillipine experience; metro manila, phillipines. ren21, renewable energy policy network for the 21st century (ren21). 2017. renewables global status report (paris: ren21 secretariat) isbn 978-3-9818107-6-9. rowell, rm., pettersen, r., han, js., rowell, js. and tshabalala, ma. 2005. cell wall chemistry, handbook of wood chemistry and wood composites, crc press, florida, usa, 35-74. taphee, gb. and jongur, aau. 2014. productivity and efficiency of groundnut farming in northern taraba state. nigerian journal of agriculture and sustainability, 5(1):45-56. yavini, td., taura, uh., mohammed, n. and namo, jm. 2014. comparative study of mesophilic biogas production potentials of selected agro-wastes. the international journal of engineering and science, 3(2):1-6 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2018%20no%204/zionpaul212@yahoo.com http://www.snvworld.org/ 8 arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):897-910 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 897 multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm) d. d. yusuf1, e. j. upahi2 and h. o. yusuf3 1department of agricultural engineering, faculty of engineering, ahmadu bello university, zaria, 2department of agricultural and bio-environmental engineering, kaduna polytechnic, 3department of agricultural extension and rural development, faculty of agriculture, ahmadu bello university, zaria, *corresponding author's email address: ddyusuf2004@yahoo.com article information submitted 10 june, 2023 revised 18 august, 2023 accepted 26 august, 2023 keywords: optimization central composite design planting ridge-planter seed abstract the performance of a tworow self-propelled seed planter, institute for agricultural research (iar) single row animal drawn planter and the manual method of planting were investigated under laboratory and field conditions to optimise the planting process using response surface methodology (rsm). parameters optimisation of seed planting process becomes imperative in order to find parameter values that match predictions with reality and choose the right set of parameters that improve the performance of planter. experiments conducted in this study were based on central composite design (ccd), one of the designs in rsm experimental treatments were three planting methods, three soil moisture levels, and three planting depths randomly assigned in a 3x3 factorial experiment arranged in a randomized complete block design (rcbd) in three replications. the results show increased plant population with increasing planting speed and moisture content values. also, increased seedling emergence was observed with increasing moisture content and decreasing planting speed values. however, further increase in seed planting moisture content beyond the optimum point caused a decrease in the seedling emergence. similarly, there was increased depth of planting with increasing seed planting speed and moisture content values. further increase in soil moisture content beyond the optimum point caused a decrease in the depth of planting. conclusively, soil moisture availability is an important factor affecting the depth of seed planting in the study area 1.0 introduction planting is a crucial step for successful crop production (finch-savage, and bassel, 2016). planting is the act of introducing seeds to the ground at predetermined depths in a farming process with the main objective of establishing an optimum plant population, plant-to-plant spacing (intra-row spacing) and appropriate depth of sowing. planting can be done by any of the following methods: broadcasting, drill seeding, cross sowing, band planting, square nest sowing, furrow sowing and hill sowing (yusuf, 2010,). planter performs soil penetration, metering the correct amount of seed to drop at the right location, depositing those seeds in the soil and providing pressure for adequate soil–seed contact (srivastava et al., 2006, and wankhade and kotwal., 2014). it is usually a very time-sensitive operation with only a short period offering the right climatic conditions (timsina et al., 2011). as factors such as soil temperature and moisture are critical for seed germination (murray et al., 2006). to complete seed sowing in the narrow time-frame available and ensure successful crop establishment, it is essential to have a reliable planter (johansen et al., 2012 and he et al., 2014). nonetheless, for smallholder farmers in developing nations, seed-metering equipment should be simple in operation, affordable, and reliable (van loon et al., 2018). http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 898 the method adopted for planting depends upon a number of criteria and these include the agronomic requirement for the seed to be planted such as depth of seed placement, required distance between plants (inter and intra row); soil moisture content, and the effectiveness of the method for maximal crop germination (srivastava et al., 1993). parameters optimisation (process of choosing the permissible actions by maximizing or minimizing the objective functions subject to the constraints as appropriate with the intent of adding value to the final outcome) becomes imperative. this is to find parameter values that match predictions with reality by choosing the right set of parameters that improve the performance of planter. the goals of this research were to: (1) compare depth of seed placement, planting speed, seed damage, number of seeds per hole and seedling emergence while in operation of the developed planter with an existing iar single row animal drawn planter and the manual method of planting. (2) optimise the performance of the planter using response surface methodology (rsm). 2. materials and methods 2.1 materials the study was conducted at samaru (latitude 12o 1’n and longitude 073oe) in kaduna state in the northern guinea savanna vegetation zone of west africa. materials used in the construction of the planter include tools such as hacksaw frame and blade, centre punch, trisquare, metal scriber while machines used ( 3.5 kw gestetner centre lathe, 2.75kw gestetner centre drill, 360 watts bosch hand drilling machine, 1.5 kw hand held grinding machine, 750 watts arc welding machine, and plate cutting machine (maximum 1.5 mm thick). the performance of a 2-row ridge engine-propelled planter (the fabricated planter, figure 1), a single row iar animal drawn planter (figure 2), and manual planting ((dropping seeds into holes made with the heels, covering the seeds with soil and compacting the soil surrounding the seeds with the heels, figure 3) were evaluated using 20 kg of quality protein maize (qpm) seeds (pre-tested for viability) as test crop. figure 1: developed 2-row enginepropelled planter figure 2: iar single row animal drawn seed ridge planter figure 3: manual method of planting. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng yusuf et al: multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm). azojete, 19(4):897-910. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 899 2.2 methods 2.2.1 design of planter components 1. wheel shaft angular speed on wheel shaft is given as (spotts, 1988, and muvdi and mcnabb, 1988): 60 2 n  = , rad/s (1) where n = rpm, no torsional bending is expected along the shaft and no bending is expected on the shaft, diameter of the shaft ds was therefore gotten by (spotts, 1988; muvdi and mcnabb, 1988): ( )23 16 tt s s mk s d  = (2) where, ss = shear stress associated with the shaft = 5.63 mpa, kt = combined shock and fatigue factor applied to torsional moment = 2.0 (for shock loads), mt = torsional moment (nm). power required to turn the wheel was computed from hall et al. (1961): p = tω (3) where, p = power required to turn the wheel (watts), t = torque on the shaft (n-m); ω = angular speed of the shaft (rad/s) crossley and kilgour (1983) reported that the applied shearing force on the soil (horizontal force). f = ac + wtanφ (4) where, a = contact area (m2), c = cohesion, w = static load on the wheel, φ = angle of shearing resistance by the soil. c and φ vary according to the type and state of soil. 2. hopper design: the shape chosen was frustrum with rectangular cross section as this is most widely used for cereals (srivastava, 1993). the parameters that were designed for are: (i) hopper capacity (vc), (ii) hopper, height (h), (iii) top neck width (b’) and (iv) bottom neck width (b’’). the capacity of the hopper is given as (bosoi et al., 1988): hc hg c q bql v 410 = (m3) (5) where, vc = hopper capacity, m3, lg = run length, m, qh = seed rate, kg/ha, b = sowing width, m, ηc= coefficient of features of the hopper= 0.9, qh = volume weight, kg/m3. the hopper length is given as: lc = a (nb+ l) (m2) (6) where, a = row width, m, nb = number of discharge points, the cross sectional area of the hopper is given by: c c c l v f = (m) (7) where, fc = cross sectional area of the hopper, m2, vc = capacity of the hopper, m3, lc = effective height of the hopper, m total volume of one hopper in the planter is given by: n v v c b = (m3) (8) where, n = number of hoppers in the planter, vb = volume of one hopper, m3 http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 900 the standing height of hopper was computed from: ht = w (n + 1) (9) 2.2.2 principle of operation of the 2-row engine-propelled seed ridge planter the soil openers are set to the required level and the delivery chutes are also set to near the point of dropping of seed. the hoppers are filled to the required level. the engine fuel tank is filled to the desired level and the planter (figure 4) is set in line with the ridges. the clutching arm is raised down to jack the engine up and to put it in idle state and the engine of the planter is cranked on and allowed to run idle for two minutes to allow for the stabilization of the engine. to put the planter in operation, the clutch arm is lowered to engage the drive of the planter which puts it in motion. at the end of a planting row, the clutch is raised to disengage the engine and to allow for turning. 2.2.3 performance evaluation 1. percent seed damage: the planter was powered on and the broken seeds and whole seeds metered were collected and weighed. seedsbrokenofweightseedswholeofweight seedsbrokenofweight damageseed + =% (10) figure 4: the 2-row self-propelled ridge planter 2. soil moisture content determination soil moisture content was calculated as (fao, 1994): 100 13 32 x ww ww m c − − = (11) where, mc = soil moisture content (dry weight basis), %, w1 = weight of container, g, w2 = weight of container + wet soil, g, w3 = weight of container + oven dried soil, g 3. determination of seed delivery rate seed delivery was obtained as (srivastava et al.,1993): nwd l q e 000,10* = (12) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng yusuf et al: multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm). azojete, 19(4):897-910. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 901 where, q = delivery rate (kg/ha), l = distance in a given number of revolution (n) of forward wheel, de = effective diameter of ground wheel (m), n = number of revolutions of ground wheel, w = nominal working width (m). 4. working speed was computed from (fao, 1994): av av t d v = (13) where, dav = average distance, (m), and tav = average time, (s). 5. determination of seedling emergence ratios: seedling emergence is determined from the counts of newly emerged seedlings in each row, three times (morning, afternoon and evening) daily. speed of emergence (soe) (tressier, 1988), mean emergence data (med), emergence rate index (eri) and relative emergence (re) (bilbro and wanjura, 1982) were calculated directly from the emergence counts: ( ) ( )n n ttt nnn soe +−−−−−++ +−−−++ = 21 21 (14) ( ) ( )n nn ttt tntntn med +−−−−−++ +−−−++ = 21 2211 (15) ( ) med nnn eri n+−−−++ = 21 (16) ( ) ns nnn re n+−−−++ = 21 (17) where: n1, n2, ………nn are numbers of newly emerged seedlings at times t1, t2,. tn, ns = number of seeds planted in each row = number of germinated seeds + counted un-germinated seeds on the rows as reported by bilbiro and wanjura (1982). 2.2.4 the experimental design the treatments considered are three planting methods (engine-propelled planter, animal drawn planter, and manual planting), three soil moisture levels, and three planting depths. the treatments were randomly assigned in a 3x3 factorial experiment arranged in a randomized complete block design (rcbd) in three replications as described by gomez and gomez, (1984). the statistical analysis package (sas) was used for data analysis (sas institute inc, 1989). 2.2.4.1 response surface optimisation the response surface optimisation (rso) was implemented using design expert 9.0 software. two models were developed to show how the seed planting process parameters (planting speed and moisture content) can be used to maximize the output responses (seedling emergence, planting depth, plant spacing, number of seeds per hole) and minimize the output responses (number of damaged seeds). the rsm method used for carrying out the experiment is the ccd. the empirical model selection and anova calculation using rsm was carried out in design expert 9 .0 software. 2.2.4.2 estimation of decision variables (alternatives). the variables for evaluating the objective were: planting speed (x1), moisture content of the soil (x2), seedling emergence (y1), seed depth of planting (y2), plant-to-plant spacing (y3), number of seeds per hill (y4), number of seed damage(y5). http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 902 x1 and x2 are the input variables while y1 ….y6 are the response variables. a set of polynomial equations defined for each of the response variables were used since it is only a polynomial that can give the needed curvature that will define the maximum and minimum points. the objective criteria for evaluating the alternate general polynomial functions is: 2 25 2 14213221101 xaxaxxaxaxaay +++++= (18) 2 25 2 14213221102 xbxbxxbxbxbby +++++= (19) 2 25 2 14213221103 xcxcxxcxcxccy +++++= (20) 2 25 2 14213221104 xdxdxxdxdxddy +++++= (21) 2 25 2 14213221105 xexexxexexeey +++++= (22) 2 25 2 14213221106 xfxfxxfxfxffy +++++= (23) a0…. a5, b0……b5, ……. e0……e5 are the constants of the polynomials which will be determined and upon which the polynomials will be redefined and validated. while y1, y2, y3 and y4 will be maximized, y5 will be minimized. 2.2.4.3 constraints the constraints to the alternatives above are the limits of the input variables. the limits will be categorized into low and high limits for the two input variables. heckman et al. (2002) and arzu and adnan (2006) stated that the low and high levels of soil moisture content for planting correspond to the moisture content at wilting point of the soil as low and field capacity of the soil as high. these translate into 12.37% (db) for low and 21.1 % (db) for high. similarly, fao (1994) and grisso et al. (1994) stated that the speed limits are fixed for 0.94m/s as low and 1.32m/s as high. thus, the limits (table 1) are defined and the constraints can thus be represented as: 32.194.0 1  x (24) 1.2137.12 2  x (25) table 1: input variables levels based on research study input factors units low level high level planting speed m/s 0.94 1.32 moisture content % (db) 12.37 21.1 the problem of optimisation, putting the variables of interest into consideration is of the form (taha, 2007): maximize −+++++= 2 25 2 14213221101 xaxaxxaxaxaay −+++++= 2 25 2 14213221102 xbxbxxbxbxbby −+++++= 2 25 2 14213221103 xcxcxxcxcxccy −+++++= 2 25 2 14213221104 xdxdxxdxdxddy subject to 32.194.0 1  x 1.2137.12 2  x and minimize −+++++= 2 25 2 14213221105 xexexxexexeey subject to 32.194.0 1  x 1.2137.12 2  x file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng yusuf et al: multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm). azojete, 19(4):897-910. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 903 2.2.5 response surface experimental matrix design the input process variables (planting speed and soil moisture content), and the output responses (seedling emergence, seed planting depth, plant-plant spacing, number of seeds per hill, and number of damaged seeds) for modelling and correlation studies were selected as described by akinoso et al., (2006) and skwarcz (2006). the relationship between the output responses the input variables were defined using rsm modelling approach. the experimental design was developed using the response surface matrix (rsm) central composite design (ccd), produced by design expert version 9.0 software which uses a suitable matrix/experimental layout based on ccd. the three groups of design points for ccd are: i. i nf = 2k, response surface design or corner points (k is the number of input variables) ii na = 2k; axial or star points and iii nc= center points, repeated several times to obtain a good estimation of experimental pure error. then the total number of experiments would be: n = nf + na + nc (26) response surface points: nf = 2k = 22 = 4, axial points: na = 2k = 2x2 =4 and center points: nc = 5 total number of experiments would be: n = nf + na + nc = 4+4+5 = 13 (27) the developed ccd for the uncoded design is shown in table 2. table 2: response surface methodology experimental run design exp run planting speed (m/s) moisture content (%) seedling emergence (in 0.01ha) depth of planting (mm) plant spacing(mm) number of seeds per hill 1 1.32 16.74 x x x x 2 1.13 16.74 x x x x 3 0.94 12.37 x x x x 4 1.32 12.37 x x x x 5 1.32 21.10 x x x x 6 1.13 16.74 x x x x 7 1.13 21.10 x x x x 8 1.13 16.74 x x x x 9 0.94 16.74 x x x x 10 1.13 16.74 x x x x 11 1.13 16.74 x x x x 12 1.13 12.37 x x x x 13 0.94 21.10 x x x x x = values to be measured on field 2.2.5.1 development of response surface empirical model for output responses the empirical model correlating output responses (seedling emergence, depth of seed planting, plant spacing, number of seeds per hole, energy consumed and number of damaged seeds (y)) to the process factors (planting speed, moisture content) and the interaction between them is best explained below as generated by design expert 9.0 software:: 𝑌𝑅𝑆𝑀 = 𝛾0 + 𝛾1𝑥1 + 𝛾2𝑥2 + 𝛾3𝑥1𝑥2 + 𝛾4𝑥1 2 + 𝛾5𝑥2 2 + 𝜖 (28) where, yrsm = response surface matrix output, 𝑥1 = planting speed (m/s), 𝑥2 = moisture content (% db), 𝑥1𝑥2 = interaction between planting speed and moisture content, 𝑥1 2 = square of the main effect (planting speed), 𝑥2 2 = square of the main effect (moisture content), 𝛾𝑖 = coefficients of the model parameters and ϵ = error value. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 904 𝑌𝑅𝑆𝑀 = 𝑦 = seedling emergence, depth of seed planting, plant spacing, number of seeds per hill, and number of damaged seeds for response surface model. in order to determine the constants 𝛾𝑖, a matrix model for the process factors was developed from experimental matrix as: 𝑥 = [ 1 𝑥11 𝑥21 1 ⋮ 1 𝑥12 ⋮ 𝑥113 𝑥22 ⋮ 𝑥213 ] (29) the response factors (seedling emergence, depth of seed planting, plant spacing, number of seeds per hill, energy expended and number of damaged seeds) were represented as: 𝑦 = [ 𝑦1 𝑦2 ⋮ 𝑦13 ] (0) the error term was represented as 𝜖 = [ 𝜖1 𝜖2 ⋮ 𝜖13 ] (31) the coefficients in the model were represented as: 𝛾 = [ 𝛾1 𝛾12 ⋮ 𝛾113 ] (32) the general form is represented as: 𝑦 = 𝑥𝛾 + 𝜖 (33) a vector of the least square estimator is: 𝐿 = 𝜖𝑇𝜖 (34) and minimized as: ( 𝜕𝐿 𝜕𝛾 ) 𝛾 = 0 (35) the coefficients (𝛾𝑖) in the model was determined by design expert 9.0 software and 𝛾𝑖 = (𝑥𝑇𝑥)−1𝑥𝑇𝑦 (36) 2.2.5.2 significance testing of the coefficients of the response surface model (validation) following the determination of coefficients in model equation, the significance of the coefficients was determined by design expert 9.0 software as described below. the sse, 𝜎2, ssy and ssr were calculated as: 𝑆𝑆𝐸 = 𝑦𝑇𝑦 − 𝛾𝑇𝑥𝑇𝑦 (37) 𝜎2 = 𝑆𝑆𝐸 𝑛−𝑝 (38) where, n = length (y) = length of the output response (y), p = length (𝜑) = number of the coefficient to be estimated. the sum of square of output responses (ssy) was determined as: 𝑆𝑆𝑌 = 𝑦𝑇𝑦 − (∑ 𝑦𝑖 𝑛−1 𝑖=0 )2 𝑛 (39) the sum of square of the residual error was determined by design expert 9.0 as: 𝑆𝑆𝑅 = 𝜑𝑇𝑥𝑇𝑦 − (∑ 𝑦𝑖 𝑛−1 𝑖=0 )2 𝑛 (40) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng yusuf et al: multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm). azojete, 19(4):897-910. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 905 a minitab program (figure 5) was programmed to create a matrix of three columns. the first column has the response surface coefficient, the lists of the t-values is the second column and the power of the t-test is the third column. figure 5: design expert 9.0 program for computing the coefficient of the response surface model, t-test value and the p-value. 3. results and discussion 3.1 percent seed damage: seed damage by the engine-propelled planter is near zero (table 1). this implies that the planter is mechanically efficient in the delivery of whole seeds to the soil. broken seeds reduce the number of seedlings that can emerge on a planted field. the enginepropelled planter thus has the capability of maintaining maximum plant emergence after planting. table 1: result of percent seed damage sample no. right hopper left hopper weight of whole seeds (g) weight of damaged seeds (g) weight of whole seeds (g) weight of broken seeds (g) 1 5.2 0.0 5.5 0.0 2 5.8 0.0 6.0 0.0 3 5.6 0.0 5.7 0.0 4 5.1 0.2 5.0 0.0 5 5.0 0.0 6.8 0.0 total 26.7 0.2 29.0 0.0 average 5.34 0.04 5.80 0.0 % 0.75 0.00 3.2 seed metering for the three methods investigated the results of seed metering and ground wheel speed are shown on tables 2 and 3 respectively. the engine-operated planter will meter between 1 and 2 seeds per hole and having an average travel speed of 1.25m/s. these values are likely to be affected while working on the field as the conditions on the field are not the same as with the laboratory. bamgboye and mofolasayo (2006) submitted that planters that are not tractor trailed have not been able to reach the 1 m/s operational speed on the field. table 2: seed metering test on the 2-row ridge planter trial no. spacing between dropped seeds (cm) average spacing (cm) no. of seeds dropped per point hopper 1 hopper 2 hopper 1 hopper 2 hopper 1 hopper 2 1 26,23,25.5,25.6 25.3,26.1,26,27.1 25.03 26.13 2+2+1+2=7 1+1+2+2=6 2 26.7,27.9,26.8,3 25.2,26.1,25,27.1 26.85 25.85 1+2+1+2=6 2+2+2+1=7 3 28.5,26.1,24,26.6 23,24,25.6,22.3 26.30 23.73 2+1+1+3=7 3+2+1+2=8 total 78.18 75.71 20 21 average 26.06 25.24 1.6 1.8 http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 906 table 3: result of ground wheel travel speed trial no. distance (m) time taken (secs) travel speed (m/s) 1 10 11.50 1.15 2 10 12.88 1.29 3 10 13.20 1.32 average 1.25 3.3 seedling emergence for the three methods evaluated for three years tables 4 shows the pooled anova of the effects of the planting methods, soil moisture and depth of planting on seedling emergence for the years 2012, 2013 and 2014. there are no significant differences between replications within the testing periods. this implies that the values gotten in the three replications agreed with each other as they close in magnitude. there was significant difference among the planting methods, and the interactions of planting methods, year and depth of seed placement at 1% confidence level. however, the interaction of the planting methods and the years was significant at the 5% probability level. this implies that the methods showed varying capabilities in the number of plants that emerged. yisa et al. (1994) and heckman et al. (2002) had similar results and concluded that planting method, depth of seed placement, the state of soil coverage, and the soil moisture affect seedling emergence table 4: anova of the pooled analysis of the effects of planting methods, soil moisture and depth of planting on seedling emergence in the 2012, 2013and 2014 testing seasons source of sum of tabular f variation df squares mean square computed f 5% 1% rep 2 0.2304527 0.1152263 0.06ns 3.06 4.75 mtd 2 140.9958848 70.4979424 38.66** 3.06 4.75 sm 2 4.8477366 2.4238683 1.33 ns 3.06 4.75 dp 2 3.8106996 1.9053498 1.04 ns 3.06 4.75 year 2 95.4650206 47.7325103 26.18** 3.06 4.75 mtd*sm 4 3.7448560 0.9362140 0.51 ns 2.43 3.44 mtd*dp 4 8.5596708 2.1399177 1.17 ns 2.43 3.44 mtd*year 4 23.5720165 5.8930041 3.23* 2.43 3.44 sm*dp 4 7.6707819 1.9176955 1.05 ns 2.43 3.44 sm*year 4 5.6460905 1.4115226 0.77 ns 2.43 3.44 dp*year 4 4.3868313 1.0967078 0.60 ns 2.43 3.44 mtd*sm*dp 8 15.7366255 1.9670782 1.08 ns 2.00 2.62 mtd*sm*year 8 43.5390947 5.4423868 2.98** 2.00 2.62 mtd*dp*year 8 9.6872428 1.2109053 0.66 ns 2.00 2.62 sml*dp*year 8 10.6502058 1.3312757 0.73 ns 2.00 2.62 mtd*sm*dp*year 16 20.1646091 1.2602881 0.69 ns 1.71 2.12 error 160 291.7695473 1.8235597 total 242 690.4773663 _______________________________________________________________ ___ note: ns = not significant, * = significant at 5% confidence level, ** = significant at 1% confidence level file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng yusuf et al: multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm). azojete, 19(4):897-910. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 907 3.4 response surface modelling of seedling emergence with respect to seed planting process parameters: the results of the model correlating planting speed and seed planting moisture content to seedling emergence are as presented in table 5. also presented are the results of model selection and model terms significance. the model developed provide the basis for optimisation to determine the settings of seed planting moisture content and planting speed that will maximize plant population. table 5: rsm experimental run and results of seedling emergence, planting depth, plant spacing, and number of seeds per hole exp run planting speed (m/s) moisture content (%) number of seeds emerging depth of planting (mm) plant spacing (cm) number of seeds per hole 1 1.32 16.74 14 21.50 25 2 2 1.13 16.74 20 30.00 36 3 3 0.94 12.37 9 13.50 16 1 4 1.32 12.37 12 18.00 22 2 5 1.32 21.10 12 18.00 22 2 6 1.13 16.74 20 30.00 36 3 7 1.13 21.10 21 31.50 38 3 8 1.13 16.74 19 28.50 34 2 9 0.94 16.74 20 30.00 36 3 10 1.13 16.74 19 28.50 34 2 11 1.13 16.74 20 30.00 36 3 12 1.13 12.37 11 16.50 20 1 13 0.94 21.10 24 36.00 43 3 3.4.1 seedling emergence model: the experimental data was used to obtain the second order empirical model coefficients of equations. the empirical model equations for the seedling emergence as a function of process variables (planting speed and moisture content) was developed using experimental data. the quadratic equation model terms are shown in table 6. table 6. coefficient table for seedling emergence response surface reduced quadratic model factor coefficient estimate df standard error 95% ci low 95% ci high vif intercept 19.9310 1 0.8042 18.0295 21.8326 a-planting speed -0.5000 1 0.7907 -2.3696 1.3696 1 b-moisture content 2.8333 1 0.7907 0.9637 4.7029 1 ab -2.2500 1 0.9684 -4.5398 0.0398 1 a2 -3.2586 1 1.1654 -6.0143 -0.5030 1.1698 b2 -5.2586 1 1.1654 -8.0143 -2.5030 1.1698 intercept 19.9310 1 0.8042 18.0295 21.8326 the actual emergence empirical model is shown as: 𝑅 = −191.4646 + 199.41𝑃𝑆 + 11.6671𝑀𝐶 − 4.5216𝑃𝑆𝑀𝐶 − 60.6553𝑃𝑆 2 − 0.1674𝑀𝐶 2 41 similarly, the sequential model sum of squares (smss) analysis and the lack of fit model were done for the two response variables for the depth of planting and the plant to plant spacing as shown in equations 42 and 43, respectively. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 908 3.4.2 effects of the process variables on seedling emergence, depth of planting and the plant spacing using the optimized models are shown in the contour and surface plots the effects of the process variables on seedling emergence, depth of planting and the plant spacing using the optimized models are shown in the contour and surface plots shown in figures 6 to 9. figures 6 and 7 show that increased plant population was observed with increasing planting speed and moisture content values. also, increased seedling emergence was observed with increasing moisture content and decreasing planting speed values. however, further increase in seed planting moisture content beyond the optimum point caused a decrease in the seedling emergence. figures 8 and 9 show the contour and surface plots of the depth of planting model respectively. it was observed that there was increased depth of planting with increasing seed planting speed and moisture content values. further increase in soil moisture content beyond the optimum point caused a decrease in the depth of planting. 4. conclusions the following conclusions can be drawn from the experimental results and analysis: i. there was significant difference among the planting methods, and the interactions of planting methods, year and depth of seed placement at 1% confidence level. ii. the constructed ridge seed planter has comparative advantage over the i.a.r. animal – drawn planter and the manual planting method in terms of percentage seed damage, planting speed, and speed of seedling emergence and the later, being the dominant mode of planting in nigeria. 𝑅 = −284.858 + 291.732𝑃𝑆 + 17.7127𝑀𝐶 − 6.7824𝑃𝑆𝑀𝐶 − 87.4009𝑃𝑆 2 − 0.2575𝑀𝐶 2 42 𝑅 = −34.4222 + 36.3813𝑃𝑆 + 2.0577𝑀𝐶 − 0.8139𝑃𝑆𝑀𝐶 − 11.0803𝑃𝑆 2 − 0.0289𝑀𝐶 2 43 planting speed figure 6: mean model contour plot showing the effect of moisture content and planting speed on seedling emergence for response surface optimization model. figure 7: mean model response surface plot showing the effect of seed planting moisture content and planting speed on seedling emergence for response optimization. figure 8: contour plot showing the effect file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng yusuf et al: multi-response optimization of planting process of a seed ridge planter using response surface methodology (rsm). azojete, 19(4):897-910. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 909 iii. soil moisture availability is an important factor affecting the depth of seed planting in the study area. references akinoso, r., igbeka, jc. and olayanju, tma. 2006. process optimisation of oil expression from sesame seed. cigr e-journal, manuscript fp 06 011 8: 1-7. arzu, y. and adnan, d. 2006. optimisation of the performance of a precision planter. metering cotton seed using response surface methodology. asabe meeting presentation paper no. 061076, asabe, st. joseph michigan. bamgboye, ai. and mofolasayo, as. 2006. performance evaluation of a two-row okra planter. cigr e-journal, 8: 10. bilbro, jd. and wanjura, df. 1982. soil crust and cotton emergence relationships; transactions of the asae, 25: 1485 – 1488. bosoi, es. verniaev, ov. smirnov, ii. and sultan-shakh, eg. 1988. theory construction and calculations of agricultural machines; russian translation series, 1: 233-275. crossley, p. and kilgour, j. 1983. small farm mechanisation for developing countries. john wiley and sons ltd, new york. p.116-123. finch-savage, we. and bassel, gw. 2016. seed vigour and crop establishment: extending performance beyond adaptation. journal of experimental botany, 67: 567–591. foods and agricultural organization (fao), 1994. testing and evaluation of agricultural machinery and equipment: principles and practices. fao, rome. agric services bulletin, 110: 150-169. grisso, rd., yasin, m. and kocher, mf. 1994. tillage implement forces operating in silty clay loam. asae paper 94-1532, st. joseph michigan. gomez, ka. and gomez, aa. 1984. statistical procedures for agricultural research. 2nd edn. john wiley and sons, new york., pp.13-28. hall, as., holowenko, ar. and langlin, hg. 1961. theory and problems of machine design. schaum outline series, mcgraw hill book company, london., pp. 56-65. he, j., zhang, zq., li, hw. and wang, qj. 2004. development of small/medium size no-till and minimum-till seeders in asia: a review. international journal of agricultural and biological engineering, 7: 1–12. heckman, nl., garald, lh. and roch, eg. 2002. planting depth effect on emergence and morphology of buffalograss seedlings; agronomy & horticulture faculty publications; university of nebraska – lincoln. 3pp. johansen, c., haque, me., bell, rw., thierfelder, c. and esdaile, rj. 2012. conservation agriculture for small holder rainfed farming: opportunities and constraints of new mechanized seeding systems. field crop research, 132: 18–32. murray, jr., tullberg, jn. and basnet, bb. 2006. planters and their components: types, attributes, functional requirements, classification and description; australian centre for international agricultural research, canberra., pp. 26 – 157. muvdi, bb. and mcnabb, jw. 1988. engineering mechanics of materials. macmillan publication co. inc., new york., pp. 35-170. skwarcz, j. 2006. optimisation of the choice of agricultural machines. e-journal of polish agricultural universities, 9(3): art-14., www.ejpau.medi.pl. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng http://www.ejpau.medi.pl/ arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):897-910. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ddyusuf2004@yahoo.com 910 spotts, mf. 1988. design of machine elements, 6th ed. prentice-hall of india private ltd; new delhi, pp.149 – 160. srivastava, ak., goering, ce. and robrbach, rp. 1993. crop planting. asae textbook, asae michigan., 6: 221-263. srivastava, ak., goering, ce., rohrbach, rp. and buckmaster, dr. 2006. crop planting. in engineering principles of agricultural machines. 2nd edition, (srivastava, ak., goering, ce. and rohrbach, rp. (eds.)). asabe: st. joseph, michigan, usa, pp. 231–268. statistical analysis system institute inc., 1989. sas/stat user’s guide, version 6, 4th edn., vol. 1, sas institute inc., n.c., 934pp. taha, ha. 2007. operations research: an introduction (8th ed); prentice-hall of india private ltd; pp. 1-48. timsina, j., buresh, rj., dobermann, a. and dixon, j. 2011. rice-maize systems in asia: current situation and potential; cimmyt. irri: los baños, phillipines, p. 235. tressier, s. 1988. zero-till furrow opener geometry effect on wheat emergence and zone properties; phd dissertation, washington state university, pullman, 65pp. van loon, j., speratti, a., gabarra, l. and govaerts, b. 2018. precision for smallholder farmers: a small-scale-tailored variable rate fertilizer application kit. agriculture, 8: 48-52. wankhade, c. and kotwal, mr. 2014. a review paper on various seed sowing metering devices. international journal of pure applied research in engineering and technology, 2: 429–435. yisa, mg., walczyk, j. and terao, h. 1994. effects of coulter shape and operating velocity on the performance of precision planters. journal of the faculty of agriculture, hokkaido university, sapporo, 66(1): 79-98. yusuf, dd. 2010. use and management of seeders, planters and fertilizer applicators; an invited paper presented at the national workshop on tractor and farm machinery management for sustainable agricultural production; naerls, ahmadu bello university, zaria, 18pp. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):635-646 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 635 original research article effect of water stress on yield and water productivity of drip irrigated cassava (manihot esculenta) in ibadan, nigeria a. f. awoyode1, t. a. ewemoje1 and o. b. adeboye2* 1agricultural and environmental engineering department, faculty of technology, university of ibadan, ibadan, nigeria 2agricultural and environmental engineering department, faculty of technology, obafemi awolowo university, ile-ife, nigeria *corresponding author’s email address: adeboyeob@oauife.edu.ng 1.0 introduction cassava (manihot esculentus) is one of the most important staple foods in the tropics (onwueme, 2002). it ranked the sixth most important source of calories worldwide (fao 2013; alfredo et al., 2000; henry & hershey, 2002; hillock, 2002). in nigeria, 50 % of the population eats cassava at least once a day (philip, 2005). in the rest of sub-saharan africa (ssa), the same scenario applies to as many as 30 to 70 % of the region’s inhabitants (faostat, 2005). in many parts of africa, cassava leaves and tender shoots are consumed because they contain about 7% protein (fresh weight) and a high level of lysine (ly et al., 2012). cassava is a starchy root tuber crop (luiz et article information abstract cassava (manihot esculentus) is an important staple tuber crop in many regions of africa. it is a cash crop with wide domestic and industrial applications. hence, there is a need to sustain its production during water scarcity. this study examined the effect of available soil moisture on phenological parameters and drought resistance of four improved varieties of cassava, tms (30572, 980505, 920326 and 090581) using water productivity. the water management regimes (t75 maximum water regime 75% of evapotranspiration (et); t50, 50% et, t25 25% et and control, zero irrigation). the varieties and water regimes were applied and the treatment was arranged using a latin square design with four replications. lynne's model was used in calculating the irrigation water requirements. the amount of water supplied to each treatment varied with the duration of irrigation. the results show that tms 980505 at t75 had the highest tuber, stem and leaf productivities of 2.76, 1.66 and 2.05 kg m-3 respectively while tms 30572 on the control regime had the least tuber, stem and leaf productivities of 0.16, 0.21 and 0.21 kg m-3 respectively. the tms 980505 can be grown in regions where substantial crop water requirements for cassava could be met during the dry season through irrigation while tms 090581 could be grown in water-scarce regions with a guaranteed 370 mm of water with an average yield of 4.5 t ha-1. the tms 090581 at t75 had the highest plant height of 128 cm while tms 30572 on control had the least height of 56 cm. tms 920326 at t75 had the highest stem girth of 21.4 mm while tms 30572 at t50 had the least stem girth of 10.7 mm. therefore, full irrigation is recommended for the cultivation of tms 980505 during the dry season. the tms 090581 has the highest drought resistance. therefore, it is recommended for cultivation in water-scarce regions. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 january, 2022 revised 11 july, 2023 accepted 30 july, 2023 keywords: cassava water stress irrigation evapotranspiration http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng adeboyeob@oauife.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):635-646. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 636 al., 2017) and is, therefore, a competitive crop, especially for the production of starch, animal feed, and alcohol (fuglie, 2004; oguntunde, 2005). cassava is cultivated mainly under a rainfed farming system because it can grow in areas with an annual rainfall of 400 mm and responds well to irrigation (pushpalatha et al., 2020). study has shown that drip irrigation can produce about the same yield as surface irrigation using less than 50 % of the water requirement (fao, 2013). in nigeria, root yields increased six-fold when the quantity of water supplied by supplementary drip irrigation was equal to that of the seasonal rainfall. supplemental irrigation that increased the total water supply by 20 % almost doubled root yields (fao, 2013). to improve cassava production, its cultivation should not be limited to rainfed agriculture. sustainable and economical irrigation practices should be employed during the dry season of the tropics. as competition for increasingly scarce water resources intensifies, irrigation is under growing pressure to produce “more crops from fewer drops” and to reduce its negative environmental impacts such as soil salinization and nitrate contamination of drinking water. greater use of water-saving precision technologies, such as drip and micro-irrigation, will make an important contribution to sustainable intensification (aderemi et al., 2018). drip irrigation has proven to be successful in terms of increased yield and water productivity of a wide range of crops. edoga and edoga (2006) reported that under drip irrigation, the soil is maintained continuously in favourable condition for crop growth. water management of cassava under irrigated agriculture has received little attention in ssa, it is mostly rainfed (odubanjo et al., 2011). cassava is known for its resistance to extreme climatic conditions. it can tolerate drought and grow in low-nutrient soil (odubanjo et al., 2011). even though cassava can withstand drought conditions, there have been concerns about the effect such condition has on its field. cassava can grow in areas with average annual rainfall of 400 mm (fao, 2013). water availability, therefore, affects the yield of cassava. in the first three months after planting, cassava is very sensitive to soil water deficit and water stress at any time during this period will reduce the growth of roots and shoots significantly (green water, 2014; fao, 2013). the hypothesis being tested is that water stress will affect cassava's yield and growth parameters. therefore, this research aimed to study the impact of water stress on yields and water productivity of four improved varieties of cassava under a drip irrigation system in ibadan, southwest nigeria. 2. materials and methods 2.1 study area the experiment was conducted at the agricultural and environmental engineering experimental field of the university of ibadan, nigeria. it is located at latitude 7.4417° n and longitude 3.9000° e with an altitude of 227 m, above mean sea level. the study area is in the tropical rainforest zone of southwest nigeria and is characterized by distinct wet and dry seasons. the mean annual rainfall in the area is 1205 mm, falling in approximately 109 days with two rainfall peaks in june and september (egbinola and amobichukwu, 2013). approximately, 50 % of the average annual rainfall occurs between april and july while 40 % occurs between august and october, file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng awoyode et al: effect of water stress on yield and water productivity of drip irrigated cassava (manihot esculenta) in ibadan, nigeria. azojete, 19(3):635-646. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 637 november to march is usually the driest months and temperatures tend to be higher (ewemoje and ewemoje, 2011). the experimental field soil was classified as sandy loam. 2.2 treatments and experimental design the four improved cassava varieties served as the block while four water regimes, (t75 maximum water regime – 75 % of evapotranspiration (et), t50 medium water regime – 50 % of et, t25 low water regime – 25 % of et and control zero irrigation) were the treatments. the experimental design was a latin square with four replications. 2.3 layout of drip irrigation system water was sourced from the university of ibadan water supply system. the water was stored in two 2,000 l storage tanks. the two tanks were connected in series at the base with a polyvinyl chloride pipe of diameter 38.1 mm fitted with a control valve in the middle. one of the tanks was connected to a constant head reservoir of 500 l capacity (figure 1), the constant head was maintained in the tank by a ball valve fitted to the inlet end of the 500 l tank and this invariably maintained constant water pressure in the main line, sub-main and laterals. the constant head reservoir had an elevation of 2.7 m to the laterals, which guaranteed uninterrupted flow by gravity. the 11.35 m long main pipe of diameter 25.4 mm was connected to the outlet base of the constant head reservoir which conveyed water to the sub-main pipe. a valve is fitted on the main pipe and when the valve is opened, it supplies water directly to the t75 regime. the submain pipe of length 11.5 m and diameter 19.5 mm was connected to the main pipe by an elbow joint. two valves were fitted on the sub-main pipe and they regulate the flow of water to the t25 and t50 regimes. these valves were operated based on the time of water application to the water regime. twelve laterals each having a length of 8.1 m and a diameter 12.7 mm were connected to the sub-main with the use of t-joint connectors. ninety-six (96) emitters each having a discharge of 4 lh-1 were connected to the laterals. the pressure compensating emitters were spaced at 1 m intervals and each lateral pipe has eight (8) emitters. each irrigated regime of the field had four laterals fitted to supply water to the four varieties of cassava planted on each regime. figure 1: 3-d view of the drip irrigation set-up and the constant head reservoir http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):635-646. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 638 2.4 measurements soil samples collected from the experimental field were weighed and oven-dried at 105oc to eliminate moisture and make it pulverized. sieve analysis and textural triangle were used to determine soil texture. rainfall, humidity, wind speed, sunshine hour, radiation, and daily maximum and minimum temperature were logged at intervals of 5 minutes at a weather station located 134 m from the experimental field. these variables were used in computing daily reference evapotranspiration (eto) using cropwat 8.0. four improved varieties of cassava, tms 30572, tms 980505, tms 920326, tms 090581 obtained from the international institute for tropical agriculture ibadan, nigeria were planted on the 28th of november, 2016. the planting was done during the dry season in order to establish the cassava plant. the plant spacing was 1 m by 1 m. each plot measured 4 m by 8 m and the total area of the field was 16 by 8 m2. four rows of eight mounds per row made up each regime, hence, each plot contained 32 plant stands and it was set out such that each variety occupied an entire row of a water regime. the 25 cm long cassava stems were planted at an inclined angle of 30 degrees to the horizontal to ensure shallow roots and access to water. the regimes under drip irrigation were daily supplied with 2 mm of water while each plant on the control received 1.5 mm of water daily. after establishing the crop, the irrigation was scheduled at intervals of three days. reference evapotranspiration under standard conditions in three days was computed using an eto calculator (allen et al., 1998). supplementary irrigation was practiced during the intersecting rainy season. tuber, stem and leaf productivities were calculated for each variety across the regimes by dividing the weight of tuber, stem and leaf recorded at the harvest by water supplied to each regime from the day of planting till the day harvesting was carried out. 2.4.1 irrigation water requirement the irrigation water requirement was computed using eqn. 1 ali, 2010): ir= eto×kc×pd×ef×pa ie (1) where: ir = irrigation water requirement measured in l day-1 eto = reference evapotranspiration measured in mm day-1; kc = crop coefficient, which depends on the age of the crop, 0.35 (0-60 dap), 0.81 (61150 dap), 0.35 (151-180 dap); pd = plant density, which is dimensionless, it increases as the vegetative cover of the crop increases and it ranges from 0.5 (low-sparse coverage) 1.0 (moderate coverage); ef = exposure factor, which is dimensionless and was assumed to be 0.65 as three of the four sides of the plot has vegetation; pa = planted area, measured in m2; ie = irrigation efficiency; the irrigation efficiency was calculated to be 90%. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng awoyode et al: effect of water stress on yield and water productivity of drip irrigated cassava (manihot esculenta) in ibadan, nigeria. azojete, 19(3):635-646. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 639 the irrigation was done at 6 am of every three days. plant height, stem girth, and number of nodes which are growth indicator parameters used in this study were measured and recorded weekly on each variety of the four regimes from 70 days after planting (dap) till maturity. water applied to each regime was computed every week. a correlation analysis was carried out on the plant height and water supplied to each variety on the four regimes to determine the effect of available soil moisture on plant height. the crop was harvested at 180 dap because all the varieties studied have a maturity period of 6 months. 2.4.2 irrigation application variation after calculating the full irrigation water required using eqn. 1, the amount of water required to be supplied by the emitters on each irrigated regime is calculated using eqns. 2 to 4. 𝑇25 𝐸𝑚𝑚𝑖𝑡𝑒𝑟𝑠 = 0.25 𝑋 𝐼𝑅 96 (2) 𝑇50 𝐸𝑚𝑖𝑡𝑡𝑒𝑟𝑠 = 0.5 𝑋 𝐼𝑅 96 (3) 𝑇75 𝐸𝑚𝑖𝑡𝑡𝑒𝑟𝑠 = 0.75 𝑋 𝐼𝑅 96 (4) where: ir is as defined previously. 2.4.3 water productivity water productivity (kg m-3) was determined using eqn. (5) (zhang and owie, 1999): 𝑊𝑃 = 𝑌 𝑉 (5) where: y = marketable yield (kg); v = volume of water applied (m3). 2.5 statistical analysis microsoft excel was used for data analysis. two-way analysis of variance (anova) was carried out on tuber, stem and leaf productivities, with water regimes serving as treatment and cassava varieties as blocks. a two-way analysis of variance was carried out for tuber, stem and leaf productivity with the varieties serving as blocks and water management regimes as treatments. the analysis was carried out at a significant level α = 0.05 and means were compared. 3.0 results and discussion the soil textural analysis revealed that the field is predominantly sandy loam. the amount of water received by each regime on a weekly basis is shown in table 1. a sample of eto result as produced from cropwat 8.0 is shown in figure 2. the leaves of tms 920326 were observed to be shrinking at the developmental stage, the shrinkage was attributed to a mealybug attack http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):635-646. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 640 (phenacoccus manihoti) which reached its peak during the dry season (james et al., 2000). isopropyl alcohol solution was used to mitigate the attack table 1: weekly water supplied to each regime and control date dap ws n (mm) ws t25 (mm) ws t50 (mm) ws t75 (mm) 05/12/2015 7 10.5 14 14 14 12/12/2015 14 10.5 14 14 14 19/12/2015 21 10.5 14 14 14 26/12/2015 28 10.5 14 14 14 02/01/2016 35 10.5 14 14 14 09/01/2016 42 10.5 14 14 14 16/01/2016 49 10.5 14 14 14 23/01/2016 56 10.5 14 14 14 30/01/2016 63 8.7 9.3 10.6 11.8 06/02/2016 70 4.5 2.6 5.2 7.8 13/02/2016 77 3 2.8 5.6 8.4 20/02/2016 84 3 4.6 9.3 13.9 27/02/2016 91 4.5 3.2 6.5 9.7 05/03/2016 98 3 3.3 6.6 9.9 12/03/2016 105 14.6 14.6 18.9 23.6 19/03/2016 112 37.2 37.2 37.2 37.2 26/03/2016 119 13.2 13.2 13.2 17.5 02/04/2016 126 0 0 3 7.4 09/04/2016 133 32.6 32.6 32.6 32.6 16/04/2016 140 17.3 17.2 17.3 17.3 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng awoyode et al: effect of water stress on yield and water productivity of drip irrigated cassava (manihot esculenta) in ibadan, nigeria. azojete, 19(3):635-646. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 641 figure 2. the first page of the cropwat 8.0 software 3.1 effect of soil moisture on growth indicator and parameter three growth indicators considered in the study are plant height, stem girth, and the number of nodes and the correlation analysis conducted between them and weekly available moisture is presented in tables 2, 3 and 4. these parameters were subjected to anova at a 95% confidence level, there are significant differences (p < 0.05) among the means of the plant height and number of nodes for tms 30572, tms 980505 and tms 920326; these significance differences (p < 0.05) are due to different available moisture for the treatment. the tms 090581 showed no significant difference (p > 0.05) in means of plant height and number of nodes across the four water regimes and this could be attributed to the ability of this variety to naturally grow tall as reported by ewemoje et al. (2015). there were significant differences (p < 0.05) in stem diameter across the four water regimes in all four varieties. 3.1.1 plant height tms 980505 and 920326 had the highest coefficients of correlation (r2 > 0.50) for 25 % regime while they had the least r2 (≤ 0.30) for the 50 % regime (table 2). tms 30572 and 090851 had the highest r2 at 25% regime while they have the least at 75% regime. this means that 25% regime for all the varieties made optimal use of water applied for phenological development than all other water regimes. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):635-646. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 642 table 2. coefficient of correlation (r2) for plant height water regimes (%) variety control 25% 50% 75% tms 30572 0.45 0.50 0.36 -0.20 tms 980505 0.31 0.50 0.25 0.38 tms 920326 0.49 0.57 0.30 0.37 tms 090851 0.28 0.33 0.32 0.05 3.1.2 stem diameter for tms 30572, the r2 increased from 0.20 for the control to 0.30 for the 25% water regime but decreased from 0.32 for the 25% regime to 0.09 for the 50% regime and nosedived to produce a weak negative r2 of -0.20 from 50% regime to 75% water regime (table). tms 980505 had the highest r2 of 0.71 for the 50% water regime and was followed by the control while the 75% regime produced the third highest and the 25% regime produced the least. tms 920326 had the highest r2 of 0.41 for the 50% regime followed by 75% water regime while the 25% regime produced the third highest and the control regime produced the least. tms 090581 had an r2 which decreased gradually from 0.46 for the control to 0.29 for the 25% water regime, 0.28 and 0.23 for 50% and 75% water regimes respectively. table 3. coefficient of correlation (r2) for stem diameter water regimes (%) variety control 25% 50% 75% tms 30572 0.20 0.32 0.09 -0.20 tms 980505 0.68 0.27 0.71 0.38 tms 920326 0.12 0.16 0.41 0.36 tms 090851 0.46 0.29 0.28 0.23 3.1.3 number of nodes tms 30572 and tms 920326 had r2 which decreased gradually from control to 25 % regime to 50 % regime and to 75 % water regime (table 4). tms 980505 produced a positive correlation which increased from 0.20 for the control to 0.33 for the 25 % water regime, at the 50 % regime; the r2 gave a negative value which further decreased to -0.22 at the 75 % regime. tms 090581 produced a positive correlation in all four regimes, with 25% and 75% regimes producing the highest and the second highest value respectively while the control produced the third highest while the 50% regime produced the least r2. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng awoyode et al: effect of water stress on yield and water productivity of drip irrigated cassava (manihot esculenta) in ibadan, nigeria. azojete, 19(3):635-646. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 643 table 4. coefficient of correlation (r2) for the number of nodes water regimes (%) variety control 25% 50% 75% tms 30572 0.44 0.15 0.14 -0.02 tms 980505 0.20 0.33 -0.17 -0.22 tms 920326 0.70 0.50 0.28 0.26 tms 090851 0.21 0.35 0.20 0.29 3.2 crop productivities there is no significant difference (p > 0.05) in the tuber, stem and leaf productivities of the varieties (table 5). this implies that the varieties can be assumed to produce equal yields of tuber, stem and leaf. there is a significant difference (p < 0.05) in the tuber and stem yields within the regimes. this implies that the difference in tuber and stem yields in tables 5 to 8 were significantly different due to water regimes. there was no significant difference (p > 0.05) in leaf productivity within the regimes. the significant difference within the regimes for tuber and stem productivity can be attributed to cassava’s characteristic of storing a larger part of its dry matter and water in its root and stem (carvalho et al., 2017). table 5. water productivities for tms 30572 parameters water regime control t25 t50 t75 water applied (m3 ha-1) 3433 3704 3955 4268 tuber yield (kg ha-1) 549 2667 3797 5292 tuber productivity (kg m-3) 0.16 0.72 0.96 1.24 stem yield (kg ha-1) 721 1408 1384 1408 stem productivity (kg m-3) 0.21 0.38 0.35 0.33 leaf yield (kg ha-1) 721 2371 2690 2219 leaf productivity (kg m-3) 0.21 0.64 0.68 0.52 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):635-646. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 644 3.2.1 effect of water stress on tuber yield the control and t25 produced the lowest tuber yield and subsequently least tuber productivity while t50 and t75 regimes produced much better tuber yield and tuber productivity (tables 5 to 8). tuber yield of tms 30572 at t25, t50 and t75 increased significantly by 385.8%, 591.6% and 863.9% respectively (table 5). tuber yields of tms 980505 at t25 decreased significantly by 18.3% and increased significantly at t50 and t75 by 91.5% and 363.7% respectively (table 6). tuber yields of tms 920326 at t25, t50 and t75 increased significantly by 16.9%, 461.7% and 412.7% respectively (table 7). tuber yields of tms 090581 at t25, t50 and t75 increased significantly by 452.9%, 864.8% and 552.6% respectively. table 6. water productivities for tms 980505 water regime control t25 t50 t75 water applied (m3 ha-1) 3433 3704 3955 4268 tuber yield (kg ha-1) 2540 2074 4865 11779 tuber productivity (kg m-3) 0.74 0.56 1.23 2.76 stem yield (kg ha-1) 1064 1593 2690 7085 stem productivity (kg m-3) 0.31 0.43 0.68 1.66 leaf yield (kg ha-1) 1545 2852 4786 8792 leaf productivity (kg m-3) 0.45 0.77 1.21 2.06 table 7. productivities for tms 920326 water regime control t25 t50 t75 water applied (m3 ha-1) 3433 3704 3955 4268 tuber yield (kg ha-1) 824 963 4628 4225 tuber productivity (kg m-3) 0.24 0.26 1.17 0.99 stem yield (kg ha-1) 1339 1519 1147 2177 stem productivity (kg m-3) 0.39 0.41 0.29 0.51 leaf yield (kg ha-1) 1991 2260 1899 3073 leaf productivity (kg m-3) 0.58 0.61 0.48 0.72 table 8. productivities for tms 090581 parameters water regime control t25 t50 t75 water applied (m3 ha-1) 3433 3704 3955 4268 tuber yield (kg ha-1) 824 4556 7950 5378 tuber productivity (kg m-3) 0.24 1.23 2.01 1.26 stem yield (kg ha-1) 1613 2556 1463 3030 stem productivity (kg m-3) 0.47 0.69 0.37 0.71 leaf yield (kg ha-1) 2780 3222 1938 3628 leaf productivity (kg m-3) 0.81 0.87 0.49 0.85 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng awoyode et al: effect of water stress on yield and water productivity of drip irrigated cassava (manihot esculenta) in ibadan, nigeria. azojete, 19(3):635-646. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 645 4 conclusion the study showed that irrigation is necessary for cassava cultivation during the dry season. this is because there were significant differences (p < 0.05) in the tuber and stem productivities within the water regimes. based on the water productivity of the cassava tuber, stem and leaf productivities, tms 980505 performed more than the other varieties and is therefore recommended for farmers during the dry season using a drip irrigation system. tms 30572 was the most stressed variety as seen in its phenological growth parameters in the control. it is, therefore, not suitable to be grown in water-scarce regions. tms 090851 didn’t exhibit variations in stem and leaf yield across the water regimes. therefore, it is recommended for smallholder cassava farmers in water-scarce regions because of its high resistance to drought. references aderemi, am., adedipe, jo., oyewo, io., ewemoje, ta. and balogun, la. 2018. determination of water productivity of cassava in ibadan, south western nigeria. arid zone journal of engineering and technology, 14(4): 237-246. alfredo, ac., alves, aac. and tim, ls. 2000. response of cassava to water deficit: leaf area growth and abscisic acid. crop science, 40:133–137. allen, rg., pereira, ls., raes, d. and smith, m. 1998. crop evapotranspiration-guidelines for computing crop water requirements. food and agriculture organization, italy, rome, pp. 339. ali, mh. 2010. fundamentals of irrigation and on-farm water management. springer, https://doi.org/10.1007/978-1-4419-6335-2 luiz, jcbc., josefino, ff., james, va., priscila, gf. and songbi, c. 2017. storage root of cassava: morphological types, anatomy, formation, growth, development and harvest time. in w. viduranga (ed.), cassava (pp. ch. 4). intechopen, london, uk. edoga, rn. and edoga, mo. 2006. design of drip irrigation set for small vegetable gardens. notulae botanicae horti agrobotanici cluj napoca, 34:134-139. egbinola, cn. and amobichukwu, ac. 2013. climate variation assessment based on rainfall and temperature in ibadan, south-western, nigeria. journal of environment and earth science, 3(11): 32-45. ewemoje, ta., tayo, ba. and afolayan, io. 2015. determination of yield response factor of four improved cassava varieties under rain-fed tropical environment. proceedings of the nigerian institute of industrial engineers (niie) 2015, international conference at the university of ibadan, 26 – 28 november, 2015. pp., 31 – 37 ewemoje, ta. and ewemoje, os. 2011. best distribution and plotting positions of daily maximum flood estimation at ona river in ogun-oshun river basin, nigeria. agricultural engineering international: cigr journal, 13(3):1-13. fao. 2013. save and grow cassava: a guide to sustainable production intensification. food and agriculture organization of the united nations, rome faostat, 2005. statistical database of the food and agricultural organization of the united nations, rome. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng https://doi.org/10.1007/978-1-4419-6335-2 arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):635-646. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adeboyeob@oauife.edu.ng 646 fuglie, ko. 2004. challenging bennet’s law: the new economics of starchy staples in asia. food policy, 29(2): 187-202. https://doi.org/10.1016/j.foodpol.2004.03.003 greenwater, 2014. water management tools for cassava growers in ganze subdivision, kilifi, kenya. technical report, greenwater, nairobi, kenya henry, g. and hershey, c. 2001. cassava in south america and the caribbean. cabi. pp. 17-40. 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(eds.)). cassava: biology, production and utilization, cabi publishing oxon, uk and new york, usa, pp. 40-54. pp. 40-54. https://doi.org/10.1079/9780851995243.0041 james, b., yaninek, j., neuenschwander, p., cudjoe, a., modder, w., echendu, n. and toko, m. 2000. pest control in cassava farms. wordsmithes printers, lagos. kijne, jw., barker, r. and molden, d. 2003. water productivity in agriculture: limits and opportunities for improvement. cab. international, wallingford, uk. mabrouk, a., el-sharkawy, ma. and james, hc. 1987. response of cassava to water stress. plant and soil, 100: 345–360. odubanjo, oo., olufayo, aa. and oguntunde, pg. 2011. water use, growth, and yield of drip irrigated cassava in a humid tropical environment. soil and water research, 6(1): 10-20. oguntunde, pg. 2005. whole-plant water use and canopy conductance of cassava under limited available soil water and varying evaporative demand. plant and soil, 278: 371–383. onwueme, ic. 2002. cassava in asia and the pacific. 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(eds.)). cassava: biology, production and utilization, cabi publishing, oxon, uk and new york, usa, pp. 55-65 phillip, ta., taylor, dp., sanni, lo., akoroda, m., ezedinm, c., dixon, a., okoro, e. and tarawali, g. 2005. the nigerian cassava industry handbook, international institute of tropical agriculture, ibadan, nigeria. sander, jz., bastiaanssen,w. and wim, gm. 2004. review of measured crop water productivity values for irrigated wheat, rice, cotton and maize. agricultural water management, 67:115-133. zhang, h. and owie, t. 1999. water-yield relations and optimal irrigation scheduling of wheat in the mediterranean region. agricultural water management, 38:195–211 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adeboyeob@oauife.edu.ng https://doi.org/10.1016/j.foodpol.2004.03.003 https://doi.org/10.1079/9780851995243.0017 https://doi.org/10.1079/9780851995243.0041 corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 589 arid zone journal of engineering, technology & environment original research article investigation of plantain extract for enhancing copper durability in acid-based corrosive environments o.s.i. fayomi1, 2* 1department of mechanical engineering, bells university of technology, p.m.b. 1015, ota, ogun state, nigeria 2department of mechanical engineering science, university of johannesburg, auckland park, kingsway campus, johannesburg, south africa p. o. box 534, johannesburg, south africa *corresponding author’s email: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng article information abstract this study investigates the application of plantain peduncle extract (ppe) as a green corrosion inhibitor of copper in 1 m hydrochloric acid (hcl) using electrochemical, adsorption, and surface analysis techniques. ethanol-extracted ppe was tested at concentrations of 0.1–0.3 ml and temperatures of 30–50°c. electrochemical tests, such as potentiodynamic polarization and open circuit potential (ocp) measurement, proved ppe to inhibit corrosion current density (jcorr) by a maximum of 88% and anodically shift corrosion potential (ecorr), with the maximum inhibition efficiency of 89.5% occurring at 0.3 ml ppe and 40°c. similarly, adsorption experiments confirmed that freundlich isotherm (r² = 0.906 at 40°c) best described the process, indicating heterogeneous multilayer physisorption, also confirmed by gibbs free energy values (δgads = -16.58 to 19.78 kj/mol). in addition, optical micrographs confirmed these findings, with minimal pitting and smooth surfaces in ideal conditions (0.3 ml ppe, 40°c), compared to extensive corrosion in uninhibited samples. statistical comparison using analysis of variance, (anova) revealed the significant influence of concentration (p < 0.0001) and temperature (p = 0.0048), with their interaction (p = 0.0213) showing the necessity of balanced operating parameters. while ppe functioned well under middle temperatures, efficiency reduced at 50°c (ie% = 80.2%), reflecting thermal limitations. received: 29th april 2025 revised: 4th may 2025 accepted: 4th may 2025 keywords: copper corrosion inhibition optimization plantain peduncle extract © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction corrosion is the natural degradation of materials in various situations, which is undesirable. scientifically, it is described as the simultaneous exchange of mass and charge at the material-solution interface (frankel, 2014). in other words, it is the attack on metal through biological or electrochemical interactions with its surrounding environment corrosion is among the processes with which man has had to cope ever since engineering materials have been extensively utilised (bilgiç, 2023; farag et al., 2022; mccafferty, 2010). preventing engineering materials from corroding is a significant challenge in the industrial sector (savita et al., 2016). the effects of corrosion have evolved into a persistent and major issue on a global scale (roberge & eng, 2005). copper and its alloys are widely utilized in industrial applications owing to their superior mechanical properties, necessitating a focus on their corrosion behaviour (tan et al., 2023). while copper resists atmospheric and chemical degradation through a naturally forming protective oxide layer, it becomes highly prone to corrosion in acidic, chloride-rich environments, such as during acid cleaning treatments (zhang et al., 2018). to address this vulnerability, corrosion inhibitors—chemical additives that minimize metal degradation—are critical (tamalmani & husin, 2020; olajire, 2017). these inhibitors fall into two categories: inorganic (e.g., chromates) and organic (e.g., plant extracts), each tailored to specific corrosive conditions (wu et al., 2024). azojete june 2025. vol.21(2):589-600 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/023 www.azojete.com.ng mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 590 however, the traditional corrosion inhibitors currently employed are susceptible to environmental pollution as a result of high toxicity (qiang et al., 2018). with the evolution of green chemistry and growing concern for environmental health, the development and investigation of eco-friendly and efficient corrosion inhibitors have become a crucial focus in recent times (asadi et al., 2019). corrosion inhibitors need to be cost-effective and safe, making plant extracts an environmentally friendly, readily available, and renewable option. these represent a rich source of ingredients, having a high inhibition efficiency (raja et al., 2008). extensive research has been conducted to identify green corrosion inhibitors that are more cost-effective than the toxic inhibitors traditionally used (zdravković et al., 2023; kehinde et al., 2025) a study by wu et al., (2024) investigating ipomoea batatas leaf extract as a biodegradable corrosion inhibitor for copper in 0.5m h2so4 s solution concluded that the electrochemical tests revealed a remarkable inhibition efficiency of 96.7% with an 800 mg/l concentration of ible. despite an increase in temperature, ible continued to exhibit high anti-corrosion performance with an efficiency of over 95% at a temperature of 315 k (wu et al., 2024). another study by dahmani et al., (2023) reveals that an electrochemical impedance spectroscopy evaluation shows that the inhibitor efficiency increases with increased inhibitor concentrations and reaches 94% efficiency with the use of 2 g/l of cupressus sempervirens (eo), supported by potentiodynamic polarization studies. plantain extract has been studied by es’hagi et al., (2018) as an eco-friendly corrosion inhibitor on mild steel in 1m hcl solution, confirming its potential as an eco-friendly corrosion inhibitor. similarly, essang (2022) investigated plantain peduncle extract as a corrosion inhibitor for mild carbon steel and reported reduced weight loss and corrosion rates across inhibited samples. the highest inhibition efficiency was observed at a 3.0% v/v concentration, followed by 2.0% v/v. however, no prior studies have specifically examined plantain extract as a corrosion inhibitor for copper. to address this gap, the objective of this research is to evaluate the inhibitory properties of plantain extract on copper in a 1 m hcl medium 2. materials and method 2.1 preparation of materials the test copper samples were machined using a manual lathe machine (jet ghb-1340a) to achieve the desired (4×2×0.3) cm dimension. the dimensioned samples were mechanically polished using emery paper, washed with ethanol before being dried. a 1 m hydrochloric acid (hcl) solution was prepared in the laboratory by diluting concentrated hcl (37% w/w, analytical grade) with deionized water, using a calibrated volumetric flask to ensure precise molarity. fresh plantain peduncles were obtained from local markets in ogun state, nigeria, as agricultural waste in order to make the inhibitor. to guarantee uniform drying and effective extraction of bioactive components, the peduncles were manually cut into 1-2 cm segments using a sterile stainless-steel blade after being properly cleaned with distilled water to eliminate surface contaminants. they were then further sliced into 0.3-0.5 cm thick cross-sections. to prepare the inhibitor, the plantain peduncle was obtained from the waste, washed thoroughly with distilled water and then cut reduced to. they were then placed in an oven at 60℃ to dry for 10 hours and ground into fine powder using a blender. a mixture of a 70% ethanol-water solution and the dried plantain powder is combined in a ratio of 1:10 (w/v). to ensure homogeneity, the mixture was mechanically stirred for 30 minutes at 300 rpm using a magnetic stirrer. this was followed by a 24-hour equilibration phase at room temperature to promote the diffusion of phytochemicals. it was then filtered with a filter paper. the resulting extract of plantain peduncle was placed in an evaporator to concentrate the extract. table 1a shows the compositional properties of the copper coupons, which were dimensioned to (4×2×0.3cm). table 1b show the present phytochemicals in the plantain extract. similar methodology was carried out by oyewole et al., (2025). table 1a: chemical composition of copper sample element m (mass%) ×10⁻³ si 7 p 16.5 ti 0.4 v 0.3 mn 2.65 sb 0.6 co 0.15 ni 2.8 nb 1.6 mo 1.1 sn 2.7 cu bal. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 591 table 1b: phytochemicals present in the plantain extract phytochemical plantain extract alkaloid + flavonoid saponin phenol terpenoid + phlobatannin steroid + + rep. present – rep. absent 2.2 experimental procedures the electrode employed as the working electrode for the electrochemical experiments is the already polished and dimensioned copper samples. the tests were carried out in batches of 50ml 1m hcl solutions at a temperature of 30℃ (303k). the plantain peduncle extract (ppe) was added to the acidic corrosion medium in different volumes of 0.1ml, 0.2ml, 0.3ml, and the control solution with 0ml. table 2 shows the experimental setup of the samples table 2: experimental arrangement experimental arrangement test environment control (0.0 ml ppe) 50ml hcl 0.1ml ppe 0.1ml ppe + 50ml hcl 0.2ml ppe 0.2ml ppe + 50ml hcl 0.3ml ppe 0.3ml ppe + 50ml hcl 2.3 electrochemical test set-up the tests were carried out in line with astm g5-14 and astm g59-97 standards using a three-electrode setup within a study cell, comprising a copper working electrode, a graphite counter electrode, and a reference electrode filled with kcl. the autolab pgstat 101 metrohm potentiostat (plate 1) was used for potentiodynamic linear polarization tests on the copper samples. the scanning speed used in this study was 0.01 mv/s in the sinusoidal voltage range of 1.5 v to +1.5 v. in all the experimental conditions, the stability of the free potential was ensured. corrosion parameters such as corrosion potential (ecorr), the corrosion current density (jcorr), inhibition efficiency (ie%), and the surface coverage were determined from tafel plots in addition to the use of equations 1 and 2. further, adsorption behavior of the inhibitor was studied based on some models that included langmuir, freundlich, and temkin isotherms. surface coverage (θ) = 𝑗0𝑐𝑜𝑟𝑟 – 𝑗𝑐𝑜𝑟𝑟 𝑗0𝑐𝑜𝑟𝑟 1 % ie = 𝑗0𝑐𝑜𝑟𝑟 – 𝑗𝑐𝑜𝑟𝑟 𝑗0𝑐𝑜𝑟𝑟 × 100 2 where j0corr and jcorr are the corrosion current densities with and without the inhibitor, respectively. 2.4 surface characterisation the copper (4×2×0.3cm) was dipped in 50ml hcl acid solution at varying temperatures of 30℃, 40℃, and 50℃, both without the ppe (control) and at the different volumes of 0.1ml, 0.2ml, and 0.3ml, and polarisation was applied. metallurgical microscopy (olympus bx53m) was deployed to study the surface morphology of the inhibited copper samples. 2.5 statistical analysis statistical analysis was conducted using design expert software 13. mathematical regression models and response surface methodology (rsm) were used to evaluate and predict the performance of the inhibitor. analysis of variance (anova) also assessed the significance of the input experimental variables on the response properties, providing critical insights for optimizing the process. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 592 plate 1: electrochemical setup 3. results and discussion 3.1 response of uninhibited and inhibited test samples to corrosion the tafel polarisation and open circuit potential (ocp) measurements were used to assess the electrochemical behaviour of copper in 1 m hcl, both uninhibited and inhibited with plantain peduncle extract (ppe). table 3 shows some important patterns in corrosion metrics at different inhibitor concentrations (0– 0.3 ml) and temperatures (30–50°c). with a corrosion potential (ecorr) of -0.625 v, a corrosion current density (jcorr) of 1.94×10⁻⁴ a/cm², and a corrosion rate (cr) of 2.27 mm/year, the control sample showed aggressive corrosion at 30°c. significant anodic inhibition was indicated by ecorr shifting favourably to -0.091 v (0.3 ml), jcorr decreasing to 1.06×10⁻⁴ a/cm², and cr decreasing by about 45% as the ppe concentration increased (aslam et al., 2022). as a result of impeded charge transfer reactions, polarisation resistance (pr) also increased from 134 ω (control) to 246 ω (0.3 ml). table 3: inhibited samples tafel data figure 1 illustrates the open circuit potential (ocp) of copper in 1 m hcl at 30℃ for various concentrations of ppe (0–0.3 ml). the control sample (0 ml ppe) records a highly negative potential (-0.625 v), an indicator of active corrosion. with rising inhibitor concentration, the ocp shifts more and more towards positive directions (e.g., -0.091 v at 0.3 ml), an indicator of surface stabilization by adsorption of the inhibitor. stabilization is quicker at high concentration, suggesting rapid development of a protective film. for 40℃, the ocp plot (figure 2) shows maximum value of positive shift potential (-0.364 v for control to -0.135 v for 0.3 ml ppe), demonstrating maximum inhibition efficiency (89.5%). the plateau potentials at the higher concentrations indicate good adsorption, likely due to greater molecular interaction between the copper 30℃ samples ecorr (v) jcorr (a/cm2) cr (mm/yr) pr (ω control -0.625 1.94e-04 2.27 1.34e+02 0.1ml -0.318 1.81e-04 2.12 1.44e+02 0.2ml -0.175 1.08e-04 1.26 2.41e+02 0.3ml -0.091 1.06e-04 1.24 2.46e+02 40℃ control -0.364 4.55e-04 5.34 5.71e+01 0.1ml -0.292 3.02e-04 3.08 9.91e+01 0.2ml -0.152 8.26e-05 0.97 3.15e+02 0.3ml -0.135 5.60e-05 0.75 4.64e+02 50℃ control -0.341 5.13e-04 6.02 5.07e+01 0.1ml -0.247 3.598e-04 3.61 8.45e+01 0.2ml -0.127 2.62e-04 2.95 1.03e+02 0.3ml -0.083 9.76e-05 1.15 2.66e+02 http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 593 surface and ppe at this intermediate temperature. the ocp curve at 50℃ (figure 3) indicates less positive shift (-0.341 v for control to -0.083 v at 0.3 ml ppe), suggesting decreased inhibitor efficiency. thermal agitation likely ruins the adsorbed film of the inhibitor and leads to partial desorption and weaker surface protection (shwetha et al., 2024). figure 1: ocp plot at 30℃ figure 2: ocp plot at 40℃ figure 3: ocp plot at 50℃ the linear sweep voltammetry (lsv) scans at 30℃ yield suppressed anodic currents with improved ppe concentrations, figure 4. the control sample yields a steep anodic slope, indicating quick metal dissolution. with 0.3 ml ppe, the anodic current density falls quickly, displaying considerable suppression of copper oxidation. at 40℃ (figure 5), the lsv plot yields the greatest suppression of anodic and cathodic currents. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 594 the curves become flatter at 0.3 ml ppe, which indicates mixed-type inhibition. decrease in cathodic current shows that hydrogen evolution is also inhibited by ppe, and the nearly horizontal anodic segment shows good blocking of metal dissolution. lsv plot at 50℃ (figure 6) shows partial recovery of anodic and cathodic currents even at 0.3 ml ppe, indicating thermal degradation of the inhibitor film. the anodic slope remains more sloping than at 40℃, and the cathodic currents are less repressed, showing disordered adsorption. figure 4: lsv plot at 30℃ figure 5: lsv plot at 40℃ figure 6: lsv plot at 50℃ http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 595 3.2 plantain peduncle extract inhibitory efficiency the efficacy of the plantain peduncle extract on copper in a 1m hcl acidic solution can be further examined from the plot of inhibitory efficiency (ie) % against inhibitor concentration (ml) in figure 7. it can be observed that an increase in the concentration of the inhibitor generally increases inhibitor efficiency, with the trend strongest at 50℃. at 40℃ and 50℃, the increase in inhibitor concentration from 0.2ml to 0.3ml shows only slight increase in inhibitor efficiency, suggesting that after corrosion inhibition with 0.2ml at 40℃, plantain peduncle inhibition becomes negligible. however, corrosion inhibition was most effective across 40℃, suggesting it to be the optimal temperature for the inhibition process. rahal et al. (2016) examined olive leaf extract (ole) as a corrosion inhibitor for copper in 0.5 m nacl, and their results are consistent with the inhibitory efficiency trend seen in this work. both investigations show concentration-dependent ie%; rahal et al. used 2.42 mm ole to achieve ~90% efficiency at 24 hours. similarly, at 40°c and 0.3 ml, plantain peduncle extract (ppe) in this study achieved 89.5% ie. however, ppe showed decreased efficacy at 50°c (ie% = 80.2%), most likely as a result of thermal desorption of physisorbed chemicals, whereas rahal et al. found sustained ie% at greater temperatures (up to 328 k). in contrast, ole's cathodic inhibitory mechanism preserved a high ie% because of oleuropein's strong adsorption. figure 7: inhibitor efficiency of plantain peduncle. 3.3 adsorption response of copper samples the adsorption behaviour of plantain peduncle extract (ppe) on copper surfaces in 1 m hcl was studied using langmuir, freundlich, and temkin isotherm models to describe the inhibition process. freundlich isotherm (table 4) had the best correlation at 40°c (r² = 0.906), indicating heterogeneous adsorption with multilayer formation (al-ghouti & da'ana, 2020). this shows that ppe molecules adsorb on copper through multiple surface sites of varying affinities due to the complex phytochemical nature of the extract (foo & hameed, 2010). in contrast, the langmuir model (r² = 0.572–0.804) poorly described the data, dismissing the hypothesis of monolayer adsorption over homogeneous surfaces (stefaniu et al., 2014). table 4: adsorption parameters from the langmuir and freundlich isotherm. temperature (℃) kads(mol-1) r2 langmuir adsorption isotherm 30 0.579093767 0.572488467 40 6.10392394 0.803656758 50 4.617737838 0.621181637 freundlich adsorption isotherm 30 5.668432644 0.87279269 40 2.121607455 0.906101717 50 1.549941388 0.896110591 temkin isotherm (r² = 0.840–0.919 for 40–50°c) also highlighted adsorbate-adsorbate interaction role as its linearity implied reducing adsorption energy with coverage due to repulsive forces (table 5) (johnson & arnold, 1995; ayawei et al., 2017). thermodynamic study revealed gibbs free energy (δgads) ranges of -16.58 to -19.78 kj/mol, which is characteristic of spontaneous physisorption driven by weak van der waals forces rather than chemisorption (rouquerol et al., 2013). temperature dependence of the rise in adsorption equilibrium constants (kads) at 40°c (29.66 mol⁻¹) and 50°c (28.44 mol⁻¹) also revealed stronger inhibitorhttp://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 596 surface interaction with rising temperature, though thermal agitation at 50°c might have reduced adsorption stability (ituen et al., 2017). table 5: adsorption parameters from the temkin isotherm. temp. (ᵒc) kads(mol-1) δgads (kjmol1) r2 ln(kads) 1/t δgads/t b= slope 30 13.0113 -16.5845 0.8801 2.5658 0.0033 -0.0547 0.3737 40 29.6603 -19.2765 0.9194 3.3898 0.0032 -0.0616 0.4158 50 28.4378 -19.7793 0.8400 3.3477 0.0031 -0.0612 0.3489 the transition from temkin-controlled adsorption at 30°c to freundlich-controlled behavior at higher temperatures is in line with enhanced molecular mobility and multilayer development at intermediate temperatures (40°c), at which ppe exhibited highest inhibition efficiency (89.5%). this temperature sensitivity indicates the balance between adsorption intensity and thermal degradation of the protective film similar to the study by atiba & fayomi, (2024). figure 8 plots surface coverage (θ) against the natural logarithm of inhibitor concentration (ln c) to analyze adsorption behavior. at 30°c, the lower slope suggests weaker adsorption, aligning with temkin’s model (ayawei et al., 2017; kehinde et al., 2025), which accounts for repulsive interactions at low coverage. figure 8: a graph of θ against ln c. 3.4 optical micrographs the optical micrographs of the copper samples exposed to a corrosive environment are displayed in plate 2(a-d). the surface showed clear evidence of corrosion in the absence of the inhibitor (plate 2(a)). the addition of different amounts of the ppe (plate 2(b-c)) showed surface features with minimal corrosive behaviour and therefore indicated a good inhibition effect. plate 2(d) displays similar surface features; however, slight pitting was observed at the highest inhibitor concentration. 3.5 empirical optimization to systematically evaluate the inhibitory performance of plantain peduncle extract (ppe) on copper in 1 m hcl, the study employed two critical operating parameters: inhibitor concentration (0.0–0.3 ml in 50 ml hcl) and temperature (30–50°c). these parameters were selected to reflect realistic industrial conditions while probing the thermal stability and dose-dependent efficacy of ppe. lower concentrations (0.1–0.3 ml) tested the extract’s ability to mitigate corrosion at minimal doses. table 6 lists the experimental data from the iterations of the operational parameters. it shows that the highest corrosion rate (cr) occurs at 60℃ without any inhibitor, which aligns with increase in corrosion with temperature. also, the lowest corrosion rate is recorded at 40℃ with 0.3ml of the plantain peduncle inhibitor, with a value of 0.75 mm/yr. table 7 displays the data of the analysis of variance (anova) for the designed experiment, investigating the effects of concentration and temperature and their interaction on the rate of corrosion as the response variable. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 597 (a) (b) (c) (d) plate 2 (a-d): optical micrographs of copper samples (control, 0.1ml, 0.2ml, 0.3ml). table 6: design of experiment (dof) data factor a: concentration (g) factor b: temperature (ᵒc) response 1: cr (mm/yr) 0 30 2.27 0.1 30 2.12 0.2 30 1.26 0.3 30 1.24 0 40 5.34 0.1 40 3.08 0.2 40 0.97 0.3 40 0.75 0 50 6.02 0.1 50 3.61 0.2 50 2.95 0.3 50 1.15 the p-value for the model is 0.0002, which is much less than 0.05, indicating that the model is statistically significant. also, the f-value for the model is 25.11, which further supports the significance of the model. the concentration parameter gave an ss value of 20.53, an f-value of 52.28, and a p-value < 0.0001. this indicates that factor a (concentration) has a highly significant effect on the response variable. similarly, the temperature parameter gave an ss value of 5.85, an f-value of 14.89, and a p-value = 0.0048. this indicates that factor b (temperature) also has a significant effect on the response variable. the p-value of 0.0213 for ab interaction indicates that the interaction between a and b is statistically significant, meaning the effect of one factor depends on the level of the other factor. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 598 the fisher test was utilized in the evaluation of the statistical measurements by way of comparison of the model’s mean square values with its residue and validate the sensitivity and repeatability of the model in figure 9. to optimize efficiency of the ppe inhibitor, a central composite design (ccd) was used to generate a firstorder polynomial regression model that explains the combined effect of concentration and temperature on the corrosion rate in equation 3. the high r² (90.40%) and adjusted r² (86.80%) values suggest that the model fits the data well. the predicted r² likewise (79.73%) indicates that the model has good predictive capability. furthermore, the relatively low cv% (24.45%) suggests that the experimental data is precise and reliable table 7: anova data for the optimized copper response to ppe inhibition source ss df ms f-value p-value remark model 29.59 3 9.86 25.11 0.0002 sig. a-conc. 20.53 1 20.53 52.28 < 0.0001 b-temp. 5.85 1 5.85 14.89 0.0048 ab 3.2 1 3.2 8.16 0.0213 residual 3.14 8 0.3928 cor total 32.73 11 r2 = 90.40%; adjusted r2 = 86.80%; predicted r2 = 79.73%; cv%= 24.45 ** sssum of square; dfdegree of freedom; msmean square; sig.significant** cr = 2.563 – 1.755a + 0.855b – 0.849ab (3) figure 9: effect of plantain peduncle extract concentration and temperature on the rate of corrosion on sample copper 4. conclusion the results of this study unequivocally show that plantain peduncle extract (ppe) is an effective green corrosion inhibitor for copper in 1 m hcl. according to electrochemical measurements, the corrosion rate (cr) decreased from 5.34 mm/yr (control) to 0.75 mm/yr, with 0.3 ml ppe at 40°c achieving the best inhibition efficiency (ie% = 89.5%). this performance is in line with environmentally friendly goals and outperforms many synthetic inhibitors. the adsorption process, which is primarily driven by physisorption (δgads = -19.28 kj/mol), was corroborated by the freundlich isotherm (r2 = 0.906 at 40°c). the efficiency of ppe decreased at 50°c (ie% = 80.2%, cr = 1.15 mm/yr), despite its strong inhibition at intermediate temperatures. this highlights thermal constraints brought on by possible desorption or molecular breakdown. the importance of temperature (p = 0.0048) and concentration (p< 0.0001) was validated statistically using anova. their interaction (p = 0.0213) underscored the necessity of balanced operating parameters. these findings support the industrial use of ppe in mild-to-moderately acidic conditions, but temperature control is still essential. to improve thermal stability and expand their application to harsher environments, future research should optimise extraction processes. this study provides a workable substitute for harmful synthetic inhibitors by bridging sustainable innovation with real-world corrosion prevention. 30 35 40 45 50 0 0.06 0.12 0.18 0.24 0.3 0 1 2 3 4 5 6 7 c r ( m m /y r) a: conc. (ml)b: temp. (c) 0.802333 3d surface factor coding: actual cr (mm/yr) design points: above surface below surface 0.75 6.02 x1 = a x2 = b http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 599 references al-ghouti, ma. and da’ana, da. 2020. guidelines for the use and interpretation of adsorption isotherm models: a review. journal of hazardous materials, 393(1): 122–129. asadi, n., ramezanzadeh, m., bahlakeh, g. and ramezanzadeh, b. 2019. utilizing lemon balm extract as an effective green corrosion inhibitor for mild steel in 1m hcl solution: a detailed experimental, molecular dynamics, monte carlo and quantum mechanics study. journal of the taiwan institute of chemical engineers, 95(1): 252–272. aslam, r., mobin, m., zehra, s. and aslam, j. 2022. a comprehensive review of corrosion inhibitors employed to mitigate stainless steel corrosion in different environments. journal of molecular liquids, 364(2): 119–122. atiba, jo. and fayomi, osi. 2024. corrosion resistance and inhibition behavior of aa6063 in acidic chloride medium: a study using amoxicillin and griseofulvin. chemical data collections, 10(1): 10–17. ayawei, n., ebelegi, an. and wankasi, d. 2017. modelling and interpretation of adsorption isotherms. journal of chemistry, 2017(1): 10–13. bilgiç, s. 2023. plant extracts as corrosion inhibitors against copper corrosion – an overview. international journal of corrosion and scale inhibition, 12(3): 1224–1260. dahmani, k., galai, m., ech-chebab, a., al-zaqri, n., ouakki, m., elgendy, a., ... and cherkaoui, m. 2023. investigating the inhibitory properties of cupressus sempervirens extract against copper corrosion in 0.5 m h₂so₄: combining quantum (density functional theory calculation–monte carlo simulation) and electrochemical-surface studies. acs omega, 8(27): 24218–24232. essang, np. 2022. investigation of the inhibition properties of plantain peduncle on the corrosion rate of mild carbon steel. journal of scientific research and reports, 10(1): 1–4. es’haghi, m., amjad, a., asghari, s. and lotfi, a. 2018. studying effect of plantain extract behavior as an ecofriendly corrosion inhibitor on the mild steel in 1 m hcl solution. anti-corrosion methods and materials, 65(3): 310–316. farag, aa., toghan, a., mostafa, ms., lan, c. and ge, g. 2022. environmental remediation through catalytic inhibition of steel corrosion by schiff’s bases: electrochemical and biological aspects. catalysts, 12(8): 838– 841. foo, ky. and hameed, bh. 2010. insights into the modeling of adsorption isotherm systems. chemical engineering journal, 156(1): 2–5. ituen, e., akaranta, o. and james, a. 2017. evaluation of performance of corrosion inhibitors using adsorption isotherm models: an overview. chemical science international journal, 18(1): 1–4. johnson, r.d. & arnold, f.h. 1995. the temkin isotherm describes heterogeneous protein adsorption. biochimica et biophysica acta (bba) protein structure and molecular enzymology, 1247(2): 293–297. kehinde, ei., fayomi, osi. and atiba, jo. 2025. corrosion behaviour of aa6063 alloy in acidic chloride conditions: inhibition by pennisetum glaucum extract. journal of bioand tribo-corrosion, 11(2): 1–4. mccafferty, e. 2010. introduction to corrosion science. springer science & business media. olajire, aa. 2017. corrosion inhibition of offshore oil and gas production facilities using organic compound inhibitors – a review. journal of molecular liquids, 248(1): 775–778. oyewole, om., fayomi, os. and atiba, jo. 2024. evaluating palm kernel extract as a green inhibitor for copper corrosion in acidic environments: mechanistic insights and efficiency analysis. 2024 ieee 5th international conference on electro-computing technologies for humanity (nigercon): 1–3. qiang, y., zhang, s., tan, b. and chen, s. 2018. evaluation of ginkgo leaf extract as an eco-friendly corrosion inhibitor of x70 steel in hcl solution. corrosion science, 133(1): 6–9. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 589-600. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 600 rahal, c., masmoudi, m., abdelhedi, r., sabot, r., jeannin, m., bouaziz, m. and refait, p. 2016. olive leaf extract as natural corrosion inhibitor for pure copper in 0.5 m nacl solution: a study by voltammetry around ocp. journal of electroanalytical chemistry, 769(1): 53–56. raja, pb. and sethuraman, mg. 2008. natural products as corrosion inhibitor for metals in corrosive media— a review. materials letters, 62(1): 113–116. roberge, pr. and eng, p. 2005. corrosion engineering: principles and practice. 1st ed., mcgraw-hill education. rouquerol, j., rouquerol, f., llewellyn, p., maurin, g. and sing, k. 2013. adsorption by powders and porous solids: principles, methodology and applications. academic press. savita, et al. 2016. strychnos nuxvomica, piper longum and mucuna pruriens seed extracts as eco-friendly corrosion inhibitors for copper in nitric acid. rsc advances, 6(10): 1–4. shwetha, km., praveen, bm. and devendra, bk. 2024. a review on corrosion inhibitors: types, mechanisms, electrochemical analysis, corrosion rate and efficiency of corrosion inhibitors on mild steel in an acidic environment. results in surfaces and interfaces, 8(1): 100258–100261. stefaniu, c., brezesinski, g. and möhwald, h. 2014. langmuir monolayers as models to study processes at membrane surfaces. advances in colloid and interface science, 208(1): 197–200. tamalmani, k. and husin, h. 2020. review on corrosion inhibitors for oil and gas corrosion issues. applied sciences, 10(10): 3389–3392. tan, l., et al. 2023. interfacial adsorption and corrosion inhibition behavior of environmentally friendly imidazole derivatives for copper in the marine environment. langmuir, 39(7): 2579–2582. wu, y., gong, z., guo, l. and alobaid, a. 2024. batatas lam leaf extract as a biodegradable corrosion inhibitor for copper in 0.5 m h₂so₄ solution. sustainable chemistry and pharmacy, 10(1): 10–13. zdravković, m., et al. 2023. influence of blackberry leaf extract on the copper corrosion behaviour in 0.5 m nacl. bioelectrochemistry, 151(3): 108–111. zhang, j., zhang, l. and tao, g. 2018. a novel and high-efficiency inhibitor of 5-(4-methoxyphenyl)-3h-1,2dithiole-3-thione for copper corrosion inhibition in sulfuric acid at different temperatures. journal of molecular liquids, 272(1): 369–372. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng corresponding author’s email address: omale.paul@uam.edu.ng 903 arid zone journal of engineering, technology & environment original research article stress relaxation behavior of different varieties of potato tubers under compressive mechanical loading p. a. omale1*, j. f. tsanan1, o. h. salaudeen2, and t. o. olanrewaju2 1department of agricultural and environmental engineering, joseph sarwuan tarka university, makurdi, benue state, 2department of biosystems and agricultural engineering, university of kentucky, lexington, usa *corresponding author’s email address: omale.paul@uam.edu.ng article information abstract potatoes tubers obtain several mechanical injuries during its harvesting, handling and storage and the knowledge of the mechanical properties of potatoes is very important for improving these operations. the stress relaxation of three varieties of benue state-grown potato tubers was determined using the universal testing machine to study the behavior of the named varieties; orange potato, purple potato and white potato tubers under loading. the potato tubers were cut into cubes of 2700 mm3 and the stress relaxation was observed under the application of compressive force. it was observed that the compressive stress at total relaxation across the three varieties of potato ranged from 0.040-0.071 mpa with orange potato having the highest value of 0.071 mpa while white potato had the least value of 0.040 mpa. the compressive strain at total relaxation for the three varieties of potato tubers ranged from 0.00010 to 0.00011 mm/mm. the compressive load at total relaxation for the three varieties of potato ranged from 15.937 to 28.293 n. the compressive extension at total relaxation for the three varieties of potato tubers ranged from 0.0015 to 0.0020 mm. the load at total relaxation for the three varieties of potato tubers ranged from 15.937 to 28.293 n. extension at total relaxation for the three varieties of potato tubers ranged from 0.0015 to 0.0020 mm. the maximum compressive stress for the three varieties of potato tubers ranged from 0.133 to 0.188 mpa. the compressive strain at maximum compressive stress for the three varieties of potato tubers ranged from 0.0598 to 0.0601 mm/mm. the compressive load at maximum compressive stress for the three varieties of potato tubers ranged from 53.274 to 75.170 n. the extension at maximum compressive stress for the three varieties of potato tubers ranged from 1.196 to 1.202 mm. load at maximum compressive stress for the three varieties of potato tubers ranged from 53.27 to 75.17 n. anova and duncan test at 95% confidence level revealed there was no significant difference across the stress relaxation of the three varieties of potato tubers investigated. the data generated on the three varieties of potatoes indicate that it is safe if the various potatoes varieties are packaged and transported together, and that this will not cause any mechanical damage to the potatoes. it can be concluded that the various varieties of benue grown potato can use the same post harvest processing and handling machines. these data are also important for maximum efficiency in designing equipment for further processing of potatoes and the reduction of its mechanical damage during postharvest operations such as transportation, packaging and storage of potato tubers. submitted: 14 december, 2023 revised: 11 july, 2024 accepted: 20 july, 2024 keywords: stress strain potato tubers compressive load stress relaxation © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. azojete december 2024. vol.20(4):903-912 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:omale.paul@uam.edu.ng mailto:omale.paul@uam.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 904 1.0 introduction sweet potato (ipomoea batatas l. lam.), is an important economic crop, grown in nearly every corner of the globe, most widely consumed and versatile crop. in 2023, the world produced over 440 million metric tons of potatoes, making it the third most important staple crop after rice and wheat (usda, 2024). china is the largest potato producer, followed by india and russia (fao, 2016) and also ranked the 2nd largest cultivated root crop (7.9 million ha) after cassava worldwide (makos, 2016). sweet potato roots have high nutritional value and sensory versatility in terms of taste, texture, and flesh colour (white, cream, yellow, orange, purple). the varieties with high dry matter (>25%), white‐cream flesh colour, and mealy firm texture after cooking are preferred by consumers in the tropics (ray, 2017). the purple‐fleshed sweet potato varieties with attractive colour and high anthocyanin content are the specialty type in asia. the international potato centre (cip) holds the largest sweet potato gene bank in the world with more than 6.500 wild, traditional and improved varieties. according to fao (2006) statistics, west african sweet potato production stood at 2,516 million metric tons. sweet potato is high in nutritive value, outranking most carbohydrate foods in vitamins, minerals, protein and energy content (onuh et al., 2004). sweet potato serves as a staple food (fleshy roots and tender leaves), snack food, weaning food, animal feed, as well as raw material for industrial starch and alcohol. it is processed into diverse products (udensi, 2000). some of the root and tuber crops cultivated by farmers in the country include cassava, yam and sweet potato. the global, ranking of sweet potato-producing countries showed nigeria to be the largest producer in africa, and the second largest producer in the world after china in 2014, (fao, 2015). it requires fewer inputs and less labour than other crops, is more productive, and is adaptable to marginal growing conditions (drought and poor soils). harvesting, handling and storage of potatoes produce several mechanical injuries therefore the study of mechanical properties is very important for improving the technology of these processes (omale and omobowale, 2018). storage processes produce stress effect and bring about physiological changes and water loss, affecting the mechanical properties. according to mohsenin(1986) and negar (2019), mechanical properties in agricultural products are due to external and internal forces. external forces affect fruits or vegetables when they are subjected to several static and dynamic loads causing mechanical injuries, while internal forces may be a result of physical changes, such as variations in temperature and moisture content, or as a result of chemical and biological changes. different varieties of potatoes are cultivated in benue state and during harvest season, these different varieties are sometimes packaged and transported differently by some farmers while other farmers package and transport them together to the market or processing industries. the benue state potato farmers are not sure of which method is proper for packaging and transporting their harvested potatoes. hence, this study was conducted to investigate the mechanical properties of the various potato varieties grown in benue state so as to provide the benue farmers with data on their engineering properties relevant for transportation and packaging of products. 2. materials and methods 2.1 materials the three varieties of benue-grown potato tubers (orange potato, purple potato, and white potato) used for this study were procured directly from a farm at yaikyo, makurdi, benue state, nigeria and transported in perforated cartons to the centre for energy research and development (cerd), obafemi awolowo university, ile-ife, nigeria, for experimentation. the three varieties of potatoes used are shown on figures 1, 2 and 3 respectively while the major apparatus used was the universal testing machine shown in figure 4. 2.2 methods each of the samples was cut into cubes of ten replications with dimensions of approximately 30 mm by 30 mm by 30 mm. the specimen was fixed up to the jigs of the universal testing machine (figure 4) and the load balanced on the specimen by clicking on the load cell soft key which displayed zero. the extension was set to zero and the extensometer was allowed to balance for the test to begin. the crossed head moved at the specified rate of 1.0 mm/min until the test was stopped. as the end of the test conditions were met, the screen returned to the beginning of the test screen. the extensometer was balanced on the specimen by pulling the http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 905 spring clips back. after the specimen was stretched, the readings were computed automatically by the computer and this procedure was repeated for all the three varieties of potatoes. 3. results and discussion 3.1 results the experimental results data obtained from this study are shown in table 1. http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 906 table 1: mean value of the mechanical properties of the three varieties of potatoes grown in benue state parameters variety n mean std. deviation minimum maximum compressive stress at total relaxation (mpa) orange potatoes 10 0.0707 0.0462 0.0279 0.1631 purple potatoes 10 0.0564 0.0449 0.0046 0.1560 white potatoes 10 0.0398 0.0404 0.0075 0.1394 compressive strain at total relaxation (mm/mm) orange potatoes 10 0.0001 0.0000 0.0000 0.0001 purple potatoes 10 0.0001 0.0000 0.0001 0.0001 white potatoes 10 0.0001 0.0001 0.0000 0.0001 compressive load at total relaxation (n) orange potatoes 10 28.2934 18.4738 11.1531 65.2471 purple potatoes 10 22.5391 17.9497 1.8443 62.4001 white potatoes 10 15.9371 16.1421 3.0062 55.7729 compressive extension at total relaxation (mm) orange potatoes 10 0.0017 0.0006 0.0003 0.0023 purple potatoes 10 0.0020 0.0004 0.0014 0.0024 white potatoes 10 0.0015 0.0009 0.0002 0.0025 load at total relaxation (n) orange potatoes 10 28.2934 18.4738 11.1531 65.2471 purple potatoes 10 22.5391 17.9497 1.8443 62.4001 white potatoes 10 15.9371 16.1421 3.0062 55.7729 extension at total relaxation (mm) orange potatoes 10 0.0017 0.0006 0.0003 0.0023 purple potatoes 10 0.0020 0.0004 0.0014 0.0024 white potatoes 10 0.0015 0.0009 0.0002 0.0025 maximum compressive stress (mpa) orange potatoes 10 0.1879 0.1238 0.0660 0.4010 purple potatoes 10 0.1670 0.1151 0.0712 0.3924 white potatoes 10 0.1332 0.1032 0.0543 0.3887 compressive strain at maximum compressive stress (mm/mm) orange potatoes 10 0.0601 0.0000 0.0600 0.0601 http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 907 purple potatoes 10 0.0599 0.0005 0.0585 0.0601 white potatoes 10 0.0598 0.0006 0.0582 0.0601 compressive load at maximum compressive stress (n) orange potatoes 10 75.1704 49.5288 26.3870 160.3815 purple potatoes 10 66.8140 46.0210 28.4648 156.9669 white potatoes 10 53.2736 41.2770 21.7152 155.4623 compressive extension at maximum compressive stress (mm) orange potatoes 10 1.2017 0.0007 1.2000 1.2023 purple potatoes 10 1.1988 0.0101 1.1701 1.2024 white potatoes 10 1.1955 0.0124 1.1630 1.2024 load at maximum compressive stress (n) orange potatoes 10 75.1704 49.5288 26.3870 160.3815 purple potatoes 10 66.8140 46.0210 28.4648 156.967 white potatoes 10 53.2736 41.2770 21.7152 155.4623 extension at maximum compressive stress (mm) orange potatoes 10 1.2017 0.0007 1.2000 1.2023 purple potatoes 10 1.1988 0.0101 1.1701 1.2024 white potatoes 10 1.1955 0.0124 1.1630 1.2024 3.2 discussion of results the compressive properties of different potato varieties (orange, purple, and white) were evaluated under total relaxation and maximum compressive stress conditions. the results highlight variations in mechanical behavior, which could have implications for storage, processing, and handling. 3.2.1 compressive stress at total relaxation orange potatoes exhibited the highest mean compressive stress at total relaxation (0.0707 mpa), followed by purple potatoes (0.0564 mpa) and white potatoes (0.0398 mpa). the higher stress in orange potatoes suggests greater resistance to deformation, possibly due to differences in cell structure or moisture content. the standard deviation values indicate variability in stress distribution among the samples, with white potatoes showing the least variation. 3.2.2 compressive strain at total relaxation the mean compressive strain at total relaxation was relatively uniform across all varieties, with minimal differences. this suggests that despite variations in stress, the degree of strain upon relaxation remained within a narrow range, indicating similar structural responses after compression. 3.2.3 compressive load at total relaxation orange potatoes required the highest load (28.29 n) to reach total relaxation, while white potatoes required the lowest (15.94 n). this trend aligns with the compressive stress results, reinforcing the observation that orange potatoes exhibit higher mechanical strength. the greater load-bearing capacity of orange potatoes could be advantageous in handling and transportation, reducing susceptibility to mechanical damage. http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 908 3.2.4 compressive extension at total relaxation purple potatoes exhibited the highest mean extension (0.0020 mm), followed by orange (0.0017 mm) and white potatoes (0.0015 mm). the variations in extension values may be attributed to differences in cell wall elasticity and moisture content, with purple potatoes being slightly more extensible before full relaxation. 3.2.5 maximum compressive stress at maximum compressive stress, orange potatoes demonstrated the highest mean value (0.1879 mpa), while white potatoes had the lowest (0.1332 mpa). this indicates that orange potatoes can withstand greater compressive forces before failure, making them mechanically stronger. the differences in stress resistance could be linked to genetic and compositional differences among the varieties. 3.2.6 compressive strain at maximum stress the mean compressive strain at maximum stress remained nearly constant across all varieties, with orange potatoes having a slightly higher value (0.0601 mm/mm) compared to white potatoes (0.0598 mm/mm). the small variations suggest that all three varieties exhibit similar deformation behavior at peak stress. 3.2.7 compressive load at maximum stress the highest compressive load was observed in orange potatoes (75.17 n), followed by purple potatoes (66.81 n) and white potatoes (53.27 n). these results are consistent with the compressive stress findings, indicating that orange potatoes require a significantly higher force to reach their maximum stress threshold. this property may make them more resistant to mechanical damage during storage and transportation. 3.2.8 compressive extension at maximum stress the extension at maximum compressive stress was slightly higher in orange potatoes (1.2017 mm) compared to purple (1.1988 mm) and white potatoes (1.1955 mm). although the differences are minor, they suggest that orange potatoes undergo slightly greater elongation before failure, possibly due to higher turgor pressure or structural differences. 3.2.9 statistical analysis analysis of variance and duncan test were carried out on the result data at a 95% confidence level using spps 2021 packaged (version 20). it revealed that the compression stress, strain, extension at the total relaxation among all other properties investigated are not significantly different across the three varieties of potato tubers (orange potato, purple potato and white potato) as shown in table 2 and figure 5 (a, b, c) displays the graphical results of the compression relaxation test / creep test of the three varieties of potatoes investigated. the result shows that the stress relaxation of the three varieties of benue state grown potatoes were not significantly different as affected by compressive force, the report in this study is the opposite in the case of yam as reported by omale et al. (2021) in their study that investigated the stress relaxation of three varieties of benue state grown yam tubers as affected by compressive force. http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 909 table 2: analysis of variance sum of squares df mean square f sig. compressive stress at total relaxation (mpa) between groups .005 2 .002 1.241 .305ns within groups .052 27 .002 total .057 29 compressive strain at total relaxation (mm/mm) between groups .000 2 .000 1.509 .239 ns within groups .000 27 .000 total .000 29 compressive load at total relaxation (n) between groups 764.597 2 382.299 1.241 .305 ns within groups 8316.350 27 308.013 total 9080.947 29 compressive extension at total relaxation (mm) between groups .000 2 .000 1.643 .212 ns within groups .000 27 .000 total .000 29 load at total relaxation (n) between groups 764.597 2 382.299 1.241 .305 ns within groups 8316.350 27 308.013 total 9080.947 29 extension at total relaxation (mm) between groups .000 2 .000 1.643 .212 ns within groups .000 27 .000 total .000 29 maximum compressive stress (mpa) between groups .015 2 .008 .584 .565 ns within groups .353 27 .013 total .368 29 compressive strain at maximum compressive stress (mm/mm) between groups .000 2 .000 1.128 .339 ns within groups .000 27 .000 total .000 29 compressive load at maximum compressive stress (n) between groups 2442.139 2 1221.069 .584 .565 ns within groups 56473.444 27 2091.609 total 58915.583 29 compressive extension at maximum compressive stress (mm) between groups .000 2 .000 1.139 .335 ns within groups .002 27 .000 total .002 29 load at maximum compressive stress (n) between groups 2442.139 2 1221.069 .584 .565 ns within groups 56473.444 27 2091.609 total 58915.583 29 extension at maximum compressive stress (mm) between groups .000 2 .000 1.139 .335 ns within groups .002 27 .000 total .002 29 note: sig. values with a superscript (ns) show there’s no significant difference at p>0.05 http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 910 figure 5 (a): compression relaxation test / creep test on the orange variety of potatoes figure 5 (b): compression relaxation test / creep test on the pink variety of potatoes figure 5 (c): compression relaxation test / creep test on the white variety of potatoes 4. conclusion the compression test of three varieties of benue state-grown potato tubers (orange, purple, and white) was conducted using a universal testing machine. the results indicate that orange potatoes generally exhibit the highest mechanical strength, followed by purple, while white potatoes have the lowest compressive strength. this suggests that orange potatoes are more resistant to mechanical damage, making them more suitable for extended storage and transportation. the compressive stress relaxation of white potatoes was found to be lower compared to orange and purple varieties. orange potatoes had the highest compressive stress http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 911 relaxation, followed by purple and then white. the compressive stress at total relaxation ranged from 0.040– 0.071 mpa, with orange potatoes having the highest value (0.071 mpa) and white potatoes the lowest (0.040 mpa). similarly, the compressive strain at total relaxation ranged from 0.00010 to 0.00011 mm/mm, while the compressive load at total relaxation varied between 15.937 and 28.293 n. the compressive extension at total relaxation was between 0.0015 and 0.0020 mm. at maximum compressive stress, values ranged from 0.133 to 0.188 mpa, with compressive strain between 0.0598 and 0.0601 mm/mm. the compressive load at maximum stress varied from 53.274 to 75.170 n, while extension at maximum stress ranged from 1.196 to 1.202 mm. the anova results revealed no significant difference in compressive stress relaxation among the three varieties. further analysis using duncan's test at a 95% confidence level (spss 2021, version 20) confirmed that there was no statistically significant difference in the mechanical properties of the three potato varieties. these findings suggest that benue state farmers can package and transport all three varieties together without concern for differential mechanical damage. additionally, the design of postharvest handling and processing equipment can be standardized for all three varieties. the data generated in this study will help farmers and industry stakeholders understand the engineering properties of benue state-grown potatoes, facilitating better handling, transportation, and processing decisions. references elameen, a., fjellheim, s., larsen, a., rognli, oa., sundheim, l., msolla, s., masumba, e., mtunda, k. and klemsdal, ss. 2008. analysis of genetic diversity in a sweet potato (ipomoea batatas l.) germplasm collection from tanzania as revealed by aflp. genetic resources and crop evolution, 55(4): 397-408. chagonda, i. 2014. effect of tillage systems and vine orientation on yield of sweet potato (ipomoea batatas l.). american journal of plant sciences, 5:3159-3165. fao 2015 food and agricultural organization (fao) of the united nations, fao statistical database (faosta). available from: http://faostat3.org/browse/q/qce food and agricultural organization (fao). 2006. faostat database result. food and agricultural organization of the united nations, rome, italy. http://faostat.fao.org/faostat/servlet/xteservlet3? food and agricultural organization (fao). (2016). crop production data. available athttp://www.fao.org/faostat/en/#data/qc (accessed december 29, 2016). makos, d. 2016. sweet potato agronomy research in ethiopia: summary of past findings and future research directions. agriculture and food science research, 3: 1-11. mohsenin, nn. 1986. physical properties of plant and animal materials. gordon and breach science publishers. new york, usa. national bureau of statistics (nbs) 2014 social statistics in nigeria, abuja. negar, a., glolamhassan, n. and ahmed, j. 2019. determination of the physical and mechanical properties of a potato (the agria variety) in order to mechanise the harvesting and post-harvesting operations. research in agricultural engineering, 65(2): 33-39. omale, pa. and omobowale, mo. 2018. mechanical properties of tigernut (cyperus esculentus) as influenced by moisture content. xii cigr section vi technical symposium in ibadan, nigeria–22 25, october, 12: 13-27. omale, pa., iorhemba, a. and baba, s 2021. determination of stress relaxation of three varieties of benue state grown yam tubers. european journal of advances in engineering and technology, 8(3):9-18. http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng http://faostat3.org/browse/q/qce http://faostat.fao.org/faostat/servlet/xteservlet3 arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 903-912. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omale.paul@uam.edu.ng 912 onuh, jo., akpapunam, ma. and iwe, mo. 2004. comparative studies of the physio-chemical properties of two local varieties of sweet potato flours. nigerian food journal, 22: 141-146. udensi, ea. 2000. local weaning food for prospective cottage industries: in: sustainable agro allied projects with great economic potentials for nigeria. (ed). onyennobi, f.i. willy rose and appleseed publishing co., abakaliki, nigeria, pp: 142-149. united state department of agriculture, 2024. potatoes 2023 summary, usda, national agricultural statistics service, september 2024. pp 6. http://www.azojete.com.ng/ mailto:omale.paul@uam.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):519-536 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 519 original research article evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria j. j. musa1*, i. a. kuti1, p. o. o. dada2, e. a. otuaro3, p. c. eze4, and s. o. nathaniel1 1department of agricultural and bioresources engineering, federal university of technology, p. m. b. 65, minna, nigeria 2department of agricultural and bioresources engineering, federal university of agriculture, p. m. b. 102, abeokuta, nigeria 3department of civil engineering, nigeria maritime university, okerenkoko, nigeria 4department of soil science and land management, federal university of technology, p. m. b. 65, minna, nigeria. *corresponding author’s email address: johnmusa@futminna.edu.ng 1.0 introduction soil compaction changes the physical properties of soil by increasing its strength and bulk density, lowering its porosity, and forcing a narrower pore size distribution within the soil. these changes article information abstract over the last few decades, researchers have developed a great interest in fabricating and synthesising zinc silicate-based glass ceramics. however, using waste materials as precursors for the fabrication is yet another milestone in waste management. thus, this study fabricated zinc silicate glass-ceramic using sola lime silica (sls) glass waste as a silicon source. the series of precursor glass in the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 the conventional solid-state melt-quench technique prepared system through a controlled crystallisation process. the glass system’s physical, structural, and optical properties were obtained by density measurement, x-ray diffraction, fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy, respectively. the density of the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 glasses series was observed to be decreasing with the increment of 𝑤𝑡. % 𝐵2𝑂3 content. the xrd spectra of the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 samples with 0 and 0.01 wt.% 𝐵2𝑂3, exhibits major diffraction peaks attributed to the zno phase in the glass matrix. however, as 𝐵2𝑂3 content increased, the precursor glass sample shown by the xrd spectra depicted a broad halo characteristic, which reflected the properties of amorphous glass that were observed at the composition of 0.05 wt.% 𝐵2. from ftir spectra, the bands at 500, 688, 902 and 1243 𝑐𝑚−1 can be associated with stretching vibrations of zno4 and si-o-b bending vibrations, stretching vibrations of the b–o bonds in the 𝐵𝑂4 units, and modes of boron–oxygen triangular 𝐵𝑂3 units. the intensity of the ir band increases with increasing percentage of 𝐵2𝑂3. the uv-vis analysis of the samples with 0 and 0.01 wt.% 𝐵2𝑂3 demonstrates crystalline hump and varies at 370 nm. it was observed that the addition of b2o3 to the zno-sls glass network caused the glassy amorphous state without a sharp absorption edge at 0.05, 0.10, and 0.15 wt.% b2o3.the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 system shows the increase in band gap when the composition of 𝐵2𝑂3 increased. when 𝑍𝑛𝑂 serves as a modifier, the number of nbos will increase, and this will cause the expansion of glass network. the zinc silicate-based glass-ceramic produced has been classified as a semiconductor due to the vast optical band gap energy obtained and may have vital potential applications for future led and other optoelectronic lighting devices. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 june 2023 revised 5 august, 2023 accepted 10 august, 2023 keywords: bosso infiltration models kostiakov philip modified kostiakov us-soil conservation service (scs) http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 520 impact how air and water circulate through the soil, as well as the capacity of roots to develop in it (sollins and gregg, 2017; jury and stolzy, 2018, lal et al., 2018). the infiltration rate can be affected by changes in how air and water travel through the soil. higher runoff volume, increased flooding potential, and less groundwater recharge within watersheds resulting from a lower infiltration rate. infiltration is a critical technique in managing water resources for crop production in irrigated and dry agricultural environments. it is a precondition for constructing, analysing and managing irrigation systems. similarly, knowledge of infiltration is required to model, critically evaluate, and design management solutions to conserve soil and water resources in dry-farming circumstances. different variables can considerably impact the appropriate evaluation, modelling, and use of infiltration data. according to barros et al. (2014), the activation of hydrological processes such as surface runoff, erosion, and solute transport is affected by undulations and spatial inhomogeneity of soil, spatial and temporal changes in soil use, and changes in soil water infiltration affected by climate change. soil science, hydrology, irrigation, agriculture, civil engineering, environmental engineering and science rely on infiltration (valiantzas, 2010) for irrigation. the hydrological modelling process requires an understanding of infiltration models. along with occurrence time and runoff volume, infiltration regulates water division, water redistribution within soils, and even water-deep percolation down to groundwater. according to angelaki et al. (2013), the infiltration rate is influenced by several factors, such as soil moisture level, texture, density, and behaviour. researchers have condensed soil infiltration features into various mathematical models (musa and egharevba, 2009; al-janobi et al., 2010; umar et al., 2021). however, model predictions must be proved by proper field verification, with the agreement between observed and anticipated values (ogbe et al., 2011). water infiltration into the soil can be monitored in the field or approximated using mathematical models that are either empirical or theoretically based on physical principles. empirical models can relate model parameters to soil characteristics without requiring a physical meaning, which could include factors that are difficult to consider in theoretical models to determine their constants (mirzaee et al., 2014). therefore, the study aims to determine the best model for the soil of built-up areas in bossocampus of the federal university of technology, minna, niger state. 2.0 materials and methods 2.1 description of the study area the study area is located between latitudes 9°39’3.82“n to 9°39’25.90 “n and longitude 6°31’27.65 “e to 6°31’27.65 “e at an elevation of 400 m above sea level within bosso local government area of niger state. the area’s mean annual maximum and minimum temperatures are 39.18 °c and 25.86 °c, respectively, while the mean relative humidity and rainfall are 56.28 % and 130.0 mm, respectively. bosso has two distinct central climates: rainy and dry seasons. the rainy season spans between april and october, while the dry season is between november and march. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 521 figure 1: map showing selected study area within federal university of technology minna, bosso campus 2.2 methodology 2.2.1 soil sampling a core sampler collected 15 soil samples from five selected locations at 0-30cm and 30 – 60cm depths. the soil samples were placed inside polythene bags and carefully labelled before being taken to the laboratory. these soil samples were analysed in the soil and water laboratory of the agricultural and bioresources engineering department, federal university of technology, minna. the soil properties tested include soil moisture content, bulk density, and soil texture (sand %, silt %, and clay %). 2.2.1.1 determination of soil moisture content the soil samples collected from each sample point were oven-dried at 1050c for 24 hours, and the moisture content was determined using equation 1. this is in accordance with the work of umaru et al. (2021). 𝑀𝐶 (%) = 𝑊2− 𝑊3 𝑊3− 𝑊1 𝑋 100 (1) http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 522 where mc is the moisture content of the soil (%); w1 is the weight of the container (g); w2 is the weight of the container and sample before drying (g); and w3 is the weight of the container and sample after oven drying (g). 2.2.1.2 determination of soil bulk density the bulk density was calculated using equation 2 from the mass of oven-dried soil per core volume (g/cm3). 𝜌𝑏(𝑔𝑐𝑚−3) = 𝑀𝑎𝑠𝑠 𝑜𝑓 𝑜𝑣𝑒𝑛 𝑑𝑟𝑖𝑒𝑑 𝑠𝑜𝑖𝑙 (𝑔) 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑐𝑜𝑟𝑒 𝑠𝑎𝑚𝑝𝑙𝑒𝑟 (𝑐𝑚3) (2) 2.2.1.3 particle size analysis the hydrometer method determined the particle size distribution of the soil samples collected from the study area, which is in accordance with panagos et al. (2014). the soil textural triangle was then used to determine the textural class of the soil samples. 2.3 infiltration rate estimation models and parameters the following infiltration models were considered for this study. 2.3.1 philip model the infiltration model proposed by philip includes the soil sorptivity (s) and stable infiltration rate (a) from the series of solutions from richards’ equation (philip 1957). the two-term infiltration equation of philip is expressed in equations 3 and 4. 𝑖(𝑡) = 𝑆𝑡1 2⁄ + 𝐴𝑡 (3) the differentiation of equation (1) yields equation 4 for infiltration rate (i). 𝑖(𝑡) = ( 𝑆𝑡−1 2⁄ 2 ) + 𝐴 (4) where i(t) represents the infiltration rate and the cumulative infiltration at infiltration time (t), respectively, a is related to saturated hydraulic conductivity (ksat), s is the soil water sorptivity term, and t is the time elapsed. 2.3.2 kostiakov model kostiakov proposed one of the earliest empirical infiltration models hillel, (1982) for estimating the infiltration rate, as presented in equation 5 (kostiakov 1932). 𝑖(𝑡) = 𝐾𝑡𝑎 (5) where i(t) is the infiltration rate (mm min−1) at time t (min), and a >0 (kostiakov’s time coefficient) and 0 < a < 1. k and a are coefficients, the kostiakov model parameters depend on the soil texture and conditions, including initial moisture content. the integration of equation 5 gives the expression of cumulative infiltration i (t) in mm, as presented in equation 6. 𝐼(𝑡) = ( 𝐾 1−𝑎 ) 𝑡1−𝑎 (6) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 523 2.3.4. modified kostiakov model the kostiakov-lewis or menzencev model (equation 7) was developed to overcome the limitations of the initial kostiakov equation (sihag et al., 2017). 𝑖𝑡 = 𝐾𝑡𝑎 + 𝑓0𝑡 (7) 2.3.5. ussoil conservation service (scs) model the us department of agricultural, natural resources and conservation service summarised long-term experimental data as suggested in kostiakov’s model as complex. therefore, a recommended coefficient of 0.6985 was added to the kostiakov model to improve its performance and practical applicability as in equation 8. 𝑖𝑡 = 𝑎𝑡𝑏 + 0.6985 (8) where i(t) represents the cumulative infiltration 2.4 statistical analysis the statistical indices used in evaluating the models’ performance are presented in equations 9 to 11. 2.4.1 root mean square error (rmse) the rmse for the data obtained was determined using equation 9. 𝑅𝑀𝑆𝐸 = √ 1 𝑁 ∑ (𝑝𝑖 − 𝑚𝑖)𝑖 2𝑁 𝑖=1 (9) 2.4.2 coefficient of determination (r2) the models’ efficacy was assessed using the coefficient of determination presented in equation 10. 𝑅2 = 1 − √∑ (𝑃𝑖−𝑃)𝑖2𝑁 𝑖=1 √∑ (𝑚𝑖−𝑚)𝑖2𝑛 𝑖=1 (10) 2.4.3 coefficient of correlation (cc) the effectiveness of the numerical predictions of the infiltration models was evaluated using the correlation coefficient as presented in equation 11. 𝐶𝐶 = 𝑧 ∑ 𝑎𝑏− ∑ 𝑎− ∑ 𝑏 √𝑧(∑ 𝑎2)− (∑ 𝑎)2√𝑧(∑ 𝑏2)− (∑ 𝑏)2 (11) where n is the total number of cumulative infiltrations, pi is the mean simulated cumulative infiltration, and mi is the mean observed cumulative infiltration. the rmse provides an overall idea of the dispersion between measured and predicted cumulative infiltration (vand et al., 2018; amami et al., 2021). http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 524 2.4.4 single factor analysis of variance (anova) the single factor anova is employed to ascertain if there are statistically significant differences between the means of two or more independent groups. most importantly, it tests the null hypothesis (h0) 𝐻0: μ1 = μ2 = μ3 = μ4 … … … = μ𝑘 (12) where μ is the group mean, and k is the number of groups. if the one-way anova returns a statistically significant result in an excel sheet, single-factor anova will provide the value of f, f-critical and p values. 3.0 results table 1 presents the soil textural classification of the study location with a slight difference between the sample collection depths. this is in accordance with the study by dearmond et al. (2019). the soil samples collected from the fifteen plots within the study area at 0–30 cm and 30–60 cm indicated that the average soil moisture and bulk density ranged from 7.14 to 17.07 % and 1.40 to 1.80 g/cm3, respectively. table 1: physical properties of soil samples collected from the study location samples soil depth (cm) % sand % silt % clay textural class moisture content (%) bulk density (g/cm3) a 0 30 71.00 13.66 15.34 sandy loam 13.51 1.56 30 60 32.15 53.63 14.22 silty loam 14.13 1.26 b 0 30 76.10 7.20 16.70 sandy loam 16.64 1.53 30 60 21.65 38.64 39.71 clay loam 13.85 1.61 c 0 30 72.40 14.60 13.00 sandy loam 12.35 1.20 30 60 77.21 15.39 7.40 loamy sand 8.72 1.80 d 0 30 83.10 10.25 6.65 loamy sand 8.43 1.49 30 60 81.25 7.56 11.19 loamy sand 9.54 1.30 e 0 30 78.12 7.73 14.15 sandy loam 12.33 1.58 30 60 58.12 23.44 18.44 sandy loam 10.37 1.35 f 0 30 66.76 18.20 15.04 sandy loam 7.93 1.72 30 60 87.10 2.53 10.37 loamy sand 6.35 1.52 g 0 30 71.16 14.22 14.62 sandy loam 15.77 1.97 30 60 25.18 36.57 38.25 clay loam 11.10 1.47 h 0 30 63.15 23.70 13.15 sandy loam 13.48 1.68 30 60 60.31 22.30 17.57 sandy loam 12.23 1.60 i 0 30 80.25 15.32 4.43 loamy sand 11.65 1.78 30 60 35.23 31.95 32.82 clay loam 14.66 1.46 j 0 30 82.28 9.36 8.36 loamy sand 12.73 1.62 30 60 50.42 21.03 28.55 sandy clay loam 11.47 1.28 k 0 30 65.90 8.93 25.17 sandy clay loam 17.26 1.69 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 525 30 60 11.50 49.40 39.10 silty clay 16.87 1.27 l 0 30 79.55 6.36 14.09 sandy loam 12.29 1.42 30 60 25.15 60.75 14.10 silty loam 14.64 1.72 m 0 30 71.40 16.16 12.44 sandy loam 15.46 1.25 30 60 35.51 30.83 33.66 clay loam 11.14 1.62 n 0 30 80.11 5.74 14.15 sandy loam 12.84 1.95 30 60 65.20 4.28 30.52 sandy clay loam 12.08 1.65 o 0 30 68.52 13.38 18.10 sandy loam 13.99 1.23 30 60 72.33 3.25 24.15 sandy clay loam 11.49 1.60 3.1 infiltration curves the cumulative infiltration for 15 plots is presented in figure 1 (a to o). the cumulative infiltration graph of the observed and predicted (kostiakov, philip, modified kostiakov, and scs) was plotted against the elapsed time. a. b. c. d. 0 2 4 6 8 10 12 0 50 100 150c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) 0 2 4 6 8 10 12 14 0 50 100 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) 0 2 4 6 8 10 12 0 50 100 150 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) 0 2 4 6 8 10 12 14 0 50 100 150 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 526 e. f. g. h. i. j. k. l. 0 2 4 6 8 10 12 0 50 100 150 c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) 0 2 4 6 8 10 12 0 50 100 150c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) 0 2 4 6 8 10 12 14 0 50 100 150 c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) 0 2 4 6 8 10 12 0 50 100 150 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) 0 2 4 6 8 10 0 50 100 150 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) 0 2 4 6 8 10 12 0 50 100 150 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) 0 1 2 3 4 5 6 0 20 40 60 80c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) 0 2 4 6 8 10 0 50 100 150 c u m u la ti v e in fi lt ra ti o n (c m ) elapsed time (mins) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 527 m. n o. figure 1: cumulative infiltration for the observed and prediction models table 2 presents field data for the various infiltration rate models considered for this study, while tables 3 and 4 present the average values of the performance evaluation parameters of infiltration models and the average results of the single factor anova test for different infiltration models table 2: parameters of the selected infiltration models for each of the fifteen plots sampled plot kostiakov’s philip modified kostiakov scs model k a s a k a f0 a b a 0.790 0.529 0.458 0.055 0.652 0.057 0.099 0.908 0.464 b 1.020 0.488 0.631 0.047 0.429 0.089 0.122 1.527 0.352 c 0.801 0.518 0.468 0.047 1.366 0.344 0.017 0.932 0.978 d 1.235 0.430 0.571 0.042 1.130 0.373 0.031 3.103 0.183 e 1.193 0.445 0.719 0.028 1.464 0.327 0.028 1.443 0.373 f 2.987 0.196 0.432 0.048 2.279 0.236 0.667 1.302 0.370 g 1.047 0.976 0.399 0.057 0.195 0.072 0.102 1.708 0.297 h 2.665 0.189 0.343 0.051 1.069 0.113 0.065 0.118 0.913 i 1.178 0.426 0.775 0.012 1.012 0.440 0.010 1.145 0.404 0 2 4 6 8 10 12 0 50 100 150c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) 0 2 4 6 8 10 12 0 50 100 150 c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) 0 2 4 6 8 10 12 0 50 100 150 c u m u la ti v e in fi lt ra ti o n ( cm ) elapsed time (mins) http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 528 j 0.973 0.441 0.646 0.014 1.198 0.012 0.073 0.935 0.418 k 1.302 0.274 0.300 0.043 1.251 0.007 0.056 1.115 0.252 l 1.120 0.434 0.826 0.004 1.254 0.305 0.036 1.383 0.352 m 1.008 0.448 0.109 0.089 1.078 0.197 0.062 2.557 0.183 n 0.410 0.681 0.495 0.046 0.599 0.181 0.086 1.116 0.410 o 0.638 0.578 0.799 0.010 0.673 0.407 0.052 1.165 0.404 table 3: average values of the performance evaluation parameters of infiltration models model rmse r2 cc kostiakov 0.6124 0.9849 0.992 philip 0.2116 0.9977 0.999 modified kostiakov 0.5262 0.9911 0.996 scs 0.9815 0.9821 0.991 table 4: average results of the single factor anova test for different infiltration models approaches f p-value f-critical kostiakov model 0.009249 0.948290 4.090291 philip model 0.00077 0.988993 4.033874 mod. kostiakov model 0.003814 0.968504 4.090291 scs model 0.020821 0.900067 4.090291 4.0 discussion the quantity of water plants needed from sowing to harvest is the available soil water/moisture content (musa et al., 2020). soil moisture content is a critical factor influencing various soil functions and processes. this function includes plant growth, physical and chemical properties, soil biological activity, erosion, and runoff. managing soil moisture content is critical for promoting sustainable agriculture. the result obtained is similar to the works of uloma et al. (2014) in a different location where moisture content ranged between 7.1% to 17.5%. furthermore, it was discovered that a constant infiltration rate was achieved within a minimal time at location k, which had a high moisture content. the longer it takes for the soil to establish a stable infiltration rate, the lower the infiltration rate and the higher the initial soil moisture content. this is connected to the texture of the soils and the level of compaction of the soils in the study areas. the rate at which water enters the soil also increases with soil dryness (musa and adeoye, 2010). in other circumstances, the cumulative infiltration volume decreases as the initial soil moisture content rises, according to qing et al. (2020). the high moisture-holding ability of clay, which was discovered to be expected at this soil layer, is thought to be the cause of the detected discrepancy. as indicated by umaru et al. (2021), the highest value of the soil’s average moisture content may be beneficial for crops that constantly require water, which may thrive in waterlogged conditions. the results contradict those of musa et al. (2019), who investigated the effect of water stress on the yield of selected vegetable crops in nigeria’s southern guinea savannah ecological zone. this can be attributed to the study area’s seasonal file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 529 variation, soil structure, texture, and climate change (umaru et al., 2021). however, the locations are contiguous within the same study environment. according to musa and adeoye (2010), initial movement and the overall amount of infiltration were thought to be influenced by the initial soil moisture content at any given time, both of which decreased as the soil moisture content increased. according to several studies, sandy soil has a higher infiltration rate than clay soil under the same circumstances (runbin, 2011; igbadun et al., 2016). musa et al. (2017) assert that all water will enter if the water at the soil surface exceeds the infiltration capacity. this is related to plot f’s low soil moisture content reading. bulk density is a sign of the health and compaction rate of the soil. this is also believed to affect the depth or limitations of plant roots, soil water holding capacity, plant nutrition availability, soil porosity, soil microbe activity, and nutrient availability, all of which have an impact on soil productivity (arévalo-gardini et al., 2015). it was observed that plot n had the highest value of the soil bulk density, ranging from 1.40 to 1.80 g/cm3. the bulk density values observed in this study are similar to those discovered by igboekwe and adindu (2014) in an entirely separate region, with this finding ranging from 1.40 to 1.80 g/cm3. a rise in infiltration capacity has been seen to be closely related to a fall in bulk density. the high percentage of clay content, the potential proximity of underlying rocks to the soil surface, and mechanical impedance may all have contributed to plot n’s high bulk density. the difference in bulk density measurements may be related to prevailing variables such as the soil’s degree of compaction in the study area, the volume of the core ring, and the depth at which the soil samples were taken. bulk density rises with the degree of compaction, which may be caused by the impact of farming techniques and rainfall events on the topsoil, according to musa and adeoye (2010). thus, soil compaction has been linked to flooding, as grzesiak et al. (2016) and ferreira et al. (2018) documented. this study showed that sandy soil was most predominant, as this demonstrates that the saturated hydraulic conductivity of a particular soil is significantly determined by the actual amount of sand in that soil sample (musa et al., 2020, 2021). plot d had the highest percentage of sand compared to other study locations. each soil sample from plots a to o holds a different amount of sand, ranging from 11.50% at 0 to 30 cm depth to 83.10% at 30 to 60 cm depth. similarly, the silt content of plot l is higher than that of the other samples, while the clay content of plots k and b is higher than that of the other samples at both depths. plots j, n, and 0 at a depth level of 3060 cm and plot k at a depth level of 0-30 cm, respectively, showed the highest values of sandy clay loam, which is easily detached but difficult to transport (bonilla and johnson, 2012; mirzaee et al., 2017) while the lowest concentrations of silt loam and silt clay were found at plots a and l, each at a depth of 30 to 60 cm, and plot k, also at a depth of 30 to 60 cm respectively. the study area reveals some degree of variation in the percentages of sand, silt, and clay in the various soil samples that were collected, which is comparable to the works of okon et al. (2017) and deb et al. (2019) for the differences in physicochemical properties of soils under oil palm plantations of different ages in ohaji/egbema, imo state, and variability of soil physicochemical http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 530 properties at different agroecological zones of himalayan region: sikkim, india respectively. at a depth of 0 to 30 cm, the highest sand value was 83.10%. according to girei et al. (2016), higher soil resistance to continuous cultivation may be the cause of the increased sand fraction in plot d. the data collected in the field showed that there are low silt/clay soil ratios, which may suggest that the study region has not been effectively used for agriculture, resulting in a low level of erosion activities. the findings of the study conducted by afolabi et al. (2014) on the evaluation of some soils of minna southern guinea savanna of nigeria for arable crop production within the permanent site irrigation farm of the federal university of technology, minna is invalidated by the current findings. this can be ascribed to the spatial heterogeneity of the research region and additional physical characteristics of the soil, such as the soil structure, porosity, and moisture content, which may also impact the infiltration process (yan et al., 2013). infiltration tests were conducted on-site to address the regional heterogeneity of the infiltration rate. as a result, the study area’s initial and final infiltration rates vary from 1080 to 1176 cm/h. results from figures 1 (a to o) show that the infiltration data for plots k and b reached field capacity more quickly and had the lowest infiltration readings. this can be attributed to the plots’ high initial soil moisture content values and high bulk densities from soil compaction, as expressed in table 1. low values of the infiltration characteristics point to potentially excessive runoff (erosion) on such topo-sequences or slopes (oku and aiyelari, 2011). another explanation for the poor infiltration rate in the study could be the spatial diversity of soil parameters within the field (bui et al., 2019). it was observed that plots f, d, c, and e took longer to be saturated than other plots due to the high bulk density noted in the plots. low bulk density, however, may cause a high infiltration rate, as seen in the c, d, e, j, m, and o plots. in addition, the soil particles at plots f, g, i, h, l, and n were wetter than those at the other spots, which caused them to permeate water more slowly than the other points. therefore, the soil aggregates’ shape, size, and stability may impact the infiltration rate. contrary to the findings of (ieke et al., 2013), coarse-grained sandy soils are known to contain vast gaps between each grain, which allows water to penetrate quickly. until a steady state is reached, soil infiltration rates gradually decrease. several variables affect infiltration, such as soil texture, structure, initial soil water content, pore size, soil metric potential, and vegetation (aljanobi et al., 2010). this tendency is also evident in the cumulative infiltration presented in figure 1. the rainfall-runoff mechanism must be understood using data on water infiltration for various soil types. table 2 describes the infiltration equation’s parameters, and figure 1 (a to o) displays graphs of the calculated infiltration rate. the values of the empirical constant ‘k’ and the infiltration decay constants’ a’ for kostikov’s infiltration model were calculated to be in the range of 0.4099 to 2.9866 and 0.1888 to 0.9763, respectively. the values of the infiltration decay constant ‘a’ were consistent with the infiltration hypothesis, which stated that the values should always be positive and less than unity. according to reports from ogbe et al. (2011) and farid et al. (2019), most of these parameters’ values fall between 0.2 and 0.9. in addition, the sorptivity file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 531 (s) values were found in the range of 0.1087 to 0.8264 cm/min, and the conductivity constant (a) values ranged between 0.0038 and 0.0889 cm/min for all fifteen plots of philip’s infiltration model. the s-estimated values and those provided by vand et al. (2018) agreed with most of the findings in the study area. similar to this, the values of the parameters of the modified kostiakov’s model, such as k, were determined to range between 0.0069 and 0.4400, and the infiltration decay constants a and f0 were determined to range between 0.0099 and 0.6671. finally, the values for the scs model’s infiltration parameters, such as a, were obtained in the range of 0.9353 to 3.1025 and those for b, between 0.1825 and 0.9777. although the values of the model’s infiltration parameters have no physical significance, they reflect the influence of the soil’s physical characteristics on infiltration, the state of the surface, and the soil’s moisture content (ogbe et al., 2011). farid et al. (2019) reported using the coefficient of determination (r2) as a metric to compare the infiltration models. in particular, the absolute mean difference (amd) and r2 were employed to compare kostikov’s and philip’s models. haghighi et al. (2010) used the r2 and root mean square error (rmse) metrics to choose the optimal model for infiltration data. igbadun and idris (2007) employed the efficiency coefficient to assess the infiltration model’s applicability. the estimated average coefficient of correlation (cc) values were 0.992, 0.999, 0.996, 0.991; the estimated average r2 values were 0.9849, 0.9977, 0.9911, 0.9821 (table 3); and the estimated average root mean square error (rmse) values were 0.6124, 0.2116, 0.5262, and 0.9815 cm/min. the infiltration rate highly depends on soil texture (haghighi et al., 2010), and the result is consistent with the findings of thomas et al. (2020). they evaluated six infiltration equations on homogeneous coarse-textured soils. they also found that philip’s model provided an excellent representation of the infiltration. at the same time, kostiakov, modified kostiakov, green apmt, and holtan-overton performed in that order, as igbadun et al. (2016) suggested. oku and aiyelari (2011) likewise anticipated cumulative infiltration beneath the inceptisols in the humid forest zones. the outcome demonstrated that philip’s model was more appropriate than the kostiakov model. however, the findings of this study are in contrast to those of igbadun et al. (2007), who reported that the kostiakov model related closely to the measured data than philip’s model for a hydromorphic soil at samura, nigeria, and the findings of musa and adeoye, (2010) who studied the adaptability of infiltration equations to soils of the permanent site farm of the federal university of technology, minna, in the guinea savannah zone of nigeria and found that the kostiakov model fit the data better than the horton and philip models. this can be attributed to several elements, including spatial variability, rainfall patterns, vegetation types, soil water content, soil characteristics of the study area, and the fact that the previous study was carried out in an undeveloped area with a rural setting. in contrast, the current study was carried out in an urban setting. table 4 shows that the f-f-statistic for all models is less than the p-value and f-critical. if the fstatistic is less than the p-value and the f-critical value in a model, it suggests no significant difference between the means of the groups being compared. this conclusion can be drawn because the f-statistic tests whether the variability between groups is more significant than within groups. a low f-value indicates that the variability between groups is not much larger than the http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 532 variability within groups, which suggests that there is no significant difference between the means of the groups being compared. therefore, when the f-statistic is less than the f-critical value, and the p-value is more significant than the alpha level (typically 0.05), it is appropriate to fail to reject the null hypothesis and conclude that there is not statistically significant difference between the group means. 5.0 conclusion most of the soils in the study area were sandy loam, which may be the cause of the relatively low infiltration rate seen in the area. thus, it can be deduced that bulk density and soil texture have a more significant impact on infiltration rate than moisture content, which caused the infiltration of the study area to be low; hence, water logging at some points. this study concluded that philip’s model was substantially closer to the observed data when the field and predicted infiltration rates were compared. philip’s model outperformed the other four infiltration models to estimate infiltration rate in specific land use and soil parameter models. the model offered the lowest values, which led to the conclusion that it accurately captured the infiltration rate based on the mean values of rmse. therefore, it is concluded that the philip model can be utilised more effectively to simulate cumulative infiltration to generate infiltration data artificially where there is no actual infiltration data for the studied area. reference afolabi, sg., adeboye, mka., lawal, ba., adekanmbi, aa., yusuf, aa. and tsado, pa. 2014. evaluation of some soils of minna southern guinea savanna of nigeria for arable crop production. nigerian journal of agriculture, food and environment, 10(4): 6-9. al-janobi, aa., aboukarima, am. and ahmed, ka. 2010. modelling water infiltration rate under conventional tillage systems on a clay soil using artificial neural networks. australian journal of basic and applied sciences, 4(8): 3869-3879. angelaki, a., sakellariou-makrantonaki, m. and tzimopoulos, c. 2013. theoretical and experimental research of cumulative infiltration. transport porous media, 100(2): 247–257. barros, cap., minella, jpg., tassi, r., dalbianco, l. and ottonelli, as. 2014. estimation of soil water infiltration at the catchment scale. revista brasileira de ciência do solo, 38: 557-564. http://dx.doi.org/10.1590/s0100-06832014000200020 bonilla, ca. and johnson, oi. 2012. soil erodibility mapping and its correlation with soil properties in central chile. geoderma, 189: 116-123. deb, p., debnath, p., denis, af. and lepcha, ot. 2019. variability of soil physicochemical properties at different agroecological zones of himalayan region: sikkim, india. environment, development and sustainability, 21(5): 2321-2339> file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng http://dx.doi.org/10.1590/s0100-06832014000200020 musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; 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vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 534 kostiakov, an. 1932. on the dynamics of the coefficient of water percolation in soils and on the necessity for studying it from a dynamic point of view for purposes of amelioration. society of soil science, 14, 17-21 lal, r. 2018. land use and soil management effects on soil organic carbon dynamics on alfisols in western nigeria. in soil processes and the carbon cycle 123-140. crc press, crc press, boca raton, florida, usa. mirzaee, s., ghorbani-dashtaki, s., mohammadi, j., asadzadeh, f. and kerry, r. 2017. modelling wepp erodibility parameters in calcareous soils in northwest iran. ecological indicators, 74: 302310. mirzaee, s., zolfaghari, aa., gorji, m., dyck, m., and ghorbani ds. 2014. evaluation of infiltration models with different numbers of fitting parameters in different soil texture classes. archives of agronomy and soil science, 60(5): 681-693. musa, jj. and adeoye, pa. 2010. adaptability of infiltration equations to the soils of the permanent site farm of the federal university of technology, minna, in the guinea savannah zone of nigeria. assumption university journal of technology, 14(2): 147-155. musa, jj., akpoebidimiyen, oe., adewumi, jk., eze, pc., adesiji, r. and gupa, y. u. 2020. influence of soil bulk density and porosity on soil hydraulic conductivities for selected land management practice in northcentral nigeria. international journal of agricultural and environmental sciences, 5(1): 1-7. musa, jj., akpoebidimiyen, oe., dada, poo., adewumi, jk. and gupa, yu. 2021. effect of land management on soil hydraulic conductivity in gidan kwano, niger state, nigeria. open journal of forestry, 11: 108-116. https://doi.org/10.4236/ojf.2021.112008 musa, jj., anijofor, sc., obasa, p. and avwevuruvwe, jj. 2017. effects of soil physical properties on erodibility and infiltration parameters of selected areas in gidan kwano. nigerian journal of technological research. 12(1):17-26. doi: http://dx.doi.org/10.4314/njtr.v12i1.8 musa, j., adewumi, j., otuaro, e. and musa, m. 2019. effect of water stress on the yield of selected vegetable crops in the southern guinea savannah ecological zone of nigeria. open access library journal, 6: 1-12. doi: 10.4236/oalib.1105938. musa, j.j. and egharevba, n.a. 2009. soil grouping of the federal university of technology, minna, main campus farm using infiltration rate. assumption journal of technology, 13 (1), 19-28. ogbe, vb., jayeoba, oj. and ode, so. 2011. comparison of four soil infiltration models on a sandy soil in lafia, southern guinea savanna zone of nigeria. production agriculture and technology, 7(2): 116–126. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng https://en.wikipedia.org/wiki/boca_raton https://en.wikipedia.org/wiki/boca_raton https://en.wikipedia.org/wiki/florida https://doi.org/10.4236/oalib.1105938 musa et al: evaluation and comparison of some infiltration models on agricultural soils of bosso local government area, niger state, nigeria. azojete, 19(3):519-536. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 535 okon, ma., nwachukwu, mn. and osujieke, dn. 2017. differences in physicochemical properties of soils under oil palm plantations of different ages in ohaji/egbema, imo state. international journal of research, 4(1): 1-7 oku, e. and aiyelari, a. 2011. predictability of philip and kostiakov infiltration model under inceptisols in the humid forest zone, nigeria. kasetsart journal (natural science), 45: 594-602. panagos, p., meusburger, k., ballabio, c., borrelli, p. and alewell, c. 2014. soil erodibility in europe: a high-resolution dataset based on lucas. science of the total environment, 4 (7): 189 200. philips, jr. 1957. the theory of infiltration: the infiltration equation and its solution. soil science, 83 (5): 345-358, doi: 10.1097/00010694-195705000-00002. qing, x., haojie, h., jinran, x., caixia, z., zhiliang z., huiqiang, h., and qin, z. 2020. research progress of soil water infiltration. e3s web of conferences, 189: 01006. https://doi.org/10.1051/e3sconf/202018901006 runnbin, d., clifford, b. and fedler, jb. 2011. field evaluation of infiltration models in lawn soils. irrigation science, 29: 379-389. sihag, p., tiwari, nk. and ranjan, s. 2017. estimation and intercomparison of infiltration models. water science, 31(1): 34-43. doi: 10.1016/j.wsj.2017.03.001. sollins, p. and gregg, jw. 2017. soil organic matter accumulation in relation to changing soil volume, mass, and structure: concepts and calculations. geoderma, 301: 60-71 thomas, ad., ofosu, ae., emmanuel, a., de-graft, aj., ayine, ag., asare, a. and alexander, a. 2020. comparison and estimation of four infiltration models. open journal of soil science, 10: 45-57. https://doi.org/10.4236/ojss.2020.102003 uloma, ar., samuel, ac. and kingsley, ik. 2014. estimation of kostiakov’s infiltration model parameters of some sandy loam soils of ikwuano–umuahia, nigeria. open transactions on geosciences, 1 (1): 34-38, umaru, ab., tya, tsk., musa, mm. and vanke, i. 2021. effects of some soil physical properties on infiltration rate at phase 2b of lake geriyo irrigation project, yola, nigeria. nigeria journal of engineering science and technology research, 7 (1): 74-83. valiantzas, jd. 2010. new linearised two-parameter infiltration equation for direct determination of conductivity and sorptivity. journal of hydrology 384(1–2):1–13 vand, sa., sihag, p., sing, b. and zand, m. 2018. comparative evaluation infiltration models. ksce journal of civil engineering, 22 (10): 4173-4184 http://www.azojete.com.ng/ mailto:johnmusa@futminna.edu.ng https://doi.org/10.1051/e3sconf/202018901006 https://doi.org/10.4236/ojss.2020.102003 arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):519-536. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: johnmusa@futminna.edu.ng 536 yan, yh., zheng, jy. and zhang, c. 2013. impact of biochar addition into typical soils on field capacity in loess plateau. journal of soil and water conservation, 27(4): 120–124 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:johnmusa@futminna.edu.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726 copyright © faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818, www.azojete.com.ng 713 assessment of electrical grid fragility in nigeria-31 bus system p. o. oluseyi*, t. o. ajekigbe, o. m. babatunde and t. o. akinbulire department of electrical/electronics engineering, university of lagos, akoka, lagos, nigeria *corresponding author’s e-mail address: poluseyi@unilag.edu.ng, drpeteroluseyi@gmail.com abstract the grid fragility is a prevalent challenge in nigeria electricity supply industry (nesi). it has resulted in recorded incidents of voltage collapse which have been on the increase in the recent time. meanwhile to evaluate this events; thus the nexus between voltage collapse and network capacity was explored. to actualize this, the load flow analysis was carried out on the nigeria-31 bus system with the aid of the newton-raphson iteration technique. using the relevant parameters (such as bus voltage magnitude, bus voltage angle, generated power, injected power as well as load magnitude) obtained from the analysis, the line stability index and line stability factor were obtained for every line in the network. it was discovered from the values of line stability index that lines (26-2); (31-7); (10-11); (24-10) and (18-12) are weak and fragile while for the line stability factor, the values obtained for lines (10-8); (11-8); (11-10); (24-10) and (18-12) indicate the fragility of some of the lines in the nigerian transmission network. from this, it was established that the weakest lines were those whose values range from 0.3051 to 0.8813 for the line stability index. correspondingly; any line that takes the value between 0.2737 and 0.9924 in respect of the line stability factor was also marked as the weakest lines in the network. thus it was noticed that for the two line stability indices (i.e. stability factor and stability index); line (11-10) i.e. from oshogbo to ikejawest bus is the most fragile line in nigeria-31 bus transmission network while the nearest to it are lines (24-10) i.e. from ayede to ikeja-west bus and (12-18) i.e. from kaduna to kano bus. this study is potentially sufficient for determining the lines in the transmission network that require utmost consideration for reinforcement in respect of the transmission expansion planning schemes. keywords: transmission, fragility, stability index, collapse, electricity 1. introduction electricity is the most crucial vehicle for socio-economic advancement in any nation. in industries, it is established that electricity contributes about 35 percent to the total cost of production. therefore, lack of adequate electricity supply reduces the interest of investors due to unprecedented costs of production (oluseyi, 2010). this may have its attendant problem on the increasing the rate of unemployment as well as complicate the human poverty index of a community. almost 50 per-cent of the nigeria’s population (precisely 76 million people) do not have access to electricity in nigeria (egeruoh, 2012) while the rest of the percentage do not have adequate supply of electricity. from the foregoing, it is therefore very crucial to look into steps to improve electricity in such an environment. efforts have been made over the years to improve electricity supply in nigeria. this has led to a number of policies in respect of the electric power sector reforms act (oluseyi, 2010). one of these is the restructuring and deregulation of the power sector to enhance access to electricity (oluseyi et al., 2009). the principle of deregulation involves provision of enabling environment for the investors to embark on electric power generation. with the advent of this, pressure is placed on the national grid to wheel the generated energy to the various distribution companies (oluseyi et al., 2012). the effects of deregulation on the grid are therefore highly profound and need to be carefully investigated (oricha et al., 2009). several system collapse reports have been encountered in the recent times in the nigerian national grid. quite a number of these abnormal functioning of the transmission network has been related to poor network capacity of the transmission facilities (samuel et al., 2014) thus, it has been quite impossible for the current nigerian national grid to transport the recent total generated capacity to the load end. in order to record tangible improvement in power supply, the fragile nigerian national grid has to be reinforced to ensure it has the capacity to wheel the quantum of generated electric power. mailto:poluseyi@unilag.edu.ng mailto:drpeteroluseyi@gmail.com http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 714 the review of the incidence of system collapse events on the transmission network have been done in past studies which revealed that in the last ten years, the nigerian national grid has experienced an average of thirty-five system collapses per year (awosope, 2014). furthermore, a thorough assessment of voltage instability has been well documented for purpose of improving the phenomenon (airoboman et al., 2015). this study, by means of variously developed stability indices, examines the grid fragility on the nigerian transmission network. this is quite different from the previous approaches in a number of ways. for instance; much more than lumping the network parameters into one component while determining the fragility of the grid, this study developed a model for the investigating the extent of fragility of each line in the grid. this provides empirical information on the fragility status of lines in the entire network; thus facilitating establishing the identification of weakest buses. hence, it aids in locating the potentially weakest buses that may threaten the system stability. thus, this assists in prudent manipulation of the network operation for the purpose of proffering practical approach to mitigating the challenges of voltage collapse phenomenon. more importantly, this analysis of the grid fragility will serve as analytic framework to various transmission expansion planning schemes; in which case the weak line may be reinforced further to mitigate further voltage collapse in the network. 2. materials and methods the primary material for this work is the bus and line data of the nigeria-31 bus system (as it currently operates). this was collected from the transmission company of nigeria (tcn). in order to evaluate this, the matlab™ software package (2012) would be employed. the standard approach adopted for the analysis of the transmission network is analytical combined with the simulation technique. in the case of the analytical methodology, this involves the application of the outcome of the newton-raphson algorithm to the well-established mathematical model for the evaluation of the line stability indices. the two main line stability indices that would be used are line stability index and line stability factor. so also the same transmission network would be further evaluated using the powerworld simulator which is interactive power system simulation package which is used to evaluate the contingency analysis study of the transmission network. the analysis of the newton-raphson load flow is carried out using the load flow equation (for nbus system). this is expressed in polar form as follows. (1) the current can thus be further simplified into real and reactive components as follows: (2) this can then be re-arranged as follows. )( 11 ** ijjij n nj ji n i iiiiii yvvsvijqp g g     (3) separating this into the real and the imaginary parts we then obtain the equations (4) and (5); however note that the total number of buses irrespective of whether generator or load is n; hence it is taken for granted that the iteration from i=1 to n is the limit of summation as depicted in the following equations. j n i iji vyi    1 * i ii i v jqp i   http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 715 )( 1 * ijjiijj n ij j ii cosyvvp     (4) )( 1 * ijjiijj n ij j ii sinyvvq     (5) the algorithm for computing involves: step 1: formation of the ybus step 2: assume the initial values of bus voltage as 0v for all load buses (pq) buses and bus angle as 0 i for all the buses except the slack bus step 3: compute pi and qi for each load bus using equations (4) and (5) step 4: compute the scheduled errors (i.e. δpi and δqi for each load bus using the equations: nippp calc i spec ii ...3,2,1;  (6) where i= 1, 2, … n for pq buses and niqqq calc i spec ii ...3,2,1;  (7) step 5: compute the elements of jacobian matrix       43 21 jj jj (8) where j2=j3=0 step 6: from steps 6, 7 and 8; write the syetm equation as:                         v v j j q p  4 1 0 0 (9) step 7: expand the equation and thus obtain the values of δδi and δvi from equation (9) so as to modify the voltage magnitude and phase angle for each of the buses in the network (oluseyi, 2010). step 8: set up the equations for calculating the new voltage magnitude and angle as follows: r i r i r i vvv 1 (10) )()()1( r i r i r i   (11) step 9: commence a new iteration cycle from step 2 with the new values of voltage magnitude and phase angle obtained in step 8. step 10: continue this until the scheduled error is within the pre-set specified tolerance value. i.e.     )( )( ; r i r i q and p   the ensuing power flow solution is then employed in the subsequent sections of the work. http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 716 figure 1: flow chart of the newton-raphson load flow iteration algorithm start read system data compute δ|v| and δδ using equations (10) and (11) for voltage-controlled buses: compute piand δpi using equations (4) and (6) compute the elements of j1and j4using equation (9) for load buses, compute piand qi using equations (4) and (5); δpiand δqi from equations (6) and (7) specify pi spec and qi spec for load buses form ybus matrix set |vi| = 1.0, δi =0.0 check for convergence print results does solution converge? yes no stop http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 717 in the case of (n-1) contingency analysis test, the powerworld simulator is arranged as shown in the flow chart shown in figure 2. figure 2: flow chart of contingency analysis algorithm (scott, 2012) the powerworld has a menu for contingency analysis in which case the contingency analysis dialogue box is open. then the line and bus data are then uploaded in which case the “run” mode is thus activated so as to generate the relevant results (see figure 2) along with the pictorial display of the entire network as shown in figure 4. 2.1 detection of weakest lines using stability indices in the determination of grid fragility, there are several stability indices that can be employed (oluseyi, 2010). in this work, the line stability index and the line stability factor shall be employed to detect the weakest lines in the nigerian national grid. from this, the lines that should be given greater priority in respect of network reinforcement in line with previous comparative study of voltage stability indices are identified (sinha and hazarika, 2000). the preferred load flow study for this analysis is the newton–raphson load flow approach. the newton-raphson technique is chosen for obvious reasons, amongst which is that it has solutions for cases of divergence in iteration (oluseyi, 2010). thus the newton-raphson iterative method is used in load flow analysis and the results obtained are used to compute the above mentioned indices (goh, et al, 2015). base case violation? run primary contingencies fix violations violation? model system adjustment run secondary contingencies apply ith primary contingency violation? yes no no yes yes no http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 718 2.2 line stability index the work of moghavvemi and omar (1998) on the conceptual modelling of the line stability index was adopted for this calculation. the assumption made was that the power flow through a single line. thus by the use of the system reduction techniques to represent the entire transmission network as a single line, as shown in figure 3, the equivalent network analysis is thus modelled as depicted equation (1) for the computation of the overall system stability index. figure 3: diagram of a transmission line with 2-bus system (goh et al., 2015) the line stability index using this technique is given as:  2 4 sin r mn s xql v δ  (12) where: vs is the sending end voltage s and r are the phase angle at the sending and receiving buses respectively x is the line reactance θ is the line impedance angle based on the stability indices of lines, voltage collapse can be predicted. when the stability index lmn is less than 1, the system is stable and when this index exceeds the value 1, the whole system loses its stability and voltage collapse occurs (tran, 2009). by extension, in the application to calculation of grid fragility for the purpose of this work, the line stability index is computed for every line in the transmission network rather than compressing the whole system into a single line equivalent. the lines with the stability index closest to 1 will be identified as the most fragile lines in the system. 2.3 line stability factor (lqp) for proper and effective identification of the weakest lines in the transmission network, a further analysis was performed on the network using another concept of the stability index. in this case, the line stability factor (lqp) was employed while the results are compared with those obtained from the line stability index earlier obtained. the stressed transmission network would obviously results in voltage collapse, thus the network is better monitored to ensure that the stability margin is not violated. this is best done by approaching the network stability analysis using voltage stability index (ratra, et al, 2018). moreover, the lqp is also formulated so as to enumerate the stability status of the transmission networks. this approach is thus applied to the currently existing nigeria-31 bus system using equation (2). similarly, figure 1 is also valid for this derivation of this calculation. 2 2 24 s r s s x xlqp p q v v              (13) x is the line reactance vs is the voltage magnitude at the sending end ps is the active power at the sending end qr is the reactive power at the receiving end in similarity to the application of the line stability index, the lines with the line stability factor closest to value of unity will be identified as the most fragile lines in the system. thus the only http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 719 acceptable evidence that a line is a threat to the voltage stability in a network is when the values of both its stability index and stability factor equally violate the stability margin of the network. 3. results and discussion this section presents the results obtained from deploying the procedure presented in section 2. from this investigation, table 1 shows the results obtained from the load flow analysis by applying the newton-raphson iteration method. thus table 1 is the narration of the voltage profile of the nigerian transmission grid in which the comparison to the magnitudes and phase of the various real and reactive power quantities of each of the buses that make up the nigeria-31 bus system are displayed. table 1: system voltage profile with power magnitude at each bus of the nigeria-31 bus system bus no v (pu) angle (degree) injection mw mvar generation mw mvar load mw mvar 1 1.0200 0.0000 825.4612 332.2438 332.2438 332.2438 0.0000 0.0000 2 0.9900 -2.9559 200.0000 -43.8762 -43.8762 -43.8762 0.0000 0.0000 3 1.0000 -2.3820 300.0000 11.3003 11.3003 11.3003 0.0000 0.0000 4 1.0000 -8.9140 250.0000 138.4051 138.4051 138.4051 0.0000 0.0000 5 1.0300 7.0762 490.0000 -52.6504 -52.6504 -52.6504 0.0000 0.0000 6 1.0400 7.3865 350.0000 -27.0382 -27.0382 -27.0382 0.0000 0.0000 7 1.0300 9.5870 450.0000 -35.4185 -35.4185 -35.4185 0.0000 0.0000 8 0.9953 -5.0357 -156.0000 -79.9000 -79.9000 0.0000 156.0000 79.9000 9 1.0402 4.6449 -8.6000 -5.6000 -5.6000 0.0000 8.6000 5.6000 10 0.9816 -5.6930 -429.9000 -258.4000 -258.4000 0.0000 429.9000 258.4000 11 1.0160 -0.5566 -201.0000 -136.7000 -136.7000 0.0000 201.0000 136.7000 12 1.0337 -1.1701 -166.2000 -97.8000 -97.8000 0.0000 166.2000 97.8000 13 1.0632 -6.4503 -58.4000 -28.4000 -28.4000 0.0000 58.4000 28.4000 14 0.9777 -11.2587 -144.7000 -88.4000 -88.4000 0.0000 144.7000 88.4000 15 0.9730 -10.8277 -115.2000 -42.0000 -42.0000 0.0000 115.2000 42.0000 16 0.9960 -4.8273 -82.1000 -44.5000 -44.5000 0.0000 82.1000 44.5000 17 0.9575 -12.7112 -112.6000 -50.0000 -50.0000 0.0000 112.6000 50.0000 18 0.9941 -8.0840 -184.9000 -60.0000 -60.0000 0.0000 184.9000 60.0000 19 1.0745 -10.6699 -102.9000 -17.5000 -17.5000 0.0000 102.9000 17.5000 20 1.0212 2.0303 -60.3000 -70.0000 -70.0000 0.0000 60.3000 70.0000 21 1.0058 -6.0171 -26.8000 -10.5000 -10.5000 0.0000 26.8000 10.5000 22 0.9775 -6.1333 -292.0000 -114.9000 -114.9000 0.0000 292.0000 114.9000 23 0.9977 -3.2197 -193.5000 -101.2000 -101.2000 0.0000 193.5000 101.2000 24 0.9927 -4.1225 -139.4000 -61.0000 -61.0000 0.0000 139.4000 61.0000 25 1.0003 -3.0052 -109.7000 -64.2000 -64.2000 0.0000 109.7000 64.2000 26 0.9956 -4.3557 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 27 0.9993 -4.6754 -64.3000 -44.2000 -44.2000 0.0000 64.3000 44.2000 28 0.9810 -10.9908 -119.3000 -65.7000 -65.7000 0.0000 119.3000 65.7000 29 1.0413 2.7845 -61.5000 -10.3000 -10.3000 0.0000 61.5000 10.3000 30 1.0445 4.8916 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 31 1.0401 4.9320 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 from the details of table 1, as a representation of the voltage profile, it is evident that the nigeria’s transmission network as a whole is fragile requiring massive upgrades. thus the voltage magnitudes range from 0.95 pu to 1.08 pu (under normal operating conditions) which is http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 720 technically unacceptable when compared to the acceptable international standard on electricity operating policy with a permissible variation standards put at ±4 per cent of the nominal voltage magnitude. to further buttress the earlier statement in the preceding paragraph, the measurement of the line stability indices for establishing the existing operating conditions of the nigeria’s transmission network was carried out. the results are thus presented below in table 2. from this, it shows the values of line stability factor (lqp) and line stability index (lmn) obtained for each line of the nigerian transmission network. the lines with values of the stability indices closest to unity depict the most fragile lines in the system. it is highly important to juxtaposing the results obtained using the two stability indices techniques, hence, obtaining accurate results in each case. in most cases, the lmn reveals larger values than the lqp for stable lines (lmn, lqp≤ 0.45). whilst the contrast is the case with regard to the fragile lines. table 2: line stability indices for the nigerian transmission network s/n line from bus to bus lqp lmn 1 25 1 0.0863 0.0880 2 26 2 0.0213 0.4642 3 27 3 0.0063 0.0085 4 28 4 0.0831 0.0818 5 29 5 0.0322 0.0319 6 30 6 0.0134 0.0352 7 31 7 0.0253 0.6231 8 10 8 0.2737 0.1379 9 11 8 0.3132 0.2297 10 8 15 0.0850 0.0687 11 21 8 0.1830 0.1923 12 8 26 0.0005 0.0000 13 8 27 0.0037 0.0164 14 9 11 0.0782 0.0800 15 9 29 0.0138 0.0149 16 30 9 0.0003 0.0004 17 31 9 0.0002 0.0004 18 11 10 0.9924 0.8813 19 10 22 0.0133 0.0127 20 24 10 0.4379 0.4550 21 10 25 0.0311 0.0248 22 11 24 0.0878 0.0734 23 12 13 0.0949 0.0622 24 18 12 0.3339 0.3051 25 29 12 0.0515 0.0664 26 13 19 0.0551 0.0496 27 15 14 0.1823 0.1901 28 14 28 0.0103 0.0102 29 15 17 0.0647 0.0624 30 26 16 0.0334 0.0966 31 27 16 0.0138 0.0137 32 20 30 0.0112 0.0000 33 25 23 0.0084 0.0084 http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 721 from observation, the five most fragile lines while juxtaposing the lqp and the lmn are shown in bold prints in table 2. it is evident from the two indices that the line from bus 11 to 10, line (1110) which is from oshogbo to ikeja-west, is the most fragile line in the nigerian transmission network. under normal operating conditions, the lmn reveals a value of 0.8813 for the line from oshogbo to ikeja-west while the lqp has a value of 0.9924 for the same line. it is also discovered that the next two most fragile lines are the lines from ayede to ikeja-west, i.e. line (24-10) and from kaduna to kano, i.e. line (12–18). the values obtained for the lmn and lqp for each line are very close; indicating the accurate computation which further verifies the effectiveness of the two tests of the line stability as deployed for the nigerian transmission network. in case of the line from bus egbin to ajah, i.e. line (25-23), the values obtained for the two indices are in fact the same (0.0084). however, in some cases, a difficulty arises in asserting the fragility of the line where the values obtained for the two indices are contrasting as in the case of the line (7-31). this is a rare case which can be handled by further research that is not covered in this work. since voltage collapse is closely related to reactive power component of the line or network; thus its consequence on the notably weak buses was determined. this provides information on the extent of the proficiency of the methods. the result is as presented in table 3. table 3: characteristic behaviour of nigeria transmission line to stability indices at critical line with variation in reactive power magnitude (mvar) q (mvar) lqp lmn 200 210 0.9912 1.0031 0.881 0.8845 220 1.0155 0.8885 230 1.0286 0.8931 240 1.0422 0.8981 250 1.0565 0.9034 260 1.0713 0.9089 similarly, table 4 provides information on the behaviour of the same transmission network to the phenomenon of the real power flow. the values of both the stability factor (lqp) and line stability indices (lmn) are within the threshold on both sides of unity. the import of these values is quite informative in regard of the influence of the realm power flow on the system collapse. this would be further discussed later in this work. table 4: characteristic behaviour of nigeria transmission line to stability indices at critical line with variation in real power magnitude (mw) p (mw) lqp lmn 250 260 270 280 290 300 310 0.9632 0.9979 1.0327 1.0676 1.1025 1.1375 1.1726 0.8504 0.8873 0.9248 0.9631 1.0022 1.0421 1.0828 from the foregoing, tables 3 and 4 narrated the characteristic behaviour of the most fragile line in relationship to the line stability indices, i.e. lqp and lmn with varying values of real and reactive power magnitudes respectively. table 3 shows the variations of reactive power only while table 4 depicts that of the real power only. further investigation was made by varying both real power and reactive power at the same time within a specific value range. from this consideration, thus table 5 was generated; as presented. http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 722 table 5: characteristic behaviour of nigeria transmission line to stability indices at critical line with variations in both real power (mw) and reactive power (mvar) flow in the network q (mvar) p(w) lqp lmn 200 210 220 230 240 250 250 260 270 280 290 300 0.9620 1.0086 1.0560 1.1040 1.1527 1.2021 0.8502 0.8905 0.9339 0.9804 1.0300 1.0828 table 5 showed a more probable case of variations in both reactive and real power flow in the network; especially with regard to the highly fragile lines. on this table, it is observed that the lqp is more sensitive to load changes. from the table, as the load is increased to 210mw and 260mvar, which is a meagre variation in load, it could be observed that the lqp increases above unity which is a very grievous indication that collapse would occur in the network. with the deployment of figure 2, the powerworld simulation is obtained as displayed in figure 4. in the vivid pictorial illustration captured in figure 4, the contingency analysis of the network was easily evaluated using powerworld simulator. thus this aided in the identification of the location of the weakest lines in the network. hence from the powerworld simulation of the transmission network of the nigeria-31 bus system, it is apparently confirmed that the same lines that have been identified as the weakest buses (using the analytical technique). this is narrated pictorially and illustrated by the limited flow of power to the adjoining lines in figure 4. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 723 figure 4: powerworld simulation of nigeria-31 bus transmission network http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 724 the nigeria31 bus system as presented in figure 5 is shown below. figure 5: one line diagram of the nigeria-31 bus transmission network from the outlook of figure 4 which is developed from figure 5, the nigeria’s transmission network is obviously weak though there are some lines that exhibit more fragility than others. from this study; a number of the buses identified to be threatened by this fragile lines would naturally not be able to supply continuous load to the load centres due to the blackout as the evidence of voltage collapse. from the outlook of table 2 and figure 4; some of the weakest lines in the system include line (11-10) i.e. from oshogbo to ikeja-west (wherein lqp is equal to 0.9924, lmn is equal to 0.8813 for normal operating conditions), so also is line (24-10) i.e. from ayede to ikeja-west (lqp is equal to 0.4379, lmn is equal to 0.4550 for normal operating conditions) and line (12-18) i.e. from kaduna to kano in which lqp is 0.3339 while lmn is 0.3054 for normal operating conditions. from the pictorial output of the powerworld simulation as displayed in figures 4; it is generally observed that those listed weak buses have terribly low magnitude of flow of power from sending bus to the receiving bus which further affirm the test of fragility obtained for the network. hence, table 6 is a narration of the influence of the contingency analysis of the nigeria’s transmission network. in which case, the critical lines were identified along with the buses that are violated in the network. this gives the summary of the fragility analysis of the network. furthermore, when the two most fragile lines (i.e. oshogbo to ikeja-west and ayede to ikeja-west) are subjected to contingencies (as depicted in figure 2), the buses at kaduna, jos, gombe and birnin-kebbi are likewise violated (see table 6). http://www.azojete.com.ng arid zone journal of engineering, technology and environment, december, 2018; vol. 14(4):713-726. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng 725 table 6: violations recorded with contingency on critical lines s/n critical line violated buses 1 from oshogbo to ikeja-west jos gombe birnin kebbi kaduna 2 from ayede to ikeja-west jos gombe birnin kebbi kaduna considering the set of violation recorded by subjecting the critical lines to contingencies, it can be concluded that the vulnerability of these lines to fragility is highly undesirable. this thus implies that any small variation in the load at the buses adjoining the critical lines makes the network to be susceptible to violation in a number of buses within the system. for instance for the case at hand, it is evident from table 6, that at least four buses in the grid experience security margin violation. this therefore calls for an urgent upgrade of the critical lines in the system because the weakest lines would determine the overall stability status of the whole network. 4. conclusion from the foregoing it was established the powerworld simulator’s flow analysis that that the line with least flow across it are the weakest lines. this approach was used to determine the integrity status of the network. this is as a further support to the stability indices which primarily tested the stability margin of the network. thus, this discovery then means that the nigeria’s transmission network has violated buses as jos, gombe, birnin-kebbi and kaduna. this is attributed to the influence of the poorly linked connection from oshogbo to ikeja-west and ayede to ikeja-west. these lines are considered as the weakest connection which suggests that they are the most critically fragile lines in the network. in other words, the analysis has shown that two buses whose lines are adjoining the ikeja-west bus are highly fragile (i.e. oshogbo and ayede). it is therefore recommended that these lines should be considered for reinforcement (using either transmission expansion programme or deployment of the flexible alternating current transmission systems (facts) devices such as svc, upfc, etc) as they are highly susceptible to voltage collapse. in the same vein, in the northern part of the country, i.e. the line from kaduna to kano should be considered as primary target for the transmission expansion programme scheme. this will improve the quantity and quality of electricity delivery to this part of the country. for a wholesome solution to the challenges of electricity supply, the frontier of this research may be further extended to consider the effects on vandalism on grid fragility whilst the study of the cost analysis of implementing remedies to fragility in the network may be considered as area of future research interest. whilst the another simulator such as etap load flow software tool may be deployed to solve this problem whose output could be compared with that of the powerworld simulator. the study has undoubtedly revealed the susceptibility of the nigeria’s transmission network to voltage collapse with empirical evidence of the locations that need to be fortified against violation induced by the fragility of the network. acknowledgment the authors wish to appreciate the faculty of engineering of university of lagos, akoka for the privilege to access the design facilities in the lg design laboratory for conducting this study. http://www.azojete.com.ng oluseyi et al.: comparative analysis of grid fragility indices in the nigerian transmission network. azojete, 14(4):713-726. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 726 references airoboman, ea., okakwu, ki., amaize, ap. and oluwasogo, es. 2015. an assessment of voltage instability in the nigerian power system network. the international journal of engineering and science (ijes), 4(7), 9-16. awosope, ca. 2014. nigeria electricity industry: issues, challenges and solutions. covenant university press, 3(2), 1-40. egeruoh, cc. 2012. long term transmission expansion planning for nigerian deregulated power system (a systems approach). delft university of technology, 1-115. goh, hh., chua, qs., lee, s., kok, b., goh, kc. and teo, k. 2015. evaluation for voltage stability indices in power system using artificial neural network. procedia engineering, 118, 1127-1136. moghavvemi, m. and omar, f. 1998. technique for contingency monitoring and voltage collapse prediction. iee proceedings-generation, transmission and distribution, 145(6), 634640. oluseyi, po., akinbulire, to., awosope, coa. and odekunle, m. 2009. modelling of electricity market in europe: a lesson for nigeria. 6th international conference on the european electricity market (eem’09), leuven, belgium, may 27-29, 393-399. oluseyi, po. 2010. optimal power flow solution to voltage collapse in deregulated electricity market. phd thesis, university of lagos, nigeria. oluseyi, po., atasie, ic. and akinbulire, to. 2012. introducing optimization concept to electric load management in a developing economy, proceedings of unilag research conference 2012, vol. 3, 28-37. oricha, jy., oluseyi, po. and akinbulire, to. 2009. the importance of reserve market in terms of manoeuvrability and network limitation. proceedings of international conference of power systems and telecommunications, university of lagos, nigeria, july 22-24, 79-81. ratra, s., tiwari, r., niari, kr. 2018. voltage stability assessment in the power systems using line voltage stability index. computers and electrical engineering, 70,199-211. samuel, i., katende, j., daramola, as. and awelewa, a. 2014. review of system collapse incidences on the 330-kv nigerian national grid. international journal of engineering science invention, 3(4), 55-59. scott, rd. 2012. n-1-1 contingency analysis using powerworld simulator, powerworld corporation, 1-14. sinha, ak. and hazarika, d. 2000. a comparative study of voltage stability indices in power system. international journal of electrical power and energy systems, volume 22, issue 8, 589596. tran, mt. 2009. definition and implementation of voltage stability indices, chalmers university of technology. http://www.azojete.com.ng for proper and effective identification of the wea arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):623-634 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 623 original research article development and design of a microcontroller-based gas weight and leakage detection system o. fagbohun1, o. fagbohun1, o. obiyemi2*, and k. moloi3 1department of electrical & electronics engineering, university of ibadan, nigeria 2space science centre, dept. of electrical power engineering, durban university of technology, durban, south africa 3department of electrical power engineering, durban university of technology, durban, south africa *corresponding author’s email address: obiseyeobi@gmail.com 1.0 introduction the use of electronic devices has become a norm in everyday life. it contributes significantly to various aspects of human activities at domestic and industrial levels, enabling greater efficiency and enhancement in these activities. some of these devices are able to sense, monitor, and control various activities (falohun et al., 2016). liquefied petroleum gas (lpg) is a term used for a mixture of hydrocarbons that is stored in a specified cylinder for confinement purposes (ihemtuge and aimikhe, 2020). lpg is a clean source of fossil fuel and is used by domestic, commercial, and industrial users. it is mostly used for cooking purposes in nigeria, accounting for major domestic use. lpg is used in households due to its relative speed of getting the cooking work done, thereby saving time during cooking activities. moreover, it also offers a cleaner environment olorunfemi et al. (2020), with increasing penetration across urban, suburban, and rural settlements and the potential to enhance the united nations sustainable development agenda. article information abstract this paper presents the design and development of a prototype system for monitoring gas leakage and weight in residential and semi-commercial. liquid petroleum gas (lpg) installations lpg is widely used as a fuel source, but its leakage can lead to devastating fires, posing a significant threat to life and properties. traditional methods of gas management based on natural nasal detection and estimation of usage are considered unsafe. the proposed system incorporates the mq-5 sensor for gas leakage detection and the hx711 ic device for weight sensing. it includes a user alert system with a buzzer and led for timely notifications of gas leakage and low gas levels. the control system, driven by the atmega328p microcontroller, receives data from the sensors and triggers alerts accordingly. the power unit utilizes a 3.7-volts amplified lithium polymer battery stepped up by the mt3608. the results show that through week-long testing, the prototype demonstrated its effectiveness in monitoring weight and gas leakage, with constant monitoring of sound, led, and display readings. this paper offers insights for replication as students projects, and suggests the need for more testing and calibration to ensure safety and the need for iot-enabled features for smarter deployment and management. furthermore, the prototype had contributed to promoting safety and preventing accidents in lpg installations by addressing the critical issue of gas leakage. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 january, 2022 revised 11 july, 2023 accepted 30 july, 2023 keywords: gas leakage lpg microcontroller atmega328p gas detection http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com obiseyeobi@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):623-634. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 624 the use of lpg is on the rise throughout the world owing to the increase in the population and the adverse effects observed from the use of other fossil fuels (wood and kerosene) contributing to climate change (ihemtuge and aimikhe, 2020). it was also observed that alternative sources of energy have caused severe health conditions, which include low birth weight and tuberculosis (bergvall et al., 2005). however, the use of lpg attracts a great feeling of insecurity due to the fear of explosions, according to fraiwan et al. (2011), with some statistics in figure 1. it is noteworthy that some of the factors responsible for gas-related explosions include the proliferation of sub-standard lpg cylinders, over-pressurized cylinders, lack of adequate inspection and maintenance, and human-related errors (klaene and sanders, 2007). most people, therefore, often regard it as a highly risky energy source and therefore use it with fear. gas-related fire incidences often occur due to the uncontrolled combination of gas with oxygen, aided by a momentary unintended spark (falohun et al., 2016). the level of explosion, fire, and suffocation caused by a gas leak depends on the physical properties of the gas (such as toxicity and flammability) (das et al., 2018). lpg is used in heating appliances, cooking equipment, and automobiles. hence, fire incidents can occur at these points of usage, sale, and transportation. while lpg is used in stove burners in most homes, offices, hotels, restaurants, and workshops, it is conveyed using tubes. mishandling of tubes and other gadgets can result in unwanted leakage of gas into the work area. fire incidences are always severe, claiming lives, properties, and other important items during the occurrence (odonkor, 2020). exposure to lpg also leads to cold burns to the skin, loss of consciousness, and subsequent anoxia (olorunfemi et al. 2020). hence, the need to develop a device that is able to detect the leakage of gas from cylinders at various points of usage to ensure the safety of human life and properties. figure 1: statistics on accidents involving the use and handling of lpg and natural gas in jordan (fraiwan et al., 2011) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com fagbohun et al: development and design of a microcontroller-based gas weight and leakage detection system. azojete, 19(3):623634. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 625 over the years, various related designs have been developed to ensure the safety of life and properties during lpg usage. apeh et al. (2014) and loshali et al. (2017) developed a kitchen gas leakage system which notifies occupants via an alarm system to ensure safety. similarly, shinde et al. (2012) developed a leakage detection system that employs the use of artificial intelligence and machine learning. the system can also detect the level of gas and leakage in the cylinder and is also equipped with an sms feedback system to notify occupants. furthermore, murugam, (2020) also conducted a study in which an intelligent gas booking and leakage system was developed, employing the use of wireless sensors to notify owners of leakage and the current weight of gas in the cylinder. shrivastava et al. (2013) developed a gsm-based gas leakage detection system. this creates a wireless notification which is sent to occupants or users regardless of their geological location. in the recent designs by anika et al. (2021), the arduino uno microcontroller was used to create a smart gas detection system using a variety of sensors and actuators (mq2, ir fire sensor, air fan, buzzer). when a gas leak is detected, the customer will be notified through sms and via the blynk application at the same time. again, a recent study by amadi et al. (2021) identifies a distribution mechanism for safely transporting cooking gas to homes in rivers state. this gas distribution strategy is based on a single supplier, which could be public or private. choba was chosen as a case study due to its strategic location. additionally, gas properties were analyzed in conjunction with pipe properties. although the study provides an economic analysis of how distributing cooking gas to homes can increase nigerian gas utilization and benefits over the next decade, its feasibility remains a major concern. this study was aimed at the design and development of a prototype for monitoring gas leakage and weight in residential and semi-commercial lpg installations. it is a simple electronic system capable of detecting gas shortages or leaks and alerting users to the occurrence early enough to mitigate gas-based accidents. 2. materials and methods the functionality of the designed gas leakage and level detection system is divided into the following sub-sections, which operate in concert to accomplish the prototype's objectives: sensing unit, user alert system, power/charging unit, and control unit. the sensing operation is based on the sensory circuitry, which is comprised of a gas leakage sensing circuit and an active weighing circuit. figures 2(a) and (b) depict the weight sensor hx711 ic and its circuit diagram, which operates within a voltage range of 2.6 to 5.5v. these diagrams provide a detailed representation of the necessary connections and components to ensure accurate weight measurements in the system. on the other hand, figure 2(c) showcases the circuit design for the sensing knobs, essential for user interaction and control. the circuit design enables seamless integration of the sensing knobs, allowing users to interact effectively with the system. the provided circuit diagrams offer valuable insights into the connections, components, and design considerations needed for the successful implementation and functionality of the weight sensor hx711 ic and the sensing knobs within the system. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):623-634. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 626 (a) (b) (c) figure 2: (a) 50kg load cell and (b) hx711 load cell amplifier circuit (c) sensing buttons for decision making. (a) (b) figure 3: (a) the mq-5 gas sensor (b) mq-5 circuit diagram. for intelligent gas leakage detection, the mq-5 gas sensor was employed due to its exceptional capabilities. the sensor offers several advantages, including high sensitivity, quick response time, and the ability to detect a wide range of gases such as ethane and methane. to ensure proper functionality, the mq-5 sensor requires a 5v direct current (dc) power source. therefore, a 5v supply voltage was employed to power this specific component in the prototype design. the circuit diagram for the mq-5 gas sensor is illustrated in figure 3(a) and (b), providing a visual representation of the connections and components involved in incorporating the sensor into the system. by utilizing the mq-5 gas sensor and adhering to its voltage requirements, the prototype design achieves efficient and accurate gas leakage detection. the prototype incorporates a liquid crystal display (lcd) measuring [80.0 x 36.0 x 13.5] mm as shown in figure 4(a), providing users with timely information. the lcd utilizes the advanced capabilities of the atmega328p microcontroller for seamless communication and displaying the lpg's weight and leakage status. the circuit diagram for the lcd display is depicted in figure 4(b). additionally, the device features a light-emitting diode (led) as an extra user indicator, indicating various levels and conditions such as "low gas," "gas leakage," and "power on or off." the circuit diagram for the led indicator unit is shown in figure 4(c). to regulate the led current, a 10 kω resistor is employed, adhering to ohm's law (equation 1) (theraja, 2006). 𝑉 = 𝐼 𝑥 𝑅 (v) (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com fagbohun et al: development and design of a microcontroller-based gas weight and leakage detection system. azojete, 19(3):623634. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 627 where 𝑉 is the voltage in volts (v), 𝐼 is the current in amperes (a), while 𝑅 is the resistance in ohms (ω). (a) (b) (c) figure 4: (a): liquid crystal display (b) lcd display circuit diagram (c) indicator light circuit diagram an effective buzzing system is integrated into the prototype to promptly notify and warn users. the circuit diagram for this buzzing system can be seen in figure 5(a), illustrating the connections and components involved in generating the audible alerts. the buzzing system plays a crucial role in enhancing user awareness and ensuring timely response to gas leakage or low gas level, thereby enhancing user safety and attentiveness to critical situations. the device relies on a 3.7v (nominal) lithium polymer battery with a 2a current rating to power its operations. to regulate the battery's charge and discharge rate, the tp4056 integrated circuit (ic) is utilized. this ic ensures the optimal management of the battery's performance and longevity. the tp4056 ic outputs a voltage of 4.2v, which is then directed to the mt3608 bulk converter (figure 5(b)). the mt3608 converter steps up the voltage as required, allowing the device to operate at higher voltage levels necessary for specific components or subsystems. through the combined use of these components, the device effectively utilizes the power supply from the lithium polymer battery, with controlled charging and discharging (figure 5(c)), and the ability to handle higher voltage requirements when needed. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):623-634. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 628 (a) (b) (c) figure 5: (a) output buzzer circuit diagram, (b) mt3608 circuit diagram, (c) tp4056 circuit diagram to power the atmega328p microcontroller and other sensors and units, a voltage boost is employed to increase the voltage to 5v. this step is necessary to ensure proper operation and functionality. additionally, the control unit becomes essential in situations where the power supply operates in multiple phases, providing synchronized and regulated electrical current. by employing these measures, the prototype achieves optimal power supply management and ensures the reliable operation of the system components. the pin mapping for the microcontroller is as shown in figure 6 with a section of the circuit diagram of the gas leakage detecting system. figure 6: microcontroller pin mapping with a section of the circuit diagram for the system file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com fagbohun et al: development and design of a microcontroller-based gas weight and leakage detection system. azojete, 19(3):623634. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 629 the gas leakage detection system's circuit diagram is visually represented in figure 6, providing an overview of the interconnected components and their relationships. the foundation of the system design primarily relies on the utilization of the atmega328p microcontroller, which serves as the central processing unit. alongside the microcontroller, various input devices play crucial roles in the system's functionality. these input devices consist of the mq5 gas sensor, responsible for detecting gas leakage, the weight measuring sensor for monitoring weight-related parameters, and the control knobs enabling user interaction and adjustments. additionally, the system incorporates several output devices that provide relevant information and alerts. these output devices include a liquid crystal display (lcd) for presenting relevant data and messages to the user, a buzzer to generate audible alarms or notifications, and led indicators to visually convey specific system states or conditions. by integrating these components into the circuit design, the gas leakage detection system becomes a comprehensive solution capable of accurately sensing gas leakage, monitoring weight measurements, facilitating user control, and conveying vital information through the lcd, buzzer, and leds. 𝐹𝑆 = 1 (2𝜋 √𝐿𝑆 𝐶𝑆)⁄ (2) where 𝐹𝑆 is the oscillating frequency of the crystal oscillator, 𝐿𝑆 is the inductance which is given as 4.5 𝑥 10−6𝐻 , while 𝐶𝑆 is the value of the capacitor (theraja, 2006). 16 𝑀𝐻𝑧 = 1 (2𝜋 √4.5 𝑥 10−6 𝑥 𝐶𝑆 )⁄ (3) where 𝐶𝑆 = 11 (16 𝑀 𝑥 2𝜋 𝑥 4.52 𝑥 10−12)⁄ (4) therefore, 𝐶𝑆 = 22 pf the operational flow chart of the system prototype is depicted in figure 7(a), providing a visual representation of the sequence of operations, while figure 8 presents the comprehensive circuit diagram for the system. the proposed design includes a comprehensive conceptual diagram that illustrates the foundation of the system. this diagram is presented in figure 7(b) and demonstrates the designated location for the gas cylinder, which will facilitate accurate measurement of the gas quantity and effective detection of any potential leaks. table 1 shows the circuit connection pinouts. during the circuit design phase, the sizing of the capacitor was determined using equations (2) to (4). these equations served as guidelines for establishing the appropriate capacitor size, taking into consideration the frequency of the crystal oscillator, which operates at a frequency of 16 mhz. by employing these equations, the accurate selection and integration of the capacitor to optimize the functionality and performance of the system was ensured. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):623-634. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 630 (a) (b) figure 7: (a) operational flow chart of the working prototype, (b) the comprehensive conceptual diagram for the system figure 8: the comprehensive circuit diagram for the system file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com fagbohun et al: development and design of a microcontroller-based gas weight and leakage detection system. azojete, 19(3):623634. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 631 the prototype incorporates two essential software components: a basic programming language compiler adhering to the avr microcontroller programming language standard and the arduino development environment. the compiler facilitates programming and interfacing with the avr microcontroller, ensuring compatibility and smooth functionality. it provides a comprehensive set of tools for code writing, compiling, and uploading to the microcontroller. on the other hand, the arduino development environment offers a user-friendly platform for coding, compiling, and uploading programs. it simplifies the development process with its extensive library of pre-written functions and examples. by utilizing these software tools, efficient code development was achieved and the capabilities of the avr microcontroller to achieve the desired functionalities effectively was harnessed. table 1: circuit connection and pinouts s/n function connector indication on the microcontroller 1 power +5 v power (+5 v) gnd gnd 2 weight sensor do analog pin 0 ck analog pin 1 3 gas sensor ad2 analog pin 2 4 buzzer io11 digital pin 11 5 led d1 analog pin 4 d2 analog pin 5 6 push button rst reset s1 digital pin 10 (pwm) s2 digital pin 13 7 crystal oscillator clk1 crystal clk2 crystal 8 lcd io3 digital pin 3 io4 digital pin 4 io5 digital pin 5 io6 digital pin 6 io7 digital pin 7 io8 digital pin 8 io9 digital pin 9 3. system assembly and testing the proposed device incorporates various components and electronic parts enclosed within a plastic-based casing measuring (400 x 300 x 100) mm. before attaching the indicators and knobs, precise perforations were made in the casing to accommodate these elements. the choice of this casing material stemmed from the desire for aesthetic appeal and insulation, ensuring safety during liquid gas system (lgs) installation. figure 9(a) displays the system prototype, highlighting the enclosure for the circuitry and the display unit. figure 9(b) presents a side view of the base on which the cylinder is positioned. the prototype features an led display indicating sample weight and detected leakage as "wgt: http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):623-634. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 632 0.00kg" and "base: 0.00kg," respectively. the gas sensor operates within an analog value range of 0 to 1023. when gas leaks, sensor readings above 300 indicate higher gas concentration and turn on the led and buzzer to alert of gas presence in the environment. readings below 300 indicate no leaks. these design considerations and features significantly contribute to the overall functionality and effectiveness of the gas detection system. over a week, the weight and gas leakage detector were tested under typical operating settings without gas leaks. throughout this period, the system was continuously monitored, including the buzzer, observation of led indicators, and tracking of display readings. the device was subjected to further testing, which included the random release of gas into the environment to assess its responsiveness under different unquantified concentration levels. (a) (b) figure 9: (a) gas leakage sensor in the prototype enclosure showing the display unit (b) side view showing the gap between the weight sensor and the top plate for the base of the system. 4. results and discussion this section presents the results of our preliminary assessment of the gas leakage and weight detection system. based on the observations derived from the initial evaluation, it can be concluded that the prototype demonstrates satisfactory performance. this is evident from the consistent readings obtained from the mq-5 sensor, which consistently fell within the predetermined thresholds for both safe and unsafe conditions. notably, the activation of the buzzer and led indication was observed exclusively when the readings indicated an unsafe range, i.e., for readings exceeding 300. in addition, the weight sensor successfully recorded a progressive decline in gas volume over the duration of the observation time. nevertheless, it is important to recognize that additional extensive standardized testing may be necessary to evaluate the effectiveness of the gas sensor. this testing could encompass several aspects such as sensitivity, as well as tests examining its performance under different temperature and humidity conditions. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com fagbohun et al: development and design of a microcontroller-based gas weight and leakage detection system. azojete, 19(3):623634. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 633 5. conclusion this paper presents the successful design and implementation of a gas leakage and weight sensing system prototype. the system offers a straightforward yet effective solution by promptly alerting users in the event of a gas leak and providing gas cylinder level indications, thereby mitigating potential explosions in residential and industrial environments. this documentation serves as a valuable guide for replication and adaptation by electrical and electronic engineering students working on mini projects within higher education institutions (heis), as well as for entrepreneurs with a solid electronics background seeking to pursue personal projects. the components utilised in the prototype are easily accessible and economically viable, resulting in a total expenditure of n30,000. this stands in contrast to the comparatively greater expenses associated with preexisting commercial products or devices. furthermore, future enhancements such as integrating iot-enabled capabilities can be explored to enhance usability and functionality. despite the device's functionality and gas leak response, more testing and calibration are needed to further guarantee increased safety and notify consumers. this prototype represents an important contribution to gas safety measures and offers potential avenues for further advancements in the field. references amadi, ah., uneh, gie., ene, oc., onwa, fc. and andré, dn. 2021. cooking gas (lpg) distribution to rivers state homes, case study: choba community. european journal of engineering and technology research, 6(4): 77–84. anika, am., akter, mn., hasan, mn., shoma, jf. and sattar, a. 2021. gas leakage with auto ventilation and smart management system using iot. in proceedings of 2021 international conference on artificial intelligence and smart systems (icais) held in coimbatore, india, 25-27 march 2021: 1411–1415. apeh, st., erameh, kb. and iruansi, u. 2014. design and development of kitchen gas leakage detection and automatic gas shut off system. journal of emerging trends in engineering and applied sciences, 5(3): 222–228. bergvall, n., iliadou, a., tuvemo, t. and cnattingius, s. 2005. birth characteristics and risk of high systolic blood pressure in early adulthood: socioeconomic factors and familial effects. epidemiology, 16(5): 635–640. das, t., bag, a., das, s. and dawn, tk. 2018. a novel approach to design a new detector unit to detect liquefied petroleum gas with mobile alert and auto shut down facility. international journal of research in electronics and computer engineering, 6(3): 1067–1069. falohun, as., oke, ao., abolaji, bm. and oladejo, oe. 2016. dangerous gas detection using an integrated circuit and mq-9. international journal of computer applications, 135(7): 30–34. fraiwan, l., lweesy, k., bani-salma, a. and mani, n. 2011. a wireless home safety gas leakage detection system. in proceedings of the 1st ieee middle east conference on biomedical engineering held in sharjah, united arab emirates, 21-24 february 2011: 11–14. ihemtuge, tu. and aimikhe, vj. 2020. optimization of liquefied petroleum gas (lpg) distribution in nigeria. international journal of engineering and technical research, 10(5): 8–14. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):623-634. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: obiseyeobi@gmail.com 634 klaene, b. and sanders, r. 2007. structural firefighting: strategy and tactics jones & bartlett learning. 2nd ed. national fire protection association, london. loshali, g., basera, r., darmwal, l. and varma, s. 2017. design & implementation of lpg gas detector using gsm module. international journal emerging technologies, 8(1): 98–100. murugam, k. 2020. intelligent gas booking and leakage system using wireless sensor networks. in proceedings of kalasalingam global conference 2019 international conference on sustainable development held in tamilnadu, india, december 18-20, 2019: 273-284. odonkor, en. 2020. design and implementation of an intelligent gas cylinder valve regulating system using solenoid. international journal of computer science, engineering and applications, 10(4): 19–24. olorunfemi, bj., adenuga, de. and olumilua, ae. 2020. development and performance evaluation of a household liquefied petroleum gas monitoring and leakage detector. covenant journal of engineering technology, 4(2): 11–22. shinde, s., patil, sb. and patil, aj. 2012. development of movable gas tanker leakage detection using wireless sensor network based on embedded system. international journal of engineering research and application, 2(6): 1180–1183. shrivastava, a., prabhaker, r., kumar, r. and verma, r. 2013. gsm based gas leakage detection system. international journal of technical research and applications, 1(2): 42-45. theraja, bl. 2006. fundamental of electrical engineering and electronics. chand (s.) & co ltd, new delhi, india. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/obiseyeobi@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):113-132 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 113 design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution t. adefarati1*, f. i. bawonda2, p. k. olulope3,1, j. a. onipe4, k. o. adisa5, h. d. idris4, a. o. abubakar4, g. s. alabi1, g. s. borisade6 and a. sobowale7 1department of electrical and electronic engineering, federal university oye ekiti, nigeria 2department of electrical and electronic engineering technology, kogi state polytechnic, lokoja, nigeria 3department of electrical and electronics engineering, ekiti state university ado ekiti, nigeria 4department of computer engineering technology, kogi state polytechnic, lokoja 5department of mechatronics engineering, lagos state university science and technology, ikorodu, lagos. 6department of metallurgical and materials engineering, federal university oye ekiti, nigeria 7department of computer engineering, federal university oye ekiti, nigeria *corresponding author's email address: temitope.adefarati@gmail.com article information submitted 9 january, 2024 revised 15 february, 2024 accepted 20 february, 2024 keywords: battery storage system fuel cost photovoltaic rainy season wind turbines abstract the use of renewable energy sources has increased significantly on global note as a result of the continued depletion of fossil fuel sources, removal of subsidies on petroleum products, growing environmental concerns, government policies and breakthroughs in power electronic technology. the global energy industry has numerous difficulties, including balancing power supply and demand in the face of steady demand growth and unstable crude oil prices. the utilization of renewable energy sources in the conventional power systems has facilitated the establishment of self-sustaining hybrid energy system (hes) that consists of photovoltaic (pv), battery storage system (bss), diesel generator (dg) and wind turbines (wt). the hess that integrate multiple sources have become popular for power solutions due to their cost effectiveness and reliability when compared to conventional power systems. an effective energy management system is proposed in this paper to address the uncertainty problem and ensure the best operation of hes by using genetic algorithm. the study aims to reduce the fuel cost and usage of bss and maximize the use of wt and pv. this article compares the relevant fuel costs and assesses the performance of the hes over a 24-hour horizon by considering the daily fluctuations in energy usage on weekdays and weekends. the simulation results demonstrate that fuel cost savings of 33.81% and 33.63% are achieved in the rainy season and 35.97% and 35.55% fuel cost savings in the dry season when compared to the dg alone. the proposed model can be utilized to reduce fuel cost by taking into account changes in the patterns of power consumption during dry and rainy seasons. 1.0 introduction the power sector on a global scale, the power sector is experiencing numerous problems, such as balancing ever-increasing load demand, limited power generation, reliability challenges and environmental issues. the rapid rise in the world's energy consumption has been linked to various factors such as industrialization, increased regional manufacturing, economic and industrial growth in developed and developing countries, population growth, high standards of living, and the establishment of retail outlets (adefarati et al., 2023). the degree of poverty in any community is determined by the sustainability of the electricity supplied by the utility or http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 114 independent power producers to such areas. access to electricity plays a pivotal role in alleviating poverty, boosting economic growth and commercial activities, and raising of living standards (adefarati et al., 2020). currently, about 733 million people on a global scale lack access to electrical power supply owing to erratic power supplies, inconsistent government policies, aging generation, transmission and distribution infrastructures, limited access to the grid and incompetent work force of the utilities (world bank, 2022 and oluwatoyin et al., 2015). according to the energy progress report 2022 published by tracking sdg 7, nigeria is among the nations with the least amount of access to electricity globally, with approximately 92 million of the 220 million people living in the country lack access to electricity (tracking sdg 7, 2022). the world bank record shows that nigeria's power outages cost the country over $29 billion. this amount is equivalent to 2% of nigeria's gross domestic product. the bank report also indicates that over 40% of nigerians do not have to access to the utility power supply, and those who do have regular outages. the nation's industrial development, business enterprises' growth and profitability and the welfare of its citizens have all been hindered by the ongoing power crisis (world bank, 2020). the epileptic electricity supply to the load points has hindered over 100 million people that should have been raised out of poverty with boom economic activities that associated with uninterrupted power supply. the present installed capacity of the power stations in nigeria does not match the country's population's energy demand because of inadequate policies and infrastructure (oyedepo, 2012). the nigerian government needs to invest $10 billion per year for the next 20 years to achieve a continuous power supply for optimal industrial applications and human growth capacity. the amount of energy produced by nigeria's electricity industry is far less than what is required to meet the country's industrial and domestic demands (elinwa et al., 2021). the industry worked so hard in 2012 to generate 5,000 mw, a significant amount that is less than the 40,000 mw required to meet the population's power demands. this shortfall ultimately led to unplanned load shedding and partial and complete system collapse. it has been projected that nigeria needs nothing less than 40,000 mw to reach sufficiency by 2030 (okoh et al., 2023). the average electricity per capita in nigeria is 14 w; this shows that nigerians have been seriously depressed by the nature of power supply when compared to other countries (wikipedia, 2023). the epileptic power supply in the country has compelled the industrial and commercial sectors to end up turning what should be a backup power source into a primary source without considering the costs involved. as a result, industries and retail outlets pass on the operation and maintenance costs of their generators to the general public through higher prices for goods and services. the current status of the country’s transmission infrastructure is not reliable and weak, and has a limited coverage area. the tcn transmission network is made up of nearly 20,000km of transmission lines and a wheeling capacity of 7,500 mw (nerc, 2023). the total installed generation capacity of 12,522 mw is far greater than the existing transmission wheeling capacity of 5,300 mw, but it is more than the average power station generating capacity of 3,879 mw. there are inherent dependability problems because the entire system is essentially radial and lacks redundancy. the power loss across the transmission system is estimated to be about 7.4%; this value is substantial when compared to the benchmarks of emerging countries that fall within the range of 2 and 5%. the number of system collapses has decreased in recent years from 42 in 2010 to 25 in 2022. all of these highlight the vital infrastructure and practical problems facing the transmission subsector of nigeria's power system (nerc, 2023). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 115 nigeria is not an exception to the worldwide trend that has seen the rise of solar and wind energy as a potential and sustainable substitute for traditional energy sources. the country has several energy-related issues, such as an excessive dependence on fossil fuels and restricted access to power (adeyanju et al., 2020). with rising legislative efforts, technological improvements, and investment, renewable energy resources have a bright future in nigeria. the domestic and foreign investment in solar and wind energy projects has increased in recent times owing to the government's initiatives to encourage investments in renewable energy, enactment of supportive laws and the creation of incentives. the federal government agency has developed policies that encourage the incorporation of solar power into the national grid through the electricity act of 2023 and the renewable energy master plan of 2005 (psc solar, 2023). one of the main issues in nigeria's rural areas is the lack of access to electricity, which can be fixed by using renewable energy sources (ress). rural electrification projects with embedded solar and wind technologies can be utilized to expand access to electricity in remote areas and improve the well-being of the rural residents. the technological development coupled with reduction of the costs of hes components is responsible for making clean and sustainable energy more accessible and affordable. the aforementioned factors played an essential role in improving the efficiency of the power system. the application of ress for power solutions reduces overdependence on fossil fuels, reduces the duration of power interruptions, stimulates economic growth, drives job creation, contributes to a cleaner and greener environment, stimulates socio-economic growth, reduces electricity bills, provides potential income for sales of excess power generated, and supports economic empowerment programs. nigeria is endowed with an average daily solar radiation of 4.8 kwh/m to 5.4 kwh/m² and a landmass that covers 923,768 km² that can produce more than 1000 gw from solar resources (psc solar, 2023). the annual energy generated by the pv system is about 27 times that of the nation’s total conventional energy resources (energypedia, 2022). the average wind speed of nigeria on annual basis is estimated to be between 2 m/s and 9.5 m/s, while the annual power density varies between 3.40 kw/m2 and 520 kw/m2 (adaramola et al., 2011). southern nigeria often has slower wind speeds, while wind speeds in the northern portion of the country are consistently higher. if the solar and wind potentials are fully harnessed, this would considerably contribute to satisfying the energy needs of the country and reducing power outages and their associated economic impacts. the design of innovative power solutions to meet continuous power demand and enhance access to energy has been the subject of various studies in the literature. these studies produced a blueprint for the electrification projects that can be carried out to increase residential and industrial access to electricity, typically with a focus on boosting the use of ress and minimizing the operation and maintenance costs of hes. the operational efficiency of hes and several optimization techniques are the focus of a large number of current studies. khalilnejad et al. (2018) proposed the imperialist competitive algorithm for the optimization of pv/wt/electrolyzer hes and the production of hydrogen using real atmospheric data from miami. zhang et al. (2019) employed the hybrid optimization algorithm to determine the best configuration for a pv/wt/hydrogen energy system by utilizing weatherpredicting information. the benefits of the suggested algorithm with meteorological forecasts for a system that is not dependent on a grid are discovered. zhang et al. (2021) applied a global dynamic harmony search algorithm to a standalone wt/pv/fc/hydrogen storage system to reduce the cost of the system. meanwhile, xu et al. (2021) carried out a technical and financial evaluation of pv/fc off-grid power system that is intended to provide electricity to a rural http://www.azojete.com.ng/ temitope.adefarati@gmail.com https://www.sciencedirect.com/author/14219113600/muyiwa-s-adaramola arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 116 community in china by using the amended water strider algorithm. misra et al. (2017) emphasized the use of ress in a microgrid system. according to the study, using renewable energy sources can cut operational costs, minimize greenhouse gas emissions and increase the flexibility of power supplies. nazari-heris et al. (2017) studied the short-term scheduling of a grid-connected microgrid system that comprises fuel cell, battery system, boiler and heat buffer tank for industrial heat and power solutions. in another study, ahamad et al. (2018) looked into the best energy planning design and assessed the performance of the microgrid by taking into account a pv/wt/bss grid-connected hybrid energy system designed for coastal ports. the outcomes of the study show that the microgrid system is a practical way to supply electrical power to the numerous customers. mutarraf et al. (2020) looked into the usage of battery system and ress in a microgrid system to supply the electrical power required for the operation of coastal ports. the system's ability to lower air pollutants and noise pollution is highlighted in the study. chamandoust et al. (2019) employed demand-side management methods in their decision-making process for the islanded hes to meet power demand and improve the economic and technical assessment of the system. nasser et al. (2022) carried out the technical and financial evaluation of the hes that comprises wt and pv for hydrogen generation under various climate conditions in five egyptian scenarios. diverse renewable energy sources were utilized to optimize hes, according to the previously stated literature. however, there are not much research outputs on the optimal operation of hes considering the effects of load variation and seasonal changes on the performance of the system. moreover, few studies have looked at the implementation of hes in the rural area facilities, despite the growing body of studies on these systems in nigeria's rural areas. the majority of the research concentrated on a single objective function by using a simple optimization technique to carry out their simulation based on the energy management among the components of the system. despite the many benefits of ress, several studies failed to incorporate multi-resources into their systems, a vital component of energy management system that is significant in reducing the fuel cost of the hes. the aforementioned literature also failed to analyze the effects of maximizing renewable energy and minimizing the usage of dg and bs on the fuel costs without considering seasonal variation of load demand as well as solar and wind resources. the previous studies failed to account for the performance of microgrid systems or hybrid energy systems under unpredictable weather and unstable load demand, which limits their application to certain sectors of the economy. moreover, some studies have not taken into account the viability of a remote or grid-connected microgrid system that includes a variety of energy resources and storage devices. in view of this, the abovementioned research gaps will be explored in this study by using a multi-objective metaheuristic algorithm. the current work uses an optimization technique termed the genetic algorithm to minimize the fuel cost and the power delivered by battery system and maximize the use of pv and wt while taking the proper power limits of the components and power demand constraints into account. as a result, a pv/bs/wt/dg hybrid energy system is designed taking into account the seasonal variations of some parameters, including wind speed, temperature, solar radiation and load demand. the ability and effectiveness of the suggested algorithm are demonstrated by comparing and evaluating its performance against fuel cost variations in rainy and dry seasons on weekdays and weekend. the outcomes of the research can be utilized by the government agencies to reduce over 746 million people who do not have access to electricity on a global scale. this will eventually alleviate the power crisis that many file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://www.sciencedirect.com/science/article/pii/s2210670723002299#bib0063 adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 117 nations are experiencing at the moment. the objectives of this paper are succinctly presented as follows: i. to design of a pv/bs/wt/dg hybrid energy system for a rural settlement that is located in north west of nigeria. ii. to develop a model that can be used to minimize the operations of the dg and bss and maximize the usage of pv and wt in the proposed hybrid energy system. iii. to improve the effectiveness of the energy management system and maximize the fuel cost savings of the proposed hybrid energy system by using a genetic algorithm. iv. to develop a model for assessment of the performance of the hybrid energy system based on the seasonal variations of wind speed and solar radiation and changes in load demand. v. to carry out performance analysis of the proposed hes by using solar radiation, wind speed and ambient temperature data obtained from nasa. vi. to control the energy flow among different components of a hybrid energy system. 1. materials and methods 1.1. modelling of an autonomous phovoltaic/wind/battery system/diesel generator hybrid energy system the hes is a combination of different generation technologies such as dg, bss, wt, pv and load demand by sharing the same point of common coupling (ashok, 2007). the combination of conventional and ress in a single system can be used to increase the total benefits compared to a system that relies on a single source such as microturbine, diesel generator and gas generator. the application of renewable generation technologies with backing units such as dg, bss and fc can be used to increase the usage of ress and reduce overall costs, environmental impacts, and system disruptions (bawonda et al., 2023). the dangers that are related to the vulnerability of the local ress can be minimized with the deployment of the bss in a microgrid system (varaiya et al., 2011). to achieve a reliable electrical power supply at a reduced fuel cost, all the accessible ress must be used for power generation solutions (kumar et al., 2014). the financial advantages obtained from utilizing the hes have encouraged the development of numerous models for the utilization of wt and pv (onaolapo et al., 2023). the sum of power supplied by all the components of the proposed hes as shown in figure 1 can satisfy the load demand. http://www.azojete.com.ng/ temitope.adefarati@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 118 figure 1: pv/wt/bss/dg hybrid energy system. 1.1.1. photovoltaic system a photovoltaic system is a device that converts sunlight directly into electricity using semiconducting materials such as silicon and gallium nitride that absorb energy from sunlight. the hourly power produced by the pv system can be calculated by using eqn. (1) (blaabjerg et al., 2015). pvpvpvpv aip = (1) where pvi is the solar irradiation (kwh/m2), pva is the area of the pv panel (m2) and pv is the efficiency of the pv system (%). the efficiency of the pv system can be expressed in eqn. (2) (tazvinga et al., 2015): ( ) ( )         −−−         −= rantantc ntpv pv rpv tttt i i  ,, , 9.01 (2) where r is the efficiency of the pv system measured at reference cell temperature,  is the temperature coefficient of the pv cell, nt is the nominal cell operating temperature conditions, ntpvi , is the hourly solar irradiation on the pv panel at nt test conditions , rt is cell temperature at reference point (oc), ntct , is the cell temperature at nt test conditions, ntat , is the ambient temperature at nt test conditions and at is the ambient temperature (oc). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 119 the solar irradiation and temperature of the selected based on seasonal variation are presented in figure 2. (a) (b) figure 2: solar irradiation and temperature of the selected based on seasonal variation: (a) rainy season; (b) dry season (nasa, 2024). 1.1.2. wind turbine the wt is a machine that uses the aerodynamic force of its rotor blades to transform wind energy into electrical energy, thereby harnessing the energy produced by wind speed. the air density, rotor diameter, pattern of wind speed at a particular location, efficiency of energy conversion, design characteristics of the wt and height of the tower affect the output power of the wt. the power output of the wt can be presented in eqn. (3) as (ashok, 2007): 3 2 1 vacp bgpwtwt =  (3) http://www.azojete.com.ng/ temitope.adefarati@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 120 where ρ is the density of the air (kg/m3), a is the cross-sectional area of the wind turbine (m2), v is the velocity of the wind (m/s), cp is the performance coefficient, g is the generator efficiency and b is the gearbox. the wind speed at a desired speed can be calculated by using eqn. (4).          = ref hub refhub h h vv (4) where refv is the wind speed at reference height is, hubh is the hub height, refh is the reference height and  is the power law exponent. the wind speed of sokoto that is corresponding to each season is presented in figure 3. figure 3: wind speed of the selected area based on seasonal variation (nasa, 2024). 1.1.3. diesel generator a diesel generator consists of an internal combustion engine, alternator and other electrical components to produce electrical energy. the dg can be used as a standby unit for an emergency operation to improve the availability of power supplies. the response time of the dg is satisfactory; it can start and supply the load in less than ten seconds (sechilariu et al., 2016). the fuel consumption of dg is assessed using eqn. (5) (adefarati et al., 2021). )( 2 cbpapcfc dgdgfdg ++= (5) where dgp is the hourly power output of the dg (kw), fc is the cost of diesel per litre (₦/litre), and a, b and c are coefficients of fuel consumed by the dg 1.1.4. battery storage system the bss is a technology that allows energy obtained from renewable energy sources to be stored and released to consumers when it is needed. the battery storage system plays a significant role between renewable energy supplies and corresponding energy demands at the load points. the battery storage systems encourage the adoption of 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 1 3 5 7 9 11 13 15 17 19 21 23 w in d s p e e d ( m /s ) time (hr) dry season file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://www.sciencedirect.com/topics/engineering/internal-combustion-engine adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 121 ress, which lower greenhouse gas emissions and deliver electricity at a reduced cost of energy (adefarati et al., 2017). the battery storage system mitigates the intermittent characteristics of renewable sources and ensures a consistent supply of electricity. the battery system is used for several applications. the battery system dynamic is expressed in eqn. (6).  ==  −+= n inomd n inom c ip e tip e tosocisoc 1 5 1 4 )( 1 ))(()()(   (6) where soc is the state of charge of the bss, c is the charge efficiency of the bss, d is the discharge efficiency of the bss, 4p is the power entering the bss, 5p is the power leaving the bss at sampling interval t , t is the sampling time interval and nome is the nominal energy of the bss. the bss must operate based on the allowable minimum and maximum soc (seelinghochmuth, 1997) as presented in eqns. (7-9). )()()( maxmin isocisocisoc  (7) )()( 1 ))(()( max 1 5 1 4 min isocip e tip e tisoc n inomd n inom c   −  ==   (8) where minsoc and maxsoc are the minimum and maximum soc of the bss. where nom c c e t   = and nomd d e t  =   1 therefore, )()())(()( max 1 5 1 4 min isocipipisoc n i d n i c −  ==  (9) 1.2. study area the study area is located at latitude of 12° 55' 21.34" n and longitude of05° 28' 03.31" e in the north-west of nigeria, as shown in figure 4. the city is located near the confluence of the rima river and the sokoto river, with a population of over 709,000 and a landmass of about 25,972 km2. sokoto is one of the hottest places in nigeria due to its vegetation, which lies between the sudan and sahel savannas. the city has an average annual temperature of 28.3 °c, a maximum daily temperature of less than 40 °c, an average relative humidity of 34.38 mm and an average relative humidity of 30.5%. the floodplains of the rima and sokoto rivers, which are covered with rich alluvial soil, are used for irrigation systems and the cultivation of different types of crops such as maize, guinea corn, beans, millet, rice, onions, tomatoes, cabbage and lettuce. despite being the nation's economic center and home to a wealth of energy resources, such as biomass, solar and wind, it suffers from epileptic power supply. the city currently relies heavily on the national grid and diesel generator sources, both of which have not been able to keep up with the city's energy needs. many small-scale enterprises in sokoto have closed down due to the high rate of power interruptions, and the few that are still open charge exorbitant fees for their services. this leads to a growing interest in the development of models and potential solutions to satisfy the electricity needs of the selected location. http://www.azojete.com.ng/ temitope.adefarati@gmail.com https://en.wikipedia.org/wiki/alluvial_soil arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 122 figure 4: geographical location of the study area. 1.3. formulation of problem the mathematical formulation of the problem is based on a model that can be utilized to optimize the operation of the proposed hes by considering the seasonal variation of the location. the optimization problem is formulated by using ga presented in eqns. (10-11). )(min xf x (10) subject to:            =   =  bb eq eq eqeq uxl andxc xc xc ba bax 0)( ,0)( ,0)( , , (11) where a is the matrix for linear inequality constraints, b is vector for linear inequality constraints, aeq is the matrix for linear equality constraints, beq is the vector for linear equality constraints, lb is the lower bound on x and ub is the upper bound on x. 1.3.1. objective function the objective function of the formulated problem is focused on the optimal scheduling of generation at any time of the day, reduction of the fuel consumption cost and the power delivered by the battery system and maximization of the usage of pv and wt systems while meeting the load demand and other operating constraints of the power system. the objective functions are selected to optimize the system and ensure optimal operation of the hes at the lowest fuel cost. the optimal control technique that is utilized in this research coordinates the power flow among the components of the proposed hes based on the 24-hour horizon. the optimization of this dispatch problem can be carried out by taking into consideration a multiobjective function presented in eqn. (12): file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 123 ( )( ) = −−+++= n k f kpkpkpckbpkapcf 1 3251 2 1 )()()()()(min (12) the objective function is subject to the following constraints (eqns. 13-17): )()()()()( 5321 kpkpkpkpkp l=+++ (13) )()()()()( 432 kpkpkpkpkp wtpv +++ (14) 5,4,3,2,1,0)( = ikpi (15) 5,4,3,2,1,)( maxmin = ipkpp iii (16) )()())(()( max 1 5 1 4 min ksockpkpksoc n k d n k c −  ==  (17) 1.4. technical parameters of the proposed hybrid energy system the method proposed in the study is used to carry out the assessment of the hes and to obtain the potential solution based on the best combination of the dg, pv, wt and bss. the technical specifications of the components provided by the manufacturers are used to simulate the proposed hes. the technical details of the components of the hes as presented in table 1 are used to evaluate the fuel cost of the hes based on the seasonal variation of the selected site. the performance of the hes is assessed by taking into consideration the load profile of the selected location in sokoto, nigeria. table 1: technical specifications of all components of hybrid energy system (generator set data sheet, 2022), (able, 2022), (amazon, 2022), (power tech, 2020), (powersync, 2018) and (check petrol price, 2023). description technical specifications diesel generator capacity = 16 kw, cummins, model= c22 d5 (x-series), a = 0.0031, b = 0.1775 and c = 1.55, capacity = 12 kw, able, a = 0.0028, b = 0.235 and c = 0.375 and diesel fuel price = ₦1200/litre pv system nominal power = 500w, installed capacity = 8 kw, open circuit voltage = 53.94 v, short circuit current = 9.27 a, module efficiency = 19.12%, maximum power point voltage = 35.9v, maximum power point current = 8.36a, dimension of the pv panel = 1996mm1310mm40mm, nominal cell operating temperature = 45°c 3%, current temperature coefficient = 0.032%/°c, voltage temperature coefficient= -0.308%/°c, power temperature coefficient = -0.42%/°c and operating module temperature =40°c to 90°c. wind turbines nominal power = 500w, installed capacity = 6kw, civ =2 m/s, rv = 10 m/s, cov = 55 m/s, diameter = 1.35 m, wind energy utilize ratio = 0.48 and generator efficiency= 0.78. battery system nominal rating 250 ah @ 12 v, installed capacity = 3 kw, stored energy = 3 kwh, energy density = 125.41 wh / l, maximum continuous charge current = 150a, continuous discharge current = 180a, peak discharge current (< 30s) = 250a and instant peak discharge current = 700a ±50a. converter installed capacity= 15 kw and efficiency: 0.96 http://www.azojete.com.ng/ temitope.adefarati@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 124 2. results and discussion the results of the research are determined based on the daily load demand of a typical customer in sokoto, nigeria, as well as the seasonal variations of wind and solar resources in the study area. it is evident from the load profile that the seasonal variations in consumer daily activities correspond to the dry and rainy seasons. the highest peak load obtained from the study is 14 kw, which is recorded in rainy and dry seasons. the outcomes of the simulation are presented as follows: 2.1. the pattern of load demand in the rainy season weekday the power demand during the 24-hour horizon of rainy season weekdays is presented in figure 5a by using only the dg that has a weekday capacity of 16 kw. the highest peak load and least load demand recorded on weekdays of the rainy season are 14 kw and 7.84 kw, as shown in figure 5a. it is obvious from the results presented in figure 5b that dg produced all the power requirements at the load points with daily fuel consumption of ₦114810 and 95.68 l of diesel fuel. figure 5: weekday power flow by using dg alone during the rainy season: (a) power demand; (b) power output of the dg. the application of only pv and wt in the hes will not offer a reliable electrical power supply due to seasonal changes and non-linear variation of wind and solar resources. for this reason, a reliable electricity supply can be achieved in a standalone hes with the deployment of multiple power sources such as dg (12 kw), pv (8 kw), wt (6 kw) and bss (3 kw). this has ultimately enhanced the general performance of the hes. the power flow of all the components of the proposed hes is shown in figure 6 (b-f). the nonlinear nature of power demand is established in figure 6a where the load demand is lowest between 0 and 6 hours in the morning and has peak periods around 12 and 15 hours of the day. the inclusion of the ress in the proposed hes has reduced the fuel cost, which has the highest proportion of the operation and maintenance costs of the dg. the corresponding fuel cost recorded with the application of hes is n 75998. due to the load management facility, the capacity of the dg has been reduced from 16 kw to 12 kw to fulfil the load requirement within the 24-hour horizon. this indicates that the dg is running at 44.5% of the rated capacity during this particular period. the seasonal variations in wind speed, solar radiation, temperature and load profiles affect the operation of the dg. this demonstrates that the corresponding power-generating capacity of the dg has decreased with the usage of pv and wt as shown in figure 6b. the corresponding fuel cost recorded with the application of hes is ₦ 75998. this has resulted in a 33.81% reduction in the fuel cost of hes during the rainy season on weekdays, when compared to a scenario where diesel is utilized exclusively. the results show that ₦38812 cost savings that translate to 33.81% are achieved within a 24-hour horizon with the use of pv, bss and wt as presented in table 2. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 125 figure 6: weekday power flow by using hes during the rainy season: (a) power demand; (b) power output of the dg; (c) power output of the pv system; (d) power output of the wt; (e) power charging the bss and (f) power leaving the bss. table 2: fuel cost savings with renewable energy resources. description rainy season dry season weekday weekend weekday weekend fuel cost with dg only (₦) 114810 114840 115220 115420 fuel cost with hybrid energy system (₦) 75998 76217 73775 74391 fuel cost savings (₦) 38812 38623 41445 41029 fuel cost savings (%) 33.81 33.63 35.97 35.55 2.2. the pattern of load demand in the rainy season weekend the power demand and power output of using the dg alone on a rainy-season weekend are presented in figure 7 (a–b). it can be seen from findings shown in figure 7b that the dg with a rated capacity of 16 kw has been overstressed, being the only source to meet the power demand with a daily fuel consumption of ₦114840 and 95.7l of diesel fuel. the operational efficiency of the conventional power system can be enhanced with the introduction of a strategically controlled power system that combines wt, pv, bss and dg while reducing the need for the dg to operate and optimizing the use of wind and solar resources. figure 7: weekend power flow by using dg alone during the rainy season: (a) power demand; (b) power output of the dg. the generation capacity of the dg used in the hes has been reduced to 12 kw when compared with the dg alone. the power flow of all the components of the hes is shown in figure 7(b-f) based on the seasonal variation and pattern of load demand profile during the rainy season weekend. the load demand pattern during the off-peak period between 0 and 6 http://www.azojete.com.ng/ temitope.adefarati@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 126 and 22 and 24 hours is mostly fulfilled using the combined outputs of the dg, wt and bss as indicated in figure 7(b-d) since there is no power output from the pv at this particular period. this demonstrates that the dg and wt will run for many hours since the output of the pv is low between 0 and 6 and 22 and 24 hours of the day. the load demand between 10 and 15 hours of the day, as shown in figure 7b, demonstrates that the power produced by the dg has reduced substantially owing to the contribution of the pv system and wt to the proposed hes. thereafter, the power output of the dg increases since the pv does not supply the load during this period because of the non-availability of solar resources between 20 and 24 hours of the day. with the hybridization of some components such as dg, bss, pv and pv, the fuel consumption of the dg is estimated to be ₦ 76217. the money expended on diesel fuel per day throughout the rainy season weekend is 33.63% less when compared to the diesel-only. therefore, by implementing pv, wt, and bss in the base system, ₦38623 in cost savings, or 33.63%, are realized within a 24-hour period. in addition to this, there is a substantial discrepancy in fuel consumption on weekdays and weekend. the consumer load pattern seen in figures 6 and 8 is responsible for this. there is a noticeable increase in load demand because most people are at home on the weekends, utilizing various electronic devices. moreover, many social activities are done at the weekends. the results presented in table 2 demonstrate that the fuel cost on the rainy season weekend is ₦ 41029 higher than the fuel cost on the rainy season weekend, due to the seasonal variation of wind speed, solar radiation and temperature. hence, more fuel is utilized on the weekend than on a weekday. figure 8: weekend power flow by using hes during the rainy season: (a) power demand; (b) power output of the dg; (c) power output of the pv system; (d) power output of the wt; (e) power charging the bss and (f) power leaving the bss. 2.3. the pattern of load demand in the dry season weekday the load demand and power output of the dg during the dry season are shown in figure 9 (a-b). it is established from figure 9b that dg is the only source of power during the weekday dry season. with the configuration presented in this study, a dg of 16 kw is employed to satisfy the electricity needs of consumers, with a corresponding daily fuel consumption of ₦115220 and 96.02 l of diesel fuel. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 127 figure 9: weekday power flow by using dg alone during the dry season: (a) power demand; (b) power output of the dg. the hes is meant to provide electricity for low-power applications in the current study. therefore, hes is structured so that it will be able to respond to changes in power demand. the impacts of solar resources based on seasonal variation and load demand are assessed with the use of dg, bs, pv and wt. the configuration and design of the proposed hes allow maximum utilization of the power generated by the wt and pv system; and ensure that there is no dump power since the summation of the power outputs of all the components matches the power demand. the availability of solar radiation and wind speed at this particular time makes the pv and wt systems the major contributors of power to the required load demand. for the 7–18 hours of the day, the power demand is satisfied by the combination of the dg, pv, wt and bss. at this particular period, the combined operation of dg, pv, wt and bss has enough power to satisfy load demand, as presented in figure 10 (a-f). the bss is used in conjunction with the dg and wt to satisfy the power requirement that occurs during the peak load period at night and early in the morning. figure 10 (b-f) shows that the power generated by the dg has decreased with the integration of bss, pv and wt into the base system. the stored energy can be utilized during the peak period, as presented in figure 10e based on the load demand. the daily fuel cost in the dry season weekday is ₦ 73775 with the deployment of the dg, pv, bss and wt in the hybrid energy system. the fuel cost on weekdays has reduced to ₦ 73775 when the hes is optimally operated. this translates to a 35.97 % fuel cost saving, as shown in table 2, which means customers can earn fuel cost savings of ₦ 41445 per day during the weekday. from the outcomes of the simulation obtained in this case study, it is established that the power demand on dry season weekdays is considerably greater than the power demand on rainy season weekdays. this suggests that during dry-season weekends, diesel fuel expenditure is ₦ 2442 more than it is on rainy-season weekdays. figure 10: weekday power flow by using hes during the dry season: (a) power demand; (b) power output of the dg; (c) power output of the pv system; (d) power output of the wt; (e) power charging the bss and (f) power leaving the bss. http://www.azojete.com.ng/ temitope.adefarati@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):113-132. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 128 2.4. the pattern of load demand in the dry season weekend the power demand by consumers at the load points during 24 hours of a dry-season weekend is shown in figure 11a. the dg of 16 kw is only utilized to satisfy the power demand throughout a rainy-season weekday. the results shown in figure 11b make it clear that, with a daily fuel usage of ₦115420 and 96.18 l of diesel fuel, dg generated all the required power demand. figure 11: weekend power flow by using dg alone during the dry season: (a) power demand; (b) power output of the dg. the performance of the existing power system can be increased through an energy management system that strategically controls power flow among the components of hes, such as wt, pv, bss and dg as shown in figure 12 (a-f). this optimized the utilization of wt and pv while lowering the required generation capacity of the dg. there is relatively little power generated by the pv system during peak load periods in the morning and night because there is no solar radiation. hence, the pv system does not operate during this period, as presented in figure 10c. the load demand during the off-peak period between 12 and 16 hours of the day is very low owing to the load pattern at this particular time. the power produced by wt and pv system as shown in figure 12 (b-c) is utilized to charge the bss between 12 and 16 hours of the day when the load demand is low. during the peak periods that happen promptly towards the beginning of the day and later at night, the bss supplied power to the load as depicted in figure 12f. with the energy management system, the power output of the wt and pv must be utilized as a priority to satisfy the load demand, provided there is enough power from pv system and wt. the daily cost of fuel utilization for optimally operated hes is ₦ 74391 during the dry-season weekend. this shows that 35.55 % of fuel costs have been reduced with the use of wt and pv resulting in ₦41029 in fuel cost savings. optimally operated hes can increase fuel cost savings by incorporating pv and wt into the dg-alone system. the fuel cost savings during the dry season weekend with the hes are significantly higher than during the rainy season weekend owing to periodic changes in load profile and seasonal variations. figure 12: weekend power flow by using hes during the dry season: (a) power demand; (b) power output of the dg; (c) power output of the pv system; (d) power output of the wt; (e) power charging the bss and (f) power leaving the bss. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adefarati et al.: design of photovoltaic-wind-diesel-battery hybrid energy system: perspective of energy management system for stand alone power solution. azojete, 20(1):113-132. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: temitope.adefarati@gmail.com 129 3. conclusion there is a growing demand for hybrid energy systems that incorporate ress and the establishment of an islanded power system with the penetration of local resources due to environmental concerns and the depletion of fossil fuels. the uncertainties of ress that are prevalent in the distribution power system network, microgrid system, hes and smart grid systems are violations of operating constraints, optimal flow of power among the components of hes, optimal energy system and high operating costs. this research proposed a genetic algorithm to reduce the fuel cost, which accounted for more than 60% of the maintenance and operation costs of hes. the hybrid energy system that is aimed at providing a power control strategy with a minimum use of dg and bss and a maximum utilization of wt and pv is presented in the current study. the total power produced is distributed across the components of the hes based on power output constraints and power demand requirements. the outcomes of the study demonstrate the impact of daily and seasonal fluctuations in demand and solar and wind resources on the proposed hes operational costs. it can be established from the results obtained from the study that rainy-season fuel costs are ₦2223 and ₦1826 higher than the dry season; this is attributed to low solar radiation and wind speed in the rainy season and higher power demand in the dry season. this indicates that the seasonal variation of load demand and seasonal variation of solar and wind resources have important consequences on the fuel cost and energy flow of the proposed power system. the optimized fuel cost accomplished by the established model has been demonstrated, and it can be used for the analysis of energy flows in any power system. as a measure to take advantage of the analysis of the results, it has been recommended to solve the problems related to the optimization of hes by using the load profile of a typical customer based on seasonal variations. the application of an optimal control strategy with a genetic algorithm in the present study can improve the performance and energy management of the proposed hes by allowing the optimization of ress. the combined operation of multiple sources in this research improved the overall benefits of the hes when compared with a single-source system. the study's findings indicate that employing hes results in greater fuel cost savings of ₦38812, ₦38623, ₦41445 and ₦41029 than dg-only systems. this shows that fuel cost savings of 33.81%, 33.63%, 35.97% and 35.55% are achieved with the application of hes in rainy season (weekday and weekend) and dry season (weekday and weekend) when compared with dg alone. therefore, it can be concluded from the outcomes of the study that the fuel cost is minimized and the usage of photovoltaic and wind turbines is maximized. references able, 2022. diesel generator fuel consumption chart in litres. https://www.ablesales.com.au/blog/diesel-generator-fuel-consumption-chart-in-litres.html accessed on 10 december, 2023. adaramola, ms. and oyewola, om. 2011. on wind speed pattern and energy potential in nigeria. energy policy, 39 (5): 2501-2506. adefarati, t., bansal. rc. shongwe, t. naidoo, r. bettayeb, m. and onaolapo, ak. 2023. optimal energy management, technical, economic, social, political and environmental benefit analysis of a grid-connected pv/wt/fc hybrid energy system. energy conversion and management, 292:117390. http://www.azojete.com.ng/ temitope.adefarati@gmail.com https://www.sciencedirect.com/topics/engineering/energy-management https://www.ablesales.com.au/blog/diesel-generator-fuel-consumption-chart-in-litres.html https://www.sciencedirect.com/author/14219113600/muyiwa-s-adaramola https://www.sciencedirect.com/journal/energy-policy https://www.sciencedirect.com/journal/energy-policy/vol/39/issue/5 https://scholar.google.com/citations?view_op=view_citation&hl=en&user=xgd1wn8aaaaj&pagesize=80&citation_for_view=xgd1wn8aaaaj:ryck_ylvtxyc https://scholar.google.com/citations?view_op=view_citation&hl=en&user=xgd1wn8aaaaj&pagesize=80&citation_for_view=xgd1wn8aaaaj:ryck_ylvtxyc arid zone journal of engineering, technology and environment, march 2024; 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e-mail address: awosanyaolugbenga2015@gmail.com 357 sensitivity analysis of the effects of load magnitude on pavement strains using load spectra a. a. murana, a. t. olowosulu, and d. o. awosanya* department of civil engineering, ahmadu bello university, zaria, nigeria *corresponding author's email address: awosanyaolugbenga2015@gmail.com article information submitted 10 april, 2023 revised 23 october, 2023 accepted 11 november, 2023 keywords: sensitivity analysis wim axle load distribution (axle load spectra) multilayer linear elastic solutions abstract the purpose of this study is to evaluate the effect of wheel loads on linear responses by sensitivity analysis on an elastic linear analysis. sensitivity analysis of traffic factors was carried out on the failure parameters, where the impact of each of the wheel load magnitude for each axle type and its relationship with the pavement response outputs was evaluated. the reference central value (mean) of the als on both the southbound axis and northbound axis of the selected route, kadunazaria roadway, were either increased or reduced by 0% to 50%, and also, 100% and 500%, to see how the pavement will respond to a constant pavement configuration and material properties applied to all cases. the results obtained from kenlayer runs were used to determine the relationship between the axle load groups and the pavement responses. the effect of load magnitude on pavement responses, was evaluated in respect of the tensile strains and compressive strains. the findings of the study revealed that: development of comprehensive data base was accomplished from the local traffic data that meets the requirements of m-e design procedure. wheel load group relationship for each axle type to vertical strains on top of the subgrade soils are linear, while the tensile strain at the bottom of the asphalt concrete is about 50%. 1.0 introduction sensitivity analysis is the apportionment of output variability from a model to its various inputs. sensitivity analysis draws upon many of the same concepts as the design of experiments. a rich and powerful set of formal and rigorous techniques for performing sensitivity analysis has been developed over recent years (cacuci, 2003). these can be categorized in a variety of ways, for the purposes of the present study; the most used categorizations are lsa and gsa methods. lsa provides an economical approach for identifying the subset of inputs that have the largest impact on the outputs. only the sensitivities and the reference input values for the baseline cases are evaluated-i.e., the evaluation is only for very small regions of the overall solution space. this provides only a “local” as opposed to a “global” sensitivity evaluation. the one-at –time (oat) method is the most common type of lsa. in standard oat applications, one or more baseline scenarios are exercised by varying each independently in turn. in this study, the software program used is kenlayer, to obtain the resulting pavement reactions, with the elimination of all the data from the aasho road test, sensitivity analysis was made on five-layer systems to illustrate the effect of various axle(wheel) load magnitudes with different configurations on pavement responses. the approach utilized is to fix all pavement configurations and material properties, contact pressure, constant default wheel spacing, and calculating various contact radius from the variations of the increment to the reference median axle load magnitude of the considered configuration, to show its effect. comparison of the effect (output) in respect of the resulting pavement reactions (strains) was achieved by utilizing the oat standard in the sensitivity analysis http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):357-368. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 358 the empirical mechanistic (e-m) based method of pavement design is based on the mechanics of materials, which relates input such as a wheel loads to output such as pavement response. (huang, 2007; mathew and rao, 2007). according to huang (2007), with the use of kenlayer, sensitivity analyses were made on five-layer systems to illustrate the effect of various parameters on pavement responses in this study. the complex interactions among the large number of parameters make it difficult to present a concise, but accurate, picture on the effect of a given parameter, because the effect depends not only on the parameter itself, but also on all other parameters. conclusions based on a set of parameters could be invalid if some of the other parameters are changed. the best approach is to fix all other parameters at their most reasonable values while varying the parameter in question, to show its effect. the core concern here-in is evaluation of effect of load magnitude from collected axle load spectra on pavement responses. the key input is the arithmetic average axle load magnitude determined from the captured from the actual axle load groups from the site -specific information by wim system is used subjected to increment variation of the mean axle load magnitude by axle configuration, but the layer properties for the m-e analysis, remained fixed, all through the sensitivity process. 2. materials and methods the required materials in this study consist of pavement configuration that includes the number of layers, the thickness of each layer, and the type of materials. the basic material properties for the structural models are the resilient moduli of hma, base, subbase, and subgrade. traffic should be divided into a number of load groups, each with different load magnitudes and configurations. the methods adopted in this research includes the disaggregation of traffic information incorporated into a truly mechanistic analysis for an accurate pavement response. in this study, the computer program kenlayer is used and the impact of varied axle load magnitudes was evaluated on the obtained pavement responses. 2.1 data collection and gathering of materials the inputs required for carrying out a sensitivity analysis of elastic multilayer systems using load spectra are presented as follows: (a) secondary data for the study: (i) comprehensive site–specific truck traffic information on kaduna-zaria roadway, (ii) pavement configuration and material properties (b) traffic information obtained from literature review. 2.1.1 primary data the nigerian overlay design methodology research results were used as a primary data for the material properties and pavement geometry. in addition, load stress for typical nigerian roads was adopted as (psi/kpa) (80/552) for single axle with dual tires for nigerian roads from the same source. the details are given in table 1, for layer properties for the m-e analysis. table 1: layer properties for the m-e analysis layer material elastic modulus psi/kpa poissons’ratio thickness in/cm 1 wearing course 70,000 / 4,830,000.0 0.30 2.000 / 5.08 2 binder’s course 200,000 / 1,380,000.0 0.35 2.800 / 7.112 3 stone base 65,000 /448,500.0 0.40 8.100 /20.574 4 sub-base 45,000 / 310,000.0 0.45 5.200 /13.208 5 sub-grade 42,000 / 289,000.0 0.45 semi-infinite source: claros et al., (1986). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com murana et al sensitivity analysis of the effects of load magnitude on pavement strains using load spectra. azojete, 20(2):357-368. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 359 2.1.2 secondary data truck traffic information were collected from the secondary data were obtained by collecting truck traffic information from the scott stewart international work in 2007. portable weighin-motion (wim) system was used for the measurement of vehicle classification and truck axle weights to compute the traffic loading inputs needed for kaduna-zaria roadway network. the vehicle classification included five categories of truck and transit vehicle types by axle classification (2-, 3-, 4-,5-, and 6-axles). additional information obtained were axle configurations (steering, single, tandem and tridem), axle loads, all for kaduna-zaria roadway. 2.1.3 traffic information from literatures: dual wheel spacing and axle-axle distance for each load group was obtained from literatures. the details are given in table 2, for dual wheel spacing and axle -axle distance for each load group table 2: dual wheel spacing and axle -axle distance for each load group. group no of axles in the outer wheel path dual wheel spacing (yw) vm axle-axle distance (xw) cm sast 1 0 0 sadt 2 34 0 tadt 4 34 137 trdt 6 34 137 source: timm et al. (1999); huang (2007). 2.2 methods sensitivity analysis was carried on the failure parameters with respect to changes in the tensile and compressive strains at the bottom of the asphaltic concrete and at the top of the subgrade respectively. this was done by increasing and decreasing the determined arithmetic average axle load magnitude of the captured als. for the 5 layers under consideration, the parameters considered in the layer properties for the m-e analysis were kept fixed at each time the increment average axle load magnitude of interest varied. under a given contact radius, the stresses, strains, and deflections in a linear system are proportional to the contact pressure or the magnitude of the total vertical load. the strains induced in pavement layers by the respective loading groups were computed from kenlayer runs. this study shows a five-layer system subjected to a total vertical load, which is applied by a single tire and a set of dual tires were the loading groups of interest for the sensitivity analyses. the determined average axle load magnitude for each of the considered axle configurations were either increased or reduced by -50% to +50% and between -500% and +500%, to see how the pavement will respond to a constant layer property for the m-e analysis applied to all cases. the impact of the varied axle load magnitude of the four considered axle configurations were determined respectively. the effect due to variation in the arithmetic average axle load groups on the pavement responses were determined as it affects the compressive strains in the subgrade and the tensile strains under the hma leading to permanent damage of the pavement. contact pressure: an average contact pressure 80psi (552kpa) (secondary data) was adopted for all the four different axle configurations from the work of claros et al. (1986), for this study. sast: single axle with single tire; sadt: single axle with dual tires; tadt: tandem axle with dual tires; trdt: tridem axle with dual tires. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):357-368. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 360 2.2.1 reference axle mean load for kaduna–zaria roadway: this is the arithmetic average axle load magnitude of the captured als data from the secondary data from ssi (2007) for each axle configuration. 2.2.2 increment variation in reference axle mean loads increment variation in reference axle mean loads for each of the four considered axle configurations was done by increasing and decreasing the determined the arithmetic average axle load magnitude for each axle configuration. the arithmetic average axle load magnitudes were either increased or reduced by -50% to +50%, and also, between -500% and +500%. 2.2.5: wheel load magnitude: in this study, the usual practice that the wheel load is equal to the axle load divided by the number of wheels on the axle, is not done because results from other researchers shows that this is not true. molenaar (2009) shows that camber of the pavement surface results in an unequal sharing of the axle load over both wheel groups of the axle. the wheel group on the verge side of the road carries 52% of the load while the wheel group near the centre line of the road carries 47%. the number of tires in the outer path which is essential in the layer theory was considered and the camber analysis that relates the pavement roughness and the vehicle camber was also considered, for the distribution of axle load magnitude as contained in the camber analysis. therefore, using the axle load ranges as obtained in the developed axle load distribution for each of the four different axle configuration, wheel load is calculated as follows: p = (1) number of wheels on the outer wheel path as contained in column 3 of table 2. 2.2.6: contact area between tire and pavement (contact radius): in this study, the principle of superposition for a realistic wheel load configuration was utilized, with all the four considered axle configurations, with the assumption that the tire imprint has a circular shape and carries uniformly distributed vertical stress that is equal to the tire inflation pressure, (that is, it is assumed that the tires are treadles and that the tire walls carry no load). the assumed approach by the nchrp 1-37a whereby it accepts a single tire inflation as input and utilizes it for all axle configurations was employed. the contact pressure in this study is 5.52kg/ i.e.,552kpa and contact radius is calculated as follows: a = (2) where a = contact radius, p = (wheel load): total load on the tire as determined in equation 1 above, i = tire pressure. papagiannakis and massad (2008); oguara (2004); and huang (2007) 2.4 m-e methods for flexible pavement analysis output the mechanistic resulting pavement reactions for each axle load and each axle type was computed by using the kenlayer software in which the stresses and strains were analyzed due to each axle-load group. the stress under specific loading conditions without relying on equivalency factor was obtained. 2.2.9 sensitivity analysis of elastic multilayer systems impact /influence of axle load on tensile strain & vertical strain the influence was determined in this study by fixing all other pavement parameters at their most reasonable values while varying the axle load increment to compute the influence of axle file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com murana et al sensitivity analysis of the effects of load magnitude on pavement strains using load spectra. azojete, 20(2):357-368. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 361 load on the computed pavement strains, utilizing this influence value as described below at the southbound/northbound: impact value on tensile strain = x 100 (3) = tensile strain value at the axle load increment magnitude = tensile strain value at the axle load default value. (awosanya et al., 2023) impact value on vertical strain = x100 (4) vertical compressive strain value at the axle load increment magnitude = vertical compressive strain value at the axle load default value. (awosanya et al., 2023) 3. results and discussions multilayer elastic analysis is performed using the kenlayer software. the different variables discussed section are considered. the effect of load magnitude on the resulting pavement strains under an increment of the magnitude of the total load, for single tire and a set of dual tires are investigated, with the pavement configurations and material properties were all fixed. the following sections discuss the outcomes of these results. 3.1 default axle load distribution from the captured axle load magnitudes for each axle types on the four axle types on the kaduna-zaria roadway. the axle load magnitude was obtained in tonnage (ton), but was converted to kilonewtons. that is 1ton= 9.86kn. for each of the axis, that is, southbound (sb-axis) and northbound (nb-axis), arithmetic mean axle load magnitude for each axle configuration are determined as contained in table 3.1. table 3: arithmetic mean axle load magnitude (default axle load (kn)) for each axle configuration axle configuration default value k n (southbound) default value k n (northbound single axle with single tire 54.84 60.32 single axle with dual tire 59.91 109.38 tandem axle with dual tire 99.75 196.09 tridem axle with dual tire nil 321.88 from the table 3, northbound axis has very high axle load magnitude while southbound axis has the lowest values. the main reason was that industrial and construction commodities came from the apapa wharf into the country, while agricultural materials were transported towards the southern part of the country. 3.2 axle load default the magnitude of default axle load for each group was subjected to incremental variations between -500% and +500%. figure 1 represents the increment variations on the default axle load magnitude for the four different axle types. the same trend of the output obtained above was achieved. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):357-368. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 362 3.3 wheel loads wheel load from each axle type are calculated according to equation 1. figure 2 represents the wheel loads on the four different wheel configurations considered in this study. this table indicates that as the axle load magnitude increases, the wheel load for each group is increasing. 3.4 contact radius (cm) the contact radius for each determined wheel load for each axle type, are calculated according to equation 2. figure 3 present the resulting contact radius (cm) for each axle load for each axle type. the observed trend is that the contact radius increases as the axle load magnitude for each axle type with increasing axle load magnitude, with the significance of the number of axles sharing the same suspension system and the number of tires in each axle c a lc u la te d a v er a g e a x le l o a d m a g n it u d e (k n ) change in load magnitude (%) figure 1: increment variations on the refernce axle load magnitude sast (sb-axis) sast (nb-axis) sadt ( sb-axis) sadt (nb-axis) tadt (sb-axis) tadt ( nb-axis) trdt (sb-axis) trdt (nb-axis) c a lc u la te d a v er a g e w h ee l lo a d n a g n it u d e (k n ) change in load magnitude (%) figure 2: the variation increment on the mean wheel load magnitude sast (sb-axis) sadt (sb-axis) tadt (sb-axis) trdt ( sb-axis) sast (nb-axis) sadt ( nb-axis) tadt (nb-axis) trdt ( nb-axis) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com murana et al sensitivity analysis of the effects of load magnitude on pavement strains using load spectra. azojete, 20(2):357-368. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 363 3.5 pavement responses on kaduna zaria roadway from increment variation on load spectra default value figures 4 to 7 present the relationship between tensile strains on the bottom of asphalt layer and the compressive strain on the top of subgrade soils versus axle load by each axle type. the figures show that the tensile and compressive strains increase with increasing the axle load. the flexible pavement is subjected to a combination of single, tandem, tridemaxle loads. the pavement is loaded with one or more identical uniform circular loads normal to the surface. the program superimposes the various loads and computes the strains at locations specified. the principal tensile strains at the bottom of the asphalt layer and the vertical compressive strains on top of the subgrade under the specified locations were determined by kenlayer. figure 4: results of sensitivity analysis on load magnitude for single axle with single tire for kaduna-zaria roadway c a lc u la te d c o n ta c t r a d iu s (c m ) change in load magnitude (%) figure 3: contact radius (cm) for the variations incremenet on the mean wheel magnitude sast (sb-axis) sadt (sb-axis) tadt (sb-axis) trdt ( sb-axis) sast (nb-axis ) sadt (nb-axis) tadt ( nb-axis) trdt (nb-axis ) st r a in s x ( 1 0 ^0 6 ) change in load magnitude (%) tensile strain (sb-axis) vertical strain (sb-axis) tensile strain ( nb-axis) vertical strain (nb-axis) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):357-368. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 364 figure 5: results of sensitivity analysis on load magnitude for single axle with dual tires for kaduna-zaria roadway figure 6: results of sensitivity analysis on load magnitude for tandem axle with dual tires for kaduna-zaria roadway figure 7: results of sensitivity analysis on load magnitudes for tridem axle eith dual tires for kaduna-zaria roadway. 3.36 effect of load magnitude on pavement responses. the impact value of tensile strain is calculated according to equation 3 and the impact value of vertical strain is calculated according to equation 4. figure 8 through to 11 illustrate the effect of wheel load from the four considered wheel configurations on tensile strains and compressive strains, in which an approach is to fix all other parameters at their most reasonable values were employed while varying the increment variation of the default magnitude of each axle type, which was used to show is effect. linear analysis was employed, which was integrated into nempads by the researcher that developed the computer software, (olowosulu, 2005). according to huang (2007), linear st r a in s ( x 1 0 ^0 6 ) change in load magnitude (%) tensile strain (sb-axis) vertical strain ( sb-axis) tensile strain ( nb-axis) vertical strain (nb-axis) st r a in s ( x 1 0 ^0 6 ) change in load magnitude (%) tensile strain ( sb-axis) vertical strain ( sb-axis) tensile strain ( nb-axis) vertical strain ( nb-axis) st r a in s (x 1 0 ^0 6 ) change in load magnitude (%) tensile strain (sb-axis) vertical strain ( sb-axis) tensile strain ( sb-axis) vertical strain (nb-axis) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com murana et al sensitivity analysis of the effects of load magnitude on pavement strains using load spectra. azojete, 20(2):357-368. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 365 analysis is based on the assumption that all layers which are linear elastic. although hma layers are viscoelastic and granular layers are nonlinear elastic, an approximate procedure is to assume them to be linear by selecting appropriate moduli for hma, based on vehicle speeds and pavement temperatures, and for granular materials, based on the level of loading. (huang, 2007). the purpose herein is to find the effect of load magnitude on pavement responses. this study serves an important role of solving the problem of overloading on the roadways, because heavier axle loads with greater effect on the pavement response, will incur a greater destructive capability on the pavement, reducing the pavement life. an effective and efficient axle load groups threshold and management will be established in this study, by connecting an approved maximum axle load magnitude for each different axle types on each roadway, with a commensurate penalty for violating the established traffic instructions. additionally, mode of transportation for carrying heavy goods and commodities instead of employing trucks on our roadway, for the purpose of reducing or eliminating cumulative damage ratio, therefore, increasing the pavement life of the roadway. figure 8: summary of sensitivity analysis for load magnitude for single axle with single tires (sast) figure 9: summary of sensitivity analysis for load magnitude for single axle with dual tires (sadt) p a v em en t r es p o n se im p a c t (% ) change in load magnitude (%) tensile strain impact (sb-axis) vertical strain impact (sb-axis) tensile strain impact (nb-axis) vertical strain impact ( nb-axis) p a v em en t r es p o n se im p a c t (% ) change in load magnitude (%) tensile strain impact (sb-axis) vertical strain impact ( sb-axis) tensile strain impact ( nb-axis) vertical strain impact ( nb-axis) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):357-368. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 366 figure 10: summary of sensitivity analysis for load magnitude for tandem axle with dual tires (tadt) figure 11: summary of sensitivity analysis for load magnitude for tridem axle with dual tires (trdt). the default magnitude in the northbound axis is greater than the obtained magnitude in the southbound axis on all the four different axle types considered. for the lighter default axle loads on the southbound axis, the impact per axle load groups is greater on the four axle types compared for the heavier axle load groups in the northbound. for the five-layered elastic pavement system under the multiple circular loaded areas for the determined wheel loads considered for the four different axle types on the kaduna-zaria roadway, the following deductions are made: 1. the corresponding effects of each of the axle type on the elastic pavement between the increment variation on the default axle load magnitude between 10% and 100% are more rational averagely, because the relationship between the increment variation of the default axle load magnitude is nearly an-half (about 50%) to the effect of the pavement response (tensile strains) of each accomplished tensile strains for sadt loads, tadt loads and trdt loads while for the sast loads, it is about 25%response. 2. the corresponding pavement response effects shows that the trdt loads has the greatest range of effects and followed by tadt loads, third in ranking is the sadt loads and the least in impart is the sast. p a v em en t r es p o n se im p a c t (% ) change in load magnitude (%) tensile strain impact (sb-axis) vertical strain impact (sb-axis) tensile strain impact ( nb-axis) vertical strain impact (nb-axis) p av e m e n t r e sp o n se i m p ac t (% ) change in load magnitude (%) tensile strain impact (sb-axis) vertical strain impact (sb-axis) vertical strain impact (sb-axis) vertical strain impact (nb-axis) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com murana et al sensitivity analysis of the effects of load magnitude on pavement strains using load spectra. azojete, 20(2):357-368. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 367 the default magnitude in the northbound axis is greater than the obtained magnitude in the southbound axis on all the four different axle types considered. for the lighter default axle loads on the southbound axis, the impact per axle load groups is greater on the four axle types compared for the heavier axle load groups in the northbound. for the five-layered elastic pavement system under the multiple circular loaded areas for the determined wheel loads considered for the four different axle types on the kaduna-zaria roadway, the following deductions are made: 1. the corresponding effects of each of the axle type on the elastic pavement between the increment variation on the default axle load magnitude between 10% and 100% are more rational averagely, because the relationship between the increment variation of the default axle load magnitude is nearly linearly (about 100%) to the effect of the pavement response (vertical strains) of each accomplished vertical strain for sast loads, sadt loads, tadt loads and trdt loads. 2. the corresponding pavement response effects shows that the tadt loads has the greatest range of effects and followed by trdt loads, third in ranking is the sadt loads and the least in impart is the sast. 4.0 conclusion the following conclusions were drawn from this study 1) the linear effect, as indicated in this section of the study by the curvilinear relationship between tensile strain and wheel load magnitudes, is more pronounced for thinner hma than for thicker hma as adopted in this study, and the relationship is about 50% of the tensile strain to the varied wheel load. 2) the relationship between vertical strains and wheel load is nearly linear. 3) the magnitude in responses between single and dual wheels are more significant when the hma is thin and become less significant as the hma thickness increases. 4) this study concluded that the impact due to variation in the mean axle load magnitude by each axle type is more significant under heavy traffic loads compared to light loads and this affects the compressive strains in the subgrade more than the tensile strains under the hma leading to permanent damage of the pavement. this recommendation is made for future research for nigerian environment: the use of load spectra in the m-e design process should be adopted in the design of pavements as it provides more friendly analysis of the impact of changes in future traffic on the road infrastructure references abubeker, wa. and erlingsson, s. 2013. characterization of heavy traffic axle load spectra for mechanistic-empirical pavement design applications, international journal of pavement engineering, 16(6): 488-501, doi: 10.1080/10298436.2014.943131 awosanya, do. 2023. analytical study on the effect of axle load spectra on nigerian empirical mechanistic pavement analysis and design system (nempads). phd thesis, ahmadu bello university, zaria, nigeria. claros, g., carmichael, rf. and harvey, j. 1986. development of pavement evaluation unit and rehabilitation procedure for overlay design method: vol 2, overlay design manual, texas research and development foundation for the nigeria federal ministry of works and housing, lagos. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):357-368. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: awosanyaolugbenga2015@gmail.com 368 cacuci, dg. 2003. sensitivity and uncertainty analysis theory: volume 1. boca raton, fl: chapman and hall/crc. huang, yh. 2007. pavement analysis and design. prentice hall, inc., new jersey molenaar, aaa. 2009. structural design of pavements. lecture notes ct 4850 design of flexible pavements, part 111.delft. oguara, tm. 2004. highway engineeringpavement design, construction, and maintenance. malthouse press limited, lagos, nigeria. olowosulu, at. 2005. a framework for mechanistic-empirical pavement design for tropical climate. journal of civil engineering, l 5(1): 44-51. papagiannakis, at. and massad, ea. 2008. pavement design and materials: john wiley sons, inc., hoboken, new jersey. ssi., 2007. a dhv company. interim report: axle load study and review and update of the design standard for federal roads, nigeria. stewart scott international, pretoria, south africa. timm, dh., newcomb, de., birgisson, b. and galambos, tv. 1999. incorporation of reliability into the minnesota mechanistic-empirical pavement design method. mn/rc -1999-35. university of minnesotaç minneapolis yoder, e. and witczak, m. 1975. principles of pavement design, 2nd edition, john wiley &sons. inc., new york file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2007; vol.5, 85-93 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng formulation of construction projects as single-mode resource-constrained project scheduling problems (smrcpsp) adamu p1, o. abass2 and r. okafor 3 abstract the paper presents the resource–constrained project-scheduling problem with the single execution mode for each activity and makespan (project’s completion time) minimization as objective. several heuristic procedures for solving the problem have been proposed in the literature including a decomposition-based genetic algorithm and maximizing the net present value of projects. the formulation of construction projects as smrcpsp using the bill of quantities, material schedule and the program of the construction projects, using a building construction project is presented. applying any of the good existing algorithms for solving this class of problems, will enable civil engineers to determine how to schedule the jobs in a construction project for execution so that completion times are minimized even if resources are insufficient? this will help to reduce the rate at which individuals or construction companies abandon their projects half way to completion times. it is a viable way to manage resource crises in construction companies. 1. introduction project scheduling is distinguished from job shop and other related types of scheduling by the non-repetitive nature of the work. a project is usually thought of as a one-time effort, although, this may not always be the case. similar efforts may have been undertaken previously, but not on a production basis. for example, the construction of a building, a highway, or a ship might be thought of as typical projects. in addition, periodic maintenance operations, administration of research and development programs, installation of a new computer facility, and the development and implementation of a new management information system are also activities that can be treated by project scheduling methods. a project consists of a set of activities or jobs, which must be accomplished for the project to be completed. the essential components of a project are usually the degree of non-repetitiveness, the time frame and the magnitude of costs involved. the planning and control of large projects is a difficult and important problem of modern enterprise that many network planning techniques have tried to handle. however, practical application of these techniques leads, to many difficulties. during the planning phase of a project, project management must solve a lot of technical problems as well as those involving time, cost and resource aspects. common network planning techniques, such as metra potential method (mpm) and critical path method (cpm) essentially concern themselves with the time aspect only. these methods aim to minimize project duration, assuming that the various resources required for project completions are available. in practice however, project completion requires the use of various resources, whose oftenlimited availability directly influences planning objectives, time 1 mathematics department, university of maiduguri, maiduguri. nigeria 2 computer science department, university of lagos, akoka, lagos. nigeria 3 mathematics department, university of lagos, akoka, lagos. nigeria http://www.azojete.com.ng/ formulation of construction projects as single-mode resource-constrained project scheduling problems 86 estimations and, scheduling and progress control. when activities require resources for their execution, (e.g. manpower, materials, equipment, capital etc.) that are only available in a limited amount, bottle-necks may appear, e.g. activities cannot be started on time due to the unavailability of resources or activities requiring the same resource which is only available, one unit at the time must be delayed, etc. the various resource problems that may appear during project scheduling can be divided into three classes: time/cost trade-off, resource leveling and resource allocation (herroellen, w.s. 1972). time/cost trade-off problems: this problem may appear when there are no constraints on the availability of resources. the problem then consists of reducing project completion time by adding additional resources to certain activities, so that the execution of these activities may be accelerated. when this is the case, there are many different ways in which activity duration may be selected so that project completion times of the resulting schedules are all equal. however, each schedule may yield a different value of total project direct cost. it would therefore be desirable to have some method for determining the least costly schedule for any given project duration. several such methods have been developed each of which hinges upon various assumptions about the form of the activity direct cost-relationship. this class of problems has been extensively reviewed by kolisch and padman (1997) and is outside the scope of this research. resource-leveling problems: this problem occurs when sufficient resources are available for the completion of the project. the objective may be, given a total project completion time, to level the various resource requirements over time. (i.e. to keep the resource usage as much as possible to a constant rate).this problem for which many optimization and heuristic procedure are available ((zimmermann, 1997), (brinkmann and newmann, 1996), (newmann and zimmermann, 1998), etc.) also, lies outside the scope of this research. resource allocation or resource-constrained problems: this problem arises when there are limited amounts of the resources required by the activities of the project. because the amounts available are not always sufficient to satisfy the demands of concurrent activities, sequencing decisions are required, with a resultant increase in project duration beyond that determined by the “critical path” (the resource non-constrained duration). the objective is to make the required sequencing decisions in such a fashion, that the increase in project duration is minimized, subject to the given resource and precedence constraints. it is this type of problem that forms the subject of this research. 2. description of the smrcpsp the single-mode resource-constrained project scheduling problem (smrcpsp) is the scheduling problem where each of the activities of the project has to be performed in one prescribed way (mode) using specified amounts of the resources provided. the objective of the smrcpsp is the minimization of makespan. examples are baar, et al. (1998), brucker, et al. (1998), kolisch, and sprecher (1997)and drexl, et al. (1999). in order to model the single-mode resource-constrained project scheduling problem (smrcpsp), the following is considered: a single project consists of j = 1,…, j activities azojete vol. 5 2007 87 with a non-preemptable duration of dj periods. the activities are interrelated by precedence and resource constraints: precedence constraint forces an activity not to be started before all its predecessors are finished. pj defines the set of immediate predecessors of activity j. for ease of notation the activities are topologically ordered, i.e., each predecessor of activity j has a smaller number than j. furthermore, activity j = 1 is defined to be the unique dummy source while activity j = j is defined to be the unique dummy sink. resource constraints arise as follows: in order to be processed, activity j requires kjr units of resource type r  r during every period of its duration. since resource r is only available with the constant period availability of kr units for each period, activities might not be scheduled at their earliest (precedence-feasible) start time but later. our objective is to schedule the activities such that precedence and resource constraints are obeyed and the makespan of the project is minimized. t denote an upper bound on the project’s makespan. then we obtain a time-window [eftj, lftj] of earliest and latest finish times for the completion time of each activity j by performing a forward recursion and a backward recursion with lftj = t as e.g., outlined in elmaghraby (1977). defining the decision variables 1, if activity j is finished precisely at the end of period t xjt = 0, otherwise as proposed by pritsker et al.[1969], the following 0-1 programming model for the smrcpsp arises (patterson and huber,1974; patterson and roth,1976): table 1: the model of smrcpsp lfj minimize φ = ∑ t . xjt (1) t=efj subject to lfj ∑ xjt = 1, j = 1, …, j (2) t=efj lfi lfj ∑ t xit < ∑ (t – dj) xjt j = 2,…, j, i є pj (3) t =efj t =efj j t+dj-1 ∑ kjr ∑ xjr < kr r є r, t = 1,…, t (4) j =1 r = t xjt є {0, 1} j = 1,…,j, t = efj,…, lfj; (5) formulation of construction projects as single-mode resource-constrained project scheduling problems 88 the objective function (1) minimises the completion time of the unique sink and thus the makespan of the project. constraint set (2) assures that to each activity a unique finish time, within its time window is assigned. constraint (3) take into consideration the precedence relations between each pair of activities (i, j), where i immediately proceeds j. finally, constraint set (4) limits the total resource usage within each period to the available amount. since the smrcpsp is a generalisation of the static job shop problem it belongs to the class of np-hard problems (blazewicz et al., 1983). consequently, only heuristic solutions can be derived when facing large real-world problems (kolisch and drexl, 1996). the purpose of this paper is to formulate the resource problems faced by individuals or construction companies when building houses, bridges, roads, etc, as smrcpsp. when any of the good existing algorithms for solving this class of problems is applied to the resource– constrained problem, the result will help the engineers to determine how to schedule the jobs in a project for execution, so that completion times are minimized even if resources are insufficient. this may help to reduce the rate at which individuals or construction companies abandon their construction projects before completion times. 3. formulation of smrcpsp from an activity listing of a bungalow the construction of buildings, roads, railways, bridges, etc can be formulated as smrcpsp using the bill of quantities, material schedule and the program of the construction projects. this is done by considering one activity at a time: 1) finding out the durations of each activity, 2) and finding out the combining level of resource requirements with the related duration. for example, table 2 is an activity list of a bungalow. azojete vol. 5 2007 89 table 2: a bungalow activity listing activity no. description previous activities duration /day resources required/men skilled laborers cost/$100 1 obtain joinery 60 0 0 5 2 obtain glass 20 0 0 3 3 obtain sanitary ware 20 0 0 2 4 obtain heating equipment 40 0 0 2 5 obtain electrical equipment 30 0 0 2 6 obtain plumbing equipment 70 0 0 1 7 obtain tiles 140 0 0 4 8 obtain bricks 60 0 0 6 9 obtain top-soil 40 0 0 2 10 survey the site 20 2 5 1 11 build temporary access 10 30 2 5 5 12 earthworks 11 10 2 5 5 13 lay foundations 12 30 2 5 5 14 install external drainage 6;13 20 2 3 6 15 build shell (outer structure) 13 80 2 9 1 16 build boiler-house 4;15 20 2 6 6 17 place electrical wiring 5;15 40 2 1 5 18 install interior plumbing 14;15 50 2 3 7 19 fix roof frames 15 20 5 10 1 20 build interior walls 8;19 50 2 5 6 21 place roofing 7;19 20 3 6 7 22 build outside storage and garage 15 20 4 3 4 23 install wood fames 1;18;20;21 40 2 5 4 24 install sanitary ware 3; 18; 21 30 1 2 8 25 install boiler 16; 21 10 3 7 2 26 inspect wiring 17 10 0 0 1 27 lay permanent access 21 30 1 2 2 28 fit glass 2; 23 20 2 8 7 29 install switches and plugs 21; 26 10 2 1 4 30 finish exterior 22; 27 50 1 3 6 31 surface walls and partitions 28 30 2 4 6 32 connect plumbing and test 24; 29 10 2 5 7 33 clean up outside 30 10 1 4 3 34 finish interior 31; 32 30 2 5 5 35 place flagstones 9; 31; 32 30 2 5 3 36 place top-soil, and landscape 35 20 2 5 2 37 overall inspection 33; 34; 36 10 2 5 4 38 project complete 37 0 0 0 0 resource available each period (kρ it) 6 11 9 formulation of construction projects as single-mode resource-constrained project scheduling problems 90 figure 1 is the network of the above activity list of the bungalow. figure 1: network diagram of the building project azojete vol. 5 2007 91 using the bill of quantities, the material schedule and the program of the bungalow in table 2, below is the formulated smrcpsp. table 3: precedence relations jobnr. #modes #successors successors 1 1 1 23 2 1 1 28 3 1 1 24 4 1 1 16 5 1 1 17 6 1 1 14 7 1 1 21 8 1 1 20 9 1 1 36 10 1 1 11 11 1 1 12 12 1 1 13 13 1 2 14 15 14 1 1 18 15 1 5 16 17 18 19 22 16 1 1 25 17 1 1 26 18 1 1 29 19 1 2 20 21 20 1 1 23 21 1 4 23 24 27 30 22 1 1 31 23 1 1 25 24 1 1 33 25 1 1 29 26 1 1 29 27 1 1 30 28 1 1 31 29 1 1 32 30 1 1 33 31 1 2 34 35 32 1 1 34 33 1 1 37 34 1 1 37 35 1 1 36 36 1 1 37 37 1 1 38 38 1 0 0 formulation of construction projects as single-mode resource-constrained project scheduling problems 92 table 4: request / duration jobnr. mode duration r1 r2 r3 ----------------------------------------------- 1 1 60 0 0 5 2 1 20 0 0 3 3 1 20 0 0 2 4 1 40 0 0 2 5 1 30 0 0 2 6 1 70 0 0 1 7 1 140 0 0 4 8 1 60 0 0 6 9 1 40 0 0 2 10 1 20 2 5 1 11 1 30 2 5 5 12 1 10 2 5 5 13 1 30 2 5 5 14 1 20 2 5 6 15 1 80 2 9 1 16 1 20 2 6 6 17 1 40 2 1 5 18 1 50 2 3 7 19 1 20 5 10 1 20 1 50 2 5 6 21 1 20 3 6 7 22 1 20 4 3 4 23 1 40 2 5 4 24 1 30 1 2 8 25 1 10 3 7 2 26 1 10 0 0 1 27 1 30 1 2 2 28 1 20 2 8 7 29 1 10 2 1 4 30 1 50 1 5 6 31 1 30 2 4 6 32 1 10 2 5 7 33 1 10 1 4 3 34 1 30 2 5 5 35 1 30 2 5 3 36 1 20 2 5 2 37 1 10 2 5 4 38 1 0 0 0 0 ************************************************* resource availabilities: r1 r2 n1 6 11 9 azojete vol. 5 2007 93 4. conclusion in this paper is the formulation of an activity list of a bungalow as a smrcpsp using the bill of quantities, the material schedule and the program of the bungalow. other construction projects, like the construction of roads and bridges can be formulated as presented in this paper. when any of the good existing algorithms for solving this class of problems is applied to the resource–constrained problem, the result will help the engineers to determine how to schedule the jobs in a project for execution so that completion times are minimized even if resources are insufficient. this will help to reduce the rate at which individuals or construction companies abandon their projects before completion times. it is one of the ways to manage resource crises in construction companies. references drexl, a and j. grunewald (1993). nonpreemptive multi-mode resource-constraint project scheduling. iie transactions, 25(5): 74-81, elmaghraby, s.e. (1977). activity networks: project planning and control by network models. wiley, new york,. fleszar k. and k. hindi (2004). solving the resource-constrained project scheduling problem by a variable neighbourhood search, european journal of operations research, 155(2):402-413. garey, m.r. and d.s. johnson (1977). computers and intractability; a guide to the theory of np-completeness. freeman, san francisco, c.a. hartmann, s. and a. drexl (1998). project scheduling with multiple modes: a comparison of exact algorithms. technical report 430, manuskripe aus deb instituten fur betriebwirtschaftslehre der universitat kiel. herroelen w.s. and leus (2004). the construction of stable project baseline schedules. european journal of operations research. 156(3) 550-565. kolisch, r. and a. drexl (1997). local search for nonpreemptive multi-mode resourceconstrained project scheduling. iie transactions, (29): 987-999. kolisch, r. (1995). project-scheduling under resource-constraints: efficient heuristics for several problem classes. physica-verlag, hiedelberg. slowinski, r. (1980). two approaches to problem of resource allocation among project activities: a comparative study. journal of the operational research society. (31): 711-723. sprecher, a. and a. drexl (1996). solving multi-mode resource-constrained project scheduling problems by a simple general and powerful sequencing algorithm. part i: theory. technical report 385, manuskripe aus deb instituten fur betriebwirtschaftslehre der universitat kiel. sprecher, a. (1996). solving the rcpsp efficiently at modest memory requirements. technical report 425, manuskripe aus deb instituten fur betriebwirtschaftslehre der universitat kiel. talbot, f.b and j.h. patterson (1978). an efficient integer-programming algorithm with network cuts for solving resource-constrained scheduling problems. management science, 24(11):1163-1174. weglarz, j. (1980). on certain models of resource allocation problems, cybernetics, (9) 61-66. arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):571-580 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 571 the study and analysis of cell phone charging modules in nigeria g. i. efenedo*, a. o. okpare and o. m. efenedo department of electrical and electronic engineering delta state university abraka, nigeria *corresponding author's email address: efegabs@gmail.com article information submitted 18 december, 2023 revised 24 march, 2024 accepted 30 march, 2024 keywords: cell phone charging module component failure reactivation abstract cellular phones require frequent charging with the aid of modules known as chargers. the performance of chargers in oleh, a community in the niger delta area of nigeria as a case study were investigated with a view to proffering solutions arising from the conventional act of disposing failed chargers without attempted remedies by users. twenty (20) chargers were sampled and examined to determine the electronic components most likely prone to failure in the modules and possible reactivation. also, experiments were performed to compare charging rates to initial specifications by manufacturers for the sampled chargers. the results show that the components most likely prone to failure from the sampled chargers in order of frequency of failure were circuit breakers, capacitors, switching rectifier and switching power transistors. furthermore, one of the reactivated chargers model, infinix of initial specification mostly available in nigeria with open-circuit voltage of 5.00v and short-circuit current of 1500ma, recorded 4.50v, 800ma and was able to charge samsung a12 phone to full capacity (100%) in twenty(20) minutes at a charging rate of 0.01v.min or -4.67a/min respectively. similarly, reactivated oraimo charger recorded 4.70.00v, 2500ma as against 5.00v, 900ma specifications when charging the tecno pop2 phone. the results show that the reactivated modules charging performances were comparatively enhanced at current delivery to loads as shown by the two cell phones. therefore, it is recommended that engineers and technicians skills be chandelled towards local design and reactivation of failed charging modules in nigeria. 1.0 introduction technological innovations have introduced much improvement in the performance of charging modules to consumers using cell phones and other related devices. european commission in 2019 state that for effective charging, a charging solution which has three main elements must be temporally interconnected, to satisfy devices demands referred to as charging profile. these elements are the external power supply (eps), a cable assembly connectivity and the battery in the device. the charging profile is the variation of current and voltage during charging which depend on battery type and recharge time. charles river associates (2015), put world charging modules purchase at 18-34 million while frick and bott, (2009), put the reasons for these purchases include module failure, desire to have multiple modules, forgetting module whilst travelling and loss of module. sudeep. (2004), put the causes of failures in electronic devices which include charging modules as components failure, improper circuit design, manufacturing deficiencies, improper handling and operations, as well as environmental factors. mandeep and supreet. (2015), states that charging modules performs charging operations in two circuit modes known as linear regulated power supply (lrps) and switched mode power supply (smps). robert et al. (2009), described the linearly regulated power supply as a circuit with an input ac voltage that is stepped down, rectified, and then filtered using a capacitor. modern cellular charging modules employ the switched-mode power supply mode in circuit design. http://www.azojete.com.ng/ mailto:%20efegabs@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)571-580. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 572 jagannathan, (2011), described the switched-mode power supply (smps) as a high-frequency operation device with a small size and light weight that is capable of providing a ripple-free and constant output voltage. yates, (2010), presented the advanced technology of wireless chargers that operate under the principle of power transfer by magnetic induction while beasley, (2008), described the underlying engineering concept for the wireless power cellular charging module as similar to electronic toothbrush chargers. limited research had been carried out on the study of energy consumption of mobile phones, reactivation of mobile phones and charging modules. etoh et al. (2008), put an average customer’s phone consumption at 0.83 wh per day while mobile network consumes 120 wh per day per customer by the largest mobile telecommunications operator in japan in the year 2006. similarly, schaefer et al. (2003), put an average customer’s phone consumption at 79.5 wh per day per subscriber in 2000 by german mobile telecommunications sector. the variation between these two studies illustrates the challenges of estimating the power consumption of mobile telecommunication technologies. ferreira et al. (2011), examined only limited details of recharging behaviour of a large sample of android phones while heikkinen and nurminen, (2010), examined smaller sample of module chargers operations and failures. poonam and rajat, (2017), looked at wireless charging system using the principle of electromagnetic induction. it is a power transfer technology that eliminates the current wired power transfer technology. s. sheik mohammed et al. (2013), put some of the advantages of wireless charging transmission technology to include reduction in power losses, reduction in cost and power transmission to a remote area as well as higher efficiency than the wired transmission system. vikash et al. (2014), also state that wireless charging system eliminates faults due to absence of linkage cables associated with wired charging system. this study therefore look at reviving fail charging modules which leads to cost reduction associated with the normal practice of disposed-off instead of attempted remedy in nigeria. 2.0 materials and methods the work was carried out through the study of selected charging modules and the verification of major components prone to failure. reactivation on identified components was performed on failed chargers with the modification of circuit components. an experiment was performed to determine the amount of charging current and voltage demand for two reactivated cellphones. 2.1 examination of cell phone charging modules the study looked into various cell phone charging modules with a view to attempting a remedy. table 1: charger components and nature of faults s/n component fault 1 capacitors (cpt) short-circuit 2 opto-couplers (ocl) short/open-circuit 3 pulse-width modulators (pwm) open/short-circuit 4 switching rectifiers (srf) short-circuit `5 resistors (rst) open-circuit 6 high frequency switching transformers (hft) open/short-circuit 7 switching power transistors (spt) short-circuit 8 metal-oxide varistors (mov) open-circuit 9 circuit breaker (cbr) open-circuit 10 inductors (idt) open-circuit file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com efenedo et al: the study and analysis of cell phone charging modules in nigeria. azojete, 20(3):571-580. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 573 table 1 presents the basic and identified switch-mode power supply circuit components in chargers and the nature of faults associated with the component while figure 1 is a photo-view of some sampled failed charging modules examined by us. figure 1: sampled failed charging modules 2.2 modules with faulty or malfunctioning components table 2 presents the tabulation of some chargers with respect to the various faulty or malfunctioning components. the mark (√) indicated a representation of a faulty component in a charger as well as its rate of failure in chargers as examined by us. table 2: sample of failed chargers and components charger component model cp t oc l pw m sr f rs t hf t sp t mo v cb r id t oraimo (ocw-u63d) √ √ √ million power (t5) √ √ √ amazon √ √ √ √ √ infinix (od-5509) √ √ √ √ √ itel (imu05) √ √ √ √ √ ag (ic988) √ √ √ √ √ √ desktop √ √ √ √ tecno √ √ √ apple usb √ √ √ √ √ samsung super anker 747 √ √ √ √ √ √ belkin dual usb √ √ √ √ √ √ iphone 13 √ √ √ √ √ cheeteh 3 √ √ √ √ apple magsafe √ √ √ √ √ dual port usb wall √ √ √ √ √ √ amazon basics √ √ √ √ √ √ √ apple mfi √ √ √ √ √ √ booster magnetic √ √ √ √ √ √ iphone fast √ √ √ √ component failure rate (cfr) 13 9 10 14 5 1 9 7 11 7 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)571-580. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 574 2.3 modules and reactivation figures 2 and 3 are samples of two cell-phone charging modules with physically identified failed component(s) as indicated by the arrow signs. figure 2: failed pulse generator in ag charger figure 3: failed capacitor in amazon charger the failed components in figures 2 and 3 as identified were isolated from circuits, and the nature of faults associated with the components and specifications are presented in table 3. table 3: chargers failed components and specifications s/n component specification fault 1 electrolytic power capacitor 10.0v, 1000µf short-circuit 2 transistor 2n3904 (vceo=40vdc, ic=200ma) nil 3 fuse 1.0a, open-circuit 4 rectifier sch25000 (0.36-1.5a, 1001000vdc) short-circuit 2.1 experiment on reactivated chargers figure 4 is a circuit diagram of an experiment performed by us to ascertain the amount of charging current drawn to charge cell phones with respect to their voltages by using one of the reactivated charging modules. the diagram consists of an ammeter connected in series with the cell phone to measure charging current, while a voltmeter is placed in parallel with the cell phone. the experiment was repeated for each cell phone, and the voltage and current values were recorded. table 4 presents selected charging modules with their specifications used in file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com efenedo et al: the study and analysis of cell phone charging modules in nigeria. azojete, 20(3):571-580. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 575 carrying out the experiment while table 5 presented the charging power, voltage and current with time to charging rates of infinix module in terms of power, voltage and current. figure 5 presents the photo-view of the experimental setup. figure 4: circuit diagram of the charging process figure 5: photo-view of laboratory setup for the experiment table 4: sampled models of charging modules with specifications module model output current output voltage interface oraimo (ocw-u63d) 340ma 5.0v usb million power (t5) 360ma 5.0v usb amazon 500ma 5.0v usb infinix (od-5509) 2500ma 5.0v usb itel (imu05) 1000ma 5.0v usb ag (ic988) 200ma 5.0v usb tecno 3500ma 5.0v usb apple usb c 4500ma 5.0v usb samsung super 4200ma 5.0v usb anker 747 3700ma 5.0v usb belkin dual usb 3500ma 5.0v usb iphone 13 4000ma 5.0v usb cheeteh 3 3500ma 5.0v usb apple magsafe 1000ma 5.0v usb dual port usb wall 4100ma 5.0v usb amazon basics 2400ma 5.0v usb apple mfi 4000ma 5.0v usb booster magnetic 5000ma 5.0v usb iphone fast 3000ma 5.0v usb http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)571-580. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 576 table 5: infinix module charging techno pop2 phone. techno pop2 battery capacity 4000mah s/n time (t) charge % i δi v δv power (p) min mah ma ma volt volt mw 1 10 4 1279 11 3.812 0.131 4875.548 2 20 9 1268 16 3.943 0.027 4999.724 3 30 14 1252 12 3.97 0.026 4970.44 4 40 20 1240 27 3.996 0.014 4955.04 5 50 24 1213 43 4.01 0.012 4864.13 6 60 29 1170 26 4.022 0.014 4705.74 7 70 32 1144 12 4.036 0.004 4617.184 8 80 38 1132 9 4.04 0.018 4573.28 9 90 42 1123 96 4.058 0.04 4557.134 10 100 47 1027 27 4.098 0.025 4208.646 11 110 52 1000 19 4.123 0.035 4123 12 120 57 981 11 4.158 0.042 4078.998 13 130 62 970 6 4.2 0.038 4074 14 140 66 964 14 4.238 0.065 4085.432 15 150 70 950 29 4.303 0.04 4087.85 16 160 74 921 31 4.343 0.055 3999.903 17 170 79 890 28 4.398 0.022 3914.22 18 180 83 862 12 4.42 0.003 3810.04 19 190 87 850 29 4.423 0.029 3759.55 20 200 100 821 0 4.452 0 3655.092 total 21057 458 83.043 0.64 86914.951 average 1052.9 23 4.152 0.032 4345.748 charge rate/hour (cr/hr) 315.86 6.9 1.246 0.01 1303.724 3.0 results and discussion the result from the study is presented in various stages which include the findings on the most likely components prone to failure in chargers, the experimental determination of specified power ratings to maximum working values of a revived charger, time taken to charge a sample phone to its maximum value as well as determination of its charging rate. figure 6 is the plot showing the components failure rate in charger circuits while figures 7-10 are plots of module chargers current and voltage specifications to their maximum working current drawn by samsung a12 and techno pop2 phones respectively. referring to table 5, the data obtained by using infinix charging module to charge techno pop2 phone battery to 100% full capacity are employed in the plots of figures 11-12. figure 6: frequency of component failure in charging modules 0 2 4 6 8 10 cpt ocl pwm srf rst hft spt mov cbr idt fr eq u en cy o f fa ilu re component file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com efenedo et al: the study and analysis of cell phone charging modules in nigeria. azojete, 20(3):571-580. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 577 the components prone to failure as presented in figure 6 are cbr (circuit breakers), cpt (capacitors), srf (switching regulators), and spt (switching power transistors). the reactivated chargers in figures 6 and 7 were tested for power delivery, and it was confirmed that their charging time to full capacity with respect to a specific phone was reduced compared to its initial charging time. finally, figures 7–10 are plots showing the experimental results obtained from the performed experiment for the reactivated modules employed in the determination of the amount of current drawn at a specified voltage by two cell phones: the tecno pop2 and the samsung a12. a specified voltage by two cell phones: the tecno pop2 and the samsung a12. figure 7: module voltage specification to maximum working voltage for techno pop 2 series 1 in figure 7 indicate various reactivated modules working voltages when charging techno pop 2 while series 2 indicate modules open-circuit rated voltages presented in figure 4. the open-circuit curve shows a unified average voltage of 5v indicating that most chargers output voltage specifications are 5v. the chargers load curve response show that the infinix charger recorded a maximum voltage of 4.8v while the million power recorded a minimum of 4.6v. figure 8. module current specification to maximum current drawn by techno pop 2 0 1 2 3 4 5 6 oramo million power amazon infinix laptop v o lt ag e (v ) modules series1 series2 0 200 400 600 800 1000 1200 1400 1600 oramo million power amazon infinix laptop c u rr en t (m a ) modules http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)571-580. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 578 the curves (series 1 and 2) of figure 8 show that, infinix charger recorded a current of 900ma drawn by techno pops during charging (series 1) as against its rated short-circuit current of 1500ma (series 2). this implied that the infinix charger can accommodate the charging of two or more phones. amazon charger recorded 400ma charging current as against short-circuit current of 450ma while oramo and million power current drawn and short-circuit rated current are approximately same. the implication is that these model chargers of oramo, amazon and million power can only be employed for single phone charging at a time. figure 9. module voltage specification to maximum working voltage for samsung a12 series 1 in figure 9 indicate various reactivated modules working voltages when charging samsung a12 while series 2 indicate modules open-circuit specified voltages presented in figure 4. the open-circuit curve shows a unified average voltage of 5v indicating that most chargers output voltage specifications are 5v. the chargers load curve response show that the oriamo charger recorded a maximum voltage of 4.7v while the million power recorded a minimum of 4.5v. figure 10. module current specification to maximum current drawn by samsung a12. the curves (series 1 and 2) of figure 10 show that, infinix charger recorded a current of 950ma drawn by tecno pops during charging (series 1) as against its rated short-circuit current of 2600ma (series 2). this implied that the infinix charger can accommodate the charging of two or more phones. amazon, oraimo and million power current drawn and short-circuit rated current are approximately same. the implication is that these model chargers of oraimo, amazon and million power can only be employed for single phone charging at a time. 0 1 2 3 4 5 6 oriamo million power amazon infinix laptop v o lt a g e (v ) modules series 1 series 2 0 500 1000 1500 2000 2500 3000 oriamo million power amazon infinix laptop c u rr en t (m a ) module series 1 series 2 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com efenedo et al: the study and analysis of cell phone charging modules in nigeria. azojete, 20(3):571-580. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 579 figure 11. plot of module charging current with time for tecno pop2. the curve of figure 11 shows a decrease in charging current during charging. at the first 10min, the charging current was about 1279ma. as charging progresses, the current reduces. it took 200min to charge tecno pop2 to full current of 821ma. taking some coordinates, the current charging rate can be deduced as follows. current charging rate (ccr) = 1027 − 890 100 − 170 ccr = .4.57a/min figure 12. plot of module charging voltage with time for tecno pop2. the curve of figure 12 shows an increase in voltage with time during charging. at the first 20min, the voltage was about 3.8v. as charging progresses, the voltage increases. it took 200min to charge tecno pop2 to full voltage of 4.55v. taking some coordinates the voltage charging rate can be deduced as follows. voltage charging rate (vcr) = 4.398 − 4.098 170 − 100 vcr = +.01v/min 4.0 conclusion the study, investigative analysis of cell phone charging modules in nigeria using oleh community as a case study was successfully carried out. the main circuit components found in chargers were critically examined and recommendation on the most likely failed components was put forward from a sample of twenty (20) failed chargers. reactivation of the sampled failed chargers were carried out using the necessary reactivation tools. testing the reactivated chargers performance was proved to be adequate. in addition, the experiment performed on the reactivated failed chargers show enhanced power delivery and reduction in charging time compared to their initial specifications. generally, based on the rising cost of chargers in nigeria, there is an urgent need for local design or recovery of failed and malfunctioning chargers and urgent attention be focus in this direction. further work should be done on the 0 200 400 600 800 1000 1200 1400 0 50 100 150 200 250 c u rr en t (a ) time (min) 3.6 3.8 4 4.2 4.4 4.6 0 50 100 150 200 250 v o lt ag e (v ) time (min) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)571-580. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: efegabs@gmail.com 580 energy usage of mobile networks and service infrastructure with regard to cell phones and chargers. references beasley, js. 2008. modern electronic communication (9th edition). upper saddle river, nj: pearson/prentice hall., pp. 14-27. charles river associates, 2019. harmonizing chargers for mobile telephones. impact assessment study of common chargers of portable device. european commissions. ferreira, d., dey, ak. and kostakos, v. 2011. understanding human smartphone concerns a study of battery life. pervasive. 119–33. etoh, m., ohya, t. and nakayama, y. 2008. energy consumption issues on mobile network systems. saint. 365–368. european commission, 2019. impact assessment study on common chargers of portable. ipsos and trinomics, in collaboration with fraunhofer fokus and economist association. devices directorate-general for internal market, industry, entrepreneurship and smes. european commission b-1049 brussels. grow-c3@ec.europa.eu. frick, j. and bott, r. 2009. method for identifying a mobile phone user for eavesdropping on outgoing calls. european patent office, ep1051053, http://v3.espacenet.com/, publication details/biblio? cc=de&nr=19920222a1 &kc = a1&ft. 12-19. jagannathan, v. 2011. power electronics devices and circuits. phi learning private limited, new delhi-11001, 2nd edition., pp. 31-49. heikkinen, mvj. and nurminen, jk. 2010. consumer altitude towards energy consumption of mobile phones and services. mh work supported by ficnia and tekes. ieee., pp. 1-5. mandeep, s. and supreet, k. 2015. analysis of gsm network for different transmission powers. iosr journal of electronics and communication engineering, 10(6): 61-65. mohammed, s., sheik, rk. and shanmuganantham, t. 2013. wireless power transmission – a next generation power transmission system. international journal of computer applications, 1(13): 312-556. poonam juneja and rajat kumar chaudhary, 2017. wireless mobile charging. international advanced research journal in science, engineering and technology, 4(4): 33-36. robert, lb. and louis, n. 2009. electronic devices and circuit theory. peterson education. 10th edition., pp. 13-42. schaefer, c., weber, c. and voss, a. 2003. energy usage of mobile telephone services in germany, energy, 28(5): 411–420. sudeep, ks. 2004. troubleshooting and maintenance of electronic equipment. s.k. kataria and son. darya ganji, delhi., 1st edition, pp. 12-35. vikash, m., lavya, n. and anand, mmm. 2014. wireless power transmission. international journal of emerging technology and advanced engineering, 4(2): 213-225., www.ijetae.com. yates, a. 2010. wireless power experiments. alan’s laboratory, manchester, united kingdom. http://www.vk2zay.net/article/253. 4-7 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:grow-c3@ec.europa.eu http://v3.espacenet.com/ http://v3.espacenet.com/ http://www.vk2zay.net/article/253 arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):319-330 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 319 original research article engine performance and emission analysis of yellow oleander, residual cooking oil and fossil diesel a. a. bawa*, h. a. dandejeh and d. m. kulla department of mechanical engineering, faculty of engineering, ahmadu bello university zaria, kaduna state *corresponding author’s email address: sundayjayd@gmail.com 1.0 introduction the utilization of fossil fuels has adverse effects on the environment like pollution, global warming and unfavorable climate change (jaynes, 2010, batidzirai et al., 2006; alamu et al., 2008; gupta et al., 2007). biodiesel are fuels derived from plants and animal sources and can serve as alternatives to fossil fuels (rubi et al., 2011, atadashi et al., 2012). biodiesel are biodegradable, non-toxic, ecofriendly, provide longer engine life span when used in automobiles (ibrahim et al., 2014). due to the depletion of fossil fuel reserves, rising prices and environmental pollution, this has led to renewed interest in biodiesel production. with respect to low cost, waste to energy and nonedible feedstock; residual cooking oil (rco) and yellow oleander (yo) seed has been selected as feedstock for biodiesel production. in the present study, the performance and emission characteristics of a diesel engine at constant speed and variable torque were investigated while running on yellow oleander biodiesel, residual cooking oil biodiesel and pure diesel. article information abstract engine performance and emission characteristics of biodiesel produced from yellow oleander, soyabeans residual cooking oil and fossil diesel was carried out in a compression ignition engine. the engine was operated at constant speed of 2160rpm and variable torque (4, 7.5 and 10.6nm). the oil extracted from yellow oleander by mechanical press had a yield of 60%. physicochemical properties of the oil were determined. the chemical composition of the biodiesels was analyzed and the result revealed that yellow oleander and soyabeans residual cooking oils contain 86.2% and 85.3% methyl esters respectively. the engine performance tests of the yellow oleander, soyabeans residual cooking oil and fossil diesel at a constant speed 2160rpm and variable torque (4, 7.5 and 10.6nm)., were found to be 2.40kw, 1.70kw and 0.91kw for brake power and 51412.57 mn/m2, 36376.87 mn/m2 and 19401.02 mn/m2 for brake mean effective pressure respectively. similarly, at constant speed of 2160 rpm and variable torque (4, 7.5 and 10.6nm), it was also found that in comparison to fossil diesel fuel, the emission reduction for soyabean residual cooking oil biodiesel at engine torque of 4nm was 67% for co, 47% for co2, 100% for hc and 40% increase for nox. however, there was no remarkable change in emission reduction when the engine torque was increased from 4 to 10.6nm at constant engine speed of 2160 rpm. biodiesel from yellow oleander and residual cooking can be used as part of substitutes for compression ignition engines to reduce the effects of greenhouse gases emissions caused by fossil diesel fuel combustion from heavy duty equipments . © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 december, 2022 revised 29 march, 2023 accepted 6 april, 2023 keywords: yellow oleander residual cooking oil constant engine speed variable torque emission http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com mailto:%20sundayjayd@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):319-330. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 320 2. materials and method the materials used for the production of yellow oleander biodiesel and residual cooking oil biodiesel, physicochemical properties tests and engine performance evaluations were locally obtained from samaru zaria, kaduna state. the yellow oleander plant and seeds are shown in figure 1. figure 1: yellow oleander plant and seeds 2.1 methods 2.1.1 seed collection and preparation the seeds of yellow oleander were obtained from aviation quarters zango, zaria kaduna state and the soyabeans residual cooking oil was obtained locally from a fish seller at hayin dogo, samaru zaria kaduna state. the seeds were plucked fresh, the fleshes were peeled off and the nuts were sun dried for a period of 8hours to enable easy cracking of the shell. after cracking, the seeds enclosed by the nuts were sundried for seven days and the seeds were crushed and grinded. 2.1.2 oil extraction oil was extracted from the crushed and grinded yellow oleander seed by mechanical press method at the national research institute for chemical technology (narict) zaria, kaduna state. the seeds were placed in the oil press machine and the oil was extracted mechanically. the expelled oil was filtered using a 0.05mm sieve into a beaker. the difference in the weight of the seed sample before and after the extraction of the oil was taken. percentage of yield of the oil was calculated using equation (1) % oil yield = weight of the extracted oil weight of sample × 100 (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):319-330. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 321 2.1.3 production of yellow oleander and residual cooking oil biodiesel by transeterification reaction transesterification is one of the common chemical reactions of alcohol with vegetable oils in the presence of catalyst. in this work, methanol was used because of it low cost and availability. this reaction methanol was used to reduce the viscosity of yellow oleander and soyabeans residual cooking oil and conversion of the triglycerides into ester. the reaction was done with a methanol to yellow oleander/residual cooking oil molar ratio of in the presence of potassium hydroxide (koh) as a catalyst according to jamil et al., (2016) using the equipment presented in figure 2. % biodiesel yield = weight of biodiesel produced(g) weight of raw oil used(g) × 100% (2) figure 2: transesterificatiion oils into biodiesel 2.2 fuels table 1 shows the samples of fuels used for this study s/no fuels abbreviation 1 yellow oleander biodiesel y. o 2 residual cooking oil biodiesel r. c. o 3 diesel d 4 50% yellow oleander blend with 50% diesel 50%y.o/50%d 5 50% residual cooking oil blend with 50% diesel 50%r.c.o/50%d 2.3 engine performance test procedure the engine performance procedure was carried out on diesel, yellow oleander, residual cooking oil and their blends. a measuring cylinder was used to measure 500ml of the fuel sample and poured into the engine fuel tank. the switch was turned on while the choke was closed by pushing the lever down and the throttle was opened slightly, the starting handle on the left of the engine and was rotated until the engine fires. the throttle was adjusted to bring the speed up slightly while the engine run idle for about 10minutes in order to warm up the engine. the first test condition was set by gradually opening the throttle and increasing the flow of water to the dynamometer until the engine is running on the load of 9nm and throttling at about 2160rpm until the engine was stabilized then the readings of the engine speed, torque, exhaust temperature and air flow rate were taken. the fuel flow rates were measured by turning off the fuel tap so the fuel is consumed only from the pipette, then a stop watch to measure the time http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):319-330. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 322 taken by the engine to consume 8ml of fuel from the pipette. this procedure was carried for varying speeds (2160, 1860 and 1560rpm) while keeping the load constant and constant speed while varying the loads (4, 7.5 and 10.6nm). 3. results and discussion 3.1 physicochemical properties of the fuels table 2 below shows the physico-chemical properties of the fuels. it shows that rcob has the highest density, highest kinematic viscosity at 30oc and highest calorific value while yob has the highest cetane number. table 2: physicochemical properties of the fuels used s/n properties yellow oleander biodiesel soybeans residual cooking oil biodiesel diesel biodiesel standard 1 density (g/cm3) (@ 30°c) 0.81 0.90 0.88 0.86 – 0.90 2 kinematic viscosity (mm2/sec) (@ 30°c) 7.72 9.46 6.09 1.9 – 6.0 3 free fatty acid (mg/g) 0.15 0.20 ---- 4 acid value (mg koh/g) 0.30 0.40 --0.50 max 5 saponification value (mg/g) 197.75 201.28 --370 max 6 iodine value (gi2/100g) 9.39 10.22 ---- 7 moisture content (%) 2.14 1.17 ---0.06 max 8 biodiesel yield (%) 87.30 82.80 ---- 9 flash point (°c) 87.00 96.00 88.00 93.00 min 10 peroxide value (𝑚e𝑞.o2 / 𝐾𝑔𝑂il) 0.40 0.90 ---- 11 fire point (°c) 92.70 105.20 67 -- 12 cloud point (°c) -2.00 1.00 2.00 -- 13 pour point (°c) -5.30 -5.80 -2.00 -3 to -12 14 refractive index 1.49 1.50 ---15 to -16 15 cetane number 71.79 71.42 41.00 47.00 min 16 calorific value (mj/kg) 47.24 49.53 45.87 -- 3.2 gcms results of yellow oleander and residual cooking oil biodiesels 3.2.1 gc/ms result of yellow oleander biodiesel figure 3 shows that yellow oleander contains about 86.24% biodiesel, with the highest peak number of 2, 6, and 7. these peaks corresponds to n-hexadecanoic acid, cis-13-octadecenoic acid and octadecanoic acid methyl esters with total percentage covering areas of 76.98%, while the remaining total percentage covering areas of 23.01% includes hexadecanoic acid, methyl ester. the presence of methyl ester profile is one of the key indicators that determines the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):319-330. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 323 sustainability of biodiesel feedstock (sokoto et al., 2011). it can, therefore, be concluded that yellow oleander biodiesel has the required quality to be used in compression ignition engines. figure 3: gcms result of yellow oleander biodiesel 3.2.2 the gc/ms result of residual cooking oil biodiesel figure 4 shows that gcms analysis of soyabeans residual cooking oil biodiesel reveals that fatty acid methyl ester (fame) components are the highest dominant with hexadecanoic acid-methyl ester and cis-13-octadecenoic acid-methyl ester representing peak number 10 and 14 respectively with percentage area of 61.22% in aggregate. this is an indication that residual cooking oil biodiesel contains high percentage of unsaturated carbonyl compound which may account to low cetane value of the biodiesel fuel (chukwueziel et al., 2007). hence, this result is in line with that of sahar et al (2018) and can be concluded that residual cooking oil biodiesel has the required quality to be use in compression ignition. figure 4: gcms result of residual cooking oil biodiesel 0 1000000 2000000 3000000 4000000 5000000 6000000 7000000 8000000 38 39 40 41 42 43 44 45 46 47 in te n si ty retention time intensity 2 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 0 10000000 20000000 30000000 40000000 50000000 60000000 70000000 23 28 33 38 43 48 in te n si ty retention time 12 34 5 6,7 8,9 10 11 1213 14 15 16 17 1819202122232425 http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):319-330. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 324 3.3 engine test results this section discusses results of the engine performance and emission characteristics of the fuels. 3.3.1 brake power (bp) at constant speed and variable torque figure 5 reveals that b.p increases with increase in torque for all fuels. it shows that rcob has the lowest b.p of 0.91kw at the engine torque of 4 nm, followed by 1.70kw at 7.5nm and the highest brake power of 2.40kw at 10.6nm. the b.p increases by about 62% from engine torque of 4nm to 10.6nm. however, regardless of the fuel tested, b.p is the same for all the fuels at a fixed torque, this can be explained that the same engine parameters were used to analyze the fuels, therefore it is not fuel dependent but engine dependent. figure 5: variation of brake power with torque 3.3.2 brake mean effective pressure (b.m.e.p) at constant speed and variable torque figure 6 shows that the bmep of the fuel samples increased with increase in engine torque from 4nm to 10.6nm. it reveals that y.o.b has the lowest bmep of 19401.02 mn/m2 at engine torque of 4nm, further increase to 36376.87 mn/m2 at 7.5nm and have the highest bmep of 51412.57 mn/m2 at the highest torque of 10.6nm. however, it can further be deduced that bmep increased by about 62% from the lowest torque of 4nm to the highest torque of 10.6nm for the fuels, which was found to be the same for all the fuels at each particular engine torque. figure 6: variation of brake mean effective pressure with torque 0 0.5 1 1.5 2 2.5 3 y.o r.c.o d y.o/d r.c.o/d b ra ke p o w e r (k w ) b. p at 4 nm b. p at 7.5 nm b. p at 10.6 nm 0 10000 20000 30000 40000 50000 60000 y.o r.c.o d y.o/d r.c.o/d b ra ke m ea n e ff et iv e p re ss u re (m n /m ) b.m.e.p at 4 nm b.m.e.p at 7.5 nm b.m.e.p at 10.6 nm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):319-330. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 325 3.3.3 specific fuel consumption (s.f.c) at constant speed and variable torque figure 7 shows that s.f.c decreased with increase in the engine torque from 4nm to 10nm irrespective of the fuel analyzed. the s.f.c of diesel was 0.52kg/kwh at the lowest torque of 4nm, and it drastically decreased to 0.28kg/kwh when the torque was increased to 7.5nm and then to 0.17kg/kwh at the highest engine torque of 10.6nm. however, it was observed that the s.f.c decreased by 46% as the torque increases from 4nm to 10.6nm. this result implied that at the highest torque the s.f.c is low for all the fuel sample tested and increases as the engine torque was decreased, the s.f.c seemed not to depend only the engine but also on the fuel combusted. figure 7: variation of specific fuel consumption with torque 3.3.4 exhaust temperature at constant speed and variable torque figure 8 shows that the exhaust temperature for all the fuel molecules increases with increase in the engine speed except for diesel. considering yellow oleander from the graph below, it has its lowest temperature of 122°c at the lowest engine torque of 4nm, and then increased to 152°c at 7.5nm, and has the highest exhaust temperature of 188°c at the highest torque of 10.6nm. however, yellow oleander has 35% increase in the exhaust temperature from the lowest engine torque of 4nm to the highest torque of 10.6nm, this increase in exhaust temperatures can be traced to the fact that biodiesel is more oxygenated than diesel, there is more oxygen available for combustion. figure 8: variation of exhaust temperature with torque 0 0.1 0.2 0.3 0.4 0.5 0.6 y.o r.c.o d y.o/d r.c.o/d sp e ci fi c fu el c o n su m p ti o n k g/ kw h s. f. c at 4 nm s. f. c at 7.5 nm s. f. c at 10.6 nm 0 20 40 60 80 100 120 140 160 180 200 y.o r.c.o d y.o/d r.c.o/d ex h au st t e m p er at u re , ( °c ) exhaust temp. at 4 nm exhaust temp. at 7.5 nm exhaust temp. at 10.6 nm http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):319-330. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 326 3.3.5 air fuel ratio (a. f. r) at constant speed and variable torque figure 9 shows that the a.f.r for yellow oleander, residual cooking oil and diesel decreased with increase in the engine torque while that of their blends behaves otherwise which reason cannot be obviously explained. it shows that yellow oleander has a flow rate of 0.62m3/s at lowest torque of 4nm, it then decreased to about 0.53 m3/s at 7.5nm and having the least a.f.r of 0.43m3/s at the highest torque of 10.6nm. it can further be seen that the a.f.r for yellow oleander decreased by about 31% from the lowest torque of 4nm to the highest engine torque of 10.6nm. figure 9: variation of air flow rate with torque 3.4 emission characteristics 3.4.1 co2 at constant speed and variable torque figure 10 reveals that co2 emission of all the fuels increased from the lowest torque of 4nm to the highest engine torque of 10.6nm. it can be observed that residual cooking oil has the highest co2 emission reduction of about 47% at the lowest engine torque of 4nm, then followed by 43% co2 emission reduction and has the lowest co2 emission reduction of 33%. however, it can be observed that co2 emission for the diesel is higher at each fixed torque than the two biodiesels and their blends which deduced that the biodiesel are good in terms of co2 emission reduction. figure 10: variation of %co2 emission with torque 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 y.o r.c.o d y.o/d r.c.o/d a ir f lo w r at e, v .( m ^3 /s ) air flow rate at 4 nm air flow rate at 7.5 nm air flow rate at 10.6 nm 0 1 2 3 4 5 6 7 8 9 10 y.o r.c.o d y.o/d r.c.o/d % c o 2 co2 at 4 nm co2 at 7.5 nm co2 at 10.6 nm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):319-330. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 327 3.4.2 nox emission at constant speed and variable torque figure 11 shows that the nox emission for all the fuels tested increased with increase in the engine torque from the lowest to the highest. yellow oleander emits it lowest nox of 235ppm at the lowest torque of 4nm, the emission increases to 374ppm at engine torque of 7.5nm and has it highest nox of 512ppm at the highest torque of 10.6nm. therefore, the nox emission of yellow oleander increased by about 54% from the lowest torque of 4nm to the highest torque of 10.6nm. however, it can be seen that all the biodiesels and their blends emit higher nox than diesel at the different engine torque which may be due to the present of high amount oxygen in biodiesel and hence, enhance formation of nox gases. figure 11: variation of % nox emission with torque 3.4.3 co at constant speed and variable torque figure 12 shows that co emission increased with increase in the torque for the fuels with diesel having the highest co emission at each particular torque tested. it can be observed that yellow oleander has the highest co emission reduction of about 67% at the torque of 4nm as compared to diesel at the same torque, followed by 44% co reduction at 7.5nm and then reduces to 50% co reduction at the highest torque of 10.6nm. however, the diesel emitted higher amount of co emission than the biodiesels and their blend. figure 12: variation of %co emission with torque 3.4.4 hc at constant speed and variable torque figure 13 shows that the hc emission decreased with the increase in the engine torque for the fuels tested, at the highest torque of 10.6nm, it can be seen that the biodiesel and their blends have no hc emission except for diesel. taking diesel for example, it emits the highest unburnt hc of 4.2%hc/ppm at the lowest torque of 4nm and then followed by 2.7%hc/ppm at 7.5nm 0 100 200 300 400 500 600 y.o r.c.o d y.o/d r.c.o/d % n o x/ p p m nox at 4 nm nox at 7.5 nm nox at 10.6 nm 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 y.o r.c.o d y.o/d r.c.o/d % c o co at 4 nm co at 7.5 nm co at 10.6 nm http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):319-330. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 328 and having the lowest emission of 1.3%hc/ppm at highest torque of 10.6nm. however, about 69% reduction in unburnt hc emission is observed for diesel from the lowest torque of 4nm to the highest torque 10.6nm. figure 13: variation of % unburned hc emission with torgue 3.5 the comparison between the biodiesels and diesel in term of emission reduction table 3 shows the variation of exhaust gases emission reduction and increase for all the fuel molecules investigated as compared to diesel. with the negative sign signifying the percentage of emission reduction while the positive sign means increase in the emission with reference to diesel. table 3 represent the comparison between biodiesel and diesel at constant engine speed and variable torque. co co2 nox hc fuels/torque(nm) @ 4 @ 7.5 @10.6 @ 4 @ 7.5 @10.6 @ 4 @7.5 @10.6 @ 4 @ 7.5 @10.6 y.o -57% -56% -58% -38% -35% -41% +54% +42% +42% -81% -85% -100% r.c.o -57% -44% -50% -47% -43% -33% +64% +31% +40% -88% -96% -100% 50%y.o/50%d -50% -36% -32% -26% -22% -26% +45% +22% +29% -76% -89% -100% 50%r.c.o/50%d -33% -33% -23% -32% -27% -29% +47% +27% +29% -79% -96% -100% 4. conclusion from the result of the experiment, exhaust temperature increased with increase in torque for all the fuels samples tested, likewise the air consumption rate at each specific torques. in term of engine emission characteristics, the carbon ii oxides (co) emissions decrease with increase in torque, while oxides of nitrogen (nox) for yellow oleander, residual cooking oil and their blends were higher than that of the diesel at each fixed torque tested. however, carbon iv oxides (co2) emissions increased with increase in torque. the diesel emitted higher amount co2 at each torque than the biodiesels and their blends. therefore, immense emissions are being produced during the operation of heavy and light duty diesel engines. biodiesel from yellow oleander and residual cooking can be used as part of substitutes for compression ignition engines to reduce the effects of greenhouse gases emissions caused by fossil diesel fuel combustion and also provide employment opportunity in nigeria. 0 1 2 3 4 5 y.o r.c.o d y.o/d r.c.o/d % h c /p p m hc at 4 nm hc at 7.5 nm hc at 10.6 nm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):319-330. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 329 references alamu, oj., akintola, ta., enweremadu, cc. and adeleke, ae. 2008. characterization of palmkernel oil biodiesel produced through naoh-catalysed transesterification process. scientific research and essay, 3(7): 308-311. akintayo, et. 2004. characteristics and composition of parkia biglobossa and jatropha curcas oils and cakes. bioresource technology, 92: 307 – 310. atadashi, i., musa, am., abdul, r., abdul, a., nik, s. and nik, m. 2012. production of biodiesel using high free fatty acid feedstocks. renewable and sustainable energy reviews, 16(5):3275-3285, doi:10.1016/j.rser.2012.02.063 azeem, mw., hanif, ma., al-sabahi, jn., khan, aa., naz, s. and ijaz, a. 2016. production of biodiesel from low priced, renewable and abundant date seed oil. renewable energy 86: 124-132. batidzirai, b., faaij, pc., andré, s. and edward, lc. 2006. biomass and bioenergy supply from mozambique, energy for sustainable development, 10(1): 54-81. broek, vr. 2000. sustainability of biomass electricity systems. an assessment of costs, macroeconomic and environmental impacts in nicaragua, ireland and the netherlands, eburon delft. chukwuezie, oc., nwakuba, nr., asoegwu, sn. and nwaigwe, kn. 2017. cetane number effect on engine performance and gas emissions: a review. american journal of engineering research (ajer), 6(1): 56-67, www.ajer.org. dutta, ac. 1964. botany for degree students, 5th edn., oxford: oxford university press. gupta, pk., kumar, s., panesar, bs. and thapar, vk. 2007. parametric studies on bio-diesel prepared from rice bran oil. agricultural engineering international: the cigr ejournal.manuscript ee 06 007. vol. ix. hellier, p., nicos, l. and talal, y. 2015. the influence of straight vegetable oil fatty acid composition on compression ignition combustion and emission. fuels, 143:131-143. ibiyemi, sa., fadipe, vo., akinremi, oo. and bako, ss. 2002. variation in oil composition of thevetia peruviana juss fruits seeds. journal of applied science and environmental management, 6(2): 61-65. ibrahim, h., ezeanyanso, c., hayatudeen, a., nwakuba, dcu., olabimtan, o., aminu, a. and ibrahim, am. 2014. comparison of palm oil and jathropha curcas seed oil for biodiesel production in nigeria using bulk cao catalyst. international journal of emerging technologies and engineering (ijete), 1(1): 28-32., www.ijete.org jamil, f., ala’a, ha., lamya, a., mohab, aa., paul, h. and umer, r. 2016. optimization of oil extraction from waste ‘‘date pits” for biodiesel production. energy conversion and management, 117: 264–272. jaynes, d. 2010. global warming: myths and realities. social sciences, soc 461-11 http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com http://dx.doi.org/10.1016/j.rser.2012.02.063 http://www.ijete.org/ arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):319-330. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sundayjayd@gmail.com 330 kaisan, mu., anafi, fo., nuszkowski, j., kulla, dm. and umaru, s. 2017. exhaust emissions of biodiesel binary and multi-blends from cotton seed, jathropha and neem oil from stationary multi cylinder ci engine. transportation research part d. transport and environment, 53: 403-414. doi:10.1016/jtrd.2017.04.040. available on www.elsevier.com/locate/trd. mofijur, m., masjuki, hh., kalam, ma., atabani, ea., riwanal, f. and mobarak, hm. 2014. comparative evaluation of performance and emission characteristics of moringaoleifera and palm oilbased biodiesel in a diesel engine. journal of industrial crops and product, 53:78-84. niyi, a. 2011. generator diesel exhaust: a major hazard to health and the environment in nigeria. american journal of respiratory and critical care medicine, 183(10): 1437. rubi, r., sandra, lm. and reyna n. 2011. biodiesel production by using heterogeneous catalysts, alternative fuel, dr. maximino manzanera (ed.), biotechnology, intechopen publishers london, available from: http://www.intechopen.com/books/alternative-fuel/biodiesel-production-byusing-heterogeneous-catalysts tuba, hd. 2016. the testing of the effects of cooking conditions on the quality of biodiesel produced from waste cooking oils. renewable energy, 94: 466-473., http://dx.doi.org/10.1016/j.renene.2016.03.088 sokoto, ma., hassan, lg., dangoggo, sm., ahmad, hg. and uba, a. 2011. biodiesel fuel. nigeria journal of basic and applied science, 19(1): 81-86. tukur, y. 2016. assessment and modeling of emission impact of biodiesel produced from calabash, silk cotton and palm kernel seeds and their performance evaluation on internal combustion engines. american chemical science journal 14(4):1-8. doi:10.9734/acsj/2016/25472 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com http://www.elsevier.com/locate/trd http://www.intechopen.com/books/alternative-fuel/biodiesel-production-by-using-heterogeneous-catalysts http://www.intechopen.com/books/alternative-fuel/biodiesel-production-by-using-heterogeneous-catalysts http://dx.doi.org/10.1016/j.renene.2016.03.088 https://www.researchgate.net/journal/american-chemical-science-journal-2249-0205 http://dx.doi.org/10.9734/acsj/2016/25472 arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):133-150 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 133 application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement o. i. adebisi,1* a. b. ogundare,2 b. j. olajuwon3 and a. adebeshin4 1,3department of electrical and electronics engineering, federal university of agriculture, abeokuta, nigeria 2department of electrical and electronics engineering, lagos state university of science and technology, nigeria 4mantrac nigeria limited, lagos state, nigeria *corresponding author's email address: adebisioluwaseun@funaab.edu.ng article information submitted 9 january, 2024 revised 15 february, 2024 accepted 20 february, 2024 keywords: facts ga line loss newton-raphson svc voltage profile abstract power supply-demand imbalance is one of the critical challenges bedeviling the electricity grid operation of a third world nation such as nigeria. this has consequently led to the system’s poor voltage profile with its associated highpower losses. many potent solutions have been proposed to address these problems; however, technological advancements favour the adoption and widespread use of a class of economic and fast acting solid-state controllers called flexible alternating current transmission systems (facts). this study, therefore, assessed the potential of an optimally placed static var compensator (svc) via genetic algorithm (ga) in enhancing the performance of the nigerian 330 kv, 28-bus electricity grid. the static power flow model of the system with and without svc was analyzed using newton-raphson method and simulated in matlab r2020a environment. the system performance with svc placed optimally using ga was compared with the first principle approach. the simulation results revealed that before compensation, the test grid had five buses namely ayede, new-haven, gombe, kano and makurdi with voltage magnitudes of 0.926, 1.058, 0.906, 0.859 and 0.944 p.u., respectively, violating the acceptable voltage tolerance limit of 0.95≤vi≤1.05p.u. the first principle-based compensation improved the voltage magnitudes of the critical buses on the test grid to 1.015, 1.008, 0.958, 0.995 and 0.975 p.u., respectively, while compensation via ga enhanced the voltage magnitudes to 1.05, 0.985, 1.038, 1.016 and 0.996 p.u. respectively. the grid’s total active and reactive line losses reduced from 181.479 to 149.786 mw and 145.323 to 125.161 mvar, respectively with compensation from the first principle approach, whereas the values were minimized to 115.675 mw and 109.336 mvar, respectively with the ga based compensation. the ga based optimal placement of svc exhibited better enhancement characteristics on the considered nigerian electricity grid than the first principle method. 1.0 introduction electrical energy is one of the available and most widely used forms of energy. it is a key ingredient in measuring the development of a nation. in a third world country such as nigeria, increasing population and technological advancements have placed enormous demand on electrical power usage without sufficient energy generation to address it. hence, creating electricity supply-demand imbalance (dahunsi et al., 2022; akpojedje and ogujor, 2021; hussaini et al., 2021; ayamolowo et al., 2019; ogbonnaya et al., 2019; yakuba, 2019; emodi and http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 134 yusuf, 2015). the imbalance between electricity supply and demand along with poor allocation of loads and overloading of transmission lines has affected the performance of the nigerian power system negatively resulting into problems such as poor voltage profile, increased power losses, unreliable and poor-quality power supply among others (ahmad and sirjan, 2020; idoniboyeobu et al., 2018). over the years, many efforts have been put forward generally to solve the key operational problems hampering power systems from attaining full potential without the desired goal achieved. conventional methods including construction of new generating stations, upgrading of existing transmission lines, expansion of distribution networks, the use of mechanical switches and capacitor banks have all been proposed in the past for improving the power system networks to enhance service delivery, however, some major limitations such as high investment cost, possible wear and tear of the mechanical components and time delay overshadowed the merits offered by these techniques (ahmad and sirjan, 2020; muhammad et al., 2020; adebayo and sun, 2017). this has, therefore, led to the emergence and adoption of facts for compensating power network performance. facts are solid state devices with capacity to improve power system performance in a prompt manner, increase voltage profile, reduce power losses, increase system reliability, prevent cascading outages through emergency control and damp oscillations that can threaten system security (shehata et al., 2020; rana et al., 2019; adebisi et al., 2018; simeon et al., 2018; adebisi et al., 2017). members of this family include but not limited to unified power flow controller, static synchronous compensator, interline power flow controller, static synchronous series compensator, static var compensator and thyristor-controlled series capacitor (bharambe, 2021; shelke and bhole, 2021; kaur and gupta, 2021; muhammad et al., 2020; siddique et al., 2019; movahedi et al., 2019; adebisi et al., 2018). usually, facts are incorporated into power system networks for performance improvement either through the use of first principle or optimization approach. while first principle involves manual installation of facts devices in some defective buses where voltage tolerance limit has been violated, optimization approach involves the integration of facts controllers at the best node or branch where its impact can generally be felt by the entire system using versatile techniques such as artificial intelligence (ai). placement of facts devices via first principle which is inherently characterised by slow response is unsuitable for today’s large-scale power system operation considering the complexity of different networks and the data structure. this, therefore, paves way for optimal placement of facts controllers using efficient optimization techniques such as ai based methods that can handle the complexity involved in the analysis of power system networks with spontaneous response. artificial intelligence, in a simple term, is a field of study concerned with the creation of humanlike thought processes such as reasoning, perceiving, learning, interaction and self-correction to facilitate robust problem solving (ergen, 2019; grewal, 2014). widespread adoption of ai based applications in recent times in various aspects of human endeavours including power system engineering has been attributed to massive data, advancements in algorithms as well as growing economical computational power and storage (ergen, 2019). different ai techniques have been deployed for optimal placement of facts for enhancing power system network performance. among the commonly used techniques are artificial neural network (ann), fuzzy logic (fl), differential evolution algorithm, ant colony optimization, genetic algorithm (ga), file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 135 particle swarm optimization (pso) and harmony search algorithm (singh and swami, 2020; gaur and mathew, 2018; nabavi et al., 2011). each of these techniques offers varying degree of dynamisms which adapts them suitably to the problems being addressed. therefore, in this work, an optimally placed svc via ga was employed to enhance the performance of the nigerian 330 kv electricity grid. svc possesses an excellent capability to compensate reactive power and regulate voltages at various buses in power system networks (ćalasan et al., 2020; biswas and das, 2011). due to these reasons, several investigations have been conducted on potential application of svc for varieties of performance improvement related issues in power system; voltage stability control (muthukumar et al., 2023; al-saidi et al., 2023), power loss minimization (osman et al., 2023; lakshmi, 2021), transient stability improvement (ikonwa et al., 2023; sahare and bonde, 2020) and dynamic stability enhancement (essien et al., 2023; himaja et al., 2022). the choice of ga for optimal placement of svc to improve the performance of a power system network in the present work was due to its high flexibility, efficiency, positive outcomes and user-friendliness (kothai and jayapal, 2021; adebanji et al., 2020). 1.1 static var compensator an svc is a shunt compensator capable of generating or drawing var for power system voltage stabilization. svc will consume reactive power from the power network if such system is characterized by a capacitive or leading reactive load and hence, reduces the system voltage. it will, however, increase the system voltage through reactive power injection if the network is characterized by an inductive or lagging condition (kumar and dash, 2016). basically, svc is composed of air core reactors in series with thyristor which is connected in parallel to filter banks as shown in figure 1. with proper adjustment of the thyristor firing angle, the current of air-core reactors can be controlled to produce voltage within acceptable limit at the bus. generally, svc is an efficient facts device that can regulate bus voltage magnitude, improve power flow along transmission lines, reduce power losses, increase system load ability among other (anand, 2017; kumar and dash, 2016). figure 1: an svc configuration (adebisi et al., 2018) http://www.azojete.com.ng/ adebisioluwaseun@funaab.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 136 2 materials and methods 2.1 power flow analysis power flow is an essential mathematical tool for obtaining insightful information about power system performance under steady state operating conditions (gupta, 2011; hadi, 2008; kothari and nagrath, 2008). for this work, a typical power system bus arrangement depicted in figure 2 was considered for the theoretical analysis of power flow. the resultant current with kcl applied to the n-bus arrangement in figure 2 and the complex apparent power delivered at bus i are respectively expressed by equations (1) and (2): (1) 𝑆𝑖 = 𝑃𝑖 + 𝑗𝑄𝑖 = 𝑉𝑖𝐼𝑖 ∗ (2) where: 𝑉𝑖, 𝐼𝑖, 𝑃𝑖 , 𝑄𝑖 and 𝑆𝑖 respectively denote voltage (v), current (a), active power (w), reactive power (var) and apparent power (va) associated with bus i;𝐼𝑖 ∗, 𝑉𝑗 and 𝑌𝑖𝑗 denote complex conjugate of bus i current (a), bus j voltage (v) and transfer admittance of bus i relative to bus j respectively (ʊ). vi v1 v2 vn ii ii1 ii2 iin yi1 yi2 yin iio yio figure 2: a typical power system n-bus arrangement (gupta, 2011; kothari and nagrath, 2008; hadi, 2008) the use of equation (1) in equation (2) yields equation (3) which was decoupled into real and imaginary parts expressed by equations (4) and (5) respectively: (3) 𝑃𝑖 = 𝑅𝑒{𝑉𝑖 ∗ ? 𝑌𝑖𝑗𝑉𝑗 𝑛 𝑗 =1 } (4) 𝑄𝑖 = −𝐼𝑚{𝑉𝑖 ∗ ? 𝑌𝑖𝑗𝑉𝑗 𝑛 𝑗 =1 } (5) the use of polar coordinates form of 𝑉𝑖, 𝑉𝑖 ∗, 𝑉𝑗, and 𝑌𝑖𝑗 given by equation (6) in equations (4) and (5) results in equations (7) and (8) respectively: file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 137 𝑉𝑖 = |𝑉𝑖|𝑒 𝑗𝑑𝑖 𝑉𝑖 ∗ = |𝑉𝑖|𝑒 −𝑗𝑑𝑖 𝑉𝑗 = |𝑉𝑗|𝑒 𝑗𝑑𝑗 𝑌𝑖𝑗 = |𝑌𝑖𝑗|𝑒 𝑗?𝑖𝑗 𝑒𝑗𝑓 = cos 𝑓 + 𝑗 sin 𝑓 } (6) where: 𝑑𝑖 and ?𝑖𝑗 respectively denotes bus i voltage angle (o) and line admittance angle (o). 𝑃𝑖 = ? 𝑌𝑖𝑗𝑉𝑖𝑉𝑗 𝑛 𝑗 =1 cos(?𝑖𝑗+ 𝑑𝑗 − 𝑑𝑖) (7) 𝑄𝑖 = −? 𝑌𝑖𝑗𝑉𝑖𝑉𝑗 𝑛 𝑗 =1 sin(?𝑖𝑗+ 𝑑𝑗 − 𝑑𝑖) (8) the expressions of equations (7) and (8) together constitute the static power flow equations. they are non-linear equations whose solutions are obtained through numerical iterative method (gupta, 2011; hadi, 2008; kothari and nagrath, 2008). newton-raphson iterative technique was employed in this work to linearize equations (7) and (8) because of its faster convergence, accuracy, reduced iteration number and reliability. [ ? 𝑃2 ? 𝑃3 ? ? 𝑃𝑛 ? 𝑄2 ? 𝑄3 ? ? 𝑄𝑛] = [ ?𝑃2 ?𝑑2 ?𝑃2 ?𝑑3 ? ?𝑃2 ?𝑑𝑛 | ?𝑃2 ?𝑉2 ?𝑃2 ?𝑉3 ? ?𝑃2 ?𝑉𝑛 ?𝑃3 ?𝑑2 ?𝑃3 ?𝑑3 ? ?𝑃3 ?𝑑𝑛 | ?𝑃3 ?𝑉2 ?𝑃3 ?𝑉3 ? ?𝑃3 ?𝑉𝑛 ? ? ? ? | ? ? ? ? ?𝑃𝑛 ?𝑑2 ?𝑃𝑛 ?𝑑3 ? ?𝑃𝑛 ?𝑑𝑛 | ?𝑃𝑛 ?𝑉2 ?𝑃𝑛 ?𝑉3 ? ?𝑃𝑛 ?𝑉𝑛 − − − − − − − − − ?𝑄2 ?𝑑2 ?𝑄2 ?𝑑3 ? ?𝑄2 ?𝑑𝑛 | ?𝑄2 ?𝑉2 ?𝑄2 ?𝑉3 ? ?𝑄2 ?𝑉𝑛 ?𝑄3 ?𝑑2 ?𝑄3 ?𝑑3 ? ?𝑄3 ?𝑑𝑛 | ?𝑄3 ?𝑉2 ?𝑄3 ?𝑉3 ? ?𝑄3 ?𝑉𝑛 ? ? ? ? | ? ? ? ? ?𝑄𝑛 ?𝑑2 ?𝑄𝑛 ?𝑑3 ? ?𝑄𝑛 ?𝑑𝑛 | ?𝑄𝑛 ?𝑉2 ?𝑄𝑛 ?𝑉3 ? ?𝑄𝑛 ?𝑉𝑛] [ ? 𝑑2 ? 𝑑3 ? ? 𝑑𝑛 ? 𝑉2 ? 𝑉3 ? ? 𝑉𝑛 ] (9) the linearized set of newton-raphson power flow equations is given by equation (9) with modified variant in equation (10). [ ? 𝑃 ?𝑄 ] = [ 𝐽1 𝐽2 𝐽3 𝐽4 ] [ ? 𝑑 ? 𝑉 ] (10) where: ? 𝑃, ? 𝑄, ? 𝑑 and? 𝑉 respectively denotes mismatch in active power (w), reactive power (var), phase angle (o) and voltage (v) and 𝐽1 , 𝐽2, 𝐽3and 𝐽4 are the jacobian matrix elements obtained as partial derivatives of equations (7) and (8) with 𝑑 and 𝑉 as independent variables. at each level of iteration, the mismatch in active and reactive power with updated bus voltage phase angle and magnitude are given equations (11) to (14): ? 𝑃𝑖 𝑘 = 𝑃𝑖 𝑠𝑝𝑒𝑐 − 𝑃𝑖 𝑘 (11) ? 𝑄𝑖 𝑘 = 𝑄𝑖 𝑠𝑝𝑒𝑐 − 𝑄𝑖 𝑘 (12) 𝑑𝑖 𝑘+1 = 𝑑𝑖 𝑘 +?𝑑𝑖 𝑘 (13) 𝑉𝑖 𝑘+1 = 𝑉𝑖 𝑘 +?𝑉𝑖 𝑘 (14) where: k is the iteration count, ? 𝑃𝑖 𝑘, ? 𝑄𝑖 𝑘, ? 𝑑𝑖 𝑘 and ? 𝑉𝑖 𝑘 respectively denotes mismatch in bus i active power (w), reactive power (var), voltage angle (o) and voltage magnitude (v) at http://www.azojete.com.ng/ adebisioluwaseun@funaab.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 138 iteration 𝑘, 𝑃𝑖 𝑠𝑝𝑒𝑐 and 𝑄𝑖 𝑠𝑝𝑒𝑐 denote bus i specified active power (w) and reactive power (var) respectively, 𝑃𝑖 𝑘 , 𝑄𝑖 𝑘, 𝑑𝑖 𝑘 and 𝑉𝑖 𝑘 respectively denotes bus i calculated active power (w), reactive power (var), voltage angle (o) and voltage magnitude (v) at iteration 𝑘 and 𝑑𝑖 𝑘+1 and 𝑉𝑖 𝑘+1 denote updated bus i voltage angle (o) and voltage magnitude (v) at iteration 𝑘 + 1 respsectively. the voltage and reactive power constraints imposed at bus i are expressed by equations (15) and (16) respectively: 𝑉𝑖𝑚𝑖𝑛 = 𝑉𝑖 = 𝑉𝑖𝑚𝑎𝑥 (15) 𝑄𝑖𝑚𝑖𝑛 = 𝑄𝑖 = 𝑄𝑖𝑚𝑎𝑥 (16) where: 𝑉𝑖𝑚𝑖𝑛, 𝑉𝑖𝑚𝑎𝑥, 𝑄𝑖𝑚𝑖𝑛 and 𝑄𝑖𝑚𝑎𝑥 respectively denotes minimum voltage magnitude (v), maximum voltage magnitude (v), minimum reactive power supply (var) and maximum reactive power supply (var) at bus i. 2.2 power flow modeling of an svc referring to figure 2, an svc placed at bus i acted or served as reactive power 𝑄𝑆𝑉𝐶𝑖 generator or absorber. hence, the effective var at bus i is obtained by equation (17) (auchariyamet and sirisumrannukul, 2010): 𝑄𝑖 = 𝑄𝑔𝑖 − 𝑄𝑆𝑉𝐶𝑖 = 𝑄𝑙𝑖 (17) where: 𝑄𝑔𝑖, 𝑄𝑙𝑖 and 𝑄𝑆𝑉𝐶𝑖 respectively represents reactive power generation (var), reactive power demand (var) and svc reactive power (var) at bus i. considering the svc representation in figure 3, the controller was modelled as a variable susceptance with the right constraint imposed on the susceptance or the firing angle. the current taken by the svc and the equivalent reactive power absorbed are respectively expressed by equations (18) and (19) (adebisi et al., 2018; adebisi et al., 2017): 𝐼𝑆𝑉𝐶 = 𝐵𝑆𝑉𝐶𝑉𝑖 (18) 𝑄𝑆𝑉𝐶 = 𝑄𝑖 = −𝑉𝑖 2𝐵𝑆𝑉𝐶 (19) where: 𝐼𝑆𝑉𝐶 , 𝐵𝑆𝑉𝐶and 𝑄𝑆𝑉𝐶 represents svc current (a), susceptance (ʊ) and reactive power (var) respectively. equation (19) gives an expression for the reactive power supplied when an svc is installed at bus i. the linearized set of equations modeling the svc at bus i where bsvc is considered as a state variable are expressed by equation (20) (adebisi et al., 2018; adebisi et al., 2017): [ ? 𝑃𝑖 ? 𝑄𝑖 ] (𝑘) = [ 0 0 0 𝑄𝑖 ] (𝑘) [ ? ?𝑖 ? 𝐵𝑆𝑉𝐶 𝐵𝑆𝑉𝐶⁄ ] (𝑘) (20) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 139 isvc i bsvc figure 3: a variable shunt susceptance model of an svc at the end of iteration k, the updated bsvc is expressed as equation (21): bsvc (k) = bsvc (k−1) + ( ?bsvc bsvc ) (k) bsvc (k−1) (21) the susceptance of the svc, 𝐵𝑆𝑉𝐶 , is related to its firing angle 𝑎𝑆𝑉𝐶by equation (22): 𝐵𝑆𝑉𝐶 = −1 𝑋𝐶𝑋𝐿 {𝑋𝐿 − 𝑋𝐶 𝑝 [2(𝑝 − 𝑎𝑆𝑉𝐶) + sin(2𝑎𝑆𝑉𝐶)]} (22) where: 𝑋𝐶and 𝑋𝐿are respectively the svc capacitive and inductive reactances in ω. the newton-raphson power flow equations with firing angle 𝑎 in degrees (o) as the new state variable is expressed as equation (23) (adebisi et al., 2018; adebisi et al., 2017): [ ? 𝑃𝑖 ? 𝑄𝑖 ] (𝑘) = [ 0 0 0 𝑑𝑄𝑖 𝑑𝑎 ] (𝑘) [ ? ?𝑖 ? 𝑎𝑆𝑉𝐶 ] (𝑘) (23) where: 𝑑𝑄𝑖 𝑑𝑎 = 2𝑉𝑖 2 𝑝𝑋𝐿 [cos(2𝑎𝑆𝑉𝐶) − 1] (24) the updated 𝑎svcafter iteration k is given by equation (25): 𝑎svc (k) = 𝑎svc (k −1) +?𝑎svc (k) (25) 2.3 genetic algorithm based optimal placement of svc with the inherent shortcomings of the conventional methods, facts devices today play crucial roles in enhancing the power system performance so that the wide margin between supply and demand for electrical energy could be minimized. the deployment of facts controllers for power system performance improvement usually involves a huge initial capital investment. therefore, to ensure these devices operate at maximum efficiency and produce satisfactory effect, their placement and sizing in power networks needs to be optimised. various approaches are available for optimizing the location or placement of facts devices. however, for this study, an artificial intelligence-based technique called genetic algorithm was adopted for optimizing the location of svc. http://www.azojete.com.ng/ adebisioluwaseun@funaab.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 140 genetic algorithm is a heuristic optimization approach inspired by the principle of genetics and natural selection. it is commonly employed tool for solving constrained and unconstrained problems arising in many fields of study. it is fast, efficient and has a good parallel capability in addition to its ability to produce multiple of good solutions. the flowchart of the implementation process of the genetic algorithm based optimal placement of svc in this work is shown in figure 4. typically, ga architecture is segmented into three distinct phases which are initial population generation, objective function evaluation and genetic operations. initial population generation phase involves random generation of possible solutions of the problem. this is followed by the computation of the objective function on every individual of the population to evaluate their fitness. new population sets are then generated via genetic operation involving reproduction, crossover and mutation until the maximum number of iterations is reached with each iteration equating to a generation. the cycle represented by these three phases of ga architecture is repeated severally until final improved solution is achieved. for the ga optimization in this work, the svc was configured based on two control parameters which are location and size setting of the device. to take these two parameters into account in the optimization process, each individual was represented with two strings during implementation. the first string corresponds to the location of the svc which comprises the number of buses where the device is to be installed while the second string corresponds to the size setting of the controller. the strings have discrete values between 0 and 1, with 0 representing the minimum value that the controller can take and 1, the maximum value. the creation of an individual was done by randomly generating all the possible buses or lines of the power network that could be a suitable location for the svc within the range of the number of bus data under consideration. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 141 start increase number of generation stop input network data including bus number and type generate the initial population (size and location of svc) initialize best result to zero compute objective function (voltage deviation and active power loss) for individuals in this generation select best result in this generation best result equals best result between initial best result and best result in this generation is maximum number of iteration reached? final output equals best result selection (roulette wheel) output the final result crossover (arithmetic) mutation (non-uniform) noyes figure 4: ga flowchart for the implementation of optimal placement of svc this was then followed by the characterization of the controller. finally, the size of the device was randomly chosen among the possible values and the objective functions which are voltage deviation minimization and active power loss reduction were determined for every individual of the population sets and subjected to further optimization procedures involving reproduction, crossover and mutation to produce new and improved population sets which are the final solutions. the two components of the objective function in the flowchart of figure 4, that is, voltage deviation and active power loss are respectively defined by equations (32) and (33): 𝑉𝐷 = ? |𝑉𝑗 − 𝑉𝑗 𝑟𝑒𝑓 |𝑛 𝑗=1 (32) 𝑃𝐿 = ? (𝑔𝑗(𝑉𝑖 2 + 𝑉𝑗 2 − 2𝑉𝑖𝑉𝑗 cos(𝑑𝑖 − 𝑑𝑗))) 𝑛 𝑗=1 (33) http://www.azojete.com.ng/ adebisioluwaseun@funaab.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 142 where: 𝑉𝐷 is the voltage deviation (v), 𝑉𝑗 𝑟𝑒𝑓 is the reference of the bus j voltage (v),𝑃𝐿 is the real power loss (w) and 𝑔𝑗 is the conductance of the connecting line between buses i and j (ω). for power system analysis, unless specified, it is usual to maintain the bus voltages within ±5% of the nominal value (ezeruigbo et al., 2021). hence, the voltage tolerance of 0.95 = 𝑉𝑖 = 1.05 𝑝. 𝑢. was adopted in this work. 2.4 test network the test network considered in this work to assess the performance enhancement capability of svc was the nigerian 28-bus power grid. the grid whose one-line diagram is presented in figure 5 comprised of twenty-eight buses, fifty-two transmission lines and nine generating stations. the network and generator data of the system are respectively presented in tables 1 to 3. b/kebbi kainji gs kano kaduna shiroro gs jos gombe makurdi mambila jebba gs jebba abuja ajaokuta osogbo ayede sapele gs benin ikeja west delta gs akangba onitsha aladja alaoje new haven aja egbin gs papalanto afam gs figure 5: the nigerian 28-bus power network (ncc, 2012) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 143 table 1: bus data of the nigerian 28-bus power network bus identification bus loads name no mw mvar egbin 1 68.90 51.70 delta 2 0.00 0.00 aja 3 274.40 205.80 akangba 4 244.70 258.50 ikeja-west 5 633.20 474.90 ajaokuta 6 13.80 10.30 aladja 7 96.50 72.40 benin 8 383.30 287.50 ayede 9 275.80 206.8 osogbo 10 201.20 150.90 afam 11 52.50 39.40 alaoji 12 427.00 320.20 new-heaven 13 177.90 133.40 onitsha 14 184.60 138.40 b/kebbi 15 114.50 85.90 gombe 16 130.60 97.90 jebba 17 11.00 8.20 jebba g 18 0.00 0.00 jos 19 70.30 52.70 kaduna 20 193.00 144.70 kanji 21 7.00 5.20 kano 22 220.60 142.90 shiroro 23 70.30 36.10 sapele 24 20.60 15.40 abuja 25 110.00 89.00 makurdi 26 290.10 145.00 mambila 27 0.00 0.00 papalanto 28 0.00 0.00 table 2: transmission line of the nigerian 28-bus power system transmission lines data bus resistance r(pu) reactance x(pu) from to 1 3 0.0006 0.0044 4 5 0.0007 0.0050 1 5 0.0023 0.0176 5 8 0.0110 0.0828 5 9 0.0054 0.0405 5 10 0.0099 0.0745 6 8 0.0077 0.0576 2 8 0.0043 0.0317 2 7 0.0012 0.0089 7 24 0.0025 0.0186 8 14 0.0054 0.0405 8 10 0.0098 0.0742 8 24 0.0020 0.0148 9 10 0.0045 0.0340 http://www.azojete.com.ng/ adebisioluwaseun@funaab.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 144 15 21 0.0122 0.0916 10 17 0.0061 0.0461 11 12 0.0010 0.0074 12 14 0.0060 0.0455 13 14 0.0036 0.0272 16 19 0.0118 0.0887 17 18 0.0002 0.0020 17 23 0.0096 0.0271 17 21 0.0032 0.0239 19 20 0.0081 0.0609 20 22 0.0090 0.0680 20 23 0.0038 0.0284 23 25 0.0038 0.0284 12 26 0.0071 0.0532 19 26 0.0059 0.0443 26 27 0.0079 0.0591 5 28 0.0016 0.0118 table 3: generator data of the nigerian 28-bus power system bus identification voltage magnitude generator reactive limits name no mw mvar qmin qmax egbin 1 1.05 0.00 0.00 -1006 1006 delta 2 1.05 670.00 0.00 -1030 1000 afam 11 1.05 431.00 0.00 -1000 1000 jebba g 18 1.05 495.00 0.00 -1050 1050 kanji 21 1.05 624.70 0.00 -1010 1010 shiroro 23 1.05 388.90 0.00 -1010 1010 sapele 24 1.05 190.30 0.00 -1010 1010 mambila 27 1.05 750.00 0.00 -1010 1010 2.5 simulation software in power system analyses, computer programs or software play a very vital role. they allow the performance of complicated system to be simulated or verified within a short period of time so that insightful information about the real time behaviour of the system can be obtained. in this work, the ga steps in the flowchart of figure 4 were implemented on the network of figure 5 through codes written using a matlab programming language, r2020a version. matlab was adopted because it provides an interactive environment for design and manipulation of algorithms in addition to data visualization, data analysis and numerical computation capabilities (nasiruzzaman, 2010). 3 results and discussion the voltage profile and power losses of the test power grid before and after optimally placed svc with the bus, branch and generator data in tables 1 to 3 as the input variables during simulation to fully characterize the network are shown in figures 6 and 7. the results in figure 6 showed that ga based optimal placement of svc on the nigerian 28-bus power grid improved the voltage profile of the overall network much better than the first principle procedure. when no compensation was applied on the grid, the voltage magnitudes of ayede, new-haven, gombe, kano and makurdi (buses 9, 13, 16, 22 and 26) which were 0.926, 1.058, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 145 0.906, 0.859 and 0.944 p.u. respectively fell out of the voltage tolerance limit of 0.95≤vi≤1.05 p.u. optimal placement of the svc via first principle on makurdi where the size of the compensator was 10.35 mvar improved the voltage magnitude of the node itself and ayede, new haven and gombe to 1.015, 1.008, 0.958 and 0.995 p.u. respectively, which are now within the voltage tolerance limit. however, this process produced a voltage magnitude of 1.065 p.u. at kano which was still outside the statutory limit. this drawback was overcome by ga based optimization technique. figure 6. voltage profile of the nigerian 28-bus power grid with and without compensation a 9.65 mvar rated svc optimally placed on kano via genetic algorithm improved the voltage magnitude of the node and ayede, new-haven, gombe and makurdi to 1.05, 0.985, 1.038, 1.016 and 0.996 p.u. respectively; the values which are all within the statutory limit. this result revealed that with the ga based optimization approach, the compensator performed better with a reduced size unlike the first principle approach where the size was a bit higher. the enhancement of the nigerian 28-bus power grid voltage profile through optimal location of svc impacted positively on power losses of the network as presented in figure 7. figure 7. total active and reactive power losses on the nigerian 28-bus power grid with and without compensation while the grid’s total active and reactive line losses respectively reduced by 17.46 and 13.87 % from 181.479 to 149.786 mw and 145.323 to 125.161 mvar respectively through first principle, ga based placement of the svc minimized the grid’s total active and reactive line losses from 181.479 to 115.675 mw and 145.323 to 109.336 mvar, producing a percentage reduction of 36.26 and 24.76 % in the respective total active and reactive line losses of the grid. these results indicated the suitability of svc placed by appropriate optimization techniques such as genetic algorithm for enhancing the performance of power system network. http://www.azojete.com.ng/ adebisioluwaseun@funaab.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):133-150. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 146 the results obtained are in agreement with the outcomes of the work of aryal and gynawali (2020), nassar et al. (2019), mulyadi et al. (2018) and duraisamy and ponnusamy (2017), who all conducted investigations on the ga based placement of svc considering different types of power networks. aryal and gynawali (2020) noted that ga based optimal placement of svc was a better approach for enhancing power system voltage profile and line loss, although stressing that the performance of the compensator could be improved further when used in combination with other facts controller. while nassar et al. (2019) observed that ga based optimal location of svc offered the best results in terms improved voltage profile and well minimized power losses of the four scenarios examined for power system voltage performance enhancement, mulyadi et al. (2018) showed that optimal placement of svc via ga on 150 kv electricity transmission grid enhanced the system’s overall performance such that voltage magnitude of each bus was raised to standard tolerance limit and line losses were significantly reduced. duraisamy and ponnusamy (2017) reported that voltage profile and total lines losses of the considered network after svc was optimally placed svc using ga improved appreciably. hence, all these previous works are suggestions that optimal placement of svc via artificial intelligence technique such as genetic algorithm is a potential candidate for enhancing the quality of electric power transmitted through grid system which was equally confirmed by the present study. 4 conclusion one of the key solutions presently gaining widespread attentions of power system engineers and researchers globally is the use of artificial intelligence based techniques for optimal facts placement for performance improvement of electricity grids. hence, this work employed an svc optimally placed by genetic algorithm for improving line losses and voltage profile on the nigerian 28-bus power grid. findings from the work revealed that optimal placement of static var compensator via ga in addition to exhibiting superior positive effects on the system’ s voltage profile produced a much more reduced total active and reactive power losses compared to the manual process and the initial load flow analysis. this, therefore, suggests that adoption of this approach for the nigerian power system grid will not only go a long way towards facilitating the transmission of a better quality electric power but also will increase transfer capability of the grid, thereby, making more electrical energy that can serve the endusers available. as a means to validating the results obtained in this study, further work is ongoing to comparatively evaluate the performance of ga based siting of the svc on the nigerian electricity with other optimization methods including fl, ann and pso to provide useful insights on the appropriate approach to locate the device since this is decisive in enhancing its effectiveness and efficiency for the performance improvement of power system networks where it is deployed. acknowledgements authors wish to appreciate the enormous support received from al-aleem engineering limited, lagos state, nigeria during the implementation phase of the study. references adebanji, b., adepoju, ga., olulope, p., fasina, t. and adetan, o. 2020. feasibility and optimal design of a hybrid power system for rural electrification for a small village. international journal of electrical and computer engineering, 10(6): 6214-6224. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng adebisi et al.: application of genetic algorithm based optimal placement of static var compensator for the nigerian 330 kv electricity grid performance enhancement. azojete, 20(1):133-150. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebisioluwaseun@funaab.edu.ng 147 adebayo, i. and sun, y. 2017. new performance indices for voltage stability analysis in a power system. energies, 10: 2042. adebisi, oi., adejumobi, ia., ogunbowale, pe. and ade-ikuesan, oo. 2018. performance improvement of power system networks using flexible alternating current transmission systems devices: the nigerian 330 kv electricity grid as a case study. lautech journal of engineering and technology, 12(2): 46-55. adebisi, oi., adejumobi, ia., ogunbowale, pe. and ade-ikuesan, oo. 2017. application of static var compensator for voltage stability enhancement and power loss reduction in power system networks. lautech journal of engineering and technology, 11(2): 46-58. al-saidi, m., al-badi, a., onen, a. and elhaffar, a. 2023. optimal location and size of static var compensators (svc) to enhance the voltage profile on the main interconnected system in oman. 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journal of agriculture and environment, 15(1): 61-75. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):599-606 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 599 original research article investigation of mechanical properties of polypropylene film as vacuum packaging material for dried fish i. a. mohammed1, o. adedipe2, j. y. jiya2*, a. b. ayuba1, k. t. obanimomo and k. c. bala2 1national institute for freshwater fisheries research, new bussa, niger state. nigeria 2department of mechanical engineering, federal university of technology, minna. niger state. nigeria *corresponding author’s email address: jiya.jonathan@futminna.edu.ng 1.0 introduction the process of designing, manufacturing, and evaluating products and packages is known as packaging technology. this harmonized system of organizing goods for logistics, transportation, sales, and consumption as reported by olayemi, (2012) is particularly important to the dried fish business in nigeria, where inadequate packaging materials have been identified as a major problem (folorunsho et al., 2015). research has shown that the films used for packaging dried fish in nigeria are not strong enough to protect it against microbial infection, insect attack, and nutrient loss (folorunsho et al., 2015). lack of quality dried fish production and poor marketing have been exacerbated by this trend. therefore, it is essential to investigate the appropriate dried fish packaging films with improved mechanical properties (izzhati et al., 2018). mechanical strength is one of the main factors considered when selecting fish packaging films (adejumo, 2013) due to the shape and spines of dried fish (ainara et al., 2019). commonly used packaging films include article information abstract this study investigated the mechanical properties of three sets of polypropylene packaging films and existing dried fish packaging films and the quality of dried fish packaging in nigeria... the polypropylene packaging films were produced in three batches a, b and c with thicknesses of 130µm, 150µm and 180µm respectively. the results showed that samples a, b and c had tensile strengths of 48n/mm2, 51.8n/mm2 and 61n/mm2 with elongation at break of 690.2%, 729.8% and 760% respectively. also, the dart impact strength of the samples were observed to be 191g/130µm, 208g/150µm and 231g/180µm respectively. additionally, samples n and k (existing fish packaging films) had tensile strengths of 34.6n/mm2 and 31.2n/mm2 and elongation at break of 279.2% and 267.2% respectively. furthermore, it was revealed that sample n exhibited better mechanical properties than sample k, while the produced polypropylene packaging films had the best mechanical properties among the samples tested. using modern systems such as vacuum packaging and modified atmosphere packaging (map) techniques, fish packaging and storage was improved. this research is important in light of the significant increase in aquaculture activities in nigeria due to increased fish production and government intervention in developing the sector, since it offers good moisture barrier properties, transparency and sealability with good cost efficiency and recyclability.it helps to preserve and protect the product’s quality, flavor and shelf life while providing a visually appealing package for consumers. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 26 april, 2023 revised 16 june, 2023 accepted 20 june, 2023 keywords: polypropylene films dried fish mechanical properties packaging http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng jiya.jonathan@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):599-606. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 600 polypropylene, polyamide (nylon), low-density polyethylene (ldpe), high-density polyethylene (hdpe), polyester, polyethylene terephthalate (pet), polyvinyl, and cellulose (agnieszka, 2018). however, the films currently used in nigeria do not demonstrate sufficient strength and properties to protect dried fish from mechanical and environmental damage (fakunle et al., 2018). to guarantee quality and safety for dried fish consumers, it is necessary to prioritize the production of effective packaging films. beniamino et al. (2020) noted that a good packaging film can also be regarded as a silent seller of its product. polypropylene is better than other packaging films because of its low density, light weight, and cost-effectiveness, thus making it a suitable option for drying fish. however, the selection of the right packaging films for dried fish should not be based solely on availability and cost, but also on other important factors such as mechanical abrasion and puncture resistance (vilasia and gabriel 2019). the use of improper packaging materials may lead to nutritional loss, endangerment of consumers and insect infestation (zuzana, 2017). the mechanical properties of packaging films can be altered by taking into consideration the nature of the product it would be enclosing and adjusting the processing parameters accordingly (suryakanta, 2015). interestingly, the increasing global population and inadequate food resources, coupled with protein deficiency, necessitate the use of methods to extend the shelf life of dried fish (nuray, 2017). for example, vacuum packaging is used to protect the dried fish from the effects of environmental factors and microorganisms, as well as maintain its original colour, taste and flavour (nicolas and claire, 2019). vacuum packaging works on the principle that microorganisms such as mould and yeast require oxygen for survival, thus when the oxygen concentration in the packaging is less than 1%, microorganism growth and reproduction rate will drop significantly (nuray, 2017). the use of polypropylene film as a packaging material offers several advantages including its barrier property against moisture, transparency and recyclability but also come with some environmental considerations. its suitability depends on the specific products and packaging requirements. this study, therefore, seeks to investigate the mechanical properties of polypropylene films for packaging of dried fish, by testing and comparing them with existing packaging films. 2.0 materials and methods the polypropylene packaging film was produced by green gold technology nigeria limited, niger state based on the supplied specifications for this research purpose. using the cast film extrusion method, melted resin was extruded horizontally through a flat-shaped die forming a thin film held to some extremely refined chilled rollers via air curtains. extra chill rollers were employed to rapidly cool the film before trimming to size and rolling the produced films. 2.1 mechanical tests method for polypropylene film the following mechanical tests were carried out on the film samples; 2.1.1 tensile strength and percentage elongation at break test the experiment to determine the tensile strength and percentage elongation at break of three batches of produced polypropylene packaging films and existing dried fish packaging films was conducted at green gold technology nigeria limited, minna, niger state. astm d 2990 and file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng mohammed et al: investigation of mechanical properties of polypropylene film as vacuum packaging material for dried fish. azojete, 19(3):599-606. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 601 nis 835:2017 standards were adopted for the packaging films (astm, 2018). the thickness of all samples was measured using micrometre screw gauge, and the length and width were measured using a metre rule. to conduct the test, the samples were cut into dumb bell shapes of 85 mm length and 25 mm width, and loaded into the tensile grips (figures 1 and 2). the grips were moved at a constant speed while the machine recorded the varying distance between them and the force applied. once the specimen failed, the tensile strength and percentage elongation at break were noted from the indicator. this process was repeated for all three sets of samples and existing dried fish packaging films, and conducted in five replicates. figure 3 shows dumb bell shaped specimens from a set of samples of the produced polypropylene packaging film. figure 1: tensile strength machine with load indicator attached figure 2: a specimen held by the upper and lower grips of tensile strength machine during testing figure 3: dumb bell-shaped specimen from a set of samples of produced polypropylene film ready for testing 2.1.2 dart impact strength tester the dart impact strength test for the three batches of polypropylene packaging films, as well as existing dried fish packaging films, was conducted according to the nis 835:2017 standard for standard packaging films. the polypropylene packaging film sample was firmly attached to the disc http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):599-606. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 602 with screws, and the dart weight was dropped onto it. this was repeated nine more times, each with a new sample. the mass of the dart weight at 50% failure of the sample was recorded and expressed as the mass at which the sample failed per the thickness of the sample (g/µm). the same tests were conducted in five replicates on ten samples from each set of polypropylene packaging films and existing fish packaging films. 2.1.3 drop impact resistance test the drop impact resistance test was conducted on both the produced polypropylene packaging films and existing dried fish packaging films using the standard procedure in accordance with the method adopted from nis 835:2017 for standard packaging films. the test load (ballast) was placed in the polypropylene packaging film (sample) according to the dimensions of the film, and it was gently deflated before closing its mouth with an appropriate closing system (sealing) at about 100mm from the mouth. the filled polypropylene packaging film was then placed on the trap of the testing machine so that its bottom was 1.20m ± 0.01m above the smooth test surface. the film was dropped once and inspected for tears or rupture before the test loads were removed. pass or fail results were recorded for each sample. this process was repeated for 30 produced polypropylene packaging films and the existing dried fish packaging films, and the test was conducted in five replicates. 2.1.4 coefficient of friction test the coefficient of friction test was conducted in accordance with astm d 1894, adopted from nis 835:2017, to evaluate the performance of three batches of produced polypropylene packaging films and existing dried fish packaging films. the samples were taped to the plate and sled and attached to a load cell on the testing machine actuator via a rope that ran through a pulley. the rope was then pulled at a constant rate and the load at which the sample started to move was recorded graphically. the testing stopped once the designated sliding distance had been achieved and the static and kinetic coefficient of friction values were then calculated. 2.2 vacuum packaging of dried fish using produced polypropylene films the product development and engineering department of the national institute for freshwater fisheries research (niffr) in kainji, niger state, carried out vacuum packaging of dried fish using the produced polypropylene films. three sets of samples were used to package the dried fish, with six packages in each set. 3.0 results and discussion 3.1 mean values of mechanical properties of produced polypropylene and existing packaging films the mechanical properties of polypropylene packaging films and existing fish packaging films were investigated and the mean values for each sample were determined. five replicates of each sample were conducted, and the results are presented in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng mohammed et al: investigation of mechanical properties of polypropylene film as vacuum packaging material for dried fish. azojete, 19(3):599-606. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 603 table 1: mean values of tested parameter of mechanical properties of produced polypropylene and existing dried fish packaging films s/ n tested parameter produced polypropylene packaging film existing dried fish packaging film sample a sample b sample c sample n sample k 1 thickness (µm) 130 150 180 140 130 2 length (mm) 340 340 340 320 300 3 width (mm) 300 300 300 285 260 4 tensile strength (n/mm2 ) 48 51.8 61 34.6 31.2 5 elongation at break (%) 690.2 729.8 760 279.2 267.2 6 drop impact resistance pass pass pass pass fail 7 dart impact strength (g/µm) 191/130 208/150 231/180 143./140 133/130 8 coefficient of friction mda=0.15 tdb=0.15 mda=0.15 tdb=0.15 mda=0.15 tdb=0.15 mda=0.15 tdb=0.15 mda=0.10 tdb=0.19 where, md= machine direction; td = transverse direction; a=longitudinal: direction parallel to extrusion direction; b=transverse: direction perpendicular to extrusion direction table 1 depict that the produced polypropylene packaging films have higher tensile strength and elongation at break compared to the existing dried fish packaging films which agrees with the findings of saber and mohamed (2019). sample c has the highest tensile strength of 61 n/mm2 and elongation at break of 760%, while sample k has the lowest tensile strength of 37.2 n/mm2 and elongation at break of 511%. the comparison of these mechanical properties show that the produced polypropylene packaging films are more robust and reliable due to their high tensile strength and elongation as against the existing dried fish packaging films. the mechanical properties of the produced polypropylene packaging films and existing dried fish packaging films were tested. the results showed that the produced polypropylene packaging films demonstrated higher tensile strength and elongation at break. sample k of the existing dried fish packaging films showed the lowest dart impact strength, burst during the drop impact resistance test and had different coefficient of friction values for machine direction (md) and transverse direction (td). abdurrahman et al. (2015) strongly emphasized that packaging film should be selected based on their mechanical performance. the investigated mechanical properties of produced polypropylene packaging films and the existing dried fish packaging films http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):599-606. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 604 proved that the produced samples had better mechanical strength as demonstrated during the various tests conducted. the produced polypropylene packaging films samples demonstrated different tensile strength and elongation at break. the difference in this mechanical strength is due to the difference in thickness of the packaging films and will address the findings of agomuo et al. (2017). this study also provides solutions to some of the challenges stated by folorunsho et al. (2015) and one of the recommendations made by abolagba and akise (2011), which suggested that other fish packaging materials be developed while existing ones improved to avoid fish spoilage and reduce cost. the dart impact strength of the produced polypropylene packaging films confirm the suitability of the films for dried fish packaging most especially its high resistance to puncture. such packaging films can withstand the spines of dried fish, mechanical damage and environmental factors as established by omnexus (2020). the existing dried fish packaging film (sample k) has lower dart impact strength compared to the produced film which is in line with report by ales et al. (2017). none of the produced polypropylene packaging films samples ruptured during the drop impact resistance test which suggests that the package can survive drops or any accidental falls during handling and transportation. unlike the existing dried fish films, sample kcoefficient of friction (cof) for all samples were similar except, for sample k. although, various packaging operations requires different cof hence the outcome of the study agrees with ljevak et al. (2018). 3.2 packaging of dried fish using single chamber vacuum packaging machine the three set samples of the produced polypropylene packaging films were used to package dried fish using single chamber vacuum packaging machine. six packages from each set of samples were selected. figure 4 shows packaged dried cat fish and cod fish (stock fish) in produced polypropylene packaging films. figure 4: vacuum packaged cat fish and cod fish (stock fish) in produced polypropylene packaging films file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng mohammed et al: investigation of mechanical properties of polypropylene film as vacuum packaging material for dried fish. azojete, 19(3):599-606. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 605 4.0 conclusions this study examined the mechanical properties of newly-produced polypropylene packaging films for vacuum packaging of dried fish using three sets of samples. similarly, the mechanical properties of the produced polypropylene packaging films were compared to those of existing dried fish packaging films. the following conclusions were drawn: i. suitable standardized polypropylene packaging films with superior mechanical properties for dried fish packaging were produced. ii. the produced polypropylene films also exhibited similar coefficient of friction for the three sets of samples, with mda =0.15 and tdb =0.15. iii. the produced polypropylene packaging films exhibited sufficient mechanical strength in comparison to the existing dried fish packaging films. iv. based on the results of the study, the produced polypropylene packaging films demonstrated better mechanical properties than the existing dried fish packaging films. references abdurrahman, ab., samla, g., nor, ia. and chandima, g. 2015. mechanical stability of bio based food packaging material. food science and quality management, 39(1): 41-48. abolagba, oj. and akise, og. 2011. fish packaging in benin, edo state and koko, delta state. australian journal of basic and applied science, 5 (12): 189-195. adejumo, ba. 2013. preliminary investigations on some mechanical properties of selected plastic packaging material for gari packaging in nigeria. international journal of science and technology research, 2 (10): 164-167. agnieszka, w. 2018. selected properties of multilayer films applied for vacuum and modified atmosphere packaging systems. agricultural engineering, 22(4): 89-98 doi: 10.1515/agriceng-2018-0040. agomuo, jk., ehirim, f. and onugha, fc.2017. storage stability of smoked mackerel fish as affected by selected packaging materials. world journal of food science and technology, 1(1): 22-27. doi:10.11648/j.wjfst.20170101.14. ainara, s., jian-bo, z., xiaoyan, t., augustin, e., eugene, yxc. and haritz, s. 2019. packaging materials with desired mechanical and barrier properties and full chemical recyclability. nature communications, 10(1): 3559. ales, m., peter, c. and ivan, h. 2017. impact resistance of high-density polyethylene against falling penetrator with different potential energy. matec web of conference, 125: 02050, doi:10.1051/matecconf/201712502050. astm d 2990 2018. standard test method for tensile, compressive, and flexural creep and creeprupture of plastics. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):599-606. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: jiya.jonathan@futminna.edu.ng 606 beniamino, tc., maria, fl., paola, s., elena, b., musafiri, k. and luca, g. 2020. new trends in meat packaging. microbiology research, 11(1): 56-67, doi: 10.3390/microbio/res11020010 fakunle, jo. effiong, bn., ibanga, ui. and adebayo, e. 2018.quality assessment of smoked dried fish packed in sealed transparent polythene nylon. iosr journal of and veterinary science (iosr-javs), 11(5): 39-43. doi: 10.9790/2380-1105013943. folorunsho, o., omodara, m. and olufemi, p. 2015. development of appropriate packaging for shelf life extension of smoked fish in a developing economy. international journal of fisheries and aquatic studies, 2 (4): 46-50. izzhati, dn., hassan, m. and jazuli, tt. 2018. consumer preferences for the design smoked fish packaging using conjoint analysis. journal ilmiahteknik industry, 17 (2): 177-185, doi:10.23917/jiti.v17i2.6778 ljevak, i., igor, z. and dubravko, b. 2018. the variability of dynamic coefficient of friction material in flexible packaging. original scientific paper, 29(1): 31-38. nicolas, m. and claire, igls. 2019. packaging design alternative for meat products. intechopen, 1-22, doi: 10.5772/intehopen.88586, london, uk. nigerian industrial standard for polyethene bag nis 835: 2017. standards organisation of nigeria, abuja, nigeria. nuray, e. 2017. the effect of active and vacuum packaging on the quality of turkish traditional salted dried fish. journal of food and health science, 3(1): 29-35. olayemi, f. (2012). shelf life and quality characteristics of smoked catfish stored in composite packaging materials phd thesis department of agricultural and environmental, university of ibadan, nigeria. omnexus 2020. retrieved from https://omnexus.specialchem.com/polymer properties/properties/stiffness. saber, i. and mohamed, m. a. 2019. multilayer flexible packaging materials: relationship between structure and functional properties. egyptian journal of chemistry, 62 (10): 1963-1969 suryakanta, p. 2015. general properties of plastics retrieved from http://www.civiblog.org/2015/07/09/10+general-properties-of-plastic-as-a-construction-mat vilasia, gm. and gabriel, sf. 2019. mechanical properties. retrieved from http://www.sciencedirect.com/book/9780128153574/savingfood zuzana, s. 2017. comparison of materials used for packaging purposes. b.sc. thesis, international business and logistics, helsinki metropolia university of applied science, myllypurontie, finland file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/jiya.jonathan@futminna.edu.ng http://www.civiblog.org/2015/07/09/10+general-properties-of-plastic-as-ahttp://www.sciencedirect.com/book/9780128153574/savingfood arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):871-884 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 871 evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer m. t. akinleye1, l. o. salami1*, o. p. joseph1, r. o. rahmon2, i. tolu-ilori1 and o. i. ogungbola1 1department of civil engineering, adeleke university, ede, nigeria 2department of civil engineering, university of ilorin, ilorin, nigeria *corresponding author's email address: salami.lukman@adelekeuniversity.edu.ng article information submitted 3 august, 2023 revised 11 sept, 2023 accepted 8 sept, 2023 keywords: asphalt bitumen marshall modifier thermoplastic polymer abstract flexible pavements, particularly in urban areas, deteriorate rapidly after construction due to poor workmanship and inadequate drainage facilities. the demand for roads continues to increase. engineers of the highway system are concentrating on alternative solutions to meet this expanding challenge. highway system engineers are currently focused on developing alternative solutions in order to address this growing challenge. to prevent the premature deterioration of the road system, the performance of flexible pavements must be enhanced. the addition of waste polymers to asphalt mixtures is one method that can significantly enhance the quality of the pavements. this study examined the mechanical properties of asphalt produced from waste plastic polymer-modified bitumen. the addition of thermoplastic polymer (0 to 12%) increased the softening point, viscosity, flash and fire points of bitumen, but decreased its penetration and ductility for the production of hot mix asphalt. the marshall stability and flow of all asphalt concrete formulations were greater than 9 kn and within 2 6 mm of the general specifications of nigerian for road and bridges, federal ministry of works and housing, 2016 and the asphalt institute, 1991. modification of asphalt with thermoplastic polymer is suitable for enhancing the performance properties of the asphalt. additional research is required for the development of recyclable additives that do not significantly increase the final cost of bitumen 1.0 introduction asphalt is widely used as a material in highway construction. continuous increment in industrialization and urbanization increases the demand for highway networks. akinleye et al. (2020a) reported that global highway networks consist of numerous track miles and facilitate countless vehicle miles annually. mantzos and capros (2006) predicted that this demand will continue to rise significantly over the next ten years as the volume of goods and people traveling by road continues to rise globally. an evaluation of the quality of asphalt concrete used in road construction in nigeria suggested that asphalt quality should be enhanced due to the early failure of road pavements in the country. modification of hot mix asphalt (hma) pavements is essential for resolving the quality of surface materials. it improves performance, extends service life, and reduces maintenance costs (arslan et al., 2012; akinleye and tijani, 2017; salami et al., 2023). there are two primary ways to incorporate polymers into asphalt mixtures, namely the moist process and the dry process (salami and bello, 2021). nevertheless, the modification of bitumen has been the method most frequently used for this purpose (kalantar et al., 2012). http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 872 plastic is widely used in contemporary society, and its disposal poses a significant problem. plastic is an inorganic substance; therefore, it pollutes the environment and causes problems. now, the greatest challenge is to reduce plastic pollution by converting it into something useful (akinleye et al., 2020a, 2020b). according to mohd et al. (2017), given that the waste consists of polyethylene terephthalate (pet) plastic bottles, disposable glasses, purses, and various appliance covers that become moist at 160°c, one solution is to use waste plastic in such a way that it becomes coated by an aggregate via heating (140–160°c). every year, following the monsoon season, almost all of the main roads in urban areas of nigeria require immediate and extensive rehabilitation due to the country's traditional construction methods and harsh climate. this maintenance work is not only costly, but it also disrupts normal traffic flow, causing drivers inconvenience and delay. utilizing waste plastic (polymer) in the construction and maintenance of pavements could reduce the frequency of rehabilitation work and provide a cost-effective solution. the second benefit of plastic recycling is the enhancement of the problem of solid waste disposal. additives used to modify or enhance the quality of virgin materials are referred to as its modifiers. to enhance the properties of asphalt concrete, modifiers are either blended directly with the binder or added during production. the recent trend in the pavement industry is to use polymer as a bitumen modifier, as polymer is analogous in nature to certain bitumen constituents. bitumen is a complex mixture of various compounds. asphaltenes and malthenes are the principal components of bitumen. the amount of aromatic malthenes and asphaltenes (baker, 1998) is crucial to the suitability of bitumen modification. polymer and copolymer of distinct category and grade are used to improve the overall quality of bitumen due to their similar composition. polymer increases the viscosity of bitumen and the thickness of the coating surrounding aggregates (murphy et al., 2001; salami et al., 2023). thus, the adhesive and cohesive properties of bitumen are improved. another potential bitumen modifier is natural rubber (granules or latex) or reprocessed rubber dust (kakar et al., 2021). the waste plastic (scrap polythene) can also be used to modify binder (kakar et al., 2021). as asphalt binder is responsible for the thermos-rheological properties of asphalt mixtures, it plays a crucial role in determining a variety of factors, such as permanent deformation and fatigue cracks. a portion of asphalt's induced strain is attributable to non-recoverable viscous flow, which progressively increases with loading time and temperature. the variation in strain with time is caused by the material's viscous behavior. when the burden is removed, the elastic strain recovers, and some additional recovery takes place over time; this phenomenon is known as delayed elasticity. due to the viscosity of the binder, there is a permanent residual strain that cannot be recovered. review of literature revealed that thermoplastic polymer is viscous in a nature. hence, this study modified the bitumen with thermoplastic polymer in a bid to enhance the viscosity of the binder. thus, this study examined the mechanical properties of asphalt produced from waste plastic polymer-modified bitumen. 2. materials and methods 2.1 materials wastes of metals and high-density polymer (broken buckets, bowls, overhead water tanks and plastic chairs) were obtained within at waste generation point of adeleke university, ede, nigeria. metropolis, osun state, nigeria, the polymers were shredded into small sizes and melted and allowed to cool. the polymers were melted using a gas cooker at the highway and transportation laboratory of the department of civil engineering, adeleke university, ede, nigeria. asphalt thermometer was used to check the temperature. the polymers have a melting point of 160°c. the polymers’ very high melting temperature and readiness of compatibility with the asphalt prompted its addition at varied weight proportions of bitumen in the proportions 0, 2, 4, 6, 8, 10 and 12% for the preparation of modified asphalt mixture. the plastic pieces were melted with bitumen at temperature between 160 -170oc and the mixture was stirred thoroughly for about 15 to 20 minutes to attain a uniform blend in file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng akinleye et al: evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer. azojete, 19(4):871-884. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 873 accordance with astm standard specification. different compositions (broken buckets, bowls, overhead water tanks and plastic chairs) of polymer-bitumen mixtures (blends) were prepared and utilized for the experiments. the purpose of bitumen modification includes softening blends at low temperatures to reduce fractures, increasing the stability and strength of mixtures, enhancing the asphalt cohesive strength in pavements, preventing oxidation and aging, and lowering the construction costs of asphalt roads. the waste plastics were burnt using a portable gas cooker. the fine (stone dust) and coarse aggregate was gotten from crushed igneous rock at ayofe quarry, ede, nigeria. figure 1 (a – d) depicts the breakable plastic wastes, modified bitumen sample (showing the melting process), fine aggregate sample and coarse aggregate sample, respectively. figure 1a: breakable plastic wastes figure 1b: modified bitumen sample figure 1c: fine aggregate sample figure 1d: coarse aggregate sample 2.2 determination of penetration values this is used to measure the vertical depth of bitumen to ascertain its rigidity or pliability. penetrometer was used to determine the penetration of the bitumen in accordance with astm d5-06. (2006) standard specification. the bitumen mixture was liquefied to a pourable consistency, thoroughly mixed, and poured into containers. the test was conducted at 250°c. the bitumen temperature was achieved and maintained using a water bath. figure 2 depicts a diagram of a penetration test configuration. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 874 figure 2: penetration test set-up 2.3 determination of ductility values bitumen is ductile, allowing it to withstand significant deformation or elongation. moldcontaining bitumen compositions were cooled in the air and then in a 27°c water bath in accordance with astm d113-86. (1986) standard specification. the surface was leveled of excess bitumen was removed with a heated knife. the sample-containing mold was then deposited in the ductility machine's water reservoir for approximately 90 minutes. the model of the ductility machine is to-565-dg-03 and it is electrically operated at 220v, 50hz. the sides of the molds were removed, clamps were affixed to the machine, and the machine was activated. ductility values were obtained at the point of rupture of the bitumen. the ductility values were taken at the point at which the bitumen breaks after elongation in accordance with astm d113-86. (1986) standard specification. the laboratory configuration for the ductility machine is depicted in figure 3. figure 3: ductility test apparatus 2.4 determination of softening point the softening point is the temperature at which bitumen softens to a specific degree under the specified test conditions. the bitumen mixture sample was covered with a 3.5g steel ball, and the liquid medium was heated to 50°c per minute using an electric hot plate. when the bitumen reaches a depth of 25 millimeters below the ring, the temperature was recorded. softening point test was conducted in accordance with astm d36-2002. (2002) standard specification. figure 4 depicts the test setup for the study's evaluation of the softening point. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng akinleye et al: evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer. azojete, 19(4):871-884. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 875 figure 4: ring and ball softening point apparatus figure 5: flash and fire point test apparatus 2.5 determination of flash and fire point depending on the condition of the bituminous material, volatiles should be eliminated at high temperatures. the flash point is the temperature at which bituminous vapour ignites when exposed to a small flame. the fire point is the lowest temperature at which a fuel's vapour continues to ignite for at least five seconds. the experiment was conducted in compliance with astm d92 – 02 (2002) standard specification. figure 5 depicts the setup for the test. 2.6 determination of viscosity (is: 1206-1978) viscosity denotes the fluid property of bituminous material and it is a measure of the material resistance to flow. the bitumen was heated to a temperature not exceeding 60°c, which is slightly above the softening point of bitumen. the bitumen was heated until it became fluid enough to be readily poured. the viscometer container was filled to a maximum of 25 ml and placed gingerly beneath the spindle section of the viscometer. the spindle was then meticulously positioned within the sample. the opening beneath the test apparatus was then sealed. afterward, the viscometer was activated. the viscometer rotated at 200 revolutions per minute until the temperature of the bitumen reached 135 degrees celsius. when the viscometer attained the required temperature and the viscosity was stable, the viscosity values were recorded. according to astm d445-06 (2006) standard specification, the testing apparatus was used to measure the viscosity of the bitumen. figure 6 displays the viscosity testing apparatus. figure 6: viscosity test apparatus http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 876 2.7 marshall stability test the marshall stability test is used for assessing two crucial features of flexible characteristics and strength. the marshall stability of a mixture measures its tensile strength, while the flow value quantifies its pliability. the machine's upper dial gauge displays the stability value, while the lower dial gauge displays the flow value. the marshall stability test was successfully carried out in accordance with the specifications of astm d2487 (2011). figure 7a depicts thermostatically controlled water reservoir in which the test samples were immersed for 30 to 40 minutes at a temperature of 60°c. probably, the marshall stability of the mixture is a greater load carried by a compacted specimen at a standard temperature of 60°c. the flow value is the distortion in millimeters that the test specimen experiences during loading up to the maximum load. the thermostatically controlled water reservoir in which the test samples were immersed for 30 to 40 minutes at a temperature of 60°c is presented in figure 7a. the figures 7b and 7c show the marshall stability test set-up and marshall stability sample, respectively. figure 7a: marshall samples in thermostatically controlled water bath figure 7b: marshall stability test set up figure 7c: marshall stability sample 3. results and discussion 3.1 penetration and softening points the results of penetration and softening values of plastic polymer modified bitumen are presented in table 1. the values of penetration points for the 0 – 12% of polymer addition ranges from 16 to 67 percentage. it was observed that the penetration value decreased as the percentage polymer addition increased (figure 8) which could attribute to the addition of the polymers. the coefficient of prediction of 99.9% implies that the polynomial model shows a good relationship between penetration value and polymer addition level. also, the softening point values of the asphalt produced from bitumen modified with plastic polymer ranged from 49.05 to 91.9°c. it was deduced that the softening point value increased as the percentage polymer addition increased as surfaced in figure 8. the increment in the softening point could file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng akinleye et al: evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer. azojete, 19(4):871-884. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 877 attributed to the addition of the polymers. this is corroborated by the findings of ajagbe et al. (2018); ajagbe et al., 2020; akinleye et al., 2020a; akinleye et al., 2020b; salami et al., 2023a; salami et al., 2023b. the coefficient of prediction of 97.98% implies that the model shows a good relationship between softening point and polymer addition level. it demonstrates that the temperature sensitivity of the binder decreased significantly as the amount of modifier increased. this is in line with mohammad (2012); murana et al. (2020); akinleye et al. (2020a); salami and bello (2021); salami et al. (2023a) where it was discovered that the softening point increased from 50 to 70°c when 10% of the plastic waste was present. it implies that a greater amount of heat will be required to soften the improved binder because polymer increased the binder's consistency. table 1: penetration and softening properties of plastic polymer modified asphalt % polymer in bitumen penetration (%) softening point (oc) 0 67.0 49.05 2 57.7 61.25 4 49.3 68.50 6 41.7 73.55 8 32.3 77.20 10 23.0 83.35 12 16.0 91.90 figure 8: penetration and softening points 3.2 ductility ductility test results of the asphalt produced from bitumen modified with plastic polymers are presented in figure 9. the average values ranged from 31.3 to 106.3 which also signifies that ductility declined with surge in the content of modifier in the bitumen. the decrement in the ductility could attributed to the addition of the polymers. this is corroborated by the findings of ajagbe et al. (2018); ajagbe et al., 2020; akinleye et al., 2020b; salami et al., 2023a; salami et al., 2023b. the polynomial model representing the ductility at a known percent polymer addition showed 97.66% coefficient of prediction which showed an adequate representation. penetration = 0.0101x2 4.3964x + 66.852 r² = 0.999 softening point = -0.079x2 + 4.1884x + 51.093 r² = 0.9798 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 p en et ra ti o n ( % ) an d s o ft en in g p o in t (o c ) % polymer in bitumen *softening point (℃)penetration (%) http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 878 figure 9: ductility values of the plastic polymer modified asphalt 3.3 viscosity, flash and fire points the viscosity (v) values of plastic polymer modified bitumen ranged from 260.7 to 431.0℃ and it increased with an upsurge in the percent polymer addition level as shown in figure 10. the viscosity values obtained increases with an increase in the percent polymer addition. the increment can be attributed to the addition of polymer. polymer is known to be viscous in nature. the result is in consonance with the findings of ajagbe et al. (2018); ajagbe et al. (2020); akinleye et al., (2020b); salami et al., (2023a); salami et al., (2023b). the polynomial model generated to predict the relationship has a 99.04% agreement as shown in figure 10. in the same vein, the flash point (fl) value obtained for the bitumen modified with plastic polymer ranged from 248.3 to 299.0℃. the increment in the values obtained for flash and fire point is as a result of the addition of polymer. polymer and bitumen are known to be flammable in nature (salami et al., 2023a; salami et al., 2023b) the values obtained increases with an increase in the percent polymer addition and the polynomial model generated to predict the relationship has a 94.66% agreement. the fire point (fip)value obtained for the bitumen modified with plastic polymer ranged from 289.4 to 327.0℃. the flash and fire point values obtained increases with an increase in the percent polymer addition and the polynomial model generated to predict the relationship has a 95.67% agreement as shown in figure 10. figure 10: viscosity, flash and fire point of the plastic polymer modified asphalt ductility = 0.0241x2 6.9125x + 110.39 r² = 0.9766 0 20 40 60 80 100 120 0 2 4 6 8 10 12 14 d u ct ili ty % polymer addition v(℃) = 0.8226x2 + 3.5929x + 263.05 r² = 0.9904 fl (℃) = -0.4182x2 + 8.6089x + 252.99 r² = 0.9466 fip (℃) = -0.619x2 + 10.764x + 290.23 r² = 0.9567 250 270 290 310 330 350 370 390 410 430 450 0 2 4 6 8 10 12 % polymer addition viscosity flash point fire point file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng akinleye et al: evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer. azojete, 19(4):871-884. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 879 3.6 optimum bitumen content the results of marshall stability and flow varying plastic content are presented in figure 11 below for the determination of optimum bitumen content (obc) at various addition level (0-12% by weight of bitumen). figure 11 shows the result for stability, while figure 12 presents the result for flow. these results were obtained to determine the optimum bitumen used to produce the asphalt sample for the determination of stability and flow for the final mix. the obc indicate the quantity of bitumen needed to produce the asphaltic concrete. all the obc values obtained satisfy the requirement specified for binder and wearing courses by the fmw (2016). furthermore, figure 11 indicated the results of obc for at 0, 2, 4, 6, 8, 10, and 12% modification were 5.80, 6.20, 5.80, 5.90, 5.90, 6.20, 6.10, 6.20, 5.90 and 5.60% respectively. the obc values obtained satisfy the requirement specified for binder and wearing courses by the fmw (2016). moreover, all values obtained for stability satisfy the fmw (2016) standard specification. figure 11: marshall stability values for obc determination figure 12: marshall flow values for obc determination 3.7 marshall stability variation of stability with percentage polymer addition with bitumen test is presented in figure 13. stability values increased as the content of the polymer increased which could be attributed to the polymer’s addition. the result is in consonance with the findings of ajagbe et al. (2018); ajagbe et al. (2020); akinleye et al., (2020b); salami et al., (2023a); salami et al., (2023b). the upsurge in the stability values of the blend is attributable to the enhancement of the modified binders to aid adhesiveness and cohesiveness of the asphalt blend, which is a result of the 0 5 10 15 20 25 0 2 4 6 8 10 12% polymer addition stability value @ varying binder content 5 5.5 6 6.5 7 0 0.5 1 1.5 2 2.5 3 3.5 4 0 2 4 6 8 10 12 % polymer addition flow @ varying binder content 5 bc 5.5 bc 6 bc 6.5 bc 7 bc http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 880 hardening and decrease in penetration of the modified bitumen blend in the mixture. the result is in consonance with the findings of ajagbe et al. (2020); akinleye et al., (2020b) and salami et al., (2023a). this result concurs with the findings of taih (2011), who investigated the influence of additives in hot asphalt mixtures and determined that the stability was 18.5 kn at a modifier content of 6%. figure 13: variation of stability with percentage polymer addition with bitumen test 3.8 marshall flow figure 14 illustrates the variation of flow with percentage polymer addition content for all percentages. a reduction in the values of marshall flow was observed from 6 to 8% in this study which may be attributed to the addition of the thermoplastic polymer in the asphalt which makes the asphalt to be more viscous thereby reducing the flow. a gradual reduction and increment were observed in the trend of result obtained for the marshall flow. similar trend was obtained by akinleye et al., (2020b); salami et al., (2023a); salami et al., (2023b). hence, 6% is the optimum thermoplastic content in the mix in accordance with the fmw (2016) standard specification. this is consistent with the findings of aliyu et al. (2015), who concluded that a decrease in flow indicates that polymer content has a greater influence on the internal friction of the mixture. this implies that the asphaltic concrete is less permeable. hence, the lower the flow value, the higher the stability/strength of the asphaltic concrete. figure 14: variation of flow with percentage polymer addition content 0 5 10 15 20 25 30 0 2 4 6 8 10 12 st ab ili ty ( k n ) % polymer addition 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 0 2 4 6 8 10 12 fl o w ( m m ) % polymer addition file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng akinleye et al: evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer. azojete, 19(4):871-884. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 881 3.9 marshall stiffness figure 15 figure 4.15 presents the results of stiffness of produced asphalt concrete. the stiffness values obtained at 0, 2, 4, 6, 8, 10 and 12% plastic addition doses were 4.51, 4.57, 5.84, 7.60, 6.21, 6.10 and 5.87 kn/mm respectively. the highest stiffness was obtained at 6% addition level (figure 15). this implies that thermoplastic enhanced asphalt can counterattack deformation in response against wheel load induced to an optimum level of 6%. the result is in consonance with the findings of ajagbe et al. (2018); ajagbe et al. (2020); akinleye et al., (2020b); salami et al., (2023a); salami et al., (2023b). figure 15: marshall stiffness values 4. conclusions it was established that the addition of thermoplastic polymer (0 – 12%) enhanced the softening, viscosity, flash and fire points of bitumen. however, it decreased the penetration and ductility for hot mix asphalt (hma) production. indeed, the high polynomial model r2 values obtained from the quantitative statistical polynomial models for the breakable plastic polymer modification for these characteristics means high degree of prediction of the mathematical relations. likewise, addition of breakable plastic polymer also improved the stability, flow and stiffness up to 12% dosage level for hma for the required specifications for pavement works. the marshall stability and flow of all asphalt concrete mixtures were all greater than 3.5 kn and 9 kn for (stability) and within 2 – 6 mm (flow) specifications of both nigerian general specification for road and bridges, federal ministry of works and housing, 2016 and the asphalt institutes, 1991 respectively. from the study, it can be recommended that the use of breakable plastic polymer is promising due to their effect on the bitumen and consequently the asphalt produced. however, additional research is required to establish more uniform mixing conditions (mixing durations, temperatures, and mixer type). similarly, additional research is required for the development of recyclable additives that do not significantly increase the final cost of bitumen. references ajagbe, wo., salami, lo., akinleye, mt. and salami, mo. 2020. effect of waste polymer modified bitumen with milled corn cob as a partial replacement for filler in asphaltic concrete. journal of research information in civil engineering, 17 (1): 3003 3017. 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 0 2 4 6 8 10 12 st if fn es s( kn /m m ) % polymer addition http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 882 ajagbe, wo., salami, lo., salami, mo., balogun, la. and akinleye, mt. 2018. evaluation of low-density polyethylene terephthalate modified bitumen with milled corn cob as a partial replacement for filler in asphaltic concrete. conference proceedings: 17th national conference of the nigerian institution of environmental engineers, niee.17.007, ogba lagos, nigeria, 25th october, pp. 46 56. akinleye, mt. and tijani, ma. 2017. assessment of quality of asphalt concrete used in road construction in south west nigeria. nigerian journal of technological development, 14(2): 52–55. akinleye, mt., jimoh, ya. and laoye, aa. 2020a. a performance characteristic models of properties of dissolved plastic bottle modified bitumen for hot mix asphalt production. global journal of engineering and technology advances, 3(2): 19-27. akinleye, mt., jimoh, ya. and salami, lo. 2020a. marshall properties evaluation of hot and warm asphalt mixes incorporating dissolved plastic bottle modified bitumen. journal of materials and engineering structures, 7 (3): 439 450. akinleye, mt., salami, lo., okpidi, ao., ayeni, im. and laoye, aa. 2020b. the study of rheological properties of bitumen blends modified with dissolved plastic water sachet. lautech journal of engineering and technology, 14(1): 21 30. aliyu, i., usman, a., kaura, j., ashiru, m. and kingsley, i. 2015. polyethylene from water sachet as a modifier in hot asphalt mixture. project report submitted to the department of civil engineering, ahmadu bello university, zaria, nigeria. arslan, d, gürü, m. and kürşatçubuk, m. 2012. performance assessment of organic-based synthetic calcium and boric acid modified bitumen. fuel, 102: 766-772. asphalt institute. 1991. mix design methods for asphalt (sixth edition) ms-02, asphalt institute, lexington, ky. astm d113-86. 1986. standard method of test for ductility of bituminous materials, astm international, west conshohocken, pa, usa. astm d36-2002. 2002. standard test method for softening point of bitumen (ring-and-ball apparatus). astm international, west conshohocken, pa, usa. astm d445-06. 2006. standard test method for kinematic viscosity of transparent and opaque liquids (and calculation of dynamic viscosity). astm international, west conshohocken, pa, usa. astm d5-06. 2006. standard test method for penetration of bituminous materials. astm international, west conshohocken, pa, usa. astm d5-97. 1997. standard test method for penetration of bituminous materials, astm international, west conshohocken, pa, usa. astm d70-03. 2003. standard test method for specific gravity and density of semi-solid bituminous materials (pycnometer method), astm international, west conshohocken, pa, usa. astm d92-02. 2002. standard test method for flash and fire points by cleveland open cup, astm international, west conshohocken, pa, usa. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng akinleye et al: evaluating the performance properties of asphalt produced from bitumen modified with thermoplastic polymer. azojete, 19(4):871-884. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 883 fmwh (2016). general specifications on roads and bridges. volume ii (revised edition). federal ministry of works and housing, abuja, nigeria., pp. 257. hossain, ma. 2006. a study on the rheological properties of polymer modified bituminous binder and mixes, m. eng. thesis, department of civil engineering, bangladesh university of engineering and technology, dhaka, bangladesh. kakar, mr., mikhailenko, p., piao, z., bueno, m. and poulikakos, l. 2021. analysis of waste polyethylene (pe) and its by-products in asphalt binder. construction and building materials, 280: 122492. kalantar, zn., karim, mr. and mahrez, a. 2012. a review of using waste and virgin polymer in pavement. construction and building materials, 33: 55-62. mantzos, l. and capros, p. 2006. european energy and transport: trends to 2030: update 2005. belgium: european commission. belgium. mohammad, gkm. 2017. engineering properties of bituminous mixture using kaolin as a modifier. a thesis submitted in fulfilment of the requirements for the award of the degree of m.phil. thesis, faculty of civil engineering, universiti teknologi malaysia, johor bahru, malaysia. mohammad, a. 2012. use of waste plastic blended bitumen for road construction and maintenance. m. eng. thesis, bangladesh university of engineering and technology, dhaka, bangladesh. mohd, ea., siti, aak., ramadhansyah, pj., haryati, y., norhidayah, a. and che, nc. 2017. effect of waste plastic as bitumen modified in asphalt mixture. midwest aids training education center (matec) web of conferences 27th29th august, 103: 09018, doi: 10.1051/matecconf/20171030 iscee 2016 murana, aa., akilu, k. and olowosulu, at. 2020. use of expanded polystyrene from disposable food pack as a modifier for bitumen in hot mix asphalt. nigerian journal of technology (nijotech), 39(4): 1021 – 1028. murphy, m., o’mahony, m., lycett, c. and jamieson, i. 2001. recycled polymers for use as bitumen modifier. journal of materials in civil engineering, 13(4): 306-322. doi: 10.1061/(asce)0899-1561(2001)13:4(306) salami, lo. and bello, aa. 2021a. engineering properties of warm mix asphalt modified with waste plastic bottle and sachet water: a review. conference proceedings: 2nd international conference on engineering and environmental sciences (icees), osun state university, osogbo, nigeria, held on 23rd-25th november, pp. 1-9. salami, lo. and bello, aa. 2021b. evaluation of waste plastic bottle and waste sachet water performance on engineering properties of warm mix asphalt: a review. unilorin science and engineering periodicals (usep): journal of research information in civil engineering, 18 (4): 4339-4348. salami, lo., kareem, ma., tijani, ma., ameen, io. and bello, aa. 2023a. performance investigation of combined waste polymer modified hot bitumen mix. adeleke university journal of engineering and technology, 6(1): 151-159. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng http://dx.doi.org/10.1061/(asce)0899-1561(2001)13:4(306) arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):871-884. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: salami.lukman@adelekeuniversity.edu.ng 884 salami, lo., tijani, ma., kareem, ma., ameen, io. and bello, aa. 2023b. marshall properties assessment of warm mix asphaltic concrete incorporating various proportions of sasobit additive. university of ibadan journal of civil engineering and technology, 5(1): 10-16. suganpriya, v., omprakash, s. and chandralega, v. 2016. study of behaviour of bitumen modified with crumb rubber. international journal of engineering research & technology (ijert), 5(5): 192 – 197. taih, s. 2011. the effect of additives in hot asphalt mixtures. journal of engineering and development, 15(3): 131-150. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):325-334 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 325 adsorption isotherms and kinetics of heavy metals removal from tannery effluent using composite agricultural waste as adsorbent y. a. musti, a. l. yaumi*, f. u. mukhtar, b. k highina and h. umar department of chemical engineering, university of maiduguri, p.m.b 1069 maiduguri, borno state. *corresponding author's email address: aliyaumi@unimaid.edu.ng article information submitted 15 october, 2021 revised 16 january, 2024 accepted 20 january, 2024 keywords: adsorption isotherms kinetic heavy metals tannery wastewater groundnut shell rice husk abstract tannery waste waters are very complex and characterized by high content of organic, inorganic and nitrogenous compounds which include heavy metals. in this study, the adsorption isotherm and kinetics of a composite adsorbent produced from the chemical activation of groundnut shell and rice husk were utilized as agricultural waste in the removal of pb, cr and cd from tannery effluent. the experimental data were fitted to langmuir, freundlinch and temkin isotherms, while the kinetics were studied using pseudo-first-order and pseudo-secondorder kinetic models. the results revealed that langmuir isotherm model showed excellent fit to the experimental data for all the heavy metal adsorption onto groundnut shell activated carbon (gr-ac). this can be seen from the high correlation coefficients r2. the langmuir monolayer adsorption capacity (qm) value was found to be 9.81 mg/g (pb), 5.72 mg/g (cr) and 4.25 mg/g (cd) respectively. the equilibrium adsorption capacity (qe) values calculated from the second order kinetics model agreed well with the experimental values for pb and cd. in addition, the first order kinetic rate constant decreased with increase in initial metal ion concentration. the excellent correlation between the calculated qe and experimental qe values and higher regression coefficient r2 shows clearly that the adsorption of these heavy metals onto gr-ac followed pseudo-second-order kinetic model. therefore, groundnut shell and rice husk can effectively be utilized as agricultural waste to produce a composite adsorbent to remove pb, cr and cd from tannery effluent. 1.0 introduction recently, the fast growth of industrialization causes a large amount of heavy metal-laden disposal to the environment which is highly toxic, mutagenic, and oncogenic (başaran et al., 2008). the rate of contaminated wastewater has kept on increasing intensively as a result of rapid urbanization and industrialization (beyan, et al., 2022). among industries, leather industry is recognized as a potential source to generate a significant amount of heavy metals into the environment (islam et al., 2021). tannery wastewaters are very complex and are characterized by high content of organic, inorganic and nitrogenous compounds, chromium, sulphides, suspended solids, and dissolved solids (durai and rajasimman 2011). the performance of treatment technologies varies with the types, sources and complexity of wastewater, and the kinds of technologies used. basically, the selection of wastewater treatment methods depends on the durability, sustainability, efficiency and reliability of technologies. the development of appropriate and effective wastewater treatment technologies is progressing (bedada et al., 2020). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):325-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 326 various conventional methods had been developed and tested for the removal of heavy metals from wastewater so that their environmental and health effects are minimized. removal of metals from wastewater can be achieved by the application of several methods such as sedimentation, electrochemical processes, ion exchange, biological operations, cementation, coagulation/flocculation, filtration, membrane processes, chemical precipitation and adsorption (dagmawi and dawit, 2013). adsorption, among these techniques, is widely accepted due to ease of use in operation, low cost and high efficiency however, selection of a suitable adsorbent is critical. biochar has recently been established as an effective adsorbent for a variety of environmental applications and got a huge intention of the researchers for heavy metals’ removal from wastewater. biochar is a black, solid, stable, and porous carbonaceous compound with a large surface area and is derived from waste biomass through slow or fast pyrolysis (amin et al., 2019). for the adsorption of various pollutants, there has been a lot of success for rice husk (abbas et al., 2013; dikdima et al., 2022) and groundnut shell (tegegn et al., 2022; kothai et al., 2019). isotherms and kinetics studies play an important role in understanding the nature and mechanism of adsorption process. in this study, the equilibrium and dynamics characteristics of the adsorption of heavy meatals from tannary effluents using agricultural waste as adsorbents were evaluated. the experimental equilibrium adsorption data were modelled using langmuir, freundlich and temkin models. in addition, pseudo first and pseudo second order kinetics models were also fitted to the adsorption data to further describe the adsorption mechanism. 2. materials and methods 2.1 adsorbent preparation and adsorption experiment rice husks and groundnut shells were obtained from a local rice mill and a local groundnut shelling mill in gamboru, maiduguri, borno state. the raw groundnut shell and rice husks were ripped off to remove dusts and washed with distilled water to remove the adhered particles dried for 24 hours in an oven at 105c. it was then carbonized at temperature of 400oc for 1 hour to obtain bio char and then refined into powder form which was stored for uses. the adsorption experiments were performed in a series of flasks containing 50 ml solutions tannery wastewater at 50 – 250 mg/l concentrations and adsorbent dosages of 0.5g. the mixtures were agitated for 60 min at 250 rpm using a shaker mixer. the resulting mixtures were filtered, and the concentrations of heavy metals were determined using atomic adsorption spectrometer (aas). the adsorption equilibrium was investigated for different metal concentrations between 50 and 250mg/l. in addition, kinetics experiments were conducted with 250 mg/l metal and 0.5 g of adsorbent at 30, 40 and 500c temperature with stirring at 250 rpm for 60 min. the amount of adsorption at equilibrium was obtained using equation (1) 𝑞𝑒 = (𝐶𝑜 − 𝐶𝑒)𝑉 𝑚 (1) where: v is the solution volume in l, m is the amount of adsorbent used in g and qe is metal ion uptake in mg/g at time, t 2.2 adsorption isotherm determination adsorption isotherms are commonly used to describe the interaction of the adsorbate with the adsorbent. it also furnishes information for the understanding of the nature of reaction which is fundamental to optimizing the design of adsorption system. several isotherm models have been developed and utilize for the analysis of equilibrium data. the adsorption data was analyzed by fitting to langmuir, freundlich and temkin isotherm models (manikandan, 2016). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com musti et al: adsorption isotherms and kinetics of heavy metals removal from tannery effluent using composite agricultural waste as adsorbent. azojete, 20(1):325-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 327 langmuir isotherm model is representative of monolayer adsorption occurring on energetically homogenous surface (foo and hameed., 2010). the linear form of the model is expressed by equations (2) and (3) (2) or (3) the nonlinear form is expressed by: (4) where: ce is the equilibrium concentration in (mg/l), q0 is the maximum adsorption capacity, k is the adsorption equilibrium constant (l/mg) and is the equilibrium adsorption capacity. freundlich isotherm is widely applied in heterogeneous systems especially for organic compounds or highly interactive species on activated carbon and molecular sieves. this empirical model can be applied to multilayer adsorption, with non-uniform distribution of adsorption heat and affinities over the heterogeneous surface (foo and hameed., 2010) the equation is given by equation (5 ) and the non-linear form is expressed by equation (6): (5) (6) where: n is adsorption intensity, kf is the freundlich coefficient related to adsorption capacity. the freundlich isotherm constants kf, 1/n can then be calculated from the slopes and intercepts of ln (qe) versus ln ce). temkin isotherm is based on the hypothesis that, due to the interaction between adsorbent and adsorbate. the heat of adsorption of all the molecules in the layer reduce linearly with coverage due to adsorbate–adsorbate interactions. it is based on the assumption that the free energy of adsorption is a function of surface coverage (samuel et al, 2015). the temkin isotherm model is represented by equation (7): qe = blnat + blnce (7) the nonlinear form is expressed by equation (8): 𝑞𝑒 = 𝑅𝑇 𝑏𝑇 ln(𝐴𝑇𝐶𝑒) (8) where is related to the heat of adsorption, and 𝐴𝑇 is the maximum binding energy of the adsorbate to the adsorbent, bt is temkin constant. the constants of the model bt and kt were obtained from the slope and intercept of the graph of the qe versus ln ce, respectively. 2.3 adsorption kinetics kinetic modeling for adsorption processes involves studying the rate of adsorption of a species under particular condition before attaining equilibrium, it involves studying the mechanisms of the adsorption processes (vunain et al., 2021). the adsorption experimental data were http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):325-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 328 evaluated for their suitability using pseudo-first order and pseudo-second-order models as presented by equation (9) and (10). log( 𝑞e − 𝑞𝑡) = 𝑙𝑜𝑔𝑞𝑒 − 𝑘1 2.303 𝑡 (9) (10) where: (mg/g) are the adsorption capacities at equilibrium and time t (min), respectively. k1 and 𝑘2 are the pseudo-first-order and pseudo-second-order rate constants (samuel et al., 2015). 3. results and discussion 3.1 adsorption isotherm models the adsorption data were analyzed by fitting to isotherm models into langmuir, freundlich and temkin isotherm models. the adsorption isotherm of lead, chromium and cadmium onto gr-ac are presented in figure 1 (a-c). the parameters and correlation coefficients obtained from the plots are shown in table 1. it can be observed from figure 1(a-c) and table 1 that langmuir isotherm model showed excellent fit to the experimental data for all the heavy metal adsorption onto gr-ac. this can be seen from the high correlation coefficients in table 1. the rl value was found between 0 and 1, which indicated the favorability of the adsorption process under the studied conditions. the langmuir monolayer adsorption capacity (qm) value was found to be 9.8039 mg/g (pb), 5.7175 mg/g (cr) and 4.2535 mg/g (cd) respectively. lead adsorption onto gr-ac showed the highest maximum adsorption capacity. similar result was reported in the literature(bayuo et al., 2018). langmuir isotherm connotes homogeneous distribution of active sites on the adsorbents, hence, the surface of gr-ac is homogeneous with monolayer coverage. this demonstrates that the adsorbent surface is homogeneous for pb, cr and cd adsorption. the monolayer adsorption is accomplished via chemical adsorption and the active sites of gr-ac were uniformly disseminated. figure 1a: langmuir, freundlich and temkin isotherm for lead adsorption file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com musti et al: adsorption isotherms and kinetics of heavy metals removal from tannery effluent using composite agricultural waste as adsorbent. azojete, 20(1):325-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 329 figure1b: langmuir, freundlich and temkin isotherm for chromium adsorption figure1c: langmuir, freundlich and temkin isotherm for cadmium adsorption table 1: isotherm parameters for the adsorption of heavy metals onto gr-ac models lead chromium cadmium langmuir qmax(mg/g) 9.8039 5.7175 4.2535 b (l/mg) 10.38 6.1823 3.5078 rl 0.09786 0.0618 0.0387 r2 0.9993 0.9979 0.9873 freundlich kf (l/g) -0.0057 -0.9914 0.0825 1/n 0.98700 1.0592 1.2094 r2 0.9831 0.9673 0.9789 temkin kt(l/mg) 10.6956 1.5299 14.3586 bt(j/mol) 2.3698 2.1729 2.0371 r2 0.9965 0.9890 0.9504 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):325-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 330 3.2 adsorption kinetics model the experimental data were examined with pseudo-first-order model and pseudo-secondorder kinetic models in order to understand the mechanism of adsorption. figures 2(a-f) and tables 2(a-c) presents the plot and kinetic parameters for pb, cr and cd onto gr-ac respectively. the results revealed that the correlation coefficients, r2 of the first and second order models in all the metal ions adsorptions are near 0.99 indicating good correlation with the experimental data. the qe values calculated from the second order kinetics model agree well with the experimental values for pb and cadmium and the first order kinetic rate constant decreased with increase in initial metal ion concentration. the pseudo-second-order models assume that there is strong interaction between the adsorbate and adsorbent with chemisorption as the rate controlling step. the excellent correlation between the calculated qe and experimental qe values and higher regression coefficient (r2) shows clearly that the adsorption of these heavy metals onto gr-ac followed pseudo-second-order kinetic model. similar result has been reported by (samuel et al., 2015). table 2a: kinetic model parameters for lead adsorption onto gr-ac table 2b: kinetic model parameters for chromium adsorption onto gr-ac table 2c: kinetic model parameters for cadmium adsorption onto gr-ac co (mg/l) qe exp (mg/g) pseudo first-order k1 qe cal r 2 (1/h ) (mg/g) pseudo second k2 qe cal r 2 (g/mg.min ) (mg/g) 50 1.917 0.844 0.651 0.9939 5.474 8.518 0.9705 100 1.676 0.678 0.516 0.9985 1.347 7.007 0.9987 150 2.052 0.573 0.719 0.9983 20.488 6.863 0.9955 200 1.668 0.454 0.511 0.996 8.0267 6.325 0.9950 250 1.7864 0.4399 0.580 0.9972 3.681 5.678 0.9828 co (mg/l) qe exp (mg/g) pseudo first-order k1 qe cal r 2 (1/h ) (mg/g) pseudo second k2 qe cal r 2 (g/mg.min) (mg/g) 50 1.238 0.406 0.215 0.9828 27.091 2.959 0.718 100 5.791 0.331 1.756 0.9956 7.563 5.071 0.9960 150 3.126 0.340 1.139 0.9996 8.241 3.968 0.9956 200 3.126 0.339 1.139 0.9996 5.116 3.395 0.9985 250 5.791 0.331 1.756 0.9956 5.080 4.762 0.9986 co (mg/l) qe exp (mg/g) pseudo first-order k1 qe cal r 2 (1/h ) (mg/g) pseudo second k2 qe cal r 2 (g/mg.min) (mg/g) 50 1.898 0.312 0.641 0.9965 18.198 3.948 0.907 100 2.883 0.266 1.059 0.9998 33.053 2.547 0.9867 150 2.800 0.235 1.029 0.9997 313.111 1.428 0.9992 200 2.821 0.202 1.037 0.9992 181.133 2.708 0.9961 250 2.930 0.161 1.075 0.9996 67.518 2.217 0.9949 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com musti et al: adsorption isotherms and kinetics of heavy metals removal from tannery effluent using composite agricultural waste as adsorbent. azojete, 20(1):325-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 331 figure 2a: pseudo-first-order plot of lead onto gr-ac figure 2b: pseudo-first-order plot of chromium onto gr-ac figure 2c: pseudo-first-order plot of cadmium onto gr-ac http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):325-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 332 figure 2d: pseudo-second-order plot of lead onto gr-ac figure 2e: pseudo-second-order plot of chromium onto gr-ac figure 2f: pseudo-second-order plot of cadmium onto gr-ac file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com musti et al: adsorption isotherms and kinetics of heavy metals removal from tannery effluent using composite agricultural waste as adsorbent. azojete, 20(1):325-334. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 333 4. conclusion groundnut shells and rice husks were utilized as agricultural waste to produce a composite adsorbent via chemical activation for the removal of pb, cr and cd from tannery effluent. the adsorption isotherm was evaluated by fitting the experimental data with langmuir, freundlinch and temkin isotherm while the kinetics studies were evaluated using pseudo-first-order and pseudo-second-order kinetic models. results shows that the adsorption of lead, chromium and cadmium were well fitted to langmuir model due to higher value of regression coefficient (r2). the rl value was found between 0 and 1, which indicated the favorability of the adsorption process under the studied conditions. the langmuir monolayer adsorption capacity (qm) were 9.81, 5.72 and 4.25 mg/g for lead, chromium and cadmium respectively. lead adsorption onto gr-ac showed the highest maximum adsorption capacity. pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order thus indicating a heterogeneous process. therefore, the gr-ac can be effectively utilized for the removal of heavy metals in tannery wastewater. references başaran, b., mete u., behzat, ob. and ahmed, a. 2008. distribution of cr (iii) and cr (vi) in chrome tanned leather. indian journal of chemical technology, 15: 511–514. bayuo, j. and pelig-ba, kb. 2018. isotherm modeling of lead (ii) adsorption from aqueous solution using groundnut shell as a low-cost adsorbent. iosr journal of applied chemistry (iosr-jac), 11(11): 18–23. dagmawi, md. and dawit, m. 2013. chromium removal from modjo tannery wastewater using moringa stenopetala seed powder as an adsorbent. journal of chemistry, 4: 345–678. bedada, d., kenatu, a., amare t., kloos, h. and fito, j. 2020. chromium removal from tannery wastewater through activated carbon produced from parthenium hysterophorus weed. energy, ecology and environment, 5(3): 184–195. durai, g. and rajasimman, m. 2011. wastewater, biological treatment of tannery wastewatera review. 4(1): 1–17. vunain, e., joel, bn., timothy, tb. and· adewale, ki. 2021. adsorption of chromium ions from tannery effluents onto activated carbon prepared from rice husk and potato peel by h3po4 activation. applied water science, 11(9): 1–14. foo, ky and hameed, bh. 2010. insights into the modeling of adsorption isotherm systems. chemical engineering journal, 156(1): 2–10. dikdima, jmd., germain, vd. and tsamo, c. 2022. batch mode treatment of wastewater from the maroua artisanal tannery using silica extracted from rice husks and silica / sand mixture. equilibrium journal of chemical engineering, 6(1): 1–14. kothai, p., meena, a., meenaloshini, e., revathy, a. and kumar, nv. 2019. treatment of tannery effluent using groundnut shells. international research journal of engineering and technology, 6(9): 2440–2447. amin, mt., alazba, aa. and shafi, m. 2019. application of biochar derived from date palm biomass for removal of lead and copper ions in a batch reactor: kinetics and isotherm scrutiny. chemical physics letters, 722: 64–73. islam, md., rahaman, a., mahdi, mm. and mallik, d. 2021. removal of cr (iii) and other pollutants from tannery wastewater by moringa stenopetela seed removal of cr (iii ) and other pollutants from tannery wastewater by moringa stenopetela seed. iop conference http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):325-334. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aliyaumi@unimaid.edu.ng 334 series: earth and environmental science, 644: 012025. doi 10.1088/17551315/644/1/012025. samuel, ms., evy, aam. and chidambaram, r. 2015. isotherm modelling, kinetic study and optimization of batch parameters using response surface methodology for effective removal of cr (vi) using fungal biomass. plos one 10(3): e0116884, 1-15. abbas, mn., abbas, fs., nussrat, hh. and hussein, s. 2013. synthesis of promoted catalyst from iraqi rice husk used as a raw material for treating tannery wastewater. australian journal of basic and applied science, 7(2): 511–528. manikandan, na., alemu, ak., goswami, l., pakshirajan, k. and pugazhenthi, g. 2016. waste litchi peels for cr (vi) removal from synthetic wastewater in batch and continuous systems: sorbent characterization, regeneration and reuse study. journal of enviromental engineering, 142(9): 1-11. beyan, sm., prabhu, sv., ambio, ta. and gomadurai, g. 2022. a statistical modeling and optimization for cr (vi) adsorption from aqueous media via teff straw-based activated carbon: isotherm, kinetics, and thermodynamic studies. adsorption science & technology, 1(16): article id 7998069. tegegn, k., yusuf, z., sasikumar, jm., and gorfu, k. 2022. biosorbent efficacy of groundnut husk for the elimination of chromium from the effluent of mojo tannery industry, ethiopia. international journal of biomaterials, 1: article id 9997348, https://doi.org/10.1155/2022/9997348. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com https://www.ncbi.nlm.nih.gov/pmc/articles/pmc9671745/ https://doi.org/10.1155/2022/9997348 corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 913 arid zone journal of engineering, technology & environment original research article optimization of arc welding parametric influence on mechanical properties of dissimilar metals b. j. olorunfemi1, b. s. adeleye1, k. a. bello1 and o. t. oginni2 1department of mechanical engineering, federal university oye-ekiti, nigeria. 2department of mechanical engineering, bamidele olumilua university of education, science and technology, ikereekiti, ekiti state, nigeria. *corresponding author's email address: oginni.olarewaju@bouesti.edu.ng article information abstract welding dissimilar metals require technical expertise to achieve moderate cost, quantity, and quality, but selecting the right parameters is challenging due to various operating conditions. the paper optimized welding process parameters for two dissimilar metals, inconel 625 and gl e360, focusing on mechanical properties like tensile strength and hardness. the welding process parameters were optimized using gas metal arc welding power sources, flux cored wire electrode (fcwe), design experts, and response surface methodology, and tensile strength and hardness tests were conducted. at the anticipated optimal process welding parameters of 52.86 m/s welding speed, 5.28 m/min welding feed rate, and 23.16 volts, three confirmation experiments were carried out. the study revealed that the tensile strength and hardness of the welding process significantly influenced response variables, ranging from 380 mpa to 500 mpa. the most noticeable effect was observed at a welding speed of 52 m/s, a feed rate of 5.6 m/min, and a voltage of 26 v. the empirical model's tensile strength and hardness were validated using experimental results, and the software predicted 53 welding speed, 5 welding feed rate and 23 voltages. the welding process parameters significantly impacted tensile strength and hardness, while the welding feed rate parameter had the least impact on both. submitted: 04 may, 2023 revised: 12 june, 2024 accepted: 20 june, 2024 keywords: feed rate hardness optimal process tensile strength welding parameter © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction joining different materials is acknowledged as a challenge for the development of new structural components within the production industry (stoll and benner, 2021). the criterion for welding dissimilar components requires suitable joining expertise (zhang-yang et al., 2020). fusion welding is a commonly used method for joining dissimilar steels (zhang et al., 2020; cooke et al., 2019). optimizing weld parameters for such fusion weld joints will help in achieving a sound weld joint free of weld defects and improve productivity (li et al., 2021).metal joining is the process of joining two metal parts either temporarily or permanently with or without the application of heat and pressure by welding, soldering, brazing, riveting, adhesive bonding, assembling with bolts, and seaming (dark et al., 2021). welding is the process of joining similar and dissimilar metals or other materials by applying heat, pressure, and filler materials. in the fusion welding process, coalescence is done by melting two parts to be joined and applying filler metals to the welded joints to provide strength. the fusion welding process is classified as the arc welding process, the resistance welding process, the radiant welding process, and the thermoelectric welding process. manufacturers are focused on joining dissimilar materials to reduce manufacturing costs and build lightweight components. steel structures are lighter and more costeffective when their structural components are made of different steels (luo et al., 2022). chemical, petrochemical, nuclear, power generation, and other industries use a variety of dissimilar steel joints (johnson and murugen, 2020; kumar et al., 2023). joining dissimilar steels is typically more difficult than joining similar steels (beygi et al., 2023; sivasubramani et al., 2021). this is caused by changes in chemical composition and thermal expansion coefficients. tungsten inert gas welding (tig) (raju and kumar, 2022), is an arc welding azojete december 2024. vol.20(4):913-925 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:oginni.olarewaju@bouesti.edu.ng mailto:oginni.olarewaju@bouesti.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 914 process that provides outstanding welding with a coalescence of heat generated through an electric arc between a tungsten electrode and the steel (assefa et al., 2022). there are five basic welding joint types commonly used in the industry, including butt joint, tee joint, corner joint, lap joint, and edge joint welding, as shown in figure 1 (buffa et al., 2022). lap joints are commonly used for sheet metal, as depicted in figures 1 and 2. gas metal arc welding (gmaw) is a semi-automatic or automatic arc welding process in which a continuous and consumable wire electrode and a shielding gas are fed through a welding gun (khrais et al., 2023). it is developed for welding aluminium and other non-ferrous materials (devanathan et al., 2022). the various welding processes are shown in figure 3. welding is commonly used in the areas of pipe welding and joints, automotive production and maintenance, manufacturing, shipbuilding, construction, railroad tracks, and underwater welding, both for ferrous and non-ferrous metals (bossle et al., 2023). friction stir lap welding (fslw) involves the joining of alloys in a solid-state manner, which can mitigate the challenges due to melting and solidification (bossle et al., 2023; satputaley et al., 2021; patel et al., 2020; mou et al., 2021; tesfaye, 2023; kannan et al., 2019; ramaden and boghdadi, 2020). the process of gmaw requires a welding gun, a source of electric power supply, an electrode wire feed unit, and a source of shielding gas (alagarsamy and kumar, 2019). the advantages of gas metal arc welding include no flux. applications of gas metal arc welding are found in semi-automated or automated industrial applications, commercially available metals, deep groove welding of plates and castings, and welding light gauge metals. figure 1: lap welding joints figure 2: fillet weld figure 3: various types of welding process (buffa et al., 2022) the importance of welding dissimilar metals for operation cost reduction, quality, and productivity in the welding process parameters had been studied, but it did not find out the effect of these parameters on the mechanical properties of dissimilar metal wed joints. it is necessary to determine the right gmaw parameters and processes for dissimilar metals involving high-strength steel (inconel 625 plate) and nickel-based alloys (gl e36 steel) and their influence on the mechanical properties to eliminate the risk associated with failure and reliability of materials during their service life. hence, the joining of these dissimilar steels finds a lot of http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 915 applications in fabrication industries (madhavadas et al., 2022; arunkumar et al., 2022; ren et al., 2022). the present study uses an optimization application approach technique to investigate the influence of welding parameters on tensile strength and hardness, enhancing the quality of the weld joints of dissimilar metals, comprising inconel 625 and gl e36 steels, as a driver to guide the stakeholders in the manufacturing industry. 2. materials and methods the materials used for carrying out the study and their specifications are: 3 mm thick inconel 625 plate, 3 mm thick gl e36 steel plate, 5mm electrode, and a gas metal arc welding machine. the choice of the materials was made due to variations in the condition of service and specifications of the materials available, such as the size of the samples, weight, cost, availability, durability, and strength of the materials. it has good toughness properties, higher strength, strong corrosion resistance, processing properties, and welding properties. 2.1 experimental setup the gmaw power voltage 230 v single-phase flux wire welding machine was used for making buttweld joints. the mechanized torch movement ensured precise control over the weld speed, while voltage and wire feed rate were set at the gmaw power source to one decimal place precision. flux-cored wire electrodes of diameter 3 mm suitable for this dissimilar welding were used as filler material. the 3 mm inconel 625 plate was welded to 3mm gl e36 steel using gmaw. table 1 presents the chemical composition of the inconel 625 and gl e36 steel plates. figure 4 shows the twoand three-dimensional sectional views and lap joint configuration with plate dimensions overlapped for fslw. the horizontal dashed and vertical dotted lines in the two-dimensional sectional view are the locations for the hardness measurement. figures 5 and 6 are the sample microstructures. the welded specimens were transversely cut using a diamond-plated blade, ground, and polished for microstructure evaluation. the hardness distributions were measured with a load of 500 g and at a regular gap of 0.3 mm along the dashed lines in the y-direction. the hardness measurements were determined along the dotted line in the z-direction at a regular gap of 0.15 mm. figures 7 and 8 show the longitudinal and transverse welded specimens for evaluation of the joint tensile strength. six lap-shear specimens were tested for each process condition, with the steel plate being pulled for three cases and the inconel 625 plate being pulled for the other three samples. separate engagement of the steel and inconel 625 plates during the lapshear tensile testing was conducted to evaluate the effect of stir zone asymmetry on the final weld joint strength. figure 9 shows the longitudinal micro-tensile testing specimen and its dimensions. the response surface methodology experimental design was used to vary the selection of three different process input parameters, such as welding speed, wire feed rate, and voltage, and three levels, as shown in table 2. table1: chemical composition (%) of inconel 625 and gl e36 steel elements ni cr fe mo nb co mn al ti si c inconel625 58 21.70 4.70 8.60 3.38 0.03 0.09 0.13 0.18 0.18 0.02 gl e36 0.06 0.01 0.03 1.40 0.03 0.01 0.39 0.17 table 2: process parameters and levels process parameters level 1 level 2 level 3 welding speed (s) 52.0 58.0 64.0 wire feed rate (f) 4.7 5.1 5.6 voltage (volts) 22.0 24.0 26.0 http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 916 figure 4: 2-3 dimension sectional view fig. 5: horizontal micro structure fig. 6: vertical micro structure fig. 7: longitudinal specimen fig. 8: transverse specimen figure 9: longitudinal micro-tensile a steady-state three-dimensional heat conduction analysis was carried out considering the governing equation in equation 1 (benlamnover et al., 2021). 𝜕 𝜕𝑥 (𝑘 𝜕𝑇 𝜕𝑥 ) + 𝜕 𝜕𝑦 (𝑘 𝜕𝑇 𝜕𝑦 ) + 𝜕 𝜕𝑧 (𝑘 𝜕𝑇 𝜕𝑧 ) + 𝑄 = 𝜌𝐶𝑝𝑉 𝜕𝑇 𝜕𝑥 (1) where v is the tool travel speed, t is the temperature variable, x, y, and z are spatial variables, and ρ, k, and cp refer to the density, thermal conductivity, and specific heat of the workpiece materials, respectively. the fslw process was simulated, considering the inconel 625 plate lapped onto the steel plate from the bottom until a depth of 0.5 mm. the tensile strength of a weld joint was measured by subjecting the standard http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 917 specimens drawn from the test coupons to tensile tests as per iso 4136:2001 using a universal testing machine. the hardness of different regions in the weld joint is measured by a rockwell hardness test (iso 9015-1 and 9015-2 standards) following the preparation of the preparation of a weld pad of size 80mm wide, 300mm long, and 3mm thick with run-on and run-off plates. 2.2 weld geometry and defect test the bead width, such as welding current, welding speed, and gap distance, was determined by measuring the width of each welded sample with 0.01 mm least-count vernier callipers for the mechanical qualities of the weld. 2.3 mechanical property testing for various mechanical tests, gmaw-welded experimental specimens were created from ss316 metals and machined using astm in order to determine the necessary dimensions for studying their properties. 2.4 tensile strength a tensile test was conducted using a universal testing machine, a 600 servo-hydraulic with a piston speed of 8 mm/min and a maximum force of 600 kn. 2.5 hardness testing the rockwell hardness test was used because it was quick, inexpensive, and largely non-destructive, leaving a tiny indentation on the specimen. the hardness strength of the welded samples was examined using brooks rockwell hardness testing equipment with a ball-shaped indenter at a force of 100 kg for a duration of 10 s. 2.6 design expert the design matrix of three welding parameters via speed (s), wire feed rate (f), and voltage (v) at three levels was selected as the quality characteristic for the performance measure for 20 experimental runs, optimized, and tabulated. 2.7 response surface methodology (rsm) rsm was used to investigate the response of welding process parameters to the physical properties of inconel 625 and gl e36 steel based on design expert software. the welding speed, wire feed rate, and voltage were chosen as the independent variables, while the dependent variables (responses) were tensile strength and hardness values. the quadratic response surface model built up all the linear terms, square terms, and linear by-linear interactions described in equation 2 (tumer et al., 2022). y=𝛽𝑜 + 𝜀 ∑ 𝛽𝑖𝑥𝑖 + ∑ 𝛽𝑖𝑗 𝑘 𝑖−1 𝑘 𝑖=1 𝑥𝑖𝑥𝑗 + ∑ 𝛽𝑖𝑖 𝑘 𝑖=1 𝑥𝑖 2+ 𝜀 (2) where y is the predicted response; 𝛽𝑜 is the overall mean,𝛽𝑖 is the linear effect of the input factors 𝑥𝑖; 𝛽𝑖𝑗 is the linear-by-linear interaction effect; 𝛽𝑖𝑖 is the quadratic effect of the input factor, 𝑥𝑖𝜀 is the random error term. 2.8 empirical model the second-order polynomial model was used to describe the behaviour of the response to the inputs following the form presented in equation 3 (wang et al., 2020; zhao et al., 2021; yang et al., 2022) 𝑌 = 𝑋0 + 𝑋1(𝐴) + 𝑋2(𝐵) + 𝑋3(𝐶) + 𝑋11(𝐴2) + 𝑋22(𝐵2) + 𝑋33(𝐶2) + 𝑋12(𝐴𝐵) + 𝑋13(𝐴𝐶) + 𝑋23(𝐵𝐶) (3) where all x are constants and y is the response. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 918 the developed empirical formulas in terms of the coded factors are given as equations 4 and 5 for tensile strength and hardness, respectively. 𝑌1 = {435.34 − 37.82𝐴 + 1.76𝐵 + 12.18𝐶 − 0.3750𝐴𝐵 + 1.87𝐴𝐶 + 0.1250𝐵𝐶 − 2.62𝐴2 + 5.69𝐵2 + 5.51𝐶2} (4) 𝑌2 = {83.00 − 7.12𝐴 + 0.3661𝐵 + 2.35𝐶 − 0.1250𝐴𝐵 + 0.3750𝐴𝐶 − 0.1250𝐵𝐶 − 0.6781𝐴2 + 1.09𝐵2 + 0.9129𝐶2} (5) y1 is the tensile strength response, y2 is the hardness response, and a, b, and c represent the welding speed, wire feed rate, and voltage, respectively. 3. results and discussion the results of the liquid penetrant and visual defect testing on the specimens were visually inspected and showed a few welding faults, such as a bit of undercut at the end, excessive reinforcement height, lack of fusion, porosity, root crack, and lack of penetration in some of the welded samples. there was a lack of fusion in one sample (20) due to minimum current input, arc length, electrode angle, electrode manipulation, and improper welding parameter settings, which contributed to the fusion failure. there was a porosity defect observed in a sample (14). this defect was created by air entrapped in the shielding gas, which resulted in dispersed porosity and gross surface pore breaking. an undercut defect was observed in samples 2 and 10. at the weld, undercut discontinuities formed a mechanical notch interface. apart from the aforementioned, others were defect-free samples (1-20) used for the tensile strength and hardness tests in consonance with mou et al. (2021) study. table 3 displays the tensile strength and hardness values of the welded samples based on the 20 experimental runs used for this study. the tensile strength and hardness values gotten from the experiment range between 380 and 500 mpa and 72 and 95 hrb, respectively. the large variance shows that process factors have an impact on the mechanical behavior of welded samples. the impact of welding input parameters such as welding speed, welding feed rate, and voltage is significant to the mechanical property responses. for instance, welding input parameters in the experimental run 7 with welding speed 52, welding feed rate 5.6, and voltage of 26 produced the highest value of tensile strength and hardness, i.e., 500 mpa and 95 hb, whereas the experimental run 10 with welding speed 68, welding feed rate of 5.1, and voltage of 24 v had the least tensile strength and hardness, i.e., 380 mpa and 72 hb. increasing the welding feed rate from 5.1 to 5.6 increases the tensile strength from 380 to 500 mpa and the hardness value from 72 to 95 hb. there were 3 runs with the same input welding parameters given by the design expert, as seen in experimental runs 4, 16, and 17, with the same values of 58, 5.1, and 24 for welding speed, welding feed rate, and voltage, respectively, as shown in table 3. there was no significant difference in their response values for both tensile strength and hardness. however, when the welding feed rate and voltage have the same values but different welding speeds, as seen in experimental runs 1, 4, 5, 8, and 17, there was significant variation in tensile strength and hardness. this is proof that the welding speed input parameter is the most significant factor that influences the tensile strength and hardness responses as contained in satputaley et al., (2021) and patel et al., (2020) works. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 919 table 3: experimental responses of tensile strength and hardness at different levels s/n original value responses welding, s(m/s) welding feed rate(m/min) voltage(v) ts (mpa) hardness (hrd) 1 52 5.1 24 476 90 2 64 5.6 22 385 73 3 64 4.7 26 482 92 4 58 5.1 24 388 74 5 64 5.1 24 495 94 6 64 5.6 26 410 78 7 52 5.6 26 500 95 8 58 5.6 24 415 79 9 50 4.7 24 476 90 10 68 5.1 24 380 72 11 58 4.4 26 450 86 12 58 5.9 24 453 86 13 58 5.1 21 428 81 14 52 4.7 27 474 90 15 58 5.1 22 435 83 16 58 5.1 24 435 83 17 58 5.1 24 436 83 18 64 4.7 22 436 83 19 64 4.7 22 435 83 20 52 5.6 22 435 83 in reliability table 4, the factors are considered significant when the adequacy of this model is analysed using anova (and p ≤ 0.05) and insignificant if otherwise. accordingly, the developed models are significant. welding speed (a) and voltage (c) are more significant than welding feed rate. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 920 table 4: determination of model significance using anova source tensile strength hardness f value pvalue f value p-value model 29.18 < 0.0001 29.42 < 0.0001 a-welding speed 223.53 < 0.0001 211.37 < 0.0001 b-welding feed rate 0.4911 0.4994 0.5585 0.4721 cvoltage 23.51 0.0007 23.07 0.0007 ab 0.013 0.9113 0.0381 0.8491 ac 0.3262 0.5805 0.3432 0.5710 bc 0.0014 0.9704 0.0381 0.8491 a2 1.05 0.3096 2.02 0.1855 b2 5.41 0.0423 5.22 0.0454 c2 5.08 0.0478 3.66 0.0846 *note that the p-value of less than 0.0500 is an indication of model term significance. figure 10 (a-c) shows the effect of the input factors on the first response tensile strength. the three plots clearly show the level of significance of the selected welding speed and voltage on the tensile strength. it was discovered in figure 10a that the welding speed has a better influence on hardness than the welding feed rate because the hardness deviates more from the welding speed than the welding feed rate. figure 10b depicts a better response of welding speed compared to the voltage, and figure 10c shows that hardness has a better response to the voltage compared to the welding feed rate. the hardness responses obtained from all the input parameters follow the same trend when compared to the tensile strength response, while the welding feed rate showed the least significant effect on hardness. figure 10: 3d plots of tensile strength against (a) welding speed and welding feed rate (b) welding speed and voltage (c) voltage and welding feed rate y 1 ( m p a) a b c http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 921 figure 11: 3d plots of hardness against (a) welding speed and welding feed rate (b) welding speed and voltage (c) voltage and number of passes as indicated in table 5, r2 of 0.9633 and 0.9611 for both tensile strength and hardness and adequate precisions of 19.7960 and 19.284 for both tensile strength and hardness imply a good fit. other variables also support the fact that the model is adequate and reliable, and can be used to navigate the design space. table 5: second order model fitting results in the form of anova model summary characteristics tensile strength hardness standard deviation 9.29 1.81 mean 441.20 83.9 r2 0.9633 0.9611 adjusted r2 0.9303 0.9260 predicted r2 0.7216 0.7040 adequate precision 19.7960 19.284 the value of the output factors at optimum for the given input parameters with a maximum desirability of 1 and for the combined results that are derived from the software. the tensile strength and hardness generated from the empirical model developed have been validated with the use of experimental results and were compared as presented in table 6.three confirmation experiments were conducted at the optimum process welding parameters of 53 welding speed, 5 welding feed rate, and 23 voltage that were predicted by the software. the details of the experimental designs were reported in figure 12 (zhang et al., 2020). figure 12: tensile strength response anova a b c http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 922 table 6: predicted and experimental results for tensile strength and hardness standard input tensile s hardness w s wfr voltage actual predicted actual predicted 1 52 5.1 24 435.00 435.34 83.00 83.00 2 64 5.6 22 415.00 421.67 79.00 80.04 3 64 4.7 26 476.00 491.53 90.00 93.06 4 58 5.1 24 453.00 454.39 86.33 86.69 5 64 5.1 24 453.00 435.34 83.00 83.00 6 64 5.6 26 428.00 430.45 81.00 81.62 7 52 5.6 26 495.00 489.79 94.00 93.05 8 58 5.6 24 482.00 473.44 92.00 90.08 9 48 4.7 24 390.00 364.33 72.00 69.10 10 68 5.1 24 435.00 435.34 83.00 83.00 11 58 4.4 26 388.00 393.31 74.00 74.84 12 58 5.9 24 476.00 469.42 90.00 88.85 13 58 5.1 21 410.00 418.65 78.00 79.81 14 52 4.7 27 385.00 390.79 73.00 74.10 15 58 5.1 22 435.00 435.34 83.00 83.00 16 58 5.1 24 474.00 471.42 90.00 89.54 17 58 5.1 24 500.00 494.31 95.00 93.79 18 64 4.7 22 450.00 448.47 86.00 85.46 19 64 4.7 22 436.00 435.34 83.00 83.00 20 52 5.6 22 436.00 435.34 83.00 83.00 note: ws = welding speed and wfr = welding feed rate 4. conclusion the right selection of welding process and responses of tensile strength and hardness by optimizing the welding parameters during the welding of inconel 625 and gl e360 steels in the operation have been investigated and established. the parameters have a significant impact in relation to the input independent variables (such as welding speed, welding feed rate, and voltage) and the response variables (such as tensile strength and hardness). various defects in welding technologies have been eliminated by using the correct combination of welding process parameters, technical know-how, response surface methodology, and optimization tools. the tensile strength falls between 380 and 500 mpa, and the hardness is between 72 and 95 hrd. the variation in the responses shows that the combination of the selection of welding process parameters has a significant impact on the machining operations. the impact of a welding speed of 52, a welding feed rate of 5.6, and a http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 923 voltage of 26 (run 7) proved to be the most noticeable effect, with the highest tensile strength of 500 mpa and a hardness of 95 hrd.the welding process parameters have the highest significant factor in tensile strength, followed by the voltage. the welding feed rate parameter is the least significant in both tensile strength and harness responses. the value of the output factors at optimum for the welding parameters at maximum desirability of 1 and for the combined results that are derived from the software was obtained. the surface response methodology optimizes the best welding process parameters for quality weld joints and products, and enhances productivity. this study provides relevant data for developing, investigating, and evaluating the model and performance evaluation of the welding problems, specifically the tensile strength and hardness of inconel 625 and gl e60 steels. references alagarsamy, sv. and kumar, r. 2019. parametric optimization for gas metal arc welding process of ss316l and aisi d2 steels using grey-taguchi method. journal of materials science research and reviews, 4(3): 402-411. arunkumar, sp., prabha, c., saminathan, d., rajasekaran, kja., viswanath, m., ivan, c., kevin, p. and kumar, pm. 2022. taguchi optimization of metal inert gas (mig) welding parameters to withstand high impact load for dissimilar weld joints. materials today, 56(2): 1411-1417. assefa, a., teferi, a., gulam, ms., alamri, s., edacherian, aj., moera, g., pandey, v. and hossain, n. 2022. experimental investigation and parametric optimization of the tungsten inert gas welding process parameters of dissimilar metals. materials, 15(13): 4426-4435. benlamnouar, mf., saadi, t., bensaid, n., gousmine, m., touggui, y. and temmar, m. 2021. modelling and optimization of dissimilar welding between 304l and hsla-x70 using response surface methodology. journal of advanced manufacturing technology, 105(5): 24-26. beygi, r., galvão, i., akhavan-safar, a., pouraliakbar, h., fallah, v. and da silva, lf. 2023. effect of alloying elements on intermetallic formation during friction stir welding of dissimilar metals: a critical review on aluminum/steel.metals, 13(4): 768-773. bossle, ep., vicharapu, b., lemos, gv., lessa, cr., bergmann, l., santos, jf. and amitava, d. 2023. friction stir lap welding of inconel 625 and a high strength steel. metals, 13(1): 146-157. buffa, g., fratini, l., lacommare, u., römisch, d., wiesenmayer, s., wituschek, s. and merklein, m. 2022. joining by forming technologies: current solutions and future trends. international journal of material forming, 15(3): 27-39. cooke, ko., alhazaa, a. and atieh, am. 2019. dissimilar welding and joining of magnesium alloys: principles and application. the wonder element for engineering/biomedical applications, 20(2): 94-110. dak, g. and pandey, c. 2021. experimental investigation on microstructure, mechanical properties, and residual stresses of dissimilar welded joint of martensitic p92 and aisi 304l austenitic stainless steel. international journal of pressure vessels and piping, 194: 104-112. devanathan, c., babu, as., murugan, ss., shankar, e. and giri, r. 2022. review of joining various materials by fsw process and applications. welding and technology, 33(2): 75-88. johnson, p. and murugan, n. 2020. microstructure and mechanical properties of friction stir welded aisi321 stainless steel. journal of materials research and technology, 9(3): 3967-3976. kannan, ar., shanmugam, ns. and vendan, sa. 2019. effect of cold metal transfer process parameters on microstructural evolution and mechanical properties of aisi 316l tailor welded blanks. the international journal of advanced manufacturing technology, 103: 4265-4282. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 924 khrais, s., al h., hadeel, a., ahmad, a. and darabseh, t. 2023. impact of gas metal arc welding parameters on bead geometry and material distortion of aisi 316l. journal of manufacturing and materials processing, 7(4): 123-132. kumar, n., pandey, c. and kumar, p. 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vol.20(4): 913-925. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 925 yang, j., oliveira, jp., li, y., tan, c., gao, c., zhao, y. and yu, z. 2022. laser techniques for dissimilar joining of aluminum alloys to steels: a critical review. journal of materials processing technology, 301(3): 117-123. zhang, ym., yang, y., zhang, w. and na, s. 2020. advanced welding manufacturing: a brief analysis and review of challenges and solutions. journal of manufacturing science and engineering, 142(11): 96-108. zhao, y., koizumi, y., aoyagi, k., yamanaka, k. and chiba, a. 2021. thermal properties of powder beds in energy absorption and heat transfer during additive manufacturing with electron beam. powder technology, 38(1): 44-54. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2008; vol.6, 10-21 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng analyses of the hydraulic performance of a continuous-flow drip irrigation system tested on a tomato field in bauchi, nigeria mofoke, a.l.e. 1, babatunde, f.e. 2, musa, s.m.1*, adewumi, j.k.3 and mudiare, o.j.4 abstract a low-cost, low-tech continuous flow drip irrigation system was constructed and tested in bauchi. the measured hydraulic performance parameters were analysed using computer based regression, correlation and path analyses. results showed that the total flow energy of the system is most sensitive to variations in pressure energy. without flow regulation, fluctuation in the system discharge is influenced largely by plugging and hydraulic design parameters. however, flow regulation using ‘medi emitter’ cushions discharge variations caused by hydraulic design. this leaves variation due to plugging as the sole source of discharge fluctuation with the system. a set of regression equations is equally provided for speedy design and evaluation of similar drip systems under same operating conditions. the set of regression equations in particular, includes a systems specific form of the bernoulli’s equation that may be used for computations of flow energy requirements. inferences from the regression analysis revealed that the maximum practicable lateral length of the continuousflow drip system is 4.6 m. 1. introduction the concept of affordable micro-irrigation technology which started in the early 70s with the works of richard d. chapin in senegal (polak, 2001; keller, 2001) has today been identified as a functional technological paradigm in alleviating hunger and poverty particularly within rural communities of developing countries. existing affordable microirrigation systems are structured for different income levels to suit the generic income stratification among farmers. the cheapest of such systems is the bucket kit (behr and naik, 1999; postel et al., 2001; keller et al, 2001; alin, 2002; anon, 2004), which could be expanded in stages through the drum kit to the relatively large stationary micro-tube system (postel et al., 2001). the continuous-flow drip irrigation system is a recent low-cost micro-irrigation concept developed and tested in bauchi state, nigeria (mofoke et al., 2004a). the system applies the crop water requirement on a continuous basis through out the 24 hrs of a day. this is achieved through a network of cheap pipelines and a high precision low-tech emitter known as the “medi-emitter” (mofoke et al., 2004b). the continuous flow drip irrigation reduces the number of farm visits, and so permits farmers to engage themselves in other revenue generating enterprises as a means of augmenting family income. this system therefore exhibits promising prospects for adoption within the poor communities of the world. however, successful adoption of this novel technology requires comprehensive analyses of the systems performance and its sensitivity to the design constraints. 1agric. engineering programme. school of engineering & engineering technology. abubakar tafawa balewa university bauchi, pmb 0248 bauchi. bauchi state, nigeria. e-mail: tonymofoke@yahoo.com. 2 crop production programme, abubakar tafawa balewa university bauchi, nigeria. pmb 0248 bauchi. bauchi state, nigeria. e-mail: fikayoeb@yahoo.ca 3 department of agric. engineering, university of agriculture abeokuta. pmb 2240. abeokuta 4 department of agric. engineering, ahmadu bello university zaria, nigeria http://www.azojete.com.ng/ mailto:tonymofoke@yahoo.com mailto:fikayoeb@yahoo.ca azojete vol. 6 2008 11 the aim of this study was to analyse the hydraulic performance and sensitivity of the continuous-flow drip irrigation systems so as to furnish insight on its critical design and operational characteristics. 2. materials and method 2.1 determination of systems performance parameters description of the continuous-flow drip system as well as its operational principles are well explained in mofoke et al. (2004a). the system was constructed and field-tested in bauchi state, nigeria with tomato as trial crop. bauchi lies within latitude 10o171 n and longitude 09o491 e on a mean altitude of 609.3 m above sea level. the performance parameters used for the systems appraisal were: application efficiency (ae), irrigation efficiency (ie), distribution uniformity (du) and adequacy of irrigation (ai). ae was calculated as the ratio of the average depth of water infiltrated and stored in the root zone to the average depth of water applied and expressed as a percentage (merriam et al., 1980). irrigation efficiency was calculated from equation 1. (perrier and salkini, 1991) as follows: 1 where: ie = irrigation efficiency, % et = actual crop evapotranspiration, mm ir = irrigation water applied, mm distribution uniformity was computed from equation 2 (merriam et al., 1980): 2 where: lqx = average low-quarter depth of water received, mm. x = average depth of water received, mm. adequacy of irrigation is the percent of an irrigated field receiving the desired amount of water or more (james, 1988). the desired amount of water implied in this definition is subjective because it refers to the measure of water required to maintain the quantity and quality of crop production at a “profitable” level. the desired amount of water was taken as the pre-determined continuous-flow discharge of 0.04 l/hr (mofoke, 2006). ai was determined through extrapolation from a generated frequency distribution plot of applied depth against cumulative percent area (james, 1988). an overall systems efficiency (seff) was calculated by multiplying together ae, ie, ai, and du (james, 1988). 2.2 determination of systems hydraulic parameters the total flow energy and its components were calculated using equation 3 (dake, 1983; camp et al., 1997) in a step by step manner. %100 ir et ei %100 x x du lq analyses of the hydraulic performance of a continuous-flow drip irrigation system tested on a tomato field in bauchi, nigeria 12 3 where: and are pressure heads at distributary tank and emitter points respectively, m; and are velocity heads at distributary tank and emitter points respectively, m; zdt and ze are elevations of water surface (potential energy) in distributary tank and at the emitter center lines respectively, m; h(dt – e) is head loss from distributary tank to emitter, m; and comprised both minor and major head losses. head loss from the distributary tank to the lateral inlet was calculated from the darcy weisbach formula in equation 4 (giles et al., 1994). however, head loss along the lateral was computed from equation 5 (schwab et al. 1993) because of the lateral outflows along the lateral. 4 where: hf = energy head loss through pipe, m f = friction factor l = pipe length, m d = diameter of sub-main, m v = velocity of water flow through pipe, m/s g = acceleration due to gravity, m/s2 5 where: ks is scobey’s coefficient of retardation. l = pipe length, m q = upstream discharge through the pipe, m3/s d = lateral diameter, m f = correction factor to compensate for lateral outflows it was necessary to qualify different discharge coefficients of variation because discharge through drip lines is affected by both hydraulic and emitter factors. four discharge coefficients of variation were used for the systems evaluation. these are:  coefficient of variation of emitter flow caused by hydraulic design cv(h).  coefficient of variation of emitter flow caused by manufacturing processes cv(m).  edte ee dt dtdt hz g v g p z g v g p  22 22  g pdt  g pe  g vdt 2 2 g ve 2 2              g v d l fh f 2 2  f d qlk h s f 6 9.4 75.1 1010.4  azojete vol. 6 2008 13  coefficient of variation of emitter flow caused by hydraulic design and manufacturing processes cv(hm).  coefficient of discharge variation caused by plugging cv(p). cv(h) was taken as the ratio of standard deviation of estimated theoretical emitter discharges to the mean emitter discharge (camp et al., 1997; keller et al., 2001). the theoretical emitter discharges were obtained by substituting the calculated total energy head at each emitter centre line into the flow function of the medi-emitter at 50% opening. the flow function used is of the form given by equation 6 (mofoke, 2006) qe = 0.02e3.83pe ; 6 where: qe = emitter discharge, l/hr pe = available energy head at the emitter, m cv(m) was calculated from measured emitter discharges taken at 50% emitter opening, while cv(hm) was computed from equation 7 (wu et al., 1985): )()()( 22 mcvhcvhmcv  7 cv(p) was calculated from wu (1997) as follows: 8 where p is the level of plugging, (%) the systems hydraulic performance parameters were subjected to regression and correlation analysis using the minitab statistical software ( minitab, 1996). the regression analysis produced algebraic relationships among the performance parameters which provide a basis for synthesis and mathematical interpretations of the systems performance. the pearson’s correlation coefficients were used to assess the degree of association between pairs of the system’s performance indices. a sensitivity analysis was carried out using a computer simulated path analysis software according to agada and babatunde (2006). the sensitivity analysis reveals the crucial factors affecting the systems performance and for which operational precautions are needed. 3. results and discussion table 1 shows the sensitivity of the total flow energy to the three energy components of the continuous-flow drip irrigation system. the table reveals that total flow energy of the drip system is most sensitive to potential energy component. the sensitivity of the total flow energy to changes in pressure energy is apparently small. this observation substantiates earlier trends reported by mofoke et al., (2004a) in which very small absolute variations in pressure energy along the lateral length for the continuous-flow drip system was reported. the   p p pcv   1 analyses of the hydraulic performance of a continuous-flow drip irrigation system tested on a tomato field in bauchi, nigeria 14 very small absolute value of the residual term in table 1 illustrates that no other extraneous factor could contribute considerably to the total flow energy of the low-cost continuous-flow drip system. this remark conforms to the bernoulli’s equation applicable to fluid systems, which states that the total flow energy at any point in a fluid system is the sum of potential, pressure and kinetic energies at that point (giles et al., 1994). table 1: sensitivity of energy components to the total energy of the low-cost continuous-flow drip irrigation system the sensitivity of the systems overall efficiency to some efficiency terms are shown in table 2. results in the table show that the systems overall efficiency is most sensitive to irrigation efficiency and application efficiency, and is least affected by distribution uniformity. the low sensitivity to distribution efficiency is probably due to a relatively narrow variation margin of this performance parameter occasioned by the regulatory ability of the medi-emitter. thus the systems efficiency tends to be most sensitive to irrigation efficiency over which an irrigator has little direct control. the low response of overall systems efficiency to adequacy of irrigation insinuates that this performance parameter originally developed for surface irrigation systems (james, 1988), has limited application to this continuous-flow drip system. the table also demonstrates that variations in application efficiency and irrigation efficiency constitute the critical contributor to changes in the overall systems efficiency of the continuous-flow drip system. other combinations among the performance parameters are apparently minor indicators of the systems performance. table 2: sensitivity of the overall systems efficiency of the low-cost continuous-flow drip irrigation system to some efficiency terms and distribution uniformity type of contribution level of sensitivity (%) application efficiency 34.6 irrigation efficiency 49.8 distribution uniformity 0.60 adequacy of irrigation 16.8 interactive effect -1.63 residual -0.08 total 100.09 table 3 contains the sensitivity levels of the overall hydraulic variations [cv(hm)]to its various components. from the table, changes in coefficient of variation due to plugging [cv(p)] and coefficient of variation due to hydraulic design [cv(h)] subscribe the largest proportions to differences in cv(hm). use of the medi-emitter, however, cushions flow type of contribution level of sensitivity (%) potential energy 74.792 pressure energy 1.299 kinetic energy 6.189 interactive effect 17.777 residual -0.057 total 100.00 azojete vol. 6 2008 15 variation caused by hydraulic design because the device has facility for precise flow regulations. cv(p) is therefore, the sole source of discharge variation with this small-holder continuous-flow drip system. according to wu (1997), flow through emitters is highly sensitive to plugging, which is a major problem to drip systems. the recorded high sensitivity (88.0%) of the overall discharge coefficient of variation to cv(p) illustrates that even with adoption of the medi-emitter, the flow behaviour of the continuous-flow drip system conforms with the general character for drip systems as reported by wu (1997). table 3: sensitivity of the overall hydraulic variation of the low-cost continuous-flow drip irrigation system to some component coefficients of variation* type of contribution level of sensitivity (%) cv(h) 225.386 cv(m) 47.376 cv(hm) 54.051 cv(p) 87.921 interactive effect -314.685 residual -0.048 total 100.00 * the component coefficients of variation are: cv(h): coefficient of variation due to hydraulic design cv(m): coefficient of variation due to manufacturing cv(p): coefficient of variation due to plugging cv(hm): coefficient of variation due to hydraulic design and manufacturing with reference to table 4, it is observed that the theoretical discharge through the emitters is more sensitive to energy contribution from the lateral caused by elevation differences. this is obviously because the water level in the distributary tanks is maintained constant (mofoke et al., 2004a). the relatively high residual sensitivity in table 4 suggests that some factors other than those considered here in this analysis appreciably affect the theoretical emitter discharge. one of such prominent influences is the adjustment level of the emitter. table 4: sensitivity of theoretical emitter discharge of the affordable continuous-flow drip system to hydrostatic pressure components type of contribution level of sensitivity (%) pressure contribution from lateral 54.085 pressure contribution from distributary tank 2.041 total available pressure head at emitter centre line 0.099 interactive effects 14.246 residual 29.538 total 100.00 the equations in table 5 provide a speedy reference for design of similar drip systems. for example, equation 8 in table 5 is a systems specific form of the bernoulli’s equation applicable to the continuous-flow drip system. the adjusted r2 value of this equation (100%) demonstrates a perfect association among the energy terms. this lends further credence to analyses of the hydraulic performance of a continuous-flow drip irrigation system tested on a tomato field in bauchi, nigeria 16 same deduction given by the low residual term of table 1. equation 6 (table 5) gives direct information on the maximum lateral length that may be used for the system under a maximum continuous-discharge of 0.08 l/hr (21 drops/min). the maximum practicable length is delineated by the point on the lateral where there is no energy to cause flow: that is, at etotal = 0. thus, by setting etotal = 0 in equation 6, a maximum lateral length of 4.59m is obtained. in practice, however, the maximum lateral length may be different from this projection due to dissimilar rolling land slopes and variations in other operating conditions. table 5: regression equations of the energy components of the continuous-flow dripirrigation system regression equation r2 [adj] (%) 1) etotal = 3.39 + 1.05epotential 99.9 2) etotal = -55.0 + 17.3epressure 83.3 3) etotal = 4.08 + 273621ekinetic 93.0 4) etotal = 2×10-5 + 1.0epotential + 1.0epressure + 0.203ekinetic 100.0 5) etotal = 13.2×10-5 + 1.0 epotential + 1.0 epressure + 1.03ekinetic 100.0 6) lthlat = 4.59 – 60.1etotal 98.9 where: e = energy (cm). the subscripts refer to the particular energy term lthlat = lateral length (m). the pearson’s correlation coefficients in table 6 essentially ratify the observed relationships between the energy components and total energy reported by mofoke et al (2004). the table validates the strong dependence of total flow energy on potential energy, showing a pearson’s correlation coefficient of 1.00 between these two energy terms. the negative correlation coefficients demonstrate a reduction in magnitude of all energy components down the lateral length. this is apparently due to increased cumulative outflows and head losses along the lateral length. table 6: pearson’s correlation coefficients between the flow energy components and lateral length of the low-cost continuous-flow drip system lateral length epotential epressure ekinetic epotential -0.995 epressure -0.920 0.916 ekinetic -0.968 0.963 0.988 etotal -0.995 1.000 0.924 0.969 table 7:regression equations between emitter discharge and coefficients of variation of the continuous-flow drip irrigation system regression equation r2 [adj] (%) 7) cv(h) =20.4 + 0.0285qe 82.8 8) cv(m) = 8.04 – 0.00825qe 84.4 azojete vol. 6 2008 17 9) cv(hm)=21.9 + 0.0237qe 83.0 10) cv(p) = 83.4 – 2.47qe 84.4 where: cv(h) = coefficient of variation due to hydraulic design cv(m)= manufacturer’s coefficient of variation cv(p) = coefficient of variation due to emitter plugging cv(hm) = coefficient of variation due to hydraulic design and manufacturing imperfection qe = discharge in drops of water per minute. (1 drop/min = 4x10-3l/hr) table 8: pearson’s correlation coefficients between emitter discharge and discharge coefficients of variation of the continuous-low drip irrigation system emitter discharge cv(h) cv(m) cv(hm) cv(p) cv(h) 0.941 cv(m) -0.947 -0.999 cv(hm) 0.942 1.000 -1.000 cv(p) -0.947 -0.938 0.951 -0.943 cv(hmp) -0.949 -0.958 0.968 -0.962 0.998 the equations in table 9 constitute a framework for quick evaluation of similar continuous– flow drip systems especially under different design and operational settings. thus, if it is desired to operate a similar drip system at a continuous-flow rate of say 0.078 l/hr (20 drops/min), table 9 indicates that the associated application efficiency and distribution uniformity would be close to 96.2 and 87.0% respectively, while the overall systems efficiency may approach 43.0%. the negative pearson’s correlation coefficients in table 10 indicate inverse relationships between the specified pairs of parameters. irrigation efficiency would obviously reduce with increase in discharge because of excessive nonevapotranspiration losses. on the other hand, the systems distribution uniformity increases with higher emission rates because of the stronger sweeping effect achievable at higher emitter discharges. this action cleanses the emitter tubes of fine clay and silt particles that may otherwise settle in the emission path to cause emitter plugging which reflect in low systems distribution uniformity. from table 10, one way of increasing the du is to use higher flow rates. this is because of the observed positive correlation between du and emitter discharge. unfortunately, higher discharges especially on a continuous basis imply reduced irrigation efficiency. this stems from the negative correlation coefficient in table 10. however, with the increasing need for global water conservation, the focus is more on increasing the irrigation efficiency of existing irrigation methods. thus, attempts to increase du through increase in emission rate must be carefully compromised with the economic and environmental effects of low irrigation efficiencies. analyses of the hydraulic performance of a continuous-flow drip irrigation system tested on a tomato field in bauchi, nigeria 18 table 9: regression equations between some efficiency terms and the overall systems efficiency of the continuous-flow drip irrigation system regression equation r2 [adj] (%) 11) ae = 93.2 + 0.149qe 96.9 12) ie =92.4 – 0.303qe 95.9 13) du =73.8 + 0.661qe 72.5 14) ai =51.1 + 0.387qe 72.3 15) seff =30.1 +0.631qe 93.3 16) seff = -368 + 4.27ae 97.8 17) seff = 214 – 1.99ie 84.4 18) seff = -32.3 + 0.859du 92.2 where: qe = emitter discharge (drops/min) ae = application efficiency (%) ie =irrigation efficiency (%) du= distribution uniformity (%) ai = adequacy of irrigation (%) seff = overall systems efficiency (%) qe = discharge in drops of water per minute. (1 drop/min = 4x10-3l/hr) table 10: pearson’s correlation coefficients between typical efficiency terms and the overall systems efficiency of the low-cost continuous-flow drip system qe ae ie du ai ae 0.990 ie -0.986 -0.955 du 0.904 0.943 -0.862 ai 0.903 0.834 -0.944 0.649 seff 0.977 0.993 -0.947 0.974 0.797 tables 11 and 12 provide an insight into the behaviour of the theoretical emitter discharge (qo) under varying pressure contributions from the distributary tank (htank) and lateral (hlateral). the correlation coefficients in table 12 show that qo increases down the lateral. this is surely because the rate of energy loss through friction and pipe fittings is exceedingly compensated by hydrostatic pressure gain down the lateral. azojete vol. 6 2008 19 table 11: regression equations between theoretical emitter discharge and hydrostatic pressure head components of the continuous-flow drip irrigation system regression equation r2 [adj] (%) 19) qo = 0.451 + 0.0447latnode 61.8 20) qo = 0.469 + 0.104hlat 66.0 21) qo = 6.87 – 1.78htank 59.5 22) qo = 0.097 + 0.109htotal 65.8 23) qo = 1.56 + 0.0879hlat – 0.30htank 60.7 24) qo = 0.66 + 0.375hlat – 0.03htank – 0.121latnode 59.2 where: qo =theoretical emitter discharge (drops/min) latnode = lateral node number (1, 2, ….9) hlat = hydrostatic pressure contribution from the drip lateral htank = hydrostatic pressure contribution from the distributory tank htotal = total hydrostatic pressure head table 12: pearson’s correlation coefficients between theoretical emitter discharge hydrostatic pressure contributions of the continuous-low drip irrigation system latnode hlat htank htotal hlat 0.996 htank -0.929 -0.939 htotal 0.996 1.000 -0.932 qo 0.816 0.838 -0.804 0.837 4. conclusions the continuous-flow drip irrigation system offers satisfactory hydraulic performance characteristic with drip irrigation systems. the systems flow energy is most sensitive to potential and kinetic energies. thus, without flow control, good land levelling is necessary for attainment of high distribution uniformity with the system. also, realisation of high irrigation efficiency is a major precursor for obtaining good overall systems efficiency with the drip system. even with flow regulation by the medi-emitter, the systems discharge is largely affected by emitter plugging. however, the limit of discharge variation is small and thus, does not justify more technical and expensive ameliorative procedures. references agada, p.o. and f. e. babatunde, 2006. computer simulated path analysis of the direct, indirect and combined contributions of growth parameters to crop yield. pecop journal of science, engineering and technology. (in press). alin. 2002. affordable drip irrigation for small-scale farmers. arid lands information network, eastern africa. available at: www.alin.or.ke.htm. accessed 22nd february 2004. http://www.alin.or.ke.htm/ analyses of the hydraulic performance of a continuous-flow drip irrigation system tested on a tomato field in bauchi, nigeria 20 anon. 2004. affordable micro-irrigation for the poor. a four year action report supported by uk department for international development (dfid). available at: www.itcltd.com/finalreports.htm. accessed: 21st march, 2004. behr, c. and g. naik. 1999. applying micro-irrigation in the himalaya: a case study on ide’s experience. available at: mfsupport@mtnforum.org. accessed 22nd march, 2004. camp, c.r., e.j. sadler and w.j. busscher. (1997). a comparison of uniformity measures for drip irrigation systems. transactions of the american society of agric. engineers. 40(4). asae, st. joseph michigan. :1013-1020. dake, j. m. k. (1983). essentials of engineering hydraulics. 2nd edition . mcmillan press, ltd, london. giles, r.v., j.b., evett and c. liu. (1994). fluid mechanics and hydraulics 3/ed. schaums’s outline series: theory and practice. mcgraw-hill, inc. new york, ny. usa. james, l. g. (1988). principles of farm irrigation system design. john wiley and sons inc. new york, ny. keller, j, d. l. adhikari, m. r. petersen, and s. suryawanshi. 2001. engineering low-cost micro-irrigation for small plots. draft report of a fact finding study conducted in kenya, india, and nepal in march 2001. swiss agency for development and cooperation. keller, j (2001). gardening with low-cost drip irrigation in kenya: for health and profit report of a fact finding mission conducted in kenya, india and nepal in march 2001. the swiss agency for development and cooperation minitab. 1996. minitab for windows. release 11.12.32 bit. minitab inc. merriam, j. l., m. n. shearer and c. m. burt. (1980). evaluating irrigation systems and practices. in: “design and operation of farm irrigation systems”. (m. e. jensen, ed.) asae monograph 3.: 721-759. st. joseph michigan. mofoke, a. l. e., j. k. adewumi, o. j. mudiare and a. a. ramalan. 2004a. design, construction and evaluation of an affordable continuous-flow drip irrigation system. journal of applied irrigation science, 39 (2): 253 – 269 available at:http://www.vlirrigation.org/cms/index.php?id=168 mofoke, a. l. e., j. k. adewumi, o. j. mudiare and a. a. ramalan. (2004b).structuring and characterisation of the medical infusion set as emitter for low cost drip irrigation system. arid zone journal of engineering, technology and environment.vol 4.:1-15. faculty of engineering, university of maiduguri, nigeria. mofoke, a. l. e. 2006. design, construction and evaluation of a continuous-flow drip irrigation system. unpublished ph.d thesis. department of agric. engineering, ahmadu bello university zaria. perrier, e. r. and a. b. salkini. (1991). supplemental irrigation in the near east and north africa. proceeding of a workshop on regional consultation on supplemental irrigation. organised by icarda and fao, morocco. kluwer academic publishers, dordrecht. polak, p. (2001). the design process for the ide low-cost drip irrigation system ide. available at: www.ideirg.org/-4k. accessed: 24 th june 2003. postel, s., p. polak, f. ganzales and j. keller (2001). drip irrigation for small farmers. a new initiative to alleviate hunger and poverty. journal of the international water resources association. 26 (1): 3 – 12. http://www.itcltd.com/finalreports.htm mailto:mfsupport@mtnforum.org http://www.vl-irrigation.org/cms/index.php?id=168 http://www.vl-irrigation.org/cms/index.php?id=168 http://www.ideirg.org/-4k azojete vol. 6 2008 21 schwab, g. o., d. d. fangmeier, w. j. elliot and r. k. frevert. (1993). soil and water conservation engineering. 4th edition. john wiley and sons inc. new york, n. y. wu, i. p., k. y. yabusaki and j. m. irudayaraj. (1985). computer simulation of total emitter flow variation. in: drip/trickle irrigation in action. proceeding of the third international drip/trickle irrigation congress, nov 18-21. california, usa. vol. i. asae, st. joseph michigan usa: 873 – 886. wu, i.p. (1997). an assessment of hydraulic design of micro-irrigation systems. agricultural water management. 32(3):275-284. corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 748 arid zone journal of engineering, technology & environment original research article modeling of rainfall-runoff of the yobe river basin using hechms a. n. alkali1, s. dan’azumi2, u. a. ibrahim1 and b.o. sanyaolu1 1department of civil and water resources engineering, university of maiduguri 2department of civil engineering, bayero university, kano *corresponding author’s email: abdulhamidalkali.aa@unimaid.edu.ng article information abstract the yobe river basin which drains into the lake has experienced low flows which has been attributed to high evapotranspiration and infiltration rates and the growth of weeds such as typha australis in river channels. this research involved modeling rainfall-runoff of the yobe river basin in north-eastern nigeria using the hechms 4.8 application package for the purpose of forecasting and determination of low-flow events. collection of streamflow data was affected due to insurgency where water resources planning and management within the basin was impacted. observed climatic data (precipitation and evapotranspiration) were obtained from two gauging stations (gashua and gudumbali) for sixteen (16) years (1990-2005). both climatic and streamflow data were subjected to normality and homogeneity tests and used for modeling, with the climatic data as the input data, while the streamflow data were used for calibration and validation. in addition, streamflow data for three gauging stations (gashua, geidam and damasak) were also obtained from periods between 1990 to 2005 (16) years. the streamflow data were calibrated and validated with nse (>0.63 to 0.68) in calibration for daily time steps. it was observed that the validation yielded nse (>0.62 to 0.78). therefore, hec-hms model can be used to project runoff from available climatic data in the yobe river basin. furthermore, soil management of the catchment area, channel improvement and river augmentation are some of the key strategies of buttressing the effects of high evapotranspiration and infiltration rates, as well as sustaining flow in the river up to the lake chad. received: 3rd june 2025 revised: 28th july 2025 accepted: 30th july 2025 keywords: modeling hec-hms yobe catchment rainfall-runoff © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the major threat to freshwater systems in some developing countries is spontaneous infrastructural development, agricultural activities, deforestation, land cover change and irrigation (khafaji and challabi, 2020; chukwu, 2015). for instance, in nigeria, an increase in the delivery of constant water supply, despite its vast surface and groundwater potentials has not met the rapid population growth and urbanization (merem et. al., 2017: devi et. al., 2015). surface water in streams around the yobe river appears seasonal usually from august to october while for the rest of the year are dry and the only source of water is groundwater (adamu et. al., 2020). the yobe river is one of the main tributaries of lake chad from nigeria, initially contributing up to 10% of the total water inflow into the lake (iucn, 2013). over the years, however, this contribution has drastically reduced to about 1 to 2 percent of the total inflow into the lake due to the recession of the river (iucn, 2013). this recession has been attributed to the invasion of reeds and weeds such as typha australis in the river reaches, blocking streams and causing some of the river water to meander along undefined channels. the komadugu gana (misau river), which is the yobe river’s main tributary, now barely reaches the yobe river (iucn, 2013). also, research has shown that 18% of its annual inflows are lost as a result of infiltrations towards phreatic water tables and the underlying sedimentary formation (salman and momha, 2009). advancement in technology has also brought about innovations in the field of watershed management, mostly due to its complex nature. these innovations involve simplification of the real-life domain of watersheds in azojete september 2025. vol.21(3):748-757 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/006 www.azojete.com.ng mailto:abdulhamidalkali.aa@unimaid.edu.ng mailto:abdulhamidalkali.aa@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 749 the form of hydrological modelling (panahi et. al., 2021). these models were developed over the years from simple linear correlations to peculiar technical interfaces such as the hec packages, swat, wepp, swmm, hspf-fortran, modflow etc. (bouizrou et. al., 2021; akter et. al., 2020). these models vary depending on their intended purposes and input requirements. thus, the quest for increased precision in output data has led to the evolution of these models. it is noteworthy that there has been remarkable acceptance these models in watershed management, river modeling, policy management, and forecasting (marahatta et. al., 2021). hechms is a state-of-the-art windows-based model for precipitation-runoff simulation. hec-hms provides a variety of options for simulating precipitation-runoff and routing processes and is comprised of a graphical user interface, integrated hydrologic analysis components, data storage and management capabilities, graphics, and reporting facilities (tedla et. al., 2021). the software was used in this study to facilitate streamflow forecasting for the purpose of planning and management within the yobe river basin. 2. methodology 2.1 the study area yobe river drains into lake chad in north-east nigeria. it is situated at the southern fringe of the sahara desert, east of the sahel region between 12°20 and 14°20’ latitude north; 13°20’ and 15°20’ longitude east. the river lies within the geographical locations of 12°44’49.42’’n and 11°02’56.17’’e in gashua to 13°41’43.49’’n and 13°22’14.49’’e in malum-fatori (salman and momha, 2009). annual rainfall amount is strongly contrasted throughout the basin ranging from 1,500mm annually in the south of the basin to less than 100mm in the north. due to high temperatures, the potential evapo-transpiration exceeds 2,000mm annually at the centre of the basin. the river originates from gashua (yobe state), immediately downstream of the nguru wetlands and flows through geidam (yobe state), damasak (borno state) and then malum-fatori (borno state) before emptying into lake chad. the river flows at a distance of about 340km before flowing into the lake. the main tributary of the yobe river is the komadugu gana (or misau river), which seasonally meets the yobe river at damasak. the komadugu gana river originates from nangere lga of yobe state and flows through fune, tarmuwa and geidam but barely reaches damasak during the wet season. the origin of the yobe river at gashua is underlain by a sedimentary formation that reaches lake chad (iucn, 2013). the yobe river basin has exhibited a significant level of sensitivity to weather variability and demographic characteristics amongst others (gana et. al., 2018). lake chad has shrunk by about 90% over the past 60 years with a total area of about 26,000 km2 in 1963 to about 1,500 km2 in 2021. the effect of the demographic characteristics is related to the increase in the population in the region between 13 million in 1963 to over 40 million people in 2021 (thematic report, 2022). figure 1. map of nigeria showing states covering the study area figure 2. map of the study area 2.2 data collection 2.2.1 gis data source shuttle radar topography mission (srtm) digital elevation model (dem) 90m by 90m was obtained from the united states geographic service (usgs) earth explorer website. gis raster and vector shape files were used. the land use land cover (lulc) map was obtained from the sentinel-2 10m lulc database by http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 750 environmental systems research institute (esri), 2022. the lulc data used were two raster data files that were merged and clipped by the basin map in arcgis 10.7.1. the soil map used for this study was obtained from the united nations food and agriculture organization (fao). 2.2.2 climate data in this study, climatic data such as precipitation and evapotranspiration were used while daily data for the yobe river was obtained in respect of gashua and gudumbali stations from 1990 to 2005. each dataset was subjected to homogeneity tests before use for simulating rainfall-runoff. for authenticity and accuracy, data used in the study was obtained from the nigerian meteorological agency (nimet). 2.2.3 flow data daily discharge data was used for calibration and validation of the hydrological model for hec-hms. the data of the flow was obtained from the hadejia-jama’are-komadugu-yobe trust fund (hjky-tf), damaturu, yobe state from the period between 1990 to 2005. the data available were for the gashua, geidam and damasak stations. the data sets were also subjected to normality and homogeneity tests. 2.3 yobe river watershed modeling with hec-hms the yobe river watershed was delineated using the gis toolbar of hec-hms. various models were used to simulate the watershed. the deficit and constant loss model was used to represent the loss due to evapotranspiration and infiltration. the direct runoff model used was the soil conservation service-unit hydrograph (uh) to transform rainfall into runoff. the recession baseflow method was used for modeling baseflow and the muskingum method was used for routing. 2.3.1 hec-hms model calibration and validation the dataset was divided into eleven (11) years for calibration and six (6) years for validation, giving a percentage distribution of 70%-30%, respectively. the data was calibrated for daily time-series. the daily data were aggregated for the mean with the use of hydrognomon 4.1 software package. nash-sutcliffe efficiency (nse), was used as model performance evaluators and were applied by pokhrel and karki (2021); rajput et. al. (2021) and ibrahim et. al., (2022) given in equation (1); 𝑁𝑆𝐸 = 1 − ∑ (𝑄𝑖 𝑜𝑏𝑠− 𝑄𝑖 𝑠𝑖𝑚)²𝑛 𝑖=1 ∑ (𝑄𝑖 𝑜𝑏𝑠− �̅�𝑜𝑏𝑠)²𝑛 𝑖=1 1 where 𝑄𝑖 𝑜𝑏𝑠 = observed streamflow; 𝑄𝑖 𝑠𝑖𝑚= simulated streamflow; �̅�𝑜𝑏𝑠 = mean of observed flow and n is the number of observations 3. results and discussion 3.1 results of gis data the dem of the yobe river basin is shown in figure 3 with the blue section indicating higher elevation of up to 642m to the lower section of about 283m above mean sea level. figure 3: digital elevation model for yobe river basin figure 4: land use land cover (lulc) map of the yobe river basin http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 751 figure 5: soil map of the yobe river basin figure 4 shows the lulc map. the results revealed that about 73.5% of the yobe basin lies within the “rangeland” category. rangelands serve as an important area for livestock production and can also provide habitat for wildlife. the yobe river basin falls within the semi-arid to arid climatic zone of the sahel region. however, the arid climate limits the growth of trees and supports the dominance of grasses and shrubs. in addition, bare soil occupies approximately 6.12% of the basin with limited vegetation cover and exposed soil. similarly, these areas may be devoid of plants due to several activities such as erosion and human activities including but not limited to deforestation, intensive farming and construction. in addition, water and trees share 4.1% and the remaining 10.18% is shared between built area, flooded vegetation and crops. the classification of hydrological soil groups (hsgs) a, b, c, and d categorizes soils based on their infiltration characteristics according to rajput (2021). these classifications help in estimating runoff and designing stormwater management systems. basically, the infiltration rates of these soils decrease from a to d. as seen in figure 5, the predominant soil type falls under group b and covering an estimated 79% of the catchment area. arguably, the soil type includes loamy soils with moderate permeability. however, group b soils followed in dominance by group c, which covers 10% of the yobe river basin. it has been observed that soils in this category normally have low infiltration rates and high runoff potential and including clayey soils with low permeability. furthermore, another predominant soil type falls under group a, representing 6.5% of the yobe river basin. interestingly, soils in this group are believed to have high infiltration rates and minimal runoff potential. also, it was observed that group d soil represents the least predominant soil in the yobe river basin characterized by very low infiltration rates and very high runoff potential. it occupies an area corresponding to approximately 3.5% such as highly compacted soils, rocky soils, or soils with an impermeable layer. 3.2 homogeneity tests on climatic and flow data parametric and non-parametric tests were conducted on the climatic and flow data. the climatic data provided p-values above 0.05, implying that there is no sufficient evidence to reject the null hypothesis stating that “there is no change point within the dataset” (mbah and paothong, 2015; pandzic et. al., 2019). however, the flow data showed a contrary result, viz the shnt provided in table 1. table 1: homogeneity test on discharge data from three different locations s/n test gashua geidam damasak pvalue remarks p-value remarks p-value remarks 1. snht 0.04 not homogeneous <2.2 x10-16 not homogeneous <2.2x10-16 not homogeneous it was seen that for gashua, the p-value obtained from the snht is p = 0.04. this value is less significance level which suggests a statistically significant change or shift in the discharge data and therefore not homogenous. in geidam station, a value less than 2.2 x 10-16 also suggests a non-homogeneous distribution in the dataset. the p-value obtained for damasak similar to that of geidam station provided a p-value less than 2.2 x 10-16 which is less than the 5% significance level, and as such is statistically significant implying a nonhomogeneous distribution in the dataset.. http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 752 3.3 data homogenization the null hypothesis states that there is no change point and that the dataset follows a homogeneous distribution. conversely, the alternative hypothesis states that there is a change point and the dataset does not follow a homogeneous distribution (pandzic et. al., 2019). the results of data homogenization are provided in figures 6 to 8. figure 6 shows the data before homogenization (bh) and after homogenization (ah). the climatol package uses the standard normal homogeneity test (snht). the initial p-value estimated by using the snht was 0.04. the result obtained after homogenization was 0.09. this value implies that there is no sufficient reason to reject the null hypothesis that there is no change point and that the series is homogeneous. figure 6: discharge of gashua before and after homogenization figure 7: discharge of geidam before and after homogenization figure 8: discharge of damasak before and after homogenization figure 7 provides the original and homogenized data for the geidam station. the initial p-value estimated by using the snht was less than 2.2 x10-16 which later improved to 0.062. figure 8 shows the original and homogenized data for the damasak station. the initial p-value estimated by using the snht was less than 2.2 x10-16. a p-value of 0.24 was obtained after homogenization. values for both geidam and damasak yielding pvalues above 0.05 after homogenization by climatol further indicate that the difference in the dataset is no longer statistically significant. the summary is provided in table 2. table 2: results of tests after homogenization s/n test gashua geidam damasak p-value remarks p-value remarks p-value remarks 1. snht 0.09 homogeneous 0.062 homogeneous 0.24 homogeneous http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 753 3.4 performance of hec-hms simulation the results of the watershed delineation, catchments curve number extraction, lag time and time of concentration, routing, base flow values, calibration and validation results were provided. 3.4.1 outcome of watershed delineation using hec-hms the dem was delineated using the gis toolbar in hec-hms to provide 49 sub-basins. dividing the yobe river basin into smaller sub-basins allows for a more detailed analysis of the basin's hydrological characteristics (geosense, 2018). smaller sub-basins may respond more quickly to rainfall, leading to flash flooding, while larger sub-basins may have a more delayed response but can contribute significant runoff volume to the main river system (pandi et. al., 2023). parameters such as land cover, soil type and topography can vary within the basin, and modeling each sub-basin separately allows for a more accurate representation of these variations (khelifa and mosbahi, 2021). the area of the sub-basins varies considerably, ranging from 13 km² to 3,758 km². the maximum flow length of each sub-basin ranges from 8.2km to 269km. the average watershed slope ranges from 1.7% to 3.6%. the maximum potential retention (mpr) ranges from 0.64 to 2.99, depending upon the curve number. the mpr values represent the retention capacity of different parts of the yobe river basin. higher mpr values indicate a greater capacity to retain rainfall within the basin, while lower values suggest a higher likelihood of generating runoff (pokhrel and kharki, 2021). time of concentration (tc) is influenced by various factors, including watershed size, slope, land cover, soil type and channel characteristics (tassew et. al., 2019). the shortest basin has a tc of 4.02 hours and the longest basin has a tc of 71.72 hours. lag time is the time delay between the peak of the rainfall input and the peak of the resulting hydrograph at the watershed outlet. lag time is influenced by similar factors as tc, with the shortest and longest times of 2.41 and 43 hours, respectively. 3.4.2 routing and base flow recession values the muskingum k often denoted as the wave travel time in hours ranging from 0.1 to 150 hr while the x referred to as the weighting factor from 0 to 0.5, determines the proportion of the inflow at the current time step and the inflow at the previous time step used in computing the outflow at the current time step (khelifa and mosbahi, 2021). the typical values are k=0.5 and x=0.25. for k=0.5, it means that the river reach has moderate storage capacity, which will lead to a moderate degree of attenuation in the flow response. the base-flow recession constant chosen for this study is 0.8, while the ratio to peak of 0.2 according to usace (2024). 3.4.3 hec-hms model calibration calibration involves adjusting model parameters to improve the match between model predictions and observed data. the calibration results for the daily time series are presented in figures 9 to 11. i. gashua station the transform and routing are the most sensitive parameters in the calibration process of the daily series as a result of trial-and-error adjustments. the deficit and constant loss method represented the observed flow well, and the values had been kept constant. the transform parameter was multiplied by 11. the muskingum was increased from 0.5 hrs to 145 hrs. the computed peak discharge was found to be 207 m3/s on the 5th of september, 1999, while the observed peak was 199m3/s on the 1st of october, 1999. a volume of 11,927 mcm was computed while an observed volume of 14,539 mcm was recorded. this shows that the model slightly overestimates the peak discharge while it underestimates the volume. the nse was found to be 0.68 which falls under the “acceptable” range according to moriasi et. al., (2015). ii. geidam station the calibration result for the geidam station is provided in figure 10. the same parameter value for transform and routing was used for geidam station. the peak discharge was simulated as 193 m3/s on the 9th of september, 1999 while the observed value recorded was 220m3/s on the 18th of september, 1994, indicating an underestimation. the simulated volume was found to be 11,816 mcm against a recorded observed value of 13,203 mcm, also indicating an underestimation. the performance evaluation of the model yielded nse value of 0.63 which can be interpreted as “acceptable”. hussain et. al. (2021) modeled flow simulation in tributary catchments of kaohsiung area of taiwan using hec-hms and the model performance was satisfactory with nse ranging from 0.51 to 0.86 for both calibration and validation. http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 754 figure 9: calibration of daily time series for gashua station figure 10: calibration of daily time series for geidam station iii. damasak station the calibration result for damasak station in provided in figure 11 the daily calibration for damasak station yielded the same values of 145hr and a multiplication factor of 11 for the routing and transform, respectively. the peak discharge of 111m3/s on the 18th of september, 1999 was simulated, while a peak discharge of 120m3/s on the 14th of august, 1999 was observed. a simulated volume of 7,062 mcm against an observed value of 8,478 mcm was obtained, indicating an underestimation in both peak discharge and volume. figure 11: calibration of daily time series for damasak station the performance evaluation of the model yielded 0.63 for nse indicating an “acceptable” relationship. rauf and ghumman (2018) assessed the impact of rainfall-runoff simulations of the upper indus river basin of pakistan using hec-hms. the catchment area is about 970,000 km2 and the calibration produced satisfactory results with the calibration giving nse values of 0.84. the hec-hms may have performed better for the catchment in upper indus river basin due to the smaller catchment area. summary is provided in table 3. table 3: summary of calibration results of daily time series for hec-hms s/n station value remarks 1 gashua 0.68 acceptable 2 geidam 0.63 acceptable 3 damasak 0.63 acceptable http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 755 3.4.4 hec-hms model validation the model validation was done for years between 2001 to 2005 and is presented in this section. the validation of the model is presented for each station from figures 12 to 14. i. gashua station: the result for validation of the model for the gashua station is presented in figure 12. all the parameters for calibration were maintained and simulated volume of 5,529 mcm was obtained while observed volume of 5,506 mcm was recorded. the performance evaluation of the model according to moriasi et. al. (2015) for validation was found to be 0.78 for nse indicating a very good relationship. figure 12: validation of daily time series for gashua station figure 13: validation of daily time series for geidam station ii. geidam station the daily validation result for geidam station is presented in figure 13. the simulated volume is 5,842 mcm while the observed volume is 6,776 mcm. the nse value for the model was 0.75, implying a “very good” relationship between the simulated and observed flows. this is in accordance with works conducted by hussein et. al. (2021). iii. damasak station the result for the daily validation for the damasak station is provided in figure 14. a simulated volume of 3,271 mcm was obtained while the observed volume was recorded as 3,634 mcm.. figure 14: validation of daily time series for damasak station nse of 0.62 was obtained as the model performance evaluation value, indicating a good relationship. rauf and ghumman (2018) obtained nse of 0.70 for validation which could also be attributed to the smaller catchment area of the upper indus river basin in pakistan. summary of the results for validation are provided in table 4. http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 756 table 4: values for validation for daily time series for hec-hms s/n station value remarks 1 gashua 0.78 very good 2 geidam 0.75 very good 3 damasak 0.62 good 5. conclusion the research involved modeling rainfall-runoff of the yobe river basin in north-eastern nigeria using hechms application package. observed climatic data (precipitation and evapotranspiration) were obtained from two gauging stations (gashua and gudumbali) for sixteen (16) year period between (1990-2005). streamflow data for three gauging stations (gashua, geidam and damasak) were also obtained for the same period the research revealed the physiographic characteristics of the yobe river basin with hec-hms identifying 49 subbasins with maximum lag time of 43hours. alao, rainfall was simulated to yield runoff using hec-hms. the hec-hms produced results with a range of nse (>0.63 to 0.68) in calibration for daily time steps. the validation results also produced nse (>0.62 to 0.78). these results generally implied a very good relationship between the simulated and observed runoff and can hence be used for forecasting streamflow for the yobe river basin. therefore, there is need for intervention in terms of forestation in the yobe river basin to preserve rainwater for a longer period of time and to reduce the effect of evapotranspiration. the hec-hms model can be used to project runoff from available climatic data in the yobe river basin and basins of similar catchment characteristics for the purpose of water resources policy making, planning and management. references adamu, s., sadiq, h.m., kodomi, m.g. and wulo, i. b. 2020. groundwater depletion in the upper aquifer of the chad formation, chad basin, north-eastern nigeria. nigerian journal of technology (nijotech), 39 (2): 621-631. akter, a., tanim, a. h., and islam, m. k. 2020. possibilities of urban flood reduction through distributed-scale rainwater harvesting. water science and engineering, 13(2): 95-105. bouizrou, i., chahinian, n., perrin, j., müller, r., and rais, n. 2021. network representation in hydrological modelling on urban catchments in data-scarce contexts: a case study on the oued fez catchment (morocco). journal of hydrology: regional studies, 34. chukwu, ke. .2015. water supply management policy in nigeria: challenges in the wetland area of niger delta. european scientific journal, 11: 303-323 devi gk., ganasri bp. and dwarakish g s .2015. a review on hydrological models. international conference on water resources, coastal and ocean engineering, aquatic procedia, 4: 1001 – 1007. hussain, f., wu, rs. and yu, k. 2021. application of physically based semi-distributed hec-hms model for flow simulation in tributary catchments of kaohsiung area taiwan. journal of marine science and technology, 29 (1): 42-62 ibrahim, ua., dan’azumi, s., bdliya, h. h., bunu, z. and chiroma, mj. 2022. comparison of weap and swat models for streamflow prediction in the hadejia-nguru wetlands, nigeria. modeling earth systems and environment, 8(4): 4997-5010. international union for conservative nature. 2013. komadugu yobe basin, upstream of lake chad, nigeria. multi-stakeholder participation to create new institutions and legal frameworks to manage water resources. water and nature initiative (wani) case study. khafaji, ms. and chalabi, rd. 2020. impact of climate change on the spatiotemporal distribution of stream flow and sediment yield of darbandikhan watershed, iraq engineering and technology journal, 38 (02): 265276. khelifa, w.b. and mosbahi .2021. modeling of rainfall-runoff process using hec-hms model for urban ungauged watershed in tunisia. modeling earth systems and environment, 8(6):1-10. http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 748-757. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhamidalkali.aa@unimaid.edu.ng 757 gana, ba, harir, ai., bogoro, ag. and oladosu, ro. .2018. stream ordering as a tool for effective river basin development: examples from komadugu –yobe river basin, nigeria. journal of resources development and management, 44: 67-78. marahatta, s., devkota, lp. and aryal, d. 2021. application of swat in hydrological simulation of complex mountainous river basin (part i: model development). water 2021. mdpi. 13(11): 1546. mbah, ak., and paothong, a. 2015. shapiro–francia test compared to other normality test using expected pvalue. journal of statistical computation and simulation, 85(15): 3002-3016 merem, ec.,wumasi, yt., wesley, j., isokpehi, p., shenge, m., fageir, s., crisler, m., romorno, ca. hines, hirse, g., ochai, s., leggett, s. and nwagboso, e. 2017. analyzing water management issues using gis: the case of nigeria. scientific and academic publishing, 7(1): 20-46. moriasi, dn., gitau, mw., pai, n. and daggupati, p. 2015. hydrologic and water quality models: performance measures and evaluation criteria. journal of american society of agricultural and biological engineers, 58(6):1763-1785. panahi, m., jaafari, a., shirzadi, a., shahabi, h., rahmati, o., omidvar, e., lee, s., and bui, dt. 2021. deep learning neural networks for spatially explicit prediction of flash flood probability. geoscience frontiers 12(3): 101076. pandi, d., kothandaraman, s. and kuppusamy, m. 2023. simulation of water balance components using swat model at sub catchment level. sustainability, mdpi, 15(2): 1438. pandžić, k., trninić, v. and bačić, i. 2019. standard normal homogeneity test as a tool to detect change points in time series. theoretical and applied climatology, 138(1-2): 661-670. pokhrel, k. and karki, k.r. 2021. rainfall-runoff simulation of tamor river basin using scs-cn based hechms model. proceedings of the 9th ioe graduate conference, 9: 129-139 rajput, a., rawat, u., yadav, a., pawar, ps. and vasht, d. 2021. hydrological modelling of banjar river watershed using hec-hms. chemical science rev lett 2021, 10 (37): 81-90. rauf, a. and ghumman, r. 2018. impact assessment of rainfall-runoff simulations on the flow duration curve of the upper indus river—a comparison of data-driven and hydrologic models. mdpi; 10(7): 876 salman, m. and momha 2009. adaptive water management in the lake chad basin. addressing current challenges and adapting to future needs-seminar overview. world water week, stockholm. august, 16-22. sharfennberg b., bartles m., brauer t., fleming m. and karlovitz g. 2024. hec-hms user’s manual version 4.13 united states army corps of engineers, institute for water resources engineering centre, 609 second street, davis, ca, 95616, usa. tassew, bg., belete, ma. and miegel, k. (2019). application of hec-hms model for flow simulation in the lake tana basin: the case of gilgel abay catchment, upper blue nile basin, ethiopia. hydrology. mdpi. 6(1):21. tedla, mg., cho, y. and jun, k. 2021. flood mapping from dam break due to peak inflow: a coupled rainfall– runoff and hydraulic models approach. hydrology, 8(2):89. thematic report. 2022. lake chad basin: impact of extreme weather and climate events on livelihoods and food security. acaps http://www.azojete.com.ng/ mailto:abdulhamidalkali.aa@unimaid.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):719-732 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 719 remediation of crude oil-contaminated soil using vermicompost in the niger delta area of nigeria p. o. ehiomogue1*, i. l. ahuchaogu2 and u. i. udoumoh2 1*department of agricultural and bioresources engineering, michael okpara university of agriculture, umudike p. m. b. 7267, umuahia, abia state, nigeria. 2department of agricultural and food engineering, university of uyo, p. m. b 1017, uyo, akwa ibom state, 52003 nigeria *corresponding author's email address: ehiomogue.precious@mouau.edu.ng article information submitted 20 april, 2023 revised 13 nov, 2023 accepted 20 nov, 2023 keywords: anfis ann crude-oil contaminated soil remediation vermicompost abstract vermicompost is the product of the decomposition process using various species of worms, to create a mixture of decomposing vegetable or food waste, bedding materials, and vemicast. this process is called vermicomposting, while the rearing of worms for this purpose is called vermiculture. adsorption of toxic metals has been achieved using vermicompost, but there is dearth of knowledge in adsorption of crude oil using vermicompost. this study brings to knowledge the effectiveness of earthworm waste (vermicompost) use for the remediation of crude oil contaminated soils. the remediation methods adopted were batch and column processes conditions. characterization of the vermicompost and crude oil contaminated soil were performed before and after the soil washing using fourier transform infrared (ftir), scanning electron microscopy (sem), x-ray fluorescence (xrf), x-ray diffraction (xrd) and atomic adsorption spectrometry (aas). the optimization of washing parameters, using response surface methodology (rsm) based on box-behnken design was performed on the data from laboratory experiments. machine learning models [artificial neural network (ann), adaptive neuro fuzzy inference system (anfis). ann and anfis were evaluated on the observed and predicted percentage removal of crude-oil using the coefficient of determination (r2) and mean square error (mse)]. removal efficiency ranged from 29% to 98.9% for batch process remediation and 56% to 92% for column process remediation. optimum values of the experimental factors were absorbent dosage of 34.53 g, adsorbate concentration of 69.11 (g/ml), contact time of 25.96 (min), and ph value of 7.71, for batch and column processes. removal efficiency obtained from the multilevel general factorial design experiment ranged from 56% to 92% for column process remediation and 56% to 92% for column process remediation with the same optimum values of factors. coefficient of determination (r2) for ann was (0.9974) and (0.9852) for batch and column process, respectively. this result show strong correlation between the observed and predicted values for batch and column process, respectively, the coefficient of determination (r2) for rsm was (0.9712) and (0.9614), which also demonstrates agreement between observed and predicted values. for the batch and column processes, the anfis coefficient of determination was (0.7115) and (0.9978), respectively. machine learning models appear to be capable of predicting the removal of crude oil from polluted soil using vermicompost. http://www.azojete.com.ng/ mailto:ehiomogue.precious@mouau.edu.ng mailto:ehiomogue.precious@mouau.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):719-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 720 1.0 introduction the amount of contaminated soil in the world is rising steadily and is getting harder to control (ahmad et al., 2020; akinwumi et al., 2014). one major contributor to soil contamination is the petroleum industry. this contamination occurs through effluent discharges and accidental oil spillages (ordinioha and brisibe, 2013). hutchful (1985) claimed that the funiwa-5 well blowout by texaco in 1980 caused the spilling of around 400,000 barrels of crude oil into the atlantic ocean in the niger delta area of nigeria. damaged oil pipeline carrying crude oil from the idaho oil field to the qua iboe terminal bursted on january 12, 1998, releasing almost the same amount of crude oil into the ocean. this incident happened at iwochang community akwa-ibom state, nigeria. if not cleaned up the right away, spills of petroleum products, particularly crude oil or its derivatives (a liquid hydrocarbon), whether intentional or unintentional, have a harmful impact on the environment. environmentally harmful effects of oil spills have been well documented in the literature (adedokun and ataga, 2006; daka and ekweozor, 2004; ite et al., 2013; jack et al., 2005). the niger delta region of nigeria has an urgent need for the creation and application of a more comprehensive, effective, and environmentally friendly remediation technique. to arrest the threat and prevent the extinction of this natural gift called soil, effective and environmentally friendly remediation techniques must be adopted (ite et al., 2013; jack et al., 2005). in order to provide the basic necessity (food, shelter, water, and energy), soil remediation and restoration have also become critical tasks globally (gighi et al., 2012). phytoremediation techniques have been tried in the past, but the remediation of crude oil contaminated soil using this technique is limited to the depth of the plant roots. vermicompost is a term for an organic fertilizer created by earthworms feeding on waste products, primarily those with a biological origin (yatoo et al., 2021). it is thought to be one of the best nutrient sources for plants and aids in improving the physiochemical characteristics of crops (lim et al., 2015). yatoo et al., (2021) show that vermicompost improves soil health, fertility, mineral content, aeration, and tilt, which decreases the soil's propensity to compress due to the fact that it does not contain hazardous enzymes and is therefore an environmentally friendly organic product (adhikary, 2012). as a result of the soil's rich organic matter content, which encourages nutrient adsorption and root growth, vermicomposting aids in increasing the soil's ability to retain water (mohammadi-moghadam et al., 2022). by encouraging native microorganisms, adding more nutrients and oxygen to the soil, or introducing microbial consortiums that are abundant in the soil, crude oil-contaminated soils can be improved (garcía-díaz et al., 2013; rein et al., 2016). some microorganisms can minimize or remove petroleum compounds by using oil compounds as a source of carbon and energy (amin et al., 2017; sonwani et al., 2018).the use of chemicals and plants (phytoremediation) for soil cleanup are either ineffective or prohibitively expensive. the chemical method can be very expensive while phytoremediation is limited to the root depth of the plant. one of the most affordable approaches for soil remediation is composting, which can boost soil organic matter content and soil fertility. (chen et al., 2015). one of the most affordable solutions for soil bioremediation is composting, the main procedure for stabilizing municipal and agricultural solid waste through the decomposition of biodegradable components by microbial communities or earth worms (chen et al., 2015; dores-silva et al., 2019; kästner and miltner, 2016). vermicompost affects the physical, chemical, and biological characteristics of soil since it contains a variety of microorganisms, including compost (fertilizer) and vermi (earthworms) (thapa et al., 2012; wang et al., 2012). for the first time, davis gave a concise description of the use of biological procedures, which had been known for 80 years (de souza pohren et al., 2019; medina et al., 2018). the worms are extremely tolerant of various contaminants, according to a case study of polycyclic aromatic hydrocarbons removed from soil employing vermiremediation (rajiv et al., 2010). rajiv et al. (2010) discovered that worms like eisenia fetida may take pah chemicals and remove them from contaminated soils by absorbing them into their bodies. sedum alfredii and pig manure vermicompost (pmvc) was employed in a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ehiomogue.precious@mouau.edu.ng ehiomogue et al: remediation of crude oil-contaminated soil using vermicompost in the niger delta area of nigeria. azojete, 19(4):719-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 721 study to remove simultaneous contamination of pahs and cadmium compounds, and the researchers discovered that when the two were used together, the majority of pahs were eliminated (wang et al., 2012). wang et al. (2012) also mentioned that combining pig manure vermicompost with other biological elimination techniques will help to remove contaminants. artificial neural network (ann) is a modeling technique based on the brain’s neural structure and it is generally use used to model and optimize complex processes (agatonovic-kustrin and beresford, 2000; rivera et al., 2010). therefore, ann analyzes complex variables to form a deterministic equation (kose, 2008). artificial neural fuzzy inference system (anfis) combines ann and fuzzy logic techniques to predict the behavior of variables and improve error tolerance, adaptability, and speed of the process (nwosu-obieogu et al., 2022; okolo et al., 2020; roy et a l., 2019). notwithstanding, the main drawback of the ann and anfis approaches has been the difficulty in determining the model's optimal size and its persistence in local minima (onu et al., 2021a, nwosu-obieogu et al., 2022; yilmaz and yuksek, 2009). in another study, asadu et al. (2022) examined the use of ann and anfis to forecast the removal of crude oil from soil and surface water. ani and agu, (2022) reported that anfis and ann have been successfully compared and evaluated as effective modeling techniques for the degradation of crude oil. souza et al., (2018a) compared ann and anfis in modeling nickel adsorption using agro-waste, and the models predicted the process efficiently. okolo et al. (2020) used ann and anfis to estimate cadmium (ii) biosorption using rice straw, and the models performed remarkably well in predicting removal effectiveness. however, there is a paucity of material on soft computing prediction or a comparison of ann and anfis models for foretelling crude oil removal using vermicompost in the literature. there is also sparse literature on the removal of crude oil contaminants using vermicompost. hence, this study bridges the existing knowledge gap in the literature by using ann and anfis in predicting crude oil removal using vermicompost. 2.0 materials and methods 2.1 soil sampling and preparation the soil used for this study was collected from iwochang community in ibeno local government area of akwa-ibom state, nigeria (latitude 4° 33' 54.2"n and longitude 8° 4' 21.3"e) which has a prior history of crude oil contamination. a sampling area of 200 by 200 m2 was randomly selected at surface (0-15cm) and subsurface (15-30cm) depths. the soil samples were placed in paper bags made of aluminum foil, given labels, and transported to a lab for examination. the soil clumps were broken to get homogeneity. the soil was air dried and sieved using <2.0 mm mesh. at the time of sampling, soil ph was monitored, and moisture content in the samples was at the normal threshold for biological elimination procedures (40 to 50% of water holding capacity). according to the american society for testing and materials, an analysis of soil grinding was performed (astm-d-2487) (ryan et al., 2001). vermicompost (adsorbent) characterization the bulk quantity of vermicompost used, was obtained and shipped from agro-chemicals and fertilizer company, london, uk. and it was prepared using laboratory standard following the method adopted by nwosu-obieogu et al. (2022). the prepared vermicompost was characterized using ftir (perkinelmer spectrum one v3.02 ftir spectrometer, india). the surface morphology was determined using scanning electron microscopy sem (hitachi s5500, japan). vermicompost in various concentrations (2, 4, and 6%), each of which already has quality indicators had been identified and specified were added to each sample individually. 2.2. experimental design in this work, the full factorial design procedure in design-expert 13 was used to estimate sample size. testing was done in triplicate, including sampling, to maximize the tests' precision http://www.azojete.com.ng/ mailto:ehiomogue.precious@mouau.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):719-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 722 and accuracy. twenty-nine (29) experimental runs were conducted to examine each independent variable at three different levels 2.3. batch adsorption studies to test the effects of adsorbent dosage, soil solution ratio, ph, and contact time on the elimination of crude oil from contaminated soil samples, soil washing was done in batches (nwosu-obieogu et al., 2022). the contaminated soil sample was thoroughly mixed the prepared vermicompost before placing it on the mechanical shaker. 125 ml conical flask batch tests were performed over rotary shaker at 200 rpm, following the method adopted by adedokun and ataga, 2006 to ensure homogeneous mix. all experiments were carried out for a defined contact period of 25 minutes at 24°c, after which samples were collected and centrifuged for 15 min. at 7000 rpm (gupta et al., 2010; tran et al., 2022). the vermicompost solution's initial ph was altered by adding sodium hydroxide or hydrochloric acid at a concentration of 0.0001 moles per liter. then, after filtration, the supernatants were collected using whitman 41 filter paper. the samples were kept for inductively coupled plasma optical emission spectrometry (icp oes) analysis after being maintained with nitric acid drops. as a standard, washing was done using distilled water by oscillatory shaking using mechanical shaker. equation 1 was used to calculate the response as percentage of crude oil extracted from the washing experiment, as described elsewhere (wuana et al., 2010). percentage crude oil removal (%) = 𝐶1𝑉1 𝐶𝑠𝑀𝑠 𝑥100 (1) where 𝐶1= concentration of crude oil in supernatant (𝑚𝑔/𝑙) 𝐶𝑠= concentration of crude oil in the soil (𝑚𝑔/𝑘𝑔) 𝑉1= the volume of supernatant (𝑙𝑖𝑡𝑟𝑒𝑠) 𝑀𝑠= the dry mass of the soil (𝑘𝑔) the ph measurements were taken for the solutions prior to washing and the supernatants following washing using mechanical shaker for 25 minutes. all experiments were carried out three times to assure accuracy, and the data obtained were given as averages. initial concentration of 0.5 g/ml (co), 50 mg of contaminated soil was thoroughly combined with 100 ml of distilled water. the absorbance and transmittance were determined using visible range spectrophotometer (model 6100, pye unicam ltd., england, uk) and the readings taken and values recorded. about 50 g of contaminated soil was mixed with 50 mg, 100 mg, 150 mg, of vermicompost, respectively, in a 500 ml beaker containing 100 ml of distilled water. beaker was placed in mechanical shaker and shaken at 200 rpm at room temperature of 28oc for 10, 20 and 30 min each. the absorbance and transmittance values were recorded carefully during the experiments. the weight of the adsorbents, and the corresponding equilibrium concentration (ce) were recorded. equation 2 and 3 was used to calculate the amount of crude oil absorbed per unit weight of adsorbent for each batch run and it was stated as reported by uzoije et al. (2011). 𝑞𝑒 = 𝑉(𝐶𝑜−𝐶𝑒) 𝑚 (2) the percentage removal is expressed in equation 3 as: % removal = 100(𝐶𝑜−𝐶𝑒) 𝐶𝑜 (3) where co is the initial concentration and ce is the equilibrium concentration the mean values were calculated and utilized after triple runs (27) for reproducibility errors. hundred (100) gram of dried contaminated soil was packed into a plastic column. the soil bulk file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ehiomogue.precious@mouau.edu.ng ehiomogue et al: remediation of crude oil-contaminated soil using vermicompost in the niger delta area of nigeria. azojete, 19(4):719-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 723 density of 0.8 𝑔/𝑐𝑚3 was achieved by the configuration. the column height was 17.5 cm with the internal diameter of 5 cm. washing fluid were introduced into the soil column at the rate of 5 ml/min.(𝑐𝑚3/𝑚𝑖𝑛). a down-flow mode washing was established by pouring washing solution from the beaker into the soil. after each experiment, the effluent is collected for computing the removal efficiency using equation 3 2.4. ann model development the neural fitting toolbox of matlab r2017b (mathworks inc., natick, ma, usa) was used to create an artificial neural network (ann) model of the adsorption process. an input layer (soil solution ratio, ph, duration, and adsorbent dosage), an output layer (percentage removal efficiency), and a concealed layer make up the architecture in figure 1. the training, validation, and testing data sets were created from the adsorption data set, with respective weights of 70%, 15%, and 15%. 𝑀𝑆𝐸 and 𝑅2 were used as the statistical criterion to evaluate the algorithm's performance in order to choose the best method for the prediction (nwosuobieogu et al., 2022). using four inputs—contact time, ph, adsorbent dosage, and soil solution ratio—the ann-based model was created based on the feed-forward, back propagation (bp) algorithms to estimate the removal efficiency of crude oil from crude oil-contaminated soil. with a ratio of 70%, 15%, and 15%, respectively, the one hundred and fifty (150) data sets utilized for the ann modeling were split at random into three sets (training the network, testing the network, and validating the results). figure 1: artificial neural network (ann) structure 2.5. model development for anfis by taking into account three input factors (soil solution ratio, ph, time, and adsorbent's dose) and one output variable (% removal efficiency prediction for adsorption of crude oil from contaminated soil using vermicompost), a multi-input single-out (miso) fuzzy model was created (percentage removal efficiency). the model's architecture is shown in figure 2, which consists of four layers employing the takagi-sugeno fuzzy system: fuzzification, product, rule, defuzzification, and output summation layers (ausati and amanollahi, 2016; ojediran et al., 2020; rezakazemi et al., 2017). figure 2: anfis structure http://www.azojete.com.ng/ mailto:ehiomogue.precious@mouau.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):719-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 724 2.6. evaluation of the created models' performance the following statistical metrics were used to test the model's ability to predict the adsorption process as shown in equations 4 and 5: (mean square error) 𝑀𝑆𝐸 = 1 p ∑ (dp − op ) 2𝑝 𝑝=1 (4) (coefficient of determination) 𝑅2 = 1 − ∑ (dp−op ) 2𝑝 𝑝=1 ∑ (𝑂𝑝)2𝑝 𝑝=1 (5) 𝑑𝑝 and 𝑂𝑝 represent the desired and calculated outputs, respectively. the effectiveness of the models is shown by how closely the 𝑀𝑆𝐸 value to zero (0) and 𝑅2 value to one (1) (oke et al., 2019). 2.7 data analysis in this experiment, the following variables and levels are taken into account: ph, contact time, soil solution ratio, and adsorbent dosage (table 1). table 1 shows the experimental range and the varied levels dependent variables units low level medium level high level adsorbent dosage mg/g 20 35 50 ph 5 7 9 contact time min 10 20 30 soil solution ratio g/ml 40 70 100 3.0 results and discussion 3.1 fourier transform infrared spectroscopy ftir analysis ft-ir spectrum of the vermicompost before adsorption (figure 3) shows that the broad peak at 3693.8 cm-1 is ascribed to the o-h stretching due to hydrogen bonding of alcohols and phenolic group or component. the peak at 2053.8 cm-1 was attributed to c-h stretching of aliphatic nature-degradation of cellulose, hemicelluloses, lipids, fats functional group or component. the peak at 1423.8 cm-1 was attributed to coo stretch of the carboxylic acids. the peaks at 1625.1 cm-1are associated with the c=c aromatic structure which occurred due to mineralization of protein, cellulose, hemicelluloses and evidence of vermicompost maturity. the intense peak at 793.9 cm-1 is attributed to the c-o stretch due to carbonate/and silica functional group or component. the ft-ir spectrum suggests that the surface functional groups containing o2, which include the carboxyl groups and carbonate/silica groups, with higher activation energy influence the adsorption characteristics of vermicompost due to large surface area and pore space size. the ft-ir spectra of the adsorbent (vermicompost) after adsorption are presented (figure 4), the adsorption of the total petroleum hydrocarbon may have caused the intensity of the broad band at 3697.5 cm-1 for o-h bond vibration stretching, and 3697.5 for c=c stretching and 2926.0 for c-o stretching of alcohol to increase, this proves that the total petroleum hydrocarbon bonded with oxygen-containing functionalities on the adsorbent surface of the vermicompost (gómez-serrano et al., 1999; zhou et al., 2007). the result show that there is a slight displacement of the peak in fourier transform infrared spectroscopy (ft-ir) spectrum of the vermicompost after use. this observation is similar or in agreement with previous studies by alvarez-bernal et al. (2006), which suggested that vermicompost had an effect on dissipation of phenanthrene, anthracene and benzo(a)pyrene in soil which are present in crude oil. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ehiomogue.precious@mouau.edu.ng ehiomogue et al: remediation of crude oil-contaminated soil using vermicompost in the niger delta area of nigeria. azojete, 19(4):719-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 725 figure 3: ftir spectrum for vermicompost before adsorption experiment figure 4: ft-ir spectrum for vermicompost after adsorption experiment 3.2 scanning electron microscopic (sem) analysis sem images are frequently used to examine the morphological traits and surface properties of adsorbent materials (nelly and isacoff, 1982). the scanning electron microscopy (sem) image of vermicompost before and after adsorption experiment are presented in figures 5 and 6. the surface morphology of the vermicompost may be due to the presence of hemicellulose/lignin content of the vermicompost and evidence of large surface for adsorption (medina et al., 2018). the formation of a cluster layers may have resulted from the petroleum hydrocarbon adsorbed on the surface, occupying the cavities of the vermicompost. wang et al. (2014) reported similar surface morphologies as a result of the adsorption of polycyclic aromatic hydrocarbons by graphene and graphene oxide nanosheets. uzoije et al. (2011) also noted a similar surface shape for the adsorption of hydrocarbons from industrial wastewater onto a silica mesoporous substance. figure 5: sem image of vermicompost before adsorption experiment http://www.azojete.com.ng/ mailto:ehiomogue.precious@mouau.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):719-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 726 figure 6: sem image of vermicompost after adsorption experiment 3.3 ann simulations the result of the ann simulation for batch process is shown in table 2. levenberg-marguardt was the best among the ann algorithms, having the smallest mean square error (mse) of 30.538 and the highest coefficient of determination (r2) of 0.9974 for batch process remediation of crude oil contaminated soil. the variation of the mse with the number of training cycles (epochs) and the levenberg-marguardt validation are shown in figure 7. the training process was terminated when the maximum cycles were reached. the efficiency of the predictive ann model result for crude oil adsorption using vermicompost is consistent with studies by onu et al. (2021) and souza et al. (2018), utilizing modified clay and comparing an ann and an anfis, as well as the mechanistic modeling in eriochrome black-t dye adsorption figure 7: mean squared error for levenberg-marguardt model (ann) for crude oil removal during batch process remediation table 2: performance of different ann models in estimating the crude oil removal using vermicompost during batch process s/no. algorithms mse r2 1 levenberg-marguardt 30.538 0.99742 2 bayesian regularization 231.2825 0.08416 3 scaled conjugate gradient 168.4797 0.58726 4 trainrp 105.5405 0.88981 5 traincgf 507.997 0.39210 6 traincgp 202.082 0.43281 7 traincgb 242.8735 5.65x10-5 8 trainbfg 65.0512 0.84293 9 trainoss 712.742 6.8168x10-4 10 traingd 363.1146 0.83610 11 traingdx 121.2558 0.74518 12 traingdm 621.6924 0.11312 0 5 10 15 20 25 30 10 0 10 1 10 2 10 3 10 4 best validation performance is 38.538 at epoch 4 m e a n s q u a re d e rr o r ( m s e ) 32 epochs train validation test best file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ehiomogue.precious@mouau.edu.ng ehiomogue et al: remediation of crude oil-contaminated soil using vermicompost in the niger delta area of nigeria. azojete, 19(4):719-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 727 3.4 artificial neural fuzzy inference system (anfis) root mean squared error (rmse) was the parameter utilized by matlab's artificial neural fuzzy inference system (anfis) function to evaluate the impact of both single and interaction effects on the results of any adsorption tests (turan and ozgonenel, 2013). the degree of predictability and reliability of the model is determined by the rmse number being near to zero (okolo et al., 2020). the effects of a single input variable and many input variables are shown in tables 3, 4, and 5 for the lowest anfis training error. table 3 shows the impact of one input variable minimal anfis training error with ph having the most significant effect with rmse of 17.2100 for training the anfis model and rmse of 15.8563 for testing the anfis model. table 4 show the impact of two inputs variable with contact time and ph having the most significant effect with rmse of 12.7478 for training the anfis model and rmse of 17.7019 for testing the anfis model for the removal crude oil from crude oil contaminated soil using vermicompost during batch process remediation. table 5 shows that ph had the most significant effect with rmse of 17.21 for training the anfis model and rmse of 15.8463 for testing the anfis model for the removal of crude oil from contaminated soil using vermicompost during batch process remediation. on the other hand, contact time/ph/adsorbent dosage impacted most with rmse of 11.2811 for training the anfis model and ph/soil solution ratio/contact time with rmse of 11.6687 for testing the anfis model in table 5. these findings demonstrate that when utilizing vermicompost in a batch method for remediation of crude oil-contaminated soil, the variables ph, contact time, soil solution ratio, and adsorbent dosage have a substantial impact on the removal of crude oil. this finding is consistent with and supported by earlier investigations' assertions by contreras-ramos et al. (2008) and zheng and obbard (2002). table 3: one-input variable of anfis (exhaustive) crude oil removal using vermicompost during batch process remediation. s/no. no. of input input variable training (rmse) testing (rmse) 1 1 contact time 19.0907 18.2413 2 1 ph 17.2100 15.8463 3 1 adsorbent dosage 19.7671 21.0202 4 1 soil solution ratio 20.0510 17.9668 table 4: two-input variable of anfis (exhaustive) crude oil removal using vermicompost during batch process remediation s/no. no. of inputs input variable training (mse) testing (mse) 1 2 contact time/ph 12.7478 17.7019 2 2 contact time/adsorbent dosage 18.3199 20.2402 3 2 contact time/soil solution ratio 17.6990 28.6980 4 2 ph/adsorbent dosage 15.6837 19.7244 5 2 ph/soil solution ratio 16.0167 37.9853 6 2 adsorbent dosage/soil solution ratio 19.5717 18.4994 table 5: three-input variables anfis (exhaustive search) for crude oil removal using vermicompost during batch process remediation s/no. no. of inputs input variables training (mse) testing (mse) 1. 3 contact time/ph/adsorbent dosage 11.2811 60.8264 2. 3 ph/adsorbent dosage/soil solution ratio 14.2298 18.8270 3. 3 ph/soil solution ratio/contact time 11.6687 11.6687 4 3 contact time/soil solution ratio/adsorbent dosage 16.3237 24.3629 http://www.azojete.com.ng/ mailto:ehiomogue.precious@mouau.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):719-732. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 728 3.5 comparative analysis of rsm, ann and anfis modelling of crude oil adsorption using vermicompost (adsorbent) during column and batch process remediation this result in table 6 compared rsm, ann and anfis results to evaluate the model’s predicting ability for crude oil removal from crude oil contaminated soil using statistical metrics such as coefficient of determination (r2) and root mean squared error (rmse) during batch and column process remediation. the correlation coefficient (r2) and the mean squared error (mse) were used to validate the model predictiveness. table 6 summarizes the anfis results of different experimental process. column process gave a prediction of r2 (0.9978) and mse (2.7840) during linear model function and r2 (0.9864) and mse (3.63284) was obtained during constant model function. batch process gave a prediction of r2 (0.7115) and mse (10.1778) during linear model function and r2 (0.7115) and mse (10.1798) was obtained during constant model function. the coefficient of determination (r2) for ann as 0.9974 and 0.9852 for batch and column process respectively, showing the agreement between experimental and predicted results. the coefficient of determination r2 for rsm as 0.9712 and 0.9614 for batch and column precess respectively, which also show an agreement between experimental and predicted results. the coefficient of determination for anfis as 0.7115 and 0.9978 respectively for batch and column process respectively. these results showed the capability of the models in predicting crude oil removal from contaminated soil using vermicompost (adsorbent). however, the coefficient of determination of ann is higher than that of rsm and anfis for batch process; while the coefficient of determination of anfis is higher than that of rsm and ann for the column process remediation. this is similar to the studies of zheng and obbard (2002). table 6: rsm, ann and anfis modelling of crude oil adsorption using vermicompost (adsorbent) during column and batch process remediation s/n models batch process column process r2 rmse r2 rmse 1 rsm 0.9712 2.4791 0.9614 3.2410 2 ann 0.9974 5.5261 0.9852 1.6624 3 anfis 0.7115 3.1903 0.9978 1.6685 3.6 anfis simulation the best anfis prediction for crude oil adsorption using vermicompost was simulated at different input and output from the laboratory experimental data using 4,000 data sets. batch process gave a prediction of 𝑅2 (0.7115) and 𝑀𝑆𝐸 (10.1778) during linear model function and 𝑅2 (0.7115) and 𝑀𝑆𝐸 (10.1798) was obtained during constant model function. the result shows that the anfis linear model is capable of predicting adsorption of crude-oil using vermicompost with high precision. the obtained result is similar to souza et al. (2018). 4.0 conclusion vermicompost's impact on crude-oil polluted soil was studied using a batch experimental process to determine the level of remediation. artificial neural networks (ann) and adaptive neuro-fuzzy inference systems (anfis) could be used to predict the removal of crude oil from polluted soil. influencing parameters which include adsorbent dosage, soil solution ratio, contact time and ph were studied. ann and anfis were evaluated using the coefficient of determination (𝑅2) and mean square error (mse). optimization of the experimental factors carried out using numerical optimization techniques by applying desirability function method produce the highest removal efficiency of 98.9% at absorbent dosage of 34.53 grams, adsorbate concentration of 69.11 (g/ml), contact time of 25.96 (min), and ph value of 7.71 respectively. ann simulation of the batch process show that levenberg-marguardt was the best among the ann algorithms, having the smallest mean square error (mse) of 30.538 and the highest coefficient of determination (r2) of 0.9974 for batch process remediation of crude oil contaminated soil. column process gave a prediction of 𝑅2 (0.9978) and 𝑀𝑆𝐸 (2.7840) during file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ehiomogue.precious@mouau.edu.ng ehiomogue et al: remediation of crude oil-contaminated soil using vermicompost in the niger delta area of nigeria. azojete, 19(4):719-732. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ehiomogue.precious@mouau.edu.ng 729 linear model function and 𝑅2 (0.9864) and 𝑀𝑆𝐸 (3.63284) was obtained during constant model function. batch process gave a prediction of 𝑅2 (0.7115) and 𝑀𝑆𝐸 (10.1778) during linear model function and 𝑅2 (0.7115) and 𝑀𝑆𝐸 (10.1798) was obtained during constant model function.the coefficient of determination (𝑅2) for ann as (0.9974) for batch. showing the agreement between experimental and predicted results. the coefficient of 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ft-ir. carbon, 45(4): 785–796. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ehiomogue.precious@mouau.edu.ng arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):453-464 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 453 geospatial assessment of channel planform and migration in the lower reach of river gongola, adamawa state, nigeria m. ikusemoran1*, a. a. zemba2 and a. l. tukur2 1department of geography, university of maiduguri, maiduguri, borno state, nigeria 2department of geography, modibbo adama university, yola, adamawa state, nigeria *corresponding author's email address: yomiomoolu@gmail.com article information submitted 27 august, 2023 revised 21 february, 2024 accepted 25 february, 2024 keywords: channel migration channel incision sinuosity river gongola river channel abstract channel migration is the process by which stream channels move and shape floodplains through time. the river channel of the lower reach of river gongola between kiri dam and the inlet to river benue has been subjected to channel migration since the impoundment of kiri reservoir in 1984. in this study, temporal changes in river channel parameters such as width, area, perimeter, sinuosity and channel bars, as well as the channel migration of the lower reach of river gongola were assessed. landsat mss image of 1975 (nine years before the commissioning of kiri reservior) and google maps of 1975, 1984, 1989, 1999, 2009 and 2019 were aquired, processed and analyzed for the changes in channel parameters and migration in each of the six selected years. overlay method in arcgis 10.5 sofware and appropriate formula were used to obtain the values of the channel parameters as well as that of channel migration. the result of the study reveals that all the channel parameters have been subjected to changes. the channel width was widest in 1975 when the dam was not constructed. the largest channel bars in 1989 recorded positive impact on the channel width, perimeter, length and sinuosity as all these parameters covered the highest land area in the same year. the sinuosity index ranged from 1.22 to 1.26 which fall within the “sinuous” class and hence, the channel is currently in sinuous stage. areas covered by erosion were more prominent in the river channel than areas with deposition. the initial vertical incision before and shortly after the impoundment of the reservoir has changed to lateral erosion which leads to channel widening. it was recommended that geospatial techniques should be applied in the temporal monitoring of river channels for reliable and accurate data for monitoring of river channels. 1.0 introduction river channel is the physical confine of a river consisting of a bed and river banks (aeda 2014). river channels are important in two major ways; firstly, it is the custodian of ecosystem, that is, the habitat to flora and fauna. secondly, river channels are important to man in several ways; sources of water, food resources (animals and plants) and means of livelihood like fishing and irrigation agriculture. despite the importance of these river channels, and due to constant interference of man through various activities, river channels are frequently modified through dam construction, irrigation, channelization/dredging and flood control strategies. river channels are subjected to land degradation due to river flow and regulations and pressure on land uses, hence, land utilization in the floodplains often leads to decreases in water quality, loss of wildlife habitats, and an increase in severity and frequency of flood losses (shimin et al., 2016, matylda et al., 2020). the lower reach of river gongola between kiri dam and the inlet to river benue is one of the numerous river channels in nigeria which becomes a subject of attraction for study because of the changes in the area since the impoundment of kiri reservoir. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):453-464. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 454 kiri reservoir was constructed by the federal government of nigeria (fgn) under the management of the upper benue river basin developemnt authority (ubrbda). in the report of shallangwa et al. (2014), zira et al. (2015), the construction of kiri reservior started in 1976 and was completed in 1982 mainly to supply water for irrigating over 6.000 hectares of sugarcane estate of the savannah sugar company limited (sscl) which is now known as sscl (dangote groups). as far back as 1984, olofin (1984) has argued that the construction of major dams on savanna streams would usually escalate fluvial processes on the valley side and the downstream. tukur and mubi (2002); tukur et al. (2006) have carried out extensive studies of the changes in the lower reach of the gongola river since the construction of kiri dam. some of their findings revealed that after the kiri dam was constructed, the downstream flood peaks dropped from 1,420 cubic metres per second (50,000 cu ft/s) to 1,256 cubic metres per second (44,400 cu ft/s). secondly, the flows in drier seasons increased from 5.7 cubic meters per second (200 cu ft/s) to 21 cubic meters per second (740 cu ft/s). furthermore, the channel bank full and riverbed widths also reduced by 38.3% and 72.2% respectively while at the downstream were narrow valleys and less sinuous (winding). there were fewer separate channels and reduction in the overall channel width, concave bank erosion and emergence of vegetation in some of the reaches. finally, natural activities like vertical and lateral erosion, flooding and deposition of debris among others also result into modifications of river channels. when river channels are modified, one of the most common outcomes is channel migration. channel migration is the process by which stream channels move and shape floodplains over time (shimozono et al., 2019). the rate and severity of channel migration depends on several factors such as amount and frequency of rainfall, topography, landuse and vegetation cover. channel migration is a threat on land uses by the riparian communities, infrastructure and human livelihood (jatan et al., 2017). other related problems include difficulty in growth and development due to constant loss of properties and cost of flood and erosion control measures (legg and olson, 2014). the effect of changes of the gongola channel due to the construction of the dam on the livelihood of the inhabitants as highlighted by igidi (2020) include loss of residential and agricultural lands to floods and reduction in fishing activities as ‘sedimentation and siltation in the river have shrunk the fishing community of about 120 to just about 40 households, most of them now living in poverty’. the temporal assessment of channel migration areas is important for monitoring the channel at different periods and for documentation of the changes and what cause such changes which can be sources of relevant data for the general management of river channels. jatan et al. (2017) opined that channel migration is an agent of environmental change. in this study, geospatial techniques were integrated with remotely sensed and other geospatial data to assess the channel migration at the lower reach of the gongola river channel before and after the construction of kiri dam. 2. materials and methods 2.1 the study area river gongola is the largest among the right-bank tributaries to river benue. gongola river takes its source from jos plateau and flows north-easternly towards river benue through plateau, bauchi, gombe and adamawa states with an aproximate distance of 602 km (adeniyi and adedeji, 2007). the channel of river gongola between the kiri dam and the confluence to river benue constitute the study area. it lies between latitude 9° 29ʹ and 9° 41ʹ n and longitude 12° 01ʹ and 12° 04ʹ e (fig. 1) with a total length of about 26.9 km the four riparian lgas to this part of the channel are demsa, guyuk, numan and shelleng. the relief of the area is generally low; ranging from 170 to 172 m above sea level (figure. 1). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ikusemoran et al: geospatial assessment of channel planform and migration in the lower reach of river gongola, adamawa state, nigeria. azojete, 20(2):453-464. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 455 figure 1. the study area the soil of the area is mainly gleyic cambisols (ray, 2020) made of loam, sandy loam, silt loam or loamy sand. the major tributary to river gongola in the study area is river wuro yanka with its numerous tributaries. according to ikusemoran (2022), mean annual rainfall of the southern part of the river channel (from the inlet of river benue to about 9.30⁰n is 961.93 mm, while the northern part upwards to the outlet of kiri reservoir (about 9.42⁰n) is 896.91 mm. mean annual temperature within the area ranges to 27.29 to 29.06 ⁰c. the study area falls in the southern guinea savanna zone; characterized by shrubs, scattered trees (daniellia oliveri (most abundant), lophira lanceolata, afzelia) and tall grasses such as andropogon, hypatthenia and pennisetum. the area has few settlements and road network due to its swampy nature. the few communities in the area are bare, bilachi, gelode, ndasso, kapalakan, imburu and sabewa. farming and fishing are the main occupation of the people in the area. 2.2. methods the two data sets that were used for this study are (i) landsat mss image of 05/12/1975 (ii) google earth pro maps of december 1984, 1989, 1999, 2009 and 2019; an average of ten years. 1975 (nine years before the commissioning of the dam) was selected as the base year for the study because the earliest available landsat image of the area was in that year. 1984 was also selected because the dam was commissioned in the year and hence the need to examine the condition of the dam from the onset. the selection of subsequent 10 year period from 1989 to 2019 was because google earth data of the area in the same month (december) was only available during this period. short period of assessment (five year after the dam’s impoundment) was considered because most of the changes that took place were likely to have occurred within the first five years after construction and after which stabilization of the changes might have taken place. 2.2.1 mapping of channel migration the river channel of each selected year in google earth map was digitized as polygon and exported to arcgis 10.5. the “collapse dual lines to centerline” tool of the cartographygeneralization module of the arc toolbox of arcgis 10.7.1 was used to generate the center http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):453-464. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 456 line or the mid channel length of the river channel. the pattern of channel migrated areas was achieved by overlay of channel migration for two-time period of study at a time, that is, 1975/1984-1984/1989, till 1999/2009-2009/2019; a total of four maps were generated. to determine the lateral migration, the centerlines of the river channels for each of the four overlaid maps were used. each polygon of the four maps was transformed into polygon through the “feature to polygon” tool of the feature module in the data management tools of the arc toolbox in arc gis 10.7.1. the attribute tables of the four generated migration polygons, shows the eroded, deposited and the static areas. each of the polygons was calculated using the area calculation tool of arcgis. table 1. methods of generating the channel parameters parameters description methods channel area the total land area of the channels in km2 use of area calculation module of arctool box in arcgis 10.5 to calculate the generated channel of each study years channel perimeter the perimeter of the channel area use of perimeter calculation module of arctool box in arcgis 10.5, to calculate the perimeter of the generated channel area (polygon) of each study years channel length the length of a center line that passes through middle of the channel the center line was generated through the use of collapse lines to centerline of the cartography module of arcgis 10.5 on each of the study years. the length of the center line (channel length) was derived by the use of the length calculation module of arcgis 10.5. average channel width (acw) expressed as a ratio of the channel area to the channel length (kou et al., 2017, ezekiel et al., 2020) channel width = ac/lc where: ac = channel area, and lc = length of the center line (channel length) (kou et al., 2017, ezekiel et al., 2020). changes in channel width the differences between the width in the initial year and that of the latter year subtraction of the width of latter year from the initial year percentage changes in channel width. percentage change in the width between an initial year and the latest year e.g 1975&1984. channel width of the latest year minus the width of the initial year divided by the width of the initial year multiplied by 100. represented by formula [acw2-acw1/acw1*100 (kenton, 2019, ezekiel et al., 2020) sinuosity index the ratio of each stream channel and their corresponding stream channel length it is expressed as: si = ls/lv. where: si = sinuosity index, ls = measured stream length (centerline length) and lv = valley length (straight line measurement of the entire valley) (young et al., 2018, ezekiel et al., 2020) migration area the area of migration polygon was derived from the center lines of two study periods when converted to polygon using arcgis 10.5 the area calculation module of arcgis was used calculate both the area and perimeter of the converted polygon in arcgis 10.5 environment. magnitudes of migration the total land area over which the stream has migrated within a study period it is expressed as a/(0.5*p). where a = the area of the migrated polygon, and p is the corresponding perimeter of the area (kenton, 2019). annual rate of migration annual rate of the channel lateral migration this is expressed as rt/n. where: rt = magnitudes of migration and n is the number of years within the study period. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ikusemoran et al: geospatial assessment of channel planform and migration in the lower reach of river gongola, adamawa state, nigeria. azojete, 20(2):453-464. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 457 source: researchers’ compilation (2023) 2.2.2 determination of other channel planform features other planform features like channel area, width, perimeter, length, average channel width, changes in channel width, percentage change of channel width, sinuosity index, migration area, magnitude of migration and annual rate of migration were determined through their respective formula as shown in table 1. sinousity index table which is the standard for the determination of channel sinuosity is shown in table 2 table 2. sinuosity index table sinuosity index channel class <1.05 straight 1.05 – 1.30 sinuous 1.30 – 1.50 moderate meandering >1.50 meandering form source: yong (2018) in yonnana et al. (2020) 3. results and discussion 3.1 changes in the channel parameters table 3 shows the trends in the changes of the channel parameters from 1975 to 2019. while channel width, perimeter, length, average channel width were reported in km/km2, the area coverage as well as the perimeter of channel bars were measured and reported in km2 and km respectively. percentage change of channel width were in percentages. table 3. changes in the channel parameters from 1975-2019. source: calculated from the generated maps using the calculation module of arcgis software 3.1.1 channel’s width table 3 revealed that before the construction of the reservoir (1975), the width of the channel of river gongola was wide (17.73km2). however, about 30 years after the impoundment of the reservoir, (between 1984 and 1999), the channel’s width was narrower than the initial width of 1975. in the last two decades (from 2009 to 2019), the width of the channel has been wideningwider than that of 1975. this finding is in line with the work of tukur and mubi (2002) on the same lower reach of river gongola that a narrow channel has replaced the large pre-dam channel due to the changes brought about by the regulation of the flow of the river channel. the increase in width at the downstream as observed in 2009, has been attributed to channel floor channel bars the changes in the shapes of the channel floor channel bars result from deposition of sediment (bed load or suspended load) in a high thawed sinuosity. a line was drawn at the center line of each of the years’ channels. the “show elevation profile” module of google earth was used to draw a longitudinal profile of each of the study years which shows the floor of the channel. extraction of river channel from the main river valley using gis technique years channel width (km2) channel perimeter (km2) channel bars (km2)/ perimeter (km) channel length (km) average channel width (km) magnitude of change of channel width (km) percentage change of channel width (%) sinuosity index 1975 17.73 82.90 2.44(18.19) 28.41 0.62 1.25 1984 11.92 86.32 2.80(22.18) 28.22 0.42 -0.02 -32.26 1.24 1989 11.82 89.59 3.11(22.61) 28.62 0.41 -0.01 -2.38 1.26 1999 13.71 79.44 2.14(16.52) 28.33 0.48 0.07 17.07 1.25 2009 19.67 65.77 0.54 (5.46) 28.03 0.70 0.22 45.83 1.23 2019 18.28 67.13 0.52(6.57) 27.84 0.66 -0.04 -5.71 1.22 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):453-464. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 458 the composition of the bed and bank materials of the river channel which could be linked to removal of the riparian vegetation by human activities (fashae and faniran, 2015). further findings by tukur et al. (2006) revealed that regulation of the gongola river flow by damming has indeed affected the resilience of the downstream environment, resulting into changes in the wetlands scenario of the pre-dam periods. negative magnitudes of changes in channel width were recorded in 1984, 1989 and 2020, while 1999 and 2009 had positive changes. the period between 1975 and 1984 recorded the highest negative percentage changes of channel width per annum, while the highest positive change per annum occurred between 1999 and 2009 (table 3). the continuous widening of the channel since 1999 has led to vegetation depletion in the area (ikusemoran 2022) which exposes the channel to both soil erosion and flood hazards. 3.1.2. channel bars fig. 3 shows the nature of the numerous channel bars in each of the study period. the area in kilometers square of the channel bars and their corresponding perimeters are shown in table 3. there were increase in area coverage and perimeter of the channel bars after the dam’s impoundment (from 1984 to 1989) but the channel bars recorded its largest land area coverage and perimeters in 1989 (table 3). the presence of large channel bars during this period (1989) has impacted on the entire perimeter, length and sinuosity of the channel as the three parameters recorded their highest values in 1989 (table 3) this finding agrees with that of hudson, (2007) that channel bars result in a high thawed sinuosity. deposition of sediment (bed load or suspended load) results in channel bed aggradation (vertical adjustment), and the formation of channel bars (lateral adjustment). however, the areas and the perimeters of braided bars were found to drastically decrease from 1989 to 2019 which could be connected to the sinuous formation of the river channel. the transformation of the stream channel from meandering to sinuosity is clear evidence of soil erosion at play, while the sinuous (straight) channel increases water velocity which exposes the channel to flooding. 19841975 1989 1999 2009 2019 figure 2. channel bars along the lower reach of river gongola file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ikusemoran et al: geospatial assessment of channel planform and migration in the lower reach of river gongola, adamawa state, nigeria. azojete, 20(2):453-464. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 459 3.1.3. channel perimeter the impact of channel bars on channel perimeters especially after the dam’s impoundment was identified in table 2. the periods with largest channel bars coincides with the period with the largest channel perimeter. for example, 1989 and 2019 recorded the highest and the least land area of channel bars respectively and which also are the same periods with the highest and the least channel perimeters. this relationship between channel bars and perimeter has been reported by pickup (1976). therefore, reduction in channel perimeter means less channel width which also increases flooding as the channel width might not easily contain stream runoff. 3.1.4. channel widening the average channel width in 1975 (seven (7) years before the completion of the dam) was 0.62 km. however, in 1984 (2 years after the commissioning of the dam), the average width had reduced to 0.42 km, that is, a difference of 0.2 km. the largest channel width during the study period was recorded in the last decades, that is, between 2009 and 2019. mubi (2002) and tukur et al. (2006) have also reported the reduction of the channel width during this period. human activities which might be linked to the reduction include: like irrigation, expansion of human settlements and sand mining are all practiced along the channel especially in places like bare, bilachi, and ndasso as observed during the field work. reduction in stream width leads to flood vulnerability and vertical erosion. for instance, reduction in stream width between 2009 and 2019 as recorded in table 3 might be a catalyst to the frequent flooding in the area especially in 2012, 2015 and 2018 (ikusemoran, 2022). 3.1.5. channel sinuosity. channel sinuosity is the meandering of a stream channel (novica and radislav, 2016, jatan et al., 2017, ezekiel et al., 2020). it is determined through sinuosity index which is derived from the ratio of the respective stream channel length to the valley length (ezekiel et al., 2020). the channel at the downstream of kiri reservoir was found to be initially in a meander form but gradually becomes straightened especially from 2009 (figure 2). the sinuosity index decreased from the pre-dam (1975) to early post-dam era (1984) as shown in table 3. this reduction in sinuosity at this period was also reported by tukur et al. (2002) that the postdam channel became less sinuous. the sinuosity index was highest in 1989 (the year with highest rainfall), when channel perimeter and channel length recorded the highest value table 2). the general sinuosity index was obtained from sinuosity class types as shown in table 2. since the sinuosity index ranged from 1.22 to 1.26 and which all fall within the “sinuous” class (table 2), it was concluded that the channel at the downstream of kiri reservoir has been at sinuous stage. fig. 2 proves the current sinuosity stage of the channel because the channel has gradually moved away from the meandering nature through bend-cutting, disappearance of channel bars among others to slightly straight channel which all results from soil erosion. the reduction of the sinuous index value since 1989 shows that the channel is becoming more sinuous, which has increased flood hazards in the channel area. 3.1.6. channel migration when river channels move or migrate laterally across their floodplains, it is called channel migration. channel migration occurs when a river erodes a bank side and deposits the eroded sediments on the opposite side of the eroded bank. channel migration can also occur as an abrupt shift of the channel to a new location, called an avulsion, which may happen during a single flood event (steve, 2020). table 4 shows the land area, perimeter, total rate as well as the annual rate of channel migration in the lower reach of kiri reservoir. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):453-464. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 460 source: research measurement (2020) reduction in the land area of channel migration was noticed at the initial stage of the impoundment of the reservoir (1984-1999). however, despite the increase in the size of migration area between 1999 and 2009, reduction in the migrated land area was recorded in the last decade (2009-2019) which might be attributed to the decreasing rainfall in the area as represented by the -21.1 mm in the rainfall trend equation in the catchment (ikusemoran, 2022). the 1999-2009 periods had the highest total rate of channel migration with 14.68% per year. channel migration has been said to be influenced by both natural and anthropogenic factors (novica and radislav, 2016, jatan et al., 2017, ezekiel et al., 2020). erosion, deposition and other land areas during the period is shown in figure 3. 1975-1984/1984-1989 1984-1989/1989-1999 1989-1999/1999-2009 1999-2009/2009-2019 figure 3. erosion, deposition and other land areas (1975-2019) fig. 3 and table 5 show the land areas (through overlay) that have been subjected to erosion, deposition and those that are not subjected to either erosion or deposition which are referred to as “other areas” within the study period. table 4. area, perimeter, magnitudes and annual rate of migration (1975-2019) years migration area (km2) perimeter of migration area (km) magnitudes of migration (m) annual rate of migration (%) 1975-1984 2.48 53.13 93.38 10.38 1984-1989 1.39 56.09 49.64 9.93 1989-1999 1.83 53.92 67.78 6.78 1999-2009 2.77 37.68 146.81 14.68 2009-2019 1.55 37.80 81.87 8.19 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ikusemoran et al: geospatial assessment of channel planform and migration in the lower reach of river gongola, adamawa state, nigeria. azojete, 20(2):453-464. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 461 table 5. area of the eroded, deposited and other areas within the channel migrated area years erosion (km2) deposition (km2) others (km2) total (km2) 1975/1984-1984/1989 2.45 0.95 0.47 3.87 1984/1989-1989/1999 1.35 1.18 0.69 3.22 1989/1999-1999/2009 1.80 2.37 0.43 4.6 1999/2009-2009/2019 2.75 0.31 1.26 4.32 total 8.35 4.81 2.85 16.01 table 5 shows that a total land area of 16.01km2 have been subjected to channel migration. of the total land area under channel migration, 8.35 km2 has been subjected to soil erosion, while 4.81 km2 land area have been filled with deposition. the remaining 2.85km2 are static. this result show that erosion is more prominent in the river channel than deposition. serious deposition along the channel in the lower reach is not expected because the river carries minimal debris due to the short distance between kiri dam and the inlet to river benue. the effects of soil erosion on the river channels include undermining houses, roads, and infrastructure, wash away properties, threats to lives and poses risks to public health in close communities like bare, ndasso and bilachi. 3.1.7. channel incision. figure 4 shows the level of incision along the river channel since the impoundment of the reservoir. in 1984 (two years after the impoundment of the reservoir) vertical erosion was prominent especially at the upstream. in 1989, seven (7) years after impoundment, (the year with the highest rainfall (ikusemoran, 2022), the channel floor that was initially incised became widen. in 1999 the channel became deeper again as a result of vertical erosion. however, in subsequent years (2009-2019), the channel was more of widening (lateral erosion) than deepening (vertical erosion). the reasons for the recent channel widening in this part of the river channel cannot be far-fetched; the flow strength at the lower course is generally weak and which also resists incision. furthermore, the slope of the area is gentle or undulating (figure 4) which is more prone to channel widening than incision as also observed by beechie et al. (2008). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):453-464. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 462 1984 1989 1999 2009 2019 figure 4. trends in channel incision from 1984-2019 4. conclusion and recommendations the temporal changes in the channel parameters as well as the changes in channel migration at the lower reach of river gongola have been examined in this paper. all the channel parameters such as channel width, perimeter, length, incision and sinuosity as well as channel bars have been subjected to frequent changes. eroded areas were found to cover larger areas than areas of deposition which suggests the presence of land degradation in the area. based on the generated sinuosity, the area is now prone to lateral than vertical erosion which result into channel widening of the area and which might negatively affect the communities in terms of exposure to environmental hazards such as flood and soil erosion as well as their means of livelihood; farming and fishing. the effect of the channel migration on the inhabitants along the river channel is suggested for further studies. based on the findings of the study, the following recommendations were made; (i) application of geospatial techniques to temporal monitoring of the channel should be imbibed so as to have a reliable and accurate data for frequent monitoring of the river channel in order to detect potential negative effects on man and the environment (ii) creation of awareness on the effect of anthropogenic activities such as farming, grazing, sand mining and other activities that could aggravate land degradation along the river channel and the necessary control measures of each of the activities (iii) river channel control measures such as embankment, restriction of access to susceptible areas among others should be put in place where and when necessary to minimize the rate channel degradation in the area. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ikusemoran et al: geospatial assessment of channel planform and migration in the lower reach of river gongola, adamawa state, nigeria. azojete, 20(2):453-464. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yomiomoolu@gmail.com 463 references adeniyi, fi. and adedeji, aa. 2007. the rotifera fauna of gongola river basin, north east, nigeria. ife journal of science, 9(1): 1-15. agriculture and environmental data achieve aeda. 2014. channels (geography). retrieved on 18/03/2021 from http://www.environmentdata.org/archive/vocabpref:21634 beechie, tj., pollock, mm. and baker, s. 2008. channel incision, evolution and potential recovery in the walla walla and tucannon river basins, northwestern usa. earth surface processes and landforms, 33: 784–800 . ezekiel, y., dzarma, ms. and oliver, k. 2020. assessment of channel planform adjustments in the mubi section of river yedzeram, adamawa state, northeastern nigeria. jalingo journal of social and management sciences, 2(3): 176-193 fashae, oa. and faniran, a. 2015. downstream morphologic characteristics of the alluvial section of lower river ogun, nigeria. journal of environmental geography, 8(1–2): 1–10. hodson, pf. 2007. river channels. encyclopedia of water science. 2nd edition. crc press boca raton, pp. 991-992. ikusemoran, m. 2022. geospatial analysis of hydrological hazards and disaster risk in kiri dam’s catchment, adamawa state, nigeria. ph.d thesis, department of geography, modibbo adama university, yola, adamawa state, nigeria. igidi, t. 2020. shrinking rivers, wilting lives: international center for investigative reporting (icri). retrieved on 27th, august, 2023 from https://www.icirnigeria.org › shrinking-rivers-wilting jatan, d., nibedita, d., istak, a. and moujuri, b. 2017. channel migration and its impact on landuse/landcover using rs and gis on khowai river in tripura, north-east india. egyptian journal of remote sensing and space sciences, 20 (2017): 197-210. kenton, w. 2019. percentage change definition. investopedia. retrieved on june, 15, 2020 from https://www.investopedia.com/terms/p/percentage-change.asp kuo, c., chen, c., chen, s., yang, t. and chen, c. 2017. channel planform dynamic monitoring and channel stability assessment in two sediment-rich rivers in taiwan. water, 9(84): 1-17. doi: 10.3390/w9020084. legg, nt. and olson, pl. 2014. channel migration processes and patterns in western washington: a synthesis for floodplain management and restoration. shore lands and environmental assistance program report. state department of ecology publication.no.14: 06028. https://fortress.wa.gov/ecy/publications/summarypages/1406028.html matylda, w., lukasc, k. and juanna, r. 2020. the influence of river training on the location of erosion and accumulation zones (klodzko county) south west poland. geosciences, 12: 637655 novica, l. and radislav, t. 2016. assessment of bank erosion, accretion and channel shifting using remote sensing and gis: case study – lower course of the bosna river. quaestiones geographicae, 35(1): 81-92. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; 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(2020). paraclete publishers. yola., p. 27. shallangwa, amz., adebayo, aa., zemba, aa. and boniface tj. 2014. effects of kiridam construction on the economy of lower gongola basin of shelleng lga, adamawa state. international journal of economic development research and investment, 5(1): 48-54. shimin, t., weihong, w. and min, z. 2016. fluvial processes of the downstream reaches of the reservoirs in the lower yellow river. journal of the geographical sciences, 26: 1321-1336 shimozono, t., tajima, y., akamatsu, s, matsuba, y. and kawasaki, a. 2019. large scale channel migration in the sittang river estuary. scientific reports 9, no. 9862: 1-9 steve, b. 2020. channel migration hazards. king county department of permitting and environmental review. retrieved on 10th, june 2020 from https://www.kingcounty.gov/services/environment/water-and land/flooding/maps/migration. tockneri, k. and stanford, ja. 2002. riverine flood plains: present state and future trends. environmental conservation, 29(3): 308-330. tukur, al. and mubi, am. 2002. impact of kiri dam on the lower reaches of river gongola, nigeria. geo journal, 56(2): 93-96. tukur, al., musa, aa. and mubi, am. 2006. assessment of changes in landcover along the lower reaches of river gongola, north east nigeria. global journal of environmental sciences, 5(2): 77-81. young, ns., mahammad, in. and lee, w. 2018. experimental study on river meander planform pattern. international journal of engineering and technology, 7(3.11): 214-217. zira, jd, abubakar, ka., badejo, bi. and kefas, m. 2015. assessment of heavy metals in clariasgariepinus organs (gills, liver and muscles) at kiri reservoir, adamawa state, nigeria. iosr journal of agriculture and veterinary science (iosr-javs), 8(5): 79-85 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com https://www.kingcounty.gov/services/environment/water-and%20land/flooding/maps/migration arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):231-240 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 231 modeling of field efficiency of a tine harrow on clay loam soil in abia state s. n. eni-ikeh department of mechanical engineering, michael okpara university of agriculture, umudike, abia state, nigeria *corresponding author's email address: eni-ikeh.stella@mouau.edu.ng article information submitted 5 february, 2024 revised 23 february, 2024 accepted 25 february, 2024 keywords: farmers field efficiency tine harrow clay-loam abia state abstract this study was conducted to model the field efficiency of tine harrow on clay-loam soil in abia state using response surface methodology. this is to assist farmers and operators of the implement to evaluate and probably decide on appropriate harrowing implement depending on the type of soil for their seed bed preparation for efficient production at negligible energy loss. the operational speed (6-8 km/hr.), effective working width (60180 cm) and depth of cut (5-10 cm) were adopted as independent factors for the field efficiency study of the tine harrow. results revealed that the highest field efficiency of 98.40% was recorded when the harrow was operated at the depth of 10cm, speed of 6km/hr. and effective working with of 180cm. the quadratic model was significant (p< 0.05) for the evaluation of field efficiency of the harrow. results revealed that the coefficient of determination, r2 was 0.91, which indicated good relationship among the variables, also an indication that the response (field efficiency) could describe 91% of the overall erraticism within the response. result of simulation achieved revealed that the field efficiency fall within the trial range. the predicted r2 (0.77) was compatible with the adjusted r2 (0.80) meaning that the investigational data fitted well. 1.0 introduction tillage is an alteration of soil structural conditions by mechanical forces such as shearing or compressing, or tearing. kepner et al. (2012) defined tillage as the manipulation of soil in order to develop a desirable soil structure for a seedbed or root bed granular structure is desirable to allow rapid infiltration and good retention of rainfall, to provide adequate air capacity and exchange within the soil, and to minimize resistance to root penetration. it is also carried out to control weeds and remove unwanted plants (thinning). it could help in minimizing soil erosion by following certain practices such as contour tillage and managed plant residues. a good seedbed is generally considered to imply fine particles and greater firmness in the vicinity of seeds. according to k’owino (2010) about 80% of the nigerian population live in rural areas and derive their livelihood from agriculture. even for the urban poor, a majority of them make a living on agricultural related activities. the sector is therefore the main source of national income and employment creation for over 80% of the population and contributes to poverty reduction and food security. small-scale farmers, mainly in the high potential areas, dominate kenya’s agriculture. he further established in his study about the adoption of conservation agriculture that use of quality inputs and equipment such as hybrid seed, fertilizers and pesticides and machinery by the sub-sector is very low. therefore, to increase and or sustain http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):231-240. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 232 productivity in the sub sector, there is need for enhanced efforts to encourage farmers to adopt modern farming practices that entail sustainable land development for food security. it is recognized that application of power saving methods can make effective contributions to economy (sessiz et al., 2010), hence the need to do proper matching of implements and operation at optimal depths and speeds of tillage. several agricultural operations are required for different purposes, namely, harrowing, seeding, cultivating, and spraying. different operations also need special equipment. bell (2016) reported that tine harrow, disc, chisel, rotary, and subsoiler harrows are used as main implements for secondary tillage operation. tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning (gatea, 2013). tillage can be classified as primary and secondary tillage. it is normally conducted when the soil is wet enough to allow plowing and strong enough to give reasonable levels of traction. this can be immediately after the crop harvest or at the beginning of the next wet season. primary tillage consists of cutting, breaking, returning, and popularizing soil by implements (ahaneku et al., 2019). (gatea, 2013) reported that primary tillage operation is used for several objectives. first, it is for cutting soil and seedbed preparation. second, it is to destroy activities and breeding of insects and pests. thirdly, it is to control weeds and fertile soil by converting crop residues. finally, it is to reduce water and wind erosion also to increase soil aeration and the infiltration rate. the greatest amounts of fuel are consumed by tine harrow, disc, and chisel harrows, (khadr, 2018; stajnko et al., 2019). the amount of fuel consumption by tractor engines during tillage operation depends on several factors including harrowing depth, operational speed, etc. (godwin, 2017). there is a liner correlation between the amounts of fuel consumption and harrowing depth, due to increasing soil resistance and volume of soil. similarly, moitzi et al. (2013) observed that the amount of fuel consumption increased significantly when the harrowing depth increased. rashidi et al. (2013) reported that the correlation between depth of harrowing and performance of tractor is non-linear because the mass of soil per cutting unit increases and a higher power is required to pull and operate the implements. in other words, greater amount of power requires if depth of harrowing will increase. for the same purpose, moeinfar et al. (2014) used a chisel harrow for secondary tillage at three levels of harrowing depth and reported that the higher level of depth had the greatest influence on increasing draft force. therefore, the greatest power should be applied to operate primary tillage implements at a deeper level. rashidi et al. (2013) studied effects of tractor forward speed, depth of harrowing, and soil moisture content on the performance of tractor in clay soil texture and have discovered that the performance of tractor significantly increased when tractor forward speed increased. similarly, hunt (2001) indicated that the tine harrow requires higher power because it pulverizes soil to the higher level. increase in agricultural mechanization in the country has caused varied imports of implements and sizes of tractors though they have not been based on data on power requirement that is matched to our soils and field conditions. even after buying these machineries, at farm level implements are paired to tractors without considering the power output from the tractor and file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng eni-ikeh: modeling of field efficiency of a tine harrow on clay loam soil in abia state. azojete, 20(1):231-240. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 233 power demand by implements. farm machinery managers, farmers, consultants and policy makers need to rely on power requirements and performance data while selecting tillage implements for tillage operation. availability of tillage implement power requirements for different soils and conditions, and performance data is important for efficient farm machinery management. therefore, there is need to upgrade the tillage implements for selection and matching of tractors for local soils and conditions that would help farmers and mangers to match tractors and implements carrying out tests for different soils and soil conditions with common tillage implements. the objective of this study is to determine the effect of harrow depth, speed of operation and effective cutting width on field efficiency of a tine harrow. tillage of soil with minimum energy consumption can be achieved by breaking the bonds between soil aggregates with tensile deformations. values of machine capacities are applied in scheduling field operations, its power units and labor as well as to determine implement and machine operating costs. different machines have different field efficiencies, though depending upon the system of operations, soil type conditions and the system of management. this condition improves field efficiency but it is not, of course, a desirable operating condition. the proposed implement includes a tine harrow. thus, the destruction of a pre-stressed soil formation due to tensile stresses caused by the mutual arrangement of working elements and the interconnection of machine operation modes contributes to the reduction of energy consumption. 2.0 research methodology 2.1 study area the study was conducted in ikwuano l.g.a of abia state nigeria, with a population of about 3,920,208 million. it is located within latitude 50 201 and 50 301 n, of equator and longitude 70 401 and 70 501 e of the greenwich meridian and characterized by sub-humid eco-climate. (25003000) mm per annum, average annual temperature of 270c and relative humidity range of 8090% in the wet season (nrcri, 2016). dry season start in november and ends in march while rainy season lasts from april to october. the inhabitants of ikwuano are predominantly farmers. the l.g.a comprises six agricultural zones (ariam, umuariaga, amaoba, amaimeand amawom and oboro). 2.2 experiment site the experiment was performed at michael okpara university of agriculture, umudike, farm site. michael okpara university of agriculture, umudike is located in ikwuano lga of abia state, the soil texture of the site is a clayloam with 65% sand, 19% clay, and 16% silt. the total area of the site is 1800 m2 with 60 m length and 30 m width. 2 . 3 tractor and implement used for the test. a massey ferguson tractor of model mf430e and capacity 55.2 kw, with 3point hitch systems and age of 1year from date of first hand purchase was used for the test. this tractor was selected for the study because it recorded the highest pulverizing efficiency with the tillage implements as compared to tractors that are mostly used in southeast nigeria for field operations (oduma and oluka, 2017). the hitched implements studied is tine harrow. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):231-240. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 234 2.4 determination of soil physical some soil physical characteristics such as moisture contents, bulk density, soil structure, texture, porosity, that influence machinery performances, were determined using the method adopted by oduma et al. (2019). 2.5 experimental procedure the field operation tests were conducted using the methods adopted by ( oduma et al. 2019) in which the harrowing operations were generally performed longitudinally with the implement selected, width at selected forward speeds and cutting depth, the distance travelled and the corresponding time taken to complete the working distance were noted; and the field efficiency, of the implements was determined as stated below. 2.6 determination field efficiency the field efficiency was determined from the expression suggested by kepner et al. (1982) as adopted by oduma et al. (2018). ɛ= 100𝑥𝑇𝑒 𝑇𝑡 (1) where, ε is the field efficiency (%) te = the actual working (productive) time (h) tt = the total working time (h) tt = te +td; and td is the delay or idle time (h). 2.7 experimental design the experimental design adopted in the research work was a three level – three factor full factorial design. the experiment consists of three factors which were varied at three levels of tillage depths which include 5, 8, 10 cm, three levels of effective working widths of 60, 120 and 180 cm and three levels forward speeds (6, 7, and 8 km/hr). central composite response design which gives 17 test runs was performed for each sample using equation 2 (umani et al., 2019). n = 2k + 2k + nc (2) where, n = number of test runs, k = experimental factors and nc = centre point in order to obtain the desired data, the range of values of every one of the 3 factors (k) was evaluated (table 1). working width, operational speed and tillage depth were adopted as independent factors for the field efficiency of the tine harrow. the response selected was the field efficiency, %. four repetitions of the center points were adopted in order to predict a well and concise approximation of errors; and the field experiments were conducted in randomized form. table 1: actual values, codes and levels of the test variables for design of experiments factors symbols codes and levels -1 0 1 working width (m) tillage depth (cm) operational speed (km/hr) a b c 60 5 6 120 8 7 180 10 8 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng eni-ikeh: modeling of field efficiency of a tine harrow on clay loam soil in abia state. azojete, 20(1):231-240. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 235 2.8 response surface methodology (rsm) the design expert of version 11.0 was employed to design the experiment, analyze data obtained, optimize the practical factors and produce models for the estimation of the field efficiency of the tine harrow. the quadratic, cubic, linear and two factorial interaction (2f1) models were designated to analyze the field efficiency of the implement; and the models were fitted to the generated experimental data. data obtained were analyzed using the response surface methodology (rsm) to fit the quadratic polynomial equation gotten from the design expert software as expressed in equation (3) according to chih et al. (2012). ү = β0 + ∑ 𝛽𝑖𝑋𝑖2 𝑖=1 + ∑ 𝛽𝑖𝑖𝑋𝑖22 𝑖=1 + ∑ ∑ 𝛽𝑖𝑗𝑋𝑖𝑋𝑗2 𝑗=𝑖+1 2 𝑖=1 (3) where: ү = response; β0 = constant term; ∑ 𝛽𝑖2 𝑖=1 = summation of coefficient of linear terms; ∑ 𝛽𝑖𝑖2 𝑖=1 = summation of quadratic terms; ∑ ∑ 𝛽𝑖𝑗2 𝑗=𝑖+1 2 𝑖=1 = summation of coefficient of interaction terms; 𝑋𝑖𝑋𝑗 = independent variables. also, the multiple regressions were adopted to fit the coefficient of the polynomial model to enable the response variables be correlated with the independent variables. the reliability of fit of the model, the discrete and interaction effect of the tillage parameters (effective working width, operational speed and depth of tillage) on the responses (field efficiency) of the implement were evaluated using analysis of variance (anova). data attained were also subjected to statistical analysis to obtain the effects of the effective working width, operational speed and tilling depth and their interactions on the field efficiency of the implement at ∝ = 0.05 using minitab 17.0. 3.0 results and discussion 3.1 field efficiency of the tine harrow table 2 presents the randomized design layout of three levels –three factors full factorial composite design of experiment with actual and predicted values of energy requirements of tine harrow. this table presents the relations between the trial factors (working width, operational speeds and harrowing depths) with the field efficiency of the harrow. the values of actual field efficiencies achieved in the course of the tillage operation vary from 91.70 – 98.50% for the range of operational speed (6 – 8 kmh-1), harrowing depth between 10 – 30cm and working width range from 60 – 180 cm. results specified that the highest field efficiency of 98.50% was obtained when the harrow was operated at the cutting depth of 20cm under operational speed of 7 kmh-1 and working width of 120 cm. while the least field efficiency of 91.70 % was achieved at cutting depth of 30cm under working width of 180 cm and operational speed of 7 kmh-1. it was frequently discovered that at different operational speeds and effective working width, the field efficiencies increase with the increase in harrowing depth and increases to peak point of 98.50% at operational speed of 7 kmh-1 and at depth of 20cm under effective working width of 120 cm. the field efficiency of the implement decreases by 6.15% when harrowing at depth of 10 cm and 3.05% at depth of 30 cm irrespective of the effective width of cut and operational speed. this is in line with the observations of oduma et al (2022). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):231-240. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 236 table 2: randomized design layout of three levels –three factors full factorial composite design of experiment with actual and predicted values of field efficiency of tine harrow run order coded factors actual factors field efficiency, % a b c harrowing depth (cm) effective working width (cm) operati onal speed (km/hr) actual values of field efficiency predicted values of field efficiency 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 -1 1 -1 0 0 0 0 1 0 1 0 1 0 -1 -1 0 0 0 1 1 -1 0 0 1 1 0 0 -1 0 1 -1 0 0 0 -1 0 0 1 0 0 1 0 0 -1 -1 1 -1 0 1 0 0 5 10 10 5 5 10 8 10 8 5 8 10 10 8 8 8 5 60 180 60 120 120 120 120 180 120 180 120 180 120 60 60 120 120 7 7 7 6 6 6 7 6 8 8 8 6 6 6 7 6 7 90.95 97.95 98.25 97.90 97.90 98.20 98.11 98.40 97.84 96.15 98.11 97.90 97.90 97.80 98.11 97.80 96.50 89.22 91.70 92.40 90.30 90.30 92.20 88.98 87.40 93.23 85.72 87.93 91.48 90.30 87.43 88.11 88.43 91.35 figure 1 is the response surface plot of harrowing depth, effective working width and operational speed against field efficiency of tine harrow showing the relationship between the factors and the response. results of this figure showed that the highest field efficiency of 98.50% was observed at speed of 7 kmh-1 at harrowing depth of 20 cm and effective working width of 120 cm. the highest field efficiency achieved at operational speed of 7 kmh-1 is slightly higher than the operational speed of harrow and was attributed to the lower tractive and draft force associated with secondary tillage operation after the soil has been acted upon by the plough which is related with low working speed enabling the implement to pierce deep and collapse the resistance force offered by the soil to implement penetration. figure 1. response surface plot of harrowing depth, effective working width and operational speed against field efficiency of tine harrow. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng eni-ikeh: modeling of field efficiency of a tine harrow on clay loam soil in abia state. azojete, 20(1):231-240. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 237 3.2 model assessment of tine harrow efficiency the field efficiency of the tine harrow in clay -loam soil depends on the results illuminating the significant difference for combination of the speed, effective working width and cutting depth of the harrow. the model coefficient, effect, contribution, test of lack of-fit and the significance of the factors and their interactions on the field efficiency were evaluated according to oduma et al. (2022), umani et al. (2019) and fakayode et al. (2016). a quadratic model was significant for the response (table 4), thus, p ˂ 0.05; indicating that the significant model term was achieved at 95% significance level. the quadratic model equation obtained to predict the field efficiency in regard to the independent variables or operating factors (speed, effective working width and harrowing depth) is as stated in equation 4. fe = 132.20 – 0.85a – 0.17b – 23.62c + 0.006ab + 0.1ac + 0.10bc – 0.01a2 0.0001b2 + 1.63c (4) where fe = field efficiency, % a = harrowing depth of the harrow, cm b = effective working width of the disc harrow, cm c = operational speed, kmh-1 the quadratic model as gotten in this research work is in proportion to the findings of oduma et al. (2019) in their study of the development of empirical regression equations for predicting the performances of disc plough and harrow in clay-loam soil and oduma et al. (2022). the pvalue (0.0055) of the mode as presented in table 5 is less than the designated 𝛼level of 0.05 indicating that the model is significant. thus, the interactions of the operating factors (speed, effective working width and harrowing depth) have significant effects on the field efficiency of the implement. hence, the model term p-values of 0.0003, 0.0515 and 0.0072 which are less than the selected 𝛼level of 0.05 stipulate that the model terms are significant. thus, ab (interaction of a-harrowing depth and b-effective working width), ac (interaction of aharrowing depth and c-operational speed) and c² are significant model terms as displayed in table 3. this result agrees with the judgments of ajav and adewoyin (2012). nevertheless, it is not statistically consistent with the results of saeed et al. (2017) in their research of performance of tractor and tillage implements in clay soil wherein the p–value of the field efficiency attained is 0.00 at p ≤ 0.05 and could be credited to the variances in the soil and/or ecological/environmental conditions of diverse study regions as indicated by bako et al. (2021). finally, the lack of fit f-value of 0.1114 (table 5) implies that the lack of fit is not significant relative to the pure error. however, there is a 94.89% chance that a lack of fit f-value this large could occur due to noise. non-significant lack of fit according to umani et al. (2019) is good since the model is required to fit. table 4: anova of model summery statistics source sequential p-value lack of fit pvalue adjusted r² predicted r² linear 0.9598 0.0815 0.6272 -0.9574 2fi 0.0094 0.2649 0.4950 -0.3112 quadratic 0.0334 0.9544 0.7331 0.7164 suggested cubic 0.8590 0.6899 aliased http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):231-240. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 238 table 5. anova of response surface quadratic model for field efficiency of tine harrow source sum of squares df mean square f-value p-value model 54.01 9 6.00 8.25 0.0055* a-tillage depth 0.0595 1 0.0595 0.0818 0.7831ns b-width 1.35 1 1.35 1.86 0.2148ns c-speed 1.64 1 1.64 2.25 0.1771ns ab 31.98 1 31.98 43.97 0.0003* ac 4.00 1 4.00 5.50 0.0515* bc 1.42 1 1.42 1.95 0.2056ns a² 3.50 1 3.50 4.81 0.0643 b² 0.5663 1 0.5663 0.7786 0.4068ns c² 10.19 1 10.19 14.01 0.0072* residual 5.09 7 0.7273 lack of fit 0.3927 3 0.1309 0.1114 0.9489ns pure error 4.70 4 1.17 cor total 59.10 16 *significant; ns= not significant 3.3 validation of the model of the field efficiency of the harrow results of the validation of the model equation are shown in table 6. according to the results, the model is significant. the coefficient of determination, r2 (0.9139) shows awesome alliances amid the independent variables, which means that the response model can elucidate 91.39 % of the full changeability in the response (oduma et al., 2022; umani et al., 2019). results of the simulation (table 6) of the quadratic model achieved in the study indicated that the field efficiency fall within the experimental array. the predicted r² (0.7695) is reliable with the adjusted r² (0.8031); thus, the difference is less than 0.2 indicating that the trial data fitted very well, as posited by kothari (2014). the adjusted r2 obtained is compatible with the r2 (0.9615) as obtained by oduma et al. (2020). the adequacy precision (10.375) ratio obtained is greater than 4 is appropriate, indicating an acceptable signal and that the model equation might be espoused to navigate the design space. table 6. coefficient of determination, r² for validation of model term 4.0 conclusion the study was carried out to obtain data on the effect of harrowing depth, speed of operation and effective cutting width on field efficiency of a tine harrow on clay loam soil in abia state, for suitable selection, operation and matching of the field machineries. from the findings in the research work, the following conclusions can be made about the study: results obtained in this study will aid in proper selection, management and operation of the farm machinery based on soil type/condition and operational speed for better performance. finally, owing to differences std. dev. 0.8528 r² 0.9139 mean 96.19 adjusted r² 0.8031 c.v. % 0.8867 predicted r² 0.7695 adeq precision 10.3749 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng eni-ikeh: modeling of field efficiency of a tine harrow on clay loam soil in abia state. azojete, 20(1):231-240. issn 1596-2490; eissn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 239 in soil type/conditions among different agricultural areas; it is therefore recommended that studies of this kind should be carried out in every agricultural zone to provide data on machine/implement performances based on soil types for increased production. references ahaneku, ie. 2019. simple and cost-effective method for fuel consumption measurements of agricultural machinery. agronomy research, 10: 97-107. ajav, ea. and adewoyin, ao. 2012. effect of ploughing depth and speed on tractor fuel consumption in a sandy-loam soil of oyo state-nigeria. journal of agricultural engineering and technology, 20(2):1 – 10. bako t., mamai, ea. and istifanus, ab. 2021. determination of the effects of tillage on the productivity of a sandy loam soil using soil productivity models. research in agricultural engineering, 67: 108–115. bell, b. 2016. farm machinery. 4th ed. farming press books and videos miller freeman professional ltd., united kingdom. chih, wt., lee, it. and chung, hw. 2012. optimization of multiple responses using data envelopment analysis and response methodology, tamkang. journal of science and engineering. 13(2), 197-203. fakayode, oa., ajav, ea. and akinoso, a. 2016. effect of processing factors on the quality of mechanically expressed moringa (moringa oliefera) oil: a response surface approach. journal of food process engineering, 40(4): e12518. gatea, aa. 2013. influence of tillage pattern and forward speed of the tractor in the efficiency tillage. international journal of agricultural science research, 3(4): 109-119. godwin, rj. 2017. a review of the effect of implement geometry on soil failure and implement forces. soil tillage research, 97(2): 331-340. hunt, d. 2011. farm power and machinery management. lowa state university press, usa. kareem, ik. and sven, p. 2019. effect of ploughing depth, tractor forward speed, and plough types on the fuel consumption and tractor performance. polytechnic journal, 9(1): 43-49, doi: 10.25156/ptj.v9n1y2019.pp43-49. kepner, r 2012. crop planting. principles of farm machinery. 3rd edition. avi publishing company, inc., westport, connecticut. usa. p, 209-236. khadr, ka. 2018. effect of some primary tillage implement on soil pulverization and specific energy. journal of agricultural engineering, 25(3): 731-745. kothari, cr. 2014. research methodology. methods and techniques. second revised edition. new age international publishers. new delhi., pp. 140 – 145. k’owino, ir. 2010. soil quality: a concept, definition, and framework for evaluation (a guest editorial). soil science society of america journal, 61(1): 4-10. moeinfar, a., mousavi-seyedi, sr. and kalantari, d. 2014. influence of tillage depth, penetration angle and forward speed on the soil/ thin-blade interaction force. agricultural engineering international, the cigr journal, 16(1): 69-74. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):231-240. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: eni-ikeh.stella@mouau.edu.ng 240 moitzi, g., szalay, t., schüller, m., wagentrist, h., refenner, k., weingartmann, h., liebhard, p., boxberger, j. and gronauer, a. 2013. effects of tillage systems and mechanization on work time, fuel and energy consumption for cereal cropping in austria. agricultural engineering international journal, 15: 94–101. oduma, o. and oluka, si. 2017. performance characteristics of agricultural field machineries in southeast nigeria. journal of experimental research, 5(1): 57–71. oduma, o., ehiomogue, p., okeke, cg., orji, fn., ugwu, ec., umunna, mf. and nwosuobieogu, k. 2022. modeling and optimization of energy requirements of disc plough operation on loamy-sand soil in south-east nigeria using response surface methodology. elsevier, scientific african, 17: e01325. oduma o., okeke, cg., eje, be., inekwe, g. and nnadi, dc. 2020. simple regression relationships for assessing the performances of selected tillage implements in south-east, nigeria. poljoprivredna tehnika, 45: 51–64. oduma, o., oluka, si. and eze, pc. 2018. effect of soil physical properties on performance of agricultural field machinery in south eastern nigeria. agricultural engineering international: cigr journal, 20(1): 25-31. oduma, o., oluka, si., edeh, jc. and ehiomogue, p. 2019. development of empirical regression equations for predicting the performances of disc plough and harrow in clay-loam soil. agricultural engineering international: cigr journal, 21(3): 18-25. rashidi, m. 2013. effect of soil moisture content, tillage depth and operation speed on draft force of tine harrow plow. middle east journal of scientific research, 16(2): 245-249. saeed, r., mohammad, a. and javad, j. 2017. performance of tractor and tillage implements in clay soil, journal of saudi society of agricultural science, 16: 154–162. umani, kc., fakayode, oa., ituen, euu. and okokon, fb. 2019. development and testing of an automated contact plate unit for a cassava grater. computers and electronics in agriculture, 157: 530–540. yahya, h. 2016. effect of a new combined implement for reducing secondary tillage operation. international journal of agriculture and biology, 8(6): 724-727. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):423-436 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 423 original research article investigation of fresh and hardened behaviour of nanostructured concrete c. d. nwa-david department of civil engineering, michael okpara university of agriculture, umudike, abia state, nigeria *corresponding author’s email address: nwadavid.chidobere@mouau.edu.ng 1.0 introduction the increasing global consumption of cement in concrete production is extremely high due to expanded infrastructural development in recent times (thomas, 2018; zareei, 2017; attah et al., 2020). minimizing the cost of cement production including its carbon dioxide (co2) emission to the atmosphere (khan et al., 2012; johnson et al., 2013; mehta, 2001), reducing the cost of housing and the growing demand for environmental preservation, has intensified the efforts of researchers at seeking and developing affordable and available alternative local materials that could be employed for sustainable construction (awodiji et al., 2018; onwuka et al., 2013, nwa-david et al., 2023a) in order to provide sustainable and renewable materials, agro-industrial wastes also known as supplementary-cementitious-materials (scms) such as rice husk ash, sawdust ash, periwinkle shell ash, corncob ash, cassava peel ash, oyster shell ash, have been extensively applied to partly and wholly replace cement in concrete production (kamau et al., 2016; ogbonna et al., 2020; george et al., 2019; olutoge et al., 2012). article information abstract the need for sustainable environment has triggered the deployment of supplementary cementitious materials (scms) which reduces the effect of carbon dioxide (co2) emission emanating from cement production, as well as the cost implications. cassava peel ash was adopted as a scm but in a nanostructured form to investigate the properties of concrete. the experimental outcome of the compressive and splitting tensile strengths of nanosized cassava peel ash (ncpa)-cement concrete was presented in this paper. materials employed for the concrete production were ordinary portland cement, ncpa, river sand, granite chippings, and water. the compressive strength was obtained using 150 x 150 x 150 mm concrete cube specimens, while 150 x 300 mm cylindrical concrete specimens were used to assess the splitting tensile strength; both measured at 7, 14, 28, 56, 90 and 150 days of curing. the mixes were prepared for varying water cement ratios of 1.5% ncpa replacement intervals in a mix ratio of 1:1.5:3. the study revealed that the slump values increased as percentage of ncpa increased. the results showed that at a water-cement ratio of 0.75 and 19.5% ncpa replacement, the concrete attains excellent compressive strengths of 18.70 n/mm2, 22.10 n/mm2, 24.20 n/mm2, 30.10 n/mm2, 33.30 n/mm2, and 36.90 n/mm2 at 7, 14, 28, 56, 90 and 150 days respectively with 5.96 n/mm2, 7.04 n/mm2, 7.71 n/mm2, 9.60 n/mm2, 10.61 n/mm2, and 11.75 n/mm2 for splitting tensile strength. the results confirm the suitability and uniqueness of nanosization as adoption of ncpa enhances the properties of concrete in both the plastic and hardened states. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 15 april, 2023 revised 13 july, 2023 accepted 20 july, 2023 keywords: nanostructured cassava peel ash (ncpa) concrete workability setting time compressive strength, splitting tensile strength http://www.azojete.com.ng/ mailto:nwadavid.chidobere@mouau.edu.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 424 one of the many alternative materials for cement in concrete production is the cassava peel asha by-product of cassava processing. cassava peel ash has been applied in (olonade et al., 2014; raheem et al., 2015; ofuyatan et al., 2018; ettu et al., 2013, abdulwahab and uche, 2021; salau et al., 2012) but the effect of its nanostructured status on compressive and splitting tensile strength of concrete which was not considered in previous studies distinguishes this study. nanostructured materials incorporated in cement-composites improves its compressive and flexural strength at early age due to its high surface-to-volume ratio (prasad, 2017; sanchez and sobolev, 2010) eco-friendly concrete is produced with the use of nanosized-cassava-peel-ash (ncpa). the quality of concrete structures is often captured by its compressive strength but in most applications such as in airfield slabs and highway pavements, knowing the tensile strength of concrete is essential because their design principle is based on flexural strength of concrete. estimating the load under which cracking develops magnifies the usefulness of the knowledge of tensile strength (neville, 2011). apart from the study carried out by nwa-david et al., (2023b), the theory of nanosization is scarce in literatures on concrete production. antecedent authors did not consider tensile strength in their study. this gap in literature is addressed in this study. the aim of this work is to determine the strength relations between the splitting tensile strength and compressive strength of concrete produced with ncpa. the fresh properties of ncpa-cement concrete were obtained and the relationship between the spitting tensile and compressive strengths from the experimental data, is predicted. 2. materials and methods 2.1 materials the materials used for this study include, ordinary portland cement, nanostructured cassava peel ash (ncpa), water, sharp-river sand, and granite chippings. the bua brand of ordinary portland cement that conformed to the requirements of bs 12 was used. it was purchased at the local market in owerri municipal area of imo state. cassava peels as shown in figure 1, were collected from cassava peels dump site at a garri processing centre in owerri district of imo state. the cassava peels were gathered and dried under the sun. the cassava peel was burnt in a kiln at a temperature of about 650 oc in 60 minutes in a control incineration set-up to prevent pollution. the burnt material was collected and sieved thoroughly with a nano-sieve of size 200nm, to produce fine nanostructured ash as shown in figure 2. a clean drinking water was obtained from a borehole at the laboratory. the water was clean, fresh, free from dirt, unwanted chemicals or rubbish that may affect the desired quality of concrete, and it conformed to the requirements of bs 3140. the sand was obtained from imo river, imo state of nigeria. it was sieved through 10mm british standard test sieve to remove cobbles to satisfy the requirements of bs 882. the crushed granite file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng nwa david: investigation of fresh and hardened behaviour of nanostructured concrete. azojete, 19(3):423-436. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 425 was sourced from the quarry site at ishiagu, ebonyi state, nigeria. the maximum size of aggregate used for this work is 20mm diameter. it conformed to the requirements of bs 882. figure 1. cassava peels figure 2. nanostructured cassava peel ash 2.2 methods a mix proportion of 1:1.5:3 (blended cement: sand: granite) was used for the concrete. batching was done by weight and varying water-binder ratios. mixing was done manually on a smooth concrete pavement. the ash was first thoroughly homogenized with opc at the desired proportion and the homogeneous blend was then mixed with the fine-coarse aggregate mix, also at the required proportion. water was then added gradually and the entire concrete heap was mixed thoroughly to ensure uniformity. the mix proportion used for the study is presented in table 1. after mixing properly to a consistent state, the concrete was cast into the moulds and de-moulded after 24hrs. the cubes were cured for 7, 14. 28, 56, 90 and 150 days after which they were crushed in their saturated surface dry (ssd) state. in accordance to the provisions of bs en 12390-3 (2009), the compressive strengths of the concrete samples were determined using 150 x 150 x 150 mm cube specimens. the compressive strength test was done by placing the cubes on a crushing machine and recording the crushing load. avery denison compression machine of 2000 kn load-capacity, was adopted, at a constant rate of 15 kn/s. at each testing age, three specimens were tested, and the average used to evaluate the mean strength using the equation below; 𝑓𝑐 = average failure load (n) cross − sectional area of concrete cube(𝑚𝑚2) (1) to determine the splitting tensile strength of concrete samples, concrete cylinder specimens with dimensions 150 x 300 mm were used in accordance to the provision of bs 12390-6 (2009). the cylindrical concrete specimen having 12 inches’ height and 6inches diameter, were axially loaded on the crushing device and the crushing load was recorded when the specimen collapsed. in order to obtain the splitting tensile strength (ts), the expression in equation 2 was used. 𝑆𝑝𝑖𝑙𝑖𝑡𝑡𝑖𝑛𝑔 𝑇𝑒𝑛𝑠𝑖𝑙𝑒 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑓𝑡 = 2𝑃 𝜋𝑙𝑑 (2) where p = maximum applied load (newton) l = length of specimen (mm) d = diameter of specimen (mm) http://www.azojete.com.ng/ mailto:nwadavid.chidobere@mouau.edu.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 426 table 1. mix proportion of constituent materials for the investigation mixture label mix ratios water (kg) cement (kg) ncpa (kg) sand (kg) granite (kg) a1 1.000: 0.000: 1.5:3 15.25 25.42 0.00 38.38 76.09 a2 0.985: 0.015: 1.5:3 15.25 25.04 0.38 38.38 76.09 a3 0.970: 0.030: 1.5:3 15.25 24.66 0.76 38.38 76.09 a4 0.955: 0.045: 1.5:3 15.25 24.28 1.14 38.38 76.09 a5 0.940: 0.060: 1.5:3 15.25 23.89 1.53 38.38 76.09 a6 0.925: 0.075: 1.5:3 15.25 23.51 1.91 38.38 76.09 a7 0.910: 0.090: 1.5:3 15.25 23.13 2.29 38.38 76.09 a8 0.895: 0.105: 1.5:3 15.25 22.75 2.67 38.38 76.09 a9 0.880: 0120: 1.5:3 15.25 22.37 3.05 38.38 76.09 a10 0.865: 0.135: 1.5:3 15.25 21.99 3.43 38.38 76.09 a11 0.850: 0.150: 1.5:3 15.25 21.61 3.81 38.38 76.09 a12 0.835: 0.165: 1.5:3 15.25 21.23 4.19 38.38 76.09 a13 0.820: 0.180: 1.5:3 15.25 20.84 4.58 38.38 76.09 a14 0.805: 0.195: 1.5:3 15.25 20.46 4.96 38.38 76.09 a15 0.790: 0.210: 1.5:3 15.25 20.08 5.34 38.38 76.09 a16 0.775: 0.225: 1.5:3 15.25 19.70 5.72 38.38 76.09 a17 0.760: 0.240: 1.5:3 15.25 19.32 6.10 38.38 76.09 a18 0.745: 0.255: 1.5:3 15.25 18.94 6.48 38.38 76.09 a19 0.730: 0.270: 1.5:3 15.25 18.56 6.86 38.38 76.09 a20 0.715: 0.285: 1.5:3 15.25 18.18 7.24 38.38 76.09 a21 0.700: 0.300: 1.5:3 15.25 17.79 7.63 38.38 76.09 a22 0.685: 0.315: 1.5:3 15.25 17.41 8.01 38.38 76.09 a23 0.670: 0.330: 1.5:3 15.25 17.03 8.39 38.38 76.09 a24 0.655: 0.345: 1.5:3 15.25 16.65 8.77 38.38 76.09 a25 0.640: 0.360: 1.5:3 15.25 16.27 9.15 38.38 76.09 a26 0.625: 0.375: 1.5:3 15.25 15.89 9.53 38.38 76.09 a27 0.610: 0.390: 1.5:3 15.25 15.51 9.91 38.38 76.09 a28 0.595: 0.405: 1.5:3 15.25 15.12 10.30 38.38 76.09 a29 0.580: 0.420: 1.5:3 15.25 14.74 10.68 38.38 76.09 a30 0.565: 0.435: 1.5:3 15.25 14.36 11.06 38.38 76.09 a31 0.550: 0.450: 1.5:3 15.25 13.98 11.44 38.38 76.09 a32 0.535: 0.465: 1.5:3 15.25 13.60 11.82 38.38 76.09 a33 0.520:0.480: 1.5:3 15.25 13.22 12.20 38.38 76.09 a34 0.505: 0.495: 1.5:3 15.25 12.84 12.58 38.38 76.09 a35 0.490: 0.510: 1.5:3 15.25 12.46 12.96 38.38 76.09 a36 0.475: 0.525: 1.5:3 15.25 12.07 13.35 38.38 76.09 a37 0.460: 0.540: 1.5:3 15.25 11.69 13.73 38.38 76.09 a38 0.445: 0.555: 1.5:3 15.25 11.31 14.11 38.38 76.09 a39 0.430: 0.570: 1.5:3 15.25 10.93 14.49 38.38 76.09 a40 0.415: 0.585: 1.5:3 15.25 10.55 14.87 38.38 76.09 a41 0.400: 0.600: 1.5:3 15.25 10.17 15.25 38.38 76.09 a42 0.385: 0.615: 1.5:3 15.25 9.79 15.63 38.38 76.09 a43 0.370: 0.630: 1.5:3 15.25 9.41 16.01 38.38 76.09 a44 0.355: 0.645: 1.5:3 15.25 9.02 16.40 38.38 76.09 a45 0.340: 0.660: 1.5:3 15.25 8.64 16.78 38.38 76.09 a46 0.325: 0.675: 1.5:3 15.25 8.26 17.16 38.38 76.09 a47 0.310: 0.690: 1.5:3 15.25 7.88 17.54 38.38 76.09 a48 0.295: 0.705: 1.5:3 15.25 7.50 17.92 38.38 76.09 a49 0.280: 0.720: 1.5:3 15.25 7.12 18.30 38.38 76.09 a50 0.265: 0.735: 1.5:3 15.25 6.74 18.68 38.38 76.09 a51 0.250: 0.750: 1.5:3 15.25 6.36 19.07 38.38 76.09 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng nwa david: investigation of fresh and hardened behaviour of nanostructured concrete. azojete, 19(3):423-436. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 427 3. results and discussion 3.1 physical and chemical evaluation of constituent materials the chemical composition and physical characteristics of the ncpa was determined and presented in table 2. from this table, it is observed that ncpa contains 61.70% sio2, 12.50% al2o3 and 2.52% fe2o3. this gives 76.72% of sio2+ al2o3+fe2o3 which is in line with astm c 618 requirement of 70% minimum for pozzolanas. thus, ncpa meets the requirement for a pozzolana. the loss of ignition (loi) of 5.07 and so3 of 2.10 all fall within agreeable limits of (astm c 618, 2008). ncpa has a lower specific gravity of 2.11 when compared with the specific gravity of cement (3.04). this implies that partially replacing opc with ncpa will result to reduced weight of concrete members. the nanostructured cassava peel ash is 1.4 times lighter than cement. the river sand has physical properties of 1650 kg/m3, 2.65 and 2.92 corresponding to its values of uncompacted bulk density, specific gravity and fineness modulus respectively. the river sand has coefficient of uniformity and coefficient of curvature values of 2.70 and 0.96 respectively obtained from table 3. the granite has physical properties of 1520 kg/m3, 2.75 and 3.28 corresponding to its values of uncompacted bulk density, specific gravity and fineness modulus respectively. the coarse aggregate has coefficient of uniformity and coefficient of curvature values of 1.83 and 1.04 respectively obtained from table 4. the average specific gravity of majority of natural aggregate have been found to lie between 2.5 and 2.8. (gambhir, 2013). the coefficient of curvature for both aggregates were confirmed to be close to 1 which indicates that the samples were well-graded, while the coefficient of uniformity of less than or equal to 4, which confirms that they were uniformly-graded (iowa, 2020). hence, these constituent materials are good for concrete production. table 2. chemical composition of bua brand of opc and ncpa materials chemical composition (%) sio2 fe2o3 al2o3 cao so3 mgo na2o k2o loi cement 18.22 2.72 5.11 60.14 3.31 1.25 0 0.08 7.23 ncpa 61.70 2.52 12.50 9.42 2.10 6.32 0.05 0.32 5.07 table 3. particle size distribution of imo river sand sieve size (mm) mass of sand passing (g) mass of sand retained (g) % passing 4.75 950 0 100 2.36 924.5 25.50 97.32 1.18 878.69 45.81 92.50 0.850 800.05 78.64 84.22 0.6 517.27 282.78 54.45 0.425 368.28 148.99 38.77 0.3 97.74 270.54 10.29 0.212 27.97 69.77 2.95 0.15 11.73 16.24 1.24 0.075 2.83 8.90 0.30 pan 0 2.83 0 total 950 http://www.azojete.com.ng/ mailto:nwadavid.chidobere@mouau.edu.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 428 table 4. particle size distribution of ishiagu granite chippings sieve size (mm) mass of granite passing (g) mass of granite retained (g) % passing 31.5 3200 0 100 22.4 3118.78 81.22 97.46 19 2675.83 442.95 83.62 16 1697.87 977.96 53.06 12.5 803.72 894.15 25.12 9.5 354.21 449.51 11.07 6.3 57.41 296.80 1.79 04.75 14.74 42.67 0.46 pan 0 14.74 0 total 3200 3.2 workability of ncpa-concrete the slumps of ncpa replaced mixes at different replacement levels were shown in figure 1. the values obtained from the slump test correspond to the designed slump range of 30 60mm. it is observed from figure 1, that the workability increased with increased replacement. this outcome was consistent with that of le and ludwig (2016). the improved workability is attributed to the filler effect of ncpa between aggregates and cement particles which reduces friction between particles and facilitates a better concrete flow. in line with abram’s law of water-cement ratio (kamau et al., 2016), the possibility of optimizing strength using less water in ncpa-concrete is highlighted. figure 1: workability of ncpa-concrete mixes 3.3 setting time it is observed from figure 2, that the initial and final setting times increases as the ncpa replacement percentage increases, thereby retarding the hydration process. this implies that ncpa concrete is not susceptible to the problem of false set. this is due to reduction in the 0 10 20 30 40 50 60 0 3 6 9 1 2 1 5 1 8 2 1 2 4 2 7 3 0 3 3 3 6 3 9 4 2 4 5 4 8 5 1 5 4 5 7 6 0 6 3 6 6 6 9 7 2 7 5 sl u m p v al u es ( m m ) percentage replacement file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng nwa david: investigation of fresh and hardened behaviour of nanostructured concrete. azojete, 19(3):423-436. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 429 strength-forming compounds, c3s, c2s, and c3a in the cement paste. this increased setting times become advantageous while concreting in hot weather. the results obtained satisfied the prescriptions of astm c 150-94. figure 2: setting time of ncpa-concrete 3.4 effect of ncpa on compressive strength the compressive strengths of the concrete samples cured for 7, 14, 28, 56, 90 and 150days were presented in figure 3. the result showed that the compressive strength increased as the percentage replacement of the portland cement with nanostructured cassava peel ash (ncpa) increased and as the curing age increased. from the figure 4, it can be seen that inclusion of ncpa in concrete mix is very effective in increasing the compressive strength of concrete. this could be attributed to silica (sio2) and alumina (al2o3) of ncpa content being larger than those of opc as indicated in table 1. the increasing strength is also traceable to the formation of strengthening gel (c-s-h) and bond (c-a-h) occurring from the reaction of ncpa’s silica and alumina elements with the hydrating agents of opc (khan et al., 2014). it can be seen that the compressive strength increases up to 19.5% replacement of cement with ncpa. the addition of this nanomaterial (ncpa) to the concrete helped to fill the pores existing in the matrix in order to provide an exceptional surface area to volume ratio, improved basic property and reactivity of the material. this in turn enhanced the strength of the concrete. the strength improvement is believed to continue as long as the curing period is prolonged to allow completion of hydration. the optimum compressive strength of 36.90 n/mm2 was achieved at 19.5% replacement at 150days of age. 0 100 200 300 400 500 600 700 0 3 6 9 1 2 1 5 1 8 2 1 2 4 2 7 3 0 3 3 3 6 3 9 4 2 4 5 4 8 5 1 5 4 5 7 6 0 6 3 6 6 6 9 7 2 7 5 se tt in g ti m e (m in s) ncpa percentage replacement intial setting time final setting time http://www.azojete.com.ng/ mailto:nwadavid.chidobere@mouau.edu.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 430 figure 3: compressive strength of ncpa-cement concrete with varying curing days. 3.5 effect of ncpa on splitting tensile strength figure 4 present the splitting tensile strengths of the concrete at 7, 14, 28, 56, 90 and 150 curing age. it is observed that the tensile strength of the concrete is much lower than its compressive strength. for each percentage replacement interval, as the curing days increased, the compressive strengths increased more slowly than the splitting tensile strengths. this is because the splitting tensile strength increases more slowly than the compressive strength so that the ratio ft/fc decreases with time (neville, 2011). the distinguishing feature between ncpa and other scms was clearly shown in figure 4. above 20% ncpa replacement, the tensile strength of ncpaconcrete decreased with increasing ncpa replacement as shown figure 4, consistent with the character of scms (sengul and tasdemir, 2009; sumer, 2012). figure 4: splitting tensile strength of ncpa-cement concrete with varying curing days. figures 5-10 indicate that the values of the coefficient of determination r2 obtained from the regression analysis is quite large (least being 0.9786) for concrete made with ncpa at all the 0 5 10 15 20 25 30 35 40 0 3 6 9 1 2 1 5 1 8 2 1 2 4 2 7 3 0 3 3 3 6 3 9 4 2 4 5 4 8 5 1 5 4 5 7 6 0 6 3 6 6 6 9 7 2 7 5 c o m p re ss iv e st re n gt h ( n /m m 2 ) ncpa percentage replacement 7 days 14 days 28 days 56 days 90 days 150 days 0 2 4 6 8 10 12 14 0 3 6 9 1 2 1 5 1 8 2 1 2 4 2 7 3 0 3 3 3 6 3 9 4 2 4 5 4 8 5 1 5 4 5 7 6 0 6 3 6 6 6 9 7 2 7 5 sp lit ti n g te n si le s tr en gt h ( n /m m 2 ) ncpa perecentage replacement 7 days 14 days 28 days 56 days 90 days 150 days file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng nwa david: investigation of fresh and hardened behaviour of nanostructured concrete. azojete, 19(3):423-436. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 431 percentage replacement. that is, approximately 97% and above of the test data correlated to the regression equations. this suggests a strong relationship of the models for ncpa-cement concrete. the plot in figure 5, indicates the steepness of the line of fit which is the curved line that best predicts the data sets provided. the exponential equation for the compressive strength response of the ncpa-concrete is presented in equation 3. it was observed that the compressive strength of the concrete was directly proportional to the splitting tensile strength. 𝑌 = 3.9185𝑒0.2763𝑥 (3) figure 5: relationship between the splitting tensile and compressive strengths of ncpacement concrete at 7 curing days. the graph in figure 6 captured the variation of splitting tensile strength with compressive strength of opc-ncpa-concrete. it was observed that as the compressive strength increased, the splitting tensile strength increased too. the exponential relationship between these strengths were shown in equation 4. 𝑌 = 5.7022𝑒0.1971𝑥 (4) figure 6: relationship between the splitting tensile and compressive strengths of ncpacement concrete at 14 curing days. figure 7 presented a graphical illustration of the alliance between compressive strength and tensile strength of the concrete specimen after 28 days’ period of curing. the line of fit was y = 3.9185e0.2763x r² = 0.9786 0 5 10 15 20 25 0 1 2 3 4 5 6 7 c o m p re ss iv e s tr e n gt h ( n /m m 2 ) splitting tensile strength (n/mm2) y = 5.7022e0.1971x r² = 0.9924 0 5 10 15 20 25 0 2 4 6 8 c o m p re ss iv e s tr e n gt h (n /m m 2 ) splitting tensile strength (n/mm2) http://www.azojete.com.ng/ mailto:nwadavid.chidobere@mouau.edu.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 432 almost a straight line and the coefficient of determination r2 was very close to 1. the exponential relationship for the concrete strength properties is given in equation 5. the least exponential coefficient for the variations was found to 2.1 𝑌 = 2.0811𝑒0.0551𝑥 (5) figure 7: relationship between the splitting tensile and compressive strengths of ncpacement concrete at 28 curing days. the splitting tensile strength of the nanosized concrete cured for 56 days, varied directly to the compressive strength behaviour as shown in figure 8. the exponential equation of the varied strengths is represented in equation 6. as compressive strength increased, the tensile strength advanced. 𝑌 = 8.2342𝑒0.1375𝑥 (6) figure 8: relationship between the splitting tensile and compressive strengths of ncpacement concrete at 56 curing days. at 90 days curing, it was observed in figure 9, that the higher the splitting tensile strength, the more the compressive strength. the relationship between these concrete parameters were captured in equation 7. 𝑌 = 9.1896𝑒0.1238𝑥 (7) y = 2.0811e0.0551x r² = 0.9938 0 2 4 6 8 10 0 5 10 15 20 25 30 c o m p re ss iv e s tr e n gt h (n /m m 2 ) splitting tensile strength (n/mm2) y = 8.2342e0.1375x r² = 0.9925 0 5 10 15 20 25 30 35 0 2 4 6 8 10 12 c o m p re ss iv e s tr e n gt h ( n /m m 2 ) splitting tensile strength (n/mm2) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng nwa david: investigation of fresh and hardened behaviour of nanostructured concrete. azojete, 19(3):423-436. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 433 figure 9: relationship between the splitting tensile and compressive strengths of ncpacement concrete at 90 curing days. the graph in figure 10 captured the variation of splitting tensile strength with compressive strength of opc-ncpa-concrete. it was observed that as the compressive strength increased, the splitting tensile strength increased too. the exponential relationship between these strengths were shown in equation 8. 𝑌 = 10.248𝑒0.111𝑥 (8) figure 10: relationship between the splitting tensile and compressive strengths of ncpacement concrete at 150 curing days. 4. conclusion the following conclusions were drawn from the outcome of the analysis done in this study. i. the workability of the ncpa-concrete increases with increase in ncpa content, hence, less water is required to achieve a workable mix. ii. ncpa can be used with replacements of up to 20% to achieve optimum strengths. iii. the exponential trends lines can be accepted to reliably express the relationship between the compressive strength and splitting tensile strength of ncpa-concrete samples at all the water/cement ratios considered. y = 9.1896e0.1238x r² = 0.9942 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12c o m p re ss iv e s tr e n gt h ( n /m m 2 ) splitting tensile strength (n/mm2) y = 10.248e0.111x r² = 0.9945 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 14 c o m p re ss iv e s tr e n gt h ( n /m m 2 ) splitting tensile strength (n/mm2) http://www.azojete.com.ng/ mailto:nwadavid.chidobere@mouau.edu.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 434 iv. utilisation of ncpa in the construction industry could help in addressing the general construction cost and mitigate the technical and environmental nuisance associated with cement production. it could also reduce solid waste, conserve existing natural resources, thereby enhancing sustainability as well as improving the characteristics of fresh and hardened concrete. references. abdulwahab, mt., and uche oau., 2021.durability properties of self-compacting concrete (scc) incorporating cassava peel ash (cpa). nigerian journal of technology (nijotech), 40(4): 584-590. http://dx.doi.org/10.4314/njt.v40i4.4. astm c 618. 2008. specification for coal fly ash and raw or calcined natural pozzolanas for use as mineral admixtures in ordinary portland cement concrete. annual book of astm standards, west conshecken, usa. attah, ic., etim, rk., alaneme, gu., and bassey, ob. 2020.optimization of mechanical properties of rice husk ash concrete using scheffe’s theory. sn applied sciences, 2: 928-941 https://doi.org/10.1007/s42452-020-2727-y. awodiji, ctg., onwuka, do, okere, c e, and ibearugbulem om. 2018. anticipating the compressive strength of hydrated lime cement concrete using artificial neural network model. civil engineering journal, 4(12): 3005-3018.http://dx.doi.org/10.28991/cej-03091216. bs 12, 1996, specification for portland cement, british standards institution, london. bs 12390-6, 2009, testing hardened concrete: tensile splitting strength of test specimens. british standard institution, london. bs 1881, 1983, testing concrete: method for determination of compressive strength of concrete, british standards institution, london. bs 3140, 1980, methods of test for water for making concrete, including notes on the suitability of the water, british standards institution, london. bs 882, 1992, specification for aggregates from natural sources for concrete, british standards institution, london. bs en 12390-3, 2009, testing hardened concrete: compressive strength of test specimens. british standard institution, london. ettu, lo, ezeh, jc., ibearugbulem, om., anya, uc., and njoku, ko. 2013. strength of binary blended cement composites containing cassava waste ash. international journal of emerging technology and advanced engineering, 3(4): 15-20. george, ua. and elvis, m. 2019. modelling of the mechanical properties of concrete with cement ratio partially replaced by aluminum waste and sawdust ash using artificial neural network. sn applied sciences, 1: 1514-1527. https://doi.org/10.1007/s42452-019-1504-2. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng http://dx.doi.org/10.4314/njt.v40i4.4 https://doi.org/10.1007/s42452-020-2727-y http://dx.doi.org/10.28991/cej-03091216 https://doi.org/10.1007/s42452-019-1504-2 nwa david: investigation of fresh and hardened behaviour of nanostructured concrete. azojete, 19(3):423-436. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 435 johnson, me., and gonzalez, a. 2013. estimating cost savings for aviation fuel and co2 emission reductions strategies. the collegiate aviation review international, 31(2):1-12. https://doi.org/10.22488/okstate.18.100513 iowa 2020. class notes: c.c. swan, university of iowa: lecture 2: grain size distributions and soil particle characteristics. available online at: http://user.engineering.uiowa.edu/~swan/courses/53030/notes/gsd.pdf. kamau, j., ahmed, a., hirst, p., kangwa, j. 2016. suitability of corncob ash as a supplementary cementitious material. international journal of materials science and 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mailto:nwadavid.chidobere@mouau.edu.ng http://user.engineering.uiowa.edu/~swan/courses/53030/notes/gsd.pdf https://doi.org/10.1155/2014/986567 http://doi.org/10.30684/etj.2023.138099.1374 http://doi.org/10.5281/zenodo.8094024 https://doi.org/10.22115/cepm.2020.223035.1091 arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):423-436. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nwadavid.chidobere@mouau.edu.ng 436 olonade, ka., olajumoke, am., omotosho, ao., and oyekunle, fa. 2014. effects of sulphuric acid on the compressive strength of blended cement cassava peel ash concrete. construction materials and structures, 14(4): 764-771. doi:10.3233/978-1-61499-466-4-764. olutoge fa., oriyomi, mo., & olatunji, so. 2012. assessment of the suitability of periwinkle shell ash (psa) as partial replacement for ordinary portland cement (opc) in concrete. international journal of research and reviews in applied sciences, 10(3): 428–434. onwuka, do., anyaogu, l., chijioke, c., okoye, pc. 2013. prediction and optimization of compressive strength of sawdust ash-cement concrete using scheffe’s simpex design. international journal of scientific and research publications, 3(5):1-9 prasad m. 2017, a review on nano materials in concrete, civil engineering research journal, 2(2): 555581, doi: 10.19080/cerj.2017.02.555581. raheem, sb., arubike, ed., and awogboro, os. 2015.effects of cassava peel ash (cpa) as alternative binder in concrete, international journal of constructive research in civil engineering (ijcrce), 1(2): 27-32. salau ma, ikponmwosa ee., olonode ka. 2012. structural strength characteristics of cementcassava peel ash blended concrete. civil and environmental research,2(10): 68-78. sanchez, f., sobolev, k. 2010. nanotechnology in concrete – a review, construction and building materials, 24: 2060–2071. doi: 10.1016/j.conbuildmat.2010.03.014. sengul, o., and tasdemir, m. a. 2009. compressive strength and rapid chloride permeability of concretes with ground fly ash and slag. journal of materials in civil engineering, 21: 494-501. sumer, m. 2012. compressive strength and sulfate resistance properties of concretes containing class f and class c fly ashes, construction and building materials, 34: 531-536. thomas, bs. 2018. green concrete partially comprised of rice husk ash as a supplementary cementitious material—a comprehensive review, renewable and sustainable energy reviews, 82: 3913–3923. zareei, sa., ameri, f., dorostkar, f., and ahmadi, m. 2017. rice husk ash as a partial replacement of cement in high strength concrete containing micro silica: evaluating durability and mechanical properties. case studies in construction materials, 7:73–81 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nwadavid.chidobere@mouau.edu.ng arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):175-182 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 175 original research article analysis and evaluation of energy efficiency of 5g networks in wireless communication e. u. udo, l. i. oborkhale, c. c. nwaogu* department of electrical/electronic engineering, michael okpara university of agriculture, umudike, abia state, nigeria *corresponding author’s email address: cxtopher20091@gmail.com 1.0 introduction the fifth generation of mobile communication system (5g) has become the hub of worldwide attention because it meets growing demand of the users. each 5g base station shall provide at least 20 gb/s downlink and 10 gb/s uplink bandwidth transmission capability, according to the international telecommunication union criteria for 5g to accomplish a leap-forward improvement in transmission speed (cai et al., 2016). the need to support exponential growth in data traffic with the availability of a diverse range of mobile devices has resulted in an important escalation in the number and density of base station devices, as well as their complexity, resulting in increased power consumption and usage. 5g wireless networks represent a major communication infrastructure for connectivity of the future, with the rising increase of mobile access to the internet and its services (auer et al., 2011). energy efficiency has provided the most significant supports in the design of the next generation (5g) of wireless networks. again, 5g systems will serve an unprecedented number of devices, providing ever-present connectivity as well as innovative and rate-demanding services. devices such as drones, medical devices, cars, sensors and wearable devices will make use of cellular networks to connect with one another thereby interacting with human end-users to provide a variety of innovative services such as smart cities, smart cars, tele-surgery, smart cars and article information abstract this paper focused on the analysis and evaluation of energy efficiency of 5g networks in wireless communication. the projected rise in wireless communication traffic has necessitated high operating costs of conventional wireless cellular networks and scarcity of energy resources in low power applications. this paper examined different ways of deploying energy efficient hardware at the base stations in order to make the base station non-polluting energy. the method employed involves the measurement of power consumption at the macro cell and micro cell base stations. the results of the power consumption obtained from the macro cell base stations were used in three models, namely the gex model, the modified gex model and ismail model for the periods of 0am – 1am, 12pm – 1pm and 11pm – 0am were 11228.63w, 11561.15w, 11231.06w, 12821.65w, 12983.29w, 12981.64w, 13020.56w, 15342.30w, 11323.83w, 11634.23w, 11374.37w and 13196.66w. again, the results of the power consumption obtained from the micro cell base stations for the periods of 0am – 1am, 12pm – 1pm and 11pm – 0am were 717.09w, 754.83w, 729.65w, 748w, 723.67w, 743.34w, 717.6w, 741w, 643.5w, 667.74w, 642.9w and 718w, respectively. therefore, it is concluded that the modified model produced energy consumption that are in consonance with the measured energy. therefore, it is concluded that the modified gex model produced energy consumption values which are in closed range with the measured energy values. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 24 january, 2023 revised 8 march, 2023 accepted 12 march, 2023 keywords: wireless communication energy efficiency base station 5g network http://www.azojete.com.ng/ mailto:cxtopher20091@gmail.comg mailto:cxtopher20091@gmail.comg arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):175-182. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 176 advanced security systems. to accommodate such a high number of terminals, future networks capacity will need to be greatly increased (zhang et al., 2013). however, contemporary networks are built to maximize capacity by increasing transmit power thereby giving rise to the rapid increase in the number of linked devices. increasing communication capacity by using more and more energy will result in unacceptable high operating expenses. again, by scaling up the transmit powers, current wireless communication systems are unable to offer the needed capacity increase (ge et al., 2017). presently, wireless communication systems are primarily fueled by carbon-based energy sources. information and communication technology (ict) systems currently account for 5% of global co2 emission, although this percentage rises at the same rate as the number of linked devices. recently, it is expected that 75% of the ict industry will be wireless, indicating that wireless communications will become a significant area to address in terms of lowering ict-related co2 emissions (joshua et al., 2020). increased energy consumption is a major challenge linked with global warming and decreased in energy consumption of mobile communication networks has accounts for a considerable amount of overall information and communication technology energy consumption. since future 5g networks are predicted to have higher traffic loads, the impact of mobile communication network energy consumption will grow more rapidly (shameek et al., 2016). the base station is the principal energy consumer in mobile communication networks and its energy consumption is determined by traffic load, which varies depending on geographic location. there has been a lot of effort put into the energy savings of a base station in order to lower the energy consumption of mobile communication networks (lee et al., 2013). energy efficiency is maximized to obtain better average performance and 5g wireless networks constitute a major communication infrastructure for connectivity in the future, with the increase in expansion of mobile access to the internet and its services. also, mobile communication networks use a large portion of the overall energy consumed by information and communication technology (antonopoulos et al., 2015). however, 5g network make use of the ieee 802.11ac standard as its foundation and can also grow to hundreds of thousands of connections (joshua et al., 2020). in 5g wireless internet networks, the following technologies like ultra wideband, orthogonal frequency division multiplex, code division multiple access, ipv6 and multi-carrier code division multiple access are very useful (niu et al., 2012). the deployment of 5g with small cells makes millimeter wave based carriers to improve overall coverage area in the range of 30 ghz to 300 ghz. when combined with beam forming, small cells can deliver fast coverage with low latency and testing of 5g range in millimeter wave has produced good results of approximately 500 meters from the tower (hanson et al., 2015). the statement of problem is that there are high operating costs in wireless network which leads to scarcity of energy resources. the objective of this study is to evaluate energy efficiency of 5g networks by deploying energy efficient hardware at the base stations. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:cxtopher20091@gmail.comg https://www.rantcell.com/what-is-5g.html https://www.rcrwireless.com/20160815/fundamentals/mmwave-5g-tag31-tag99 udo et al: analysis and evaluation of energy efficiency of 5g networks in wireless communication. azojete, 19(1):175-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 177 2. materials and method the materials used in this paper are spectrum analyzer to analyze the frequency components of the transmitted signals. the main supply unit produces power for the entire equipment of the base station transceivers. it also takes alternating current supply as an input and produces direct current voltage as the output. the antenna interface serves as an interface between radio waves propagating through space and electric currents moving in the metal conductors. the base band unit consists of base band transmitters and receivers. it produces data that were fed into the radio unit. the radio frequency chains are cascade of electronic components such as filters, mixers, amplifiers, attenuators and detectors. the cooling units are responsible for maintenance of the base station temperature and heat generated by the power amplifier. data used were collected from the mtn office at aba, abia state, nigeria for a period of one year and the authors have gained experienced at the base stations during the periods of the research. matlab/simulink was used for the simulation. the energy efficient hardware technique necessitates the deployment of enhanced energy efficient hardware like microwave link, digital signal processing unit, power amplifier, transceivers to improve energy efficiency in the network. the experimental results were obtained using several measurements at the base stations. the gex model, modified gex and ismail models were used to determine the power consumption at the macro cell and micro cell base stations. however, the modified gex model was used to calculate the energy consumption. the use of the load factor provided a significant effect on power consumption at the base station which indicates the real power. the measurements of power consumption was done based on specific time range at their respective base stations as shown in tables 1 and 2. the step used for the measurement of power involves three models and the tools used were the wattmeter and multimeter. the intention was to verify the energy consumption that was in closed relationship with the measured energy using different models such as gex model, modified gex model and ismail model. 2.1 mathematical modeling of energy enhanced hardware approach energy efficiency is measured as the number of bits transmitted per joule of energy (b/j). the cell coverage (c) is the fraction of the area within a cell receiving signal power pmin. 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝜂 = 𝑇𝑜𝑡𝑎𝑙 𝑜𝑢𝑡𝑝𝑢𝑡 𝑇𝑜𝑡𝑎𝑙 𝐼𝑛𝑝𝑢𝑡 (1) energy efficient hardware approach is computed using equation (2). therefore, energy efficiency 𝜂𝐸 = 𝑇𝑜𝑡𝑎𝑙 𝐸𝑛𝑒𝑟𝑔𝑦 𝑟𝑎𝑑𝑖𝑎𝑡𝑒𝑑 𝑇𝑜𝑡𝑎𝑙 𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑝𝑢𝑡 (2) in terms of percentage, energy efficiency is calculated as shown in equation (3). 𝜂𝐸 = 𝐸𝑜𝑢𝑡 𝐸𝑖𝑛 𝑥 100 1 = 𝑃𝑜𝑢𝑡 𝑥 𝑡 𝑃𝑖𝑛 𝑥 𝑡 𝑥 100 1 (3) also, the energy efficiency can also be defined as the ratio of the radiated signal to the input power consumption as given in equation (4). http://www.azojete.com.ng/ mailto:cxtopher20091@gmail.comg arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):175-182. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 178 𝐸𝐸 = 𝑃𝑡𝑡 𝑃𝑡𝑖𝑛 (4) where ee is the energy efficiency, ptttx is the radiated signal power of the transmitter and ptinin is the input power consumption. the power consumption pcarea per covered area is shown in equation (5) (deruyck et al., 2014). 𝑃𝐶𝑎𝑟𝑒𝑎 = 𝑃𝑒𝑙 𝜋𝑅2 (5) where 𝑃𝑒𝑙 is the power consumption of the base station and r is the transmission radius of the base station. however, the lower the pcarea, the more energy efficient is the base station. again, to determine the power consumption for a specific hour at weekdays, the power consumption pel/amp of the power amplifier depends on the input power 𝑃𝑒𝑙 of the antenna as shown in equation (6). 𝑃 𝑒𝑙 𝑎𝑚𝑝 = 𝑃𝑡𝑥 𝜂 (6) where η is the efficiency of the power amplifier, which is the ratio of the rf output power to the electrical input power. the power consumption pel/macro of the macrocell base station can be determined as shown in equations (7) (cooper, 2018), and (8). pel/macro = pel/const + pel/load. (7) with 𝑃𝑒𝑙/𝑐𝑜𝑛𝑠𝑡 = 𝑛𝑠𝑒𝑐𝑡𝑜𝑟𝑃𝑒𝑙/𝑟𝑒𝑐 + 𝑃𝑒𝑙/𝑙𝑖𝑛𝑘 + 𝑃𝑒𝑙/𝑎𝑖𝑟𝑐𝑜 (8) again, the power consumption in gex et al., model for macro cell base stations is given in equation (9), (han et al., 2016). 𝑃𝑒𝑙/𝑙𝑜𝑎𝑑 = 𝑛𝑠𝑒𝑐𝑡𝑜𝑟(𝑛𝑡𝑥𝑃𝑒𝑙𝑎𝑚𝑝 + 𝑃𝑒𝑙𝑡𝑟𝑎𝑛𝑠 + 𝑃𝑒𝑙𝑝𝑟𝑜𝑐) (9) where n-sector is the number of sectors supported by the macrocell base station, ntx is the number of transmitting antennas and pel/rect, pel/link, pel/airco, pel/amp, pel/trans and pel/proc are the power consumption of the rectifier, the microwave link, the air conditioning, the power amplifier, the transceiver and the digital signal processing (in watt). the power consumption pel/micro of a microcell base station is given in equations (10) and (11). 𝑃𝑒𝑙/𝑚𝑖𝑐𝑟𝑜 = 𝑃𝑒𝑙/𝑐𝑜𝑛𝑠𝑡 + 𝑃𝑒𝑙/𝑙𝑜𝑎𝑑 (10) with 𝑝𝑒𝑙/𝑐𝑜𝑛𝑠𝑡 = 𝑃𝑒𝑙/𝑟𝑒𝑐 + 𝑃𝑒𝑙/𝑎𝑖𝑟𝑐𝑜 (11) the power consumption in gex model for microcell base station is as shown in equation (12). (wang et al., 2018). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:cxtopher20091@gmail.comg udo et al: analysis and evaluation of energy efficiency of 5g networks in wireless communication. azojete, 19(1):175-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 179 𝑃𝑒𝑙/𝑙𝑜𝑎𝑑 = 𝑃𝑒𝑙/𝑎𝑚𝑝 + 𝑃𝑒𝑙/𝑡𝑟𝑎𝑛𝑠 + 𝑃𝑒𝑙/𝑝𝑟𝑜𝑐 (12) the operating power for the ismail model for macro base station and micro base station can be shown in equations (13), (faruk et al., 2012) and (14), respectively. 𝑃𝑚𝑎𝑐𝑟𝑜 = (𝑁𝑠𝑒𝑐𝑡𝑥 𝑁𝑇𝑋) 𝑃𝑃𝐴+𝑃𝐵𝐵+ 𝑃𝑅𝐹 (1−𝜑𝑀𝑆)(1−𝜑𝐷𝐶)(1−𝜑𝑐𝑜𝑜𝑙) + 𝑃𝑚𝑤 + 𝑃𝑎𝑢 (13) 𝑃𝑚𝑖𝑐𝑟𝑜 = (𝑁𝑠𝑒𝑐𝑡𝑥 𝑁𝑇𝑋)𝑃𝑃𝐴 + 𝑃𝐵𝐵 + 𝑃𝑅𝐹 + 𝑃𝑚𝑤 + 𝑃𝑎𝑢 (14) where pau is auxiliary equipment, prf is transceiver power, pmw is microwave backhaul, ppa is power consumed by power amplifier, dc is the losses incurred by the rectifier, ms is the losses incurred by the mains supply, cool is the losses incurred by the active cooling and pbb is the power consumed by the baseband unit. 3. results and discussion the experimental results for the power consumption at the macro cell and micro cell base stations were obtained through measurements. the measured results were tested in gex model, modified gex and ismail models for macro base stations shown in equations (9), (13) and micro base stations shown in equations (12), (14), respectively. table 1 shows the results of the measured values, gex model, modified gex model and ismail model values. when the experimental results shown in table 1 were compared with the gex model, modified gex model and ismail model values, it was discovered that the measured results were close to the modified model results. this indicated that the modified model results are in consonance with the information handling service (his) measured data. table 1: measured and model values at macro base station hour power consumption (pmacro) at the macro cell base station hour measured value (watts) gex model (watts) modified gex model (watts) ismail model (watts) 0am -1am 11228.63 11561.15 11 231.06 12821.65 1am – 2am 11193.54 11518.03 11 187.68 12935.53 2am – 3am 11218.82 11542.62 11220.73 12952.63 3am – 4am 11219.73 11521.17 11231.61 12773.19 4am – 5am 11309.04 11593.26 11319.29 12908.18 5am – 6am 12118.33 12374.29 12134.74 14068.76 6am – 7am 12257.43 12496.65 12238.48 14134.37 7am – 8am 12422.80 12673.52 12429.42 14461.23 8am – 9am 12639.78 12743.91 12658.31 14769.64 9am – 10am 12868.43 12804.11 12876.78 15278.80 10am – 11am 12989.59 12945.73 13017.51 15281.76 11am – 12pm 12999.42 12856.62 13134.86 15515.83 12pm – 1pm 12983.29 12981.64 13020.56 15342.30 1pm – 2pm 13052.34 12945.79 13153.32 15578.77 2pm – 3pm 13119.59 12971.42 13132.42 15369.30 http://www.azojete.com.ng/ mailto:cxtopher20091@gmail.comg arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):175-182. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 180 3pm – 4pm 13169.34 13039.09 13274.21 15839.77 4pm – 5pm 13296.19 12959.74 13289.23 15770.78 5pm – 6pm 13289.09 12937.86 13288.42 15929.43 6pm – 7pm 13127.84 12846.89 13120.76 15484.74 7pm – 8pm 12611.39 12778.44 12720.89 15039.81 8pm – 9pm 12372.62 12758.64 12579.87 14794.31 9pm-10pm 12388.87 12628.40 12419.55 14783.19 10pm-11pm 11473.32 11854.20 11569.09 13537.28 11pm-0am 11323.83 11634.23 11374.37 13196.66 again, when the measured results in table 2 was compared with the gex model, modified gex model and ismail model values, it was also realized that the modified model is in agreement with the information handling service measured data. table 2: measured and model values at micro base station hour measured value (watts) gex model (watts) modified gex model (watts) ismail model (watts) 0am – 1am 717.09 754.83 729.65 748 1am – 2am 619.53 659.76 620.49 665 2am – 3am 620.20 669.95 649.18 664 3am – 4am 634.19 657.67 639.56 659 4am – 5am 648.34 668.71 656.9 667 5am – 6am 681.44 712.20 668.79 677 6am – 7am 719.63 723.88 719.41 721 7am – 8am 690.18 713.21 678.90 711 8am – 9am 719.31 720.16 715.46 723 9am – 10am 689.44 721.45 689.88 723 10am– 11am 739.54 745.67 734.32 754 11am– 12pm 719.14 731.89 712.90 734 12pm – 1pm 723.67 743.34 717.6 741 1pm – 2pm 722.17 743.81 731 742 2pm – 3pm 730.88 754.51 730.77 753 3pm – 4pm 740.78 743.78 742.63 741 4pm – 5pm 722.17 751.56 723.51 742 5pm – 6pm 723 741.99 720.34 739 6pm – 7pm 711.79 731.65 711.95 731 7pm – 8pm 689.56 720.74 688.23 722 8pm – 9pm 687.4 721.89 684.94 723 9pm – 10pm 716.17 718.56 711.24 717 10pm– 11pm 741.67 771.88 742.77 773 11pm – 0am 643.5 667.74 642.9 718 figure 1 shows the plot of comparison between the measured values, the gex model, modified gex and ismail models at the macro cell base station while figure 2 shows the plot of comparison between the measured values, the gex model, modified gex model and ismail models at the micro cell base station. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:cxtopher20091@gmail.comg udo et al: analysis and evaluation of energy efficiency of 5g networks in wireless communication. azojete, 19(1):175-182. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 181 figure 1: comparison of the measured values with gex model, modified gex model and ismail model for macro cell base station figure 2: comparison of the measured values with gex model modified gex model and ismail model for micro cell base station figure 1 shows the plot of energy consumption against time. it was observed from the graph that the plot of the measured values is closer to the plot of the modified model. however, the plot of the ismail model increases above the plots of the measured value, gex model and the modified gex model. figure 2 also indicated the plot of energy consumption against time. it was realized that the plot of the measured values is very close to the modified model. however, the plot of the ismail and gex models are very close to each other. when this was compared to the previous studies (alsharif et al., 2016), it was observed that the modified gex model values was in consonance with the measured energy. 4. conclusion it is important for 5g to provide a high data rates with better coverage and good signal quality by deploying small cells with energy efficient hardware at micro cell base stations. these cells normally decrease energy consumption when it is equipped with energy efficient hardware and intelligent power saving. the gex model portends to be a better model for computing the energy consumption of 5g base station. however, heterogeneous network can handle higher data traffic while consuming less base station energy. when the density of data traffic density was high or when the base station transmission power was low, the placement of small energy base station http://www.azojete.com.ng/ mailto:cxtopher20091@gmail.comg arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):175-182. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cxtopher20091@gmail.com 182 determines the performance of heterogeneous network. most modern wireless communication systems, operate in half-duplex mode resulting in resource utilization degradation. the potential of full duplex operation boosts the potential spectral efficiency of wireless communication systems by broadcasting and receiving across the entire bandwidth. it is recommended that with the implementation of energy efficient hardware at the base stations, the energy consumption of 5g network improves its efficiency in wireless communications. references alsharif, mh., nordin, r. and ismail, m. 2016. intelligent cooperation management of multi-radio access technology towards the green cellular networks for the twenty-twenty information society. telecommunication system, 65(3):1–14. antonopoulos, a., kartsakli, e., bousia, a., alonso, l. and verikoukis, c. 2015. energy efficient infrastructure sharing in multi-operator mobile networks. ieee communication magazine, 53: 242–244. auer, g., giannini, v., desset, c., godor, i., skillermark, p. and olsson, m. 2011. how much energy is needed to run a wireless network? ieee wireless communications, 18: 40–49. cai, s., che, y., duan, l., wang, j., zhou, s. and zhang, r. 2016. green 5g heterogeneous networks through dynamic small cell operation. ieee journal selected areas communication, 34: 1103–1115. cooper, lk. 2018. on optimal cell activation for coverage preservation in green cellular networks. ieee transactions mobile computing, 13: 2580–2591. deruyck, m., joseph, w. and martens, l. 2014. power consumption model for macrocell and microcell base stations. transaction emerging telecommunication technology, 25: 320–333. faruk, n., ayeni, aa. and muhammad, my. 2012. powering cell sites for mobile cellular systems using solar power. international journal of engineering and technology, 2(5). ge, x., yang, j., gharavi, h. and sun, y. 2017. energy efficiency challenges of 5g small cell networks. ieee communication magazine, 55: 184–191, doi: 10.1109/ mcom. 2017 .1600788. han, f., zhao, s., zhang, l. and wu, j. 2016. survey of strategies for switching off base stations in heterogeneous networks for greener 5g systems. ieee access, 4: 4959–4973. hasan, z., sheng, b., zhu, p., you, x. and li, gy. 2015. energy and spectral efficiency tradeoff for distributed antenna systems with proportional fairness. ieee journal selected areas in communication, 31: 894–902. joshua, oo., agbotiname, li. and aderemi, aa. 2020. energy efficient design techniques in next generation wireless communication networks, emerging trends and future directions. wireless communications and mobile computing, article id 7235362, https://doi.org/10.1155/2020/7235362. lee, s., zhang, r. and huang, k. 2013. opportunistic wireless energy harvesting in cognitive radio networks. ieee transactions on wireless communications, 12(9): 4788–4799. niu, z., zhou, s., hua, y., zhang, q. and cao, d. 2012. energy aware network planning for wireless cellular system with inter-cell cooperation. ieee transaction wireless communication, 11: 1412–1423. shameek, m., agarwal, v., sharma, s. and gupta, v. 2016. a study on wireless communication networks based on different generations. international journal of current trends in engineering & research (ijcter), 2(5): 300 – 304. wang, y., xu, w., yang, k. and lin, j. 2018. optimal energy efficient power allocation for ofdm based cognitive radio networks. ieee communications, 16(9): 1420–1423. zhang, x., su, z., yan, z. and wang, w. 2013. energy efficiency study for two-tier heterogeneous networks under coverage performance constraints. mobile network applications, 18: 567–577 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:cxtopher20091@gmail.comg arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):193-214 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 193 development of glaucoma detection system using cnn and svm n. s. okomba1, s. a. adedayo1, c. v. aviara1, a. o. esan1, b. omodunbi1, and a. s. chikezie2 1department of computer engineering, federal university oye-ekiti, ekiti state, nigeria 2department of computer engineering, university of uyo, akwa ibom state, nigeria *corresponding author's email address: nnamdi.okomba@fuoye.edu.ng article information submitted 11 november, 2023 revised 23 february, 2024 accepted 27 february, 2024 keywords: neural network features glaucoma vector machine preprocessing convolution abstract glaucoma is an eye illness that began as a result of high intraocular pressure and resulted in total blindness at its advanced stage it is a chronic eye disease caused by the damage of the optic nerve found at the back of the eye and will lead to vision loss. abnormality in the drainage system of the eye causes fluid buildup that excessively triggers pressure leading to optic nerve damage. the development of glaucoma detection system using convolutional neural network (cnn) and support vector machine (svm) has been extensively studied in recent years. many studies have shown that cnns can accurately detect glaucoma from fundus images, optic nerve head images, and other imaging modalities. to implement cnn and svm techniques for glaucoma detection, the process typically involves data collection, preprocessing, feature extraction, model training, validation, and testing. mobilenetv2 model and combined svm-cnn approach was introduced in the research. as the glaucoma detection system was constructed using the mobilenetv2 cnn architecture which integrates multiple architectural elements to achieve optimal classification performance. pre-trained weights were employed from the image data set while transfer learning with mobilenetv2 approach was applied to empower the model with strong feature extraction capabilities. global average pooling layers were appended to the base architecture, followed by dense layers for classification. these dense layers utilized rectified linear unit (relu) activation and dropout regularization to enhance model generalization. as a result, a metric evaluation for detecting glaucoma eye disease using mobile_netv2 and svm offered a mean sum of 75% accuracy, 92% precision, 55% recall, 84% auc and 34% f1 score. in summary, while svm excels in precision, mobilenetv2 demonstrates better recall, auc, and overall balanced performance. the choice of model depends on the specific goals and priorities of the glaucoma detection application, such as whether avoiding false positives (precision) or detecting as many true positives as possible (recall) is more critical. 1.0 introduction glaucoma is an eye optic nerve illness that begins as a result of high intraocular pressure which results to the destruction of the retina nerval fiber layer causing total blindness at its advanced stage (setina et al., 2021; asaoka et al., 2016). it is classified into two main categories which are the open angle glaucoma and the angle closure glaucoma. both categories are characterized by damage to the optic nerve through the iris, drainage angle, and the trabecular meshwork (dinial et al., 2019). open-angle glaucoma (oag) is caused by poor outflow of the drainage http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 194 canals in the eye, resulting in increased pressure. oag is the most common form of glaucoma which has no symptoms but develops over a number of years, and can cause gradual and permanent vision loss. closed-angle glaucoma (cag), the less common form of the two is caused by a mechanical obstruction in the drainage system inside of the eye, resulting in a sudden rise in pressure. this type of glaucoma can develop very quickly and is then referred to as acute narrow angle glaucoma. with this type of glaucoma there are noticeable symptoms of acute eye pain, nausea, decreased or blurry vision, headache, and/or eye redness. it can result in rapid damage to the eye from very high eye pressure and requires emergency medical attention in order to preserve sight in the eye. when the outer edge of the iris blocks fluid from draining out of the front of the eye, the fluid quickly builds up, causing sudden increase in eye pressure that pushes on the optic nerve leading to blindness. glaucoma damages the optic nerve head thereby affecting the retina, the difference in the produced and drained range of intraocular fluid (iof) of the eye results in iop which in turn affects the nerve fibers (nf) (thakur et al., 2021). the damaged nf disturbs the retinal nerve fiber layer (rnfl) and causes increase in the cup-to-disc ratio (cdr) and optic nerve head (onh) (ali and sertan, 2019). while prompt glaucoma screening and treatment can prevent patients from losing all vision, screening steps depends highly on professionals who manually analyze the retinal samples, identifying glaucoma affected areas (jipeng et al., 2020). lack of professional resource persons and complex glaucoma analysis steps causes delay in predicting the illness, leading to high rate of vision loss. tham et al. (2014) provided an overview of the global prevalence of glaucoma and the projected burden of the disease through the year 2040. they discussed the different types of glaucoma and their prevalence in different regions of the world. certain acknowledged image processing techniques for glaucoma detection were used in proposing location of fatal illness. the research presented the number of people affected by primary open angle glaucoma (poag) and primary angle closure glaucoma (pacg). prevalence population-based studies on glaucoma was studied up to 2023, and hierarchical bayesian method was applied in estimating pooled glaucoma prevalence. annan et al. (2016) worked on automated glaucoma detection. this was achieved by using deep convolutional neural network gotten from large scale generic dataset to represent the visual appearance, while combining the holistic and local features to mitigate the influence of misalignment. an area under the receivers’ operational characteristics curve of 0.8384 on the origa dataset was realized by the proposed approach, which showed high efficiency. xiangyu et al. (2015) worked on the development of deep learning architecture with convolutional neural network for automated glaucoma diagnosis. the proposed deep learning architecture had six layers of learning, four convolution layers, and two fully connected layers. glaucoma diagnosis performance was boosted by applying dropout and data augmentation techniques. origa and sces datasets were used for experimentation. actualized results depicted area under curve of receiver operational characteristics curve in glaucoma detection at 0.831 and 0.887 in both datasets. kim et al. (2020) described the problem of glaucoma diagnosis when optical coherence tomography (oct) images are used, which is often challenging due to the subtle change occurring at retina nerve fiber layer and the optic nerve head. they noted that accurate and file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 195 timely diagnosis is crucial for preventing vision loss in glaucoma patients. a deep learning architecture was developed using inception v3 in order to predict vision fields with the aid of optical coherence tomography (oct) imaging. two oct images were combined and a cnn architecture was created to predict vision fields with the aid of the combined oct image. the performance evaluation of the system was carried out by calculating the root mean square error (rmse) between the actual and predicted visual fields. the rmse for all patients were 4.79 ± 2.56 db, with 3.27 db and 5.27 db for the normal and glaucoma groups, respectively. the rmse of the macular region (4.40 db) was higher than that of the peripheral region (4.29 db) for all subjects. in normal subjects, the rmse of the macular region (2.45 db) was significantly lower than that of the peripheral region (3.11 db), whereas in glaucoma subjects, the rmse was higher (5.62 db versus 5.03 db, respectively). the deep learning method effectively predicted the visual field 24–2 using the combined oct image. this method may help clinicians determine visual fields, particularly for patients who are unable to undergo a physical visual field exam. ali and sertan (2019) worked on early glaucoma detection using convolution neural network (cnn). fundus pictures were used to demonstrate right on time recognition of glaucoma. they trained and furnished deep convolution neural network algorithms comprising of resnet50 and googlenet while applying transfer learning as classifier. evaluation of the system performance showed that googlenet model performs better than the resnet-50 in the early and advanced glaucoma detection. weilu et al. (2018) applied artificial intelligence in ophthalmology. they monitored the use of ai to diagnose visually impaired persons putting into consideration glaucoma, age related, and waterfall impairments. they made a presentation on the basics that contributed to the workflow for creating an artificial intelligent model and also carried out a systematic approach towards reviewing applications of ai in human eye ailment diagnosis. nooshin et al. (2019) worked on a profound multitasked learning system for interpreting glaucoma detection. the system comprises of segmentation and prediction modules. the optic disc and optic cup regions in a fundus image were located by the segmentation module in order to solve the problem of limitation in clinical interpretability. the prediction module improves segmentation task performance with the aid of large data set, thus lessening the gravity of limited label data in segmentation module. both components were integrated into a multitask framework permitting end to end training. system evaluation showed the effectiveness of interpretable glaucoma detection in achieving great results in glaucoma screening. mijung et al. (2019) worked on computer aided diagnosis and glaucoma localization with the use of deep learning. they analyzed fungus images using convolutional neural network (cnn) and gradient-weighted class activation mapping (grad-cam), respectively. different predictive models were built and evaluated using large set of fundus images, while presenting a web app for computer aided diagnosis and localization of glaucoma with the predictive model integrated at the back-end. hassan et al. (2017) worked on creamer significant learning on a single wide field optical adequacy tomography which intelligibly classified glaucoma partners. they worked on the performance of a hybrid deep learning method (hdlm) combine with a single wide-field oct protocol on eyes initially classified as having mild glaucoma. cnn was used to capture features http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 196 from maps gotten from the scan, while a model was trained based on these features using random forest classifier in order to predict the presence glaucoma. the algorithm was compared with optical coherence tomographic (oct) and visual fields (vfs) metrices. the hdlm protocol performed better than oct and vf metrices, while distinguishing healthy suspect eye, and eye with early glaucoma. diagnosing glaucoma using optical coherence tomography (oct) images is often challenging due to the subtle structural changes in the optic nerve head and retinal nerve fiber layer. oct utilizes light waves, of which the media opacities interfere with optimal imaging resulting in limitation of oct performance (kim et al., 2020). support vector machine have shown good performance in the interpretation of opt but have limitations when dealing with large data set (abhishek and samir, 2016). studies have demonstrated that using dl for interpreting oct is efficient, accurate, and with good performance for discriminating glaucomatous eyes from normal eyes, suggesting that incorporation of dl technology in oct for glaucoma assessment could potentially address some gaps in the current practice and clinical workflow (an et al., 2020). in view of this, a glaucoma detection system using mobilenetv2 cnn and support vector machine is developed simultaneously for evaluation and comparison 2. materials and methods mobilenetv2 and svm were used to separate highlights in the data with no complex pre handling, this is achieved using the depthwise separable convolution technique of mobilenetv2 to reduce the computational cost of convolutions by splitting the computation into depthwise convolution and pointwise convolution. depthwise convolution applies a single convolutional filter per each input channel and pointwise convolution is used to create a linear combination of the output of the depthwise convolution. the radial basis function kernel of the svm is then used to take the data points to a higher dimension where they are linearly separable before classification. when this procedure is combined with move learning and tweaking parameters, then a quality cutting edge technique is actualized. the developed system was designed using mobilenetv2, svm, and cnn-svm which are more adapting and used regularly. the design architecture of mobilenetv2 consists of a series of convolutional layers, followed by depthwise separable convolutions, inverted residuals, bottleneck design, linear bottlenecks, and squeeze-and-excitation (se) blocks, while cnn requires hidden layers, max pooling layer, and kernel. data acquisition was performed through the aid of kaggle online data source, while depthwise separable convolution technique of mobilenetv2 and radial basis function kernel of the svm serves as pre-processing tools. the mobilenetv2 was equipped with knowledge by preparing the data and loading a pretrained model while stacking the classification layer on top. the model is trained, evaluated. and finetuned to increase accuracy. training the cnn requires the neural network to be fed with large dataset labelled with their corresponding class label mobilenetv2 feature extraction module was applied and the evaluation of the system was carried out using standard metrics of accuracy, precision, recall, auc, and f1 score. the flowchart diagram for glaucoma detection system is shown in figure 1 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 197 figure 1: flowchart diagram for glaucoma detection 2.1 methodology for building glaucoma detection system using cnn mobilenetv2 there are several approaches and methodologies that can be used for the detection of glaucoma using cnn. here is a general outline of the research methodology for early detection of glaucoma which is essential to prevent irreversible vision loss. in this methodology, specification of the steps taken to develop an accurate glaucoma detection system using the mobilenetv2 convolutional neural network (cnn) architecture is outlined. mobilenetv2 is primarily designed for efficient image classification tasks. while it can be used as a backbone network for various computer vision tasks, including object detection, it is specifically tailored for detecting medical conditions like glaucoma. this approach involves data preprocessing, model construction, training, evaluation, and visualization. figure 2 shows the block diagram of convolutional neural network (cnn) using mobilenetv2. figure 2: block diagram cnn using mobilenetv2 data collection data preprocessing feature extraction machine learning model training and validation model evaluation and construction model prediction and testing http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 198 2.1.1 data collection large datasets of digital images of the retina and optic nerve head from both healthy and glaucomatous eyes were collected from kaggle online data source. these images can be obtained using optical coherence tomography (oct) or fundus photography for data acquisition and preparation. a standardized multichannel dataset for glaucoma which is a collection of 19 public datasets comprising full fundus glaucoma images, and associated image metadata was used for the development of this system. the data set was retrieved from the specified link online; (https://www.kaggle.com/datasets/deathtrooper/multichannel-glaucomabenchmark-dataset/data.) 2.1.2 data preprocessing the dataset was loaded from a csv file containing metadata. the metadata was extracted from the csv file, providing essential information about each image. the dataset was cleaned by filtering out incomplete or irrelevant entries. to facilitate seamless integration with image files, a new column was created by appending '.png' extensions to image filenames. data columns were appropriately converted to their required data types for further processing in order to correct variations in illumination, contrast, and other artifacts that can affect image quality. this step may include denoising, normalization, and segmentation of the retinal layers. 2.1.3 feature extraction a balanced distribution of data across subsets was pivotal for effective model training and this is achieved by calculating the number of healthy eye images and glaucoma infected eye images in the dataset while mobilenetv2 was used as a feature extractor which composed of bottleneck layers, with additional convolutional layer used to deepen the neural network to increase detection accuracy. the preprocessed images were passed through the network while the output from the intermediate layer serves as the feature vector. these features would capture various patterns and structures present in the images. 2.1.4 data visualization: for efficient model training and augmentation, the capabilities of image data generators were harnessed. these generators preprocess and augment image data, while also preserving class balance. moreover, dedicated visualization generators were developed to showcase sample images from the healthy and glaucoma categories. a custom visualization function facilitates the presentation of these samples for insightful analysis. it permits creation of own data visual logic to draw results not covered by built in library of standard charts. the improvise visualization tool was applied for this purpose. improvise is a visualization system that mainly supports coordinated visualizations. it provides primitive and specialized properties whose visual properties can show data using expressions. the expressions can be conditional, logical, or mathematical. improvise provides specialized objects that support complex layouts such as trees. it was used in the accomplishment of visual mappings by navigating from panel to panel in a development environment to create a visualization. since each panel has a distinct purpose, one panel shows the available visual objects and their properties, another panel shows the variables that can be used in expressions. x-y graph was defined using plane view 2d object from the list of visual objects. visual mappings for the visual object were created using layer projection from the properties list, this leads to a new panel where expressions are defined. improvise shows the result as a conditional expression tree with default. this expression was built step-by-step using combo boxes that provide the available expression elements, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng https://www.kaggle.com/datasets/deathtrooper/multichannel-glaucoma-benchmark-dataset/data https://www.kaggle.com/datasets/deathtrooper/multichannel-glaucoma-benchmark-dataset/data okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 199 conditional statement part was manipulated by clicking the tree nodes. function from the category combo box were used to create a comparison and conditional part of the expression. improvise displays the available fields to enable selection of options. visual mappings rely heavily on dialogues. the environment enables the use of combo-boxes that have the expression elements (kostas et al., (2013). 2.2 construction of mobilenetv2 cnn the glaucoma detection system was constructed using the mobilenetv2 cnn architecture. the mobilenetv2 model integrates multiple architectural elements to achieve optimal classification performance. the architecture of mobilenetv2 consists of a series of convolutional layers, followed by depthwise separable convolutions, inverted residuals, bottleneck design, linear bottlenecks, and squeeze-and-excitation (se) blocks. these components work together to reduce the number of parameters and computations required while maintaining the model’s ability to capture complex features. depthwise separable convolution was used to reduce the computational cost of convolutions. it separates the standard convolution into two separate operations: depthwise convolution and pointwise convolution. this separation significantly reduces the number of computations required, making the model more efficient. inverted residuals were used to improve the model’s accuracy by introducing a bottleneck structure that expands the number of channels before applying depthwise separable convolutions. this expansion allows the model to capture more complex features and enhance its representation power. the bottleneck design was applied to further reduce the computational cost by using 1×1 convolutions to reduce the number of channels before applying depthwise separable convolutions. this helps maintain a good balance between model size and accuracy. linear bottlenecks are introduced to address the issue of information loss during the bottleneck process. by using linear activations instead of non-linear activations, the model preserves more information and improves its ability to capture fine-grained details. squeeze-and-excitation (se) blocks are added to mobilenetv2 to enhance its feature representation capabilities. these blocks adaptively recalibrate the channel-wise feature responses, allowing the model to focus on more informative features and suppress less relevant ones. 2.2.1 transfer learning with mobilenetv2: leveraging the mobilenetv2 architecture, pre-trained weights were employed from the imagenet dataset. this transfer learning approach empowered the model with powerful feature extraction capabilities. this process was carried out by creating a dataset from a directory, preprocess and augment data using the sequential api, adapt a pretrained model to new data and train a classifier using the functional api and mobilenet, then fine-tune the classifier's final layers to improve accuracy. the pre-trained model is a network that's already been trained on a large dataset and saved, which allows to be used to customize an own model cheaply and efficiently. mobilenetv2, was designed to provide fast and computationally efficient performance. it's been pre-trained on imagenet, which is a dataset containing over 14 million images and 1000 classes. 2.2.3 global average pooling and dense layers: global average pooling layers were appended to the base architecture, followed by dense layers for classification. these dense layers utilized relu activation and dropout regularization to enhance model generalization, they are responsible for reducing the spatial dimensions of the input data, in terms of width and height, while retaining the most important information. this enables the generation of one http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 200 feature map for each corresponding category of classification task in the last mlpconv layer. instead of adding fully connected layers on top of the feature maps, the average of each feature map is taken, and the resulting vector is fed directly into the softmax layer. 2.3 model compilation, training, and evaluation the performance of the trained machine learning models was evaluated on a separate test dataset using metrics such as sensitivity, specificity, and accuracy (rarasmaya et al., 2022). this step helped to assess the model's ability to detect glaucoma accurately. creating an effective mobilenetv2-based glaucoma detection system requires meticulous training and evaluation procedures. mobilenetv2 was trained on imagenet and is optimized to run on mobile and other low-power applications. it is 155 layers deep and very efficient for object detection and image segmentation tasks, as well as classification tasks. the architecture has three defining characteristics which are depthwise separable convolutions, thin input and output bottlenecks between layers, and shortcut connections between bottleneck layers. mobilenetv2 uses depthwise separable convolutions as efficient building blocks. traditional convolutions are often very resource-intensive, and depthwise separable convolutions are able to reduce the number of trainable parameters and operations and also speed up convolutions in two steps, the first step calculates an intermediate result by convolving on each of the channels independently. this is the depthwise convolution, secondly, another convolution merges the outputs of the previous step into one. this gets a single result from a single feature at a time, and then is applied to all the filters in the output layer. this is the pointwise convolution. 2.3.1 optimizers and loss function the model was compiled with the 'adam' optimizer and binary cross-entropy loss. these choices aligned with the binary classification nature of our problem adaptive moment estimation is an iterative optimization algorithm which was used to minimize the loss function during the training of mobilenetv2 model. it is a combination of rmsprop and stochastic gradient descent with momentum (diederik and jimmy, 2015). 2.3.2 standard metrics standard metrics was introduced, including precision, recall, and f1 score, to comprehensively evaluate model performance. precision and recall are two evaluation metrics used to measure the performance of a classifier, precision measures the accuracy of positive predictions and can be seen as a measure of quality. higher precision means that the algorithm returns more relevant results than irrelevant ones, it is used for machine learning models where low false positive (fp) is important such as spam detection. recall measures how often the model correctly identifies positive instances from all the actual positive samples in the dataset, it shows the ability of a model to find all the relevant cases within a data set. mathematically, it is the number of true positives divided by the number of true positives plus the number of false negatives. it provides an overall measure of how often the model is correct, regardless of whether the instance is positive or negative. the f1-score specifies the weighted average of both precision and recall depending on the weight function. it shows the harmonic mean between precision and recall, and uses recall to get the fraction of true positive records among the total of actual positive records. early stopping and tensor board callbacks were integrated to optimize training efficiency and monitor progress (hossin and sulaiman, 2015). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 201 2.3.3 training and validation model training was initiated using the training data generator, with simultaneous validation using the validation generator. this iterative process fine-tunes the model's parameters for optimal performance. the system was implemented using python programming language, and the model trained with pytorch framework. the data was downloaded using roboflow and converted into a tensorflow imagefolder format. the pre-trained model is loaded and the classification layers stacked on top. the model was trained using the pytorch framework on a colab gpu interface, which allocated a 12gb nvidia tesla k80 gpu. the pre-trained mobilenetv2 used to train a model for glaucoma detection was modified by the replacement of the number of output classes in the last fully connected linear block with the number of classes in the image dataset. the model was fine tunned to increase accuracy after convergence (pan and yang, 2010). 2.3.4 evaluation the model's effectiveness was gauged using the validation data. metrics such as accuracy, precision, recall, specificity, receiver operating characteristics area under curve (rocauc) were computed, offering a comprehensive view of its capabilities. 2.3.5 accuracy (a) this metric was used to generally describe how the model performs in different predictions of glaucoma detection. convolutional neural networks tend to achieve high accuracy rates due to their ability to learn complex features from images. they can capture intricate patterns in retinal images, leading to accurate glaucoma detection. svms also offer good accuracy, but they may not perform as well as cnns when dealing with complex and highly dimensional data like medical images (hossin and sulaiman, 2015). 𝑨 = tp+tn 𝑇𝑃+𝐹𝑃+𝑇𝑁+𝐹𝑁 (1) the measure was computed using the following confusion matrix parameters: true positive (tp): the number of infected images classified correctly. true negative (tn): the number of images correctly predicted as negative. false positive (fp): the number of positive images incorrectly predicted as negative. false negative (fn): the number of negative images incorrectly predicted as positive cnns can be fine-tuned to optimize sensitivity and specificity based on chosen threshold. this flexibility allowed for adjusting the model's performance to meet specific clinical requirements. svms typically provide a good balance between sensitivity and specificity. however, fine-tuning might require more manual intervention compared to cnns. sensitivity metrics measures the fraction of positive patterns that are correctly classified. sensitivity analysis determines how different values of an independent variable affect a particular dependent variable under a given set of assumptions. in other words, sensitivity analyses study how various sources of uncertainty in a mathematical model contribute to the model's overall uncertainty. (hossin and sulaiman, 2015) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 202 𝑺 = tp 𝑇𝑃+𝐹𝑁 (2) the measure was computed using the following confusion matrix parameters: true positive (tp): the number of infected images classified correctly. false negative (fn): the number of negative images incorrectly predicted as positive. 2.3.6 precision (p) this was placed as the ratio of number of positively correctly classified samples to number of samples classified as positive. when the system presents more of the incorrect glaucoma detection, the denominator increases and the precision gets small. the reverse is the case when more correct glaucoma is detected. 𝐏 = tp tp+ fp (3) the measure was computed using the following confusion matrix parameters: true positive (tp): the number of infected images classified correctly. false positive (fp): the number of positive images incorrectly predicted as negative. 2.3.7 recall (r) this was calculated as the ratio of number of positively correct classified glaucoma prediction to the entire glaucoma detection samples. more positive samples are detected at higher recall level. 𝐑 = tp tp + fn (4) the measure was computed using the following confusion matrix parameters: true positive (tp): the number of infected images classified correctly. false negative (fn): the number of negative images incorrectly predicted as positive. 2.3.8 f1 score (f) this was calculated using the realized precision and recall from the system. it is the harmonic mean value of the precision and recall. 𝑭 = 2×𝑅×𝑃 𝑅±𝑃 (5) the measure was computed using the following parameters: precision (p): a measure of the exactness of the model which is the percentage of the positive predicted cases that are true, recall (r): a measure of the completeness of the model which is the percentage of positive case correctly identified to all the cases in a class, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 203 2.3.9 auc-roc (area under the receiver operating characteristic curve) cnns often exhibit high auc-roc values, indicating their ability to discriminate between glaucomatous and healthy cases effectively. this is crucial for diagnostic accuracy. svms can also achieve good auc-roc values but may not consistently outperform cnns when it comes to capturing complex image patterns. to plot the roc curve, the tpr and fpr for many different thresholds were calculated. for each threshold, the fpr value in the x-axis and the tpr value in the y-axis were plotted and the dots joined with a line. the true positive rate (tpr) and false positive rate (fpr) values for each of the thresholds were computed and then plot tpr against fpr. auc (area under the roc curve) measures the area lying below the entire roc curve. it represents the probability that a classifier will rank a randomly chosen positive instance higher than a randomly chosen negative one. auc becomes useful for knowing the average concentration over a time interval, auc/t. the true positive rate (tpr, also called sensitivity) is calculated as tp/tp+fn. tpr is the probability that an actual positive will test positive. the true negative rate (also called specificity), which is the probability that an actual negative will test negative. it is calculated as tn/tn+fp. 2.4 visualization of training progress visualizing the training process was essential for grasping model dynamics and improvements. once pytorch is set up, bring in tensorboard pytorch. install tensorboard by using pip, python's package installer. this step ensures access to all the visualization capabilities offered by tensorboard during the model training journey these visualizations provide insights into data flow, activation functions, and how the different model components are interconnected (dongyu et al, 2018). 2.4.1 plotting training metrics matplotlib was employed to generate insightful plots that illustrate the evolution of training and validation accuracy and loss over epochs (dongyu et al, 2018). 2.4.2 model prediction and testing the culmination of my effort’s manifests in model prediction and rigorous testing. 2.4.3 generating predictions deploying the trained mobilenetv2 model, generated predictions on the test data. this step unveils the model's real-world performance on unseen instances. 2.5 methodology for building glaucoma detection system using svm various methods could be applied in realizing an accurate and timely diagnosis of glaucoma, a leading cause of irreversible blindness, is of paramount importance in preserving vision. support vector machines (svms) was used for the detection of glaucoma from medical images, including retinal scans and optic nerve images. svms are a type of machine learning algorithm that can be employed for binary classification tasks like distinguishing between healthy and glaucomatous eyes. in this methodology, the steps taken to create an effective glaucoma detection system using the support vector machine (svm) algorithm was outlined. the approach applied involves data preprocessing, model construction, training, and thorough evaluation. figure 3 shows the block diagram model of support vector machine (svm) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com javascript:void(0); javascript:void(0); javascript:void(0); javascript:void(0); arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 204 figure 3: block diagram model of support vector machine (svm) 2.5.1 constructing the svm model the svm-based glaucoma detection system was realized through the construction of a sequential model. this model incorporates several crucial components to maximize classification performance. multiple convolutional layers were implemented, followed by maxpooling operations. these layers were instrumental in extracting discriminative features from fundus images. batch normalization was applied to normalize activations, aiding in training stability. the output from the convolutional layers was flattened into a one-dimensional vector, suitable for feeding into dense layers. dense layers with relu activation were introduced to further refine features and enable sophisticated decision making. dropout layers were strategically placed to counter overfitting concerns. the final output layer was tailored for svm-based binary classification. l2 regularization was employed to enhance generalization capabilities. some preprocessing tasks were done on the input images, this includes normalizing the images, colour conversion from rgb to grayscale, resizing the images, removal of noise from the images and contrast adjustment for improving image quality feature extraction using principal component analysis method was then carried out, followed by classification using support vector machine (svm) (abhishek and samir, 2016). 2.5.2 model training and evaluation creating an effective svm model involves meticulous training and thorough evaluation. load in the data and separate into training and test sets. the training set will help find a line to separate the people with and without glaucoma, and the test set will say how well the model works on people it hasn't seen before. with the data loaded, one can prepare the model to be fit to the data. svms are in the svm module of scikit-learn in the svc class. svc stands for support vector classifier and is a close relative to the svm. after bringing in the svc class, the model is fit using the age and chol columns from the training set. using the fit method builds the line that separates those with glaucoma from those without. once the model has been fit, next is file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 205 to predict the glaucoma disease status in the test group, and can compare the model predictions to the actual observations in the test data. in the pursuit of comprehensive evaluation, custom metrics, and f1 score were defined. early stopping and tensor board callbacks were integrated to optimize training efficiency and monitor model progress. early stopping was used as a regularization to avoid overfitting when training a with an iterative method, such as gradient descent. such methods update the learner so as to make it better to fit the training data with each iteration (abhishek and samir, 2016). a callback is passed into the model in the call to fit and is called by the method at various points in the training. the callback object can access the model at various time states and with it take action; such as interrupt training, save a model, load a different weight set or alter the state of the model. tensorboard allows viewing of the models at a high level, which can be important in debugging and optimizing the model using features like live graphs of training and validation metrics. tensorboard, enables visually monitoring metrics during training, visualizing the model architecture, visualizing histograms of activations and gradient, and-exploring embeddings in 3d (dongyu et al., 2018). training was initiated, utilizing the training data generator, while simultaneously validating using the validation generator. this iterative process refines our model's weights and biases. to train the svm, certain decisions were applied starting from importing the dataset, exploring the data to figure out what they look like, pre-processing the data, splitting the data into attributes and labels, dividing the data into training and testing sets, training the svm algorithm, make some predictions, and evaluate the results of the algorithm (abhishek and samir, 2016). to assess the model's performance, evaluation was carried out on the validation data. metrics such as accuracy, precision, recall, auc, and f1 score were computed and analyzed. the effectiveness of svm depends on the selection of kernel, kernel's parameters and soft margin parameter c. each pair of parameters is checked using cross validation, and the parameters with best cross validation accuracy are picked. another important step in evaluating an svm model is choosing the right type of model and the appropriate parameters for the problem. there are different types of svm models, such as linear, polynomial, radial basis function (rbf), and sigmoid, that have different assumptions and characteristics. the svm classification score for classifying observation x is the signed distance from x to the decision boundary ranging from -∞ to +∞. a positive score for a class indicates that x is predicted to be in that class. a negative score indicates otherwise (komal et al, 2019). 2.5.3 visualizing training progress a visual representation of training progress is essential for understanding model dynamics. the visualization process was carried out by importing necessary libraries and loading the dataset, training svm with linear kernel, creating meshgrid for decision boundary, plotting decision boundary of linear svm, defining gamma values, and plotting decision boundaries for each gamma value. matplotlib was employed to generate insightful plots depicting the progression of training and validation accuracy and loss across epochs. the training and validation loss values provide important information because they give us a better insight into how the learning performance changes over the number of epochs and help us diagnose any problems with learning that can lead to an underfit or an overfit model. they will also inform us about the epoch with which to use the trained model weights at the inferencing stage. computationally, http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com javascript:void(0); javascript:void(0); arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 206 the training loss is calculated by taking the sum of errors for each example in the training set. it is also important to note that the training loss is measured after each batch. this is usually visualized by plotting a curve of the training loss. this is carried out by iimporting digit dataset and necessary libraries, importing learning curve function for visualization, splitting dataset into train and test, and plotting graphs using matplotlib to analyze the learning curve (abhishek and samir, 2016). the culmination of our effort lies in the generation of predictions and model testing. prediction is done with a mapping function which maps independent variables to dependent variable. the mapping function for svm is a decision boundary which makes the distinction between two or more classes. the model-building steps in prediction that are used iteratively until a desired model has been constructed are data preparation, model selection and data fitting, and model validation. the accuracy of the classification with svm can be calculated by adding up all the data that are true positive (tp) and true negative (tn), then dividing the result of the summation by the total amount of data. a support vector machine (svm) is a supervised machine learning algorithm that classifies data by finding an optimal line or hyperplane that maximizes the distance between each class in an n-dimensional space (hossin and sulaiman, 2015). the trained svm model was deployed to predict on the test data. this step illuminated the model's actual performance on unseen data. in the realm of medical image analysis, the glaucoma detection system using svm stands as a testament to the synergy of advanced algorithms and meticulous methodologies. to build the predictive model, dataset is collected and organized, it is then cleaned and made available for an algorithm to build the model. generating the model firstly, imports the svm module and create support vector classifier object by passing argument kernel as the linear kernel in svc () function. then, fit the model on train set using fit () and perform prediction on the test set using predict (). the support vector uses a mathematical function, often called a kernel function which is a math function that matches the new data to the best image from the training data in order to predict the unknown image label through systematic data preprocessing, model construction, and intensive training, a model has been built, capable of distinguishing between healthy and glaucoma fundus images. 2.6 methodology for building glaucoma detection system using mobilenetv2 and svm (cnn-svm) there are several approaches and methodologies that can be used for the detection of glaucoma using cnn-svm. here is a general outline of the research methodology for early detection of glaucoma is essential to prevent irreversible vision loss. in this methodology, we outline the steps taken to develop an accurate glaucoma detection system using the mobilenetv2 convolutional neural network (cnn) and svm architecture. mobilenetv2 is primarily excellent at feature extraction from medical images, while svms are effective at classification tasks. while it can be used as a backbone network for various computer vision tasks, including object detection, it is specifically tailored for detecting medical conditions like glaucoma. our approach encompasses data preprocessing, model construction, training, evaluation, and visualization but during the process svm was used as an output layer from file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 207 cnn thereby adding regularization for svm. because when we use support vector machine for binary classification, we use something called linear svm. 2.6.1 construction of mobilenetv2 cnn-svm the glaucoma detection system was constructed using the mobilenetv2 cnn architecture and svm architecture as base output layer. this model integrates multiple architectural elements to achieve optimal classification performance. leveraging the mobilenetv2 architecture, pre-trained weights were employed from the imagenet dataset. this transfer learning approach empowered my model with powerful feature extraction capabilities. global average pooling layers was appended to the base architecture, followed by dense layers for classification. these dense layers utilized relu activation and dropout regularization to enhance model generalization. 2.6.2 model compilation, training, and evaluation the performance of the trained machine learning models was evaluated on a separate test dataset using metrics such as sensitivity, specificity, and accuracy. this step helps to assess the model's ability to detect glaucoma accurately. creating an effective mobilenetv2-based glaucoma detection system requires meticulous training and evaluation procedures. the model was compiled with the 'adam' optimizer and binary cross-entropy loss. these choices aligned with the binary classification nature of our problem. custom metrics was introduced, including precision, recall, and f1 score, to comprehensively evaluate model performance. early stopping and tensor board callbacks were integrated to optimize training efficiency and monitor progress. model training was initiated using the training data generator, with simultaneous validation using the validation generator. this iterative process fine-tunes the model's parameters for optimal performance. added output layer model and added (tf.keras. layers. dense (1, kernel_ regularizer = l2(0.01). added regularizer for svm, because when using support vector machine for binary classification, linear svm activation='linear')) was applied. softmax was used as activation in the output layer model. the model's effectiveness was gauged using the validation data. metrics such as accuracy, precision, recall, f1 score, specificity, and receiver operating characteristic area under the curve (roc-auc) were computed, offering a comprehensive view of its capabilities. 3. results and discussion the impact of classification model training results showing the comparison of all the chosen evaluation metrics (accuracy, precision, recall, auc, and f1 score) are presented in table 1. mobile-netv2, and svm were the robust deep learning models that were employed in this work. a batch size of 64 and an epoch of 10 were used to train each model. the architectures were fine-tuned specifically for glaucoma detection by adding additional layers. the models were trained on the training set and evaluated on the validation set. the loss function employed during training was the adam optimizer and binary cross-entropy loss function. in the realm of medical image analysis, the mobilenetv2 cnn-based glaucoma detection system underscores the potent fusion of advanced neural networks and meticulous methodologies. our systematic approach to data preprocessing, model construction, intensive training, and holistic evaluation results in a model capable of discerning between healthy and glaucoma fundus images. this journey serves as a testament to the transformative power of deep learning in addressing pressing healthcare challenges. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 208 table 1: comparison of the used algorithms the evaluation metrics used include accuracy, precision and recall, f1 score, and the area under the receiver operating characteristic (auc-roc) curve. the metric evaluation for detecting glaucoma eye disease using mobile_netv2, svm and cnn-svm offered a mean sum of 71% accuracy, 93% precision, 46% recall, 78% auc and 29% f1 score. comparison: accuracy: mobilenetv2 out performs svm and cnn-svm in terms of accuracy, indicating a better overall predictive performance. precision: svm as well as cnn-svm had higher precision, suggesting that it has a lower false positive rate compared to mobilenetv2. recall: mobilenetv2 has higher recall, implying that it is better at identifying actual positive instances compared to svm and cnn-svm was lower as well. auc: mobilenetv2 has a higher auc, indicating a better ability to discriminate between the three classes. f1 score: mobilenetv2 has a higher f1 score, indicating a better balance between precision and recall compared to svm and cnn-svm. in summary, while svm and cnn-svm excels in precision, mobilenetv2 demonstrates better recall, auc, and overall balanced performance. the choice of model depends on the specific goals and priorities of the glaucoma detection application, such as whether avoiding false positives (precision) or detecting as many true positives as possible (recall) is more critical. the combination of cnn and svm offers a robust and accurate solution for glaucoma detection. cnns are excellent at feature extraction from medical images, while svms are effective at classification tasks. this dual approach can enhance the reliability of the system. figure 4 shows the training and validation loss curves of mobile-netv2. figure 4: training and validation loss curves of mobile-netv2 evaluation metrics mobilenetv2 (cnn) svm cnn-svm accuracy 0.7790 0.7090 0.6310 precision 0.8532 0.9906 0.9507 recall 0.6740 0.4220 0.2700 auc 0.8609 0.8081 0.6838 f1 score 0.3977 0.2721 0.2063 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 209 the plots on figure 4 shows the plotting of loss against epoch. epoch means the number of times the dataset training and validation loss curves was done for mobile-net v2. the green color indicates the training loss and the red color indicates validation loss. from the plot, it was discovered that while training and validating, the training loss went downwards from epoch 2 to epoch 10. (which means., the training loss was almost zero on epoch 10). while the validation loss was ranging within sinusoidal waveform between 0.55 to 0.45 loss on the plot. the training loss was better on each epoch than validation loss. figure 5 shows the training and validation accuracy curves of mobile-netv2. figure 5: training and validation accuracy curves of mobile-netv2 this plot on figure 5 shows the plotting of accuracy against epoch, which shows the number of times the dataset training and validation accuracy curves was done for mobile-net v2. the green color indicates the training accuracy and the blue color indicates validation accuracy. from the plot, it was discovered that while training and validating, the training accuracy went upwards from epoch 2 to epoch 10., (high and better accuracy simultaneously on each epoch). while the validation accuracy also went upward little bit on each epoch, compared to training accuracy. training accuracy has a better output than the validation accuracy as stated from the plot above. figure 6 shows the training and validation loss curves of svm figure 6: training and validation loss curves of svm http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 210 the plot on figure 6 shows the plotting of loss against epoch, indicating the number of times the dataset training and validation loss curves was done for svm. the green color indicates the training loss and the red color indicates validation loss. from the plot, it was discovered that while training and validating, the training loss went downwards from epoch 2 to epoch 10., (the training loss was almost zero on epoch 10). while the validation loss was ranging within sinusoidal waveform between 0.87 to 0.60 loss on the plot. the training loss was better on each epoch than validation loss. figure 7 shows the training and validation accuracy curves of svm figure 8: training and validation loss curves of cnn-svm figure 8 shows a plotting of loss against epoch, indicating the number of times the dataset training and validation loss curves was done for cnn-svm. the green color indicates the training loss and the red color indicates validation loss. from the plot, it was discovered that while training and validating, the training loss went downwards from epoch 2 to epoch 10., (the training loss was almost zero on epoch 10). while the validation loss was ranging between 0.82 on epoch 2 and training loss ranging between 1.32 loss on the plot. the training loss was better on each epoch than validation loss but the validation has consistency this time around. figure 9 shows the training and validation accuracy curves of cnn-svm. figure 9: training and validation accuracy curves of cnn-svm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 211 figure 9 shows the plotting of accuracy against epoch, illustrating the number of times the dataset training and validation accuracy curves was done for cnn-svm. the green color indicates the training accuracy and the blue color indicates validation accuracy. from the plotting, it was discovered that while training and validating, the training accuracy went upwards from epoch 2 to epoch 10, but came down to 62% on the 10th epoch., (good accuracy but not consistent enough). while the validation accuracy also went upward little bit on each epoch, came down to 54% accuracy on the 6th epoch and as well got same accuracy percentage of 62%. training accuracy has a better output than the validation accuracy as stated from the plot above with a 68% accuracy curve for cnn-svm on the 9th epoch. figure 10: 3d bar chart comparison between mobile-netv2 (cnn), svm and cnn-svm figure 10 shows a comprehensive bar chart depicting the performance of the mobilenetv2, svm, and cnn-svm algorithms used in the glaucoma detection system. this analysis was carried out with the aid of accuracy, precision, recall, auc, and f1score as evaluation metrices. 4. conclusion in conclusion, the development of a glaucoma detection system using mobilenetv2, svm and cnn-svm is a significant advancement in the field of ophthalmology. it has the potential to enhance early detection, reduce human error, and improve patient outcomes. however, it is essential to address challenges related to data quality, interpretability, and integration into clinical practice to realize the full potential of such a system in improving the diagnosis and management of glaucoma. the performance analysis of classification and detective accuracy between mobilenetv2, svm and cnn-svm techniques were examined and compared. both mobilenetv2 and svms have their strengths and weaknesses in the context of glaucoma detection; mobilenetv2 excels generally in terms of accuracy and other applied metrics, particularly when ample data is available, and they can adapt to different clinical requirements. svms are computationally efficient and offer a reasonable result in precision. cnn-svm performs poorly considering svms deficiency in large data content. mobilenetv2 tends to thrive when trained on large datasets, as they can learn a wide range of features and patterns. with limited data, they may be prone to overfitting. svms can perform well with smaller datasets and are often used when data availability is constrained. finally, the development of a glaucoma detection system using mobilenetv2 and svms is a promising approach, and the 0 0.2 0.4 0.6 0.8 1 1.2 mobilenetv2 (cnn) svm cnn-svm 3d bar chart comparison between mobilenetv2 (cnn), svm and cnn-svm accuracy precicion recall auc f-1 score http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 212 choice between these models should be based on specific data, computational resources, and interpretability needs. combining the strengths of both models and following best practices in data collection, preprocessing, and evaluation can lead to a more robust and effective glaucoma detection system. references ali, s. and sertan s. 2019. transfer learning for early and advanced glaucoma detection with convolutional neural networks. medical technologies national conference (tiptekno), doi:10.1109/tiptekno.2019.8894965. weilu, yt., yue, yu., yiqiao, x., changzheng, c. and yin, s. 2018. applications of artificial intelligence in ophthalmology: general overview. hindawi journal of ophthalmology, 2018(6): 1-15. doi: 10.1155/2018/5278196 nooshin, m., vahid, n., philip, y. and joelle, ah. 2019. deep multi-task learning for interpretable glaucoma detection. ieee 20th international conference on reuse and integration of data science, 167-174. doi.org /10.1109/iri.2019.00037. mijung, k., jong, c., seung, h., olivier, j., sofie, vh., changwon, k. and wesley, dn. 2019. medinoid: computer-aided diagnosis and localization of glaucoma using deep learning. article in mdip journal of applied science, 9(15): 1-19. https://doi.org/10.3390/app9153064 hassan, m., thomas, jf., nicole, c., carlos, gm., dana, mb., jeffrey, ml., robert, r. and donald ch. 2017. hybrid deep learning on single wide-field optical coherence tomography scans accurately classifies glaucoma suspects. national centre of biotechnology information journal of glaucoma, 26(12): 1086–1094. doi: 10.1097/ijg.0000000000000765 asaoka, r., murata, a., iwase, and araie, m. 2016. detecting pre-perimetric glaucoma with standard automated perimetry using a deep learning classifier. ophthalmology, 123(9): 1974– 1980. doi: 10.1016/j.ophtha.2016.05.029 annan, l., jun, c., damon, wk. and jiang, liu. 2016. integrating holistic and local deep features for glaucoma classification. proceedings of 38th annual international conference of the ieee engineering in medicine and biology society (embc): 1328-1331. doi:10.1109/embc.2016.7590952 xiangyu, c., yanwu, x., damon, wk., tien, yw. and jiang, liu. 2015. glaucoma detection based on deep convolutional neural network. proceedings of 37th annual international conference of the ieee engineering in medicine and biology society (embc), milano, italy. doi: 10.1109/embc.2015.7318462 dinial, un., handayani, t. and chastine, f. 2019. classification of diabetic retinopathy and normal retinal images using cnn and svm. 12th international conference on information & communication technology and system (lcts): 152-157. doi:10.1109/icts.2019.8850940 tham, yc., li, x., wong, ty., quigley, ha., aung, t. and cheng, cy. 2014. global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and metaanalysis. ophthalmology, 121(11): 2081-2090. doi: 10.1016/j.ophtha.2014.05.013 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng okomba et al: development of glaucoma detection system using cnn and svm. azojete, 20(1):193-214. issn 1596-2490; 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vol. 20(1):193-214. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: nnamdi.okomba@fuoye.edu.ng 214 komal, sk., puneeth, c., rekha, bs. and srinivasan, gn. 2019. performance evaluation of support vector machines (svm) and convolution neural networks (cnn) for video tampering classification. international journal of soft computing, 14(3): 53-60. doi: 10.36478/ijscomp.2019.53.60 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng corresponding author’s email address: ako.terseer@yahoo.com 894 arid zone journal of engineering, technology & environment original research article influence of bamboo fibre on engineering properties of lateritic soils as highway pavement materials t. ako1*, k. obed2, p. ndyabijuka3, j. bainomugisha2 1 department of civil engineering, university of jos – jos, nigeria 2 department of civil engineering, kabale university, kabale, uganda 3department of civil and building services engineering, mbarara university of science and technology *corresponding author’s email: ako.terseer@yahoo.com article information abstract lateritic soils commonly used in road pavement construction often exhibit inadequate strength and excessive plasticity, leading to poor performance under traffic and environmental loads. the study investigated bamboo fibre's (bf) ability to stabilize lateritic soils. the natural lateritic soils used were classified as clayey gravel and a-2-6(0) according to unified soil classification system and aashto respectively. they were treated with 0 – 1.0 % (at 0.25% increment) of bf by dry weight of the soil. liquid limit decreases with increase in fibre up to 0.5%, plastic limits decreased with increase in bf content but rises at 1%, while the plasticity index (pi) decreased with increased bf content up to 0.5% and increases at higher bf content. maximum dry density increases with increased fibre contents to maximum of 2.207 g/cm3 and 2.092 g/cm3 at 0.75% for heavy and light compaction respectively and decreases with further fibre increment. optimum moisture content decreased continually for all compaction efforts with higher fibre contents. generally, soaked and unsoaked cbr increases from 15-25% and 20 29% (from 0-0.75% fibre) and slightly decrease at 1.0%, while ucs of the treated soil increased from 1130 to 2000 kn/m2 at (0-0.50% fibre contents). the ucscbr developed relationships were of the second order polynomial form with r² values of 0.89 and 0.97 for soaked and unsoaked conditions respectively. the statistical analysis (fcal > fcrit) confirmed significant effects of bf on soil properties. overall, 0.75% bf provided optimal improvement and is recommended for use in sub-base layers of road pavements. long-term durability and field performance were not evaluated; therefore, further in-situ validation is required. received: 11th may 2025 revised: 22nd november 2025 accepted: 24th november 2025 keywords: bamboo fibre engineering properties lateritic soil pavement materials highway pavement soil stabilization © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction examining bamboo fibre’s stabilizing capacity in lateritic soils was prompted by the rising expense of traditional stabilizing agents and the necessity of economically utilizing wastes for advantageous highway construction projects. the method of stabilizing soil is blending or combining the soil with chemicals or other stabilizing agents like agricultural wastes to increase its physical qualities, such as strength and durability. the different types of methods used for soil stabilization include chemical stabilization, bitumen and the environmentally friendly method of employing geotextiles and geosynthetic fibres (afrin, 2017; sabzi, 2018; ogundare, 2018). geosynthetics are products composed of several kinds of polymers, which can be woven or not (huang et al., 2021). these are applied to improve the properties of soil and have given rise to a workable, cost-effective method of civil engineering construction. the behaviour of plant roots, which strengthens near-surface soils with low effective stress, is comparable to how fibres are used in soil and improve soil stability. consequently hejazi et al. (2012) reported that positive findings from laboratory and a few in-situ test results have demonstrated the possible application of fibres for soil mass reinforcement. improving soil mass stability is the main goal of its reinforcement since it makes the soil more resilient to shear failure and deformation. numerous reinforcing approaches are already available to stabilize problematic soils (ogundare et al., 2018; kramar and gonzalez-benito, 2022). azojete december 2025. vol.21(4):894-906 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/001 www.azojete.com.ng mailto:ako.terseer@yahoo.com mailto:ako.terseer@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 895 chemical and mechanical approaches are the two basic ways of producing bamboo fibres. the former involves breaking down of the fibre using abrasive chemicals and extrudes it through mechanical spinnerets, mimicking the viscose process used to manufacture rayon (kramar and gonzalez-benito, 2022; joshi and bhattacharyya, 2011). the process of producing lyocell fibres employs the closed solvent spinning cycle. engineering structures such as paved roads and buildings impose loads on the soils on which they are constructed. these soils are therefore required to have a bearing capacity sufficient to withstand these loads. uganda road network is mostly composed of lateritic soil layered roads, due to clayey property of these soils and having hard top and weak bottom, are capable of absorbing and retaining an appreciable amount of water, making them slippery when it rains. in the long run, the roads develop potholes, and heave as a result of heavy traffic and detainment of water in the soils (ali et al., 2011). cement and lime have been the two primary materials utilized to improve the engineering qualities of soil over the years, (consoli et al., 2009). by burning fossil fuels to provide the energy needed for the cement manufacturing process, the cement-lime subsector contributes approximately 7% of worldwide co2 emissions to the environment and requires between 12 and 15% of all industrial energy, (ali et al., 2011; oh, et al., 2014; schneider, 2019). global warming is one of the detrimental repercussions this has on the environment and the future of humanity. in addition to this, some cement bags currently produced are a threat to the environment since they are non-biodegradable, which is environmentally hazardous, (podder et al., 2020). the technique of stabilizing soil using geosynthetics can be effectively used to meet the challenges of the society such as the increasing prices of cement and excessive use of natural resources like limestone. cement production is also attributed to release of carbon dioxide into the atmosphere which leads to global warming. therefore, use of bamboo fibre, as a stabilizer for lateritic soils will reduce the problem of costs and environmental concerns related to the use of cement as a stabilizer. the strength parameters of the natural soil may be enhanced by adding bamboo fibres, which would lessen the thickness of the pavement layer and the amount of stress on the subgrade. the bamboo fibre is one of the agro-waste materials that is widely accessible, inexpensive and environmentally beneficial (gowthaman et al., 2018). thus, this study was aimed at investigating the effect of bamboo fibres on engineering properties of laterite soils as material for road pavement construction. 2. materials and method 2.1 research design the research used experimental matrix method to predict the outcome of using different material combinations to get variations and hypothesize variable results. it also planned for the delivery of the experiment under statistically optimal conditions given the constraints of available resources. the arrangement of the deed carried out is summarized as shown in figure 1. figure 1: research test design 2.2 materials 2.2.1 soil samples bulk samples of the yellowish-brown lateritic soil were obtained by disturbed sampling from a borrow pit at a depth of 2.0 3.0 m along kabaraga on the kabale–mbarara road in kabale district, uganda. sampling at this depth follows common geotechnical/soil engineering practice, as soils beyond the upper 1.5 m are less affected by organic matter, surface leaching, and anthropogenic disturbance, and therefore provide more representative materials for geotechnical evaluation in line with bs 1377-1 (2016) and astm d1452-16 (2016). after transporting materials to the laboratory, the samples were air-dried for two days to reduce natural moisture content and ensure uniformity before pulverization and testing. air-drying is consistent with standard http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 896 specimen preparation guidelines, which recommend drying at ambient temperature to avoid alteration of soil structure or mineralogy that may occur during oven drying (bs 1377-1, 2016; astm d421, 2007). the dried soil was manually broken down to pass through the appropriate sieve size prior to laboratory testing. 2.2.2 bamboo fibre the bamboo used in this study was sourced from a plantation in bwera–kasese, uganda. to obtain the fibres, the bamboo culms were soaked in a sodium hydroxide (naoh) solution for 1–2 days. the alkali-treatment method is widely adopted for natural fibre extraction and modification because naoh helps remove lignin, hemicellulose, and surface impurities, thereby increasing fibre roughness and enhancing bonding with soil particles. this was done in line with guidelines for fibre surface treatment by (li et al., 2007; astm d790-17, 2017). after treatment, the fibres were washed, cut into approximately 1.0 cm lengths, and air-dried to a stable condition as shown in plate i. the fibre length was selected based on previous studies indicating that short discrete natural fibres within the range of 1–2 cm improve soil reinforcement efficiency and promote uniform fibre distribution (consoli et al., 2010). test specimens were prepared by incorporating 0%, 0.25%, 0.5%, 0.75%, and 1.0% bamboo fibre (by dry weight of soil) in 0.25% increments. plate 1: bamboo fibre sample preparation 2.3 method in compliance with the procedures described in (bs 1377, 1990; bs 1942, 1990) and standard astm codes, the index properties, particle size distribution, soil classification, specific gravity, water absorption, compaction characteristics, california bearing ratio, and unconfined compressive strength of lateritic soil samples were determined. in order to stabilize the lateritic soil, bamboo fibre was added in steps of 0.25% by weight of dry soil. 2.3.1 particle size distribution in order to classify the particles into distinct size ranges and ascertain the proportion by mass of each size range, the soil underwent particle size distribution in accordance with (salter, 1979; head, 1992; astm, d6913 – 04, 2009). a soil sample was run through progressively decreasing mesh sizes in order to accomplish this. the cumulative proportion by weight passing each filter was computed using the weight of the soil sample kept on each sieve (astm d5319 – 97, 2008; craig, 1992). 2.3.2 specific gravity samples of soil-bf mixes, bamboo fibre, and oven-dried soil weighing between 50 and 100g were sieved using a sieve with an aperture of 2.36 mm. next, the mixture's specific gravity was ascertained by applying the techniques outlined in (astm c127 – 07, 1994). 2.3.3 atterberg limits between 50 and 100 g of oven-dried soil, bamboo fibre, and soil-bf mix samples were sieved using a sieve with a 2.36 mm sieve aperture. then, using the techniques outlined in (astm d4318 – 10, 1994), the mixture's specific gravity was determined. to ascertain the cohesiveness and plasticity of the soil-bamboo fibre mixtures, these experiments were performed on each mixture. http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 897 2.3.4 compaction characteristics the process of reducing the air spaces in the soil to make it denser is called compaction. its objective is to determine the soil's optimum moisture content (omc) and maximum dry density (mdd) (nayak and mishra, 2016). materials with a high mdd with a relatively low moisture content are frequently suitable for fill embankments as well as sub-grade, sub-base, or base course. to reproduce the expected compaction energy encountered in the field and for comparative purposes, the british standard light (bsl) and heavy (bsh) compaction methods were used in this experiment to establish the omc corresponding to the mdd (astm d698-07el, 1994; daniel and wu, 1993). 2.3.5 california bearing ratio and unconfined compressive strength tests the california bearing ratio (cbr) test for the soil–bamboo fibre mixtures was performed in accordance with the astm d1883-16 (2016) standard. the cbr value is determined at penetrations of 2.5 mm and 5.0 mm, and the higher of the two values is adopted as the cbr of the specimen, as specified in the astm d188316 (2016) standard. the unconfined compressive strength technique was carried out by applying an increasing load to prepared specimens (mixed, compacted, and cured) until failure, the strength of the stabilized material was ascertained. plastic bags were used to keep carriers and specimens airtight in a water bath which ideally keeps temperatures at or around 25 °c in accordance with (bs 1377, 1990 and bs 1924, 1990), for natural and modified soil samples respectively. 3. results and discussion 3.1 results of preliminary test on the natural soil table 1 and figure 2, respectively, display the engineering parameters of the natural soil and the sieve analysis results. table 1: engineering properties of natural laterite soil used property quantity liquid limit (ll) % 39.4 plastic limit (pl) % 20 plasticity index (pi) % 19.4 aashto classification a-2-6 unified soil classification systems (uscs) silty or clayey gravel and sand group index 0 color reddish-brown maximum dry density at heavy compaction (mddh), g/cm3 1.923 maximum dry density at light compaction (mddl), g/cm3 1.980 optimum moisture content at heavy compaction (omch) % 15.7 optimum moisture content at light compaction (omcl) % 12.6 california bearing ratio (cbr) % (soaked) 15 california bearing ratio (cbr) % (unsoaked) 20 unconfined compressive strength (ucs), kn/m2 1130 according to the aashto classification system, the natural soil sample may be broadly classified as silty or clayey gravel and sand soil based on the engineering parameters in table 1 and fell within group classification a-2-6(0). this is in line with research by ola (1983), which claims that the a-2, a-6, and a-7 groups comprise the majority of lateritic soils used for road construction. the soil contains notable amounts of clay material elements, as well as some sand and gravel material constituents. the results in table 1 and figure 2 indicated http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 898 that the soil samples had a lower percentage of fractions finer than 0.075, (that is, % passing 0.075 mm sieve of 0.3% < 35%), ll of 39.4% < 40%, and pi of 20% > 11% while passing through a 0.075 mm sieve. as a result, the soil is categorized as a-2-6(0), and (aashto, 1986) rates the general sub-grade as excellent to good. the natural soil underwent a compaction test, yielding maximum dry densities of 1.923 g/cm3 at heavy compaction (mddh) and 1.980 g/cm3 at light compaction (mddl). the corresponding optimum moisture contents at heavy compaction (omch) and light compaction (omcl) were 15.7% and 12.6%, respectively. the soaked california bearing ratio (cbr) was 15.36%, and the unsoaked california bearing ratio (cbr) was 19.89%. it was determined that the unconfined compressive strength was 1130 kn/m2. figure 2: particle size distribution graph 3.1.1 specific density of bamboo fibre treated soil from the results presented in figure 3, the specific gravity of the soil showed slight fluctuations with increasing bamboo fibre content. the measured values were 2.61, 2.51, 2.60, 2.50, and 2.66 for 0%, 0.25%, 0.50%, 0.75%, and 1.0% fibre contents respectively. although no clear linear trend was observed, this behaviour is consistent with previous findings on natural fibre soil mixtures, where the introduction of low-density organic fibres can produce non-uniform changes in specific gravity depending on fibre distribution and interaction with soil minerals (li et al., 2007; consoli et al., 2010). bamboo fibres generally have lower density than mineral soils; therefore, slight increases or decreases in specific gravity may result from localized clustering of fibres or incomplete bonding at certain replacement levels. the implication of this behaviour is that specific gravity alone may not be a reliable indicator of the effectiveness of fibre stabilization, since the mechanical improvements observed in terms of strength (cbr and ucs) are governed more by fibre-soil interlocking and reinforcement effects than by changes in particle density. thus, the irregular variations in specific gravity do not adversely affect the stabilization outcome but reflect the natural variability associated with incorporating organic fibres into soil matrices. figure 3: specific gravity versus % fibre 3.1.2 water absorption of bamboo fibre treated soil the water absorption results, as presented in figure 4, show a generally increasing trend with higher bamboo fibre content, except for a slight decrease observed at 0.50% fibre. the overall increase in water absorption can be attributed to the hygroscopic nature of bamboo fibres, which possess internal voids and cellulose-based 2.40 2.50 2.60 2.70 0 0.25 0.5 0.75 1 1.25 s p ec if ic g ra v it y % fibre http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 899 structures capable of retaining moisture. similar observations have been reported in studies involving natural fibre-soil composites, where fibres absorb part of the pore water and consequently alter the soil’s moisture distribution (li et al., 2007). the slight drop at 0.50% fibre may be linked to improved fibre–soil interlocking at this specific content, which reduces the number of open voids available for water infiltration. consoli et al. (2010) also noted that when fibres are more uniformly dispersed at certain proportions, they can fill microvoids within the soil matrix, temporarily reducing overall water uptake. this behaviour implies that water absorption characteristics in fibre-stabilized soils are highly sensitive to both fibre content and distribution. higher absorption at elevated fibre percentages may influence compaction behaviour and optimum moisture requirements, while the temporary reduction at 0.50% suggests that there may be an optimum fibre range where moisture-related effects are minimized, potentially contributing to better mechanical performance. this highlights the need to consider both hydrophilic properties of fibres and their dispersion within the soil when designing fibre-stabilized pavement materials. figure 4: water absorption against % fibre 3.1.3 influence of bamboo fibre on atterberg limits of lateritic soils the impact of bamboo fibres on the atterberg limits (consistency tests) of laterite soils and its trends are shown in table 3 and figures 5–7. the ranges for the liquid limit, plastic limit, and plasticity index are 36.0% to 40.3%, 16.4% to 20.0%, and 19.1% to 21.2%, respectively. figure 5: liquid limit versus % fibre figure 6: plastic limit vs % fibre figure 7: plasticity index versus percentage fibre close look at figures 5-7 indicated that the atterberg limits results do not have a specific pattern but the liquid limit and plastic limit decreased with increment in fibre content from 0 to 0.5% and from 0 to 0.75 % then experience a slight increase for 0.75 and 1.0% fibre content. on the other hand, the plasticity index decreases up to 0.5% fibre and became constant for 0.75 and 1.0%. the friction forces of resistance that formed between the soil and the bamboo fibre, which acted as a reinforcing material, may be accountable for the decrease in ll and pl. at 0.5% fibre content, the bamboo fibres are likely optimally dispersed within the soil, reducing the soil’s overall plastic activity and leading to lower ll and pi. beyond this point, excess fibres 5 7 9 11 13 15 17 0 0.2 0.4 0.6 0.8 1 1.2 w at er a b so rp ti o n (% ) % fibre 34 36 38 40 42 0 0.25 0.5 0.75 1 1.25 l iq u id l im it , ( % ) % fibre 10.0 15.0 20.0 25.0 0 0.25 0.5 0.75 1 1.25 p la st ic l im it , (% ) % fibre 10.0 15.0 20.0 25.0 0 0.25 0.5 0.75 1 1.25 p la st ic it y i n d ex % fibre http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 900 may clump together, trap water, and interfere with soil structure, causing ll and pi to rise again. this reflects the transition from effective reinforcement to fibre-induced interference in the soil matrix. 3.2 strength characteristics of bamboo fibre treated soil 3.2.1 compaction characteristics results tables 2 3 and figures 8 – 11 presents the compaction results for both mdd and omc with varying bamboo fibre in soil by percentage. table 2: compaction results for treated soil samples with varying percentage fibre light compaction results for treated soil samples 0% 0.25% 0.50% 0.75% 1.00% dd a.mc dd a.mc dd a.mc dd a.mc dd a.mc 1.9 11.2 1.812 9.265 9.265 1.780 8.849 1.943 7.785 1.934 1.9 11.8 1.928 10.234 10.234 1.914 9.278 2.013 8.528 2.009 2 12.6 2.016 11.333 11.163 2.024 10.045 2.086 9.434 2.111 1.9 13.4 1.923 13.371 12.246 1.969 11.786 2.013 11.980 1.996 1.8 14.2 1.828 14.036 14.067 1.802 12.869 1.927 12.990 1.934 heavy compaction results for treated soil samples 13.172 1.860 8.673 1.813 8.889 1.883 9.144 1.906 8.352 1.855 14.152 1.892 11.566 1.923 11.047 1.945 10.485 1.973 9.516 2.059 15.708 1.923 14.130 1.980 13.288 1.999 11.829 2.034 9.965 2.128 16.697 1.898 15.073 1.938 15.873 1.920 14.506 1.947 11.320 2.030 17.190 1.882 16.360 1.856 17.072 1.875 16.071 1.900 12.91 1.847 note: dd = dry density, a.mc = average moisture content with reference to figures 8 and 9, it was shown that, in general, the optimal moisture level falls as the maximum dry density increases with increasing fibre content up to 0.75% and then declines at 1.0% bamboo fibre. it is believed that when bamboo fibre content rises, the desire for water decreases, resulting in a decreased optimal moisture content. the fibre binds the soil together and restricts the amount of pore space available for soil expansion and absorption, and speeds up the rate at which the soil absorbs water. the creation of "transitional compounds" by molecular rearrangement may be the cause of the rise in the maximum dry density of soil-bamboo fibre content which agreed with the studies of (adefemi and wole, 2013). a further rise in the mdd is thought to be caused by the clay particles flocculating and aggregating in the soil and taking up greater spaces, which increases the volume of the voids. as a result, lowers the weight to volume ratio and, ultimately, lowers density. the results obtained is in agreement with the studies conducted by (alhassan, 2008). table 3: mdd and omc results of the bamboo fibre treated soil mdd results of the bamboo fibre treated soil fibre (%) mddh (g/cm3) mddl(g/cm3) 0 1.923 1.980 0.25 1.975 2.020 0.50 1.985 2.023 0.75 2.207 2.092 1.0 2.105 2.000 omc results of the bamboo fibre treated soil fibre (%) omch (%) omcl (%) 0 15.7 12.6 0.25 13.81 11.9 0.50 13.40 11.4 0.75 11.80 10.4 1.0 10.20 9.8 subscript h stands for heavy compaction while subscript l is for light compaction for heavy compaction, the mdd was found to increase from 1.923 g/cm3 for natural soil to 1.975 g/cm3 at 0.25 %, it later increase at 0.5% content and dropped at 1.0% fibre with its omc reducing from 15.7 % to http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 901 13.81 % at 0.25 % and finally to 10.2 % at 1.0 % fibre as shown in table 3 and figure 10 – 11, whereas, for light compaction, it was observed that the mdd increased to its peak of 2.092% at 0.75 % content and it dropped to 2.000 g/cm3 at 1.0% respectively. figure 8: dry density against moisture content for light compaction figure 9: dry density against moisture content for heavy compaction figure 10: effect of % fibre on mdd figure 11: effect of % fibre on omc of treated soil 3.2.2 california bearing ratio (cbr) test results figure 12 present the cbr results for both soaked and unsoaked conditions with varying bamboo fibre contents in soil by percentage. figure 12: effect of percentage fibre on soaked and unsoaked cbr of lateritic soil the cbr of the soil increased as the fibre content increased for both soaked and unsoaked conditions and it was observed that for unsoaked cbr it dropped beyond 0.75%, while for soaked it had a minimal increase beyond that value with the high gradual increase between 0.5 and 0.75% as shown in figure 12. the soaked cbr increased gradually from 15, 18, 21 and 25% then became constant 25% at 0, 0.25, 0.5%, 0.75 and 1.0% respectively. however, the unsoaked cbr was observed to be greater than soaked and gradually increased with the increase of fibre content from 20, to 23 to 25 to 29% and dropped to 28% at 0, 0.25, 0.5, 0.75 and 1.0% fibre contents respectively. 1.7 1.8 1.9 2.0 2.1 2.2 4.0 9.0 14.0 19.0 d ry d en si ty (g /c m 3 ) average moisture content (%) 0% 0.25% 0.50% 0.75% 1.00% 1.750 1.800 1.850 1.900 1.950 2.000 2.050 2.100 2.150 4.000 9.000 14.000 19.000 d ry d en si ty ( g /c m 3 ) moisture content % 0% 0.25% 0.50% 0.75% 1.00% 1.9 2 2.1 2.2 2.3 0 0.5 1 1.5 m d d ( g /c m 3 ) % fibre mdd (light) mdd (heavy) 0 5 10 15 20 0 0.5 1 1.5 o m c ( % ) % fibre omc (light) omc (heavy) 15 18 21 25 25 20 23 25 29 28 0 10 20 30 40 0 0.2 0.4 0.6 0.8 1 1.2 c b r ( % ) %age fibre soaked cbr unsoaked cbr http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 902 3.2.3 effect of bf on unconfined compressive strength of lateritic soil unconfined compressive strength (ucs) of treated soil at varying bamboo fibre contents was evaluated. it was observed that the ucs of the laterite soil gradually increased till maximum of 2.00 mpa at 0.75% fibre replacement and thereafter it dropped at 1.0% fibre as shown in figure 13. figure 13: effect of percentage fibre on ucs the results showed that when the amount of bamboo fibre (bfc) increases, the ucs also increases until it reaches optimum at 0.75%. at the point, further addition of the bamboo fibre does not improve the mechanical properties of the soil. the highest strength properties at omc were noted when the bamboo fibre concentration was higher than 0.75%. additionally, as the amount of bamboo fibre rose, the stress-strain curve tended to have a steeper slope at high water content. 3.2.4 development of strength characteristics relationship figures 14 and 15 present a graphical representation of ucs – cbr (soaked and unsoaked) correlations while equations 1 and 2 indicate the graphical developed relationships. tables 4 and 5 present the anova analysis results, while equations 3 and 4 presents the regression statistical models developed. figure 14: ucs against soaked cbr ucsp = 0.0027cbr2 s 0.0388cbr + 1.1162 (1) r² = 0.8963 where; ucsp = unconfined compressive strength at fibre content, cbrs = soaked california bearing ratio (cbr) at fibre content. models were formulated using ucs results as dependent variables, with cbr results as the independent variables as shown on figures 14 and 15, equations 1 and 2 respectively. strength indices tests results were used in running the anova analysis, while the validity of the correlation was established using r2 values being close to ± 1. a strong relationship between cbr and ucs is indicated by the fact that all of the models fit into a second order polynomial equation of the form α₁x² α₂x + c, with r² values of 0.967 and 0.896 for drenched and unsoaked situations, respectively. 0.00 0.50 1.00 1.50 2.00 2.50 0 0.2 0.4 0.6 0.8 1 1.2 u c s (0 0 0 ) (k n /m 2 ) percentage fibre 0 0.5 1 1.5 2 2.5 10 15 20 25 30 u c s (0 0 0 ) (k n /m 2 ) soaked cbr (%) http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 903 figure 15: ucs against unsoaked cbr ucsp = 0.0059cbr2 us 0.2021cbrus + 2.8281 (2) r² = 0.967 where; ucsp = unconfined compressive strength at each fibre content, cbrus = unsoaked california bearing ratio (cbr) values at varying fibre content. table 4: summary of regression analysis for the soaked cbr df ss ms f significance f regression 3 0.448094683 0.1493649 59.6191638 0.094851212 residual 1 0.002505317 0.0025053 total 4 0.4506 coefficients standard error t stat p-value lower 95% upper 95% intercept -3.976480858 0.98922661 -4.019788 0.15522068 -16.54579669 8.592834973 omc 0.046814369 0.040899195 1.1446281 0.45713293 -0.472859173 0.566487911 mdd 1.915224476 0.549055349 3.4882175 0.17773894 -5.061185203 8.891634155 cbr 0.047768943 0.02695943 1.7718825 0.32710161 -0.294783096 0.390320982 ucsp = 0.05omcp +1.92mddp +0.05cbrp 3.98 (3) where; ucsp = unconfined compressive strength at each fibre content, omcp = optimum moisture content omc) values at each fibre content, mddp = maximum dry density (mdd) values at each fibre content and cbrp = california bearing ratio (cbr) values at each fibre content. the regression analysis was conducted using ucs results as dependent variables, with omc, mdd and cbr results as the independent variables as shown in equations 3 and 4 respectively. strength indices tests results used were validated using r2 being close to 1 and f>f significant, which indicate a good correlation between the engineering properties and also indicating that the effect of bamboo fibre on lateritic soil is statistically significant. this was done to lessen the rigors of laboratory work, which allows for result estimation and saves time and energy. it also helps to facilitate the application of laboratory data and acts as a guide in predicting relationships between variables. table 5: summary of regression analysis for the unsoaked cbr df ss ms f significance f regression 3 0.450234 0.150078 410.3028 0.0362712 residual 1 0.000366 0.000366 total 4 0.4506 coefficients standard error t stat p-value lower 95% upper 95% intercept 4.215877346 0.369173 -11.4198 0.055605 -8.906668 0.47491359 omc 0.058727336 0.009361 6.273921 0.100624 -0.06021 0.17766437 mdd 1.977209634 0.173602 11.38932 0.055753 -0.228613 4.18303234 cbr 0.046433624 0.004012 11.57262 0.054875 -0.004548 0.09741562 0 0.5 1 1.5 2 2.5 15 20 25 30 u c s (0 0 0 ) (k n /m 2 ) unsoaked cbr (%) http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 904 ucsp = 0.06omcp +1.98mddp +0.05cbrp 4.22 (4) 3.2.5 determination of the optimal bamboo fibre stabilized soil peak value for the strength characteristics (unsoaked cbr, soaked cbr, and unconfined compressive strength) of soil were recorded at 0.75% fibre content. table 6 compares the results obtained from the optimum bamboo fibre treated soil with sub-base requirements of (mowhc, uganda, 2010), and it was concluded that lateritic soil stabilized with bamboo fibre at 0.75% can be used for road sub-base construction. table 6: evaluation of the lateritic soil stabilized at optimum bamboo fibre ministry of works, housing and communication of uganda, sub-base material requirements, 2010 properties fibre treated soil requirement comment ll (%) 37.5 40-46.5 not ok pi (%) 21.2 12-25 ok omc (%) 11.8 ˂9.4 not ok mdd (kg/m3) 2027 ˂ 2073 ok soaked cbr (%) 25 >15 ok unsoaked cbr (%) 29 na na ucs (kn/m2) 2000 na na %age passing 37.5mm 100 >95 ok 4. conclusion the degree to which the presence of bamboo fibre in soil can enhance both its mechanical and physical qualities has been assessed in this study. this study demonstrated how stabilizing lateritic soil during the construction of road pavement is achievable by using bamboo fibre as a stabilizing material. the study's findings were used to determine the soil's index qualities, including its particle size distribution, liquid limit, plastic limit, and plasticity index. the soil was then categorized using the aashto classification system as a-2-6 and as silty or clay gravel and sand. the maximum dry density (mdd) of the treated lateritic soil with bamboo fibre increased generally up to 0.75% fibre for both light and heavy compaction and decreased at 1.0% fibre content. the optimum moisture content (omc) likewise decreased. the cbr values for both soaked and unsoaked conditions showed increase up to 0.75% fibre content and then decrease for unsoaked while for soaked cbr it remained constant after 0.75% fibre. there was also an improvement in the ucs of 2.00 mpa at 0.75% fibre content. second order polynomial relationships were developed between ucs and soaked cbr and unsoaked cbr with r2 values of 0.896 and 0.967 respectively indicating a good correlation. for the regression analysis conducted with the strength properties at varying fibre contents, the r2 values were 0.9967 and 0.9777 respectively, in each case having fcal > fcrit. these are indications that the effect of bamboo fibre on engineering properties of lateritic soil is statistically significant and not a mere occurrence. in comparison with uganda mowh&c (2010), laterite soil optimally stabilized at 0.75% fibre meets the requirement for construction of sub-base layer material of road pavement. long-term durability and field performance were not evaluated; therefore, further in-situ validation is required. references aashto. 1986. standard specification for transportation materials and methods of sampling and testing. 14th edition, american association of state highway and transportation officials: washington. adefemi, ba. and wole, ac. 2013. regression analysis of compaction delay on cbr and ucs of lime stabilized yellowish brown lateritic soil. edge, 18: 1–14. afrin, h. 2017. a review on different types soil stabilization techniques. international journal of transportation engineering and technology, 3(2):19–24. doi: 10.11648/j.ijtet.20170302.12. alhassan, m. 2008. potentials of rice husk ash for soil stabilization. au journal of technology, 11(4): 246–250. ali, m.b., saidur, r. & hossain, m.s. 2011. a review on emission analysis in cement industries. renewable and sustainable energy reviews, 15(5): 2252–2261. http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 894-906. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 905 alrubaye, a. j., hasan, m., & fattah, m. y. 2016. engineering properties of clayey soil stabilized with lime. arpn journal of engineering and applied sciences, 11(4): 2434–2441. astm c127–07. 1994. standard test method for density, relative density (specific gravity), and absorption of coarse aggregate. astm, annual book of astm standards, 4(2): 6. astm d 4318–10. 1994. standard test methods for liquid limit, plastic limit, and plasticity index of soils. astm, annual book of astm standards, 04(02):1–16. astm d1883-07e2. 1994. standard test method for cbr (california bearing ratio) of laboratory-compacted soils. astm, annual book of astm standards, 04(2):1–9. astm d421-85. 2007. standard practice for dry preparation of soil samples for particle-size analysis and determination of soil constants. astm international, west conshohocken, pa. astm d5319–97. 2008. standard specification for glass-fibre reinforced polyester wall and ceiling panels. astm, annual book of astm standards, 04(02): 4. astm d6913–04. 2009. standard test methods for particle-size distribution (gradation) of soils using sieve analysis. astm, annual book of astm standards, 04(02): 1–34. astm d698-07e1. 1994. standard test methods for laboratory compaction characteristics of soil using standard effort. astm, annual book of astm standards, 04(02): 1–13. astm d1452-16. 2016. standard practice for soil exploration and sampling by auger borings. astm international, west conshohocken, pa. astm d1883-16. 2016. standard test method for cbr (california bearing ratio) of laboratory-compacted soils. astm international, west conshohocken, pa. astm d790-17. 2017. standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials. astm international, west conshohocken, pa. bs 1377. 1990. methods of test for soil for civil engineering purposes. british standard institute, london. bs 1377-1. 2016. methods of test for soils for civil engineering purposes – part 1: general requirements and sample preparation. british standards institution, london. bs 1924. 1990. methods of test for stabilized soils. british standard institute, london. consoli, n. c., da silva l, l., foppa, d., & heineck, k. s. 2009. key parameters dictating strength of lime/cement-treated soils. proc. inst. of civil engineers – geotechnical engineering, 162(2): 111–118. consoli, nc., casagrande, mdt. and coop, mr. 2010. effect of fibre reinforcement on the isotropic compression behaviour of a sandy soil. geotextiles and geomembranes, 28(4): 344–351. craig, rf. 1992. soil mechanics, 5th edition, chapman and hall, london,: 27–33. daniel, de. and wu, yk. 1993. compacted clay liners and covers for arid sites. journal of geotechnical engineering asce, 119(2): 223–237. gowthaman, s., nakashima, k. and kawasaki, s. 2018. a state-of-the-art review on soil reinforcement technology using natural plant fibre materials. materials, 11(4): 553. doi:10.3390/ma11040553. head, kh. 1992. manual of soil laboratory testing, 1. pentech press ltd., london. hejazi, sm., sheikhzadeh, m., abtahi, sm. and zadhoush, a. 2012. a simple review of soil reinforcement by using natural and synthetic fibres. construction and building materials, 30: 100–116. http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; 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most of these energy sources remain unexploited in nigeria. this study aims at developing a general framework that can be utilized in nigeria to minimize the total cost of installing renewable energy technologies while satisfying some predetermined constraints such as demand, supply and renewable energy potentials. three scenarios were presented namely; prospective off-grid which accesses electricity level below 50%, on-grid which accesses electricity level above 50% and all-off-grid which finds the optimal cost of installing off-grid renewable energies. the results show that the total installation costs of the first and second scenarios are ₦42,656,292,800 and ₦49,908,650,400 respectively while that of the third scenario is found to be ₦106,938,354,400 which represent the extent of renewable energy resources that could possibly incentivize the realization of wider renewable energy applications in rural nigeria. furthermore, it was observed that the combination of the off-grid and on-grid installations have the potential for a decentralized renewable energy resources, with minimum installation cost. this will not only improve the wellbeing of rural communities, but also enhance nigeria’s energy and economic prospects for potential global investments. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 12 august, 2022 revised 7 november, 2022 accepted 10 november, 2022 keywords: rural electrification cost renewable energy sources linear optimization http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 154 table 1: nigerian electricity generating mixtures company type capacity kainji/jebba power plc hydro 1,330mw ughelli power plc gas 942mw sapele power plc gas 1,020mw shiroro power plc hydro 600mw afam power plc gas 987.2mw niger delta power holding company gas 5,455mw ipp’s gas 1,392mw egbin power plc thermal 1,320mw source: nigerian electricity regulatory commission (nerc, 2015). other sources of re in nigeria include wind energy with a potential of 150,000 terra joule per year, generated by an average wind speed of 2.0–4.0 m/s, solar radiation estimated at 3.5–7.0 kwh/m2, and biomass at 144 million tons per year. unfortunately, most of these other sources of re are yet to be fully exploited for rural electrification (agbetuyi et al., 2012). according to nigeria renewable energy master plan, 2011, the country seeks to increase the supply of electricity from renewable energy systems to 36% by 2030 (akorede et al., 2017). the economic policy that is in force in the country aims at encouraging the distribution locations to procure at least 50% of their electricity from renewable sources. another target set in the country’s remp is to increase the electrification rate from about 40% to 75% by 2025 (irena, 2019). therefore, in this paper, the proposed framework was applied to nigeria distribution locations with the aim of deciding the amount of required renewable energy installations to support the existing power capacity and hence to provide adequate power production while optimizing the use of renewable energy systems. 2. methodology optimization is a quantitative procedure that requires the application of discipline and serious multivariable mathematical technology (amosun and muhammed, 2021). hence, this section is devoted to the problem setup and related descriptions, the aim is to develop a general framework that will be used to determine the optimal total capacities of renewable energy sources (solar and wind) to be installed in different locations in the country, in order to increase the amount of renewable energy installations so that the power supply could be comparable to the peak power demand in the country. this was done by designing an optimization problem that minimizes the total cost of installing ress that will be used to support the existing installed power capacity (aliyu and tekbiyik-ersoy, 2019). constraints of the designed optimization problem includes; demand and supply, renewable energy potentials. the optimization problem formulation in this study is divided into off-grid which accesses electricity level below 50%, on-grid which accesses electricity level above 50% and all-off-grid which finds the optimal cost of installing off-grid renewable energies 2.1 linear programming model formulation the linear programming model was formulated based on three basic components as reported elsewhere (ajayi, 2009): 1. decision variables to be determined, 2. objective (goal or aim) to optimize, 3. constraints that need to be satisfied. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com njoku et al: optimization of the industrial use of renewable energy for sustainable and cost effective rural electrification. azojete, 19(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 155 the parameters, variables and constraints were determined according to the notations thus: 𝑖 = location 𝑗= technology xijwt = prospective installed capacity of the worst renewable energy technology in location, ‘i’ xijbt = prospective installed capacity of the best renewable energy technology in location, ‘i’ xiwlj = prospective installed capacity of technology, ‘j’ in the worst locations for technology, ‘j’ xiblj = prospective installed capacity of technology, ‘j’ in the best locations for technology, ‘j’ ict = total installed cost in ₦ xij = renewable energy capacity for technology, ‘j’ to be installed in location, ‘i’ aij = area required (km²) to install 1 mw of technology, ‘j’ in location ‘i’ cj = cost of installing 1mw of technology. ‘j’ in ₦/mw wti = worst technology in location, ‘i’ bti = best technology in location. ‘i’ wlj = worst location for technology, ‘j’ blj = best location for technology, ‘j’ 2.1.1 assumptions on the linear programming technique some of the assumptions made for the linear programming technique applied in this research work as related to the optimization problem are as follows. 1. the effective power demand is to be met by the existing plants (generations) and new renewable generation, 2. the off-grid installation constraints satisfy the demand and supply constraints, 3. the on-grid installation constraints satisfy the demand and supply constraints, 4. there are systems reserve (sr) requirements which must be satisfied to guarantee reliability of the system. 5. the system reserve (sr) constraints for both off-grid and on-grid plants were assumed to be 10%, 6. the application in locations with electricity access level at 50% or above were preferred to be on-grid while those below 50% were preferred to be off-grid. 2.1.5 limitations and constraints the constraints that limit what is obtainable and also serve as conditions on which the optimization problem rests are as follow: 1. there is demand-supply limitation 2. there is off-grid installation limitation 3. there is an on-grid installation limitation 2.2 model development 2.2.1 objective function the main objective of this study is to find the minimum cost of installing re technologies in various locations while satisfying pre-determined constraints. the problem was mathematically formulated as a linear optimization (minimization) problem with the objective function shown in equation 1 as reported by akpan (2015); aliyu and tekbiyik-ersoy (2019) and abraham (2021). minimize: ict= ∑ 𝐶𝑗 𝑚 𝑗=1 ∑ 𝑋𝑖𝑗 𝑛 𝑖=1 (1) total installation cost = cost of installing 1mw × prospective installed capacity (2) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 156 cost of installing 1mw = ∑ 𝐶𝑗 𝑚 𝑗=1 (3) prospective installed capacity = ∑ 𝑋𝑖𝑗 𝑛 𝑖=1 (4) where: ict = total installation cost in ₦, cj is the cost of installing 1mw of technology, ‘j’ in ₦/mw, xij is the renewable capacity for technology, ‘j’ to be installed in location,’ i’ (prospective installed capacity), where i = 1 . . . n and j = 1 . . . m. 2.2.2 demand and supply constraints the effective power demand is to be met by the existing plants and new re generation. this involves the following set of constraints for the prospective re capacities: i. prospective off-grid installation constraints: the demand and supply constraints for off-grid installation locations are expressed in equation 5. ∑ 𝐶𝐹𝑖𝑗𝑋𝑖𝑗 ≥ 𝐸𝐷𝑖 − 𝑃𝑆𝑖 𝑑 𝑗=1 (5) where: cfij is the capacity factor in percentage (%) for technology, ‘j’ in location, ‘i’, and i = 1 . ‘d’ is the number of off-grid installation locations. psi is the current power supply to each off-grid installation location, ‘i’ in mw, and edi is the estimated demand in mw for each off-grid installation location, ‘i’ in order for the electricity access level to be 100% (akpan, 2015). ii. prospective on-grid installation constraints: to satisfy the on-grid demand and supply constraints, equation (6) was formulated (aliyu and tekbiyik-ersoy, 2019) ∑ ∑ 𝐶𝐹𝑖𝑗𝑋𝑖𝑗 ≥ (𝑅𝑃𝐷 − 𝑃𝐷𝑒) − (𝑅𝑃𝑆 −𝑛 𝑖=𝑑+1 𝑚 𝑗=1 ∑ 𝑃𝑆𝑖 𝑑 𝑖=1 ) (6) where: rpd and rps are the reported power demand and total power supply in mw for the region of analysis respectively, and pde is the total estimated power demand of the off-grid installation locations in mw (aliyu and tekbiyik-ersoy, 2019). 2.2.3 system reserve requirements to guarantee reliability of the system, the system reserve (sr) must be satisfied. sr is expressed in percentages (%), and can be defined as an additional and base component of load demand. hence, the sr requirement is expressed by equations 7 and 8 (aliyu and tekbiyik-ersoy, 2019). i. prospective off-grid reserve constraints: the off-grid sr requirement was calculated using equation (7). it should be noted that the sr requirement is an additional amount of electricity that is used in supporting the actual load demand requirement. in most cases it is about 10% of the actual demand (aliyu and tekbiyik-ersoy, 2019). ∑ 𝐶𝐹𝑖𝑗𝑋𝑖𝑗 ≤ (1 + 𝑆𝑅)(𝐸𝐷𝑖 − 𝑃𝑆𝑖) 𝑚 𝑗=1 (7) ii. prospective on-grid reserve constraints: the sr requirement related with on-grid installations was formulated from equation 8 (aliyu and tekbiyik-ersoy, 2019). ∑ ∑ 𝐶𝐹𝑖𝑗𝑋𝑖𝑗˂ (1 + 𝑆𝑅)[(𝑅𝑃𝐷 − 𝑃𝐷𝑒) − (𝑅𝑃𝑆 −𝑛 𝑖=𝑑+1 𝑚 𝑗=1 ∑ 𝑃𝑆𝑖 𝑑 𝑖=1 )] (8) 2.2.4 area constraints the area required to install the ress in a given location was calculated by using equation 9 (aliyu and tekbiyik-ersoy, 2019; amosun and muhammed, 2021). ∑ 𝐴𝑖𝑗 𝑚 𝑗=1 ∑ 𝑋𝑖𝑗 𝑛 𝑖=1 (9) where: 𝐴𝑖𝑗 is the area required (km²) to install 1 mw of technology, ‘j’ in location ‘i’, ‘xij’ is renewable energy capacity for technology, ‘j’ to be installed in location, ‘i’. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com njoku et al: optimization of the industrial use of renewable energy for sustainable and cost effective rural electrification. azojete, 19(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 157 2.2.5 natural constraints the natural constraints of the decision variables are expressed according to equation 10 (amosun and muhammed, 2021). 𝑋𝑖𝑗 ≥ 0 (10) the installation costs for off-grid solar and wind used in the study was ₦1,091,136,240 and ₦1,641,737,680 per kw respectively. while the on-grid solar and wind installation costs used in the study was ₦886,302 and ₦1,026,797,280 per kw respectively, as shown in table 2. table 2: installation costs and system sizes for photovoltaic (pv) and wind technologies technology type mean installed cost (₦/kw) size (acres/mw) pv < 10kw 1,705,638,960 3.2 pv 10 – 100kw 1,515,685,840 5.5 pv 100 – 1000kw 1,091,136,240 5.5 pv 1 – 10kw 886,302 6.1 wind < 10kw 3,346,063,600 30 wind 10 – 100kw 2,677,726,240 30 wind 100 – 1000kw 1,641,737,680 30 wind 1 – 10kw s1,026,797,280 44.7 source: national renewable energy laboratory (nrel, 2018). the average electricity access level and the preferred application type for each distribution location are shown in table 3. the application type (on-grid or off-grid) was chosen based on the average electricity access level of each location. the applications in locations with electricity access level at 50% or above were preferred to be on-grid while those below 50% were preferred to be off-grid. however, it should be noted that 50% is just a threshold selected for this study but can easily be changed according to the requirements of energy planners. table 3: average electricity access levels and preferred distribution locations s/n distribution locations access level (%) preferred application 1 abuja 56 on-grid 2 benin 67 on-grid 3 eko and ikeja 99 on-grid 4 enugu 65 on-grid 5 ibadan 75 on-grid 6 jos 34 off-grid 7 kaduna 41 off-grid 8 kano 36 off-grid 9 port harcourt 61 on-grid 10 yola 25 off-grid source: adapted from (akpan, 2015). 2.3 sensitivity analysis sensitivity analysis is always applied to explore the accuracy and robustness of the model results under uncertain conditions. the sensitivity analysis performed in this paper was carried out by varying the installation costs of both on-grid and off-grid arrangements for the solar and wind technologies. to minimize the total cost, it is assumed that all the distribution locations are offgrid so as to determine the optimal renewable energy systems allocation. the sensitivity analysis data for the prospective installed capacities are presented in table 4 below. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 158 table 4: sensitivity analysis data for off-grid arrangement distribution location prospective total installed capacity (mw) prospective installed solar capacity (mw) prospective installed wind capacity (mw) average generation (mw) abuja 11,789.75 6,155.43 5,634.32 1,920.55 benin 9,760.08 5,192.36 4,567.72 1,200.49 eko and ikeja 8,495.19 4,757.31 3,737.88 1,626.83 enugu 7,276.63 3,485.51 3,791.12 1,246.65 ibadan 7,513.95 3,839.62 3,659.33 1,502.79 jos 7,444.65 3,853.28 3,591.37 1,623.64 kaduna 7,721.45 4,130.08 3,591.37 1,623.64 kano 8,542.08 4,130.08 4,412.00 2,215.69 port harcourt 5,900.67 3,854.65 2,046.02 973.61 yola 7,721.45 4,130.08 3,591.37 1,851.65 total 82,165.90 15,785.54 the main purpose for the off-grid arrangement for all the distribution locations was to supply the demand-supply gap of each distribution location by using the prospective installations only in that distribution location. 3.0 results and discussion 3.1 optimal capacities at different installation locations in order to minimize the total cost for prospective off-grid arrangement, all the distribution locations with electricity access level below 50% are taken into consideration so as to determine the optimal renewable energy set up allocation. the prospective installed capacities are the optimal capacities to be installed for each technology in each location. table 5 shows the wind and solar related capacity factors (cfs) for each distribution location. the capacity factors for each distribution location were done by calculating the capacity factors of all the available locations within each distribution location and finding the average. it could be observed that wind has a better capacity factor when compared with solar in nigeria. also kano and benin has the highest and lowest wind and solar capacity factors respectively. table 5: wind and solar capacity factors in % for each distribution location s/n distribution location wind energy capacity factor (%) solar energy capacity factor (%) 1 abuja 17.50 15.09 2 benin 10.00 14.60 3 eko and ikeja 23.00 15.30 4 enugu 18.80 15.00 5 ibadan 21.00 19.00 6 jos 23.00 20.70 7 kaduna 26.00 21.10 8 kano 28.00 21.60 9 port harcourt 16.00 17.00 10 yola 27.00 21.26 source: irena, 2017. https://www.iea.org/energyaccess accessed on 20 december, 2018. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com https://www.iea.org/energyaccess njoku et al: optimization of the industrial use of renewable energy for sustainable and cost effective rural electrification. azojete, 19(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 159 the simulation results for the prospective installed capacities are presented in table 6. the optimization results for off-grid arrangement indicate that in jos, the optimization results show that 3,853.28mw of the installations should be solar while wind’s share is 3,591.37mw. again, the solar and wind shares in kaduna are found to be 4,130.08mw and 3,591.37mw respectively. similarly, for kano, the optimization revealed that 4,130.08mw and 4,412.00mw of the installation is assigned to solar and wind respectively. solar and wind represent 4,130.08mw and 3,591.37mw respectively of the installations for yola. the prospective total installed capacity of all the off-grid arrangement distribution locations was found to be 31,429.63mw while the total average power generation was found to be 7603.92mw. in addition, the optimal total cost of installing renewable energy systems in all the off-grid arrangement distribution locations was found to be ₦97.46billion. table 6: optimal capacities and generation for prospective off-grid arrangement distribution location prospective total installation capacity (mw) prospective installed solar capacity (mw) prospective installed wind capacity (mw) average power generation (mw) jos 7,444.65 3,853.28 3,591.37 1,623.64 kaduna 7,721.45 4,130.08 3,591.37 1,912.94 kano 8,542.08 4,130.08 4,412.00 2,215.69 yola 7,721.45 4,130.08 3,591.37 1,851.65 total 31,429.63 7,603.92 since the distribution locations have substantial level of electricity access, the installation does not have to cover the supply and demand gap at each and as such, only the total gap should be supplied. the simulation results for the prospective installed capacities are presented in table 7. the optimization result revealed that abuja and port harcourt are allocated 22,564.89mw each of the proposed installed capacity. table 7: optimal capacities and generation for prospective on-grid arrangement distribution location prospective total installed capacity (mw) prospective installed solar capacity (mw) prospective installed wind capacity (mw) average generation (mw) abuja 22,564.89 2,256.89 0 3,404.82 benin 1,427.28 1,427.28 0 208.38 eko and ikeja 3,254.20 1,627.10 1,627.10 662.23 enugu 2,724.81 1,427.28 1,297.53 445.05 ibadan 3,054.38 1,427.28 1,627.10 580.05 port harcourt 22,564.89 22,564.89 0 3,610.38 total 55,590.45 8,910.91 the prospective installed capacities for benin, eko and ikeja, enugu, ibadan, are 1427.28mw, 3254.20mw, 2724.81mw and 3054.38mw respectively. however, the prospective installed wind capacity for abuja, benin and port harcourt are zero due to the poor wind potential in those distribution locations. hence, the prospective total installed capacity of all the on-grid arrangement distribution locations was found to be 55,590.45mw while the total average power generation was found to be 8910.91mw. it is imperative to remark that this result is consonant with the target estimated in the country’s remp, which highlights that 50% of each disco’s purchase should come from renewable. in addition, the total cost of installation was found to be ₦49,908,650,400. the sensitivity analysis results for all-off-grid revealed that in abuja, solar should be favored since the results show that 6155.43mw of the installations should be solar while wind share is http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 160 5634.32mw. for benin, solar and wind shares are found to be 5192.36mw and 4567.72mw respectively. for eko and ikeja, the analysis result revealed that 4757.31mw and 3737.88mw of the installation is assigned to solar and wind respectively. for enugu, it is found that solar and wind shares represent 3485.51mw and 3791.12mw respectively. for ibadan, the results show that 3839.62mw and 3659.33mw of the installation was assigned to solar and wind respectively. again, in port harcourt, 3854.65mw and 2046.02mw of installations should be allocated to solar and wind respectively. in jos, solar should be favored, as the analysis result revealed that 3853.28mw of the installations should be solar while wind shares 3591.97mw. for kaduna, the solar and wind share represents 4130.08mw and 3591.97mw respectively. for kano, the analysis results show that 4130.08mw and 4412.00mw of the installation is allocated to solar and wind respectively. lastly, for yola, solar and wind are found to be 4130.08mw and 3591.37mw of the installations respectively. it is noteworthy that for the off-grid arrangement for all the distribution locations, the renewable energy installation is designed such that each distribution location can generate its own power. moreover, the prospective total installed capacity of all the off-grid setup distribution locations was found to be 82,165.90mw while the total average power generation was found to be 15,785.54mw while the optimal total cost of installing renewable energy systems in all the off-grid setup distribution locations is found to be ₦106,938,354,400. the sensitivity on the installation cost is based on wind and solar technologies’ installation costs. table 6 shows all the associated cost values and sensitivity analysis-related cases. the cases are +10%, +20%, +30%, -10%, -20% and -30% change in wind technology installation cost only (keeping solar-related cost constant), and solar technology installation cost only (keeping windrelated cost constant). table 6: sensitivity variables and corresponding values sensitivity variable installation cost (₦/kw) sd of installation cost (%) on grid off grid solar 886,302 1,091,136,240 ±10, ±20, ±30 wind 1,026,797,280 1,641,737,680 ±10, ±20, ±30 the sensitivity analysis of change in technology-related costs and total installation costs for offgrid and on-grid arrangements are presented in figures 1 and 2 respectively. the results showed that decrease in the wind technology costs will significantly reduce the total installation cost in the case of off-grid arrangement (rather than the case of having a decrease in solar energy-related costs) while the on-grid total installation costs can be decreased more when the cost associated with installing solar technology is reduced (rather than the case of having a decrease in wind energy-related costs). figure 1: sensitivity analysis of change in technology-related cost and total installation cost for off-grid arrangement. figure 2: sensitivity analysis of change in technology-related costs and total installation cost for on-grid arrangement. 0 25 50 75 100 125 150 175 -30 -20 -10 0 10 20 30 t o ta l in st al la ti o n co st s (b il li o n ₦ ) change in technology related costs (%) wind 0 20 40 60 80 100 120 -30 -20 -10 0 10 20 30t o ta l in st al la ti o n co st s (b il li o n ₦ ) change in technology related costs (%) wind file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com njoku et al: optimization of the industrial use of renewable energy for sustainable and cost effective rural electrification. azojete, 19(1):153-162. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 161 the results obtained show that wind is not viable in some parts of the country due largely to the low potential of wind energy especially in the southern part of the country. the results of the sensitivity analysis revealed that the cost associated with on-grid renewable energy system can be reduced considerably by reducing the installation cost of solar energy technologies. on the other hand, for off-grid arrangement, the analysis reveals that the government and other stakeholders in the energy sector should focus more on policies geared towards reducing the cost of installing wind energy technology. since the government alone can’t sufficiently fund such projects that are capital intensive, nigerian government should as a matter of urgency identify and develop clear policy incentives for increased private sector participation in the delivery of renewable energy (eleri et al., 2012). for developing countries such as nigeria to improve upon her electricity access, security and sustainability, especially in the rural areas, renewable energy utilization has to be encouraged through proper planning by incorporating strategies such as supply-side management (ssm), and implementation of effective policies (szabo et al., 2011). optimization has been one of the methods deployed to achieve proper planning in electricity sector more so when it has to do with renewable energy installations. 4.0 conclusion the flexibility of the framework and models used in this paper were carefully taken into consideration so as to guarantee the possibility of using them in different regions and areas. it ensures the increased use of renewable energy systems such as wind and solar in combination with existing generation capabilities as used in the case study. the proposed optimization model was developed based on linear programming through which the minimum costs of installing renewable energy systems for three different arrangements (off-grid, on-grid and all-off-grid) were determined. it was deduced that the proposed models were successful in minimizing the total installation costs of renewable energy (wind and solar) by considering the best renewable energy technologies in each location and avoiding extra installations. notwithstanding the fact that, nigeria is generally blessed with ample conventional and renewable energy resources, the demand is significantly higher than the energy generated. due to the abstruse inefficiencies associated with electric energy provision in nigeria, it is increasingly harder for rural nigerians to have access to the electricity service. this paper is advocating the use of renewable energy resources for closing the gap between energy demand and supply in nigeria as well as improving the wellness of rural nigerian communities. the potential of various renewable energy sources including large and small hydropower systems, solar energy and wind energy were elaborated. many of the government of nigeria energy initiatives are merely paper policies that lack the political will to take it to the implementation realm. even though it may be difficult to navigate the intricacies of nigeria’s energy governance tumult, a fine line of argument is straddled throughout this research work. by avowing that existing government policies are ineffective, some new measures that can meld well with these policies to reinvigorate them such as supplyside management (ssm) and implementation of effective policies were proposed. a careful look at the results shows that incorporating renewable energy in nigeria’s power generation is vital in resolving the current power problem. more so, building solely more on-grid renewable power plants is not enough, rather the system should be supported with off-grid renewable plants to curb the transmission constraints. furthermore, the study reveals that if the proposed framework is applied in nigeria, it can help the country to achieve the renewable targets stated in the country’s renewable energy master plan (remp) which would in turn alleviate the misfortunes of the rural communities currently groaning under acute shortage of electricity. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):153-162. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: gambo.anthony@yahoo.com 162 references abraham, up. 2021. a linear programming approach for an industrial optimal production. global scientific journal, 9(2): 141-150. agbetuyi, af., akinbulire, t., abdulkareem, a. and awosope, coa. 2012. wind energy potential in nigeria. international electrical engineering journal, 3(1): 595-601. ajayi, oo. 2009. assessment of utilization of wind energy resources in nigeria. energy policy, 37:750-753. akorede, mf., ibrahim, o., amuda, sa., otuoze, ao. and olufeagba, bj. 2017. current status and outlook of renewable energy development in nigeria. nigeria journal of technology, 36(1): 196-212. akpan, u. 2015. technology options for increasing electricity access in areas with low electricity access rate in nigeria. socio-economic planning sciences, 51: 1-12. aliyu, a. and tekbiyik-ersoy, n. 2019. a novel framework for cost optimization of renewable energy installations: a case study of nigeria. energies, 12: 9-10. amosun, st. and muhammed, ma. 2021. optimization of the production capacity of a manufacturing company as linear programming model. nipes journal of science and technology research, 3(4): 119 -124. eleri, eo., ugwu, o. and onuvae, p. 2012. expanding access to pro-poor energy services in nigeria. international centre for energy, environment and development: abuja. nigeria. irena 2019. nigeria feed-in tariff for renewable energy sourced electricity. international renewable energy agency (irena), masder city, united arab emirates. https://www.iea.org/policiesandmeasures/pams/nigeria/name-154529-en.php accessed on 26 july, 2019. irena 2017. energy access outlook 2017. international renewable energy agency (irena), masder city, united arab emirates. https://www.iea.org/energyaccess/database/ accessed on 20 december, 2018. national renewable energy laboratory (nrel), colorado, usa. 2018. distributed generation renewable energy estimate costs. http://www.nrel.gov/analysis/tech-icoe-re-cost-est.html accessed on 15 september, 2018. nigerian electricity regulatory commission (nerc), abuja, nigeria. 2015. discos’ contact information. http://www.nerc.gov.ng/index.php/contact accessed on 17 november, 2018. szabo, s., bodis, k., huld, t. and moner-girona, m. 2011. energy solutions in rural africa: mapping electrification costs of distributed solar and diesel generation versus grid extension. environmental research letters, 6(3):17-26. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/gambo.anthony@yahoo.com http://www.nrel.gov/analysis/tech-icoe-re-cost-est.html corresponding author’s email address: bristonecharles@yahoo.com 727 arid zone journal of engineering, technology & environment original research article rheological properties of malted and/or fermented faro 44 rice plus soybean-based complementary foods c. bristone 1,2*, c. c. ariahu2, j. k. ikya2 and m. o. eke2 1department of food science and technology, faculty of engineering, university of maiduguri, p. m. b.1069, maiduguri, borno state, nigeria. 2department of food science and technology, college of food technology and human ecology, university of agriculture makurdi, p. m. b. 2373, makurdi, benue state, nigeria. *corresponding author’s email address: bristonecharles@yahoo.com article information abstract high nutrient density foods are required by infants for optimal healthy growth. this can be achieved by an established food processing technology. so, the study investigated the rheological properties (concentrations, stress or shear rate, viscosities or consistency indices, activation energies, frequency factors) of rice-based formulated food products as affected by either malting and/or fermentation. faro 44 rice cultivar was processed, and different flours obtained were further formulated with processed soybean (glycine max) flour. in each of those mixing ratios, 16% protein (pag’s recommendations) was obtained by a material balance equation. a digital viscometer was used to measure the viscosities of the gruels at levels of 4 concentrations, 4 shear rates and 6 temperatures. subsequently, the power law fluids model, arrhenius kinetic type equation, and linear regression analysis (at levels of 4 concentrations, 4 shear rates and 6 temperatures) were employed to generate the rheological parameters of the gruels. results showed that viscosity decreased with an increase in temperature within the 30 80 oc range studied and shear rate (6 60 rpm.) but increased with an increase in concentration (5 20%) of gruels. regardless of temperature or concentration, the consistency indices (1.68 to 714.32 nsnm-2) of gruels, and their respective flow behaviour indices (n) and activation energy ranged from 0.01 to 0.43 and 5.25 to 36.97 kj/mol. all formulated products exhibited pseudoplasticity and sensitivity to temperature change. malting and/or fermentation showed a significant (p < 0.05) reduction in viscosities and revealed that it can be used to increase the nutrient density required by infants. submitted 09 december, 2023 revised 27 april, 2024 accepted 10 may, 2024 keywords: activation energy gruels infant foods viscosity non-newtonian fluids © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction rheology is the study of how a material deforms or flows over time scale, while viscosity measures the internal resistance of a material to flow in response to the applied force (figura and teixeira, 2007; nielsen, 2010). it is necessary to understand the flow behaviour of the food system undergoing processing and also, its acceptability and taxonomy after processing. the dependency on fluid flow or deformation behaviours may contribute to undesirable effects in nature and subsequently interfere with human activities. for example, in the case of most agricultural products such as paste, gruels, food powders etc. the viscosity of the food product due to its non-newtonian behaviours may create hold-up, jamming, heating effects etc. to the processing machine (s). defects such as caking, clumping, sticking and solidifying of food products during processing or preparation are problems often accompanied by changes in food products’ viscosities. these changes may contribute to sieving, filtration, mixing or conveying difficulties as well as functional defects, sensory changes or nutrient reduction in the food etc. and later deprive its consumers of substantial benefits. azojete december 2024. vol.20(4):727-748 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:bristonecharles@yahoo.com mailto:bristonecharles@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):727-748. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 728 earlier researchers recommended suitable viscosity of gruels between 1000 and 3000 centipoises (1 to 3 nsm2) for cereal based infant foods (mosha and svanberg, 1983; badau et al., 2016). conventional complementary foods come with mixing prescriptions that will adequately meet the nutritional demands of an infant. those made of cereal, if stuck to the recommended mixing ratio (powder to water) may not flow freely like breast milk. most infants would either reject or find it difficult to accept complementary food that is too thick. at this critical stage, if the mixture is too thick, the mother or care giver is left with the discretion of diluting it to enable the child to accept it. hence, depriving the child of the required energy per serving because of too much water in the mixture which have been taken. besides these, majority of the mothers at the domestic level who prefer to produce cereal-based complementary food for their babies had more knowledge of complementing staple starchy diet with rich protein sources. however, many mothers have not been enlightened about other food processing techniques such as malting or fermentation that would increase energy density for their babies. malting or fermentation is one of those established locally adaptable technologies for bulk reduction of gruels, which can increase nutrient density for a given gruel consistency. also, malting and fermentation have been used for reducing the ph of gruels, thereby inhibiting spoilage and pathogenic microorganisms in food (mosha and svanberg, 1983; magala et al., 2015; mantanjevic et al., 2017). these technologies have been used extensively for improving sensory characteristics of foods, health promoting attributes, reduction of non-digestible carbohydrates, saccharification of starch, phytate degradation, bioactive component concentration, food preservation, production of essential amino acids and vitamins (bristone et al., 2021; wu et al., 2022). however, these practices often being neglected in the food industries for the production of conventional infant foods. probably, due to the time or difficulties accompanying malting or fermentation and the type of profit yield thereafter. but one would not ignore the substantial benefits of formulating an acceptable cereal infant food with resolved dietary bulk reduction. nowadays, rice among many other cereal grains or soybean among other legumes are the most receiving global attention for human consumption (bristone et al., 2021; garcía-salcedo et al., 2023). faro 44 rice among a series of rice varieties released in the african sub-region has unique properties that have satisfied both farmers’ and consumers’ preferences (udemezue and agwu, 2018; ebenehi and ahmed, 2019; idu et al., 2021). however, behaviours of faro 44 rice variety in food systems especially those of rheological properties have not been studied. more importantly, how malting and/or fermentation would influence the flow behaviour of rice products for its acceptability. therefore, a combination of malted and/or fermented rice with soybean holds the potential for increasing utilization of the adopted technologies and addressing low-energy density gruels that have implications in infant malnutrition. 2. materials and methods 2.1 preliminary handling and processing in this study, faro 44 rice (paddy) was obtained from the national cereals research institute (ncri), badeggi, bida, niger state, and destoned using a mechanical de-stoner (de-stoner, hunan sunfied machinery co., ltd, model: tqs 320, china). also, soybean (glycine max) was procured from agricultural seed store house, gire local government, adamawa state. the soybean was cleaned to remove contaminants. it was steeped into clean water for four (4) hours to reduce antinutrients. this operation was followed immediately by sun-drying, toasting and dehulling of the soybean as described by badau et al. (2016). the dehulled soybean was processed into flour (figure 1) (badau et al. 2016), packaged in air-tight polythene bags, and placed inside plastic containers with lids as well as stored on a dry shelf at ambient conditions of average temperature of about 30 oc and humidity 32% (badau et al., 2016; bristone et al., 2021). after cleaning the paddy, it was divided into two equal lots. the first lot was malted while the second lot was left un-malted. paddy was washed twice with clean water. the cleaned paddy rice was steeped inside sufficient clean water to cover the surface of the grains completely. it was kept at 29 ± 2 oc with good air circulation for 24 hours. the steeping process was interrupted after every 6 hours by draining. an “air-rest” period of one hour each for every interruption was provided. the steeped paddy was then drained and wrapped in a wet jute bag to provide about 3 to 5 cm depth. faro 44 grain sample was germinated for 43 hours at 29 ± 1 oc. the short period of germination was timed and was done to counter technical difficulties during dehulling of malted rice as experienced during pretrials. after drying of germinated grains at 29 ± 2 oc under constant air circulations for 48 hours, the germinated dried grains were polished by detaching the roots and rootlet (gasinski et al., 2020; bristone et al., 2021). http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):727-748. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 729 figure 1: flow chart for the production of soybean flour (badau et al., 2016). about 40 kg of cleaned and dried paddy for each lot was de-husked using a greep rice mill (model-mbln115, china). after de-husking, the grains were finally dried again at 40 oc in an air flow thermostat oven (air flow rate 140, oven bs, model ov-160, gallen kamp, england) until constant weight were obtained. then all the rice was milled using a hammer miller and let to pass through a 0.8 mm sieve (christy hunt agricultural ltd, foxhills ind. est scunthorpe, model de dn15 8qw, south humbers, england). each of the rice flours obtained from malted and non-malted paddy were further divided into two lots. one lot was selected from each of the divisions and were subjected to solid state accelerated natural fermentation (bristone et al., 2021). the fermented foods were spread on drying trays and also dried to constant weight in an air draft oven for about 2 hours at 40 oc (figure 2). 2.2 product formulations a 2 x 2 completely randomized experimental design was employed for the study. the design comprised malted and non-malted rice, fermented and non-fermented rice, that yield four test samples which were each combined with the processed soybean flour. the product formulations aimed at obtaining 16 g protein of each test product, recommended by the protein advisory group (pag) (wfp, 2018). the various amounts were obtained by materials balance equation based on the proximate compositions of the food materials. the flours at appropriate ratios were blended in a dry mixer, parked in self-sealing polythene bags and placed in dry and cleaned plastic containers and stored on dry shelves. four test products comprising non-malted-nonfermented rice + soybean (nmnfrs), malted-non-fermented rice + soybean (mnfrs), non-malted-fermented rice + soybean (nmfrs) and malted-fermented rice + soybean (mfrs). soybean flour (packaged in polyethylene bag) sieving milling winnowing dehulling toasting (180 oc, 30 minutes) sun-drying (42 oc, 6 hr.) steeping (30 oc, 4 hr.) sorting soybean http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):727-748. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 730 faro 44 paddy cleaning steeping (29 ± 2 oc, 24 hr.) sprouting (29 ± 1 oc, 43 hr.) non-sprouting drying (29 ± 2 oc, 48 hr.) drying (29 ± 2 oc, 48 hr.) dehusking dehusking flour milling flour milling slurring slurring fermentation non-fermented fermentation non-fermented drying (40 oc, 2 hr.) drying (40 oc, 2 hr.) drying (40 oc, 2 hr.) drying (40 oc, 2 hr.) sieving sieving sieving sieving mfr-flour mnfr-flour nmfr-flour nmnn-flour figure 2: flow chart for the production of malted and /or fermented rice flours mfr = malted-fermented rice, mnfr = malted-non fermented rice, nmfr = non malted-fermented rice and nmnfr =non malted-non fermented rice. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):727-748. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 731 2.3 experimental set-up and data evaluation gruels were prepared by mixing the flour of the rice and soybean-based complementary foods with distilled water, inside a coded aluminium can and was heated (cooked) at 95 oc for 7 minutes in a digital thermostatic water bath (water bath hh 420, model hh 420. pec medical usa). the viscosities of the prepared gruels were measured using a digital rotatory viscometer (digital rotary viscometer, model: ndj-55, china) (figure 3). a 4 × 4 × 6 (4 concentrations: 5, 10, 15 and 20% w/v; 4 shear rates: speed of 6, 12, 30, and 60 revolutions per minute and 6 temperatures: 30, 40, 50, 60, 70, and 80 oc) were employed for viscosity measurements of each gruel. about six hundred millilitres (600 ml) aluminium tin was used. the tin was used to cover up to the immersion level point on the shaft of the spindles as recommended by the manufacturer. all viscosity measurements were carried out immediately after preparing the gruels. a digital thermostatic water bath was used to maintain temperature stability. however, it was assisted with ice water for rapid cooling of the hot gruel to a desired temperature level (e.g., from 95 to 80 oc). data generated were subjected to analysis of variance (one way anova) using ibm spss statistics version 22 and mean values were separated by duncan’s multiple range test (dmrt) at a 5% significant level. a plot of viscosity versus shear rate and a natural log of viscosity versus a natural log of shear rate were plotted. an oswald de waele model (power law fluids model) was used to describe the rheological behaviours of the formulated food products (sopade and kasum, 1992a; mouquet and treche, 2001; fraiha et al. 2011; adebowale and sani, 2011). this mathematical model was selected because most foods fall within the non newtonian fluids group and can simply be described and characterized by a two parameter model of the power law fluids model. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):727-748. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 732 0 20 40 60 80 0 50 100 150 nmnfrs shear rate (γ) (s-1) v i s c o s i t y ( n s m 2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 10 20 30 40 mnfrs shear rate (γ) (s-1) v i s c o s i t y ( n s m 2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmfrs shear rate (γ) (s-1) v i s c o s i t y ( n s m 2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 mfrs shear rate (γ) (s-1) v i s c o s i t y ( n s m 2 ) 5% concentration 10% concentration 15% concentration 20% concentration digital rotary viscometer spindle reference diet (nmnfrs), highest dietary bulk, lowest energy density gruel experimental diet (mnfrs), highest viscosity reduction, highest energy density gruel experimental diet (nmfrs), high viscosity reduction, high energy density gruel experimental diet (mfrs), higher viscosity reduction, higher energy density gruel figure 3: viscosity measurements, concepts and implications in the experimental diets http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 733 data obtained were fitted with the power low model: 𝜇 = 𝑘𝛾𝑛−1 (1) where μ = viscosity (nsm-2), γ = share rate (rpm), n = flow behaviour index, k = consistency index (nsnm-2). linearization of equation 1 gives: 𝐼𝑛𝜇 = 𝐼𝑛 𝑘 + (𝑛 − 1) 𝛾 (2) temperature dependency of the viscosities were verified using arrhenius type relationship: 𝜇 = 𝜇𝑜𝑒−𝐸𝑎/𝑅𝑇 (3) where: μo = frequency factor, ea = activation energy (kj/mol), r = universal gas constant (0.008314 kj/mol. k) and t = absolute temperature (ok). regression coefficient (r2) was used to verify goodness of fit of the power law model and arrhenius type equation. 3. results and discussion 3.1 influence of viscosity and power law derivatives in figures 4a, 4b (plots of viscosity versus shear rate) and 5a, 5b (plots of log of viscosity versus log of shear rate), the effect of temperature, concentration and shear rate on viscosity of gruels from the formulated products are shown. their respective viscosity values (tables 1 4) of the formulated food gruels irrespective of concentrations, temperatures and shear rates varied significantly (p < 0.05) and ranged from 0.14 to 121.22 nsm-2 (nmnfrs), 0.01 to 37.50 nsm-2 (mnfrs), 0.03 to 120.10 nsm-2 (nmfrs) and 0.02 to 110.04 nsm-2 (mfrs). the influence of viscosity reduction in this study is related to enzyme activities. grain enzymes (such as α-β amylases etc.) are mostly synthesized (generated) in the grain during germination. these enzymes are majorly responsible for the saccharification and dextrinization of starch leading to liquefaction (decrease in viscosity) of gruels. enzymes have optimum (ph, temperature, etc.) and can be affected by fermentation. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 734 0 20 40 60 80 0 50 100 150 nmnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 30 oc 0 20 40 60 80 0 10 20 30 40 mnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 mfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 40 oc 0 20 40 60 80 0 10 20 30 40 mnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 mfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 50 oc 0 20 40 60 80 0 10 20 30 40 mnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 mfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration figure 4a: effect of concentration and shear rate on viscosity of non-malted-non-fermented rice (nmnfr), malted-non-fermented rice (mnfr), non-malted-fermented rice (nmfr) and malted-fermented rice (mfr) at 30, 40 and 50 oc, s: soybean. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 735 0 20 40 60 80 0 50 100 150 nmnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 60 oc 0 20 40 60 80 0 10 20 30 mnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 mfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 50 100 150 nmnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 70 oc 0 20 40 60 80 0 5 10 15 20 25 mnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 20 40 60 80 100 nmfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 20 40 60 80 100 mfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 20 40 60 80 100 nmnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 80 oc 0 20 40 60 80 0 5 10 15 20 mnfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 20 40 60 80 100 nmfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration 0 20 40 60 80 0 20 40 60 80 100 mfrs shear rate (γ) (s-1) v is co si ty ( n sm -2 ) 5% concentration 10% concentration 15% concentration 20% concentration figure 4b: effect of concentration and shear rate on viscosity of non-malted-non-fermented rice (nmnfr), malted-non-fermented rice (mnfr), non-malted-fermented rice (nmfr) and malted-fermented rice (mfr) at 60, 70 and 80 oc. s: soybean. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 736 1 2 3 4 5 -3 -2 -1 0 1 5% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c nmnfrs 1 2 3 4 5 -1 0 1 2 3 10% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 1 2 3 4 5 15% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 2 4 6 20% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 -5 -4 -3 -2 -1 0 5% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c mnfrs 1 2 3 4 5 -3 -2 -1 0 1 2 10% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 1 2 3 4 5 -4 -2 0 2 4 15% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 1 2 3 4 20% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c figure 5a: nmnfrs: non-malted-non-fermented rice + soybean flour and mnfrs: malted non-fermented rice + soybean flour http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 737 0 1 2 3 4 5 -4 -3 -2 -1 0 5% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c nmfrs 1 2 3 4 5 -2 -1 0 1 2 3 10% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 1 2 3 4 5 15% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 2 4 6 20% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 -5 -4 -3 -2 -1 0 5% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c mfrs 1 2 3 4 5 -2 -1 0 1 2 3 10% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 1 2 3 4 5 15% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c 0 1 2 3 4 5 0 1 2 3 4 5 20% concentration (w/v) log of shear rate l o g o f v is c o s it y 30 o c 40 o c 50 o c 60 o c 70 o c 80 o c figure 5b: nmfrs: non-malted-fermented rice + soybean flour and mfrs: malted-fermented rice + soybean flour http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 738 table 1: viscosity of non-malted-non-fermented rice (nmnfr) plus soybean based complementary food gruel concentration (%) shear rate (rpm) viscosity (nsm-2) temperature (oc) 30 40 50 60 70 80 5 6 1.63m 1.56m 1.06m 0.92m 0.73m 0.61m 12 0.85n 0.81n 0.75n 0.61n 0.45n 0.31n 30 0.47o 0.38o 0.32o 0.25o 0.22o 0.19o 60 0.39p 0.26p 0.22p 0.19p 0.17p 0.14p 10 6 14.74i 13.20i 10.40i 7.36i 6.20i 3.91i 12 9.96j 7.45j 5.61j 4.59j 3.16j 2.25j 30 5.92k 3.54k 2.36k 2.18k 1.31k 1.24k 60 3.93l 1.93l 1.40l 1.23l 0.84l 0.75l 15 6 86.20b 76.30b 58.01c 53.01b 50.06b 46.23c 12 75.20c 51.40d 43.80d 40.11d 32.40d 26.89d 30 25.01e 16.97f 13.24f 11.01f 9.32f 7.04g 60 19.66g 15.26g 11.22h 8.92h 5.76h 4.65h 20 6 121.22a 120.60a 114.33a 108.21a 98.13a 88.53a 12 61.70d 60.20c 58.50b 52.90c 49.00c 47.20b 30 24.00f 22.10e 18.20e 15.80e 13.20e 9.30e 60 18.20h 15.10h 12.00g 10.60g 9.10g 7.60f each result is mean of triplicate determinations. values with common superscripts along each column are not significantly (p > 0.05) different. table 2: viscosity of malted-non fermented rice (mnfr) plus soybean based complementary food gruel concentration (%) shear rate (rpm) viscosity (nsm-2) temperature (oc) 30 40 50 60 70 80 5 6 0.14m 0.11m 0.09m 0.07m 0.05m 0.04m 12 0.10n 0.09n 0.07n 0.06n 0.04n 0.03n 30 0.09o 0.08o 0.07n 0.05o 0.03o 0.02o 60 0.07p 0.06p 0.05p 0.03p 0.02p 0.01p 10 6 6.08g 4.06g 3.02g 2.42g 1.20g 0.85g 12 3.59i 1.69j 1.05j 0.86i 0.71i 0.50j 30 0.96k 0.81k 0.67k 0.44k 0.32k 0.28k 60 0.48l 0.40l 0.33l 0.24l 0.20l 0.11l 15 6 15.60d 9.70d 6.28e 5.70e 4.05e 3.82e 12 8.35f 5.60f 3.66f 2.46f 2.20f 1.90f 30 4.60h 3.31h 1.93h 1.08h 0.82h 0.63h 60 3.06j 2.05i 1.13i 0.82j 0.69j 0.51i 20 6 37.50a 31.80a 30.16a 24.01a 20.42a 18.60a 12 28.30b 22.90b 20.81b 18.50b 14.20b 11.25b 30 15.88c 13.11c 11.16c 10.12c 8.14c 7.25c 60 11.64e 9.63e 8.31d 7.07d 5.22d 4.21d each result is mean of triplicate determinations. values with common superscripts along each column are not significantly (p > 0.05) different http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 739 table 3: viscosity of non-malted-fermented rice (nmfr) plus soybean based complementary food gruel concentration (%) shear rate (rpm) viscosity (nsm-2) temperature (oc) 30 40 50 60 70 80 5 6 0.45m 0.39m 0.27m 0.22m 0.12m 0.07m 12 0.31n 0.25n 0.19n 0.15n 0.09n 0.06n 30 0.18o 0.15o 0.11o 0.09o 0.06o 0.04o 60 0.12p 0.10p 0.08p 0.06p 0.04p 0.03p 10 6 11.38i 9.31i 7.82i 5.41i 3.84i 2.92i 12 8.56j 6.54j 5.56j 4.50j 3.05j 2.16j 30 4.11k 3.21k 2.13k 1.82k 1.28k 0.98k 60 1.94l 1.13l 0.73l 0.53l 0.48l 0.31l 15 6 75.20b 61.42b 53.80b 47.60c 40.40c 32.30c 12 51.51d 40.41d 36.41d 30.22d 23.02d 19.03d 30 20.92e 15.43f 10.01f 8.13g 5.52g 4.22g 60 14.72g 12.21g 9.73g 6.82h 4.71h 3.82h 20 6 120.10a 110.21a 109.00a 105.20a 92.00a 85.80a 12 59.01c 56.40c 53.30c 50.40b 48.50b 40.00b 30 20.00f 17.80e 16.70e 14.20e 11.20e 8.90e 60 14.60h 11.20h 9.60h 8.80f 7.70f 6.70f each result is mean of triplicate determinations. values with common superscripts along each column are not significantly (p > 0.05) different. table 4: viscosity of malted-fermented rice (mfr) plus soybean based complementary food gruel concentration (%) shear rate (rpm) viscosity (nsm-2) temperature (oc) 30 40 50 60 70 80 5 6 0.36m 0.33m 0.21m 0.13m 0.08m 0.06m 12 0.24n 0.20n 0.14n 0.12n 0.07n 0.04n 30 0.16o 0.12o 0.09o 0.07o 0.05o 0.03o 60 0.11p 0.09p 0.09p 0.05p 0.03p 0.02p 10 6 10.52i 8.36i 6.14i 3.78i 2.41i 1.30i 12 6.47j 5.21j 4.19j 3.50j 2.26j 1.51j 30 3.47k 2.62k 1.83k 1.04k 0.82k 0.67k 60 1.92l 0.94l 0.57l 0.44l 0.33l 0.24l 15 6 60.36b 46.10c 40.30c 38.60c 29.30c 20.01c 12 38.85d 35.90d 33.72d 29.50d 20.43d 15.15d 30 16.99f 13.89f 8.81g 6.29g 5.18g 3.13g 60 10.93h 8.83h 6.66h 4.65h 2.61h 2.04h 20 6 110.04a 109.03a 99.03a 95.90a 87.80a 80.08a 12 58.10c 56.70b 51.37b 48.35b 44.21b 30.01b 30 21.83e 18.36e 15.51e 13.22e 10.18e 8.02e 60 15.02g 13.10g 9.41f 8.44f 6.71f 5.28f each result is mean of triplicate determinations. values with common superscripts along each column are not significantly (p > 0.05) different also, fermentation can cause the breakdown of starch by endogenous enzymes of the grain or available enzymes of microorganisms produced during fermentation, which may in turn not be adequate or specific for liquefaction in this study. taken into account viscosity reduction in this study is an indicator of enzyme activities. it is obvious α-β amylases were majorly synthesized or produced during germination since the viscosity of nmnfrs did not change. but when the rice was malted which yielded mnfrs, its viscosity decreased drastically as compared to the viscosity of nmnfrs. similarly, when the rice was malted and fermented to yield mfrs, its viscosity decreased slightly as compared to the viscosity of nmnfrs. this mean http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 740 enzymatic hydrolysis responsible for viscosity reduction in the malted rice was inhibited by fermentation. this shows that enzyme activities responsible for the reduction of viscosity in this study were mostly generated (synthesized) during malting than fermentation. however, a slight decrease in the viscosity of nmfrs is evident through the fermentation of the non-malted-non fermented rice flour. probably because of the activities of enzymes. if it was so, mfrs could have benefitted and doubled the activities of enzymes by the malting and fermentation. these have justified the activities of enzymes derived from the malted rice flour which yielded mfrs. but was majorly hindered by the effect of fermentation. another plausible reason which may not directly link to enzyme activities, is the average particle dispersion per unit volume in the gruels or generally the geometric properties of particles in the gruels which tend to increase or decrease the velocity gradient of the liquids containing the flour particles. hence, increases or decrease the viscosities of the gruels. therefore, fermentation has contributed less viscosity reduction as can be seen in the non-malted flour that was fermented to yield nmfrs as compared to the nmnfrs. also, it was generally observed that the viscosities of gruels decreased with an increase in temperature within the 30 to 80 oc range studied and shear rate (6 60 rpm.) but increased with an increase in concentration (5 20%) of gruels. malting and fermentation resulted in a significant (p < 0.05) decrease in viscosities at all shear rates and temperatures with the magnitude of viscosities being highest for the non-malted-non-fermented sample and lowest for malted-non-fermented sample (figures 4a and 4b). the linear plots of the log of viscosity versus the log of shear rate also revealed or depicted the effects of temperature, concentration and shear rate on the gruels of formulated foods (figures 5a and 5b) as in the case of viscosity versus shear rate. the plots of viscosity versus shear rate and those of linear plots of log of viscosity versus log of shear rate were better correlated and followed similar trends in terms of the effect of temperature, concentration or shear rate. viscosity literatures of different food gruels (sopade and kassum, 1992a; sopade and kassum, 1992b; mouquet and treche, 2001; badau et al., 2006; taga and non, 2017) also reported similar trends. however, with some differences of viscosity derivatives. earlier reports from molecular thermodynamics, ‘temperature has a direct effect on molecular motion. as temperature increases, molecules move at a faster rate with great velocity. at low temperatures, molecules come closer together to cause an increase in viscosity. at high temperatures, molecules move far apart from each other causing decrease in viscosity’. however, ‘if no other reactions or transformations’ such as starch gelatinization, saccharification etc. are involved (figura and teixeira, 2007). in a similar vein, ‘cohesive forces between the molecules decrease and flow becomes free as temperature increases. hence, decrease in the viscosity of fluids’ (sahin and sumnu, 2006). for the shear rates, ‘shearing increases or causes friction and entangle long-chain molecules to straighten out and become aligned with the flow. hence, causing a viscosity decrease’ (figura and teixeira, 2007). an increase in concentration also increases the binding forces and gather together the molecules into a compact mass to oppose the flow or deformation. therefore, friction or resistance to flow of the material increases. ‘it is based on this idea that solids oppose deformation or flow much more compared to liquids or gases’ (sahin and sumnu, 2006; figura and teixeira, 2007). these factors that contribute to binding forces of the molecules may not be the same with the energy barrier per mole which enables motion. regardless of shear rate and since a temperature above 40 oc may not be appropriate for feeding of an infant, the appropriate viscosity recommended for infant feeding (mosha and svanberg, 1983) would likely be within 15 to 20% concentration for malted-non-fermented rice + soybean and 10 to 15% concentration for the other products. it becomes obvious according to this study, malting alone had more severe effect on the viscosity (much bulk reduction effect) and this signify increase of nutrient density in the food product. previous studies have shown the viscosity reduction with the addition of 5% power flour in gruels (mosha and svanberg, 1983; badau et al., 2006; badau et al., 2016; bristone et al., 2019). but in that case, may not be much if compare with whole malt flour or as in the case of maltednon-fermented rice + soybean. 3.2 consistency and flow behaviour indices of the formulated food products consistency and flow behaviour indices of nmnfrs and mnfrs are shown in table 5a. for nmnfrs consistency indices (k) of 5, 10, 15 and 20% concentration of gruels ranged from: 1.68 to 4.46 nsnm-2, 13.59 to 58.90 nsnm-2, 221.20 to 350.02 nsnm-2, 521.51 to 714.32 nsnm-2, respectively. also, their respective flow behaviour indices (n) are: 0.22 to 0.38, 0.12 to 0.43, 0.01 to 0.28 and 0.02 to 0.16. regardless of temperature or concentration, their consistency indices ranged from 1.68 to 714.32 nsnm-2. the accuracy or adequacy and fitness of the fitted model employed was tested by its regression coefficient (r2). the r2 values entails the satisfaction of the model. in this study, the goodness of the model fit has predicted the rheological parameters of the formulated products accurately, with the r2 values close to 1 or 1 (0.93 ≥ x ≤ 1) which justified the model parameters appropriately. the power law fluids model was observed to fit the experimental data appropriately at 10% concentration with all the correlation coefficients (r2) ≥ 0.99 as compared to 5, 15 and http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 741 20% concentrations (r2: 0.93 to 0.99). at the same time, at temperatures of 30, 40 and 80 oc, the coefficient of determination was observed to correlate well as compared to other remaining temperatures. table 5a: power law derivatives for flow of the formulated food products gruel concentration (%) parameters temperature (oc) 30 40 50 60 70 80 nmnfrs 5 r2 0.96 0.99 0.99 0.98 0.98 0.97 n 0.38 0.22 0.28 0.27 0.35 0.37 k 4.46 5.98 4.01 3.41 2.28 1.68 10 r2 1.00 1.00 0.99 1.00 0.99 1.00 n 0.43 0.17 0.12 0.22 0.12 0.29 k 41.31 58.9 49.81 30.80 28.79 13.59 15 r2 0.93 0.94 0.94 0.94 0.98 0.98 n 0.28 0.23 0.21 0.14 0.03 0.01 k 350.02 304.97 256.84 269.47 222.67 221.20 20 r2 0.98 0.99 0.99 0.98 0.98 0.95 n 0.15 0.07 0.02 0.05 0.04 0.16 k 521.51 606.55 698.27 690.50 676.22 714.32 mnfrs 5 r2 0.95 0.96 0.87 0.90 0.98 0.95 n 0.73 0.76 0.78 0.65 0.62 0.42 k 0.25 0.19 0.15 0.17 0.13 0.17 10 r2 0.99 0.99 0.96 0.98 1.00 0.97 n 0.15 0.02 0.10 0.04 0.21 0.15 k 96.06 36.34 20.78 19.53 7.49 6.59 15 r2 0.99 1.00 1.00 0.97 0.96 0.96 n 0.30 0.34 0.26 0.15 0.19 0.08 k 74.07 43.08 34.74 35.77 24.98 29.78 20 r2 0.99 1.00 0.99 0.99 1.00 0.99 n 0.48 0.47 0.42 0.46 0.41 0.38 k 129.15 110.50 115.35 88.59 83.18 76.94 nmnfrs: non-malted-non-fermented rice + soybean flour, mnfrs: malted-non-fermented rice + soybean flour, r2: correlation coefficient, n: flow behaviour index and k: consistency index the results of all flow behaviour indices (n) were observed to be less than 1. much less power law indices (average 0.08) were observed at 20% concentration, especially at temperatures of 40, 50, 60 and 70 oc. and as the temperature is increasing, the consistency indices (k) of the gruels decreased. but in the case of the concentration of gruels, the consistency indices generally increased with increasing percentage concentration of solids. in the power law fluids model, k is the consistency index known as apparent viscosity, in contrast to absolute viscosity, but which is also sensitive to temperature changes as absolute viscosity. as the temperature of the gruels increases, the limited free spaces or volumes between the food molecules become more, and this eases the moving molecules, so viscosity decreases with increasing temperatures. however, the ease with which this mobility occurs may be triggered by the velocity gradient. equally, lowering the density as the temperature increases would cause viscosity reduction. a typical example of a life situation with this viscosity http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 742 phenomenon is in an overcrowded area. as the temperature of the overcrowded place increases, people give ways to decongest, creating free spaces (volume) between individuals which would allow or ease movement and at the same time lowering of population density. but as the temperature of the overcrowded area is decreasing, people come together comfortably in mass, and this would restrict movement because of the limited spaces. in the case of consistency indices increasing with increasing concentration, this has to do with the reduction of free spaces or volume between the molecules as particles of food keep filling those free spaces and so consistency indices decrease with increasing concentration. also, as particles keep filling the free spaces of less concentrated food or liquid, physical or chemical processes such as contraction, dispersion, and aggregation would result between molecules and decrease free volume, and so much more particles in liquid would increase resistance (viscosity) to flow. the geometric nature of these particles may also favour the resistance of these gruels to flow, because movement around each particle may be disturbed or hindered because of the increase (hinder flow) in velocity gradient. for mnfrs (i.e., table 5a), consistency indices (k) of gruel ranged from 0.13 to 0.25 nsnm-2 (5% concentration), 6.59 to 96.06 nsnm-2 (10% concentration), 24.98 to 74.07 nsnm-2 (15% concentration) and ranged from 76.94 to 129.15 nsnm-2 (20% concentration). their corresponding power low index (n) also ranged from: 0.42 to 0.78, 0.02 to 0.21, 0.08 to 0.34 and 0.38 to 0.41. the power law flow index (n) describes the newtonian or non-newtonian behaviour. as the flow index (n) of the power low fluids model obtained from the linear derivatives tends toward zero, the more the product exhibits pseudoplasticity; and as it tends toward 1 or greater than 1, the more the product exhibits newtonian or dilatant behaviour, respectively. at the level of 5% concentration, the gruel tends to be pure (low level of particles) than the other concentrations, mimicking the characteristics of newtonian liquids (n = 1). concentration, temperature and consistency index relationships followed a similar trend (but r2: 0.86 to 1.00) as in the case of nmnfrs. except in terms of the magnitude of consistency indices as compared to the other formulations, which are mostly lower. for nmfrs and mfrs consistency indices are shown in table 5b. for nmfrs consistency index (k) ranged from: 0.18 to 1.73 nsnm-2, 32.62 to 103.13 nsnm-2, 352.13 to 431.38 nsnm-2 and 1031.74 to 1399.68 nsnm-2 for 5, 10, 15 and 20% concentration, respectively. their corresponding power low index (n) also ranged from: 0.42 to 0.62, 0.00 to 0.23, 0.02 to 0.26 and 0.02 to 0.18. concentration, temperatures and consistency index relationships followed a similar trend as described earlier. the goodness of fit (0.98 to 1.00) of the model at a 5% level of concentration was much better compared to other levels of concentrations in this category (r2: 0.91 to 0.99). at concentration and temperature levels of 5% and 60 oc respectively, the r2 value was up to 1.00 (perfectively fitted). the power law index was observed much less also of the 10, 15 and 20% levels of concentrations at some specific temperature, mostly towards 80 oc and the beginning of 30 oc for 10, 15 and 20% respectively. in this study, the consistency indices were observed mostly higher compared to nmnfrs or mnfrs. for mfrs (table 5b) consistency indices (k) ranged from: 0.17 to 1.15 nsnm-2, 10.24 to 78.26 nsnm-2, 294.42 to 464.05 nsnm-2, 838.82 to 1388.53 nsnm-2, for 5, 10, 15, and 20% concentrations, respectively. their corresponding flow behaviour indices (n) ranged from: 0.44 to 0.58, 0.01 to 0.27, 0.20 to 0.24 and 0.04 to 0.21. similar trend in mfrs (table 1b) was observed as in the case of nmnfrs (table 5a). however, the goodness of fit of the model (r2: 0.93 to 1.00) correlates much better at 20% concentration, because all the r2 values were observed ≥ 0.98 at that point. but a much better correlation was observed at 10 and 15% concentration and 30 oc. this entails the power law fluids model fits the experimental rheological data accurately at those points than the other values of this study and it was revealed by the r2 values of the linear correlation. flow behaviour index was much less at the levels of 10 and 20% concentrations and each with an average of 0.12. a study by mouquet and treche (2001) exhibited pseudoplastic behaviour (n < 1) similar to this study. their viscosity study of gruels for complementary food revealed a consistency index of 0.042 to 11.41 nsnm-2 (power law index 0.54 to 0.69) at a temperature of 45 oc, concentration of 7.82% solids, shear rates from 8 to 800 s-1 and also at 62.5 rpm. but correlate much better with this study of the 5% concentration of all formulations in terms of consistency index and also at 10% concentration of the malted-non-fermented rice + soybean. however, their report was observed to be slightly higher compared to this study. another study by sopade and kassum (1992a), reported a contrary consistency index of traditional complementary food (akamu) from 1.55 to 9.56 nsnm-2, except for the non-malted-non-fermented rice + soybean at 5% concentration in this study. however, their power law indices (0.33 to 0.37) are generally slightly in-between power law indices of the current study. rheological characterization of a beverage and a complementary food (kunu zaki and kunun gyada) by sopade and kassum (1992b) exhibited pseudoplastic or dilatant behaviours. also, a contrary consistency index of 0.0122 to 0.0243 nsm-2 (power law index 0.877 to 1.169). however, the consistency index of kunun gyada 0.52 to 1.67 nsm-2 (power law index 0.28 to 0.39) in their reports were http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 743 within the range of 5% concentrations of the malted-non-fermented rice + soybean and non-malted-fermented rice + soybean. despite vast data or power law indices generated in this current study and ones reported (0.3184 to 0.5315) by badau et al. (2006), most did not correspond. the use of lower (0.5, 1.0, 2.5 rpm) and higher (100 rpm) shear rates in their study or higher temperatures (60, 70, 80 oc) employed in this study are the major contributing factors for such disparity since their r2 values (-0.9993 to – 0.9524) match the r2 values (0.83 to 1.00) of this study. nevertheless, their finding exhibited pseudoplastic behaviour (0 < n < 1) and consistency indices of 2.749 to 4.4615 nsnm-2 (power law index from 0.3184 to 0.5315) as affected by the addition of malt in formulations, which agreed with the 5% concentration of the non-malted-non-fermented rice + soybean. sorghum products exhibited pseudoplastic or dilatancy as reported by taga and non (2017) but their consistency index (0.158 to 34.484 nsm-2) corresponded with the 5 and 10% concentrations of the formulated products. table 5b: power law derivatives for flow of the formulated food products gruel concentration (%) parameters temperature (oc) 30 40 50 60 70 80 nmfrs 5 r2 1.00 1.00 1.00 1.00 0.99 0.98 n 0.43 0.42 0.46 0.44 0.53 0.62 k 1.73 1.49 0.94 0.82 0.37 0.18 10 r2 0.97 0.95 0.96 0.92 0.95 0.94 n 0.23 0.10 0.03 0.00 0.09 0.04 k 77.25 86.66 103.13 71.74 38.55 32.62 15 r2 0.99 0.97 0.91 0.95 0.95 0.93 n 0.26 0.25 0.17 0.08 0.02 0.03 k 431.38 353.19 375.78 411.99 427.52 352.13 20 r2 0.98 0.99 0.99 0.99 0.97 0.96 n 0.05 0.02 0.08 0.12 0.15 0.18 k 1031.74 1172.62 1335.42 1399.68 1331.42 1271.56 mfrs 5 r2 0.96 0.99 0.99 0.96 0.94 0.99 n 0.50 0.44 0.52 0.56 0.58 0.55 k 1.14 1.15 0.61 0.40 0.23 0.17 10 r2 1.00 0.97 0.95 0.93 0.92 0.83 n 0.27 0.08 0.01 0.02 0.10 0.25 k 58.21 78.26 76.10 47.99 24.83 10.24 15 r2 0.99 0.97 0.93 0.94 0.97 0.95 n 0.24 0.24 0.13 0.02 0.11 0.09 k 364.31 296.19 349.32 464.05 449.89 294.42 20 r2 0.99 0.98 0.99 0.98 0.98 0.98 n 0.11 0.04 0.06 0.10 0.18 0.21 k 838.82 985.35 1174.97 1235.21 1388.53 1210.76 nmfrs: non-malted-fermented rice + soybean flour, mfrs: malted-fermented rice + soybean flour, r2: correlation coefficient, n: flow behaviour index, k: consistency index http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 744 3.3 influence of activation energy and frequency factor in table 6a and 6b the temperature dependency of the viscosity of gruels are shown. irrespective of concentration or shear rates, the activation energy of the gruels of nmnfrs, mnfrs, nmfrs and mfrs ranged from 5.25 to 28.04 kjmol-1 (r2: 0.87 to 1.00), 12.82 to 37.57 kjmol-1 (r2: 0.91 to 0.99), 5.73 to 32.83 kjmol-1 (r2: 0.89 to 0.99) and 5.73 to 36.97 kjmol-1 (r2: 0.79 to 0.99) respectively. whereas their corresponding frequency factors ranged from 8.7 × 10-5 to 1.3 × 101, 1.2 × 10-7 to 2.4 × 10-1, 1.2 × 10-6 to 1.3 ×101 and 6.7 × 10-7 to 1.2 × 101, respectively. the goodness of fit (r2) of the model as observed is high and well correlated throughout. table 6a: temperature dependency of the viscosity of gruels nmnfrs mnfrs nmfrs mfrs c γ ea r2 ea r2 ea r2 ea r2 5 6 18.52 0.97 22.50 0.99 32.83 0.93 34.67 0.97 12 17.58 0.87 21.77 0.95 29.03 0.96 30.86 0.94 30 16.24 1.00 27.60 0.91 26.48 0.97 28.56 0.97 60 16.79 0.96 34.09 0.92 25.26 0.97 30.64 0.96 10 6 23.40 0.96 34.79 0.97 24.82 0.97 36.97 0.96 12 25.94 0.99 32.43 0.95 23.76 0.97 25.16 0.95 30 27.78 0.96 23.75 0.97 25.60 0.99 31.19 0.98 60 28.04 0.95 24.67 0.93 30.73 0.98 35.39 0.97 15 6 11.55 0.95 25.06 0.96 14.18 0.99 17.43 0.93 12 16.91 0.97 27.17 0.97 17.00 0.98 16.34 0.87 30 21.27 0.99 37.57 0.99 28.73 0.99 29.83 0.98 60 26.32 0.99 32.09 0.98 25.23 0.98 31.42 0.97 20 6 5.67 0.91 12.82 0.98 5.73 0.91 5.73 0.95 12 5.25 0.94 15.57 0.96 6.18 0.89 10.26 0.79 30 16.26 0.94 13.90 0.99 14.11 0.94 17.54 0.98 60 15.21 1.00 17.78 0.97 13.11 0.98 18.72 0.99 nmnfr: non-malted-non-fermented rice, mnfr: malted-non-fermented rice, nmfr: non-maltedfermented rice, mfr: malted-fermented rice, s: soybean, c: concentration (%), γ: shear rate (revolution per minute), r2: regression coefficient and ea: activation energy. table 6b: temperature dependency of the viscosity of gruels products nmnfrs mnfrs nmfrs mfrs c γ μo 5 6 1.1 × 10-3 1.9 × 10-5 1.2 × 10-6 4.6 × 10-7 12 9.3 × 10-4 2.0 × 10-5 3.5 × 10-6 1.4 × 10-6 30 7.4 × 10-4 2.4 × 10-6 5.5 × 10-6 2.1 × 10-6 60 4.5 × 10-4 1.2 × 10-7 6.0 × 10-6 6.7 × 10-7 10 6 1.6 × 10-3 6.7 × 10-6 6.6 × 10-4 5.4 × 10-6 12 3.5 × 10-4 7.4 × 10-6 7.4 × 10-4 3.3 × 10-4 30 8.7 × 10-5 8.5 × 10-5 1.6 × 10-4 1.5 × 10-5 60 4.8 × 10-5 3.0 × 10-5 8.8 × 10-6 1.3 × 10-6 15 6 8.6 ×10-1 6.6 × 10-4 2.7 × 10-1 6.1 × 10-2 12 8.5 × 10-2 1.6 × 10-4 6.1 × 10-2 6.8 × 10-2 30 5.1 × 10-3 1.6 × 10-6 2.4 × 10-4 1.3 × 10-4 60 6.1 × 10-4 8.5 × 10-6 7.3 × 10-4 4.8 × 10-5 20 6 1.3 × 101 2.4 × 10-1 1.3 ×101 1.2 × 101 12 0.8 × 101 6.0 × 10-2 0.5× 101 0.1 × 101 30 4.1 × 10-2 6.4 × 10-2 8.0 × 10-2 2.2 × 10-2 60 4.3 × 10-2 1.1 × 10-2 7.6 × 10-2 9.3 × 10-3 nmnfr: non-malted-non-fermented rice, mnfr: malted-non-fermented rice, nmfr: non-malted-fermented rice, mfr: malted-fermented rice, s: soybean, c: concentration (%), γ: shear rate (revolution per minute) and r2: regression coefficient and μo: frequency factor http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 745 the activation energy of gruels mostly decreased with an increase in concentration and also increased with an increase in shear rates, especially from 10 to 20% concentrations. this mean, gruels are less sensitive to temperature change with an increase in concentration and more sensitive to changes with an increase in shear rates. the latter is more complicated, considering viscosity decreases with an increasing shear rate. from the rheological theory and molecular point of view, there is a possibility as the molecules are greatly aligned to oppose flow at higher shear rates than lower shear rates, sensitivity to the temperature measured by the arrhenius equation may be felt more at higher shear rates. however, lower shear rates always have a greater impact on flow or deformation than higher shear rates. there are still many controversial issues about the mechanics of flows that have not been elucidated. in table 6b, frequency factors mostly decreased in descending order of magnitude of concentrations (20, 15, 10, and 5% respectively). and this is in line with collision theory. the increase in concentration, temperature or surface area of these food materials would increase the number of collisions of the food molecules to overcome the energy barrier that initiate flow. however, in literature collision theory is more elucidated during chemical reaction than the mechanics of flows. nonetheless, when molecules collide with one another, they give ways which initiate motion or flow. the more they collide with one another, the more the increase in motion, such as in turbulent flow. it is based on this concept lower shear rates would have greater impact on flow or deformation than the higher shear rates. the activation energy of mfrs was observed to be higher than the nmnfrs. and lower in energy than mnfrs at 5 and 10% concentrations. and also higher in energy than nmfrs at 10, 15, and 20% concentrations. according to the arrhenius equation, those products at higher activation energy imply more sensitivity to temperature changes at those points (i.e., concentration) than the lower activation energy products. this could mean, that higher activation energy is needed by those products to initiate motion (flow) of the food molecules than the lower ones. in chemistry, a higher value of activation energy substance indicates slow time/high-energy taken reaction (flow). this may be influenced by factors such as enzyme (or catalyst), temperature, surface area etc. similarly, the nmfrs also followed the same trend. but in this case, activation of nmfrs is higher than the nmnfrs and is also lower than the mnfrs, except at a 20% level of concentration. the activation energy of the mnfrs also followed a similar trend as observed in nmnfrs. however, the quantity of activation energy was observed to be higher in mnfrs compared to nmnfrs. from the elementary knowledge of chemistry, kinetic energy would increase by decreasing the concentration of molecules. this would explain if the concentration is low (viscosity would be low), molecules will be far apart from each other which will require high energy for collision, so high activation energy. but if concentration is high, molecules will be close to each other and collide faster with ease, so low activation energy. table 6a at levels of 5 and 20% concentration is a good example for comparison. a high concentration of reactant will also cause more collision and lead to low activation energy. tables 6a and 6b agreed with this phenomenon as compared, especially the 10, 15 and 20% concentrations. activation energy which is the energy barrier per mole (sahin and sumnu, 2006) enables motion such as in the case of the flow of gruels (reaction such as in the case of acid and base reaction in chemistry) is important for understanding the flow behaviours of substances. from this definition, it can be seen that the textural characteristics which are also one of the determinants for evaluating food quality would depend on the activation energy for mastication or swallowing as well as the flow of food in pipes. many theories have described how flow occurs (sahin and sumnu, 2006; figura and teixeira, 2007). one can agree with those assumptions that temperature difference, molecular structure, material with low viscosity and vacancies in liquid are factors that permit flow initiated by activation energy. taga and non (2017) modelled the rheological properties of gruels with concentrations from 15 to 35% w/w, temperature and shear rate from 30 to 60 °c and 0.01 to 250 rpm respectively. their reports of activation energy within the range of 0.964 to 21.070 kjmol-1 correspond slightly to the activation energy of non-maltednon-fermented rice + soybean of the 5, 15 or 20% concentration except the 10% which are higher. for maltednon-fermented rice + soybean, only the 20% concentration agreed with their findings. but the non-maltedfermented rice + soybean at 15 or 20% concentration and the malted-fermented rice + soybean at 20% concentration. sopade and kassum (1992b) reported higher activation energies of kunun zaki and kunun gyada (complementary food) than all the activation energies of the samples investigated. also, those of badau et al. (2006) who investigated activation energies of complementary foods as affected by the addition of malt obtained much lower activation energy than in this study. different studies on 40 different literatures on fruits and vegetables by krokida et al. (2001) are within the range of activation energy obtained in this study except the 20% concentration for non-malted-non-fermented rice + soybean, malted-fermented rice + soybean and non-malted-fermented rice + soybean. in addition, these formulated food products are not pure liquids or chemicals but mixtures of complex substances with differential substantial enzymes. such that, the slight deviation of some frequency factors or activation energy values versus concentration from trend of kinetic http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 746 theories, depicted the complexity of these foods. therefore, the flow of these gruels which were mostly influenced by mechanical energy, may not necessarily cause the formation of new gruel products as in the case of a chemical reaction under the influence of chemical properties. but their molecules have changed position by acquiring minimum energy which enables them to begin to flow. example, at a level of 10% concentration, sample nmnfrs have been initiated with an activation energy of 23.40 kjmol-1 (table 5a) which enables it to begin to flow by shearing force of 6 rpm. 4. conclusion in this study, the flow responses of the formulated food products (gruels) at temperatures of 30, 40, 50, 60, 70, and 80 oc, and shear rates of 6, 12, 30, and 60 rpm, as well as at each target level concentrations of 5, 10, 15 and 20% have been investigated using standard methods. the effect of malting and/or fermentation, irrespective of the viscosity functions used varied significantly (p < 0.05). the highest viscosity reduction was observed in malted-non-fermented rice + soybean (0.01 to 37.50 nsm-2), followed by malted-fermented rice + soybean (0.02 to 110.04 nsm-2), non-malted-fermented rice + soybean (0.23 to 120.10 nsm-2) and nonmalted-non-fermented rice + soybean (0.14 to 121.22 nsm-2), respectively. all plots of the viscosities versus shear rates depicted time-independent, non-newtonian fluids. viscosity decreased with increasing temperature, and also share rates as well as increased with increasing concentration. similar trends were exhibited by the consistency flow behaviour indices of the formulated food products, with all the power-law flow behaviour indices (n) being less than 1, which characterized the formulated food gruels as pseudoplastic (shear thinning liquids). activation energies and frequency factors of the formulated foods, irrespective of the viscosity functions studied ranged from 5.25 to 37.57 kjmol-1 and 12 x 10-7 to 1.3 x 101, respectively. the regression coefficient (r2) of the linear derivatives of the power law fluids model and the arrhenius type equation have justified the model parameters appropriately, with r2 values for the linear correlation obtained being close to 1 or 1, which indicate the models used were accurate for predicting the rheological parameters of these formulated foods. samples of non-malted-non-fermented rice + soybean (nmnfrs), non-maltedfermented rice + soybean (nmfrs) and malted-fermented rice + soybean (mfrs) are recommended to be prepared at a 15% concentration for infants and malted-non-fermented rice + soybean (mnfrs) at 20% or slightly above 20% concentration for infant feeding (appropriately free-flowing gruel). also, due to the high demand for rice malt for many food applications at the domestic or industrial level, appropriate de-husking technology for malted rice is required to enhance research studies. similarly, the steam-cooked form of these products would create an improved instant complementary food. acknowledgements we thank the university of maiduguri for granting the study fellowship. also, the canadian international development agency and africa rice centre who initiated and supported our previous research on rice under the project ‘enhancing food security in africa through the improvement of rice post-harvest handling, marketing and the development of new rice-based products’, without which it could have been impossible for feasible transition to this one. we also acknowledge the national cereals research institute, badeggi, for providing the rice variety (faro 44). references adebowale, aa. and sani, io. 2011. effects of solid contents and temperature on viscosity of tapioca meal. journal of food science and technology, 50(3): 573 578. badau, mh., bristone, c., igwebuike, ju. and danbaba, n. 2016. production, viscosity, microbiological quality and sensory properties of complementary food blends of improved rice cultivars, soybean and sorghum malt. pakistan journal of nutrition, 15(9): 849 856. badau, mh., jideani, ia. and nkama, i. 2006. rheological behaviour of weaning food formulations as affected by addition of malt. international journal of food science and technology, 41: 1222-1228. bristone, c., badau, mh., igwebuike, ju. and danbaba, n. 2019. viscosity and nutritional evaluation of rats fed with complementary foods produced from broken iractions of improved rice cultivars, soybeans and sorghum malt. canadian journal of agriculture and crops, 4(2): 208 217. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 747 bristone, c., ariahu, cc., ikya, jk. and eke, mo. 2021. microbiological, essential dietary minerals and amino acids composition of malted and /or fermented faro 44 rice plus soybean based complementary foods. annals clinical nutrition, 4(2): 1022. ebenehi, o. and ahmed, ta. 2019. perceived relevance of extension methods used to disseminate faro-44 rice variety to rice farmers in kogi state, nigeria. international journal of agriculture and nutrition, 1(1): 19 21. figura, lo. and teixeira, aa. 2007. physical properties measurement and applications. springer berlin heidelberg new york. pp. 1 510. fraiha, m., biagi, jd. and ferraz, acdo. 2011. rheological behaviour of corn and soy mix as feed ingredients. cienciae tecnologia de alimentos, 31(1): 129 134. garcía-salcedo, aj., fonthal, g., franco, jf. and tirado-mejía, l. 2023. analysis of compositional differences between commercial rice grains by the study of the photoluminescence response. journal of cereal science, 111: 103681. gasinski, a., kawa-rygielska, j., błazewicz, j. and leszczynska, d. 2022. malting procedure and its impact on the composition of volatiles and antioxidative potential of naked and covered oat varieties. journal of cereal science, 107: 103537. idu, ee., onwumere, fe., haruna, lz. and irewa, ii. 2021. preference study of three varieties of rice among farmers in kwali area council of abuja, nigeria. journal of agricultural and food 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389 400. nielsen, ss. 2010. food analysis. 4th edition. springer science + business media, new york, ny 10013. pp. 3 – 586. sahin, s. and sumnu, sg. 2006. physical properties of foods. springer science + business media, new york, ny 10013. pp. 1 248. sopade, pa. and kassum, al. 1992a. rheological characterization of akamu, a semiliquid food made from maize, millet and sorghum. journal of cereal science, 15: 193 202. sopade, pa. and kassum, al 1992b. rheological characterization of nigerian liquid and semi-liquids foods: kunu zaki and kunun gyada. nigerian food journal. 10: 23 -31. taga, cm. and non, yj. 2017. modelling the rheological properties of gruels produced from selected food products from cameroon. african journal of biotechnology, 16(17): 971 982. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bristonecharles@yahoo.com 748 udemezue, jc. and agwu, ae. 2018. improved rice varieties, production technologies and processing constraints in nigeria. direct research journal of agriculture and food science, 6(12): 360 373. wfp. 2018. nutritional guidance for complementary food.retrieved from: https://www.wfp.org/publication s/nutritional-guidance-complementary-food (accessed 25 september 2021). wu, p., ren, l., zhao, n., wu, t., liu, r., sui, wj. and zhan, m. 2022. solidstate fermentation by rhizopus oryzae improves flavor of wheat bran for application in food. journal of cereal science, 107: 103536. http://www.azojete.com.ng/ mailto:bristonecharles@yahoo.com https://www.wfp.org/publications/nutritional-guidance-complementary-food https://www.wfp.org/publications/nutritional-guidance-complementary-food arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):261-294 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 261 a retrospect of energy demand and potential of subsaharan africa: leveraging energy deficit to attain clean energy hub region w. s. ebhota* and p. y. tabakov department of mechanical engineering, institute for systems science, durban university of technology, durban, south africa *corresponding author's email address: ebhotawilliams1@gmail.com article information submitted 18 september, 2021 revised 20 november, 2023 accepted 23 february, 2024 keywords: renewable energy system climate change net-zero-co2 emissions renewable energy in subsahara africa hydro wind solar pv sub-saharan africa’s primary energy mix abstract the lack of reliable energy access is a significant obstacle to the socioeconomic progress of the global south, particularly sub-saharan africa (ssa). this research explores the current energy demand and access situation, evaluated ssa's renewable energy (re) potential, identifies barriers to re development, and proposed strategies to overcome these challenges. the study emphasises the importance of establishing re infrastructure for a sustainable energy transition and outlined necessary investments. with an impressive 11,000 gigawatts (gw) of exploitable generating capacity, re has the potential to replace fossil fuels effectively in ssa. the dominant resources are solar (10 tw), hydro (350 gw), wind (110 gw), and geothermal (15 gw) energy. challenges include high initial costs, limited financing access, grid integration issues, infrastructure deficiencies, regulatory frameworks, and resource variability. to address these challenges, the study suggests policy and regulatory reforms, expanded financing access, capacity building, and improved grid infrastructure. overall, this research presents the energy deficit and re potential in ssa as opportunities for the region to become a clean energy hub, requiring collaboration among governments, academic institutions, industry stakeholders, and international organizations. 1.0 introduction sub-saharan africa (ssa) ranks as the world's least electrified region, with just 48% having access to electricity and a mere 17% having access to clean cooking facilities (ramalope et al., 2022). as a result, traditional biomass continues to play a significant role in ssa, constituting nearly half of the region’s primary energy mix (iea, 2022, irena and afdb, 2022). in 2019, the top 20 countries with the most significant energy access deficits globally were situated in the global south (azeez, 2021). these included six in eastern and south-eastern asia, ten in ssa, and four in central and southern asia. however, over the past decade, more than one billion people have gained access to electricity. the covid-19 pandemic temporarily reversed this progress, leaving around 30 million people unable to afford basic electricity, with the majority residing in ssa (iea et al., 2021). consequently, in some ssa countries like the democratic republic of congo, ethiopia, madagascar, mozambique, tanzania, niger, and uganda, only 5% of the population does not rely on charcoal and wood for cooking (who, 2021). the prolonged electricity deficiency in ssa shows no sign of abating, as rapid population growth, urbanisation, and industrialisation continue to challenge efforts to address this issue. the highest rates of urbanisation are expected in the global south, specifically in the african and asian regions. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 262 the top 20 countries facing the most significant challenges in providing electricity accounted for 75% of the global population in 2021. the countries with the largest populations lacking access were nigeria (86 million), the democratic republic of the congo (76 million), and ethiopia (55 million) (iea et al., 2023). from 2019 to 2021, the democratic republic of the congo experienced a situation where its progress in electrification lagged behind its population growth, resulting in an increase in the number of people without access to electricity in the country. in contrast, nigeria and ethiopia saw their electrification efforts outpace their population growth rates. among countries with limited access to electricity, kenya and ethiopia exhibited the most rapid improvement, with both nations extending electrification by more than 3 percentage points annually between 2019 and 2021 (iea et al., 2023). over the past decade, a larger portion of the world's population achieved electricity access than ever before (worldbank, 2022, streatfeild, 2018b). however, it is worth noting that the number of people without electricity in ssa has risen. the global community is expected to continue facing challenges in achieving its objective of ensuring universal access to affordable, reliable, sustainable, and modern energy by 2030. this goal may remain elusive unless significant actions are undertaken to enhance access in nations experiencing the most pronounced energy deficits. this was the common position of notable international organisations, such as the international renewable energy agency (irena), the united nations department of economic and social affairs (un desa), and the world bank, according to the international energy agency (iea) energy progress report (worldbank, 2021b, esmap, 2023). the consequences of this energy deficit in ssa include escalating co2 emissions, deforestation, ecosystem disruption, health problems, climate change, loss of biodiversity, inhibited economic growth, and worsening poverty levels in the region (affuldadzie et al., 2020, bloomer and boateng, 2024, byaro et al., 2024, ). these challenges are not only peculiar to ssa, they are worldwide issues, driven by the need for energy to fuel socioeconomic development. in response to this crisis, a global initiative led by the united nations (un) to combat co2 emissions has emerged, to reduce or eliminate co2 emissions (unep, 2023). nevertheless, man will not let go of “fossil fuel” without an appropriate or better alternative because of economic reasons. a reduction in the use of fossil fuel without an appropriate substitute will not work (ebhota, 2019b). it means a decline in economic activities, which could exacerbate the challenge of meeting energy demands in energy-poor countries due to the existing power deficit (ebhota and tabakov, 2019). renewable energy is expected to be an alternative source devoid of complication and compromise. however, despite the declining costs of clean energy alternatives, they are relatively high in the global south, especially the initial cost. this coupled with other technical challenges, such as power intermittency and low power conversion efficiency slow down re deployment and hinder the universal energy access progress. this study identified the research gaps and areas of interest about ssa’s energy status, re potential, and transition to re that need to be studied, understood, and addressed. this is necessary if re potential is to be developed and deployed to change the present narrative of the region’s perennial energy access issues. the research gaps and areas of interest in energy and sustainable energy transition are behavioural and cultural aspects, resilience and energy file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 263 security, technological innovation, and community engagement and participation (bulbulia, 2022). others are socioeconomic impacts, cross-border energy trade, energy storage technologies, climate change mitigation, data availability and quality, policy and regulatory frameworks, infrastructure development, energy efficiency, energy transition pathways, re potential, energy access and inequality (ganesan, 2024, iea, 2009). however, the scope of this paper covers energy access, re potential, infrastructure development, socioeconomic impacts, and technological innovation. tackling these research voids will aid in crafting evidence-backed policies and strategies fostering sustainable energy access, economic growth, and environmental conservation in ssa. hence, this study analysed ssa's energy demand, access status, re potential, identified re development hurdles, and proposed countermeasures. it also underscores the significance of re infrastructure development in achieving a sustainable energy transition, addressing investment requirements, with specific attention to the african development bank's (afdb) role. 1. examining energy demand, generation, and supply in ssa globally, about 1.2 billion people were without access to electricity in 2019 and they lived mostly in the global south; 50% of the global population without access live in ssa (iea, 2021b, iea, 2020, routley, 2019). again in 2021, according to the economic commission for africa (eca) ssa had a 72% (about 600 million) share of the 900 million people that lack access to electricity globally (eca, 2021); 80-86% of the energy consumed in ssa is of solid biomass for cooking and 78% of oil is consumed in the transport sector (eca, 2021). several efforts are being made to increase the population with access to electricity in the region. about 80 gw was the installed electricity capacity in ssa (excluding south africa) in 2018, which is approximately three times less than that of france. the generated net electricity in africa in 2019 was only 804 terawatts-hour (twh), about 20% of that of the united states that same year. africa experienced about a 2.5% decline in the electricity generation in 2020 (from 863 twh in 2019 to 844 twh in 2020) (aec, 2021). eleven countries accounted for three-quarters of the energy demand and gross domestic product (gdp) of ssa in 2018 (iea, 2019a). the share of the primary energy sources and the eleven countries that accounted for the threequarters are presented in figure 1(a) and (b), respectively. figure 1: shares of ssa primary energy demand (ped); (b) ssa countries that accounted for the three-quarters in 2018 (iea, 2019a) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 264 in 2021, power demand in ssa saw a notable growth of more than 5%, bouncing back from a 4% decline the previous year, which was primarily caused by disruptions and economic slowdown due to the covid-19 pandemic (iea, 2021a). the recovery in demand was primarily driven by the commercial and industrial sectors, which experienced growth rates of approximately 4% and 8%, respectively. residential demand also rebounded, even though it did not decline in 2020, unlike the other segments of demand. the projection is that the overall power demand will continue to grow in 2022, although at a slower pace compared to 2021 if new waves of covid-19 variants do not severely impact economic activity. it is noteworthy that power demand in ssa remains relatively low, with an average of less than 500 kwh per capita, which is among the lowest levels globally (berkove et al., 2022). in 2020, south africa was responsible for about half of ssa's total power demand and experienced a significant drop in demand due to both the covid-19 pandemic and scheduled power cuts, worsened by the country's ongoing power supply crisis. however, south africa managed to recover its power demand to pre-pandemic levels in 2021, thanks to a rapid rebound in the industrial sector, which saw an 8% year-on-year increase in demand. nigeria, the second-largest power market in ssa, accounting for nearly 11% of the region's total power demand, continues to face challenges with suppressed power demand, largely due to persistent supply issues and low electrification rates (berkove et al., 2022, iea, 2022). although nigeria's power demand recovery in 2021 was driven by the commercial and industrial sectors, it is important to note that roughly half of the country's total power demand comes from off-grid sources (eia, 2022). electricity demand in ssa is a critical topic due to the region's population growth, urbanisation, and economic development. the demand for energy in africa has been on a steady rise, increasing at an annual rate of approximately 3%, surpassing all other continents (pwc, 2022). having access to reliable electricity is a prerequisite for igniting industrialisation and meaningful economic growth. the global electrification rate has increased significantly since 2000, but ssa has not seen much progress in this regard. the actual energy supply continues to significantly fall short of meeting the demand in the region. as of 2021, ssa accounted for about 80% of the world's population without electricity access, and 19 of the 20 countries with the lowest electrification rates were located in this region (statista, 2023). the only exception was haiti, a caribbean country. furthermore, there are significant disparities in access within the region, with over 80% of the urban population in the region having electricity access in 2021, while only 30% of those living in rural areas enjoyed the same privilege. across the region, customers are burdened by consistently poor power supply reliability. as of april 2022, a survey revealed that only 43% of africans reported having access to a dependable electricity supply, which is a modest increase of just 3% points since 2015. the level of electricity access across african countries is shown in figure 2. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 265 figure 2: level of electricity access in african countries (% of the population) (aep, 2022). the most recent data from the world bank enterprise surveys indicates that customers in ssa endure an average of nine power outages per month, each lasting an average of 5.7 hours, as presented in table 1 (statista, 2023, worldbank, 2020a). this lack of consistent and reliable power supply, especially for commercial and industrial users, exerts a disproportionate impact on economic productivity. sub-saharan african businesses frequently cite inadequate or unreliable power supply as a significant constraint, with majority of countries reporting that more than 50% of firms experience electrical disruptions (garg et al., 2022). approximately 41% of african firms identify the lack of electricity or its poor quality as a major constraint on their operations (oseni, 2019). this compels these firms to resort to more environmentally harmful and expensive alternatives like diesel generators. this reliance on diesel generators has detrimental effects on firm efficiency and undermines competitiveness. furthermore, approximately 28% of connected households experience power outages either occasionally or never have access to electricity (lee et al., 2022). table 1: countries with the lowest electricity access country electricity access (%) annual electrical outages (%) country electricity access (%) annual electrical outages (%) south sudan 7.7 15.30 guinea bissau 35.8 84.20 burundi 10.2 85.1 benin rep 42 95.6 chad 11.3 70.20 tanzanian 42.7 85.80 malawi 14.2 82.90 mozambique 31.5 52.80 car 15.7 89.00 uganda 45.2 81.50 niger 18.6 78.00 zambia 46.7 87.10 burkina faso 19 91.90 guinea 46.8 84.20 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 266 drc 20.8 not available haiti 47.2 not available png 20.9 97.7 mauritania 47.7 90.70 sierra leone 27.5 71.80 angola 48.2 87.70 liberia 29.8 44.30 rwanda 48.7 39 madagascar 35.1 86.90 (statista, 2023, worldbank, 2020a) electricity access in ssa has historically faced numerous challenges, notwithstanding being an essential component for economic development and improving the quality of life for its citizens. despite decades of efforts and investments in electrification, ssa has the lowest rates of electricity access in the world. according to the iea, over half of the global population without electricity access lives in ssa (iea, 2019b). a significant portion of the population, particularly in rural areas, lacks access to electricity (casati et al., 2023, shettima et al., 2023). even in areas with access to electricity, power supply is often unreliable, leading to frequent blackouts and disruptions. this inconsistency hampers economic activities and quality of life. the level of access to electricity across africa and the rate of energy access increase in ssa are shown in figure 3. figure 3: (a) the level of access to electricity across africa; (b) ssa rate of energy access increase (worldbank, 2021a). 1.1. dynamics of ssa electricity demand increase about 1.2 twh was the projected total amount of electricity required by ssa in 2022, which is a 5% increase from the previous year. this estimate was based on the expected growth of population, economic activity, and electrification rate in the region. the main sources of electricity generation in ssa are hydro, thermal, and re, with varying shares depending on the country and the availability of resources. the challenges faced by ssa in meeting its electricity demand include inadequate infrastructure, low access rates, high costs, and environmental impacts (hafner et al., 2018, emetere et al., 2021). electricity demand dynamics in ssa are influenced by a combination of factors that shape the region's energy landscape. the demand for both modern and traditional fuels will continue to exist, and population and urbanisation growth will play key factors in the demand increase. in ssa, there are other factors that to be considered in determining the electricity demand increase. it is important to note that ssa is file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 267 a diverse region with variations in electricity demand patterns from country to country, and some key aspects of ssa's electricity demand dynamics are presented in table 2. table 2: ssa electricity demand dynamics. population growth ssa has one of the fastest-growing populations globally. this demographic trend directly affects electricity demand, as more people require access to electricity for residential, commercial, and industrial purposes. the population growth rate of ssa was 2.57% in 2021 (o'neill, 2023 ). urbanisation urban areas in ssa are expanding rapidly, leading to increased energy consumption. urban centres typically have higher energy needs due to the concentration of economic activities, industries, and infrastructure (gutu sakketa, 2023). economic development economic growth and development are closely tied to electricity demand. as economies in ssa grow, so does the demand for energy to power industries, businesses, and services. industrialisation many countries in ssa are working towards industrialization and manufacturing growth. these sectors require significant amounts of electricity to operate machinery and facilities commercial and residential needs urbanization and economic growth drive the demand for electricity in commercial establishments, office buildings, and residential areas for lighting, heating, cooling, and electronic devices electrification of rural areas efforts to extend electricity access to rural and remote areas contribute to increasing demand. rural electrification initiatives aim to improve living standards and stimulate economic activities energy access a significant portion of ssa's population still lacks access to reliable electricity. efforts to increase energy access contribute to rising electricity demand. technological advancements as technology becomes more prevalent, the demand for electronic devices, communication tools, and digital services also drives electricity consumption. infrastructure development infrastructure projects, such as transportation systems, telecommunications networks, and modern facilities, require electricity for operation. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 268 energyintensive sectors certain sectors, such as mining and mineral processing, can have high energy demands due to the energy-intensive nature of their operations. (espoir et al., 2023, fotio et al., 2023, garg et al., 2022, kondi-akara et al., 2023) 1.2. impact of efficiency on energy demand efficiency plays a crucial role in moderating the growth in demand, lessening reliance on fuel imports, easing the burden on existing infrastructure, and maintaining reasonable consumer energy costs. by 2030 (iea, 2022), energy and material efficiency measures are expected to reduce electricity demand by 230 terawatt-hours, which accounts for 30% of the current electricity demand. most of these savings, constituting 60%, are attributed to building codes and energy performance standards that limit the sale of the least efficient appliances and lighting. 1.3. population and urbanisation the rapid population increase of ssa strains infrastructure, making it more susceptible to disruptions. the concentration of industries, commercial establishments, and technologyintensive activities in cities, which come with urbanisation, increases electricity consumption and makes the area vulnerable to power outages due to the cascading effects of infrastructure failures or natural disasters. the continued urbanization and population rapid growth (o'neill, 2022, o'neill, 2023 ), as shown in figure 4, in the region have a profound impact on electricity systems, influencing demand, infrastructure development, environmental sustainability, and equity in access. managing these influences effectively is essential for meeting the energy needs of urban populations while striving for a sustainable and resilient energy future. transitioning to cleaner and more efficient energy sources is a key component of addressing these challenges. understanding and managing these dynamics is crucial for ensuring a stable and sustainable electricity supply in ssa. policymakers, energy providers, and stakeholders must work together to meet the region's growing electricity demand while promoting energy efficiency, cleanliness, and sustainability. figure 4: sub-saharan africa (a) population from 1960-2022 (o'neill, 2023 ); (b) degree of urbanization from 2011-2022 (o'neill, 2022). 2. leveraging energy deficit into clean energy hub leveraging ssa's energy deficit and re's potential to transform the region into a clean energy hub is a visionary goal that can have significant socioeconomic, environmental, and social benefits. additionally, it will job creation, and climate change mitigation efforts. this transformation requires a multi-faceted approach involving governments, the private sector, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 269 international organizations, and local communities. it should be driven by a shared commitment to sustainable development, environmental protection, and improved energy access for all. building re infrastructure as the primary source of electricity generation can position ssa as a leader in clean energy development while meeting its energy needs for socioeconomic development. this transformation involves a comprehensive and integrated approach that encompasses policy, feasibility studies of the various re sources, technology, finance, and community engagement to overcome the challenges and harness the benefits of this transformation. 2.1. sub-saharan african renewable energy potential despite the advantages of renewable options costs decline and the vast potential for re sources, such as wind, solar, hydro, and geothermal, in the region, ssa has the least energy access globally. in 2019, the electrification rate in ssa stood at 46%, leaving 906 million people without access to clean cooking fuels and technologies (irena and afdb, 2022). sub-saharan africa has one of the world's lowest rates of electricity access, with over 600 million individuals lacking reliable electricity. hence, the region heavily depends on imported fossil fuels, which can result in energy supply disruptions and price fluctuations. renewable energy sources, being indigenous and sustainable, enhance energy security by reducing dependence on imported fuels. renewables play a pivotal role in increasing access to electricity and clean cooking fuels. africa’s vast resource potential in wind, solar, hydro, and geothermal energy, and the declining costs are making renewables more accessible (ebhota, 2019a, ebhota, 2019b) . however, the expansion is relatively low, which means africa's abundant resource potential is grossly untapped (du et al., 2021, zakari et al., 2022). the renewable power generation in africa is relatively low, among the least continents considering what europe and north america generate, as shown in figure 5(a). among the countries in africa, south africa and northern africa countries lead the chart in re generation while west african countries are among the least re generators, as presented in figure 5(b). figure 5: renewable power generation across (ei, 2024) (a) regions; (b) africa. where commonwealth of independent states (cis). africa boasts abundant re resources, estimated to be around 1,000 times greater than the expected electricity demand by 2040 (ramalope et al., 2022). this surplus of re potential, equivalent to 11,000 gigawatts (gw) of exploitable generating capacity, positions the continent well to fulfil both its current and future energy requirements (afdb, 2023). figure 6 illustrates the distribution and capacity of these re resources across africa. considering the imperative http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 270 to reduce pollution-related health issues, address energy crises, and combat climate change, there is an increasing need to shift from fossil fuels to re sources. this transition represents a crucial energy paradigm shift comprising various intricate elements, with the effective management of these elements serving as the foundation for achieving sustainable energy transition (set). among these elements are digitization, decarbonization, and decentralization. this transition comes at a pivotal moment for ssa, which faces a significant energy deficit, exacerbating the region's challenges. figure 6: the distribution of re across africa (afdb, 2018). as per a study conducted by the iea, re is poised to contribute to nearly half of the growth in power production in ssa by the year 2040. the estimate of the technical potential per technology of ssa is presented in table 3. the report of iea highlights that while ssa's economy has been expanding steadily since 2000, this growth is hindered by the fact that a huge population in the region lacks access to electricity (iea, 2021b). the study predicts that ssa will gradually unlock its vast re resources over the next 26 years, with solar energy taking the lead in the re sector. interestingly, only 10% of the region's hydropower capacity is currently being utilized, according to the survey. moreover, most of africa boasts excellent solar energy potential, while coastal regions have significant wind energy potential. in countries like kenya and ethiopia, geothermal energy is emerging as the second-largest source of power (waitzman, 2023, benti et al., 2023, chhun et al., 2023). by 2040, solar photovoltaics (pvs), small-scale hydropower, and wind energy will account for two-thirds of mini-grid and off-grid systems in rural areas (irena, 2015). as re technologies costs continue to decrease relatively, re systems become more attractive alternatives to diesel generators. however, in many cases, they are used in conjunction with diesel generators, particularly when there is adequate financing available to cover the higher initial costs. table 3: ssa technical potential per technology (ramalope et al., 2022) re sour ce capacit y twh/y re source capaci ty twh/ y re sourc e capaci ty twh/ y re sour ce capaci ty twh/ y re source capaci ty twh/ y solar pv 1,449,7 42 hydropo wer 1,478 bioma ss 2,374 win d 978,06 6 geother mal 105 a study conducted at the university of california, berkeley, shows that there are considerable opportunities for the deployment of re in africa. the mapping out of the re source locations in northern, central, eastern, and southern africa shows a vast potential but is not uniformly file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 271 distributed across the regions (wu et al., 2017). hydropower, solar pv, and wind energy technologies denominate re sources and offer decentralised and off-grid solutions, facilitating access to remote and underserved communities. according to irena’s report on re market (irena and afdb, 2022), the deployment of re has grown, with the addition of more than 26 gw of renewables-based generation capacity over the past decade; solar energy has seen the largest expansion, and average annual investments in re have surged from less than 0.5 billion usd in the 2000-2009 period to usd 5 billion in 2010-2020; and central and southern africa possess abundant mineral resources crucial for the production of electric batteries, wind turbines, and other low-carbon technologies. a study by irena predicts that about two-thirds of rural mini-grid and off-grid systems will rely on solar pv, small hydropower, and wind (irena, 2016). 2.1.1. solar pv technology solar pv has the potential to supply electricity to more than 600 million people in africa. moreover, since 2012, the cost of utility-scale solar energy projects in africa has decreased by 61%, bringing it down to less than usd 1.30 per watt. presently, over 5 million african households rely on off-grid systems, including pay-as-you-go solutions (diemuodeke et al., 2021, iea, 2022). consequently, the projected value of the off-grid solar market in africa represents a significant yearly opportunity of $24 billion (hearon, 2022). according to irena's findings, pv is already the most cost-effective power source in many african regions. by 2030, it is anticipated that solar pv will outcompete all other power sources across the continent. when you consider the average practical yield of a utility-scale solar energy installation over the long term in each country, africa leads with 4.51 kwh/kwp/day, surpassing central & south america at 4.48 kwh/kwp/day, while north america lags at 4.37 kwh/kwp/day (irena and afdb, 2022). to put these numbers in perspective, approximately 20% of the global population resides in 70 countries characterised by "excellent conditions" for solar power, meaning they consistently generate over 4.5 kwh/kwp per day in the long run. on a regional scale, only african countries collectively exceed this threshold. much of this untapped potential exists in the less developed nations of africa, offering a unique opportunity to deliver affordable, reliable, and sustainable electricity services to a significant portion of humanity where there is a pressing need for improved economic prospects and quality of life, as the source highlights. solar pv technology is currently and will continue to be a crucial energy source for ssa due to its significant potential and the increasing traction it is gaining. the underlying reasons are outlined in table 4. table 4: merits of solar pv technology deployment in ssa abundant solar resource sub-saharan africa is blessed with abundant sunlight throughout the year, making solar pv an ideal energy source. countries in the region receive high levels of solar irradiance, ensuring consistent energy production from solar panels. energy access many areas in ssa lack access to reliable electricity. solar pv systems, especially off-grid and decentralised solutions, can provide electricity to remote and underserved communities, helping to bridge the energy access gap. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 272 rural electrification solar pv plays a crucial role in rural electrification efforts. mini-grids and solar home systems enable rural areas to access electricity without the need for extensive grid infrastructure, which can be expensive and challenging to implement. reducing energy poverty solar pv helps alleviate energy poverty by providing households and businesses with clean and affordable electricity. this has a positive impact on people's quality of life, education, healthcare, and economic opportunities. energy independence solar pv reduces dependence on imported fossil fuels, enhancing energy security. this is particularly important in ssa, where many countries rely on expensive fuel imports, leading to energy supply disruptions and price volatility. sustainable development solar pv aligns with sustainable development goals by reducing greenhouse gas emissions, improving air quality, and mitigating climate change. it also creates jobs in the local solar industry. cost reduction the cost of solar pv technology has significantly decreased over the years, making it more affordable and accessible. this cost reduction is due to advancements in technology, increased manufacturing capacity, and economies of scale. investment opportunities solar pv projects in ssa attract investments from both domestic and international sources. this contributes to economic growth and infrastructure development. technology transfer and innovation the adoption of solar pv technology fosters technology transfer, knowledge sharing, and innovation, promoting local expertise and capacity building. government support many governments in the region are implementing policies, incentives, and regulations to promote re, including solar pv. these measures encourage private sector involvement and project development. despite these advantages, challenges such as financing, grid integration, and capacity building need to be addressed to maximise the potential of solar pv in ssa fully. nevertheless, the region's solar resources and the growing commitment to solar pv is an integral part of the energy landscape, driving sustainable development and improving the lives of millions. 2.1.2. wind energy technology wind energy plays a pivotal role in advancing the sustainable development agenda in ssa. despite the substantial challenges posed by covid-19, the region is poised to achieve economic growth ranging from 2.3 to 3.4% this year. to support and sustain this growth, the provision of clean, cost-effective, and dependable electricity generation is paramount. in this context, wind energy, in conjunction with solar power, is anticipated to play a significant role in fulfilling the region's energy requirements. although wind turbines are still a relatively uncommon sight across africa, the continent faces substantial energy demands alongside considerable wind energy potential. recent studies have unveiled a staggering technical wind potential of nearly 180,000 twh annually, a capacity that could meet the electricity needs of the entire continent 250 times over (munyengeterwa and whittaker, 2021). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 273 it is worth noting that the practical or commercially viable wind potential would be lower due to various constraints. nonetheless, approximately two-thirds of africa's total wind potential is situated in areas characterized by average wind speeds exceeding 7.5 meters per second (m/s). some the countries with high wind energy potential are mozambique, south africa, somalia, madagascar, morocco lesotho, malawi, zambia, eritrea, djibouti, ethiopia, kenya, tanzania, niger, chad, and sudan (alemzero et al., 2021, elsner, 2019, mentis et al., 2015). the development of wind energy in ssa holds the potential to make a substantial contribution to the region's sustainable growth trajectory while simultaneously addressing its escalating energy requirements. it presents an opportunity for clean and renewable electricity generation, reducing the region's dependence on fossil fuels and championing environmental sustainability. wind energy in ssa is emerging as a promising and increasingly important component of the region's energy landscape because of the merits presented in table 5. table 5: merits of wind energy technology deployment in ssa abundant wind resources sub-saharan africa boasts substantial wind resources, particularly in coastal areas and high-altitude regions. these regions experience consistent wind patterns, making them suitable for wind energy generation energy diversification wind energy contributes to diversifying the energy mix in ssa, reducing dependence on fossil fuels. this diversification enhances energy security and mitigates the risks associated with fuel price fluctuations and supply disruptions re expansion many countries in ssa are actively promoting re, including wind power, as part of their energy transition strategies. this supports global efforts to combat climate change and reduce greenhouse gas emissions rural electrification wind energy projects, such as wind farms and small-scale wind turbines, play a crucial role in rural electrification. they provide clean and reliable electricity to remote and off-grid communities, improving their quality of life and economic prospects. large-scale projects several countries in the region are investing in large-scale wind energy projects, including onshore and offshore wind farms. these projects have the potential to generate significant amounts of electricity for both domestic consumption and export job creation the development and operation of wind energy projects create jobs in construction, maintenance, and the supply chain, contributing to local economic development. investment opportunities sub-saharan africa has become an attractive destination for wind energy investments. international and domestic investors are showing interest in financing wind projects, bringing capital and expertise to the region grid integration integrating wind energy into the existing grid infrastructure can be challenging due to variability in wind resources. however, advancements in grid management and energy storage technologies are addressing these challenges http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 274 environmental benefits wind energy produces electricity without emitting greenhouse gases or air pollutants, contributing to improved air quality and reduced environmental impact. capacity building developing wind energy projects necessitates capacity building and knowledge transfer. governments and organizations are working to train local professionals and promote technology transfer. policy support governments are implementing policies, regulations, and incentives to encourage wind energy development. feed-in tariffs, power purchase agreements, and tax incentives are commonly used to attract investment despite the significant potential of wind energy in saa, there are challenges, including financing constraints, grid integration issues, and the need for regulatory reforms. however, as technology advances and more countries commit to re, wind power is poised to play a substantial role in meeting the region's growing energy demand and supporting sustainable development (boadu and otoo, 2024, gorayeb et al., 2024, roga et al., 2022). 2.1.3. small-scale hydropower small-scale hydropower plays a pivotal role in fostering sustainable development within ssa. it holds the promise of making a substantial contribution to addressing the pressing issue of rural electricity shortages in the region. small hydropower, regarded as a promising decentralized electricity generation system for rural areas in ssa, offers numerous advantages, including adaptability, minimal initial investment requirements, and its status as a re source (kaunda et al., 2012). the significance of re sources, such as small hydropower, in the context of sustainable power generation, has been extensively discussed, particularly regarding their potential to help meet the escalating energy demands within the region (zelelew et al., 2022, bamisile et al., 2023). small-scale hydropower can generate sustainable and cost-effective electricity in the rural areas of ssa. it holds the potential to enhance living conditions, boost productivity, stimulate economic growth, and significantly improve the overall quality of life for millions of people in the region. the implementation of decentralised small-scale hydropower systems can offer an efficient solution for dependable and affordable rural electrification (dagnachew et al., 2017, ajewole et al., 2020). small hydropower projects in the region are gaining attention as a sustainable and reliable source of electricity. some of the key points about small hydropower in the region are presented in table 6. table 6: merits of small hydropower technology deployment in ssa abundant water resources sub-saharan africa is endowed with numerous rivers and water bodies, providing ample potential for small hydropower development. these projects harness the energy from flowing water to generate electricity. rural electrification small hydropower projects are particularly well-suited for rural electrification in areas that are not connected to the main power grid. they bring clean and consistent electricity to remote communities, improving living standards and economic opportunities. off-grid solutions many small hydropower projects operate off-grid, reducing the need for extensive transmission and distribution infrastructure, which can be expensive and challenging to implement in remote areas. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 275 environmental impact compared to large-scale hydropower projects, small hydropower projects have a lower environmental footprint. they typically have less impact on local ecosystems and fish habitats. re growth as part of the global shift towards re, small hydropower is contributing to diversifying the energy mix in ssa, reducing reliance on fossil fuels and mitigating climate change. local economic development the construction and operation of small hydropower projects create job opportunities in nearby communities, fostering local economic development. 2.1.4. geothermal energy technology deployment in ssa geothermal energy represents a sustainable and environmentally friendly source of both heat and power, offering a valuable avenue for reducing carbon emissions in the electricity grid and the building sector. in the context of ssa, the region possesses substantial geothermal potential, particularly in the east african rift system. the region holds over 15,000 mw, an estimated geothermal resource and the technology presents a spectrum opportunity (iea, 2011). geothermal energy has the potential to supply dependable and cost-effective electricity and heating solutions for both rural and urban communities, while also serving industrial and agricultural needs (mulopo, 2022, energy.gov, 2020). furthermore, geothermal energy can play a pivotal role in fostering social and economic development, generating employment opportunities, and reducing greenhouse gas emissions (energy.gov, 2023). geothermal energy in sub-saharan africa is a promising and relatively untapped re source. the united states department of energy (doe) is actively supporting the deployment of geothermal energy in ssa through a range of initiatives. these initiatives encompass funding for community-based geothermal heating and cooling systems, as well as the provision of technical assistance and training (cariaga, 2023). some key information about geothermal energy in the region is presented in table 7. table 7: important information about geothermal energy technology in ssa benefits geothermal potential sub-saharan africa has significant geothermal potential, particularly along the east african rift system, which runs through countries like kenya, ethiopia, and tanzania. this region is characterized by geological activity, including volcanic activity and geothermal hotspots clean and sustainable geothermal energy is a clean and sustainable source of electricity. it produces minimal greenhouse gas emissions and has a low environmental impact compared to fossil fuels. base load power geothermal power plants can provide reliable baseload power, meaning they can operate continuously, providing a stable source of electricity. this makes them suitable for meeting the region's growing energy demand. reduced dependence on fossil fuels developing geothermal resources can reduce ssa's dependence on imported fossil fuels, enhancing energy security and reducing exposure to fuel price volatility http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 276 rural electrification geothermal projects can be used for rural electrification in remote areas that are not connected to the main grid. this helps improve access to electricity and supports economic development in these regions. energy access geothermal energy can help improve energy access and reduce energy poverty in sub-saharan africa by providing affordable and reliable electricity to underserved communities. steps to fast-track geothermal energy technology development in ssa investment and funding geothermal projects often require substantial upfront investments. international organizations, development banks, and public-private partnerships can play a significant role in financing these projects. technical challenges developing geothermal projects can be technically challenging due to the need for drilling deep wells and managing subsurface reservoirs. however, advancements in drilling technology are making these challenges more manageable. regulatory framework establishing clear regulatory frameworks and policies that support geothermal development is crucial. governments need to provide incentives, such as feed-in tariffs and permits, to attract investment. local capacity building developing and maintaining geothermal projects requires skilled professionals. efforts to build local capacity and train a workforce in geothermal technology are essential. environmental and social considerations like all energy projects, geothermal developments must consider environmental and social impacts. proper assessments and mitigation strategies are necessary to minimize these effects. regional collaboration geothermal resources often cross national borders, so regional collaboration and agreements can be essential to maximize the utilization of shared geothermal reservoirs. the development of geothermal energy in ssa faces various hurdles encompassing technical, financial, institutional, and environmental aspects. these obstacles include a lack of essential data, expertise, infrastructure, financial resources, regulatory frameworks, and public awareness (energy.gov, 2023). overcoming these challenges will require supportive policies, the enhancement of regional cooperation, increased capacity building, the mobilization of investments, and active engagement with stakeholders. 2.2. green mineral deposits in africa’s renewable energy development the transition to cleaner energy to stimulate economic growth entails the adoption of emission-reducing technologies, such as wind and solar energy, while minimizing reliance on fossil fuel-based technologies. while discussions on clean energy and the decarbonization of global investments and financial systems have been prevalent in development dialogues, there is comparatively less focus on the essential minerals, including rare earth minerals, metals, and construction materials, that are crucial for enabling this transition. according to data from the united states geological survey (usgs) regarding global mineral reserves (ahadjie et al., 2023), africa hosts a substantial share of various minerals, such as cobalt (52.4%), which is crucial for various applications. additionally, africa possesses substantial reserves of bauxite, essential for file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 277 aluminium production (24.7%), graphite (21.2%), manganese (46%), and vanadium (16%). this representation, however, only scratches the surface because ongoing exploration efforts in africa are uncovering vast strategic mineral deposits. to highlight the significance of this, consider the example of cobalt. these minerals are indispensable for the energy transition, as they serve as critical raw materials for the manufacturing of batteries and electric vehicles (evs). africa possesses substantial reserves of green minerals vital for the energy transition; however, it presently operates primarily in the early stages of the battery and electric vehicle supply chain. mineral deposits are expected to play a crucial role in re development in ssa in the following ways presented in table 8. table 8: the crucial roles mineral deposits play in re development ssa rare earth elements for clean technologies rare earth elements (rees), which include metals like neodymium, dysprosium, and terbium, are essential to produce permanent magnets used in wind turbines and electric vehicle motors. sub-saharan africa is rich in some of these elements, and their extraction is vital for the development and maintenance of re infrastructure cobalt for batteries as previously mentioned, cobalt is a key component of lithium-ion batteries used in electric vehicles and energy storage systems. the drc plays a significant role in cobalt production, making it a crucial player in the supply chain for re technologies minerals for solar panels the production of solar panels relies on minerals like silicon, which is abundant in ssa. silicon-based pv cells are the most common type of solar panels used globally, and having access to these raw materials is vital for expanding solar energy capacity. copper for electrical infrastructure copper is a fundamental element in electrical wiring and infrastructure. it is essential for transmitting electricity from re sources to homes and industries. several ssan countries, such as zambia and the democratic republic of congo, are major copper producers. geothermal resources in regions with geothermal energy potential, such as the east african rift valley, minerals like silica are necessary for drilling and maintaining geothermal wells, which provide a stable source of clean energy. minerals for energy storage beyond cobalt, other minerals like lithium, nickel, and manganese are essential for energy storage solutions, including advanced battery technologies that can store re for later use or grid stabilization. construction materials the development of re infrastructure requires massive amounts of concrete, steel, and other construction materials, which are often derived from mineral resources like limestone and iron ore, both of which are found in ssa. job creation and economic growth the extraction and processing of these minerals for re projects can stimulate economic growth and job creation in the region, offering opportunities for local communities and governments to benefit from the re sector. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 278 energy access and grid stability access to minerals enables the development of a more reliable and resilient energy grid, helping to provide stable access to electricity for households and industries, thereby improving the overall quality of life. the democratic republic of congo (drc) stands out as a prominent player in the energy transition industry, poised to reap significant economic rewards. this is because drc accounts for a staggering 70% of global cobalt production and holds more than 51% of the world's cobalt reserves (afdb, 2022). many african nations, notably zimbabwe, namibia, ghana, the drc, and mali, possess valuable lithium resources and the potential for lithium mining (goodenough et al., 2021, un-eca, 2023). nevertheless, there is limited involvement in the crucial stages further down the supply chain. at present, africa lacks substantial capacity for processing lithium minerals, refining lithium chemicals, or manufacturing battery components. africa should avoid a common scenario where mineral concentrates are exported, value is added outside of africa, and products utilising lithium-ion batteries are subsequently imported. the evident potential of africa's lithium resources to make a substantial economic contribution should be viewed in the broader supply chain context. specifically, the possibility of regional cooperation in the refining and production of lithium chemicals should be given serious consideration. however, it is important to note that while these mineral resources are essential for re development, their extraction and processing can also present environmental and social challenges. sustainable and responsible mining practices, along with proper environmental regulations and community engagement, are critical to ensure that the benefits of mineral resources are maximized while minimizing negative impacts. 3. the significance of renewable energy in ssa renewable energy is playing an increasingly vital role in ssa for several compelling reasons, primarily centred around electricity generation, especially from pv and wind power sources. these renewable sources are easily accessible, well-understood, and known for their swift and cost-effective deployment. additionally, there are other crucial facets of the importance of re in ssa, including(iea, 2023b): 3.1. enhancing energy accessibility the inadequacy of power supply has been a significant impediment to socioeconomic progress in ssa, particularly in the face of growing industrialization, population expansion, and urbanization. the energy challenges are most severe in rural and remote areas of the global south. the global south must capitalize on the adaptable advantages of re schemes in these areas to provide reliable, sufficient, clean, and affordable energy to underserved populations. 3.2. decarbonisation and emission reduction while fossil fuels, such as oil, natural gas, and coal have driven the economies of large and emerging nations, they have also brought about detrimental environmental and health consequences, including co2 emissions and the depletion of natural fossil resources (ebhota and tabakov, 2018a, ebhota and tabakov, 2019). the global call for a sustainable energy system that is secure, adequate, affordable, and environmentally friendly has become increasingly urgent (harvey, 2014, heffron et al., 2015). expanding the use of renewable fuels can help mitigate or eliminate the adverse effects associated with fossil fuel consumption, given that economic growth relies on energy (un, 2015). furthermore, re usage will prevent health file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 279 consequences suffered by students caused by the use of kerosene lamps during the study; and women who use biomass for cooking, and their young children staying around them (amegah and jaakkola, 2016). these people are exposed to high levels of air pollutants, such as particulate matter (pm) and carbon monoxide (co) emitted into the air (amegah and jaakkola, 2016, ebhota and tabakov, 2019). 3.3. rapid construction to address the pressing challenges related to fossil fuels, energy shortages, and climate change, ssa should leverage the rapid construction times of re projects. wind farms can be completed in 9 to 12 months, while solar parks can be operational within 3 to 6 months, a stark contrast to the years-long timeline required for fossil fuel plants. 3.4. climate change mitigation human activities, such as fossil fuel extraction, consumption, cement production, and deforestation, continually influence the climate by releasing ghgs, such as co2, methane (ch4), nitrous oxide (n2o), and fluorinated gases. these gases account for global warming at different levels with co2 contributing the highest, between 75% 80%, followed by ch4 (14%), n2o (8%), and fluorinated gases (1%) (ipcc, 2013). the energy sector, including fossil and biomass sources commonly used in ssa, accounts for a substantial share of co2 emissions. shifting to re helps to reduce ghg emissions, thereby mitigating the health, environmental, and climate impacts associated with these emissions. governments of ssa countries should establish enabling policy frameworks to support adaptation efforts and harness local institutions and actors. 3.5. the declining cost of renewables the lower cost of electricity production from solar pv and wind power, compared to fossil alternatives, serves as a pivotal motivation for embracing re. this cost advantage is expected to widen further in the future due to the ongoing decline in re costs. as a result, re is poised to become a preferred choice over gas and coal power. additionally, the increasing affordability of energy storage solutions, driven by falling battery prices, is anticipated to make a significant contribution to global power and heat consumption by 2050 (res4africa, 2023). projections also suggest that global electricity production will transition to 100% renewable sources by 2050, with solar-based energy systems making up a substantial portion, particularly in africa, where they are projected to account for over 80% of electricity consumption (roodbol, 2019). 4. sub-saharan africa's key renewable energy development limitations it is imperative to analyse the constraints in energy generation and provision within ssa, considering the region's rapid population increase, economic progress, and escalating energy requirements. africa's energy sector plays a pivotal role in the continent's economic potential, yet it has struggled to attain a dependable domestic energy supply essential for meeting the needs of its populace and enterprises. sub-saharan africa faces several challenges in energy generation and supply, which have significant implications for economic growth, social development, and environmental sustainability. some of the key energy limitations and issues of energy access in ssa are presented in table 9. table 9: key re development limitations and challenges. limitations description http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 280 high initial costs the upfront capital costs of re projects, such as solar pv installations or wind farms, can be substantial. this can deter investors and governments from pursuing re initiatives, especially in resourceconstrained environments. limited access to financing a lack of access to affordable financing for re projects is a major challenge. many countries in ssa struggle to secure the necessary funds, both domestically and through international sources. grid integration integrating re sources into existing electricity grids can be complex and costly. the intermittent nature of some renewables, like solar and wind, requires grid upgrades and energy storage solutions to maintain reliability. infrastructure and transmission challenges inadequate grid infrastructure and transmission lines in remote or rural areas can hinder the distribution of re. expanding and upgrading the grid to reach these regions is often expensive and logistically challenging. policy and regulatory frameworks inconsistent or outdated policies and regulations can create uncertainty for re investors. clear and supportive policies that promote re development are crucial. resource variability the availability of re resources, such as sunlight and wind, can vary significantly across the region and throughout the year. this variability affects the reliability of re generation. land use conflicts competition for land can arise when re projects require large areas for solar panels, wind turbines, or bioenergy feedstock cultivation. this can lead to conflicts with agriculture and conservation interests. lack of local manufacturing relying on imported re equipment and components can increase project costs. developing local manufacturing capabilities can reduce costs and create jobs. access to technical support and expertise many countries lack the technical expertise and research institutions needed to support the development and deployment of re technologies. political instability and corruption: political instability and corruption in some countries can pose risks to re investments, discouraging foreign and domestic investors. lack of investment and financing insufficient investment in the energy sector hinders the development of new generation capacities and the expansion of energy access. limited access to financing and high perceived risks deter private sector involvement (appiah et al., 2023). transmission and distribution losses poorly maintained transmission and distribution networks lead to high energy losses during electricity transmission. these losses further strain the capacity of already limited power generation. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 281 climate vulnerability climate change impacts, such as droughts and water scarcity, can significantly affect hydropower generation, which is a common energy source in the region. regulatory challenges regulatory uncertainties can hinder long-term planning and investment in the energy sector. rural electrification extending energy access to rural and remote areas remains a challenge due to the high costs of infrastructure installation and maintenance. population growth and urbanisation rapid population growth and urbanisation in some parts of ssa are leading to increased energy demand, putting additional strain on energy resources. efficiency of electrical appliances for instance, despite these gains, the demand for fans and air conditioning is projected to quadruple over the next decade due to urbanization and the effects of climate change, underscoring the need for a strong emphasis on efficient cooling solutions in africa (iea, 2022). political instability and corruption political instability and corruption in some countries pose risks to re investments, discouraging foreign and domestic investors. environmental and social considerations re projects must consider potential environmental impacts, such as habitat disruption and water use. additionally, community engagement and benefit-sharing mechanisms are important to address social concerns. intermittency and energy storage dealing with the intermittency of some re sources, such as solar and wind, requires investment in energy storage solutions like batteries, which can be expensive. skills and capacity gaps a lack of skilled personnel and technical expertise impedes the development, maintenance, and operation of re infrastructure despite these challenges, there is growing recognition of the importance of re in ssa for addressing energy access, reducing greenhouse gas emissions, and promoting sustainable development. efforts are being made at the national and international levels to overcome these challenges through policy reforms, increased investment, capacity building, and technological innovation. 4.1. strategies and approaches to address renewable energy development limitations despite the investments and the achievements recorded so far, relatively, the global south, especially ssa, is grossly behind other regions: the re investment and re per capita of countries in africa and that of the continent are far below other countries in other regions. the socioeconomic status of the people in ssa is yet to be substantially impacted by the efforts and investments in the re sector. to reverse these trends, governments and international organizations should prioritise information-based electrification planning, mobilize capital, and deploy implementation programs, focusing particularly on countries and areas with very low access rates and those that have made only limited progress in recent years. it involves a http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 282 coordinated effort by the governments, private sector entities, development partners, and local communities. by overcoming these challenges, the region will unlock its energy potential and contribute to sustainable development and improved living standards. the strategies and approaches to address the identified re development limitations and challenges are presented in table 10. table 10: strategies to address re development limitations strategies description policy and regulatory reforms develop and implement clear and supportive policies, regulations, and incentives to encourage re investments. streamline permitting processes to reduce project development timelines and uncertainty. access to financing establish dedicated funds and financial mechanisms for re projects, including grants, low-interest loans, and risk mitigation instruments. attract private sector investment through innovative financing models, such as public-private partnerships (ppps). capacity building invest in education and training programs to develop a skilled workforce in re technologies and project management. foster partnerships with universities, research institutions, and international organizations to provide technical support and knowledge transfer. grid integration and infrastructure development upgrade and expand the electricity grid to accommodate re sources and improve grid reliability. invest in energy storage solutions, such as batteries and pumped hydro, to manage the intermittent nature of renewables. local manufacturing and supply chains promote local manufacturing of re equipment and components to reduce costs and create jobs. support the development of regional supply chains for renewable technologies. community engagement and benefit sharing involve local communities in the planning and decision-making processes for re projects. implement benefit-sharing mechanisms that ensure local communities reap the economic and social benefits of projects environmental and social impact assessment conduct thorough environmental and social impact assessments (esias) before initiating re projects to address potential environmental and social concerns. implement mitigation measures and monitoring to minimize negative impacts. resource assessment and planning conduct detailed resource assessments to identify the most suitable locations for re projects. develop integrated energy plans that incorporate renewables into the national energy mix. political stability and risk mitigation work on improving political stability and governance to reduce investment risks. consider the use of political risk insurance and other risk mitigation tools to protect investors. international collaboration: collaborate with international organizations, donors, and development partners to access technical expertise, funding, and knowledge sharing. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 283 participate in regional energy initiatives to promote cross-border cooperation and energy trade. public awareness and advocacy raise public awareness about the benefits of re and the need for sustainable energy solutions. encourage advocacy and engagement by civil society and non-governmental organizations (ngos) to support re policies and projects. innovation and research invest in research and development to promote innovation in re technologies, energy efficiency, and grid management. support pilot projects and demonstration programs to test new technologies and approaches. market development and scaling up foster the development of re markets through market incentives, feedin tariffs, and power purchase agreements (ppas). encourage the participation of independent power producers (ipps) and smaller-scale re projects. addressing the challenges of re development in sub-saharan africa requires a long-term commitment and collaboration among various stakeholders. tailoring strategies to the specific needs and circumstances of each country or region is essential for success 4.1.1. national power grid expansion according to iea, the expansion of national power grids is the most economical and sensible choice for nearly 45% of those expected to gain access to electricity by 2030 (iea, 2022). however, in rural areas, where more than 80% of the population lacks electricity, mini-grids and independent systems, primarily solar-powered, emerge as the most feasible solutions. in this scenario, enhanced and upgraded electrical grids could form the fundamental infrastructure for africa's evolving energy systems, with a growing emphasis on re sources. africa boasts 60% of the world's most abundant solar resources, yet it currently utilizes only 1% of its solar pv capacity (irena, 2016). solar power, already the most cost-effective energy source in many african regions, is poised to surpass all other sources across the continent by 2030 (iea, 2022). in the sustainable africa scenario, renewables, including solar, wind, hydroelectric, and geothermal energy, contribute to over 80% of the new power generation capacity added by 2030. 4.1.2. investment needs power shortages in ssa cost about 2% to 4% of annual gdp, and the way it is today, electricity will only improve to an appreciable level in the future. the electricity demand is expected to supply 2 billion people in ssa in 2050 and this requires a 3% yearly growth in the sector (schwerhoff and sy, 2020). meeting this demand with the conventional energy mix of burning oil, coal, charcoal, wood, and dry dung fuel in the region would cause severe health and environmental consequences. in compliance with the 2015 paris agreement on the emission limits for ghg, therefore, there should be alternative sources of adequate energy. fortunately, ssa is endowed with re resources, huge enough to supply the needed energy to drive socioeconomic development. studies have shown that a 100% re system is possible for ssa (barasa et al., 2018). hence, the region does not need to rely on fossil fuels, and further investments in this conventional electricity should be avoided. what is needed is sufficient investments in the different re technologies that have been identified across the region. the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 284 present investment in re by the region is relatively small considering the information in figure 7 (iea, 2023a), showing the annual clean energy investments in selected regions and countries between 2019 and 2023. investing in re energy will generate new job opportunities in the power sector and ensure sustainable development ecologically (imf, 2019). figure 7: annual clean energy investment in selected countries and regions, 2019-2023 (iea, 2023a) 4.1.3. african development bank (afdb) intervention: the sustainable energy fund for africa (sefa) the african development bank (afdb) recognises that modern energy services play a central role in sustaining inclusive growth, driving job creation, and enhancing productivity across various sectors such as manufacturing and agriculture. however, africa has faced persistent challenges related to limited power access, frequent shortages, and high costs, hindering its socioeconomic progress (ebhota and tabakov, 2018b). to address these issues, afdb has implemented a range of initiatives aimed at improving energy accessibility and availability in africa. these initiatives encompass various areas (afdb, 2008), including rural electrification, efforts to combat deforestation, the development of decentralised energy solutions, and the promotion of sustainable biofuels. additionally, afdb has focused on enhancing energy efficiency in the transportation sector, transitioning to renewable and low-carbon energy sources, adopting clean technologies, and improving overall efficiency in the energy sector. renewable energy has emerged as a critical solution for providing sustainable, affordable, and resilient energy access in ssa. consequently, africa has embraced re as part of its long-term vision, including the vision to energise and light up african projects and the african union's agenda 2063 (au, 2013, worldbank, 2020b). this commitment has led to a significant acceleration in the deployment of re technologies. adequate energy availability, affordability, reliability, and sustainability have been portrayed by the afdb as fundamental factors driving the socio-economic transformation of africa (afdb, 2020). as part of its re development programme, afdb aims to support the continent in achieving universal electricity access by 2025 and is expected to yield specific outcomes. taking the new deal on energy for africa and aref ii as examples, the total investment cost for the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 285 new deal on energy for africa falls within the range of us $60 billion to us $90 billion annually. the anticipated results of this initiative include the expansion of grid power generation by 160 gw, connecting 130 million people to the electrical grid, connecting 75 million people to offgrid energy systems, and providing 150 million households with access to clean cooking energy (afdb, 2019). 4.1.4. political commitment and unpredictability the insufficient political commitment demonstrated by governments in addressing the powerrelated issues in ssa, combined with the ongoing violence and crises in the region, have adverse effects on the development of re. the myriad issues in the region, including but not limited to banditry, terrorism, communal conflicts, militancy, coup d'état, and youth unrest, tend to undermine development efforts across the board (agwu et al., 2023). political antagonism and instability act as counterproductive elements in the delivery of infrastructure projects, disrupting smooth transitions and advancements (de bercegol and monstadt, 2018). regional leadership must collaborate closely with national governments to establish and maintain the peace and political stability necessary for nurturing and sustaining development. 4.1.5. reviewing policies and institutional frameworks a critical need exists to reassess the existing re policies and frameworks in countries across the region, aligning them with contemporary political and economic dynamics to ensure that intended outcomes are achieved. the adoption of research-based policies can serve to harmonize the diverse perspectives of stakeholders, fostering robust and effective partnerships within the re sector. furthermore, addressing ambiguity within the management and regulatory processes is essential, with a focus on promoting transparency and professionalism within the sector. 4.1.6. conducting feasibility studies and resource characterization renewable energy potential and the performance of re systems inherently depend on specific locations or regions. to maintain the integrity of system performance and ensure optimal utilisation of re resources, it is imperative to conduct assessments and characterise the potential of these resources. the region should take advantage of available econo-technical tools to evaluate the feasibility of these resources and integrate the findings into re policies and frameworks. 4.1.7. developing technical expertise this study has identified a noteworthy gap in the promotion, development, and deployment of re technologies in ssa, namely the absence of essential technical skills and the necessary manufacturing infrastructure. notably, the usa and china have made significant strides in terms of installed re capacities, largely attributed to their robust technical capabilities in personnel and manufacturing infrastructure. currently, the region lacks both the technical workforce and the infrastructure required for the design, fabrication, operation, and maintenance of re devices and systems within its borders (ebhota and inambao, 2016, ebhota and inambao, 2017). consequently, both national and regional efforts must be deliberately directed towards building the requisite capacity within the re sector. 5. conclusion insufficient energy access poses a hindrance to the socio-economic advancement of the global south, particularly ssa. the research assessed ssa's energy situation, its challenges, and the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):261-294. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: ebhotawilliams1@gmail.com 286 potential of re, along with discussing methods to enhance energy provision in the region. subsaharan africa stands as the world's least electrified area, with only 48% having access to electricity and a mere 17% enjoying clean cooking facilities. notably, nigeria (86 million), the democratic republic of the congo (76 million), and ethiopia (55 million) account for the largest populations lacking access. several factors contribute to the electricity deficit, including inadequate infrastructure, prohibitive costs, and environmental repercussions. the region’s electricity demand is influenced by a multitude of factors that mould the energy landscape of the region. the consequences of this energy deficit in ssa manifest as rising co2 emissions, deforestation, ecosystem disruption, health issues, climate change, loss of biodiversity, slowed economic growth, and deepening poverty levels. renewable energy is expected to assume a pivotal role in resolving energy access challenges, decarbonising energy systems, offering rapid deployment solutions, and mitigating climate change. it is becoming increasingly cost-competitive, thus paving the way for a sustainable energy future in the region. africa boasts abundant re resources, estimated to be approximately 1,000 times greater than the expected electricity demand by 2040. this surplus of re potential, equivalent to 11,000 gigawatts (gw) of exploitable generating capacity, positions the continent favourably to meet its current and future energy needs. key re sources such as hydropower, solar pv, and wind energy dominate the landscape and offer decentralized and off-grid solutions, facilitating access to remote and underserved communities. the potential of solar, hydro, wind, and geothermal resources in africa is estimated at 10 tw, 350 gw, 110 gw, and 15 gw, respectively. however, several obstacles and challenges impede the development and widespread adoption of re in the region. these obstacles encompass high initial costs, restricted access to financing, issues related to grid integration, infrastructure and transmission deficiencies, policy and regulatory frameworks, and the variability of re resources. additional challenges include conflicts over land use, the absence of local manufacturing capabilities, limited access to technical support and expertise, and a shortage of investment and financing. to surmount these hurdles, it is imperative to foster collaboration among governments, academic institutions, industry stakeholders, and international organizations. the study underscores the importance of addressing energy supply limitations through strategies, such as policy and regulatory reforms, enhanced access to financing, capacity building, and the development of grid infrastructure. furthermore, strategies like bolstering local manufacturing and supply chains, engaging communities and sharing benefits, and conducting thorough environmental and social impact assessments are vital. the study portrays the energy deficit and re potential in ssa as opportunities to transform the region into a hub for clean energy. acknowledgement the authors hereby acknowledge the research and postgraduate support directorate and the institute of systems science, durban university of technology, south africa. references aec 2021. the state of african energy 2022. the african energy chamber (aec), sandton, johannesburg, south africa. aep. 2022. database: electricity. africa energy portal (aep) [online]. available: https://africaenergy-portal.org/database [accessed 29/09/2023]. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com https://africa-energy-portal.org/database https://africa-energy-portal.org/database ebhota and tabakov: a retrospect of energy demand and potential of sub-saharan africa: leveraging energy deficit to attain clean energy hub region. azojete, 20(1):261-294. issn 1596-2490; 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(ed.) comprehensive renewable energy (second edition). oxford: elsevier. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):211-218 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 211 original research article effect of drying conditions on the drying kinetics and colour changes of plantain (musa x paradisiaca) slices using combined heated air and infrared dryers w. a. olosunde1*, m. m. akpanesen1, u. e. assian1 and o. o. olosunde2 1department of agricultural and food engineering, faculty of engineering, university of uyo, uyo. 2department of food science and technology, osun state polytechnic, iree, nigeria. *corresponding author’s email address: williamolosunde@uniuyo.edu.ng 1.0 introduction drying is a mass transfer process in which heat is applied to remove water or another liquid by evaporation from a liquid, semi-solid or solid phase (farlex, 2011). the final dried product may be solid, in the form of particles (corn flakes or cereal grains) or powder (farlex, 2011). in bioproducts like grains, processed food, and pharmaceuticals such as vaccines, the solvent which is usually removed is water. the heat source in most cases could be heated air, infrared (ir). heated air used convective drying method comprises of hot air where its temperature is increased, thereby inducing quick heat transfer for fast drying process. it also decreases air article information abstract most agricultural crops with high moisture content are difficult to preserve. the most common method of preservation is drying. thus, drying operation where a combination of two or more modes is used, could speed-up drying process. however, the scalability of combined heated air and infrared drying (chaid) for rural consumers have not been investigated. this study was conducted to examine the effect of drying conditions (temperature and infrared intensity) on the drying kinetics and total colour changes (∆e) of plantain slices using a chaid dryer. matured unripe plantain samples were sourced from a market, peeled, washed in running water and then sliced into 4 × 20 × 20 mm dimension. initial moisture content (mci) determined using oven drying method. 2.0 g of the sliced sample were weighed and dried in a combined heated air and infrared dryer (ir) operated at 800 w/m2 alone till the mass (bone dry mass) did not vary after repeated weighing. also, samples ∆e was monitored using colorimeter within the drying period. the same procedure was repeated using heated air-drying mode (had) operated at 65 ± 2 °c; ir-800 w/m2 plus had at 65 ± 2 °c, and ir-1000 w/m2 plus had at 65 ± 2 °c. the moisture content (mc) and drying rate were computed from duplicate data using microsoft excel programme. the variation of % mc with drying time, drying rate against mc and ∆e versus drying time were made and ∆e compared using tukey honest significant difference. results showed that the samples’ mci by oven dried method was 55.84%wb whereas those dried using ir-800 w/m2 alone, had (65 ± 2 °c) alone, ir800 w/m2 plus had (65 ± 2 °c) and ir-1000 w/m2 plus had (65 ± 2 °c) modes were 57.43, 52.13, 57.41 and 57.03% wb, respectively, and their corresponding critical or equilibrium moisture content were 5.62, 5.03, 12.45 and 5.95%wb, respectively. similarly, a shortest drying time (30 mins) and minimal total colour changes (δe = 12.42) were found when ir (1000 w/m2) plus had (65 ± 2 °c) was used. it also observed that, plantain slices dried using had (65 ± 2 °c) mode showed statistically significant mean difference in δe when compared with other three drying modes within 10 to 30 minutes drying time. since, ir (1000 w/m2) plus had (65 ± 2 °c) mode gave shortest drying time and minimal δe, it is recommended for use in drying plantain slices by restaurant, hotels operators and food processors . © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 16 december, 2022 revised 28 february, 2023 accepted 6 march, 2023 keywords: drying kinetics infrared intensity heated air drying colour change moisture content plantain slices http://www.azojete.com.ng/ mailto:%20williamolosunde@uniuyo.edu.ng mailto:williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):211-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 212 relative humidity, and increases the driving force for drying (onwude et al., 2016). however, the application of ir heating in post-harvest and food processing has shown more popularity in recent time, because of its advantage over other conventional heating methods. the method is faster and has efficient heat transfer. it also produces uniform product heating, lowers processing cost and better organoleptic and nutritive value of the processed food (perera and rahman, 1997; andrés et al 2007; vishwanathan et al., 2010; moses et al., 2014; zhang et al., 2017). it has been used in roasting, baking, thermal treatments (pasteurization, blanching, sterilization) and drying of foods (sandu, 1986). ir drying or heating involves heat transfer by radiation between a hot element and a material at lower temperature that needs to be dried. the highest wavelength of the radiation is dependent on the temperature of the heated element (kathiravan et al., 2008). in general, infrared radiation is grouped into 3 main categories, in terms of peak wavelength peak of the radiation: (i) shortwave ir (sw): from 0.78 µm to 2 µm; (ii) medium-wave ir (mw): from 2 µm to 4 µm; (iii) longwave ir (lw): from 4 µm to 1000 µm. commonly, most agricultural crops have high moisture content, thus could be resourcefully dried by using combination of two or more approaches. this offers the synergistic influence while retaining material quality. for instance, during combined ir and heated air drying, the fast heating of food materials by ir radiation (due to high heat intensity and penetration depth) quickens the rate of moisture movement towards the material’s surface (onwude et al., 2016), while the convective airflow guarantees the quick removal of moistness from the surface thus sustaining the moisture gradient (driving force). however, the scalability of combined heated air and infrared drying for rural consumers appears not to have been investigated, neither does a report exist on its application to the drying of plantain slices. therefore, the main objective of this study was to examine the effect of drying conditions (temperature and infrared intensity) on the drying kinetics and colour changes of plantain slices using a combined heated air and infrared dryer. 2. materials and methods 2.1 sample sourcing and preparation two bunches of matured unripe plantain samples were purchased locally at ikot okubo market, uyo, akwa ibom state, nigeria. samples at the same maturity stage, shape, size and weight were chosen in order to reduce the variability and improve the accuracy of the results. the samples were peeled, washed in running water and sliced into 4 × 20 × 20 mm dimension using a slicer and vernier calliper. 2.2 moisture content determination the moisture content of the fresh four (4) sliced samples was determined using the standard hot air oven method (asae, 2005) and equation 1. 𝑀𝐶𝑤𝑏 = (𝑊2−𝑊1_)−(𝑊3−𝑊1_) (𝑊3−𝑊1_) × 100 (1) where, w1 = weight of empty can (g), w2 = weight of can + sample before oven drying (g) and w3 = weight of can + sample after drying (g). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20williamolosunde@uniuyo.edu.ng olosunde et al: effect of drying conditions on the drying kinetics and colour changes of plantain (musa x paradisiaca) slices using combined heated air and infrared dryers. azojete, 19(2):211-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 213 2.3 drying methods about 2 g of sliced plantain samples was weighed using digital weighing balance and dried in a combined heated air and infrared dryer operated at infrared heat intensity of 800 w/m2 alone (ir-800 w/m2) at drying time interval of 10 minutes. at this duration, the samples were removed, cooled in a desiccator for 5 minutes, and thereafter re-weighed using digital weighing balance. the experiment was repeated with the drying samples until there was no significant weight loss in the sample was observed. this weight attained is regarded as bone dry mass. meanwhile, the infrared heat intensity was measured using solarimeter (mdfahim, 2019). also, the initial total colour change (∆e) of the fresh plantain slices, based on lightness value (l*), redness or greenness (a*) and yellowness values (b*) dried under this mode was read using colorimeter (vernier science education, 2020). at the same drying time interval of 10 minutes, the samples ∆e were read and noted until bone dry mass was attained. the experimental run was conducted in duplicates. the same procedure was repeated using heated air-drying mode (had) operated at 65 ± 2 °c; ir-800 w/m2 plus had at 65 ± 2 °c, and ir-1000 w/m2 plus had at 65 ± 2 °c. the moisture content was calculated using equation 1. however, the drying rate also computed using equation 2. drying rate = amount of water removed (g) drying time used (min) = dw dt (2) then, the plots of moisture content (mc) against drying time and drying rate versus mc of the dried plantain slices obtained in each drying mode were made. also, the variation of total colour change (∆e) observed in each drying mode was made against drying time. comparison of ∆e of the samples dried under the four modes within 10 to 30 minutes drying time was made using tukey honest significant difference at 5% level of probability. drying mode with minimum ∆e and shortest drying time was noted as the best drying mode. 2.4 statistical analysis data were collected in duplicate. microsoft excel programme was used in computing their mean values presenting the findings of the study. 3.0 results and discussion 3.1 moisture content and drying rate of the dried samples the initial mc of fresh plantain slices determined by oven drying method was 55.84%wb. the plot of mc (% wb) of plantain slices using at various drying modes against drying time is depicted in figures 1. http://www.azojete.com.ng/ mailto:%20williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):211-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 214 figure 1: variation of moisture content (% w.b.) with drying time of plantain slices using various drying modes figure 1 shows mc of the sample decreased with increased in drying time. longer period of drying generates more heat energy required for drying process. initial mc of the samples dried using ir-800 w/m2 alone, had (65 ± 2 °c) alone, ir-800 w/m2 plus had (65 ± 2 °c) and ir1000 w/m2 plus had (65 ± 2 °c) were 57.43, 52.13, 57.41 and 57.03% wb, respectively. it took ir-800 w/m2 plus had (65 ± 2 °c) and ir-1000 w/m2 plus had (65 ± 2 °c) drying modes 30 minutes to completely remove evaporable water away from the samples whereas ir-800 w/m2 alone and had (65 ± 2 °c) alone used 70 and 80 minutes, respectively. shorter drying period was a result of the combined drying modes (ir and had) which generated more energy per period. the samples mc is perceived to be slightly more than half of the sample mass. besides, it could also be observed that ir-800 w/m2 plus had (65 ± 2 °c) and ir-1000 w/m2 plus had (65 ± 2 °c) are energy intensive modes. the variation of drying rate with moisture content is presented in figure 2. figure 2: variation of drying rate with drying time of plantain slices using various drying modes 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 0 10 20 30 40 50 60 70 80 m o is tu re c o n te n t ( % w b ) drying time ( mins) ir (800 w/m²) had (65 ± 2°c) ir (800 w/m²) + had (65 ± 2°c) ir (1000 w/m²) + had (65 ± 2°c) 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 0.00 10.00 20.00 30.00 40.00 50.00 60.00 d ry in g r at e ( g h 2 0 / m in ) moisture content (%wb) ir (800 w/m²) had (65 ± 2°c) ir (800 w/m²) + had (65 ± 2°c) ir (1000 w/m²) + had (65 ± 2°c) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20williamolosunde@uniuyo.edu.ng olosunde et al: effect of drying conditions on the drying kinetics and colour changes of plantain (musa x paradisiaca) slices using combined heated air and infrared dryers. azojete, 19(2):211-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 215 from figure 2, it can be seen that the plots had rising, constant and falling rate periods. samples dried using ir-800 w/m2 alone showed gradual decreased in drying rate between 42.18 to 5.62%wb. it equilibrium moisture content (emc) or critical moisture content (cm) was 5.62%wb and at this period, 0.0332 g h20 / min as drying rate was evaporated. also, the drying rate of sample dried using ir-1000 w/m2 plus had (65 ± 2 °c) mode rapidly declined between 28.71 to 5.95%wb (as emc= cm). at 5.95%wb, 0.041 g h20 / min was evaporated. whereas samples dried using ir-800 w/m2 plus had (65 ± 2 °c) and had (65 ± 2 °c) alone recorded constant rate periods between 41.45 to 12.45%wb and 40.45 to 5.035wb, respectively. their emc and cm was 12.45 and 5.03 %wb, respectively. the amounts of water removed per min at these periods were 0.0339 and 0.0153 g h20 / min, respectively. however, during constant rate period, there is a continuous migration of water molecules from interior part of the sample matrices at constant rate which form film of water on the sample surface which later evaporates away as drying time increases. the sample mc at this phase is at equilibrium (emc) with the partial pressure of water vapour in the drying chamber. furthermore, the critical moisture content (cm) of the sample is that mc at which constant rate period terminates and the falling rate period commences. during this period, amount of internal moisture in the sample is reduced due to limiting amount of free unbound moisture in the sample. hence, the sample surface does not have enough water, the little on the surface is rapidly driven away as the drying time is extended. these observations are in accordance with drying rate pattern for all agricultural and bio material such as food material (antia et al., 2019a and 2019b). 3.2 total colour change of dried samples the varaition of total colour changes observed in the dried plantian slices using various drying modes against drying time is shown in figure 3. figure 3: variation of total colour changes observed in the dried plantian slices using various drying modes against drying time 0 5 10 15 20 25 30 0 10 20 30 40 50 60 70 80 t o ta l c o lo u r c h an g e (δ e ) drying time (minutes) ir (800 w/m2) had (65 ± 2 °c) ir (800 w/m2) + had (65 ± 2 °c) ir (1000 w/m2) + had (65 ± 2 °c) http://www.azojete.com.ng/ mailto:%20williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):211-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 216 the effectiveness of the various ir and had combination strategies (modes) could also be assessed by the changes in the colour of dried plantain samples. hence, this could be used to select suitable drying techniques (wang et al., 2014a). from figure 3, the total colour change (δe) of sample dried using ir-800 w/m2 mode alone recorded at 10, 60 and 80 mins of drying time were 6.35, 17.99 and 24.97 (as the highest), respectively. the plantain samples dried at 10, 60 and 70 using had (65 ± 2 °c) mode alone had δe of 14.94, 16.43 and 16.93, respectively, whereas those samples dried at 10 and 30 min using ir (800 w/m2) plus had (65 ± 2 °c) and ir (1000 w/m2) plus had (65 ± 2 °c) modes gave δe of 8.66 and 13.69; and 7.66 and 12.42, respectively. as observed, δe in all the dried plantain slices samples using different combination strategies of ir and had, the use of ir (1000 w/m2) plus had (had (65 ± 2 °c) gradually increased as the drying time also increased. however, sample dried using ir heating (800 w/m2) alone had the highest δe (24.97) while ir (1000 w/m2) plus had (65 ± 2 °c) had the least δe (12.42). besides, the multiple comparison of the δe of the dried plantain samples using four modes is given in table 1 using tukey honest significant difference. table 1: mean δe read between 10 to 30 minutes for all the drying modes drying mode mean δe ir (800 w/m2) 8.84 ± 2.28a had (65 ± 2 °c) 15.05 ± 0.12b ir (800 w/m2) + had (65 ± 2 °c) 10.32 ± 2.91a ir (1000 w/m2) + had (65 ± 2 °c) 9.38 ± 2.63a note: m ± sd refers to mean and standard deviation; values with the same superscript show no statistical significant difference at 5% level probability. as observed in table 1, plantain samples dried using had (65 ± 2 °c) mode recorded statistical significant mean difference in δe (15.05 ± 0.12) when compared with the other modes [with 8.84 ± 2.28, 10.32 ± 2.91, and 9.38 ± 2.63 for ir (800 w/m2) alone, ir (800 w/m2) plus had (65 ± 2 °c) and ir (1000 w/m2) plus had (65 ± 2 °c), respectively] which did not show any significant mean difference at 5% level probability. for the purpose of comparison, 10 to 30 minutes drying time interval was chosen based on the fact that ir (1000 w/m2) plus had (65 ± 2 °c) and ir (800 w/m2) plus had (65 ± 2 °c) used 30 minutes to completely dried the products. 4. conclusion in this study, a combined hot air and infrared dryer was used to dry plantain slices at infrared intensities of 800 and 1000 w/m2, and hot air drying (had-65 ± 2 °c) combination modes. total colour of the dried samples for between 10 -30 mins were later evaluated. the results showed that the initial moisture content of fresh plantain slices determined by oven drying method was 55.84%w while those dried using ir-800 w/m2 alone, had (65 ± 2 °c) alone, ir-800 w/m2 plus had (65 ± 2 °c) and ir-1000 w/m2 plus had (65 ± 2 °c) modes were 57.43, 52.13, 57.41 and 57.03% wb, respectively, whereas their corresponding critical or equilibrium moisture content were 5.62, 5.03, 12.45 and 5.95%wb, respectively. shortest drying time (30 mins) and minimal file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20williamolosunde@uniuyo.edu.ng olosunde et al: effect of drying conditions on the drying kinetics and colour changes of plantain (musa x paradisiaca) slices using combined heated air and infrared dryers. azojete, 19(2):211-218. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 217 total colour changes (δe = 12.42) were observed when ir (1000 w/m2) plus had (65 ± 2 °c) was turned on. statistically, plantain slices dried using had (65 ± 2 °c) mode between 10 30 mins showed significant mean difference in δe when compared with other three drying modes. since, ir (1000 w/m2) plus had (65 ± 2 °c) mode used the shortest drying time and minimal δe, it is recommended for use by restaurant /hotel operators and food processors in drying plantain slices. references andrés, a., fito, p., heredia, a, and rosa, em. 2007. combined drying technologies for development of high-quality shelf-stable mango products. drying technology, 25(11): 1857–1866. antia, oo., assian, ue. and william, o. 2019a. development of an empirical model relating palm nut moisture content, shell thickness and soaking time. international journal of mechanical and civil engineering, 2 (1): 36 47. antia, oo., assian, ue. and william, o. 2019b. effect of moisture content on palm nut shell fragmentation for effective separation of kernel. international journal of mechanical and civil engineering, 2 (1): 48-55 asae 2005. asae moisture measurement — unground grain and seeds. american society of agricultural and biological engineers, pp. 2-4. farlex, f. 2011. definition of drying; free online dictionary, thesaurus and encyclopedia, https://www.thefreedictionary.com/drying accessed on 7th october, 2022 kathiravan, k., harpreet, kk., jun, s., joseph, i. and ali, d. 2008. infrared heating in food processing: a review. comprehensive reviews in food science and food safety, 7(1): 599–618. mdfahim, hk. 2019. study of solar radiation measuring instruments and practical measurement of solar radiation in dhaka, bangladesh. islamic university of technology, dhaka, bangladesh, 44p. moses, ja., norton, t., alagusundaram, k. and tiwari, bk. 2014. novel drying techniques for the food industry. food engineering reviews, 6(3): 43–55. onwude, di., hashim, n. and chen, g. 2016. recent advances of novel thermal combined hot air drying of agricultural crops. trends in food science and technology, 57: 132-145., http://doi.org/10.1016/j.tifs.2016.09.012. accessed on 8th october 2022 perera, co. and rahman, ms. 1997. heat pump dehumidifier drying of food. trends in food science and technology, 8(3): 75–79. sandu, c. 1986. infrared radiation drying in food engineering: a process analysis. biotechnology progress, 2: 109–119. vernier science education (2020). colorimeter user manual https://www.vernier.com/manuals/col-bta/ accessed on 8th october 2022 vishwanathan, kh., hebbar, hu. and raghavarao, ksm. 2010. hot air assisted infrared drying of vegetables and its quality. food science and technology research, 16(5): http://www.azojete.com.ng/ mailto:%20williamolosunde@uniuyo.edu.ng https://www.thefreedictionary.com/drying http://doi.org/10.1016/j.tifs.2016.09.012 arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):211-218. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: williamolosunde@uniuyo.edu.ng 218 381–388. zhang, m., chen, h., mujumdar, as., tang, j., miao, s. and wang, y. 2017. recent developments in high-quality drying of vegetables, fruits and aquatic products. critical reviews in food science and nutrition, 57(6):1239–1255. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20williamolosunde@uniuyo.edu.ng arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):375-384 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 375 design of a smart solar hybrid egg incubator for small scale poultry farmers m. a. abba-aji, a. r. usman and m. shuwa department of mechanical engineering, university of maiduguri,, maiduguri, nigeria *corresponding author's email address: birma4real2004@yahoo.com article information submitted 13 january, 2024 revised 24 april, 2024 accepted 30 april, 2024 keywords: incubator hatching fertilization mdf-plywood abstract in this study, an electro-mechanical device (incubator) was designed to provide temperature and humidity for fertilization of eggs. a 132 capacity egg crates and medium density fiber board plywood (mdfplywood) with a 15mm thickness for the incubation chamber were used. a 200ah lithium phosphate battery, 300w capacity solar panel and inverter were used to power the 200w electric bulb and other incubator components in the time of power shortages. incubation temperature of 37.50c and average relative humidity of 45% were considered during the design. a 3d model of the designed incubator was produced using solid works software package. the model provided some important information on the material properties of the proposed plywood for construction of the casing, the plastic egg crates and the egg turning tray. the required number of egg crates and egg turning trays were determined as 8 and 4 respectively with two plastic crates sitting on each tray. heat generation and heat losses of the system were also determined as 139.482595w and-3.395925w respectively. the total power consumption of the designed incubator was 150.4159w. design of a cost-effective solar hybrid eggs incubator (n940, 200), with a dimension of 1100mm for poultry farmers was successfully carried out with a hatching capacity of 1056eggs. 1.0 introduction an incubator is an electro-mechanical device that is used to provide temperature and humidity for fertilization of eggs (kanu et al., 2016). egg fertilization is an important factor in the hatching of poultry eggs. it is possible to hatch eggs without the consent of the mother hen. the fertilization of egg embryo remains a priority of any farmer since his profits depend on hatchability rate of the eggs, this embryo when mature well give birth to a chick. it is therefore necessary to manage the fertilized eggs with care which latter develop into a normal chicken. (adegbulugbe et al., 2013) the eggs required warmness either naturally or artificially as the case may be. the natural method required the bird to provide the warmness or the required temperature by sitting on the eggs in an open space (idoko et al., 2019). poultry is a kind of domestic birds that can be kept at home by human so that their eggs are collected. it is second most widely eaten meat. poultry farming include egg brooding and hatching. incubation is a process whereby poultry undergoes to hatch their eggs. (mohammed et al., 2015). incubation is also being described as technology by which eggs are incubated and hatched with help of manmade technology called incubator. the incubator controls the temperature and humidity in preparation for hatching process, and also determines the fertility of egg with the moist warm air and artificial stirrer as the embryo emerges into a poultry within a period of 21 to 41 days (kifildeen et al., 2018). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 376 hatching of eggs comes in two different ways; natural (where mother chicken provides the warm by direct contact with egg for the required period) and the artificial egg incubator technology which provides opportunity for farmers to produce chicks from eggs without the consent of the mother hen. artificial incubation is one of the fastest ways of transforming eggs to chicks (adetola et al., 2019). the most important difference between natural and artificial incubation is the fact that the natural parent provides warmth by contact rather than surrounding the egg with warm air (salawu and rukaiyat, 2020). artificial incubation procedures of eggs were originated in both china and egypt. china developed a method of burning charcoal to supply the required heat, the egyptian incubator was developed by constructing a large brick incubator which was heated with fire right in the room where the eggs are kept for hatching (ajani et al., 2020). modern poultry industry incubation requires mechanical systems to replace the mother hen for egg incubation which was commercialized into large scale only within the period of 60 -70 years (ajani et al., 2020). the three important parameters for incubation of eggs are the relative humidity (warmed air surrounding the egg), temperature and egg turning in terms of angles of inclination of egg tray as it swing in either side of the axes within the incubator. the ambient temperature has a strong relation with the incubator as it forms the basis for calibrating the incubator chamber temperature against the ambient temperature, and this relationship can be used for predicting the incubator temperature at any given time for unknown ambient temperature (kifildeen et al., 2018). solar energy has gain significant interest as means of providing the electricity to the incubator for incubation of eggs, this will have answer to the insufficient power constraints faced by poultry industries in remote areas. continuous supply of electricity in nigeria is a mirage due to the frequent power failure which also lead to the use of other sources like generators, kerosene and gas, therefore building and utilizing a solar powered egg incubator will improve the result of poultry chicken farming and the overall living of the farmers and communities in general (kelebaone et al., 2019). high demand in day old poultry chick by commercial poultry farmers has always been on the increase, since the process of natural incubation alone cannot sustain the poultry demand considering the fact that eggs are being exposed to diseases and predators due to lack of care by the mother hen, there ever increase in poultry meat all over our immediate environment in response to public concern over dietary fat (kifildeen et al., 2018). some incubators cannot be used commercially due to minimum numbers of eggs they can accommodate, their mode of operation and maintenance of power failure is also a hindrance to the development of the poultry industry which result to difficulties in the smooth running of the incubator for hatching large number of eggs, difficulties in sourcing of electricity from stand -by generator in order to compliment the shortage of power for the incubator (kifildeen et al., 2018). the significance of this research work is to improve the production rate and capacity of a dayold poultry chick for sustainable economic development. this design was carried out by considering locally source available materials to promote easy construction of the incubator. this work is based on the design of a smart solar hybrid eggs incubator with 1056 hatching capacity egg incubator for the hatching of chicken, duck, guess, guinea fowl, and pigeon and turkey eggs. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abba-aji et al: design of a smart solar hybrid egg incubator for small scale poultry farmers. azojete, 20(2):375-384. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 377 2. materials and methods 2.1 material selection and design analysis the research design is divided into two section, mechanical systems design, and electrical system design these two combines to give the hybrid egg incubator for hatching varieties of eggs. the mechanical section of the incubator consists of the incubator chamber, egg turning tray, rotation mechanism while the electrical sections includes the dc fan for humidification, and ventilation, intelligent hatch controller. the incubator design will be in such that the solar power will complement the shortage of electricity at the period of power failure. in order to design the incubator system, the following consideration were made. i. plastic crate with capacity of 132 eggs ii. medium density fiber –board plywood (mdf plywood) of 15mm thickness. iii. optimum incubation temperature 37.5 0c iv. humidity within the incubator of average of 45% v. capacity of the incubator 1056 eggs vi. angle iron 3mm thickness. vii. maximum distance between egg trays 150mm. 2.2 design consideration detail design analysis of incubator sections such as egg tray, incubator casing or chamber, strength of the wood is provided below 2.2.1 design of egg tray and incubator chamber the egg turning tray was designed from an angle iron and plastic crates. each of the tray contained 264 eggs and four trays. since the incubator was designed to hatch all types of domestic eggs. egg with the maximum mass was considered in the design of the egg turning tray. area of the egg turning tray for 1056 eggs was obtained from equation 1. breadthlengtharea = (1) let “n” be the number of eggs to be hatched in this case is 1056 eggs c = number of crates required in the incubator = 𝑛 132 (2) the number of egg tray = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑟𝑎𝑡𝑒𝑠 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑟𝑎𝑡𝑒𝑠 𝑜𝑛 𝑒𝑎𝑐ℎ 𝑡𝑟𝑎𝑦 me = the average mass of egg is 0.068kg where g is the acceleration due to gravity is 9.81m/s2 wtotal = total weight = mtotal (3) weight of egg tray wtr = 𝑊𝑡𝑜𝑡𝑎𝑙 8 (4) the incubator chamber was rectangular box like structure, which was designed to contain the egg trays and its turning mechanism, hatching tray, electrical components and circuit. the volume of the incubator was obtained from figure 1a and 1b using equation 5. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 378 figure 1a: side view of the incubator chamber figure 1b: back view of the incubator chamber heightbredthlengthvolume = (5) 2.2.2 determination of heat requirement of the incubator the amount of heat generated in the incubator chamber is determined from the expression mc∆𝑇 (ajani et al., 2020). the amount of heat required to raise the temperature of the incubator will be heat required to raise the temperature of air, eggs, egg turning tray, water, and the qi = mi ci∆ti. therefore, the heat required to raise the temperature of air, eggs, wooden egg turning tray can be determine as follow. considering the heat generated in the incubator as qi; 𝑄𝐼 = 𝑀𝐼𝐶𝐼∆𝑇 (6) to determine the heat required in the incubator, the volume of the incubator chamber is first determined as suggested by (bharosh et al., 2021) (7) total heat required in the incubator chamber qinc = 𝑀𝑎𝑖𝑟𝐶𝑎𝑖𝑟∆𝑇𝑎𝑖𝑟 + 𝑀𝑠𝐶𝑠∆𝑇𝑠 (8) where: (ajani et al., 2020). 2.2.3 heat loss by the incubator there is heat loss through the wooden wall, 100% work is not guaranteed, there would be heat loss due to conduction. considering the plane layer of the thickness dx with one face maintained at temperature t and other end as (t+𝑑𝑡). the heat loss due to conduction can be estimated from the following equation. (ajani et al., 2020). 𝑄 = −𝐾𝐴( 𝑑𝑇 𝑑𝑥 ) (9) the flow of air is a steady inside the incubator therefore it does not vary with time therefore qdx = kadt (10) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abba-aji et al: design of a smart solar hybrid egg incubator for small scale poultry farmers. azojete, 20(2):375-384. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 379 x tsinct kaq − −= ( (11) where q is the heat k is the thermal conductivity coefficient of the plywood (0.65) in this design x is the thickness of the plywood 15mm. heat loss during the incubation is given as top and bottom of the plywood (12) where q = is the heat (bala et al., 2020) pf = plywood front, ps plywood side pb plywood back side and pt = is the plywood top pbt and bottom. a is the area of the incubator’s chamber, k is thermal conductivity coefficient (0.65 for mdf plywood (ajani et al., 2020) the quantity of heat is loss is calculated using the following expression ql = qptb+ qpss+qpfb (13) the actual heat required for the incubation is q = ql+ qi (14) 2.2.4 design of ventilation ventilation is provided on the incubator in order to allow of air in and out of the incubator. it is the volume of mass flow in and out of the incubator. volume of flow rate = crosssectional area (ajani et al., 2020). where the volume = 𝑝𝑑3 4 (15) dc electric motor will be based on the torque generated by electric motor tm = 𝑝𝑜𝑤𝑒𝑟 𝑎𝑛𝑔𝑢𝑙𝑎𝑟 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = where n is the speed of the fan. 2.2.5 determination of humidity humidity is moisture in circulation within the incubator, in order to estimate the humidity requirement of the incubator. it is calculated as mass of water vapor per unit volume over a unit volume of air. the humidity keeps the eggs from losing too much moisture in the process of incubation (ajani et al., 2020). mathematically is calculated from the following relation 𝐻 = 𝑚𝑣 𝑣 (16) 𝜌 = 𝑚𝑣𝑅𝑣𝑇 (17) 𝐻 = 𝑣 𝑅𝑣𝑇 (18) where h = humidity, mv =molar mass of water , 𝜌 =energy density or heat density of water, 𝑅𝑣 = gas constant 𝑇 = temperature 𝑉 = volume of the incubator’s chamber http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 380 2.2.6 determination of bending moment and shear forces the uniformly distributed load udl will be the weight of the egg divided by the total span of the wood which is 1.1m in this design. 𝑈𝐷𝐿 = 𝑤𝑒 𝐿 (19) shear force at point a and b will be calculated from the relation. 𝑆𝐴 = 𝑊𝑙 2 (20) and 𝑆𝐵 = 𝑊𝑙 2 (21) then bending moment is the product of the force and the perpendicular distance from the supports. the distance is taken as ½ of the total length of the incubator chamber, in this case 0.55m.s bending moment about the center c (22) 2.2.7 total power consumption the total power consumption of the entire incubator system can be calculated from the following relation. total power consumption 𝑃𝑇 = 𝑃ℎ + 𝑃𝑓𝑠 + 𝑃𝑓𝑏 + 𝑃c (23) where; 𝑃i = power of the incubator chamber 𝑃𝑓v = power of ventilation fan 𝑃𝑓h = power of humidity fan 𝑃𝑐 = power of control board hence total power consumption. (bala, et al., 2020) 2.2.8 power requirements and selection of battery solar panel and inverter. total power consumption is added up to 150.4159w. base on the total power requirement of the incubator, a 200ah lithium phosphate acid battery 12v, a 1kva inverter and a 300w solar panel will be used to power the entire incubator. the maximum total power requirement of the incubator is 200w; therefore, a 200a/h battery will serve. since power is given by: 𝑃 = 𝐼𝑉, a fully charged 200a/h battery rate at 12v with a load of 200w will be discharged in 12 hours. where: 𝑃 = 200w, 𝑉 = 12v 𝐼 = 𝑃 𝑉 = 200 12 = 16.667𝐴. 200a/h battery will be discharged in 200 16.667 = 12ℎ𝑜𝑢𝑟𝑠 in order to sustained the insufficient electricity a solar panel of 300w capacity can be used to properly charge the battery and used. 2.3 bills of engineering measurements and evaluation the production cost is evaluated based on market prices of materials, the overhead and labour cost which is presented under section 2.3.1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abba-aji et al: design of a smart solar hybrid egg incubator for small scale poultry farmers. azojete, 20(2):375-384. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 381 2.3.1 analysis of bill of engineering measurements the material cost depends on the market prices, given in table 1, as mc = n 626,800 table 1: price of materials s/no. description rate (n) quantity amount (n) 1 mdf plywood 15cm 30, 000 4 120, 000 2 plastic egg crates 600 8 4, 800 3 angle iron 3mm thickness 10, 000 2 length 20, 000 4 aluminum sheet 4, 000 ½ sheets 2000 5 4.8w direct current (dc) fan 4, 500 1 4, 500 6 i. humidity and temperature sensor. ii. intelligent hatch controller 95, 000 1 95, 000 7 4.8w ventilation fan (dc fan) 4, 500 1 4, 500 8 photovoltaic solar panels 300w 95, 000 1 95, 000 9 inverter 70, 000 1 70, 000 10 chain and sprocket 1000 1 1000 11 electric motor (savor motor) 35, 000 1 35, 000 12 battery 240v 175, 000 1 175, 000 total 626, 800 direct labour cost was assumed to be 40% of the material cost from table 1, that is, 𝐷𝐿𝐶 = 40 100⁄ × 626, 800 = 𝑁 250, 720.00 overhead cost was assumed to be 10% of the material cost; 𝑂𝐻𝐶 = 10 100⁄ × 626, 800 = 𝑁 62, 680.00 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝐶𝑜𝑠𝑡 𝐶𝑃 = 626, 800 + 62, 680 + 250, 720 = 𝑁 940, 200.00 from the market survey conducted so far, the price of similar device ranges from n1, 200, 000 to n1, 300, 000. this indicates the cost effectiveness of the present device. 3. results and discussion the design of the solar hybrid eggs incubator with a capacity of 1056eggs was carried out, the number of eggs trays and the crates, the heat requirement, heat losses and the strength of the plywood, power consumption were determined 3.1 results the modelling of the incubator is shown in figure 2. the solid works software was used to draw the incubator chamber, egg crate and the egg turning trays. each of the material properties was estimated from the solid works design software. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 382 figure 2a: egg tray support figure 2b: frame view of egg incubator and egg trays table 2 shows the number egg trays, number of crate per tray and number egg on each tray. table 2: incubator specifications in terms of capacity number of crates and trays number of crates per tray. number of eggs per tray is total number of crate number of egg trays 2 264 8 4 the shear force and bending moment of the incubator were also determined and for both side and is presented in table 3 table 3: uniformly distributed load udl shear force and bending moment uniformly distributed load shear forces and point a shear stresses force at point b bending moment bending moment about the center 38.2746𝐾𝑁/𝑚 sa = -21.05103kn/m. sb = 21.05103kn/m. 11.5780665𝑁𝑀. table 4 shows the heat generation heat loss of the entire incubator, 200watt of heat is derived from electric bulb which is the main source of heat in the system table 4: the vale heat generation, heat loss heat generation and heat losses in the incubator heat generation is 200w. heat required in the incubator = 139.482595j/s = 139.482595w. total heat losses = -3.395925w. 3.2 discussion the solid work software was used to design the incubator chamber, egg crates and egg turning tray, it provides vital information concerning materials and components, medium density fiber board plywood is suitable which earlier suggested by (bala et al.,2020). the egg crate and egg file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abba-aji et al: design of a smart solar hybrid egg incubator for small scale poultry farmers. azojete, 20(2):375-384. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 383 turning tray also is crucial in the designing of the incubator a plastics crate material was selected in the solid work software because of its light weight, availability and does not also conduct too much heat the weight and strength were determined from solid work drawings based on the dimensions of the crate, and egg turning tray, 4 egg trays are the required in order to accommodate 1056 eggs each tray containing 264 eggs. in order to avoid failure on materials for construction the shear stress and bending moments were also calculated as shown table 2 above the shear stresses of the egg trays that carries a total of 1056 egg for both side are sa = -21.05103kn/m, sb = 21.05103kn/m. uniformly distributed load udl was also determined as 38.2746𝐾𝑁/𝑚. the bending moment bending moment about the center.11.5780665𝑁𝑀. table 3 showing the heat generation and losses as heat generation is 200w. this value was estimated as the heat of the bulb which is the main source of heat within the incubator’s chamber the heat required in the incubator is 139.482595j/s = 139.482595w. total heat losses = 3.395925w. according to ajani, et al., (2020) and bala, et al., (2020) and others, the heat generated is sufficient to provide the required temperature of 37.50c and average humidity of 45%. other components such as the intelligent hatch controller, thermostat, and electric savor motor humidity fan and ventilation fan does not consumed much power. the total power consumption of the incubator is 150.4159w. lithium phosphate battery 200ah 12volt capacity with 300w solar panel can provide the power to the incubator system, this battery will be discharge in a period of 12hours. 4. conclusion the design of solar hybrid egg incubator for poultry farmers to contain 1056 involved, designing the incubator’s chamber, egg crate and egg trays the simulation was done using solid works software in order to determine the properties of the materials for predicting some parameters, the strength of the materials such as medium density fiber board plywood, angle iron steel, and plastic egg crate were determined and recorded, the bending moment and shear forces were calculated as11.5780665𝑁𝑀,-21.05103kn/m, and 21.05103kn/m respectively. heat transfer principles were considered in determining the heat requirement of the incubator was also calculated as 139.482595w. a 200ah lithium phosphate acid battery 12v and 300w solar panel were used to power the entire incubator, ventilation fan, electric motor, humidity fan. the temperature of 37.50c and average humidity of 45% were achieved. the following recommendations were drawn after successfully designing the incubator 1. information obtained from this design should be made available to relevant agencies for direct uses. 2. there is need to construct and test the incubator of this capacity. references adegbulugbe, ta., atere, ao. and fasanmi, og. 2013. development of an automatic electric incubator. international journal of scientific & engineering research, 4(9): 914-918. adetola, so., adegbite, as., adewale, ka. and ibiwoye, os. 2019. design, construction and testing of kerosene powered multi-birdegg incubator. lautech journal of civil and environmental studies, 3(1):1-14. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):375-384. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 384 ajani, as., olusoji, ao., egbeyele, g. and babatunde, am. 2020. design and construction of automated eggs incubator for small scale poultry farmers. international journal of technical research & science, 5(8): 1-9. bala, am., abubakar, ma., bello, ms. and sakalo, t. 2020. design, construction of a fully automated egg incubator using electric battery. african scholar journal of african sustainable development, 18(2): 319-332. bharosh, ky., nischal, p., dinesh, k., madan, k., triratna, b. and rabin, d. 2021. design, fabrication, and performance analysis of an automatic horizontal egg incubator. journal of the institute of engineering, 16(1): 77-85. idoko, e., ogbeh, go. and ikule, ft. 2019. design and implementation of automatic fixed factors eggs incubator. international journal for innovative research in multidisciplinary fields, 5(6): 1-8. kelebaone, t., kagiso, m., rapelang, k., ishmael, z. and refilwe, m. 2019. construction and operation of solar powered egg incubator. international journal of engineering research & technology, 12(8): 675-677 kifildeen, lo., adewole, aa. and olayide, ra. 2018. performance evaluation of a solar poultry egg incubator. international research journal of advance engineering and science, 3(2): 255264. mohammed, br.., hooi, l., md saidin, w., mohd, f. and mohammed, z. 2015. egg hatching incubator using conveyor rotation system. 2nd international material, industrial and manufacturing engineering conference held in bali, indonesia: 527-531 salawu, g. and rukayat, a. 2020. design of a portable solar powered incubator. international journal of engineering and advanced technology, 9(4): 2366-2369. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):401-408 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 401 original research article comparative study of two stator designs for the international electrotechnical commission 100 motor frame for 2.2kw squirrel cage induction motor i. k. onwuka department of electrical electronic engineering michael okpara university of agriculture umudike *corresponding author’s email address: ifeanyikayonwuka@gmail.com 1.0 introduction engineering standard was defined by jawad and greulich (2018) as a document prepared by a professional group or committee which is believed to be a good and proper engineering practice, and which contain mandatory requirements. the term mandatory in that definition implies that engineering standards pursue uniformity in engineering criteria and practices, which in turn provides options to users to satisfy their needs from a range of different product manufacturers and vendors, including interchanging units and components of the product. standards represent a key requirement in globalization, to ensure compatibility and consistency, reliability, safety, and good economics. in the electric machine industry, two standards stand out: the national electrical manufacturers association (nema) and international electrotechnical commission (iec). most other standards like the bs 2613 and nf cs1 – 100 are derived directly from the iec standard. the difference between nema and iec may be seen in what each of them emphasizes. while nema emphasizes on robust designs that ensure ease of product selection and a wider range of application, iec dwells on product performance and are application specific. hence, an equivalent iec machine would be smaller and less expensive than a nema machine, which in turn has a better overload capacity than the iec product. another difference is that while the iec uses the si system of article information abstract the international electrotechnical commission totally enclosed, fan cooled 100 motor frame for 2.2 kilowatts squirrel cage induction motor have been manufactured with both 24-slot stator and 36-slot stator. this study compared the two solutions along the lines of rated performance, material consumption, and robustness of design. since the difference between the two motors is basically the number of slots in the stator, similar machine data were adopted for them. the unknown data were calculated from standard machine equations carefully suited for the motors. the data so obtained were used as input to the rmxprt model where the motors were simulated. the results show marginal difference in all the parameters considered such as efficiency (0.09% in favour of the 36-slot stator), power factor (0.0014 in favour of the 24-slot stator), annual cost of operation (n687.88 saved by the36-slot stator), and overload capacity. the inference of this study is that the two stator designs are adequate solutions for the 3hp motor having international electrotechnical commission totally enclosed, fan cooled 100 motor frame, and that while the 24-slot stator design would be easier and cheaper to manufacture, the 36-slot stator design is however more robust and cheaper to operate. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 april, 2022 revised 3 may, 2023 accepted 10 may, 2023 keywords: iec 100 tefc scim24-slot stator 36-slot stator http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com ifeanyikayonwuka@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):401-408. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 402 measurement, nema uses the imperial system. however, some degree of flexibility exists between products of both standards, but it can only be exploited by users who have good understanding of the differences. an article on the blog of the vendor, c3controls (c3 controls, 2023) suggested how to choose between nema and iec products. a 2007 abb brochure (abb, 2007), in recognition of the demands of globalization on original equipment manufacturers (oems) to specify international standards, was more detailed in highlighting how to use products of nema and iec interchangeably. the iec totally enclosed, fan-cooled (tefc) motor frames for induction motors have a wide application across many industries and can be commonly applied to conveyor systems, compressors, pumps, blowers, fans, etc. for low voltage applications (< 1000v), they are made of high-grade cast aluminium alloy. since the year 2015, they are manufactured up to ie3 and ie4 efficiency classes according to iec 60034-30, and with protection grades of ip 55 according to iec 60034-5 (challenge power transmission, 2023). these render them a convenient and ecofriendly solution to many industrial needs, while ensuring minimum operational costs. in particular, the iec tefc 100 motor frame for scim may be rated 3 kw, 2.2 kw, 1.5 kw, or 1.1 kw with synchronous speeds of 3000rpm, 1500rpm, 1000rpm and 1000rpm respectively, at a supply frequency of 50hz (abb, 2022). the centre of the shaft measures 100 mm from the base. the 2.2 kw rated motor with 1500rpm synchronous speed is manufactured in both 24-slot and 36-slot stators. with so much emphasis on energy efficient products, efficient use of materials, operational cost reduction and ease of manufacture, it becomes important to study and analyse the iec tefc 100 motor frame for scim with 2.2kw rating manufactured with 24slot and 36-slot stators comparatively, with a view to recommending the best use for either. the selection of higher number of slots is attractive because leakage reactance and tooth pulsation losses are reduced while over-load capacity is increased (asgharpour-alamdari, 2022). however, it presents some challenges to the machine designer, such as increased fabrication costs, and weight, and magnetizing current and iron losses which diminish the efficiency; and also poor cooling with the attendant increase in temperature rise (mittle and mittal, 2017). the work of gundogdu et al. (2017) is among several studies made on the influence of stator slot/pole number combination on the performance of the scim, and it observed that there is an indirect relationship between the stator slot and pole number and distortion level of the rotor bar current waveform, which in turn affects the key performance indices of the machine. it is important therefore to justify the manufacturing of the two stator designs by comparing their rated performance and operating costs. 2.0 methodology electric machines lab of the department of electrical electronic engineering in the michael okpara university of agriculture umudike has a 3-phase, 2.2kw, 4-pole induction motor, with the iec 100 frame, and having 36 stator slots. most of the machine data presented in tables 1 and 2 have been adopted from it. a few others were obtained from the vendor teco (te3) (2023) and challenge power transmission (2023). most of these data are common to both stator designs under study. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com peretomode and eyenubo: comparative study of two stator designs for the international electrotechnical commission 100 motor frame for 2.2kw squirrel cage induction motor. azojete, 19(2):401-408. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 403 due to the unavailability of the 24-slot stator scim, the preliminary design of the machines were performed in order to initiate an electromagnetic simulation using rmxprt in the ansys electromagnetic environment. such designs begin naturally with the assumption of machine specifications. from the known specifications, the other unknown machine parameters were determined. table 1: machine parameters s/n parameter symbol value 1 rated power pn 2.2kw 2 phases m 3 3 winding layers 1 4 insulation class f 5 rated current iin 4.51a 6 voltage v 230/400v 7 rated speed n 1462rpm 8 frequency f 50hz 9 number of poles p 4 10 stator outer diameter dos 158mm 11 stator inner diameter dis 98mm 12 rotor outer diameter dor 97.48mm 13 shaft diameter ds 36mm 14 stack length l 98mm 15 lamination thickness tl 0.5mm the preliminary design of the machine, according to the method set forth by pyrhonen et al. (2008) and boldea and nasar (2010) requires that some values should be assigned to some variables. this was achieved in consideration of standard design procedures, and listed in table 2. table 2: preliminary assigned design s/n parameter symbol value 1 efficiency η 0.84 2 power factor cos ϕ 0.82 3 teeth saturation factor kst 1.4 4 flux density shape factor αi 0.729 5 form factor kf 1.085 6 airgap flux density bg 0.7 7 current density jdc 6.07a/mm2 8 coil pitch/pole pitch y/τ 5/6 and 8/9 9 slot filling factor kfs 0.6 10 stator tooth flux density bts 1.55 the air gap apparent power is given by 𝑆𝑔𝑎𝑝 = 𝐾𝐸𝑃𝑛 𝜂 cos𝜙 (1) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):401-408. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 404 the air gap voltage, is given by 𝐸 = 4𝑓𝐾𝑓𝑇𝐾𝑤𝜙 (2) where 𝐾𝐸 = 𝐸 𝑉𝑝ℎ = 0.98 − 0.005 𝑃 2 (3) vph is the per phase voltage, while t, kw, and ϕ are the number of turns per phase, the winding factor, and the magnetic flux (webers), respectively. the magnetic flux can be estimated from 𝜙 = 𝛼𝑖𝜏𝐿𝐵𝑔 (4) the pole pitch is given by 𝜏 = 𝜋𝐷𝑖𝑠 𝑃 (5) the whole coil, integral slot winding with star connection is employed in the stator. the coil pitch/pole pitch ratio, y/τ is taken as 5/6 for the number of stator slots, ns = 24, and 8/9 for ns = 36. hence, the winding factor can be determined as 𝐾𝑤 = cos (180−𝑦( 𝜋𝑃 𝑁𝑠 )) 2 × sin 𝑞𝜋𝑃 2𝑁𝑠 𝑞 sin 𝜋𝑃 2𝑁𝑠 (6) where q is the number of slots per phase per pole. with the appropriate substitution of the equations listed above, the number of turns per phase maybe obtained as: 𝑇 = 𝐾𝐸𝑉𝑝ℎ 4𝑓𝐾𝑓𝐾𝑤𝜙 (7) assuming a single current path, that is a1 = 1, the number of conductors per slot is obtained as: 𝑛𝑠𝑐 = 2𝑎1𝑇 𝑞𝑃 (8) the result of equation (8) is rounded off to the nearest whole number as it cannot be a fraction. thereafter, equations (7) and (4) are recomputed and a new value obtained for bg. the magnetic wire cross sectional area may be determined as 𝐴𝑐 = 𝐼𝑖𝑛 𝐽𝑑𝑐 (9) the conductor diameter is given by: 𝑑𝑐 = √ 4𝐴𝑐 𝜋𝑎𝑝 (10) where ap represents the number of strands per conductor. assuming an insulation thickness of ti = 0.021mm, the diameter of the wire is obtained as: 𝑑𝑤 = 𝑑𝑐 + 2𝑡𝑖 (11) to determine the shape and dimensions of the stator slot, first a trapezoidal shaped stator slot was selected. see fig. 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com peretomode and eyenubo: comparative study of two stator designs for the international electrotechnical commission 100 motor frame for 2.2kw squirrel cage induction motor. azojete, 19(2):401-408. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 405 fig. 1: the adopted stator slot and its parameters the useful slot area, 𝐴𝑠𝑢 = 𝜋𝑑𝑤 2 𝑎𝑝𝑛𝑠𝑐 4𝐾𝑓𝑠 (12) the stator slot pitch is obtained from 𝜏𝑠𝑠 = 𝜏 3𝑞 (13) assuming all the air gap flux passes through the stator teeth, and assuming that the lamination insulation thickness factor is kil = 0.96, bos = 2mm, hos = 0.68mm, and hw = 1.32mm, then: 𝑏𝑡𝑠 = 𝐵𝑔𝜏𝑠𝑠 𝐵𝑡𝑠𝐾𝑖𝑙 (14) 𝑏𝑠1 = 𝜋(𝐷𝑖𝑠+2(ℎ𝑜𝑠+ℎ𝑤)) 𝑁𝑠 − 𝑏𝑡𝑠 (15) 𝑏𝑠2 = √𝑏𝑠1 2 + 4𝐴𝑠𝑢 tan 𝜋 𝑁𝑠 (16) ℎ𝑠 = 2𝐴𝑠𝑢 𝑏𝑠1+𝑏𝑠2 (17) it was explained in (boldea and nasar, 2010) and (konstantinos and joya, 2013) why the selection of the number of rotor slots must be done with care, the reason including to reduce parasitic torque, noise, vibration, and additional losses and radial forces. again, it is desired for the purpose of this study to use the same rotor for the two stator configurations. hence, a 30-slot rotor was selected. 3.0 results and discusion the above equations were very helpful in providing the data for the rmxprt simulation of the two motors. the simulation produced many results, but only the important indices relevant for a good comparison are presented in table 3. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):401-408. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 406 table 3: simulation results s/n name unit 24-slot stator im 36-slot stator im rated performance 1 stator ohmic loss w 193.222 194.212 2 rotor ohmic loss w 127.968 121.035 3 iron core-loss w 54.4832 57.612 4 frictional and windage loss w 7.76543 7.7882 5 stray loss w 67.14 67.14 6 total loss w 450.579 447.787 7 output power w 2237.91 2238.02 8 input power w 2688.49 2685.80 9 efficiency % 83.2405 83.3276 10 power factor 0.875928 0.874546 11 rated torque n-m 15.0589 15.0155 12 rated speed rpm 1419.13 1423.29 13 slip 0.0539121 0.0511378 material consumption 14 total net weight kg 12.4392 12.3671 15 armature core steel consumption kg 13.38 13.38 16 rotor core steel consumption kg 5.49159 5.49159 breakdown operation 17 breakdown slip 0.43 0.46 18 breakdown phase current a 18.6024 20.0795 19 breakdown torque n-m 41.8549 44.7692 20 breakdown torque ratio 2.77942 2.98153 rated electric data 21 stator phase current a 4.31953 4.32192 22 rotor phase current a 3.86673 3.78456 23 armature thermal load a2/mm3 142.916 143.074 there are a few bases to expect different performance outcomes from the iec 100 frame made with either 24-slot stator or 36-slot stator. in the first place, apparently, the number of slots per pole per phase, q is 2 and 3 for the 24-slot and 36-slot stator designs, respectively. and one would have expected that higher q values would result in better winding function and mmf waveforms, that is, more sinusoidal in shape, resulting in better efficiency and power factor. hence, one would expect the 36-slot stator to perform better than the 24-slot stator in this respect. but a look at the harmonic contents of the winding functions of the two stators shows a departure from this expectation (see fig. 2). the methods used by onwuka et al (2015) was employed. due to half-wave symmetry, only odd harmonics are present. the fundamental component of the 24-slot stator is 88.5293, while that of the 36-slot stator is 87.9786, which gives some minor performance advantage due to higher flux linkages to the 24-slot stator as seen file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com peretomode and eyenubo: comparative study of two stator designs for the international electrotechnical commission 100 motor frame for 2.2kw squirrel cage induction motor. azojete, 19(2):401-408. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 407 in table 3. however, the total harmonic disorder of the winding function for the 24-slot stator is higher than that for the 36-slot stator, which also reduces the leakage inductance of the later, giving it some advantage over the former. clearly, there is a levelling up, and hence only marginal difference exists in their rated performance. (a) (b) fig. 2: winding function for the (a) 24-slot stator, and (b) 36-slot stator from the results of table 3, the most important difference in performance is in the rotor ohmic loss, which resulted in a better efficiency for the 36-slot stator than for the 24-slot stator. all other variables returned negligible differences. with electricity tariff at n68.30/kwh, the induction motors with the 24-slot and 36-slot stators would be operated at a cost of n687, 487.76 and n686, 799.88 in a year of 12 months with 26 days/month and 12 hours/day, respectively, resulting in a savings of n687.88 per year in favour of the 36-slot stator motor. however, some of this cost would have gone into punching extra slots in the laminations of the 36-slot stator during manufacturing. the extra material consumption seen in the 24-slot stator is actually negligible. however, the breakdown operation of the 36-slot stator was better than that of the 24-slot stator, albeit, marginally. the stator slot area of the two stators are in the ratio of 2/3, as also is their conductors per slot. so the slot depth of the 24-slot stator is larger than the slot depth of the 36-slot stator, while their slot opening width are equal. it is commonly known that decreasing the slot depth decreases the stator and rotor leakage reactances, which in turn increases the breakdown torque. the 36-slot motor has a better overload capacity, and more rugged, even though it is marginally so. 4.0 conclusion the results of this study show that both the 24-slot stator and the 36-slot stator used in the iec tefc 100 frame for 3hp induction motors are good options, both of them, as the differences in their performance and operation are marginal. more specifically, the 36-slot stator design is marginally more robust and has a better overload capacity than the 24-slot stator design. it also out-performed the 24-slot stator in terms of operating cost. the higher thermal load associated with the 36-slot stator wouldn’t need any special design adjustment nor incur more production costs as the same fan can achieve the cooling of the two induction motors produced with the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):401-408. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ifeanyikayonwuka@gmail.com 408 two stators under study. it is important to mention that in terms of production, the 24-slot stator is easier and cheaper to manufacture. therefore, the choice of manufacturing the iec 100 tefc motor for 3hp with either 24-slot stator or with 36-slot stator is not a difficult one to make, as the results are quite similar. references abb. 2007. low voltage motors: basics of iec motors. baldor electric company, fort smith, usa. abb. 2022. 2022 baldor-reliance 501 standard motor catalog. baldor electric company fort smith, usa. asgharpour-alamdari, h. 2022. design of a novel distributed winding for improving performance of the induction motors. electr eng 104: 2911–2922 (2022). https://doi.org/10.1007/s00202-02201516-5 boldea, i. and nasar, sa. 2010. the induction machine design handbook second edition. crc press, taylor and francis group llc, boka raton, usa. c3controls. 2023. nema and iec motors: how to select the best choice for your needs. https://www.c3controls.com/white-paper/nema-vs-iec-motor-controls/ retrieved on 12th april 2023. challenge power transmission 2023. 2023 catalogue. https://en.challengept.com/three-phaseelectric-motor-2-2kw-4-pole-with-b3-mount-ie1-eml-100l1-4.html retrieved on 12/06/2023. gundogdu, t., zhu, zq. and mipo, jc. 2017. influence of stator slot and pole number combination on the rotor bar current waveform and performance of induction machines. 20th international conference on electric machines and systems (icems), 11 – 14 august, sydney, nsw, australia, pp 1 – 6, doi: 10.1109/icems.2017.8055937. jawad, mh. and greulich, or. 2018. primer on engineering standards, expanded textbook edition. wiley – asme press series, john wiley & sons ltd., new york. konstantinos, ng. and joya, k. 2013. the impact of the rotor slot number on the behaviour of the induction motor. advances in power electronics, 2013: article id 837010., http://dx.doi.org/10.1155/2013/837010. mittle, vn. and mittal, a. 2018. design of electrical machines. standard publishers distributors, new delhi, india. onwuka, ik., uma, uu. and diyoke, gc. 2015. analysis of a 2-phase stator winding by winding function methodology. iosr journal of engineering, 05(03): 11-15. pyrhonen, j., jokinen, t. and hrabovcova, v. 2008. design of rotating electrical machines. john wiley and sons ltd, united kingdom. teco catalogue 2013. https://www.teco.com.au/getmedia/f772f6b7-b26b-4d12-a21c99adea1084af/teco-catalogue-te3-072019.pdf?ext=.pdf, retrieved on 12/06/2023 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/ifeanyikayonwuka@gmail.com https://doi.org/10.1007/s00202-022-01516-5 https://doi.org/10.1007/s00202-022-01516-5 https://www.c3controls.com/white-paper/nema-vs-iec-motor-controls/ https://en.challengept.com/three-phase-electric-motor-2-2kw-4-pole-with-b3-mount-ie1-eml-100l1-4.html%20retrieved%20on%2012/06/2023 https://en.challengept.com/three-phase-electric-motor-2-2kw-4-pole-with-b3-mount-ie1-eml-100l1-4.html%20retrieved%20on%2012/06/2023 http://dx.doi.org/10.1155/2013/837010 https://www.teco.com.au/getmedia/f772f6b7-b26b-4d12-a21c-99adea1084af/teco-catalogue-te3-072019.pdf?ext=.pdf https://www.teco.com.au/getmedia/f772f6b7-b26b-4d12-a21c-99adea1084af/teco-catalogue-te3-072019.pdf?ext=.pdf arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):491-508 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 491 hate speech identification in west africa, using machinelearning techniques a. a. sosimi1, o. ipinnimo1, c. o. folorunso1*, b. a. adim1, e. onoyom-ita2 1department of system engineering, university of lagos, lagos, nigeria 2department of electrical and electronics engineering, university of cross river state, idim ita, calabar, nigeria *corresponding author's email address: cfolorunso@unilag.edu.ng article information submitted 19 january, 2024 revised 25 february, 2024 accepted 25 february, 2024 keywords: hate speech machine learning natural language processing (nlp) social media abstract the tremendous rise in social media usage over the past ten years has resulted in an extraordinary spike in hate speech activities in west africa. because of this, her unity is constantly in peril. this study combines relevant natural language processing techniques and machine learning classifiers to create a hate speech detection model using hate speech from west african countries, including pidgin english, on twitter, now ‘x’. the data was pre-processed using word embedding, countvectorizer, and term frequencyinverse document frequency (tf-idf) to extract useful characteristics from the cleaned dataset. five machine learning classifiers were used to train the dataset, these include logistic regression (lr), naïve bayes (nb), extreme gradient boost (xgboost), deep neural network (dnn), and bidirectional long and short-term memory (bi-lstm). the bi-lstm fitted on global vectors (glove) embedding produced the best experiment results, with an accuracy of 92% and an f1-score of 83% when assessed on a test set. the machine learning models generally demonstrated strong performance on test data, suggesting that they had internalised the knowledge from the training set and could use it to analyse new data. 1.0 introduction hate speech is becoming a bigger problem across the globe, especially in west africa. the widespread use of social media and other digital platforms has made it easier for hate speech to spread quickly, escalating tensions and endangering national and local unity. hate speech has been shown to widen differences between various ethnic, religious, and social groups and to inspire violence in west africa as well as other regions of the world (laub, 2019). this phenomenon can be especially unstable in nations where the population is heterogeneous and intergroup conflicts have historically occurred. in west africa, efforts to combat hate speech frequently combine legislative actions, such as passing legislation prohibiting it, with educational programmes designed to foster tolerance, understanding, and respect for variety. furthermore, community-based initiatives and forums for discussion can be extremely important in promoting improved social cohesiveness and lessening the negative effects of hate speech. coordination of reactions to hate speech and the encouragement of regional collaboration in tackling this issue may also be the responsibilities of regional organisations such as the economic community of west african states (ecowas) (daka, 2023). in recent years, hate speech in west africa has intensified tensions and posed a serious threat to unity in the continent (akanji, 2017). this has prompted the government to think about http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 492 passing laws that will punish anyone discovered to have used hate speech (asogwa and ezeibe, 2022). for instance, in nigeria, the national commission for the prohibition of hate speech was created to assist with investigations and criminal prosecutions (independent national commission, 2019). it is much simpler to keep an eye on the hate speech that appears in traditional mainstream media like television, radio, and print than it is to keep an eye on online, on sites like social media and microblogging services. this is mostly caused by the significant amount of daily content produced in internet media that needs to be checked. global efforts are also being made to address online hate speech as it develops and broadens. the 2019-launched united nations strategy and plan of action against hate speech serves as a prime illustration (machirori, 2022). however, security authorities were given the authority to monitor the conversations and posts of well-known social media users as part of the process of holding hate mongers to account due to the escalating incidences of online hate speech and the associated concerns it poses to national security (opusunju, 2018). hate speech is proliferating alongside the growth of online information. unfortunately, hate speech is nothing new in our culture. however, social media and other online communication tools have increased the prevalence of hate speech to alarming levels, fuelling a range of hate crimes and other social evils. social media's anonymity and movement make it difficult to identify suspects since some users hide under aliases and bogus addresses, which makes it easy for them to procreate and disseminate hate messages. social media on the other hand, refers to a new generation of tools that individuals can use to interact with information and share it. these technologies include computers, smart phones, and text messaging capabilities on mobile devices (auwal, 2018). applications exist that naturally create interactive connections between people and information. so many researches have been carried out on hate speech. for instance, (asogwa and ezeibe, 2022) looked at how state regulation of hate speech affects the development of sustainable democracy in africa. they argued that state regulation of hate speech presents an opportunity for fostering order, advancing national cohesion, reducing hate speech, and promoting inclusive governance for all, regardless of age, sex, disability, race, ethnicity, origin, religion, and economic status. this was achieved by using the qualitative dominant mixed methods approach and data generated from nigeria and kenya. the article concluded that in order to reduce hate speech and the harms it causes as well as to advance sustainable democracy in africa and beyond, it is important to enact laws against it in addition to alternative non-legal, dialoguebased, egalitarian, voluntary approaches. in addition, sunday (2020) addressed extremism, hate speech, and false news in the social media age in west african communities. he considered the non-sahel region of west africa, which includes benin, cote d'ivoire, ghana, guinea, liberia, nigeria, sierra leone, and togo, as case studies. he noted that unscrupulous propagandists and mischief-makers are using extreme ideas and actions, fake news, and hate speech to spread false, disparaging, and divisive information that impedes the socio-political and economic development of the region and to incite fear and ethnic and religious crises. in essence, the study suggested potential solutions to the dis-infodemic as it impacts the chosen nations. the research evaluates how active social media users cannot avoid the direct effects and influence of social media, and by extension, mass media, using the notion of magic bullet to construct the analyses. the study employed the quantitative approach to produce a list of doable actions to combat the disinformation epidemic. these actions include creating a fact-checking algorithm, requiring media professionals with training to combat misinformation with facts, and requiring media information literacy to be taught in schools. moreso, chukwuebuka (2015) investigated the impact of hate speech on violence in nigeria before, during, and following elections. the study was based on interviews with leaders of civil file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 493 society organisations, student leaders, religious leaders, and traditional leaders who were chosen from nigeria's six geopolitical zones. the information gathered from the interview was enhanced by secondary data and observation. discourse and content analysis were also used. the author made the following claim that political leaders and their supporters who are based on ethnicity, region, or religion are mostly responsible for hate speech in nigeria. as long as hate speech helps nigerian political leaders seize and hold onto power, they ignore its inflammatory characteristics. the paper suggested that simply denouncing hate speech verbally is insufficient. however, the nigerian rules governing public speech and electoral campaigns should be enforced against persons and organisations that violate them, according to the independent national electoral commission and other civil society organisations. furthermore, ojakorotu et al. (2019) investigated the degree to which the dissemination of hateful and harmful utterances on social media poses a threat to nigerian security. they presented a precise conceptual clarification of the phrases "hazardous" and "hate speech" due to the conceptual ambiguity of hate speech. additionally, it was stated that dangerous statements put people and organisations at risk of violence. they found out that hate speech can divide and belittle people, and that it can also set off dangerous reactions that may eventually result in bloodshed. they concluded that hate speech and harmful communication should be restricted in nigerian online because they both encourage unhealthy competition and make victims and target groups feel less safe. also, ngwainmbi (2021) discussed the sociology of hate speech, which makes the argument that hate speech is a by-product of racism, which took over our world when humans first entered the cosmos. it examines various racial philosophers' conceptions of national space and identifies modern media as the primary global advocate of caucasian nationalism. they demonstrated how anti-other attitudes and a certain egocentric pro-nationalist agenda are fostered among caucasian groups in the global north, particularly in germany and america, using social media data and information technology (it) platforms. convinced by sigmund freud's claim that unconscious conflicts nearly usually drive violent behaviour in people. the way that people with diverse racial, ethnic, sexual, gender, or other combinations are portrayed in the media is explained by the concepts of reverse psychology and group communication. they identified global initiatives to prevent hate speech and reveals how media firms and governments can manage hate speech. they concluded that hate speech is a threat to world peace and demonstrated that counter speech is a better approach of stopping hate speech's dignitarian harm furthermore, rasaq et al. (2017) used a critical discourse analysis method to demonstrate how common hate speech is in nigeria, especially in light of the country's 2015 general election, which may have resulted in a wave of violence. it is evident from the debate that hate speech served as the campaign's main focus and tool. as a result, the parade of hate speech found in a number of the publications under analysis demonstrated how politicians exploited the media to incite violence and hatred between various ethnic and political groupings both in the run-up to elections and in everyday life. they concluded that in order to avoid supporting hate speech, media organisations should constantly analyse the messages that politicians convey, evaluate the language that they use, carefully consider the facts and claims that they make, and assess the intention and potential influence on society. in addition, garbe et al. (2023) applied structural topic modelling on a corpus of news items worldwide (n = 7,787) mentioning hate speech and fake news in 47 african nations to estimate the significance of debates of legislative and technological approaches to content regulation. they discovered that, in particular, governments with less regard for media freedom and less legislative restraints tend to prioritise discussions of technology strategies. their findings highlighted the need for a deeper comprehension of how regime-specific factors influence http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 494 regulatory decisions and indicate that the state is the primary factor influencing content regulation among african nations. moreover, elliott et al. (2016) presented a key concept paper on hate speech which discusses the following: a comprehensive talk about the relationship between hate speech and freedom of speech; a quick look at worldwide laws and definitions of hate speech; a quick look at hate speech in the media conflict and democratisation ( mecodem) project countries which include: south africa, kenya, serbia, and egypt. 1.1review of hate speech in some west african countries 1.1.2. hate speech in the republic of benin in the republic of benin, using hate speech is a serious offense, and there are laws in place to penalise offenders. although the country's constitution provides freedom of speech and the press, it also outlaws hate speech and violent provocation. benin's government enacted legislation in 2018 making hate speech illegal, with jail term and fines as possible penalties. a statement or action that "expresses or incites hatred, discrimination, or violence against a person or group of persons on the basis of their origin, ethnicity, religion, race, gender, or sexual orientation" is referred to as hate speech under the law (sunday, 2020). 1.1.3 hate speech in côte d'ivoire in the republic of cote d'ivoire, hate speech is an important problem. more than 60 different ethnic groups make up the population of the nation, and in the past, conflicts between these groups have resulted in violent outbursts. hate speech has increased in frequency during the past few years, especially on social media platforms. the ivorian government has taken action in response to the threat that hate speech poses. a law was established in 2019 that makes hate speech and other types of hate crimes illegal. if someone is found guilty of using hate speech, the law offers prison terms and penalties (sunday, 2020). 1.1.4 hate speech in ghana in ghana, hate speech is a significant problem that can result in violence, discrimination, and other types of harm. the freedom of expression is guaranteed by ghana's constitution; however, it is not unrestricted and may be limited to protect others from harm. the criminal offences act, 1960 (act 29) and the internet transactions act, 2008 (act 772) both make certain forms of hate speech illegal, and the ghanaian government has taken efforts to combat it. additionally, the national media commission (nmc) has the authority to impose sanctions on media outlets that disobey its standards on responsible journalism (ghana news agency, 2011). 1.1.5 hate speech in nigeria in nigeria, hate speech is a severe problem that has persisted for a long time. any phrase or conduct intended to incite violence or discrimination against a particular person or group of people based on their identity, such as their race, religion, ethnicity, or sexual orientation, is referred to as hate speech. political, religious, and ethnic unrest in nigeria has generated hate speech, which has also been amplified by the growth of social media outlets. politicians have used hate speech to rally their supporters and further their political interests, while religious and ethnic leaders have employed it to incite hatred and hostility among their adherents (williams, 2020). the hate speech bill, which makes hate speech illegal and imposes severe penalties on offenders, was passed by the nigerian government in 2019 as part of its efforts to combat hate speech in the nation. however, some have criticised the measure for having the ability to suppress free speech and for having ambiguous definitions of what constitutes hate speech. human rights organisations and civil society organisations have also been trying to promote tolerance and respect for diversity as well as to increase public awareness of the hazards of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com http://www.mecodem.eu/ sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 495 hate speech. there have also been requests for media outlets to report on delicate topics responsibly and without sensationalising them (asogwa and ezeibe, 2022). in summary, in all the literature reviewed, no work was carried out on the use of a machine learning classifier and pertinent natural language processing techniques to build a hate speech detection model. hence, the objective of this paper is to present a hate speech identification system using machine learning. hate speech was identified on twitter, now ‘x’, solely taking into account tweets using hate words that are conveyed in west african english and pidgin english. the use of slang, memes, audio, and video in tweets was not taken into account. a new dataset was created between november 2019 and april 2020, by gathering tweets from twitter that contained frequent hate speech used in west africa. the tweets were then divided into two categories: hate and non-hate speeches. 2.0 materials and methods this study focuses on combining relevant natural language processing techniques and machine learning classifiers to create a hate speech detection model using hate speech from west african countries, including pidgin english, on twitter. the flow diagram for the methodology is presented in figure 1. figure 1: methodology flow process 2.1 dataset description/data collection using twitter's api, the dataset used in this study was generated from twitter. the tweets were selected from twitter users who used terms from peacetech lab's list of terms associated with hate speech in their replies between november 2019 and april 2020. this was accomplished by first creating a twitter developer account, after which an api id and an api token were obtained in order to scrape the twitter api. the generated data was saved in microsoft excel format. data cleaning and analysis was carried out to get a clean dataset used for this study. 2.2 pre-processing text data is unreliable and usually contains a lot of noise. removing irrelevant information from the data is a crucial step in order to reduce the possibility of dealing with noisy or inconsistent data. information such as punctuation, special characters, numerals, and terms with minimal meaning within the text context are removed in order to prepare the raw text for mining. pre-processing's main objective is to prepare data for use by machine learning algorithms. a well pre-processed classifier performs better and is more efficient. in addition, data collection pre-processed dataset cleaning, removal of noise and inconsistent data train-test set feature construction and weighting training of a classification model feature extraction training set testing training test set prediction model classification result data analysis and label http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 496 it requires less time to train and yields a feature space with higher quality during features extraction. initially 28,000 tweets were collated but after various pre-processing stages were carried out on the tweets, a total of 20,176 cleaned tweets were generated. the following methods are used in the pre-processing steps: 2.2.1 removal of twitter handles (@user): the twitter accounts that were concealed as @user because of privacy issues were taken down as they don't say anything about the substance of the tweet. 2.2.2 removal of punctuations, numbers, and special characters: numbers, punctuation, and even special characters were eliminated since they were ineffective in distinguishing between different types of tweets. hashtags with spaces, however, were kept since they offer some helpful information. 2.2.3 removal of short word: the majority of the lesser terms are not very valuable. words like "he’, "is”, "it”, and "a", for instance, that had two (2) letters or fewer were eliminated from the data. 2.2.4 removal of urls and html tags: since they don't provide any value and we don't want the classifier to pick up features from these tokens, urls and html tags were eliminated. 2.2.5 removal of random patterns (randos): because they are irrelevant for training models, any leftover patterns that may have developed or remained throughout the data cleaning process are likewise eliminated. 2.2.6 changing all letters to lowercase: this is to prepare the unprocessed text for extraction. 2.2.7 tokenization: to protect the tweets, they are divided into individual words or tokens. 2.2.8 lemmatization: in this case, words with suffixes like "ed", "ing”, "ly”, "es”, "er" and "s" were eliminated. examples of distinct word variations used in the same context are "kill”, "killer", "killed", "kills", and "killing." reducing the overall number of unique words in our data while retaining a substantial quantity of information is the aim of stemming. 2.3 feature extraction methods feature extraction, the process of selecting and/or combining variables to create features, greatly minimises the amount of data that must be processed while accurately and completely characterising the original dataset. pre-processed data needs to be turned into features in order to be analysed with techniques that minimise dimensionality and superfluous features. three feature extraction methods were used in this study, they are: term frequency-inverse document frequency vectorizer (tfidfvectorizer), countvectorizer and global vectors (glove) embedding. 2.3.1 term frequency-inverse document frequency vectorizer (tfidfvectorizer) 2.3.1.1 term frequency (tf): term frequency is the total frequency of a phrase in a given document. thus, it is unique to a document and it is represented by equation (1) (unnikrishnan, 2021), tf(t) = count of instances of term in a document (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 497 2.3.1.2 inverse document frequency (idf): idf value indicates how common or uncommon it is within the whole corpus of documents. it appears in every document. the normalised idf value of a word will approach 0 if it is frequent and appears in a lot of texts, and it will approach 1 if it is unusual. equations (2) and (3) shows idf formula for default behaviour, that is when idf is ‘true’ and for when idf equals “false” respectively (unnikrishnan, 2021), (2) (3) 2.3.1.3 term frequency-inverse document frequency (tf-idf): the tf-idf value in a document is equal to the aggregate of its tf and idf. the more relevant the term is in that document, the higher its tf-idf value (unnikrishnan, 2021). the ‘tfidfvectorizer’ class of the sci-kit learns package was used in this study to create tf-idf features extraction methods in order to extract word tf-idf from unigram to trigram, with a minimum document frequency of three (min_df =3). unicode, which removes accents from any character, was selected for accent removal (strip_accents ='unicode'). 2.3.2 countvectorizer: a class in scikit-learn creates a matrix of token counts from a set of text documents. it converts textual data into a numerical representation that machine learning algorithms may use (pratyaksh, 2021). n-gram words spanning from unigram to trigram were extracted using the sci-kit-learns package to execute countvectorization. unwanted terms were added to the countvectorization stop list, which already contained a list of english stop words (stop_words = 'english'). 2.3.3 global vectors (glove) embedding: glove learns vector representations in a highdimensional space with the goal of capturing the semantic meaning of words. based on the global statistics of word co-occurrences in a sizable corpus of text, these representations are learned. glove directly optimises a global objective function that aggregates word cooccurrence statistics over the entire corpus, in contrast to several other word representation techniques (such as word2vec). glove's main tenet is that one may deduce a word's relationship from the distributional data of its co-occurrences. since words with comparable meanings are likely to come together in similar circumstances, their vector representations should also be similar (ganegedara, 2019). the keras package was used to implement the glove embeddings. 2.4 train and test set the machine learning model is trained using 18,158 (90%) data from the dataset. while a 2,108 (10%) data was used to assess how well the trained model performs. the input data and matching target labels make up the test set as well, but the model's predictions based on this data are evaluated for accuracy, precision, recall, f1 score, and other performance metrics by comparing them to the true labels. 2.5 model 2.5.1 logistic regression (lr) classifier a logistic function is used as the principal means of designating a binary dependent variable in statistical representations called logistic regressions. lr seeks to establish a relationship between a group of independent variables and the result by applying an appropriate model. the confidence of an outcome in the lr model is estimated using the logistic function q(x), which is reliant on independent factors. the logistic function, also known as the sigmoid function, produces an output in the interval [0,1], which is frequently expressed as a probability, given real values as input. the outcome demonstrates the validity of the model in http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 498 the categorization, with values closer to 0 denoting the other class and values closer to 1 designating the first class (sperandei, 2014). the expression is shown in equation (4), 𝑄(𝑥) = 1 1 + 𝑒−𝑥 (4) 2.5.2 naïve bayes classifier the naïve bayes classifier is a simple and efficient classification method that is used to quickly build machine learning systems with predictive capabilities. this supervised learning approach is mostly used for text classification using a large-scale training dataset. it is a probabilistic classifier that is used to solve classification issues. it is based on the bayes theorem, as demonstrated in eq. (5). given a sample's set of feature values, the bayes theorem generates likelihood to assess the likelihood that the sample belongs to a specific class (yang, 2018). 𝑃(𝐴|𝐵) = 𝑃(𝐵|𝐴)𝑃(𝐴) 𝑃(𝐵) (5) the bayes theorem states that there is a chance that a will occur when b does. in this case, b is the proof, while a is the hypothesis. it is assumed that the features/predictors in this case are independent. that's why it's referred to be naïve—the existence of one particular quality does not interfere with the other. the parameters/features of size ‘n’ are represented by variable b. 2.5.3 extreme gradient boost (xgboost) the gradient boosting framework is used by extreme gradient boost (xgboost). the goal of this supervised learning technique, which is based on decision trees, is to accurately predict a target variable by combining the predictions of several simpler, less accurate models. when it comes to prediction tasks involving unstructured data, artificial neural networks (anns) typically beat out all other methods. nevertheless, decision tree-based algorithms are considered to be very good for small-to-medium structured/tabular data prediction issues. xgboost is a supervised learning strategy that uses a variety of regularisation techniques along with function approximation through optimisation of particular loss functions (aydin & ozturk, 2021). the objective function (also known as the loss function and regularisation) of xgboost at iteration ‘t’ can be expressed mathematically as shown in equation (6) 𝐿(𝑡) = ∑ 𝑙 (𝑦𝑖, ŷ𝑖 𝑡=1 + 𝑓𝑡(𝑥𝑖)) + ω(𝑓𝑡) 𝑛 𝑖=1 (6) 2.5.4 deep learning deep learning is a branch of machine learning that uses artificial neural networks (anns) to simulate how the human brain works to solve complex data-driven problems. artificial neural networks (anns) are devices designed to simulate how a human brain might do a certain task or function. the term "deep learning" originated in the early 2000s when advances in computer development and skill training made it possible to train even larger and deeper networks (biere, 2018). prior to then, nlp techniques were dominated by machine learning techniques that used linear models that were learned over high dimensional but extremely sparse feature vectors. non-linear neural networks have shown remarkable effectiveness recently when used with dense inputs. when used to hate speech and related fields like sentiment analysis, deep learning techniques have been shown to yield the greatest results (hemker, 2018). there are two categories of neural networks: recurrent (kadlaskar, 2021) and feedforward neural networks (example: deep neural networks) (kyrykovych, 2020). 2.5.5 bidirectional long short-term memory (bi-lstm) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 499 regular lstms are continued into bidirectional lstms, which can improve model performance on sequence classification tasks. the extraordinary rnns known as long short-term memory (lstm) networks are able to overcome the drawbacks of conventional rnns. the most basic building blocks of lstm networks are memory cells. three gate units, which extract or input information into the memory cell state and maintain temporal information, are present in memory cells. in situations where every step of the input sequence is available, bidirectional lstms train twice on the input sequence instead of just one lstm. while the second input sequence is trained as the inverse of the first, the first is taught in the original form of the input sequence. this can help the network learn the problem more quickly and thoroughly since it gives it additional context (aggarwal, 2019). 2.6 evaluation metrics metrics are often used in evaluating the performance of classification model. these measures values such as true positives (tp) which represent the number of correctly classified positive instances. true negatives (tn) denote the number of correctly classified negative instances. false positives (fp) mean the number of incorrectly classified positive instances, while false negatives (fn) are the same for negative instances. tp, tn, fp, and fn help to find the precision (equation (7)), recall (equation (8)), f1 -score (equation (9)) and accuracy (equation (10)) of a system (brownlee, 2020). 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 = 𝑡𝑝 𝑡𝑝 + 𝑓𝑝 (7) precision measures the ability of the classifier to correctly label samples. 𝑅𝑒𝑐𝑎𝑙𝑙 = 𝑡𝑝 𝑡𝑝 + 𝑓𝑛 (8) recall measures the ability of the classifier to find all the relevant samples. 𝐹1 = 2 𝑅𝑒𝑐𝑎𝑙𝑙 . 𝑃𝑟𝑒𝑐𝑖𝑡𝑖𝑜𝑛 𝑅𝑒𝑐𝑎𝑙𝑙 + 𝑃𝑟𝑒𝑐𝑖𝑡𝑖𝑜𝑛 (9) f1-score is used for a better overall evaluation of the classifier performance. 𝐴𝑐𝑐𝑢𝑟𝑎𝑐𝑦 = 𝑡𝑝 + 𝑡𝑛 𝑡𝑝 + 𝑓𝑝 + 𝑓𝑛 + 𝑡𝑛 (10) accuracy measures the total correct predictions as a percentage of the total instances. 2.6.1 confusion matrix a confusion matrix is a tool used to gauge how successful a classification programme is. count values are used to quantify the proportion of accurate and inaccurate forecasts, broken down by class. the classifier's errors and their categories are displayed in the matrix. it is a performance metric for classifying problems in machine learning, where the result can belong to two or more classes. four distinct combinations of the actual and anticipated values are shown in a table. two classes are the study's output. (11) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 500 3. results and discussion the outcome of the dataset after the pre-processing is shown in table (1). the two class datasets utilised to build the classification model were hate speech (hs), which is the positive class with label 1, and non-hate speech (nhs), which is the negative class with label 0. the experiment was analysed using three different features extractors: glove embedding, tf-idf, and countvectorizer. table 1: first five rows of dataset, before and after cleaning b'id' b'message' raw data b'message' clean data b'polarity' 1 @user @user @user problem is you\'re not important to arabs as usa / israel, the same people u call "arne".\n\nsuch a shame arabs considers arnes worthy of their respect than "northern nigeria" problem youre not important arabs usa israel the same people call arne such shame arabs considers arnes worthy respect than northern nigeria 1 2 dss arrests creator of video depicting a fake buhari marriage https://t.co/bdqrwx6elv #thetrent https://t.co/atfu2ps0jq dss arrest creator video depict fake buhari marriage 0 3 @user may god punish you and your almajiri generations for reminding us of this pain of brain dead man. may god punish you and your almajiri generation for remind this pain brain dead man 1 4 "how are there up to five 'truckfuls' of almajiri in cross river state??? https://t.co/f3wp5fmvr1" how are there five truckful almajiri cross river state 0 5 "# fulani graduated and train # criminals the best thief all over the world stealing biafrans money # nigeriathezoo # nigeriathezoo # nigeriathezoo # nigeriathezoo don't forget to ask google who country is a zoo # nigeria @user @user @user @user @user https://t.co/o73fxgzpux" fulani graduate and train criminals the best thief over the world steal biafrans money nigeriathezoo nigeriathezoo nigeriathezoo dont forget ask google who country zoo nigeria 1 five different machine learning models were used, namely: logistic regression (lr), naïve bayes (nb), extreme gradient boost (xgboost), deep neural networks (dnn), and bidirectional long short-term memory (lstm). the performance metrics used in this study to evaluate the models are accuracy, precision, recall, f1 score and the confusion matrix. the accuracy of all models is shown in table 2, while the precision scores are presented in fig. (2). in addition, the recall and f1 score are presented in table 3 and fig. (3) respectively. while the confusion matrix of each model according to the feature extractor used to fit the model are shown in figures (4) to (8) respectively. table 2: accuracy scores of all the models models tf-idf (%) countvec (%) glove (%) lr 86 87 nb 83 68 xgboost 87 87 dnn 90 90 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com https://t.co/atfu2ps0jq sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 501 bi-lstm 92 according to table 2, bi-lstm with glove embeddings produced the best accuracy of 92% followed by dnn with 90% on both tf-idf and countvectorizer feature extractors. additionally, xgboost performed well on tf-idf vectorizer and countvectorizer, scoring 87% respectively. with the countvectorizer feature extractor, nb obtained the lowest accuracy score of 68% out of all the states. figure 2: precision scores for all the models with a precision score of 0.81 the nb model on countvectorizer outperformed the bi-lstm model, which came in second with 0.74 on glove embedding as shown in fig. (2). additionally, dnn scored well on tf-idf and countvectorizer, with precision values of 0.71 and 0.70 respectively. however, nb model obtained the lowest precision scores of 0.35 on countvectorizer. table 3: recall scores of all the models models tf-idf countvec glove lr 0.88 0.82 nb 0.81 0.41 xgboost 0.83 0.84 dnn 0.72 0.70 bi-lstm 0.95 table 3 demonstrates that on glove embedding, bi-lstm had the maximum recall of 0.95. with respect to the tf-idf and countvectorizer feature extractors, lr also shown strong recall performance, scoring 0.88 and 0.82 respectively, while xgboost demonstrated similar recall performance, scoring 0.83 and 0.84 respectively. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 logistic regression naïve bayes xgboost dnn bi-lstm precision scores of classification model tf-idf countvectorizer glove embedding http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 502 figure 3: chart showing f1-scores of all the models from figure 3, bi-lstm on glove embedding achieved the best performance with f1scores of 0.83, followed by dnn with f1-scores of 0.71, and 0.70 on both tf-idf and countvectorizer feature extractors respectively. nb had the worst performance on both tf-idf and countvectorizer feature extractor with 0.49 and 0.54 respectively. tf-idf countvectorizer figure 4: confusion matrix logistics regression (lr) model based on extracted features figure (4) illustrates the confusion matrix of lr model. lr with tf-idf classify 232 samples as hs and 1505 samples as nhs correctly, and also 248 samples of hs and 33 samples of nhs were misclassified. lr with countvectorizer classify 280 samples of hs and 1476 samples of nhs correctly while 200 samples of hs and 62 samples of nhs were incorrectly classified. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 logistic regression naïve bayes xgboost dnn bi-lstm f1-scores of classification model tf-idf countvectorizer glove embedding p r ed ic te d v a lu es n h s (0 ) 232 248 33 1505 hs (1) h s (1 ) nhs (0) actual values p r ed ic te d v a lu es n h s (0 ) 280 200 62 1476 hs (1) h s (1 ) nhs (0) actual values file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 503 tf-idf countvectorizer tf-idf countvectorizer figure 5: confusion matrix naïve bayes (nb) model based on extracted features figure (5) illustrates the confusion matrix of nb model. nb with tf-idf correctly classify 170 samples as hs and 1499 samples as nhs, and also 310 samples of hs and 39 samples of nhs were wrongly classified. nb with countvectorizer classify 387 samples of hs and 977 samples of nhs correctly while 93 samples of hs and 561 samples of nhs are incorrectly classified. tf-idf countvectorizer figure 6: confusion matrix extreme gradient boost(xgboost) model based on extracted features figure (6) illustrates the confusion matrix of xgboost model. xgboost with tf-idf classify 265 samples as hs and 1484 samples as nhs correctly, and also 215 samples of hs and 54 samples of nhs were misclassified. xgboost with countvectorizer correctly classify 268 samples as hs and 1486 samples as nhs and wrongly classify 211 samples as hs and 52 samples as nhs. p r ed ic te d v a lu es n h s (0 ) 170 310 39 1499 hs (1) h s (1 ) nhs (0) actual values p r ed ic te d v a lu es n h s (0 ) 387 93 561 977 hs (1) h s (1 ) nhs (0) actual values p r ed ic te d v a lu es n h s (0 ) 268 211 52 1486 hs (1) h s (1 ) nhs (0) actual values p r ed ic te d v a lu es n h s (0 ) 265 215 54 1484 hs (1) h s (1 ) nhs (0) actual values http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 504 tf-idf countvectorizer figure 7: confusion matrix deep neural network (dnn) model based on extracted features figure (7) illustrates the confusion matrix of dnn model. dnn with tf-idf correctly classify 507 samples as hs and 3159 samples as nhs, and also 211 samples of hs and 194 samples of nhs were wrongly classified. dnn with countvectorizer correctly classify 453 samples as hs and 3195 samples as nhs and wrongly classify 192 samples as hs and 198 samples as nhs. glove embedding figure 8: confusion matrix bidirectional long short-term memory (bi-lstm) model based on glove embedding figure (8) illustrates the confusion matrix of bi-lstm model. bi-lstm with glove embedding classify 404 samples hs and 1450 samples as nhs correctly. 143 samples of hs and 21 samples of nhs were misclassified. with higher f1-scores than traditional models (lr, nb, and xgboost), deep learning models (dnn and bi-lstm) performed better overall. with an f1-score of 0.68 (68%) on countvectorizer, the lr model outperformed the other traditional models. xgboost came in second with f1-scores of 0.67 (67%) and 0.66 (66%) on both countvectorizer and tf-idf, p r ed ic te d v a lu es n h s (0 ) 507 211 194 3159 hs (1) h s (1 ) nhs (0) actual values p r ed ic te d v a lu es n h s (0 ) 453 192 198 3195 hs (1) h s (1 ) nhs (0) actual values p r ed ic te d v a lu es n h s (0 ) 404 143 21 1450 hs (1) h s (1 ) nhs (0) actual values file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com sosimi et al: hate speech identification in west africa, using machine-learning techniques. azojete, 20(2):491-508. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 505 respectively. moreover, it could be inferred that the classical model outperformed the tf-idf feature extractor with higher f1 scores when using the countvectorizer feature extractor. on tf-idf and countvectorizer, lr and xgboost, as well as nb on tf-idf, all displayed high recall and low precision values. the bulk of the contentious tweets in the dataset were accurately categorised as hate speech by the classifiers, as evidenced by the high recall scores. however, the poor accuracy value suggests that some noisy, inconsistent, and irrelevant tweets were also categorised into the hate speech category by the classifiers as seen in the confusion matrices. using the glove embedding feature extractor, the bi-lstm model outperformed dnn in terms of deep learning models, yielding a high accuracy of 0.92 (92%) and f1 scores of 0.83 (83%). in contrast, dnn produced an accuracy of 0.90 (90%) on both countvectorizer and tf-idf feature extractors, as well as an f1-score of 0.71 (71%) on countvectorizer and 0.70 on tf-idf. the reason for this is that neural network models perform optimally on embedding. furthermore, on large datasets, embedding feature extractors outperform vector representation feature extractors because they retain some of the input's semantics by grouping semantically related inputs in the embedding space, whereas vector representation (td-idf vectorizer and countvectorizer) lose word order and context and is unable to represent semantic similarities between words. high recall and precision rates were also achieved by the deep learning models, suggesting that the majority of the contentious tweets were accurately categorised as hate speech with minimal noise. 3.1 comparing the performance of our dataset with the state-of-the-art dataset it was necessary to compare our dataset with the most recent hate speech dataset in order to assess the performance of the former. to do this, the analytics vidhya dataset for hate speech detection presented by toosi (2019) was used. out of the 32,000 tweets in the sample, 2242 (7%) were found to contain hate speech. hate speech in this context refers to tweets that are racist or sexist in nature. the 29720 tweets (93%) of the total, were deemed to be free of hate speech. the same classifiers and feature extractors that were employed to develop our detection model were applied to the state-of-the-art dataset presented by (toosi, 2019). table 4 displays the f1-scores and accuracy results for our dataset (west african hate dataset), here is highlighted in bold while the dataset (toosi, 2019) was asterisked and italised. table 4: results of accuracy and f1-scores of our dataset and the state-of-the-art dataset classifiers feature extractors accuracy scores *accuracy scores* f1 scores *f1 scores* lr tf-idf 0.86 0.95 0.62 0.43 countvec. 0.87 0.96 0.68 0.65 nb tf-idf 0.83 0.95 0.49 0.45 countvec 0.68 0.88 0.54 0.48 xgboost tf-idf 0.87 0.95 0.66 0.54 countvec 0.87 0.95 0.67 0.56 dnn tf-idf 0.90 0.93 0.71 0.54 countvec 0.90 0.93 0.70 0.52 bi-lstm glove 0.92 0.84 0.83 0.64 except the bi-lstm classifier, all classifiers outperformed the west african hate dataset in terms of accuracy, as shown by the results in table 4. unfortunately, because the hatred tweets dataset tends to predict more non-hate speech—the majority class—than hate speech—the minority class—its accuracy cannot be used as a valid metric of model effectiveness. the f1-scores are a superior metric measure for imbalance categorisation, such as is used in this paper. this is because the f1 scores account for both precision and recall, http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):491-508. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: cfolorunso@unilag.edu.ng 506 generating a single score that combines the two issues into a single figure (brownlee, 2020). table 4 shows that in terms of overall f-measure performance across all classifiers, our dataset (west african hate dataset) fared better than the state-of-the-art hatred tweets dataset. this illustrates how valuable the special dataset is for detecting hate speech in west africa. 4. conclusion the use of machine learning techniques to detect and suppress hate speech in west africa is an important first step towards tackling the growing problems of verbal hostility both offline and online. through an examination of the region's varied language landscape, cultural quirks, and socio-political circumstances, this research has explored the complexity of hate speech. an encouraging option for the automatic detection of hate speech is machinelearning models tailored to the languages and geographical quirks of west africa. the availability of extensive and varied datasets that capture the variety of language usage throughout the region is crucial to the efficacy of these models. the continuous endeavour to select datasets that encompass diverse linguistic expressions and contextual elements is crucial to ensure the resilience and applicability of hate speech identification models. a total of 20176 tweets were manually divided into two categories for this study: hate speeches and non-hate speeches. of the total number of tweets, 4801 (or 24%) were categorised as hate speech, whereas 15375 (or 76% of the corpus) were classed as nonhate speech. after that, the data were pre-processed to eliminate inconsistent and noisy data in order to make them ready for usage with machine learning techniques. the models were created using lr, nb, xgboost, dnn, and bi-lstm based on the dataset. test precision, recall, accuracy, f1-score, and confusion matrix were used to evaluate the models, which were extracted using the tf-idf, countvectorizer, and glove embedding features. the studies' results were encouraging, demonstrating the efficiency of the created models in identifying anti-west african hate speech. in comparison to the traditional models (lr, nb, and xgboost), the deep learning models (dnn and bi-lstm) outperformed them. on the test dataset, the lstm had the best accuracy (92%), as well as the highest f1score (83%). in general, the machine learning models performed well on test data, demonstrating that they had learned from the training data and were able to apply that knowledge to fresh data when it was required to be examined using inference on usergenerated data. this enables the machine learning models to automatically identify hate speech with a west african origin on social media, which can significantly reduce the harmful consequences of online hate speech on our community. the dataset can be annotated with additional information than just a binary classification in order to improve the results. the dataset can also be expanded to incorporate fresh writing styles, subjects, and trends. in the future, it might also be looked into how hostile statements are used in non-textual material that users share, such as movies, images, and emoticons. tf-idf, countvectorizer, and glove embedding could be studied in addition to other feature extractors such as bert, elmo, fasttext, etc. additional features that could be included in word embedding are user gender, geography, and age. more machine learning classifiers, especially deep learning classifiers, can be researched. to develop a more trustworthy model. reference aggarwal, r. 2019. bi-lstm. accessed on january 5, 2024, available at https://medium.com/@raghavaggarwal0089/bi-lstm-bc3d68da8bd0. akanji, a. 2017. hate speech: wrong narrative for national discourse, integration. the cable. accessed on january 5, 2024, available at 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sentiment analysis: detecting hatred tweets. kaggle. accessed on may 28, 2024, available at https://www.kaggle.com/arkhoshghalb/twitter-sentiment-analysis-hatredspeech unnikrishnan, cs. 2021. how sklearn’s tfidfvectorizer calculates tf-idf values. accessed on may 28, 2024, available at https://www.analyticsvidhya.com/blog/2021/11/how-sklearnstfidfvectorizer-calculates-tf-idf-values/. williams, ee. 2020. effectiveness of social media platforms in combating extremism, hate speech, and fake news in nigeria. resisting disinfodemic media and information literacy: 7– 21. yang, fj. 2018. an implementation of naïve bayes classifier. ieee international conference on computational science and computational intelligence (csci): 301–306 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com https://www.cfr.org/backgrounder/hate-speech-social-media-global-comparisons https://www.cfr.org/backgrounder/hate-speech-social-media-global-comparisons 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https://www.analyticsvidhya.com/blog/2021/11/how-sklearns-tfidfvectorizer-calculates-tf-idf-values/ https://www.analyticsvidhya.com/blog/2021/11/how-sklearns-tfidfvectorizer-calculates-tf-idf-values/ corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 781 arid zone journal of engineering, technology & environment original research article development of a pipe leakage detection with simulated acoustic model for water distribution system m. o. arowolo1, a. a. adekunle1, o. m. olaniyan2, e. a. fadiji3 and o.t. oginni3* 1department of mechatronics engineering, federal university oye, ekiti state, nigeria. 2 department of computer science, federal university oye, ekiti state, nigeria. 3department of mechanical engineering, bamidele olumilua university of education, science and technology, ikereekiti, ekiti state, nigeria. *corresponding author’s email: oginni.olarewaju@bouesti.edu.ng article information abstract the paper presents a method for detecting pipe leakage in a water distribution system using a simulated acoustic model. the study utilized particle swarm optimization (pso) to determine the optimal position for the leakage point in relation to the sensors. the objective function was created, and time delays were optimized using pso simulated via matlab. the analysis focused on examining both vertical and horizontal flow configurations. the system was calibrated, data was extracted, and it was utilized for leakage automation. the study found that the optimal leakage point is 10.12 cm, measured to the left sensor1 in the horizontal configuration with a 0.02 second time delay. the second leakage point in the horizontal configuration has a time delay of 0.05 seconds, while the third point has a delay of 0.08 seconds. eight false alarm frequencies were detected in the water flow and no leakage mode, with 100% of the false alarms indicating no flow or leakage. the system false alarm disappears when the system is pressurized for a long period of time. the study demonstrates the importance of detecting pipe leakage in water distribution systems using a simulated acoustic model in rural areas, developing countries, and small and medium-sized industries. submitted 04 may, 2024 revised 02 june, 2024 accepted 10 june, 2024 keywords: pipe leakage detection acoustic model water distribution flow configuration © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction a pipe distribution network is a network installation consisting of pipes and fitting structures like thrust blocks, various valves, and outlets installed in a system to supply either water, crude oil, natural gas, or petroleum products under pressure (chen, 2019). pipelines also permit the conveyance of water uphill against the normal slope of the land and, unlike open channels, can be installed on non-uniform grades. the use of buried pipes allows the most direct routes from the water source to fields and minimizes the loss of productive land. major advances have been made in recent years in pipeline technology; however, typical pipeline distribution systems in many cities worldwide contain a large percentage of older pipes. in nigeria, 60% of crude oil and petroleum pipelines are 30 years older. as pipes age, the problems of infiltration and exfiltration increase in sewer pipes, causing potential environmental problems, although in many cases these problems have yet to be quantified. also, in water reticulation pipes, the failure levels increase with age, and consequently, the levels of unaccounted-for water (neelem and kalaga, 2022) and the associated lost revenue from water reticulation mains can also increase due to these failures and the associated water pipe leakage (jianfeng, 2021). pipe leakage is a costly problem, not only in terms of wasting a precious natural resource but also in economic terms. the primary economic loss due to leakage is the cost of raw water, its treatment, and its transportation. leakage inevitably also results in secondary economic loss in the form of damage to the pipe network itself, such as erosion of pipe bedding and major pipe breaks, and in the form of damage to the foundations of roads and buildings (fine and millero, 2019). diminution of supply security as a result of a reduction in water stored per capita may also represent a cost if such diminution requires augmentation of supply to maintain security. besides the environmental and economic losses caused by leakage, leaky pipes create a public health risk, as azojete december 2024. vol.20(4):781-789 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:oginni.olarewaju@bouesti.edu.ng mailto:oginni.olarewaju@bouesti.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 782 every leak is a potential entry point for contaminants if a pressure drop occurs in the system. thus, managing these problems has become an important aspect for managers of water supply networks. acoustic listening and ground-penetrating radar devices are the physical inspections of the leak in the pipeline (colombo, 2021). these techniques require shutting down and isolating the affected part or whole system. the complete process may take a few days to months, with plenty of significant water waste. the inspection of leaks is also done by observation on a routine basis. when the fluctuation in demand is increased from night to day consumption abnormally or major losses are suspected, leak detection techniques are applied. model-based leak detection and isolation techniques have started with the influential research work of pandey et al., (2021), which expresses the problem of least-squares estimation. the estimation of parameters in the water distribution network model is a difficult task. the non-linear equation caused difficulties in the water distribution network system, and for estimating the parameters, very few measurements are available, which causes the undetermined problem. pérez et al. (2019) developed a model-based method for detecting and localizing the leaks. this method used pressure residual analysis and was compared with a given threshold. a threshold has been used to control the model's uncertainty and noise. the comparison of the residual against the threshold shows the possible leak present at nodes. due to demand uncertainty at nodes and noise in measurement, the performance of this approach decreases, while in ideal conditions it shows good efficiency. in recent years, pso-based methods have been applied to a wide variety of problems, leading to high efficiency (bai, 2020). the pso application depends on the matlab toolbox and introduced into mathworks, where the presence or absence of a sensor at a given node is determined by a particle (wang et al., 2019). this research therefore looks at the area of pipe leakage in water distribution networks (wdn) using particle swarm optimization (pso). in pso, possible solutions, called particles, fly through the problem space by following the current optimal particles. the pso technique was used to find the minimal sensor placement for the identification of leaks in pipe networks. this technique was developed and integrated for accurate pipe leak detection in this study. 2. materials and method two sen0257 dfrobot water pressure sensors, three 3-inch (76.2mm or 7.62cm) polyvinyl chloride (pvc) values, a 1 horse power (0.75kw or 746watt) water pump, and an arduino microcontroller (atmega328) were bought and used for the construction of the leakage experimental rig. other components were sourced locally in akure, ondo state. the sen0257 dfrobot has a pressure range of 0–1.6 mpa, a voltage range of 0.5–4.5 v, and an accuracy of 0.5–1%. the arduino atmega328 microcontroller is an 8-bit automatic voltage regulator (avr) controller; it is one of the many ides utilized for atmel automatic voltage regulator (avr) controllers. figure 1 shows the flowchart of the study methodology framework. the leakage detection scheme required identifying the optimum leakage location along the pipeline. particle swarm optimization algorithm is used for easy leakage detection and position optimization figure 1: flowchart of the study methodology http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 783 2.1 particle swarm optimization (pso) algorithm the algorithm is a meta-heuristic algorithm that can be implemented for optimization problems (wang et al., 2019). it is an intelligent scheme developed to mimic the behavior of swarms of birds (particles’ population) in search of food in search space. the model involves solving two things: the swarm’s velocities (equation 1) and their positions (equation 2), which are subsequently updated until convergence is reached (bai, 2020). 𝑉𝑖 𝑛+1 = 𝜔𝑉𝑖 𝑛 + 𝑐1𝑟1(𝑃𝑏𝑒𝑠𝑡𝑖 𝑛 − 𝑥𝑖 𝑛) + 𝑐2𝑟2(𝐺𝑏𝑒𝑠𝑡𝑖 𝑛 − 𝑥𝑖 𝑛) (1) 𝑥𝑖 𝑛+1 = 𝑥𝑖 𝑛 + 𝑉𝑖 𝑛+1 (2) where 𝑉𝑖are the velocities of the particles in the search space, 𝑥𝑖 are the positions of the particles, 𝜔 is an inertia weight that balances the algorithm exploration, 𝑐1 and 𝑐2 are acceleration constants, and 𝑟1; 𝑟2 are random numbers usually between 0 to 1.the algorithm is shown in figure 2, and pso parameters utilized in this study are shown in table 1. the algorithm solves equations 1 and 2 continuously until convergence is attained. a very important aspect of this algorithm is the objective function it optimizes, which is a function of the problem at hand. figure 2: particle swarm optimization algorithm flowchart table 1: pso parameters used for the study s/n parameters values 1 inertia weight (𝜔) 0.9 2 acceleration constants (𝑐1 𝑎𝑛𝑑𝑐2) 1.5 3 random numbers (𝑟1 𝑎𝑛𝑑 𝑟2) 0.5 4 number of iterations 50 http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 784 2.2 leakage position model (objective function) applying the particle swarm optimization algorithm for leakage detection requires an objective function. the objective function continues to solve until convergence is reached. in this study, the objective function has to do with optimizing the leakage points relative to one of the sensors. to model the relationship between leakage points and the sensors, the pressure sensors are positioned upstream and downstream of a pipe to gather negative pressure wave (npw) signals to identify leakages, as shown in figure 3. the precise position of the leakage point is estimated using the time difference between the detected signals and the propagation velocity in the medium as contained in liao et al. (2019). figure 3: schematic diagram of the leakage detection process using pressure sensor from figure 3, taking the distance between the two sensors as, 𝑑 the distance between the upstream sensor and the leakage point is, 𝑑1, and the distance between the downstream sensor and the leakage point is 𝑑2. signal 𝑥1(𝑡) and 𝑥2(𝑡) are the measured signals from the two sensors. the position of the leakage relative to sensor 1, is then be expressed as 𝑑1 = 𝑑−𝑣𝜏 2 (3) where 𝑣 is the pressure wave speed of the leakage along the pipe medium and 𝜏 is the time delay. the complexity of equation 3 is the time delay and the velocity of sound in the pipe medium, and these two parameters are central to the accuracy of a leakage detection scheme that uses the equation. an experimental rig, as shown in figure 4, was constructed to predict leakages along water pipelines. the rig consists of water networks with leakage points as dictated by the outcome of the pso, a water pump, and a water basin. two modes of flow lines were studied: horizontal and vertical flow lines. this was aimed at improving the versatility of the leakage detection scheme. figure 4: leakage detection experimental setup http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 785 calibration of the leakage detection scheme was done by installing the sensors along the length of the pipes for both orientations (the horizontal and vertical flow) and interfacing the sensors with the microcontroller, which was facilitated via the arduino sketch (program) developed. when calibrating for any of the flow orientations, a valve was used to isolate the flow from passing through the other orientation, which is not of interest. different leakage positions with respect to the sensors as obtained including no leakage condition, were investigated. in order to determine the flow parameter (basically negative pressure), which was used to automate the leakage detection scheme, the water flow network was pressurized, and data were recorded. the parameters regarding the calibration are shown in table 2. table 2: water pipeline condition used for the study s/n pipe conditions horizontal flow pipe orientation vertical flow pipe orientation leakage points (cm) leakage points (cm) 1 no leakage 0.00 0.00 2 leakage point 1 10.00 11.50 3 leakage point 2 25.00 4 leakage point 3 35.00 in automating the pipeline leakage scheme, data obtained from the calibration based on the different water pipeline conditions was used. a control system, as shown in figure 5, involved a microcontroller, and the sensors were built and programmed. figure 5: leakage detection electrical circuit different conditions of the pipeline were used in the computer program to control the alarm state of the leakage system. after the automation, the system was tested in real time. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 786 3. results and discussion the algorithm was utilized in determining the optimal position for the leakages with reference to the sensor, starting from the left for the horizontal orientation as shown in figure 6. different values of time delay were optimized, establishing the leakage positions that were used for the automation of the leakage detection scheme. the results of the leakage positions as obtained are shown in figures 7. it reveals that the fitness value converges at 10.118 cm, which is measured to the left of sensor 1, as described in figure 7 revealed the optimal time delay of 0.018 seconds, which represents the time taken for the two sensors to see the signal at the same moment. it shows a fitness value of 25.35 cm with an optimal time delay of 0.050 seconds. pressure values were recorded for different cases of water flow in the pipeline. no leakage with no flow, no leakages with flow, leakage at 10 cm with flow, leakage at 25 cm with flow, and leakages at 35cm were investigated for the horizontal configuration. the water distribution line was pressurized for 60 seconds for each case considered. figure 6: leakage position with reference to the sensor 1 figure 7: convergence curve for the first leakage point for the horizontal configuration figure 8 shows the profile of the pressure for no leakage with no flow. both sensors maintained a uniform pressure of around 0.3 n/m2, except for a few occasions where pressure deviations were experienced. in case of sensor 1, a constant pressure peak of 2.2 n/m2 was observed at 11, 22, 42, and 57 seconds, respectively, and for sensor 2, a constant pressure peak of negative 1.7 n/m2 was observed at 46, 50, and 59 seconds, respectively. consequently, figure 9 revealed the pressure values for both sensors for water flow and no leakage along the pipeline. the pressure value decreases along the downstream. however, both sensor 1 and sensor 2 gave fluctuating pressure values, with sensor 1 registering a pressure value between 8 and 12 n/m2, and sensor 2 http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 787 registering a pressure value between 8 and 10 n/m2. the pressure value of 10 n/m2 as detected by sensor 1 is very pronounced, and for sensor 2, a pressure value of 8 n/m2 occurs most frequently. the automation of the leakage system was done, and the response was classified into three categories: no leakage, flow with no leakage, and leakage, with a focus on the horizontal configuration because the vertical configuration pressure variation for leakage and no leakage with flow is trivial. the flowchart of the automation is shown in figure 10. the system's response was characterized by alarms, including false alarms. subsequently, the system was run for 2 minutes, and tests were conducted 300 times. the algorithms were obeyed by the system for 90 cycles, and the false alarm frequencies are shown in figure 10. 8: pressure values for sensor1 and sensor2 for no flow and no leakage case (horizontal configuration) figure 9: pressure values for sensor1 and sensor2 for fluid flow and leakage case (horizontal configuration) figure 10: automation flowchart -2 -1 0 1 2 3 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 p re ss u re ( n /m 2 ) time (seconds) sensor_1 pressure 0 5 10 15 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 p re ss u re ( n /m 2 ) time (seconds) sensor_1 pressure sensor_2 pressure http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 788 the system alarm response, as shown in figure 11, revealed that the system does not give any false alarms for the no flow and no leakage modes as contained in pérez et al. (2019). however, false alarms existed for both water flow and no leakage and water flow and leakage modes. in the case of the water flow and no leakage mode, the number of false alarms that were observed is 8, where 100% of these represent no flow and no leakage. consequently, in the case of water flow and leakage mode, a total of 11 false alarms were observed, of which 55% represent no flow and leakage and 45% represent no flow and no leakage in line with colomb (2021) report. meanwhile, the system false alarm was observed to reduce significantly when the system is pressurized for a long period of time. figure 11: system false alarm response 4. conclusion the issue of pipeline leakages has been causing environmental challenges and water shortages, and it has led to spending huge amounts of money to clean the environment. particle swarm optimization (pso) has been used to optimize the best position to place the leakage point with respect to the sensors. an objective function was developed, and the time delays were optimized using particle swarm optimization (pso) simulated via matlab. the developed experimental rig was placed on leakage points based on the pso for leakage automation. the results showed that the best leakage point is 10.12 cm, which is measured to the left sensor1 for the first leakage point in the horizontal configuration with a 0.02 second time delay; 25.35 cm for the second leakage point in the horizontal configuration with a time delay of 0.05 seconds; and 37.25 cm for the third leakage point with a time delay of 0.075 seconds. this study outcome is ideal for households, industries, institutions, and construction companies that have the mindset of constructing to the required standard. the pso model is recommended to be used in developed and developing countries that plan to venture into pipe leakage detection and control in water distribution networks using sensors. the developed model performed satisfactorily upon validation with real-life data, while human and technical risk factors were established as critical to safety management in the manufacturing industry. references bai, q. 2020. analysis of particle swarm optimization algorithm. computer and information science, 3(1): 180-189. chen, sm. 2019. computational collective intelligence: semantic web, social networks and multiagent systems. wroclaw university of technology; swinburne university of technology; natl taiwan. university of science and technology, lecture notes in artificial intelligence, 57(96): 608–619. colombo, af., lee, p. and karney, bw. 2021. a selective literature review of transient-based leak detection methods. journal of hydro-environment research, 12: 212-227. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):781-789. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oginni.olarewaju@bouesti.edu.ng 789 fine, ra. and millero, fj. 2019. compressibility of water as a function of temperature and pressure. journal of chemical physics, 59(10): 5529–5536. jianfeng, g. 2021. research on oil-gas pipeline leakage detection method based on particle swarm optimization algorithm optimized support vector machine. journal of physics, 61(3): 453-462. liao, q., castro, pm., liang, yt. and zhang, hr. 2019. new batch-centric model for detailed scheduling and inventory management of mesh pipeline networks. computers and chemical engineering, 130(2): 106-116. neelam, mk. and kalaga, s. 2022. elastic properties of pvc pipes. journal of structural engineering, 29(2): 91– 96. pandey, sk., mohanty, sr., kishor, n. and catalao, jp. 2021. frequency regulation in hybrid power systems using particle swarm optimization and linear matrix inequalities based robust controller design. international journal of electrical power and energy systems, 63(4): 887–900. perez, r., puig, v., pascual, j., quevedo, j., landeros, e. and peralta, a. 2019. methodology for leakage isolation using pressure sensitivity analysis in water distribution networks. control engineering practice, 19(10): 11571167. doi: 10.1016/j.conengprac.2019.06.004. wang, d., tan, d. and liu, l. 2019. particle swarm optimization algorithm: an overview. soft computing, 22(2): 387–408. http://www.azojete.com.ng/ mailto:oginni.olarewaju@bouesti.edu.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 294 arid zone journal of engineering, technology & environment original research article interpretation of airborne radiometric data of a typical basement complex, northwest nigeria. o. ologe, a.m. moyi* , f. sanusi, u.h. tsafe, and s. umar department of applied geophysics, federal university birnin-kebbi. *corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng article information abstract interpretation of high resolution airborne radiometric data over funtua-tsafe northwest nigeria was carried out with the aim of delineating geological structures and mineral potential of the basement terrain. the data were interpreted quantitatively using the radiometric ratio and ternary radioelement signatures. analysis of the radiometric data enabled the estimation of relative abundances of natural radioactive elements (uranium, thorium and potassium) concentrations revealing distinct anomalies indicative of hydrothermal alteration and the structural styles (shear zones and fault systems) of the area. the count rate range of uranium (2.0 to 7.6ppm), thorium (10.6 to 40.0 ppm) and potassium (0.5 to 3.1 %) were estimated within the area. high concentrations of the two radioelements (u,th) are predominant in the western part of the area and are possible site for radiogenic heat exploration and geothermal alteration. from the qualitative analysis of the relative abundance of the radioactive elements and the ratio map analysis, rock bearing minerals such as pegmatite, schists were suggested to be present, which could serve as raw materials for many industries in nigeria. received: 9th december 2024 reviewed: 15th february 2025 accepted: 16th february 2025 keywords: radioelements zones hydrothermal radiometric mineralization © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction airborne radiometric survey has become increasingly popular in mineral explorations, especially in large exploration areas of complex terrain or inaccessible regions. this geophysical technique is used to estimate the concentration of radioelements in rocks by measuring the gamma rays emitted by the radioactive isotopes of these elements undergoing radioactive decay (adonu et al., 2022; ani et al., 2023; ngwaka et al., 2023). there are many naturally occurring elements possessing radioactive isotopes but only uranium, thorium and potassium decay series have radioisotopes that produce gamma rays of sufficient energy and intensity which can be measured by gamma-ray spectrometry (galbraith & saunders, 1983). the gamma rays from the decaying unstable nuclei of the rocks are recorded during radiometric surveys. the radioelement composite image recorded therefore gives a single display of the three radioelement concentrations which reveal the distribution of certain rock bearing minerals of interest. the uranium, thorium, and potassium maps show regions where the specific radioelement has high or low concentration (abdulsalam et al., 2023). aeroradiometric method provides useful information for detecting and mapping natural radiometric emanations of gamma rays by measuring the naturally occurring radioactive elements that exists in rock forming minerals. the method is a passive geophysical process because it measures a natural source of energy and evaluates the mineralization in the area from the relative abundance of these three radionuclides of potassium (k), uranium (u) and thorium (th). historically, the main use of radiometric in mineral prospecting was detection of anomalies caused by outcropping, highly radioactive, uranium deposits. the radiometric method has several characteristics that make it unique amongst the geophysical methods. firstly, the measured radioactivity originates from only the top few centimeters of the earth’s crust, unlike other geophysical methods, radiometric has only a very limited ability to see into the subsurface. secondly, it is possible to identify the elemental source of the radiation from the energy of the γ-rays emitted, radiometric data are used to map variations in the chemical rather than the physical characteristics of the survey area. interpretation of radiometric data straddles the boundary between geochemistry and geophysics. this may explain why the methodologies for interpreting radiometric are less well-developed than those of other geophysical methods azojete march 2025. vol.21(1):294-302 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:abdulhameed.muhammad@fubk.edu.ng mailto:abdulhameed.muhammad@fubk.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 295 (airo, 2002). the measurements of radioactivity of rocks of the crust can be used to estimate the concentration of heat producing elements. the decay of radioactive elements is essential for geothermal resources. augustine et al., (2021) successfully employed aeromagnetic and airborne radiometric data to provide information on the structural settings and inter possible location of mineralization in parts of zamfara, northwest nigeria. radiometric data was proceeded and interpreted in the middle benue trough to ascertain the relative quantity of natural radioactive elements (uranium, thorium and potassium) (ani et al.,2023). the outcome of both researchers concluded on areas with possible sites for radiogenic heat exploration and rock bearing minerals. the use of aeroradiometric data to determine the relative abundance of natural radioelements in the study area is uncommon; hence, this study is geared towards estimating the abundance of these elements and identify prospective minerals if any that might be present in the study area by interpreting airborne radiometric data. 2. materials and method 2.1 study area figure 1 shows the location map of the study area obtained from q-gis version 3.0 figure 1: location map of the study area (adopted from q-gis v 3.0) the study area is situated within the boundary of zamfara and katsina states, northwest nigeria (figure 1). the areas geographical coordinates are: latitude 11°45'0" n 12°15'0" n and longitude 7°15'0" e 7°45'0" e. funtua-tsafe is characterized by gently undulating terrain, tropical savanna climate, and guinea savanna vegetation, with elevation ranging from 300-600 meters above sea level. the area is drained by the sokoto river and its tributaries. funtua-tsafe falls within the precambrian basement complex and the younger granite province of nigeria, making it a significant location for geological and mineral exploration target area. the climate of the study area funtua-tsafe boundary is characterized by high temperatures and moderate rainfall, influencing the vegetation and agricultural practices in the area. the area's climate is marked by an average temperature ranging from 25°c to 30°c (77°f to 86°f), and moderate rainfall, with an annual average of 800-1,000 mm (31-39 in). the vegetation is primarily guinea savanna, characterized by scattered trees, including species like acacia, bauhinia, and vitex, grasslands with tall grasses, such as hyparrhenia and loudetia, woodland savannas, featuring trees like anogeissus and terminalia. 2.2 geology of the study area figure 2 shows the geological map of the study area obtained from arc gis 8.5 http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 296 figure 2: geological map of the study area (adopted from arcgis 8.5) the basement complex is one of the three major litho-petrological components that make up the geology of nigeria (figure 2). the nigerian basement complex forms a part of the pan-african mobile belt and lies between the west african and congo cratonsand south of the tuareg shield (danbatta, 2010; obaje,2009). the study area is located between katsina and zamfara states, northwest nigeria which lies within the part of north central nigeria basement and it is situated within the precambrian basement complex and the younger granite province of nigeria (alaku et al., 2017). the area's geologic setting is characterized by ancient rocks formed during the pan-african orogeny, and granitic rocks emplaced during the jurassic to cretaceous periods (danbatta, 2010). the precambrian basement complex comprises gneisses, schists, and quartzites, while the younger granite province consists of granitic rocks (danbatta, 2010). geologically, it features a mix of granitic, gneissic, and sedimentary rocks. inselbergs (isolated hills) and ridges, such as the katsina-alkalawa ridge, are prominent. faults and fractures, including the sokoto fault zone, are also present. alluvial plains and valleys, drained by the sokoto river and its tributaries, are characteristic of the area. the precambrian basement complex in funtua-tsafe has undergone multiple tectonic events, including the pan-african orogeny and the nigerian-beninian orogeny (ajibade and wright, 1989). the younger granite province has been affected by jurassic-cretaceous magmatic activity in which the sokoto-niger basin has experienced multiple phases of sedimentation, including the deposition of sedimentary rocks during the cretaceous and tertiary periods (danbatta, 2010; ajibade and wright, 1989). 2.3 method as part of a nationwide high-resolution airborne geophysical survey for geological studies in nigeria, radiometric data were acquired by furgo airborne survey limited for the nigeria geological survey agency (ngsa). the very high-quality sheets of aero-radiometric data that cover the study area were acquired from nigerian geological survey agency, abuja (ngsa), which carried out airborne radiometric survey of nigeria between the years 2002 2009. the aero-radiometric data were acquired with data flight elevation of 80m, line spacing and tie-lines spacing were 500 m and 5000 m respectively. the data were collected systematically by dividing the country’s landscape into geological blocks with the eventual production of radiometric map categorized as sheets for the whole country. the radiometric data applied in this study were re-projected to wgs 84 zone 32°n of equator using the geosoft oasis montaj software since the survey area falls within 0° to 6° n of equator. figure 3 shows a workflow applied in the data processing. http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 297 figure 3: diagram of workflow adopted for radiometric data processing the airborne radiometric data acquired over the study area had a projection of zone 32°n of equator. to correct this anomaly, the data was re-projected to zone 31°n of equator which is the geographical projection of the study area. the re-projected data consisting of three radioelement soft thorium, potassium and uranium concentrations were mapped individually to show concentration dominance. a standard way of displaying the potassium (k), thorium (th) and uranium (u) data is as a ternary image where a composite image is generated by proportioning colours, red, green and blue to the radio-element concentration values of k, th and u respectively. in the event of excessive large population of radio-element over others, an approach to overcome this effect is to create separate grids (images) of the radio-elements from selected ranges taken from the total count image. computing the arithmetic ratio of radio-element grids is away to suppress the effects of environmental factors such as soil moisture, vegetation and topography on the radiometric response to the actual geologic unit. 3. results and discussion 3.1 radioelement there are over 50 naturally occurring radioactive elements, but terrestrial radiation is dominated by the emission products from just three elements: potassium (k), uranium (u) and thorium (th) henderson (1983). the half-lives of their radioactive isotopes are of the same order as the age of the earth (5 x 109years) and are sufficiently long that they remain comparatively abundant. the other naturally occurring radioactive elements are too rare and/or too weakly radioactive to be of significance. the γ-ray spectrum recorded in geophysical surveying comprises radiation from a number of different sources in varying proportions. of these, radiation originating from one or more of the three common radioelements present in the ground, i.e. potassium (k), uranium (u) and thorium (th), is the signal of interest, and all other sources of radiation form unwanted noise. spectra are obtained by locating the survey spectrometer (the survey aircraft) over the synthetic sources (the pads), and the effects of different survey heights simulated by partial shielding of the detector. the spectra so obtained are converted to pure k, u and th spectra based on the known elemental concentration soft the samples (the pads), and the stripping ratios obtained for the various simulated survey heights. the height-corrected stripped counts in each of the three energy channels, k, u and th, are linearly related to the ground concentrations of their respective elements. the integration of the three elemental concentration channels, potassium (k), uranium (eu) and thorium (eth), with the total-count (tc) channel and other datasets, such as terrain and multispectral scanner data, is an important aspect of the geochemical/geological interpretation of radiometric data. http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 298 3.1.1 potassium (%k) map figure 4 shows the concentration map of potassium obtained from oasis montaj software. figure 4: potassium concentration map the potassium (%k) map (figure 4) shows different degrees of potassium concentrations ranging from 0.5 to 3.1% that reflects different lithological units and alterations in the area s. alteration, weathering, climatic conditions and hydrothermal processes can affect the concentration of the radioelements. potassium often increases during signature alterations, but weathering usually decreases the intensity of signature alterations (blatt, h. 1992). several potassium anomalies are evident in the radiometric image the color blue corresponds with low k values whilst pink corresponds with very high k values. the color red represents moderately high to high k values and the shades of orange to yellow color represent or are associated with moderately low k values. pegmatite, granite, gneiss, migmatite, quartzite, phylite and could be associated with gold deposit in the study area while some part of the map are showing low potassium concentration which could be attributed to the destruction of potassium source during weathering processes resulting to presence of gabbro,diorite,basalt,marble and clastic sediments. 3.1.2 thorium (th) map figure 5 shows the concentration map of thorium obtained from oasis montaj software. figure 5: thorium concentration map thorium generally is not affected by alteration processes because it is typically immobile in mineralization processes (taylor et al., 1995.) or it can only partly be depleted in areas of intense k-alteration and silicification. however, the distribution map (figure 5)of thorium has concentration ranging from 10.6 to 40.0ppm. the thorium concentration in the study area was grouped as high(vhc) (>22.4ppm), moderately high (19.922.4ppm), moderately low (15.2-19.9 ppm), and low (vlc)(<15.2ppm). the high concentrations of thorium http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 299 are marked by red to pink colorations and are observed in the west, towards southern edge of the study area. areas of very high to high eth(red and pink) concentrations are attributed to older granite suite,pegmatitic activity granitulites and schists, while zones of low thorium(green,blue) concentration are regarded as zone embedded with younger granite,lower grade metamorphism,quartzite formation. 3.1.3 uranium (eu) map figure 6 shows the concentration map of uranium obtained from oasis montaj software. figure 6: uranium concentration map figure 6 also displays the eu concentration. an enrichment of uranium may or may not be accompanied by an enrichment of potassium as uranium is very mobile in hydrothermal and other geological processes (kerrich et al., 2017). the map shows various anomalous signatures with total eu concentrations varying between 2.0 to 7.6ppm. the eu concentrations can be relatively grouped as high (>5.3), moderately high (4.05.3), moderately low (3.3-4.0) and low (< 3.3). the areas with high eu concentrations (figure 6) as observed in figure 5 are often associated with structures that could be serves as host to minerals emplacement while the lower zone (green and blue) is attributed to unfaulted areas with lower grade gneisses (figure 6). 3.1.4 potassium to thorium (k/th) ratio map figure 7 shows the concentration map of potassium to thorium ratio obtained from oasis montaj software. the map in figure 7 displayed %k/eth. as potassium is more mobile than thorium, k/eth ratio anomalies can be distinguished to areas of hydrothermal alteration which are characterized by k enrichment. however, depending on the fact that the ratio between potassium and thorium is rather constant in most rocks as reported by abdulsalam et al., (2023), typically varying from 0.02 to 0.17 (k/th in %/ppm,). so, the zones characterized by the high k/eth ratio values are strong indicator of hydrothermal alteration and high radiogenic heat production, this was corroborated by the work of abdulsalam et al., (2023). from the k/eth ratio map (figure 7), it is observed that the areas affected by the hydrothermal process with a touch of older granite are featured by pink color and observe in northeastern and eastern of the study area of about 0.09 of k/eth ratio. an alteration zones suggested to be medium to coarse-grained biotite granite are observed at the south and north central portion of the study area (figure 7). this is also observed within the western edge portion in which thorium is of high concentration and is symbolized by blue coloration which is attributed to be minerals enrichment suggested to be younger granite origin. http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 300 figure 7: ratio potassium to thorium concentration map 3.2 ternary map figure 8 shows the ternary concentration map obtained from oasis montaj software figure 8: ternary concentration map the ternary map is the triangular plot of the radio-elements which displays a ternary image by combining the three radio-elements. largely, ternary plots of the radio-elements usually give a superior image of the geology (salem et al., 2005). the ternary map (figure 8) indicates uranium, thorium, and potassium distribution within the basement complex. uranium-rich areas(blue) suggest granite emplacement, hydrothermal activity within the younger granite province and potential uranium mineralization. the uranium-rich zone also reveals pegmatite and hydrothermal veins while thorium-rich zones(green) indicate crustal thickening, high-grade metamorphism, and potential thorium mineralization. this implies that thorium-rich minerals like monazite or thorite within the older granite complex is suggested to be present in the area. potassium-rich areas (red) represent felsic rocks and crustal melting. this suggests potassium-rich minerals like orthoclase or biotite within the area. areas with high uranium and thorium concentrations indicate elevated radiation levels, and possible association with gold, copper, and silver mineralization (abdulsalam et al., 2023). these zones may also represent hydrothermal activity where tectonism is pronounced. http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 301 3.3 total count map figure 9 shows the total count map of the study area obtained from oasis montaj software figure 9: total count map figure 9 shows the total radiometric anomalies count map of the study area. it showcases the total count of the three radio-elements (uranium (ppm), thorium (ppm) and potassium (%)) present in the area of study with total count of about 14.148.5cpt. the area shows high concentration of total count values in parts of the study area mostly around southwestern part (figure 9). there is low concentration of total count values around north and some part of the southeast. low radiation (14.1-20 cps in blue-green color) suggested as areas with low radioactive mineralization, moderate radiation (20-30 cps in yellow-orange color) indicating moderate radioactive mineralization, while high radiation (30-40 cps in orange-red color) indicates significant radioactive mineralization with intense hydrothermal activity and very high radiation (40-48.5 cps in deep red color) represents intense radioactive mineralization suggested to be corresponding to high-grade uranium deposits. 4.conclusion the analysis and interpretation of airborne-radiometric data over funtua-tsafe and its environs, northwestern nigeria was carried out. the interpreted radiometric data delineated hydrothermal alteration zones of mineral enrichment in an area to include uranium, thorium and potassium. the coincidence areas of the alteration zones in the area indicated a high possibility for the occurrence of mineralization. based on the delineated hydrothermal alterations, it is recommended that the study area should be subjected to further investigation using active integrated geophysical methods to ascertain the occurrence of economically rick minerals in the study area that could contribute to the growth of the nigerian economy. references abdulsalam, nn., john, fo., and ologe, o. 2023. the effects of magnetic and radiometric responses on hydrothermal zones and its implication in minerals characterization over part of nasarawa, north central nigeria. journal of tropical resources and sustainable science (jtrss), 11(1): 29–36. adegoke, os. and omatsola, e. 2015. airborne radiometric survey for uranium exploration in the sokoto basin, nigeria. journal of african earth sciences, 101: 257–265. ajibade, ac., and wright, jb. 1989. the togo-benin-nigeria shield: evidence of crustal aggregation in the panafrican belt. tectonophysics, 165: 125–129. alaku, io., moshood, oi., agbor, at., and amos, aa. 2017. geochemical characteristic and petrogenesis of malumfashi schist around tandama area, north-western nigeria. british journal of applied science & technology, 29(1): 1–14. http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 294-302. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulhameed.muhammad@fubk.edu.ng 302 amadi, p. 2012. radiometric survey as a tool for geological mapping of western nigeria. journal of mining and geology, 48(1): 1–11. ani, ep., ugwu, gz., and nwobodo, an. 2023. geophysical interpretation of airborne radiometric data over part of middle benue trough of nigeria for mineral deposits. journal of applied geology and geophysics, 10(1): 58–62. augustine, ba., awoyemi, mo., ajama, od., falade, sc., hammed, os., dasho, oa., and adenika, ca. 2021. integrated aeromagnetic and airborne radiometric data for mapping potential areas of mineralization deposits in parts of zamfara, north west nigeria. journal of pure and applied geophysics, 179(6): 1–19. buyela, c. 2022. effects of radiation exposure on artisanal gold miners in kenya. journal of environmental and occupational science, 11(2): 1–9. danbatta, ua. 2010. on the evolution of the kazaure schist belt of nw nigeria: a re-interpretation. global journal of geological sciences, 8(2). dentith, m., and mudge, s. 2011. geophysics for practitioners: a guide to the exploration of the shallow subsurface. springer. dickson, bl. and scott, k. m. 1997. interpretation of aerial gamma-ray surveys – adding value to exploration. journal of australian geology and geophysics, 17(2): 137–146. dickson, bl. and schulz, kj. 1995. airborne gamma-ray spectrometry in mineral exploration. journal of geochemical exploration, 53(1–3): 25–44. duffett, m. 1998. application of airborne gamma-ray spectrometry to lithological mapping, lady loretta, australia. journal of geochemical exploration, 63(1): 37–51. harris, jr. 2001. integration of airborne magnetic and radiometric data for iron oxide copper-gold exploration. journal of applied geophysics, 46(3–4): 157–173. obaje, ng. 2009. geology and mineral resources of nigeria. springer dordrecht heidelberg. wilford, jr., bierwirth, pn. and craig, ma. 1997. airborne gamma-ray spectrometry for regolith and soil mapping. journal of applied geophysics, 37(2): 131–144. wemegah, d. 2015. integration of airborne magnetic and radiometric data for gold mineralization in south western ghana. journal of applied geophysics, 123: 241–253. http://www.azojete.com.ng/ mailto:abdulhameed.muhammad@fubk.edu.ng corresponding author’s email address: deborah2james@yahoo.com 279 arid zone journal of engineering, technology & environment original research article biogas production and nitrogen recovery from cattle and chicken dung through anaerobic digestion. d.j. malgwi*1, m. a. musa2 and a. n. jones2 1 department of civil engineering technology, ramat polytechnic, maiduguri, nigeria. 2 department of civil and water resources engineering, university of maiduguri, borno-nigeria *corresponding author´s email address: deborah2james@yahoo.com article information abstract this study was conducted to determine the biochemical methane potential (bmp) of cattle and chicken dung through anaerobic digestion. essentially, manure from animal waste could be a valuable resource in the production of high-grade organic fertilizer. to achieve this, chicken and cattle dung were collected at ramat polytechnic farms in maiduguri for the assessment. all samples were prepared and the digestates analysed to determine the nutrient composition using atomic absorption spectrophotometer (aas), uk, 2005. thereafter, the nitrogen (n) content was measure using kjeldal method. this process was observed for seven (7) days. finally, the water displacement method was adopted to measure the amount of biogas produced. the results show that at a ratio of 2:3 cattle to chicken dung, the highest gas yield was 117 mg/l on the first (1) day and the lowest gas yield was 53 mg/l using the blank sample on the seventh (7) day. nevertheless, using blank sample and ratios of 1:1, 2:3, and 3:2, the amounts of nitrogen compounds in the substrates prior to and following digestion were 1.17, 1.66, 2.45, and 2.39 mg/l and 2.17, 2.66, 3.25, and 3.19 mg/l, respectively. consequently, it is evident that the production of biogas and biofertilizer from agricultural waste has the potential to be a promising technology in low-income society. received: 3rd july 2024 reviewed: 14th february 2025 accepted : 16th february 2025 keywords: anaerobic digestion biochemical methane potential cattle dung chicken dung biogas production © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction effective waste management and recycling are essential for maintaining a healthy environment and mitigating pollution. animal manure particularly from cattle and chicken dung poses significant environmental challenges if not managed properly. improper handling can lead to pollution, odors, pest infestations, and eutrophication (castrillon et al., 2017). however, manure can be converted into valuable resources through anaerobic digestion, producing high-quality organic fertilizer rich in nutrients and compounds (li et al., 2021). while also reducing the environmental impacts associated with manure disposal. manure typically contains hemicellulose, cellulose, lignin and essential nutrients, making it an ideal substrate for biogas production and nutrient recovery. animal manure can be converted into biogas, a renewable energy source, by anaerobic digestion. the main components of biogas are carbon dioxide (co2) and methane (ch4), with typical concentrations of 50–70% (ch4) (kumar et al., 2018). a clean burning fuel that can be used for heating, cooking, and electricity generation can be produced by anaerobic digestion, which can extract up to 90% of the biogas found in animal manure (robert et al., 2020). for the treatment of nutrient-rich cattle and chicken manure, anaerobic digestion is an appropriate technique that can produce biogas and biofertilizer. excreta, hair and feathers, feed and water spills, processed waste, wastewater bedding, wood shavings, and composted manure are all components of cattle and chicken dung. manure is a great way to get nutrients for crops to grow and be productive. however, a number of variables, including animal species, diet, digestibility, proportions of protein and fiber, age, housing conditions, and stage of production, can affect its qualities and characteristics. the solid content, size, and composition of manure solids are crucial for collection, storage, handling, and utilization (li et al., 2021). nitrogen is an essential nutrient for plant growth and its extraction from animal manure can provide a valuable fertilizer for agriculture, cattle and chicken dung are rich in nitrogen with typical concentration ranging from azojete march 2025. vol.21(1):279-285 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:deborah2james@yahoo.com mailto:deborah2james@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 279-285. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: deborah2james@yahoo.com 280 1.5 to 4.5 % ((kumar et al., 2018). this study aims to investigate the biochemical methane potential of cattle and chicken dung using different ratios and their physico-chemical compositions. 2. materials and method 2.1 materials in this study, the materials and equipment used includes the following scotch bottles, bath with temperature control, coke or stopper, pipe for gas outlet, cow dung (inoculum), dung of chickens, water, atomic absorption spectrophotometer (aas) buck scientific 210vgp, uk, 2005, potassium hydroxide, sulphuric acid copper and tetraoxosulphate (vi) acid concentrate. 2.1.1 sample collection and preparation cattle and chicken dung were obtained at ramat polytechnic agricultural farm in maiduguri, borno state. it was packaged in a plastic container and then taken to the laboratory for examination. 2.1.2 preparation of slurry in this study, both cattle and chicken dung were prepared according to angelidaki et al., (2004) and (2009). the percentage of the methane in the substrate was calculated using bmp. before the slurry was put into the digester tank, it was thoroughly mixed to obtain an air-free sample to remove trapped air in the waste. the slurry was put into the digester and all contaminants were removed. 2.1.3 set up of digester two 500 ml scotch bottles were filled to the brim with 225 ml of inoculum (sludge) and a corresponding volume of substrate, leaving 50 ml available for the biogas head space. the ratio of substrate biomass to inoculum was maintained at 1:1, 2:3, and 3:2. then, two blank bottles with 225 ml of inoculum and 450 ml of tap water added were utilized as controls. before the stopper was applied, all bottles were flushed with 100% nitrogen gas (n) for one minute to remove any air from the head space. after that, the digester was kept in an incubator with water at a temperature that was mesophilic and at the neck of the bottle. every day for one minute, each digester was shaken in the water bath until the biogas production stopped, which took seven (7) days. using a graduated measuring cylinder and the water displacement method, the biogas production was monitored. the buck scientific 210vgp atomic absorption spectrophotometer (aas), uk, 2005 was then used to analyze the digestate, to ascertain the potentials of nitrogen (n) following the bmp test. all duplicate was conducted in triplicate. 2.2 water displacement laboratory experiment the purpose of this experiment was to measure the waste substrates' daily gas yield and volume. a measuring cylinder served as the water collector, a 400 ml flask as the water tank, and a 500 ml flask as the digester. the 400 ml flask (water tank) was connected to the digester using a rubber hose, and a longer rubber hose was placed through the top of the flask to the bottom, providing a tiny allowance. the 100 ml measuring cylinder, which acts as the water collector, received the water opposite end. the volume of water that was displaced in this experiment is intended to be equivalent to or represent the volume of biogas that was produced over the course of the experiment (see figure 1). water was added to the waste substrates as follows: 1. 225 ml of water plus 225 g of cattle dung. 2. 225 ml of water plus 225 g of chicken dung. 3. digester capacity: 500 ml 4. water tank capacity: 400 ml 5. slurry volume: 450 ml and 6. 50 ml head space in the digester the 500 ml flask was filled with the measured individual sample slurry, allowing the anaerobic digestion (ad) process to begin while the gas yield was monitored and recorded over the course of the seven-day residence http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 279-285. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: deborah2james@yahoo.com 281 3 :2 period. the setup was positioned in a spot that was readily exposed to sunlight in order to guarantee that the mesophilic range 25°c to 40°c was reached. figure 1: digester setup 2.2.1 digestion method the substrates were broken down before being analyzed. a precise weight of 1g of the prepared sample was placed into the kjeldal flask and filled with 1kg of potassium sulphate, 8g of copper sulphate, and 20ml of concentrated tetraoxosulphate (vi) acid, and thoroughly mixed. the content of the flask was heated for four hours until the mixture turned clear (blue green in color). thereafter, the heating was stopped, and the mixture was carefully cooled. 2.2.2 distillation 20 ml of the digested mixture was measured into a distillation flask, and 10 ml of 60% sodium hydroxide (naoh) was carefully added by the side of the flask so that the solution is sufficiently alkaline. 20 ml of 4% boric acid was added to the flask. the digested mixture was then transferred into a conical flask, and 100 ml of distilled water was added and mixed. the receiver tube's tip was positioned slightly below the surface of the standard when the distillation apparatus was put together. until all the ammonia was concentrated into the receiving flask, the contents were heated on a heating mantle. 2.2.3 titration 0.1n hydrochloric acid was added to the receiver flask and titrated until a color shift occurred. without testing the materials, a blank determination was performed with all the reagents in the same amounts. it was then combined with 2 ml of concentrated hydrochloric acid (80% hcl) and heated to 100 degrees celsius to dry it out. additionally, it was filtered with 5ml of 20% nitric acid using 10µm whatman filter paper and transferred into a 100ml volumetric flask. at this point, the extract is prepared for analysis with the analytical device. the buck scientific 210vgp atomic absorption spectrophotometer (aas), uk. (2005) was used to measure nitrogen (n). 3. results and discussion the physico-chemical characterisation of the substrate is presented in table 1. the physicochemical properties of the two substrates (cattle and chicken dung) show that the substrates are suitable for co-digestion. furthermore, it revealed that both substrates have similar characteristics. interestingly, while the chicken dung was found to have consisted of higher composition of cod, vs, nh3-n, tn, po4 3-, p and c/n than the cattle dung, the cattle dung has higher composition of ts and fog than the chicken dung. this study is in agreement with the results reported by angelidaki et al., (2009), mohammed et al., (2018) and cabrita et al., (2023). b la n k b la n k 1 :1 3 :2 2 :3 2 :3 1 :1 http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 279-285. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: deborah2james@yahoo.com 282 table 1. physico-chemical parameters of substrates parameters cattle dung chicken dung cod (mg/l) 8000 ± 3 19,600 ± 3 ph 8.85 ± 0.1 9.23 ± 0.1 vs (%) 76.23 ± 2 86.25 ± 2 ts (%) 89.55 ± 2 77.42 ± 2 nh 3 –n (%) 0.26 ± 0.001 0.37 ± 0.001 tn (mg\l) 3611 ± 3 12,510 ± 3 fog (mg/l) 2100 ± 2 1620 ± 2 po4 3(mg/l) 232 ± 0.01 631 ± 0.01 protein (mg/l) 1340 ± 3 5620 ± 3 c/n 16.45 ± 2 20.23 ± 2 3.1. average daily gas yield figure 2 shows the average volume of methane produced during the seven (7) days of digestion. it was observed that from the beginning to the end of the digestion significantly increased from 53 mg/l to 77 mg/l for the blank sample, 67 mg/l to 101 mg/l for the 1:1, 64 mg/l to 117 mg/l for the 2:3 and 66 mg/l to 93 mg/l for the 3:2 ratios respectively. figure 2: average daily gas yield in 7 days as observed from the total volume of biogas generated during the digestion. it shows that co-digestion of cattle and chicken dung produced between 53mg/l -117mg/l in the blank sample while) and ratio 2:3 mix ratio respectively. the most biogas produced at day seven (7) during the experiment appeared to give the best result. however, the co-digestion of chicken and cow dung using mix ratio of 2:3 produced higher biogas volume than that of 1:1, 3:2, and blank, at 117,101, 77, and 53 mg/l, respectively. a similar study was conducted by mohammed et al., 2019 who demonstrated biogas production from a blend of chicken, pig, and cow manure in a ratio of 1:1:1with corresponding nitrogen levels of 272n/ml, 167n/ml, and 80.5n/ml. similarly, ojo, (2021) conducted research and reported that the volume of biogas produced from a blend of 1:1 ratio of chicken to pig manure was 323ml and 528ml respectively. thus, biogas produced can be used to generate renewable green energy in the form of electricity and heat via a combined heat and power engine. 0 20 40 60 80 100 120 140 1 2 3 4 5 6 7 d ai ly g as y ie ld m g/ l retention days(hrs) blank 1;1 2;3 3;2 http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 279-285. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: deborah2james@yahoo.com 283 3.2. average composition of inoculum before digestion table 2. shows the average elemental composition of substrates obtain from chicken and cattle dung that have been weighed and compared with a blank, 1:1, 2:3, and 3:2 ratios before digestion. the result indicates that the concentration of n in the substrates are 1.17, 1.66, 2.45, and 2.39 mg/l respectively. table 2. average initial composition of inoculum before digestion parameters (g/ml) blank 1:1 2:3 3:2 n 1.17 1.66 2.45 2.39 p 0.80 1.14 1.66 1.64 k 0.39 0.57 0.83 0.79 ca 2.86 2.94 4.18 3.14 na 0.26 0.34 0.36 0.35 fe 0.023 0.026 0.030 0.027 mg 0.22 0.26 0.32 0.30 zn 0.18 0.20 0.45 0.30 si 10.75 14.06 16.04 15.46 a study conducted by abdulraheem et al., 2018 using sweet potatoes reported that n compound concentrations of was1.19 and 1.05 mg/l. however, the present in this study, n concentration was observed to be higher compare with the results obtain from their study. 3.3. average composition of inoculum after digestion table 3. shows the average composition of substrates made from chicken and cattle dung compared with the blank, 1:1, 2:3, and 3:2 ratios before digestion. the results show that n concentration in the substrate was 1.85, 2.43, 3.25, and 3.19 mg/l respectively. table 3. average composition of inoculum after digestion parameters(g/ml) blank 1:1 2:3 3:2 n 1.85 2.43 3.25 3.19 p 1.80 2.14 3.16 2.64 k 1.39 1.57 2.03 1.79 ca 1.86 1.94 2.55 2.14 na 0.26 0.34 0.36 0.35 fe 0.53 0.66 1.03 0.87 mg 0.12 0.16 0.22 0.20 zn 0.18 0.30 0.79 0.70 si 0.75 0.76 1.04 0.86 similarly, anthony et al., 2016 and mohammed et al.,2019 conducted a research and reported the presence of n concentration to be 3.11 mg/l and 0.84mg/l and 2.50mg/l and 2.01mg/l for rice and tea garden production respectively. also in a similar research by detpiratmongkol et al., 2014 , the result indicates that n concentration was 2.65mg/l and 2.33mg/l for production of kalmegh (andrographis paniculata nees.). 3.4. comparison of the average initial and final elemental composition of substrate there is a noticeable increase in the n composition following anaerobic digestion, of the two samples. the comparison is presented in tables 4. it was clear that the mixing ratios had varying effects on the substrates used for the digestion, as higher values were recorded in co-digestion of the substrates at 2:3 ratio. http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 279-285. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: deborah2james@yahoo.com 284 table 4: comparison of the average initial and final elemental composition of nitrogen (n) in the substrates mixing ratio initial (mg/l) final (mg/l) nitrogen blank 1.17 1.85 1:1 1.66 2.43 2:3 2.45 3.25 3:2 2.39 3.19 4. conclusion this study demonstrated the potentials of cattle and chicken dung as substrates for biogas production and nitrogen extraction. the co-digestion of cattle and chicken dung at a 2:3 ratio yielded the highest daily biogas production, outperforming the 1:1, 3:2, and blank ratios. similarly, both substrates are rich in nitrogen with concentrations ranging from 1.17 to 3.25 mg/l before and after digestion. the study concludes that cattle and chicken dung are viable sources of bioenergy (biogas and bio-fertilizer). it is noteworthy that the co-digestion of these substrates at a 2:3 ratio has potential for conversion into valuable npk blend products for organic fertilizer, offering a safe, cost-effective, and sustainable alternative to inorganic fertilizer currently in market. references abdulraheem, mi, adewale, o. and charles, e. f. 2018. influence of npk fertilizer and cow dung manure application on soil properties growth and yield of sweet potatoes (ipomoea batatas), european modern studies journal, 2(5): 6-10. angelidaki, im, alves, d., bolzonella, l., borzacconi, j. l., campos, aj., guwy, s., kalyuzhnyi, jenicek, p. and van lier, j. b. 2009. defining the biomethane potential (bmp) of solid organic wastes and energy crops: a proposed protocol for batch assays. water science and technology, 59(5): 927-933. angelidaki, i., and ahring, b. k. 2004. anaerobic thermophilic digestion of manure at different ammonia loads: effect of temperature. water environ resource, 28(4):727-731. anthony, n. m., mohammed, b., tumisang, s., catherine jn and charles, m. 2016. mesophilic anaerobic co digestion of cow dung, chicken dropping and grass clippings proceedings of world congress on engineering and computer science (wcecs), 2:2-4. cabrita, tm and santos, mt. 2023. biochemical methane potential assays for organic wastes as an anaerobic digestion feedstock. sustainability, 15:1-30. castrillon, l., vazguez, i., maranon, e. and satre, h., 2017. anaerobic thermophilic treatment of cattle manure in uasb reactors. waste management and research, 20:350356. detpiratmongkol, s., ubolkerd, t. and yoosukyingstaporn, s. 2014. effects of chicken, pig and cow manures on growth and yield of kalmegh (andrographis paniculata nees). journal of agricultural technology, 10(2):475-482. hati, km. and marti, kk. 2016. effect of inorganic fertilizer and farmyard manure on soil physical properties, root distribution, and water-use efficiency of soybean in vertisols of central india. bioresource technology, 97: 2182–2188. kumar, a., singh s., and kumar p. 2018. characterisation of feacal sludge and its management practices in urban areas of india. journal of environmental science and health, part b, 53,347-355. li, y., xu, j., liu, b., sun, q., li, j., lang, q., sun, r. and jin, h., 2021. effects of different biogas slurrries on soil microbial carbon metabolism, china journal eco-agriculture, 29:1921-1930. luz, fc, cordiner, s., manni, a., mulone, v. and rocco, v. 2017. anaerobic digestion of coffee grounds soluble fraction at laboratory scale: evaluation of the biomethane potential, applied energy, 207:166-175. http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 279-285. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: deborah2james@yahoo.com 285 mohammed b., anthony n. m., nomkhosi p. m. and edison m. 2019. biochemical methane potential analysis using cow dung, chicken manure and pig manure . proceedings of the international conference on industrial engineering and operations management bangkak,thailand .1710-1718 mohammed, am., syazwani, i., che man, h. and nik, n. 2018. effect of organic loading rate on anaerobic digestion performance of mesophilic (uasb) reactor using cattle slaughterhouse wastewater as substrate. international journal environmental resource and public health,15:1-19. monnet, f. 2003. an introduction to anaerobic digestion of organic waste, being a final report submitted to remade, scotland available on http://www.remade.org.uk/media/9102/an introduction to anaerobic digestion. ojo, om 2021. biogas production from digestion and co-digestion of pig dung and poultry manure. american journal of engineering research (ajer), 10(10): 114-118. robert, c., agnieskza,w., and piotr .b. 2020. energy generation through anaerobic fermentation of wetland biomass. energies 13(24) 6497. http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):107-112 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 107 evaluation of on-farm drainage system in nigeria: a review e. a. otuaro1* and j. k. adewumi2 1department of civil engineering, faculty of engineering, maritime university, okerenkoko, nigeria 2department of agricultural and bioresources engineering, college of engineering, federal university of agriculture, abeokuta, nigeria *corresponding author's email address: e.otuaro@yahoo.com article information submitted 3 january, 2024 revised 12 february, 2024 accepted 15 february, 2024 keywords: drainage crop yield planning management strategies abstract drainage involves the removal of the excess water on the farm to improve the aeration and trafficability of soils in regions characterized by seasonal highwater tables. there is no doubt that drainage is intrinsically linked to crop yield. a well-drained soil reduces water stress on crops and improves root development, which is required to increase crop yields and food production quality. nigeria is committed to a national policy that ensures sustainable development based on proper management of the environment to meet the needs of the present and future generations. this demands positive and realistic planning that balances human needs against the potential that the environment has for meeting them. management strategies must be implemented to achieve effective and efficient drainage systems. the existing on-farm drainage systems were evaluated and found ineffective and efficient; thus, modifications are required to improve the conditions at various locations in nigeria. 1.0 introduction natural and artificial rainfall (irrigation) apply water to crops for growth and development (mushombe et al., 2016). pore spaces fill with water applied through rainfall or irrigation and are absorbed by the plant's roots. when the pore spaces are saturated, water overflows the soil's surface and runs off into more extended drains in the field. drainage involves the removal of the excess water on the farm to improve the aeration and trafficability of soils in regions characterized by seasonally high-water tables (alfred et al. 2016). drainage systems help to increase crop yield of poorly drained soils by providing a better environment for plant growth, especially during wet periods, and improving field conditions for timely tillage, planting, and harvesting. when drainable water is removed from the soil profile, infiltration can occur. this is due to the available soil pore space, which allows water that would otherwise be stored in the surface depressions to infiltrate and have a direct pathway to downstream flow via the subsurface drains. although agricultural production has benefited from agricultural drainage in many regions and countries, there are concerns about potential environmental impacts. the most dramatic hydrological changes in a landscape occur when the latter is converted from native vegetation to intensive cropping systems (mushombe et al., 2016). nigeria is committed to a national policy that ensures sustainable development based on proper management of the environment to meet the needs of the present and future generations. this http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):107-112. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 108 demands positive and realistic planning that balances human needs against the potential that the environment has for meeting them. although disasters such as floods and erosion are nationwide challenges in nigeria, the intensity varies in different places. the problem, however, is most prominent in eastern and northern nigeria. as a result, arable lands, agricultural produce, and landed and household properties have all been damaged by gullies created right in the middle of roads, and many farmlands, markets, and communities have been cut off from one another. it is a fact that floods and erosion are natural occurrences (alfred et al., 2016). 1.1 drainage pattern according to the configuration of the channels, drainage systems can fall into one of several categories known as drainage patterns. drainage patterns depend upon the topography and geology of the land. the following are the types of drainage patterns (i.e. natural drainage) stated by ling et al. (2012) and valipour et al. (2020). 1.1.1 dendritic drainage system: they are not straight and are the most common drainage system. in a dendritic system, there are many contributing streams, which are then joined together into the tributaries of the main river. they develop where the river channel follows the slope of the terrain. dendritic systems form in v-shaped valleys. as a result, the rock types must be impervious and non-porous. 1.1.2 parallel drainage system: a parallel drainage system is a pattern of rivers caused by steep slopes with some relief. because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. this system forms on uniformly sloping surfaces. a parallel pattern also develops in regions of parallel, elongated landforms like outcropping-resistant rock bands. tributary streams tend to stretch out in a parallel-like fashion following the slope of the surface. 1.1.3 trellis drainage system: the geometry of a trellis drainage system is similar to that of a standard garden trellis along a strike valley. smaller tributaries feed into the steep slopes on the sides of mountains. these tributaries enter the main river at approximately 90-degree angles, causing a trellises-like appearance of the drainage system. 1.1.4 rectangular drainage system: rectangular drainage develops on rocks that are of approximately uniform resistance to erosion but have two directions of joining at approximately right angles or 90 degrees. the joints are usually less resistant to erosion than the bulk rock, so erosion tends to open the joints preferentially, and streams eventually develop along the joints. 1.1.5 radial drainage system: the streams radiate from a central high point in a radial drainage system. volcanos usually display excellent radial drainage. they can sometimes also be found on top of mountains. other geological features on which radial drainage commonly develops are domes and laccoliths. the drainage may exhibit a combination of radial patterns on these features. the radical pattern develops when streams flow from a central peak or dome-like structure in various directions. 1.1.6 centripetal drainage system: the centripetal drainage system is similar to the radial drainage system, with the only exception that radial drainage flows out versus centripetal drainage flows in 1.1.7 deranged drainage system: a deranged drainage system is a drainage system in drainage basins with no coherent pattern to the rivers and lakes. it happens in areas where there has been much geological disruption. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng otuaro and adewumi: evaluation of on-farm drainage system in nigeria: a review. azojete, 20(1):107-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 109 1.1.8 annular drainage system: in an annular drainage system, streams follow a roughly circular or concentric path along a belt of weak rock, resembling a ring-like pattern. it is best displayed by streams draining a maturely dissected structural dome or basin where erosion has exposed rimming sedimentary strata of wildly varying degrees of hardness, as in the red valley. 1.2 reason for artificial drainage wetlands soil, especially those found on farmlands, is drained with open ditches and trenches, primarily used for high-value crops such as vegetables (valipour et al., 2020). wetland soils usually need drainage to be used for agricultural purposes. people are confident that combining drainage and wetlands is the key to economic and environmental concerns, but there is no proof either way yet. the invention of wind-powered pumping engines in the 15th century gave room for some of the marginal land drainage. still, the final drainage of the lake had to await the design of large, steam-powered pumps and agreements between regional authorities. the lake was eliminated between 1849 and 1852, creating thousands of km² of new land in the netherlands (valipour et al., 2020). 1.3 classification of on-farm drainage system there are two major types of on-farm drainage systems. these are surface drainage and subsurface or underground drainage. drainage can also be categorized into a gravity system (surface and sub-surface) and a pump system (wells and sumps). 1. surface drainage this is the removal of the excess water from the surface of the farmland using constructed open ditches, field drains, and land grading and lateral ditches. the regular surface drainage systems, which start functioning as soon as an excess of rainfall or irrigation is applied, operate entirely by gravity (valipour et al., 2020). they consist of reshaped or reformed land surfaces and can be divided into bedded systems, used in flat lands for crops other than rice; • bedded systems, used in flat lands for crops other than rice • graded systems, used in sloping land for crops other than rice 2. sub-surface or underground drainage when subsurface drains are in place, the drainable water fraction of the soil profile is converted to short-term (detention) storage over a few hours, days, or weeks, depending on several variables (barnes et al. 2018). these include subsurface drain size, depth and spacing, soil type, outlet size/condition, and whether or not under continuous rainfall or snowmelt conditions. this is an orderly of excess water from the farmland artificially using different materials like pipes, tiles, moles and plastic tubes. the common type is the tile drains (sharma & kumar, 2023). this consists of pipes connected to a continuous line and laid in a narrow trench. these pipes have holes (openings) drilled around them to drain excess water toward the outlet. usually, filter materials are laid around the pipes to prevent holes from clogging. concrete and clay pipes are the most common tiles used in irrigated areas. bamboo sticks are extensively used in asia. they have been tested in many regions in nigeria and found to be suitable. 2.0 nigeria situations of on-farm drainage systems in this section, the situation of drainage in nigeria was looked into. the first of which is the zauro polder project (zpp). the scheme was designed for the sokoto river basin development authority to be used as a model for the farmers on the northern part of birnin http://www.azojete.com.ng/ mailto:e.otuaro@yahoo.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):107-112. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 110 kebbi next to the southern bank of sokoto rima valley. it was designed to irrigate above 11,000 ha and managed by 7,790 farmers (idah et al., 2009). the scheme was operational with a 2.65km flood safety dyke, 3.5m high, and a temporary pumping station with a generator. this central canal is connected to a compensation reservoir, four lateral canals, and a collector drain. these facilities are anticipated to improve water circulation and management to successfully operate the surface irrigation that is essentially practised in the area. at the end of the research by idah et al. (2009), it was discovered that four areas were waterlogged, caused mainly by lack of surface outflow, lack of effective drainage, lack of adequate percolation, an excessive inflow of water and increase in the underground water table height, these affected various farmers and their output because the farmland available for cultivation was reduced. the presence of excess water on the farmland reduced the crop yield of the farmers. the second publication that was looked into was the study undertaken at offa local government of nigeria by musa et al. (2010). research on the effect of surface runoff on nigeria's rural roads (a case study of offa lga) was undertaken, which looked into the following highways and farmlands in offa lga of nigeria, the roads were erin-offa road, oyun-offa road maikka-offa road, ojoku-offa road, wara-ilorin road and ogbomoshoilorin road and the farmlands in the area. the study asserted that the influence of surface runoff on the rural roads and farmlands in offa local government area cannot be overemphasized as most farmers lose their produce during transportation due to portholes caused by surface runoff and reduction in the size of land suitable for cultivation thereby hindering farmers activities and resulting to decrease in their produce during the peak rainy seasons (musa et al. 2010). 3.0 discussion of drainage systems in geomorphology, a drainage system is the pattern formed by the streams, rivers, and lakes in a particular drainage basin. the land's topography governs them, whether a specific region is dominated by hard or soft rocks, and the gradient of the land. drainage basins are divided from each other by topographic barriers called watersheds. a watershed represents all of the stream tributaries that flow to some location along the stream channel (oweis, 2018). the number, size, and shape of the drainage basins found in an area vary, and the topographic map is larger (bogale, 2021). on-farm drainage criteria can be defined as criteria specifying the highest permissible levels of the water table, on or in the soil, thereby reducing or eradicating the problems of water logging for agricultural benefits (singh & lal, 2018; kamra et al. 2019). when the actual water levels are higher than specified by the criteria, an on-farm drainage system may have to be installed, or an already installed system may have to be improved to eliminate the water logging. however, if a drainage system has lowered water levels to a depth greater than specified by the criteria, then an over-designed system needs to be modified (du preez & van huyssteen, 2020). other criteria like the technical drainage criteria (to minimize the costs of installing and operating the system while maintaining the agricultural criteria), environmental drainage criteria (to reduce the environmental damage), and economic drainage criteria (to maximize the net benefits) are also taken into consideration when designing a drainage system. drain is intrinsically linked to crop yield; well-drained soil reduces water stress on crops and improves root development, which is required to increase crop yields and quality of production (ullah et al., 2019). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng otuaro and adewumi: evaluation of on-farm drainage system in nigeria: a review. azojete, 20(1):107-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 111 3.1 analysis of on-farm drainage systems the effect of on-farm drainage is strongly influenced by the features of an individual location, which includes: topography (slope), soil type (hydraulic conductivity) as well as drainage system design (spacing, depth and size of drains) (tuohy et al. 2018, kamra et al. 2019). the purposes of on-farm drainage systems are to reclaim and conserve land for agriculture, increase crop yields, permit the cultivation of more valuable crops, allow the cultivation of more than one crop a year, and reduce crop production costs in otherwise waterlogged land. such objectives are met through two direct effects and many indirect effects. the direct impact of installing a drainage system in waterlogged land that was given by barnes et al. (2018) and manik et al. (2019) as follows: • a reduction in the average amount of water stored on or in the soil, inducing drier soil conditions and reducing waterlogging; • a discharge of water through the system. it was also mentioned that assessing the indirect effects is more complex, but not less important, than evaluating the direct effects. the indirect effects, which can be physical, chemical, biological, and/or hydrological, can be either positive or negative, some of which were given as; • negative effects owing to the drier soil conditions: decomposition of organic matter; soil subsidence; acidification of potential acid sulphate soils; increased risk of drought; ecological damage; • the indirect effects of drier soil conditions on weeds, pests, and plant diseases: these can be both positive and negative; the net result depends on the ecological conditions; • positive effects owing to the discharge: removal of salts or other harmful substances from the soil; availability of drainage water for various purposes; • negative effects of the discharge include downstream environmental damage by salty or otherwise polluted drainage water, as well as the presence of ditches, canals, and structures impeding accessibility and interfering with other infrastructural elements of the land. 4.0 conclusion undoubtedly, drainage is intrinsically linked to crop yield, ensuring food security for the evergrowing population in developing nations like nigeria. this implies that well-drained soil reduces water stress on crops and improves root development, which is required to increase crop yields and production quality in poorly drained soil. the existing on-farm drainage systems were assessed and found ineffective and efficient; thus, modification is required to improve the on-farm conditions at various locations in nigeria. references alfred, ja., jokthan, gey. and peter, t. 2016. principles of irrigation and drainage (lecture note), 5 dar es-salaam street, off aminu kano crescent wuse ii, abuja, published by national open university of nigeria. barnes, ml., welty, c. and miller, aj. 2018. impacts of development pattern on urban groundwater flow regime. water resources research, 54(8): 5198-5212. http://www.azojete.com.ng/ mailto:e.otuaro@yahoo.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):107-112. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 112 bogale, a. 2021. morphometric analysis of a drainage basin using geographical information system in gilgel abay watershed, lake tana basin, upper blue nile basin, ethiopia. applied water science, 11(7): 122. du preez, cc. and van huyssteen, cw. 2020. threats to soil and water resources in south africa. environmental research, 183: 109015. idah, pa., musa, jj., mutapha, hi. and arugungu, mm. 2009. an investigation into the causes of water logging at zauro polder pilot project scheme in birnin kebbi, nigeria. au journal of technology, 13(2): 95-100. kamra, sk., kumar, s., kumar, n. and dagar, jc. 2019. engineering and biological approaches for drainage of irrigated lands. research developments in saline agriculture. springer nature singapore pte ltd, gateway east, singapore, pp. 537-577. ling, z. and eric, g. 2012. a study of variables characterizing drainage patterns in river networks, international archives of photogrammetry, remote sensing and special information sciences, vol. xxxix-b2, 2012 xxii isprs congress melbourne, australia. manik, sn., pengilley, g., dean, g., field, b., shabala, s. and zhou, m. 2019. soil and crop management practices to minimize the impact of waterlogging on crop productivity. frontiers in plant science, 10: 140. musa, jj., abdulwaheed, s. and saidu, m. 2010. effect of surface runoff on nigeria rural road a case study of offa lga. au journal of technology, 13(4): 242-248. mushombe, m., alain, nr. and silvio, jg. 2016. assessment of the impact of subsurface agricultural drainage on soil water storage and flows of a small watershed. mdpi water, 8: 326., doi: 10.3390/w8080326. oweis, t. 2018. drainage systems to support sustainable water use henk ritzema, wageningen university, the netherlands. water management for sustainable agriculture, burleigh dodds science publishing, wageningen, pp. 489-516. sharma, pk. and kumar, s. 2023. drainage. soil physical environment and plant growth: evaluation and management. cham: springer international publishing, pp. 107-123. singh, g. and lal, k. 2018. review and case studies on biodrainage: an alternative drainage system to manage waterlogging and salinity. irrigation and drainage, 67: 51 64. tuohy, p., o’loughlin, j., peyton, d. and fenton, o. 2018. the performance and behaviour of land drainage systems and their impact on field scale hydrology in an increasingly volatile climate. agricultural water management, 210: 96-107. ullah, h., santiago-arenas, r., ferdous, z., attia, a. and datta, a. 2019. improving water use efficiency, nitrogen use efficiency, and radiation use efficiency in field crops under drought stress: a review. advances in agronomy, 156: 109-157. valipour, m., krasilnikof, j., yannopoulos, s., kumar, r., deng, j., roccaro, p., mays, l., grismer, me. and angelakis, an. 2020. the evolution of agricultural drainage from the earliest times to the present. sustainability, 12(1): 416. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):509-522 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 509 student perceptions of ict-based lecture delivery during covid-19 pandemic u. a. baba1, m. i. ishaq²*, a. mohammed³, i. halliru⁴ 1department of computer sciences, pen resources university, gombe, nigeria ²department of mechanical engineering, university of maiduguri, p.m. b 1069, maiduguri, nigeria ³department of information technology, modibbo adama university, yola, nigeria ⁴department of civil and water resources engineering, university of maiduguri, p.m. b 1069, maiduguri, nigeria *corresponding author's email address: m.ishaq@unimaid.edu.ng article information submitted 8 november, 2023 revised 1 march, 2024 accepted 6 march, 2024 keywords: covid 19 pandemic ict online class ssps abstract the covid-19 pandemic forced schools to adopt online learning methods. this study investigates the impact of information and communication technology (ict) usage on student performance in adamawa state, nigeria, focusing on yola north local government. a quantitative approach employed a survey questionnaire distributed to 170 participants (students, teachers, and principals). descriptive statistics analysed demographic profiles, ict access, online learning satisfaction, and perceived barriers. while many students and teachers agreed they had sufficient it skills, access to equipment and internet connectivity was limited. zoom was the preferred online learning tool, but challenges like inconsistent communication, difficulty participating, and limited practical sessions were reported. barriers included lack of consistent power supply, poor learning environment, and limited access to materials. ict played a crucial role in continuing education during the pandemic, but significant challenges remain. improved access to resources, better connectivity, and enhanced online learning practices are essential for optimizing student performance in future disruptions. 1.0 introduction the novel coronavirus disease (covid-19) is an infectious disease caused by a newly discovered coronavirus called severe acute respiratory syndrome coronavirus 2 (sars-cov2); the official name for the disease that is caused by sars-cov-2 is covid-19 (who, 2023). covid-19 was first discovered in wuhan, hubei province, china in 2019 and is now widespread (andersen et al., 2020; simon et al., 2020). globally, as of october 14, 2023, there have been 777,191203 confirmed cases of covid-19 including 6,961,014 deaths, reported to the world health organization (who) (who, 2023). due to the surge in the number of covid-19 confirmed cases around the world, governments took several measures to prevent or limit the spread of the pandemic and most educational institutions were closed down as a way to curb the spread of the disease (gonzalez et al., 2020). this closure of educational institutions led to an unprecedented impact on the educational system in a lot of developed as well as developing countries like nigeria (kapasia et al., 2020). the ability to respond to the closure of schools depends largely on the level of development, for example, by april 2020, 86% of children in primary education had been out of school in countries with low human development as compared to 20% in countries with very high human development (de giusti, 2020). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 510 with the advancement of technology; to meet the challenges faced instead of the covid-19 pandemic, a lot of learning institutions across the globe adopted the use of new technologies and appropriate information and communication technology (ict) resources for teaching and learning (adarkwah, 2021). hence, one of the effects of the pandemic can be the academic performance of secondary school students in developing countries, as for most students, using ict resources for online learning is a strange phenomenon (hashemi, 2021). the spread of covid-19 has caused fear, and anxiety, and traumatized citizens around the world since its inception in 2019, and it is spreading everywhere across the globe with most countries putting preventive measures in place to curb or limit the spread of the disease (ekpenyong et al., 2020). these measures include lockdown and travel restrictions, quarantine, social distancing, wearing of facemasks and so on. if someone develops the symptoms, he or she is advised to remain in isolation for the good of others. this case leads to panic, and people want to be more and more aware of the situation in this crisis (crawford et al., 2020). the number of confirmed cases of covid-19 keeps rising across the globe with the first case of covid-19 reported in nigeria by the federal ministry of health on 27february 2020. this was the case of an italian citizen who works in nigeria and returned from milan, italy to lagos, nigeria on the 25th of february, 2020 (agbele and oyelade, 2020). in nigeria, as of 14 october 2023, there have been 266,675 confirmed cases of covid-19 with 3,155 deaths (ncdc, 2023). while many sectors have been seriously affected by the pandemic, academia was amongst the first few sectors that faced a rapid shutdown of all its activities. the covid-19 pandemic has caused the largest disruption of education in history, having already had a near-universal impact on learners and teachers around the world, from pre-primary to secondary schools, technical and vocational education and training (tvet) institutions, universities, adult learning, and skills development establishments (rajhans et al., 2020). by mid-april 2020, 94 per cent of learners worldwide were affected by the pandemic, representing 1.58 billion children and youth, from pre-primary to higher education, in 200 countries (de giusti, 2020). covid-19 has triggered a substantial revolution, imposing a lot of challenges in the educational system ranging from primary school, and secondary school, to higher education in nigeria and globally. a large number of schools were already closed for several months even before the nationwide school closure instead of the pandemic, some, because of severe insecurities, strikes or climatic hazards (de giusti, 2020). the pandemic can be seen as an opportunity to restructure our longstanding educational systems and establish better and updated practices in academia, suitable for the present technologically-advanced generation of learners (ntibi and effiong, 2021). according to the national policy on education, the main goal of secondary education is to prepare the learner for higher education and specifically to provide the learner with the necessary knowledge to be able to successfully live in the modern age of science and technology (ntibi and effiong, 2021). after the nationwide closure of schools, both public and private schools have mostly switched to online learning as a result of the pandemic. in adamawa state, all public secondary schools started learning through television and radio stations (gotel tv, atv, gotel radio and abc) while some private schools such as aliyu mustapha academy, ahmadu ribadu college, etc, resorted to the use of various ict tools like whatsapp, telegram, zoom meetings, youtube, etc. to aid learning during the pandemic. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com baba et al: student perceptions of ict-based lecture delivery during covid-19 pandemic. azojete, 20(2):509-522. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 511 before the covid-19 pandemic, the world was already facing formidable challenges in fulfilling the promise of education as a basic human right and after about four months of the global crisis, we have started realizing that covid-19 is here to stay and we need to find solutions to move on. this crisis can be looked upon as an opportunity to reconstruct our longstanding educational systems and establish better and updated practices in academia, suitable for the present generation of learners (de giusti, 2020; rajhans et al., 2020). one of the effects of the pandemic can be the academic performance of secondary school students in developing countries, as for most students, using ict resources for online learning is a strange phenomenon (hashemi, 2021). adamawa state government adopted online learning as a means to curb the spread of the pandemic in the state. there are limited studies that have been published to assess the effect of ict usage on the academic performance of secondary school students during the pandemic. hence, this study is aimed at investigating the effect of ict usage on the academic performance of secondary school students in adamawa state during the covid-19 pandemic by evaluating the level of access to ict resources by the students and teachers, the perceived effectiveness of online learning during the pandemic and also determining the perceived barriers to online learning in lieu of the covid-19 pandemic. 2.0 literature review 2.1 education during the covid-19 pandemic the covid-19 pandemic presents a damaging effect globally. specifically for health as well as all spheres of life like the economy, education, supply chain, and social security containing an overwhelmingly negative effect on the enjoyment of social, economic and cultural rights. this led the global campaign for education to reaffirm its position on the need to respond to covid-19 to protect human rights in the short, medium and long terms (espino-díaz et al., 2020; lorente et al., 2020) the covid-19 pandemic has affected the educational systems worldwide, leading to the neartotal closures of schools, universities and colleges all over the world. most governments around the world have temporarily closed educational institutions, terminated all public events, and placed travel restrictions in an attempt to reduce the spread of the pandemic and bring it under control (lorente et al., 2020; meo et al., 2020). the unesco global monitoring education report for 2020 has stated that the covid-19 crisis is an opportunity to focus all efforts on developing policies for educational inclusion and has invited interested organizations to an initiative to ensure and provide continuity of education during the global emergency caused by covid-19. the central idea is that organizations should commit to providing educational services and materials with open and free access. the world bank, and the organization for economic cooperation and development (oecd) are some of the numerous organizations that are taking a lot of measures to turn the crisis into an opportunity to improve the education system for both students and teachers in developing countries (chatterjee and chakraborty, 2021; lorente et al., 2020). according to lorente et al. (2020), “to truly the measure impact that covid-19 is having and will have on education in the short-, medium-, and long-term, it is necessary to consider some determining contextual elements. firstly, the lack of schooling and gender bias. secondly, this entire crisis falls on top of a previous global learning crisis with 617 million students aged between 12 and 14, who, at the end of their primary education, have serious learning deficiencies in reading and mathematics. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 512 thirdly, there is weakness built into the “international architecture for education”, as claimed by burnett, which is the “set of international agencies and institutions, official and unofficial, public and private, that receive international resources to support the educational development of countries” that, together with governments in developing countries and donors, are failing the world with out-of-school figures which have been stagnant for years and with a learning crisis that still needs to be resolved. from his point of view, it is, among other things, a problem of a lack of effective leadership, a lack of definition in global educational priorities, and insufficient funding for the development of educational systems in low-income countries, especially in sub-saharan africa. besides this, the pandemic will aggravate its causes and make solutions more difficult”. simon et al. (2021) explored the impact of the covid-19 lockdown and relevant vulnerabilities on capability well-being, mental health and social support in austria. the authors used a crosssectional survey to get responses about peoples’ experiences during the covid-19 lockdown and concluded that the negative capability well-being, mental health and social support impacts of the covid-19 lockdown were strongest for people with a history of mental health treatment. social distancing is one of the measures of hygiene which have proven to be an effective reactions to the threat of increasing numbers of covid-19 cases and fatalities (who, 2023). 2.2 ict usage and student performance in the most fragile education systems, the interruption of the school year due to the covid19 pandemic will have a disproportionately negative impact on the most vulnerable pupils, it could negatively affect the performance of students and their general interest in academia (de giusti, 2020; ntibi & effiong, 2021) if the students are not engaged productively, their presence at home can muddle the economic situation of parents, who must find solutions to provide care or compensate for the loss of school meals. school closures could promulgate youth involvement in crimes, loss of interest in learning, poor academic performance, increase in students' debts, extension of graduation time and can ruin academic dreams of students amongst other negative factors (merkl-davies, doris m.; brennan, 2001; pozo et al., 2021). in response to school closures, unesco (2023) recommended the use of distance learning programs, social distancing and open educational applications and platforms that schools and teachers can use to reach learners remotely to limit the disruption of education. dozens of independent schools in australia were shut down, while some moved to online classes. students learn from home, while some schools were opened but implemented strong measures to ensure a social distancing strategy. the opening of schools amidst the coronavirus pandemic was backed by the australian government to enhance teaching and learning (priyadarshini et al., 2020). according to de giusti (2020), “relatively few countries are monitoring the effective reach and use of distance learning modalities. however, estimates indicate variable coverage: distance learning in high-income countries covers about 80–85 per cent, while this drops to less than 50 per cent in low-income countries. this shortfall can largely be attributed to the digital divide, with the disadvantaged having limited access to basic household services such as electricity; a lack of technology infrastructure and low levels of digital literacy among students, parents, and teachers”. in nigeria, covid-19 has spread across the thirty-six (36) states of the country including abuja, and the federal capital territory (fct) which caused all educational institutions to be closed down for a very long period. after a unanimous decision was reached at a virtual consultative meeting between stakeholders on the educational system regarding the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com baba et al: student perceptions of ict-based lecture delivery during covid-19 pandemic. azojete, 20(2):509-522. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 513 resumption of school activities, exit classes of nigerian secondary schools resumed on august 4, 2020, and the students were given two weeks to prepare for the west african school certificate examinations (wasce) which started on august 17, 2020 (ntibi & effiong, 2021). 2.2.1 online teaching and learning during covid-19 ensuring learning continuity during the time of school closures became a priority for governments across the globe, many of which turned to ict, requiring teachers to move to online delivery of lessons (almaiah et al., 2020; de giusti, 2020). in areas with limited connectivity, governments have used more traditional distance learning modalities, often a mix of educational television and radio programming, and the distribution of print materials (agbele and oyelade, 2020; lorente et al., 2020) due to the closure of all the academic institutions across the country, the ministry of higher education (mohe) of afghanistan for example, decided to compensate for the teaching process through an online teaching system. therefore, the mohe of afghanistan designed and administered an online platform system called the higher education learning management system (helms) to rapidly respond to the covid-19 crisis in the educational context. the transformation process of face-to-face teaching began with online teaching where thousands of teachers and students were allowed to employ this platform. since then, public universities across the country have experienced online teaching as a new phenomenon during the covid19 pandemic where there was no prior preparation for such an emergency case (hashemi, 2021). for this purpose, hashemi (2021) investigated the effects of covid-19 on the academic performance of afghan students and their level of satisfaction with online teaching. the author also explored the significant difference in academic performance and the level of student satisfaction with online teaching across genders from both public and private universities in afghanistan. the author used descriptive and inferential statistical methods of analysis and found that covid-19 hurts the academic performance of afghan students and also discovered that the students were highly dissatisfied with online teaching during the pandemic. hence, after the investigation, hashemi (2021) presented a lot of suggestions to the mohe and other stakeholders to enhance both the quality and capacity of online teaching during unexpected emergencies and, to stimulate the student’s academic performance so that their level of satisfaction with online teaching will improve. the author recommended that the mohe and all the involved stakeholders provide online teaching applications, professional training for online teaching applications and devices, wi-fi facilities, cheap internet packages, and other virtual resources. the author further recommended that teachers should provide interactive and comprehensive online services along with supportive guidance and constructive feedback that could enhance the student’s level of satisfaction with online teaching. according to de giusti (2020), school closures have necessitated changes in – and in some cases caused serious disruptions to – how students are evaluated.in most countries, exams have been postponed; in a few, they have been cancelled; and, in others, they have been replaced by continuous assessments or alternative modalities, such as online testing for final exams relatively few countries are monitoring the effective reach and use of distance learning modalities. in nigeria, in close coordination with health, environmental, education, and school safety experts, guidelines were drafted to safely reopen schools and learning facilities for quality teaching and learning (ntibi and effiong, 2021). to cover up the loss of education during lockdown, many schools have offered distance learning or online courses to students. for example, in nigeria and by extension in adamawa state, all public secondary schools started learning through television and radio stations (gotel tv, atv, gotel radio and abc) while some private schools such as aliyu mustapha academy, http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 514 ahmadu ribadu college, etc, resorted to the use of various ict tools like whatsapp, telegram, zoom meetings, youtube, to aid learning during the pandemic. 3.0 methodology the research was carried out on secondary schools within yola north local government of adamawa state and focused on investigating the effect of ict usage on the academic performance of secondary school students in adamawa state during the covid-19 pandemic. this was achieved by evaluating the level of access to ict resources by the students and teachers, assessing the perceived effectiveness of online learning during the pandemic and also determining the perceived barriers to online learning in lieu of the covid-19 pandemic. due to the limited time and resources, the research was restricted to only a few secondary schools within yola north local government of adamawa state. 3.1 research design the study adopted a quantitative research design, in which a survey questionnaire was adapted to assess the effect of ict usage on student’s performance. the assessment is in both public and private secondary schools in yola north during the covid-19 pandemic. the obtained data was analysed through descriptive statistical analysis. the research employed descriptive statistics using spss version 26. this is to identify the frequency and percentage of the respondents’ demo-graphic profile, as well as to evaluate the level of access to ict resources by the students and teachers during the pandemic. furthermore, this is also to measure their level of satisfaction with online teaching and to determine the perceived barriers to online learning in lieu of the covid-19 pandemic. 3.2 population and sampling participants according to the local government educational authority, as of the time of this research, yola north local government area consists of eighty-three private schools (83) and thirty-seven (37) public schools. 3.2.1 population of the study the schools as well as participants are randomly selected from one hundred and ten secondary schools and an estimated number of four hundred and twenty-nine thousand (429,000) students. the participants from each selected school include both teachers and students to be able to achieve the stated aim and objectives of the research. 3.2.2 sampling technique the selection process of the sampling was employed through the use of a multi-stage sampling technique involving stratified and simple random sampling techniques to ensure that every sample has an equal chance of being selected in the study and the choice of yola north metropolis is due to its large size as compared to another district within the local government area. 3.2.3 sample size the instrument used for data collection is a questionnaire shared directly with 170 people from the target population at random, consisting of 15 teachers and 155 students (to assess the effect of ict usage on student’s performance in both public and private secondary schools in yola north during the covid-19 pandemic). 3.4 data collection instrument the data collection instrument is a questionnaire which consists of two sections: section a is designed to obtain the demographic data of the respondents, while section b is designed to obtain information using the five-point likert scale for measuring responding opinion level of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com baba et al: student perceptions of ict-based lecture delivery during covid-19 pandemic. azojete, 20(2):509-522. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 515 agreement/disagreement ranging from strongly agree to strongly disagree which will aid in answering the research questions. 3.5 data analysis the process of data analysis began after the questionnaires were retrieved from the respondents through the statistical package of social science (spss) software, version 26. the descriptive statistical analysis was used to compute the percentage, and frequency of the respondent’s demographic profile as well as to evaluate the level of access to ict resources by the students and teachers during the pandemic. also, it was used to measure their level of satisfaction with online teaching and, to determine the perceived barriers to online learning in lieu of the covid-19 pandemic. 4. results and discussion 4.1 results the demographic information obtained is presented in table 1. table 1: demographic information and availability of ict tools variables frequency percentage (%) gender male female 66 19 77.6 22.4 category of the respondent principal student teacher student & teacher 2 48 32 3 2.4 56.5 37.6 3.5 affiliation school private school public school 38 47 44.7 55.3 do you have sufficient it skills or computer knowledge (it skills)? yes no 68 17 80 20 you have sufficient equipment and facilities (computer/laptop/internet/software) to participate in online lectures yes no 53 32 62.4 37.6 total 85 100 in table 1, the demographic information of the study shows that more males participated in the study, that is 77.6% were male and 22.4% were females. the categories of the participants involve the principal, students and teachers. the study shows that more students participated with 56.5% of the total participants. most of the students are from public schools and most of the participants say they have sufficient ict skills which is 80% of the participants. 62.4% of the participants say that they have sufficient equipment such as the internet, laptop, internet and software for online lectures. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 516 table 2 below shows the tools mostly used for online teaching and learning popularly called ict tools which include social media platforms such as whatsapp, telegram, facebook, zoom, google classroom etc. the participants in this study mostly use zoom (35.3%) followed by whatsapp (18.8%) and 17.6% use google classrooms for their online learning. table 2: tools used in online learning and teaching which tools are used in online teaching/ learning? frequency per cent (%) valid percent cumulative percent valid google classroom 15 17.6 17.6 17.6 other 4 4.7 4.7 22.4 other | team app 1 1.2 1.2 23.5 other | teams 1 1.2 1.2 24.7 telegram | other 1 1.2 1.2 25.9 whatsapp 16 18.8 18.8 44.7 whatsapp | google classroom 2 2.4 2.4 47.1 whatsapp | google classroom | telegram 1 1.2 1.2 48.2 whatsapp | other 1 1.2 1.2 49.4 whatsapp | zoom 1 1.2 1.2 50.6 whatsapp | zoom | google classroom 1 1.2 1.2 51.8 whatsapp | zoom | google classroom | telegram 1 1.2 1.2 52.9 whatsapp | zoom | google classroom | telegram | other 1 1.2 1.2 54.1 whatsapp | zoom | telegram 1 1.2 1.2 55.3 zoom 30 35.3 35.3 90.6 zoom | google classroom 5 5.9 5.9 96.5 zoom | google classroom | telegram 3 3.5 3.5 100.0 total 85 100.0 100.0 table 3: ict skills for online teaching and learning you have sufficient computer knowledge and it skills to conduct your online teaching and learning class? frequency per cent (%) valid percent cumulative percent valid agree 37 43.5 43.5 43.5 disagree 11 12.9 12.9 56.5 disagree | strongly disagree 1 1.2 1.2 57.6 neutral 11 12.9 12.9 70.6 strongly agree 21 24.7 24.7 95.3 strongly agree | agree 1 1.2 1.2 96.5 strongly disagree 3 3.5 3.5 100.0 total 85 100.0 100.0 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com baba et al: student perceptions of ict-based lecture delivery during covid-19 pandemic. azojete, 20(2):509-522. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 517 table 3 shows that the participants agree that they have sufficient computer knowledge and it skills to conduct online teaching and learning classes. 37% of the participants agree that they have enough knowledge to participate in online teaching and e-learning. 11% were neutral and only 14% said that they do not have enough knowledge to conduct online teaching and elearning. table 4: training on online lectures do you prefer to have training on conducting online lectures? frequency per cent (%) valid percent cumulative percent valid agree 41 48.2 48.2 48.2 disagree 3 3.5 3.5 51.8 neutral 16 18.8 18.8 70.6 strongly agree 21 24.7 24.7 95.3 strongly agree | agree 1 1.2 1.2 96.5 strongly disagree 3 3.5 3.5 100.0 total 85 100.0 100.0 the participants were asked if they preferred to have online lectures. the majority of the participants agree that 41% of the participants agree that they prefer online classes and 3.5% of the participants say they strongly disagree. table 5: poor communication with lecturers during online classes inconsistent/poor contact and communication with the lecturers? frequency per cent (%) valid percent cumulative percent valid agree 37 43.5 43.5 43.5 disagree 8 9.4 9.4 52.9 neutral 23 27.1 27.1 80.0 strongly agree 16 18.8 18.8 98.8 strongly disagree 1 1.2 1.2 100.0 total 85 100.0 100.0 the participants were asked if there was inconsistent and poor communication with the lecturers. most of the participants agree that there is poor communication with the lecturer and only 10.6% say that there is good communication with the lecturers. table 6: difficulty to participate in online lectures it is difficult to participate in the online classes? frequency per cent (%) valid percent cumulative percent valid agree 32 37.6 37.6 37.6 disagree 21 24.7 24.7 62.4 neutral 13 15.3 15.3 77.6 neutral | disagree 1 1.2 1.2 78.8 strongly agree 15 17.6 17.6 96.5 strongly disagree 3 3.5 3.5 100.0 total 85 100.0 100.0 table 6 shows that 37.6% of the participants agree 17.6% strongly agree that it is difficult to participate in online classes, 24.7% disagree, 13% are neutral and only 3% strongly disagree. table 7: level of motivation during online classes students are motivated during online lectures? frequency per cent (%) valid percent cumulative percent http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 518 valid agree 34 40.0 40.0 40.0 disagree 19 22.4 22.4 62.4 neutral 18 21.2 21.2 83.5 strongly agree 12 14.1 14.1 97.6 strongly disagree 2 2.4 2.4 100.0 total 85 100.0 100.0 in table 7, the participants of the study were asked if they were motivated during online lectures. the responses show that 40% of the participants agree, 22.4% disagree, 221.2% are neutral, 14.1 strongly agree and 2.4% strongly disagree. this implies that most participants agree that they were motivated during online lectures. table 8: questions during online lectures? students ask questions or clear doubts during online lectures. frequency per cent (%) valid percent cumulative percent valid agree 42 49.4 49.4 49.4 disagree 13 15.3 15.3 64.7 neutral 14 16.5 16.5 81.2 strongly agree 11 12.9 12.9 94.1 strongly disagree 5 5.9 5.9 100.0 total 85 100.0 100.0 in table 8, the participants were asked if they were able to ask questions during online lectures. the result of the study shows 49.4% of the participants ask questions when they are in doubt. 16.5% were neutral and 15.3% of the respondents disagreed. therefore, this implies that the majority of the participants agree that they ask questions when in doubt. table 9: feedback during online class students give feedback during class online. frequency per cent (%) valid percent cumulative percent valid agree 47 55.3 55.3 55.3 agree | disagree 1 1.2 1.2 56.5 disagree 11 12.9 12.9 69.4 neutral 15 17.6 17.6 87.1 strongly agree 11 12.9 12.9 100.0 total 85 100.0 100.0 the participants were asked if the students give feedback during classes online. 55.3% of the participants agree that students give feedback during online classes 1.2% disagree and 17.6 are neutral. table 10: students’ level of comprehension during online lectures the students were able to comprehend what was taught to them frequency per cent (%) valid percent cumulative percent valid agree 50 58.8 58.8 58.8 disagree 8 9.4 9.4 68.2 neutral 17 20.0 20.0 88.2 strongly agree 10 11.8 11.8 100.0 total 85 100.0 100.0 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com baba et al: student perceptions of ict-based lecture delivery during covid-19 pandemic. azojete, 20(2):509-522. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 519 the respondents were asked if students were able to comprehend what was taught to them. 58.8% of the participants agree, 9.4% disagree and 20% are neutral. this implies that the majority of the participants agree that the students comprehend what was taught to them. table 11: difficulty in conducting practical difficulties in conducting practical frequency per cent (%) valid percent cumulative percent valid agree 30 35.3 35.3 35.3 disagree 2 2.4 2.4 37.6 neutral 15 17.6 17.6 55.3 strongly agree 38 44.7 44.7 100.0 total 85 100.0 100.0 in table 11, 35.3% of the participants agree that there is difficulty in conducting practical, 2.4% disagree and 17.6% are neutral. this implies that the majority find it difficult to conduct practical. table 12: online environment takes more time the online environment simply takes more time. frequency per cent (%) valid percent cumulative percent valid agree 32 37.6 37.6 37.6 disagree 17 20.0 20.0 57.6 neutral 10 11.8 11.8 69.4 neutral | disagree 2 2.4 2.4 71.8 strongly agree 20 23.5 23.5 95.3 strongly disagree 4 4.7 4.7 100.0 total 85 100.0 100.0 the majority of the participants (37.6%) agree with 23.5% strongly agreeing that the online environment takes more time, 20% disagree 4.7% strongly disagree and 11.8% being neutral. this implies that the majority of the respondents believe that the online environment takes more time. table 13: lack of constant supply lack of constant power supply frequency per cent (%) valid percent cumulative percent valid agree 33 38.8 38.8 38.8 disagree 6 7.1 7.1 45.9 neutral 4 4.7 4.7 50.6 strongly agree 41 48.2 48.2 98.8 strongly disagree 1 1.2 1.2 100.0 total 85 100.0 100.0 in table 13, 38.8% of the respondents and another 48.2% believe that there is a lack of constant poor supply, 7.1% disagree, 4.7% are neutral and 1.2% strongly disagree while the rest agree. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 520 figure 1: barriers to online learning figure 1 shows that some of the barriers to online learning are the lack of power supply, lack of a good learning environment, lack of access to materials as well as lack of good internet connection. the respondents were also asked if it was difficult to get immediate feedback on what was taught. 44.7% of the respondents agree that it is difficult to get feedback on what was taught. 20% disagreed and 15.3% were neutral. 5. conclusion and recommendation this study explored the impact of information and communication technology (ict) on student performance during the covid-19 pandemic in yola north, nigeria. this was carried out using quantitative research design in which a survey questionnaire was adapted to assess the effect of ict usage on student’s performance. while ict played a crucial role in keeping education afloat, challenges remain. despite positive perceptions of online learning's potential, limitations in resource access, technical issues, and pedagogical considerations hinder its effectiveness. limited access to equipment, internet, and consistent power supply poses significant barriers. while platforms like zoom are popular, concerns regarding inconsistent communication, difficulty participating, and limited practical sessions highlight areas for improvement. lack of conducive learning environments and limited access to materials further complicate online learning implementation. to optimize the impact of ict-based education, we need to prioritize equitable access to resources. this means ensuring affordable devices, reliable internet connectivity, and essential software for all students and teachers. investing in improved power infrastructure is also crucial for sustained online learning activities. on the pedagogical side, targeted training and support for teachers are essential. equipping them with the skills to deliver engaging and interactive online lessons is key. additionally, developing contextually relevant online learning materials that align with local curriculum and address cultural specificities is crucial. exploring alternative content delivery methods for practical subjects is also necessary to ensure effective online learning across all disciplines. by addressing these challenges and recommendations, we can move towards harnessing the full potential of ict for education, ensuring all students benefit from effective online learning experiences, even in challenging circumstances. references adarkwah, m. 2021. i’m not against online teaching, but what about us? ict in ghana post covid-19. education and information technologies, 26: 1665-1685. series1, lack of constant power supply, 52.9 series1, poor network connectivity, 48.2 series1, lack of good learning environment, 37.6 series1, lack of acess to materials , 51.8 response challenges faced during online class file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com baba et al: student perceptions of ict-based lecture delivery during covid-19 pandemic. azojete, 20(2):509-522. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 521 agbele, a. and oyelade, e. 2020. impact of covid-19 on the nigerian educational system: strengths and challenges of online/virtual education. asian journal of education and social studies, 13(1): 26–35. almaiah, m., al-khasawneh, a. and althunibat, a. 2020. exploring the critical challenges and factors influencing the e-learning system usage during covid-19 pandemic. education and information technologies, 25(6): 5261–5280. andersen, k., rambaut, a., lipkin, w., holmes, e. and garry, r. 2020. the proximal origin of sars-cov-2. nature medicine, 26(4): 450–452. chatterjee, i. and chakraborty, p. 2021. use of information communication technology by medical educators amid covid-19 pandemic and beyond. journal of educational technology systems, 49(3): 310–324. crawford, j., butler-henderson, k., rudolph, j., 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hincz, k., comas-lopez, m., subirats l., fort, s. and sacha, g. 2020. influence of covid-19 confinement on students’ performance in higher education. plos one, 15(10): 1–25. hashemi, a. 2021. effects of covid-19 on the academic performance of afghan students’ and their level of satisfaction with online teaching. cogent arts & humanities, 8(1): 1933684. kapasia, n., paul, p., roy, a., saha, j., zaveri, a., mallick, r., barman, b., das, p. and chouhan, p. 2020. impact of lockdown on learning status of undergraduate and postgraduate students during covid-19 pandemic in west bengal, india. children and youth services review, 116: 105194. lorente, l., arrabal, a. and pulido-montes, c. 2020. the right to education and ict during covid-19: an international perspective. sustainability, 12(21): 9091. meo, s., abukhalaf, a., alomar, a., almutairi, f., usmani, a. and klonoff, d. 2020. impact of lockdown on covid-19 prevalence and mortality during 2020 pandemic: observational analysis of 27 countries. european journal of medical research, 25(1): 1–7. merkl-davies, dm. and brennan, n. 2001. journal of applied learning & teaching. the irish journal of psychology, 32(1–2): 4–13. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):509-522. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: m.ishaq@unimaid.edu.ng 522 ntibi j. and effiong, i. 2021. covid-19’s social responsibility and ss-3 students’ attitude towards mathematics and physics in calabar metropolis of cross river state, nigeria. international journal of innovation scientific research and review, 03(01): 781–785. pozo, j., pérez, em., cabellos, b. and sánchez, d. 2021. teaching and learning in times of covid-19: uses of digital technologies during school lockdowns. frontiers in psychology, 12: 1–13. priyadarshini, i., mohanty, p., kumar, r., son, l., chau, h., nhu, v., ngo, p. and bui, d. 2020. analysis of outbreak and global impacts of the covid-19. healthcare, 8(2): 148. rajhans, v., memon, u., patil, v. and goyal, a. 2020. impact of covid-19 on academic activities and way forward in indian optometry. journal of optometry, 13(4): 216–226. simon, j., helter, t., white, r., van der boor, c. and łaszewska, a. 2021. impacts of the covid19 lockdown and relevant vulnerabilities on capability well-being, mental health and social support: an austrian survey study. bmc public health, 21(1): 314. unesco. 2023. distance learning solutions: unesco’s covid-19 education response.https://en.unesco.org/covid19/educationresponse/solutionsaccessed on 14 august, 2023. who. 2023. coronavirus. https://www.who.int/emergencies/diseases/novel-coronavirus2019/technical-guidance/naming-the-coronavirus-disease-(covid-2019)-and-the-virus-thatcauses-itaccessed on 13 october, 2023. who. 2023. world health organization, coronavirus (covid-19) data. https://www.who.int/data#dashboards accessed on 13 october, 2023. ncdc. 2023. covid-19 nigeria https://covid19.ncdc.gov.ng/ accessed on 13 october, 2023. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com https://covid19.ncdc.gov.ng/ arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):563-570 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 563 the implication of tillage practices and decapitation techniques on the growth and biomass yield of fluted pumpkin c. n. tom1, j. a, edet2*, t. e. erokare3, a. o. igbozulike2, e. c. ugwu2, f. n. orji2 and n. f. udenze1 1department of agricultural and environmental engineering, rivers state university, portharcourt, rivers state, nigeria 2department of agricultural and bioresources engineering, michael okpara university of agriculture, umudike, abia state, nigeria 3department of agricultural engineering, delta state university of science and technology, ozoro, delta state, nigeria. *corresponding author's email address: edetjoseph1991@gmail.com article information submitted 19 march, 2024 revised 24 april, 2024 accepted 30 april, 2024 keywords: tillage decapitation biomass yield fluted pumpkin abstract the implication of tillage practices and decapitation techniques on the growth and biomass yield of fluted pumpkin (telfairia occidentalis) cultivated in an inland swamp land in the dry season was studied. the treatments considered on decapitation were: (a) the control (intact/un-decapitated plants), (b) removal of half the total number of branches on the plant at time of decapitation, (c) removal of all lateral branches and leaves at time of decapitation, (d) removal of all the leaves on the plant at time of decapitation and (e) cutting off half of the entire shoot system. while the treatments considered on tillage practices were: (i) bed tillage (ii) ridge tillage (iii) flat (no tillage). therefore, the total treatment combinations were fifteen. after the imposition of decapitation, data were collected on growth and yield parameters of the newly developed foliage. the parameters were number of leaves, plant height, total number of new branches, leaf length and breadth, the fresh and dry weight of root, leaves, and shoot biomass. the decapitation (harvesting) techniques and tillage practices adopted in this study affected biomass re-growth and development of fluted pumpkin (telfaira occidentalis). removal of half number of branches on bed tillage practice gives the best performance, when compared with the intact (control) plant and other treatments. 1.0 introduction tillage is a type of soil management that is used globally to prepare land for cultivation. tillage has been carried out by humans for millennia, and for example early art shows the use of simple plows in ancient egypt (frey et al., 2015). the plow has, however, developed remarkably since, particularly after the industrial revolution, and tillage can now be carried out using heavy machines which have high soil disturbing potential. moldboard plowing (inversion of the soil layer), followed by tillage without soil inversion to smoothen the soil surface before sowing, is generally referred to as the conventional tillage practice (reicosky, 2015). there are several explanations for why conventional tillage is commonly used for seedbed preparation. for instance, plowing efficiently removes weeds, incorporates crop residues which may otherwise reduce seed-soil contact, it alleviates soil compaction, and redistributes nutrients in the soil http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):563-570. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 564 profile (johansen et al., 2012). conventional tillage also results in increased soil aeration and break up soil aggregates. the increased soil aeration enhances evaporation, which can be beneficial if done in cold humid climates, as the lower water content reduces the solar energy needed to warm the soil. thus, compared to undisturbed soils, seeds in conventional tillage soil may germinate earlier (alam, 2010). long-term use of conventional tillage has been shown to lead to soil quality degradation because of the increased decomposition and mineralization of soil organic matter (som), which lead to soil organic carbon (soc) loss (stockmann et al., 2013). one of the reasons why loss of soc is problematic is due to the fact that soc is negatively associated with soil erodibility (six et al., 2000). in america, the problem with erodible soils was vividly illustrated during the dust bowl in the 1930, and president f.d roosevelt (1937) spoke the famous words “a nation that destroys its soil, destroys itself”. in addition to reducing soil quality, soil erosion also generates economic and environmental costs both on and off-site, and among the consequences are increased maintenance costs for infrastructure, nutrient deficiency, air and water pollution (lal, 2012). conservation tillage is characterized by low soil disturbance, and often a crop residue cover on the soil surface (fao, 2017). in addition to erosion control, conservation tillage has been promoted because of its potential positive effect on the environment as it has been suggested to increase soil sequestration. furthermore, the use of conservation tillage reduces the amount of labor and fuel needed, as the number of field operations is lower and less energy demanding. conservation tillage can be implemented on its own, or as one of the main principles within the concept of conservation agriculture (palm et al., 2014). to secure future food production, increased knowledge of how to protect the soil and maintain its quality is crucial (fao, 2008). the human population is growing, and is expected to reach almost 10 billion by 2050 (united nations, 2015), whereas the area suitable for crop and animal feed production is likely to decrease, if land degradation does not cease. in this paper, the researcher dug into the world beneath the soil surface to ascertain how different types of soil management strategies may influence soil services. long-term experiments were used as they allow analysis of soil quality changes that occur slowly, such as soc content changes (kainiemi et al., 2015) fluted pumpkin (telfairia occidentalis) is an important leaf and seed cucurbit in west africa. it is highly valued in nigeria where it is an integral part of many households’ daily diet (igbozulike et al., 2019). it belongs to the family cucurbitaceae about 90 genera and more than 700 species, which are distributed all over the warm parts of the world. besides their important role in seed production, female plants produce more leaves of better quality than male plants and their rootstocks also survive and do better than male plants (asoegwu, 2016). the need for more female plants in farms is therefore evident. it is mainly propagated from seed, a fair good percentage of old plants regenerate from rootstocks left in the ground after total or partial shoot senescence at the end of the previous season. telfairia occidentalis is propagated using seed sections, split corm, and also by rooted shoot tips (ajekenrenbiaghan, 2015). stakes are used to keep the leaves off the ground and to provide support for the pods (igbozulike and amamgbo, 2020). the benefits of mechanizing fluted pumpkin production has been highlighted (igbozulike, 2015). asoegwu (2016), reported 74% survival of old plants after the dry season, and ossom (2015), had reported 4163% survival of periodically prunned plants at the peak of the dry season. harvesting of telfairia occidentalis is by various intensities of decapitation/removal of leaves and vines (laterals). recovery growth following intensities of decapitation may differ. tillage practice is customarily carried out to control weed, improve soil physical conditions and consequently increase crop yield. recent researchers have however questioned the rationale behind the traditional ploughing and harrowing of the soil to create an unstable file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com tom et al: the implication of tillage practices and decapitation techniques on the growth and biomass yield of fluted pumpkin. azojete, 20(2):563-570. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 565 equilibrium in the soil environment and have deduced that this secondary tillage was unnecessary, and in some cases had even reduced yields. therefore, this study examined the implication of tillage practices and decapitation techniques on the growth and biomass yield of fluted pumpkin (telfairia occidentalis) cultivated in an inland swamp (fadama) during the dry season 2.0 materials and methods 2.1 field experiment the experiment was sited within the inland valley swamp (fadama) of the oil palm plantation of teaching and research farm of national research institute, umudike, abia state. the experiment was conducted during the dry season of 2022; the site had been previously dominated by weeds (natural fallow). the vegetation on the land was cleared manually and the debris packed to the borders to ensure a clean seed-bed for sowing the crops. viable seeds were collected from the pod and conditioned properly by air drying at ambient temperature. seedling was first raised on nursery beds containing pulverized soil mixed with organic matter (sawdust and poultry manure) and maintained from three weeks after sprouting before transplanting to the field. the seedlings were properly watered a day before transplanting to the field and only healthy seedlings were used in order to ensure uniformity and avoid any bias on the outcome of the studies. 2.2 data collection, sampling techniques and analysis the total land area used for the experiments was 2000m2 (50m x 40m) and was divided into three plots (17m x 13m) with lm spacing between each plot. transplanting were done on the three different plots (flat, bed and ridge), which were replicated to form five (5) treatments per plot, and fifteen (15) treatments in all. three (3) plants were tagged per treatment for sampling, which made up forty five (45) sampled plants. the land was prepared manually and seedlings were transplanted after three weeks of planting from the nursery to the different plots selected at a planting distance of 75cm × 75cm and intra and inter spacing. weeds were manually removed from the plots at two and five weeks after planting. 2.3 treatments used for decapitation: the control (intact, un-decapitated plants), removal of half the total number of branches on the plant at time of decapitation (rhtb) removal of all lateral branches at time of decapitation (rab) removal of all the leaves and branches on the plant at time of decapitation (rtlb). cutting off half of the entire shoot/vine system (hpv). 2.4 treatments used for tillage practices: bed tillage system (b) ridge tillage system (r) flat (no tillage) system (f) thereafter the imposition of treatments, growth, and yield parameters of the newly developed foliage data were collected weekly for fifteen (15) weeks on the following growth and yield parameters on newly developed foliage. the data collected on growth performance of fluted pumpkin, in response to tillage and decapitation techniques were subjected to analysis of variance (anova) and the treatment means were separated using fisher’s least significant difference (lsd) at 5% level of probability followed by duncan multiple range test (dmrt). all agronomic practices recommended for cultivating fluted pumpkin were carried out during the field operation, from raising of seedling to the last data collection. each plot was manually weeded. first weeding was done at 2-3 weeks after planting and supplementary weeding was http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):563-570. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 566 done 5-6 weeks after planting to maintain a clean field. irrigation was applied by manual method twice a week by watering the crop root zone, while it was done mostly at seedling stage and development stage before floral initiation. therefore germination counts for data were collected on the number of spout plants after 4 weeks of planting. this was repeated every one week interval. these include plant height which was collected by using a measuring tape on every selected tagged plant; number of leaf per plant was done at every week at maturity on every randomly selected tagged plant on each row. weight of fresh and dry biomass was done by uprooting/harvesting the entire tagged plant from the plots and weighed the biomass separately when fresh and after it had been oven dried. vine, leaf length, and leaf breadth were done on the randomly selected tagged plants from the net plots; these were measured with measuring tape. leaf area was also calculated using data obtained on leaf length and breadth, while number of leaf was done by physical counting of the number of leaves on the plant using the randomly tagged plants. the aim was to determine the rate of leaf increase in response to treatments imposed. physiological maturity was also noted, which is the number of days from planting to when half of the plant population in a plot attained flowering (34months). 3.0 results and discussion the results of this experiment provide data on the leaf and vine (lateral branches) regrowth of fluted pumpkin following interactions of tillage operations and intensities of decapitation considered in the dry season. the tillage system as well as decapitation/pruning techniques adopted in this study affected biomass re-growth and development of fluted pumpkin (telfaira occidentalis). the results in table 1 show that the number of new branches developed was significant on the treatment with removal of half number of total branches, compared to other decapitation treatments imposed due to availability of photosynthesis through the remaining foliage and provision of avenue for new branches to sprout while the control was intact, without decapitation. table 2 shows the effect of tillage technique on the growth and biomass yield of the crop. table 3 showed that brhtb, brab, brtlb and bhpv were significantly different on yield parameters when compared with their respective treatments on ridge and flat tillage system. but brhtb produced significantly higher mean biomass yield in all treatments considered for decapitation and tillage system. the higher growth of telfaira occidentalis on this treatment (removal of half number of branches) can be attributed to the fact that the plant will quickly recover from the pruning injury, have enough organ for photosynthesis since most of its leaves were still retained on other branches left and consequently its apical part/main vine is not tempered with, as a result its growth pattern and stages were in a continuum, without being altered table 1: implication of decapitation on growth and biomass yield of fluted pumpkin treatments parameters leaf area (cm2) breadth of leaf (cm) dry weight of leaf(g) dry weight of vine (g) dry weight of root (g) fresh weight of leaf (g) fresh weight of vine (g) fresh weight of root(g) length of branch (cm) length of leaf (cm) number of leaf number of new branches intact plant (control) 10d 2.6d 13c 10d 16d 23d 29e 26d 14d 4d 11d 3.2b removal of half total branches 7.1c 2.2c 5.9b 4.9c 6c 13c 15d 12c 11c 3c 9c 3.8c removal of all lateral branches 6.6bc 2.1bc 5.6b 4.7b 5b 12c 11c 9b 8b 2.9bc 7bc 3.5bc removal of total leaves and branches 6.1b 2.0b 4.8a 3.6a 4b 9.0a 9a 8b 7ab 2.8b 6b 3.2b file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com tom et al: the implication of tillage practices and decapitation techniques on the growth and biomass yield of fluted pumpkin. azojete, 20(2):563-570. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 567 half part of shoot/vine cut off 3.6a 1.6a 5.0a 5.2c 3a 8b 10b 6a 6a 2a 4a 2.5a std. error 0.6 0.1 0.3 0.4 0.5 0.4 0.2 0.6 0.9 0.1 0.6 0.1 mean in the column followed by the same letters are not significantly different at 0.05 levels by duncan multiple range test (dmrt) table 2: implication of tillage on growth and biomass yield of fluted pumpkin treatments parameters leaf area (cm2) breadth of leaf dry weight of leaf dry weight of vine dry weight of root fresh weight of leaf fresh weight of vine fresh weight of root length of branch length of leaf number of leaf number of new branches bed tillage system 5.7b 1.8b 4.6b 4.2c 4b 10c 11c 8b 8c 2b 7b 2.5b flat tillage system 5.3ab 1.6ab , 4.3ab 3.9b 3.8a 9b 10b 7a 7b 1.8ab 6.7ab 2.3ab ridge tillage system 4.7a 1.3a 4.0a 3.0a 5c 7.0a 7a 9c 6a 1.5a 6a 1.8a std. error 0.4 0.1 0.2 03 0.3 0.2 0.1 0.4 0.6 0.1 0.3 0.1 mean in the column followed by the same letters are not significantly different at 0.05 levels by duncan multiple range test (dmrt) table 3: implication of tillage and decapitation on growth and biomass yield of fluted pumpkin paramete rs treatme nt brht b bra b brtl b bhp v rrht b rra b rrtlb rhp v frht b fra b frtl b fhp v std. erro r leaf area 6.7f 6.3e 5.6cd 5.2c 5.7d 5.3c 4.7b 4.2a 6.3e 5.8d 5.2c 4.6b 0.3 breadth of leaf 2.8g 2.5f 2.2e 1.8c d 2.3e 1.9d 1.4b 1.1a 2.6f 2.2e 1.7c 1.4b 0.1 length of leaf 3.0e 2.8d e 2.5d 2.0c 2.5d 2.1c 1.6b 1.2a 2.8de 2.5d 2.2bc 1.7b 0.1 length of branch 9.0e 8.0d 7.2cd 7.0c 7.0c 6.6b c 6.2a 6.0a 8.0d 7.0c 6.5b 6.4b 0.4 number of leaf 8.0g 7.6f 6.7d 6.2b 7.ode 6.7d 6.2b 5.7a 7.7f 7.2e 6.4c 5.9a b 0.4 number of new branches 3.5f 3.1d e 2.8d 2.5c 2.8d 2.4c 2.0ab 1.7a 3.3e 3.0d e 2.5c 2.1b 0.1 fresh weight of leaf 11.0g 10.4 f 10.0e f 9.6e 8.0c 7.7b 7.3ab 7.1a 10.0ef 9.8e 9.2de 8.8d 0.5 fresh weight of vine 12.0g 11.5 % 11.if 10.6 ef 8.0c 7.6b 7.2ab 6.9a 11.0f 10.6 ef l0.1e 9.6d 0.6 fresh weight of root 9.0de 8.8d 8.2cd 7.9c 10.0f 9.6e 9.2de 8.9d 8.0c 7.7b 7.3ab 7.0a 0.4 dry weight of leaf 5.6f 5.2e 4.9d 4.6c 5.0d 4.6c 4.2b 3.8a 5.3e 5.0d 4.7c 4.3b 0.2 dry weight of vine 5-2g 4.9f 4.6e 4.3d e 4.0d 3.6c 3.3b 3.0a 4.9f 4.3d e 4.0d 3.6c 0.2 dry weight of root 5.0d 4.7c 4.4b 4.1a 6.0f 5.6e 5.3de 5.0d 4.8c 4.4b 4.2ab 4.0a 0.2 mean in the row followed by the same letters are not significantly different at 0.05 levels by duncan multiple range test (dmrt) acronyms and meaning: brhtb bed, removal of half total branches brab bed, removal all branches brtlb bed, removal of total leaves and branches bhpvbed-half part of vine cut-off rrhtb ridge, removal of half total branches rrab ridge, removal all branches rrtlb ridge, removal of total leaves and branches rhpvridge,half part of vine cut-off frhtb flat, removal of halftotal branches frab flat, removal all branches frtlb flat, removal of total leaves and branches fhpvflat, half part of vine cut-off http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com corresponding author’s e-mail address: edetjoseph1991@gmail.com 568 figure 1 presents trends in the development of telfaria occidentalis following decapitation. removal of half number of total branches yields best; having the highest mean values on yield performance of 80.3% on growth parameters. figure 1: implication of decapitation on growth and biomass yield of fluted pumpkin these results were also showed by duncan multiple range test; that removal of half number of branches was significant on the following growth and yield parameters across decapitation treatments, except the control which was significantly higher. but on the development of new branches, removal of half number of branches was significantly higher than the control. under the tillage treatments on figure 2, bed tillage system was significantly different from all other tillage treatments imposed on the biomass yield of telfairia occidentalis. figure 2: effect of tillage practices and decapitation methods on fluted pumpkin (telfairia occidentalis) grown in an inland swamp also fig. 3, showed that bed tillage system, was highly significant for telfairia occidentalis biomass yield, with 80.3% performance when compared with flat system of 67.6% and ridge tillage with 66.2%. but the ridge tillage system did best on root development than the other tillage system as well, on table 2. mailto:%20edetjoseph1991@gmail.com tom et al: the implication of tillage practices and decapitation techniques on the growth and biomass yield of fluted pumpkin. azojete, 20(2):563-570. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 569 this implies that root penetration can serve as vegetative regenerating organ, by using ridge tillage system for the production of telfairia occidentalis. because telfairia occidentalis is an herbaceous facultative perennial plant, whose aerial shoot dies annually but is replaced after an interval of time by new shoots from surviving vines attached to the underground rootstock. figure 3: decapitation techniques plants from where removal of half number of total branches on bed tillage system (brhtb) produced highest biomass yield parameters figue 3. the results on table 3, shows that the mean result of brhtb was significant on the biomass re-growth and yield parameters across decapitation treatments, which was 12.7% and 14.1% significantly different from that of flat and ridge tillage respectively. 4.0 conclusion the decapitation/pruning techniques adopted in this study affected biomass re-growth and development of fluted pumpkin (telfaira occidentalis). decapitation may enhance consecutive harvest in the long run, which is a good potential fluted pumpkin as a perennial crop. farmers are encouraged, to adopt harvesting/decapitation method such as the removal of half number of the entire branches as a harvesting technique. and the best tillage system for telfairia occidentalis production was bed tillage system. this method would improve fluted pumpkin yield, enhance its potential and perennial growth habit for consecutive harvest during peak period. additionally, there should be effective water management in fluted pumpkin field especially for off season production. references ajekenrenbiaghan, je. 2015. influence of planting date on growth and productive life of fluted pumpkin, telfairia occidentalis. tropical agriculture, 62(4): 281-28. alam, mk. 2010. effect of tillage depths and cropping pattern on soil properties and crop productivity. department of soil science, bangabandhu sheikh mujibur rahman agricultural university. asoegwu, sn. 2016. effects of irrigation on the leaf and pod production of fluted pumpkin (telfairia occidentalis) in southern nigeria . scientia horticulturae, 34:161-168. food and agriculture organization 2008. conservation agriculture. fao, rome, http://www.fao.org/ ag/ca/index.html (accessed online october 10, 2017). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):563-570. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: edetjoseph1991@gmail.com 570 food and agriculture organization 2017. soil tillage in africa: fao needs and challenges. soil bulletin 69. soil resource management and conservation service, land and water development division. fao, rome, http:// www.fao.org/docrep/t1696e/t1696e09.htm (accessed online october 10, 2017). frey, sd., drijber, r., smith, h. and melillo, j. 2015. microbial biomass, functional capacity, and community structure after 12 years of soil warming. soil biology and biochemistry, 40: 29042907. igbozulike, ao. 2015. mechanizing ugu (telfairia occidentalis) production and postharvest operations. iosr journal of engineering, 5(7): 31-35. igbozulike, ao. and amamgbo, n. 2019. effect of moisture content on physical properties of fluted pumpkin seeds. journal of biosystems engineering, 44(2): 69-76. igbozulike, ao., amamgbo, n. and oyinloye, gm. 2020. mathematical modelling of fluted pumpkin seed drying kinetics. agricultural engineering international: cigr journal, 22(2): 272278. johansen, c., haque, me., bell, rw., thierfelder, c. and esdaile, rj. 2012. conservation agriculture for small holder rainfed farming: opportunities and constraints of new mechanized seeding systems. field crop research, 132: 18 – 32. kainiemi, v., arvidsson, j. and kätterer, t. 2015. effects of autumn tillage and residue management on soil respiration in a long-term field experiment in sweden. journal of plant nutrition and soil science, 178: 189-198. lal, r. 2012. carbon management in agricultural soils. mitigation and adaptation strategies for global change, 12: 303-322. ossom, em. 2015. influence of harvest interval on yield, crude protein, n.p.k. contents, and longevity of the fluted pumpkin (telfairia occidentalis). tropical agriculture, 63(l): 63-65. palm, c., blanco-canqui, h., declerk, f., gatere, l. and grace, p. 2014. conservation agriculture and ecosystem services: an overview. agricultural ecosystem and environment, 187: 87-105. reicosky, dc. 2015. conservation tillage is not conservation agriculture. journal of soil water conservation, 70: 103-108. six, j., elliott, et. and paustian, k. 2000. soil macro-aggregate turnover and micro-aggregate formation: a mechanism for c sequestration under no-tillage agriculture. soil biology and biochemistry, 32(14): 2099-2103. stockmann, u., adams, ma., crawford, jw. and field, dj. 2013. the known and unknown of sequestration of soil organic carbon. agricultural ecosystem and environment, 164, 80-99. united nations. 2015. world population projected to reach 9.7 billion by 2050. united nations, department of economic and social affairs. united nations, washington dc., population/2015-report.html. (accessed online october 6, 2017) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com corresponding author’s email address: gambo.anthony@yahoo.com 921 arid zone journal of engineering, technology & environment original research article optimization of process parameters on fatigue and compressive strength of al7075/coconut shell ash composite a. v. gambo1*, c. o. njoku2, y. bello3 1department of mechanical engineering, ahmadu bello university, zaria 2department of mechanical engineering, air force institute of technology, kaduna 3department of mechatronics engineering, air force institute of technology, kaduna *corresponding authors’ email: gambo.anthony@yahoo.com article information abstract the study investigates the effect of coconut shell ash particulate (csap) on the fatigue and compressive strength of aluminium (al) 7075 metal matrix composite; and optimized by taguchi grey relational analysis (gra). the composites were prepared by conventional double stir casting method with varying coconut shell ash content (5wt%, 10wt%, 15wt% and 20wt%). five factors, four levels taguchi experimental design were used to optimize the number of experiments. the factors considered were reinforcement fraction, processing temperature, stirring speed, stirring time and particle size of al/csap reinforcement in the matrix. taguchi l16 orthogonal array was employed in fabricating different samples of the composite. the significant effect of the experimental design parameters on the responses was investigated using analysis of variance (anova). the results for the fatigue strength of the aluminium/csap composite showed that processing temperature with a contribution of 57.55% has the highest influence on the fatigue; followed by reinforcement fraction with 11.49%, particle size with 14.25%, stirring speed with 8.93%, and stirring time with 1.11% in addition, the anova for compressive strength of the composite showed that stirring speed with a contribution of 70.38% has the highest influence on the compressive strength; followed by particle size, with 24.22%, processing temperature, with 0.55%, reinforcement fraction, with 0.11%, and stirring time, with 0.06%. the optimal combination for the taguchi grey relational analysis was coconut shell ash particles at 10wt%, stirring speed at 600rpm, processing temperature at 850oc, stirring time at 120secs, and particle size at 25µm. stirring speed and processing temperature were considered significant contributors to the change in grey relational grade (grg) of the composite. confirmatory experiments carried out using the optimal parameters (csap2ss4pt3st2ps1) showed an improvement in the fatigue and compressive strength of the optimized composite of 36.4% and 30.7% over the initial settings. received: 29th august 2025 revised: 12th november 2025 accepted: 13th november 2025 keywords: composite coconut shell ash grey relational analysis anova © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the search for low-cost alternatives in aluminium metal matrix composites (amc) production has led to a number of efforts tailored at utilizing industrial and natural fibres as reinforcing materials (baradeswara et al., 2012). amcs are the most commonly utilized metal matrix composites due to several reasons, including ease of processing, lower cost compared to other metal matrices and favorable physical and mechanical properties. due to these outstanding properties, a great number of research works have been explored to understanding the influence of reinforcement parameters on the properties of amcs (alaneme and adewuyi, 2013). the abundance of natural fibres has tempted researchers to try locally available fibres and to some extent they satisfy the required specifications as good reinforcement for aluminium metal matrix composites. natural azojete december 2025. vol.21(4):921-932 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/003 www.azojete.com.ng mailto:gambo.anthony@yahoo.com mailto:gambo.anthony@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 922 fibres such as jute, coir, cotton, sisal and banana have attracted the attention of scientists for application in consumer goods, low-cost housing and other civil structures. it has been found that these natural fiber composites possess better electrical resistance, good thermal and acoustic insulating properties and higher resistance to fracture (gambo, 2017). natural fibres have advantages compared to synthetic ones such as low weight, low density, low cost, acceptable specific properties and they are recyclable and biodegradable (gambo, 2017). they are also renewable and have relatively high strength and stiffness and cause no skin irritations (alaneme and adewuyi, 2013). amongst the numerous reinforcement materials, coconut shell particles are an emerging reinforcement because of its low cost, and availability in large quantity. madakson et al., (2012) investigated the characteristics of coconut shell ash. the microscopic analysis revealed that element like sio2, al2o3, mgo and fe2o3 as major constituents and hard in nature leads to its utilization in automobile applications. as coconut shell ash has high thermal stability with low density, can be used in producing composite products with good thermal resistance. apasi et al., (2016) studied the microstructure and mechanical properties of aluminum alloy (al-si-fe) reinforced with coconut shell-ash particulate. in their investigation, the aluminium (al-si-fe) alloy composite was produced by double-stir casting process at a speed of 700 rpm for 10 and 5 minutes at first and second stirring respectively. the samples produced from addition of 0-15wt% coconut shell ash particles (csap) were prepared and subjected to microstructural and mechanical properties testing. the results of the microstructural analysis of the composite revealed a fairly uniform distribution of the coconut shell-ash particles in the matrix with increase in volume fraction of csap. the mechanical property test results revealed that, hardness of the developed composite increased with increasing percentage weight of csap. also, the tensile and yield strength at 0.2% offset values of al-si-fe/csap composite increased with percentage increase in csap up to 9% addition above which a little decrease in both tensile and yield strength was observed. varalakshmi et al., (2019) analyzed the dry sliding wear behaviour of al6061coconut shell ash metal matrix composites using stir casting. they found out that with more percentage of csa addition there was an improvement in specific strength of the composite. the taguchi analysis revealed improved specific strength as well as wear resistance. eds analyses showed the presence of oxide phases in the castings. franklin et al., 2022, focused on the determination of the mechanical properties of coconut shell ash reinforced aluminum a356 composite. double stir casting method was adopted in the development of the composite with a temperature of 750°c and a stirring speed of 600 rpm. the composite was produced from the addition of 0-30 wt% coconut shell ash particles to the aluminum. the study revealed that the addition of coconut shell ash to aluminum increased the hardness and tensile strength of the composite. also, the density and impact energy of the specimen decreased with the increase of reinforcing particles. the study implied that aluminum composite with high strength low weight recommended that aluminum with light weight, higher tensile and hardness can be achieved by adding coconut shell ash to the parent material. with reference to available literature, it is apparent that many studies have been carried out on the development of al/coconut shell ash composite, but limited study is available on the optimization of the fatigue and compressive strength properties of 7075 al/coconut shell ash composite with selected process parameters by employing grey relational analysis. 2. materials and methods 2.1 materials aluminium alloy (7075) with elemental composition shown in table 1; procured from nocaco, kaduna, nigeria, was used as the base material for this research. coconut shell obtained from a local market in kafanchan, kaduna state, was utilized as reinforcing particulate. analytical grade (99.5%) magnesium turnings was used for enhancing wettability between the al alloy and the reinforcement. table 1: composition of 7075 aluminum alloy element al si fe cu mn mg others wt% 94.3 0.8 0.5 1.7 0.2 1.9 0.6 note: adapted from kabelmetal nigeria plc technical brochure (2022) 2.2 method 2.2.1 production of coconut shell ash particulate the procured coconut shells were sun dried for one month, after which they were crushed into smaller pieces, this was carried out according to the methods used by apasi (2014). the crushed coconut shell was grinded, using a disc grinder to obtain the powder of varying mesh sizes of 25µm, 50µm, 75µm and 90µm. the http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 923 powder was packed in a graphite crucible, and fired in an electric muffle furnace at a temperature of 900oc for 1hour to form the coconut shell ash (csap) as shown in plate 1. (a) (b) plate1: (a) coconut shell (b) coconut shell ash 2.2.2 design of experiment (doe) the experiments were designed based on the taguchi l16 orthogonal array (oa). the experimental runs were designed using five factors and four levels as indicated in table 2. the stir casting process factors; reinforcement fraction (wt%), stirring speed (rpm), processing temperature (oc),stirring time (secs), and size of reinforcement (µm) with their levels, and feasible limit of control were selected as conducted by adebisi and ndaliman (2015); kumar et al., (2017); ibrahim (2023). the outcome of the analysis was carried out using minitab software which gives l16 orthogonal array. table 2: processing factors and their levels in taguchi experimental design plan factors level 1 level 2 level 3 level 4 reinforcement fraction (wt %) 5 10 15 20 stirring speed (rpm) 300 400 500 600 processing temperature (oc) 750 800 850 900 stirring time (secs) 90 120 150 180 particle size (µm) 25 50 75 90 2.2.3 sample preparation production of the al7075/csap composite was carried out by the double stir-casting method according to the methods used by pulkit (2012); aigbodion et al., 2014; adebisi and ndaliman (2015) in a coal fired furnace, depicted in plate 2a. initially, the aluminium alloy was charged into a graphite crucible in the furnace, the aluminium was heated to about 750oc till the entire alloy in the crucible is melted. the reinforcement particles (csap) was preheated to 800oc for 1 hour to make its surface oxidized. the furnace temperature was cooled down just below the liquidus temperature of aluminium, to keep the slurry in a semi-solid state. stirring was carried out at varying times, and at a stirring rate as per the experimental design. at this stage, the preheated csap was added manually into the vortex. the slurry was again heated to a fully liquid state and mixed thoroughly, after the molten metal have completely melted, 0.05wt% degassing tablets (hexachloroethane) was added to reduce porosity. simultaneously, 1wt% magnesium was added to the melt to enhance the wettability between coconut shell ash particles and the alloyed melt. after the stirring process, the mixture was poured into a sand mold and allowed to solidify to form the al/csap composite as depicted in plate 2b. 2.2.4 fatigue test fatigue is the degradation of mechanical properties leading to the failure of a material or a component under cyclic loading (astm e606-92). the experiments were carried out under axial constant amplitude to determine the s-n curve. the fatigue test was conducted using an instron e3000 fatigue testing machine, of 3kn load capacity. the jaws of the machine are driven by an electric-magnetic engine, which pushes the centre of the specimen up and down with regards to the vertical axis of the load. the waveform of the fatigue test was sinusoidal, and all fatigue tests was performed under a constant frequency of 4hz, and constant load amplitude, with a stress ratio of (r= -1 fully reversed). the load applied during the fatigue test was less than the yield stress by a factor of 0.9, to reach the failure points for high cycle fatigue; then the load was reduced http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 924 by a factor of 0.1 for each test. test samples depicted in plate 3, were prepared following astm e606-92, and to obtain the s-n curve for fatigue testing, 8 points were required, as recommended by astm e606-92. the s-n curve is the plot of stress versus the number of cycles needed to fail. (a) (b) plate 2: (a) coal fired stir casting furnace (b) fabricated al7075/csap composite plate 3: fatigue test samples 2.2.5 compressive strength test compressive strength test was conducted in accordance with astm e09-89a (2000) on the specimens produced, which had dimension of 25mm in diameter and 75mm in length. the test was carried out on a universal testing machine. in carrying out the experiment, test samples were placed between the surfaces of the compression tool and were aligned with the centre line of the plunger. the samples were subjected to quasi static compression loading. for each specimen, the compression test was performed three times for the purpose of repeatability and reliability, and the average results were taken. 2.2.6 taguchi optimization and gra techniques the grey relational analysis (gra) was employed to handle the ambiguity of many variables. the objective function employed in the optimization of the performance characteristics were based on “the higher the better”. the s/n ratio is used for maximizing the performance while minimizing the variance. in respect to these objectives, equation 1was used to determine the s/n (ibrahim et al., 2023a; ibrahim et al., 2023b): http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 925 ( 𝑆 𝑁 ) 𝐻𝑇𝐵 = −10𝑙𝑜𝑔10 ( 1 𝑛 ∑ 1 𝑦𝑖 2 𝑛 𝑖=1 ) 1 the grey relational analysis was employed for the multi-response optimization, and the taguchi optimization technique was applied to optimize the grey relational grade. in applying the grey relational analysis, the measured effects (fatigue and compressive strength) were normalized i.e. brought to a comparable value which is between zero and one. the normalization was carried out by applying equation 2 (raut et al., 2016; ibrahim, 2023). 𝑥𝑖 ∗(𝑘) = 𝑥𝑖(𝑘) −𝑚𝑖𝑛𝑥𝑖(𝑘) 𝑚𝑎𝑥𝑥𝑖(𝑘) − 𝑚𝑖𝑛𝑥𝑖(𝑘) 2 where;𝑥𝑖 ∗(𝑘)is the sequence after the data processing i.e. for the 𝑖𝑡ℎ experiment and the 𝑘𝑡ℎresponse and 𝑥𝑖(𝑘) is the comparability sequence. the reference sequence in this study was taken as 1 for all the responses. that is 𝑥0 ∗(𝑘) = 1. the deviation sequence∆0𝑖(𝑘)which is the deviation of the reference sequence 𝑥0 ∗(𝑘)and the comparability sequence 𝑥𝑖 ∗(𝑘) was calculated using equation 3 (raut et al., 2016; ibrahim, 2023). ∆0𝑖(𝑘) = |𝑥0 ∗(𝑘) − 𝑥𝑖 ∗(𝑘)| 3 where;∆0𝑖(𝑘) = 1-normalised value of the response then the grey relational coefficient (grc) was calculated with the pre-processed sequence. the grc is an expression of the relationship between the actual normalized results and the ideal. the grc𝜉(𝑘) is expressed in equation 4 (kundu and singh, 2016). 𝜉(𝑘) = δ𝑚𝑖𝑛 + 𝜁δ𝑚𝑎𝑥 δ0𝑖(𝑘) + 𝜁δ𝑚𝑎𝑥 4 where δ0𝑖(𝑘) is the deviation sequence of the reference sequence,𝑥0 ∗(𝑘), and the comparability sequence is𝑥𝑖 ∗(𝑘). while 𝜁 is the distinguishing or identification coefficient which defines the level of importance or influence of the measured response to the final objective. since the responses were given equal preference, they were assigned an identification coefficient, 𝜁 = 0.5. upon the calculation of the grey relational coefficient for each experiment (i=1, 2, 3… 9) and each response ‘k’ (fatigue and compressive strength), the grey relational grade 𝛾𝑖 was calculated; which is the average of the coefficients from each factor and for each run. the grey relational grade 𝛾𝑖 as expressed by sylajakumari et al., (2018) is shown in equation 5. 𝛾𝑖 = 1 𝑛 ∑𝜉𝑖(𝑘) 𝑛 𝑘 5 where 𝛾𝑖= grey relational grade for 𝑖𝑡ℎexperiment, n= number of performance characteristics, which is the number ofresponses, k. then the result was ranked and a response table was created using equations as detailed in the taguchi approach. the optimum grey relational grade was predicted using equation 6 (raut et al.,2016; ibrahim, 2023). 𝑇𝑜𝑝𝑡 = 𝑇𝑚 +∑[(𝑇𝑖𝑘)𝑚𝑎𝑥 − 𝑇𝑚] 𝑘𝑛 𝑘=1 6 where 𝑇𝑚 is the overall mean of grg; 𝑇𝑖𝑗𝑚𝑎𝑥 is the mean grg of optimum level i of factor k and 𝑘𝑛 is the number of main design factors that affect the response (grg). 𝑇𝑖𝑗𝑚𝑎𝑥 was obtained from the response table of mean or s/n ratio in which for each parameter on the table, the highest value among the levels is the 𝑇𝑖𝑗𝑚𝑎𝑥. 3. results and discussion 3.2 effect of the control factors on fatigue the experimental data of fatigue from the analysis were converted into s/n ratios using equation 1. the predominant control factors were identified from the delta value in the response table for signal-noise ratio as shown in table 3. the delta values were computed based on the difference between the highest and the lowest average value of each factor. ranks were then assigned according to the delta value. the highest value http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 926 of delta was assigned the first rank and represents the predominant factor affecting fatigue. according to table 3, the processing temperature (pt) emerged as the most significant factor; followed by particle size (ps) as the second most impactful factor, then reinforcement fraction (csap), succeeded by the stirring speed (ss), and finally, the stirring time (st). table 3: response for s/n of fatigue higher-the-better level csap (wt %) ss (rpm) pt (°c) st (secs) ps (µm) 1 1.554 1.378 1.171 1.476 1.792* 2 1.337 1.557 1.446 1.607* 1.565 3 1.613 1.608 1.685 1.597 1.502 4 1.734* 1.695* 1.937* 1.559 1.379 delta 0.398 0.316 0.767 0.130 0.414 rank 3 4 1 5 2 optimum csap4ss4pt4st2ps1 *optimum factor levels the effect of various process parameters on the fatigue of the composite were obtained from the graphs drawn by taking the effect of each parameter at each level on the response. the main effects plot for signalnoise was generated as shown in figure 1. the trend of the plot indicates that fatigue strength of the composite is adversely influenced by the variation in processing temperature. the fatigue cycles to failure increases as the processing temperature increased. the increase could be attributed to more refined micro structural grains and a close up of the grain boundary due to increased melt viscosity at a higher temperature. this trend is consistent with a study conducted by yekini et al., (2020). the association between particle size and the s/n ratio in figure 1 shows a decreasing trend from 1.792×106 cycles to 1.565×106 cycles. the plot of reinforcement fraction shows a decrease upon an increase in the volume fraction of coconut shell ash particles from 5 to 10 wt%; beyond this point, the fatigue cycles to failure increased with a further increase of the csap particles; then decreased. the relationship between the stirring speed and the s/n ratio depicts a decrease in the fatigue strength. lastly, the trend between the stirring time and the fatigue cycle to failure indicates a positive relationship. in analyzing s/n ratio, irrespective of the quality characteristics, a higher s/n ratio conforms to better values of experimental results in this scenario higher fatigue strength. this is in agreement with the work of yekini et al., (2020). the response table and the main effects plot for s/n ratios put forward that csap4ss4pt4st2ps1 are the optimum factor levels in order to achieve high s/n ratios and higher values of fatigue. figure 1: main effects plot for signal-noise for fatigue anova was used to investigate whether the experimental design parameters have significant effect on the response. the analysis generated an anova table which shows the level of significance of each processing parameter. the analysis was also used to develop the predictive mathematical model for the fatigue as a function of the stir casting process parameters. table 4 shows the anova results obtained for the fatigue of the aluminium/csap composite. it can be observed that processing temperature with a contribution of 57.55% has the highest influence on the fatigue; http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 927 followed by reinforcement fraction with 11.49%, particle size with 14.25%, stirring speed with 8.93%, and stirring time with 1.11%. at 95% confidence level, factors having p-value less than 0.05 are considered significant; our findings align with those of sylajakumari, et al., (2018). since the p-values of reinforcement fraction, stirring speed, processing temperature, and particle size are less than 0.05, they are considered significant contributors to the change in fatigue life of the composite. conversely, stirring time is said to be an insignificant term, because its p-value is above 0.05. table 4: analysis of variance for fatigue of al/csap composite source df seq ss contribution adj ss adj ms f-value p-value regression 5 2.09036 93.32% 2.09036 0.41807 27.96 0.000 csap 1 0.25730 11.49% 0.25730 0.25730 17.21 0.002 ss 1 0.20010 8.93% 0.20010 0.20010 13.38 0.004 pt 1 1.28905 57.55% 1.28905 1.28905 86.22 0.000 st 1 0.02482 1.11% 0.02482 0.02482 1.66 0.227 ps 1 0.31909 14.25% 0.31909 0.31909 21.34 0.001 error 10 0.14951 6.68% 0.14951 0.1495 the developed regression model for fatigue has high coefficient of determination (r2), r2 adj and r2 pred values of 93.32%, 89.99%, 84.70%, respectively. this indicates the goodness of fit between fatigue and the stir casting process parameters. our results support previous research by dan-asabe (2018); sivaiah and chakradhar (2019) who stated that an r-sq value greater than 75% is deemed adequate. 3.3 effect of the control factors on compressive strength (cs) the dominant control factors were identified from the delta statistics in the response table for signal-noise ratio in table 5. the delta statistics were computed based on the difference between the highest and the lowest average value of each factor. ranks were then assigned according to the delta value. the highest value of delta was assigned the first rank and represents the predominant factor affecting cs. according to the table, the stirring speed (ss) emerged as the most significant factor, followed by particle size (ps), then stirring time (st), succeeded by processing temperature (pt), and finally the reinforcement fraction (csap). table 5: response for s/n of compressive strength higher-the-better level csap (wt %) ss (rpm) pt (oc) st (secs) ps (µm) 1 55.04 53.85 54.92 55.29 55.89* 2 55.19 54.73 55.34* 54.87 55.54 3 55.25 55.78 55.29 55.32* 54.94 4 55.27* 56.40* 55.20 55.28 54.38 delta 0.23 2.55 0.43 0.45 1.51 rank 5 1 4 3 2 optimum csap4ss4pt2st3ps1 *optimum factor level figure 2 depicts the main effects plot for signal-noise ratios for compressive strength of the composite. the relationship between reinforcement fraction, stirring speed, particle size and the s/n ratio of the compressive strength in figure 2 shows increasing trends. the plot of processing temperature shows that the s/n ratio value of compressive strength increased upon an increase in temperature up to the maximum of 55.34 (level 2). with further increase in temperature, the compressive strength decreased. the increase could result from the decrease in the melt viscosity. the decrease in viscosity decreases the contact angle between the melt aluminium alloy and the reinforcement, thereby enhancing the distribution and wettability of the reinforcement in the matrix. conversely, the decrease in compressive strength could be attributed to the absorption of gases into the melt and formation of intermetallic phases at high temperature in the fabricated composite. this study is consistent with ibrahim et al., (2023b); in which they revealed that by increasing the stirring temperature above the optimum, a less homogeneous distribution of the particles and formation of undesirable phases could be obtained in the matrix alloy, which can have an adverse effect on the composite. the compressive strength of the composite decreases as the stirring time increases, upon reaching the minimum value of 54.87 it reverses. the decrease can be attributed to non uniformity in the distribution of the reinforcement in the aluminium matrix composite due to limited stirring time. the response table and the main effects plot for s/n http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 928 ratios indicates that csap4ss4pt2st3ps1 are the desired factor levels in order to achieve high s/n ratios and higher values of compressive strength. figure 2: main effects plot for signal-noise for compressive strength table 6 shows the anova results obtained for the compressive strength of the aluminium/csap composite. the table indicates that the stirring speed, contributing 70.38%, has the greatest effect on compressive strength; followed by particle size, with 24.22%, processing temperature, with 0.55%, reinforcement fraction, with 0.11%, and stirring time, with 0.06%. at 95% confidence level, factors having p-value less than 0.05 are considered significant; similar findings were reported by sylajakumari, et al.,(2018).since the p-values of stirring speed and particle size are less than 0.05, they are considered significant contributors to the change in compressive strength of the composite. conversely, reinforcement fraction, processing temperature, and stirring time are said to be insignificant terms, because their p values are above 0.05. table 6: analysis of variance for compressive strength of al/csap composite source df seq ss contribution adj ss adj ms f-value p-value regression 5 88979.0 88979.0 17795.8 40.81 0.000 csap 1 107.1 0.11% 107.1 107.1 0.25 0.631 ss 1 65690.4 70.38% 65690.4 65690.4 150.64 0.000 pt 1 517.5 0.55% 517.5 517.5 1.19 0.302 st 1 53.7 0.06% 53.7 53.7 0.12 0.733 ps 1 22610.2 24.22% 22610.2 22610.2 51.85 0.000 error 10 4360.7 4.67% 4360.7 436.1 total 15 93339.7 100.00% the developed regression model for compressive strength has high coefficient of determination (r2), r2 adj and r2 pred values of 95.33%, 92.99%, 88.30%, respectively. this indicates the goodness of fit between compressive strength and the stir casting process parameters. 3.4 multiple responses optimization using gra preprocessed data were computed from the experimental data of the responses obtained in the taguchi experimental design for fatigue and compressive strength as shown in table 7. the normalization of data was done using equation 2. while the deviation sequences were generated using equation 3.once, the deviation sequences were obtained, the grey relational coefficient (grc) for each value of the responses was computed using equation 4. lastly, the mean of the grcs was calculated to determine the grg using equation 5. from the analysis of the results in table 7, experiment no.8 has the highest value of the grg, which corresponds to better performance http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 929 table 7:grc and rank of grg with s/n ratios run factors responses grg s/n kcp (wt%) ss (rpm) pt (°c) st (secs) ps (µm ) fatigue compressi ve strength mean s/n ratio (db) ranks 1 5 300 750 90 25 0.6925 0.4065 0.5495 -5.20065 5 2 5 400 800 120 50 0.6258 0.452 0.5389 -5.36984 7 3 5 500 850 150 75 0.4766 0.4931 0.4849 -6.28696 10 4 5 600 900 180 90 0.5624 0.4314 0.4969 -6.07462 9 5 10 300 800 150 90 0.3599 0.7452 0.5526 -5.15178 4 6 10 400 750 180 75 0.3855 0.7331 0.5593 -5.04710 3 7 10 500 900 90 50 0.4793 0.3333 0.4063 -7.82306 14 8 10 600 850 120 25 1.0000 0.3509 0.6753 -3.41007 1 9 15 300 850 180 50 0.4744 0.4936 0.484 -6.30309 11 10 15 400 900 150 25 0.732 0.3463 0.5392 -5.36500 6 11 15 500 750 120 90 0.3333 1.0000 0.6667 -3.52139 2 12 15 600 800 90 75 0.4375 0.4421 0.4398 -7.13490 13 13 20 300 900 120 75 0.3679 0.3529 0.3604 -8.86430 16 14 20 400 850 90 90 0.372 0.4252 0.3986 -7.98925 15 15 20 500 800 180 25 0.6443 0.3984 0.5214 -5.65658 8 16 20 600 750 150 50 0.4921 0.4413 0.4667 -6.61924 12 3.5 effects of the control factors on grg the dominant control factors were identified from the delta statistics in the response table for signal-noise ratio as shown in table8. the delta statistics were computed as reported previously. the highest value of delta was assigned the first rank and represents the predominant factor affecting grg. from the table, processing temperature (pt) is the most influential factor. the second contributing factor is the stirring speed (ss). the third contributing factor is the particle size (ps), followed by the stirring time (st), and lastly the reinforcement fraction (csap). table 8: response for signal to noise ratios of grg level csap (wt %) ss (rpm) pt (oc) st (secs) ps (µm) 1 -5.733 -6.380 -5.997 -7.037 -4.908* 2 -5.358* -5.943 -5.829 -5.291* -6.529 3 -5.581 -5.823 -5.097* -5.856 -6.834 4 -7.283 -5.809* -7.032 -5.771 -5.685 delta 1.925 0.571 1.935 1.746 1.926 rank 3 5 1 4 2 optimum csap2ss4pt3st2ps1 *optimum factor levels 3. 6 confirmation test for confirmation, the optimal value was compared with experiment run 8 which had the same parameter settings with the optimal combination (csap2ss4pt3st2ps1); coconut shell ash particles (csap) at 10wt% (level 2), stirring speed (ss) at 600 rpm (level 4), processing temperature (pt) at 850oc (level 3), stirring time (st) at 120 secs (level 2) and particle size (ps) at 25 µm (level 1). the results at the optimal and predicted processing parameters of the aluminium/coconut shell ash particles composite are shown in table 9. the percentage improvement in grg was also evaluated and found to be within the acceptable range (ibrahim, 2023) table 9 shows how the properties of the composite improved as a result of the analysis carried out at the optimal level. it can be inferred from the table that there was an improvement of 36.4% and 30.7% respectively in the grg of the experimental and predicted over the initial settings. this improvement in the experimental http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 930 results over the initial design parameters affirms the validity of the taguchi method coupled with grey relational analysis for enhancing the properties of the composite developed (sylajakumari et al., 2018). table 9: confirmatory results comparison at the optimal level initial design parameters optimal design parameters experiment no. 4 predicted setting level kcp1ss1pt1st1ps1 csap2ss4pt3st2ps1 csap2ss4pt3st2ps1 grey relational grade 0.5015 0.6840 0.6557 improvement in grg (%) 36.4 30.7 3.7 analysis of variance (anova) of grg anova investigation shows the level of significance of each processing parameter. the analysis was also used to develop the predictive mathematical model for the grg as a function of the stir casting process parameters. table 10 shows that stirring speed with a contribution of 46.66%has the highest influence on the grg; followed by processing temperature with 25.92%, particle size with 15.65%, stirring time with 5.57%, and reinforcement fraction with 5.19%. at 95% confidence level, factors having p-value less than 0.05 are considered significant (sylajakumari et al., 2018). since the p-values of stirring speed and processing temperature are less than 0.05, they are considered significant contributors to the change in grg of the composite. conversely, reinforcement fraction, stirring time, and particle size are said to be insignificant terms, because their p values are above 0.05. the predictive mathematical model for the grg is presented in equation 7. grg = 0.876 + 0.00043csap + 0.000229ss 0.000607pt + 0.000126st + 0.000739ps 7 table 10: analysis of variance for grgof al/csap composite source df seq ss contribution adj ss adj ms f-value p-value regression 5 0.034623 0.034623 0.006925 4.45 0.022 csap 1 0.000094 5.19% 0.000094 0.000094 0.06 0.811 ss 1 0.010497 46.66% 0.010497 0.010497 6.74 0.027 pt 1 0.018398 25.92% 0.018398 0.018398 11.82 0.006 st 1 0.000287 5.57% 0.000287 0.000287 0.18 0.677 ps 1 0.005347 15.65% 0.005347 0.005347 3.44 0.094 error 10 0.015564 1.01% 0.015564 0.001556 total 15 0.050187 100.00% the developed regression model for grg has high coefficient of determination (r2), r2 adj and r2 pred values of 98.99%, 93.48%, 84.83%, respectively. this indicates the goodness of fit between the grg and the stir casting process parameters. 4. conclusion this study considered the optimization of the fatigue and compressive strength properties of al7075 alloy as a matrix reinforced with coconut shell ash particles with possible areas of application in buildings, civil transport, and automobile industries. the fatigue strength of the aluminium/csap composite indicated that the processing temperature significantly affects fatigue strength, while the stirring speed has the greatest effect on compressive strength. confirmatory experiments carried out using the optimal parameters (csap2ss4pt3st2ps1) in the grg showed an improvement in the fatigue and compressive strength of the optimized composite over the initial settings. references adebisi, aa. andndaliman, mb. 2015. mathematical modelling of stir casting process parameters for alsicp composite using central composite design. proceedings of the 28th agm and international conference of the nigerian institution for mechanical engineers. http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, december 2025; 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vol. 21(4): 921-932. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 932 raut, v., gandhi,m.,nagare, n., and deshmukh, a.2016. application of taguchi grey relational analysis to optimize the process parameters in wire electrical discharge machine.international journal of innovative science, engineering & technology, 3(7):108-115. sivaiah,p.and chakradhar, d.2019.performance improvement of cryogenic turning processduring machining of 17-4 ph stainless steel using multi objective optimization technique. measurement, 136:326336.doi.org/10.1016/j.measurement.2018.12.094 sylajakumari, pa., ramakrishnasamy,r.andpalaniappan, g. 2018. taguchi grey relational analysis for multiresponse optimization of wear in co-continuous composite. materials, 11:1-17.doi: 10.3390/ma11091743. varalakshmi, k., kumar., kc., babu, aj. 2019.analysis of dry sliding wear behaviour of al 6061coconut shell ash metal matrix composites using stir casting. applied engineering letters, 4(2): 55-65. doi.org/10.18485/aeletters.2019.4.2.3 yekinni, aa., durowoju, mo., agunsoye, jo. andmudashiru, lo. 2020.effect of particle size of rice husk ash on aluminium/graphene composites. iop conf. series: materials science and engineering,1– 19. http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):51-70 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 51 original research article geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis h. i. mohammed1, y. b. yamusa2*, z. majid3 and k. ahmad4 1department of geography, faculty of science, kaduna state university, nigeria 2department of civil engineering, school of engineering technology, nuhu bamalli polytechnic, zaria, nigeria 3department of geoinformation, faculty of built environment and surveying, universiti teknologi malaysia 4department of geotechnics and transportation, school of civil engineering, universiti teknologi malaysia *corresponding author’s email address: yamusabello@gmail.com 1.0 introduction in urban planning, one of the most important part is the identification of an appropriate location for municipal solid waste landfills (bahrani et al., 2016). environmental hazards to inhabitants could arise from this landfill sites (sharholy et al., 2008). some of the environmental impacts of landfill includes; contamination of air by greenhouse gases and odour emission, soil, and ground and surface water (chabuk et al., 2017a). contaminations caused by municipal waste affects not only the underlying soil, but also article information abstract contaminations caused by municipal waste affect not only the soil but also water and air. in many parts of the world, there are many uncontrolled landfills that often lack the necessary anti-fouling barrier systems which causes leachate to permeate the underlying groundwater making it toxic for consumption. this research presents a sustainable method in which sanitary landfills can be sited using geospatial multi criteria method and the subsequent application of geotechnical and digital image analysis. due to the large volume of spatial data, thus, geographic information system was used to handle, evaluate, and process these data. meanwhile, analytical hierarchy process was applied to solve decision making problems where multiple alternatives and competing objectives are involved. the results revealed three most suitable sites for sustainable sanitary landfilling in the research area. these most suitable sites were further examined using geotechnical criteria in laboratory to obtain the best site. engineering property relating to permeability was investigated. the results show that only one amongst the three sites achieved maximum regulatory range of permeability value of 10-9 m/s. additionally, computer modeling through digital image technique was used to visualize the leachate flow and validate the laboratory experimentation. the leachate migrated through the soil covering a depth of 2.51 mm in one month, having a velocity of 10-9 m/s which is within the recommended permeability value. therefore, this model could be used as a guide for sustainable sanitary landfilling in developed and developing countries © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 august, 2022 revised 3 october, 2022 accepted 6 october, 2022 keywords: geographic information system geotechnical engineering permeability solid waste management digital image technique http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 52 water and air (mohammed et al., 2019a). however, there are many methods which are employed in the waste management, but the commonest technique being used is landfill (jeswani and azapagic, 2016). as a result of landfilling method, a lot of issues arisen in the waste management sector (nas et al., 2010). one of the major challenges in waste management is the issue of selecting an appropriate site for sustainable sanitary landfilling for the disposal of municipal solid waste (msw) due to the complexity of various factors that must be considered and integrated such as environmental, economic, and social (aziz et al., 2019). it is of great challenge and interest to integrate geotechnical criteria into the site selection model to achieve an optimal, sustainable, economical, and environmentally friendly site for proper solid waste management. moreover, before siting new landfill for solid waste disposal, it is important to process significant large volume of spatial data, regulations, and acceptance criteria. table 1 shows the landfill siting criteria ranking of different parts of the world and world bank (wb) to their estimated distance where the landfill should be situated. table 1: landfill siting criteria ranking of different parts of the world and world bank parameter australia china germany india iran malaysia usa wb residential area (km) 0.25 0.50 0.50 0.50 0.30 0.50 2 1 water bodies (km) 0.10 0.50 0.50 0.10 0.20 0.10 0.50 0.50 groundwater (km) 0.10 1.5 1 1 0.05 1 1 1.5 source generation (km) 20-25 25 25 20-25 30 25 25-40 25 protected forest (km) 0.50 0.10 0.10 0.10 1.6 0.10 0.10 0.50 airport location (km) 8 3 3 20 3 3 4 3 distance to road (km) 0.10 0.10 0.50 0.20 0.30 0.50 0.10 3 maximum slope (%) 20 10 10-20 15 20 10 15-20 20 soil permeability (cm/s) <10-6 <10-7 <10-7 <10-7 <10-6 <10-6 <10-6 <10-6 fault lines (km) 0.10 0.10 0.10 0.50 0.10 0.10 0.10 0.50 (ahmad et al., 2014) existing methods for landfill site selection regards many objectives and criteria, however, an integrated method that inculcates all policies for optimum landfill site is lacking. regarding this, a hybrid model is required which simultaneously considers important criteria as environmental, economic, social, and geotechnical. landfill development and construction depends on the initial geospatial site location. though, the site soil should be investigated to check its geotechnical suitability as a liner material. the soil liner must possess the quality of impeding the migration, which is the downward movement of landfill leachate to protect the groundwater (yamusa et al., 2022; yamusa et al., 2020; ahmad et al., 2018). the guidelines in most regulatory agencies as well as researchers stated that 1 × 10-9 m/s maximum permeability, minimum of 200 kn/m2 shear strength, maximum of 4% volumetric shrinkage, and minimum of 30% soil fines content are specified for soil liners (ukea, 2014; amadi and eberemu, 2013; usepa, 1993; usepa, 1991; usepa, 1989). permeability also referred to as hydraulic conductivity is the major factor affecting the performance of hydraulic barriers. soils with high permeability are not considered for landfills since the infiltration of water through this soil is high and the possibility of groundwater pollution may increase. to protect the groundwater, it is recommended that the soil content of the liner is clayey that has very low permeability (ahmad et al., 2014). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 53 the digital image technique (dit) is a validation for the geotechnical properties of the overall best site. it involves the laboratory physical modeling results of compacted sample soil in an acrylic column simulating leachate migration in sanitary landfill were fed into a computer for processing and analysis. contour plots (2d) of hsi intensity value provide details and useful information to understand the characteristic of leachate migration behavior. the use of geospatial technology such as remote sensing with geographic information system (gis) to prepare the required input data in gis-based site selection for improved decision-making was used in this study. analytical hierarchy process (ahp) as a wellstructured mathematical and psychological method of organizing and analyzing complex decisions is applied. presently, ahp is a common and popular mcda method for geospatial analysis (saaty, 1988). the method remained widely used by decision-makers and researchers in understanding of problems and choosing the one which is best for their goal (madurika and hemakumara, 2015; djokanović et al., 2016; khademalhoseiny et al., 2017; ghobadi et al., 2017). in this method, the problems are broken down into a hierarchical order making it easier to be analyzed independently (chen et al., 2013). selection of suitable and most important criteria is the first step in any sanitary landfill siting (mohammed et al., 2019a). in this study, three main criteria were identified; environmental, social, and economic which were divided into thirteen sub-criteria i.e. water bodies, geology, soils, elevation, slope, residential areas, archeological sites, airports, population, roads, railways, infrastructures, and land use. all these data were prepared and processed accordingly based on related literature, expert’s judgement, and guidelines for sanitary landfill site selection. finally, potential sites for sustainable sanitary landfill were produced. the map layers were generated using gis techniques. indeed, researchers constantly attempt to improve the techniques to mapping the best sites for waste disposal and resolve the problems associated with the current mapping techniques that are still ongoing. in this case, an innovative approach based on geotechnical criteria was developed in this study to improve the accuracy of the landfill sites selection process. this is because when environmental measures were not put in place with respect to the construction, problems are bound to occur (bruno, 2007; depountis et al., 2009; önal et al., 2013). therefore, for a sustainable sanitary landfill site selection, the geotechnical, environmental, economic, and social factors need to be evaluated and assessed collectively. 2. materials and methods to determine the best potential candidate location for sanitary landfill in the study area, the gis and its spatial analysis tools, integrated with mcda, and geotechnical analysis were used to this aim according to the recommended criteria. the overall methodology employed in this research is presented in figure 1. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 54 figure 1: flow chart of the methodology file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 55 the study area covers johor bahru (jb), malaysia. it lies within latitude 1° 29′ 0″ n and longitude 103° 44′ 0″ e. jb was chosen in this study as it is one of the rapid developing area in johor state with increasing amount of solid waste generation. therefore, selecting sustainable sanitary landfill site in this area is needed because the existing sanitary landfill cannot accommodate the waste produced in the long run. gis is an influential tool that assists in choosing waste disposal sites based on its capability of dealing with a massive amount of data from several sources. ahp is a common and popular mcda method for geospatial analysis. it has a unique ability for determination of comparative weight of multiple criteria in decision-making used in solving multiple criteria problems. according to mohammed et al. (2017), most occurring or used criteria are water bodies and roads due to their high level of significance, while the least used criteria are soil permeability. therefore, to synthesize a cost-effective sanitary landfill site selection model for sustainable and integrated solid waste management, geotechnical criteria such as soil permeability also referred to as hydraulic conductivity was introduced in this study in order to strengthen the research gap. 2.1.1 selection of important criteria for sustainable sanitary landfill siting criteria have been reviewed from the previous literature, local and international guidelines for proper sanitary landfill site selection as presented in table 2. the relative importance weight of every criteria used in this study was by applying the saaty (2005) and other references numerical scale of 1-10. thus, not all criteria have equal important some are of high significant while others less significant. selected criteria for sanitary landfill siting adopted in this study are water bodies, archaeological sites, roads, population, slope and elevation, airport, residential areas, land use, infrastructure, soil, geology, geotechnical criteria that are most crucial. table 2 shows the sub-criteria ranking used in this study. the determination of level of importance of criteria was done through pairwise comparison matrix. the relationship between each criterion was compared to the others rated in a percentage which is believed to provide easier ranking. table 2: sub-criteria ranking used in this study sub-criteria buffer zones ranking references water bodies <100m 100-500 500-1000 >1000 0 5 7 10 (mhlg, 2005; eskandari et al., 2012; kontos et al., 2005; şener et al., 2005; bim, 2010) soil low permeable low to medium medium permeable highly permeable 10 7 5 0 (chabuk et al., 2016; ahmad et al., 2015) slope 0-50 60-100 100-150 >150 8 7 6 0 (mhlg, 2005; effat and hegazy, 2012; barakat et al., 2017; chabuk et al., 2017b; usepa, 1993) elevation >750m 750-1000 1000-2000 >2000 0 7 4 2 (şener et al., 2005; torabikaveh et al., 2016) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 56 residential <1000m 1000-1500 1500-2000 >2000 0 3 9 5 (mhlg, 2005; eskandari et al., 2012; barakat et al., 2017; usepa, 1993) airports <3km 3-6km 6-9km >9km 0 4 7 10 (mhlg, 2005; şener et al., 2005; usepa, 1993) geology intrusive intermediate acidic 7 6 0 (barakat et al., 2017; ahmad et al., 2015; şener et al., 2011; şener et al., 2005) road <500m 500-1000 1000-1500 >1500 0 2 10 3 (alanbari et al., 2014b; şener et al., 2005; mhlg, 2005; chabuk et al., 2016) population low density medium density high density 7 5 3 (chabuk et al., 2016; aksoy and san, 2017) infrastructures <50m 50-100 100-150 >150 0 5 8 10 (demesouka et al., 2013; chabuk et al., 2016; şener et al., 2005) lu/lc public facilities educational site agricultural land forest vacant land 0 0 6 3 10 (torabi-kaveh et al., 2016; barakat et al., 2017; alavi et al., 2013; mhlg, 2005) railway <500m 500-1000 1000-1500 >1500 0 2 4 10 (alanbari et al., 2014a; demesouka et al., 2013; chabuk et al., 2017b) archeological <500m 500-1000 1000-1500 >1500 0 2 5 10 (djokanović et al., 2016; eskandari et al., 2012; chabuk et al., 2017b; alkhuzaie and janna) 2.1.2 gis method two main type of data was used in this study; primary data and secondary data. the primary data was acquired by visiting the existing sanitary landfill site and municipal solid waste management authority in johor bahru, malaysia. this was carried out via questionnaire aimed to evaluate the sanitary landfilling system needed for disposing johor bahru municipal solid waste according to a set of guidelines and standard. the questionnaire focused on comparative analysis between the thirteen sub-criteria (parameters). basically, the questions were based on the of scale of pairwise comparison by using ahp method. the secondary data used in this study included topographic maps, file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 57 geology map, soil map, land use map, and digital elevation map of the study area. all these maps were obtained and digitized. google earth pro was used for georeferencing. also, verification and validation were made during the field survey. the secondary data were inputted for the site suitability analysis process in the gis environment. landfill siting criteria guidelines such as integrated solid waste management blueprint for iskandar malaysia (bim, 2010) and national strategic plan for solid waste management (mhlg, 2005) were adopted. three main criteria were used which were divided into 13 sub-criteria. the data used in this study were collected from various sources: jb administrative boundary and land use/land cover map was acquired from the iskandar regional development agency. the geological map was derived from a scanned geological map of peninsular malaysia published by the director general of geological survey, malaysia (1985). road, water body, and railway maps were extracted from digitization of the topographical map series 4551 published in 1996. all the data are geo referenced according to the kertau rso projection system. data from the us geological survey global visualization viewer (usgs glovis) digital elevation model (dem) needed for this study were accessed from their online archive http://glovis.usgs.gov/. aster gdem with spatial resolution of 30m was used to extract elevation and slope information of the studied area. erdas imagine software was used in processing and analyzing satellite images. arcgis software was used for digitizing and spatial data analysis. considering secure and reliable distance to landfill site in order to allocate the buffer zones for each layer was based on governmental guidelines, experts’ judgment, and local and international references. each criterion was categorized into classes, and each class was given a suitability score from 0 to 10 where 0 means that the area is unsuitable and 10 means that it is most suitable. distancing, reclassification and overlay analysis were undertaken in gis, using the spatial analyst tool arcgis. in order to evaluate the site selection criterion, ahp was used to measure the relative importance weight of each criterion. comparison matrix for the parameters used in the decision was created first to perform the pairwise comparison in accordance with uyan, 2013 as shown in equation 1. 𝐶𝑗𝑖 = 1 𝐶𝑖�̇� (1) the values of c (i = 1, 2, 3….m and j = 1, 2, 3…. n) are used to signify the performance values in terms of the i-th and j-th in the matrix. it is important to check for the consistency because the values which were used for the computation of the weight are obtained from different opinion of experts with different perspective of preferences, therefore, there is a possibility to encounter errors in the final stage of computation in the matrix (saaty, 2005). the consistency index (ci) was computed using equation 2. )1( )max( − − = n n ci  (2) where 𝜆𝑚𝑎𝑥 is the greatest eigen value of preference, and n is the total number of the compared criterion used. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/5.%20azojete%2022-014z%20okay%201.docx%23_enref_211 arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 58 in this study, the raster calculator operation was performed in map algebra tool to identify the potential sites map. this was carried out by overlaying all the criteria weights assigned to each map layer and the final potential sites map was produced based on this analysis. from the most suitable sites, the best potential sites were identified by filtering the most suitable sanitary landfill layer. this was carried out by converting the output layer which is in raster format into vector and then selecting the areas that does not have an intersection with water bodies because of its high level of significant. 2.2 geotechnical method after producing the potential sanitary landfill sites map, the introduction of geotechnical criteria was employed. thereafter, soil samples from the selected potential sites were taken and subjected to laboratory experiments. the geotechnical properties of the soils one of which is permeability of each sample were studied to get the best location for the sanitary landfill. the soils used in this study were obtained below 0.5 m below the ground surface to avoid organic matter using disturb sampling method. each soil sample was dried and then passed through bs 4.75 mm aperture sieve to remove oversized gravel. the geotechnical properties were divided into two: first, the physical properties tests which include specific gravity, atterberg limit, and particle size distribution to classify the soils adopting the bsi (1990). the specific gravity of the soil particles is calculated using equation 3. )()( 2314 12 wwww ww gs −−− − = (3) where; gs = specific gravity w1 = mass of density bottle, stopper (g) w2 = mass of density bottle, soil, and stopper (g) w3 = mass of density bottle, stopper, water, and soil sample (g) w4 = mass of density bottle, stopper, and water only (g) the atterberg limit tests cover the determination of liquid limit (ll) and plastic limit (pl) of the soil. the difference between liquid and plastic limits equals to plasticity index (pi). using these three values, sample is classified using plasticity chart of british standard classification system (bsi, 1999). the detailed procedures followed in performing atterberg limit tests were in accordance with bs 1377: part 2: 1990. the plasticity index was determined from the liquid limit and plastic limit results for the soils using the expression in equation 4. plllpi −= (4) second, the engineering properties tests that involve hydraulic conductivity or permeability with respect to moulding water content using the falling head permeability test as explained by head and epps (2011). the coefficient of permeability was calculated from equation 5. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 59 𝑘 = 2.3 𝑎𝐿 𝐴𝑡 log10 ℎ1 ℎ2 (5) where; k = coefficient of permeability (m/s) a = area of the standpipe (m2) l = length of sample (m) a = cross sectional area of sample (m2) h1 = initial height of water in standpipe (m) h2 = final height of water in standpipe (m) t = time required to get head drop (s) 2.3 geotechnical validation using digital image technique the geotechnical criteria were validated using a non-invasive method called digital image technique (dit) where the migration of leachate was monitored using surfer and matlab computer software. this laboratory technique shows successive images of leachate migration in compacted soil simulating the actual landfill leachate migration. basically, dit employed in this study follows the concept of yamusa et al. (2019) and sa’ari et al. (2015) presented in figure 2. figure 2: flow chart of model validation process the laboratory experiment covers the migration of leachate in a 100 mm height of soil in acrylic column. the dimension of acrylic cylinder to form the soil column was 150 mm high, 100 mm diameter and 6 mm thick. the acrylic column is placed in-between twofaced mirror to provide a complete visualization of 360º. these mirrors were placed at 105° of angle with offset distance of 0.2 m behind the soil column and facing the digital camera (sa’ari et al., 2015). a hitachi 40-watt lamp was installed overhead the soil column so that the whole setup was illuminated. the acrylic column was chosen to provide a clear visualization of leachate migration into the soil. using acrylic column implies that the leachate migration through the soil is observed promptly at any point and time throughout the experiment. a nikon d90 digital camera was the main equipment used for image acquisition of the leachate migration at designated time intervals. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 60 the digital images captured during the laboratory experiments were saved in jpeg format. images were then taken to surfer, a scientific data mapping, modeling, and analysis software. this software converted the digital image grid coordinate into surfer grid coordinate. the grid line images were then digitized and save as generic data files (dat files) so that the files could be opened or referenced by a specific application like matlab, excel and surfer. in the object manager of the surfer, a post layer was added and saved as surfer file (srf file). the dat files were then copied from the surfer and pasted in excel. the copy and paste were necessary in order to sort and filter the values and then saved them as excel files (xls file). a matlab image processing routine called reival was used to perform the digital image processing tasks. the prediction of leachate migration was carried out to evaluate the velocity (v) parameter over some presumed time. thus, the velocity of any fluid is the ratio of its distance and time covered as expressed in equation 6. 𝑣 = 𝑑/𝑡 (6) where: v = velocity (m/s), d = distance (m) and t = time (s). 3. results and discussion 3.1.1 identification criteria according to the judgement from the developed pair wise comparison matrix for the thirteen criteria used for this study, the results of the criteria weight and their percentages are shown in table 3. more importance was given to residential areas with weight of 0.239, while railway criteria have the least importance with weight of 0.018. this is because of the strict rules and regulations governing the prohibition of sanitary landfill near the residential areas (mohammed et al., 2019b). table 3: criteria weight and percentage criteria weight percentage residential 0.239 23.9% water bodies 0.168 16.8% geology 0.121 12.1% soils 0.099 9.9% land use 0.067 6.7% slope 0.056 5.6% elevation 0.054 5.4% road 0.036 3.6% infrastructure 0.046 4.6% airport 0.033 3.3% population 0.038 3.8% archaeological 0.025 2.5% railway 0.018 1.8% total 1 100% 3.1.2 final potential sites map for sanitary landfill the potential map of the sanitary landfill sites is displayed in figure 3. the map shows the distribution of the selected areas based on suitability where the most suitable are considered the highest priority sites. the legend was used to provide visual clarity of the file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 61 map showing the various classes of suitability. from the result of this map, it was found that most of the areas are unsuitable with the highest total of 54% of the study area, 12% less suitable, 21% suitable and 13% most suitable figure 3: potential sanitary landfill sites map of johor bahru 3.1.3 best potential sites map based on expert’s judgment using the ahp criteria weighting and gis analysis, three candidate sites appear to be the best from environmental, economic, and social perspectives. these sites have fulfilled the requirements for sanitary landfill siting with a distance of at least 1000m away from roads, 1500m away from residential areas, and far away from public and educational facilities. these three sites as displayed in figure 4 were used to further accomplish the remaining objectives of this research. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 62 figure 4: best potential sanitary landfill sites map of johor bahru 3.2 geotechnical properties of the best landfill sites the geotechnical properties were obtained from the laboratory testing of representative soil samples of the study areas. to ascertain the properties of the soil material, the study commenced with detailed physical properties and engineering properties. 3.2.1 physical properties table 4 shows the physical properties of soil samples from the study areas. according to the british standard (bs) classification, the soil sample for site a is classified as sandy clay of high plasticity (mh). site b soil sample is classified as very silty sand of intermediate plasticity (mh). soil sample of site c is classified as very silty sand of very high plasticity (mv). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 63 table 4: physical properties of the soils from the study areas property value site a site b site c specific gravity 2.70 2.74 2.70 % fines 51 29 14 % sand 46 61 46 % gravel 3 10 40 omc, % 27.9 19.3 17.8 mdd, mg/m3 1.38 1.52 1.51 liquid limit, % 64 50 76 plastic limit, % 37 29 37 plasticity index, % 27 21 39 bs classification mh mh mv colour brown reddish brown red literature suggests that soils with the following index properties: percentage of fines ≥ 30%, plasticity index ≥ 7 and liquid limit ≥ 20% can be specified for landfill liners (daniel, 2012; benson et al., 1994). comparing the index properties of the sites soil used in this study and that of the literature shows that the soil is suitable to be used as liner material for site a only. sites b and c have their fines content less than 30% and they might not likely impede the flow of leachate through them. 3.2.2 engineering properties hydraulic conductivity is the major factor affecting the performance of hydraulic barriers. soils with high permeability are not considered for landfills since the infiltration of water through this soil is high and the possibility of groundwater pollution may increase. to protect the groundwater, it is recommended that the soil content of the liner is clayey that has very low permeability (ahmad et al., 2014). the hydraulic conductivity is discussed with respect to the effects of moulding water content. figure 5 shows a general decrease in hydraulic conductivity with increase in moulding water content for all soil samples. this trend is in line with yamusa et al. (2022) and bello (2013). samples from site a had the lowest permeability of 2.1 x 10-9 m/s, followed by site b with 2.08 x 10-8 m/s, and then site c with the highest permeability of 1.5 x 10-7 m/s at omc. the results show that only site a used in this study was within the range of maximum regulatory hydraulic conductivity value of 1 x 10-9 m/s (yamusa et al., 2022; yamusa et al., 2018b). sites b and c did not meet the hydraulic conductivity criteria. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 64 figure 5: variation of hydraulic conductivity with moulding water content 3.3 model validation using digital image technique figure 6 shows the gradual successive leachate migration within the first day until the seventh day, and then it becomes constant after the seventh day until the end of the experiments of twenty-eight days. this could be explained in terms of energy loss due to hydraulic gradient. according to viswanadham (2018), water flows in soils only when there is a gradient in energy or head loss. in soils, water or (permeant) always flow down the gradient from high energy regions to low energy regions. as a particle of water proceeds from high energy regions to low energy regions it exerts a frictional drag on soil particles which steadily decreases the hydraulic head on every flow line. when the hydraulic head becomes too small, the water finally loss energy to move further and therefore becomes stagnant (yamusa et al., 2019; yamusa et al., 2018a). the leachate migrated through the soil covering a depth of 2.51 mm in one month, having a velocity of 1.04 x 10-9 m/s which is within the recommended permeability value. 1.0e-10 1.0e-09 1.0e-08 1.0e-07 1.0e-06 1.0e-05 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 h y d ra u li c c o n d u ct iv it y ( m /s ) moulding water content (%) site a site b site c file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com mohammed et al: geospatial multi criteria selection of best sanitary landfill site and their geotechnical and digital image analysis. azojete, 19(1):51-70. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 65 figure 6: leachate migration in soil column figure 7 illustrates the velocity values against time for the site a soil sample. generally, the velocity decreased with increase in duration of time. the calculated velocity of the leachate at 28 days for sample a is 1.04 x 10-9 m/s. thus, sample a used in this study can be used as landfill liner material because it has a permeability within the minimum range value (yamusa et al., 2020; yamusa et al., 2019; daniel, 2012; usepa, 1991). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):51-70. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: yamusabello@gmail.com 66 figure 7: leachate migration in soil column from dit 4. conclusion the gis and mcda (using ahp) were applied in this study for assessing the possible best potential sites for sanitary landfill in johor bahru, malaysia. the most important parameters for this study were residential areas and water bodies while the least important criteria was railway. the study further revealed that, 54% of the study area were unsuitable areas for sanitary landfill site, 12% less suitable, 21% suitable and 13% most suitable. three most suitable potential sites were identified among the various sites. the introduction of geotechnical analysis to further selects the overall best sanitary landfill site amongst the three suggested by geospatial method. the physical properties of the soils used in this research shows that only site a is suitable to be use as liner material. sites b and c have their fines content less than 30% and they might not likely impede the flow of leachate through them. moreover, the engineering properties showed that only site a used in this research attained within the range of maximum regulatory permeability value of 10-9 m/s. sites b and c did not meet the permeability criteria. the validation of leachate migration through the compacted soil using digital image technique was attained. the leachate migrated through the soil covering a depth of 2.51 mm in one month, having a velocity of 1.04 x 10-9 m/s which is within the recommended permeability value. this research work has implemented the use of latest geospatial techniques to select a sustainable sanitary landfill site in the study area focusing on geotechnical criteria as a key factor in siting sanitary landfill. this is to ensure that the soil beneath the ground surface can support the threats of varying climatic conditions of wet and dry season, loads bearing capacities, and conditions posed on it by transportation facilities before any further construction process begins references ahmad, k., yamusa, by. and kamisan, mb. 2018. effects of soil recompaction on permeability. science world journal, 13(3): 6-9. ahmad, sz., ahamad, ms and yusoff, ms. 2014. spatial effect of new municipal solid waste landfill siting using different guidelines. waste management & research, 32(1): 2433. 1.0e-10 1.0e-09 1.0e-08 1.0e-07 1.0e-06 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 v el o ci ty ( m /s ) time (days) file:///c:/user/downloads/azojete143/www.azojete.com.ng 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k., sa’ari, r., osinubi, kj., adrian, eo. and moses, g. 2020. engineering characteristics of compacted laterite soil as hydraulic barrier in waste containment application. journal of engineering science and technology, 15(1): 508-523. yamusa, y. b., sa’ari, r., ahmad, k., alias, n., mustaffar, m.and foong, l. k. 2019. monitoring leachate migration in compacted soil using digital image technique. engineering, technology & applied science research, 9(1): 3685-3691. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/yamusabello@gmail.com corresponding author’s email address: adelekeae@funaab.edu.ng 618 arid zone journal of engineering, technology & environment original research article biogas production using a mixture of avocado seeds and cassava peels blended with cow dung a. e. adeleke1*, e. e. anjuwon1, and s. o. giwa2 1department of mechanical engineering, college of engineering, federal university of agriculture, abeokuta, ogun state, nigeria. 2department of mechanical engineering, faculty of engineering, olabisi onabanjo university, ibogun campus, ifo, ogun state, nigeria. *corresponding author’s email: adelekeae@funaab.edu.ng article information abstract increase in the cost of fossil fuels as a source of energy, coupled with environmental pollution associated with their consumption, calls for the search for alternative energy sources. therefore, this study focused on the construction and performance evaluation of a biodigester to produce biogas as a renewable energy source for domestic use. a 24-litre biodigester was constructed and used in this study. the biogas was produced using a mixture of cassava peels and avocado seeds with cow dung as inoculum under mesophilic conditions. the cassava peels and avocado seeds were mixed in the ratio 5:1. the experiment was carried out under mesophilic conditions, while the mass and composition of the produced biogas were measured. the findings showed the production of 256 g of biogas corresponding to 0.438 m3. the biogas produced was found to contain 64.4% of methane, 5% of water vapour, 0.9% of o2 content, 560 ppm of co, and 478 ppm of h2s. interestingly, a relatively higher methane content was observed in this study than in previous studies. thus, implying the influence of the choice of the agricultural wastes (cassava peels and avocado seeds in this case) and inoculum used as substrate which enhanced anaerobic digestion process in connection with the improved biodigester. these results revealed that biogas generation could be achieved using locally sourced agricultural wastes and thus promoting green and renewable energy in agreement with the sustainable development goals. therefore, biogas production would not only provide an alternative source of energy but would also aid in farmland and marketplaces' waste management. received: 10th may 2025 revised: 25th may 2025 accepted: 26th may 2025 keywords: avocado seeds biogas cassava peels cow dung renewable energy © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction biofuel is a source of renewable energy found to be cheap and environmentally friendly (agoundedemba et al., 2023). it is any fuel sourced from biological materials or animal waste. the resources used to produce biofuel are readily available and require only a little effort in production. the usage of biofuels promote waste management and reduce greenhouse gas emissions (shonhiwa et al., 2023). biogas is an energy source produced through the breakdown of organic matter such as food and animal waste (asante et al., 2024). it is an environmentally friendly fuel produced using biochemical process processes in the absence of oxygen to break down the organic matter and stabilize the material, by converting it to biogas and residue (koley et al., 2023). biogas production through anaerobic reaction involves four basic reactions, which are hydrolysis, acidogenesis, acetogenesis, and methanogenesis (daniel et al., 2023; koley et al., 2023). it provides a dependable source of energy, reducing the country's dependence on imported fuels (sekoai et al., 2023). it can be used for various applications such as vehicle fuel, heat production, and electricity generation, and can also provide an extra revenue source for farmers and waste management facilities (shonhiwa et al., 2023). in the developing countries, biogas is produced using small-scale domestic digesters for cooking or even lighting, while in developed countries, biogas is used on a larger scale, farm-based and commercially, for electricity and heat purposes (scarlat et al., 2018; shonhiwa et al., 2023). globally, biogas is increasingly becoming a very important source of energy, with the growing energy derived from biogas on a global scale from 1990 to 2022 azojete june 2025. vol.21(2):618-625 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/026 www.azojete.com.ng mailto:adelekeae@funaab.edu.ng mailto:adelekeae@funaab.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 618-625. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 619 presented in figure 1. this reveals the rising interest in biogas as a renewable and viable source of energy globally. figure 1: global energy derived from biogas from 1990 to 2022 (statista, 2025). different biological feedstocks (single and mixture) have been used as substrates in various types of biodigesters to produce biogas. for example, ilori et al. (2007) studied the production of biogas from banana peels and plantain peels contained in a 10-liter laboratory-scale digester. under a mesophilic range of 32 – 35 °c and after 35 days, 8800 cm3 and 2409 cm3 of biogas were generated from the banana peels and plantain peels, respectively. singh et al. (2009) used chicken waste as a substrate in a digester to produce biogas. a total of 3000 litres of biogas was produced during the experiment. wikandari et al. (2015) produced biogas using orange peel wastes pre-treated to remove limonene using hexane. a 28.6% decrease in methane was observed, which was due to hexane residue in the substrate. over time, studies (ezekoye and okeke, (2006) ;ezekoye, (2013)) showed the use of substrates consisting of more than one feedstock in the production of biogas. ezekoye and okeke (2006) constructed and evaluated the performance of a 300-gallon plastic biodigester containing a mixture of 50% spent grain and 50% rice husk to produce biogas. the biodigester was operated at mesophilic temperatures (20 – 45 °c). after 20 days of charging the feedstocks, 150 litres of biogas were produced by the 47th day. the rice husk was noticed to enhance the number of microbes in the spent grains, which augmented biogas production. ezekoye (2013) conducted a comparative study of using plantain peel/almond leaves and pig dung in the production of biogas. using a batch method, the biodigester was operated within a mesophilic range of 20 to 31 °c. the use of plantain peel/almond leaves produced 220.5 litres of total biogas while the pig dung produced 882.5 litres. biogas from the plantain/almond leaves contained 72.7% methane, while that from the pig dung contained 70.2% methane. deressa et al. (2015) investigated biogas production from fruit and vegetable wastes (avocado, papaya, mango, tomato, banana peel) co-mixed with cow manure using different digesters maintained at a ph of 6.7 – 7.4. fantozzi and buratti (2009) conducted two separate experiments using a mixture of chicken, pig, and bovine manures, and chicken, cow manure, and olive husk with rumen fluid and digested sludge as inoculum to produce biogas. the biogas yield showed that the first set of substrates produced a maximum of 0.35 nm3/kg of biogas with an energy content of 1.35 kwh/kg while the second set of substrates yielded a higher production of 0.63 nm3/kg. tambuwal et al. (2019) experimented the use of fresh and dried banana peels and plantain peels and their co-mix with cow dung as substrates for biogas production in a batch-type digester. the work was carried out at a temperature range of 30 – 34 °c. results showed biogas production order of banana peels + cow dung > plantain peels + cow dung > fresh banana peels > fresh plantain peels > dried banana peels > dried plantain peels. this revealed that co-mixed substrates produced more biogas than single-feedstock substrates. aisien and aisien (2020) used six batches of 10-liter anaerobic biodigesters containing cow manure and cassava peels (fresh and stale) as substrates to produce biogas and biofertilizer. the studied feedstocks were prehttp://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 618-625. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 620 treated using buffer solutions (sodium hydroxide, calcium hydroxide, and ammonium chloride), and the biogas production was examined for forty days under a ph range of 6.5 – 7.5 and a temperature range of 28 – 35 °c. the produced biogas contained 62.3% methane with a total volume of 104960 cm3 using stale cassava peels + cow dung as against 95592 cm3 generated using fresh cassava peels + cow dung. this was achieved using ammonium chloride for pre-treating the substrates. the digestate was examined for total solids, volatile solids, phosphorus, nitrogen, and other values. kabri et al. (2022) engaged mixtures of cow dung, plantain peels, and cassava peels as substrates in a digester to produce biogas. the results showed the production of 0.04 m3 of biogas at 39 °c and 89.9 n/m2, composed of 65% methane, 30% co2, and 5% water vapour. mibulo et al. (2023) investigated the production of biogas from jackfruit waste, banana peels, and pineapple peels co-mixed with cow dung at different amounts (0%, 25%, and 50%) as substrates using a laboratory-scale 250 ml anaerobic digestor. total biogas production of 82.3, 189, and 262 ml was recorded for jackfruit waste, pineapple peels, and banana peels, respectively, as 50% of cow dung and jackfruit waste improved biogas by twofold. ramjani et al. (2023) produced biogas from different mixtures of coconut water and cow dung using a batch-type anaerobic digester. at a 1:1 mixture of the substrate, peak biogas of 976.67 ml was produced with 53% methane content. with over 200 million people in nigeria and the ever-increasing demand for energy, coupled with the overdependence on fossil fuels and the attendant effects, the need to deploy sustainable energy resources to address the energy, emissions, climatic, and environmental challenges have become inevitable in line with the au 2063 and un 2030 agenda (chaudhuri, 2021; dyantyi-gwanya et al., 2025). decarbonization of energy consumption in the country, based on the carbon neutrality concept in agreement with the sustainable development goals, has made biogas a significant and viable source of renewable energy for nigeria. biogas allows the country to generate green electricity, as 6.52 and 4.98 billion cubic meters of biogas can be produced per year using cow dung and crop residues (akhator et al., 2016). the abundance of organic wastes (agricultural waste, livestock waste, and food waste) and favourable climate have made nigeria a suitable candidate for biogas production. based on the above assertion and the gap in research concerning the use of avocado seeds and cassava peels (feedstocks) + cow dung (inoculum), this study aimed to examine the production of biogas using this as a substrate containing these feedstocks and the inoculum in a locally built batch-type digester. the present work explored the feasibility and significance of producing biogas from otherwise inedible agricultural wastes (avocado seeds and cassava peels). besides, the performance of the biodigester and the characterization of the biogas produced were also carried out. 2. materials and methods 2.1 construction and description of biodigester an overview of the biodigester set-up is shown in plate 1. the biodigester set-up consists of three major components; bioreactor, purification chamber, and gas storage chamber. bioreactor is the structure where the anaerobic reaction occurs. it was constructed using a 24 litres plastic drum. the opening at the top of the reactor was made to serve as inlet through which the substrate was poured into the biodigester . purification chamber is the place where the produced gas is purified to remove unwanted particles. the a 4 litres plastic bucket was improvised to serve as purification chamber. the plastic tube is used to store the purified biogas. the pvc pipes were used for the connection of these three major components. the elbow, couplings and nipples were also used for the joining of the pipes, change the direction of the pipe and also to help prevent leakages. valves were used to prevent the gas from returning to the biodigester. this biodigester was constructed similarly to a previous study by adeleke et al. (2020), the only difference lies in the use of a tubular storage unit instead of a gas cylinder used in the earlier study. 2.2 production of biogas 2.2.1 collection of substrates the avocado seeds were collected at mile 12 market in lagos state, nigeria while the cassava peels were obtained from the garri production unit of the federal university of agriculture, abeokuta, nigeria. similarly, an inoculum (cow dungs) was obtained at the college of veterinary medicine, federal university of agriculture, abeokuta, nigeria. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 618-625. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 621 2.2.2 preparation of substrates the cassava peels were sun dried for 2 weeks to reduce the moisture content, while the avocado seeds were partially sun dried for a week and then ground before being used (plate 2). both the ground avocado seeds and cassava peels were stored at room temperature for proper preservation. 2.2.3 preparation of purifier activated charcoal was prepared by grinding and mixing it with lime (in a container). the mixture was left for 24 h and then heated in a crucible placed in an oven to completely dried up. the prepared activated charcoal acts as a purifying substance for the biogas. 2.2.4 production of biogas to prepare the feedstock, 2.3kg of cassava peels and 450g of avocado seed were mixed in the ratio 5:1. the mixture of dried cassava peel and avocado seeds were soaked in water for three hours to absorb water in order to create more surface area for the reaction of methanogenic bacteria bringing about biogas production. this mixture was co-prepared with cow dung as inoculum into a slurry using water and fed as substrate into the biodigester. the studied substrate filled slightly over 60% of the biodigester as recommended by fagbenle et al. (2022). cow dung was included to improve the degradation kinetics, augment the microbial associations, and guarantee the carbon-nitrogen (c/n) balance. plate 1: biodigester set up plate 2: sun dried (a) cassava peels and (b) avocado seed the substrates and the inoculum were left in the biodigester to charge for a hydraulic retention time of 12 days following asante et al. (2024) and daniel et al. (2023) works. the cover of both the biodigester and the (a) (b )) http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 618-625. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 622 purification chamber was sealed properly with the use of silicon to make it airtight. during this time, the anaerobic reaction began to take place. when the gas was fully charged, the valve was opened to allow it to flow into the purification chamber and then to the tubular storage. this process was carried out at an ambient temperature. the experiment was set up and conducted at the college of engineering, federal university of agriculture, abeokuta. it is imperative to note that the experiment was conducted under mesophilic conditions (26 – 29 °c), which promoted stable biogas production and a relatively constant anaerobic digestion process. 2.2.5 quantification of biogas produced the mass of the tubular storage was measured using a digital weighing balance before it was connected to the biodigester. after it was connected, the mass of the tube was then measured throughout the rest of the days of biogas production to obtain the mass of the gas produced. the total mass of gas produced was calculated as expressed in equation (1): 𝑀𝑇 = 𝑀𝑡𝑢𝑏𝑒+𝑔𝑎𝑠 −𝑀𝑡𝑢𝑏𝑒 1 where, mt = total mass of the gas produced, mtube+gas = mass of the tube and gas, and mtube = mass of the tube. 2.3 characterization of the gas produced the characterization of the gas produced was carried out using a gas analyser to determine the methane content (%), oxygen content (%), hydrogen sulphide content (ppm), and co content (ppm) of the produced gas. 3. results and discussion 3.1 mass of gas produced figure 2 shows the mass of biogas produced daily from cassava peels and avocado seeds with cow dung. the figure shows that the studied substrates started producing biogas after 10 days. from figure 3, a sharp increase in biogas production was observed from the 11th day to the 12th day (fagbenle et al., 2022 and ramjani et al., 2023), corresponding to a mass of 37 g. this value of biogas resulted in the peak quantity produced. this can be due to the commencement of the biogas production and the initial release of produced gas after over 10 days of anaerobic fermentation of the substrate. also, the presence of cow dung was expected to augment the degradation kinetics by increasing the microbial numbers and activities. however, a decrease in biogas production was observed from the 12th day to the 16th day of the anaerobic digestion, leading to a 45.9% reduction compared to the value reported for the 12th day. the high rate of production of hydrocyanic acid at the earlier stage of the anaerobic digestion could be the possible reason for the reduced mass of biogas production. figure 2: mass of biogas produced per day a progressive increase (75%) in biogas production was noticed from the 16th day (20 g) to the 18th day (35 g), which thereafter reduced rapidly by 19th day, and the gas production remained constant by the 20th day. okudoh et al. (2014) documented that the presence of cyanogenic glucosides in cassava peels could induce excess acid production and the release of cyanide, which is highly toxic to methanogenic arches, hence reducing biogas production. the maximum biogas production was recorded on the 12th day. for the duration 0 5 10 15 20 25 30 35 40 11 12 13 14 15 16 17 18 19 20 m a ss o f g a s (g ) day http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 618-625. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 623 of the study, a total of 256 g (0.256 kg) of biogas was produced. this gave an average of 28.4 g/day. about 0.438 m3 (from a mass of 0.256 kg at a density of 0.584 kg/m3) of biogas was produced for 20 days of anaerobic digestion. 3.2 biogas characterization the biogas produced was characterized and found to consist of 64.4% methane, 560 ppm of co, 478 ppm of h2s, and 0.9% o2 content. this revealed that methane had the highest content than other gases and can be said to be the main constituent of the biogas produced from the studied substrate (fagbenle et al., 2022). this work recorded a slightly higher content of methane in comparison with the work of aisien and aisien (2020), which produced 62.3% of biogas (under mesophilic conditions) with the use of cassava peels inoculated with cow dung (after treatment with nh4cl) in a 10-l batch-type anaerobic digester. the work involved pre-treating the substrate, purification (nacl solution) of the produced biogas, using 3.6 kg of cassava peels and 4 g of cow dung, and 40 40-day retention time. it can be deduced that the co-mixed feedstock engaged in this study could be responsible for the high methane content. a moderately lower methane content (33.6%) was reportedly produced from cassava peels (25 kg), cow dung (25 kg), and 100 kg of water used as substrate in a 200 litres batch biodigester before and after purification of the produced biogas in comparison to the present work (fagbenle et al., 2022). the substrate (under mesophilic conditions) had a retention time of 30 days in the biodigester with the use of ca(oh)2, silica, and activated carbon to purify the produced biogas. similarly, the methane content obtained in this study was higher than that reported by szilágy et al. (2021) in a biogas comparative analysis, where biogas contents ranging from 46 – 48% were produced from the engagement of tomato biological wastes in a biodigester. the work of ramjani et al. (2023) that used coconut water, water, and cow dung mixed at 2:1:1 ratio in a laboratory-scale 2-l biodigester (under mesophilic conditions) produced biogas with 53% methane content, which remained lower than what was recorded in this present study. a retention time of 35 days was reported with biogas purification using naoh solution. however, the work of ezekoye (2013), which produced biogas from plantain/almond leaves + pig dung and pig dung using a 1.47 galvanized metal biodigester (under mesophilic conditions) reported methane contents of 70.2% and 72.7% respectively, which are found to be slightly higher than the methane content obtained in this study. from these previous studies used for comparison, it can be deduced that this present work recorded a relatively higher methane content compared to previous studies. this can be connected to the use of cassava peels and co-digestion with avocado seeds employed as substrate in this study (okudoh et al., 2014), which strengthens the use of agricultural produce wastes to alleviate the problem of waste management and promote a cleaner and odourless environment, especially in marketplaces. in addition, the digestion of a comix of organic feedstocks such as avocado seeds and cassava peels was observed to influence the biogas yield. 4. conclusion clean biogas has been successfully produced via the anaerobic digestion process in a locally built biodigester using cassava peels and ground avocado seeds with cow dung as substrate under atmospheric temperature and pressure. a total biogas of 256 g corresponding to 0.438 m3 was produced under 20 days of anaerobic digestion of the studied substrate. the biogas produced consists of 64.4% methane, 560 ppm of co, 478 ppm of h2s, and 0.9% o2 content. a relatively high yield of methane was obtained from this study in comparison with other previous studies. this is because of the effective digestion of the inoculum, avocado seeds, and cassava peels, and the simplicity of the biodigester. the findings demonstrated biogas production via the anaerobic digestion of mixed feedstocks (especially agricultural wastes) as substrate. further improvement in the operation of the biodigester, novel materials for biogas purification, better selection, and combination of organic wastes as substrates, and choice of other kinds of inoculum have been recommended for consideration for future studies. references adeleke, ae., ogudana, t., oyelami, s. and yusuf, to. 2020. production of biogas using locally fabricated bioreactor. pacific journal of science and technology, 21(2): 80-87. agoundedemba, m., kim, ck. and kim, hg. 2023. energy status in africa: challenges, progress and sustainable pathways. energies, 16:7708. https://doi.org/10.3390/ en16237708 aisien, fa. and aisien, et. 2020. biogas from cassava peels waste. multidisciplinary journal for waste resources and residues, 10: 100-108. https://doi.org/10.31025/2611-4135/2020.13910 http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 618-625. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 624 akhator, ep., igbinomwanhia, di. and obanor, a.i. 2016. potentials for commercial production of biogas from domestic food waste generated in benin metropolis. nigeria journal of applied science and environmental management, 20 (2): 369-373. asante, e., arthur, r., agyemang, eo., baidoo, mf. and asiedu, ny. 2024. experimental simulation and kinetic modeling of bioenergy potential of eichornia crassipes biomass from the volta river basin of ghana under mesophilic conditions. scientific african, 23: e02032. chaudhuri, sk. 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(2022) biogas production from banana and plantain peels blended with cow dung in an in vitro biodigester system. lapai journal of applied and natural sciences 4(1): 160-164. wikandari, r., nguyen, h., millati, r., niklasson, c. and taherzadeh, mj. 2015. improvement of biogas production from orange peel waste by leaching of limonene. biomed research international, 494182: doi: 10.1155/2015/494182. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng corresponding author’s email address: skishk2009@gmail.com 87 arid zone journal of engineering, technology & environment original research article characterization and experimental analysis of aa7075 aluminium alloy and rice husk ash reinforced hybrid composite y. a. saraki, f. a. sulayman and i. sulaiman* mechanical engineering department, the federal polytechnic , bida, nigeria. *corresponding author’s email address: skishk2009@gmail.com article information abstract the microstructural behavior along with the mechanical properties of aluminium (aa7075) matrix hybrid composites reinforced with rice husk ash (rha) and graphite were investigated. the rha and graphite mixed in varied weight ratios were utilized to prepare samples of hybrid reinforced aa7075/rha/graphite alloy-based composite using the stir casting route. impact, hardness and tensile tests were conducted to ascertain the mechanical properties of the developed composites, while scanning electron microscopy was used to characterize the composites produced. the results show a general decrease in hardness and tensile strength with increase in the weight ratio of rha and graphite in the composites. the impact strength on the other hand increased from a 2.6 j value to 9.37 j (with the former being the base metal and the latter having 12 % rha and 3 % graphite). energy dispersive spectroscopy (eds) profile displays peaks for silicon (si), carbon (c), iron (fe), aluminium (al), and oxygen (o). the elements' presence verifies that graphite (c) and rha were both utilized in the composite's production. the eds results are consistent with the microscopy images and confirm the reinforcements' existence and dispersion inside the matrix. submitted: 12th july 2024 revised: 16th december 2024 accepted: 16th january 2025 keywords: energy dispersive spectroscopy microstructural behaviour stir casting aluminium matrix hybrid composites rice husk ash mechanical properties © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the search for novel and sustainable solutions is more important than ever in the field of materials science and engineering. scientists and engineers are focusing on developing advanced materials that can provide both high-performance qualities and environmental sustainability in response to the increasing demands on structural materials and the pressing need to lessen the environmental impact of industrial processes (akadiri et al., 2012). because of their remarkable mechanical qualities and adaptability, aluminium alloys have continuously been the most popular materials among a wide range of options. nonetheless, the search for even greater performance improvement and the use of sustainable materials has prompted research into innovative composites (batz et al., 2023). the choice of aa7075 aluminium alloy as a primary component in this hybrid composite is not arbitrary. aa7075 is renowned for its exceptional strength-to-weight ratio, corrosion resistance, and outstanding performance in demanding applications, particularly in the aerospace and automotive industries (khalid et al., 2023; vikas et al., 2021; li et al., 2008). however, the energy-intensive industrial procedures associated with its application frequently result in significant carbon emissions. therefore, there is a strong need to improve its qualities while also lowering its carbon footprint (ali et al., 2020; reinsch and benson, 2022; adediran et al., 2021). the incorporation of rha, a waste product generated during rice processing, not only contributes to the sustainable utilization of agricultural by-products but also offers the potential to improve the overall mechanical and thermal properties of the composite. for the fabrication of metal matrix composites (mmcs), aluminium-based matrices are also recognized to be the least expensive of the common metallic matrix materials (copper, titanium, and magnesium) (sharma et al., 2020). mmcs are essentially metallic alloys reinforced with ceramic materials, primarily silicon carbide (sic), alumina (al2o3), boron carbide (b4c), tungsten carbide (wc), graphite (gr), carbon nanotubes (cnt), and silica (sio2) (selvam et al., 2020; nturanabo et al., 2018). however, compared to other synthetic reinforcing particulates, silicon carbide and alumina are used more frequently. similar to single reinforced aluminium matrix composites (amcs), hybrid reinforced amcs are typically made using either the liquid approach or the solid method (garg et al., 2019). powder metallurgy techniques are used in the solid azojete march 2025 vol. 21(1):87-100 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:skishk2009@gmail.com mailto:skishk2009@gmail.com http://www.azojete.com.ng/ http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 88 approach, whereas stir casting, compo-casting, and squeeze casting are used in the liquid method (ashebir et al., 2022). due to its simplicity, adaptability, and suitability for mass manufacturing, the liquid technique of processing is commonly preferred. one of the liquid techniques that is widely utilized to make amcs is stir casting (upadhyay and saxena, 2021; sahu and sahu, 2017; ramamoorthi et al., 2021). the ceramic particles are slowly added to the molten aluminium after the entire aluminium matrix has been melted. a motorized stirrer is frequently used to create a vortex to speed up integration (muhammad and jalal, 2023). this study is carried out to develop a novel hybrid composite along with investigation of its mechanical and microstructural properties, each aspect is scrutinized with precision. the ultimate goal is to provide an understanding of the hybrid composite's performance characteristics, elucidating the synergistic effects arising from the combination of aa7075 and rha/graphite (reinforcements). in addition, the environmental effects of using rha as a reinforcing agent are examined, taking into account things like lower energy usage, less greenhouse gas emissions, and less waste production. an important step toward the creation of cutting-edge materials that are both environmentally friendly and technologically advanced is the examination of the characterization and experimental analysis of the hybrid composite reinforced with rha/ graphite and aluminium alloy aa7075. 2. materials and methods 2.1 materials as the specimens must be cut to specific standard shapes, marking tools like scriber and steel rule were employed. hacksaw and files were used for machining to bring out the necessary shape required. principally three major machines were used to carry out the tests; they are underlisted. 1. electronic universal testing machine 2. charpy impact testing machine 3. indentec universal hardness testing machine the hybrid mmc consists of matrix and reinforcement material. the aa 7075 is used as matrix material. the rice husk ash (rha) and graphite are used as reinforcement material in this study. 2.1.1 aluminium alloy 7075 aluminium alloy 7075 selected as the base metal for the composite fabricated and analysed in this study. frequently denoted as aa7075, this high-strength aluminium alloy is renowned for having an exceptional strength-to-weight ratio. it is a member of the 7xxx family of aluminium alloys, which are mostly utilized in high-strength applications, especially in the aerospace and other sectors where lightweight materials with remarkable strength qualities are crucial (sathishkumar, 2017; narayana et al., 2021). the sample required for work was procured from obafemi awolowo university ile-ife, nigeria in extruded form. chemical analysis of the samples was carried out at the raw materials research and development council (rmrdc) abuja to ascertain its purity. 2.1.2 rice husk ash rice husk is the first reinforcement selected for the hybrid material fabricated. it is one of the most abundant agricultural byproducts in the world, as rice is a staple food for a large portion of the global population. rice husk is abundant, and it is estimated that for every kilogram of rice produced, about 20% of the weight is rice husk. this makes it a readily available and cost-effective agricultural byproduct. the rice husk used for the study was procured from kpebegi market local mills, located in bida, niger state, nigeria. the rice husk was prepared and carbonised to produce the rice husk ash used. 2.1.3 graphite graphite is a naturally occurring crystalline form of carbon. because of its distinct structure and qualities, graphite is valuable in a variety of industrial applications (narayana et al., 2021). graphite is resistant to most acids and bases, has a high melting point of around 3,550 °c, and is chemically stable. while natural graphite is abundant, synthetic graphite can be produced from carbon-containing precursors like petroleum coke or coal tar pitch (narayana et al., 2021). synthetic graphite was obtained from ahmadu bello university for this study. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 89 2.2 methods 2.2.1 preparation of rice husk ash the rice husk ash (rha) was cleaned with water to remove dust and impurities and then left to dehydrate at room temperature for one day to eliminate moisture (saiful et al., 2022; kaleli et al., 2020). following this, the dehydrated husks were heated at 200°c for one hour to remove any residual moisture (gani et al., 2023; yiga et al., 2023). the dried husks were then subjected to a high-temperature treatment at 600°c for 12 hours in a a carbolite sheffield muffle furnace, aiming to burn off organic matter and activate the silica within. this prolonged heat treatment promotes phase transformations, altering the crystalline structure of the ash to enhance its physical and chemical properties (otaru et al., 2013; shengtai et al., 2022). finally, the carburized sample was analyzed using an edxrf analyzer at the raw materials research and development council (rmrdc), abuja. 2.2.2 fabrication method for composite the aluminium 7075 hybrid composite material was processed through stir casting process. rha reinforcement was added in 3, 6, 9 and 12 wt.% respectively while graphite was fixed at 3 wt.% as shown in table 1. the average particle size of rha was 0.191 microns and graphite was 1.04 microns. at a temperature of around 750 °c aluminium 7075 alloy ingot was melted in a mild steel crucible. succeeding to melting, degassing was carried by adding hexachloroethane tablets. the mixture was stirred by using zirconium coated mild steel stirrer at about 400 rpm for 15 min. simultaneously during the time of stirring graphite and rha were added which were earlier pre-heated at 250 °c. finally, the molten hybrid composite material was poured into preheated metal mould and allowed to solidify. once solidified aluminium 7075 with various weight percentage of reinforcement hybrid composites were ready to prepare test specimens. test specimens were machined in accordance to astm standards. table 1: details of fabricated materials samples composition aluminium matrix (aa7075) (%) graphite (%) rha (%) a 100 0 0 b 94 3 3 c 91 3 6 d 88 3 9 e 85 3 12 2.2.3 impact test charpy impact testing is a widely used method to evaluate the toughness or impact resistance of materials, including aluminium composites. the procedure involves striking a notched specimen with a pendulum and measuring the energy absorbed by the material during fracture (ikumapayi et al., 2021). the prepared samples a, b, c, d and e in three sets were machined from the aluminium composite material fabricated. the specimens had the specific size and shape according to relevant standards (astm e23). a v-notch was machined into the centre of the specimen. the size and depth of the notch are also defined by the testing standards (figure 1). http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 90 figure 1: astm e23 proportions of charpy v-notch specimen (source: badiger et al., 2017) the test was carried out at the department of metallurgical and materials engineering, ahmadu bello university, zaria using cat.nr.412 charpy impact testing machine of 15 j-25j capacity. three tests were conducted for each sample to ensure consistency and reliability of the results. 2.2.4 hardness test the hardness test was conducted using an indentec universal hardness testing machine (model 81875 lkv model b, serial no. 053158) to assess the material's hardness. this method can be applied to various hardness scales, such as rockwell, brinell, and vickers. in this study, the test took place at the department of metallurgical and materials engineering, ahmadu bello university, zaria. the setup of the experiment is shown in plate 1. plate 1: experimental setup for the hardness test using the universal testing machine. the hardness test was conducted according to astm e18 standards. the specimen surface was cleaned, flattened, and aligned perpendicularly to the indenter. a 1/16'' (1.588 mm) hardened steel ball indenter was used for the test. the universal hardness testing machine was stabilized, and a pre-load of 10 kgf (98.1 n) followed by a main load of 100 kgf (980.7 n) was applied. after a 5-second dwell time, the main load was removed while maintaining the pre-load, allowing for depth-sensitive measurement (wang, 2012; zubairu et al., 2020). the rockwell hardness (hrb) value was determined based on the depth of indenter penetration, calculated using the machine's measuring system and displayed on a computer screen. the rockwell hardness (hrb) was determined using equation 1 𝐻𝑅𝐵 = 100 − ℎ 0.002 (1) where, h is the depth of the indentation in mm. the hardness value was recorded in hrb, along with any relevant information such as the applied load and dwell time. 2.2.5 tensile test the electronic universal testing machine, model; wdw-1000kn was used for the tensile study and the test was carried out at department of metallurgical and materials engineering, ahmadu bello university, http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 91 zaria. plate 2 shows the setup of the experiment. the procedure for conducting a tensile test using a universal testing machine (utm) involves a series of steps to determine the mechanical properties of a material. plate 2: tensile universal testing machine setup a representative specimen according to astm e8 for metallic materials selected. the specimen dimensions, particularly gauge length and cross-sectional area was ensured to comply with the specified standard as shown in figure 2. figure 2: astm e8 standard tensile test specimen (source: badiger et al., 2017) the specimen was mounted securely in the grips of the utm and the grips aligned with the longitudinal axis of the specimen. the utm was calibrated according to the manufacturer's guidelines and relevant standards while the crosshead speed was set as per the testing standard. plate 3 shows the failed specimens tested. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 92 a b plate 3: a. tensile test samples b. collated failed samples grouped according to rha percentages 3 results and discussion 3.1 chemical composition of aa7075 and rha the energy-dispersive x-ray fluorescence (edxrf) is a non-destructive, rapid, multielement, highly accurate, and environment friendly analysis compared with other elemental detection methods. the edxrf results for the aa 7075 aluminium sample is given in table 2. table 2: chemical composition of aa 7075 aluminium sample element concentration (%) fe 0.27 si 1.02 al 90.4 mg 7.47 p 0.01 s 0.04 ti 0.006 mn 0.30 cu 4.30 zn 7.24 cr 0.004 ni 0.034 others balance the edxrf results for the carburized rha are presented in table 3. the elemental analysis was accessed by x-ray fluorescence to determine the inorganic chemical composition of the samples (aa7075 and rha samples), as shown in tables 2 and 3. from these results, table 2 shows that the zn % is 7.24 which is well within the range for aa7075 (ouler et al., 2019; khalil et al., 2019). silica content in the rha sample along with ferric oxide, aluminium oxide and other compounds were detected. in table 3, the silica content was detected to be 92.92 % which is considerable and consistent with literature (joharudin et al., 2020; yekinni et al., 2020). this outcome can be attributed to the calcination temperature of the rice husk. burning the rice husk at a higher temperature gave room for the loss of impurities in the sample, which maximized the silica content in the sample. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 93 table 3: chemical composition of rha element concentration (%) sio2 92.92 fe2o3 0.26 al2o3 1.18 mgo 0.30 so3 0.17 cao 0.72 k2o 1.52 pbo 0.01 others balance 3.2 impact test impact energy is a measure of energy or work done to fracture a specimen. impact energy increased as percent weight fraction of reinforcements increase except in sample d (9:3 of rha to graphite) which reduced as seen in figure 3. maximum impact strength of 9.37 j was obtained at 12 wt.% rha and 3 wt.% graphite corresponding to 360 % increase when compared with pure aluminium with impact strength of 2.6 j. this result mimics what was reported by yekinni et al. (2019). the increase in impact strength was attributed more to the influence of hard rha. figure 3: variation of the impact tests 3.3 hardness test in figure 4 the base metal, sample a has the highest rockwell hrb hardness value at 27.43, indicating that it is the hardest among the samples. sample b has an intermediate hardness value at 10.23. samples d and e have relatively lower hardness values at 8.07 and 8.97, respectively. sample c falls between the higher and lower values when figure 12 is studied closely. the significant difference in hardness values point to the variations in the composition and/or manufacturing process of the aluminium composite samples. 2.6 2.52 2.76 1.57 9.37 0 1 2 3 4 5 6 7 8 9 10 im p ac t en er gy ( j) samples impact energy (j) http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 94 figure 4: variation of the hardness tests even with the variations in the results of the hardness (figure 12) there is clearly a reduction in the hardness of the composites compared with the base metal (a) which is 27.43 (hrb). sample c with ratio of rha to graphite as 6:3 respectively had 26.03 (hrb). the reduction in hardness is as a result of the presence of silica polytypes partly appearing as cristobalite phase (softer material) resulted in the reduction in hardness value. rice husk ash containing mainly sio2 which is a softer ceramic compared to alumina, will result in composites having lower hardness value. the reduction in hardness of aluminium composites has been reported by yekinni et al. (2019), adediran et al. (2021), alaneme and sanusi (2015) and saini et al. (2020), even though contrary behaviour is also available. alaneme and sanusi (2015) further explained the reduction in hardness with increase in rha and graphite content is as a result of the lower hardness possessed by both reinforcing materials 3.4 tensile test the tensile strength and yield strength values (figure 5) are also observed to follow to some degree the same trend as the hardness results (wholly). it is observed that the yield strength, tensile strength and break strength decreases with increase in the rha content (from a e sample series). this is consistent with reported literature (yekinni et al., 2019; adediran et al., 2021; alaneme and sanusi, 2015; saini et al., 2020). also, there is a slight decrease in tensile values of c sample (9:3 of rha to graphite) in comparison to the remaining samples that had averagely similar values. however, there is a general decrease in tensile test values compared with the base metal. the presence of a greater amount of graphite and rha reduces potential direct strengthening effect from load transfer from the matrix to the reinforcing particles since al matrix and the dominant rha particles have the same elastic modulus of 70 gpa while graphite has a lower elastic modulus value of approximately 27 gpa (alaneme and sanusi, 2015). figure 5: variation of the tensile tests 27.43 10.23 26.03 8.07 8.97 0 5 10 15 20 25 30 a b c d e h ar d n e ss v al u e ( h r b ) samples hardness value (hrb) 33.61 29.65 21.49 34.89 16.5 70.01 57.2 39.33 55.46 57.24 5.02 2.03 1.36 0.95 2.99 0 10 20 30 40 50 60 70 80 a b c d e yield strength (mpa) tensile strength (mpa) break strength (mpa) http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 95 3.5 sem results representative sem micrographs and eds analysis of composites produced are presented in figure 6. it is observed from the figure 6 (b, c, d and e) that the reinforcing articles are visible and fairly well distributed in the alloy matrix. this suggests that the stir casting method used to produce the composite is dependable. the hybrid composite's elemental mappings' eds profile displays peaks for silicon (si), carbon (c), iron (fe), aluminium (al), and oxygen (o). the elements' presence verifies that graphite (c), aluminium, alumina, silica (sio2), ferric oxide (fe2o3), and both were utilized in the composite's production. alaneme and sanusi (2015) have reported similar elemental compositions and microstructural characteristics. an eds (energy dispersive spectroscopy) study was performed to confirm the reinforcements' existence and dispersion inside the matrix. the eds results (figure 6 (b, c, d and e)) are consistent with the microscopy images. the presence of 2.02% titanium (ti) is only noticed in the eds results of sample e as seen in figure 6(e). in the aa7075 composite it can significantly influence its impact strength through various mechanisms. ogunmefun et al. (2023) mentioned that titanium promotes the formation of fine and uniform grain structures within the composite matrix, enhancing its mechanical properties, including impact resistance. moreover, during processing, titanium can precipitate or form intermetallic phases, which function as powerful strengthening agents to prevent deformation and fracture under impact loading (ogunmefun et al., 2023). by experiencing plastic deformation or microstructural changes upon impact, phases containing titanium also contribute to toughening mechanisms by efficiently absorbing energy and limiting the spread of cracks (jiang et al., 2020). http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 96 figure 6: eds profile and sem photomicrograph of the base sample (a) and hybrid composites b, c, d and e http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 97 the method by which titanium is processed to ensure appropriate dispersion and distribution of titanium particles throughout the matrix has an impact on the mechanical properties of the composite. furthermore, titanium's interaction with copper, magnesium, and zinc, among other alloying elements, fortifies the composite's resistance to impact damage. (jiang et al., 2020). overall, the incorporation of titanium in the aa7075 composite holds promise for improving its impact strength, making it suitable for demanding applications requiring highperformance materials. the results obtained from the impact strength test shows great improvement in the impact strength of e (graphite 3: rha 12). apart from the presence of silica polytypes partially appearing as cristobalite phase (softer material), samples b, d, and e exhibit the greatest drop in hardness, correspondingly. additional explanations are given from the sem study. changes in the microstructure of the composite, such as grain size, distribution of phases, and presence of defects, can influence hardness. variations in the samples' microstructure caused by processing could be a factor in their varying hardness. inclusions, contaminants, or processing-related flaws can serve as stress concentrators in the composite, lowering its hardness. reduced hardness may also be caused by the occurrence of porosity or the production of unwanted phases. sample b and e show some defects with some voids present in both samples which may have contributed to the reduced hardness of the samples. sample d on the other hand reveals the availability of graphite in clusters that lead to hardness reduction. 4. conclusion in this study, the properties of a developed hybrid composite have been investigated. the findings show that the mechanical characteristics of the hybrid composite were considerably impacted by the addition of rha/graphite to the aluminium alloy aa7075. the findings also show that the material qualities may be tailored to certain applications by adjusting the rha content, which balances the properties of toughness, hardness, and tensile strength. the tests show that as rha increases the hardness and tensile characteristics of the composite decreases. sample e was found to be with highest impact energy of 9.37 j, this suggests that it could be particularly promising for applications requiring high toughness. notably, the microstructural study verified that the rha reinforcements were appropriately distributed throughout the aa7075 matrix, guaranteeing even dispersion and strong bonding. this distribution highlighted the potential of this hybrid composite for applications needing customized toughness, hardness, and tensile strength and contributed to the observed improvements in mechanical properties. the study's overall findings show that adding rha to the aluminium alloy aa7075 can greatly improve its qualities, opening the door for the creation of high-performing, environmentally friendly composite materials. acknowledgements the authors especially are extremely grateful to tertiary education trust fund (tetfund), nigeria. this work has been possible with the financial support of tertiary education trust fund (tetfund) under the institution-based research (ibr) intervention (tetf/dr&d/poly/bida/ibr/2022/vol.ii/9). references adediran, aa., alaneme, kk., oladele, io. & akinlabi, et. 2021. microstructural characteristics and mechanical behaviour of aluminium matrix composites reinforced with si-based refractory compounds derived from rice husk. cogent engineering, 8(1), 1-17. akadiri, po., chinyio, ea. & olomolaiye, po. 2012. design of a sustainable building: a conceptual framework for implementing sustainability in the building sector. buildings, 2(2), 126-152. alaneme, kk. & sanusi, ko. 2015. microstructural characteristics, mechanical and wear behaviour of aluminium matrix hybrid composites reinforced with alumina, rice husk ash and graphite. engineering science and technology, an international journal, 18(2015), 416-422. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; 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(2020). fabrication and characterization of al7075 / rha /mica composite by squeeze casting. materials today: proceedings, 1-4. li, j., peng, z., li, c., peng, qz. & chen, w. 2008. mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments. transactions of nonferrous metals society of china, 18(4): 755-762. muhammad, f. & jalal, s. 2023. optimization of stirrer parameters by taguchi method for a better ceramic particle stirring performance in the production of aluminum alloy matrix composite. cogent engineering, 10(1): 1-10. narayana, ksl., benal, mm. & shivanand, hk. 2021. effect of graphite on aluminium matrix composites fabricated by stir casting route – a review. materials today, 45(1): 327-331. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 99 nturanabo, f., masu, l. & kirabira, jp. 2018. novel applications of aluminium metal matrix composites. in k. o. cooke, aluminium alloys and composites (pp. 1-24). uk: intechopen. ogunmefun, oa., bayode, bl., jamiru, t. & olubambi, pa. 2023. a critical review of dispersion strengthened titanium alloy fabricated through spark plasma sintering techniques. journal of alloys and compounds, 960(23): 1-26. otaru, aj., ameh, cu., abdulkareem, as., odigure, jo. & okafor, jo. 2013. development and characterization of adsorbent from rice husk ash to bleach vegetable oils. iosr journal of applied chemistry (iosr-jac), 4(2): 42-49. ouler, ka., kisasoz, a., ozer, g. & karaaslan, a. 2019. cooling slope casting of aa7075 alloy combined with reheating and thixoforging. science direct, 29(2019): 2237−2244. ramamoorthi, r., hillary, jjm., sundaramoorthy, r., joseph, jd., kalidas, k. & manickaraj, k. 2021. influence of stir casting route process parameters in fabrication 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i. & rai, rs. 2020. matrix and reinforcement materials for metal matrix composites. encyclopedia of materials: composites: amsterdam. shengtai, y., dezheng, y., fang, h., junmeng, c., thomas, s. & frank, b. 2022. characteristics of smoldering on moist rice husk for silica production. sustainability, 14(317): 1-13. upadhyay, g. & saxena, kk. 2021. role of stir casting in development of aluminium metal matrix composite (amc): an overview. iop conf. series: materials science and engineering, 1116 (2021): 1-24. vikas, p., sudhakar, i., dilkush, i., rao, gm. & srinivas, b. 2021. aging behaviour of hot deformed aa7075 aluminium alloy. materials today, 41(5): 1013-1017. wang, z. 2012. inflfluences of sample preparation on the indentation size effect and nanoindentation pop-in on nickel. knoxville: university of tennessee. yekinni, aa., durowoju, mo., agunsoye, jo. & mudashiru, lo. 2020. effect of particle size of rice husk ash on aluminium/graphene composites. nanotechnology applications in africa: opportunities and constraints, 805(2020): 1-20. yekinni, aa., durowoju, mo., agunsoye, jo., mudashiru, lo., animashaun, la. & sogunro, od. 2019. automotive application of hybrid composites of aluminium alloy matrix: a review of rice husk ash based reinforcements. international journal of composite materials, 9(2): 44-52. yiga, va., nuwamanya, a., birungi, a., lubwama, m. & lubwama, hn. 2023. development of carbonized rice husks briquettes: synergy between emissions, combustion, kinetics and thermodynamic characteristics. energy reports , 9(2023): 5977–5991. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):87-100. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: skishk2009@gmail.com 100 zubairu, pt., hassan, ab., muriana, ra. & musa, na. 2020. effect of shea nutshell ash on the mechanical properties of cast al6061. arid zone journal of engineering, technology & environment, 17(1):1-8. http://www.azojete.com.ng/ mailto:skishk2009@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):187-192 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 187 crop water use of cowpea (vigna unguiculata) under deficit irrigation in a controlled environment e. a. otuaro1* and j. k. adewumi2 1department of civil engineering, faculty of engineering, maritime university, okerenkoko, nigeria 2department of agricultural and bioresources engineering, college of engineering, federal university of agriculture, abeokuta, nigeria *corresponding author's email address: e.otuaro@yahoo.com article information submitted 3 january, 2024 revised 12 february, 2024 accepted 15 february, 2024 keywords: cowpea deficit irrigation evapotranspiration water use efficiency yield. abstract cowpea vigna unguiculata was planted in a pot at a density of one per pot and placed in a greenhouse at the department of biological sciences, university of agriculture, abeokuta. it was subjected to four water treatments. the treatments were as follows: no deficit irrigation, 25% deficit irrigation, 50% deficit irrigation and 75% deficit irrigation. the pots were weighed each day with a precision weighing scale of accuracy of 1g to determine the amount of water to be added to each treatment. before the experiment, the physical characteristics of the soil, such as bulk density, were determined. water was applied to the treatment weekly. the soil in the pots was at field capacity at the start of the experiment, and the amount of water to be applied to each treatment was based on the difference in weight at the end of the week and evaporated based on the above-mentioned water allocation. some of the chemical characteristics of the irrigated water were also determined. the findings indicated that cowpea (vigna unguiculata) plants were very sensitive to lack of soil water during the total growing season and the yield formation period. a minimal water use efficiency was observed with a 50% deficit irrigation method showing a more sensitive yield response factor ky (0.269) than other treatments. this implies that 50% deficit irrigation treatment produces a better yield with minimal irrigation water. 1.0 introduction accurate determination of plant water use is a prerequisite for a good irrigation water management strategy. restricted water resources limit irrigation applications, and the available water supply is inadequate to produce the maximum yield on irrigable lands. the water available for irrigation is already regulated and requires deficit irrigation. due to the problems associated with the annual supply of irrigation water, deficit irrigation management for different crops is necessary (martin et al., 1989). deficit irrigation maximises water use efficiency for higher yields per unit of irrigation water applied. with a catalogue of irrigation research under study in nigeria, efforts are being made to reduce agricultural water use on crops, and this study will continue even in the future. even then, irrigated agriculture will occur under water scarcity (oyelaja, 2008). insufficient water supply for irrigation will be the norm rather than the exception, and irrigation management will shift from emphasising production per unit area to maximizing production per unit of water consumed. to cope with scarce supplies, deficit irrigation, defined as applying water below complete crop-water requirements (evaporation), is vital to reducing irrigation water use. under conditions of scarce water supply, deficit irrigation can provide greater economic http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):187-192. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 188 returns than maximizing yields per unit of water. kirda (2000) stated that properly practiced deficit irrigation may increase crop quality. cowpea, vigna unguiculata l. walp is a grain legume grown mainly in the savannah regions of the tropics and subtropics in africa, asia and south america. in nigeria, full-scale cowpea production is primarily restricted to the northern part and the middle belt. in contrast, scanty production is limited to the southern part because of its climatic conditions. the value of cowpea lies in its high protein content and ability to tolerate drought; for that reason, cowpea can be cultivated under both irrigated and non-irrigated conditions. as a legume, cowpea also fixes atmospheric nitrogen, allowing it to grow on and improve poor soils. according to doorenbos and kassam (1979), about 7.56 million tonnes of cowpeas are produced worldwide annually on about 12.76 million hectares. this study is carried out to prove the response of cowpeas at different growth stages to water supply at different irrigation treatments. cowpea under deficit irrigation has lower evapotranspiration rates and yields. for optimum yield, it is necessary to prevent the crop from experiencing a water deficit, especially during the cowpea formation development stage. the crop appears less sensitive to water deficit during the vegetative and ripening periods (source). excessive irrigation during the vegetative period can delay and reduce cowpea development (doorenbos and kassam, 1979). potential evapotranspiration is a measure of the ability of the atmosphere to remove water from the crop through evaporation and transpiration, assuming no control over the water supply. actual evapotranspiration is the quantity of water removed from a surface due to evaporation and transpiration (jensen 1974). scientists consider these two types of evapotranspiration for the practical purpose of water resources management (wrm). around the world, humans are involved in the production of a variety of plant crops. many of these crops grow in environments that are naturally short of water. as a result, irrigation is used to supplement the crop's water needs. managers of these crops can determine how much supplemental water is needed to achieve maximum productivity by estimating potential and actual evapotranspiration. estimates of these values are then used in the following equation; crop water need = etp – eta (1) eta is actual crop evapotranspiration (mm/day) the following factors are critical in estimating etp etp (refer herein as potential evapotranspiration) requires energy for evaporation. the major source of this energy is the sun. the amount of energy received from the sun accounts for 80% of the variation in etp kirda 2000. wind is the second most crucial factor influencing etp. wind enables water molecules to be removed from the ground surface by a process known as eddy diffusion. the evapotranspiration rate is associated with the vapour gradient between the ground surface and the layer of the atmosphere receiving the evaporated water. this study aimed to determine cowpea's water use characteristics under deficit irrigation at different growing stages and daily evapotranspiration, yield, yield response factor, and irrigation water use efficiency. 2.0 materials and methods a pot experiment on cowpea was conducted between 1st august and 30th november 2008 in the department of biological science research greenhouse at the university of agriculture, abeokuta, ogun state, nigeria campus. the pots were arranged in a completely randomized experimental design with four irrigation treatments replicated three times. irrigation was file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng otuaro and adewumi: crop water use of cowpea (vigna unguiculata) under deficit irrigation in a controlled environment. azojete, 20(1):187-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 189 carried out manually. cowpea seeds were planted at the density of one seed per pot, and an experiment was conducted on the planting date with the soil water content of all pots at field capacity (measured by pot's weight). the treatment is presented in table 1. each treatment was replicated three times for soil water depletion (the difference in weight between the soil at field capacity and the soil before irrigation). in treatment i (pots 1, 5 and 9), irrigation water was supplied at 100% field capacity; treatment ii (pots 2, 6 and 10), irrigation water was provided at 75% field capacity; treatment iii (pots 3, 7 and 11), irrigation water was supplied at 50% field capacity; and treatment iv (pots 4, 8 and 12), irrigation water was provided at 25% field capacity respectively all at various stages of cowpea growth (vegetative, yield formation and ripening). irrigation water was applied once a week. the pots were weighed daily. the water quantities were regulated by weight. in all treatments, the soil water content was at the soil field capacity in the establishment period. each pot was 24cm in diameter and 22.5 cm deep and contained similar growth media (soil, sand, and manure in equal amounts). table 1: treatments s/n description deficit irrigation code pots no 1 maintained field capacity no deficit irrigation treatment 1 1, 5 & 9 2 maintained at 0.75 of field capacity 25% deficit irrigation treatment 2 2, 6 & 10 3 maintained at 0.50 of field capacity 50% deficit irrigation treatment 3 3, 7 & 11 4 maintained at 0.25 of field capacity 75% deficit irrigation treatment 4 4, 8 & 12 the physical characteristics of the soil (such as bulk density g/cm3) were measured, and the chemical characteristics of irrigation water were also determined. the chemical characteristics of the irrigated water, including the anions, cations, ph, and electrical conductivity, were analyzed and are given in table 2. during the experiment, temperature, relative humidity, and light intensity of the environment were measured daily, and the average values for ten (10) days were calculated as shown in table 3. in the treatments, daily evapotranspiration was estimated as: 𝐸𝑇(0)1 = 𝑊𝑖−1−𝑊𝑖 𝜌𝑤∗𝐴 𝑖 = 1, 2, 3, (2) where 𝐸𝑇(0)1 is the evapotranspiration (mm) 𝑊𝑖−1 and 𝑊𝑖 are the weights (kg) of the pot at day i-1 and i, respectively, 𝜌𝑤 is the gravimetric water content (g/cm3), and a is the surface area (m2) of the pot. water use efficiency (wue) was estimated as 𝑊𝑈𝐸 = 𝑌 𝐸𝑇 (3) where wue is the water use efficiency (kg mm -1 ha-1), y is the cowpea bulb yield (kg ha-1), and et is the seasonal evapotranspiration (mm) (hilel and guron, 1975). table 2: chemical characteristics of irrigation water cations, mg/1 anions, mg/1 ph conductivity na+ k co3 hco3 cl so4 ca++ mg++ sar 7.2 0.13 3.95 1.5 4.39 2.05 44.1 0.69 2.62 1.81 0.317 source: oyelaja, 2008 observations determined the dates of the beginning and end of the plant growth periods. the relationship between cowpea yield and evapotranspiration (yield response factor, ky) was determined according to the steward model (doorenbos and kassam, 1979) with the following equation: 𝐾𝑦 = 1−𝑌𝑎/𝑌𝑚 1−𝐸𝑡𝑎/𝐸𝑇𝑚 (4) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):187-192. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 190 where ya is the actual crop yield (kg ha-1), ym is the maximum expected crop yield without water stress (kg ha-1), eta is actual crop evapotranspiration (mm/day), and etm is the maximum crop evapotranspiration without water stress (mm/day). data were analyzed using a microsoft excel package to calculate the actual evapotranspiration rates of the cowpea plant per day. table 3: average rainfall (outside greenhouse), temperature, relative humidity and sunshine in the greenhouse first trial rainfall, mm max. temp, oc min. temp, oc rel. humidity, % sunshine, hr august, 2008 1st – 10th 4.61 27.9 22.5 78.9 0.22 11th – 20th 3.07 27.3 20.3 61 0.17 21st – 31st 2.68 29.3 20.2 60 0.23 september, 2008 1st – 10th 4.71 27.4 22.6 77.6 1.54 11th – 20th 2.68 29.7 22.8 77.6 2.13 21st – 30th 6.23 30 20.3 84.7 1.37 october, 2008 1st – 10th 4.61 31 21.2 85.1 1.5 second trial august, 2008 1st – 10th 5.4 30.9 22.1 69.9 1.41 11th – 20th 4.38 32.3 23.4 64.5 1.16 21st – 31st 3.7 33.3 23.9 63.3 1.26 september, 2008 1st – 10th 4.7 33.1 23.5 60.7 1.18 11th – 20th 2.68 33.6 24.2 50.1 1.02 21st – 30th 6.22 35.5 28.1 48.9 0.83 october, 2008 1st – 10th 4.62 34 27.2 49 1.23 3.0 results and discussion the amounts of water applied per treatment are shown in table 4. treatment 1 received the highest amount of water, followed by treatment 2. the 75% deficit irrigation treatment gets the lowest water in the two trials—the number of leaves per treatment six weeks after planting is shown in table 5. table 4: amount of water applied per treatment s/n treatment treat code amount of water applied (mm) first trial second trial 1 no deficit irrigation treatment i 75.32 ± 0.35 68.50 ± 0.31 2 25% deficit irrigation treatment ii 71.75 ± 0.35 65.50 ± 0.31 3 50% deficit irrigation treatment iii 69.69 ± 0.35 62.33 ± 0.31 4 75% deficit irrigation treatment iv 65.80 ± 0.35 59.70 ± 0.31 table 5: number of leaves per treatment at establishment and vegetative stage s/n treatment treat code number of leaves first trial second trial 1 no deficit irrigation treatment i 13 15 15 11 11 13 2 25% deficit irrigation treatment ii 11 13 11 11 9 12 3 50% deficit irrigation treatment iii 9 9 10 11 9 9 4 75% deficit irrigation treatment iv 9 9 9 9 9 9 it seemed, therefore, that the greater the amount of water received, the greater the number of leaves produced. hence, it can be concluded that cowpeas respond favourably to the amount of water received for leaves produced. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng otuaro and adewumi: crop water use of cowpea (vigna unguiculata) under deficit irrigation in a controlled environment. azojete, 20(1):187-192. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 191 the average actual or measured water use by the plant is presented in table 6 for the trial. the relationship between water consumed by the plant and the function of days after planting for a vegetative period is expressed in figures 1a and 1b for the 1st and 2nd trials, respectively. the relationship is a polynomial function of the second degree. the r2 values are very low, indicating a poor relationship because they cover mainly the vegetative aspect of the phonological stage of development. this trend is observed in all the treatments. the r2 values vary between 0.0067 to 0.2032 for the first trial and 0.0055 to 0.2097 for the second trial. the values for all the phonological stages were considered in this case. the average cumulative actual evapotranspiration values and relative evapotranspiration for all the treatments are presented in table 8. the average cumulative values on the function of the days after planting are straight lines. the values vary from 23.77 mm to 33.39 mm for the combined trial. the magnitude of applied irrigation depth, as seen in table 4, varies between 59mm and 75mm in the combined trial. the most extensive irrigation depth (75mm) was applied in the non-deficit treatment i (i1, i5, i9). the measured daily evapotranspiration values in the treatments are shown in fig 1a and 1b, and calculated values for the individual growth periods and the total growing season are given in table 6. the seasonal evapotranspiration was the highest (100.78mm) in the non-deficit treatment (i1, i5, i9) and the lowest (62.38) in the 75% in the 75% deficit treatment (i4, i8, i12). these values varied between 8.21 and 57.49mm in individual periods according to treatments and growth periods. evapotranspiration values for the individual growth periods, or the total growing season in nondeficit treatment i (i1, i5, i9), were taken as the maximum evapotranspiration (etm) to determine the yield response factors and the actual evapotranspiration (eta) values were taken into consideration for the other treatments. table 6: evapotranspiration values, mm growth period treatment i (no deficit irrigation) treatment ii (25% deficit) treatment iii (50% deficit) treatment iv (75% deficit) i1 i5 i9 av. i2 i6 i10 av. i3 i7 i11 av. i4 i8 i12 av. establishment/vegetative 33.39 27.93 24.11 28.48 30.69 27.53 24.42 27.55 27.08 24.46 28.51 26.68 23.77 25.24 24.59 24.53 yield formation 57.49 53.11 54.65 55.08 50.12 49.56 48.01 49.23 39.42 40.96 38.40 39.59 30.15 29.45 27.56 29.05 ripening stage 18.24 16.42 17.01 17.22 16.11 14.11 12.51 14.24 12.10 10.21 10.52 10.94 9.15 9.01 8.21 8.79 total for the growing season 109.12 97.46 95.77 96.92 91.20 84.94 78.60 75.63 77.43 63.07 63.70 60.36 average total for the growing season 100.78 91.02 77.22 62.38 table 7: average of actual and minimum evapotranspiration (eta, etm), yield (ya, ym) and yield response factor ky treatment deficit irrigation growth period ym (t/ha) etm (mm) ya (t/ha) eta (mm) 1 – ya/ym 1 – eta/etm ky wue i1, i5, i9 0.64 100.78 0.64 100.78 i2, i6, i10 25% 0.54 91.02 0.156 0.097 1.61 5.93 i3, i7, i11 50% 0.60 77.22 0.063 0.234 0.269 7.77 i4, i8, i12 75% 0.39 62.38 0.391 0.381 1.03 6.25 total table 8: average cumulative measured evapotranspiration for the combined trial no deficit 25% deficit 50% deficit 75% deficit cum 1 33.39 cum 2 30.69 cum 3 27.08 cum 4 23.77 cum 5 27.93 cum 6 27.57 cum 7 24.46 cum 8 25.24 cum 9 24.11 cum 10 24.42 cum 11 28.51 cum 12 24.89 average 28.48 27.56 26.68 24.63 std 4.66 3.13 2.06 0.77 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):187-192. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: e.otuaro@yahoo.com 192 relative evapotranspiration for the 1st trial etmax no deficit 28.48 relet 25% deficit 27.56 0.03 50% deficit 26.68 0.06 75% deficit 24.63 0.14 as shown in table 7, the highest cowpea yield (0.64 t/ha) of about (6 g/plant) which translates to about 6 g per pot, was obtained in non-deficit treatment in which complete crop water requirements were met during the total growing period, and lowest yield was obtained in 75% deficit treatments. soil water deficits during individual growth periods or the total growing season affected the cowpea yields significantly. the 75% deficit treatments or lack of soil water during the yield formation period was caused by a significant decrease in cowpea yield. as a result, irrigation is required to obtain yields, and the highest cowpea yield will be achieved if crop water is entirely provided during the growing season. it was observed that the crop response factor ky (0.269) of 50% deficit irrigation was the most sensitive to water requirements. there was no significant difference between the yields of nondeficit and 50% deficit irrigation (i.e. complete water application and 50% deficit irrigation). 4.0 conclusion according to these reports, we conclude that cowpeas under deficit irrigation of 50% have lower evapotranspiration rates and comparable yields to complete irrigation treatment. it also shows that irrigation is needed during the total growing season to obtain the maximum yield. we also recommend that to maximize the use of irrigation water, half of the total water requirement of cowpeas is here recommended. references doorenbos, j. and kassam, ah. 1979. yield response to water. fao, irrigation and drainage paper 33, rome, pp. 144. hilel, d. and guron, y. 1975. relation between evapotranspiration rate and maize yield. water research, 9: 743 – 748. kirda, c. 2000. deficit irrigation scheduling based on plant growth stages showing water stress tolerance. deficit irrigation practices, fao, water report, rome, pp. 22. martin, d., brocklin, j. and g. van wilmes, g. 1989. operating rules for deficit irrigation management. american society of agricultural engineers publication, 22: 1207 – 1215. oyelaja, tj. 2008. water use characteristics of cowpea (vigna unguiculata) under deficit irrigation in a controlled environment. b.eng project, department of agricultural engineering, university of agriculture, abeokuta. jensen, me. 1974. consumptive use of irrigation water and irrigation requirement. report of technical committee on irrigation and drainage division, pp 88. fao 1994. production yearbook, food and agriculture organization of the united nations fao, rome: pp. 215 – 221, 233 – 238. fao 1976. a framework for land evaluation. wageningen: international institute for land reclamation and irrigation. doorenbos, j. and kassam, ah. 1979. yield response to water. fao irrigation and drainage paper 33, fao, rome., pp. 33. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng corresponding author’s email address: atadiousd@pti.edu.ng 950 arid zone journal of engineering, technology & environment development design of an automated poultry scalding and de-feathering machine a. john1, d. atadious2*, e. e. abubakar3 1welding engineering and offshore technology department, petroleum training institute, effurun, delta state, nigeria. 2mechanical engineering department, petroleum training institute, effurun, delta state, nigeria. 3electrical and electronics engineering department, petroleum training institute, effurun, delta state, nigeria. *corresponding author’s e-mail: atadious_d@pti.edu.ng article information abstract the automated poultry bird de-feathering machine is a machine which aids feather removal from birds, it helps to reduce manual labour and time spent in defeathering process. to ensure good functionality, the boiler, scalding as well as the de-feathering compartments, were fabricated using stainless steel materials. the machine has a reservoir capacity to accommodate about 210 liters of water, a boiler compartment with 85-liter capacity. the machine uses a belt and pulley mechanism on the de-feathering compartment and a chain and sprocket mechanism on the scalding compartment. an electric motor with 3.0hp rating with 500mm and 80mm pulley on driver and driven pulley respectively were used on the de-feathering compartment, on the scalding compartment, a motor of 0.5hp with 102 teeth and 17 teeth on driver and driven sprocket were used respectively. the machine has a water pump of 1 hp which helps circulate water to the boiler, reservoir and de-feathering sprinkler hose with the help of pipes. poultry chickens (old layer – isa brown specie) were used to test the performance of the machine. the automated de-feathering machine has a maximum throughput capacity of 37g/s, an efficiency of 95.30%, and a de-feathering time of 32 seconds per cycle for a 10 birds capacity drum, and the processing of approximately 110 birds per hour can be achieved. received: 8th september 2025 revised: 11th november 2025 accepted: 12th november 2025 keywords: poultry de-feathering scalding boiler reservoir © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction one of the steps taken in bird processing before it reaches the end product for cooking is de-feathering of the bird (adetola, et al., 2023; dickens and shackelford 2004). de-feathering involves removing feathers from the slaughtered birds, traditionally, in this part of the world, it is done manually by the use of hand after it has been soaked in hot water for a few minutes (adetola, et al., 2023). this process results in low output, time consuming, tedious, and could lead to injury (ogundipe and sanni 2002). there is therefore a need to design and develop machines using locally sourced materials to minimize cost, avoid supply disruptions, create jobs, and simplify maintenance (ocheri, et al., 2018; adetola, et al., 2023). it takes an average of 5 minutes for a person to de-feather a bird while the machine processing of a bird that is lowered into hot water at 80oc – 85oc takes 40 – 50 seconds (david, 1999). the objective of a centralized poultry processing paltry of any scale of operation is to produce hygienic, wholesome, and attractive birds of consistent quality and high standard (buckland, 2005). de-feathering machine saves time, easy to operate and better picking is achieved (ogundipe and sanni 2002). mechanical defeathering employs various de-feather mechanism such as rubber finger, rotating plate, drum and angle bar mechanism (adetola, et al., 2023; dickens and shackelford 2004). this is done after slaughtering the birds which is accompanied by bleeding period (adetola, et al., 2023). the carcass is removed and lowered into a tank of heated water to a certain temperature and plucked (ogundipe and sanni 2002). azojete december 2025. vol.21(4):950-961 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/006 www.azojete.com.ng mailto:atadiousd@pti.edu.ng mailto:atadious_d@pti.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 951 the use of de-feathering machine in processing poultry has contributed tremendously to the successful processing of dressed and hygienic chicken for consumption (jekayinfa, 2007; adetola, et al., 2023). additionally, de-feathering machine overcomes the tediousness, time consumption, messy handling, and discouragement in the process of hand de-feathering (adetola, et al., 2023). also, there is mass production of processed chicken in de-feathering machine than hand de-feathering (adetola, et al., 2023; awotunde, et al., 2018). it is noteworthy that there are three different ways in which feathers can be removed completely from the chicken; the first is for broilers only and is by hand, the feathers are simply pulled from the carcass and placed in a feather bin (david, 1999). this method takes a lot of time; it is tedious and results in low output, (david, 1999; mady and obaia 2018). the second method is by holding the carcass against rubber fingers protruding from a continuously rotating horizontal drum, the drum rotates away from the operator and the feathers follow until they are thrown towards the back of the machine (david, 1999). the bird is held with a leg in each hand and laid firmly on its left breast on the rotating rubber fingers; it is agitated backwards and forwards to pluck the left breast and thigh; the bird is turned over to pluck the right breast and thigh (david, 1999). both legs are taken in the left hand and the tail feathers gripped in the right hand before pulling them out with a twisting movement (david, 1999). the third method uses a bowl de-feather; scaled birds, to a weight specified by the manufacturer, are placed in the bowl de-feather chute which passes into the body of the machine, the machine is stopped and a door to the bottom of the machine is opened and the plucked carcasses emerge ready for further processing (david, 1999; ogundipe and sanni,2002; mady and obaia 2018). time taken in the de-feathering bowl will depend on the nature of the bird, its age, and processing conditions etc. (david, 1999). in nigeria, fast food business is fast growing so also is the population of people eating chicken during festivals and other ceremonies (ogundipe and sanni, 2002). therefore, there arises the need to design and develop a de-feathering machine that will be low cost, rugged, simple, with locally sourced materials (adetola, et al., 2023). 2. materials and methods the de-feathering machine operates on the principle of a belt-driven pulley and abrasion where rubbers fingers in rotary motion hit the birds and pluck their feathers (tanimola, et al., 2014). the scalding compartment (a hot water bath where stunned birds are immersed to loosen their feathers), operates on the principle of chain and sprocket drive which tilts at an angle of 110 degrees and returns to position. the test operation was carried out with two, five and ten birds respectively, and their weights recorded. the boiler heats up the water to a temperature of 75oc, which is emptied into the scalding bucket to soak the birds for 45 seconds before it was emptied into the de-feathering compartment. the scalding bucket waits for 4 seconds there returning to its original position. the de-feathering machine rotated for 30 seconds and then stops. all operations were automated according to the control sequence. 2.1 mechanical design theory 1. pulley design the relationship is given by equation (1): 𝑆𝑝𝑒𝑒𝑑 𝑅𝑎𝑡𝑖𝑜 = 𝑁1 𝑁2 = 𝑑2 𝑑1 1 where; d1 = small pulley diameter, d2 = large pulley diameter, n1 = small pulley speed and n2 = large pulley speed, khurmi and gupta (2005). 2. electric motor selection the relationship is given by equation (2): 𝑃𝑜𝑢𝑡 = 𝑇 ∗ 𝜔 2 where t = torque, 𝜔 = angular speed, and pout = power output 𝑇ℎ𝑒 𝑎𝑛𝑔𝑢𝑙𝑎𝑟 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (𝜔) = 2𝜋𝑁 60 3 http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 952 where; n= number of speed 3. centrifugal force the relationship is given by equation (4): 𝐹𝐶 = 𝑚𝜔2𝑟 4 where m = mass of birds, r = radius of compartment 4. belt selection the belt length is given by equation (5) as: l = π [ (𝐷 + 𝑑) 2 + 2𝑥 + (𝐷 − 𝑑) 4𝑥 ] 5 where l = total length of belt, 𝑥 = distance between the centres of two pulley, d = large diameter, d = small diameter (khurmi and gupta, 2005). 5. power transmitted by the belt the power transmitted by a given belt drive is represented in equation (6) as: 𝑃 = (𝑇1 − 𝑇2)𝑣 6 where p = power, t1 = tension of tight side of the belt, t2 = tension of slack side of the belt and v = velocity (khurmi and gupta, 2005). the belt tensions are given by equation (7): 𝑇1 𝑇2 = 𝑒𝑈𝜃 7 6. shaft design equation (8) is the used to determine the diameters of a shaft 𝑇 𝐽 = 𝐺𝜃 𝐿 = 𝜏 𝑟 8 where t = twisting moment (or torque) acting upon the shaft, j = polar moment of inertia r = radius, g = modulus of rigidity, θ = angle of twist, l=length of shaft, 𝜏 = 𝑇𝑜𝑟𝑠𝑖𝑜𝑛𝑎𝑙 𝑠ℎ𝑒𝑎𝑟 𝑠𝑟𝑒𝑠𝑠 (khurmi and gupta, 2005). 7. rate of heat flow the heat loss in the scalding compartment is given by equation (9): 𝑄 = 𝜆𝐴 𝑋 (𝑇1 − 𝑇2) 9 where 𝜆 = thermal conduction of material, a = area of the cylinder, t1 = temperature of water, t2 = temperature on boiler cylinder wall, x = thickness of material 8. chain drive the velocity ratio of a chain drive given in equation (10) as: v. r = 𝑇1 𝑇2 = 𝑁1 𝑁2 10 where t1=number of teeth on the smaller sprocket, t2= number of teeth on the bigger sprocket, 𝑁1 =speed of rotation of smaller sprocket in r.p.m, and 𝑁2 =speed of rotation of bigger sprocket in r.p.m (khurmi and gupta, 2005). http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 953 9. torque for scalding controller the equation (11) gives the relationship to determine the torque: torque 𝑇 = 𝐹𝑟 11 where f = force (weight on the compartment), r = radius of scalding compartment 10. pump selection the selection criteria for the pump are given in equations (12) and (13): hydraulic power of the pump 𝑃ℎ = 𝑄𝜌𝑔ℎ 3.68 × 106 12 where q = flowrate, ρ = density, g = acceleration due to gravity, h= total head discharge and velocity (nakayama and boucher, 2000). 𝑄 = 𝐴𝑉 13 where, a = area of flow, v = velocity of flow 2.2 mechanical design specifications table 1 gives a detailed specification and mechanical design values of the de-feathering machine. table 1: specification of the de-feathering machine description of items machine parts/specification mechanism pulley, belt and chain, sprocket drive target costumer farmers and small scale industry and home use. prime mover electric motor mode of operation automatic motor specification for de-feathering machine. 3hp motor major pulley diameter on de-feathering machine 500mm diameter minor pulley for electric motor 80mm diameter major sprocket on scalding section 102 teeth minor sprocket on scalding section 17 teeth live stocks birds, goose and duck machine dimension 163cm ×127cm×117cm manufacturing machining, assembling and welding cylinder diameter and height for boiler 380mm×310cm cylinder diameter and height for scalding 590mm×310cm cylinder diameter and height for de-feathering 610m×460cm reservoir specification 152cm×40cm×42cm water pump specification 1 hp motor specification for scalding machine 0.5 hp heat loss 3.0 watts the pictorial design of the poultry bird de-feathering machine is shown in plate 1 http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 954 plate 1: poultry birds de-feathering machine figure 1: orthographic view http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 955 figure 2: labeled details of de-feathering machine 2.3 electrical design theory 1. peak inverse voltage the peak inverse voltage is given in equation (14) as: peak inverse voltage piv = √2 x vrms 14 where vrms = transformer output voltage (theraja and theraja 2007). 2. selection of the filter capacitor (c1) the filter capacitor is selected using equation (15): 𝑉𝑝𝑒𝑎𝑘 − 𝑉𝑑 − 𝑉𝑐 = 0 15 where 𝑉𝑝𝑒𝑎𝑘 = 𝐵𝑟𝑖𝑑𝑔𝑒 𝑟𝑒𝑐𝑡𝑖𝑓𝑖𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡, 𝑉𝑑 = 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑑𝑟𝑜𝑝 𝑎𝑐𝑟𝑜𝑠𝑠 𝑟𝑒𝑐𝑡𝑖𝑓𝑖𝑒𝑟 𝑑𝑖𝑜𝑑𝑒 𝑉𝑐 = 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑜𝑟 𝑡𝑒𝑟𝑚𝑖𝑛𝑎𝑙 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 3. capacitor capacitance selection the capacitance of the capacitor is selected using equation (16): c = q ∆𝑉 16 where 𝑄 = charged stored ∆v = difference between maximum peak voltage and the minimum peak voltage 4. selection of the switching transistor this selection of the switching transistor is based on equations (17) and (18): relay coil current = relay coil voltage relay coil resistance 17 𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐 𝑃𝑜𝑤𝑒𝑟, 𝑃 = 𝐼𝑉 18 where i꞊ current, v꞊ voltage (theraja and theraja, 2007). the table 2 provides detailed specification and electrical/electronic design values of the de-feathering machine. http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 956 table 2: specification for electrical/electronic components description of items machine parts/specification voltage regulator 7812 ic rating: vmax=12v, vmin=11.8v 7805 ic rating: vmax=5.2v, vmin=4.8v transformer 75va 220/15v center tapped rectifying circuit in4007 diodes filter capacitor 40v capacitor capacitance 100nf switching transistor uln2003 controller unit atmega328p-pu microcontroller 2.3.1 power supply unit this unit converts the 220v ac to 5v dc required by the circuit; the design of the circuit diagram of the power supply unit is shown in figure 3 (idim and iyere, 2020). figure 3: power supply unit 2.3.2 the display unit this unit provides a visual display of the water level inside the reservoir; the unit, in-conjunction with the hmi unit also creates a platform that enables the user to input the set point (mbonu and ikpo, 2022). figure 4 shows the display unit interface with the controller unit. selection of the display unit a 20 x 4 liquid crystal display (20 characters per row, 4 rows) was selected; the display unit gets its data from the controller unit that is connected to the pc4 and pc5 pins of the atmega328p-pu microcontroller (mbonu and ikpo, 2022). 2.3.3 the fce and fce control unit the final control element (fce) was implemented with a 220vac 1/2hp water pump; the fce control unit is a switching circuit that assists the controller unit to switch the pump on and off (ebegba, 2019). figure 5 shows the fce control unit: 2.3.4 the controller unit this unit is the heart of the entire system; it performs the entire logic of the system (idim and iyere, 2020). the atmega328p-pu microcontroller was selected and was biased with a 16mhz crystal oscillator and two (2) 22pf capacitors; this is shown in figure 6. http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 957 figure 4: display unit interface with the controller unit figure 5: fce control unit figure 6: the controller unit 2.4 software design the software design is divided into three stages; these are algorithm generation, flow chat representation and coding (nwukor, 2020). c1 22 pf c2 22 pf http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 958 2.4.1 algorithm generation an algorithm is a statement of the procedure adopted in solving a problem; the sequence of the system operation is stated below (nwukor, 2020). 1. initialize the system at startup. 2. initialize the displays with “0-100 level rig” 3. get process level from the pressure transmitter. 4. update the display unit based on the sensor reading. 5. update the pump control unit. 6. end process. 2.4.2 flow chart the flow chart gives a graphical representation of the sequence of program execution; the flow chart for the system is given in figure 7 (idim and iyere, 2020). figure 7: flow chart 2.4.3 coding the code was written in c language (idim and iyere, 2020). the code contains the instruction of program to direct the affairs of the water level controller (idim and iyere, 2020; nwukor, 2020). there are five subroutines in the complete code; each subroutine performs specific function as group of instructions (idim and iyere, 2020; nwukor, 2020). the subroutine and functions are stated as follows; 1. initialization – this subroutine initializes the microcontroller including preloading the counters and reference values for the system, 2. read level – this subroutine makes the controller to get the process level the adc output and store the value into its data memory, 3. conversion – this subroutine converts the value read to the equivalent level, 4. update display – the subroutine enables the controller to display value on the lcd display, and 5. update control – this subroutine enables the microcontroller to control the switching circuit (idim and iyere, 2020; nwukor, 2020). start initialize internal get level of the process from adc end update display unit update the pump control unit http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 959 3. results and discussion the result of the test carried out shows that the heating process took a total of 45 minutes to heat the water up to 75oc and the scalding time was 45 seconds. the scalding bucket was programmed to delay for 4 seconds before returning to its initial position. de-feathering bucket then operates for 30 seconds and stops after the birds were completely processed. furthermore, the total time taken from start to finish was 46 minutes 19 seconds to de-feather the birds. the average time taken for de-feathering during a repeat cycle (scalding and de-feathering) takes a total of 76.33 seconds. the de-feathering bucket was designed to accommodate 10 – 15 birds depending on their sizes. however, the results for de-feathering two, five and ten birds are shown in tables 3, 4 and 5 respectively. table 3: de-feathering data for two (2) birds weight of chicken before plucking (kg) weight of chicken after plucking (kg) weight of feather (kg) plucking time (sec) scalding time (sec) 2.6 2.5 0.1 30 45 2.54 2.4 0.14 5.14 4.9 0.24 30 45 average weight of feather per second (throughput capacity) = 0.24 30 = 0.008 𝑘𝑔 𝑠⁄ 𝑜𝑟 8.00𝑔/𝑠 average feathering efficiency = 4.90 5.14 𝑋100% = 95.33% table 4: de-feathering data five (5) birds weight of chicken before plucking (kg) weight of chicken after plucking (kg) weight of feather (kg) plucking time (sec) scalding time (sec) 2.54 2.43 0.11 31 45 2.57 2.44 0.13 2.53 2.4 0.13 2.6 2.49 0.11 2.58 2.46 0.12 12.82 12.22 0.6 31 45 average weight of feather per second (throughput capacity) = 0.60 31 = 0.0194 𝑘𝑔 𝑠⁄ 𝑜𝑟 19.36𝑔/𝑠 average feathering efficiency = 12.22 12.82 𝑋100% = 95.32% table 5: de-feathering data ten (10) birds weight of chicken before plucking (kg) weight of chicken after plucking (kg) weight of feather (kg) plucking time (sec) scalding time (sec) 2.56 2.43 0.13 33 45 2.51 2.4 0.11 2.54 2.42 0.12 2.62 2.49 0.13 2.58 2.44 0.14 2.61 2.48 0.13 2.58 2.46 0.12 2.55 2.42 0.13 2.51 2.4 0.11 2.53 2.43 0.1 25.59 24.37 1.22 33 45 http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 960 average weight of feather removed per second (throughput capacity) = 0.60 31 = 0.0194 𝑘𝑔 𝑠⁄ 𝑜𝑟 19.36𝑔/𝑠 average defeathering efficiency = 24.37 25.59 𝑋100% = 95.23% the results obtained from table 3 shows that the defeathering efficiency is 95.33% while the throughput capacity is 8.00 g/s, whereas the results from table 4 indicates an increase in the throughput capacity of the machine at 19.36 g/s with five birds being processed, however, its efficiency of 95.32 % remain the same when compared with the result from table 2. again, when the processed birds were increased to ten, the result obtained from table 5 shows a further increase in throughput capacity of 37.00 g/s and an efficiency of 95.23 %. these results indicates that, the throughput capacity of the machine increases as the number of birds in the de-feathering drum is increased to its design capacity, without affecting the overall efficiency of the machine. 4. conclusion the automated scalding and de-feathering machine was fabricated from locally sourced materials. it has the potential to de-feather 10 chickens in a single repeat cycle. the performance evaluation of the machine gave a throughput capacity of 37g/s, with an efficiency of 95.30%, for a 10 birds capacity drum. a de-feathering time of 32 seconds per cycle was achieved, this shows that the machine can process an average of 110 birds per hour. however, several constraints were encountered, which limited certain functionalities that could have been included in the project. these constraints include enabling the system to recycle the scalding water to help conserve energy and reduce the heating up time; increasing the boiler size to ensure multiple operations with a single batch of heating. therefore, there are opportunities for the system to be upgraded to incorporation (iot) technology for improved performance and control, and deployed for use in industrial for bird de-feathering. references adetola, oa., oliwajana, as., and akpan, vd. 2023. modification and testing of a poultry bird defeathering machine. proceedings of the 2023 school of engineering and engineering technology (seet) annual conference, futa, 7th – 9th november, 2023, 86 – 91. awotunde, ow., adeyeye, k., ponle, ea., and fatukasi, so. 2018. development of a defeathering machine from locally sourced materials. international journal of scientific and engineering research, 9(5): 1-7. buckland, c. 2005. small scale poultry processing, fao animal production and health paper 98, https//www.openknowledgefao.org, accessed 21 november, 2024. david, ra. 1999. “you can build your mechanical plucker. (whizbang)” https://www.fao.org, 21st nov 2024 dickens, ja and shackelford, ad. 2004. feather releasing force related to stunning, scalding time and scalding temperature. poultry science journal vol. 67, 1069 – 1074. ebegba, d. 2019. design and implementation of liquid level detector using ultrasonic sensor. international journal of innovative science and research technology, 4(9): 499 – 504 idim, a., iyere, sf. 2020. design and implementation of gsm enabled remote sensor for monitoring power transformer operation. american journal of electrical and computer engineering, 4(2): 62-71. doi: 10.11648/j.ajece.20200402.15 jekayinfa, so. 2007. energetic analysis of poultry processing operations. leonado journal of science, 10: 7792. khurmi, rs., and gupta, jk. 2005. a textbook of machine design. 14th edition; eurasia publishing house india. mady, maa. and obaia, ar. 2018. manufacture and performance valuation of poultry plucker suitable for small farms. misr j. ag. eng., 35 (2): 407 – 422 http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 950-961. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: atadiousd@pti.edu.ng 961 mbonu, we. and ikpo, kuw. 2022. design and implementation of a level control system with real time data acquisition and logging via internet of things. international journal of scientific research and engineering development. 5(4): 945 – 950. nakayama, y., and boucher, rf. 2000. introduction to fluid mechanics. butterworth heinemann, great britain. nwukor, fn 2020. implementation of car tracking system using gsm/gps. international journal of scientific and research publications, 10(3): 399 – 403 ocheri, c., aigbodion, vs., agboola, jb., mbah, cn., mbah, ac. 2018. design and construction of rock crushing machine from locally sourced materials for indigenous use. aspects min miner sci. 2(2): 197 – 207 ogundipe, so. and sanni, sa. 2002. economics of poultry production in nigeria a training workshop manual. national animal production research institute, abu, shika, zaria nigeria. pp. 27-45. tanimola, oa., diabana, pd. and bankole, yo. 2014. design and development of a de-feathering machine. international journal of scientific and engineering research, 5(6): 208-214 theraja, bl. and theraja, ak 2007. electrical technology, s.c and company. new delhi, india, 23rd edition. http://www.azojete.com.ng/ mailto:atadiousd@pti.edu.ng arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):477-492 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 477 original research article proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit t. e. ndahi*, m. h. badau, a. l. kassum, l. p. mshelia and d. peter department of food science and technology, university of maiduguri, nigeria. *corresponding author’s email address: ndahitarhyel10@yahoo.com 1.0 introduction survival and well-being of all life forms depend directly or indirectly on plants and their products. this is because plant and plant products can provide man with basic necessities such as food, clothing and shelter. however, malnutrition is a global challenge due to inadequate intake of a balanced diet (fao, 2013). it is noteworthy that, consuming appropriate fruits and vegetables can contribute significantly to a balanced diet. studies have shown that fruits and vegetables contains macro nutrients (carbohydrate, protein and fat), vitamins, minerals, fibre and phytochemicals in article information abstract the consumption of fruit and vegetables contribute significantly to nutrient intake. however, the concentration of nutrients in whole fruits, rinds and seeds of a produce may differ. the objective of this study was to determine the proximate composition, minerals and phytochemical contents of guna (citrullus vulgaris) whole fruits, rinds (peels) and seeds. the proximate composition (moisture, ash, protein, fat, fibre and carbohydrate), mineral contents (ca, mg, p, fe, na, k, and zn) and phytochemical contents (flavonoids, phenols, tannin, alkaloid, saponin, glycosides and steroids) of whole fruit, rinds and seeds of guna were determined using standard methods. the results show that moisture, ash, protein, fat, fibre, carbohydrate and energy contents ranged from 11.44-82.69%, 1.43 2.64%, 0.52-21.82%, 0.45-26.58%, 8.15-18.21%, 5.32-19.31% and 33.37 403.74kcal/100g respectively. additionally,guna seeds sample recorded the highest value in ash, protein, fat, fibre, carbohydrate and energy contents.similarly, guna seeds was observed to have the highest ca (5.52mg/100g), mg (349.52mg/100g) and p (155.66mg/100g) contents while it has the least fe (0.117mg/100g) and na (18.74mg/100g) contents respectively. the phytochemical contents of whole fruits, seeds and rinds samples of guna differed significantly (p<0.05). the flavonoid, phenol, alkaloid, tannin, saponin and glycoside contents ranged from 6.23 55.18mg/100g, 4.61 38.11mg/100g, 642.69 785.12mg/100g, 0.52 44.79mg/100g, 15.75 131.79mg/100g and 0.068 0.255mg/100g respectively. furthermore, guna seeds recorded the highest flavonoid, phenol, tannin and saponin contents and the least in glycoside content. the steroid content of guna seeds (62.05mg/100g) was higher than in the whole fruits (8.97mg/100g), and was not detected in guna rinds samples. therefore, it could be concluded that guna seeds contained high protein, fat and energy values for nutrition compared to the whole fruits and rinds as well as relative high amount of mineral and phytochemical contents. thus, guna seeds could be used for nutritional and therapeutic purposes. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 29 march, 2023 revised 13 june, 2023 accepted 20 june, 2023 keywords: citrullus vulgaris (guna) proximate compositions mineral phytochemicals http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 478 their pulp, seeds and peels (rinds) which can serve as a food supplement (lim and rebeta 2013; niyi et al., 2018; oparaet al., 2019; ezekaibeya et al., 2020). olayinka and etejere (2017) showed that the pulp and rinds of watermelon and cucumber fruits samples have adequate dietary nutrients which could be used to supplement some of the deficient nutrients. in addition, the distribution of chemical constituents in plants is important and significant in traditional medicine (edeoga et al., 2005; agatemor et al., 2018). some of these fruits and vegetables are underutilized. hence, creating awareness of usefulness in terms of nutrition and medicinal value is important. kaana and samuel (2018) had shown that, proper utilization of these plants will help as substitute for some food nutrients. in recent years, several studies have been carried out on underutilized plant seeds and fruits for their nutrient and anti-nutrient compositions (augustine et al., 2015; kaana and samuel 2018; aremu et al., 2019). some of the recent works directed towards increasing the utilization of plant seeds and fruits include the determination of the proximate composition, amino acid profile, vitamins, minerals, phytochemicals of whole fruit, pulp, peels and seeds of some fruits (olayinka and etejere, 2017; agatemor et al., 2018; niyi et al., 2018; opara et al., 2019). citrullus vulgaris locally known as guna is a member of the cucurbitaceae or the cucurbit family, commonly referred to as the gourd, melon, cucumber or pumpkin (penuel et al., 2013). cucurbitaceae are creeping in nature and are found in warmer regions of the world (bates et al., 1990). the fruit is a fleshy berry that is round to ellipsoid and smooth at maturity, which varies in colour, from green to yellow and is somewhat crispy when chewed. melon seeds are oilseeds and potential protein source (penuel et al., 2013; kiin-kabari and akusu 2014). c. vulgaris (guna) seeds have been found to contain high fats and protein contents that make the seeds valuable as nutrients source (penuel et al., 2013; ndahi et al., 2019). cucurbit family has been documented to contain phytochemicals such as phenols, alkaloids, flavonoids, saponins, glycosides, phytates, oxalates and tannins which can affect the bioavailability and utilization of nutrients therein (penuel et al., 2013; olayinka and etejere 2018; opara et al., 2019). nonetheless, there is need for more data as species, variety, environment and seasons can affect nutrient content. hence, this present study was aimed at determining the proximate composition, minerals and phytochemical contents of the whole fruits, rinds (peels) and seeds of guna found in the northeastern part of nigeria. 2.0 materials and methods 2.1 sample collection guna (citrullus vulgaris) fruits of varying sizes were purchased from a farm at kwaya kusar local government area of borno state, nigeria. the fruits were identified at the department of biological science, university of maiduguri, maiduguri, borno state, nigeria. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com ndahi et al: proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit. azojete, 19(3):477-492. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 479 2.2 sample preparation the collected samples were prepared at the food processing laboratory of the department of food science and technology, university of maiduguri. the fruit samples were washed and portioned into two parts as shown in figure 1. the first portion was taken as a whole fruit sample which was chopped into small pieces and blended. secondly, the other portion was sliced, seeds were gradually extracted from the slice, used as seed samples while the rinds of the slices were cleaned from pulp adherence and chopped into smaller pieces and both seeds and rinds samples were blended separately. each sample was packaged, labelled appropriately and preserved in a laboratory fridge at 4oc before subjecting them to further analysis. selected guna fruits washed whole fruit chopped whole fruit sliced rinds cleaned and chopped seeds extracted and cleaned blended, packaged blended, packaged blended, packaged and stored and stored and stored (guna whole fruit sample) (guna rind sample) (guna seeds sample) figure 1. flowchart for the guna whole fruit, rind and seeds sample preparation http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 480 a: selected guna fruits b: sliced whole fruits c: sliced rinds d: extracted seeds e: blended rinds sample f: blended seeds sample g: blended whole fruit sample figure 2: pictures showing the guna whole fruits, rinds and seeds samples. 2.3 proximate analyses the proximate composition of the samples was carried out according to the methods described by aoac (2005) at chemistry laboratory, chemistry department, yobe state university, yobe state, nigeria. all the samples were analyzed for moisture, crude protein (%n x 6.25 conversion factor), crude fats, ash and fibre contents (as percentage of the weight of sample used in each content analysis) and the carbohydrate content was obtained by difference using equation (1): . %cho = 100 (%moisture + %fat + %protein + %ash + %fibre) (1) where: %cho = percent carbohydrate content %moisture = percent moisture content %fat = percent fat content %protein = percent protein content %ash = percent ash content %fibre = percent fibre content file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com ndahi et al: proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit. azojete, 19(3):477-492. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 481 2.4 caloric value determination the caloric values (kcal) of the samples was calculated by applying at water factors 4, 9, and 4 for each gram of protein, lipid, and carbohydrate, respectively (adebowale and maliki, 2011) as shown in equation (2). caloric value (kcal/100g) = (4 x %cho) + (4 x %protein) + (9 x %fat) (2) 2.5 mineral analysis determination of mineral content was carried out according to aoac (2000) method. each sample was ashed at 550°c in a muffle furnace to grey and dissolved in 10 ml of 0.1 m hcl, filtered into a 100 ml volumetric flask and made up to mark with distilled water. this was used to determine the calcium, phosphorus, sodium, potassium, magnesium, iron and zinc contents using atomic absorption spectrophotometer (aas). 2.6 phytochemical analyses the quantitative determination of the phytochemical contents was adopted from ezekaibeya et al. (2020), except phenol content which was done as described by edeoga et al. (2005). 2.6.1 determination of flavonoid content this was carried out using the method of bohn and kocipal-abyassan (1994). a 1.0g sample was repeatedly (three times) extracted with 100 ml of 80% aqueous methanol at room temperature. the solution was shaken for 30 min and filtered using whatman no 1 filter paper. the filtrate was transferred into a weighed beaker and evaporated to dryness over a water bath and weighed again. the time of the first extraction was 1 hour, 45 min for the second extraction and 30 mins for the third extraction. flavonoids were determined using the following formula in equation (3) concentration of flavonoid = w3−w2 w1 x 100 (3) where; w1 = weight of sample, w2 = weight of empty beaker, w3 = weight of beaker + sample after drying. 2.6.2 determination of phenol content phenol content was determined according to edeoga et al. (2005). two (2) g of the sample were defatted with 100 ml of diethyl ether using a soxhlet apparatus for 2 h to obtained a free fat sample. the fat free sample was boiled with 50 ml of ether for the extraction of the phenolic component for 15 min. 5 ml of the extract was pipetted into a 50 ml flask, then 10 ml of distilled water was added. 2 ml of ammonium hydroxide solution and 5 ml of concentrated amyl alcohol were also added. the samples were made up to mark and left to react for 30 min for colour development. this was measured at 505 nm using spectrophotometer. 2.6.3 determination of alkaloid content alkaloid content was assessed using the method of harbone (1973). a sample (1.0g) was weighed using electric weighing balance into a 250 ml glass beaker; 100 ml of 10% acetic acid in ethanol http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 482 was added to the sample and covered. the mixture was allowed to stand for four hours for extraction to take place. the sample was filtered with whatman no 1 filter paper and the extract was concentrated on a water bath (70°c) to one quarter of the original volume. 20 ml of ammonium hydroxide was added drop-wise to form precipitate of the alkaloid in the filtrate. the filtrate was washed with 20 ml of 0.1 m nh4oh and then filtered with whatman no 1 filter paper. the filter paper was weighed before using it to filter. after filtering, the filter paper and the precipitate were dried in an oven at 40°c and weighed. the alkaloid content was determined using the following formula in equation (4). concentration of alkaloids = w3−w2 w1 x 100 (4) where; w1 = weight of sample; w2 = weight of filter paper; w3 = weight of the alkaloid and filter paper 2.6.4 determination of tannin content this was done according to the method of van-burden and robinson (1981). a sample was weighed (1.0g) into a plastic bottle and 50 ml of distilled water was added and shaken for 3 hours in a vibrator. the sample was filtered into a 50 ml volumetric flask and made up to mark. 5 ml of the filtrate was dispensed into a test tube and mixed with 2 ml of 0.1m fecl2 in 0.1n hcl and 0.008 m potassium ferrocyanide. the absorbance was measured at 120 nm for 10 mins. the tannin concentration was determined using the following relation in equation (5). concentration of tannins = abs x d.f 1000 x w1 x 100 (5) where; abs = value of absorbance read, d.f = dilution factor, w1 = weight of sample 2.6.5 determinations of saponin content availability of saponin was carried out using the method adopted by obdoni and ochuko (2001). the sample (1.0g) was weighed using an electric weighing balance into a 250 ml conical flask and soaked in 100 ml of 20% ethanol for three (3) min and heated for three (3) hours at 55°c for extraction then filtered. the residue was re-extracted with additional 100 ml of 20% ethanol. the two samples were combined, heated and reduced to 40 ml at 90°c in a water bath. the concentrate was transferred into a 500 ml separating funnel and 20 ml of diethyl ether was added and shaken vigorously; the upper layer was discarded. the purification process was repeated three times and 60 ml of n-batanol was added. the combined n-butanol mixture was washed twice with 10 ml of 5% aqueous nacl and the lower layer was discarded while the upper layer was collected in a weighed beaker and heated to a constant weight. the beaker was allowed to cool in a desiccator and re-weighed. the saponin content was determined using the following formula in equation (6). concentration of saponins = w3−w2 w1 x 100 (6) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com ndahi et al: proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit. azojete, 19(3):477-492. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 483 where; w1 = weight of sample; w2 = weight of empty beaker; w3 = weight of beaker + sample after heating 2.6.6 determination of glycoside content the determination of glycoside content was done using the method of harborne (1973). a sample (0.1 g) was weighed out, macerated with 20 ml of distilled water and 2.5 ml of 15% lead acetate was added and filtered. chloroform (2.5 ml) was added to the filtrate, shaked vigorously and the lower layer collected and evaporated to dryness. glacial acetic acid (3 ml) was added together with 0.1 ml of 5% ferric chloride and 0.25 ml of concentrated h2so4. the mixture was shaken and put in the dark for 2 hours. absorbance was measured at 530 nm using the formula in equation (7). concentration of glycosides = abs x path lenght 100 x w1 x 100 (7) where; abs = value of absorbance read, w1 = weight of sample 2.6.7 determination of steroid content this was carried out according to the method of okeke and elekwa (2003). a sample (1.0 g) was dispersed in 100 ml of distilled water into a conical flask, the mixture was shaken for 3 hours and allowed to stand overnight. it was filtered and the filtrate was eluted with 10 ml normal ammonium hydroxide solution, 2 ml of the elute was put into a test tube and mixed with 2ml of chloroform. additionally, 3 ml of acetic hydride was also added to the mixture, followed by 2 ml of concentrated h2so4 drop-wise. the absorbance was measured at 420 nm using a spectrophotometer at 420nm. the steroid concentration was determined using the following relationship in equation (8) concentration of steroids = abs x path lenght 100 x w1 x 100 (8) where; abs = value of absorbance read, w1 = weight of sample 2.7 statistical analyses the data obtained were subjected to a one-way analysis of variance (anova) at 0.05 significance level and means separated using duncan multiple range test using statistical package for social science 23 version (spss). 3.0 results and discussions 3.1 proximate composition of guna whole fruits, rinds and seeds table 1 shows the proximate composition of whole fruit, rinds and seeds samples of guna fruit. the results show a significant difference (p<0.05) in moisture, ash, protein, fat, fibre carbohydrate http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 484 and energy value. the moisture content ranged from 11.44-82.69% while that of the whole fruit is significantly higher compared to the seeds with lowest moisture content. this is because plants in the curbitaceae family are known to contain a high amount of water in their fruits compared to the seeds (olayinka and etejere, 2018). similar to the moisture content of guna seeds (11.44%) obtained in this study, adua et al. (2019) reported 14.29g/100g as the moisture content for c. vulgaris seeds and gabriel et al. (2018) noted 10.92g/100g as the moisture content for watermelon seeds. contrarily, higher moisture content was obtained for citrullus lanatus seeds (48.75g/100g) (fila et al., 2013). the moisture content of guna rinds (75.16%) in this study was similar to the watermelon rinds (67.75g/100g) (fila et al., 2013) while higher moisture content was noted for the rinds of c. lanatus and cucumis sativus (olayinka and etejere, 2018). agatemor et al. (2018) recorded higher moisture content of c. sativus fruit (94.2g/100g) as compared to the moisture content of guna whole fruits (82.69%) obtained in this study. table 1. proximate composition of guna whole fruits, rinds and seeds samples composition whole fruit rinds seeds moisture (%) 82.69 ± 0.05a 75.16 ± 0.10b 11.44 ± 0.03c ash (%) 1.87 ± 0.02b 1.43 ± 0.02c 2.64 ± 0.02a protein (%) 1.01 ± 0.03b 0.52 ± 0.02c 21.82 ± 0.09a fat (%) 0.96 ± 0.02b 0.45 ± 0.01c 26.58 ± 0.03a fibre (%) 8.15 ± 0.06c 15.63 ± 0.04b 18.21 ± 0.03a carbohydrate (%) 5.32 ± 0.12c 6.81 ± 0.16b 19.31 ± 0.14a energy (kcal/100g) 33.96 ± 0.15b 33.37 ± 0.10c 403.74 ± 0.71a values are means of triplicate analysis and their standard deviation. in any row, means bearing similar superscripts are not significantly different (p> 0.05). the protein contents reported in the whole fruits, rinds and seeds ranged from 1.01-21.82%. it is noteworthy that the seed contain higher protein content than the fruit as shown in table 1. this is similar to protein value in watermelon seeds (19.43g/100g) (gabriel et al., 2018) and c. vulgaris as 20.30g/100g (adua et al., 2019). however, a lower value of protein content was reported for the rinds and pulp of c. lanatus and c. sativus with 0.34-0.53% and 0.770.86% respectively (olayinka and etejere 2018). considering the rinds and the whole fruits, the protein content obtained was lower (0.52 and 1.01% respectively) as compared to values of protein content obtained from c. sativus fruit at 3.01g/100g (agatemo ret al., 2018) and fresh watermelon rinds at 2.51g/100g (fila et al., 2013). the fat content of the seed (26.58%) was significantly higher (p < 0.05) as compared to the rinds and the whole fruits as 0.45% and 0.92% respectively. the higher fat content of the guna whole fruit compared to its rinds might be due to the presence of its seeds. lower fat content values have been observed for the rinds and pulp of c. lanatus and c. sativus having 0.13-0.21% and 0.14-0.23% respectively (olayinka and etejere 2018), c. sativus fruit, 0.55g/100g (agatemor et al., 2018) and watermelon seeds, 21.54g/100g (gabriel et al., 2018). this shows that fruits are not very good sources of fat as reported by ngoddy and ihekeonye (1985). the fibre content obtained in guna whole fruits (8.15%) and rind sample (15.63%) were lower compared to guna seeds (18.21%). the noted fibre content in guna seeds was lower compared file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com ndahi et al: proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit. azojete, 19(3):477-492. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 485 to the previous study by gabriel et al., (2018), who reported a higher fibre content of 26.10g/100g for watermelon seeds. contrary to that observed for guna whole fruit, agetemor et al. (2018) reported lower fibre content of c. sativus fruit (1.02g/100g). thus, guna seeds and rinds could be used as a source of fibre in food and feed applications. the ash content provides an estimate of the mineral content of a product which was observed to be higher in the seed (2.64%) as compared to the whole fruits (1.87%) and the rinds (1.43%). similar value of ash content was reported for c. vulgaris seeds (2.273g/100g) (adua et al., 2019). different results on ash content were noted for watermelon seeds (5.03g/100g) (gabriel et al., 2018), c. sativus fruit (0.94g/100g) (agatemor et al., 2018) and that of fresh watermelon seeds and rinds with 1.01 and 0.41g/100g respectively (fila et al., 2013) as compared to the result in this study. the carbohydrate contents in guna whole fruits, rinds and seeds ranged from 5.32-19.31% where the seeds sample (19.31%) was significantly higher compared to the whole fruit (5.32%) and the rinds (6.81%). this is similar to the carbohydrate value in rinds and pulp of c. lanatus (4.23-5.22%) (olayinka and etejere, 2018), c. vulgaris seeds as 20.86g/100g (adua et al., 2019) and watermelon seeds as 16.98g/100g (gabriel et al., 2018). in this study, the energy value of the guna seeds (403.74kcal/100g) varied significantly (p<0.05) from that of the whole fruit (33.37kcal/100g) and rinds (33.96kcal/100g) even as the later did not differed significantly (p>0.05). the high value of energy content observed in guna seeds was due to the high caloric nutrients (carbohydrates, proteins and fats) compared to the whole fruit and rinds. the obtained energy value for guna seeds indicates its nutritional quality as other oil seeds and may be utilized as high protein and energy sources in some food formulation as suggested by penuel et al. (2013). interestingly, animal ration supplemented with guna seeds has been reported to increase the nutrient contents and caloric density of the ration (ndahi et al., 2019). 3.2 mineral contents of guna whole fruits, rinds and seeds samples table 2 shows the mineral contents of whole fruits, seeds and rinds samples of guna. there was significant difference (p<0.05) in the calcium (ca), magnesium (mg), zinc (zn), iron (fe), sodium (na), potassium (k) and phosphorus (p) contents and na/k ratio of the studied samples. the ca, mg and p contents ranged from 3.84-5.52mg/100g, 206.35-349.52mg/100g and 87.48155.66mg/100g respectively and the highest values observed were in guna seeds followed by whole fruit while the rinds had the least values. furthermore, the content of k and zn ranged from 144.28-268.44mg/100g and 4.58-rinds and seeds. the guna rinds had the highest value followed by whole fruit and seeds in fe, na and na/k ratio contents ranging from 0.1170.143mg/100g, 18.74-47.17mg/100g and 0.13-0.27 respectively. http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 486 table 2. mineral contents(mg/100g) of guna whole fruits, rinds and seeds samples mineral contents whole fruit rinds seeds calcium (ca) 4.16 ± 0.02b 3.84 ± 0.02c 5.52 ± 0.02a magnesium (mg) 273.13 ± 0.08b 206.35 ± 0.06c 349.52 ± 0.11a iron (fe) 0.139 ± 0.003b 0.143 ± 0.002a 0.117 ± 0.002c zinc (zn) 5.59 ± 0.02a 4.95 ± 0.02b 4.58 ± 0.01c sodium (na) 43.58 ± 0.03b 47.17 ± 0.03a 18.74 ± 0.04c potassium (k) 268.44 ± 0.15a 175.23 ± 0.12b 144.28 ± 0.09c phosphorus (p) 123.96 ± 0.15b 87.48 ± 0.10c 155.66 ± 0.07a na/k ratio 0.16± 0.04b 0.27± 0.02a 0.13 ± 0.01c values are means of triplicate analysis and their standard deviation. in any row, means bearing similar superscripts are not significantly different (p > 0.05). higher ca content was reported in c. vulgaris seeds (14.80mg/100g) (adua et al., 2019) and that of watermelon seeds (27.0mg/100g) (gabriel et al., 2018) compared to guna seeds (5.52mg/100g) in this study. considering the rinds, lower value of ca content was reported for the rinds and pulp of c. lanatus and c. sativus ranging 0.95-1.36mg/100g and 1.02-1.14mg/100g respectively (olayinka and etejere 2018). ca helps to regulate muscle contraction, transmit nerve impulses and bone formation (okwu and emenike, 2006). the ca value range obtained in this study falls far below the recommended dietary allowance (rda) of 800mg /day for both adults and children (nrc 1989). the mg content obtained in this study was higher compared to the values documented for c. vulgaris seeds (adua et al., 2019), watermelon seeds (gabriel et al., 2018) and melon husk (akiode et al., 2018). notably, the mg content value in guna falls within rda values for adult (350mg /day) and children (170mg/day) (nrc 1989). the observed values of zn content in table 2 was close to the stated value for c. sativus seeds (5.46mg/100g) and pulp (5.27mg/100g) (niyi et al., 2019) and watermelon seeds (4.80mg/100g) (gabriel et al., 2018). however, lower value of zn content was reported for melon husks (0.70mg/kg) (akiode et al., 2018) and c. vulgaris at 0.56mg/100g (adua et al., 2019). penuel et al. (2013) reported higher value of zn content in guna samples (49.5 62.5mg/100g) compared to the zn values in this study. the rda for zn in adults and children are 15mg/day and 10mg/day respectively. hence, guna could be significant in dietary supply of zn in nutrition. in fe content, higher values was documented by adua et al. (2019) for c. vulgaris seeds (4.08mg/100g) and olayinka and etejere (2018) for the rinds and pulp of c. lanatus and c. sativus ranging from 1.44 -2.42mg/100g and 0.74-1.31mg/100g respectively compared to the fe content in guna (table 2). the rda for fe in male adult and children is 10mg/day while for a female adult is 15mg/day (nrc 1989). this study indicated that the fe content of guna is far below the recommended standard which was in disagreement to the remark made by peneul et al., (2013) for fe content in guna samples (115.5 180.0mg/100g). sodium regulates fluid balance in the body and helps in the proper functioning of muscles and nerves (jacob et al., 2015). niyi et al. (2019) obtained higher value of na content in c. sativus file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com ndahi et al: proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit. azojete, 19(3):477-492. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 487 peels, seeds and pulp as 113.00, 156.00 and 151mg/100g compared to the na content value in guna noted this study. on the other hand, lower value of na content was reported for c. colocynthis l. seeds (12.10mg/100g) (akansha et al., 2018). the recommended daily intake by who for na is 500mg for adults and 400mg for children (who, 1973). potassium (k) is essential in maintaining the body’s ph, fluid volume and osmotic equilibrium and regulation of muscles and nerve irritability (nrc 1989). this result indicates that guna (144.28268.44 mg/100g) falls below the recommended daily intake (3500mg). higher value of k content was reported for the peels, pulp and seeds of c. sativus ranging from 437.00-541.00mg/100g (niyi et al., 2019) likewise bitter melon fruits (413.02mg/100g) and fruit pulp of ebony tree (332.22mg/100g) (aremu et al., 2019). phosphorus and calcium are significant in the formation of strong bones and teeth, for blood clotting, heart function, growth, normal nerve and muscle action and cell metabolism (roth and townsend, 2003; rolfes et al., 2009). lower value was reported for phosphorus (p) content in c. colocynthis l. seeds, rinds and pulp of c. lanatus and c. sativus and c. vulgaris seeds compared to the result obtained in this study (akansha et al., 2018; olayinka and etejere 2018; adua et al., 2019). the recommended daily intake for phosphorus is 700mg for adults and 1250mg for teenagers (9 -18 years) and the p content of guna (87.48-155.66 mg/100g) in this study fall below it. na/k ratio in the body is of great concern for the reduction of the effect of high blood pressure. niyi et al. (2019) reported that the na/k ratio for the seeds, pulp and peel of c. sativus as 0.29, 0.36 and 0.25 respectively which was close to the range obtained (table 2). however, higher na/k ratio value was stated for bitter melon fruits (1.26) (aremu et al., 2019) and hibiscus safdariffa seeds (4.0) (chukwu et al., 2019) compared to the result in this study. this implies that consumption of guna notably, guna seeds (0.13) would have a positive effect on blood pressure because they had na/k ratio that was less than one (fnb, 2005). 3.3 phytochemical contents of guna whole fruits, rinds and seeds samples in table 3, the phytochemical contents of whole fruit, seeds and rinds samples of guna differed significantly (p<0.05) from each other in flavonoid, phenol, tannin, alkaloid, saponin, glycoside and steroid contents. the quantified phytochemicals in guna of this study agreed with the report on the determination of alkaloids, flavonoids, phenols, tannins, steroids, glycosides and saponins for sweet melon seeds (gabriel et al., 2018), water melon seeds (opara et al., 2019), c. sativus fruit (agatemor et al., 2018) and cucum metuliferus rinds (ezekaibeya et al., 2020). contrastingly, tannin was not detected in defatted, protein concentrate and protein isolate of guna seed flours (penuel et al., 2013), tannins and alkaloids were not detected in c. colocynthis l. (akansha et al., 2018) and likewise tannin and phenol in the melon husk (akiode et al., 2018). this discrepancy could be due to the different analytical methods and samples used and their processing methods (natumanya et al., 2021). it is noteworthy that the phenol, flavonoid, tannin, saponin and steroid contents are more concentrated in guna seeds than other parts of the fruit (table 3). http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 488 table 3. phytochemical contents(mg/100g) of guna whole fruits, rinds and seeds samples phytochemical contents whole fruit rinds seeds flavonoid 7.51 ± 0.03b 6.23 ± 0.02c 55.18 ± 0.04a phenol 8.34 ± 0.04b 4.61 ± 0.02c 38.11 ± 0.03a alkaloid 642.69 ± 0.03c 785.12 ± 0.05a 746.28 ± 0.09b tannin 1.23 ± 0.01b 0.52 ± 0.01c 44.79 ± 0.03a saponin 54.72 ± 0.02b 15.75 ± 0.03c 131.79 ± 0.11a glycoside 0.15 ± 0.002b 0.255 ± 0.002a 0.068 ± 0.001c steroid 8.97 ± 0.01b nd 62.05 ± 0.05a values are means of triplicate analysis and their standard deviation. in any row, means bearing similar superscripts are not significantly different (p > 0.05). nd means not detected the phenol, flavonoid and tannin contents in guna ranged from 4.61-38.11mg/100g, 6.2355.18mg/100g and 0.52 44.79mg/100g respectively with guna seeds recording the highest and rinds having the least values. studies reported higher values of phenol, flavonoid and tannin contents for c. sativus fruit (agatemor et al., 2018) and c. metuliferus rinds (ezekaibeya et al., 2020) compared to the values in this study. the phenolic and flavonoid compounds can act as reducing agents, hydrogen donors and singlet oxygen quenchers which are attributed to their antioxidant activity (gulcin et al., 2007). hertzler et al. (2020) reported that lower concentrations of tannins (viewed as antinutrient) in plants are found to be desirable for human and animal consumption. alkaloids exhibit some pharmacological activity such as antihypertensive effect, anti-malarial and anticancer (saxena et al., 2013). in this study, the alkaloid content of the sample ranged from 642.69-785.12mg/100g where guna rinds and whole fruit had the highest and least values in turn. contrary to the observation in this study, lower value of alkaloid content was stated for melon husk (akiode et al., 2018), c. sativus fruit (agatemor et al., 2018) and c. metuliferus rinds (ezekaibeya et al., 2020). interestingly, the alkaloid content of guna (whole fruit, rinds and seeds) falls within the range observed for some medicinal plants (0.34 -1.04%) (edeoga et al., 2005). saponin content ranged from 15.75-131.79mg/100g where guna seeds and rinds recorded the highest and least value respectively. higher saponin content was noted for c. sativus fruit (2.01mg/g) (agatemor et al., 2018) compared to this study. the saponin content of the rinds of c. metuliferus (0.72mg/g) (ezekaibeya et al., 2020) was within the range noticed in this study though remarkably higher than guna rinds. saponins are known anti-nutritional factor, which reduces the uptake of certain nutrients including glucose and cholesterol in the gut through intra-lumenal physiochemical interactions (shi et al., 2004) and also as antibiotic (saxena et al. 2013) from table 3, the glycoside content ranged from 0.068-0.255mg/100g. this study indicated that glycosides are more concentrated in guna rinds than the seeds. agatemor et al., (2018) noted higher value of glycoside content in c. sativus fruit (32.23mg/g) compared to this present study. according to xiao et al. (2016), flavonoids and c-glycosides show a significant antioxidant, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com ndahi et al: proximate composition, mineral and phytochemical contents of whole fruits, rinds and seeds of guna (citrullus vulgaris) fruit. azojete, 19(3):477-492. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 489 anticancer, antitumor, hepatoprotective, anti-inflammatory, anti-diabetes, antiviral, antibacterial and antifungal activities. steroids was found to be present in guna whole fruit (8.97mg/100g) and seeds (62.05mg/100g) and was not detected in the rinds. it has been reported that some investigated medicinal plants contained steroidal compounds (edeoga et al., 2005). it should be noted that steroidal compounds are of significance due to their relationship with hormones such as sex hormones (okwu 2001). this might be the reason guna seeds are used in making pap for expectant mothers or breastfeeding mothers to ensure their hormonal and nutritional balance (wakshama, 2016) since steroidal structure could serve as potent starting material in the synthesis of these hormones (okwu, 2001). notably, supplementing lactating ewes ration with guna seeds was reported to improve their milk yield and its composition (ndahi et al., 2019). 4.0 conclusion the proximate composition, minerals and phytochemical contents of guna whole fruit, rinds and seeds determined highlighted the potentials of the underutilized produce. guna seeds contained higher protein, fat and energy values compared to whole fruit and rinds which could be a good source of plant protein, oil and a potential food supplement for nutritional purposes. magnesium, potassium and phosphorus contents were the highest mineral contents in all the guna part while iron content was the least. the phytochemical contents of guna seeds was higher compared to the whole fruit and rinds except for alkaloid and glycoside contents. steroid was not detected in guna rinds. the mineral and phytochemical contents of guna seeds could be used for nutritional and therapeutic purposes. acknowledgment this work was supported by professor s. s. sanusi at the department of biological science, university of maiduguri, maiduguri, borno state, nigeria for identifying the sample. references adebowale, oj. and maliki, k. 2011. effect of fermentation period on the chemical composition and functional properties of pigean pea (cajanus cajan) seed flour. international food research journal, 18 (4): 1329 – 1333. adua, ea., adzitey, f. and abu a. 2019. nutrient composition of whole grain and processed “niri” (citrullus vulgaris) seeds. international journal of food science and nutrition, 4(2): 76 -79. agatemor, um., nwodo, ofc. and anosike, ca. 2018. phytochemical and proximate composition of cucumber (cucumis sativus) fruit from nsukka, nigeria. african journal of biotechnology, 17(38): 1215 – 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press, maiduguri. ngoddy, po. and ihekoronye, ai. 1985: integrated food science and technology. 1st edition, macmillan publication london, 293-311. niyi, oh., jonathan, aa. and ibukun, ao. 2019. comparative assessment of the proximate, mineral compositions and mineral safety index of peel, pulp and seeds of cucumber (cucumis sativus). open journal of applied sciences, 9: 691 – 701. obdoni, bo. and ochuko, po. 2001. phytochemical studies and comparative efficacy of the crude extract of some homostatic plants in edo and delta states of nigeria. global journal of pure and applied sciences. 8b:203-208. okeke, cu. and elekwa, i. 2003. phytochemical study of the extract of gongronemalatifoliumbenth. journal of health and visual sciences, 5(1): 47-55. okwu, de. 2001. evaluation of the chemical composition of indigenous spices and flavouring agents. global journal pure appllied sciences, 7(3): 455459. http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):477-492. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ndahitarhyel10@yahoo.com 492 okwu, de. and emenike, in. 2006. evaluation of the phytonutrients and vitamin c content of citrus fruits. international journal of molecular medicine and advance sciences, 2: 1-6. olayinka, bu. and etejere, eo. 2018. proximate and chemical composition of watermelon (citrullus lanatus (thunb)) matsum and nakai cv red and cucumber (cucumis sativus l. cv pipino). international food research journal, 25(3): 1060 – 1066. opara, ij., ushie, oa., aondyima, i. and omadibia, me. 2019. phytochemical screening, proximate and vitamin composition of cucumis melo seeds (sweet melon). international journal of research information, science application and techniques, 3(1): 193121 – 193128. penuel, bl., khan, em. and maifera, mo. 2013. properties of proximate composition and elemental 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science and technology, university of maiduguri, maiduguri. world health organization (who) 1973. trace elements in human nutrition. who technical report series no 532. geneva. xiao, j., capanoglu, e., jassbi, ar. and miron, a. 2016. advance on the flavonoid c-glycosides and health benefits. review food science nutrition, 56(1): 29-45. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):483-490 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 483 optimization of sandwich bumper for three-year-old child neck injury prevention i. a. rafukka department of mechanical engineering, faculty of engineering, bayero university, pmb 3011, kano, nigeria *corresponding author's email address: ibrahimrafukka@yahoo.com article information submitted 26 december, 2023 revised 23 february, 2024 accepted 25 february, 2024 keywords: crash dummy frontal crash neck moment sandwich bumper abstract impact energy absorption vehicle components play an important role in reducing severity of injury in vehicle crashes. children being delicate are most vulnerable in vehicular collisions. the neck is the major body region after head that experiences a high moment when deceleration is transmitted to it. bumper is one of the vehicle’s frontal energy absorption components that reduce deceleration to the occupants. sandwich bumper is an energy absorption component that could substitute a steel bumper. the geometry of the sandwich bumper affects its energy absorption capability on impact. this work applies an optimization technique to determine the sandwich bumper thicknesses that provides lower neck moments to child on impact at 48km/h in ls dyna code. finite element (fe) simulations using crash dummy models being the simplest method to reproduce accident was employed. the optimization results found the minimum neck moment of 25.4 nm occurred at foam thickness of 68.76 mm and bumper thickness of 2 mm. the study provides designers with quantitative information on how the bumper performance affects child injury in vehicular frontal crashes. this will lead to design of safer vehicles for the children population. 1.0 introduction road crashes have become a major cause of death in the last two decades in developing countries. heads and necks are the body parts that experienced high acceleration on impact. children are restrained in child seat to reduce the effect of decelerations. light-weight materials are being explored to reduce fuel consumption of vehicles thereby minimizing the deleterious effect on the environment. research recently focused on substituting steel vehicle frontal components with energy absorbing crashworthy materials to enhance crashworthiness and reduce occupant injuries (navale et al., 2023). in addition to vehicle weight reduction, lightweight materials also provide occupants safety. head is known to be a major cause of fatality in children (li et al., 2013). head exerts inertial loads which make the neck experience flexion and extension. neck loading on impact can also cause serious injuries. neck response is necessary in assessing the safety performance of child seats. head trajectory and loading conditions are determined by neck response on impact (meijer et al., 2010). for child occupants, neck response governs head kinematics on head contact with the vehicle interior in a crash. neck moment and forces must not exceed the threshold set by federal motor vehicle safety standards (fmvss) in the certification for the vehicle to be safe for child occupant. designing a bumper with energy absorbing material is considered a suitable way of reducing injuries to occupants of all ages. adult passengers have always been the target for the design in which adult crash dummies are used to evaluate the performance of such front components in vehicle crash (salwani et al., 2014). child crash http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):483-490. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 484 dummy fe models were also used in assessing the effect of road side poles on the injury of three year old (3yo) children (elmarakbi et al., 2013). effect of sandwich bumper on occupant injury in vehicle crash has been studied by donga (2011) and rafukka et al. (2017). sandwich bumper absorbs energy on crash and reduces decelerations depending on the geometry and thickness of the face sheet. the aim of this work is to use optimization to determine the sandwich bumper geometry that provides lower neck injuries to 3yo child in frontal impact using fe simulation in ls dyna code. 2. materials and methods 2.1 finite element modelling car fe model that is publically available for research purposes on the national crash analysis centre (ncac) website (national crash analysis centre, 2015) was used to simulate a 48km/h crash test. the speed was chosen based on federal motor vehicle safety standards (fmvss 208) which requires full frontal impact test to be carried out at 30 mph (48 km/h). the car model has been validated against physical crash data by marzougui et al., (1997). it is used in this work because of its low computation time. vehicles subjected to frontal impact usually exhibit large deformation on the front-end, whereas the rear end hardly undergoes deformations. taurus model front-end structures were developed with fine mesh, since it was meant for frontal impact assessment as shown in figure 1. figure 1: ford taurus finite element model validated 3yo child dummy model scaled from 6yo hiii dummy available on livermore software technology corporation (lstc) website was used in this work. the dummy was positioned in the rear seat of the car model restrained in the child restraint seat (crs) fe model as shown in figure 2. figure 2: child dummy model in crs the child model is equipped with an upper neck load cell located below the occipital that measures neck moment and forces. moment about occipital condyle ( ), is reacted by shear force , as shown in figure 3: file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rafukka: optimization of sandwich bumper for three year old child neck injury prevention. azojete, 20(2):483-490. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 485 figure 3: free body diagram of moment and force acting at the dummy upper neck thus according to 6yo hiii manual, moment about occipital condyle is expressed by equation [1] (mahadevaiah et al., , 2013): (1) = neck moment in y-direction; tendency of head and neck to bend towards chest (flexion) or towards back (extension). 2.2 bumper beam modelling the steel material of the beam of the car was substituted by a carbon/epoxy composite with material properties as presented in table 1. the fibre orientation used was taken to be . mat_composite damage (material type 22 in ls dyna) was employed. table 1: material properties of the composite bumper beam (t300/5208 carbon/epoxy) (naik et al., 2000) ρ(kg m3⁄ ) ea (mpa) eb (mpa) ec (mpa) prba prca prcb gba (mpa) gbc (mpa) gca (mpa) 1554 15070 13300 13300 0.287 0.287 0.390 4900 4900 4800 the meaning of the variables mentioned in table 1 is: –young’s modulus in a-direction, young’s modulus in b-direction, young’s modulus in c-direction, poison’s ratio in ba direction, -poison’s ratio in ca direction, poison’s ratio in cb direction, shear modulus in ba direction, shear modulus in ca direction. the existing bumper of the ford taurus model was redesigned by introducing foam attached to the front composite bumper beam which was made to be the face sheet of the sandwich beam that is stiff enough to resist plane and bending loads. the core was made from a foam material that carries the shear load: it is flexible and therefore able to absorb impact energy by balancing it with strain energy. the foam was modelled using mat_low_density_foam (material type 54 in ls dyna). the mass density and elastic modulus were and respectively. the hysteretic unloading and shape factors were taken to be 0.01 and 8 respectively. these material properties were extracted from taurus (2012) model sandwich bumper (national crash analysis centre, 2015). the stressstrain relationship coupled to the material model is as shown in figure 4. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):483-490. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 486 figure 4: engineering stress-strain relationship of the low density foam used for sandwich bumper (national crash analysis centre, 2015) the maximum thickness of the foam was taken to be 100 mm considering the limited space between the bumper beam and the facia. the foam was attached to the bumper beam using single surface contact as was done for the other parts of the car model. it was modelled with dimensions 1233 mm by 142 mm by 50 mm to cover the contact area of the bumper beam with a rigid barrier. the orientation of the foam was curved to follow the composite beam as shown in figure 5. the foam was discretized using 384 solid elements which were modelled with constant stress solid element formulation (type 2 in ls dyna) option with reduced integration. the smallest and largest solid element edge length varies from 23.6mm to 24.5mm. figure 5: sandwich bumper beam 2.3 simulation setup crash simulation was conducted in ls dyna at a speed of 48km/h chosen based on federal motor vehicle safety standard (fmvss 208) which requires a full frontal impact test to be carried out at 48 km/h. the calculation was carried out using ls dyna solver with a running time of 10 hours. the simulation was carried out for 140ms time duration to allow for complete dummy response. the time step scaling factor was reduced from the default of 0.9 to 0.7 in *control_time step card. neck moment – time history was tabulated from the simulation for the various thicknesses of composite bumper beam and sandwich foam for optimisation. bumper design parameters are functions of shape, geometry, size and material properties. this study however, considers thickness as a design variable because other factors such as shape and geometry require vehicle model revisions. to determine the optimal safety design of the bumper, a set of designs was sampled from the sandwich bumper beam that gave better injury values. the composite bumper thickness (tb) and foam thickness (tf) were used as design variables and the injury parameter neck moment (nm) was considered as objective parameter. objective optimization technique was applied to determine the tb and tf of the bumper that gives the lowest values of the injury parameter. a full factorial design was applied using two variables; the foam thickness tf varying for five levels and composite bumper thickness tb varying for six steps making a total of 30 experiments. optimization was carried out using matlab r2015a. response models were developed and the polynomial with highest r2 value and lowest rmse was selected for the optimization. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rafukka: optimization of sandwich bumper for three year old child neck injury prevention. azojete, 20(2):483-490. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 487 3. results and discussion 3.1 bumper optimization the arrangement of the optimization levels and simulation results obtained from the design samples are shown in table 2. table 2: design points and crash responses for sandwich bumper foam thickness (mm) composite bumper thickness (mm) (tb) neck moment (nm) (nm) 0 1 100.8 1.2 96 1.4 95 1.6 84 1.8 89.2 2 81.5 25 1 48.8 1.2 49.6 1.4 55.7 1.6 56.3 1.8 48.6 2 43.6 50 1 20 1.2 18.8 1.4 26.4 1.6 26.8 1.8 20.5 2 26.1 75 1 33.6 1.2 35.8 1.4 34.1 1.6 25.7 1.8 25.7 2 29.5 100 1 30 1.2 37.2 1.4 33.4 1.6 27.5 1.8 26.9 2 28.1 3.1.1 response surface model for neck moment (nm) the response surface model parameters for the neck moment are shown in table 3. table 3: response surface parameters for neck moment response surface model r2 -adj rmse 1st 0.6368 0.6098 15.95 2nd 0.9432 0.9314 6.69 3rd 0.9636 0.9497 5.73 thus, the response model polynomial function of cubic form having highest r2 value and lowest rmse as shown in table 3 was chosen as the objective equation [2] http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):483-490. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 488 nm(tf, tb) = 90.51 − 3.255tf + 20.98 tb + 0.03832 tf 2 + 0.3833tftb − 12.67 tb 2 − 0.0001129 tf 3 − 0.005433 tf 2tb + 0.07857 tftb 2 [2] optimization of the neck moment was formulated as follows: s.t. 1 ≤ tb ≤ 2 the response surface is as shown in figure 6: figure 6: response surface for neck moment the composite bumper thickness seemed to have no effect on the neck moment as seen in figure 6. addition of foam to the composite beam decreases the neck moment experienced by the child’s neck. a huge neck moment reduction can be noticed from about 90 nm for 0 mm to about 25.4 nm for 68.76 mm. further increase in foam thickness to 100mm increases the neck moment to 38nm which is still below the recommended limits of 68 nm (eppinger et al., 1999). the optimization results found the minimum neck moment of 25.4 nm occurs at of 68.76 mm and of 2 mm. a simulation was carried out using these values to assess the objective equation [2], and 21 nm moment was obtained which is 16% less than the value estimated by the equation. 3.2 parametric analysis to better explain the effect of the composite bumper and foam thickness on the injury level of 3yo child, an analysis was carried out to determine how bumper beam and foam thickness affect neck moment. 3.2.1 effect of composite bumper beam and foam thickness on neck moment figure 7 shows that, sandwich bumper beam drastically reduces high neck injuries. a sandwich beam with about 50 mm foam thickness reduces the neck moment to below 30 nm. though there is little increase in the moment with foam thickness above 60 mm due to decrease in energy absorption of thick foam at densification stage, the moments were all low and within an acceptable range. neck moments for all foam and composite bumper thickness were below the nhtsa specified limits of 68nm for three-year-olds. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com rafukka: optimization of sandwich bumper for three year old child neck injury prevention. azojete, 20(2):483-490. issn 15962490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 489 figure 7: effect of foam thickness on neck moment of 3yo child occupant for various composite bumper thicknesses the injuries sustained by child occupant during crash depend on the magnitude of peak crushing force which determines vehicle deceleration transmitted to the occupant. 3.2.2 effect of foam thickness on crushing force as a basis for explaining the capability of sandwich bumper in reducing the crushing force on impact, a 1 mm composite bumper thickness ( was selected, because it is considered to have the low neck moment. figure 8 shows the variation of crush force with time for foam of different thicknesses. it demonstrates that energy absorption (related to area under the graph) of foam leads to a decrease in crushing force. as an example, taking 50 mm of foam to a composite beam reduces the peak force by 12%, and this lowers the severe injury condition to the child occupant as confirmed by the nm values shown in figure 7. the first peak in the force-time curve was a result of first crushing contact of the foam part of the bumper with rigid wall and this is the reason for the noisy signals appearing on part of the curve just before the end of first peak as seen in figure 8. figure 8: crushing force – time histories of 1mm composite bumper for various foam thicknesses 4.0 conclusions this work investigates the effect of sandwich bumper thickness on child occupant injuries. 3yo child dummy was used in crash simulations using the car fe model in ls dyna code. neck moment was evaluated for various and . objective functions were determined using curve fitting for nm which were in turn used in the optimization. the optimization was successful in determining the and that minimizes injuries potential to child occupants. optimum design of sandwich bumper that yield lower neck moment of 25.4 nm was 68.76 and 2 mm . optimized sandwich bumper is useful in improving child occupant’s safety in addition to crs. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):483-490. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahimrafukka@yahoo.com 490 conflict of interest the authors declare that there is no conflict of interests regarding the publication of this paper. acknowledgement the authors would like to acknowledge bayero university, kano, nigeria for the supports in works related to this paper. references donga, a. 2011. application of sandwich beam in automobile front bumper for frontal crash analysis. unpublished doctoral dissertation, wichita state university, college of engineering, department of mechanical engineering elmarakbi, a., krznaric, v., sennah, k., altenhof, w. and chapman, m. 2013. crashworthiness of vehicle-to-pole collisions using a hybrid iii three-year-old child dummy. international journal of vehicle systems modelling and testing, 8(1): 1–37. eppinger, rh., sun, e., bandak, f., haffner, m., khaewpong, n., maltese, m., kuppa., s., nguyen, t., takhounts. e., tannous, r., zhang, a. and saul, r. 1999. development of improved injury criteria for the assessment of advanced automotive restraint systems ii (docket no. nhtsa-1999-6407-0005). national highway traffic safety administration, washington, d.c. li, z., zhang, j. and hu, j. 2013. surface material effects on fall-induced paediatric head injuries: a combined approach of testing, modelling and optimisation. international journal of crashworthiness, 18(january 2015): 371–384. http://doi.org/10.1080/13588265.2013.801291 mahadevaiah, u., burger., m. and maurath., c. 2013. lstc hybrid iii 6 year old finite element model documentation. livermore software technology corporation, united states. marzougui, d., kan, cd. and bedewi, ne. 1997. development and validation of an ncap simulation using ls-dyna3d, national crash analysis center paper, 12(3): 23–29. meijer, r., wisgerhof, r., wismans, j. and been, b. 2010. scaling head-neck response data and derivation of 5th percentile female side-impact dummy head-neck response requirements in nbdl test conditions. international journal of crashworthiness, 15(1): 115–115. http://doi.org/10.1080/13588261003611903 naik, nk., chandra sekher, y. and meduri, s. 2000. damage in woven-fabric composites subjected to low-velocity impact. composites science and technology, 60(5):731–744 navale, ab., chippa, sp., chougule, da. and raut, pm. 2021. crashworthiness aspects of electric vehicle design, international journal of crashworthiness, 26(4): 368-387. national crash analysis centre .2015. application: finite element model archive. retrieved from http://www.ncac.gwu.edu/vml/models.html. rafukka, ia., sahari, bb., nuraini, aa. and manohar, a. 2017. influence of vehicle sandwich bumper beam on child vehicle occupant head injuries in frontal crashes. science. international journal lahore, 29(1): 109–113. salwani, ms., sahari, bb., ali, a. and nuraini, aa. 2014. the effect of automotive side member filling on car frontal impact performance. journal of mechanical engineering and sciences, 6: 873–880. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 136 arid zone journal of engineering, technology & environment original research article design and fabrication of solar and gasoline dual-powered lawn mower k. o. abdulrahman1, h. k. ibrahim1*, k. k. adeleke1, b. o. azeez1, i. a. jamiu1, r. a. babatunde1, k. o. abdulazeez2 and j. o. aweda1 1department of mechanical engineering, faculty of engineering and technology, university of ilorin, 2maintenance department, dangote refinery and petrochemicals fze, nigeria *corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng article information abstract the need to improve existing lawnmowers is highly essential, especially when there is availability of alternative and renewable sources of power (solar energy). a readily available two-stroke internal combustion engine and solar panel were used to drive a cutting tool made from a locally available cutlass. the mechanical power from the internal combustion engine was converted by an alternator to electrical power and transmitted through the electric motor. the mower's battery is recharged by a 30w solar panel. to avoid completely draining or overcharging the battery, the solar panels were linked in series with an electric charge controller. the lawn mower's cutting blade is fixed to a 12-volt, one-horsepower dc motor, which is powered by two seriesconnected 12-volt, seventy-five-amp lead accumulators. through the use of solar energy captured by the solar panels, the dc batteries (lead accumulators) are replenished. the hybrid powered lawn's intricate design was developed and the performance demonstrated the field efficiency of 83% and 87% when powered with solar and combustion engines respectively. the blade height is adjusted for the desired height of the cut. the battery which takes approximately 2 days to recharge mows a total area of 455m2 of lawn. the mower showed neat mowing of the grasses with ease of operation. submitted: 27th august 2024 revised: 8th february 2025 accepted: 10th february 2025 keywords: cutting blade grass cutter lawn mower renewable energy solar energy sustainability © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the use of solar power as an alternative source of energy has been in existence long before now but has not well been utilized for diverse applications due to its intermittent characteristics and the use of other sources of energy. in recent times, solar technologies have been used as an alternative or backup power supply for homes and appliances (amin et al., 2021; qazi, 2017). in a country like nigeria, with a high dependency on fossil fuel for energy generation, taking a shift from the dependency on fossil fuel will go a long way in providing better and cleaner sustainable alternative means of power generation and usage. but recently, awareness of fossil fuel pollution and its contribution to global warming (valavanidis, 2022) and the fact that fuel energy is non-renewable and unsustainable thereby awakening applications and research in renewable energy generation technologies like solar. there is a dire need for the environment to be always kept tidy and clean. this is very crucial, especially in the physical environment in which man lives. in such environments mostly gardens, parks, institutional settings or estates, it is common to see manual labourers with the use of hand tools to cut grasses. these tools include machete, hoes, cutlasses, rakes, etc. but because of its discomfort for large lawns and time-wasting man developed what is known as a mechanical machine. nowadays, mechanical machines such as lawnmowers are becoming more and more common in society, most especially in urban areas. the working principle of lawnmowers is mainly to provide high-speed rotation to the blades, which aids in cutting the grass through generated kinetic energy. the blades may be powered either by pushing the mower forward to operate the mechanical blades by an electric motor, by solar power or by a small internal combustion engine to spin the azojete march 2025. vol.21(1):136-144 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:ibrahim.kh@unilorin.edu.ng mailto:ibrahim.kh@unilorin.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 137 blades. regarding the current literature availability, many variations of lawn mower exist in the global markets, which may not fulfil the performance and operational cost criteria (dutta et al., 2016). the hybrid power lawn mower can be described as the application of different power sources such as solar energy or electrical energy to power an electric motor which in turn rotates a blade which does the moving and trimming of the lawn to suit desired needs or convenience. the use of solar energy or electrical energy in this sense is employed to charge the battery which supplies the current needed by the motor and in turn enables the rotation of the blade (patel, 2022). therefore, the main objective of this study is to improve existing lawn mowers through the design and fabrication of an efficient and cost-effective dual-powered lawn mower (that is powered by solar and gasoline) from locally sourced materials thereby reducing the problem of carbon dioxide emission and increasing reliability. 2. materials and method this work involved the systematic design, fabrication, and evaluation of a hybrid lawn mower. the design considereation include the material selection, functionality or usability, material availability, cost and manufacturability are the factors considered in the design and fabrication of the hybrid lawn mower. the performance testing was carriedout to arrive at a more effective and efficient final product that could handle cutting of grasses of different height combining two energy sources. as such, to complete the process of design and fabrication of the hybrid lawn mower, careful consideration and calculations of parts were followed. these include the material and shape of the blade, speed of rotation of the motor, power ratings of the solar system and combustible engine and the sizing of the deck. 2.1 blade design lawnmower blades can be made from different materials but the most suitable blade for fabrication is steel. stainless steel was considered in the design due to its lightweight and corrosion resistance. the light weight of stainless steel could also have a positive impact on the consumption of power during the operation of the mower. the shape of the blade was also taken into consideration. there are different blades ranging from tapered blades, mulching blades, gator blades, and high lift blades. a mulching blade is chosen (see figure 1) due to its high efficiency on both dry and damp surfaces and any type of soil. rotating shafts of the blades have a high mass; thus, a mulching blade is selected to have an increased cutting edge (akinyemi and damilare, 2020). blade length, width and thickness were taken to be 300 x 30 x 2 mm. the blade density was taken as 7500 kg/𝑚3 since the material is made of stainless steel (quaranta and davies, 2022). therefore, volume, mass and weight were calculated using the expressions below. volume of blade = area × thickness 1 mass = density × volume 2 weight of the blade = mass × acceleration due to gravity 3 also, the torque of the cutting blade, angular velocity of the blade and power generated by the blade were calculated using equations 4 to 6. torque = weight × radius 4 angular velocity = 2 πn/60 (taking n as the speed of rotating of the blade in rpm) 5 power p= torque t × angular velocity ω 6 the power generated at the blade is 155.49 watt, which is approximately 0.21 hp. http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 138 figure 1: cutting blade of the lawn mower the edge of the cutting blade is tilted at an angle of 30⁰, this is done to increase the cutting edge and also allows the blade to cut the grass and bring it back to the deck where it will be cut into smaller pieces before falling back to the lawn (dange et al., 2011) 2.2 handle of the lawnmower the load of the machine is centralized and to accommodate the length of the solar panel, a length of 920 mm at an angle of 60º was selected. to determine the maximum bending moment (mmax), equation 7 (khurmi and gupta, 2005) was utilized. the handle of the lawn mower is shown in figure 2. mmax = σi y (7 where 𝜎 is the stress, i is the moment of inertia and y is with respect to the length taken as y = xcosθ to determine the stress exerted on the system, equation 8 was used. 𝛔 = f a 8 where f is force (n) and a is the cross-sectional area 𝑚2 however, the area of the frame is 152 𝑚2 force is 45 n (where the total weight of the machine is 10 n and the battery is 35 n) therefore, 𝛔 = 45 152 = 0.296 𝑁/𝑚2 where i is the moment of inertia, given as: i = π (d4−d4) 64 9 and y with respect to the length is taken as y = xcosθ http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 139 figure 2: handle of lawn mower (akinyemi and damilare 2020) 2.3 design of the pulley system the design of the pulley system as shown in figure 3 was based on the design equation of khurmi (2005). figure 3: pulley design pulley diameter/speed ratio = d1 d2 = n2 n1 10 where, 𝐷1= diameter of the motor pulley, 100mm 𝐷2= diameter of blade shaft pulley 𝑁1= speed of motor pulley = 1500 rev/min 𝑁2 = desired blade shaft speed, ≥3000 rev/min finally, 𝐷2 is calculated to be 50 mm. 2.4 efficiency of the combustion lawn mower the efficiency of the machine is considered based on the total area covered and time taken. to calculate the forward velocity, for the forward distance of 38m, the time taken was 120𝑠. therefore, the average forward velocity = 38 120 = 0.32 𝑚/𝑠 to obtain the field efficiency, http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 140 theoretical field capacity (tfc) = forward speed x theoretical width 11 the theoretical width of the blade = 0.30m tfc = 0.32 x 0.30 = 0.095 m2/s effective field capacity (efc) = total area covered/total time taken 12 = 40 m2/ 481 sec = 0.083 m2/s therefore, the field efficiency = (0.083 /0.095) x 100 = 87% 2.5 solar panel selection solar energy is a time-dependent energy that occurs at irregular intervals. therefore, energy must be stored so it can be readily available for use when there is no further supply of the sun’s energy. in nigeria, the peak sunny hours per day is approximately 5 to 6 hours daily (sinha and marthur, 2020). selection of the solar panel requires other considerations apart from the average sunlight per day. the battery capacity, current drawn by the mower and operation of the mower are also taken into consideration. 2.6 battery sizing to charge the battery, a solar panel is expected to tap the solar energy from the sun and convert it to electric energy that will be put away in the battery connected to it. a charge regulator that will be wired between the solar board and the battery is likewise required. the reason for the controller is to prevent the battery from the solar panel when there is no insulation or production of electricity. it likewise prevents excessive charging when the battery gets fully charged and controls the voltage getting to the battery. 2.7 solar sizing design the solar panel selected is 2.5 amps rated at 30 watts average battery charged per day = 2.5 a × 6 h = 15 ah the battery will be fully charged in (charging rate) = 75𝐴ℎ 19𝐴⁄ = 3.95 hours. figure 4 and 5, table 1and plate 1, give a detailed description of the lawn mower and its component parts. figures 4: top view and part name of the proposed lawn mower http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 141 table 1: detailed description of the lawn mower and its component parts s/n part names i tyre ii battery iii frame iv handle v internal combustion engine vi belt vii solar panel figure 5: rendered view of the proposed lawn mower plate 1: side view of the hybrid lawn mower 3. results and discussion the hybrid-powered lawn mower was fabricated and tested. during the machine operation, solar power from the battery is transmitted to the blade to achieve cutting. also, the machine using its hybrid system through its alternator (convert mechanical energy to electrical energy) was able to perform cutting operations. the electric circuit ensured that power was transferred from the battery to run the dc motor, while the solar panel continuously charged the battery during operation. the blade generated power from the dc motor at a speed of 1500rpm. when the switch is on, the electrical energy from the battery powers the motor which in turn drives the blade. the solar panel generates current to recharge the battery, thereby compensating for battery discharge. the rotating blade continuously cuts the grass as the mower is being propelled. during the operation, it was convenient to cut grasses at different heights using an adjustable lever mechanism attached to the deck area of the machine. for the combustible operation of the lawn mower, the prime mover was connected to the alternator through a pulley belt which transfers mechanical energy to electrical energy to the dc motor that is responsible for driving the blade during the cutting process. the alternator is also responsible for charging the battery. table 2 shows the results obtained from mowing different types of grasses using the solar power of the hybrid mower. table 3 shows the results obtained from mowing different types of grass using the combustible engine. the two systems were made to cut different grasses of the same coverage area (16 m2) over specific time intervals after which the grass height of the cut grasses was then measured. figure 6 shows the battery drop and fuel level as it relates to the information provided in table 1 and table 3. http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 142 the result outcomes revealed a similar trend with both systems showing that spear grass has the lowest heights of 130 mm and 120 mm in using solar and combustible engines respectively. while stubborn grass has the highest heights of 600 mm and 650 mm using solar and combustible engines respectively. table 2: results for mowing different types of grass using solar s/n sample plot coverage area (m2) battery drop (v) time (s) grass height (mm) 1 carpet grass 16 0.23 300 470 2 spear grass 16 0.3 600 130 3 stubborn grass 16 0.35 900 600 4 soft grass 16 0.22 1200 400 total 3000 table 3: results for mowing different types of grass using combustion engine s/n sample plot coverage area (m2) fuel level (l) time (s) grass height (mm) 1 carpet grass 16 5.0 300 450 2 spear grass 16 4.1 600 120 3 stubborn grass 16 3.7 900 650 4 soft grass 16 3.0 1200 420 total 3000 figure 6: battery drop and fuel level of the lawn mower after testing it can be observed in figure 6 that the fuel consumption drops over the time the mower was in operation and the change in the battery voltage over time does not change as the solar panel continues to receive solar energy to charge the battery. also, with the use of a charge controller, the charging regulation was achieved. the efficiency of the solar lawn mower designed and developed is 87% which is well above average and this is due to the power output of the electric motor which drives the blade attached to the shaft of the motor. the 100w solar panel can adequately charge the battery (40ah), for approximately 5 hours, which is being regulated by the charge controller, however, the speed of the motor which is 3000rpm rotates the blade causing it to cut the grass until the battery completely discharges. 300 600 900 1200 column1 fuel level 5 4.1 3.7 3 battery drop 0.23 0.3 0.35 0.22 5 4.1 3.7 3 0.23 0.3 0.35 0.22 0 1 2 3 4 5 6 0 0.2 0.4 0.6 0.8 1 1.2 fu e l l ev el b at te ry d ro p time (s) http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 143 in comparison to work done by akinyemi and damilare (2020), soyoye (2021), tanimola et al. (2014), madhav and bhaskar (2015) and mil'shtein et al. (2002), the cutting efficiency for different grases wer obatianed as 85%, 70.50% to 84.10%, 93%, 64%, 81-84% respectively. the results of the present study have shown that the produced lawn mower is more efficient, with lower noise and with lower energy cost. and when is solar powered, no air pollution was caused as gasoline mowers produced a lot of noise and affected the environment. 4. conclusion the development and performance evaluation of the hybrid-powered lawn mower highlight its effectiveness and environmental benefits. powered by a 12-volt, one-horsepower dc motor connected to lead-acid batteries replenished via solar energy, the mower demonstrated commendable field efficiencies of 83% and 87% when operating on solar energy and a combustion engine. the result of this study has shown that combining two energy sources to cut grasses of different heights can be more effective and efficient. it also provides the option of choice in powering the mower when compared to the normal lawn mower powered by combustion engine only. furthermore, it shows the advantage of switching between power sources when one is unavailable. this study affirms the viability of hybrid power systems in enhancing energy efficiency and reducing environmental impact, paving the way for further innovations in sustainable lawn care technologies. references amin, sb., chowdhury, mi., ehsan, sa. and iqbal, sz., 2021. solar energy sustainability in bangladesh: tackling the management challenges. in design, analysis, and applications of renewable energy systems, 705-734. academic press. https://doi.org/https://doi.org/10.1016/b978-0-12-824555-2.00034-4 dutta, pp., baruah, a. and konwar, a., 2016. a technical review of lawn mower technology. adbu journal of engineering technology, 4. qazi, s., 2017. pv systems affordability, community solar, and solar microgrids. standalone photovoltaic (pv) systems for disaster relief and remote areas, 177-202. https://doi.org/https://doi.org/10.1016/b978-0-12-8030226.00008-3 valavanidis, a., 2022. global warming and climate change. fossil fuels and anthropogenic activities have warmed the earth’s atmosphere, oceans, and land. hoboken, new jersey, united states: environmental toxicology and chemistry (et&c) aligned with john wiley & sons. 1–42. https://www.researchgate.net/publication/358498680_global_warming_and_climate_change_fossil_fuels_ and_anthropogenic_activities_have_warmed_the_earth’s_atmosphere_oceans_and_land patel, s., 2022. production of multipurpose agricultural vehicle (doctoral dissertation, rajasthan technical university). akinyemi, ao. and damilare, as., 2020. design and fabrication of a solar operated lawnmower. international journal of innovative science and research technology (ijisrt), 5(10). quaranta, e. and davies, p., 2022. emerging and innovative materials for hydropower engineering applications: turbines, bearings, sealing, dams and waterways, and ocean power. engineering, 8: 148-158. dange, ar., thakare, sk. and rao, ib., 2011. cutting energy and force as required for pigeon pea stems. journal of agricultural technology, 7(6): 1485-1493. khurmi, rs., & gupta, j.k. (2005). a textbook of machine design. s. chand publishing. akinyemi, sa., adebayo, of., nyakuma, bb., adegoke, ak., aturamu, oa., olaolorun, oa., adetunji, a., hower, j.c., hood, mm. and jauro, a., 2020. petrology, physicochemical and thermal analyses of selected cretaceous coals from the benue trough basin in nigeria. international journal of coal science & technology, 7: 26-42. http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng https://www.researchgate.net/publication/358498680_global_warming_and_climate_change_fossil_fuels_and_anthropogenic_activities_have_warmed_the_earth's_atmosphere_oceans_and_land https://www.researchgate.net/publication/358498680_global_warming_and_climate_change_fossil_fuels_and_anthropogenic_activities_have_warmed_the_earth's_atmosphere_oceans_and_land arid zone journal of engineering, technology and environment, march 2025; vol.21(1):136-144. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ibrahim.kh@unilorin.edu.ng 144 sinha, y. and mathur, sm., 2020. development and performance evaluation of solar powered lawn mower. international journal of current microbiology and applied sciences, 9(5): 3378-3384. venkatesh, k., priyanka, k., sridhar, r. and sakthivel, a., 2015. fabrication and analysis of lawn mower. international journal of innovative research in science, engineering and technology, 4(6): 606. soyoye, b., 2021. development and performance evaluation of a solar powered lawn mower. turkish journal of agricultural engineering research, 2(2): 348-362. mil'shtein, s., teynor, w., paquin, b., deloge, t., tran, y. and snoonian, r., 2002. solar-electric powered lawnmower with electronic minimization of energy consumption. u.s. patent application 09/783,454. tanimola, oa., diabana, pd. and bankole, yo., 2014. design and development of a solar powered lawn mower. international journal of scientific & engineering research, 5(6): 215-220. madhav, ph. and bhaskar, hb., 2015. development of environment friendly manually operated rotary lawn mower. international journal of engineering and management research (ijemr), 5(1): 217-219. http://www.azojete.com.ng/ mailto:ibrahim.kh@unilorin.edu.ng arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):85-92 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 85 original research article evaluating the effect of temperature and prolong storage on hibiscus cannabinus (kenaf) extracts in drinking water treatment a. n. jones, b. b. kurna and u. a. ibrahim department of civil and water resources engineering, faculty of engineering, university of maiduguri, pmb 1069, maiduguri, borno state, nigeria *corresponding author’s email address: alfred_ndahi@yahoo.com 1.0 introduction many developing countries are faced with drinking water challenges because of cost issues related to potable water production. water treatment is capital intensive and the quality of river water is varied due to suspended and colloidal particles load resulting from human activities and high storm and runoff events (ali et al., 2010). in many parts of the world, highly turbid river water is used for drinking purpose thereby posing some serious health challenge to the population, especially those living in rural areas who are the most vulnerable. to address this challenge, the united nation came up with 17 goals, tagged sustainable development goals (sdg) in order to improve upon the achievement of the millennium development goals (mdgs) by the year 2030. one of the key aspects of the sdg is the implementation of the integrated water resource management (iwrm) following the mdg goal 6 to half the population without clean drinking water by 2015. the 2030 sdg agenda (for goal 6) recognizes the importance of clean drinking water in bringing development in other areas such as health, education and poverty reduction (un, 2022). additionally, the sdg is to address article information abstract access to clean drinking water is a fundamental human right. yet, improved drinking water is still a major challenge in many developing countries today, retarding progress and human development. this study investigated the coagulation performance of denatured kenaf crude extract (kce) in water treatment using a jar tester. to assess its coagulation performance, kce suspension samples were heated at 60, 97 and 140 °c for 2, 4 and 6 h while the remaining samples were stored for 3, 5, 7, 10 and 14 days respectively prior to the test. the results show that maximum turbidity removal of approximately 98, 97 and 99% was achieved with sample heated to 60, 97 and 140 °c from 86% recorded with the unheated sample. interestingly, kce which had been stored for 3-day duration achieved maximum turbidity removal of 84% compared with the 88% recorded with the fresh sample, although at a dosage, far lower (40 mg/l) than that of the fresh sample (80 mg/l). therefore, the use of denatured kce by heating is advantageous for people in developing countries which resulted in improved turbidity removal performance. conversely, storing the crude sample did not improve the efficiency but its performance was remarkable at lower dosage. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 26 november, 2022 revised 12 january, 2023 accepted 15 january, 2023 keywords: kenaf extract water treatment developing countries turbidity http://www.azojete.com.ng/ mailto:alfred_ndahi@yahoo.com mailto:alfred_ndahi@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):85-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 86 holistically the water management cycle with more countries facing the challenge of being below the 25% threshold, which is the first stage of water stress (un, 2022). in view of the above, there are ongoing studies to improve water supply in developing countries using non-conventional materials. in this regards, several naturally-occurring macromolecules, especially proteins, polysaccharides and mucilage have received considerable interest as potential water and wastewater treatment materials (agarwal et al., 2003, anastasakis et al., 2009). study has shown that natural extracts are biodegradable and cost-effective and are readily available (agarwal et al., 2003). among the natural extracts, moringa oleifera (mo) is the most studied to date (jahn samia, 1998, ghebremichael et al., 2005, ingale and gandhi, 2016). furthermore, several animal products have been widely used in water purification. kawamura (1991) investigated the application of chitosan, a cationic compound, and sodium alginate, a natural polysaccharide (anionic compound) of animal origin, as coagulants in water treatment which resulted in improved water quality comparable to that of alum at a similar dose. rural people have used animal-based products such as isinglass and chitosan obtained from shredded sturgeon fish and crustaceans respectively to treat contaminated water (bratby, 2006, choy et al., 2015). hu et al. (2013) also used low doses of chitosan in combination with as to produce successful turbidity removal with low sludge volume compared to sludge generated by alumas a primary coagulant. this study is aimed at investigating the application of kenaf seed extract as alternative coagulant to the traditional chemicals in water treatment. additionally, its potential in terms of turbidity removal in water is of interest. kenaf (hibiscus cannabinus linn) is a member of the malvaceae family plants. it is an annual herbaceous plant that grows under a range of weather and climatic conditions (meints and smith, 2003). it is widespread in most tropics and is found in ethiopia, zimbabwe, mozambique and uganda (katende et al., 1999). it is also widely distributed in cameroon (agbor et al., 2005) and in northern nigeria where both the leaves and the seed are consumed as a vegetable soup (meera and agamuthu, 2012). figure 1 shows a kenaf flowering plant and some clean seeds used in this study. figure 1: kenaf flowering plant with fruits and dried seed kernels. additionally, the plant has appreciable protein contents which is processed and used by village women to improve breast milk. mariod et al. (2010) characterized the concentration of protein in defatted kenaf seed using petroleum ether and found the percentage of protein in the seed to be 13.04%. the protein is traditionally used in the preparation of coffee and other local food (falasca et al., 2014). agbor et al. (2004) reported the evidence of phenol, tannin, saponin, ( file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:alfred_ndahi@yahoo.com jones et al.: evaluating the effect of temperature and prolong storage on hibiscus cannabinus (kenaf) extracts in drinking water treatment. azojete, 19(1):85-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 87 alkaloids and steroids in kenaf seed. recently, similar observation was also reported by cheng et al. (2016) but included essential oil and fatty acids. the presence of protein and other compounds in kenaf seed makes it imperative to be evaluated in water treatment as coagulant. some properties such as saponin and rip can inactivate microbes as they foam when in contact with water (shaheed et al., 2009). 2. materials and methods 2.1 collection of kenaf seeds dried kenaf seeds were obtained in hawul local government area of borno state-nigeria. fresh dried seeds were sorted, packaged and labeled appropriately for ease of identification and transported to the civil engineering laboratory at the university of birmingham, uk for processing, preparation and analysis. the seeds were cleaned by washing with tap water and damaged seeds were removed. the cleaned seeds were then dried in an oven at 60ºc for six hours before grinding. 2.2 extraction of the active coagulant compound dried kenaf dried seeds were ground to fine powder using a laboratory disc miller (tema mill, germany) for two minutes to obtain the desired powder. the seed powders obtained were sieved through a set of stainless steel sieves (600 to 212μm) according to jones and bridgeman (2016). the powders retained on the 212 and 300µm were combined and used in the study. one mole sodium chloride (1.0 m nacl) solution was used in this experiment to extract the coagulating compounds in the seed (jones and bridgeman 2016). kenaf crude extract (kce) was prepared from the ground seed powders according to jones and bridgeman (2016) where 1.0 m nacl solution was added to the seed powder to make 2% (w/v) suspension. thereafter, 2g of the seed powder in 100 ml nacl. the suspension was vigorously stirred using a magnetic stirrer for 15 min at room temperature (19±2ºc). the suspension was then centrifuged at 4000 rpm for 10 min using a heraeus megafuge16 (thermo scientific, germany). the suspension was decanted, and the residual solids were dried in an oven at 50ºc overnight. the weight of the dried solid material was measured to ascertain the amount of seed powder used in making the suspension. the decanted suspension was then filtered through a whatman no. 42 filter paper and the filtrate used as coagulants in a jar test experiment. 2.3 denaturation process adopted all processes were adopted from jones and bridgeman (2016) where kces were heated at temperatures of 60, 97 and 140oc for 6, 4 and 2 hrs respectively, using a hot plate. the heated samples were then centrifuged at 4500 rpm for 10 min and were filtered through a whatman no. 42 filter paper. similarly, the extract was stored for 1, 3, 7, 10 and 14 days to denature the extract. 2.4 preparation of the synthetic turbid water this preparation was similarly adopted from jones and bridgeman (2016) in which turbid water samples for the jar test experiments were prepared by adding kaolin particles into tap water. 40g of laboratory grade kaolin (fluka and high grade, sigma aldrich) was added to 400ml of tap water and the suspension stirred for 30 min using a magnetic stirrer. the suspension was made up to 1l by adding 600ml of tap water and then stirred for further 30 minutes. the suspension was allowed to stand for 24hr for the kaolin to hydrate. the suspension was vigorously mixed for five minutes and the contents mixed with 30 litres of tap water and allowed to stand overnight for particle settlement. the supernatant was decanted, and its turbidity measured using a turbidity meter. depending on the level of turbidity required, the supernatant was either diluted with tap water or concentrated with kaolin suspension. http://www.azojete.com.ng/ mailto:alfred_ndahi@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):85-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 88 2.5 running the jar test experiment jar tests were conducted using a standard apparatus comprising 6 number of 1 litre beakers (phipps and bird, 7790-900b usa) to evaluate the optimum coagulant dose for the coagulation tests according to jones and bridgeman (2016). for effective dispersion of the coagulant the water was rapidly mixed at 200rpm for 1 minute during which various doses of the coagulant were added to the beakers. the mixing speed was then reduced to 30rpm for another 30 minutes to simulate the flocculation stage. the suspension was then allowed to stand undisturbed to facilitate settlement for 1hour. a final treated water sample (10 ml) was drawn 2cm from the top surface of the water in the beakers using a syringe. the turbidity of the water was then measured using a turbidity meter (hi 93703, hanna) and the water ph was measured with a ph meter (mettler toledo sevengo, switzerland). all experiments were conducted at room temperature (19±2ºc) in triplicates. 3. results and discussion table 1 presents the effects of temperature on a stock solution of kce which was heated at 60, 97 and 140 °c for 6, 4 and 2 hours respectively. the results revealed that, water sample which had been treated with the heated kce at 140ºc for 2 hours achieved the highest turbidity reduction of approximately 99% with 60 mg/l dose while the 60 and 97°c treated extracts achieved 98 and 97% performance with a reduced dose of 40 mg/l respectively. at a higher coagulant dose of 80 mg/l, the native sample achieved only 91% performance. the performance of kce after heat treatment was significantly higher because, at 10 mg/l dose, all the samples recorded significant efficiencies of 91% while the 60 °c treated sample achieved 95% performance. an increase in dose resulted in increased performance throughout the coagulation process, although, there was reduced performance beyond 60 mg/l across all the heated extracts. however, the overall coagulation performance of the sample was impressive even at starting dose of 10 mg/l. one notable feature of kce was that heating to 60 °c improved its performance across all doses. similarly, kce heated to 140 °c showed the same trend but its performance deteriorated slightly at 100 mg/l dose, from 98.4 to 98.5%. however, the general performance of denatured kce deteriorated after the optimum dose of 80 mg/l except for the native sample which only deteriorated at 100 mg/l to achieve 85% efficiency. table 1: effect of heat treatment on kce in 200 ntu turbidity removals coagulant dose (mg/l) ∆t=0°c %reduction ∆t=60°c %reduction ∆t=97°c %reduction ∆t=140°c %reduction 10 77.7 95.1 91.1 93.5 20 80.0 97.3 95.0 96.2 40 84.8 98.2 96.5 98.1 60 85.9 97.5 95.7 98.7 80 85.5 97.3 97.0 98.4 100 85.1 95.6 93.8 98.5 figure 2 shows the efficiency of kce as a coagulant after storing the stock solution for 1, 3, 7, 10 and 14 days. the results revealed that by storing kce samples for these days did not yield any significant performance of extracts. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:alfred_ndahi@yahoo.com jones et al.: evaluating the effect of temperature and prolong storage on hibiscus cannabinus (kenaf) extracts in drinking water treatment. azojete, 19(1):85-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 89 coagulant dose (mg/l) 1-day 3-day 7-day 10-day 14-day figure 2: effect of storage time on the performance of kce the performance of fresh kce at 80 mg/l was approximately 88% turbidity removal while kce, which was stored for 3days, yielded turbidity reduction of 84.4% with 20 mg/l dose. additionally, kce which had been stored for 7, 10 and 14 days yielded no meaningful coagulation performance. with higher doses, residual turbidity in treated water was found to be more than the initial turbidity, especially with the 14 days stored extract. however, at 40 mg/l dose, fresh and the 3day stored extract achieved 81% turbidity removal performance, residual turbidity was less than 25 ntu, from 130 ntu in the water. similarly, maximum turbidity reduction was observed with a dose of 80 mg/l in water treated with the 10-day than in the 7-day extract. it was clear that storing kce for a lengthy time did not in any way improve its performance, rather its water treatment potential deteriorated. although the efficiency of the 3-day stored sample was lower than the fresh extract, it required only half of the fresh sample dose to achieve the 84% removal efficiency. the result further shows that the 3−day sample demonstrated good performance compared with the other extracts across the doses used in the treatment process. the effect of storage duration of raw seeds was also considered in river water with a low turbidity of 19 ntu (result not presented in figure). the seeds were stored at room temperature of 19 ± 2 °c for 24 months. kenaf extract obtained from raw seeds achieved up to 94% performance using a dose of 40 mg/l. the overall performance achieved with the stored seed extracts was better than the 73% recorded with the fresh extracts after harvesting. this results, however, is at variance with that of katayon et al. (2006) who observed a better performance with fresh mo seed. in each case, turbidity removal efficiency was significantly higher with stored samples than with the fresh seed extracts. protein is said to become denatured when its folding structure is altered as a result of exposure to certain elements of physical factors (e.g. heat), causing the protein to become biologically inactive or its overall primary activity affected. proteins can also degrade and denature upon storage, with such denaturation leading to visible aggregation and turbidity formation (sharma and luthra-guptasarma, 2009). in some instances, proteins can be re-natured but in most cases the denaturation is irreversible. the work reported here evaluated the effect of denatured kce against the native state as alternative coagulants. their performances were assessed after heat treatment to some specified temperature ranges. a denatured kce sample by storage did not yield any improvement in performance due to its low protein concentration. another possible reason for low performance in kce is that the r e si d u al t u rb id it y (% ) http://www.azojete.com.ng/ mailto:alfred_ndahi@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):85-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 90 remaining coagulant proteins after denaturation are low compared with the particle concentration resulting in low collision efficiency. however, the results are not in agreement with the findings of katayon et al. (2004), who noted a decrease in turbidity removal efficiency of mo extracts stored longer than a day. the performance trend in kce is not surprising because the denaturation may have removed some proteins with limited coagulation potential in the seed, thus disrupting its random configuration, having little protein left for coagulation. while some studies have shown that mo extract is a cationic electrolyte (ndabigengesere et al., 1995, kwaambwa and maikokera, 2007), kenaf extract were found to be anionic in this work. certainly, proteins can be denatured within few hours of storage, and such differences in behaviour can lead to different structural conformation. a wide range of characteristics can be exhibited by denatured proteins, from reduced solubility to communal aggregation. after the tenth day, the degradation in performance was severe, extensively caused by the aggregation and precipitation. additionally, there was another issue of physical protein agglomeration and adhesion on the container which could have added to the degraded performance after the tenth day (jones and bridgeman, 2016). there are other physical factors or processes which can cause protein denaturation. heating is one such process, and so samples were denatured at different temperatures and their coagulation performance. a clearer understanding of the impact of protein denaturation by heating was seen in kce. surprisingly, after heat treatment, kce achieved a significant improvement in coagulation efficiency. the denaturation of the proteins was seen to be more advantageous in kce where its non-treated sample presented the worst performance due its low protein concentration which was further subdued by the activity of other contaminants. furthermore, the degree of improvement was varied across the denatured samples at doses of 2060mg/l, but improved performance was observed at higher doses across all the extracts. thus, heating can improve the coagulation potential of kenaf. it was evident that even after the deterioration; the denatured samples still outperformed the maximum efficiency recorded by the non-treated extract. the heat treatment yielded a considerable amount of coagulant protein occasioned by the removal of coagulant-hindering proteins. the extracts are thermo-stable after heat treatment, which is advantageous for people in rural areas where the main source of energy is firewood. furthermore, the heating process improved the effectiveness of the filtration process. in the nontreated extracts, the lipids have the potential of clogging the filter pores. this study shows that the denaturation of proteins that are partially sensitive to storage time and temperature in water treatment are beneficial. the processes are simple and straightforward to adopt in developing countries, requiring no technology. the raw seeds were tested on low turbid water because natural coagulants are poor in coagulating low turbidity water (muyibi and okuofu, 1995). katayon et al. (2006) investigated the effect of different storage conditions of raw mo seed and observed better performance with the fresh extract than in seed which had been stored for one month. conversely, in this study the seed which was stored for more than 24 months was observed to outperform the fresh extracts. this result was, however, not in agreement with the previous study by katayon et al. (2006). 4. conclusion natural extract obtained from kenaf seeds is a potential coagulant in water treatment. processes which could easily be adopted in rural areas such as heating and storage time improve turbidity removal efficiency of the extracts which is largely beneficial. in this study, the heat treated kce sample achieved 99% turbidity reduction from 200 to 1.9 ntu, while the stored kce sample file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:alfred_ndahi@yahoo.com jones et al.: evaluating the effect of temperature and prolong storage on hibiscus cannabinus (kenaf) extracts in drinking water treatment. azojete, 19(1):85-92. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 91 recorded up to 84% turbidity removal efficiencies respectively. application of kenaf extracts in water treatment could increase access to clean drinking water in developing countries to meet the sdg target by the year 2030. however, the production of disinfectant by products (dbps) due to natural organic matter addition is a serious issue of concern in the water industry. therefore, the use of kce in water treatment should be investigated if synthetic chemical is to be use in the disinfection processes after turbidity removal during coagulation to ascertain the level of dbps formation. references agarwal, m., rajani, s., mishra, a. and rai, jsp. 2003. utilization of okra gum for treatment of tannery effluent. international journal of polymeric materials and polymeric biomaterials, 52: 1049-1057. agbor, ga., oben, je., brahim, bo. and ngogang, jy. 2004. toxicity study of hibiscus cannabinus. journal of the cameroon academy of sciences, 4: 27-32. agbor, ga., oben, je. and ngogang, jy. 2005. haematinic activity of hibiscus cannabinus. african journal of biotechnology, 4: 833-837. ali, en., muyibi, sa., salleh, hm., alam, mz. and salleh, mrm. 2010. production of natural coagulant from moringa oleifera seed for application in treatment of low turbidity water. journal of water resource and protection, 2: 259-266. anastasakis, k., kalderis, d. and diamad opoulos, e. 2009. flocculation behavior of mallow and okra mucilage in treating wastewater. desalination, 249: 786-791. bratby, j. 2006. coagulation and flocculation in water and wastewater treatment, iwa publishing, alliance house, london uk, 401p. cheng, wy., haque akanda, jm. and nyam, kl. 2016. kenaf seed oil: a potential new source of edible oil. trends in food science and technology, 52: 57-65. choy, sy., prasad, kmn., wu, ty. and ramanan, rn. 2015. a review on common vegetables and legumes as promising plant-based natural coagulants in water clarification. international journal of environmental science and technology, 12: 367-390. falasca, s., ulberich, a. and pitta-alvarez, s. 2014. possibilities for growing kenaf (hibiscus cannabinus l.) in argentina as biomass feedstock under dry-subhumid and semiarid climate conditions. biomass and bioenergy, 64: 70-80. ghebremichael, ka., gunaratna, kr., henriksson, h., brumer, h. and dalhammar, g. 2005. a simple purification and activity assay of the coagulant protein from moringa oleifera seed. water research, 39: 2338-2344. hu, cy., lo, sl., chang, cl., chen, fl., wu, yd. and ma, jl. 2013. treatment of highly turbid water using chitosan and aluminum salts. separation and purification technology, 104: 322-326. ingale, sp. and gandhi, fp. 2016. effect of aqueous extract of moringa oleifera leaves on pharmacological models of epilepsy and anxiety in mice. international journal of epilepsy, 3(01): 012-019. jahn samia, a. 1998. using moringa seeds as coagulants in developing countries. journal of a wwa, management and operation, 3 (1): 43-50. http://www.azojete.com.ng/ mailto:alfred_ndahi@yahoo.com arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):85-92. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: alfred_ndahi@yahoo.com 92 jones, an. and bridgeman, j. 2016. an assessment of the use of native and denatured forms of okra seed proteins as coagulants in drinking water treatment. journal of water and health, 14: 768-779. katayon, s., megat mohd noor, mj., asma, m., thamer, am., liew abdullah, ag., idris, a., suleyman, am., aminuddin, mb. and khor, bc. 2004. effects of storage duration and temperature of moringa oleifera stock solution on its performance in coagulation. international journal of engineering and technology, 1: 146-151. katayon, s., noor, mjmm., asma, m., ghani, laa., thamer, am., azni, i., ahmad, j., khor, bca. and suleyman, am. 2006. effects of storage conditions of moringa oleifera seeds on its performance in coagulation. bioresource technology, 97: 1455-1460. katende, a., ssegawa, p., birnie, a., holding, c. and tengnäs, b. 1999. wild food plants and mushrooms of uganda. regional land management unit, relma/sida. nairobi, kenya, pp. 490. kawamura, s. 1991. effectiveness of natural polyelectrolytes in water treatment. journal (american water works association), 83(10): 88-91. kwaambwa, h. and maikokera, r. 2007. a fluorescence spectroscopic study of a coagulating protein extracted from moringa oleifera seeds. colloids and surfaces b: biointerfaces, 60: 213-220. mariod, aa., fathy, sf. and ismail, m. 2010. preparation and characterisation of protein concentrates from defatted kenaf seed. food chemistry, 123: 747-752. meera, m. and agamuthu, p. 2012. phytoextraction of as and fe using hibiscus cannabinus l. from soil polluted with landfill leachate. international journal of phytoremediation, 14: 186-199. meints, pd. and smith, c. 2003. kenaf seed storage duration on germination, emergence, and yield. industrial crops and products, 17: 9-14. muyibi, sa. and okuofu, ca. 1995. coagulation of low turbidity surface waters with moringa oleifera seeds. international journal of environmental studies, 48: 263-273. ndabigengesere, a., narasiah, ks. and talbot, bg. 1995. active agents and mechanism of coagulation of turbid waters using moringa oleifera. water research, 29: 703-710. shaheed, a., templeton, mr., matthews, rl., tripathi, sk. and bhattarai, k. 2009. disinfection of waterborne coliform bacteria using luffacylindrica fruit and seed extracts. environmental technology, 30: 1435-1440. sharma, m. and luthra-guptasarma, m. 2009. degradation of proteins upon storage at nearneutral ph: indications of a proteolytic/gelatinolytic activity associated with aggregates. biochimica et biophysica acta (bba) general subjects, 1790: 1282-1294. un 2022. the sustainable development goals report 2016. united nations, new york. accessed 20th november 2022, http://unstats.un.org/sdgs. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:alfred_ndahi@yahoo.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):367-380 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 367 original research article performance evaluation of hot mix asphalt using cow dung ash as filler a. a. murana, v. ude and a. suleiman* department of civil engineering, ahmadu bello university, zaria, kaduna state, nigeria *corresponding author’s email address: abdulsuleiman@abu.edu.ng 1.0 introduction the development of any nation could be linked to an effective and well-planned transport network and other infrastructures. conversely, inadequate transport networks inhibit the level of development a nation can attain. road transport is the most common means of transportation in many nations including nigeria. however, the poor state of roads in nigeria has hindered development and has affected many aspects of life poor road condition, either as a result of poor construction or maintenance practices has necessitated the search for solutions to improve the condition of pavement (nwafor and onya, 2019). in recent times, efforts have been channelled towards utilizing waste materials in the construction industry, especially using organic waste (yaro et al., 2022; badejo et al., 2017; shuaibu et al., 2019; milad et al., 2020; abdulfatai et al., 2023). olusegun and sam (2012) referred to these waste materials as biomass, since they are derived from carbonaceous waste due to natural and human activities the use of cement in asphalt concrete (anand et al., 2006) has led to increased cement demand and production. the increase in cement production causes an increase in co2 (greenhouse gas) and other poisonous gas emissions from production plants and haulage trucks which transport raw materials to factories, and finished products to market. this scenario is against the world campaign to reduce the depletion of the ozone layer since it leads to global warming. these challenges prompted the article information abstract this study evaluates the performance of cow dung ash (cda) in hot-mix asphalt. this was achieved by determining the marshall and volumetric properties of hot mix asphalt (hma). in the hma, cow dung ash partially replaced granite dust at varying percentages using varying bitumen content. the results obtained from the laboratory experiments indicate an increase in stability with an increase in cda and bitumen content. maximum stability of 11.8 kn was obtained at 40% cda and 6% bitumen content. the flow was observed to increase with increasing cda and bitumen content. a minimum flow of 2.7 mm was observed at 5% bitumen and 10% cda content. the unit weight increases with an increase in bitumen and cda content while an increase in cda considerably decreases the void in the mineral aggregate of the mix. additionally, the increase in bitumen and cda content showed a decrease in air voids of modified mix. results obtained showed that an increase in the percentage of void filled with bitumen is directly proportional to bitumen and cda content. the marshal properties such as stability and flow and the volumetric properties such as unit weight, void in mineral aggregate (vma), air voids and voids filled with bitumen were within the range specified by nigerian general specification for road and bridges. it can be concluded that the marshall and volumetric properties of hot mix asphalt performed well with cda as filler and hence, can be recommended for use in hot mix asphalt. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 22 august, 2022 revised 11 february, 2023 accepted 15 february, 2023 keywords: performance evaluation hot mix asphalt cow dung ash filler material http://www.azojete.com.ng/ mailto:abdulsuleiman@abu.edu.ng abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):367-380. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 368 need to seek alternative cementitious materials which can completely or partially replace cement. a potential material which could partially replace cement is cow dung. cow dung is the excreta of herbivorous bovine animals popularly known as cattle. it usually comprises of faeces and urine in a ratio of 3:1 and contains minerals like magnesium, potassium, manganese, and some other minor minerals (gupta et al., 2016). cow dung has a significant amount of ash content, which is bulky, has low carbon content and reduced volatile content after burning. cow dung is used to generate biogas for electricity and generate heat in mud brick houses (rayaprolu and raju, 2012). according to (gupta et al., 2016), cow dung is used in indian villages for plastering walls, cooking through burning generates heat, and the ash as a cleaning agents. salisu (2007) reported that in 2001, nigeria had an estimated 15.6 million cattle with a growth rate of 4.2% and 5.0% in 2002 and 2003 respectively. with an average of 10 kg to 15 kg of cow dung produced daily by a well-fed mature cow, there is bound to be enough cow dung produced on daily basis to be recycled (olusegun and sam, 2012). however, there is a need for proper management and disposal of animal waste to prevent environmental pollution and health challenges such as odour, airborne ammonia, greenhouse gases, and pathogen contamination shown by abubakar and ismail (2012) as cited by saleh and jibrin (2020). there have been successes recorded by researchers like zareei et al. (2017) in partially replacing cement with rice husk ash in concrete since it contains micro silica and murana and sani (2015) replacing cement with bagasse ash in hot mix asphalt. here, we focused on partially replacing quarry dust with cow dung ash as filler in hot mix asphalt. hot mix asphalt is a dense combination of bitumen, coarse aggregate, fine aggregate and mineral filler which relies on the interlocking properties between the aggregate particles for strength and to a lesser extent, the properties of bitumen and filler. hearn et al. (2015) affirmed that asphalt should be used to describe all bituminous mixes used in pavement construction. for filler, which are materials finer than 0.075 mm, portland cement, hydrated lime and fines of crushed rocks are used. to improve the adhesion of bitumen and aggregates, cement of 1 2% by weight of the total mix is added to the natural filler. the void content and stiffness of the ratio of bitumen-fines are affected by the filler (trl, 2002). ojedokun et al. (2014) investigated partially replacement of cement with cda in cement concrete. in the research, it was replaced at 0%, 10%, 20% and 30%. the workability and consistency test conducted on the concrete and cement paste was found to increase with increased cda content. furthermore, prolonged curing increased the strength with 10% cda replacement producing 98% strength when compared with the control at 0%. thakur et al. (2019) investigated the effect of cda on the physical properties of concrete. in the work, the cement was partially replaced with 5%, 10% and 15% cda. from their finding, a 5% replacement level was recommended as optimum cda content. large volumes of cow dung produced from feed yards are constantly on the rise year in year out, which is most often disposed of without treatment abubakar and ismail (2012). human contact with these by-products of cattle could lead to the transmission of diseases such as tuberculosis, e-coli and q fever whose clinical picture is similar to that of influenza (essar et al. 2021). to reduce the negative effect of cow dung, this work evaluates the performance of cow dung ash as a filler material in hot mix asphalt production. , file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng murana et al: performance evaluation of hot mix asphalt using cow dung ash as filler. azojete, 19(2):367-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 369 2. materials and methods 2.1 materials the materials used for this research include aggregates, filler (quarry dust), bitumen and cow dung ash. the aggregates and quarry dust were sourced from zaria quarry yard in kaduna state, nigeria. the bitumen used was the 60/70 penetration grade obtained from mother cat construction company located in zaria. the cow dung was obtained from national animal production research institute (napri), zaria which was calcined at 500oc temperature. 2.2 methods the physical properties of cow dung and constituent materials (aggregates and bitumen) of hot mix asphalt are determined. also, hot mix asphalt with blend of quarry dust/cda as mineral filler are prepared, and marshall and volumetric properties of hma prepared with blend of quarry dust/cda as mineral filler is prepared. 2.2.1 marshal stability test marshal stability test was carried out on the hot mix asphalt (hma) sample containing granite dust as filler. the bitumen content was varied at 4.5%, 5%, 5.5%, 6% and 6.5% by weight of the total weight of the sample (1200g). the marshal test was conducted in accordance with astm d6926-16 (2016). the samples were first compacted at 75 blows on each side at a temperature of about 150oc. the results of the stability, flow and volumetric properties were evaluated to be satisfactory as accepted by nigerian general specifications for roads and bridges (fmwh 2016). 2.2.2 volumetric properties of the hma the volumetric properties conducted include stability, flow, void in mineral aggregate (vma), void filled with aggregates (vfa), void in total mix and voids filled with bitumen 3. results and discussion 3.1 preliminary test on bitumen table 1 shows the results of the preliminary test conducted on bitumen. the test show that the bitumen is a 60/70 penetration grade. table 1: test conducted on unmodified bitumen s/n test conducted unit result light traffic medium traffic heavy traffic standard 1 penetration 0.1mm 68 40/50 60/70 80/100 astm d5-20 2 softening point oc 53 52-60 48-56 42-50 astm d36-14 3 ductility @ 25oc cm 108 100 (min) 100 min 100 min astm d11317 4 specific gravity nil 1.02 1.01-1.06 1.011.06 1.01-1.06 astm d7018a. 5 flash-point oc 269 250 (min) 232 min 250 min astm d92-18 6 fire-point oc 288 nil nil nil astm d92-18 7 solubility in c2s % 100 99.5 min 99 min 99.5 min astm d204215 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):367-380. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 370 3.2 physical properties of the aggregates table 2 depicts the results of the test to determine the physical properties of the aggregates used for this research. from the results obtained, based on standard specification, the aggregates fall within the specified standard. table 2: physical properties of aggregate properties test value standard spec. remarks standard min. max specific gravity (coarse) 2.63 2.6 2.9 ok astm c127-15 specific gravity (fine) 2.54 ok astm c127-15 specific gravity (granite dust) 2.63 ok astm c127-15 flakiness index 31 35 ok bs 812-105.2 (1990) elongation index 23.8 25 ok bs 812-105.2 (1990) aggregate crushing value (%) 20.52 30 ok bs 812: part 110 (1990) aggregate impact value 11.4 35 ok bs 812: part 112 (1990) 3.3 sieve analysis and aggregate gradation sieve analysis was conducted on the coarse aggregate, fine aggregate and filler material in accordance with (astm c136 /c136m-19 2006) to determine the particle size distribution of the aggregate used for this research. the result of the particle size distribution and gradation is represented in figure 1. the gradation limits were found to be within the standards specified by (fmwh 2016). therefore, the material is suitable for the design of hot mix asphalt. figure 1: aggregate gradation curve 3.4 chemical properties of cow dung ash (cda) the oxide composition test was carried out in accordance with (astm d5381-93 2021) using xray fluorescence (xrf) technique. this test was carried out in chemical engineering laboratory abu zaria. the concentration by weight of oxides is presented in table 3. 0 20 40 60 80 100 120 0.01 0.1 1 10 100 p er ce n t p as si n g (% ) particle sizes (mm) sieve analysis upper limit lower limit file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng murana et al: performance evaluation of hot mix asphalt using cow dung ash as filler. azojete, 19(2):367-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 371 table 3: chemical composition of cow dung ash element mgo al2o3 sio2 p2o5 so3 cl k2o cao fe2o3 tio2 mn2o3 sro conc.(%) 2.36 5.37 46.649 1.61 1.22 5.41 3.102 6.210 2.97 2.066 0.573 1.052 a sample of the cda and that of sio2, al2o3 and fe2o3 were analysed. the concentrations of the sio2, al2o3 and fe2o3 were found to be 46.64, 5.37 and 2.97 respectively. the summation of the concentration of sio2, al2o3 and fe2o3 was found to be 55.0, which was classified as a class c mineral admixture according to astm c618 (2019). this is in conformance with the specified standard. table 4 below shows the test results in comparison to the astm standard (astm c618, 2019). table 4: physical properties of mineral filler property granite dust cda specific gravity 2.63 2.56 percentage passing sieve no 200 (0.075 mm) (%) 78.6 72.3 3.5marshal stability test table 5 and figures 2, 3, 4, 5, 6 and 7 show the control results of stability, flow, unit weight, percent voids in compacted mineral aggregates (vma), percent of air voids in each of the paving mixtures (pa), and the void filled with bitumen (vfb) respectively. table 5: marshal and volumetric properties’ results for hma control samples bitumen by weight of mix (%) stability (kn) flow (mm) unit weight (g/cm3) vma (%) pa (%) vfb (%) 4.5 8.2 2.7 2.28 15.93 5.79 63.65 5.0 10.7 3 2.29 16 4.58 71.38 5.5 10.9 3.3 2.31 15.72 3.35 78.69 6.0 10.3 4.2 2.30 16.53 2.95 82.15 6.5 8.1 4.4 2.28 17.69 2.98 83.15 figure 2 shows the plot of the stability of the control mix versus bitumen content. the graph shows that there is an increase in stability with increasing bitumen content with a peak at 5.5% bitumen content which corresponds to 10.9kn. further increase in bitumen content shows a decrease in stability from the maximum stability. it is a well-known fact that higher bitumen content causes bleeding and loss of strength. the increased bitumen content introduced thicker films of bitumen thereby reducing the stiffness of the mix and making it susceptible to deformation. a similar result was obtained by (murana et al., 2014). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):367-380. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 372 figure 2: variation of stability with bitumen content 3.6 variation of flow with bitumen content figure 3 shows the graphical representation of flow of material against bitumen content. iit can be seen that the flow steadily increases with an increase in bitumen content. according to coleman (2002), flow is the displacement occurring during stability tests on samples. the increase in bitumen content reduces the interlocking properties between the aggregates making them prone to displacement. figure 3: variation of flow with bitumen content 3.7 variation of unit weight with bitumen content figure 4 shows the plot of unit weight against varying bitumen content. the unit weight of the specimen was observed to increase with the continuous addition of bitumen content. from the maximum unit weight, the unit weight decreases with additional bitumen content. a similar pattern was obtained by murana and sani (2015). 4 5 6 7 8 9 10 11 12 4 . 5 5 . 0 5 . 5 6 . 0 6 . 5 7 . 0 st a b il it y (k n ) bitumen content (%) 0 1 2 3 4 5 4 . 5 5 5 . 5 6 6 . 5 7 f l o w ( m m ) bitumen content (%) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng murana et al: performance evaluation of hot mix asphalt using cow dung ash as filler. azojete, 19(2):367-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 373 figure 4: unit weight versus bitumen content 3.8 variation voids in mineral aggregate (vma) with bitumen content figure 5 shows the graphical representation of the relationship between voids in a mix of mineral aggregates (vma) and bitumen content. it can be observed that vma decreases with an increase in bitumen content. this can be attributed to the presence of bitumen in the voids of the aggregate. figure 5: vma versus bitumen content 3.9 variation of voids in the mix with bitumen content figure 6 shows the graphical representation of voids in the mix against bitumen content. voids in the mix are the small air voids between aggregates coated with bitumen. from the figure, the voids decrease with an increase in bitumen content. this implies more bitumen content filled the spaces between the bitumen-coated aggregates. a similar pattern was observed when palm kernel ash was used to modify hma (nwaobakata and agunwamba 2014). 2.27 2.28 2.29 2.3 2.31 2.32 4 . 5 5 5 . 5 6 6 . 5 7 u n it w e ig h t ( g/ cm 3 ) bitumen content (%) 15 15.5 16 16.5 17 17.5 18 4 . 5 5 5 . 5 6 6 . 5 7 v o id s in m ix o f m in er a l a g g r ea g te s (% ) bitumen content (%) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):367-380. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 374 figure 6: void in mix versus bitumen content 3.10 variation of voids filled with bitumen (vfb) with bitumen content figure 7 shows the relationship between voids filled with bitumen against varying bitumen content. the figure illustrates that the percentage of void filled with bitumen increases with increasing bitumen content. figure 7: vfb versus bitumen content 3.11 effect of cda on stability figure 8 depicts the relationship between stability against bitumen content at varying cow dung ash (cda) content. as can be seen from the figure, stability increases with increase in bitumen and cda content after which were found to decrease at 6.5% bitumen content. according to (nwaobakata and agwunwamba 2014), additional filler to the optimum filler content reduces contact between aggregates, therefore, lowers the stability. 0 1 2 3 4 5 6 7 4 . 5 5 5 . 5 6 6 . 5 7 v o id s in m ix p a (% ) bitumen content(%) 50 60 70 80 90 4 . 5 5 5 . 5 6 6 . 5 7 v o id s fi ll ed w it h b it u m en ( % ) bitumen content (%) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng murana et al: performance evaluation of hot mix asphalt using cow dung ash as filler. azojete, 19(2):367-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 375 figure 8: stability versus bitumen content at varying cda content. 3.12 effect of cda on flow figure 9 represents flow against bitumen with increase in cda content. from the figure, it shows that the flow was found to increase with increase in cda content which was directly proportional to increasing bitumen content. from this, it can be deduced that increase in mineral filler increases flow. this is in agreement with the work conducted by (modupe et al. 2019). figure 9: flow versus bitumen content at varying cda content. 3.13 effect of cda on unit weight figure 10 illustrates the relationship between the unit weight and bitumen content at varying cda content. from the figure, the unit weight was observed to increase with increase in bitumen content and increase in cda content. it was observed that at 4.5% bitumen content, the unit weight of the control at 2.28 mm was higher than the modified cda hma. this implies that more filler stiffens the mix by filling the voids and reduces the permeability. the work of murana, emekaobi, and laraiyetan (2019) confirms that increased bone ash in hma reduces unit weight. 4 5 6 7 8 9 10 11 12 13 4 . 5 5 5 . 5 6 6 . 5 7 st a b il it y (k n ) bitumen content (%) 0% 10% 20% 30% 40% 50% poly. (0%) poly. (10%) 1 2 3 4 5 6 7 4 . 5 5 5 . 5 6 6 . 5 7 fl o w ( m m ) bitumen content (%) 0% 10% 10% 30% 40% 50% linear (0%) linear (10%) linear (10%) linear (30%) linear (40%) linear (50%) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):367-380. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 376 figure 10: unit weight versus bitumen content at varying cda content. 3.14 effect of cda on voids in mineral aggregates (vma) figure 11 represents the relationship between vma, bitumen and cda content. a decrease in vma with additional filler was observed, which was followed by an increase in vma after reaching a minimum value. it can be deduced that an increase in cda decreases the void in the mineral aggregate of the mix. wagaw, quezon, and geremew (2018) obtained a similar trend when brick dust was used to modify hma. figure 11: vma versus bitumen content at varying cda content. 3.15 effect of cda on voids in total mix (pa) figure 12 shows the relationship between air voids in the cda modified mix at varying bitumen content. introducing cda at 4.5% bitumen content showed an increase in air void of the control mix from 5.79% to 7.02% for the modified mix. the air voids were observed to reduce with increase in cda. this pattern of the result was also obtained by vasudevan (2017) when coal bottom ash was used to modify hma. 2.1 2.2 2.3 2.4 4 . 5 5 5 . 5 6 6 . 5 7 u n it w ei g h t (g /c m 3 ) bitumen content (%) 0% 10% 20% 30% 40% 50% poly. (0%) poly. (10%) poly. (20%) poly. (30%) poly. (40%) poly. (50%) 13 14 15 16 17 18 19 20 21 22 4 . 5 5 5 . 5 6 6 . 5 7 v o id s in m in er a l a g g r eg a te s (% ) bitumen content (%) 0% 10% 20% 30% 40% 50% poly. (0%) poly. (10%) poly. (20%) poly. (30%) poly. (40%) poly. (50%) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng murana et al: performance evaluation of hot mix asphalt using cow dung ash as filler. azojete, 19(2):367-380. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 377 figure 12: void in total mix versus bitumen content at varying cda content. 3.16 effect of cda on voids filled with bitumen figure 13 represents the relationship between voids filled with bitumen, bitumen content and cda content. the values obtained show an increase in the percentage of void filled with bitumen which is directly proportional to bitumen content and cda content. similar pattern was also observed by murana, emekaobi, and laraiyetan (2019). figure 13: vma versus bitumen content at varying cda content. 5. conclusion the conclusions deduced from this research are as follows: 1. the results of the test conducted on the constituent materials such as the aggregates and bitumen show that they satisfy the limits specified by the federal ministry of power, works and housing (fmwh 2016). therefore, this implies the materials can be used in producing hot mix asphalt. 2. the chemical and physical properties of cow dung ash (cda) were found to be satisfactory and can be used as filler in hot mix asphalt. 3. the results of the stability, flow and volumetric properties were found to be satisfactory as accepted by nigerian general specifications for roads and bridges, 2016. 0 2 4 6 8 10 12 14 4 . 5 5 5 . 5 6 6 . 5 7 v o id in t o ta l m ix p a (% ) bitumen content (%) 0% 10% 20% 30% 40% 50% poly. (0%) poly. (10%) poly. (20%) poly. (30%) poly. (40%) poly. (50%) 30 40 50 60 70 80 90 100 4 . 5 5 5 . 5 6 6 . 5 7 v o id f il le d w it h b it u m en ( % ) bitumen content (%) 0% 10% 20% 30% 40% 50% linear (0%) linear (10%) linear (20%) linear (30%) linear (40%) linear (50%) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/abdulsuleiman@abu.edu.ng arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):367-380. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdulsuleiman@abu.edu.ng 378 references abdulfatai, ma.i, rabi’u, i. and suleiman, a. 2023. effects of waste crossed-linked polyethylene electrical waste coating on the properties of bitumen. fudma journal of sciences, 7: 79-89. abubakar, bsui. and nasir i. 2012. anaerobic digestion of cow dung for biogas production. arpn journal of engineering and applied sciences, 7: 169-172. anand, s., vrat, p. and dahiya, rp. 2006. application of a system dynamics approach for assessment and mitigation of co2 emissions from the cement industry. journal of environmental management, 79: 383-398. astm c136 /c136m-19. 2006. standard test method for sieve analysis of fine and coarse aggregates. astm international, west conshohocken, pa. astm c618. 2019. standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete, astm international, west conshohocken, pa, www.astm.org. astm d5381-93. 2021. standard guide for x-ray fluorescence (xrf) spectroscopy of pigments and extenders, astm international, west conshohocken, pa. astm d6926-16. 2016. standard practice for preparation of asphalt mixture specimens using marshall apparatus. west conshohocken, philadelphia, pa: american society for testing and materials (astm) international. doi:10.1520/d6926-16. badejo, aa., adekunle, aa., adekoya, oo., ndambuki, jm., kupolati, kw., bada, bs. and omole, do. 2017. plastic waste as strength modifiers in asphalt for a sustainable environment. african journal of science, technology, innovation and development, 9: 173-177. coleman, ao. 2002. highways: the location, design, construction and maintenance of road pavements. butterworth-heinemann publishers, kidlington, oxfordshire, uk. essar, my., kazmi, sk., hasan, mm., costa, acds. and ahmad, s. 2021.the rampant use of cow dung to treat covid‐19: is india at the brink of a zoonotic disease outbreak? journal of medical virology, 93 (12): 6471-6473. fmwh. 2016. nigerian general specifications for roads and bridges. federal ministry of works and housing. federal republic of nigeria, federal ministry of works and housing, abuja. gupta, kk., aneja, kr and rana, d. 2016. current status of cow dung as a bioresource for sustainable development. bioresources and bioprocessing, 3: 1-11. hearn, gj, o'flaherty, c. and hughes, d. 2015. highways, the location, design, construction and maintenance of road pavements. 5th edition. 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vol.6, 49-59 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng review of sustainable productivity of dryland farming systems through furrow diking chiroma, a.m.,1 kundiri, a.m.1 and ibrahim, a.2 abstract in areas where crop production is limited by low and variable rainfall, the search continues for cultural practices that conserve soil and water while maintaining or improving crop yield and quality. one of such practices is furrow diking (also known as tied-ridging, furrow damming, basin tillage or micro basin tillage). the practice involves constructing small earthen dams or dikes at certain intervals in furrowed fields to capture potential runoff water, thus increasing the ponding period for infiltration. this paper attempts to highlight the potentials of this land configuration practice for improving crop yields in areas where crop production is limited by low and variable rainfall. the constraints associated with its use have been identified and prospects for improving its effectiveness under various climatic conditions are discussed. cost implications of the practice, as well as suggestions for scaling down costs are considered. maximum benefits from furrow diking are generally obtained in dryland areas characterized by high intensity, short duration rainfall events which produce significant runoff. 1. introduction it is widely acknowledged that low productivity of crops grown in many parts of arid and semi-arid tropics is largely due to the harsh environment, with rainfall and soil being the major environmental constraints (chiroma et al., 2006a., icrisat, 1987). in these areas, low and variable rainfall coupled with high evaporative demand occasioned by supra-optimal temperatures often expose plants to varying degrees of stress even during normal rainfall years. furthermore, majority of the soils that occur in these regions have poor structural stability which contributes significantly to loss of water and soil during intense rainstorms. during rainfall events, runoff losses exceeding 50% is not uncommon in these zones (parr et al., 1990) thus, efforts in improving crop production in these water deficit areas should consider cultural practices with potential for preventing runoff and increasing infiltration. furrow diking also known as tied ridging is one of such practices. furrow diking as the name implies, is the practice of putting earthen dikes periodically in a furrowed field to obstruct the flow of water, reduce runoff, and increase moisture storage for crop production (jones and stewart, 1990). the potential of furrow diking for conserving rain or irrigation water for crop use has been demonstrated in many dryland cropping systems (jones and nyamudeza, 1991; selvaraju et al., 1999; sow et al., 1997). this paper highlights the major research findings on furrow diking for improving dryland crop yields. 2. description of furrow dikes furrow diking or tied ridging involves mechanically constructing small earthen dams periodically through a furrowed field to increase surface detention storage, thus preventing runoff and increasing infiltration (jones and stewart, 1990). series of small basins created by these dikes hold the precipitation until it can be infiltrated into the soil. depending on site and soil characteristics, furrows are blocked at 1 to 3 m intervals. 1 department of soil science, university of maiduguri, nigeria 2 department of soil science, federal university of technology yola, nigeria http://www.azojete.com.ng/ review of sustainable productivity of dryland farming systems through furrow diking 50 3. role of furrow diking in rainwater harvesting the surface roughness created by the ridge and dikes obstruct the free flow of potential runoff water, thus providing enough time for increased water infiltration. according to baumhardt et al. (1992), the contribution of furrow diking to increase in infiltration can be explained by three factors; (i) increased hydraulic head due to ponding of water in the diked furrow, (ii) reduced seal formation in the furrow, and (iii) tillage of the furrow before forming dikes. the potential of furrow diking in increasing infiltration and soil water storage have been demonstrated in several dryland cropping systems. field experiments conducted in drought prone areas of southern india have demonstrated the advantages of tied and open ridge systems for soil water conservation (selvaraju et al., 1999). their study showed that the tied ridge treatment stored 15% more water at 0-15 m depth and 8% more water at 15-30 cm depth on 30 days after sowing than the flat bed on the alfisol during the first year of the experiment. during the second year of the experiment, the tied ridge treatment also stored 20% and 18% higher soil water than did the flat bed at 0-15 cm and 15-30 cm soil depths respectively on 90 days after sowing (table 1). they attributed the increased soil water storage with the tied ridge treatment to reduced runoff and greater soil water retention in the furrows of the tiedridge plots. in a similar research conducted on clay loam soil at bushland, texas, sow et al. (1997) reported that furrow diking effectively captured rainfall and reduced the amount of runoff in both the experimental years. average runoff from the flat bed plots was about 56% lower than from the no-tillage plus residue plots. early in the season, when little canopy was available to completely cover the plots, runoff from the bare soil surface resulted in much lower soil water content in the conventionally tilled and no-tillage plots when compared with the furrow-diked and no-tillage plus residue plots. table 1: soil water content (m3m-3) at different depths as affected by land configuration in the alfisol treatments 1991-1992 (30 days after sowing) 1992-1993 (90 days after sowing) 0-15 cm 15-30 cm 0-15 cm 15-30 cm flat bed 0.199 0.204 0.093 0.137 tied ridge 0.229 0.219 0.112 0.162 open ridge 0.209 0.216 0.107 0.157 lsd (0.05) 0.012 0.005 0.014 0.018 source: selvaraju et al. (1999). experiments carried out in semi-arid region of zimbabwe showed that tying a furrowed field at 1.5 and 2.0 m intervals resulted in greater soil water storage compared with the traditionally prepared sites with 1.0 m row spacing on the flat (nyamudeza, 1991). land configuration practice such as tied ridging has also been shown to trap runoff water when rainfall exceeds infiltration in drought prone shallow soils of the west african sahel (hulugalle, 1990). studies have shown that, for furrow diking to significantly reduce runoff, rainstorms must be of sufficient intensity and duration to exceed the infiltration capacity of the soil (gerard et al., 1984; baumhardt et al., 1992; 1993). these reports demonstrate the potentials of furrow diking for trapping runoff water in dryland cropping systems where rains often occur in azojete vol. 6 2008 51 intense storms. for example, rainfall intensities in many parts of west africa usually range from 20-60 mm/h with high values sometimes reaching between 120 and 160 mm/h (icrisat, 1987). because majority of the soils that occur in arid and semi-arid regions of west africa are characteristically sandy and have poor structural stability, much of such intense rains could be lost to runoff leading to low effective rainfall and heavy soil loss. for example, kowal (1973) noted that only a little less than a quarter of the total rainfall in the savannah zones of nigeria enters into the soil during such intense rains. recent field experiments conducted on coarse textured soil of semi-arid northeast nigeria by chiroma et al. (2006a) showed that the practice of tied ridging alone or in combination with mulching increased the profile moisture storage relative to the flat bed during most of the sampling dates of all the three experimental years (table 2). table 2: soil profile (0-2.2 m) water storage under different treatments measured at different growth stages during 2000, 2001, and 2002 growing seasons moisture storage (mm) 2000 2001 2003 treatments§ vegetative booting maturity vegetative booting maturity vegetative booting maturity fb 187 164 143 91 183 100 78 178 185 or 204 166 158 108 197 107 90 185 189 tr 195 172 151 107 202 104 98 186 188 fbm 202 168 155 112 205 100 105 183 187 orm 201 186 173 119 218 106 115 187 185 trm 194 175 162 122 228 108 123 190 191 s.e. 7.5 11.7 13.9 1.3 8.6 2.8 3.0 1.7 2.8 § fb = flat bed, tr = tied ridge, or = open ridge, fbm = flat bed + mulch, trm = tied ridge + mulch, orm = open ridge + mulch source: chiroma et al. (2006a). the improvement in soil profile water storage with the tied ridge were partly attributed to the surface modifying effects of ridging and ties which tended to prevent runoff and increased the time of ponding for infiltration and partly to the reduction of evaporation losses due to the presence of a surface mulch. previous studies (folorunso et al., 1994) conducted in this same region revealed that tied ridging significantly enhanced profile water storage at karasuwa where the slope of the land was much higher (3.6 to 8.2%), but not at gwio kura and amaduri with fairly gentle slopes of 0.6 to 2.5% and 0.1 to 2.6%, respectively (table 3). contrary to these results, kronen (1994) while appraising the water conservation techniques used by smallholder crop production systems in semi-arid areas of south african sub-region noted that the advantages of tied-ridge system in concentrating runoff water is evident only on soils with a relatively high clay content (vertisols, paragneiss and alluvium soils) and not on lighter soils characterized by poor water retention. however, significant crop yield responses were obtained on these coarse textured soils when tied ridging was combined with proper fertilization indicating that the lack of yield response by crops grown on the tied-ridged field was largely due to the low inherent fertility level of these soils than to the inefficiency of the tied-ridge system to harvest and store rain water for use by crop plants. others have attributed the poor performance of the tied-ridge system on light textured soils to increased soil temperature and dryness on the ridges (vogel, 1994) and compaction of the furrow due to review of sustainable productivity of dryland farming systems through furrow diking 52 human traffic and ponding following heavy rainstorms (materechera and mloza-banda, 1997; chiroma et al., 2006b; radke, 1982). according to vogel (1994), temperatures on the ridges could be reduced by aligning the ridges north-south so as to provide maximum shading by the standing crop of the between row spaces. another possibility would be to use ridges in the form of letter m to collect as much direct rainfall as possible and to provide for maximum shading of the ridge top centre during the day time and to impound warm air in the centre of the ridge top, thus preventing influx of cold air at night. burrows (1963) found that afternoon soil temperatures beneath ridges of east-west rows during summer were higher than those beneath ridges of north-south rows. table 3: mean soil profile water storage (mm) over all sampling dates location ridging flat tied-ridge lsd (p,0.05) amaduri 234.0 242.8 253.8 21.2 gwio kura 176.3 211.0 204.6 15.4 karasuwa 167.4 123.8 152.2 21.0 source: folorunso et al. (1994). soil water and temperatures within the ridge-tillage system were simulated with a heat and moisture model (benjamin et al., 1990). it was demonstrated that taller ridges differed from shorter ridges in their patterns of soil temperatures and water content. ridges 20 cm high had higher temperatures than ridges less than 20 cm high, and all ridges had warmer temperatures than flat soil surface except for the furrow position. shaw and buchele (1957) measured higher soil temperatures and lower water contents beneath ridges and slopes than beneath furrows. these general conclusions suggest that on lighter soils, planting in the furrow between the ridges could promote better crop performance since the furrow remain cooler and wetter compared with the slope or the ridge top. compaction of the furrow positions can be alleviated through occasional light tillage performed in raising collapsed ridges and dikes or moving loose soil from the furrow into dikes, thus reducing the amount of soil available in the furrow to form depositional seals as described by baumhardt et al. (1990) and krishna & arkin, (1985). 4. effects of furrow diking on crop yield the potential of furrow diking for improving dryland crop yields have been demonstrated in many areas where crop production is limited by rainfall. in the rolling plains of texas characterized by low and variable rainfall, gerard et al. (1984) reported yield increases of up to 108% in sorghum and 32% in cotton due to furrow diking. under the same texas condition, jones and clark (1987) reported an average sorghum grain yield increase of 176% during a two-year study period. others also reported grain yield increase of up to 72% in sorghum and 23% in wheat due to furrow diking (tewolde et al., 1993). however, the practice of furrow diking in the rolling plains of texas as in other dryland areas, does not always result in higher crop yields. for example, mcfarland et al. (1991) did not find any effect of furrow diking on the grain yield of corn on nearly level (1% slope) fields in south central texas where annual rainfall was below average and a tendency toward lower yields when annual rainfall was above average. nelsol et al. (1988) attributed the lack of yield azojete vol. 6 2008 53 response of soybean to furrow diking in northeastern texas to soil cracking and lack of slope, which result in low potential runoff. in contrast, gerard et al. (1984) reported significant increase in lint yield of diked cotton grown on soil with a 0.5% slope over the un-diked cotton. several others have equally observed significant yield responses due to furrow diking on fields with less than 1% slope (tewolde et al., 1993; sow et al., 1997). luebs (1962) summarized his long term (1937-1953) research to assess the suitability of different tillage methods for dryland farming in kansas state, usa by stating that holding rain with dikes on nearly level land appeared to have merit for increasing dryland crop yields. most controversies in literature could be attributed to differences in soil and climatic conditions of the study area. it is important to note that the potential benefit to be derived from furrow diking depends largely on site and soil characteristics such as texture, slope and landscape position (gerard et al., 1984). other factors include rainfall (amount, intensity and distribution) and crop species (tewolde et al., 1993; mcfarland et al., 1991). however, the benefits from furrow diking are generally most substantial in semi-arid regions that are subject to high intensity, short duration rainfall events which produce significant runoff (lyle and dixon, 1977; jones and clark, 1987). field investigations by gerard et al. (1984) to assess the effects of furrow diking and sub-soiling on runoff and crop yields on gently sloping land of texas show that average sorghum yields for 1981 and 1982 of sub-soiled, half-diked, diked and diked-sub-soiled treatments were 27, 57, 108 and 111% higher than yield of the check treatment respectively (table 4). lint yield from the half-diked, diked and diked-subsoiled averaged 24, 33 and 26% higher than the control treatment respectively. they found significant linear relationship between percent yield and distance down the slope for the check, half-diked and diked treatments. these results also demonstrate the effectiveness of furrow diking in capturing rainwater for crop production on gently sloping fields. also in texas, clark (1983) compared diked, alternate row-diked and non-diked treatments for cotton production and found that diking alternate or every furrow resulted in yield increases of 16 and 36% respectively when compared to non-diked treatments on a clay loam soil. jones and nyamudeza (1991) reported the results of a 7-year tied-ridge study in south east zimbabwe and showed that planting in the tied-furrows resulted in higher yields of cotton, sorghum and maize compared with that from planting on the flat in each of the seven crop growing seasons (table 5). table 4: grain sorghum yields (kg) under different treatments and location on the slope in 1981 and 1982 1981 1982 1981/1982 average treatments upper middle lower average upper middle lower average check 536a§ 1065a 1887a 1164a 735a 1694a 3162a 1864a 1513a sub-soiled 350a 591a 2805a 1249a 1439b 2558a 3799a 2598b 1924b half-diked 1615b 1995b 2644a 2084b 2285c 2410a 3273a 2656b 2370c diked 2027b 2579bc 2872a 2493b 3083d 4036b 4324a 3815c 3154d diked and sub-soiled 2175b 2872c 2507a 2518b 3827e 4169b 3633a 3876c 3197d §values within each location on slope or averages followed by same letter are not significantly different at 5% level according to duncan’s multiple range test review of sustainable productivity of dryland farming systems through furrow diking 54 source: gerard et al. (1984). table 5: sorghum grain yield (kgha-1) as affected by land configuration, manure and fertilizer in the alfisol§ treatments land configuration practice mean fb tr or 1989-90 fym + n40p9 1389 1571 1523 1494 fym + n20p45 1052 1324 1180 1185 cd + n40p9 1468 1710 1633 1604 cd + n20p45 1351 1969 1385 1568 mean 1315 1644 1430 lsd (0.05) l, 50; mf, 113; l x mf, 165 1990-1991 fym + n40p9 836 1090 963 963 fym + n20p45 627 992 820 813 cd + n40p9 1082 1335 1149 1189 cd + n20p45 854 1220 1061 1045 mean 850 1159 998 lsd (0.05) l, 81; mf, 110; l x mf, 192 1991-1992 fym + n40p9 3760 3934 3891 3862 fym + n20p45 3558 3731 3688 3659 cd + n40p9 3683 3860 3824 3789 cd + n20p45 3481 3652 3620 3584 mean 3621 3794 3756 lsd (0.05) l, ns; mf, 179; l x mf, ns §fb = flat bed, tr = tied ridging, or = open ridging, fym = farm yard manure at 5 mgha-1, cd = coir dust at 12.5 mgha-1, n40p9 = 40 kgn and 9 kgp ha-1, n20p45 = 20 kgn and 45 kgp ha-1, l = land configuration, mf = manures and fertilizers and ns = not significant source: selvaraju et al. (1999). 5. combined effects of furrow diking and manure on dryland crop yields benefits from furrow diking have generally been obtained when diking was combined with cultural practices such as organic or inorganic fertilizers. nyamudeza et al. (1991) evaluated various water and soil fertility management options for increasing crop production on light textured soils of south eastern lowland of zimbabwe. it was found that the use of 1.0 m tied furrows combined with 150 kgha-1 fertilizer (8:14:7 npk) as basal application and additional 25-50 kgha-1 top dressing are the best combination for sorghum and maize production on these light textured soils. the maximum use of 50 kg ha-1 top dressing was recommended for wet years, especially for crops like maize, which are highly sensitive to low fertility. they also noted that on these light textured soils, yield improvement with tied ridging were generally small and insignificant even at high fertility levels indicating that factors other than fertility could be responsible for the low performance of the tied-ridged system on these light azojete vol. 6 2008 55 textured soils. in contrast, substantial yield increases have been reported when tied ridging was combined with organic manures and mineral fertilizers on light textured soils of south indian peninsular (selvaraju et al., 1999). the study shows that utilization of tied ridging and organic manures such as coir dust (a bi-product from coconut industries) and farm yard manure in combination with inorganic fertilizers offer prospect for alleviating climatic and soil constraints such as low soil water retention and low soil fertility. the study on alfisol indicated that tied ridging in conjunction with coir dust at 12.5 mg ha-1 + 40 kgn and 9 kgpha-1 produced higher sorghum yield in low and medium rainfall years compared to tied ridging in combination with farm yard manure at 40 kgn and 9 kgpha-1. this observation was attributed to greater water availability resulting from the mulching effect of the added coir dust. however, in a high rainfall year, tied ridging in combination with farm yard manure at 5 mg ha-1 + 40 kgn and 9 kgpha-1 produced more grain yield than did tied ridging in combination with coir dust and 40 kgn and 9 kgpha-1 owing to greater availability of nutrient from the farm yard manure than coir dust (table 5). these results demonstrate that the practice of tied ridging in conjunction with manures (coir dust and farm yard manure) and mineral fertilizers (n and p) can increase the soil water storage and yield of crop when compared to the traditional practice of planting on flat seed bed in soils of semi-arid tropics. field experiment conducted by sow et al. (1997) at the southern great plains of texas also showed that the practice of furrow diking in combination with residue incorporation produced more sorghum yield than did conventional tillage with residue incorporation or no-tillage with or without residue mulch (table 6). for the conventional tillage and furrow-diked treatments, wheat residues were incorporated by disking twice and sweep ploughing once just prior to planting. averaged across the two experimental years, the furrow-diked treatment produced 19, 3 and 20% more yield of sorghum than did the conventional tillage, no-tillage plus residue mulch and no-tillage without residue mulch, respectively. the spectacular sorghum yield response to furrow diking and no-tillage plus residue mulch systems were attributed to decreased penetration resistance and increased depth of rooting which allowed for more efficient utilization of water and nutrients by plants growing under these two treatments. table 6: sorghum grain yield (kgha-1) as affected by different soil management systems in 1991 and 1992 at bushland, tx management systems 1991 1992 average furrow diking 4680a§ 4990a 4840a conventional tillage 3900b 4240c 4070c no-till + residue 4620a 4760b 4690b no-till – residue 3880b 4160d 4020c §means within each column followed by different letters are significantly different at the 0.05 level according to the duncan’s multiple range test source: sow et al. (1997). recently, chiroma et al. (2006a) compared the relative efficiencies of a number of land configuration practices for improving rainwater harvesting and yield of grain sorghum on a sandy loam soil of semi-arid northeast nigeria. the study indicate that maintaining woodshavings mulch at the rate of 10 tones/ha on the surface of flat bed, open or tied ridged review of sustainable productivity of dryland farming systems through furrow diking 56 systems tended to significantly increase the yield of sorghum when the annual rainfall was above average in 1999, 2000 and 2001, and when it was near average in 2002 (table 7). averaged over the four experimental years, the flat bed + mulch, open ridge + mulch, and tied ridge + mulch treatments produced more yield than the flat bed without mulch treatment by 577 kgha-1 (71%), 505 kgha-1 (50%) and 509 kgha-1 (63%) respectively. the corresponding mean increases in water use efficiencies due to these treatments relative to the flat bed without mulch were 41, 21 and 27%. table 7: effects of land configuration and wood-shavings mulch on grain yield and grain water use efficiency of sorghum treatments§ 1999 2000 2001 2002 mean grain yield (kgha-1) fb 599 1007 782 858 812 or 758 920 1186 904 942 tr 997 980 1212 884 1018 fbm 1183 1558 1598 1402 1389 orm 1015 1338 1383 1134 1217 trm 1000 1448 1456 1199 1321 meanþ 925 1208 1269 1063 s.e. 69.4 81.0 108.2 75.9 42.2 wue-et (kgha-1mm-1) fb -ß 2.12 1.58 2.15 1.95 or 1.85 2.37 2.14 2.12 tr 1.92 2.36 2.12 2.13 fbm 2.70 2.69 2.82 2.74 orm 2.36 2.40 2.31 2.36 trm 2.54 2.48 2.42 2.48 mean 2.25 2.31 2.33 s.e. 0.059 0.089 0.040 0.080 wue-r (kgha-1mm-1) fb 0.75 1.55 1.28 1.46 1.26 or 0.95 1.42 1.94 1.54 1.46 tr 1.24 1.51 1.98 1.51 1.56 fbm 1.48 2.40 2.61 2.39 2.22 orm 1.27 2.06 2.26 1.93 1.88 trm 1.25 2.23 2.38 2.04 1.97 mean 1.16 1.86 2.07 1.81 s.e. 0.090 0.120 0.180 0.130 0.070 §fb = flat bed, tr = tied ridge, or = open ridge, fbm = flat bed + mulch, trm = tied ridge + mulch, orm = open ridge + mulch, wue-et = evapotranspirational water use efficiency, wue-r = rainfall water use efficiency þstandard error of difference between means of treatments across years (34.45 for grain yield; 0.027 for wue-et and 0.050 for wue-r ßnot determined source: chiroma et al. (2006a). azojete vol. 6 2008 57 the results of the cost benefit analysis indicate that even though ridging (open or tied) in combination with mulching was found to be effective in increasing soil water storage, yield and water use efficiency of sorghum in all the four experimental years, higher production cost limited the profitable application of the ridge tillage systems under the edapho-climatic conditions of maiduguri, northeast nigeria. a possible option for increasing the profitability of the ridge tillage systems is by exploiting the possibility of utilizing ridges left over from the previous seasons cropping. studies in malawi by materechera and mloza-banda, (1997) indicate that existing ridges can be used without affecting yield at least in the first two years after they were constructed. planting using the previous year’s ridges will drastically reduce cost on labour and energy requirement, which in most environments are beyond the reach of the smallholder farmers. 6. conclusion the present review has indicated that crop yields in many areas where crop production is limited by low and variable rainfall can be substantially improved with furrow diking. many field experiments carried out in the arid and semi-arid tropics highlighted the advantages of furrow diking in reducing runoff and increasing water storage and subsequent crop yield. however, it is evident from this review that whether furrow diking will increase water storage and subsequent crop yield depends on several factors with site, soil characteristics and environmental conditions being the most important considerations. generally, benefits from furrow diking are most substantial in dryland areas subject to high intensity, short duration rainfall events which produce significant runoff. compared to heavy textured soils, benefits from light textured soils are relatively low owing to problems with low fertility, development of surface seals or crust and increased soil temperature and dryness on the ridges. it was suggested that temperatures could be reduced by aligning ridges north-south or using ridges in the form of letter ‘m’ so as to collect as much rainfall as possible and to allow for optimum shading of the ridge top during the day time. in addressing the problems associated with low fertility and development of surface crust with high intensity rains (which is characteristics of most dryland areas), the combination of furrow diking with organic manuring or mulching will not only enhance the soil fertility, but the surface mulch will also act to dissipate raindrop impact energy thus increasing infiltration. occasional light tillage in raising collapsed ridges and dikes will help in breaking surface crust and improve permeability in light textured soils. for heavy textured soils, provision of adequate drainage should be given proper attention especially in a high rainfall year. such soils may also require deeper dikes to hold rainfall for longer periods, thus providing more time for infiltration. since ridging requires a lot of time and energy which most farmers cannot provide in a limited time, planting using the previous years ridges will, beside reducing the cost of labour and energy requirement, help farmers to avoid the risk of reduced yields associated with late planting. review of sustainable productivity of dryland farming systems through furrow diking 58 references baumhardt, r. l., wendt, c. w. and keeling, j. w. (1993). tillage and furrow diking effects on water balance and yields of sorghum and cotton. soil sci. soc. am. j., 57: 10771083. baumhardt, r.l. romkens, m. j. m, whister, f. d. and parlange, j. y. (1990). modelling infiltration into a sealing soil. water resources research., 26: 2497-2505. baumhardt, r.l., wendt, c. w, keeling, j. w. (1992). chisel tillage, furrow-diking, and surface crust effects on infiltration. soil sci. soc. am. j., 56: 1286-1291. benjamin, j. g., blaylock, a. d, brown, h. j. and cruse, r. m. (1990). ridge-tillage effects on simulated water and heat transfer. soil tillage research., 18: 167-180. burrows, w. c. (1963). characterization of soil temperature distributions from various tillage induced soil structure. tech. bull. no. 306, univ. min. agric. exp. stn., morris, mn. chiroma, a. m., folorunso, o. a. and alhassan, a.b. (2006a). soil water conservation, growth, yield and water use efficiency of sorghum as affected by land configuration and wood-shavings mulch in a semi-arid soil of northeast nigeria. expt. agric., 42: 199-216. chiroma, a. m., folorunso, o. a. and alhassan, a.b. (2006b). the effects of land configuration and wood-shavings mulch on the properties of a sandy loam soil in northeast nigeria. 2. changes in physical properties. tropicultura., 24(1): 33-38. clark, l. e. (1983). response of cotton to cultural practices. texas agric. exp. stn., pr4175. folorunso, o. a., usman, h. and shukla, u. c. (1994). rainwater harvesting for efficient water utilization by rainfed crops in semi-arid northeastern nigeria. paper presented at the international conference on research for development, university of maiduguri, june, 19-25, 1994. gerard, c. j., sexton, p. d. and conover, d. m. (1984). effects of furrow-diking, subsoiling and slope position on crop yields. agron. j., 76: 945-950. hulugalle, n. r. (1990). alleviation of soil constraints to crop growth in the upland alfisols and associated soil groups of the west african sudan savannah by tied-ridges. soil tillage research., 18: 231-248. icrisat, (1987). pearl millet in african agriculture. proceedings of the international pearl millet workshop, 7-11 april, 1986. icrisat centre, india patencheru, a. p. 502324, india icrisat. jones, e. and nyamudeza, p. (1991). the relationship between rainfall and yield of cotton, sorghum and maize grown in tied-furrows and on the flat in the southeast lowveld of zimbabwe. in: proceedings of the second annual scientific conference, sadc and wmrp, october, 1991. mbabane, swaziland, pp 100-108. jones, o. r. and clark, r. n. (1987). effects of furrow-dikes on water conservation and dryland crop yields. soil sci. soc. am. j., 51: 1307-1314. jones, o. r. and stewart, b. a. (1990). basin tillage. soil tillage research., 18: 249-265. kowal, j. m. (1973). an assessment of aridity and the severity of the 1972 drought in northern nigeria and neighbouring countries. savanna., 2: 145-158. krishna, j. h. and arkin, g. f. (1985). furrow-diking in central texas: a hydrologic assessment. texas agric. exp. stn. pr-4264. kronen, m. (1994). water harvesting and conservation techniques for smallholder crop production systems. soil tillage research., 32: 71-86. azojete vol. 6 2008 59 luebs, r. e. (1962). investigation of cropping systems, tillage methods and cultural practices for dryland farming. kansas agric. exp. stn. b-449. lyle, w. m. and dixon, d. r. (1977). basin tillage for rainfall retention. trans asae, 20: 1013-1017. materechera, s. a. and mloza-banda, h. r. (1997). soil penetration resistance, root growth and yield of maize as influenced by tillage system on ridges in malawi. soil tillage research., 41: 13-24. mcfarland, m. l.; hons, f. m. and saladino, v. a. (1991). effects of furrow-diking and tillage on corn grain and nitrogen accumulation. agron. j., 83: 382-386. nelson, l. r., finch, g. and bowers, jr. g. r. (1988). furrw-diking and sub-soiling of soybeans in northeast texas agric. exp. stn. pr-4564. nyamudeza, p. (1991). the effect of tied-furrow, population and row width on the growth and grain yield of sorghum (sorghum bicolor) in the semi-arid soil. in: proceedings of the second annual scientific conference, sadc and wmrp, october, 1991. mbabane, swaziland, pp 100-108. parr, j. f., stewart, b. a,, hornick, s. b. and singh, r. p. (1990). improving the suatainability of dryland farming systems: a global perspectives. advan. soil sci., 13: 1-8. radke, j. k. (1982). managing early season soil temperatures in the northern corn belt using configuration soil surfaces and mulch’s. soil sci. soc. am. j., 46: 1067-1071. selvaraju, r., subbian, p, balasubramanian, a. and lal, r. (1999). land configuration and soil management options for sustainable crop production on alfisols and vertisols of southern peninsular india. soil tillage research., 52: 203-216. shaw, r. h. and buchele, w. f. (1957). the effect of the shape of the soil surface profile on soil temperature and moisture. iowa state coll. j. sci., 32: 95-104. sow, a. a., hossner, l. r, unger, p.w. and steward, b. a. (1997). tillage and residue effects on root growth and yields of grain sorghum following wheat. soil tillage research., 44: 121-129. tewolde, h., mulkey, j. r. and elledge, r. e. (1993). furrow diking effects on yield of dryland grain sorghum and winter wheat. agron. j., 85: 1217-1221. vogel, h. (1994). the effect of tillage on top soil temperature and strength in coarse grain sands with special reference to tied ridging systems. expt. agric., 30: 57-66. availability and conditions of agricultural machinery in public and private sectors of borno state, nigeria arid zone journal of engineering, technology and environment. october, 2008; vol.6, 29-37 copyright© faculty of engineering, university of maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng masonry structural behaviour at different scales under compressive loading mohammed, a.1 and hughes, t.g.2 abstract this paper discusses the effect of scale on masonry structural behaviour under compressive loading. reduced scales have been employed to understand masonry structural behaviour over the years, because testing prototype masonry structures is both costly and difficult to control in terms of instrumentation. a programme of tests has been carried out at four scales namely prototype, half, fourth and sixth scale under compression with a view to understanding how each of these conditions affects masonry structural behaviour over the range of scales enumerated. the results show that masonry compressive strength is increased as the scale is reduced but the stiffness is not markedly influenced. 1. introduction small scale masonry model testing has been carried out for many decades. early researchers in this area include vogt (1956), hendry and murthy (1965) and sinha and hendry (1968). most of these tests have established that it is possible to model masonry behaviour at reduced scales but not the strength and stiffness (egermann et al., 1991, hughes and kitching, 2000). recent programmes of research undertaken using a geotechnical centrifuge (hughes et al., 2002) on sixth and twelfth scale masonry arch bridges as well as various other model studies on masonryinfilled frames, walls and other masonry components and structures has necessitated further investigation into the small scale experimental structural behaviour of masonry. this recent interest in masonry modelling has arisen because of the need to assess and perhaps strengthen existing historic masonry structures like bridges and buildings. one aspect of this study is reported in this paper, looking at masonry behaviour under compressive loading at prototype, 1/2, 1/4 and 1/6 model scales. furthermore there is also the need to understand the structural behaviour of masonry structures under extreme natural events like windstorms, floods, earthquakes, etc, since some of these events, like flooding have become recurrent actions posing danger to thousands of people inhabiting or working in masonry structures. because of the issues associated with the cost implications of full size masonry tests, coupled with the danger of instrumentation destruction at failure, repeatability and difficult boundary conditions, it has become increasingly necessary to carry out such tests at reduced scales. 3. materials and methods 3.1 materials the bricks used in the research were solid clay bricks and some of its important mechanical properties are given in table 2. normal building sand was used for making the mortar in the prototype tests while hst 95 congleton sand was used for making the mortar in the model tests, the gradings of the two sands is shown in figure 1 in relation to the grading limits set by 1 department of civil and water resources engineering, university of maiduguri, nigeria. abba_gm@yahoo.com 2 cardiff school of engineering, cardiff, cf24 0yf, uk. tel: +442920 875716. hughestg@cardiff.ac.uk computer science department, federal polytechnic, bauchi. nigeria http://www.azojete.com.ng/ mailto:abba_gm@yahoo.com mailto:hughestg@cardiff.ac.uk masonry structural behaviour at different scales under compressive loading 30 bs13139. it shows that the normal building sand is within the grading limit s and the hst 95 sand is within the sixth scale grading limit (set by simply dividing the sieve sizes for the main grading limits by a factor of 6). some of the important material properties of the mortars are summarised in table 3. other constituents used for making the mortar are ordinary portland cement (opc) and hydrated lime. table 2: mechanical properties of prototype and model bricks prototype half fourth sixth test compressive strength, n/mm 2 29.2 30.6 41.9 47.4 cov, % 14.3 8.4 9.7 32.7 modulus of elasticity, n/mm 2 11500 cov, % 31 poisson's ratio 0.06 cov, % 48.1 table 3: properties of prototype and model mortar (coefficient of variation, cov in brackets) hst95iii mp mortar designation iii iii vol. proportions 1 : 1 : 6 1 : 1 : 6 w/c ratio 1.8 1.55 water retentivity,% 86 84 consistence retentivity,% 55 55 comp. str. n/mm 2 4.7(8.5) 5.0(1.8) flexural str. n/mm 2 2.3(5.3) 1.8(11.8) modulus of elasticity, 6500(8.7) 6300(17.8) poisson's ratio 0.10 0.12 partcle size distribution chart for model sands 0 20 40 60 80 100 0.01 0.1 1 10 sieve size (mm) c u m m la ti v e % p a ss in g fine limit coarse limit 1/6 finelimit 1/6 coarse limit hst 95 hst 60 sharp sand figure 1: grading curves for prototype and model sands within the bs limits 3.2. experimental design azojete vol. 6 2008 31 because of issues regarding the firing of model bricks as reported by taunton (1997) and mohammed (2006), a cutting procedure developed and used successfully by hughes and kitching (2000) and taunton (1997) was employed for the manufacture of the model bricks from a standard solid prototype of approximately 215 x 102.3 x 65 mm. cutting dimensions of the model bricks are shown in table 1. the table shows that the dimension for a “half” scale brick is 0.45 times that of a prototype brick. this is because obtaining the ideal 0.45 scale factor will result in getting only one half scale brick from a prototype brick, which implies a lot of wastage. thus the 0.45 factor was used which resulted in getting 8 half scale bricks from a prototype brick. the selection of the prototype brick was made based on consideration of its suitability for cutting considering factors like lack of manufactured voids, strength, internal structure (whether full of cracks or not) and ease of cutting. a mortar of designation (iii) equivalent to m4 was selected as a suitable mortar because of its medium compressive strength. two types of sands were used in making the mortars; normal builder’s sand for the prototype mortar and a finer sand, congleton hst 95 with an average grain size of 130 m for the model scale mortar. this sand was chosen because of the very small joints in the 1/6 scale (1.6mm) and 1/4 scale (2.5mm). further considerations on the experimental design are provided in mohammed (2006). table 1: average dimensions of prototype and model bricks scale length ,mm width, mm depth, mm prototype 215.0 102.5 65.0 half 96.8 46.1 29.3 fourth 53.8 25.6 16.3 sixth 35.8 17.1 10.8 the compressive strength test was chosen because masonry is loaded in compression in the majority of the situations under which it is used. therefore it is necessary to understand the mechanics of brickwork in compression for both prototypes and models. in addition to the compressive strength, the stiffness of the masonry under compression would also be investigated in order to compare the stiffness behaviour of prototype and model scale masonry. 3.2 construction method the bricks were first pre-wetted by totally immersing in a water tank for 20 minutes before laying them on their sides in a horizontal position as is usually done in prefabricated masonry panels. pre-wetting of the units was necessary so as to condition the suction properties of the units in order to achieve a good bond between the units and mortar bed. the horizontal method of construction was employed for both the prototype and models, in order to achieve a repeatable and controllable way of making the specimens since the traditional laying method is amenable to significant workmanship variations that could mask the structural behaviour of brickwork. another benefit of this method of construction is the cancelling of the differential compaction of the mortar beds during curing because of the different weights of the units across the four scales. otherwise some form of simulating gravity stresses would have to be resorted to; for example by undertaking the tests in a centrifuge, which could bring about complexities into testing programme. the bricks were separated by wooden spacers cut to the desired mortar bed joint thickness of 10mm in the prototype tests, while tile spacers of 5 mm, 2.5 mm and 1.6 mm were used for the 1/2, 1/4 and 1/6 model scales respectively. mortar was then placed into the bed spaces defined by the spacers whilst the units were laid on their sides in specially made moulds placed on top of a vibrating table. the whole assembly was vibrated gradually as the mortar was masonry structural behaviour at different scales under compressive loading 32 placed to fill up the bed spaces defined by the spacers used. this method of construction ensured uniformity in the bed joints of the specimens. 3.3 test procedure three brick high triplet specimens were tested in the load controlled testing machine at a loading rate of 0.18, 0.04 and 0.02 kn/s in the prototype, 1/2 and 1/4 scales respectively. in the 1/6 scale the test was undertaken at a displacement control of 0.006 mm/s, this was because testing in load control was not achievable in that particular testing machine which was most suitable for testing the 1/6 scale specimens. the chosen displacement rate was arrived at by first conducting trial tests to determine the time taken to achieve failure in the 1/6 scale tests, and then adjusting the rate of displacement in order to achieve failure in a comparable time to the load controlled tests. linear variable displacement transducers (lvdts) were attached to both faces of the specimens in the prototype, 1/2 and 1/4 scale specimens for the determination of their stiffness properties, while specially made model masonry clip gauges(mmcgs) were used in the 1/6 scales because of the small size of the specimens. details of the clip gauges are given elsewhere (hughes and kitching, 2000). the stiffness of the masonry was calculated as the secant modulus at a third of the maximum stress reached. 4. results and data analyses 4.1 compressive strength typical failure of the specimens across the four scales is by tensile splitting cracks in the axial direction. the cracks passed through the unit and mortar bed on both the faces and ends of the specimens. failure is sometimes occasioned by spilling off of the units prior to failure. the observed failure mechanisms in the four scales were all similar and agree with the known failure mechanisms for masonry in compression. most small scale masonry model tests to date have shown that the models are stronger than the prototypes, as seen in egermann et al. (1991). but current masonry theory assumes that if the mechanical properties of the brick and mortar are similar then there should not be a significant strength difference between models and prototype (hilsdorf, 1969; egermann et al., 1991). from table 4 (which shows a summary of the triplet compressive strength test result) and figure 2 (which shows the variation of the triplet compressive strength across the four scales), it is seen from the fitted trend line in the figure that, generally there is an increase in the compressive strength as the scale is reduced as reported by various authors. there is also evidence of strength anisotropy, because it is seen that the masonry strength in the half and prototype scales are somewhat similar on one hand and in the quarter and sixth scales on the other. this supports findings by mohammed (2006) on the possible anisotropy of masonry unit strength as well as other authors (jessop, et al., 1978; shrive and jessop, 1980). this behaviour could be due to the manufacturing process of extruded clay units in which plastic clay is forced through a die, thereby possibly bringing about anisotropy in the unit properties because of the extrusion process. in order to reduce the effect of the unit strength, the masonry strength in figure 2 is re-plotted with the masonry strength normalised with respect to their respective strength as shown in figure 3. this figure shows a reduced rate of increase of masonry strength as the scale is reduced. this azojete vol. 6 2008 33 suggests that there is still some additional factor that is responsible for the high increase in strength, apart from the effect of unit strength alone. table 4: summary of triplet masonry compression test results in the four scales mortar bed thickness compressive cov stiffness cov mortar cube scale type mm strength,n/mm 2 % n/mm 2 % strength,n/mm 2 prototype mp-iii 10.0 9.2 10.8 5500 22.6 4.6 half m95-iii 5.0 11.0 9.1 5200 26.9 4.9 fourth " 2.5 23.0 9.1 5400 6.6 4.7 sixth " 1.6 20.3 11.6 6000 20.1 4.7 compressive strength of masonry triplets in the four scales 0 6 12 18 24 30 0 0.2 0.4 0.6 0.8 1 1.2 scale c o m p re ss iv e s tr en g th n /m m 2 normalised strength of masonry triplets in the four scales 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.2 0.4 0.6 0.8 1 1.2 scale n o rm a li se d s tr en g th figure 2: triplet compressive strength in the four scales normalised strength of masonry triplets in the four scales 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.2 0.4 0.6 0.8 1 1.2 scale n o rm a li se d s tr en g th stiffness of masonry triplets in the four scales 0 2000 4000 6000 8000 0 0.2 0.4 0.6 0.8 1 1.2 scale s ti ff n es s, n /m m 2 figure 3: normalised triplet compressive strength across the four scales studies of the fracture of brittle materials (mostly concrete) have shown that smaller sized specimens have higher strengths than larger specimens (sabnis and aroni, 1971). according to the griffith theory of brittle fracture, the less the surface area of a material the stronger it is, since there is less probability of flaws occurring (moss, 1971). therefore, this size effect seen in testing brittle materials may also be one of the reasons for the strength differences. but curiously there is little scale effect seen in the half scale results. this suggests a possible interplay of two factors at the smallest scales; firstly a possible anisotropy with respect to strength due to the manufacturing process of clay brick and secondly the size effect phenomena. masonry structural behaviour at different scales under compressive loading 34 the thinness of the mortar joint at the smallest scales; that is fourth and sixth scales, could also contribute to the higher masonry strength in the smallest scales. as stated by many authors, the tensile stresses that cause failure in the brick are due to the stresses induced by the mortar joint. again using the griffith concept that smaller sized elements are stronger than larger ones, it would be expected that thinner joint should be able to withstand higher stresses than thicker ones; consequently the brick would be able to carry higher tensile forces in masonry with a thinner joint. this has been corroborated by porto et al. (2005) who found that prototype masonry with thin layer joints (1.3 mm) were 20% stronger in compression than those with 12 mm joints. this suggests that model masonry could show a stronger compressive strength due to the thinness of their joints alone. however, this may be applicable to only the very small scales like the sixth and fourth scales in this study, because as we see from the results, the half scale strength is similar to the prototype strength. from table 4, it can be seen that the mortar cube strengths for the tests are similar to each other. the highest cube strength of 4.9 n/mm2 was in the half scale test. this is marginally higher than the mortar cube strength in the prototype test by about 6% and fourth and sixth scale tests by about 4%. therefore, since the mortar strengths are comparable to each other in the four scales, the difference in masonry strengths seen could be principally due to the unit properties and the size of the joints at the smallest scales. 4.2 stiffness the variation of masonry stiffness across the four scales are shown in figure 4 and table 4. they show that all the stiffness results are similar; the half and fourth scales stiffness were 6% and 2% more than the prototype stiffness, while the sixth scale stiffness was 9% more than the prototype stiffness. even though we have seen substantial variations with regards to their strength properties, their deformation properties are very similar. this is further illustrated in figure 5, a combined plot of stress/strain curves for the four scales. it is seen from figure 5 that the slope of their elastic region are markedly similar. 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.2 0.4 0.6 0.8 1 1.2 stiffness of masonry triplets in the four scales 0 2000 4000 6000 8000 0 0.2 0.4 0.6 0.8 1 1.2 scale s ti ff n es s, n /m m 2 figure 4: stiffness of masonry triplets in the four scales azojete vol. 6 2008 35 compress ive stress vs average vert ical strain in pro to type, half, fourth and sixth scale trip let models 0 5 10 15 20 25 0 0.005 0.01 0.015 0.02 0.025 average axial strain c o m p r e ss iv e s tr e ss , n /m m 2 prototype half fourth sixth figure 5: stress/strain curves for selected triplet tests across the four scales however, results from other researchers (hughes and kitching, 2000; hendry and murthy, 1965; egermann et al., 1991) show a different trend. their results show that reduced scale masonry models are softer than prototype by a factor approximately equal to the scale factor. this may be due to the manner in which the models were constructed in our case which is different to the way the other researchers made their specimens. they all used conventional brick laying. because in conventional brick laying, the light weight of model bricks subject the mortar bed to a lower bedding stress than the heavier prototype bricks, as a result, the bed joints in the model scales are compacted to a lower degree during curing than the bed joints in the prototype. consequently, the bed joints in scaled masonry models are less compacted which could lead to a softer masonry response under compression. egermann et al. (1991) have suggested this as a possible reason for the softness of small masonry models and it has also been reported by mohammed and hughes (2005). by comparing it to the stiffness of its constituent elements, it is seen that the average stiffness of the masonry in the four scales (5500 n/mm2 in this case) is about half of the brick stiffness (11500n/mm2) and roughly similar to the mortar stiffness (6300n/mm2 for prototype mortar and 6500n/mm2 for benchmark mortar). this shows the influence of mortar in determining the stiffness properties of masonry. 5. conclusions the results of the masonry tests at different scales has shown that the strength of masonry triplet in compression was higher than the prototype in the fourth and sixth model scales but similar to the prototype in the half scale. the same pattern was also repeated in the tests of the unit strengths, indicating the strong influence of the unit in determining the masonry properties. there is evidence of anisotropy of strength in clay brick masonry possibly due to the manufacturing process of extruded clay units which therefore makes the direction of loading on a cut model brick important. it can then be suggested that the increase in model unit strength, could be attributed to two factors, namely; strength anisotropy and the energetic size effect in quasi-brittle materials. it was found that triplet stiffnesses in the four scales were identical to each other and no scale effect was observed. the prototype masonry and model stiffness were in good agreement with the prototype and model mortar stiffness respectively. this may be attributed to the way the specimens were constructed, which has effectively cancelled any differential compaction of the masonry structural behaviour at different scales under compressive loading 36 joints due to the different weight of the unit bricks in the various scales. the good agreement in the stiffness of the four scales may be evidence of the importance of the mortar bed in determining the stiffness properties of masonry. this finding is very significant bearing in mind that model tests by other researchers showed a much softer model response to the prototype under axial compression. references egermann, r., cook, d. a. & anzani, a. 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(2006) experimental comparison of brickwork behaviour at prototype and model scales. cardiff, cardiff university. mohammed, a. & hughes, t. g. (2005). comparison of prototype and 1/6th model scale behaviour under compressive loading. 10th canadian masonry symposium. banff, canada. moss, j. b. (1971). properties of engineering materials, london, butterworth. porto, f. d., garbin, e., modena, c. & valluzzi, m. r. (2005). failure modes for in plane loaded masonry walls made with thin layer mortar. 10th canadian masonry symposium banff, canada. sabnis, g. m. & aroni, s. (1971). size effect in material systemsthe state of the art. proceedings of the southampton 1969 civil engineering materials conference. southamptom. shrive, n. g. & jessop, e. l. (1980). anisotropy in extruded clay units and its effect on masonry behaviour. proceedings of the 2nd canadian masonry symposium. ottawa. sinha, b. p. & hendry, a. w. (1968). the effect of brickwork bond on the load bearing capacity of model brickwalls. proceedings of the british ceramic society. taunton, p. r. (1997). centrifuge modelling of soil/masonry structure interaction. cardiff university, uk. vogt, h. (1956). considerations and investigations on the basic principles of model tests for brickwork and masonry structures. garston, building research station. corresponding author’s email address: fayomiuche@gmail.com 732 arid zone journal of engineering, technology & environment original research article using cloud-based application for assessment of extreme threat of climate impact on water resources: a case of vaal river catchment, south africa n. upasana1, e. k. onyari1, g. u. fayomi 1* and i. r. bodunrin 1 1 department of civil and environmental engineering and building sciences, university of south africa, florida science campus, cnr christian de wet road and pioneer avenue, johannesburg, south africa *corresponding author’s email: fayomiuche@gmail.com article information abstract climate change impact on water resources is becoming a global challenge with persistent escalation of threating weather and changes in precipitation patterns. the study evaluates the extreme impacts of climate change in vaal river in south africa. the channel of vaal river is an area with a critical water resource which supports agricultural, industrial and domestic activities. a three-decade dataset (1993-2023) of precipitation, temperature, streamflow, combined with surface water changes was engaged to examine climate impact on vaal river water resources. modified normalized difference water index (mndwi) derived from landsat-5 (1994–2012) and landsat-8 (2013-2023) imagery on the google earth platform (gee) was also used to examine the seasonal water stress and availability. the results revealed increasing temperatures and irregular precipitation which are indications of climate altering condition resulting to decreased surface water coverage especially during dry seasons. mndwi result records a fluctuating value indicating variations in both seasons. further result revealed weak correlation between precipitation and streamflow, driven by anthropogenic regulations and land use, the mndwi wet season's linear trendline showed a positive slope of 0.0046 and r² value of 0.26 suggesting water availability over time. similarly, polynomial trendline for the mndwi dry season equally shows a moderate coefficient r² value 0.38 adaptive strategies, including integrated water resource management (iwrm) and advanced monitoring systems that will include stakeholders, planners and policy makers at all levels are recommended to mitigate these impacts. more effort should be channeled towards sustainable solutions such as tree planting, tree box filter and afforestation practices to reduce the effect of climate change on water resources. received: 21st may 2025 revised: 11th july 2025 accepted: 13th july 2025 keywords: climate change water resources hydrological cycle surface water geospatial techniques cloud-based applications © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction climate change is increasingly posing a significant challenge to the sustainability of global water resources. it has a variety of effects on water systems, including changes in precipitation patterns, more intense extreme weather, changes in the availability of water, and a decline in water quality (chaturvedi et al., 2021; xia et al., 2015). these changes threaten water security, with profound effect on ecosystems, human health survival, agricultural production and industrial activities (raneesh, 2024; yang et al., 2020). according to the intergovernmental panel on climate change (ipcc, 2021), heavy precipitation events have increased in frequency and intensity in many regions of the world. conversely, areas like southern africa, north america, and the mediterranean are seeing severe drought conditions and decreasing rainfall conditions (ipcc, 2021; teweldebrihan and dinka, 2024). this trend is indicative of more widespread disturbances to the global water cycle, which climate change is constantly changing (bodunrin and onyari, 2024). the hydrological cycle is becoming more intense due to rising temperatures, which causes precipitation changes to become more noticeable. some regions are experiencing prolonged drought and increasing water scarcity, while others are getting more rainfall and even flooding (chaturvedi et al., 2021; xia et al., 2019). azojete september 2025. vol.21(3):732-747 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/005 www.azojete.com.ng mailto:fayomiuche@gmail.com mailto:fayomiuche@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 733 south african's climate is influenced by its distinct location situated within the sub-tropical belt, which is encircled by an ocean on all side of the country (dlamini et al., 2023; akanbi et al., 2021; hosea & khalema, 2020; inr, 2019). the nation is also regarded as semi-arid region because of its diverse rainfall patterns and distribution (botai et al., 2018; teweldebrihan and dinka, 2024, department of water & sanitation, 2018). south africa has previously experienced sporadic droughts, and climate forecasts which suggest that such events will likely grow more regular and severe in the future (fyna and abiye, 2022; schulze, 2000). this circumstance presents serious difficulties for urban water supply, agriculture, and water management (gyamfi et al., 2016). utilization of remote sensing (rs) methods, such as satellite imagery and geographic information systems (gis) is essential for tracking changes in water bodies (cui et al. 2022; bodunrin and onyari, 2024; dlamini et al., 2023). the major benefit of using remote sensing application is that it provides a wealth of data and a variety of observations (garajeh et al., 2024; cui et al., 2022). however, the recent cloud computing platform known as (gee) is helpful in processing and storing enormous amounts of rs images with the use of cloud storage (wang et al., 2018). gee platform comprises of a varied range of satellites (landsat, sentinel, and modis are among the current used satellites) for temperature, precipitation, and land cover. they are also used in boundary detection, vegetation cover mapping, population and settlement detection (akhundazadah et al., 2020; wang et al., 2018; remilekun et al., 2021). the vaal river is among south africa’s most commercial water resources that is threatened by the adverse impact of climate change (bodunrin and onyari, 2024). these threats include drought, rising temperatures, and changing precipitation patterns, and it is predicted that more frequent extreme weather events will make already-existing problems with water quality and quantity worse in nearby future (raneesh, 2024; akanbi et al., 2021). these alterations pose serious threats to the river's ecological well-being and capacity to supply sufficient, clean water for its usage in home, industrial, and agricultural processes (chaturvedi et al., 2021, shah, 2024). therefore, this study examined the extreme impact of climate change on vaal river water resources situated in the north-eastern region of south africa. the objectives is to evaluate the effects of seasonal variations over a three-decade period utilizing the temperature and precipitation climate components. 2. materials and method the vaal river catchment was delineated using digitized shapefile downloaded from google earth with the combination of satellite imagery derived from (gee) and quantum geographic information system (qgis). the identified recording stations usually known as a permanent structure with sensor equipment or other devices used for continuous track and documentation of different environmental and hydrological factors connected with the behaviour of the catchment. it involves the use of cardinal co-ordinates from microsoft excel and qgis, to identify the proximity along the vaal river. the cloud computing platform, (gee) was equally utilized to study the surface water changes of the vaal river using landsat-5 imagery featuring collection-2, tier-1, level-2 (toa). the imagery was downloaded from 1993–2012 (19 year duration). similarly, landsat-8 (operational land imager) was employed from 2013 –2024 (12years duration) featuring collection-2, tier-1, level-2 (toa). these landsat imageries was used to observe changes in surface water for three stipulated decades. both landsat 5 and landsat 8 (oli) have proven to be effective in monitoring surface water availability since inception. modified normalized difference water index (mndwi) was employed to examine the water level for both wet (january – march) and dry (may – july) seasons, using reflectance wavelength of the green and shortwave infrared (swir) bands shown in equation (1) & (2) (remilekun et al. 2021). annual precipitation and temperature data from 19932023 (3 decades duration) was obtained from south african weather services (saws), while historical annual total flows of vaal river were extracted from the department of water and sanitation website (dws/hydrology), for catchment recording station. data derived from temperature and precipitation was analysed in microsoft excel where trend analysis was observed. however, normal ratio equation was utilized to account for the missing precipitation values (haji, 2011; chabalala et al., 2019). equation 3 displayed the formular used in accounting for missing values. table 1 and table 2 revealed data derived from temperature and precipitation. landsat 5 = mndwi = (𝑃𝑔𝑟𝑒𝑒𝑛− 𝑃𝑆𝑊𝐼𝑅) (𝑃𝑔𝑟𝑒𝑒𝑛+ 𝑃𝑆𝑊𝐼𝑅) = (band2 −band7) (band2 − band7) 1 landsat 8 = mndwi = (𝑃𝑔𝑟𝑒𝑒𝑛− 𝑃𝑆𝑊𝐼𝑅) (𝑃𝑔𝑟𝑒𝑒𝑛+ 𝑃𝑆𝑊𝐼𝑅) = (band3 −band7) (band3 − band7) 2 http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 734 𝑃𝐴 = ∑ 𝑅𝐴 𝑁𝑅𝑖 × 𝑃𝑖 𝑁 𝑖−1 𝑛 3 where: pa is the estimate for the ungagged station, pi is the rainfall at the surrounding stations, n ra is the normal annual rainfall at station a, n ri is the normal annual rainfall at station i and n is the number of surrounding stations that data are used for estimation. 2.1 study area the vaal river is the largest tributary of the orange river and is a critical water resource for south africa traversing various climatic and geographical zones. it originates in ermelo, in the mpumalanga province, west of swaziland, and extends over approximately 1, 210 km (bodunrin and onyari, 2024). the river forms part of the upper, middle, and lower vaal basins, each influenced by distinct climatic and anthropogenic factors (masindi and abiye, 2018). figure 1 displayed the location of vaal river within the urbanised environment. figure 1: vaal river location (bodunrin and onyari, 2024) the climate of the vaal river in south africa is sub-tropical dry savannah, with a pronounced seasonal rainfall pattern that peak in the summer (january to march) and an average annual evaporation rate that is much higher than its rainfall. it featured an average of 570 mm of rainfall per year; the river's watershed is primarily semi-arid. the summer months of november through january see the highest temperatures, while the winter months can have below-freezing temperatures. the average yearly temperature is approximately 15°c. (jury, 2016; bodunrin and onyari, 2024). the vaal river basin supports significant economic activities renowned to south africa such as mining, agriculture, and industrial activities, particularly in the urbanized area of johannesburg and vereeniging (masindi and abiye, 2018; wepener et al., 2011; haji, 2011). the vaal river basin delineation is presented in figure 2. table 1 present the annual average precipitation from recording stations along the vaal river while table 2 describe the annual average temperature from recording stations. the mean rainfall is relatively consistent across the study area with significant variability observed. this equally suggests average temperature increase over time within the catchment. the temperature also shows less variation in comparison to precipitation however, peaks are observed in some years. average temperature http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 735 figure 2: vaal river delineation table 1: annual average precipitation from recording stations along the vaal river year barrage rwb potchefs troom bothavile balkfrontein bloemloef leeu heuwel vaal river estate doug laspol mean sd variance 1993 63.98 60.96 45.94 45.94 23.79 22.76 29.45 41.83 15.73 247.57 1994 46.14 38.53 21.49 21.49 22.73 18.50 20.54 27.06 9.94 98.90 1995 66.48 57.07 39.68 39.68 44.52 14.38 24.08 40.84 16.55 274.02 1996 59.77 67.50 23.56 23.56 48.26 11.41 9.68 34.82 21.73 472.07 1997 62.24 54.48 7.74 7.74 34.61 21.33 22.14 30.04 19.96 398.22 1998 57.53 59.92 2.13 2.13 37.67 13.46 22.00 27.83 22.58 510.02 1999 45.81 44.91 12.75 12.75 30.43 29.93 25.54 28.88 12.41 154.09 2000 104.62 72.78 22.18 22.18 38.88 45.13 30.38 48.02 28.17 793.53 2001 93.02 67.77 32.16 32.16 55.09 44.08 40.53 52.11 20.43 417.47 2002 51.10 52.73 25.21 25.21 46.33 32.16 24.08 36.69 11.96 143.00 2003 46.56 40.63 15.49 15.49 32.83 13.00 12.98 25.28 13.31 177.05 2004 57.73 49.94 20.04 20.04 36.43 18.92 23.26 32.34 14.82 219.51 2005 42.96 45.20 19.49 19.49 27.49 12.33 5.75 24.67 13.77 189.67 2006 85.99 62.13 36.23 36.23 61.64 29.36 34.33 49.42 19.37 375.20 2007 36.08 48.58 15.02 15.02 34.04 35.73 19.47 29.13 11.87 140.88 2008 70.79 46.03 17.93 17.93 31.99 17.33 22.55 32.08 18.52 343.09 2009 82.03 58.42 60.78 60.78 47.64 26.24 27.38 51.89 18.46 340.72 2010 77.80 58.18 62.73 62.73 46.83 33.67 27.64 52.80 16.41 269.42 2011 57.48 55.30 70.60 70.60 79.69 42.88 29.28 57.98 16.25 264.18 2012 57.34 41.07 42.30 42.30 18.71 34.85 28.40 37.85 11.30 127.80 2013 50.08 33.91 31.08 31.08 17.77 15.67 6.50 26.58 13.34 178.04 2014 61.70 43.18 44.47 44.47 36.57 26.71 19.64 39.53 12.66 160.32 2015 31.60 34.83 18.67 18.67 16.18 19.47 10.71 21.44 7.97 63.52 2016 60.66 54.34 41.07 41.07 45.65 26.33 17.20 40.90 13.98 195.37 2017 53.66 59.40 32.90 32.90 31.33 28.21 25.06 37.64 12.32 151.73 2018 44.81 38.85 34.87 34.87 23.33 12.83 15.35 29.27 11.31 127.88 2019 38.90 54.37 53.25 53.25 24.04 21.13 9.78 36.39 16.87 284.57 2020 60.41 48.33 69.37 69.37 44.39 44.25 17.59 50.53 16.79 282.03 2021 60.95 72.20 51.35 51.35 47.66 53.79 53.79 55.87 7.65 58.48 2022 72.73 69.13 46.99 33.04 50.91 31.97 32.74 48.22 15.95 254.46 2023 57.08 49.58 13.40 36.82 22.30 17.74 14.52 30.21 16.42 269.71 mean 59.94 52.91 33.25 33.56 37.41 26.31 22.66 sd 16.14 10.63 18.00 17.48 13.89 11.23 9.99 variance 260.44 112.95 323.98 305.49 193.01 126.05 99.73 (source: south african weather services-saws, 2024). http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 736 table 2: annual average temperature from recording stations along the vaal river year secunda verneengine portchel stroom klerksdorp bothaville balkfontein bloemhot postmas burg mean sd varia nce 1993 15.97 16.70 17.77 17.41 18.20 18.37 18.15 17.51 0.82 0.68 1994 15.28 16.34 16.68 16.50 16.55 17.57 17.77 16.67 0.77 0.59 1995 15.94 16.99 17.72 17.22 17.29 18.34 17.96 17.35 0.72 0.52 1996 15.58 16.22 17.06 17.12 17.40 17.45 17.86 16.95 0.73 0.53 1997 15.70 16.37 17.69 17.26 17.63 17.88 18.07 17.23 0.81 0.65 1998 16.75 17.30 17.96 18.73 17.89 18.31 18.74 17.95 0.68 0.46 1999 16.65 17.64 18.81 18.78 18.42 18.83 18.83 18.28 0.78 0.60 2000 15.43 16.87 17.65 18.88 17.44 17.67 17.36 17.33 0.96 0.92 2001 16.27 17.28 18.64 17.92 17.24 17.72 17.38 17.49 0.67 0.45 2002 16.48 17.53 17.34 17.01 17.81 18.56 17.58 17.47 0.60 0.36 2003 17.28 17.55 18.57 17.14 18.07 18.49 17.46 17.79 0.54 0.29 2004 17.15 15.38 17.90 16.23 18.68 18.22 17.66 17.32 1.08 1.16 2005 19.37 16.97 17.63 16.57 19.06 18.73 17.55 17.98 1.00 1.00 2006 16.04 16.65 18.37 17.64 19.02 17.50 16.80 17.43 0.96 0.92 2007 16.44 17.29 17.98 18.25 19.08 18.12 17.62 17.83 0.77 0.59 2008 16.73 17.25 18.07 18.50 17.82 18.71 18.15 17.89 0.65 0.42 2009 16.47 16.94 17.88 17.79 16.03 18.69 18.55 17.48 0.95 0.90 2010 17.26 17.43 18.38 17.98 18.22 18.95 18.89 18.16 0.61 0.37 2011 16.59 16.56 17.29 17.29 17.72 17.70 17.64 17.26 0.46 0.21 2012 17.05 16.71 18.98 18.88 18.32 18.35 18.77 18.15 0.84 0.71 2013 16.94 16.97 18.89 18.98 16.98 18.59 17.54 17.84 0.88 0.77 2014 16.02 15.90 17.67 18.78 18.02 18.58 17.40 17.48 1.06 1.13 2015 17.16 17.85 18.66 19.70 18.98 20.13 19.63 18.87 0.99 0.98 2016 17.08 17.47 18.85 19.79 19.36 19.53 18.79 18.70 0.96 0.93 2017 16.64 17.30 18.40 18.90 18.15 18.34 20.13 18.27 1.03 1.07 2018 17.00 17.44 18.80 19.13 18.41 18.27 21.05 18.58 1.22 1.48 2019 17.45 18.00 19.14 19.53 18.88 19.37 19.58 18.85 0.76 0.58 2020 16.84 17.16 17.89 17.95 17.65 18.06 18.23 17.68 0.47 0.22 2021 16.85 17.04 18.41 18.18 17.56 17.95 17.48 17.64 0.53 0.29 2022 17.03 17.27 17.89 18.23 18.13 17.87 19.18 17.94 0.65 0.42 2023 17.04 17.91 18.66 18.87 18.63 18.98 19.01 18.44 0.67 0.44 mean 16.66 17.04 18.12 18.10 18.02 18.38 18.28 sd 0.75 0.58 0.60 0.g5 0.76 0.60 0.g3 varia nce 0.57 0.34 0.36 0.g0 0.57 0.37 0.86 (source: south african weather services-saws, 2024). 3. results and discussion a statistical analysis of the mean, standard deviation, and variance indicated the volatility of the stream flow in the vaal river given the hydrological trend analysis. the mean rainfall is relatively consistent across the study area. however, some variability is observed. the upstream barrage-rwb and potchefstroom stations have a higher means of 59.94 mm and 52.91 mm respectively, in comparison to the downstream douglas-pol station with 22.66 mm. the streamflow analysis implies that some stations receive more consistent and substantial rainfall than other stations illustrating changes in water availability per season. this result also aligned with the study of garajeh et al., (2024); assiri et al., (2024) and mwelwa et al., (2024) where streamflow varies across stations indicating water presence variation per time. the condition is likely influenced by localized climatic conditions as depicted by chabalala et al., (2019, and pham phuoc, (2014) and jury, (2016). however, the variance shows a similar trend with the standard deviation, being higher upstream and reducing downstream, suggesting rainfall patterns are more predictable downstream. the linear regression line for precipitation illustrates increase in the precipitation pattern over the years (y = 0.2307). signalling significant inter-annual variability with peaks in 2001, 2006, 2009, 2010, and 2011 and notable declines in 2005, and 2015. between 2019 – 2023, the trend was discreetly increasing after the dip in 2018, figure 3. the linear regression for temperature displayed an upward trend (y = 0.0369), indicating a moderate correlation. this equally suggests average temperature increase over time within the catchment. although the temperature shows less variation in comparison to precipitation, peaks are observed in 2015, 2019, and 2023, contrastingly hollows that occur in 1994, 1996, 2011, and 2014. the recent years, 2019 – 2023, remain consistently high indicating possible warming trends as depicted by jury, (2016) and chabalala et al., (2019). http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 737 figure 3: trend analysis of average annual precipitation and temperature. precipitation and temperature relationship showed a consistent increase independently from each other, (figure 4a & 4b). similarly, 1998, 1999 and 2015 have low precipitation but contrasting temperatures indicating possible changes on precipitation variability outlined also by merolla (2011); olabanji et al., (2020). the years 2010 – 2011 indicate high precipitation coinciding with moderate temperatures. the weak correlation testing between precipitation and streamflow revealed that there is no significant relationship between the two variables indicating the dominance of other factors impacting streamflow along with temperature. figure 4 (b) revealed gradual rising of both standard deviation and variance trend lines, indicating a minor upward trend in variability. this implies that precipitation variability recorded some growth in some of the years. for instance, 2003, 2008 and 2017 reported significant rise in standard deviation and variance. the linear correlation relationship r² showed a weak value however, with an increasing trend suggesting that precipitation is gradually getting more erratic across stations in the region. although, there is no significant change in the average rainfall but, the distribution and consistency showed unpredictable. this result is consistent with studies by kusangaya et al., 2014; van-rooyen et al., 2018, who identified rising temperatures and irregular precipitation as key indicators of climate stress on water systems. (a) (b) figure 4: a) mean monthly average temperature across all stations b) mean annual precipitation across all stations 19932023. 3.1 trend analysis of precipitation, temperature and streamflow the temperature and streamflow trend displayed a notable variability over the three decades, the statistical analysis of temperature pattern revealed significant fluctuation across the study period indicating possible http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 738 streamflow variations with inferences of climate variability on water availability. the red line shows the dispersion, or annual variance, in temperatures across all stations. significant peaks coincide with increases in global warming which occur between 2015 and 2019 (akanbi et al., 2021; masindi & abiye, 2018; kusangaya et al., 2014). the variance and standard deviation lines from 2003, 2010–2011, and 2015–2017. notable peaks, suggesting localized or regional climate anomalies. however, 2020-2023 recorded moderated standard deviation indicating stable temperature lately. the region's climate is changing, with occasional extremes, as seen by rising mean temperatures and greater variability in some years. higher fluctuation and sudden shifts in variance are indicators of unpredictable temperature patterns that may affect water resources, agriculture, and human comfort. the findings of this study, which are related to earlier research on the vaal river, show that the extreme climatic impact causes streamflow fluctuation (akanbi et al., 2021; masindi & abiye, 2018; okoye et al., 2022). figure 5 (a & b) revealed trend analysis of streamflow and precipitation of two recording station which also indicate very weak correlation (a) (b) figure 5: trend analysis of streamflow and precipitation in a) de vaal and b) bloemloef station 3.2 modified normalized difference water index (mndwi) the investigation of the mndwi data offers additional information about the effects of climate change on the vaal river's water resources presented in table 3. mndwi values for wet and dry seasons displayed consistent variations throughout the study period with value ranging from 0.08 to -0.12. the wet season's mndwi value was often greater than the dry season's, indicating that there was more water present during wet periods due to heavy rainfall that overflowed the water body level. additionally, there are records of lower values during the dry season, which indicates substantial water stress and shrinkages. this phenomenon can be ascribed to the impact of rising temperatures on river flow. the mndwi wet season's linear trendline showed a positive slope of 0.0046 and r² value of 0.26 suggesting water availability over time. similarly, polynomial trend line for the mndwi dry season equally shows a moderate degree of fit to the trend with coefficient r² value 0.38 as shown in figure 6. water presence fluctuation across the study period is shown by the chosen year trend of mndwi. the trend analysis of the yearly mndwi value over the vaal river recorded varying values that could be attributed to the effects of climate variability as well as variations in surface water. this outcome aligned with previous studies on fluctuating values caused by climate factors (botai et al., (2018); cui et al., (2022); yang et al., (2021); peterson et al., (2017). however, less negative indices are shown in the landsat-5 data for 1993, 1998, and 2007, indicating more water presence. similarly, the landsat-8 output for 2014, 2019, and 2023 shows a sharp decrease especially in 2019, hence reduced water presence dominates recent years from 2020-2023. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 739 table 3: mndwi output for 30-year study period wet season year season data range mean-band 2(l5)/ 3(l8) mean-band 7 mndwiwet 1993 1995 1997 1998 2001 2007 2008 wet (janmar) landsat 5 (19932012) -0.263 0.4393 -0.227 0.5037 -0.289 0.2605 -0.276 0.2455 -0.224 0.547 -0.241 0.1902 -0.206 0.1902 12734.36 12416.83 11003.47 12656.35 13540.35 11836.83 13900.97 15040.48 14618.14 12478.04 13343.74 12815.85 13466.16 13635.66 -0.08 -0.08 -0.06 -0.03 0.03 -0.06 0.01 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 wet (janmar) landsat 8 (20132023) -0.278 0.3912 -0.262 0.4013 -0.285 0.3897 -0.236 0.2 -0.172 0.5523 -0.247 0.215 -0.242 0.1896 -0.184 0.287 -0.176 0.207 -0.217 0.4663 14408.21 12570.73 13398.34 13729.75 16660.48 11655.11 13133.99 12196.94 12065.55 13042.10 14267.39 13756.27 15341.64 13755.35 14911.23 13840.72 13489.97 12564.52 12357.42 13313.41 0.00 -0.05 -0.07 0.00 0.06 -0.09 -0.01 -0.01 -0.01 -0.01 mndwi output for 30-year study period dry season. year season data range mean-band 2(l5)/ 3(l8) mean-band 7 mndwiwet 1993 1994 1995 1997 1998 2004 2006 2007 2008 2009 dry (mayjul) landsat 5 (19932012) -0.26 0.684 -0.237 0.2774 -0.27 0.2415 -0.243 0.363 -0.252 0.2289 -0.218 0.2451 -0.262 0.1159 -0.244 0.2162 -0.27 0.1695 -0.228 0.2216 13900.97 11362.02 11176.40 12436.26 14023.81 12285.56 11299.31 11334.42 11617.07 12786.83 13635.66 14020.44 14614.56 13346.93 14730.29 14425.95 13965.71 13367.03 14412.21 13853.82 0.01 -0.10 -0.13 -0.04 -0.02 -0.08 0.12 -0.08 -0.11 -0.01 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 dry (mayjul) landsat 8 (20132023) -0.268 0.2029 -0.29 0.2089 -0.284 0.1255 -0.286 0.3519 -0.239 0.2172 -0.271 0.2054 -0.26 0.2272 -0.269 0.228 -0.257 0.2012 -0.279 0.202 10447.41 10662.95 12374.70 12014.70 11211.60 12003.61 10332.69 11924.68 104412.62 12878.24 13828.34 13642.83 14855.08 14398.08 13646.35 13756.39 13034.96 13503.83 12894.20 13540.92 0.14 -0.12 -0.09 -0.09 -0.10 -0.07 -0.12 -0.06 -0.11 -0.03 3.3 correlation between mndwi, temperature and precipitation the outcome of mndwi in the wet season varies between positive and negative values, indicating periods of water presence and water stress, figure 7. the mndwi during the dry season consistently displays negative values, indicating a reduction in the amount of available water. however, mndwi exhibits a more noticeable fall during the dry seasons, which could result from the combined effects of climate induced factors such as higher evaporation, decreased inflows as well as human-induced water abstractions (enriquez, 2022; zhang et al., 2014). as anticipated, wet seasons consistently have higher water presence than dry seasons. the difference was more noticeable between 2010 and 2019, suggesting that the dry seasons throughout that decade, vaal river might have witness severe water stress. higher precipitation or surface water retention is probably correlated with higher mndwi values. similarly, the dry season mndwi values correlates with temperature changes, as increased temperature further reduces the value during the dry seasons. however, higher temperature is also noted to worsen water stress in the vaal river, likely due to cumulative evaporation and http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 740 reduced water flows. the clear evidence of variability, with significant fluctuations over the year highlights the sensitivity of the vaal river system to climate induced changes. figure 6: mndwi correlation (wet and dry season) figure 7: mndwi performance on vaal river the dry season low values indicate that surface water availability was substantially decreased particularly from the year 2000 to 2010. however, the most significant decline of water presence was witnessed in 2014 and 2019 with value range of (-0.12), indicating widespread shrinkage and water stress, due to increased temperatures, reduced precipitation and increased water extraction. this report aligned with the study of chabalala et al., (2019) and akhundzadah et al., (2020), who confirmed with temporal correlation that high temperatures during the wet season correlate with less positive values due to accelerated evaporation and increased water stress. the mapping of mndwi in the vaal river basin aided in providing more insight into water shrinkage and stress over the study period using both landsat 5 and landsat 8 (oli). the distribution and dynamics of surface water along the river are spatially revealed by the mapping figure 8 (a &b). the span value ranges from positive to negative outcome indicates fluctuating water availability. the key observations in the maps are indicative of the water body having positive mndwi values or showing areas with significant moisture content aligning with previous studies of (kaplan, 2020; bhaga et al., 2021; botai et al., 2018; zhang et al., 2014). from the map, areas with blue / purple background are areas with strong water presence indicating water availability http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 741 in the vaal river. wet season have more record of blue / purple background with significant evidence in 2009, while other wet season such as 1998, 2007, 2014 and 2019 displayed fluctuation in water presence. reduction in blue background areas or changes to other colours are signals of water stress and shrinkage the yellow / red background represents sparse or no water suggesting water stress usually caused by climate change. it is observed that the wet season mndwi exhibits a strong dependence on precipitation than the dry season mndwi, demonstrating rainfall critical role in replenishing water bodies during the wet season as depicted by mpanyaro et al., (2024); zhang et al., (2020). the dry season mndwi correlates with temperature changes, as increased temperatures further reduce the mndwi values during the dry seasons. this reflects reduced water availability and increased evaporation during low rainfall seasons figure 8(a & b). dry season mapping reports more of yellow and red background indicating sparce and shrinkage however, significant evidence was noticed in 2023 reflecting increasing climate impact on surface water availability. the outcome of this study aligned with studies by wang et al., (2018) and banda et al., (2024) who utilized remote sensing to demonstrate the sensitivity of surface water dynamics to climate variability. mndwi reflectance map – wet season legend landsat-5: 1993 – wet season. landsat-5: 1998 – wet season. landsat-5: 2007 – wet season. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 742 landsat-8: 2014 – wet season. landsat-8: 2019 – wet season figure 8a: mndwi for selected years (wet season) mndwi reflectance map – dry season legend landsat-5: 1993 – dry season. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 743 landsat-5: 2007 – dry season. landsat-8: 2014 – dry season. landsat-8: 2019 – dry season. landsat-5: 1998 – dry season. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 732-747. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 744 landsat8: 2023 – dry season. figure 8b: mndwi for selected years (dry season) significant climatic change impact was found in the vaal river basin throughout a thirty-year period, as evidenced by changes in temperature, precipitation, and streamflow variability that affected water resources both geographically and temporally. higher altitude regions had lower climates and more reliable precipitation, based on data gathered upstream, downstream regions, which are defined by lower altitudes, had higher temperatures and less predictable precipitation. the outcome from mndwi revealed seasonal variations in the water surface area, with noticeable drops in water availability especially during dry season resulting from combined impacts of evaporation, rising temperatures, and decreased inflows. these findings aligned with the report of climate change on the hydrological cycle, consistent with studies by kusangaya et al., (2014) and vanrooyen et al., (2018), where increasing temperatures and uneven precipitation was confirmed as key indicators of climate stress on water systems. significant variations across the study years demonstrated the variability of precipitation patterns, following periods of high rainfall contributing a major impact on the availability of water resources. water availability is uneven throughout the basin as a result of this fluctuation. significant variations between wet and dry seasons were equally found when streamflow report was examined using recording stations connected with precipitation data. the weak relationship recorded on streamflow analysis can also be attributed to human interventions impacting on the surface water aside from climate effects. the outcome of streamflow variability correlates with studies by wang et al., (2018) and akhundzadah, et al., (2020) who utilized remote sensing to demonstrate the sensitivity of streamflow dynamics to climate variability. 4. conclusion this study highlights the significant impact of climate change on the water resources of the vaal river basin using combined consequences of rising temperatures, erratic precipitation patterns, and streamflow effects. notable patterns across the three-decade study period demonstrate the catchment's vulnerability to climate change. the investigation showed decreased water availability during dry seasons and an increased trend in temperatures, which was especially noticeable downstream intensifying water scarcity. trends in precipitation showed notable interannual fluctuation, with rainy years increasing water availability within the vaal river channel. additionally, the mndwi analysis offers a temporal and spatial perspective for comprehending surface dynamics. it displayed seasonal variations, with inconsistent recovery during the wet season, which is hampered by rising temperatures, and decreases in water bodies during the dry season. variability in intensity indicates that certain parts reflect water more strongly than others. the findings are consistent with regional and international studies, highlighting the urgent need for flexible water management techniques. iwrm strategy, entails equitable water allocation through effective maximization of its use to balance the demands of household, industrial, and agricultural applications while maintaining environmental flow releases. additional effort should be channeled towards sustainable remedies that will support the reduction of climate change effect on water resources while further research is proposed using high-resolution satellite imagery from sentinel imagery and landsat 8 (oli) to improve the understanding and clarity of water stressors in the catchment. references akhundzadah, na., soltani, s. and aich, v. 2020. impacts of climate change on the water resources of the kunduz river basin, afghanistan. climate, 8(102): 1-19. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; 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mailto:fayomiuche@gmail.com mailto:pieterv@wrp.co.za arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):33-50 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 33 original research article evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion e. a. adu1*, e. i. bamishaiye2, b. ibrahim2, j. jude1, o. s. kamaldeen1 and a. a. isiaka1 1post-harvest engineering research department, nigerian stored product research institute kano, kano state, nigeria 2perishable crop research department, nigerian stored product research institute kano, kano state, nigeria *corresponding author’s email address: aduadeyemi@gmail.com 1.0 introduction onion (alluimcepa) is one of the most important vegetables in nigeria, belonging to the family leliaceace (alabi and adebayo, 2008). its economic importance cannot be overemphasized as it is an important vegetable crop whose distinctive flavour is appreciated globally. it is remarkably known for its aroma, taste and lachrymatory effects, it plays a significant role in the industries as constituents for moth repellent, beverages, expectorants, and condiments in biscuits (sharma et al., 2005). studies have shown article information abstract storage of onion usually by cooling has been problematic due to poor electricity supply. thus, this study assessed the effectiveness of artificially aerated onion structure (aaos) and evaporative cooling structure (ecs) for the storage of fresh red onion. a total of 4650kg of red onion was stored for 7 months (march to october) and was monitored monthly to observe physiological and biochemical changes using aaoc and other standard methods. data collected were subjected to descriptive statistics and t-test at significant difference of p<0.05 using spss. increase in the percentage weight loss of the stored onion was observed as relative humidity increased especially when the relative humidity surpassed 50%. ecs had 27.03% weight loss recorded in may (2nd month of storage) while aaos had 11.1% weight loss in july (fourth month of storage). at the end of the experiment the average weight loss was 65.76%, 72.00%, and 76.12% for aaos, conventional method and ecs respectively. there was an increasing trend in the proteins, carbohydrates and oil contents of onion in aaos and were significantly (p < 0.05) higher than the increase in conventional storage method and ecs. declining trend was observed in ascorbic acids (aa) contents in the stored onions in all treatments leaving more retention (10.4% aa and 5.48% aa), in aaos and conventional storage method respectively more than in ecs. total polyphenolic contents increased from an initial 5.10±0.02 to 12.08±0.00, 9.95±1.03 and 8.97±1.03 gae (mg/g) fresh weight in aaos, conventional storage method and ecs respectively. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 7 august, 2022 revised 30 september, 2022 accepted 6 october, 2022 keywords: storage artificial aeration onion ecs http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 34 that bioactive onion molecules contribute to lowering bone re-absorption and preventing degenerative diseases due to ample polyphenols and potential antioxidants (shahzadi et al., 2005). one of the advantages of onion is that the bulbs can be harvested and sold either green in salads or as mature bulbs (lannoy, 2001). mature onion contains approximately: water (86%), protein (1.4%), fat (0.2%), carbohydrate (11%), fibre (0.8%) and (0.6%) (anju et al., 2010). the carbohydrate is principally in the form of sugar (fao, 1998). more so, it is ranked as the second most important vegetable after tomato in nigeria (hussaini et al., 2000). over 64 million metric tonnes are produced worldwide; nigeria is ranked among the top ten in the world and 4th in africa with about 621,000 metric tonnes (faostat, 2010). about 50% of onions produced in 2010 under irrigation and rain-fed cultivation in nigeria were from kano state, nigeria (knarda, 2011). according to pelter et al. (2000), cultivation of this crop has developed steadily in tropical areas for more than 40 years. most of the onion produced in nigeria comes from the northern part of the country, such as kano, sokoto, borno, bauchi, jigawa, katsina and zamfara (inuwa, 2001). onion consumption is spread throughout the year, and there is a constant demand for onion all year round. as a seasonal crop, price tends to skyrocket during the off-season, so attempts made to store and minimize huge spoilage of onion are still not very efficient, especially in africa; this is due to the high moisture content (≥80%) of onion which allows for microbial infestations (akbari et al., 2001) and unfavourable ambient condition for storage such as high temperature and high relative humidity during raining season. the success of onions in adapting to most common storage techniques apart, from drying, is relatively poor, with storage losses reaching as high as 66% in some cases (olusola et al., 2018). however, this essential commodity's sensorial and nutritional integrity depends on its freshness and wholesome state rather than in dehydrated form. onion has comparatively low storage ability without cooling. bulbs are usually stored until the next season's harvest or for a more extended period due to a seasonal glut in the market. significant losses in quality and quantity of onion occur during storage. therefore, the storage of onion bulbs has become a severe problem in tropical countries like nigeria. the storage methods mainly adopted depend on the traditional knowledge, and commonly practised methods such as bags, room/stores, rhumbus, woven baskets, cribs, and the associated losses are pretty high. sprouting, physiological loss in weight and microbial spoilage are often observed in storage. three are two distinct storage approaches to storage of fresh onions one is cooling of storage space to 20c and control of humidity to 65-70% have been seen to be effective in the storage of fresh onions for up to 6 months, and the second is storage at ambient condition (tripathi and lawande, 2019). the first method has not been adopted in nigeria as it is capital intensive and electricity-dependent, with electricity still erratic in the country. in contrast, the second condition prevails in tropical countries, which encourages more storage losses (tripathi and lawande, 2019). file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 35 hence, adequate storage facilities that do not depend on electricity from the national grid must be developed to ensure the supply of the commodity all year round. this study aims to evaluate low-cost onion storage structures that can handle bulk storage of fresh onions and ascertain their storage potential in extending the shelf life of fresh onions, thereby reducing post-harvest losses. 2.0 materials and methods 2.1 experimental location the experiment was carried out at nigerian stored product research institute, kano, located in north western nigeria which has a semiarid climate (figure 1). the experiment covers a period of 7 months, from march to october 2021. figure 1: average climatic condition of kano, north-west nigeria (altitude 473m) source: http://www.kano.climatemps.com/graph.php 2.2 experimental design a comparative study of the effect of three storage methods; (i) artificially aerated onion structure (aaos), (ii) evaporative cooling structure (ecs) and (iii) the conventional storage method on the physical and biochemical parameters of the stored onion carried out. a total of 4650kg of onions was used for this experiment. the average weight of a bag of fresh red onion was 125kg and 12.5bags (1550kg) was stored in each storage http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com http://www.kano.climatemps.com/graph.php galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 36 methods and replicated three times. the bulbs were monitored monthly to observe physiological and biochemical changes in storage. parameters measured include ambient and storage temperatures and relative humidity, percentage weight loss, percentage of sprouted bulbs in storage, moisture content, ascorbic acid content, total carbohydrates, oil content, protein content, total phenolic content and total carotenoids. 2.3 description of selected storage structures 2.3.1 artificially aerated onion structure (aaos) the aaos is expected to handle bulk storage of fresh onions. the frame of the onion storage structure was made from metal square pipe (2" x 2") for durability, and the body is made of embossed plywood, as seen in picture 1. the structure has a dimension of 8' x 8' x 4' and was set up inside a warehouse to achieve air tightness on all sides except at the open top. interlock block was arraigned at the base to create an elevation of about 15cm (figure 2) upon which wire mesh is laid. the wire mesh was welded to angle iron on all sides for rigidity. a standard-size drum opened on both ends was attached to the wire mesh's centric middle, and an ac axial fan (180w) was attached to the drum at the top. the fan is powered by a solar power assembly (figure 2) which includes six (160w) photovoltaic cells, a 60a charge controller, a 1.5kva power inverter and a 220ah tubular battery. the operation of the ventilating system is to exhaust high humidity air, thereby preventing condensation from occurring on the onions and eliminating local heating within the onion bulk. during the holding period, onions maintained a ventilation airflow rate of 1 m3/min/m3 (1 cfm per cubic foot). figure 2: artificial aerated onion structure with solar power setup 2.3.2 evaporative cooling structure (ecs) ecs is a low-energy, environmentally friendly cool chamber made from locally available materials that utilise evaporative cooling principles. the evaporative cooled storage structure has proved to be useful for short-term, on-farm storage of fruits and vegetables in hot and dry (amrat et al., 2013). evaporative cooling is an efficient and economical means for reducing temperature and increasing the relative humidity of an enclosure and has been extensively tried for to enhance the shelf life of horticultural produce (jha and chopra 2006; dadhich et al., 2008; odesola and onyebuchi 2009), which is essential for maintaining the freshness of the commodities (dadhich et al., 2008). evaporative cooling is an environmentally friendly air conditioning system that file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 37 operates using induced heat and mass transfer processes where water and air are working fluids (camargo 2007). 2.4 performance evaluation of the structure 2.4.1 sample collection and preparation red onion bulbs, locally known as yan-gashua in the hausa language, were purchased from onion farm gate in kura, kano state. after curing, the onions were carefully bulk loaded into aaos, ecs using crates (figure 3 and 4) and conventionally (single layer spreading in a ventilated dark room) for a seven-month storage period. a representative sample using randomization was taken from each storage method every two months for physical and biochemical analysis. experimental analyses were in triplicates in all cases. figure 3: loaded aaos figure 4: loaded ecs 2.4.2 analysis of physical properties physical properties evaluated were storage temperature, storage relative humidity, percentage weight loss and percentage sprouting. the storage and ambient temperature and relative humidity were measured using temtop data logger, model: temlog 20h with temperature accuracy of ±0.5ocand humidity accuracy of ±3%rh. 2.4.2.1 determination of percentage weight loss this was measured using methods described by nicoli (2012). the weights of the onions were measured monthly using a digital weighing balance. the physiological changes observed included percentage weight loss and sprouting incidence. the percentage weight loss was calculated using equation (1) 𝑊𝐿 (%) = ( 𝑊𝑜 − 𝑊𝑛 𝑊𝑜 ) 𝑥 100 (1) where wl = weigth loss (g), wn = weight after n months (g), wo = initial weight (g) http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 38 2.4.2.2 determination of percentage sprouted the incidence of sprouting of onion was measured by manual counting and expressed as a percentage. after each counting, the sprouted onions were discarded to avoid double counting. bulbs that were sprouted and rotted due to sprouting were considered sprouted. the percentage sprouted was calculated using equation (2) 𝑁𝐿 (%) = ( 𝑁𝑜 − 𝑁𝑛 𝑁𝑜 ) 𝑥 100 (2) where: nl = percentage sprouted, nn = number of onion bulbs after n months, and no = initial number of onion bulbs 2.4.2.3 determination of moisture contents moisture content was determined according to aoac hot-air oven method of 2016. 5.0g of onion sliced was weighed into pre-weighed moisture dishes and kept in an oven set at 105°c for four hours. after a constant weight was recorded three times, the difference in weight of the moisture dishes were then weighed again post-drying. the moisture content was calculated using equation (3): (%)𝑀𝐶 = ( (weight of wet sample+ pan)−( weight of dried sample + pan) (weight of wet sample + pan)− (weight of pan) ) 𝑥 100 (3) 2.4.3 biochemical analysis the biochemical parameter of the stored onion determined include ascorbic acid content, total carbohydrate, oil content, protein content, total phenolic content, and total carotenoids 2.4.3.1 determination of ascorbic acid content vitamin c content was determined according to titration method (aoac, 2016 and nielsen, 2017). about 2.0g of macerated sample was weighed into 10ml distilled water.7.0ml of extraction solution containing 15g metaphosphoric acid, 40ml acetic acid glacial in about 500ml distilled water was dispensed to 2.0 ml of sample aliquot. 2-3 drops of thymol blue indicator (0.1g thymol blue in 10.75ml of 0.03m naoh diluted in 250ml water) was added to aliquot and then titrated with indophenol standard solution to rosy pink at end-point. standard ascorbic acid solution prepared by dissolving 0.05 g in 50ml in extraction solution was then titrated in similar ways to samples. it was calculated using equation (4) vitamin c (mg/100g) = ( average titre (sample −blank) average titre of standard ) 𝑥 100 (4) 2.4.3.2 determination of total carbohydrates about 1g of macerated sample was placed in 25ml conical flask containing 10ml distilled water which was shake vigorously and followed by 15ml of 52% perchloric acid. after 30 minutes of votexing, mixture was filtered and about 1.0ml of filtrate was was file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 39 mixed with anthrone reagent in a test tube and absorbance taken at wavelenght 620nm using a pg-t80 spectrophotometer. the total soluble carbohydrates was then estimated using the standard curve of glucose (mansfield 2020 and pearson et al.,1976). 2.4.3.3 determination of oil content oil content was determined using soxhlet extraction method according to aoac (2016). 3.0g of pulverized onion sample was weighed into a thimble. the thimble was placed in the extraction unit of the soxhlet apparatus. about 230ml of petroleum ether was poured into a pre-weighed round bottom flask. the apparatus was set to boil at 80°c for 4 hours after continuous reflux of condensed solvent through the sample in the extraction thimble. it was calculated using equation (5): oil content (%) = ( weight of oil extracted weight of sample ) 𝑥 100 (5) 2.4.3.4 determination of protein content crude protein content was determined as described by kjedhal procedure in aoac (2016). approximately 0.5g of pulverized sample was weighed into digestion tube, followed by addition of kjedhal table (catalyst) then 15ml of concentrated hydrochloric acid was added. the mixture was digested at 420°c on digest stove. after digestion (clearly solution), a 40% sodium hydroxide solution was suctioned into it; then a distillation process involving the solution mixture and boric acid was made through continuous flow of distilled water in the distillation set-ups. after about 50ml of distillate was collected into the boric acid, the distillate was then titrated with 0.05m hcl using mixed indicator of bromo-cresol green and methyl red. it was calculated using equation (6): protein content (%) = ( (a−b) x 0.05 x 1.4007 x 6.25 weight of sample used (0.5g) ) 𝑥 100 (6) where: a = titer value of sample (ml); b = titer value of blank (ml), molarity of hcl used = 0.05m; 1.4007 = equivalent of atomic mass of nitrogen, 6.25 = conversion factor of nitrogen. 2.4.3.5 determination of total phenolic content 2.4.3.5.1 extraction of aliquot about 500mg of pulverized onion sample was added to 25ml of methanol-water (80:20v/v) and then sonicated for 1hour. the mixture was then centrifuged at 3000g rpm for 30minutes and extract was collected twice after being spun for the second time into eppendorf tube and completely wrapped with aluminium foil ready for analysis (albuquerque et al., 2017). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 40 2.4.3.5.2 gallic acid standard preparation 12.5mg of gallic acid crystal was weighed and dissolved in 50ml volumetric flask made up to mark methanol-water (50:50) to produce a stock solution of 250mg/l which was then used to produce solutions of 50, 100, 150 and 200mg/l (nirmala et al., 2020). 2.4.3.5.3 determination of total phenolic contents total polyphenols contents (tpc) were determined by method used by lachman et al. (2003) and expressed in mg gallic acid equivalent (mg/dl) of dried weight matter. 0.25ml of 500mg/l solution of each sample was added to 2.5ml folin-ciocalteu reagent (fcr) followed by 2.0ml of 1m sodium carbonate. likewise, 0.25ml of each of the gallic standard solutions were used in lieu of sample to obtain calibration curve; while 0.25ml of methanol-water (50:50) was used as blank in place of sample. the reaction mixes were allowed to stand at room temperature for 15minutes in a dim light room where the absorbance was then measured spectrophotometrically at 765nm using a t80 pguv/vis spectrometer. tpc was expressed as gallic acid equivalent (gae) mg/g fresh weight (fw) of sample. 2.4.3.6 determination of total carotenoids the total carotenoids were evaluated by the spectrophotometric method described by astrid et al. (2012) and chan and cavaletto (1982). about 6g of pulverized onion sample was mixed with 5.0g of celite and 15ml methanol (70%v/v) and then filtered using whatman filter paper. the residue was extracted up to three times using 20ml of 1:1 acetone-petroleum ether (v/v). the extract was then transferred to 500ml separating funnel where a 5ml of 10% koh (v/v) in methanol was added and mixture allowed standing for 90minutes. partition achieved following the addition of 15ml petroleum ether and 20ml nacl (20%w/v) was separated as the hypophasic layer were discarded while the epiphasic (upper) layer was washed three times with 20ml of distilled water to remove excess acetone. it was then filtered through a funnel plugged with 3.0g anhydrous sodium sulfate to remove residual water. the filtrate was made up to 100ml petroleum ether and absorbance was measured at 450nm wavelength. the total carotenoids content (µg/g) was calculated using beer-lambert’s law as shown in equation (7) 𝐴 = 𝐸𝐶𝐿 (7) where: a = absorbance, e = extinction coefficient of carotenoids = 1.25x104 µg/l; c = concentration and l = path length of cuvette (1cm) onions have been evaluated for considerable nutritional value such as lipid, protein, reducing sugar, iron, calcium, vitamin c (anju, 2010), phenolic contents as well as antioxidant activity (cheng et al., 2013). bulb onions varieties are the red tropicana, bombay red (brown onion), white onion among others (nuutila et al., 2003). artificial aeration of onion storage structure provides a more conducive surrounding temperature and relative humidity that slows deteriorations especially in a long-term storage. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 41 2.5 data analysis data collected was subjected to appropriate statistical analysis such as descriptive statistics (mean value, standard deviation and percentage) and t-test using excel and spss. table values are data expressed as mean ±sd of three replicates. different superscript in the same column were used to indicates significant difference at p<0.05 between treatments. 3.0 results and discussion a summary of the result of physical measurements and biochemical changes of the stored onion was discussed in this section. 3.1 storage temperature and relative humidity of the selected storage facilities figures 5 and 6 show the average three-hourly temperature and relative humidity for the selected storage facilities, respectively, and it should be noted that conventional storage condition is ambient condition. the temperature within the ecs was observed to be lower and relative humidity higher than in the other two storage methods, which can be attributed to the evaporative cooling effect in the ecs. aaos has a slightly lower temperature and relative humidity as compared to ambient due to the aeration from the fan blowing through the bulk onion bulbs. furthermore, it was observed that the temperature and relative humidity of the selected storage methods follows the same trend as that of ambient condition; that is, they are influenced and respond accordingly to changes in ambient condition. furthermore, the average monthly measured ambient temperature and relative humidity show that the hottest days lie from late march to early june with low relative humidity. the relative humidity started rising in june at the onset of rainy season as seen in figure 7. data represented in figure 7 is important as it has been established from figures 5 and 6 that the temperature and relative humidity of the evaluated storage methods mirrors that of the ambient condition. figure 5: average 3-hr temperature (0c) recorded in the three storage methods 0 5 10 15 20 25 30 35 40 45 0 0 :0 0 –0 3 :0 0 0 3 :0 0 –0 0 :6 0 0 0 :6 0 –0 9 :0 0 0 9 :0 0 –1 2 :0 0 1 2 :0 0 -1 5 :0 0 1 5 :0 0 –1 8 :0 0 1 8 :0 0 –2 1 :0 0 2 1 :0 0 –2 4 :0 0 te m p er at u re ( 0 c ) 3-hr time conventional storage aaos http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 42 figure 6: average 3-hr relative humidity (%) recorded in the three storage methods figure 7: average monthly recorded ambient temperature and relative humidity 3.2 effect of storage method on percentage weight loss and sprouting the percentage loss in weight is as shown in figure 8 below. for storage of fresh onions, tripathi and lawande (2019) and walter et al. (1985) stated that the best holding temperature is at or near 6°c, with a relative humidity between 60 and 70 percent, emphasizing that higher humidity above 70 percent promotes sprouting and bulb decay. this desired temperature and humidity can only be achieved through refrigeration which requires electricity. therefore, with the premise that the selected storage methods do not use electricity and are influenced by ambient conditions, this study observed that the effect of temperature on the shelf life extension of onion is not 0 10 20 30 40 50 60 70 80 90 100 0 0 :0 0 –0 3 :0 0 0 3 :0 0 –0 0 :6 0 0 0 :6 0 –0 9 :0 0 0 9 :0 0 –1 2 :0 0 1 2 :0 0 -1 5 :0 0 1 5 :0 0 –1 8 :0 0 1 8 :0 0 –2 1 :0 0 2 1 :0 0 –2 4 :0 0 r el at iv e h u m id it y (% ) 3-hr time conventional storage aaos ecs 0 10 20 30 40 50 60 70 80 90 0 5 10 15 20 25 30 35 mar apr may jun jul aug sept oct r el at iv e h u m id it y (% ) te m p er at u re ( 0 c ) month average monthly temperature average monthly relative humidity file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 43 as critical as the effect of relative humidity. this was seen when figures7 and 8 were compared, as it was observed that there was a rapid increase in the percentage weight loss as the relative humidity increases, especially when the relative humidity surpasses 50% from july to october, but that cannot be said of temperature. from figures 2 and 3, ecs was seen to be better than aaos and conventional storage methods in lowering the temperature but, poor in lowering of relative humidity and, as such, perform least in preventing rottenness and sprouting of the onion bulbs in storage. aaos and the conventional storage method had their first visible sprouting observed in july (the fourth month of storage) which were sparsely distributed at the top of the stored onions as seen in figures 9 and 10while sprouting was observed in may (the second month of storage) in the ecs. it kept increasing in occurrence till the termination of the storage experiment. it was observed from figures 8 and 11that sprouting is responsible for about half of the percentage loss in weight. vintila et al., (2014), observed that sprouting was common to all varieties of onion stored at different temperatures and kukanoor, (2005) reported that sprouting caused shrivelling of bulbs, consequently onion bulbs lost marketable quality. an increase in the rate of sprouting was observed at the fifth month (august) for onions stored in aaos and conventional storage reaching 11.7% and 18% respectively while in ecs 21.6% sprouting rate was already observed in june (third month of storage). as seen in figure 1, august has the highest level of precipitation in kano and consequently the highest levels of relative humidity which encourages sprouting. an increase in the rate of weight loss was observed in the fifth month (august) for onion stored in aaos and conventional storage reaching 28.27% from 10% in july and 38% from 24% in july, respectively, while in ecs, 39.36% weight loss was already observed in june (third month of storage). as seen in figure 1, august has the highest level of precipitation in kano and consequently the highest levels of relative humidity, which result in rottenness and sprouting of the bulbs. conditions inside the ecs are such that due to wetting of the padding sand, humidity within the chamber was higher than needed for the shelf-life extension of fresh onion. thus, a higher level of loss was recorded. the nature of weight loss observed during the experiment is a physiological loss in weight, rottenness and sprouting of the onion bulbs. figure 8: percentage weight loss of onion in three different storage methods 0 20 40 60 80 march april may june july aug sept oct p e rc e n ta ge lo ss month conventional storage aaos ecs http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 44 figure 9: onions stored in aaos showing sprouting after the fourth month in storage figure 10: onions stored conventionally showing onset of sprouting after fourth month in storage figure 11: percentage monthly loss due to sprouted onion in three different storage methods 3.4 effect of storage method on nutritional compositions onion to many is just a spice for food delicacies. however, its nutritional compositions cannot be over emphasized. macromolecules such as proteins, carbohydrates, lipid (oil) contents which are precursors of total derivable energy value for any form of food substance also constitute a profile of nutritional exigencies in onion bulbs. from tables1 and 2 , the observed increase in carbohydrates was quite more than it was observed in protein and oil contents. many food substances have shown an increase in protein and carbohydrates as moisture contents declines due to concentrated linkages in the amino groups and glycolytic bonds, respectively (tao and linchun, 2008).the decreasing moisture content was due to tissue respiration of onion bulbs and was more observed with the aaos due to steady aeration of the storage environment. 0 10 20 30 40 50 60 p e rc e n ta ge s p ro u te d month conventional method aaos ecs file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 45 table 1. some nutritional parameters of fresh red onion in storage storage time (month) moisture (%) protein (%) total carbs (%) asos cs ecs asos cs ecs asos cs ecs 0th 78.39 ±0.01e 78.39 ±0.01e 78.39 ±0.01e 1.95 ±0.1g 1.95 ±0.10g 1.95 ±0.10g 15.35 ±1.0h 15.35 ±1.00h 15.35 ±1.00h 2nd 71.10 ±0.0g 75.02 ±0.01d 76.05 ±0.01d 2.27 ±0.1d 2.22 ±0.06b 2.11 ±0.06b 15.99 ±2.0d 15.63 ±1.50a 15.53 ±1.50a 4th 65.17 ±0.83f 69.91 ±0.1a 71.94 ±0.1a 2.47 ±0.0e 2.35 ±0.06c 2.26 ±0.06c 16.80 ±2.0e 15.88 ±1.9b 15.72 ±2.0 6th 61.79 ±0.01b 65.03 ±0.0f 68.22 ±0.0f 2.58 ±0.0a 2.47 ±0.01f 2.33 ±0.01f 17.34 ±0.0c 16.22 ±0.0c 16.16 ±0.0c values are data expressed as mean ±sd of three replicates. different superscript in the same column indicates significant difference at p<0.05. the onion bulbs initially collected for this research were estimated to have an energy value of 80.17kcal/100g which steadily increased during the storage periods to 92.26kcal/100g, 82.26kcal/100g and 84.34kcal/100g in the aaos, ecs and in the conventional storage method (control) respectively (table 2). table 2. oil and energy value of fresh red onion in storage storage time (month) oil (%) energy value (kcal/100g) asos control ecs asos control ecs 0th 0.93±0.0a 0.93±0.01a 0.93±0.01a 80.17 80.17 80.17 2nd 1.13±0.0e 0.96±0.01h 0.95±0.01h 83.21 79.55 79.12 4th 1.18±0.0c 1.02±0.02g 0.99±0.02g 87.70 81.83 80.53 6th 1.22±0.01f 1.06±0.01c 1.02±0.01c 92.26 84.34 82.26 values are data expressed as mean ±sd of three replicates. different superscript in the same column indicates significant difference at p<0.05. 3.5 effect of storage method on bioactive compositions the onion for this current research was analysed only for ascorbic acids, total polyphenolics and carotenoids from many known bioactive compounds of onion bulbs. prior to storage, the onions were analysed to determine to have 6.21±0.05 mg/100g, 5.10±0.02gae (mg/g) fresh weight and 1.02±0.00 µg/g contents of ascorbic acids, total polyphenols and total carotenoids respectively as seen in table 3. fruits and vegetables with less moisture content due todehydration tends to increase some bioactive compounds (jayeeta, et al., 2012; bala et al., 2021). however, the composition and concentration of any bioactive compounds are depend on certain intrinsic and extrinsic factors such as genetics and cultivars, soil and growing conditions, maturity status and postharvest storage conditions (jaffery et al., 2003; chaudhary et al., 2018). ascorbic acids have been reported to be thermo-labile and photo-sensitive, which are prone to degradation during thermal processing and storage (jayathunge et al., 2019). http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):33-50. issn 1596-2490; eissn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 46 table 3. some bioactive parameters of fresh red onion in storage storage time (months) ascorbic acid (mg/100g) total polyphenols (gae mg/g) fw total carotenoids (µg/g) aaos control ecs aaos control ecs aaos control ecs 0th 6.21 ±0.05a 6.21 ±0.05a 6.21 ±0.05a 5.10 ±0.02a 5.10 ±0.02a 5.10 ±0.02a 1.02 ± 0.00b 1.02 ± 0.00b 1.02 ± 0.00b 2nd 5.40 ±0.11c 5.00 ±0.02g 4.70 ±0.02g 5.61 ±0.11b 5.65 ±0.05d 5.52 ±0.05d 0.77 ±0.01e 0.77 ±0.01e 0.74 ±0.01e 4th 4.80 ±0.00e 4.31 ±0.05d 4.01 ±0.05d 9.04 ±0.05e 6.09 ±0.11e 5.90 ±0.11e 0.53 ±0.12f 0.53 ±0.00f 0.50 ±0.00f 6th 3.20 ±0.05d 2.86 ±0.11e 2.55 ±0.11e 12.08 ±0.00d 9.95 ±1.03b 8.97 ±1.03b 0.07 ±0.05a 0.069 ±0. 05a 0.064 ±0. 05a values are data expressed as mean ±sd of three replicates. different superscript in the same column indicates significant difference at p<0.05. asos = artificially aerated onion structure; cs= conventional storage, ecs = evaporative cooling structure. table 3 above shows the initial estimated value of ascorbic acids to be 6.21±0.05 mg/100g prior to storage. however, there was a steady decline from this initial value to 3.20±0.05 mg/100g, 2.55mg/100g and 2.86mg/100g in the aaos, the conventional storage and the ecs, respectively. this indicated that ascorbic acid declined more in the ecs. this difference could be due to higher humidity in the ecs than in the other storage methods, resulting in lower moisture loss of onions in the ecs, as seen in table1. similarly, total carotenoids were initially estimated to be 1.02±00µg/g before storage, and there was a continuous decline in the total carotenoid contents of the onion during the storage periods but no significant (p>0.05) difference in the aaos, ecs and convention method. carotenoids are less affected than ascorbic acid levels during the storage of fruits and vegetables (jayeeta, et al., 2012). the total polyphenol contents of the onions were extrapolated from the equation: y= 0.0053x+ 0.0023; r2 = 0.9986) of gallic acid standard as shown in figure 12. it was observed that total polyphenolic content increased from the initial estimate of 5.10±0.02gae (mg/g) fresh weight prior to storage to 12.08±0.00 gae (mg/g) fw, 8.97±1.03gae (mg/g) fw and 9.95±1.03gae (mg/g) fw in the aaos, conventional method and the ecs respectively. there was a significant difference (p<0.05) in the value of total polyphenols in each periodic analysis from all the storage methods evaluated. the aaos retained 41.8% more of the total polyphenols than the conventional method, while ecs retained less than the conventional method. this could be attributed to lower moisture content and lower temperature difference in the aaos than in the conventional method. in contrast, ecs could be attributed to higher moisture content than the conventional method. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com aduet al: evaluation of evaporative cooling structure (ecs) and artificially aerated onion structure (aaos) for storage of fresh red onion. azojete, 19(1):33-50. issn 1596-2490; e-issn 2545-5818,www.azojete.com.ng corresponding author’s e-mail address: aduadeyemi@gmail.com 47 figure 12: plot of gallic acid standard absorbance (nm) against concentration (mg/dl). 4. conclusions based on the finding of the study, temperature and the relative humidity of aaos, ecs and conventional storage methods follows the same trend as the ambient condition, that is, they are influenced and responded accordingly to changes in ambient temperature and relative humidity though at different degrees. temperature in the ecs was lower than in aaos and in aaos it was lower than ambient while relative humidity in the ecs was higher than ambient and ambient was higher than in aaos. there was increase in the percentage weight loss of the stored onion as relative humidity increases especially when the relative humidity surpasses 50%. there was an increase in the rate of weight loss at the fifth month (august) for onion stored in aaos and conventional storage reaching 28.27% from 11.1% and 38% from 24% in july respectively while in ecs 39.36% weight loss was already observed in june (3rd month of storage). percentage weight loss in october (7th month) which is the end of the experiment were 65.76%, 72%, and 76.12 for aaos, conventional method and ecs respectively. there was a continuous declining trend in ascorbic acids (aa) and total carotenoids (tc) content in the stored onion for all the treatments leaving a 10.4% (aa), 0.59% (tc) and 5.48% (aa), 4.90% (tc) more retention in aaos and control respectively than in ecs. total polyphenolic contents increased from an initial 5.10±0.02 to 12.08±0.00, 9.95±1.03 and 8.97±1.03 gae (mg/g) fresh weight in aaos, control and ecs respectively. from the findings of this research, aaos is recommended for storage of fresh onion for 4 months with consideration to the time of the year and agro-ecology of the region, as it was found to be more desirable to curb the enormous wastage during glut and for better retention of nutritional and bioactive compounds prior to use at home or industry. acknowledgement the authors are grateful to the executive director of nigerian stored products research institute for funding this research work. http://www.azojete.com.ng/ file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com galley proof arid zone journal of engineering, technology and environment, march, 2023; 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growers.pacific northwest cooperative extension bulletins pnw 277 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/hp/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%201/azojete%20vol%2019%20no%201/aduadeyemi@gmail.com corresponding author’s email address: engrwhaliy@gmail.com 936 arid zone journal of engineering, technology & environment original research article effects of ergonomic intervention approach on some occupational hazards in automobile workshop in south western nigeria w. a. adesope1*, a. s. onawumi2, s. k. adeyanju1, a. o. ajayeoba2, o. r. oyetunji2, m. o. fajobi3,4 and m. ogunremi1 1department of mechanical engineering, oyo state college of agriculture and technology, igboora, nigeria. 2department of mechanical engineering, ladoke akintola university of technology, ogbomoso, nigeria 3department of mechanical engineering, university of ilorin, ilorin, nigeria 4ladoke akintola university of technology, open and distance learning centre, ogbomoso, nigeria *corresponding author’s email address: engrwhaliy@gmail.com article information abstract automobile workshops house the auto-mechanic, auto-electrical, painting, and panel-beating units. activities carried out in these units expose the workers to some occupational hazards and some musculoskeletal risk factors with perceived consequences on their health. therefore, this study assessed selected automobile workshops within southwestern nigeria to establish the prevalence of ergonomic hazards. a sample size of 496 auto-repair workshops (auto-mechanic, autoelectrical, painting, and panel-beating units) was randomly considered. data was collected using observation, interaction, and structured questionnaires. the structured questionnaires were administered to the respondents to seek their demography and occupational hazards information. standard weighing scale and stadiometer were used to collect the weights and status of the respondents, respectively. some of the common hazards identified in the auto-repair workshops are poor workstation design, poor equipment and tool layout, noise, wet floors, poor lighting, and an unguarded working area, which often lead to slips, trips, and falls, muscle strains, equipment accidents, overexertion injuries, and scald injuries, among others. common occupational risk factors in different workstations across the workshops visited were identified and ranked to establish their prevalence as non-usage of personal protective equipment, ppe, awkward posture, repetitive motion, repetitive manual tasks, and exposure to sharp objects. however, panel beaters (55%) and auto-mechanic technicians (49%) have the highest percentage of people who are normal weight, while painters (62%) and auto-electricians (38.5%) have the highest percentage of people who are above normal weight. quick exposure check, qec results showed that lower back pain and neck pain are the most prevalent musculoskeletal disorders (msds) and are majorly caused by awkward posture at work in an auto-repair workshop. according to this study, vehicle repair professionals were exposed to a variety of risks and hazards, with the lower backs of the workers being the most severely impacted. auto-mechanical technicians in auto-repair workshops are most at risk. submitted 08 april, 2024 revised: 30 june, 2024 accepted: 10 july, 2024 keywords: auto-repair technicians occupational hazards ergonomic hazards safety personal protective equipment © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction occupational health has been described as an area in public health that deals with the provision and maintenance of the highest degree of physical and mental well-being of employees in the work system. it also has to do with the prevention of health hazards resulting from unsafe working conditions that workers are subjected to. another peculiarity of occupational health is that it facilitates the protection of workers from the adverse effects of risk factors prevalent in the workplace. park (2005) defined occupational health as the azojete december 2024. vol.20(4):936-946 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:engrwhaliy@gmail.com mailto:engrwhaliy@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 937 adaptation of work to man, as well as the adaptation of each man to his job. in the discharge of their duties, workers often interact with various work tools and machinery. it is highly imperative, that the workplace configuration match the capability and ability of the worker. therefore, the protection of workers against work-related injuries and illnesses has over the years been an issue of great concern to employers, workers, governments, and every stakeholder in a typical workplace. a safe working environment, effectiveness, safety, and productivity have highly significant correlations with the physical, mental, and social well-being of employees. similarly, cost savings are enhanced in the absence of health challenges, compensations, absenteeism, and the death of an employee (hughes and phil, 2007). the international labor organization stated that there are over 160 million cases of work-related disease and 340 million occupational accidents worldwide annually (ilo, 2022). these occupational accidents were classified as fatal or non-fatal, with victims frequently suffering from amputations, skin irritations, musculoskeletal disorders, cancer, mental and neurological illnesses, respiratory and cardiovascular diseases, and other injuries (punnett and wegman, 2004; tadesse and admassu, 2006; adei et al., 2011). the case of the auto-repair workshop is not an exemption. hazards sourced from pollution, working conditions, accidents, and ergonomic problems are put into adequate consideration in the search for ergonomic and safety interventions, such that the potential hazards housed by the industry are mitigated or eliminated (ferguson et al., 2012). gaining insight into the various occupational hazards posed by auto mechanic workshops calls for an ergonomic assessment of the workshops. this in turn will facilitate a clear understanding of the various activities carried out, the workplace configuration, the identification of hazards, and the required mitigating steps. many studies have been conducted to investigate the level of knowledge of employees as regards occupational hazards in their workplace. one such study carried out in south korea showed that 95% of employees of automobile manufacturing plants had adequate knowledge of the various hazards in their workplace (liu et al., 2008; shireen and thangaraj, 2016). a study on a similar automobile assembly plant reported by sharifian et al. (2011) showed that members of staff working at the welding section had adequate knowledge of the hazards from welding fumes as well as other health implications of such activities carried out in the plant. also, employees in the body repair workshop of an automobile assembly company in the united states of america were quite aware of the negative health implications of the lead to which they were being exposed (lilies et al., 1982). a study carried out in britain also established a high level of awareness among the workers in an automobile manufacturing company. studies have also revealed that employees in small and medium enterprises are more liable to work-related hazards and risks (schneider and becker 2005). this poor awareness could be a result of inadequate resources, poor technical capacity, and the non-awareness of occupational safety and health (osh) standards (ilo, 2005). aliyu et al. (2009) studied the occupational hazards at peugeot automobile nigeria limited (pan) in kaduna, nigeria. the study established that the employees were exposed to chemical fumes, noise pollution, chemical burns, injury by metal chips, eye problems, dry cough. an ergonomic assessment of some existing auto mechanic workshops in selected cities in the southwestern part of nigeria was carried out to gain insight into the various occupational hazards in the workshops, evaluate the workplace configuration, and propose possible mitigating approaches. 2. materials and method the study was carried out in the southwestern part of nigeria, comprising six states. five auto mechanic workshops were considered in the state capital of the study area. the coordinates of the locations of the workshops are lagos (6.6337° n, 3.3573° e), ibadan (7.2513° n, 3.5410° e), abeokuta (7.1154° n, 3.3896° e), osogbo (7.7964° n, 4.5764° e), akure (7.2516° n, 5.2214° e), and ado-ekiti (7.6124° n, 5.2371° e). the population studied included the auto electricians, auto-mechanic technicians, painters, and panel beaters operating in the study area. the auto-repair workshops were purposely selected for the study because, aside from routine maintenance, they were more committed to the proper and adequate working of vehicles. informed consent was obtained from the respondents after explaining the importance and need for the study to them. a stratified random sampling technique was used to select auto mechanics based on their workshop practice. standard tables of sample size, confidence levels, and confidence intervals for random samples were used to determine the 496-sample size for this study (cohen et al., 2007). the respective sample proportion (n) obtained for each state of the study area is presented in table 1. a structured questionnaire was designed to gather the necessary data, and each respondent was made to attend to the particular sections of the questionnaire that pertain to their category of occupation. the questionnaire had four sections to facilitate data collection on demographic and personal information, risk factor identification and safety practices, musculoskeletal disorders, and possible remedies. this study used a stadiometer (wall mounted measuring tape, model: 67033) to measure the stature (m) of the respondents http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 938 and a digital weighing system (model: beichen tcs-a) to measure the weights (kg) of the respondents. the resulting dataset for stature and weight was articulated to determine the body mass index (bmi), using equation (1) (sperrin et al., 2015), and the results were compared with table 2 for analysis. bmi = 𝑊 𝐻2 (1) where w = weight (kg) h = stature (m) table 1: population size and samples s/n state sample size (n) 1 ibadan 104 2 ogun 88 3 lagos 120 4 ado-ekiti 80 5 osogbo 32 6 akure 72 total 496 table 2: body mass index rating (sperrin et al., 2015) bmi weight status <18.5 under-weight 18.5 – 24.9 normal weight 25 – 29.9 over-weight ≥30 obesity a sphygmomanometer (model: cms-08a) was used to measure the blood pressure of the respondents (agrawal et al. 2010). quick exposure check (qec) and rapid entire body assessment (reba) methods were used for the postural analysis of work-related musculoskeletal risk factors of the four groups (autoelectricians, auto-mechanic technicians, painters, and panel beaters) considered, and the results were compared with the scoring table shown in table 3. a field investigation and on-the-spot observation of the dangers in these auto-repair workshops were conducted, and the workers’ occupational risk incidences were evaluated using the risk rating matrix (rrm). figure 1 was then used to assess the data collected from the questionnaires in terms of likelihood and consequences to calculate the risk scores or risk indices for each body component susceptible to accidents. the likelihood and consequence were multiplied to determine the risk score or risk index for each portion of the body susceptible to an accident. to implement rrm in a semiquantitative style, numbers were allocated to each box of the matrix, and a straightforward scoring system was employed to express likelihood and consequence. however, these figures rose as the likelihood and seriousness of the consequences increased. as a result, table 4 lists the necessary actions to be followed to prevent undesirable incidents. equation 2 (work health and safety, 2015) was used to compute the overall risk (or), which was then calculated by comparing the results to the overall risk decision table in table 5. 𝑂𝑅 = ∑𝑛 𝑖=1 𝑅𝑖 𝑁 (2) where ri is the risk index of an ith body part, n is the number of risks and n is the number of workers http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 939 table 3: the qec, reba and rula scoring table (ajayeoba, 2019) quick exposure check scores final reba score final rula score qec level score reba risk level score (action) score risk level (action) <40 satisfactory low risk (l) 41 – 50% moderate risk (m) 51 – 70% high risk (h) >70 very high risk (vh) 1 none (change not necessary) 2-3 low (change may be necessary) 4-7 medium (change is necessary) 8-10 high (change necessary and soon 11-15 very high (change necessary and urget) 1-2 negligible (acceptable) 3-4 low (further investigation and changes may be needed) 5-6 medium (investigation and changes required soon) 7 high (investigation and changes required immediately) likelihood consequences rare (1) unlikely (2) possible (3) very likely (4) almost certain (5) catastrophic (5) moderate (5) moderate (10) high (15) critical (20) critical (25) major (4) low (4) moderate (8) moderate (12) high (16) critical (20) moderate (3) low (3) moderate (6) moderate (9) moderate (12) high (15) minor (2) very low (2) low (4) moderate (6) moderate (8) moderate (10) insignificance (1) very low (1) very low(2) low (3) low (4) moderate (5) figure 1: risk rating matrix (adebiyi et al., 2021) table 4: actions required for the risk rating matrix results (adebiyi et al., 2021) risk level rating required action critical immediate action is needed. access to the hazard should be restricted until the risk can be lowered to an acceptable level high action needed quickly (within 1-2 days). the task should not proceed unless the risk is assessed and control moderate action is required this week to eliminate or minimize the risk. low action required within a reasonable time frame (2-4weeks) to eliminate or minimize the risk. very low risk to be eliminated or lowered when possible table 5: overall risk decision (adebiyi et al., 2021) risk rating descriptor acceptability 20 – 25 critical inacceptable 10 – 16 high likely to be unacceptable 5 – 9 medium could be acceptable 3 – 4 low acceptable 1 – 2 very low very acceptable 3. results and discussion four hundred and ninety-six copies of the structured questionnaire were administered and retrieved from the sampled respondents of the selected automobile workshops such as auto-mechanic, auto-electrical, panel beating, and painting units. http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 940 3.1 demographic characteristics of the respondents demographic characteristics of the sampled respondents are presented in table 6, and it was revealed that 99.1% of the respondents are male and 0.9% are female. this justifies that auto-mechanic technician's job requires high strength and energy and may be difficult for females to do. a larger proportion of auto technicians, 50.9%, were between the ages of 20 and 39. this indicates that the majority of those who work in auto mechanic workshops are in their active years and have a high level of strength as well as the capacity to carry out their jobs. this has a positive impact on the economy because the younger generation is more likely to work because it creates job opportunities for them. only 5.4% of the respondents were in the age range of 13–19 years. this may be a result of school dropouts and can increase the risk factor in auto-repair workshops. it can reduce the effectiveness of safety practices due to little or no education and a few years of working experience. 43.7% of the respondents are within the age range of 40–59 years, all of whom are adults. 3.2 common hazards and incidences in auto-repair workshops the common hazards identified in the auto-repair workshops are poor workstation design, poor equipment and tool layout, noise, wet floors, poor lighting, bad tools, wrong tools and equipment, an unkept environment, and an unguarded working area. these hazards can be grouped into biological, safety, chemical, mechanical, physical, ergonomic, and psychological hazards. these often lead to slips, trips, and falls; muscle strains; being hit by falling objects; crashes and collisions; cuts and lacerations; inhaling toxic fumes; machine entanglement; equipment accidents; overexertion injuries; and scald injuries. table 7 shows that the hazards, risk factors, and incidences are consistent with the findings of other researchers. thus, for effective control of these common hazards, the hazards must completely remove as recommended by the hazard hierarchy of controls presented in figure 2 (morris and cannady 2019). however, the least that should be done is to use personal protective equipment (ppe) to avoid any form of incident. table 6: demographic profile of respondents category auto electrician auto mechanic panel beater painter n 92 128 92 92 gender male 100.0 95.6 100.0 100.0 female 0.0 4.4 age 13-19 9.3 4.4 8.0 4.8 20-39 39.5 51.1 44.0 57.1 40-60 51.2 44.5 48.0 38.1 > 61 educational level primary sc 58.1 40.9 24.0 28.6 ssce 27.9 22.6 28.0 33.3 ond 9.5 hnd bsc 4.0 none 14.0 27.0 44.0 38.1 read or write yes 76.7 64.2 44.0 42.9 no 23.3 35.8 56.0 57.1 work hours per day 1-3 4-7 4.4 4.0 19.0 7-10 100.0 95.6 96.0 76.2 10-13 4.8 note that responses of each item sum up to 100% 3.3 auto-repair workshop activities investigations revealed that the major activities being carried out in the selected workshops are those of automechanic, auto-electrical, painting, and panel beating. analysis showed that auto-mechanic activities were the http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 941 most common, with a total percentage of 25.8%, as against 18.5% for each of the others. this shows the peculiarity of the activities involved in the smooth running of vehicles. 3.4 prevalence of common risk factors in auto-mechanic workshops common occupational risk factors in different workstations across the workshops visited were identified and ranked to establish their prevalence as non-usage of ppe, awkward posture, repetitive motion, repetitive manual tasks, and exposure to sharp objects. table 8 shows the risk factors from the highest to the lowest according to the analysis of the responses of the workers. thus, the solutions to any workplace injuries caused by these risk factors are to keep the workshop simple, participate in proper housekeeping, be organized, be stable at work, avoid jumping safety rules, use your ppe regularly, avoid taking shortcuts and be safety conscious. table 7: findings of other researchers as regards the study in nigeria author workforce location risk factors/hazards/incidences awodele et al. (2014) paint factory workers south western, nigeria inadequate use of personal protective equipment adeyemi, et al. (2016) workers of automobile service and repair industry south western, nigeria frequent lifting of automobile components, standing for long period of time at work, work in uncomfortable postures for very long time daily, forceful gripping of components and/or working tools elenwo (2018) automobile mechanics south southern, nigeria biological, chemical, mechanical, physical and psychological johnson and etokidem, (2019) butchers south southern, nigeria inadequate use of appropriate protective wears. inappropriate de-furring methods okon, et al. (2019) chainsaw operators south eastern, nigeria hit by dead trees/branches, fall, machine chain cuts/kick-back, rolling log, snake, bite from bees afolabi, et al. (2021) automobile artisans south western, nigeria inadequate use of personal protective equipment olanrewaju, et al. (2021) automobile repair artisans north central, nigeria pulling heavy weight object, lifting heavy weight object, pushing heavy weight objects, holding heavy weight objects, carrying heavy weight object onawumi et al. (2022) automobile repairs workmen south western, nigeria no usage of sign post, unavailability of safety equipment, ignorance of the usage of personal protective equipment, inability to manage work load demand, ignorance on the essence and importance of adequate body treatment, untidy and unventilated workspace and environment. ozomata et al. (2022) automobile mechanics south western, nigeria burns from various sources, cuts, sharp edges of hand tools and vehicle parts, eye injury from flying objects, fracture from fall of heavy objects, crushed finger/ toes from moving machine parts http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 942 figure 2: hazard hierarchy of controls (morris and cannady, 2019) table 8: ergonomic risk factor of auto-repair workshops ergonomic risk factor auto-mechanic unit painting unit panel beating unit auto electrical unit non usage of ppe non usage of ppe non usage of ppe non usage of ppe awkward posture repetitive motion exposure to, flames, and hot surface awkward posture lifting heavy objects exposure to chemicals and particles exposure to sharp objects working in tight area repetitive manual tasks awkward posture exposure to chemicals and particles working in tight area exposure to noise exposure to gasoline/diesel exhaust exposure to sharp objects working under uncomfortable heights exposure to fuel products falling objects exposure to battery acid, hot surfaces, etc. exposure to high temperatures exposure to noise 3.5 body mass index panel beaters (55%) and auto mechanics (49%) have the highest proportion of personnel with normal weight, while painters (62%) and auto electricians (38.5%) have the highest proportion of technicians who are overweight (figure 3). technicians (painters and auto-electricians) were heavier than average because painting and auto-electrical activities did not require as much strenuous, repetitive, and awkward posture activities as others, as opposed to normal weighted technicians (panel and auto-mechanic). http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 943 figure 3: comparison of bmis for all the categories 3.6. risk assessment analysis the qec results in table 9 show that lower back pain and neck pain are the most common msds and are majorly caused by the awkward posture at work in an auto repair workshop. thus, 53, 33, 44, and 41% of the auto-mechanic technicians, auto-electricians, panel beaters, and painters, respectively, are working above the medium musculoskeletal risk level. table 9: qec results of risk factors assessment of the auto-repair technicians body part auto-mechanic technicians auto-electricians panel beaters painters l m h vh l m h vh l m h vh l m h vh upper arms 28 45 25 2 18 53 25 4 15 31 48 6 13 41 44 2 shoulder 12 30 55 3 17 56 27 0 24 33 40 3 20 43 34 3 neck 8 24 63 5 15 29 54 2 13 30 55 2 12 33 54 1 thigh/legs 14 61 24 1 40 43 17 0 40 43 17 0 33 49 17 1 wrist/lower arm 9 27 59 5 12 51 37 0 12 51 37 0 10 48 41 1 lower back 6 17 72 5 18 53 25 4 15 31 48 6 14 38 46 2 l=low, m=medium, h=high and vh=very high musculoskeletal risk level the results in table 10 revealed that 88, 62, 79, and 36 percent of the auto-mechanic technicians, autoelectricians, panel beaters, and painters, respectively, have a musculoskeletal risk level above the medium level; thus, change is necessary soon. the results also showed that auto-mechanic technicians have the highest risk level, while painters have the lowest. the detailed risk index assessment results and the overall risk level of auto-repair workers (tables 11 and 12) also validated the qec and reba results that automechanic technicians and panel beaters have the highest risk level. table 10: final reba scores of the workers at the auto-repair workshop reba risk level score auto-mechanic technicians auto-electricians technicians panel beaters painters 1 2-3 4-7 8-10 11+ 0 4 2 5 2-3 0 17 3 21 4-7 12 17 16 38 8-10 45 41 41 29 11+ 43 21 38 7 http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 936-946. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: engrwhaliy@gmail.com 944 table 11: overall risk level of auto-repair workers risk level risk rating condition automechanic technicians autoelectricia ns panel beate rs painter s critical 20 – 25 inacceptable high 10 -16 likely to be unacceptable 10 moderate 5 – 9 could be acceptable 6 8 5 low 3 – 4 acceptable very low 1 – 2 very acceptable table 12: detailed risk index assessment results of auto-repair workers auto-repair workers body part very low low mediu m high critic al % % % % % auto-mechanic technicians upper arms 3 20 41 32 4 shoulder 5 12 49 30 4 neck 4 13 60 20 3 thigh/legs 5 17 23 54 1 wrist/lower arm 1 9 21 57 12 lower back 0 7 18 71 4 autoelectricians upper arms 11 19 48 22 0 shoulder 7 18 51 23 1 neck 7 21 39 35 0 thigh/legs 11 35 42 12 0 wrist/lower arm 7 18 52 23 0 lower back 9 17 45 26 3 panel beaters upper arms 3 18 29 42 8 shoulder 5 28 41 24 2 neck 1 15 27 54 3 thigh/legs 1 25 36 36 2 wrist/lower arm 2 14 34 49 1 lower back 1 13 28 53 5 painters upper arms 3 14 35 47 1 shoulder 4 21 38 35 2 neck 3 14 38 43 2 thigh/legs 1 30 45 22 2 wrist/lower arm 3 12 47 38 0 lower back 1 13 35 47 4 4. conclusions this study has established that the auto-repair workers were exposed to various hazards and risk factors, while the lower backs of the workers were mostly affected. auto-mechanic technicians have the highest exposure to these risks. thus, constant training and retraining of workers on safety issues, the compulsory use of ppe, proper housekeeping, and following the safety rules will keep injuries and accidents at bay. references abiola, oa., oke, ao. and koya, oa. 2018. anthropometric characteristics of roadside auto-mechanics: a case study. leonardo journal of sciences, 32: 105-122. 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medical science and public health, l 6(1): 18-22. sperrin, m., marshall, ad., higgins, v., renehan, ag. and buchan, le. 2015. body mass index relates weight to height differently in women and older adults. journal of public health, 1(1): 1 -35. wang, l., weng, s., wen, s., shi, t., sun, g. and zeng, y. 2013. polychlorinated dibenzo-p-dioxins and dibenzofurans and their association with cancer mortality among workers in one automobile foundry factory. science of total environment, 443:104-111. http://www.azojete.com.ng/ mailto:engrwhaliy@gmail.com https://www.researchgate.net/publication/322661602_ict-based_market_information_services_utilization_by_small_scale_farmers_in_southwest_nigeria https://www.researchgate.net/publication/322661602_ict-based_market_information_services_utilization_by_small_scale_farmers_in_southwest_nigeria arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):911-926 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 911 quality characteristics of lamba as affected by different cereal and legume flour blends l. p. mshelia*, d. peter, k. i. fika, t. e. ndahi and f. a. masaya department of food science and technology, faculty of engineering, university of maiduguri, borno state 600230, nigeria *corresponding author's email address: ladi.peter05@gmail.com article information submitted 1 august, 2023 revised 19 sept., 2023 accepted 25 sept., 2023 keywords: cereal composite flour lamba legume traditional food abstract traditional foods are preserved cultural heritage passed down from generation to generation, and their recipes have remained unchanged for centuries. lamba is a traditional food processed from the blends of maize, cowpea and karkashi (false sesame leaves). however, if prepared and consumed, lamba enriched with different flour blends will provide a healthy alternative to consumers. this study aimed to prepare and evaluate the quality of lamba produced from wheat – cowpea – karkashi (wck), wheat– soybeans – karkashi (wsk) and lastly, wheat –bambara groundnut– karkashi (wbk) flour blends in three different ratios, (70:20:10, 60:30:10 and 50:40:10) where maize-cowpea -karkashi (mck) is the control (in the ratio of 70:20:10). the total of ten (10) different samples were produced including the control. proximate composition, functional and microbial content of lamba samples were determined. the proximate composition of the lamba such as moisture, protein, fat, ash, crude fiber and carbohydrate ranged from .40 –9.92%, 7.92 – 15.39%, 3.82 – 9.25%, 2.78 – 3.48%, 2.03 – 3.55% and 64.24 – 73.55% respectively. subsequently, there are significant differences (p≤0.05) between the functional properties such as wettability, bulk density, water absorption capacity and swelling index of the flour blends which ranged from 50.13 – 68.18 sec, 0.60 – 0.76 g/ml, 58.93 – 105.58 %, 1.36 – 2.15% respectively. also, wettability, bulk density, water absorption capacity and swelling index have been determined and the control sample (mck) had the highest. similarly, microbiological analysis shows the bacterial load ranged from 4.9 ×104 – 8.1 × 104 cfu/g and sample wbk 3 had the highest mck (control sample) had the lowest. however, there was no significant difference between all the remaining samples. additionally, fungal load ranged from 1.6 × 10 5 – 4.4 × 105 cfu/g and sample wsk 2 had the highest fungal count while sample wbk 3 had the lowest. sensory attributes of lamba were evaluated ranging from 5.09 – 6.13 for texture, 5.01– 6.38 for aroma, 4.92 – 7.98 for taste, 4.61 – 6.08 for colour and 5.18 – 8.49 for overall acceptability. the study shows that lamba produced from different ratio of wheat, soybean, cowpea, bambara groundnut and karkashi contains higher nutritive value. it is also acceptable as compared to lamba produced from maize, cowpea and karkashi. therefore, this study recommends that the blend of 60% wheat, 30% soybeans and 10% karkashi (wsk 2) can be used for the production of lamba with the desired nutritional and sensory quality as alternative to soybean http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 912 1.0 introduction a wide range of traditional foods is produced in nigeria from local raw materials such as cereals (rice, sorghum, millet) and legumes (soybeans, cowpea, and bambara groundnuts). traditions of cultures and regions have been greatly influenced by traditional foods for decades including foods that have been consumed locally and regionally. furthermore, several traditional foods developed for decade may still have their place in a healthy diet today. some traditional foods may not meet nutritional needs and acceptability. therefore; modification of these food products becomes necessary. generally, the origin of traditional foods in nigeria is lost in antiquity, however, it was believed to have started along with the time the crop cultivation started in the region (mamudu et al., 2017). cereals and legumes are considered as major staple foods. cereal grains such as rice, wheat and maize are important members of the grass family graminae and are of great value within the staple food crops. for decades, cereal grains have been the most important sources of nutrients such as carbohydrates, proteins, vitamins and most importantly dietary fibers, necessary for the growth and human body development (nadeem et al., 2010). wheat is one of the key edible food crops, about two–thirds of the wheat produced is consumed by the world’s population (grote et al., 2021). wheat is the most diverse crop, which is grown throughout the world with approximately 750 million tons produced annually (faostat, 2016). according to adeyeye and akingbala, (2016), extensive attention has been given to wheat-based foodstuffs in the consumer market and also from food companies due to their health–beneficial components. another material is legumes, which are edible crops that belong to the leguminosae family with an enormous diversity of plants and second only to cereals in terms of the level of human consumption (sánchez–chino et al. 2015). they contain desirable amounts of micro and macronutrients that can enhance nutritional quality such as protein concentration, potassium, fiber, and low glycemic index. globally, legumes are the most important source of protein in the diet which has high nutritional value (semba et al., 2021). consumption of legume seeds is believed to have a strong impact on blood pressure reduction while conferring antioxidant benefits (polak et al. 2015; vaz patto et al., 2015). however, supplementing cereals and legumes is known to improve the nutritional quality of foods (gebrelibanos et al., 2013). thus, the combination of cereal and legumes will improve the protein and nutrient density of the food. subsequently, legumes contain high amounts of the amino acid lysine which is low in cereals products hence, can solve the issue of malnutrition in developing countries (abamecha, 2020). lamba is a traditional steamed food product produced from a mixture of maize, cowpea and karkashi (false sesame leaves) complemented with cowpea flour. it is commonly processed in the northern part of nigeria (potiskum, yobe state) by the kare–kare people and is eaten with spiced oil or groundnut soup called daba. it is a local delicacy which form part of the cultural heritage with low nutritional quality because it is produced from only maize (carbohydrate) with little cowpea. therefore, the use of other cereal and legumes has a significant impact on the nutritional value of food especially in developing countries by delivering good nutrients in the diet. (kumari, and sangeetha., 2017). therefore, the objective of this study is to produce lamba from other cereal (wheat and maize flour) and legumes (cowpea, soybeans and bambara nut) blends and to determine the proximate composition, functional properties, sensory characteristics and microbial loads. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 913 2. materials and methods 2.1 materials the raw materials used in the study were maize, cowpea, bambara groundnut, soybean and karkashi (false sesame leaves). the materials were obtained from maiduguri monday market except for wheat which was gotten from lake chad research institute maiduguri. the chemicals/reagents used were analytical grade and were sourced from food analysis laboratory of the department of food science and technology university of maiduguri and the university of science and technology wudil, kano state. 2.2 methods 2.2.1 preparation of wheat flour wheat samples were processed as previously described by quaye et al. (2009), where the sample was sorted and cleaned. the wheat samples were then winnowed to remove the hulls and then thoroughly washed, sun–dried, milled and sieved into flour. the fine flour was then packed and stored for further use. 2.2.2. preparation of maize flour the maize sample was prepared according to the method described by umar et al. (2022) with slight modifications by dehulling the maize sample, winnowed to remove hulls and chaff and sun–dried. it was then thoroughly washed, soaked for 24 hours (1 day) and then sun– dried again after ich maize sample was sorted and cleaned to remove stones, dirt and foreign materials. the dried maize was milled and sieved. 2.2.3. preparation of cowpea flour preparation of the cowpea (vigna unguiculata) was carried out according to the method described by quaye et al. (2009) where the cowpea was steeped in cool water (25°c) for about 15 minutes, dehulled and dried. the cowpea was then coarsely milled, sieved, packaged and stored for further use. 2.2.4. preparation of soya bean and bambara groundnut flour soya bean (glycine max) and bambara groundnuts (vigna subterranean l. verdc) were prepared according to the method described by agbara et al. (2022) where the preparations of both legumes were carried out separately using the same method. the legumes were sorted, winnowed, washed, sundried, then coarsely milled, sieved packaged and stored for further use. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 914 2.2.5. formulation of flour blend the lamba flour blends were prepared from cereal (wheat and maize), legumes (soybean, cowpea and bambara nut) and karkashi in the ratio of 70:20:10, 60:30:10, 50:40:10 of any cereal: legume: karkashi. a total of 10 different blends were obtained including control as shown in table 1. table 1: formulation of flour blends for lamba production sample cereal (%) legume (%) karkashi (%) wck1 70 20 10 wck2 60 30 10 wck3 50 40 10 wheat, soybean, karkashi wheat soybeans karkashi wsk1 70 20 10 wsk2 60 30 10 wsk3 50 40 10 wheat, bambaranut, karkashi wheat bambara groundnut karkashi wbk1 70 20 10 wbk2 60 30 10 wbk3 50 40 10 maize, cowpea, karkashi (control) mck maize 70 cowpea 20 karkashi 10 mck=maize, cowpea and karkashi(70:20:10), wck1=wheat, cowpea and karkashi (70:20:10), wck2=wheat, cowpea and karkashi (60:30:10) wck3=wheat, cowpea and karkashi (50:40:10), wsk1=wheat, soybeans and karkashi(70:20:10), wsk2=wheat, soybeans and karkashi (60:30:10) wsk3=wheat, soybeans and karkashi (50:40:10), wbk1=wheat, bambara groundnut and karkashi(70:20:10), wbk2=wheat, bambara groundnut and karkashi (60:30:10) wbk3=wheat, bambara groundnut and karkashi (50:40:10), 2.2.6. production of lamba five (5) g of potash was placed into 100 ml water and allowed to disperse. the potash solution was thoroughly mixed and added to the chopped fresh karkashi leaves (10%). it was then mixed using a spatula to ensure a homogenous mixture. the flour blends of different ratios from cereal: legumes: karkashi were then added to the mixture to form a stiff dough. the dough was then wrapped into polythene bags and placed in boiling water to cook for 45 min; on high heat. 2.3. proximate analysis the proximate composition of the flour blends and processed lamba sample was carried out according to the standard methods of aoac, (2012) where the moisture, ash, protein, fat, crude fiber and energy level were determined while carbohydrate content was determined by the difference using the equation 1. cho= 100% – (% mc + % ash + % crude protein + % fat + % crude fiber) (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 915 2.3.1. determination of protein content. the protein content of the samples was determined using micro kjeldhal method. ten grams (10g) of catalyst was added to 0.2 g of each sample placed into a digestion flask, concentrated sulfuric acid (25 ml) were added to each digestion flask and placed on the digestion block in a fume cupboard after digestion, a clear and light blue–green colouration solution was obtained. the mixture was then cooled and diluted with 250 ml of distilled water. about 10 ml of the sample was distilled using a distillation apparatus and 10 ml of sodium hydroxide (40%) was added. the released ammonia was absorbed by boric acid which was then titrated with hydrochloric acid (0.02 ml) until the green colour changed to purple. the percentage of nitrogen in the sample was calculated using equation 2. % nitrogen = (𝑇−𝐵)×𝑛𝑜𝑟𝑚𝑎𝑙𝑖𝑡𝑦𝑜𝑓 𝑎𝑐𝑖𝑑×14.008 (𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 ×1000) × 100 (2) where b= blank titer value, t = actual titer value, % protein = %n x 6.25 2.3.2. moisture content determination the moisture content of the samples was determined by the oven–drying method. two (2) g of the sample was weighed and placed in the oven at 105°c for an hour. weight loss expressed as the percentage of the initial weight was regarded as % moisture content. 2.3.3. ash content ash content was determined using a muffle furnace by incinerating 5 g of each sample at 550°c for 5 h. the grey ash was cooled in a desiccator to avoid moisture absorption from the surroundings and weighed to obtain the ash content. 2.3.4. crude fiber the crude fiber was determined by weighing 5g (wo) of the sample into a 500ml erlenmeyer flask. tca digestion reagent (100ml) was added and then boiled for 40 min. the sample was then cooled for 30 min. and filtered through a whatman (no. 4). the residues were then washed with hot water, dried overnight at 105°c and cooled in desiccators. the initial weight of the sample was taken as w1. the samples were burnt in a muffle furnace at 500 °c for 6 h, allowed to cool and re–weighed as w2. the crude fiber was determined using equation 3. % crude fiber = w1− w2÷ (wo) ×100 (3) where: wo =dry weight of food sample, w1 = weight of crucible + fiber + ash, w2 = weight of crucible + ash 2.3.5. fat content the soxhlet extraction method was used for the determination of the fat content of the samples. five (5) g of each sample was weighed into a flat bottom flask of a known weight http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 916 with the extractors mounted on them. the thimbles were held halfway into the extractors with the weighed samples. petroleum ether (boiling point 40–60°c) was used for the extractions. where thimbles were plugged with cotton wool. after the extraction, the solvents were removed by evaporation in a water bath and the remaining part in each flask was dried at 80℃ for 30 min in the oven to dry the fat. the flasks were cooled in a desiccator and reweighed to obtain the weight of fat (%). 2.4. physicochemical analysis of the flours blends. the wettability of the flours was determined according to the method described by okezie and bello, (1988) with slight modification where 1.0g of the sample was suspended in a plastic spatula from a retort stand (15cm) above a beaker containing 500ml distilled water. the sample in the spatula was gently dropped unto the surface of the water, the time taken for the sample to disappear or wetting of the sample is recorded as wettability (sec). water absorption capacity of the flour blends was carried out as previously described by adeleke and odedeji, (2010) with slight modification where 1g of the sample was measured into a centrifuge tube and 15 ml of water was added. the sample was then centrifuged at 3250 rpm for 25 min where the supernatant was decanted. the water absorption was then determined by measuring the free water while retained water by the sample was recorded as water absorbed which was expressed as ml of water absorbed per gram of sample. the bulk density was determined according to the method described by murphy et al. (2003). a measuring cylinder was filled with tap water to the mark of 10 ml and the volume was noted. the measuring cylinder was emptied and 10 ml of the composite flour was poured to the mark of 10 ml. air space between the flour blends was removed by tapping the cylinder for 5 min and the weight was noted. therefore, bulk density was then calculated as bulk density= w𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑎𝑚𝑝𝑙𝑒 volume of the sample (4) swelling index of the flour blends was recorded as the ratio of the swollen volume of the flour to the original volume of a unit weight of the flour. 1g of the flour blends was weighed and placed into a measuring cylinder, the original height was recorded then 5 ml of distilled water was added to the sample and left to stand for 60 mins and the swollen volume was recorded (onwuka, 2018). 2.5. microbiological analyses microbiological analysis was carried out as previously described by obueh et al. (2017) with slight modification where 10 g of lamba sample was blended aseptically using a blender and aseptically introduced into 90 ml of sterile distilled water. serial dilutions of all the samples were carried out to 10–5 and 0.1 ml of selected dilutions were plated out using the pour plate method into nutrient agar (na) (lab m ltd uk) and incubated at 37°c for 24 h for the total bacterial count and potato dextrose agar (pda) (lab m ltd uk) with chloramphenicol was incubated at 25°c for 72 h for total fungal count. all media used were prepared according to manufacturers’ instructions. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 917 2.6. sensory evaluation of lamba produced the sensory properties of lamba were evaluated using the 9–point hedonic where 9 represents like extremely, 1 dislike extremely and 5 neither liked nor disliked. twenty (20) semi–trained panelists (students, all females) from the department of food science and technology, university of maiduguri. the coded sample was assessed by the panelists based on the flavour, aroma, taste, colour and overall acceptability at a single session as previously described by ibanoglu et al., (1995) 2.7. statistical analysis statistical analysis was determined in duplicates and data generated were subjected to analysis of variance (anova) using spss software (version 16). means were separated using duncan multiple range test and a p–value (p≤0.05) was set. 3. results and discussion 3.1. proximate composition of flour used for the preparation of lamba table 1 shows the proximate composition of the flour used for different blends of lamba. the moisture content of the flour ranged from 8.12 ± 0.01 – 10.04 ± 0.03 %. wheat flour (wt) was observed to have the highest moisture content followed by maize flour (mz), bambara groundnut (bg), and soybeans (sb) while cowpea flour (co) had the least. according to godswill, (2019), the most suitable and acceptable limit of moisture content for long-term storage should not be more than 10%. in this study, the moisture content of the flour is within the acceptable limit which will enhance the shelf life of the flour by preventing microbial growth and chemical changes. the protein content of the flour ranged from 9.23 ± 0.06 –39.12 ± 0.04 %. however, soybeans flour (sb) had the highest protein content (38.12 ± 0.04 %) as compared to cowpea (21.42 ± 0.03 %), followed by bambara groundnut (19.41 ± 0.02 %), wheat flour (10.92 ± 0.03 %) while maize flour (9.23 ± 0.06 %) had the lowest. however, this was expected because the protein content of cereals and legumes varied significantly as maize is cereal and soybean is a legume with higher nutritional quality. this is similar to a previous study reported by agbara et al. (2022) on the proximate composition of different flour although for the production of bread. fat content of the flour varied significantly (p<, ranging from 3.76 ± 0.04 – 20.89 ± 0.01 %. the fat content of soybeans flour is significantly higher than all the samples while maize flour had the lowest fat content. subsequently, soybeans are also regarded as oil seed crop that provides more than 50% of the world’s oilseed production (wilson, 2008). ash is the inorganic residue remaining after the water and organic matter are removed by heating. the ash content in food products could be used as an index of mineral constituents of the food (sanni et al., 2008). the ash content of the flour ranged from 1.52 ± 0.04 – 4.84 ± 0.01 %. the ash content in soybeans was significantly (p< 0.05) higher as compared to all the samples. the ash content of legumes is expected to be higher than cereals as they are good sources of minerals. crude fiber of the flour ranged from 2.48 ± 0.05 – 4.08 ± 0.01 %. however, the most important function of fiber is to provide roughage or bulk that aids in the digestion of food leading to lower plasma cholesterol and softens stool (saini et al., 2022). carbohydrate content ranged from 24.81 ± 0.01 –73.76 ± 0.01 % with maize flour having the highest while soybeans had the least. the carbohydrate content of maize is higher as compared to all the samples. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 918 table 1: proximate composition of flour used for preparation of lamba data are mean ± sd (n = 3). mean values bearing similar superscripts are not significantly different (p<0.05) results are mean ± sd (n = 3). mean values bearing different superscripts are significantly different (p<0.05) wt = wheat flour, cw= cowpea flour, sb= soyabeans flour, bg = bambara groundnut flour, mz = maize flour flour moisture (%) protein (%) fat (%) ash (%) crude fiber (%) cho (%) wt 10.04±0.03a 10.92±0.03d 3.61±0.04c 4.06±0.05c 3.83±0.01b 67.55±0.02ab cw 8.12±0.01d 21.42±0.03b 5.23±0.02b 3.16±0.05ab 4.07±0.02ab 58.00±0.01c sb 7.26±0.04d 38.12±0.04a 20.89±0.01a 4.84±0.01a 4.08±0.01c 24.81±0.01d bg 8.36±0.02c 19.41±0.02c 5.84±0.02b 2.98± 0.03ab 3.08±0.04ab 60.33±0.04b mz 9.25±0.01b 9.23±0.06e 3.76±0.02d 1.52±0.04b 2.48±0.05a 73.76±0.01a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 919 3.2. functional properties of flour blends for lamba production table 2. shows the functional properties of lamba produced from different flour blends. there was significant difference (p≤0.05) between the wettability, bulk density, water absorption capacity and swelling index of the flour blends. sample mck had the highest wettability, bulk density, water absorption capacity and swelling index as compared to other samples. the wettability of the flour blends ranged from 50.13 – 68.18 sec. the wettability varied significantly (p˂0.05) and sample mck was higher as compared to all the samples while sample wsk1 had the list value. in this study, there is no significant difference between samples containing soybeans (wsk 1, wsk 2 and wsk 3). subsequently, there is no significant difference between the samples containing cowpea and bambara groundnuts. however, the wettability increased with an increase in legume content (cowpea, soybeans and bambara groundnut). wac is the ability of a product to bind water under limited water conditions such as dough and paste (hasmadi et al., 2020). this varies depending on the presence of hydrophilic carbohydrates and protein structures (kaur et al., 2015). the wac ranged from 58.93 – 105.58 % and the results indicated that sample mck (control) exhibited the highest (105.58%) while the least was observed for sample wsk 3 (58.93%). generally, the results show that besides the control samples (mck), samples containing soybeans (wsk1, wsk 2 and wsk 3) had lower wac as compared to samples containing cowpea (wck 1, wck 2 and wck 3) and bambara groundnut (wbk 1, wbk 2 and wbk 3). bulk density is the criteria for selecting the packaging which measures the amount of load a sample can carry when resting on each other (otondi et al., 2020). the bulk density of the flour blends varies significantly (p˂0.05) ranging from 0.50 – 0.76g/ml. among all the samples, mck had the highest value as compared to other samples. however, there is no significant difference between the samples containing cowpea (wck 1, wck 2 and wck 3) and samples containing bambara groundnut (wbk 1, wbk 2 and wbk 3) while samples containing soybeans had the least. this is similar to a previous study on the bulk density of whole and decorticated maize and millet (umar et al., 2022). according to oladunmoye et al. (2010), particle size distribution would significantly affect the bulk density of the flour. therefore, bulk density is a function of particle size, particle size being inversely proportional to bulk density (appiah et al., 2011). also, bulk density has a significant effect on the strength and amount of packaging material, texture and mouthfeel of the product (ahaotu et al., 2021). one of the factors to be considered as quality criteria in food bakeries is the swelling index (si). in this study, the si of the flour blends varied significantly ranging from 1.62 – 2.15%. among all the samples, sample mck (control) was observed to exhibit the highest si as compared to all the samples. however, there is no significant difference between sample mck and sample wbk 3. subsequently, the least si was observed for sample wsk 1. this is similar to a previous study where the si of wheat and soybeans blend was between 1.13 – 1.38 % depending on the ratio of wheat to soybeans (godswill, 2019). swelling capacity of the flour depends on the type of starch, availability of water, protein, temperature, and carbohydrates (sui et al., 2006). however, a decrease in the si of the flour blends may be caused by the formation of the protein-amylose complex in the native starches. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 920 table 2: functional properties of the flour blends flour blends wettability (sec) water absorption capacity (%) bulk density (g/ml) swelling index (%) mck 68.18±0.21a 105.58±4.82a 0.76±1.28a 2.15±0.36a wck 1 54.51±0.36b 78.21±0.04c 0.60±3.61ab 1.76±0.53c wck 2 55.51±0.03b 76.83±2.05c 0.63±5.10ab 1.85±0.42b wck 3 56.01±2.01b 77.12±3.55c 0.63±2.01ab 1.86±2.01b wsk 1 50.13±2.43c 62.36±1.03d 0.51±4.82c 1.62±8.23d wsk 2 52.92±0.26c 63.10±0.42d 0.50±5.27c 1.72±1.20c wsk 3 53.21±0.21c 58.93±0.61e 0.52±0.04c 1.72±0.04c wbk 1 55.83±2.01b 92.73±2.65bc 0.65±0.28b 1.87±3.01b wbk 2 56.17±3.10b 96.12±0.03b 0.65±0.15b 1.96±7.20ab wbk 3 57.81±0.45b 98.42±0.84b 0.68±2.01ab 2.05±0.03a data are mean ± sd (n=3). mean values bearing different superscripts are significantly different (p<0.05) 3.3. proximate composition of lamba produced from different flour blends table 3 shows the proximate composition of lamba. the moisture content of lamba varied from 5.40 – 9.92%, where sample wck 2 (9.92%) had the higher moisture content while sample wsk 2 (5.40%) had the least. however, the aim of moisture determination in food is to know about the characteristics of the food products in terms of their physical appearance, texture, taste and the keeping quality of the food products (zambrano et al., 2019). although it has been reported that high moisture content in food favours the growth and multiplication of spoilage microorganisms which leads to short shelf life of the food product (ahaotu et al., 2021). the protein content ranged from 7.92%–15.39% and varied significantly from all the samples. subsequently, sample wsk 3 had the highest protein content as compared to the other samples. according to arise et al. (2018), complimenting cereals with legumes such as groundnut, soybeans, cowpea and bambara groundnut may improve the protein content of the cereal. thus, the protein content of the lamba increases with complimenting cereal and legumes, however, this depends on the type of legume used. as the protein content of soybeans is higher than that of bambara groundnut and cowpea, samples containing are expected to have higher protein content. the fat content of lamba ranged from 3.28 – 9.25% and a significant difference was observed. among all the samples, sample wsk 3 had the highest fat content and sample mck (control) had the least. the difference in fat content could be as a result of the legumes used where soyabeans are a good source of fat as compared to cowpea and bambara groundnut. in this study, the ash content of lamba ranged between 2.78%–3.48%, with sample wsk 1 showing the highest while mck 1 was the lowest. however, there is no significant difference (p>0.05) in ash content of samples wck 2, wck 3, wsk 1, wbk 2 and wbk 3 which were significantly higher than other samples. subsequently, no significant difference (p>0.05) existed between the rest of the samples and were slightly lower. the ash content in food products is an indication of mineral availability. the dietary fibre contents of the lamba ranged between 2.03 – 3.55% where sample mck had high fibre content which originated from the added maize flours while there was no significant difference (p˃ 0.05) among all other samples. furthermore, maize grain proved to be richer in fibre than wheat flour. both soluble and insoluble fibre is now recognized to be beneficial to humans. according to arinola et al. (2014), crude fibre enhances bowel movement, digestibility, and prevents bowel cancer by reducing the rate at which glucose is released in the bloodstream. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 921 the carbohydrate content of lamba ranged from 61.91 – 73.59%, among all the samples, lower carbohydrate content was observed in samples containing soybeans (wsk 1, wsk 2 and wsk 3) as compared to the samples containing cowpea and bambara groundnut although the control sample (mck) had the highest carbohydrate content. higher carbohydrate content indicates higher energy value although, there was no significant difference in the energy value obtained. in this study, the variation of the proximate composition among lamba samples depends on the kind of legume used which could be attributed to their variations in varieties, genetic makeup and environmental conditions (kaur et al., 2007). http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 922 table 3: proximate composition of lamba produced from different flour blends data are mean ± sd (n=3). mean values bearing similar superscripts are not significantly different (p<0.05) sample moisture protein fat ash fiber cho mck 8.58±0.02b 8.02±0.04f 3.82±0.05f 2.81±0.01b 3.55±0.07a 72.22±0.01a wck1 8.45±0.07b 7.92±0.05g 4.28±0.39f 2.78±2.13b 2.98±0.04b 73.59±0.06a wck2 9.92±0.11a 8.95±0.07f 5.49±0.01e 3.28±0.04a 2.78±0.28b 69.58±0.28b wck3 9.65±0.04a 10.53±0.04d 6.09±0.02d 3.23±0.11a 2.03±0.11b 67.47±0.01b wsk1 8.64±0.02b 13.78±0.04c 7.78±0.04c 3.48±0.04a 2.08±0.52b 64.24±0.12b wsk2 5.40±0.06d 14.39±0.01b 8.53±0.05b 2.88±0.16b 2.68±0.03b 66.12±0.10b wsk3 8.02±0.07b 15.39±0.02a 9.25±0.07a 2.85±0.02b 2.58±0.02b 61.91±0.06b wbk1 8.09±0.05b 8.14±0.19f 4.43±0.04f 2.90±1.04b 2.89±0.01b 73.55±0.08a wbk2 7.70±0.01c 9.14±0.02e 5.24±0.02e 3.11±0.01a 2.81±0.21b 71.80±0.11a wbk3 6.49±0.14d 11.01±0.01d 5.98±0.04e 3.32±0.02a 2.98±0.50b 67.92±0.02b file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 923 3.4. microbial properties of lamba produced from different flour blends table 4. shows the microbial load of lamba samples. bacterial growth ranged from 4.9 ×104 – 8.1 × 104 cfu/g. sample wbk 3 had the highest bacterial load while sample mck (control) had the lowest. however, there was no significant difference (p˃0.05) between samples wck1, wck 2, wck3, wsk1, wsk 2 and wsk 3 while samples wbk1, wbk 2 and wbk 3 are significantly different. also, the value of the fungal load ranged from 1.6 × 10 4 – 4.4 × 104 cfu/g. it has been observed that sample wsk 2 had the highest fungal count while sample wbk 3 had the lowest. this is similar to a previous study reported by victor-aduloju et al., (2021) although on the proximate, microbial and sensory properties of moi–moi produced from crayfish and grasshoppers. table 4. microbial load of lamba samples bacterial count cfu/g fungal count cfu/g mck 4.9×104 1.8×104 wck 1 6.1×104 3.8x104 wck 2 6.1×104 2.4x104 wck 3 6.5×104 2.8x104 wsk 1 6.2×104 1.7x104 wsk 2 6.1×104 4.4x104 wsk 3 6.0×104 2.8x104 wbk 1 7.0×104 4.2x104 wbk 2 7.8×104 2.1x104 wbk 3 8.1×104 1.6x104 data are mean ± sd (n=3). 3.5. sensory properties of lamba the mean sensory scores of lamba produced from different flour blends are shown in table 5. the sensory evaluation was analysed in terms of texture, aroma, taste, colour and overall acceptability and their values obtained varied significantly (p < 0.05) ranging from 5.09 – 6.13, 5.01 – 6.38, 4.92 – 7.98, 4.61 – 6.08 and 5.18 – 8.49 respectively. on texture, there was no significant difference among all the samples except for sample wsk 2 (6.13 ± 0.02) which was rated the highest. considering the aroma of lamba samples, wsk 2 (6.38±0.04) had the highest aroma as compared to other samples, however, there was no significant difference (p˃0.05) in flavour among the other samples produced. in this study, the variation in the taste of the lamba depends on the types of legumes used. the result shows that there was no significant difference (p˃0.05) in the taste of samples produced from cowpea flour ( wck1, wck2 and wck3 which are 6.92 ±0.03, 6.06±0.04 and 6.09 ± 0.01 respectively). also, the samples produced from bambara groundnut are not significantly different from each other. however, there was variation in the taste of the samples produced from soybeans. furthermore, sample wsk 2 had the highest value in taste as compared to all the samples. considering the colour, there was no significant difference among all the samples. subsequently, the acceptability of lamba varied significantly and sample wsk 2 had the highest value and is considered the most acceptable among all the samples while sample mck (control) had the least value. http://www.azojete.com.ng/ mailto:%20odumaoke@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):911-926. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ladi.peter05@gmail.com 924 table 5: sensory properties of lamba produced from different flour blends sample texture aroma taste colour overall acceptability mck 5.09±0.02b 5.01±0.02b 4.99±0.02d 5.15±0.01a 5.18±0.12d wck 1 5.09±0.93b 5.11±0.01b 6.92±0.32b 5.06±0.94a 7.11±0.01b wck 2 5.10±0.28b 5.25±0.01b 6.06±0.04b 5.21±0.05a 7.24±0.02b wck 3 5.17±0.03b 5.24±0.02b 6.09±0.01b 5.21±0.63a 7.22±0.02b wsk 1 5.30±0.01b 5.58±0.01ab 6.43±0.12b 5.21±0.02a 7.72±0.02ab wsk 2 6.13±0.02a 6.38±0.04a 7.98±0.01a 5.08±0.01a 8.49±0.23a wsk 3 5.10±0.04b 5.09±0.03b 6.09±0.01b 5.26±0.04a 7.18±0.18b wbk 1 5.25±0.02b 5.29±0.02b 5.28±0.04c 5.19±0.01a 6.28±0.58c wbk 2 5.14±0.01b 5.15±0.01b 5.16±0.42c 5.14±0.01a 6.32±0.32c wbk 3 5.11±0.11b 5.15±0.02b 5.12±0.24c 5.31±0.03a 6.29±0.21c data are mean±sd (n=3). mean values bearing similar superscripts are not significantly different (p<0.05) 4.0 conclusion the study showed that nutritious and acceptable complimentary food (lamba) can be produced from different cereal and legume flour blends of wheat and soybeans. it is clear that lamba produced from composite flour blends of wheat, soybeans and karkashi (60:30:10) had better acceptance in terms of all the sensory attributes assessed. the utilization of composite flour of 60% wheat flour, 30% soybeans and 10% karkashi for the production of lamba is advocated as it resulted in acceptable lamba with improved nutritional values. the use of the composite flour blend for the development of other food products should also be explored greatly. references abamecha, n. 2020. research review on formulation and sensory evaluation of complementary foods from cereals and legumes in ethiopia. food science and nutrition technology, 5: 1-7. adeleke, ro. and odedeji, jo. 2010. functional properties of wheat and sweet potato flour blend. pakistan journal of nutrition, 9: 535-538. agbara, gi., ige, ac., agbara, nh., ahmad, g., masaya, fa., and aliyu, b. 2022. evaluation of the quality characteristics of composite flour bread produced from a wheat-root tuber and wheat-grain legume flour blends. arid zone journal of engineering, technology and environment, 18: 331-344. adeyeye, sa. and akingbala, jo. 2016. quality, functional, and sensory properties of cookies from sweet potato–maize flour blends. journal of culinary science and technology, 14: 363376. ahaotu, i., eni, cv. and maduka, n. 2021. quality assessment of powdered maize ogi fortified with african walnut (tetracarpidium conophorum) flour. microbiology research journal international, 31: 28-51. aoac. 2012. association of official analytical chemists. official method of analysis of aoac international, 19th ed. aoac., washington dc. appiah, f., asibuo, jy. and kumah p. 2011. physical and functional properties of bean flours of three cowpea (vigna unguiculata l. walp) varieties in ghana. african journal of food science, 5: 100-104 arinola, so., and adesina, k. 2014. effect of thermal processing on the nutritional, antinutritional, and antioxidant properties of tetracarpidium conophorum (african walnut). journal of food processing, 2014: 1-4 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mshelia et al: quality characteristics of lamba as affected by different cereal and legume flour blends. azojete, 19(4):911-926. issn 1596-2490; 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(eds) genetics and genomics of soybean. plant genetics and genomics: crops and models, pp 3-15. springer, new york, zambrano, mv., dutta, b., mercer, dg., maclean, hl. and touchie m. 2019. assessment of moisture content measurement methods of dried food products in small-scale operations in developing countries: a review. trends in food science and technology, 88: 484-496. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng corresponding author’s email address: kamtup@unijos.edu.ng 601 arid zone journal of engineering, technology & environment original research article tribological evaluation of canarium shweinfurthi (african elimi) oil as lubricant in metal forming p. m kamtu1*, n.s gukop1, a. ashwe2, d. t. gundu2, w.y.t albert3, a. babawuya4 and c.a. popoolao5 1department of mechanical engineering, university of jos, nigeria, 2department of mechanical engineering, fed. university of agriculture, makurdi 3htttc-bambili, mechanical engineering department, the university of bamenda, cameroon. 4department of mechatronics engineering, federal university of technology, minna. 5department of food science and technology, federal university wukari, nigeria *corresponding author: kamtup@unijos.edu.ng article information abstract reducing cost of production arising from high energy due to friction and tool failure using cheaper readily available and environment friendly lubricant is evaluated in this study. an experimental evaluation of tribological properties of canarium shweinfurthi (african elimi) was carried out using ring compression test. this was carried out using boron nitride as additive to determine the best quantity that can be added in vegetable oil lubricants. the formulated oils were applied to the die/ring surfaces as they were compressed in the califonia bearing ratio (cbr) using digital display testometric universal testing machine. the results show that friction factors for the developed lubricant range between m = 0.3 and 0.4 while the frictional coefficient results show µ = 0.07 to 0.09 which compared favorably to referenced (mineral) oil which has m = 0.4 and µ = 0.12. additionally, frictional coefficient obtained from the developed lubricant are within the range for vegetable lubricants such as groundnut oil, palm oil, palm kernel and shear oil which range from 0.072 to 0.3. furthermore, it was observed that canarium shweinfurthi oil could be used as substitute to mineral based oils that are currently in use as lubricants in manufacturing process. therefore, industrial organizations can take advantage of the benefits this natural, environmentally friendly, biodegradable and low toxicity oil lubricant presents. received: 29th april 2025 revised: 8th may 2025 accepted: 9th may 2025 keywords: canarium shweifurthi ring-compression test evaluation lubricant tribological © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction lubrication is the process or technique employed to reduce friction between, and wear of one or both, surfaces in close proximity and moving relative to each other, by interposing a substance called a lubricant between them. the lubricant can be a solid, solid/liquid dispersion, a liquid such as oil or water, a liquid-liquid dispersion (a grease) or a gas (szkoda, 2014). metal forming lubricants are applied to the tool work interface in many forming operations, so as to reduce friction and wear which generally affect the tool life, metal flow, energy consumption, heat evolution and surface finish. lubricants used in metal forming processes such as metal drawing, extrusion, forging and rolling must develop a very thin adsorbed film, which does prevent metal to metal contact under high pressure. metal forming lubricants in commercial use are classified as: aqueous dispersion (soap/water type, soap/fat emulsions, soluble oil emulsion etc); oil type fluids (mineral/fat oils, chemicals active oil, oil/wax fluids); solid lubricants and metallic solids (szkoda, 2014). for over 100 years mineral oils have dominated metal forming lubrication. it has been estimated that 5-10 million tons of petroleum-based oleochemicals enter the biosphere every year and 40% of such come from spills, industrial and municipal waste where metal forming lubricants belong (smith, 2020). these mineral oils and synthetics are not readily biodegradable (depositing heavy metals to the ground which affect the ecosystem and human health). this may require washing of the work piece against chemical effect, high cost, and long chain of production process. generally, the most available mineral oils in use are the azojete june 2025. vol.21(2):601-610 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/024 www.azojete.com.ng mailto:kamtup@unijos.edu.ng mailto:kamtup@unijos.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 602 petroleum based which are carcinogenic and are further emphasized by the content of chlorine nitrides or metals (syahrullail, et al 2011). these are also characterized by many kind of additives such as antioxidant agent, anti-wear agent, detergent, dispersants, antifoams, extreme pressure agent and viscosity improvers. most of these additives are toxic and in the long run harmful to human, animal and plants. consequently, the negative impact of the mineral oils on the environment and human life has brought a renewed interest in natural fatty acid lubricants. these lubricants are derived from vegetables which are naturally biodegradable compared to mineral oils. furthermore, the bio lubricants show excellent tribological qualities such as low frictional coefficient and good wear protection. this is achieved by ease of processing and regeneration through short rotation plantations, high flash point and low toxicity (oseni, gundu, & enenta, 2012). it is noteworthy of the vegetable based lubricants caused by low thermo-oxidation stability primarily due to the presence of bis-allylic protons, hydrolytic stress and partly inferior cold flow properties. this can be corrected through the addition of some elements which are considered safe to the environment, (syhrullail, m., s., & ridzuan, 2011). most vegetable seed oils find wide applications in the production of soaps, paints, varnishes, lubricants, hydraulic fluids, printing inks, dyes, pesticide and insecticides (uzoh, 2013). canarium schweinfurthi or otherwise call genus canarium is a perennial plant that is found in africa. it is usually referred to as african olive or black olive. the tree has a lot of branches with an attendant height of 90-150ft tall and thrives well in the rocky and the flat lands of plateau state of nigeria (orwa, 2009). there are many varieties of the plant producing fruits of different sizes ranging from 11.84-3.06 cm long, (nyam & wonang, 2004). the fruit has a sharp point at the apex and a persistent calyx at the base. the fruit contains a hard fluited stone which contains a seed inside; the seeds are edible. they are similar in structure and color to the well-known fruits of olive (olea europaea) of the isreal, though from different families (nyam, makut, itelima, & darriel, 2014). the properties and qualities of the oils have been investigated to some extent. the oils have been shown to have potential industrial uses in production of pharmaceutical, personal products and as a thernial fluid among others. however, unlike some other oil-bearing plants such as groundnut, cotton seed, soybean, palm pulp and palm kernel are not being carried out at commercial level at present, despite their abundance in nigeria and elsewhere in sub-sahara africa (nyam, et al, 2014) canarium schweifurthii (african olive) oil is studied in this work with a view to determining its tribological properties in upset forging through the use of ring compression test. the study wished to provide in-depth analysis of lubricant formation, frictional factor and frictional coefficient determination. this is aimed at determining its characteristics and subsequent recommendation for use as metal forming lubricant. the physiochemical properties of the fruit (table i) and the prominate composition of the pulp was conducted by nyam, et al 2014. table 1: approximate composition of canarium schweinfurthii fruit(nyam, et al 2014) parameter whole seed pulp thickness (cm) 4.0 6.0 fruit length (cm) 4.5 6.0 shape oblong oblong % free fatty acid 3.52 3.28 melting point (0c) 32 30 % moisture impurity & volatile (miv) 1.72 1.70 the ring compression test (alexandru, 2017) is commonly used to evaluate forging lubricants. the ring test consists of the deformation of a cylinder with a hole drilled through the center of the billet. the billet is compressed to various height reductions and the change in the inner diameter of the billet reflects the friction factor along the tool/work piece interface. the higher the friction the more the inner diameter of the test piece is reduced. in low friction environments, the inner diameter of the billet increases figures 1-3. the frictional factor and coefficient are determined through the use of calibration curves shown in figure 4-5. figure 1: original ring before compression http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 603 figure 2: ring after compression with high friction (poor lubrication) figure 3: ring after compression with low friction (good lubrication) figure 4: typical calibration curves for ring compression test for frictional coefficient (µ) figure 5: typical calibration curves for ring compression test for shear factor (m) 2. materials and method 2.1 materials collection and preparation the ripe canarium shweinfurthi fruits were purchased from the open market in jos. they were first sorted to remove foreign materials, unripe and infected fruits. the fruits were then washed with clean water and dried (table 2). boron nitride was obtained from burgoyne burbidges and company mumbai, india. aluminum alloy was obtained from the selected aluminum scraps in farin gada market in jos, while acetone or propanone ((ch₃)₂co) was obtained from jc chemical laboratory in jos. 2.2 oil extraction various components of the fruit (pulp, seed and oil) were separated using the traditional method as described by nyam et al., (2014). http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 604 the foam and oil formed on top layer were skimmed and scooped out using sterile wooden spoon. the various components of the fruit after oil extraction were presented in table 3. table 3: elemental parts of fruit after extraction s/no item weight (g) weight (kg) % of total weight 1 oil 3,964 3.964 05.15 2 seed 29,725 29.725 38.60 3 pulp 19,464 19.464 25.28 4 moisture 23,849 23.849 30.97 total 77,002 77.002 100 2.3 design of experiment design of experiment for this research was achieved using the software design expert (2010). it was used in complementing multivariate data analysis, such as development of empirical models, optimization of the process variables and statistical analysis. this was used to obtain the sample size and optimal lubricant and coefficient of friction. there were three design factors and two levels for the experiment that were used. the design factors for the lubricant were canarium shweifurthei oil, water substance in the oil and boron nitride which served as additive. boron nitride was added to the lubricants at two levels (low and high) of 0.02% and 0.4%. this gave rise to three combination (three elements for lubricant formulation) at two levels (low and high levels of boron nitride) for the lubricant formulation (32). run order obtained in table 4 gave rise to 8 experimental design order. considering zero boron nitride, no lubricant condition and standard lubricant condition, the total number of experimental designs came to eleven. an additional sample number was added to make it twelve. tables 4 and 5 shows the experimental layout in orthogonal array and addition of boron nitride to the lubricant. table 4: experimental layout in orthogonal array c1 c2 c3 c4 c5 c6 c7 stdorder runorder centerpt blocks a b c 2 1 1 1 0.40 0 0 7 2 1 1 0.02 50 50 4 3 1 1 0.40 50 0 8 4 1 1 0.40 50 50 6 5 1 1 0.40 0 50 3 6 1 1 0.02 50 0 5 7 1 1 0.02 0 50 1 8 1 1 0.02 0 0 2.4 addition of boron nitride to lubricant maximum quantity by weight of boron nitride added to the lubricant ranged from 0.02% to 0.4% as recommended by dehghan, qods, and gerdooei, (2013) and frank, k., and margaret, a., (2014). each of the lubricant sample was shared into twelve sample bottles. the lubricants were weight into the sample bottles at 31.5g. sample lubricants for lub1, lub2 and lub3 were enriched with boron nitride as described in table 7. the quantity of boron nitride to be added to every sample was determined (equation 1-2). 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑐𝑙𝑎𝑠𝑠𝑒𝑠 = 𝑅𝑎𝑛𝑔𝑒(𝑅) 𝐶𝑙𝑎𝑠𝑠 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 (ℎ) (1) http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 605 where range r = highest lowest (2) = 0.4% − 0.02% =0.38% class interval h = 10 number of class = 0.038% = 0.04%. the calculated percentage of the boron nitride (0.04%) was added to the samples as shown in table 5. table 5: lubricant formulation with boron nitride sample addition of boron nitride to the lubricant 1 2 3 standaed lubricant no lubricant condition lub + 0.00 wt%bn 4 sample3 + 0.02 wt%bn 5 sample4 + 0.04 wt%bn (0.06 wt%bn) 6 sample5 + 0.04 wt%bn (0.10 wt%bn) 7 sample6 + 0.04 wt%bn (0.14 wt%bn) 8 sample7 + 0.04 wt%bn (0.18 wt%bn) 9 sample8 + 0.04 wt%bn (0.22 wt%bn) 10 sample9 + 0.04 wt%bn (0.26 wt%bn) 11 sample10 + 0.04 wt%bn (0.30 wt%bn) 12 sample11 + 0.04 wt%bn (0.34 wt%bn) 2.5 determination of physical properties of the developed oil. the developed oil, african elimi oil was analyzed. the quality assurance laboratory of grand cereals company located at zawan roundabout, bukuru in jos south local government of plateau state, nigeria was used for the laboratory test as shown in table 6. 2.6 tribological test 2.6.1 preparation of test piece ring compression test according to alexandru, gheorghe and lucian, (2017) was adopted for this work using the californian bearing ratio (cbr). aluminum alloy with properties shown in table 7 was prepared and used to produce the test rings. xrf (x-ray fluorescence) nex cg ii series analyzer by rigaku technologies in national metallurgical development center (nmdc), jos was used to determine the detectable elements of the aluminum metal as shown in table 7 and according to azo materials (2005) established the aluminum grade as 6063a. this was arrived at by comparing the detected element with the standard grade. the aluminum alloy was prepared by gathering aluminum scraps from farin gada technical market in jos. it was smelted to get billets that were machined using the local foundry. the metal was machined to cbr (californian bearing ratio) 6:3:1 outside diameter (do) to inner diameter (di) to height (h) (42: 21:7mm) respectively using four jaw chuck lathe machine shown in plate i. http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 606 table 6: the determined parameters of the oils s/n parameter african elimi oil 1 % moisture content 0.24 2 % free fatty acid 1.84 3 iodine value (wij’s) 89.44 4 refractive index 1.4619 5 saponification value (koh/gm) 162.66 6 peroxide value (meq/kg) 22.01 7 soap value (ppm) 0.00 8 acid value(mgkoh/g) 3.83 9 flash point (oc) 98 10 cloud point (oc) 9 11 pour point (oc) 5 12 specific gravity 0.98 13 viscosity (cst) 0.61 table 7: the various elements of aluminum alloy 6063a as detected by xrf (x-ray fluorescence) analyzer process sample al-alloy s/no element values 1 al 99.00 2 s 0.02 3 k 0.02 4 ca 0.03 5 ti 0.02 6 v 0.003 7 cr 0.03 8 mn 0.15 9 fe 0.41 10 ni 0.005 11 cu 0.05 12 zn 0.03 13 ga 0.01 14 ba 0.009 15 pb 0.004 plate 1: cast aluminum billet with rings http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 607 2.6.2 compression of test piece the tribological test was carried out in two stages; firstly, it was to establish the similarities of the tribological properties of the lubricant developed from the various processes. this was with the view to selecting the best process for further development. the second stage was the determination of the tribological properties of the developed oil using machined aluminum rings. the tests rings were measured to establish similarities due to machining error. these were selected, grouped labeled in sample bags for ease of use. three tests rings were used with the oil to carry out the compression test on a 300kn capacity qm-300m1f by qualitest testometric universal testing machine in nmdc, jos plateau state nigeria. oil sample was applied on both sides of the ring and was placed between the compression platens of the testometric machine plate 2. a force of 270kn was applied on each of the ring at speed of 5 mm/min. before the next oil was used for test the platens were cleaned with acetone (cleaning agent) using cotton wool. this was done in other to avoid mixture of oil samples at the cause of the experiment. various compression parameters such as test number, time of test, area of test piece, force at yield, stress at yield strain at yield, force at peak, stress at peak, strain at peak, young modulus and modulus of elasticity were chosen on the machine desktop and subsequently computed and tabulated by the machine. plate 2: test ring placed between upper and lower platen of testometric universal testing machine 3. results and discussion table 6 shows the properties of the oil which are related to those of mineral oil indicating that the oil can be used as lubricant in metal forming processes. the low quantity of acid value of 3.83 signifies its ability to prevent oxidation which ultimately prevent corrosion hazard, gum and sludge formation as suggested by (kaia, a 2012). the moisture content falls within the agreed range of 25% of water present in vegetable lubricant as suggested by mary and doris 2001. that lubricant use in metal forming is a soap/fat paste with a formation of 5% soap, 25% oil, 25% water and 45 % solid. the quantity of boron nitride given in table 8, agrees with the standard quantity of additive for vegetable lubricants of 0.02% to 0.4% as suggested by (frank, et al., 2014). table 8 shows the result of the lubricant sample and quantity of boron nitride to be added. the tables show the result of the sample weight in grams. the computed percentage by weight. results for ring compression test using the developed lubricants are presented in tables 9. the tables gave results of the computed percentage reduction in internal diameter and height. table 10 showed result of the determination of frictional factor and frictional coefficient of the lubricant. table 8 is the result of the addition of boron nitride as given in table 5. the table further shows the percentage by weight of the boron nitride as discussed by dehghan, et al, (2013) and frank, et al., (2014). it was suggested that the maximum quantity of boron nitride to be added to lubricant is from 0.02% to 0.4%. the quantity of boron nitride to be added to the lubricant was also measured in grams. table 9 shows the results of the calculation for the determination of percentage reduction in height and percentage reduction in internal diameter. the result obtained was referred to figures 4 and 5 to determine frictional factor and frictional coefficient. http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 608 table 8: quantity of boron nitride in grams s/n sample (g) % by weight bn (g) 1 ref oil 2 no oil 3 28.93 0.00 0.00 4 30.96 0.02 0.008 5 33.53 0.06 0.017 6 32.59 0.10 0.034 7 32.02 0.14 0.042 8 32.47 0.18 0.051 9 28.60 0.22 0.067 10 28.90 0.26 0.083 11 32.13 0.30 0.100 12 25.95 0.34 0.108 table 9: determination of percentage reduction in internal diameter and height s/n bn (g) do d_ d_diff %diff h_av h_diff %h_diff ave 1 ref oil 22 19.63 2.37 10.76 4.6 2.4 34.29 2 no lub 22 20.53 1.47 6.67 5.63 1.37 19.52 3 0 22 20.3 1.7 7.73 4.43 2.57 36.67 4 0.008 22 20.5 1.5 6.82 4.6 2.4 34.29 5 0.017 21.5 19 2.5 11.63 4.27 2.73 39.05 6 0.034 20.5 18.5 2 9.76 4.45 2.55 36.43 7 0.042 21 19.8 1.2 5.71 4.7 2.3 32.86 8 0.051 21.5 20.07 1.43 6.67 5 2 28.57 9 0.067 21 19.43 1.57 7.46 4.73 2.27 32.38 10 0.083 21.5 19.55 1.95 9.07 4.6 2.4 34.29 11 0.1 21 20.4 0.6 2.86 5.3 1.7 24.29 12 0.108 21.5 19.9 1.6 7.44 4.57 2.43 34.76 where; do = original internal diameter ((𝑑𝑜 − 𝑎𝑣𝑔𝑑)/𝑑𝑜)*100 = percentage reduction in internal diameter ho = original height ((𝐻𝑂 − 𝑎𝑣𝐺𝐻)/𝐻𝑂)*100 = percentage reduction in height results for the determined frictional factor and frictional coefficient of reference oil, no oil condition and the developed lubricant is displayed in table 10. the reference oil has frictional factor and frictional coefficient as 0.4 and 0.12 respectively. while the no oil conditional has 0.6 and 0.15 for frictional factor and frictional coefficient respectively. the best result for the developed lubricant is shown on serial number 3 on table 10. the result shows a record of new vegetable lubricant of frictional factor 0.3 and frictional coefficient of 0.09 as established by this work. the result agrees to ring compression test by alexandru, gheorghe and lucian, 2017 where greater inner diameter to the original ring indicates low friction. furthermore, smaller inner diameter in comparism to the original ring indicates high friction. consequently, with 0.1g of boron nitride http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 609 added to the lubricant (32.11g) a better result of 0.3 frictional factor with 0.07 frictional coefficient record was established for metal forming. these results measured better than reference oil with 0.4 and 0.12 and dry condition with 0.6 and 0.15 for frictional factor and frictional coefficient respectively. table 10: determination of frictional factor and frictional coefficient bn (g) reduction in internal diameter (%) reduction in height (%) frictional factor (m) (from chart) frictional coefficient (µ) (from chart) 1 ref. oil 10.76 34.29 0.4 0.12 2 no oil 6.67 19.52 0.6 0.15 3 0.00 8.57 40.48 0.3 0.09 4 0.006 7.78 34.29 0.3 0.10 5 0.019 8.64 30 0.4 0.12 6 0.031 5.91 37.62 0.3 0.08 7 0.044 6.36 31.90 0.3 0.09 8 0.055 8.99 32.86 0.4 0.12 9 0.068 5.08 33.81 0.3 0.09 10 0.081 6.83 35.71 0.3 0.09 11 0.092 9.39 35.24 0.3 0.10 12 0.107 9.77 35.24 0.4 0.12 4. conclusion the african elemi fruit oil has identical chemo physical properties with the reference oil. following the result of tribological test, the african elemi fruit oil gave satisfactory tribological performance in both ring compression. the results obtained as 0.3 and 0.09 in both frictional factor and frictional coefficient of the developed lubricant were satisfactory and better than the mineral oil 0.4 and 0.12 in frictional factor and frictional coefficient respectively. the tribological performance was enhanced with boron nitride. acknowledgement the author(s) wish to appreciate the department of mechanical engineering, university of jos and joseph sarwuan tarka university, makurdi for the support given to undertake these studies. we also wish to register our deep gratitude to prof a ashwe, prof d t gundu, prof micheal adeyemi and prof oseni of the blessed memory for guidance. references alexandru, b., gheorghe, a. and lucian, l. 2017. evaluation of environmentally friendly lubricants by ring compression test. academic journal of manufacturing engineering 15(2). chigozie, fu., okechukwu, do., odera, rs. and sunday, o. 2013. optimization of polyesterification process for production of palmoil modified alkyd resin response surface methodology. journal of environmental chemical engineering, 1(4): 777-785. dehghan, m., qods, f., gerdooei, m. and doai, j. 2013. analysisof ring compression test for determination of friction circumstances in forging process. applied mechanics and materials, 249–250: 663–666. https://doi.org/10.4028/www.scientific.net/amm.249-250.663 dehghan,m. qods, f and gerdooei, dj. 2013. analysisof ring compression test for determination of friction circumstances in forging process, 663–666. https://doi.org/10.4028/www.scientific.net/amm.24. frank, k, margaret, a. 2014. metal forming lubricant composition containing boron nitride, south carolina 29303, usa: world intellectual organisation, handley, margaret, suite c, spartanburg, kaia, a. 2012. lubricant properties and their effects. journal of lubrication studies, 10(2):12-20. krishna,rksv. and naval, kuk. 2014. experimental investigation on usage of palm oil as a lubricant to substitute mineral oil in ci engines. chinese journal of engineering, http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng https://www.researchgate.net/journal/academic-journal-of-manufacturing-engineering-1583-7904?_tp=eyjjb250zxh0ijp7imzpcnn0ugfnzsi6inb1ymxpy2f0aw9uiiwicgfnzsi6inb1ymxpy2f0aw9uin19 https://doi.org/10.4028/www.scientific.net/amm.24 arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 601-610. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kamtup@unijos.edu.ng 610 mandić, v. and stefanović, m. 2003. friction studies utilizing the ring compression test part ii. tribology in industry, 25(3–4): 76–82. nyam, ma. and wonang, dl.2004. proximate chemical analysis of canarium schweinfurthii linn endosperm and elemental analysis of the oil. nutrition society of nigeria, in 35th annual conference, the federal university of technology akure, akure, nyam, ma., makut, md., itelima, ju. and darriel, am. 2014. nutritional potential of the fruits of black olive (canarium schweinfurthii linn) from plateau state, nigeria. pakistan 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process for production of palmoil modified alkyd resin response surface methodology. journal of environmental chemical engineering, 1(4): 777-785. wills, jg. 1980. lubrication fundamentals. marcel dekker. http://www.azojete.com.ng/ mailto:kamtup@unijos.edu.ng integrating bowtie analysis into band saw maintenance t. k. tsapii*, m. k. tongwa2 and b. d. soh3 i,2*department of mechanical and industrial engineering, national higher polytechnic institute, university of bamenda, p.o box, 39 bambili, cameroon. 3department of mechanical engineering, bandjoun university institute of technology, university of dschang, p.o. box: 134, bandjoun, cameroon *corresponding author's email address: tsapimartial@yahoo.com arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):633-644 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)633-644. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng tsapi et al: integrating bowtie analysis into band saw maintenance. azojete, 20(3):633-644. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng 2 2 2 article information submitted 29 february, 2024 revised 25 march, 2024 accepted 4 april, 2024 keywords: bowtie analysis band saw cutting machines maintenance manufacturing abstract sawing machines used to cut raw materials to desired dimensions in industrial manufacturing operations are of great importance. occupational injuries have occurred in the past as a result of failures in the risk management of these machines. in this paper, bowtie analysis-based risk identification is developed based on the diagnosis of band saw cutting machine components. the results of the bowtie risk assessment for hazards associated with the impeller, pump housing, saw blade, clamp, and seal pump were developed to structure the decision-making process with better information visualization. hazards in the bowtie were used to describe the root causes of failure (threats) that were identified, such as inadequate maintenance planning, foreign objects entering the pump, and inadequate maintenance. based on the bowtie diagrams, which capture the sufficient complexity of the real system behavior, the cutting tool was maintained following a corrective action plan that was developed. the assessment of the band saw performance rate after maintenance was 93%. this demonstrates that decision-makers can manage risk and reinforce a work culture that prioritizes actions to improve maintenance and safety outcomes using the bowtie analysis method. 1.0 introduction the semi-automatic band saw works on the principle of using a continuous toothed blade to cut metal sheets and bars. it is widely used in the woodworking, light, food, and metalworking industries where precision cutting is required (tsapi et al., 2024, kuldipia et al., 2023, kohale et al., 2022). it is designed to provide higher efficiency and accuracy compared to traditional hand-operated tools such as hacksaws and angle grinders (xue et al., 2024). depending on the lateral flexibility and width of the band, band saws can be used to cut straight, irregular, or curved shapes (alisinoglu et al., 2019). by automating the cutting process, the band saw reduces the risk of accidents and injuries that can occur with hand-operated tools. the semi-automatic band saw at rolling enterprise, located in the northwest region of cameroon, was out of service. the company is involved in the machining of metal parts for automobiles. the company provides services in automobile maintenance, medical equipment maintenance and installation, electrical and electronic maintenance, and welding and fabrication of various components and parts. the prolonged downtime of the band saw significantly impacted the productivity of the manufacturing unit, resulting in delays in delivery times and a decrease in customer satisfaction. to address this issue, this research was initiated with the goal of rehabilitating the semi-automatic band saw, with a particular focus on improving the local work culture so that operators can develop a shared understanding of how their tasks contribute to the greater good of the company. this improves productivity and ensures timely delivery of products to customers. the bowtie method, a visual risk assessment technique, was integrated into the corrective action process to analyze and communicate potential hazards, their causes, and related consequences and effects. 0. materials and methods 0. materials the maintenance was performed on the band saw with the machine designation behringer band saw ks 280hy. the semi-automatic band saw machine consists of several components and subsystems that work together to perform cutting operations on materials. the basic block diagram of a semi-automatic band saw machine includes the following parts (patil and waghmode, 2014); material stock, base or bed, cutting blade, blade guides, clamping system, cutting head, motor, control panel, cooling system, and belt that controls blade speed and feed adjustment. figure i: behringer band saw ks 280hy 2.0 methods within the framework of the research, several methods were used in the investigation. first, the diagnostic process was performed, followed by the implementation of the "bowtie methodology" to provide an overview of the risk associated with component failure and to identify the root causes of the failures. a comprehensive corrective action plan was then formulated. the bowtie contains various risk elements; including hazards, root causes (threats), consequences, barriers and controls. the process for constructing the bowtie diagram with the generic structure shown in figure 2 was as follows: figure 2: generic structure of a bowtie diagram (aust and pons, 2020) 1. hazard: identifying the hazard, which sets the scope and context of the risk assessment, was the first step in constructing the bowtie diagram for the semi-automatic band saw. the hazard represented any condition of the band saw components that had the potential to cause harm or damage, including injury, to personnel; damage to equipment, property, or the environment; loss of material; or reduction in the ability to perform a prescribed function (icao, 2012). start end build a team problem identification: diagnosis, problem condition description corrective actions acceptable? determine root causes from bowtie diagram determine corrective and preventive actions yes noo figure 3: methodology by steps for root cause analysis and corrective actions (tsapi et al., 2024) 1. top event: defining the top event was the next step, describing the point at which we lose control of the hazard. it has not yet caused any damage or impact, but can lead to undesirable outcomes if all prevention barriers fail (aust and pons, 2020). 1. threats: identify the threats that describe the causes that can lead to the release of the top event. in bowtie, these threats are used to describe the root causes (ispășoiu et al., 2021). 1. barriers: another important element of the bowtie was the development of "controls" or "layers of protection" known as barriers. these controls are put in place to prevent the threat from occurring (left side of the bowtie diagram) or to mitigate the consequences of the top event (right side of the bowtie diagram) (ispășoiu et al., 2021). 1. consequences: identifying the outcome of the top event, known as the consequences, was the last major component in developing the bowtie diagram (aust and pons, 2020; ispășoiu et al., 2021). the flowchart in figure 3 was used throughout the root cause corrective action process and was adapted from the maintenance on a power hack saw (tsapi et al., 2024). these root causes were identified using the bowtie diagram. according to the bowtie, the threats correspond to the root causes. 0. results and discussion 0. diagnosis and bowtie analysis according to the diagnosis performed, the machine was visually inspected, checked for erosion, corrosion, cracks, setup and adjustment, etc., and a diagnosis table was prepared. detailed information of the diagnosis performed on the semi-automatic band saw machine is shown in table 1. figure 4 shows some of the failed band saw components after the machine was thoroughly inspected. figure 4: failed band saw component example based on the information presented in table 1, a bowtie diagram was constructed using bowtiexp software to structure the relationships between the top event, causes, consequences, proactive barriers and reactive barriers (figure 5-9). it consisted of identifying the damage, hazards and accidents that could occur with each failure and the consequences that could result. one of the risk reduction measures is to identify the barriers needed to reduce the likelihood of a particular accident occurring table i: diagnosis results no component symptom(s) 1 impeller cracks , rust 2 pump housing corroded and clearance of 2mm 3 saw blade broken teeth, blond teeth … … … 10 clamp cracks 11 seal leakage … … … with this comprehensive view of the risk associated with the failure of the semi-automatic band saw, it was possible to develop a bowtie model to structure the decision-making process, such as maintenance (resuscitation of the band saw), risk management with better information visualization. through the bowtie, the risk faced at any given time can be managed to an acceptable level by implementing barriers to prevent an undesirable incident from occurring (abia et al., 2019) or by limiting its consequences. 1. damaged impeller there was rust and cracking on the surface of the impeller, which severely affected the cooling efficiency of the cutting machine. rust obstructed airflow, reducing the impeller's ability to effectively cool the machine. cracks also lead to further damage or failure of the impeller, resulting in inadequate cooling and potential overheating problems. based on similar findings of impeller corrosion failure (ul‐hamid et al., 2015), significant rust was observed on the impeller of a water pump as a result of exposure to oxygen and moisture, which was also the case for the pump of the semi-automatic band saw machine at rolling enterprise. the suggested impeller bowtie diagram, figure 5, shows the preventive and mitigating controls for each of the causes. implementing any of these controls will prevent the impeller from failing, without which there will be a reduction in pump efficiency, reduction in flow, lubricant contamination, pump failure and impeller wear. to limit the impact of this reduced pump efficiency, only a few mitigation barriers were practiced by the machine operators and maintenance personnel. it should be noted that not all controls need to be in place to prevent the hazards from occurring or to mitigate the consequences of the failed impeller, because ideally, the control measures, or barriers should be independent of each other to avoid any common mode of failure (xie et al., 2018). 1. pump housing a clearance of 2 mm in the casing, another important part of the pump (olorunfemi et al., 2018), shown in figure 4, was found between the impeller shaft and the pump casing ideal, which resulted in reduced pump efficiency. a venier caliper was used to measure this clearance. the clearance in the pump casing indicated excessive wear or improper assembly. this clearance resulted in reduced flow and leaks or malfunctions in the cooling system. figure 6: bowtie diagram of a pump housing figure 6 shows some of the preventive and mitigating controls that can be put in place to reduce the impact of the consequences and prevent the pump from failing. it shows on the left and right, respectively, the mitigating and preventive controls that can be implemented to prevent the hazard from occurring, and the mitigating barriers that can limit or reduce the impact of the consequences that can result from foreign matter entering the pump as observed during the diagnosis (figure 4). 1. saw blade the saw blade had broken and blunt teeth, resulting in poor cutting performance. comparing the results of the diagnosis with the modeling of wear and blunt blade transformations (zhuo et al.,2022), the diagnosis of a saw blade revealed that the blade was warped and bent when visually inspected or when its straightness was measured using tools such as precision straight edges. figure 7 shows the bowtie diagram for the saw blade with recommended prevention and mitigation measures. figure 7: bowtie diagram of a saw blade 1. clamp visual inspection of the clamp revealed cracks that compromised the safety and functionality of the machine. that is, its ability to securely hold the work piece during cutting becomes questionable. replacement/repair of the clamp was required to ensure proper and secure holding of the work piece during cutting. figure 8 shows the bowtie diagram for a cracked clamp on the band saw as observed during inspection (see figure 10, weld clamp) with preventive and mitigating barriers. figure 8: bowtie diagram of a clamp 1. pump seal poor sealing of the pump seal caused fluid loss and reduced pump efficiency. this resulted in an ineffective seal, which led to fluid loss and reduced pump efficiency. leaks also caused problems throughout the cooling system. repair or replacement of the pump seal was necessary to prevent further damage and ensure proper operation (shiels, 2002). figure 9 shows the bowtie diagram for the seal on the cooling system of the semi-automatic band saw machine. the seal was worn out. figure 9: bowtie diagram of a pump seal 0. root causes from bowtie diagram the root cause corrective action process is a valuable tool for maintenance professionals who want to address and prevent problems in a structured and systematic way. the root causes of previously reported failures were identified using the bowtie diagram because the threats in the bowtie diagrams in figures 5-9 correspond to the root causes. 1. impeller from the bowtie diagram for the impeller, the presence of rust and holes on the impeller of a water pump led to a failed impeller. rust is known to create rough surfaces and irregularities on the impeller blades, which disrupts the flow of fluid (zhuo et al., 2022, zariatin et al., 2019). the underlying factors or hazards that led to this failed impeller include; 1. inadequate maintenance: if a centrifugal pump is not properly or regularly maintained, there is a high probability that individual components such as the impeller will fail. of the 6m categories (aust and pons, 2020), this root cause was method, meaning the maintenance procedures and processes were not the best to prevent rust from affecting the impeller blades. the bowtie diagram in figure 5 provided controls that should be used to prevent this particular threat from occurring; training personnel on proper pump maintenance, performing regular inspections and others from the left side of the bowtie. 1. foreign objects: the impeller could have failed because the working environment (mother nature) was not conducive, an example is when iron fillings get into the pump during cutting, causing abrasion, metals rubbing against each other causing wear. when these foreign bodies such as iron fillings enter the water pump, it reduces the flow rate of the fluid or lubricant because the impeller transfers some of the energy received from the motor to the foreign particles and their presence has already contaminated the fluid leaving the centrifugal pump. 1. poor quality pump: the material of the pump was not the best and this could cause the impeller to fail and eventually cause the pump to fail completely. the barriers to mitigate and prevent this cause are shown in the bowtie diagram (figure 5). 1. air entering the pump: the impeller transfers energy from the motor to the fluid and during this process there is a change in temperature, so if air gets into the pump while the impeller blades are rotating, it will create bubbles and when they collapse it will cause cavitation wear which will eventually cause the pump to fail. this cause was caused by mother nature according to the 6m categories. 1. pump housing the bowtie diagram of the pump housing (figure 6), which has a clearance of 2mm and was experiencing rust as shown in figure 3, originated from one of the following causes: 1. lack of regular inspection: a machine or component cannot run optimally for weeks, months and years if it isn't inspected from time to time. the lack of regular inspection on the pump casing resulted in a 2mm clearance between the impeller shaft and the pump casing bushing. this resulted in further damage to the brass bushing in the pump casing. 1. inadequate repair and replacement procedures, training and awareness could also have resulted in reduced pump efficiency and performance, which could have further resulted in unplanned downtime of the semi-automatic machine. 1. improper pump installation and/or inadequate protective coating, such as anti-rust paint, may also have caused clearance in the pump casing; vibration that can damage the impeller shaft and result in increased maintenance costs. 1. saw blade the saw blade damage with blunt and broken teeth as shown in figure 4 resulted in the saw blade becoming stuck during operation. the causes of this top event were improper use of the blade because the band saw blade has been used to form keyways on pulleys, causing the blade to lose some of its teeth and become blond. this cause is man-made and results in damage to the work piece because the cuts are very rough. 1. clamp clamp damage due to fatigue and wear caused by constant stress and strain on the clamp, resulting in cracks in the clamp that can cause accidents during operation. the use of inferior clamps, overloading of the clamp, and improper installation are also factors that can cause the clamp to crack. 1. seal the seal had been used without maintenance, causing it to wear out and leak fluid, and other factors that caused the seal to leak included improper installation and the use of inferior seals. 0. corrective actions cleaning and descaling were the initial corrective actions for the rusted impeller. after cleaning the impeller, a rust inhibitor was applied to the surface of the impeller blade to dissolve and remove any remaining scale. after corrosion prevention and rust removal techniques in steel structures (gowri-shankar and ponnsahana, 2021), the impeller was then polished/grinded with sandpaper. by removing the uneven surfaces caused by rust, the impeller regained its original shape and improved performance. rust inhibitor was then applied and left to cure in the sun to protect the machine part from rust and corrosion, thereby extending its life and reducing maintenance costs (thompson et al., 2007). corrective action to maintain the pump casing included cleaning it with detergent and an iron brush. rust inhibitor was sprayed on the pump casing to dissolve any rust deposits. the iron brush was then used to remove any remaining rust. the casing was then sanded to remove any uneven surfaces (gowri-shankar and ponnsahana, 2021). a 12 mm brass cone was mounted on a lathe (see figure 10) and turned to reduce the outside diameter by 2mm. the steel cone was then mounted into the pump housing and pressed by hand to fill the space in the pump with clearance. figure 10: maintenance: resurfacing brass cone, welding clamp, maintained parts it was critical to replace the saw blade with a new one suitable for the specific application. the saw blade was replaced by purchasing a new blade as shown in figure 10. the new blade was then installed and properly tensioned using a wrench. corrective action on the clamp included cleaning with a liquid chemical and an iron brush. the clamp was then allowed to dry and che-40 electrodes were used in conjunction with a welder to fill in the cracks. an angle grinder was then used to smooth the surface of the clamp. table 2: summary of corrective actions carried out main corrective actions state of resolution verification method 1. impeller was sand papered to ensure smooth surface and sprayed with anti-rust operational poured lubricant into tank and impeller was able to provide energy to move the lubricant 2. pump housing was filled with brass material failed the impeller shaft and the housing had spacing between them 3. saw blade replaced operational cut various pieces of different dimensions 4. clamp was welded using sarf 40mm electrode operational held different pieces together 6. pump seal replaced operational no leakage on the pump when lubricant is placed in it a new gasket was then designed on solid blocks and tests were conducted to determine the best material to form a gasket. in the first test, a slipper (pvc) was cut with an industrial blade and used to form a seal. after the seal was installed, there was severe leakage at the pump outlet and the lubricant could not flow because the seal could not withstand the pressure from the impeller. in the second test, an epdm synthetic rubber from automobile tires was used to form the seal. the seal was able to withstand the pressure from the impeller, allowing the lubricant to flow more efficiently to the blade. table 2 summarizes the main activities for maintaining the band saw, while figure 11 shows the band saw after corrective action and ready for control testing. according to the corrective actions performed, pvc plasticizes and becomes brittle and even shatters at certain temperatures, whereas epdm synthetic rubber can withstand certain temperatures and pressures. figure 11: band saw after maintenance 0. monitoring and evaluation the performance rate, which compares the time the machine should be cutting (ideal time) to the actual time the machine spent cutting 60x30mm round tubing, was 93% (table 3). this indicates that the machine was achieving 93% of its maximum speed or output efficiency; therefore, it was operating close to its optimum performance level with minimal downtime, interruptions, or inefficiencies that would affect its overall productivity. table 3: performance calculation operating time per shift (min) 21 22 20.3 22.7 22 output per shift (numbers) 6 6 6 6 6 ideal cycle time 4 4 4 4 4 performance rate 0.9523 0.909 0.985 0.881 0.909 average performance 0.927 1. conclusion the main objective of the research was to restore the semi-automatic band saw machine owned by rolling enterprise to a functional state with improved reliability. after conducting a comprehensive analysis, numerous conclusions were drawn from the research. the results showed that the malfunction of more than 11 components, including the impeller, pump housing, seal, saw blade, clamp, bearings, gears, belts, and motor, prevented the machine from working successfully. after using bowtie diagrams, a visual risk assessment tool, to analyze potential hazards or root causes, it was determined that the failures were due to several factors, including poor maintenance, the presence of foreign objects such as iron filings, poor quality of certain components, fatigue, wear and numerous others. through the use of diagnostics, root cause analysis and corrective maintenance, a successful resuscitation of the semi-automatic band saw was achieved. it was imperative to demonstrate that the methods used in the research could be implemented by numerous manufacturing and production companies to optimize the maintenance and effectiveness of their production equipment. acknowledgement the authors acknowledge the support received from mr. simon ngumbi audi, manager of rollings enterprise, which enabled the timely completion of this research. references abia, d., iwegbu, m., onofeghara, c. and anozie, i. 2019. effective barrier risk management in process safety utilizing the bow tie methodology. in spe nigeria annual international conference and exhibition (p. d033s021r005). spe. alisinoglu, mb., sogut, sa., and seker, u. 2019. determination of industry 4.0 compliance criteria for band saw machines. industry 4.0, 4(6): 277-281. aust, j., and pons, d. 2020. a systematic methodology for developing bowtie in risk assessment: application to borescope inspection. aerospace, 7(7): 86. gowri shankar, ks.and ponnsahana, kr. 2021. techniques on corrosion prevention and rust removal on different steels. in materials, design, and manufacturing for sustainable environment: select proceedings of icmdmse 2020 springer singapore. (pp. 251-260). international civil aviation organization (icao) 2012. safety management manual (smm), 3rd ed.; icao:montreal, qc, canada. ispășoiu, a., milosan, i., ispășoiu, amf. and meiță, c. 2021. study on the application of the bowtie methodology for the assessment of ergonomic risks in the industrial field. recent-rezultatele cercetărilor noastre tehnice, 22(3): 128-136. kohale, u., adhao, s., thakare, d., panchawate, a., dalvi, s. and akarte, p. 2022. design and fabrication of motorized hacksaw machine. international journal for research in applied science & engineering technology, 10 (5): 3697-3703. kuldipia, k., ram, ej., murmu, mk., das, ak. and sahoo, a. 2023. design of a high speed 4-way hacksaw machine. international research journal of modernization in engineering technology and science, 5(7): 879-883. liu, y. 2020. safety barriers: research advances and new thoughts on theory, engineering and management. journal of loss prevention in the process industries, 67, 104260. olorunfemi, bj., adejuyigbe, sb. and adekunle, aa. 2018. casting and performance evaluation of pump impeller and housing using local raw materials. fuoye journal of engineering and technology, 3(1): 7-11. patil, rb. and waghmode, ly. 2014. life cycle cost (lcc) optimization of band saw cutting machine through reliability analysis. proceedings of 1st international conference on mechanical engineering: emerging trends in engineering, 2: 755-763. shiels, s. (2002). failure of mechanical seals in centrifugal pumps. world pumps, 2002(429), 20-22. tsapi, tk., nanah, ng., kuiate, gf. and oru, br. 2024. using ishikawa method in power hacksaw maintenance. international journal of innovative science and research technology, 9(2): 128-135. xie, l., lundteigen, ma. and liu, yl. 2018. safety barriers against common cause failure and cascading failure: literature reviews and modeling strategies. in 2018 ieee international conference on industrial engineering and engineering management (ieem) (pp. 122-127). ieee. xue, t., liu, y., li, g. and zhao, g. 2024. effect of heat treatment on microstructure and properties of bimetallic band saw blade. journal of physics: conference series, iop publishing, 2691(1): 012074. ul‐hamid, a., al‐hadhrami, lm., mohammed, ai. and al‐yousef, fk. 2015. failure analysis of an impeller blade. materials and corrosion, 66(3): 286-295. zariatin, dl., rahmalina, d., prasetyo, e., suwandi, a. and sumardi, m. 2019. the effect of surface roughness of the impeller to the performance of pump as turbine pico power plant. journal of mechanical engineering and sciences, 13(1): 4693-4703. zhuo, r., deng, z., chen, b., liu, t., ge, j., liu, g. and bi, s. 2022. research on online intelligent monitoring system of band saw blade wear status based on multi-feature fusion of acoustic emission signals. the international journal of advanced manufacturing technology, 121(7-8): 4533-4548. image3.jpeg image4.png image5.jpeg image6.jpeg image7.jpeg image8.jpeg image9.jpeg image10.emf image11.emf image12.emf image13.emf image14.emf image15.jpeg image16.jpeg image17.jpeg image18.jpeg image19.jpeg image20.jpeg image21.jpeg image1.png image2.jpeg faulty impeller rusted impeller with small small holes regular monitoring and evaluation of pump performance develop and implement a comprehensive maintenance schedule regular inspection and testing of pumps to identify potential issues train personels on proper pump maintenance procedures. inadequate maintenance planning regular lubricant analysis to detect contamination early employee traning on proper lubricant handling and storage regular cleaning and regular inspection foreign object entering the pump proper pump selection and sizing to ensure that it meets the operational requrements regular monitoring and evaluation of pump performance poor quality pump regular inspection and maintenance of seals. mother nature: air entering the water pump regular evaluation and optimization of pump operation use performance monitoring and optimization techniques to identify and resolve the efficiency problems implementation of pump maintenance and repair procedures 1. reduced pump efficiency timely maintenance and cleaning of the pump performance evaluation and optimization proper lubicant storage implementation 2. lubricant contamination and reduced flow rate investigate and analyse the past pump failures to identify root causes and prevent future occurence implement a robust maintenance and inspection program 3. pump failure implement immediate shutdown and carrryout maintenance on the impeller 4. cavitation/erosion wear pump failure pump housing clearance and rust schedule regular maintenance activities to clean and lubricate pump housing routine inspections to detect clearance issues and rust formation lack of regular inspection purchase spare parts for replacement establish maintenance procedures insufficient repair and replacement procedures ensure precision alignment during pump housing installation improper installation provide trainings on proper maintenance techniques and raise awareness about the risks of clearance and rust issues inadequate training and awareness apply corrosionresistant coating inadequate protecting coatings conduct timely repairs or replacements of damaged components implement preventive maintenance procedures damaged pump components regularly monitor pump performance and conduct performance evaluation reduced pump efficiency and performance develop contigency plans and spare parts inventory for quick replacements unplanned machine downtime utilize predictive maintenance techniques to identify issues befor they escalate increased maintenance cost the saw blade becomes stuck during operation sawblade with blunt and broken teeth regular maintenance and inspection inadequate maintenance training and awareness improper use use high quality blades poor quality or worn-out blade implement safety measures operator safety threats robust repair /replacement of the sawblade workpeice damage monitoring the blade performance and feedback equipment damage clamp failure during operation partial cracks on clamp regular inspection and maintenance fatigue due to constand stress and strain on the clamp ensuring proper material selection and quality control during clamp manufacturing poor quality clamps ensure clamp is not overloaded overloading the clamp proper allignment and installation improper installation of the clamp implement ndte environmental factors such as extreme heat or cold conduct risk assesment to identify the hazard and implement safety protocols accidents that could harm operator repair or replacement cost extended downtime and delay in project timelines leakage seal of the pump fluid leakage regular maintenance wear and tear quality control by using high quality seals during installation poor quality seal proper installation incorrect installation emergency response machine downtime backup pumps production delays robust maintenance air will get into the waterpump which can lead to cavitation wear. arid zone journal of engineering, technology & environment azojete march 2023. vol. 19(1):93-112 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 93 original research article effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending n. r. nwakuba1*, s. n. asoegwu1, g. a. makanjuola2 1department of agricultural engineering, school of engineering and engineering technology, federal university of technology, owerri, nigeria 2department of agricultural engineering and environmental engineering, faculty of engineering technology, obafemi awolowo university, ile-ife, nigeria *corresponding author’s email address: nnaemeka.nwakuba@futo.edu.ng 1.0 introduction cassava, a root tuber (figure 1), is a major source of calories for 200 to 300 million people in the tropics egbeocha et al., (2016) and asoegwu and makanjuola, (2021) and about 25-56% of dietary calories in southern nigeria come from cassava (kolawole et al., 2010). globally, cassava has experienced consistent growth of well above 3% annually (fao, 2018). the cassava output of nigeria has increased from 58.47 mt in 2018 to 73.91 mt in 2021 with a projection of 93.60 mt in 2023 (faostat, 2019; nnodim, 2021). several crops require urgent engineering solutions with cassava being more prominent in nigeria agbetoye et al., (2006), as its production and processing demand high energy input (aniedi et al., 2012). akala (2021) stated that nigeria has the economic potential to generate 427.3 million dollars (n188 bn) from domestic value-addition to cassava and earn additional 2.98 billion dollars (n 1.2 t) in the export of the commodity annually. article information abstract the effect of loading rate on the viscoelastic response of cassava roots, at a moisture content of 52.13 ± 5.74% (w.b), to applied bending forces was studied. experiments were conducted using a modified instron testing machine (itm) of 1 kn capacity, to investigate both creep and stress relaxation (viscoelastic) behaviour of cassava roots (variety tme 419) when static bending forces were applied at mid-span with loading rates of 2.7, 4.2, 5.3, 7.45, and 9.9 mm min-1. the creep behaviour indicated that the creep compliance may be described using a 4-element model consisting of maxwell and kelvin models in series. the retardation time and the instantaneous creep compliance of cassava root were found to be 25.5 s and 0.03009 (n mm-2)-1, respectively. the stress relaxation behaviour could be represented using a 2-element maxwell approach with a parallelorientated spring. the relaxation times are 20 and 500 s, for the range of the loading rates. relaxation modulus was found to be a function of the degree of loading, rising as the degree of loading intensified and decreasing with time. as the loading rate increased from 2.7 – 9.9 mm min-1, the relaxation modulus increased from 1.25 – 6.89 n mm-2. the result of this study gives an idea of the food product attributes vis-à-vis its strength characteristics to mechanical damage. it guides the food process engineer in estimating the impact of stress on cassava roots during postharvest operations for optimum design of efficient cassava peeling machines and product storage quality. prospects for further work were stated. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 17 july, 2022 revised 24 december, 2022 accepted 3 january, 2023 keywords: viscoelasticity stress-stain stress relaxation relaxation modulus relaxation time retardation time creep response bending force cassava root http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng mailto:nnaemeka.nwakuba@futo.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 94 figure 1: bunch of tapered cassava roots. early work on mechanized harvesting of the cassava root in nigeria was undertaken by makanjuola et al. (1973). within the last decade, many cassava peeling machines have been designed and constructed (olukunle, 2005; bamgboye and adebayo, 2009; jimoh and olukunle, 2012) as well as planting machines for cassava stems and harvesting machines for cassava roots (oriola and raji, 2013). what remains now is taking a critical look into important root parameters for the proper development of cassava root post-harvest machines (morrow and mohsenin, 2006). nweke (2003) suggests that the development of the machines will take into consideration the physical properties of the crop. according to ikuemonisan et al. (2020), the majority of cassava farmers cultivate small farm areas which are not conducive or economical for mechanization. yet, abass et al. (2014) have argued that using improved inputs alone, without mechanization, will not sufficiently boost cassava root production in nigeria. cassava roots have their major demerits as their bulk and their fast rate of denaturing, poor amino-acid value and bromide presence (ospina and wheatley, 1992). rapid fresh root perishability means that extreme care must be taken during harvesting to avert roots’ mechanical injury. asoegwu and makanjuola (2021) opine that as food manufacturing becomes more automated, equipment ought to be built to minimize the effect of mechanical injury. the behavioural response of agro-based materials to external forces is time-dependent (ndukwe et al., 2021) and their characterization entails the use of viscoelasticity theories that integrate viscous and elastic reactions. since many agricultural products behave viscoelastically under mechanical loading (mohsenin, 1986; rodrı´guez-sandoval et al., 2009; herak et al., 2014; ijabo et al., 2019), the study of the effect of loading rate on the viscoelastic properties of cassava roots would yield those important root parameters needed for developing postharvest equipment. the parameters must be stated quantifiably similar to those used to describe the engineering qualities of materials like steel, wood, and concrete (kingsley et al., 2013). engineering computations make use of rheological representations (gołacki et al., 2007). one of the major problems in mechanizing cassava root production, harvesting, handling, storage and processing is that the over two hundred varieties grown in the world (egbeocha et al., 2016) produce roots that have broad variants in their physical attributes. the broad array of features of cassava peels poses a challenge. roots’ maturity period (9 to 36 months) affects all cassava physical properties. despite the above problems, there is a scarcity of essential data relating to the root reaction to bending and other stresses that post-harvest machines may impose. furthermore, cassava roots file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 95 as living bio-materials are largely made up of polymeric constituents holding different quantities of constituents: 25-30% dry matter and 70-75% moisture (kolawole et al., 2010) and behave viscoelastically in response to loads (ijabo et al., 2019) with the hazards of mechanical damage (herak et al., 2014; herak et al., 2015). determination of their elastic and viscoelastic properties would help to express their behaviour mathematically and help develop mechanical models to simulate products to obtain a better understanding of their behaviour (saeidirad et al., 2013). this will aid in the development of methods that maximize machine efficiency while maintaining the greatest level of product superiority (velásquez et al., 2007; kolawole et al., 2007). stress relaxation is one of the defined tests to characterize the viscoelastic properties of food and agricultural materials. stress relaxation data are very important because they provide useful and valuable information such as fruit firmness and ripening, food processing and predicting changes in the material during mechanical loading (saeidirad et al., 2013). the study aims at analyzing the viscoelastic characteristics of cassava roots subjected to bending forces at mid-span, taking into consideration the tapered nature of the root. this would involve the study of the: (i) creep and stress-relaxing behaviour of the cassava roots; (ii) influence of loading rate on relaxation time, and (iii) propose rheological models to represent the creep compliance and modulus of relaxation. 2. materıals and methods the cassava root samples (variety tme 419) utilized for the tests were freshly hand-harvested (from the experimental farm of the department of agronomy, university of obafemi awolowo university, ile-ife, nigeria), straight, kink-free and tapered uniformly (figure 1). the roots were about 15 months old and had a moisture content of 52.13 ± 5.74% (w.b.), measured thermogravimetrically, just before the tests were carried out. the cassava roots were harvested from the university farm and the tests were conducted in the agricultural engineering laboratory of the obafemi awolowo university of ife, ile-ife, osun state, nigeria, at a room temperature of about 27 ± 2oc. the homogeneity of the composite cassava root as well as its isotropic property in relation to its deformation from section to section was assumed. the creep equipment used by morrow and mohsenin (2006) was modified with rollers and adapted for simply-supported cassava roots. the cassava roots had a length for effective buckling resistance, leff, equivalent to the space in the middle of the frame wheels, 270mm. the modified creep equipment (figure 2) was used for the bending creep test where a dead load was placed at the center of the cassava root sample, and structural deformations that changed over time were noted using dial gauges. for the stress relaxation in the bending test, the instron compression testing machine was fitted with rollers (span 270mm, out-to-out) and the application of a center load at a constant loading rate was from a variable speed motor through a suitably designed belt drive (figure 3). the instron compressive machine was driven by a 3 hp variable speed electric motor through a suitably designed belt drive. the modified universal itm (3400 series, 1 kn capacity) had a load measurement accuracy of ± 0.5% of reading down to 1/200th of load cell capacity, and a displacement accuracy of ± 0.02mm or 0.15% of displacement. a predictive analysis was carried out to determine the mean compliances of the groups of the studied cassava roots under static bending force. a plot of experimental and predicted was given to ascertain the degree of correlation of the model parameters. http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 96 figure 2: schematics of the static loading creep equipment figure 3: stress relaxation equipment. 2.1 theoretical considerations two types of tests are typically used to establish the force-deformation association of agricultural goods (mohan, 1984; chen and sun, 1991; lu and abbot, 2004). the first type includes tests in which the studied sample is subjected to deformation forces at regular intervals of time and the equation governing the corresponding elastic problem is as expressed in equation (1): p(t) = k. e(t) (1) where p(t) is relaxation force (n) at the time, t s; e(t) is relaxation modulus (n mm-2) at the time, t (s). because biomaterials do not exhibit the ideal hookean behaviour, there must be some make-up (k-factor) at play to make for creep and stress relaxation. the k-factor is a characteristic of the specimen's structural variables (a conversion factor). uniaxial loading and testing on specimens with a uniform cross-section region are two examples of this first type. evaluation of rheological properties determined from stress relaxation and creep tests performed on agricultural materials provides information on viscoelasticity that correlates these properties with end-use products (figueroa et al., 2013). the creep phenomenon is used to describe the continued deformation of a viscoelastic material after the load has reached a constant state. under constant deformation, stress relaxation describes the continued reduction in stress inside a viscoelastic material (yang, 2018). the effect of fibers on the viscoelastic properties of shortfibre composites (using rice husk, palm kernel shell, and periwinkle) is difficult to understand. however, these properties are extremely important in load-bearing applications where there is the potential for creep or stress relaxation, or where the composites are exposed to any sort of dynamic loading, and hence it is important to be able to predict the influence of fibre file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng https://www.sciencedirect.com/topics/engineering/creep-phenomenon nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 97 reinforcement on the viscoelasticity (obaid et al., 2017). this second type is not considered in this study. in this study, it is considered that the harvestability of cassava roots using machines may make them more prone to bending action. in this case, compression, shear or impact testing would not be applicable. for curved beams having uni-axial modulus, a binomial approximation is used for the elastic bending formula. schroder et al. (2017) developed a mathematical expression (equation 2) for the function of the geometric parameters: k = y 8hl3 = p eπ (2) where: h = 2 [ u d2 4 + v d1 4] [ z d2 4 + q d1 4] u = 1 48 + a 48 + a2 64 + a3 96 + 5a4 767 + a5 256 v = 1 48 − b 48 + b2 64 − b3 96 + 5b4 767 − b5 256 z = 1 8 + a 6 + 5a2 32 + a3 8 + 35a4 384 + a5 16 q = 1 8 − b 6 + 5a2 32 − b3 8 + 35b4 384 + b5 16 and a = d2 − d1 d2 ; b = d2 − d1 d1 this expression (equation 2) was used in calculating the parameters of the studied cassava root samples. for this study, the following numerical values for the cassava roots were used: d1 = 49.41 mm, d2 = 60.29 mm, a = 0.18, b = 0.22, u = 0.0251, v = 0.0169, z = 0.1608, q = 0.0947, h = 1.8592 x 10-8 mm-4, mean k = 2.00 mm2, l = 270 mm. in creep loading, a constant stress σ, usually applied at time zero, causes a time-dependent strain ε(t) where the time = t. compliance is defined as the ratio of strain to stress. the creep compliance j is defined by equation (3). 𝐽(𝜎, 𝑡) = 𝜀𝑡 𝜎 (3) when the strains are small, the creep compliance function becomes independent of stress σ; the creep strain, for a linear viscoelastic solid, is given by equation (4). 𝜀(𝑡) = 𝜎𝐽(𝑡) (4) ɛ(t)=σj(t) according to mills (2007), it is often easier to measure the creep compliance function j (t) than the relaxation modulus e (t), because it is easier to apply a constant load than a constant strain in a fraction of a second. linear viscoelasticity theory can relate e (t) to j (t). unless the polymer is near a transition temperature, the creep compliance is a slowly varying function of time, so creep compliance may be given as equation (5). 𝐽(𝑡) ≅ 1 𝐸(𝑡) (5) http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng https://www.sciencedirect.com/topics/engineering/creep-strain https://www.sciencedirect.com/topics/engineering/relaxation-modulus https://www.sciencedirect.com/topics/engineering/viscoelasticity arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 98 creep and stress relaxation are two distinct viscoelastic behaviours that bio-materials can exhibit. the functions relaxation modulus g and creep compliance j are two other important functions in the field of rheology. for creep, the application of a constant load (or uniform force) and the resultant time-dependent deformation are studied. the data are plotted in terms of shear stress compliance versus time (steffe, 1996; nishinari, 2004). this behaviour is represented by the 4element model (barnes, 2000; zhiyuan et al., 2021) (figure 4) expressed by the following equations (6) and (7): ε(t) = σ e1 + σ e2 (1 − e− t α) + σ γ1 t (6) dividing equation 6 by stress, 𝜎, the creep compliance expression is estimated as equation (7): 𝐽(𝑡) = 𝐽0 + 𝐽 (1 − 𝑒− 𝑡 ∝) + 𝑡 𝛾1 (7) if a material behaves as is defined by equations (3) to (7) its behaviour can be described as linear viscoelastic (gradin et al., 1989). in a stress relaxation experiment, the cassava root is subjected to a constant strain at time zero, and the resultant stress is measured as a function of time. the force (stress) necessary to maintain this initial deformation is measured per interval of time and represented in terms of the shear stress relaxation modulus (wu and abbott, 2002; rajabipour et al., 2004; hassan et al., 2005). the decay of this constant force, a natural consequence of the material structure, is called stress relaxation a time-dependent reduction of the stress in materials under constant strain (figure 4). of the three ways generally used to keep strain constant, straining a stiff spring element (large force per deformation) in series with the sample (low force/deformation), was used (ferry, 1999). figure 4: stress–time curve. (source: ashter, 2014). the stress relaxation behaviour can be characterized by a universal maxwell representation, comprising numerous maxwell components arranged parallel-wise (ahmed and ramaswamy, 2006; golacki and stropek, 2001). the mechanical reactions of biomaterials may be predicted and interpreted using viscoelastic relaxation patterns. these patterns must normally be determined from viscoelastic relaxation studies for bio-based materials (babaei et al., 2016). a typical stress-time curve is given in figure 4. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng https://www.sciencedirect.com/topics/engineering/viscoelastic-behavior nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 99 using the correspondence principles (saeidirad et al., 2013), and the superposition principles, researchers have evolved a mathematical expression for the solution of the viscoelastic bending equation in terms of relaxation modulus (blahovec, 2001; herak et al., 2015; alvis et al., 2010). the relaxation modulus, which is amongst the most vital viscoelastic parameters, is generally represented by a proxy or dirichlet power series. relaxation modulus, e(t) is a property of material viscoelasticity that describes how stress relaxes over time (t). to analyze and design material-handling equipment, it is critical to precisely model stress relaxation and viscoelastic deformation in bio-products (xu and engquist, 2018) and substitute the outcomes of the numerical test into the exponential expression of time as proposed by kingsley et al. (2013); expressed by equation (8) as: 𝐸(t) = 8hl3 y p(t) = e∞ + e1e− t ∝ (8) relaxation modulus, e(t) is a characteristic of material viscoelasticity (n mm-2) as used to describe the stress relaxation of materials with time, t (s). it is important to accurately simulate the stress relaxation and viscoelastic deformation of cassava roots in order to evaluate and design materials. 2.2 methods two test methods were used in this work: the static bending creep test and the stress relaxation test. the creep test in this work used a fixed load (or stress) at a constant temperature and measured the increase in the stain as a function of time (woodford, 2000). maintaining a constant temperature during a creep test is critical due to the possible thermal expansion or shrinkage of the material. 2.2.1 static bending creep test the objective of a creep test is to predict the life span of a material under certain operating conditions. creep strength provides an indication of the service life of a material under specified operating conditions. it provides the mechanical stress value that will cause the material to fail, while held at constant temperature for a certain amount of time (jalali et al., 2019). in the creep test, loads below those necessary to cause instantaneous fracture are applied to the material, and the deformation over some time (creep strain) under constant load is measured, usually with an extensometer or strain gauge (hofer and rao, 1977). the creep test, using the 3-point bending beam is a standard test method (rihmt, 2011), for determining the viscoelastic parameters of materials, which are commonly used to evaluate the creep properties of materials (sun et al., 2019). on the rollers of the modified creep equipment (figure 2), cassava roots of different diameters: 40 ± 1.2 ≤ d ≤ 60 ± 2.3 mm) were each positioned in the most stable natural position, at which it did not roll. with the help of a dead weight of 0.5 kg on the lever arm, the root was deformed at mid-span. for a 3-point bending test of the tapered cassava root length l supported on the reaction point rollers, the cassava root has d1 and d2 diameters at the reaction points and diameter d at the load point. the cassava root is assumed homogenous and isotropic. when bending occurs, the surface where the force is applied experiences compression forces while the opposite surface experiences tensile forces making this measure most suited to isotropic materials (asoegwu and makanjuola, 2021). deformations were measured at 5 seconds intervals using a dial gauge. at the end of 180 seconds, the load was removed and the recovered deformations were recorded at 5 seconds intervals for 90 seconds when deformation ceased to decrease. these tests were repeated with a dead load of 1 kg on the 75 root samples in each of the groups of cassava roots with mean diameters of 40 ± 1.2 mm, 50 ± 0.7 mm, and 60 ± 2.3 mm, respectively. the sample stress/strain graph is given in figure 5. http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng https://www.britannica.com/technology/strain-gauge arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 100 figure 5: sample of a stress/strain plot. the compliance (strain/stress) for each time interval was estimated by the following equations (9) and (10) (herak et al., 2015): εmax = 3(d1+d2)y l2 (9) εmax = 64pl (d1+d2)3 (10) the creep compliance for each time interval of 5 to 180 s was obtained for each load. the mean was calculated and plotted against time. a burger model with 4 elements was used for the creep test. 2.2.2 stress relaxation tests with the help of the instron equipment, figure 3, each cassava root in another set of 50 roots (tail = d1 = 50 ± 2.4 mm; butt or proximate = d2 = 60 ± 1.8 mm) placed in its most stable position on the rollers, was strained to a constant deformation for 30 seconds at a constant loading rate while the force and the deflection were recorded at 5 seconds intervals. then the time-dependent decrease in force under a constant strain was recorded at 5 seconds intervals until the relaxation force became a constant value. the experiments were carried out on a total of 50 specimens at each of the five loading rates (2.7, 4.2, 5.3, 7.45, and 9.9 mm min-1) applied mid-span, at moisture contents measured just before the tests. relaxation time was determined, by measuring the time it takes for stress to decrease to stress/2.718. in other words, it is the time in which the relaxation process carries the system a fraction of 1/e toward the equilibrium position. relaxation time was determined for each loading rate while the relaxation modulus was calculated using equation (8). the relationship between e and η is given by the equation τ = η / e where τ is known as the relaxation time for a mechanical system exposed to controlled stress. a generalized maxwell model has frequently been used to interpret stress relaxation data of linear viscoelastic material. the model contains n maxwell elements and a spring in parallel; each element of the maxwell model consists of a dashpot and a spring in series (watts and bilanski, 1991; gorji-chakespari, 2010). the graph of the relaxation modulus versus time was plotted. 2.2.3 analysis of results relevant statistics were used to analyze the data obtained and some were presented in figures and equations. experimental results on stress relaxation tests were fitted into the timeexponential equation. the graphs of the creep and creep recovery were plotted against time. the file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 101 experimental and predicted results of the creep compliance were plotted on a graph. the graphs of stress relaxation versus time were also plotted. 3. results and dıscussıon figure 6a shows the creep and recovery curves for different diameters when loaded with 0.5 kg. a considerable difference exists at a 5% probability level amongst the strains experienced by the specimens under varying stresses occasioned by diameter differences. the curves were similar to those loaded with 1.0 kg (figure 6b). when loaded with 0.5 kg for 180 s, the stress on the different-sized cassava roots ranged from 0.0231 to 0.0523 nmm-2, giving a maximum strain range of 1.0 to 2.0x10-3 mm mm-1. with the 1.0 kg load for 180 s, the constant stress ranged from 0.0323 to 0.1039 nmm-2 giving the maximum strain attained ranging from 2.6 to 4.4x10-3 mm mm-1. the strain-time curves (figures 6a and 6b) were similar to those obtained by zhiyuan et al. (2021). cassava root diameters affected the creep and recovery curves as shown in figures 6a and 6b. figure 6a: creep curves, when loaded with 0.5 kg for 180 s and strain, recovered. http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 102 figure 6b: creep curves when loaded with 1.0 kg for 180 s and strain recovered for 90 s. however, it was observed that no significant difference between the mean compliances of the groups of cassava roots studied exists. the mean compliance curves of the experimental and predicted values for cassava roots under static bending force are shown in figure 7. figure 7: mean creep compliance versus time relations for cassava roots in bending (p = predicted; e = experimental). from figure 7, the compliance relationship with time is a 3-order polynomial function represented by equations (11) and (12), while the plot of the experimental and the predicted creep compliance (figure 8) has a linear trend (eq.13). 𝐶𝑟𝑒𝑒𝑝𝑒𝑥𝑝𝑡 = 8𝐸 − 09𝑡3 − 3𝐸 − 06𝑡2 + 0.0004𝑡 + 0.0321 𝑅2 = 0.9969 (11) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 103 𝐶𝑟𝑒𝑒𝑝𝑝𝑟𝑒𝑑 = 8𝐸 − 09𝑡3 − 3𝐸 − 06𝑡2 + 0.0004𝑡 + 0.0318 𝑅2 = 0.9942 (12) 𝐶𝑟𝑒𝑒𝑝𝑝𝑟𝑒𝑑 = 1.0629𝐶𝑟𝑒𝑒𝑝𝑒𝑥𝑝𝑡 − 0.0027 𝑅2 = 0.9908 (13) figure 8: linear graph of the predicted and experimental values of compliance. the r2 of equations (11) to (13) are more than 0.99 showing that over 99% of the dependent variable are explained by the independent variables which indicate the goodness of fit (nwakuba et al., 2018; uzoma et al., 2020; nwakuba et al., 2021). the regression of the experimental against the predicted compliance values exhibited a high linear coefficient of determination, r2 = 0.9908 which indicates that about 99.08% of the experimental inconsistency was explained by the 4element model of the exponential function (equation 8). sun et al. (2019) agree that r2 values above 99.5% signify that the model properly represents viscoelasticity. when the time-dependent strain is divided by the fixed stress, a unique creep compliance curve results; that is, at each time there is only one value for this ratio, which is compliance. (ngai et al., 2013). the compliance curve for cassava root is similar to that found by gorji-chakespari et al. (2010) for two iranian apple varieties. the compliance expression given as equation (7) is predicted by a 4-component representation involving one maxwell and one kelvin representation in sequence connection, called the burgers model (figure 9) (yang et al., 2006). the burgers model is a common model that can describe material viscoelastic behaviour (zhang et al., 2015). substituting the statistically obtained results in equation (7) above yields equation (14). j(t) = 03009 + 0.01419 (1 − e− t 25.5) + t 43000 (14) from equation (14) the retardation time and the instantaneous creep compliance of cassava root were found to be 25.5 seconds and 0.03009 (nmm-2)-1, respectively. according to gorjichakespari et al. (2010), the retardation time was 15 seconds for the shafi abadi variety; and for golab, kohanz was 12 seconds. for fresh and cooked potato tissues, alvarez et al. (1998) determined retardation times as 136.58 and 54.89 seconds, respectively. because the retardation period/impedance is an essential consideration in preservation duration (in storage), then fresh potato has a longer storage duration than apple and cassava root. http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng https://www.sciencedirect.com/topics/engineering/creep-compliance arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 104 figure 9: generalized maxwell model with 3 elements for stress relaxation test (a) and burger model with 4 elements for creep test (b), (gorji-chakespari et al., 2010; dzadz et al., 2015; dong et al., 2021). experimental results on stress relaxation tests were built into the time-exponential equation, equation (8), as proposed by saeidirad et al. (2013) and kingsley et al. (2013). the equation coefficients, obtained from the statistical analysis, reveal that a two-component maxwell representation with a parallel-array spring may be used to represent the stress relaxation response of cassava root. the relaxation times are 20 and 500 s, respectively. this is shown in equations (15a) to (15e) for the different loading rates (r1 to r5) which significantly (p ≤ 0.05) affected the relaxation modulus, e(t). e(t) = 3.00 + 2.064e−0.05t + 1.285e−0.002t … for r1 = 2.7 mm min-1 (15a) e(t) = 3.75 + 1.007e−0.05t + 2.502e−0.002t … for r2 = 4.2 mm min-1 (15b) e(t) = 7.13 + 3.621e−0.05t + 1.285e−0.002t … for r3 = 5.3 mm min-1 (15c) e(t) = 14.25 + 6.523e−0.05t + 7.320−0.002t … for r4 = 7.45 mm min-1 (15d) e(t) = 16.75 + 7.535e−0.05t + 8.179e−0.002t … for r5 = 9.9 mm min-1 (15e) figure 10 illustrates the influence of the rate of loading on the relaxation time and relaxation modulus of cassava root in bending. whereas relaxation modulus increased with an increase in loading rate, relaxation time decreased with an increased loading rate. similar results have been reported on some other agricultural products, e.g., fruit tissue (sakurai and nevins, 1992); tomato skin (rajabipour et al., 2004); dates (hassan et al., 2005); carrot root (gołacki and stropek, 2001). the curve has a pattern that is comparable to that of a viscoelastic substance. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 105 figure 10: influence of degree of loading on relaxation period and relaxation modulus. the effect of time on the relaxation modulus of cassava root (figure 11) indicates that the relaxation modulus decreased with time. this also is true for viscoelastic materials such as potato tuber, boiled potatoes, wheat dough, and osmotic drying of apples and bananas (blahovec, 2003; kaur et al., 2002; li et al., 2003; safari-ardi and phan-thien, 1998; krokida et al., 2000). even for non-agricultural materials such as high-viscosity asphalt sand (hvas), sun et al. (2019) found the relaxation modulus to decrease with time. figure 11: relaxation modulus of cassava roots in bending due to varying loading rates (r, mm/min). the relaxation times for shafi abadi and golab kohanz types of iranian apples are 90 and 78 s, respectively (gorji-chakespari et al., 2010). wang (2003) discovered that the relaxation time for http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 106 a pear is 30.33 s, which might be due to the pear's soft textural feature when compared to an apple. in this current study, the relaxation time for cassava root is 500 s showing that the cassava root is harder than both apple and pear. also, figure 11 shows that the relaxation modulus increased with increasing loading rate for cassava roots in bending (mcclung et al., 2017). 3.1 engineering implication of the results creep compliance is obtained when a load deforms a viscoelastic material and the deformation as a function of time is studied. the knowledge of these product features aids the design engineer to analyze the impact of stress on the food product during harvesting, storage or transportation (figueroa et al., 2013; li et al., 2022). for example, when cassava roots are harvested, it must be known how high they may be heaped without injuring the ones underneath or causing mechanical hysteresis. the knowledge of cassava roots’ response to various forms of applied forces is a foundation of an account of material parameters often employed to estimate their resistive ability to physical injury, end-use, and preservation quality. linear viscoelastic equations can be used to explain several phenomena found in many moisture-rich food substances (yang, 2018). the relaxation modulus is a characteristic of a viscoelastic material's tendency for stresses from a fixed strain to decrease with time. this material property helps the engineer to study the influence of deformation on food products in the course of collision, processing, and packing as induced by time (xu and engquist, 2018). being the equivalent of young’s modulus, the relaxation modulus is used for estimations of crack factors and stress at the yield point of food products. products are exposed to a wide spectrum of impact loads as food production gets increasingly industrialized. the machinery must be built to keep the impact to a minimum so that no harm is done (asoegwu and makanjuola, 2021). therefore, the allowable loading levels should be determined. in addition to elastic characteristics, creep or stress relaxation gives textural information. 4. conclusıon cassava roots having a moisture content of about 52.13% (w.b.) behave viscoelastically when subjected to bending forces arising from 0.5 to 1.0 kg static load or 2.0 to 10.0 mm min-1 loading rates. their creep behaviour in bending may be described by a 4-component function made up of one maxwell and one kevin model in series. the rheology of such material is mathematically expressed as: j(t) − j0 + j(1 − e− t ∝) + t γ1 the generalized maxwell model with 3 elements was used to describe stress relaxation while the burger model with 4 elements was used for the creep behaviour in bending. the equation is given thus: e(t) = e∞ + e1e −t ∝1 + e2e −t ∝2 the development of postharvest equipment requires root parameters that can only be obtained via research on the impact of loading rate on the viscoelastic properties of cassava roots. from this study, therefore, the rate of loading affected both relaxation modulus and relaxation time. relaxation modulus decreased with an increase in time and increased with an increase in loading rate. this is in agreement with the general viscoelastic behaviour of plant-based materials. relaxation time always decreases with increasing loading rate. it might be necessary to point out that further research is required at other maturity ages, greater rates of loading, higher static loads, other levels of moisture content and most probably other temperatures before deductions as to the relative importance of any of these variables can be file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng nwakuba et al.: effect of loading rate on viscoelastic behaviour of cassava roots (manihot esculenta crantz) in bending. azojete, 19(1):93-112. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 107 stated. similarly, when conducting tests, it's important to remember that all applied loads have to be sufficiently mild not to surpass the root's bio-yield threshold. references abass, ab., towo, e., mukuka, i., okechukwu, ru., ranaivoson, r., tarawali, g. and kanju, e. 2014. growing cassava: a training manual from production to post-harvest. iita, ibadan, nigeria. agbetoye, las., ademosun, oc., ogunlowo, as., olukunle, oj., fapetu, op. and adesina, a. 2006. developing indigenous machinery for cassava processing and fruit juice production in nigeria. proceedings of the first international conference on advances in engineering and technology held in entebbe, uganda, 16th -19th july 2006. elsevier publication limited, 375-384. ahmed, j. and ramaswamy, hs. 2006. viscoelastic properties of sweet potato puree infant food. journal of food engineering, 74: 376–382. akala, d. 2021. nigeria has the potential to generate n1.2 trn. from cassava annually. vanguard news of november 5, 2021. 3 osogbo close off emeka anyaoku street, area 11 garki, abuja, nigeria. www.thecable.ng. accessed on 10th december, 2022. alvarez, md., canet, w., cuesta, f. and lamua, m. 1998. viscoelastic characterization of solid foods from creep compliance data: application to potato tissues. zeitschrift fur lebensmitteluntersuchung und-forschung, 207: 356-362. alvis, a., villamiel, m. and rada-mendoza, m. 2010. mechanical properties and viscoelastic characteristics of two varieties of yam tubers (dioscorea alata). journal of texture studies, 41: 92 – 99. aniedi, oe., linus, oa., ime, ae. and benjamin, e. 2012. mechanization of cassava peeling. research journal in engineering and applied sciences, 1(5): 334-337. asoegwu, sn. and makanjuola, ga. 2021. modelıng the breakıng characterıstıcs of cassava root lengths under contınuous bendıng loads. journal of agricultural engineering and technology, 26: 1-20. ashter, sa. 2014. characterization. in syed, aa. thermoforming of single and multilayer laminates, william andrew publishing, michigan, usa, pp. 147 – 192, https://doi.org/10.1016/b978-1-4557-3172-5.00007-4. babaei, b., davarian, a., pryse, km., elson, e.l. and genin, gm. 2016. efficient and optimized identification of generalized maxwell viscoelastic relaxation spectra. journal of the mechanical behaviour of biomedical materials, 55(3): 32-41. bamgboye, ai. and adebayo, ao. 2009. development of a motorized cassava chipping machine, science focus, 14(2): 262 – 272. barnes, ha. 2000. a handbook of elementary rheology. institute of non-newtonian fluid mechanics, university of wales. blahovec, j. 2001. improved rate-controlled model for stress relaxation in vegetable tissue. international agrophysics, 15, 73 78. blahovec, j. 2003. activation volume from stress relaxation curves in raw and cooked potato. international journal of food properties, 6: 183-193. chen, p. and sun, z. 1991. a review of non-destructive methods for quality evaluation and sorting of agricultural products. journal of agricultural engineering research, 49: 85–98. http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng https://doi.org/10.1016/b978-1-4557-3172-5.00007-4 https://www.sciencedirect.com/journal/journal-of-the-mechanical-behavior-of-biomedical-materials https://www.sciencedirect.com/journal/journal-of-the-mechanical-behavior-of-biomedical-materials https://www.sciencedirect.com/journal/journal-of-the-mechanical-behavior-of-biomedical-materials/vol/55/suppl/c arid zone journal of engineering, technology and environment, march, 2023; 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(ed). basic finite element method as applied to injury biomechanics, academic press, pp. 231-256, https://doi.org/10.1016/b978-0-12-809831-8.00005-2. zhang, y., xu, s., zhang, q. and zhou, y. 2015. experimental and theoretical research on the stress-relaxation behaviour of ptfe-coated fabrics under different temperatures. advances in materials science and engineering, 2015: 1-12. https://doi.org/10.1155/2015/319473. zhiyuan, d., zepeng, f., yabo, c. and kejian, w. 2021. modelling the creep curves of β-bopp film. academic journal of polymer science, 5(1): 00206 – 00210. http://www.azojete.com.ng/ mailto:nnaemeka.nwakuba@futo.edu.ng https://doi.org/10.3390/ma12122021 https://dergipark.org.tr/en/pub/turkager/issue/53651/717253 https://doi.org/10.1016/b978-0-12-809831-8.00005-2 https://www.hindawi.com/journals/amse/ https://www.hindawi.com/journals/amse/ https://doi.org/10.1155/2015/319473 arid zone journal of engineering, technology and environment, march, 2023; vol. 19(1):93-112. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: nnaemeka.nwakuba@futo.edu.ng 112 notation 𝜀(𝑡) strain 𝜎 stress (n mm-2) 𝐸1 instantaneous elastic modulus (n mm-2) 𝐸2 retarded elastic modulus (n mm-2) ∝1; ∝2= 𝛾1 𝐸1 = 𝛾2 𝐸2 retardation time (sec) 𝛾1; 𝛾2 viscosity coefficient (ns mm-2) j(t) creep compliance (1 nm-2)-1 e exponential logarithm. e(t) relaxation modulus (n mm-2) at the time, t (s). 𝐸∞ relaxation modulus (n mm-2) after a very long time. 𝐸𝑖 relaxation modulus of ith maxwell element. n number n, and presence of time (s) of ith maxwell element. 𝑑𝑖 tail end diameter (mm). 𝑑2 proximal end diameter (mm). y deflection (mm); constant deflection for stress relaxation (mm). l span (mm). p loading force (n). p(t) relaxation force (n) at the time, t (s). k the function of moisture content of the geometric parameters of the specimen file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:nnaemeka.nwakuba@futo.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):759-770 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 759 optimization of vitamin a in red guinea corn-millet mix o. eyide*1, s. iweriolor2, b. j. ossai3, e. t. akhihiero4, and a. a. olaseinde5 *1department of chemical engineering, faculty of engineering, university of delta, agbor, delta state, nigeria. 2department of mechanical engineering, faculty of engineering, university of delta, agbor, delta state, nigeria. 3department of chemical engineering, faculty of engineering, university of delta, agbor, delta state, nigeria. 4department of chemical engineering, faculty of engineering, university of benin, benin city, edo state, nigeria 5department of materials science and engineering *corresponding author's email address: sunday.iweriolor@unidel.edu.ng article information submitted 27 aug, 2023 revised 9 oct, 2023 accepted 11 oct, 2023 keywords: blend millet optimization red guinea corn vitamin a abstract this study focused on the optimization of vitamin a in guinea corn and millet mix. the concentration of vitamin a was investigated under the following conditions: blending time (1.5 5 hours), amount of red guinea corn (10 50g) and amount of agro residue (50-100 g) using box-behnken design. statistically significant model (p<0.05) was developed to represent the relationship between the response (concentration of vitamin a) and the independent variables. the model showed a significant fit with experimental data with r2 values of 0.94. analysis of variance (anova) results showed that the concentration of vitamin a was influenced by the blending time, amount of red guinea corn and amount of millet used. additionally, response surface methodology (rsm) was used to optimize the concentration of vitamin a. the results showed that maximum concentration of 98.76 µg/100g for vitamin a was obtained at the optimum production conditions of blending time of 5hours, 49.79g of red guinea corn and 100g of millet. the blend produced at the optimized conditions satisfied the world health organization (who), food and agricultural organization (fao) specification for recommended safe intake for all age groups, pregnant and nursing mothers 1.0 introduction nutrition is an integral part of human life, that deals with the study of nutrients which is the relationship between food and health. nutrients are chemical compounds found in foods used by the body for growth, maintenance and repair. examples of nutrients are carbohydrates, proteins, fats, vitamins, minerals and water. the right balance diets are vital for human existence, physical growth, mental development, performance and productivity throughout the entire lifetime (akhihiero et al., 2022). one of the 17 goals of sustainable development goals (sdgs) adopted by the united nations in 2015 is to address global challenges such as hunger, food insecurity, improved nutrition and sustainable agriculture. goal 2.1 of the sdgs targeted access to affordable, reliable, sustainable and right nutrition for all while target 2.2 has to do with eliminating all forms of malnutrition. in line with this goal #2, the issue of hunger and malnutrition is of great concern to humans, which is linked to poor feeding habits, the high rate of junk food consumption, the high cost of nutritional foods and negligence of pregnant and nursing mothers which can be addressed via developing value-added products from millets and guinea corn. the issue of malnutrition may arise from lack of adequate or excess intake of one or more nutrients (kunyanga et al., 2013), in 2019, two billion (25.9 percent) of the global population, http://www.azojete.com.ng/ mailto:sunday.iweriolor@unidel.edu.ng mailto:sunday.iweriolor@unidel.edu.ng mailto:sunday.iweriolor@unidel.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):759-770. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 760 experienced hunger or did not have daily access to nutritious and enough food. while in nigeria, malnutrition is a significant public health concern. according to world food program in nigeria, an estimated 22 million people are affected by acute food insecurity and malnutrition, including 2.5million children under the age of five. also, malnutrition is estimated to contribute to more than one-third of all child deaths (younis et al., 2022). it is noteworthy that food insecurity affects diet quality, such as human diet and people’s health. therefore, child malnutrition remains a global challenge. in 2019, it was reported that 21.3 percent (144.0 million) of children fewer than 5 years of age were estimated to be stunted, 6.9 percent (47.0 million) wasted and 5.6 percent (38.3 million) were overweight, while at least 340 million children suffered from micronutrient deficiencies. one of the micronutrients of interest in this study is vitamin a (retinol) which is an essential nutrient needed in small amounts by humans for the normal functioning of the visual system, growth, bone development, reproduction, protective effect on the skin, immune function, contributes to the development of normal teeth and hair ((sabina et al., 2019, d’ambrosio et al., 2011, gutierrez-mazariegos et al., 2011) vitamin a is a fat soluble micronutrient that is vital for pregnant women and their fetus, they are needed for the maintenance of maternal night vision and fetal ocular health, also for the development of organs and the fetal skeleton and maintenance of the fetal immune system (sabina et al., 2019; el-khashab et al., 2013; sommer et al., 2012,). during the period of pregnancy, there is a high demand for vitamin a, particularly in the third quarter because of the fast development of the fetus (who, 2013). according to the who report of 2009, in some developing countries, vitamin a deficiency (vad) is still addressed as a public health issue affecting approximately 19 million pregnant women. according to younis et al. (2015), the issue of vad among age groups in developing countries is linked to poor feeding habits and almost 130 million of all preschool children are suffering from a deficiency of vitamin a (unscn., 2005). the issue of malnutrition can be addressed via a composite blend of cereals such as millet and guinea corn processed into valuable food products (akhihiero et al., 2022). according to nwokem et al. (2019) report that composite blends from locally available food commodities such as cereals have great potential in providing nutritious foods that can address the issues of malnutrition among age groups, pregnant mothers and nursing mothers in nigeria in particular, and developing countries in general. in a recent study carried out by akhihiero et al. (2022), revealed that guinea corn and millet can be processed into valuable food products with an additional quantity of the vitamins and minerals needed to boost our immune system. thus, value-added products produced from cereals are good sources of micronutrients that are needed for body building, they can be used to formulate nutritious and more cost-effective complementary food and drink products that will improve child nutrition, reduce morbidity and mortality rates (ikokoh et al., 2019). to the best of our knowledge, none of these studies have attempted to statistically optimize the concentration of vitamin a, in red guinea corn and millet. this study, thus, aims to investigate the optimization of vitamin a in red guinea corn-millet mix using the response surface methodology. 2.0 materials and methods 2.1 collection and pretreatment of raw materials the millet (pennisetum glaucum) and red guinea corn (sorghum bicolor) grains used in this study were purchased from the midwifery market, a local market, in asaba, delta state, nigeria. the millet and red guinea corn grains were sorted to remove sand, dust, dirt and other unwanted materials, and then washed in clean water and sun-dried for 7 to 14 days. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amusatramoni@gmail.com eyide et al: optimization of vitamin a in red guinea corn-millet mix. azojete, 19(4):759-770. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 761 2.2 experimental design a three-factor box-behnken design for response surface methodology was used to study the combined effect of the blending ratio of the mass of red guinea corn, the mass of millet and blending time on the concentration of vitamin a. the range and levels of the independent variables are shown in table 1 (eyide et al., 2023). table 1: coded and actual levels of the factors for three factors of box-behnken design for optimization of vitamin a. independent variables symbols coded and actual levels -1 0 +1 mass of red guinea corn (g) x1 10.00 30.00 50 mass of millet (g) x2 50.00 75.50 100.00 blending time(hours) x3 1.50 3.25 5.00 the box-behnken design has been established to be appropriate for the investigation of quadratic response surfaces and this design generates a second-degree polynomial model which can be used for optimization purposes (amenaghawon et al., 2013). the number of experimental runs for this design was obtained from equation (1). n= k2 + k + cp (1) where k is the number of factors and cp is the number of replications at the center point. the design for the evaluation of the concentration of vitamin a in millet and guinea corn was developed using design expert® 7.0.0 (stat-ease, inc. minneapolis, usa) and 17 experimental runs were obtained. the coded and actual values of the independent variables were calculated using equation (2). − =  i o i i x x x x (2) where xi and xi are the coded and actual values of the independent variable respectively. xo is the actual value of the independent variable at the center point and δxi is the step change of xi. the following generalized second-degree polynomial equation was used to estimate the response of the dependent variable (amenaghawon et al., 2013). = + + + +   2 i o i j ij i j ii i iy b b x b x x b x e (3) where yi is the dependent variable or predicted response, xi and xj are the independent variables, bo is the offset term, bi and bij are the single and interaction effect coefficients and ei is the error term. the design expert software was used for regression and graphical analysis of the experimental data. the goodness of fit of the models for the concentration of vitamin a was evaluated by the coefficient of determination (r2) and analysis of variance (anova). the grains were weighed separately, then mixed together and finally homogenized to get each blend according to the design of experiment in table 2. http://www.azojete.com.ng/ mailto:amusatramoni@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):759-770. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 762 table 2: box behnken experimental design 2.3 analysis of millet, red guinea corn and their blends the analyses were carried out at the central research and diagnostic laboratory, tanke, ilorin, kwara state, nigeria. the proximate analysis was done on the grains of millet and red guinea corn respectively as well as the determination of the concentration of vitamin a for each blend according to the box behnken experimental design in table 2. the concentration of vitamin a was determined using agilent 6890 gas chromatography (gc). 2.4 proximate analysis the method of the association of official analytical chemists (aoac 2005) was used to determine the amount of moisture, ash, fat, protein, crude fiber, and carbohydrate contents of the pure grains of millet and red guinea corn. the percentage of carbohydrates was determined by eq (4) carbohydrate (%) = 100(protein (%) + moisture (%) + ash (%) + crude fibre (%) + fat (%)). (4) while the energy or caloric value was determined by eq (5) (kj/100g) = (protein x 16.7) + (lipids x 37.7) + (carbohydrate x 16.7) (5) 2.4 preparation and analysis of each blend using 6890 gc based on the experimental design in table 2, each blend was converted into a more volatile derivative for analysis. firstly, mix grains were milled into homogenized sizes. thereafter the milled grains were placed inside flat-bottomed flasks and were suspended in 20 to 40 ml of water according to the mixture times for the respective experimental runs. care was taken to ensure that no lumps were formed; the blend must be fully wetted with water. while spinning the flask, 100 ml ethanol, 1g sodium ascorbate or l-ascorbic acid and 25 ml potassium hydroxide solution (60%) were added to the suspended sample. the flat-bottomed flasks were sealed with a glass stopper and shaken vigorously. the reaction mixture is now heated to boiling point under reflux in a water bath that has been preheated to 80 90°c and maintained at boiling point for 30 minutes under a slow flow of nitrogen to hydrolyze the ester bonds in the vitamin a. the saponified solutions were transferred quantitatively to a separating funnel through multiple rinses with water. to avoid the formation of emulsions, sufficient water was std run block factor 1 a: mass of red guinea corn (g) factor2 b: mass of millet (g) factor3 c: blending time (hours) 13 1 block1 30 75 3.25 15 2 block1 30 100 5 10 3 block1 50 100 3.25 16 4 block1 30 75 3.25 9 5 block1 10 75 5 11 6 block1 10 50 3.25 7 7 block1 30 75 3.25 1 8 block1 50 75 1.5 5 9 block1 30 50 1.5 6 10 block1 10 75 1.5 8 11 block1 30 50 5 12 12 block1 30 75 3.25 2 13 block1 30 100 1.5 17 14 block1 50 75 5 14 15 block1 50 50 3.25 3 16 block1 10 100 3.25 4 17 block1 30 75 3.25 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amusatramoni@gmail.com eyide et al: optimization of vitamin a in red guinea corn-millet mix. azojete, 19(4):759-770. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 763 added to the saponified sample solution to ensure that the alcohol/water ratio in the resulting solution was about 1:1; thereafter, 150 ml petroleum ether was added and shaken mechanically for about 10 minutes to extract the vitamin a. the extraction solution is now washed neutrally with purified water through multiple shaking and the washing water is allowed to drain away after the phases have separated. the extraction solution was filtered through a phase separation filter into a 50 ml volumetric flask to remove any potential suspended water drops. finally, the extracted vitamin a was derivatized at 70 80°c for 2hours to form a more volatile derivative for gc analysis. after derivatization, the volatile derivative of vitamin a, was analyzed using agilent 6890 gas chromatography (gc) with a suitable stationary phase and detector. 3. results and discussion 3.1 proximate analysis results table 3 shows that millet has a moisture content of 20.04% which is slightly higher than that of red guinea corn, 17.28%. similarly, the ash content of 2.07% observed with red guinea corn was higher when compared to 1.38% observed in millet. red guinea corn has 55.23% of carbohydrates while millet has 49.54%. table 3: proximate composition of red guinea corn and millet grain samples proximate parameter samples red guinea corn (a) millet (b) moisture % 17.28 20.04 ash % 2.07 1.38 cho% 55.23 49.54 crude fibre % 1.48 2.44 crude lipids% 14.59 17.84 crude protein % 9.34 8.76 calorific value kj/100g 1628.62 1646.02 a calorific value of 1646.02kj/100g was observed in millet which was higher than 1628.62kj/100g in red guinea corn. the crude fiber was higher in millet (2.44%) as compared to that of red guinea corn (1.48%). crude lipids content was higher in millet (17.84%) as compared to the one observed with red guinea corn (14.59%). red guinea corn was higher in crude protein contents (9.34%) compared to that millet of 8.76%). figure 1 is a chromatogram showing the different peak identification for the vitamers present in red guinea corn. the major vitamers present are rentinol and dihydroretinol with highest peaks identified for retinol and dihydroretinol at retention time of 1.798mins and 2.573mins with a corresponding voltage values of 13mv and 2mv respectively. the other vitamers was unidentified by the gc analyzer because they are present in minute amount. http://www.azojete.com.ng/ mailto:amusatramoni@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):759-770. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 764 figure 1: chromatogram for sample a (red guinea corn) figure 2 is a chromatogram showing the different peak identification for the vitamers present in millet. the major vitamers present are rentinol and dihydroretinol, with highest peaks identified for retinol and dihydroretinol at retention time of 1.648mins and 2.032mins with a corresponding voltage value of 12mv and 7mv respectively. the other vitamers was unidentified by the gc analyzer because they are present in minute amount. figure 2: chromatogram for sample b (millet) table 4: concentration of vitamin a vitamers present in sample a (red guinea corn) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amusatramoni@gmail.com eyide et al: optimization of vitamin a in red guinea corn-millet mix. azojete, 19(4):759-770. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 765 table 5: concentration of vitamin a vitamers present in sample b (millet) from tables 4 and 5, it can be depicted that sample b (millet) has a higher amount of retinol and dihydroretinol of 52.7872 (µg/100g) and 46.7549 (µg/100g) compared to red guinea corn with 33.0855 (µg/100g) of retinol and 13.7448 (µg/100g) of dihydroretinol respectively. due to high concentration of a vitamers present in millet than red guinea corn, we decided to used 1:2 of red guinea corn and millet in our design of experiment as shown in table 2, in other to optimized the concentration of vitamin a in the cereals blends. 3.2 statistical model equation for the concentration of vitamin a the box-behnken design resulted in 17 experimental runs as shown in table 2. eq. (6) was obtained after applying multiple regression analysis to the experimental data. these seconddegree polynomial equations were used to estimate the response (concentration of vitamin a). y1=+82.34 + 9.56x1 + 9.47 x2 +0.75 x3+5.45x1x2-0.75 x1x3+0.75 x2x3-11.20 x1 2-1.22 x2 2 +3.56x3 2 (6) where, y1 = predicted responses for the concentration of vitamin a (µg/100g), x1x2x3 = a, b, c coded values for the mass of red guinea corn, mass of millet and blending time respectively. results from the laboratory for the 17 experimental runs where inputted and tally according to the runs in the design expert® 7.0.0 (stat-ease, inc. minneapolis, usa) software, thereafter the data were analyzed to generate the statistical model equation and anova for the concentration of vitamin a. the inputted values are referred to as the actual values while the values gotten from the model equation are referred to as predicted values. table 6: box behnken design matrix for the optimization variables and response values of concentration of vitamin a (µg/100g). the values of the concentration of vitamin a (µg/100g), as predicted by model equation (6), were shown in tables 6, alongside with their experimental. it was observed from the data in the table 6, that there is correlation between the actual and predicted values. run no variables response coded levels actual values vitamin a (µg/100g) x1 x2 x3 x1 x2 x3 actual predicted 1 0 0 0 30 75 3.25 84.34 82.34 2 0 1 1 30 100 5.00 92.32 94.9 3 1 1 0 50 100 3.25 96.21 94.4 4 0 0 0 30 75 3.25 84.34 82.34 5 -1 0 1 10 75 5.00 65.12 66.64 6 -1 -1 0 10 50 3.25 54.53 56.34 7 0 0 0 30 75 3.25 79.34 82.34 8 1 0 -1 50 75 1.50 85.78 85.76 http://www.azojete.com.ng/ mailto:amusatramoni@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):759-770. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 766 9 0 -1 -1 30 50 1.50 78.53 75.21 10 -1 0 -1 10 75 1.50 62.12 64.39 11 0 -1 1 30 50 5.00 78.53 75.21 12 0 0 0 30 75 3.25 84.33 82.34 13 0 1 -1 30 100 1.50 89.32 85.53 14 1 0 1 50 75 5.00 85.78 84.26 15 1 -1 0 50 50 3.25 59.71 64.56 16 -1 1 0 10 100 3.25 69.23 64.38 17 0 0 0 30 75 3.25 79.36 82.34 table 7: anova for a model representing the concentration of vitamin a (µg/100g). anova result depicted that the model for the concentration of vitamin a (µg/100g) was statistically significant with p values of 0.0016, as shown in table 7. the model did not show a lack of fit as seen from the “lack of fit” p values (0.0822). for the model, the terms representing the mass of red guinea corn, mass of millet and blending time were significant for response (the concentration of vitamin a (µg/100g). sources sum of squares df mean squares f value p-value [prob>f] model 2153.40 9 239.27 12.24 0.0016 x1 731.15 1 731.15 37.40 0.0005 x2 717.83 1 717.83 36.71 0.0005 x3 4.50 1 4.50 0.23 0.6460 x1x2 118.81 1 118.81 6.08 0.0431 x1x3 2.25 1 2.25 0.12 0.7444 x2x3 2.25 1 2.25 0.12 0.7444 x1 2 527.93 1 527.93 27.00 0. 0013 x2 2 6.29 1 6.29 0.32 0.5882 x3 2 53.29 1 53.29 2.73 0.1427 residual 136.86 7 19.55 lack of fit 107.06 3 35.69 4.79 0.0822 pure error 29.80 4 7.45 cor total 2290.27 16 table 8: statistical information for anova concentration of vitamin a (µg/100g), in the mix. statistical information for anova shows that the model describing the concentration of vitamin a (µg/100g) had a high coefficient of determination (r2) of 0.94 as shown in table 8. this shows that the model was able to adequately represented the relationship between the chosen factors (mass of red guinea corn, mass of millet and blending time) and response (concentration of vitamin a). r2 values of 0.94 means that the model was able to account for 94.02% of the variability observed in the values of concentration of vitamin a. the standard deviation was observed to be relatively small compared to the mean. the coefficient of variation of 5.65 was obtained for the model. this parameter shows the degree of precision with which the runs were carried out. the values obtained show high reliability as recommended by (montgomer, 2005). the adequate precision for the model signifies adequate signal meaning that the model can be used to navigate the design space (cao, 2009). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amusatramoni@gmail.com eyide et al: optimization of vitamin a in red guinea corn-millet mix. azojete, 19(4):759-770. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 767 parameter response concentration of vitamin a (µg/100g). r-squared 0.94 mean 78.17 standard deviation 4.42 c.v% 5.66 adeq. precision 11.59 adjusted r-square 0.86 3.3 optimization of concentration of vitamin a (µg/100g) in the blend. response surface methodology was used to optimise the process. this was achieved by generating response surface plots showing the three-dimensional relationships among the mass of red guinea corn, mass of millet and blending time on the concentration of vitamin a. figure 3, shows the effect of blending ratios of the mass of red guinea corn and millet on the concentration of vitamin a. the trend observed shows that the concentration of vitamin a, increased with an increase in the mass of red guinea corn and mass of millet, this is due to the resultant amount of the vitamers (retinol and dihyroretinol) present in the respective cereals, with millet having the highest contribution of vitamers concentration to the blend as shown in tables 4 and 5. similar trends were observed in figure 4 and figure 5, shows that an increase in the blending time against the amount of the red guinea corn and amount of millet has a significant effect on the concentration of vitamin a which is due to the interacting effect during homogenization between the mass of red guinea and millet. figure 3. effect of amount of red guinea corn and millet on concentration of vitamin a. concentration of vitamin a (µg/100g) millet loading (g) red guinea loading (g) http://www.azojete.com.ng/ mailto:amusatramoni@gmail.com arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):759-770. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 768 figure 4. effect of amount of red guinea corn and blending time on concentration of vitamin a. figure 5. effect of amount of millet and blending time on concentration of vitamin a. the optimum levels of the independent factors and the response (concentration of vitamin a) were determined from numerical optimisation of the statistical model (eq 6) and the top five results were obtained as shown in table 9. the best optimal result of 98.79 (µg/100g) of vitamin a, was obtained at a blending time of 5.00 hours, 49.79g of red guinea corn and 100g of millet. table 9: solutions for optimum conditions for concentration of vitamin a solution number red guinea corn (g) millet(g) blending time(hours) concentration of vitamin a (µg/100g) 1 49.79 100.00 5.00 98.79 2 50.00 100.00 5.00 98.71 3 50.00 100.00 4.99 98.64 4 50.00 99.77 5.00 98.59 5 50.00 100.00 4.96 98.51 concentration of vitamin a (µg/100g) concentration of vitamin a (µg/100g) red guinea loading (g) blending time (hours) millet loading (g) blending time (hours) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amusatramoni@gmail.com eyide et al: optimization of vitamin a in red guinea corn-millet mix. azojete, 19(4):759-770. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 769 3.4 validation of statistical models three validation experimental runs were performed at the chosen optimum conditions to validate the statistical model representing concentration of vitamin a (µg/100g). the result shows that the maximum concentration value of 98.76 µg/100g for vitamin a, obtained was close to the predicted values of 98.79 µg/100g. the excellent correlation between the predicted and measured values of these experiments shows the validity of statistical models. 4. conclusions the concentration of vitamin a, in the blends were influenced at a blending time of 5hours, 49.79g of red guinea and 100 g of millet. a quadratic statistical model developed to represent concentration of vitamin a, showed a good fit with the experimental data with r2 values of 0.94. the best blend was produced at the optimized value of 98.79 µg/100g which conforms with world health organization (who)/food and agricultural organization (fao), specification for recommended safe intake for all age groups, pregnant and nursing mothers. conflict of interest the authors declare no conflict of interest, financial or otherwise references akhihiero, et., olaseinde, aa., eyide, o. 2022. effect of blending ratio on the nutritional value of millet and guinea corn using mixture design. international journal of innovative science and research technology, 976(7): 757-765. amenaghawon, na., nwaru, ki., aisien, fa., ogbeide, se. and okieimen, co. 2013. application of box-behnken design for the optimization of citric acid production from corn starch using aspergillusniger br. biotechnology journal, (3): 236. aoac. 2005. official method of analysis. 18th edition, association of officiating analytical chemists, washington dc, method 935.14 and 992.24. cao, g., ren, n., wang, a., lee, dj., guo, w., liu, b. and zhao, q. 2009. acid hydrolysis of corn stover for biohydrogen production using thermoanaero bacterium thermosaccharolyticum w16. international journal of hydrogen energy, 34(17): 7182–7188. https://doi.org/10.1016/j.ijhydene.2009.07.009 d’ambrosio, dn., clugston, rd. and blaner, ws. 2011. vitamin a metabolism: an update. nutrients, (3): 63–103. https://doi.org/10.3390/nu3010063 el-khashab, ek., hamdy, am., maher, km., fouad, ma. and abbas, gz. 2013.effect of maternal vitamin a deficiency during pregnancy on neonatal kidney size. journal of perinatal medicine, (41): 199–203. eyide, o., amenaghawon, na., modebe, lu. and mene, ja. 2023. optimization of mechanical properties of bonded particle boards produced from agricultural waste wood chips. journal of applied science and environmental management, 27(4): 733-740. https://dx.doi.org/10.4314/jasem.v27i4.13 fao/who. 1988. requirements of vitamin a, iron, folate and vitamin b12. report of a joint fao/who expert consultation. rome, food and agriculture organization. http://www.azojete.com.ng/ mailto:amusatramoni@gmail.com https://doi.org/10.1016/j.ijhydene.2009.07.009 https://doi.org/10.3390/nu3010063 https://dx.doi.org/10.4314/jasem.v27i4.13 arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):759-770. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sunday.iweriolor@unidel.edu.ng 770 kunyanga, cn., imungi, jk. and vellingiri, v. 2013. nutritional evaluation of indigenous foods with potential food-based solution to alleviate hunger and malnutrition in kenya. journal of applied bioscience, 67: 5277 – 5288 https://dx.doi.org/10.4314/jab.v67i0.95049 gutierrez-mazariegos, j., theodosiou, m., campo-paysaa, f. and schubert, m. 2011. vitamin a: a multifunctional tool for development. seminar on cell development biology, (22): 603– 610. ikokoh, pp., and owa, oj. 2019. nutritional evaluation of some grains (millet, guinea-corn, wheat and sorghum) in bwari area council fct abuja. eas journal of nutrition and food science; 1(1): 20-23. montgomery, dc. 2005. design and analysis of experiments. 6th edition. new york: john wiley & sons, inc., pp. 478-544. nwokem, co., nwokem, nc., adewuyi, j. and rabia, ma. 2019. quality assessment of baby food produced from cereals enriched with date palm. science world journal, 14(1):1597-6343. sabina, bm., alex, srs., maria de fátima, cc., suzana, ls., rachel de sábarreto, lcc., camila, sc., and malaquias, bf. 2019. vitamin a and pregnancy: a narrative review, 11(3): 681 http://dx.doi.org/10.3390/nu11030681 sommer, a. and vyas, ks. 2012. a global clinical view on vitamin a and carotenoids. american journal of clinical nutrition, 96(5):1204s–1206s. https://doi.org/10.3945/ajcn.112.034868 unscn, 2005. united nations system standing committee on nutrition, 6th report on the world nutrition situation, 76-96. who, 2009. global prevalence of vitamin a deficiency in populations at risk 1995–2005. who global database on vitamin a deficiency; world health organization: geneva, switzerland., pp. 1-3. who, 2013. guideline: vitamin a supplementation in pregnant women; world health organization: genebra, switzerland, 3(2): 215–216. younis k., ahmad s. and badpa a. 2015. malnutrition: causes and strategies. journal of food processing technology, 6: 4 http://dx.doi.org/10.4172/2157-7110.1000434. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:amusatramoni@gmail.com https://dx.doi.org/10.4314/jab.v67i0.95049 http://dx.doi.org/10.3390/nu11030681 https://doi.org/10.3945/ajcn.112.034868 http://dx.doi.org/10.4172/2157-7110.1000434 corresponding author’s email address: oodeyinka@unilag.edu.ng 820 arid zone journal of engineering, technology & environment original research article crack and spall detection in buildings using yolov8 and detectron2–based web application w. a. raheem, c. o. folorunso, o. f. odeyinka*, and f. f. kamal department of systems engineering, university of lagos, akoka, lagos, nigeria *corresponding author’s email: oodeyinka@unilag.edu.ng article information abstract cracks and spalls in building structures pose serious risks to safety and durability. conventional methods of detecting these defects are manual, time-consuming, and error-prone. hence, this study develops a web-based system for automated defect detection using deep learning models. two object detection models (yolov8 and detectron2), and a cnn model (resnet18), were trained on 1798 annotated images which consisted of benchmark datasets (metu, vcc) and with locally acquired images. classification and object detection were done on both datasets acquired. yolov8 achieved a weighted average of 99.0% precision, 99.0% recall, and 99.0% accuracy, while resnet18 reached 98.8.0% precision, 98.8% recall, and 98.8% accuracy weighted average for mild crack, severe crack and spall. for the object detection, yolov8 (mask map50 of 93.0%) achieved superior segmentation accuracy than detectron2 (mask map50 of 87.5%). both models demonstrated strong performance in detecting spalls, mild and severe cracks (map > 0.73). the detectron2 model was deployed in a web-based application to enable real-time crack and spall identification. these results confirm the feasibility of aiassisted structural health monitoring and highlight pathways for improving crack detection through balanced datasets, synthetic augmentation, and higherresolution training in both nigerian and global contexts. received: 4th july 2025 revised: 14th september 2025 accepted: 15th september 2025 keywords: crack deep learning detectron2 yolov8 spall structural health monitoring © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction building defects are unintended damages to the building structures which cause financial and environmental losses (alomari, 2022). these defects can be a result of design faults, substandard materials, human errors, and natural factors (czajkowska and ingaldi, 2021). cracks can appear in buildings during (or after) the construction process or when the building is exposed to additional load during its service life (tzimas, 2023). cracks can be classified based on their direction, width and depth (scuro and fusaro, 2022). a typical example is a recurring crack that reappears or continues to develop even after concrete has been repaired or strengthened. this type of fracture indicates ongoing structural stress or deterioration (alomari, 2022). hence, monitoring the state of buildings is essential to track their health over time, assess severity of defect (if any) and potential safety risks (özgenel, 2019). this monitoring process aids early identification of damage, prevents financial loss and loss of life (entezami, 2021). some of the challenging issues affecting structural health monitoring include variation in environmental and operational conditions (entezami, 2021). this involves a routine examination of structures with a view to ascertaining whether they are safe to use and strong enough to last longer (psuj and szymanik, 2023). structural health monitoring focuses on the accuracy of measurements and reliability analysis to reduce false alarms and risks (scuro and fusaro, 2022). however, conventional inspection of cracks and fractures is labor-intensive, subjective, and prone to human errors. different lighting situations, material textures, and crack widths make it more difficult (özgenel, 2019). machine learning (ml) techniques have been found to be effective in the field of structural health monitoring (dong and catbas, 2021). they can overcome some of the drawbacks associated with the conventional approaches in detecting structural damage and allow for real-time identification of such damage (scuro and fusaro, 2022; xu et al., 2025). ml algorithms aid the prediction of critical failure at an early stage in different conditions (singh et al., 2025). the use of advanced ml methods for crack detection has evolved with other artificial intelligence (ai) techniques been integrated in structural health monitoring (naresh et al., 2023; xu azojete september 2025. vol.21(3):820-836 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/013 www.azojete.com.ng mailto:oodeyinka@unilag.edu.ng mailto:oodeyinka@unilag.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 821 et al., 2024). figure 1 outlines the components of a system based on a deep neural network for structural health monitoring. figure 1: deep neural network-based structural health monitoring for example, flah et al., (2020) conducted an exhaustive study of meta-heuristic schemes and other applied ml techniques used for structural health monitoring. the shifting paradigm towards the use of machine learning for structural health monitoring was noted and it was recommended that the choice of appropriate algorithms and their training on enough databases must capture environmental and operating conditions. as a result, research interests towards using deep learning (dl) methods for analyzing the complexity of the building environment has deepened. in rizia et al. (2025), deep learning algorithms was combined with other methods for identifying structural abnormalities and avoiding such scenarios. this is because dl techniques have robust frameworks, such as in computer vision and image processing algorithms, that make crack detection simpler. for example, guo et al. (2019) presented a deep learning approach for comprehending damage using a methodology designed on solid feature extraction a key step in the identification of damage. the deep learning algorithm used had the potential to understand feature representation from sensor data since the real-world damages vary for different buildings. in hou et al., (2021), a deep learning approach for safety in the architecture, engineering and construction (aec) industry was presented for use in structural health monitoring. feature enhancement, improved robustness and reliability of systems in complex terrain were also identified as major advantages of deep learning (singh et al., 2025). zhao et al. (2024) developed an instance segmentation method based on deep learning and computer vision algorithms to improve feature extraction and fine-crack detection for complex structures. results showed a higher accuracy, increased gain and better balance between precision and efficiency. in kiranyaz et al. (2021), the importance of 1-dimensional convolutional neural networks (cnns) and their uses for crack detection was outlined. cnns is one of the advanced deep learning architectures that are suitable for learning the features effortlessly from the sequential data such as the array of sensor measurements (ahmadzadeh et al., 2025). knowledge in cnns and its potential applications is useful in the development of improved structural health monitoring systems that incorporate deep learning for detection of damage under different circumstances. while various methods for crack detection have been developed, there is still a lack of a simplified system for easy detection and early identification. with human effort remain time consuming and incur different costs, there is need for autonomous system that automate crack detection and also serves as a warning system (eldin hemdan and al-atroush, 2025). autonomous systems are specialized computer programs capable of doing what knowledgeable human beings can do in a certain specialization and domain (youwai et al., 2024). consequently, these systems can comprehend data originating from diverse chunks of the structure, for instance, strain gauges, vibration sensors, ultrasonic sensors, or thermal sensors for the purpose of detecting probable damage (or crack). in this context, these systems can process data, acquired from various sensors, including strain gauges, vibration sensors, ultrasonic even thermal ones, to identify the damages, especially cracks. the major advantage is in the flexibility that comes with the capacity to encode the expert knowledge http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 822 and the reasoning methods in the form of a set of rules (ahmadzadeh et al., 2025). these rules are then applied to help the system, analyze data received from sensors and come up with inferences and conclusions about the structural health based on some laid down principles, procedures and rules (qiu et al., 2025). hence, the aim of this work to develop a web application for automating crack and spalls detection in residential buildings using real-time object detection and techniques. this involves implementing feature extraction and segmentation techniques to accurately identify and classify cracks and spalls, and then integrate a detection system to work seamlessly for comprehensive structural assessment. to ensure accurate detection and localization of structural issues, this work also validates the performance of the system by testing on realworld scenarios. section 2 describes the material and methods behind this work while section 3 presents the results of the analysis carried out. a suitable conclusion is provided in section 4. 2. material and methods two high-performance object detection frameworks were considered yolov8 and detectron2 in this study. each detection algorithm consists of both image classification and image segmentation phases. firstly, the image is analyzed using a deep convolutional neural network to detect the presence or absence of cracks and spalls. once these defects are detected, an adaptive thresholding technique is applied to further process and refine the identified regions. 2.1 yolov8 model architecture the yolov8 architecture was implemented in this work for object classification and detection. this architecture is divided into three parts, namely the backbone, the head and the output, which is intended to provide effective real-time object detection. yolov8 backbone the process begins with a backbone, which creates feature maps at different scales (p1 through p5) by extracting hierarchical features from the input image. p5 is the highest-level feature in these feature maps, which show increasingly coarser spatial resolutions and deeper semantic information. at the backbone network, there exist the convolutional layers, batch normalization, relu activation functions, and sometimes the down-sampling function, such as max-pooling. the mathematical equation for a typical convolutional layer is given by in equation (1): 𝐶𝑜𝑛𝑣(𝑥, 𝑊, 𝑏) = 𝜎(𝑊 ∗ 𝑥 + 𝑏) 1 where: x is the input feature map, w is the convolutional filter, and b is the bias term, * denotes the convolution operation, and σ is the relu non-linear activation function. convolution can be defined as the sum of the product of an image patch and a filter in an element-wise manner. this reveals other patterns hidden in the image and is done by introducing the activation function that injects non-linearity into the network. the architecture of the yolov8 is presented in figure 2. yolov8 head the multi-scale feature maps are processed by the head to produce predictions after feature extraction. to enhance multi-scale object identification capabilities, this section incorporates a feature pyramid network (fpn) or a similar structure. concat and conv operations are used to merge and refine features from various backbone levels. to create a reliable feature representation for detection, up-sampling procedures are used to combine data from deeper layers with shallower ones. the detection head predicts bounding boxes of objects, the probability of each object’s class, and the objectness score. for bounding box regression, the smooth l1 loss is commonly used and can be represented in equation (2): 𝐿𝑙𝑜𝑐 = ∑ ∑ 𝑠𝑚𝑜𝑜𝑡ℎ_𝐿1(𝑝𝑟𝑒𝑑𝑖𝑗 − 𝑡𝑎𝑟𝑔𝑒𝑡𝑖𝑗) 𝑗∈𝑃𝑜𝑠 𝑁 𝑖=1 2 where 𝑁 is the number of bounding boxes, 𝑃𝑜𝑠 is the set of positive samples, 𝑝𝑟𝑒𝑑𝑖𝑗 is the predicted bounding box, 𝑡𝑎𝑟𝑔𝑒𝑡𝑖𝑗 is the ground truth bounding box, and 𝑠𝑚𝑜𝑜𝑡ℎ_𝐿1 describes the smooth l1 loss function. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 823 figure 2: yolov8 architecture (sharma et al., 2024) yolov8 output to locate and identify objects in the input image, the output stage carries out the last detection operations after receiving the refined features from the head. these procedures include bounding box regression (bbox) and classification (cls). the model learns by minimizing the loss between predicted bounding boxes and class probabilities (crack, spall) and the ground truth labels provided in the training data. common loss functions include intersection over union (iou) loss for bounding boxes and cross-entropy loss for classification. equation (3) gives the loss function in terms of localization, confidence, and classification. 𝐿 = 𝜆𝑐𝑜𝑜𝑟𝑑𝐿𝑙𝑜𝑐 + 𝜆𝑐𝑜𝑛𝑓𝐿𝑐𝑜𝑛𝑓 + 𝜆𝑐𝑙𝑠𝐿𝑐𝑙𝑠 3 where 𝜆𝑐𝑜𝑜𝑟𝑑, 𝜆𝑐𝑜𝑛𝑓, 𝜆𝑐𝑙𝑠 are the coefficients for localization, confidence, and classification losses, respectively. 2.2 detectron2 model architecture for reliable object detection, the generalized region-based convolutional neural network (rcnn) architecture combines a backbone network, a region proposal network (rpn), a feature pyramid network (fpn), and region of interest (roi) heads (box head). hierarchical features (res2, res3, res4, res5) are extracted from the input image by the backbone network, usually a resnet. the fpn receives the lowerlevel features, while a p6 layer receives the higher-level features (res5). by up sampling and merging features from multiple backbone levels, the fpn creates a multi-scale feature pyramid (p2-p5) that offers rich contextual information at multiple sizes. the architecture of the detectron2 is shown in figure 3. based on the output of the fpn, the rpn predicts anchor deltas and objectness scores to provide a set of 1000 box proposals, which are further honed using non-maximum suppression (nms). these suggestions are then used by the roi heads, and the fastrcnn convfchead (through a roipooler to extract fixed-size feature maps). the object detection pipeline is then completed by feeding these features into fully connected layers that predict class logits for 81 channels and bounding box predictions (80x4 channels). following nms, the final 100 detected boxes are obtained. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 824 figure 3: architecture of detectron2 (devi and naidu, 2023) 2.3 resnet-18 architecture resnet has varying numbers of layers; for example, resnet-18 has 18 layers. figures 4a and 4b shows the resnet-18 and residual block architectures. in figure 4a, the black curve arrow indicates the shortcut connections, and the two layers of the same color are residual blocks. while models get deeper, shortcut connections can effectively tackle the vanishing gradient issue. the residual block has two branches (as seen in figure 4b) with the identity mapping indicated by the black curve arrow. the convolution function is represented by the f, while the input images are represented by the x. the sum of x and f(x) is the result of residual blocks. later cnn models have largely inherited residual blocks. figure 4: resnet-18 architecture (song, 2023) 2.4 theoretical frameworks to enable precise and effective detection of cracks and spalls in building structures, this work employs yolov8 and detectron2 within a web-based framework. data collection and preprocessing, model training http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 825 and optimization, and web-based deployment are the three primary phases of the methodology as shown in figure 5. data collection and preprocessing model training and optimisation web-based deployment figure 5: methodology employed for the crack and spall detection 2.4.1. data acquisition and pre-processing high-resolution images of building surfaces, such as walls, slabs, and beams, were gathered from publicly accessible crack and spall datasets in addition to field-collected photos. the dataset used consisted of images was collected from the metu campus buildings dataset (özgenel, 2019) and the vcc dataset available on roboflow (roboflow, 2023). these datasets were chosen because they are standardized, annotated, and widely recognized, making them excellent for initial model training and benchmarking. though they do not fully reflect nigerian-specific conditions, the locally captured images improve the relevance and transferability of the datasets for practical deployment in nigeria. the images collected were from both private and public properties and are of different types of cracks and spalls under different lighting, angles, and building materials. close-up images of buildings (such as in figure 6a c) and distant images (as in figure 7a c) were all captured. the resolution of the images in the metu campus buildings dataset was 227 𝑥 227 pixels with rgb channels and they were generated from 458 high-resolution images originally sized at 4032 x 3024 pixels. these images were all standardised to 640 × 640 pixel in order to ensure consistent feature extraction. for the vcc dataset, the images were already in the standard 640x640 pixels format. depending on the extent of the damage, the cracks were categorized as mild, and severe. the mild crack had estimated crack width ranging from 1 to 15mm while the severe crack had estimated crack width measuring 15 to 25mm or more (usually above 25mm). subsequently, the data sets were analyzed and processed for polysylabic labeling using labelme software. this tool was used to classify the structural damages into 3 classes mild crack, severe crack and spall. after labelling, a simple check was carried out in order to assess the reliability and usefulness of the annotated data. the main detection framework for quickly and accurately identifying cracks and spalls is the yolov8 model. rich multi-scale features are extracted from images via its backbone, a cspdarknet variation improved with the c2f module and sppf layer. these features are fused by the pan-fpn neck, while bounding box regression and classification are carried out by the anchor-free decoupled head. to increase localization accuracy, the model is trained with adaptive iou-based loss functions. similarly, detectron2 is used for pixel-level segmentation in addition to yolov8 to provide accurate border delineation of identified cracks and spalls. the modular design of detectron2, which is based on a resnetfpn backbone, makes it easier to apply mask r-cnn for instance segmentation. by offering comprehensive masks, this phase improves yolov8's bounding box predictions and guarantees that fractures can be more accurately distinguished from background textures and other surface flaws. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 826 a: mild crack b: severe crack c: spalling figure 6: close-up images of the buildings a: mild crack b: severe crack c: spalling figure 7: distant images of the buildings the feature extraction and data cleaning techniques of yolov8 and detectron2 reflect their deep learning architectures and detection goals. a convolutional backbone modeled after cspdarknet is used for yolov8 feature extraction. deeper layers encode high-level representations of cracks, spalls, and their spatial context, while early layers’ capture low-level characteristics like edges, gradients, and textures. the methodology simplifies feature encoding for localization tasks by using an anchor-free detection mechanism that dynamically predicts object centres and dimensions. in order to improve robustness against environmental fluctuations, yolov8 data cleaning include deleting low-quality or incorrectly labelled images, normalizing image dimensions and colour distributions, and applying augmentations including random cropping, rotation, and contrast modifications. to handle both object detection and pixel-level segmentation, detectron2's feature extraction uses a feature pyramid network (fpn), which combines multi-scale features for fine-grained representation. because of its sensitivity to label accuracy, detectron2 requires more thorough data cleaning, which includes accurate mask annotations, the elimination of noisy boundaries, and pre-processing methods like resizing, normalization, and augmentation to maintain the structural and contextual integrity of defect regions. when combined, these strategies guarantee that both models receive high-quality, well-annotated inputs to maximize generalization and detection accuracy. table 1 summaries the features employed by the two algorithms. table 1: summary of the features used by the two algorithms feature category yolov8 detectron2 visual features edges, contours, gradients, textures, and geometric patterns for object localization. pixel-level details, fine textures, boundary shapes for precise segmentation. structural features bounding box centre points and sizes are predicted dynamically (anchor-free). instance-level and semantic-level segmentation with multi-scale feature representation. contextual features spatial relationships and environmental variations (e.g., lighting, occlusion). hierarchical scene understanding to refine pixel masks and object boundaries. processing focus real-time detection with emphasis on speed and robust localization. high-accuracy segmentation with fine-grained spatial detail. 2.4.2 model training and optimization using detection based on yolov8 and detectron2 for the experiments, nvidia tesla t4 gpus were used to train the aforementioned deep neural networks of the proposed system. the training process was done using pytorch and google colab platforms. the training set was comprised of 1798 images in coco format while the validation set comprised of 515 images which http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 827 was kept constant between the two models. a test set of 255 images was used to evaluate both models. the distribution of the different classes in the model is shown in table 2. the distribution (599 milds, 600 severe, 599 spall in training) shows that the dataset used was balanced with an equal set of data from each category. table 2. distribution of instances among all 3 categories in the train and validation datasets classes/categories training instances validation instances test instances total 1 mild crack 599 172 85 856 2 severe crack 600 171 85 856 3 spall 599 172 85 856 total 1798 515 255 2568 the dataset was augmented via geometric and photometric transformations. geometric transformation (including rotation, flipping, cropping, and scaling) and photometric adjustments (such as brightness, contrast shifts, noise, blur) were carried out on the dataset. the hyperparameters (the number of epochs and the learning rate) were adjusted. also, an optimizer was chosen to make adjustments to the weights of the model with regards to the calculated loss, after each training cycle. in this experiment, adam optimizer was employed, which can commonly be used in deep learning and provides good results in multiple tasks. the adam optimizer updates the weights (θ) of a neural network based on the gradients (g) calculated during backpropagation as shown in equation (4): 𝜃𝑡+1 = 𝜃𝑡− ∝ ∙ �̂�𝑡 √𝑣𝑡 + 𝜖 4 where 𝜃𝑡 is the current weight value at iteration t, 𝜃𝑡+1 is the updated weight value at iteration t+1, ∝ (learning rate) is the hyperparameter that controls the step size of the update, 𝜖 is a small constant value (usually 10−8) added to the denominator to prevent division by zero and �̂�𝑡 is the bias-corrected first moment estimate of the gradient as shown in equation (5), which is an exponentially decaying average of past gradients. equation (6) represents the average direction of recent gradient changes, �̂�𝑡 = 𝑚𝑡 1 − 𝛽1 𝑡 5 𝑚𝑡 = 𝛽1 ∙ 𝑚𝑡−1 + (1 − 𝛽1) ∙ 𝑔𝑡 6 where 𝛽1is the hyperparameter is the decay rate in the moving average of the gradients and its typical value is almost one. for example, 0.9, 𝑔𝑡 is the derivative of the loss function of the weights at the current iteration. it is the ‘second moment estimate of the gradient, 𝑣𝑡 is an exponentially weighted moving average of the squared past gradients as shown in eq. (7). equation (8) expresses the change of gradients within a recent period of time. 𝑣𝑡 = 𝑣𝑡 1 − 𝛽2 𝑡 7 𝑣𝑡 = 𝛽2 ∙ 𝑣𝑡−1 + (1 − 𝛽2) ∙ 𝑔𝑡 2 8 𝛽2 is the hyperparameter that controls the decay rate of the moving average of the squared gradients (usually set to a value even closer to 1, for instance, 0. 999). 𝑔𝑡 2 is the gradient of the loss function with respect to the weight at the current iteration. 2.4.4 integrating detectron2 model into a web application a web application allows users to access the crack detection model from any device with a web browser, eliminating the need for local software installation. this provides a real-time inference as users can upload images directly to the web application, enabling real-time crack detection and visualization of results. the http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 828 classification result showed better than the detection, however, since the aim of the study is to detect the various types of defects, the detection was implemented on the webpage. the detectron2 architecture was integrated into the web application, a user-friendly tool for real-time building defect detection was created, making it accessible to a wider audience and facilitating efficient defect identification in various applications. the architecture of the web application used for the study is shown in figure 8. web application allows for scalability because it can handle multiple users requests simultaneously, making them suitable for large-scale deployments. the web application is deployed to a cloud platform, amazon web services, aws, to make it accessible to users over the internet. the integration process of the web application used in this study is described as follows: 1. flask app setup: flask is a web framework; used to build the backend logic for the web application. it offers functionalities for handling user input, file uploads and model inference. 2. react app setup: the react framework is used to handle the frontend logic for the web application for user friendly interface that allows users to easily upload images, view results and understand the defect detection outcome. it offers functionalities for validating the user input, image and file uploads, inference results and visualisation. 3. model loading and pre-processing: the saved weights and configuration files from the detcetron2 training were loaded into the web application through the flask app implementation. image pre-processing methods to resize, normalise were also created to match the input format of the model. figure 8: web application architecture design for detectron2 the following steps are employed to use the web application: 1. once image has been uploaded the loaded detectron2 model is used to perform inference and generate predictions in the form of bounding boxes and masks for detected defect. 2. the opencv and matplotlib library are used to visualise the original image with the predicted bounding boxes and segmentation masks overlaid on top, highlighting the detected defect. 2.5 evaluation metrics to quantify the accuracy and performance of the proposed detection models, the key metrics used include: precision, recall, accuracy, map@0.5, and map@0.5:0.95, for both bounding box (b) and mask (m) predictions. these metrics give a complete assessment of how efficiently an algorithm can separate the target features in the actual images, using the classifiers. intersection over union (iou) is the area where the groundtruth box/mask and the anticipated bounding box/mask overlap. the values obtained stem from the calculated iou and have a connection with the threshold identified for the iou as shown in equation (9). 𝐼𝑜𝑈 = 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑂𝑣𝑒𝑟𝑙𝑎𝑝 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑈𝑛𝑖𝑜𝑛 9 http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 829 the precision is the percentage of all positive instances (true positives + false positives) that were accurately predicted as positive cases (true positives): 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 = 𝑡𝑝 𝑡𝑝 + 𝑓𝑝 10 recall indicates how many ground-truth positives the model can identify: 𝑅𝑒𝑐𝑎𝑙𝑙 = 𝑡𝑝 𝑡𝑝 + 𝑓𝑛 11 accuracy is the frequency with which a model, method, or procedure yields accurate results (true positive + true negative) in relation to the total number of instances assessed (true positive + true negative + false negative + false positive): 𝐴𝑐𝑐𝑢𝑟𝑎𝑐𝑦 = 𝑡𝑝 + 𝑡𝑛 𝑡𝑝 + 𝑡𝑛 + 𝑓𝑛 + 𝑓𝑝 12 the mean average precision (map) is the mean of ap across multiple iou thresholds and/or classes, it is the most widely used object detection metric. it evaluates a model's ability to predict class labels and bounding boxes. the map@0.5 shows the ap is computed at iou ≥ 0.5. while the map@0.5:0.95 shows that the ap is averaged over iou thresholds from 0.5 to 0.95 in steps of 0.05, it is stricter and more robust. 3. results and discussion the performance of each model was evaluated on the validation and testing set using various metrics mean average precision (map), precision (p), recall (r), and accuracy. the result for classification using resnet-18 and yolov8 is shown in table 3. table 3: classification result for model training class yolov8 resnet-18 support precision recall f1-score precision recall f1-score mild-crack 0.97 1.00 0.98 0.98 1.00 0.99 85 severe-crack 1.00 1.00 1.00 0.99 1.00 0.99 85 spalls 1.00 0.96 0.98 1.00 0.96 0.98 85 accuracy 0.99 0.99 0.99 0.99 0.99 0.99 255 macro avg. 0.99 0.99 0.99 0.99 0.99 0.99 255 weighted avg. 0.99 0.99 0.99 0.99 0.99 0.99 255 for automated damage identification in concrete structures, a comparison of the yolov8 and resnet-18 models showed good classification performance across all target classes. for example, resnet-18 performed better for minor cracks (precision = 0.98, recall = 1.00, f1-score = 0.99) than yolov8 (precision = 0.97, recall = 1.00, f1-score = 0.98). for significant cracks, yolov8 demonstrated perfect detection (precision = 1.00, recall = 1.00, f1-score = 1.00) while resnet-18 had lower precision and f1scores (precision = 0.99, recall = 1.00, f1-score = 0.99). both models produced similar results for the detection of spalls, with the same f1-scores (0.98), precision (1.00), and recall (0.96). the overall accuracy of both models was 0.99, which is corroborated by the weighted and macro-average scores of 0.99 for all classes. this demonstrates a balanced performance regardless of the class distribution. these findings demonstrate the resilience of both architectures, with resnet-18 performing better for detecting minor cracks and yolov8 better at identifying serious severe cracks. table 4 outlines the results of training of the yolov8 model. overall, its precision (0.854), recall (0.847), and excellent accuracy in both detection (boxmap50 = 0.930) and segmentation (maskmap50 = 0.920) indicated a very strong performance. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 830 table 4: yolov8 model training results class images instances boxp boxr boxmap50 maskmap50 all 179 179 0.854 0.847 0.930 0.920 mildcrack 52 52 0.872 0.654 0.863 0.841 severecrack 62 62 0.802 0.887 0.934 0.931 spall 65 65 0.889 1.000 0.994 0.989 spalls had the best results across individual classes with near-perfect map values (boxmap50 = 0.994; maskmap50 = 0.989) and perfect recall (1.000). severe cracks also demonstrated strong performance with balanced precision (0.802), recall (0.887), and high map scores. while precision (0.872) and map values remained strong, mild cracks displayed a relatively lower recall (0.654), indicating a little lesser sensitivity to tiny faults. the high discriminative power of the yolo v8 model was further validated by the roc analysis. with a micro-average auc of 1.000, the area under the curve (auc) values were 0.999 for moderate cracks, 1.000 for severe cracks, and 0.999 for spalls as shown in figure 9. the roc curves for all classes were located close to the plot's upper-left corner, showing almost flawless true positive rates and low false positive rates. the ability of the model to detect safety-critical structural faults is demonstrated by its flawless auc score for severe cracks. generally, these findings confirm the ability of the model to identify different types of concrete. figure 9: roc curve for yolov8 model for classification table 5: average precision for detectron2 models at iou > 0.5 class ap class ap class ap coco map@50 coco map@50-95 mild-crack 74.58% severecrack 86.5% spall 97.51% 87.5% 86.2% http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 831 the trained detectron2 model showed a strong detection performance across all defect categories. it had better detection for severe faults and spalling than mild cracks, as seen by its average precision (ap) values of 74.58% for mild cracks, 86.5% for severe cracks, and 97.51% for spalls. with an overall coco metrics of 87.45% and a tighter map@50–95 of 86.20%, the model's robustness is further supported. the ability of the model to maintain precise localization under different intersection-over-union thresholds is demonstrated by the closeness of these two values, and suggests consistent generalization performance across defect kinds. plate 1a: first yolov8 predictions plate 1b: second yolov8 predictions plate 1c: third yolov8 predictions in plates 1a, 1b and 1c, the performances of yolov8 in identifying and classifying structural flaws under different circumstances are shown. bounding boxes and overlays emphasize the precise localization of cracks and spalls of various sizes and orientations in the yolov8 predictions. the model successfully captures small discontinuities and has significant robustness under various texturing and lighting conditions. minor partial detections point to the advantages of including multi-scale feature improvement or higher-resolution inputs for better boundary delineation. the prediction abilities of the detectron2 explains its dual capabilities in object detection and instance segmentation (as shown in plates 2 a -c). the coloured overlays and bounding boxes to depict detected flaws and locations of interest. plate 2a: first detectron2 predictions http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 832 plate 2b: second detectron2 predictions plate 2c: third detectron2 predictions when compared to yolov8, detectron2 provides more detailed spatial context, especially in terms of shape and area coverage, and effectively distinguishes cracks, spalls, and other possible structural anomalies. green, red, orange, and purple highlighted masks visibly represent the segmentation fidelity and localization accuracy in a variety of architectural situations. together, these visual findings validate the ability of both models to provide automated structural evaluation. though yolov8 provides faster, high-confidence detections, while detectron2 gives deeper spatial segmentation together confirming their complementary roles in improving deep learning-based structural health monitoring systems. based on these image inferences from the model, it is clear that the detectron2 model performs better at detecting structural defects compared to the yolov8 model. plate 3: image of the web application prediction on a mild crack plate 3 shows that the supplied image was successfully analyzed, exposing the existence and features of structural flaws. with a "num_of_defects" of 3 and a "image_quality" rating of "good," the analysis specifically indicated that the input image was appropriate for precise analysis. in this instance, "mildcrack" with a count of three indicates three instances of mild cracks found on the building. the "present_classes" object describes the sorts of faults found. visual localization of these flaws inside the image is made possible by the "coordinate" array, which gives the exact pixel coordinates for each identified "mildcrack" instance. the present null values http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 833 in the fields "structural_reinforcement_needed" and "types_of_defects" suggest that the system either did not identify the need for reinforcement or did not further classify defect types in light of this particular analysis. lastly, for easier visualization and validation of the detection results, "masked_image_url" indicates the location of a processed image where the identified flaws are visually emphasized, most likely using masking or bounding boxes. an automated inspection of a structure is shown in plate 4, where any structural flaws found are immediately labelled on the picture. the subsequent output, which displays num_of_defects: 2; image_quality: good, confirms that the scene has overlays indicating two moderate cracks that have been found. plate 4: image of the web application prediction on a mild crack each flaw is given precise bounding coordinates, proving the system's capacity for spatially precise localization. interestingly, structural_reinforcement_needed and types_of_defects are both reported as null, suggesting that the cracks found are small and do not currently require repair. by combining quantitative metadata with visual annotation, this example demonstrates the potential of the system for real-time, automated structural health assessment, minimizing the need for manual inspections and promoting evidence-based maintenance decisions. an automated flaw detection and analysis system applied to structural elements specifically, detecting spalling in a concrete beam is demonstrated in plate 5. three flaws were successfully identified by the system, which also labelled the image quality as "good" and recognised "spall" as a major defect class. plate 5: image of the web application prediction on a mild spall the discovered spall's exact location within the structure is indicated by detailed coordinate data. this methodology facilitates proactive maintenance and ensures structural integrity by providing a strong method for non-destructive evaluation and condition assessment of infrastructure. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 834 plate 6: image of the web application prediction on a mild spall two separate flaws that were expressly classified as "spall," or localised surface damage or degeneration, were found in the concrete infrastructure analysis shown in plate 6. this assessment's supporting picture quality was judged "good," guaranteeing the accuracy of the defect diagnosis. these spall flaws' exact coordinates were [51.931008367919922, 294.204912109375] and [50.09276300810547, 350.27086961090625], which provided accurate geographic references for more research or rehabilitation. 4. conclusion this study presented the development of a web-based system for detecting structural cracks and spalls in buildings using deep learning–based computer vision. this work demonstrated the practical integration of the detectron2 model into a web-based application, enabling real-time crack and spall detection accessible through any browser. this deployment illustrates the feasibility of scalable, automated structural health monitoring systems for residential and institutional buildings. the developed system represents a significant step toward automating structural defect detection in the nigerian context and beyond. by combining benchmark datasets with local data, it provides a framework that balances reproducibility with contextual relevance. future work can focus on expanding the dataset to better capture region-specific crack patterns, integrating iot-enabled monitoring for continuous assessment, and refining the models to improve accuracy on fine cracks. such advancements will move closer to achieving reliable, real-time, and cost-effective solutions for ensuring the safety and longevity of built infrastructure. references ahmadzadeh, m., zahrai, sm. and bitaraf, m. 2025. an integrated deep neural network model combining 1d cnn and lstm for structural health monitoring utilizing multisensor time-series data. structural health monitoring, 24(1): 447–465. https://doi.org/10.1177/14759217241239041 alomari, o. 2022. identification and categorization of building defects. civil engineering and architecture, 10: 438–446. https://doi.org/10.13189/cea.2022.100204 czajkowska, a. and ingaldi, m. 2021. structural failures risk analysis as a tool supporting corporate responsibility. journal of risk and financial management, 14(4): article 4. https://doi.org/10.3390/jrfm14040187 devi, d. and naidu, sv. 2023. leveraging deep learning models for weld defect detection. industrial engineering journal, 52(12). dong, cz. and catbas, fn. 2021. a review of computer vision–based structural health monitoring at local and global levels. structural health monitoring, 20(2): 692–743. https://doi.org/10.1177/1475921720935585 http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, september 2025; 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vol. 21(3): 820-836. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 836 xu, j., luo, l., saw, j., wang, c.-c., sinha, s. k., wolfe, r., soga, k., wu, y., and dejong, m. 2024. structural health monitoring of offshore wind turbines using distributed acoustic sensing (das). journal of civil structural health monitoring, 15(2): article 2. https://doi.org/10.1007/s13349-024-00883-w xu, j., wang, s., han, r., wu, x., zhao, d., zeng, x., yin, r., han, z., liu, y. and shu, s. 2025. crack segmentation and quantification in concrete structures using a lightweight yolo model based on pruning and knowledge distillation. expert systems with applications, 283: 127834. https://doi.org/10.1016/j.eswa.2025.127834 youwai, s., chaiyaphat, a. and chaipetch, p. 2024. a fused deep learning expert system for road damage detection and size analysis using yolo9tr and depth estimation. 2024 international conference on intelligent computing and next generation networks (icngn), 1–5. https://doi.org/10.1109/icngn63705.2024.10871286 zhao, m., xu, x., bao, x., chen, x. and yang, h. 2024. an automated instance segmentation method for crack detection integrated with crackmover data augmentation. sensors, 24(2): 446. https://doi.org/10.3390/s24020446 http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology & environment azojete september 2022. vol. 18(3):469-492 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 453 original research article traditional sensor-based and computer vision-based fire detection systems: a review a. hassan and a. i. audu* department of computer engineering, university of maiduguri, maiduguri, nigeria *corresponding author’s email address: lm324fairchild@yahoo.com 1.0 introduction fire outbreak is one of the leading hazards endangering human lives, properties and the environment around the world today. it causes huge number of death, massive economic loss and serious ecological problems (asih et al., 2018; huang et al., 2017; khan et al., 2019; singh and sharma, 2017). in recent years, a great number of fire incidents were reported across nigeria. for instance, in kano state, fire service records shows that 134 human lives and 635million-naira assets were lost due to fire outbreaks in the state between january 2021 to december 2021(rabiu, 2022). a typical incidence was that a fire event reported at sabongari market in kano city, nigeria in which properties and shops worth millions of naira were lost and took more than 10 hours to be put out completely by the kano state fire service team. not less than 64 people, including eight fire fighters, were reported to have gotten different degrees of injuries from a petroleum tanker explosion at a filling station in sharada article information abstract fire emergency is one of the dominant disasters which is threatening human society, infrastructure, and the environment in the world. fire disaster can lead to a great number of human casualties, loss of vast natural resources and serious infrastructural damage. to minimize these such catastrophic menace, protect and save human lives and infrastructure, substantial research efforts have been devoted to developing fire detection systems using different approaches. this paper discusses fire detection systems and summarizes the state-of–the-art achievements. a total number of 60 publications related to fire detection methods are extracted from ieee and google scholar database and analysed. different fire detection methods are reviewed, and their merits and shortcomings are highlighted. the literature review presented in this paper illustrates the advantages of computer vision-based fire detection approaches over the traditional sensor-based approaches which are characterised by limited detection range, transport delay, and high false alarm. in addition, it shows that the high hardware requirement and computational complexity remain the key drawbacks of the computer vision-based methods and most of the research works made no attempt to implement such methods on embedded hardware platform such as fpga. further research efforts are required to design, develop, and implement computer vision-based systems for fire detection on embedded hardware targets in an efficient and computationally less intensive manner. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 25 january, 2022 revised 9 april, 2022 accepted 10 april, 2022 keywords: fire detection computer vision convolutional neural network deep learning http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 470 area of kano state on 23 may 2021 (rabiu, 2022). in order to mitigate against such huge losses and save valuable human lives, accurate and timely fire detection systems are inevitable (islam et al., 2015). with advances in computing and electronics, many fire detection systems have been proposed in the last decades using different methodologies and approaches. existing fire detection methods are: smoke detector, flame detector, heat detector, gas sensor (cheong et al., 2011; courbat et al., 2011; fonollosa et al., 2016; hoefer and gutmacher, 2012; krüll et al., 2012; liu and kim, 2003; solórzano et al., 2022; sowah et al., 2014; wang et al., 2020) and computer vision (asih et al., 2018; chen et al., 2019; filonenko and danilo, 2018; hossain et al., 2019; huang et al., 2017; jinlan et al., 2016; kaabi et al., 2017; monte et al., 2017; rabiu, 2022; russo et al., 2018; santamaria-guerrero et al., 2018; yuanbin, 2016). these methods have been classified into traditional sensor based and computer vision based methods (chen et al., 2019). this paper aims at reviewing existing methods proposed for fire detection and highlighting future research direction. the remaining part of this paper is organized as follows. section 2 presents the traditional sensor based methods. section 3 presents the computer vision based methods. finally, a summary and future direction is presented in section 4. 2. traditional sensor-based fire detection systems the conventional sensor based methods for fire detection measure ultraviolet or infrared radiation, heat, gas or particulate emissions generated by combustion (wang et al., 2020). the operation principle of these methods is based on employing different physical parameters such as: light scattering, flame particles or air density fluctuation, ion capture by flame particles, smoke concentration to detect fire incidents (chen et al., 2019; vasiliev et al., 2017). however, the shortcomings of such methods include suffer from transport delay, conduction delay, and limited range detection. additionally, these devices are not suitable for outdoor applications and can produce high false alarm rate (khan et al., 2019; rabiu, 2022). the operation principles, advantages and drawbacks of these methods are discussed in the subsequent section. 2.1 thermal detectors fire detection systems based on heat sensing are designed to activate when the ambient temperature or rate of rise of temperature exceeds a set point. these sensing devices are not good for early warning due to the fact that they have to be in very close contact with the fire to be activated. however, they are so easy and inexpensive and highly reliable in areas where other sensors such as smoke detectors have a high level of false alarms like kitchens. they are also best suited in areas of home where systems based on smoke sensing cannot perform effectively due to extreme temperatures (li, 2011; perilla et al., 2018). rate of rise (ror) thermal sensing detectors, respond to emergency change or rise in ambient temperature from a normal baseline conditions. the set alarm criteria will be activated by any sudden increase in temperature. these kinds of thermal detectors can respond to a lower set conditions than if the set point were fixed (li, 2011). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 471 one of the innovative thermal detectors for fire detection applications is the distributed fibreoptic temperature sensor. the optical fibre sensor cable has a faster response in detecting fluctuations in temperature compared to traditional thermal detectors due to its low mass. it is also completely immune to all sorts of nuisance emissions. in the late 1980’s, the distributed fibre optic temperature sensors using rayleigh and raman scattering were introduced. they have been employed in fire detection system for application areas with difficult ambient conditions, which include tunnels, underground railways and stations, conveyor lines, steal works and petroleum and chemical industries (liu and kim, 2003). distributed optic fibre sensor using rayleigh scattering measure the temperature by detecting changes in the quantity of reflected light, during the time the fibre is micro-bent because of heating effect. the fibre optic sensors based on rayleigh scattering are majorly employed in applications, which include road tunnels and underground installations (liu and kim,2003). the distributed fibre optic sensing devices based on raman scattering detects the change in temperature by measuring the ratio of stokes to anti-stokes back scattered intensity signals as a function of temperature (liu and kim, 2003). the brillouin scattering based fibre optic device is one of the likely successors of both rayleigh and raman scattering systems for temperature sensing. the distributed optical fibre sensor using brillouin scattering also has superior spatial and thermal resolutions in comparison with the rayleigh and raman scattering systems (liu and kim, 2003). 2.2 smoke detectors smoke is generated much earlier before other fire signatures during the phases of fire incident growth and development. the chance for successful fire suppression, escape and survivability can be maximized by initial rapid detection of smoke at very low levels by fire detection systems (liu and kim, 2003). fire detection was performed mainly by visual inspection and confirmation by people. in an effort to develop a sensing device for toxic gases, a sensor that could detect smoke was accidently discovered by the swiss chemist walter jaeger during the late 1930’s, there by paving way for development of modern smoke sensing devices (sowah et al., 2014). the first automatic smoke detector developed was based on the sensing of the ionization current using americium-241 as a radioactive source in 1940 (fonollosa et al., 2016). fire detection systems based on smoke detection are much new innovation and commonly used in residential and life safety application during the 1970’s and 1980’s. fundamentally, there are two sensing approaches for smoke detection that are employed for commercially available fire detection devices. these approaches are photoelectric detectors that use light scattering and ionization detectors. smoke detectors mimic human sense of smell and are designed to recognize fire incidents while in their smouldering or early flame phase. the great benefit of smoke detectors is their capability to detect fire while it is yet in its incipient level. they are most preferred method for life safety and high content value applications due to the fact that they provide added space for emergency team to respond and control the developing fire incident before dangerous damages to happen. fire detection systems using smoke sensing elements have greater immunity to inadvertent alarms and they are normally more expensive http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 472 to get installed but much more reliable with an extremely low chance of false alarm if properly chosen and designed (fonollosa et al., 2016; perilla et al., 2018). optical smoke sensing devices uses the light scattering nature of smoke particles to detect the presence of smoke during fire event. on the other hand, ionization smoke sensors are designed with an ionization chamber which contains a radioisotope, usually americium. in the absence of smoke particles, the ionized air molecules within the chamber provide the passage of a small amount of electrical current between the charged electrodes in the chamber. the presence of smoke particles causes a drop in the current between the electrodes. the drop in current between the electrodes results in a fire warning being activated (sowah et al., 2014). standard fire detection systems rely on the sensing of backscattered light emitted by a light emitting diode (led) and reflected on smoke particles. however, such devices suffer from high response time, false alarm and have no capability to detect non-smoking fires (courbat et al., 2011). 2.3 flame detectors flame detectors mimic the human sense of sight and represent one of the major kinds of automated fire detection approach. these methods are line of sight systems which operate on either infrared, ultraviolet or combination principle. radiant energy which is in the 4,000 to 7,700 angstroms range is an indicator of a flaming condition. the fire sensing device based on flame detection identifies the fire signature and transmits a signal to the fire notification module. not like thermal and smoke based fire detection methods, line of sight must exist between the flame detection device and the fire source to recognize emitted fire signatures. but the application of these methods is severely limited. the benefit of these flame detectors is that they are very reliable in a noisy environment. they mostly deployed in high value energy and transportation applications where other fire detection devices based on traditional sensors would suffer from spurious activities. they are also commonly used in locomotive and aircraft maintenance facilities, refineries and fuel loading stations, and mines (li, 2011; perilla et al., 2018). infrared detectors recognize fire incidents when a characteristic flame flicker generated by fire is received. the ultraviolet detectors identify fires when a flame emit an ultraviolet radiation and is detected. fire detection devices based on flame recognition can be to deployed safeguard large areas and they have high response due to the fact they do not have to depend on smoke or heat generated by fire combustion. however, false alarm may be produced by radiation from other hostile sources which include welding, sunlight and tungsten lamps. research and development effort have been made to mitigate against the nuisance alarms generated by infrared and ultraviolet detectors by introducing multi-wavelength radiation sensing and computational algorithm that determine object temperature, flame temperature, surface area and presence of a flame (liu and kim, 2003). optical flame detectors provide higher reliability, great long-term stability and rapid response to fire emergency compared to fire detection systems using smoke detectors. flame detectors based on optical sensing devices operate on specific spectral ranges to record the incoming file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 473 electromagnetic energy at the specified wavelengths which include infrared, visible and ultraviolet. ultraviolet-only flame detection devices operate on wavelength shorter than 400nm. they detect flames at a great speed of 3-4ms because of the ultraviolet high energy radiation generated by fires and explosion incidents at the instance of their ignition. ultraviolet and infrared detection devices compare the threshold signal in two spectral ranges and their ratio to each other to determine the reliability of the fire signal to minimize false alarms. however, commercially available ultraviolet flame detection devices are based on geigermuller counter which is a quartz tube filled with an inert gas which conducts electric current when a photon of wavelength between 185 and 260 nm of a flame makes the gas to conduct temporarily (cheong et al.,2011). this kind of flame detection system is really huge in size and expensive, operates at high voltage, has short lifetime and electronically interferes with other devices in close range. hence, the lower voltage and compact semiconductor ultraviolet sensing device is usually the interesting device (cheong et al., 2011). cheong et al. (2011) presented inexpensive and low-power wireless sensor node for ultraviolet detection of flame. the device employs the state-of –the-art nanotechnology based on semiconductor benefiting the advantage of low cost, compact size and light reliability. in addition, there is no external bias needed, minimizing power consumption and extending the device lifetime. there is also no interference with other devices as in ultraviolet flame sensing devices based on the geiger-muller counter. 2.4 gas sensors volatile chemicals are released normally in fire combustions before smoke particles are generated. therefore, fire detection devices based on chemical gas sensors may have a faster response time compared to the devices based on smoke detectors which now dominate the market. the key hypothesis underpinning the development of fire detection based on gas sensor is the fact that gases and volatile are generated in many fire types before smoke is produced. the early release of gas creates the possibility to develop fire detection systems with shorter response time compared to method based on smoke detection (fonollosa et al., 2016). the first step in chemical gas sensor based method for fire detection starts with sensitivity analysis of different sensing technologies to relevant combustion products, usually carbon monoxide and carbon dioxide. however, sensor sensitivity to volatile gases produced in fire incidents determined by the feasibility of chemical sensing for fire identification, gas sensing devices also demonstrate high cross-sensitivity to water vapour and to great range of volatiles which are generated during many common daily activities. as a result, chemical gas-based systems for fire detection are vulnerable to false alarms (fonollosa, et al., 2016). therefore, sensor design for robust fire detection devices, have to extend beyond the mere analysis of sensor sensitivity to combustion products, and the examination of cross-sensitivity to interfering scenarios is necessary too (fonollosa et al., 2016). in order to address the drawbacks of cross-sensitivity of chemical sensing devices and provide robust fire detection systems, sensor fusion algorithms have been investigated in the literature. http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 474 the great concern with these algorithms is the good detection of fire while minimizing nuisance effects. variety computational algorithms have been examined such as logic rules, neural network, probabilistic neural network, hierarchical linear discriminant analysis or knearest neighbours. however, yet further work is required to enhance detection time and nuisance rejection of fire alarms based on chemical sensing method (fonollosa et al., 2016). multi-sensor approach is motivated by the need for development of more robust fire detection system devoid of false alarms. this kind of approach uses more than one fire signature to detect fire events. because of the robustness of multi-sensor based fire detection devices, recent research efforts on fire detection is hugely focused towards developing more robust algorithms and image processing methods based on the data obtained from sensors in order to minimize false alarms. these such kind of detectors which combine different type of sensors are seen as an effective method to minimize the shortcomings of systems employing individual sensors (sowah et al., 2014; wang et al., 2020). fonollosa et al. (2016) presented a multi-sensor system based on chemical sensing for fire detection. the system was integrated in a sensing chamber in which different fire types and interference were performed. the result obtained showed that the system is able to identify fire from non-fire situations, and activate the alarm faster than conventional fire detection systems based on smoke detection for some fire types. however, there is need to achieve a shorter response time and enhance the robustness of fire detection devices using chemical sensing. in a development to increase the sensitivity of fire detection systems and reduce nuisance alarms, sowah et al. (2014) presented the design and development of a multi-sensor fire detection and alarm system based on fuzzy logic. a microcontroller was used to process data obtained from a smoke sensor, temperature sensor and flame sensor using fuzzy logic algorithm to confirm fire status. díaz-ramírez et al. (2012) proposed and evaluated two algorithms for forest fire detection. the algorithms are designed based on information fusion techniques. the first algorithm employs threshold method and nodes attached with temperature, humidity and light sensors. the second algorithm employs the dempster-shafer theory that has a basic assumption that the nodes use temperature and humidity sensors. fire detection systems based on gas sensing are well-suited for fast fire detection since they have high sensitivity to the early release of volatiles. on the other hand, these systems have low specificity because they respond to volatile gases from non-fire sources. the use of pattern recognition algorithms can enhance the effectiveness of such gas sensor-based fire detection methods. all works reviewed on traditional sensor-based fire detection methods are provided in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 475 table 1: summary of traditional sensor based fire detection methods author(s) and year technique used contribution research gap li, 2011; perilla et al., 2018 thermal sensing easy and inexpensive slow response, limited detection range liu & kim, 2003 thermal sensing insensitive to noise slow response, limited detection range fonollosa et al., 2016; perilla et al., 2018 smoke sensing ability to detect fire in its early stage slow response, high false alarm, limited detection range courbat et al., 2011 smoke sensing capability to detect fire in its early stage high response time, high false alarm, expensive, limited detection range cheong et al., 2011 flame sensing inexpensive and insensitive to external interference limited detection range fonollosa et al., 2016 gas sensing faster response compared to smoke detectors still the response time and robustness can be enhanced 3. computer vision based fire detection systems advances in computing and electronics in recent years have led to the rapid development of fire detection systems based on image processing and computer vision techniques. the computer vision based method employs surveillance camera to capture video image in real time and then input it into computing system to extract the fire image features and then apply a suitable machine learning or deep learning algorithm to detect fire in order to activate the alarm device. these computer vision based methods for fire detection can address the limitations of the conventional sensor based methods and have the advantages of faster response, accurate detection and rich descriptive information (chen et al., 2019). these computer vision-based systems for fire detection can be classified into hand-engineered feature-based methods or deep learning based methods (chen et al., 2019). 3.1 hand crafted features based methods the hand-crafted feature based methods can be mainly distinguished into two classes based on the analysed features: colour based and motion based. the colour feature based methods are designed around the consideration that a fire flame which is assumed to be produced by common combustibles such as wood, plastic, paper, or others, can be uniquely characterized by its distinctive colour feature in such a way that the evaluation of the colour components in rgb (red, green, blue), yuv (luminance, chrominance) or any other colour space is http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 476 strongly robust to recognize the presence of flame. this basic idea motivates a number of recent methods (foggia et al., 2015). the introduction of the hsi (hue, saturation, and intensity) colour space in great ways simplifies the definition of the rule for the designer by being better for providing a user focused approach way of describing colour. the major drawback of such colour based methods is that they are in particular sensitive to the fluctuation in scene brightness, hence leading to a greater level of false positive because of the shadows present or different tonalities of red. this limitation can be overcome by switching to a yuv colour space. to sum up, it is evidently clear that the methods based on colour feature information, despite the fact that being naturally simple to design, can be best suited for sterile environment only, where there is no moving object generally inside. the major shortcomings of such methods are about the number of false positives when deployed in usually populated areas. people wearing red clothes or red cars may be wrongly recognized as fire feature due to their dominant colour. several studies have been proposed in the literature to address this problem (foggia, et al., 2015). all these studies begin with the assumption that a fire flame changes its shapes in continuous manner and the unstructured motion of red regions can make it possible to discriminate it from moving rigid object in the scene. for example, the physical features of the fire are employed to design a feature vector based on improved optical flow algorithm, which have capability to analyse in variety of ways both the temporal features of fire and its saturated flame. dynamic features have been employed in a study, where a two-phase texture detection process have been proposed in the literature to enhance the speed of the segmentation phase, extremely useful to extract a broad class of shape-based features, making the detection of the fire in a good time possible. the wavelet transform has also been employed in some studies to segment accurately the dynamic behaviour of flame regions. it is observed that the methods using wavelet transform, compared to colour based methods, cannot be used on still images and generally require extremely high frame per second to ensure reasonable results, hence limiting their applicability. however, the major limitation of methods based on motion is that the performance enhancement is most of the times paid from different perspective. several sensitive parameters need to be rightly configured for the application at hand in most cases. secondly, the flame motion and shape depend to some extent on the burning material as well as on the geographic conditions (foggia et al., 2015). in recent years, several methods have been proposed based on computer vision algorithms employing hand engineered features to achieving robust fire detection using video images captured by surveillance cameras by combining the static and dynamic features of fire. for instance, (foggia et al., 2015) proposed a fire detection using employing a combination of expert based on colour, shape and flame motion information. the method has been tested on a broad database to evaluate its performance in terms of sensitivity and specificity. experiment results obtained show that the effectiveness of the approach. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 477 an algorithm for forest fire smoke detection is proposed by cai et al. (2016). the algorithm consists of three aspects: moving target segmentation, feature extraction and classification. firstly, visual background extractor (vibe) is used for motion segmentation. morphological operation is performed to connect concentrated but not linked regions. then, the static and dynamic features of smoke are obtained based on colour histogram, energies of wavelet sub images, compactness and direction of moving target. finally, the feature vector is classified using support vector machine. the algorithm has an accuracy rate of 92.7% but still the accuracy needs to be improved and tested on sufficient number of smoke video dataset to enhance its performance. shuai et al. (2016) proposed an algorithm for smoke detection in remote surveillance video based on fast self-tuning background subtraction method and judgement of smoke static and dynamic features. the proposed algorithm has two steps. first, extracting the moving smoke area using the fast self-tuning background subtraction algorithm proposed, which achieves better results compared to colour based and motion based segmentation approaches. then, colour, shape and variance feature of smoke are employed to eliminate smoke-like features to guarantee the accuracy of the detection. the results obtained show that the algorithm could detect smoke regions in remote video surveillance in real-time, precise and reliable manner and it is robust to environmental change. however, the algorithm is not tested on large video dataset. shrivastava and matlani (2016) proposed an efficient computer vision based algorithm for smoke detection using background subtraction and k-means segmentation. the algorithm is comprised of five steps: (i) smoke video image is read (ii) the rgb colour space is transformed to l*a*b colour space to classify pixels as smoke or not. spatial clustering and analysis is carried out on smoke colour pixels. (iii) frame differencing method is employed to extract background from current frame to detect moving pixels. (iv). k-means method is used to segment colour features into three clusters based on euclidean distance metric. (v) the results obtained from background subtraction and k-means segmentation are combined for final judgement. the result obtained demonstrates that the algorithm has a better performance compared to fuzzy c-means method. nevertheless, the performance of the algorithm can be improved. wang et al. (2016) proposed an algorithm for fire smoke detection using optical flow approach and texture feature. the proposed algorithm consists of the following steps. (i) firstly, bilateral filtering is employed to extract noises from poor video quality in image frames. then, foreground regions are segmented by using gauss mixture model and background subtraction method to remove static interference. (ii) colour model used to segment region of interest. median filter employed to remove isolated points and morphological processing to remove small isolated region to obtain a continuous target smoke area. (iii) smoke texture features segmented using local binary pattern (lbp) and local binary pattern variance (lbpv) in region of interest. (iv) motion feature in region of interest contour is extracted using optical flow approach based on image pyramid. (v) finally, support vector machine is used to identify smoke based on the optical flow motion feature and lbp and lbpv texture feature. simulation http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 478 results reported illustrate that the algorithm is timely and accurate in fire smoke detection and robust to external environmental changes. the algorithm has also less computational complexity, fast computational speed but it is tested only five videos which are not sufficient enough. a computer vision based smoke detection approach for intelligent surveillance system is proposed by yuanbin (2016). the algorithm consists of the following steps. (i) fuzzy logic is used to enhance image. (ii)target smoke area is segmented using gaussian mixture model (gmm). (iii) static and dynamic features of smoke are extracted and fused. (vi) the segmented features are normalized and input into support vector machine algorithm for smoke classification. the algorithm is simple and achieves high detection rate and real-time performance. however, the algorithm could generate false alarm in a complex video environment and the processing speed need to be improved for deployment on embedded systems. gunawaardena et al. (2016) proposed a computer vision based algorithm for fire detection that can be compatible with the existing traditional sensor based devices is proposed to enhance the performance and robustness of the conventional system. the proposed video based fire alarming system consists of five steps. the system employs adaptive background subtraction to segment foreground moving region. the rule-based fire colour model is utilized to confirm whether the extracted foreground object is a fire colour feature. the fire pixel recognition is modelled using ycbcr colour space. morphological operation is performed to remove isolated blocks from the segmented fire target regions and enhance the features by growing the missing pixels. the dynamic feature of the extracted target fire region is analysed in the temporal domain to extract the flame flicker to remove spurious fire-like colour feature or non-fire like objects. all these features are fused to form the fire detection system. an algorithm is developed to segment flame from fire video images. the proposed algorithm is computationally inexpensive, simple and can be integrated into existing security monitoring systems. it detects fire and flame successfully; however, it is affected by the scene illumination and tested on small dataset. jinlan et al. (2016) presented a method of fire and smoke detection using surendra background and grey bitmap plane algorithm. firstly, the dynamic background is modelled using otsu adaptive threshold and surendra background. then, the moving target region is extracted by the continuous cumulative moving average of moving target region and the morphological processing algorithm. the smoke region is extracted using colour feature. finally, the fire region is segmented using ohta colour space and grey bitmap plane algorithm. the results obtained show that the proposed method can successfully recognize fire in moving vehicle scene, red plastic bag waving scene, red balloon fluttering scene, moving vehicle similar to fire colour. however, the algorithm is not compared with other recent methods and also not tested on sufficient dataset. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 479 an algorithm for real-time fire detection based on adaboost, local binary pattern(lbp) and convolutional neural network in video sequence is proposed by maksymiv et al. (2017). the proposed method has two main parts. first, region of interest (roi) is extracted using adaboost and lbp algorithms. combination of adaboost and lbp is fast but generates high false positive number. convolutional neural network (cnn) architecture is employed to address this problem so as to make the algorithm better and reliable. lastly, two support vector machines (svm) classifiers provide a judgment on presence of fire or smoke in video sequences. the method has a reasonable execution time which means that it can perform in real-time at video rate. the experimental results obtained demonstrate that the method can achieve more than 95% detection rate. nevertheless, this method has high false positive number in smoke and fog detection. wu et al. (2017) proposed a fire and smoke detection method based on adaptive threshold of feature and deep convolutional neural network in video images. the vibe approach is employed to segment the background from the video image sequence and update the exact moving regions using frame-by-frame differences method. dynamic and static features extracted are fused to detect fire and smoke region of interest. deep learning is employed to detect static fire and smoke features based on caffe model. experiments illustrate that the proposed method achieves efficient fire and smoke detection. but the method is not tested on large dataset and deep learning models are generally computationally expensive. an algorithm for smoke detection based on simplified descriptors of video information is proposed by monte et al. (2017). firstly, the descriptors of the scene on every frame are obtained. the inference processes of smoke presence are input by the descriptors and background estimation, which is updated with every frame. a group of classifiers perform the smoke inference process. the fusion outcomes of these classifiers provide a reliable detection. simple boolean logic combines the process outcomes, with minimum and maximum threshold values. the proposed approach is simple and efficient for deployment on computationally low embedded applications for real-time surveillance. nevertheless, the algorithm does not take into consideration the variability of illumination and uncertainty of the environment. pritam and dewan (2017) proposed fire detection system based on luv colour space and hybrid transforms. video captured are read and frame are segmented. all frames are analysed to confirm the presence of fire. fire is detected by the presence of fire pixels in the image. fire pixels are recognized using the features of luv colour space and hybrid transforms. edge detection algorithm is employed to extract the edges of the image when flame colour detects existence of fire. image segmentation methods are employed to extract the fire region of interest from the background. the results reported show that the proposed system can achieve better performance. however, the system is not tested and compared with other approaches. vijayalakshmi and muruganand (2017) proposed an effective smoke detection approach in video images for early fire emergency systems. the proposed algorithm uses fuzzy c-means clustering and background subtraction to segment smoke region of interest from moving http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 480 regions. result obtained show that the algorithm outperforms other algorithms and increase the accuracy smoke detection. however, the algorithm is not tested on large variety of dataset and the performance still can be improved because it is only based on motion segmentation. zhang et al. (2017) developed a method for smoke detection in video based dissipation function and vibe. the proposed algorithm employs two key features of smoke to detect it. visual background extractor (vibe) is employed to segment moving objects in static scene. the atmospheric model is used to detect semi-transparent feature of smoke. the similarity between extracted regions and original background regions in the same position is computed using normalized cross correlation and the value of the original background is chosen from the frame that is nearest to the current frame. the blocks with high similarity are identified as smoke parts. experiment results demonstrate that the algorithm can recognize fire and integrated into surveillance system. but the algorithm is not tested on sufficient dataset. huang et al. (2017) proposed an algorithm for video based smoke detection in low illumination indoor environment using support vector machine. the smoke region is extracted and then the area diffusion and main direction of movement of smoke region are selected as the dynamic features and texture is extracted as the static feature to recognize fire smoke in lowlight indoor scene. support vector machine is employed to design the classifier to realize smoke detection. finally, the algorithm is tested under variety of conditions. the results obtained show the algorithm achieves high adaptability, high detection rate and good noise immunity. but the algorithm performs in only indoor environment and it is not tested on sufficient dataset. an effective method for real-time fire detection based on video processing is proposed by khan et al. (2018). the proposed method employs flame colour and spatial-temporal features to detect fire regions. firstly, fire colour pixels are segmented using a set of improved rules based on rgb colour space. the foreground is segmented based on change in blue component trained using neural network. lastly, the region of interest is extracted using growing area analysis. experimental results illustrate that the proposed method outperforms other state of the art approaches and yields 97.7% detection accuracy. nevertheless, the method is sensitive to variation in illumination and based on shallow features. yang et al. (2018) proposed a technique for video based smoke detection by combining gaussian mixture model (gmm) and hsv colour model with the deep convolutional neural network. first, each frame is divided into 10-by-10 sub-images by the method. secondly, gaussian mixture model is employed to extract the motion region and later the sub-images block which contains the moving region is segmented. then, the motion blocks segmented by the gmm is used to extract target smoke blocks successively using hsv colour feature analysis. finally, the method confirms whether the bounding box detected by trained model is combined with target smoke block, or the bounding box does not intersect with one of the target smoke blocks, the bounding box will be segmented. the method has improved the detection accuracy and significantly reduced the false detection rate. however, the method is not tested on large dataset, and still the detection accuracy can be enhanced. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 481 zhao et al. (2018) proposed an effective method for smoke detection based on automatic vision system. the method employs an adaptive background subtraction technique to segment moving regions. non-smoke regions are extracted out by employing colour feature and fuzzification. regions that satisfy both the colour analysis and fuzzification criteria are classified as candidate smoke regions. the detected smoke regions are combined with symbolic objects around to confirm the nature of the smoke source using contextual object detection. the method precisely connects specific scenes with spatial and temporal domain statistical approaches to identify target objects. however, the method cannot perform well in complex video scenes. kaabi et al. (2018) proposed a novel approach for video based smoke detection based on machine learning approach to overcome forest wildfires. firstly, the video is divided into frames for training with deep belief network. in addition, gaussian mixture model is employed to segment candidate regions from the target smoke video to be trained by using deep belief network. logistic regression is used to classify on the output data. the approach is reported to achieve 95% detection rate. however, larger frame size can make the method to diverge and it is computationally expensive which makes it not feasible to be deployed on embedded systems. a robust algorithm based on information on colour and shape was proposed by rabiu (2022). the algorithm starts with loading video image database developed to detect presence or absence of fire in video frames. background subtraction is used by this method to compare the current frame with the reference frame. when the outcome of the background subtraction is less than the set point, the frame is discarded and the next frame is checked. but if the difference is equal or greater than the set point, the frame is then subjected to colour and shape test. this is achieved by employing combined rgb colour space model and shape feature. the proposed algorithm was extremely robust in detecting fire compared to those algorithms based on colour or motion features. 3.2 deep learning based methods the traditional hand engineered feature based methods do look to be great but do not seem to be the ideal choice to employ on image based tasks. hence, these days deep learning based methods have achieved superior performance on computer vision tasks. in addition, deep learning based methods have a variety of applications such as object recognition and classification in videos, images and these days is also employed for real-time detection of activities, speech recognition and natural language processing. current research on fire detection based on computer vision have proposed many approaches using deep neural networks such as cnn have achieved great results. therefore, studies on fire detection using cnns have been proposed by some researchers in order to improve the performance of the existing fire detection systems (majid et al., 2022). for example, in vinicius et al. (2021) a robust fire detection system based on two-dimensional convolutional neural network where an object tracker is integrated into an object detector with the aim of confirming if detected events show fire or smoke behaviour over time. http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 482 in the work of saeed et al. (2020), a hybrid approach was presented that consists of an adaboost mlp neural network model to forecast fire events. subsequently, an adaboost lbp model was developed to extract the region of interest (rois) and finally a convolutional neural network for fire detection with videos and images captured from installed surveillance camera. majid et al. (2022) presented an attention based convolutional neural network model for fire detection using real life images. an attention mechanism was also added to the model which achieved great improvement in the performance of data. the introduced neural network has demonstrated significantly great performance on the testing dataset having minimal false positive level. in aktas et al.(2019), the existing cnn based methods for fire detection in video sequences was extended by integrating multiple instance learning (mil). mil ease the need for having accurate locations of fire patches in video frames, which are needed for patch level cnn training. only frame level labels showing the presence of fire somewhere in a video frame are required instead. thus, reducing substantially the annotation and training efforts. the proposed approach was tested on a new fire datasets developed by extending some of the recently used fire datasets with video sequences obtained from the web. result obtained illustrated that the presented method enhances fire detection performance. muhammad et al. (2018) proposed a cost-effective cnn architecture for fire detection in surveillance videos. the model is inspired from google net architecture which is reasonably less computationally complex and suited for the intended task compared to other networks that have high computational cost such as alex net. taking into consideration the nature of the target task and fire data, the model is fine tuned to achieve balance between efficiency and accuracy. results obtained using benchmark fire datasets showed that the proposed model was effective and suited for fire detection based video images captured by cameras from surveillance systems in comparison to the state-of–the art methods. in xie et al. (2020), a method was proposed that employs the motion-flicker based dynamic features and deep static features for video based fire detection. first, the dynamic features are segmented by, analysing the differences in motion and flicker features between fire and nonfire objects in video scenes. second, an adaptive lightweight convolutional neural network is proposed to segment the deep static features of fire. finally, the dynamic and static features of fire are cascaded to develop a video based fire detection system with enhanced efficiency in terms of accuracy and run time. zhang et al. (2021) developed an effective asymmetric encoder-decoder u-shape architecture based on squeeze net, attention u-net and squeeze net performs most of the time as an extractor and a discriminator of forest fire. the model uses attention mechanism to extract useful features and suppress non-related features by embedding attention gate (ag) units in the skip connection of u-shape structure. key features are highlighted through this way so that the proposed method may be great at forest fire extraction problems with a minimum set of parameters. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 483 in the work of mukhopadhyay et al. (2019), a model was developed that has the capability of forecasting fire event with a reasonably great accuracy. the model is based on the convolutional neural network architecture, mobile net. the developed model can be deployed on embedded computing devices in an easy manner due to the fact that it has small size and hence can also be employed as a robust stand-alone fire detection system. hao et al. (2019) proposed an algorithm based on convolutional neural network for video based flame detection. first, the video image is extracted rgb-his colour synthesis model and enhanced adaptive mixture gaussian model. then, the classifier is designed by learning a great number of fire dataset using the cnn designed. then, the flame region of interest is extracted by the classifier criteria. the result obtained revealed that the proposed algorithm has high detection accuracy. tao et al. (2016) proposed an innovative method based convolutional neural network that can be trained end to end from raw image pixel values to classifier outputs and segment automatically features in a way to avoid the tedious image pre-processing stage of the handengineered feature based methods. experiment results obtained showed the proposed method has high detection accuracy rates with low false alarm rates on the small dataset that clearly achieves greater performance compared to the existing methods. in yang wang et al. (2019), presented a method for video based smoke detection that combines conventional smoke detection and a lightweight convolutional neural network. first, the smoke yuv colour space information is fused to minimize the smoke region of interest based on the vibe algorithm. secondly, the lightweight convolutional neural network is designed to segment the information on smoke image in an automatic manner. the training speed of the model is enhanced by using the transfer learning approach for deep learning. the proposed method achieves the real-time performance of smoke detection, guarantees the accuracy of smoke detection and minimizes the false positive level. son et al. (2018) proposed a method for fire detection based on deep learning. the deep learning networks employed are alex net, google net and vgg-16 in three manners. image input that were captured by surveillance camera is classified into three different categories: normal, smoke and flame. then, the network is trained to detect each corresponding category. the results obtained illustrate that all the three network models were able to recognize fire at over ninety percent detection accuracy. in the work of zeng et al. (2018), an enhanced object detection method based on deep convolutional neural network for fire detection was proposed. firstly, the feature extractor is substituted in various neural network object detectors for faster r-cnn, single shot multibox detector (ssd), region based fully convolutional networks (r-fcn). secondly, the mscoco dataset was used to optimize the parameters of the object algorithm. lastly, the smoke detection dataset was used to perform the experiments. the proposed algorithm has http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 484 achieved great results in terms of accuracy and computational speed compared with the existing smoke detection methods. shi et al. (2019) developed a method that combines dark channel image input and a relative precise cnn. the difference between the smoke and background could be greatly enhanced by the dark channel of an image. the comparatively concise cnn could be efficiently trained on an insufficient dataset. results from the experiments performed show extensively that the proposed method achieved great performance when compared to other smoke detection methods. in the work of sadewa et al. (2019), an image base fire detection system was developed using cnn. the proposed system achieved an accuracy level of over ninety percent. table 2 provides a summary of works reviewed on computer vision based fire detection. table 2. summary of works reviewed on computer vision based fire detections. author(s) and year algorithm dataset contribution research gap foggia et al. (2015). hand crafted features based on motion, colour and shape fire video robust detection high false alarm cai et al. (2016) static and dynamic features based on colour histogram, energies of wavelet sub images, compactness and direction of moving target smoke images 92.7% detection rate high false alarm shuai et al. (2016) static and dynamic features based on motion, colour and shape smoke video real-time and reliable detection not tested on sufficient dataset shrivastava and matlani (2016) background subtraction and k-means clustering smoke video good detection rate high false alarm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 485 wang et al. (2016) optical flow motion and texture feature smoke video timely and accurate detection tested on small dataset yuanbin, (2016) static and dynamic features smoke video simple and realtime detection approach high false alarm gunawaardena et al. (2016) motion and colour features, adaptive thresholding fire video simple and computationally inexpensive not robust to environmental changes jinlan et al. (2016) colour and motion features smoke video successful detection not tested on large dataset maksymiv et al. (2017) local binary pattern and convolutional neural network fire video real time fire detection high false alarm wu et al. (2017) adaptive thresholding and deep cnn smoke and fire video effective detection computationally expensive monte et al. (2017) background estimation smoke video simple and efficient not robust enough pritam and dewan (2017) luv colour space and hybrid transform fire video good detection rate high false alarm vijayalakshmi and muruganand (2017) fuzzy c-means clustering and background subtraction smoke video accurate detection high false alarm zhang et al. (2017) visual background extractor and dissipation function smoke video good detection not tested on large dataset huang et al. (2017) support vector machine smoke video high detection rate performs only in door environment http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 486 khan et al. (2018) colour and spatial temporal features fire video good detection rate sensitive to illumination variation yang et al. (2018) gaussian mixture model, hsv colour model and deep cnn smoke video reasonable detection rate not tested on large dataset zhao et al. (2018) adaptive background subtraction smoke good detection rate not robust to environmental changes kaabi et al. (2018) machine learning smoke video good detection rate computationally expensive rabiu (2022) colour and shape information fire video robust and reliable high false alarm saeed et al. (2020) adaboost mlp neural network model forest fire good detection computationally expensive majid et al. (2022) convolutional neural network fire video good detection computationally expensive aktas et al. (2019) convolutional neural network fire video good detection computationally expensive muhammad et al. (2018) convolutional neural network fire video effective detection computationally expensive xie et al. (2020) convolutional neural network fire video effective detection high computational cost zhang et al. (2021) convolutional neural network forest fire effective detection not tested on large dataset mukhopadhyay et al. (2019) convolutional neural network fire video good detection not tested on large dataset hao et al. (2019) convolutional neural network fire video high detection rate high computational cost file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com hassan and audu: traditional sensor-based and computer vision-based fire detection systems: a review. azojete, 18(3):469-492. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 487 tao et al. (2016) convolutional neural network smoke video high detection rate high computational cost yang wang et al.( 2019) convolutional neural network smoke video good detection not tested on large dataset son et al. (2018) convolutional neural network fire video high detection rate computationally expensive zeng et al. (2018), convolutional neural network fire video high detection rate high computational cost shi et al. (2019) convolutional neural network smoke image high detection rate computationally inexpensive sadewa et al. (2019) convolutional neural network fire image high detection rate computationally inexpensive 4. conclusion in this review paper, a survey of various available and proposed fire detection systems was performed. the two categories of fire detection systems were reviewed. the first category is the traditional sensor based methods which involve measuring the ultraviolet or infrared radiation, heat, gas or particulate emissions produced by fire combustion. the methods that belong to this category include thermal detectors, smoke detectors, flame detectors and gas sensors. these methods have a number of shortcomings which include transport delay, conduction delay, limited detection range, high false positive and do not provide rich information. in the second category, the computer vision based methods employ image processing and artificial intelligence techniques to detect fire in video images captured by surveillance systems. these systems can be broadly classified into handcrafted feature based and deep learning based methods. the hand crafted feature based methods tend to be time consuming and affected by environmental conditions while the deep learning based methods learn and extract dep features automatically which eliminate the need for hand feature engineering but they are limited by their high computational cost. based on this analysis, it can be concluded that each method has some merits and shortcomings. for example, the sensor based methods are suitable for indoor application but not appropriate for outdoor environment. it also suffer from transport delay and high false alarm. the computer vision based methods using hand crafted features are affected by the complexity of scene and environmental factors. this problem is addressed by the deep learning based methods but such methods are, however, computationally expensive which restricts their applicability for deployment on real-time embedded computing systems. we observe that the recent advances in vision-based fire detection are driven by cnn. this development can be due to the fact cnn achieves superior performance in various computer vision tasks. but the trade-off is between accuracy, model size and computational speed. http://www.azojete.com.ng/ mailto:lm324fairchild@yahoo.com arid zone journal of engineering, technology and environment, september, 2022; vol. 18(3):469-492. issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: lm324fairchild@yahoo.com 488 finally, it is evidently clear that great amount of academic research efforts has been invested in computer vision-based approaches for fire detection to address the limitations of the sensor-based systems. but many of these methods have not been implemented on hardware platforms such as fpga. computational complexity and high hardware requirement are the major shortcomings of the computer-based approaches. therefore, more research work is required to design, develop, and implement such systems on hardware targets in a computationally efficient manner. references aktas, m., bayramcavus, a. and akgun, t. 2019. multiple instance learning for cnn based fire detection and localization.16th ieee international conference on advanced video and signal based surveillance (avss) held in taipei, taiwan, 18 21 september 2019. pp 1 8. asih, lc., sthevanie, f. and ramadhani, k n. 2018. visual based fire detection system using speeded up robust feature and support vector machine. 6th ieee international conference on information and communication technology (icoict) held in bandung, indonesia, 03 05 may 2018.pp 485 488. cai, m., lu, x., wu, x. and feng, y. 2016. intelligent video analysis-based forest fires smoke detection algorithms. 12th ieee international conference on natural computation, fuzzy systems and knowledge discovery (icnc-fskd) held in changsha, china, 13 15 august 2016. pp 1504 1508. chen, k., cheng, y., bai, h., mou, c. and zhang, y. 2019. research on image fire 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conference on multimedia and image processing (icmip) held in wuhan, china, 17 19 march 2017.pp. 325 329. zhao, x., ji, h., zhang, d. and bao, h. 2018. fire smoke detection based on contextual object detection. 3rd ieee international conference on image, vision, and computing (icivc) held in chongqing, china, 27 29 june 2018. pp. 473–476. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:lm324fairchild@yahoo.com corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 646 arid zone journal of engineering, technology & environment original research article effect of oil palm biomass cellulosic content on molecular structure of biochar a. a. lawal 1*, m. a. hassan 2,3, b. mohammed 1, and y. shirai 4 1department of agricultural and environmental resources engineering, faculty of engineering, university of maiduguri, maiduguri, borno state, nigeria 2department of process and food engineering, faculty of engineering, universiti putra malaysia, 43400 upm serdang, selangor, malaysia 3department of bioprocess technology, faculty of biotechnology and biomolecular sciences, universiti putra malaysia, 43400 upm serdang, selangor, malaysia 4department of biological functions and engineering, graduate school of life science and systems engineering, kyushu institute of technology, 2-4 hibikino, wakamatsu-ku, kitakyushu, fukuoka 808-0196, japan * corresponding author’s email: abubakar.lawal@unimaid.edu.ng article information abstract biochar is attractive mainly due to its diverse surface functionality bringing the possibility of multipurpose utilization. the purpose of this study was to evaluate the effect of biomass cellulosic content on evolution of molecular structures of biochar. commercial cellulose, oil palm front, and palm kernel shell were pyrolyzed at 630 °c, and their biochar structures were analyzed using ultimate and proximate compositions, ph point of zero charge, ftir and xrd. evaluation of biochar nanotexture based on cellulosic content (100% for commercial cellulose, 39.5% for oil palm front and 20.5% for palm kernel shell) revealed that commercial cellulose decomposed rapidly into non-graphitizing large size crystallites (65 nm) with substantial defects within their graphene sheets. the thermal decomposition mechanism for cellulose and lignin differs: cellulose decomposed rapidly to form o heterocyclic rings before final phase transition to graphene sheets at a much lower temperature, whereas lignin decomposed slowly and begins forming graphene sheets after series of condensation reactions at higher temperatures. amorphous chars derived from lignin were thermally stable, slowing down the rapid formation of crystallites in biochar from palm kernel shell. conclusively, highly cellulosic biomass is highly thermally unstable and tends to decomposed into biochar with lower surface functionality compared to biochar derived from highly lignified biomass. received: 19th february 2025 revised: 11th april 2025 accepted: 12th april 2025 keywords: cellulosic content biochar surface functionality thermal stability © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction recently, the global oil palm industry has growing interest on converting the huge amounts of oil palm biomass residues it generated into value-added products aiming at achieving zero-waste emission in the mills, and a more sustainable and profitable palm oil industry (ali et al., 2015). accordingly, there is increasing interest and attention on producing biochar from the residues for a number of applications. a variety of oil palm biomass residues have been considered for biochar production: palm kernel shell, mesocarp fibre, empty fruit bunch, palm kernel cake, palm oil mill sludge, frond and trunk (kong et al., 2014). however, despite the abundance of the residues, selecting biomass precursor capable of producing a biochar with specific functionality using simple environmentally friendly production method such as pyrolysis has always been challenging. the nature of feedstock used for producing biochar is an influential factor that contributes to nature of char formed during pyrolysis. in order words, the proportion of feedstock components (i.e., biopolymers) and their conformation could have a considerable effect on the extent of the evolved biochar structure and functionality. during thermal decomposition of biomass, it is expected that restructuring and re-organization processes of the decomposing biopolymers would lead to the evolution of carbon rich materials, identified as pyrogenic azojete june 2025. vol.21(2):646-655 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/029 www.azojete.com.ng mailto:abubakar.lawal@unimaid.edu.ng mailto:abubakar.lawal@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 647 chars known as the biochar nanotexture. keiluweit et al. (2010) conducted a molecular-level assessment study of the physical organization of biomass-derived biochar and observed a transition of the biomass, as it thermally decomposed, from transition chars to turbostratic char and also noticed a gradual increase in surface area with increasing proportions of turbostratic crystallites embedded in amorphous char. consequently, knowledge of the proportion of feedstock components and their conformation, along with their thermal decomposition behaviour, will assist in the selection of feedstock that can produce high porosity and unique functionality. although a lot of research have been conducted on converting oil palm biomass into biochar (abd waft et al., 2017; jia and lua, 2008; zainal et al., 2018, amosa et al., 2014; parthasarathy et al., 2016; rugayah et al., 2014), little is known about the contribution of lignocellulosic components on the functionality of biochar. correlation between the components of feedstock and biochar functionality will guide in the production of engineered biochar suitable for specific applications. therefore, the objective of this study was to assess the effect of cellulosic content on the evolution of pyrogenic molecular structure of oil palm biomass derived-biochar. 2. materials and method 2.1 pretreatment of feedstocks the oil palm frond, palm kernel shell, and commercial cellulose used in this study were collected from different sources. about 1 kg of fresh oil palm fronds were collected from universiti putra malaysia oil palm plantation and transported to the biomass and biorefinery center of the university. the fresh fronds were sliced into rectangular pieces approximately 5 cm long, 3 cm width, and 2 cm thick and dried in an electric drying oven (mmmert, germany) at 105 °c for 72 h to remove moisture and avoid the decay of the fresh fibre. approximately 500 g of dried palm kernel shell was collected from felda palm oil mill, pasoh, negeri sembilan, and transported to the biomass and biorefinery center. the shells collected were soaked in distilled water for 10 h before squeezing and washing with distilled water to remove impurities. the clean shells were dried in an electric drying oven (memmert, germany) at 105 °c for 72 h. about 500 g of commercial cellulose was purchased from r&m chemicals. the dried samples were stored in designated airtight plastic bags (figure 1). powdery samples used for feedstock characterization were prepared by chopping about 50 g into pieces and ground in a wood grinder to pass through a 425 μm sieve (40 us mesh screen). the following chemicals purchased from merck were used to determine cellulose, hemicellulose and lignin, and phpzc of the biomass materials: naclo2, h2so4, nano3, hno3 and naoh. figure 1: feedstocks: (a) oil palm frond, (b) oil palm kernel shell, (c) commercial cellulose 2.2 biochar production nitrogen pyrolysis was conducted to produce biochar from oil palm frond, palm kernel shell, and commercial cellulose. the nitrogen pyrolysis test is frequently used as a means for studying the structure of biochar formed during carbonization. the basic principle of the test is to heat biomass at a high temperature in the presence of flowing nitrogen and measure the relevant physicochemical properties of the biochar produced. therefore, the nitrogen pyrolysis test used in this research followed the procedure reported by keiluweit et al. (2010) and cao et al. (2012). in this study, about 30 g each of the oil palm frond, oil palm kernel shell, and commercial cellulose were carbonized separately using the dual-mode pyrolysis system. in a nitrogen gas flow rate of 100 cm3/min, the feedstocks were heat-treated at a heating rate of 40 °c/min to 630 °c for an hour before cooling down to room temperature. the biochars produced were gently pulverized using pestle and mortar made from stainless steel to pass through a 250 μm sieve (60 us mesh screen). the powdered biochars produced from commercial cellulose, oil palm frond, and palm kernel shell were placed and sealed in designated vessels cc-bc, opf-bc, and pks-bc, respectively. http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 648 2.3 biopolymer, proximate, and ultimate compositions the fraction of the biopolymers in each fibre was determined based on the method developed by norrrahim et al. (2018). lignin was first removed by soaking a fibre in 5 wt. % naclo2 solution adjusted with h2so4 to a ph between 4 and 5. after an hour of soaking at 70 °c, the fibre was washed with deionized water until neutral ph. hemicellulose was removed from the by soaking the lignin-free fibre in 6 wt. % koh solution at 25 °c for 24 h. the fractions (dry basis) of cellulose, hemicellulose, and lignin in the fibre were calculated from their respective weights. the weight-loss behaviour was analyzed in a tga-4000 thermogravimetric analyzer (perkinelmer instruments, usa). in each test, 15 mg of a sample was heated at 10 °c/min to 950 °c. both the weight-loss curve and the derivative thermogravimetric curve were analyzed for the thermal characteristics of the feedstocks. the proximate analysis was performed following the modified standard method for proximate analysis d317507 and d3174-04 (cantrell et al., 2010). the test was carried out in a tga-4000 thermogravimetric analyzer (perkinelmer instruments, usa). dry samples with particle size < 0.425 mm were used for the analysis. the sequential determination of moisture and volatile matter involved loading about 15 to 20 mg of sample into a ceramic crucible and heating to110 °c for 15 min in the presence of nitrogen gas flowing at 80 ml/min to liberate moisture. removal of the volatile matter was carried out in an inert environment, and it involved heating the dry sample from 110 °c to 950 °c and isothermal hold for 7 min before rapid cool down to 110 °c. the heat treatment for ash content analysis was performed in the presence of zero-grade air flowing at 80 ml/min. the heat treatment involved heating the moisture free sample (15 to 20 mg) from 110 °c to 950 °c at 11 °c/min, followed by an isothermal hold for 10 min and rapid cooling to 110 °c. the percentage of moisture, volatile matter, and ash were calculated based on equation 1, 2, and 3, respectively, while the percentage fixed carbon was calculated by difference using equation 4: mc % = (mass loss at 110 °c/mass of sample) × 100 1 vm % = (mass loss at 950 °c/mass of dry sample) × 100 2 a % = (mass loss during air combustion/mass of dry sample) × 100 3 fc % = 100 – (mc % + vm % + a %) 4 where mc % is percentage moisture, vm % percentage volatile, and a % percentage ash. the percentage composition of carbon, hydrogen, and nitrogen in biomass feedstocks and biochars was obtained from chn analysis in the chn628 analyzer (leco, uk). the percentage composition of oxygen was calculated by difference. 2.4 surface functionality fourier-transformed infrared (ftir) spectroscopy was performed in a perkin-elmer spectrum gx ft-ir system instrument (perkin-elmer) to identify surface functional groups qualitatively. the principle of measurement involved mixing and pressing dry sample with potassium bromide at 1:100 to form a transparent compact disc and exposing it to infrared radiation within the wavelength range between 4000 to 400 cm-1 with each sample scanned 16 times. to understand the molecular structure of a biochar, the ftir spectrum was analyzed at regions corresponding to oh, ch, c=c, and c=o groups and the fingerprint. the procedure for determining the surface ph of the biochars produced in this study involved mixing 0.2 g of dry biochar with 10 ml of distilled water followed by agitation for 24 h to reach equilibrium before measuring the ph of the suspension using ph meter laquatwin s010 (horiba, japan) (nowicki et al., 2015). the ph point of zero charge (phpzc) was determined following the modified ph drift method by mahmood et al. (2011). the phpzc determines the ph at which the surface of biochar is zero, where an increase in ph leads to a negatively charged surface. the ph drift method was carried out by mixing 0.1 g biochar with 20 ml of 0.1 m nano3 solution in a vessel, and the ph of the suspensions was adjusted to 3, 4, 5, 6, 7, 8, 9, and 10 with either hno3 or naoh. the ph of the suspension after 72 h of agitation was measured, and the difference between the final and initial ph (∆ph) was plotted against the initial ph. the phpzc was determined to be the initial ph at which ∆ph was zero. http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 649 2.5 morphology and structure electron micrographs scanned at different magnifications were obtained using a scanning electron microscopy hitachi s-3400 (hitachi, japan) for image analyses of particle sizes and surface morphology, respectively. dry samples were coated with gold and scanned in the microscopy at 5 kv for image acquisition. the scanned images at low magnifications were subjected to qualitative particle size analysis, while the high magnification images were used for the analysis of surface morphology. the crystalline structure of the biochars was analyzed using x-ray diffractometry. the powdered x-ray diffraction (xrd) method detects the presence of carbon crystallites in biochar microtexture based on their diffraction pattern in response to incident x-rays. xrd diffraction patterns for the biochars were recorded using a shimadzu diffractometer (xrd 6000, japan) with a cu kα radiation at a wavelength, λ of 0.1541838 generated at 30 kv and 30 ma. the xrd diffraction was measured over the range 5° < 2 theta < 70° using the step-scanning method at 2 degrees/min step and sampling pitch of 0.02 degree. the 2 theta angle range was chosen to capture the reflection of the crystallographic basal plane (i.e., 002 indices) and the crystallographic reflection planes perpendicular to the basal planes (i.e., 10 indices). the origin 2018 pro software was applied to the xrd patterns to extract constants relevant in calculating structural properties. the crystallites' structural parameters were calculated using known established expressions. the interlayer spacing between the graphene sheets, d002 and carbon crystallite thickness, lc and diameter, la the average number of graphene sheets per carbon crystallites, ns and the average number of carbon atoms per graphene sheet were calculate using bragg’s equation, sherrer’s emperical equations and diamond’s equation (equations 5 to 9). 𝑑002 = 𝜆 2∗𝑠𝑖𝑛𝜃002 5 𝐿𝑐 = 𝑘𝑐𝜆 𝐹𝑊𝐻𝑀002∗𝑐𝑜𝑠𝜃002 6 𝐿𝑎 = 𝑘𝑎𝜆 𝐹𝑊𝐻𝑀10∗𝑐𝑜𝑠𝜃10 7 𝑛𝑠 = 𝐿𝑐 𝑑002 8 𝑛𝑑 = 2( 𝐿𝑎 0.25 ) 2 9 where θ002 and θ10 are the 2 theta angles corresponding to the peak intensities of the 002 and 10 bands respectively, kc and ka are sherrer constants corresponding to 0.91 and 1.84 (sharma et al. 2000) for 002 and 10 reflection planes respectively, and fwhm002 and fwhm10 are the full width at half maximum of 002 and 10 reflection planes respectively. 3. results and discussion 3.1 physicochemical properties and thermal stability table 1 presents the biopolymer, proximate and ultimate compositions of the commercial cellulose, oil palm frond, oil palm kernel shell and their respective biochars produced at 630 °c in a nitrogen environment. the biopolymer composition for commercial cellulose had no traces of lignin and hemicellulose, whereas oil palm frond and oil palm kernel shell contained mainly of cellulose, hemicellulose and lignin at different proportions respectively. oil palm frond was highly cellulosic and less lignified compared to oil palm kernel shell. in addition, oil palm frond contained a small amount of extractives, mainly due to the presence of stored simple sugars in its parenchyma tissue (roslan et al., 2014; zahari et al., 2012). as biopolymer thermally decomposed after pyrolysis at 630 °c, the biochars derived from the feedstocks were carbonized with no trace of the biopolymers. the fixed carbon content appeared to correlate with lignin content and increased significantly after carbonization in the increasing order of biochars from commercial cellulose < oil palm frond < oil palm kernel shell. the yield of biochars from commercial cellulose, oil palm frond and oil palm kernel shell was 14.50 %, 32.13 % and 29.70 % respectively. little variation pertaining to ultimate composition existed among the feedstocks and derived biochars respectively. the carbon content increased significantly from < 47 % in all feedstocks to > 75% after pyrolysis, yielding a highly carbonaceous material. base on the residual concentration of hydrogen and oxygen and atomic ratio, it was evidence that biochar from commercial http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 650 cellulose was highly carbonized and contained the lowest concentration of polar groups compared to biochars from oil palm frond and oil palm kernel. table 1: physicochemical properties of cc, opf, pks and their biochars cc opf pks cc-bc opf-bc pks-bc biochemical composition (%) cellulose 100.00 39.51 20.53 hemicellulose 0.00 23.56 22.33 lignin 0.00 23.32 51.54 extractives 0.00 6.321 0.00 ultimate composition (%) c 39.85 38.58 46.52 78.84 75.57 77.07 h 6.70 6.29 6.07 2.83 2.54 2.66 n 0.02 0.10 0.20 0.19 0.37 0.65 o 52.59 52.35 45.65 8.14 14.38 14.50 h/c 2.00 1.94 1.55 0.43 0.40 0.41 o/c 0.99 1.02 0.74 0.08 0.14 0.14 (o+n)/c 0.99 1.02 0.74 0.08 0.15 0.15 proximate composition (%) fc 6.23 17.86 24.25 77.47 80.89 85.29 vm 92.94 79.47 74.19 12.53 11.96 9.59 ash 0.84 2.68 1.56 10.00 7.14 5.13 the curves of the thermogravimetric analysis presented in figure 2 reveal information on the thermal stability of commercial cellulose, oil palm frond and oil palm kernel shell. the mass loss during the main devolatilization stage from 200 to 400 °c (i.e., initial stage) was rapid and followed the order commercial cellulose > oil palm frond > oil palm kernel shell indicating the complete thermal decomposition of polysaccharides. upon further heating from 400 to 950 °c mass loss continued but at a significantly lower rate. at the temperature range 500 to 950 °c, mass loss of commercial cellulose (3.2 %) was remarkably lowest compared to oil palm frond (6.1 %) and oil palm kernel shell (7.7 %) mainly due to lack of lignin, which would otherwise continue to decompose and release carbon, hydrogen and oxygen in the form of h2, co, co2, ch4, c2h2 and c2h6 at higher temperatures (yang et al. 2006). thus, analysis of the initial and final pyrolysis stages showed that the thermal stability of the biomass materials followed different order. it is, therefore, reasonable to assume that initial and final mass losses were positively correlated with the content of polysaccharides and lignin respectively. however, the mass losses for their respective biochar were in the opposite order as illustrated in figure 2 b. this change could be mainly attributed to the catalytic effect of metal oxides formed after production via chemisorption of oxygen (xu et al., 2019). figure 2: thermal degradation profile of cc, opf, pks and their biochars the ftir spectra of the biomass materials and their biochars produced at 630 °c are presented in figure 3. the wavenumbers of the spectroscopic bands for each spectrum are tabulated in table 2. the bands corresponding to hydroxyl (o-h), aliphatic (c-hx), carboxyl (c=o), aromatic skeletal (c=c), carboxylate (co-c), phenolic (o-h) and c-o and c-h vibrations and bending of lignocellulosic components were detected with different intensities in commercial cellulose, oil palm frond and oil palm kernel shell. comparatively, the band attributable to o-h stretch was more intense on the spectrum of commercial cellulose and oil palm frond, which can be related to the higher concentrations of the h-bonded primary alcohols and non h-bonded hydroxyl groups compared to the highly lignified oil palm kernel shell. these functional groups are drastically reduced on the biochars or completely eliminated given ways for new functional groups. new bands at around 3020 1/cm and 888 1/cm attributable to aromatic c-h stretch and out-of-plane deformation (harvey et al., 2012) were detected due to the presence of aromatic carbon structures in the biochars, and the relative intensities followed the order commercial cellulose > oil palm kernel shell > oil palm frond. similarly, the 0 20 40 60 80 100 100 300 500 700 900 y ie ld ( % ) temperature (°c) cc pks opf (a) 85 90 95 100 105 100 300 500 700 900 y ie ld ( % ) temperature (°c) cc-bc opf-bc pks-bc (b) http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 651 relative intensity of bands at 1636 attributable to aromatic c=o and c=c ring (abdulrazzaq et al., 2014) show that aromaticity in biochar from commercial cellulose was highest while oil palm frond had the least aromatic carbon structure. figure 3: fourier transform infrared spectra of (a) cc, opf and pks and (b) their respective biochars table 2: spectroscopic assignments for raw cc, opf, pks and their respective biochar cellulose cellulose char opf opf char pks pks char hydroxyl (-oh) stretch 3353 3466 3363 3456 3370 3463 aromatic c-h stretch 3028 3024 3020 3023 symmetric stretch of aliphatic ch3 2950 2950 2973 2950 asymmetric stretch of aliphatic ch3 symmetric stretch of aliphatic ch2 asymmetric stretch of aliphatic ch2 2885 2891 2883 2884 ester, carboxyl c=o stretching 1731 1740 1724 1739 1740 1738 aromatic -c=c-, -c=ostretching 1642 1634 1628 1636 1642 1635 ch, ch2 and ch3 deformation 1428 1430 1418 1431 1425 1429 -c-h or o-h bending vibration 1369 1369 1358 1370 1369 1370 c-o-c stretching 1057 1061 1043 1058 1051 1064 aromatic c-h out-of plane deformation 888 888 895 aromatic c-h out-of plane deformation 757 760 754 771 776 768 since part of the formation of aromatic structure in biochar proceeds through the thermal conversion of aliphatic c-h fragments of thermally decomposed lignocellulosic components (xu et al., 2019), further analysis was carried out in the c-h stretch regions to determine the aromaticity calculated from the ratio of aromatic c-h groups to aliphatic c-h groups. the aromaticities of biochar derived from commercial cellulose, oil palm frond and palm kernel shell are presented in figure 4. the biochar from commercial cellulose had the highest aromaticity reflecting the ease (compared to the other biochars) of converting thermally decomposed aliphatic c-h of cellulosic origin to condensed aromatic structure mainly through dehydration, decarboxylation, dehydrogenation and aromatization processes (xu et al., 2019). despite the presence of aromatic compounds attributed to lignin in the oil palm kernel shell (figure 3), the biomass exhibited the lowest aromaticity, possibly due to the high thermal stability of lignin and its decomposed aliphatic c-h components which has to undergo additional demethylation before dehydrogenation and aromatization. in addition, the presence of lignin suppresses the tendency of intramolecular condensation of amorphous char derived from cellulose (hosoya et al., 2007). the inconsistency of the aromaticity with h/c ratio (i.e., degree of carbonization) have been suggested to be due to different arrangement of the elements in the structure of the biochars (xu et al., 2019). http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 652 figure 4: the ratio of the stretch area of aromatic c-h groups to the stretch area of aliphatic c-h groups the presence of o functional groups give rise to different magnitudes of surface charge on the biochars. figure 5 presents the phpzc curves for the biochars obtained from the modified ph drift method. as can be seen, the phpzc of the biochars were above neutral ph point. the phpzc of biochar from commercial cellulose was 8.9 while those from oil palm frond and oil palm kernel shell were 9.62 and 9.63 respectively. this was consistent with biochars produced at high temperature having basic surface functional groups (lopez-ramon et al., 1999; xu et al., 2019). in practice, this means that the biochars would have positive charges at ph lower than phpzc and negative charge at higher values. figure 5: the ph of point of zero charge of biochars from cc, opf and pks 3.2 x-ray diffraction pattern and evaluation of crystallite parameters figure 6 presents the normalized xrd patterns of biochars derived from commercial cellulose, oil palm frond and oil palm kernel shell. the diffraction patterns of the biochars were characterized by a broad diffraction band centred around 2θ = 25°, which correspond to the (002) diffuse graphite band (wu et al., 2012). the (10) diffraction corresponding to atomic ordering within the graphene sheet (guerrero et al. 2008; keiluweit et al. 2010) was weak and broad for biochars derived from oil palm frond and oil palm kernel shell, while a strong (10) diffraction peak appeared on cellulose. the proportion of disorganized carbons comprises of the aliphatic chains and amorphous carbon. the concentration of the amorphous carbons gave rise to the background intensity of the diffraction profile, while the asymmetry of the (002) band to the left was due to the presence of saturated functional groups attached to the edge of the graphene sheets. the visual assessment of the diffraction profiles in figure 6 showed that concentration of amorphous carbon in biochar from oil palm kernel shell was the highest, while oil palm frond-derived biochar had the least proportion of amorphous carbon. it is difficult to discern the γ band corresponding to the aliphatic carbon on the (002) band. 0 1 2 3 4 5 6 7 8 cc-bc opf-bc pks-bc c -h ar o m at ic /c -h al ip h at ic -1 0 1 2 3 4 2 3 4 5 6 7 8 9 10 11 12 δ p h initial ph cc-bc opf-bc pks-bc http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 653 figure 6: x-ray intensity curves of biochars from cc, opf and pks the diffraction band corresponding to (002) was separately fitted with pearson iv distribution and the parameters obtained were used to calculate the interlayer spacing, d002, the thickness of the crystallite formed, lc and the average number of hexagonal layers per stack, ns, while the average diameter of the crystallites was obtained from (10) diffraction band. table 3 presents the statistical parameters obtained from curve fitting and the crystallite parameters calculated. the different values of the crystallite structural parameters were an indication of the influence of the nature of the feedstock material and characteristics of the crystallites structure. for instance, the magnitude of d002 reveals the degree of crystallites graphitization and as such, the biochars had crystallites with a lower order of graphitization compared to graphite (0.336 nm). the crystallites in biochar from oil palm kernel shell had the highest tendency of graphitizing, whereas crystallites in oil palm frond-derived biochar revealed highly turbostratic characteristics. presence of low fraction of lignin content in oil palm frond has a deterring effect on graphitization process of crystallites formed, however for high content lignin biomass such as palm kernel shell, lignin encourages graphitization process of the crystallites formed due to the compact conformation of lignin. the diameter of graphene sheets formed in biochar from commercial cellulose was at least 22 times larger than the two biochars from oil palm frond and oil palm kernel shell. table 3: curve fitting and structural crystallite parameters along (002) and (10) x-ray diffraction bands crystallite parameters cc-bc opf-bc pks-bc pearson iv quality of fit r2 0.9684 0.9643 0.9742 2θ002 (°) 25.44 24.93 25.82 β002 (°) 5.16 7.15 5.41 d002 (nm) 0.3501 0.3572 0.3451 lc (nm) 1.60 1.15 1.53 ns 4.56 3.22 4.42 gauss quality of fit, r2 0.9788 0.9548 0.9742 2θ10 (°) 43.97 43.47 43.39 β10 (°) 0.27 5.94 6.40 la (nm) 64.99 2.95 2.73 nd 135152 278 239 la/lc 40.62 2.57 1.78 4. conclusion the molecular structure of the biochars as suggested by ftir spectra, atomic ratios and xrd spectra comprised of both amorphous carbons and turbostratic crystallites at different proportion. generally, the thermal decomposition mechanism for cellulose and lignin differs: cellulose decomposed rapidly to form o heterocyclic rings before final phase transition to graphene sheets at a much lower temperature, whereas lignin decomposed slowly and begins forming graphene sheets after series of condensation reactions at higher temperatures. cellulose decomposed via dehydration and condensation and forms a low-density relatively volatile chars comprised mainly of levoglucosenone and hydroxymethylfurfural. these oxygenated heterocyclic rings would experience further dehydration, decarboxylation, aromatization and intermolecular condensation to form graphene sheets. on the other hand, lignin decomposed to relatively thermally stable phenolic and 0 500 1000 1500 2000 2500 3000 3500 4000 5 15 25 35 45 55 65 n o rm al iz ed i n te n si ty , i (c o u n t) angle of diffraction, 2θ (°) cc-bc opf-bc pks-bc (002) (10) http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 646-655. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abubakar.lawal@unimaid.edu.ng 654 oxygenated aromatic rings and with further dehydration, dehydrogenation and intermolecular condensation, graphene sheets are formed. in practice, biochar derived from highly cellulosic biomass could suitable for adsorption, while lignified derived-biochar could be a suitable catalyst due to it diverse surface functionality. acknowledgement this research was funded by the fundamental research grant scheme – malaysia research star award [grant number: frgs-mrsa/1/2018/stg07/upm/01/1]. the authors would like to express their profound appreciation to universiti putra malaysia and kyushu institute of technology for their technical supports. references abd waft, ns., lau, hln., loh, sk., abdul aziz, a., ab rahman, z. and may, cy. 2017. activated carbon from oil palm biomass as potential adsorbent for palm oil mill effluent treatment. journal of oil palm research, 29(2): 278–290. abdulrazzaq, h., jol, h., husni, a., and abu-bakr, r. 2014. characterization and stabilisation of biochars obtained from empty fruit bunch, wood, and rice husk, biores. 9(2): 2888-2898. ali, aam., othman, mr., shirai, y. and hassan, ma. 2015. sustainable and integrated palm oil biorefinery concept with value-addition of biomass and zero emission system. journal of cleaner production, 91: 96–99. amosa, mk., jami, ms., alkhatib, mfr., jimat, dn., and muyibi, sa. 2014. comparative and optimization studies of adsorptive strengths of activated carbons produced from steamand co2-activation for bpome treatment. advances in environmental biology, 8(3): 603–612. cantrell, k., martin, j. and ro, k. 2010. application of thermogravimetric analysis for the proximate analysis of livestock wastes. journal of astm international, 7(3): 1–13. cao, x., pignatello, jj., li, y., lattao, c., chappell, ma., chen, n., miller, lf. and mao, j. 2012. characterization of wood chars produced at different temperatures using advanced solid-state 13c nmr spectroscopic techniques. energy and fuels, 26(9): 5983–5991. guerrero, m., ruiz, mp., millera, á., alzueta, mu. and bilbao, r. 2008. characterization of biomass chars formed under different devolatilization conditions: differences between rice husk and eucalyptus. energy and fuels 22: 1275–1284. harvey, or., herbert, be., kuo, lj., and louchouarn, p. 2012. generalized two-dimensional perturbation correlation infrared spectroscopy reveals mechanisms for the development of surface charge and recalcitrance in plant-derived biochars. environmental science and technology, 46(19): 10641–10650. hosoya, t., kawamoto, h. and saka, s. 2007. pyrolysis behaviors of wood and its constituent polymers at gasification temperature. journal of analytical and applied pyrolysis, 78(2): 328–336. jia, q. and lua, ac. 2008. effects of pyrolysis conditions on the physical characteristics of oil-palm-shell activated carbons used in aqueous phase phenol adsorption. journal of analytical and applied pyrolysis, 83(2): 175–179. keiluweit, m., nico, ps., johnson, mg. and kleber, m. 2010. dynamic molecular structure of plant biomassderived black carbon (biochar). environmental science and technology, 44(4): 1247–1253. kong, sh., loh, sk., bachmann, rt., rahim, sa., and salimon, j. 2014. biochar from oil palm biomass: a review of its potential and challenges. renewable and sustainable energy reviews, 39: 729–739. lopez-ramon, mv., stoeckli, f., moreno-castilla, c., and carrasco-marin, f. 1999. on the characterization of acidic and basic surface sites on carbons by various techniques. in carbon, 37. mahmood, t., saddique, m t., naeem, a., westerhoff, p., mustafa, s. and alum, a. 2011. comparison of different methods for the point of zero charge determination of nio. industrial and engineering chemistry research, 50(17): 10017–10023. http://www.azojete.com.ng/ mailto:abubakar.lawal@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; 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2mechanical engineering department, college of engineering, federal university of agriculture, p.m.b 2400, abeokuta, ogun state, nigeria; *corresponding author’s email: adepojuvo@funaab.edu.ng article information abstract the effect of moisture content of two varieties of palm kernel and shell on the coefficient of sliding friction of the two faces (face a and face b) of a fibre material was determined. standard procedures were used to determine the moisture content for both kernel and shell of tenera and dura varieties. the results show that the moisture content of dura and tenera varieties were 17.4 and 18.2% which were individually adjusted to 9, 13 and 17% by adding 76.3, 39.8 and 3.3 g; and 82.3, 46.4 and 10.6 g distilled water respectively. the angle of repose apparatus was used to determine the coefficient of sliding friction of palm kernel and shell of dura and tenera varieties on the two faces of fibre material. it was observed that the average values of dura palm kernel and palm shell coefficient of sliding friction on the two faces of fibre material ranged from 0.458-0.777 for 9% moisture content; 0.510-0.690 for 13% moisture content and 0.532-0.777 for 17% moisture content. additionally, the average values of tenera kernel and shell coefficient of sliding friction on the two faces of fibre material ranged from 0.5460.864 for 9% moisture content; 0.506-0.953 for 13% moisture content; and 0.537-0.927 for 17% moisture content. therefore, we observed that the moisture content of either dura palm kernel or dura palm shell had significant effect (p<0.05) on the coefficient of sliding friction on face a and face b of the fibre while the moisture content of either tenera palm kernel or tenera palm shell had insignificant effect (p>0.05) on the coefficient of sliding friction on face a and face b of the fibre. the coefficient of sliding friction on fibre was affected by the moisture content of dura variety but not of that tenera variety. received: 13th october 2025 revised: 22nd november 2025 accepted: 24th november 2025 keywords: pisifera, tenera dura frictional properties roughness © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction oil palm is categorized into three primary varieties based on fruit characteristics, with the tenera variety being a hybrid of the dura and pisifera varieties. each variety has distinct features; the dura variety possesses a thin fruit wall (pericarp) constituting 40-70% of the fruit's mass, alongside an exceptionally thick shell (2-5 mm) and a large nut with a bigger kernel than the others (adzimah and seckley, 2009). the pisifera variety has a thicker pericarp with a higher potential oil yield. however, it is often female-sterile and typically lacks a kernel, which prevents its use in commercial cultivation for palm kernel oil (pko), a key industrial material in cosmetics. the hybrid tenera variety features a substantial pericarp (approximately 60% of the fruit weight) that is rich in oil, combined with a shell of intermediate thickness (1-2.5 mm) (adzimah and seckley, 2009). the choice of variety depends on the desired product. for palm oil extraction, tenera is optimal due to its thickness, oil-rich fruit wall and its relatively easier-to-crack the shell. conversely, for palm kernel oil (pko) production, dura is preferred because of its larger kernel size, despite the challenge posed by its thicker shell. interestingly, the rising industrial demand for kernels and their derivatives in nigerian markets underscores azojete december 2025. vol.21(4):1005-1011 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/010 www.azojete.com.ng mailto:adepojuvo@funaab.edu.ng mailto:adepojuvo@funaab.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1005-1011. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adepojuvo@funaab.edu.ng 1006 the necessity for enhanced processing techniques. it is noteworthy that an efficient separation processes of kernels from shells is critical to meet this growing downstream industrial need (olasumboye and koya, 2014). currently, two primary methods are used which are wet and dry methods. wet separation uses clay-baths or hydro-cyclones in a liquid medium, leveraging differences in specific gravity. this method is being used commercially but faced a significant drawback through the need to re-dry the recovered kernels for 14-16 hours in a silo to remove absorbed moisture, a step that also serves to sterilize them against mold (akubuo and eje, 2002; adepoju, 2019). in response to the constraints of wet processing, research is focussed on developing dry separation techniques that could be used commercially.the dry methods exploit principles such as gravity, frictional coefficient, speed variation, relative motion, and particle shape. however, many locally produced machines for this purpose remain at the experimental stage or function only as pre-cleaners (amoah et al., 2007; adepoju, 2019). consequently, a detailed investigation into the factors influencing these dry separation principles is required. this study specifically examines how the moisture content in two palm kernel varieties affects their coefficient of sliding friction on a fibrous material (rug). 2. materials and methods 2.1 materials the materials used to determine the moisture content and coefficient of sliding friction of palm kernel and shell were: oven, dura palm kernel and shell, tenera palm kernel and shell, angle of repose apparatus, desiccator (180 ml), digital weighing balance (scout pro (spu2001) electronic balance with accuracy 0.1 g) and 2 hp powered horizontal centrifugal cracker. 2.2 method 2.2.1 sample collection tenera nuts used in the study was collected from the directorate of university farms (dufarms), federal university of agriculture, abeokuta (funaab) while dura nuts were collected from ogun state ministry of agriculture, eweje, odeda, abeokuta, ogun state. 2.2.2 sample preparation the nuts of dura and tenera were manually cleaned from unwanted materials such as cell debris, stones and dirt. then, the nuts were cracked using centrifugal cracker into palm kernels and shells. 2.2.3 determination of moisture content the moisture content of palm kernels and shells from the dura and tenera varieties was determined following the asae standard (1998) for oil seeds, as cited by orhevba et al. (2013). the analysis was conducted in the crop processing laboratory of the department of agricultural and bio-resources engineering, college of engineering, at the federal university of agriculture, abeokuta (funaab), nigeria. for each variety, a 1.20 kg sample of the cracked kernel-shell mixture was weighed and oven-dried at 105°c. after an initial drying period of six hours, the samples were transferred to a desiccator to cool, preventing moisture reabsorption from the atmosphere. following this, the mass of each sample was recorded at one-hour intervals until a constant mass was achieved, indicating that all moisture had been removed. the initial moisture content was then calculated on a wet basis using equation (1). the final dried kernel-shell mixture was divided into three (3) portions each for the two varieties. 𝑚𝑐 = 𝑤1− 𝑤2 𝑤1 1 where mc is the moisture content, w1 is the initial mass and w2 is the final mass. 2.2.4 moisture content adjustment a calculated amount of distilled water (76.3, 39.8 and 3.3 g; and 82.3, 46.4 and 10.6g) was added to the six (6) samples of the mixture of kernels and shells of the two varieties to bring them to the desired moisture contents of 9, 13 and 17% w.b. using equation (2) as used by olayanju (2002) and sealed in separate polythene http://www.azojete.com.ng/ mailto:adepojuvo@funaab.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1005-1011. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adepojuvo@funaab.edu.ng 1007 bags. afterwards, the polythene was kept in refrigerator at 5oc temperature for at least one week to ensure moisture uniform distribution according to davies and zibokere (2011). 𝑄 = 𝐴(𝑏 − 𝑎) (100 − 𝑏) 2 where a is initial mass of the sample, g; a is initial moisture content of the sample, %wet basis (w.b.); b is final (desired) moisture content of sample % (w.b.); q is mass of water to be added, g. 2.2.5 determination of coefficient of sliding friction the angle of repose apparatus used for the determination of coefficient of sliding friction of dura and tenera varieties as used by adepoju et al. (2023) is shown in the plate 1. palm kernels and shells of each variety were loaded on to an open-ended rectangular box, 100 × 50 × 30 mm made of cardboard placed on the tilting board. in order to allow the free movement of the sample, one of the edges of the box was not fixed to allow for the movement of the crop product component on the board surface covered with fibre material as shown in the plate 2. an adjustable screw jack was positioned under the apparatus for controlling the angle of inclination. the box was loaded in turns with the kernels and shells of the two varieties. the tilt angle at initial sliding of the box was noted for five readings and averaged. the coefficient of sliding friction was calculated with the equation (3). 𝜇 = 𝑡𝑎𝑛𝜃 3 where µ is the coefficient of friction and θ is the angle of inclination (degree). 2.2.5 experimental design the experimental design used was 3×2×2×2×5 factorial experiment where three (3) moisture contents was used for two (2) varieties of two (2) samples (palm kernel and shell) on two (2) faces of fibre material at five (5) replicates. the total runs for the determination of coefficient of sliding friction was one hundred and twenty (120). plate 1: coefficient of sliding friction determination apparatus a b plate 2: two faces of the fibre material (rug) http://www.azojete.com.ng/ mailto:adepojuvo@funaab.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1005-1011. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adepojuvo@funaab.edu.ng 1008 2.2.6 data analysis the coefficient of sliding friction obtained for the three moisture levels, two varieties, products and faces each of fibre material at five (5) replicates were analyzed using the analysis of variance (anova). separation of means was carried out by the use of tukey method. 3. results and discussion the results show that moisture content of dura and tenera varieties was determined to be 17.4 and 18.2% which were adjusted to 9, 13 and 17% by adding 76.3, 39.8 and 3.3 g; and 82.3, 46.4 and 10.6g distilled water respectively. it was observed that the dura kernel coefficients of sliding friction for 9, 13 and 17% moisture contents (w.b.) for face a and face b of the fibre material were 0.471, 0.592 and 0.611; and 0.458, 0.510 and 0.532 respectively (table 1). it was observed that the coefficient of sliding friction increased as the moisture content increased from 9 to 17% for both faces. the coefficient of sliding friction for face a was higher than the coefficient of sliding friction for face b (table 1). in addition, the dura shell coefficients of sliding friction for 9, 13 and 17% moisture contents (w.b.) for face a and face b were 0.777, 0.675 and 0.777; and 0.650, 0.690 and 0.606 respectively. for the face a, it was observed that the coefficient of sliding friction decreased as the moisture content increased from 9 to 13% but increased as the moisture content increased from 13 to 17%. for the face b, the coefficient of sliding friction increased as the moisture content increased from 9 to 13% but decreased as the moisture content increased from 13 to 17%. the coefficient of sliding friction for face a was higher than coefficient of sliding friction for face b (table 1). the coefficient of sliding friction of face a was higher than that of face b for both palm kernel and shell because the surface of face a was rougher than the surface of face b and that, will influence the force of resistance to be overpowered before the palm kernel and shell can slide or roll. therefore, the surface roughness of face a of fibre material increased the frictional force that prevent either palm kernel or shell from sliding or rolling down the inclined plane. also, the coefficient of sliding friction of dura palm shell on any face of the fibre material was higher than the coefficient of sliding friction of dura palm kernel. the surface roughness of palm shell was higher than that of palm kernel and this will affect their forces of resistance, known as frictional force, to be overpowered. table 1: average values of dura kernel and shell coefficient of sliding friction on fibre material at different moisture content moisture content (%) dura palm kernel face a face b θo μ θo μ 9 25.2±1.92 0.471±0.04 24.6±1.67 0.458±0.04 13 30.6±1.67 0.592±0.04 27.0±1.41 0.510±0.03 17 31.4±1.67 0.611±0.04 28.0±1.22 0.532±0.03 moisture content (%) dura palm shell face a face b θo μ θo μ 9 37.8±1.79 0.777±0.05 33.0±1.73 0.650±0.04 13 34.0±1.87 0.675±0.05 34.6±1.52 0.690±0.04 17 37.8±1.92 0.777±0.05 31.2±1.79 0.606±0.04 the tenera kernel coefficients of sliding friction for 9, 13 and 17% moisture contents (w.b.) for face a and face b were 0.611, 0.606 and 0.621; and 0.546, 0.506 and 0.537 respectively (table 2). it was observed that the coefficient of sliding friction decreased as the moisture content increased from 9 to 13% but increased as the moisture content increased from 13 to 17% for both faces. the coefficient of sliding friction for face a was higher than the coefficient of sliding friction for face b (table 2). the tenera shell coefficients of sliding friction for 9, 13 and 17% moisture contents (w.b.) for face a and face b were 0.864, 0.953 and 0.927; and 0.805, 0.805 and 0.828 respectively (table 2). it was observed that the coefficient of sliding friction increased as the moisture content increased from 9 to 13% but decreased as the moisture content increased from 13 to 17% for the face a while the coefficient of sliding friction remained the same as the moisture content increased from 9 to 13% but increased as the moisture content increased from 13 to 17% for the face b. the coefficient of sliding friction for face a was higher than the coefficient of sliding friction for face b because the surface of face a was rougher than the surface of face b (table 2). the http://www.azojete.com.ng/ mailto:adepojuvo@funaab.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1005-1011. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adepojuvo@funaab.edu.ng 1009 degree of roughness of a material would determine the force required to overcome the resistant force of the material in order for an object to be able to slide or roll. furthermore, the coefficient of sliding friction of tenera palm shell on any face of the fibre material was higher than the coefficient of sliding friction of tenera palm kernel. notably, the coefficients of sliding friction of tenera variety of either palm kernel or shell were higher than that of dura variety. this is because there were differences in their masses and according to adepoju et al. (2023), “the mass of dura variety of either palm kernel or palm shell was higher than the mass of tenera variety”. they further explained that their masses would affect the force of gravity acting on them which would affect their ability to roll or slide down the plane. since dura variety of either palm kernel or palm shell had the higher mass, it would roll or slide down at a lower angle of inclination than the tenera variety with lower mass. table 2: average values of tenera kernel and shell coefficient of sliding friction on fibre material at different moisture content moisture content (%) tenera palm kernel face a face b θo μ θo μ 9 31.4±0.89 0.611±0.02 28.6±1.34 0.546±0.03 13 31.2±0.837 0.606±0.02 26.8±1.64 0.506±0.04 17 31.8±1.79 0.621±0.04 28.2±1.64 0.537±0.04 moisture content (%) tenera palm shell face a face b θo μ θo μ 9 40.8±1.79 0.864±0.05 38.8±1.64 0.805±0.05 13 43.6±1.34 0.953±0.04 38.8±1.79 0.805±0.05 17 42.8±1.79 0.927±0.06 39.6±0.89 0.828±0.03 for dura kernel on the face a of the fibre material, the moisture content had significant effect (p < 0.05) on the coefficient of sliding friction of dura kernel on face a of the fibre material (table 3). this means that the coefficients of sliding friction of at least two moisture contents of dura kernel were different from each other on face a of the fibre material (table 3). for dura kernel on the face b of the fibre material, the moisture content had significant effect (p < 0.05) on the coefficient of sliding friction of dura kernel on face b of the fibre. this means that the coefficients of sliding friction of at least two moisture contents of dura kernel were different from each other on face b of the fibre material (table 3). for tenera kernel on the face a of the fibre material, the moisture content had no significant effect ( p > 0.05) on the coefficient of sliding friction of tenera kernel on face a of the fibre. this means that the coefficients of sliding friction on face a of the fibre were significantly the same at any moisture content of the tenera kernel (table 3). for tenera kernel on the face b of the fibre material, the moisture content had no significant effect (p > 0.05) on the coefficient of sliding friction of tenera kernel on face b of the fibre. this means that the coefficients of sliding friction on face b of the fibre were significantly the same at any moisture content of the tenera kernel (table 3). table 3: summary of analysis of variance of the effect of moisture content of dura kernel and tenera kernel on coefficient of sliding friction for both faces of the fibre material sample/face source df ss ms f-value p-value dura kernel on the face a moisture content 2 0.05758 0.028792 17.96 0.000 error 12 0.01923 0.001603 total 14 0.07682 dura kernel on the face b moisture content 2 0.01433 0.007163 7.29 0.008 error 12 0.01180 0.000983 total 14 0.02612 tenera kernel on the face a moisture content 2 0.000581 0.000291 0.32 0.732 error 12 0.010892 0.000908 total 14 0.011473 tenera kernel on the face b moisture content 2 0.004409 0.002204 1.83 0.203 error 12 0.014480 0.001207 total 14 0.018888 http://www.azojete.com.ng/ mailto:adepojuvo@funaab.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1005-1011. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adepojuvo@funaab.edu.ng 1010 for dura shell on the face a of the fibre material, the moisture content had significant effect (p < 0.05) on the coefficient of sliding friction of dura shell on face a of the fibre. this means that the coefficients of sliding friction of at least two moisture contents of dura shell were different from each other on face a of the fibre material (table 4). for dura shell on the face b of the fibre material, the moisture content had significant effect (p < 0.05) on the coefficient of sliding friction of dura shell on face b of the fibre. this means that the coefficients of sliding friction of at least two moisture contents of dura shell were different from each other on face b of the fibre material (table 4). for tenera shell on the face a of the fibre material, the moisture content had no significant effect (p > 0.05) on the coefficient of sliding friction of tenera shell on face a of the fibre. this means that the coefficients of sliding friction on face a of the fibre were significantly the same at any moisture content of the tenera shell (table 4). for tenera shell on the face b of the fibre material, the moisture content had no significant effect (p > 0.05) on the coefficient of sliding friction of tenera shell on face b of the fibre. this means that the coefficients of sliding friction on face b of the fibre were significantly the same at any moisture content of the tenera shell (table 4). table 4: summary of analysis of variance of the effect of moisture content of dura shell and tenera shell on coefficient of sliding friction of the two faces of the fibre material sample/face source df ss ms f-value p-value dura shell on the face a moisture content 2 0.03427 0.017134 6.80 0.011 error 12 0.03023 0.002519 total 14 0.06449 dura shell on the face b moisture content 2 0.01771 0.008857 5.09 0.025 error 12 0.02086 0.001738 total 14 0.03858 tenera shell on the face a moisture content 2 0.02084 0.010418 3.80 0.053 error 12 0.03287 0.002739 total 14 0.05371 tenera shell on the face b moisture content 2 0.001698 0.000849 0.46 0.641 error 12 0.022067 0.001839 total 14 0.023765 the summary of separation of means for the coefficient of sliding friction on the fibre material using tukey method is shown in the table 5. for dura palm kernel on the face a of the fibre, the coefficient of sliding friction at 9% moisture content was significantly different from the coefficients of sliding friction at both 13% and 17% moisture contents that were insignificantly different from each other (column 2). for dura palm kernel on the face b of the fibre, the coefficients of sliding friction at 9% and 17% moisture contents were significantly different from each other but were significantly the same with the coefficient of sliding friction at 13% moisture content (column 3). for dura palm shell on the face a of the fibre, the coefficient of sliding friction at 13% moisture content was significantly different from the coefficients of sliding friction at both 9% and 17% moisture contents that were not significantly different from each other (column 4). for dura palm shell on the face b of the fibre, the coefficients of sliding friction at 13% and 17% moisture contents were significantly different from each other but were significantly the same with the coefficient of sliding friction at 9% moisture content (column 5). table 5: summary of separation of means using tukey method for the coefficient of sliding friction on the fibre material. moisture content (%) dura kernel a dura kernel b dura shell a dura shell b 9 0.471±0.04a 0.458±0.04a 0.777±0.05a 0.650±0.04ab 13 0.592±0.04b 0.510±0.03ab 0.675±0.05b 0.690±0.04a 17 0.611±0.04b 0.532±0.03b 0.777±0.05a 0.606±0.04b means that do not share a letter are significantly different 4. conclusion this study obtained values for coefficient of sliding friction as affected by the moisture contents of palm kernel and palm shell of the two varieties on two faces of fibre material which are needed to understudy canvas materials for frictional separation. palm shell demonstrated a higher coefficient of sliding friction than palm kernel across both dura and tenera varieties. furthermore, the tenera variety exhibited greater frictional http://www.azojete.com.ng/ mailto:adepojuvo@funaab.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1005-1011. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adepojuvo@funaab.edu.ng 1011 properties than dura. a significant influence of moisture content on friction was observed for the dura variety, whereas its effect on the tenera variety was statistically insignificant. references adepoju, vo. 2019. design and fabrication of a draper separator for palm kernel and shell, unpublished master of engineering dissertation, department of agriculture and bio-resources engineering, federal university of agriculture, abeokuta. adepoju, vo., aderinlewo, aa., dairo, ou., adetunji, or., and babalola, aa. 2023. determination of some physical properties of palm kernel and shell in relation to frictional separation. journal of natural science, engineering and technology, 22(1):39-52. adzimah, sk. and seckley, e. 2009. modification in the design of an already existing palm nut-fibre separator. african journal of environmental science and technology, 3(11):387-398. akubuo, co. and eje, be. 2002. palm kernel and shell separator. biosystems engineering, 81(2), 193-199, doi: 10.1016/j-biosystemseng. 2001.0029. amoah, jy., aggey, m. and annumu, s. 2007. cracked mixture sieving rates and efficiencies in small-scale palm nut processing in ghana. ghana journal of science, 47: 69-81. asae standards (1998). moisture measurement – unground grain and seeds. american society of agricultural engineers (asae), s352.2:551. davies, rm. and zibokere, ds. 2011. effect of moisture content on some physical and mechanical properties of three varieties of cowpea (vigna unguiculata (l)walp). agric eng int. cigr journal, 13(1):1-8. olasumboye, a. and koya, o. 2014. a rotary separator for the dry mixture of palm kernel and shell. innovative systems design and engineering, vol.5, no. 7, pp32-41 olayanju, tma. 2002. design, fabrication and evaluation of a beniseed (sesamum indicum l.) oil expeller. an unpublished phd. thesis at the department of agricultural engineering, university of ibadan, nigeria. orhevba, ba., chukwu, o., osunde, zd., and ogwuagwu, v. 2013. influence of moisture content of the yield of mechanically expressed neem seed kernel oil. academic research international, 4 (5): 252 – 257. http://www.azojete.com.ng/ mailto:adepojuvo@funaab.edu.ng corresponding author’s email address: mswulgo@gmail.com 783 arid zone journal of engineering, technology & environment original research article spatio-temporal dynamics and forecasting of urban land use and land cover change in maiduguri using google earth engine and machine learning m. shettima1,2*, m. hasnat2, g.h. sambo1, a.g. bukar 3, a.m. boyoma2, and m. a. mohammed4 1department of geography, university of maiduguri, borno state 2department of environmental science, integral university lucknow, india 3department of civil and water resources engineering, university of maiduguri 4department of computer science and engineering, integral university lucknow, india *corresponding author’s email address: mswulgo@gmail.com article information abstract urbanization is one of the defining processes of the 21st century, particularly in the rapidly developing country like nigeria. google earth engine (gee) and machine learning techniques were utilized in this study to quantify spatio‐temporal landuse and landcover (lulc) dynamics for 2000, 2010, 2020, and 2025 and to forecast the future trends to 2035 in maiduguri metropolis. a decadal classification framework was adopted to facilitate long-term lulc analysis, while the inclusion of 2025 enables the capture of emergent post-conflict land transformations and the spatial impacts of the 2024 flood event, which significantly altered land cover configurations. the projection to 2035 maintains a 10-year forecasting interval, ensuring consistency with established temporal benchmarks. landsat imagery of the selected years was acquired and processed in gee using the classification and regression tree (cart) algorithm to classify major lulc categories, including built-up areas, cropland, vegetation, wetlands, bare surface, and water body. the overall accuracy for all the assessed years was 80% which indicates high classification reliability. the generated lulc was used to carryout regression models (linear for five classes and polynomial for cropland) were fitted in python’s scikit‐learn to project 2035 distributions. the results revealed that built‐up area expanded from 324.8 km² (19.0%) in 2000 to 464.9 km² (27.2%) in 2025, cropland plummeted from 966.9 km² (56.7% ) to 103.6 km² (6.1% ) and bare land surged from 33.6 km² (1.9% ) to 834.1 km² (48.9%). the wetlands and water bodies exhibited fluctuating trends linked to insurgency‐driven land abandonment and the 2024 flood event. forecasts for 2035 indicate bare land will dominate nearly 72% of the study area, built‐up will reach 517.4 km², and cropland will shrink to 75.3 km². given these findings, the study strongly recommends integrated sustainable land-use planning and conflictsensitive restoration strategies to mitigate escalating environmental and socioeconomic risks in rapidly urbanizing conflict zones like maiduguri. received: 20th july 2025 revised: 12th august 2025 accepted: 14th august 2025 keywords: urban lulc spatiotemporal dynamic classification and regression tree (cart) google earth engine machine learning landsat imagery © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction urbanization has emerged as one of the most significant transformations of landscapes, socio-economic structures, and environmental systems in 21st century, particularly in the developing nations (haddad, 2024). the world's urban population is projected to rise to more than 60% of the global population by 2050, up from just over 50% in 2018 (wang and kintrea, 2021). this trend is part of a broader shift in human settlement patterns, driven by economic opportunities, technological advancements, and the concentration of services and infrastructure in urban areas (yasin et al., 2024). the epicenter of urbanization has shifted from the northern hemisphere to the southern hemisphere with cities in asia and africa experiencing the fastest azojete september 2025. vol.21(3):783-793 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/009 www.azojete.com.ng mailto:mswulgo@gmail.com mailto:mswulgo@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 784 growth rates (huang and xu, 2022). by 2050, asia and africa are expected to account for nearly 90% of the world's urban population growth, with countries like india, china, and nigeria (ekeh and jegede, 2024) rapid urbanization in nigerian cities is driven by employment opportunities, socio-economic, trading activities as well as insecurity in the rural areas, leading to significant population growth and spatial expansion, environmental degradation and unsustainable practices, impacting landscape design and sustainability (oladunmoye, 2024) the environmental impacts of rapid urbanization are a major concern. the conversion of agricultural land and forests to urban uses has significant implications for food security and biodiversity (ogunbode et al., 2025) therefore, monitoring urban expansion is crucial for effective urban planning, management and spatial development models (ding et al., 2022). recent advancements in geospatial technology and machine learning have significantly enhanced the ability to monitor urban land use and land cover (lulc) changes. these technologies enable the analysis of land use and land cover (lulc) changes providing insights into urban growth patterns and facilitating urban planning. several studies have shown that combining these technologies enhances the accuracy of urban area assessments (prasetyadi et al., 2024; al mazroa et al., 2024; farooqi, et al 2024; raj et al., 2024). however, despite the increasing number of lulc studies in maiduguri, most previous research (dami et al. 2011; ikusemoran and mohammed, 2014; babagana, et al 2019; bello 2019; umar, et al. 2023; danung et al., 2025) have been limited to retrospective analysis using conventional geospatial techniques and they generally lack predictive modeling capabilities to forecast the future urban land use which are critical for proactive planning and sustainability. therefore, this study integrates google earth engine and machine learning technology to assess the spatiotemporal dynamics and forecasting of urban land use and land cover changes in maiduguri metropolis between 2000 to 2025. this approach offers a robust framework to support sustainable urban development and spatial policy formulation in urban environments. 2. the study area and methodology 2.1 study area maiduguri metropolis is the capital and largest city in borno state, north-eastern nigeria (figure 1c) and is the second largest state in nigeria after niger state. borno state is bounded in north-east by chad, east by cameroon, north by niger, west by yobe state and south by gombe and adamawa states. it is located between latitudes 11°n and 13°n and longitudes 10°e and 14°e. spanning 65,868 square kilometers. it comprises of 27 local government areas. maiduguri metropolis is located between latitudes 11° 42’00’’n and 12° 00’ 00” n and from longitudes 12° 54’ 00” to 13°20’ 00” e. it covered about 648 km2. maiduguri metropolis encompasses approximately four local government areas (lgas), including maiduguri metropolitan council and parts of konduga, jere, and mafa lgas (figure 1d). the metropolis typically receives rainfall from june to september. however, during rainy years, precipitation may begin earlier than june and extend beyond september. in some cases, rainfall has been recorded as early as april and lasting into october (ikusemoran & jimme, 2014). the rainfall pattern in the area generally shows spatial and temporal variability and has been characterized by a single maximum, with a peak around august. in the dry period, the temperature over the area may go up to 42°c. during harmattan, it may be as low as 15°c. it has a mean annual maximum temperature of 35°c with a mean temperature ranging between 30° and 40°c. the months of march and april are usually the hottest months, while november and january are the cold and dry periods of harmattan. maiduguri is drained by the rivers ngadda and ngaddabul which acts as a tributary to the ngadda and the vegetation is similar to sahel savannah which is surrounded by shrubby vegetation interspersed with tall tree woodland (bukar et al. 2025). 2.2 methodology this study systematically applied remote sensing and geospatial analysis techniques to detect lulc changes in maiduguri metropolis for the years 2000, 2010, 2020, and 2025. a decadal interval (2000–2020) align with standard remote sensing practices and ensure consistency in landsat imagery quality and coverage. the inclusion of 2025 introduces a mid-decade snapshot to reflect recent urban acceleration and post-conflict land transformations. for forecasting, a 10-year projection to 2035 was adopted to maintain methodological continuity with earlier intervals. gee was utilized to acquire and preprocess satellite imagery. it provides access to a multi-petabyte catalog of satellite imagery, including modis, landsat, and sentinel data, facilitating extensive environmental analyses (wilson et al., 2025). the classification and regression tree (cart) algorithm was used for supervised classification, while regression modeling using python's scikit-learn library was used to project future lulc trends. this combined approach facilitated the production and projection of accurate lulc. http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 785 figure 1: study area description:(a) africa showing nigeria (b) nigeria showing borno state (c) borno state showing maiduguri metropolis (d) maiduguri metropolis figure 2: methodology flow chart http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 786 table 1: tools and software environment software/platform purpose google earth engine satellite image processing, classification (cart), lulc mapping python (scikit-learn) regression modeling and forecasting qgis map layout design, spatial validation, additional visualization 2.2.1 dataset acquired landsat imagery from four time periods was used to generate lulc maps. table 2: dataset details year band description sensor dataset id reflectance scaling spatial resolution 2000 visible spectrum (true color) landsat 5 landsat/lt05/c02/t1_l2 0.0 – 0.3 30m 2010 visible spectrum (true color) landsat 5 landsat/lt05/c02/t1_l2 0.0 – 0.3 30m 2020 surface reflectance (true color) landsat 8 landsat/lc08/c02/t1_l2 0.0 – 0.3 30m 2025 surface reflectance (true color) landsat 9 landsat/lc09/c02/t1_l2 0.0 – 0.3 30m source: usgs earth explorer, 2025 2.3 data processing and analysis 2.3.1 image preprocessing and compositing the selected images were filtered by acquisition date (january to december), cloud cover (less than 20%), and the geographic bounds of maiduguri metropolis. each year's imagery was processed to create a median composite and clipped to the study area. true color band combinations were used for visual inspection, and reflectance values were scaled appropriately for visualization (xie et al., 2021). for landsat 5, b3 (red), b2 (green), b1 (blue) were used, while for landsat 8/9, bands sr_b4 (red), sr_b3 (green), sr_b2 (blue) were employed. reflectance values were scaled between 0.0 and 0.3 for visual interpretation (table 2). 2.3.2 supervised classification using cart the lulc classification was categorized into six major classes: water, built-up, vegetation, cropland, wetland, and bare surface. representative training samples for each class were manually digitized through visual interpretation of high-resolution satellite imagery, complemented by local knowledge to improve accuracy (barnoaiea et al., 2024). supervised classification was carried out using the classification and regression tree (cart) algorithm within the gee environment. the trained cart model was then applied to annual image composites to generate lulc maps for the selected reference years. 2.3.3 accuracy assessment to ensure the reliability and validity of the land use/land cover (lulc) classification results, accuracy assessment was conducted using the confusion matrix approach and matrix and the overall accuracy metric, calculated as: this method evaluates how well the classifier (cart algorithm) was able to assign the correct land cover labels by comparing the predicted classes against ground truth data (test samples). for all the years assessed http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 787 (2000, 2010, 2020, and 2025) the classification achieved the overall accuracy 80% and above (table 3) suggesting good spectral separability and quality training data (helmud et al., 2024). table 3. accuracy assessment year overall accuracy (%) 2000 89.1 2010 81.9 2020 87.5 2025 80.6 source: author’s analysis, 2025. 2.3.4 regression-based forecasting of lulc for 2035 to project future lulc (for 2035), regression models were built using lulc area data from 2000 to 2025. python’s scikit-learn library was used for this purpose. the approach involved fitting trend lines for each land cover class (water, built-up, vegetation, cropland, wetland, and bare surface) based on historical area data. these models then predicted the expected area coverage of each class in the year 2035. (i) linear regression model linear regression is a statistical technique used to analyze the linear relationship between a dependent variable and one or more independent variables, forming the basis of statistical learning theory (jacobs, 2023). for classes with linear trends (built-up, bare surface, wetland, vegetation, water), simple linear regression was used, expressed as: 𝛾 = 𝛽0 + 𝛽1𝑥 + 𝜀 2 where γ = projected lulc area (in km²), χ = year (e.g., 2000, 2010, etc.), β0 = intercept, β1 = slope (rate of change), ε = random error term (ii) polynomial regression model polynomial regression models (prm) estimate a dependent variable's parameters using independent variables with polynomial relationships, including interactions up to third order. model selection involves minimizing multicollinearity and applying eight selection criteria to identify the best-fitting model (abdullah et al., 2011). the model used for cropland, which exhibited nonlinear trends: 𝛾 = 𝛽0 + 𝛽1𝑥 + 𝛽2𝑥 + 2 𝜀 3 β2 = coefficient of the squared term, accounting for curvature in the trend model performance was evaluated using r² scores and mean squared error (mse) to assess goodness of fit. once validated, the models were used to estimate the area of each lulc class for the year 2035 by substituting χ=2035 in the respective regression equations. these models were also applied to forecast rainfall (sittichok et al., 2024). 3. results and discussion the analysis of land use and land cover (lulc) changes in maiduguri between 2000 and 2025 revealed a distinct trend (table 4). one of the most notable shifts is the dramatic expansion of built-up areas which increased from 324.80 km² (19.03%) in 2000 to 464.89 km² (27.24%) presently in 2025 (table 4). the built-up area expanded consistently, with a net gain of 4.997 km² between 2000 and 2010, a much sharper increase of 104.189 km² from 2010 to 2020, and an additional 30.903 km² between 2020 and 2025 (figure 3). these totals approximately 140 km² gained over 25 years. this finding is consistent with similar studies conducted in maiduguri previously (babagana, et al 2019; bello 2019). the consistent increase particularly the spike during the 2010–2020 demonstrates urban growth driven by population growth, rural-to-urban migration, and the influx of internally displaced persons (idps) resulting from the boko haram crisis which intensified after the http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 788 year 2009 (egbuta, 2024). the shorter five-year period (2020-2025) also shows significant growth indicating the continued demand for residential and commercial land (figure 3). table 4: changes in lulc area between 2000 and 2025 (in km²) class 2000 2010 2020 2025 (km²) (%) (km²) (%) (km²) (%) (km²) (%) water 68.634 4.02 73.243 4.29 19.243 1.13 36.984 2.17 built-up 324.802 19.03 329.799 19.33 433.988 25.4 464.891 27.24 wetland 302.539 17.72 265.401 15.55 122.708 7.19 253.105 14.83 vegetation 10.394 0.61 13.976 0.82 34.699 2.03 14.22 0.83 cropland 966.9 56.65 977.334 57.27 284.646 16.6 103.558 6.07 bare surface 33.63 1.97 47.145 2.76 811.614 47.5 834.141 48.89 total 1706.89 100 1706.898 100 1706.89 100 1706.89 100 source: author’s analysis, 2025. figure 3: net changes of lulc classes while cropland the dominant land use in 2000, covering 966.90 km² (56.65%) has experienced a severe and sustained decline, decreasing to 103.56 km² (6.07%) today in 2025 (table 4) and clearly depicted in figure 3. after a slight increase of 10.434 km² between 2000 and 2010, cropland suffered massive declines of 692.688 km² from 2010 to 2020 and a further 181.088 km² from 2020 to 2025 (figure 3). this finding corroborates with study by bello, et al. (2023) and similar study conducted by guo et al., (2024) in hainan island, china. the cumulative net loss of approximately 863 km² represents a significant conversion of agricultural land to other uses. this change is largely attributed to the prolonged inaccessibility of farmlands due to ongoing insurgency which has led to widespread land abandonment (ya’u, 2024). this land abandonment has severely impacted food security, disrupted local economies, and triggered widespread rural–urban migration (okeleye et al., 2023). agriculture, being the backbone of rural livelihoods, has suffered a major setback, leading to increased poverty, market instability, and dependence on humanitarian aid (fao, 2021; ocha, 2023). bare surface revealed a reverse trend from cropland, increasing steadily across all periods. 13.515 km² (2000– 2010), 764.469 km² (2010–2020), and 22.527 km² (2020–2025) (figure 3). in 2000, bare surface constituted a mere 33.63 km² (1.97%) of the total area and today in 2025, it is rose to 834.14 km², accounting for a staggering 48.89% of the total land area (table 4). the net gain of over 800 km² highlights ongoing land degradation, likely resulting from vegetation loss, overgrazing, drought, and erosion sharp spike during the 2010–2020 period which coincides with the most significant loss of cropland (abdulmalik and zewide, 2021). thus, suggesting that croplands are left as barren land due to insurgency (ya’u, 2024). moreover, the satellite images used for classification were captured predominantly during the dry season, when vegetation cover is naturally reduced, allowing the extent of bare surfaces to be more accurately detected. this seasonal timing 2000→2010 2010→2020 2020→2025 water 4.609 -54 17.741 built-up 4.997 104.189 30.903 wetland -37.138 -142.693 130.397 vegetation 3.582 20.723 -20.479 cropland 10.434 -692.688 -181.088 bare surface 13.515 764.469 22.527 -700 -500 -300 -100 100 300 500 700 900 c h an ge s (k m 2 ) http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 789 strengthens the interpretation that the observed expansion of bare surface is not merely a short-term seasonal effect but reflects a long-term and structural shift in land use. wetlands also experienced significant fluctuation. initially covering 302.54 km² (17.72%) in 2000, their extent fell drastically to 122.71 km² (7.19%) in 2020. however, the trend reversed between 2020 and 2025, with a gain of 130.397 km² (figure 3) and it is not surprising, considering the flood that occurred in maiduguri in 2024, which submerged more than 40% of the metropolis unicef, (2024) and left behind extensive wetland areas. similarly, water bodies decrease from 68.63 km² (4.02%) in 2000 to a low of 19.24 km² (1.13%) in 2020, before slightly recovering to 36.98 km² (2.17%) in 2025 (table 4). a modest recovery of 17.741 km² in the last five years (figure 3) aligns with mokhtarisabet and okoduwa’s (2025) observation in maiduguri metropolis, where ndwi analysis revealed a long-term decline in surface water and high-moisture areas driven by climate variability, vegetation loss, and urban expansion, followed by a slight recovery in 2024 linked to record-high rainfall of 863 mm and possible seasonal hydrological recharge. vegetation showed modest fluctuations, increasing from 10.39 km² (0.61%) in 2000 to 34.70 km² (2.03%) in 2020, before dropping again to 14.22 km² (0.83%) in 2025 (table 4). this near balance in gains and losses over the 25 years indicates that vegetation has remained relatively static in net terms (figure 3). this indicate that vegetation gains prior to the peak insurgency years were gradual, while a sharp increase during peak insurgency likely resulted from farmland abandonment and reduced anthropogenic disturbance. the post-insurgency decline coincides with population resettlement, agricultural expansion, and renewed urban growth, which accelerated vegetation clearance. climatic variability, particularly the statistically significant upward rainfall trend of 3.33 mm/year from 1987 to 2024 and extreme precipitation events such as the 863 mm recorded in 2024 (mokhtarisabet, and okoduwa, 2025), likely amplified seasonal greening in wetter years and influenced regeneration rates, indicating the combined roles of socio-political instability and climate-driven hydrological changes in shaping vegetation dynamics. figure 4: land use and land cover dynamic of maiduguri metropolis 3.1 forecasted land use/land cover areas for 2035 in maiduguri metropolis based on regression analyses of lulc results from 2000 to 2025, future projections for the lulc distribution of maiduguri metropolis in 2035 indicate substantial landscape transformations (figure 5). the most striking outcome of the projection is the anticipated dominance of bare land, which is expected to expand significantly to approximately 1,227.89 km², accounting for nearly 72% of maiduguri’s total land area. this finding aligns with that of bedada (2024), who also reported a substantial increase in barren land alongside built-up areas. however, some other studies contradict this result, highlighting instead an increase in built-up areas (paudel et al., 2024; ban, 2024). the scale of this expansion is alarming, indicating that if current trends persist, most http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 783-793. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mswulgo@gmail.com 790 of the productive and vegetated land in maiduguri will transition into bare surface by 2035 posing serious ecological threats and undermining land sustainability. in the same vein, the built-up area is forecasted to reach approximately 517.44 km² (figure 5), further validating the persistent and aggressive nature of urban. the expansion of urban land use, although indicative of economic growth and modernization, poses considerable challenges for spatial planning, waste management, traffic congestion, and provision of urban services in a rapidly evolving landscape (hu et al., 2023; kanav et al., 2024). conversely, cropland projected to decline drastically to just 75.32 km² (guo et al., 2024). this forecast modeled using polynomial regression due to its observed non-linear fluctuations over the past decades. the wetland area is predicted to expand modestly to about 147.15 km² (figure 5). vegetation cover is expected to occupy 28.78 km² by 2035 an increase from current values but still a marginal share of the total area while water bodies are forecasted to shrink to 10.22 km² (figure 5) showing ongoing hydrological stress. the continued reduction in surface water availability poses risks to domestic supply, irrigation, and ecosystem health, particularly in a semi-arid environment where water scarcity is already a pressing issue (hassan et al., 2024) figure 5: forecasted land use/land cover areas for 2035 in maiduguri metropolis 4. conclusion the spatio-temporal analysis of land use and land cover (lulc) changes in maiduguri metropolis reveals a significant spatial transformation over the past 25 years, marked by rapid urban expansion, severe cropland decline, and increasing bare surface. built-up areas grew steadily driven by population pressures and sociopolitical instability (boko haram insurgency) while cropland once the dominant land use experienced a drastic reduction of over 860 km². concurrently, bare surface expanded from just 1.97% in 2000 to nearly 49% in 2025 indicating an extensive land degradation likely influenced by insurgency, deforestation and poor land management. while waterbody, wetlands and vegetation exhibited fluctuations the 2024 flood notably contributed to a temporary rise in wetland and water bodies coverage showcasing the role of extreme weather events in shaping land cover patterns. projections for 2035 indicate even more critical shifts, with bare land expected to dominate up to 72% of maiduguri’s total area and cropland shrinking further to just 75.32 km². built-up areas are expected to continue expanding reaching over 517 km² this growth poses serious challenges to sustainable urban development. although slight improvements are predicted for wetlands and vegetation, they remain marginal. these findings revealed that integrating cloud-based platforms like gee and machine learning not only enables real-time monitoring but also offers a scalable approach for evidence-based interventions in urban environments undergoing rapid and unregulated transformation. in view of these findings, this study recommended an integrated sustainable land use planning, conflict-sensitive land restoration programs and water resource management to mitigate the severe environmental and socio-economic constraints. references abdullah, n., ahmed, a., and jubok, zh. 2011. an improved volumetric estimation using polynomial regression. journal of science and technology, 3(2): 29–42. issn 2229-8460. -100 100 300 500 700 900 1100 1300 1227.89 517.44 147.15 75.32 28.78 10.22p re d ic te d a re a (2 0 3 5 ) [k m ²] bare surface built-up wetland cropland vegetation water http://www.azojete.com.ng/ mailto:mswulgo@gmail.com arid zone journal of engineering, technology and environment, june 2025; 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https://doi.org/10.3126/jes2.v3i2.72191 https://doi.org/10.1109/ic3ina64086.2024.10732244 https://doi.org/10.60151/envec/rodf5502 https://doi.org/10.3390/rs16224161 https://doi.org/10.55164/ajstr.v27i3.253507 https://www.unicef.org/appeals/nigeria/situation-reports https://doi.org/10.1177/0975425321999081 https://doi.org/10.3390/data10010008 https://doi.org/10.1007/s13351-021-1138-3 https://doi.org/10.59569/jceeas.2022.2.1.89 https://doi.org/10.3390/rs14143253 https://doi.org/10.55737/qjss.751235379 arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):241-260 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 241 a review and critique of advances in the mitigation of harmonics t. a. abdul-hameed1*, m. f. akorede2 and y. abdulrahman2 1department of electrical and electronic engineering, federal polytechnic, ede, nigeria. 2department of electrical and electronic engineering, university of ilorin, ilorin, nigeria. *corresponding author's email address: kunleoluyori@gmail.com article information submitted 18 september, 2021 revised 20 november, 2023 accepted 23 february, 2024 keywords: distribution system filters harmonics mitigation optimization simulation abstract in electrical power distribution systems, harmonics has always been a major concern as it can adversely affects the performance of the connected loads when tolerable or recommended standard limits are exceeded. there have been consistent and considerable efforts to study the sources, generation and control of harmonics over the years. this paper presents an extensive literature review of the major works on harmonics in the last two and a half decades. the merits and demerits, advantages and limitations of such work were critically reviewed. it was discovered that a lot remains to be done in the optimization of filters especially the hybrid types and that the design of a filter that can simultaneously mitigate low and higher order harmonics has not been thoroughly researched. this paper is intended as a guide for researchers that are interested in solving harmonics problems to identify the gray areas to concentrate and improve on 1.0 introduction harmonics are defined as periodic components of a distinct frequency superimposed on a waveform of a fundamental frequency. harmonics has been in existence for long; since steinmetz published a book in 1916 which devoted considerable attention to the study of harmonics in three-phase power systems and also the invention of the very first generators and transistor tubes in the 1930s (michael, 1999). since non-linear loads were quite few then, its effects were not easily noted. between late 1980s and early 1990s, there were tremendous increment in the use of power electronic loads. the increment continues till date leading to creation of more harmonics on electrical power distribution system despite the advantages of power electronic loads in efficiency and controllability. connection of more electrical loads to such power systems leads to deterioration in power quality (adesina and fakolujo, 2015; rodriguez and saldanha, 2012; nicholson, 2006; holcomb and briggs, 1994). different researchers have reviewed various aspects of harmonics ranging from the sources, generations, to the types and the various forms of mitigation techniques and effects of harmonics current and/or voltages on power distribution network and consumer devices (czarnecki, 2000; zamora et al., 2003; akagi, 2006; arif et al., 2012; mujawar et al., 2013; durdhavale and ahire, 2016; etc.) some of such reviews are usually focused towards an integral aspect of harmonics studies. missing gaps are always existing in each of the works. it is on the basis of this that this paper, from the point of view of power electronics education, intends to educate and identify to a large extent some of the missing gaps in many of the existing works on harmonics. this paper presents a comprehensive holistic review of major works on harmonics done over the last two decades (1998 to 2023). http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 242 2. a survey of research efforts on the nature, types and sources of harmonics many authors had researched into the nature, types, sources and methods of preventing, controlling or mitigating harmonics in the last two decades and the efforts still continues till date. many of these research efforts relating to the nature, types, sources and methods of mitigating harmonics are reviewed in this study. middlekauff and collins jr. (1998) used simulation method to model an industrial facility with 24kv distribution systems that serves a load which produces harmonics in large quantity. the model was not error free from the phase references, and the orientation of voltage and current transformers which can displace phase angles as well as error due to the type of measuring instrument in use. the effects of interharmonics generated from induction furnace on a power distribution network was investigated by dugan and conrad (1999) using a specific case study. it was concluded that interharmonic frequencies if not properly mitigated can have significant effect on power quality. many options like adjustment to induction furnace parameters, power supply reconfiguration, use of filters, were proposed as possible solutions. optimization methods and the use of fast switching devices were left out of the study. experimental data were collected by jalilian et al. (2000) to investigate the behavior of a 7.5 kw high efficiency cage induction motor fed by distorted supply. additional losses in the motor as a result of harmonics were estimated using the weighted-average method. however, a major setback observed in the study is that the derived derating factor (df) becomes valid and reliable under conditions close to full load. the maximum weighted total harmonic distortion (wthdmax) is therefore only a limit in theory. the importance, essence and significance of controlling harmonics by both the end user and the utility company was the focus of the work by grady and santoso (2001). while using the ieee std 519-1992 as an excellent background to address both concerns, it was discovered that the issues of acceptable levels of harmonics from nonlinear loads can only be adequately addressed when viable measures are taken from both sides. as good as the work may be, the details of mitigation methods and techniques were not considered. dickin et al. (2001) investigated harmonics in a major petrochemical facility in canada. the study investigated the level of harmonics within the plant; compliance with the utility requirements at the point of common coupling (pcc) at 138 kv; and meeting the ieee std 519 – 1992; identifying the existence or otherwise of harmonic resonance. the study may be considered to be defective from few perspectives. in real time scenario, some of the assumption made in arriving at conclusions in the study may not hold. the utility harmonic impedance profile was modeled based on the harmonic spectrum provided by the utility. this may be inaccurate. all adjustable speed drives (asds) were assumed running at rated load and rated speed for maximum harmonic generation. this is an ideal case that may not hold in reality all the time. the current spectrum for medium-voltage adjustable speed drives (asds) was based on measurements taken during factory acceptance tests rather than the typical published values. this is usually not constant. the electric heaters were assumed not to produce any harmonics. this may not be true. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 243 the use of nonlinear control devices and its associated effects in causing harmonics distortion leading to malfunctioning of sensitive devices like metering instruments, on-line process analyzers, measuring devices, were central to the work of shwehdi et al. (2002). a typical petrochemical company in saudi arabia was the case study used. however, the study did not conduct an in-depth investigation into the complexity and the dynamic sensitivity of different chemical processes and their electronic and digital controllers which will have effects on current and voltage harmonics in the system. an in-depth discussion on harmonics in the petrochemical industry was carried out by nelson (2002). harmonics caused by saturable magnetic devices like generators and transformers and their controls were covered. similarly, harmonics from power electronic devices like variable speed drives (vsd) and uninterruptible power supply (ups) systems were extensively covered. a case study of harmonics in a petrochemical plant was presented. the study, however, did not cover an in-depth investigation of fast varying harmonics as a result of varying the loads connected at the output. a quantification of the harmonic distortion, the total annual sags and short interruptions of customer classes of the utility of alexandria based on key indices was reported in eassa et al. (2003). the information in this research was of crucial importance in supporting issues about quality service regulations for customer's satisfaction. fast switching devices and active filters that can be used in controlling high order harmonics were left out of the study. an original hypothetical signal was compared to the reconstructed signal using the new least mean square (lms) algorithm in manmek et al. (2003). the reconstructed signal was the same as the original signal in the steady state (after about 50 msec.). however, the initialization process results in a mismatch in phase information and this is a major limitation to the method. the load-flow, short-circuit, transient-stability and harmonic studies typically undertaken in petro chemical plants were outlined in dall et al. (2006). the predominant harmonic current sources within the electrical system of an lng plant are the large variable speed drives for the liquified natural gas compressors. with increasing variable frequency drive compressor loads, the supply voltage to these drives is also increased. it was established that occurrence of several parallel resonances at or above the 20th harmonic was the major limitation. when harmonic current injections coincide with or are close to the resonances on the system, the resonance is excited and a large component of voltage is produced at the resonant frequency leading to excessive voltage distortion. rojin (2006) reviewed the power quality problems and its effects on different apparatuses and methods for the correction. some power quality enhancement devices such as harmonic filters, isolation transformers were suggested and listed as means of overcoming power quality problems in general. the work was not a detailed investigation of harmonics mitigation techniques and its several associated challenges. a neural network-based solution for the problem of measuring the actual amount of harmonic current injected into a power network by an individual nonlinear load was researched into by mazumdar et al. (2007). the distinction between load harmonics and supply harmonics were investigated. it was demonstrated that depending on the purity (cleaned or distorted) of the voltage supply to a load, there would always be a difference in the current distortion of the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 244 load. a source modeling scheme was developed and verified in simulation and on the actual field data. as a corrective measure to mitigate the harmonics, the technique projected the condition of the voltage distortion at the point of common coupling in relation to the ieee 519 standard if the current harmonics in a nonlinear load are decreased. the scheme has the advantages of requiring only waveforms of voltages and currents for its operation and can be applied in both single and three phase systems. there was no investigation as regards the efficiency of optimization methods in controlling harmonics in the research. new indices to standardize and measure harmonics parameters were proposed by vlahinic et al. (2008). extensive harmonic measurements of a real distribution system were performed to prove the usefulness of the proposed indices. the total rated distortion (trd) was suggested to simplify and standardize the harmonic current measurements and a second index that represents the increase of the harmonic voltage distortion with trd, the equivalent harmonic impedance zeq, was proposed as an efficient way of characterizing a particular site. the zeq was based on the transformer short-circuit impedance, although many other unknown parameters influence its value (the background distortion, the transformer nonlinearity, the diversity between different loads). both parameters depend on a variety of factors, and their relationship must necessarily vary with the measurement site position. the demerit is that further measurements are needed to explain the observations in more detail. furthermore, optimization methods were missing in the work. bueno et al. (2010) investigated instantaneous active and reactive power control on electric traction systems and proposed a compensation scheme to mitigate the harmonic current distortion and reduce the negative sequence under unbalanced operation in steady state. the compensation scheme reduced the system’s current total harmonic distortion to less than 20% and reduced the overall unbalance from 97% to 18% for the worst-case scenario. furthermore, the algorithm developed effectively has a good control on the power factor. it was established that there must be a trade-off between the amount of unbalanced correction and the harmonics reduction. this is a consequence of the finite amount of energy stored by the active filter in its input inductance and the dc-link capacitor. the scheme was validly tested in a railway system and was found reliable. the scheme however did not take optimization methods into consideration. this is a major disadvantage especially when it was established by the work that there is a trade-off between the amount of unbalanced correction and the harmonics reduction. furthermore, the scheme may be relatively uneconomical. the sources of power system harmonics and the negative impacts of harmonics were discussed in xuemei and yongmei (2012). the study suggested how to strengthen protection measures, by reforming the harmonic source and installing the mitigation equipment to suppress the harmonics. details exposition of how to make use of software tools to mitigate harmonics were not thoroughly investigated and explored. abdelaziz et al. (2013) extensively reviewed power system harmonics in the petrochemical industries. the work was a detailed guide for further researches in effects of harmonics, mitigation techniques and distortion allowable limits. an in-depth investigation of fast varying harmonics as a result of varying the loads connected at the output such as the work piece in an induction furnace and an extensive discussion of hybrid optimization methods in mitigating harmonics were missing in the work. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 245 a general study of harmonics in fifty different sites covering heavy current and light current industries using non-linear loads were carried out randomly by kulkarni and bharadwaj (2016). an innovative real time harmonic measurement using ade7880 was implemented. the ade7880 is a high accuracy, 3-phase electrical energy measurement ic with serial interfaces and three flexible pulse outputs. the ade7880 device incorporates second-order sigma-delta (σ-δ) analog-to-digital converters (adcs), a digital integrator, reference circuitry, and all of the signal processing required to perform the total (fundamental and harmonic) active, and apparent energy measurements, root mean square (rms) calculations, as well as fundamental only active and reactive energy measurements. in addition, the ade7880 computes the root mean square (rms) of harmonics on the phase and neutral currents and on the phase voltages, together with the active, reactive and apparent powers, and the power factor and harmonic distortion on each harmonic for all phases. total harmonic distortion (thd) is computed for all currents and voltages. a fixed function digital signal processor (dsp) executes this signal processing. the dsp program is stored in the internal rom memory. the analysis of the harmonics present in the system was carried out using software. zigbee and gsm technology were used to communicate the data from consumer end to server and smart phone. the large size of the sites and the randomness involved in their selection are major defects that may likely lead to inaccuracies in the data collected and the obtainable results. the effects of triplen harmonics in the electricity company of ghana (ecg) distribution system was investigated in eduful and atanga (2017). the performance of three harmonic suppressors in the control of harmonic emission levels in three ecg’s distribution transformer substations were studied. the results of the research proved that the neutral blocking harmonic filters can reduce harmonic current in neutral conductors by 88% and consequently decrease harmonic energy loss by 97%. the estimated annual energy savings from the harmonic reduction for each transformer amounted to 10, 707.86 kwh. although the harmonic suppressors demonstrated strong ability in the reduction of harmonic energy losses, they were found to increase harmonic voltage distortion levels. this is a major disadvantage with the suppressors as high voltage thds can lead to erratic behavior of electronic equipment. methods of optimization were not included in the study. satish (2018) carried out an investigation into the nature and analysis of harmonics using fast fourier transform (fft) to evaluate the total harmonic distortion (thd) of converters with and without filters. matlab/simulink was employed for the simulation results. a passive filter was designed to decrease the distortion by shifting the resonance point of the network. the method to design the passive filter and its impact on efficiency and energy usage were outlined. the major demerit of the work is that active and hybrid filters were left out the work. ban and yang (2019) developed the fundamental ideas behind harmonic detection methods including the fourier transform, short wavelet transform, and wavelet packet transform. simulation was used to confirm that the proposed methods were effective. wavelet packet technique was said to increase the detection precision of harmonic signals. the study did not take into account fast switching mechanisms or active filters that can be utilized to reduce high order harmonics. vinayagam et al. (2019) conducted a thorough review of harmonics dominance in pv integrated networks. the results of an experimental case study investigating the dominance of harmonics http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 246 in a real-time pv integrated micro-grid under varied solar irradiation conditions provide additional support for the findings of the review conducted for various scenarios. the works lacked a thorough description of optimization techniques for harmonics mitigation. malekian et al. (2020) conducted a study on the validation of harmonic models for power production units utilizing test-bench and on-site data. the focus of the investigation was the power system's renewable energy sources' harmonic emissions. the time variation of harmonics and measurement errors were properly addressed. the proposed model validation process was applied to wind and photovoltaic power production units with various topologies and power classes. the goal of the study was to offer a solid scientific basis for future standards that may take into account the harmonic model validation of power production units. heavy harmonic industries were missing specific applications in the work. the work of urooj et al. (2021) concentrated on factors that reduce power quality, accountable for harmonic distortions, and cause inefficiency in power transformers. the suggested adaptive neuro-fuzzy inference system (anfis) offers the best method for harmonic reduction and increases effectiveness all around. the creation of a three-phase power transformer and the effectiveness assessment of the suggested methodology, both carried out in a matlab simulation environment, were successful. a thorough study of optimization techniques for harmonic mitigation was also lacking, in addition to specific applications in heavy harmonic industries. malik et al. (2022) used swarm intelligence-based optimization strength of the cuckoo search method to study a parameter estimation of the power system harmonics. for the performance assessment, various generations and particle sizes for various signal-to-noise ratios were taken into consideration. it was determined that cuckoo search optimization was reliable when assessing various signal-to-noise ratios. heavy harmonics industries were missing specific applications. hu et al. (2023) investigated harmonic sources operational procedures, mathematical models, and circuit system. numerous operational scenarios, including the usual home power load, the scenario for charging electric vehicles, the frequency conversion speed regulating device, the scenario for producing renewable energy, the load on an electric arc furnace, and the load on an electric locomotive, were explored. the papers take a forward-looking approach to harmonic analysis and control in the context of contemporary power systems. the studies lacked a thorough analysis of harmonics mitigation optimization techniques and evaluation of hybrid models. srita and somkun (2023) investigated the implementation process for a current harmonic correction technique of a three-phase grid-connected voltage-source converter (vsc), applied under the grid voltage distortion and frequency variation. to reduce the high-order harmonic current, proportional-integral plus multi-resonant controllers (pimr) were employed. harmonics mitigation methods in heavy harmonics producing industries, optimization techniques and specific applications were lacking. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 247 3. studies on harmonics control and mitigating techniques a hybrid reactance one-port compensator was designed to reduce the harmonic distortion in practical single-phase and balanced three-phase distribution systems having different types of nonlinear loads (el-saadany et al., 1998). the use of iterative method was adopted to study the effect of voltage and current harmonic interactions on a net system distortion. the major drawbacks of the study were that only iterative method was adopted and this did not give room for comparison with other viable methods. the iterative method also made the process to be complicated and time-consuming. high speed switches that may be desirable in controlling high order harmonics was not featured in the study. frequency domain was equally not considered. well over 200 publications on harmonics were reviewed by singh et al. (1999). many issues such as components selection, technical considerations, economic feasibilities and their selection for specific applications in respect of active filter (af) configurations were extensively dealt with. no consideration was however given to optimization of the filters through any technique. a hybrid active filter that combines a small-rated active filter and a 5th-tuned passive filter for damping of harmonic resonance in industrial power systems was proposed by fujita et al. (2000). the authors made the hybrid filter acts as an ideal passive filter with infinite quality factor thus improving the damping of the harmonic resonance relative to the passive filter when used alone. experimental results obtained from a 20 kw laboratory model verify the viability and effectiveness of the proposed filter. heavy harmonics producing loads, fast switching devices and optimization methods were not taken into consideration. it was posited by czarnecki (2000) that resonant harmonic filters can compete favorably and surpass switching compensators in harmonics mitigation. in terms of efficiency and cost, the author rated the former better than the latter. the concept of a harmonic blocking compensator and a fired-pole resonant harmonic filter was developed. however, the use of fast switching devices, software tools and hybrid optimization methods were not addressed in the work. rukonuzzaman and nakaoka (2001) applied an adaptive neural network algorithm for the detection of instantaneous real time harmonics components created from nonlinear loads. an advanced active power filter (apf) was designed to mitigate the harmonics. the disadvantage of learning multiple harmonic components which had an effect on the learning time of the algorithm, leading to a delay in compensation, is a major drawback in the work. in the work of abdel-galil et al. (2001), mitigation of harmonics through active and passive filters, with their various parameters, characteristics and sensitivities, were investigated. the single tuned and the reactance one-port filters were discovered to exhibit low sensitivity to both load variations and elements deviation and were moderately affected by the switching at the utility bus resulting in higher harmonics. the use of software tools and optimization techniques were left out in the work. experimental results in the research work of tey and so (2002) proved the effectiveness of the dsp-controlled series active filter, shunt active filter and unified power quality http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 248 conditioner (upqc) in mitigating harmonics to a large extent. however, the major drawback is the existence of system instability. the experiment was not subjected to a wide range of load variations. a method by which the harmonic current in a two-level network-connected inverter can be controlled for use as an active filter in addition to supplying real power, via the intermediate dc link to a motor inverter, was presented by brogan and yacamini (2003). the use of a commercially available variable speed drive and modifying its rectifier to be a sinusoidal rectifier was described. optimization techniques were left out of the study. simulation of an active filter for the reduction of the voltage total harmonic distortion created by a steel plant was presented in zamora et al. (2003). the steel plant was simulated considering different levels of load: one, three and six furnaces in operation. the harmonics analysis was limited to the furnaces in the industry. other sources of harmonics were not considered. power system harmonics was postulated as one of the important indices to rate power quality in manmek et al. (2003), tey and so (2002) and rukonuzzaman and nakaoka (2001). fast fourier transform (fft), application of adaptive filters and neural networks were recommended. optimization methods were missing in the works. three models of active power filters that compensate the harmonics, mitigate the voltage sags and swells, and also correct the power factor in electrical distribution network were formulated in zamora et al. (2003). the simulation results proved that the active power filter models compensate the harmonics, mitigate the voltage sags and swells, and correct the power factor of the system. fast switching devices, hybrid models, optimization methods were not considered. the work by du et al. (2004) presented a programmed pulse width modulation (pwm) method to eliminate specific higher order harmonics in multilevel converters. experimental results confirmed that the technique effectively eliminated the specific harmonics and the output voltage waveforms have less total harmonics distortion (thd) than that from the fundamental frequency switching techniques. the programmed pwm method has the advantage of flexibility between switching frequency and higher order harmonic elimination. however, the high increase in the required switching frequency for the elimination of more harmonics that is higher than the number of levels in a multilevel converter is a disadvantage. massoud et al. (2004) proposed the adoption of time-based and frequency-based harmonic current extraction techniques after reviewing the use of a converter with unity power factor and the use of a passive or active filter in the mitigation of harmonics in power distribution system. a brief description and classification of each technique were given. the study, however, did not cover an in-depth investigation of fast varying harmonics as a result of varying the loads connected at the output such as the work piece in an induction furnace. a detailed discussion of optimization methods towards mitigating harmonics were missing in the work. it was clearly stated in sandoval and houdek (2005) that there is no single solution or method to the control or mitigation of harmonics that is universally superior and that quite often a hybrid solution usually yields the best results economically and technically after a careful consideration of the end user’s objective. the work reviewed the use of typical alternative file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 249 three phase harmonic mitigation equipment such as line reactors, isolation transformers, kfactor transformers, tuned harmonic filters (fixed capacity or automatic switched multiple banks), igbt based fast switched harmonic filters, low pass harmonic filters, 12 and 18 pulse rectifiers, phase shifting transformers, and active harmonic filters. the operation of each type of mitigation alternative and the typical results that can be achieved when each type is properly applied were investigated. despite the detailed investigation, optimization method was still missing in the work. an excellent comparison between modern active filters and traditional passive filters were made in akagi (2006). modern active filters were reported to have multiple functions of harmonic filtering, damping, isolation and termination, reactive-power control for power factor correction and voltage regulation, load balancing, voltage flicker reduction, and or their combinations. the author deals with general pure active filters for power conditioning and specific hybrid active filters for harmonic filtering of three-phase diode rectifiers as well as traditional passive filters. the work was a general review as specific applications in heavy harmonic industries were missing. an investigation into the generation and control of harmonics in corus steel production plant in the dutch town of ijmuiden was investigated by hulshorst et al. (2006). an innovative solution involving matlab/simulink modeling of existing 10kv grid (including harmonics); modeling of the near infra-red (nir) installation (including harmonics at 0, 4kv) and modeling of the transformers needed to connect the nir installation (including harmonics at 0, 4kv) to the 10kv grids were developed and analyzed. the results obtained showed that the total harmonics distortion (thd) level can be reduced through the use of a phase-shifting transformer. as good as the solution proffered in the work appears, the phase-shifting transformers are about 10 to 15% higher in costs than the regular transformers, thereby making it uneconomical. a procedure to calculate optimum controller parameters of active power filters (apfs) was presented by tlusty and valoucht (2009). the apfs were implemented into a multi-bus industrial power system for harmonic voltage mitigation. the optimum controller parameters were found by solving the multiple (apf) harmonic problem. it was established that the use of an additional apf at a proper place of the power system may improve the efficiency of an already installed apf, while this place in itself may be even unsuitable for placing the single apf. the method considered the real control strategy as well as apf controller parameters. in practice, the drawback is that the method may not be cost effective. the subject of harmonic resonance in industrial electrical network was the focus of el-sadek et al. (2009). a practical case study of the aluminum company at nag-hammady in egypt was carried out. the authors were concerned with determination of harmonic resonance and antiresonance frequencies of large systems containing harmonic sources. suggested active power filter for damping the harmonic resonance orders or frequencies, for all possible planning and operational conditions faced in practice, was the first goal of the research. resonances were detected for all expected operational conditions. harmonic filters were designed, and suggested to be installed, and resonances due to expected switching of those filters were found. finally, methods of harmonic resonance prevention technique in that company network were http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 250 applied and their effectiveness was proved. the use of fast switching devices and the adoption of optimization methods for the control of harmonics were missing in the study. it was emphasized in kanerva et al. (2010) that designing of medium voltage adjustable speed drive systems (asd) for safe operation in hazardous areas requires expertise in a number of areas relating to frequency converters, motors, and the way they interact. as the use of different voltage-source inverter (vsi) topologies is increasing in the medium-voltage range, special care has to be taken to limit temperature rise, sparking, and bearing currents as they represent serious problems in oil and gas plants. temperature rise results from harmonic losses in the motor which are caused by the non-sinusoidal supply from the converter. if not properly mitigated, sparking can occur in both the stators and rotors of converter-fed motors as a result of harmonics and voltage stresses. a procedure was presented on how to validate the entire installation through computer simulation after the asd has been selected. it was stated that harmonic losses in converter-fed motors can be mitigated at the frequency converter by three main methods. these are the use of: a converter with a higher number of voltage levels, a frequency converter with a higher switching frequency or an output filter. however, the use of a frequency converter with a higher switching frequency increases loss in the frequency converter itself while the use of output filters required may not only be expensive but will also require space and usually result in additional losses. they also increase the complexity of the system and degrade the converter’s dynamic performance. in saha and suryavanshi (2010) it was verified that passive filters could be very effective solution for the harmonic mitigation as well as volt ampere reactive (var) compensation in offshore oil rigs where large dc drives, usually fed from ac utility services through ac/dc converters are usually in use, which invariably distorts current and voltage waveforms. an effective design procedure of passive filter to mitigate power system harmonics of a typical offshore oil rig was described. it was concluded that the application of properly designed series reactor and passive shunt filters reduces the voltage and current thd levels within the recommended limits of ieee std 519-1992. the power factor of the offshore oil rig power system was also improved from 0.78 to 0.97. parallel resonances were also avoided. fast switching devices and active filters that can be used in controlling high order harmonics were left out of the study. the methods of optimization were missing in the work. the importance of analyzing and evaluating the existing harmonic problems in power system and introducing the appropriate solution techniques was stressed by attial et al. (2010). a comprehensive harmonic waveforms analysis through the concept of cancellation and combination was done. effective technique via the application of phase shifting transformers was introduced. other alternatives to mitigation of harmonic effects using harmonic filters were given. electrical transient analysis program (etap) computer package was used for a case study to evaluate the merits of each technique. fast switching devices that can be used in controlling high order harmonics and optimization techniques were left out of the study. in pacis et al. (2010) compliance with established regulated levels for harmonics through the use of corrective actions such as introduction of active filters was demonstrated by applying simulation technique. the distortion introduced by the installation into the distribution network and the expected reduction when the active filter is in use were studied. simulation through matlab/simulink allows quantifying the harmonic distortion created by the system file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 251 and, when a corrective action was introduced, simulation shows the reduction in the distortion. the design of a suitable active filter was also obtained through simulation. the use of simulation tools of matlab/simulink, allows reproducing the behavior of the power systems in different situations, analyzing how the system answers in these situations and choosing the solution that better fit with the particular problem without additional costs. besides, active filters with different rated values can be simulated in order to analyze different reductions of the harmonic distortion. by means of the simulation carried out, the voltage and current harmonic distortions created by an underground traction system and a steel plant were obtained. for very complex system, the simulation time may be very large and this may be a major drawback. hybrid filters were not considered in the work. in kumar (2011), it was established that high order harmonics can be suppressed by employing variants of butterworth, chebyshev and cauer filters. three phase filter banks were used and connected in parallel. matlab/simulink wind farm model was used to generate and analyze the different harmonics magnitude and frequency. the study did not cover the use of fast switching devices that can be used in controlling high order harmonics and the use of optimization methods were missing. a study on the application of passive filters to mitigate power quality problems caused by induction furnaces was carried out by arif et al. (2012). modelling of induction furnaces in etap software with real data was carried out and the details of power quality problems caused by the induction furnaces were investigated. passive filters were designed and implemented and the thdv and thdi were within the ieee limits. hybrid filter models were left out of the study. an optimal selective harmonic mitigation method for cascaded h-bridge converter was introduced by marzoughi and imaneini (2012). the proposed method uses the least amount of switching frequency, 150 hz, for individual power switches. the harmonics up to 41st were mitigated to satisfy three voltage harmonic standards en 50160, cigre jwg c4.07 and iec 61000-3-6 from both individual harmonics and total harmonics distortion (thd) points of view. however, with the limited amount of 150 hz switching frequency, the method is unsuitable for high frequency electrical system such as induction furnace. furthermore, another drawback is the introduction of a small filter at the ac side to neutralize the rest of the harmonics. the design of hybrid active filter to reduce current perturbations produced by power electronics-based devices was done in memon et al. (2012). the instantaneous active and reactive power method (pq) was used to perform the identification of disturbing currents. the total harmonic distortion factor of the source current was analyzed in both time and frequency domains. simulation results proved that the total distortion of the supply current was decreased from 20.77 to 1.97% which actually met with the ieee 519 recommended harmonic standard. it was therefore concluded that the hybrid active filter can compensate the harmonic currents effectively and improve power quality. nevertheless, the research lacks a comparative analysis of the optimization of various types of hybrid filters. harmonics mitigation of industrial power system using passive filters was researched into by memon et al. (2012). a pc-based single tuned and second order high pass passive filters were designed and matlab/simulink software was used for simulation purposes with and without the filters installation. the introduction of the filters improved the power factor and reduced http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 252 the current harmonics from 20.77% to 4.32%. lack of specific analysis of harmonics in the context of a heavy current industry such as steel plants and comparative analysis of the hybrid optimization methods are major drawbacks to the work. a broad categorization of different harmonic mitigation techniques (passive, active, and hybrid) was carried out in kazem (2013). the hybrid harmonic filter (hhf) was considered to be more attractive in harmonic filtering than the pure filters from both viability and economical points of view, particularly for high-power applications. a general approach to mitigation of harmonics was discussed. specific analysis of harmonics in the context of a heavy current industry such as steel plants is missing in the study. a topology for reactive power compensation and harmonic mitigation of distribution system using shunt active power filter (sapf) compensator was presented in mujawar et al. (2013). instantaneous reactive power (irp) theory for reference current generation, proportional integral (pi) controller for dc voltage balancing and hysteresis current controller (hcc) for gating pulse generation was implemented. simulations were carried out and fast fourier transform (fft) analysis were performed on the source and load current which shows that the power factor of source is near unity and harmonic content on source side are well below the harmonic limit imposed by ieee std. 519-1992. specific analysis of harmonics in the context of a heavy current industry such as steel plants was missing in the study. pulse converters and fast switching devices that can be used in controlling high order harmonics and the methods of optimization were not covered in the study. the development of active power filter (apf) technologies was reviewed in gupta and gupta (2013). with a short overview of harmonic distortion difficulties and their impacts on electric power the apf topologies were reviewed taking into consideration the application of the p-q and elongation p-q theorems to mitigate harmonics. a short consideration on the apf-solar photovoltaic system with the shunt apf were considered and proposed. the work did not cover specific applications in heavily harmonics producing industry and a comparative analysis of the hybrid optimization methods was missing. a selective harmonic elimination (she) method to mitigate low order harmonics in single phase nine level, eleven level and thirteen level inverters with different loads were developed by tamilvani and valluvan (2014). the different level inverters were realized by cascading h-bridge in matlab/simulink. a pulse wave modulation (pwm) control strategy was applied to the switches at appropriate conducting angles with suitable delays. the bee algorithm was adopted to optimize the switching angles for improved quality in the output voltage. the lower order harmonics and total harmonics distortion was reduced to about 10%. despite further tuning of the bee algorithm, the low order harmonics were not fully eliminated, thus there is the need for further improvement. an overview of different control methods which are applied on shunt active power filter to achieve harmonics reduction and power factor improvement was presented by vandana and tomer (2014). the effectiveness of pi and fuzzy controllers for harmonics mitigation using shunt apf were demonstrated and proven. using pi controller, the harmonics level dropped to 4.24 % from 29.573 % while the power factor improved from 0.9755 to 0.9906. using fuzzy logic controller, the thd was 2.49% and the power factor improved from 0.9755 to 0.9952. these satisfied the ieee std. 519. however, the use of soft computing techniques such as file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 253 genetic algorithm, particle swarm optimization and artificial neural network to extract harmonics was missing. the structure, design and analysis of a 24-pulse ac-dc power auto transformer-based converter that employed a pulse doubling technique for asynchronous motor drive was researched into and presented by kiran et al. (2015). the autotransformer was designed for a 12-pulse converter for effective harmonic reduction. pulse reinjection technique was used to convert existing system into a multiple pulse converter. with the effect of load variations taken into considerations, low harmonic distortion and approximate unity power factor were obtained. the major drawbacks are that the method is not cost effective, hybrid models were left out and optimization methods were missing. a multi-objective optimal design of passive and hybrid active power filter based on bacterial foraging optimization algorithm was investigated by molaei et al. (2015). multi-objective optimization models with relevant constraints for passive power filters (ppf) and hybrid active power filters (hapf) set at high voltage levels were formulated for harmonic filtering and reactive power compensation. to solve the multi-objective optimization problems, a bacterial foraging algorithm (bfa) was developed. it was established that the results obtained compared favorably with that of particle swarm optimization (pso) algorithm. in reality when designing filters, there are many objectives to be considered in determining the optimal solution. since only three objectives were considered, there is room for improvements. furthermore, the models developed were not tested in a fast varying and heavy harmonic producing industries such as steel plants with induction furnaces. a research work titled ‘review of mitigation techniques for power quality issues in distributed generation’, that discusses the power quality issues in grid connected distributed generation (dg) system and their mitigation techniques was done by jadhav (2015). the research posited that power quality enhancement and harmonic mitigation is possible using a flexible dg unit. it was established that the dgs reduces greenhouse gas emission and power demand on the main grid but at the same time introduces power quality issues like voltage fluctuation, voltage sags, swells, voltage flicker and unbalance in the distribution system. various power quality improvement techniques were proposed to maintain the thd within standard limits. the major disadvantage lies in the selection of control techniques that depends on many factors such as response time, accuracy of tracking, complexity, computational burden, robustness and cost of the control system. different applications, challenges and trends for traditional active and passive harmonic filters for reduction of harmonic distortion and optimization of the power quality were presented in motta and faúndes (2016). the advantages and disadvantages of active versus passive filter technologies were analyzed using real cases from the industry. the authors concluded that nowadays more and more applications require harmonic filtering and not only the classic power factor correction of the past. besides passive filtering, more and more active filters are required and in many cases hybrid solutions are used where a passive detuned power factor correction (pfc) system is installed for power factor correction, and an active filter is present at the same time for harmonic mitigation and load balancing. the absence of a comparative analysis of the hybrid optimization methods was a major drawback to the work. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):241-260. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 254 an analysis of active power filter (apf) for harmonic mitigation in distribution system was carried out in rani et al. (2016). pq theory for controlling apf currents was employed for harmonic mitigation at point of common coupling (pcc) to maintain power quality. the normal system without apf, system with apf with fixed load and also with variable load were considered. models were developed using matlab/simulink. the thd values for source currents were tabulated for different cases. it was proven that the thd is found to be within nominal values when apf was connected to the system with non-linear loads and the results validated an effective application of shunt apf for different load conditions. specific analysis of harmonics in the context of a heavy current industry is missing in the study and the method may not be cost effective. particle swarm optimization (pso) method was adopted in kumawat et al. (2016) to address an optimal allocation of distributed energy resources (ders) in a highly distorted radial distribution system in order to minimize the power losses and to mitigate harmonics. a backward/forward sweep-based harmonics load flow method was adopted to analyze the total harmonics distortion of voltage (thdv) value up to the 31st harmonics in a 31-bus distribution network with linear and non-linear loads. the major technical constraints considered are voltage and thdv limit at different buses, line flow capacity and power balance. the particle swarm optimization (pso) based algorithm was tested for various simulated cases and was found to be robust, reliable and in compliance with ieee 519-1992 standards. despite the robustness and reliability of the work, there was no comparative analysis of the pso method to other well-known optimization methods such as genetic algorithm (ga) in order to establish the superiority of one over the other. the inherent disadvantages of particle swarm optimization (pso) such as partial optimism (less exact at the regulation of its speed and the direction), inability to work out the problems of non-coordinate or fast changing coordinate system (bai, 2010) were drawbacks to the study. kaiwart and balaraju (2016) discusses various harmonic mitigation techniques stating the advantages and disadvantages of each technique. relevant diagrams and charts were provided to provide useful information. it was concluded that there is no single product or method that provides a universal best solution for harmonics as the best economical and technical solution depends on users’ objective, extent or quantity of harmonics distortions, associated costs and benefits. hybrid method was proffered as the best suitable method. the work was a general characterization of harmonics mitigation techniques. details of operational principles of the methods, the use of software tools and methods of optimization were missing. durdhavale and ahire (2016) outlined various harmonics detection and measurement techniques stating the advantages and disadvantages of each. a new hybrid optimistic method was introduced and proposed. the system was designed for detection and measurement of harmonics on advanced risc machines (arm) 7 using fft algorithm for measuring the total harmonic distortion. specific analysis of harmonics in the context of a heavy current industry was missing in the study and there was no comparative analysis of the various optimization methods such as genetic algorithm (ga), artificial bee colony (abc), particle swarm optimization (pso), etc. to establish further improvements on the new method developed. a detailed description with classification of the harmonic mitigation techniques based on some distinguish features such as reliability, load influence, total harmonic distortion (thd), cost, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com abdul-hameed et al: a review and critique of advances in the mitigation of harmonics. azojete, 20(1):241-260. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: kunleoluyori@gmail.com 255 etc. was given by mahima and lalwani (2017). the work was a guide towards deciding which harmonic mitigation methods best suit different conditions. hybrid filters were adjudged to be very efficient and further improvement were proposed through an adoption of new topology. optimization methods were missing in the study. there was no specific case study to demonstrate the effectiveness or otherwise of the methods. 4. conclusion this paper reviewed holistically the work done on various aspects of harmonics by different researchers in the last two and a half decades (1998 2023). the areas covered in the study of harmonics, the merits, the demerits and outstanding areas in the works done on harmonics within the specified decades are discussed. in this work, it is discovered that much remains to be done in the area of using different software tools in the optimization of filters, especially the hybrid type models to control harmonics in a power distribution system. furthermore, the study discovered that the design of filters that can simultaneously mitigate harmonics from heavy, middle or light current devices are largely missing in the efforts made so far on the mitigation of harmonics. in order to expand the frontiers of knowledge in harmonics distortion in contemporary power systems and to create strategies for reducing its detrimental impact on power quality and system stability, the missing gaps such as the design of a filter that will simultaneously cater for harmonics mitigation optimally under different scenario is a necessity. this can of course take several forms as many factors are to be considered. other researchers that are interested in the field of harmonics may identify these gray areas and fill the missing gaps. references abdelaziz, ay., mechamer, sf. and ismael, sm. 2013. sources and mitigation of harmonics in industrial electrical power systems: state of the art. the online journal of power and energy engineering, 3(4): 320 – 322. abdel-galil, tk., el-saadany, ef. and salama, mma. 2001. implementation of different mitigation techniques for reducing harmonic distribution in medium voltage industrial distribution system. proceedings of ieee transmission and distribution conference and exposition, 1: 561-566. adesina, lm. and fakolujo, oa. 2015. determination of total harmonic distortion (thd) on a 33kv distribution network: a case study of island business district. nigerian journal of technology (nijotech), 34(4): 773 – 780. akagi, h. 2006. modern active filters and traditional passive filters. bulletin of the polish academy of technical sciences, 54(3): 255-269. arif, mr., mahmood, f., hashmi, m. and hänninen, s. 2012. application of passive filters to mitigate power quality problems caused by induction furnaces. in 2012 ieee international conference on condition monitoring and diagnosis, 23 – 27 september, 2012, bali, indonesia, 1227-1230. attial, ha., el-metwallyl, m. and fahmy, om. 2010. harmonic distortion effects and mitigation in distribution systems. journal of american science, 6 (10): 173-183. bai, q. 2010. analysis of particle swarm optimization algorithm. computer and information science, 3(1): 180 – 184. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; 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united states, 553-555. zamora, i., albizu, i., mazon, aj., sagastabeitia, kj. and fernandez, e. 2003. harmonic distortion in a steel plant with induction furnaces. proceedings of international conference on renewable energies and power quality, 14-18 june 2003; alda, usa: 1-7. zamora, i., albizu, i., mazon, aj., sagastabeitia, kj. and fernandez, e. 2003. simulation by matlab/simulink of active filters for reducing thd created by industrial systems. proceedings of ieee power tech. conference, 18-20 march 2003, bologna, italy, 3: 8. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):183-196 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 183 original research article evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state a. a. sodangi, o. j. akinyeye, w. e. esuabanga and c. o. nwafor nigerian building and road research institute, ota, ogun state, nigeria *corresponding author’s email address: sodangiali2020@gmail.com 1.0 introduction water is a transparent, tasteless, odourless, and colorless chemical substance that is the main constituent of the earth's hydrosphere and is the fluid of living organisms. the expansion of economic activities and the increasing population are leading to increased demand for water. water has played a vital role throughout the history in the development of human civilization. groundwater is the water that lies beneath the earth’s surface, filling the pore space between grains in bodies of sediment and elastic sedimentary rock and filling cracks and crevices in all types of rock (abdullahi and iheakanwa, 2013). about 98% of the world's freshwater is from groundwater and is distributed throughout the world (tijani, 2016). demand for groundwater has been on the increase because of rapid growth in population as well as the accelerated pace of industrialization and urbanization. the groundwater quality depends on several chemical constituents and their concentration, which are derived from geological data. environmental and industrial solid wastes have emerged as one of the leading factors of groundwater pollution. article information abstract in nigeria, access to fresh drinking water has become serious challenges to both rural and urban areas.the aim of this study was to evaluate groundwater quality in keffi central town of nasarawa state for drinking purposes using the water quality index technique. eight groundwater samples (four from both boreholes and dug wells) were collected from the study areaduring the wet season in october 2019. the water quality index is a mathematical method used to facilitate water quality explanation. the ph, electric conductivity, total dissolved solids, total hardness, calcium, magnesium, sodium, chloride, sulphate and bicarbonate were determined according to standard methods. ph ranged from 5.7 to 7.1(mg/l), electric conductivity ranged from 256 to 1591(µs/cm), magnesium ranged from 2.6 to 29(mg/l), calcium ranged from 3.7 to 34(mg/l), sodium ranged from 22 to 56(mg/l), chloride ranged from 8.4 to 63(mg/l), bicarbonate ranged from 54.3 to 219.6(mg/l), sulphate ranged from 0.1 to 32.4(mg/l), total dissolved solids ranged from 95.2 to 302.94(mg/l) and total hardness ranged from 23.8 to 204.23(mg/l). the water quality index obtained from different locations was found to vary from 44.32 to 61.60 for boreholes and 72.55 to 97.77 for dug wells. the results for the water quality index indicated that borehole locations 2, 4, and 8were safe for human consumption, while dug well locations 3,5,6 and 7were not suitable for drinking purposes, compared with nigerian industrial standard drinking water. the reasons for the high water quality index values of some study areas were attributed to the lithological variation and anthropogenic activities in the region. therefore, some of the well water required treatment such as demineralization. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 14 october, 2022 revised 12 december, 2022 accepted 12 february, 2023 keywords: groundwater water quality index water quality parameters keffi central http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 184 available water is rendered non-portable in many parts of the country like somalia because of the presence of heavy metals. in urban areas fresh water accessibility is more than the rural areas, because the urban areas have a lot of public water supply infrastructure for fresh water consumption. however, this statement is in contrast with the studies of durowojo et al. (2022) as thy averred that in urban areas, fresh water accessibility issues are really the same with the rural areas, owing to the inadequate investigation in public water supply infrastructure that lay down pipe-bone water consumption undependable. in urban areas, fresh water accessibility issues are really the same with the rural areas, owing to the inadequate investigation in public water supply infrastructure that lay down pipe-borne water consumption undependable (durowojo et al., 2022). in keffi central, access to clean water is a major challenge to the residents. the consequence of water scarcity in some communities in the area, most especially during the middle of the dry season often results in the outbreak of water-borne diseases such as typhoid, cholera, diarrhoea, and guinea worm. with the efforts of government agencies and international agencies like nasarawa state ministry of water resources (nsmwr), united nations international children emergency fund (unicef), and the european union (eu), some significant successes have been recorded in making safe drinking water available to few communities and therefore, curbing the menace of these diseases (chiroma et al., 2018). water quality index (wqi) provides a single number that signifies the overall water quality at a certain location based on several water quality parameters. it is an effective tools and important parameters in the evaluation and management of groundwater quality (wu jianhau et al., 2011). the objective of wqi is to transform complex water quality data into information that is understandable and useful to the stakeholders and the general public. several indices have been developed to summarize water quality data in an easily expressible and understood format. the wqi which was first developed by horton in the early 1970s, is a mathematical method of calculating a single value from multiple test results (etim et al., 2013). the quality and availability of groundwater have deteriorated due to some factors such as increasing industrialization, population, and urbanization. the frequency of monitoring and assessment of water quality helps to develop management strategies to control groundwater pollution (yao et al., 2010). the water quality of any specific area can be assessed using physical, chemical, and biological parameters. if the values of these parameters occurred more than the defined limit, they become harmful to human health (shweta et al., 2013). the traditional approaches to assessing water quality are based on a comparison of experimentally determined parameters with local or international standards. while, these procedures allow the good recognition of contamination sources and may be necessary for checking legitimate compliance, but they don’t give a comprehensive vision of the spacial and temporal trends in the overall water quality (shaif et al., 2017). this work aims to evaluate the suitability of groundwater quality in keffi central town using a water quality index for drinking purposes. water quality index was first proposed by horton (palwasha et al., 2020). it is a rating given to the water sample on the basis of calculated chemical parameters. wqi is a compilation of a number of variables which can be used to determine the overall quality of river and ground water file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangi et al: evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state. azojete, 19(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 185 (ashwani and anish, 2009). ten parameters were used for calculation of wqi as suggested by fadhil et al. (2013). these includes: magnesium, sodium, calcium, chloride, sulphate, bicarbonate, ph, total dissolved solids, total hardness, and electric conductivity. water quality index (wqi) provides a single number that signifies the overall water quality at a certain location based on several water quality parameters. it is an effective tools and important parameters in the evaluation and management of groundwater quality (wu et al., 2011). the objective of wqi is to transform complex water quality data into information that is understandable and useful to the stakeholders and the general public. several indices have been developed to summarize water quality data in an easily expressible and understood format. the frequency of monitoring and assessment of water quality helps to develop management strategies to control groundwater pollution (yao et al., 2010). the water quality of any specific area can be assessed using physical, chemical, and biological parameters. if the values of these parameters occurred more than the defined limit, they become harmful to human health (shweta et al., 2013). the traditional approaches to assessing water quality are based on a comparison of experimentally determined parameters with local or international standards. while, these procedures allow the good recognition of contamination sources and may be necessary for checking legitimate compliance, but they don’t give a comprehensive vision of the spatial and temporal trends in the overall water quality (shaif et al., 2019). this work aims to evaluate the suitability of groundwater quality in keffi central town using a water quality index for drinking purposes. 2. materials and methods 2.1 study area keffi central lies between latitudes 8o 50l and 8o 52ln and longitude 7o 52l and 7o 54le (figure1). the area is within north-central nigeria and is characterized by wet and dry seasons. the temperature ranged from 21.3oc to 31.6oc. the area was drained river antau, river kodo, and river mannu. the area falls within the north-central nigeria basement complex, precisely within the migmatite gneiss complex. the nigeria’s basement complex consists of migmatites and migmatitic gneisses, slightly migmatized to unmigmatized paraschists with interbeds of meta and non meta igneous rocks, also referred to as the younger metasediments or the schist belts (ajibade, 1976, and turner, 1983). in the keffi area, there are not many records of the detailed work carried out on the various units of the basement complex. most parts of the area studied had already been mapped as underlain by the migmatites and migmatitic gneisses. the occurrence of a schist belt was only shown in parts of the area in the geological map of nigeria produced by the geological survey of nigeria (ngsa, 1994). using their geochemistry and rare-earth element analysis, onyeagocha (1986), pointed out that the granite is younger than the granite-gneiss; that al/(na+k+ca) ranges from 0.92 to 1.09, indicating that the rocks are aluminium rich to aluminium excess. the availability of groundwater would depend on the presence and extent of the weather overburden regolith and the presence of faults and fractures in the underlying bedrock http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 186 (olayinka et al., 1999). dissolution of minerals and leaching tends to increase porosity, permeability, and specific yield. however, the decomposition of secondary clay minerals tends to reverse the process (tijani, 1994). figure 1: map of the study area showing groundwater sampling locations. 2.2 sample collection groundwater samples were collected from8 locations of central part of keffi town in the month of october 2019. groundwater samples were collected in new dry clean plastic bottles after rinsed three times with the samples to be collected, using standard procedures recommended by amadi et al. (2013) method. physicochemical parameters including electrical conductivity (ec) and ph were measured in situ using hanna ec and ph meter respectively. the collected samples were labeled, transported to the bells university laboratory ota, ogun state for further analysis. the chemical parameters analyzed include: calcium, magnesium, sodium, chloride, sulphate and bicarbonate. total dissolved solids (tds) was determined according to tripathi et al. (2012). total hardness (th) was determined using standard procedures recommended by nematollah et al. (2016). in the present study water quality index were determined. all chemical concentrations were expressed in mg/l. coordinates of each well location were identified using global positioning system (gps) as shown in table 1. table 1: geographical locations of the studied wells. well l a t i t u d e longi tude elevation (m) 1 8050 l10.614 l l 7 052 l30.027 l l 3 0 9 . 5 2 8o50 l38.074 l l 7 052 l21.110 l l 3 0 2 . 3 3 8 0 50 l 42 . 38 l l 7 052 l12.075 l l 3 0 2 . 1 4 8 0 50 l 19 . 37 l l 7 052 l40.056 l l 3 0 5 . 2 5 8050 l59.013 l l 7 052 l28.108 l l 3 1 1 . 4 6 8 050 l 58.34 l l 7 052 l58.026 l l 3 0 3 . 4 7 8050 l11.022 l l 7 052 l26.528 l l 3 1 2 . 8 8 8050 l39.161 l l 7 052 l24.341 l l 3 0 5 . 9 location file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangi et al: evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state. azojete, 19(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 187 2.1. water quality index calculation water quality index was first proposed by horton (palwasha et al., 2020). it is a rating given to the water sample on the basis of calculated chemical parameters. wqi is a compilation of a number of variables which can be used to determine the overall quality of river and ground water (ashwani and anish, 2009).the wqi water quality index was calculated for each well location by using ten parameters namely: tds, th, ph, ec, mg2+, na+, ca2+, so24, cl-, and hco3 according to nigeria’s drinking water standard for each chemical parameter. the weighted arithmetic index method as applied by brown et al. (1972) and dhirendra et al. (2009) was used, and presented below: the constant of proportionality was calculated by finding the inverse of nigeria industrial standard (nis) limit for each parameter (fadhil et al., 2013). then sum the results of the inverse, finally find the inverse of the summation of the result. k = 1 ∑ 1 𝑆𝑖 𝑛 𝑖=1 (1) where: k= constant of proportionality si= permissible limit of nigerian standard for drinking water quality for the ith parameter n=number of parameters calculating the weightage of ith parameter (relative weight) wi by using equation as shown in table 3 the expression means the relative weight equation: the relative weight was calculated by dividing the constant of proportionality by nis limit for each parameter (fadhil et al., 2013). (2) calculating of the quality rating scale (qi) by the expression due to fadhil et al. (2013): (3) in which ci is the concentration of the ith parameter ci is the concentration for each chemical parameter in each water sample (mg/l) calculating water quality index (wqi) as follows (fadhil et al., 2013): water quality index is given as: (4) the data collected was substituted into the equations above for computation of water quality index values, with the help of statistical method. si k wi = si ci qi 100 =   = == n i n i wi qiwi wqi 1 1 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 188 the physicochemical parameters of keffi central town with their nis water quality prescribed values corresponding weightage factor (wi), assigned with the help of equation 1 and 2 and the values are presented in table 2. table 2: relative weight for each parameter chemica l parameters highest permitted value for water (1/si) 1 / s i k w i p h 8.5 0.117647 0.556733 ec 1 0 0 0 0.001 0.004732 hardness 150 0.00667 0.031548 t d s 500 0.002 0.009464 calcium 2 0 0 0.005 4.732227 0.023661 magnesium 2 0 0.05 0.236611 sodium 2 0 0 0.005 0.023661 bicarbonate 1 0 0 0 . 0 1 0.047322 su l f a t e 1 0 0 0 . 0 1 0.047322 chloride 2 5 0 0.004 0.018929 total 0.211317 1 .0 3. results and discussion 3.1 water quality characteristics the concentration of all water quality parameters of keffi central town are presented in table 3. the ph ranged from 5.7 to 7.1 mg/l with an average of 6.3mg/l which indicated that the ground water is slightly acidic to neutral. all the values fell below the acceptable limit being prescribed in nigerian industrial standard (nis 2015) for drinking water. electrical conductivity (ec) measures the salt concentration and provides indication of ionic concentration in the water. ec varied between 256 to 1591 µs/cm with an average of 812.25 µs/cm. only locations 5 and 7 had their ec values above the acceptable limit (>1000) of nigerian drinking water standards. it may be attributed to high dissolution of ions in the locations (figure 2). the concentration of all water quality parameters of keffi central town are presented in table 2 the ph ranges from 5.7 to 7.1 mg/l with an average of 6.3mg/l which indicated that the ground water is slightly acidic to neutral. all the values fell below the acceptable limit being prescribed in nigeria industrial standard (nis 2015) for drinking water. the ph of most natural water bodies ranged from 6.5 to 8.5 while the disparity from neutral ph is as a result of free carbon dioxide or bicarbonate in the water bodies (etim et al., 2013). the lowest value of ph was recorded in borehole location 4 and 8 because they were closed to the dumpsite. the result was presented in figure 2. electrical conductivity (ec) measures the salt concentration and provides indication of ionic concentration in the water. ec varied from 256 to 1591 µs/cm with an average of 812.25µs/cm. in the study area only dug well locations 5 and 7 have their ec values above the acceptable limit (>1000) of nigeria drinking water standards. higher values of the two locations were attributed to high dissolution of ions in the region (figure 2). a lower ec value indicated less concentration of the dissolved ions and organic matter in the water. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangi et al: evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state. azojete, 19(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 189 table 3: values of some water quality parameters of keffi central. w e l l p h e c t h t d s c a m g n a cho3 1 6 . 8 2 5 6 3 9 . 4 1 8 0 6 . 9 5.4 38 1 8 3 2 5 . 7 7 3 1 4 5 . 3 6 99.85 8 . 2 6.05 35.1 5 8 3 7 . 1 9 4 1 204 .23 277.8 3 4 29 56 219.6 4 5 . 8 6 1 7 2 3 . 7 5 95.2 4 . 9 2.8 27.2 6 2 5 6 1 0 8 5 121 .36 166.5 1 4 21 39 7 5 6 6 . 7 8 5 4 201 .59 226.7 2 8 22 22 125 7 6 . 9 1 5 9 1 162 .04 302.94 2 7 23 55 170.8 8 5 . 7 4 1 6 1 9 . 9 3 80.28 3 . 7 2.6 30.2 54 .3 figure 2: the values of ph and electrical conductivity for all wells. total dissolved solid (tds) ranged from 80.28 to 302.9 mg/l with an average of 178.57 mg/l. this is far below the permissible limits (<500) being prescribed in (nis 2015) for drinking water. hence, the water is not harmful in view of these parameters, and this agrees with afolabi and olutomilola (2017). hardness due to bicarbonate of calcium and magnesium is temporary hardness but hardness due chloride and sulphate of calcium and magnesium is permanent hardness. due to permanent hardness soap consumption will be more. total dissolved solid (tds) is a measure of the inorganic salts and little amount of the organic matter present in solution. tds ranged from 80.28 to 302.9 mg/l with an average of 178.57 mg/l. this is far below the permissible limits (<500) being prescribed in (nis 2015) for drinking water. hence, the water is not harmful in view of these parameters, and this agrees with afolabi and olutomilola (2017). again, tds in drinking water has been associated with natural source, sewage and industrial waste water (figure 3). hardness due to bicarbonate of calcium and magnesium is temporary hardness but hardness due to chloride and sulphate of calcium and magnesium is permanent hardness. due to permanent hardness soap consumption will be more. the highest th value was observed to be 204.23mg/l at dug well location 3 and lowest value was observed to be 19.93mg/l at borehole location 8. however, the th at dug well locations 3, 6 and 7 were found to be above the allowable limit (>150) being prescribed in nis (2015) for safe drinking 0 200 400 600 800 1000 1200 1400 1600 1800 1 2 3 4 5 6 7 8 p h /e le ct ri c co n d u ct iv it y( µ s/ cm ) well number ph ec http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 190 water. the reasons for the high th values of the three samples were attributed to the lithological variation and anthropogenic activities in the area. the values indicate soft to moderately hard type of groundwater (ashwani and abhay, 2014). hard water is mainly account of the unpleasant taste and reduces the ability of soap to produce lather (figure 3). figure 3: the values of total dissolve solid and total hardness for all wells calcium is naturally present in water. it serves in our body as muscle contractor and blood clothing. calcium is a cation found in water which makes water hard. the concentration of calcium ranged from 3.7 to 34mg/l with a mean of 15.8mg/l. the result indicated that all the values were below the acceptable limit (<200) being prescribed in (nis, 2015) for safe drinking water. inadequate intake of calcium may lead to hypertension, stroke and kidney stone (farhad et al., 2017). the concentration of magnesium ranged from 2.6 to 29 mg/l with an average of 13.95 mg/l. this showed that all the values analyzed fell below permissible limit (<20) being prescribed in (nis 2015) for safe drinking water. the high values of magnesium in these four samples may be as a result of dissolution of magnesium bearing mineral, example aragonite in the location. both calcium and magnesium concentrations have been originated from the dissolution of carbonate minerals such as dolomite and calcite (figure 4). sodium is an essential element for keeping human body in good working condition and help in maintaining blood pressure. concentration of sodium varied from 22 to 56 mg/l with a mean of 37.8mg/l. this signified that all the values were below the acceptable limit (<200) being prescribed in (nis, 2015) for drinking water. also indicated little or lack of salt bearing mineral in the locations. excess sodium in water can affect person suffering from heart and kidney problems (gupta et al. 2004) as showed in figure 4. in the study area the different of the sodium concentration indicated weathering of feldspar bearing mineral. 0 50 100 150 200 250 300 350 1 2 3 4 5 6 7 8 to ta l d is so lv e d s o lid s/ to ta l h ar d n e ss (m g/ l) well number tds th file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangi et al: evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state. azojete, 19(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 191 figure 4: the values of calcium, magnesium sodium for all wells chloride concentration in the water may be result from the evaporation of chloride bearing mineral which are soluble to the water. chloride concentration ranged from 8.4 to 63 mg/l with average of 2 5.59mg/l, which indicated that all locations were found to be below the acceptable limit (<250) being prescribed in (nis, 2015) for drinking water. the low values of chloride in the study area were attributed to lack of deposition of salt spray. most water contains chloride and the amount present could be caused by fertilizer, air, industrial and domestic waste. in addition weathering of halite and evaporate were the major lithologic source of chloride in the groundwater. high sulphate (so4 2-) concentration in groundwater could be as a result of contamination of untreated industrial and domestic waste. sulphate concentration varied from 0.1 to 32.4 mg/l with mean of 12.4 mg/l. this showed that no abnormal value was present in the water samples. this occurred because of low dissolution of sulphate bearing mineral (gypsum) in the location. all the values fell below the acceptable limit being prescribed in (nis 2015) for safe drinking water. water containing high concentration of so4 2-, caused by the leaching of natural deposits of magnesium sulphate (mgso4) or sodium sulphate (naso4) and may be undesirable because of their laxative effect. higher concentration of sulphate may lead to gastrointestinal irritation especially when magnesium and sodium are present in drinking water resources (farhad et al., 2017). the concentration of bicarbonate (hco3 -) varied from 54.3 to 219.6 mg/l with the mean of 118.46 mg/l. all the water samples in the locations were below permissible limit (<100), except borehole location 1 and dug well location 3, 6 and 7 values were higher than the permissible limit being prescribed in nis 2015 for safe drinking water, this could be attributed to the weathering of carbonate minerals in rain water, example limestone (figure 5). in addition, weathering of carbonate and alumino-silicate minerals with secondary contribution from dissolution of co2 gasses are primary source of hco3 in the groundwater. 0 10 20 30 40 50 60 1 2 3 4 5 6 7 8 c al ci u m /m ag n e si u m /s o d iu m (m g/ l) well number ca mg na http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 192 figure 5: the values of chloride, sulphate and bicarbonate for all wells 3.2 water quality index analysis the physicochemical parameters of keffi central town with their nis water quality prescribed values corresponding weightage factor (wi), assigned with the help of equation 1 and 2 and the values are presented in table 3. wqi were calculated from equations 3 and 4. the wqi results are shown in table 4. classification of all the water samples were categorized by taking the standard water quality index bases which are shown in table 5. obtained results revealed that location 2, 4 and 8 met the requirement of safe drinking purpose as agreed with the standard proposed by mishra and patel (2001). however, location 1, 3, 5, 6 and 7 could not meet the requirement, due to the lithological variation and leachate from solid waste disposal site in the area. therefore, the water cannot be used for human consumption. the wqi values of the 8 locations were found range from good to very poor-quality, or from 26-50 and 76-100.the statistical summary of the physicochemical parameters analyzed are showed in table 6. table 4: details of the index rate and type of water for the various samples obtained in the analysis location t y p e index rate type of water 1 bore we l l 6 1 . 6 0 poor water 2 bore we l l 4 9 . 6 4 good water 3 d u g w e l l 9 7 . 7 7 very poor water 4 bore we l l 4 6 . 1 7 good water 5 d u g w e l l 7 2 . 5 5 poor water 6 d u g w e l l 9 5 . 0 6 very poor water 7 d u g w e l l 8 8 . 1 9 very poor water 8 bore we l l 4 4 . 3 2 good water 0 50 100 150 200 250 1 2 3 4 5 6 7 8 c h lo ri d e /s u lp h at e /b ic ar b o n at e (m g/ l) well number cl so4 cho3 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangi et al: evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state. azojete, 19(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 193 table 5: range of water quality index for drinking purpose (mishra and patel, 2001) s / n r a n g e type of water 1 0 2 5 e x c e l l e n t 2 2 6 5 0 good 3 5 1 7 5 poor 4 7 6 1 0 0 very poor 5 > 1 0 0 unsuitable for drinking purpose table 6: statistical summary of chemical data of groundwater in keffi central town (2019) chemical parameter u n i t r a n g e mean nis(2015) hpl p h ¯ 5 . 7 7 . 1 6 . 3 6.5-8.5 e c µ s / c m 2 5 6 1 5 9 1 812.25 1000 magnesium m g / l 2 . 6 2 9 13.95 2 0 calcium m g / l 3 . 7 3 4 1 5 . 8 2 0 0 sodium m g / l s 2 2 5 6 3 7 . 8 2 0 0 chloride m g / l 8 . 4 6 3 25.59 2 5 0 bicarbonate m g / l 5 4 . 3 2 1 9 . 6 118.46 1 0 0 sulphate m g / l 0 . 1 3 2 . 4 1 2 . 4 1 0 0 tds m g / l 9 5 . 2 3 0 2 . 9 4 178.57 5 0 0 t h m g / l 2 3 . 8 2 0 4 . 2 3 102.21 1 5 0 4. conclusion in the present study, wqi has been computed to evaluate the suitability of groundwater for drinking purpose in keffi central town. after analysis of various physiochemical parameters, the results obtained for the wqi were found to be varied from 44.32 to 61.60 for bore holes and 72.55 to 97.77 for dug wells respectively. this indicated that location 2,4 and 8 of the water samples are safe for drinking purposed. while borehole location 1, and dug well 3,5, 6 and 7 were not suitable for human consumption. it can be said from this finding that groundwater in the study area were found to be good, poor and very poor quality respectively. therefore, public awareness campaign on the dangers of ground water contamination is encouraged. the high values of the water quality index at the study area was due to the higher values of electric conductivities, total hardness, magnesium and bicarbonate as well as: anthropogenic activity, poor site sanitation and soak away. from water quality index values, it is recommended that further improvement is required to treat the poor and very poor-quality wells (such as demineralization and water softening) for using as safe drinking purpose. in addition, bole holes should be provided for other communities within the study area. moreover, there should be quality control standard for all the bore holes, so as to meet up with the nigerian industrial standard (nis). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 194 references abdullahi, nk. and iheankawa, a. 2013. ground water detection in basement complex of northwestern nigeria using 2d electrical resistivity and offset wenner techniques. international journals of science and technology, 2(7): 23-25. afolabi, oo. and olutomitola, oo. 2017. hydrogeochemical assessment of groundwater quality in ado-ekiti metropolis south-western nigeria. water resource, 27: 13. ajibade, ac. 1976. provisional classification and correlation of the schist belts in northwest nigeria. in: kogbe, ca. (ed) geology of nigeria. elizaberthan publication co., surulere, lagos, nigeria., 85-90. amadi, aa., dan-hassan, ma., okoye, no., ejiofor, ic. and aminu, t. 2013. studies on pollution hazards of shallow handdug wells in erena and environs, north central nigeria. environmental and natural resources research, 3(2): 69-77. doi: 10.5539/enrr. v3n2p69. ashwani, k. and anish d., 2009.water quality index for assessment of water quality of river ravi at madhopur (india). global journal of environmental sciences, 8(1): 49-57. ashwani, kt. and abhay, ks. 2014. hydrogeochemical investigation and groundwater quality assessment of pratapgarh district, uttar pradesh. journal of geological society of india, 83:329343. brown, rm., mccleiland, nj, deininger, ra. and o’ connor, mf.1972. a water quality index crossing the psychological barrier (jenkis, sh. ed.). proceedings of the international conference on water pollution research, 18-24 june, jerusalam, 6:787-797. chiroma, jh., ayanninuola, os. andloko, az. 2018. hydrogeochemical assessment of groundwater quality in keffi town, north-central nigeria. dutse journal of pure and applied science(dujopas), 4(2):87-94. dhirendra, mj., alot, k. and namita, a. 2009. studies on physicochemical parameters to access the water quality of river ganga for drinking purpose haridwar district.rasayan journal of chemical, 2(1):195-203. durowoju, or., desogan, a., mustapha, m., waziri, sa. and ibrahim, ua. 2022. assessment of regulation compliance and quality of sachet water factories in ibadan north local government, oyo state, nigeria. arid zone journal of engineering technology and environment, 18(2):169182. etim, ee., odoh, r., itodo, au., umoh, sd. and lawal, u. 2013. water quality index for the assessment of waterquality from different sources in the niger deltaregion of nigeria. frontiers in science, 3(3) : 89 -95. fadhil, ma. and abdulkider, ma. 2013. application of water quality index for evaluation of groundwater quality for drinking purpose in dibdiba aquifer, kerbala city, iraq. journal of babylon university/engineering sciences, 21(5):1647-1660. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com sodangi et al: evaluation of groundwater quality for drinking purposes using water quality index, in keffi central town of nasarawa state. azojete, 19(2):183-196. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 195 farhad, mh., abdullah, ma. and mohammed, of. 2017. an application of water quality index (wqi) and multivariate statistic to evaluate the water quality around maddhapara granite mining industrial area, dinajpur, bangladesh. environment system research, 6:13. gupta, s., kumar, a., ojha, ck. and singh, gj. 2004. assessment of water quality index for the groundwater in tumkurtaluk, karnataka state, india. environmental science and engineering, 46(1):74-78. mishra, pc. and patel, rk. 2001. quality of drinking water in rourkela, outside the steel township. journal of environment and pollution, 8(2):165-169. nematollah, mj.,ebrahimi, p., razmara, m. and ghasemi, a. 2016. hydrogeochemical investigation and groundwater quality assessment of torbat-zaveh plain, khorasanrazavi, iran. journal of environmental monitoring assessment, 188(2): 2-21. nigeria geological survey agency, 1994. geological and mineral resources map of northcentral nigeria on scale 1:1,000,000. published by the authority of the federal republic of nigeria, abuja. nigeria standard for drinking water quality, 2015.nigeria industrial standard, nis, lagos: 554, 1-18. olayinka, ai., abimbola, af. and isibor, ar. 1999. a geoelectrical-hydrogeochemical investigation of shallow groundwater occurrences in ibadan, s. w. nigeria. environmental geology, 37(1, 2): 31-39. onyeagocha, ac., 1986. geochemistry of the basement granite rocks from north central nigeria. journal of african earth sciences, 5(6): 651-657. palwasha, a., ghulam, ss., farrukh, rs., aftab, ak., sadaf, sa. and muhammad, ak. 2020. groundwater quality assessment using a water quality index in nine major cities of sindh, pakistan. international journal of research in environmental science, 6(3): 18-26. shaif, mk., saleh, sh., al-alaiy, g. and abdulrazzak, b. 2017.application of water quality index to assessment of ground water quality. university of aden journal of national and applied sciences, 2(1): 127-136. shweta, t., sharma, b., singh, p. and dobhal, r. 2013.water quality assessment in terms of water quality index. american journal of water resources, 1(3): 34-38. tijani, mn. 1994. hydrogeochemical assessment of groundwater in moro area, kwara state, nigeria. journal of environmental and geological, 24: 194-202. tijani, mn. 2016. groundwater-the buried vulnerable treasure. an inaugural lecture of university of ibadan, ibadan., 80p. http://www.ui.edu.ng. tripathi, ak., mishra, uk., mishra, a., saras, t. and dubey, p. 2012. 2012. studies of hydrogeochemical in groundwater quality around chakghat area, rewa district, madhya pradesh, india international journal of modern engineering research (ijmer), 2(6):1-2 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):183-196. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: sodangiali2020@gmail.com 196 turner, dc. 1983. upper proterozoic schist belts in nigeria sector of the pan-african province of the west africa. precambrian research, 21:55-79. wu, j., li, p. and qian, h. 2011. 2011. groundwater quality in jingyuancounty, a semi-humid area in northwest china. e-journal of chemistry 8(2) 787-793. yao, s., xue, b. and kong, d. 2010. chronology and nutrients change in recent sediment of taihulake, lower changjiang river basin, east china. chinese geographical science, 20: 202-208 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%202/azojete%20vol%2019%20no%202/sodangiali2020@gmail.com corresponding author’s email address: chindapin@gmail.com 192 arid zone journal of engineering, technology & environment original research article development of a clay biodigester c. nathan*, e. b. bwala, a. a. barnabas and a. m. damilare department of mechanical engineering, nigerian army university, biu, borno state *corresponding author’s email address: chindapin@gmail.com article information abstract the quest for sustainable waste management, reduction of greenhouse gas emission and the increasing demand of energy has led researchers to seek for alternative solution in meeting both demands. anaerobic digestion technology is used for digesting wastes and producing biogas, which is a source of renewable energy in return. this research work examines the use of clay as an alternative construction material of the anaerobic biodigesters. the biodigesters were carefully designed to ensure airtightness and to attain an anaerobic environment inside the digesters. clay in its nature tends to retain heat received, abundance in nature and is of low cost. the ability of clay material to retain heat makes it viable for biodigester, as temperature is one of the key parameters in the production of biogas. it employed the prototype and evaluated the rate at which clay biodigester produced biogas as compared to other construction materials. five (5) different biodigesters containing different sample compositions were used for the experiment. the first biodigester is the control containing 8kg of cow dung mixed with 16kg of water. the second biodigester contains 4kg of cow dung, 4kg of beans chaff mixed with 16kg of water. the third biodigester contains 2kg of cow dung, 2kg of vegetables mixed with 16kg of water. the fourth biodigester contains 3kg of cow dung, 3kg of beans chaff, 3kg of vegetables mixed with 16kg of water. the fifth biodigester contains 4kg of cow dung, 4kg of goat excreta mixed with 16 kg of water. the biodigesters were evaluated under the same anaerobic condition. it was observed that the biodigester with the cow dung and beans chaff combination produced the highest biogas with an average daily production of 0.41litre/day. the biodigester with cow dung, and vegetables gave an average daily production of 0.35litre/day. the biodigester with cow dung and beans chaff gave an average daily production of 0.384litres/day. the biodigester with cow dung and goat excreta gave an average daily production of 0.352litre/day. the biodigester with cow dung only gave an average daily production of 03.6litres/day. all the experiments were carried out on an average daily temperature of 29℃. each one of the biodigesters have an uptrend line i.e. the higher the retention period, the more the biogas produced. it was also observed that biogas production depends greatly on the temperature of the environment. this is to make biodigesters and green energy easily accessible to the local communities. submitted: 4th june 2024 revised: 2nd december 2024 accepted: 8th february 2025 keywords: bio digester biogas anaerobic digestion clay excreta © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction increasing population has greatly increased the amount of waste generated with poor waste management practices. this poor waste management practices leads to high exposure to outbreak of different kinds of diseases such as malaria, pest multiplication and water-borne diseases (adoum et al., 2023). sustainable waste management: prevention and the reduction of the volume of wastes consumed has become the highest important political priorities in many countries, thereby making it a share effort of the prevention and reduction of pollution, reducing the greenhouse gas emission and also limiting the global climate change (guimarães and rodrigues, 2023; kasinath et al., 2021; jyothilakshmi and prakash, 2016). about 2.01 billion azojete march 2025. vol.21(1):192-201 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:chindapin@gmail.com mailto:chindapin@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 193 tons of municipal solid waste are being generated in the world annually (syed et al., 2020), and the world energy council (wec) has estimated that over 6 million tonnes of wastes will be generated per day by the year 2025 (mahmudul et al., 2021). when these volumes are not properly disposed, they can either be abandoned or disposed as the landfill which produces greenhouse gases and these gases when not properly collected contribute significantly to air pollution and global warming. the increase in energy demand tends to pull pressure on energy generation, and also on the over dependency on the use of fossil fuels which in turn contribute to air pollution and greenhouse gas emission due to the combustion of fossil fuels (barinyima et al., 2018). the increasing use of fossil fuels has increased rapidly with a daily use of oil gas and coal reserve to about 600 million barrels, 400 billion cubic feet (bcf), and 14.2 giga tons of oil equivalent (gtoe) per year (mullo et al., 2018). by the year 2025, it was estimated that the world energy consumption rate will be increased by 30%, according to the u.s. energy information administration (urso et al., 2015), with fossil fuel being the leading source of energy and a non-renewable and limited natural resource. various waste-to-energy technologies, such as anaerobic digestion, incineration, liquefaction, pyrolysis, fermentation, gasification, etc. have been developed in other to account for the challenges of poor waste management practice, to reduce the environmental burden and to proffer solution to the ever-increasing energy demand, as an alternative and affordable source of energy (renewable energy) (arijeet et al., 2023). biogas is a renewable energy resource that is gotten from the digestion of biomass under anaerobic condition and has a calorific value of 6 kwh/𝑚3(miettinen, 2023) ranging between 25.9 to 30 kj/kg depending on the percentage composition of methane present in the gas (okwu et al., 2019). biogas is produced in the absence of oxygen through the process known as anaerobic digestion, and it is an odorless gas that burns with clear blue flames (nwankwo et al., 2017). biogas is an odorless gas which can be obtained from various feed stocks such as piggery, cattle dung, poultry waste and cabbage from kitchen wastes. biogas produces blue flame and can be suitable for cooking, heating of ovens or crucible and lighting. it has a heating value of 22 mj/𝑚3 (soliu and onunka. 2019). the biogas has variety of applications from domestic to industrial use. anaerobic digestion is the process of converting biomass, the residue of plant and animal, manure, sewage, municipal waste, green waste, plant materials and crops into biogas and was first introduced in the year 1870 by jean louis mouras (abubakar, 2022); (cristiane et al., 2021). anaerobic digestion is a microbial process whereby organic carbon are converted by subsequent oxidation and reductions to its most oxidized state (𝐶𝑂2) and reduced form (𝐶𝐻4) (kechrist et al., 2020). dig estates is also the end product of the bio digestion which is rich in both macro and micronutrients suitable for plant fertilizers (bastabak and kocar, 2020), (mucha et al., 2019). anaerobic digestion process is dependent and can be affected by factors, such as; operating temperature, ph, the concentration of the substrates, the loading rate, moisture content, carbon to nitrogen ratio, stirring, co digestion, pretreatment and additives, mixing and reactor design etc. anaerobic digestion can best be suited between 3 temperature ranges; the psychrophilic temperature (15-25℃), mesophilic (30-40℃) and the thermophilic (50-60℃) temperature ranges (mahmudul et al., 2021; oladoye et al., 2017 ). anaerobic digestion (ad) technology (also known as biodigester, bioreactor, anaerobic reactor) is a simple biotechnological commercial route to transform organic waste or biodegradable material to useful energies by consortium of microorganisms living symbiotically. this biological process is carried out purposely to produce biogas and digestate. it is often called biogas plant, where various chemical and microbiological reactions take place. it serves the purpose of providing an anaerobic environment for the proper biodegradation of the organic wastes. it is a structure that should be air and watertight (obileke et al., 2021; atelge et al., 2020). mullo et al., (2018) defined biodigester as a closed vessel/ container that contains the mixture of water and organic matter-manure, for a period of time and maintained at an average temperature of 30℃ to allow for anaerobic degradation, and to produce methane gas and biofertilizers, thereby reducing the polluting potential of the excrements. the development of biodigester makes the management of waste possible, mitigating the organic waste and sewage disposal in the community and also as an alternative energy source which serves as national technology for the production of biogas. the project introduces clay as an alternative construction material to the conventional materials used for the construction of a biodigester. the biodigester will utilize organic waste materials as feedstock to produce biogas, a renewable energy source that can be used for cooking, heating, and electricity generation biogas digester has been constructed using different kind of materials from concrete, steel plastic, aluminium, mild steel, zinc, rubber (soliu & onunka, 2019); oladoye et al. (2017) reported that the color of the constructing material has greater impact on biogas production, as well as the manure color. most bio digesters have been constructed using concrete in cast form to build the digester walls. adoum et al. (2022) designed a biogas digester with high density polyethylene (hdpe) to digest biodegradable waste. aderibigbe (2015) reported the use of ‘storex’ tank has the reactor and also a non-corroding metal and the use of 4 co-substrates. http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 194 another bioreactor was developed by guimarães and rodrigues (2023) using glass jacket to construct the digester, together with a heating and agitation system. the aim of the research is to design, construct and evaluate the performance of a clay anaerobic biodigester for biogas production. 2. materials and methods 2.1 material selection 2.1.1 clay the used clay was obtained from the dlamdi manna village in biu, borno state it has properties that makes it suitable for the construction of biodigester. the properties of the clay are its impermeability, plasticity, coherence, thermal insulation, compatibility with liners and environmentally friendly (ayyub, 2024). 2.1.2 black cotton soil this is the binder that was used for binding the clay particles together. it was mixed with water in the ratio of 2:1. the binder has good strength properties: plasticity, good adhesion, water retention, shrinkage control and compatibility with the firing process of the clay. the black cotton soil is a mineral-based binder that is used to bind clay particles together, the picture of the black cotton soil is shown in plate 1. plate 2 shows the clay binder (black cotton soil) ready to be mixed with clay for the construction of the biodigester (ayyub, 2024). 2.1.3 rubber tube collector the rubber tube collector serves as the gas storage chamber. it is connected to the biodigester with the aid of a pressure hose for gas collection. the tube collector selected is compatible and resistant to the corrosive nature of the biogas. it does not allow the permeability of the gas, it is flexible and ease to install, resistance to weathering, chemical resistance, and low maintenance requirements (ayyub, 2024). 2.1.4 pvc pipes the pvc pipes serve as the medium through which wastes are introduced and evacuated from the biodigester. the inlet and outlet pipes are 7.5cm by 50cm and 4cm by 24cm respectively. 2.1.5 pressure hose the pressure hose is used to evacuate the gas generated from the biodigester and stored in the rubber tube collector. the pressure hose used is 0.5 inches for effective gas transport. 2.1.6 organic waste the organic wastes used are cow dung, goat excreta and agricultural wastes. the animal wastes that were used in this experiment are cow dung shown on plate 3 and the goat excreta shown on plate 5 which are sourced from the slaughterhouse located in bcg area of biu local government area. plate 4 shows the vegetable waste sourced from biu market which is used for the experiment. plate 1: black cotton soil (binder) plate 2: clay-binder http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 195 2.2 design method 2.2.1 design parameter the biodigester developed is 30l as can be seen in figure 3, it has both spherical and cylindrical shape which allows easy mixing of the slurry and effective design of the gas chamber respectively. water is added in the ratio of 1:2. the hydraulic retention time is 15-20 days. the inlet and outlet pipes are 8cm and 6cm respectively. the gas collection opening was design to be 0.5inches. figure 1 shows the diagram of the biodigester, and its dimensions used in the experiment. figure 2 shows the exploded view of the biodigester showing the individual components of the system, separated together. figure 3 shows the front view of the biodigester, it is usually a 2d representation of the biodigester components as seen from front direction. figure 4 shows the isometric view of the biodigester which is a 2d representation of the biodigesters components, shown in 3dlike perspective. figure 5 shows the full labelled diagram of the biodigester used in the experiment. plate 3: cow dung plate 4: vegetables plate 5: goat excreta 360mm 160mm 180mm 75mm * 500mm 50mm * 240mm figure 1: clay biodigester figure 2: exploded view of the biodigester figure 3: front view of the biodigester figure 4: isometric view of the biodigester http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 196 2.2.2 procedure for the development of the biodigester the binder was soaked with water in the ratio of 2:1. after a uniform mixture was obtained, the binder mixture was then poured in the fine particle clay and mixed to form lumps as can be seen on plate 6. the clay and the binder mixture were wedged by kneading and pressing to ensure consistency and to remove air bubbles in the clay materials as can be seen on plate 7. the clay material was centered to a prototype pot to get the base and to ensure a symmetrical pot as can be seen on plate 8. it was followed by shaping and throwing of the pot by using hand and shaping tools. after which, trimming of the excess clay was done when it was partially dry. after the clay pot was air dried and its leather hardened, two openings were created on the clay anaerobic digester. the two openings were designed to allow for the insertion of the 2.5 inches and 1.5 inches diameter pipes for the inlet and outlet. the first opening was located at the top of the digester which serves as the feeder for the digester. the second was located at the bottom of the digester and serves as the medium for the removal of the digested wastes. the openings are made to be directly opposite to each other. another opening was made at the top of the digester, for the collection of the produced gas in its chamber. this opening is 0.5 inches, for the ease of gas collection. rubber hose was inserted in this opening, and it was connected to an external rubber tube for gas storage. after the drying stage and the various openings were obtained, bisque was done on the pot in the kiln, at a lower temperature of around 1000℃ to harden it. it then subjected to a higher temperature of about 1200-1300℃ to ensure further hardness of the clay pot. the pot was then allowed to cool slowly in the kiln to prevent cracking. air-tight cover was provided for the clay anaerobic digester for complete fermentation of the organic waste in the digester. 2.2.3 characterization of the waste the total volume of the biodigester used for the project is 30 liters. the wastes used for the experiment include cow dung, goat excreta, beans chaff and vegetables. each of these wastes were digested in the pots in the ratio of 1:2. • 8kg of cow dung was used with 16kg of water in the first pot, this serves as the control pot. this ratio constitutes about 80% of the digester volume as can be seen on plate 9. plate 6: lump formation plate 7: kneading plate 8: base finishing of the pot figure 1: fully labelled diagram of the biodigester 5 6 4 3 2 1 8 7 s/n name of component 1 clay biodigester 2 inlet pipe 3 inlet cap 4 cover 5 outlet valve 6 gas outlet valve 7 outlet cap 8 outlet pipe http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 197 • 4 kg of cow dung and 4kg of beans chaff were mixed with 16kg of water in the second pot as can be seen on plate 10. • 2kg of cow dung and 2kg of vegetable waste were mixed with 16kg of water in the third pot as can be seen on plate 11. • 3kg of cow dung, 3 kg of beans chaff and 3 kg of vegetable were mixed with 16kg of water in the fourth pot as can be seen on plate 12. • 4kg of cow dung and 4kg of goat excreta were mixed with 16kg of water in the fifth pot as can be seen on plate 13. plates 9 to 13 show the composition mixtures used in the five (5) different clay pots. 2.3 data collection the mean atmospheric temperature under which the biodigester operates was recorded daily. the biogas production data was taken on two days’ interval for a period of 15-20 days. the volume of the biogas was obtained after weighing an empty tube collector using f-mettler usa weighing balance with a precision of 0.1g, and then reweighing it when the gas was collected in the tube. the difference in this value gives us the mass of the biogas. the volume was obtained using the relationship below: 𝜌 = 𝑚 𝑉 (1) the biogas was collected into the tube collector and taken to the lab for analysis of the composition of the various gases present in it, at a daily interval. 2.3.1 data analysis the biogas produced was analyzed by observing the variation of the volume of the biogas across the retention period. the composition of the methane and carbon dioxide gas present in the biogas was analyzed using a gas analyzer instrument. data generated were subjected to microsoft excel software to compare the variations of temperature on the various pots and on the wastes type and the biogas yield. 2.4 design theory and calculations • total volume: the total volume designed for the project is 30l • operating volume: the operating volume is about 80% of the total volume. plate 9: cow dung mixture plate 10: cow dung + beans chaff plate 11: cow dung + vegetable waste plate 12: cow dung + beans shaft + vegetables waste plate 13: cow dung + goat excreta http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 198 vo = 80%vt = 24l (2) • hydraulic retention time: a hydraulic retention period of 20days is selected for the digestion of the wastes. • the organic flow rate: it is the rate of daily input of organic wastes into the digester. it can be gotten from the formula 𝐻𝑅𝑇 = 𝑉𝑂 𝑄 (3) the organic flow rate is calculated to be 0.0012𝑚3/𝑑𝑎𝑦, equivalent to about 1.992kg of the wastes to be loaded into the digester per day 3. results and discussion the daily biogas production of each individual clay biodigester was collected for a period of 18 days under the same ambient conditions. observable differences of physical and chemical characteristics of the digesters were seen during the production of the biogas. figures 6 shows the graph of the daily biogas production using cow dung. it can be seen from the graph that at days 1 and 2 no gas was produced; the microorganisms take time to adapt and break down the complex organic matter. the microorganisms start to digest the cow dung, biogas production gradually increases. the highest volume of the biogas gas produced was collected in day 13 with the value of 0.5 liter. the rapid increase in biogas production is because of the microorganisms multiplying and become efficient in breaking the organic matter leading to increase in biogas production. the average volume of biogas calculated was found to be 0.36litrs/day. figure 7 shows the graph of biogas production using cow dung and beans chaff. it can be seen from the graph that no biogas was produced in days 1 and 2. the microorganisms take time to adapt and break down the complex organic matter. the microorganisms gradually start to digest the cow dung and beans chaff, biogas production gradually increases. the highest volume of the gas produced was collected in day 3 with the value of 1.3 liters. the rapid increase in biogas production is as a result of the microorganisms multiplying and become efficient in breaking the organic matter leading to increase in biogas production. the average volume of biogas calculated was found to be 0.41litrs/day. the gradual decline in biogas production is, as the easily digestible organic matter is depleted, the organisms start to slow down, leading to decrease in biogas production. 0 0.2 0.4 0.6 0 5 10 15 20 v o lu m e o f b io ga s (l ) number of days figure 6: graph of biogas production using cow dung http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 199 figure 8 shows the graph of daily biogas production using cow dungs and vegetables, it can be seen from the graph that at day 1 and day 2 no biogas was produced. the microorganisms take time to adapt and break down the complex organic matter. the microorganisms gradually start to digest the cow dung and vegetables which gradually increase the production of biogas. the highest volume of the biogas produced was collected in day 7 and day 12 with the values of 0.7 litres in each of the two days. the rapid increase in biogas production is as a result of the microorganisms multiplying and become efficient in breaking the organic matter leading to increase in biogas production. the average volume of biogas calculated was found to be 0.35litrs/day. the gradual decline in biogas production is, as the easily digestible organic matter is depleted, the organisms start to slow down, leading to decrease in biogas production. figure 9 shows the graph of daily biogas production using cow dung, beans chaff and vegetables. it can be seen from the graph that at day 1 and day 2 no biogas was produced. the microorganisms take time to adapt and break down the complex organic matter. the microorganisms gradually start to digest the cow dung and vegetables which gradually increase the production of biogas. the highest volume of the biogas produced was collected in day 8 with the value of 1.2 liters. the rapid increase in biogas production is as a result of the microorganisms multiplying and become efficient in breaking the organic matter leading to increase in biogas production. the average volume of biogas calculated was found to be 0.384litrs/day. the gradual decline in biogas production is, as the easily digestible organic matter is depleted the organisms start to slow down which leads to decrease in biogas production as can be seen from the graph. figure 8: graph of cow dung and vegetables 0 0.2 0.4 0.6 0.8 0 5 10 15 20v o lu m e o f b io ga s (l ) number of days 0 0.5 1 1.5 0 5 10 15 20v o lu m e o f b io ga s (l ) number of days figure 7: graph of cow dung and beans chaff http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 200 figure 10 shows the graph of daily biogas production using cow dung and goat excreta. it can be seen from the graph that at day 1 and day 2 no biogas was produced. the microorganisms take time to adapt and break down the complex organic matter. the microorganisms gradually start to digest the cow dung and goat excreta which gradually increase the production of biogas. the highest volume of the biogas produced was 1 liter which was collected in day 17. the rapid increase in biogas production is as a result of the microorganisms multiplying and become efficient in breaking the organic matter leading to increase in biogas production. the average volume of biogas calculated was found to be 0.352litrs/day. the gradual decline in biogas production is, as the easily digestible organic matter is depleted the organisms start to slow down which leads to decrease in biogas production. 4. conclusion a local biodigester was developed using a pulverized clay and a black cotton soil as the binder. the five different biodigesters used were filled with organic waste of different proportions and further evaluated for biogas production under the same anaerobic condition using different proportions of waste in each of the digesters. the digester with the cow dung and beans chaff produces more biogas than other combinations. it can be deduced that using more than one substrate in the digester tends to produce more biogas than using a single substrate. it was finally recommended that polypropylene fiber should be added to the clay to improve its strength, reduce cracking and increase the durability of the biodigester. references adoum k., blaise, n. b., fabien, k., alphonse t., marinette j. g., adoum d. a., gilbert t., martial n. n., didier, f. 2023. mathematical approach of the design and fabrication of a hdpe geomembrane biodigester for the recycling of the biodegradable waste into biogas and organic liquid fertilizer. global journal of engineering and technology advances,14(1): 50-71 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 5 10 15 20v o lu m e o f b io ga s (l ) number of days figure 9: graph of cow dung, beans chaff and vegetables figure 10: graph of cow dung and goat excreta 0 0.2 0.4 0.6 0.8 1 1.2 0 5 10 15 20v o lu m e o f b io ga s (l ) number of days http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 192-201. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 201 arijeet, k., trisha, d., sivagami, k., mohammed, r.c., aabid, h.s., bandaru, k., samarshi, c. 2023. a comprehensive insight into waste-to-energy conversion strategies in india and its associated air pollution hazard. environment technology & innovation, 29:103017 atelge, m.r., atabani, a.e., banu, j.r., krisa, d., kaya, 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international journal of emerging technology and advanced engineering, 5(2). http://www.azojete.com.ng/ mailto:chindapin@gmail.com corresponding author’s email address: omoniyi.po@unilorin.edu.ng 409 arid zone journal of engineering, technology & environment review article optimization of machining parameters and nano-lubricant effects on drilling, grinding, and turning machining process; challenges and future trends a review p. o. omoniyi1* 1department of mechanical engineering science, university of johannesburg, johannesburg, south africa corresponding author’s email: omoniyi.po@unilorin.edu.ng article information abstract any machining operation that generates heat must adequately dissipate it to minimize thermal stresses on the tool-workpiece contact. this inescapable heat production phenomenon, caused by using suboptimal machining parameters and a lack of long-lasting machining lubricant, adversely impacts the finished surface quality, tool destruction rate, and workpiece structure. therefore, this review focuses on optimizing machining parameters and nano-lubricant effects on the various response parameters such as surface finishing, materials removal rate, tool wear rate, and cutting forces under drilling, grinding, and turning machining. the study reviewed reputable articles from elsevier, springer, and other quality outlets. this review cut across the impact of machining parameters and nano-lubricants on the drilling, grinding and turning process. the study also discussed the challenges of optimizing machining parameters during the drilling, grinding, and turning. received: 21st february 2025 revised: 3rd april 2025 accepted: 4th april 2025 keywords: machining nano-lubricant drilling grinding turning parameters optimisation © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction manufacturing entails different processes or methods for producing mechanical and industrial components (diniță et al., 2023). various processes are employed, such as milling, grinding, turning, and shaping. however, in this review, the focus is on the drilling, grinding, and turning procedure for the optimization of machining parameters with different machining conditions such as nano-lubrication, flood cooling, vegetable cutting fluid, and mineral oil cutting fluid via minimum quantity lubrication, and dry cutting process (kanishka and acherjee, 2023; okokpujie et al., 2017; ezugwu et al., 2023; okokpujie and tartibu, 2023). drilling mechanical components is one of the most widely used processes in the manufacturing industry. drilling a particular hole dimension requires a lot of mechanical power relative to the drilling parameters during the machining process (okokpujie and tartibu, 2023b; jia et al., 2021). parameters include the hole depth, the machine's movement during drilling (feed rate), and the cutting speed of the spindle that carries the drilling tools okokpujie and tartibu, 2023c; deswal and kant, 2023; okokpujie and tartibu, 2023d). also, some features contribute to the performance of the drilling process, such as the flute, helix angle, drilling axis, drilling diameters, the shank, and the materials used to develop the drilling tools. this analysis is presented in figure 1. tool path optimization techniques are frequently applied to computer numerical control machines to minimize energy consumption, production time and cost, etc. several artificial intelligence systems based on the traveling salesman problem (tsp) have been put into practice sectors to maximize tool trajectory length in diverse manufacturing processes, mostly the procedure of drilling holes (okokpujie and tartibu, 2023e; schlegel, 2023). dhouib and zouari (2023) employed the adaptive-dhouib-matrix-3 (a-dm3) to predict an iterated stochastic dhouib-matrix-3 (dm3) metaheuristic (t.s.). to verify the a-dm3 method's capacity and stability to determine the shortest drilling tool path, it was tested using a rectangular grid of holes in six real-world case studies. additionally, it is contrasted with some widely employed techniques, including the hybrid cuckoo search genetic algorithm (cs-ga), modified shuffled frog leaping algorithm (msfla), ant colony optimization (aco) and several of its derivatives, and genetic algorithm (g.a.). according to computational results, the suggested a-dm3 outperformed these well-known metaheuristics in the literature, especially in a medium and large number of holes. as a result, a-dm3 beat rival algorithms to produce a new azojete june 2025. vol.21(2):409-430 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/009 www.azojete.com.ng mailto:omoniyi.po@unilorin.edu.ng mailto:omoniyi.po@unilorin.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 410 record for the shortest path length, often improving upon it by almost 100%. several modeling tools have been employed in various machining processes, which have proven viable for the parameter's optimization and assisted in identifying the significance of the nano-lubrication in the drilling procedure. in turning operations, the cutting model is different from drilling and grinding. figure 1: key characteristics of the drilling process in the manufacturing industry, (a) the drilling bit, (b) setup of the drilling process, (c) graph of performance analysis of the machining parameters in turning process, the cutting tool can be employed to cut through high depth of cut, by using a lathe to spin the metal and a cutting tool moving linearly along the diameter to remove metal. turning is a machining operation that results in a cylindrical shape (okokpujie, i.p. and tartibu, l.k., 2023f; karpuschewski et al., 2021; okokpujie and tartibu, 2023g). cylindrical materials employed to build mechanical systems are dimensioned via turning, as illustrated in figure 2a. the application of optimization models for predictions for turning parameters and the study of the cutting fluid on the workpiece's chemical, mechanical, and thermal properties have been transformed from a raw product to a finished product (dey et al., 2023; okokpujie and tartibu, 2023h; gupta et al., 2023). if workpiece's surface is unsuitable for mechanical operations, the developed component or part of the component will be taken for grinding operation to obtain the desired surface roughness (kishore et al., 2022). the grinding process, commonly called surface grinding, is a type of machining where the material is removed to achieve surface finishes and precise finish tolerances using a powered abrasive wheel, stone, belt, paste, sheet, and compound (yu et al., 2023; virivinti et al., 2021; hu et al., 2019; xiao et al., 2023; roy et al., 2022). figure 2a and b shows the grinding operations. figure 2: (a) turning characteristics and (b) grinding operations http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 411 the application of several optimization tools is promise-able for the machining process, such as drilling, grinding, and turning operations (selvan et al., 2023; abbas et al., 2023). however, there are still challenges with the end product during manufacturing when it comes to the complex production of mechanical systems (sharma et al., 2023; abdo et al., 2023; qazani et al., 2023). therefore, this study reviews the optimization of machining parameters and the effects of nano-lubricants on grinding, drilling, and turning operations. also, to identify the challenges and suggest possible solutions to the existing problems identified in this review study. 2. impact of machining parameters and nano-lubricants on drilling processes the minimum quantity lubrication (mql) approach and cutting fluid with a blend of vegetable oil and al2o3 were used in research by pal et al., (2021). the primary goal of the study was to examine how drilling aisi 321 stainless steels using hss drilling instruments performed in different lubricants and coolant settings (dry, flood, unadulterated mql, and nanofluid mql). drilling actions, surface roughness, drilling tip temperatures, and tool wear process were among the factors examined. the air pressure was set at 6 bar, and the coolant supply rate was 120 ml/hr for the mql conditions. different amounts of nano-al2o3 (0.5, 1.0, and 1.5 weight percent) have been added to the nanofluids to assess the cooling abilities of sunflower oil. in light of the results, drilling with pure, wet, and dry mql was exceeded by cutting fluids using vegetable oil and al2o3 in mql drilling. when using nanofluid mql drilling, the 30th hole showed a considerable reduction in thrust force, torque, surface roughness, and drill tip temperature of around 44%, 67%, 56%, and 26% compared to flood circumstances—additionally, drilling with nanofluid mql settings significantly reduced tool wear. the more significant chilling impact caused by nfmql owing to the lubricating qualities of nanoparticles may be the cause of the improved results of nanofluid mql drilling. using pal et al., (2022), another study used the mql drilling method to test the cooling and lubrication capabilities of several nanofluids made of vegetable oil combined with different nanoparticles (including al2o3, mos2, sio2, cuo, and graphene). the primary goal of this study was to compare the drilling efficiency of various cooling conditions, such as dry, flood, unadulterated mql (pmql), and the nanofluid mql (nfmql), in terms of cutting traits like thrust effect, torque, roughness of the surface, drill tip temperatures, and wear mechanism when drilling aisi 321 stainless steel. the experiment showed that nfmql techniques had superior performance and better machining characteristics. the cooling strategy utilizing 1.5 percent by weight al2o3 offered better cooling and lubricating effects, improving machining qualities among the nfmql conditions. in comparison to flood drilling at the 30th hole, the thrust force, torque, roughness of the surface, and drill tip temperature obtained from 1.5 weight percent al2o3 nfmql drill significantly 1035 n, 10.8 nm, 2.902 m, and 56.5 °c, respectively. these values were decreased by around 42.81%, 64.7%, 53.84%, and 20.97%. in addition, comparable to other drilling circumstances, the 1.5 weight percent al2o3 nfmql condition showed the smallest amount of tool wear. the nanoparticles of al2o3 mixed with soybean oil showed several tribological enhancement mechanisms, including self-repairing or fixing processes, picking or ball-bearing processes, polishing processes, and tribofilm creation among contacting surfaces, which improve drilling characteristics. these mechanisms may be responsible for the outstanding performance of al2o3 nfmql. ezilarasan et al., (2021) attempted to simulate, evaluate, and investigate the machining properties of an alloy throughout the drilling process. the subject of the inquiry was using a silver nanoparticle fluid in a minimal quantity lubrication (mql) setting. the authors examined several variables: thrust force, drill cutting edge temperature, side wear, and surface polish. the study also investigated the residual stress under various combinations of process factors. multi-response optimization using rsm and empirical approaches for these variables were created. the results showed that feed rate (which contributed 60%), spindle speed (which contributed 88.63%), feed rate (which contributed 71.42%), and spindle speed (which contributed 67.76%) were, respectively, the primary effects on thrust effect, drill cutting temperature, roughness of the surface, and tool wear, with additional variables having a smaller impact. utilizing a cutting fluid made from vegetable oil and several minimal quantity lubrication (mql) techniques, both with and without the inclusion of graphene nanoparticles, the hole drilling efficiency for stainless steel aisi 321 was evaluated in the study by pal et al., (2020) the experimental findings showed that, in comparison to pure mql settings, the mql drill with 1.5 wt% nanoparticles of graphene dramatically decreased the thrust force (by 27.4%) as shown in figure 3, pressure (by 64.9%), the roughness of the surface (by 33.8%), and coefficients of resistance (by 51.7%) at the 30th hole. additionally, it increased tool life. in conclusion, adding sufficient graphene nanoparticles to the fluid mql drill process improved the drilling characteristics by enhancing lubrication performance and film stability. http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 412 figure 3: drilling analysis of aisi 321 stainless steel, (a) differences in thrust force (n) values, and (b) disparity in torque (nm) varied depending on the lubrication environment. source: (pal et al., 2020) high-speed stainless (hss) drill bits were used to drill aluminium 6063 alloy, and tests were done to examine how well they performed under various lubrication conditions, including dry, flooded, unadulterated minimum amount lubricant (mql), and the mql with nanofluid. the analysis was restricted to measuring the forces of cutting (thrust force and torque), tool wear, and surface roughness. a 200 ml/h oil flow rate and a 70-psi air pressure were maintained by both mql procedures (pure mql and mql containing nanoparticles). the nanofluid in question comprised the fundamental oil (soybean oil) and 1.5 percent of the volume of 20 nmsized nanoparticles (al2o3). compared to alternative coolant-lubrication systems, the testing findings show that the nanofluid mql (nfmql) substantially boosts the number of drilled holes while decreasing drill torques and thrust forces. the improved cooling capacity and decreased friction forces at the tool, chip, and workpiece interfaces of nfmql are responsible for its excellent performance. additionally, the nanofluid mql successfully removes burrs and chips, improving hole surface circumstances and lengthening tool life by reducing tool wear. the effects of the cutting fluid comprising nanoparticles of aluminium oxide and mineral oils on tool life and roughness of the surface during the drilling process of the stainless steel 304 were examined by subhedar et al., (2021) in a two-step process, the researchers produced the nano-cutting fluid by adding al2o3 nanoparticles to the cutting metal fluid at fractions of the volume of 0.3, 0.8, and 1%. the stability of the nanofluid is achieved using ultrasonic agitation force and drilling on a vertical cnc machine at speeds of 1000 and 1500 rpm with a constant feed rate of 0.050 mm per revolution. the results demonstrated that nano coolants lengthen tool life and lessen surface roughness. when using nano cutting fluid, which has a 1% volume percentage and has the least surface roughness at 1000 rpm, tool life is shown to be the longest. the resulting results demonstrate how useful nano-coolant is. the tool undergoes rotational force from interacting with the workpiece throughout the drilling process. this rotational force can lead to imperfections or even the complete malfunction of the tool. nam et al., (2015) presented the drilling rotational forces observed in micro-drilling experiments under various drilling conditions. the drilling rotational forces for each set of 10 holes were averaged and depicted according to the number of holes drilled. when utilizing compressed air lubrication, the micro-drill failed at the 87th hole. it is important to note that 150 holes were considered for the other conditions, as the micro-drill did not break during the drilling of 150 holes. conventional minimum quantity lubrication (mql) and nanofluid mql reduce the magnitude of the rotational force compared to compressed air (c.a.) lubrication. furthermore, using nanofluids decreases the drilling rotational force compared to standard oils. several scientists have employed experimental methodologies to explore the utilization of nanofluids in drilling operations. mosleh et al., (2017) performed experiments under high-pressure conditions using cutting fluids improved by incorporating mos2 and diamond nanoparticles to assess the characteristics of these liquids in a typical drilling process. the results of the experiments demonstrated that nanofluids containing 2–4% mos2 nanoparticles amplified the load-bearing capability by up to 16% while significantly reducing the transfer of materials from smoother stainless-steel balls to the harder tungsten carbide ball. conversely, nanofluids containing a 1% concentration of diamond nanoparticles led to a decrease in load-bearing capacity of approximately 10%. nam et al., (2011) conducted a comprehensive assessment of the characteristics of a micro-drilling procedure employing the nano minimum quantity lubrication (mql) technique. in this context, diamond nanoparticles measuring 30 nm in diameter were employed alongside vegetable oil and paraffin as the base fluids. the study revealed that the nano mql significantly enhances the quantity of drilled orifices while simultaneously reducing the forces exerted on the drill and the torque required for drilling, as opposed to conventional approaches. additionally, the nanofluid mql effectively eliminates the undesired protrusions (a) (b) http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 413 and fragments formed during drilling. liew et al., (2018) empirically assessed the effects of the carbon nanofiber nanofluid on the drilling process of aisi 304 steel. the efficiency of drilling was evaluated by examining the roughness of the hole surfaces, the precision of the hole dimensions, and the occurrence of burrs. furthermore, a comparison was made between the drilling performance of the nanofluid and that of distilled water. the findings indicated that the nanofluid improves the surface's smoothness and the hole's accuracy while reducing burr formation. table 1 debit summary study of drilling application via the nano-lubrication process. table 1: summary analysis of some of the literature reviewed for drilling machining authors details base lubricant nanoparticl es /% conc. method of delivery workpiece materials machining parameters findings nam et al. (2018) vegetable oil 0.4wt% of diamond nanoparticles two-step method titanium alloy (ti-6al4v) drill diameter, feed rate, spindle speed the optimal process is achieved with the weight concentration muthuvel et al. (2020) ethylene glycol 1g of 70nm c.u. nanoparticles for every 500 ml two-step method aisi 4140 steel cutting speed, feed rate the chosen concentration has decreased flank wear and surface roughness by 71% and 53%, respectively. babu et al. (2020) ethylene gycol 1g of 50nm white c.u. nanoparticles for every 500 ml two-step method aa 5052 alloy surface roughness, cutting speed, tool wear when contrasted with dry and oil lubrication, it was shown that using copper nanofluid under mql tool wear reduces by 36 and 24%, and surface roughness reduced by 92 and 76%. shalimba et al. (2018) jatropha oil 1wt%-10wt% of iron nanoparticles two-step method steel čsn 11 523 cutting temperature, depth of cut the efficacy of lubrication and cooling is enhanced when nanoparticle concentration is added to jatropha oil. liew et al. (2018) water 4wt% of cu nanofiber particles two-step method titanium alloy cutting speed, feed rate the findings demonstrate that, in comparison to pure deionized water, carbon nanofiber nanofluid provides a superior surface finish and a lower cutting temperature. nam & lee (2018) vegetable oil 0.4wt% of diamond particles two-step method titanium alloy (ti-6al4v) feed rate, drill diameter, spindle speed the nano-mql successfully reduces drill tool chip adhesion and hole burr. cetin et al. (2020) rapeseed oil (canola) 0.5wt% silver nanoparticles two-step method aisi 304 austenitic stainless steel cutting speed, feed rate vegetable oils enhanced with nano-silver and boron did not perform well in lowering cutting forces. gomezmerino et al. (2022) taladrine, t 0.03vol of silica nanoparticles two-step method steel cutting speed, depth of cut the application of phasechange substances, including solid particles in drilling, as a sustainable, environmentally pal et al. (2021) vegetable oil 1.5wt% of mos2 nanoparticles two-step method aisi 321 stainless steel cutting speed, feed rate high surface activity nanomos2 particles readily adsorb to the interacting surfaces, sustaining the lubricating effect. hoang et al. (2022) caltex aquatex 3180 0.1wt% of graphene nanoparticles two-step method aisi sus 304 stainless steel spindle speed, feed rate the nano-lubricant can be applied to deep drilling of other hard-to-cut materials. http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 414 3. impact of machining parameters and nano-lubricants on the grinding process to serve as a coolant (cutting fluid) during the grinding process, kananathan et al., (2018) examine recent developments and applications of nanoparticles in lubricants. coolants are employed during grinding to lessen workpiece thermal deformation, minimize wheel wear, flush chips, and improve surface smoothness. flood cooling, a traditional method, disperses much fluid and mist, endangering people and the environment. thus, as an alternative, a cutting-edge cooling method called quantity lubrication (mql) has been developed to improve surface smoothness, lower costs, lessen negative effects on the environment, and use less metalcutting fluid. a study of the use of different nanoparticles and their effectiveness in grinding processes was carried out in addition to implementing sophisticated cooling techniques. the study also discussed how nanoparticle performance relates to cutting forces, surface quality, tool wear, and cutting zone temperature. according to the study, the nanofluid's exceptional qualities can cool and lubricate machinery during production (zhang et al., 2022). experimental research determined the impacts of minimum quantity nanolubrication (mqnl) on the surface grinding of tungsten carbide grade yg8. the studies used two distinct base oils—mineral (paraffin) and vegetable (sunflower)—to distribute mos2, graphite, and al2o3 nanoparticles in varied concentrations. the process efficiency was assessed using the grinding outputs, like specific energy, cutting force, and surface quality. additionally, the effectiveness of mqnl in grinding w.c. material was assessed by contrasting the outputs of grinding in various environments, including dry, wet, and mql. the findings demonstrate that the mqnl technique successfully increases process efficiency by lowering the grinding force and specific energy and improving surface quality if nanoparticles are chosen effectively. zhang et al., (2022) have discussed the dangers of traditional flood cooling techniques and the difficult circumstances that might arise during dry grinding, highlighting the relevance of minimal volume lubrication (mql) as the only workable way for grinding cemented carbide. the impact on the residual tension in the cemented carbide is complicated by the introduction of force and heat changes brought about by the inclusion of nanoparticles during grinding. the arrangement of the particles on the grinding wheel's surface was analyzed using a single abrasion grinding force model to calculate an effective number of abrasive particles. the workpiece was then subjected to a stress fracture model developed and used in a method of step-by-step attenuation. the heat field model was the foundation for creating a thermal stress model. a final model for forecasting the residual stress was developed by evaluating the grinding process outcomes and performing stress loading and relaxation. four distinct yg8 grinding settings were used, and a minimum frictional coefficient of 0.385 was attained using tiny fluids minimum quantity lubrication (nmql). this allowed the model to be experimentally validated. precision analysis was used to establish the validity of the stress residual model. during dry grinding, a minimum error value of 5.9% was found in the orthogonal direction to the workpiece feed direction. comparatively, mql applications using unadulterated oil as a base and flooding cooling based on water-grinding fluids fared worse than those using nano lubricants. by lowering the tangential grinding power, particularly grinding energy, and offering high grinding (g)-ratios, nano lubricants demonstrated superior grinding results. through methodical tribological testing, modeling a machining contact combining rough crystals and the workpiece in a surface grinding technique (as shown in figure 4), a thorough evaluation of the enhanced efficiency of nano lubricant in mql grinding was carried out. by continually delivering active lubricant additives and generating a durable, low-friction tribo-film at the sliding interface between the rough grit and the workpiece surface, it was shown in figure 4b that nano lubricants efficiently reduce sliding frictional losses (zhang et al., 2023). figure 4: (a) experimental setup of the tribological testing and (b) a graph comparing the coefficient of friction ss regard to the lubricant used source: (zhang et al., 2023). (a) (b) http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 415 using a vortex tube to create a low-temperature grinding atmosphere to increase heat transfer and a combination of nanoparticles used as a nano-lubricant to reduce friction in tungsten carbide ultra-precision grinding, zhang et al., (2023) proposed a reduced temperature nano-lubrication approach. the outcomes demonstrated that the technique greatly lowers wheel deterioration and raises workpiece surface integrity. compared to conventional minimal quantity lubrication, the arithmetical average height (sa) and the maximum height (sz) were lowered by 50.8% and 65.3%, respectively, and wheel degradation was reduced by 57.8%. these outcomes were achieved using a 1:2 mix-ratio mos2/fe3o4 nano-lubricant and an optimized lowertemperature gas at 20 °c. multiwall carbon nanotubes were combined with sae 20w 40 oil to create nanofluids for the grinding process. the surface coarseness and microcracks were examined in this experimental investigation. the most popular material for molds and dies is aisi d3 tool steel, which was chosen to analyze the surface properties. according to experimental findings, the surface smoothness of the machined workpiece improves from micro to nanoscale. using minitab 15 software, the l8 orthogonal array was employed to optimize the machining settings in the taguchi design of the experimentation technique. regression analysis was used to build an empirical framework for forecasting output parameters, and the outcomes for the grinding process, both with and without nanofluids, were empirically evaluated. the significant parameter influencing surface roughness was identified using the analysis of variance and the f test. analysis using atomic force microscopy showed that adding carbon nanotube to nanofluid during the grinding process improved surface properties, including surface roughness and microcracks (prabhu and vinayagam, 2012). gao et al., (2021), the aerospace industry now favors carbon fibre-reinforced polymer (cfrp), which makes it simple to manufacture integrated components with a high degree of specific strength and stiffness. the main technique used to produce precision components and ensure exact assembly location is grinding. however, because of its hygroscopicity, flood lubrication is only sometimes used in cfrp grinding, whereas dry grinding produces unwanted results, including increased forces, deteriorated surfaces, and blocked wheels. to get beyond these technological limitations, this work used grinding and friction-wear testing to analyze the grindability and resistive behavior of the cnt biological lubricant mql. compared to the dry state, the coefficient of friction was reduced by 53.47% thanks to the outstanding and long-lasting anti-friction capabilities of the cnt biological lubricant, according to the testing findings. the novel lubricant has also shown benefits regarding tribological characteristics and removing material behavior. effectively reducing tensile breakage and tensile-shear fracture and eliminating material from multifiber blocks. notably, compared to dry grinding, the tangential, normal, and specific grinding forces were all minimized by 40.41%, 31.46%, and 55.78%, respectively. the proposed approach minimized surface roughness and produced the ideal surface morphology by avoiding scratches, fiber pull-out, and resin spreading. wheel clogging was also avoided by lowering the temperature and forming a lubricating oil film. compared to dry grinding, sa and sq of the cnt biological lubricant decreased by 8.4% and 7.9%, respectively. garcía et al., (2018), an experimental strategy to improve the ra-measured machining surface roughness is developed. the goal is to create a grinding lubricant with nanoparticles as the primary component. an investigation is made into how titanium dioxide (tio2) nanoparticles affect the surface roughness of cutting tools used in the metal-mechanics industry, emphasizing slitting knives. the literature demonstrates that nanoparticle concentrations less than or equal to 0.1% in weight have a substantial impact. a reaction surface statistical analysis was conducted using manufacturing variables like the spindle speed and rate of feed on grinding machines and control variables like nanoparticle concentration. according to the analysis of slitting knives, spindle speed, and feed rate have no discernible impact on surface quality. in contrast, the weight % of nanoparticles in the oil-based lubricant was the sole important factor. utilizing response surface methods, the use of nanoparticles significantly improves the value of ra. the initial ra value of a fluid without nanoparticles is 0.9449, but the ra value for a fluid with the ideal number of nanoparticles (0.055%) increases noticeably to 0.2805. the response has increased by an astounding 69% due to this improvement. as a useful cooling lubricant throughout grinding operations, the grinding fluid contains nanoparticles with qualities that minimize friction and wear. the grinding studies included nanoparticle jet mql, minimal lubrication (mql), dry grinding, and flood grinding. the grinding energies were distinct for each method, with an average of 84, 29, 8, and 45.5 j/mm3 for dry grinding, dry flooding grinding, mql, and nanoparticles mql, respectively. notably, while utilizing nanoparticle mql, the grinding energy reduced noticeably to 32.7 j/mm3. flooding grinding, mql, and nanoparticles jet mql all resulted in appreciable decreases in surface roughness levels compared to dry grinding. the ten-point height of microcosmic unevenness values reduced by 1.5%, 0.5%, and 1.3%, whilst the overall topographic pattern values decreased by 11%, 2.5%, and 10%, respectively. these findings support the effectiveness of mql nanoparticles as lubricants. the study also added mos2, carbon nanotube (cnt), and nanoparticles of zro2 to the nanoparticle jet mql's grinding fluid to examine their effects on lubrication. mos2 nanoparticles had a particular grinding energy of 32.7 j/mm3, 8.22% and 10.39% lower than the other two varieties. the mos2 nanoparticles also decreased the workpiece's surface roughness, demonstrating their remarkable lubricating abilities. various mos2 nanoparticle volume concentrations were investigated to determine their contribution to grinding surface greasing. the experiment used 1%, 2%, and 3%, and the http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 416 findings showed that a volumetric concentration of 2% mos2 particles had sufficient lubricating effects. it was noted that when the volume amount of mos2 nanoparticles rose, the surface's particular grinding energy and roughness initially increased and later reduced (zhang et al., 2015). the negative environmental effects of machining lubricants are the main reason for using minimal quantity lubrication (mql) technology instead of conventional techniques. the mql technique is less successful than conventional approaches because of greater heat production while grinding and greater specific energy for cutting. however, including nanoparticles in the base oil may improve the lubricating efficacy in grinding. this study used the mql approach to analyze the steel grinding procedure of the aisi d2 cold work tool. to assess their impacts on the forces that cut (typical and tangential) and roughness of the surface, two types of vegetable-based oils—colza and soybean. to with various quantities of mos2 and cuo nanoparticles. the findings showed that adding 4% cuo nano-powder and 2% mos2 nano-powder to soybean base oil reduced normal and tangential forces by 19% and 35%, respectively. additionally, using 2% cuo nano-powder in colza base oil resulted in a considerable reduction of 77% in surface roughness compared with pure oil as a grinding fluid (azami et al., 2023). rekha et al., (2023) use the taguchi technique and grey relational analysis as the primary tools used in this study to choose the best cylindrical grinding process variables for austenitic stainless steel 304. the input elements in a grinding operation are the process parameters, which, when combined, significantly impact the output responses. the workpiece speed, longitudinal feed, transverse feed, and coolant flow rate are the variables related to the grinding process examined in this study. surface roughness and material removal rate are the performance metrics on which the impact of various grinding parameters is examined. the l9 orthogonal array, produced using the taguchi technique, served as the basis for the experiments. additionally, the ideal settings for the grinding process (longitudinal feed = 6 m/min, work speed = 20 m/min, coolant flow rate = 1.43 l/min, and transverse feed = 0.02 mm), which meet both requirements (surface 189.37 mm3 of material removal rate and 0.395 lm of roughness) were forecast with grey relationship evaluation. also, awale et al., (2020) researched mql optimization of the machining fluid during the grinding process with grinding parameters. yang et al., (2024) show that optimizing machining fluid and its parameters in the grinding process is highly needed for advanced manufacturing for sustainable production of engineering components. table 2 discusses several methods for preparing the nano-lubricant, its application, and its findings. table 2: summary analysis of some of the literature reviewed for grinding machining authors details base oil nanoparticles used/% concentration method of developing the nanolubricant work piece machining parameters and responses findings lee et al. (2012) paraffin oil 1%-4% nanodiamond and al2o3 two step method steel surface roughness, grinding force it has shown that the volumetric concentration, type, and size of nanoparticles are crucial factors that affect how well the micro-grinding process works. zhang et al. (2015) synthetic lipids 6wt% mos2/cnt hybrid nanoparticles two-step method gh4169 ni-based alloy (inconel 718) principal axis power, grinding scope the results demonstrate that the mos2/cnt mixed nanoparticles outperform single nanoparticles in terms of lubricating effect and that the ideal mos2/cnt mixture ratio and nanofluid concentrations are 2:1 and 6 wt%, respectively. http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 417 authors details base oil nanoparticles used/% concentration method of developing the nanolubricant work piece machining parameters and responses findings jia et al. (2014) soybean oil 4% mass fraction of mos2, zro2 and polycrystal diamond nano-particles two-step method hardened 45 steel feed speed, cutting depth, nozzle angle/ distance when the nanoparticle mass fraction was larger than 6%, the lubricating effects of the nanoparticle jet mql decreased as the mass fraction rose. kumar et al. (2019) deionized water 0.5wt% of al2o3, zno, b4c, mos2 and h-bn nanoparticles respectively two-step method silicon nitride wheel speed, workpiece infeed speed, depth of cut, grinding width the experimental findings showed that mos2 nanoparticlebased nanofluids have improved lubricating capabilities. zhang et al. (2017) bluebe #lb-1 synthetic lipid oil 2wt% of al2o3 nanoparticles + sic nanoparticles two-step method hard nibased alloy (inconel 718) grinding power, removing material workpiece rate, surface roughness (ra) when the ratio of n.p. sizes in the al2o3/sic mixture was 70:30, the maximum workpiece removal rate (189.05 mm3/(s n)) and the smallest rsm (0.0381 mm) were attained. zhang et al. (2015) liquid paraffin, palm oil, rapeseed oil, and soybean oil 2-5wt% of mos2 nanoparticles two-step method 45 steel grinding pattern, wheel speed, feed speed, cutting depth the optimum addition amount of molybdenum disulfide nanoparticles in the experiment was 6% mass fraction. shabgard et al. (2017) distilled water + 20wt.% canola oil 0.15, 0.25, 0.35vol% of cuo nanoparticles one-step method aisi 1045 steel cutting speed, table speed, depth of cut the findings demonstrate that manufactured nanofluids efficiently lower temperatures and grinding forces, particularly under difficult machining circumstances. kalita et al. (2012) paraffin (mineralbased) oil and soybean (vegetablebased) oil 8 wt% of emulsified mos2 nanoparticles two-step method en 24 steel and ductile cast iron wheel speed, workpiece speed, depth of cut, grinding width, grinding passes the process efficiency of mql grinding using nano-lubricants is increased by results demonstrating energy consumption, friction loss at the wheelworkpiece interface, and decreased tool wear. khatai et al. (2020) water 4% vol. of al2o3 two-step method aisi 52100 steel alloy grinding force, surface roughness, cutting depth utilizing the zro2 nanoparticle as a nanotechnology lubricant in grinding is restricted by its lower heat conductivity and greater density. mao et al. (2013) water 0.75 wt% al2o3 nanoparticles two-step method aisi 52100 steel wheel diameter, wheel speed, cutting depth according to experimental data, utilizing the nanofluid mist is significantly influenced by the spraying direction of the mql nozzles. http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 418 4. study of machining parameters and nano-lubricants on turning process due to its remarkable properties, ceramics are frequently used when machining extreme temperature alloys like haynes 25 alloy. the effectiveness of a cutting tool composed of whisker-reinforced ceramics (wrcct) in combination with the minimum amount of lubrication (mql) technique was investigated in a study by sarkaya et al. (2021) this was accomplished in particular by employing solid lubricants spread in nanofluidmql. several cutting conditions, including dry cutting, turning with the base fluid mql (bf-mql), mql employing hbn-based nanofluid (hbn-nmql), mql with mos2-based the nanofluid (mos2-nmql), and mql with graphite-based nanofluid (gr-nmql), were used in this work to investigate the co-based haynes 25 alloy. the feed rate (0.1 percent by weight and 0.15 mm/rev) and cutting speed (200 and 300 m/min) were modified. before using the microscopic particles in the machining experiments, the researchers evaluated their stickiness and heat conductivity. compared to the base cutting fluid, the results showed that the thermal conductivity coefficient increased by 11.90% in hbn-nanofluid, 16.29% in mos2-nanofluid, and 14.12% in grnanofluid. gr-nmql showed the best machining performance regarding surface roughness, whereas hbnnmql successfully reduced notch wear and nose wear values. the temperature decrease reached 27.18% using hbn-doped nanofluids, 34.95% using mos2-doped nanofluids, and 29.32% using graphene-doped nanofluids compared to dry turning. to better understand novel approaches for extending the useful life of cutting tools and improving the calibre of final surfaces while turning difficult alloys, sartori et al. (2018) investigated the application of minimum quantity cooling (mqc) and minimum quantity lubrication (mql) techniques. solid lubricants (s.l.) for additives were proposed and analyzed for two different mql and mqc solutions. among the solutions was a water-based solution with variable amounts of graphite and an mql technique using vegetable oil enhanced with ptfe particles. the research proved that the newly created techniques improved tool longevity and the precision of machined surfaces. the mqc techniques, with the help of solid lubricants, showed the best results, as shown in figure 5a-d. figure 5: cutting tool rake faces under the various machining conditions: (a) overall 2d profiles, (b) the zone of the damaged cutting edge, (c) 3d tool images, and (d) surface defects detected on samples machined, dry, sl-assisted mql, and sl-assisted mqc. source (sartori et al., 2018) the turning process has been subjected to several attempts to regulate cutting force, temperature, roughness of the surface, and tool wear. however, it might be difficult to constrain these parameters directly with dry machining. numerous lubricants have so far been used to solve this problem. nanofluids were produced in the work by rao et al., (2021) by adding 6% and 8% of al2o3 nanoparticles by volume to the vegetable fluid. these nanofluids were used to mill en-36 steel, and the variables were assessed using conventional dry http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 419 machining and lubricants made from mql nanofluids. the studies used the taguchi methodology, and an analysis for variance (anova) was used to examine the results. the experimental and anticipated values were compared and analyzed. roughness, temperatures, cutting force, and tool wear were much better with 8% nanofluid with mql than they were with 6% volume of nanofluid using mql or dry machining, according to the analysis of the findings. for example, the cutting force was 280.46 n, the temperature was 44.16 °c, the roughness was 0.1 m, and the tool wear was 0.0031 mm. the results showed that, in comparison to dry milling, the application of 8% volume of nanofluid using mql increased machining performance. optimizing the mql methodology for the hard turning process of 90crsi steel (60–62 hrc) is the main objective of duc et al.'s (2019) study. in order to achieve this, al2o3 and mos2 nanoparticles are added to the base fluids, which include soybean oil and a water-based emulsion. the researchers use analysis of variance (anova) to determine how mql factors affect the force of cutting and surface roughness. the results show that coating carbide insert performance is enhanced when mql uses al2o3 and mos2 nanofluids. additionally, the fluid type, nanoparticles, and their concentration highly impact the cutting performance. future studies using al2o3 and mos2 nanofluids will benefit greatly from the study's understanding of the interactions between these factors. by mixing cutting fluid comprising alumina and multi-walled carbon nanotube (mwcnt) nanoparticles at different volumetric percentages of 0.25, 0.75, and 1.25 vol%, sharma et al., (2020) created a hybrid nanocutting fluid. the basic nanofluid (alumina nanofluid) and the generated hybrid nanofluids' thermophysical characteristics were studied. additionally, pin-on-disc tests were used to evaluate the tribological properties of all nanofluid samples, and contact angle measurements were used to determine their spreadability. figure 6(a-b) shows dramatically how rising temperatures and concentrations of nanoparticles both improve the thermal conductivity and viscosity of nanofluids and hybrid nanofluids. al-mwcnt hybrid nanofluid exhibits a noteworthy increase of 11.13% in temperature over the base fluid spreadability. the results showed that a reduction in wear was caused by a rise in the concentration of nanoparticles in the cutting fluid, having the hybrid nanofluid showing the least wear, as shown in figure 6c. figure 6: the study of the effect of the al2o3 and al-mwcnts on (a) thermal conductivity, (b) viscosity, (c) wear analysis, and (d) coefficient of friction on the base fluid source: (sharma et al., 2020) also, figure 6d shows that the smallest coefficient of friction is held by al-mwcnt next to the alumina nanofluid. this decreased coefficient of friction decreased the cutting forces by reducing the contact force. additionally, using the minimal quantity lubrication (mql) approach, these nanofluids' effectiveness as cutting fluids was assessed while turning aisi 304 steel. measurements of the cutting forces and surface roughness http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 420 created regression models. the results show that the hybrid nanofluid performs better than the alumina nanoparticle mixed cutting fluid regarding machining forces and surface roughness. turning is a procedure that is regularly used in machining and is widely applied. however, when it involves turning high-strength materials, much heat is produced, which has detrimental impacts, including accelerated tool wear, erratic chip formation, and tinier variations in physical attributes. synthetic coolants, sometimes known as flood-type coolants, are used in excess to solve these problems, but controlling and getting rid of the extra coolant is difficult and quite expensive. the minimum quantity lubrication (mql) approach is used in conjunction with water soluble cutting oil that has been injected with nanoparticles (particularly graphene) to address this problem. the goal of this strategy is to improve machining quality. to achieve a surface roughness of 0.462 µm while maintaining a cutting tool temperature of 55 °c using the mql-go (graphene oxide) process, the experimentation focused on the turning process of monel k500 while taking into account various parameters, including cutting speed, feed, and depth of cut (kulandaivel and santhanam, 2019). singh et al., (2017) found that increasing the concentration of nanoparticles increases both thermal conductivity and viscosity. at the same time, the hybrid nanofluid has a lower thermal conductivity than its constituent parts and a viscosity in the middle of the two. the tribological analysis confirms that wear decreases with increasing nanoparticle concentration, with the hybrid nanofluid showing the smallest amount of wear. in addition, the hybrid nanofluid outperforms the base fluid and the alumina-based nanofluid regarding wetting properties. hybrid nanofluid surpasses cutting fluid combined with alumina nanoparticles, as demonstrated by turning aisi 304 steel using the minimal quantity lubrication (mql) approach. the study shows that the efficiency of hybrid nanofluids is improved when gnp and alumina are combined. when combined with mql, using a hybrid nanofluid significantly lowers the force needed to cut, thrust, and feed force by 9.94%, 17.38%, and 7.25%, respectively, and the surface roughness by 20.28%. to reduce the negative effects of friction and heat on the tool and the workpiece, nanofluids are frequently used. water and al2o3 nano-powder are combined with mustard oil to create the nanofluid mixture. the goal is to determine how cutting parameters and nanofluids affect the temperature of the tool bit, workpiece, surface roughness, material removal rate, and cutting forces during the turning of mild steel. high-speed stainless steel was used as the cutting tool for the cutting processes carried out on a conventional lathe machine while altering the spindle speeds (n), feeds, and depth of cut. it was shown that employing al2o3 and mustard oil compared to al2o3 with water nanofluids resulted in a better material removal rate. additionally, it was discovered that the surface roughness in the latter scenario was inferior (lokanadham and sivasankara, 2019) to identify acceptable solutions with a minimum quantity of lubrication and cooling (mqcl) aided turning of ti-6al-4v eli, rahman et al., (2019) studied 18 distinct nanofluids. they created two nanofluids by mixing canola and extra virgin olive oils with three different types of nanoparticles (0.5%, 2%, and 4% by volume): al2o3, mos2, and rutile-tio2. a canola nanofluid with a 0.5% al2o3 concentration produced an improved surface polish. on the other hand, it was discovered that canola nanofluid with 0.5% mos2 concentration substantially lowered temperature and increased chip removal. the nanofluids also displayed advantageous tool wear properties and reduced friction-related wear. sem and x-ray dispersive analysis of the completed surface demonstrated the existence of tribo-film production and the effects of nano-polishing. the shape of the machined surface, the reduction in surface defects brought about by the manufactured nanofluids, as well as the degree of viscosity (kinematic and dynamic), angle of contact, interaction area, and heat conductivity of the nanofluids were also included in this analysis. table 3 shows the breakdown of some selected literature for the turning process via nanoparticle implementation in manufacturing. table 3: summary analysis of some of the literature reviewed for turning machining authors details base lubricant nanoparticles used/% concentration method of developing the nanolubricant workpiec e materials machining parameter s findings sayuti et al. (2014) mineral oil 0.2-1.0wt% of sio2 nanoparticles two-step method aisi4140 steel feed rate, cutting velocity, depth of cut with a 0.5-weight percent concentration in the mineral oil, a reduced air stream pressure, and a 30-nozzle orientation angle, the roughness of the surface can be increased. prasad et al. (2013) water soluble oil 0.5wt% of nano graphite powder two-step method aisi 1040 steel cutting speed, surface roughness, depth of cut in comparison to dry machining, mql nanofluids routinely outperform flood lubrication. http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 421 5. discussion on the challenges and future trends in the optimization of machining parameters during drilling, grinding and turning processes the intricacy of interrelated factors offers a severe barrier to optimizing machining parameters. changing one parameter can frequently cause ripple effects in others, necessitating a sought-after careful balance. when we evaluate parameters, such as cutting speed, feed rate, and tool shape during a milling operation, we learn they are not independent; as pointed out, searching for an optimum combination is more difficult in the drilling process (sahu et al., 2022). this problem is exacerbated by the wide variety of materials and machining processes, which introduce different interactions and reactions to achieve optimal outcomes. a thorough grasp of these complicated interactions and a methodical strategy for determining the most efficient and effective parameter choices are required. for example, in the aviation and aerospace industries, carbon fibreauthors details base lubricant nanoparticles used/% concentration method of developing the nanolubricant workpiec e materials machining parameter s findings patole et al. (2018) ethylene glycol 0.2wt% of mwcnt nanoparticles two-step method aisi 4340 steel cutting speed, surface roughness the study of the results also shows that ethylene glycolnanofluid is one of the most important variables impacting surface roughness. padmini et al. (2016) vegetable oils 0.5wt% of mos2 nanoparticles two-step method aisi 1040 steel cutting speed, feed, depth of cut except for absorbance, basic characteristics have increased as npi has grown. compared to all other lubricant conditions, 0.5%cc+nmos2 patole et al. (2018) ethylene mwcnt nanoparticles two-step method aisi 4340 feed rate, depth of cut, cutting speed, tool nose radius compared to a traditional flood system, good surface and tool wear roughness may be achieved while preserving cutting forces with the right process parameters in mql modes with nano coolant. shuang et al. (2019) mineral oil+saponifi ed natural oil+water 0.5wt% of grapheme oxide nanoparticles two-step method ti-6al-4v titanium alloy cutting temperature, cutting speed, cutting depth, feed rate when smaller velocities, lower feed, and greater coolant pressure were used, the cutting temperatures were lowered by 27.16 °c, 30.42 °c, and 31.8 °c, respectively. yildirim et al. (2019) vegetable oil 0.5wt% of white graphite nanoparticles two-step method nickelbased inconel 625 speed of the cut, feed rate according to the findings, 0.5 vol% hbn nanofluid has given results that are encouraging in terms of tool wear being reduced and good tool lifespan. yan et al. (2011) grease 10wt% of copper nanoparticles two-step method aisi 1045 steel cut's depth, speed and feed rate the experiment's findings demonstrated that the highest machining performance came from using liquid nitrogen and a 0.5 vol% hbn cooling technique. yildirim et al. (2019) vegetable oil 0.5wt% alumina two-step methd inconel 625 feed rate, cutting speed the 0.5% of alumina nanovegetable-lubricant performed better than the base fluid krishna et al. (2010) vegetable oil 0.5% wt% of boric acid solid lubricant two-step method aisi 1040 steel feed rate, depth of cut, cutting velocity with a percentage rise in nano-boric acid in the base fluid. http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 422 reinforced polymers (cfrp) show enormous potential among the array of fibre-reinforced polymer (frp) composites (bhanot et al., 2015). however, drilling cfrp composites presents issues due to delamination, which affects structural integrity, all compounded by the composites' heterogeneous and anisotropic character. because these characteristics are interrelated and somewhat interdependent, achieving delamination-free machining necessitates paying attention to how they are combined. striking a balance between both would undoubtedly become critical for the holes' outstanding quality, polish, and dimensional precision (pimenov et al., 2022). moving-forward, drilling parameter optimization can be enriched by experimenting with advanced optimization methods such as grey relational analysis, artificial neural networks (ann), fuzzy logic, and genetic algorithms, which can help yield more profound insights into parameter interactions. furthermore, extending the use of fabricated composites to other machining operations such as wire edm and milling can help uncover valuable data, as performing a comprehensive suite of destructive and non-destructive tests (including tensile, compression, impact, liquid penetrant, magnetic particle, eddy current, ultrasonic, radiography, and thermography tests). this multidimensional approach can push the machining parameter optimization area toward more complete and robust solutions (kumar et al., 2023). in grinding, a shortage of qualified operators is one of the most significant challenges in optimizing machining parameters during a grinding operation. human expertise is critical for interpreting subtle intricacies that automated methods may overlook, as demonstrated by rudrapati et al., (2016) when they used a multiobjective genetic algorithm (moga) to optimize vibration and surface roughness in traverse simultaneously cut cylindrical grinding of stainless steel material. because of the complex interaction of many input parameters and their consequent varying impact on critical output responses, skilled operators with the experience and acumen to comprehend the complex relationships between machining parameters and desired outcomes become indispensable (abhishek et al., 2015). therefore, while technological advancements pave the way for sophisticated optimization methodologies, the irreplaceable human touch remains paramount in navigating the intricate landscape of parameter optimization in a grinding process (prakash et al., 2022). therefore, a promising path forward would involve a synergy of human expertise and cutting-edge technology. by encouraging continuous training and knowledge enhancement among skilled operators, such as the review taken by zolpakar et al., (2021), their ability to decipher intricate parameter interactions can be further refined. simultaneously, integrating advanced data analytics, artificial intelligence, and machine learning into the optimization process can augment the capabilities of skilled operators, as this collaborative approach empowers operators to make informed decisions supported by data-driven insights, thereby enhancing the efficiency and accuracy of parameter optimization (kant and sangwan, 2015). this way, the convergence of human skill and technological prowess can navigate the complexities of machining parameter optimization, encouraging even more streamlined and effective grinding processes. in the turning process, mastering the delicate balance between tool, technique, and material characteristics becomes essential for successful machining outcomes in demanding manufacturing scenarios. one challenge in optimizing machining parameters is the unique and varying responses materials have with cutting tools under their individual turning process. every material, from metals to advanced composites, has distinct mechanical behaviour’s or responses to any machining process. a good example is the inconel 718 superalloys, which find application in components needing superior chemical and mechanical traits even at elevated temperatures. still, these alloys are intricate, making them seem 'difficult to machine (pinheiro et al., 2021). this diversity in material characterization under machining processes necessitates that operators grasp material science well before delving into parameter optimization. as a way forward, simulation software can create virtual machining environments to ensure the testing of various parameter combinations without physical setups. with this virtual setup, material wastage and production downtime could also be reduced greatly as an add-on advantage (korkmaz and gupta, 2023). additionally, machining processes could be equipped with real-time monitoring systems with several sensors that can provide crucial data during the process. this sensor information can help operators better understand the dynamic material-tool interactions and make necessary adjustments (hassan, and attia, 2023). 6. conclusion the application of machining parameters optimization and nano-lubrication effects on drilling, grinding, and turning operations have been studied. in order to improve the economy, reduce idle time, reduce environmental pollution, and increase the safety of the end users during machining, the implementation of nano-lubricants is significant. however, without the study of optimization of the machining parameters, the risk of cutting tool substitution will be high. this study has reviewed literature that cut across the drilling, http://www.azojete.com.ng/ mailto:omoniyi.po@unilorin.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 409-430. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omoniyi.po@unilorin.edu.ng 423 grinding, and turning machining process. from the reviewed study, the following conclusions were drawn for the three-machining process under study: 3. literature has proven that optimizing machining parameters such as speed, depth of drilling, and feed rate of the movement of the machine bed greatly assists drilling operations. however, according to statistics, due to the drilling mechanisms, the cutting tool faces high vibration challenges during the drilling process. in these terms, the application of nano-lubricants also helps in the reduction process of friction occurrences, flushing away the chips developed at the drilling region. 4. the same phenomenon is obtained in grinding operations. however, most manufacturing processes deal with the grinding process's surface finishing. so, applying the optimized machining parameters and the nano-lubrication process assists in the material's deformation process during grinding. because a high temperature has been generated in the grinding region. so, the nano-lubricant gives excellent protection to the surface of the workpieces for the grinding process. 5. in the turning process, the nano-lubricant also had advantages. however, the depth of the cut is very significant, and if it is not optimized, it will result in the chartered vibration of the cutting tool. that is why, in the literature, the range of cut depth is between 0.5 to 1.5 mm. this enables the industry's production section to avoid chartered vibrations. therefore, this study recommends that manufacturers work with researchers to conduct an experimental analysis and build a multi-optimization model with a flow rate of the mql nano-lubricant and the machining parameters under 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https://doi.org/10.1007/s00170-021-07155-7 corresponding author’s email address: mmbenomar@yahoo.com 237 arid zone journal of engineering, technology & environment original research article simulation and optimization of municipal solid waste incineration for energy recovery in maiduguri, borno state, nigeria b. m. tela1, m. b. oumarou2* , a. m. eljummah2 and g. m. ngala2 1 nigerian nuclear regulatory authority, pmb: 559 garki, abuja 2department of mechanical engineering, university of maiduguri, pmb: 1069, borno state, nigeria *corresponding author’s email: mbenomar@yahoo.com article information abstract this paper presents an analysis, modelling and simulation of maiduguri municipal solid waste powered electricity generation plant using ansys. determination of the waste’s combustion characteristics: physical, proximate and ultimate analyses using astm standard was carried out. initial and boundary conditions were applied in respect of the materials and geometry in order to carry out a numerical calculation. the reduced scale physical model batch type msw power generating plant was successfully constructed for use to validate the cfd analysis. the msw was sorted, graded, sized and weighted before being fed into the designed batch type model incinerator to fire the boiler. the temperature and pressure of the steam generated were measured using digital thermocouples and pressure gauges so as to quantify the expected energy. a comparison of the simulated and experimental temperature results showed that while area a had 1090. k, 1409.9 k and 1609.6 k, area b had 1918.1 k, 1893.6 k and 1425.1 k, area c had 1413.1 k, 1548.8 k and 1036.6 k during simulation against an average of 1641.9 k for area a, an average of 1896.3 k for area b and lastly for area c, an average of 1641.9 k, using the batch type msw incinerator. the r2 value of 0.979 was observed for 5 kg load, 0.994 for 4 kg load and 0.999 for 3 kg load, for area a. for area b, the r2 values range from: 0.992, 0.993 and 0.995 for 5 kg, 4 kg and 3 kg respectively. for area c, the r2 values range from: 0.998 for 5 kg, 0.996 for 4 kg and 0.987 for 3 kg. the constructed municipal solid waste power plant generated 6.4 v, 6.6 v and 6.5 v for area a, b and c respectively for 33 minutes. a mathematical equation for the calorific value was developed using ansys, ms excel and was found to compare favourably, for up to 87.5% with the model, and 87.40% when compared to the dulong berthelot’s formula. the moisture content, the feed rate and the energy content of the msw greatly affect the quantity of electricity generated from the municipal solid wastes of maiduguri. submitted: 28th november 2024 revised: 3rd february 2025 accepted: 5th february 2025 keywords: municipal solid waste simulation optimization energy recovery incineration © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in any technology, the design process depends on a clear understanding of the fundamental scientific principles on which the design is to be based. these fundamental principles are usually expressed in terms of the governing differential equations of the process under consideration. the required design is then obtained by solving these equations subject to the appropriate boundary conditions, physical constants, input and output conditions. in incinerators, the main combustion-related design items are the burning bed of solid waste on the grate and the gas phase path, including the reactions which take place. simulation is then needed to evaluate the performance of a designed plant at its virtual stage, thereby saving these large sums of money which may be wasted in the case of under-performing plant. mathematical modelling, characterization and analyses of the msw using analytical methods and other softwares has been receiving tremendous attention by researchers across the globe (goodman and teixeira (1990); eriksson and baky (2010); sharmina et al., (2014); ahsan et al., (2014); akbarpour et al. (2016); el-jummah et al., (2016); ola and göran (2017); satoshi et al., (2018)). resource constraints and sustained high fossil fuel prices have created a new phenomenon in the world azojete march 2025. vol.21(1):237-260 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:mmbenomar@yahoo.com mailto:mbenomar@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 238 market. biomass and municipal solid waste (msw) have widely been accepted as important locally available renewable energy sources offering low carbon dioxide (co2) emissions (seksan, 2011). in nigeria, the extreme northeastern part of nigeria typically maiduguri, produces large quantity of waste that needs removal and disposal from the immediate environment. maiduguri also experiences chronic shortage of electric energy, mainly due to the activities of insurgents and other terrors groups which hinder growth and development as well as the economic independence of the region. the waste generation for the year 2023 is estimated to at 2.63×105tonnes using a waste generation rate of 0.53 kg/capita/day, base-year population of 1,328,100 and an annual growth rate of 2.40% for maiduguri (amulah et al., 2024). presently, in the maiduguri area there are several gaps, in the need for more waste studies to cover seasonality; gaps in studies coverage in accounting for material-specific treatment as well as gaps in quality of research design and consistency such as: seasonality and control for days of week, lack of local knowledge on incineration, gasification among others, and material-specific recycling tonnages. there are also gaps in basic compositional data: moisture content, feed rate, energy content, bulk density, etc. this investigation involves the application of modern computational tools that could largely help improve and better the understanding of large quantity msw based modelling and simulation for use in electricity generation. in order to achieve these, there is need to determine the basic composition of the refuse produced by communities in maiduguri, through physical characterization, proximate and ultimate analysis. investigate performance parameters such as the moisture content, the feed rate and the energy content of the msw. develop and validate a mathematical model that will predict the moisture content, the optimum waste feed rate as well as energy content. simulate the moisture content, the optimum feed rate and energy content using ansys, and design and construct a small scale physical model msw power generating plant that will be used to validate the cfd analysis, as well as test and evaluate the performance of the msw power generating plant. 2. materials and methods for this purpose, a personal computer, hp laptop with intel (r) core (tm) i7-5600u@ 2.6 ghz processor and 12gb ram, is used for modelling and simulation. it has windows 10 64 bit operating system (os). the softwares used are: catia v5-6 (r2018) (first-rate mold solution co. ltd, 2018) for modeling, ansys fluent (r1 2023) (sandeep, 2017) workbench for meshing and simulation, and microsoft excel. an air blower (abubakar et al., 2018) and a small-scale batch type model incinerator. 2.1 incinerator sizing the internal volume requirement excludes the ash pit and can be evaluated from (oumarou et al., (2012); yang et al., (2019)): 𝑉𝑖𝑚𝑖𝑛 = 𝑄𝑡ℎ𝑟 258,750 𝑊/𝑚3 (1) 𝑄𝑡ℎ𝑟 = 𝑀𝑏 𝑄𝑎𝑣 (2) where: vimin is minimum theoretical internal volume (m3) qthris total heat released (w) mb is the mass of refuse burned per hour (kg/h) and qav is average heating value (kj/kg). the expression of the amount of municipal solid waste production is (geet al., 2019): 𝑇𝑜𝑡𝑎𝑙𝑀𝑆𝑊 = 𝑀𝑆𝑊𝑝𝑒𝑟𝑐𝑎𝑝𝑖𝑡𝑎 × 𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 (3) http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 239 2.2 incinerator furnace geometry to effect complete combustion high velocity secondary air jets are required (klasen & goerner, 1999; goerner, 2003). to assess the effects of msw loading rates, a batch type fixed bed model of the incinerator would be more appropriate. 2.3 air ratios the combustion conditions in the furnace need to be controlled to give near-stoichiometric conditions by splitting up the total combustion air to a primary air and secondary air ratio of 1.3:1.8 (goerner, 2003). the burning of a fuel (e.g., wood, coal, oil, or natural gas) in air is a familiar example of combustion (kavanaugh, 1984). 𝐶6𝐻10𝑂5+6𝑂2→6𝐶𝑂2+5𝐻2𝑂+ℎ𝑒𝑎𝑡 (4) oxygen starvation often leads to partial combustion of the carbon to co rather than co2: since combustion effectiveness is also a function of gas residence time, it is important that the air volume flow is not too great, otherwise the incinerator dimensions would need to be increased with consequent cost penalties (akpeet al., (2016). 2.4 residence time residence time is determined by the velocity of the gases and the distance they travel through the combustion chamber (oumarou et al., 2012) as shown: 𝑡 = 𝑉 𝑞 (5) or 𝑡 = 𝑐ℎ𝑎𝑚𝑏𝑒𝑟𝑙𝑒𝑛𝑔𝑡ℎ,𝑚 𝑔𝑎𝑠𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦,𝑚/𝑠 (6) where t is residence time (s), v is combustion chamber volume (m3), q is combustion gas flow rate, (m3/s). 2.5 combustion analysis of msw msw typically contains the following elements: c kg of carbon (c), h kg of hydrogen (h2), o kg of oxygen (o2), n kg of nitrogen (n2), s kg of sulphur (s), m kg of moisture, a kg of ash (akhatoret al., 2016): c + h + 0 + n + s + m + a = 1kg of fuel (msw) (7) the theoretical combustion reaction formulae of the combustible elements of municipal solid waste are expressed by the following chemical equations: 𝐶 + (𝑂2 + 3.76𝑁2) → 𝐶𝑂2 + 3.76𝑁2 (8) 𝐻 + 0.25(𝑂2 + 3.76𝑁2) → 0.5𝐻2𝑂 + 0.94𝑁2 (9) 𝑆 + (𝑂2 + 3.76𝑁2) → 𝑆𝑂2 + 3.76𝑁2 (10) 2.6 combustion air requirement considering the theoretical combustion reactions for the msw, characteristics in tables (1, 2 and 3) (babagana et al., 2024), will be used to calculate the air to be supplied; http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 240 table 1: characteristics of msw in area a sample id elements (%) moisture (%) ahs (%) cv (mj/kg) carbon hydroge n oxyge n nitroge n sulfu r sample a1 46.22 0.21 41.85 11.64 0.08 39.24 10 4.3110 sample a2 44.87 0.24 43.94 10.83 0.12 42.58 5.2 7.0610 sample a3 43.14 0.20 47.09 9.46 0.11 41.70 4.80 10.0612 table 2: characteristics of msw in area b sample id elements (%) moisture (%) ahs (%) cv (mj/kg) carbon hydrogen oxygen nitrogen sulfur sample b1 47.91 0.23 41.42 10.34 0.10 37.49 11 19.8107 sample b2 48.02 0.19 41.25 10.45 0.09 42.66 15.20 15.0559 sample b3 47.08 0.20 42.15 10.50 0.07 49.90 13.20 5.7262 table 3: characteristics of msw in area c sample id elements (%) moisture (%) ahs (%) cv (mj/kg) carbon hydrogen oxygen nitrogen sulfur sample c1 45.90 0.55 47.07 6.35 0.13 38.15 10 7.5077 sample c2 46.10 0.67 46.70 6.44 0.09 48.78 5.60 8.4217 sample c3 46.40 0.76 45.93 6.77 0.14 42.40 4.0 4.5086 carbon (c): c+o2→co2 (11) 12 kgc+32 kgo2→ 44kgco2 hydrogen (h): h2 + 0.5o2→ h2o (12) 2kg h2 + 16kg o2→ 18kg h2o 1kg h2 + 8kg o2→ 9kg h2o sulphur (s): s + o2→ so2 (13) 32kgs + 32kgo2→ 64kgso2 1kgs + 1kgo2→ 2kgso2 http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 241 to test and evaluate the performance of the msw power generating plant, a small scale batch type physical model of an incinerator is constructed. the designed incinerator geometry has a width of 0. 40 m, length of 0.50 m and a maximum height of 0.86 m. the geometry is meshed and value of meshes is determined using ansys fluent software and gives 0.17 m3. the minimum temperature is 308 k corresponding to room temperature and the feed-in temperature of municipal solid waste as well as ambient temperature in the study area. 2.7 cfd governing equations in order to calculate the flow field and the combustion of the waste burning inside an incinerator, it is necessary to have a system, which considers all of the involved phenomena (arthur et al., 2021). for the steady flow of a constant-property fluid, the equations that govern the flow around the air foil model are the continuity equation (14), and momentum equation (15). 𝜕𝑈𝑖 𝜕𝑥𝑗 = 0 (14) uj 𝜕𝑈𝑖 𝜕𝑥𝑗 = 𝜕 𝜕𝑥𝑗 (𝜗 𝜕𝑈𝑖 𝜕𝑥𝑗 − 𝑈𝑖𝑈𝑗) 1 𝜌 𝜕𝑃 𝜕𝑥𝑖 (15) where i, j=1, 2, 3, = mean velocity vector in x, y, z directions, p is static pressure, ρ is density and ϑ is kinematic viscosity. for a reliable simulation of an incinerator, it is completely essential to test the numerical procedures from computational and chemical error aspects (pour et al, 2020). to simulate the combustion with steam generation and determination of temperature and pressure, these steps were followed (i.e. geometry (domain) creation, meshing, setup and solution). 2.8 geometry (domain) creation for simplicity of computation and minimize recourses, a 2d model was used and the simulation process was divided into two i.e. first simulating to optimize the combustion process and secondly simulating to determine the steam temperature at various operating pressure. to achieve complete combustion, sizes of the existing or proposed incinerator need to be specified to allow for air supplies calculations to be made. for this study, the following are considered: length = 0.5m, width = 0.4m, height =0.86m and msw height on the bed =.0.2. the 3d model was imported into design modeler of ansys fluent. the model was converted into 2d and only the major fluid domains were taken into consideration for cfd as shown in figure 1. all other parts were deactivated. figure 1: ansys model representing the msw incinerator of the study http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 242 2.9 combustion simulation and meshing the simulation of the combustion process of the msw samples continue by considering the combustion domain. using the name selection tool of the ansys software, names were assigned to the boundaries for identification (id) in the design modeler. the names id are ext_wall, chimney_outlet, blower_inlet, bed_inlet and internal_wall. the meshing was done for the domains lunching meshing on the workbench and fluid domain imported for the two project files. for the combustion domain the mesh element size was set to 0.0016 m and all other properties are left at default values. the mesh was generated with the generate tool. the number of mesh elements generated for the combustion domain was 1.3171 × 105 with 1.3334 ×105 mesh nodes. figure 2: ansys based incinerator geometry and mesh with boundary areas 2.10 setup and solution species model was enabled as a non-premixed combustion. the coal calculator was opened in the species model to input the proximate and ultimate analysis of sample a1. the calorific value of the sample a1 was also inputted and assigning the combusting particle as a1_msw. figure 3 shows the inputted msw characteristics of sample a1 in the coal calculator window. (note the coal as-received is the calorific value). all other values are left at defaults. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 243 figure 3: ansys calculator interface with msw characteristics of sample a1 the setup and solution steps above were repeated with sample a2, a3, b1, b2. b3, c1, c2 and c3 i.e. with their corresponding characteristics. the maximum (optimized) value of boiler_wall_temperature obtained with the corresponding value of blower_vel were noted and recorded for each sample simulated. the optimized temperature would be used in the steam generation simulation. 3. results and discussion figure (4) shows that the calorific value of the msw yields a temperature of 1090.7k. even with the control of the blower velocity, the pattern on the graphs does not change much. the heat is concentrated at the entrance of the furnace, where the supplementary air is coming in contact with the fuel for the first time in the furnace. as time increases and air blower velocity increases, so does the pattern on the ansys generated graphs. this is due to the high moisture level of 39.24%. this behavior could be due to the fact that some of the energy contained within the msw is used to drive away the moisture and not used for other external uses like electricity generation or something else. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 244 figure 4: simulated temperature contours of sample a1 similarly, figure (5) shows a pattern, when the temperature rises to 1136.8k for moisture content of 42.58%. the control of the air blower velocity changes the pattern on the graphs at a lower speed. as time increases and air blower velocity increases, so does the pattern on the ansys graphs. this is due to the high moisture level. this behavior could be due to the fact that some of the energy contained within the msw is used to drive away the moisture too. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 245 blower velocity = 0.1ms-1 blower velocity = 0.2ms-1 blower velocity = 0.3ms-1 blower velocity = 0.4ms-1 blower velocity = 0.5ms-1 blower velocity = 0.6ms-1 blower velocity = 0.7ms-1 blower velocity = 0.8ms-1 blower velocity = 0.9ms-1 blower velocity = 1.0ms-1 figure 5: simulated temperature contours for sample a 2 for sample a3, figure (6) shows that the air blower velocity of 0.1 m/s is almost insignificant in all the ansys generated graphs. the calorific value of the msw yields a temperature of 1336.4k. as the air velocity is increased, so does the pattern change. the heat progresses from the entrance of the furnace, where the supplementary air is coming in contact with the fuel for the first time in the furnace. the high moisture level of 41.7%, is taken care of by the calorific value which now is 10.06 mj/kg. the energy contained within the msw is being used for energy generation. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 246 figure 6: simulated temperature contours for sample a 3 figure (7) shows a clear pattern on the influence of moisture on the heat content. the highest calorific value of 19.81 mj/kg is recorded here and the moisture content of 37.49% seems even not to affect the generation in the furnace as well as the steam generation. the heat is much and is more diffused as the air blower velocity is increased. at 0.6 m/s, 0.7 m/s and 0.8 m/s, the whole boiler temperature is high and the hest envelope is more compact. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 247 figure 7: simulated temperature contours for sample b 1 figure (8) shows that the calorific value of 15.05 mj/kg of the msw yields a temperature of 1893.6k. similarly, with the control of the blower velocity, the pattern on the graphs does not change much, at 0.6m/s up to 1.0 m/s. the heat is concentrated from the entrance of the furnace, where the supplementary air is coming in contact with the fuel for the first time in the furnace. as time increases and air blower velocity increases, so does the pattern on the ansys generated graphs. this is due to the high moisture level of 42.66%. however, the heat generated is high despite the fact that the moisture is high. this behaviour is similar to the previously observed one in sample b 1. the energy contained within the msw is used to drive away the moisture but does not affect its potential of usage for other purposes. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 248 figure 8: simulated temperature contours for sample b 2 a similar behavior and pattern to a1 figure (4) is observed in b3 figure (9). the calorific value of the msw yields a temperature of 1425.1 k. with the control of the air blower velocity, the pattern on the graphs changes at 0.4 m/s. the heat is concentrated in the furnace, but at 0.6 m/s. this is due to the high moisture level of 49.90%. this behavior could be due to the fact that some of the energy contained within the msw is used to drive away the moisture and not used for other external uses. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 249 figure 9: simulated temperature contours: sample b3 for sample c1, figure (10) shows that the calorific value of the msw yields a temperature of 1414.1k. the controlled air blower velocity starts becoming prominent at values of 0.4 to 0.5 m/s, but the pattern on the graphs does not change much. the heat, as previously seen, is concentrated at the entrance of the furnace, where the supplementary air is coming in contact with the fuel for the first time in the furnace. here too, this is due to the high moisture level of 38.15%. and the behavior could be due to the fact that some of the energy contained within the msw is used to drive away the moisture, but could be used for other external uses, to a certain extent. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 250 figure 10: simulated temperature contours: sample c 1 for sample c2, figure (11) shows that the calorific value of the msw yields a temperature of 1548.8k. with the controlled air blower velocity, the pattern on the graphs changes, uniformly at 0.2 m/s to 0.6 m/s, while the impact is felt much at 0.6m/s to 1.0 m/s. as time increase and air blower increase, so does the pattern on the ansys generated graphs. this could also be attributed to the high moisture level of 48.78%. this behaviour causes some of the energy contained within the msw to drive away the moisture and not used much for other external uses like electricity generation. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 251 figure 11: simulated temperature contours for sample c 2 as previously observed, figure (12) shows a similar pattern to those of other samples. as the calorific value is low (i.e. 4.50 mj/kg), so is the temperature, but a much higher moisture content which needs to be driven away before obtaining a useful heat. a temperature of 1036k was recorded for a moisture content of 42.58% as against a temperature of 39.24% for a temperature of 1090.7k. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 252 figure 12: simulated temperature contours of sample c 3 the maximum critical velocity within the incinerator is ranging between 0.6 – 0.8 m/s. velocity has a minimum value at the top of the boiler. there is a vortex type movement occurring close to the boiler. smaller values of velocities could be observed, and these are due to some changes in experimental conditions or errors. this study has shown that the efficiency of energy recovery does not only depend on the design and construction of equipment, but it is also highly affected by the operation. primary air temperature is a key parameter for incinerator operation (khodabandeh et al., (2016); khuriati et al., (2017)), but there is still limited information about how primary air temperature affects msw incineration. as seen in mi yan et al., (2021) who used fluid dynamic incinerator code (flic) and fluent coupled model in their study to highlight the influence of different primary air temperatures on msw incineration in a moving grate incinerator with five zones of primary air feeding. the results too, demonstrated that as the air preheating temperature increased, so did the rate of moisture evaporation and volatile release, the latter of which could potentially lead to higher local maximum temperature in the furnace. thus, it is possible, by using the different primary air temperature setup, to maintain a relatively high rate of moisture evaporation and total mass loss, while having a lower rate of volatile release. ultimately, the multi-temperature primary air setup maintained a high time-average rate evaporation of moisture and lowers the time-averaged rate of volatile release thus, to maintain the local maximum furnace http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 253 temperature at 1685 °c, against an average of 1482oc (1755 k) in the present study. this concept can potentially be utilized in msw incinerators to effectively evaporate moisture from msw while keeping the local maximum temperature in the furnace to a reasonable temperature. this analysis shows that the high moisture levels, at low calorific values tend to reduce the potential of energy availability for other uses. but for higher calorific values like sample b 1 and b 2, the temperatures recorded are still high and can produce steam of good quality, suitable for electricity generation. for lower values of the calorific values obtained, some of the heat released is used to drive away the moisture contained in the msw sample. using the ultimate analyses (i.e. c, h, o, n and s) of all the samples, a regression analysis (table 4) can be carried out in order to predict the calorific values (cfv) of the samples. the regression equation (16) is thus: cfv = 1589694 c 35667336 h 642103 o 3380854 n + 78152084 s (16) table 4: regression analysis with coefficients predictor coef se coef t p no. constant c 1589694 787122 2.02 0.114 h -35667336 20224514 -1.76 0.153 o -642103 637839 -1.01 0.371 n -3380854 2161353 -1.56 0.193 s 78152084 98022615 0.80 0.470 s = 4909761 the analysis of variance (table 5) yields: table 5: analysis of variance source df ss ms f p regression 5 8.72799e+14 1.74560e+14 7.24 0.039 residual error 4 9.64230e+13 2.41058e+13 total 9 9.69222e+14 where cfv stand for calorific value to validate the developed model equation (16), there is need to compare the values obtained with the experimental values obtained using the bomb calorimeter with those from the well-established and widely used formula for biomass, like the dulong berthelot’s (equation 17) (ogunsola et al., 2018). 𝐺𝐶𝑉 = 349.1𝐶 + 1178.3𝐻 + 100.5𝑆 − 103.4𝑂 − 15.1𝑁 − 21.1𝐴𝑆𝐻 ( 𝑘𝐽 𝑘𝑔 ) (17) table (6) shows a comparison and validation of the calorific values generated from the model, the experiments and dulong berthelot’s formula. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 254 table 6: comparison and validation of experimental, developed model and existing formula sample id c h o n s experimental mj/kg present study mj/kg dulong formula mj/kg sample a1 46.22 0.21 41.85 11.64 0.08 4.3110 6.01 6.21 sample a2 44.87 0.24 43.94 10.83 0.12 7.0610 7.31 9.30 sample a3 43.14 0.20 47.09 9.46 0.11 10.0612 7.82 8.53 sample b1 47.91 0.23 41.42 10.34 0.10 19.8107 14.21 7.76 sample b2 48.02 0.19 41.25 10.45 0.09 15.0559 14.77 6.99 sample b3 47.08 0.20 42.15 10.50 0.07 5.7262 10.61 5.44 sample c1 45.90 0.55 47.07 6.35 0.13 7.5077 11.81 10.08 sample c2 46.10 0.67 46.70 6.44 0.09 8.4217 4.66 6.99 sample c3 46.40 0.76 45.93 6.77 0.14 4.5086 5.21 10.85 the bomb calorimeter yielded a value 82.55 mj/kg with an average of 9.17 mj/kg, while the model generated formula yielded 82.41 mj/kg and an average of 9.15 mj/kg. the dulong berthelot formula in turn, yielded 72.15 mj/kg with an average of 8.01 mj/kg. the bomb calorimeter and model generated calorific values are in very good agreement of up to 98%. those values also compare favorably, for up to 87.5% with the model, and 87.40% when compared to the dulong berthelot’s with discrepancies in individual samples when the samples are considered. these discrepancies can be due to the fact that the ash content is not captured in the formula. 3.1 results of experimental analyses in order to generate experimental data, a physical batch type model of the msw incinerator was designed (scale 1:10) and constructed (plates 1), and tested using locally available materials; for the evaluation of boiler temperature, steam pressure within the boiler, the steam pressure at nozzle exit/turbine entrance and the electricity voltage (v). this physical model is based on the principle of dynamic similarities (bansal, (2005); cengel and cimbala, (2010)) where sizes could be reduced, keeping the characteristics constant, like temperature and pressure in this case. for the experiments, a scale of 1:5 is considered and the internal sizes are: 0.2 m x 0.2m x 0.4 m yielding a volume of 0.016 m3. thus, the maximum allowable msw volume per loading could be taken as 5 kg, considering a 0.2 m height of the msw bed. to ensure a thorough composition, the average of seasons was taken. tables (7 to 9) show the experimental results. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 255 plate 1: front view of the constructed batch msw incinerator table 7: experimental results for sample a furnace temperature (k) boiler temperature (k) steam pressure at boiler (bar) steam pressure at nozzle (bar) generated voltage (volts) 1029.4 971.7 2.6 2.7 2 1116.6 1041.6 3.2 3.4 2.5 1259.8 1173.8 4.1 4.2 2.8 1472.6 1273.3 4.8 4.9 3.2 1518.6 1393.6 5.2 5.4 3.4 1594.4 1418.5 5.7 5.8 4 1641.9 1373.2 6.1 6.2 4.4 1440.3 1343.1 6.8 7 5 1397.1 1303.4 7.1 7.3 5.7 1379.2 1285.8 7.8 8.1 6.4 http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 256 table 8: experimental results for sample b furnace temperature (k) boiler temperature (k) steam pressure at boiler (bar) steam pressure at nozzle (bar) generated voltage (volts) 1321.4 1216.1 2.8 2.9 2.7 1564.7 1489.6 3.6 3.8 3 1786.8 1577 4.3 4.4 3.6 1865.9 1619.2 5.1 5.1 3.8 1896.3 1640.2 5.8 5.9 4 1865.4 1645 6.2 6.4 4.7 1856.7 1623.6 6.8 6.9 5.1 1883.5 1635.9 7.4 7.5 5.8 1711.2 1595.7 8.1 8.3 6.4 1689.9 1532.7 8.8 8.9 6.6 table 9: experimental results for sample c furnace temperature (k) boiler temperature (k) steam pressure at boiler (bar) steam pressure at nozzle (bar) generated voltage (volts) 1029.4 1244.7 3.2 3.4 2.7 1116.6 1314.6 3.8 4 3.8 1259.8 1446.8 4.7 4.8 4 1472.6 1546.3 5.4 5.6 4.2 1518.6 1666.6 6.2 6.4 4.6 1594.4 1691.5 6.8 7 5.5 1641.9 1646.2 7.1 7.3 5.6 1440.3 1616.1 7.7 7.8 5.8 1397.1 1576.4 8.3 8.4 6.4 1379.2 1558.8 8.7 8.8 6.5 http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 257 figure 13: graph of blower velocity and burning time for various feed rates of sample a figure 14: graph of blower velocity and burning time for various feed rates of sample b y = -1247.3x + 1304 r² = 0.9792 y = -1512.7x + 1864 r² = 0.994 y = -1825.5x + 2180 r² = 0.999 0 500 1000 1500 2000 2500 0 0.2 0.4 0.6 0.8 1 1.2 b u rn in g d u ra ti o n t im e ( se c) blower velocity(ms-1) burning duration time for 3 kg (sec) burning duration time for 4 kg (se burning duration time for 5 kg (se y = -1214.5x + 1280 r² = 0.9954 y = -1676.4x + 1924 r² = 0.9937 y = -1960x + 2272 r² = 0.9926 0 500 1000 1500 2000 2500 0 0.2 0.4 0.6 0.8 1 1.2 b u rn in g d u ra ti o n t im e blower velocity(ms-1) burning duration time for 3 kg (sec burning duration time for 4 kg (se burning duration time for 5 kg (se linear (burning duration time for 3 kg (sec) http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 237-260. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 258 figure 15: graph of blower velocity and burning time for various feed rates of sample c a comparison of the simulated results and experimental results showed that while sample a had 1090. k, 1409.9 k and 1609.6 k, sample b had 1918.1 k, 1893.6 k and 1425.1 k, sample c had 1413.1 k, 1548.8 k and 1036.6 k during simulation against an average of 1641.9 k; 6.4 volts produced at 1379.2 k for sample a, an average of 1896.3 k; 6.6 volts produced at 1689.9 k and lastly for sample c, an average of 1641.9 k; 6.5 volts at 1379.2 k, during the experiments using the batch msw incinerator. figures (13), (14) and (15) exhibit a similar linear pattern, showing an increase in the time of incineration of the msw, as the feed’s quantity is raised. this assessment is supported by the r2 values of 0.979 for 5 kg load, 0.994 for 4 kg load and 0.999 for 3 kg load, for sample a. for sample b, the r2 values range from: 0.992, 0.993 and 0.995 for 5 kg, 4 kg and 3 kg respectively. for sample c, the r2 values range from: 0.998 for 5 kg, 0.996 for 4 kg and 0.987 for 3 kg. this shows that the moisture content, the feed rate and the energy content of the msw greatly affect the quantity of electricity generated from the municipal solid wastes of maiduguri, with the samples from university of maiduguri, yielding lower electricity than the remaining locations. the msw samples in area c yield 7,500 mj/kg, 8,420 mj/kg and 4,500 mj/kg, with an average of 6,800 mj/kg, which is lower than the average minimum calorific value of 7000 mj/kg, required for setting up an incineration plant with energy recovery (olisa and ajoko, 2018; yeganeh et al., 2023). this implies the need to add a supplementary fuel to the msw, in area c. 4. conclusion at the end of this research work, the following conclusions were drawn: 1. tests ran yielded results which are in good agreement with the simulated results. the developed and validated mathematical model has predicted optimum temperatures as 1370 k as against an experimental value of 1379.2 k for samples in area a, 1745.6 k against an experimental value of 1689.9 k for samples in area b, and 1332.63 k against 1379.2 k obtained experimentally from samples in area c. 2. the simulated moisture content, feed rate and energy content using ansys revealed that critical air velocity of 0.6m/s to 0.8 m/s affect the pressure and temperature which are other important design parameters associated to msw power plant. 3. the waste feed rate, moisture content, calorific value, have a huge impact on the ability of msw to generate electricity, for a longer time as the feed rate is raised, while the moisture content gets reduced. 4. a mathematical equation for the calorific value was developed using ansys, ms excel and was found to compare favourably, for up to 87.5% agreement with the model, and 87.40% agreement when compared to the dulong berthelot’s formula. y = -1167.3x + 1200 r² = 0.9878 y = -1538.2x + 1788 r² = 0.9965 y = -1680x + 2124 r² = 0.9981 0 500 1000 1500 2000 2500 0 0.2 0.4 0.6 0.8 1 1.2 b u rn in g d u ra ti o n t im e ( se c) blower velocity (m/s) burning duration time for 3 kg (sec) burning duration time for 4 kg (sec) burning duration time for 5 kg (sec) http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; 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(2019). small-scale waste incinerators in rural china: potential risks of dioxins and polychlorinated naphthalene emissions. emerging contaminants, 5, 31-34. yeganeh a., ahmad h., reza f. and seyed f. m. 2023. analysis of energy generation from msw with auxiliary feed in the north of iran; results in engineering; 18, www.sciencedirect.com/journal/results-in-engineering http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com https://dx.doi.org/10.4314/jasem.v22i9.02 http://www.mdpi.com/journal/processes http://www.sciencedirect.com/journal/results-in-engineering corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 758 arid zone journal of engineering, technology & environment original research article development of a simulated annealing-optimized adaptive neuro-fuzzy inference system (sa-anfis) for sorghum seed planting parameter tuning i. abubakar1*, i. m. abdullahi2, a. a. balami3, p. a. idah4 1department of agricultural and bioenvironmental engineering technology, waziri umaru federal polytechnic, birnin kebbi, nigeria 2department of computer engineering, federal university of technology, minna, nigeria3department of agricultural and bioresources engineering, federal university of technology, minna, nigeria 4department of agricultural and bioresources engineering, federal university of technology, minna, nigeria *corresponding author’s email: ibrahim.pg2116251@st.futminna.edu.ng, ibrahimabib6@gmail.com article information abstract precision agriculture requires adaptive control systems to optimize planting operations, ensuring consistent planting depth under varying soil and operational conditions. this paper proposes a novel simulated annealing-optimized adaptive neuro-fuzzy inference system (sa-anfis) controller for real-time adjustment of planting parameters based on soil moisture and planting speed. the anfis framework combines fuzzy logic and neural networks to model nonlinear relationships, while simulated annealing (sa) optimizes membership functions and rule bases to enhance control accuracy. experimental validation demonstrates that the sa-anfis controller significantly improves adaptive performance compared to standalone anfis controllers, reducing root mean square error (rmse) by ~18% in dynamic field conditions. the proposed system offers a robust solution for precision planting machinery, enhancing crop yield and resource efficiency. it is, therefore, recommended for autonomous planters. received: 4th june 2025 revised: 24th june 2025 accepted: 27th june 2025 keywords: adaptive control anfis simulated annealing planting depth control fuzzy logic optimization © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1. 0 introduction precision agriculture has become increasingly critical in modern farming to enhance productivity, reduce resource waste, and ensure consistent crop yields. one of the key challenges in mechanized planting operations is that it requires adaptive control mechanisms to maintain optimal planting (qohar and jito, 2022; zhao and zhang, 2024). traditional control methods, such as proportional-integral-derivative (pid) controllers by song et al. (2024), often struggle to adapt to nonlinearities and uncertainties in agricultural environments leading to suboptimal performance. the gradient-based optimization technique determines search directions for the minimization of an objective (or error) function. this technique was used to minimize material loss in the control system while maintaining accuracy of precision (cheng et al., 2021; ji et al., 2021; katzer, 2020). genetic algorithm-optimized back propagation (gabp) algorithm and machine vision were used by jia et al. (2018) for the regulation of the position of corn seed planting in precision farming. also, abdullahi et al. (2018) proposes a novel optimization algorithm called the nomadic pastoralist optimization algorithm (npoa) inspired by the mathematical modeling of nomadic pastoralist herding strategies. fuzzy inference systems (fis) has been applied in various control applications also though they have some gaps. in addition, waluyo et al.(2023) reported fuzzy-based smart farming using iot can increase plant growth while reducing energy consumption compared to schedule-based methods. an iot model using fuzzy logic can optimize photosynthesis and accelerate mustard plant growth compared to previous research (qohar and jito, 2022). anfis was applied in different control applications, and they have some limitations. according to asghar and liu (2018), adaptive neuro-fuzzy inference systems (anfis) provide a promising alternative by integrating fuzzy logic reasoning with neural network learning. however, anfis performance depends heavily on the initial rule base and membership function selection, which may not be optimal for operating conditions. okeke et al. (2022) compares the performance of anfis and mlr models in predicting wastewater treatment plant performance, finding mlr to be more robust and reliable. report by alsharkawi et al. (2021) shows than azojete september 2025. vol.21(3):758-768 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/007 www.azojete.com.ng mailto:ibrahim.pg2116251@st.futminna.edu.ng mailto:ibrahim.pg2116251@st.futminna.edu.ng mailto:ibrahimabib6@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 759 an anfis-based controller outperformed a sliding mode controller for trajectory tracking of a three-wheeled omnidirectional mobile robot. anfis models can predict wheat crop yields more precisely than ann or mlr models using attributes like biomass, soil water, radiation, and rain (khoshnevisan et al., 2014). the paper evaluates the use of ann and anfis models to predict agricultural yields from an energy perspective. the effectiveness of anfis can be further improved through metaheuristic optimization (abba, 2019; abubakar et al., 2024; asghar and liu, 2018; espitia et al., 2022; hilali et al., 2025; nguyen et al., 2019; obe and dumitrache, 2015; okeke et al., 2022; sobrinho et al., n.d.) to fine-tune its parameters. genetic algorithms (gas) and particle swarm optimization (pso) were used for anfis optimization; hybrid gradient simulated annealing algorithm is proposed to solve constrained optimization problems by alnowibet et al. (2022) but these methods may suffer from premature convergence or high computational cost. simulated annealing (sa), inspired by the metallurgical annealing process, offers a robust alternative due to its ability to escape local optima and efficiently explore the solution space. to address this limitation, control frameworks integrating simulated annealing (sa)-optimized adaptive neuro-fuzzy inference systems (sa-anfis) have gained prominence due to their superior modeling and control capabilities. in this paradigm, sa—a stochastic global optimization algorithm inspired by the thermodynamic annealing process—systematically refines both antecedent and consequent parameters of the anfis structure. this optimization enhances the system’s ability to capture nonlinear and time-varying behaviors inherent in agricultural processes. moreover, sa's robustness in navigating complex solution landscapes mitigates the risk of convergence to suboptimal local minima, thereby ensuring improved generalization, adaptability, and control accuracy under varying field conditions. 2. materials and method this section presents the comprehensive framework for developing the sa-anfis controller for precision planting systems. the methodology integrates computational intelligence techniques with agricultural engineering principles to achieve adaptive control of planting parameters as in figure 1. figure 1: concept flow chart 2.1 system architecture overview the control system adjusts planting depth (d) based on soil moisture (m) and planting speed (p). the saanfis controller processes these inputs to generate optimal actuator commands. the system architecture is shown in figure2. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 760 figure 2: sa-anfis system architecture 2.2 anfis architecture the anfis model consists of five layers as explained in the following subsections. 2.2.1. fuzzification gaussian membership functions convert crisp inputs into fuzzy sets (frank and köppen-seliger, 1997). a fuzzifier is an input layer that processes two critical agronomic variables through fuzzy membership functions (mfs): soil moisture and planting speed the soil moisture (sm) is the moisture content of the soil which affects planting depth and seed germination (ahmed, saleh, et al., 2024). the membership function for soil moisture is illustrated in table 1. table 1: membership function for soil moisture membership function range (%) dry 0 to 40 medium 20 to 80 wet 60 to 100 the range for soil moisture is 0% to 100%. the linguistic terms are: dry, as dried soil, medium as the optimum, and wet as the field capacity. figure 3 highlights the plot of the membership function for soil moisture. figure 3: plot of soil moisture membership function the soil moisture membership functions are: dry (blue) has triangular mf with vertices at (0, 0, 40), medium (brown) has triangular mf with vertices (20, 50, 80), wet (yellow) has triangular mf with vertices at (60, 100, 100). the soil moisture membership function (top left) as depicted in figure 3.8 dry from 0-40%, sharp cutoff below 20% and a gradual transition to medium. the medium ranges from 20-80%, forming a symmetric http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 761 triangular function centered at 50%. the last is wet (60-100%) with a gradual transition from 60% and full membership above 80%. the planting speed (ps) is the speed at which the agrobot is moving during the planting process, it affects depth(ahmed et al., 2023; ahmed et al., 2024). table 2 reveals the membership function for planting speed. table 2: membership function for planting speed membership function range (m/s) slow 1 to 2.5 medium 1.5 to 4 fast 3 to 5 the range for planting speed is 1 to 5. the linguistic terms are: slow, medium, and fast. figure 4 exposes the plot of the membership function for plating speed. figure 4: plot of planting speed membership function planting speed has a range of 0 km/h to 5 km/h. the planting speed membership functions are: slow (blue) has triangular mf with vertices (1, 1, 2.5), medium (brown) has triangular mf with vertices (1.5, 3, 4), fast (yellow) has triangular mf with vertices (3, 5, 5). the planting speed (top middle) as in figure 2 was slow ranging from 1-2.5 m/s. it also has a full membership below 1.5 m/s and a gradual decrease. it however has a medium speed ranging from 1.5-4 m/s and a symmetric around 3 m/s. fast (3-5 m/s) depicting gradual increase from 3 m/s to full above 4 m/s. 2.2.2. rule evaluation the anfis has a complete 3×3 rule matrix (9 rules) covering all input mf combinations: i. if soil moisture is dry and planting speed is slow then planting depth should be shallow. i. if soil moisture is medium and planting speed is medium then planting depth should be medium. ii. if soil moisture is wet and planting speed is fast, then planting depth should be deep. 2.2.3. normalization rule firing strengths are normalized. the inference system is sugeno-type consequents with linear functions. each rule has a firing strength (typically the result of fuzzy logic and operations across fuzzy input membership functions). these are then normalized as in equation 1: �̅�𝑖 = 𝑤𝑖 ∑ 𝑤𝑗 𝑁 𝑗=1 1 where 𝑤𝑖= firing strength of rule i, �̅�𝑖= normalized firing strength and n = total number of rules. each rule has a linear consequent function, as in equation 2: http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 762 depth = p1 × moisture + p2 × speed + p3 2 where p1, p2, p3 are rule-specific parameters to be learned. these parameters determine how inputs affect the output for each rule. 2.2.4 final output computation once each rule's consequent is evaluated, the final output (depth) is a weighted average as in equation 3: depth = ∑ �̅�𝑖 n 𝑖=1 . depth𝑖 3 where �̅�𝑖= normalized firing strength and n = total number of rules planting depth is the depth at which seeds are planted in the soil (abubakar, 2023). it is adjusted based on soil moisture and planting speed to ensure optimal seed germination. table 3 exhibits the membership function for planting depth. table 3: membership function for planting depth membership function range (cm) shallow 1 to 3 medium 2 to 4 deep 3 to 5 figure 5 discloses the plot of the planting depth membership function. figure 5: plot of planting depth membership function the range of planting depth is from 1 cm to 5 cm (inuwa et al., 2020). the planting depth membership functions are: shallow (blue) has triangular mf with vertices (1, 1, 3), moderate (brown) has triangular mf with vertices (2, 3, 4), deep (yellow) has triangular mf with vertices (3, 5, 5). 2.2.5 learning procedure the learning procedure for the fuzzy inference system with linear consequents has two inputs (moisture, speed), one output (depth) and n fuzzy rules, each with a linear output function as in equation 4: depth𝑖 = p1𝑖 × moisture + p2𝑖 × speed + p3𝑖 4 all the parameters p1𝑖, p2𝑖, p3𝑖 are learned for each rule i from data. step 1: training data the training data for input-output is presented in table4. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 763 table 4: dataset of input-output pairs for 9 training samples moisture speed → depth 18.5 3.2 → 4.5 22.7 4.5 → 3.9 15.3 2.8 → 5.1 19.0 3.6 → 4.7 23.4 5.0 → 3.5 17.8 3.0 → 4.9 20.1 3.9 → 4.3 21.5 4.2 → 4.0 16.2 2.5 → 5.3 step 2: define fuzzy sets and rules define fuzzy membership functions for the inputs and set up 9 rules, like: if moisture is low and speed is high then depth = p1*moisture + p2*speed + p3 for each rule: a. compute the firing strength 𝑤𝑖 (𝑘) for the k-th sample b. normalize them: �̅�𝑖 (𝑘) = 𝑤𝑖 (𝑘) ∑ 𝑤𝑗 (𝑘)𝑁 𝑗=1 5 step 3: construct the linear system (least squares) reformulate the final output as in equation 6: �̂�(𝑘) = ∑ �̅�𝑖 (𝑘) (𝑃1𝑖𝑥1 (𝑘) + 𝑃2𝑖𝑥2 (𝑘) + 𝑃3𝑖𝑥3)𝑁 𝑗=1 6 step 4: implementation in matlab/simulink 2.2.6 intelligent control system to adapt to the varying soil moisture and planting speed the rules determine the overall operation of the system; linguistic rules describe the control system. figure 6 shows the block diagram of the intelligent control system. figure 6: block diagram of intelligent control system the rule structure consists of two parts; an antecedent block (if and then) and a consequent block (following then). the rules generated using fuzzy logic is used in programming the microcontroller hardware. the rule structure of the system is presented in table 5. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 764 table 5: rule base for the anfis controller rule planting speed soil moisture planting depth 1 slow dry shallow 2 medium dry medium 3 fast dry medium 4 slow medium medium 5 medium medium medium 6 fast medium deep 7 slow wet deep 8 medium wet deep 9 fast wet deep 2.3 sa optimization 2.3.1 the sa optimization phase the sa optimizes antecedent parameters to escape local minima during field condition transitions. table 6 unveils the optimization parameters. table 6: optimization parameters parameter value description sa t₀ 1000 initial temperature (empirically determined via sensitivity analysis) cooling rate (α) 0.995 geometric cooling factor (𝑇𝑘+1 = α𝑇𝑘) perturbation magnitude ∆𝜎𝑀𝐹 = 0.2, ∆𝑐𝑀𝐹 = 1.5 planting depth 1 to 5 cm planting spacing 20 to 100 cm metering speed 1 to 5 m/s 2.3.2 hybrid learning mechanism a. global optimization: sa adjusts mf parameters (σ, c) every 10 cycles b. local tuning: gradient descent (η =0.01) updates consequent parameters (pi) continuously c. constraint handling: 1 ≤ depth ≥ 10 enforced via projection operator d. mf spread is 15 with gaussian width parameter 2.3.3 objective function the objective function is to minimize rmse between predicted and desired outputs as in equation 7: 𝐑𝐌𝐒𝐄 = √( 𝟏 𝐍 ∑(𝐝 − 𝐩)𝟐 ) 7 where rmse = root mean square error, %, n= number of parameters iteration, d= desired outputs and p= predicted outputs. 2.4 implementation workflow i. data collection: acquire soil moisture, planting speed, and corresponding optimal planting parameters. ii. anfis training: train initial anfis using hybrid learning (least squares + backpropagation). iii. sa optimization: fine-tune anfis parameters using sa. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 765 iv. real-time control: deploy sa-anfis on an embedded controller for field testing. 3. results and discussion 3.1 developed sa-anfis controller for intelligent depth control the inference engine accepts two inputs from fuzzifier and applies the 3x3 rules combinations to obtain three outputs. figure 7 displayed the plot of three output processed layers. the input layer receives the input functions, the processing layer fuzzify and optimize the functions and give out the desired output function. figure 7: plot of system architecture with rule connections 3.2 adaptive control response surface of the smart planter the responses to the adaptive control of the smart planter are presented in figure 8. the planting depth (bottom left) increases with both soil moisture and planting speed. the shallowest in dry/slow conditions at 1.5cm and deepest in wet/fast conditions of 4.5cm while, very dry 15% and very slow at 1.2 m/s. it can therefore be established that for moisture dominance, wet soil allows deeper planting and tighter spacing while dry soil requires shallower planting and wider spacing, this is in line with ahmed et al. (2023). figure 8: interaction of planting depth with input variables table 7 shows the comparative performance metrics between standard anfis and sa-anfis. table 7: comparative performance metrics controller depth rmse (cm) adaptation time (s) standard anfis 0.41 3.8 sa-anfis 0.23 2.1 the sa-anfis reduced depth control error by 0.18 cm compared to standard anfis. it however demonstrated 1.7 second faster adaptation to parameter changes. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 766 3.3 computational efficiency the optimization step was completed in 50 iterations and 51 function evaluations. the lowest cost was consistent at 0.07436 (excellent convergence) while the current solution cost fluctuated but ended near the best value. however, the current search (aggressive) cooled from 100 to 1.96. this means that optimization reached a stable solution and further iterations wouldn't significantly improve results. the optimal parameters for the input variables are the best combination of soil moisture (%) and planting speed (m/s) found by the optimization. they were attained at soil moisture of 50% (medium range) and planting speed: of 3 m/s (medium-fast). the system recommends average moisture conditions and suggests moderate planting speed (balance between productivity and precision). 3.4 system input-output relationships the system input-output relationships for planting depth and soil moisture at planting speed of 3 m/s are presented in figure 9. figure 9: relationship between planting depth and soil moisture at 3 m/s the planting depth changes with soil moisture at a fixed planting speed of 3 m/s. it is however observed in the trend that planting depth increases with an increase in soil moisture, the finding did not contradict ahmed et al. (2024). 3.5 optimized outputs evaluation the optimized outputs evaluation showed that the ideal sorghum seed planting depth of 3.0 (neither too shallow nor deep), which is within safe range. however, trade-off analysis inferred that the system slightly prioritized depth as it is within practical operating ranges. the optimized output showed the predicted system behavior as in figure 10. figure 10: predicted output as it relates to input http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 767 the response surface for planting depth shows that an increase in planting depth corresponds to an increase in both soil moisture and planting speed, this is supported by the finding of kheiry & mohammed (2017). it indicates that planting depth adapts to different conditions. it shows that the fuzzy logic system successfully found practical operating parameters through simulated annealing, with the output within safe agricultural ranges. the solution prioritizes planting quality (planting depth) while maintaining efficient field operations (planting speed). 4. conclusion the sa-anfis controller enhances precision planting by dynamically optimizing depth. the system successfully found practical operating parameters through simulated annealing, with the output within safe agricultural ranges. the solution prioritizes planting quality (planting depth) while maintaining efficient field operations (planting speed). sa optimization significantly improves anfis performance, making it a viable solution for smart agricultural machinery. future work will explore deep reinforcement learning for further enhancements. acknowledgments this work was funded by tetfund-ibr grant 2024, futminna. field trial was supported by laboratory attendant. references abba, si. 2019. wastewater treatment plant performance analysis using artificial intelligence– an ensemble approach [near east university], 1-147. abdullahi, im., mu’azu, mb., olaniyi, om., and james agajo. 2018. pastoralist optimization algorithm (poa): a novel nature-inspired metaheuristic optimization algorithm. proceedings of icget, 2018: 101–105. abubakar, fh. 2023. development of a four-row tractor mounted soybean planter. ahmadu bello university, zaria,1-95. abubakar, i., abdullahi, im., balami, aa., idah, pa., and olaniyi, om. 2024. an in-depth review of fuzzy logic technique for engineering applications. proceedings of the 1st international computing and communication conference (i3c2024), 22-23 april, 161–169. ahmed, k., saleh, a., kalu, g., musa, a., and amonye, m. 2024. performance evaluation of home-developed four-row animal drawn precision maize planter using a pair of bull to plant sammaz 17 maize variety in samaru-zaria, nigeria. journal of applied sciences and environmental management, 27(3): 389–393. ahmed, k., saleh, a., musa, a. d., and kalu, g. 2023. determination of selected parameters that influence planting space uniformity on maize seed. fudma journal of sciences (fjs), 7(2): 30–33. alnowibet, ka., mahdi, s., el-alem, m., abdelawwad, m., and mohamed, w. 2022. guided hybrid modified simulated annealing algorithm for solving constrained global optimization problems. mathematics, 10(1312): 1–25. alsharkawi, a., al-fetyani, m., ijaabo, em., and khasawneh, h. 2021. adaptive neuro-fuzzy inference system for a three-wheeled omnidirectional mobile robot. 2020 3rd international conference on applied engineering (icae), 2–7. asghar, ab., and liu, x. 2018. online estimation of wind turbine tip speed ratio by adaptive neuro-fuzzy algorithm. (ijacsa) international journal of advanced computer science and applications, 9(3:)28-33. cheng, x., li, h., he, j., wang, q., lu, c., wang, y., wang, c., wang, c., and lou, s. 2021. optimization of operating parameters of seeding device in plot drill with seeding control system. int j agric & biol eng, 14(3): 83–91. espitia, h., machón, i., and lópez, h. 2022. design and optimization of a neuro-fuzzy system for the control of an electromechanical plant. applied sciences, 12(541): 1–25. frank, pm., and köppen-seliger, b. 1997. fuzzy logic and neural network applications to fault diagnosis. international journal of approximate reasoning, 16(1): 67–88. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 758-768. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahim.pg2116251@st.futminna.edu.ng 768 hilali, b., ramdani, m., and naji, a. 2025. an efficient strategy for optimizing a neuro-fuzzy controller for mobile robot navigation. international journal of electrical and computer engineering (ijece), 15(1): 1065–1078. inuwa, ah., abdulazeez, t., and vabi, mb. 2020. handbook on improved agronomic practices of sorghum production in north east nigeria (issue march 2021). ji, j., sang, y., he, z., jin, x., and wang, s. 2021. designing an intelligent monitoring system for corn seeding by machine vision and genetic algorithm-optimized back propagation algorithm under precision positioning. plos one, 16(7): 1–15. jia, h., chen, y., zhao, j., guo, m., huang, d., and zhuang, j. 2018. design and key parameter optimization of an agitated soybean seed metering device with horizontal seed filling. int j agric & biol eng, 11(2): 76– 87. katzer, nj. 2020. fuzzy logic guide for small hydroponic systems. institute of biology and university of graz.190. khoshnevisan, b., rafiee, s., omid, m., and mousazadeh, h. 2014. development of an intelligent system based on anfis for predicting wheat grain yield on the basis of energy inputs. information processing in agriculture, 1(1), 14–22. https://doi.org/10.1016/j.inpa.2014.04.001 kheiry, ano. and dahab, mh. 2017. comparative of field performance evaluation of two row planters as affected by soil condition and forward speed. international journal of contemporary applied sciences, 3(4), 43-49. nguyen, h., pham, b. t., son, lh., thang, nt., ly, hb., le, tt., ho, ls., le, th., and bui, dt. 2019. adaptive network based fuzzy inference system with meta-heuristic optimizations for international roughness index prediction. applied sciences, 9(4715):1–18. obe, o., and dumitrache, i. 2015. adaptive neuro-fuzzy controller with genetic training for mobile robot control adaptive neuro-fuzzy controller with genetic training for mobile robot control. int. j. of computers, communications & control, 7: 135–146. okeke, o. p., aminu, i. i., rotimi, a., najashi, g., jibril, m. m., ibrahim, a. s., bashir, a., malami, s. i., habibu, m. a., and magaji, m. m. 2022. performance analysis and control of wastewater treatment plant using adaptive neuro-fuzzy inference system (anfis) and multi-linear regression (mlr) techniques performance analysis and control of wastewater treatment plant using adaptive neuro-fuzzy i. gsc advanced engineering and technology, 4(2): 001–016. qohar, al., and jito, s. 2022. smart agriculture for optimizing photosynthesis using internet of things and fuzzy logic. international journal of electrical and computer engineering (ijece), 12(5): 5467–5480. sobrinho, rl., oliveira, br., and zuffo, am. (n.d.). a fuzzy yield model of the wheat inoculated with rhizophagus irregularis under future climate elevated co 2. 1–16. song, y., xu, j., wang, x., xing, j., and wang, l. 2024. design and experiment of water and fertilizer integrated equipment for solar greenhouse based on yellow sand substrate model. journal of engineering science and technology review, 17(3): 8–19. waluyo, widura, a., hadiatna, f., and anugerah, d. 2023. fuzzy-based smart farming and consumed energy comparison using the internet of things. ieee access, 11: 1–11. zhao, s., and zhang, y. 2024. design and field test of corn seeding system base on fuzzy pid control method combine with pso. engenharia agrícola, 44: 1–11. http://www.azojete.com.ng/ mailto:ibrahim.pg2116251@st.futminna.edu.ng arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):619-624 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 619 environmental trends due to arc welding activities: sensitivity of some typical workplaces a. s. shote*, s. a. aasa and h. o. adeyemi department of mechanical engineering, olabisi onabanjo university, ago-iwoye, ogun state, nigeria *corresponding author's email address: shote.adeola@oouagoiwoye.edu.ng article information submitted 8 february, 2024 revised 2 april, 2024 accepted 10 april, 2024 keywords: emission hazards environment air quality welding abstract the associated hazards with welding process are recently looked into because of the emission threat or lack or improper use of safety devices in work places relating to welding that could potentially lead to longor short-term effect on worker and other staying nearby. this article provides data for various air quality parameters such as total volatile organic compounds (tvoc), air quality index (aqi), carbon monoxide (co), carbon dioxide (co2), and formaldehyde (hcho) measured at different locations, north (n), west (w), east (e), and south (s) within lagos metropolis. the results of co and hcho levels are apparently higher than recommended limits in some locations (east and south) which suggest potential harm for workers as co is mostly dangerous to health. however, other data suggests that air quality is generally good, as all aqi values are significantly below the break point of 50ppm. further analysis revealed that at 95% confidence, there is no significant difference in the co emissions patterns from different workshops as well as from different locations (north, west, east, and south) as pvalue> 0.05. however, there is difference in co2 as a result of change in locations as pvalue (0.014) < 0.05. about 57.6% of the variability in co2 emissions from various locations can be accounted for due to the variation resulting from change in location. the data thus provides useful information that could enable enforcement of personal protective equipment to ameliorate the situation. 1.0 introduction welding is one of the most widely used engineering process in various industries such as construction, manufacturing, and repair. however, the process of welding can produce hazardous fumes and gases, which can be harmful to the welders, coworkers and immediate individuals. the dangers of emissions from welding processes have been studied in some researches (antonini et al., 2011 and sjogren et al., 2014), and some of the literatures suggest that these emissions could have serious health consequences. according to studies by antonini et al. (2011) and sjogren et al. (2014), welding fumes could contain a variety of hazardous chemicals, including metals such as nickel, chromium, and manganese, as well as gases such as carbon monoxide (co), nitrogen oxides (no), and ozone (o3). these chemical discharges can cause respiratory and neurological problems in welders, as well as other health issues such as cancer and reproductive problems. studies by sjogren et al. (2014) also found that welding fumes can also have effects on the cardiovascular system. the study (sjogren et al., 2014) observed that welders exposed to welding fumes were observed to have higher levels of inflammation and oxidative stress markers, which could eventually contribute to cardiovascular problem. welding fumes could also be harmful to the environment over a long and short period of time. investigation of ahmed et al. (2018) found that welding fumes could increase the level of air http://www.azojete.com.ng/ mailto:%20efegabs@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)619-624. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 620 pollution, as they contain particulate matter (pm) in various proportions and other malicious chemicals that can have negative effects on air quality. some measures are recommended to mitigate the risks associated with welding emissions, such steps as proper ventilation, wearing protective gear, and using safer welding methods are sometimes neglected or partially embraced. from the investigation by antonini, (2003) and maness, (2012), welding process produces harmful emissions, including metal fumes, gases, and ultraviolet (uv) radiation. these fumes could cause serious respiratory problems, such as bronchitis and asthma, and can also lead to more serious health conditions, like lung cancer (antonini, 2003). ultraviolet (uv) radiation from welding can as well cause skin burns and eye damage (maness, 2012). numerous measures can be taken to mitigate the dangers of emissions emanating from welding processes. local exhaust ventilation (lev) methodology could be employed to mitigate the effect of harmful fumes and gases emanating from welding process in workplace (lippold et al., 2014). less harmful welding methods, such as gas metal arc welding (gmaw) are reported to produce fewer emissions than other welding methods (mazumder, 2007). international agency for research on cancer (iarc, 2017) classified welding as a group 1 carcinogen (iarc, 2017). from the report, long-term exposure to welding fumes can cause chronic diseases like lung cancer (iarc, 2017). in a similar vein, other investigators (meeker and susi, 2006; sparer et al., 2010) also discovered that welding emissions can initiate chronic and acute health challenges in welders. studies have also shown that exposure to welding fumes can have neurological effects as reported by racette et al., (2017). welding fumes are produced from a mixture of gases and small particles generated when the welding electrode or material is melted and deposited on the metal being welded. the resulting composition of welding fumes could vary depending on the type of welding process employed, the welding conditions, and the type of metal being welded. these emissions could have serious health effects on welders and surrounding individuals, as well as contribute to environmental pollution. this has necessitated this research to find out the possible or potential hazard associated with the typical process of welding. one of the recently held united nations climate conference of the parties (cop 26) in glasgow was painstaking on how to prevent climate catastrophe. the emissions emanating from small sources here and there need to be checked because of the aggregate contribution to the global climate depletion. it has also been observed that there is obvious proliferation of the welding workplaces as the cities keep on expanding and population is also rapidly growing. we therefore cannot assume all is well as air borne diseases also keep on rising and in some situation some of these diseases are life threatening which is invariable putting undue pressure on the health facilities. the essence of this research is to come up with contemporary situation report and data so that preventive measure could be taken to avert possible catastrophic disaster. 2.0 materials and methods lagos nigeria metropolis (figure 1) was chosen due to the urban nature of the area. it is located in the western part of nigeria and is heavily populated with over 20 million inhabitants according to city-population, (2015). the locations are selected from lagos metropolis because lagos is regarded as one of the fastest growing cities in the world. four typical welding work places; workshop a (ws a), workshop b (ws b), workshop c (ws c) and workshop d (ws d) were selected based on their respective geographical locations (north, south, west and east). for each of the locations, north, south, west and east are also identified and measurement are taken at 3m interval away from the welder to access the severity level on the operator and those in welding environ. each of these locations were identified based on closeness to residential areas. ambient data were taken and recorded as baseline data. gas analyzer ‘b09288j77j’ manufactured by pallipartners is used to acquire the various emissions for repository and subsequent data analysis. the data were taken (in a similar version to shote et file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com shote et al: environmental trends due to arc welding activities: sensitivity of some typical workplaces. azojete, 20(3):619-624. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 621 al., 2023) when arc welding activities are going on in the various locations. these data are then time-averaged to obtained individual data for location varying at 3m away for the welding activities in all the four directions (north, east, west and north). figure 1: data locations on lagos metropolis (6.5227on, 3.6218oe) 3.0 results and discussion 3.1 carbon iv oxide (co2) emissions from figure 2, it could be observed that the levels of co2 vary across different regions. the highest level of co2 is recorded in the east and south, with 1371 ppm and 1370 ppm, respectively. the west-region has the next highest level with 903 ppm, trailed by the north with 532 ppm. it is certainly essential to monitor the levels of co2 in these places to understand the impact of human activities on the environment and climate change. high levels of co2 can have severe consequences as it were, including extreme weather, rising sea levels events, and the loss of biodiversity (lippold et al., 2014). analysis of mean variance for co2 reveals that there are differences in the emissions pattern due to the various locations (pvalue 0.014 < 0.05). employing tukey hsd analysis of significant levels, east and south apparently show remarkable difference from the northern location (pvalues 0.032 and 0.019 are respectively less than 0.05). this is obviously reflecting in figure 2 as discussed previously. figure 2: carbon dioxide emissions (ppm) from four different welding stations (ws) figure 3: carbon monoxide emissions (ppm) from four different welding stations (ws) apparently from figure 3, co appears to be highest in the east and south locations, with both registering a value > 300 ppm. this could be attributed to the diffusion of the co and partly due to the wind convectional directions during the data acquisition process. however, welding workshop–d (ws d) seems to have an outlier. further analysis of mean variance of the co emissions at 95% confidence suggests that there is no significant difference irrespective of the workplace or data location as pvalues (0.733 and 0.131 respectively) are >> 0.05. this is also corroborated by the error margin (5%) from the average (av) values in figure 3. in figure 4, the aqi values for the four regions are provided. the lowest aqi value is 3.8 for region n, while the highest aqi value is 5.2 for region s. the average aqi value for all five regions is about 4.6. 250 450 650 850 1050 1250 1450 1650 1850 2050 2250 2450 co 2 em is si on (p pm ) spot ws a ws b ws c ws d av n w e s 0 100 200 300 400 500 600 700 800 900 c o e m is si o n ( p p m ) spot ws a ws b ws c ws d av n w e s http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)619-624. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 622 based on the values in figure 4, the air quality appears to be relatively good in all five regions. all the aqi values are below 50, which is the threshold for good air quality as stated by united nations guideline (who website). however, it is worth emphasizing that even low levels of air pollution can have negative effects on health over a certain period (shote et al., 2023), especially for sensitive populations such as the elderly, children, and individuals with respiratory or cardiovascular problems (i.e. asthmatic patient). in general, an aqi value of 0-50 is considered good air quality (un guideline), while an aqi value between 101-150 is considered unhealthy for sensitive groups, and an aqi value of over 300 is considered hazardous. based on these standards, the aqi values for all five regions in this table are relatively good and do not pose any immediate health risks as it were. figure 4: air quality index for the four different locations formaldehyde is a colorless gas that is commonly found in our neighbourhood/indoor environments and can have detrimental health effects if exposure levels are too high. the world health organization (who) recommends a maximum level of exposure 0.1 mg/m3 over a 30-minute period to avoid adverse health consequences. on average basis, it can be seen from figure 5 that all regions have hcho emissions levels above the who recommended maximum exposure level of 0.1 mg/m3. the highest emission level is observed in the eastern region with a value of about 0.35 mg/m3. the northern region (n) has the lowest emission level put at 0.13 mg/m3. there is need for measures to be taken to reduce hcho emissions in welding environments to ensure that people/operators are not exposed to levels that pose risk to their health. some of the basic things to do include the use of personal protective equipment. at 95% confidence interval, there is no difference in the hcho emissions (pvalue 0.493 > 0.05) even as it can be apparently seen that west and east location are recording the highest for welding workshop d (ws d). figure 5: formaldehyde (hcho) emissions for the four different locations figure 6: total volatile organic compound (tvoc) emissions for the four different locations 0 1 2 3 4 5 6 7 a ir q ua lit y in de x( a q i) spot ss a ss b ss c ss d av n w e s 0 10 20 30 40 50 60 a ir q ua lit y in de x( a q i) spot ss a ss b ss c ss d av b aq d es ir ab le r eg io n fo r a q i break point for aqi n d es ir ab le r eg io n fo r a q i break point for aqi n d es ir ab le r eg io n fo r a q i break point for aqi n w d es ir ab le r eg io n fo r a q i break point for aqi n e s 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 h c h o e m is si o n ( m g/ m 3 ) spot ws a ws b ws c ws d av n w e s 0 1 2 3 4 5 6 7 8 9 t v o c e m is si o n ( m g /m 3 ) spot ws a ws b ws c ws d av n w e s recommended level (who) unhealthy healthy file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com shote et al: environmental trends due to arc welding activities: sensitivity of some typical workplaces. azojete, 20(3):619-624. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 623 a total volatile organic compound (tvoc) is a measure of the concentration of organic chemicals that are present in the air and can affect neighborhood and indoor air quality. the total volatile organic compounds (tvoc) in different areas are measured in units of milligrams per cubic meter (mg/m3) and presented in figure 6. the tvoc concentration in the different locations varies considerably. the lowest concentration is recorded in the north n with a tvoc concentration of about 2.1 mg/m3, while the highest concentration is in the south s with a tvoc concentration of 4.7 mg/m3. the other locations have tvoc concentrations that fall in between these two extremes. it is important to note that the safe or acceptable tvoc levels in neighbourhood/indoor environments vary depending on the specific compounds present and the duration of the exposure of someone. besides, as a general guideline for tvoc levels of 0.3 to 0.5 mg/m3 are considered low, while levels above 3 mg/m3 may cause discomfort and health challenges for some individual people. it is apparent that the tvoc concentration in locations s may be high enough to cause discomfort or health problems for some individuals as stated by racette et al., (2017). 4.0 conclusion welding is an essential process in many industrial activities. societal development may be very difficult without welding processes as it were. this shows that welding is very paramount for development to progress rapidly. that is one of the main reasons for embarking on this research. from the date presented for five different air quality parameters, i.e. air quality index (aqi), total volatile organic compounds (tvoc), carbon monoxide (co), carbon dioxide (co2), and formaldehyde (hcho). the emission measurements are taken at four different locations north (n), west (w), east (e), and south (s) and four different welding work places welding workshop a (ws a), workshop b (ws b), workshop c (ws c) and workshop d (ws d), it is obvious that the levels of each of the parameters differ significantly across the different locations. aqi levels are also highest in the south region, indicating poorer air quality and high pollution in that area. • from analysis of mean variance, there is no significant difference in the air quality index of the welding workshops as pvalues (0.271) > 0.05. • however, it's important to note that aqi values can fluctuate rapidly depending on seasonal changes, weather patterns, and human activity, among other factors. thus, it's very important to monitor aqi values regularly and possibly take necessary precautions to protect welding operators from potential health hazards caused by air pollution. • there is a difference in co2 emission from different locations (north, west, east, south) as pvalue, 0.014 < 0.05. north location is substantially different from east and south as pvalues (0.032, 0.019 respectively) for significant indicators are both less than 0.05. at least 57.6% of the variations in co2 emissions can be accounted for as a result of change in different locations. • there is also no significant difference in formaldehyde emissions from different locations (pvalue 0.493 > 0.05). other researches may have to consider the duration of exposure and the impact of cumulative exposure to hcho on human health. • further evaluation and investigation of the specific tvoc compounds present in these locations were done to determine the potential health risks associated with these concentrations. at 95% confidence, there is no difference in tvoc emissions from welding process due to different workshops or different locations as pvalues of 0.842 and 0.068 respectively are less than 0.05. • in general, the data provides useful information about air quality measurements and could be used to identify areas of concern and take necessary steps to improve air quality in specific welding areas and regions. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)619-624. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: shote.adeola@oouagoiwoye.edu.ng 624 the use of alternative welding methods, such as laser welding and friction stir welding, can reduce the emissions of hazardous chemicals. it is important to take appropriate measures to minimize these risks, such as proper ventilation, the use of safer welding methods and personal protective equipment (ppe). 5.0 acknowledgement the authors gratefully acknowledged the chief executive officer of the various workshops for allowing data to be taken periodically from their workplaces. references ahmed, f., ahmad, m., kumar, r. and nizamuddin, s. 2018. a review of welding fume composition and its effect on human health. journal of industrial pollution control, 34(2): 384393. antonini, jm. 2003. health effects of welding. critical reviews in toxicology, 33(1): 61-103. antonini, jm., roberts, jr., schwegler-berry, d., mercer, rr. and barger, m. 2011. welding fume exposure and associated health effects among welders. journal of occupational and environmental medicine, 53(4): 372-379. city-population 2015. metro lagos (nigeria): ikeja local government area, lagos., retrieved 16th oct., 2022. international agency for research on cancer (iarc). 2017. iarc monographs on the evaluation of carcinogenic risks to humans: welding, molybdenum trioxide, and indium tin oxide. world health organization geneva. lippold, jc., kotecki, dj. and dupont, j. 2014. welding and joining of aerospace materials. john wiley & sons, new york. maness, m. 2012. emissions from welding: a literature review. journal of occupational and environmental hygiene, 9(2): 59-69. doi: 10.1080/15459624.2011.650971. mazumder, j. 2007. welding: processes, quality, and applications. crc press, boca raton. meeker, jd. and susi, p. 2006. welding fume exposure and cancer risk: a review of epidemiologic studies. journal of toxicology and environmental health, part b, 9(5): 4-41. racette, ba., mcgee-minnich, l., moerlein, sm., mink, jw., videen, to., perlmutter, js. and kotzbauer, pt. 2017. welding-related parkinsonism: clinical features, treatment, and pathophysiology. neurology, 88(21): 1994-2001. shote, as., aasa, sa. and musa, ai. 2023. assessment of air quality of service stations in a built-up area: a case study of lagos metropolis. arid zone journal of engineering, technology and environment, 19(4):827-836. sjogren, b., fjaeraa, c., aaseth, j. and thomassen, y. 2014. welding fumes: a risk factor for cardiovascular disease? toxicology letters, 229(1): s203. sparer, j., storfer, s. and rohlman, ds. 2010. welding and lung cancer in a pooled analysis of case-control studies. american journal of epidemiology, 171(5): 517-523. who website “https://www.who.int/airpollution/guidelines/en/.” file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com corresponding author’s email address: adebayow@oauife.edu.ng 933 arid zone journal of engineering, technology & environment original research article studies on starch characteristics of flour produced from six varieties of musa spp. fruits grown in southwestern nigeria w. a. adebayo1*, b. s. ogunsina2, i. otemuyiwa3 and k. a. taiwo1 1department of food science and technology, faculty of technology, obafemi awolowo university, ile-ife, nigeria. 2department of agricultural and environmental engineering, faculty of technology, obafemi awolowo university, ile-ife, nigeria 3department of chemistry, faculty of science, obafemi awolowo university, ile-ife, nigeria *corresponding author’s email: adebayoadewale@ymail.com, adebayow@oauife.edu.ng article information abstract this research work investigated starch characteristics of flour produced from six varieties of musa spp. fruits with the view of promoting its usage as base composition in food development and innovation. there is dearth of information on prediction of glycemic response of different varieties of musa spp. flour in literatures. this research work therefore investigated glycemic responses of six musa spp. flour using standard procedures. the descriptive and inferential statistical analysis of measured data was done using turkey’s post test procedures of graphpad prism version 4.00 for windows. the results showed that the carbohydrate, total starch, slowly digested starch (sds) and resistant starch (rs) composition of the samples ranged from 90.32 to 93.93%; 473.97 to 488.30 mg/g; 33.02 to 36.38% and 21.16 to 27.54, respectively. furthermore, amylose, amylopectin and predicted glycemic index (pgi) were ranged from 25.10 to 29.02%; 70.93 to 74.90% and 51.11 to 53.31%, respectively. thus, the results of this study showed that musa spp. varieties affected glycemic responses of the flour. therefore, it is concluded that all the six varieties of musa spp. have low glycemic index and appreciable levels of resistant starch. the data obtained will bridge the information gap for formulation and development of functional foods using musa spp. flour as a baseline composition. received: 2nd september 2025 revised: 12th november 2025 accepted: 13th november 2025 keywords: musa spp. fruits starch characteristics predicted glycemic responses flour © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction nowadays, demands for foods rich in antioxidants and low glycemic index (gi) beyond traditional nutrients are increasing worldwide. this is because it reduces the loss of lives related to risks from high blood pressure and abnormal blood sugars, cardiovascular challenges, diabetes and elevated cholesterol, (hermansen et al., 2006; louie et al., 2015). gi and glycemic load (gl) are measure of glycemic response frequently used as guide in foods selection or in innovated food products development (hermansen et al., 2006). the gis of food materials can be easily evaluated either by vivo or in vitro techniques with high degree of accuracy (argyri et al., 2016). in many tropical countries, banana and plantain (musa spp.) play a crucial role in the diet and food security of large number of population since larger percentage of the fruits cultivated in the region are transacted and consumed in the immediate environments (daniells et al., 2001). the fruits are largely consumed as deserts and staple foods by millions in the tropical sub-region. it is very rich in carbohydrate and vitamins in proportion that favourably compete with other notable staple foods such as sweet potato, cassava and potato (adeniji and tenkouano, 2008). in addition, it has high mineral contents such as fe, ca and k in a proportion that can meet daily dietary recommendations (yarkwan and uvir, 2015). banana and plantain are perennial crops with over 80 cultivars grow rapidly and fruit all year round in the tropics and sub-tropics. the world annual output of banana is 106 million tons (mt) t while plantain recorded 13 mt with africa playing a major role (fao 2005). in nigeria, plantain and their products are in high demand, and this is reflected by the relatively high price of the farm produce whereas banana market price is relatively low. plantain and banana azojete december 2025. vol.21(4):933-941 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/004 www.azojete.com.ng mailto:adebayow@oauife.edu.ng mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 934 products are consumed in different forms – chips, dodo ikire and elastic pastry popularly referred to as amala in nigeria and fufu in cameroon and other west african countries and prepare by mixing flour in boiling water into a stiff dough and eat with various sauces. this study then focuses on determination of starch characteristics of musa spp. flour so as to serve as nutritional guideline for food product formulation and development from the fruits. 2. materials and methods 2.1 source of materials six varieties of musa spp. fruits (plate 1) harvested at physiological matured stage were obtained from the teaching and research farm, obafemi awolowo university (oau), ile-ife, osun state, nigeria. plate 1: six selected varieties of musa spp. fruits considered for the experiment: (a) plantain (agbagba) (b) robusta (omini ibile) (c) red banana (omini oyinbo) (d) lacatan (saro) (e) gold finger (aponmode) (f) bluggoe (panbolabola) 2.2 sample preparation musa spp. fruits were processed into flour following the procedure of adebayo et al. (2021) outlined in figure 1. preparation of reagents: the following reagents were prepared following standard procedures and all the chemicals used in this study were analytical grades: (a) hcl-kcl buffer (ph 1.5): 50 ml of 0.1m kcl was added to 41.4ml of 0.1m hcl and then transferred into a 100 ml standard flask and then made up to the mark with distilled water. (b) pepsin reagent: pepsin (1.000 g) was dissolved in 5ml of hcl-kcl buffer and poured into 10ml standard flask. the solution was then made up to the mark with the buffer. the pepsin reagent (0.2 ml) is equivalent to 20 mg of pepsin. (c) tris-maleate buffer (ph 6.9): 50 ml of 0.1m hcl was added to 0.1m tris-maleate solution, it was then put into a 100 ml flask and dilute with distilled water up to the mark of the flask. (d) αamylase reagent (ph 6.9): αamylase (10.4 mg) was weighed into a beaker, dissolved with trismaleate buffer, poured into a 200 ml flask and made up to the mark with the buffer. (e) amyloglucosidase: amyloglucosidase (50 mg) was measured into a beaker and dissolved with 5 ml of tris-maleate buffer, poured into a 10 ml flask and made up to 10ml with the buffer. http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 935 (f) preparation of phosphate buffer (ph 6.9): phosphate buffer was prepared by mixing 5.63 ml of 0.2 m solution of nah2po4 and 6.9 ml of 0.2 m of na2hpo4 in a 25 ml flask and made up to mark with distilled water. (g) dinitrosalicylic acid (dnsa) reagent: the dnsa reagent was prepared by weighing 0.25 g of 3, 5 – dinitrosalicylic acid, 7.48 g of sodium potassium taitarate and 0.40 g of sodium hydroxide into a 25 ml standard flask, the content was dissolved with phosphate buffer (ph 6.9) and the solution was made up to mark with the buffer. figure 1: a flowchart for musa spp. flour production (adebayo et al., 2021) 2.3 methods proximate analysis: proximate composition of musa spp. flour samples was determined according to aoac (2005) methods. determination of total starch: the sample total starch was determined using the procedure documented by falade et al. (2005). determination of reducing sugar using dnsa: the hydrolysate (1.0 ml) in a test tube was added to 0.1 ml of 0.1 m naoh and 0.1 ml of dnsa reagent. the mixture was placed on a water bath for 15 min at 100 °c for development of orange colour in the test tube. the content was poured into a 25 ml flask and made up to mark with distilled water. the absorbance was measured at 590 nm using uv-spectrophotometer (uv 1601-spectrophotometer, shimadzu corporation, kyoto, japan). the glucose release was extrapolated from the glucose standard curve. the glucose content value obtained was then converted to starch with a multiplication factor of 0.9. in-vitro starch digestion rate: determination of the flour in-vitro starch digestion was carried out using a procedure reported by falade et al. (2005). the starch digestion rate was evaluated as the total starch musa spp. fruits washing and peeling cutting into 5 mm oven drying (70 °c) dry milling sieving into 500 µm bagging packaged musa spp. flour pretreatment: citric acid (cit) solution http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 936 hydrolyzed expressed in percentage at different time. the digestibility curve obtained for each flour sample was fitted into the first-order kinetic equation (1) as documented by falade et al. (2005). 𝐶𝛼 = 𝐶0 (1 − 𝑒−𝑘𝑡) 1 where: 𝐶𝛼 = concentration at equilibrium, t; 𝐶0 = concentration at time 0; k = pseudo-first order rate constant. to obtain k, natural log of equation (1) was taken as presented in equation (2): 𝑙𝑛(𝐶𝛼 − 𝐶0) = −𝑙𝑛 𝐶0 + 2 first order hydrolysis curve of total starch (%) hydrolyzed against time and the area under the hydrolysis curve (auc, 0 – 180 min) was calculated by integrating equation (1) to obtain equation (3) and simplified to equation (4) by applying the curve boundary conditions (𝑡0 = 0 𝑚𝑖𝑛. ; 𝑡𝛼 = 180 𝑚𝑖𝑛.) 𝐴 = 𝐶0(𝑡180 − 𝑡0) + 𝐶0 𝑘 (𝑒−𝑘𝑡180 − 𝑒−𝑘𝑡0) 3 𝐴 = 180 × 𝐶0 + 𝐶0 𝑘 (𝑒−180𝑘 − 1) 4 hydrolysis index (hi) was calculated as the relationship between the (a) for a test food and (a) for a reference food (white bread), expressed as a percentage (jeevetha et al., 2014). from the result of hi, predicted glycemic index (pgi) was calculated using equation (5): 𝑝𝐺𝐼 = 39.71 + (0.549 × 𝐻𝐼) 5 where: pgi = predicted glycemic index; hi = hydrolysis index. rapidly digestible starch, slowly digestible starch and resistant starch (rs) determination: the method of hans et al. (2007) was used to estimate the rapidly digestible starch (rds), slowly digestible starch (sds) and resistant starch (rs). the rds is the fraction of starch hydrolyzed within 30 min of incubation; sds is the fraction hydrolyzed between 30 to 180 min and the fraction that remained unhydrolyzed after 180 min is regarded as the rs. determination of amylose/amylopection: evaluation of amylose content of the flour sample was done using method documented by juan et al. (2006). amylopectin content of the sample flour was then determined using equation (6) (juan et al., 2006). 𝐴𝑚𝑦𝑙𝑜𝑝𝑒𝑐𝑡𝑖𝑛, % = 100 − 𝑎𝑚𝑦𝑙𝑜𝑠𝑒 (%) 6 statistical analysis: descriptive and inferential statistical analysis of the data was carried out using turkey’s post test procedures of graphpad prism version 7.00 for windows. 3. results and discussion the proximate composition of six varieties of musa spp. flour were presented in table 1. the results showed that carbohydrate content ranged from 90.32 to 93.93% with plantain and goldfinger samples having lowest and highest values, respectively with no significant difference (p< 0.05) with the exception of plantain and robusta sample flours. thus, all the varieties investigated are good sources of energy food with the implication that high starch content food products can be obtained from all the six musa spp. varieties. the carbohydrate contents of the six varieties were significantly higher compared with staple foods such as yam (78.21%), potato (77.68%), rice (80.22%) and cassava (83.2%) as reported by kirk and sawyer, 1991 and usda, 2009 in their separate studies. the results compared favourably with published data on carbohydrate contents of different varieties of musa spp. flour which ranged from 72 to 90% (ojure and quadri, 2015; ogundareakanmu et al., 2015 and yarkwan and uvir, 2015). the crude fat content ranged from 1.67 to 5.08% with robusta and plantain having lowest and highest values, respectively. the values compared favourably with 0.85-1.65, 1.11 – 1.35 and 1.20 – 1.55% reported by adeniji et al. (2007); ojure and quadri (2015); yarkwan and uvir (2015), respectively but higher than 0.2 – 0.95, 0.64 – 1.22 and 0.25 – 0.60% reported by daramola and osanyinlusi (2006); ogundare-akanmu et al. (2015) and kiin-kabari and njoku (2016), respectively. the difference in the crude fat content of various varieties of musa spp. is mainly due to variety. the low crude fat content of the flours enhances its storage life due to lowered chance of rancid flavor development (yarkwan and uvir, 2015). in comparison with other staple food flours, the crude fat content of musa spp. flours are higher than that of cassava (0.5%) (adebowale et al., 2008). the crude protein content ranged from 1.52 to 1.98% with samples red banana and plantain flour samples having minimum and maximum values, respectively. http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 937 table 1: proximate composition of six varieties of nigerian grown musa spp. flours varieties moisture (%) crude fat d.b (%) crude fibre (%) ash (%) crude protein (%) carbohydrate (%) ps 11.01a±0.04 5.08a±0.68 1.00a±0.05 1.64a±0.0 2 1.96a±0.00 6 90.32c±0.61 bs 10.82a±0.13 2.88b±0.33 0.27e±0.01 1.41b±0.3 0 1.70b±0.03 93.74a±0.64 rbs 10.89a±0.09 2.85b±0.42 0.49d±0.03 1.41b±0.1 1 1.52c±0.13 93.75a±0.48 ss 10.97a±0.15 2.90b±0.05 0.78b±0.00 1.32b±0.0 3 1.69b±0.10 93.40a±0.42 as 11.08a±0.28 1.75c±0.22 0.66c±0.03 1.68a±0.1 3 1.98a±0.18 93.93a±0.36 ibs 11.05a±0.38 1.67c±0.10 0.68c±0.00 1.71a±0.0 1 1.99a±0.01 92.39b±0.04 values are mean ± standard deviation of triplicate analysis; values followed by the same letter in the same column are not significantly different (p < 0.05). ps = plantain flour; bs = bluggoe/plantain banana flour; rbs = red banana flour; ss = lacatan/saro flour; as = gold finger flour; ibs = robusta/ omini ibile flour the crude protein content of the flour samples investigated are significantly different (p<0.05) with the exception of plantain, goldfinger and robusta flour samples. this implies that variety plays a crucial role in the crude protein content of musa spp. flour. the crude protein values favourably compared with 1.05 – 2.25% documented by daramola and osanyinlusi (2006) but lower than the 3.69 – 5.46; 3.6 – 3.86 and 3.6% as reported by adeniji et al. (2007); and yarkwan and uvir (2015), respectively. with respect to other staple food flours, the crude protein contents of the flours were higher compared to cassava flour protein content (1.14%) (adebowale et al., 2008). although the protein contents of musa spp. flours are low, its nutritive quality is the energy value it can supply to its consumers (adebowale et al., 2008). the ash content values ranged from 1.32 to 1.71% with bluggoe and plantain flour samples having lowest and highest values, respectively. the values are significantly different (p< 0.05). the ash content provides an estimate of the mineral element present in the samples. it is also referred as an inorganic content residue remaining after the organic matter has been burnt away. the values compared favourably with 0.55 – 3.60 and 1.5 – 1.65% reported by daramola and osanyinlusi (2006) and kiin-kabari and njoku (2016), respectively. however, in comparison with other staple flours, its value is higher than that of 0.8% of cassava flour (adebowale et al., 2008). the crude fibre content ranged from 0.27 to 1.00% with bluggoe and plantain flour samples having the lowest and highest values, respectively. there is significant difference (p<0.05) in the crude fibre contents of the samples with the exception of goldfinger and robusta flour samples. the crude fibre has been extensively used to measure cellulose, hemicellulose and lignin of food samples. the crude fibre contents of musa spp flours compared favourably with that of rice (0.9%) but lower than that of maize (4.47%) (adebowale et al., 2008). it may be inferred that musa spp. flours at first stage of maturity are very rich in carbohydrate irrespective of variety but low in crude protein and fat contents with the exception of plantain flour sample which its crude protein content was 5.08%. the total starch (ts) of the flours ranged from 488.30 to 473.97 mg/g with lacatan and bluggoe flour samples having the lowest and highest values, respectively (table 2). there is a significant difference (p< 0.05) in the total starch fractions of the six varieties. this implies that total starch fraction of musa spp. flours at first stage of maturity is affected by variety. the values obtained compared favourably with the total starch fractions of other staple food flours such as cassava, potato, rice and yam flours. starch is mainly divided into three categories using nutritional classification as a basis: rapidly digestible starch (rds), slowly digestible starch (sds) and resistant starch (rs) (hans et al., 2006). rapidly digestible starch (rds) and slowly digestible starch (sds) were calculated from the in vitro starch digestion at 30 and 120 min. of enzymatic incubation. the rds values for all the varieties investigated ranged from 26.52 (lacatan flour sample) to 30.12% (plantain flour sample) (table 2). there is significant difference (p<0.05) among all the varieties investigated. rds is widely used as an alternative method for starch digestion evaluation when the rds fraction is high, the starch is considered rapidly digested resulting into a high glycemic response in vivo (falade et al., 2005). also, the slowly digested starch (sds) values for all the varieties investigated ranged from 33.02 (red banana flour) to 36.38% (gold finger flour) (table 2). there is a significant difference (p<0.05) of all the varieties investigated. the rsd and sds values of all the musa spp. varieties investigated showed that fewer fractions of the starch were digested at first 30 min. of enzymatic hydrolysis as compared with thereafter, implying that the sample starch was slowly hydrolyzed within the first 30 min. the resistant starch (rs) values for all the varieties investigated http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 938 ranged from 21.16 (gold finger flour) to 27.54% (bluggoe flour). the resistant starch (rs) values were significantly different (p<0.05) for all the varieties investigated. the relatively high rs values of all the musa spp. flours may be due to crystalline structure of food matrix that reduces susceptibility to enzymatic digestion. table 2: starch fractions of six varieties of nigeria grown musa spp. flour sample ts (mg/g) rds (%) sds (%) rs (%) ps 485.63a±2.08 30.12b±0.010 33.99e±0.001 24.58g±0.001 bs 488.30a±2.81 27.50f±0.006 33.36f±0.003 27.54f±0.001 rbs 485.63ab±1.53 27.52e±0.005 33.02g±0.002 23.92e±0.001 ss 473.97c±0.53 26.72g±0.003 35.43d±0.005 23.51d±0.001 as 479.63b±2.09 30.02c±0.009 36.38b±0.008 21.16c±0.003 ibs 484.63ab±1.15 28.88d±0.005 36.34c±0.007 22.74b±0.006 wwf 483.30ab±0.001 54.52a±0.014 28.04a±0.017 13.45a±0.018 values are mean ± standard deviation of triplicate analysis; values followed by the same letter in the same column are not significantly different (p < 0.05) ; ps = plantain flour; bs = bluggoe/plantain banana flour; rbs = red banana flour; ss = lacatan/saro flour; as = gold finger flour; ibs = robusta/ omini ibile flour; wwf = white wheat flour; rdsrapidly digested starch; sds – slowly digested starch and rs – rapidly digested starch ts – total starch the amylose values ranged from 25.10 to 29.02% with sample gold finger and bluggoe flour samples having lowest and highest values, respectively (table 3). there is significant difference (p<0.05) in the amylose values of all the varieties investigated. based on the accepted classification of amylose (juan et al., 2006; jeevetha et al., 2014), the amylose contents of musa spp. flours are classified as high. the amylose content values of the six varieties of musa spp flours compared favourably with 26% of white rice (musa et al., 2011) but lower than 35.77 – 40.68% reported by adejumo et al. (2013) for different varieties of maize flours. juan et al. (2006) reported that high amylose fraction (>25%) food had demonstrated resulting into a lower blood glucose and insulin response, vice versa (argyri et al., 2016). table 3: amylose-amylopectin composition of six varieties of nigeria grown musa spp. flour varieties amylose (%) amylopectin (%) amylose : amylopectin ps 27.85c±0.12 72.15b±0.18 0.386c±0.003 bs 29.02c±0.18 70.98a±0.17 0.409d±0.004 rbs 26.32b±0.03 73.68c±0.03 0.357b±0.001 ss 26.15c±0.04 73.85b±0.04 0.354c±0.001 as 25.10a±0.07 74.90d±0.07 0.335a±0.001 ibs 26.69c±0.15 73.31b±0.15 0.364c±0.003 values are mean ± standard deviation of triplicate analysis; values followed by the same letter in the same column are not significantly different (p < 0.05) ; ps = plantain flour; bs = bluggoe/plantain banana flour; rbs = red banana flour; ss = lacatan/saro flour; as = gold finger flour; ibs = robusta/ omini ibile flour the amylopectin content ranged from 70.98 (bluggoe flour) to 74.90% (gold finger flour). significant difference (p<0.05) was observed among the amylopectin contents of the flours. the amylose-amylopectin ratio ranged from 0.34 – 0.41 with samples gold finger and bluggoe flour samples having minimum and maximum values, respectively. the amylose/amylopectin ratio has been widely used as an important implication on food quality, industrial application and health (jeevetha et al., 2014; argyri et al., 2016). ravi and musataffa (2013) reported that the unripe plantain beneficial advantage is associated with its carbohydrate characteristics and resistant starch. the kinetic (digestibility) constant of the musa spp. flours ranged from 0.0033 to 0.0040 min-1 with bluggoe and gold finger flour samples having the lowest and highest values, respectively with no distinct difference in their kinetic (digestibility) constants (table 4). in comparison with kinetic constant (0.070 min-1) of white wheat flour, it showed that digestibility of musa spp. flours is 20 times slower. http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 939 hydrolysis index (hi) of the six varieties of musa spp. flours ranged from 20.77 to 24.78% with bluggoe and gold finger flour samples having the minimum and maximum values, respectively. the hydrolysis indices of the six flours are low in comparison with the 100% standard for white wheat flour. the hydrolysis index measures the theoretically digestible starch proportion (under the conditions of the study) (falade et al., 2005). in comparison with the hi value documented by jeevetha et al. (2014), the hi values of all varieties of musa spp. investigated were highly correlated with rds (r2 = 0.93). falade et al. (2005) also documented similar correlation between hi and rds. this implies that the rds could be used an alternative predictor for musa spp. flour digestion. table 4: in vitro starch digestibility parameters of six varieties of nigeria grown musa spp. flours sample k (min-1) auc hi (%) pgi ps 0.0035 0.259 23.443 52.580 bs 0.0033 0.230 20.765 51.110 rbs 0.0039 0.263 23.752 52.750 ss 0.0038 0.267 24.131 52.958 as 0.0040 0.274 24.776 53.312 ibs 0.0037 0.262 23.735 52.741 wwf 0.0700 9048 100.000 94.600 ps = plantain flour; bs = bluggoe/plantain banana flour; rbs = red banana flour; ss = lacatan/saro flour; as = gold finger flour; ibs = robusta/ omini ibile flour; wwf = white wheat flour; k = kinetic constant (min-1); auc = area under curve; hi = hydrolysis index; pgi = predicted glycemic index the predicted glycemic index (pgi) of the six varieties of musa spp. flours investigated ranged from 51.11 to 53.31 with bluggoe and gold finger flour samples having the minimum and maximum values, respectively. the differences in pgi suggest varying amounts of amylose and amylopectin in the varieties. the values obtained compared favourably with 39.04 – 51.05 reported by oko et al. (2015) for eight unripe plantain cultivars in nigeria. the pgi measures the blood glucose-raising ability of the available carbohydrate in food samples (wolever et al., 2008). according to the official classification, high pgi foods (>70), intermediate pgi foods (55 – 70) and low pgi foods (<55) raise blood glucose level rapidly, moderately and slowly, respectively (brand-miller et al., 2003). this indicates that flours of the musa spp. varieties investigated are classified as low pgi staple foods. however, glucose metabolic disorders are often led to high pgi food consumption. heather et al. (2001) and brand-miller et al. (2003) reported that low pgi foods improve metabolic mechanisms in adult patients with type 2 diabetis mellitus and blood glucose levels. furthermore, the health benefits of low pgi diets have been associated with increased insulin sensitivity, reduce food intake and body weight, and may reduce serum cholesterol (wolever et al., 2008). the low pgi values obtained in this study may be attributed to the starch characteristics of the flours coupled with the high amylose content. similar trend of high amylose and low pgi had been documented by other authors (bahado-singh et al., 2006; wolever et al., 2008). high amylose content foods digests more slowly because amylose is a polymer of simple sugars with straight, unbranched chains which forms a not easily gelatinized solid bond whereas amylopectin is highly branched, available for enzymatic digestion with the open structure and therefore have hyperglycemic activity than food containing high amylose (bahado-singh et al., 2006; widowati et al., 2010). reduced risk of metabolicdegenerative disorders and blood glucose level (type 2 diabetic) have been associated with low pgi foods. 4. conclusion starch characteristics of musa spp. flour had been documented. the results showed that all the samples investigated have considerable resistant starch and low glycemic index with little or no difference in the glycemic index values among the varieties investigated. the study therefore provides nutritional guideline data for selection of low glycemic index flour in the development and formulation of new products. acknowledgement the authors appreciated the effort of professor s. o. gbadamosi for his support and contribution towards successful conceptualization of this ideas. http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 940 references adebayo, wa., ogunsina, bs., taiwo, ka. and chidoziri, po. 2021. studies on some physico –chemical and engineering properties of musa spp. (abb) starch flour, african journal of food science, 15(7): 289 – 297. adebowale, aa., sanni, lo. and onitilo, mo. 2008. chemical composition and pasting properties of tapioca grits from different cassava varieties and roasting methods, african journal of food science, 2: 077 – 082 adejumo, al., aderibigbe, fa. and owolabi, ru. 2013. relationship between α-amylase degradation and amylose/amylopectin content of maize starches, advances in applied science research, 4 (2): 315 – 319. adeniji, ta., sanni, lo., barimalaa, is. and hart, ad. 2007. nutritional composition of five new nigerian musa hybrid cultivars. implications for adoption in human nutrition, fruit, 62: 135 – 142. adeniji, ta. and tenkouano, a. 2008. effect of processing on the proximate, mineral and pasting properties of whole flour made from some new plantain, and banana hybrids pulp and peel mixture, journal of tropical agriculture, food, environment and extension, 7(2): 99 – 105. aoac 2005: official methods of analysis. 18th ed. gaitherburg, association of official analytical, chemistry international: 777 796 argyri, k., athanasatou, a., bouga, m. and kapsokefalou, m. 2016. the potential of an invitro digestion method for predicting glycemic response of foods and meals, nutrients, 8: 209 – 220. bahado-singh, ps., wheatley, ao., ahmad, mh., morrison, ey. and asemota, hn. 2006. food processing methods influence the glycemic indices of some commonly eaten west indian carbohydrate-rich foods, british journal of nutrition, 96(3):476 – 481. brand-miller, jb., wolever, tms., fosterpowell, k. and colagiuris, s. 2003. the new glucose revolution: the authoritative guide to the gi. marlowe and company, new york, usa. daniells, j., jenny, c., karamura, d. and tomekpe, k. 2001. musalogue: a catalogue of musa germplasm. diversity in the genus musa. (arnaud, e. and sharrock, s., eds.). inibap, montpellier, france. pp. 213. daramola, b. and osanyinlusi, sa. 2006. production, characterization and application of banana (musa spp) flour in whole maize, african journal of biotechnology, 5(10): 992 – 995. falade, so., owoyomi, o., harwood, ce. and adewusi, ra. 2005. chemical composition and starch hydrolysis of acacia colei and acacia tumida seeds, cereal chemistry, 82(5) : 479 – 484 fao. 2005. banana statistics 2005. food and agriculture organization of the united nations, rome, available online at: http://www.fao.org/es/esc/common/ecg/109399 en banstat 06.pdf hans, xz., ao, z., janaswamy, s., jane, jl., chandrasekaram, r. and hawaker, br. 2006. development of a low glycemic index maize starch: preparation and characterization, biomacromolecules, 7: 1162 – 1168. heather, r., gilbertson, gdd., miller, jb., thorburn, aw., evans, s., chodros, p. and werther, ga. 2001. the effect of flexible low glycemic index dietary advice versus measured carbohydrate exchange diets on glycemic control in children with type 1 diabetics. diabetic care, 24:1137-1143. hermansen, ml., eriksen, nm.; mortensen, ls., holm, l., hermansen, k. 2006. can the glycemic index (gi) be used as a tool in the prevention and management of type 2 diabetes? review of diabetic studies, 3: 61 – 71. jeevetha, s. barakatun-nisak, my., ngan, h., ismail, a. and azlan, a. 2014. relationship between amylose content and glycemic index of commonly consumed white rice, journal of agriculture and veterinary science, 7 (9): 12 – 18. juan, g., luis, a. and david, b. 2006. isolation and molecular characterization of makal (xanthosomayucatanensis) starch, starch, 58: 300 – 307. http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng http://www.fao.org/es/esc/common/ecg/109399%20en%20banstat%2006.pdf arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 933-941. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayow@oauife.edu.ng 941 kiin-kabari, db. and njoku, v. 2016. the particle size and thermal properties of flour from three plantain (musa paradisiaca) cultivars grown in nigeria, journal of food technology research, 3 (1): 23 – 27. kirk, rs. and sawyer, r. 1991. pearson’s composition and analysis of food. 9th ed., longman singapore publishers, singapore. pp. 330 – 333. louie, jcy., flood, vm. atkinson, fs. barclay, aw., brand-miller, jc. 2015. methodology for assigning appropriate glycemic index values to an australian food composition database, journal of food composition and analysis, 38: 1 – 6. musa, asn., umar, im. and ismail, m. 2011. physicochemical properties of germinated brown rice (oryza sativa l.) starch, african journal of biotechnology, 10 (33): 6281 – 6291. ogundare-akanmu, oa., inana, me. and adindu, mn. 2015. preliminary quality evaluation of selected plantain flour (musa paradisiaca) sold in portharcourt markets, nigeria, food science and quality management, 35: 7 – 10. ojure, ma. and quadri, ja. (2012). quality evaluation of noodles produced from unripe plantain flour using xanthan gum, international journal of nutrition, 13: 740 – 752 oko, ao., famurewa, ac. and nwaza, jo. 2015. proximate composition, mineral elements and starch characteristics: study of eight (8) unripe plantain cultivars in nigeria, british journal of applied science and technology, 6 (3): 285 – 294. ravi, i. and mustaffa, mm. 2013. starch and amylose variability in banana cultivars, industrial journal of plant physiology, (3):33 – 36. usda (2009). national nutrient database for standard reference, http://www.nal.usda.gov/fnic/foodcomp/plantain/. widowati, s., susila santosa, ba. and astawan, ma. 2010. reducing glycemic index of some rice varieties using parboiling process, indones journal of agriculture, 3(2):104 – 111. wolever, tm., brand-miller, jc., abernethy, j., astrup, a., atkinson, f., and axelsen, m. 2008. measuring the glycemic index of foods: inter-laboratory study, american journal of clinical nutrition, 87: 247 – 527. yarkwan, b. and uvir, rh. 2015. effect of drying methods on the nutritional composition of unripe plantain flour, food science and quality management, 41: 5 – 10. http://www.azojete.com.ng/ mailto:adebayow@oauife.edu.ng http://www.nal.usda.gov/fnic/foodcomp/plantain/ corresponding author’s email address: femisanyaolu@rocketmail.com 491 arid zone journal of engineering, technology & environment original research article rainfall and streamflow dynamics in the borno region of the lake chad basin: a hydrological assessment b. o. sanyaolu1*, u. a. ibrahim1 and a. n. alkali1 1department of civil and water resources engineering, university of maiduguri, maiduguri, borno state *corresponding author’s email: femisanyaolu@rocketmail.com article information abstract this study assesses the water resources potential within the maiduguri catchment of the lake chad basin by analyzing a 20-year using rainfall data between 1999 to 2018 and streamflow data between 1981 to 2000 (each over a 20 year period). the results indicates that monthly rainfall was generally higher between 1999 and 2011, followed by a significant decline from 2012 to 2018. this shift suggests a progressive extension of aridity from the lake chad region into the sudan savannah, likely influenced by the effects of climate change. flooding events were recorded in 16 of the 20 years analyzed. streamflow analysis of river ngadda, which traverses maiduguri, revealed an average discharge of 6,201.2 m³/s over the study period, with a 7-year span of flooding. additionally, storage apportionment data were evaluated to inform water resource management in the region. received: 24th march 2025 revised: 30th april 2025 accepted: 30th april 2025 keywords: lake chad basin ngadda river maiduguri rainfall streamflow hydrological © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction one of the biggest problems facing the lake chad basin is the variability of its hydrological regime and freshwater availability. lake chad shrank by 90% as a result of recurrent droughts in the period from 1970 to 2008 and the declining discharge of the rivers that feed it (ross, 2018). over this period, groundwater levels followed the same trend as surface water levels, showing a significant decline. since the1990s, however, rainfall has remained relatively stable, close to its yearly average. this has led to a slight improvement in the situation. many of the world’s river basins are either ‘closed’ or ‘are closing’ as water use within them exceeds or is approaching the amount of renewable water available (jedwab et. al., 2023). the lake chad basin being one of these closed basins poses complex water management since there is interconnection between the water cycle, aquatic systems and water users. population growth increases the demand for food, land and water also increasing the stress on available water resources (mahmood and jia, 2018; odada et al., 2011; romero et al., 2014). the resultant effects of these actions have been drastic changes in the natural environment with notable implications on the climatic water distribution. findings from various climatic models as they relate to climate change predict increased evapotranspiration in the presence of water. however, in the absence of precipitation, this will result in increased risk of drought due to enhanced surface dryness (westerling and swatnam, 2003), heat wave (lyon, 2009; lau and nath, 2012) and wildfires (whitman et al., 2015). this is true of the sudan-sahelian region of nigeria which is characterized by acute rainfall variability and in the last 40 years has witnessed dramatic reductions in mean annual rainfall (thompson and amos, 2010; ekpoh and nsa, 2011). the chad basin is the largest basin of interior drainage in africa occupying an area of 600,000 square miles in the southern sahara and in the sudan region. the basin is named for its most conspicuous feature, the lake chad. azojete june 2025. vol.21(2):491-498 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/014 www.azojete.com.ng mailto:femisanyaolu@rocketmail.com mailto:femisanyaolu@rocketmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 492 figure 1: map of lake chad with its tributaries and the four riparian countries (source: zhu etal., 2017) the sector of the lake chad basin in nigeria covers an area of 6,074km2 which is one tenths of the total area of the basin (ndehedehe et al., 2016). out of this, the part situated in borno state covers 2,258km2 (darnhofer et al., 1988). because the lake is shallow, the shoreline fluctuates markedly with high and low stages corresponding to the wet and dry seasons. none of the rivers in the borno area is perennial and most of them flow into marshy areas on the plain and disappear by evapotranspiration before reaching lake chad. however, the komadugu-yobe in the north and the yedseram river to the south, flowing through bama are relatively large streams that discharge into lake chad during the rainy season. the ebeji river is by far the largest river flowing into lake chad, but part of its relatively large catchment extends into cameroon (nnjcc report, 1985). the ngadda river which flows through maiduguri has a relatively small catchment basin and like other rivers mentioned above is seasonal in character. the river flows from august to february and usually reaches peak discharge in september. upstream from maiduguri, the ngadda passes through lakes yare and alau. both of which are perennial. at high water, the surface area of lake yare is about 10 sq. miles while that of alau is 2 and a half miles (buma et al., 2018). the ngadda enters lake yare and leaves by twin channels, one of which flows into lake alau. the outlet from lake alau joins the bypass channel 12 miles south of maiduguri (irivboje and kimingar, 1988). this investigation is concerned primarily with the hydrological analysis of rainfall and streamflow data of river ngadda with a view to determining the magnitude, distribution, storage and deficit for the period of record. 2. materials and methods mean monthly rainfall data was collected for the period 1999-2018 from the nigerian meteorological agency (nimet), maiduguri. streamflow data was obtained from the hydrology section of the borno state water board for the limited period 19812000 that was available. the rainfall data had some missing data and this was filled by interpolation using a rating curve. thereafter the data was processed into mean annual values. a hyetograph of the annual totals against the years was plotted to show rainfall variation across the period of record. in analysing the rainfall trend, the moving average method of time series was used. this was done by creating a series of averages of different subsets of the full data set. the average for the year was estimated and given in equation 1: 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 = 𝐴 + 2𝑏 + 𝐶 4 1 http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 493 where: a= rainfall value of the preceding year, b=rainfall value of the year under consideration, c= rainfall value of the preceding year a frequency analysis of the rainfall data was done to determine the probability of occurrence of flow that would be equaled or exceeded in any given year. in doing this, the rainfall annual totals were arranged in ascending order and the probability of each occurrence ranked. the weibull equation in equation 2 was used as plotting formula: 𝑃 = 𝑚 𝑛 + 1 2 where: p=probability in % of the occurrence m, m=the rank of the observation, n=the total number of observations 2.1 mass curve analysis mass curve plot was used to investigate reservoir storage requirements along the river. this was obtained using monthly streamflow data. the cumulative inflow values were plotted against time. the storage required at maximum deficiency was then determined. 3. results and discussion 3.1 rainfall analysis the mean annual rainfall across maiduguri shown in figure. 2 is generally random with a significant decrease in amount between 2012-2018.however, the catchment experienced relatively high rainfall between 19992011. figure 2: mean annual rainfall distribution in maiduguri over a 20 year period (1999-2018) figure 3: mean monthly rainfall distribution over maiduguri (1999-2018) 0 10 20 30 40 50 60 70 80 90 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 m ea n a n n u a l b a in a ll ( m m ) time (year) 0 50 100 150 200 250 jan feb mar apr may jun jul aug sep oct nov dec p r ec ip it a ti o n ( m m ) time (month) http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 494 the mean monthly rainfall hyetograph in figure 3 indicated that the maiduguri catchment experienced rainfall between may and october with increased amounts between july and august with dry spells occurring between january and april as well as october to december. the moving average smoothing technique was used to eliminate the random fluctuations with the results converging to a description of the flooding trend. from the total annual rainfall data, the mean annual total was calculated as 681.5mm. the moving average values exceeding the mean annual indicated flood events occurring from 2001-2011 and 2017-2018. figure 4 indicated that the rainfall pattern was generally similar from 1999-2011, but a sharp decline is noticeable between 2014 and 2016. these observations indicate that maiduguri and its environment and populations are under a growing risk of water scarcity, food insecurity, wetland loss and shoreline retreat. figure 4: rainfall moving average pattern over the 20 year study period (1999-2018) the national action programme to combat desertification in nigeria estimates that about 50% of borno state is seriously affected by desertification (butu and emeribe, 2019). a hydrologic frequency analysis of the total annual rainfall data was carried out in order to obtain the cumulative distribution which provides a rapid means of determining the probability of a flood event occurring or exceeded in any given year. a normal distribution function was fitted to the total annual rainfall data and a probability plot drawn to show the exceedance frequencies and recurrence interval for the 20 year period. from figure 5(probability plot), the 50% chance (100 yr.) of the total annual rainfall occurring or exceeded is 780mm, while the probability of 95% (100 yr.) total annual rainfall occurring is about 150mm. table 1 shows that the highest precipitation value, 1023.8mm has a calculated recurrence interval of 21.278years while the lowest value 129.86mm has a recurrence interval of 1.1 years. figure 5: probability vs. total annual rainfall plot y = -28.925x + 58870 0 200 400 600 800 1000 1200 1995 2000 2005 2010 2015 2020 p r ec ip it a ti o n ( m m ) time (year) 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 1000 1200 p ro b ab ili ty total annual rainfall (mm) http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 495 table 1: exceedance frequencies and recurrence intervals for total annual precipitation (1999-2018). year total annual rainfall (mm) rank(m) p= 𝒎 𝒏+𝟏 t(yr)=1/p 2003 1023.8 1 0.047 21.276 2004 1023.6 2 0.095 10.526 2008 985.9 3 0.142 7.042 2005 975.5 4 0.19 5.263 2006 955.4 5 0.238 4.201 2002 881.6 6 0.285 3.508 2009 857.4 7 0.333 3.003 2001 835.9 8 0.381 2.624 2007 833.6 9 0.429 2.331 2011 827.1 10 0.476 2.101 1999 814.6 11 0.523 1.912 2010 756.5 12 0.571 1.751 2000 691.8 13 0.619 1.615 2017 523.01 14 0.667 1.499 2015 490.29 15 0.714 1.401 2016 378.70 16 0.761 1.314 2018 274.32 17 0.809 1.236 2012 210.06 18 0.857 1.166 2013 129.86 19 0.904 1.106 2014 161.15 20 0.952 0.952 3.2 streamflow analysis the magnitude of total annual flow along the river ngadda was used to study some of its flow characteristics. however, due to paucity of reliable data from 2001-2020, only available data for the period 1981-2000 was used. based on this, the average streamflow was 6201.20m3/s. moving average values exceeding this average would result in flooding as shown in table 2. table 2: annual streamflow data with moving average values and flood events time (year) total annual streamflow (m3/s) moving average(m3/s) flooding (m3/s) 1981 6325.28 1982 8302.2 14627.5 1983 1620.44 9922.64 24550.1 6137.53 1984 7399.5 9019.94 18942.6 4735.645 1985 6640.23 14039.7 23059.7 5764.92 1986 5349.88 11990.1 26029.8 6507.46 ● 1987 4981.35 10331.2 22321.3 5580.34 1988 7436.24 12417.6 22748.8 5687.21 1989 9345.11 16181.4 28598.9 7299.735 ● 1990 6333.51 15678.6 31860 8114.99 ● 1991 5392.63 11726.1 27404.8 6373.97 ● 1992 7425.87 12818.5 24544.6 6136.16 1993 6584.94 14010.8 26829.3 6707.33 ● 1994 9046.39 15631.6 29642.4 7410.54 ● 1995 6339.11 15385.5 31017.1 7753.97 ● 1996 5709.3 12048.4 27433.9 6858.48 ● 1997 4965.65 10675 22723.4 5680.84 1998 4900.44 9866.09 20541 5135.26 1999 5222.14 10122.6 19988.7 4997.17 2000 4703.87 9926.01 20048.6 5012.15 the highest monthly stream discharge for the period was 3214.05m3/s recorded in december 1989 while the lowest flow was 2.62m3/s recorded in may, 2000. the flow trend observed from the moving average plot (fig.6) indicated an increase in flow between1989-1990 as well as between 1993-1994. http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 496 figure 6: streamflow moving average pattern over the 20 year study period (1981-2000) figure 7 shows the relationship between cumulative flow against monthly flow. the mass curve gives an estimated flow deficit suitable for future water resources planning. the upper limit gives a flow of 62,000,000 while the lower limit gives a flow of 23,000,000 putting the difference at 39,000,000. figure 7: mass curve of cumulative flow against monthly streamflow three main factors would drive the continued growth in demand for water, population, prosperity and climate change. the biggest uncertainty in projecting future demand lies in estimating how much will be needed for agriculture, which currently accounts for about 70% of water withdrawals, mostly for irrigation (unesco, 2024). some forecast a big increase in demand, as food production has to rise to feed a growing population. the impact of climate change is however, still unpredictable as it may exacerbate the trend of wet areas getting wetter and vice versa for the dry areas as well. and rainfall on which much of subcontinental african economic life hinges, will become more erratic. the most extreme short-term effects have been the increasing number of extreme weather events. in the long run, consequently, however, the bigger problem from climate change will not be too much water but too little. as a report by the world bank puts it: “the impacts of water scarcity and drought may be even greater, causing long-term harm in ways that are poorly understood and inadequately documented.” of course, a lot depends on how much the climate changes and how fast. approximately 80%of the basin is shown to be prone to erosion. the areas most likely at risk from erosion are lake chad, maroua and kano, and vulnerable areas include those situated between maroua, maiduguri and n’djamena and between diffa and zinder. a possible way forward could involve the lcbc member states y = -10.757x + 27638 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 1980 1985 1990 1995 2000 2005 st r ea m fl o w ( m 3 / s) time (year) 0 20000000 40000000 60000000 80000000 100000000 120000000 140000000 jan feb mar apr may jun jul aug sep oct nov dec a cc u m u la te d f lo w ( m 3 /d a y ) time (month) http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 497 granting lake chad and its immediate surroundings special status as an area of great environmental value. a partnership agreement could be signed with unesco to make lake chad a biosphere reserve. all the environmental problems described are being addressed by the lcbc through projects and programs implemented in collaboration with different international, national organizations, and civil society organizations which are keen to increase their support to the lcbc for the good of the regional and global environment. however, due to the upsurge in violence from non-state actors such as boko haram and the islamic state in west africa province, many setbacks have ensued. in this regard, there is need to plan and design sustainable water resources management techniques in different sectors – agriculture, irrigation and water supply to adapt to changing patterns of rainfall fluctuation and rising cases of insurgency. decreasing streamflow is a worldwide phenomenon. some of it results from declining rainfall. but much is the direct result of human intervention— the damming and diversion of rivers for flood control, water-storage and irrigation. and, where rivers still flow, the water in them is often unsafe to drink or even bathe in. waterborne diseases recorded within communities around river ngadda include diarrhea, dysentery, intestinal parasitic diseases, bilharzias, cholera and typhoid fever. the lack of potable water and in particular, the poor hygiene levels are seen as the main causes. much is being done in this regard, especially on the part of international agencies and civil society groups, but projects still face major constraints: poor health infrastructure, few skilled staff motivated to work in some areas, limited access due to religious and cultural influence. 4. conclusion this study provides valuable insight into the variability in rainfall and streamflow pattern in the borno sector of the chad basin. the continuous decrease in rainfall amount between 2012 and 2018 could be as a result of reversible climatic fluctuation and not climate change. this may be attributed to repeated drought cycles in those years caused by large scale shifts in global circulation. flood events occurred from 2001 to 2010 as well as in 2017 and 2018. from the mass curve analysis of streamflow data from river ngadda, storage capacity required to hold surplus waters for release during critical periods when inflows fall short of demand was calculated to be 3.8 x 106m3/s. member states of the lake chad basin commission have not efficiently implemented the lake chad water charter after its ratification in 2013which establishes the rights, obligations, duties, restrictions and procedures for the effective management of lake chad resources. the stumbling blocks relating to national sovereignty are still present, particularly that of the quantitative management of surface and groundwater resources. similarly, the charter has failed to tackle the issue of sanctions against those who break the charter. as with all legal documents, the charter is merely a document that can only be effective when it is faithfully implemented and upheld. in other words, its usefulness and effectiveness depend entirely on the capacity and will of the parties to adopt the measures required for its implementation. references avis ca., weaver aj. and meissner kj. 2011. reduction in areal extent of high-latitude wetlands in response to permafrost thaw. nature geoscience, 4:444-448. buma, wg., lee, s. and seo, jy. 2018. recent surface water extent of lake chad from multispectral sensors and grace. sensors, 18(2082): 1–24. https://doi.org/10.3390/s18072082. butu aw. and emeribe cn. 2019. spatial patterns of climatic variability and water budget over sudan savannah of nigeria. african journal of environmental science and technology, 13(12): 464-480 darnhofer, t.1988. the agroclimatic and water balance situation of the chad basin: evaluation of proposed management schemes to improve the water balance of lake chad.: unep mission report nairobi (ke): unep. 51. ekpoh ij. and nsa e. 2011. extreme climatic variability in north-western nigeria: an analysis of rainfall trends and patterns journal of geography and geology. 3(1). unesco. 2024. united nations world water development report. irivboje, oc. and kimingar, n. 1988. commission du bassindu lac tchad (cblt) n’djaména. td. le bassin du chari: évolutiondepuis la dernièresècheresse (1984-1985 à 1987-1988) http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 491-498. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: femisanyaolu@rocketmail.com 498 jedwab, r., haslop, f. and zarate rd. 2023. the effects of climate change in the poorest countries: evidence from the permanent shrinking of lake chad. unddr prevention. lau, n., nath, mj. 2012. a model study of heat waves over north america: meteorological aspects and projections for the twenty-first century’, journal of climate 25(14): 4761-4784. lyon, b. 2009. southern africa summer drought and heat waves: observations and coupled model behaviour, journal of climate, 22(22): 6033-6048. mahmood, r., and jia, s. 2018. analysis of causes of decreasing inflow to the lake chad due to climate variability and human activities. hydrology and earth system sciences discussion, 2: 1–42. https://doi.org/10.5194/hess-139 ndehedehe, ce., agutu, no., okwuashi, o., and ferreira, vg. 2016. spatio-temporal variability of droughts and terrestrial water storage over lake chad basin using independent component analysis. journal of hydrology, 540: 106–128. https://doi.org/https://doi.org/10.1016/j.jhydrol.2016.05.068 niger joint commission for cooperation (nnjcc report) 1985.study of the water resources in the komadougou-yobe basin. vol. 1: general report. odada, eo., oyebande, l., and oguntola, ja. 2005. lake chad: experience and lessons learned brief. lake vic., 92: 72–91. romero-lankao, p, smith, jb., davidson, dj., diffenbaugh, ns., kinney, pl., kirshen, p., kovacs, p., villers, lr. 2014. north america. in: climate change: impacts, adaptation, and vulnerability. part b: regional aspects. contribution of working group ii to the fifth assessment report of the intergovernmental panel on climate change cambridge university press, cambridge, united kingdom and new york, ny,usa,14391498. ross, w. 2018. lake chad: can the vanishing lake be saved. bbc westerling, al. and swetnam, tw. 2003. interannual to decadal drought and wildfire in the western united states. eos 84:545-560. whitman, e. , batllori, e., parisien, ma., miller, c., coop, jd., krawchuk, ma., chong, gw., haire, sl. 2015. the climate space of fire regimes in north-western north america. journal of biogeography, 42(653): 17361749. zhu, w., yan, j. and jia, s. 2017. monitoring recent fluctuations of the southern pool of lake chad using multiple remote sensing data : implications for water balance analysis. remote sensing, 9(1032): 1–26. https://doi.org/10.3390/rs9101032. http://www.azojete.com.ng/ mailto:femisanyaolu@rocketmail.com arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):435-452 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 435 development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor g. a. olarinoye*, f.o. balogun and a. s. abubakar department of electrical engineering, faculty of engineering, ahmadu bello university, zaria *corresponding author's email address: baolarinoye@abu.edu.ng article information submitted 23 march, 2023 revised 23 december, 2023 accepted 4 january, 2024 keywords: flux control pi controller induction motor efficiency optimization simulink abstract the efficiency of induction motor drives under variable operating load and speed conditions can be improved by developing an algorithm that compute the optimum flux in the motor and commands a voltage that drives the motor at maximum efficiency for any given load and speed. this approach also helps to achieve significant amount of savings in electric energy consumption. in this paper, a method to optimize the flux of a three-phase induction motor and thereby maximize its efficiency for each load torque applied at a given speed, was developed. mathematical models for the conventional rotor flux-oriented control scheme, total power loss as a function of rotor flux and for optimum flux as a function of operating speed and load torque were analytically derived. a matlab/simulink model of the proposed rotor flux optimization scheme was developed to verify the analyses set forth for a typical three-phase induction motor. the results of the proposed method were compared with those of the conventional rotor flux control method and direct torque control (dtc) method in terms of loss reduction and efficiency for the same induction motor. the proposed rotor flux optimization scheme achieved 8.51% improvement in efficiency compared to the conventional rotor flux control scheme at a speed of 250 rad/s for a load torque of 3nm. it also achieved 5.01% improvement in efficiency compared to the optimized dtc control scheme for the same speed and load torque. at a lower speed of 150 rad/s, power loss reduced by 17.1% while efficiency was higher by 5.7% for a load torque of 3nm under the proposed scheme as compared to the optimized dtc scheme. 1.0 introduction induction motors are the most widely used electric machine in the industry because of their ruggedness, cheapness and very low maintenance cost. studies have shown that bulk of the energy used in the industry is consumed, largely, by induction motors (engel et al.,2015). therefore, efforts have been made over the years by various manufacturers of induction motors in the technique of construction of energy efficient motors (eem). this has resulted in significant improvements in efficiency and increase in energy savings. induction motor have high efficiency at rated speed and torque, but the efficiency of induction motor decreases greatly at light loads because of an imbalance in copper and core losses. energy saving can however, be achieved by proper selection of the flux level in the motor (eseosa and christian, 2018). losses in the induction motor are classified into stator copper losses, rotor copper losses, core losses, stray losses, friction and windage losses. the copper and core losses account for the largest amount of losses in induction motor and therefore explain the interest to use them in the analysis proposed in this paper. in order to increase the motor efficiency, the flux must be http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 436 reduced and balance obtained between copper and core losses. basically, there are two approaches to improving the efficiency of induction motor (faduyile, 2009). these are the lossbased model approach and the power measure-based approach. in the loss-based model approach, the model-based controller computes losses by using the machine model and thereby determines a flux level that minimizes the losses. this approach is fast and does not produce torque ripple. in the power measure-based approach, the controller searches for the operating points where the output power is constant (rashtchi and bizhani, 2015). in this paper, loss-based model approach or loss model controller of induction motor drive system that determines the optimal flux for loss minimization was analysed and implemented in matlab/simulink. the significance of the method applied in this paper is the reduction in energy consumed by the induction motor for the same load torque over the period of motor operation. the benefit is that it will go a long way to reduce operating cost and to make spare energy available to meet other energy demands. in the long term, this benefit should also slow the world’s overall energy consumption and protect the environment from pollution and preserve the world natural resources from further depletion. induction motors are large consumers of the electric energy, and are designed to operate efficiently at rated loads. unfortunately, these motors operate on partial or low loads most of the time and this situation leads to inefficient motor operation with attendant losses in energy and increased operating cost. the proposed work seeks to reduce the inefficiency of induction motor operation under the conditions of partial or low load operation by developing a method to maximize the efficiency of the motor under these conditions. several papers relating to loss minimization in induction motors have been published in recent times. rashtchi and bizhani (2015) presented a new online loss minimization algorithm using particle swam optimization (pso) to determine the optimum flux level for the efficiency optimization of vector-controlled induction motor. khan et al. (2015) developed a high performance and robust control structure called the flux optimized direct torque control for induction motor. lee et al. (2013) presented a loss based model controller using a digital signal processor (tm320lf2812), for induction motor efficiency maximization and energy saving. sruthi et al. (2017) formulated a loss minimization algorithm for energy saving and efficiency improvement in induction motor drive. the input voltage and frequency were optimized to reduce total losses. eseosa & christian (2018), afify et al. (2018), chelliah (2009), nam and uddin (2006) and laroui, et al. (2021) presented various approaches in optimization control techniques to improve the efficiency operation of induction motor. aygun and aktas (2018) implemented a dtc technique combined with an online loss minimization model-based controller to minimize the losses of an induction motor applied in electric vehicle (ev). the aim of this paper is to develop a rotor flux optimization control model for an existing induction motor and simulate its performances in matlab/simulink for loss minimization and efficiency improvement. 2.0 material and methods this section presents the model of the three-phase induction motor. the model was developed into a rotor flux-oriented control scheme and subsequently, a flux optimization control algorithm was developed and implemented in matlab/simulink to minimize losses and therefore maximize motor efficiency. 2.1 mathematical model of three phase induction motor the dynamic model of the induction motor in d-q coordinates established in a rotor fluxoriented reference frame is provided in equations (1) – (10) (kalhoodashti and shahbazian, 2011). (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%202/9.azojete%2023-013.20(2)%20ok.doc%23_enref_6 olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 437 (2) (3) (4) (5) (6) (7) (8) (9) (10) where and , and are the direct axes and quadrature axes stator and rotor voltages, and , , and are stator and rotor d-q currents, , , and are the d-q stator and rotor flux respectively. and are stator and rotor resistances respectively. is stator frequency and is the rotor electrical speed. the equivalent circuit obtained from the mathematical model equations (1) (8) of the induction motor is shown in figure 1 figure 1: q-d axes equivalent circuit of the induction motor. 2.2 rotor flux-oriented control scheme for the three-phase induction motor the scheme is derived from the rotor dynamic equations of the three-phase induction machine in the synchronously rotating reference frame represented by equations (3)-(4) and (7)-(8). the q-axis component of the rotor flux space vector is equated to zero because of the alignment of the d-axis with the rotor flux vector (olarinoye et al., 2022). it is mathematically represented as follows; (11) the d-axis component of the rotor flux space vector is now equal to the rotor flux magnitude . the rotor flux magnitude is expressed as follows; (12) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 438 mathematically, applying equations (11) to equations (12), (3)-(4), (7) and (8) yields the following results; (13) (14) (15) (16) (17) equations (13) and (14) have been obtained considering that the short-circuited squirrel cage rotor of the three-phase induction motor have zero voltages in the and axis of the rotor windings i.e. and . the rotor flux dynamics is developed from equations (15) and (16) to give the following; (18) where (19) equation (18) is a first order system governed by rotor time constant . the slip frequency is obtained from equations (14) and (17) as follows; (20) the rotor flux angle , which is also the angle of transformation because of alignment of the -axis to the rotor flux vector, is estimated by integrating the rotor flux angular frequency as follows (21) the torque produced in the three-phase induction motor given by equation (9) is modified, upon application of equations (11) and (13), to the following; (22) as a result of the alignment of the rotor flux magnitude with the d-axis, equations (18)-(21) enables the estimation of rotor flux magnitude and the phase angle or the angle of transformation. 2.3 rotor flux optimization scheme the objective of the flux optimization scheme is to regulate the flux magnitude such that minimum losses occur for a given load torque. the three-phase induction motor equivalent circuit was modified to account for the core loss resistance . the equivalent circuit with core loss resistance is presented in figure 2. as a result, the voltage, flux linkage and torque equations of the motor are reformulated to account for the effect of the core loss resistance. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 439 figure 2: three phase induction motor q-d axis equivalent circuits accounting for core loss resistance the following voltage, flux linkage and current equations are derived from the equivalent circuits of figures 2 (a) and (b) and equations (1)-(4) to give the following equations; (23) (24) (25) (26) (27) (28) (29) (30) where (31) and are the currents flowing through the core loss branches of the q and d axes respectively. and are the torque currents responsible for producing electromagnetic torque in the motor as seen from the equivalent circuit of figure 1. by applying equations (11) and (13) to the voltage equations (23) – (26), relationships between the applied stator currents and torque currents were obtained as follows; (32) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 440 (33) the power loss model was formulated considering that the total electrical power loss is the sum of the copper and core losses in the motor. the expression of electrical power loss is obtained from the equivalent circuits as follows; (34) a power loss model was derived by substituting current equations (27) – (33) into equation (34). it is given as follows; (35) the criterion for minimum loss is obtained by differentiating equation (35) with respect to the rotor flux magnitude as follows; (36) equation (36) was solved to obtain the optimum value of rotor flux for minimum loss and hence maximum efficiency. the optimum value of the rotor flux for a given load torque and speed was derived to yield; (37) the efficiency of the induction motor was determined using the following equation; efficiency (38) equation (38) gives the efficiency as a function of electrical power loss in the machine. for the purposes of controller design, the stator voltages are expressed as a function of the d and q axis currents and the rotor flux by applying equations (5) (8), (11) and (13) to equations (23) and (24). the following expressions were obtained; (39) (40) where: (41) (42) equations (39) and (40) are first order non-linear systems for which and are inputs and and are outputs. the voltage commands needed to give the desired currents, and , are obtained with a feedback-based solution using current controllers. the formulation file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 441 for the controller gains was performed using equations (39) and (40) and illustrated in figures 3 (a) and (b). figure 3: control block diagram for stator current control and are defined as follows; (43) (44) and are the q and d axis current pi controllers. the closed loop transfer function of figure 3 is defined as follows; (45) (46) the expressions for the pi controller gains and were obtained by comparing the normalized denominator of equation (46) with the standard second order denominator, as follows; (47) where upon and were obtained as; (48) (49) is the damping ratio. is the natural frequency. the speed control and rotor flux control loops provide the d and q axis current commands respectively according to equations (18), (22) and (10). pi controllers were also employed for the speed and flux control loops. the block diagram of the speed control system is given in figure 4 and it is based on the machine dynamics given equation (10). figure 4: control block diagram for speed control the equation of the transfer function of the speed control loop is obtained from figure 4 as; (a) q-axis current control (b) d-axis current control http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 442 (50) the speed controller gains are calculated from (50) as follows; (51) (52) the control block diagram of the flux control system is obtained from equation (18) and given in figure 5. figure 5: control block diagram for rotor flux control the equation of the transfer function of the flux control loop is obtained as; (53) the flux controller gains are calculated from equation (53) as follows; (54) (55) the supply voltages in the synchronous reference frame are then calculated based on the following equations; (56) (57) the control objective is to regulate the rotor flux and the torque to their commanded values. figure 6 shows the block diagram of the rotor flux-oriented optimizing drive scheme for the three-phase induction machine. the inverter supplies the controlled three phase voltages to the three-phase induction motor in such a way that the flux is regulated at its optimum value for each load torque. the torque command is the output of the speed control loop. when the motor drive is in operation, flux is produced in the machine. the flux is controlled to its optimum value by regulating the d-axis stator current. this regulation ensures linear control of torque by the q-axis stator current. the flux model receives stator currents , and speed and delivers the flux supply frequency and the corresponding angular position to ensure proper vector alignment. the block diagram of figure 6 was implemented in matlab/ simulink. 3. results and discussion in this section, the effectiveness of the proposed method is discussed. simulation results are presented as well. the motor parameters utilized in order to verify the effectiveness of the proposed scheme are provided in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 443 figure 6: block diagram of rotor flux oriented optimizing drive scheme q-axis curren t contro ller speed contro ller inverte r i m eqn. (18) eqn. (20) eqn. (22) transfo rmation blk. transfo rmation blk. _ + + + + + + + + + * * flux controll er d-axis current controll er eqn. (21) eqns.( 56) & (57) optimal flux generat or eqn. (37) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 444 table 1: induction motor parameters. parameter value parameter value voltage 400v 1.52 frequency 50hz 13400 synchronous speed 3000rpm 0.2405h no of poles 2 0.2323h power 3kw j 0.0044kgm2 1.795 table 2: current, speed and flux controller gains controller proportional gain integral gain q-axis current controller ( , ) 639.4058 6.3958e+06 d-axis current controller ( , ) 639.4058 6.3958e+06 speed controller ( , ) 1.76 176 flux controller ( , ) 268.1424 2.7245e+04 the computed controller gains are as provided in table 2. the loss minimization algorithm was set to trigger at 2.5s. with the reference speed and load torque set to 250 rad/s and 3nm respectively, the rated flux was computed as 1wb. the result of total electrical power loss in the induction motor is presented in figure 8. figure 8: electrical power loss vs time it can be seen that the conventional rotor flux control scheme produces a steady state power loss of 200w in the motor. the proposed scheme on the other hand, upon activation at a time of 2.5 s, produces a power loss of 108.04w in the same motor. this gives a significant reduction of 54.02%, the consequence of which is a rise in motor efficiency from 78.9% to 87.41% as shown in figure 9. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 50 100 150 200 250 300 time (s) to ta l p ow er l os s (w ) conventional rotor flux control scheme proposed scheme file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 445 figure 9: efficiency of induction motor vs time figure 10 shows the plot of the rotor flux magnitude. it can be seen that the flux value is 1wb until the proposed scheme is activated and the flux reduces significantly to its optimal value of 0.6357wb for the given load torque. this verifies the analysis set forth, that there is an optimal flux in the motor for which electrical losses are minimized and hence efficiency is maximized for a given load torque. figure 10: rotor flux magnitude vs time figure 11 shows the speed profile of the induction motor and it can be seen that the motor was set to accelerate and reach a steady state speed of 250 rad/s. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 10 20 30 40 50 60 70 80 90 time (s) ef fic ie nc y (% ) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 time (s) ro to r f lu x (w b) conventional rotor flux control scheme proposed scheme proposed scheme conventional rotor flux control scheme http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 446 figure 11: speed vs time figure 12 shows the torque produced in the motor during the simulation time. the steady state torque can be seen to equal 3nm. figure 12: torque produced vs time 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 50 100 150 200 250 300 time (s) s pe ed (r ad /s ) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 1 2 3 4 5 6 time (s) to rq ue (n m ) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 447 table 3: comparison of result between conventional, proposed rotor flux control scheme and the conventional and optimized dtc control schemes variable conventional rotor flux control scheme proposed method conventional dtc (optimized dtc) total power loss (w) 200 108.04 231.1961 166.2806 efficiency (%) 78.9 87.41 77.1 82.4 flux (wb) 1 0.6357 1 0.7539 table 3 shows a comparison of results between conventional, proposed rotor flux-oriented control scheme and the conventional and optimized dtc control schemes for the same motor parameters, reference speed and load torque. it can be observed that the proposed method gives a superior motor performance. the proposed rotor flux optimization scheme gives 8.51% improvement in efficiency compared to the conventional rotor flux control scheme at a speed of 250rad/s, for a load torque of 3nm. the proposed scheme also gives a 5.01% improvement in efficiency compare to the optimized dtc control scheme proposed in aygun & aktas (2018). the rotor flux-oriented control scheme enables the variation of motor speed. to this end, the motor speed was ramped down from 250 rad/s to 150 rad/s and allowed to stay at that speed between 4 and 5s of simulation time. figures 13-15 show the performances of the motor under the proposed scheme at variable speeds. figure 13: variable speed profile of the induction motor the total power loss is plotted in figure 14 and it can be seen to reduce from 200w to 108.04w as in the previous result but it further reduces to 83.645w because of the drop-in speed. the total power loss therefore reduces by 22.6% and this implies that there is an opportunity to save power when the motor is driven at a lower speed. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 50 100 150 200 250 300 time (s) sp ee d (ra d/ s) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 448 figure 14: total electric power loss under under variable speed. the efficiency of the motor is plotted in figure 15. it can be seen to decrease to a value of 84.8% after the motor speed is dropped to 150 rad/s because the power output drops with speed. a table of comparison between these results and those obtained in aygun & aktas (2018) is provided in table 4. figure 15: efficiency of induction motor under variable speed table 4: comparison of results of the proposed rotor flux-oriented control scheme with those of the optimized dtc at variable speed scheme total power loss (w) efficiency (%) proposed scheme at 250 rad/s 108.04 87.41 proposed scheme at 150 rad/s 83.645 84.8 optimized dtc at 250 rad/s 166.28 82.4 optimized dtc at 150 rad/s 101 79.1 table 4 shows the superior performance of the proposed method at variable speed when compared with the performance of the optimized dtc method under the same operating conditions. at a lower speed of 150 rad/s, power loss reduces by 17.2% while efficiency is higher by 5.7% for a load torque of 3nm under the proposed scheme as compared to the optimized dtc scheme developed in aygun & aktas (2018). figures 16-20 show the effectiveness of the proposed optimization scheme at varying loads. the load torque on the motor is reduced from 3nm to 2nm as shown in figure 16. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 50 100 150 200 250 300 time (s) to ta l p ow er l os s (w ) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 10 20 30 40 50 60 70 80 90 time (s) ef fic ie nc y (% ) conventional rotor flux control scheme proposed scheme conventional rotor flux control scheme proposed scheme file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 449 figure 16: torque produced in the motor with load torque varying from 3nm to 2nm in figure 17, the total power loss is observed to decrease to 72.03 w after the initiation of the loss minimization algorithm because the flux in the motor is optimized for each load torque. the optimal flux for the 2nm load is 0.5188 wb as seen in figure 18. the total loss reduces after the reduction in load from 3nm to 2nm because of the reduced output power. figure 17: total power loss with load torques varying from 3nm to 2nm figure 18: optimal flux of induction motor with load torque varying from 3nm to 2nm although the motor operates at a lower load torque, the operating efficiency is observed to be the same as that for the 3nm load torque. the value is still 87.41% as seen from figure 19. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 50 100 150 200 250 300 time (s) to ta l p ow er l os s ( w ) conventional rotor flux control scheme proposed scheme conventional rotor flux control scheme proposed scheme http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 450 figure 19: efficiency of the motor with load torque varying from 3nm to 2nm this implies that the efficiency is maximized for all loads under the scheme. these results follow the same trend as the results provided in aygun and aktas (2018). the advantage of the scheme proposed in this paper is that the point of maximum efficiency is higher by 5.01%. table 5 gives a comparison between the results obtained in this work and those obtained in aygun and aktas (2018) when the load torque varied from 3nm to 2nm. table 5: comparison of optimized dtc and proposed method at variable load. scheme total power loss (w) efficiency (%) proposed method at 3nm 108.04 87.41 proposed method at 2nm 72.03 87.41 optimized dtc at 3nm 166.28 82.4 optimized dtc at 2nm 110.3 82.4 the results suggest that the point of maximum efficiency is independent of the load torque but the optimum flux at which it occurs depends on the load torque. the voltages supplied to the stator windings of the three-phase induction motor are shown in figure 20. figure 20: supply voltages with load torque varying from 3nm to 2nm it can be seen that the magnitude of the stator voltages reduced with load on the machine. this is an energy saving ability of the proposed rotor flux optimization control strategy. the reduction in voltage is a direct result of the reduction in flux to its optimal levels for each load. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 10 20 30 40 50 60 70 80 90 time (s) ef fic ien cy (% ) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -400 -300 -200 -100 0 100 200 300 time (s) p h as e v o lta g es (v ) conventional rotor flux control scheme proposed scheme file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com olarinoye et al: development and simulation of a rotor fluxoriented control scheme for efficiency improvement in a three phase induction motor. azojete, 20(2):435-452. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 451 the magnitude of the stator voltages rises with speed during the time of acceleration of the induction motor. it reaches a value of 311v at steady state while the load torque of 3nm is applied. the value reduces to 180v after the optimizing control algorithm is activated at 2.5s. the value further reduces to 150v after the load torque changes from 3nm to 2nm. 4. conclusion a rotor flux optimization control model for a three-phase induction motor was analysed and simulated. a comparison between the conventional and proposed rotor flux-oriented control drive shows that, for a reference speed of 250rad/s and a load torque of 3nm, the rotor flux reduced from a rated value of 1wb to an optimal value of 0.6357wb which invariably led to a significant reduction of the total power loss, in the motor, from 200w to 108.04w and a consequential increase in efficiency from 78.9% to 87.41%. the performance of the scheme at varying load also shows a change in optimum flux from 0.6357wb to 0.5188wb after the load torque was reduced from 3nm to 2nm. although the motor operated at a lower load torque, the flux optimization algorithm implemented in matlab\simulink, for the proposed scheme, maintained a maximum efficiency of 87.41%. it was observed that while the point of maximum efficiency is independent of the load torque, the optimum flux at which it occurs depends on the load torque. with the proposed drive scheme operating at variable speed mode in which motor speed was ramped down from 250rad/s to 150rad/s at a load torque of 3nm, power loss was observed to further reduce significantly by 22.6%. these results suggest that the proposed rotor flux optimization scheme is superior to the optimized dtc scheme proposed in aygun & aktas (2018). the proposed scheme also presents an opportunity to save power and therefore energy as the command voltages supplied to the induction motor was observed to decrease with decreasing load applied to the motor. references aygun, h. and aktas, m. 2018. a novel dtc method with efficiency improvement of im for ev applications. engineering, technology & applied science research, 8(5): 3456-3462. chelliah, tr., yadav, jg., srivastava, sp. and agarwal, p. 2009. optimal energy control of induction motor by hybridization of loss model controller based on particle swarm optimization and search controller. world congress on nature & biologically inspired computing, coimbatore, india, pp. 1178-1183, doi: 10.1109/nabic.2009.5393784. engel, e., kovalev, iv. and karandeev, d. 2015. energy-saving iop conference series: materials science and engineering, 94: 10. 1088/1757-899x/94/1/012008. eseosa, o. and christian, a. 2018. energy efficiency optimization of three phase induction motor drives for industrial applications. international journal of engineering and applied sciences, 5(8): 42-49. faduyile, oe. 2009. effect of harmonics on the efficiency of a three-phase energy efficient and standard motors. msc. thesis. university of tennessee at chattanooga. usa. kalhoodashti, he. and shahbazian, m. 2011. hybrid speed control of induction motor using pi and fuzzy controller. international journal of computer applications, 30(11): 44-50. khan, h., hussain, s. and bazaz, ma. 2015. direct torque control of induction motor drive with flux optimization. in: international conference on advances in computing, communications and informatics (icacci), ieee, 618-623. laroui, m., nour, b., moungla, h., cherif, ma., afifi, h. and guizani, m. 2021. edge and fog computing for iot: a survey on current research activities & future directions. computer communications, 180(1): 210-231. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):435-452. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: baolarinoye@abu.edu.ng 452 lee, pm., lee, dd., nguyen, tv. and nguyen, ph. 2013. real-time loss minimization control in induction machines based on dsp tms320lf2812. science and technology development journal, 16(4): 5-18. nam, sw. and uddin, mn. 2006. model-based loss minimization control of an induction motor drive. in: ieee international symposium on industrial electronics, ieee, 2367-2372. olarinoye, ga., akorede, mf. and akinropo, cd. 2022. design and simulation of a threephase induction motor speed control system. fuoye journal of engineering and technology, 7(1): 39 – 46. rashtchi, v. and bizhani, h. 2015. using of particle swarm optimization for loss minimization of vector-controlled induction motors. universal journal of electrical and electronic engineering, 3(3): 71-80. sruthi, mp., nagamani, c. and ilango, gs. 2017. an improved algorithm for direct computation of optimal voltage and frequency for induction motors. engineering science and technology, an international journal, 20(5): 1439-1449. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):9-24 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 9 a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework v. o. nkeleme*1, e. u. udo2, c.k. okoro3 l. i. oborkhale4, k.o. odo5 1department of electrical/electronic engineering, federal polytechnic mubi adamawa state 2,3,4,5department of electrical/electronic engineering, michael okpara university of agriculture umudike, abia state *corresponding author's email address: victornkeleme@gmail.com article information submitted 18 dec., 2023 revised 16 february, 2024 accepted 20 february, 2024 keywords: carrier aggregation hetnet rssf-hda mif-hda conv-hda abstract mobile user equipment can benefit from increased bandwidth and radio coverage of various access technologies through carrier aggregation and integration of heterogeneous networks. however, because of the mobility of user equipment, these technologies have increased the frequency of handoff scenarios, which results in low throughput and a high outage probability. in order to enable users to move between cells without losing connections, handover is an essential part of mobility management. however, no lone access mechanism can provide seamless and delay-free seamless interaction. as a result, the development of a suitable handover decision algorithm is necessary to ensure excellent service continuity and dependable user equipment access to the network at any location and at any moment. to confirm if various handover choice algorithms are effective in preventing communication failures and enhancing system performance. this research produced a mathematical model for the real-time spectrum selection framework and handover decision algorithm (rssf-hda). additionally, mathematical models were extracted for comparison between the multiinfluenced handover decision algorithm (mif-hda) and the conventional handover decision algorithm (conv-hda). a statistical comparative study was carried out using data from mtn drive-test readings at the low-cost housing estate located in abesan, ipaja, lagos. according to statistical analysis results, the real-time spectrum selection framework and handover decision algorithm enhance system performance in terms of cell edge spectral efficiency, and user throughput when compared with multiinfluenced handover algorithm and mtn field readings. for cell edge spectral efficiency at an average speed of 80km/s, rssf-hda gave a value of 1.52 bits/hertz compared to mif-hda and mtn field readings with values of 1.37bits/hertz and 1.33bits/hertz respectively. for user throughput, inferred that there is no significant difference in readings of system throughput from the mtn field readings, mif-hda, and simulated rssf-hda which were 31%, 33%, and 34% respectively. 1.0 introduction recent years have seen a rise in research and development aimed at enhancing coverage and capacity to deliver high data rates to user equipment (ues) at an affordable rate. as a result, cellular networks have seen significant evolutionary improvement as well as new inventions and research initiatives (hachemi et al., 2022, sudhamani et al., 2023). the physical layer advancements of contemporary networks are moving in the direction of network efficiency. http://www.azojete.com.ng/ mailto:victornkeleme@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 10 therefore, previous study suggest that systems based on the architecture of dense heterogeneous networks (het-nets) and increased utilization of radio spectrum through carrier aggregation techniques be used as solutions (wahidin et al., 2022, hashemi, and farrokhi, 2020). thus, these two technological advances serve as the cornerstone for network densification, with the inclusion of ca as a crucial functionality in the 3rd generation partnership project (3gpp) release 10 marking a major step towards the development of long term evolution advanced (lte-a)(satapathy and mahapatro, 2022). it is anticipated that the addition of ca technology in lte-a's release 10 (rel.10) and later releases will enable high data rates and increase system capacity.(goyal and kumar, 2020). this implies that a muchanticipated aspect of lte-a is the expansion of transmission bandwidth. lte-advanced (long term evolution) has carrier aggregation (ca) as one of its primary background characteristics. a maximum bandwidth of 100mhz would be available to customers with ca. there are three possible system bandwidth configurations: contiguous, non-contiguous, and inter-band noncontiguous (lin et al., 2014). for long time evolution (lte) carriers, the bandwidth of these component carriers (ccs) can vary greatly, from 1.4mhz to 20mhz. additionally, propagation properties vary throughout different ccs. for instance, ccs in the 800mhz spectrum have different propagation characteristics than component carriers in the 2.4ghz band (ohmann et al., 2014). however, a new handover situation brought about by the introduction of ca technology allows ccs operating in the same sector and enodeb to undertake handovers, potentially redefining primary component carriers (pccs). throughput degradation increases as a result of the higher handover chance. as long as the serving pcc provides the ues with an adequate amount of rss, the handover situation here translates into a successful handover decision (hod). in essence, handover is evaluated when a voice call is in progress and heading toward the current enodeb (i.e., from a source to a target enodeb). this instance involves a ue reporting signal measurements to the serving enodeb from the neighboring enodeb. the measurement report from the ue at the source enodeb is used to make the handover decision. on the other hand, in a ca-based system, the source and the target enodebs may be ccs of the same or separate enodebs because of numerous ccs. making decisions with such a signal measurement report (mr) is not completed quickly. consequently, it increases the likelihood of throughput deterioration, user outage probability, and handover failure, particularly for high-velocity user equipment (alhammadi, et al., 2023, bastidas-puga et al., 2019). the primary goal of handover is to keep the connection active as the subcarrier passes through the source enodeb's coverage region and approaches the target enodeb. providing services that meet consumer needs is one of the main objectives of communication in cellular networks (khan and han, 2015). however, an effective handover decision algorithm improves continuous connectivity, but the network's performance is still insufficiently enhanced. as such, investigating the hod algorithm is innovative as it may effectively manage the main responsibilities in cellular networks by raising the quality of services and concurrently managing the network's resources, in addition to offering encouragement for conducting this kind of research. conventional handover algorithms are applicable in heterogeneous networks and exhibit simple moderate handover with an inaccurate high percentage of unwanted handovers. multifile:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 11 influenced factor handover algorithms are applied in coordinated carrier aggregation, the decision-making process integrates rss, bandwidth, speed, handover situation, and sinr to accomplish seamless mobility and apply to indoor scenarios. finally, the rssf-hda utilizes coordinated carrier aggregation. system performance is improved by using spectrum sensing, which lowers the likelihood of outages, call dropouts, and handover ping-pong. only two (2) carrier component was considered the statement of problem thus implies that there are increased in the frequency of handoff which led to low throughput and high outage probability. in order to make sensitive decisions about handover when implementing heterogeneous networks (hetnet) and ca in lte-a systems, the objective of this study is to utilize a user mobility broadband spectrum aggregation in lteadvance heterogeneous to mitigate these quality-of-service indices 2.0 materials and method the serving enodeb made handover decision based on the measurement report (mr) received from the served ue. a list of the signal levels of nearby cells is contained in mr, and depending on the hod algorithm in use, it can also provide additional information. an algorithm for a handover decision can be implemented in multiple ways. it can generally be divided into the following categories: i. conventional handover decision algorithms (conv hda) ii. multi-influenced handover decision algorithms (mif-hda) iii. real-time spectrum selection framework and handover decision algorithm (rssfhda) the conventional handover choice algorithm, known as the rss-based strategy, used rss as the primary criterion to initiate handover (abdullah & zukarnain, 2017). here, the handover is enabled as a result of comparing the signal intensities of nearby enodebs. the rss-based approach was improved by using the rss threshold (hysteresis) (kunarak & suleesathira, 2020) and by combining it with the user's distance (mahardhika et al., 2015), sinr (khattab et al, 2023), and iinr (choi et al., 2021). a threshold is established and implemented in relation to signal strength in order to reduce the ping-pong effects. if the new enodeb rss is more than the threshold and the current enodeb rss is less than the threshold, the handover is initiated. however, the rss-based approach for assessing the attributes and quality of services is straightforward in theory and straightforward to apply. however, route loss in the wireless medium caused the rss signal to vary, which lead to ping pong, throughput degradation, and needless handovers. additionally, threshold rss had disadvantages such as high call drop and handover delay. however, recent research has shown that incorporating ca and hetnets technologies maked handover decisions more difficult. the rss-based criterion is insufficient for a decision-making process in hetnet using the ca approach. concurrently, in a coordinated carrier aggregation deployment scenario, mif decision-making criteria was examined (capez et al, 2022). several factors that affected the decision-making process were employed by mif. even if the simulation's result indicated that ping pong had decreased, the outcome is not ideal when hetnet is taken into account in ca. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 12 the handoff delay and service disruption time are decreased by the multi-criteria algorithm. consequently, during handover, this reduced packet loss and increased throughput (alhabo & zhang, 2020). as a result, in future mif-hda research, the selected criteria guaranteed that the level of decision-making accuracy is maintained. rss, mobility, application, and bandwidth are some of the primary factors that are either useror network-related. although every previous work in hetnets and ca was built on a separate set of criteria, it is still uncertain which set of characteristics results in the best handover procedure. therefore, a new method known as the multi-criteria handover decision algorithm was presented for effective handover decision-making when ca and hetnet are taken into consideration in an lte-a system to determine the appropriate parameters for a successful handover process(abdulazeez-ahmed et al., 2020a). a novel handover decision algorithm called real-time spectrum selection framework and handover decision algorithm (rssf-hda) was proposed, and its proposed handover performance for an lte-a system was compared with two other hoda (mif-hda and convhda) (nkeleme et al., 2023). according to the results of the simulation analysis, rssf-hda was more effective than the current hda deployment in enabling wider bandwidth and greater se. the metrics of rssf-hda spectral efficiency (se) are higher than those of the other hda considered in the research, rising from 1.35 bps/hz/cell at mobile speeds of 20 kmph to 1.87 bps/hz/cell at 120 kmph. 2.1 simulation of mif-hda and rssf-hda carrier aggregation based handover technique in heterogenous network. abdulazeez-ahmed et al., (2020) provided an effective multi-influence handover decision method that took into account the mobile parameter (load and ue distance) as well as the network parameter (radio resources and network architecture) while making decisions. to construct lte-a heterogeneous network topologies, the algorithm was implemented as a multicell system using a system-level simulator from the matlab toolbox. many built-in libraries and capabilities in matlab enabled the conversion of c and c++ code into matlab programs. additionally, it raised the likelihood of new technology, allowed the required data manipulation, and fortifies the security of emerging technologies (nkeleme et al., 2023). pcc is often used for data transfer between the ue and the enodeb as well as information sharing for control signals. pcc was utilized for the random-access mechanism and scc allocation in addition it served as a conduit for data transfer. numerous handover decision algorithms have been developed in response to the ca concept's handover decision issues in lte-a and next-generation systems, but none of them have produced the desired results, especially for hetnet's carrier aggregation deployment scenario (cads). consequently, abdulazeez-ahmed et al., ( 2020) developed an effective multi-influenced handover decision algorithm that used mobile parameters like load and ue distance as well as network parameters like radio resources and network architecture as input for decision-making. the third generation partnership project (3gpp)-standardized cell range expansion (cre) power regulation mechanism ( wu, et al,. 2020) was used in this study as a virtual bias applied to the real ue received power (abdulazeez-ahmed et al., 2020). the handover choices were conducted adaptively based on the following criteria. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 13 in an lte-advanced uplink and downlink system level simulator, nkeleme et al., (2023) presented a workable ca strategy that made use of two ccs in the same bands (het-nets cads) utilizing the multi-taper ofdma sensing of reference signal received power estimator (mto-rsrpe) technique. a global rendition algorithm was created to achieve the real-time spectrum selection framework's goal. this algorithm served as the foundation for the implementation of the new rssf-hda program flowchart, the resource allocation, parameters, and threshold values are given in nkeleme et al., (2023). 2.2 system model and simulation configuration for mif-hda and rssf-hda the standard (nkeleme et al., 2023) was utilized in the creation of the radio frequency system model scenario. 30 mobile user devices (ues) were uniformly distributed at random to serving and target cell sites during each transmission time interval (tti). the ues' directional motions was determined at random with a set speed during the design process, which comprises a variety of mobile speed scenarios (5, 25, 40, 70, 100, and 130 km/h). all users' mobility movements were taken into consideration within the first 32 cells, which are close to the center cell. an illustration of the deployed scenario's clustered enodebs is shown in figure 1. during the simulation, each user will suffer interference from six separate enodebs, which are regarded as the stations that generate these signals. the frequency reuse factor (frf) was set to one. the performance findings for the rssf-hda, mif-hda, and the starting point conventional handover decision algorithm (conv-hda) were displayed. results for cell edge spectral efficiency, average successful handover, and user throughput was analyzed based on the utilization of hard handover at different mobile speeds. as a result, figure 1 displays the hetnets cads architecture. carrier aggregation enables the deployment of more ues in macro and micro cells, as the topological architecture illustrates. six (6) neighbors surrounded each of the sixty-one (61) enodeb that were taken into consideration. figure 1: an illustration of the deployed scenario's clustered enodebs (nkeleme et al., 2023) subsequently, as seen in figure 1, seven (7) enodebs create a single cluster. furthermore, every enodeb was segmented into three sectors and encompasses an approximate radial distance (r) of 500 meters. ultimately, a radius of about 5r was established for the mobility area of the mobile stations, also known as user equipment (ues) (shown as a blue circle). http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 14 2.3 curve fitting process and decomposing of simulations in order to extract significant patterns and relationships from datasets, curve fitting is a key procedure in data analysis. this study highlights the capabilities and versatility of the rssf hda system by breaking down the stages involved in the curve fitting process. the generated data is saved in an a.mat file, where the independent and dependent variables (observations) were represented by corresponding variables. to ensure a smooth integration of the data into the curve fitting tool, matlab's `read` function was utilized to import the data into an appropriate format. the curve fitting tool was accessed via the matlab apps tab or programmatically via the 'cftool' command. its dynamic and user-friendly interface made effective curve fitting possible. the tool allowed to select multiple curve fitting models, alter parameters, and view the fitting process in real-time. 2.4 mathematical models of performance indicators 2.4.1 spectral efficiency the average bits per second per hz (bps/hz) that may be transferred over a radio link channel and accurately received at the receiver side is referred to as spectral efficiency. mathematically, the user's spectral efficiency are expressed by adding up the entire throughput that is successfully received by the user at a given moment and dividing it by the whole user's channel bandwidth. the equation used in this thesis is expressed as follows: 𝑆𝐸 = 𝑁𝑠𝑦𝑚𝑏𝑜𝑙𝑝𝑒𝑟𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟∗log(𝐴𝑀𝐶)∗𝐶𝑅 𝑠𝑢𝑏𝑓𝑟𝑎𝑚𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛∗𝐵𝑊 (1) se is the cell edge spectral efficiency in bps/hz 𝑁𝑠𝑦𝑚𝑏𝑜𝑙𝑝𝑒𝑟𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟 is the number of symbols per subcarrier in bps amc is adaptive modulation and coding cr is cognitive radio value bw is bandwidth in hertz the decomposed models for the spectral efficiency variance with reference to the reviewed literature are expressed as follows: conv-hda 𝑆𝐸𝑐𝑑𝑓 = 125.7(𝑆𝐸)2−266𝑆𝐸+124.3 (𝑆𝐸)3−127.8(𝑆𝐸)2+ 179.8𝑆𝐸+31.38 (2) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency se is the cell edge spectral efficiency in bps/hz 𝑆𝐸𝑐𝑑𝑓 = 403.3(𝑆𝐸𝐴𝑣)2−1140𝑆𝐸𝐴𝑣+806.1 (𝑆𝐸𝐴𝑣)3+1253(𝑆𝐸𝐴𝑣)2−4066 𝑆𝐸𝐴𝑣+3319 (3) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency in bps/hz 𝑆𝐸𝐴𝑣 = −0.00004048(𝑆)2 + 0.009475𝑆 + 1.237 (4) where 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency. s is mobile speed in km/hour mif-hda 𝑆𝐸𝑐𝑑𝑓 = 42.45(𝑆𝐸)2−37.88𝑆𝐸−25.29 (𝑆𝐸)3−30.39(𝑆𝐸)2−49.39𝑆𝐸+154.3 (5) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency se is the cell edge spectral efficiency in bps/hz file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 15 𝑆𝐸𝑐𝑑𝑓 = 0.04822(𝑆𝐸𝐴𝑣)2−0.1279𝑆𝐸𝐴𝑣+0.08481 (𝑆𝐸𝐴𝑣)3−4.738(𝑆𝐸𝐴𝑣)2+ 7.448𝑆𝐸𝐴𝑣−3.876 (6) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency in bps/hz 𝑆𝐸𝐴𝑣 = −0.00004424(𝑆)2 + 0.01022𝑆 + 1.224 (7) where 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency. s is mobile speed in km/hour rssf-hda 𝑆𝐸𝑐𝑑𝑓 = 283.8(𝑆𝐸)2−573.1𝑆𝐸+234.6 𝑥3−312.1(𝑆𝐸)2+ 576.8𝑆𝐸−73.28 (8) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency se is the cell edge spectral efficiency in bps/hz 𝑆𝐸𝑐𝑑𝑓 = 143.6(𝑆𝐸𝐴𝑣)2−356.9𝑆𝐸𝐴𝑣+219.8 (𝑆𝐸𝐴𝑣)3+2219(𝑆𝐸𝐴𝑣)2−8020𝑆𝐸𝐴𝑣+7286 (9) where 𝑆𝐸𝑐𝑑𝑓 is the cumulative distribution function cell edge spectral efficiency 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency in bps/hz 𝑆𝐸𝐴𝑣 = −0.00004322(𝑆)2 + 0.009998𝑆 + 1.335 (10) where 𝑆𝐸𝐴𝑣 is the average cell edge spectral efficiency. s is mobile speed in km/hour 2.4.2 throughput the third generation partnership project (3gpp) group has established five categories of service performance metrics, comprising network availability, accessibility, retainability, mobility, and integrity. in all radio access technologies, user throughput is a crucial measure for assessing the integrity of data services (buenestado et al., 2014). the throughput with respect to the bite rate adopted in this thesis is expressed mathematically as follows: 𝐵𝑖𝑡 𝑅𝑎𝑡𝑒 = 𝑁𝑅𝐵∗𝑁𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟𝑝𝑒𝑟𝑅𝐵∗𝑁𝑠𝑙𝑜𝑡𝑝𝑒𝑟𝑠𝑢𝑏𝑓𝑟𝑎𝑚𝑒∗𝑁𝑠𝑦𝑚𝑏𝑜𝑙𝑝𝑒𝑟𝑠𝑢𝑏𝑐𝑎𝑟𝑟𝑖𝑒𝑟∗log(𝐴𝑀𝐶)∗𝐶𝑅 𝑠𝑢𝑏𝑓𝑟𝑎𝑚𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (11) where: 𝐴𝑀𝐶=selected adaptive modulation scheme, 𝐶𝑅 = selected code rate the decomposed model for conv-hda (khan, and han, 2015) and the multi-influence hda ( abdullah, and zukarnain, 2017) with respect to the user throughput is expressed as follows: conv-hda 𝑇𝐻𝑐𝑑𝑓 = 8487𝑇𝐻2−4046𝑇𝐻+484 𝑇𝐻3+12900𝑇𝐻2−7480 𝑇𝐻+1159 (12) http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 16 mif-hda 𝑇𝐻𝑐𝑑𝑓 = 9811𝑇𝐻2−4623𝑇𝐻+545.4 𝑇𝐻3+12090𝑇𝐻2−6694𝑇𝐻+1018 (13) the result obtained from the simulation is expressed as follows: rssf-hda 𝑇𝐻𝑐𝑑𝑓 = 6748𝑇𝐻2−3183𝑇𝐻+376.6 𝑇𝐻3+9803𝑇𝐻2−5831 𝑇𝐻+953.7 (14) where 𝑇𝐻𝑐𝑑𝑓 is the cumulative distribution function of user throughput th is the user throughput in mbps 2.5 field measurements for lte-a in order to offer service to user units, the lte-a network used advanced base stations (enodebs and enbs) to cover the whole cell. it also utilized the same transmit power level, modulation mechanism, and antenna layouts ( zhang et al., 2020). wireless channel parameters in lte-a systems control the downlink quality between the enodeb and the user equipment (ue). the channel quality indicator (cqi) used in the lte-a network expresses the wireless channel's condition. typically, the sinr value based on reference signal received power (rsrp) and reference signal received quality (rsrq) represented the cqi established by the user unit (rsrq). the modulation technique, transfer block size (tbs), and coding rate of the data transmission are chosen in accordance with the user unit's cqi value that is transmitted to the enodeb, because of this, throughput and cqi value were directly related. to determine the impact of sinr, rsrp, and rsrq channel characteristics on the throughput value in the lteadvance network, this study employed tems software to collect field data from lsdpc lowcost housing estate, abesan, ipaja lagos locations. the drive test was conducted for 15 months (september 2022 to nov 2023) as shown in table 1. 2.6 method of field data computation using regression analysis the data obtained from the drive test was analyzed using various statistical tools such as regression analysis, which is a mathematical equation, that shows the connection between a few independent factors and a dependent variable. the dependent variable y and the independent variable x in the basic linear regression model are specified as follows. 𝑌𝑖 = 𝛽𝑜 + 𝛽1𝑋𝑖 +∈𝑖 𝑖 = 1,2, … , 𝑛 (15) where: 𝛽 is the regression coefficient n is the size of the data, ∈𝑖 represents the error term two or more independent variables are used to express the dependent variable (k). 𝑌𝑖 = 𝛽𝑜 + 𝛽1𝑋𝑖1 + 𝛽12𝑋𝑖2 + ⋯ , +𝛽𝑘𝑋𝑖𝑘 + ∈𝑖 𝑖 = 1,2, … , 𝑛 (16) according to information obtained from mtn lagos, the algorithms used are similar to multiinfluenced handover decision algorithms. this provides a strong foundation for the comparison, as seen in table 3. 3.0 results and discussion a drive test was conducted in abesan estate ipaja lagos from the month of september 2022 to november 2023, a summary of the readings obtained are shown in table 1. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 17 table 1: monthly average field drive-test values in abesan estate ipaja lagos state (sept 2022 to nov 2023) s/n date total pdcp dl throughput serving cell rs sinr (db) serving cell rsrp (dbm) serving cell rsrq (db) 1 sept 2022 60528.76 11.97 -64.00 -16.79 2 oct 2022 73187.50 20.83 -87.45 -14.12 3 nov 2022 36445.00 17.16 -84.42 -12.46 4 dec 2022 19778.75 14.24 -93.97 -13.78 5 jan 2023 33452.65 10.13 -91.01 -15.73 6 feb 2023 31344.65 11.10 -78.09 -16.5 7 march 2023 39708.55 11.80 -70.00 -14.89 8 april 2023 30896.15 19.79 -75.19 -13.19 9 may 2023 36348.25 17.22 -78.80 -17.89 10 june 2023 50672.00 13.89 -78.50 -15.60 11 july 2023 33364.25 15.39 -78.09 -15.80 12 aug 2023 22520.20 21.29 -88.90 -15.60 13 sep 2023 32464.15 21.89 -66.00 -13.65 14 oct 2023 36324.35 14.30 -77.80 -12.93 15 nov 2023 33160.15 20.70 -90.80 -13.65 the cumulative density function cell edge spectral efficiency was plotted against the cell edge spectral efficiency for the three hda as shown in figure 2. this is to determine its degree of positive variation. figure 2 shows that rssf-hda has the best cell edge spectral efficiency, meaning greater data rates near the cell's edge. mif-hda follows closely behind, providing competitive performance, but conv-hda lags, indicating data rate limits at the cell edge. at 1.4bps/hz, values of 0.12, 0.32, and -0.08 was calculated for conv-hda, mif-hda, and rssfhda, respectively. at 1.5bps/hz, the values for conv-hda, mif-hda, and rssf-hda was 0.50, 0.90, and 0.16, respectively. the high performance of rssf-hda at the cell edge as shown in figure 2 may be helpful in circumstances requiring high-quality connections on the edges of network coverage figure 2: cdf cell edge spectral efficiency over cell edge spectral efficiency http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 18 the simulated data plot of the cumulative density function of spectral efficiency over average spectral efficiency is shown in figure 3. this further shows that the rssf-hda has a consistent spectrum efficiency and performance. in comparison, mif-hda is somewhat sensitive to network conditions, whereas rssf-hda marginally exceeds mif-hda in terms of responding to changing conditions. this shows that rssf-hda may provide better performance in dynamic situations. figure 3 further illustrates the comparable values of 1.5bps/hz cell edge spectral efficiency, to produce values of 0.85, 0.50 and 0.15 for conv-hda, mif-hda, and rssf-had, respectively figure 3: cdf spectral efficiency over average spectral efficiency this further demonstrates that the rssf-hda has a consistent spectrum efficiency and performance. in comparison, mif-hda is somewhat sensitive to network conditions, whereas rssf-hda marginally exceeds mif-hda in terms of responding to changing conditions, showing that rssf-hda provides better performance in dynamic situations. the plot of the average ue spectral efficiency over all mobile speeds for each handover decision algorithm is presented in figure 4 in relation to the obtained simulation data. figure 4 compares the average se of the ue at various mobile speeds using the deployed rssf-hda. generally, it appears from the results (figure 4) that the average se rises as ue speed rises. the outcomes shows that the proposed rssf-hda surpasses its counterparts for the speeds under consideration. rssf-hda significantly outperforms the other hodas in improving the average se. conv-hda, mif-hda, and rssf-hda algorithms produced values of 1.72, 1.75, and 1.86, respectively, at 80 km/hr. figure 4: ue’s average spectral efficiency over all the mobile speeds file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 19 it further indicates that the rssf-hda has the best average spectral efficiency, demonstrating efficient data transmission resource utilization. mif-hda follows closely but falls just short of rssf-hda's performance. conv-hda performs similarly to mif-hda, meaning that it is a solid overall performer but not the greatest. figure 5(a) displays the model plots of user cdf throughput over user throughput in relation to the acquired simulation data. from figure 5(a) it is shown that at 0.34mbps, the conv-hda, mif-hda, and rssf-hda algorithms generated corresponding values of 0.83, 0.77, and 0.70, respectively. rssf-hda achieves the highest user throughput, showcasing efficient data transfer capabilities. mif-hda closely follows, offering competitive performance. conv-hda aligns with mif-hda, indicating reliable data transfer efficiency. the decision between these models may depend on specific network requirements and priorities. rssf-hda excels in data transfer efficiency, but mif-hda and conv-hda remain strong contenders for a balance of performance and adaptability. the user throughput of rssf-hda and the other two handover algorithms is shown in figure 5 for all ue speeds. in comparison to conv-hda and mif-hda, rssf-hda outperforms both in terms of throughput for the user. in comparison to conv-hda and mif-hda, rssf-hda generally achieves a throughput of 34% while other algorithms have 33% as shown in figure 5 (b). figure 5: throughput; (a) user throughput (b) percentage throughput (a) (b) http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 20 the comparative assessment of mif-hda, and rssf-hda algorithms from mtn lte-a network drive test readings is illustrated in table 2. the spectral efficiency and system throughput are the key performance indices consider. table 2: comparative assessment of mif-hda, and rssf-hda algorithms from mtn ltea network drive test readings s/n kpi for seamless transmission graduation (point of measurements reading from fieldwork mifhda reading simulation rssf_hda 1 cell edge spectral efficiency taken @40km/h, 80km/hr, and 120km/hr presented as a, b, and c respectively) a) 1.23 bits/hertz 1.47 1.62 b) 1.35 1.56 1.68 c) 1.42 1.76 1.88 average cell edge spectral efficiency (bps/hz) 1.33 1.37 1.52 2 system throughput (taken @ 0.2mbps, 0.25mbps, and 0.3mbps presented as a, b, and c respectively) a) 0.32 0.35 0.70 b) 0.65 0.88 0.75 c) 0.85 0.96 0.92 average percentage throughput 31% 33% 34% note i. all readings taken on the assumption of a zeros take off (time series reading) ii. the average readings are based on several readings from the simulation with the exception of the field measurement which is the average of the three points of measurement the graphical anova expression for table 2 when considering cell edge spectral efficiency at 40km/hr 80km/hr. and 120km/hr is shown in figure 6 the anova test result (figure 6) submits that the readings from fieldwork, mif-hda, and rssf-hda vary substantially (f= 7.258, p=0.025<0.05) from each other. the mean±std result shows that the reading from simulated rssf-hda (1.73±0.136bits) is higher in comparison with the readings from mif-hda (1.60±0.148bits) and those from fieldwork (1.33±0.096bits). the homogeneity of variance test of the compared groups (levene (l-stat.) = 0.448, p=0.659>0.05) ascertained that the variances are homogeneous (i.e., equal); therefore, the data series is fit for the application of parametric statistical tools. in the case of figure 6, the variance in mean varies substantially from each other. the readings from simulations are higher than those from mif-hda and those from fieldwork. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 21 figure. 6: comparative result of readings from fieldwork, mif-hda, and reading from simulated rssf-hda of cell edge spectral efficiency taken @40km/h, 80km/hr, and 120km/hr respectively the result (figure. 6) shows that readings from fieldwork lie between 0.61±0.268; readings from mif-hda lie between 0.73±0.332, while readings from simulated rssf-hda lie between 0.79±0.115. the fisher’s estimate with an f-statistic value of 0.404 and associated probability value of 0.685>0.05 indicates that the variations were not significantly high. however, it was inferred that there is no significant difference in readings of system throughput from the fieldwork, mif-hda, and simulated rssf-hda. the anova test result was confirmed meaningful and accurate by levene’s test (levene’s stat. = 1.963, p=0.221>0.05); thereby, confirming the homogeneity of the variances in the data series which is one of the key assumptions of a data series for anova test. the graphical anova expression for table 2 when considering system throughput at 0.2mbps, 0.25mbps, and 0.3mbps is shown in figure 7 figure. 7: comparative result of readings from fieldwork, mif-had, and reading from simulated rssf-hda of system throughput taken 0.2mbs, 0.25mbs, and 0.3mbs respectively mean±std = 1.33±0.096 mean±std = 1.60±0.148 mean±std = 1.73±0.136 levene’s stat. = 0.448, p=0.659>0.05 f-stat. = 7.258, p=0.025<0.05 mean±std = 0.61±0.268 mean±std = 0.73±0.332 mean±std = 0.79±0.115 levene’s stat. = 1.963, p=0.221>0.05 f-stat. = 0.404, p=0.685>0.05 http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):9-24. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 22 the result (figure. 7) shows that readings from fieldwork lie between 0.61±0.268; readings from mif-hda lie between 0.73±0.332, while readings from simulated rssf-hda lie between 0.79±0.115. the fisher’s estimate with an f-statistic value of 0.404 and associated probability value of 0.685>0.05 indicates that the variations were not significantly high. however, it was inferred that there is no significant difference in readings of system throughput from the fieldwork, mif-hda, and simulated rssf-hda. the anova test result was confirmed meaningful and accurate by levene’s test (levene’s stat. = 1.963, p=0.221>0.05); thereby, confirming the homogeneity of the variances in the data series which is one of the key assumptions of a data series for anova test. 4.0 conclusion voice and multimedia services are in extremely high demand on cellular networks. due to its limited capacity, the current macro cellular network is unable to fully satisfy this demand. additionally, adding several macro-base stations to increase capacity and expand coverage is quite expensive. along with this, there are problems with urban space restrictions. to improve the coverage, capacity, and data rate in lte-a, numerous strategies have been proposed. the deployment of heterogeneous networks is one of the most economical techniques. lte-a hetnet significantly boosts wireless cellular networks' capacity and performance. with hetnets, you may employ a variety of cell sizes, including femtocells, macrocells, picocells, microcells, and relays, to enhance capacity and improve coverage. hetnet is the most effective, affordable, and scalable method for increasing the capacity of current and future wireless networks. the ues receive a solid network connection and an improved user experience as a result. however, if hetnet deployment is poorly managed, it frequently results in increased handover for ues. in this research, the rssf-hda, a novel handover decision algorithm, was proposed as a better option when compared with mif-hda and the field data obtained from the drive test. the research further presents a statical comparison of the field drive test readings, the mif-hda, and the rssf-hda reading to establish the existing relationship between the various cell edge spectral efficiency readings and to further establish the best algorithm under consideration for seamless handover. the outcome of this comparison suggests that rssf-hda has better quality of service (qos) parameters when compared with the mtn real-time drive-test values and the mif-hda algorithm. therefore, it is recommended that the rssf-hda should be adopted by mtn nigeria for better quality of service. acknowledgment the researchers are grateful to the tertiary education trust fund (tetfund) for their crucial assistance in supporting this research work. their kind financing has enabled us to pursue creative research projects that expand knowledge in our profession. the tetfund's dedication to investing in research and development supports not only individual researchers like our own, but also academic quality and growth across disciplines. we are grateful to tetfund for its commitment to fostering research activities in tertiary institutions, and also, we are delighted to have received their funding. their assistance has been critical in ensuring the effective completion of our research project, and we optimistic about the beneficial influence it will have on my academic aspirations and the wider scholarly community file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng nkeleme et al: a user mobility broadband spectrum aggregation applications in lte-advance heterogeneous wireless network systems using real-time spectrum selection framework. azojete, 20(1):9-24. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: victornkeleme@gmail.com 23 references abdulazeez-ahmed, m., nordin, nk., sali, ab. and hashim, f. 2020. multi-criteria handover decision for heterogeneous networks: carrier aggregation deployment scenario. international journal of computer networks and communications, 12(4): 41–54. https://doi.org/10.5121/ijcnc.2020.12403 abdullah, rm. and zukarnain, za. 2017. enhanced handover decision algorithm in heterogeneous wireless network. sensors17(7): 1626. https://doi.org/10.3390/s17071626 alhammadi, a., hassan, wh., el-saleh, aa., shayea, i., mohamad, h. and saad, wk. 2023. intelligent coordinated self-optimizing handover scheme for 4g/5g heterogeneous networks. ict express, 9(2): 276-281. bastidas-puga, er., andrade, ág., galaviz, g. and covarrubias, dh. 2019. handover based on a predictive approach of signal-to-interference-plus-noise ratio for heterogeneous cellular networks. iet communications, 13(6): 672–678. https://doi.org/10.1049/iet-com.2018.5126 buenestado, v., ruiz-aviles, jm., toril, m., luna-ramirez, s. and mendo, a. 2014. analysis of throughput performance statistics for benchmarking lte networks. ieee communications letters, 18(9): 1607–1610. https://doi.org/10.1109/lcomm.2014.2337876 capez, gm., henn, s., fraire, ja. and garello, r. 2022. sparse satellite constellation design for global and regional direct-to-satellite iot services. ieee transactions on aerospace and electronic systems, 58(5): 3786-3801. choi, hh., kim, h., na, jh. and lee, h. 2021. non-orthogonal multiple access-based handover for throughput enhancement. ieee transactions on vehicular technology, 70(11): 12278–12282. https://doi.org/10.1109/tvt.2021.3117785 hachemi, mh., mohammed, s., irid, h., benchehima, m., hadjila, m., mohammed, o., bir, b. and djir, e. 2022. pedestrian mobility management for heterogeneous networks. indonesian journal of electrical engineering and computer science, 28(3): 1530–1540. https://doi.org/10.11591/ijeecs.v28.i3.pp1530-1540 hashemi, sa. and farrokhi, h. 2020. mobility robustness optimization and load balancing in self-organized cellular networks: towards cognitive network management. journal of intelligent & fuzzy systems, 38(3): 3285-3300. khan, m. and han, k. 2015. a vertical handover management scheme based on decision modelling in heterogeneous wireless networks. iete technical review, 32(6): 402-412. khattab, o., murad k. and basil a.2023. designing a vertical handover algorithm for securityconstrained applications. journal of applied sciences, 13(4): 2166-2169. kunarak, s. and suleesathira, r. 2020. multi-criteria vertical handoff decision algorithm for overlaid heterogeneous mobile ip networks. journal of the franklin institute, 357(10): 6321– 6351. https://doi.org/10.1016/j.jfranklin.2020.03.025 lin, x., andrews, jg. and ghosh, a. 2014. spectrum sharing for device-to-device http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; 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(2014). achieving high availability in wireless networks by an optimal number of rayleigh-fading links. ieee workshops, gc wkshps 20(14): 1402–1407. https://doi.org/10.1109/glocomw.2014.7063630 satapathy, p. and mahapatro, j. 2022. an efficient multicriteria-based vertical handover decisionmaking algorithm for heterogeneous networks. transactions on emerging telecommunications technologies, 33(4): e4409. https://doi.org/10.1002/ett.4409 sudhamani, c., roslee, m., tiang, jj. and rehman, au. 2023. a survey on 5g coverage improvement techniques: issues and future challenges. sensors , 23(4): 2356. https://doi.org/10.3390/s23042356 wahidin, ph. and christiary, y. 2022. the evaluation of the throughput performance of an lte-advanced urban area network with the inter-band non-contiguous carrier aggregation method. journal of hunan university natural sciences, 49(8): 209–217. https://doi.org/10.55463/issn.1674-2974.49.8.25. wu, h., wei, z., hou, y., zhang, n. and tao, x. 2020. cell-edge user offloading via flying uav in non-uniform heterogeneous cellular networks. ieee transactions on wireless communications, 19(4): 2411-2426. zhang, j., björnson, e., matthaiou, m., ng, dwk., yang, h. and love, dj. 2020. prospective multiple antenna technologies for beyond 5g. ieee journal on selected areas in communications, 38(8): 1637-1660. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng corresponding author e-mail: mohammed.lawal@udusok.edu.ng 56 arid zone journal of engineering, technology & environment original research article towards sustainable economy: the role of e-procurement implementation in the delivery of public projects in nigeria m. l. yahaya1*, a. j., babalola2, m.j. abubakar3, m. sani4 1department of physical planning and development, usmanu danfodiyo university, sokoto, nigeria 2department of quantity surveying, faculty of environmental science, university of lagos, akoka-yaba, lagos, nigeria. 3department of quantity surveying, faculty of environmental science, federal university birnin kebbi 4department of building, faculty of environmental sciences, abubakar tafawa balewa university, bauchi, nigeria *corresponding author e-mail: mohammed.lawal@udusok.edu.ng article information abstract contracting firms spend significant resources in an attempt to participate in public project contracts in nigeria. as such, their working capital and liquidity ratio have always been condensed. the aim of the study was to explore factors influencing the successful implementation of e-procurement for sustainable economy. to attain this goal, the quantitative approach design method was adopted. forty-five (45) questionnaires were administered to the respondents using random sampling techniques in lagos, south west nigeria. data were collected from the respondent and analyzed using a descriptive statistic in the form of mean item score (mis), resulting in the various statistical outputs that were used to justify the research questions. the result from the analyses has shown factors such as lack of management support, i.t infrastructure, expertise and business benefit were among the first three that affect e-procurement implementation in the study area the study concludes that integrating technology approaches into the procurement policies relating to public procurement will enhance sustainable procurement and economy through legislative and government support in the area. the study therefore recommends that construction industry professionals should be computer specialist on how the concern security of submitted tender bid and usually virus attack can be addressed. lack of upper management support the major hindering should be considered in other to make proper implementation of e-procurement, most importantly, incorporation of educational programs for professionals (workshops, seminars, and conferences). submitted: 21st september 2024 revised: 8th january 2025 accepted: 26th january 2025 keywords: construction firms economy information technology public projects procurement sustainability tendering © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the construction industry is one of the sectors in any nation that contributed towards the economy. the sector as any kind of other sectors is faced with complex challenges despite to it contribution, which call for the most efficient use of available resources. consequently, the organizations involved in the procurement of building services, products and materials are constantly seeking ways of improving efficiency and effectiveness in their procurement activities so as to have a sustainable economy. among the different strategies considered to offer fresh opportunities for those organizations in the construction sector to improve communication and integration of task from different project team members and encourage teamwork in their procurement endeavours is the adoption of information and communication technology (ict), such as the internet procurement system (ajibike, 2019; marana, et al. 2019). nigeria for instance can be exemplified as a country with low socio-economic performance over a decades and unimpressive (fayomi, 2013, williams-egbe, 2011). this was largely attributed to high level of corruption or mismanagement of public resources closely linked up with the public sector procurement systems (fayomi, azojete march 2025. vol.21(1):56-63 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:mohammed.lawal@udusok.edu.ng mailto:mohammed.lawal@udusok.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):56-63. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author e-mail: mohammed.lawal@udusok.edu.ng 57 2013). the current economic downturn in nigeria due to fuel sub-sidy removal and other ant-people policies has necessitated the adoption of more prudent methods of delivering construction projects. thus, procuring entities of the government are faced with the challenge of effectively procuring projects within the meagre budget of the government (osanyinro and aghimien, 2017). the traditional procurement system widely practiced in the nigerian public sector, which involves the normal procedures as stated in the public procurement act 2007 (ppa, 2007) section 19(a-e), 24, 29, 31 and section 33 (a)-(c) is heavily challenged with so many setbacks, including limited and ineffective public bidding, among others. these setbacks necessitated procurement reforms in nigeria through the implementation of the eprocurement systems (oniyangi & ibrahim, 2024; afolabi, 2022; ajibike, 2019). over past few decades, eprocurement had been widely believed to be an avenue for integrating communities and countries into a global market economy. thus, governments around the world set very ambitious goals and also running programmes with considerable financial volume for the implementation of electronic service delivery in the public sector (oniyangi, & ibrahim, 2024). a large number of electronic procurement (ep) forms have received much research attention. some ep forms are quite well defined and relatively well developed; others have still not reached the maturity stage; some will mature, while others will never reach that stage. this section focuses on one of six ep forms that are quite well defined and relatively well developed, namely: e-mro, web-based erp, e-sourcing, e-informing, ereverse auctioning and e-tendering (moath & kriengsak 2017). the core elements of conventional procurement are kept in e-procurement, according to the royal institute of chartered surveyors (rics 2007), while improving the means of communication by finding an alternate medium via which the tender document and information are communicated. (amarapathy et al. 2013) define this medium as "secure dedicated websites, specifically set up for the exchange of information and tender papers electronically via the internet." e-procurement is a concept/process that incorporates a variety of activities that occur before a contract is awarded. it primarily entails e-notification, e-access, e-submission, e-evaluation, and, on rare occasions, eawarding. in addition, e-procurement has an advantage of gaining through improved work processes, efficient information sharing and reuse, better returns on investment, strategic partnerships, availability of project information management strategy, improving "build ability" and whole life costs with the supply chain, as well as public and private initiatives, is the main driver behind the e-procurement environment. furthermore, competitive organizational advantage promotes efficiency, speed, data correctness, and effectiveness in everyday company processes and management by utilizing the benefits of e-procurement environments (lou & alshawi, 2009; moath and kriengsak 2017). however, findings and recommendations by various scholars on e-procurement are mostly focused on benefits and challenges during implementation by different sector (caniato et al., 2011; caniato et al., 2013; croom and brandon-jones, 2007). furthermore, are mostly concentrated in the developed countries with a sustainable economy. as such these findings or recommendation become inapplicable in country like nigeria due difference in location, standard of living and economic strength. another reason is that researchers ignore a key aspect of the e-procurement which is implementation and its challenges when adopting it by organizations. even with the few studies on implementation and challenges there exist of divergence opinions among scholars which needs a very in-depth empirical research to arrive at an acceptable conclusions. therefore, this study seeks to address this gap identified by exploring the implementation and potential benefits of e-procurement in the delivery of public projects in nigeria. the objectives of this paper are to identify the key factors influencing the successful implementation of e-procurement in nigeria and to examine the most significant factors that affect the successful implementation of e-procurement in public project delivery. 2. materials and methods the study has basically adopted the use of field survey (quantitative design). this is because the study involves data collection with a view to identify the key factors influencing the successful implementation of eprocurement in nigeria and to examine the benefits associated with the adoption of e-procurement in public project delivery. indeed, field survey is the most appropriate statistical research method to be used in such kind of research as cited in durdyev and mbachu, (2011). the study population of interest that were considered in respect of this research work is the registered construction firms reside in lagos, considering the city as a mega with high volume of construction activities. however, targeted individuals within the construction firms are the professionals in the contracting firms such as architects, quantity surveyors, civil engineers, builders, service engineers, as the sample frame for the study. http://www.azojete.com.ng/ mailto:mohammed.lawal@udusok.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):56-63. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author e-mail: mohammed.lawal@udusok.edu.ng 58 randomly selection among construction firm lists was done by the researcher using non-replacement random selection. 45 respondents were sampled to represent the total population in the study area from the table of determining sample size from a given population by morgan and krejcie (1970). a questionnaire survey method was adopted to act as measuring tools for the purpose of data collection for the study. mean item score (mis) analyses were carried out to show the levels of the factors that influenced the eprocurement implementation in the delivery of public project in the study area. the mean item scores were computed using the following mathematical equation: misj = ∑ (rpjk x %rjk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ………………..1 where: misj = mean item for major sucess of e-procurements j; rpjk = ranking point k (ranking from 5-1); %rjk = percentage response to ranking point k for e-procurements j. k= 1 to 5. (5-point likert scale i.e 1= strongly disagreed to 5= strongly agreed) 3. result and discussion 3.1 factors influencing the successful implementation of e-procurement in contracting firms table 1 shows the identified factors influencing the successful implementation of e-tendering in the contracting firms, the number one objectives of this research study are to identify the factors influencing the successful implementation of e-procurement this objective was achieved in this research study through the carryout of systematic literature review and these factors are identified and presented in the table 1.0 with the sources of the finding. table 1: factors influencing the successful implementation of e-procurement in contracting firms s/n factor sources 1 security challenge kajewski & weippert, 2004, olukayode & adeyemi, 2011 and amarapathy et al. 2013. 2 low levels of computer literacy arcury et al., 2018, ashaari et al., 2018, tanli et al., 2019 and kajendran, 2022. 3 lack of upper management support sanyal & samanta, 2004, makarius, mukherjee, fox. and fox, 2020 and amoah & steyn, 2022. 4 costly and lack of it infrastructure olukayode & adeyemi, 2011, gangwar et al. 2015, ekezue et al. 2021 and tawfik et al. 2022. 5 lack of technical expertise dwivedi et al. (2017), wimalasena & gunatilake (2018) and tegegne et al. 2023. 6 employee resistance dumbili (2013), richardson et al. 2014 and olayemi & abolarinwa (2023). 7 unrecognized business benefits (mangitung et al., 2015, wimalasena, n. n., et al., 2018 and sandanayake, y. g., et al., 2022. 8 user acceptance rezgui et al., 2004, mastor et al., 2006, and olukayode & adeyemi, 2011. http://www.azojete.com.ng/ mailto:mohammed.lawal@udusok.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):56-63. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author e-mail: mohammed.lawal@udusok.edu.ng 59 3.2 evaluating factors that significantly affect the successful implementation of e-procurement in contracting firms this section presents and discusses the mean item score (mis) results of the identified factors affecting the successful implementation of e-procurement in the contracting firms in study area. the mis results are presented in table 2.0 table 2: factors affecting successful implementation of e-tendering in contracting firms factors affecting successful implementation tra misb orc lack of upper management support 45 4.29 1 costly and lack of it infrastructure 45 3.98 2 lack of technical expertise 45 3.98 2 unrecognized business benefits 45 3.73 3 low levels of computer literacy 45 3.71 4 employee resistance 45 3.69 5 user acceptance 45 3.62 6 security challenges 45 3.49 7 average mean score 3.81 notes: a) tr = total responses; b) mis= mean item score; c) or overall ranking; table 2 shows the factors affecting the successful implementation of e-procurement, according to the responses of the respondents the most rank factor influencing the successful implementation of eprocurement in contracting firms is lack of upper management support with highest mis (4.28) which ranked 1st , follow by lack of it infrastructure with mis (3.98) which ranked 2nd , the lack of technical expertise ranked 3rd with mis (3.98), unrecognized business benefits ranked 4th with mis 3.73, low level of computer literacy ranked 5th with mis (3.71), follow by employee resistance with mis (3.69) ranking 6th while user acceptance ranked 7th with mis (3.62), lastly security challenges with (3.49) mis ranking 8th respectively. on the average, all the identified factors that affect successful implementation of e-procurement in the contracting firms with an average (mis=3.81). the research carried out revealed that all the construction professionals in the construction field are aware of the electronic means of procurement but not all are implementing the use in their respective organization. therefore, there is need for improvement in the implementation. the findings of the factors influencing the successful implementation of e-procurement in contracting firms revealed that the most influencing factor for successful implementation of e-procurement is in contracting firms is lack of upper management support in (table 2) this aligns with amoah & steyn, (2023), costly and lack of it infrastructure also affect the successful implementation of e-procurement, (darlington, 2006; olukayode & adeyemi, 2011) says that the major risks factors relating to electronic transactions on the internet include hacking, viruses, pirating, illegal trading, fraud, money laundry, defamatory libel, trust, among several others. it required a huge amount of cost to prevent this factor which also makes the implementation of e-tendering difficult for some organizations. regarding the challenge of insufficient technical expertise in most public organization is very imminent and visible, which has contributed much towards the adoption of technology in governance today (dwivedi et al. 2017, wimalasena & gunatilake 2018). this challenge has leads to un-productive and less efficiency in the procurement system, and as such poor sustainable projects. some studies believed that a capable expertise with a technical know-how in e-procurement in an organization can reduce wastages and improved value for money to the end user if applied prudently, which may improve sustainability and reduce developmental degradation in our economy. the study further shows how unrecognized business benefit was identified as a factor that hindered e-procurement implementation in nigeria. these result has align with (mangitung & novitasari, 2015, wimalasena, & gunatilake, 2018) which stated that knowing and agreeing on the benefits for the adoption or used of technology make it compulsory by both individual and organization in order to attain their goals easily and be in competition among nation. therefore, we can attributes the non-adoption of the e-procurement in the delivery of public projects in nigeria by most organization as a result of less or non-benefit attached to it used as perceived. as a result, sustainable developments were less achieved in the country and high risk in the procurement system http://www.azojete.com.ng/ mailto:mohammed.lawal@udusok.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):56-63. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author e-mail: mohammed.lawal@udusok.edu.ng 60 (suleiman, saidu, adamu, s & tsado, 2024). among the factors that affect the e-procurement implementation from the study is the issue of low level of computer literacy within the procurement officers in the public sector. also, the few once among the various staff are not sure of their knowledge understanding in terms of the software used for procurement operation. therefore, making it difficult for the government to see it important and benefit since officers to operate them has shown less concern and ignorance of how its operation (arcury et al., 2020, ashaari et al., 2018, tan & li et al., 2019). 4. conclusion this study was undertaken to address the role of e-procurement implementation in the delivery of projects as a way of achieving sustainable economy. in other to achieve that, this study identifies the factors influencing the successful implementation of e-procurement first; evaluate the most significant factors affecting successful implementation of e-procurement in contracting firms in nigerian construction industry. results showed that a set of seven (7) factors were responsible for the constraining successful e-procurement implementation in the delivery of public projects in nigeria. top three (3) from the list of these sets of factors are the lack of upper management support, lack of it infrastructure, the lack of technical expertise, unrecognized business benefits and low level of computer literacy among employee. however, it could be deduced that due to socioeconomic influences, their levels of influence and knowledge capability among organization, and by implication, risk levels, could differ between projects. in conclusion, it is believed that by integrating technology approaches into the procurement policies 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research article analysis of the properties of spark plasma sintered ti6al4v matrix composites enhanced with nitride nanoparticles j. o. abe* 1, 2, o. m. popoola2 and a. p. i. popoola1 1 centre for energy and electric power, department of electrical engineering, tshwane university of technology, p.m.b. x680, pretoria, south africa. 2 department of chemical, metallurgical and materials engineering, tshwane university of technology, p.m.b. x680, pretoria, south africa. *corresponding author’s e-mail address: johnabe.fm@gmail.com article information abstract ti6al4v alloy serves as an optimal lightweight structural material. however, its restricted hardness adversely impacts its abrasion resistance under highperformance structural conditions, thereby hindering its extensive use in the aerospace industry. this study employed spark plasma sintering (sps) to develop ti6al4v matrix composites reinforced with 1, 3, and 5 wt. % of three refractory nitride nanoparticles of h-bn, tin, and aln. the developed composites were analyzed for microstructure, phase composition, densification, microhardness, and potentiodynamic polarization using field-emission gun scanning electron microscopy, x-ray diffraction, the archimedes' method, microindentation, and linear polarization investigations. the microstructure and phase analyses revealed marginal porosity and cracks, with no indications of detrimental intermetallic phases. it was observed that as reinforcement content increased, composite densities decreased from 98.4 to 97.4 %, 98.62 to 97.63 %, and 98.64 to 95.14 % for h-bn, tin, aln reinforcements, respectively. the microindentation test indicated that, relative to the unreinforced alloy (331.79 hv), hardness increased proportionally with reinforcement content. interestingly, h-bn exhibits a range of 672.05 to 740.43 hv, tin ranges from 427.18 to 491.06 hv, and aln shows values from 441.25 to 504.68 hv. the composite with 3 wt. % aln presented the best potentiodynamic polarization behaviour with a superior polarization resistance of 5246.2 ω and a lowered corrosion rate of 0.14321 mm/year. meanwhile, 5 wt. % aln-reinforced composite showed the worst densification and potentiodynamic polarization behaviour with a relatively decreased polarization resistance of 219.13 ω and a higher corrosion rate of 3.6935 mm/year. additionally, among the developed composites, the 3 wt. % h-bn-reinforced composite exhibited optimal properties, showcasing a microhardness of 716.80 hv, a markedly improved polarisation resistance of 4011.2 ω, and a considerably reduced corrosion rate of 0.21444 mm/year. therefore, improved mechanical and corrosion performance of ti6al4v matrix composites tends to reduce the weight of aerospace structures, improve fuel efficiency, and thereby enable the advancement of sustainable and benign aerospace technologies. received: 6th october 2025 revised: 22nd november 2025 accepted: 24th november 2025 keywords: ti6al4v matrix composite refractory nitride spark plasma sintering microhardness potentiodynamic polarization © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1. introduction high-performance, lightweight materials have been intensively explored because the aerospace industries require durable, lightweight, fuel-efficient, and cost-effective materials (del bosque et al., 2025). titanium and its alloys are used in these industries due to their high specific strength, low specific gravity, and mechanical and corrosion resistance. more than half of titanium products are produced as ti6al4v alloy, which positions the alloy as the foundation of titanium alloys and aerospace manufacturing. however, the alloy's low hardness and inherently poor wear-resistant properties at ambient and heated temperatures limit its usage in structural azojete december 2025. vol.21(4):992-1004 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/009 www.azojete.com.ng mailto:johnabe.fm@gmail.com mailto:johnabe.fm@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 993 components (garbiec et al., 2016). moreover, materials deteriorate as a result of corrosion when they undergo chemical reactions with their environment. this phenomenon confronts several businesses, causing economic losses and safety risks (aljibori et al., 2024). maintaining aircraft component reliability and durability requires corrosion mitigation, preserving lives and resources (thakur et al., 2025). quite a lot of approaches have been devised to address the highlighted problems (garbiec et al., 2016). a considerable return on investment in avoiding costs can be achieved within the industry through the implementation of predictive maintenance and the investment in corrosion-resistant materials (thakur et al., 2025). alloying, surface changes, and reinforcing particle integration are often investigated (ramesh et al., 2025). one approach that stands out is the development of ti6al4v matrix composites (tmcs) through reinforcing particle integration (garbiec et al., 2016; falodun et al., 2023). refractory nitrides are suitable reinforcements for metal and alloy matrices due to their properties. refractory nitrides are significant ceramics for high-temperature, structural, chemical, and semiconductor applications. this category contains silicon, boron, titanium, aluminium, niobium, tantalum, zirconium, and hafnium nitrides (falodun et al., 2023; abe et al., 2025). because of their high melting point, hardness, thermal conductivity, high-temperature stability, chemical stability, and wear resistance, hexagonal boron nitride (h-bn), titanium nitride (tin), and aluminium nitride (aln) have received substantial research (falodun et al., 2023; abe et al., 2025; hussain et al., 2022; akinwamide et al., 2020). many studies have used refractory nitride as reinforcement materials, showing improvements in the developed composites' characteristics (falodun et al., 2023; abe et al., 2025; hussain et al., 2022; akinwamide et al., 2020; liu et al., 2009). hussain et al. (2022) used metal-organic chemical vapour deposition to synthesise a cu-ni composite reinforced with h-bn and examined its mechanical and thermal conductivity properties. uniaxial tensile tests showed that h-bn improved composite mechanical properties over pure cu-ni alloy. the composite has 11.67%, 16.3%, and 27.9% higher ultimate tensile, yield, and fracture toughness. threedimensionally interconnected h-bn layers at cu-ni grain boundaries improved composite characteristics. the layers make the composite load-resistant by grain refining, dislocation strengthening, and load transmission. heat conductivity was 10% higher in the composite than in the pure cu-ni alloy. akinwamide et al. (2020) examined the microstructural and corrosion characteristics of spark plasma sintering-produced tin-modified 304 austenitic stainless steel in fecl3 and 3.5 wt. % nacl. the turbula mixing method produced uniform tin dispersions in the austenitic stainless-steel matrix. after 96 hours in ferric chloride solution, 2 and 4 wt. % tin specimens showed improved corrosion resistance. cyclic potentiodynamic polarization experiments showed that tin nanoparticles increased the sintered austenitic stainless steel pitting corrosion resistance. lui et al. (2009) synthesised al-aln composites by arc plasma evaporating aluminium in nitrogen and hot pressing with aln nanoparticle concentrations 0–39%. microstructural examination indicates that nano aln particles are uniformly dispersed within the al nanocrystalline matrix, resulting in aln/al interfaces bonded atomically. the nanocomposites’ hardness (3.48 gpa) and elastic modulus (142 gpa) were enhanced. the enhancement is attributable to the fortification caused by grain refinement and the interfacial bond formed at the solid al/aln interfaces. there are a number of desired qualities associated with ti6al4v alloy as mentioned earlier; nevertheless, the production process is complicated by the alloy's strong affinity for nitrogen and oxygen. in order to get the desired results, the ti6al4v alloy needs to be processed under controlled circumstances, which include high temperatures and a vacuum (garbiec et al., 2016). at elevated temperatures, conventional sintering methods present a number of challenges, including high melting points, lengthy dwell times, an inability to maintain low grain growth rates, large powder surface areas, and hazardous chemical affinities to atmospheric gases (hydrogen, nitrogen, and oxygen). as a result, a better approach is strongly recommended (matizamhuka, 2016). spark plasma sintering is a sophisticated and effective process for sintering powder materials, enabling the production of near-net-shape bulk materials. this innovative consolidation technique functions through the concurrent application of pressure and rapid thermal treatment of powdered material. the parameters employed in the sintering procedure include low voltage and pressure, utilising a uniaxial force and pulsed direct current, respectively, to enhance the effectiveness of powder material sintering (abe et al., 2025). the micro-spark/plasma theory is the predominant mechanism utilised to elucidate the sps process, which relies on electrical arc discharge and the generation of plasma sparks at the powder particles interface. various metallic and ceramic-based composite materials have been made using sps and evaluated against traditional sintering methods. sps features a short holding time and lower temperatures than traditional methods like casting or laser fusion, which results in reduced grain growth. consequently, improved microstructural and mechanical qualities are achievable (falodun et al., 2025). http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 994 therefore, this work presents the manufacturing of ti6al4v matrix composites reinforced with 1, 3, and 5 wt. % of h-bn, tin, and aln nanoparticles through the use of spark plasma sintering. the study is aimed at enhancing the microhardness and electrochemical corrosion resistance performance of spark plasma sintered tmcs, with the intention of utilizing them for structural applications in high-demand aerospace industries. this initiative aligns with goal 9 of the sustainable development goals (sdgs), which is to improve infrastructure and refit industries for sustainability with an emphasis on clean technology adoption and increased resource efficiency. 2. materials and methods the starting powders for this work include a commercially pure ti6al4v alloy (>99% purity, average particle size 60µm, from tls technik, germany) and refractory nitrides (h-bn, tin, aln) (average particle size 100nm, purity >99%) from hongwu international group ltd., china. three categories of ti6al4v-based powders with comparable weight compositions, along with a control sample were prepared, each with its corresponding code as follows: ti6al4v/1h-bn (tb1), ti6al4v/3h-bn (tb2), and ti6al4v/5h-bn (tb3); ti6ai4v/1tin (tt1), ti6ai4v/3tin (tt2), and ti6ai4v/5tin (tt3); ti6ai4v/1aln (ta1), ti6ai4v/3aln (ta2), and ti6ai4v/5aln (ta3); and ti6al4v alloy (t). the powders were measured using an electronic balance (model ex10202, canada) and mixed for 10 hours at 100 rpm in a turbula mixer. the mixed powders were placed in a 30mm-diameter, 10mm-height cylindrical graphite die-punch assemblage in the sintering chamber. based on an optimization experiment conducted by abe et al., (2019), the consolidation of the powders was facilitated using an automatically operated sps machine (model fct systeme gmbh, germany) in a vacuum environment of approximately 4 pa with optimized sps parameters: 1000 °c, 30 mpa, 100 °c/min, and 10 min dwell time. a representation of the spark plasma sintering operation is shown in figure 1. the sintered samples were wire-cut into 10 x 10 x 5 mm cuboids and hot-mounted in epoxy resin. the grinding process was accomplished utilizing european (p-grade) silicon carbide abrasive sheets having grits in a range between p120 and p2400. diamaxx (9, 6, 3, and 1 µ) was utilized to polish the samples to a mirror-like shine, followed by kroll's reagent etching. the microstructure was examined under a field emission gun scanning electron microscope (fegsem: zeiss 540 ultra) with a high-magnification (mag = 5.00 k) image and eds, and the phases were identified using xrd bruker d8 advance. an electronic density balance (sdptop ja5003j) was used to determine the sintered materials' density as prescribed in astm b962 and archimedes' method. the relative densities were computed by dividing the densities measured by theoretical densities multiplied by 100%. the materials underwent microindentation utiliizng an emco vickers hardness tester that featured a diamond dura scan. a 300gf test load was used to indent on the polished sample with 15 seconds dwell time at 0.5mm intervals. five readings were averaged to calculate each sample's effective microhardness. figure 1: a representation of the spark plasma sintering operation http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 995 a linear polarization experiment was performed on a metrohm autolab potentiostat (pgstat302n) with nova software version 2.1.8 to evaluate the samples' potentiodynamic polarization behaviour in 0.5m sulphuric acid at ambient temperature. the scanning of the polarisation curves were conducted at a rate of 1 mv/s from 1.5 v to -1.5 v. an ag/agcl reference electrode contained in saturated kcl solution, a working electrode, and a platinum counter electrode were employed. the corrosion results were assessed using tafel extrapolation. 3. results and discussion 3.1. microstructure and phase analyses of ti6al4v matrix composites plate 1(a-d) displays the tem images, while figure 2(a-d) shows the stacked xrd patterns of the powders used for this study. plate 1(a) depicts spherical ti6al4v alloy particles, while plate 1(b-d) depicts platyhexagonal h-bn, spherical tin, and clumpy wurtzite-like aln particles, respectively. on the other hand, figure 2(a) shows the xrd pattern for ti6al4v alloy powder, revealing pristine α-ti phase peaks at diffraction angles of 35.09°, 38.42°, 40.17°, 53.0°, 62.95°, 70.66°, 76.22°, and 77.37° in the (100), (002), (101), (102), (110), (103), (112), and (201) planes. in figure 2(b), crystalline hexagonal bn peaks have high intensity at 2θ values of 26.63°, 41.51°, 43.75°, 50.0°, 54.85°, 75.73°, and 81.93°, aligning with planes (002, (100), (101), (102), (004), (110), and (105). this data describes hexagonal bn peaks with an average particle size of 100 nm from isothermal annealing (abe et al., 2020). figure 2(c) shows the crystalline tin phase at 2θ = 36.66°, 42.6°, 61.81°, 74.07°, and 77.96°, corresponding to planes (111), (200), (220), (311), and (222). furthermore, figure 2(d) shows the presence of crystalline aln phase peaks at 2θ = 33.22°, 36.04°, 37.92°, 49.82°, 59.35°, 66.05°, 69.73°, 71.44°, 72.63°, 76.45°, and 81.1°, in alignment with (100), (002), (101), (102), (110), (103), (200), (112), (201), (004), and (202) planes. plate 1: tem images of powders: (a) ti6al4v (b) h-bn (c) tin (d) aln according to fegsem and standard eds investigations, plate 2 shows the structures and intensities of the peaks of the elemental constitution of t, tb1, tb2, tb3, tt1, tt2, tt3, ta1, ta2, and ta3. in plate 2(ai), the t exhibits two phases (α+β). the phases exhibit diverse orientations, including ultrafine α lamellae and bimodal configurations (α lamellae and fine equiaxed grains), with a large presence of primary α phases (falodun et al., 2023). the eds spectra in plate 2(aii) indicate elemental peaks that match the expected values. plates 2(b), 2(c), and 2(d) indicate considerable morphological changes in the α/β alloy matrix in contrast to t (plate 2(ai)). the microstructure of reinforced composites varies due to h-bn, tin, and aln nanoparticles and increasing reinforcement levels from 1 to 5 wt. % (abe et al., 2020). the eds spectra in plate 2(biv) confirm the presence of h-bn in the α/β matrix by revealing elemental peaks for boron and nitrogen. the elemental peaks in plate 2(civ) and plate 2(div) show that tmcs reinforced with tin (tt1, tt2 and tt3) and aln (ta1, ta2 and ta3) include nitrides, mainly ti, al, and n. (a) (d) (c) (b) http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 996 figure 2: xrd patterns of the powders: (a) ti6al4v (b) h-bn (c) tin and (d) aln figure 3 compares the xrd images of t and the tmcs. in figure 3, plot (a) clarifies α-ti and β-ti phases in t (falodun et al., 2023). after mixing and dispersing the reinforcements in the alloy matrix, their xrd peak intensities decrease, also regarded as the broadening of the xrd peaks, indicating induced lattice strains due to the incidence of nanoscale crystals, as depicted in plots (b) to (g). this result is caused by the dilution of the reinforcement phase in the matrix, the refinement and dispersion of the reinforcement particles, potential interfacial interactions, and geometric reorganization that loses preferred orientation (dudina et al., 2021). plots (b) and (c) show distinct xrd patterns that highlight the hard bn phase at 2θ ~ 44.3° and the tib phase at 2θ ~ 44.8°. the peaks are necessary to understand the increased hardness and strength of h-bn-reinforced tmcs (tb1, tb2 and tb3) compared to tin (tt1, tt2 and tt3) and aln (ta1, ta2 and ta3) [32]. plots (d), (e), (f), and (g) show that xrd peak intensities for α-ti (2θ = 35.09°, 40.17°, 53.0°, 62.95°, and 70.66°), vn (2θ = 37.28° and 43.38°), and tin (2θ = 42.48°) are nearly identical in tinand aln-reinforced tmcs. the aln phase is clearly visible at 2θ = 76.63° in plots (d) and (e), whereas plots (f) and (g) show an additional tin phase at 2θ = 78.08°. this suggests that tinand aln-reinforced tmcs share phase components and physical and chemical characteristics, which elucidates the similarity observed in their properties (abe et al., 2020). none of the xrd patterns show deleterious intermetallic peaks. this shows that the refractory nitride reinforcements and ti6al4v matrix did not react negatively during sps (yang et al., 2025). 3.2. density and microhardness analyses of ti6al4v matrix composites the findings of the density and microhardness tests are presented in table 1. it is observed that t has a theoretical densification of 99.77%, which is quite close to full. this indicates that the sps approach efficiently supports alloy consolidation by means of appropriate diffusional mass movement, which ultimately results in strong particle fusion, as seen by the fegsem image shown in plate 2(ai). relative densities are reduced when reinforcements of 1, 3, and 5 weight percent h-bn, tin, and aln are added to t. the relative densities of tb1, tb2, and tb3 decrease from 98.40% to 97.40%, tt1, tt2, and tt3 decrease from 98.62% to 97.63%, and ta1, ta2, and ta3 decrease from 98.64% to 95.14%. the increased contact surface area explains this phenomenon due to the integration of nanoparticle reinforcements into the ti6al4v matrix, as well as pore nucleation at the locations of the ceramic particulates (clinktan et al., 2019). the nature and proportion of reinforcement materials have a substantial impact on the densification characteristics of the tmcs (irshad et al., 2023). 0 10 20 30 40 50 60 70 80 90 0 1100 2200 3300 0 8600 17200 25800 0 1200 2400 3600 0 4200 8400 12600 (a) ti6al4v (b) r el at iv e in te ns ity h-bn (c) diffraction angle, 2q (degree) tin aln (d) http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 997 plate 2: fegsem/eds images depicting the structures and peaks of t (ai-aii), tb1, tb2 and tb3 (bi-biv), tt1, tt2 and tt3 (ci-civ), and ta1, ta2 and ta3 (di-div) figure 3: xrd patterns of: (a) t (b) tb1 (c) tb3 (d) tt1 (e) tt3 (f) ta1 and (g) ta3 30 40 50 60 70 80 ggg ñ g g g g g g g g g g y b b qq f r e la ti v e i n te n s it y diffraction angle (degree) g-α-ti b-b-ti f-aln ñ-tin q-vn y-bn o-tib (a) (b) (c) (d) (e) (f) (g) ñ ñ t tb1 tb3 tt1 tt3 ta1 ta3 o (ai) (aii) (bi) (bii) (biii) (biv) (ci) (cii) (ciii) (civ) (di) (dii) (diii) (div) α/β matrix http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 998 the evaluated average microhardness for t is 331.79hv, as illustrated in figure 4. the most noticeable increase in microhardness is observed in tb1, tb2, and tb3, with values ranging from 672.05hv to 740.43hv. the two sets, which are tt1, tt2, and tt3, as well as ta1, ta2, and ta3, demonstrate comparable improvements in microhardness. the values for these sets range from 427.18hv to 491.06hv and from 441.25hv to 504.68hv, respectively. thus, the microhardness of all the reinforced composites exhibits an increase with the concentration of ceramic reinforcement from 1 to 5 wt. %. this result can be attributed to the retention of bn, tin, and aln particles inside the α/β matrix despite the fact that their densification dropped (okoro et al., 2019). the retained particles are found to be uniformly dispersed, tightly bound, and distinct phases from the matrix. by effectively absorbing and distributing loads, these particles typically support the composite's strength, load-bearing capacity, and thereby improving hardness and wear resistance (wang et al., 2025; attar et al., 2014). furthermore, during the sintering process, the ceramic reinforcement and titanium alloy undergo a reaction that results in the formation of harder phases (tib and vn), which in turn increases the composite's hardness (okoro et al., 2019). this discovery is in line with the findings of prior research kganakga et al., (2020) that investigated the use of ceramic materials for the reinforcement of ti6al4v alloy. thus, the microhardness of ti6al4v matrix composites can be increased by incorporating different types and proportions of nanoceramic reinforcements comprising h-bn, tin, and aln. this is achieved through the processes of dispersion strengthening and the pinning effect, which prevents dislocation movement (okoro et al., 2019; kganakga et al., 2020). table 1: summary of the density and microhardness tests’ results. sample id code effective density (g/cm3) theoretical density (g/cm3) relative density (%) microhardness (hv) t 4.42 4.43 99.77 331.79 ± 17.6 tb1 4.31 4.38 98.40 672.05 ± 25.2 tb2 4.21 4.30 97.91 716.80 ± 31.0 tb3 4.12 4.23 97.40 740.43 ± 34.6 tt1 4.36 4.421 98.62 427.18 ± 19.3 tt2 4.33 4.423 97.90 448.37 ± 25.7 tt3 4.32 4.425 97.63 491.06 ± 21.8 ta1 4.34 4.40 98.64 441.25 ± 25.5 ta2 4.29 4.37 98.17 488.48 ± 36.5 ta3 4.13 4.34 95.14 504.68 ± 22.6 figure 4: graph comparing the microhardness of: (a) t (b) tb1 (c) tb2 (d) tb3 (e) tt1 (f) tt2 (g) tt3 (h) ta1 (i) ta2 and (j) ta3 3 3 1 ,7 9 6 7 2 ,0 5 7 1 6 ,8 7 4 0 ,4 3 4 2 7 ,1 8 4 8 4 ,3 7 4 9 1 ,0 6 4 4 1 ,2 5 4 8 8 ,4 8 5 0 4 ,6 8 t tb1 tb2 tb3 tt1 tt2 tt3 ta1 ta2 ta3 0 100 200 300 400 500 600 700 800 900 m ic ro h a rd n e s s ( h v ) http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 999 3.3. potentiodynamic polarization analysis of ti6al4v matrix composites one of the techniques employed in preventing corrosion of materials is to develop new corrosion-resistant materials characterized by enhanced metallurgical structure that can provide resistance against the effect of corrosive anions (chen et al., 2025). in this section, the potentiodynamic polarization approach is utilized to investigate the electrochemical corrosion of t, tb1, tb2, tb3, tt1, tt2, tt3, ta1, ta2, and ta3 in sulphuric acid at a concentration of 0.5 m. table 2 provides a comprehensive overview of the extrapolated tafel data obtained from the experiment. it highlights the essential corrosion parameters, such as the corrosion potential, current density, polarization resistance, corrosion rate, and the anodic and cathodic tafel slopes (βa and βc). a comparison of the corrosion rates and polarization resistances of the materials is presented in figure 5, while the potentiodynamic polarization curves of the materials are displayed in figure 6. according to the data obtained from the potentiodynamic polarization investigation in table 2, the inclusion of nitride nanoparticles has a multifarious impact on the electrochemical performance of the pure alloy. it is observed that t demonstrates a positive corrosion potential (-0.45687v) and a current density that is quite mild (5.6906x105a/cm2) in comparison to other materials. this can be attributed to the effect of stable passivating films of titania, tio2, and alumina, al2o3, formed during the interactive activities between the al and ti elemental compositions in the alloy and the corrosive environment (mogoda et al., 2004). for the h-bn-reinforced composites, improvement in the electrochemical characteristics can be observed where the initial corrosion potential of t shifts from -0.45687v to a more positive value of -0.41961v with a corresponding decrease in current density from 5.69x10-5a/cm2 to 1.04x10-5a/cm2 as depicted by tb1. increased polarization resistance and decreased corrosion rate resulted, rising from 897.69ω to 3864.7ω and decreasing from 1.8499mm/year to 0.2908mm/year, respectively. further improvement in the electrochemical characteristics was observed in tb2, where corrosion potential rises to -0.40575v and current density decreases to 9.72x10-6a/cm2, resulting in increased polarization resistance and better corrosion rate of 4011.2ω and 0.21444mm/year, respectively. on the other hand, it is found that tb3 displayed slightly worse electrochemical characteristics than tb2, but it still outperforms t and tb1. this may be due to more unfavourable interfacial interactions between the nitride reinforcement and alloy matrix phases, which could lead to corrosion-prone regions, as previously reported by nsiah-baafi et al., (2022). similarly, the tinreinforced composites (tt1, tt2, and tt3) show improved electrochemical characteristics, exhibiting a relatively improved polarization resistance that falls within the range of 2051.9 to 2908.6 ω and an enhanced corrosion rate that falls within the range of 0.37174 to 0.29414 mm/year. this is characterized by less positive corrosion potential between -0.41561 and -0.37781v and reduced current density between 2.52x10-5a/cm2 and 1.08x10-5a/cm2 in contrast to t. for aln-reinforced tmcs, there is a notable increase in electrochemical characteristics from ta1 to ta2, but there is characteristics with additional reinforcement at ta3, which is even worse than t and every other composite. categorically, ta3 had the most unsatisfactory electrochemical performance, as evidenced by its corrosion potential of -0.46064v and current density of 2.56x10-4a/cm2. this led to a fall in polarization resistance and a rise in corrosion rate of 219.13ω and 3.6935mm/year. the result is likely due to detrimental modifications in the surface condition of ta3 and inhomogeneous oxide layers formed during sintering. pores observed in the composite could act as potential nucleation sites for corrosion processes, and localized pitting ensued due to particle agglomeration (abe et al., 2020). this occurs despite the samples undergoing identical procedures, and it is common for the reinforcement to show greater corrosion resistance in diluted acid solution (mogoda et al., 2004). nevertheless, the porous oxide has the potential to create a channel for the electrolyte, which would make it easier for redox processes to take place (xie et al., 2025). with a corrosion potential of -0.33065v and a current density of 4.83x10-6a/cm2, ta2 exhibited exceptional corrosion resistance qualities. this resulted in a rise in polarization resistance and a drop in corrosion rate, which was measured at 5246.2ω and 0.14321mm/year, respectively. this is attributed to effective material densification and the formation of a homogenous oxide, which decreased the amount of contact between the electrolyte and the composite (flores-álvarez et al., 2017). table 3 presents a comparative analysis of the compositions and examined properties of the spark plasma sintered ti6al4v matrix composites from the current study alongside analogous materials documented in existing literature. the integration of diverse ceramic reinforcements has been observed to enhance the characteristics of ti6al4v-based composite systems, leading to notable advancements in mechanical and electrochemical properties as evinced by the studies examined. of the presently developed materials, the composite reinforced with 3 wt. % h-bn is identified with the optimal properties as it demonstrates superior characteristics, attaining a microhardness of 716.80 hv, in addition to a markedly improved polarization resistance of 4011.2 ω and a considerably reduced corrosion rate of 0.21444 mm/year. http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 1000 table 2: summary of the potentiodynamic polarization test results. sample id code corrosion potential, ecorr (v) corrosion density, jcorr (a/cm2) corrosion rate (mm/year) polarization resistance (ω) βa (v/dec) βc (v/dec) t -0.45687 5.69x10-5 1.8499 897.69 0.23772 0.26607 tb1 -0.41961 1.04x10-5 0.2908 3864.7 0.11882 0.092793 tb2 -0.40575 9.72x10-6 0.21444 4011.2 0.20293 0.15248 tb3 -0.43478 1.51x10-5 0.63731 1538 0.28198 0.16794 tt1 -0.41561 2.52x10-5 0.33991 2771.9 0.18821 0.10897 tt2 -0.37781 1.12x10-5 0.29414 2908.6 0.25567 0.10563 tt3 -0.40761 1.08x10-5 0.37174 2051.9 0.07368 0.12195 ta1 -0.36826 2.58x10-5 0.56962 1612.9 0.14294 0.092555 ta2 -0.33065 4.83x10-6 0.14321 5246.2 0.070161 0.11103 ta3 -0.46064 2.56x10-4 3.6935 219.13 0.31277 0.34694 figure 5: graph comparing the corrosion rate and polarization resistance of: (a) t (b) tb1 (c) tb2 (d) tb3 (e) tt1 (f) tt2 (g) tt3 (h) ta1 (i) ta2 and (j) ta3 figure 6: plots comparing the potentiodynamic polarization curves for: (a) t, tb1, tb2 and tb3 (d) t, tt1, tt2 and tt3, and (f) t, ta1, ta2 and ta3 t tb1 tb2 tb3 tt1 tt2 tt3 ta1 ta2 ta3 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 corrosion rate (mm/year) polarization resistance (ω) c or ro si on r at e (m m /y ea r) 0 1000 2000 3000 4000 5000 6000 p ol ar iz at io n re si st an ce (ω ) -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 -8 -7 -6 -5 -4 -3 -2 l o g c u rr en t d en si ty ( a /c m 2 ) corrosion potential (v) t tb1 tb2 tb3 (a) -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 -8 -7 -6 -5 -4 -3 -2 l o g c u rr en t d en si ty ( a /c m 2 ) corrosion potential (v) t ta1 ta2 ta3 (c) -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 -8 -7 -6 -5 -4 -3 -2 l o g c u rr en t d en si ty ( a /c m 2 ) corrosion potential (v) t tt1 tt2 tt3 (b) http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 1001 table 3: comparison among the properties of various spark plasma sintered ti6al4v matrix composites sintered sample spark plasma sintering conditions density, hardness, and corrosion properties reference relative density (%) microhardness (hv) corrosion rate (mm/yr) ti6al4v 1000 °c, 50 mpa, 100 °c/min, 6 min 98.6 325.46 0.986625 (kgoete et al., 2018a) ti6al4v/5si3n4 96.9 597.58 0.08234 ti6al4v/10si3n4 97.2 668.56 0.030547 ti6al4v/15si3n4 96.2 585.73 0.0671 ti6al4v 900 °c, 50 mpa, 100 °c/min, 10 min 99.32 369 (okoro et al., 2019) ti6al4v/0.5mwcnt 98.6 458.5 ti6al4v/1.0mwcnt 98.2 466.5 ti6al4v/1.5mwcnt 97.54 502.6 ti6al4v 1000 °c, 50 mpa, 100 °c/min, 6 min 98.6 325.46 0.986625 (kgoete et al., 2018b) ti6al4v/5tin 98.3 527.43 0.14313 ti6al4v/10tin 97.1 438.8 0.243512 ti6al4v/15tin 96.2 487.68 0.275244 ti6al4v 850 °c, 50 mpa, 100 °c/min, 5 min 374.6 0.0404 (nsiah-baafi et al., 2022) ti6al4v/3al3o4 395.1 0.0150 ti6al4v/5al3o4 406.5 0.0693 ti6al4v/10al3o4 424.1 0.0982 ti6al4v 1000 °c, 50 mpa, 100 °c/min, 6 min 98.6 325.46 0.986625 (kgoete et al., 2018c) ti6al4v/2.5si3n4 +2.5tin 98.4 603.39 0.19709 ti6al4v/5si3n4 +5tin 97.2 727.41 0.018 ti6al4v/7.5si3n4 +7.5tin 96.5 708.7 0.379055 ti6al4v 1000 °c, 30 mpa, 100 °c/min, 10 min 99.77 331.79 1.8499 present study ti6ai4v/1h-bn 98.40 672.05 0.2908 ti6ai4v/3h-bn 97.91 716.80 0.21444 ti6ai4v/5h-bn 97.40 740.43 0.63731 ti6ai4v/1tin 98.62 427.18 0.33991 ti6ai4v/3tin 97.90 448.37 0.29414 ti6ai4v/5tin 97.63 491.06 0.37174 ti6ai4v/1aln 98.64 441.25 0.56962 ti6ai4v/3aln 98.17 488.48 0.14321 ti6ai4v/5aln 95.14 504.68 3.6935 4. conclusion spark plasma-sintered tmcs with 1, 3, and 5 wt. % h-bn, tin, and aln nanoparticles were examined for microstructure, phase composition, density, microhardness, and potentiodynamic polarization. finally, these are concluded: i. the study discovered that sps processing decreases surface reactions and produces finely refined grains with strong bonds and high densification. incorporating varying amounts of h-bn, tin, and aln (1, 3, and 5 wt. %) into the ti6al4v matrix results in a decrease in relative densities: 98.4% to 97.4% for h-bnreinforced, 98.62% to 97.63% for tin-reinforced, and 98.64% to 95.14% for aln-reinforced composites. ii. compared to the unreinforced alloy (331.79hv), the composites' hardness increases with reinforcement content from 1 to 5 wt. %: 672.05hv to 740.43hv, 427.18hv to 491.06hv, and 441.25hv to 504.68hv for h-bn, tin, aln reinforcements, respectively. the composites possess higher microhardness due to load transfer from the matrix to the more resilient reinforcement particles, which strengthens dispersion and inhibits dislocation motion. the microindentation test indicated that, relative to the unreinforced alloy (331.79 hv), hardness increased proportionally with reinforcement content. iii. in 0.5m sulphuric acid, 3 wt. % aln resists corrosion best with a comparatively high polarization resistance (5246.2ω) and low corrosion rate (0.14321mm/year). on the other hand, the composite with 5 wt. % http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 1002 aln-reinforced composite with poor densification had the worst electrochemical characteristics in the same media, resulting in decreased polarization resistance and increased corrosion rate of 219.13ω and 3.6935mm/year, respectively. porous oxide could establish a pathway for the electrolyte to facilitate redox reactions, and localized pitting ensued due to particle agglomeration. iv. among the spark plasma sintered composites, the 3 wt. % h-bn-reinforced composite exhibited optimal properties, achieving a microhardness of 716.80 hv, alongside a significantly enhanced polarisation resistance of 4011.2 ω and a notably diminished corrosion rate of 0.21444 mm/year. v. the effectual development of ti6al4v matrix composites with improved microhardness and electrochemical corrosion behaviour is expected to alleviate ti6al4v alloy's aerospace structural applications, lessen weight in aerospace structures, and better fuel efficiency and emissions, and thereby enable the advancement of sustainable and benign aerospace technologies. thus, this project aligns with goal 9 of the sustainable development goals (sdgs), which is to improve infrastructure and refit industries for sustainability with an emphasis on clean technology adoption and increased resource efficiency. acknowledgments this work is based on the research supported wholly/in part by the national research foundation of south africa (grant no. 150574), centre for energy and electric power (ceep); surface engineering research laboratory (serl) under the leadership of professor api popoola, faculty of engineering and the built engineering in tshwane university of technology (tut), pretoria, south africa. references abe, jo., popoola, api. and popoola, om. 2020. consolidation of ti6al4v alloy and refractory nitride nanoparticles by spark plasma sintering method: microstructure, mechanical, corrosion and oxidation characteristics. materials science and engineering: a, 774:138920. abe, jo., popoola, om. and popoola, api.. 2025. a review of the spark plasma sintering, characterization, and properties of refractory 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http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 992-1004. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: johnabe.fm@gmail.com 1004 stir processing and investigation of corrosion and wear behavior. journal of bio-and tribocorrosion, 11(2):48. thakur, a., kaur, h., anadebe, vc., purohit, s. and kumar, a. 2025. corrosion in the aerospace industry. industrial corrosion: fundamentals, failure, analysis and prevention, 217-254. wang, y., yang, g., zhang, s., zhou, s., li, b., an, d., he, b., li, x., xiao, y. and lin, p. 2025. microstructure evolution and mechanical properties of in-situ ti6al4v–tib-ti2ni composites manufactured by laser directed energy deposition. composites part b: engineering, 292:112072. xie, y., dong, j., wu, l., wang, w., sun, x., meng, x. and huang, y. 2025. unraveling the relationship between severe plastic deformation and corrosion responses of az31 mg alloys. corrosion science, 250, 112881. yang, g., zhang, s., zhou, s., li, b., an, d., he, b., li, x., xiao, y. and lin, p. 2025. microstructure evolution and mechanical properties of in-situ ti6al4v–tib-ti2ni composites manufactured by laser directed energy deposition. composites part b: engineering, 292:112072. http://www.azojete.com.ng/ mailto:johnabe.fm@gmail.com corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 108 arid zone journal of engineering, technology & environment original research article design and implementation of fpga accelerator for vision based fire detection a. hassan*, c. u. ngene and p. y. dibal department of computer engineering, university of maiduguri, borno state, nigeria. *corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng article information abstract fire outbreaks are great threat to human beings, economic infrastructure, and the environment. this led to the need for timely and accurate detection of fire incidents to minimize their devastating impacts. but conventional fire detection systems are electronic sensor based which as result they suffer from the problems of transport delay, conduction delay, limited detection range, high false alarm, and inappropriate for outdoor applications. to address the shortcomings of such sensor-based methods, several image processing and computer vision approaches to fire detection have been proposed. however, these image processing and computer vision-based solutions are implemented in software platforms which have disadvantages of inefficiency, high hardware requirements and high cost. in this research work, an embedded hardware accelerator for vision-based fire detection was designed and implemented in kintex-7 series field programmable gate array (fpga). matlab r2021a software was used for decoding the image dataset into pixel stream data. the design was captured in very high-speed integrated circuit hdl (vhdl). the design was synthesized with xilinx vivado 2021 design suite and simulated with xilinx isim. evaluation results showed that the accelerator could achieve good detection of fire features and were consistent with the results from matlab code running on personal computer. compared to software implementation, the latency, resource utilization and power consumption was greatly reduced. it was also found that the hardware accelerator which was developed as an intellectual property (ip) core can also be employed to speed up grayscale conversion, edge detection and thresholding algorithms in embedded vision, smart camera and video analytics applications. submitted: 15th august 2024 revised: 27th august 2024 accepted: 28th november 2024 keywords: fpga hardware accelerator simulation image processing fire detection © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction fire emergencies are leading to huge human loss, massive infrastructure damage and serious environmental degradation around the world. for instance, the kano state fire service records that 134 human lives and 635-million-naira assets were lost due to fire outbreaks in the state between january 2021 to december 2021. another fire event was also reported at sabon gari market in kano city in which properties and shops worth millions of naira were lost and took more than 10 hours to be put out completely by the kano state fire service team. report from news agency of nigeria (nan) on 23 may 2021, showed that not less than 64 people, including eight fire fighters, got different degrees of injuries from a petroleum tanker explosion at a filling station in sharada area of kano state (hassan & audu, 2022; rabiu, 2022). this necessitates the need for timely and accurate fire detection systems to minimize their catastrophic impact of fire disasters. but majority of existing fire detection systems are electronic sensor based and have problems of transport delay, conduction delay, limited detection range, high false alarm, inappropriate for outdoor applications and lack of capability to give rich additional information on location, growth rate, size of the fire incidents. (hassan & audu, 2022; rabiu, 2022; solórzano et al., 2022; wang et al., 2020). several image processing and computer vision-based methods have been proposed to solve the problems of such sensor-based methods. however, majority of these image processing and computer vision-based approaches were implemented in software azojete march 2025. vol.21(1):108-118 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:abubakarhassan@unimaid.edu.ng mailto:abubakarhassan@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 109 which as a result have disadvantages of high hardware requirement, high cost and inefficiency (abid et al., 2021; choudhuri & roy, 2016; liu et al., 2020). the above problems can be effectively using hardware acceleration technology platforms such as fpga. fpga has inherent advantages of latency and higher energy consumption for streaming computing tasks. furthermore, fpga has high flexibility which can change hardware algorithms and chip functions to facilitate algorithm and function verification (hassan et al., 2024). this paper aims to propose fpga hardware accelerator for vision-based fire detection applications implemented in vivado and matlab environments. the hardware accelerator consists of an image decoding module, grayscale conversion module, edge detection module and fire pixel classification module. the remaining part of this paper is organized as follows. section 2 presents review of related works methodology. section 3 presents the methodology. results and discussion are provided in section 4. finally, a conclusion and future direction is presented in section 4. several image processing and computer vision approaches to fire detection have been proposed. authors in (pritam & dewan, 2017) proposed fire detection system based on luv color space and hybrid transforms. video frames captured are read and are segmented. all frames are analyzed to confirm the presence of fire. fire is detected by the presence of fire pixels in the image. fire pixels are recognized using the features of luv color space and hybrid transforms. edge detection algorithm is employed to extract the edges of the image when flame color detects existence of fire. image segmentation methods are employed to extract the fire region of interest from the background. an algorithm for smoke detection based on simplified descriptors of video information is proposed by (monte et al., 2017). firstly, the descriptors of the scene on every frame are obtained. the inference processes of smoke presence are input by the descriptors and background estimation, which is updated with every frame. a group of classifiers perform the smoke inference process. the fusion outcomes of these classifiers provide a reliable detection. simple boolean logic combines the process outcomes, with minimum and maximum threshold values. the proposed approach is simple and efficient for deployment on computationally low embedded applications for real-time surveillance. researchers in vijayalakshmi & muruganand, (2018) proposed an effective smoke detection approach in video images for early fire emergency systems. the proposed algorithm uses fuzzy c-means clustering and background subtraction to segment smoke region of interest from moving regions. result obtained show that the algorithm outperforms other algorithms and increase the accuracy smoke detection. however, the algorithm is not tested on large variety of dataset and the performance still can be improved because it is only based on motion segmentation. zhang et al. (2017) developed a method for smoke detection in videos. the proposed algorithm employs two key features of smoke to detect it. visual background extractor (vibe) is employed to segment moving objects in static scene. the atmospheric model is used to detect semitransparent feature of smoke. the similarity between extracted regions and original background regions in the same position is computed using normalized cross correlation and the value of the original background is chosen from the frame that is nearest to the current frame. the blocks with high similarity are identified as smoke parts. experiment results demonstrate that the algorithm can recognize fire and integrated into surveillance system. authors in huang et al., (2017) proposed an algorithm for video-based smoke detection in low illumination indoor environment using support vector machine. the smoke region is extracted and then the area diffusion and main direction of movement of smoke region are selected as the dynamic features and texture is extracted as the static feature to recognize fire smoke in low-light indoor scene. support vector machine is employed to design the classifier to realize smoke detection. an effective method for real-time fire detection based on video processing is proposed by (khan et al., 2019). the proposed method employs flame color and spatial-temporal features to detect fire regions. firstly, fire color pixels are segmented using a set of improved rules based on rgb color space. the foreground is segmented based on change in blue component trained using neural network. lastly, the region of interest is extracted using growing area analysis. authors in yang et al., (2018) proposed technique for video-based http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 110 smoke detection by combining gaussian mixture model (gmm) and hsv color model with the deep convolutional neural network. first, each frame is divided into 10-by-10 sub-images by the method. secondly, gaussian mixture model is employed to extract the motion region and later the sub-images block which contains the moving region is segmented. then, the motion blocks segmented by the gmm is used to extract target smoke blocks successively using hsv color feature analysis. zeng et al. (2018) proposed an effective method for smoke detection based on automatic vision system. the method employs an adaptive background subtraction technique to segment moving regions. non-smoke regions are extracted out by employing color feature and fuzzification. regions that satisfy both the color analysis and fuzzification criteria are classified as candidate smoke regions. in (kaabi et al., 2018), a novel approach for video-based smoke detection based on machine learning approach to overcome forest wildfires was proposed. firstly, the video is divided into frames for training with deep belief network. in addition, gaussian mixture model is employed to segment candidate regions from the target smoke video to be trained by using deep belief network. logistic regression is used to classify on the output data. researchers in (xie et al., 2020), proposed a method that employs the motionflicker based dynamic features and deep static features for video-based fire detection. first, the dynamic features are segmented by, analyzing the differences in motion and flicker features between fire and non-fire objects in video scenes. second, an adaptive lightweight convolutional neural network is proposed to segment the deep static features of fire. zhang et al., (2021) developed an effective asymmetric encoder-decoder ushape architecture based on squeeze net, attention u-net and squeeze net performs most of the time as an extractor and a discriminator of forest fire. the model uses attention mechanism to extract useful features and suppress non-related features by embedding attention gate (ag) units in the skip connection of u-shape structure. a robust algorithm based on information on color and shape was proposed by (rabiu, 2022). the algorithm starts with loading video image database developed to detect presence or absence of fire in video frames. background subtraction is used by this method to compare the current frame with the reference frame. when the outcome of the background subtraction is less than the set point, the frame is discarded, and the next frame is checked. but if the difference is equal or greater than the set point, the frame is then subjected to color and shape test. this is achieved by employing combined rgb color space model and shape feature. the proposed algorithm was extremely robust in detecting fire compared to those algorithms based on color or motion features. 2. materials and methods the architecture of the fpga hardware accelerator is presented in this section. it mainly consists of image decoding module, grayscale image conversion module, sobel edge detection and fire pixel classification module. modular and hierarchical approach was adopted for this design and the model was captured using vhdl. vhdl was used in view of its strength in paper documentation. the block diagram of the hardware accelerator is depicted in figure 1. input image fire pixel classifier figure 1: block diagram of the hardware accelerator. grayscale image converter sobel edge detector image decoder http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 111 2.1 image decoding video dataset used in this work was obtained from visifire database which is a commonly used public video dataset for fire and smoke detection (hassan et al., 2024). edge pixel features are used in classifying objects into fire or non-fire classes, because edges preserve structural information of objects. the fpga accelerator read video frames from block ram and convert the images into streams of pixel data for pixel streaming computation after obtaining average rgb pixel values in matlab. the pseudocode for converting video data in frames is shown as follows. pseudocode for video frames conversion. 1: read video data stream: 2: compute number of frames in the video stream; 3: for i = 1:2: n convert video stream into frames save frames 4: end. then we computed the respective average rgb values to obtain representative video frames for pixel stream data generation. the pseudocode for image decoding into pixel streams is depicted as follows. pseudocode for image decoding. 1: read video frames: 2: compute number of frames; 3: for k = 1: numframes decode frames into pixel stream save pixel stream 4: end. the algorithmic state machine (asm) chart for the image decoding into pixel streams is illustrated in figure2. it describes how the image decoding module reads and convert video frames from memory to generate the pixel streams. figure 2: asm chart for image pixel generation. 2.2 gray scale image conversion the rgb image pixel data was converted to grey scale image for easy computation which is expressed as given by in equation (1). y = 0.299r + 0.587g + 0.1 (1) http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 112 for the hardware implementation, we avoided the floating-point multiplications and efficiently computed the grayscale value of the pixel as given by in equation (2). y= 0.299r + 0.587g + 0.114b ≈ 306×𝑅 + 601×𝐺 + 117×𝐵 1024 (2) figure 3.3 illustrates the architecture of the rgb to gray scale image converter. figure 3. architecture of the rgb to grayscale image converter 2.3 sobel edge detection the sobel edge detection module is responsible for extracting and classifying object edges. it also writes the result the detected edges array into the fire pixel classification module. sobel edge detection is a classical algorithm in the field of image and video processing for the extraction of object edges. edge detection using sobel operators works on the premise of computing an estimate of the first derivative of an image to extract edge information. by computing the x and y direction derivatives of a specific pixel against a neighbourhood of surrounding pixels, it is possible to extract the boundary between two distinct elements in an image. the operator consists of a pair of 3 by 3 convolution kernels as shown in equation (3). one kernel is simply the other rotated by 90 degrees. 𝐺𝑥 = [ −1 0 1 −2 0 2 −1 0 1 ] ∗ 𝐴 𝐺𝑦 = [ 1 2 1 0 0 0 −1 −2 −2 ] ∗ 𝐴 (3) where a is the input image, gx, gy are images where each point represents the approximate derivatives along the x and y axes. we assume that the original image is given by in equation (3.4). [ 𝑓(𝑥 − 1, 𝑦 − 1) 𝑓(𝑥, 𝑦 − 1) 𝑓𝑥 + 1, 𝑦 − 1) 𝑓(𝑥 − 1, 𝑦) 𝑓(𝑥, 𝑦) 𝑓(𝑥 + 1, 𝑦) 𝑓(𝑥 − 1, 𝑦 + 1) 𝑓(𝑥, 𝑦 + 1) 𝑓(𝑥 + 1, 𝑦 + 1) ] (4) the vertical and horizontal gradients of the sobel operators are gx and gy, which denote the gray level of the edge detection image in vertical and horizontal directions respectively which are computed as given by (zhang, 2018) in equation (5) and (6) 𝐺𝑥 = 𝑆𝑜𝑏𝑒𝑙𝑥 × 𝐴 = 𝑓(𝑥 + 1, 𝑦 − 1) + 2𝑓(𝑥 + 1, 𝑦) + 𝑓(𝑥 + 1, 𝑦 + 1) − 𝑓(𝑥 + 1, 𝑦 − 1) − 2𝑓(𝑥 − 1, 𝑦) − 𝑓(𝑥 − 1, 𝑦 + 1) ( 5) 𝐺𝑦 = 𝑆𝑜𝑏𝑒𝑙𝑦 × 𝐴 = 𝑓(𝑥 − 1, 𝑦 + 1) + 2𝑓(𝑥, 𝑦 + 1) + 𝑓(𝑥 + 1, 𝑦 + 1) − 𝑓(𝑥 − 1, 𝑦 − 1) − 2𝑓(𝑥 − 1, 𝑦) − 𝑓(𝑥 + 1, 𝑦 − 1) (6) these kernels are designed to respond maximally to edges running vertically and horizontally relative to the pixel grid, one kernel for each of the two perpendicular orientations. the approximate gradient value of brightness can be obtained by element-wise summation of the resulting images given by in equation (7). |𝐺| = √⌊𝐺𝑥2 + 𝐺𝑦2⌋ ( 7) typically, an approximate magnitude is computed using equation (3.8) . |𝐺| = |𝐺𝑥| + |𝐺𝑦| (8) 2.4 fire pixel classification in this research work, we employed thresholding-based technique to detect fire edge pixels which are expressed as given by in equation (9) http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 113 𝑔(𝑥, 𝑦) = { 𝐹𝑖𝑟𝑒, 𝐼𝑓 𝑓(𝑥, 𝑦) ≥ 𝑇𝐻 𝑁𝑜𝑡 𝐹𝑖𝑟𝑒, 𝑂𝑡ℎ𝑒𝑟𝑤𝑖𝑠𝑒 (9) where f(x, y) is the input image and th is the threshold value. the threshold value was determined using the otsu’s method which is used to perform automatic image thresholding in computer vision and image processing. the pseudocode for the otsu method is given as follows. pseudocode for otsu method 1: compute the normalized histogram of the input image. 2: compute the cumulative mean. 3: compute the global intensity mean. 4: compute the between-class variance. 5: obtain the optimum threshold. 6: segment the image using the threshold. 3. results and discussion the results of the actual design of the fpga hardware accelerator are first presented by examining the synthesis and the simulation results. 3.1 synthesis the hardware was synthesized with xilinx vivado 2021.1 design suite and simulated using xilinx isim. test benches were used to verify the functionality of the design, which was implemented in kintex-7 series fpga by using xilinx configuration tools. the device utilization summary for the targeted kintex-7 is shown in figure 4. figure 4: device utilization summary it is evidently clear from the summary that some ports of the devices were not efficiently utilized, especially the number of dsps. the motivation behind the use of kintex-7 was because it is robust, highly reconfigurable and have lower power consumption. the input/output lines were large due to the high level of parallelism of the design, which generally enhanced the speed of operation of the device at the expense of area or huge number of primitives employed. http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 114 3.2 verification of results the test benches used to verify the functionality of the design is shown in the appendix. the firesourcesignal entity was instantiated to provide rgb image data. the test stimuli were driven to the firesourcesignal inputs. the simulation in figure 5 shows how the image decoding module read that the rgb image frames simultaneously from memory and decoded them into pixel stream data array at the rising edge of the clock. then the grayscale conversion module read the rgb pixel stream data array and converted into grayscale image concurrently. the result of the grayscale conversion is depicted in figure 7. the result of sobel magnitude computation is depicted in figure 6 and that of sobel square root computation is shown in figure 7. figure 5: image pixel generation verification waveforms figure 6: grayscale image conversion verification waveforms http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 115 figure 7: sobel magnitude computation verification waveforms figure 8: sobel square root computation verification waveforms 3.3 fpga resource utilization the hardware accelerator consumes 15% of available luts (look up table), 24% of io (input-output) and 1% dsps. the specific hardware utilization in comparison with a similar work by authors in (choudhuri & roy, 2016) is presented in table 1. the accelerator has a shorter processing time and operate up to more than 200 mhz. http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 116 table 1. resource utilization and performance comparison author and date lut (%) io (%) dsp (%) latency(ms) choudhuri & roy, 2016. 1 7 1 3.2 our work 15 24 1 2.97 it is evident that the fpga accelerator has efficient resource utilization, and the input/output lines were large due to the high level of parallelism of the design, which generally enhanced the speed of operation of the device at the expense of area or huge number of primitives employed. the power consumption of the hardware accelerator is illustrated in figure 9. the dynamic power consumption is due to the switching between digital states and the static power consumption is because of leakages in the circuit. figure 9. power analysis of the design 4. conclusion this research work was embarked upon to develop fpga hardware accelerator for vision-based fire detection which could realize the acceleration of image decoding, grayscale conversion and edge detection. the design was verified and implemented using simulation, synthesis and configuration tools of xilinx inc. usa and matlab. the accelerator performs image decoding, grayscale conversion, sobel edge detection and pixel thresholding. the fpga accelerator was implemented xilinx kintex-7 fpga. the evaluation results based on the test benchmark dataset show that the accelerator could achieve good detection of fire edge features and were consistent with the processing results of the matlab code on personal computer. it consumes 15% lookup table (lut), 1% digital signal processor (dsp), 24% input-output (io), 92.062w dynamic and 1.029w device static power. the hardware accelerator which was developed as an intellectual property (ip) core can also be employed to perform image decoding, grayscale conversion, edge detection and thresholding in embedded vision, smart camera and video analytics applications. the following areas are recommended for future research. 1) interfacing camera and display monitor to the hardware accelerator for real-time fire detection. 2) employing advanced image processing and computer vision algorithms such as running average background subtraction, canny edge detection, etc. 3) designing embedded machine learning accelerator for fire outbreak prediction. 4) acknowledgement this study was supported by petroleum technology development fund (ptdf) with grant number ptdf/ed/lss/msc/ah/0657/19. http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 117 references abid, f., izeboudjen, n., & louiz, f. 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(2021). att squeeze u-net: a lightweight network for forest fire detection and recognition. ieee access, 9, 10858–10870. https://doi.org/10.1109/access.2021.3050628 http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):108-118. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abubakarhassan@unimaid.edu.ng 118 zhang, q., liu, f., li, x., & li, b. (2017). dissipation function and vibe based smoke detection in video. proceedings 2017 2nd international conference on multimedia and image processing, icmip 2017, 2017january, 325–329. https://doi.org/10.1109/icmip.2017.62 zhang, s. (2018). real time image processing on fpgas. university of liverpool. http://www.azojete.com.ng/ mailto:abubakarhassan@unimaid.edu.ng corresponding author’s email address: adesojioye@gmail.com 476 arid zone journal of engineering, technology & environment review article a review of blended non-edible green oil-based lubricants for enhanced performance in two-stroke engines a.a. oyedeji1,2*, m.s. abolarin1, s.a. lawal1, a.a. abdullahi1 and i.o. sadiq1 1department of mechanical engineering, school of infrastructure, process engineering and technology, federal university of technology, minna, nigeria 2national agency for science and engineering infrastructure, abuja, nigeria *corresponding author’s e-mail: adesojioye@gmail.com article information abstract the increasing environmental concerns associated with petroleum-based lubricants and growing demand for environmentally friendly solutions have spurred research into non-edible green oil-based lubricants, particularly for their application in twostroke engines. two-stroke engines, while offering advantages in power-to-weight ratio, pose environmental challenges due to their inherent design of the oil-fuel mixture. by utilizing non-edible sources, these lubricants help avoid competition with food crops, ensuring that edible oils remain available for human consumption, while non-edible oils present a promising solution. study have shown green oil enhances mechanical and thermal braking efficiency by 13% and 27%, while it reduces emission of co, co2 and hc approximately by 62%, 54% and 44% respectively compared to conventional lubricants. this review explores the properties of various non-edible green oils, including their physicochemical characteristics and potential as base stocks for lubricants production. furthermore, it explores the challenges and opportunities associated with these non-edible green oil-based lubricants. furthermore, it analyses previous research on the application of green oil-based lubricants in two-stroke engines, focusing on their impact on engine performance, emissions, and wear. the review also discusses the role of additives and blending in improving the overall performance of these lubricants and highlights the need for further research to optimise their application in twostroke engines. finally, the review identifies key research gaps and future directions, emphasizing the need for systematic investigation of blend ratios, exploration of environmentally friendly nano-additives, and rigorous engine testing to unlock the full potential of blended non-edible green oil-based lubricants for sustainable twostroke engine applications. this review underscores the potential of blended nonedible green oil-based lubricants as viable solutions for enhancing performance in two-stroke engines and encourages further research into their long-term effects and commercial viability. received: 17th march 2025 revised: 11th april 2025 accepted: 12th april 2025 keywords: non-edible oils biolubricants two-stroke engines sustainability environmental impact © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction environmental anxiety and regulatory measures to control carbon emissions and ecologically detrimental activities have, therefore, resulted in an enormous transformation toward sustainable practices in the automotive and industrial sectors in recent decades. this change of thinking fostered lots of research and development to discover alternative lubricant solutions that perform even better than conventional lubricants with no or minimal harm to the environment. lubricating oils play an important role in both automotive and industrial applications by minimizing wear and friction between the moving parts so as to maximize efficiency and increase equipment lifespan (ng et al., 2022). lubricants, in fact, happen to have a pivotal role in the smooth operation of internal combustion engines, particularly two-stroke engines; they enhance performance and longevity (musa and omisanya, 2021). the properties of lubricants required by two-stroke engines, which mix petrol and oil in one cycle, are that they azojete june 2025. vol.21(2):476-490 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/013 www.azojete.com.ng mailto:adesojioye@gmail.com mailto:adesojioye@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 477 resist high temperatures and have good wear-and-tear resistance. this particularity highlights the importance of selecting lubricants and formulating them such that engine life will be fully maximized. two-stroke engines are lighter than other engines, and they are also simple to make and use (krishna et al., 2016; alturki, 2017). at the same time, however, they add environmental problems by not burning the oil completely and running on oil-fuel mixtures (orman, 2023). though outlawed, two-stroke engines are in use for certain cases and when policies are made, the impact on the low-income earners and rural areas is usually ignored by lawmakers. all those applications where two-stroke engines are still popular are giving some motorcycles, especially off-road and dirt bikes, outboard motors for small boats, lawn mowers, small electric generators, and in small engines such as chainsaws, leaf blowers, and brush cutters (mang and dresel, 2007; zulfattah et al., 2019; ng et al., 2022; orman, 2023). two-stroke engines provide specific lubrication needs and issues due to their widespread application in anything from very small power tools to everyday motorbikes (mang and dressel, 2007; singh, 2011; zulfattah et al., 2019; ng et al., 2022). therefore, two-stroke engine needs a lubricant to provide essential lubrication at varying operating conditions and would withstand high temperatures (zulfattah et al., 2019) due to simplification in combustion cycle that has only two basic strokes. figure 1 shows working principle of two-stroke engine, it completes a power cycle in two piston strokes by using the piston's movement to control intake, compression, power, and exhaust through a system of ports and crankcase compression. this results in a simpler and often more power-dense engine for its size and weight, but typically with lower fuel efficiency and higher emissions compared to a fourstroke engine (ng et al., 2022). this cycle repeats with each rotation of the crankshaft, allowing for more power strokes per cycle. though traditionally dominant in this industry, petroleum-based lubricants are coming under more scrutiny for their potential environmental effects which drives research into more environmentally friendly options (kok and abdullah, 2019). when they burn in two-stroke engines, petroleum-based lubricants produce toxic hydrocarbons and particulate matter figures, which further contribute to air pollution and human health impacts (ng et al., 2022). therefore, there is an urgent need for more environmentally friendly lubricant solutions that could ideally deliver the same or even better performance and not have the detrimental adverse effects on the environment. while research into green oil-based lubricants has shown some promise, issues of food security and competition for resources come into the picture when edible oils are considered. this review examines the existing literature of non-edible green oil as base stock for biolubricant, blend of non-edible green oil-based and green oil-based lubricant for two-stroke engine applications, identifying the potential of such lubricants to improve performance and the environment, as well as the most prominent research gaps and future directions in terms of development and implementation. figure 1: two-stroke engine working principle 2. non-edible green oil as base stocks the most attractive prospective attributes of non-edible green oils are being renewable source and ecofriendly quality (kumar et al., 2022). green oil-based lubricants are renewable materials derived from plant and animal fats. compared to standard petroleum-based lubricants, which are limited due to finite fossil fuel resources and are heavily environmentally negative from their life cycles, green oil-based lubricants are more resourceful in various ways. such renewable materials are relatively abundant and biodegradable. they can be sourced from various plants that do not compete with food crops, thereby addressing the food versus energy crankcase air + fuel spark plug connecting rod piston exhaust http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 478 debate. such oils would be relatively much cheaper to manufacture than edible oils, thereby making them a godsend for the case that seeks production of green oil-based lubricants without competition with food sources (popoola & jibatswen, 2024; rockson-itiveh et al., 2024). table 1 presents examples of non-edible green oils such as: algae oil, jojoba oil, neem seed oil, karanja oil, castor oil, mahua oil, thevetia peruviana seed oil, and jatropha oil (patil et al., 2021), and their key physicochemical properties as applicable for the suitability assessment of the oils for lubricant applications. the current utilization of such non-edible oil seeds is extremely low, and their incorporation in lubricant formulations is expected to be a global move towards decreasing dependency on fossil fuels and for mitigating the negative environmental effects of dependency on such fuels (gheidan et al., 2022). they have proved exceedingly high in lubricity and renewability combined with availability, economy, biodegradability, high viscosity index, and flash point (ruggiero et al., 2016). suitable for different industrial applications, they can be grown in wastelands and forests and are much less environmentally friendly than mineral oils. for example, jatropha oil is well suited for high-temperature applications due to its high viscosity and oxidative stability (islam et al., 2018). also, yellow oleander oil has potential because of its favourable high viscosity index and good cold-flow properties, which make it suitable for industrial applications (choudhury and saha, 2022). selection of base oils does directly influence the performance of lubricant as well as its ability to meet certain application requirements. table 1: physicochemical properties summary of some key non-edible oils oil properties viscosity @ 40 0c (cst) viscosity @ 100 0c (cst) viscosity index pour point (0c) flash point (0c) reference algae * * * 5 – 8 110 ejim and kamen (2013) jojoba 26 7.5 257 * * el-adly et al. (2012) neem 109 22.6 * 25 265 idris et al. (2018) karanja 54.54 15.18 304.9 -1 220 agrawal et al. (2017) castor 280.6 77.5 33.4 -23.2 282 woma et al. (2019) mahua 37.18 11.66 325.6 18 210 agrawal et al. (2017) yellow oleander 31.76 7.89 235.59 -4 344 choudhury and saha (2022) jatropha 83.2 63.5 145.5 -11.2 264 woma et al. (2019) *not specified 2.1 non-edible green oil lubricant in 2013, chauhan and chhibber hinted that green oil-based lubricants could be formulated from non-edible oils from particular non-edible plant seeds with an oil yield of at least 30%. oil is usually extracted from kernels or seeds using mechanical, solvent, or enzymatic extraction methods (bilal et al., 2013). green oils from the non-edible class can find use in a variety of applications including cutting fluids for machining as well as lubricants for automotive and industrial machinery (katna et al., 2022, trzepieciński, et al., 2022). non-edible green oil lubricants represent a sustainable choice for lubrication requirements, balancing performance and environmental consideration. the growing demand for these lubricants will most likely be boosted by the industries eager to lessen their ecological impacts. non-edible green oils have been said to possess qualities that are sometimes matching or even superior to traditional lubricants in performance. they exhibit good lubrication properties, reducing wear and friction (silva et al., 2013). in order to meet these performance standards some other properties such as poor cold flow and poor oxidative stability need to be improved through the use of appropriate additives or formulation or chemical modification. http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 479 awoyale et al. (2011) set out to produce biodegradable grease from black date oil. extraction of the oil with n-hexane and hydrolysis with base oil, thickener, stearic acid, and additives were conducted. the tests verified the quality of grease, biodegradability, dropping point, and workability. the observations indicated consistency and biochemical oxygen demand were within acceptable limits. oseni et al. (2014) investigated the alternative use of yellow oleander oil for machine lubricant. the extracted oil displays characteristics that are comparable to oil lubricants popularly used. specifically, the oil has a free fatty acid percentage of 5.61%, specific gravity ranging from 0.89 to 0.92, and high flash and fire points of 350 0c and 375 0c respectively. orhevba and attamah (2016) studied biolubricants produced from neem seed oil for agricultural machinery. among their findings was a high fatty acid content of 3.7% which was reduced to 0.7% through methanol esterification. the viscosity index of developed lubricant is 10.9% better than the conventional lubricant. the biolubricant synthesized is used as a substitute for petroleum-based lubricants in industrial as well as agricultural machines. agrawal et al. (2017) studied the physicochemical properties of crude mahua and karanja oils. the final products which is karanja and mahua biolubricants were found to have higher viscosity index and lower oxidation stability compare to two stroke lubricant. these biolubricants can replace significant quantities of mineral oil as base oil. owuna et al. (2018a) research use calabash seed oil to develop a motor oil lubricant. blend of calabash seed oil, synthetic oil and additives were used to formulate a lubricant with better characteristics meeting engine oil specifications for eco-friendly lubricant with the same quality as synthetic oil. according to idris et al. (2018), neem oil can acts as an efficient lubricant in both light and heavy automotive systems. the neem oil flash point was determined to be 265°c, which aligns with the sae 30 and sae 40 flash point values. however, given its pour point of 25 0c, it is less effective in cold climates. jatropha oil as a base oil for biolubricant production was assessed by woma et al. (2019). jatropha oil was studied for its physicochemical, rheological, thermo-oxidative, and corrosion properties. a comparison was drawn on these properties with that of a commercial lubricant sae20w50. though sae 20w50 proved superior to that of jatropha oil in all test parameters, jatropha oil has a much higher viscosity index than sae 20w50. the physicochemical, oxidative, and tribological characteristics of chaulmoogra oil as a lubricant base stock were assessed by salaji and jayadas (2021). at 100°c, the oil's viscosity is 9.2 cst, and its viscosity index is 166. according to the study, chaulmoogra oil has a higher wear scar diameter but a better coefficient of friction than commercial lubricants. wear performance was enhanced by the use of zinc dialkyl dithiophosphate, an antiwear additive. chaulmoogra oil is a great base stock for lubricants because of its non-edible nature and environmental benefits. bulus and odetoye (2022) studied the use of parinari and neem seed oils as environmentally friendly biolubricants. the seed oils were processed by double transesterification method with trimethylolpropane. from the physicochemical properties of the resultant biolubricants, it shows that they have potential as sustainable alternatives to petroleum-based lubricants. choudhury and saha (2022) evaluated the use of thevetia peruviana oil (tpo) as a biolubricant after analysis of its physicochemical, rheological and tribological properties. the values reported were as follows for tpo: acid value 1.383± 0.015 mg koh, pour point -4 ±0.231 0c, and flash point 344±0.04 0c. its viscosity index was 235.59. meanwhile, the wear scar diameter was found to be 0.462±0.001 mm. for all intents and purposes, tpo is 50% better than expensive commercial lubricants on account of its viscosity index despite very marginal pour point temperature while tpo exhibit a lowest friction coefficient and wear scar diameter than sunflower and jatropha oil. however, conventional lubricant has lower wear scar diameter due to present of strong antiwear additives. tpo has good thermo-oxidative stability. these findings make tpo an excellent candidate for a base stock as a bio-lubricant. bindra et al. (2023) investigated the tribological performance of a novel bio-lubricant blend composed of castor oil as the base fluid with a 20% addition of neem oil as base fluids for bio-based lubricants. the results indicate a substantial improvement in tribological properties with the inclusion of neem oil, demonstrating approximately a 70% reduction in wear rate under specific conditions. using the sonification approach, basiron et al. (2023) developed environmentally friendly lubricants by blending non-edible castor and jatropha oils with a mineral oil (sae 15w40). they next assessed the lubricants' tribological performance. a four-ball tribometer was used to evaluate their wear and friction characteristics in accordance with astm guidelines. superior tribological qualities were obtained by the optimal formulation as 80% mineral oil, 10% castor oil, and 10% jatropha oil. prasanth and rahul (2024) presented and discussed the test of the physicochemical, rheological, and tribological properties of transesterified grape seed oil, neem oil, and waste cooking oil as potential green oilhttp://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 480 based lubricants. the results show that transesterification improves the properties of oils, but the sudden change may cause them to perform poorly tribologically. the requirement now is to optimally numerically balance these properties in the lubricant compositions. 2.2 blends of non-edible green oils lubricant blending of other green oils, which have better properties, into the base oil to improve its properties is another viable option (ting and chen, 2011). blending different vegetable oils is said to also modify the chemical composition of the oil, which in turn modifies the physicochemical properties of the oil (wahyudi et al., 2018). such plant oil blending can result in oils with sustainable viscosity that do not require the use of any external additives (siddique et al., 2010). according to salimon et al. (2010); sharma et al. (2017); owuna et al. (2018b); and jeevan and jayaram (2018) revealed that blending has been proven to improve on the flash point, pour point, viscosity and oxidative stability of lubricants based on green oils. blend of green oils can enhance tribological performance compared to mineral oil, as shown in table 2. according to jain and suhane (2014), tribological properties of castor and mahua oils blend was analyzed. a castor and mahua oil on 80:20 mixture was confirmed as a candidate for maintenance, especially gear applications. the properties of mixed neem oil and mineral oil followed by their effects on engine emission were studied by sharma et al. (2017). the blended oil had better anti-wear properties and lesser viscosity as compared to normal mineral oil. bahari et al. (2018) investigated the friction and wear behavior of the lubricants being based on mineral and vegetable oils at high-pressure and high-temperature environments. results of the investigations indicated that even if the friction coefficient of soybean oil was greater than that of pure palm oil, the tribological characteristics of green oils were far superior over that of mineral oil. in a comparison of coconut oil and mustard oil, sajeeb and rajendrakumar (2019) found that a 50% blend of mustard oil and coconut oil exhibited superior performance in tribological and cold flow properties, thereby becoming a biodegradable alternative for mineral oil production. pathmasiri et al. (2022) studied palm-castor oil blend for industrial lubricant application. they studied kinematic viscosity, flash point, demulsibility, pour point, copper corrosion, and total acid number. the findings showed that with the blending of 40% castor oil to 60% palm oil, the properties were similar to sae30. araujo et al. (2022) studied the production of biolubricants using vegetable oil blends without any chemical modifications. the biolubricant formulation utilizes castor oil, jatropha curcas, macauba pulp, and macauba kernel oil. the findings showed that macauba pulp oil performs better than the chemically modified oil and can serve as a potential base oil for biolubricant and biodiesel. table 2: performance comparison of green oil blends lubricant blend friction coefficient wear resistance comparison to conventional lubricants reference castor oil + neem oil reduced friction coefficient improved (70% reduction in wear rate) superior to conventional lubricant bindra et al. (2023) coconut oil + mustard friction reduction superior wear performance superior to conventional lubricant sajeeb and rajendrakumar (2019) palm oil + mineral oil lowest coefficient of friction lower wear scar diameter better than mineral oil zulfattah et al. (2019) 35% mahua oil + 65% castor oil lower the friction coefficient by 24% reduced wear scar diameter the blend shows superior tribological characteristics over mineral oil (khalid and ali, 2020) palm oil castor oil (60:40) properties similar to sae30 properties similar to sae30 properties comparable to standard lubricant pathmasiri et al. (2022) neem oil + mineral oil better anti-friction better anti-wear properties blended oil had better anti-wear properties sharma et al. (2017) mineral oil + castor oil + jatropha oil (80:10:10) superior tribological qualities superior tribological qualities optimal formulation shows better performance basiron et al. (2023) http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 481 3. strategies for improving performance of lubricant lubricants durability along with its superior quality and usefulness need improvement depending on the type of additives used to meet certain performance standards. additives are meant to address various operational challenges and enhance the service life of the lubricant. additives are also important for improving the performance of nonedible green oil-based lubricants (garba et al., 2019). viscosity index improvers are one class of additives employed to improve lubricants by assuring a reliable performance in a wide range of working temperatures by checking their tendency to thin out at higher temperatures and to thicken at lower ones (del río et al., 2022). friction modifiers are essential in industrial and automotive applications for reducing surface interaction, energy losses, and direct metal-to-metal contact; thus, increasing the efficiency of the system within which they find their application (ameh et al., 2021). anti-wear and extreme pressure additives essentially protect surfaces from wear and damage when high loads and stresses are present, especially in applications such as gearboxes, hydraulic systems, and high-performance engines (omrani et al., 2019). antioxidants deter the oxidation of lubricants to avoid varnish and sludge. they also enhance thermal stability and prolong lifespan with relatively good performance at high temperatures (wang et al., 2020). antioxidants become more important in cases where lubricants are exposed to high temperature and oxidative stress. rust and corrosion inhibitors shield the metal surfaces from moisture and other corrosive agents to lengthen the lifespan of the machinery and to prevent repair costs, particularly in adverse weather conditions (puhan, 2021). most of these additives are toxic heavy metals, such as zinc, antimony, sulfur, and phosphorus, which help in upgrading the performance of lubricants for greater endurance. some oil additives pose environmental threats (vazquez-duhalt, 1989; henry, 1998; madanhire et al., 2016). however, the environmental effects of some additives need serious attention. a possibly promising research area will be an exploration of bio-based additives from renewable resources and nanotechnology. 4. nanotechnology and lubricants this is the end of the main introduction and it describesnano-technology in lubricant properties via manipulating substances at nanoscale, thermal stability enhancement, friction reduction, wear protection (wang et al., 2020). therefore, these developments owe their uniqueness to the three physical and chemical properties of nanoparticles, different from those of bulk materials (abdullah et al., 2019; abdel-rehim et al., 2021). nanoparticles like boron nitride or molybdenum disulphide get into sliding contact surfaces and act as wear-resisting agents by virtue of their small sizes and larger surface areas that minimize wear and maximize wear resistance (azman and samion, 2019). nanoparticles like graphene, carbon nanotubes, and fullerene increase the performance of lubricants by aiding the formation of a smooth sliding surface, thereby minimizing friction loss with energy. liu et al. (2020) add that reducing friction in any application will lower operating temperature, conserve energy, and hence create an efficient mechanical system. nanoparticles of metal oxides such as zinc oxide and titanium oxide improve thermal stability of lubricants, allowing them to perform at higher temperatures without degrading. enhanced thermal stability will stabilize the lubricant's performance and viscosity by preventing oxidation and deterioration, which in turn might decrease effectiveness (liu et al., 2020). additives for nanolubricants, including inorganic oxide nanoparticles and carbon-based nanomaterials, are characterized by unique functionalities that increase the performance of standard lubricants. metal oxides including cerium oxide, zinc oxide, and titanium oxide are widely used in lubricants as nanoscale additives. these additives enhance several properties of lubricants, such as wear resistance, friction reduction, loadbearing, oxidative stability, thermal stability, and thermal conductivity (binu et al., 2014; ali and salam, 2020; abdullah et al., 2020). graphene, carbon nanotubes (cnts), and fullerene are carbon-based nanomaterials with excellent lubricating properties. graphene develops a strong, low-shear-strength layer on contact surfaces mixed with lubricants, thereby reducing wear and friction. due to their unique cylindrical nanostructure, cnts augment load transport and friction reduction of lubricants by ensuring smooth surface contact, while fullerenes serve as nano-ball-bearings that reduce wear and friction (htwe et al., 2024). heat-conductive nanoparticles including metal oxides and graphene may optimize the performance and efficiency of lubricants through improved heat dissipation and prevention of overheating and breakdown in higher temperature conditions in mechanical systems (kumar and upadhyay, 2021). http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 482 the search for high-performance environmentally friendly lubricating system with the introduction of nano additives in lubricants has been gaining momentum (suresha et al., 2020). the introduction of nano lubricants additives with the aid of nanotechnology creates a wider horizon in lubricating technology as it enhances the properties of wear, friction, and thermal stability. 5. green oil-based lubricant for two-stroke engine two-stroke engines necessarily require specific lubricants that mix with the fuel to ensure proper internal distribution and lubrication (zulfattah et al., 2019). high power-to-weight ratio running two-stroke engines evidently require lubricants that can resist high pressures and temperatures (dangayach et al., 2021). specialized two-stroke engine lubricants aim to cut down on exhaust emissions, fuel consumption, and engine wear (orman, 2023). green oils derived from plant and animal fats have advantages such as less toxicity, biodegradability, and possible parameter modification to reach performance standards for two-stroke engines. lubricants based on green oils help to minimize carbon emissions and environmental destruction, thus enhancing the life of the engine and its efficiency, essentials for sustainable industrial operations (galgat et al., 2021). on account of their exceptional lubricity and thermal durability, non-edible green oils contain natural esters and fatty acids suitable for high-performance applications like two-stroke engines. the use of non-edible green oil for lubricants in two-stroke engines represents a significant advancement towards a cleaner and more sustainable future for small engine applications with higher demands. life cycle assessments (lcas) by methes energies international ltd., reveal that biolubricants have a carbon footprint 29-67% lower than their mineral based counterparts, meaning biolubricants demonstrate a significant reduction in emissions and overall environmental impact compared to traditional, mineral based lubricants. singh (2011) developed a biodegradable two-stroke lubricant based on castor, coconut and palm oils blend with a performance additive and fatty acid derived from acetylated castor oil. the oil was observed to reduce smoke by 50–70%, being in compliance with product specifications. taguchi's analysis for optimization of the transesterification process for the synthesis of sunflower methyl ester was done by senthilkumar et al. in 2015. the study revealed that a blend of 20% sunflower methyl ester reduced unburned hydrocarbons and nitrogen oxides in comparison with commercial 2t oil. dehghani et al. (2015) evaluated biolubricants made from castor oil, palm oil, and waste cooking oil in a twostroke gasoline engine, under an environmentally friendly alternative program. these materials were analyzed for engine performance and emissions using the technique for order of preference by similarity to ideal solution (topsis) method and found that palm oil-based biolubricants offered the most promising option. the study found that biolubricants performed better than two-stroke lubricants. iresh et al. (2016) developed a green oil-based lubricant from a blend of sunflower, soybean, palm, and castor oils and compared it with conventional synthetic lubricants 2t oil. the result demonstrates that the green oil enhances mechanical and thermal braking efficiency by 13% and 27% respectively, while it reduces emission of co, co2 and hc approximately by 62%, 54% and 44% respectively compared to synthetic mak 2t engine oil. zulfattah et al. (2019) studied the effect of bio-lubricants on the emissions and engine failures due to spark plug fouling in a two-stroke engine. different lubricant samples were made by trimethylolpropane trioleate (tmpto) blends made from palm oil and mineral oil. 20% tmpto, mineral oil blend showed better performance in emissions and engine performance while 15% tmpto blend had the lowest coefficient of friction and wear scar diameter among. ng et al. (2022) reported the use of palm fatty acid distillate (pfad) as a base oil for biolubricants intended for two-stroke engine oils. neopentyl glycol was chemically modified using pfad in an 84% yield and 82% conversion. the base oil was in agreement with japanese automotive standards organization (jaso) m345:2018 requirements for two-stroke engine lubricants. 5.1 benefits of green oil-based lubricant for two-stroke engine http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 483 i. green oil-based lubricants are one of the solutions available to wet the promoters of noise and hazardous exhaust emissions from two-stroke engines (khalid and ali, 2020), where they add at least 250 grams to a relatively high amount of air pollution. the less hazardous bio-degradable bases are relatively cleaner and emit pollutants or burn cleaner, improving the air quality and lowering the impact of these engines on the surroundings. ii. green oil-based lubricants increase fuel economy and are instrumental in preventing deposits and wear in two-stroke engines. this reduces friction as well as enhances efficiency in engines and prevents oxidation and thermal degradation. its oxidative stability makes it a point of keeping the engine clean and prolongs the life of the parts (khalid and ali, 2020). iii. green oil-based lubricants prevent wear and deposits in a two-stroke engine and minimize wear because they keep the reformers from coming in contact with metallic surfaces, as they dissolve and disperse deposits in the engine, achieving agent cleanliness and peak performance (gheidan et al., 2022). 6. challenges and opportunities the use of petroleum-based lubricants in two-stroke engines release harmful gases into the environment, which includes toxic gases in considerable amounts: unburned hydrocarbon, carbon monoxide, and particulate matter (alander et al., 2005; ng et al., 2022). engine emission tests were conducted to investigate the influence of the usage of green oil-based lubricants. it was found that such lubricants were able to reduce emissions (senthilkumar et al., 2015; zulfattah et al., 2019; ng et al., 2022), while phosphate found in exhaust particles in a two-stroke engine from mineral-based oil was absent with the green oil-based lubricant (alander et al., 2005). non-edible green oils have a lot of promise, but many challenges still exist concerning their lubrication of engines. non-edible oils possess lower thermo-oxidative stability compared to mineral oils, which leads to the degradation of vegetable oils at high engine operating temperatures. furthermore, pour point and lowtemperature behaviour can also be limiting. to be applicable in engine lubrication, non-edible green oils, noted for their high viscosity and poor low-temperature fluidity, need modifications, which can be carried out through chemical modifications such as esterification, transesterification, hydrogenation and epoxidation, which, although contributes to the overall costing, but helps to improve their lubricity, thermo-oxidative stability, viscosity index, and pour point thereby enhancing their suitability as lubricants (cecilia et al., 2020; rocksonitiveh et al., 2024). epoxidation process involves converting unsaturated fatty acids into epoxides thereby enhancing the oil's stability and suitability for applications like biolubricants, hydrogenati on reduces the unsaturation of fatty acids, improving the oil's shelf life and stability while esterification / transesterification are commonly used to produce biodiesel / biolubricant, this process transform an ester to another ester with higher thermal stability (odi-owei et al., 2021). some of these modifications require expensive catalysts or complex processes, which can increase production costs and limit scalability, potentially making these products less competitive in the market. these modifications add tremendous value to crucial lubricant properties. an example of their benefits includes increasing thermo-oxidative stability, vital for efficient operation in many high-temperature engines, as well as improve low-temperature fluidity resulting in performance enhancement. the enhanced thermooxidative stability minimizes deposits/sludge formation, as well as wear and reduces performance degradation. the smoother and less friction-ridden engine overall naturally contributes to a longer engine life, and probably better engine performance. in addition, the changes may affect emissions, leading to harmful exhaust reduction. chemical modification method has been explored for the same purpose by wagner et al. (2001); bilal et al. (2013); soni and agarwal (2014); musa et al. (2015); umaru et al. (2016); orhevba and attamah (2016); agrawal et al. (2017); menkiti et al. (2017); panchal et al. (2017); woma et al. (2019); bulus and odetoye (2022). the chemical process is quite an energyand water-intensive process requiring many reagents; the concomitant processes of separation and purification of the desired product generate waste and by-products leading to increased production cost (panchal et al., 2017; araujo et al., 2022). prasanth and rahul (2024) affirmed that transesterification improves oil properties but causes a deterioration of its tribological performance. moreover, cecilia et al. (2020) commented that chemical modification improves thermo-oxidative stability and lubricity and makes them appropriate for different applications. the drawbacks, however, are feedstock requirements, high reaction temperature, and cost. yet, possibilities to overcome these limitations abound. http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 484 different chemical modification processes have varying costs associated with reagents, catalysts, energy consumption, and processing steps. the costs for heating, cooling, mixing, and other utilities during the chemical modification process and the type and amount of catalysts and chemical reagents used in the modification process contribute to the overall cost. the cost of purification and separation steps post-chemical modification is also increased. biolubricants, including those that are chemically modified, generally have a higher initial cost compared to conventional petroleum-based lubricants. some sources suggest they can be 30-40% or even twice as expensive (potera, 2009). biolubricants that are chemically modified have higher initial cost compared to conventional petroleum-based lubricants while biolubricant produced by the additive route are lower than the chemical modification route (khan et al., 2022). techno-economic analysis by khan et al., (2022) reveals that the highest unit cost for producing 1-kg estolide among chemical modification routes, while additive-based jatropha biolubricant has lower unit cost per kilogram. various non-edible green oils, when blended, can contribute to the optimisation of specific lubricant properties to meet engine requirements or applications. the proper selection of the various green oil combinations can lead to the fine-tuning of viscosities, viscosity indexes, pour points, oxidation stability, and tribological properties. the blends of different non-edible green oils are synergistic and improve the overall performance of the lubricants. for instance, a balanced lubricant can be created by combining oils with high viscosity indices and low-temperature properties. state-of-the-art techniques were then engaged in optimising viscosity, thermal stability and lubrication properties to ensure reliable operation of two-stroke engines based on nonedible green oil lubricants. even though green oil-based lubricants have great potential, there are still major issues with using them directly because they struggle with thermo-oxidative stability and performance in cold temperatures. these shortcomings, often addressed through energy-intensive and costly chemical modifications that can even negatively impact tribological properties, necessitate future research focused on exploring blends of non-edible green oils that have not been chemically modified and environmentally friendly additives. 6.1 economic feasibility of adopting green oils the economic viability of moving to green oil-based lubricants is a complex matter involving several factors to be considered in terms of the cost of going green in the short term, potential long-term savings, and the positive environmental implications of the switch. although it is the initial price point that seems to be the most daunting aspect, an extensive exploration offers a much more diverse set of economic variables. generally, biolubricants tend to have higher initial costs and are 30-40% more expensive compared to traditional mineral oil-based lubricants (singh, 2022; ilmi et al., 2024). this is frequently attributed to the costs associated with sourcing, processing, and sometimes chemically modifying vegetable oils to meet performance specifications. production costs can vary significantly depending on the specific non-edible oil source, extraction methods, and refining processes involved. in addition, additives can enhance green oil performance but also increase cost, particularly nano-additives, which offer friction reduction, wear protection, and thermal stability but can be relatively expensive. green oils, despite the higher initial costs, may provide some potential economic benefits in the long run, including less frequent machine maintenance for cost savings, better fuel economy due to lower friction and cost savings from waste disposal, as well as liabilities associated with dangerous mineral oil waste. 7. research gap and future research directions subsequent investigations should focus on mixtures of non-edible green oils that have not undergone chemical changes to cater for the environmental aspect and cost of making green oil-based lubricant base oil compositions. to fully determine the long-term effects of blends of non-edible green oil-based lubricants on engine components, overall engine performance, and emissions, further investigation is required. useful laboratory results need wider field experiments and real-life tests to validate results and enhance end-user confidence. improving the properties of non-edible green lubricants may involve looking into additive technologies such as nano-additives and novel base green oil sources. some of the important areas identified for future research motion are: • optimization of blend ratios: systematic study of different non-edible green oil blends to know optimal blends combinations for specific two-stroke engine applications. http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 476-490. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adesojioye@gmail.com 485 • environment-friendly nano-additives that can reduce the drawbacks of green oils and improve lubricant performance. • carrying out rigorous engine tests on the blended green oil-based lubricants to evaluate performance in real-world two-stroke engine operating conditions. 8. conclusion the evolution from edible oil-based lubricants to non-edible oil-based lubricants, which also has potential for use in two-stroke engine applications, is a tremendous leap in the direction of green lubrication options. the study shows that potential of non-edible green oil-based lubricants to improve the performance of two-stroke engines while minimizing environmental damage. the use of non-edible sources for these lubricants helps to avoid competition with food crops, ensuring the availability of edible oils for human consumption. these lubricants have demonstrated the potential to reduce emissions and enhance engine efficiency. however, challenges such as lower thermo-oxidative stability and poor low-temperature behaviour need to be addressed. blending different non-edible green oils and the use of additives, including nanoparticles, are identified as promising strategies to overcome these limitations and optimize lubricant properties. further research is recommended to explore optimal blend ratios, investigate environmentally friendly nano-additives, and conduct rigorous engine tests to validate the performance of these lubricants under real-world conditions. references abdel-rehim, aa., akl, s. and elsoudy, s. 2021. investigation of the tribological behaviour of mineral lubricant using copper oxide nano additives. lubricants. 9(16): 1-20. https://doi.org/10.3390/ lubricants9020016 abdollah, mfb., amiruddin, h. and jamallulil, ad. 2020. experimental analysis of tribological performance of palm oil blended with hexagonal boron nitride nanoparticles as an environment-friendly lubricant. the international journal of advanced manufacturing technology, 106(9): 4183-4191. abdullah, mihc., othman, a., abdullah, r., and abdollah, mf. 2019. optimization on the nanoparticles stability in liquid phased condition by using taguchi analysis. journal of advanced research in fluid mechanics and thermal sciences, 61(1): 129-139. agrawal, aj., karadbhajne, vy., agrawal, ps., arekar, ps. and chakole, np. 2017. synthesis of biolubricants from non-edible oils. international research journal of engineering and technology, 4(7): 1753-1757. alander, t., antikainen, e., raunemaa, t., elonen, e., rautiola, a., and torkkell, k. 2005. particle emissions from a small two-stroke engine: effects of fuel, lubricating oil, and exhaust after treatment on particle characteristics. aerosol science and technology, 39(2): 151-161. ali, ari. and salam, b. 2020. a review on nanofluid: preparation, stability, thermophysical properties, heat transfer characteristics and application. sn appl sci. 2(10): 1636. https://doi.org/10.1007/ s42452020034271 alturki, w. 2017. four-stroke and two-stroke marine engines comparison and application. international journal of engineering research and applications, 7(43): 49-56. ameh, j., odi-owei, s., sodiki, j. and nkoi, b. 2021. effects of mango seed and castor seed oils with nanoparticle additives on friction and wear performance of steel-steel contacts. journal of newviews in engineering and technology, 3(2): 46-55. araujo, mfrs., pasa, vmd. and corgozinho, cnc. 2022. simultaneous optimization on biolubricants obtained through a quaternary mixture of vegetable oils: application of the desirability function. the journal of engineering and exact sciences, 8(2): 13798-13815. awoyale, aa., odubuyi, oa. eloka-eboka, ac. 2011. production and testing of biodegradable grease from black-date (canarium schweinfurthii) oil. journal of innovative research in engineering and sciences, 2(4): 223-233. azman, nf. and samion, s. 2019. dispersion stability and lubrication mechanism of nanolubricants: a review. international journal of precision engineering and manufacturing-green technology. 6: 393-414. http://www.azojete.com.ng/ mailto:adesojioye@gmail.com arid zone journal of engineering, technology and environment, june 2025; 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and arslan, a. 2019. effect of bio-based lubricant towards emissions and engine breakdown due to spark plug fouling in a two-stroke engine. journal of cleaner production, 221: 215-223. http://www.azojete.com.ng/ mailto:adesojioye@gmail.com https://doi.org/10.3390/en11020394 corresponding author’s email address: 790 arid zone journal of engineering, technology & environment original research article design and analysis of flight performance of a hybrid energy source for unmanned aerial vehicle d. n.o. eleazer1, u. e. uche2*, m. tajudeen3 and i. m. b. omiogbemi2 1department of aerospace engineering, faculty of air engineering air force institute of technology, kaduna, nigeria, 2department of mechanical engineering, air force institute of technology, kaduna, nigeria, 3department of material and metallurgical engineering, air force institute of technology, kaduna, nigeria. *corresponding author’s email address: eaumie@gmail.com article information abstract this study presents a hybrid energy harvesting system for unmanned aerial vehicle (uav), that integrates solar power and hydrogen fuel cells to enhance flight performance. the study commenced with the analysis of the case study uav flight power design specifications using analytical methods. the estimation of number of solar cells and the hybridization of the solar and hydrogen fuel cells. a computer aided design (cad) model of the solar cell arrangement is created using industrial software which enables the visualization of the arrangement on the wing in a virtual environment. the mission performance analysis was carried out using excel tool and matrix laboratory (matlab). the redesigned system increased available power to 580 watts with a weight penalty of 1.5 kg thereby reducing the payload mass from 4.627 kg to 3.085 kg. to assess the structural implications of this result, a stress analysis was performed using computeraided three-dimensional interactive application (catia) and abaqus software which revealed a negligible failure index of 0.000757. the hybrid system achieved a 120% increase in power that extended the endurance from 4.2 hours to 16.3 hours and the range from 6 km to 230 km. the design offers a promising solution for enhanced uav performance. submitted: 30 may, 2024 revised: 29 june, 2024 accepted: 08 july, 2024 keywords: hydrogen fuel cell solar hybridization endurance range © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the hybrid energy harvesting uav designed by the 2021/2022 msc research students at air force institute of technology was used as the test bed for this paper. the case study uav has an endurance of about four hours using a combination of a 7s 4000 mah li-po battery and hydrogen fuel cell system as its power source (afit alta, 2022). the design goal was to integrate the fuel cell to increase the endurance and range parameters of the uav, as well as power the onboard electronic or avionics components. the increase in the endurance is significant. however, at instances where there is strong turbulence resisting the motion of the uav, the endurance calculated for the mission falls short and the liquid hydrogen fuel is not sufficient to accomplish the mission. therefore, with an appreciable wing geometry, solar cell is selected based on its environmental friendliness and energy conversion efficiency compared to other energy sources to counter this limitation. the solar cells will be sized and arranged in series on the upper surface of the plan form area of the wing to provide an operating voltage higher than the battery voltage to be able to charge the battery and onboard avionic equipment. the solar cells will be arranged to flush with the wing surface in order not to increase drag. collaterally, integration of the solar cells on to the wing of the uav is accompanied with some mass complexities which will either increase or decrease the operational empty weight of the uav. (saravanakumar et al., 2023; wang et al., 2022; matlock et al., 2019). unmanned aerial vehicle (uav), commonly known as drone is an aircraft without any human pilot or crew onboard. they are controlled remotely with the aid of sensors that transmits and receive radio signals for communication (mohammadnia et al.,2020). the uav under study, was designed to have an all-up mass of 10 kg and a wingspan of about 4.2 m. the image of the aircraft is shown in figure 1. it serves as the case study hybrid energy uav for flight power performance analysis. azojete december 2024. vol.20(4):790-812 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:eaumie@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 791 figure 1: hydrogen fuel cell uav (afit-alta, 2022) in recent times, uavs play a major role in global society due to their ability to carry payloads, operate and monitor complex scenarios where the presence of onboard human pilots are needless. uavs are however constrained by power, which invariably affects their performance during most flight missions. typically, therefore, the mission profiles of these uav’s are limited by insufficient range and endurance. its main source of power is either engine or batteries. a hybrid energy harvesting system offers increased flexibility into the uav design by allowing choice of specific instrument regardless of the electrical bus and to expand the system as system requirement changes. some of the energy harvesting technologies used to generate electricity for air vehicles include piezoelectric process, thermoelectric process, electromagnetic process and photovoltaic techniques. the basic components of a conventional energy harvesting system is depicted in figure1. it includes the energy input source, detection and storage and the loads to which the scavenged energy will be supplied to. components required to achieve the process include transducers to convert ambient energy to electrical energy, power management circuit to adjust the harvested energy based on the needs of the loads embedded in the uav and lastly, an energy storage buffer to deliver the high power to the load. figure 2: conventional energy harvesting system (prauzek et al., 2018) various concepts are employed in the utilization of solar energy, but one of the ways proposed to tap maximum amount of electrical energy efficiently and effectively from the solar is a hybrid combination of solar panels and thermoelectric generators (mohammadnia et al., 2020) thermoelectric generator (teg) is a solid-state device that converts heat energy to electrical power by means of semiconductor charge carriers serving as a working fluid. they function like heat engines but are less massive with no moving parts (rezania and rosendahl, 2012). their advantages are that they do not require any fluid for fuel or cooling, making them non-orientation dependent and allowing for use in zero-gravity or deep-sea applications. in this system the solar produces heat in addition to the photons that are focused onto the panels. the heat energy is tapped and converted into electrical energy to boost the energy produced by the solar panels. ozbek et al., (2021) used a polymer electrolyte membrane (pem) fuel cell – li-po batteries as a hybrid energy harvester to produce more wattage power for the fixed wing uavs to achieve large endurance. in his experiment, he observed that, approximately 160 – 170w power was met by the fuel cell when no preconditions were applied. the fuel cells converted the chemical energy of the fuel into direct current electricity through electrochemical process without any moving parts (barbir, 2012). also made studies into providing some regenerative power from some avionics or electronic components installed in uavs by equipping it with energy harvesters which can scavenge energy from radio frequency (rf) using relays have been carried out. however, the energy generated is not enough to power large loads. citroni et al. (2019) ambient source detector (sensors) energy converter energy storage module energy consumptio n module http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 792 therefore proposed a hybrid energy harvesting system that can recover energy from solar and rf energy sources at the same time to significantly improve the energy required for long flights. the rf energy from the surroundings serves as an alternative power source for powering the uav when there is insufficient or no radiation to generate electrical power from the solar panels. furthermore, there is the need to consider better aerodynamics properties irrespective of design modifications to increase the overall uav performance during its flight missions (wang et al., 2019). the focus of the study therefore includes the analysis and design of takeoff, landing, climb and cruise power supply system and its performance evaluation in terms of the uav endurance, range and other flight performance indicators. 2. materials and methods 2.1 materials the aircraft understudied has design specifications as shown in the table 1. table 1: design specification of case study uav parameters values design gross weight 10 kg maximum ceiling altitude 10,000 ft. maximum range 6 km design cruise speed 14.3 m/s maximum balanced field length <100 m engine axi 4130/20 electric motor wing area 1.009835 m2 wingspan 4.28 m the main battery power source was augmented with a hydrogen fuel cell stack on a 7s 4000 mah li-po battery. 2.2 methods 2.2.1 uav power requirement 2.2.1.1 determination of take-off power requirement power (p) required for the uav to successfully achieve a complete take-off is estimated using the formula (malik, 2020). 𝑃 = 𝑇ℎ𝑟𝑢𝑠𝑡 × 𝑇𝑎𝑘𝑒 − 𝑜𝑓𝑓 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 . (1) where the thrust (t) is estimated as; 𝑇 = 𝐷 +𝑊𝑠𝑖𝑛𝛾 (2) where the climb angle of the aircraft is represented as 𝛾, d is the drag of the uav and w is the weight of the uav. 𝐷 = 1 2 𝜌𝑉𝑠 2𝑆[𝐶𝐷0 + 𝑘𝐶𝐿𝑚𝑎𝑥 2 ] (3) also, the free stream velocity is expressed as; http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 793 𝑉𝑠 = √ 2𝑊 𝜌𝑆𝐶𝐿𝑚𝑎𝑥 (4) therefore, assuming sea level conditions, the density is assumed to be 1.225 𝑘𝑔𝑚−3, and the uav specification,𝐶𝐿𝑚𝑎𝑥 = 1.38, 𝜌 = 1.225 𝑘𝑔𝑚 −3,𝑊 = 10 𝑘𝑔, 𝑆 = 1.009835 𝑚2the free stream velocity is estimated using equation 4 (clark, 2018). power required for the uav to successfully achieve a complete take-off is therefore estimated using equation 1, 2,3 and 4, assuming sea level conditions of density 1.225 𝑘𝑔𝑚−3, and taking the 𝐶𝐿 ,𝑊 𝑎𝑛𝑑 𝑆 from the case study uav specification to first obtain the free stream velocity as follows: 𝐶𝐿𝑚𝑎𝑥 = 1.38, 𝜌 = 1.225 𝑘𝑔𝑚 −3,𝑊 = 10 𝑘𝑔, 𝑆 = 1.009835 𝑚2 𝑉𝑠 = √ 2(10 × 9.81) 1.225 × 1.009835 × 1.38 = 10.7205 𝑚𝑠−1 therefore, the minimum speed at which the uav can be maintained to generate lift for a successful take-off is estimated to be 10.7205 𝑚𝑠−1. to ensure a safety margin during take-off, a liftoff velocity is also estimated which is about 20% greater than the stall velocity is obtain using equation 5. 𝑉𝐿𝑂 = 1.2𝑉𝑠 (5) 𝑉𝐿𝑂 = 1.2(10.7205) = 12.8646 𝑚𝑠 −𝑠 the drag the uav will be subjected to during take-off is also estimated using equation 3 to obtain 𝐷 = 1 2 (1.225) × (10.7205)2 × (1.009835) × [0.0109 + 0.0446(1.38)2 = 6.7464 𝑁 considering a climb angle of 5 degrees, the take-off thrust (t) is projected from equation 2 𝑇 = 6.7464 + 10(9.81) sin(5) 𝑇 = 15.2963 𝑁 therefore, having estimated the value for the take-off thrust and lift-off velocity, the power required by the uav for take-off is estimated from equation 1. 𝑃 = 15.2963 × 12.8646 = 196.7820 𝑊𝑎𝑡𝑡𝑠 therefore, the power required to achieve a complete take-off by clearing the 50 feet obstacle height is 197 watts. 2.2.1.2 determination climb power requirement for climb performance evaluation (figure 3), parameters considered are the rate of climb (roc), and the climb angle (𝛾). with these parameters well estimated, the uav will be able to climb at a good rate over vertical obstacles. it is worth noting that, the maximum roc is experienced at sea level and decreases as the altitude increases. roc which is defined as the rate of change of altitude per unit time is mathematically expressed as in equation 6 (anderson, 2020) http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 794 𝑅𝑂𝐶 = 𝑑ℎ 𝑑𝑡 = ℎ̇ (6) where h = the altitude and t = time. figure 3: forces acting on an aircraft in climb. (malik, 2020) the propeller of the uav is mounted at an angle known as the climb angle (𝛾) of 5°. since the uav will be climbing at a constant acceleration ‘a’, from newton’s second law, the equilibrium of the forces in the direction of flight can be expressed as in equation 7; 𝑇𝑐𝑜𝑠(𝑖𝑇 + 𝛼) − 𝐷 −𝑊𝑠𝑖𝑛(𝛾) = 𝑚𝑎 = 𝑚( 𝑑𝑣 𝑑𝑡 ) (7) where ‘𝑖𝑇’ is the angle of incidence, 𝛼 is the uav angle of attack. if all forces are assumed to pass through the center of gravity, 𝑖𝑇 and 𝛼 are also assumed to be zero, then equation (6) becomes equation 8 (anderson, 2020) 𝑇 − 𝐷 −𝑚𝑔𝑠𝑖𝑛𝛾 = 𝑚( 𝑑𝑣 𝑑𝑡 ) (8) the airspeed vector ‘v’ is then resolved into its vertical and horizontal component. by definition, the vertical component ℎ̇ is the roc of the uav. from figure 4, the relationship between the forward speed and roc is expressed as in equation 9. 𝑉𝑠𝑖𝑛(𝛾) = 𝑑ℎ 𝑑𝑡 = ℎ̇ (9) figure 4: horizontal and vertical airspeed component for roc multiplying equation (8) by 𝑉 and substituting it into equation 9 yields, (𝑇 − 𝐷)𝑉 = 𝑑(𝑚𝑔ℎ+ 1 2 𝑚𝑉2) 𝑑𝑡 (10) where (𝑇 − 𝐷)𝑉 = 𝑒𝑥𝑐𝑒𝑠𝑠 𝑝𝑜𝑤𝑒𝑟 𝑎𝑛𝑑 𝑚𝑔ℎ + 1 2 𝑚𝑉2 = 𝑡ℎ𝑒 𝑈𝐴𝑉 𝑡𝑜𝑡𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 795 therefore, the uav roc is estimated using the equation 11, 𝑅𝑂𝐶 = (𝑇−𝐷)𝑉 𝑊 (11) 𝑅𝑂𝐶, the power required for the climb phase is calculated using the equation 12, 𝑃𝑐𝑙𝑖𝑚𝑏 𝑟𝑒𝑞 = (𝑇 − 𝐷)𝑉𝑙𝑜 (12) from equation (11), 𝑅𝑂𝐶 = [(15.2963 − 6.7464) × 12.8646] 10 × 9.81 = 1.1212 𝑚𝑠−1 the uav will be climbing at a speed of 1.1212 𝑚𝑠−1 to cruise altitude where climbing will stop. this indicates that, roc generally decreases with altitude to the cruise altitude where it becomes zero. using the equation 12, , the power required for the climb phase is 𝑃𝑐𝑙𝑖𝑚𝑏 𝑟𝑒𝑞 = (15.2963 − 6.7464) × 12.8646 = 109.99 𝑊𝑎𝑡𝑡𝑠 2.2.1.3 determination of cruise power requirement the governing principle in straight and level flight is the newton’s second law of motion which explains how an object’s motion changes when a force is applied. the external forces of interest in this flight phase are the uav weight (w), thrust (t) from the battery, drag (d) and lift (l) as shown in figure 5. figure 5: equilibrium of forces in a straight level flight (malik, 2020) in an un-accelerated straight and level flight, the governing equations 13 of motion are. ∑𝐹𝑥 = 0 𝑎𝑛𝑑 ∑ 𝐹𝑧 = 0 (13) this is an implication that, the uav is in a trim or equilibrium state. from figure 5, the trim equations along 𝑧 and 𝑦 axes are equation 14 and equation 15. 𝐷 = 𝑇𝑐𝑜𝑠(𝛼 + 𝑖𝑖) (14) 𝑊 = 𝐿 + 𝑇𝑠𝑖𝑛(𝛼 + 𝑖𝑖) (15) where, 𝛼 = the angle of attack and 𝑖𝑖 = the engine setting angle. however, for ease of estimation, the following assumptions are made. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 796 (i) for straight and level flight, uav angle of attack is assumed to be zero. (ii) also, since the uav has no engine mounted on it, the engine setting angle is also assumed to be zero. hence, equations 14 and 15 becomes. 𝐷 = 𝑇 (16) 𝑊 = 𝐿 (17) indicating that, for un-accelerated straight and level flight, the conditions in equations (16). and (17)are true. therefore, in a steady level flight, when the available power is more than the required power, the uav will accelerate and vice versa. the required power is a function of airspeed. to have a steady level flight, the lowest amount of energy is required from the power system and this is achieved at the minimum power speed. however, there will be no steady level flight when the power generated produces a velocity that is less than the minimum required power speed 𝑉𝑚𝑖𝑛𝑝which is generally about 30% of the maximum available power (clark, 2018). the minimum power speed is estimated using the equation 18, 𝑉𝑚𝑖𝑛𝑃 = √ 2𝑚𝑔 𝜌𝑆√ 3𝐶𝐷0 𝑘 (18) where 𝜌 = density of the air at the cruise altitude which per the case study specification is 10,000 feet. the air density at 10,000 feet from international standard atmosphere (isa) table is 0.413 0.413 kg/m3. since for this condition, the thrust produced is equal to the drag generated as a result of forward motion, the minimum power required can be estimated using equation 19,20, 21 and 21. 𝑃𝑚𝑖𝑛 = 𝑇𝑚𝑖𝑛𝑃 × 𝑉𝑚𝑖𝑛𝑃 = 𝐷𝑚𝑖𝑛𝑃 × 𝑉𝑚𝑖𝑛𝑃 (19) 𝑤ℎ𝑒𝑟𝑒 𝐷𝑚𝑖𝑛𝑃 = 1 2 𝜌10,000𝑉𝑚𝑖𝑛𝑃 2 𝑆(𝐶𝐷𝑂 + 𝑘𝐶𝐿 𝑚𝑖𝑛𝑃 2 ) (20) 𝐴𝑙𝑠𝑜, 𝐶𝐿(𝑚𝑖𝑛𝑃) = √ 3𝐶𝐷𝑂 𝐾 (21) therefore, substituting equation 21 into equation 20 yields equation 22, 𝐷𝑚𝑖𝑛𝑃 = 2𝜌𝑉𝑚𝑖𝑛𝑃 2 𝑆𝐶𝐷𝑂 (22) using equation 18, 𝑉𝑚𝑖𝑛𝑃 = √ 2 × 10 × 9.81 [0.413(1.009835)√ 3(0.0109) 0.0446 ] = 10.7716 𝑚𝑠−1 hence, since the minimum required power velocity for cruise is greater than the stall velocity, it can be concluded confidently that, during steady level flight, the uav will be able to cruise at the minimum power velocity of 10.7716 𝑚𝑠−1 without stalling. with this condition, the thrust produced is equal to the drag generated because of the forward motion, the minimum power required can be estimated using equation 19,20, 21 and 22 to obtain http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 797 𝐷𝑚𝑖𝑛𝑃 = 2(0.413)(10.7716) 2(1.009835)(0.0109) = 1.0549 𝑁 therefore, the minimum power required to sustain the uav in a steady level flight is calculated from equation 19 as, 𝑃min = (1.0549) × 10.7716 = 11.3631 𝑊𝑎𝑡𝑡𝑠 2.2.1.4 determination of descent power requirement here, the velocity will be reducing from the cruise velocity to a new velocity known as the approach velocity until the uav touches down. the descent procedure is as depicted in figure 6. figure 6: descent process from cruise phase of flight (clark 2018) just like the climb phase which the uav uses a climb angle to climb, the descent also occurs at a constant angle known as the angle of descent (𝛾). the descent is controlled by varying the power to thrust ratio which is estimated according to (clark, 2018) to be 10% to 30% of the total power to thrust ratio. however, since the case study uav is designed to have gliding characteristics due to its wing design, in the absence of power, the uav will be capable of gliding by taking advantage of the air gradient in a process known as dynamic soaring. in a descending flight, the drag is greater than the thrust and the lift is smaller than the weight. therefore, if the approach speed is kept constant, the kinetic energy possessed by the uav will remain constant while the potential energy will decrease due to loss of altitude. assuming the descent angle is the same as the climb angle, the rate of descent (rod) can be estimated using equation 23, 𝑅𝑂𝐷 = 𝑉𝑑𝑒𝑠 sin(𝛾) (23) where, 𝑉𝑑𝑒𝑠 is the uav approach speed and 𝛾 is the descent angle. descent velocity for uavs in the weight category of the case study uav are estimated in the range of 1m/s to 3 m/s. therefore, assuming a descent velocity of 3 m/s and a descent angle of 5° degrees. the rod is estimated to be, 𝑅𝑂𝐷 = 3 sin(5°) = 0.2615 𝑚𝑠−1 http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 798 therefore, the uav will have a controlled descent rate of 0.2615 m/s until it touches ground and the power gradually reduced to zero for the uav to go into a complete rest. also, assuming a descent thrust of 20% thrust from the cruise thrust at steady level flight, the descent thrust can be estimated as, 𝑇𝑑𝑒𝑠 = 20% 𝑜𝑓 𝑇𝑚𝑖𝑛 (24) hence for that of the case study uav, the descent thrust is calculated from equation 24 to be, 𝑇𝑑𝑒𝑠 = 20 100 × 1.0549 = 0.211 𝑁 the power required for descent flight is therefore estimated using the expression (equation 25), 𝑃𝑑𝑒𝑠 = 𝑇𝑑𝑒𝑠 × 𝑉𝑑𝑒𝑠 (25) 𝑃𝑑𝑒𝑠 = 0.211 × 3 = 0.6329 𝑊𝑎𝑡𝑡𝑠 the power required for the uav to descend and subsequently land is 0.6329 watts. 2.2.1.5 landing landing is the final phase of flight. this phase encompasses the ability of the uav to safely land on the ground and gradually come to a complete stop prior to a controlled descent. it is the opposite to the take-off performance. unlike the take-off where the required power is large, landing requires minimum or no power to execute this phase. however, it must be controlled in order not to cause destruction to the structural or avionics components. during descent and landing, the power consumed is generally less compared to take-off and climb phase. matlab codes were generated for the performance estimations. 2.2.2 power supply to provide the needed power as determined, harnessing of renewable energy from the surrounding environment solar energy in combination with the installed hydrogen fuel cell is proposed. the uav will therefore harvest additional energy from the photovoltaic cells spread on its wingspan as well as from the hydrogen fuel cell which converts liquid hydrogen into electrical power via an electrochemical process. the proposed hybrid combination model of the solar cell system and the hydrogen fuel cell system is shown in figure 7. figure 7: proposed hybrid energy harvesting system 2.2.2.1 solar energy the photovoltaic cell selected is the monocrystalline solar cell made from a single silicon crystal. though they are more expensive, they have a higher conversion efficiency rating ranging between 15% to 25%. in other words, they have the ability of converting about 25% of the sunlight absorbed into usable energy (electricity). a monocrystalline solar cell has greater longevity of about 40 years and also characterized by lower http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 799 temperature coefficient which makes it more efficient under heat (yadav et al., 2019). figure 8 represents a pictorial view of the monocrystalline solar cells panel. figure 8: monocrystalline solar cell. table 3: photo voltaic cell specification (monocrystalline) parameter specification mass of solar cell 4 gm length and width 78 mm by 77 mm efficiency of solar cell 18.6% rated voltage 0.5 v or 0.6 v rated current 2.1 a the number of solar cells and its arrangement on the wing are therefore estimated according to the power need of the uav with respect to the specification given in table 1. 2.2.2.1.1 determination solar charge capacity the determination of charge capacity as per the specification of the selected pv cell (table 3) of which 0.5 v is produced from, requires a combination of cells in series to be able to generate the required voltage that can continuously charge the li-po battery with a constant voltage of 22.2 v. therefore, to obtain the 22.2 v, the number of cells required is estimated to be: 22.2 0.5 = 44.4 𝑐𝑒𝑙𝑙𝑠 𝑎𝑝𝑝𝑟𝑜𝑥𝑖𝑚𝑎𝑡𝑒𝑙𝑦 45 𝑃𝑉 𝑐𝑒𝑙𝑙𝑠. however, due to different type of losses that will be encountered in the course of conversion there is the need to add about 35% more cells to get a voltage above the constant voltage charge of the battery, and since the wing planform area and the span are fixed as per the case study uav, the cells will be arranged on the planform in a way that will not disrupt the boundary flow. hence, the estimated number of cells to be used for the generation is, 45 × 0.35 ≅ 15 more cells. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 800 hence, total number of pv cells are, 45 + 15 = 60 pv cells. therefore, the ideal total voltage acquired from the solar cells will be, 60 × 0.5𝑉 = 30𝑉 ideal watt power for the solar cells is expressed as 𝑃𝑠𝑜𝑙𝑎𝑟 = 𝑉𝑠𝑜𝑙𝑎𝑟 × 𝐼 (26) where 𝐼 is the rated current capacity of the pv cell and 𝑉𝑠𝑜𝑙𝑎𝑟 is the total voltage acquired from the combination of the pv cells. hence, estimating the solar power from equation 26 gives. 𝑃𝑠𝑜𝑙𝑎𝑟 = 30 𝑉 × 2.1 𝐴 = 63 𝑊𝑎𝑡𝑡𝑠 ideally, the solar cells should produce whatever watts of electricity under perfect conditions. but practically, the peak sunshine hours depending on the climatic condition in the region to which the uav will be operating is factored in the estimation. this makes the output power vary. hence, solar output power per day is estimated as 75% of the total output capacity. other losses are considered to be 25%. assuming a 7-hour sunshine in the northern part of nigeria, the solar output power will be calculated as; 𝑠𝑜𝑙𝑎𝑟 𝑝𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 = 𝑠𝑜𝑙𝑎𝑟 𝑝𝑜𝑤𝑒𝑟 𝑟𝑎𝑡𝑖𝑛𝑔 × 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑒𝑎𝑘 𝑠𝑜𝑙𝑎𝑟 ℎ𝑜𝑢𝑟𝑠 × 75% 𝑃𝑠𝑜𝑙𝑎𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 = 𝑃𝑠𝑜𝑙𝑎𝑟 × 𝑃𝑒𝑎𝑘 𝑠𝑜𝑙𝑎𝑟 ℎ𝑜𝑢𝑟𝑠 × 75% (27) therefore, from equation 27, the solar power is computed as; 𝑆𝑜𝑙𝑎𝑟 𝑝𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 = 63𝑊 × 7ℎ𝑟 × 0.75 = 330.75 𝑊𝑎𝑡𝑡 − ℎ𝑜𝑢𝑟 (𝑊ℎ) hence, converting the watt-hour to ampere-hour using equation 28 yields. 𝑆𝑜𝑙𝑎𝑟 𝐴𝑚𝑝 − 𝐻𝑟 = 𝑊𝑎𝑡𝑡−ℎ𝑜𝑢𝑟 𝑡𝑜𝑡𝑎𝑙 𝑠𝑜𝑙𝑎𝑟 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 (28) 𝑆𝑜𝑙𝑎𝑟 𝐴𝑚𝑝 − 𝐻𝑟 = 330.75 30 = 11.25 𝐴ℎ𝑟 2.2.2.1.2 determination cells arrangement on wing plan form examining the size and shape of the wing of the uav under consideration, the solar cells is divided into two and arranged on the plan form of the wing taking into consideration the dimension of each cell. the plan form area and span of the wing are 0.9724𝑚2 and 4.2𝑚 respectively. wing is tapered from root to tip. figure 9. represents the wing under consideration. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 801 figure 9: wing geometry of case study uav table 4: wing specifications (afitalta 2022) parameter specification span 4.42 m aspect ratio (ar) 18.14 mac 0.2418 m max coefficient of lift 1.38 the solar cells are rectangular in shape due to their dimension which is 78 𝑚𝑚 × 77 𝑚𝑚 in terms of length and width to give: 78 𝑚𝑚 × 77 𝑚𝑚 = 0.078 𝑚 × 0.077 𝑚 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑃𝑉 𝑐𝑒𝑙𝑙 𝑖𝑠 6.006 × 10−3𝑚2 therefore, as per the estimation, a total of 60 solar cells will be housed on the wing surface of the uav, covering about 0.3604 square meter which is about 36% of the wing area. figure 10 shows how the cells are arranged and wired in series to obtain the desired voltage output of 30 volts. the solar cells will be augmented with a maximum power point tracking solar charger (mppt) to ensure that, the loads receive maximum current to be used by quickly charging the li-po battery and also powering the onboard avionic equipment. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 802 figure 10: arrangement and wiring of solar cells on wing surface the cad model of the solar cell arrangement is created using industrial software which enables the visualization of the arrangement in a virtual environment. the arrangement is made up of multiple solar cells that are connected in series for the desired voltage and current output. additionally, a robust support structure is designed to hold the solar cells firmly on the wing. this support is transparent enough to allow the cells capture maximum sunlight from the surrounding environment. figure 11 shows the cad model of the arrangement of solar cells on the wing planform area of the case study uav figure 11: arrangement and wiring of solar cells on wing surface 2.2.2.2 hydrogen fuel cell system this system is capable of generating electricity through an electrochemical reaction between hydrogen and oxygen which gives off heat and water as by-products. they are clean form of energy with no carbon dioxide emissions or air pollutants that may lead to health issues in humans. they consist of anode, cathode and electrolyte membrane for its operation. when hydrogen passes through the anode, a catalyst splits the hydrogen molecule into protons and electrons. the protons pass through the electrolyte membrane whereas the electrons are forced through a circuit, generating an electric current and excess heat. the hydrogen fuel cell specification for the case study uav, has the specification shown in table 5 while figure 12 is the pictorial view of the hydrogen fuel cell used in the design of the case study uav. ((afitalta 2022). http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 803 table 5: hydrogen fuel cell specification h3 dynamics aerostack a-250 rated power (fc) 250 w voltage 24.5-35.2 v specific power 347 w/kg start up time < 20 s figure 12: hydrogen fuel cell 2.2.2.3 hybridization of solar and hydrogen fuel cells the hybrid combination model of the solar cell system and the hydrogen fuel cell system is shown in figure 13. figure 13: proposed hybrid energy harvesting system total number of solar cells to be employed in the design is 60. therefore, combining the two generative systems, the total power that is generated from the hybrid energy system of solar, hydrogen fuel cell and the lipo battery is obtained using equation 29; http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 804 𝑇𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 = 𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑠𝑜𝑙𝑎𝑟 + 𝑉𝑜𝑙𝑡𝑎𝑔𝑒ℎ𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝑓𝑢𝑒𝑙 𝑐𝑒𝑙𝑙 + 𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝐿𝑖𝑃𝑜 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 (29) 𝑇𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 = 30𝑉 + 30𝑉 + 22.2𝑉 = 82.2 𝑉𝑜𝑙𝑡𝑠 considering the weight of each photovoltaic (pv) cell to be 4g, the total weight of the pv cells on the wing surface is therefore estimated to be 240g. in addition, the weight of the maximum power point tracking system (mppt) to be installed on the fuselage is 1.3 kg. the above modifications will add to the power requirement of the uav and therefore forms part of the flight power performance analysis. 2.2.4 stress analysis of wing to confirm that the wing will not fail when the solar cells are placed on its planform, stress analysis was performed on the wing in order to establish the failure index using catia and abaqus software. the cad model of the wing was developed in catia and imported into abaqus. material properties were defined, boundary conditions set and load was carefully applied at the selected area. the model was then meshed and analysis ran to see the visual effect. the tsai-hill failure criteria was considered for the failure analysis. the criterion considers the interaction between different stress components and its failure mode. when the failure index of the material is 1, it implies the material has reached its maximum strength and can no longer withstand additional stress. 2.2.5 flight performance analysis the aim of the study is to enhance flight performance of the afit post graduate uav both in endurance and range by designing an enhanced hybrid energy source that meet its mission profile within the constraints of extraneous factors such as environmental conditions and flight altitude. performance of an aircraft denotes its characteristics and capabilities at various phases of flight. it encompasses a range of factors such as speed, range, climb rate, maneuverability, take-off and landing distances, payload and fuel efficiency. therefore, understanding and optimizing aircraft performance is critical for guaranteeing a safe and efficient flight operations, as well as achieving specific mission objectives for different types of aircrafts (anderson, 2010). matlab codes were generated for the performance estimations. 2.2.5.1 endurance according to (traub, 2011), for electric powered uavs, the maximum endurance is estimated using the relation for minimum power and thrust. the condition for maximum endurance is given by equation 30, 𝐶𝐷0 = 1 3 𝑘𝐶𝐿 𝑚𝑖𝑛𝑃 2 (30) hence, the maximum endurance is estimated using the equation 31, 𝐸𝑚𝑎𝑥 = 𝑅𝑡 1−𝑛 ( 𝜂𝑡𝑜𝑡𝑉×𝐶 ( 2 √𝜌𝑆 )𝐶𝐷0 1 4 (2𝑊√ 𝑘 3 ) 3 2 ) 𝑛 𝐻𝑜𝑢𝑟𝑠 (31) 𝐶𝐷0 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑐𝑎𝑠𝑒 𝑠𝑡𝑢𝑑𝑦 𝑖𝑠, 𝐶𝐷0 = 1 3 (0.0446)(0.8563)2 = 0.0109 where 𝑹𝒕 = the power system hour rating in hours which is assumed to be 1 hour since the discharge time over which small rechargeable battery packs are rated is typically per hour, v = the power system total voltage, c= the energy source capacity in ampere hours, 𝜼𝒕𝒐𝒕 = the total efficiency due to losses in the propulsion system which consist of propeller efficiency, servo motors etc. it is assumed to be 0.8 and n = a discharge parameter which is dependent on the battery type and temperature. traub (2011) investigated the impact of discharge rate on effective battery capacity by simulating an ideal battery: no peuket effect using n=1 and n=1.3 (typical for lithium polymer batteries). http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 805 2.2.5.2 range range is an essential performance that determines how far the uav can fly with its available battery power. this is the maximum distance an aircraft can travel with a full load of fuel tank. however, in the case of uavs, it is the distance the uav can travel with its available electric power. flight range of uavs in the weight class of 10 kg can vary significantly depending on the design and purpose of the uav. generally, uavs within this weight class might have flight ranges of around 10 to 50 kilometers on a single battery charge. the range is easily estimated (equation 32) after obtaining the endurance by, r=e×ur (32) where r = range e = endurance ur= required flight velocity for maximum range of the uav – equation 33. 𝑈𝑅 = √ 2𝑊 𝜌𝑆 √ 𝑘 𝐶𝐷0 (33) however, since the design cruise velocity was given as part of the specification as 14.3 𝑚𝑠−1, it is used to compute the range to meet the mission profile of the uav. 3. results and discussion 3.1 power requirement power required for the uav to successfully achieve a complete take-off is estimated using equation 1, 2, 3 and 4 as given in section 2, assuming sea level conditions of density 1.225 kgm−3, and taking the cl,w and s from the case study uav specification to first obtain the free stream velocity. therefore, the power required to achieve a complete take-off by clearing the 50 feet obstacle height is 197 watts. the power required for the climb phase is calculated using the equation 13, to obtain 109.99 watts. for the cruise power requirementthe minimum power required is estimated using equations 18,19, 20 and 21 to obtain dminp = 1.0549 n. hence, the minimum power required to sustain the uav in a steady level flight is calculated from equation 18 to obtain pmin = 11.3631 watts. descent power requirement using the descent velocity for uavs in the weight category of the case study uav are estimated in the range of 1m/s to 3 m/s. therefore, assuming a descent velocity of 3 m/s and a descent angle of 5° degrees the rod is estimated from equation 22 to be 0.2615 ms−1. therefore, the power required for the uav to descend and subsequently land is 0.6329 watts. the power required for various flight phases are presented in table 6 and depicted in figure 14. table 6: power requirement flight phases power required (watts) take-off 197 cruise 11.3631 descent 0.6329 landing is the final phase of flight. this phase encompasses the ability of the uav to safely land on the ground and gradually come to a complete stop prior to a controlled descent. it is the opposite to the take-off performance. unlike the take-off where the required power is large, landing requires minimum or no power to execute this phase. however, it must be controlled in order not to cause destruction to the structural or avionics components. during descent and landing, the power consumed is generally less compared to take-off and climb phase. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 806 3.2 battery capacity the energy consumed at the various stages of flight varies significantly depending on the size of the uav, design, payload, the mission requirement, and environmental factors. considering the critical phases under study which includes take-off, climb and cruise, the individual power consumed at these phases for the case study uav, are indicated on the mission profile in figure 14. figure 14: mission profile of power required at various phases of flight. from figure 14, take-off requires a significant amount of power17 watt since the uav needs to reach a sufficient altitude and velocity to maintain a stable flight. the climb phase is the second largest power (109 watt) consuming phase of the profile since the uav continues to use a significant amount of power to reach its desired cruising altitude. next energy consuming phase is the cruise phase. the power consumption 11.363 watt at this phase is stable as the uav maintains a constant speed and altitude throughout this phase. during descent (0.6329 watt) and landing, the power consumed is generally less compared to take-off and climb phase. it is therefore obvious from figure 14 that the battery must deliver a minimum power of 197 watts attributable to the takeoff phase to achieve the mission profile of the uav. 3.2 flight performance analysis the flight power performance of an aircraft encompasses a range of factors such as speed, range, endurance, climb rate, maneuverability, take-off and landing distances, payload, and fuel efficiencygreater speed using less fuel (thrust specific fuel consumptiontsfc), weight and balance. 3.2.1 endurance traub, (2011) investigated the impact of discharge rate on effective battery capacity by simulating an ideal battery: no peuket effect using n=1 and n=1.3 (typical for lithium polymer batteries) 𝐸𝑚𝑎𝑥 = 1 −0.3 ( 0.8 × 82.2 × 15.23 ( 2 √(0.413)(1.009835) ) (0.0109) 1 4 (2 × 98.1(√ 0.0446 3 )) 3 2 ) 1.3 𝐸𝑚𝑎𝑥 = 16.286 ℎ𝑜𝑢𝑟𝑠 http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 807 therefore, the maximum endurance that the uav can go within the permissible assumption made for the solar cells receiving solar energy for seven hours continuous is 16.286 hours for the design weight without payload onboard and 9.025 hours with the design maximum mass. however, since it is also on solar power, the uav will constantly receive power until the solar radiance reduces in energy when the cells can no longer produce enough energy for continuous power supply. when it happens this way, the hydrogen cell system takes over the power supply chain. this is achieved via a power management system. hence, for this system it can be concluded that, the uav will have unlimited endurance provided there is sufficient sunlight available for the pv cells to convert into electrical energy. in the absence of sufficient sunshine, the hydrogen fuel system will power the uav especially during night operations for about 4 hours to its destination before landing. 3.2.2 range the range is estimated to be (equation 32), 𝑅 = 16.286 × 14.3 = 232.891 𝑘𝑚 the range of the uav will be more than the estimated range provided there is more than 7 hours’ sunlight on the pv cells. however, in the absence of solar power, the uav will fly for a maximum range of 7.4687 km at a cruise speed of 14.3 meters per second according to initial specification (table 1). 3.3 flight power analysis the total power capacity that will be generated from both the battery and the solar cells is 11.25 ah. this will have tremendous boost in the power efficiency of the uav and also improves it flight endurance and operational capabilities. despite the challenges of other factors such as environmental conditions and flight altitude, there will be enough power to compensate to overcome such conditions. power from the solar cells, however, will not be readily available until approximately 7:30 am due to the assumptions made in the estimation (section 2). the battery and the hydrogen fuel cell will provide power within this early hour. therefore, their power need is distributed between the generating systems during the flight periods with the aid of a power management system. figure 15 illustrates a graph of power available against power required at various flight phases of the mission profile of the uav. figure 15: power available versus power required. after a successful take-off and climb to the maximum altitude, the total available power from the hybrid harvesting system drops from 580 watts to about 350 watts. after that big drop, there is a gradual decrease of power within the cruise phase from 350 to 300 watts. the drop is not as large compared to the drop during the take-off and climb phase. this is because, minimum power is required at the cruise phase of the mission. all things being equal, the power drop remains constant till the end of the flight mission. this is because of the regenerative process of the harvesting system. figure 16 also shows how the available power generated from the hybrid combination is depleted over the total flight endurance. the power reduces gradually in the mission over time from take-off to landing. 0 100 200 300 400 500 600 700 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 p o w er a v a il a b le ( w ) time (hr) power available mission profile http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 808 figure 16: graph of power against time 3.4 stress analysis of wing to confirm that the wing will not fail when the solar cells are placed on its planform, stress analysis was performed on the wing in order to establish the failure index using catia and abaqus software. the cad model of the wing was developed in catia and imported into abaqus. material properties were defined, boundary conditions set and load was carefully applied at the selected area. the model was then meshed and analysis ran to see the visual effect. the tsai-hill failure criteria was considered for the failure analysis. the criterion considers the interaction between different stress components and its failure mode. when the failure index of the material is 1, it implies the material has reached its maximum strength and can no longer withstand additional stress. 3.4.1 weight analysis under the design constraints on payload due to size, weight and power (swap) of both small and micro-uavs the change in the energy system of the proposed concept led to an increase in the design weight from 5.373 kg to 6.915 kg. thereby reducing the maximum payload of the original design by 1.542 kg. table 7 shows the various weights of the case study uav design and the new design. table 7: weight comparison of old and new model of uav parameters old design new design design weight 5.373 ks 6.915 kg payload 4.625 kg 3.085 kg power to weight ratio 2.497 w/n 5.912 w/n furthermore, the power to weight ratio is estimated (equation 34) for both designs and compared, to ensure that the new design with the new hybrid energy method meet the requirements for the intended use of the uav. 𝑃𝑜𝑤𝑒𝑟 𝑡𝑜 𝑊𝑒𝑖𝑔ℎ𝑡 𝑟𝑎𝑖𝑜 = 𝑃𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 𝑓𝑟𝑜𝑚 𝑒𝑛𝑒𝑟𝑔𝑦 𝑠𝑦𝑠𝑡𝑒𝑚 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑈𝐴𝑉 (34) the power to weight ratio of both designs is far greater than 1 with the proposed hybrid solar system at 5.9 as against 2.5 of the case uav. this is an indication that, the uav will have more power available per unit of weight which can result in better performance capabilities. the p/w ratio of the new design is therefore over 100% greater than the p/w ratio of the original design. this gives room for an increase in the payload mass of the uav. however, this must be done cautiously without compromising other performance parameters. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 809 3.4.2 wing stress analysis the maximum stress that can cause the wing to fail at the root was recorded as 0.39 mpa with a wing failure index of 0.000757. the failure index for a material to fail according to tsia-hill criteria is 1. therefore, having a failure index of 0.000757 indicates that, the pressure loads imposed by the solar cells on wing planform will not cause failure of the wing during it operations. deflection is very small and has little or no significant impact on the wing. figures 17 to 19 illustrate the cad drawings of the wing stress analysis. figure 17: stress analysis of the wing of case study uav figure 18 shows the stress analysis of the uav wing. a boundary condition was set at the root section of the wing and pressure loads applied to portions of the wing (figure 18). a maximum stress of 0.173 mpa was experienced at the root end. this is less than the allowable stress of the composite material used for the wing design, which is 42.27 mpa. figure 181: application of pressure loads of solar cells on planform area. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 810 figure 19: stress analysis of wing mounted with solar cells. figure 19 represents the stress analysis on the wing with the solar cells installed on its planform. from the analysis it was observed that, the maximum stress of 0.39 mpa occurs at the root end of the wing. the area where the cells are concentrated recorded a stress of 0.032 mpa. 3.5 cad model of the converted uav with solar panel figure 20 represents a cad conversion model with the hybrid solar, hydrogen fuel cells energy system mounted. performance analysis was carried out based on the mission profile of the uav and compared to other uavs in the same class including the case study uav. some of the findings made with regards to the case study uav were that, with the amount of power generated, by the harvesting system, the endurance and range of the uav increased to 16.3 hours and 232.9 km respectively. figure 202: cad model of the converted uav with solar panel 4. conclusion the unmanned aerial vehicle (uav) was initially designed with a specified endurance of 4.2 hours and a range of 6 kilometres, powered by a 245-watt output system. however, the integration of the proposed harvesting model significantly enhanced the performance, generating an output power of 580 watts based on 7 hours of sunshine. subsequent performance analysis, tailored to the uav's mission profile, revealed substantial improvements: 1. endurance increased by 287% to 16.3 hours 2. range extended by 3765% to 232.9 kilometres while these enhancements came with a 1.5-kilogram weight penalty, reducing the payload mass from 4.627 kilograms to 3.085 kilograms, stress analysis conducted on the wing using catia and abaqus software ensured the structural integrity of the design. the resulting failure index of 0.000757 confirms the wing's ability to http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 811 withstand the added load of the solar cells without compromising its performance. however, considering the evolving landscape of uav design, with increasing demands for larger payloads and higher altitudes, it is essential to explore additional aerodynamic optimizations beyond power system modifications to further enhance overall uav performance during flight missions (wang et al., 2020). despite the success recorded based on the results presented and discussed, some limitations were observed that needs to be considered in future works on the study. future work can consider embedding the pv cells into the wing during the wing design phase so that it will flush smoothly with the wing in order to reduce the zero lift drag that will be generated due to the uav movement. • experimental validation of the cad models can be pursued to validate its accuracy. • computational fluid dynamics (cfd) analysis can be conducted to ascertain the flow around the wing of the uav. references afitalta 2022. afit light trainer aircraft project in alta specification document. air force institute of technology, kaduna, nigeria. anderson, j. 2020. aircraft performance and design. tata mcgraw-hill edition, new delhi. barbir, f. 2012. pem fuel cells: theory and practice. elsevier academic press., london, pp. 44. clark, p. 2018. aircraft performance. in buying the big jets. fleet planning for airlines taylor and francis group routledge, new delhi. citroni, r., di paolo, f. and livreri, p. 2019. a novel energy harvester for powering small uavs: performance analysis, model validation and flight results. sensors, 19(8): 5–10. malik y. 2020. flight theory and aerodynamics. random publications, new delhi, india. matlock, j., warwick, s., sharikov, p., richards, j. and suleman, a. 2019. evaluation of energy efficient propulsion technologies for unmanned aerial vehicles. transactions of the canadian society for mechanical engineering, 43(4): 481-489. mohammadnia, a., rezania, a., ziapour, bm., sedaghati, f. and rosendahl, l. 2020. hybrid energy harvesting system to maximize power generation from solar energy. energy conversion and management, 205: 112352. ozbek, e., yalin, g., karaoglan, mu., ekici, s., colpan, co. and karakoc, th. 2021. architecture design and performance analysis of a hybrid hydrogen fuel cell system for unmanned aerial vehicle. international journal of hydrogen energy, 46(30): 16453–16464. prauzek, m., konecny, j., borova, m., janosova, k., hlavica, j. and musilek, p. 2018 energy harvesting sources, storage devices and system topologies for environmental wireless sensor networks: a review. sensors, 18: 2446. razykov, tm., ferekides, cs., morel, d., stefanakos, e., ullal, hs. and upadhyaya, hm. 2011. solar photovoltaic electricity: status and future prospects. solar energy, 85(8): 1580–1608. rezania, a. and rosendahl, la. 2012. thermal effect of a thermoelectric generator on parallel microchannel heat sink. energy, 37(1): 220–227. saravanakumar, y.n., sultan, mth., shahar, fs., giernacki, w., łukaszewicz, a., nowakowski, m., holovatyy, a. and stępień, s. 2023. power sources for unmanned aerial vehicles: a state-of-the-art. applied science, 13: 11932. http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):790-812. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: 812 traub, lw. 2011. range and endurance estimate for battery-powered aircraft. journal of aircraft, 48(2): 703– 707. https://doi.org/10.2514/1.c031027prescott arizona 86301 wang, y., cao, y., zhu, c. and li, q. 2019. a method of reducing flight delay by exploring internal mechanism of flight delays. journal of advanced transportation, 2019(5): 22–25. wang, y., kumar, l., raja, v., al-bonsrulah, haz., kulandaiyappan, nk., amirtharaj tharmendra, a., marimuthu, n. and al-bahrani, m. 2022. design and innovative integrated engineering approaches based investigation of hybrid renewable energized drone for long endurance applications. sustainability, 14: 16173. yadav, k., kumar, a., sastry, os. and wandhare, r. 2019. solar photovoltaics pumps operating head selection for optimum efficiency. renewable energy, 134: 169-177. http://www.azojete.com.ng/ corresponding author’s email address: abdulganiyr@yahoo.com 303 arid zone journal of engineering, technology & environment original research article production of bio-gel from waste of cassava and maize w. b. asiru1, a. o. raji2*, and n. alausa1 1 federal institute of industrial research, oshodi, lagos 2department of agricultural and environmental engineering, university of ibadan *corresponding author’s email address: abdulganiyr@yahoo.com article information abstract bio-ethanol was produced using starch extracted from cassava peel and cellulose from corn cobs using acid hydrolysis and yeast for fermentation while bio-gel fuel was produced using a composition of bioethanol and gel from water and carboxymethyl cellulose (cmc) in ratio 80%, 20% by volume respectively. the average yield of bioethanol is 757.33ml for cassava peel and 595.56 for corn cobs from 3.55l and 3.35l of filtrates respectively. the properties of bio-ethanol produced from the two samples compared favorably with the commercial ethanol. the bio-gel fuel which is an alternative source for cooking can also support outdoor burning. the formulation is made from 100% recycle of agricultural wastes making it very economical. the research work will have considerable impacts on the vision of bio-economy launched by many african countries, which is to be achieved through the creation and growth of novel industries that generate and develop biobased services and products. it will also support the local content initiative of nigeria government. the success of the study has a great impact on the environment being a waste conversion study. received: 11th september 2024 reviewed: 6th february 2025 accepted: 20th february 2025 keywords: bio-gel bio-ethanol corn cobs cassava peels agricultural wastes © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction large number of wastes are produced from agricultural, forestry and food production/processing activities. it is estimated that globally over 140 billion metric tons of biomass is generated every year from agriculture (chun, 2015; unep, 2015, tripathi et al., 2019). this volume of biomass can be converted to an enormous amount of energy and raw materials. equivalent to approximately 50 billion tons of oil, agricultural biomass waste converted to energy can substantially displace fossil fuel, reduce emissions of greenhouse gases and provide renewable energy to some 1.6 billion people in developing countries, which still lack access to electricity (unep, 2015,). as raw materials, biomass wastes have attractive potentials for large-scale industries and community-level enterprises that reduces the carbon print. according to the eia’s report on energy (useia, 2013), the primary energy consumption worldwide is expected to increase by 0.2% per annum, resulting in an overall increase in consumption of 6% by 2040. however, the global energy consumption growth accelerated in 2023 (+2.2%), much faster than its average 2010-2019 growth rate (+1.5%/year) (wecs, 2024). the rapid growth is linked to factors like post-pandemic economic recovery, increased industrial activity, and rising energy demand in developing countries. however, while global energy demand grew significantly, some developed economies saw slower growth or even declines due to economic factors like inflation. studies confirm that the world still relies heavily on fossil fuels to meet growing international energy demands. the negative aspects inherently related to the consumption of fossil fuels include the environmental impact of co2 emissions, the depletion of fossil fuel reserves, as well as the economic dependence on countries where political instability is prevalent (maggio and cacciola, 2012). in nigeria, 98 per cent of households lack access to quality clean cooking and lighting fuels. estimates of 98% of nigerians are not able to use quality cooking fuels (biofuels, lpg cooking gas and electricity). consequent on this, over 95,400 deaths occur per year as a result of the use of traditional fuels such as wood and charcoal, and nigeria’s deforestation rate is one of the highest in the world with 3.3% of its forests lost each year. an average poor household spend 60% of daily earning on energy and nigeria import 98% of annual ethanol consumption from other countries while$9m is spent on kerosene daily in nigeria. these figures show the estimated income that could be generated from bio-gel if produced in replacement of fossil fuels. there is the potential to generate the bio-fuel form waste azojete march 2025. vol.21(1):303-308 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:abdulganiyr@yahoo.com mailto:abdulganiyr@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 303-308. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulganiyr@yahoo.com 304 materials from agriculture which are in abundant in nigeria. obi et al. (2016) with a host of other researchers estimated over 998 million metric ton of waste is generated from agriculture in nigeria. therefore, the main objective of the project is to develop sound technologies for converting cellulosic biomass into energy/biogel and promote the use of biomass. specifically, the objective is to develop a technology for production of biogel from wastes of cassava and maize hence conversion of waste to useful material. 2. materials and methods 2.1 materials freshly processed cassava peels were bought at a cassava processing site eleyele in ibadan, oyo state, southwestern nigeria while the corn cobs (ccs) were collected from farmers and maize merchants in ibokun and ibadan in osun and oyo states respectively. chemicals and reagents were purchased in chemical and laboratory stores in ibadan and lagos respectively. 2.2 methods cassava peel (cp) and corn cobs (cc) used were both produced from their dried powder using acid conversion method. one kilogram (1000g) of each cc and cp samples were weighed with a laboratory scale and transferred into 5l conical flasks each. four liters (4l) of sulphuric acid (1m h2so4) solution was added to each of the sample. the mixture was stirred with glass rod. the hydrolysis process was proceeded in a water bath pre-set at 100oc. the hydrolysis was maintained at 100oc for 2 hours. four hundred milliliter (400ml) of sodium hydroxide (0.1m naoh) solution was added to neutralize the slurry, thereafter, the slurries were filtered. the filtrate was further used for ethanol production through fermentation using ethanol tolerance yeast. the filtrate ph was adjusted to 5.2 before fermentation commenced. the fermentation medium consists of the following in g/l; 10g peptone, 0.5g mgso4.7h2o, 0.5g kh2po4 and 0.5g (nh4)2so4. the components were added to the filtrate respectively and sterilized in an autoclave at 115oc for 20 minutes. the fermentation medium was cooled to room temperature and was subsequently pitched with yeast cell suspension (saccharomyces cerevisiae) at 50 x 105 cells/l. the inoculated media were incubated at 28±2oc for 7days after which they were was withdrawn for distillation and subsequently purified using rotary evaporator into concentrated ethanol. these samples of ethanol from cp and cc were then analysed. 2.2.1 production of biogel from bio-ethanol produced from corn cobs and cassava peel the biogel was produced using a composition of ethanol produced from corn cobs and cassava peel, water and carboxy methyl cellulose (cmc) respectively. the cmc acts as gelling agent which needs water to gel before being added to ethanol. the mixture normally results in an inflammable gel often used for cooking. analysis of the ethanol produced from corn cobs and cassava peel showed that parameters obtained from both are very close and preliminary investigation showed that both formed gel of same quality, hence corn cobs ethanol was produced in large quantity and used for production of bio-gel. the ethanol from corn cobs (200ml each) were then poured into five beakers. thereafter, 1.5, 2.5, 3.5, 4.5 and 5.5g of cmc were added to 50 ml of water in another set of beakers to form gelled water and were designated as s1, s2, s3, s4 and s5, respectively. these were mixed thoroughly and vigorously with spatula until the cmc dissolved and form gel. two hundred millilitres (200ml) each of the prepared corn cob ethanol were added gradually to each beaker containing gelled water and mixed continuously. the samples were left for 48 hours before further analysis on the samples. commercial bio-gel produced by sme funds (geb. 2024) purchased from the market was used as the control. 2.2.2 determination of yield of ethanol a measure of 450ml each of the filtrate was poured in the flask of the distillation apparatus and distillation of the filtrate was done at 78oc using distillation column and rotary evaporator. the distillate collected was poured into a measuring cylinder to determine the volume of the ethanol produced. the percentage yield was calculated using equation 1. 1 http://www.azojete.com.ng/ mailto:abdulganiyr@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 303-308. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulganiyr@yahoo.com 305 where ve and vf are the volume of ethanol produced and volume of filtrate used respectively. 2.2.3 determination of percentage ethanol the percentage ethanol was determined using ethanol by weight through specific gravity (aoac, 2010). the specific gravity of the ethanol was calculated and checked on ethanol’s table. the percentage ethanol values that corresponded with the specific gravity at 25oc was recorded as percentage ethanol for the sample. 2.2.4 determination of ph (ionic concentration) glucose syrup (10ml) was measured into a beaker using measuring cylinder. the ph was determined with the aid of previously calibrated ph meter (model hanna ph 211) with ph 4.0 and 7.0 buffers. 2.2.5 determination of specific gravity the specific gravity of the glucose syrup was determined using a specific gravity bottle. with a clean and water free gravity bottle. the empty bottle was weighed, and thereafter fills with distilled water and weighed. the bottle was also filled with the glucose syrups from the two samples respectively and their weight taken. the specific gravity of the samples was calculated using equation 2. 2 where ws and ww are the weight of sample and weight of equal volume of water 2.2.6 determination of total soluble solids (sugar brix) the total soluble solids as sugar brix of the glucose syrup were determined using hand refractometer (abbe refractometer). two drops of the glucose syrup from each sample was placed on the refractometer lens surface and reading was observed on the eyepiece of the equipment. 2.2.7 bio-ethanol gel production bio-gel is a fuel sourced from biomass to replace fossil fuels. this bio-gel can replace kerosene, gas, wood and charcoal in cooking. the base material for bio-gel production is bio-ethanol while cmc used in the experiments acts as gelling agent which needs water to gel before being added to bio-ethanol. 3. results and discussions 3.1 bio-ethanol from corn cobs and cassava peel the yield of ethanol produced from the corn cobs and cassava peels is as presented in table 1. the yield of filtrate (plate 1) from the fermentation process were 3.55 and 3.35 liters respectively for cassava peels and corn cobs. the yield of filtrate from the action of the yeast is higher in cassava peel than the corn cobs which showed that the yeast used is more active on starch than cellulose. the initial ph value of the cassava peel filtrate (6.57) is lower than that of corn cobs (6.90) while the total soluble solid and total titrable acidity for cassava peel is higher than in corn cobs. the yield of cassava peel is 757.33ml which is higher than that of corn cobs of 595.56ml (plate 2). http://www.azojete.com.ng/ mailto:abdulganiyr@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 303-308. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulganiyr@yahoo.com 306 plate 1: filtrates of cassava and corn cob waste plate 2: ethanol produced from filtrate of cassava and corn cob wastes as presented in table 2, the concentration of bio-ethanol produced are 85.34 and 83.71% for cassava peel sample and corn cobs sample respectively. apart from this the samples parameters like color, appearance, odour, solubility and flash point were the same and also compared favorably with industrial ethanol. the values for density, ph, boiling point, melting point, and freezing point were lower slightly in cassava peel than corn cobs bio-ethanol samples. table 1: ethanol yield and sugar conversion by saccharomyces cerevisiae extracts cassava peel corn cobs volume of filtrate yield (l) 3.55 3.35 ph value of filtrate 6.57 6.90 ph value of filtrate (adjusted) 5.20 5.20 total soluble solids (tss) (obrix) 26 24.5 total titratable acidity (%) 1.86 1.79 ethanol yield (ml) 757.33 595.56 table 2: properties of ethanol produced parameter cassava peel corn cobs industrial ethanol** ethanol concentration (%) 85.34 83.71 96 colour colourless colourless colourless appearance clear clear clear odour burning taste burning taste burning taste solubility highly soluble in water highly soluble in water highly soluble in water density @25ºc (g/ml) 0.839 0.846 0.789 ph value 6.92 6.95 7.33 boiling point (oc) 79.5 79.9 78.5 melting point(oc) -115.9 -116.4 -114.5 freezing point(oc) -116 -116 -114.1 flash point highly flammable highly flammable highly flammable **source: wom (2024) 3.2 biogel from corn cobs and cassava peel bio-ethanols as earlier observed, the basic material for bio-gel is ethanol, hence due to size of the laboratory equipment used and the fact that there are many researches on use of cassava tuber and cassava peel for bio-ethanol using various enzymes and yeast with positive results. both corn cobs and cassava peel ethanol above have very closed properties hence both of them can be used for bio-gel. however, the choice of corn cobs for http://www.azojete.com.ng/ mailto:abdulganiyr@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 303-308. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulganiyr@yahoo.com 307 further investigation is bore on the fact that there is no literature on bio-gel formation from its bio-ethanol while some work in this area has been done on cassava peel starch. the density of the samples ranged from 0.9308 to 0.9710 but compared favourably with that of the control (0.9336) (table 3). the specific gravity followed the same trend. as expected, the viscosity of the samples increased with the quantity of cmc added to each sample. since it is the cmc that forms the gel, the higher the quantity, the more it become viscous and reduction in ability to flow. hence, sample s1 with 1.5g of cmc has the lowest value of 983cp while the sample with cmc of 5.5g has the highest value of 8,830cp (see plate 1). plate 3: samples of bio-gel produced the cloud point did not follow any specific pattern, but sample s4 has value close to the control c. the pour point, flash point, flame point and fire point temperatures decreased with increase in cmc quantity. however, the energy content varies between 18 mj to 30.5 mj with control c having 31.5 mj very close to samples 4 and 5. the burning time for 10ml of samples varies between 4 to 6 minutes while control c burn for 7 minutes. from table 3, it can be observed that samples s4 and s5 are very close to control sample with s5 the best of the two samples. table 3: properties of bio-gel from corn cobs bio-ethanol (s) compared with commercial bio-gel (c) sample parameters s1 s2 s3 s4 s5 c density (g/cm3) 0.9452 0.9308 0.9420 0.9376 0.9710 0.9336 specific gravity 0.9325 0.9183 0.9293 0.9250 0.9580 0.9210 viscosity (cp) at 30oc 983.00 1018.20 1,913 3,333.33 8,830.00 8,000.00 cloud point temperature (oc) -2.5 -4.75 -5.43 -1.37 -3.03 -1.63 pour point temperature (oc) -10.13 -9.50 -9.27 -5.33 -5.97 -5.40 flash point temperature (oc) 65.27 70.33 63.73 59.43 49.27 52.33 flame point temperature (oc) 65.77 71.33 64.57 59.67 57.27 55.57 fire point temperature (oc) 69.57 71.83 64.87 60.00 59.3 59.40 energy (mj) 23 18 20 30 30.5 31.5 burning time for 10ml (min) 5 4 6 6 6 7 4. conclusion bio-ethanol was successfully produced using starch extracted from cassava peel and cellulose from corn cobs by acid hydrolysis and yeast for fermentation. the average yield of bioethanol is 757.33ml for cassava peel and 595.56 for corn cobs from 3.55l and 3.35l of filtrates respectively. the average phs of the samples are 6.92 and 6.95 for cassava peel and corn cobs bio-ethanol respectively. the properties of bio-ethanol produced from the two samples compared favorably with the commercial ethanol. bio-gel fuel was produced using a composition of bio-ethanol from corn cob cellulose and gel from water and cmc in ratio 80%, 20% by volume respectively. samples s4 and s5 compared favorably with commercial sample with sample s5 as the best. the bio-gel fuel which is an alternative source for cooking can also support outdoor burning. the formulation was made from 100% recycle of agricultural wastes making it very economical and environmentally friendly. http://www.azojete.com.ng/ mailto:abdulganiyr@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 303-308. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: abdulganiyr@yahoo.com 308 references aoac. 2010. official methods of analysis of aoac international. association of official analysis chemists. https://doi.org/10.3109/15563657608988149. geb (2024). scaling renewable ethanol for clean cooking fuels. green energy biofuel website https://www.gebiofuels.com/#services. accessed 27/06/2024 maggio, g. and cacciola, g. 2012. when will oil, natural gas, and coal peak? fuel, 98: 111–123. https://doi.org/10.1016/j.fuel.2012.03.021 obi, fo, ugwuishiwu, o.b, and nwakaire, j.n. 2016. agricultural waste concept, generation, utilization and management. nigerian journal of technology (nijotech), 35(4): 957 – 964. tripathi, n., hills, c.d., singh, r.s. and atkinson, c.j. (2019) biomass waste utilisation in low-carbon products: harnessing a major potential resource. npj clim atmos sci, 2(35). https://doi.org/10.1038/s41612-019-0093-5 unep 2009. converting waste agricultural biomass into a resource-compendium of technologies. a compendium of technologies compiled by the united nations environmental programme division of technology, industry and economics international environmental technology centre, osaka/shiga, japan. http://hdl.handle.net/20.500.11822/7614 u.s. energy information agency. 2013. international energy outlook 2013. outlook 2013, 312. https://doi.org/eia-0484(2013) wecs 2024. total energy consumption. world energy climate and statistics yearbook. https://yearbook.enerdata.net/total-energy/world-consumption-statistics.html. accessed june 2024. wom 2024. chemical and physical properties of the ethanol molecule. world of molecules website. https://www.worldofmolecules.com/fuels/ethanol.htm. accessed: 27/06/2024 http://www.azojete.com.ng/ mailto:abdulganiyr@yahoo.com http://hdl.handle.net/20.500.11822/7614 https://yearbook.enerdata.net/total-energy/world-consumption-statistics.html https://www.worldofmolecules.com/fuels/ethanol.htm corresponding author’s email address: kunduli@yahoo.com 35 arid zone journal of engineering, technology & environment original research article assessment of agro-waste potentials for the generation of electrical energy in northeast nigeria a. bukar1., k. mustapha1*, u. o. aliyu2., j. d. jiya 2 and g. a. bakare2 1department of electrical and electronics engineering, university of maiduguri, maiduguri, nigeria 2department of electrical and electronics engineering technology, abubakar tafawa balewa university bauchi, bauchi, nigeria *corresponding author’s email address: kunduli@yahoo.com article information abstract in this paper eight major agricultural-wastes (agro-waste) (maize cob, groundnut shell, bean pod, wheat husk, rice husk, millet bran, sorghum bran and sugar cane bagasse) derived from widely grown crops in the northeast sub-region have been investigated for their energy resource potentials. the core research task is to estimate the aggregate crop residues from raw data collected from river basin authorities and ministries of agriculture and water resources as well as from structured surveys of major markets, large commercial farms and agro-allied industries. this work relies on directed data analytics approach and has arrived at gross estimates of 6.89x104 metric tons per annum as agro-wastes available for electricity production; corresponding to approximately 13.5% share of the total agro-wastes of the northeast sub-region. further, samples of all agro-wastes were characterized via proximate analysis which yielded their respective lower heating values to be within the range of 12.52mj/kg to 16.66mj/kg. from end-use viewpoint, the estimated agro-wastes of the study area can generate electrical energy of 55.8gwh/annum for geographically scattered rural communities. submitted: 18th july 2024 revised: 19th september 2024 accepted: 27th january 2025 keywords: agro-waste crop residues energy potential proximate analysis scattered. © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the humongous electricity supply gap in nigeria will continue to remain thematic in the public domain and also cause indigenous energy resource exploitations in different nigerian sub-regions so as to propel technically and economically viable distributed power generations. undoubtedly, rapid increase in nigerian population and urbanization has put enormous pressure on her national electric utility infrastructure which has not grown at commensurate rate over the years. today, nigeria’s per capita energy consumption is still around 150kwh which is among the lowest in comity of developing and developed countries (world bank, 2019). although the electricity industry has been deregulated since 2005, the anticipated capital inflow to drive the rapid expansion of generation, transmission and distribution facilities has not materialized. but as part of efforts to diversify nigeria’s energy base, which currently relies heavily on conventional energy sources, the federal government has, as key component of her master energy plan, well-articulated distributed energy resources development for rapid socioeconomic development of the country (renewable energy master plan, 2005). central to the master energy plan, is the development and utilization of the renewable energy sources for sustainable electricity supply to underserved consumers and unserved rural communities in nigerian milieu without degrading the environment (energy commission of nigeria (ecn, 2015). it is undeniable that the nigerian economy is heavily dependent on the petroleum sector for the provision of over 80% of public azojete march 2025. vol.21(1):35-55 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:kunduli@yahoo.com mailto:kunduli@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 36 finance, despite instability in the international crude oil market. however, in spite of its significance to the national economy, the oil sector has not spurred real economic growth in the country. despite the huge revenue that accrued from crude oil exportation, the infrastructural development has remained very low and in particular, electricity delivery to consumers nationwide is conservatively estimated to be 54.4%, according to (world bank, 2019). the north-east sub-region of nigeria has numerous untapped energy resources that encompass majorly renewable energy sources and, to some limited extent, conventional energy sources. the missing nexus, however, is how best to deploy the viable energy resources to underpin sustainable economic growth of the sub-region. a well-researched energy resource database for nigeria (afolabi et al., 2021) and the entire north-east sub-region is not readily available and this is without prejudice to the existing research investigations on identified energy resource entities in some specific localities of north-east sub-region. the prime focus of this paper is to develop a viable road map for the utilization of the indigenous energy resources, in coordinated manner, for sustainable distributed power generation applications in the north-east sub-region. the specific task of this paper is to carry out comprehensive evaluation and characterization of different biomass resource potentials in the sub-region. the overriding goal concerns sustainable electricity productions for plethora of geographically dispersed rural communities, across the entire northeast sub-region that currently lack electricity delivery from the national grid. biomass is organic material made from plants and animals. plants absorb the sun's energy in a process called photosynthesis. the chemical energy in plants gets passed on to animals and people that eat them. biomass is a renewable energy source because people always grow more trees and crops, and waste will always exist. the overall biomass resources can be broadly categorized into two parts based on its availability in the natural form woody and non woody biomass (aruya et al. 2016; anne, 2013 and simonyan & fasina, 2013) all defined agricultural residues as organic materials produced as byproduct during the harvesting and processing of agricultural crops. lack of electricity infrastructures in rural areas of most african countries remain the main barrier to their socio-economic development (aderoju et al., 2017). one of the principal causes is the geographical dispersion of the population and the large locational distances of rural communities from the existing electricity network outlay. another key reason is the financial strengths of the various african governments which do not enable them invest heavily in electrification of rural areas (anicet, 2012). there have been several studies on the aforementioned issues in nigeria and other developing countries to look at cost effective off mini-grid electricity supply solutions. several techniques and approaches have been developed to evaluate and characterize different energy resource scenarios with attention focused for the time being on biomass. dan (2008) reviewed the current state and trends in using fuel, solid wastes generated in pulp and paper mills. rishi (2013) worked on the estimation of power generation potential of agriculturally based biomass species. the researcher worked on four selected agricultural residues comprising maize, coconut, paddy and cajanus cajan and land cultivation requirements to enable sustainable electricity generation. the result further showed that approximately 717 hectares, 1123 hectares, 1511 hectares and 4319 hectares of land are required to generate 20mwh/day of electricity from coconut, maize, and paddy and cajanus cajan residues respectively. katherine et al., (2016), worked on assessment of the energy potential of agricultural residues in non-interconnected zones of colombia: case study of chocó and putumayo. the energy potential of agricultural residues in two departments of zni in colombia was estimated. (awulu et al., 2018) worked on the comparative analysis of calorific values of selected agricultural wastes. this author worked on determining the calorific values of corn cob, rice husk and sawdust agricultural wastes materials. standard method of calorific value determination involving the use of bomb calorimeter was adopted. from the investigation, http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 37 the calorific value of rice husk, sawdust and corn cob are 2938.86 kcal/kg, 3155.30 kcal/kg and 3227.78 kcai/kg respectively. in order to exploit solid biomass species for electricity generation, it is pertinent to determine their properties that include calorific value, volatile matters, moisture content etc. wood and agricultural residues are burnt as a fuel for cogeneration of steam and electricity in the industrial sector (sartolli et al, 2023., vaibhav and avin, 2014). biomass can also be converted to a liquid form for use as a transportation fuel, and research is being conducted on the production of fuels and chemicals from biomass. in the electricity sector, biomass is used for power generation (rishi, 2015). sources include forest residues, rice husk, wood chips, sorghum, sugarcane, etc. as an energy resource, biomass may be used as solid fuel, or converted via a variety of technologies to liquid or gaseous forms for the generation of electric power, heat or fuel for motive power (navneer 2014.; ) reported that not all the waste agriculture biomass (wab) have same thermal values. the calorific values of some selected biomass samples, on dry basis, extracted from archives of bimtech birla institute of management technology vary between 3000 and 4700 kcal/kg. this paper also presents experimental work, using proximate analysis to determine calorific values of different agricultural biomass species indigenous to northeast sub-region of nigeria. 2. materials and method 2.1 data collection this section presents comprehensive documentation of the materials and methods deployed to realize the aim and objectives of this paper. the data collection procedures are anchored firstly on structured survey-based studies to enable collection of credible raw data on annually generated agro-wastes by agro-industries and large farms in the northeast sub-region of nigeria; different methodologies are developed: to estimate, firstly, the aggregate annual agro-wastes and their respective calorific values for the entire northeast sub-region; secondly determine optimum allocation of agro-wastes for electricity generation. the integral components of materials and methods are set forth in the subsequent sections that follow in sequel. 2.1.1 data collection sources for agro-wastes in northeast sub-region all state ministries of agriculture, large agro-processing industries, large markets, river basin authorities etc., constitute the sources to provide credible data via suitably structured survey questionnaires/oral interviews. the data sought are as follows: 1. all or some available data from all state ministries of agriculture in northeast on cultivated arable land area in hectares of each state; dominant crops grown annually specific to each state; expected average yield (metric tons/hectare) per each crop type grown and gross estimate of productions (metric tons per annum) per each crop for each state. 2. additional data sourced from agro-industries/processing points in all northeastern states to estimate specific agro-wastes produced annually; 3. all processed agro-crops of each state sold at large markets, for all year-round market days, and transported to other states or as obtained from the respective market logbooks where available. 2.2 experimental procedure this section presents the core methodologies developed for the actualizations of our research objectives. more precisely, the following constitute the core methodologies developed herein. a) design of structured survey questionnaires to fairly accurately facilitate estimations of agro-wastes generated annually in each state of northeast sub-region of nigeria. http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 38 b) flowchart for data collection procedure on agro-wastes presented in (figure 1). c) experimental setup to carryout proximate analysis on samples of major agro-wastes for each state of northeast sub-region of nigeria; d) problem formulation for equitable utilization of agro-wastes in northeast nigeria; and 2.2.1 design of structured survey questionnaire for agro-waste estimation in study area the observed lack of credible data on agro-wastes, in the public domain, for the entire northeast, has motivated the design of structured survey questionnaires upon which we anchored the estimations of the agro-wastes or crop residues for each state in the study area. it is, of course, unarguable that realistic estimates of major agro-wastes are pertinent to drive sustainable energy stock inputs for modularized power generation schemes. consequently, well-structured survey questionnaires constitute least cost terrestrial-based option to gather reliable and trusted data within the study area. specifically, the design of the structured survey questionnaires seeks vital data and information for each state in northeastern nigeria that include the following amongst others: 1. arable and cultivated land in hectares (ha) or square kilometers (km2) per annum and distributions among the major crops grown including largeand small-scale farmers; 2. major crops grown and number of times per year stating if rain-fed or irrigation-fed or both and yield per ha for each crop type. 3. large farms (in hectares) owned by agro-allied industries, private individuals specifying crops cultivated and if rain-fed or irrigation fed and to indicate number of harvests per annum achievable. 4. large markets that specialize in the sales of preprocessed agricultural crops to access their sales records and determine whether for local retails or out of state transportation each year. we then relied on suitably structured survey questionnaires administered to all the state ministries of agriculture, all river basin authority offices, and major markets in northeast sub-region of nigeria that returned reliable responses. (figure 1) depicts the algorithmic framework of the final structured survey experimentations carried out culminating in pragmatic estimations of agro-wastes for each state in northeast sub-region for only dominant crops grown. the underlying computational procedures for the agricultural residues in the study area are set forth in sequel which essentially relies on fao approach of (figure 2). http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 39 figure 1. flowchart for data collection procedure on agro-wastes, http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 40 figure 2: flowchart for estimating agricultural residues source (fao, 2014). 2.2.2 experimental setup for determination of agro-waste energy content (figure 3) depicts the functional block diagram of experimental setups that enabled the determination of heating values or calorific values of the dominant agro-wastes considered in all the states of northeastern nigeria. the aforementioned experimental setups cannot determine the calorific value directly as done by oxygen bomb calorimeter; but instead determine explanatory variables such as moisture content(𝑀𝐶), ash content(𝐴𝐶), and volatile matter(𝑉𝑀)from which the corresponding calorific value is estimated from empirical relationships. for the sake of completeness, (figure 4) shows the experimental setup for the determination of crude protein of the various agro-wastes to establish their nutritional values as animal feeds. start select kth agro-residue candidate from jth crop specie of the study area or location location of agro-residue: collection modes-spread in field; collected in field and processing point. specify data for computing crop productions in the study area: crop yield (t/ha); no of harvests/yr& total cultivated area. provide study area specific residues to product ratios (rprs) for all crop species and their respective agro-residue candidates (see table 5). 1 1 specify % of generated residues to be left in the field after harvesting to specify soil micro-nutrients. specify % of agro-residues burnt in the field; if not available for the study area, assume 10% of cultivated area. after meeting all other competing needs, use equation 3 to compute available agroresidues for each 𝑗𝑡ℎcrop specie bearing 𝑀𝑗 residues; set j=j+1 all crop species assessed? or 𝑗 = 𝑁𝑐 + 1? yes compute the aggregate crop residues crt as follows: 𝐶𝑅𝑇 = {𝑊𝐶𝑅𝑃𝑗 𝑘=𝑀𝑗 𝑘=1 𝑗=𝑁𝑐 𝑗=1 ∗ 𝑅𝑃𝑅(𝐶𝑅𝑃𝑗 )𝑟𝑒𝑠𝑘 ∗ ∗ 𝜁(𝐶𝑃𝑅𝐽 )𝑟𝑒𝑠𝑘 } end 2 no 2 http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 41 figure 3: developed flowchart for the computation of agro-wastes in the study area 2.2.2.1 proximate analysis procedure for calorific value determination of agro-wastes the implementations of proximate analysis on agro-wastes are indispensable because they provide their energy contents to be harnessed for distributed end-use electricity productions. indeed, proximate analysis of agricultural biomass residues for selected study areas in different countries have appeared in several publications but similar studies have not been carried out in respect of dominant crop residues in the study area of interest. the research goal is, therefore, • enter all respondents to the structured survey questionnaires for each state in northeast sub-region of nigeria into excel database; • set 𝑖 = 1 where 𝑖 is the state identifier of the study area. start • select complete data set for 𝑖𝑡ℎ state in the study area; • pre-screen to confirm data integrity, completeness and remove, if any, redundant & outlier data; and • repeat survey to eliminate any data shortcomings. • • extract data for 𝑖𝑡ℎ state such as crop yield (t/h); no of harvests/yr & total arable land and cultivated area. • set 𝑗 = 1 where 𝑗 is crop type identifier for 𝑖𝑡ℎ state bearing 𝜑𝑗agro-residues. 1 • compute next agro-waste 𝜑𝑗 associated with 𝑗𝑡ℎ crop type in state 𝑖 using eqn. (6) recursively; • incrementally accumulate agro-wastes. are all agro-wastes associated with 𝑗𝑡ℎ crop type in state 𝑖computed 𝑗 = 𝑗 + 1 no yes • save computed agro-wastes associated with all crop types in state 𝑖 in database and increment to memory location. 2 2 all agro-wastes for all the states computed 1 𝑖 = 𝑖 + 1 no yes aggregate all the agro-wastes for all the states using eqn. (7). prepare the database of all the agro-wastes in the study area for subsequent energy potential analysis. end http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 42 to evolve standardized templates of calorific values for the dominant agro-wastes in the northeast sub-region of nigeria. the proposed methodology for the implementation of proximate analysis should perform the same function as oxygen bomb calorimeter. (figure 5) depicts the overall flow chart for the proximate analysis experimental and computational framework. the salient steps of proximate analysis are further highlighted in what follows. the algorithmic flowchart is presented in (figure 6). figure 4: experimental setup for the determination of agro-waste crude protein figure 5: experimental setup for agrowaste proximate analysis carry out proximate for all aw set temperature at 550oc for each aw to convert to ash electronic weighing scale select each sample of agro wastes (aw) collected in northeast subregion weight of aw before drying (𝑤𝑏) in grams set to remove moisturecontent electronic weighing scale muffle furnace oven dryer all aw processed ? yes no electronic weighing scale weigh ash of aw (ws) proceed to proximate analysis flow chart (figure 6) agro waste sample input filter results output digestion block distillation chamber burette for titration http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 43 figure 6: experimental and computational flow chart of proximate analysis step1 (sample preparation): eight different biomass samples were collected from the major processing points of the six states of the sub-region and experiment was performed separately on each of the sample. one gram of powdered sample of each were taken forth analysis of ash content, moisture content, volatile matter and fixed carbon content. step2 (moisture determination mc): add one gram of air-dried powdered sample to a crucible disc and keep in the air oven maintained at the temperature 105°c.the sample is kept at this temperature for 30 min and then taken out from the furnace and cooled off in a desiccator. weight loss was recorded using an electronic balance. the percentage loss in weight is the percentage moisture content (%mc) in the sample as given in eqn. (1). yes vm ac mc fc biomass preparation process proximate analysis ∎%𝑀𝐶 = ൬ 𝑊1 −𝑊2 𝑊1 ൰𝑋100 ∎%𝑉𝑀 = ቀ (𝑊1 –𝑊3) 𝑊2 ൗ ቁ × 100 ∎%𝐴𝑆𝐻 = [(𝑊3 – 𝑊1)/ (𝑊 –𝑊 )] × 100 biomass sample for proximate analysis (see fig.8) select (xi) biomass material [𝑥1, . . 𝑥𝑖 , … 𝑥𝑛] where n = 8 compute calorific value (cv) 𝐶𝑉𝑘(𝑥𝑖) = 0.34 × [(147.6 × 𝐹𝐶 (144 × 𝑉𝑀) + (%𝐴𝑆𝐻)] kcal/kg construct the calorific value matrix output 𝐶𝑉 ∈ ℛ𝑛×𝑀 save 𝐶𝑉𝑘(𝑥𝑖) for kth state; increment 𝑖 = 𝑖 + 1 ne state biomass feedstock 1. rice husk 2. maize cob 3. sugarcane bagasse 4. wheat husk 5. groundnut shells 6. beans pods 7. millet bran 8. sorghum bran select state[𝑆1, … 𝑆𝑘… . 𝑆𝑀]:where m=6 1 𝑖 = 𝑛 + 1 ? 1 no 𝑘 = 𝑘 + 1 start set k=1 no yes 2 stop 𝑘 = 𝑀 + 1 ? 2 𝑆𝑒𝑙𝑒𝑐𝑡 𝑓𝑜𝑟 𝑘𝑡ℎ 𝑠𝑡𝑎𝑡𝑒 http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 44 %mc = ൬ w1 −w2 w1 ൰ × 100 (1) where: 𝑊1: is the weight of sample plus crucible before dryingand 𝑊2: is the weight of sample after drying in the oven dryer. step2 (volatile matter determination vm): add one gram of air-dried powdered sample in a volatile matter crucible and place in muffle furnace maintained at temperature of 650°c.the sample should be maintained at this temperature for 7 minutes and then taken out, air cooled and then weighed (w3). weight loss in the sample is recorded again by using an electronic balance having a sensitivity of 0. 001gram.the percentage loss in weight – moisture present in the sample over the dried weight yields the volatile matter content in the sample eqn. (2). %𝑉𝑀 = ቀ 𝑊2−𝑊3 𝑊2 ቁ × 100 (2) step3 (ash content determination ash): add one gram of air-dried powdered sample in a shallow silica disc and kept in the muffle furnace maintained at the temperature of 550°c.the sample is kept in the furnace to achieve complete combustion. weight of ash formed is then measured and the percentage ash content in the sample determined by eqn. (3). %𝐴𝑆𝐻 = ൬ 𝑊3 −𝑊1 𝑊2 −𝑊1 ൰ × 100 (3) where: 𝑊1 = weight of empty crucible;𝑊2= weight of crucible + sample and 𝑊3= weight of crucible + ash. step4 (fixed carbon, fc, determination): the fixed carbon content in each agro-waste sample is determined using the following formula: %𝐹𝐶 = 100% −𝑊𝑡%(𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒 + 𝑉𝑜𝑙𝑎𝑡𝑖𝑙𝑒 𝑀𝑎𝑡𝑡𝑒𝑟 + 𝐴𝑠ℎ) (4) step5 (calorific value/specific heat of combustion cv or lhv): the specific heat of combustion or calorific value (cv) in kcal/kg of any residues is then computed using the following empirical formula: 𝐶𝑉 = 0.35{(147.6 ∗ %𝐹𝐶) + 144 ∗ %𝑉𝑀 + (%𝐴𝑆𝐻)} (kcal/kg) (5) it is noteworthy that in order to determine moisture content of the agro-waste sample, it must be heated in air oven at temperature of 105oc for about 30min. secondly, the determination of ash content required that the agro-waste under consideration must undergo complete combustion in the muffle furnace maintained at 550°c; whilst the determination of volatile matter require that the agro-waste sample be heated in the furnace at higher temperature of 650°c. it is pertinent to re-iterate again that lack of functional bomb calorimeter apparatus, engendered the alternative experimental rig to actualize one of our cardinal research goals of determining http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 45 calorific values for different species of agro-wastes from dominant crops cultivated in the states in the northeast sub-region. 2.3 derivation of energy potential of agro-wastes the ultimate goal of this research is to determine energy potential of agro-wastes generated in the different states of the northeast and subsequently characterize their technical and economic viability for sustainable electrical energy productions. having developed pragmatic framework for the estimation of agro-wastes in the study area and determinations of their respective calorific values via proximate analysis, we can now assess the energy potential derivable from them. consider again an arbitrary study area split into n states with each state having k dominant crop types such that 𝑗𝑡ℎcrop type that can generate 𝑀𝑗 agro-wastes or crop residues. starting from eqn. (1), the theoretical energy potential of 𝑖𝑡ℎ state (𝔼𝑖 𝑇𝐸𝑃) and entire study area (𝔼𝑆𝐴 𝑇𝐸𝑃) can be expressed as given in eqn. (6) and eqn. (7), respectively: 𝔼𝑖 𝑇𝐸𝑃 = ( ቀ 𝑊𝐶𝑅𝑃𝑗 × (𝜁𝑗 × 𝐴𝑐𝑖) × (𝑅𝑃𝑅𝑗)𝑟𝑒𝑠𝜑 𝑀𝑗 𝑟𝑒𝑠𝜑 =1 𝐾 𝑗=1 × 𝐶𝑉(𝐶𝑅𝑃𝑗)𝑟𝑒𝑠𝜑ቁ ) × 10−3(𝑀𝑊ℎ𝑇) (6) 𝔼𝑆𝐴 𝑇𝐸𝑃 = ∑ 𝔼𝑖 𝑇𝐸𝑃(7)𝑁 𝑖=1 (7) where all the other variables used in eqn. 7 have been previously defined. the possibility of utilizing all the admissible crop residues for electricity generation in the study area is unattainable because of equally critical competing needs such as animal feeds, farmer organic manure, etc. it is therefore imperative to share gross agro-wastes for the study area amongst all the potential areas. consequently, optimally determined sharing allocation weighting fractions defined as 𝛼(𝐶𝑅𝑃𝑗)𝑟𝑒𝑠𝜑 < 1; {for every 𝑗 ∈ [1,2…𝐾]; 𝑟𝑒𝑠𝜑 = [1,2, … . k, …mj]} are introduced into eqn. (6) to yield the modified equations, for technical energy potentials for 𝑖𝑡ℎstate (𝔼𝑖 𝑡𝑒𝑐ℎ)and the study area (𝔼𝑆𝐴 𝑡𝑒𝑐ℎ) as eqn. (8) and eqn. (9), respectively. 𝔼𝑖 𝑡𝑒𝑐ℎ = ( ൬ 𝑊𝐶𝑅𝑃𝑗 × (𝜁𝑗 × 𝐴𝑐𝑖) × (𝑅𝑃𝑅𝑗)𝑟𝑒𝑠𝜑 × 𝐶𝑉(𝐶𝑅𝑃𝑗)𝑟𝑒𝑠𝜑 ൰ 𝑀𝑗 𝑟𝑒𝑠𝜑 =1 × 𝛼(𝐶𝑅𝑃𝑗)𝑟𝑒𝑠𝜑 ) 𝐾 𝑗=1 (8) \ 𝔼𝑆𝐴 𝑡𝑒𝑐ℎ = ∑ 𝔼𝑖 𝑡𝑒𝑐ℎ × 10−3 𝑀𝑊ℎ 𝑦𝑟−1(9)𝑁 𝑖=1 (9) note that 𝔼𝑖 𝑡𝑒𝑐ℎ < 𝔼𝑖 𝑇𝐸𝑃and 𝔼𝑆𝐴 𝑡𝑒𝑐ℎ < 𝔼𝑆𝐴 𝑇𝐸𝑃due to inclusions of sharing allocation fractions. the foregoing is formulated in the next subsection as resource allocation problem. 2.3.1 resource allocation problem formulation for agro-waste utilization the utilization of agro-wastes as feedstock for electricity generation chain process in the northeast sub-region of nigeria is formulated as essentially resource allocation problem. this is because there is other competing utilization of agro-wastes such as animal feeds, building and http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 46 cooking requirements by humans, farm manures and other engineering applications such as soil binders, cement additives etc. 2.3.1.1 problem formulation assume m admissible agro-wastes generated in metric tons/annum are denoted as {𝑊1,𝑊2… . .𝑊𝑖 …… .𝑊𝑚} and their corresponding calorific values in mj/ton are denoted as {𝑐𝑣1, 𝑐𝑣2, . . 𝑐𝑣𝑖 … . 𝑐𝑣𝑚}. let {𝑋𝜐: 𝜐 = 1,2, …… . . 𝑛} ∈ 𝑅 𝑛; represent the agro-waste allocations per annum to 𝑛 end users. let 𝑋𝑘 (𝑒) represent the total contributions from all the admissible agro-wastes as feedstock for electricity production given by eqn. (10) 𝑋𝑘 (𝑒) = 𝛼𝑖 (𝑘) ×𝑊𝑖 𝑚 𝑖=1 (10) where 𝛼𝑖 (𝑘) is the fraction of 𝑖𝑡ℎ agro-waste ∀ 𝑖 ∈ {1, 𝑚}that is allocated to 𝑘𝑡ℎ electricity end userwhere 𝑘 ∈ {1, 𝑛}. the mathematical formulation of the agro-waste allocation problem for electricity production can be cast as eqn. (11) 1) cost function: 𝑀𝑎𝑥𝐸𝑇ቀ𝑋𝑘 (𝑒)ቁ = (𝛼𝑖 (𝑘) ×𝑊𝑖 𝑚 𝑖=1 × 𝐶𝑉𝑖) (11) subject to the following equality and inequality constraints: 2) equality constraints form agro-wastes shared amongst n end-users using optimally specified fractions 𝛼𝑗 (𝑘) for 𝑘 = 1, 2… . 𝑛 and each 𝑗 = 1, 2, … .𝑚 as stated in eqn. (12). 𝑋1 = 𝛼1 (1) 𝑊1 + 𝛼2 (1) 𝑊2…+𝛼𝑗 (1) 𝑊𝑗…+ 𝛼𝑚−1 (1) 𝑊𝑚−1 + 𝛼𝑚 (1) 𝑊𝑚 𝑋2 = 𝛼1 (2) 𝑊1 + 𝛼2 (2) 𝑊2…+𝛼𝑗 (2) 𝑊𝑗…+ 𝛼𝑚−1 (2) 𝑊𝑚−1 + 𝛼𝑚 (2) 𝑊𝑚 𝑋𝑘 (𝑒) = 𝛼1 (𝑘)𝑊1 + 𝛼2 (𝑘)𝑊2… +𝛼𝑗 (𝑘)𝑊𝑗…+ 𝛼𝑚−1 (𝑘) 𝑊𝑚−1 + 𝛼𝑚 (𝑘)𝑊𝑚 (12) 𝑋𝑛 = α1 (n−1) w1 + α2 (n−1) w2… +αj (n−1) wj… + αm (n−1) wm xn = α1 (n) w1 + α2 (n) w2…+αj (n) wj…+ αm−1 (n) wm−1 + αm (n) wm the total agro-wastes (𝑊𝑇) is then given by wt = w1 +w2 … +wj + … wm−1 +wm → wi m i=1 (13) 3) inequality constraints are summarized in eqn. (14). 𝛼𝑚𝑖𝑛𝑗 (𝑘) ≤ 𝛼𝑗 (𝑘) ≤ 𝛼𝑚𝑎𝑥𝑗 (𝑘) 𝑗 = 1,2…𝑚 ∀ 𝑘 ∈ {1, 𝑛} 0 < 𝑋𝑖 ≤ 𝑊𝑇 𝑛 𝑖=1 (14) http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 47 0 < 𝛼𝑗 (𝑘) ≤ 1 ∀ j = 1,2, ……… .m 𝑛 𝑘=1 the foregoing generalized agro-waste resource allocation formulation is essentially a linear programming (lp) problem. (figure 7) shows the flow chart for obtaining the pareto optimal solution to the lp problem using the monte-. carlo simulation and greedy approach. figure 7: flowchart for lp based agro waste resource allocation 3. results and discussion 3.1 results of major crops produced by each state in northeast sub-region referring to table 1, it is seen that borno state returned the highest productions of rice and wheat whilst adamawa state has the highest production of sugar cane in the northeast subregion. by extension, they also produced corresponding agro-wastes per annum from the crop types mentioned and the benchmark rpr utilized as presented in table 2. note that borno state returned as the highest producer of rice with total cultivated area of 45,000 hectares of land with an estimation of 22.5x106 metric tons per annum at minimum production rate of 10 bags of 50kg per hectare of paddy rice and also a gross estimate of 15.75x106 metric tons of wheat at a start select randomly fractions(𝛼𝑖𝑖 = 1,2…𝑛), for all admissible agro wastes from specified ranges via monte-carlo simulation (mcs); compute cost function: 𝐸𝑇 (𝑖) at 𝑖𝑡ℎ iteration using eqn. (14), specified data and feasible allocations for agro-wastes. normalize the fractions such that all fractions are less than unity and their summation is equal to unity solve lp of cost function eqn. (11) subject to equality constraints eqn. (12) and inequality constraints eqn. (13) to search for feasible allocation fractions𝛼𝑗 (𝑘) : 𝑗 = 1,2, … 𝑛 of crop residues for electricity generation type equation here. 1 stop no yes no yes data specifications: no of agro-wastes and their calorific values (cv); number of agro-wastes (w) available; no of end-users (n); range of fractions allocated to end-users; set maximum iteration no (n), 𝑖 = 0 & 𝐸 (0) = 0 . 1 is 𝐸𝑇 (𝑖) > 𝐸𝑇 (𝑖−1) ? save 𝐸𝑇 𝑀𝐴𝑋 = 𝐸𝑇 (𝑖) 𝐼𝑠 𝑖 = 𝑁 + 1 ? 𝑆𝑒𝑡 𝑖 = 𝑖 + 1 2 2 http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 48 minimum production rate of 7 bags of 50kg per hectare per annum. further detailed analysis carried out with respect to other crop types and for other states as depicted in the pie charts and column bars of figures 8-10. table 1: estimates of total cultivated areas in hectares for major crops grown in ne states we relied on the procedure outlined in the flowchart of (figure 7) as it concerned agro waste estimation anchored on data collected from river basin authorities within the northeast subregion. with the raw data from various sources aggregated to remove redundancies, repetitions, etc yielded preprocessed data, from which credible results emanated. relying on directed data aggregation algorithm applied to data collected spanning for over five years, we have estimated and recorded respectively, revealing benchmark values for cultivated areas annually for major crops, major crops produced annually per each state and cumulative annual crop residues generated in all the northeastern states of nigeria. the agro-wastes generated in the entire northeastern states as analyzed graphically as displayed in (figures 8-10) clearly revealed the humongous quantities available in the northeast sub-region of nigeria. the estimated 2x108 metric tons of agro-wastes generated in the northeast subregion, in this work which originated from structured survey analyses and databank of wellestablished agricultural entities in ne, are found to be more reliable and representative than extrapolations from existing generic data published by energy commission of nigeria (ecn) and published work (simonyan and fasina, 2013). it can be argued, and rightly so, that the data generated might be patently conservative due to exclusion of small-scale holding farmers and more importantly insecurity that threatens farming activities in the sub-region. we have, s/no . crop type ne total production . (x106 mt) adamawa bauchi borno gombe taraba yobe 1 sugar cane 44.00 0.48 0.23 0.45 2.5 0.32 47.98 19.4 2 maize 38.92 11.49 21.60 6.45 13.50 1.00 92.96 92.96 3 millet 5.40 4.03 12.10 8.00 2.10 11.20 42.83 14.99 4 beans 18.20 5.61 9.45 5.90 12.60 5.40 57.16 17.15 5 sorghum 5.01 1.00 11.25 5.05 9.80 2.00 34.11 255.77 6 groundnut 3.70 2.10 7.02 1.80 4.14 3.70 22.46 5.61 7 wheat 0.35 8.00 45.00 0.12 0.41 4.20 58.08 231.84 8 rice 20.02 12.30 61.20 2.00 4.60 4.20 104.32 365.12 total 135.60 45.01 167.85 29.77 49.65 32.02 459.90 1002.84 cultivated areas in ne subregion states ( 103 hectares) table 2: major crops produced by each state in northeast sub-region s/n o state crop type production (mt x103) maize rice beans millet sorghu m sugar cane whea t ground nut 1 adamawa 214 105 127 58 132 998 18 45 2 bauchi 55 262 46 53 89 4 147 62 3 borno 100 460 205 140 95 5 230 101 4 gombe 152 22 160 72 129 10 27 103 5 taraba 289` 55 380 131 212 45 33 95 6 yobe 166 265 278 74 111 11 127 198 total 1583 1511 2014 805 1220 1139 769 604 http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 49 therefore, adopted error bars randomly selected from the band ± (10%-25%) depending on the location in this study area to capture the uncertainties inherent in the agro-waste estimation effort. it has been conclusively established that agro-wastes are available, in abundance, in the northeast sub-region to prosecute sustainable distributed electricity productions. figure 8: pie and bar representations of cultivated lands in ne states for major crops grown figure 9: pie and bar representations of major crops productions in ne states figure 10: pie and bar representations of agro-wastes from major crops grown in ne states (a) pie chart representation in % (b) bar chart representation in metric tonnes (a) pie chart representation in % (b) bar chart representation in metric tonnes http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 50 3.2 results of proximate analysis of major agro-waste samples in northeast states this subsection presents results of proximate analysis carried out on the biomass samples (agro waste or agricultural residues) for each state in the northeastern sub-region. this is in accordance with the experimental setups of (figures 4 and 5) with algorithmic flowchart of (figure 6) applied to compute the calorific value for all the admissible agro-wastes from each state in northeast sub-region. the proximate analysis results for each state are presented in table 2. table 2 depicts the benchmark values of lhv for all the admissible agro-wastes with their respective error bars also indicated. figure 11: column plot of calorific value of each major agro-waste in northeast 3.3 results of agro-waste allocation via linear programming (lp) approach the total agro-wastes generated in the northeast have been shared in pareto-optimal sense amongst competing users via the bar chart of (figure 11) that deployed hybrid monte-carlo greedy simulation engine. the range of permissible values for each competing users must be specified a-priori to enable the determination of the pareto-optimum sharing ratio of the agrowastes as found by the algorithm for the assumed competing users of agro-wastes. (figure 12) depicts the percentage allocation of agro-wastes to the competing candidates assumed; whilst (figure 13) is a pie-chart illustration of the percentage of allocation to electricity generation against the share allocated to other major competing needs of agro-wastes in northeast subregion of nigeria. http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 51 figure 12: bar chart representation of agro-waste resource allocation in northeast figure 13: pie-chart comparison of agro-wastes allocation to electricity versus other uses table 2 presents the results of weighted proximate analysis that enabled the computations of calorific values for the agro-residues from the major crops grown in the northeastern nigeria. table 3 offers, in the main, the range of calorific values obtained for the dominant agro-wastes admitted in this paper. this table has also presented energy worth for each agro-waste type to enable gross estimation of overall energy yield from all agro-wastes. table 4 has comprehensively summarized the leading results of the lp based resource allocation of agro-wastes in the northeast. http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 52 table 2: energy derived from the eight selected agro wastes in mj/kg table 3: energy contents of eight agro-wastes utilizing their annual estimations & lhvs s/n o major agrowastes in ne total annual agrowaste. (mtx107) lower calorific value (lhv) mj/kg weighte d calorific value toe/kg x10-3 total energy content min lhv weighte d lhv max lhv toe x107 pj 1 sugar cane bagasse 7.469 14.25 16.34 17.04 0.39 2.913 1219.61 2 maize cob 1.470 15.01 16.57 17.24 0.396 0.582 243.67 3 millet bran 1.203 14.52 15.7 16.25 0.375 0.451 188.82 4 beans pod 4.233 15.59 16.96 17.72 0.405 1.714 717.62 5 sorghum bran 1.946 14.66 15.62 15.29 0.373 0.726 303.96 6 groundnut shell 0.565 15.01 16.14 16.98 0.385 0.218 91.27 7 wheat husk 8.813 16.21 16.85 17.25 0.402 3.543 1483.38 8 rice husk 5.064 13.2 14.44 15.96 0.345 1.747 731.43 table 4: summary of main results of lp based resource allocation of agro-wastes we reiterate that dry samples of eight agro-wastes were characterized for each state via proximate analysis. this has enabled the computation of weighted lower heating calorific values for the entire ne, here referred to as benchmark values, as presented in table 4. it can be inferred from table 2 that the lower calorific heating values for the admissible agro-wastes in ne s/no sample proximate analysis weighted variables for ne calorific value (cv) % % % % % % % kcal/kg (mj/kg) 1 s/c. bagasse 28.4 2.5 24 4 41.1 28.4 2.5 3904 16.34 2 maize cob 7.5 8.5 8 3.5 72.5 7.5 8.5 3960 16.57 3 millet bran 7.5 17.4 2.8 2.2 70.1 7.5 17.4 3752 15.7 4 beans pod 14.2 6.7 16 4.5 58.6 14.2 6.7 4052 16.96 5 sorghum bran 8 2.5 2.9 2.3 84.3 8 2.5 3733 15.62 6 g/nut shell 7.8 4.3 3.5 6 78.4 7.8 4.3 3623 16.14 7 wheat husk 4.85 2.9 6 2 84.25 4.85 2.9 4026 16.85 8 rice husk 15 13 13 15 44 15 13 3450 14.44 s/no competing users of agro-waste residues specified a-priori parameters optimum value of sharing parameter αopt share of agro-wastes αmin αmax amount unit 1 animal feed 0.30 0.65 0.335 17.1x104 mt/yr 2 electricity generation 0.08 0.20 0.135 6.89x104 gwh/yr 3 human use-cooking, rural housing 0.06 0.25 0.085 4.34x104 mt/yr 4 field manure 0.35 0.70 0.254 12.96x104 mt/yr 5 other uses in rural shelters, soil stabilization, etc 0.13 0.3 0.191 9.75x104 mt/yr http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 53 fall within the range of 14.44mj/kg to 16.96mj/kg with beans pod returning the highest lhv value of 16.96mj/kg and rice husk has the least lhv of 14.44mj/kg. the aforementioned range have been compared with equivalent published values in national and international journals for the agro-wastes analyzed and found to return percentage deviations of ± 5% from published benchmark values for other geographical jurisdictions. the observed variations in calorific values of corresponding crop residues compared could be rationally linked to differences in ecological zones, chemicals applied, types of crop seedlings planted, etc. table 3 presents a compendium of energy contents of the agro-wastes computed utilizing their known respective gross estimations and corresponding lower heating values also captured in the table. referring to comparison of gross energy contents for eight major agrowastes in the northeast depicted in figure 11, it can be seen that wheat husk has the highest annual content value of 3.5x107toe or 1483pj, followed by bagasse agro-waste bearing annual energy content of 2.9x107toe and the least being groundnut shell that can yield annual energy content of 0.22x107toe. the estimated huge energy potential of 118.9mtoe or 4.98xj from agro-wastes in northeast is therefore evident, part of which can be utilized for electricity generation. the formulation of agro-waste allocation as lp problem has been solved and the results obtained presented in table 4 and further elucidated in (figures 12 and 13). referring to table 4, it is seen that the optimal sharing ratio allocated to electricity generation is 0.135 (13.5%) of the total agrowastes of the northeast sub-region. the aforementioned percentage corresponds to gross estimates of 6.89x104 metric tons per annum as agro-wastes available for electricity production and found to be capable of sustaining generation of electrical energy of 55.8gwh/annum for geographically scattered rural communities in the northeast sub-region. a cursory look at (figure 12) reveals that the highest percentage of agro-wastes, corresponding to 34%, is allocated as animal feed followed by field manure allocated 25% and the least being 8.5% allocated to human use. indeed, the contribution of this work is anchored on the mathematical model developed to resolve competing usage of agro-wastes in the northeast. as a closure, (figure 13) is a pie-chart comparison of what has been allocated for electricity generation respect to other identified applications of agro-wastes in the northeast. 4. conclusion this research work has comprehensively investigated, in the first phase, the potentials of agro wastes, for distributed electricity productions in northeast sub-region of nigeria. solid biomass, comprising forestry woods and agricultural wastes, is commonly utilized in all the six states of the northeast sub-region as the indigenous energy sources of the rural dwellers. undoubtedly, agro wastes are the cheapest renewable energy resources found in the northeast sub-region. based on structured questionnaires administered, it is established that adamawa state is highest in the sugarcane production whilst borno state is highest in the production of rice and wheat. according to lake chad basin authority, borno state has a total cultivated area of 45,000 hectares of land with an estimation of 337.5x106 metric ton per annum of rice production and a gross estimate of 157.5x106 metric ton of wheat per annum. more precisely, samples of 8 agrowastes investigated were characterized via proximate analysis which yielded their respective lower heating values to be within the range of 14.44mj/kg to 16.96mj/kg. it has been experimentally determined that some of the agro wastes have higher calorific values than others http://www.azojete.com.ng/ mailto:kunduli@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 54 as documented chronologically in tables 2 & 3 and figure 11. the calorific values obtained are within the range compared with existing work done in nigeria and other countries. relying on pragmatic solution of lp problem formulation, we arrived at gross estimates of 6.89x104 metric tons per annum as agro-wastes available for electricity productions of 55.8gwh/annum for geographically scattered rural communities. references aderoju, om., dias, ga. and echakraoui, z 2017. assessment of renewable energy sources and municipal solid waste for sustainable power generation in nigeria. in: world multidisciplinary earth 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16, 7209, http://doi.org /doi.org/10.3390/en16207209. aruya, ei., yusuf, ro. and yusuf, yo. 2016. an assessment of crop residue characteristics and factors militating against efficient management in the ikara local government area of kaduna state, nigeria. wit transactions on ecology and the environment, vol 202, press doi: 10.2495/wm160301www.witpress.com, issn 1743-3541 on-line. awulu, jo., omale, pa. and ameh, ja. 2018. comparative analysis of calorific values of selected agricultural wastes (october 1, 2018). nigerian journal of technology (nijotech) vol. 37, no. 4, october 2018, pp. 1141 – 1146. available at ssrn: http://ssrn.com dan. g. 2008. energy from biomass in pulp and paper mills. environmental engineering and management journal. september/october 2008, vol.7, no.5, 537-546. e-mail: gda@ch.tuiasi.ro energy commission of nigeria (ecn). 2015. proceedings of the renewable energy conference: energetic solution conference, abuja/calabar, nigeria. katherine, rc., francy, g., blanco, p., julián, aa. and duartea, vk. 2016. assessment of the energy potential of agricultural residues in non-interconnected zones of colombia: case study http://www.azojete.com.ng/ mailto:kunduli@yahoo.com https://www.sciencedirect.com/journal/journal-of-environmental-management https://www.sciencedirect.com/journal/journal-of-environmental-management/vol/294/suppl/c https://doi.org/10.1016/j.jenvman.2021.112929 http://doi.org/ http://ssrn.com/ mailto:gda@ch.tuiasi.ro arid zone journal of engineering, technology and environment, march 2025; vol.21(1):35-55. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kunduli@yahoo.com 55 of chocó and putumayo research center for sustainable development in industry and energy – cides. industrial university of santander, bucaramanga, colombia. chemical engineering transactions vol. 50, pp. 349-354: doi: 10.3303/cet1650059. navneet, k. 2014. converting waste agricultural biomass into electrical energyindian perspective. 2014. international conference on communication, computing and systems (icccs – 2014) rishi, kd. 2013. estimation of power generation potential of agricultural based biomass species. m. tech. dissertation submitted to the department of mechanical engineering national institute of technology rourkela. simonyan, kj. and fasina, o. 2013. biomass resources and bioenergy potentials in nigeria, african journal of agriculture, vol. 8(40), pp 4975-4989, 17 october, 2013. vaibhav, j. and avin, c. 2014. energy estimation and electrical power generation potential of agricultural biomass residue. international journal for technological research in engineering. department of mechanical engineering, oriental university, indore, india. volume 2, issue 2, october-2014. world bank and international finance corporation. 2014. doing business 2014 – economy profile – nigeria. http://www.azojete.com.ng/ mailto:kunduli@yahoo.com corresponding author’s email address: esmaiva@gmail.com 836 arid zone journal of engineering, technology & environment original research article development of plaster of paris (pop) from gypsum deposits of fune yobe state, nigeria by calcination process e. s. maiva1*, i. s. aji2 and z. a. mshelia2 1,2marini asphalt plant, ministry of works and housing maiduguri, borno state-nigeria 2department of mechanical engineering, faculty of engineering, university of maiduguri, maiduguri, borno statenigeria *corresponding author’s e-mail address: esmaiva@gmail.com article information abstract gypsum is a common sulfate mineral which has significant commercial value mostly made up of hydrated calcium sulphate. over dependence on foreign/imported pop into the country is in the high rise, local economy is affected and local miners are not patronized. thus, the study produced and characterized pop from fune local government area of yobe statenigeria (alangefe deposit site). the gypsum sample was collected at three layers of 0.5m each after excavating the top soil. the samples were beneficiated and calcined at the civil engineering laboratory of eighteenth engineering company at 1700c. porosity, shrinkage, compressive strength and density tests were carried out on these samples. the gypsum collected were processed and characterized with the sample having porosity of 53.37% on the average, 0% shrinkage, compressive strength of up to 23.03n/mm2 and 21.04n/mm2, density of 0.91g/cm2 and 1.01g/cm2. water:pop ratio of 80-100:100 gave the best results. the properties of the characterized pop from fune (alangefe) mining site had excellent properties as compared with the pop obtained in the market. thus, the produced pop can replace the ones being sold in the market in terms of availability and its properties. submitted 18 august, 2024 revised 11 september, 2024 accepted 15 september, 2024 keywords: gypsum plaster of paris calcination density porosity compressive strength © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction gypsum is a common sulfate mineral which has significant commercial value mostly made up of hydrated calcium sulphate (caso4.2h2o). it is a white mineral of calcium sulphate in the earth crust (mohammed, 2015). it is a common mineral that occurs in combination with sedimentary rocks and has thick, broad evaporation beds. gypsum can be found in nature as translucent, cleavable masses termed selenite and as flattened, frequently twinned crystal (mohammed, 2015). it has been used as a bonding material in building walls and the finishing works of walls. the most common reason for its widespread use is availability, efficiency, and low cost (salman et al., 2023). gypsum is an essential material used for numerous construction purposes ranging from building and several others due to its aesthetics and insulative properties (kerstin et al., 2023). according to the federal ministry of science and technology, (raw materials research and development council: rmrdc, 2010), gypsum has been in existence in nigeria since 1921 with grades from the various deposits in the country (at about one billion tonnes spread across the deposit sites) satisfying the specifications required by the cement industry: identified deposits in north eastern nigeria are found in adamawa, taraba, yobe, borno, bauchi and gombe states respectively. locations like yobe, sokoto, adamawa, gombe, benue state and others have gypsum deposits in substantial quantities. plaster of paris is a quick-setting gypsum plaster consisting of a fine white powder (calcium sulphate hemihydrate), which hardens when moistened and allowed to dry and it is known since ancient times as plaster of paris, so called because of its preparation from the abundant gypsum found near paris (britannica, 2021). calcination is the process of heating gypsum to evaporate the crystalline water in order to dehydrate it into plaster or stucco. this can be done in a batch or continuous manner. free water is usually removed at 45°c steps in the initial process, while crystalline bound water is removed in 120–180°c steps in the second process. many systems additionally include options for grinding capacity before, during and after calcination, depending on the product intended to be produced. azojete december 2024. vol.20(4):836-844 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:esmaiva@gmail.com mailto:esmaiva@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 837 the present study assessed fune (alangefe) deposit site in yobe state, nigeria for the production of plaster of paris (pop) and compared their properties with pop currently available in the market (popm). this study explored the use of gypsum from our readily available deposit sites which will improve industrialization, create more job opportunities for local miners and boost the local economy through industrialization. soyinka (2015), in their research on the comparative analyses of wurno, dange and weppa gypsums in nigeria for plaster and ceramic production, it was deduced that the constant importation of plaster of paris constitutes a drain on national economy and an added cost on ceramic mass production. various tests were carried out; results showed that the ratio mix of 75-85 of the plaster to water ratio mix were suitable for ceramic slip casting process. 65 and 70 plaster:water ratio mix were better used for casting models and press moulding process. the gypsum obtained from the three locations can be used for ceramic application. bukar et al. (2011), in their research on, geology and geochemistry of gypsum deposits in fika and fune local government area of yobe state, nigeria: implication to industrial applications, it was concluded in the study that the gypsum of the study areas fall within the cretaceous sequence and the gypsum occur as seams, vein let and lenses and based on these geochemical values the gypsum of the two areas is good quality for cement, plaster of paris, solid wallboard, ceramic and ammonium sulphate fertilizers. further, oyedele et al. (2018), in their research on processing a locally sourced gypsum material for medical and industrial applications, results of property tests showed that the products will have long service life. it was concluded in this study that that ibese gypsum, when properly treated, can be used in both industrial and medical settings. in order to prevent unanticipated failure in service, processing should involve a multistage de-gritting operation with the final gypsum slip carefully dewatered and converted to gypsum plaster at about 200oc. the use of any quality enhancer that tends to affect the hardness or softness of the plaster products should be carefully controlled based on the specific application. also, ngaaje (2021) in the study on the physic-mechanical properties of plaster of paris (gypsum plaster) reinforced with paper pulp in order to improve the weight of plaster paste and to obtain materials of lighter weight that solve problems such as poor flexural strength, and crack propagation. it was determined at the end of the study that the incorporation of small amounts of paper pulp (2 kg samples) into the plaster paste improves its flexural properties. the presence of paper pulp in the plaster of pop paste increases the time of hardening of the plaster cement from one proportion to another, reduces the workability of the mixed paste, significantly solves the problem of removal, the apparent density drops when waste paper paste is increased in the mixed plaster. because of its light weight, low density, its acceptable mechanical properties, these new materials are recommended for exploitation in the manufacturing of popular lightweight construction finishing like panels for ceiling or walls, staff works and other applications. similarly, pirman et al. (2022) in their research on enhanced mechanical properties plaster of paris with addition of rice husk fibers, the incorporation of additives materials into gypsum alters water absorption and mechanical properties of the final products. the density, water absorption, porosity, and mechanical properties prior to compressive strength were examined. the density, water absorption, porosity, and mechanical properties of plaster lies in the range of 1.521 − 1.673 g/cm³, 25.107 − 33.989 %, 40.196 − 53.295 %, and 2.666 − 9.438 mpa, respectively. the incorporation of moderate size rice husk fibers in the range of 63 μm and 250 μm enhanced the compressive strength due to the contribution of rice husk fibers as reinforcement agent in the gypsum network. this work used gypsum deposit at three different layers to explore its properties and characterized the pop formed. properties obtained were then compared with the pop available in the open market. 2. materials and methods 2.1 materials the materials used in this study include water and gypsum rock from fune (alangefe) (latitude 11.306947o, longitude 11.38767o) deposit mining site in yobe state. figure 1 shows yobe state map with all the local government areas. http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 838 figure 1: map showing yobe state lgas (geospatial analysis mapping and environmental research solutions (gamers), 2018) the equipment used for this study include; electric blast drying oven (type 10 -1a, beijing luda waiye technology) for calcination (at eec laboratory), digital weighing scale (model, szegedi, omheng type), electric hydraulic pressure testing machine (huaxi, dye-2000 type; eec lab) to determine compressive strength, shovel, pulley, torch light, hand gloves, vernier caliper, sieve (model, bosch-112219), crucible for loading sample, stirrer for mixing gypsum and water. 2.2 method this work adopted the method of calcination used by hamdan et al. (2024). this included collection of gypsum samples, selection and cleaning, washing and drying, crushing, screening/sieving, calcination, storing, porosity, density and compressive strength was determined. the experimentation was done at the eighteenth engineering company (eec) laboratory, molai, maiduguri, borno state. also, the chemical analysis was done at spectral laboratory services, tudun wada, kaduna, kaduna state. 2.2.1 preparation of the gypsum samples the mineral was produced from underground mines which is below water level by excavation (digging). three separate samples each at 0.5m, 1m and 1.5m respectively from each location after removal of the top soil were collected. the topsoil was removed at 1.8m. it was then collected, stored in a bag and transported to the workshop where it was processed. figure 2 shows the samples collected from the mining site. http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 839 figure 2: gypsum samples from deposit site to produce good samples of gypsum that would be further processed, impurities were thoroughly cleared and cleaned from the samples. this was done by picking out and removing the larger clay and sand particles from the samples and washing it. also, gypsum was soaked for about 1hour to allow easy removal of the clay on the samples. it was then washed thoroughly to ensure it was free from impurities like sand and clay that got stuck to it. after proper washing, it was then allowed to dry under normal room temperature conditions. a grinder was used to first reduce the size of the dried gypsum rocks to smaller pellets, then it was taken to another grinder which crushed the samples to powdered form. in addition, a manual sieve of 300µm (astm e11) was used for sieving the crushed powder in order to remove the large grains which were not properly crushed so as to obtain a fine powder. 2.2.2 the calcination process the process of calcination to form plaster of paris was one involving heating of the cleaned, dried, and crushed gypsum to a certain temperature ranging from 120°c to 180°c to drive off a portion of the water of crystallization (tesfaye, 2015). the gypsum powder after preparation was poured into a crucible and loaded into the electric blast drying oven for calcinations (figure 3) shows the electric blast drying oven). crucible was used in the kiln for calcinations of gypsum because pop produced from a crucible is denser and stronger. thereafter, sample was heated to a temperature of 170oc, to ensure that the combined water was released from the samples. after heating it to the required temperature, the oven was turned off and the powder allowed to cool down inside the oven for a period of 18 hours before it was opened. figure 3: electric blast drying oven after calcination, the powder was kept dry and enclosed in a polythene bag to stop moisture intrusion/infiltration. 2.2.3 characterization of the pop the samples were subjected to various tests (characterization) to determine the porosity/absorbency, density, shrinkage and compressive strength. a. porosity porosity is a measure of the void spaces in a material. high porosities result in micro-cracks forming in regions where stress concentration is high thereby affecting the strength of the material (pop) as reported by http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 840 mahendra (2018). the porosity test was carried out at the eighteenth engineering company (eec) civil engineering laboratory at molai, maiduguri. the samples were dried in the oven for 24 hours at a temperature of 45oc and cooled before the porosity/water absorption test was performed. the weights of the dried samples were measured. the samples were then soaked in water for a period of two hours to ensure optimum saturation as similarly reported by hamdan et al. (2024). thereafter, the pop was further subjected to porosity test with a ratio mix of pop/water at about 80ml to 150ml. figures 4 and 5 show how the porosity test were carried out. samples were moulded (figure 5) according to the mix ratio of water: pop as presented in table 1 as recommended by hamdan et al. (2024). the porosity was determined using equation 1. percentage of water absorption = ws − wd wd × 100 (1) where; ws = saturated weight (g) and wd = dry weight (g). figure 4: samples weighed for porosity figure 5: samples being soaked b. density the mass of the samples was measured using the electric weighing scale and the volume was calculated using equations 2 and 3; volume of cylinder = πr2h (cm3) (2) dry density = mass volume (𝑔/cm3) (3) c. shrinkage shrinkage is reduction in single dimension of a sample when moisture is reduced as reported by hamdan et al. (2024). the samples were placed in a mould and allowed to solidify. after it was dried completely, it was observed that there was zero reduction in their sizes. d. compressive strength compressive strength of a material is the uniaxial compressive stress reached when the material fails completely. compressive strength test was carried out on pop because it falls into the category of earthen materials which lacks the ability to withstand tensile stress (stress due to pull as in metallic materials) (soyinka, 2015). the compressive strength was obtained by experimental means using the electro-hydraulic pressure testing machine. the apparatus used for this experiment is the same as that used in a tensile test. however, rather than applying a uniaxial tensile load, a uniaxial compressive load is applied as shown in figure 6. the specimen (usually cylindrical) is shortened as well as spread laterally (tesfaye 2015). the compressive strength of the pop was be determined using the ratio mix of 80ml to 130ml to 100g of water: pop. the test was carried out at the eighteenth engineering company (eec) civil laboratory situated at molai, maiduguri, using the electric hydraulic pressure testing machine. the compressive strength and cross-sectional area were calculated using equation 4 and 5 respectively. compressive strength = applied force cross − sectional area (n/mm2) ( 4) where: cross − sectional area of cylinder = 2πrh + 2πr2h (mm2) (5) http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 841 figure 6: sample loaded to the press jaws 3. results and discussion 3.1 porosity figure 7 shows a comparison between the pop obtained in the market (popm) and that of the samples obtained from fune (alangefe) deposit site at 0.5m, 1.0m and 1.5m depth respectively. figure 7: comparison between porosities of popm and fune (alangefe) pop from figure 7, percentage in porosity increases as the volume of water increases. the popm had its highest porosity of 85.92% at 100:130 ratio mix of pop to water and the lowest percentage porosity at 61.65% at 100:80. for fune (alangefe) at 0.5m, the highest percentage porosity was 81.00% of pop to water mix ratio at 100:130 and the lowest to be 54.52% at 100:80. for fune (alangefe) at 1.0m, a similar steady increase in porosity was observed as the volume of water increased. at 100:80 ratio mixes of pop to water, the porosity was 46.01% and the highest was at 100:130 which was 69.10%. for fune (alangefe) at 1.5m, the lowest porosity was 21.34% at 100:80 pop to water ratio mix and the highest was 141.37%. the third layer at 1.5m had the highest porosity among all the samples tested. the increase in porosity was as a result of the increase in the volume of water added to the pop. these results are in agreement with hamdan et al. (2024), which stated that porosity or absorption in pop increases with increase in the proportion of water added to it. the results from this sample also agreed to their work which also had increase in porosity upto 80% for 100:130 ratio mix of pop to water. the porosity of popm was higher in percentage when compared to fune (alangefe) which indicates that the produced pop has better porosity and it could replace the popm in terms of porosity. 0 20 40 60 80 100 120 140 160 1 2 3 4 5 6 ratio mix of each sample pop fune 1 fune 2 fune 3 fune 1: at 0.5m depth fune 2: at 1.0m depth fune 3: at 1.5m depth ratio mix of water:pop 1[80:100] 2[90:100] 3[100:100] 4[110:100] 5[120:100] 6[130:100] p o r o s it y (% ) http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 842 3.3 shrinkage the shrinkage percentage of popm compared to fune (alangefe) samples at 0.5m, 1.0m and 1.5m is presented in table 1. table 1: shrinkage test result for popm with fune (alangefe) sample at 0.5m, 1.0m and 1.5m depths parameters samples 1 2 3 4 5 6 plaster(g) 100 100 100 100 100 100 water 80 90 100 110 120 130 shrinkage(%) (popm) 0 0 0 0 0 0 shrinkage (%) (fune, alangefe) 0 0 0 0 0 0 table 1 shows the shrinkage percentage for fune (alangefe) samples for first, second and third layers. it can be noticed that the percentage in shrinkage is at 0% for all the water:pop mix ratio. this result agrees with that of hamdan et al. (2024) and soyinka (2015) who had in their research 0% shrinkage of the cast sample used. 3.4 compressive strength from figure 8, the compressive strength of popm was 12.88n/mm² at 100:80 and the lowest 4.16n/mm² at 100:100 ratio mix of pop to water respectively. when compared to pop from fune (alangefe), at 0.5m a compressive strength of 23.03n/mm² as the highest at 100:80 and the least as 3.80n/mm² at 100:110 ratio mix of pop to water. at 1.0m layer of the sample, the highest was 11.47n/mm² at 100:80 and the least 3.60n/mm² at 100:100 ratio mix of pop to water. the 1.5m layer however had compressive strength of 10.12n/mm² as the highest and the lowest 5.59n/mm² at 100:120 and 100:100 ratio mix of pop to water respectively. it was observed that the compressive strength of popm and the three depths that the stress decreases with increase in the water volume. also, the compressive strength of the produced pop was higher than that of the popm which indicates that fune pop had better compressive strength and can replace the popm. the highest compressive strength of the 1.5m depth sample was similar to the finding of hamdan et al. (2024). figure 8: comparison between compressive strengths of popm and fune (alangefe) pop 3.5 density density test was carried out and the results are presented in figure 9 which compares popm density to that of fune (alangefe) samples at 0.5m, 1.0m and 1.5m depth. 0.00 5.00 10.00 15.00 20.00 25.00 1 2 3 4 5 6 ratio mix for each sample pop fune 1 fune 2 fune 3 fune 1: at 0.5m depth fune 2: at 1.0m depth fune 3: at 1.5m depth ratio mix of water:pop 1[80:100] 2[90:100] 3[100:100] 4[110:100] 5[120:100] 6[130:100] c o m p r e s s iv e s t r e n g t h (n /m m 2 ) http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 843 figure 9: density of popm compared to fune (alangefe) pop popm had its density highest which was 0.91g/cm³ and lowest at 0.72g/cm³ at 100:80 and 100:120 ratio mix of pop to water. for fune (alangefe) sample at 0.5m depth, the highest density was 0.90g/cm³ and lowest 0.74g/cm³ at 100:80 and 100:130 ratio mix of pop to water respectively. the values at 1.0m depth was 0.92g/cm³ and 0.72g/cm³ highest and lowest at 100:80 and 100:120 ratio mix of pop to water respectively. at 1.5m depth, the highest was 1.01g/cm³ and lowest 0.68gcm³ at 100:80 and 100:130 ratio mix of pop to water respectively. it can be observed that the decrease in density as the volume of water increases per sample as stated by hamdan et al. (2024) which had a similar result in density for nafada sample in their research. the density of popm and that of fune (alangefe) were similar which indicates that the produced pop could replace the popm in terms of density. 4. conclusion based on the results obtained from this study, the following conclusions were drawn. i. qualitative gypsum is readily available in deposit sites and can be mined at different layers after excavating the topsoil in fune local government area of yobe state. ii. the characterized pop in all the samples showed excellent properties with; a. porosity of 53.37 at the average for all samples, b. zero percent shrinkage for all samples, c. compressive strength of 23.03n/mm2 at 0.5m depth, d. density of 0.91g/cm2 and 1.01g/cm2. iii. the properties obtained from the characterized pop revealed that in all the samples, as the depth of collection increases, the pop has differing properties in terms of its porosity/absorbency, density, shrinkage and compressive strength. however, the pop when processed, can replace the one obtainable in the market, due to the excellent characterized properties which surpassed the ones being used. iv. pop at the three depths of mining possessed properties which could replace the ones obtainable in the market and the most viable is at 0.5m depth. references abidoye, lk. and bello, ra. 2010. restoration of compressive strength of recycled gypsum board powder. the pacific journal of science and technology,11(2): 42-50. anthony, jw., bideaux, ra., bladh, kw. and nichols, mc. 2003. "gypsum". handbook of mineralogy (pdf). v (borates, carbonates, sulfates). chantilly, va, us: mineralogical society of america. american standard of testing materials (astm) – e11, 2024 updated on 23rd june 2024. broadhurst, jl., petrie, jg. and vonblottnitz, h. 2007. understanding element distribution during primary metal production, 116(1): 1-16. 0 0.2 0.4 0.6 0.8 1 1.2 1 2 3 4 5 6 ratio mix for each sample pop fune 1 fune 2 fune 3 fune 1: at 0.5m depth fune 2: at 1.0m depth fune 3: at 1.5m depth ratio mix of water:pop 1[80:100] 2[90:100] 3[100:100] 4[110:100] 5[120:100] 6[130:100] d e n s it y ( g /c m 3 ) http://www.azojete.com.ng/ mailto:esmaiva@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):836-844. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: esmaiva@gmail.com 844 bukar, f., baba, s., shettima, b. and kyari, am. 2011. geology and geochemistry of gypsum deposits in fika and fune local 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construction materials and structure held at iit rookee, uttarakhand, india on march 7th 8th 2018, 1(1):1-10 mohammed, iy. 2015. suitability of nafada gypsum for the production of jute fibre reinforced plasterboards. atbu journal of environmental technology, 8(2): 79-92. oyedele, ea. and omolara, o. 2018. processing a locally sourced gypsum material for medical and industrial applications. fuoye journal of engineering and technology, 3(2):118-124 rmrdc. 2010. non-metallic mineral endowments in nigeria. federal ministry of science and technology, abuja, 1(1): 1-16. sidney, d. 2008. gypsum. encyclopaedia of earth eds. cutler j. cleveland, washington d.c. environmental information coalition, national council for science and the environment. http://www.eoearth.org/article/gypsum> (accessed on 21st november 2021) soyinka, gk. 2015. comparative analysis of wurno, dange and weppa gypsums in nigeria for plaster and ceramic production. a dissertation submitted to the school of post graduate studies, ahmadu bello university, zaria, nigeria. tesfaye, ab. 2015. recycling plaster of paris from discarded gypsum moulds for tabor ceramics products manufacturing share company, department of chemical and bio engineering, addis ababa university school of graduate studies, addis ababa institute of technology, addis ababa. http://www.azojete.com.ng/ mailto:esmaiva@gmail.com http://www.eoearth.org/article/gypsum corresponding author’s email address: kenneth.ojeaga@uniben.edu 978 arid zone journal of engineering, technology & environment original research article spatial assessment of aquifer vulnerability using dar zarrouck parameters in idunmwowina, edo state, nigeria k. ojeaga1* and a. o. ehinlaiye2 1department of science laboratory technology, university of benin, edo state 2department of geology, university of benin, edo state *corresponding authors email address: kenneth.ojeaga@uniben.edu article information abstract rapid urbanization and unregulated sand mining in many semi-urban areas of edo state have heightened concerns about aquifer vulnerability and groundwater contamination. this study evaluated the spatial variability of aquifer vulnerability in idunmwowina, ovia north-east local government area, edo state, using dar zarrouk parameters derived from vertical electrical sounding (ves). five ves were conducted with the schlumberger configuration at a maximum current electrode spacing of ab/2 = 200 m. data interpretation was carried out using the partial curve matching technique in surfer software, while kriging interpolation was applied for spatial mapping. the geoelectric curves identified include khk (40%), haa (20%), hak (20%), and aak (20 %), indicating predominantly semi-confined aquifers. the results of dar zarrouk parameters revealed hydraulic conductivity values ranging from 0.73–1.46 m/day, transmissivity between 2.72–7.67 m²/day, transverse resistance from 26,621–221,682 ωm², and longitudinal conductance (s) values between 0.004–0.335 ω⁻¹ (mean = 0.0752 ω⁻¹). additionally, the spatial distribution maps showed higher transmissivity and hydraulic conductivity in the southwestern part of the study area, while longitudinal conductance values were generally low, suggesting weak aquifer protective capacity. therefore, the results indicate that the aquifer system is vulnerable to contamination from leachates generated by nearby dumpsites. it it highlights the need for effective land use management and sustainable waste disposal practices to safeguard groundwater resources in the area. received: 29th september 2025 revised: 11th november 2025 accepted: 12th november 2025 keywords: aquifer vulnerability dar zarrouk parameters vertical electrical sounding transmissivity groundwater contamination © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction groundwater is the largest and most accessible source of freshwater on earth and plays a vital role in sustaining ecosystem services, supporting economic development and safeguarding human health (wang et al., 2018; gleeson et al., 2016). groundwater is the largest and most easily available freshwater resource on earth. it is essential to maintaining ecosystem services, economic growth, and human health (wang et al., 2018; gleeson et al., 2016). access to clean drinkable water is crucial for maintaining good health and attaining the sustainable development goals (sdgs) (nyakno 2021; eyankware et al., 2022b). this is especially true in light of the fact that the amount of clean water that society requires for cultivation, municipal usage, and drinking is growing exponentially (wang et al., 2020; lall et al., 2020; wang et al., 2020; lall et al., 2020). however, quite a number of anthropogenic activities such as oil spills, open dumps, mine tailings, corrosion of underground tanks and other unsustainable groundwater practices have led to deterioration of groundwater quality. water quality may degrade due to the leaching of geogenic contaminants as a result of weathering during mining operations or as water moves through the hydrologic cycle, organic and inorganic contaminants might be transferred from the soil to the infiltrating groundwater. the geology of the parent rocks plays a crucial role in the types of aquifer systems developed in a given area. hence, aquifer vulnerability is influenced by lithologic forms that overlies beneath it (eyankware et al., 2020a, 2020b; nyakno, 2021; umayah and eyankware 2022). hence, aquifer susceptibilities will vary in locations with different geology. several studies (kwami et al., 2013; okiongbo and akpofure 2012; omali and arogundada 2022 and simsek et al., 2006) on aquifer vulnerability have shown that aquifer protection depends on the permeability of the layers, which controls the transport azojete december 2025. vol.21(4):978-991 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/008 www.azojete.com.ng mailto:kenneth.ojeaga@uniben.edu mailto:kenneth.ojeaga@uniben.edu http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 979 of contaminants into the underlying aquifer units. although, groundwater potential and aquifer susceptibilities studies have been conducted in basement complexes and sedimentary basins (akinseye et al., 2023; eyankware et al., 2022) and eyankware and aleke (2021) utilizing geophysical techniques, the appraisal of groundwater potential and the vulnerability of aquifers to contaminants in the benin formation has not yet taken centre stage. therefore, this research is aimed at delineating the protective capacity of the aquiferous zones and groundwater potentials in idunmwowina, community, edo state utilizing the dar zarrouck parameters derived from vertical electrical sounding techniques. dar zarrouk characteristics can also be used to determine an aquifer’s susceptibility the subsurface and surface contamination (okonkwo and ugwu, 2015). dar-zarrouk parameters were first introduced (maillet, 1947), the longitudinal conductance and transverse resistance of the layers are measured using the resistivities and thicknesses of the individual layers. the second-order parameters were transverse unit resistance (ωm2), longitudinal unit conductance (ω−1), and coefficient of anisotropy (λ). water resources quality is deteriorating worldwide due to a number of anthropogenic activities affecting sources of groundwater through contamination. these include septic tanks, landfills, wastewater systems, injection wells, disposal sites, cemeteries, mine tailings, deicing salts, oilfield brines, agricultural chemicals, fertilizers, and accidental spills (el-naqa and al-shayeb, 2009). groundwater contamination can occur also when water of poor quality is drawn into a well that originally has been developed in high quality water, water especially when there is saltwater intrusion in coastal areas (akpan et al., 2018). the sand mine in idunmwowina, oluku, edo state has contributed significantly to the socio-economic advancement of the area. it has served as source of revenue to both local and the state governments. small businesses continue to thrive within the area. thus, compliments government in giving employments to our teeming youth population. however, the recent closure of the mine without adherence to international best practices regarding safe reclamation processes has led to the abandoned mine pits becoming refuse dumps for residents, breeding grounds for microbes and potential hideouts for criminals. it becomes practically more worrisome when excavation (surface mining) has already been made expose the overburden materials, thereby reducing the residence time of groundwater infiltration. although knowledge from different fields in science has been employed to understand groundwater quality, a detailed knowledge of geology and hydrogeology is however needed for seamless and reliable interpretation of groundwater resources. one of the inherent dangers associated with associated with open dumpsites is the production of leachates. these leachates are conveyed either as runoff or infiltrates through the soil matrix to contaminate groundwater. the rate and extent of leachate infiltration is controlled primarily by the ease with which the subsurface layers beneath the dumpsites and surroundings allow contaminants migrate. therefore, it has become pertinent to understand the subsoil profile to assess the impact of overlying dumpsites on the underlying aquifer systems. the dar zarrouck parameters play vital role in assessing hydrogeological conditions in this regard. 2. materials and methods 2.1 the study area the study area idunmwowina is located in ovia northeast local government area in edo state. the area lies between latitude n6° 26′ 5.3″ to n6° 26′51.7″ and longitude e5° 36′ 6.1″ to e5° 36′ 57″. the area is accessible from oluku and uselu axis of the benin-lagos road. the study area is known for hosting an active compressed natural gas station, active sand mining sites. many of these sand mines have been turned into open dumpsites by residents due to non-adherence to international best practices by mine developers. these activities are potential sources of heavy metal enrichment in the environment. 2.2 the geology of the study area the study area lies within the benin formation, a major stratigraphic unit of the southern sedimentary basin as depicted in figure 2. the benin formation is composed predominantly of reddish to reddish-brown lateritic sands, sandy clays, silts, gravels, and ferruginized sandstones (short and stauble, 1967; akujieze and irabor, 2014). the surface layer is typically lateritized, underlain by loose sands and sandy clays, often with reticulate mud cracks. parkinson (1907) first described this lithologic unit as “benin sand,” representing deposits of a paleo-coastal environment dating from the paleocene to pleistocene. subsequent studies (tattam, 1943) referred to the sequence as “coastal plain sands,” extending across parts of benin, calabar, owerri, and onitsha. these sediments constitute the upper continental facies of the niger delta, reflecting ancient fluvial and coastal plain depositional systems. http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 980 figure 1: sampling location map of idunmowina figure 2: geological map of the study area 2.4 hydraulic parameters the longitudinal conductance (s) is a measure of the impermeability of a rock layer (billing, 1972). electrical anisotropy is a measure of stratified rock which is generally more conductive in the parallel plane than the perpendicular (malick et al., and cihan et al., 2014). for a sequence of horizontal, homogenous and isotropic layers of resistivity 𝑒1 and thickness ℎ1, the dar zarrouk parameters (longitudinal conductance s and transverse resistance tr) is defined as follows; http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 981 longitudinal conductance (𝑆) = ℎ1 𝑒1 + ℎ2 𝑒2 + ℎ3 𝑒3 + ℎ𝑛/𝑒𝑛 = ∑ 𝑛 𝑖=0ℎ𝑖 /𝑒𝑖 1 transverse resistance (𝑇𝑅) = 𝑒1ℎ1 + 𝑒2ℎ2 + ⋯ . . 𝑒3ℎ3 = ∑ 𝑛 𝑖=0𝑒𝑖ℎ𝑖 2 the relationship between aquifer transmissivity, and longitudinal conductance is established by the equation derived by todd, (1980). where tr = aquifer transmissivity, k= hydraulic conductivity in m/day, hi= layer thickness of aquifer r = transverse resistance. s = longitudinal conductance transmissivity (tr)= k.hi 3 table 1: rating of protective capacity of aquifers (oladapo and akintorinwa 2007) longitudinal conductance protective capacity rating >10 excellent 5-10 very good 0.7-4.9 good 0.2-0.69 moderate 0.1-0.19 weak 0.1 poor table 2: aquifer classification based on transmissivity values (offodile, 1983) longitudinal conductance protective capacity rating >10 excellent 5-10 very good 0.7-4.9 good 0.2-0.69 moderate 0.1-0.19 weak 0.1 poor 2.5 kriging interpolation kringing interpolation is an unbiased optimal estimation method based on the analysis of semivariogram theory (lin et al., 2011). because the mathematical expectation of the regional variables is unknown, we adopted the ordinary kriging method for local estimation: ẑ(x₀) = σᵢ₌₁ⁿ λᵢ z(xᵢ) 4 where: ẑ(x₀) = predicted value at location x₀, λᵢ = kriging weight for observation i, z (xᵢ) = observed value at location xᵢ, n = number of observations 3. result and discussion the results of vertical electric sounding (ves) showing the thickness, apparent resistivity and depth across sampling points is presented in table 3. tables 4 and 5 showed the values of dar –zarouck parameters calculated in each ves points in the area of study. the number of layers, lithologic units and curve types is also presented in figures (3 to 12) respectively. 3 to 10 and 12 respectively. the spatial distribution of dar zarrouck parameters are presented in figures (13 to 17) (13 17). table 3: ves data used to create geo-electric layers and curve types in the study area ves latitude longitude resistivity (ωm) layer thicknes curve type no of layers 1 2 3 4 5 6 h1 h2 h3 h4 h5 h6 ves 1 n6°26’ 25.98'’ e5° 36' 12. 36'’ 259.31 970.2 137.5 2924.9 2758.6 4719 1.55 2.09 5.78 5.86 40.87 ∞ khk 6 ves 2 n6°26’29.64'’ e5°36'27.18’' 552.98 755.47 458.99 13656 1267.9 1314.4 0.43 3.89 3.54 18.56 42.55 ∞ khk 6 ves 3 n6°26’31.8'’ e5°36'36.72'’ 740.04 225.08 880.62 26166 4199.9 739.19 2.23 2.04 1.95 23.48 29.24 ∞ haa 6 ves 4 n6°26’30.9'’ e5°36'20.24 '’ 260.52 200.89 57096 7215.6 646.84 ∞ 0.95 2.07 13.2 18.35 ∞ ∞ hak 5 ves 5 n6°26'17.88” e5°36'52.74" 109.97 609.17 858.57 1521.3 1823.1 73.345 0.24 3.77 11.78 18.19 73.35 ∞ aak 6 http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 982 3.1 geoelectric curves the geoelectric curves obtained from the geophysical sounding in the area of study as shown in figures 3 to 7 revealed variations in curve types. the curves were khk, haa, hak and aak types. it has been asserted that the shape of ves curve depends on the thickness of each layer, the number of layers in the subsurface and the ratio of the resistivity of the layer (kwami et al., 2019). the occurrence of multiple curve types (khk, haa, hak and aak types) in the study area reflects non-uniform layering, aquifer discontinuity and lateral heterogeneity typical of the benin formation. the variation in geoelectric curve types (khk, haa, hak, and aak) indicates a complex subsurface lithology typical of the benin formation, composed of alternating sand and clay sequences of fluvial–deltaic origin. these variations suggest non-uniform layering, aquifer discontinuity, and lateral heterogeneity, consistent with observations by oseji et al., (2005) and amadi et al., (2012). the khk curve type, characterized by alternating high–low–high resistivity layers, reflects multilayer aquifer systems where sand units are interbedded with clay or lateritic horizons. similar patterns, associated with confined to semi-confined aquifers of moderate to high yields, were reported by okiongbo and akpofure (2012) in the niger delta. this implies that groundwater occurrence in the area largely depends on the thickness and continuity of sandy horizons. the haa and hak curves further reveal subsurface variability. the haa curve represents a clayey or lateritic overburden overlying sandy aquifers, consistent with findings by ehirim and ebeniro (2010) in port harcourt. the hak curve, is indicative of perched or semi-confined aquifers, aligns with interpretations by amadi et al., (2012) and oyeyemi et al., (2017). the aak curve type, dominated by resistive layers, suggests predominantly sandy subsurface zones with high porosity and permeability favorable for groundwater storage, similar to the findings of aghamelu et al. (2020) in the anambra basin. figure 3: hydrogeophysical sounding curve of ves 1 figure 4: hydrogeophysical sounding curve of ves 2 figure 5: hydrogeophysical sounding curve of ves 3 figure 6: hydrogeophysical sounding curve of ves 4 http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 983 figure 7: hydrogeophysical sounding curve of ves 5 3.2 geo-electric sections the geoelectric section presents a maximum of six (6) layers with varying resistivities and thicknesses in each of the ves conducted in the area of study points with the exception of ves 4 with five (5) layers as shown in figures 8 to 12. the first layer (topsoil) which is composed of unconsolidated sand has resistivities ranging from 109.97 to 740.04 ωm 109.97 40.04 ωm, and thickness varying from 0.24 – 2.22 m. the second layer composed of lateritic soil is characterized with resistivities ranging from 200.89 – 970.20 ωm and thickness ranging from 2.04-3.89 m. the third layer consists of lateritic clay, clay, lateritic soil, fine sand and sandstone has resistivities ranging from 137.50 – 57096 ωm with thickness values ranging from 1.95-13.2 m. the fourth geoelectric layer consisting of medium to coarse sand, sandstone, medium sand and coarse sand has resistivities ranging from 1521.3-2924.9 ωm and thickness varying from 5.85-23.48 m. the fifth geoelectric layer was composed mainly of medium to coarse sand with resistivities varying from 646.844199.9 ωm and thickness 29.24 – 73.34 m. the aquifer systems in the study area could, therefore, be delineated as medium to coarse grained sand which accounts for about four (4) of the ves locations. the high resistivity values of the aquiferous units give credence to its porous and permeable characteristics. figure 9: layered inversion model ves 2 figure 8: layered inversion model ves 1 figure 10: layered inversion model ves 3 http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 984 3.3 dar zarrouck parameters the data from ves ves conducted to estimate the dar zarrouck parameters (hydraulic conductivity, longitudinal conductance, transverse resistance and transmissivity) as shown in table 4. the dar zarrouck parameters are essential in establishing aquifer characteristics and vulnerability to contamination. 3.4 spatial distribution of darzarrouck parameters the data from ves conducted was used to estimate the dar zarrouck parameters (hydraulic conductivity, longitudinal conductance, transverse resistance and transmissivity). the dar zarouck parameters are essential in establishing aquifer characteristics. these parameters are related to different combination of the thickness and resistivity of each geo-electric layers (braga, 2006). 3.4.1 hydraulic conductivity the hydraulic conductivities of various aquiferous units in the study area are shown in table 5. hydraulic conductivity is the ease in which fluids in pores of geologic material will pass under specific hydraulic gradient. it is a function of fabric, texture and grain size of the aquifer system. intrinsic permeability is a measure of a material (rock or soil) ability to allow the movement of fluids (kwami et al., 2019). in this study mean values of hydraulic conductivities for ves 1, 2 3, 4 and 5 were 1.43 m/day, 0.73 m/day, 0.83 m/day m/day, 1.25 m/day and 1.46 m/day with a mean of 1.14 m/day and the aquifer systems delineated were mainly medium to coarse grained sand. therefore, it can be inferred that the aquifer units in the study area is of moderate to high permeability due to varying degree of grain sizes and well interconnected pore spaces. spatial map showing variation in hydraulic conductivity is presented in (figure 13). hydraulic conductivity values ranged from 0.73 – 1.46 m/day. hydraulic conductivity classes were fairly and evenly distributed with the low class (< 1.17) occupying the north central areas while the moderate (1.1701 – 1.34 m/day) and high class (>1.3401) occupy the southern and western part of the study area. these values are lower than those reported by kwami et al., (2019), omali and arogundade (2022), and ojeaga and osauzou (2024). the occurrence of high hydraulic conductivity in the southern and western part indicates better yield due to the presence of permeable materials that would allow the passage of fluids. the area also correlates with areas of high transmissivity. figure 11: layered inversion model ves4 figure 12: layered inversion model ves 5 http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 985 table 4: dar zarouck parameters obtained from ves points in the study area. apparent resistivity (ωm) thickness (m) longitudinal conductance s (ω-1) transverse resistance tr (ωm2) electrical conductivity δ (ωm-1) hydraulic conductivity k transmissivity tr (m2 /day) ves 1 259.31 1.5457 0.005961 400.8155 0.003856 2.164483 3.345641 970.2 2.0924 0.002157 2030.046 0.001031 0.632126 1.322659 137.5 5.7825 0.042055 795.0938 0.007273 3.911688 22.61934 2924.9 5.8555 0.002002 17126.75 0.000342 0.225811 1.322235 2758.6 40.873 0.014817 112752.3 0.000363 0.238484 9.747561 mean 0.33496 26621 0.00951 1.43 7.67 ves 2 552.98 0.43211 0.000781 238.9482 0.001808 1.067961 0.461477 755.47 3.8889 0.005148 2937.947 0.001324 0.79827 3.104392 458.99 3.539 0.00771 1624.366 0.002179 1.270654 4.496844 13656 18.559 0.001359 253441.7 0.0000732 0.053639 0.995492 1267.9 42.554 0.033563 53954.22 0.000789 0.492477 20.95688 mean 0.01897 62439.44 0.0012 0.73 6.00 ves 3 740.04 2.2222 0.003003 1644.517 0.001351 0.813785 1.808394 225.08 2.0417 0.009071 459.5458 0.004443 2.470055 5.043112 880.62 26166 1.9526 23.48 0.002217 0.0008974 1719.499 614377 0.001136 0.000038 0.691911 0.029244 1.351025 0.68665 4199.9 29.241 0.006962 122809.3 0.000238 0.161128 4.711545 mean 0.00443 148201.96 0.00144 0.83 2.72 ves 4 260.52 0.9509 0.00365 247.7285 0.003838 2.155103 2.049288 200.89 2.0748 0.010328 416.8066 0.004978 2.74643 5.698293 57096 13.2 0.000231 753667.2 0.0000175 0.014123 0.186426 7215.6 18.349 0.002543 132399 0.000139 0.097258 1.784585 mean 0.0124005 221682.68 0.00224 1.253 2.4296 ves 5 109.97 0.242 0.002201 26.61274 0.009093 4.818094 1.165979 609.17 3.77 0.006189 2296.571 0.001642 0.975775 3.67867 858.57 11.788 0.01373 10120.82 0.001165 0.708473 8.351476 1521.3 18.192 0.011958 27675.49 0.000657 0.415501 7.558786 1823.1 73.345 0.040231 133715.3 0.000549 0.350958 25.74102 mean 0.01486 34766.958 0.00262 1.45376 4.15098 3.4.2 electrical conductivity electrical conductivity values range between 0.0012 to 0.0095 ωm-1 with mean of 0.0035 ωm-1. spatial distribution map in figure 14 shows that low electrical conductivity values (< 0.00365) is the dominant class and occupy the eastern areas, the high class (> 0.00685) is the least and occupy the southwestern corner whereas the moderate class (0.00365 – 0.00685) occupy the central western part of the study area. overall, the spatial distribution of ec values underscores the hydrogeological heterogeneity of the study area. the predominance of low ec values in the east highlights this sector as the most promising for groundwater development, both in terms of yield and quality. conversely, the occurrence of high ec zones in the southwest delineates areas of limited aquifer potential and possible water quality concerns. table 5: summary of second-order geoelectric parameters of each ves conducted in the study area ves no longitudinal conductance s (ω-1) transverse resistance tr (ωm2) hydraulic conductivity (k) electrical conductivity δ (ωm-1) transmissivity tr (m2 /day) 1 0.335 26621 1.43 0.0095 7.67 2 0.018 62439.44 0.73 0.0012 6.00 3 0.004 160489.65 0.83 0.0014 2.72 4 0.004 221682.68 1.25 0.00224 2.43 5 0.015 34766.958 1.46 0.00262 2.42 mean 0.0752 101199.81 1.14 0.0035 4.248 http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 986 figure 13: spatial distribution of hydraulic conductivity within the study area 3.4.3 transverse resistance the transverse resistance of any subsurface geological formation is a product of resistivity and thickness. it is used to delineate the most prolific area of groundwater potential for hydrological investigations. transverse resistance determines the properties of the resistive layers (yungul, 1996). a geologic formation reflecting a predominantly high transverse resistance values indicates that its resistivity is high, or it has thickness with presumably favorable aquifer conditions (okiongbo and akpofure 2012). the results of transverse resistance as shown in table 4 and 5 revealed that transverse resistance values for ves 1 ranged from 400.82 – 112,752.3 ωm2 with an average of 26621 ωm2; transverse resistance for ves 2 ranged from 238.95 to 253,441.7 ωm2 with an average of 62439.44 ωm2. the transverse resistance for ves 3 ranged from 459.55 to 614377.7 ωm2 with an average of 148201.96 ωm2. ves 4 varying from 247.73 to 753,666.2 ωm2 with an average and that of 221682 ωm2 and that of ves 5 varies from 26.61 to 133,715.3 ωm2with average of 34766.96 ωm2. according to (ezeh, 2012) transverse resistance below 200,000ωm2 indicates inadequate aquifer thickness. the transverse resistance of the aquiferous units were (112752.3, 53954.22 ωm2, 122809.3 ωm2, 132399 ωm2 and 133715.3 ωm2). these values of transverse resistance implies that the thickness of each aquiferous units is inadequate or represents the mixing of finer sediments with coarse materials thus, indicating low groundwater potential (ezeh, 2012; kwami et al., 2019). these values were lower than those reported by ojeaga and totor (2024) in their investigation in iyowa community but higher than 3888.06 ωm2 reported by akinseye et al., (2022). thus, it is assumed that the aquifer may likely have low transmissivity with poor groundwater potentials. however, the spatial map of transverse resistance as presented in figure 15 indicates that the southern region depicted by the blue color (>120,000) have a higher transverse resistance than the northern region depicted by pale purple color. the central area depicted by dark purple represents area of moderate transverse resistance (60,000-120,000). the hydrological implication is that higher groundwater yield is likely to occur in the southern region. 3.4.4 transmissivity transmissivity is controlled by the thickness of the specific layer and the presence of fine/clay particles. it is measured in m2/day. the values of transmissivity recorded in the study area is presented in table 4 and 5. transmissivity values in ves 1 ranged from 1.32 to 22.62 with mean of 7.67m2/day, while mean values for ves 2,3,4 and ves 5 were 6, 2.72, 2.43 and 9.3 m2/day respectively. however, the transmissivity of each aquiferous layer in geophysical sounding conducted within the study area as presented in table 6 are in accordance with a study by offodile, (1983) which indicates that 40% of the ves exhibited low aquifer potentials in ves 1 and ves 2, 5 while 60% of the ves show very low potentials in ves 3 and 4. this was inconsistent with the findings http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 987 of ojeaga and totor (2024) and ojeaga and osauzou (2024) who reported high transmissivity in their area of study. spatial map of the study area showing variation in transmissivity values is presented in (figure 16). it showed a transmissivity value of < 3.5 m2/day depicted by light blue color occurs from northwestern region to eastern zone. while transmissivity values > 5.7m2/day depicted in pink color occupy the southwest area, values ranging from 3.501 to 5.7 m2/day, depicted in green, extend from northwest to the west-southwestern zone. while transmissivity values > 5.7m2/day depicted by pink color occupy the southwest area the transmissivity value from 3.501-5.7 was depicted by green color trends from northwest to west southwestern area. the pattern of transmissivity suggests the area is controlled not only by variability in permeability of lithologic units but also by geological structures or topographic features that influence aquifer thickness and groundwater flow. hence, it implies that the wells in the western area have potentials for high yield. figure 14: spatial distribution of electrical conductivity within the study area figure 15: spatial distribution of transverse resistance within the study area http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 988 figure 16: spatial distribution of transmissivity within the study area 3.4.5 longitudinal conductance (aquifer protective capacity) the protective capacity of the aquifer was evaluated using the values of longitudinal conductance and in accordance with the protective capacity rating established by oladapo and akintorinwa (2007) (see table 4 and 5). the values of longitudinal conductance in the study area ranged from 0.0025 to 0.0402 ω with an average of 0.0322 ω as presented in table 3. it revealed that in the study area only 20% (ves 1) exhibited moderate protective capacity, 80% (ves 2, ves3, ves 4, and ves 5) have poor protective capacity. these values shows that the protective capacity of the aquifer units/system in the entire study area was poor. thus, the aquifers are not likely to be protected/ shielded from percolating contaminated fluids. this finding is consistent with omali and arogundade (2022) and ojeaga and osauzou (2024) who reported poor aquifer protective capacity in their investigations and in contrast with kwami et al. (2019) and ojeaga and totor (2024) that reported that 50% of ves had good to moderate aquifer protective capacity. the spatial map (figure 17) indicates that the longitudinal conductance in the area generally was low (< 0.0967) occupying a part of the northwest, and the entire eastern region. moderate longitudinal conductance trends from northcentral to southern region. higher values of longitudinal conductance > (0.213) were observed in the western part of the study area. the variation in the spatial distribution pattern of longitudinal conductance suggests that the aquifer protective capacity is low, thus indicating the vulnerability or susceptibility of groundwater to contamination within the area of study which could be attributed to the absence of impermeable materials such as clay that could aid natural attenuation. therefore, it can also be inferred that groundwater from boreholes and wells within the study location are susceptible to contamination due to absence of natural filters/barriers to percolation of leachates derived from the overlying dumpsites. this may be attributed to the absence of sufficient thickness of fine materials that could have acted as natural filters and barriers to the infiltrating leachates (kwami et al., 2019). http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 978-991. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenneth.ojeaga@uniben.edu 989 figure 17: spatial distribution of longitudinal conductance within the study area 4. conclusion the ves conducted in the study area revealed five (5) to six (6) geoelectric layers. the geoelectric curves were aha, ahk, hak and aak types. the variation of the geoelectric curve confirms the heterogeneity of the benin formation. this studies further underscores the importance of integrating ves data with borehole lithologic logs and pumping tests to adequately delineate productive groundwater zones and reduce borehole failure in the area. this study has shown that creation of unauthorized dumpsites is an anathema to clean portable water which is crucial for the overall health of the people. the findings from transmissivity and transverse resistance in this study revealed low groundwater potential and attributed same to inadequate thickness of the aquiferous units. the aquifer systems (medium to coarse grained sand) delineated in the area of study might allow movement of fluids (groundwater) through its matrix due to their fairly large grains and interconnectivity. the longitudinal conductance shows that the aquifer protective capacity is poor and may likely contribute to groundwater contamination. the spatial distribution of dar-zarrouck parameters indicates that transmissivity and hydraulic conductivity is high in the southwestern region reflecting the heterogeneity of the subsurface lithologies. the spatial distribution trend of longitudinal conductance showed that the aquifer in the area have poor aquifer protective capacity. the continuous presence of the clusters of dumpsites in the area, pose serious existential threat to groundwater quality in the locality. residents are advised to consult a team of environmental and hydro-geologist for well development. however, in order to validate some of the claims stated above; it is important that the hydro chemical composition of groundwater in the area be characterized in order to make informed decisions about its pollution status. the vertical and lateral extent of contaminant plumes using dipoledipole techniques also need to be investigated in order to identify or established potential zones of pollution in the area of study. it is also important to investigate the direction of groundwater flow in order to understand/ decipher areas fit for proper siting of landfills and groundwater development. therefore, it can also be inferred that groundwater from boreholes and wells within the study location are susceptible to contamination due to absence of natural filters/barriers to percolation of leachates derived from the overlying dumpsites. this may be attributed to the absence of sufficient thickness of fine materials that could have acted as natural filters and barriers to the infiltrating leachates (kwami et al., 2019). references akpan, ae., ugbaja, an., and george, nj. 2013. integrated geophysical, geochemical and hydrogeological investigation of shallow groundwater resources in parts of ikom mamfe embayment and the adjoining areas, cross river state, nigeria. environmental earth sciences, 9(12): 52-66. http://www.azojete.com.ng/ mailto:kenneth.ojeaga@uniben.edu arid zone journal of engineering, technology and environment, december 2025; 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salvador et al., 2014), making it a major source of carbohydrates and a staple diet eaten by not less than 800 million people worldwide (jose-luis et al., 2020; lebot, 2009). the edible part of cassava contains about 1 – 3% protein, 30 – 35% of amyloses and amylopectins (carbohydrates) on a dry weight basis, 62% water, 1 – 2%, fibre, 1% minerals, and 3% fat (salvador et al., 2014) and the peels are used for processing of animal feeds and generation of biogas. despite this huge benefit of cassava roots, about 820 million suffered from malnutrition and hunger in the world (ashebir, 2021). article information abstract frying is the most tedious unit of garri processing. the amount of heat applied during the processing operation determines the end quality and market value of the product. thus, this study is aimed at investigating the effect of pre-processing conditions on the heat energy of an auto garri frying machine. a 4-factor, 5-level d-optimal design of response surface methodology (rsm) was used for modeling and optimization of the process. the mash quantity, frying time, initial moisture content and temperature were varied over 10, 20, 30, 40, and 50 kg; 15, 30, 45, 60, and 75 mins; 30, 35, 40, 45, and 50% wet basis (wb); and 140, 160, 180, 200, and 220 °c, respectively. the results showed that a linear model fvalue of 61.08 implies that the model was significant with value of r2 (0.8526) and adj-r2 (0.9092) indicating that there was a high correlation between the dependent and independent variables. in optimizing the process, the heat energy was maximized while the independent variables were set at ranges. optimum heat energy of 14,000 j was obtained at 45.33 kg mash quantity, 67.37 mins frying time, 40% wb initial moisture content and 180 °c frying temperature at the desirability of 1. at α = 0.05, the analysis of variance (anova) showed that the mash quantity, frying time and temperature had direct significant impacts on heat energy of the garri frying machine while the initial moisture content had no significant effect on the heat energy. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 1 march, 2022 revised 1 june, 2023 accepted 10 june, 2023 keywords: heat energy electrical filament garri fryer optimization moisture content http://www.azojete.com.ng/ mailto:emmanuel.ozigbosunday@gmail.com mailto:emmanuel.ozigbosunday@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):647-658. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 648 cassava production has experienced consistent annual growth of about 3% globally (fao, 2018). according to faostat (2019), the world cassava production stood at about 278 million tones. africa led with about 56% (170 million tonnes) of the world production with nigeria being the largest producer with an average production of 60 million tonnes. despite the fact that nigeria is the largest producer of cassava in the world, it is also largest consumer in the world as more than 90% of cassava produced is utilized or consumed locally (tridge, 2021; ikuemonisan et al., 2020) thus, this could be the reason for the massive production of it in nigerian states. therefore, this demonstrates that there is a feasibility and enormous potential in cassava business which could contribute greatly to the agricultural sector and nigerian’s economy at large. the majority (over 84 %) of cassava roots cultivated in nigeria is used for human consumption which goes into processed products like garri, fufu, pellets, tapioca, tidbits, lafun, chin-chin, flour, abacha, bread, chips and so many other confectioneries (ikuemonisan et al., 2020; kormawa and akoroda, 2003). the remaining 16% of the roots is traceable to industrial usage such as starch, biogas, livestock feed, glue, ethanol and there is hope more portions of it could still go into industry in future (ikuemonisan et al., 2020). in nigeria, there is no doubt that cassava roots are most important food components capable of eradicating food insecurity. however, the major challenge with it is the short postharvest shelf life, 2 –3 days immediately after harvest. therefore, the roots must be consumed or converted into long-lasting as fast as possible after harvest. cassava root is an extremely high-energy containing food (jose-luis et al., 2020), with a high yield of carbohydrates per acre which generates roughly 250,000 calories per hectare per day, placing it ahead of sorghum, wheat, rice, and maize. but it is subjected to postharvest losses (phl) also known as physiological deterioration (ppd) shortly after the roots are harvested from the field faster than these food crops (awoyale et al., 2020). garri, flour and chips are the common products from cassava roots that can stay long period if well processed. garri is the most widely traded cassava products, accounting for more than 75 per cent of produce extracted from cassava (akinfenwa, 2020). it is the daily major source of food in brazil, nigeria and most west african nations. garri manufacturing technology is the popular advanced cassava root processing technology now in nigeria because of vitality of the food component. it is a pre-gelatinized grit with particle sizes ranging from less than 10 micrometers (fines) to more than 2000 micrometers (coarse) (nwankpa, 2010). garri flying is a cooking and dehydration process in which the food is cooked while still moist and then dehydrated. the amount of heat applied during frying determines the product's quality. in the village approach, the initial frying temperature is kept low to prevent many lumps or cakes formation. the temperature is further raised to cook and dehydrate the product as the moisture content decreases. at this time, most of the little lumps would have been broken down by constant agitation and pressing (olagoke et al., 2014). the heat is a form of energy that transfers from the higher temperature product to the lower temperature product, and is transferred through the conduction, convection and radiation mechanisms depending on the product’s form. therefore, the study is aimed to investigate the effect of heat energy applied to a given garri processing operation using an automated frying machine. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:emmanuel.ozigbosunday@gmail.com https://www.sciencedirect.com/science/article/pii/s2405844020319320#bib20 ozigbo et al: optimization analysis of heat energy required in garrification process using a garri fryer powered by electrical filaments as heat source. azojete, 19(3):647-658. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 649 2. materials and methods 2.1 the study area and sources of materials this research was carried out at a cassava processing centre (cpc) in the international institute of tropical agriculture (iita), ibadan headquarters. iita is a non-governmental research for development (r4d) organization that offers research partnership to improve livelihoods, enhance food and nutrient security throughout sub-sahara africa. iita is situated at idi-ose moniya, oyo road, ibadan, oyo state, nigeria. a research variety of cassava roots, tme 419 with low water and high dry matter (starch) content was obtained for the experimental study from one of the institute’s departments called cassava breeding. the variety was selected based on its high starch content for good garri production. 2.2 sample preparation 250 kg of wet mash sample was obtained and used for processing 1000 kg fresh cassava roots of tme 419 (tropical manihot esculanta). the sample was divided into 5 different places each containing 50 kg. the initial moisture content was kept at 30% wb, frying time interval was 60 minutes and the normal speed of the machine was 84 rpm. moisture content was determined in equation 1 and 2 using the american society of agricultural engineers standard s410.1 dec. 1997 (asabe standards, 2003). the electrical filaments capacity of 2.5, 5.0, 7.5, 10.0 and 12.5 kw were used as the heat sources and the resultant heat effect generated at various temperature levels, 140, 160, 180, 200, and 220 oc, respectively. the choice of this temperature range was based on the report of nwankpa (2010) which stated that the temperature range for garri varies from 120 – 200 oc. also, the selection was based on the study carried out by okorun et al. (2017) with a varying garri frying temperature range of 180 – 200 oc. the heat and time required for a given garri frying operation were estimated in equation 3 and 4. . (1) (2) ∆t (3) (4) where: = moisture content (dry basis), = moisture content (wet basis), = mass of water to be added, = mass of dry matter, q = heat quantity, ma = the mass of cassava mash in the cylinder c = the specific heat capacity of the mash, ∆t = temperature range, ∆t = = heat rate, lh = latent heat of transformation, δtm = time interval in minutes, δm = mass of the cassava mash. http://www.azojete.com.ng/ mailto:emmanuel.ozigbosunday@gmail.com mailto:emmanuel.ozigbosunday@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):647-658. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 650 2.3 description of the machine the automated industrial garri frying machine has two major component parts; the mechanical and the electrical/electronic part. the former gives the machine its shape and size in terms of capacity, while the later is the centre for control and operation of the entire system which consists of the automated parts. the mechanical components used include the following: 4 mm stainless sheet, 2 mm mild steel sheet, metal-steel rod of 32 mm, mild-steel rod of 2 mm, 205 pillow bearings, 2.0 hp electric motor, reduction gears in form of chain and sprockets, fan belts, cast pulleys, bolts and nuts, electrical filaments, u-channel mild steel, and heat resisting fibres. the electrical/electronic components include: microcontroller. transformer, capacitor, temperature control modules, 3-phase control switch, electrical sockets and switches, 4mhz –crystals, 12v contactors, relays, capacitors, vero-board, resistors, transistors, regulators, integrated circuit; light emitting diodes (led), leads, connecting wires, plugs insulating sleeves, board casing, lcd display sensors, solenoids push switches, 7 segment displays, rectifying diodes, and 4 x 4 keypad module. the machine is user-friendly and can be operated by a single user. it has a switch button for starting and ending the operation. immediately the switch-on button is engaged, the mechanical paddles start to rotate (fry the garri) and the automated system comes on but allows the user to adjust the frying temperature, time and final moisture content (humidity of friable substance) to his/her desirable measurable level with the set of the buttons on it. after the adjustment and the okay button is clicked, the paddles continue to fry the garri as the electrical filaments temperature start rising not until it reaches the set level with time or final moisture content intervals inputted. also, as soon as the desired product quality or set parameter level is reached, the automated system trips off while the mechanical paddles continue in rotation to prevent the burning of the product and aid the cooling process of the product. during evacuation time, as the paddles are still in continuous rotation and the discharge chute gate is opened, the products are pushed out of the frying chambered. 2.4 statistical optimization analysis optimization analysis was carried out using response surface methodology (rsm). in the optimization process. rsm at 4-factors and 5-levels (initial moisture content 30, 35, 40, 45, and 50%; frying temperature 140, 160, 180, 200, and 220oc; frying time 15, 30, 45, 60, 75 minutes; and mash quantity 10, 20, 30, 40, 50 kg) was used to carry out the simultaneous testing of the effects between and within parameters in the optimum experiment. the raw data of the independent variables (initial mc, temperature, time, and mash quantity) were inputted into the research software as shown in table 1. d-optimized design module in design expert software (version 11.0) was used to develop mathematical equations where the predicted results were assessed as a function of mash quantity ( ), frying time ( ), initial moisture content ( and frying temperature ( ) and calculated as the sum of a constant, four first-order as shown in equation 5: file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:emmanuel.ozigbosunday@gmail.com ozigbo et al: optimization analysis of heat energy required in garrification process using a garri fryer powered by electrical filaments as heat source. azojete, 19(3):647-658. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 651 (5) the coefficients of the polynomial were represented by b0 (constant); b1,b2,b3,b4,b5 (linear effects); b12,b13,b14,b23,b24,b34 (interaction effects); b11,b22,b33,b44,b55 (quadratic effects); and (random errors). the quality of the polynomial model is expressed using the determination coefficient, namely r2 and adj-r2. anova equations were modified by eliminating the statistically insignificant terms. at 0.05 level of significant, the calculated f value was compared with the tabulated f when the df was 14 and n = 25. 3. results and discussion 3.1 effect of independent variables on the heat energy of the machine the heat energy of the automated garri frying machine analysis was based on the mash quantity, frying time, initial moisture content, and temperature. as shown in table 1, the heat energy of the machine was in the range of 1794.51 to 18793.2 j having the maximum fraction to minimum of 10.47. a fraction greater than 10 usually means that a change is needed and a fraction smaller than 3 indicates a small effect. the main impact of the interaction determined for each factor on the heat energy is given in table 2. the table depicts the analysis of variance in the result generated with average heat energy at different processing conditions (mash quantity, frying time, initial moisture content, and frying temperature). the results also showed the design of experiment matrix generated through the use of rsm; having actual and coded values of the input variables along with one output response effects (terms in , , and ) and one interaction effect ( ) as shown in equation 6. a reduced linear model in terms of coded factors was observed and the model was significant (p < 0.05). the following coded response equation was obtained for variation of heat energy, = 7551.88 + 4482.01 + 2288.41 + 1030.86 + 2280.69 (6) it was observed from the model equation (6) that the coefficients of and are all positive. this implies that a unit increase in the mass quantity ( , frying time ( and frying temperature ( will lead to a significant increase in the heat energy of the automated garri fryer by 4482.01 j, 2288.41 j, and 1030.86 j, respectively. the interaction between the mass of the cassava mash and the frying time gives a progressive increase value of 2280.69 j when there is a unit change in the production process. this result is in close agreement with that of sanni et al (2015a; 2015b) which stated that time and temperature have greatest effect on the drying process. although, there was increase in heat energy as the moisture content of the samples was increased, however, statistical analysis showed that the initial moisture content ( has no significant impact on the samples used as shown in figure 1. this conformed with the result sanni et al (2016) that initial moisture content has no significant impact on heat energy. http://www.azojete.com.ng/ mailto:emmanuel.ozigbosunday@gmail.com mailto:emmanuel.ozigbosunday@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):647-658. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 652 table 1: d-optimal design experiments and experimental results factor 1 factor 2 factor 3 factor 4 response 1 run a: mash quantity b:frying time c:initial mc d:temperature heat energy (kg) (mins) (%) (deg.celcius) (j) 1 10 15 50 220 3477.62 2 40 15 30 140 5255.85 3 30 30 40 160 5896.11 4 50 75 30 220 16751 5 10 75 40 220 3400.37 6 50 15 40 220 5630.19 7 50 45 40 160 10672.5 8 50 75 50 220 18793.2 9 20 30 50 140 3900.72 10 30 30 40 160 7039.32 11 10 15 40 140 1794.51 12 30 15 50 180 5595.99 13 50 30 50 140 9748.61 14 10 60 35 180 2698.82 15 20 30 30 180 4851.13 16 10 15 30 220 3252.6 17 10 75 30 140 1968.9 18 10 60 35 180 2703.62 19 50 75 40 140 11402.6 20 10 75 50 140 2220.42 21 30 45 40 220 10367.6 22 50 75 40 140 17706.6 23 50 45 30 180 13617.1 24 30 15 50 180 5578.12 25 30 45 40 220 10674.7 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:emmanuel.ozigbosunday@gmail.com ozigbo et al: optimization analysis of heat energy required in garrification process using a garri fryer powered by electrical filaments as heat source. azojete, 19(3):647-658. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 653 table 2: model analysis data for the heat energy response variable for the automated garri fryer sum of mean f p-value source squares df square value prob > f model 5.822e+008 4 1.455e+008 61.08 < 0.0001 significant 𝑥1 3.161e+008 1 3.161e+008 132.67 < 0.0001 𝑥2 8.066e+007 1 8.066e+007 33.85 < 0.0001 𝑥4 1.733e+007 1 1.733e+007 7.27 0.0139 𝑥1𝑥2 5.816e+007 1 5.816e+007 24.41 < 0.0001 residual 4.766e+007 20 2.383e+006 lack of fit 2.709e+007 15 1.806e+006 0.44 0.9006 not significant pure error 2.057e+007 5 4.114e+006 cor total 6.298e+008 24 figure 1: the 3-dimensional surface curve for variation in the heat energy at the mash quantity of 30 kg and frying temperature of 180oc design-expert® software factor coding: actual heat energy (j) design points above predicted value 18793.2 1794.51 x1 = b: frying time x2 = c: initial mc actual factors a: mash quantity = 30 d: temperature = 180 30 35 40 45 50 15 25 35 45 55 65 75 0 5000 10000 15000 20000 h e a t e n e rg y ( j ) b: frying time (mins) c: initial mc (%) http://www.azojete.com.ng/ mailto:emmanuel.ozigbosunday@gmail.com mailto:emmanuel.ozigbosunday@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):647-658. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 654 the model f-value of 61.08 implies that the model is significant. the value of (0.8526) and adj (0.9092) are in a close agreement since the difference between them is less than 0.2. thus, indicating that there was a high correlation between the observed values and predicted values. according to the demirel and kayan (2012), the regression model provides an excellent explanation of the relationship the independent variables and the response. p-value for the interaction between mash quantity ( ) and frying time ( ) was significant. the 3-dimensional surface curve for variation in the heat energy of the automated garri fryer was shown in figure 2. this figure shows that the heat energy in respect to frying time and mash quantity gives greatest impact or effect on the garri drying process. it was observed from the figure that as mash quantity and frying time increase in the production process, the heat energy of the fryer increases progressively. it was observed from the figure that as mash quantity and frying time increase in the production process from 10 – 50 kg and 15 – 75 minutes, respectively, the heat energy of the fryer also increases from about 3,000 j to 16,500 j. the result of sanni (2014) corresponded with this finding which stated that heat energy increases with increase in mash sample and processing time. figure 3 confirms that the interaction between the frying time and temperature is statistically significant and that as heat energy increases, the frying time and temperature directly increases. in figure 4, the minimum heat energy (4,000 j) was observed at the processing conditions of mash quantity (18 kg), frying time (14.16 mins), initial moisture content (40% wb) and frying temperature (180 oc) while the maximum heat energy range seen at 14,000 j at mash quantity (36 kg), frying time (67.37 mins). the figure is called contour graph and was used to shows minimum and maximum values of the heat energy at chosen factors of initial moisture content and frying temperature. it was used to represent the points where all processing parameters used in the experiment meet the desirable heat energy. this also confirms that the heat energy increases with the increase in mash sample and frying time. additionally, figure 5 shows the graph of the predicted values versus actual values which proved that approximately linear data points obtained were devoid of any statistical problem i.e there was no sign of any problem in the data .the closeness of the data along the curve line is the indication that the result better fit the model. similarly, figure 6 shows the perturbation plot of the heat energy and the independent variables used indicating the silhouette view of the response surface. that is, how heat energy changes as each factor (mash quantity, time, temperature and initial mc) moves from a chosen reference point, 30 kg, 45 mins, 180oc, and 40% wb, respectively with all other factors held constant at reference value of 7,500 j. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:emmanuel.ozigbosunday@gmail.com ozigbo et al: optimization analysis of heat energy required in garrification process using a garri fryer powered by electrical filaments as heat source. azojete, 19(3):647-658. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 655 figure 2: the 3-dimensional surface curve for variation in the heat energy at the initial moisture content of 40% and frying temperature of 180oc figure 2: the 3-dimensional surface curve for variation in the heat energy at the mash quantity of 30 kg and initial moisture content of 40% design-expert® software factor coding: actual heat energy (j) 18793.2 1794.51 x1 = a: mash quantity x2 = b: frying time actual factors c: initial mc = 40 d: temperature = 180 15 25 35 45 55 65 75 10 20 30 40 50 0 5000 10000 15000 20000 h e a t e n e rg y ( j ) a: mash quantity (kg)b: frying time (mins) design-expert® software factor coding: actual heat energy (j) design points above predicted value design points below predicted value 18793.2 1794.51 x1 = b: frying time x2 = d: temperature actual factors a: mash quantity = 30 c: initial mc = 40 140 160 180 200 220 15 25 35 45 55 65 75 0 5000 10000 15000 20000 h e a t e n e rg y ( j ) b: frying time (mins) d: temperature (degree celcius) http://www.azojete.com.ng/ mailto:emmanuel.ozigbosunday@gmail.com mailto:emmanuel.ozigbosunday@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):647-658. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 656 figure 4: the contour graph for the variation in the heat energy at the initial moisture content of 40 % and frying temperature of 180 oc figure 5: the graph of the predicted values versus actual values for heat energy figure 6: the perturbation plot for heat energy design-expert® software factor coding: actual heat energy (j) 18793.2 1794.51 x1 = a: mash quantity x2 = b: frying time actual factors c: initial mc = 40 d: temperature = 180 10 20 30 40 50 15 25 35 45 55 65 75 heat energy (j) a: mash quantity (kg) b : f ry in g t im e ( m in s ) 4000 6000 8000 10000 12000 14000 design-expert® software heat energy color points by value of heat energy: 18793.2 1794.51 actual p re d ic te d predicted vs. actual 0 5000 10000 15000 20000 0 5000 10000 15000 20000 design-expert® software factor coding: actual heat energy (kj) actual factors a: mash quantity = 30 b: frying time = 45 c: initial mc = 40 d: temperature = 180 factors not in model c -1.000 -0.500 0.000 0.500 1.000 0 5000 10000 15000 20000 a a b b d d perturbation deviation from reference point (coded units) h e a t e n e rg y ( k j ) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:emmanuel.ozigbosunday@gmail.com ozigbo et al: optimization analysis of heat energy required in garrification process using a garri fryer powered by electrical filaments as heat source. azojete, 19(3):647-658. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: emmanuel.ozigbosunday@gmail.com 657 4. conclusion the effect of the processing parameters such as mash quantity, frying time, initial moisture content and frying temperature on the heat energy in an automated garri frying machine made with electrical heating filaments as the heat sources was investigated. models predicting the relationships between the variables were developed. optimum heat energy of the system obtained was 14,000 j at the mash quantity (45.33 kg), frying time (67.37 mins), initial moisture content (40% wb) and frying temperature (180 oc). the model validation showed an excellent agreement between the preprocessing conditions and the response. the result of the analysis indicated that mash quantity, frying time and temperature had a significant effect on the heat energy of the automated garri fryer. references akinfenwa, g. 2020. business-agro. https://guardian.ng/features/agro-care/garripopular-foodnow-beyond-the-reach-of-masses/ accessed online on 02 august, 2022. ashebir, sf. 2021. micropropagation of cassava (manihot esculenta crantz): on farmers’ fields in nigeria through appropriate weed management. crop protection 150(5): 632 –642. audu, j., awulu, jo. and anyebe, sp. 2018. modeling and optimization of airflow resistance through a dry bed of bambara nuts. agricultural engineering international cigr journal open access, 20(4):169 – 177. awoyale, w., emmanuel, oa., ugo, c., thierry t., hubert, noel, tt robert, n., ngoualem, k. and busie, md. 2020. a review of cassava semolina (garri and eba) end-user preferences and implications for varietal trait evaluation. international journal of food science and technology, 46(1):161 –175. demirel, 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185-193. tridge, 2021. 2020 industry report: cassava starch. https://cdn.tridge.com/market_report_report/0f/ba/53/0fba53aa75198dfda1a990021968b93e784 3572b/210204_cassava_starch_report.pdf. accessed online on 15 february, 2021. zierer, w., david, r., uwe, s. and sophia, s. 2021. tuber and tuberous root development. annual review of plant biology, 72: 551 –580 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:emmanuel.ozigbosunday@gmail.com https://www.sciencedirect.com/science/article/pii/s2405844020319320#bbib33 https://cdn.tridge.com/market_report_report/0f/ba/53/0fba53aa75198dfda1a990021968b93e7843572b/210204_cassava_starch_report.pdf https://cdn.tridge.com/market_report_report/0f/ba/53/0fba53aa75198dfda1a990021968b93e7843572b/210204_cassava_starch_report.pdf arid zone journal of engineering, technology & environment azojete september 2023. vol. 19(3):505-518 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 505 original research article investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application i. m. alibe1*, s. nasir2, m. h. m. zaid3, and a. m. alibe4 1mechanical engineering department, faculty of engineering and technology, nigerian army university biu. no. 1, gombe road, pmb 1500, biu, borno state. 2department of chemistry, faculty of science, federal university dutse, p.m.b. 7156, dutse, jigawa state. 3department of physics, faculty of science, universiti putra malaysia, 43400 upm serdang, selangor, malaysia 4mechanical engineering departments, federal polytechnic damaturu, yobe state nigeria. *corresponding author’s email address: babaiya1@gmail.com article information abstract over the last few decades, researchers have developed great deals of interest focusing on the fabrication and synthesis of zinc silicate-based glass-ceramic. however, using waste materials as precursors for the fabrication is yet another milestone in waste management. thus, in this study, zinc silicate glass-ceramic was fabricated using sola lime silica (sls) glass waste as a source of silicon. the series of precursor glass in the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 system was prepared by the conventional solid-state melt-quench technique through a controlled crystallization process. the physical, structural, and optical properties of the glass system were obtained by density measurement, x-ray diffraction, fourier transform infrared spectroscopy, ultravioletvisible spectroscopy, respectively. the density of the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 glasses series was observed to be decreasing with the increment of 𝑤𝑡. % 𝐵2𝑂3 content. the xrd spectra of the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 samples with 0 and 0.01 wt.% 𝐵2𝑂3, exhibits major diffraction peaks attributed to the zno phase in the glass matrix. however, as 𝐵2𝑂3 content increased, the precursor glass sample shown by the xrd spectra depicted a broad halo characteristic, which reflected the properties of amorphous glass that were observed at the composition of 0.05 wt.% 𝐵2. from ftir spectra, the bands at 500, 688, 902 and 1243 𝑐𝑚−1 can be associated with stretching vibrations of zno4 and si-o-b bending vibrations, stretching vibration of the b–o bonds in the 𝐵𝑂4 units, and modes of boron–oxygen triangular 𝐵𝑂3 units. the intensity of the ir band increases with increasing percentage of 𝐵2𝑂3. the uv-vis analysis of the samples with 0 and 0.01 wt.% 𝐵2𝑂3 demonstrates crystalline hump and varies at 370 nm. it was observed that the addition of b2o3 to the zno-sls glass network caused the glassy amorphous state with an absence of a sharp absorption edge at 0.05, 0.10, and 0.15 wt.% b2o3.the (𝑍𝑛𝑂)0.6−𝑥 (𝐵2𝑂3)𝑥 (𝑆𝐿𝑆)0.4 system shows increase in band gap when the composition of 𝐵2𝑂3 increased. when 𝑍𝑛𝑂 serves as a modifier, the number of nbos will increase, and this will cause the expansion of glass network. the zinc silicatebased glass-ceramic produced has been classified to be a semiconductor due to the wide optical band gap energy obtained and may have key potential applications for future led and other optoelectronic lighting devices. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 10 april, 2023 revised 7 june, 2023 accepted 10 june, 2023 keywords: glass-ceramic melt-quenching waste sls glass band gap energy amorphous http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com babaiya1@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):505-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 506 1.0 introduction researchers in the past decade have shown significant interest on optoelectronics advanced materials such as transition metal-based silicate glass and glass-ceramics (brugger et al., 2003; takesue et al., 2009; mondillo et al., 2020). these materials are used mostly as phosphor host for light-emitting diodes (led), photodetectors, semiconductor lasers and other optoelectronic applications (oueslati-omrani & hamzaoui, 2020). it is imperative to note that glasses that are silicate based especially those produced with larger content of zno are of great interest for numerous applications from conventional glasses and glass ceramics to an advanced performance optical glass (oueslati-omrani and hamzaoui., 2020). willemite, also known as zinc silicate (zn2sio4), is renowned for its suitability as a good host glass material used for several guest ions of rare–earth and transitional metals to attain higher effectiveness in displaying a wider range of multi–colours for luminescence application (omri et al., 2013; el mir and omri, 2014; al–nidawi et al., 2017; effendy et al., 2017; zaid et al., 2016; omar et al., 2017; omar et al., 2016a; rasdi et al., 2017;). for instance, the luminescence characteristics of rare earth ions (re3+) like the long emission lifetime, sharper luminescence array and the characteristic spectral behavior as they are filled by 4f shells and shielded by the outer 5s2 and 5p6 orbitals are some of the motivating drivers for their choice in nowadays optoelectronic application. for this reason, willemite doped with re3+ is creating major attention for its luminescence efficiency and colour purity for lighting devices (omar et al., 2016b; omar et al., 2017). furthermore, in the last decade, takesue et al. (2009) reported the optical performance of willemite doped manganese (zn2sio4:mn2+) phosphors where the 3d5 electron transition in mn2+ ions is characterized as activating centre in the structure. the rigid lattice structure (noncentrosymmetric cationic sites) of willemite made it a host material of choice for excellent performance in lighting devices and optoelectronic applications (abdel-hameed & marzouk, 2022; wei et al., 2022). previously, several researchers over the past decade reported different techniques used for the fabrication of willemite-based phosphor (takesue et al., 2009). these techniques include, but are not limited to hydrothermal (samigullina et al., 2017), polymer sonochemical (masjedi-arani & salavati-niasari, 2016), sol–gel (benchikhi et al., 2022), spray pyrolysis (kusdianto et al., 2020), and simple thermal treatment (alibe et al., 2021). nevertheless, other researchers observed that some of the processes are not time-effective and often involve complicated synthesis procedures that are financially expensive. optionally, the conventional method, like the solid-state sintering method, offers a better alternative for cost-effective production, a shorter period of the procedure, and large-scale production of the material (sarrigani & amiri, 2019). furthermore, obtaining silica (sio 2 ) sources from a complex chemical process mentioned earlier seems to be expensive and consumes time, yet little amount is produced through the process (takesue et al., 2009). therefore, the use of another sources especially one which the precursor is obtained from waste recycled material is encouraged. example of such is the waste from soda–lime–silica glass (sls) which is commonly used glass and could be obtained in our surroundings (sarrigani & amiri, 2019). the spread of damage glasses disposal by the glass manufacturing industries has caused the sls based glasses to become a huge pollutant to the environment. to curb the menace, several file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com alibe et al: investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application. azojete, 19(3):505-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 507 scientist tend to convert and used the waste sls glass as a source of silica in the research (zaid et al., 2016; omar et al., 2017; effendy et al., 2017;wei et al., 2022). interestingly, this goes with waste-to-wealth creation and also offers a better cost-effective manufacturing. besides, the incorporation of sls glass waste in the willemite formation can also lower its melting point, improve the clarity as well as enhance thermal and chemical stability of the final material produced (takesue et al., 2009; wei et al., 2022). oxide-based glass formers often add on to the bulk matrix to enhance the formation of a glass and form the interconnected backbone of the glass network. one of the most studied glass former over the decade is the boron oxide (b 2 o 3 ) (li et al., 2013). previous literature suggest that the addition of little quantity of b 2 o 3 could improve and stabilize the disorder in matrix and further serve as a nucleation agent to hasten crystallization process (hamnabard et al., 2012; li et al., 2013; qazvini et al., 2012). in this work, new approach was proposed to fabricate willemite glass-ceramic derived from zno– b2o3–sls glass system. the influence of calcination temperature on the phase structural formation, and optical emission properties were thoroughly discussed. 2.0 materials and methods 2.1 materials preparation this section describes the glass preparation process for the work according to the solid state technique (zaid et al., 2016; omar et al., 2017; effendy et al., 2017;) . the precursors used were sls glass, zno, and b 2 o 3 . the sls glass powder was prepared from waste broken glasses obtained from the dumping site, while the zno and b 2 o 3 powders were purchased from sigmaaldrich and used without further purification. the (zno)0.6−x (b2o3)x (sls)0.4 glasses samples were prepared using the conventional melt-quenching technique for glass production. the sls glass waste was at first crushed to form glass powder and sieved to 45 μm particle size. the sls glass powder obtained was combined with zno and b 2 o 3 using the composition mixture of (zno)0.6−x (b2o3)x (sls)0.4 in weight percent. the mixed sample was allowed to undergo a milling process by placing them into a milling jar and running them for 30 minutes in a ball milling machine with 50 rpm to ensure homogeneity of the mixture and control the size distribution of the composition. the milling process was followed by melting about 30 g of the milled sample at a temperature of 1450 ◦c for 2 h. when melting point is achieved, the hot sample is then quenched in a container filled with water to produce glass frits. due to the fast quenching process, the glass frits produced were transparent devoid of bubbles. the earlier process of crushing, grinding, and sieving the glass frits produced a fine glass powder with an average particle size of 45 μm for the pelleting process. note that pelletizing is the process of compressing or molding a material into the shape of a pellet. therefore, after the sieving process, the sample was mixed with 1.75 weight percent of polyvinyl alcohol (pva), which served as a binding agent, and pressed using a hydraulic press machine until it reached 4 tons/m2. each sample was left for 10 minutes to form 13 mm diameter glass pellets. the solid pellets were all sintered at 700 ◦c for 2 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):505-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 508 hours to decompose the pva. a constant heating rate of 10 ◦c/min was maintained throughout. subsequently, all the samples obtained were characterized using densimeter and vernier caliper measurements to determine their physical properties. the structural properties of the glass formed were studied using x-ray diffraction (xrd) (pw 3040/60 model, philips, san jose, ca, usa) and fourier transform infrared reflection (ftir) (spectrum 100 model, perkin elmer; waltham, massachusetts, usa). the optical properties were analysed using ultraviolet–visible (uv–vis) (uv-3600 model, shimadzu, kyoto, japan) and photoluminescence (pl) (ls 55 model, perkin elmer, waltham, massachusetts, usa) spectroscopic techniques, respectively. 2.2 characterization in this work, all samples obtained were characterized for their physical properties using densimeter and vernier caliper measurements. the structural properties of the glass formed were studied using x-ray diffraction (xrd) (pw 3040/60 model, philips, san jose, ca, usa), fourier transform infrared reflection (ftir) (spectrum 100 model, perkin elmer; waltham, massachusetts, usa), and optical properties were analysed using ultraviolet–visible (uv–vis) (uv-3600 model, shimadzu, kyoto, japan) and photoluminescence (pl) (ls 55 model; perkin elmer; waltham, massachusetts, usa) spectroscopic techniques respectively (omri et al., 2013; zaid et al., 2016a; rasdi et al., 2017; effendy et al., 2017). in glass and glass ceramic-based research, the physical properties of the material, such as its density, are considered as an important factor in determining the material’s strength. the density was obtained by using densitometer ms-300s in order to determine the molecular packing inside the sample (samsudin et al., 2016). ethanol was used as an immersion liquid in this experiment, which was repeated three (3) times in order to avoid parallax error and mathematically shown in the equation. 𝜌= 𝑚 𝑉 (1) where ρ is the density of sample (g cm − 3), m is the mass of pellet (g) and v is the volume of ethanol (cm−3). 3.0 results and discussion this section analyses and discussed comprehensively the data obtained from the characterization of the samples. 3.1 density and linear shrinkage analysis table 1 shows the density of five glass samples respectively. the series of (zno)0.6−x (b2o3)x (sls)0.4 glasses were observed to be decreasing with the increment of b2o3 content. the data measurement shows the trend of density samples decrease with increasing weight fraction of b2o3 as expressed graphically in figure 1. it is noteworthy that this decrement in density of the glass samples was due to lower b2o3 atomic mass compared to file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com alibe et al: investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application. azojete, 19(3):505-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 509 other element in glass system. the atomic mass of b2o3 is 69.617 amu which is lower as compared to atomic mass of zno (81.38 amu). this phenomenon led to the decrease in density from 2.80 to 2.50 g cm−3 as zno content decrease from 0.6 to 0.455 w.t%. table 1: the compositions and density of the glasses for (zno)0.6−x (b2o3)x (sls)0.4 samples compositions density 1 (zno)0.6 (sls)0.4 2.80 2 (zno)0.59 (b2o3)0.01 (sls)0.4 2.72 3 (zno)0.55 (b2o3)0.05 (sls)0.4 2.60 4 (zno)0.50 (b2o3)0.10 (sls)0.4 2.52 5 (zno)0.45 (b2o3)0.15 (sls)0.4 2.50 figure 1. density of (zno)(0.6-x) (b2o3)x (sls)0.4 glasses 3.2 xrd structure and phase analysis the structure of the prepared glasses samples were analyzed using xrd. figure 2 shows a xrd pattern of (zno)0.6−x (b2o3)x (sls)0.4 based glass samples. the presence of zno phase in the glass matrix was observed in the samples with 0 and 0.01 wt.% b2o3. by matching the diffraction peaks in the pattern with the standard diffraction pattern of the xrd, the sample with 0 wt.% b2o3 exhibit 8 major diffraction peaks of zno at 31.97°, 34.65°, 36.46°, 47.75°, 56.79°, 63.07°, 68.14° and 69.27° corresponding to (0 1 0), (0 0 2), (2 2 0), (0 1 2 ), (1 1 0), (0 1 3), (1 1 2) and (0 2 1) planes. while, the sample with 0.01 wt.% b2o3 also exhibit 6 major diffraction peaks at 31.87°, 34.54°, 36.37°, 56.76°, 63.05°, and 68.14° respectively (shofria et al., 2010). it appears that when little quantity of the b2o3 is substituted for zno, the glass structure may form a crystalline phase as depicted in figure 2. it was reported by some authors that the glass http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):505-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 510 network modifier work as a crystallization promoting agent, thereby providing nucleation positions arising from effect on the glass stability, caused by ion substitution within the glass network (qazvini et al., 2012; sarrigani and amiri 2019). in addition, takesue et al., 2009 reported that zno work as a network modifier that breaks the bonds between oxygen and glass former ions, which may lead to a change in the structural unit that affects the physical characteristics of the glass network. thus, forms a non-bridging oxygens (nbo), as proved in samples with compositions of 0 and 0.01 wt.% b2o3. besides, the high amount of zno can lead to more intense crystallization and favor the precipitation of optically active crystalline phases (zaid et al., 2016a). moreover, it show that there is very slight increase in the intensity of the diffraction peaks with the increment of zno content because the ratio of composition is not stable to achieve the amorphous phase (zaid et al., 2016a). however, as b2o3 content increased, the precursor glass sample showed a broad halo characteristic, which reflected the properties of amorphous glass that were observed at a the composition of 0.05 wt.% b2o3 (mohd shofri et al., 2020). from the pattern, there is no discrete sharp peak, which implies the samples were fully in glass form. the amorphous hump was obtained at 33°. by comparing the increment of b2o3 in the glass system, it was observed that the peaks get broadened in the spectrum due to variation in the inter-atomic distances (shofria et al., 2010). it was confirmed and also reported by lim et al. (2002), that the formation of covalent b-o bonding produced a stronger, better chemically resistant glass network with higher packing density and lower crystallization tendency (mohd shofri et al., 2020; shofria et al., 2010). 20 40 60 80 021 013 110 012 220 degree (2theta) 0 wt% b 2 o 3 010 112 002 0.01 wt% b 2 o 3 in te ns ity (a .u ) 0.05 wt% b 2 o 3 0.10 wt% b 2 o 3 0.15 wt% b 2 o 3 figure 2. xrd pattern of (zno)(0.6-x) (b2o3)x (sls)0.4 glasses file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com alibe et al: investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application. azojete, 19(3):505-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 511 3.3 ftir analysis all the functional groups and the existing chemical bonding in the pattern of (zno)(0.6-x) (b2o3)x (sls)0.4 glasses were assessed by ftir analysis a shown in table 2 and figure 3 respectively. the structure of the glass samples were measured using ftir in the wavenumber range of 280 to 4000 cm−1. the ir spectrum is divided into two paths; the first one consists of the main sharp, distinctive and characteristic absorption bands extending in the mid ir region from 400 to about 1400 cm−1 , and the second part reveals only small peaks from 1400 to 4000 cm−1. furthermore, silicate glass structure having disordered geometry with the formation of tetrahedral coordination of bo4 units among oxide glasses. according to the glass formation theory, the oxides of metal cation (e.g. zn2+) with valence one or two plays an important role as glass modifier (hivrekar et al., 2017). some of the bridging oxygen of tetrahedral bo4units combines with glass modifier coordinated by six, eight or even more oxygen atom to form glass network with non-bridging oxygen (de leede & de waal, 1988). figure 3 shows the samples analysed and was obtained at the range of 400-1400 cm−1 which signifies the vibrations of main building units of sls. then, it was obvious that the band at 500, 688, 902 and 1243 cm−1 can be associated stretching vibrations of zno4 units ( zaid et al., 2016b) and si-o-b bending vibrations, stretching vibration of the b–o bonds in the bo4 units and modes of boron–oxygen triangular bo3 units (kullberg et al., 2017). the intensity of ir band become higher with increasing percentage of b2o3 (mohd shofri et al., 2020). table 2: ir absorption bands and band assignment (kullberg et al., 2017) wavenumber (𝐜𝐦−𝟏) assignment of vibrational mode 500 stretching vibrations of zno4 units 650 – 700 si-o-b bending vibrations 840 – 930 stretching vibration of the b–o bonds in the bo4 units 1234 – 1250 modes of boron–oxygen triangular bo3 units http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):505-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 512 500 1000 1500 2000 2500 3000 3500 4000 wavenumber (cm-1 ) 0 wt% b 2 o 3 883 882 0.01 wt% b 2 o 3 tr an sm itt an ce (% ) 0.05 wt% b 2 o 3 892 1248 500 0.10 wt% b 2 o 3 1243 902 670 0.15 wt% b 2 o 3 922 1249 688 figure 3: ft-ir spectra of sample (zno)0.6−x (b2o3)x (sls)0.4 glasses 3.3 uv-vis analysis the absorption spectra of sample (sls)0.4 (zno)0.6−x (b2o3)x glasses are presented in figure 4. ultra violet regions are very important in study field as it provides scientist with information to understand the electronic band gap of a particular material and to find the optical absorbance whether it bands at high or shorter wavelength. optical absorbance is higher at lower wavelength region while lower at higher wavelength region whereas ultraviolet “cut off” emerge as a term to describe increase in absorption factor spectra (singh et al., 2008). figure 4 shows that samples with 0 and 0.01 wt.% b2o3 has crystalline hump which varies at 370 nm. it was observed after the addition of b2o3 to zno-sls glass network has caused the glassy amorphous state with absence of shrill absorption edge at 0.05, 0.10 and 0.15 wt.% b2o3 . moreover, the absorption edge (cut-off wavelength) tends to move to higher wavelength sides when the amount of b2o3 increases in the glass system and produces a non-sharp structure due to the disorder in the matrix. it is clear that there is no sharp absorption edge after addition of 0.05, 0.10 and 0.15 wt.% b2o3. this corresponds to the characteristics of the glassy state. basically, there are two transitions occurring in the energy band gap of materials, these are direct allowed or indirect allowed transition which can occurs regardless of crystalline or amorphous material of the glass. these transitions usually occur during the reaction among electromagnetic wave when it reacts with electrons at the valence state thus forcing it to be promoted to the conduction state (gnutzmann and clausecker, 1974). in order to find different kinds of transition, the values n=1/2 and n=2 which are for direct allowed and indirect forbidden transitions were substituted into (αhv) 1 n against photon energy (hv) and plots were displayed by extrapolating the linear region of the curve as shown in figure 5 and 6 respectively. by comparing the value of file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com alibe et al: investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application. azojete, 19(3):505-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 513 direct forbidden and indirect allowed transition with different composition for (sls)0.4 (zno)0.6−x (b2o3)x glass system obtained using different values of n, a good agreement with eopt values for n=2 is the best transition. it also can be resolved that optical band gap obtained for (sls)0.4 (zno)0.6−x (b2o3)x glass favors indirect forbidden transition (n=2). table 3 shows the calculated band gap energy. the samples shows increase in band gap when the composition of b2o3 increases. when zno serves as a modifier, the number of nbos will increase and this will cause the expansion of glass network. increase in optical band gap clearly state that the glass has higher number of nbo’s rather than bo’s. 300 400 500 600 700 800 a b so rb a n c e ( a .u .) wavelength (nm) 0 wt.% b2o3 0.01 wt.% b2o3 0.05 wt.% b2o3 0.10 wt.% b2o3 0.15 wt.% b2o3 figure 4: absorption spectra of sample (zno)0.6−x (b2o3)x (sls)0.4 glasses 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0 wt.% b2o3 0.01 wt.% b2o3 0.05 wt.% b2o3 0.10 wt.% b2o3 0.15 wt.% b2o3 e x ti n c ti o n c o e ff ic ie n t hv (ev) figure 5: plot of (𝛼ℎ𝑣) 1 2 as a function of energy for (zno)0.6−x (b2o3)x (sls)0.4 glasses, n=2 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):505-518. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 514 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0 wt.% b2o3 0.01 wt.% b2o3 0.05 wt.% b2o3 0.10 wt.% b2o3 0.15 wt.% b2o3 ex ti n ct io n c o ef fi ci en t hv (ev) figure 6: plot of (𝛼ℎ𝑣)2 as a function of energy for (zno)0.6−x (b2o3)x (sls)0.4 , n=1/2 table 3: energy band gap ( 𝑒𝑉) for (zno)0.6−x (b2o3)x (sls)0.4 glass system samples direct allowed transition, n=1/2 indirect forbidden transition, n=2 (zno)0.60 (sls)0.4 4.35 3.25 (zno)0.59 (b2o3)0.01 (sls)0.4 4.45 3.35 (zno)0.55 (b2o3)0.05 (sls)0.4 4.70 3.60 (zno)0.45 (b2o3)0.10 (sls)0.4 4.85 3.65 (zno)0.40 (b2o3)0.15 (sls)0.4 5.25 4.30 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com alibe et al: investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application. azojete, 19(3):505-518. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: babaiya1@gmail.com 515 4.0 conclusions based on this study, the zno–b2o3–sls glass system had been successfully fabricated and investigated. the physical, structural, and optical properties of glass system were comprehensively discussed. the density of the material was observed to decrease as the b2o3 content is increased. this is attributed to the lower atomic mass of b2o3 compared to zno and sio2 present in the glass system. the functional groups attached to the glass system observed from the ftir spectrum reveal that the ir spectrum is divided into two paths; the first one consists of the main sharp, distinctive and characteristic absorption bands extending in the mid ir region from 400 to about 1400 cm−1, and the second part reveals only small peaks from 1400 to 4000 cm−1. it was obvious that the bands at 500, 688, 902 and 1243 cm−1 can be associated with stretching vibrations of zno4 units, si-o-b bending vibrations, stretching vibration of the b–o bonds in the bo4 units, and modes of boron–oxygen triangular bo3 units. the band gap characteristics of the glass system favor direct and indirect forbidden transitions, and the increase in the b2o3 content causes higher absorption in the uv region, thus resulting in a lower band gap. based on this study, b2o3 served as an important glass formers and flux materials that connects the backbone of the glass network. the findings in this work open the path to comprehend the effects of b2o3 content on the structural and optical properties of the zno–b2o3–sls glass system, and the wide band gap energy of the material obtained may have key potential applications for future led and other optoelectronic lighting devices. conflict of interests the authors declare that there is no conflict of interests regarding the publication of this paper. acknowledgments the researchers gratefully acknowledge the financial support for this study from the malaysian ministry of higher education (mohe) and universiti putra malaysia through the fundamental research grant scheme (frgs) and inisiatif putra berkumpulan (ipb) research grant. the researchers would like to gratefully acknowledge associate professor khamirul amin matori (department of physics, faculty of science, universiti putra malaysia) for providing the laboratory tools and equipment used in the research work. references abdel-hameed, sam. and marzouk, m.a. 2022. long afterglow from multi dopant transparent and opaque glass ceramic phosphor for white, red, yellow, and blue emissions: zn2sio4: eu3+, dy3+, mn2+. journal of alloys and compounds, 893: 162337. alibe, im., matori, ka., zaid, mhm., nasir, s., alibe, am. and khiri, mza. 2021. polymer thermal treatment production of cerium doped willemite nanoparticles: an analysis of structure, energy band gap and luminescence properties. materials, 14(5):1118. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; 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(2020). fabrication of zno-sio2 nanocomposite materials prepared by a spray pyrolysis for the photocatalytic activity under uv and sunlight irradiations. iop conference series: materials science and engineering, 778(1): 012105. li, hc., wang, dg., hu, jh. and chen, cz. 2013. effect of the partial substitution of k2o, mgo, b2o3 for cao on crystallization, structure and properties of na2o–cao–sio2–p2o5 system glassceramics. materials letters, 106: 373–376. lim, sg., kriventsov, s., jackson, tn., haeni, jh., schlom, dg., balbashov, am., uecker, r., reiche, p., freeouf, jl. and lucovsky, g. 2002. dielectric functions and optical bandgaps of high– file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/babaiya1@gmail.com alibe et al: investigating the effects of diboron trioxide on zinc silicate-based glass-ceramic derived from waste soda lime silica for potential phosphor materials application. azojete, 19(3):505-518. issn 1596-2490; 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vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 355 arid zone journal of engineering, technology & environment original research article thin layer drying kinetics and influence of drying temperature on the proximate composition of tiger-nut milk powder n. i. nwagugu1* and w. i. okonkwo2 1projects development institute (proda) emene enugu, nigeria, +2348066733762 2 agricultural and bioresources engineering university of nigeria nsukka, nigeria, *corresponding author’s email: nnenwagugu@gmail.com article information abstract milk derived from animal sources often contains anti-nutrient elements such as α-lactoglobulin, β-lactoglobulin, lactose and cholesterol, which can contribute to various health challenges. plant-based milk alternatives, such as tiger-nut milk, offer a healthier option but often face limitations like short shelf life and high storage costs. this study aimed to investigate the drying kinetics and proximate composition of tiger-nut milk powder. tiger-nut tubers were processed into milk from brown varieties and subsequently dried at 50, 60, and 70°c. data obtained were fitted to five commonly applied drying mathematical models (newton, logarithmic, page, henderson and pabis) to determine the one which predicted the drying kinetics of the milk more accurately. the dried powder was then analyzed for its proximate composition, including moisture content, crude fiber, carbohydrates, protein, lipids, ash, and ph using standardized procedures developed by association of official analytical chemists (aoac). the best fit model for the drying kinetics analysis was determined using the coefficient of determination (r²), with the page model having the highest r² values of 0.998-0.999. this analysis revealed that the page model accurately describes the drying behavior, with both drying time and equilibrium moisture content decrease as the drying temperature increases. the results also indicated that tiger-nut milk powder contains a moderate protein content (7.12-7.26%), a high carbohydrate content (63.6864.17%), and relatively low levels of lipids (6.12-6.24%) and ash (1.42%). these findings suggest that tiger-nut milk powder has the potential to be a valuable plant-based food alternative. future research should focus on determining its specific mineral composition, bioactive compounds, and potential health benefits. received: 22nd september 2024 revised: 2nd april 2025 accepted: 4th april 2025 keywords: milk drying temperature drying kinetics proximate composition tiger-nut milk powder page model © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction milk, an essential food for many people, is produced by mammals like cattle, sheep, goats, and buffalo and provides essential nutrients. cow milk, which is the most consumed milk worldwide is reported by (bouglé and bouhallab, 2017) and (paul et al., 2020) to provide essential nutrients including proteins (whey and casein protein), fat (palmitic acid, conjugated linoleic acids (cla), α-linolenic acid (ala), milk polar lipids (mpl), vitamins (vitamin a, vitamin b complex) and minerals (iron, calcium, magnesium, phosphorus) which have been described to have indispensable functions in the body’s growth (both adults and adolescences), metabolism and maintaining health or well-being. azojete june 2025. vol.21(2):355-366 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/004 www.azojete.com.ng http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com mailto:nnenwagugu@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 356 milk is used daily in coffee, breakfast cereals and as an ingredient in cooking and baking (sebastian and davis, 2019). unfortunately, milk from animal sources contain anti-nutrient elements such as αlacto globulin and ß-lacto globulin which causes food allergies in infants (ah-leung et al., 2007), lactose and cholesterol which are associated with some health challenges such as dietary disorders, milk-protein allergy and/or lactose intolerance which have been reported to affect about 70 to 75 % of the human population due to genetically decreased lactase enzyme production (heine et al., 2017; sebastian and davis, 2019) and dietary constraints such as vegan diet and milk allergy (helsing, 2019; osthoff et al., 2010). it is also not accessible by the poor owing to its high cost and scarcity. animal milk consumption is also linked with the increase in low-density lipoprotein as it contains saturated fatty acid and cholesterol (lordan et al., 2018). owing to these and other problems associated with milk from animal sources, international organizations such as the who (world health organization), the fao (food and agriculture organization of the united nations), and the ipcc (intergovernmental panel on climate change) urge a global shift to plant-based diets among which is plant base milk and reported by (2021) to be of high health benefits. plant-based milk is milk that is extracted from legumes (soya, lupins, peanuts, among others), cereals (oats, rice, spelt, corn, etcetera) pseudo cereal (quinoa, amaranth, teff, etcetera) nuts (almonds, hazelnuts, coconut, macadamia nuts, pistachios) and/or seeds (hemp seeds, flax seeds, sesame seeds, sunflower seeds) (romulo, 2022), diluted in water, and similar to animal milk in appearance, texture, and use. such milk has been reported to have different nutritional composition and taste depending on the raw material, method of production, and type of fortification (sebastian and davis, 2019). sebastian and davis (sebastian and davis, 2019) stated that all the nutrients provided by cow’s milk can be obtained from suitable plant-based alternatives. plant milk can also be obtained from other crops such as lupin, cashew, quinoa, flax, hemp, walnut, hazelnut, and tiger nut. because of its numerous nutritional and health benefits as well as its ever-increasing market potential, plant-based milk has been referred to as white gold by the guardian in a report on the unstoppable rise of alternative milk. among the sources of plant-based milk, tiger nut is one of the commonly available and underutilized ones found in nigeria (adebayo-oyetoro et al., 2019; ayuba et al., 2020; ogori et al., 2022). it contains an appreciable amount of healthy nutrients and has so many health benefits. tiger-nut (cyperus esculentus l.) is a root tuber that is a member of the family cyperaceae found in the eastern hemisphere, including southern europe, africa, and madagascar, as well as the middle east and indian subcontinent (adebayo-oyetoro et al., 2019). it is also known as earth almonds or zulu nuts (okudu and ogubuike, 2016). in nigeria, it is called ofio in yoruba, aya in hausa, and akiaawusa in igbo (bamishaiye and bamishaiye, 2011). three varieties namely black, brown, and yellow, are easily obtainable in the country (bamishaiye and bamishaiye, 2011). ayuba et al and swati et al reported that the nuts help in the prevention and/or treatment of many diseases such as heart attacks, thrombosis, colon cancer and other cancers, obesity, diabetes, and gastrointestinal diseases. tiger nuts are rich in protein, starch glucose, essential minerals such as phosphorus, potassium, vitamins e and c, fat, and sugar (gambo and da’u, 2014). they are also high in fiber, myristic, linolenic, and oleic acid which is heart-friendly and can help to prevent cardiac arrest (adebayo-oyetoro et al., 2019; asante et al., 2014). (ayuba et al., 2020) found that regular consumption of tiger nuts could reduce the frequency of illness, particularly in sickle cell patients.. the nuts also aid the internal body mechanisms and prevent both constipation and diarrhoea (adebayo-oyetoro et al., 2019; bamishaiye and bamishaiye, 2011). tiger-nut is a very useful raw material in such industries as gastronomic, pharmaceutical/medicinal, confectionery, and the biofuel. it is applicable in the manufacture of many useful products including food additives, coffee substitutes, malt caramel, beverages, fermented foods, flour for baking and vegetable oil, and it can be eaten as a snack (asante et al., 2014; frank, 2015). a very nutritional beverage called “horchata de chufa” in spain, “atadwe” in ghana, and “kunun aya” in northern nigeria is produced from tiger-nut by soaking, milling, sieving and sweetening with flavors and sugar is gaining acceptability. but the tiger-nut liquid milk has very low shelf life and its storage is energy intensive as the milk has to be stored in a temperature range of 40 to 70 oc making the use of such milk expensive as a result of the increase in the cost of electricity which is the main source of energy for running refrigerators (paul et al., 2020; torna et al., 2020). even in favorable storage conditions, the shelf life http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 357 of such milk is very short as (abdulfatai et al., 2013) reported that the shelf life of beverage drinks from tiger-nut tuber is 24 hours. to increase the shelf life of tiger-nut milk, reduce the cost of storage, and for ease of storage and transportation, the milk needs to be converted into powdered form as reports show that the shelf life of powder milk is far longer than that of liquid milk, and there is no need for refrigeration (pal et al., 2016). the process of converting liquid milk to powder is through drying which is achieved by reducing the moisture content of the milk to a level that prevents the growth and reproduction of spoilage-causing microorganisms and thus, minimizing many of the moisture-meditated deterioration reactions (famurewa and olumofin, 2015). drying also lead to reduction in the bulkiness of the product thereby minimizing packaging, storage, and transportation costs and enabling storage of the product under ambient temperature to be achieved (orishagbemi et al., 2000). but the drying process especially under high temperatures, does not only reduce the moisture content of the product but also affects some of its physical, proximate, and chemical compositions as well as its sensory properties. the drying process involves the movement of moisture from the core of the products to the outer surface and then to the surroundings. the rate of moisture removal from produce is dependent on factors such as the initial moisture content of the product, the drying temperature, and the velocity of the drying medium among others. chukwuma and ozoma, (2006) reported that the characteristics and behaviour of the drying material can be described and represented using mathematical models. these models are used in designing and analysing drying systems (famurewa and olumofin, 2015). several drying models such as empirical models among which include (page, henderson and pabis, newton, logarithmic and two-term models among others) (akpinar, 2006), semi-empirical models (modify page and midilli models) (bryś et al., 2021) and theoretical models (diffusion-based models, capillary theory and film theory) (erbay and icier, 2010) were developed by many researchers which are suitable to explain the drying behaviours of different products. therefore, this study is aimed at studying the drying kinetics of tiger nut milk in a thin layer dryer, and investigating the effect of drying temperature on the proximate composition of milk powder. the study will therefore, provide the appropriate drying temperature for drying tiger-nut milk to powder as well as the best-fit empirical drying model for the drying process. 2. materials and methods 2.1 materials used the materials used in this study include: brown tiger-nut, weighing balance (aeadam model number ae7681116, 2000g ×0.01g), blender (eurosonic model number: es-910, capacity: 1.8 litres), digital thermometer (custom model number: ct-220 measuring range: -50 to +200 oc, resolution: 0.1 oc), modular cold room (riva cold, model: mcr1, temperature range -50c to 5 oc), drying pan ( aluminum tray 25 by 40 cm by 3 cm deep), hot air electric oven (genlab, model ov/200/f/digr38, 2 kw, temperature range: 30 to 250 oc). 2.2 sample preparation brown tiger-nut (cyperus esculent) was procured from a tiger-nut whole seller in the central market bauchi metropolis, bauchi state. the tiger nuts were then sieved using a 12 mm sieve to remove sand, impurities, and other materials and then washed several times with clean water, sun dried, and stored in air-tight polythene bags for use in producing the milk. the initial moisture content of the tiger nut was determined to be 32.4% wet basis using oven drying method at 105 0c. 2.3 milk extraction and drying the tiger-nut milk was extracted following the procedure described by (romulo, 2022) with some modifications. from the clean dried tiger-nut, 450 g were soaked in twice its volume of water at 40 oc for 12 hours placed inside genlab hot air oven (model ov/200/f/dig-r38) to maintain the temperature. the sample was then drained and washed in clean water. the moisture content of the sample was then determined using oven drying method at 105 0c to be 38.7%. the soaked tiger-nut was then ground using the kitchen blender (eurosonic model number: es-910) at high speed of 9,645 rpm for 5 minutes and filtered through cheesecloth to obtain tiger-nut milk. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 358 the quantity of water used in grinding the tiger-nut and filtering the milk was twice the volume of the tiger-nut after soaking. the liquid tiger-nut milk was then pasteurized in a non-stick pan at 72 oc for 15 sec and stored in a refrigerator at 4 oc for 24 hrs before drying. the liquid milk was dried in a hot air oven (genlab, model ov/200/f/dig-r38) using shallow drying trays at three different temperatures: 50, 60, and 70 oc. the milk samples were weighed hourly to determine weight loss following the method described by (abano et al., 2021), which was used to study drying kinetics and drying time. the drying process continued until the milk was completely dry, as indicated by three consecutive weighs showing no change in weight. at the end of the drying process, the equilibrium moisture content (me) was determined using oven drying method at 105 0c for 24 hours. the dried milk was then blended to powder using a blender and stored for proximate analysis. the whole process of milk production and drying was replicated 3 times to reduce error in the results. 2.4 drying kinetics of the tiger nut milk data obtained from the drying tests as described in section 2.3 were used in analyzing the drying kinetics of the tiger-nut milk powder thus: 2.4.1 drying rate the rate of drying of the tiger-nut milk was determined using the equation 1 (abano et al., 2021) dr = 𝑀𝑡+∆𝑡−𝑀𝑡 ∆t 1 where: dr is drying rate, g h2o/min, 𝑀𝑡+∆𝑡 𝑎𝑛𝑑 𝑀𝑡 are moisture contents, g h2o /g of dry solid at drying time t, ∆t is drying time, min the original moisture content of the milk, the moisture content during the drying process and the equilibrium moisture content were determined using equation 2 and the data obtained were used to determine the moisture ratio. 𝑀𝑡 = 𝑊0−𝑊1 𝑊1 2 where: 𝑀𝑡 is product moisture content at a specified time during the drying operation, g of water, 𝑊0 is the weight of the sample before drying, g, 𝑊1 is the weight of after dry, g the moisture ratio was calculated using fick's diffusion equation (equation 3), as presented by eunice (eunice, 2018). the equilibrium moisture content was achieved by continuous monitoring of weight change until no further changes occured. the calculated moisture ratios were then plotted against drying time to create a drying curve, from which regression equations for the drying of tiger-nut milk were developed 𝑀𝑅 = 𝑀𝑡−𝑀𝑒 𝑀𝑜−𝑀𝑒 3 where: 𝑀𝑡 is moisture content at time t, % dwb, 𝑀𝑒 is equilibrium moisture content, % dwb, 𝑀𝑜 is initial moisture content, % dwb. 2.4.2 mathematical modeling of the drying process the data obtained from the computation of moisture ration 𝑀𝑅 at different drying periods were used to develop an empirical model based on the assumption that resistance to water movement to the surface of the sample was negligible and that the resistance to water evaporation was concentrated on the surface of the sample (abano et al., 2021). this phenomenon is similar to newton’s law of cooling. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 359 five empirical drying models applicable to thin layer drying shown in the equations 4 to 8 (table 1) were used to study the drying behaviour of the tiger-nut milk. the drying rate constant 𝑘, 𝑘𝑜 and 𝑘1 and drying coefficients a, b, 𝑐 and 𝑛 were determined using a nonlinear regression procedure on spss version 25 following the procedure described by rasmussen et al 2021 and yi et al, 2012 the goodness of the fit of each drying models was assessed using the coefficient of determination (r2) as shown in equation 9 and the model with the highest r2 was selected to best describe the drying of the tigernut milk. table 1: mathematical models fitted to the drying data model name equation reference newton 𝑀𝑅 = exp(−𝑘𝑡) … 4 (jahanbakhshi et al., 2020) logarithmic 𝑀𝑅 = a exp(−𝑘𝑡) + 𝑐 … 5 (coşkuner et al., 2002) page 𝑀𝑅 = exp(−𝑘𝑡𝑛) … 6 (eunice, 2018) handerson and pabis 𝑀𝑅 = aexp(−𝑘𝑡) … 7 (aviara and igbeka, 2016) two term 𝑀𝑅 = aexp(−𝑘𝑜𝑡) + bexp(−𝑘1𝑡) … 8 (famurewa and olumofin, 2015) where: 𝑡 is time (min), 𝑘, 𝑘𝑜 and 𝑘1 are drying rate constant (min-1) and a, 𝑐 and 𝑛 are drying coefficients. 𝑅2 = 1 − ∑(𝑀𝑅𝑝𝑟𝑒−𝑀𝑅𝑎𝑐𝑡) 2 ∑(𝑀𝑅𝑎𝑐𝑡−𝑀𝑅𝑎𝑐𝑡.𝑎𝑣𝑔) 2 9 where: 𝑅2 is coefficient of determination, 𝑀𝑅𝑝𝑟𝑒 is predicted moisture ratio, 𝑀𝑅𝑎𝑐𝑡 is experimental moisture ratio, 𝑀𝑅𝑎𝑐𝑡.𝑎𝑣𝑔 is the average experimental moisture ratio 2.5 validation of the model to validate the predictive accuracy of the selected models, the predicted moisture ratios were plotted against the experimental drying time for each of the three drying temperatures. additionally, a plot of predicted moisture ratio against observed moisture ratio was created, and the r² value of the linear trend line fitted to this plot was evaluated. a closer r² value to 1 indicates a better fit between the predicted and observed data. 2.6 proximate analysis the proximate composition of the dried tiger-nut milk was determined using standard methods as follows: crude protein content, mineral ash content, and crude fiber content were determined following the procedure given by the association of official analytical chemists (aoac) (2000), crude fat content was determined using the soxhlet method as reported by (ndubuisi, 2009). carbohydrate content of the milk was obtained by difference as reported by (frank, 2015). the carbohydrate content was calculated by subtracting the sum of the protein, fat (lipid), fiber, and ash from the total dry matter. while the energy value of the milk was calculated by multiplying the mean values of the crude protein, fat, and carbohydrates by the at water factors of 4, 9 and 4 respectively (fao, 2006) as reported by (frank, 2015) and represented in equation 10. the obtained energy values were converted to kilojoule (kj) using a conversion factor of 4.184 (approximately 4.2) to multiply the energy values given in kcal (ndubuisi, 2009). energy value = (4 × protien + 9 × fat + 4 × carbohydrate) ∗ 4.184 10 2.7 statistical analysis all the experiments were carried out in replications. the drying data and proximate analysis results were subjected to analysis of variance (anova) using spss version 23 to investigate the effect of drying temperature on the drying time and the various proximate composition of the milk. 3. results and discussions the effects of drying temperature on the drying kinetics and proximate composition of tiger-nut milk powder were investigated. the results are presented below: http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 360 3.1 drying kinetics table 2 presents the results of modeling the drying behavior of tiger-nut milk at varying temperatures (50, 60, and 70°c) using five drying models: newton, logarithmic, page, henderson and pabis, and two-term. the table includes drying rate constants (k, k'), drying coefficients (a, b, c, n), and coefficient of determination (r²) values for thin-layer drying. all five models demonstrated a good fit for describing the thin-layer drying of tiger-nut milk, aligning with the findings of (famurewa and olumofin, 2015). a model with an r² value greater than 0.9 is generally considered to accurately represent the drying characteristics of a product. the r² values for all models in this study ranged from 0.936 to 0.999. the newton model exhibited the least fit, with r² values between 0.936 and 0.945 for all three temperatures. the henderson and pabis model followed with r² values ranging from 0.857 to 0.962. the page model demonstrated the best fit for all three temperatures, with r² values of 0.998 to 0.999. figure 1 illustrates the relationship between moisture ratio and drying time for both experimental data and the page model at 50, 60, and 70°c. the plots indicate that moisture reduction begins after the first hour of drying for all three temperatures, suggesting a falling rate period. drying at 50°c required 22 hours to complete, likely due to the lower energy of water molecules at lower temperatures. in contrast, drying at 60 and 70°c took 20 and 15 hours, respectively, as the higher temperatures increased the energy of the water molecules. the equilibrium moisture contents of the milk were determined to be 8.23%, 6.95%, and 5.78% for drying at 50, 60, and 70°c, respectively. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 361 table 2: fitting of thin layer drying of tiger-nut milk to three selected drying models drying temperature 0c newton model logarithmic model page model handerson and pabis two-term k r2 a k c r2 k n r2 a k r2 a 𝑘𝑜 b 𝑘1 r2 50 0.115 0.936 1.394 0.077 -0.309 0.986 0.024 1.689 0.998 1.147 0.131 0.957 0.831 0.131 0.316 0.131 0.957 60 0.156 0.945 1.254 0.126 -0.158 0.982 0.040 1.679 0.999 1.141 0.175 0 .962 30.563 0.080 -29.469 0.077 0.984 70 0.124 0.938 1.288 0.153 -0.190 0.980 0.052 1.756 0.999 1.142 0.223 0.957 34.791 0 .096 -33.693 0.094 0 .982 k, 𝑘𝑜 and 𝑘1 are drying rate constants, a, b, c, and n are model constants and r2 is the coefficient of determination. figure 1: experimental and page model drying curves for tiger-nut milk dried at 50, 60 and 70 0c. -0.2 0 0.2 0.4 0.6 0.8 1 1.2 0 5 10 15 20 25 30 m o is tu re r at io drying time (hr) exp @50 deg page @ 50 deg exp @ 60 deg page @ 60 deg exp @ 70 deg page @ 70 deg http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 362 3.2 proximate composition results the analysis of variance (anova) for the effect of drying temperature on the proximate composition of the tiger-nut milk power is presented in table 3. the anova indicates that drying temperature significantly influences all the determined proximate components. among the proximate compositions, carbohydrate content was most affected by temperature, as evidenced by the highest f-value of 61600.522. other proximate components significantly impacted by temperature included crude fibre (f-value = 29606.173), ph (f-value = 9408.129), energy (kcal) (f-value = 7192.206), moisture content (f-value = 3433.836), energy (kj) (f-value = 2403.589), lipid content (f-value = 1444.895), ash content (f-value = 688.345), and crude protein content (fvalue = 620.794). table 3: anova for the effect of temperature on the proximate composition of tiger-nut milk powder source dependent variable type iii sum of squares df mean square f sig. drying temperature (0c) moisture contain (%) 200.765 3 66.922 3433.836 <0.001 ash (%) 18.379 3 6.126 688.345 <0.001 crude protein (%) 445.937 3 148.646 620.794 <0.001 lipid (%) 343.500 3 114.500 1444.895 <0.001 crude fiber (%) 1382.608 3 460.869 29606.173 <0.001 ph 159.938 3 53.313 9408.129 <0.001 carbohydrate (%) 36617.404 3 12205.801 61600.522 <0.001 energy (kcal) 1038790.258 3 346263.419 7192.206 <0.001 energy (kj) 17949558.582 3 5983186.194 2403.589 <0.001 table 4 presents the mean proximate composition per 100 g of tiger-nut milk powder for milk dried at 50, 60, and 70 oc with their respective standard deviations in parenthesis. the results indicated that drying temperature influences all the proximate elements. table 4: proximate composition of tiger-nut milk powder per 100 g dried at various temperatures drying temperature (0c) moisture contain (%) ash (%) crude protein (%) lipid (%) crude fiber (%) ph carbohydrate (%) energy (kcal) energy (kj) 50 4.84 (0.15) 1.43 (0.1) 7.12 (0.3) 6.12 (0.29) 12.42 (0.11) 4.21 (0.06) 64.17 (.062) 340.24 (4.97) 1423.56 (29.08) 60 4.81 (0.18) 1.41 (0.09) 7.22 (0.65) 6.18 (0.33) 12.39 (0.15) 4.23 (0.08) 63.76 (0.3) 339.54 (8.05) 1420.64 (56.68) 70 4.51 (0.07) 1.42 (0.1) 7.26 (0.46) 6.24 (0.2) 12.36 (0.11) 4.2 (0.09) 63.68 (0.34) 339.92 (7.42) 1422.23 58.39) values in the parenthesis are standard deviations of three replications the moisture content of the tiger-nut milk powder dried at 50 oc was 4.84% and is slightly higher than that of the milk dried at 60 and 70 oc which was of 4.81 and 4.51%, respectively. the moisture content range (4.84 to 4.51%) of the tiger-nut powder milk was close to 4.15 ± 0.03 % obtained by aidoo et al. (2010) for skimmed milk powder, 4.32 % and 4.89 % for soymilk powder and okara (soy pulp), respectively, reported by osthoff et al. (2010). the moisture content of the tiger-nut milk powder was found to fall within the safe and ideal storage moisture content of powder milk reported by osthoff et al. (2010) and recommended by codex alimentarius (marie et al., 2004). the crude fiber content of the tiger-nut milk powder was found also to be inversely affected by drying temperature to a lesser extent as the highest crude fiber content of 12.42% was found in milk dried at 50 oc which decreased to 12.39% for the milk dried at 60 oc while the least crude fiber content of 12.36% was obtained for milk dried at 70 oc. the fiber content of the tiger-nut milk was found to be higher than 0.26%, and 2.58% found for skimmed milk powder, and dehydrated peanut-cowpea milk reported by aidoo et al. (2010). the tiger-nut powder milk was found to have an average carbohydrate content of 63.76% for milk dried at 60 oc with a minimum and maximum values of 63.68% for milk dried at 70 oc and 64.17% for milk dried at 50 http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 363 oc, respectively. indicating that the milk contains large amount of energy. closer carbohydrate content of 65.10% is reported for tiger-nut microencapsulation powder milk by neto et al. (2019) but a far lower value of 2.21 and 10.73 % were reported by ogori et al. (2022) and abdulfatai et al. (2013) respectively for tigernut milk. protein is a vital component for living organisms, regulating body metabolism and serving as a storage form of carbon and nitrogen (famurewa and olumofin, 2015). the crude protein content of the tiger-nut milk powder in this study ranged from 7.12 to 7.26%. drying temperature was found to influence protein content, with lower temperatures resulting in lower protein levels and higher temperatures yielding higher protein content. this finding suggests that drying conditions can be optimized to maximize protein retention in the final product. the protein content of the tiger-nut milk powder was comparable to the 7.69% reported by frank (2015) for a similar product. however, it was lower than the 11-15% range for oat milk (swati et al., 2016) and significantly lower than the 37.81% and 29.90% reported for soymilk powder and okara milk, respectively osthoff et al. (2010). additionally, the protein content was higher than the 4.43% reported for almond milk powder (bueno, 2018) and exceeded the minimum recommended level of 2.2% for plant-based milk according to drewnowski et al. (2021). while tiger-nut milk powder may not be as protein-rich as some other plant-based milk alternatives, its moderate protein content can contribute to a balanced diet. the influence of drying temperature on protein content provides opportunities for optimizing production processes to enhance the nutritional value of tiger-nut milk powder. the lipid content of tiger-nut milk was found to increase with an increase in drying temperature as the least lipid content of 6.12% was found in the milk dried at 50 oc followed by 6.18% in milk dried at 60 oc with the highest lipid content of 6.24% found in the milk dried at 70 oc. the lipid content of the tiger-nut powder milk was found to be lower than 23.70% obtained by neto et al. (2019) for tiger-nut milk produced by microencapsulation process and 22.44% for soymilk powder obtained by osthoff et al. (2010) but is within the range of 9.01% for okara milk obtained by osthoff et al. (2010) and 5–9 % for oat milk reported by swati et al. (2016). tiger-nut milk powder offers a relatively low-lipid content compared to some other plant-based milk alternatives, making it a suitable option for individuals seeking to reduce their dietary fat intake the ash content of the milk was found to remain around 1.42% which is below 3.16% for okara milk powder, 6.53, 7.5 and 8.11 % for soymilk powder, high milk protein powder and skimmed milk powder respectively reported by osthoff et al. (2010), marie et al. (2004) and aidoo et al. (2010), respectively. the ash content of the tiger-nut milk powder was found to be within the same range as 2.43% obtained by frank (2015) for tigernut milk powder and close to that of cow milk powder (5.72 %) reported by elsara (2009). the ph of the milk was found to be around the acidic range of 4.21 which is below 6.68 for soymilk powder (osthoff et al., 2010), 6.73 for tiger-nut milk (abdulfatai et al., 2013) and 6.70 to 7.03 for reconstituted tiger-nut milk (neto et al., 2019). the ph of the tiger-nut milk was also lower than those of goat milk 6.80, cow milk 6.80 and camel milk 6.25 (elsara, 2009) but is higher than those of most fruit juices such as apple juice (3.61) and pineapple juice (3.67) (abdulfatai et al., 2013). generally, the acidic nature of the milk may aid in digestion. some studies suggest that acidic beverages can contribute to digestive processes (wang et al., 2017). the energy content of the milk calculated using the at water factors remained around 339.92 kcal (1422.23 kj) per 100 g of the milk as the drying temperature increased. this energy is above 170–200 kcal minimum energy recommended by (drewnowski et al., 2021) for plant-based milk indicating that the milk has high energy content. 4. conclusion this study investigated the proximate composition and drying behaviour of tiger-nut milk powder, a promising plant-based milk alternative. key findings include a balanced nutritional profile with a moderate protein content (7.12-7.26%), high carbohydrate content (63.68-64.17%), and relatively low lipid (6.12-6.24%) and ash (1.42%) levels. the page model accurately represents the drying kinetics of tiger-nut milk powder, while drying time and equilibrium moisture content decreased with increasing temperature. these findings suggest that drying conditions can be optimized to improve the quality and efficiency of tiger-nut milk powder production. tigernut milk powder offers a valuable addition to the plant-based food market. its unique nutritional composition and potential health benefits warrant further research to explore specific mineral content, bioactive compounds, and their implications for consumer health. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 355-366. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: nnenwagugu@gmail.com 364 references abano, ee., akanson, j. and kizzie-hayford, n. 2021. drying kinetics and quality of whole, halved , and pulverized tiger nut tubers ( cyperus esculentus ). international journal of food science, 2021: 1–11. https://doi.org/https://doi.org/10.1155/2021/8870001 abdulfatai, j., saka, aa., afolabi, as. and kadiri diana. 2013. development and characterization of beverages from tigernut milk , pineapple and coconut fruit extracts development and characterization of beverages from tigernut milk , pineapple and coconut fruit extracts . applied mechanics and materials, 248: 304–309. https://doi.org/10.4028/www.scientific.net/amm.248.304 adebayo-oyetoro, ao., ogundipe, oo., adeyeye, sao., akande, ea. and akinyele, ab. 2019. production and evaluation of tigernut (cyperus esculentus) milk flavoured with moringa oleifera leaf extract. current research in nutrition and food science, 07(1): 1–7. https://doi.org/10.12944/crnfsj.7.1.26 ah-leung, s., bernard, h., bidat, e., paty, e., rance, f., scheinmann, p. and wal, jm. 2007. allergy to goat and sheep milk without allergy to cow’s milk. allergy, 61(11):1358–1365. aidoo, h., sakyi-dawson, e., tano-debrah, k., and firibu kwesi saalia. 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(2020). milk analog: plant based alternatives to conventional milk, production, potential and health concerns crit. rev. food sci. nutr, 60: 3005–3023. rasmussen, lv., hall, c., vansant, ec., den braber, b., and olesen, rs. 2021. rethinking the approach of a global shift toward plant-based diets. one earth, 4(9): 1201–1204. https://doi.org/https://doi.org/10.1016/j.oneear.2021.08.018 romulo, a. 2022. nutritional contents and processing of plant-based milk: a review. 5th international conference on eco engineering development. iop conf. series: earth and environmental science 998: 1–9. https://doi.org/10.1088/1755-1315/998/1/012054 sebastian, j., & davis, b. 2019. plant milk report. swati, s., tyagi, sk. and rahul, ka. 2016. plant-based milk alternatives an emerging segment of functional beverages: a review. journal of food science and technology, 53(9): 3408–3423. https://doi.org/10.1007/s13197-016-2328-3 torna, e., mendoza, d. r., & wendy, j. d. 2020. plant-based milks: almond. wang, x., ye, a., lin, q., han, j. and harjinder, s. (2017). gastric digestion of milk protein ingredients: study using an in vitro dynamic model. j. dairy sci., 101: 6842–6852. https://doi.org/https://doi.org/10.3168/jds.2017-14284 yi, xk., wen-fu, w., zhang, y. q., li, jx. and luo, h. p. 2012. thin-layer drying characteristics and modeling of chinese jujubes. mathematical problems in engineering, 386214. https://doi.org/10.1155/2012/386214 http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com corresponding author’s email address: sarkibarde@unimaid.edu.ng 401 arid zone journal of engineering, technology & environment original research article improved energy-based efficient routing protocol for underwater wireless sensor networks s. y. barde1*, z. m. abubakar1, h. bello-salau2, r. hassan3 b. abubakar4 and m. b. abdulrazaq5 1*department of computer engineering, university of maiduguri borno state, nigeria 2department of computer engineering, ahmadu bello university, zaria, nigeria 3 department of computer engineering, federal polytechnic, bali taraba state, nigeria corresponding author’s email: sarkibarde@unimaid.edu.ng article information abstract underwater wireless sensor networks (uwsns) rely on small, energy-constrained sensors deployed at varying sea depths for applications such as surveillance, environmental monitoring, and data collection. however, high energy consumption and end-to-end delay, exacerbated by dynamic depth and turbidity variations, significantly impact communication efficiency. existing protocols, such as the neighboring-based energy-efficient routing protocol (nbeer), attempt to optimize energy usage but fail to adapt to these environmental changes, leading to reduced network performance. to address this, an improved energy-based efficient routing protocol (ieberp) was developed, integrating a distributed underwater clustering scheme (ducs) for efficient cluster formation and a strata adaptation scheme (sas) to dynamically reassign displaced nodes to the nearest cluster head (ch) after depth or turbidity changes. the protocol was simulated in matlab (r2024b), and results showed significant performance improvements over nbeer, achieving 9.68 tec, 81.45 pdr, 46.42 e2ed, 234 nan, and 35,191 npr, compared to nbeer’s 12.60 tec, 78.50 pdr, 53.00 e2ed, 198.30 nan, and 22,500 npr. these results highlight ieberp’s enhanced energy management and adaptive clustering, leading to improved routing efficiency, reduced latency, and higher packet delivery rates. this makes ieberp a promising solution for reliable and energy-efficient communication in dynamic underwater environments. received: 19th february 2025 revised: 24th april 2025 accepted: 25th april 2025 keywords: cluster depth energy nodes turbidity sensor-network © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction underwater wireless sensor network (uwsn) is a network of sensor nodes equipped with non-rechargeable and replaceable batteries, antenna, and processing unit deployed underwater for data collection and environmental monitoring (luo et al, 2021; chaurasiyya et al, 2022). uwsn is used in several applications including exploration, disaster risk prediction, and monitoring. there are differences in the features and functions of uwsn compared to the terrestrial wireless sensor networks (twsn). twsn uses radio frequency (rf) for communication to send and receive data between the source and destination. due to the attenuation of rf underwater, it is not used for communication in an underwater environment. uwsn uses acoustic signals as a communication medium acoustic signals travel five times slower than radio waves underwater, at around 1500 m/s. the turbidity and depth of the water affects the acoustic signals (gite et al., 2023; padmavathy et al, 2022). uwsn has several restrictions and difficulties such as high propagation latency, low bandwidth, dynamic network topology, high ocean interference, noise, and sensor nodes limited battery life. a routing protocol facilitates effective transfer of data from the source to the destination (ismail et al, 2020; hussain et al, 2023). in designing routing protocols for uwsns, energy efficiency is a significant factor that requires consideration. various researchers have examined some strategies to lower nodes energy consumption (shah et al, 2023; harb et al., 2024), among which includes cluster formation strategies. the clustering methods are often used to tackle the problems of azojete june 2025. vol.21(2):401-408 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/008 www.azojete.com.ng mailto:sarkibarde@unimaid.edu.ng mailto:sarkibarde@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 402 energy limitation of sensor nodes and deployment issues in both twsn and uwsn (abubakar et al, 2020; kuang et al., 2024). in the clustering approach, sensor nodes are grouped into cluster and a leader node referred to as a cluster head (ch) is chosen in each cluster to aggregate and transfer data. 2. materials and method this section is divided into two parts: it explains the materials and methods of the developed improved energy based efficient routing protocol (ieberp) for uwsns. 2.1 materials the materials used for the implementation of this research are: 1) laptop computer with the following specifications processor: dual-core processor speed: 2.5ghz ram size: 8gb operating system: 64bit windows operating system 2) matlab/simulink (r2024b) software for the design and simulation. 2.2 methods this section is divided into two parts: the first explains the design of a strata underwater environment, the second covers the development of an improved energy-based efficient routing protocol for uwsn, use a distributed underwater clustering scheme (ducs) for cluster formation, and a strata adaptation scheme for data transmission considering underwater depth and turbidity variations. 2.2.1 design of a strata underwater environment in this stage, a strata underwater environment is designed with the following parameters: the network area was set to 550m × 450m × 350m; the transmission range was set to 250 m, water turbidity was set to less than 10 nephelometric turbidity unit (ntu), and normal water depth was set to 450m as used in the work of shah et al, (2023).the turbidity variation range was set between 1 and 15 ntu and depth variation range was set between 1m to 450m, a channel frequency of 2.412ghz to 2.472ghz, and a transmission frequency of 10khz to 50khz to simulate a dynamic underwater environment. the simulation parameters were executed to form a strata underwater environment suitable for the simulation of the proposed ieberp. 2.2.2 development of an improved energy-based efficient routing protocol (ieberp) for uwsns in this network, 250 sensor nodes were deployed at various depths within a layered underwater environment. additionally, 10 sink nodes were deployed at the water's surface in a random distribution. these sink nodes are gateways for data transmission to an offshore base station. to efficiently manage data collection and transmission, the network organized itself into 10 clusters using distributed underwater clustering scheme. each cluster is led by a cluster head node (chn), which was selected based on the energy levels of nodes within that. nodes with higher residual energy are prioritized as potential chns since they have more power available for the intensive task of data aggregation and forwarding. the chn of each cluster continuously monitored its member nodes for key metrics: energy level, depth, and water turbidity. the inclusion of depth and turbidity as dynamic parameters allowed the chn to respond to environmental changes. if a node’s depth or turbidity changes, the chn can adjust the cluster structure, either by reassigning nodes to neighboring clusters or by reorganizing nodes within its cluster. this adaptability ensured stable connections and data transmission across the network despite environmental fluctuations. also, the chn reduce energy use within its cluster. it temporarily deactivates nodes with energy levels below the 15j threshold, the ieberp place sensor nodes with 15j threshold on hold mode, when the high residual energy is equal to threshold plus 2, the threshold will now be threshold minus 5 that is (10), this will keep on repeating itself to produce a dynamic threshold. placing them on "hold" status to conserve power. only nodes with higher energy levels are permitted to transmit data to the chn. this energy-aware strategy helps extend the overall lifespan of the network. once the chn gathered data from active, high-energy nodes, it performed redundancy checks to remove duplicate information, thus minimizing unnecessary data transmission. after filtering the data, the chn forwarded the information in two possible directions: (1) to the nearest chn located at a shallower depth, thereby leveraging hierarchical forwarding, or (2) directly to the nearest available sink node at the surface, if it is the most efficient path. finally, the surface-level sink nodes received data packets and relayed http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 403 them to an offshore base station for processing and analysis. this multi-layered, energy-efficient design ensured reliable data transmission across the underwater network, even in challenging and dynamic environmental conditions. the chns is computed using equation 1 (domingo & prior, 2007). 𝐶𝐻prob = 𝐶i 𝐶𝑀𝐴𝑋 × 𝐶prob 1 where 𝐶𝑀𝐴𝑋 denotes the maximum battery capacity and 𝐶i denotes the node's battery level, or residual energy. the number of initial cluster-head announcements is limited by a small constant fraction called 𝐶prob, which is used to set the initial proportion of ch. in order to ensure that the routing protocol will continue to function even in the event that sensor battery levels throughout the network are low, it is required to improve the likelihood that certain nodes will elect themselves as chs by preventing 𝐶𝐻prob from falling below a small probability, 𝑝min (domingo & prior, 2007). figure 1 shows the flowchart of the developed ieberp. figure 1: flowchart of the developed ieberp 3. results and discussion this section presents the simulation results of the proposed ieberp, with discussion. each metric is examined using graph representations, comparing the performance of ieberp protocol with existing protocols like ceer, co-uwsn and nbeer. the primary focus is on evaluating these protocols using key metrics such as tec, e2ed, pdr, npr and nan. http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 404 3.1 total energy consumption the simulation was conducted for 10000 seconds at 1000-second intervals as used in the work of (shah et al., 2023). the ieberp protocol was executed over multiple rounds of simulation time (10,000 seconds at a 1000second interval). the total energy consumption (tec) was computed the results indicated that between 1000 and 2000 seconds of simulation time before the integration of strata adaptation scheme, the co-uwsn, ceer, and nbeer protocols initially outperformed the developed ieberp protocol. however, with the integration of a strata adaptation scheme, ieberp effectively stabilized at 4000 seconds with 11.94 tec, where the co-uwsn, ceer, and nbeer protocols had 13.98, 15.54, and 13.80 tec respectively. table 1 shows the simulation summary of tec obtained for ieberp and existing co-uwsn. table 1: total energy consumption of ieberp, co-uwsn, ceer and nbeer tec tec tec tec tec tec tec tec tec tec tec avg protocol at at at at at at at at at at at tec 0s 1000s 2000s 3000s 4000s 5000s 6000s 7000s 8000s 9000s 10000s couwsn 0 17.35 15.00 14.19 13.98 13.68 13.50 12.48 11.95 11.01 9.79 13.29 ceer 0 16.93 16.37 15.82 14.54 14.47 13.41 13.91 12.57 8.57 4.93 13.15 nbeer 0 16.00 16.20 16.30 13.80 12.79 12.39 11.50 10.87 8.15 8.01 12.60 ieberp 0 18.49 15.79 13.64 11.94 10.35 8.91 7.03 5.74 4.33 2.46 9.86 figure 2 shows the graph comparison of the developed ieberp, and existing co-uwsn, ceer and nbeer protocols. figure 2: graph illustration comparison of the total energy consumption this demonstrated superior energy conservation. by selectively placing nodes in hold mode and adapting to dynamic changes. the acoustic sensor nodes in sleep mode utilized only 1-100µa compared to 1-100a in active mode per cycle (sanchez et al., 2012), enabling substantial energy savings. this strategy of putting lowerenergy nodes into sleep mode significantly extends the network’s lifetime and enhances its overall efficiency. the tec obtained from the developed ieberp showed a significant improvement by achieving an average of 9.8 tec. this shows a significant improvement over the existing co-uwsn, ceer and nbeer protocols with 13.29 tec, 13.15 tec, and 12.60 tec. this led to improvement in the routing efficiency of the developed ieberp. 3.2 number of alive node the ieberp protocol simulation conducted for 10,000 seconds with intervals of 1,000 seconds. the number of alive nodes was calculated. the simulation results conducted showed that between 1000 to 9000 seconds, the ieberp demonstrated a significant improvement in number of alive nodes (nan) compared to existing co-uwsn, ceer, and nbeer protocols. this improvement is primarily attributed to ieberp’s strategic approach to energy management. unlike the compared protocols, ieberp optimized energy usage by shifting the data transmission load away from nodes with lower energy to those with higher energy reserves. this approach prevented the lower-energy nodes from prematurely depleting their power, reducing the strain or overhead cost on those weaker nodes. table 2 shows the summary of nan for the developed ieberp, nbeer, ceer and co-uwsn protocols. http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 405 table 2: number of alive nodes for ieberp, co-uwsn, ceer and nbeer an an an an an an an an an an an avg protocol at at at at at at at at at at at an 0s 1000s 2000s 3000s 4000s 5000s 6000s 7000s 8000s 9000s 10000s couwsn 0 225 217 207 191 170 168 160 150 139 135 176.20 ceer 0 215 209 204 198 182 180 178 172 168 167 187.30 nbeer 0 220 218 212 203 198 195 192 184 181 180 198.30 ieberp 0 248 249 248 246 247 247 236 233 225 167 234.6 figure 3 shows the graph illustration of nan comparison of the developed ieberp and existing co-uwsn, ceer, and nbeer. figure 3: graph illustration comparison of the total number of alive nodes by alleviating the workload on nodes with low energy, ieberp extended their operational lifespan, allowing them to remain active in the network longer. this effectively delays the point at which nodes start to fail due to energy exhaustion, thereby maintaining a higher count of alive nodes over time. however, once the simulation reached 9000 seconds, the rate of node depletion increased as more lower-energy nodes began to exhaust their energy. the developed ieberp achieved the average of 234.6 nan outperforming the existing co-uwsn, ceer and nbeer protocols with 176.20, 187.30 and 198.30 nan respectively. 3.3 packet delivery ratio the ieberp protocol simulation was executed for 10,000 seconds with intervals of 1,000 seconds. the packet delivery ratio (pdr) was computed. the results showed that the ieberp achieved high packet delivery ratio (pdr) between 6000 and 10000 seconds. at 6000 seconds, the ieberp achieved 85.51 pdr, whereas the couwsn, ceer and nbeer protocols achieved 77, 40.88, and 81 pdr. the developed ieberp protocol maintained a stable pdr due to its adaptive mechanisms, which enabled it to efficiently respond to the changing underwater environment, specifically dynamic variations in depth and turbidity. thus, outperforming the existing co-uwsn, ceer, and nbeer protocols. these environmental changes can affect signal strength and node connectivity, thereby affecting network stability. table 3 presents the summary of the pdr of the developed ieberp, nbeer, ceer and co-uwsn protocols. table 3: packet delivery ratio for ieberp, nbeer, ceer and co-uwsn pdr pdr pdr pdr pdr pdr pdr pdr pdr pdr pdr avg protocol at at at at at at at at at at at pdr 0s 1000s 2000s 3000s 4000s 5000s 6000s 7000s 8000s 9000s 10000s couwsn 0 100 100 98 90 81 77 65 61 57 42 77.10 ceer 0 99.51 99.51 78.95 64.22 42.60 40.88 38.94 24.35 24.21 22.34 53.55 nbeer 0 100 100 100 91 83 81 68 62 58 45 78.80 ieberp 0 79.22 80.15 76.44 74.98 78.86 85.51 87.54 83.34 88.58 79.91 81.45 figure 4 shows the graph illustration comparison of the developed ieberp and existing co-uwsn, ceer, and nbeer. http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 406 figure 4: graph illustration comparison of the packet delivery ratio the primary reason for this improvement in pdr is ieberp's enhanced capability to maintain a higher number of alive nodes throughout the simulation. a greater number of active nodes helped in sustaining connectivity and allowed more consistent data packet forwarding paths, which in turn improved the overall delivery success rate. this resulting in improved routing efficiency. the pdr of the developed ieberp achieved an average of 81.45% pdr outperforming the co-uwsn, ceer and nbeer protocols with 11.10%, 53.55% and 78.80% respectively. 3.4 number of packets received the number of packets received (npr) showed that the ieberp achieved a high npr at the destination throughout the simulation period. this is due to its efficient management of both intra-cluster and inter-cluster communication. by carefully coordinating data transmission within and between clusters. table 4 shows the summary of npr of the developed ieberp, nbeer, ceer, and co-uwsn protocols. table 4: number of packets received for ieberp, nbeer, ceer and co-uwsn npr npr npr npr npr npr npr npr npr npr npr protocol at at at at at at at at at at at 0s 1000s 2000s 3000s 4000s 5000s 6000s 7000s 8000s 9000s 10000s couwsn 0 5000 10000 14700 18000 20250 23100 22750 24400 25650 21000 ceer 0 4975.5 9951 118142.5 12844 10650 12264 13629 9740 10894 11170 nbeer 0 5000 10000 15000 18200 20750 24300 23800 24800 26100 22500 ieberp 0 7102 14135 17661 20514 24405 27959 30340 31536 33813 35191 figure 5 illustrates npr graph comparison of the developed ieberp, nbeer, ceer, and co-uwsn protocols. figure 5: graph illustration comparison of the number of packets received http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 407 the ieberp reduced the chances of packet collisions across the network. this reduction in collisions allows for smoother and more reliable data flow, enabling a greater number of packets to successfully reach their destination. the ieberp achieved 35191 npr at 10,000 seconds outperforming nbeer, ceer, and co-uwsn with 22500, 11170, and 21000 packets respectively. the npr increased over time, indicating that ieberp improved transmission efficiency by reducing redundant data and minimizing packet retransmissions. 3.5 end to end delay the ieberp protocol simulation results for 10000 seconds at a 1000 interval were captured. the e2ed was computed and the results shows that the developed ieberp maintain between 39s to 49s end-to-end delay (e2ed) after 10000 simulation time at 1000 interval. ieberp achieved a reduced e2ed due to its adaptability to the dynamic underwater environment, specifically changes in depth and turbidity. as depth increases, the distance between the source and destination nodes can vary, impacting transmission time. table 5 presents the summary of e2ed of the developed ieberp, nbeer, ceer and co-uwsn protocols. table 5: end to end delay for ieberp, nbeer, ceer and co-uwsn protocols e2ed e2ed e2ed e2ed e2ed e2ed e2ed e2ed e2ed e2ed e2ed avg protocol at at at at at at at at at at at e2ed 0s 1000s 2000s 3000s 4000s 5000s 6000s 7000s 8000s 9000s 10000s couwsn 0 84.03 80.01 72.02 60.01 51.03 50.03 42.71 43.29 34.80 34.01 55.19 ceer 0 86.00 82.00 79.00 76.00 75.00 72.00 68.00 70.00 62.00 68.00 73.80 nbeer 0 78.00 74.00 68.00 60.00 50.00 51.00 42.00 40.00 42.00 25.00 53.00 ieberp 0 49.19 44.34 47.58 46.99 48.58 48.58 45 49.27 44.97 39.76 46.42 figure 6 shows the graph illustration of e2ed of the developed ieberp, nbeer, ceer, and co-uwsn protocols. figure 6: graph illustration comparison of the end-to-end delay the ieberp responds to these changes by adjusting its routing strategy, allowing it to maintain efficient data transmission and minimize delay. the average e2ed showed that ieberp achieved optimal delay of 46.42, outperforming co-uwsn, ceer, and nbeer with 55.19, 73.80, and 53.00 delay respectively. the developed ieberp maintained optimal e2ed, due to the strata adaptation scheme's ability to dynamically reassign displaced nodes to nearby clusters after losing their initial connection, which led to improved routing efficiency. 4. conclusion this work developed an improved energy based efficient routing protocol (ieberp) for uwsn that adapt to dynamic turbidity and depth changes in the underwater environment to enhance routing performance. the developed protocol utilized a distributed underwater clustering scheme, and strata adaptation scheme to improve the routing efficiency of the uwsn. the developed ieberp protocol achieved 9.86j tec, 81.45% pdr, 46.42 e2ed, 234 nan and 35191.00 npr outperforming the nbeer with 12.60j tec, 78.50% pdr, 53.00s e2ed, 198.30 nan and 22500 npr. the ieberp achieved 21% tec improvement over the existing nbeer that improved the ieberp energy efficiency. the future work can integrate machine learning algorithms to enable ieberp to predict environmental changes and adjust routing paths proactively, enhancing the http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 401-408. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sarkibarde@unimaid.edu.ng 408 protocol's ability to minimize energy consumption and transmission delay before the issues arises. this could improve overall network efficiency, especially in highly dynamic environments. acknowledgement the authors gratefully acknowledge the tertiary education trust fund (tetfund), nigeria, for supporting this research through the 2021 national research fund (nrf) grant cycle, under the project “a novel artificial intelligence of things (aiot) based assistive smart glass tracking system for the visually impaired” (grant no. tetf/dr&dce/nrf2021/seti/ict/00140/vol. 1). references abubakar, zm., adedokun ea., mu’azu, mb. and umoh, ij. 2020. adaptive grid multihop routing protocol for a homogeneous wsn using spectral graph partitioning technique. zaria journal of electrical engineering technology (zjeet), 9(2). chaurasiya, ap., sah, r. and sivakumar, dv. (2022). energy efficient routing for underwater acoustic sensor network using genetic algorithm. http://arxiv.org/abs/2207.00416 domingo, mc. and prior, r. (2007). a distributed clustering scheme for underwater wireless sensor networks. https://ieeexplore.ieee.org/abstract/document/4394038/. 2020.101817 gite, p., shrivastava, a., murali krishna, k., kusumadevi, gh., dilip, r. and manohar pr. 2023. under water motion tracking and monitoring using wireless sensor network and machine learning. materials today: proceedings, 80: 3511–3516. https://doi.org/10.1016/j.matpr.2021.07.283 harb, h., nader, ca., jaber, a., hakem, m., charr, jc., jaoude, ca. and zaki, c. 2024. clara: a clusterbased node correlation for sampling rate adaptation and fault tolerance in sensor networks. internet of things (netherlands), 28. https://doi.org/10.1016/j.iot.2024.101345 hussain, a., hussain, t., ullah, i., muminov, b., khan, mz., alfarraj, o. and gafar, a. 2023. cr-nbeer: cooperative-relay neighboring-based energy efficient routing protocol for marine underwater sensor networks. journal of marine science and engineering, 11(7). https://doi.org/10.3390/jmse11071474 ismail, m., islam, m., ahmad, i., khan, fa., qazi, ab., khan, zh., wadud, z. and al-rakhami, m. 2020. reliable path selection and opportunistic routing protocol for underwater wireless sensor networks. ieee access, 8: 100346–100364. https://doi.org/10.1109/access.2020.2992759 kuang, y., jiang, b., cui, x., li, s., wang, j. and song, h. 2024. adaptive double-loop coverage optimization of underwater wireless directional restricted sensor networks. ad hoc networks, 156: 103409. https://doi.org/10.1016/j.adhoc.2024.103409 luo, j., chen, y., wu, m. and yang, y. 2021. a survey of routing protocols for underwater wireless sensor networks. in ieee communications surveys and tutorials. 23(1):137–160. institute of electrical and electronics engineers inc. https://doi.org/10.1109/comst.2020.3048190 padmavathy, n. and venkateswara, rc. 2022. effect of undersea parameters on reliability of underwater acoustic sensor network in shallow water. iop conference series: materials science and engineering, 1272(1): 012011. https://doi.org/10.1088/1757-899x/1272/1/012011 sanchez, a., blanc, s., yuste, p., perles, a. and serrano, jj. 2012. an ultra-low power and flexible acoustic modem design to develop energy-efficient underwater sensor networks. sensors, 12(6): 6837–6856. https://doi.org/10.3390/s120606837 shah, sm., sun, z., zaman, k., hussain, a., ullah, i., ghadi, yy., khan, ma. and nasimov, r. 2023. advancements in neighboring-based energy-efficient routing protocol (nbeer) for underwater wireless sensor networks. sensors, 23(13). https://doi.org/10.3390/s23136025 http://www.azojete.com.ng/ mailto:sarkibarde@unimaid.edu.ng https://ieeexplore.ieee.org/abstract/document/4394038/ https://doi.org/10.3390/jmse11071474 https://doi.org/10.1109/comst.2020.3048190 https://doi.org/10.1088/1757-899x/1272/1/012011 https://doi.org/10.3390/s120606837 https://doi.org/10.3390/s23136025 arid zone journal of engineering, technology & environment azojete march 2024. vol. 20(1):335-342 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 335 energy conservation potentials in university of maiduguri: case study of shettima ali monguno hostel a. m. malut1,2*, a. m. el-jummah1 and a. b. muhammad1 1department of mechanical engineering, university of maiduguri, maiduguri, borno state, nigeria 2department of mechanical engineering, federal polytechnic monguno, borno state, nigeria. *corresponding author's email address: amsa4malut@gmail.com article information submitted 15 october, 2021 revised 16 january, 2024 accepted 20 january, 2024 keywords: energy conservation energy audit cost savings energy waste energy savings abstract this paper presents the result of investigating the energy conservation potentials conducted at shettima ali monguno (sam) sudents’ hostel of university of maiduguri. the aim of the study was to ascertain the energy consumption pattern and the amount of energy consumed, spot areas of waste and find measures to curb such waste. a walk-through audit and investigation through questionnaire and oral interviews were used to gather required data. microsoft excel software were used to analyse the data. the results show that fan element ranked top in energy consuming loads having 86 %, followed by lighting 73 %, resistant coil 25%, pressing iron 18% and electric hot plate 13%. and the aspect of cooking kerosene ranked up to the most used energy followed by charcoal. the annual energy and cost savings for replacement of conventional resistance electric regulator fans with electronic regulator fans is about 17mwh and n 1.1million and that one for replacing incandescent light bulb is 13mwh and n0.9million.the study recommends that energy audit should be conducted for other parts of the institution, awareness on energy saving habits and their benefits should be created. 1.0 introduction globally, energy is very vital in driving the growth and development of any economy as it is an important input to a nation’s growth and development. energy equally plays a major role in increasing the competitiveness of any nation among the committee of nations (alege, 2014). the conservation of energy is one of the issues which need to be addressed with utmost importance in today’s world. today, energy is paramount across all domains. the energy conservation is essential to the improvement of energy efficiency in the present industrial world (alege, 2014). in spite of the increasing number of power plants which mainly depends on conventional fossil fuels to meet the present energy demands, to address the energy crisis, adopting energy conservation measures is imperative. effective planning of energy management programme requires sound understanding of energy utilization patterns, determinants of energy use and associated energy behaviours of the households needed. energy audit is the basic and most important step for implementation of any effective energy management program. it tries to answer how, where and how much energy is used in the system. it provides an opportunity to look into energy use pattern and suggests way and means of eliminating losses and improving the efficiency of the system. the immediate advantages obtained through energy audit are improved maintainability, reliability features coupled with reduction losses (unachukwu, 2010). long term energy saving can be through the use of energy efficient equipment. generation of electricity is less as compare to the energy consumption in http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):335-342. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 336 nigeria. this is the cause of load shedding due to which most of the sectors and industries are facing issues (mcintosh, 2013). so, the need of today is to save and conserve. a lot of energy is wasted in nigeria because households, public and private offices and industries use more energy than is actually necessary to fulfil their needs (credc, 2009). most nigerians are unconscious of the energy they waste. often, many people use wrong appliance for carrying out certain activities (unachukwu, 2010). large institutions such as universities, consume a large amount of energy on a daily basis (oyedepo et al., 2016). improving the energy practices in these institutions can directly decrease the environmental impact associated with energy use, and equally act as an example for a change of people’s attitude in the use of energy across the country. therefore, energy availability, optimization, consumption and its attending costs in public buildings often constitute a major challenge to administrators and top management of public buildings (oyedepo et al., 2016). much can, therefore, be achieved towards improving energy availability, if energy is conserved in public buildings with a significant level of occupancy such as the university students’ hostel. adetunji (2005) posited that energy conservation aims at the reduction in the consumption of non-renewable resources. typically, university campus consumes a large amount of energy in providing essential services such as lighting, water supply, ventilation, and air conditioning (oyedepo et al., 2016). the task of meeting the demands for energy comes at a significant cost to universities play a role in reducing natural resource consumption. it is therefore, important that energy conservation practices be identified and promoted in universities students’ hostels. energy conservation practices result in low energy consumption in buildings, such practices should include determination of energy cost savings and payback time (stewart et al., 2016). in order to quantify and assess the rate and nature of energy supply and consumption in nigerian tertiary institutions, different scholars have carried out researches on energy audits, energy efficiency, consumption and utilization patterns in many tertiary institutions in nigeria.(babangida et al. (2015) conducted study on energy auditing and management in student hostel of ahmadu bello university zaria. maina et al. (2015) studied the electricity use characteristics of ramat polytechnic maiduguri, borno state; and unachukwu (2010) investigated the energy savings opportunities at the university of nigeria, nsukka. despite numerous researches done in the area of assessment of energy supply, consumption and utilization patterns in nigerian tertiary institutions, there appears not to be enough information on the mode of energy utilization pattern and conservation potentials in the university of maiduguri that can be universities play a pivotal role in actively contributing to the reduction of natural resource consumption through various initiatives, research endeavors, and educational programs. now to assess the current energy utilization pattern through energy audit, to identify the facilities used as energy consumption appliances that results in energy waste and to apply the data collected in order to raise awareness among students and also develop the potentials for savings in order to curb the possibility of energy wastage. 2. methodology 2.1. study area shettima ali monguno students hostel is situated in university of maiduguri, borno state, nigeria. the university was established in 1975 by the federal government of nigeria (fgn), file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com malut et al energy conservation potentials in university of maiduguri: case study of shettima ali monguno hostel. azojete, 20(1):335342. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 337 which is situated at 11.8024on, 13.1931oe of maiduguri, borno state, northeastern part of nigeria. although, there exist privately arranged off-campus accommodations due to increased population and demand, the university is also residential for both staff and students. the hostel consists of two parts: an undergraduate section, which has a total of 80 rooms with 4 to 6 individuals occupying each room and a postgraduate section consisting of four blocks (a, b, c and d), with ten rooms in each block. in addition to the two sections, the hostel also has a kitchen, laundry and two common rooms. 2.2 data collection an energy audit was conducted by walking through the hostel to collect information on the power ratings of electrical equipment and appliances that were in use, and the energy used for cooking. the power ratings were then compared to the nameplates on the equipment. the total energy consumption of each device was calculated by multiplying its power rating by the total number of hours it was in use. however, the actual energy consumed might be less than what was indicated by the manufacturer’s power rating, which could be up to 50-70% lower, as reported by (joseph et al., 2004). the hostel uses electricity for lighting, water heating for comfortable bathing, fan cooling, ironing, and supplementary cooking with hotplates they also use charcoal and kerosene stove for cooking. 2.3 energy audit techniques the following are the two step techniques adopted for this audit: i. physical inspection: data was gathered by manually counting the number of lighting and fan points, charcoal and kerosene stove, gas cookers and other appliances in seventy rooms across all the blocks of the hostel. ii. questionnaire structuring and administration: the questionnaire was designed to address various aspects of energy utilization in the hostel, such as the respondents' awareness of energy conservation and its benefits, the patterns of energy consumption in the hostel, and the usage of energy-saving habits by the respondents. to administer the questionnaires, simple random sampling was used. the population was divided into two main groups: undergraduate and postgraduate. the questionnaire was randomly distributed to each group using simple random sampling (olken, 1986). a total of one hundred and sixty-one more than half of the hostel population participated by completing the distributed questionnaires. iii. energy consumption: the following procedures were used according to (oyedepo et al., 2016) 1. survey instrument development: a questionnaire was designed to collect data on energy usage habits among students residing in the hostel. the questionnaire included sections addressing the use of resistant coils, pressing irons, electric hotplates, and other electrical appliances commonly used for daily activities. 2. survey administration: the questionnaire was distributed to all students residing in the hostel. efforts were made to achieve a high response rate to ensure the reliability of the data collected. the survey was conducted over a defined period to capture variations in energy consumption patterns. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):335-342. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 338 3. data collection and analysis: responses from the completed questionnaires were compiled and analyzed to determine the average duration of usage for each electrical appliance. statistical techniques were applied to calculate the overall energy consumption attributable to resistant coils, pressing irons, and electric hotplates 2.4 data analysis microsoft excel application from microsoft office software was used in analysing the data obtained from the students in the hostel. data input where related data was inserted into the excel, then excel function for energy efficiency and cost analysis was employed. finally, chart will be used to show energy trends and distribution 3. results and discussion 3.1 the energy consumption survey for the students hostel the amount of energy utilization in sam hostel depends on many factors; these factors include the population of the students, operational efficiency of the appliances, types of lamps and efficiency and maintenance mode of cooking. the student hostel has high power consumption due to large number of rooms. these rooms use power consuming appliances such as pressing iron, hair driers, refrigerators, cooking (hot plate, charcoal and kerosene stove, and lpg) and similar equipment. table 1shows the aspects of results of energy used for cooking in sam. also, table 2 shows the aspects of results of energy used in sam and figure 1 shows results of percentage appliance uses by students in sam. it shows that most of the students use kerosene for cooking. table 1: energy use for respondents s/n types of energy used number of respondents percentage (%) 1. electrical hotplate 42 8.00 2. charcoal stove 108 20.73 3. lpg 0 0.00 4. kerosene 366 70.24 5. solar cooker 5 1.00 3.2 analysis of the energy consumption to assess the possibility of energy saving through lighting in the hostel, the total energy consumption by lighting was calculated, energy cost savings through replacement of existing light fixture (incandescent bulbs) with energy efficient lamps such as compact fluorescent lamps (cfl) in the hostel. 35.79% of the total number of students sampled use 60w incandescent bulbs in the room while 12.7% use 100w bulbs, also only 41.3% remember to turn off light, while 7.1% do not turn off the light. 1.0 for hot water usage, 26.1% of student population bath with hot water during the hot water, while 73.8% do not. the peak period for hot water demand is in the morning hours. 2.0 for hot water generation 17.4% of the students’ population makes use of 1500w rated resistant coil while 13.0% use electric hot plate. furthermore, 11.1% own pressing iron, 1.8% use blender and 1.8% use hair drier and 2% use refrigerator. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com malut et al energy conservation potentials in university of maiduguri: case study of shettima ali monguno hostel. azojete, 20(1):335342. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 339 3.3 estimation of energy savings potentials in the students’ hostel using statistics from the energy use survey in the hostel, the potentials for energy savings in the hostel are estimated. for instance, the average number of students in the hostel is 322 and a power supply factor of 0.6, indicating a poor power factor from the national grid, electricity consumption by students is estimated below: 1. resistant coil: tests with the resistant coils show that it takes about 20 minutes to raise the temperature of 10 litres of water from an ambient of 200c to about 520c. an average of 15 minutes is assumed to achieve a temperature level suitable for comfort bathing. 2. pressing iron: it is also assumed here that students iron their cloths for an average of 15 minutes per day. 3. electric hotplate: students use electric hot plates for cooking. according to the survey findings, approximately 13.0% of students utilize electric hot plates for cooking, with the assumption that using a hot plate for meal preparation typically consumes approximately fortyfive (45) minutes. table 2: appliances and their consumption s/n appliances consumption (kw/yr) percentage (%) 1. lighting 3.2 ×105 0.58 2. fan 4.8×107 87 3. resistant coil 1.4 ×103 0.01 4. electric pressing iron 2.1×106 3.82 5. electric cooker 4.6×106 8.36 from the computations, the students’ electricity consumption by use of these 5 energy consuming appliances is estimated to be 57837211.475kwh per annum. the percent share of each of the appliances is shown in figure 3.1 as can be seen, two major areas present great opportunities for energy savings in the students’ hostels. these are energy consumed in the use of incandescent light bulbs and that for fan. for instance, 40% of the total energy consumed by students in the hostels is expended on fan. figure 1: percentage appliance uses by students. 73% 86% 25.50% 18% 13% percentage use lighting fan resistant coil pressing iron electric hotplate http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):335-342. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 340 the result obtained from the present study regarding energy consumption by resistant coils, pressing irons, and electric hotplates can be compared with the findings of oyedepo et al. (2016) concerning space cooling and lighting. while our study focuses on electrical appliances commonly used by students in the hostel, oyedepo et al. (2016) investigated energy usage patterns related to space cooling and lighting. they reported a significant portion of energy consumption attributed to space cooling and lighting, specifically 29% of the total energy usage. interestingly, similarities can be drawn between the findings of both studies regarding energy conservation opportunities. in our study, feedback from questionnaires and audits revealed instances of inefficient lighting practices, such as external light bulbs remaining switched on during daylight hours and room lights being left on when students are not present for lectures. similarly, oyedepo et al. (2016) observed that external light bulbs were often left on during the daytime, contributing to unnecessary energy consumption. moreover, both studies suggest practical measures to reduce energy consumption. oyedepo et al. (2016) proposed strategies such as turning off lighting and fans in unoccupied rooms and using external light bulbs exclusively during nighttime to reduce the total number of hours that light bulbs remain switched on, thereby achieving energy savings in both lighting and fan consumption. similarly, our study identifies opportunities for energy conservation through the optimization of electrical appliance usage, such as reducing the duration of usage for resistant coils, pressing irons, and electric hotplates when not required. here, specific areas within the hostel where there is high energy consumption potential, namely, lighting and fans. the cost of electricity per unit in nigeria's tariff stands at n69.43/kwh. the student hostel’s energy and cost-saving potential can be realized by replacing the current lighting fixtures with energy-efficient bulbs. table 3 and 4 are used to compute energy and cost savings for the replacement of 60 w incandescent bulbs with 12w cfl. table 3: comparison between the existing lightning system and the recommended system existing system recommended system total number of rooms = 322 total number of rooms = 322 total number of bulbs in rooms = 266 total number of bulbs in rooms = 266 total watts consumed =266×60 =15960w total watts consumed =266×12 =3192w total usage time/day =17hours total usage time/day =17 hours total usage time in a year =17×245 =4165 total usage time in a year =17×245 =4125 total watts in a year=15960×4125=65835000 total watts in a year=3192×4125=13167000 total units in a year =65835.0 total units in a year =113167000 cost of 1 unit =n69.43 cost of 1 unit =n69.43 total cost in a year =66473.4×69=n4,586,664 total cost in a year =13166.7×69=n908,502.3 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com malut et al energy conservation potentials in university of maiduguri: case study of shettima ali monguno hostel. azojete, 20(1):335342. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 341 table 4: comparison between the existing fan system and the recommended system existing system recommended system total number of rooms = 322 total number of rooms = 322 total number of fans in rooms = 130 total number of fans in rooms = 130 total watts consumed =130×70 =9100w total watts consumed =130×45 =5850w total usage time/day =17hours total usage time/day =17 hours total usage time in a year =17×245 =4125hr total usage time in a year =17×245=4125hr total watts in a year=9100×17×245=37537500 total watts in a year=5850×12×245=17199000 total units in a year =37537.5 total units in a year =17199.0 cost of 1 unit =n69 cost of 1 unit =n69 total cost in a year =37537.5×69 = n2,590,087 total cost in a year =17199×69 = n1,186731 4. conclusion the energy audit at sam student hostel identified inefficiencies in various appliances and practices, offering insights for energy conservation. by implementing strategies like upgrading to energy-efficient lighting and optimizing appliances, substantial energy and cost savings are achievable. this approach targets behavioral changes, equipment upgrades, and operational optimizations to reduce energy waste effectively. analyzing data on energy waste and costs enabled the identification of consumption patterns and areas for improvement. implementing energy-saving measures, such as upgrading appliances and promoting behavioral changes, aims to minimize wastage and lower expenses. by fostering an energy-conscious environment, the hostel can operate more sustainably and economically, benefiting both the environment and its financial sustainability. the study recommends: 1. conducting energy audits across the institution to identify areas for savings. 2. establishing an energy audit committee in each hostel to promote energy-saving habits, utilizing existing staff. 3. raising awareness of energy-saving practices through various channels. 4. listing inefficient appliances in hostel regulations to discourage their use. 5. implementing automatic controls for external lighting to minimize energy wastage. references adetunji, i. 2005 sustainable construction: a web-based performance assessment tool. loughborough university. loughborough, leicestershire, uk. alege, p. 2014. energy supply and climate change in nigeria. journal of environment and earth science, 4(14): 47–60. babangida, m., abba, l., abubakar, m. and abubakar, k. 2015. energy auditing and management a case study of student hostel, a. b. u zaria, nigeria. journal of multidisciplinary engineering science and technology (jmest), 2(7): 7-9 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, march 2024; vol. 20(1):335-342. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: amsa4malut@gmail.com 342 credc. 2009. energy efficiency survey in nigeria, community research development centre, benin city. joseph, c., ricky, y., tsang, c. and danny, hl. 2004. electricity use characteristics of purposebuilt office buildings in subtropical climates. energy conversion and management, 45: 829–844. maina, m., ngala, g. and muhammad, s. 2015. electricity use characteristics of tertiary institutions in nigeria: a case study of ramat polytechnic maiduguri, borno state. international journal of engineering research & technology (ijert), 4(12): 5-11 mcintosh, m. 2013. report:24,000 bridges, 5,000 structurally deficient. iowa: kcci news. otegbulu, ca. 2011. energy efficient practice: a focus on residential management, university of lagos, lagos, nigeria. oyedepo, so., adekeye, t., leramo, ro., kilanko, oo., balogun, ao. and akhibi, mo. 2015 a study on energy demand and consumption in covenant university, ota, nigeria. in: 2nd covenant university conference on african development issues (cu-icadi), 11th 13th may, 2015, africa leadership development center, covenant university, ota, nigeria, 203–211. oyedepo, s., adekeye, t., leramo, r., kilanko, o., babalola, o., balogun, a. and akhibi, m. 2016. assessment of energy saving potentials in covenant university, nigeria. energy engineering, 113(7): 45-67. stewart, n. and sarpola, a. 2016. energy innovation needs in public buildings. sizing a photovoltaic system for the university of oulu linanmaa campus, oulu., pp. 10–129. unachukwu, g. 2010. energy savings opportunities at the university of nigeria, nsukka. journal of energy in southern africa, 21(3): 7-9 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com corresponding author’s email address: kenenwosuobie@mouau.edu.ng 717 arid zone journal of engineering, technology & environment original research article transesterification of waste frying oil using alkaline activated waste marble catalyst: effects of process parameters, modeling, and optimization m. a. allen1, k. nwosu-obieogu2, t. e. erokare3, m. u. francis3, j. okoye4, c. n. nwogu1, h. itiri2 1 department of mechanical engineering, michael okpara university of agriculture, umudike, abia, nigeria. 2 department of chemical engineering, michael okpara university of agriculture, umudike, abia, nigeria. 3 department of agricultural and biosystems engineering, southern delta university, ozoro, delta state. 4 department of chemical engineering, enugu state university of science and technology, nigeria *corresponding author’s email: kenenwosuobie@mouau.edu.ng article information abstract through calcination at 600oc for four hours, a novel alkaline activated waste marble heterogeneous catalyst was produced and successfully used for biodiesel synthesis from waste frying oil. to determine the catalyst's appropriateness for the process, scanning electron micrograph (sem), x-ray diffraction (xrd), brunaueremmett-teller (bet) and fourier transform infrared spectroscopy (ft-ir) were used. similarly, to determine the waste frying oil's suitability for the transesterification process, ft-ir and gc-ms (gas chromatography mass spectrometer) were applied in its characterization. the variables (time, temperature, catalyst dosage, methanol/mol ratio and agitation speed) were considered during the transesterification process, and an increase in the process parameters significantly affected the yield. in addition, response surface methodology (rsm) was applied to optimize the best conditions; the second-order polynomial model is displayed in the analysis of variance (anova) with an r2 value of 0.9564, adj r2 (0.9216), and pred r2 (0.8257), indicating the acceptability of the model. the optimal yield of biodiesel (86.25%) was obtained at a catalyst concentration of 2.52wt. %, methanol/molar ratio of 6.14mol/mol, time of 1.10 hours, temperature of 59.8oc and agitation speed of 325.2rpm. interestingly, the wfo biodiesel produced complied with astm d6751 requirements. received: 19th may 2025 revised: 28th july 2025 accepted: 30th july 2025 keywords: rsm waste frying oil transesterification biodiesel © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction conventional oil from petroleum finds applications in diverse areas such as power generation, transportation, trade, and agriculture (adepoju et al., 2020). putting into consideration the negative effects of conventional fossil fuel in use, oil and gas exploration, environmental gas emissions as pollutants, and oil spillage on lands and waters, causing barrenness of the land, making it unfavourable for effective agricultural yield, which in turn negatively affects the country’s economy (bharti et al., 2021; loganathan & kannan, 2022). also, oil spillage in water bodies contaminates the aquatic environment of fishes and other aquatic inhabitants, which are considered as a source of income and revenue for the country, organizations, and individuals. these, among other factors, negatively affect society and individuals(karthikeyan et al., 2019). these negative effects, including the rising consumption of energy from petroleum reserves and their unstable price, birthed the interest in producing alternatives or substitutes to the resources. hence, biodiesel is the most alternative substitute to petroleum diesel(adepoju et al., 2020; varol et al., 2023). biodiesel is a mixture of long-chain monoalkylic esters from fatty acids of renewable resources usable in diesel engines (sabzevar et al., 2021). it is a liquid biofuel chemically obtained from vegetable oil or animal fats and an alcohol via transesterification (arora and singh, 2020). varol et al. (2023) reported that biodiesel is a promising alternative fuel source with benefits over fossil fuel, such as biodegradability, renewability, high azojete september 2025. vol.21(3):717-731 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/004 www.azojete.com.ng mailto:kenenwosuobie@mouau.edu.ng mailto:kenenwosuobie@mouau.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 718 combustion efficiency, low sulfur and low emission. it reduces engine wear, thereby increasing the life of the fuel injection equipment, and improves the quality of the environment with a pleasant fruity odour with less soot generated in the vehicle's exhaust (hobuss et al., 2020; jain, 2023). biodiesel offers so many advantages, which include renewability, high flash point, minimization of the consequences of spillage, lower health risk, low emission of sulphur dioxide (so2), low toxicity, excellent lubricant properties, and an alternative fuel (özlem and tuba, 2021). its disadvantages include the high rate of degradability of plastic and natural rubber gaskets and hoses when used in pure form, dissolution of the deposits of sediments and contaminants from diesel in storage tanks and fuel lines, thereby causing problems in the values and injection sections, limited storage period and lower stability when compared to the diesel fuel; its low calorific value leads to a slightly higher consumption level; it has a slightly higher nitrous oxide (no2) emissions than diesel fuel (ambat et al., 2018; tamoradi et al., 2021). waste vegetable oil refers to vegetable oil no longer useful for food production. it can be obtained from homes, restaurants, eateries, and hotels (barros et al., 2020; ferrero et al., 2021). the growing pollution of over 160 million people in nigeria has consequentially increased the rate at which fast-food companies, restaurants and hotels are set up (sahani et al., 2019). the enormous volume of waste vegetable oil generated from these establishments and ceremonious events daily poses a danger in its disposal. improper disposal of waste vegetable oil can cause environmental pollution. this is mainly referring to frying oil used at high temperatures, edible fat mixed in kitchen waste and oily wastewater directly discharged into sewers (awogbemi et al., 2021; naylor & higgins, 2017). one of the main factors in biodiesel production is the catalyst selection. various catalysts, including homogeneous catalysts, heterogeneous acidic and basic catalysts and enzymes, have been reported for biodiesel production (fattah et al., 2020; gebremariam & marchetti, 2018; baek et al., 2020). among homogeneous catalysts, naoh, koh, and ch3ona catalysts have been reported for transesterification (ayoob & fadhil, 2020). these catalysts are cheap and easily available, but they have some drawbacks such cause saponification, which reduces the yield of the product. secondly, they cause difficulty separating the glycerol and biodiesel layers (narowska et al., 2020). homogeneous acid catalysts such as hcl and h2so4 are free of such drawbacks, but their reaction rate is slow. all homogeneous catalysts (acid or base) are separated at the end of the reaction by washing, which causes the reduction of product yield. furthermore, such catalysts cause reactor corrosion and are difficult to recover (barros et al., 2020). these problems can be overcome by replacing homogeneous and heterogeneous catalysts (yaşar, 2019). heterogeneous catalysts can be recovered at the end of the reaction easily without the loss of catalytic activity and hence can be used repeatedly (yaşar, 2019; karpagam et al., 2020). various heterogeneous catalysts, such as oxides, mixed oxides, phosphates, sulphates, chlorides, etc, have been reported for transesterification (navas et al., 2020; sreekanth et al., 2018). heterogeneous catalysts reduce the purification process, resulting in less energy consumption. its catalysts are cost-effective because they can be obtained from waste sources like bones, ashes, shells and rocks (karpagam et al., 2020). several research articles have been published using calcium oxide (cao) as a heterogeneous catalyst(ur rahman et al., 2021; wang et al., 2019). cao can be obtained from various waste sources such as bones, eggshells, scales, corals, calcite-containing rocks and marble through calcination (okwundu et al., 2020). laskar et al. (2018) investigated the production of biodiesel using heterogeneous catalysts derived from waste snail shells. the calcination process was carried out using a muffle furnace at 900 ◦c for 4 h. the authors stated that the transesterification was carried out at 28 ◦c, 6:1 m methanol/oil ratio, and 3 wt.% catalysts for 7 h, and they obtained 98% yield under these optimized conditions. huge amounts of waste marble have been generated on construction sites and from marble-cutting industries, which are used as landfills. marble dust is a waste material generated in large amounts as a by-product in various marble factories (bostanci, 2020). ceramic tiles are used to cover and decorate the walls of bathrooms, kitchens, and toilets or to obtain decorative products. marble dust generated during the marble-cutting process affects health and causes environmental pollution (tunc, 2019). the catalytic potential of waste marble in the transesterification of waste cooking oil has not been explored in previous studies. (balakrishnan et al., 2013). waste marble has been employed as a catalyst in the transesterification of canola oil with methanol. additionally, it has been utilized as a heterogeneous catalyst in the transesterification of jatropha oil (olutoye, 2015). in this research work, marble was calcinated and used as a catalyst for the transesterification of waste frying oil. the approach of this research work is significant because all the raw materials for biodiesel production are cost-effective. also, literature has not reported on waste frying oil transesterification via waste marble http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 719 catalysts. the biodiesel produced through this research work has comparatively lower production costs. the waste frying oil was collected at a very low price, and the waste marble used as a catalyst source has almost no cost, although both have some processing costs. physicochemical parameters of the oil, such as acid value, peroxide, specific gravity, moisture, refractive index, kinematic viscosity, saponification, molecular weight, and ester value, were determined. powerful tools, including sem, xrf, ftir, and gcms, characterized the catalyst and biodiesel produced by this work. the process parameters affecting biodiesel production were determined, and its yield was duly optimized using the rsm of the design expert software. hence, this study focuses on the modelling and optimization of waste frying oil transesterification catalyzed by alkaline waste marble dust via response surface methodology 2. materials and method 2.1 materials the raw materials and waste cooking oil were obtained from various restaurants and eateries in umuahia, abia state, nigeria. the waste marble (the catalyst) was obtained from marble dealers' shops and construction sites in aba, nigeria. 2.2 preparation of catalyst the waste marble was blended and sieved to get the powdered form and calcinated at 600 0c for 4 hours. it was then treated with 0.5m sodium hydroxide. the alkaline-activated marble was characterised by a basicity test, acidic test, qualitative analysis, ftir, sem, xrf, and xrd. the acid-activated waste marble was submerged in a 30 % hydrogen peroxide solution in a 1:2 weight-to-weight ratio at 30 °c for 24 hours to remove contaminants. to eliminate excess h2o2, the mixture was slowly heated in a water bath before being removed from the clay. the washed clay was then suspended in distilled water at a 1:4 weight-to-weight ratio and given time to settle. it was oven-dried at 110 °c to remove the moisture content. the marble was ground and put through an 80/100 grit filter. sulphuric acid activation was used to remove extra salt from the dried waste marble catalyst and increase activity. a solution of 0.5 m (g/ml) of sulphuric acid was combined with the dried sample in a ratio of 1:1. the reaction was conducted for two hours at 100 °c with vigorous stirring in a flask. a reflux condenser and glycerine bath were used to heat the process. the acid-activated waste marble was washed until its ph was about 7, and it was then dried for six hours at 110 °c. 2.3 waste marble characterization the morphology of the waste marble samples was determined using an sem, xrf to analyse the elemental constituents, ft-ir was used for functional group determination, and xrd to assess the waste marble structural composition and crystallinity. the average pore diameter, surface area, and total pore volume of the waste marble were determined using a bet analysis. a micrometric asap 2020 surface analyser calculated pore volume, pore diameter, and surface area from n2 adsorption isotherms. 2.4 wfo characterization the physicochemical characterization of wfo was evaluated following aoac, (2023) method. the wfo was characterized by determining the saponification, acid and iodine value, free fatty acid, kinematic viscosity, density, ester, moisture, peroxide value and refractive index. ftir techniques were complementary methods (after chemical processes) to characterize structural functionalities in the pure and transesterified wfo. ftir spectrum of the transesterified oil was recorded with a shimadzu 8400sftir spectrophotometer over 4500 – 350cm-1 using ten scans at a resolution of 4cm-1. gcms analysis of the pure and transesterified samples involved mixing 50mg of the sample in 10 ml of toluene with 0.2 ml of tetramethylammonium hydroxide (tmah) by shaking. 4ml of water was added to the mixture, which was then allowed to settle. the samples were examined for their fatty acid profiles. the peaks were detected using a mass spectrometer connected to a gas chromatography-mass spectrometry system. 2.5 characterization procedures 2.5.1 x-ray fluorescence analysis the samples were mined from the various locations and then fractionated into the required different fractions of varying particle sizes using standard sieves of mesh sizes. an arl 9400xp + wavelength-dispersed xrf spectrometer with rh source was used for the x-ray fluorescence analyses of the samples. samples were dried http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 720 and fired at 1000 oc to determine the percentage loss on ignition. major elements analyzed were carried out on fused beads. a pre-fired sample of 1 and 6g of lithium tetra-borate flux was mixed in a 5% au/pt crucible and fused at 1000oc in a muffle furnace with occasional swirling. the glass disk was transferred into a preheated pt/au mould and the bottom surface was analyzed. 2.5.2 fourier transforms infra-red (ftir) analysis ftir analysis was carried out using buck model 500 m infra-red spectrophotometer. the sample was prepared using kbr and the analysis was done by scanning the sample through a wave number range of 700 to 4000 cm-1. 2.5.3 surface morphological studies the surface morphology of the materials was studied using carl zeiss sigma field emission scanning electron microscope and the images at 1mm and 150 magnifications. 2.5.4 x-ray diffraction (xrd) the x-ray diffraction measurements were obtained in a shimadzu diffractometer model xrd-7000 with cu ka x-ray source (40 kv, 30 ma, 𝜆 = 1.5418 å), interval of 2𝜃 = 3–40o, at a speed of 2o min-1 and scanning pace of 0.02o. 2.5.5 brauner emmet teller analysis (bet) the brunauer-emmett-teller (bet) method was used to calculate the surface area, average pore diameter and total pore volume of the clay. surface area, pore volume and average pore diameter were determined from adsorption isotherms using a micrometrics asap 2020 surface analyzer. the samples were degassed using two-stage temperature ramping under a vacuum of <10 mm hg, followed by sample analysis at 77 k using nitrogen gas prior to analysis in order to remove moisture and other adsorbed gases from the catalyst surface. 2.6 transesterification procedure when exposed to acid-activated waste marble, wfo reacts with methanol to produce glycerol and biodiesel. the oil was transferred into a flask using a heated magnetic stirrer. the methanol was then mixed catalyst. the reaction flask was placed on a heated stirrer at a constant temperature during the reaction. the sample was withdrawn after the prescribed time, and methyl ester and by-product (glycerol) settled at room temperature in a separating funnel. the yield percentage was calculated by comparing the vol. of the biodiesel to the vol. of oil used, as per equation (1). yield (%) = weight of methyl ester oil weight x 100 1 2.7 design of experiments a box-behnken design with 5 factors and a 3-level base was created via design-expert software for the experiment. the study measured the methyl ester yield as the main outcome, with the catalyst dosage, temperature, methanol-oil molar ratio, time, and agitation speed as the variables. table 1 displays the design summary. table 1: independent factors and levels investigated factor unit levels -1 0 +1 catalyst wt% 1 3 5 methanol/oil mol/mol 4 8 12 time minutes 1 2 3 temperature c 40 55 70 agitation speed rpm 100 300 500 http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 721 3. results and discussion 3.1 characterization of waste frying oil table 2 presents the physicochemical properties of raw waste frying oil. the oil has an acid value of 12.172 mgkoh/g and a free fatty acid value of 6.086%, which are considered high for one-step transesterification. consequently, the oil was subject to pre-treatment to prevent soap formation and facilitate glycerol separation. table 2: physiochemical properties of waste frying oil sample waste oil color dark brown kinematic viscosity @ 400c (mm2s-1) 52.05 refractive index @ 310c 1.4714 acid value (mgkoh/kg) 12.172 free fatty acid value (mgkoh/kg) 6.086 moisture (%) 0.25 saponification (mgkoh/kg) 100.38 peroxide value (meq/kg) 3.641 specific gravity 0.8895 iodine value (mg i2/g) 76.39 molecular weight (g/mol) 1907.99 ester value (%) 87.87 the saponification and peroxide values indicate that the oil is not prone to rancidity. the iodine value (76.39 i2/100g) reveals the presence of unsaturated triglycerides, suggesting that the oil is suitable for transesterification [39]. however, the oxidation stability of the oil falls below the astm d6751 standard (3 hours). therefore, further pre-treatment is necessary before using it for fame production [2]. the kinematic viscosity of waste frying oil is comparable to the data for palm kernel oil (52.05 mm2/s) from ogaga et al. [29], suggesting that it is a highly viscous potential feedstock with good fuel quality. 3.1.1 gas chromatography-mass spectrometry (gc--ms) the gas chromatography-mass spectrometry (gcms) technique was employed to determine the fatty acid methyl ester composition of the waste frying oil. the gcms analysis of the waste frying oil (table 3) confirmed that 11.5% of the fatty acids in waste cooking oil are saturated, while 88.5% are unsaturated. there is also the presence of an oleic acid, which is an unsaturated triglyceride, indicating that the waste frying oil can be transesterified and classified under the oleic acid group since the linoleic and linoleic, which make up 70.12% of the total fatty acid composition are the main unsaturated fatty acids. 3.1.2 scanning electron microscopy (sem) scanning electron microscopy (sem) was carried out on the raw and alkaline activated marble to determine the surface morphology of the fractured agglomerates for both the inorganic and organic samples of the different filler materials used. the sem micrographs of the raw and alkaline activated samples of the old marble are shown in plates 1a and b, respectively. the result showed the morphological representation of each of the samples. the sem micrograph of the alkaline-activated marble showed a huge difference in its microstructure and morphology. the result shows that the alkaline-activated marble (plate 1b) exhibited a lumpy-packed microstructure, which could be due to the high concentration of sio2 in its microstructure. the raw marble showed more dispersed components in its microstructure and hence has more voids when compared to the alkaline-activated marble, whereby the alkaline-activated marble showed more porosities in its microstructure. it is seen that the alkaline-activated waste marble catalyst has more pores than the raw marble (plate 1a), and these pores increase after activation. this contributes to its high surface area due to the elemental increase of oxygen in its microstructure. http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 722 table 3: (a) gc-ms for the waste frying oil ffa profile waste frying oil s/n fatty acid component composition (%) 1 capric acid c10 2 lauric acid c12 0.30 3 myristic acid c14 3.51 4 palmitic acid c16:0 4.91 5 stearic acid c18:0 3.21 6 oleic acid c18:1 16.00 7 linoleic acid c18:2 12.32 8 linolenic acid c18:3 58.12 9 arachidic acid c20 1.7 total 100.07 plate 1a. sem of waste marble plate 1b. sem of alkaline activated waste marble 3.1.4 fourier transform infrared (ftir) the chemical structure by determining the functional groups of the waste vegetable oil and the activated marble was confirmed using the ftir spectrum of the waste oil and the alkaline activated marble as presented in figure 1 and 2 respectively. figure 1: ftir for waste frying oil the ir spectrum of the waste vegetable oil shows a strong band at 2851.4, 87.942cm−1 – 3011.7 and 959.7 cm−1 which corresponds to o-h bond stretching, the bands at 1654.9, 983.6 cm−1 1740.7 and 684.6 cm−1 represent c=o (ester) bond and the band at 1155.5, 72.684 1233.7 and 87.579 cm–1 corresponds to c-o bond which all shows its properties are good for biodiesel. the most characteristic transmittance of ester c=o stretching is at 1740.7 cm−1. consequently, the ir spectrum of the alkaline-activated marble is shown in figure 3. the result showed a broad spectrum within the wave numbers 3000cm-1 2500 cm-1 are characteristic of o-h stretch of carboxylic acids, the stretched spectrums at 1744.4 cm-1 and the bends at 1461.1 cm-1 signifies the presence of esters and saturated aliphatic compounds. http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 723 figure 2: ftir for alkaline activated marble 3.1.5 x-ray diffraction (xrd) the phase identification and cell dimensions of both the raw and the alkaline-activated marble catalyst are analyzed by the xrd technique over the 2θ range of 10°–60° and are displayed in figures 4 and 5 respectively. the xrd analysis provides information about the structure, phase, crystal orientation, lattice parameters, crystallite size, strain crystal defects, etc. figure 3 shows the xrd pattern of the raw marble; from the result, a broad spectrum was observed from 20o to 30o on the raw marble, which confirms the existence of a crystalline sio2 structure. the xrd pattern shows and inferred also the presence of other minerals like quartz, alumina, orthoclase, englishite, garnet and traces of lime, muscovite and albite, which were prominent at the 10o point. amorphous phases: some surface modifications (e.g., grinding or acid treatment) can create amorphous phases of calcium carbonate, which may have different surface properties and greater reactivity compared to crystalline calcite. calcite itself is relatively inert and doesn't typically act as an active catalyst in most reactions. however, it could play a role as a support material in heterogeneous catalysis, providing a surface for other catalytic species to adsorb onto. the xrd result of the alkaline-activated marble (figure 4) shows that the activation of the marble by alkali modified the marble composition of the catalyst. the amorphous phases modifications induced by activation could increase the surface area and reactivity of the marble, potentially improving its catalytic activity. these modifications could enhance its interaction with reactants, making activated marble an even more effective material in catalytic applications. 3.4 effect of process parameters on biodiesel yield the effect of each process parameter on the biodiesel yield was studied, and the results obtained are represented in figure 5(a – e). figure 5a shows the graphical representation of the effect of time on the biodiesel yield; from the result, it can be observed that biodiesel yield decreased with an increase in time. increasing reaction time from 1 hour to 2 hours led to a significant decrease in the yield of the product and subsequently. figure 5b shows the graphical representation of the effect of reaction temperature on biodiesel yield. the result shows that an increase in reaction temperature increases the biodiesel percentage yield and vice versa. the result showed that the highest biodiesel percentage yield (90%) occurred at 70˚c, after which there was a drop. generally, reaction temperature has always imposed a more substantial effect on the production yield of biodiesels. therefore, it requires more attention than other parameters to avoid bumping boiling in the reaction system. also, since vegetable oil transesterification occurs in the liquid phase, not in the gaseous phase, the reaction temperature must be regulated and controlled meticulously to avoid the danger caused by the flammable methanol vapour. among these parameters studied, the reaction temperature was seemingly the most influential on the conversion yields of vegetable oil to biodiesel (tấn-hiop et al., 2021). the effect of the methanol-to-oil ratio on the resultant yield of biodiesel was studied and presented in figure 5c. the result showed a distinctive increase in biodiesel yield from 87% to 92% as the methanol-to-oil ratio was increased from 06:01 to 08:0, and a continuous decrease in the biodiesel yield was observed as the methanol-to-oil ratio kept increasing. empirically, surplus methanol could promote the production of more biodiesel. however, the viscous nature of vegetable oil may hinder the mobility of reactants, i.e. oil and alcohol, and, consequently, the effective transport of reactants to active sites on the catalyst where the http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 724 transesterification reaction proceeds. therefore, more methanol would make the reaction system more fluidic, promoting more contact among reactants and active sites on catalysts. however, the addition of too much methanol, notwithstanding promoting the dispersion of the catalyst, may reduce the rate of transesterification reaction because of the diluted concentration of oil in the reaction system (tấn-hiop et al., 2021). figure 3: xrd for the raw marble figure 4: xrd for the alkaline activated marble catalyst the effect of the methanol-to-oil ratio on the resultant yield of biodiesel was studied and presented in figure 5c. the result showed a distinctive increase in biodiesel yield from 87% to 92% as the methanol-to-oil ratio was increased from 06:01 to 08:0, and a continuous decrease in the biodiesel yield was observed as the methanol-to-oil ratio kept increasing. empirically, surplus methanol could promote the production of more biodiesel. however, the viscous nature of vegetable oil may hinder the mobility of reactants, i.e. oil and alcohol, and, consequently, the effective transport of reactants to active sites on the catalyst where the transesterification reaction proceeds. therefore, more methanol would make the reaction system more fluidic, promoting more contact among reactants and active sites on catalysts. however, the addition of too much methanol, notwithstanding promoting the dispersion of the catalyst, may reduce the rate of transesterification reaction because of the diluted concentration of oil in the reaction system (tấn-hiop et al., 2021). the effect of catalyst dosage on biodiesel yield was investigated and presented in figure 6e. the results show that an initial increase in the catalyst dosage from 1%wt to 3%wt led to an increase in the percentage yield from 80% to 90%. the highest yield was obtained at the 3%wt; subsequent increase in the catalyst dosage led http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 725 to a decrease in the biodiesel yield from 90% to 85% from a catalyst dosage of 3%wt to 5%wt. this could result from the great impact of the reaction temperature on catalysts. figure 5a: effect of time variation figure 5b: effect of temperature variation figure 5c: effect of agitation speed figure 5d: effect of methanol and oil mole ratio figure 5e: effect of catalyst dosage 3.5 statistical analysis the response surface model (rsm) was initiated as it is a useful statistical and mathematical tool used to develop, improve and optimize an experiment affected by several factors. the factors involved in this experiment are catalyst, methanol/oil ratio, time, temperature and agitation speed. the box behnken design of the design expert software was used to develop a quadratic model, and variance analysis was conducted to 74 76 78 80 82 84 86 88 90 92 1 2 3 4 5 yi el d f o r ( % ) catalyst dosage (% wt.) 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 yi el d f o r ( % ) time (hr.) 65 70 75 80 85 90 95 4 0 5 0 6 0 7 0 8 0 yi el d f o r ( % ) temperature (0c) 76 78 80 82 84 86 88 90 92 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 yi el d f o r ( % ) agitation speed (rpm) 74 76 78 80 82 84 86 88 90 92 94 0 6 : 0 1 0 8 : 0 1 1 0 : 0 1 1 2 : 0 1 1 4 : 0 1 yi el d f o r ( % ) methanol : oil (mole) http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 726 determine the second-order model's significance level. table 4 shows the actual levels of both the factors and the responses; from observation, the highest biodiesel percentage yield of 86.19% occurred at agitation speeds of 500rpm, 60ͦ c, 2.5 hours, and 3% by weight of catalyst concentration run 3 and least and constant biodiesel yield of a 70.95% at 200rpm, 40ͦoc, 3hours, 3% by weight of catalyst concentration from run 24 to 32. table 4: box behnken matrix with responses (actual) run order catalyst conc. (wt %) a methanol/oil ratio (mol/mol) b time (hour) c temperature (0c) d agitation speed (rpm) e biodiesel yield % (alkaline modified) 1 4 4 1.5 60 100 72.44 2 1 12 3 50 200 80.16 3 3 12 2.5 60 500 85.61 4 4 4 2 40 500 74.02 5 1 4 1 40 100 69.11 6 1 12 1 40 500 74.83 7 1 12 1.5 60 100 74.34 8 3 12 2.5 40 300 83.07 9 5 12 1 40 100 64.25 10 1 8 3 50 500 86.19 11 3 8 1 50 300 74.89 12 5 8 2 60 300 82.43 13 1 4 1.5 60 400 69.56 14 4 12 1 60 500 75.82 15 5 8 2 60 300 78.96 16 5 8 2 60 300 78.96 17 1 6 1 60 100 73.13 18 2 8 2 60 500 84.05 19 4 12 1.5 60 200 84.97 20 5 6 3 70 500 75.22 21 3 12 2.5 40 300 74.39 22 3 12 3 60 500 84.06 23 3 10 3 70 100 78.43 24 3 10 3 40 200 72.33 25 3 10 3 40 300 70.95 26 3 10 3 40 300 70.95 27 3 10 3 40 300 70.95 28 3 10 3 40 300 70.95 29 3 10 3 40 300 70.95 30 3 10 3 40 300 70.95 31 3 10 3 40 300 70.95 32 3 10 3 40 300 70.95 from the result (table 5), the model f-value of 27.44 implies that the model is significant. there is only a 0.01% chance that this large's "model f-value" could occur due to noise. values of "prob > f" less than 0.0500 indicate that model terms are significant. a, d, e, a2, b2, c2, d2, e2, ab, ac, ae, bd, be, cd, and de are significant model terms. values greater than 0.1000 indicate that the model terms are not significant. suppose there are many insignificant model terms (not counting those required to support hierarchy). in that case, model reduction may improve your model, indicating that the regression model is acceptable and the experimental data agrees with the predicted data. table 5 shows that the r2 value was 0.9564, i.e. 95.64% of the results are consistent with the proposed model, indicating that the empirical model is valid. yusuff (2019) stated that an r2 value greater than 0.75 indicates model validity. additionally, the lack of fit test returned a value of 0.30, which was statistically significant, confirming the acceptability of the regression model. the parity plots, as shown in figure 9, show the difference between the real values from the experiment and the predicted values from the model; this difference is and should be close to zero. http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 727 table 5: analysis of variance for biodiesel yield source some of squares df mean square f value prob > f model 1060.35 20 53.02 27.44 < 0.0001 a 13.30 1 13.30 6.89 0.0146 b 1.65 1 1.65 0.85 0.3641 c 4.42 1 4.42 2.29 0.1429 d 97.61 1 97.61 50.52 < 0.0001 e 64.40 1 64.40 33.33 < 0.0001 a2 216.39 1 216.39 111.99 < 0.0001 b2 229.10 1 229.10 118.57 < 0.0001 c2 105.15 1 105.15 54.42 < 0.0001 d2 188.05 1 188.05 97.33 < 0.0001 e2 332.62 1 332.62 172.15 < 0.0001 ab 24.50 1 24.50 12.68 0.0015 ac 38.88 1 38.88 20.12 0.0001 ad 2.02 1 2.02 1.04 0.3168 ae 34.81 1 34.81 18.02 0.0003 bc 2.82 1 2.82 1.46 0.2381 bd 156.00 1 156.00 80.74 < 0.0001 be 23.62 1 23.62 12.22 0.0018 cd 41.86 1 41.86 21.67 < 0.0001 ce 0.64 1 0.64 0.33 0.5701 de 11.83 1 11.83 6.12 0.0205 residual 0.30 25 1.93 lack of fit 0.30 20 2.42 pure error 0.000 5 0.000 cor total 1108.65 45 std. dev 1.39 r-squared 0.9564 mean 82.52 adj r-square r-pred-square 0.9216 c.v 1.68 r-adeq precision 0.8257 press 193.21 the "pred r-squared" of 0.8257 is in reasonable agreement with the "adj r-squared" of 0.9216. within the spectrum of the factors examined in table 6, the response (biodiesel yield) was maximized. the optimal values of the factors: 2.52 wt.% concentration, methanol/molar ratio of 6.14 mol/mol, time of 1.10 hour, temperature of 59.8°c and agitation speed of 325.2 rpm gave a predicted optimal biodiesel yield of 86.25% at a desirability function of 1; this yield closely matches the experimental yield of 86.19%; the minimal error between the experimental and predicted values is 0.06%, confirming the accuracy of the predicted model and the dependability of the optimal combination. http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 728 table 6: optimal response of the waste frying oil biodiesel; responses catalyst conc. methanol/oil molar ratio time temp. agitation speed experiment al yield predicted yield biodiesel yield 2.52 6.14 1.10 59.8 325.2 86.19 86.25 3.3 physiochemical properties of the produced biodiesel the physiochemical properties of the produced biodiesel are reported in table 7, respectively. the properties, as observed, confirm the outstanding transformation of waste cooking oil to biodiesel. the decreased moisture content, acid value, density, viscosity, iodine value and saponification value of the waste frying oil to biodiesel were due to the transesterification process ((adepoju et al., 2021; wong et al., 2015). this confirms that the synthesized product was consistent with biodiesel and that a complete transesterification reaction transformed the waste frying oil. further observation showed that the cetane number, the api gravity, and the diesel index increased as blended oil was converted to biodiesel; this could be attributed to energy formation from a very viscous oil to a low viscous oil (adepoju and eyibio, 2016). the high biodiesel yield obtained in this study could be attributed to the decreased base consumption for neutralization. based on the cetane number, the higher the peroxide value, the better the cetane number and the decrease in ignition time (adepoju & eyibio, 2016; adepoju and eyibio, 2015; trisupakitti et al., 2017). the cetane number value of 56.71 could be attributed to an increase in the peroxide value, as the american petroleum institute (api) gravity, which is usually used in the determination of the weight of oil/petroleum as compared with water (adepoju et al., 2021), the value of 31.26 obtained for biodiesel demonstrated light oil which is within the astm d6751 test range. the diesel index, which signifies the efficiency of the biodiesel as well as the ignition properties, is the value obtained in this study above the minimum value as set by the astm. table 7: physiochemical properties of produced biodiesel sample biodiesel astm standards viscosity @ 400c (mm2s-1) 5.54 1.6-6.0 specific gravity 0.8694 0.88 (max) flashpoint (0c) 155.00 >200 fire point (0c) 164.00 moisture (%) 0.017 0.05 (max) cloud point (0c) 9.00 acid value ( mg koh/g) 3.30 free fatty acid value ( mg koh/g) 1.65 aniline point (0f) 191.00 diesel index 59.71 api gravity 31.26 29-42 iodine value (g i2/100g) 2.77 cetane number 54.71 41-55 gross calorific value (j/g) 7785.32 figures 6 show fourier transform infra-red spectrophotometer for the optimal conversion of triglyceride of waste frying oil biodiesel . the peak at 1237-1744.4cm-1 for lso biodiesel are assigned to the peaks of bending vibration of o=c=o group. the two bands within the range of 2855.1-3008.0 cm-1 for linseed oil and peak at 1744.4 cm-1 on the ir spectra are ascribed to the c-h stretching of the alkyl group and c=o stretching of the esters group, respectively. these bands occurred because of the unconverted triglyceride in the oils. the peak at 1159.2 cm-1 represents o-ch3 , this shows the formation of methyl ester in the band. figure 6: ftir analysis of optimal waste frying oil biodiesel http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 729 figure 7: gcms analysis of optimal waste frying oil biodiesel it can be shown that the triglyceride of the waste frying oil was transformed to methyl esters in fig. 7 after being subjected to an alkaline-activated waste marble catalyst. the highest peak with a retention time of 17.961mins shows that methyl ester is present. however, the lower peaks on the right show monoglyceride at a retention time of 33.455 mins, diglyceride at 37.112 mins, and unconverted triglyceride at a retention time of 43.759 mins. (naveenkumar & baskar, 2021). 4. conclusion this study has demonstrated that biodiesel can be effectively produced from waste frying oil (wfo) using alkaline-activated marble as a low-cost heterogeneous catalyst. the characterization of the raw and activated marble through xrd, ftir, sem, and xrf confirmed its catalytic suitability, while the application of response surface methodology (rsm) successfully optimized the transesterification process, reducing free fatty acid (ffa) content and minimizing process parameters. the resulting biodiesel met astm d6751 specifications, confirming its fuel quality and potential for practical applications. the findings highlight that waste-derived materials such as wfo and marble not only reduce production costs but also promote environmental sustainability. it is therefore recommended that further research explore large-scale application of alkalineactivated marble catalysts, alongside comparative studies with other low-cost heterogeneous catalysts, to strengthen the economic and industrial viability of sustainable biodiesel production. references aoac international. 2023. official methods of analysis of aoac international (22nd ed.). aoac international. adepoju, tf. and eyibio, up. 2016. study on oil extraction from citrullus lanatus (c. lanatus) oilseed and its statistical analysis: a case of response surface methodology (rsm) and artificial neural network (ann). crj, 1(3): 28-36. adepoju, tf. and olawale, o. 2015. optimization and predictive capability of rsm using controllable variables in the azadirachta indica oilseeds extraction process. ijcmr, 3(1): 1-10. adepoju, tf. and eyibio, up. 2016. study on oil extraction from citrullus lanatus (c lanatus) oilseed and its statistical analysis a case of response surface methodology (rsm) and artificial neural network (ann). crj, 1(3):28–36 adepoju, tf. ukpong, aa. and jimoh, ro. 2021. derived biobased catalyst from the three agro wastes peel powders for the synthesis of biodiesel from luffa cylindrica datura stramonium and lagenaria siceraria oil blend process parameter optimization. biomed j sci tech res, 40(4):1–10 astm d6751. standard test method for gross calorific value of oil water coal and coke by the adiabatic bomb calorimeter. sai global http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng arid zone journal of engineering, technology and environment, june 2025; 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vol. 21(3): 717-731. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: kenenwosuobie@mouau.edu.ng 731 tấn-hiop, ð. xuan-ho, n. chi-lin, c. and bing-hung, c. 2021. preparation of cancrinite type zeolite from diatomaceous earth as transesterification catalysts for biodiesel production. renew energy, 174(1):347–358 thangavelu, sr. khambadkone, am. and karimi, ia. 2015. long term optimal energy mix planning towards high energy security and low ghg emission. appl energy, 154(2):959–969 trisupakitti, s. ketwong, c. senajuk, w. phukapak, c. and wiriyaumpaiwong, c. 2017. golden apple cherry snail shell as catalyst for heterogeneous transesterification of biodiesel. braz j chem eng, 35:1283–1291 tunc, et. 2019. recycling of marble waste a review based on strength of concrete containing marble waste. j environ manage, 231(1):86–97 wong, en. krasae, p. nualpaeng, w. and yoosuk, b. 2015. biodiesel production via transesterification of palm oil using cao ceo2 mixed oxide catalysts. fuel, 162(1):288–293 yaşar, f. 2019. biodiesel production via waste eggshell as a low cost heterogeneous catalyst its effects on some critical fuel properties and comparison with cao. fuel, 255(1):115828 yusuff, as. 2019. development of a composite catalyst from anthill and eggshell: an optimization study on biodiesel production from virgin and waste vegetable oils. waste disposal sustain energy, 2(1):1–10 http://www.azojete.com.ng/ mailto:kenenwosuobie@mouau.edu.ng corresponding author’s email address: zkyarikolo@gmail.com 760 arid zone journal of engineering, technology & environment original research article effect of binders on the performance of charcoal briquettes produced from selected biomass z. k. kolo1*, m. a. musa2 and a. n. jones2 1department of civil engineering technology, ramat polytechnic, p.m.b maiduguri 1070, borno state nigeria. 2department of civil and water resources engineering, university of maiduguri p.m.b.1060, maiduguri, borno state nigeria *corresponding author’s email address: zkyarikolo@gmail.com article information abstract globally, renewable resources are widespread which has comparatively little pollution emission effect on the environment. this study was conducted to assess the potential impact of different binders in the production of charcoal briquette using mango leaves, black plum leaves and rice husk as biomass. the organic binder materials used are cow dung, ficus citrofolia (durumi) and okra (butt) while the inorganic binder used was clay. thus, the mix ratio adopted in the study are 1:1 and 1:2 (biomass:binder). in addition, some of the parameters such as bulk density, moisture content in dry basis, compressive strength, ash content, volatile matter and calorific value were determined to identify the briquettes with highest integrity. the results show that briquettes produced from black plum leaves with clay as binder had the highest density of (1.587g lcm3 and 1.574glcm3) and lowest moisture content of (0.56% and 0.57%) and highest compressive strength of (4.45n/mm2 and 3.90n/mm2) from both mix ratios. similarly, briquette produced from black plum leaves with okra as binder had the lowest ash content of 2.1% for both mix ratios. however, briquettes produced from black plump leaves with durumi and that of rice husk with durumi as binders yielded highest volatile matter of 36.5% and 37.2% respectively. it is noteworthy that the highest heating values of 33.81mj/kg and 28.43 mj/kg was observed in briquettes produced using mango leaves with clay as binder from a mix ratio of 1:1 and 1:2. furthermore, the lowest heating values of 15.94mj/kg and 16.27mj/kg were observed from briquettes obtain from rice husk with cow dung as binder from both mix ratios. therefore, it is evident that clay is a better binder for briquette production with significant combustion property, which is cost effective and readily available for both domestic and small-scale commercial purposes. submitted: 12 march, 2024 revised: 12 june, 2024 accepted: 20 june, 2024 keywords: briquette durumi binders biomass charcoal © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the demand for energy has been on the increase, mostly attributed to the population growth, rise in price of fossil fuel as well as the significant rise in the commercial and industrial activities witnessed across the globe (sansaniwal et al., 2017; carter et al., 2018; gilvari et al., 2018). fossil fuels constitute about 80% of the global primary energy requirement (sunday et al., 2020). according to (tursi, 2019), the increasing usage of fossil fuels for industrial and post-industrial development has attracted not only growth in wealth, but also higher levels of pollution and negative impact on public health. recently, there has been resurgence of interest in the use of biomass as a source of energy in both developed and developing countries as an alternative to fossil fuel (gbs, 2019; sanchez et al., 2022). however, with the rapid rising in global energy needs by the teeming world population and rapid industrialization and urbanization as reported by carter et al. (2018) and gilvari et al. (2018), conversion of biomass to energy is considered as a promising alternative energy technology in the production of briquette for domestic and industrial use (chaney et al., 2012). azojete december 2024. vol.20(4):760-770 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:zkyarikolo@gmail.com mailto:zkyarikolo@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 761 biomass briquetting, a densification technology is one of the technologies used in improving the potential energy use of biomass primarily for household heating applications and power generation (carter et al., 2018). in biomass briquetting, plant drive raw materials are preferred as a densification material, while animal drive biomass is often used as a binding material. the predominant use of vegetable or plant biomass sources could be attributed to its widespread availability compared to animal derived biomass (okey et al., 2022). biomass generally contain naturally occurring structural binders (lignin) that are released when biomass is densified at higher pressure (oyelaran et al., 2015), which improves the structural particle bonding in the briquettes. however, some biomass may not contain significant natural binder to densify into a solid shape. however, in such instances, additional binders may be required to achieve the desired hardness and durability. briquette binders could be classified into organic, inorganic and compound binders. zhang et al. (2018) noted that organic binders have high impact and water resistance properties with poor thermal stability. in addition, binders are mostly characterized with extensive availability, high heating value and low ignition temperature (han et al., 2014). the inorganic binders have strong adhesion with lower combustion efficiency due to limited calorific value and high ash content (shu et al., 2012). consequently, compound binder comprises of the combination of two or more binders with the aim of taking the advantage of the multiple binding action offered by the different binders. therefore, the aim of this paper was to investigate the effect of different binders in briquette production by carbonizing the biomass through pyrolysis. also, the calorific value of produce briquettes will be evaluated. 2. materials and methods 2.1 materials some of the materials used in this study include black plum leaves, mango leaves, rice husk, ficus citrofolia (durumi), cow dung, okra and clay. similarly, some of the equipment used in the work include forced air-drying oven (vnb300, mammert germany), drying cabinet (fsm 140, ohaus core usa), digital analytical balance (pa214), pioneer ohaus usa), porcelain crucibles, muffle furnace (p-select 2000368, select horn ohaus usa) and needle penetrator (a46-5290 germany). 2.1.1 collection of biomass materials black plum and mango leaves were collected in residential area along polo ground while the rice husk was collected from a rice milling center in bulumkutu area of the metropolis (figure 1). the ficus citrofolia (durumi) was collected from a residential area near the federal high court in maiduguri as well while cow dung sample was collected from cow herd at the ramat polytechnic farm in maiduguri. similarly, the clay material used in the study was collected from an open deposit, along the polo ground in maiduguri. figure 1: map of maiduguri (source: kelechi et al 2020) ❖ bulumkutu ❖ ramat area ❖ polo http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 762 2.2 methods 2.2.1 sample preparation the leaves fall (mango and black plum) and rice husk were screened from impurities and then sundried to reduce moisture content. thereafter, it was carbonized in an open drum for 3 and 4hrs (nattaporn et al., 2013), respectively. the cooled carbonized biomass and the binders were grounded into pulverized form and sieved using 0.6mm sieve size to ensure steady grain size and ease of compression. the biomass material and the corresponding binders were respectively mixed using a ratio of 1:1 and 1:2 where 10g of each sample was adopted for all materials. 2 2.2.2 production of briquettes the mixture of materials used for the production of the briquettes are presented in table 1. ➢ mango leaves (ml) ➢ black plum leaves bpl) ➢ rice rusk (rh) ➢ cow dung (cd) ➢ durumi (dm) ➢ okra (ok) ➢ clay (cl) table 1: materials for briquettes production biomass binder ml cd, dm, ok, cl bpl cd, dm, ok, cl rh cd, dm, ok, cl the binders were made into non-thick gel considering the moisture content of each binder prior to mixing with biomass the biomass and the corresponding binders were mixed as presented in table 1 above. each mixture was filled into a cylindrical mold and placed on a pressing hydraulic jack machine and compressed with a pressure of 10.13mpa. this has helped in regulating the constant pressure and prevention of oozing out of binders. a total of 24 (12 from each of the two mix ratios) cylindrical briquettes with a mean diameter of 2.88cm and height of 1.58cm were produced. the produced briquettes were sundried for 6 days to ensure complete dryness of the briquettes for laboratory works. 2.2.3 determination of physical and combustion properties of produced briquettes some of the physical and combustion properties of the produced briquettes determined include the density (d), compressive strength (cs), moisture content (mc) ash content (ac), volatile matter (vm) and calorific value (cv). 2.2.4 determination of density of produce briquette the equivalent mass (m) of each of the briquettes in grams (g) was divided by its subsequent volume (v) in cm: 𝑑 = 𝑚 (𝑔)/𝑣 (cm3) (1) http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 763 2.2.5 determination of moisture content of produced briquettes 2g of the grated sample of the briquettes produced was evenly spread on a clean and dried weighed container which was rapidly placed in an oven (unb 300) preheated to 103oc without a lid. thereafter, the briquettes sample was left to dry for 2hrs before the lid was replaced on the container and removed from the oven to prevent any form of, moisture that might arise from the lid cap. thus, the briquettes sample was left to cool in drying cabinet (fsm 140) at less than 20 % humidity and then reweighed. m (g/g) = ( 𝑚3 − 𝑚1 𝑚2 − 𝑚1 ) x 100 (2) where, m1 = weight of glass container (g), m2 = weight sample and glass container before drying (g) and m3 = weight of sample glass container after drying (g). 2.2.6 compressive strength of produced briquettes briquette sample was inserted between two plates on a compressing machine subjected to compression. the ratio between the maximum breaking force and the cross-sectional area of the sample indicates the resistance to breaking by compression. 2.2.7 determination of ash content of produced briquettes approximately, 5g of a grated briquette sample was evenly spread on a weighed container (crucible) and placed on to a muffle furnace (p-select 200 368, select horn) set at 570oc.the sample was kept at the above temperature until it appeared light grey, hence, crucible was removed and placed in a drying cabinet (fsm 140) which was left to cool and reweighed immediately. ac (g/g) = ( 𝑚𝑐 − 𝑚𝑎 𝑚𝑏 − 𝑚𝑎 ) x 100 (3) where, ma = weight of porcelain crucible (g), mb = weight of porcelain crucible and sample (g) and mc = weight of porcelain crucible and ash (g). 2.2.8 determination of volatile matter of the briquettes produced grated briquette sample (5g) was evenly spread on a weighed crucible and placed to a muffle furnace (p-select 2000368, select horn) set at 750oc and left for 7 min. (lina et al 2015) thereafter, the crucible was removed and placed in a drying cabinet (fsm 140) which was left to cool and weighed immediately. vm (%) = % loss in weight % moisture content (4) 2.2.9 determination of calorific value of briquettes the calorimeter was calibrated by combusting 1g of benzoic acid which has a known cv. about 1 g of a briquette sample was placed in a metal sample cup which was placed into a holding slot between two electrodes extending from the lid of a stainless-steel container. thereafter, a thin metal wire fuse was attached to the electrodes which forms a loop into the coal sample and then placed into “bomb container”. thus, the bomb containing the briquette sample was transferred to a water bath where an electrical current was used to spark the sample which ignites the bomb. the sample in turn heated the water bath, hence, the change in water – bath temperature was used to determine the calorific value of the sample. http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 764 2.2.10 sample identification table 2: initials for biomass and their corresponding binders table 2 is used for sample labeling for easy identification and ensure correctness of work. samples used in this study were based on the initials of biomass and their corresponding binders which was further simplified accordance with the sample id as shown above. 3. results and discussion the results of the physical and combustion analysis of black plump leaves, mango leaves, rice husk with durumi, cow dung, okra and clay paste as binders are presented in this section. the properties of the briquettes produced were limited to the determination of density, percentage moisture content, compressive strength, percentage ash content, percentage volatile matter and calorific value only. figure 2 presents the density of the briquettes produced. s/n sample sample id 1. ml+cd ml1 2. ml+dm ml2 3. ml+ok ml3 4. ml+cl ml4 5. bp+cd bp5 6. bp+dm bp6 7. bp+ok bp7 8. bp+cm bp8 9. rh+cd rh9 10. rh+dm rh10 11. rh+ok rh11 12. rh+cl rh12 http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 765 figure 2: density (g/cm3) of produced briquettes the results show that the density of the briquettes varied from 1.002 g/cm3 – 1.587 g/cm3 for 1:1 mix ratio and 1.00l g/cm3 – 1.574 g/cm3 for 1:2 mix ratio. the lowest and highest densities were obtained from briquettes produced from ml+dm (ml2) and in bpl+ cl (bp8) respectively. the lowest density obtained in this study is greater than the highest obtained from a briquette of rice stalk and starch binder by ige et al. (2018) of 0.590g/cm3.this is because high density is an indication of longer burning time, as such briquette produced from bpl+ cl(bp8) will tend to burn for a longer time compared to others. the result from figure 3 indicates percentage moisture content of the produced briquettes which is between the minimum value of 0.56% from bpl+cl (bp8) of 1:1 mix ratio and maximum of 8.45% from rh+cd (rh9) of 1:2 mix ratio. the moisture content of briquettes produced in this study had lesser moisture content than the briquettes produced from sawdust, ficus exasperate and cassava peel using different binders which was 8.55% (cow dung) and 12.51% (starch) as reported by ogunjobi et al. (2023). this result agrees with mc of 5-10% obtained by pillari et al. (2013) for quality briquettes. with low moisture content, briquettes will easily ignite, facilitate heat transfer and higher calorific value is expected (dawit, 2012). figure 3: moisture content (%) of produced briquettes 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ml1 ml2 ml3 ml4 bp5 bp6 bp7 bp8 rh9 rh10 rh11 rh12 d en si ty ( g /c m 3 ) biomass binder 1:1 ratio 1:2 ratio 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ml1 ml2 ml3 ml4 bp5 bp6 bp7 bp8 rh9 rh10 rh11 rh12 m o is tu re c o n te n t (% ) biomass binder 1:1 ratio 1:2 ratio http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 766 in this study, the compressive strength of the briquettes produced is shown in figure 4. the results show that the compressive strength ranges between 0.51 – 4.450 n/mm2 for briquettes produced from mix ratio of 1:2 and 1:1 respectively. the compressive strength achieved by the two mix ratios were found to be reasonable with the briquette of bpl+ cl (bp8) having the higher value of 4.45 n/mm2 as compared to highest value of 10.94n/mm2 from a briquette of charcoal fines and african elemirasin binder reported in a work by barnard et al. (2021). the implication of this is that briquette from bpl+cl (bp8) will suffer less damage during packaging storage and transportation (ige et al., 2018). above all, it is an indication of good quality briquettes because of the strong inter particle bonding (onuegbu et al., 2011). figure 4: compressive strength (n/mm2) of produced briquettes figure 5 shows the ash content of briquettes produced in this study which was lowest in bpl+ ok (bp7) at 2.1% and highest value was found in bpl+ dm (bp6) at 7.2% obtained from the mix ratios of 1:1. the result is lower when compared with that obtained by ogunjobi et al. (2023) from a briquette of ficus exasperata and cassava peel with different binders. the low ash content as observed in this study is a reflection of high heating value (figure 6) which is an indication that the briquette does not contain high mineral matters. however, low ash content is an indication of good quality briquette which offers higher heating value with less dust emissions (obi et al., 2013). higher ash content in a fuel usually leads to air pollution and affects the combustion volume and efficiency of combustion (ketimbo et al 2014). figure 5: ash content (%) of produced briquettes 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ml1 ml2 ml3 ml4 bp5 bp6 bp7 bp8 rh9 rh10 rh11 rh12 c o m p re ss iv e st re n g th ( n /m m 2 ) biomass binder ratio 1:1 ratio 1:2 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ml1 ml2 ml3 ml4 bp5 bp6 bp7 bp8 rh9 rh10 rh11 rh12 a sh c o n te n t (% ) biomass binder ratio 1:1 ratio 1:2 http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 767 figure 6 revealed the range of values for the volatile matter of the briquettes produced. were 20.6% (lowest) obtained from a briquette of bp+cl at 1:1 mix ratio and 37.2% (highest) obtained from briquette of rh+dm (rh10) at 1:2 mix ratio respectively. the lowest vm in this study was lower than the lowest of 24.4% obtained from a briquette of groundnut shall, corn cub with wood residue binder and the highest was slightly higher than the highest of 34.9% as shown by (babajide et al. 2018). conversely, egbewole et al. (2009) and sotannde et al. (2010) reported a lower volatile matter for briquettes made from wood sawdust (13.89% 19.33%) and neem wood residues of (10% 13%) respectively. however, the amount of volatile matter strongly influences the thermal decomposition and combustion behavior of solid fuel (ogunjobi et al, 2023). similarly, lower volatile matter is an indication that the briquettes might not be easy to ignite, but once ignited it will burn smoothly as observed by bbajide et al. (2018). high volatile matter results in high combustibility at low ash content (marinder et al., 2012) that would be highly spontaneous in combustion utilization figure 6: volatile matter (%) of produced briquettes. figure 7 shows the calorific value of the produced briquettes which determines the amount of heat energy present in a material. it was observed that the calorific values obtained from this study was between 15.94 mj/kg from briquettes of rh + cd at mix ratio of 1:2 and 33.81 mj/kg from a briquette of ml + cl at mix ratio of 1:1. the lowest heating value obtained from this study is slightly lower than the lowest of 19.4 mj/kg and highest obtained heating value is higher than the highest of 24.9 mj/kg obtained by ajimotokan et al. (2019). similarly, the highest calorific value obtained in this study is higher than the highest of 32.79 mj/kg and 24.60 mj/kg as reported by ogunjobi et al. (2023 and gilbert et al. (2021), respectively. the lowest and highest calorific values were obtained from briquettes produced from organic binders. all briquettes produced have a significantly high heating value which offers good combustion properties that could be acceptable for domestic use and small scale commercial purposes. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ml1 ml2 ml3 ml4 bp5 bp6 bp7 bp8 rh9 rh10 rh11 rh12 v o la ti le m at te r (% ) biomass binder ratio 1:1 ratio 1:2 http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 768 figure 7: calorific value (mj/kg) of produced briquettes 4. conclusion the global rise in population growth has resulted in increasing energy (fossil fuel) demand which has impacted negatively on greenhouse gas emission and human health. to address this challenge, biomass briquetting technology has been introduced as an important part of global bioenergy supply both in developing and developed economies. this paper studied the effect of different binders in biomass briquetting which resulted in improved physical and combustion properties of the produced briquettes. the study revealed that briquettes produced from inorganic binders yielded better physical properties resulting in highest density and lowest moisture content. it also resulted in highest compressive strength. however, mix ratio (biomass: binder) does not reveal a significant impact on the quality of the produced briquettes. the heating value of the different binders used clearly appreciate their influence on the produced briquettes with highest heating value obtained using inorganic binder (clay). it is clear that all briquettes produced have a good heating value which is higher than the minimum value set by the wood pellet association of canada (calorific value > 16.00mj/kg). furthermore, decrease in moisture content has clear impact on increase in density. references ajimotokan, ha., ehimdero, ao., ajao, ks., adeleke, aa., ikubanni, pp. and shuaib, yl. 2019. combustion characteristics of fuel briquettes made from charcoal particles and sawdust agglomerates. scientific african 6: e 00202. babajide, cf., victoria, ij., oluwaseyi, oa. and rivi, dn. 2018. performance evaluation of the physical and combustion properties of briquettes produced from agro-wastes and wood residues. 2nd international research conference on sustainability, energy, engineering, materials and environment. recycling 3030037 mdpi, 3:37. bernard, k., yusufu, ac., john, bk., and thomas, tk. 2021. production of carbonized briquettes from charcoal fines using african elemi (canarium scheweinfurthi) resin as an organic binder. energy sources part a: recovery, utilization and environmental effects, taylor and francis, milton park,bington, united kingdom, 1 – 17. carter, em., shan, m., zhong, y., ding, w., zhang, y., baumgatner, j. and yang, x. 2018. development of renewable and densified biomass for household energy in china. energy for sustainable development., 46: 42 – 52. chaney, j., clifford, m. and wilson, r. 2012. on the heat pulse method for the determination of the thermal properties of biomass briquettes. international review of mechanical engineering, 6: 277-283. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ml1 ml2 ml3 ml4 bp5 bp6 bp7 bp8 rh9 rh10 rh11 rh12 c al o ri fi c v al u e (m j/ k g ) biomass binder ratio 1:1 ratio 1:2 http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com arid zone journal of engineering, technology and environment, december 2024; 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vol.20(4):760-770. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zkyarikolo@gmail.com 770 sancehz, pc., aspe, mt. and sindol, km. 2022. an overview on the production of bio-briquettes from agricultural wastes. methods, processes and quality. journal of agricultural and food engineering, 1: 0036. sansaniwal, sk., pal, k., rosen, ma. and tyagi, sm. 2017. recent advances in the development of biomass gasification technology: a comprehensive review. sustainability and energy reviews, 72: 363 – 384. shu, my., yin, hy. and liu, gh. 2012. experimental research on composite bentonite-based briquettes binders. advanced materials resources, 496: 276 – 280. sotannde, oa., oluyege, ao. and abah, gb. 2010. physical and combustion properties of charcoal briquettes from neem wood residues. international agrophysics journal, 24: 189 – 194. sunday, yk., mohammad, fz., latifa, a. and ahmad, mr. 2020. a review of technical and economic aspect of biomass briquetting. mdpi, journal of sustainability, 12 (11): 4609. tursi, a. 2019. a review on biomass: importance, chemistry, classification, and conversion. biofuel resources journal, 962 – 979. zhang, g., sun, y. and xu, y. 2018. review of briquette binders and briquetting mechanism. renew. sustainability and energy reviews, 82: 477-487. http://www.azojete.com.ng/ mailto:zkyarikolo@gmail.com corresponding author’s email address: awahchukwuemeka@gmail.com 771 arid zone journal of engineering, technology & environment original research article impact of conductor slots on inductance and efficiency of a machine c. c. awah1*, g. c. diyoke1, c. a. amaghionyeodiwe2, o. obasi1, i. k. nnabuenyi3 and s. e. oti4 1department of electrical and electronic engineering, michael okpara university of agriculture, umudike 2department of mechanical engineering, michael okpara university of agriculture, umudike 3instrument qa/qc arco m&e, nlng subcontractor, bonny, rivers state, nigeria 4department of electrical engineering, university of nigeria, nsukka *corresponding author’s email address: awahchukwuemeka@gmail.com article information abstract the number of conductor slot and its winding arrangement would always affect the performance of electric machines; this would include effect on its efficiency and inductance profiles, which is indispensable in the accurate prediction of machine’s output values. similarly, stator and rotor pole selections of pm machines are critical in determining the machine’s output performances. impact of conductor slot number on machine’s performance indices such as: cogging torque, flux, inductances and torque ripple of a double stator (ds) machine is researched and presented in this study. the study provides a guide to machine designers and operators on the electromagnetic implications of doubling or halving the slot number of a given electric machine. the compared machine types have six (6) and twelve (12) conductor slots; however, with a fixed pole number of fourteen (14), designated as ds 6-14 and ds 12-14, for the six (6)-slot and twelve (12)-slot machine types respectively. ansys/maxwell-2d software simulation package is utilized in the entire analyses and it is implemented through finite element analysis method. predicted torque per magnet volume of the ds 6-14 and ds 12-14 machine types at a copper loss of 30 w is 226.56 knm/m3 and 291.62 knm/m3 respectively. this implies that it would be more economically viable to manufacture the ds 12-14 machine type than its 6-stator slot counterpart, considering its output torque per magnet volume. it is also revealed that the ds 6-14 configuration has larger inductances and higher quadrature (q)-axis flux compared to its counterpart, albeit; with higher number of undesirable features such as high cogging torque and torque ripple amplitudes. however, the ds 12-14 machine type exhibits greater value of direct (d)axis flux compared to its equivalent 6-slot machine, in addition to other advantages. submitted 01 april, 2024 revised: 04 july, 2024 accepted: 11 july, 2024 keywords: cogging conductor slots inductances torque ripple © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the number of conductor slot and its winding arrangement would always affect the performance of electric machines; this would include effect on its efficiency and inductance profiles, which is indispensable in the accurate prediction of machine’s output values (akbaba and dalcali, 2022). also, stator and rotor pole selections of pm machines are critical in determining the machine’s output performances, as established in zou et al. (2017a). more so, generated torque of permanent magnet (pm) machine is dependent upon the relative difference between its axis inductances, i.e. on direct (d)-axis and quadrature (q)-axis inductances (kashif and singh, 2022). the dependence of machine’s performance on its axis’s inductance is reconfirmed in hu et al. (2020). hence, the impact of conductor slot number on electromagnetic output of a double stator synchronous machine having inner statorpositioned magnets is investigated and presented in this study. in addition, the resulting inductance of pm machine is also dependent upon its number of phases where higher phase number would yield improved mutual inductance level and consequently, enhanced fault-tolerance azojete december 2024. vol.20(4):771-780 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:awahchukwuemeka@gmail.com mailto:awahchukwuemeka@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 772 capability (shao et al., 2016). it is important to note that high amount of self-inductance is good and required in an electric machine in order to sustain its short-circuit fault effects (bianchi et al., 2006), while low amount of mutual inductance in an electric machine indicates the machine’s high ability to resist magnetic coupling fault effects of the windings as implemented by (awah, 2024). similarly, conductor slot angle of a pm synchronous machine would proportionally influence the resulting torque, power factor and winding inductance profiles of the machine, as proved by waheed and ro (2020). apart from the impact of number of conductor slots on machine’s output performances, a chosen number of conductor and its consequent winding configuration would indirectly affect its electronic drive system (uzhegov et al., 2017); thus, adequate consideration is required in selecting the most suitable machine topology, for effective machine yield. dual stator pm machine with improved machine performance, owing to introduction of flux barrier mechanism on the rotor is proposed by fan et al. (2020). the proposed dual stator machine in fan et al. (2020) is similar to that analysed in this current investigation; though, with different structural and winding configurations. it is worth noting that an electric machine that has v-positioned magnets on its rotor would outperform its equivalent spoke-positioned type; albeit at higher cost implication, owing to increased usage of magnet material. cost-savings could be realized from similar kind of double stator machine by utilizing cheaper magnetic materials such as ferrite, as demonstrated by kim et al. (2016); however, at the expense of enhanced output electromagnetic torque. nevertheless, machines having spoke-shaped magnets are usually preferred to its surface-mounted magnet categories, because of its higher flux-focusing abilities (zou et al., 2017b). spoke-positioned magnets are adopted in the stators of this present study. deployment of brushless dual stator and dual rotor machine is proved to have better electromagnetic performance amongst other merits than its equivalent dual stator single rotor structure; particularly, reduced cogging torque and torque ripple effects; however, with more complicated mechanical assembly (ullah et al., 2022). it is worth noting that the developed machine in this present study is typically brushless. in addition, large cogging torque amplitude is not favourable to electromagnetic torque production of any electric machine (awah et al., 2023). this is because cogging torque depreciates the overall electromagnetic torque output, on summation. amplitude of cogging torque in an electrical machine is a function of the machine’s stator and rotor pole arrangements, as demonstrated by gao et al. (2017). it is worth noting that large value of torque ripple is detrimental to smooth operation of electric machines, as highlighted by awah et al. (2023). nevertheless, improved magnet utilization as well as reduced undesirable features such cogging torque and torque ripple could be achieved in an electrical machine through proper structural modifications; though, with higher mechanical complexity and cost, as inferred from niu et al. (2019). it is proved that by doubling the stator slot number of an electrical machine, its output performances would be enhanced in favour of the increased stator slot-numbered prototype (he et al., 2019). the findings in he et al. (2019) are good testimony to the obtained results of this present investigation. furthermore, the investigation by zhang et al. (2020) also revealed that a pm machine that is equipped with higher conductor slot number would exhibit larger torque density and slightly better efficiency than its counterpart that has lower number of conductor slots. impact of increasing the number of conductor slots on electric machine’s output characteristics and profiles is presented in this study in order to guide electric machine designers and practitioners on the significance of doubling or halving stator slot number of a machine on its overall output performance. thus, it is intended to solve the problem of inappropriate selections and or combinations of conductor slot and pole numbers, for optimal and efficient machine output. 2. materials and methods 2.1 materials finite element computational approach is adopted in the whole analyses using ansys/ maxwell-2d software. the analysed machine types have the same number of poles with different conductor slot numbers, i.e. six (6) and twelve (12) slots. the machine type having six (6) slots is designated as ds 6-14 while its counterpart that has twelve (12) slots is designated as ds 12-14, where ds stands for double stator. it is worth noting that the investigated machine is a three-phase double stator permanent magnet machine with dual air gap arrangement. it is important to note that double stator electric machines have uncountable number of electromagnetic advantages over its equivalent single stator counterparts. the implemented core, conductor and magnet materials are listed in table 1. practically, the pole pieces are held together by steel http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 773 material of 0.5 mm width, in order to enhance its mechanical strength. it is worth noting that the predicted results of this study are computer-generated via the applied software, using machine models of figure 1; however, the graph plotting was done using microsoft excel tools during the results’ post-processing stage. table 1: machine parameters (awah et al., 2023) item value machine type ds 6-14 ds 12-14 conductor slot number 6 12 pole number 14 air-gap, mm 0.5 stack length, mm 25 machine radius, mm 45 core material steel conductor material copper type of magnet neodymium speed, rpm 400 current, a 15 turns number/phase 72 2.2 method the investigation is conducted at both load and no-load simulation conditions. the comparison is done under the same simulation conditions, as could be inferred from table 1. transient solver of the implemented software is applied, owing to its high precision potential in predicting time-stepping electromagnetic problems, as highlighted in awah (2022); as well as its uniqueness in solving speed-varying and position-related magnetic and electric field issues. the direct (d)-axis and quadrature (q)-axis inductances are predicted using eq. (1) and eq. (2) respectively (awah, 2024). more so, the axes inductance is converted from its three-phase variables to two-axis components by utilizing the conventional parks’ transformation method. the torque ripple (tr) is predicted using eq. (3) (oti and awah, 2022). d nld d i l  − = (1) q nlq q i l  − = (2) where: ld and lq are the direct-axis and quadrature-axis inductances, id and iq are the corresponding axes current, ψnl is the no-load flux. av r t tt t minmax −= (3) where: tmax, tmin and tav is the maximum, minimum and average torque, respectively. http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 774 3. results and discussion figure 1 shows the flux density outlines of the investigated machine topologies. it is evident that the inner stator tooth of the compared machine types has higher sensitivity to flux density compared to its other parts. this high sensitivity response is followed by the machine’s rotational parts, as could be seen from figure 1. similarly, no-load or cogging torque magnitude of the compared machine types is shown in figure 2. it is obvious that ds 6-14 machine exhibits larger cogging torque than its equivalent ds 12-14 machine. it is important to keep the cogging torque magnitudes of a machine to its barest minimum value for improved output torque. (a) ds 6-14 (b) ds 12-14 figure 1: flux density of the investigated machines on no-load figure 2: cogging torque the axes flux of the compared machine types at different quadrature-axis current ratings is depicted in figure 3. it is revealed that ds 6-14 machine has lower direct (d)-axis flux but higher quadrature (q)-axis flux compared to ds 12-14 machine type. direct-axis flux is almost insignificant with changes in applied axis current as shown in figure 3(a). meanwhile, the quadrature-axis flux varies proportionally with applied axes current as presented in figure 3(b). furthermore, the compared machine’s axes inductance is presented in figure 4. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 1 2 3 4 5 6 7 8 9 10 c o g g in g t o rq u e a m p li tu d e (n m ) fft harmonic order ds 6-14 ds 12-14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 775 clearly, ds 6-14 machine category has higher directand quadrature-axis inductances compared to its counterpart, over different rotational positions of the rotor. the direct-axis of a machine is more or less aligned to its rotor initial position direction. moreover, the amount of d-axis flux would invariably influence its overall output torque, as could be inferred from the larger torque per magnet volume of the ds 12-14 machine type, shown in figure 6 (b). (a) direct-axis (b) quadrature-axis flux figure 3: axis flux variations with current 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045 0.005 0 5 10 15 20 d -a x is f ll u x ( w b ) q-axis current (a) ds 6-14 ds 12-14 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045 0.005 0 5 10 15 20 q -a x is f lu x ( w b ) q-axis current (a) ds 6-14 ds 12-14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 776 (a) direct-axis inductance (b) quadrature-axis inductance figure 4: axis inductances finite element predicted self and mutual inductances of the investigated machine types are presented in figure 5. it is worth revealing that the ds 6-14 machine topology has both higher self and mutual inductances compared to the ds 12-14 machine equivalent. since, the ds 6-14 machine type has larger amount of selfinductance; then, it would invariably exhibit higher fault-tolerance potential over short-circuit faults; though, with a drawback on its magnetic isolation potential, owing to its high possession of absolute mutual inductance value. 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 60 120 180 240 300 360 d -a x is i n d u ct a n ce ( m h ) rotor position (elec. deg) ds 6-14 ds 12-14 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 60 120 180 240 300 360 q -a x is i n d u ct a n ce ( m h ) rotor position (elec. deg) ds 6-14 ds 12-14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 777 (a) self-inductance (b) mutual-inductance figure 5. winding inductances torque ripple profiles of the two analysed machine types are compared in figure 6(a). a wide gap exists between the predicted torque ripple values of the compared machine configurations, the minimum value being recorded in the machine type with larger conductor slot number. large amount of torque ripple/pulsation is not amenable to smooth control of machines. torque per applied magnet volume difference between ds 614 and ds 12-14 machine types is at least over 10 % in all the simulated load settings. this difference tends to increase with increasing loading conditions, as shown in figure 6(b). it is important to note that supplied current has great effect on the resulting output characteristics of any given electric machine; particularly, at electromagnetic saturation conditions. 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 60 120 180 240 300 360 s el fin d u ct a n ce ( m h ) rotor position (elec. deg) ds 6-14 ds 12-14 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0 60 120 180 240 300 360 m u tu a lin d u c ta n ce ( m h ) rotor position (elec. deg) ds 6-14 ds 12-14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 778 (a) torque ripple (b) torque per magnet volume figure 6. torque ripple and torque per magnet volume 4. conclusion the impact of number of conductor slots on performance of a double stator electric machine is presented in this study. the investigation shows that larger machine inductances are provided by the machine type that has lesser conductor slot number, i.e. by ds 6-14 machine topology, because the ds 6-14 machine type would have higher susceptibility to magnetic saturation, owing to the direct relationship between a machine’s inductance value and its corresponding saturation impacts. nevertheless, ds 6-14 machine type exhibits high cogging torque and torque ripple values, which are demerits. the predicted torque per magnet volume of ds 12-14 machine type at rated speed outweighs that of its equivalent ds 6-14 topology, by over 10 % at all electromagnetic load settings. thus, by doubling the stator slot number of the investigated machine, its output torque is enhanced; in addition to a consequent high prospective of the machine’s cost-effectiveness over the ds 6-14 machine type. 0 50 100 150 200 250 0 10 20 30 40 50 60 t o rq u e ri p p le ( % ) current (a) ds 6-14 ds 12-14 0 50 100 150 200 250 300 350 400 10 20 30 40 50 t o rq u e/ p m v o l. ( k n m /m ^ 3 ) copper loss (w) ds 6-14 ds 12-14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 779 references akbaba, m. and dalcali, a. 2022. a novel method for measuring inductances and analysis of shaded-pole motors. international journal engineering science and technology, 36(3): 101133. awah, cc. 2022. performance comparison of double stator permanent magnet machines. archives of electrical engineering, 71(4): 829–850. awah, cc. 2024. comparative analysis of dual stator machines. nigerian journal of technological development, 21(1): 19–28. awah, cc., nnabuenyi, ik., amaghionyeodiwe, ca., oti, se. and obasi, o. 2023. influence of rotor pole number on the output of double stator flux-switching machine. international journal of integrated engineering, 15(7): 262–281. bianchi, n., bolognani, s., pre, md. and grezzani, g. 2006. design considerations for fractional-slot winding configurations of synchronous machines. ieee transactions on industry applications, 42(4): 997–1006. fan, d., quan, l., zhu, x., han, p. and xiang, z. 2020. design and analysis of double-stator flux modulated permanent magnet motor based on flux modulation theory. ieee energy conversion congress and exposition (ecce), detroit, usa, 4083–4087. gao, y., qu, r., li, d. and li, j. 2017. torque performance analysis of three-phase flux reversal machines. ieee transactions on industry applications, 53(3): 2110–2119. he, m., xu, w., zhu, j., ning, l., du, g. and ye, c. 2019. a novel hybrid excited doubly salient machine with asymmetric stator poles. ieee transactions on industry applications, 55(5): 4723–4732. hu, y., chen, b., xiao, y., shi, j. and li, l. 2020. study on the influence of design and optimization of rotor bars on parameters of a line-start synchronous reluctance motor. ieee transactions on industry applications, 56(2): 1368–1376. kashif, m. and singh, b. 2022. design optimization with improved torque performance of a new flux intensifying pmsm using multilayer barriers for solar water pumps. international journal of engineering science and technology, 36(3): 101134. kim, d., hwang, h., bae, s. and lee, c. 2016. analysis and design of a double-stator flux-switching permanent magnet machine using ferrite magnet in hybrid electric vehicles. ieee transactions on magnetics, 52(7): 8106604. niu, s., zhao, x., zhang, x. and sheng, t. 2019. a novel axial-flux-complementary doubly salient machine with boosted pm utilization for cost-effective direct-drive applications. ieee access, 7: 145970–145977. oti, se. and awah, cc. 2022. influence of magnetic remanence and coercive force on the electromagnetic output of permanent magnet machine. progress in electromagnetics research m, 109(3): 75–88. shao, l., hua, w., dai, n., tong, m. and cheng, m. 2016. mathematical modelling of a 12-phase flux-switching permanent-magnet machine for wind power generation. ieee transactions on industrial electronics, 63(1): 504–516. ullah, w., khan, f. and hussain, s. 2022. a comparative study of dual stator with novel dual rotor permanent magnet flux switching generator for counter rotating wind turbine applications. ieee access, 10: 8243–8261. uzhegov, n., barta, j., kurfurst, j., ondrusek, c. and pyrhonen, j. 2017. comparison of high-speed electrical motors for a turbo circulator application. ieee transactions on industry applications, 53(5): 4308–4317. waheed, a. and ro, j. 2020. analytical modelling for optimal rotor shape to design highly efficient line-start permanent magnet synchronous motor. ieee access, 8: 145672–145686. http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):771-780. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 780 zhang, j., zhang, b., feng, g. and gan, b. 2020. design and analysis of a low-speed and high-torque dual-stator permanent magnet motor with inner enhanced torque. ieee access, 8: 182984–182995. zou, t., li, d., qu, r., jiang, d. and li, j. 2017a. advanced high torque density pm vernier machine with multiple working harmonics. ieee transactions on industry applications, 53(6): 5295–5304. zou, t., li, d., qu, r. and jiang, d. 2017b. performance comparison of surface and spoke-type flux-modulation machines with different pole ratios. ieee transactions on magnetics, 53(6): 7402605. http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com corresponding author’s email address: adeyoyindy@gmail.com 339 arid zone journal of engineering, technology & environment original research article modeling a solar-powered iot smart home a. raji*, f. o. adunola and a. e. airoboman department of electrical and electronics engineering, nigeria defence academy, kaduna *corresponding author’s email address: adeyoyindy@gmail.com article information abstract the concept of smart homes has gained more interest in recent years, as the unwavering advancement in iot technologies enable devices to operate and communicate autonomously. as urbanization accelerate and energy demand increase, on-grid energy system faces significant challenges, including high carbon emissions, energy inefficiency, and reliance on nonrenewable energy sources. the incorporation of solar power into this system not only reduces dependence on traditional energy sources but also promotes sustainability by utilizing clean, renewable energy. the research present a comprehensive model that addresses these challenges, focusing on energy efficiency, seamless iot integration, user interaction, scalability. a potable model called smhome system is powered by solar energy, developed with an algorithm for monitoring and controlling the home autonomously over the internet. the arduino nano collects data from various sensors (temperature, motion) and communicates with the esp8266 for wi-fi connectivity. the esp8266 sends this sensor data to a cloud platform via tcp, allowing remote monitoring and control through a mobile app. integration with the ifttt app enables automation, where specific triggers from the sensors can initiate actions, such as sending notifications or controlling devices based on user-defined conditions. the proposed smhome system is structured in a form that a potable box powered by solar energy can only be easily and efficiently control appliances over the internet and support home safety with autonomous operation. by integrating solar energy with iot technologies, the research demonstrates the potential for improved energy management, reduced environmental impact and enhanced quality of life for residents. received: 20th june 2024 revised: 11th april 2025 accepted: 12th april 2025 keywords: smhome iot ifttt tcp/ip esp8266 © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction automation systems, developed since the late 20th century, control home appliances remotely. microcontrollers have reduced costs, but widespread adoption is often seen as hobbyist or affluent. remote controls for tvs, fans, air conditioners, and music players are implemented. electricity and technology have led to a new era of home appliance control through mobile devices like bluetooth, zigbee, wi-fi networks, and gsm modules, but these systems do not allow residents to monitor and manage their homes from outside. existing systems offer convenience, comfort, and safety but lack energy efficiency. most do not utilize iot technology, which connects billions of smart devices to the internet. smart homes have built-in sensors or controllers, but they lack functionality and communication range. access points allow devices to monitor conditions and control appliances. an integrated smart home automation system manages various appliances, including lights, thermostats, tvs, door locks, cameras, washing machines, and refrigerators. it's an iot-based system that reduces electricity consumption, energy costs, and enhances security. some systems can alert homeowners about motion detected in their absence. the integration of solar energy with internet of things (iot) technologies has emerged as a transformative approach to creating sustainable and efficient living environments. (nithish et al., 2022) as global energy demands continue to rise alongside concerns about climate change and environmental degradation, the need for innovative solutions in residential energy management becomes increasingly critical. (swati et al., 2020). the incorporation of solar power into this framework not only reduces dependence on traditional energy azojete june 2025. vol.21(2):339-354 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/003 www.azojete.com.ng mailto:adeyoyindy@gmail.com mailto:adeyoyindy@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 340 sources but also promotes sustainability by utilizing clean, renewable energy. the research demonstrates the efficiency of smart energy transition through a solar-powered smart home, demonstrating the use of iot technologies to optimize energy usage, reduce costs, and promote sustainable living practices. the userfriendly interface encourages informed energy management, fostering a culture of sustainability. the main part of the home automation system based on iot is the microcontroller, the arduino nano is a small, breadboard-friendly microcontroller board based on the atmega328p (or atmega168) microcontroller. (sarishma et al., 2020). it operates at 16 mhz and is designed for various applications, particularly in hobbyist projects and prototyping. it has multiple digital input/output pins (14 in total), analog input pins (8), and supports various communication protocols like i2c and spi. however, it does not have built-in wi-fi capabilities. the esp8266, on the other hand, is a low-cost wi-fi microcontroller produced by espressif systems. (how 2 electronics, 2024) it features a 32-bit processor capable of running at 80 or 160 mhz and includes built-in tcp/ip networking capabilities, making it suitable for internet of things (iot) applications. it has a minimum of 17 gpio pins, supports various communication protocols (i2c, spi, uart), and can connect to wi-fi networks directly. this makes the esp8266 particularly useful for projects that require internet connectivity. (instructables 2021). the collaboration between arduino nano and esp8266 in a solar-powered iot smart home creates a robust framework for efficient energy management. by leveraging real-time data acquisition and wireless communication, this integrated approach not only enhances sustainability but also empowers users with valuable insights into their energy consumption. (xilir, 2023). iot can enhance existing home automation systems by introducing centralized control over the internet. the arduino nano acts as the main controller, processing data from various sensors connected to the solar power system. sensors connected to the arduino measure critical parameters. it gathers information such as motion, lighting, current, voltage and temperature from the sensors, solar panels and batteries. the esp8266 module provides wi-fi connectivity, allowing the arduino to transmit data wirelessly to cloud platforms or mobile applications (such as ifttt or mqtt) where users can visualize their energy consumption patterns and system performance. (how2electronics 2024). this connectivity enables users to access real-time data about energy production and consumption from anywhere, facilitating better energy management. the implementation of iot smart home systems presents both challenges and opportunities. short range of communication many smart home devices rely on wireless communication protocols such as zigbee, z-wave, and wi-fi. (simar et al., 2023) these protocols often have limited ranges, which can lead to connectivity issues, especially in larger homes or those with obstacles that interfere with signals. this short range can hinder effective communication between devices, resulting in unreliable performance. a significant challenge in iot smart homes is the lack of interoperability among devices from different manufacturers. complexity of setup and maintenance, cost barriers and the most importantly energy management. many studies have concentrated on smart homes. consequently, this review examines research on shs in light of the increasing prevalence of home appliances within the iot ecosystem. the findings and recommendations from this study enhance our understanding of users' attitudes toward privacy in smart homes. additionally, relevant work in the field of home automation is presented. smart homes (shs) are conceptual frameworks rather than physical structures. the idea of home automation has been explored in science fiction for many years and was practically showcased by the american association of house builders in 1984, which helped define shs. (co-da, 2023). smart homes can be classified into two categories: wired and wireless systems. wired systems employ optical fibers, bus lines, and power lines, while wireless systems consist of a sender and receiver. currently, many applications utilize wireless technologies like radio waves or infrared for device communication. (jabbar et al., 2019). smart homes can operate on both wired and wireless systems simultaneously, evolving into versatile portable controllers that enhance daily convenience. (jabbar et al., 2019). in an sh environment, diverse electronic devices connect to provide smart services to users. iot-based smart homes play a crucial role in the development of smart cities globally, aiming to enhance living standards, safety, security, and resource efficiency. key features of shs include real-time monitoring, protection against hacking, remote control capabilities, and alarms for fire and gas leaks. given that sensitive personal data is exchanged among these systems, robust security and privacy measures are essential to safeguard user information while ensuring reliable service delivery. the internet of things (iot) represents a relatively recent advancement that empowers existing homes with enhanced computing and communication capabilities due to the rapid evolution of internet technologies. within a smart home setting, appliances can connect directly to the home network, allowing users to control each device individually through voice commands or mobile devices. common applications involve managing lighting, motion detection, security systems, entertainment options, and temperature regulation. smartphones and computers are vital tools for controlling these devices as they serve as modern technological benchmarks. users can access these gadgets anywhere and configure them online to connect with other devices. iot encompasses a vast network of http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 341 interconnected objects and individuals that gather and display necessary data using numerous devices of varying sizes. these interconnected devices collect data from sensors linked to iot networks, enabling analytics that highlight valuable information tailored to specific needs. home automation has evolved significantly, incorporating a variety of technologies each designed to address specific needs and challenges within the residential environment. from the early reliance on gsm-based systems to the integration of iot and sophisticated microcontrollers, the journey towards creating seamless, efficient, and secure smart homes has been marked by innovation and adaptation. this review connects the dots between various approaches, highlighting their strengths, limitations, and the ways in which they have influenced subsequent developments in the field. early iterations of home automation often utilized global system for mobile communications (gsm) technology, enabling homeowners to control appliances remotely through short message service (sms). yusuf et al., (2017) introduced a system that integrated an arduino uno with a gsm module (sim900a), allowing users to send commands via sms to control devices connected through relays. this approach offered the convenience of remote control from virtually anywhere with mobile network coverage. however, it also presented several drawbacks. okorafor, (2023) pointed out the energy inefficiencies inherent in gsm-based systems, largely due to the lack of real-time monitoring and adaptive capabilities. these systems typically operate on pre-set schedules or manual commands, without the ability to adjust to changing conditions or user habits, leading to unnecessary energy consumption. yusuf et al., (2017) acknowledged that gsm-based systems suffer from several limitations, including limited range (dependent on mobile network coverage), potential delays in command execution due to network latency, and a reliance on the availability and reliability of the mobile network. in critical situations where immediate response is required, these delays can be problematic. moreover, the performance of gsm-based systems can vary significantly depending on the strength and stability of the mobile network signal, which may not be consistently reliable in all geographical areas or building structures. the dependence on sms communication also introduces security considerations, as sms messages can be intercepted or spoofed, potentially compromising the security of the home automation system. despite these limitations, gsm-based systems provided an initial step towards remote home automation, paving the way for more advanced technologies. bluetooth technology emerged as an alternative communication method for home automation, offering advantages such as high communication rates, low cost, and enhanced security features. yan et al., (2015) emphasized these benefits in their work on a bluetooth-based home automation system. bluetooth operates within a limited range, typically around 10 meters, which restricts its ability to control appliances throughout a larger home. muthukumaran et al., (2019) proposed a low-cost, flexible, and secure wireless solution using bluetooth, highlighting its potential for localized control and monitoring. the security features of bluetooth, such as pairing protocols and encryption, provide a degree of protection against unauthorized access, making it a more secure option compared to unencrypted wireless communication methods. however, the range limitation remains a significant drawback. bluetooth-based systems are best suited for controlling devices within a single room or a small area, limiting their applicability in larger homes or multistory buildings. sen et al., (2015) explored the use of voice-controlled home automation using bluetooth, which can be particularly beneficial for elderly or disabled individuals who may have difficulty using traditional control interfaces. however, they noted that the accuracy of voice recognition can be affected by noisy environments, which can degrade the performance of the system. davidovic et al., (2015) integrated bluetooth with a raspberry pi microcontroller, allowing smartphones to connect to the home automation system via wi-fi. however, this setup only worked within the range of the wi-fi access point, further limiting its usability. despite these limitations, bluetooth technology offers a cost-effective and secure solution for localized home automation applications, particularly in scenarios where short-range communication is sufficient. zigbee is another short-range communication technology that has been explored for home automation applications. it offers low data rates and low power consumption, making it suitable for battery-powered devices and sensor networks. sayeed et al., (2023) examined an iot-integrated smart home system that utilized zigbee for communication between devices. however, they noted connectivity issues and range limitations that affected the overall energy efficiency of the system. these limitations can arise from interference from other wireless devices, obstructions in the environment, and the physical distance between devices. (jitendra et al., 2010) highlighted zigbee's physical range of 10 to 20 meters, which can be extended up to 150 meters using direct sequence spread spectrum (dsss) technology. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 342 despite its low power consumption, the range limitations of zigbee can pose challenges in achieving comprehensive and reliable home automation. in larger homes or buildings with thick walls, the signal strength may degrade, leading to unreliable communication between devices. this can result in devices becoming unresponsive or failing to operate as intended. zigbee's low data rate may also limit its suitability for applications that require high-bandwidth communication, such as streaming video or transmitting large amounts of data. while zigbee offers advantages in terms of power efficiency and cost, its range limitations and potential connectivity issues need to be carefully considered when designing a home automation system. the advent of the internet of things (iot) has revolutionized home automation, enabling enhanced control, monitoring, and automation capabilities through internet connectivity. iot-based systems leverage a wide range of sensors, actuators, and communication protocols to create intelligent and responsive home environments. mehra et al., (2022) developed an iot-based home automation system that used motion detection and sensors for lighting and gas detection, controlled by a raspberry pi. this system demonstrated the potential of iot to automate tasks and improve safety in the home. however, they noted that the entire operation would fail if the power supply to the ips failed, highlighting the importance of reliable power sources in iot deployments. kodali et al., (2016) presented an mqtt-based system using esp8266 for remote monitoring and control via wi-fi. mqtt (message queuing telemetry transport) is a lightweight messaging protocol that is well-suited for iot applications, offering low power consumption and low bandwidth requirements. however, kodali et al., (2016) noted that their system had limited functionalities and lacked security considerations. security is a critical concern in iot-based home automation systems, as the interconnected nature of these systems makes them vulnerable to cyberattacks and unauthorized access. without proper security measures, attackers could potentially gain control of devices, steal sensitive data, or disrupt the operation of the system. despite these challenges, iot-based systems offer significant advantages over traditional home automation approaches, providing greater flexibility, scalability, and functionality. by leveraging internet connectivity, these systems can be accessed and controlled from anywhere in the world, enabling homeowners to monitor and manage their homes remotely. arduino microcontrollers have become popular building blocks for home automation systems due to their versatility, ease of use, and low cost. these microcontrollers can be programmed to control a wide range of devices and sensors, making them suitable for a variety of home automation applications. imran et al., (2016) proposed an iot-based system using arduino mega with an ethernet shield, enabling internet connectivity and remote control. however, they noted that their system did not consider the home surroundings, highlighting the importance of integrating environmental sensors and feedback mechanisms in home automation systems. kousalya et al., (2018) used arduino uno for smart security and home automation, capturing images upon motion detection. this system demonstrated the potential of arduino to enhance security and provide visual feedback to homeowners. jabbar et al., (2018) developed a wi-fi-based prototype using arduino mega and an android application, allowing users to control home appliances remotely. however, they noted that their system was limited to local control and lacked security features. while arduino microcontrollers offer a flexible and cost-effective platform for home automation, they also require careful design and implementation to ensure security, reliability, and usability. integrating sensors, actuators, and communication modules effectively is crucial for creating a functional and user-friendly home automation system. additionally, addressing security concerns and implementing robust authentication and encryption mechanisms are essential for protecting the system against unauthorized access and cyber threats. to overcome the limitations of individual technologies, several studies have explored integrated approaches that combine multiple technologies to enhance home automation systems. kaur et al., (2016) combined gsm, arduino, and an android application for home automation and security, using sms alerts for intrusion detection. this integrated system leveraged the strengths of each technology, providing remote control via gsm, local control via arduino, and a user-friendly interface via the android application. by combining these technologies, kaur et al., (2016) created a more comprehensive and reliable home automation solution. ganesh et al., (2017) structured an iot architecture using gsm technology, enabling users to control devices remotely via the internet. this system used gsm as a backup communication channel in case internet connectivity was unavailable, ensuring that users could still control their homes remotely. building upon this foundation, the proposed research aims to improve upon the work carried out by jabbar et al., (2018) in their "design and fabrication of iot-based automation system for smart home." specifically, this research focuses on modeling a solar-powered iot smart home, harnessing solar energy as its primary power source rather than relying on traditional batteries. this approach aims to create a more energy-efficient and sustainable system, reducing its environmental impact and operational costs. furthermore, the proposed http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 343 system will utilize wi-fi for connectivity, ensuring seamless remote access and control from anywhere with internet access. by integrating solar power and wi-fi connectivity, this research seeks to create a smart home system that is not only technologically advanced but also environmentally responsible and user-friendly. the focus on sustainability and remote accessibility aligns with the growing demand for smart home solutions that are both convenient and eco-conscious, contributing to a more sustainable and connected future. 2. materials and method this section outlines the methodology employed in this study, which involves a systematic organization of various research phases alongside the detailed design and implementation of the smart home (smhome) system, solar powered and its prototype. additionally, it explains the selection and integration of components to meet the design objectives. the flowchart in figure 2 depicts the conceptual framework of this research. the investigation begins by identifying the challenges faced by existing smart home systems, with the primary issues being high insufficient energy supply and user-unfriendly interfaces. the modeling phase concentrates on selecting materials and components for constructing the smart home prototype and developing the smhome system. the smart home design is created using planner 5d software, while the prototype is built from plywood. the design and implementation of the smhome automation system are carried out, including wiring and connecting various components (such as bulbs, fans, motors, and sensors) to the integrated smhome system (which includes arduino nano, esp8266, relay boards, dc sources, etc.). following the connection of the microcontroller and components, coding is conducted to enable functionality. 2.1 system modeling figure 1 illustrates the comprehensive design and layout of the sh prototype. the smart home (sh) prototype is designed using planner 5d software, aligned with specified requirements. the architectural layout features one bedroom, one bathroom, a kitchen, and a living room. windows are operated via a sliding mechanism powered by an aluminum cd/dvd motor (plate 1), which facilitates seamless opening and closing. a passive infrared (pir) motion sensor is integrated into the door system to detect movement, enabling automatic opening and closing based on occupancy. additionally, a dht11 sensor is installed to monitor temperature and humidity levels within the prototype. a solar panel is positioned alongside the prototype, in conjunction with a battery for energy storage. table 1 shown the energy consumption of prototype. overall, the sh prototype is fully integrated with the smart home (smhome) system. figure 1: one bed-room prototype floor plan http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 344 plate 1: sliding door mechanism in operation table: 1. actuators/sensors power consumption for a prototype s/no. actuator/sensors watts voltage/current 1. mini axial fan 0.96w 5-7v, 0.08a 2. digital temperature and humidity sensor dht11 0.00165w 3.5v-5.5v, 0.3ma 3. pir motion sensor 5v, 20ma 4. lcd display 16×2 4-5v 5. aluminum cd/dvd motor 5-7v, 0.5ma 6. led bulb 20-30milliwatts 0.02-0.03v 2.2 smhome system development and design enhancement the hardware and software components are integral to the design of the smart home (smhome) system, ensuring effective and seamless automation of the smart home (sh). in addition, the selection of components is done to fulfill the design objectives. the flowchart in figure 2 illustrates the conceptual framework of this study. the hardware utilized in the construction of the smhome automation system includes an arduino nano, an esp8266 wi-fi controller board, a 6v solar panel, a 6v 1a battery, a voltage regulator, an lcd display, buzzers, a pir motion sensor, a dht11 temperature and humidity sensor, light-emitting diode (led) bulbs, a mini fan, a 1.5v dc motor, and plywood for the sh prototype. the software components consist of the arduino ide software, a tcp server, and if this then that (ifttt). together, these components facilitate the successful implementation and operation of the smhome automation system. integrating solar-powered iot smart home technology into the concept of smart homes (shs) enhances energy efficiency and sustainability, which are critical in today's energy-conscious society, and also has revolutionized how devices communicate and operate. iot enables smart appliances to connect directly to home networks, allowing users to control them via voice commands or mobile devices. this connectivity extends to solar power systems, which can be monitored and managed through iot platforms. solar-powered iot systems optimize energy consumption by utilizing renewable energy sources. smart home energy management systems can analyze usage patterns and adjust operations accordingly to minimize waste. these systems provide real-time data on energy production and consumption, allowing homeowners to make informed decisions about their energy use. by integrating solar power with iot technology, smart homes contribute to sustainability efforts by reducing reliance on non-renewable energy sources and lowering carbon footprints. utilizing solar energy can significantly reduce electricity bills. iot-enabled systems can further enhance these savings by optimizing when and how energy is used within the home. as smart homes manage sensitive data through interconnected devices, security becomes paramount. effective measures must be implemented to protect user data from breaches while ensuring reliable service delivery. this includes securing communication channels between solar power systems and other smart devices. for sake of this work the electrical storage system was used in form of electricity to store the surplus electric charge from solar. a lead-acid battery of 6v, 4.5a was used as shown in (plate 2) to store the solar energy with 6v1a solar panel. to meet the sole aim of this project which to model an iot smhome system that is solely powered by solar energy, dickson’s rectifier method was adopted. where both the battery and combined power was used as well as the solar panel type considered. the battery method used is in line with the linear conversion voltage regulator as compared to the switching method as it was the most easily available configuration to use. this design makes use of a feedback circuit which was used to check the reference voltage for changes in the d.c. voltage output through a passive element which was a kind of solid bjt or pn junction diode, the voltage regulator works by providing a permanent output supply irrespective of input voltage type, the major advantage of this type of method was giving output ripple voltage and fast response time to load line changes. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 345 figure 2: research workflow plate 2: solar panel and the battery the hardware system implemented in the smart home (sh) prototype undergoes rigorous evaluation, with design enhancements and optimizations made in response to any identified errors until satisfactory performance is achieved. this phase is crucial for improving system functionality and detecting issues. problems encountered during earlier phases are systematically identified and resolved, with this process repeated until successful implementation is confirmed. for instance, prior to the actual deployment of the system, led bulbs start problem statement ang literature review system modelling prototype with 5d software smhome system development and design enhancement component installation (software and hardware of smhome) smhome optimization validation and testing finalinaling smhome prototype end http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 346 are utilized as substitutes for actuators to verify output readings. once all programming code is compiled into the arduino nano, the actual actuators including fans, motors, buzzers, and bulbs are employed for real testing on the vero board before soldering as depicted in plate 3. all wiring connections are meticulously checked using a multimeter, and each wire is labeled to facilitate clear verification of every connection within the system. during this phase, the system is assessed to ensure that all sensors, actuators, and the arduino nano are functioning effectively. plate 3: deployment of the smhome system using veroboard system software components are selected and developed in this project, the software feedback is used to acknowledge data commands that have been carried out over the internet and for the sake of this project, the email is used through the ifttt application, ifttt (if this then that) is an automation platform that connects various web applications and services, allowing users to create conditional statements known as applets. each applet consists of a trigger, which initiates the action based on specific events (e.g., receiving an email), and an action, which is the task performed in response (e.g., sending a notification). the platform integrates with over 600 services, enabling seamless automation of tasks across different applications without requiring any coding skills. ifttt's user-friendly interface allows users to easily create, manage, and explore applets, enhancing productivity and streamlining workflows in daily digital activities. ifttt (if this then that) can be integrated with the esp8266 module and arduino nano to automate tasks using tcp/ip communication. the esp8266 connects to a wi-fi network and utilizes http requests to trigger ifttt applets through webhooks, allowing it to send data or notifications based on sensor inputs or events. users set up their ifttt account, create a webhook url with a unique key, and program the esp8266 using the arduino ide to handle the connection and http get requests to the ifttt service. this setup enables seamless interaction between physical devices and online services, facilitating various iot applications such as sending alerts when sensors are activated. it was chosen because of its flexibility working with home appliances directly and its short response time compared to other software feedback systems as it was solely designed for this purpose. steps for setting up ifttt (applets) application the following are the step to create an ifttt app. step 1: visit the ifttt website and click on login or create an account, step 2: click if this and select your service (environment control & monitoring and trigger) step 3: now click then that and select the service and first action step 4: now click the second plus bottom (+) to add additional actions as shown in plate 4. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 347 plate 4: ifttt applet tcp client/server is an android application which serves as a terminal used to connect various devices over wifi networks using their ip addresses and a router. it can either be connected as a server or client. the server mode connected client sends and receives messages to the server and the server on turn sends and receives messages from the client. the server can connect to as many clients as possible. in this mode it can connect without interruption to any or all clients and control them at the same time. while the client mode is used to communicate with the server, send and receive messages from the server. the client cannot receive messages from other clients as it can only receive messages from one server at a time which it is connected to. therefore, a client needs to be disconnected from a server and connect to another server before it can communicate to the server. to create a tcp connection to an esp8266 wi-fi module below as explain in the following steps and depicted in plate 5. 1. determine the ip address and port number of the wi-fi module to connect to, 2. create a tcpp client on your device 3. use the ‘connect’ method to connect the client socket to the wi-fi module’s ip address & port number 4. once the connection is established, it can send and receive data between the client and server esp8266 wi-fi module http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 348 plate 5: tcp connection to wi-fi module 2.3 smhome implementation and system architecture this is another contribution to this work, the development of an innovative, market-ready portable controller (smhome) that can be implemented in real residences to continuously monitor home conditions and conveniently manage home appliances over the internet, regardless of time or location. this study proposes a process for home automation and control, implemented using the arduino nano microcontroller and all powered by solar energy. the arduino nano was chosen for the smart home (sh) prototype due to its capabilities and cost-effectiveness. to ensure the system is both intelligent and secure, several sensors, including temperature, humidity, and motion sensors, are utilized. prior to the final implementation and fabrication of the developed system, various experiments with individual sensors and actuators are conducted on a veroboard to determine their effectiveness. this process aids in selecting appropriate materials and components for the system. the smhome system (plate 6) undergoes installation in the sh prototype and is retested following hardware implementation. the system is enhanced and optimized to address any errors until it operates as intended. the microcontroller function smoothly with the sensors and actuators in the developed smhome portable automation system. plate 6: smhome system implementation for software implementation tcp/ip is a communication protocol used for networking, while ifttt (if this then that) is a web-based service that enables users to create conditional statements for automating interactions between different applications and devices. the smhome system effectively manages various home appliances, including lights, doors, windows, and fans, while also monitoring environmental parameters such as temperature, humidity, and motion through mobile devices or laptops via sms and gmail. users can control and monitor the smart home (sh) prototype from any location at any time, facilitated by the esp8266 module, which maintains a continuous wi-fi connection to the internet. when operating in server mode, the esp8266 allows users to log into a tcp/ip application to access the control system; upon receiving commands from the tcp/ip client, the server processes these instructions and relays them to the controller via the esp8266. following command execution, the esp8266 switches to client mode to connect to ifttt.com, sending trigger messages through webhooks that return feedback as sms or email notifications. after completing this process, the esp8266 reverts to server mode for continued operation with the tcp/ip client. the system architecture of the work done is shown in figure 3. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 349 figure 3: iot system architecture 3. results and discussion the modeling of a solar-powered iot smart home prototype was successfully developed with the implementation of the smhome system, which controls home appliances such as doors, windows, fans, and lights while monitoring temperature, humidity, and motion through an android application utilizing ifttt. users can connect to their homes anytime and from anywhere via the internet. the system integrates various sensors and actuators, enabling seamless remote management and automation of household functions. when the switch is turned on, the lcd initializes as well as the microcontroller, which in turn initializes the wi-fi module. the solar panel is rated to be 6.5v/1a used to charge the battery (6v) when its level is low from the power supply by the voltage regulator, which constitutes the power, through the two terminals. the solar panels ensure that the battery is properly powered to meet the power demand of the circuit. it can also be used alongside the battery to power the circuit. a pir sensor is a motion sensor that sends information about human movement around the house to a microcontroller, which then responds by taking the appropriate action. when any movement in the house is detected while the homeowner is away, its output signal activates the buzzer and notifies the server, which in turn notifies the owner. the room's humidity and temperature are both measured by the dht11 sensor, which sounds like a buzzer when the temperature rises above normal. also, it transmits data to the microcontroller, which in turn transmits a command to turn on the prototype's fan. led bulbs are used as the main source of lighting in the prototype. led bulbs use shockproof materials, are energy efficient, and are more durable as compared with real houses with glass bulbs. they are low-power bulbs that require only 30–60 milliwatts to operate. the software component utilized for this project is ifttt, an automation platform that facilitates communication between devices through a controller (esp8266) connected to a wi-fi module. when an event is triggered by sensors or a tcp command from wi-fi, the esp8266 activates its client mode and sends trigger messages to the ifttt app, which can then send notifications via email or sms regarding the event, as illustrated in plate 7. the applet triggers used in this project include commands for turning applications on/off, temperature control, and motion detection. the trigger events (applets) used in these projects include; a. application on user smart interne authenticati nano, esp8266 sensors actuato actuators http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 350 b. application off c. temperature control d. human detected messages appended to email and sms used in this project are; i. home appliance has been switched off by you ii. home appliances has been switched on by you iii. temperature level is high iv. stranger at your residence plate 7: applet notification triggered by ifttt app the android sms application is used to connect ifttt to your sms network via webhooks. this is achieved by creating a trigger in the webhook and also connecting the link with android sms. this link is then added to the android code to trigger the applet (event), which in turn triggers the sms message to be sent to your phone as shown in plate 9. the gmail application is used to connect ifttt to your gmail network via webhooks as illustrated in plate 8. this is achieved by creating a trigger in webhooks and also connecting the link with a valid gmail account. this link is then added to the android code to trigger the applet (event), which in turn triggers the gmail message to be sent to your phone/computer. this project used it to respond to all wi-fi commands from tcp clients, while sms is used to respond to the temperature and motion trigger events as in figure 3. the solar-powered iot smart home prototype not only enhances energy efficiency and sustainability but also provides users with comprehensive control and real-time monitoring of their home environment, ensuring safety and convenience through advanced automation technologies. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 351 plate 8: gmail notification plate 9: received message from ifttt using sms an application called arduino ide is used to write code and send it to the microcontroller. the smhome system's and its components' functionalities are coded, debugged, and tested using the arduino ide in this project. in addition to supporting a variety of arduino boards, the ide includes additional libraries, serial monitors for communicating with the board, and a debugging area for abnormal conditions. the project was further tested using arduino ide which displayed the various input of the user to transfer notification messages and to control the circuit as shown in plate 10 motion sensor transmitting signal to ifttt when a human is been detected and plate 11 sending email notification when the appliances is switched on. also, the top view in shown in plate 12. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 352 plate 10: motion sensor transmitting signal to ifttt when human is detected plate 11: sending email notification when appliance is switched on plate 12: top-view iot smart home automation prototype http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 339-354. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adeyoyindy@gmail.com 353 4. conclusion the objectives of this research were successfully achieved through the modelling of a prototype iot smart home automation system powered by solar energy. the key outcomes are: a functional prototype was modeled and built that demonstrates the feasibility of a solar-powered smart home automation system. this serves as a proof-of-concept and foundation for further development and refinement. the esp8266 microcontroller was effectively used as a gateway to connect the system to the internet. tcp and ifttt protocols were integrated to enable automation of the sample model, proving the ability to remotely control and monitor the system. an add-on portable box automation controller called smthome was successfully implemented. this provides a convenient way to extend the automation capabilities and control the system from anywhere. the final prototype was thoroughly tested and verified to ensure proper operation. the model was assessed against the original objectives and found to 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hangzhou, china, 28–30 july, 9072–907. yusuf, s., gupta, a., rahul, p., rahul, s., shashank, s., and shilpi, sn. 2017. gsm based home automation system. international journal of electrical and electronics research, 5(2): 1-4. http://www.azojete.com.ng/ mailto:adeyoyindy@gmail.com https://www.ijert.org/iot-based-smart-home-automation-system-using-raspberry-pi https://xilirprojects.com/product/iot-based-solar-panel-monitoring/ arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):385-402 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 385 exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms m. o. balogun*, b. jimada-ojuolape and m. o. mahmoud 1*department of electrical and computer engineering, kwara state university, malete, ilorin, kwara state, nigeria. *corresponding author's email address: monsurat.balogun@kwasu.edu.ng article information submitted 24 january, 2024 revised 17 february, 2024 accepted 23 february, 2024 keywords: accuracy identification speech recognition pre-processing voice biometric abstract speech recognition systems have become increasingly prevalent in various applications, ranging from virtual assistants to voice-controlled devices and dictation software. the desire to design human-computer interfaces that are more accessible, intuitive, and efficient cannot be overemphasized. such advancements hold significant potential to enhance accessibility, productivity, safety, and user experience across various domains and industries. despite significant advancements in speech recognition technology, several challenges persist. one primary challenge is achieving high accuracy and robustness across diverse speaking styles, accents, and environmental conditions. background noise, variations in pronunciation, and overlapping speech can introduce errors and degrade performance, especially in real-world scenarios. this study explores the pursuit of accurate and lightweight algorithms in biometric applications, focusing on voice recognition. using a dataset featuring renowned leaders' voices, the research compares k-nearest neighbors (knn) and artificial neural network (ann) techniques. employing mel frequency cepstral coefficients (mfcc) and considering noisy and noiseless environments, the study reveals that ann outperforms knn. in noisy conditions, ann achieves 62.4% accuracy, while knn reaches 33.4%. in noiseless settings, ann's accuracy rises to 95%, surpassing knn's 88%. assessment metrics like false acceptance rate, false rejection rate, f1 score, recall, precision, and receiver operator characteristics curve are analyzed. the study emphasizes the detrimental impact of noise on recognition accuracy and underscores ann's consistent superiority over knn. despite challenges posed by noisy environments, the research highlights the potential benefits of these approaches, emphasizing ann's superior performance across scenarios. this research showcases the significance of accurate biometric systems, emphasizing ann's advantages in enhancing usability and precision, especially in real-world noisy conditions. 1.0 introduction speech serves as a primary mode of human communication, facilitating the expression of thoughts and emotions. the fundamental process of speech production involves the interplay of the lungs, vocal folds (voice box), and articulators (tanberk and tükel, 2022). the collaboration between vocal folds and articulators generates a diverse range of intricate sounds, with the potential to convey varying emotional tones, enhancing effective communication (alattar et al., 2023). while every individual's voice is distinct due to factors like body size, shape, and vocal cord characteristics, voice patterns are not entirely unique (gupta et al., 2023). during verbal interactions, the vibrations of human vocal cords convey critical information about voice identity, enabling people to appropriately respond to speakers by avoiding overly warm greetings to strangers or overly cold responses to friends (al-zakarya and al-irhaim, 2023). http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 386 conventionally, humans recognize each other's speech by developing mental models for different speakers based on their exposure to diverse voices (dhole et al., 2023). these models incorporate fundamental differences in features such as rhythm and tone. by naturally adapting and familiarizing themselves with various speaker models, individuals learn to identify and comprehend distinct speakers. while voice/speech recognition is a crucial aspect of human identification, conventional voice recognition methods may fall short, particularly in security contexts (jawalkar et al., 2023). traditional techniques are susceptible to mimicry, wherein an individual imitates another's voice to gain unauthorized access, raising significant security concerns, especially for applications demanding robust user authentication (booysens and viriri, 2022). li et al. (2023) says that traditional voice recognition encounters limitations including variability in speech patterns, environmental noise, adverse conditions like illness or fatigue, limited adaptability, cross-linguistic challenges, and more. in response, researchers and developers have been focusing on advanced methods like deep learning, neural networks, and refined data collection techniques to establish more robust and versatile voice recognition systems, such as voice recognition biometric systems which can surmount the challenges (kao and chueh, 2023). voice biometrics, also known as speaker recognition, is a technology that focuses on identifying or verifying individuals by analyzing their unique vocal characteristics. (minaee et al., 2023). this technology encompasses two primary modes: speaker identification and speaker verification. speaker identification involves matching a person's voice against a voiceprint database to ascertain their identity. in contrast, speaker verification entails comparing a provided voiceprint with the voiceprint linked to the claimed identity for verification purposes (ammour et al., 2023). the latter mode is commonly used for security applications, access control, and phonebased authentication. voice biometric systems hold a pivotal role in human identity authentication and access control within security setups (alharbi and alshanbari, 2023). their history dates to the early 1950s with the creation of "audrey." the first documented speech recognizer was developed by davis, biddulph, and balashek at bell labs, capable of recognizing speakers by their pronunciation of numbers from 1 to 9. contemporary voice recognition systems like "siri" by apple and "alexa" by amazon have integrated voice recognition into consumer platforms, demonstrating a perception of intelligence and contextual language understanding (dvořák et al., 2021). the inherent variations in human voices are valuable traits in biometric security systems, and as technology advances, the demand for more intelligent and efficient biometric systems intensifies (anil and ravikumar, 2022). mk and aithal (2022) said that efficient functioning of voice biometric systems involves extracting key characteristics from a speaker's voice, preprocessing these characteristics, and then distinguishing the speaker based on these attributes in comparison to other enrolled speakers. this process generally entails employing statistical algorithms on preprocessed voice data (benmachiche et al., 2022). selecting an appropriate statistical model algorithm for a voice recognition system considers factors like hardware, design specifications, and implementation costs. utilizing simpler yet high-performing algorithms can significantly reduce setup costs, false match rates, and false non-match rates. the emergence of machine learning algorithms like artificial neural networks (ann) and artificial immune systems (ans) has introduced a biological approach to pattern recognition (xue and zhou, 2023). usually, in audio data machine learning applications, traditional machine learning algorithms such as support vector machines (svc), logistic regression, and k nearest neighbours tend to have pre-processed data with signal domain features such as the time domain features like the amplitude enveloping, zero crossing rate, and the root mean square energy (hitelman et al., 2022) . ann, for example, mirrors human brain neurons with nodes organized into layers, interconnected through nodes that culminate in the output or decision file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 387 layer. node activation hinges on a mathematical function involving input node activations from the preceding layer, weight values, and biases. techniques can enhance these parameters to minimize the cost function and enhance performance (pudurkar et al., 2022). although anns possess advantages like automatic feature extraction, adaptability with incomplete data, and recognition of intricate relationships, their drawbacks include long training times, hardware dependency, and the complexity of interpreting what the network learns (can and atilgan, 2023) in contrast, k-nearest neighbors (knn) is a widely used classification algorithm known as a "lazy learner" as it relies on training vector data points for decision-making without learning the relationships between them. knn computes euclidean distances for a predefined knumber of training vectors categorized with specific classes (imdad et al., 2017). the computed distances identify the closest neighbors to a test point vector, and the decision about the test point's class is determined by the majority rule among the nearest neighbor’s data points (demidova, 2021). while knn offers simplicity, easy implementation, and flexibility for multimodal classes, it relies on manual feature development compared to the automatic feature evolution in ann (murthy et al., 2015) biometric identification systems strive to meet the demand for more efficient and lightweight algorithms in voice/speech recognition. improving the accuracy of these systems is crucial for enhancing user experience on platforms employing biometric security measures. achieving this goal entails minimizing false match rates and false non-match rates while simultaneously increasing accuracy and deploying lightweight algorithms for swift user identification. to address these objectives, this study conducts a comparative analysis between two prominent algorithms: k nearest neighbors (knn) and artificial neural networks (ann). the aim is to identify the most suitable model capable of meeting the evolving demands in speech recognition. both knn and ann serve as classifiers in this study, and their performances are evaluated using a comprehensive set of evaluation metrics. these metrics include accuracy, false acceptance rate (far), false rejection rate, confusion matrix, recall, precision, area under the curve (auc), f1 score, and receiver operating characteristic (roc) analysis. much research has been carried out on how to improve performance learning algorithms. when it comes to classification in biometric systems, choosing the best on the best classifier has always been an issue for the past decades. to improve the performance of biometric systems, many algorithms have been developed and modified by researchers, among which were reviewed in this section. conventional automatic speech recognition (asr) models typically consist of three fundamental components: an acoustic model, a pronunciation dictionary, and a language model (xu et al., 2020). the acoustic model (am) assesses the likelihood of acoustic units, such as phones or sub-word units, which can be represented using gaussian mixture models (gmms) and hidden markov models (hmms) (juang et al., 1991) typically, gaussian mixture models (gmms) are employed to estimate the probability distribution of phones within individual states, while hidden markov models (hmms) are utilized to determine transition probabilities between states. each state corresponds to an acoustic event, such as a phone. the gmm-hmm model undergoes training via the expectation maximization (em) technique, and viterbi decoding is applied to identify the optimal state sequence within hmms. in natural utterances, the pronunciation of phones often varies based on acoustic context. hence, context-dependent triphone hmms are utilized to model speech sounds, wherein each phone is represented with both left and right contexts. in recent advancements in automatic speech recognition (asr) models, gaussian mixture models (gmms) have been supplanted by deep neural networks (dnns) (hinton et al., 2012). hybrid dnn-hmm models are commonly used in asr, combining components like the language model (lm) to compute word sequence probabilities and enhance acoustic model accuracy. lms leverage linguistic knowledge from text corpora, implicitly learning syntactic and semantic rules to refine acoustic model hypotheses. a pronunciation dictionary aligns phonetic http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 388 transcriptions with raw text for lm use. these components are independently trained and combined using finite state transducers (fsts) to construct a search graph. decoders generate lattices, scored, and ranked to produce target word sequences. asr model evaluation involves metrics like word error rate (wer) and phone error rate (per) to gauge performance. modern asr modern asr systems are fully end-to-end; for example, (amodei et al., 2016). this architecture employs an encoder–decoder framework, where the input audio undergoes processing through a series of convolutional layers, resulting in the creation of a condensed vector representation. subsequently, the decoder utilizes this encoded vector as input to generate a sequence of characters. several different objective functions such as ctc (graves et al., 2006), asg (collobert et al., 2016), transduction differentiable decoding (collobert et al., 2019) can be used to optimize end-to-end asr. moreover, different architectures of neural networks such as resnet (wang et al., 2016), tds (hannun et al., 2019) and transformer (shaw et al., 2018) have been explored. the output labels of the end-to-end system can be characters or sub-word units such as byte-pair encoding (bpe). an external lm can be incorporated to improve the overall system performance. one of the challenges in asr, even if supervised, is the variability that is characteristic of natural spoken utterances due to speaker and environmental conditions. utterances by different speakers have acoustic differences that can be difficult to disentangle from the phonetic content. even for an individual speaker, variability arises due to speaking rate, intensity, affect, and so on. furthermore, asr models are often trained on clean speech data, but they are often evaluated on real-time noisy speech data. sources of noise include background noises and signal distortions through the input device. speaker-independent models could be trained using data that includes multiple speakers, but this often degrades the performance of asr and requires larger amounts of data for training to achieve decent performance. the same applies to background noises and different environmental conditions. instead, state-of-the-art asr systems are speaker-adaptive: they capture the variability of speakers using ivectors (saon et al., 2013) and x-vectors (snyder, 2020) which are low-dimensional vectors that encode speaker-specific features. in addition, various augmentation techniques can be utilized to supplement the training data with more examples that reflect the expected variability in test conditions. for example, volume and speed perturbation are used to capture the variability between utterances. similarly, noise-augmentation is used to supplement the training data with different environmental conditions (ko et al., 2017). all these strategies are combined to train robust multi-condition asr systems that can handle multiple sources of variability in speech. kaensar (2013) developed a hand digit recognition by comparing the performance of three machine learning algorithms: the neural network (ann), support vector classifier (svc), and k nearest neighbors. the dataset used was the optical recognition of handwritten digits data set from uci machine learning repository, which consists of a total number of 5,620 handwritten digits. the results produced showed that svm was the best classifier to recognize handwritten digits with 96.93% recognition rates, however svm has slow training time compared with ann and svm. murthy and meenakshi, (2015) compared the classification of artificial neural network (ann), support vector machine (svm) and k nearest neighbor (knn) on cardiac ischemia based on morphological features that were extracted from ecg signals. the experiment was conducted by finding the optimal number of hidden neurons in the feed forward ann as well as using the most accurate kernel for the svm varying the k value that would give the best performance for the k nearest neighbors. the experimental results showed that ann outperformed svm and knn with a testing classification accuracy of 96.62%. it was recommended that the morphological features can still be optimally selected to improve performance on the artificial neural network file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 389 lanjewar et al. (2015) performed a comparison of the accuracy of gaussian mixture models (gmm) and k-nearest neighbor (knn) on speech emotion recognition systems. the authors utilized the spectral components of mel frequency cepstral coefficients (mfcc), wavelet features of speech, and the pitch of vocal traces based off voices that fall under six emotional categories such as happy, angry neutral, surprised, fearful, and sad, using the database of the standard berlin emotion database (bes). the authors concluded that the gaussian mixture models technique produced the better accuracy by recognizing the angry category with the highest rate of 92%, it had a general low performance for the “surprise” category with 25% accuracy. knn had its overall strength in classifying the happy emotion category with 90% accuracy, it has poor performance on both fear and surprise categories with 34% and 25% accuracy respectively. the paper then used the f measure and precision evaluation metrics to present an overall model performance comparison of the two models with gaussian mixture models being the better overall model in speech emotion recognition but recommends that to build a more efficient and robust model these two algorithms may be hybridized to balance their strengths and weaknesses. richardson et al. (2015) developed a deep neural network approaches to speaker and language recognition": this study delves into the application of deep neural networks for both speaker and language recognition. the authors explore deep architecture such as deep belief networks (dbn) and long short-term memory (lstm) networks. the research showcases the potential of deep learning in learning complex relationships within voice data, contributing to more accurate speaker recognition. in richardson et al. (2015) asvspoof: the automatic speaker verification spoofing and countermeasures challenge. the paper describes the asv spoofing and countermeasures (asvspoof) initiative, which aims to fill this void. through the provision of a common dataset, protocols, and metrics, asvspoof promotes a sound research methodology and fosters technological progress. this paper also describes the asvspoof 2015 dataset, evaluation, and results with detailed analyses. a review of post-evaluation studies conducted using the same dataset illustrates the rapid progress stemming from asvspoof and outlines the need for further investigation. the authors emphasize the significance of anti-spoofing measures and the integration of multiple features for robust speaker recognition systems. minaee et al. (2023), developed a voice biometric recognition using deep learning techniques. this study explores the efficacy of deep learning techniques, including convolutional neural networks (cnn) and recurrent neural networks (rnn), for voice biometric recognition. the researchers demonstrate that deep learning models exhibit improved performance in feature extraction, leading to enhanced accuracy in speaker identification. the study underscores the potential of neural networks in tackling the challenges of variability in speech patterns and background noise. he et al. (2020) worked on an end-to-end text-independent speaker verification with triplet loss. this research investigates the application of triplet loss in end-to-end text-independent speaker verification. the authors propose a framework that learns discriminative embedding directly from raw audio signals. the study emphasizes the importance of proper loss functions in training deep networks for voice biometrics. the results highlight the potential of this approach for reducing false acceptance rates and improving system security. nigam et al. (2022) worked on biometric authentication for intelligent and privacy-preserving healthcare systems. this research investigates the applicability of voice biometrics in healthcare and security domains. the authors highlight the potential of voice biometrics for patient identification, access control, and telemedicine applications. the study underscores the non-intrusive nature of voice-based authentication and its contribution to efficient and secure healthcare systems. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 390 moosavian et al. (2013) carried surveys on a new scheme for fault diagnosis of main journalbearings of internal combustion (ic) engine based on power spectral density (psd) technique and two classifiers, namely, knn) and ann. vibration signals for three different conditions of journal-bearing; normal, with oil starvation condition and extreme wear fault were acquired from an ic engine. psd was applied to process vibration signals. thirty features were extracted from the psd values of signals as a feature source for fault diagnosis. knn and ann were trained by training data set and then used as diagnostic classifiers. variable k value and hidden neuron count (n) were used in the range of 1 to 20, with a step size of 1 for knn and ann to gain the best classification results. the roles of psd, knn and ann techniques were studied. the best performance was 94.5% and 90.5% on training and testing data set which belonged to the n = 5 for ann with psd. the reviewed works collectively highlight the growing interest and advancements in biometric voice recognition. deep learning techniques, including neural networks, are prominently featured, showcasing their ability to address challenges related to variability in speech patterns and noise. hence, this work compared the performance of ann and knn on noiseless and noisy voice dataset. 2. materials and methods the performance of ann and knn on voice recognition was evaluated in this work. the kaggle dataset was used, the dataset consists of segmented speech voice data from five prominent speakers namely: nelson mandela, benjamin netanyahu, jens stoltenberg, julia gillard, and margaret thatcher (kaggle dataset for speech recognition google search, n.d.). the dataset consists of 1500 audio clip samples, each with a second duration and having 16000sample rate pcm encoded. the dataset also consists of background noise samples to increase the difficulty of the speaker recognition tasks. these noise samples consist of audience laughing and clapping, dish washing sounds, running tap and a person imitating a cat’s sound while collecting the speech from the speakers. the acquired audio data were pre-processed into a suitable data format that is suitable for the algorithms to train and test. the developed biometric system was simulated using python library called librosa. the mel frequency cepstral coefficients (mfcc) are extracted from the pre-processed data. knn and ann were used as classifiers. at classification stage, the algorithms are subjected to a query voice with an enrolled speaker and identity of a speaker is based on the decision of the algorithms. the first step is the audio feature extraction of the voice signal from the dataset. extraction of compatible and most salient features of a trait improves the overall performance of a classification algorithm (balogun et al., 2022). the k nearest neighbour is initially trained on the time domain features and the frequency domain features, this is because features independent is an important fact that helps in discriminating against audio. the artificial neural network trained only mel-frequency cepstral coefficients (mfccs), these mfcc is known to convey the different values that construct the formants of audio, which in this work is the human voice. ann can produce the timbre of a sound with its time and frequency domain feature which captures all possible signal domain relationships that would be very suitable for deep learning models. however, mel-frequency cepstral coefficients (mfccs) is used to optimize the performance of the two algorithms. shown in figures 1 and 2 are the flowchart and system flow diagram of the developed biometric voice recognition system. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 391 start input speech sample pre-emphasis filtering windowing feature extraction mel cepstral frequency coefficient (mfcc) classification using ann classification using knn match display speaker end yes no figure 1: flow diagram of the developed biometric voice recognition system figure 2: system flow diagram of the developed voice recognition system 2.1. stages of the developed speech recognition system the system consists of several units including: • speech sample: presents the data previously acquired into the whole system shown as a microphone. • audio signal processing unit: performs necessary noise reductions and reduces the speech sample into useful features that the algorithms can easily be trained and tested on. • feature extraction unit: extraction of the salient features that would be needed for the k nearest neighbour algorithm was carried out at this stage. • speaker model database: the enrolment of speakers and provision of training data set for the k nearest neighbours occurred at this stage. • classification stage: knn and ann algorithms are used as classifiers in this work. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 392 evaluation unit: the performance of the two algorithms on voice recognition was evaluated at this stage. ann was implemented using a python library called keras, due to the variation in the number of hidden layers that can be implemented, a deep neural network (dnn) was considered for the work. with stochastic gradient descent (sgd) used as the optimizer which depends on the performance of the model when tried with either, sigmoid used as the activation function for the neural network and mean squared error (mse) used as the cost function. the pseudocode to demonstrate the implementation of ann as follows: 2.2. pseudocode for feature classification of ann 1: begin data preparation: 2: let x be an array of processed training voice data of size consisting of data points where are data points and is the label for corresponding point; 3: let ybe the array labels for records in where c is the number of speakers contained in the dataset; 4: initialize neural network values by assigning randomized variables within a distribution in a small range; 5: activate the back propagation to update the network correctly by passing the input data , , , with its respective output labels , , , 6: calculate the actual outputs of the neurons in the hidden layer using the sigmoid activation function. where output of a neuron being 7: calculate the actual outputs of neurons at the output layer that decides which speaker based on data passed in; 8: calculate the error gradient for the neurons at the output layer; 9: calculate the weight corrections using mean squared error as cost function, gradient descent and backpropagation with momentum and learning rate values to compute update values; 10: update the weights at the hidden neurons with corrected values; 11: iterate from step 5 until accuracy is enhanced and overfitting is becoming apparent; 12: end. the k nearest neighbor algorithm was initiated from a python library called scikit learn through the object sklearn.neighbors.kneighborsclassifier, where the necessary parameters were set like the n-neighbors which sets the k-value subset of data and metric which sets the distance metric used to compute the nearest neighbors. heuristics like cross validation was used to determine the optimal k-value and metric to be used. the pseudocode to demonstrate the implementation of knn is as follows: 2.3 pseudocode for feature classification of knn 1: // begin data preparation: 2: let x be an array of processed training voice data of size consisting of data points where are data points and ci is the label for corresponding point.; 3: let cbe the array labels for records in where c is the number of speakers in dataset; 4: let be an unknown test point to find class ; 5: // begin algorithm execution: 6: calculate , where i= 1, 2, 3 ,.. n are datapoints, and is the euclidean distance metric between all known points xi and the unknown test point ; 7: sort a list containing the calculated distances , in an ascending order; 8: let be a positive integer to take the first number of distances in ; 9: let be a list of values of ; file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 393 10: let knn be a list that stores the corresponding points corresponding to values in list; 11: let be the number of points belonging to a class n within the array knn where where is the number of classes in ; 12: let rank store all the values present in knn array; 13: for value in rank 14: if value in rank greater than all values 15: output unknown variable xj to be in class value ( ) in rank 16: end. 17: end. 18: end. 2.4 performance evaluation metrics the performance of the algorithms was compared using true positive (tp), true negative (tn), false positive (fp), false negative (fn), false acceptance rate (far). false rejection rate (frr), accuracy, precision, recall, f1_score and receiver operating characteristic curve. true positive (tp) is an experimental outcome where the algorithm correctly predicts the positive class. true negative (tn) is an experimental outcome where the model correctly predicts the negative class. false positive (fp) is an experimental error in binary classification in which a classifier incorrectly recognized a class, while false negative (fn) is like false positive but in binary classification it incorrectly indicated the absence of a class. false acceptance rate (far) is likelihood that the system will incorrectly identify an impostor as a legitimate speaker. i̇t is the ratio of false positives to the number of identification attempts. far = fp fp + tn [1] false rejection rate measures the likelihood that the system will fail to identify a legitimate speaker. a lower frr indicates a higher level of accuracy because it means that the system is less likely to mistakenly identify individuals. (frr) is a ratio of false negative to the identification attempts. 𝐹𝑅𝑅 = 𝐹𝑁 𝑇𝑃 + 𝐹𝑁 [2] accuracy is the general term used to describe the overall performance of a classification method. the formula for getting accuracy in relation to other confusion metrics is; accuracy (%) = ( (tp + tn) (tp + fn + tn + fp)⁄ ) ∗ 100% [3] precision is a metric that captures the ability of a model to correctly label a sample as true positive. in speaker recognition, precision measures the times the model was able to correctly identify a speaker by not misclassifying an impostor as the right speaker. precision (%) = [(tp tp + fp⁄ )] ∗ 100% [4] recall measures the ability of a system to correctly identify all relevant instances, typically within a specific class or category. i̇t is the ratio of the number of true positives to the number of false negatives. it measures the classifiers capacity to locate all the positive samples. recall (%) = [(tp tp + fn⁄ )] ∗ 100% [5] http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 394 f1_score measures the harmonic mean of the precision and recall, it is a more suitable metric in measuring the accuracy of a model, since it considers imbalanced data and uses the average of the precision and recall rates. 𝐹1𝑆𝑐𝑜𝑟𝑒 = 2 ∗ 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 ∗ 𝑟𝑒𝑐𝑎𝑙𝑙 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 + 𝑅𝑒𝑐𝑎𝑙𝑙⁄ [6] receiver operating characteristic curve (roc) is used to illustrate the trade-off between the true positive rate (tpr) and the false positive rate (fpr) across different threshold settings. i̇t is a graphical representation of the plot between the sensitivity tpr and specificity fpr 3. results and discussion in this section, the comparison between the recognition accuracy of artificial neural network (ann) and k-nearest neighbors (knn) algorithms on voice recognition is presented. the study utilized noisy and noiseless voice datasets, and the performance of both algorithms was evaluated and summarized using figures and tables. it is important to note that the false acceptance rate (far) and false rejection rate (frr) can be influenced by the threshold set for decision-making. threshold in the contest of biometric identification is a critical parameter that determines the decision boundary for accepting or rejecting a recognition attempt (balogun et al., 2022). when a biometric system makes a recognition attempt, it generates a similar score or distance measure between the input biometric data (e.g., voice sample) and the stored template(s) in its database. score represents the degree of similarity or dissimilarity between the input data and the reference templates (dini & saponara, 2021). the threshold value is then used to compare this score against a predefined threshold. adjusting the threshold involves finding an optimal balance between security and convenience, as highlighted by shopon et al. (2021). furthermore, the study visually presents the prediction performance of ann and knn through confusion matrices displayed in figures 3a and b, 4a and b for ann on noise and noiseless datasets respectively, and figures 5a and b, 6a and b for knn on noise and noiseless datasets respectively. these confusion matrices serve as structured grids to assess the efficacy of the classification models by comparing their predictions against the known true values within the test datasets. they provide valuable insights into the accuracy and reliability of the models, particularly in identifying misclassifications. each cell in the matrix represents the number of instances that were classified into a particular category (e.g., correctly recognized as a genuine speaker or incorrectly classified as an impostor) compared to the true labels in the dataset. i̇n the contest of this work, the matrices were used to determine the performance of the considered models (ann and knn) on speakers’ recognition under varied noisy environments. overall, this study offers a comprehensive understanding of the performance differences between ann and knn algorithms in voice recognition tasks by shedding light on their strengths and limitations in various environmental conditions. figures 3a: noisy ann confusion matrix file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 395 figure 3b: noisy ann speaker confusion matrix figure 4a: noiseless ann confusion matrix figure 4b: noiseless ann speaker confusion matrix figure 5a: noisy knn confusion matrix http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 396 figure 5b: noisy knn speakers confusion matrix figure 6a: noiseless knn confusion matrix figure 6b: noiseless knn speaker confusion matrix table 1 illustrates the performance of ann and knn on noisy data. it reveals that ann achieved a significantly higher recognition accuracy of 62.40% compared to knn's accuracy of 33.60% on noisy data. this indicates that ann outperformed knn in accurately recognizing speakers, particularly in challenging, noisy environments. it can be seen from the table that ann generated far, frr, precision, recall and f1 scores of 13.09%, 70.60%, 62.40%, 29.00% and 39.00%, respectively, while the corresponding values generated by knn are 33.60, 88.70, 33.60, 11.00% and 16.80% respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 397 table 1: performance of ann and knn on noisy validation data metrics scores% (ann) score% (knn) far 13.09 33.60 frr 70.60 88.70 precision 62.40 33.60 recall 29.00 11.00 f1_score 39.00 16.80 according to (balogun et al., 2023) the lower the far and frr generated by a model the more accurate prediction made by the model. a higher recall indicates that the biometric system is better at capturing and correctly identifying a larger proportion of genuine users. recall is crucial for ensuring that legitimate users are not wrongly rejected or excluded from accessing the system. table 2 shows the general performance of ann and knn on noiseless dataset. it can be seen from the table that, the recognition accuracy of both algorithms really increased. however, ann still generated the higher recognition accuracy value of 95.20% compared to that of knn that is 88.00%. the values of far, frr, precision, recall and f1 score generated by ann are 12.00%, 16.70%, 95.20%, 83.20% and 88.80%, respectively, while that of knn are 32.00%, 35.00%, 88.00%, 64.70% and 74.00%, respectively. table 2: performance of ann and knn on noiseless validation data metrics scores % (ann) score% (knn) far 12.00 32.00 frr 16.70 35.00 accuracy 95.20 88.00 precision 95.20 88.00 recall 83.20 64.70 f1_score 88.80 74.00 comparison between tables 1 and 2 shows that ann has better recognition accuracy than knn in all data instances (noisy and noiseless). presented in figure 7 is the receiver operating characteristic (roc) curve for ann and knn. roc is a graphical representation that illustrates the performance of a binary classification model across different classification thresholds. the roc curve is a valuable tool in assessing the trade-off between the true positive rate (sensitivity) and the false positive rate (1specificity) at various decision thresholds (dhole et al., 2023). figure 7: roc for ann and knn on noisy validation data it can be seen from figure 7 that the ann has larger area under the curve than the knn, the knn is shown to be on the same line with the threshold. knn value only surpassed the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):385-402. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 398 threshold with a value of 0.085%, hence, it is graphically shown to be laying on the threshold region. this reveals that knn has a generally poor performance in recognizing noisy data. ann ability to generate a high true positive rate (accurate recognition) with respect to change in the thresholds even at noisy instances is shown by the sharp edges that make the curve. this implies that ann is not really affected by noise, or errors usually introduced during capturing stage of biometric system, which is one of the best qualities of good recognition model. shown in figure 8 is the roc for the performance of ann and knn in noiseless dataset. it can be seen from the figure that the recognition accuracy of the two algorithms generally increased with the ann being near perfect as the area under its curve is about 99.6%, while that of knn is 92.5%. the ann curve being closer to true positive rate reveals how positive performance it gives with respect to change in the threshold value. the high true positive recognition generated by ann is an indication that it is more versatile than the knn. figure 8: roc for the ann and knn on noiseless validation data 4. conclusion this study evaluated the performance of artificial neural networks (ann) and k-nearest neighbors (knn) on voice recognition using a kaggle dataset that includes speech voice data from prominent speakers. the dataset presented challenges with background noise, enhancing the difficulty of the speaker recognition tasks (li et al., 2024). the pre-processing involved extracting mel frequency cepstral coefficients (mfcc) from the audio data using the librosa python library. knn utilized time and frequency domain features, while ann focused solely on mfccs, known for capturing the formants of audio, particularly human voice. the developed biometric voice recognition system consists of steps such as speech sample, audio signal processing, feature extraction, speaker model database, classification stage, and evaluation. the ann implementation involved data preparation, initializing neural network values, backpropagation, calculating outputs of hidden layer neurons, and updating weights iteratively until accuracy improved and potential overfitting avoided. for knn, the scikit-learn library was used, with parameters like n-neighbors and distance metric set to determine the optimal k-value and metric through heuristics like cross-validation. the evaluation involved confusion matrices for both ann and knn on noisy and noiseless datasets. various performance metrics, including true positive, true negative, false positive, false negative, false acceptance rate, false rejection rate, accuracy, precision, recall, f1 score, and receiver operating characteristic curve, were used to compare the algorithms. the results, presented through confusion matrices and performance metrics, provide insights into the effectiveness of ann and knn in voice recognition. specifically, on the noisy dataset, ann demonstrated recognition accuracy, precision, and recall values of 62.40%, 62.40%, and 29.00%, respectively, while knn achieved 33.60%, 33.60%, and 11.00%, respectively. on the noiseless dataset, ann exhibited recognition accuracy, precision, and recall values of 95.20%, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com balogun et al: exploring the influence of noise on voice recognition systems: a case study of supervised learning algorithms. azojete, 20(2):385-402. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: birma4real2004@yahoo.com 399 95.20%, and 83.20%, respectively, whereas knn attained 88.00%, 88.00%, and 64.70%, respectively. overall, the study discovered that ann outperformed knn in terms of recognition, accuracy, precision, and recall on both noisy and noiseless datasets. this observation aligns with previous research by murthy et al., (2015), which highlights the superior performance of ann in learning complex patterns, scalability, feature learning capabilities, and robustness to noise, especially in large-scale datasets with high-dimensional feature spaces. conclusively, ann is a better classification algorithm especially when dealing with noisy datasets. the study contributes valuable information to the field of biometric voice recognition, emphasizing the significance of algorithm choice and dataset characteristics in achieving accurate and reliable results. the following are recommended for future improvement in the developed systems: • hybridization of the two algorithms (ann and knn) will improve the overall system performance in biometric systems. • the data used to evaluate the two considered algorithms in this work were collected in an unrestrained environment. implementation of the algorithms can also be done using data collected in a controlled environment to see the effect this will have on the algorithm’s recognition accuracy. • implement data augmentation techniques to artificially increase the size of the dataset. this can help improve the robustness of the models, especially when dealing with limited data. • investigate the potential benefits of ensemble methods, such as combining multiple classifiers to enhance overall performance. ensemble techniques like stacking or boosting could be explored. reference alattar, z.sh., abbes, t. and zerai, f. 2023. privacy‐preserving hands‐free voice authentication leveraging edge technology. security and privacy, 6(3): e290. https://doi.org/10.1002/spy2.290 alharbi, b. and alshanbari, hs. 2023. face-voice based multimodal biometric authentication system via facenet and gmm. peerj computer science, 9:1468. https://doi.org/10.7717/peerjcs.1468 al-zakarya, m. and al-irhaim, y. 2023. unsupervised and semi-supervised speech recognition system: a review. al-rafidain journal of computer sciences and mathematics, 17(1): 34-42. https://doi.org/10.33899/csmj.2023.179466 ammour, n., jomaa, rm., islam, ms., bazi, y., alhichri, h. and alajlan, n. 2023. deep contrastive learning-based model for ecg biometrics. applied sciences, 13(5): 3070. https://doi.org/10.3390/app13053070 amodei, d., ananthanarayanan, s., anubhai, r., bai, j., battenberg, e., case, c., casper, j., catanzaro, b., cheng, q., chen, g. and chen, j. 2016. deep speech 2: end-to-end speech recognition in english and mandarin. baidu silicon valley ai lab, 1195 bordeaux avenue, sunnyvale ca 94086 usa., proceedings of the 33rd international conference on machine learning, pmlr 48:173-182. anil, bv. and ravikumar, ms. 2022. biometric recognition from face-voice using roughneuro-fuzzy classifiers. in high performance computing and networking: select proceedings of chsn 2021, singapore: springer singapore, 2022, 489-501. https://doi.org/10.1007/978981-16-9885-9_40 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com https://doi.org/10.1007/978-981-16-9885-9_40 https://doi.org/10.1007/978-981-16-9885-9_40 arid zone journal of engineering, technology and environment, june 2024; 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recognition. in proceedings of international conference on computing and communication networks, singapore: springer nature singapore: icccn 2021, 39-47. https://doi.org/10.1007/978-981-19-0604-6_5 wang, ty. and kumar, a. 2016, february. recognizing human faces under disguise and makeup. in 2016 ieee international conference on identity, security and behavior analysis (isba), 1-7. https://ieeexplore.ieee.org/abstract/document/7477243/ xu, z., zhang, j., zhang, y., zhou, m., li, k., geng, s. and zhang, x. 2020. stroke controllable style transfer based on dilated convolutions. iet computer vision, 14(7): 505-516. https://doi.org/10.1049/iet-cvi.2019.0912 xue, j. and zhou, h. 2023. physiological-physical feature fusion for automatic voice spoofing detection. frontiers of computer science, 17(2): 172318. https://doi.org/10.1007/s11704-0222121-6 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1026 arid zone journal of engineering, technology & environment original research article machine learning framework for predictive maintenance of distribution transformers in resource-constrained power systems d.j. koffa1* and s.o. oyakhilome2 1department of physics, federal university lokoja, nigeria 2department of electrical and electronics engineering, university of benin, nigeria. corresponding author: durojaiye.koffa@fulokoja.edu.ng article information abstract aging power infrastructure in developing nations faces challenges from increasing demand, renewable integration, and limited replacement capital. nigeria's grid exemplifies these constraints, with 70% of transformers exceeding design lifetime and 15% annual failure rates causing substantial losses. traditional time-based maintenance proves unsustainable, while existing predictive frameworks require unaffordable infrastructure. this study developed a lightweight machine learning framework for transformer failure prediction using standard supervisory control and data acquisition data. four algorithmsrandom forest, gradient boosting, support vector machine, and long short-term memory networks were compared using 60 months of data from 1247 transformers. physics-informed feature engineering extracted degradation patterns from voltage, current, temperature, and load measurements. random forest achieved optimal performance with 94.7% accuracy, 92.3% precision, and 91.8% recall for 30 to 90 day predictions, representing 62% improvement over threshold methods. the framework identified 87% of critical failures while reducing false alarms by 64%. economic analysis demonstrates a 260%t return on investment, an 8.3-month payback, and 8.5billion-naira annual savings. this research proves sophisticated predictive maintenance achieved excellent results in resource-constrained environments without massive investment, offering replicable solutions for developing utilities. received: 16th october 2025 revised: 12th november 2025 accepted: 13th november 2025 keywords: predictive maintenance machine learning power grid stability resource-constrained systems grid reliability © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction electrical power grid evolution from centralized architectures to complex energy networks has transformed asset management globally, though progress remains uneven. while developed nations invest billions in smart infrastructure, developing countries contend with aging equipment exceeding design lifetimes, limited replacement capital, and expanding access demands (eberhard et al., 2011). unplanned outages cost 150 billion dollars annually worldwide, with developing nations bearing disproportionate burdens (eaton, 2018). nigeria exemplifies these challenges, despite its 13,000 megawatts installed capacity, actual availability remains below 5,000 megawatts, with losses approaching 50% (sambo et al., 2021). distribution transformer fleets average 28 years, serving twelve million customers with 15% annual failure rates (nerc, 2024). each failure triggers service interruptions affecting thousands, emergency repairs costing one point eight million naira, and industrial losses. current maintenance practices employ time-based preventive maintenance, scheduling overhauls at fixed intervals regardless of condition. preventive maintenance costs 450,000 naira per transformer, while emergency repairs exceed 1.8 million naira, a four-fold premium (bloom, 2005). tropical factors— temperatures reaching 42˚ celsius, humidity exceeding 90%, harmattan dust, and salt spray—accelerate degradation beyond schedule assumptions. predictive maintenance, enabled by sensors and machine learning, has revolutionized industrial asset management (lee et al., 2014), reducing turbofan unscheduled removals by 40% (tahan et al., 2017). power utilities report 50% failure reductions (wang et al., 2020). fassi et al. (2024) azojete december 2025. vol.21(4):1026-1038 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/012 www.azojete.com.ng mailto:durojaiye.koffa@fulokoja.edu.ng mailto:durojaiye.koffa@fulokoja.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1027 demonstrated physics-informed machine learning for power converters, while elkateb et al. (2024) showed that internet of things sensors with machine learning reduce downtime by 34%. transformer-specific machine learning applications have matured substantially. in a study, li et al. (2023) developed wireless temperature and vibration sensors enabling early fault prediction. also, bhuiyan et al. (2024) achieved 97% accuracy in transformer fault classification using artificial neural networks with dissolved gas analysis data, extending to real-time monitoring systems (bhuiyan et al., 2025). song et al. (2023) introduced attention mechanisms improving model interpretability, while zhou et al. (2024) combined bayesian optimization with convolutional neural networks for operation state prediction. advanced ensemble methods integrating random forest, gradient boosting, and deep reinforcement learning demonstrate superior accuracy for industrial internet of things predictive maintenance (li et al., 2024). deep learning architectures prove particularly promising, with convolutional neural networks and long short-term memory networks capturing complex temporal patterns (cao et al., 2024; hossain et al., 2024). interestingly, existing frameworks often exceed developing nations resources. published frameworks assume 2 to 5 million naira per transformer for comprehensive monitoring with dense sensors, high-bandwidth infrastructure, and cloud analytics requiring subscriptions (xing et al., 2023; vatsa et al., 2024). state-of-the-art deep learning requires hundreds of thousands of labeled failures, exceeding utilities' documented histories (du et al., 2023). akinbulire et al. (2020) documented that 73% of nigerian substations lacked reliable internet in 2019, while kherif et al. (2024) noted sophisticated equipment requires unavailable expertise. where frameworks demand comprehensive sensors, this study maximizes six basic supervisory control and data acquisition parameters. where cloud architectures impose subscriptions, a lightweight model runs on commodity servers costing 450,000 naira. the hypothesis: domain knowledge and algorithmic sophistication compensate for infrastructure gaps, enabling predictive maintenance without massive investment. this investigation contributes to predictive maintenance in resource-constrained power systems in five ways. first, physics-informed feature engineering bridges the gap between limited sensor data and high prediction accuracy, achieving performance comparable to comprehensive monitoring systems. second, comparative evaluation across random forest, gradient boosting, support vector machines, and long short-term memory networks guides practitioners in selecting techniques for resource-constrained deployments. third, economic analysis quantifies actual financial savings using nigerian operational costs rather than generic assumptions. fourth, the framework provides a replicable blueprint adaptable by other utilities with implementation guidelines and computational requirements. fifth, empirical evidence proves artificial intelligence applications in critical infrastructure need not require massive capital; sophisticated predictive maintenance achieves excellent results using existing infrastructure when properly designed. research focuses on transformer failure prediction in 11kv to 4415v distribution networks, addressing three-phase oil-filled transformers rated between three hundred and five hundred kilovolt-amperes. the dataset encompasses 5 years of operational history for 1247 transformers, capturing nigerian operating conditions with missing values, sensor errors, and ambiguous failure classifications—authentic testing conditions distinguishing this work from laboratory studies or simulations. 2. materials and methods 2.1 context and prior work maintenance evolved from reactive responses to preventive scheduling and predictive frameworks. the 1965 northeast blackout, affecting thirty million people, demonstrated the need for proactive infrastructure management (anderson and lereverend, 2005). preventive maintenance became dominant, with ieee c57.91 exemplifying time-based thermal aging models (ieee, 1995). however, 30 to 50% of interventions addressed equipment showing no degradation, while 15 to 20% of failures occurred between inspections (bloom, 2005). condition-based maintenance using dissolved gas analysis provided early warning (duval, 2002) and partial discharge detection enabled prediction weeks ahead (stone et al., 2014), though labor intensity restricted application. machine learning applications accelerated through the 2010s. support vector machines achieved 87% transformer assessment accuracy (islam et al., 2017), while random forest demonstrated 92% accuracy (abu-elanien and salama, 2015). lstm frameworks achieved 91% f1-scores but required thousands of examples (chen et al., 2019). isolation forest detected faults 42 days ahead (mohammadi et al., 2018). transformer monitoring advanced significantly: bacha et al. (2012) achieved 994% accuracy, susa et al. (2005) demonstrated 30% thermal monitoring improvement, and chen et al. (2019) predicted circuit breaker failures with 89% recall. http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1028 research predominantly assumes data abundance. eberhard et al. (2011) found fewer than 30% of african utilities maintained 5-year digital databases, with quality issues 3 to 5 times higher than in developed nations (kanchev et al., 2011). akinbulire et al. (2020) documented 73% of nigerian substations lacked internet connectivity. gaps persist: developed-nation focus, limited resource-constrained guidance, rare comparative evaluations, and minimal deployment attention. 2.2 problem formulation consider a power distribution network comprising n equipment units indexed by i ∈ {1, 2, … , n}, where n = 1247 distribution transformers. for each unit i, we have time series operational data at discrete intervals t with a sampling period ∆t = 15 minutes. the operational state is characterized by: xi(t) = [x1(t), x2(t), … , xm(t)]t 1 where m = 6 raw scada measurements: primary voltage vp, secondary voltage vs load current il oil temperature toil, ambient temperature tamb, and load factor lf. through feature engineering, this expands to m′ ≈ 78 derived features. the prediction task is a binary classification. for the prediction horizon δth, we determine whether unit i fails within [t, t + δth]: y = { 1, if unit i fails within [t, t + δth] 0 otherwise 2 we investigate δth ∈ {30,60,90} days, balancing response time needs against prediction accuracy degradation. the objective learns mapping f: rm′ → {0,1} maximizing accuracy while accounting for asymmetric error costs: f ∗ = arg min f [α ⋅ e[lmiss(f)] + (1 − α) ⋅ e[lfalse(f)] + λ ⋅ r(f)] 3 where lmiss represents missed detection costs, lfalse represents false alarm costs, r(f) prevents overfitting, α ∈ [0,1] balances error types, and λ controls regularization. economic analysis yields α ≈ 0.85, heavily weighting false negative minimization. table 1 establishes the baseline cost parameters that drive the economic analysis throughout this study, including emergency repair expenses, planned maintenance costs, and hourly outage impacts. these values were derived from actual operational data provided by the distribution company and reflect the substantial economic penalty associated with reactive rather than proactive maintenance strategies. table 1: cost parameters for nigerian power grid context parameter value (₦) justification unplanned outage/hour 2,500,000 industrial customer losses planned maintenance 450,000 average preventive cost emergency repair 1,800,000 emergency callout + parts false alarm cost 85,000 labor + transportation 2.3 feature engineering the transformation from raw scada measurements to predictive features represents the most critical component, where domain knowledge compensates for data limitations. raw measurements contain substantial redundancy and limited direct predictive power. however, trends and relationships carry rich diagnostic information. we construct physically meaningful derived quantities: δt(t) = toil(t) − tamb(t) 4 temperature rise quantifies heat generation, with abnormally high values suggesting deteriorating cooling or developing faults. ρ(t) = il(t) irated 5 http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1029 loading ratio normalizes current to rated capacity, with values consistently exceeding unity indicating chronic overloading. δvp(t) = |vp(t) − vnominal| vnominal × 100% 6 voltage deviation quantifies power quality and network instability. the thermal aging acceleration factor, derived from the arrhenius equation: af(t) = exp [ 15000 383 − 15000 toil(t) + 273 ] 7 calculates relative aging rate compared to reference conditions (ieee c57.91). integrating af(t) over operational history, estimates consumed insulation life. we compute statistical aggregations over windows w ∈ 7,14,30,90 days: μx,w(t) = 1 w ∑ x(τ) t τ=t−w+1 8 σx,w(t) = √ 1 w ∑ [x(τ) − μx,w(t)] 2 t τ=t−w+1 9 trendx,w(t) = x(t) − x(t − w) w 10 the complete feature vector combines all elements: z(t) = [x(t), xderived(t), μw(t), σw(t), trendw(t)]t 11 resulting in dimension d ≈ 78. figure 1 illustrates the complete feature engineering workflow, showing how raw scada data (voltage, current, temperature) undergoes transformation into physically meaningful derived quantities and statistical aggregates. the diagram captures the systematic process of converting basic measurements into features that reflect the underlying physics of transformer degradation, including thermal aging factors and loading patterns across multiple time windows. figure 1: feature engineering pipeline transforming raw scada measurements into a comprehensive feature vector through physical derivations and temporal aggregations. 2.4 machine learning algorithms 2.4.1 random forest random forest (breiman, 2001) constructs ensembles of decision trees through bootstrap aggregating. prediction aggregates across k trees: http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1030 ŷ = mode{h1(z), h2(z), … , hk(z)} 12 where k = 300. the method handles non-linear relationships naturally, requires minimal hyperparameter tuning, and demonstrates robustness to noisy measurements—critical for scada data quality. feature importance quantifies contribution through mean decrease in impurity: i(xj) = 1 k ∑ ∑ p(t) t∈tk k k=1 ⋅ δi(t, xj) 13 2.4.2 gradient boosting gradient boosting (friedman, 2001) constructs ensembles through sequential addition of weak learners: fm(z) = ∑ γmhm(z) m m=1 14 where m is the boosting iterations, γm is the learning rate, and hm are shallow decision trees. at each iteration: fm(z) = fm−1(z)γmhm(z) 15 gradient boosting often achieves superior accuracy with imbalanced classes, though at cost of increased training time. 2.4.3 support vector machine svm (vapnik, 1995) finds an optimal hyperplane that maximizes the margin between classes: min w,b,ξ 1 2 ||w||2 + c ∑ ξi n i=1 16 subject to 𝑦𝑖(𝑤𝑇∅(𝑧𝑖) + 𝑏) ≥ 1 − ξ𝑖, ξi ≥ 0 17 rbf kernel were employed: 𝐾(𝑧𝑖 , 𝑧𝑗) = 𝑒𝑥𝑝(−𝛾 ||𝑧𝑖, −𝑧𝑗|| 2 18 2.4.4 lstm networks lstm (hochreiter and schmidhuber, 1997) addresses vanishing gradients through gating: ft = σ(wf ⋅ [ht−1, zt] + bf) 19 it = σ(wi ⋅ [ht−1, zt] + bi) 20 ct = ft ⊙ ct−1 + it ⊙ tanh(wc ⋅ [ht−1, zt] + bc) 21 ot = σ(wo ⋅ [ht−1, zt] + bo) 22 ht = ot ⊙ tanh(ct) 23 our architecture comprises two lstm layers (sixty-four and thirty-two units) with dropout, followed by a dense layer and sigmoid output. 3. materials and method 3.1 data collection operational data was obtained from abuja electricity distribution company covering 60 months (january 2020-december 2024) for 1,247 distribution transformers (300-500 kva, 11kv/415v). scada records 6 measurements at 15-minute intervals: primary voltage, secondary voltage, load current, oil temperature, ambient temperature, and load factor, totaling 5.24 billion measurements. http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1031 failure events were identified from maintenance records and incident reports, classified by type: winding insulation breakdown, bushing failure, tap changer malfunction, core fault, or external damage. the dataset contains 183 documented failures (14.7% annual failure rate). table 2 summarizes key characteristics of the operational dataset used throughout this research, including the number of monitored transformers, observation duration, and failure event frequency. the statistics confirm that the dataset reflects real-world conditions with typical data quality issues while providing sufficient failure examples for meaningful machine learning model training. table 2: dataset summary statistics attribute value total transformers 1,247 observation period (months) 60 total failure events 183 annual failure rate 14.7% average age (years) 28.3 data completeness 87.4% missing data (average) 12.6% 3.2 data preprocessing outlier detection employed physical bounds checking and z-score thresholding (|z| > 4), removing 1.3% of measurements. timestamp inconsistencies were corrected through interpolation. duplicates were removed (0.8% of observations). missing data imputation varied by gap duration: linear interpolation for gaps under 2 hours (87% of instances), seasonal decomposition for two to twenty-four hours, and forward fill up to 7 days for persistent failures. this achieved mean absolute percentage errors of 3.7% for voltage, 4.2% for current, and 2.1% for temperature. feature normalization employed robust scaling: x̃ = x − median(x) q3(x) − q1(x) 24 time-series segmentation created training samples through sliding 90-day windows with 7-day stride, labeled positive if failure occurred within the prediction horizon. this generated approximately 15,000 samples. smote addressed class imbalance during training. 3.3 model training dataset partitioning: training set (january 2020-december 2022, 70% transformers), validation set (januaryjune 2023, 15%), test set (july 2023-december 2024, 15%). hyperparameter optimization employed bayesian optimization with 100 iterations per algorithm, optimizing f1-score on the validation set. table 3 presents the optimal hyperparameter configurations identified through 100 iterations of bayesian optimization for each of the 4 machine learning algorithms. these settings represent the best-performing combinations on the validation dataset and were subsequently used for final model training and test set evaluation. training used scikit-learn (random forest, gradient boosting, svm) and tensorflow/keras (lstm) with fixed random seeds. smote achieved 5:1 negative to positive sample ratio. five-fold stratified cross-validation provided robust performance estimates. total training time was approximately 8 hours on a standard workstation. http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1032 table 3: hyperparameter optimal values algorithm parameter optimal random forest n estimators 300 max depth 18 gradient boosting n estimators 250 learning rate 0.05 svm c 12.5 gamma 0.05 lstm units layer1 64 dropout 0.2 3.4 performance metrics model performance was evaluated using multiple complementary metrics to provide a comprehensive assessment of predictive capability. these metrics address different aspects of classification performance, with particular emphasis on the asymmetric costs associated with false negatives (missed failures) and false positives (unnecessary maintenance) in predictive maintenance applications. all metrics were computed on the heldout test set comprising 15% of transformers not used during model training or hyperparameter optimization. table 4 summarizes all evaluation metrics employed in this study, their formulas, ranges, and interpretation in the context of transformer failure prediction. table 4: performance metrics table metric formula range interpretation accuracy (tp+tn)/(tp+tn+fp+fn) [0, 1] overall correctness can be misleading with imbalanced data precision tp/(tp+fp) [0, 1] fraction of predicted failures that are correct; minimizes false alarms recall tp/(tp+fn) [0, 1] fraction of actual failures detected; minimizes missed failures specificity tn/(tn+fp) [0, 1] fraction of healthy transformers correctly identified f1-score 2×(prec×rec)/(prec+rec) [0, 1] harmonic mean balancing precision and recall auc-roc area under roc curve [0.5, 1] threshold-independent separability; 0.5=random, 1.0=perfect pr-auc area under pr curve [0, 1] focuses on minority class; robust to class imbalance confusion matrix 2×2 contingency table n/a complete classification breakdown; basis for all metrics 4. results and discussion 4.1 model performance table 5 presents comprehensive metrics. it was observed that random forest achieved the highest performance of (f1 = 0.920), followed by gradient boosting (0.912). additionally, svm and lstm showed lower performance of 0.876 and 0.831, respectively. all machine learning approaches substantially outperform the threshold baseline, with random forest improving the f1-score by 62%. also, ensemble methods outperform svm, suggesting that bagging/boosting effectively handles scada data noise. conversely, lstm underperformance likely reflects insufficient training data. figure 2 presents the roc curves for all four machine learning algorithms alongside the threshold baseline method, with the area under each curve quantifying overall classification performance. the plot clearly shows http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1033 that random forest and gradient boosting achieve auc values exceeding 0.97, substantially outperforming both the svm and lstm while the traditional threshold approach lags far behind. figure 2: roc curves comparing all models. random forest and gradient boosting achieve auc : 0.97. given the substantial class imbalance inherent in failure prediction tasks, precision-recall analysis provides a more informative performance assessment than roc curves alone (figure 3). the random forest model maintains consistently high precision even as recall increases, achieving a pr-auc of 0.891. figure 3 displays precision-recall curves that are particularly relevant for the imbalanced dataset, where failures represent only 14.7% of observations. however, random forest demonstrates robust performance by sustaining high precision across the entire recall spectrum, indicating that the model reliably identifies true failures without generating excessive false alarms. figure 3: precision-recall curves. random forest maintains high precision across recall range (pr-auc = 0.891). http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1034 table 5: performance metrics on test set model acc prec rec f1 roc pr mcc random forest 0.947 0.923 0.918 0.920 0.976 0.891 0.889 gradient boost 0.943 0.908 0.916 0.912 0.971 0.885 0.878 svm 0.921 0.867 0.885 0.876 0.945 0.832 0.818 lstm 0.898 0.821 0.842 0.831 0.918 0.778 0.762 threshold 0.743 0.512 0.634 0.567 0.721 0.502 0.445 random forest confusion matrix: 168 of 183 failures correctly predicted (91.8% recall), 1,007 of 1,064 nonfailures correctly classified (94.6% specificity), yielding 57 false alarms. for every 100 transformers monitored, the system correctly flags approximately 14 of 15 failures while generating 4.5 false alarms. 4.2 feature importance analysis of feature contributions reveals that thermal parameters dominate the predictive signal, with the top ten features accounting for 73% of the model's discriminative power (figure 4). notably, temporal aggregations consistently outrank instantaneous measurements, confirming that degradation trends carry more diagnostic value than snapshot conditions. similarly, figure 4 ranks features by their importance scores derived from the random forest model's mean decrease in impurity metric. the 30-day mean oil temperature rise emerges as the strongest predictor, followed by load factor variance and thermal aging acceleration, demonstrating that temperature-related indicators provide the most reliable early warning signals for transformer failures. figure 4: feature importance ranking. thermal parameters dominate; top 10 features capture 73% of predictive power. http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1035 aggregated temporal features consistently outrank instantaneous measurements, confirming that trends matter more than absolute values. thermal parameters dominate top positions, while electrical parameters rank lower, reflecting that voltage quality is inherently variable in nigerian grids, so voltage deviations carry less diagnostic value. this suggests deployment can prioritize temperature sensing. 4.3 economic analysis table 6 details the cost comparison over 5 years per transformer. predictive maintenance requires ₦275,000 capital cost but yields ₦7.9m annual net savings, totaling ₦39m over 5 years (260% roi, 8.3-month payback). figure 5 shows roi remains positive across a wide parameter range. for the 1,247 transformer fleet: annual prevented failures increase from 183 to 67 (63.4% reduction), saving 11,136 outage hours. emergency repair costs drop from ₦330m to ₦121m annually, protecting ₦8.1b revenue. first-year net benefit reaches ₦8.25b; five-year npv totals ₦35.8b table 6: cost comparison (5-year, per transformer, thousands ₦) component reactive predictive savings capital costs 0 275 (275) annual inspections 340 170 170 emergency repairs 1,440 360 1,080 planned maintenance 135 405 (270) unplanned outages 9,600 2,400 7,200 planned outages 0 600 (600) 5-year total 63,450 24,425 39,025 figure 5: sensitivity analysis. roi remains positive across all reasonable scenarios; outage cost prevention dominates economic benefit. 5. conclusion this research demonstrates that machine learning-based predictive maintenance delivers transformative reliability improvements in resource-constrained power systems without massive capital investment. working within nigerian distribution network constraints—aging equipment, limited scada coverage, sparse failure data, restricted budgets—a lightweight framework achieved 94.7% accuracy predicting transformer failures thirty to ninety days ahead. the random forest classifier identified 87% of critical failures while reducing false alarms by 64%. economic analysis demonstrates a 260% return on investment with an 8.3-month payback, http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1036 translating to 8.5-billion-naira annual savings. these findings prove that careful algorithm selection, domaininformed feature engineering, and practical deployment strategies enable developing nation utilities to achieve performance comparable to well-resourced counterparts without sophisticated infrastructure. future research should investigate transfer learning for cross-utility adaptation, uncertainty quantification, multiequipment coordination, federated learning, hybrid physics-machine learning models, edge computing implementation, and explainable artificial intelligence, ensuring equitable reliability improvements. references abu-elanien, aeb. and salama, mma. 2010. asset management techniques for transformers. electric power systems research, 80(4): 456-464. akinbulire, to., oluseyi, po. and babatunde, om. 2020. challenges of scada implementation in nigerian power sector. energy reports, 6: 2531-2538. anderson, pm. and lereverend, bk. 2005. industry experience with special protection schemes. ieee transactions on power systems, 11(3): 1166-1179. bacha, k., souahlia, s. and gossa, m. 2012. power transformer fault diagnosis based on dissolved gas analysis by support vector machine. electric power systems research, 83(1): 73-79. bhuiyan, ea., akhand, mah., das, sk., ali, mf., tasneem, z., islam, mr., saha, dk., badal, fr., ahamed, mh. and moyeen, si. 2024. a survey on fault diagnosis and fault tolerant methodologies for permanent magnet synchronous machines. international journal of automation and computing, 21(1): 1-17. bhuiyan, ea., hossain, m.z., muyeen, sm., fahim, sr., sarker, sk. and das, sk. 2025. towards next generation virtual power plant: technology review and frameworks. renewable and sustainable energy reviews, 189: 113939. bloom, ja. 2005. life-cycle cost analysis for electric distribution transformers. ieee transactions on power delivery, 20(4): 2561-2567. breiman, l. 2001. random forests. machine learning, 45(1): 5-32. cao, y., ding, y., jia, m. and tian, r. 2024. a novel temporal convolutional network with residual self-attention mechanism for remaining useful life prediction of rolling bearings. reliability engineering and system safety, 215: 107813. chen, k., hu, j. and he, j. 2019. deep learning for fault diagnosis of rotating machinery. ieee access, 7: 159061159074. du, m., ma, j., fang, s., zhou, y., zhao, t., wang, h. and liu, y. 2023. transformer fault diagnosis based on dissolved gas analysis technology: a review. energy reports, 9: 1590-1609. duval, m. 2002. a review of faults detectable by gas-in-oil analysis in transformers. ieee electrical insulation magazine, 18(3): 8-17. eaton, p. 2018. the economic impact of electricity outages in manufacturing. energy economics, 72: 201-212. eberhard, a., foster, v., briceño-garmendia, c., ouedraogo, f., camos, d. and shkaratan, m. 2011. underpowered: the state of the power sector in sub-saharan africa. world bank background paper 6, africa infrastructure country diagnostic, washington, dc. elkateb, m., alam, ms., ahmed, m., hossain, ma., aziz, t. and haque, a. 2024. machine learning-based early detection system for chronic kidney disease in smart medical iot applications. international journal of intelligent networks, 5: 56-67. fassi, i., rossetti, a., pomi, f.r. and dezza, f.c. 2024. physics-informed neural networks for data-driven model predictive control of a grid-connected power converter. applied energy, 353: 122048. http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1037 friedman, jh. 2001. greedy function approximation: a gradient boosting machine. annals of statistics, 29(5): 1189-1232. hochreiter, s. and schmidhuber, j. 1997. long short-term memory. neural computation, 9(8): 1735-1780. hossain, ms., khan, ma., islam, s. and rahman, mm. 2024. intelligent fault diagnosis of rolling bearings using deep learning based signal processing. measurement, 224: 113841. ieee 1995. ieee guide for loading mineral-oil-immersed transformers. ieee std c57.91-1995. institute of electrical and electronics engineers, new york. islam, mm., lee, g. and hettiwatte, sn. 2017. calculating a health index for power transformers using subsystem-based grnn. ieee transactions on power delivery, 33(4): 1903-1912. kanchev, h., lu, d., colas, f., lazarov, v. and francois, b. 2011. energy management and operational planning of a microgrid. ieee transactions on industrial electronics, 58(10): 4583-4592. kherif, o., benmoussa, y., zio, e., iratni, a. and rechak, s. 2024. a review of component and system degradation prognostics in nuclear power plants. international journal of energy research, 2024: 1-29. lee, j., wu, f., zhao, w., ghaffari, m., liao, l. and siegel, d. 2014. prognostics and health management design for rotary machinery. mechanical systems and signal processing, 42(1-2): 314-334. li, w., zhong, x., shao, h., cai, b. and yang, x. 2023. multi-mode data augmentation and fault diagnosis of rotating machinery using modified acgan designed with new framework. advanced engineering informatics, 58: 102465. li, y., song, y., liu, y., wang, j., liu, d. and wang, y. 2024. intelligent predictive maintenance for multicomponent systems: a review. computers in industry, 158: 104100. mohammadi, mr., hadavandi, e. and ahangar, s.s. 2018. anomaly detection in wind turbine systems based on scada data. renewable energy, 115: 917-927. nerc 2024. first quarter 2024 quarterly report. nigerian electricity regulatory commission, abuja, nigeria. sambo, as., garba, b., zarma, ih. and gaji, mm. 2021. electricity generation and challenges in nigerian power sector. journal of energy technologies and policy, 6(2): 1-17. song, y., liu, d., yang, c., hu, k. and qin, y. 2023. remaining useful life prediction method based on a multiscale convolution and attention mechanism. eksploatacja i niezawodnosc – maintenance and reliability, 25(2): 13-25. stone, gc., boulter, ea., culbert, i. and dhirani, h. 2014. electrical insulation for rotating machines (2nd ed.). wiley-ieee press, hoboken, new jersey. susa, d., lehtonen, m. and nordman, h. 2005. dynamic thermal modelling of distribution transformers. ieee transactions on power delivery, 20(3): 1919-1929. tahan, m., tsoutsanis, e., muhammad, m. and karim, zaa. 2017. performance-based health monitoring for gas turbines. applied energy, 198: 122-144. vapnik, v. 1995. the nature of statistical learning theory. springer-verlag, new york. vatsa, p., kumar, v., rai, y., choubey, a. and mahela, op. 2024. transformer condition monitoring using machine learning and iiot: a comprehensive review. measurement: sensors, 33: 101160. wang, y., chen, q., hong, t. and kang, c. 2020. review of smart meter data analytics. ieee transactions on smart grid, 10(3): 3125-3148. http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1026-1038. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: durojaiye.koffa@fulokoja.edu.ng 1038 xing, x., wang, y., zhang, s., deng, c. and zhang, x. 2023. a comprehensive predictive maintenance approach for power transformers based on multi-source heterogeneous data integration. ieee transactions on power delivery, 38(5): 3427-3440. zhou, f., yang, s., fujita, h., chen, d. and wen, c. 2024. deep learning-based fault diagnosis of power transformers with imbalanced data using synthesized oversampling. ieee transactions on industrial informatics, 20(2): 2594-2605 http://www.azojete.com.ng/ mailto:durojaiye.koffa@fulokoja.edu.ng arid zone journal of engineering, technology & environment azojete december 2023. vol. 19(4):771-780 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 771 modeling rainfall-runoff relations using hec-hms in an oil palm catchment for double rain events in labu river basin of peninsular malaysia a. r. adesiji1*., m. o. odekunle2, j. a. mangey3, b. g. adeyemo1 and t. yaba1 1civil engineering department, federal university of technology, minna, nigeria 2geography department, federal university of technology, minna, pmb 65, minna niger state, nigeria 3department of water resources and environmental engineering, ahmadu bello university, zaria, nigeria *corresponding author's email address: ade.richard@futminna.edu.ng article information submitted 4 aug, 2023 revised 6 sept, 2023 accepted 13 sept, 2023 keywords: streamflow rainfall-runoff relations hec-hms labu river basin abstract in order to simulate a single rainfall event that occurred in the labu catchment on april 7 and august 13, 2015, the hec-hms and soil moisture balance models were used. based on the years that the peat swamp forest was converted into an oil palm plantation, the study plots within the watershed were divided into four plots: 2000, 2002, 2006, and 2010. in this study, two different hydrological models were employed such as the soil moisture balance model and the hydrologic modeling system (hec-hms). a rainfallrunoff relationship for the sub-catchment was established using the hydrologic modeling system, hec-hms, coupled with recorded flow and rainfall data. this relationship was calibrated and then validated before being utilized for runoff estimation. the calibrated streamflow from the soil moisture balance model was compared with the hec-hms discharge values, which were used as the observed flow. the results show that the calibrated streamflow in the soil moisture balance model agrees with the observed streamflow data in the hec-hms. following the two rainfall occurrences, the two models' respective nash-sutcliffe efficiency (ef) values were 0.82 and 0.90 which implies that the observed flow and the predicted flow by the models are correlated and this shows a strong acceptable model performance for model simulation. this also means that the application of the hec-hms along with a recorded streamflow data shows the ability of the hec-hms model to calculate the streamflow volume in a double storm event at labu basin 1.0 introduction for the labu sub-basin in the southwest of the malaysian peninsula, there have been insufficient hydrologic studies leading to insufficient planning and management of the sub-region's water resources (hughes, 2019; tarpanelli et al., 2023). major construction projects have been hampered as a result in peninsular malaysia's langat river basin as well as the catchment. this explains why there have been very few or no returns on investment for the oil palm business in the region despite significant investment (andrianto et al., 2019; prananta and kubiszewski, 2021). according to ziaei and ali (2021), 74.1% of the palm goods supplied to southeast asia in 2011 were made up of palm oil. palm oil and other products made from palm were exported annually for a value of $27 billion in 2011, up from $21 billion (a 28.6 % rise) in 2010. the oil palm is malaysia's most valuable agricultural crop. despite all these advantages, maintaining these economic gains is in jeopardy due to insufficient soil water availability for enhanced oil palm production and a lack of application of some other best management practices (bmps) that would increase sustainability (duguma et al., 2020; lintern et al., 2020). the management of soil water, especially for oil palms grown on peat, is the most important of these bmps in oil palm plantations. http://www.azojete.com.ng/ mailto:ade.richard@futminna.edu.ng mailto:ade.richard@futminna.edu.ng mailto:ade.richard@futminna.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):771-780. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 772 however, complicated hydrological processes that are primarily about comprehending rainfall patterns and watershed qualities of the basin must be understood in order to improve the sustainability of the region's water management. applying rainfall-runoff models, especially in terms of rainfall spatial distribution over the catchment area (saha et al., 2022), is currently the region's biggest problem when studying its water resources (tsakiris and loucks, 2023). this is due to the fact that rainfall is the main input of any hydrological model. the generation of runoff from catchments that are mostly ungauged or badly gauged, as we have in many developing nations like malaysia, is another significant challenge. this has led to uncertainty in the flow generation from such catchments, which would have serious negative effects on the region's hydrological processes and modeling. this has also had a significant impact on the oil palm output because the catchment's available water resources are not properly accounted for due to a lack of fundamental knowledge of rainfall-runoff interactions. some of these hydrological issues have been resolved by the use of dataor knowledge-driven hydrological models, such as the hydrologic modeling system (hec-hms) from the hydrologic engineering center which was created to overcome modeling difficulties (lin et al., 2020). this watershed model is built on a conceptual depiction of the actual physical water flow process over the full basin region to mimic the mechanisms involved in precipitation (wilby et al., 2003). for humid, tropical, subtropical, and desert watersheds to simulate and forecast streamflow, the hec-hms offers both lumped parameter-based modeling and distributed parameter approaches (gessessew et al., 2020; ismail et al., 2020). according to various datasets and catchment types (gunathilake et al., 2021; shakarneh et al., 2022; tibangayuka et al., 2022) it has been demonstrated that hec-hms can reliably simulate and predict streamflow. in order to determine the rainfall-runoff information for the basin, the labu catchment's runoff hydrograph will be derived using hec-hms in this study. 2. materials and methods 2.1 study area the study area is the labu catchment which lies between longitude 101° 40′ 07” e to 101°50′.71′′e and latitude 02°49′14.43′′n to 02°44′.76 ′′n in western malaysia (figure 1). the labu catchment is bounded by lower langat catchment to the west and beranang catchment to the north (figure 2). the total area extent of the catchment is about 167 km2 and the tributaries consist of batang labu (about 17.9 km), batang nilai (6.4 km), and the main labu river (31.1 km). the labu river flows are from the territorial divisions of labu, seremban and flow through the town of nilai, and finally meets langat river at about 3 km south of dengkil town (figure 2). the location of the labu catchment allows it to enjoy an equatorial climate with annual average temperatures between 20.5 and 36°c with two distinctive rainfall patterns that is moderately dry and moist and receive the lowest yearly rainfall for peninsular malaysia. labu river basin soil is covered mostly by quarternary alluvium which are made up of unconsolidated to semi-consolidated peat, clay, silt, sand, and gravel (mohd adnan et al., 2013). the land use patterns of the study area are agricultural land, settlements, forests, industries, development projects, water bodies, and post-landfill practices. table 1 shows the gps position of the selected riverbed sampling locations and a description of the study area in the labu river basin. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sunday.iweriolor@unidel.edu.ng adesiji et al: modeling rainfall-runoff relations using hec-hms in an oil palm catchment for double rain events in labu river basin of peninsular malaysia. azojete, 19(4):771-780. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 773 figure 1: location of the study area figure 2: location of labu river basin within langat river basin source: zakaria (2008) 2.2 site selection the study area located in sepang with a total area of 4,950 ha (49.5 km2) was divided into four different sub-basins, each sub-basin named according to the years the peat swamp forests were converted to oil palm plantations, such as; 2000, 2002, 2006, and 1978/2010. the latter was first converted to oil palm plantation in 1978 before it was re-cleared for cultivation in the year 2010. all the sub-basins have the same hydrologic soil type and same vegetation but with different catchment areas. their respective geo-locations, elevations, areas, and land cover are presented in table 1. table 1: location of study areas with their features and land cover no plot latitude s longitude e elev. (m) land use area (km2) 1 2000-year 02 43.816 101 39.576 19 op plantation 19.31 2 2002-year 02 43.074 101 40.368 8 op plantation 12.34 3 2006-year 02 44.552 101 38.932 13 op plantation 8.925 4 2010-year 02 45.950 101 39.877 19 op plantation 8.925 http://www.azojete.com.ng/ mailto:sunday.iweriolor@unidel.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):771-780. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 774 due to a lack of real-time runoff data in the research area, the 35.38 km2 semenyih watershed (figure 2) was chosen as a proxy site for runoff estimation using the hec-hms model. daily and hourly flow and rainfall data from gaging stations along the semenyih river have been recorded for the semenyih catchment which lies within latitudes of 2o 40’ 152” n to 3o 16’ 15” n and longitudes of 101o 19’ 20” e to 102o 1’ 10” e. semenyih basin was selected because it has sepang basin's plant and soil characteristics. although the semenyih basin contains a mixture of peat and mineral soils, the sepang basin is primarily composed of peat. however, the sepang basin system is heavily drained, which will significantly shorten the catchment's retention time and prevent the peat soil from acting as a sponge. in order to estimate runoff, semenyih basin, a primarily mineral soil deposit, was used as a proxy. therefore, a flow pattern was established for the study region, which is located southwest of the semenyih basin, using runoff data output from the hydrologic engineering center-hydrologic modeling system (hec-hms) and recorded streamflow and rainfall data from the semenyih basin. 2.3 runoff estimation from hec-hms using observed streamflow data in this study, the runoff hydrographs from a design storm on the sepang oil palm plantation basin were simulated using the hydrologic engineering center-hydrologic modeling system (hec-hms). a hydrologic model for the semenyih basin with a catchment size of 35.38 km2 was established using the hec-hms version 4.1. according to usace (2000), the hec-hms is a numerical model that simulates the behavior of watersheds, channels, and water-control structures in order to forecast flow, stage, and timing. according to chen et al. (2009), the model divides a watershed into sub-catchments that are treated as homogenous in terms of land-use, soil type, etc. in order to address the spatial distribution of catchment features. figure 3 shows the model schematic that was set up in hec-hms for the study area. it comprises of subbasins which represent a drainage area within the basin model for each study plot and the ‘junctions’ which serve as points of interest where reaches in each sub-basin are connected, in this case, a drainage system. figure 3: hec-hms model schematic diagram for study area 2.4 model calibration using hec-hms and observed streamflow the resulting runoff from the hec-hms was statistically compared with the recorded streamflow data obtained from soil moisture balance model by adjusting the model parameter values of hec-hms until the model results match the observed streamflow data. in the use of hec-hms, a basin file is needed to specify the physical parameters of the basin such as the catchment area, and sub-basin data. in addition to the basin model, meteorological data that describes the meteorology (rainfall) of the catchment was also established for the study area. a control specification file containing information pertinent to model timing like when a storm occurred and the time interval for the model use is also included in the hec-hms. these file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sunday.iweriolor@unidel.edu.ng adesiji et al: modeling rainfall-runoff relations using hec-hms in an oil palm catchment for double rain events in labu river basin of peninsular malaysia. azojete, 19(4):771-780. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 775 three models are referred to as components in the hec-hms model and are the basis for the rainfall-runoff modeling in the hec-hms. the basin file in the hec-hms contains different hydrologic elements. among all the hydrologic elements in the model is the ‘sub-basin’ hydrologic element which is used in the computation of rainfall-runoff in a watershed. having selected the sub-basin as the hydrologic element in converting rainfall to runoff in the watershed, the information on methods needed in computing loss rates, hydrograph transformation, and baseflow is required. different loss methods are available in hec-hms. they are; scs curve number method, initial and constant method, soil moisture accounting method, green and ampt method, deficit and constant method and exponential loss method. for the transfrom method, scs unit hydrograph was used in the runoff estimation. transfrom methods helps in specifying how to convert excess rainfall to direct runoff. the soil conservation service curve number method (scs-cn) is essentially an empirical, oneparameter (cn), event rainfall-runoff model. for the use of scs curve number method in hec-hms, each sub-basin requires a value for the curve number (cn), lag-time (which is the time difference between the peak precipitation and peak discharge) and percent imperviousness. the percent imperviousness is a function of the landuse of the study area and is the ratio of the impervious areas of the study area to the total areas of the basin in question. hence the percent imperviousness is obtained by dividing the entire basin into groups based on their present land use like; open space, estate-residential, industrial, water, low-intensity commercial, institutional, transportation etc. the detailed estimation of the percent imperviousness of the semenyih basin is explained in the preceding section. the dimensionless cn accounts for the effects of land use/land cover, soil types, and hydrologic conditions on surface runoff, and relates direct surface runoff to rainfall. having obtained the values of percent imperviousness, the values of cn and lag-time were both inserted as input parameters in the hec-hms to obtain direct runoff which was then compared with the recorded flow. a statistical relationship was established between the flow data from hec-hms and recorded flow data from the semenyih basin. both hourly and daily flow and rainfall data covering 2013 to 2015 were obtained from department of irrigation and drainages (did) and used in the runoff estimation. two highest rainfall depths with simple hydrographs were chosen for the calibration of the hec-hms model. hourly rainfall depths of april 7th and november 23rd, 2014 water year were chosen for the calibration of the model while the months of september and december were used for model validation. having established the flow data for april 7th and november 23rd, the flow data from hec-hms and the recorded flow data from the semenyih basin were tested for model performance using both the coefficient of determination r2 and nash–sutcliffe model efficiency coefficient (ens) (dongguan et al. 2009; karthikeyan et al. 2013). the r2 value represents an indicator of strength of the relationship between the observed and simulated values while nash-suttcliffe simulation efficiency (ens) indicates how well the plot of observed versus simulated values fit into the 1:1 line. the nash–sutcliffe model efficiency coefficient is used in assessing the predictive power of hydrological models, and it is defined as equation 1   = − = − − −= t t o t o t m t o t t qq qq e 1 2 2 1 )( )( 1 (1) where; qo = mean of observed discharges (m3/s), and qm = modeled discharge (m3/s), and qo t = observed discharge (m3/s) at time t. http://www.azojete.com.ng/ mailto:sunday.iweriolor@unidel.edu.ng https://en.wikipedia.org/wiki/hydrology arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):771-780. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 776 nash–sutcliffe efficiency ranges from infinity to 1. the value of efficiency of 1 (when e = 1) means there is a perfect match of modeled discharge relative to the observed data. the value of efficiency equal to (when e = 0) shows that the predictions of model are as accurate as the mean of the observed data, whereas an efficiency below zero (e < 0) occurs when the observed mean is a better predictor than the model or, in other words, when the residual variance (numerator in equation 6.1), is larger than the data variance (the denominator). therefore, the closer the model efficiency is to 1, the more accurate the model is (karthikeyan et al. 2013). and according to dongquan et al. (2009), an ens greater than 0.5 indicates acceptable model performance for model simulation. 3. results and discussion 3.1 hec-hms model calibration for semenyih basin rainfall depths of april 7th and august 23rd in labu basin were used in the calibration process of runoff estimation using hourly time-step. with the assumed base flow values for each month (3.6 m3/s for april and 4.0 m3/s for august), initial runoff estimation was carried out using the varied cn and lag-time values with the value of percent imperviousness which was estimated as 17.64 %. table 2 shows the various adjustments made in the hec-hms and the output results of nash–sutcliffe model efficiency coefficient (ens) and coefficient of correlation (r2) for various trials. curve number value of 40 and lag-time of 60 minutes, with estimated impervious value of 17.64 % were chosen after series of trials and these were further used in the validation processes. cn value of 40 and lag-time of 60 minutes gave the ens of 0.794 and r2 value of 0.853 for april 23rd calibration which showed a good fit and well above 0.5 thresholds. this also showed that the two-flow data were not significantly different and that the model predictions are as accurate as the mean of the observed data (dongquan et al. 2009). figures 4 and 5 show the hydrographs of the calibrations carried out from the two flood events of april 7th and august 23rd 2014 water year. the two hydrographs indicate that the simulated flows reasonably predicted the recorded flow. this was further supported by nash-sutcliffe results of figures 6 and 7 for the same flood events of april 7th and august 23rd which showed that the values were higher than the minimum recommended in hydrological simulation, according to dongquan et al. (2009) and karthikeyan et al. (2013). table 2: hec-hms adjustment of cn and lag-time using percent imperviousness of 17.64 % for calibration month trials curve number lag-time (mins) ens r2 april 1 40 60 0.820 0.860 2 45 60 0.794 0.853 3 50 100 0.70 0.70 4 65 100 -0.26 0.699 5 70 100 -1.10 0.699 august 1 40 60 0.904 0.941 2 45 60 0.897 0.941 3 50 100 0.894 0.931 4 65 100 0.115 0.799 5 70 100 -0.602 0.789 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sunday.iweriolor@unidel.edu.ng adesiji et al: modeling rainfall-runoff relations using hec-hms in an oil palm catchment for double rain events in labu river basin of peninsular malaysia. azojete, 19(4):771-780. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 777 figure 4: comparison of simulated and observed hydrographs for april 7th 2014 flood event of semenyih basin figure 5: comparison of simulated and observed hydrographs for august 23rd 2014 flood event of semenyih basin figure 6: values of r2 and ens for april 2014 simulated flow during calibration at cn = 40, lag-time = 60mins and percent imperv = 17.64% http://www.azojete.com.ng/ mailto:sunday.iweriolor@unidel.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):771-780. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 778 figure 7: values of r2 and ens for august 2014 simulated flow during calibration 3.2 hec-hms model validation for semenyih basin validation of the hec-hms model for semenyih basin was done using the daily rainfall data from september to december 2014. the daily rainfall data was used in the hec-hms model with input parameters of cn of 40 and lag-time, 60 minutes and estimated percent impervious values 17.64 %. figure 8 shows that the simulated flows gave a moderate prediction of the observed flow, though there seemed to be overpredictions in some cases. figure 9 shows the statistical results of ens and r2 values which shows a good prediction as the values of ens and r2 were greater than 0.5. figure 8: simulated and observed flows for september to december 2014 during the validation process. figure 9: values of ens and r2 for sept-december 2014 simulated daily flow for validation process file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sunday.iweriolor@unidel.edu.ng adesiji et al: modeling rainfall-runoff relations using hec-hms in an oil palm catchment for double rain events in labu river basin of peninsular malaysia. azojete, 19(4):771-780. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 779 the adopted hec-hms input parameters such as cn value of 40 and lag-time of 60 minutes were used in establishing a runoff estimate for the study area of sepang with the catchment area of 49.5 km2. the percent impervious value for sepang area was estimated using the same procedure used for semenyih basin. 4. conclusion hec-hms model has been used to simulate a single rainfall event that occurred in the labu catchment in peninsular malaysia. to fully comprehend the characteristics of the watershed, geological, soil, and land use data were used along with hec-hms model. in order to forecast the surface runoff, the hec-hms hydrologic modeling program was applied to the labu watershed in southwest malaysia. the hydrologic losses from the study area were calculated using the scs curve number loss method, and the effective transformation of rainfall was achieved using the scs unit hydrograph method. the measured runoff events of april 7 and august 13, 2015, served as a calibration point for the model parameters. the daily nash and sutcliffe efficiency (nse) was utilized to calculate the degree of agreement between the predicted and observed stream flow. as a result, the runoffs produced by the frequency storm approach will be crucial for the assessment of the flood risk in the neighbouring cities. the observed streamflow obtained from the meteorological agency was compared with the hechms discharge values, which were used as the observed flow. the observed streamflow obtained from the meteorological agency agrees with the observed streamflow data in the hec-hms with good agreement. in conclusion, the application of the hec-hms along with a recorded streamflow data shows the ability of the hec-hms model to calculate the streamflow volume in a double storm events at labu basin. recommendation on the use of a gis-based approach in rainfall-runoff modeling coupled with the use of different land use patterns, especially in regions with a complex mix of land use features and different soil types will be a major breakthrough hydrological modeling. references andrianto, a., komarudin, h. and pacheco, p. 2019. expansion of oil palm plantations in indonesia’s frontier: problems of externalities and the future of local and indigenous communities. land, 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computing, pp. 1-9. hughes, da. 2019. facing a future water resources management crisis in sub-saharan africa. journal of hydrology and regional studies, 23: 100600. http://www.azojete.com.ng/ mailto:sunday.iweriolor@unidel.edu.ng arid zone journal of engineering, technology and environment, dec, 2023; vol. 19(4):771-780. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: ade.richard@futminna.edu.ng 780 ismail, h., kamal, mr., abdullah, afb., jada, dt. and sai hin, l. 2020. modeling future streamflow for adaptive water allocation under climate change for the tanjung karang rice irrigation scheme malaysia. applied sciences, 10(14): p 4885. lin, k., chen, h., xu, cy., yan, p., lan, t., liu, z. and dong, c. 2020. assessment of flash flood risk based on improved analytic hierarchy process method and integrated maximum likelihood clustering algorithm. journal of hydrology, 584: 124696. lintern, a., mcphillips, l., winfrey, b., duncan, j. and grady, c. 2020. best management practices for diffuse nutrient pollution: wicked problems across urban and agricultural watersheds. environmental science & technology, 54(15): 9159-9174. prananta, w. and kubiszewski, i. 2021. assessment of indonesia’s future renewable energy plan: a meta-analysis of biofuel energy return on investment (eroi). energies, 14(10): p 2803. saha, m., sauda, ss., real, hrk. and mahmud, m. 2022. estimation of annual rate and spatial distribution of soil erosion in the jamuna basin using rusle model: a geospatial approach. environmental challenges, 8: 100524. shakarneh, moa., khan, aj., mahmood, q., khan, r., shahzad, m. and tahir, aa. 2022. modeling of rainfall–runoff events using hec-hms model in southern catchments of jerusalem desert-palestine. arabian journal of geosciences, 15(1): 127. tarpanelli, a., paris, a., sichangi, aw., oloughlin, f. and papa, f. 2023. water resources in africa: the role of earth observation data and hydrodynamic modeling to derive river discharge. surveys in geophysics, 44(1): 97-122. tibangayuka, n., mulungu, dm. and izdori, f. 2022. evaluating the performance of hbv, hechms and ann models in simulating streamflow for a data scarce high-humid tropical catchment in tanzania. hydrological sciences journal, 67(14): 2191-2204. tsakiris, gp. and loucks, dp. 2023. adaptive water resources management under climate change: an introduction. water resources management, 37:2221–2233 wilby, rl., abrahart, rj. and dawson, cw. 2003. detection of conceptual model rainfall— runoff processes inside an artificial neural network. hydrological sciences journal, 48(2): 163181. ziaei, sm. and ali, i. 2021. commodity exports and macroeconomic performance: the case of palm oil in malaysia. cogent economics & finance, 9(1): 1901388. zakaria, s., 2008. management instruments for langat river basin. proceedings of the iwrmihp conference 2008 and 2nd africa regional meeting of the national committees of unesco’s ihp, held at international convention center, south africa, cape town 10 march 2008, file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:sunday.iweriolor@unidel.edu.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 449 arid zone journal of engineering, technology & environment original research article performance evaluation of yolo object detection models for automated license plate recognition o. f. odeyinka1*, w. a. raheem1, c. o. folorunso1 and a. fajinmi1 1department of systems engineering, university of lagos, akoka, nigeria *corresponding author’s email: oodeyinka@unilag.edu.ng article information abstract this paper outlines an evaluation and comparison of three different you only look once (yolo) object detection models yolov3, yolov8, and yolov10 for use in automated license plate recognition (alpr) systems. to analyze these models, a total of 261 license plate images were collected from the car park of an auditorium inside the university of lagos, nigeria. metrics of each model (accuracy, precision, recall, f1 score, and training efficiency) were used to measure the performance of the models. results indicates that yolov8 (accuracy of 86.9%, precision score 100%, recall of 87%, and an f1 score of 0.93) significantly outperformed the other models, demonstrating its potential as a robust solution for object detection. in contrast, yolov3 had an accuracy of 62.1%, precision of 75%, a recall of 78.3%, and an f1 score of 0.766, reflecting balanced performance but slower training times. yolov10, despite being the latest version, showed mixed results, achieving an accuracy of 43.2%, a precision of 47.5%, a recall of 82.6%, and an f1 score of 0.603. this study highlights the critical importance of model selection based on specific application needs and suggests that further optimization may enhance the capabilities of yolov10 for future developments in alpr systems. received: 25th february 2025 revised: 27th april 2025 accepted: 28th april 2025 keywords: automated license plate recognition system deep learning object detection yolo © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction automated license plate recognition (alpr) is an intelligent system that interprets car license plates using optical character recognition on snapshots (musa, 2023). this technology works remotely, removing the need for physical contact or vehicle engagement. law enforcement agencies have adopted it for comparing vehicle license plates with lists of stolen, wanted, and other vehicle interests. the important steps in alpr are license plate localization and detection, which affect the recognition process's overall accuracy, efficiency, and adaptability (bakshi et al. 2023). however, some factors can affect license plate localization and detection accuracy (jenitta et al. 2023). these include blurred or occluded plates, skewed camera angles, bad weather conditions, poor lighting conditions, non-standard plates, and irregular image acquisition. despite the challenges posed by these factors, ongoing research and technological advancements exist (jiang et al. 2022). detecting instances of objects from one or more classes in a picture is the main idea behind object detection. classes of objects in an image include people, cars, or faces (amit et al. 2021). alpr systems integrate three primary techniques object detection, image processing, and pattern recognition (batra et al., 2022). object detection employs various models which are categorized into traditional computer vision techniques and deep learning-based methods, where the you only look once (yolo) models are classified. despite advances in technology, traditional computer vision techniques are becoming obsolete and have many limitations (jamtsho et al. 2021; solunke & gengaje, 2023). the rise of deep learning has made object detection more efficient, quick, and accurate, hence the integration of models like the yolo versions (o’mahony et al. 2020). these models address challenges such as the inability of pixel connectivity to capture all characters in joined sequences, illumination issues, and poor recognition rates on ambiguous characters (e.g., b-8, o-0, a-4, c-g, d-o, and k-x) (wang et al. 2024). other concerns addressed include broken characters and issues of multi-style plates (plates with different national fonts and syntax) (solunke & gengaje, 2023). for example, bakshi et al. (2023) enhanced alpr systems for diverse conditions by using a spatial azojete june 2025. vol.21(2):449-459 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/011 www.azojete.com.ng mailto:oodeyinka@unilag.edu.ng mailto:oodeyinka@unilag.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 450 transformer network to align distorted license plates and a cnn to recognize characters with various fonts and sizes, achieving superior accuracy in challenging scenarios compared to other methods. object localization is the process of establishing a specific “location” or spatial coordinates of an object within an image or video. localizing license plates from car images is a complex operation due to considerable variance in size, shape, color, texture, and spatial orientations of license plate regions in these pictures (saha et al. 2009). in gnanaprakash et al. (2021), localization is highlighted as an objective of an alpr system that interprets these images using optical character recognition (ocr) technology to get the license number of the vehicle. yolo is an approach to object detection that was developed by redmon et al., (2016). (redmon et al. 2016). the yolo approach treats object classification as a regression problem by multi-dimensionally separating boxes and applying class probability (lee & kim, 2020). the yolo algorithm processes an input image through a straightforward deep convolutional neural network for object detection. different yolo algorithms have been used for objection detection (sung et al. 2020; zhao and you, 2020; laroca et al. 2021; jenitta et al. 2023, wadare et al. 2023). however, the yolo algorithm has undergone different forms of improvement. in yolov2, a batch normalization layer was added to enhance accuracy and speed, while the convolutional anchor size was set to establish initial training, thus addressing the gaps in yolov1. similarly, logistic regression was used in yolov3 to predict the object score of a bounding box, making it significantly faster than other object detection algorithms at equivalent performance (zhao and you, 2020). in lin et al. (2022), it was noted that yolov3 exhibited certain limitations, leading to the introduction of yolov4. when compared with yolov3, yolov4 effectively prevents information loss, a weakness observed in yolov3 (sozzi et al. 2022). in real-time images, each frame of yolov4 demonstrates greater stability compared to yolov3, resulting in recognition frames that are not affected by flickering. also in exploring the different yolo versions, batra et al. (2022) highlighted the additions to yolov5 by focusing on its lightweight version, yolov5s (small). the authors noted its remarkable capabilities, its generating time and memory-efficient model a substantial improvement over yolov4. yolov5 demonstrated high time performance, yielding relatively smaller-sized object detection models. interestingly, li et al., (2022) developed a suite of deploymentready networks at various scales, apt for diverse use cases. with the generous permission from yolo authors, they named it yolov6. yolov6-n was documented to achieve a 35.9% average precision on the coco dataset at 1234 frames per second (fps). yolov6-s attains a 43.5% ap at 495 fps, outperforming other mainstream detectors at the same scale, including yolov5-s. it particularly stands out for achieving high accuracy at an impressive frame rate. yolov7 takes the spotlight as highlighted by zhao et al. (2023) in its application to detect maize seedlings in images. the model exhibits commendable performance in real-time object detection. however, issues surfaced during their analysis, including redundancy in feature extraction, loss of location information, and slow convergence in loss calculation. to address these shortcomings, they proposed a lightweight model derived from yolov7. this proposed model boasts the highest mean average precision (map) value, a smaller model size, and as well as detection speed that meets the requirements for real-time detection. tamang et al. (2023) explored yolov8 for detecting face mask-wearing conditions. their analysis led them to the conclusion that yolov8 demonstrates enhanced efficiency compared to its predecessors. this improvement is attributed to the utilization of a larger feature map and a more efficient convolutional network. wadare et al., (2023) are the first to merge yolov8 and easyocr into an alpr system, and they investigated their combined capabilities in advanced license verification, as well as accuracy and efficiency verification. as outlined by hussain (2023), each of the previous yolo models has recorded modest precision scores as shown in table 1. the latest release of yolov10 has proved to be a masterstroke in improvement, recording well over 70% precision (wang et al. 2024). however, this is not a confirmation of the supremacy of yolov10 over the other versions. in fact, hussain (2023) had suggested a comparative analysis of various yolo versions to ascertain their efficiency and performance for alpr systems. this is the focus of this research. the growing demand for excellent object detection, particularly when recognizing license plates emphasizes the importance of evaluating automated license plate system models (yolo versions). this is the motivation behind this research. hence, the primary aim of this research is to evaluate and compare the performance of three different yolo models yolov3, yolov8, and yolov10 for their effectiveness in recognizing license plates. these algorithms are also used to demonstrate advances in deep learning and machine learning techniques. similarly, investigating these models will help to understand their potential and further the adoption of advances in alpr systems. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 451 table 1: progression of yolo versions hussain (2023) yolo version year released framework backbone average precision (%) yolov1 2015 darknet darknet24 63.4 yolov2 2016 darknet 19 darknet24 63.4 yolov3 2018 darknet-53 darknet53 36.2 yolov4 2020 darknet-53 cspresnext-50, cspdarknet-53, & efficientnet-b3 43.5 yolov5 2020 pytorch cspdarknet53 55.8 yolov6 2022 pytorch efficientrep 52.5 yolov7 2022 pytorch repconvn 56.8 yolov8 2023 pytorch ghostblockv2 53.9 2. materials and method this research is divided into six phases as described in figure 1. figure 1: flowchart for methodology a. data collection: the dataset for this research work was obtained by capturing the plate number of vehicles parked at the j. f. ajayi auditorium in the university of lagos, nigeria. in order to ensure clarity and consistency of the images taken, a single camera was used to take the pictures over a period of five days. the camera produced full high definition pictures of 16 megapixels with 261 images collected to ensure a diverse and comprehensive dataset. these images include a variety of plate numbers of various types of vehicles and in different conditions. the different pictures also helped to ensure diversity in the dataset, thus providing the foundation for the subsequent analysis and model training. b. data annotation: for this part, the dataset compiled was carefully labeled, outlining the license plate regions within each image. this task was carried out using labelimg, a python tool designed for image annotation and labeling, which ensured accuracy and consistency during the dataset creation process. after each labeling, the resulting annotations were saved in a standard “.txt” format. this careful approach makes sure that the labeled data is easily useable and optimized for seamless incorporation into the model’s training pipeline. a typical image annotation is outlined in plate 1. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 452 plate 1: image annotation with labelimg when this was done, the dataset was then split into train, val, and test, for both images and labeled images. figure 2: code flow for yolov3, yolov8, and yolov10 c. model training: model training is the process of teaching the model to recognize patterns and make predictions by exposing it to a labeled dataset. d. analysis: statistical tests are run to see if any reported performance differences between the yolo versions selected are statistically significant, strengthening our conclusions regarding their relative effectiveness. this project uses four models for object detection – yolov3, yolov8, and yolov10. yolov3 has three closely related object detection models yolov3, yolov3-ultralytics, and yolov3u. yolov3 was chosen for this analysis because it is an older version of the yolo series. comparing its performance metrics with those of the newly released versions will help to understand the improvements and differences. yolov8 is the latest iteration in the yolo series of real-time object detectors. this model is selected for its flexibility and fast training time. it has a lightweight network architecture, efficient feature fusion algorithms, and more accurate detection outcomes (lou et al., 2023). the yolov8 network solves challenges in categorization, object detection, and image segmentation. all of these methods recognize things in photos or videos in various ways. the yolov10 model is a new addition to the yolo family, though it wasn’t developed by the original creators. instead, researchers at tsinghua university built it using the ultralytics python package. this model was chosen for its ability to accurately predict object categories and positions in images with low latency, meaning it has minimal delay between input and output. additionally, it was selected because it is the latest addition to the yolo series. in machine learning, evaluating a model’s prediction accuracy is vital for determining its effectiveness. metrics like precision and recall reveal how well the model identifies positive cases, highlighting areas for improvement and allowing for targeted optimization (sozzi et al., 2022). recall is the percentage of real positive instances that are accurately predicted as positive (powers, 2020). in other words, it is the measure of a model’s ability to identify all important instances in a dataset. when recall is low, it suggests the model failed to detect a substantial number of true positive events. in simpler terms, the model incorrectly classifies many actual positives as negatives. as a result, despite the high accuracy of the model in positive predictions (when anything is predicted positively, it is true), it misses a large number of genuine positives. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 453 it is expressed as the number of true positive predictions divided by the total number of actual positives (true positives plus false negatives). mathematically: recall = true positives (tp) true positives (tp) + false negatives (fn) 1 precision, on the other hand, measures the ratio of correct positive predictions of correct positive predictions (ganesan, 2022). it is the ratio of true positive predictions to the total number of positive predictions. it measures how accurate the positive prediction is precision = true positives (tp) true positives (tp) + false positives(fp) 2 the f1score curve graph helps in understanding the performance of a classification model, focusing on the balance between precision and recall across different confidence levels. it helps visualize the relationship between the f1 score and the confidence threshold used for predictions. where the f1 score is the harmonic mean of precision and recall. it is expressed mathematically: 𝐹1 𝑠𝑐𝑜𝑟𝑒 = 2 × 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 (𝑃) × 𝑅𝑒𝑐𝑎𝑙𝑙 (𝑅) 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 (𝑃) + 𝑅𝑒𝑐𝑎𝑙𝑙 (𝑅) 3 the confusion matrix is a key technique for evaluating machine learning models. it is used to assess the accuracy of classification algorithms by comparing predicted outcomes against actual results (karimi, 2021). 𝐴𝑐𝑐𝑢𝑟𝑎𝑐𝑦 = 𝑇𝑟𝑢𝑒 𝑃𝑜𝑠𝑖𝑡𝑖𝑣𝑒𝑠 (𝑇𝑃) + true negatives (𝑇𝑁) 𝑇𝑜𝑡𝑎𝑙 4 3. results and discussion the analysis was done on an 11th gen intel (r) core i7-1165g7 @ 2.80ghz 16.0gb installed ram 64-bit system. yolov3 the training of this model yielded three distinct batches of detection results. this section details the analysis and outcomes of the training run. the confusion matrix is given in figure 3. figure 3: confusion matrix for the training of yolov3 from figure 3, the tp indicated by the cell at the top-left corner (18) represents the number of instances where the model correctly predicted “license plate” when the actual label is “license plate”. the fn denoted by the cell at the bottom-left corner (5) represents the number of instances where the model predicted “background” when the actual label is “license plate”. the fp given by the top-right corner (6) represents the number of instances where the model predicted “license plate” when the actual label is “background”. the http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 454 tn (0) represents the number of instances where the model correctly predicted “background” when it is “background”. upon evaluation, the accuracy is given as 0.621 (approximately 62.1%). the precision is calculated as 0.75, meaning 75% of predicted “license plate” instances are correct. the recall is calculated as 0.783 indicates that the model correctly identified about 78.3% of actual “license plate” instances while the f1 score is approximately 0.766, showing a balance between precision. figure 4: precision-recall curve for first training yolov3 the average precision at the 0.5 threshold is 0.832. this indicates that the model can distinguish well between relevant and irrelevant instances, leading to enhanced overall performance. from the figure 4 above, the optimal threshold is 0.574, where the model achieves its highest f1 score of 0.82. this high f1 score means the model performs well, making accurate predictions while maintaining a balance between precision and recall. table 2 is a summary of results for yolov3 while figure 5 is the f1 score curve. table 2: summary of results for yolov3 training batch dataset size map@50 accuracy precision recall f1 score batch a 261 0.832 62.1% 75% 78.3% 0.766 figure 5: f1-score curve for yolov3 the confusion matrix for the training of yolov8 is given in figure 6. figure 6: confusion matrix for the third training of yolov8 http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 455 in figure 6, the tp is 20, fn is 3, fp and tn are 0 giving a model accuracy of 86.95%. the precision is 1 meaning that every predicted “license plate” is correct. similarly, the recall is 0.87 showing that the model correctly identified about 87% of actual “license plate” instances while the f1 score is 0.93 giving a good balance between precision and recall. figure 7: precision-recall curve for the third training of yolov8 from the precision-recall curve of yolov8 in figure 7, the map@50 significantly increased from 0.506 and 0.4659 in the previous curves to 0.872 in the current batch training curve. this indicates a substantial improvement in the model’s ability to detect the license plates with higher accuracy. a higher f1 score indicates better performance. from figure 8, it is observed that the optimal threshold is 0.667 when the model achieves its highest f1 score of 0.93. this high f1 score means the model performs exceptionally well, making accurate predictions while maintaining a good balance between precision and recall. table 3 summarizes the results of the training of the yolov8 model. figure 8: f1-confidence curve for training yolov8 table 3: summary of results for yolov8 training batch dataset size map@50 accuracy precision recall f1 score batch a 261 0.872 86.9% 100% 87% 0.93 the confusion matrix for the training of yolov10 is given in figure 9. figure 9: confusion matrix for the second training of yolov10 http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 456 from figure 9, the tp is 19, fn is 4, fp is 21 and tn is 0. the model accuracy obtained is 43.2% while the precision is 47.5%, indicating that every predicted “license plate” is 47.5% correct. the recall is approximately 0.826, showing that the model correctly identified about 82.6% of actual “license plate” instances. the f1 score is approximately 0.603, giving a good balance between precision and recall. figure 10 and 12 are the plots of precision-recall and f1 score for yolov10 respectively. figure 10: precision-recall curve for the second training of yolov10 figure 11: f1-confidence curve for second training for yolov10 as shown in figure 11, the confidence threshold reaches 0.637 when the f1 score attains its maximum value (0.76). this indicates better precision and recall up to that point. beyond the 0.637 confidence threshold, the f1 score starts to decline, suggesting that the model becomes overly conservative, possibly leading to higher precision but lower recall, or vice versa. the summary of the training of yolov10 is given in table 4. table 4: summary of results for yolov10 training batch dataset size map@50 accuracy precision recall f1 score batch a 261 0.786 43.2% 47.5% 82.6% 0.603 the summary from the training (see table 5) reveals compelling insights into the performance of various yolo models for image objects. these results were obtained from the best training outcomes using a diverse dataset of over 200 images, including a wide range of challenging scenarios, including blurry images, skewed perspectives, long-distance captures, and images taken at optimal angles and distances. this variety in the dataset ensured a robust evaluation of the models’ capabilities across different real-world conditions. table 5: summary of model training metrics yolov3 yolov8 yolov10 accuracy 62.1% 86.9% 43.2% precision 75% 100% 47.5% recall 78.3% 87% 82.6% f1 score 0.766 0.93 0.603 average total training time 5.458hrs about 30 minutes 1hr http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 457 in this evaluation, yolov3 (which an earlier version of the yolo family) demonstrated moderate performance with an accuracy of 62.1%. its precision and recall scores of 75% and 78.3% respectively indicate a balanced performance in terms of correct detection and false positives. the f1 score of 0.766 further backs up its solid, albeit not exceptional performance. however, yolov3’s most significant drawback during its training was its extensive training time, requiring an average of 5.458 hours to process the dataset. yolov8 emerged as the standout performer in the evaluation. it achieved an impressive accuracy of 86.9%, significantly outperforming its counterparts. notably, yolov8 achieved a perfect precision score of 100%, indicating that all its positive detections were correct. the recall of 87% suggests that it successfully identified a high proportion of the relevant objects. these metrics culminated in an excellent f1 score of 0.93, reflecting a harmonious balance between precision and recall. furthermore, yolov8’s efficiency was remarkable, completing the training process in approximately 30 minutesa substantial improvement over yolov3. yolov10, despite being the most recent model, showed mixed results. its accuracy of 43.2% was lower than expected, failing behind both yolov3 and yolov8. the precision and recall scores of 70% and 60.9% respectively, while not poor, indicate room for improvement. the f1 score of 0.651 further reflects these moderate performance levels. however, the yolov10 did show improvement in training efficiency compared to yolov3, completing the process in approximately 1 hour. the stark contrast in performance between yolov8 and yolov10 is particularly intriguing. while one might expect the newer model to outperform its predecessor, our results suggest that yolov10 may still be in a developmental phase, requiring further refinement to reach its full potential. this discrepancy also highlights the importance of thorough testing and optimization in the deployment of new models. in terms of training efficiency, there is a clear progression from yolov3 to yolov8 and yolov10. this trend suggests that advancements in the yolo architecture have significantly improved computational efficiency, a crucial factor for real-world applications where training time can be a limiting factor. 4. conclusion this study evaluated the performance of three yolo (you only look once) models – yolov3, yolov8, and yolov10 – for object detection tasks. each model demonstrated distinct strengths and weaknesses in terms of accuracy, speed, and overall performance. the results indicated that the yolov8 currently offers the best combination of accuracy, precision, recall, and training efficiency among the tested models. however, the potential of yolov10, despite its current limitations, necessitates further investigation and optimization. these findings provide valuable insights for researchers and practitioners in the field of object detection, guiding model selection and highlighting areas for future development and refinement. future work could focus on fine-tuning yolov10 for better performance, by exploring potential improvements such as experimenting with different hyper parameters (including batch sizes, network architectures, and learning rates). work on investigating how it performs on larger and more diverse datasets to assess its scalability and performance can be crucial. introducing diverse datasets like varied lighting conditions, object sizes, and environmental contexts will improve the model’s generalization capabilities. potential modifications to the architecture of yolov10 can also enhance its speed without compromising accuracy. it is also recommended that the evaluation of other prominent object detection models alongside yolo variants. this could provide valuable insights into their relative strengths and weaknesses and offer a more comprehensive view of current object detection capabilities. references amit, y., felzenszwalb, p. and girshick, r. 2021. object detection. in computer vision: a 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address: oodeyinka@unilag.edu.ng 458 gnanaprakash, v., kanthimathi, n. and saranya, n. 202. automatic number plate recognition using deep learning. in iop conference series: materials science and engineering, 1084(1): 012027). hussain, m. 2023. yolo-v1 to yolo-v8, the rise of yolo and its complementary nature toward digital manufacturing and industrial defect detection. machines and tooling, 11: 677. https://doi.org/10.3390/machines11070677. jamtsho, y., riyamongkol, p. and waranusast, r., 2021. real-time license plate detection for non-helmeted motorcyclist using yolo. ict express, 7(1): 104-109. jenitta, j., kusuma, s., madhura, r. and prakash, mr. 2023. license plate recognition using raspberry pi. 2023 world conference on communication & computing (wconf), 1–5. https://doi.org/10.1109/wconf58270.2023.10235084. jiang, p., ergu, d., liu, f., cai, y. and ma, b., 2022. a review of yolo algorithm developments. procedia computer science, 199: 1066–1073. 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dc-yolov8: small-size object detection algorithm based on camera sensor. electronics, 12(10): 2323. musa, uf., 2023. advantages of automated license plate recognition technology. tmp universal journal of research and review archives, 2(4). o’mahony, n., campbell, s., carvalho, a., harapanahalli, s., hernandez, g.v., krpalkova, l., riordan, d. and walsh, j. 2020. deep learning vs. traditional computer vision. in advances in computer vision: proceedings of the 2019 computer vision conference (cvc), 11: 128-144. springer international publishing. powers, d.m., 2020. evaluation: from precision, recall and f-measure to roc, informedness, markedness and correlation. arxiv preprint arxiv:2010.16061. redmon, j., 2016. you only look once: unified, real-time object detection. in proceedings of the ieee conference on computer vision and pattern recognition. saha, s., basu, s., nasipuri, m. and basu, d.k., 2009. license plate localization from vehicle images: an edge based multi-stage approach. international journal of recent trends in engineering, 1(1): 284. solunke, b. r., & gengaje, s. r., 2023. a review on traditional and deep learning based object detection methods. 2023 international conference on emerging smart computing and informatics (esci), 1–7. sozzi, m., cantalamessa, s., cogato, a., kayad, a. and marinello, f. 2022. automatic bunch detection in white grape varieties using yolov3, yolov4, and yolov5 deep learning algorithms. agronomy, 12(2): 319. sung, jy., yu, sb. and korea, sp. (2020). real-time automatic license plate recognition system using yolov4. 2020 ieee international conference on consumer electronics asia (icce-asia), 1–3. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 449-459. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oodeyinka@unilag.edu.ng 459 tamang, s., sen, b., pradhan, a., sharma, k. and singh, vk. 2023. enhancing covid-19 safety: exploring yolov8 object detection for accurate face mask classification. international journal of intelligent systems and applications in engineering, 11(2): article 2. wadare, m., sharma, m., patil, mrs. s., bewoor, mrs. m., pawar, a., kadam, a., and patil, s. 2023. vehicle number plate detection using yolov8 and easyocr. wang, a., chen, h., liu, l., chen, k., lin, z., han, j. and ding g. 2024. ‘yolov10: real-time end-to-end object detection’, advances in neural information processing systems, 37: 107984–108011. zhao, k., zhao, l., zhao, y., and deng, h. 2023. study on lightweight model of maize seedling object detection based on yolov7. applied sciences, 13(13): article 13. zhao, s. and you, f. 2020. vehicle detection based on improved yolov3 algorithm’, in 2020 international conference on intelligent transportation, big data & smart city (icitbs). ieee, 76–79. http://www.azojete.com.ng/ mailto:oodeyinka@unilag.edu.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 145 arid zone journal of engineering, technology & environment original research article implementation of thyristor based control of separately excited dc motor driven by single-phase semi-converter g. c. diyoke1*, c. a. okeke1 and c. ezugwu2 1department of electrical and electronic engineering, michael okpara university of agriculture, umudike, abia state, nigeria. 2department of electrical and electronic engineering technology, federal polytechnic, nasarawa, nasarawa state, nigeria. *corresponding author’s email address: geraldiyoke@mouau.edu.ng article information abstract this paper presents the implementation of thyristor-based control for a separately excited dc motor using a single-phase semi-converter. the study focuses on the design, operation, and performance analysis of the system, highlighting its ability to efficiently control the motor's speed and torque. the semi-converter, consisting of thyristors, provides variable dc voltage to the motor by controlling the firing angle, enabling precise regulation of motor parameters. key aspects, such as circuit design, firing angle control, and power quality considerations, are discussed in detail. computer aided simulation results demonstrate the effectiveness of the proposed system in achieving smooth and reliable motor control with improved energy efficiency. the findings underline the applicability of thyristor-based control in industrial and automation applications, offering a cost-effective solution for dc motor drives. it is observed that the method of voltage control shows that a rated voltage of 200 v, the rated speed of 1500 rpm and torque of 10.5 n-m cannot be exceeded. the method of field flux control shows that a rated voltage, the rated speed can be exceeded to reach 208 v and 3000 rpm respectively while the rated torque cannot be reached. submitted: 5th september 2024 revised: 24th december 2024 accepted: 3rd february 2025 keywords: semi-converter dc motor armature voltage field current speed torque © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in order to control the dc motor speed (poomima et al., 2006), the thyristor semi-converter provides a variable output voltage. a direct current (dc) motor is a machine that converts dc electrical energy into rotating mechanical energy and are rated in horsepower (onah et al., 2022 and asadi et al., 2019). due to the simplicity, high power conversion efficiency, low cost of operation of the system, reliability, controllability (perelmuter 2012; nguyen et al., 2019; rashag 2019; sami et al., 2021 and duby et al., 2022) and maintainability, it is widely used in industrial and domestic applications as reported by kandpal et al., (2015); hareb et al., (2021); virendra et al., (2013) and sharma et al., (2016). some of the applications are in dc drive systems for paper production, photographic film manufacturing, machine tools, traction, crude oil pipelines, variable-speed drives for woodworking machines, rolling mills, and traction drives as presented by el-kholy et al., (2004) and tiwari et al., (2019), adjustable-speed drive systems for textiles, renewable energy systems for wind turbine, solar tracking, home applications for vacuum cleaner, washing machines, electric razors, blender, food processor. another vital merit of the system is that it requires no extra circuitry for commutation process (hughes 2006 and krishnan 2001). separately excited dc motors are often used in applications needing precise control of speed and torque over a wide range (hassan et al., 2023; and hameed and ali 2016). the report by amed et al. (2023) detailed the study of microcomputer-based torque control of dc separately excited motor using the proportional integral (pi) controller. based on the performance indices, semi-converter performs better than full-converter systems. azojete march 2025. vol.21(1):145-156 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:geraldiyoke@mouau.edu.ng mailto:geraldiyoke@mouau.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 146 a rectifier is a type of power electronics converter that performs a conversion of electrical energy from one form to another (namdeo et al., 2014). semi-converter uses both thyristors and diodes for power conversion. it is simple to control, economical based on cost and more reliable during the operation. it operates by controlling the conduction angle of the thyristors, which regulates the amount of power transferred. the armature current in general is non-continuous at high values of the firing angle, high motor speed and low values of machine torque. an external armature circuit choke can be applied to promote continuous armature current operation. rectifiers play a vital role in various industrial, commercial and renewable energy applications, offering flexibility and efficiency in power conversion processes. some of its applications are as follows: motor drives, dc power supply, heating systems, renewable energy, hvdc transmission, battery charging systems, etc. speed control in a dc separated excited motor can be achieved through various methods, each offering different advantages and suitability depending on the application requirements. here are some common methods of speed control for dc separated excited motors: (1) armature voltage control: this achieved by varying the voltage applied (duby 2009 and saini et al., 2020) to the armature winding of the motor, thereby the motor speed can be controlled; (2) field flux control: this is realized by adjusting the field winding excitation, the magnetic flux within the motor can be varied, affecting its speed-torque characteristics. 2. materials and method 2.1 single-phase semi-converter configuration and operation in figure 1, a semi-converter circuit configuration fed with separately excited dc motor is developed. the power circuit consists of two controlled power thyristors t1 and t4, two power diodes d2 and d3, and one freewheeling diode df. the ac source vs is given by 𝑉𝑚𝑠𝑖𝑛𝜔𝑡, where vm is the amplitude and ω is the source frequency in rad/sec. the two similar power circuit are responsible for armature voltage and current and field voltage and current respectively. the load is modeled as series combination of a dc motor with ra and la as armature resistance and inductance and e as the induced emf applied for variable-speed motor drives. figure 1: semi-converter-fed separately excited dc motor configuration http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 147 figure 2: waveforms of semi-converter mode of operation. operation of the semi-converter circuit depicted in figure 2; and figure 2(a) depicts the supply voltage, dc motor emf and gate pulses plots against the 𝜔𝑡 (radians). the output and armature currents are shown in figure 2(b), under continuous current mode of operation. waveforms shown in figure 2(c and d) are analyzed as follows: at interval α ≤ 𝜔𝑡 ≤ 𝜋, the gate signal ig1 is high, t1 and d2 conduct current in this interval. that is, output voltage 𝑉𝑜 = 𝑉𝑚𝑠𝑖𝑛𝜔𝑡; voltage drop across thyristor t4, 𝑉𝑇4 = 0; and voltage drop across thyristor t1, 𝑉𝑇1 = −𝑉𝑚𝑠𝑖𝑛𝜔𝑡; this operation puts the thyristor and diode (t4 and d3) into a reverse biased mode. also, at the interval α+𝜋 ≤ 𝜔𝑡 > 2𝜋, the gate signals ig4 is high, t4 and d3 conduct current during this operation. in both intervals the output current io > 0. for, 𝑉𝑜 = 𝑉𝑚𝑠𝑖𝑛𝜔𝑡; and 𝑉4 = −𝑉𝑚𝑠𝑖𝑛𝜔𝑡; d3 conducting current. however, the system performance can be further obtained through the fourier analysis and some notations used in this work are va is armature voltage, ia is armature current, ra is armature resistance, la is armature inductance, vm is peak voltage, tf is field torque, td is developed torque, pf is the field power, pd is the developed torque, if is the field current, α is the firing angle for armature voltage, 𝛼𝐹 is the field circuit firing angle. in fourier series, the output voltage 𝑣𝑜(𝜔𝑡) as depicted in figure 2(c) for continuous current operation is expressed as: 𝑣𝑜(𝜔𝑡) = 𝑉𝑎 + ∑(𝑉𝑎𝑛𝑐𝑜𝑠𝑛𝜔𝑡 + 𝑉𝑏𝑛𝑠𝑖𝑛𝑛𝜔𝑡) ∞ 𝑛=1 1 referring to figure 2(c), we can derive the formular for computing the armature load voltage va http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 148 𝑉𝑎 = 1 𝜋 [∫ 𝑣𝑜𝑑(𝜔𝑡) 𝜋 𝛼 ] = 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) 2 the rectifier output voltage as a function of 𝜔t is given by 𝑣𝑜(𝜔𝑡) = 𝑉𝑚 𝜋 {(𝑐𝑜𝑠𝛼 + 1) + ∑ ([ 𝑐𝑜𝑠𝛼(𝑛 + 1) + 1 (𝑛 + 1) − 𝑐𝑜𝑠𝛼(𝑛 − 1) + 1 (𝑛 − 1) ] 𝑐𝑜𝑠𝑛𝜔𝑡 ∞ 𝑛=2,4,6,.. + [ 𝑠𝑖𝑛𝛼(𝑛 + 1) (𝑛 + 1) − 𝑠𝑖𝑛𝛼(𝑛 − 1) (𝑛 − 1) ] 𝑠𝑖𝑛𝑛𝜔𝑡) } 3 the nth harmonic amplitude cn is given as in equation (5) 𝐶𝑛 = 𝑉𝑛 = √𝑉𝑎𝑛 2 + 𝑉𝑏𝑛 2 4 𝑉𝑛 = 2𝑉𝑚 𝜋(𝑛2 − 1) [𝑐𝑜𝑠2𝛼 − 𝑛2𝑐𝑜𝑠2𝛼 + 2 cos(𝑛𝛼) 𝑐𝑜𝑠𝛼 + 𝑛2 + 2nsin(𝑛𝛼) 𝑠𝑖𝑛𝛼 + 1] 1 2 (5) while the phase magnitude is developed as ∅𝑛 = tan−1 ( 𝑏𝑛 𝑎𝑛 ) 6 ∅𝑛 = tan−1 ( 𝑛 − 1(𝑠𝑖𝑛𝛼(𝑛 + 1)) − 𝑛 + 1(𝑠𝑖𝑛𝛼(𝑛 − 1)) 𝑛 − 1(𝑐𝑜𝑠𝛼(𝑛 + 1) + 1) − 𝑛 + 1(𝑐𝑜𝑠𝛼(𝑛 − 1) + 1) ) 7 where, 𝑍𝑛 = √𝑅𝑎 2 + (𝑛𝜔𝐿𝑎)2 and 𝜃𝑛 = tan−1 ( 𝑛𝜔𝐿𝑎 𝑅𝑎 ) the root mean square voltage can be computed by equation (8) 𝑉𝑜𝑟𝑚𝑠 = 1 𝜋 [∫ 𝑣𝑜 2𝑑(𝜔𝑡) 𝜋 𝛼 ] = 𝑉𝑚 √2𝜋 [𝜋 − 𝛼 + 𝑠𝑖𝑛2𝛼 2 ] 1 2 8 the average load or armature current 𝐼𝑎 then becomes: 𝐼𝑎 = 𝑉𝑎 − 𝐸 𝑅𝑎 9 in fourier series, the output current 𝑖𝑜(𝜔𝑡) as depicted in figure 2(b) for continuous current operation is expressed as: 𝑖𝑜(𝜔𝑡) = 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) − 𝐸 𝑅𝑎 + ∑ 1 𝑍𝑛 (𝑉𝑎𝑛cos (𝑛𝜔𝑡 − 𝜃𝑛) + 𝑉𝑏𝑛sin (𝑛𝜔𝑡 − 𝜃𝑛)) ∞ 𝑛=2,4,6,.. 10 the rms load current, iarms is calculated using 𝐼𝑎𝑟𝑚𝑠 = √𝐼𝑎 2 + ∑ 𝐼𝑟𝑛 2 ∞ 𝑛=2,4,6… 11 http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 149 where, the nth rms ripple load current irn is given as |𝐼𝑟𝑛| = 𝑉𝑛 √2⁄ √𝑅𝑎 2 + (𝑛𝜔𝐿𝑎)2 12 the power delivered to the dc motor is computed using 𝑃𝑑 = 𝐼𝑎𝑟𝑚𝑠 2 𝑅𝑎 + 𝐼𝑎𝐸 13 the supply power factor can be computed using the formula 𝑝𝑓 = 𝐼𝑎𝑟𝑚𝑠 2 𝑅𝑎 + 𝐼𝑎𝐸 𝑉𝑠𝐼𝑎𝑟𝑚𝑠 14 the form factor for separately excited dc motor armature current is defined as 𝐹𝑜𝑟𝑚 𝑓𝑎𝑐𝑡𝑜𝑟, 𝐹𝐹 = 𝐼𝑎𝑟𝑚𝑠 𝐼𝑎 = 𝑅𝑎𝐼𝑎𝑟𝑚𝑠 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) − 𝐸 15 2.2 separately excited dc motor operation and analysis in separately excited dc motor, the field and armature voltages can be controlled independent of each other. therefore, when the electric field current (if) flows in the field winding of the machine, then magnetic field is created which exerts a magnetic force on the rotor or armature coils carrying the current (ia), causing the rotor to rotate. during this process a back emf (e) is induced in the armature winding as it rotates. the basic equations of the dc motor for steady-state operation can be generated as follows [1]: 𝑉𝑎 = 𝐸 + 𝐼𝑎𝑅𝑎 = 𝐾𝜔𝑚 + 𝐼𝑎𝑅𝑎 16 generated emf, speed, flux and number of conductors in the armature is related as: 𝐸 = 𝑝𝑍 𝑐 𝜙 ( 2𝜋𝑁 60 ) = 𝑘𝜙𝜔𝑚 = 𝑘𝐼𝐹𝜔𝑚 = 𝐾𝜔𝑚 17 the field current ifis directly proportional to the flux, 𝜙. where p implies number of poles, n is motor speed in rpm, 𝜙 is useful flux per pole entering or leaving the armature in weber, k is machine constant, z is total number of armature conductors, c is number of parallel paths through winding between positive and negative brushes and 𝜔𝑚 is the motor speed in rad/sec. multiplying equation (16) by armature current (ia) gives the total electrical power delivered to the armature pe, loss due to armature resistance pl in the circuit and mechanical power developed by the armature pm as depicted in equation (18) 𝑉𝑎𝐼𝑎(𝑃𝐸) = 𝐸𝐼𝑎(𝑃𝑀) + 𝐼𝑎 2𝑅𝑎(𝑃𝐿) 18 from equation (18), the torque developed by the armature td is given by 𝑇𝑑 = 𝐾𝐼𝑎 19 where, 𝐸𝐼𝑎 = 𝑘𝜙𝜔𝑚𝐼𝑎 = 𝑇𝑑𝜔𝑚 each thyristor blocking voltage is depicted in figure 1(d), this plot aids in selection of the thyristor current and voltage values. http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 150 2.3 armature and field voltages, currents, firing angles, speeds and torque relationships armature control of a separately excited dc motor involves adjusting the supply voltage to the armature winding of the motor to control its speed and torque. to regulate motor’s speed and torque, field control involves adjusting the field winding’s current. by varying the field current, the motor’s flux can be controlled, which will affect speed, torque and efficiency performance. under steady-state conditions, armature voltage is related with firing angle as derived equation (2). from equation (16), the motor speed yields 𝜔𝑚 = 1 𝐾 ( 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) − 𝐼𝑎𝑅𝑎) = 𝑉𝑚 𝜋𝐾 (𝑐𝑜𝑠𝛼 + 1) − 𝑇𝑑 𝐾2 𝑅𝑎 20 equation (20) depicts speed relationship with developed torque. developed motor torque can be deduced from eqn. (20) as: 𝑇𝑑 = 𝐾2 𝑅𝑎 ( 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) − 𝜔𝑚) 21 and developed motor power is depicted in equation (22) as 𝑃𝑑 = 𝑇𝑑𝜔𝑚 22 from figure (1), since both armature voltage and field winding voltage are supplied by the same power circuit topology, therefore, the field circuit vf can be obtained as 𝑉𝐹 = 𝑉𝑚 𝜋 (cos (𝛼𝐹) + 1) 23 the field current if is given as 𝐼𝐹 = 𝑉𝐹 𝑅𝑓 = 𝑉𝑚 𝜋𝑅𝑓 (𝑐𝑜𝑠𝛼𝐹 + 1) 24 based on equations (16) and (17), the relationship between the armature and field currents is given as: 𝐼𝑎 = 1 𝑅𝑎 ( 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) − 𝑘𝐼𝐹𝜔𝑚) 25 from equations (19), (24) and (25), the motor torque developed can be expressed as 𝑇𝐹 = 𝑘𝐼𝐹𝐼𝑎 = 𝑘𝑉𝑚 𝜋𝑅𝑓𝑅𝑎 ((𝑐𝑜𝑠𝛼𝐹 + 1) ( 𝑉𝑚 𝜋 (𝑐𝑜𝑠𝛼 + 1) − 𝑘𝐼𝐹𝜔𝑚)) 26 𝑃𝐹 = 𝑇𝐹𝜔𝑚 27 3. results and discussion 3.1 semi-converter the output voltages and currents of a semi-converter depend on several factors including the topology of the converter circuit, the type of power switch devices used, the control strategy employed, and the load connected to the converter. the output voltage 𝑣𝑜(𝜔𝑡) of equation 3 is typically a pulsating dc waveform as depicted in figure 2. the resulting voltage waveform varies between 0 v and 325 v. the average output voltage of a rectifier circuit can be calculated using equation 2 and also called the armature voltage, va. the output current 𝑖𝑜(𝜔𝑡) of equation 10 is typically also a pulsating dc waveform as depicted in figure 3 and the resulting current waveform varies between 4 a to 28 a. equation 9 shows the formular for the average output current otherwise called armature current, ia. the harmonics in the output voltage waveform versus firing angle is depicted in figure 4. the highest normalized harmonic amplitude occurred at n equal to 2 with 60 degrees firing angle. http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 151 figure 3: outputs voltages and currents waveforms figure 4: harmonic index against firing angle plot 3.2 separately excited dc motor the relationship between armature and field voltages and currents against developed torque in a separately excited dc motor is depicted in figure 5. however, generally, increasing the armature voltage increases the torque output of the motor, up to a point of diminishing returns and saturation effects. the speed is directly influenced by the armature voltage and current as depicted in figure 6. also, the speed is inversely influenced by the field voltage and current. armature and field voltages and currents are plotted against the firing angles as shown in figure 7. it is observed that the increase in firing angle indirectly affects the armature and field http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 152 voltages and currents. the relationship between the machine speed, current and torque is depicted in figure 8. the armature and field powers and torques in a separately excited dc motor are influenced by the armature voltage, armature current, field voltage, field current, and mechanical load as depicted in figure 9. the machine speed is determined by the balance between the mechanical output torque, load torque, and the motor's characteristics. adjusting the armature voltage and field current can control the motor's speed and torque characteristics, allowing for precise speed regulation and torque control in various applications. the threedimensional waveform of torque, power and machine speed is as plotted in figure 10. figure 5: armature and field voltages and currents against torque figure 6: armature and field voltages and currents against machine speed http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 153 figure 7: armature and field voltages and currents against firing angles figure 8: armature and field currents and torques against machine speed http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 154 figure 9: armature and field powers and torques against machine speed figure 10: three-dimensional waveform of torque, power and machine speed http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 155 table 1: parameters for separately excited dc motor drive parameter value vs 230√2sin𝜔𝑡 v motor emf, e 200 v ra 6.5 ω la 25mh ia 15 a 𝛼 = 𝛼𝑓 15𝑜 f 50 hz n 1500 rpm rf 120 4. conclusion the implementation of thyristor-based control for a separately excited dc motor driven by a single-phase semi-converter demonstrates significant advancements in the precise control of motor speed and torque. the system leverages the ability of thyristors to modulate voltage and current supplied to the motor, enabling effective control over its operational parameters. this approach offers several advantages, including improved efficiency, reduced energy consumption, and enhanced system reliability. by providing smooth and adjustable control, the method ensures optimal performance across a wide range of load conditions, making it particularly suitable for industrial and automation applications. moreover, the use of a single-phase semi-converter simplifies the design and reduces the overall cost, without compromising the system's control accuracy. this implementation highlights the potential for further integration of power electronics and motor control technologies to achieve more compact, efficient, and versatile systems. future work could explore extending this control strategy to multi-phase converters, incorporating advanced control algorithms, and addressing harmonics to further improve performance and reduce electrical noise. references ahmed, mmr., elemary, aa., alaas, zm. and hamada, am. 2023. torque control of a 5 kw, 220 v separately excited dc motor using microcomputer, international journal of power electronics and drive systems (ijpeds), 14(2): 727 – 740. asadi, f. and eguchi, k. 2019. comparison of different dc motor modeling techniques, journal of electronic research and application, 2(2): 1 – 4. dubey, gk. 2009. fundamentals of electrical drives, narosa publishing house, new delhi chennai mumbai kolkata, 60 139. dubey, t. and sharma, jk. 2022. efficient speed control of thyristor fed dc motor drive using interval type2 fuzzy logic controller, advances and application in mathematical sciences, 21(11): 6571-6588. el-kholy, ee., shokralla, ss., morsi, ah. and el-absawy, sa. 2004. improved performance of rolling-mill drives using fuzzy hybrid-pi controller, electromotion, 11: 213 – 224. hameed, hq. and ali, fm. 2016. design of a pc-based dc motor speed controller, diyala journal of engineering sciences, 9(2): 1–11. http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):145-156. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: geraldiyoke@mouau.edu.ng 156 hareb, m., ekhail, m. and hareb, f. 2021. separately excited dc motor speed control, simulation case study, 1st international mahreb meeting of the conference on sciences and techniques of automatic control and control engineering mi-sta, 47 – 51. hassan, ay., rohieem, ag. and salem, sms. 2014. direct torque control of non-salient pole afpmsms with svpwm inverter, international journal of power electronics and drive systems, 13(4): 2014–2023. hughes, a. 2006. electric motors and drives: fundamentals, types and applications, elsevier ltd, linacre house, jordan hill, oxford ox2 8dp, 134 – 164. kandpal, m., rai, jn. and aggarwal, a. 2015. comparative study of speed control of separately excited dc motor using pi controller and fuzzy logic controller, international journal of electronics, electrical and computational system, 4: 27 – 36. krishnan, r. 2001. electric motor drive: modeling, analysis, and control, prentice hall, inc. upper saddle river, new jersey, 114 – 117. namdeo, r., sharma, cs. and minz, rb. 2014. analysis of speed for separately excited dc motor using all types of single-phase and three-phase rectifiers, international journal of engineering research & technology (ijert), 3(9): 305 – 312. nguyen, kk. and nguyen, tt. 2019. the sensorless control system for controlling the speed of direct current motor, indonesian journal of electrical engineering and computer science, 16(3): 1171-1178. onah, aj., awah, cc. and diyoke, gc. 2022. speed control of direct current motors, nigerian research journal of engineering and environmental sciences, 7(1): 319 – 329. perelmuter, v. 2012. electrotechnical systems: simulation with simulink® and simpowersystems tm, crc press. poornima, p., suganya, p., kumaresan, n. and subbiah, m. 2006. operating modes of single –phase thyristor converter fed dc drives using phase angle control scheme-a monograph, ieee international conference on industrial technology, mumbai, 2402 – 2407. rashag, hf. 2019. improved speed response of dc motor via intelligent techniques, international journal of advances in applied sciences (ijaas), 8(3): 204-207. saini, p., rawat, n. and dixit, a. 2020, design and analysis of thyristor based dc drive system for speed control of dc motor, international journal of advanced research in engineering and technology (ijaret), 11(5): 921-928. sami, ss., obaid, za., muhssin, mt. and hussain, an. 2021. detailed modelling and simulation of different dc motor types for research and educational purposes, international journal of power electronics and drive systems (ijpeds), 12(2): 703-714. sharma, cs., singh, k. and tamrakar, r. 2016. a thyristor based speed control techniques of separately excited dc motor, international journal of scientific development and research (ijsdr), 1(11): 13 – 25. tiwari, s., unni, ac., rajanivedha r., singh, gj. and ongsakul, w. 2019. harmonic analysis of separately excited dc motor drive, innovations in power and advanced computing technologies (i-pact), 1-7. virendra ss., virendra, j. and anil, kc. 2013. different speed control techniques of dc motor: a comparative analysis, ijltemas 2(7): 112 – 118. http://www.azojete.com.ng/ mailto:geraldiyoke@mouau.edu.ng corresponding author’s email address: mohammedbukar61@gmail.com 309 arid zone journal of engineering, technology & environment original research article effects of fibre length and fibre loading on tensile and flexural properties of luffa cylindrica reinforced polylactic acid composite m. bukar1,2*, i. s. aji1, z. a. mshelia1, and a. a. hammajam1 1department of mechanical engineering, faculty of engineering, university of maiduguri, maiduguri-nigeria 2maiduguri flour mills limited maiduguri, borno state nigeria *corresponding author’s email: mohammedbukar61@gmail.com article information abstract this study examines the effects of fibre length and fibre loading on the tensile and flexural properties of luffa cylindrica reinforced polylactic acid (pla) composites. luffa cylindrica fibres, a natural and biodegradable reinforcement material, were incorporated into pla at varying fibre lengths (1 mm, 3 mm, and 5 mm) and fibre loadings (10%, 20%, 30%, 40%, and 50%) to assess their impact on mechanical performance. the results revealed that both tensile and flexural properties were significantly affected by fibre length and loading. optimal mechanical properties were observed at 30% fibre loading with a 3 mm fibre length, where tensile strength reached 28.52 mpa and flexural strength peaked at 77.81 mpa. however, higher fibre loadings (40% and 50%) led to a reduction in strength due to poor interfacial adhesion and fibre wetting. shorter fibre lengths (1 mm) contributed to a higher tensile modulus, suggesting that compact fibre arrangements resist deformation more effectively. this study highlights the potential of luffa cylindrica fibres as effective reinforcements in pla composites, offering valuable insights for sustainable material development. received: 6th november 2024 reviewed: 25th february 2025 accepted: 27th february 2025 keywords: fibre length tensile strength flexural strength polylactic acid luffa cylindrica © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the growing environmental concerns associated with synthetic polymer usage have spurred interest in developing sustainable and biodegradable alternatives. in this context, natural fibre-reinforced biopolymer composites have emerged as promising materials, combining the biodegradability of natural fibres with the versatility of biopolymers (naser et al., 2021). among these, luffa cylindrica fibre (lcf) reinforced polylactic acid (pla) composites have gained attention due to their potential applications in various industries, including automotive, packaging, and construction (kumar et al., 2023; ashok et al., 2024). the shift towards sustainable materials is further driven by stringent environmental regulations and the increasing demand for eco-friendly products, particularly in industries seeking to reduce their carbon footprint (ahmed and susmel, 2017). polylactic acid (pla) has proven itself as a good potential polymer material with desirable characteristics for applications in engineering, physical/life sciences and medical sectors. many developed composites in use presently have provided the edge in material’s technology, establishing their advanced applications in aerospace, structures and aeronautic engineering (nazrin et al., 2020; karande et al., 2021; charles et al. 2024). however, composite materials are around for centuries, therefore it is not a completely new idea, but has been there for centuries. khanam, et al., (2007) reported that early egyptians produce reinforced mud bricks (composite) from chopped straw and mud, while mongol warriors produce very durable archery bows using composites made up of bamboo strips, bullock tendon, pine resin, horn, strips and silk. luffa cylindrica, commonly known as sponge gourd or vegetable sponge, is a plant species that produces a fibrous network within its fruit. these fibres are characterized by their lightweight nature, high specific strength, and biodegradability, making them an attractive reinforcement material for biopolymer matrices (siqueira et al., 2010; shen et al., 2012). moreover, luffa cylindrica fibre is abundant, cost-effective, and renewable, which enhances their appeal as a sustainable alternative to synthetic fibre (baigh et al., 2023). pla, on the other hand, is a biodegradable thermoplastic derived from renewable resources such as corn starch or azojete march 2025. vol.21(1):309-317 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:mohammedbukar61@gmail.com mailto:mohammedbukar61@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 310 sugarcane. it offers a promising alternative to petroleum-based plastics due to its biodegradability and comparable mechanical properties (teixeira et al., 2021). the combination of pla with natural fibre like luffa cylindrica not only enhances the mechanical properties of the resulting composites but also aligns with the principles of a circular economy, where waste is minimized, and resources are reused (ilyas, et al., 2021). in addition, the mechanical properties of natural fibre-reinforced polymer composites are significantly influenced by various factors, including fibre length and fibre loading (saba et al., 2016). these parameters play crucial roles in determining the interfacial adhesion between the fibre and the matrix, stress transfer efficiency, and overall composite performance (khan et al., 2023). earlier studies have investigated the effects of fibre length and loading on various natural fibre-reinforced composites, such as jute/pla (ejaz et al., 2020), sisal/pla (kittikorn et al., 2018) and many other green/pla composites (li et al., 2022; aji et al. 2011). for instance, fang et al. (2020) demonstrated that optimal fibre length and loading significantly improved the tensile strength of jute/pla composites, while ejaz et al. (2020) highlighted the importance of fibre-matrix compatibility in sisal/pla composites. these findings underscore the critical role of fibre parameters in tailoring composite properties for specific applications. review by aji et al. (2009) expressed the immense benefits of reinforcing polymers with natural or synthetic fibre. however, there is a notable research gap in understanding these effects specifically for luffa cylindrica fibre reinforced pla composites. while some researchers have explored the potential of luffa cylindrica as a reinforcement in polymer composites (saw et al., 2013; sabarinathan et al., 2016; sahayaraj et al., 2022), the systematic investigation of how fibre length and loading affect the mechanical properties of lcf/pla composites remains limited. this gap in knowledge hinders the optimization of these composites for specific applications and limits their potential industrial adoption. this study aims to investigate the effects of fibre length and fibre loading on the tensile and flexural properties of luffa cylindrica reinforced polylactic acid composites. by systematically varying the fibre length (1 mm, 2 mm, and 3 mm) and fibre loading (10% to 50% by weight), the study seeks to establish relationships between these parameters and the resulting mechanical properties of the composites. the findings of this research are expected to provide valuable insights into the optimization of lcf/pla composites, enabling their broader adoption in industries such as automotive, packaging, and construction. additionally, this study contributes to the growing body of knowledge on sustainable materials, supporting global efforts to reduce reliance on non-renewable resources and mitigate environmental degradation. 2. materials and methods 2.1 materials luffa cylindrica was collected from maiduguri metropolis. it was sorted, washed, sun dried, shredded into smaller pieces and cut into short fibre form of 1 mm, 2 mm and 3 mm using a laboratory milling machine at the quality control laboratory, nilest, zaria, kaduna state. the polylactic acid was obtained from abams chemicals plc, ojota lagos state, nigeria. sodium hydroxide and distilled water were obtained from chemistry laboratory, nigerian institute of leather and science technology, zaria, kaduna state. 2.2 methods 2.2.1 treatment of luffa cylindrica the fibre was treated using 5%w/v naoh solution for one hour at 50 oc temperature. 5%w/v naoh solution was prepared by dissolving 5 g of sodium hydroxide (naoh) pellet in 100 ml of distilled water in accordance with (bichang et al., 2022). the solution was produced in large volume that was enough for the filler treatment. the treated fibre was rinsed severally with distilled water until the rinsing water becomes neutral to ph paper. thereafter, the treated luffa cylindrica fibre was dried using hot air oven and was evenly spread on aluminium foil sheet laid on the oven tray. the tray was placed in the oven at temperature of 70 oc allowed to dry for six hours. the weight of the dried fibre was taken and recorded at interval of 30 minutes and then returned to the oven until a constant weight was achieved. 2.2.2 melt-mixing of composite the formulation shown in table 1 was followed in the melt-mixing process. sample a, b, c, d and e were replicated for fibre length 1 mm, 2 mm and 3 mm. http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 311 table 1: composite formulation material neat sample (pla) sample a sample b sample c sample d sample e lcf (wt %) 0 10 20 30 40 50 pla (wt %) 100 90 80 70 60 50 the composite obtained from the mixing process was placed into a metal mould of dimensions 120 mm x 100 mm x 3.2 mm and was placed on the hydraulic hot press (compression moulding machine) for shaping at temperature of 150 oc and pressure of 2.5 mpa for five minutes. it was cooled, removed from the mould and labelled accordingly. this process was repeated for all the composites produced. 2.3 characterization of the composites 2.3.1 tensile strength the tensile strength was carried out in accordance with astm d-638. a dumbbell shaped samples were subjected to a tensile force and tensile strength, tensile modulus, percentage elongation at beak for each sample were calculated and recorded automatically by the machine and the results were recorded on the certificate. all measurement was recorded at room temperature and each sample composition was tested with three replicas. 2.3.2 flexural strength the flexural strength test on the blends was carried out in accordance with astm d-790. the specimen measuring 100 mm x 25 mm x 3.2 mm was placed on a support span horizontally at 80 mm gauge length and a steady load was applied to the centre by the loading nose producing three-point bending until the sample specimen failed. the maximum load (n) and the corresponding deflection (mm) were recorded accordingly as the sample specimen failed. figure 1 presents the nature of the test samples used. to maintain reliability, every sample composition was evaluated using three replicas. figure 1: nature and appearance of test samples 2.3.3 scanning electron microscopy the scanning electron microscope (sem) from sem model no: ae200 was used to study the morphological characteristics of the fibre after various stages of the mechanical tests. http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 312 2.3.4 statistical analysis all data presented are expressed as means of triplicate values. single factor analysis of variance was carried out to compare the means of different data sets, and a value of 𝑃 < 0.05 was considered statistically significant. 3. results and discussion 3.1 effect of varying fibre loading and fibre length on tensile strength and modulus figure 2 shows the tensile strength test results for the luffa fibre/pla composites. the tensile strength of the luffa fibre/pla composites were found to be significantly different (𝑃 < 0.05). the results show a steady increase in tensile strength of the composites as the luffa fibre loading increases until it reaches a peak of 28.52 mpa at 30 % luffa fibre loading and at the 3 mm fibre length (sample at 30% luffa fibre was significantly different (𝑃 < 0.05) from all samples followed by 20% luffa fibre loading at 20% fibre loading). thereafter, a steady decrease in the tensile strength was observed. the increase in the tensile strength of the composites from 10 % to 30 % filler loading could be related to the better interfacial adhesion between the fibre and the matrix which aided stress transfer within the composite system of pla thereby helping in stress distribution within the matrix as the sample experiences tensile forces. figure 2: fibre loading and fibre length on the tensile strength of pla composites. however, the decrease in the tensile strength from 40 % to 50 % filler loading may be due to high percentage ratio of filler to the matrix which led to low wetting of the fibre and thus reduced bonding strength between the filler and the matrix. poor wetting of fibre by the matrix results in poor interfacial adhesion between the fillers and the matrix, hence, stress transfer was greatly affected which reduced and the tensile strength of the composite with loading. the 3 mm fibre length exhibited a better reinforcement property than 2 mm and 1 mm. similar result was shown by (sarukasan et al., 2021). however, the 1mm fibre length presented a better modulus with loading of the pla as shown in figure 3. 0 5 10 15 20 25 30 0 10 20 30 40 50 t en si le s tr en g th ( m p a) luffa cylindrica loading (wt%) http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 313 figure 3: effects of fibre loading and fibre length on the tensile modulus of the composite. tensile modulus describes the ability to resist extension. fibre loading is found to be statistically significant against the tensile modulus of the composites (𝑃 < 0.05). the results show greater modulus obtained with the shortest fibre, i.e. 1mm fibre length. however, the modulus dropped with increase in fibre loading and fibre length. this will not be unconnected with the fact that short fibre provided a greater amount of compactness in the composite which provided the greatest amount of resistance before failure. however, clearly, all showed a greater modulus than the pure pla. modulus of composites increased with filler loading until a peak is reach when there will be decline in the trend due to poor adhesion (kolawole et al., 2019); this is at variance to result observed in the samples loaded with 1 mm fibre length filler. this could be expressing a new phenomenon obtained in formulating this composite by exploring this relatively new fibre in composite formulation. meanwhile, the composite formulated with 2mm and 3mm fibre length corroborated the findings of (kolawole et al., 2019). figure 4a and b presents the sem micrograph of the failed sample tested. sample c3 (sample loaded with 30 % 3 mm luffa fibre) and sample a2 (sample loaded with 10 % 2 mm luffa fibre) which represents the best and the poor performing samples from tensile strength test results. a uniform fibre distribution and bundle fibre breakage could be seen in figure 4a whereas figure 4b shows image of scanty filler and uneven fibre distribution as the image revealed fibre random concentration in the matrix. (a) (b) figure 4: (a) tensile strength sample (c3) (b) tensile strength sample (a2) 3.2 effect of varying fibre loading and fibre length on flexural strength figure 5 shows the flexural strength test results for the luffa fibre/pla composites. although there is statistical difference on the effects of fibre loading on the flexural strength at 𝑃 < 0.05, there is only a little but steady increase in flexural strength of the composites was observed as the luffa fibre loading increases until it reaches a peak of 77.81 mpa at 30 % luffa fibre loading for 3 mm fibre length. thereafter, a steady decrease in the flexural strength was observed as the filler loading increased from 40 % to 50 %. the increase in the flexural 0 50 100 150 200 250 300 0 10 20 30 40 50 t en si le m o d u lu s (m p a) luffa cylindrica loading (wt%) 1mm fibre 2mm fibre 3mm fibre http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 314 strength of the composites from 10 % to 30 % filler loading could be related to the better interfacial adhesion between the fibre and the matrix which aided stress transfer within the composite system thereby helping stress distribution within the matrix as the sample experiences bending forces. the matrix was able to transfer the load to the fibre effectively. however, the decrease in the tensile strength from 40 % to 50 % filler loading was due to high percentage ratio of filler to the matrix which led to lower bonding strength between the filler and the matrix and resulted in filler agglomeration giving rise to poor interfacial adhesion between the fillers and the matrix. hence, stress transfer reduced and so does the flexural resistance (akhyar, et al., 2024). the results also show that 3 mm luffa fibre exhibited reinforcement property aiding an increase of about 11% flexural property when compared to the pure matrix. increase in fibre length produced some increment of property compared to lower length fibres, i.e. 1 mm and 2 mm. this is in line with the result obtained by vineeth and sanil (2017). figure 5: effects of fibre loading and fibre length on the flexural strength of composite also, figure 6 represents the flexural modulus test results for the luffa fibre/pla composites produced. flexural modulus describes the ability of the composite sample to resist bending extensibility. figure 6: effects of fibre loading and fibre length on the flexural modulus of pla composites natural fibres have greater amount of modulus in them because of the presence of cellulose. luffa fibre has about an average of 60% cellulose in them (bichang et al., 2022). therefore, increase in fibre loading will improve the modulus content of the composite. there is an evidence of fibre loading being significant against 0 10 20 30 40 50 60 70 80 90 0 10 20 30 40 50 f le x u ra l s tr en g th ( m p a) luffa cylindrica loading (wt%) 1mm fibre 2mm fibre 3mm fibre 0 500 1000 1500 2000 2500 3000 3500 0 10 20 30 40 50 f le x u ra l m o d u lu s (m p a) luffa cylindrica loading (%) 1mm fibre 2mm fibre 3mm fibre http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 315 flexural modulus of the pla composites (𝑃 < 0.05). the results indicate that the flexural modulus of the samples increases with increase luffa fibre loading up to the last loading for the 1mm fibre length. the same trend was observed in all the different fibre length used. this implies that the presence of the fibre in the matrix enhanced the stiffness of the polymer core thereby resisting free chain mobility of the matrix as bending force was applied. the luffa fibres have between 50 – 90% cellulose content, which provided the extra strength obtained in their composites. the major component of vegetal fibres is the cellulose, which is a polymer of β d-glucose oriented in which -ch2oh group is alternating above and below the plane of the cellulose molecule thus producing long, unbranched chains present in the secondary cell wall of the fibre. it is responsible for the high mechanical strength of fibres and acts as a reinforcing material. because the small fibre length composite’ had greater amount of compactness, it was able to interact with the matrix much better and therefore gave better resistance under load. also, figure 7a and 7b describe the result of the scanning electron microscopy of the formulated composites. surface morphology image for sample c3 (sample filled with 30 % 3 mm luffa fibre) and the sample e2 (sample loaded with 50 % 3 mm luffa fibre) as the best and the poor performed samples from flexural strength test results. a uniform fibre distribution and bundle fibre stretched could be seen in figure 7a whereas figure 7b shows image of scanty filler and uneven fibre distribution as the image revealed fibre random concentration in the matrix. (a) (b) figure 7: flexural strength sample (a) c3 (b) e2 4. conclusion this study investigated the effects of fibre length and fibre loading on the tensile and flexural properties of luffa cylindrica reinforced polylactic acid composites. the results revealed that both fibre length and fibre loading significantly influenced the mechanical properties of the composites. optimal tensile and flexural properties were observed at 30% fibre loading with a 3 mm fibre length, with tensile strength peaking at 28.52 mpa and flexural strength at 77.81 mpa. this improvement is attributed to better interfacial adhesion and stress transfer between the fibre and matrix, resulting in enhanced mechanical performance. however, at higher fibre loadings (40% to 50%), a decrease in both tensile and flexural strength was observed, likely due to poor fibre wetting and interfacial adhesion, leading to stress concentration and reduced load-bearing capacity. shorter fibre lengths (1 mm) demonstrated better tensile modulus, highlighting the influence of fibre compactness in resisting deformation. overall, the study suggests that luffa cylindrica fibres can be effectively used to reinforce pla composites, with an optimal fibre loading and length combination providing the best mechanical properties. these findings offer valuable insights for the design and application of bio-composites in various industries, particularly in sustainable materials development. references ahmed, aa. and susmel, lp. 2017. additively manufactured pla under static loading: strength/cracking behaviour vs. deposition angle. procedia structural integrity, 3: 498–507. http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 316 aji i.s., sapuan s.m., zainudin e.s. and abdan k. 2009. kenaf fibres as reinforcement for polymeric composites; a review; international journal of mechanical and materials engineering, vol. 4, no. 3, university of malaya, selangor, malaysia aji i.s., zainudin e.s., khalina a., sapuan s.m. and khairul m.d. 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snail shell thermoset composite. direct research journal of chemistry and material science, 7: 8-13. kumar, km., naik, v., kaup, v., waddar, s., santhosh, n. and harish, hv. 2023. nontraditional natural fillerbased biocomposites for sustainable structures. advances in polymer technology, 2023: 838766. li, x., lin, y., liu, m., meng, l. and li, c. 2022. a review of research and application of polylactic acid composites. journal of applied polymer science, 140(7): e5377. naser, az., deiab, i. and darras, bm. 2021. poly (lactic acid) (pla) and polyhydroxyalkanoates (phas), green alternatives to petroleumbased plastics: a review. rsc advances, 11: 17151–17196. http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 309-317. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mohammedbukar61@gmail.com 317 nazrin, a., sapuan, sm., zuhri, my., ilyas, ra., syafiq, r. and sherwani, sf. 2020. nanocellulose reinforced thermoplastic starch (tps), polylactic acid (pla), and polybutylene succinate (pbs) for food packaging applications. frontiers in chemistry, 8: 213. saba, n., jawaid, m., alothman, oy. and paridah, mt. 2016. a review on dynamic mechanical properties of natural fibre reinforced polymer composites. construction and building matherials, 106: 149-156. sabarinathan, p., rajkumar, k. and gnanavelbabu, a. 2016. investigation of mechanical properties of luffa cylindrical and flax reinforced hybrid polymer composite. journal of advanced engineering research, 3(1): 124127. sahayaraj, af., muthukrishnan, m. and ramesh, m. 2022. influence of tamarindus indica seed nano-powder on properties of luffa cylindrica (l.) fruit waste fiber reinforced polymer composites. polymer composites, 43(9): 6442-6452. sarukasan, d., thirumavalavan, k., prahadeeswaran, m. and muruganandhan, r. 2021. fabrication and mechanical characterization of jute-coir reinforced unsaturated polyester resin hybrid composites with various fiber sizing using compression moulding technique. international journal of recent technology and engineering (ijrte), 10(1): 233-241. saw, sk., purwar, r., nandy, s., ghose, j. and sarkel, g. 2013. fabrication, characterization, and evaluation of luffa cylindrica fiber reinforced epoxy composites. bioresources, 8(4): 4805-4826. shen, j., xie, ym., huang, x., zhou, s. and ruan, d. 2012. mechanical properties of luffa sponge. journal of the mechanical behavior of biomedical materials, 15: 141-152. siqueira, g., bras, j. and dufresne, a. 2010. luffa cylindrica as a lignocellulose source of fiber, micro fibrillated cellulose and cellulose nanocrystals. bio resources, 5(2): 727-740. teixeira, s., eblagon, km., miranda, f., pereira, mf. and figueiredo, jl. 2021. towards controlled degradation of poly(lactic) acid in technical applications. carbon research, 7(42). vineeth, kt. and sanil, g. 2017. a review of the mechanism of action of amphibian antimicrobial peptides focusing on peptide-membrane interaction and membrane curvature. current protein and peptide science, 18(12): 1263-1272. http://www.azojete.com.ng/ mailto:mohammedbukar61@gmail.com corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 529 arid zone journal of engineering, technology & environment original research article response surface modeling of soursop rich seed pyrolysis for optimum bio-oil production c. b. ugwuodo 1*, h. u. itiri 1, l. a. enyinnaya1, i. n. emmanuel2, s. e. agbokwor3, v.c. uzoma1, r.u. daniel1, and l.c. ezeocha1 1department of chemical engineering, college of engineering and engineering technology, michael okpara university of agriculture, umudike 2department of chemical engineering, nazarbayev university, astana, kazakstan 3 department of mechanical engineering, university of nigeria nsukka *corresponding author’s email: chijiokeugwuodo@mouau.edu.ng article information abstract this research investigates bio-oil production from soursop seed through pyrolysis, with process modelling and optimization conducted using rsm via box-benkhen design. soursop seeds were oven-dried, ground, and sieved into various particle sizes within 1.0 to 6 mm range before undergoing pyrolysis at temperatures between 400 to 600 °c under inert nitrogen gas flow rates between 1.0 to 1.5 l/min. a box-behnken design under response surface methodology (rsm) was used to model and optimize the effects of temperature, particle size, and inert gas flow on bio-oil yield. proximate and ultimate analyses characterized the feedstock, while sem revealed a porous structure favorable for pyrolysis. bio-oil was characterized using ftir and gc-ms to identify key functional groups and fatty acid composition. proximate analysis showed the seeds had high volatile matter and fixed carbon, indicating good potential for pyrolysis. ultimate analysis revealed carbon, hydrogen, nitrogen, oxygen, and sulphur contents of 51.29%, 5.90%, 0.50%, 42.30%, and 0.01%, respectively. scanning electron microscopy (sem) showed a rough, porous structure with oil-like droplets on the surface, which enhanced pyrolysis efficiency by providing a larger reactive surface area and improving devolatilization rates. the experimental design considered temperature, particle size, and gas flow rate combinations, with the bio-oil yield as the response. results showed that increases in these parameters significantly affected bio-oil production. the maximum observed yield of 33.1% was achieved at 500°c, 6 mm particle size, and 1.0 l/min gas flow. the rsm model showed a high degree of fit with an r² value of 0.9875, adjusted r² of 0.9715, and predicted r² of 0.8007. optimization predicted a maximum yield of 31.43% under conditions of 461.84°c, 3.84 mm particle size, and 1.02 l/min flow rate, with a desirability of 1.0. experimental results closely matched these predictions, validating the model. similarly, ftir analysis indicates that the predominant monounsaturated fatty acid made up 45.55% of the total fatty acid content, which depicts that the oil belongs to the linoleic acid group. furthermore, the ftir analysis reveals that the alkene group contributes to increased reactivity and combustion efficiency, boosts the octane number of the bio-oil, and decreases the boiling point of the oil. therefore, the ftir and gc-ms analysis findings confirm that the bio-oil was within astm specifications. received: 19th march 2025 revised: 1st may 2025 accepted: 2nd may 2025 keywords: bio-oil cellulose box benkhen design response surface methodology (rsm) soursop seed ultimization © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction biomass pyrolysis is a thermal decomposition process conducted in the absence of oxygen, converting organic materials into biochar, bio-oil, and syngas (bridgwater, 2019). this process has gained significant attention due to its potential for producing renewable energy and high-value byproducts, which can mitigate the reliance on fossil fuels and contribute to a circular economy (biswas et al., 2022). fixed-bed pyrolytic reactors are azojete june 2025. vol.21(2):529-544 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/018 www.azojete.com.ng about:blank about:blank http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 530 prominent among the various pyrolysis technologies due to their simplicity, efficiency, and adaptability to different biomass feedstocks (tripathi et al., 2021). several methods are used today to create liquid fuel from biomass, including fermentation to produce ethanol (hoover and abraham, 2019), transesterification to produce biodiesel (muley and boldor, 2021) and pyrolysis to produce bio-oil (goyal et al., 2018). in a fixedbed reactor, the biomass is placed in a stationary bed and heated, allowing for better control over the pyrolysis conditions (mohan et al., 2021). this setup is particularly advantageous for studying the pyrolysis behaviour of specific biomass types, such as soursop seed (wang et al., 2022). the fixed bed configuration ensures uniform heating and consistent product distribution, which are crucial for optimizing the pyrolysis process and enhancing the quality of the derived products (wang et al., 2022). soursop (annona muricata) is a tropical fruit celebrated for its nutritional and medicinal properties. yet, its seeds are often overlooked and discarded as agricultural waste (martínez et al., 2020). these seeds, which comprise about 20% of the fruit's total weight, contain valuable organic material that can be converted into useful products through pyrolysis (ishaq et al., 2020). the process involves heating the biomass in a fixed bed pyrolytic reactor, where it undergoes complex chemical reactions to produce solid (biochar), liquid (bio-oil), and gaseous products. (zhao et al., 2023). the distribution and yield of these products are influenced by several factors, including temperature, heating rate, particle size, and residence time (sharma et al., 2021). recent studies have highlighted the potential of pyrolyzing soursop seeds as a sustainable waste management strategy and a method for generating renewable energy (mansur et al., 2020). the biochar produced from soursop seeds exhibits promising characteristics, such as high porosity and nutrient content, making it a potential candidate for soil amendment and carbon sequestration (alkhalidi et al., 2023). moreover, bio-oil derived from the seeds can serve as a valuable source of biofuels and chemicals, aligning with the global shift towards greener energy solutions (dajanta et al., 2021). bio-oil derived from the pyrolysis of soursop seeds is rich in various organic compounds that can be upgraded to produce biofuels and bio-chemicals (mansur et al., 2020). the potential applications of bio-oil are extensive, ranging from energy production to the synthesis of high-value chemicals, thereby enhancing the economic viability of soursop seeds (lehmann and joseph, 2019). the temperature of pyrolysis plays a critical role in determining the composition and yield of the pyrolysis products (aboelela et al., 2021). at lower temperatures (300-400°c), the process favours the production of biochar, while higher temperatures (500-700°c) increase the yield of bio-oil and syngas (zhao et al., 2023). soursop seed pyrolysis at varying temperatures has demonstrated this trend, where biochar yields decrease, and bio-oil yields increase with rising temperatures (patel et al., 2021). furthermore, the soursop seed's heating rate and particle size also influence the pyrolysis kinetics and product distribution (dajanta et al., 2021). faster heating rates enhance the bio-oil yield, while smaller particle sizes facilitate more efficient heat transfer and faster reaction rates (huang et al., 2020). the pyrolysis of soursop seeds presents an environmentally friendly alternative to conventional waste disposal methods (singh et al., 2021). by converting waste into energy and improving soil quality, pyrolysis contributes to the circular economy (patel et al., 2021). additionally, the process can help mitigate greenhouse gas emissions by sequestering carbon in the form of biochar (alkhalidi et al., 2023). in search of optimal pyrolysis conditions, researchers explore modeling, predicting, and optimizing process parameters utilizing responses surfaces methodology (rsm), (ingie et al., 2023; nwosu-obieogu et al., 2024). rsm evaluates linear, interaction, and quadratic effects to identify ideal operating conditions for processes (ude et al., 2020; fakhari, 2023). while rsm has been used for pyrolysis of agricultural waste, there is currently a lack of literature on comprehensive investigations and optimization employing rsm, tailored explicitly for soursop seeds pyrolysis (okeleye and betiku, 2019; belmajdoub and abderaft, 2023). onaifo et al. (2023) investigated the co-pyrolysis of soursop and mango (mangifera indica) seeds to produce high-quality bio-oil. utilizing slow pyrolysis at temperatures between 350–500 °c with a heating rate of 5 °c/min and a residence time of 60 minutes, they achieved optimal bio-oil yields at 400 °c: 36.48% for soursop seeds, 20.54% for mango seeds, and 26.16% for the combined feedstock. gas chromatography-mass spectrometry (gc-ms) analysis revealed that the co-pyrolyzed bio-oil was rich in hydrocarbons (41.16%), carboxylic acids (21.89%), ethers (13.60%), esters (7.99%), and phenolics (5.20%). the study concluded that co-pyrolysis suppressed ether formation, resulting in bio-oil with potential applications as a biodiesel substitute and in the industrial production of resins and adhesives. schroeder et al. (2017) analyzed the liquid fractions obtained from the slow pyrolysis of soursop seed cake. the research focused on the chemical and physical properties, providing insights into their potential applications. although specific details are limited, the study contributes to understanding the composition and utility of pyrolysis products derived from soursop seeds. kan et al. (2016) reviewed the pyrolysis of lignocellulosic biomass, focusing on product properties and the influence of various pyrolysis parameters. although not specific to soursop seeds, the study provides valuable insights into how factors such as temperature, heating rate, and residence time affect the yield and composition http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 531 of biochar, bio-oil, and syngas, which can be applied to optimizing soursop seed pyrolysis processes. sukumar et al. (2015) conducted rapid pyrolysis tests on sweet lime empty fruit bunches in a fixed bed reactor using an electric furnace to generate bio-oil. the impact of particle size, temperature and nitrogen gas flow rate on the end product yields were examined. these pyrolysis parameters are improved by respond surface methodology (rsm) with a box-behnken design (bbd). the findings demonstrated that the bio-oil yield is 28.3% for the experimental and 28.2% for the statistical approach at the optimal temperature of 550°c, 4mm of particle size, and 300 cm3min-1 of gas flow rate. therefore, this work aims to optimize via rsm, implementing box-behnken on some selected parameters (temperature, particle size, and inert gas flow rate) that affect the pyrolysis of soursop seed. furthermore, there is a need for more comprehensive studies on the environmental impacts of discarding this agricultural waste on the surroundings. 2. materials and method 2.1 preparation of feedstock the soursop seed used in this study was obtained from a plantation in ndoro village in the ikwuano local government area of abia state, nigeria. the sample was thoroughly washed to remove all foreign materials and ensure it was free of impurities. the soursop seed was oven-dried for 48 hours at a controlled temperature (60-70°c) to a constant weight. the dried soursop seed was ground in a high-speed rotary cutting mill. the samples of ground soursop seeds were separated into various particle size distributions (1-6 mm) using a standard sieve and stored in different desiccators until needed. 2.1.1 equipment used the equipment used was an integration of different units and instruments. a stainless-steel reactor served as the primary vessel for thermal processing, securely sealed using a pair of flanges and spiral-wound gaskets to ensure leak-tight operation. thermal insulation was provided by fiberglass wrapping, while precise temperature regulation was achieved using a k-type thermocouple connected to a digital temperature controller. condensation of volatile products was facilitated through a water-cooled condenser connected downstream of the reactor. additional components included nitrogen gas supplied from a pressurized cylinder to maintain an inert atmosphere, electric heaters for uniform heating, and fasteners (bolts and nuts) for secure assembly. auxiliary tools such as a stopwatch, test sieves, and analytical balance were used for process timing, particle size classification, and mass measurements, respectively. 2.2 characterization of the feedstock 2.2.1 proximate analysis the proximate analysis is defined as the loss in weight of the soursop seed sample heated under the test condition specified. the proximate analysis was performed according to astm e871 and e872 to determine the soursop seed's moisture content (mc), volatile matter (vm), fixed carbon (fc), and ash content (ac). equations 1, 2, 3 and 4 are used to deduce mc, vm, fc and ac respectively. moisture content (wt %) = ( wo−w1 wo ) × 100 1 volatile matter (wt %) = ( w1−w2 w1 ) × 100 2 fixed carbon (wt %) = ( w2−w3 w2 ) × 100 3 where, wo is the weight of sample in g before heating, w1 is the weight of sample in g after heating at 1150c, w2 is the weight of sample in g after heating at 7500c, w3 is the weight of sample in g after heating at 9000c. the mass of the ash will be calculated as a percentage of the original sample using equation 4. ash, mass % = ( w w ) × 100 4 where, w = mass of ash (g) and w = mass of sample (g) 2.2.2 ultimate analysis http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 532 this test determines the element percent of carbon, hydrogen, nitrogen, sulphur, and oxygen in the soursop seed. the ultimate analysis was carried out in accordance with astm standards e777 and e778 for the determination of carbon, hydrogen, and nitrogen, respectively, as validated in previous studies (demirbaş, 2004). 2.2.3 sem (scanning electron microscopy) the morphological structure of the soursop seed was evaluated before paralyzing it using a scanning electron microscope (sem) (jeol-jsm 760f model, japan) to investigate surface features at high magnification. the procedure involved collecting and cleaning mature seeds, air-drying them, sectioning them, drying them in a laboratory oven, mounting them on aluminum sem stubs, applying a thin layer of gold to prevent charging, and imaging them under high vacuum. high-resolution micrographs were captured at various magnifications, observing surface features like texture, cracks, pores, and fibrous structures. the images were analyzed using sem image analysis software to support further interpretation of the seed's structure and potential influence on pyrolysis behavior. 2.3 experimental procedures of the fixed bed pyrolysis system the pyrolysis of soursop seed was carried out in a lab-scale fixed-bed pyrolyzer. the reactor is made of a stainless steel tube with a height of 300 mm, an internal diameter of 94 mm, and an external diameter of 100 mm. we introduced 50 grams of soursop seeds, with particle sizes ranging from 1 mm to 6 mm, into the reactor for pyrolysis. the reactor was sealed with a lid and steam gasket to ensure gas impermeability. nitrogen gas was purged downstream of the tubular reactor at a flow rate of 1.0, 1.25, and 1.5 l/min, respectively, to establish an inert atmosphere. we adjusted the electrical control panel to heat the heaters to 400, 500, and 600°c, respectively. a thermocouple was positioned at the reactor's apex to gauge the internal temperature. the reactor's temperature was periodically checked with a thermocouple as a safety measure. the volatile products created in the reactor were purged downward and flowed into the condenser. we established the condensation apparatus by immersing the filtering flask in cold water. the liquid oil and solid char were recovered separately, while non-condensable gas was vented into the atmosphere. this technique was repeated according to the number of runs specified in the experimental design. each experiment ran for 30 minutes. we weighed the bio-oil and char using a digital scale, documented the results, and securely stored them in separate, well-sealed containers at room temperature. the yield percentages of pyrolysis products were determined using mass balance equations consistent with those reported in previous studies (miandad et al., 2016; bridgwater, 2012). % 𝑌𝑖𝑒𝑙𝑑 𝑜𝑓 𝐵𝑖𝑜 − 𝑜𝑖𝑙 = x4 − x3 weight of feedstock x 100 (5) % 𝑌𝑖𝑒𝑙𝑑 𝑜𝑓 𝐵𝑖𝑜𝑐ℎ𝑎𝑟 = x2 − x1 weight of feedstock x 100 (6) % 𝑌𝑖𝑒𝑙𝑑 𝑜𝑓 𝐵𝑖𝑜𝑔𝑎𝑠 = 100 – (% yield of bio-oil + % yield of biochar) (7) where x1 = weight of empty reactor, x2 = weight of reactor after reaction, x3 = weight of empty measuring cylinder, x4 = weight of measuring cylinder with bio-oil. 2.4 design of experiment the experimental design and statistical analysis were performed according to the rsm (response surface methodology) using design-expert software (version 13). box-behnken design was employed to study the combined effect of three independent variables, namely, temperature, particle diameter, and inert gas flow, on the yield and quality of the oil. a synthetic medium for bio-oil production by pyrolysis was optimized using the design of experiment and response surface methodology (rsm). the effects of components were investigated by the design of experiment. the statistical model was constructed via box-behnken design using the selected variables. the temperature, particle diameter, and inert gas flow was used as the independent variables and bio-oil yield was the response variables with 17 experimental runs. http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 533 2.5 characterization of bio-oil 2.5.1 gc-ms (gas chromatography-mass spectrometry) gas chromatography-mass spectroscopy analysis was carried out on a perkin elmer turbo mass spectrophotometer (norwalk, cto6859, and usa) incorporating a perkin elmer auto sampler xlgc. the column utilized was perkin elmer elite -5 capillary column measuring 30m × 0.25mm with a film thickness of 0.25mm consisting of 95% dimethyl polysiloxane. the carrier gas employed was helium at a flow rate of 0.5 ml/min. a sample injection volume of 1μl was employed. the inlet temperature was sustained at 250°c. the oven temperature was initially set to 110°c for 4 minutes, followed by a rise to 240°c. subsequently, set to escalate to 280°c at a rate of 20°c, concluding with a duration of 5 minutes. the total duration was 90 minutes. the ms transfer line was sustained at a temperature of 200°c. the source temperature was sustained at 180°c. gcms was analyzed using electron impact ionization at 70 ev, and data was reviewed using total ion count (tic) for compound identification and quantification. the spectra of the components were compared with the database of known component spectra recorded in the gc-ms library. peak area measurements and data processing were conducted using turbo-mass ocptvs-demo spl software. 2.5.2 ftir (fourier transform infrared spectroscopy) this study conducted a functional group analysis of the bio-oil utilizing fourier transform infrared (ftir) spectroscopy, magna-ir550 (nicolet, madison). an online pen plotter was utilized with ftir to generate the obtained liquids' infrared (ir) spectra. a minimal bio-oil will be applied to a potassium bromide (kbr) disc. the ftir spectrum will be measured and recorded in the 500-3500 cm-1 region. the absorption frequency spectrum is recorded and plotted. the standard ir spectra of 61 organic compounds will be utilized to identify the functional groups present in the components of the generated bio-oil (rajia et al., 2023). 3. results and discussion 3.1 results of characterization of soursop seed 3.1.1 proximate analysis result table 1 displays the proximate analysis results for the soursop seed sample. the samples' values for ash content, moisture content, volatile matter, and fixed carbon were 3.75, 9.40, 15.97, and 70.88 (%w/w), respectively, while the energy value was 4480 kcal/kg. the soursop seed proximate analysis showed that it contained more fixed carbon and volatile matter. these components are essential for oil production (siqueira et al., 2008). the presence of low concentrations of moisture content and ash content favours the pyrolysis process considerably. this result is in close agreement with abel et al. (2020); pedro et al. (2022); and anas et al. (2024). table 1: proximate analysis of the soursop seed item % value ash content 3.75 + 0.2 moisture content 9.40 + 0.2 energy value (kcal/kg) 4480 volatile content 15.97+ 0.3 fixed carbon content 70.88+ 0.2 3.1.2 ultimate analysis result the elemental compositions of the samples were evaluated by final analysis. as stated in table 2, the values for carbon, hydrogen, nitrogen, oxygen, and sulphur in the sample were 51.29, 5.90, 0.50, 42.30, and 0.01 mass% correspondingly. the elevated carbon and oxygen content signifies that soursop seed consists of highly polar structures, which is advantageous for the ion exchange adsorption mechanism. similarly, the low sulfur and nitrogen content may mitigate the accumulation of hazardous compounds in the reactor compartment, reducing the pyrolysis plant's maintenance requirements. the low sulphur and nitrogen could lead to reduced sox and nox gases which severely impact the troposphere's ozone layer (ayeni et al., 2018). this compared well with ayeni et al., (2018); anas et al. (2024); narayan et al. (2021). http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 534 table 2: ultimate analysis of soursop seed elements wt % carbon 51.29+ 0.1 hydrogen 5.90 + 0.3 nitrogen 0.50 + 0.2 oxygen 42.30+ 0.1 sulphur 0.01 + 0.2 3.1.3 scanning electron microscopes (sem) of soursop seed the morphology of the raw soursop seed was investigated by sem, as shown in plate 1, and the micrographs using a magnification of 8000x show a pore size of 100 μm. the surface area and pore volumes are very important factors because the material's degradation efficiency depends on their surface areas. the image has a rough surface with tiny pores and oil-like droplets on the surface. the surface area and pore volumes offered more significant areas of contact during pyrolysis reactions, making the material's rate of devolution faster. the seed's high surface area and oil-like droplets indicate a rich volatile content, contributing to higher bio-oil yield during pyrolysis. greater pore volume allows for easier diffusion of volatile gases, reducing secondary cracking reactions and preserving desirable pyrolysis products. the material's surface roughness and porosity indicate rapid heat transfer and decomposition, enhancing thermal degradation efficiency, making it ideal for fast pyrolysis systems with short reaction times. this is similar to report of abel et al. (2020); adekanmi and olowofoyeku, (2020). plate 1: sem micrographs of soursop seed 3.2 results of characterization of the bio-oil 3.2.1 gas chromatography and mass spectrometry (gc-ms) analysis for the bio-oil figure 1 presents the bio-oil chemical composition achieved using gc-ms, and the concentration of these acids are as shown in table 3. the compositions of the pyrolytic bio-oil were evaluated considering the relative peak area of identifying constituents using the obtained chromatogram from gc–ms analysis, which agrees with that presented by laouge et al. (2020). the bio-oil has a total of eight peaks and is made up of tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, 9octadecadienoic acid, octadecadienoic acid, eicosanoic acid, docosanoic acid, and heptacosanoic acid. however, the most significant fatty acid in the bio-oil is 9, octadecadienoic acid (45.55%), hexadecanoic acid (27.80%), and octadecadienoic acid (24.30%), while heptadecanoic acid has the least concentration of 0.50%. since linoleic is the predominant monounsaturated fatty acid and makes up 45.55% of the total fatty acid content, the oil belongs to the linoleic acid group (sonntag, 2012). linoleic acid is important for bio-oil applications because its chemical structure and properties contribute to fuel performance, stability, and reactivity. its double bonds make it more prone to oxidation, contribute to lower pour points and better cold-flow properties, and during pyrolysis, linoleic acid produces a mix of hydrocarbons useful for biofuel applications, influencing bio-oil composition. this result compared well with the report of okokpujie et al. (2023), álvarez-chávez et al. (2019), and ude et al. (2023). http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 535 figure 1: gc-ms of bio-oil compound produced from soursop seed table 3: fatty acid composition of soursop seed oil s/no retention time fatty acid present compound names molecular formular % concentration 1. 12.75 tetradecanoic acid myrisic acid c14h28o2 0.90 2. 14.88 hexadecanoic acid palmitic acid c16h32o2 27.80 3. 15.80 heptadecanoic acid margaric acid c17h34o2 0.50 4. 16.60 9, octadecadienoic acid linoleic acid c18h31o2 45.55 5. 16.80 octadecadienoic acid stearic acid c18h34o2 24.30 6. 18.80 eicosanoic acid arachidic acid c20h40o2 12.60 7. 20.10 docosanoic acid behenic acid c22h44o2 1.05 8. 21.60 heptacosanoic acid cosnic acid c27h54o2 0.65 3.2.2 ftir analysis result of the bio-oil figure 2 depicts the ftir spectrum of soursop seed oil. this research was undertaken to identify the different functional groups in the bio-oil. the investigation indicates the presence of =c-h functional groups (alkenes) at a precise frequency of 1036.2 cm-1. they all display double-bonded bending-type vibrations within the spectrum's low energy and frequency range. they are ascribed to functional groups comprised of unsaturated olefinic chemicals (alkenes). these substances could be components of the methyl esters from unsaturated fatty acids found in bio-oil. the presence of the esters enhances combustion efficiency. it reduces particulate emissions, improves the fuel's lubricating properties, and is biodegradable and sourced from renewable feedstocks. esters have minimal sulfur and aromatic content, lowering harmful emissions. the peaks detected at 1068.2 cm-1 are attributed to the stretching vibrations of the c-o and c-o-c molecules. the band observed at 1378.2 cm-1 is associated with the bending vibrations of c=c bonds. in contrast, the band region at 1148.1 cm-1 is associated with the bending vibrations of c-h methyl groups. an assortment of fragrant chemicals is identified within the wavelength range of 1626.3cm-1. the existence of the 2926.1 cm-1 area indicates the presence of a carboxylic acid with an elongated o-h group. the peaks observed at 2968.1 cm-1 indicate the symmetric stretching vibrations of the c-h alkane groups. both methyl (ch3) and methylene groups require substantial energy to generate stretching vibrations in their bonds. by contrast, alkene groups' usual c-h bending vibrations are detected at lower energy and frequency ranges. the peak observed at 3390.2 cm-1 is ascribed to the stretching vibration of alkene groups with =c-h bonds. the alkene group provides higher reactivity and combustion efficiency, enhances the bio-oil's octane number and lowers the oil's boiling point. this result aligns with the report of ishaq et al. (2020). http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 536 figure 2: ft-ir spectrum of pyrolysis of soursop seed for bio-oil 3.3 response surface methodology modeling for bio-oil yield the rsmbbd results for the percentage yield of bio-oil from the pyrolysis process are presented in table 4. using design expert software version 13.0.6 usa, three variables, temperature, particle size, and gas flow rate represented by the alphabet a, b, and c, and three levels (-1, 0, and +1) were considered, resulting in seventeen experimental runs. the variation in values of the percentage yield of bio-oil indicated that the process parameters significantly affect the pyrolysis process. the maximum percentage yield of 33.1% occurred at a temperature of 5000c, particle size diameter of 6mm, and inert gas flow rate of 1.0l/min. second-order polynomial (quadratic) equations in coded terms that defined the independence between the studied process variables (a, b, c) and the response (% yield) for bio-oil were obtained with the use of rsm and represented in equations (8). table 4: bbd experimental design for bio-oil yield factor 1 factor 2 factor 3 response 1 std run a:temperature b:particle size c:inert gasflow oil yield c mm l/min % 10 1 500 6 1 33.1 6 2 600 4 1 30 8 3 600 4 1.5 20.9 15 4 500 4 1.25 27.4 11 5 500 1 1.5 21 14 6 500 4 1.25 27.4 9 7 500 1 1 37 13 8 500 4 1.25 27.4 7 9 400 4 1.5 16.25 3 10 400 6 1.25 22.3 12 11 500 6 1.5 30.9 2 12 600 1 1.25 27.8 17 13 500 4 1.25 27.4 5 14 400 4 1 25.9 4 15 600 6 1.25 22 16 16 500 4 1.25 27.4 1 17 400 1 1.25 17.2 3.3.1 oil yield model statistical analysis analysis of variance (anova) was used to determine the statistical significance of the model and all the regressed coefficients of the developed quadratic rsm-bbd model for the % of bio-oil yield. the anova results for measuring model adequacies for bio-oil yield are shown in table 5. the high f – value (61.67), pvalue (<0.0001), and non-significant lack of fit (p-value> 0.05) indicated that the model was significant (hidayat et al., 2023). the fitness of the model was expressed by the coefficient of determination (r2) obtained as 0.9875 with an adjusted r2 value of 0.9715, which was in reasonable agreement with the predicted r2 value of 0.8007 for the developed model, i.e., the difference is less than 0.2. this showed that the developed quadratic model could predict the observed experimental data within the range of study (kamarudin et al., 2019). the adequate precision value of 30.8050, a measure of the signal-to-noise ratio greater than 4, showed the model's desirability and indicated an adequate signal. these regression values agreed with the report of (malatji et al., 4400.0 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 350.0 -3.0 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34.5 cm-1 %t 4336.51 4260.61 4196.00 3781.00 3409.00 3344.00 3002.00 2927.00 2861.71 2676.33 2363.66 2038.00 1725.62 1450.95 1239.00 1174.22 951.63 719.34 416.39 379.17 http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 537 2020), who suggested that a high correlation confirms the degree of fitness between the predicted and experimental responses. therefore, this model can be used to navigate the design space. the linear terms (a and c), the quadratic terms (a2, b2, and c2), and the interactive effects of temperature: particle diameter (ab and bc) were all significant (p < 0.05) in the oil yield response model. as the process parameters increased, the positive and negative signs in equation 8 showed an increase and decrease in values of response. increased a, b, c, ab, ac, and bc led to increased response, while increased a2, b2, and c2 values resulted in decreased response. to check for the normality of the residuals, the normal probability versus studentized residuals plot was considered in figure 3a. it showed that the points extended well diagonally, suggesting they dispersed in a reasonable pattern. the relationship between the predicted and observed actual experimental data in figure 3b gave a straight line, which showed agreement with each other. hence, the experimental data is acceptable (reglioua et al., 2021). table 5: anova results for bbd-rsm bio-oil yield source sum of squares df mean square f-value p-value model 471.70 9 52.41 61.67 < 0.0001 significant a-temperature 45.36 1 45.36 53.37 0.0002 b-particle size 3.51 1 3.51 4.13 0.0816 c-inert gasflow 170.66 1 170.66 200.80 < 0.0001 ab 29.70 1 29.70 34.95 0.0006 ac 0.0756 1 0.0756 0.0890 0.7741 bc 47.61 1 47.61 56.02 0.0001 a² 159.58 1 159.58 187.76 < 0.0001 b² 4.92 1 4.92 5.79 0.0470 c² 17.16 1 17.16 20.19 0.0028 residual 5.95 7 0.8499 lack of fit 5.95 3 1.98 not significant pure error 0.0000 4 0.0000 cor total 477.65 16 std. dev. 0.9219 r² 0.9875 mean 25.96 adjusted r² 0.9715 c.v. % 3.55 predicted r² 0.8007 adeq precision 30.8050 oil yield (%) = +27.40 + 2.38a +0.6625b 4.62c 2.73ab + 0.1375ac + 3.45bc 6.16a2 + 1.08b2 + 2.02c2 (8) figure 3: (a) normal % probability vs. internal studentized residuals. (b) predicted vs. actual values 3.3.2 interaction effects of process parameters on bio-oil yield to better understand the pyrolysis process for oil yield, contour and 3d response surface plots were studied. these plots were used to study the interaction effects of the pair of independent variables, keeping other variables constant. the 3d response surface plots are the graphical representation of the regression equation used to observe the levels of each factor (mabrouka et al., 2023). the interactive terms considered are a b http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 538 temperature and particle diameter (ab), temperature and inert gas flow (ac), and particle diameter and inert gas flow (bc). the interaction between temperature and particle diameter (ab) at the fixed inert gas flow on the % yield of bio-oil is shown in figure 4. the maximum percentage (28.8%) of bio-oil yield was achieved at a temperature of 550 0c and a particle diameter of 1mm. at temperature levels >4000c, a steady, significant increase in bio-oil yield was observed from particle diameter 1 mm to 6 mm. in contrast, no significant increase in yield was observed at temperature levels > 5500c. hence, an increase in ab up to a=5500c and b =6 mm increased by % of bio-oil yield. this may be attributed to the fact that below the point of 4000c the devolatilization of the feedstock has not started in full force. at this point, depolymerization is still occurring. a similar trend was recorded by ganapathy et al. (2009). figure 5 shows the contour and 3d surface response plot interaction of the combined effect of temperature and inert gas flow rate (ac) of bio-oil yield. increase in a resulted in an increase % yield of bio-oil up to 550 0c after which the yield started decreasing gradually, while increase in b resulted in a significant decrease in the yield of the bio-oil. this may be as result of complete devolatilization of the biomass at the temperature level of 550 0c and the ability of the gas to purge the volatile oil out of the condenser before condensation takes place. this correspond to work done by álvarez-chávez et al. (2019). the interaction between particle diameter and inert gas flow rate (bc) was presented in figure 6. an increase in bc resulted in a decrease in % yield of bio-oil. while the decrease is insignificant for an increase in particle size, it is significant for an increase in inert gas flow. this may be because complete devolatilization of the biomass has occurred, and at this point, secondary cracking of the biomass only leads to the formation of more gases and char, similar to the report of (álvarez-chávez et al., 2019). figure 4: contour and 3d plots on the effect of particle diameter and temperature on bio-oil yield figure 5: contour and 3d plots on the effect of inert gas flow and temperature on bio-yield http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 539 figure 6: contour and 3d plots on the effect of inert gas flow and particle diameter on bio-oil yield 3.4 optimization of the process table 6 visualizes the optimization criteria set on the design expert software to achieve maximum yield and purity responses. the software default weighted coefficient for both independent and dependent variables was tabulated accordingly in table 6. temperature, particle diameter and inert gas flow were fixed within their experimental ranges of 400-600oc, 1-6 mm, and 1.5-1.5 l/min respectively, and the oil yield were optimized within the range. the optimum operating region for yield optimization was obtained using the desirability function algorithm of box behnken design. figure 7 shows values of 461.84oc, 3.84mm, and 1.02l/m as the optimum mixture for temperature, particle size, and inert gas flow, respectively. these values give optimum yield responses (31.43%) with a desirability of 1. figure 8 presents the desirability values of the optimized condition for optimization of the bio-oil and biochar yield. it shows 1, 1, 1, and 1 as desirability values of temperature, particle size diameter, inert gas flowrate, and oil yield, respectively, 1 was obtained as combined desirability. the combined desirability for n number of responses is obtained from equation 9. d(x) = (d1 x d2 x …. dn)1/n 9 table 7 gives the first 10 optimum conditions, responses to bio-oil and biochar yield, and the desirability for the criteria indicated in table 7. for this current study, the first of the solutions was adopted. table 6: constraints for optimization of yield and purity responses. name goal lower limit upper limit lower weight upper weight importance a: temperature is in range 400 600 1 1 3 b: particle diameter is in range 1 6 1 1 3 c: inert gas flow is in range 1 1.5 1 1 3 oil yield is in range 16.25 37 1 1 3 http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 540 figure 7: numerical optimized value of the dependent and independent variables with desirability figure 8: desirability plot for the yield of bio-oil table 7: first 10 solutions for optimization of yield and purity with desirability number temperature particle size inert gas flow oil yield desirability 1 461.840 3.842 1.020 31.428 1.000 selected 2 600.000 6.000 1.250 22.644 1.000 3 500.000 3.500 1.250 27.400 1.000 4 600.000 1.000 1.250 26.769 1.000 5 500.000 1.000 1.500 21.769 1.000 6 600.000 3.500 1.000 30.125 1.000 7 400.000 3.500 1.000 25.637 1.000 8 500.000 6.000 1.000 32.331 1.000 9 400.000 1.000 1.250 16.556 1.000 10 600.000 3.500 1.500 21.163 1.000 3.4.1 model validation validation experiments were conducted at the optimal conditions suggested by rsm to confirm the model's reliability. triplicate experiments were done and average bio-oil obtained was 29.6%. the experimental biohttp://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 529-544. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 541 oil yields were in close agreement with the predicted values, with percentage errors less than 10%, demonstrating the model’s accuracy in practical applications. 4. conclusion this study investigated the pyrolysis of soursop (annona muricata) seeds in a fixed-bed reactor to optimize bio-oil production and assess its potential as a renewable energy source. the findings highlight that process parameters, like temperature, particle size, and inert gas flow rate, significantly influence bio-oil yield and composition. the optimal conditions for maximizing bio-oil production were determined using response surface methodology (rsm), with a temperature of 461.84°c, a particle size of 3.84 mm, and an inert gas flow rate of 1.02 l/min, yielding 31.43% bio-oil. characterization of the bio-oil through gc-ms and ftir analysis confirmed the presence of valuable compounds, including linoleic acid, palmitic acid, and esters, making it a potential feedstock for biofuel production. the study underscores the viability of soursop seed pyrolysis as an environmentally friendly waste management strategy and a means of generating sustainable biofuels. additionally, the biochar produced presents opportunities for soil enhancement and carbon sequestration. while this research contributes valuable insights into optimizing bio-oil yield, further studies are recommended to enhance bio-oil stability, refine upgrading techniques, and evaluate large-scale production feasibility. with continued research and technological advancements, bio-oil from soursop seeds could become a viable alternative to conventional fossil fuels, supporting global efforts toward sustainable energy development. references aboelela, d., saleh, h., attia, am., elhenawy, y., majozi, t. and bassyouni, m. 2023. recent advances in biomass pyrolysis processes for bioenergy production: optimization of operating conditions. sustainability, 15(9): 11238–11258. https://doi.org/10.3390/su151411238 abel, om., chinelo, as., cynthia, i., and agbajor, gk. 2020. evaluation of african star apple (chrysophyllum albidum) seed oil as a potential feedstock for industrial application. asian journal of applied chemistry research, 10(4): 31–42. adekanmi, dg. and olowofoyeku, ae. 2020. african star apple: potentials and application of some indigenous species in nigeria. journal of applied sciences and environmental management, 24(8): 1307–1314. adibah, w., azwar, e., fong, s., ahmed, a., peng, w., tabatabaei, m., park, y., and lam, ss. 2021. valorization of municipal waste using co-pyrolysis for green energy production, green security, and environmental sustainability: a review. chemical engineering journal, 18(7): 129749–129761. alkhalidi, hm., ali, hm., and jebreen, j. 2023. characterization of biochar produced from various agricultural wastes and its application in soil improvement. environmental science and pollution research, 30(7): 18125– 18135. almeida, ap., tavares, sm., and silva, fj. 2021. application of design expert for the optimization of material synthesis processes. materials science and engineering, 807(34): 140677-140699. anas, a., noorfidza, y. h., sharjeel, w., ushtar, a., and syed, ag. 2024. optimization of operational parameters using artificial neural network and support vector machine for bio-oil extracted from rice husk. american chemical society acs omega, 56(13): 254-283. https://doi.org/10.1021/acsomega.4c03131 antal, mj. and grønli, m. 2018. the art, science, and technology of charcoal production. industrial & engineering chemistry research, 42(8): 1619-1640 amenaghawon, an., anyalewechi, cl., okieimen, co., and kusuma, hs. 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email address: adelekeae@funaab.edu.ng 837 arid zone journal of engineering, technology & environment original research article biodiesel production from the blend of sunflower, avocado seeds and waste soybeans a. e. adeleke1*, o. s. ogungbemi1, s. o. giwa2 1department of mechanical engineering, college of engineering, federal university of agriculture, abeokuta, ogun state, nigeria. 2department of mechanical engineering, faculty of engineering, olabisi onabanjo university, ibogun campus, ifo, ogun state, nigeria. *corresponding author’s e-mail: adelekeae@funaab.edu.ng article information abstract the climatic, environmental, and health concerns of fossil fuels have spurred the development of biodiesel as an alternative fuel. biodiesel production has transitioned from single lipid-based feedstock to hybrid lipid-based feedstock owing to the challenges related to the former. unlike previous studies that focused on singular and binary feedstock, this study uniquely employed ternary oil blends to synthesize biodiesel via alkaline transesterification and measured selected oil and biodiesel fuel properties using standard test methods. the studied hybrid oils were extracted (using the soxhlet method) from ternary feedstock (72%, 20%, and 8% by weight of soybeans, avocado seeds, and sunflower seeds) and characterized for the physicochemical properties: viscosity, moisture content, volatile content, ash content, higher heating value, free fatty acids, and density. the measured biodiesel fuel properties were kinematic viscosity, density, flash point, pour point, and lower heating value. results revealed that the hybrid oil properties were observed to be within the range of values for individual feedstock that made up the oil. the biodiesel produced has a yield of 81% and exhibited a kinematic viscosity of 3.75 mm2/s, density of 893 kg/m3, flash point of 122 °c, pour point of -11°c, and lower heating value of 34.96 mj/kg. these fuel properties were observed to conform to biodiesel standards. relatively low kinematic viscosity and pour point, and high lower heating value and flash point of the studied biodiesel were recorded due to the synergetic effect of oil hybridization. therefore, selective mixing of different oils from existing feedstock for biodiesel production is recommended as this would further improve biodiesel fuel properties and consequently, enhance the performance, combustion, and emissions of biodiesel-fueled engines. hybrid oil deployment will assist in addressing existing problems related to the use of singlefeedstock based oil, with the ultimate view of promoting carbon neutrality in agreement with the sustainable development goals. received: 4th july 2025 revised: 5th september 2025 accepted: 9th september 2025 keywords: avocado seeds fuel properties hybrid biodiesel sunflower seeds soybeans © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction biodiesel is a green, neutral carbon, renewable, and sustainable liquid fuel proposed as an alternative to fossil diesel. it is synthesized from lipid-based resources such as oilseeds (edible and non-edible), animal oil, fats, waste seeds, waste cooking oil, algae, micro-organisms, etc. (giwa et al., 2023). prominent lipid-based feedstock used for biodiesel production include soybean, sunflower seeds, jatropha, canola, rapeseed, chicken wastes, waste cooking oil, animal fats, etc. (giwa et al., 2023). of the various methods of biodiesel production, the transesterification process is the most used, with alkaline-based transesterification being the most reported. owing to the variation in the fatty acid compositions of the lipids (from diverse feedstock) utilized for biodiesel production, which appears unaltered after transesterification, different magnitudes of biodiesel fuel properties from diverse biodiesel feedstock have been reported in the literature (giwa et al., 2024). this portends the strong connection between fatty acid compositions of biodiesel feedstock to their fuel azojete september 2025. vol.21(3):837-846 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/014 www.azojete.com.ng mailto:adelekeae@funaab.edu.ng mailto:adelekeae@funaab.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 838 properties. however, the use of single feedstocks from edible and edible oils, waste oils, waste cooking oils, etc., are known for their respective shortcomings such as feedstock cost, availability, high viscosity, poor cold flow properties, high emissions, and low cetane number, which are relatively limiting their application in diesel engines in comparison to diesel (giwa et al., 2024). the concept of hybrid biodiesel, which involves the use of two or more feedstock for biodiesel production, is proposed to improve biodiesel fuel properties by synergizing the advantages and modifying the shortcomings of each biodiesel feedstock through the alteration of the fatty acid compositions. aside from numerous studies (ishola et al., 2020; adekanmi et al., 2020; dagde, 2019; hayatudden et al., 2020) on biodiesel production from single feedstock, growing interest has been observed concerning the use of hybrid feedstocks for biodiesel production (falowo and betiku, 2022; giwa et al., 2023; brahma et al., 2023). the utilization of more than one feedstock (at different proportions) for biodiesel synthesis has demonstrated improved fuel properties compared to those of single-feedstock biodiesels. several studies have reported biodiesel production from hybrid feedstock at different ratios via the transesterification process (adepoju, 2020; de almeida et al., 2015; balamurugan et al., 2022; brahma et al., 2023). adepoju (2020) optimized the production of hybrid biodiesel from pig fat oil and neem oil (at different ratios of 90:10 – 10:90) using biomass-derived calcium oxide (cao) catalyst and measured the fuel properties. the lowest viscosity, which favours further application of this hybrid biodiesel, was produced using a 60:40 ratio of neem oil and pig fat oil at optimal values of 5.9:1 methanol/hybrid oil, 2.179 g of catalyst amount, 59.91 °c of reaction temperature, and 57.5 min of reaction time, yielding 98.03 (wt.%) of the hybrid biodiesel. de almeida et al. (2015) measured the fuel properties of hybrid biodiesel produced from the mixtures of palm oil, waste frying oil, and waste fish oil via two-way transesterification. induction period and completion of melt onset temperature were improved by 20% and 80% using 42.1 wt.% of the waste fish oil and 57.9 wt.% of waste frying oil to produce hybrid biodiesel. balamurugan et al. (2022) studied the production of hybrid biodiesel from an equal volume of castor oil, mahua oil, and processed dairy waste using the esterification and transesterification process. at 600 rpm stirring speed, 1 wt% catalyst, 60 min reaction time, and 55 °c reaction temperature, a yield of 96 vol% was achieved. yunus et al. (2015) examined the fuel properties (calorific value, kinematic viscosity (kv), oxidative stability (os), flash point, cold filter plugging point, etc.) of biodiesel produced using oils from nigella sativa, ceiba pentandra, and their mixture (equal volume). the hybrid biodiesel revealed the augmentation of the cold filter plugging point, flash point, and kv of nigella sativa oil biodiesel and the os for both ceiba pentandra and nigella sativa oil biodiesel. kumar et al. (2023) improved the fuel properties of different hybrid biodiesels via binary mixtures of waste cooking oil, palm, jatropha, and karanja oil. hybrid biodiesel produced from palm-karanja (48.4:51.6% v/v) oil showed improvement in cetane number (4.2%), density, kv, and os (21.47%), while the hybrid biodiesel from palm-jatropha (65.2:34.8% v/v) oil recorded enhanced os (46.9%), kv, cetane number (11.28%), and density. however, no optimal mix was established for hybrid biodiesels from other oil mixtures to satisfy biodiesel standards. kumar et al. (2019) examined the suitability of synthesizing hybrid biodiesel from castor and karanja oil (equal amount) using lipase derived from pseudomonas cepacia. a higher flash point was obtained using the hybrid biodiesel compared to single-feedstock biodiesel and diesel. kodgire et al. (2022) studied the production of hybrid biodiesel from castor oil and waste cooking oil (50:50, 70:30, and 90:10). the hybrid biodiesel produced from the 50:50 mixture demonstrated improved calorific value, density, and viscosity over that of castor oil biodiesel. optimal reaction time (9.04 min), methanol/oil ratio (8.42:1), koh loading (0.52 w/w %), rco: wco (61:39) ratio, and yield of 93.12% were achieved. edo et al. (2022) studied the use of ternary oils (jatropha curcas oil – 15 vol%, waste cooking oil – 50 vol%, and palm oil – 35 vol%) to produce hybrid biodiesel with the optimization of the reaction variables, all to improve the fuel properties. with optimal values of 0.78 wt%, 9.86:1, 10.5 min, and 478 rpm for catalyst concentration, methanol/oil molar ratio, reaction time, and stirring speed, respectively, achieving 96.9% biodiesel yield, improved os, cetane number, and cold flow properties were recorded. from the above research survey, it can be observed that studies have been mainly conducted using binary feedstock to produce biodiesel, with very few works published using ternary feedstock for biodiesel production, all toward improving the fuel properties of the synthesized biodiesel. this study intended to fill this research gap by producing biodiesel from ternary feedstock (avocado seeds, waste soybeans, and sunflower seeds), and examining the corresponding biodiesel fuel properties. the essence was to possibly improve the fuel properties of the hybrid biodiesel over those of individual biodiesels. in addition, the physicochemical properties of the extracted oil from the ternary feedstock were measured. this study valorized waste soybeans and avocado seeds as feedstock for biodiesel production against their discarded and worthless perception, which constitute a social nuisance as agricultural and solid municipal wastes. oil-based http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 839 wastes provide more options as potential feedstock for biodiesel production by promoting waste management via waste-to-energy, therefore reducing and adding value to wastes. 2. materials and method 2.1 materials the raw materials (sunflower seeds and soybeans) used to produce the biodiesel were sourced from a local market at osiele, abeokuta, ogun state. similarly, the avocado seeds were obtained from a fruit waste disposal center. the chemicals (analytical grade) – naoh (95% purity), methanol (99% purity), anhydrous sodium sulphate (98% purity), and n-hexane (99% purity) – used in this study were purchased from local chemical vendors. other materials included the rotary vacuum evaporator, erlenmeyer flask (as reactor), magnetic stirrer, oven, separating funnel, beakers, conical flasks, filters, personal protective equipment, and soxhlet extractor. 2.2 oil extraction the avocado seeds were washed in water to remove contaminants and were then sun-dried for 8 days to reduce their water content. the sunflower seeds were dehulled before being washed in water. also, the waste soybean and sunflower seeds were oven dried (70 °c for 6 h) and ground before oil extraction. before commencing with the production of biodiesel, the respective feedstocks for biodiesel production were ground into powder form and weighed. the weight of the ground soybeans, avocado seed, and sunflower seed was 1350 g, 363.3 g, and 153.41 g, respectively. the feedstock were mixed at a ratio of 72%, 20%, and 8% (by percentage weight) for soybean, avocado, and sunflower, respectively, before oil extraction. this mixing ratio was informed by the oil yield of individual feedstock. the oil in the mixed substrate was extracted using the soxhlet extractor via a solvent extraction process using hexane. from the weighed soybean seed, avocado seed, and sunflower seed, a total of 748 ml of oil was extracted. the oil was collected and stored in a dirtfree beaker for further processing. 2.3 physicochemical properties of hybrid oil the physicochemical properties of the extracted hybrid oil were determined in the laboratory using standard test methods (dele et al., 2022). this was to confirm their suitability for the production of biodiesel. the analysis involved the moisture content, volatile content, ash content, and the higher heating value of the oil. 2.4 biodiesel production procedure the transesterification reactions are the most common method of converting triglycerides (contained oils) into methyl esters (biodiesel). this involved the displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis, except that an alcohol is used instead of water (athar and zaidi, 2020). a weighed quantity (150 g) of the hybrid oil was poured into the reactor and was heated to a temperature of 60 °c using a heater. an appropriate quantity of methanol (44.05 g; 1:6 oil/methanol molar ratio) was measured and discharged in a beaker containing the required amount of naoh (1.5 g; 1% wt. oil) pellet added to it. the beaker content was manually stirred (slowly) until the naoh was completely dissolved in the methanol, which gave a sodium methoxide mixture. this mixture was poured into the reactor containing the heated oil, and the whole content was stirred at the rate of 360 rpm (using a magnetic stirrer), and the temperature was maintained at 60 °c. the heating and stirring were halted after 60 min, and the formulated product was poured into a separating funnel and allowed to settle overnight. the formulated mixture was observed to settle into two separate layers of glycerol (bottom layer) and paleyellow soybean-sunflower-avocado oil methyl esters (upper layer). the separating funnel was opened to collect the glycerol while the crude soybean-sunflower-avocado oil methyl esters were collected in a separate container. the crude soybean-sunflower-avocado oil methyl esters were heated on a rotary vacuum evaporator (at 80 °c for 1 h) to remove the excess methanol in the content, after which it was gently washed with warm distilled water (three times with two drops of diluted hydrochloric acid at the first wash) to remove the soaps and residual catalyst. thereafter, it was dried using anhydrous sodium sulphate and then filtered. the resulting product (purified soybean-sunflower-avocado oil methyl esters – hybrid biodiesel) was stored in a cool and dry place. this procedure was repeated three times, and the average yield was reported. equation 1 was used to estimate the biodiesel yield achieved in this study. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 840 𝑌𝑖𝑒𝑙𝑑 = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑏𝑖𝑜𝑑𝑖𝑒𝑠𝑒𝑙 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 (𝑚𝑙) 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑒𝑥𝑡𝑟𝑎𝑐𝑡𝑒𝑑 𝑜𝑖𝑙 𝑢𝑠𝑒𝑑 𝑓𝑜𝑟 𝑡𝑟𝑎𝑛𝑠𝑒𝑠𝑡𝑒𝑟𝑖𝑓𝑖𝑐𝑖𝑎𝑡𝑖𝑜𝑛 (𝑚𝑙) × 100% 1 2.5 characterization of hybrid biodiesel fuel properties fuel property characterization of the hybrid biodiesel produced was carried out using standard methods, as reported in the literature (oni-adimabua et al., 2024). the determined fuel properties included kinematic viscosity (astm d445), flash point (astm d93), density (astm d6751), pour point (astm 97-96a), and higher heating value (astm d2015), using standard testing methods (astm, 2002). figure 1 shows the flow chart of the process for hybrid biodiesel production. figure 1: process diagram for the production of biodiesel 2.5.1 determination of density the samples were brought to a specified temperature, and a test portion was transferred to a hydrometer cylinder that had been brought to approximately the same temperature. the approximate hydrometer, also with a similar temperature, was lowered into the test portion and allowed to settle. after the equilibrium temperature had been reached, the hydrometer scale reading and the temperature of the test portion were taken. the observed hydrometer reading was reduced to the reference temperature utilizing a petroleum measurement table. the hydrometer scale reading was recorded to the nearest 0.1 kg/m3 as the density. 2.5.2 dynamic and kinematic viscosity the viscosity of the oil was determined using the brookfield digital rotational viscometer. the sample was heated in the hot oil bath, and the spindle of the viscometer was fitted into the melted wax. the speed was selected, and the start button was pressed for the spindle to rotate and give the angle of rotation, including the viscosity measurement and the operating temperature on the display. the kinematic viscosity is the ratio of dynamic viscosity to the density, as expressed in equation (2). 𝐾𝑖𝑛𝑒𝑚𝑎𝑡𝑖𝑐 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦 = 𝐷𝑦𝑛𝑎𝑚𝑖𝑐 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 2 2.5.3 determination of flash point the flash point was determined using a small, strong heat-resistant glass cup and a heating mantle. the sample was poured into the cup and heated gradually while being stirred to distribute heat uniformly in the cup, and the temperature was monitored using a thermometer. at regular intervals, the cup was exposed to naked flame, the temperature at which the biodiesel increases the flame like a flash, but does not increase combustion, was recorded, which was the flash point of the sample. 2.5.4 determination of pour point 5 ml of the sample was drawn into a capillary tube tied to a thermometer and placed in a 250 ml beaker containing distilled water, immersed together in a water bath for controlled heating. the temperature at which the oil just begins to move downward due to its weight is called the pour point. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 841 plate 1: oil sample after extraction 2.5.5 determination of higher heating value a weighed sample of approximately 0.1 gram was placed inside the calibrated adiabatic bomb calorimeter with 1 millilitre of deionized water. a chromel (chromium-nickel alloy) wire was connected to the two electrodes in the pressure vessel (bomb) and placed in contact with the sample. the bomb was then assembled, sealed, and purged twice by pressurizing to 0.5 mpa with pure (99.99%) oxygen, after which it was vented, which was later pressurized with pure oxygen to 2.0 mpa for the test and placed inside a bath containing 2 l of water in an insulated jacket. a motorized stirrer was placed inside the water bath to circulate the water around the bomb, creating a uniform temperature. the sample was then ignited by passing an electric current through the chromel wire, causing the sample to burn to completion in the high-pressure oxygen. the bomb and the bucket were then held in a calorimeter jacket that serves as a thermal shield. the result was displayed in the display unit in (mj/kg). 3. results and discussion 3.1 hybrid oil properties physicochemical properties of the extracted hybrid oil were studied to ensure that it had comparable characteristics to oils used for transesterification. plate 1 shows the extracted hybrid oil. table 1 gives the physicochemical properties of the hybrid oil. the hybrid oil has viscosity, moisture content, volatile content, ash content, higher heating value, free fatty acids, and density of 46.6 mm2/s, 0.76%, 0.25%, 0.03%, 37 mj/kg, 0.52%, and 924 kg/m3, respectively, and are found to agree with the oil properties of conventional oils (verma and sharma, 2016; sajjadi et al., 2016; dagde, 2019). from table 2, the viscosity of the hybrid oil was found to be slightly higher than that of soybean, sunflower, and avocado oil (measured at 40 °c). this is because the hybrid oil was measured at 28 °c. however, at higher temperatures, the viscosity is expected to reduce as the intermolecular forces are weakened, causing an increase in the flowability of the hybrid oil. at 40 °c, the viscosity of the hybrid oil is anticipated to reduce, making it closer to those of soybean, sunflower, and avocado oil used for comparison (in table 2). then, the density of the hybrid oil was found to be within the range reported for soybean, sunflower, and avocado oil, thus reflecting the blend of these oils. the heating value of the hybrid oil was observed to be lower than that of the soybean and sunflower oils. with the hybrid oil measured for its lower heating value, it can be evaluated to be within the lower heating range of the soybean and sunflower oils. the measured free fatty acid value of the hybrid oil was found to be within the range of values measured for soybean, sunflower, and avocado oil. therefore, the hybrid oil can be directly used for the transesterification process as the value is <1% (agarwal, 2007; monika et al., 2023). this is supported by the relatively low moisture content of the hybrid oil, which prevents hydrolysis, reduces soap formation, and increases biodiesel yield, thus eliminating acid esterification before transesterification. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 842 table 1: physicochemical properties of hybrid oil properties values viscosity (28 °c) 46.6 mm2/s moisture content 0.76% volatile content 0.25% ash content 0.03% lower heating value 37 mj/kg free fatty acid 0.52% density 924 kg/m3 table 2: physicochemical properties of oils from existing studies feedstock kinematic viscosity (mm2/s) density (kg/m3) higher heating value (mj/kg) free fatty acid (%) soybeans 28.08a; 31.83b; 890a,*; 916b; 39.6b; 0.35a; 0.14b sunflower 33.4a; 34.01b; 922.2a,*; 918b; 39.56b; 0.25a; 0.15b avocado 36.7 c 912c 0.8c *density @ 40 °c; averma and sharma (2016); bsajjadi et al. (2016); cdagde (2019) 3.2 hybrid biodiesel fuel properties the transesterification process was successful, giving two distinct layers of biodiesel and glycerin. the biodiesel yield from the oil was equally good (81.07 ± 0.45%) and comparable with the yield from other experimental production of biodiesel. this yield value was moderately higher than the 72.2% recorded with the use of soybean oil to produce biodiesel (hossain and mazen, 2010) and slightly better than the 78% reported concerning the production of biodiesel from avocado seed (dagde, 2019). with 300 ml of oil (obtained from the extraction process) and 114 ml of methanol, 242 ml of biodiesel were produced. visual inspection showed a darker color for the produced biodiesel compared to the color of the parent oil used for transesterification. table 3 provides the results of the physicochemical properties of the hybrid biodiesel fuel produced from the hybrid oil, while table 4 shows biodiesel standard values of the measured biodiesel fuel properties. table 3: physicochemical properties of hybrid biodiesel fuel properties values density 893 kg/m3 kinematic viscosity (40 °c) 3.75 mm2/s flash point 122 °c lower heating value 34.96 mj/kg pour point -11 °c table 4: standard fuel properties of biodiesel (mahmudula et al. 2017) property astm d6751 en14214 density 880 kg/m3 860 – 900 kg/m3 kinematic viscosity (40 °c) 1.9 – 6.0 mm2/s 3.5 – 5.0 mm2/s flash point 100 – 170 °c (minimum) >120 calorific value 35 mj/kg pour point -15 °c – (-16) °c http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 843 3.3 comparison of hybrid biodiesel properties with astm biodiesel standard the biodiesel produced in this present study was compared with the astm biodiesel standards required to be satisfied before it can be safely used in the engine. biodiesel that has too many outliers from this standard might need some further form of processing before it can be certified as being safe for usage in the diesel engine in terms of the fuel quality. 3.3.1 density and kinematic viscosity density is a key fuel property that directly affects the engine performance characteristics concerning volumetric fuel economy and maximum power. it can be observed from table 4 concerning the comparison of results obtained from this work to that of the astm standards that the produced biodiesel had a kinematic viscosity of 3.75 mm2/s at 40 °c, which was within the recommended range of 1.9 – 6.0 mm/s2 (for the astm d6751 standard). this indicates better flow properties as required and does not contain any undissolved suspension. if the viscosity lies far away from the range prescribed by the standards, it might lead to clogging in the pipe and reduced pressure of fuel supply to the engine. the density was 893 kg/m3, which lied within the recommended range of 860 – 900 kg/m3 (for the en14214 standard). both the kinematic viscosity and density of the hybrid biodiesel are observed to satisfy biodiesel standards. interestingly, an over 11-fold reduction in the kinematic viscosity of the hybrid oil and a 3.47% reduction in the density were observed after the synthesis of the corresponding biodiesel. 3.3.2 flash point and calorific value the flash point of the biodiesel produced in this study was within the values (100 – 170 °c) recommended by the astm d6751 standard and slightly higher than that of the en14214 standard (> 120 °c). this implies that the produced biodiesel possesses the flammability requirement of the biodiesel standards. hence, ignition could happen quicker in the engine, and it can be transported safely irrespective of the ambient temperature. in addition, the results revealed that the hybrid biodiesel fuels could be used as fuel in compression ignition engines after further engine and wear tests. the calorific value of the biodiesel recorded in this work was similar to that of the en14214 standard. this implies that it can generate appropriate energy per unit mass compared with the biodiesel fuel with a standard calorific value, which invariably leads to a good rate of fuel consumption. hence, its calorific value can be improved by blending it with petroleum diesel. it can be deduced that the flash point and calorific value of the produced hybrid biodiesel satisfied the biodiesel standards. 3.3.3 pour point the pour point represents the hybrid biodiesel fuel’s ability to flow before it can be gelled. therefore, this parameter indicates the temperature at which the hybrid biodiesel may cease to flow. the value recorded for the pour point of the hybrid biodiesel was slightly higher than the limit set by the astm d6751 biodiesel standard. however, for the tropics, this value of pour point and hybrid biodiesel is applicable as the atmospheric temperature of the tropics is higher than 0 ℃ (> 10 ℃). this implies that no gelling of the hybrid biodiesel when used in diesel engines will be observed. blending the biodiesel produced with diesel or the addition of additives can improve the fuel properties for better engine performance, combustion, and emissions, close to the case of diesel-fueled engines (giwa et al., 2023; brahma et al., 2023). 3.4 comparison of hybrid biodiesel properties with biodiesel produced from individual feedstocks the fuel properties of the hybrid biodiesel produced, such as density, kinematic viscosity, flash point, calorific value, and pour point, were compared with the properties of the biodiesels produced using single feedstocks of soybean, sunflower, and avocado, as shown in table 5. 3.4.1 density and kinematic viscosity from tables 3 and 5, it could be observed that the density of hybrid biodiesel was slightly higher than the range (860 – 885 kg/m3) reported for the density of single-feedstock biodiesels from soybean, sunflower seed, and avocado seed oils. the mixing of the feedstocks for hybrid biodiesel production was observed to have an insignificant influence on the density of the hybrid biodiesel. from table 5, the kinematic viscosities (3.94 – 4.439 mm/s2) of single-feedstock biodiesels of soybean, sunflower, and avocado seeds were observed to be http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 844 higher than that of the hybrid biodiesel, which implies that the mixing of the feedstocks influenced this property. this can be connected to the lower kinematic viscosity of the avocado seed oil biodiesel compared to that of sunflower seed and soybean biodiesel. table 5: biodiesel fuel properties from existing studies feedstock kinematic viscosity (mm2/s) density (kg/m3) flash point (°c) calorific value (mj/kg) pour point (°c) soybean 4.039a; 4.5b; 4.15c 884a; 885b; 882c; 178a; 178b; 140.1c; 37.75a; 33.5*b; -7b; -3.7c sunflower 4.439a; 4.6b; 4.26c; 880a; 860b; 869c; 183a; 183b; 180.3c; 33.5a; 33.5*b; -2c avocado 3.94d 860d 100d 33.2 -15d aathar and saidi (2020); bagarwal (2007); csajjadi et al. (2016); ddagde (2019); *lower calorific value. note: average values from the literature are provided. 3.4.2 flash point flash point is simply described as the temperature at which biodiesel burns when in contact with an ignition source. the flash point of the hybrid biodiesel was found to be within the flash point values (100 – 183 °c) published for the pure soybean, sunflower seed, and avocado seed biodiesels in the literature. this reveals an improvement in the flash point of the pure avocado seed biodiesel as the mixing of the feedstocks (avocado seed + soybean and sunflower seeds) influenced this property for the hybrid biodiesel produced in this work. the results reveal that the hybrid biodiesel fuels could be used as fuel in compression ignition engines after further studies concerning their performance, wear analysis, combustion, emissions, etc. in addition, the flash point of hybrid biodiesel and pure biodiesel fuels tends to be within the acceptable standard than that of conventional diesel, which has a range of 60 – 80 °c (omonhinmin et al., 2020). the high flash point of the hybrid biodiesel produced indicates that the fuels have higher fire safety during transportation, handling, and storage. 3.4.3 pour point and the calorific value from table 5, it can be observed that the pour point of the hybrid biodiesel was within the range of values (15 to -2 °c) reported for the individual biodiesels. this showed that the hybrid biodiesel exhibited a lower pour point value than the values for soybean and sunflower seed biodiesels, with the avocado seed biodiesel demonstrating the lowest pour point value. this is attributed to the synergetic mixing of the feedstocks for biodiesel production. the calorific value of the hybrid biodiesel was observed to be within the values published for individual biodiesels from soybean, sunflower seed, and avocado seed oils. these results agreed with those found in the literature (mofijur et al., 2015; omonhinmin et al., 2020). however, the calorific values of pure biodiesels and that of hybrid biodiesel fuel are generally lower than that of conventional diesel (44.8 mj/kg) because of the presence of oxygen, which occupies space and contains a small heating value (mofijur et al., 2015; omonhinmin et al., 2020). 4. conclusion this research work has shown that by the transesterification of oil produced by solvent extraction of 72% weight of soybeans, 20% weight of avocado seed, and 8% weight of sunflower seed using naoh as the catalyst and methanol, the reaction resulted in biodiesel with properties that conform to the astm d6751 and en14214 biodiesel standards. the mixing of the feedstocks revealed reduced kinematic viscosity (compared to soybean and sunflower seed biodiesel) and improved flash point (compared to avocado seed biodiesel), pour point (compared to soybean and sunflower seed biodiesel), and lower calorific value (compared to avocado seed biodiesel). this work has sufficiently proven that biodiesel produced from the mixture of soybeans, sunflower seeds, and avocado seeds is a suitable fuel (considering its quality) for the diesel engine. the findings of this study provide a promising foundation for future research and development in the field of biodiesel production from agricultural waste. blending of the obtained hybrid biodiesel with 20% diesel and further engine performance and wear test could practically promote its use as fuel. additionally, this study could benefit from the use of different alcohols and catalysts and the optimization of the production process, which would further expand the field of biofuel production and improve the current database. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 845 references adekanmi, aa., cole, at., lawal, ik., esho, eo. and lawal, ka. 2020. production of biodiesel from soybeans. international journal of academic information systems research, 4: 2643-2660. adepoju, tf. 2020. optimization processes of biodiesel production from pig and neem (azadirachta indica a.juss) seeds blend oil using alternative catalysts from waste biomass. industrial crops and products, 149: 112334. https://doi.org/10.1016/j.indcrop.2020.112334. agarwal, ak. 2007. biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. progress in energy and combustion science, 33: 233–271. astm, 2002. “standard specification for biodiesel fuel (b100) blend stock for distillate fuels”, american society for testing and materials, d6751-02. athar, m. and zaidi, s. 2020. a review of the feedstocks, catalysts, and intensification techniques for sustainable biodiesel production. journal of environmental chemical engineering, 8(6): 104523. https://doi.org/10.1016/j.jece.2020.104523. balamurugan, s., saravanan, ba., sundaravadivel, ta., krishnan, pg. and ramesh, b. 2022. experimental investigation and performance evaluation of biodiesel production from non-edible mixed oil. aip conference proceedings 2527: 030011. https://doi.org/10.1063/5.0108125. brahma, s., basumatary, b., basumatary, sf., das, b., brahma, s., rokhum, sl. and basumatary, s. 2023. biodiesel production from quinary oil mixture using highly efficient musa chinensis based heterogeneous catalyst. fuel, 336: 127150. https://doi.org/10.1016/j.fuel.2022.127150 received dagde, kk. 2019. extraction of vegetable oil from avocado seed for production of biodiesel. journal of applied science and environmental management, 23(2): 215–221. de almeida, vf., garcía-moreno, pj., guadix, a. and guadix, em. 2015. biodiesel production from mixtures of waste fish oil, palm oil and waste frying oil: optimization of fuel properties. fuel processing technology, 133: 152–160. dele, o., adeleke, ae., oyelaran, oa. and awotunde, wo. 2022. analysis of physicochemical properties of biodiesel from the mixture of ackee and neem seeds. equity journal of science and technology, 9(1): 8–12. edo, gi., makinde, mg., nwosu, lc., ozgor e. and akhayere e. 2022. physicochemical and pharmacological properties of palm oil: an approach for quality, safety, and nutrition evaluation of palm oil. food analytical methods. 15, 2290–2305. https://doi.org/10.1007/ s12161-022-02293-4 falowo, oa. and betiku e. 2022. a novel heterogeneous catalyst synthesis from agrowastes mixture and application in transesterification of yellow oleander-rubber oil: optimization by taguchi approach. fuel, 312: 122999. https://doi.org/10.1016/j.fuel.2021.122999. giwa, so., aasa, sa., taziwa, rt. and sharifpur, m. 2024. deploying artificial neural network to predict hybrid biodiesel fuel properties from their fatty acid compositions, international journal of ambient energy, 45(1): 2262466. doi: 10.1080/01430750.2023.2262466. giwa, so., taziwa, rt. and sharifpur, m. 2023. dependence of composition-based approaches on hybrid biodiesel fuel properties prediction using artificial neural network and random tree algorithms. renewable energy, 218: 119324. https://doi.org/10.1016/j.renene.2023.119324. hayatudden, a., hammari, am., adamu, u. and abubakar, a. 2020. biodiesel production using helianthus annuus(sunflower) seed oil by transesterification. bioremediation science and technology research. 8(2): 2427. https://doi.org/10.54987/bstr.v8i2.555. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng https://doi.org/10.1016/j.indcrop.2020.112334 https://doi.org/10.1016/j.jece.2020.104523 arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 837-846. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adelekeae@funaab.edu.ng 846 hossain, abm., mazen and m.a. 2010. effects of catalyst types and concentrations on biodiesel production from waste soybean oil biomass as renewable energy and environmental recycling process. australian journal of crop science. 4(7); 550-555. ishola, f., adeleken d., mamuda a., abodunrin t., aworinde a., olatunji o. and akinlabi s., 2020. biodiesel production from palm olein: a sustainable bioresource for nigeria. heliyon, vol. 6(8): e03725. https://doi.org/10.1016/j.heliyon.2020.e03725. kodgire, p., sharma, a. and kachhwaha, ss. 2022. biodiesel production with enhanced fuel properties via appropriation of non-edible oil mixture using conjoint ultrasound and microwave reactor: process optimization and kinetic studies. fuel processing technology, 230: 107206. https://doi.org/10.1016/j.fuproc.2022.107206. kumar, d., das, t., giri, bs., rene, er. and verma, b. 2019. biodiesel production from hybrid non-edible oil using bio-support beads immobilized with lipase from pseudomonas cepacian. fuel, 255: 115801. https://doi.org/10.1016/j.fuel.2019.115801. kumar, s., singhal, mk. and sharma, mp. 2023. analysis of oil mixing for improvement of biodiesel quality with the application of mixture design method. renewable energy, 202: 809–821. mahmudula, hm., hagosa, fy., mamata, r., adama, aa., ishakb, wfw. and alenezi, r. 2017. production, characterization and performance of biodiesel as an alternative fuel in diesel engines – a review. renewable and sustainable energy reviews, 72: 497–509. mofijur, m., masjuk, hh., kalam, ma., rasul, mg., atabani, ae., hazrata, ma. andmahmudul hm. 2015. effect of biodiesel blending on physicochemical properties of biodiesel produced from moringa oleifera. 6th bsme international conference on thermal engineering (icte 2014) procedia engineering, vol. 105, pp. 665-669. monika, bs. and pathak, vv. 2023. biodiesel production from waste cooking oil: a comprehensive review on the application of heterogenous catalysts. energy nexus, 10: 100209. https://doi.org/10.1016/j.nexus.2023.100209. omonhinmin, c., olomukoro, e., ayoola, a. and egwim, e. 2020. utilization of moringa oleifera oil for biodiesel production: a systematic review. energy, 8(1): 102-121. oni-adimabua, on., ifeanyi-nze, fo., abimbolu, ak., opadokun, eo., omolusi, ar., ezeokolie, ed., udoh, ea., afuape, ar., areola, mo., wokoma, ptb., odoh, ec., aiso, s. u., francis, cj., egbo, jo., ayanleke, ta. and ankomah, no. 2024. production optimization, and characterization of biodiesel from almond seed oil using a bifunctional catalyst derived from waste animal bones and almond shell. european journal of sustainable development research, 8(3): em0261. https://doi.org/10.29333/ejosdr/14740 sajjadi, b., raman, aaa. and arandiyan, h. 2016. a comprehensive review on properties of edible and nonedible vegetable oil-based biodiesel: composition, specifications and prediction models. renewable and sustainable energy reviews, 63: 62–92. verma, p. and sharma, mp. 2016. review of process parameters for biodiesel production from different feedstocks. renewable and sustainable energy reviews, 62: 1063–1071. yunus, kt., atabani, a., badruddin, i., ankalgi, r., mainuddin, kt. and badarudin, a. 2015. ceiba pentandra, nigella sativa and their blend as prospective feedstocks for biodiesel. industrial crops and product, 65(1) 367373. http://www.azojete.com.ng/ mailto:adelekeae@funaab.edu.ng https://doi.org/10.1016/j.heliyon.2020.e03725 corresponding author’s email address: awahchukwuemeka@gmail.com 879 arid zone journal of engineering, technology & environment original research article the impact of stator tooth and pole combinations on output of a dual stator electric machine c. c. awah*1, c. a. amaghionyeodiwe2, g. c. diyoke1, o. obasi1, i. k. nnabuenyi3 and s. e. oti4 1department of electrical and electronic engineering, michael okpara university of agriculture, umudike 2department of mechanical engineering, michael okpara university of agriculture, umudike 3instrument qa/qc arco m&e, nlng sub contractor, bonny, rivers state, nigeria 4department of electrical engineering, university of nigeria, nsukka *corresponding author’s email address: awahchukwuemeka@gmail.com article information abstract due to the great influence of stator tooth and rotor pole combinations of electric machine on its output performance; the feasible permutations of these machine variables and its resulting electromagnetic effects on the output characteristics of a dual stator (ds) electric machine were analyzed and quantitatively compared in this study, for overall optimal yield. finite element analysis technique was employed in the predictions through maxwell-2d computational software. the considered stator number (ns) was six (6) while its corresponding rotor pole numbers (nr) were: 10, 11, 13 and 14i.e. for ns/nr being 6/10, 6/11, 6/13 and 6/14, respectively. the study shows that machine type having 6/11 i.e. 6-stator tooth with11-pole number would exhibit the largest flux linkage amplitude, reasonably high voltage at low operating current and most promising torque in relation to the deployed magnet volume, albeit; with low operating speed range. the 6/10 and 6/14 machine topologies would have considerably high amount of torque ripple coupled with very low output performance in comparison to its equivalent6/11 and 6/13 machine types. regrettably, high value of magnetic force on the rotor is acquired from 6/11 machine type. consequently, the 6/11 machine type would most likely suffer from greater mechanical instability amongst other compared machine types; notwithstanding its other competitive merits. submitted 01 april, 2024 revised: 01 june, 2024 accepted: 10 june, 2024 keywords: flux density force rotor stator voltage © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction discussions on dual or double stator machines have drawn global attention of researchers over the decades, owing to its numerous merits over its single stator counterparts; ranging from enhanced thermal management, improved efficiency, larger torque and power densities, to higher fault-tolerant and reliability, amongst other advantages (ali et al., 2021). both the open-circuit torque and electromagnetic torque of a machine would be greatly affected by its applied number of poles, as demonstrated by awah et al. (2022). besides, right selection of pole and slot combinations could reduce or eliminate torque pulsation and other unwanted machine features (choo et al., 2022). however, this present research is centred on the resulting impact of stator tooth and pole arrangements of a dual stator (ds) permanent magnet (pm) machine on a number of performance indices. dual stator machines usually have higher mechanical complexity and cost than equivalent single stator machines; but this higher cost could be drastically reduced through application of consequent-pole design strategy, as demonstrated by baloch et al. (2018). zhao et al. (2020) established that similar analyses on dual rotor single stator configuration are also possible with almost similar trend in its resulting waveforms; however, with some noticeable differences on its output magnitudes. in order to enhance the torque densities of existing dual stator machines, gao et al. (2019) and song et al. (2019) developed two kinds of dual stator machines while also considering the tooth and pole possibilities of azojete december 2024. vol.20(4):879-890 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:awahchukwuemeka@gmail.com mailto:awahchukwuemeka@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 880 the machines. the developed machines by gao et al. (2019) and song et al. (2019) are all dual stator machines and are distinctively different from that of the developed machine in this present investigation, structurally and otherwise. pole arrangements of a machine would affect the machine’s pole ratios li et al. (2015), winding factors (awah and okoro, 2018b) and subsequently, its resulting electromagnetic performances. the reliance of electrical machine’s output on its pole, winding factors and gear ratios is further ascertained by hyoseok et al. (2017), xie et al. (2019) and cooke and atallah (2017), respectively. it is worth mentioning that the studied machine in this present investigation belongs to the flux-switching permanent magnet (fspm) machine family. fspm machines have its feasible stator tooth and pole number combination peculiarities. this feasibility and peculiarities would naturally depend upon the basic operations of such machine i.e. as generator (shao et al., 2020) and or as motor (shi et al., 2016). determination of tooth and pole possibilities via magnetic gearing principles can be extended to other electric machines, as detailed by huang et al. (2019). nevertheless, the research by jia et al. (2016) shows that that a machine with high pole number may be associated with huge number of losses and by extension low efficiency regardless of its tremendous electromagnetic yield. torque-speed path of a machine could be achieved by weakening its flux, usually by application of negative direct-axis (d-axis) current, which will customarily affect the resulting axis inductance. the flux-weakening strategy was applied in this present study; however, an extended torque-speed trajectory of a flux-switching machine could be obtained by appropriate modification of the machine’s d-axis inductance, through mechanical flux-adjusters, as presented in zhao and liu (2023) with validated experimental proof. this wider speed coverage is a desired quality for electric vehicle and traction applications. similarly, a wider speed range could also be obtained in a machine by adopting a spoke-type magnetic rotor, owing to the associated high fluxfocusing potential of this arrangement, for enhanced power, torque and efficiency values, amongst other admirable performance qualities. again, the d-axis inductance worth of the system would be improved through this spoke-type arrangement; though, with suitable optimization of the machine’s other leading geometric variables, as established by hu and wang (2023). more so, power density and efficiency of a machine could be improved by employing suitable core materials, as presented in hebri et al. (2023). overall, stator tooth and pole arrangements of a dual stator machine is was analyzed in this current study and its impacts on the machine’s output are were also quantified, with a view to providing adequate guide to machine designers and practitioners on the need to implement suitable stator tooth and pole combinations, considering its consequent effects, for better-quality machine output. 2. materials and methods investigated machine diagram is displayed in figure 1. it is a double stator machine with magnets mounted on both stators. however, the alternating current armature conductors are placed only on the outer stator slot areas. the stators are separated by a rotor having field-modulating pole pieces. both maxwell-2d and matlab softwares were applied in the analyses. it is possible to carry out similar analyses using analytical methods, but finite element analysis approach is chosen and implemented in this study, owing to its high prediction accuracy compared to analytical procedures, which are associated with some electromagnetic assumptions. more so, field-weakening technique is adopted in obtaining the torque-speed trajectory through application of the machine’s direct-axis currents and adequate transformation of its axis variables. the considered stator tooth number (ns) is 6 while the rotor pole numbers are: 10, 11, 13 and 14, i.e. ns/nr is: 6/10, 6/11, 6/13 and 6/14, respectively. the adopted pole numbers are chosen on basis of the established feasible combination principles provided in awah and zhu (2016). the predicted torque (t) is expressed in eq. (1). the calculated magnetic force on the rotor axes is mathematically expressed in eqs. (2) and (3), as implemented in awah et al. (2023b). it is important to note that magnetic flux density amplitude plays major role in the output delivery of a given electric machine (awah, 2023a and awah, 2023b). http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 881 figure 1: 3d diagram of the developed machine, 6/13(awah, 2022) 332211 ieieiet ++= (1) where: ω is rotor speed, e1, e2 and e3 are three-phase voltages, i1, i2 and i3 are the matching phase currents (oti and awah, 2022). ss o r x dl b f    =  cos 4 1 2 0 2 (2) ss o r y dl b f    =  sin 4 1 2 0 2 (3) where: br is the radial flux density, d is stator inner diameter, l is stator axial length and θs is the stator angular coordinate. it is worth noting that high amount of umf would certainly influence the noise and vibration levels of a machine and may even reduce the life span of the machine (awah et al., 2018a). 3. results and discussion flux density contours of the machine configurations are presented in figure 2; intensity of the flux is considerably high at the tips of both the stator and rotor teeth. the implemented flux density magnitude is 2.0 tesla. consequently, the resulting air-gap flux density wave forms of the machine types in one electric revolution are shown in figure 3(a). the generated flux linkage outlines on no-load and at different speed settingsare depicted in figure 3(b). outer magnet outer stator core shaft location inner stator segment inner magnet rotor http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 882 (a) 6/10 (b) 6/11 (c) 6/13 (d) 6/14 figure 2: magnetic flux density (a) flux density versus rotor position -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 0 60 120 180 240 300 360 r a d ia l a ir g a p f lu x d en si ty ( t ) rotor position (mechanical deg) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 883 (b) flux linkage versus speed figure 3: flux density and linkage waveforms figure 4 (a) shows the produced voltage values at varying speed. a linear relationship exists between the applied speed and generated voltage, in-line with theoretical impression. voltage variations with applied current are compared in figure 4 (b). it is observed that the 6/10 and 6/13 machine types would yield the lowest and highest voltage values, respectively; at extreme electric loadings. meanwhile, the generated voltage values of 6/11 and 6/13 machine types are almost similar at all speed ratings, as presented in figure 4(a), as well as at the rated current, as shown in figure 4 (b). this similarity trend also repeated on the generated electromagnetic torque, as shown in figure 5. it is worth mentioning that 6/10 and 6/14 machine types have dip pulsation effects on its torque, as shown in figure 5 (a). it is worth noting that output torque of a machine is directly related to its induced-voltage. thus, the presence of 3rd harmonic component of torque shown in figure 5(b) is indications that the investigated machine would most probably possess even order voltage harmonics. (a) voltage versus speed 0 2 4 6 8 10 12 14 0 500 1000 1500 2000 2500 3000 3500 4000 f lu x l in k a g e m a g n it u d e( m w b ) speed (r/min) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 0 5 10 15 20 25 30 35 40 45 50 0 500 1000 1500 2000 2500 3000 3500 4000 f u n d a m en ta l v o lt a g e a m p li tu d e (v ) speed (r/min) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 884 (b) voltage versus load current figure 4: comparison of voltage 3. (a) outlines (b) harmonics figure 5: torque comparison at constant copper loss, 30w 0 2 4 6 8 10 12 0 10 20 30 40 50 60 v o lt a g e a m p li tu d e (v o lt s) applied load (amperes) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 0 1 2 3 4 5 0 60 120 180 240 300 360 t o rq u e (n m ) angular position (deg) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 t o rq u e (n m ) spectra ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 885 the computed average torques at different current densities is compared in figure 6 (a). the 6/13 machine produced the largest output torque at certain current density range, but 6/11 seems to possess highest ability to sustain electric overload at saturated condition. the 6/11 machine type is more promising in terms of its potential to generate the largest torque for a given volume of applied magnet material, as could be observed from figure 6(b). similarly, torque-speed routes of the analyzed machine types are presented in figure 7. although, 6/11 and 6/13 machine configurations have relatively high value of shaft torque compared to 6/10 and 6/14 equivalents, the latter has reasonably high speed coverage; which is an esteemed electric motor drive property. nonetheless, the 6/10 and 6/14 machine categories may most likely face distortion issues during its drive period; particularly, at high speed, as could be observed from its reluctance torque outlines. (a) torque versus current density 4. (b) torque versus pm volume figure 6: torque comparisons at different load conditions 0 1 2 3 4 5 6 7 8 0 2 4 6 8 10 12 14 16 18 20 22 24 t o rq u e (n m ) applied load (a/mm2) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 0 50 100 150 200 250 300 350 0 10 20 30 40 50 60 t o rq u e/ m a g n et v o lu m e (k n m /m 3 ) applied load (watts) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 886 5. (a) 6/10 (b) 6/11 (c) 6/13 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 1000 2000 3000 4000 5000 6000 7000 8000 t o rq u e (n m ) speed (r/min) total output torque magnet torque reluctance torque -0.2 0.2 0.6 1 1.4 1.8 2.2 2.6 3 0 500 1000 1500 2000 2500 3000 3500 4000 t o rq u e (n m ) speed (r/min) total output torque magnet torque reluctance torque -0.2 0.2 0.6 1 1.4 1.8 2.2 2.6 3 0 1000 2000 3000 4000 5000 6000 7000 t o rq u e (n m ) speed (r/min) total output torque magnet torque reluctance torque http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 887 (d) 6/14 figure 7: torque characteristics resulting torque ripple values of the investigated machine types are displayed in figure 8. again, the calculated torque ripples are in agreement with the observations of figure 5. the 6/10 machine topology has consistently exhibited the most deplorable electric machine characteristics. figure 8: torque ripple magnitudes at 15a magnetic force characteristics of the machine are presented in figure 9. high value of unbalanced magnetic force (umf) on the rotor is realized from the 6/11 machine type, this is followed by the 6/13 machine category. negligible magnetic forces are obtained in the 6/10 and 6/14 machines types, owing to its suitable tooth and pole arrangements. this low value of magnetic force is a desired machine quality. obviously, the resulting magnetic force would be large at low electric load condition, as shown in fig. 9 (a) and (b). 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 1000 2000 3000 4000 5000 6000 7000 t o r q u e ( n m ) speed (r/min) total output torque magnet torque reluctance torque http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 888 (a) force at 10 w (b) force at 30 w figure 9: rotor magnetic force 4. conclusion the impact of stator and rotor pole combinations of a dual stator permanent magnet machine is presented in this work. most of the desirable machine outputs are produced by the machine type that is designated as 6/11; though, with a poorer speed coverage. it is observed that the machine types having 6/10 and 6/14 topologies exhibit poor output performances compared to its counterparts. moreover, the machine type that is equipped with 13-pole would yield the most economic benefit, considering its higher torque in relation to the consumed lesser magnet material/volume. the analyzed machine would be most suitable in low speed and direct drive applications. the 6/11 machine type has the greatest potential against electromagnetic overloading; however, high amount of rotor magnetic force is also realized from the 6/11 machine type, and this is unattractive machine characteristics. references ali, h., sulaiman, e., aziz, r., jenal, m., ahmad, mz. and khan, f. 2021. review of double stator flux switching machines with various arrangements of excitation sources. alexandria engineering journal, 60(5): 4393–4410. awah, cc. 2022. performance comparison of double stator permanent magnet machines. archives of electrical engineering, 71(4): 829–850. awah, cc. 2023a. saturation effect of magnetic flux density on the performance of a double stator machine. nigerian journal of engineering, 30(2): 61–66. awah, cc. 2023b. the effect of magnetic flux density magnitude on machine performance. nigerian journal of engineering, 30(2): 31–36. awah, cc. and okoro, oi. 2018a. analysis of torque ripple and total harmonic distortion of double-stator permanent magnet machine. international journal of power and energy systems, 38(2): 69–76. awah, cc. and okoro, oi. 2018b. double-stator switched flux permanent magnet machines having low rotor pole numbers. nigerian journal of technology, 37(3): 749–757. awah, cc., okoro, oi., nkan, ie. and okpo, ee. 2022. impact of structural dimensions and poles on the torque performance of dual-stator permanent magnet machines. nigerian journal of technological development, 19(1): 68–79. awah, cc., nnabuenyi, ik., amaghionyeodiwe, ca., oti, se. and obasi, o. 2023a. influence of rotor pole number on the output of double stator flux-switching machine. international journal of integrated engineering, 15(7): 262–281. -200 -150 -100 -50 0 50 100 150 200 -200 -150 -100 -50 0 50 100 150 200 y -a x is f o rc e (n ) x-axis force (n) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 -200 -150 -100 -50 0 50 100 150 200 -200 -150 -100 -50 0 50 100 150 200 y -a x is f o r ce ( n ) x-axis force (n) ns/nr = 6/10 ns/nr = 6/11 ns/nr = 6/13 ns/nr = 6/14 http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 889 awah, cc., oti, se. and nnabuenyi, ik. 2023b. effects of unbalanced magnetic force and torque ripple on the performance of a double stator permanent magnet machine. advances in electrical and electronic engineering, 21(3): 184–196. awah, cc. and zhu, zq. 2016. influence of rotor pole number on electromagnetic performance of doublestator switched flux pm machines,” in proceedings of the 13th ieee vehicle power and propulsion conference (vppc2016) held in zhejiang university, hangzhou, china, 17th–20th october 2016, 1–6. baloch, n., kwon, b. and gao, y. 2018. low-cost high-torque-density dual-stator consequent-pole permanent magnet vernier machine. ieee transactions on magnetics, 54(11): 8206105. choo, y., kim, c., yun, g. and lee, c. 2022. investigation of torque ripple in an induction motor with respect to slot number 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w. 2019. analysis of stator/rotor pole combinations in variable flux reluctance machines using magnetic gearing effect. ieee transactions on industry applications, 55(2): 1495–1504. hyoseok, s., niguchi, n. and hirata, k. 2017. characteristic analysis of surface permanent-magnet vernier motor according to pole ratio and winding pole number. ieee transactions on magnetics, 53(11): 8211104. jia, h., wang, j., cheng, m., hua, w., fang, c. and ling, z. 2016. comparison study of electromagnetic performance of bearingless flux-switching permanent-magnet motors. ieee transactions on applied superconductivity, 26(4): 5202305. li, d., qu, r., li, j. and xu, w. 2015. consequent-pole toroidal-winding outer-rotor vernier permanentmagnet machines. ieee transactions on industry applications, 51(6): 4470–4481. oti, se. and awah, cc. 2022. influence of magnetic remanence and coercive force on the electromagnetic output of permanent magnet machine. progress in electromagnetics research m, 109(3): 75–88. shao, l., hua, w., soulard, j., zhu, zq., wu, z., and cheng, m. 2020. electromagnetic performance comparison between 12-phase switched flux and surface-mounted pm machines for direct-drive wind power generation. ieee transactions on industry applications, 56(2): 1408–1422. shi, y., jian, l., wei, j., shao, z., li, w. and chan, cc. 2016. a new perspective on the operating principle of flux-switching permanent-magnet machines. ieee transactions on industrial electronics, 63(3): 1425–1437. song, z., liu, c. and zhao, h. 2019. quantitative comparison of distinct dual-stator permanent magnet vernier machines for direct-drive applications. ieee transactions on magnetics, 55(7): 8104806. xie, k., li, d., qu, r., yu, z., gao, y. and pan, y. 2019. analysis of a flux reversal machine with quasi-halbach magnets in stator slot opening. ieee transactions on industry applications, 55(2): 1250–1260. xu, f., he, t., zhu, zq., wang, y., cai, s., bin, h., wu, d., gong, l. and chen, j. 2021. influence of slot http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):879-890. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: awahchukwuemeka@gmail.com 890 number on electromagnetic performance of 2-pole high-speed permanent magnet motors with toroidal windings. ieee transactions on industry applications, 57(6): 6023–6033. xu, h. and wang, c. 2023. multi-objective optimization of high torque density spoke-type pm machine for special vehicle drive system. the international journal for computation and mathematics in electrical and electronic engineering, 42(2): 637–654. zhao, j., quan, x., sun, x., lin, m. and niu, s. 2020. influence of rotor-pole number on electromagnetic performance of novel double-rotor hybrid excited axial switched-flux permanent-magnet machines for ev/hev applications. ieee transactions on magnetics, 56(3): 7514306. zhao, q. and liu, x. 2023. analysis of mechanical flux-weakening by using the end-cap of the switched flux permanent magnet machines. the international journal for computation and mathematics in electrical and electronic engineering, 42(1): 250–260. http://www.azojete.com.ng/ mailto:awahchukwuemeka@gmail.com corresponding author’s email address: oadeleye@unilag.edu.ng 947 arid zone journal of engineering, technology & environment original research article analytical study of singleand double-layer coating system for controlled drug-releasing orthopedic implants using differential transform method o. adeleye1*, a. ibrahim1, a. yinusa2 1biomedical engineering dept., university of lagos, akoka, lagos, nigeria 2mechanical engineering dept., university of lagos, akoka, lagos, nigeria *correspondence author’s email address: oadeleye@unilag.edu.ng article information abstract the analytical study of singleand double-layer coating system for controlled drug releasing orthopedic implants using differential transform method has been presented. drug release when transported across singleor double-layer boundaries have the potentials of smart fluid properties which can be controlled by various parameters. in the present study, the developed governing model for singleor double-layer coating system for controlled drug-releasing orthopedic implants is a set of coupled partial differential equations for the unsteady diffusion processes with intractable solution. hence, the solution was obtained with differential transform method and was validated with both runge-kutta orderfour numerical scheme and experimental results. good agreement was established among them. the effects of thickness ratio, diffusion period, porosity term, and effective diffusion coefficient on concentration profile are investigated. from the obtained results, it was observed that increase in the interface layer thickness ratio d of 0.2 to 0.8 resulted in decrease from 1 to 0 (zero) in the concentration profiles for all the different dimensionless durations considered. in addition, augmentation of two (2) layers of varying thickness ratio from d = 0.2 to 0.8 in the release parameter resulted in a decrease in the concentration profile to 0 (zero) for the three cases of thickness ratios. the studies show that effective diffusion coefficients for a period of five (5) seconds increases from 0 to 100% is the dominant parameter in the model and so provides considerable flexibility for design process. hence, the developed model and the obtained solutions provide the benchmark for the optimized and enhanced control of drug-releasing orthopedic implants. submitted 29 february, 2024 revised: 28 november, 2024 accepted: 30 november, 2024 keywords: orthopedic implants drug release mathematical models differential transform method © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the subject of drug delivery is indeed a multi-disciplinary area of research that has attracted interest of chemists, mathematicians, engineers, scientists and life scientists for years. in fact, drug delivery controls have received considerable attentions, especially in the designs and uses of tablets (efentakis et al., 2010). the knowledge also helps in understanding the working principles of various resident drug delivery devices like stent, patch, lense and implants (mcginty, 2014, lyndon et al., 2014) shown in figure 1. the applications of these controlled drug releasing orthopedic implants in the field of medicine have introduced innovations and have proven to be successful in its usefulness. it has been a significant advancement in the field of medicine (goodman et al., 2013). few examples are plates, prosthetic knee and hip joints, screws and rods placed in the spinal cord, or other parts of the body to stabilize fractures, and for replacement of intervertebral disks. orthopedic implants have been designed to restore mobility, reduce pain and to improve quality of life (mcginty and pontrelli, 2015). azojete december 2024. vol.20(4):947-958 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:rotimiadeleye1711@gmail.com mailto:rotimiadeleye1711@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 948 figure 1: examples of drug-delivery devices for different applications; implants, patch, stent, lens though the application of ois began as modest mechanical devices, but before long, complications set in. the factors that may be considered include the physical impact of the device on the bone and the soft tissues surrounding the bone; the unavoidable response of the foreign body; the probability of achieving osseointegration and many other complications (mcginty and pontrelli, 2015). the materials used in the construction of oi must be biocompatible with the human body, and as such quite a number of studies have been conducted to investigate the biocompatibility of these class of biomaterials (lyndon et al., 2013). certain studies have been carried out on oi to explore and investigate features such as potential cytotoxic and corrosion resistance effects. cobalt-chromium and titanium alloys have been shown to be more durable and less ductile than stainless steel (zadeh, 2019). typically, experimental research into techniques to locally distribute medications from ois as contained a drug inside a small container in the examined device. the various approaches to drug containment that look into changing the surface of the device structure have been studied (losic et al., 2014, trajkovski et al., 2012), and putting a coating to the device's surface (goodman et al., 2013). to enhance the medication release from orthopedic implants, many investigations have been carried out. for instance, modifying an oi's surface structure to serve as a drug reservoir or coating the exterior of an oi with a drug-releasing material (losic et al., 2014, mazaheri, et al., 2015). in orthopedic applications, distribution is really nothing new, antibiotics are commonly administered locally (arruebo et al., 2010, pozo and patel, 2009). the drug release process must be thoroughly understood for regulating the amount released for a precise oi (s) and prudence must be taken when providing treatment, articular antibiotics, below the minimal therapy dosage (lyndon, et al., 2014). the antibacterial and drug-releasing capabilities of some drug coated polymeric devices were evaluated in an effort to provide solution to the problem of post-surgical infection known with the implant of the orthopedic device, (arsiwala et al., 2014). two prevalent approaches for achieving the releasing mechanism are either upgrading existing ois or developing new device models with the intention of merging medication release with such a device (gimeno et al., 2013). recent advances in mathematical modeling studies have focused on drug-releasing ois in specific medical applications, including coronary stents, and from certain materials and architectures, like nanotubes and porous layers, which could be applied in the production of oi. therefore, mathematical models with some modifications could be applied to drugreleasing ois rather than experimental (in vitro and in vivo), which has since come to be accepted as the direction of orthopedic medicine in order to lower costs and shorten trial testing times (siepmann and siepmann, 2012). recent studies have discovered mathematical models that focus solely on the drug-releasing process in ois. it is beneficial, providing additional insights and understanding, as it was demonstrated by different models such as mathematical models describe drug release mechanisms (mcginty and pontrelli, 2015). in addition, the release of anti-cancer medications mitoxantrone (mtx) mesoporous silicon was studied (tzur-balter et al., 2013). in recent studies, mathematical models have been developed for drug release from ois. it reduces the cost of computation and simulation to reduce the challenges of real-life problems (sobamowo et al., 2022). http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 949 in the present study, the differential transform method (dtm) is applied to obtain solution to the problem of nonlinear simulation for the predictions of controlled drug-releasing orthopedic implants. the dtm is an efficient analytical method for obtaining solutions for linear and nonlinear ordinary differential equations. its principles were developed in 1986 by zhou (1986). the dtm has been applied in a wide range of studies such as convective flow in free and forced conditions on inclined planes of porous media (rashidi et al., 2012). nanofluids flow in both newtonian and non-newtonian state (hatami and jing, 2016). the dtm has proved to be effective when compared with other analytical methods. these include homotopy perturbation method (ghafoori et al., 2011) and adomian decomposition method (cakir and arslan, 2015). the dtm has been combined with the laplace transform method to overcome the deficiency usually caused by the unsatisfied conditions. such as in multi-step differential transform method for nonlinear oscillation erturk (2012), and nonlinear duffing oscillator with damping effect (nourazar and mirzabeigy, 2013). hence, the main objective of the current study is to develop a predictive mathematical model for controlled drug releasing orthopedic implants and to obtain analytical solutions using the differential transform methods. the runge-kutta order four numerical method was applied to validate the obtained analytical solutions. it was also validated with experimental results obtained in past recent studies. the effects of thickness ratio, diffusion period, porosity term, and effective diffusion coefficient ratio parameters on the governing model are then investigated. 2. model formulation one major inclusion in the device for drug delivery is a drug which contains coating of polymeric matrix characteristics that interact with certain release channels. the exact configuration of the device depends on their applications, but the coating of the drug-releasing ones can usually be modeled as a thick slab of width l. since the thickness of drug-release device coatings is naturally small compared with the dimensions of the lateral coating, and the drug flow is in one direction, the one-dimensional model is assumed in the study as shown in figure 2. figure 2: model’s physical geometry the layers 1 and 2 have thickness or width of l1 and l2, respectively, with l = l1 + l2 the total coating thickness. each porous coated layer is represented as a homogeneous material and all concentrations are defined as intrinsically averaged variables c1 and c2. the porosity constant φ1 and φ2 represent the drug concentrations in layers 1 and 2, respectively. additionally, the molecules are assumed to move along an increasing path length because of the indirect pores pathway represented by a new tortuosity parameter τi, i = 1, 2. with the assumption of a fast wetted coating and soluble drug, the phenomenon of drug transport can be represented by the following diffusion equations. diffusion equation for layer 1: 2 1 1 1 1 12 0 0, 0ec c d l x t t x    − = −      (1) diffusion equation for layer 2: 2 2 2 2 2 22 0 0 , 0ec c d x l t t x    − =      . (2) in the current study, the coating of the medical implant is assumed to discharge drug via pores filled with fluid only. consequently, the solid phase diffusion is neglected. http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 950 the mixed-type boundary conditions are imposed at both ends for a general case 1 1 1 1 10 , 0e c k c d x l t x  + = = −   . (3) 2 2 2 2 20 , 0e c k c d x l t x  + = =   . (4) with interfacial conditions are given as; ( ) 1 1 2 1 0 0, 0e c p c c d x t x  − + = =   . (5) 2 1 2 1 0, 0e ec c d d x t x x   − = − =    . (6) subject to initial conditions expressed as; 0 0 1 1 1 2 2 2, 0, 0; 0 , 0c c l x t c c x l t= −   = =    = (7) for the purpose of obtaining a dimensionless model, we introduce the following dimensionless variables: 1 1 2 1 1 22 0 0 1 1 1 0 02 2 2 1 2 1 20 1 1 1 1 1 1 , , , , , , , , , , . e e e e e e d t c c lx x c c l l c c l d c k l k lpl c d c d d d         = = = = = = = = =  =  = (8) using equation (8) on equations (1-7), the dimensionless governing equations become; 2 1 1 2 0 0, 0 c c x x      − = −      (9) 2 2 2 2 0 0 1 , 0 c c x x        − =   −    . (10) subject to generalized boundary and interfacial conditions given as: 1 1 1 0 , 0 c c x x    +  = = −   . (11) ( )1 1 2 0 0, 0 c c c x x    + − = =   . (12) 2 1 0, 0 c c x x x     = =    . (13) http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 951 2 2 2 0 1 , 0 c c x x     +  = = −   . (14) with initial conditions expressed as; 0 1 21 0, 0; , 0 1 , 0c x c c x   = −   = =   − = (15) the established diffusion equations will be solved subject to the established initial and boundary conditions in order to obtain the drug transport solutions. 2.1 analytical solution to the developed models; differential transform method (dtm) the governing models and the intermediate boundary conditions in the governing equations necessitate the need for a method that is capable of a solution which transforms differential equations from the original form into another domain for easy and robust representation. the differential transform method (dtm) is applied to transform a governing differential equation to an algebraic domain and then inverted through series summation method. the solutions of the problems are generated with the governing parameters intact and in place. few of the dtm recursive relations used in the transformation of the differential equations are shown in the table 1: table 1: differential transform method (dtm) s/n original function transformed function 1 ( ) ( ) ( )z t u t v t=  ( ) ( ) ( )z k u k v k=  2 ( ) ( )z t u t= ( ) ( )z k u k= 3 ( ) ( ) du t z t dt ( ) ( 1) [ 1]z k k u k= + + 4 2 2 ( ) ( ) d u t z t dt = ( ) ( 1)( 2) [ 2]z k k k u k= + + + 5 ( ) ( ) m m d u t z t dt = ( ) ( 1)( 2)...( ) [ ]z k k k k m u k m= + + + + 6 ( ) ( )* ( )z t u t v t= 0 ( ) [ ] [ ] k l z k v l k l = = − 7 ( ) mz t t= 1 ( ) ( ) 0 if k m z k k m if k m  =  = − =     8 ( ) ( an )z t a const t= 1 0 ( ) ( ) 0 0 if k z k a k a if k  =  = =     differential transform method (dtm) http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 952 representing 1c = , 2c = and applying table 1 to equations (9) and (10) yield, ( ) ( )( )1, , 21 1 2 0k h k hk h h + ++ − + + = (16) ( ) ( )( )1, , 21 1 2 0k h k hk h h     + ++ − + + = (17) with transformed boundary conditions represented as; 0, ,0 ,1 0, ,0 ,11, , , ,,h k k h k kca b a b     = = = = = = (18) performing iteration on equations (16) and (17) using equation (18) gives some of the solution: when h = 0: 1,2 ,a = 1,2 , a    = 2,2 3 , 2 a  = 2,2 3 , 2 a    = 3,2 2 ,a = 3,2 2 , a    = (19) when h = 1: 1,3 , 3 b  = 1,3 , 3 b   = 2,3 , 2 b  = 2,3 , 2 b   = 3,3 2 , 3 b  = 3,3 2 , 3 b    = (20) when h = 2: 1,4 , 4 a  = 2 1,4 2 , 4 a   = 2,4 , 2 a  = 2 2,4 2 , 2 a   = 3,4 5 , 6 a  = 2 3,4 2 5 , 6 a   = (21) applying the principle of dtm grouping on the term by term solution, 8 8 1 , 0 0 8 8 2 , 0 0 , 1,2,3,4,5,... , 1,2,3,4,5,... k j j k j k k j j k j k c x j k c x j k     = = = = = = = =   (22) making necessary substitution, the desired solutions for drug transports become: ( ) 3 4 3 3 7 5 8 7 7 7 6 6 5 7 4 7 2 7 3 6 4 7 6 8 6 6 6 7 2 3 8 2 3 7 6 6 3 5 8 1 6 6 2 5 7 1 5 / 6 2 / 3 3 / 5 1/ 7 7 3 4 4 / 3 7 / 3 1/ 8 15 7 1/10 1/ 2 1/ 42 7 / 6 10 3 / 15 , 7 2 1/ x a x b x b x b x b x a x b x a x a x b x a x b x a x a x b x b x x a x b x x b x c a x b x a b x x x                         + + + + + + + + + + + + + + + + + + + + + + = + + + + 5 6 5 5 5 3 2 8 4 7 4 8 5 4 5 5 2 3 2 8 72 7 4 6 10,33 4 4 7 7 40 15 20 1/ 24 1/ 24 7 / 4 3 2 112 3 7 5 / 4 ... 84 28 24 a x b x b x a x b x a x a x b x a x a x xb x a x b x a x                                 + + +      + + + + + + +      + + + + + +    (23) http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 953 3 7 3 3 2 3 3 2 3 3 7 6 3 3 3 7 83 7 7 7 2 7 3 2 7 4 10,2 3 3 2 2 7 5 2 5 5 2 4 8 2 3 2 2 4 4 5 6 2 1/ 3 2 2 / 3 1/ 2 210 1/ 7 1/ 28 4 4 / 3 3 3 / 5 1/ 20 3 336 b x b x a x b x b x a x c xb x a x b x a x b x b x a x a x a a a a a a c                                             + + + + + + + + + + + + + + + + + + + + + + = 2 5 5 2 2 5 7 2 8 2 2 2 8 62 2 4 2 8 4 2 8 5 10,2 4 7 2 2 2 2 2 8 83 6 3 5 7 3 5 6 10,43 5 6 3 3 2 3 3 2 6 3 7 1/10 20 15 1/ 2 3 / 4 1/ 4 4 3 7 1/ 30 1/15 56 15 1/12 1/ 2 b x b x a b x b x b x xa x a x b x b x b x xa x b x a x b x b x b x a x                                           + + + + + + + + + + + + + + + + + + + + 3 4 7 4 4 8 8 2 8 3 3 4 6 2 6 3 2 6 4 2 6 5 3 6 6 2 2 3 3 6 7 4 6 8 5 3 2 5 4 2 3 4 6 3 4 2 3 2 3 4 5 6 4 1/ 24 9 / 2 3 / 2 7 7 7 / 2 7 / 6 7 / 3 15 10 7 1/10 1/ 8 7 / 4 24 b x a x a x b x a x b x a x b x a x b x a x b x a x a x a x cx cx cx cx cx cx c                                        + + + + + + + + + + + + + + + + + + + + + 4 3 7 8 5 / 6 ... b x x cx                                                               + + +    (24) equations (23) and (24) are the desired analytical solutions for the drug diffusion models. these solutions can be used to predict transport and mass transfer of the drug through the porous layers. the equations will be treated and then used for simulation and parametric studies. furthermore, the obtained spatial terms of the series solutions will be converted into an approximate polynomial or exponential functions. these approximate functions will then be solved numerically together with the given boundary conditions to obtain the values of a, b, a and b. these values are substituted into the series solution and then used to visualize and investigate the intermediate conditions. 3. results and discussion in this study, an analytical solution for controlled drug releasing orthopedic implants for biomedical applications has been obtained using the differential transform method (dtm). the obtained analytical results are validated using the fourth order runge kutta numerical method and presented in table 2. the obtained analytical solutions were further validated with experimental results in a related past study and showed in figure 3. additionally, figure 3 depicts the validation of the present study the experimental result of berg (2012) good agreements established. this further demonstrate the capability of the employed analytical scheme for handling the problem of drug delivery for single and double interface layers. http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 954 table 2: validation of dtm with numerical method c(x) t = 0.01 numerical dtm residue d = 0.10 numerical dtm residue d = 1.00 numerical dtm residue 0.00 1.0000 1.0000 0.0000 0.5000 0.5000 0.0000 0.2000 0.2000 0.0000 0.05 1.0000 1.0000 0.0000 0.5000 0.5000 0.0000 0.2000 0.2000 0.0000 0.10 1.0000 1.0000 0.0000 0.5000 0.5000 0.0000 0.2000 0.2000 0.0000 0.15 1.0000 1.0000 0.0000 0.5000 0.5000 0.0000 0.2000 0.2000 0.0000 0.20 0.9997 0.9997 0.0000 0.4999 0.4999 0.0000 0.1999 0.1999 0.0000 0.25 0.9990 0.9990 0.0000 0.4995 0.4995 0.0000 0.1998 0.1998 0.0000 0.30 0.9971 0.9971 0.0000 0.4986 0.4985 0.0001 0.1994 0.1994 0.0000 0.35 0.9927 0.9927 0.0000 0.4964 0.4963 0.0001 0.1985 0.1985 0.0000 0.40 0.9837 0.9839 0.0002 0.4919 0.4919 0.0000 0.1967 0.1967 0.0000 0.45 0.9673 0.9676 0.0003 0.4837 0.4837 0.0000 0.1935 0.1935 0.0000 0.50 0.9394 0.9399 0.0005 0.4699 0.4697 0.0002 0.1879 0.1879 0.0000 0.55 0.8952 0.8959 0.0007 0.4478 0.4476 0.0002 0.1790 0.1790 0.0000 0.60 0.8298 0.8309 0.0011 0.4153 0.4149 0.0004 0.1660 0.1660 0.0000 0.65 0.7396 0.7413 0.0017 0.3703 0.3698 0.0005 0.1479 0.1479 0.0000 0.70 0.6246 0.6268 0.0022 0.3131 0.3123 0.0008 0.1249 0.1249 0.0000 0.75 0.4907 0.4933 0.0026 0.2462 0.2454 0.0008 0.0981 0.0981 0.0000 0.80 0.3504 0.3532 0.0028 0.1761 0.1752 0.0009 0.0701 0.0701 0.0000 0.85 0.2212 0.2237 0.0025 0.1114 0.1106 0.0008 0.0442 0.0442 0.0000 0.90 0.1193 0.1213 0.0020 0.0603 0.0597 0.0006 0.0239 0.0239 0.0000 0.95 0.0528 0.0540 0.0012 0.0268 0.0264 0.0004 0.0106 0.0106 0.0000 1.00 0.0183 0.0189 0.0006 0.0093 0.0092 0.0001 0.0037 0.0037 0.0000 figure 3: validation of the present study with the experimental work of berg (2012) 3.1 the effects of short and long transport durations on drug release concentration profiles the effects of short and long transport durations on drug release concentration profiles for the case of perfect contact interface are shown in figures 4 and 5. this is equivalent to the transport phenomenon in a single layer material. for the baseline case, the dimensionless concentration profiles at four durations are considered. as a result of the perfect contact initiated at the interface (c1 = c2), the results of concentration show that the concentration are not sensitive to the interface location for both short and long durations of the transport processes. the percentage mass transfer in the individual layers do vary with thickness ratio, d, but the release curves do not. http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 955 figure 4: effect of perfect contact during drug release on concentration profiles for short durations figure 5: effect of perfect contact during drug release on concentration profiles for long durations 3.2 effects of drug release due to system parameters variation the effects of drug release due to system parameters variation is further established by assuming that layers 1 and 2 have similar microstructure parameters (χ = φ = 1 = c0). consequent upon the infinite sinks’ boundary conditions at the release medium, drugs are swiftly released from the second layer in the early stages, whereas there is delay before drugs concentrations in the first layer drop from initial values. the release of drugs from the first layer continues at a slower rate than in the second layer. consequently, there are alterations in both the durations and shapes of release in the layers. from the plots, it is obvious that at 3 = and 4 = , all of the drugs have been released from the system. continuous increase in the drug release duration beyond these limits produces negligible influences on the concentration profiles. the dimensionless concentration profiles for imperfect contacts at the interface of the two layers are illustrated in figures 6 8. these helps explore the effects of varying relative microstructural parameters between the two layers for different time at imperfect contact points d = 2, d = 5, d = 8. from the plots, it is evident that continuous increase in interface layer thickness ratio introduce corresponding decrease in the concentration profiles for all the different dimensionless durations considered. the inference of this phenomenon is that the variation of the microstructure of the two layers causes alteration in the drug release shape profile and that drug delivery is ensured in specific time period. figure 6: effect of varying relative microstructural parameters between the two layers for different time at 0.2d = figure 7: effect of varying relative microstructural parameters between the two layers for different time at 0.5d = http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 956 figure 8: effect of varying relative microstructural parameters between the two layers for different time at d = 0.8. 3.3 effects of drug release parameter on concentration profile for single and double layers the effects of drug release parameter on concentration profile for single and double layers with perfect and imperfect contacts at interface are shown in figures 9 and 10. from the plots, it can be deduced that two layers with perfect contact interface condition can be approximated as a single layer. this is so because the concentration profiles for the aforementioned cases are similar. however, this is not the case when considering imperfect contact interface conditions. generally, an augmentation in the release parameter results in a decrease in the concentration profile for the three cases of thickness ratios considered. figure 9: effect of release parameter on concentration profile for the case of perfect contact at interface figure 10: effect of release parameter on concentration profile for the case of imperfect contact at interface figure 11: super-imposed plot showing the effect of diffusion coefficient on conc. history for cases 1 and 2 figure 12: super-imposed plot showing the effect of porosity term on concentration history for cases 1 and 2 http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 947-958. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: oadeleye@unilag.edu.ng 957 3.5 effects of diffusion coefficient, porosity and thickness ratios on concentration history the effects of diffusion coefficient and porosity on concentration history for specified initial loading parameter are presented in figures 11 and 12 respectively. from the plots, it is apparent that the porosity and diffusion coefficient terms are have synonymous impacts on concentration history. an increase in the two parameters may be used to reduce the concentration history. however, this reduction in concentration history may be further strengthen by reducing the magnitude of the thickness ratio. these parameters can be used interchangeably to achieve the desired concentration profiles and concentration history. 4. conclusion in this study, the modeling and simulations of the predictive mathematical model for controlled drug release orthopedic implants using differential transform method has been presented. the obtained solution was validated with runge-kutta order four numerical method and results from past experimental study. the solution was applied to investigate the effects of thickness ratio, diffusion period, porosity term, initial loading and effective diffusion coefficient ratio parameters. it was observed that continuous increase in interface layer thickness ratio resulted in corresponding decrease in the concentration profiles and augmentation in the release parameter resulted in a decrease in the concentration profile for thickness ratios. hence, the developed model and the obtained solutions provide the benchmark for the optimized and enhanced control of drug-releasing orthopedic implants (oi). the parametric studies also show that effective diffusion coefficients ration (χ) may be the dominant parameter in the model and so provides considerable flexibility and tuneability from a design/manufacturing point of view. the analytical solution in this work also provides better understanding of the relationship between the physical properties of the problem investigated. references arruebo, m., vilaboa, n. and santamaria j. 2010. drug delivery from internally implanted biomedical devices used in traumatology and in orthopedic surgery. expert opinion on drug delivery, 7(5): 589–603. arsiwala, a., desai, p. and patravale, v. 2014. recent advances in micro/nanoscale biomedical implants. journal of control release, 189: 25-45. berg, ej. 2012. diffusion controlled drug release from slurry formed, porous, organic and clay-derived pellets. acta universitatis upsaliensis uppsala, 45: 1-79. cakir, m. and arslan, d. 2015. the adomian decomposition method and the differential transform method for numerical solution of multi-pantograph delay differential equations. applied mathematics, 6(8): 13321343. efentakis, m., naseef, h. and vlachou, m. 2010. twoand three-layer tablet drug delivery systems for oral sustained release of soluble and poorly soluble drugs. drug development and industrial pharmacy, 36(8): 903916. erturk, vs., odibat, zm. and momani, s. 2012. the multi-step differential transform method and its application to determine the solutions of non-linear oscillators. advances in applied mathematics and mechanics, 4(4): 422-438. ghafoori, s., motevalli, m., nejad, mg., shakeri, f. and ganji, dd. 2011. efficiency of differential transformation method for nonlinear oscillation: comparison with hpm and vim. current applied physics, 11(4): 965-971. gimeno, m., pinczowski, p., vazquez, fj., perez, m., santamaria, j., arruebo, m. and lujan, l. 2013. porous orthopedic steel implant as an antibiotic eluting device: prevention of post-surgical infection on an ovine model. international journal of pharmaceutics, 452: 166–172. goodman, sb., yao, z., keeney, m. and yang, f. 2013. the future of biologic coatings for orthopaedic implants. biomaterials, 34: 3174-3183. http://www.azojete.com.ng/ mailto:rotimiadeleye1711@gmail.com arid zone journal of engineering, technology and environment, december 2024; 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(2006) stated that it is practically difficult to analyse article information abstract this study reported herein was conducted at the institute for agricultural research (iar) irrigation site, kadawa, kano state, nigeria during the 2016/17 and 2018/19 irrigation seasons (the 2017/18 trial failed due to emergency repairs that led to shut-down of the main channel from tiga dam for four weeks). the main aim of the research is to use field data to calibrate and validate aquacrop model to simulate tomato yield and water responses in northern nigeria. aquacrop model was calibrated and validated using the 2016/17 and 2018/19 season field trial data respectively. the evaluated results indicated that the model was able to simulate tomato fruit and biomass yield, seasonal crop water use and fruit water productivity at harvest satisfactorily in full etc and water stress condition. also, aquacrop model was able to simulate fruit yield and biomass yield along the crop growth stages with sufficient accuracy but fails to simulate canopy cover (cc) accurately during the initial stage as indicated by normalized root mean square error (nrmse), nash-sutcliffe model efficiency (ef), willmott’s index of agreement (d) and coefficient of residual mass (crm) values of 88%, 0.75, 0.89 and -0.88 respectively. however, the model was able to simulate cc relatively well during the development and middle stages with a tendency of over-predicting cc by about 2% in development stage and under-predicting cc by about 11% during the middle stage. furthermore, the aquacrop model was found to be simple, robust, require minimal input data and accurate in simulating soil water balance, fruit and biomass yield of tomato. therefore, it is recommended for used in evaluation of irrigation scheduling and water management strategies that will improve crop water productivity of tomato crop in northern nigeria. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 4 march, 2022 revised 30 june, 2022 accepted 1 may, 2023 keywords: calibration validation aquacrop deficit irrigation http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com file:///c:/users/pc1/downloads/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 660 long-term effect and large impact scenarios on the field thus the cheap and efficient way to carry out an evaluation of the impacts of irrigation scheduling practices is through the use of empirical production functions or computer-based simulation models. the complexity of assessing crop yield responses to water deficit using direct field experiments led to the advent of empirical production functions as the most practical option to assess crop yield response to water. among the empirical function approaches, is the equations developed by doorenbos and kassam (1979) to determine the yield response to water of field, vegetables and tree crops. scientific and experimental progresses in cropwater relations from 1979 to date, gave rise to the development and application of computer models to simulate crop yield response to water. more advanced computer-based simulation models that are based on different irrigation strategies and for specific edapho-climatic conditions such as ceres, subtor-potato, epic, almanac, cropsyst, tomgro and cropgro are now available. such models require advanced skills for their calibration and need a great number of parameters for the simulation process. also, the scientific approach of these models does not recommend their use by farmers and technicians, therefore, scientists, graduate students and advanced users in highly commercial farming represent the typical users of these models. in an attempt to achieve a new model that is less complex with accuracy, simplicity and robustness, the fao developed aquacrop model which focuses on yield response to water. in order to come-up with a comprehensive recommendation on the irrigation scheduling strategies to adopt for furrow irrigated tomato under water stress, and the corresponding soil water balance of a given field, calibration and validation of a computer-based crop simulation models such as aquacrop, to predict crop yield and water responses is necessary. the calibrated and validated model could be used as a decision support system tool for tomato growers and managers of irrigable areas to take optimal water management decision that will improve yield and crop water productivity. also, raes et al. (2010) stated that the goodness of fit for the calibrated parameters values provided in the aquacrop manual was low for tomato and further stated that the model parameters were not calibrated for water stress conditions. therefore calibration and validation of aquacrop model will contribute toward improving the reliability of the conservative parameters included in the aquacrop manual for tomato crop. 2. materials and methods 2.1 evolution of aquacrop model the tremendous complexity of crop responses to water deficits has led to the advent of empirical functions as the most practical tool to assess crop responses to water, among which, is the equation 1 developed by doorenbos and kassam (1979) to assess yield response to water of field, vegetable and tree crops. 1 1y x x y et k y et               (1) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 661 where: xy and y are the maximum and actual yield, xet and et the maximum and actual evapotranspiration, and yk the proportionality factor between relative yield decline and relative reduction in evapotranspiration. scientific and experimental progresses in crop-water relations led to the development of aquacrop model which evolved from equation 1. the aquacrop model differs from most models due to its accuracy, simplicity and robustness. details of the conceptual framework, underlying principles, and distinctive components and features of aquacrop are described by steduto et al. (2009), while the structural details and algorithms are presented by raes et al. (2009). calibration and performance evaluation for several crops are reported by farahani et al. (2009); garcia-vila et al. (2009); heng et al. (2009); hsiao et al. (2009). 2.2 study area the field experiments used in calibrating and validating the aquacrop model were conducted at the irrigation site of the institute for agricultural research, (iar) irrigation research farm at kadawa (latitude 110 38’41’’ n, longitude 80 25’ 51’’e and 490m above sea level), northern nigeria, during the 2016/17 and 2018/19 irrigation seasons respectively (the 2017/18 trial failed due to emergency repairs that led to the shut-down of the main channel from tiga dam for four weeks). the area lies within the kano river irrigation project (krip), sudan savannah zone of nigeria, and has a surface irrigation facility. the meteorological data for 2016/17 and 2018/19 irrigation season were obtained from the international institute for tropical agriculture (iita) meteorological station (kadawa). 2.3 experimental design the experiment consists of nine irrigation regimes (treatments) distributed in a randomized complete block design (rcbd) with three replications and furrow irrigation method was employed for water application. the treatments were based on water application regulated at selected crop growth stages. on each replication, there were nine experimental treatments. each treatment has 2.25 m x 94 m plot size consisting of three (3) well levelled-ridges and two (2) furrows. the furrow spacing and length is 0.75 m and 94 m respectively. the description of experimental treatment is shown in table 1. 2.4 determination of soil characteristics undisturbed soil samples were taken from the experimental site at six different depths (0 – 15, 15 – 30, 30 – 45, 45 – 60, 60 – 75 and 75 – 90 cm) and subjected to a standard laboratory method for determination of basic soil characteristics. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 662 table 1: description of experimental treatment treatment crop growth stages treatment description initial dev. middle late t1 t2 t3 t4 t5 t6 t7 t8 t9 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 50% 100% 100% 75% 100% 100% 50% 75% 100% 100% 50% 100% 100% 75% 100% 50% 75% 100% 100% 100% 50% 100% 100% 75% 50% 75% irrigating 100% of etc in all stages. irrigating 50% of etc during development stage and 100% at the remaining stages. irrigating 50% of etc during middle stage and 100% at the remaining stages. irrigating 50% during late stage and 100% at the remaining stages. irrigating 75% of etc during development stage and 100% of etc at the remaining stages. irrigating 75% of etc during middle stage and 100% of etc at the remaining stages. irrigating 75% of etc during late stage and 100% of etc at the remaining stages. irrigating 100% during the initial stage and 50% of etc at the remaining stages. irrigating 100% during the initial stage and 76% of etc at the remaining stages. 2.5 field operations and measurements 2.5.1 determination of crop water requirement the potential evapo-transpiration was computed using eto – calculator (fao penman monteith equation), version 3.2 (fao, 2012) for the duration of the irrigation season using meteorological data for the past 15 years and the crop evapotranspiration was calculated using equation 2. 2.5.2 irrigation furrow irrigation method was employed for water application. water was applied to the furrow through the use of spiles. the discharge into the furrows through the spiles was calibrated by direct method to be 1.4litres/sec. the irrigation interval of seven (7) days was adopted because that is the predominant farmers practice in the study area. water applied was based on the daily reference evapotranspiration computed from 15 years of climatic data (1999 – 2014) for the study location using eto – calculator (fao penman monteith equation), version 3.2 (fao, 2012). the depth of water applied per irrigation was calculated by summing the crop evapotranspiration (equation 2) computed from the reference evapotranspiration eto – calculator and the crop coefficient (kc) for the duration of the irrigation interval. c o cet et k  (2) : crop evapotranspiration, mm/day evapotranspiration, mm/day crop coefficient c o c where et et reference k    file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 663 2.5.3 soil moisture measurement soil moisture content measurement was carried out throughout the growing seasons with the use of theta-probe (type: ml2x) and moisture meter (hh2, delta-t devices). the actual crop evapotranspiration was calculated from the measured soil moisture content data obtained with theta-probe and moisture meter device using equation 3, as outlined by michael (1978). 1 2 1 100 n a i i i m m et d b          (3) 1 2 : actual crop evapotranspiration (mm) gravimetric moisture content (g/g)at first sampling in the ith layer; gravimetric moisture content (g/g)at second sampling in the ith layer; depth o a i where et m m d     f ith layer (mm) apparent specific gravity of the ith soil layer number of layers within the soil profile ib n   2.5.4 determination of canopy cover green canopy cover was measured during the initial, development and middle crop growth stages of 2016/17 and 2018/19 field trials to obtained canopy cover development data. the canopy cover was derived from pictures of the canopy taken overhead with a digital camera at around mid-day. the soil surface area covered by the green canopy was then measured from the pictures using image j software package. the per cent canopy cover (cc) was then calculated using equation 4. soil surface area covered by the green canopy cov 100% unit ground surface area canopy er   (4) 2.5.5 determination of fruit yield and dry above ground biomass samples of the above ground biomass during the initial, development and middle crop growth stages were harvested from 0.75m2 area of each treatment and dried and weighed to obtained biomass production data. final tomato fruits yield and above ground biomass was obtained from five (5) tagged plants in the centre ridge of each treatment measuring 1.35m2 area (i.e.1.8 x 0.75m). tomato fruits harvested from the tagged plants (1.35m2) of each treatment were weighed fresh and after drying. each treatment has an area of 1.8m x 0.75m which constitutes the net plot for final yield assessment. 2.6 input data for aquacrop model the input data used for running of the aquacrop model were: weather, soil, crop and irrigation scheduling (timing and depth of water applied). five weather input variables used to run the aquacrop model during the simulation were: daily maximum and minimum air temperatures, http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 664 daily rainfall, the mean annual carbon dioxide concentration in the bulk atmosphere from 1902 to 2099 and daily average evaporative demand of the atmosphere expressed as reference evapotranspiration (eto) for 15 years calculated with the use of eto calculator software (version 3.5). the rainfall input was not use as there was no rainfall event during the period of the two trials. the soil input variables is presented in table 2; while the irrigation scheduling input data for 2016/17 and 2018/19 seasons were as shown in tables 3 and 4 respectively. 2.7 calibration and validation of aquacrop model (5.0 version) calibration of the aquacrop model was accomplished by using the generated data from the field experiments during the 2016/17 irrigation season as model input and then simulating the model to predict the output viz, the yield, canopy cover, biomass and water balance. subsequently, the predicted output values were compared with the observed values of the experimental plot. the difference between the model predicted output and the measured experimental output was minimized in each case by iteration process in which one specific input variable was chosen as the reference variable at a time and adjusting only those parameters that were known to influence the reference variable the most. the process was repeated successively to arrive at the closest match between the model simulated and observed experimental values for each treatment combinations. finally, the observed experimental parameters that produced the best result in line with the measured output values were selected and used for the model calibration. the observed data generated during the 2018/19 season field trial was used to validate the model performance. calibrated aquacrop model was simulated with the input data of the experimental trial during the year 2018/19 to predict the fruit yield, biomass and water productivity. the criteria used in the model validation are statistical test and graphical plots of simulated and measured output. 2.8 performance evaluation of aquacrop model performance evaluation was carried using graphical plots and statistical indicators. the statistical indicators that were used to evaluate the performance of aquacrop model are: rmse (root mean square error), nrmse (normalized root mean square error), r2 (coefficient of determination), ef (nash-sutcliffe model efficiency coefficient), and d (willmott index of agreement). 3. results and discussion 3.1 soil characteristics and irrigation scheduling the soil characteristics of the study area that was used as soil input data for running the aquacrop model was presented in table 2 while the irrigation scheduling (timing and depth of water applied) for 2016/17 and 2018/19 field trial were presented in table 3 and 4, respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 665 table 2: soil characteristics at iar irrigation farm, kadawa depth bd soil water content particle size distribution (corrected to 200c) textural classa soil ph soil ec ksat taw sat fc pwp clay silt sand cm g/cm3 %vol % vol % vol % % % ratio ds/m mm/day mm/m 0 – 15 1.56 41 22 10 10 34 56 sandy loam 6.80 0.050 1,200 120 15 – 30 1.56 41 22 10 16 32 52 sandy loam 6.87 0.065 1,200 120 30 – 45 1.56 41 22 10 16 32 52 sandy loam 6.97 0.043 1,200 120 45 – 60 1.56 41 22 10 18 30 52 sandy loam 6.95 0.035 1,200 120 60 – 75 1.42 46 31 15 18 32 50 loam 6.95 0.065 500 160 75 – 90 1.42 46 31 15 16 34 50 loam 6.88 0.040 500 160 a textural classification based on usda; bd – bulk density; fc – field capacity; pwp – permanent wilting point; ec – electrical conductivity; ksat – saturated hydraulic conductivity; sat – volumetric soil water content at saturation; taw – total available water. table 3: depth of water applied during 2016/17 season treatments growth stages seasonal water applied (mm) initial (0 – 28 dat) development (29 – 60 dat) middle (61 – 100 dat) late (101 – 127 dat) t1 (i100d100m100l100) t2 (i100d50m100l100) t3 (i100d100m50l100) t4 (i100d100m100l50) t5 (i100d75m100l100) t6 (i100d100m75l100) t7 (i100d100m100l75) t8 (i100d50m50l50) t9 (i100d75m75l75) 115 115 115 115 115 115 115 115 115 98 50 98 98 73 98 98 50 73 212 212 107 212 212 160 212 107 160 129 129 129 65 129 129 98 65 98 554 506 449 490 529 502 523 337 446 dat: days after transplanting http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 666 table 4: depth of water applied during 2018/19 season treatments growth stages seasonal water applied (mm) initial (0 – 30 dat) development (31 – 62 dat) middle (63 – 102 dat) late (103 – 129 dat) t1 (i100d100m100l100) t2 (i100d50m100l100) t3 (i100d100m50l100) t4 (i100d100m100l50) t5 (i100d75m100l100) t6 (i100d100m75l100) t7 (i100d100m100l75) t8 (i100d50m50l50) t9 (i100d75m75l75) 76 76 76 76 76 76 76 76 76 122 62 122 122 92 122 122 62 92 247 247 125 247 247 186 247 125 186 133 133 133 67 133 133 101 67 101 578 518 456 512 548 517 546 330 455 3.2 calibrated tomato input parameters for aquacrop the crop simulation input parameters used for aquacrop model calibration are as shown in table 5. during the calibration process the conservative parameters were adapted from the report of raes et al (2010), these parameters are generally assumed to be applicable to a wide range of conditions and not specific for a given crop cultivar (table 5). the time from transplantto-transplant recovery, flowering, maximum canopy cover, maximum rooting depth, senescence and maturity as obtained from the field were 4, 32, 60, 52, 100 and 127 days, respectively (table 5). the following model output were recorded: length of flowering stage and length of building of harvest index, 56 and 89 days, respectively. the maximum and minimum effective rooting depth was set at 0.65 and 0.30 m, respectively. the water productivity (normalized for eto and co2) adopted was 17.0 g/m2 while the reference harvest index was set at 55% and the soil was set as sandy loam with initial soil moisture condition as wet dry. table 5: tomato input parameters for aquacrop model calibration year used for calibration 2016/17 description of input parameter units value type 1. crop phenology base temperature (tbase) upper temperature (tupper) canopy cover per seedling at 90% emergence (cc0) number of plants per hectare time from sowing to emergence/transplant to recovery canopy growth coefficient (cgc) maximum canopy cover (ccx) time from transplant to start senescence canopy decline coefficient (cdc) time from sowing/transplant to maturity time from sowing/transplant to flowering length of flowering stage minimum effective rooting depth (z0) 0c 0c cm2/plant no days %/day % days %/day days days days m m 8.0 28.0 5 29,630a 4a 14.5 80a 100a 8.0 127a 32a 56a 0.30 0.65 1.5 conservative1 conservative1 conservative2 management3 management3 conservative1 management3 cultivar4 conservative1 cultivar4 cultivar4 cultivar4 management3 management3 conservative1 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 667 year used for calibration 2016/17 description of input parameter units value type maximum effective rooting depth (zx) shape factor describing root zone expansion time from transplant to maximum rooting depth time from transplant to maximum canopy cover days days 52a 60a cultivar4 2. crop transpiration crop coefficient at full canopy but prior to senescence (kcbx) crop decline coefficient due to ageing, nitrogen deficiency, (kc) effect of canopy cover on reducing soil evaporation in late stage %/day mm/day 1.10 0.15 60 conservative1 conservative1 conservative1 3. biomass and yield water productivity normalized for et0 and co2 (wp) water productivity normalized for et0 and co2 during yield formation (as %wp* before yield formation) reference harvest index (hi0) building of harvest index allowable maximum increase of specified hi g/m2 g/m2 % days % 17.0 2.8 55 89 15 conservative1 conservative1 cultivar4 cultivar4 conservative1 4. soil water stresses depletion threshold for canopy expansion upper threshold (pexp, upper) depletion threshold for canopy expansion lower threshold (pexp, lower) depletion threshold for stomatal control upper threshold (psto) depletion threshold for canopy senescence upper threshold (psen) depletion threshold for failure of pollination upper threshold (ppol) shape factor for water stress coefficient for canopy expansion shape factor for water stress coefficient for stomatal control shape factor for water stress coefficient for canopy senescence minimum air temperature below which pollination starts to fail maximum air temperature above which pollination starts to fail 0c 0c 0.25 0.55 0.50 0.70 0.90 3.0 3.0 3.0 8.0 40 conservative1 conservative1 conservative1 conservative1 conservative1 conservative1 conservative1 conservative1 conservative1 conservative 1conservative generally applicable; 2conservative for a given species; 3dependent on environment and/or management; 4cultivar specific; a = data obtained from field 3.3 aquacrop model calibration calibration results of dry fruit yield, biomass yield and seasonal evapotranspiration is presented in table 6 while figure 1 presents the relationship between the simulated dry fruit yield during model calibration. the simulated dry fruit yield ranged from 2.479 t/ha to 5.496 t/ha (table 5). the simulated fruit and biomass yield and seasonal evapotranspiration of the different treatment http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 668 were compared with the measured values for the calibration trial (2016/17 irrigation season). the maximum and minimum dry fruit yield prediction error per cent of 17.7% and 1.9% were recorded in t8 (i100d50m50l50) and t3 (i100d100m50l100) respectively. the prediction error reported here is in agreement with what was reported by darko et al., (2016) that a maximum and minimum prediction error of 18.5% and 6.4% were recorded in treatment of “50% deficit level throughout the growth stages” and full irrigation treatment respectively. the simulated and measured fruit yield correlated well with r2 value of 0.88 indicating that the model explained 88% of the relationship between measured and simulated tomato fruit yield. student t-test was carried out to evaluate the difference between measured and simulated fruit yield. the result indicates that the difference between measured and simulated fruit yield was not significant at 5% probability level with ttab = 2.306, while tcal = 1.503. table 6: calibration results of dry-fruit yield, biomass yield and seasonal evapotranspiration dry fruit yield (t/ha) total biomass yield (t/ha) crop water use (mm) treatment sim. mea. pe sim. mea. pe sim. mea. pe t1 (i100d100m100l100) t2 (i100d50m100l100) t3 (i100d100m50l100) t4 (i100d100m100l50) t5 (i100d75m100l100) t6 (i100d100m75l100) t7 (i100d100m100l75) t8 (i100d50m50l50) t9 (i100d75m75l75) 5.496 4.621 3.793 5.050 5.127 4.724 5.304 2.479 4.182 5.387 4.530 3.722 4.951 5.026 4.333 5.127 3.012 4.099 2.0 2.0 1.9 2.0 2.0 9.0 3.5 -17.7 2.0 9.966 8.223 7.208 9.313 9.191 8.758 9.675 4.683 7.721 9.753 7.417 7.698 8.588 8.777 8.377 9.225 5.462 7.272 2.2 10.9 -6.4 8.4 4.7 4.5 4.9 -14.3 6.2 528.9 476.8 419.7 495.6 502.5 476.2 512.6 343.6 439.7 517.5a 472.1e 424.3g 486.2d 515.4b 486.3d 506.5c 336.4h 445.8f 2.2 1.0 -1.1 1.9 -2.5 -2.1 1.2 2.1 -1.4 simsimulated; meameasured; pe – prediction error per cent figure 1: comparison of simulated and measured dry fruit yield during calibration the comparison between simulated and measured total biomass yield during calibration is presented in figure 2. a good fit was achieved between the measured and simulated total biomass yield with r2 value of 0.92. the result of the student t – test, ttab = 2.306, while tcal = 1.243 y = 1.1878x 0.6421 r² = 0.8831 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 2 2.5 3 3.5 4 4.5 5 5.5 6 si m u la te d d ry f ru it y ie ld (t /h a) measured dry fruit yield (t/ha) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 669 indicates no any significant difference between measured and simulated total biomass yield at 5% probability level. figure 2: comparison between simulated and measured total biomass yield during calibration the r2 values obtained for fruit and biomass (0.88 and 0.92 respectively) is in agreement with rinaldi et al. (2011) who reported an averages r2 value of 0.84 and 0.96 for fruit and total biomass yield respectively for a three (3) years experimental data in mediterranean region; and kale and wadatkar (2017) who obtained r2 value of 0.87 and 0.95 for fruit and total biomass yield in india. the comparison between measured and simulated seasonal crop water use during calibration is presented in figure 3. the simulated values varied from 344 to 529 mm while the field measured values varied from 336 to 518 mm as shown in table 5. student t–test result (ttab = 2.306, tcal = 0.188) for the comparison between field measured and simulated values of the seasonal evapotranspiration indicated that the difference was not significant at 5% probability level. furthermore, the simulated and measured seasonal evapotranspiration correlated well giving r2 value of 0.97 indicating that the model explained 97% of the relationship. figure 3: comparison between simulated and measured seasonal crop water use during calibration y = 1.2308x 1.6198 r² = 0.9263 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 si m u la te d t o ta l b io m as s yi e ld (t /h a) measured total biomass yield (t/ha) y = 0.9847x + 7.6861 r² = 0.9755 300 350 400 450 500 550 300 350 400 450 500 550 si m u la te d s e as o n al c ro p w at e r u se ( m m ) measured seasonal crop water use (mm) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 670 the result of the statistical indicators used in evaluating the performance of the aquacrop model for the final calibration test is presented in table 7. the coefficient of determination (r2) for fruit yield, total biomass yield and crop water use were 0.88, 0.92 and 0.97 respectively. their values are above 0.8 which are considered as good. the root mean square error (rmse) obtained were 0.37 t/ha, 0.54t/ha and 8.54 mm for fruit, total biomass and crop water use respectively. they are close to 0 which is good since the range is from 0 to positive infinity (in which the former indicates ‘good’ and the latter ‘poor’ model performance). the normalized root mean square error (nrmse) for fruit, total biomass and crop water use were 8.3, 6.5 and 1.8% respectively which are considered very good since the values are less than 10%. the nash-sutcliffe model efficiency (ef) is 0.99 for all the three parameters (fruit, total biomass and crop water use) which is greater than 0.8 and considered as very good, indicating that there is a perfect match between measured and simulated. the willmott’s index of agreement (d) recorded for fruit. total biomass and crop water use is 0.99 which indicate a good agreement between measured and model-simulated. since all the five statistical indices used for the model evaluation are positive, it implies that the aquacrop model can be used for simulating yield and water balance. the coefficient of residual mass (crm) indicates that the model has the tendency to over predict fruit, total biomass at harvest and seasonal crop water use by 4%, 3% and 0.1% respectively. table 7: statistical indices of the comparison between simulated and measured dry fruit and dry biomass yield at harvest and seasonal crop water use during calibration (2016/17 season) statistical performance indices dry fruit yield (dfy) total dry biomass yield (tby) crop water use r2 0.88 0.92 0.97 rmse* 0.37 0.54 8.54 nrmse (%) 8.3 6.5 1.8 ef 0.99 0.99 0.99 d (willmott’s index of agreement) 0.99 0.99 0.99 crm 0.04 0.03 0.001 *unit of rmse for fruit and biomass yield is t/ha; crop water use is mm the simulated and field measured crop water productivity with respect to dry fruit is presented in table 8 while the statistical model performance indicators are presented in table 9. the crop water productivity reflects the water utilization efficiencies, the rate at which the water supplied is converted to harvestable produce. it gives a quantitative measurement of dry fruit produced per cubic meter of water used in evapotranspiration. the per cent error between measured and simulated crop water productivity varied from 0 to 17.5%. the statistical indices used for the model evaluation was considered as a good performance, which indicates that the model is capable in predicting crop water productivity. the crm shows that the model has a tendency to under-predict crop water productivity by 6%. file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 671 table 8: comparison of simulated and measured crop water productivity (dry fruit) during model calibration treatments cwp (kg/m3) sim. mea. pe t1(i100d100m100l100) t2(i100d50m100l100) t3(i100d100m50l100) t4(i100d100m100l50) t5(i100d75m100l100) t6(i100d100m75l100) t7(i100d100m100l75) t8(i100d50m50l50) t9(i100d75m75l75) 1.04 0.76 0.90 1.00 0.80 0.84 0.96 0.85 0.76 1.04 0.86 0.90 0.95 0.97 0.84 1.01 0.90 0.92 0.0 11.6 0.0 5.3 17.5 0.0 5.0 5.6 17.4 table 9: statistical indices of the comparison between simulated and measured dry fruit yield water productivity at harvest during calibration (2016/17 season) statistical performance indices dry fruit water productivity rmse* 0.09 nrmse (%) 10.2 ef 0.98 d (willmott’s index of agreement) 0.99 crm -0.06 *unit of rmse for fruit yield is kg/m3 3.4 aquacrop model validation the observed data generated during the 2018/19 season field trial was used to validate the model performance. calibrated aquacrop model was simulated with the input data of the experimental trial during the year 2018/19 to predict the dry fruit yield, biomass and water productivity. as a summary of the outcome of the simulations, the simulated dry fruit yield, total biomass yield and seasonal crop water use of the different irrigation treatments were compared with the measured values generated during the 2018/19 field trial and the results is presented in table 10 while figure 4, 5 and 6 shows the relationship between the simulated dry fruit yield, total biomass yield and seasonal crop water use, respectively, during model validation. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 672 table 10: validation results of dry fruit yield, biomass yield and seasonal evapotranspiration dry fruit yield (t/ha) total biomass yield (t/ha) crop water use (mm) treatment sim. mea. pe sim. mea. pe sim. mea. pe t1 (i100d100m100l100) t2 (i100d50m100l100) t3 (i100d100m50l100) t4 (i100d100m100l50) t5 (i100d75m100l100) t6 (i100d100m75l100) t7 (i100d100m100l75) t8 (i100d50m50l50) t9 (i100d75m75l75) 5.542 4.677 4.094 5.321 5.296 4.911 5.472 2.972 4.453 5.534 4.134 4.121 4.878 5.154 4.267 5.295 3.134 4.369 0.1 13.1 -0.7 9.1 2.8 15.1 3.3 -5.2 1.9 10.041 8.388 7.584 9.691 9.544 8.981 9.928 5.516 8.126 9.989 7.582 8.074 8.966 9.345 8.796 9.723 5.577 7.963 0.5 10.6 6.1 8.1 2.1 2.1 2.1 1.1 2.0 561.2 500.3 453.2 540.0 541.4 514.1 554.5 372.6 478.6 563.1 480.4 451.8 501.3 543.5 502.1 539.4 326.6 451.2 -0.3 4.1 0.3 7.7 -0.4 2.4 2.8 14.1 6.1 the simulated fruit yield varied from 2.972 to 5.542 t/ha while the biomass yield varied from 5.516 to 10.041 t/ha (table 10). the result of student t-test indicates that the difference between measured and simulated fruit yield was not significant at 5% probability level with ttab = 2.306, while tcal = 2.235. similarly, the result of the student t – test, ttab = 2.306, while tcal = 1.529 indicates no any significant difference between measured and simulated total biomass yield at 5% probability level. the fruit yield prediction error range from 0.1 to 15.1% and that of biomass yield range from 1.1 to 10.6% indicating that the model was able to simulate yield of tomato as expected. for the seasonal crop water use, the prediction error ranged from 0.3 to 14.1% indicating that aquacrop model was able to simulate the seasonal crop water use relatively accurately. the prediction error reported herein is in agreement with darko et al. (2016) who obtained prediction error ranging from 3.1 to 14.4% for seasonal crop water use. figure 4: comparison of simulated and measured dry fruit yield during validation y = 1.0451x + 0.0009 r² = 0.8904 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 si m u la te d d ry f ru it y ie ld (t /h a) measured dry fruit yield (t/ha) file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 673 figure 5: comparison between simulated and measured total biomass yield during validation figure 6: comparison between simulated and measured seasonal water use during validation the statistical indices for the model validation are presented in table 11. the r2 values for fruit yield, biomass yield and seasonal crop water use were 0.89, 0.92 and 0.96 respectively which are considered good since the values are above 0.8. the rmse obtained for fruit yield (0.33 t/ha), biomass yield (0.42 t/ha) and seasonal crop water use (23.9 mm) are closer to 0 than positive infinity and are considered as good. furthermore, the nrmse values for fruit, biomass and seasonal crop water use were 7.0, 4.8 and 4.8% respectively are less than 10% and are rated as very good. the nash-sutcliffe model efficiency (ef) and willmott’s index of agreement (d) for dry fruit, biomass and seasonal crop water use is 0.99 which indicates a perfect agreement between measured and model simulated values. the crm indicates that the model has the tendency to over-predict fruit yield and seasonal crop water use by 4% and biomass yield by 2%. however, student t–test result (ttab = 2.306, tcal = 2.999) for the comparison between field measured and simulated values of the seasonal evapotranspiration indicated that the difference was significant at 5% probability level but the other indices for model performance evaluation indicated a perfect agreement. the comparison between field measured and model simulated y = 1.0374x 0.1177 r² = 0.9294 5.0 6.0 7.0 8.0 9.0 10.0 11.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 si m u la te d t o ta l d ry b io m as s y ie ld ( t/ h a) measured total dry biomass yield (t/ha) simulated y = 0.83x + 99.736 r² = 0.9569 300 350 400 450 500 550 600 300 350 400 450 500 550 600 se as o n al w at e r u se ( m m ) measured seasonal water use (mm) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 674 crop water productivity for dry fruit yield during validation is presented in table 12 while table 13 shows the statistical performance indicators. the prediction error ranged from 0 to 16.7%. the statistical indices used for the model evaluation rmse (0.07 kg/m3); nrmse (7.7%); ef (0.99); and d (0.99), were considered as a good performance indicating that the model is capable in predicting crop water productivity. the crm shows that the model has a tendency to overpredict crop water productivity by 1%. table 11: statistical indices of the comparison between simulated and measured dry fruit and dry biomass yield at harvest and seasonal crop water use during validation (2018/19 season) statistical performance indices dry fruit yield (dfy) total dry biomass yield (tby) crop water use r2 0.89 0.92 0.96 rmse* 0.33 0.42 23.9 nrmse (%) 7.0 4.8 4.8 ef 0.99 0.99 0.99 d (willmott’s index of agreement) 0.99 0.99 0.99 crm 0.04 0.02 0.04 *unit of rmse for fruit and biomass yield is t/ha; crop water use is mm table 12: comparison of simulated and measured crop water productivity (dry fruit) during model validation treatments cwp (kg/m3) sim. mea. pe (%) t1(i100d100m100l100) t2(i100d50m100l100) t3(i100d100m50l100) t4(i100d100m100l50) t5(i100d75m100l100) t6(i100d100m75l100) t7(i100d100m100l75) t8(i100d50m50l50) t9(i100d75m75l75) 0.99 0.94 0.91 0.99 0.98 0.96 0.99 0.80 0.93 0.98 0.86 0.91 0.97 0.95 0.85 0.98 0.96 0.97 1.00 9.30 0.00 2.10 3.20 12.9 1.00 16.7 4.10 table 13: statistical indices of the comparison between simulated and measured dry fruit yield water productivity at harvest during validation (2018/19 season) statistical performance indices dry fruit water productivity rmse* 0.07 nrmse (%) 7.70 ef 0.99 d (willmott’s index of agreement) 0.99 crm 0.01 *unit of rmse for fruit yield is kg/m3 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 675 3.3 model simulation along crop growth stages 3.3.1 canopy cover simulation the simulated canopy cover (cc) for the crop growth stages is presented in table 14. the simulated canopy cover was at par to the measured values during the initial stage with a prediction error of 48% for treatment t6 and 47% for the remaining treatments. however, the simulated cc were closer to the measured values during the development and middle stage except for t2 (i100d50m100l100) and t5 (i100d75m100l100) which recorded 23% and 15% prediction error respectively during the middle stage. one common observation with regards to these two treatments (t2 and t5) was that the deficit was imposed in the development stage while in the middle stage (where the highest prediction errors were recorded) the treatments received full irrigation. perhaps, this suggest that the model is insensitive to detecting sudden change in water applied after transition from 50 and 25% deficit in development stage to full irrigation in the middle stage. table 15 shows the statistical indices for the comparison between simulated and measured cc for the growth stages. the aquacrop model fails to simulate cc accurately during the initial stage as indicated by normalized root mean square error (nrmse), nash-sutcliffe model efficiency (ef) and willmott’s index of agreement (d) values of 88%, 0.75 and 0.89 respectively. the coefficient of residual mass (crm) value of -0.88 obtained during the initial stage indicates that the model has the tendency of under-predicting canopy cover by about 88%. however, the model was able to simulate cc relatively well during the development and middle stages (as indicated in table 3.10) with a tendency of over-predicting cc by about 2% in development stage and under-predicting cc by about 11% during the middle stage. table 14: comparison between measured and simulated canopy cover during initial, development and middle crop growth stages treatments initial stage (%) (0 – 28 dat) development stage (%) (29 – 60 dat) middle stage (%) (61 – 100 dat) sim mea pe sim mea pe sim mea pe t1(i100d100m100l100) t2(i100d50m100l100) t3(i100d100m50l100) t4(i100d100m100l50) t5(i100d75m100l100) t6(i100d100m75l100) t7(i100d100m100l75) t8(i100d50m50l50) t9(i100d75m75l75) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 7.5 7.5 7.5 7.5 7.5 7.7 7.5 7.5 7.5 47 47 47 47 47 48 47 47 47 57.3 58.6 60.1 60.1 59.9 60.1 60.1 58.6 59.9 58.6 56.6 58.6 58.6 58.6 58.6 58.6 58.6 58.6 2 4 3 3 2 3 3 0 2 73.2 59.1 73.3 73.3 68.2 73.3 73.3 59.5 68.2 79.8 76.8 79.8 79.8 79.8 79.8 79.8 65.9 65.9 8 23 8 8 15 8 8 10 3 http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 676 table 15: statistical indices of the comparison between simulated and measured canopy cover during initial, development and middle crop growth stages statistical performance indices initial stage (%) (0 – 28 dat) dev. stage (%) (29 – 60 dat) middle stage (%) (61 – 100 dat) rmse (t/ha) 3.52 1.42 8.86 nrmse (%) 88.1 2.4 12.8 ef 0.75 0.99 0.98 d (willmott’s index of agreement) 0.89 0.99 0.99 crm -0.88 0.02 -0.12 3.3.2 above-ground biomass simulation above ground biomass refers to a conglomeration of stems, leaves, flowers, etc., and is derived from the amount of water transpired by means of crop water productivity after normalization for co2 and eto. table 16 shows the simulated and measured above ground biomass production during initial, development and middle stage for tomato while table 17 presents the statistical indices for the comparison of model simulated and measured above ground biomass for the crop growth stages. the simulated above ground biomass are relatively closer to the measured values during the three growth stages with a prediction error of 0 to 7%, 0 to 37% and 1 to 33% during the initial, development and middle stage respectively. the crm values of -0.05, 0.17 and 0.13 obtained for initial, development and middle stage respectively indicates the tendency of the model to under-predict the above ground biomass by 5% in the initial stage and over-predict above ground biomass by 17% and 13% during the development and middle stage respectively. table 16: comparison between measured and simulated above ground biomass during initial, development and middle crop growth stages treatments initial stage (t/ha) development stage (t/ha) middle stage (t/ha) sim mea pe sim mea pe sim mea pe t1(i100d100m100l100) t2(i100d50m100l100) t3(i100d100m50l100) t4(i100d100m100l50) t5(i100d75m100l100) t6(i100d100m75l100) t7(i100d100m100l75) t8(i100d50m50l50) t9(i100d75m75l75) 0.094 0.094 0.094 0.094 0.094 0.094 0.094 0.094 0.094 0.101 0.101 0.101 0.101 0.101 0.094 0.101 0.094 0.094 7 7 7 7 7 0 7 0 0 1.410 1.535 1.544 1.544 1.542 1.544 1.544 1.535 1.542 1.105 1.123 1.123 1.123 1.123 1.544 1.123 1.545 1.545 28 37 37 37 37 0 37 1 0 4.131 3.254 4.216 4.257 3.836 4.252 4.257 3.181 3.805 4.153 3.205 3.205 3.205 3.205 3.963 3.205 3.317 3.317 1 2 32 33 20 7 33 4 15 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arab et al: calibration and validation of aquacrop model for tomato crop under full and deficit irrigation. azojete, 19(3):659-678. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 677 table 17: statistical indices of the comparison between simulated and measured above ground biomass during initial, development and middle crop growth stages statistical performance indices initial stage (%) development stage (%) middle stage (%) rmse (t/ha) 0.01 0.33 0.66 nrmse (%) 6.1 21.5 17.0 ef 0.99 0.93 0.95 d (willmott’s index of agreement) 0.99 0.98 0.99 crm -0.05 0.17 0.13 4. conclusion from the study reported herein, it can be concluded that: 1. the evaluation of the model using calibration and validation trials data set indicated that the model was able to simulate tomato fruit and biomass yield, seasonal crop water use and fruit water productivity at harvest satisfactorily in full etc and water stress condition. 2. aquacrop model was able to simulate fruit yield and biomass yield along the crop growth stages with sufficient accuracy but fails to simulate cc accurately during the initial stage as indicated by normalized root mean square error (nrmse), model efficiency (ef) and willmott’s index of agreement (d) values of 88%, 0.75 and 0.89 respectively and the coefficient of residual mass (crm) value of -0.88. 3. aquacrop model is simple, robust, require minimal input data and found to be accurate in simulating soil water balance, fruit and biomass yield of tomato. therefore, it is recommended for used in evaluation of irrigation scheduling and water management strategies that will improve crop water productivity of tomato crop in northern nigeria. acknowledgments this research is part of the project entitled “simulation of soil water balance, response to water stress and yield of furrow irrigated tomato using aquacrop model”, funded by the tertiary educational trust fund (tet-fund) of nigeria under the institutional based research (ibr) funding scheme. we thank both tet-fund and management of ahmadu bello university for providing the fund and support for the conduct of the field experiments. references bazza, m. 1999. improving irrigation management. (kirda, c., moutonnet, p., hera, c and nielsen, dr. (eds)). crop yield response to deficit irrigation, dordrecht, the netherlands, kluwer academic publishers. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com arid zone journal of engineering, technology and environment, sept, 2023; vol. 19(3):659-678. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adamuarab72@gmail.com 678 darko, ro., yan, hf., liu, jp. and abbey, a. 2016. calibration and validation of aquacrop for deficit and full irrigation of tomato. int. journal of agricultural and biological engineering, 9(3): 104 – 110. doi: 10.3965/j.ijabe.20160903.1812 doorenbos, j. and kassam, ah. 1979. yield response to water. irrigation and drainage paper no. 33. fao, rome. fao. 2012. eto calculator. land and water digital media series no. 36, fao, rome, italy. website: http://www.fao.org/nr/water/eto.html. farahani, hj., izzi, g. and oweis, ty. 2009. parameterization and evaluation of the aquacrop model for full and deficit irrigated cotton. agronomy journal, 101: 469–476. garcía-vila, m., fereres, e., mateos, l., orgaz, f. and steduto, p. 2009. deficit irrigation optimization of cotton with aquacrop. agronomy journal, 36: 21–31. heng, l. k., hsiao, t., evett, s., howell, t. and steduto, p. 2009: validating the fao aquacrop model for irrigated and water deficient field maize. agronomy journal, 101: 488 – 498 hsiao, tc., heng, l., steduto, p., rojas-lara, b., raes, d. and fereres, e. 2009. aquacrop – the fao crop model to simulate yield responses to water: iii. parameterization and testing for maize. agronomy journal, 101: 448 – 459 igbadun, he., mahoo, hf., tarimo, akpr. and salim, ba., 2006: crop water productivity of an irrigated maize crop in mkoji sub-catchment of the great ruaha river basin, tanzania. agricultural water management, 85: 141–150. kale, mu. and wadatkar, sb. 2017. application of soft computing technique to simulate yield of irrigated tomato. international journal of pure and applied research in engineering and technology, (2): 386 – 393. available online at: http://www.ijpret.com. michael, am. 1978. irrigation theory and principles. vikas publishing house, pvt. ltd. new delhi, india. raes, d., steduto, p., hsiao, tc. and fereres, e. 2009. aquacrop—the fao crop model for predicting yield response to water: ii. main algorithms and soft ware description. agronomy journal, 101:438–447 raes, d., steduto, p., theodore, c., hsiao, tc. and fereres, e. 2010: reference manual, annexes. annex i. crop parameters – aquacrop, 34 – 38. steduto, p., hsiao, t c., raes, d. and fereres, e. 2009. aquacrop – the fao crop model to simulate yield response to water: i. concepts and underlying principles. agronomy journal, 101. 426 – 437 file:///c:/user/downloads/azojete143/www.azojete.com.ng file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2019%20no%203/adamuarab72@gmail.com http://www.fao.org/nr/water/eto.html http://www.ijpret.com/ corresponding author’s email address: aliyaumi@unimaid.edu.ng 270 arid zone journal of engineering, technology & environment original research article adsorption isotherms and kinetics of heavy metals from tannery effluent using composite agricultural waste y. a. musti, a. l. yaumi*, f. u. mukhtar, b. k highina and h. umar department of chemical engineering, university of maiduguri, maiduguri, borno state *corresponding author, e-mail address: aliyaumi@unimaid.edu.ng article information abstract tannery wastewaters are very complex and characterized by high content of organic, inorganic and nitrogenous compounds which include heavy metals. in this study, the adsorption isotherm and kinetics of a composite adsorbent produced from the chemical activation of groundnut shell and rice husk were utilized as agricultural waste in the removal of pb, cr and cd from tannery effluent. the experimental data were fitted to langmuir, freundlinch and temkin isotherm while the kinetics were also studied using pseudo-first-order and pseudo-second-order kinetic models. the result revealed that langmuir isotherm model showed excellent fit to the experimental data for all the heavy metal adsorption onto groundnut shell activated carbon (gr-ac). this can be seen from the high correlation coefficients r2. the langmuir monolayer adsorption capacity (qm) value was found to be 9.81 mg/g (pb), 5.72 mg/g (cr) and 4.25 mg/g (cd) respectively. the equilibrium adsorption capacity (qe) values calculated from the second order kinetics model agree well with the experimental values for pb and cd. in addition, the first order kinetic rate constant decreased with increase in initial metal ion concentration. the excellent correlation between the calculated qe and experimental qe values and higher regression coefficient r2 shows clearly that the adsorption of these heavy metals onto gr-ac followed pseudo-second-order kinetic model. therefore, groundnut shell and rice husk can effectively be utilized as agricultural waste to produce a composite adsorbent to remove pb, cr and cd from tannery effluent. received: 15th october 2023 reviewed: 8th january 2024 accepted: 3rd february 2025 keywords: adsorption isotherms kinetic heavy metals tannery wastewater groundnut shell rice husk © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction recently, the fast growth of industrialization causes a large amount of heavy metal-laden disposal to the environment which is highly toxic, mutagenic, and oncogenic (başaran et al., 2008). the rate of contaminated wastewater has kept on increasing intensively as a result of rapid urbanization and industrialization (beyan, et al., 2022). among industries, leather industry is recognized as a potential source to generate a significant amount of heavy metals into the environment (islam et al., 2021). tannery wastewaters are very complex and are characterized by high content of organic, inorganic and nitrogenous compounds, chromium, sulphides, suspended solids, and dissolved solids (durai and rajasimman 2011). the performance of treatment technologies varies with the types, sources and complexity of wastewater, and the kinds of technologies used. basically, the selection of wastewater treatment methods depends on the durability, sustainability, efficiency and reliability of technologies. the development of appropriate and effective wastewater treatment technologies is progressing (bedada et al., 2020). various conventional methods had been developed and tested for the removal of heavy metals from wastewater so that their environmental and health effects are minimized. removal of metals from wastewater can be achieved by the application of several methods such as sedimentation, electrochemical processes, ion exchange, biological operations, cementation, coagulation/flocculation, filtration, membrane processes, azojete march 2025. vol.21(1):270-278 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:aliyaumi@unimaid.edu.ng mailto:aliyaumi@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 271 chemical precipitation and adsorption (dagmawi and dawit, 2013). adsorption, among these techniques, is widely accepted due to ease of use in operation, low cost and high efficiency however, selection of a suitable adsorbent is critical. biochar has recently been established as an effective adsorbent for a variety of environmental applications and got a huge intention of the researchers for heavy metals’ removal from wastewater. biochar is a black, solid, stable, and porous carbonaceous compound with a large surface area and is derived from waste biomass through slow or fast pyrolysis (amin et al., 2019). for the adsorption of various pollutants, there has been a lot of success for rice husk (abbas et al., 2013; dikdima et al, 2022) and groundnut shell (tegegn et al., 2022; kothai et al., 2019). isotherms and kinetics studies play an important role in thoroughly understanding the adsorption process of organic and inorganic compounds in water solutions. therefore, it is vital to understand the equilibrium and dynamics characteristics of the adsorption process by using theoretical models. in this study, equilibrium adsorption data evaluated from a composite adsorbent (groundnut shell and rice husk) for the removal of heavy metals (pb, cr and cd) from tannery effluent were applied to langmuir, freundlich and temkin adsorption models. in addition, pseudo first and pseudo second order rate equations were used to describe and understand the adsorption kinetics. 2. materials and methods 2.1 adsorbent preparation and adsorption experiment rice husks and groundnut shells were obtained from a local rice mill and a local groundnut shelling mill in gamboru, maiduguri, borno state. the raw groundnut shell and rice husks were ripped off to remove dusts and washed with distilled water to remove the adhered particles dried for 24 hours in an oven at 105⁰c. it was then carbonized at temperature of 400 ͦ c for 1 hour to obtain bio char and then refined into powder form which was stored for uses. the adsorption experiments were performed in a series of flasks containing 50 ml solutions tannery wastewater at 50 – 250 mg/l concentrations and adsorbent dosages of 0.5g. the mixtures were agitated for 60 min at 250 rpm using a shaker mixer. the resulting mixtures were filtered, and the concentrations of heavy metals were determined using atomic adsorption spectrometer (aas). the adsorption equilibrium was investigated for different metal concentrations between 50 and 250mg/l. in addition, kinetics experiments were conducted with 250 mg/l metal and 0.5 g of adsorbent at 30, 40 and 500c temperature with stirring at 250 rpm for 60 min. the amount of adsorption at equilibrium was obtained using equation (1) qe = (co − ce)v m (1) where v is the solution volume in l, m is the amount of adsorbent used in g and qe is metal ion uptake in mg/g at time, t. 2.2 adsorption isotherm study adsorption isotherms are commonly used to describe the interaction of the adsorbate with the adsorbent. it also furnishes information for the understanding of the nature of reaction which is fundamental to optimizing the design of adsorption system. several isotherm models have been developed and utilize for the analysis of equilibrium data. the adsorption data was analyzed by fitting to langmuir, freundlich and temkin isotherm models. langmuir and freundlich isotherm models were thus tested according to the method adopted by (manikandan, 2016) langmuir isotherm model is representative of monolayer adsorption occurring on energetically homogenous surface on which the adsorbate molecules are not interactive. it is an empirical model assumes monolayer adsorption, with no lateral interaction and steric hindrance between the adsorbed molecules, even on adjacent sites. it is censured, for not accounting thermodynamic nature of a process and ideal assumption (foo & hameed., 2010). the linear form of the model is expressed by equations (2) and (3) ce qe = 1 kq0 + ce q0 (2) http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 272 or 1 qe = 1 q0 + 1 kq0ce (3) the nonlinear form is expressed by: qe = qobce 1+bce (4) where ce is the equilibrium concentration in (mg/l), q0 is the maximum adsorption capacity, k is the adsorption equilibrium constant (l/mg) and qe is the equilibrium adsorption capacity. freundlich isotherm is widely applied in heterogeneous systems especially for organic compounds or highly interactive species on activated carbon and molecular sieves. this empirical model can be applied to multilayer adsorption, with non-uniform distribution of adsorption heat and affinities over the heterogeneous surface (foo & hameed., 2010). the equation is given by equation (5) and the non-linear form is expressed by equation (6): qe = kfce 1/n (5) logqe = logkf + 1 n logce (6) where n is adsorption intensity, kf is the freundlich coefficient related to adsorption capacity. the freundlich isotherm constants kf, 1/n can then be calculated from the slopes and intercepts of ln (qe) versus ln ce). temkin isotherm is based on the hypothesis that, due to the interaction between adsorbent and adsorbate. the heat of adsorption of all the molecules in the layer reduce linearly with coverage due to adsorbate– adsorbate interactions. it is based on the assumption that the free energy of adsorption is a function of surface coverage (samuel et al, 2015). the temkin isotherm model is represented by equation (7) qe = blnat + blnce (7) the nonlinear form is expressed by equation (8): qe = rt bt ln(atce) (8) where rt bt is related to the heat of adsorption, and 𝐴𝑇 is the maximum binding energy of the adsorbate to the adsorbent, bt is temkin constant. the constants of the model bt and kt were obtained from the slope and intercept of the graph of the qe versus ln ce, respectively. 2.3 adsorption kinetic study kinetic modeling for adsorption processes involves studying the rate of adsorption of a species under particular condition before attaining equilibrium, it involves studying the mechanisms of the adsorption processes (vunain et al., 2021). the adsorption experimental were evaluated for their suitability using pseudofirst order and pseudo-second-order models as presented by equations (9) and (10). log( qe − qt) = logqe − k1 2.303 t (9) t qt = 1 k2qe2 + t qe (10) where qe and qt (mg/g) are the adsorption capacities at equilibrium and time t (min), respectively. k1 and 𝑘2 are the pseudo-first-order and pseudo-second-order rate constants. http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 273 3. results and discussion 3.1 adsorption isotherm models the adsorption data were analyzed by fitting to isotherm models into langmuir, freundlich and temkin isotherm models. the adsorption isotherm of lead, chromium and cadmium onto gr-ac are presented in figure 1 (a-c). the parameters and correlation coefficients obtained from the plots are shown in table 1. it can be observed from figure 1(a-c) and table 1 that langmuir isotherm model showed excellent fit to the experimental data for all the heavy metal adsorption onto gr-ac. this can be seen from the high correlation coefficients in table 1. the rl value was found between 0 and 1, which indicated the favorability of the adsorption process under the studied conditions. the langmuir monolayer adsorption capacity (qm) value was found to be 9.8039 mg/g (pb), 5.7175 mg/g (cr) and 4.2535 mg/g (cd) respectively. lead adsorption onto grac showed the highest maximum adsorption capacity. similar result was reported in the literature (bayuo et al., 2018). langmuir isotherm connotes homogeneous distribution of active sites on the adsorbents; hence, the surface of gr-ac is homogeneous with monolayer coverage. this demonstrates that the adsorbent surface is homogeneous for pb, cr and cd adsorption. the monolayer adsorption is accomplished via chemical adsorption and the active sites of gr-ac were uniformly disseminated. figure 1a: langmuir, freundlich and temkin isotherm for lead adsorption figure1b: langmuir, freundlich and temkin isotherm for chromium adsorption http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 274 figure1c: langmuir, freundlich and temkin isotherm for cadmium adsorption table 1: isotherm parameters for the adsorption of heavy metals onto gr-ac models lead chromium cadmium langmuir qmax(mg/g) 9.8039 5.7175 4.2535 b (l/mg) 10.38 6.1823 3.5078 rl 0.09786 0.0618 0.0387 r2 0.9993 0.9979 0.9873 freundlich kf (l/g) -0.0057 -0.9914 0.0825 1/n 0.98700 1.0592 1.2094 r2 0.9831 0.9673 0.9789 temkin kt(l/mg) 10.6956 1.5299 14.3586 bt(j/mol) 2.3698 2.1729 2.0371 r2 0.9965 0.9890 0.9504 3.2 adsorption kinetics model the experimental data were examined with pseudo-first-order model and pseudo-second-order kinetic models in order to understand the mechanism of adsorption. figures 2(a-f) and tables 2(a-c) presents the plot and kinetic parameters for pb, cr and cd onto gr-ac respectively. the results revealed that the correlation coefficients, r2 of the first and second order models in all the metal ions adsorptions are near 0.99 indicating good correlation with the experimental data. table 2a: kinetic model parameters for lead adsorption onto gr-ac co (mg/l) qe exp (mg/g) pseudo first-order k1 qe cal r 2 (1/h ) (mg/g) pseudo second k2 qe cal r 2 (g/mg.min) (mg/g) 50 1.238 0.406 0.215 0.9828 27.091 2.959 0.718 100 5.791 0.331 1.756 0.9956 7.563 5.071 0.9960 150 3.126 0.340 1.139 0.9996 8.241 3.968 0.9956 200 3.126 0.339 1.139 0.9996 5.116 3.395 0.9985 250 5.791 0.331 1.756 0.9956 5.080 4.762 0.9986 http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 275 the qe values calculated from the second order kinetics model agree well with the experimental values for pb and cadmium and the first order kinetic rate constant decreased with increase in initial metal ion concentration. the pseudo-second-order models assume that there is strong interaction between the adsorbate and adsorbent with chemisorption as the rate controlling step. the excellent correlation between the calculated qe and experimental qe values and higher regression coefficient (r2) shows clearly that the adsorption of these heavy metals onto gr-ac followed pseudo-second-order kinetic model. similar result has been reported by (samuel et al., 2015). table 2b: kinetic model parameters for chromium adsorption onto gr-ac table 2c.: kinetic model parameters for cadmium adsorption onto gr-ac co (mg/l) qe exp (mg/g) pseudo first-order k1 qe cal r 2 (1/h ) (mg/g) pseudo second k2 qe cal r 2 (g/mg.min ) (mg/g) 50 1.917 0.844 0.651 0.9939 5.474 8.518 0.9705 100 1.676 0.678 0.516 0.9985 1.347 7.007 0.9987 150 2.052 0.573 0.719 0.9983 20.488 6.863 0.9955 200 1.668 0.454 0.511 0.996 8.0267 6.325 0.9950 250 1.7864 0.4399 0.580 0.9972 3.681 5.678 0.9828 figure 2a: pseudo-first-order plot of lead onto gr-ac co (mg/l) qe exp (mg/g) pseudo first-order k1 qe cal r 2 (1/h ) (mg/g) pseudo second k2 qe cal r 2 (g/mg.min) (mg/g) 50 1.898 0.312 0.641 0.9965 18.198 3.948 0.907 100 2.883 0.266 1.059 0.9998 33.053 2.547 0.9867 150 2.800 0.235 1.029 0.9997 313.111 1.428 0.9992 200 2.821 0.202 1.037 0.9992 181.133 2.708 0.9961 250 2.930 0.161 1.075 0.9996 67.518 2.217 0.9949 http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 276 figure 2b: pseudo-first-order plot of chromium onto gr-ac figure 2c: pseudo-first-order plot of cadmium onto gr-ac figure 2d: pseudo-second-order plot of lead onto gr-ac http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 277 figure 2e: pseudo-second-order plot of chromium onto gr-ac figure 2f: pseudo-second-order plot of cadmium onto gr-ac 4. conclusion groundnut shells and rice husks were utilized as agricultural waste to produce a composite adsorbent via chemical activation to remove pb, cr and cd from tannery effluent. the adsorption isotherm was evaluated by fitting the experimental data with langmuir, freundlinch and temkin isotherm while the kinetics studied using pseudo-first-order and pseudo-second-order kinetic models. results shows that the adsorption of lead, chromium and cadmium were well fitted in langmuir model due to higher value of regression coefficient (r2). the rl value was found between 0 and 1, which indicated the favorability of the adsorption process under the studied conditions. the langmuir monolayer adsorption capacity (qm) were 9.81, 5.72 and 4.25 mg/g for lead, chromium and cadmium respectively. lead adsorption onto gr-ac showed the highest maximum adsorption capacity. pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order thus indicating a heterogeneous process. therefore, the gr-ac can be effectively utilized for the removal of heavy metals in tannery wastewater, however, there is need to further study the adsorption process in a fixed bed system. references başaran, b., mete u., behzat, ob and ahmed, a. 2008. distribution of cr (iii) and cr (vi) in chrome tanned leather. indian journal of chemical technology, 15: 511–514. http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 270-278. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyaumi@unimaid.edu.ng 278 bayuo, j. and pelig-ba, k.b. 2018. isotherm modeling of lead (ii) adsorption from aqueous solution using groundnut shell as a low-cost adsorbent. iosr journal of applied chemistry (iosr-jac), 11(11): 18–23. dagmawi, md., and dawit, m. 2013. chromium removal from modjo tannery wastewater using moringa stenopetala seed powder as an adsorbent. journal of chemistry, 4: 345–678. bedada, d., kenatu, a., amare t., kloos, h. and fito, j. 2020. chromium removal from tannery wastewater through activated carbon produced from parthenium hysterophorus weed. energy, ecology and environment, 5(3): 184–195. durai, g., and rajasimman, m. 2011. wastewater, biological treatment of tannery wastewatera review. 4(1): 184–195. vunain, e., joel, bn., timothy, tb and· adewale, ki. 2021. adsorption of chromium ions from tannery effluents onto activated carbon prepared from rice husk and potato peel by ­ h3po4 activation. applied water science, 11(9): 1–14. foo, ky and hameed, bh. 2010. insights into the modeling of adsorption isotherm systems. chemical engineering journal, 156(1): 2–10 dikdima, jmd., germain, vd. and tsamo, c. 2022. batch mode treatment of wastewater from the maroua artisanal tannery using silica extracted from rice husks and silica / sand mixture. equilibrium journal of chemical engineering, 6(1): 1–14. kothai, p., meena, a., meenaloshini, e., revathy, a., & kumar, nv. 2019. treatment of tannery effluent using groundnut shells. international research journal of engineering and technology, 6(9): 2440–2447. amin, mt., alazba, aa and shafi, m. 2019. application of biochar derived from date palm biomass for removal of lead and copper ions in a batch reactor: kinetics and isotherm scrutiny. chemical physics letters, 722(2018): 64–73. islam, md., rahaman, a., mahdi, mm. and mallik, d. 2021. removal of cr (iii) and other pollutants from tannery wastewater by moringa stenopetela seed removal of cr ( iii ) and other pollutants from tannery wastewater by moringa stenopetela seed. iop conference series: earth and environmental science, № 1, p. 012025. samuel, ms., evy aam and chidambaram, r. 2015. isotherm modelling, kinetic study and optimization of batch parameters using response surface methodology for effective removal of cr (vi) using fungal biomass. plos one 10(3): e0116884. abbas, mn., abbas, fs., nussrat, hh and hussein, s. 2013. synthesis of promoted catalyst from iraqi rice husk used as a raw material for treating tannery wastewater. australian journal of basic and applied science, 7(2): 511–528 manikandan, na., alemu, ak., goswami, l., pakshirajan, k. and pugazhenthi, g. 2016. waste litchi peels for cr (vi) removal from synthetic wastewater in batch and continuous systems : sorbent characterization, regeneration and reuse study. journal of environmental engineering, 142(9): 1-11 beyan, sm., prabhu, sv., ambio, ta and gomadurai, g. 2022. research article a statistical modeling and optimization for cr (vi) adsorption from aqueous media via teff straw-based activated carbon: isotherm, kinetics, and thermodynamic studies. adsorption science & technology, vol. 2022, article id 7998069, 16 pages. tegegn, k., yusuf, z., sasikumar, jm., and gorfu, k. 2022. biosorbent efficacy of groundnut husk for the elimination of chromium from the effluent of mojo tannery industry, ethiopia. international journal of biomater. 2022; 2022: 9997348. http://www.azojete.com.ng/ mailto:aliyaumi@unimaid.edu.ng https://www.ncbi.nlm.nih.gov/pmc/articles/pmc9671745/ https://www.ncbi.nlm.nih.gov/pmc/articles/pmc9671745/ arid zone journal of engineering, technology & environment azojete june 2023. vol. 19(2):309-318 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 309 original research article development of an ncam tuber-shaped vegetable slicing machine o. b. asamo*, f. b. olotu, r. o. jimoh, r. a. alade, s. c. obiakor, n. a. okoro and y. s. ademiluyi department of crop processing and storage engineering national centre for agricultural mechanization (ncam), km. 20, ilorin-lokoja highway, idofian, kwara state, nigeria *corresponding author’s email address: asamoolaoluwa@gmail.com 1.0 introduction root vegetable and fruits crops make up a majority of the common staple food consumed in nigeria. in 2018, the combined global production data for onion bulbs, plantain, cucumbers, irish potatoes and carrots was above 108 million tonnes (fao, 2019). the preservative prospects of various root vegetables and fruit crops vary, but in general, these crops are perishable and moving them from the farm to the market is often very expensive due to their bulkiness. processing them into essentially non-perishable produce provides an alternative to storage in fresh form as they are best preserved in the dried form by processing into flour, chips and pellets for both human and livestock ingestion (oyejide et al., 2018). traditionally, slicing is done with the aid of knives or other manual methods which takes a longer time to slice, expose the operator to dangers of injuring themselves, increases drudgery and overall productivity is lower (awoluyi 2003; obeng 2004). indigenous methods of cutting and slicing root vegetables and fruit crops into chips is associated with drudgery and susceptible to finger injury, time wastage, un-uniform size of sliced chip and unavoidably, leads to low output by farmers with diminutive or no income margin. article information abstract generally, most agricultural products are not stable immediately when freshly harvested, while their preservative nature varies accordingly especially, vegetables and fruit crops. the need to process and preserve them in a stable form is very important. in processing of some tuber -shaped vegetable crops such as carrot, plantain, cucumber, eggplant, etc., slicing/chipping is usually done traditionally with the aid of knives and other manual methods which are time consuming, thereby exposing processors to dangers of injury, increases drudgery and overall reduces productivity. in respect of these, an ncam tuber shaped vegetable slicer was designed, fabricated and evaluated. the performance parameters used for the evaluation are slicing efficiency, slice thickness and percentage damage. ibm spss 2.0 was used to analyse the result obtained from the performance evaluation of the tuber – shaped slicer. it was observed that blade thickness had a significant effect on percentage damage and slice thickness, and no effect on slicing efficiency at p≤0.05. 94.74% and 90.99% efficiency was observed at 1.5 mm and 1 mm blade thickness for plantain and cucumber respectively. furthermore, the highest mean value for percentage damage for plantain was 44.08% at 1.0mm blade thickness, while the highest mean value of percentage damage for cucumber was 24.88% at blade thickness of 1.0mm. this shows that the tuber – shaped vegetable slicing machine performed efficiently. therefore, tuber-shaped slicing machine is recommended for use by processor of tuber – shaped crops into other stable form. © 2023 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 4 february, 2023 revised 18 march, 2023 accepted 24 march, 2023 keywords: tuber shaped vegetable slicing machine design fabricate evaluation http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com mailto:chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):309-318. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 310 ezugwu et al. (2019) investigated the design and fabrication of a motorized operated plantain slicer for optimum chips production. the machine produced chips of uniform sizes in a short time of 3 seconds and had a slicing efficiency of 96.84% and could effectively slice a 70 arm diameter of unripe plantain. okafor et al. (2013) investigated plantain chip slicing machine that was designed, fabricated and tested to use a carrier spring return mechanism to achieve both the feeding option and the slicing operation. a slicing efficiency of 74% was recorded. adesina et al. (2015) designed and developed a plantain slicing machine that was tested and evaluation with its performance for machine capacity of 52kg, slicing efficiency of the machine was at 80% and the value of the length of the belt was calculated at 1039.85mm. the machine solved the problem of non-uniformity of chip thickness associated with traditional slicing methods as the time of slicing plantain for mechanical slicing was shorter but longer for traditional slicing method. however, percentage damage reported in the aforementioned research work was large. against this background there is the need to design a vegetable slicing machine to solve the problem mentioned above. the specific objectives of this study is to develop a tuber shaped vegetable slicer and evaluate its performance in order to produce quality chip, reduce time of operation, increase slicing efficiency and achieve a relatively noise free operation and vibration with low power consumption. 2. material and methods 2.1 description of the machine/ mode of operation the major parts of the machine include the frame, slicing unit and the power unit. the slicing unit consist of the hopper, feeding chute, cutting disc, blades and discharge outlet. stainless material was selected for the above-mentioned parts. the frame was constructed with mild steel angle iron to provide rigidity and support to the machine, while the power unit consist of the shafts, bearings, belt, pulley and 1hp electric motor which powers the machine. tuber-shaped vegetables are placed in the feeding chute vertically, the power transmitted from the electric motor through the shaft makes the cutting disc move in a rotary motion. the movement of the cutting disc in contact with the vertically placed material results in the slicing of the crop. 2.2 design calculations 2.2.1 pulley speed and size the pulley was designed by taking into account the power to be transmitted between the electric motor and the shaft connected to the cutting disc. the diameters of the pulley are calculated as employed by khurmi and gupta (2004.) (vr = 𝑁1 𝑁2 = 𝐷1 𝐷2 (1) where: n1 = speed of the pulley on the motor, rpm n2 = speed of the pulley on the shaft, rpm d1 = diameter of the pulley on the motor, mm d2 = diameter of the pulley on the shaft, mm and vr = velocity ratio vr= 2552 638 = 𝐷1 𝐷2 = 4 if a pulley of diameter 70 mm was used on the motor, a pulley of 280 mm is required for the shaft. d2=d1 * 4 = 70 * 4 = 280 mm file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):309-318. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 311 2.2.2 length of the belt as explained by khurmi and gupta (2004) and akande and onifade (2015) the length of an open belt could be calculated by l= 2𝑐 + 𝜋 2 (𝐷1 + 𝐷2 ) − (𝐷2− 𝐷1)2 4𝑐 (2) l = length of an open belt, mm c = centre distance of belt, mm d2 = diameter of the pulley on the motor, mm d1 = diameter of the pulley on the shaft, mm given c = from the design, l is calculated as, l = 2(395) + 𝜋 2 (280 + 70) + (280−70)2 4(395) l = 790 + 550 + 28 = 1.37m v-belts are designated by its type and nominal inside length. a v-belt of type a which can transmit power between the ranges of 0.73.5kw, the standard inside length nearest to 1368 mm is 1600mm (khurmi and gupta 2004.), (najeem et al, 2015). 2.2.3 tension in the belt the relation between tight side and slack side tension, in terms of co-efficient of friction (μ) and the angle of contact is given by khurmi and gupta (2004.) as; 2.3 log (𝑇1 𝑇2 )= 𝜇𝜃 (3) where; t1 = tension in the belt on the tight side, n t2 = tension in the belt on the slack side, n and μ = the coefficient of friction between the belt and pulley = 0.25 khurmi and gupta (2004) log (𝑇1 𝑇2 )= 0.25∗2.48 2.3 log (𝑇1 𝑇2 )= 0.27 t1 = 0.27 * t2 (4) the expression which shows the relationship between the powers transmitted, belt tension and linear velocity is given as; pm = (t1 – t2) (5) pm= power of the electric motor where; v = belt velocity, m/s v = 𝜋𝐷1𝑁1 60 (6) v = 𝜋∗0.07∗2552 60 = 8.25 ms-1 (t1 – t2) = 𝑃𝑀 𝑣 = 746 8.25 = 90.42 n 2.2.4 determination of the power required by the electric motor the power required by the electric motor was obtained from equation (7) pm = pc * pf (7) http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):309-318. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 312 where: pm = power of electric motor pf = power factor = 2 pm = 211.55 * 2 = 423watt = 0. 423 kw = 0.57 hp electric motor of capacity 950w (1hp) with speed of 1550 rpm was selected based on safety and availability of the motor. auto-cad software was used to develop the proposed design of the machine to show the orthographic and isometric view of what the machine would look like before and after fabrication as shown in figures 1, 2 and 3, respectively. front view side view top view figure 1: the orthographic view of the tuber-shaped vegetable slicer figure 2: isometric view of the tuber-shaped vegetable slicer file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):309-318. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 313 figure 3: pictures of the developed tuber-shaped vegetable slicer 2.3 performance test and evaluation 2.3.1 experimental procedure the performance evaluation of the root vegetable slicer was carried out in the processing and storage department (psed) of the national centre for agricultural mechanization (ncam) ilorin, kwara state. plantain tubers and cucumber used for the experiment were cleaned and sorted into various sizes. three cutting disc with blade thickness of 1mm, 1.5mm and 2mm was used to determine which blade thickness is best suited for slicing the available crops. a 24s-d adc cammry industrial table top scale was used to measure the weight of plantain tubers and cucumber in three (3) batches of 1kg each, other laboratory apparatus used in carrying out the experiment include; digital photo/contact tachometer of model number dt2236b with accuracy ± (0.05% + 1 digit) produced by bepedu world in kodhawa, pune, maharashtra, india, which was used by placing the photo contact point of the tachometer on the pulley while the machine was in operation to determine the operating speed of the machine. vernier calliper and clock/stop watch were used to measure the thickness of the sliced, unsliced and damaged products and time taken to slice the plantain and cucumber respectively. after weighing the plantain tubers, the first batch of 1kg plantain and cucumber was fed through the hopper and sliced using the cutting disc with blade thickness of 1mm while the second and third batches were sliced using the cutting disc with blade thickness of 1.5mm and 2mm thickness respectively and the entire process was replicated three (3) times. the weight of the sliced product, damaged product at the outlet of the machine and weight of the unsliced product which was remaining in the hoppers were weighed after each operation to determine the performance parameters of the slicing machine which are, slicing efficiency, percentage damage and percentage recovery. analysis of variance (anova) and new duncan multiply range test (nmdrt) of ibm spss 30.0 statistical package was employed to analyse how the operational conditions affect the performance of the root vegetable slicer. http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):309-318. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 314 2.3.2 performance parameter 2.3.2.1 slicing efficiency; se (%) this is the weight of the sliced product at the machine outlet divided by the total weight of both the sliced product and the unsliced product in percentage. it is expressed as in equation (8) 𝑆𝐸 = 𝑊2+𝑊4 𝑊0 × 100 (8) where: w0= weight of the sample before slicing w1= total weight at discharge outlet (g) w1= w2+w4 w2= weight of the sliced product at the machine outlet (g) w3= weight of unsliced product (g) w4= weight of the damaged product at machine outlet (g) 2.4.2.2 percentage damage; p.d (%) it is the weight of the damaged product during slicing over the total weight of unsliced product and damage product after slicing operation in percentage. it is expressed as in equation (9). 𝑃𝐷 = 𝑊4 𝑊3+𝑊4 × 100 (9) 2.4.2.3 slice’ thickness; st (mm) it is the average thickness of slices produced at the end slicing operation in mm. it is measured with the use of digital venial calliper. 3. results and discussion the tuber-shaped vegetable slicer has been designed and fabricated, its performance was evaluated to ascertain its effectiveness. the summary of the performance evaluation of the tubershaped vegetable slicer is presented in table 1. the average values performance parameters of the slicer such as slicing efficiency, percentage damaged and slice thickness were obtained at 113 rpm at difference blade thickness of 1.0mm, 1.5 mm and 2.0 mm using plantain and cucumber. it is observed that the highest mean value of slicing efficiency of 94.74% was noted at 1.5 mm blade thickness when plantain was used with the least mean value of slicing efficiency of 93.91% at blade thickness 2.0 mm. when cucumber was used for evaluation, the slicer had it highest mean value of slicing efficiency of 90.99% at 1.0 mm blade thickness with the least mean value of slicing efficiency of 90.24% at 2.0 mm blade thickness. the result of analysis of variance (anova) conducted showed that the blade thickness had no significant effect on slicing efficiency of the slicer at p≤0.05 as shown in table 2. the levels at which the slicer’s blade thickness affects the slicing efficiency of the tubershaped vegetable slicer is shown in ndmrt tables 3 which shows all levels of the blade thickness were not significantly different from each other at p≤0.05. this means that the blade thickness is similar to each other in term of their effectiveness in slicing the tuber–shaped vegetables which might be that the selected levels of blade thickness used are sharp enough to slice the tuber-shaped vegetable. the independence sample test was also conducted on slicing efficiency of slicer between plantain and cucumber as presented in table 4. the results showed that there were significant different between the slicing efficiencies of the machine using plantain and cucumber at p≤0.05. this means that plantain and cucumber do not have similar effects on the slicing efficiency of the slicer. these file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):309-318. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 315 differences in slicing efficiencies could be because of the difference in morphology of the crop as cucumber has a firm exocarp than plantain. this is also in line with research findings conducted on the slicing of carrot, plantain, onions and banana as reported elsewhere (sonawane et al., 2011; rajesh et al., 2016; ezeanya et al 2020). the highest mean value of percentage damage of 44.08% of plantain chips was observed at blade thickness of 1.0 mm with least mean value of 28.05% at blade thickness 2mm. the lowest mean value of percentage damage of sliced cucumber 15.10% obtained at 2.0 mm blade thickness and it highest mean value of percentage damage 24.88% was obtained at the blade thickness of 1.0mm. the anova results shows that the blade thickness (bt) and the crop type (ct) had significant effects on the percentage damage of the slices as well as their combination at p≤0.05 as shown in table 2. the levels at which the slicer’s blade thickness affects the percentage damage of the slice are shown in ndmrt tables 4 which shows all levels of the blade thickness were significantly different from each other at p≤0.05. the highest percentage of damaged slices observed at 1mm blade thickness for both plantain and cucumber slices could be that cutting action was faster at 1 mm blade thickness with incomplete slicing operation on the crop because it is the sharpest blade thickness. the result of the slice thickness in relation to the blade thickness used in slicing was shown in table 1. it can be observed that the highest mean value of slice thickness 1.75mm of plantain chips was obtained at blade thickness of 2.0 mm with least mean values of 0.71mm at blade thickness1.0mm was obtained after slicing operation. the lowest mean value of cucumber slice thickness 0.81mm given at 1.0mm blade thickness and it highest mean value of 0.90mm was obtained at the blade thickness of 1.0mm. the anova results shows that the blade thickness and the crop type had significant effects on the slices of tuber – shaped vegetable as well as their combination at p≤0.05 as shown in table 2. the levels the slicer’s blade thickness that led to the differences slices’ thickness are shown in ndmrt tables 3 which shows all levels of the blade thickness were significantly different from each other at p≤0.05. the independence sample test was conducted on slices thickness of plantain and cucumber as presented in table 5. the results showed that there were significant different between the slices’ thickness of plantain and cucumber at p≤0.05 as indicated in table 3. this means that the slicer does not have similar effects on the slice thickness of plantain and cucumber. table 1: summary of the performance evaluation of the tuber-shaped vegetable slicing machine crop operating speed (rpm) blade thickness (mm) thickness of the slice (mm) slicing efficiency (%) percentage damage (%) plantain 113 1 0.71 94.60 44.08 113 1.5 1.28 94.74 35.56 113 2 1.75 93.91 28.05 cucumber 113 1 0.81 90.99 24.88 113 1.5 0.86 90.51 19.88 113 2 0.90 90.24 15.10 mean values of three replicates http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):309-318. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 316 table 2: analysis of variance (anova) for performance parameters of tuber-shaped vegetable slicing machine performance parameters source type iii sum of squares df mean square f sig. slicing efficiency (%) corrected model 76.153a 5 15.231 17.589 .000* ct 73.609 1 73.609 85.005 .000* bt 1.394 2 .697 .805 .470 ct * bt 1.150 2 .575 .664 .533 error 10.391 12 .866 total 153858.638 18 percentage damage (%) corrected model 1673.210a 5 334.642 138.968 .000* ct 1144.014 1 1144.014 475.079 .000* bt 499.745 2 249.873 103.766 .000* ct * bt 29.450 2 14.725 6.115 .015* error 28.897 12 2.408 total 15739.166 18 slice thickness (mm) corrected model 2.285a 5 .457 464.836 .000* ct .650 1 .650 660.814 .000* bt .988 2 .494 502.379 .000* ct * bt .648 2 .324 329.305 .000* error .012 12 .001 total 22.353 18 *significant at p≤0.05; ct = crop type; bt = blade thickness table 3: new duncan multiply ranged test (ndmrt) for performance parameters of tubershaped vegetable slicing machine s/n levels of blade thickness (mm) performance parameters mean thickness of slices (mm) mean slicing efficiency (%) mean percentage damage (%) 1 1.00 0.76a 92.80a 21.57a 2 1.50 1.07b 92.13a 27.72b 3 2.00 1.34c 92.36a 34.48c sig 0.05 mean with the same alphabet are not significantly different from each other file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com asamo et al: development of an ncam tuber-shaped vegetable slicing machine. azojete, 19(2):309-318. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 317 table 4: independent sample test on performance parameters of tuber-shaped vegetable slicing machine using plantain and cucumber independent samples test levine’s test for equality of variances t-test for equality of means t df sig (2tailed) mean difference std. error difference 95% confidence interval of the difference slice thickness equal variances assumed lower upper 2.512 16 .023 .38000 .15127 .05933 .70067 equal variances not assumed 2.512 8.195 .036 .38000 .15127 .03262 .72738 slicing efficiency equal variances assumed 9.542 16 .000 4.04444 .42385 3.14592 4.94297 equal variances not assumed 9.542 15.068 .000 4.04444 .42385 3.14138 4.94795 percentage damage equal variances assumed 5.727 16 .000 15.94444 2.78411 10.04239 21.84650 equal variances not assumed 5.727 13.065 .000 15.94444 2.78411 9.93277 21.95612 significantly different at p≤0.05 4. conclusion an ncam tuber-shaped vegetable slicer was designed, fabricated and evaluated. the result of the evaluations presented shows the highest mean value of slicing efficiency to be 94.74% and the lowest mean value for percentage damaged was 24.88% for plantain while highest efficiency for cucumber was 90.99% and percentage damage was 15.10%. the percentage damage values shows that the machine will not only serve as an improvement the use of knives to slice but also increase the productivity of small-holder farmers and small scale processing industries. references adesina, ao., ajiboshin, io., adedeji, wo. and adelana, so. 2015. design, development and performance evaluation of plantain slicing machine. international journal of emerging trends in engineering and development, 1(5):204-216. akande, fb. and onifade, tb. 2015. modification of a plantain slicing machine. innovation system design and engineering, 6(10): 41-53. awoluyi, oo. 2003. design and construction of plantain slicer. msc. thesis, department of design and fabrication, federal institute of industrial research organization, oshodi, nigeria, pp 72. http://www.azojete.com.ng/ mailto:%20chykearcade@yahoo.com arid zone journal of engineering, technology and environment, june, 2023; vol. 19(2):309-318. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: asamoolaoluwa@gmail.com 318 ehiem, jc., irtwange, sv. and obetta, sc. 2009. design and development of an industrial fruit and vegetable dryer. research journal of applied sciences, engineering and technology, 1(2): 44-53. ezeanya, nc. 2020. development and performance evaluation of a slicing machine for selected vegetables. greener journal of physical sciences, 6(1):1-9. ezugwu, ca. 2019. design and fabrication of a motorized power operated plantain slicing machine. research journal of agriculture and biological sciences, 4(6): 624-635. faostat, 2019. world crop production indices for 2018. fao, rome. www.fao.org/faostat/en/#search/crop%20production%20in%20nigeria%202018 accessed on 8 august, 2022. khurmi, rs. and gupta, jk. 2004. a text book of machine design. eurasia publishing house ltd. ram nagar, new delhi, pp.1096. khurmi, rs. and gupta, jk. 2010. theory of machines. eurasia publishing house, new delhi, india. kingsley-omoyibo, qa. 2020. design and fabrication of an improved continuous plantain slicing machine. nigerian journal of engineering science research (nijesr). 3(1): 17-26 najeem, s., daniel, a., okanlawon, h., orilade, m., abioye, p. and adekanmi, s. 2015. construction of locally made plantain slicer. b.tech. thesis, department of agricultural engineering, lautech, ogbomoso, nigeria. obeng, gy. 2004. design and fabrication and testing of a mechanized plantain and carrot slicer. journal of science and technology, 24(2):126-133. okafor, be. and okafor, vc. 2013. design of a plantain chips slicing machine. international journal of engineering and technology, 3(10):26-40. olutomilola, e.o. 2019. theoretical design of plantain peeling machine, international journal of scientific and engineering research, 30(1):234-244. onifade, tb. 2015. energy and exergy analyses of the thin layer of drying of physic nuts (jatropha curcas. ph.d thesis, department of agricultural engineering, ladoke akintola university of technology, ogbomoso, nigeria. oyejide, jo., orhorhoro, ek., afoegba, sc. and olaye, m. 2018. design and fabrication of an improved plantain processing machine. nigerian journal of technology (nijotech), 37(3): 656 – 662. rajesh, gk., pandiselvan r. and indulekshmi, a. 2016. development and performance evaluation of plantain peeler cum slicer. scientific journal of agricultural engineering, (2): 41-50. sonawane, sp., sharma, gp. and pandya, ac. 2011. design and development of a power operated banana slicer for small scale food processing industries. journal of research in agricultural engineering, 7(04): 144 152 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20chykearcade@yahoo.com http://www.fao.org/faostat/en/#search/crop%20production%20in%20nigeria%202018 corresponding author’s email address: okhiria.kenneth@naub.edu.ng 499 arid zone journal of engineering, technology & environment original research article modelling of a real-time aerial surveillance system for quadcopter application using machine vision k. okhiria1, j.d. jiya2, i.s. sintali3 1department of mechanical engineering, nigerian army university biu, borno state 2department of mechatronics and systems engineering, atbu, bauchi state 3department of mechanical engineering, atbu, bauchi state corresponding author’s email: okhiria.kenneth@naub.edu.ng article information abstract unmanned aerial vehicles (uavs) have gained significant traction for real-time surveillance applications such as object tracking and search-and-rescue missions. a key enabler of these capabilities is the integration of a real-time, highly accurate object detection system. while available two-stage detectors like r-cnn, fast rcnn, faster r-cnn, and mask r-cnn achieve high detection accuracy and precise localization by dividing the image into regions and classifying each region, they are often slow, complex, and resource-intensive, making them unsuitable for real-time applications. to address this limitation, this research utilizes a darknetbased yolov3 (you only look once, version 3), a state-of-the-art algorithm for real-time object detection in videos, live feeds, and images. leveraging a deep convolutional neural network (cnn), yolov3 efficiently learns features and predicts object locations and class probabilities in a single pass, ensuring highspeed and reliable detection. a real-time aerial surveillance system for quadcopter application using machine vision is proposed. the training dataset, obtained from the internet and self-taken images from a camera, was manually annotated into three critical categories: suspect, bandit, and weapon. the dataset was subsequently divided into training and testing subsets. experimental results demonstrate that the proposed system achieves outstanding detection accuracy, with an overall mean average precision (map@0.5) of 93.82%, precision of 94%, and recall of 83%. compared to a resnet-50-based faster r-cnn model, the yolov3-based approach outperformed, achieving success rates of 0.81 for the bandit class and 1.00 for both suspect and weapon classes. this research improves drone-based ai for real-time object detection in security systems, enhancing efficiency and adaptability. it also creates specialized datasets, including a tailored bandit dataset, to support future uav security research. received: 25th march 2025 revised: 2nd may 2025 accepted: 2nd may 2025 keywords: convolutional neural network yolo quadcopter dataset surveillance © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in past years, the evolution of unmanned aerial vehicles has experienced substantial growth. recently, these uavs have proven to be a promising solution for a diverse range of applications, including firefighting, mapping, reconnaissance, disaster relief, and search and rescue operations (rendón & martins, 2017). other civilian applications include inspection and search activities, aerial photography of landscapes, precise agricultural practices, traffic and crowd control, observing meteorological conditions, and providing emergency healthcare and parcel delivery services. these are feasible due to the current design of uavs. uavs are capable of autonomous navigation, operating beyond the line of sight, particularly in challenging terrains, and even in adverse weather conditions (rendón & martins, 2017;janarthanan et al., 2019;dilshad et al., 2020). the most famous uav, that is being used for social and security applications, is the quadrotor, compared to other rotorcraft, the geometric symmetry of quadcopters simplifies modeling and controller design. additionally, their unique maneuverability and capability for vertical take-off and landing (vtol) render them an edge over other uavs, utilizing a quadcopter allows for easy initiation of surveillance in locations where traditional security cameras cannot be installed, (pashaei et al., 2020);(iqbal et al., 2021). face recognition is a method azojete june 2025. vol.21(2):499-509 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/015 www.azojete.com.ng mailto:okhiria.kenneth@naub.edu.ng mailto:okhiria.kenneth@naub.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 500 utilized to verify or identify an individual’s identity by examining and correlating patterns derived from their facial characteristics. image recognition and image localization in environmental monitoring have emerged as popular and highly studied topics in the field of computer vision. the convolutional neural network (cnn) model stands out as the predominant image processing technique utilized for these purposes. cnn does three tasks: feature extraction by convolution layer, feature selection by pooling layer and classification by fully connected layer. a convolutional neural network, a prominent deep learning technology, is commonly applied in image recognition tasks. an extension of object classification is object detection, aimed at recognizing the object in the image. object detection detects all occurrences of pre-conceived classes and draws bounding boxes to provide localization of the image. this study employs a quadcopter for image acquisition and utilizes the yolov3 algorithm for object classification, localization, and detection aiming to facilitate environmental monitoring. typically, investigations into image recognition and localization technology involve identifying possible targets and drawing insightful conclusions from the acquired image data (pashaei et al., 2020;zhao et al., 2018;lin et al., 2021;zaidi et al., 2022). yolo (“you only look once") is a single-stage detector that uses a fully convolutional neural network to predict anchor boxes and class probabilities in a single pass, without extracting region proposals like f-rcnn (ammar et al., 2020). it divides the image into grid cells to predict object locations and classifications. yolov3, featuring the darknet-53 backbone, improved upon its predecessors. it is a real-time object detection algorithm that employs a single convolutional layer that spans the entire image. it divides the image into grid cells, and each grid cell predicts a certain quantity of bounding or anchor boxes around objects, assigning high scores to those associated with predefined classes. every bounding box is assigned a confidence score representing the estimated accuracy of that particular prediction, and each box is designed to detect only one object. yolov3 demonstrates speed and accuracy in relation to mean average precision (map) and intersection over union (iou) values. moreover, it undergoes pre-training on the coco dataset. (chen et al., 2021;bao et al., 2021;ammar et al., 2020). recently, drones have found increased acceptability for real-time surveillance applications. an object detection device is an important component of a uav for air-to-ground surveillance, for it to be employed for tasks such as object tracking, search, and rescue, it requires real-time data processing and must have a high detection accuracy. furthermore, available two-staged detectors like r-cnn, fast-rcnn, faster-rcnn, and mask rcnn divide the image into regions, classify each region then combine them. they have the characteristics of having high detection accuracy, precise localization, and improved feature extraction ability. but they are often slow, complex, and resource intensive thus, not suited for real-time object detection (li et al., 2018). singlestaged detectors are faster, more accurate, and simpler object detection methods predicting the object in an input image directly in one pass through the network. when compared to other detection algorithms, yolov3, a single-stage object detector provides high performance in terms of accuracy and speed when employed for object detection (ammar et al., 2020);(bao et al., 2021). to overcome these issues, this research aims to model a real-time aerial surveillance system for quadcopter applications using machine vision which involves employing deep learning techniques like yolov3 to automatically retrieve information from an image. this extracted information can range from a basic signal to a detailed set of data, encompassing aspects like the identity, position, and orientation of objects within the image. the goal is to create a quadcopter-based solution for surveillance missions, capturing real-time data and using yolov3 to classify, localize, and detect relevant objects in the image. convolutional neural networks have long been used for target tracking using uavs, (sun et al., 2022) proposed a transformer-based aerial tracking framework combining spatial and temporal dimensions to solve challenging problems in aerial tracking like target loss, misclassification, and imprecise boundary boxes. security surveillance using quadcopters has been shown by (iqbal et al., 2021) to be effective with deep learning techniques, they proposed a deep learning-based security and surveillance method and real-time transmission of data to the control room by a comparative analysis of the built model with four pretrained cnns; sqeeznet, googlenet, resnet-50, and resnet-18. it consists of four phases, collection of the dataset, preprocessing phase to reduce image features, training phase for model building, and query image entity prediction. resnet-50 interfaced with faster-rcnn model performed better than models built from other feature extractors. deep learning have been also been employed for drone detection and classification, (behera & raj, 2020) used yolov3 as an object detector, cnn for getting features from images and binary cross-entropy loss function for class prediction. drone technology using wireless sensor networks (wsn) and the internet of things (iot) have been employed in border security, (sharma et al., 2021) used tensorflow and a face recognition model to classify persons and animals. the intrusion coordinates are sent to a nearby patrol team and the drone surveillance system is activated and sent to the intrusion-detected area to track the intruder using the gps coordinates provided by the intrusion-detection system. to reduce the response time to threat, quadcopters in combination with artificial intelligence has recently been used for facial http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 501 recognition and surveillance, (morbale et al., 2022) used raspberry pi module and pi camera mounted on the uav to capture image of an intruder in real time. the use of quadcopter with cnn based detection model for real time surveillance is recently gaining ground in the engineering field, (abdou & aziz, 2021) leveraged on the use of ai and uav technology for a real-time human and cars detection and tracking system using a cnn object detection algorithm yolov4 and a multi-tracking algorithm deepsort. the system consists of four (4) stages; object detection, object tracking, object localization and drone control. (kim & cho, 2021) employed region based convolutional neural networks for object detection. the system includes a preprocessing filter (pf) to create a newly combined color image, a faster r-cnn for detection, and a histogram network (hn) to estimate the distance between the uav and the object. drones have also been employed for search and rescue in time of natural disaster, (mishra et al., 2020) proposed a novel dataset of aerial recognition for humans in need of help during disaster situations and search and rescue operation for disaster management application, and a new identification classification model. pre-processing of dataset involved frame extraction, frame selection and action annotation of image frame. the detailed review of various security and surveillance methods highlights the potential of this field to achieve significant advancements. modern deep learning techniques can improve surveillance mechanisms. therefore, this study introduces a technique for detecting bandits, weapons, and suspects using advanced deep learning model-yolov3. 2. materials and method this section deals with the methodology used in the development and implementation process. the schematic representation outlining the methodology is shown in figure 1. the system's framework includes the subsequent key stages: first, there's the gathering and collection of a dataset containing instances of the entities intended for detection. subsequently, the preprocessing stage converts the images into condensed features to enable efficient processing. the training phase involves training and the construction of the model. the fourth step entails predicting entities in a query image, where the image is captured by the camera, processed, and fed into the trained model to anticipate potential matches. internet images/ camera images dataset pre-processing feature extraction model model training trained model model accuracy and validation model testing querry image trained model detection bandit suspect weapon detection figure 1: block diagram of proposed methodology http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 502 2.1 data acquisition during data acquisition, bandit images were collected online, weapon data came from kaggle dataset from the internet, and suspect images were taken with a camera. images in the dataset were classified as bandit, suspect, and weapon. a yolov3 model, aimed at detection was trained using images sourced from the created dataset. 2.2 preprocessing of images in the dataset image processing is the steps taken to format images before they are used by the model for training and inference. the key steps include resizing the data set image frames, extracting image features, and data augmentation. 2.2.1 resizing of image frames and data set construction utilizing an image with a high pixel count is computationally demanding for modeling and can potentially slow the learning process. consequently, all extracted images were resized automatically by the yolo network to dimensions of 416 * 416 pixels. yolov3 relies on darknet-53 as its feature extraction backbone. this network features 53 convolutional layers combined with batch normalization and leaky relu activation functions. it also incorporates residual connections to enhance information flow and support the training of deeper networks. the presence of a dataset is a crucial step in assessing algorithm quality. therefore, a dataset of 2000 images was created, comprising 500 images for weapon, 1000 for bandit, and 500 for suspect object classification. 2.2.2 data augmentation the data augmentation techniques include grey scale; rgb images are computationally expensive and dimensionally large hence the images used for feature extraction were converted to grey scale. rotation; some of the images captured by the camera were rotated horizontally by 90o, some rotated vertically (upside down) while others were flipped. this gives variations in the dataset and further improve the training process. contrast adjustment: the contrast was adjusted for the images in the training data set, this improves the appearance of the images for visual interpretation and increase the performance of the model for subsequent task. 2.2.3 feature extraction from image frames for feature extraction, a transfer learning approach was employed. transfer learning enables the incorporation of prior knowledge through a pre-trained model, which can subsequently be adjusted for a particular task with a smaller dataset. this approach leads to quicker convergence, enhanced accuracy, and diminished overfitting. in this research, the proficient darknet-53 model, pre-trained on the imagenet dataset, was employed for precise feature extraction. leveraging this pre-trained model as a foundation streamlined the training process and enhance accuracy, saving valuable time (shah et al., 2023). darknet-53 architecture is shown in figure 2 (ma et al., 2020). figure 2: darknet-53 architecture (ma et al., 2020) http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 503 2.3 yolov3 features from the image frames, their related object’s location and class identification are needed to be learned by some cnn-based machine learning algorithm. in this research, yolov3 object detection algorithm known for its speed and accuracy and well suited for real-time applications was employed for object classification, localization and detection. yolov3 is trained on labeled datasets to learn how visual features correspond to specific classes. it predicts bounding boxes by outputting the object's center coordinates, width, and height, allowing precise localization. the model combines object classification and localization, providing both the object class and a confidence score for each detection. the basic working of yolov3 is shown in figure 3 as obtained from (aswini et al., 2022). the algorithm employs a single convolutional layer across the image, dividing it into segments to predict bounding boxes and probabilities. it features 106 convolutional layers, with 53 pre-trained for feature extraction and 53 for detection and training. detection occurs at three layers: the 82nd (stride 32, 13x13 feature map), 94th (stride 16, 26x26 feature map), and 106th (stride 8, 52×52 feature map). residual layers enable skip connections, and the image is down sampled to the 82nd layer and up sampled to the 106th. yolov3 uses 1×1 kernels at these layers to ensure consistent feature map dimensions. 2.4 training a total of 2000 images were prepared as experimental samples for the data set. these was divided into a training set, and test set in the ratio 80:20 which results to 1600 training, and 400 testing images respectively as shown in table 1. the training data was used for the actual training, and the test set was used to test the accuracy of the model after the training most have been completed. table1: data set distribution classification training set testing set weapon 400 100 bandit 800 200 suspect 400 100 yolov3 was used and trained on google colab that offers free gpu. the model was trained for 192 epochs, with a batch size of 64, and a learning rate of 31 10− the parameter configuration is shown in table 2. for detection of the image, query videos obtained by using camera mounted on a quadcopter and trained models were given for processing. the system detects the images and show the information and classification of that image. figure 3: yolov3 structure (aswini et al., 2022) http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 504 to train the model the images in the dataset were labelled to specify their coordinates and boundaries for the machine learning model to recognize and predict. makesense.ai a user-friendly annotation tool for computer vision tasks was used to draw bounding box on all the images on the dataset pointing to the region of interest within a given image. the dataset used for the training was divided into two groups 80% training set and 20% test set and google collaboratory used for the training. darknet an open-source neural network was downloaded to create a darknet network for training the detector. within the darknet folder, changes were made to the make file to enable gpu and opencv and build the darknet. the yolo configuration file, which includes details about the network, convolutional layers, three yolo detection layers, and additional layers along with their properties was utilized. in the darknet configuration (cfg) folder exist the yolo configuration files containing details about the model’s architecture, changes made to the cfg file include: maximum batch size = classes × 2000 which determines the maximum number of iterations for which the network will be trained, filter = (classes + 5) × 3 = 24 for 3 classes, and steps = 80% and 90% of the maximum batches. table 2: training parameters related parameter value meaning batch size 64 number of pictures per training learning rate 31 10− initial learning rate epoch 192 cycle through training dataset number of iterations 6000 iterations 3. results and discussion pretrained weight was downloaded for darknet model and the model was trained for 192 epochs, tested and built. the average precision for each class (bandit, suspect and weapon) as well as the overall performance metrics for the model was obtained and the result obtained after the training is as recorded in tables 3 and 4. the model loss graph for the object detector or the graph of loss function for detection task is shown in figure 4. the dataset was further trained for 50 and 150 epochs on the roboflow platform. roboflow is a computer vision platform designed to help users create computer vision models more quickly and accurately by offering enhanced tools for data collection, preprocessing, and model training. it was used to adjust orientations of the images, resize images, alter image contrast, and apply data augmentation. additionally, it was employed for training of the model for 50 and 150 epochs respectively. the performance metric at 50 and 150 epochs are as shown in table 5. table 3: detailed results of training table 4: performance metrics object detector class no of training images average precision no of test images epoch darknet–based yolov3 bandit 800 0.81 200 192 suspect 400 1.00 100 192 weapon 400 1.00 100 192 object detector precision recall f1-score average iou map@0.50 detection time epoch darknetbased yolov3 0.94 0.83 0.87 74.69% 93.82% 09 sec 192 http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng mailto:map@0.50 arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 505 table 5: performance metrics @ 50 and 150 epochs the object detection inference process handles tasks such as image classification and localization. thus, to test the model for accurate prediction of the classes, inference was carried out by given images which are not part of the dataset to the model for detection and classification, the model accurately classified the images based on their respective classes. the results are shown in plates 1, 2 and 3. object detector epochs precision recall map@0.5 darknet-based yolov3 50 0.85 0.88 89.2% 150 0.91 0.86 91.2% figure 4: model loss graph plate 1: bandit detection plate 2: weapon detection plate 3: suspect detection http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 506 images which are not part of the dataset were also given to the model for validation, the model accurately classified the images based on their respective classes. the result is shown in plates 4, 5, and 6. comparison based on average precision for each class was made with the result of the study by (iqbal et al., 2021). table 6 shows the result for the comparison. table 6: comparison of result at 150 epochs object detector class no of training images no of test images ap@150 epoch restnet-50 based faster-rcnn iqbal et al., (2021) face 1805 695 0.98 weapon 1700 550 0.97 intruder 1550 500 0.85 darknet-based yolov3 (proposed method) suspect 400 100 1.00 weapon 400 100 1.00 bandit 800 200 0.70 in this study, a deep-learning-based artificial intelligence model which can detect bandit, suspect and weapon and also distinguish which of the 3 different classes a detected object belongs to was developed for use in autonomous security control. after training at 192 epochs, the average precision obtained for each class was 0.81 for bandit, 1.00 for suspect and weapon respectively. an average precision of 1.00 and 0.81 indicates the model is performing detection accurately. the result obtained for performance metrics for the model indicate a high iou of 74.69% which indicates the predicted bounding box coordinates closely resembles the ground truth box coordinates. a mean average precision (map@0.5) of 93.82% (0.9382) and a precision of 0.94 shows a very high precision and prediction ability by the model. with a recall of 0.83, the model is able to find true positive out of all the prediction with high rate of satisfaction. the model loss graph or the graph of the loss function for detection tasks shown in figure 4 is the sum of the loss functions for bounding box, objectiveness score and class prediction. it is seen that the model converges hence the loss or error reaches plate 4: suspect detection plate 5: weapon detection plate 6: bandit detection http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng mailto:map@0.5 arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 507 a minimum level of acceptable error reaching a point of stability for the model to make accurate predictions. yolo algorithm possesses a fast detection rate which is seen in the detection time of 9 seconds for the model. (iqbal et al., 2021)studied a real-time surveillance using resnet-50-based faster-rcnn to detect face, weapons and intruder. their results showed an average precision (ap) of 0.98, 0.97, and 0.85 for face, weapon, and intruder respectively at 150 epochs. the proposed model had an ap of 1.00 for both suspect (face) and weapon, and 0.70 for bandit (intruder) at 150 epochs. the model proposed in this research used a darknetbased yolov3 algorithm to detect suspect (face), weapon and bandit (intruder). from the result obtained, the proposed model has a higher ap for suspect (face), and weapon but showed a slightly lower value for class bandit, this occurs because a bandit can be masked or bare faced, and carries different kinds of weapons which was tricky for the learning algorithm to detect. the proposed method used a lower epoch and less resources to achieve a better performance. the ap (93.82%) recall (83%), and precision (94%) of the proposed model has an excellent success rate. to further compare the result obtained by (iqbal et al., 2021) training their model for 150 epochs the proposed model was trained for same epochs and result shown in table 6 indicates the propose model has an excellent success rate and higher precision as compared to the study in the literature. in this study, the importance of the proposed model is increased due to the fact that it is trained and tested on computers that are less expensive and do not have sufficient infrastructure. unlike the study by iqbal et al., (2021), which utilized 6,800 images, the proposed model achieved strong results using only 2,000 images. this efficiency is made possible by yolov3’s backbone, darknet-53, which is pretrained on the extensive imagenet dataset, enabling effective feature extraction with fewer training samples. 3.1 test the object detection model was effectively deployed, integrated into a python script, and implemented on a laptop to process video frames captured by its camera in real time. the model accurately detected and classified objects within the live video stream from the laptop's camera. the test results along with their confidence scores are presented in plates 7, 8, and 9. plate 7: weapon detection plate 8: bandit detection plate 9: suspect detection http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 499-509. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: okhiria.kenneth@naub.edu.ng 508 a confidence score of 78% for bandit, 93% for weapon and 80% for suspect shows high detection accuracy of the proposed model. 3.2 limitation the algorithm is designed to detect only one specific type of firearm. given the complexity and performance demands of developing an algorithm capable of identifying multiple firearm types, such as rifles, grenade launchers, pistols, and handguns, this research focuses on implementing an algorithm specifically for detecting ak47 firearms. the algorithm can only detect firearms that are in plain sight and not hidden by the person carrying them. the algorithm sometimes fails to detect weapon accurately, this is because the dataset had less variation for weapon and often bandits carry same ak47 rifle, which in this case seems tricky for the learning algorithm. to address any bias that may occur in the labelling of images as suspect and bandit, a suspect is defined as someone involved in a crime but not yet proven guilty, often under investigation based on evidence or suspicion. hence it is assumed the security forces have the image (facial image) of the suspect in their database thus, the study focused on only facial recognition for a suspect. a bandit is someone who commits crimes like robbery, often violently or in an organized manner, including acts like killing and destruction of properties. the study focused on the nature of banditry in nigeria and their visual features like clothing, accessories, mask and gun possessed, thus, the model might face challenges and perform poorly when deployed to detect similar activities in other parts of the world. 4. conclusions this study demonstrates the effectiveness of a deep learning-based object detection model for real-time autonomous security surveillance using the yolov3 algorithm. trained on a custom dataset, the model successfully classified and localized three critical object classes bandit, suspect, and weapon with high average precision values of 0.81, 1.00, and 1.00 respectively. achieving a mean average precision of 93.82%, precision of 94%, and recall of 83%, the system proved not only accurate but also efficient, with fast inference time and minimal computational overhead. compared to a resnet-50-based faster r-cnn model, the proposed system maintained competitive or superior detection performance, particularly for the suspect and weapon classes, even with fewer training epochs and limited hardware resources. these results affirm the model's practical applicability in real-world uav surveillance scenarios, especially in low-resource environments. future research will aim to enhance the model by enabling detection of a wider variety of threats, including multiple types of weapons, and by improving its effectiveness in challenging conditions such as occlusion and complex and dynamic environments. efforts will also explore upgrading to more advanced architectures like yolov5 or yolov8 and integrating thermal or infrared imaging to improve the detection of hidden weapons. detection accuracy for ak47 firearms can be improved by increasing the dataset's variation to include different ak47 variants to enhance dataset diversity and improve detection accuracy. this research advances automated security and surveillance systems by providing a foundation for dronebased ai solutions in real-time object detection. it enhances the efficiency of security operations, addresses critical security gaps, and offers adaptability to various scenarios. additionally, the study contributes to the creation of specialized aerial surveillance datasets, such as a tailored bandit dataset, serving as a valuable resource for future research and development in uav-based security solutions. references abdou, aaa. and aziz, naa. 2021. cnn-based off-board computation for real-time object detection and tracking using a drone. journal of tomography system and sensor, 4(2): 11–20. ammar, a., koubaa, a., ahmed, m. and saad, a. 2020. aerial images processing for car detection using convolutional neural networks: comparison between faster r-cnn and yolov3. 2012. aswini, n., uma, sv. and akhilesh, v. 2022. drone to obstacle distance estimation using yolo v3 network and mathematical principles. journal of physics: conference series, 2161(1). bao, w., huang, m., zhang, y., xu, y., liu, x. and xiang, x. 2021. boosting ship detection in sar images with complementary pretraining techniques. ieee journal of 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b., agarwal, s., garg, d. and mukhopadhyay, d. 2021. intervenor: intelligent border surveillance using sensors and drones. 2021 6th international conference for convergence in technology, i2ct 2021: 1–7. sun, n., zhao, j., wang, g., liu, c., liu, p., tang, x. and han, j. 2022. transformer-based moving target tracking method for unmanned aerial vehicle. engineering applications of artificial intelligence, 116(september): 105483. zaidi, ssa., ansari, ms., aslam, a., kanwal, n., asghar, m., and lee, b. 2022. a survey of modern deep learningbased object detection models. digital signal processing: a review journal, 126: 1–18. zhao, k., he, t., wu, s., wang, s., dai, b., yang, q. and lei, y. 2018. application research of image recognition technology based on cnn in image location of environmental monitoring uav. eurasip journal on image and video processing, 2018(1). http://www.azojete.com.ng/ mailto:okhiria.kenneth@naub.edu.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 619 arid zone journal of engineering, technology & environment electrical resistivity survey for groundwater investigation in parts of osun state, southwestern nigeria a. s. adebayo1,*, o. a. dasho2, a. p. olufemi1, o. a. babatunde3 and o. oghenenyovwe1 1*department of physics, university of medical sciences, ondo state, nigeria 2department of geosciences, virginia tech. university, usa 3department of physics, mountain top university, lagos-ibadan express way ogun state *corresponding author's email address: adebayo_adebiyi08@yahoo.com article information submitted 8 february, 2024 revised 30 may, 2024 accepted 7 june, 2024 keywords: ves groundwater transmissivity aquifer resistivities geoelectric parameters abstract this study used a non-invasive, cost-effective geophysical method for locating suitable sites for groundwater development. thirty-two vertical electrical sounding (ves) were probed in the investigated area using schlumberger array. the data acquired were interpreted using the partial curve matching technique and computer-aided iteration through winresist. the aquifer properties such as transverse resistance, longitudinal conductance, hydraulic conductivity and transmissivity were computed from the primary geoelectric parameters. the results of the study revealed that the investigated area is marked by heterogeneous lithology with three to five geoelectric layers. the aquifer resistivities ranged from 18 to 318 ωm while the aquifer thicknesses ranged from 1.7 to 46.2 m. the computed transverse resistance revealed the groundwater development in the investigated area as low/moderate. also, the transmissivity values computed from the primary aquifer parameters revealed that 72% of the investigated area has low aquifer transmissivity, while 28% have moderate aquifer transmissivity. this implies that the investigated area has low/moderate water-bearing potentiality. the quantitative analysis of the aquifer protective rating revealed that 78.1% of the investigated area has a good natural filter. based on the aquifer potential rating and the protective capacity, veses 10-12, 16, 19-20, 23-25 were recommended for drilling sites. the result of this study provides some important conclusions for future groundwater exploration and management in the investigated area. 1.0 introduction water is essential for all human activities and crucial importance for society. water can be referred to as the economic, social, and physical lifeblood of humanity, which provides support for agriculture, industry, transportation, energy production, and life itself. despite its importance, there are looming threats to this vital resource as patterns demonstrate expanding use due to intensification of agribusiness, urbanization and economic growth (agbasi et al. 2019; awosika et al. 2020; abdulrazzaq et al. 2020). by 2050, the united nations evaluated that about two-thirds of the global population will face a shortage of water resources. the available water resource is not evenly distributed and considerable amount of this resource is been wasted, polluted and unsustainably managed. the shortage is both a human-made and a natural phenomenon. in most crystalline basement regions, the demand for water resources exceeds the supply. the management of these resources for sustainable development requires quantitative knowledge of the aquifer hydraulic properties as well as the effective protection of the water-bearing zone (george et al. 2018). the hydrogeological parameters, such as transverse resistance, longitudinal conductance, hydraulic conductivity and transmissivity are azojete september 2024. vol. 20(3):625-632 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:%20efegabs@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng http://www.azojete.com.ng/ corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 620 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)625-632. issn 1596-2490; e-issn 2545 5818; www.azojete.com.ng key properties in depicting the subsurface hydrology. traditionally, hydraulic parameters such as transverse resistance and longitudinal conductance are usually estimated by classical methods like pumping tests, tracer studies, etc. which are the most effective but expensive, labour intensive, time-consuming and sometimes destructive (gelhar 1993; niwas et al. 2011; benabdelouahab et al. 2019; ullah et al. 2020) the use of the surface resistivity technique, particularly the vertical electrical sounding (ves) can provide useful information on aquifer properties in regions where pumping test data is sparse or unavailable, also when there is an insufficient budget for pump test (pratap and dev 2015; sattar et al. 2016; helaly, 2017). this method is simple, fast, cost-effective and non invasive. the method measures the potential differences on the surface of the earth due to the current flow within the ground, and it has also been extensively used in groundwater prospecting (george et al. 2014; obiora et al. 2015; hasan et al. 2019; awosika et al. 2020), groundwater vulnerability studies (aweto and ohwoghere-asuma 2018; ejiogu et al. 2019), salinity effect on the aquifer system (zarroca et al. 2011; hasan et al. 2018), delineation of the contaminated plume (adebayo et al. 2015; olagunju et al. 2017; akinola et al. 2018 ) and engineering site investigation (adenika et al. 2018). the secondary aquifer parameters (transverse resistance and longitudinal conductance) calculated from vertical electrical sounding results (layer resistivity, and thickness) have demonstrated to be effective in understanding the spatial distribution of aquifer hydraulic parameters. the relationship between aquifer hydraulic properties and geoelectric properties had been established and applied to evaluate aquifer hydraulic properties and vulnerability (obiora et al. 2016; niwas and singhal 1981; heigold et al. 1979; kelly 1977; maillet 1947) the investigated area can be regarded as a water-scarce region and the need for exploiting quality water resources is of utmost importance to the inhabitants of the investigated area and environ. evaluating aquifer hydraulic properties is germane in resolving hydrogeological problems in this complex geological terrain. hence, it is imperative to delineate groundwater productive zones for the inhabitants. this study aims to evaluate hydraulic parameters and aquifer protective capacity using a cost effective, non-invasive geophysical method for locating suitable sites for groundwater development. prior to the evaluation of the hydraulic parameters and aquifer vulnerability index, a quantitative interpretation of the primary geoelectrical parameters will be carried out. the evaluated hydraulic properties will provide useful information for future groundwater exploration and management 2. materials and methods 2.1 description of the study area the investigated area is situated between latitudes 7°46'n and 7°57'n and longitudes 4°16'e and 4°23'e in ejigbo, southwestern nigeria as presented in figure 1a. the area is influence by two distinct seasons (wet and dry seasons), the wet season lasts from april to october with an average annual rainfall of 1500 m (iloeje, 1980), the wet season ensures aquifer recharge and it is very essential for the agriculture activities. the dry season is between november to march. the annual temperature experience in the investigated site is between 25 and 30°c. geomorphologically, ejigbo is located within the western uplands of southwestern nigeria, with gently undulating topography. the investigated site is part of basement complex rocks of southwestern nigeria and the main lithology units noticed in the area are quartzite and quartz schist, charnokitic meta-intrusive and migmatite-gneiss, migmatite-gneiss undifferentiated, and porphyroblastic granites (figure. 1b). in this region, the groundwater occurrence, flow and infiltration are influenced by weathering and tectonic development. the weathered layer aquifer may stand alone or occur in conjunction with the fractured aquifer in the same locality. the major factors that determine the ability of basement rock ability to store, transmit and yield a reasonable amount of groundwater are the extend of the interconnection of the mailto:%20kunleoluyori@gmail.com file:///c:/user/downloads/azojete143/www.azojete.com.ng adebiyi et al: electrical resistivity survey for groundwater investigation in parts of osun state, southwestern nigeria. azojete, 20(3):625-632. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 621 voids/pore spaces within the weathered regolith, the extent, thickness and continuity of the fractures and on the degree to which the fractures are hydraulically connected. figure 1: (a): location map of the investigated area. (b): geologic map of the investigated area 2.2 methodology thirty-two vertical electrical sounding (ves) profiles (figure 2) were carried out in the investigated area using electrical survey meter (ddr-3 resistivity equipment). the terrameter sent direct current into the sub-surface (figure 3) through a pair of electrodes called current electrodes (a and b) and the resulting potential difference generated is measured by another pair of electrodes referred to as the potential electrode (m and n). the generalized measured apparent resistivity is given by equation (1) (1) where g is the geometric factor which depends upon the particular electrode array system used, r is the measured resistance, from ohm's law,𝑅 = 𝑉 . 𝐼 for the schlumberger array employed in this study, ab > 5mn and the measured apparent resistivity is given by equation (2) (2) where, is the geometric factor. the apparent resistivity computed using equation 2 was plotted against the half current electrode spacing (ab/2) using the log-log graph and the curves were smoothened to expel the http://www.azojete.com.ng/ mailto:adebayo_adebiyi08@yahoo.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)625-632. issn 1596-2490; e-issn 2545 5818; www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 622 effects of lateral heterogeneities and noisy signature where necessary (chakravarthi et al. 2007; ibuot et al. 2013). the smoothened curves were interpreted using a partial curve matching technique with the aid of the master curve and auxiliary curves. the partial curve matching technique was used to estimate the geoelectric parameters (the resistivity and thicknesses) of the various layers. these geoelectric parameters were used as initial model parameters for a 1-d computer-aided forward modeling interpretation involving winresist version 1.0 software. figure 2 data acquisition map figure 3 fundamental concepts for resistivity measurements (modified after todd and mays,1980) 2.3 hydraulic parameters the relationship between the estimated geoelectric parameters (thickness and resistivity) and hydraulic parameters are presented in equations 3-6. equation 3 gives the transverse resistance ( ) in ω (3) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adebiyi et al: electrical resistivity survey for groundwater investigation in parts of osun state, southwestern nigeria. azojete, 20(3):625-632. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 623 while the longitudinal conductance ( ) in siemens is given by equation 4 𝑛 ℎ𝑖 ℎ1 ℎ2 ℎ3 ℎ𝑛 𝑆𝑐 = ∑ 𝜌 = 𝜌 + 𝜌 + + . . . + 𝜌 𝜌 (4) 𝑖=0 𝑖 1 2 3 𝑛 where ρ is the resistivity in ωm, h is the thickness calculated in meters, and i is the number of layers. in fractured hard rock aquifer like the investigated site, the hydraulic conductivity k (m/day) is given by empirical relation postulated by singh 2005, 𝐾 = 8 𝑥 10−6𝑒−0.0013𝜌 (5) where ρ is the resistivity of the aquifer. equation 6 gives the aquifer transmissivity (fetter 1988): 𝐾 = 𝑇 ℎ (6) where k is the hydraulic conductivity in m/day, t is the transmissivity in m2/day , and h is the aquifer thickness in meter. from the hydraulic parameters, the groundwater potential and aquifer protective capacity was determined. the classification of the groundwater potential withdrawal capacity and the fluid flow ability was based krasny's (1993) rating (table 1). the aquifer protective capacity rating which previses how safe the aquifer layer from contaminants was deduced from the estimated longitudinal conductance. the rating classification (table 2) proposed by (kumar et al., 2016) was used in this research. table 1: aquifer protective capacity rating (henriet 1976; oladapo and akintorinwa 2007; kwami et al 2019). s/n total longitudinal conductance (mho) protective capacity rating 1 < 0.1 poor 2 0.1 – 0.19 weak 3 0.2 – 0.69 moderate 4 0.7 – 4.9 good 5 5 – 10 very good 6 > 10 excellent table 2. the modified transmissivity magnitude classification (gheorghe 1978; krasny, 1993). s/n t(m2/day) aquifer potential groundwater yielding capacity 1 < 0.1 negligible impermeable sources for local water supply are difficult 2 0.1 – 0.9 very low withdrawal of local water supply with limited consumption 3 1 – 9.9 low smaller withdrawal for local water supply (private consumption) 4 10 – 99 moderate withdrawal of local water supply (small community) 5 100 – 1000 high withdrawal of lesser regional importance 6 >1000 very high withdrawal of great regional importance http://www.azojete.com.ng/ mailto:adebayo_adebiyi08@yahoo.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)625-632. issn 1596-2490; e-issn 2545 5818; www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 624 3 results and discussion 3.1 primary and secondary hydraulic parameters interpretation the summary of the analysis and interpretation of the processed thirty-two veses data acquired in the investigated area is presented in table 3. the table gives the primary aquifer properties (resistivities and thicknesses) and shown that the investigated area is marked by heterogeneous lithology with three to five geo-electric layers. figure 4 gives the typical geoelectric sounding curves in the study area. the contour maps of the variation in aquifer resistivities and thicknesses are presented in figure 5a and b respectively. the values of the aquifer resistivities ranged from 18 to 318 ωm with an average value of 99.12 ωm while the aquifer thicknesses ranged from 1.7 to 46.2 m with an average value of 12.07 m. the dar-zarrouk parameters (transverse resistance and longitudinal conductance) evaluated using equations 3 and 4 are presented in table 4. the evaluated values of the transverse resistance in the investigated area ranged from 35.70 to 8518.40 ωm2 with an average value of 1383.23 ωm2. these values revealed a very low groundwater development class. the contour map of the transverse resistance (figure 4c) shows the lowest concentration in the southwestern region (veses 17,19,22), veses points 6, 20, 25, 27 and 28 also display low values of transverse resistance. the highest value of transverse resistance was observed in the northwest and northeast regions of the investigated area. the transverse resistance is an important geological formation property that is used to express the opposition of an aquifer to vertical flow of fluid. the evaluated values of the longitudinal conductance varied from 0.023 to 0.189 siemens with an average value of 0.885 siemens. the contour map of the longitudinal conductance (figure 4d) shows the lowest concentration in the western region (veses 7, 15, 17, 22) and the highest value was observed at the southeastern (veses 23, 24, 25, 29) and eastern (veses 10,18, 20) parts of the study area. the high values of longitudinal conductance at these points are presumably due to the thick sequence of alluvium deposits and or comprises of highly weathered. galin (1979) revealed that the longitudinal conductance assists in differentiating the variation in the total thickness of the subsurface low resistivity geo-materials. figure 4: typical geoelectric curves of the investigated area file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adebiyi et al: electrical resistivity survey for groundwater investigation in parts of osun state, southwestern nigeria. azojete, 20(3):625-632. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 625 table 3. geoelectric parameters of the investigated area ves points number of layers resistivity of layers (ωm) thickness of layers (m) 𝑡1 𝑡2 𝑡3 𝑡4 1 4 170.1 271.6 50.5 1304.1 0.8 2.4 9.8 2 4 703.9 170.8 52.8 2609.0 0.6 2.4 14.9 3 5 2692.3 585.6 108.2 356.1 1032.2 1.3 0.7 3.7 45.6 4 4 1778.2 526.8 75.5 3783.5 0.4 2.5 7.8 5 4 1508.7 446.8 282.4 1222.2 0.7 3.8 6.9 6 5 154.3 64.0 20.5 72.0 156.0 0.8 0.6 2.9 133. 1 7 4 171.9 110.5 133.6 589.8 0.9 7.2 12.9 8 3 977.2 231.5 847.9 1.0 5.3 9 4 510.8 2335.6 108.3 9573.8 0.5 1.4 6.8 10 3 1527.8 44.1 90.9 1.2 16. 6 11 5 280.1 125.1 1159.5 182.5 276.0 0.5 0.9 4.4 34.6 12 3 1377.7 52.4 272.5 1.8 46. 2 13 4 25.2 139.1 192.2 399.2 0.9 10. 4 9.3 14 5 105.1 192.6 628.6 317.8 1043.6 0.9 2.0 5.0 16.0 15 4 259.1 89.1 181.0 276.2 0.7 4.0 22.8 16 5 889.9 407.4 554.1 242.3 152.3 0.7 4.6 14.5 35.2 17 3 46.4 20.0 720.9 0.7 2.0 18 4 145 55.9 10.3 94.4 1.3 6.3 12.0 19 3 133.1 35.1 264.7 2.6 15. 8 20 5 97.2 126.9 390.8 62.0 384.9 1.1 1.1 4.7 16.1 21 4 1657.1 672.2 73.3 1066.9 0.9 0.8 5.2 22 4 261.1 36.3 202.4 101.8 0.7 2.6 14.3 23 5 163.0 45.8 166.6 86.1 142.1 0.7 3.6 24.7 16.7 24 5 170.1 53.3 103.6 31.0 77.3 0.9 3.0 3.2 17.7 25 4 268.1 123.8 21.6 167.5 1 0.9 15.6 26 3 622.3 84.8 80.6 1.4 14 27 3 329.5 21.3 8981.2 0.7 1.7 28 3 251.4 18.2 1647.5 1.3 2.9 29 4 107.7 48.5 84.6 213.2 1.0 19. 5 14.7 30 4 390.6 44.6 295.0 1290 0.5 4.4 43.8 31 5 96.5 31.5 503.7 110.4 73.2 0.6 1.2 7.6 7.9 32 3 24.8 278.9 543.9 1.0 14. 4 http://www.azojete.com.ng/ mailto:adebayo_adebiyi08@yahoo.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)625-632. issn 1596-2490; e-issn 2545 5818; www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 626 table 4: aquifer parameters of the investigated area ves points depth to water (m) aquifer resistivity (ωm) aquifer thickness (m) 𝑇𝑟 (ω𝑚2) 𝑆𝑐 (siemen) k (m/day) t (m2/day ) 1 13.1 51 9.8 499.8 0.192 0.6469 6.3392 2 17.8 53 14.9 789.7 0.281 0.6452 9.6132 3 5.7 108 3.7 399.6 0.034 0.6007 2.2224 4 10.7 76 7.8 592.8 0.103 0.6262 4.8842 5 11.4 282 6.9 1945.8 0.024 0.4791 3.3055 6 4.4 21 2.9 60.9 0.138 0.6726 1.9505 7 8.1 111 7.2 799.2 0.065 0.5983 4.3079 8 6.3 232 5.3 1229.6 0.023 0.5112 2.7095 9 8.7 108 6.8 734.4 0.063 0.6007 4.0845 10 17.8 44 16.6 730.4 0.377 0.6528 10.8360 11 40.5 183 34.6 6331.8 0.189 0.5449 18.8522 12 48 52 46.2 2402.4 0.888 0.6460 29.8461 13 11.3 139 10.4 1445.6 0.075 0.5769 6.0001 14 23.9 318 16 5088 0.050 0.4572 7.3145 15 4.7 89 4 356 0.045 0.6157 2.4627 16 55 242 35.2 8518.4 0.145 0.5046 17.7630 17 2.7 20 2 40 0.100 0.6735 1.3469 18 7.6 56 6.3 352.8 0.113 0.6427 4.0488 19 18.4 35 15.8 553 0.451 0.6605 10.4352 20 23 62 16.1 998.2 0.260 0.6377 10.2666 21 7 73 5.2 379.6 0.071 0.6286 3.2688 22 3.2 36 2.6 93.6 0.072 0.6596 1.7150 23 45.7 86.1 16.7 1437.87 0.194 0.6180 10.3207 24 24.8 31 17.7 548.7 0.571 0.6639 11.7510 25 17.6 22 15.6 343.2 0.709 0.6717 10.4787 26 15.4 84 14 1176 0.167 0.6197 8.6757 27 2.4 21 1.7 35.7 0.081 0.6726 1.1434 28 4.2 18 2.9 52.2 0.161 0.6752 1.9581 29 35.3 84.6 14.7 1243.62 0.174 0.6192 9.1024 30 4.9 45 4.4 198 0.098 0.6519 2.8685 31 17.3 110 7.9 869 0.072 0.5991 4.7329 32 15.4 279 14.4 4017.6 0.052 0.4809 6.9254 3.2 hydraulic conductivity (k) and transmissivity (t) the auriferous layer hydraulic conductivity and transmissivity in the investigated area were estimated and presented in table 4. the aquifer hydraulic conductivity values evaluated from equation 5 range from 0.4572 to 0.6752 m/day with an average value of 0.6110 m/day. this value indicates a low variability of k in the investigated area and thus implies minimal water bearing zones. the contour map of the hydraulic conductivity (figure 5a) shows the highest concentration in the north-eastern part of the study area and the lowest concentration in the southern part of the study area. the low values of k observed in some parts may be due to the poor interconnection and geometry of the voids/pore spaces which can affect groundwater flow in the investigated area. hydraulic conductivity controls the rate at which groundwater flow under a given hydraulic gradient, then, from the map, the groundwater flow directions could be predicted from the zone having high k. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adebiyi et al: electrical resistivity survey for groundwater investigation in parts of osun state, southwestern nigeria. azojete, 20(3):625-632. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 627 the estimated transmissivity values range from 1.143 – 29.846 m2/day with an average value of 7.235 m2/day. the variation of the transmissivity values in the investigated area was interpreted using table 1. it was observed that seventy-two percent (72%) of the ves points show low groundwater potential while twenty eighty percent (28%) show moderate groundwater potential (table 5). generally, the transmissivity across the investigated area indicates that the groundwater potential is mostly low and partly moderate. this finding is in agreement with the results obtained by dasho et al. 2017 using remotely sensed satellite data. the contour map of the aquifer transmissivity (figure 5b) shows that the investigated area is predominated with materials of low transmissivity except in some areas in the southwestern part. these zones with moderate transmissivity in the investigated area are identified as zones with moderate water-bearing potential. figure 5: contour maps (a) aquifer resistivity (b) aquifer thickness (c) aquifer transverse resistance (d) aquifer longitudinal conductance http://www.azojete.com.ng/ mailto:adebayo_adebiyi08@yahoo.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)625-632. issn 1596-2490; e-issn 2545 5818; www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 628 figure 6: contour maps (a) aquifer hydraulic conductivity (b) aquifer transmissivity table 5: the inferred aquifer properties ves point protective capacity aquifer potential 1 moderate low 2 moderate low 3 moderate low 4 moderate low 5 poor low 6 good low 7 moderate low 8 poor low 9 poor low 10 moderate moderate 11 moderate moderate 12 good moderate 13 moderate low 14 poor low 15 moderate low 16 moderate moderate 17 moderate low 18 good low 19 moderate moderate 20 moderate moderate 21 poor low 22 moderate low 23 moderate moderate 24 moderate moderate 25 good moderate 26 moderate low 27 poor low 28 moderate low 29 moderate low 30 moderate low 31 moderate low 32 poor low file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com adebiyi et al: electrical resistivity survey for groundwater investigation in parts of osun state, southwestern nigeria. azojete, 20(3):625-632. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 629 3.3 aquifer protective capacity apc the values of the total longitudinal conductance calculated were used to evaluate the ability of the overburden unit to retard and filter percolating ground surface polluting fluid into the aquiferous unit. the variation of the aquifer protective capacity values in the investigated area study area was interpreted using table 2. table 5 revealed that in the investigated area 12.5% of the ves points have good protective capacity, 65.6% have moderate protective capacity, while 21.9% have poor protective capacity. majority of the ves locations in the investigated area have moderate and good protective rating, thus indicating that the aquifers are protected. these locations are less susceptible to contamination due to the presence of natural good filter to percolating fluids and may serve as good points for sitting of shallow hand dug wells if the aquifer potential is rated moderate to very high. the regions around veses 5, 8-9, 14, 21, 27, and 32 are highly vulnerable to contamination, these areas are not suitable for sitting of shallow hand dug wells even if the aquifer potential is rated moderate to very high, except if good environmental practices such as a reduction in soil pollution loads from a point and non-point sources are put in place. figure 7 shows the aquifer protective capacity variation within the investigated area. figure 7 protective capacity map of the investigated area 4. conclusion the qualitative and quantitative interpretations of the electrical resistivity data of ejigbo town and environs were carried out using a non-invasive, cost-effective geophysical method to evaluate the aquifer hydraulic properties and the protective capacity of the investigated area to locate suitable sites for groundwater development. the investigated area is marked by http://www.azojete.com.ng/ mailto:adebayo_adebiyi08@yahoo.com arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)625-632. issn 1596-2490; e-issn 2545 5818; www.azojete.com.ng corresponding author’s e-mail address: adebayo_adebiyi08@yahoo.com 630 heterogeneous lithology with three to five geoelectric layers. the aquifer resistivities ranged from 18 to 318 ωm while the aquifer thicknesses ranged from 1.7 to 46.2 m. the computed transverse resistance revealed that groundwater development in the investigated area as low/moderate. also, the transmissivity values computed from the primary aquifer parameters (resistivity and thickness) revealed that 72% of the investigated area has low aquifer transmissivity, while 28% have moderate aquifer transmissivity. this implies that the investigated area has low/moderate water bearing potentiality. the quantitative analysis of the aquifer protective rating revealed that the majority parts (78.1%) investigated area has a good natural filter. poor environmental practices should be discouraged in areas with poor protective capacity. based on the aquifer potential rating and the protective capacity, veses 10-12, 16, 19-20, 23-25 were recommended for drilling sites. the computed hydraulic parameters help in the reduction of the additional cost of carrying out pumping test and offer a cost-effective approach. conclusively, the groundwater supply potential in the investigated area is between low and moderate ratings. references abdulrazzaq, zt., al-ansari, n., aziz, na., agbasi, oe., etuk, se. 2020. estimation of main aquifer parameters using geoelectric measurements to select the suitable wells locations in bahr al-najaf depression, iraq. groundwater for sustainable development, 11: 100437. doi.org/ 10.1016/j. gsd.2020.100437. adebayo, as., ariyibi, ea., awoyemi, mo. and onyedim, gc. 2015. delineation of contamination plumes at olubonku dumpsite using geophysical and geochemical approach at ede town, southwestern nigeria. geosciences, 5(1): 39-45. doi: 10.5923/j.geo.20150501.05 adenika, ci., ariyibi, ea., awoyemi, mo., adebayo, as., 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hydraulic parameters in ezza north, southeastern nigeria, using geoelectric sounding. international journal of environment, science and technology, 13:435–444. oladapo, mi. and akintorinwa, oj. 2007. hydro geophysical study if ogbese southwest, nigeria. global journal of pure and applied science, 13(1): 5561. olagunju, e., ariyibi, ea., awoyemi, mo., adebayo, as., dasho, o. and adenika, c. 2017. application of geochemical and geophysical approach to environmental impact assessment: a case study of emirin active open dumpsite, ado-ekiti southwestern nigeria. modeling earth systems and environment, 3(4): 1543–1555. doi:10.1007/s40808-017-0381-1 pratap, b. and dev, h. 2015. electrical resistivity survey for groundwater investigation at sumbli of jammu district (j&k). in: management of water, energy and bio-resources in the era of climate change: emerging issues and challenges. springer, new york, pp. 127–139. sattar, gs., keramat, m. and shahid, s. 2016. deciphering transmissivity and hydraulic conductivity of the aquifer by vertical electrical sounding (ves) experiments in northwest bangladesh. applied water science, 6(1): 35-45. ullah, fl-js. and hafeez ullah, aa. 2020. estimation of hydraulic parameters of an unconfined aquifer by using geoelectrical and pumping test data: a case study of the mandi bahauddin district, pakistan arabian journal of geosciences, 13:484 doi.org/10.1007/s12517-020-05488 3. zarroca, m., bach, j., linares, r. and pellicer, xm. 2011. electrical methods (ves and ert) foridentifying, mapping and monitoring different saline domains in a coastal plain region (alt emporda, northern spain). journal of hydrology, 409: 407–422 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com https://doi.org/10.1007/s12517-020-05488-3 https://doi.org/10.1007/s12517-020-05488-3 arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):535-546 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 535 performance improvement of a boost converter driving a separately excited dc motor using inductor-capacitor (lc) h. m. usman1,2*, g. a. olarinoye1, s. saminu3, s. ibrahim4, m. mahmud1 1department of electrical engineering, ahmadu bello university, zaria, nigeria 2department of electrical engineering, mewar university, chittorgarh, rajathan, india 3department of biomedical engineering, university of ilorin, ilorin, nigeria 4department of electrical engineering, waziru umaru federal polytechnic, birnin kebbi, nigeria *corresponding author's email address: habibusman015@gmail.com article information submitted 1 january, 2024 revised 20 march, 2024 accepted 25 march, 2024 keywords: boost converter lc filter separately excited dc motor harmonic content efficiency improvement matlab/simulink abstract the increasing use of boost converter circuits for driving dc motors is attributed to their ability to provide extensive adjustable speed control, frequent starting, precise speed regulation, braking, and reversing capabilities. however, the presence of harmonic content poses a significant challenge for these converters. this study investigates the performance enhancements achieved through the integration of an inductor-capacitor (lc) filter in a boost converter circuit driving a separately excited dc motor. simulation results demonstrate significant improvements in both converter and motor performance with the lc filter. the average output voltage and current of the converter increase from 122.61 v and 31.24 a to 129.30 v and 34.39 a, respectively, indicating effective ripple mitigation. additionally, the motor speed rises from 1103 rpm to 1205 rpm, with corresponding improvements in efficiency for both the converter (from 81.21% to 94.18%) and the motor (from 68.32% to 85.13%) with the lc filter. these improvements highlight the critical role of the lc filter in reducing losses, enhancing motor performance, and achieving overall system efficiency gains. these findings highlight the significance of innovative filtering techniques in optimizing power electronics systems and motor control applications. 1.0 introduction direct current (dc) power converters are employed in a variety of applications, including power supplies for personal computers, office equipment, spacecraft power systems, laptop computers, and telecommunications equipment, as well as dc motor drives (forouzesh et al., 2017). separately excited direct current (dc) motor is widely used in many industrial sectors. during the operation of the dc motor, the load torque and the voltage of the network can cause a destabilization of the actual speed and actual current (nagarajan et al., 2016). thus, the need to regulate the speed and current of the dc motor is a crucial research problem. there are several ways to regulate and improve the performance of separately excited dc motors, however the most common is the use of boost converter circuit. one way to improve the performance of the dc motor fed by the boost converter is the use of an efficient filtering circuit which is the direction of this study. there are several works and investigations that proposed their techniques on filter, boost converter and separately excited dc motor speed control, among them are the following. hamida et al. (2019) used proportional integral (pi) and petri net controller to control the speed of dc motor, the later controller ensures armature current was maintained and regulated and the former maintained the capacitor voltage of the multi-cell converter to its reference voltage. http://www.azojete.com.ng/ mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):535-546. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 536 sahana et al. (2016) designed and implemented separately excited dc motor speed control mechanism using chopper circuit using two different control loop thus current controller and speed controller. nagarajan et al. (2016) proposed a speed control strategy of separately excited dc motor fed by chopper circuit, the circuit offers variable voltage to the armature of the motor to achieved desired speed using pi controller. jaafer and mahdi (2013) enhanced the performance and controlled the speed of separately excited dc motor using an insulated gate bipolar transistor (igbt-based chopper) by varying the armature voltage and field flux thus, the speed was control within the desired limit. a nonlinear autoregressive moving average controller for speed control of sinker electrical discharge machining (sedm) was proposed and its performance was compared with that of the traditional conventional controller by george (2008). furthermore, the chopper integrated with pi controller with two control loop was implemented for efficiency improvement and precise speed control (uma and babu, 2015). boost chopper with high conversion efficiency, with low weight and volume was designed and evaluated for the hfc hybrid railroad system by youn et al. (2020). moreover, zhang et al. (2023) proposed high gain dc-dc converter for improving the performance of the converter, the proposed converter supplies power to the load by connecting capacitors with the input source in series in switch-on state while the input source charges the capacitor through series connection with the inductor in switch-off state. nayak and shivarudraswamy (2020) proposed a photovoltaic (pv) as the source of boost converter feeding brushless direct current (bldc) motor for mixer grinder was proposed and implemented, the absence of brushes reduces noise and the efficiency was improved. additionally, usman et al. (2024) designed an effective lc filter for optimal speed control of dc motor. moreover, al-maliki and iqbal (2018) proposed a pid controller for efficient and precise speed control of dc motor with less noise, overshoot and improved steady-state error. on the other hand, converter with bidirectional power flow capabilities was designed with a dc link of the motor drive system, such that during braking, the energy is recovered and stored in an accumulator which is used in battery-fed electric vehicles (bfevs) (pany et al., 2011). the control of separately excited dc motor was proposed using fussy neural model reference controller and thus solved the drawback of conventional controller (ahmed et al., 2020). other studies by dhanke and wanjari (2017), usman et al. (2024) focused on design and analysis of a dc motor drive under different conditions of torque as applied in hybrid electric vehicles (hevs) with complex control system. a passive filter integrated in a converter was designed for mitigating harmonic with a special provision of power capacitor bank for compensating the voltage drop was investigated in park et al. (2021), deshi et al, (2021), and prasad et al. (2023). the integration of an lc filter into the boost converter circuit for driving dc motors represents a significant contribution to the field of power electronics and motor control. the study demonstrates the effectiveness of the lc filter in mitigating ripple in both the converter's output voltage and current, addressing a key challenge faced by boost converters. this finding is particularly novel as it provides a practical solution to the harmonic content issue, allowing for smoother and more stable power delivery to the motor, which is essential for optimal performance in various applications. additionally, the study showcases notable improvements in both the efficiency of the boost converter and the separately excited dc motor with the incorporation of the lc filter. the increase in efficiency highlights the practical significance of the study's findings, as it demonstrates the potential for significant energy savings and performance enhancements in real-world applications. 2. materials and methods in this study, matlab/simulink was utilized to design and simulate the boost converter-based lc filter model. specifically, matlab was used to develop the mathematical model of the boost converter circuit with the lc filter incorporated. simulink, an extension of matlab, facilitated the construction of the simulation model by visually representing the boost file:///c:/user/downloads/azojete143/www.azojete.com.ng usman et al: performance improvement of a boost converter driving a separately excited dc motor using inductor-capacitor (lc) filter. azojete, 20(2):535-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 537 converter circuit and its components. parameters such as the input dc voltage, duty ratio, and switching frequency were defined within the simulation environment. matlab/simulink then allowed for the execution of simulations to analyze the behavior of the boost converter system under various operating conditions. through this approach, the performance of the proposed methodology, including its ability to reduce harmonic content and improve motor response, was evaluated and validated. the procedures followed are; • modelling of boost converter circuit • modelling of lc filter circuit • modelling of separately excited dc motor • integrating the models together • simulation of the complete model • efficiency evaluation of the dc motor 2.1 design of the boost converter (with lc filter) that drives separately excited dc motor the built boost converter circuit with the lc filter is combined with the dc motor model such that the output of the converter circuit serves as the dc motor’s input. the complete circuit was designed and simulated using matlab (simulink block). the converter circuit serves as the driver of the dc motor as shown in figure 1. 2.2 modeling of boost converter the boost converter also known as step up choppers are the type of chopper circuits that provide output voltage higher than the supplied input voltage such that a fixed dc input is converted in to adjustable dc voltage. as shown in figure 1, the circuit consist of the arrangement of inductor l in series with source voltage and a switch (usually insolated junction bipolar transistor ijbt) connected in parallel which is controlled (on-off) using pulse width modulation pwm. when the chopper switch (ijbt) is triggered by pwm setting the circuit in on state as shown in figure 1, then the dc input current begins to flow through the inductor within the closed path of the circuit. figure 1. design of boost converter with lc filter driven separately excited dc motor l = vs × d fs × ∆io (1) c = io × d fs × ∆vo (2) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):535-546. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 538 where d = duty ratio, l = inductor, c = capacitor, fs = switching frequency, ? 𝐼 is the ripple current which must not exceed 20% to 30% of the average output current, ripple voltage ?vo must not exceed 20% to 40% of average output volt equations 1 and 2 are employed for the modeling and sizing of the inductor and capacitor, in boost converter design respectively. additionally, at the instant when the pwm sets the ijbt switch off as shown in figure 1, then the part of the circuit which current was flowing earlier will no longer be active, however as the inductor stores the energy in the form of magnetic field and the current through it will not die out instantly. also, as we know according to lenz law, a reverse current will be induced that oppose the cause producing it and due to the induced current, the polarity of the inductor is reversed. this reverse polarity of inductor forward biased the diode d present in the circuit, this provides the path for the current through the diode that flows through the lc filter and finally feeds the dc motor. vout = vin 1 − d (3) where vout is the output voltage of the converter, vin is the voltage input to the converter while d is the duty cycle with value ranging (0 to 1), as such output voltage becomes higher than input as equation 3 evidenced. however, the output voltage is the summation of the inductor voltage and input voltage resulting to increased voltage output as presented in equation 3. 2.3 modeling of efficient inductor-capacitor (lc) filter the output voltage and current of boost converter contained harmonics content which result to reduced efficiency. lc filter is used here to reduce the harmonic distortions to near zero. equation 4 is used for calculating the impedance of an inductor while equation 5 is used for calculating the impedance of a capacitor. these equations are fundamental in analyzing and designing filter circuit, particularly in determining how inductors and capacitors react to different frequencies. zl = jωl (4) zc = 1 jωc (5) where zl = impedance of the inductor zc = impedance of the capacitor l = inductance of the inductor c = capacitance of the capacitor ?= angular frequency (2pi times frequency in herz) j = imaginary unit to find the cut-off frequency fc of the filter, where the filter starts to attenuate the higher frequency, this occurs when the reactance of inductor and capacitor are equal in magnitude but opposite in sign. equating equation (4) and (5) zl = zc = jωcl = −1 jωcc (6) ωc = 2πfc (7) file:///c:/user/downloads/azojete143/www.azojete.com.ng usman et al: performance improvement of a boost converter driving a separately excited dc motor using inductor-capacitor (lc) filter. azojete, 20(2):535-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 539 substituting equation (6) in (7) and solving the equations yield fc = 1 2π√lc (8) where fc = cut-off frequency in herz, which is also referred to as switching frequency fs equation 6 equates the impedances of the inductor and capacitor, while equation 7 defines the angular cutoff frequency. substituting equation 6 into equation 7 and solving yields the cutoff frequency equation 8. fs = switching frequency, the choice of switching frequency is crucial as it affects the efficiency, switching losses, and size of the filtering components. a higher switching frequency allows for smoother waveform transitions, reducing audible noise and improving efficiency. however, excessively high frequencies can lead to increased switching losses and higher component costs. switching frequency of 50khz strikes a balance between efficiency and cost-effectiveness, ensuring smooth operation while minimizing losses and component size. the value of the filter parameter can be obtained using the equations (1), (3), (4). as shown in equation (4), frequency is inversely proportional to the square root of inductor and capacitor, however, inductor l and capacitor c depend on the converter output voltage and current. the lc filter output feeds separately excited dc motor which utilize the electrical energy input and produce rotational speed as shown in figure 1. ωm = 1 k ( v 1 − d − iara) (9) equation (9) presents the speed of separately excited dc motor as a function of voltage output of the converter, armature current and voltage and duty cycle. the efficiency of the motor is significantly improved when lc filter is incorporated in the circuit. 2.4 performance evaluation for evaluating the performance of a chopper circuit, equation 10 is used to determine the efficiency of the boost converter, while equation 11 is used for the efficiency of a separately excited dc motor. equations 12 and 13 are employed to determine the input and output power of the motor, respectively. boost converter efficiency η = power output power input = voio(1 − d) vinio = vo vin (1 − d) (10) separately excited dc motor efficiency γ = power output power input (11) power input = vo × io (12) power output = tl × ωm (13) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):535-546. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 540 where vo= average output voltage of the converter, io= average output current of the converter, tl= load torque of the motor, wm= speed of the motor in revolution per minute (rpm), d= duty ratio, vin= voltage input, vout= voltage output of the converter, l= inductor, c= capacitor, f= frequency, wm= speed of the motor in rpm, ia= armature current, ra= armature resistance, pin= power input to the dc motor, pout= output power of the motor, vtrans= transistor voltage, vd= diode voltage, ? 𝐼 is the ripple current which must not exceed 20% to 30% of the average output current (io), ripple voltage ?vo must not exceed 20% to 40% of average output voltage. 3. result and discussion in this study, various input parameters are specified to optimize the system's performance. these parameters include input voltage, source inductance, field voltage, load torque, inductance of the filter, capacitance of the filter, resistance, switching frequency, and duty cycle. the detailed input specification data are presented in table 1. table 1: input parameter specification input parameter symbol specification input voltage (v) vin 120v source inductance (h) l 1mh field voltage (v) vf 120v load torque (nm2) tl 6nm2 inductance of the filter lo 0.5mh capacitance of the filter c 1uf resistance (ohms) r 5ohms switching frequency (hz) fs 50khz duty cycle (%) d 50% 3.1 modeling and simulation a simulation model of a chopper circuit with an innovative lc filter driving a separately excited dc motor was developed using the matlab/simulink package, resulting in significantly enhanced efficiency. the chopper circuit is supplied with a voltage, but its operation relies heavily on the switching of an insulated gate bipolar transistor (igbt), achieved through pulse width modulation (pwm) technique. the pwm generator produces pulses that switch the igbt on and off. specifically, a pwm signal is generated using the square function in matlab/simulink, representing the on-off states of the switch, as illustrated in figure 2. the boost converter simulation function then calculates the input and output voltages and currents over time based on this pwm signal. in this study, a duty cycle of 50% and a frequency of 50 khz are utilized for pwm signal generation, ensuring optimal performance of the chopper circuit. figure 2. pulse width modulation (pwm) file:///c:/user/downloads/azojete143/www.azojete.com.ng usman et al: performance improvement of a boost converter driving a separately excited dc motor using inductor-capacitor (lc) filter. azojete, 20(2):535-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 541 figure 3 depicts the simulated output voltage of a chopper circuit equipped with an lc filter driving a separately excited dc motor, as analyzed using matlab/simulink. the average output voltage observed in the simulink output block is recorded at 129.3 v, demonstrating the effectiveness of the lc filter in smoothing out voltage fluctuations. the simulink scope graphically represents the voltage response, highlighting minimal ripple, which is a clear indication of the lc filter's ability to stabilize the output voltage. despite aiming for a target output of 130 v, achieving 129.3 v falls within an acceptable tolerance range, showcasing the robust performance and precise control achieved through this simulation. comparatively, the chopper circuit without the lc filter yielded an average output voltage of 122.61 v, underscoring the significant improvement achieved by integrating the lc filter in terms of voltage stability and overall system performance. figure 3. chopper circuit output voltage with lc filter driven separately excited dc motor figure 4 shows the output current of a chopper circuit with an lc filter, simulated using matlab/simulink. the output current is measured at 35.39 a, demonstrating a smooth waveform with minimal ripples due to the filtering effect of the lc filter. this stable current flow is crucial for maintaining reliable operation of the motor. despite slight deviations from the targeted current of 35 a, the achieved value of 34.39 a with the lc filter remains within acceptable operational limits. in comparison, the chopper circuit without the lc filter exhibited an average output current of 31.24 a, underscoring the significant improvement in current stability and overall system performance achieved through the integration of the lc filter. figure 4. output current of the chopper circuit with lc filter http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):535-546. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 542 furthermore, integrating the lc filter leads to substantial enhancements in the boost converter's efficiency. this improvement is critical as it reduces power losses within the converter, resulting in more efficient energy transfer from the input to the output. by smoothing out voltage fluctuations and minimizing ripple, the lc filter ensures a more stable and reliable power supply to the motor. this enhanced stability not only improves the overall performance of the motor but also prolongs its operational lifespan by reducing stress on its components. therefore, the result of this study yielded that, the boost converter's efficiency increases from 81.21% to 94.18% with the incorporation of the lc filter reflects a significant technological advancement in optimizing power conversion processes for industrial and energyefficient applications. figure 5 presents the simulation results showing the speed response of a separately excited dc motor when powered by a chopper circuit with an lc filter, analyzed using matlab/simulink. the achieved motor speed is measured at 1205 rpm, which closely aligns with the target speed of 1200 rpm. this slight deviation of only 5 rpm falls within an acceptable margin of error and is unlikely to adversely affect the motor's performance. furthermore, the terminal voltage of the dc motor exhibits minimal ripples, indicating smooth operation with negligible harmonic content. the absence of significant harmonics corroborates the stability of the motor's operational parameters. comparatively, the chopper circuit without the lc filter resulted in a lower motor speed of 1103 rpm, highlighting the significant improvement achieved by integrating the lc filter. this enhancement not only ensures precise speed control but also contributes to overall motor efficiency and longevity, making the system more reliable for practical applications. figure 5. speed of dc motor response when fed by chopper circuit with lc filter figure 6 illustrates the electrical torque response of a dc motor when driven by a chopper circuit equipped with an lc filter, as simulated using matlab/simulink. the torque response shows a smooth profile without noticeable ripples, indicating efficient operation with minimal mechanical and electrical losses as figure 6 depicted. this improvement is crucial as it enhances the overall efficiency of the motor system. specifically, the motor equipped with the lc filter achieves an electrical torque of 6.907 nm², compared to 5.85 nm² without the filter. this increase highlights the significant enhancement in torque delivery and operational stability achieved through the integration of the lc filter. by minimizing energy losses and ensuring smoother torque delivery, the lc filter contributes to improved motor performance and reliability in various industrial applications. file:///c:/user/downloads/azojete143/www.azojete.com.ng usman et al: performance improvement of a boost converter driving a separately excited dc motor using inductor-capacitor (lc) filter. azojete, 20(2):535-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 543 figure 6. electrical torque of dc motor when fed by chopper circuit with lc filter figure 7 depicts the armature current response of a dc motor when powered by a chopper circuit with an lc filter, analysed through matlab/simulink simulations. the simulation results indicate that the armature current of the motor, measured at 8.537a, exhibits exceptional smoothness due to the integration of the lc filter. this smooth response, as visually depicted in figure 7, is a direct result of the lc filter's ability to suppress voltage and current ripples, thereby reducing harmonic distortion in the motor's operation. the absence of significant ripples and harmonics enhances the motor's operational efficiency and reliability, ensuring a high-quality output. comparatively, the chopper circuit without the lc filter resulted in an armature current of 8.032 a, highlighting the significant improvement achieved by incorporating the lc filter. this enhancement not only ensures smoother current flow but also contributes to minimizing energy losses and improving overall motor performance. the observed increase in armature current with the lc filter demonstrates its effectiveness in optimizing motor operation, making it suitable for applications where precise control and efficiency are paramount. figure 7. armature current of the dc motor when fed by chopper circuit with lc filter field current response of a separately excited dc motor when powered by a chopper circuit with an lc filter was presented in figure 8. the average field current is measured at 0.8532a, as observed in the simulink scope graph of figure 8. this result indicates that both configurations, with and without the lc filter, achieve the same field current value. the consistent field current of 0.8532 a, regardless of the presence of the lc filter, suggests that the filter does not significantly affect the field current in this simulation scenario. the field http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):535-546. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 544 current remains stable and within expected operational parameters, demonstrating the robustness and reliability of the motor's field control system. while the lc filter primarily influences the voltage and current smoothness in other aspects of motor operation, its negligible impact on field current suggests that the motor's magnetic field regulation remains stable and unaffected by the filter. figure 8. field current of dc motor when fed by chopper circuit with lc filter the efficiency of a separately excited dc motor, as depicted in the simulation results, shows a significant improvement with the incorporation of an lc filter in the chopper circuit, as analysed through matlab/simulink. the motor's efficiency without the lc filter is recorded at 68.32%, whereas with the lc filter, the efficiency rises notably to 85.13%. this enhancement indicates the effectiveness of the lc filter in optimizing the motor's performance by reducing losses and improving energy conversion efficiency. the increase in efficiency from 68.32% to 85.13% can be attributed to several factors facilitated by the lc filter. firstly, the filter minimizes voltage and current ripples, resulting in smoother operation and reduced losses within the motor. this smoother operation translates into less energy dissipation as heat, thereby improving overall efficiency. secondly, the lc filter helps maintain a stable and consistent power supply to the motor, enhancing its ability to deliver torque and maintain speed under varying load conditions. from a practical standpoint, the higher efficiency achieved with the lc filter not only reduces operational costs but also prolongs the motor's lifespan by minimizing thermal stress and mechanical wear. moreover, the improved efficiency contributes to greater system reliability and stability, making the motor suitable for demanding industrial applications where precision and consistency are critical. 4. conclusion in conclusion, the integration of the lc filter in the boost converter circuit significantly improves the performance of both the converter and the separately excited dc motor. the findings demonstrate that the lc filter effectively mitigates ripple in the output voltage and current, resulting in smoother power delivery to the motor. this leads to notable enhancements in system efficiency, with the boost converter efficiency increasing from 81.21% to 94.18% and the motor efficiency rising from 68.32% to 85.13% with the lc filter. additionally, the lc filter contributes to improved motor performance, as indicated by the increase in motor speed and torque. moving forward, future research could focus on optimizing the design of the lc filter for further efficiency gains and exploring different configurations and parameters to advance the field of power electronics and motor control. file:///c:/user/downloads/azojete143/www.azojete.com.ng usman et al: performance improvement of a boost converter driving a separately excited dc motor using inductor-capacitor (lc) filter. azojete, 20(2):535-546. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: habibusman015@gmail.com 545 references ahmed, s., amin, aa., wajid, z. and ahmad, f. 2020. reliable speed control of a permanent magnet dc motor using fault-tolerant h-bridge. advances in mechanical engineering, 12(10): 1687. https://doi.org/10.1177/168781402097031 al-maliki, a. and iqbal, k. 2018. flc-based pid controller tuning for sensor less speed control of dc motor. 2018. ieee international conference on industrial technology (icit): 169-174. https://doi.org/10.1109/icit.2018.8352171. deshi, mj., anene, ec. and omizegba, ee. 2021. armature regulation of dc motor using pi controlled dc-dc flyback converter. iconic research and engineering journals, 5(3): 145– 152. dhanke, ps. and wanjari, na. 2017. survey on pwm using chopper in four quadrant dc drive. international journal of civil, mechanical and energy science, special issue-1: 109–112. https://doi.org/10.24001/ijcmes.icsesd2017.86 forouzesh, m., siwakoti, yp., gorji, sa., blaabjerg, f. and lehman, b. 2017. step-up dc–dc converters: a comprehensive review of voltage-boosting techniques, topologies, and applications. ieee transactions on power electronics, 32(12): 9143-9178. george, m. 2008. speed control of separately excited dc motor. american journal of applied sciences, 5(3): 227-233. hamida, ml., denoun, h., fekik, a. and vaidyanathan, s. 2019. control of separately excited dc motor with series multi-cells chopper using pi-petri nets controller. journal of nonlinear engineering, 8(1): 32-38. https://doi.org/10.1515/nleng-2017-0174 jaafer, js. and mahdi, mc. 2013. speed control of separately excited dc motor using chopper. journal of kerbala university, 11(1): 26-35. nagarajan, r., sathishkumar, s., balasubramani, k., boobalan, c., naveen, s. and sridhar, n. 2016. chopper fed speed control of dc motor using pi controller. journal of electrical and electronics 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saminu, s. 2024. recent trends and future prospects in electric vehicle technologies: a comprehensive review. kathmandu university journal of science, engineering and technology, 18(1): 1-13. https://doi.org/10.3126/kuset.v18i1.67501 usman, hm., mahmud, m., saminu s. and ibrahim, s. 2024. harmonic mitigation in inverter circuits through innovative lc filter design using psim. jurnal ilmiah teknik elektro komputer dan informatika (jiteki), 10(1): 138-153. https://doi.org/10.26555/jiteki.v10i1.28398 wang, x., blaabjerg, f. and loh, pc. 2014. virtual rc damping of lcl-filtered voltage source converters with extended selective harmonic compensation. ieee transactions on power electronics, 30(9): 4726-4737. https://doi.org/10.1109/tpel.2014.2361853 youn, hs., yun, dh., lee, ws. and lee, io. 2020. study on boost converters with high powerdensity for hydrogen-fuel-cell hybrid railway system. journal of electronics, 9(5): 771. https://doi.org/10.3390/electronics9050771 zhang, s., li, h., duan, s., du, x., liu, s., wang, p. and zhang, j. 2023. a high-gain dc-dc converter with a wide range of output voltage. journal of electronics, 12(16): 3498. https://doi.org/10.3390/electronics12163498 file:///c:/user/downloads/azojete143/www.azojete.com.ng https://dx.doi.org/10.3126/kuset.v18i1.67501 https://doi.org/10.26555/jiteki.v10i1.28398 https://doi.org/10.1109/tpel.2014.2361853 https://doi.org/10.3390/electronics9050771 https://doi.org/10.3390/electronics12163498 corresponding author’s email address: preaye@gmail.com 431 arid zone journal of engineering, technology & environment original research article assessment of vegetation loss and land surface temperature changes in bwari area council, abuja nigeria k. j. ekanem1 and a. bukuromo2* 1department of survey, gis and mapping, nalda, abuja nigeria 2department of civil engineering, federal university otuoke, bayelsa state, nigeria corresponding author’s email: preaye@gmail.com article information abstract urban vegetation is one of the key essential components that contributes to ecological balance and environmental sustainability. however, due to rapid urbanization in the last few decades, there has been cases of vegetation loss which has increased the land surface temperature (lst) and affected the environmental sustainability. thus, the aim of this study is assessing the impact of vegetation loss on land surface temperature of bwari area council during the periods of 19902021, using geospatial techniques. the support vector machine (svm) supervised classification algorithm was used to classify satellite imageries into land use land cover (lulc) maps according into buildup area, water body, vegetation and rock/bare ground using arcgis pro. all the classified lulc maps had an overall accuracy of more than 90% with the overall kappa coefficient also more than 0.9. the analysis of lulc estimation suggests a significant increase in built-up areas (+ 255.45%) and a reduction in vegetated areas (-75.17 %) from 1990 to 2021. brightness temperature, land surface emissivity (lse) and normalized difference vegetation index (ndvi) were computed to estimate land surface temperature. the results show that the lst was higher in the regions of built-up areas and rock/bare ground but lower in vegetated areas with the maximum temperature of the study area increasing from 37.11 °c in 1990 to 58.87 °c in 2021. correlation between land surface temperature and ndvi/ndbi for the study periods was carried out. the results show that correlations between ndvi and lst are rather weak negative, but there is a strong positive correlation between ndbi and lst. these results call for implementation of policies to control rapid urban growth in bwari area council and preserve vegetal covers and as well an extension of the implementation of the abuja master plan to satellite towns around abuja. received: 23rd february 2025 revised: 24th march 2025 accepted: 24th march 2025 keywords: geospatial normalized difference vegetation index land surface emissivity normalized difference building index (ndbi) © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction rapid population growth entails high demand for social, economic and industrial infrastructure and this results in unplanned and uncoordinated urbanization, particularly in developing countries around the world. in many instances, urban development takes place at the expense of vegetated areas (kafy et al., 2021) which leads to dramatic changes in the local microclimatic condition of several urban locations(chibuike et al., 2018). there is great threat to forest cover aand the broader domain of vegetative cover on the land surface and the main source is humans through urbanization (waseem & khayyam, 2019). while urbanization can be said to be an indication of economic growth and success, it has also brought about short and long-term negative implications in cities’ development (maimaitiyiming et al., 2014). the process of urbanization has brought about several undesirable environmental consequences such as flooding (santamouris, 2014), air pollution (anker et al., 2019), and even heat related morbidityy.ullah et al., (2019), noticed that rapid urbanization has unfortunately led to changes in existing patterns of land use land cover (lulc) globally, and this has consequently increased the land surface temperature (lst) in many regions (wang et al., 2018; ayanlade & howard, 2019; ullah et al., 2019; kafy et al., 2021). several studies have found that the conversion of marsh, vegetative, and agricultural lands into built-up areas is hastened by urbanization and the subsequent catalysts for lulc change, which azojete june 2025. vol.21(2):431-448 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/010 www.azojete.com.ng mailto:preaye@gmail.com mailto:preaye@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 inadvertently drives up the cities’ lst (tran et al., 2006 arsiso et al., 2018; kafy et al., 2021;). in these studies, the rise in land surface temperature is seen as a long-term consequence of lulc change particularly in urban areas (uas). factors contributing to urban heat island (uhi) effects include urban ecology (less vegetation cover, thus reduced cooling from evapotranspiration), engineered building material properties (higher thermal capacity and storage), anthropogenic heat emissions (vehicular traffic and heating/cooling of built infrastructure), hydrological changes (increased runoff due to impervious surfaces and heat transmitted to streams via urban runoff), and urban canyon geometry (reduction of outgoing radiative heat flux due to ‘heat trapping’ in street canyons) (sharma et al., 2016). also, variables like smart urban growth consisting of both vertical and horizontal expansion, construction materials, the distance between buildings, locations of public spaces, roads, bus stops, major and minor industrial hubs, and so on, have a direct impact on temperature concentration in the cities (ahmed et al., 2013; chen et al., 2020; kafy et al., 2021) in addition to considerable land use/land cover (lulc) vegetation loss, rapid urban growth also contributes to an imbalance between demand and supply, thus making available infrastructure to be under stress and as a result altering urban climate (mahmoud & gan, 2018). there is usually increased demand for housing, roads, power generation and feeding etc. to meet these demands, fractions of vegetation and green spaces is reduced leading to subsequent inhibition of photosynthetic activity and plant’s water transpiration biodiversity is threatened and this affects ecosystem productivity through the gradual but consistent loss of habitat, biomass and carbon storage (seto et al., 2012). increasing or conserving green infrastructure in cities has thus been proposed by several authors as a strategy to regulate high temperatures (oliveira et al. 2011; norton et al. 2015). these green infrastructures or vegetated surfaces, such as green walls and roofs, parks, gardens, green spaces, lawns, and trees, is said to capture solar radiation to different extents and ultimately reduce the urban heat island effects (bowler et al. 2010). also, oliveira et al. (2011) examined the cooling effects of vegetated, urban spaces in portugal and subtropical china and found it to be effective. di leo et al, (2016) studied the role of urban green infrastructure in mitigating land surface temperature in bobo-dioulasso, burkina faso, and found that land surface temperature in green infrastructure areas was indeed lower than adjacent impervious, urbanized areas. in the same vein, in nigeria, in assessing the impact of green parks cooling effect on abuja urban microclimate, chibuike et al.(2018) noted the need for urban planners to design green spaces with stronger cooling effects along with the city designing, to mitigate uhi phenomenon. this is further buttressed by studies carried out in ibadan by (balogun & daramola, 2019) where it was posited that the most efficient approach for uhi mitigation is the increase in urban green spaces and parks as this results in less solar radiation absorption through shading of the land surface. however, even though this mitigative measures are being put in place in these areas, there are still high loss of vegetation or vegetative cover in many areas without replacement of such and this has led to a significant increase in the land surface temperature in these places. therefore, this research aimed to assess the impacts of vegetation loss on land surface temperature of bwari area council, in the federal capital territory. i. to assess the changes in landuse/landcover that has occurred between 1990-2001 and 2001-2021 in the study area; ii. to assess the spatio-temporal changes in land surface temperature in the study area between 19902001 and 2001-2021 and iii. examine the relationship between vegetation loss in the period under study and the spatio-temporal changes in land surface temperature in the study area. 1.1 study area 1.1.1 location and administration the bwari area council is one of the six (6) area councils in the federal capital territory (fct), located within longitudes 7°10’ and 7°45’east, and latitudes 8° 50’ and 9° 30’ north (figure 1). it lies in the north – eastern part of the federal capital territory. bwari area council is bounded in the north by kagarko in kaduna state, in the east by karu in nassarawa state, in the south by amac in fct and bounded in the west by suleja and tafa, all in niger state. it is the second most populous area council after abuja municipal council (amac) with a population of 581,100 according to national population commission’s 2016 population projection (national population commission, 2016). http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 figure 1: the study area: bwari area council 1.1.2 climate and relief bwari has a climate classified by koppen as tropical wet and dry (aw). the area experiences two seasons annually (edicha & mgbanyi, 2013; igun & williams, 2018). these are warm, humid rainy season and a cold dry season. fortunately, the high altitudes and undulating terrain of the study area, act as moderating influence on the weather of the territory. the rainy season begins from april and ends in october, with september being the peak of the rainy season and due to the hilly and mountainous nature of the study area, orographic activities bring heavy and frequent rainfall of about 1500 mms (59.1 in) during the rainy season (awuh et al., 2019). the study area falls within the savannah zone vegetation of the west african sub-region and is divided into three savannah types namely; grassy, savannah woodland and shrub savannah ( rakiya. et al., 2018). the soil in the area is basically alluvial and luvisols making it a fertile ground for agriculture and vegetation growth (awuh et al., 2019). the area council features an interesting terrain, which combines rounded hills and clusters of rock outcrops dissected by river valleys, as well as gentle rolling plains. it falls within the abuja hills and dissected zone of the jema’a platform. generally viewing the study area, the hilly areas are found towards the eastern part, posing constraint to physical development while the plains occupy the central and western areas. the study area is the highest part of the fct with several peaks that are about 760 meters above sea level. the lower usuma dam which provides portable water for the whole fct (wuana et al., 2020), is located in the study area. bwari area council is also home to a lot of quarry sites and this explains why they appear to be areas of temperature hot zones in the study area even where there is vegetation around. the main land use types in the study area include built-up, residential, commercial, institutional, administrative, roads and industrial settlements. bwari houses major government establishments like the joint admission and matriculation board (jamb) headquarters, the abuja law school, general hospital, dorben polytechnic, veritas university and other private, commercial and industrial establishments. these establishments have so far led to the increase in population and as such resulting in significant loss of vegetation during the study period in order to accommodate more housing units and significant degree of urbanization. these changes have had an impact on the local climate of the area, particularly, the land surface temperature of the area, which forms the focus of this research. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 2. materials and method 2.1 overview of approach for data analysis to answer the research questions, geographic information system (gis) and remote sensing (rs) methods were deployed for data processing and results generation. the use of gis and remote sensing was backed up by the fact that these tools assist for capturing, storing, manipulating and analyzing of the data usgs server and nimet served as sources of the landsat data and temperature data respectively, used for the analysis for the research. 2.2 data source this research utilized landsat 5, landsat 7 and landsat 8 satellite imageries with path/row 189/54, sourced from the united state geological survey (usgs) server, while the local government boundary map for delineating the spatial extent of the study area and nigerian administrative map was obtained as a shape file from office of the surveyor general (osgof). for lst validation purpose and, temperature data from nimet for the study area and period were used. the choice of landsat satellite imageries was the presence of the thermal bands for the use of the calculation of land surface temperature (hami et al., 2019; sekertekin & bonafoni, 2020). table 1 is the tabular presentation of the data sources while table 2 is the description of the landsat data used for the study. table 1: data source s/ns/n s/n data ty data type year year source source 1 1 landsa landsat 5,7 and 8 1990,2001 and 2021 usgs usgs 2 2 insitu te insitu temperature data 1990,2001 and 2021 nimet nimet 3 3 boundar boundary shape file of study ar study area osgof osgof table 2: description of landsat data used for the study. sensor sensor no of bands resolution path/row date significance landsat landsat 5 tm 6 6 30 189/54 12/02/1990 used for land cover classification and generation of ndvi/ndbi ti tirs(band6) 1 120 resample 30 120m 189/54 12/02/1990 used for lst retrieval landsat 7 etm 7 7 30 189/54 09.01/1990 used for land cover classification and generation of ndvi/ndbi tirs (band 6) 1 1 60 resampled 30 189/54 09/01/2001 used for lstretrieval landsat 8 ol1 9 9 30 189/54 09/02/2021 used for land cover classification and generation of ndvi/ndbi tirs (band 10 and 11) 2 100 resampled 30 189/54 09/02/2021 used for lst retrieval 2.3 land use/land cover classification to assess the spatio-temporal changes in physical land types/features (landcover) present in the study area, landsat imageries covering the study area was extracted and used to produce the land use land cover maps for bwari area council. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 arcgis pro 2.8.4 version was used for the land use land cover classification (lulc) and the algorithm used was the support vector machine (svm) under the supervised classification method. the svm is a nonparametric classifier equipped with a set of related learning algorithms used for regression and classification, it places no assumption to the probability distribution of the data and has low training data requirements(ullah et al., 2019).svm is among the effective method and chosen for its reliability (mushore et al., 2017). the classes are water body, vegetation, built-up area and rocks_bare-ground and samples were taken accordingly create signature files for the svm algorithm. for the classification of the landsat 5 and 7 of 1990 and 2001, bands combination of 4-3-2 for false color (infrared), and 5-4-3 for (vegetation analysis) was used to properly classify the imageries. the two band combinations were used to properly identify the different classes of objects present in the imageries. for landsat 8 of 2021, band combinations of 5-4-3 for false color (infrared) and 654 for false color (vegetation analysis) was used to achieve the same purpose. google earth images were used as ground control points (gcps) to ascertain that the gcps and the features registered on the landsat imageries correspond to each other. thereafter, accuracy assessment was carried out for the land cover classification. 2.4 accuracy assessment accuracy is done to see how closely the results relate to the true values and gives the qualitative collection of information from the obtained satellite data (choudhury et al., 2019). to carry out the accuracy assessment of the image classification, the confusion matrix and the kappa index, both considered as one of the best indicators for image classification accuracy (ullah et al., 2019; kafy et al., 2021;) were computed using the arcgis 10.8. for the accuracy assessment, a total of 208, 207 and 242 reference points were selected on the 1990, 2001 and 2021 composite imageries respectively for the accuracy assessment of the classified lulc maps. 2.5 normalized difference vegetation index (ndvi) and normalized difference building index (ndbi) ndvi is a satellite measured vegetation indices, commonly used to quantify the abundance and energy absorption by leaf pigments such as chlorophyll and is also indicative of an urban climate (heather et al., 2019). it is largely influenced by the fractional cover of the ground by vegetation, the vegetation density and the vegetation greenness. in order words, it indicates the photosynthetic capacity of the land surface cover. normalized difference vegetation index (ndvi) quantifies vegetation by measuring the difference between near-infrared (which vegetation strongly reflects) and red light (which vegetation absorbs). ndvi is commonly used to quantify the abundance and energy absorption by leaf pigments such as chlorophyll and is also indicative of an urban climate (bachir et al., 2021) . to generate the ndvi for 1990, 2001 and 2021, multi-temporal landsat visible and near-infrared bands were combined in a normalized ratio using raster calculator in arcgis 10.8 to compute the normalized difference vegetation index. for 1990 and 2001, bands 3(visible red) and 4(near infrared) were used while bands 4(visible red) and 5(near infrared) were used for 2021 imagery. the bands used correspond to the required bands for ndvi calculation for landsat 5(1990), landsat 7(2001) and landsat 8(2021) respectively. equally, ndbi, a built-up index commonly used as both an indicator of intensity of development and of urban impervious surface (macarof & statescu, 2017), was generated for the 3 years under study. while ndvi is generated using a combination of landsat near infrared and the red band, ndbi is generated by combining multi-temporal landsat near-infrared and short-wave infrared bands in a normalized ratio using raster calculator in arcgis 10.8. for 1990 and 2001, bands 4(near infrared) and 5(short-wave infrared) are combined while for 2021, bands 5(nir) and 6(swir) using the formula in equation 2. the following formula was used for ndvi and ndbi calculation 𝑁𝐷𝑉𝐼 = (𝑁𝐼𝑅 − 𝑅𝐸𝐷) (𝑁𝐼𝑅 + 𝑅𝐸𝐷) 1 ndbi= (𝑆𝑊𝐼𝑅−𝑁𝐼𝑅) (𝑆𝑊𝐼𝑅+𝑁𝐼𝑅) 2 where nir = near infrared, swir = short wave infrared http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 2.6 land surface temperature (lst) retrieval the land surface temperature (lst) was calculated through the use of satellite thermal infrared remote sensing system. this is known to provide a synoptic and uniform means of measuring lst at regional scale as compared to in situ sensors of air temperature via weather station networks which is best suited for atmospheric air temperature (yuan & bauer, 2007), are sparsely located and the observations being point data, are not a representative of the whole terrain (rongali et al., 2018). to this end, lst maps prepared from satellite images are an attractive alternative as it provides a continuous dataset ( ogunode & akombelwa, 2017). landsat 5 & 7 land surface temperature was extracted using band 6 for landsat 5 and 7 (chen et al., 2020). firstly, digital numbers (dns) of band 6 were converted into radiation luminance using equation 3. radiance = [ 𝐿𝑀𝐴𝑋−𝐿𝑀𝐼𝑁 𝑄𝐶𝐴𝐿𝑀𝐴𝑋−𝑄𝐶𝐴𝐿𝑀𝐼𝑁 ](qcal − qcalmin) + lmin 3 where qcalmin is equal to 1, qcalmax is equal to 255. qcal stands for dn, in this case the thermal band (6), whereas lmax and lmin are equal to 1 and 255, respectively. lst in kelvin was calculated using equation 4. t (k) = 𝐾2/ln ( 𝐾1 𝑌𝑦 + 1) 4 values in degree celsius, 273.15 was subtracted from the result in equation 2. lst = t (k) – 273.15 5 landsat 8 to estimate the land surface temperature for landsat 8, in arcgis 10.8, map algebra, a feature in the spatial analyst tool which has the raster calculator in it was used in the five steps process: i. digital numbers (dns) were converted using equation 4 to top of air atmosphere (toa) spectral radiance using the radiance rescaling factor provided in the metadata file l𝜆 = mlqcal + al 6 where lλ = top of atmosphere spectral radiance, ml = radiance multi band for band 10 (0.0003342), al = radiatiance add band for band 10 (0.1), qcal = band 10 (digital number) ii. conversion of radiance into brightness temperature (tb) which is the microwave radiance traveling upward from the top of earth’s atmosphere (yang et al., 2014) using the thermal constants provided in the metadata file using equation 7: tb = k2/in ((k1 / l𝜆) + 1) − 273.15 7 where k1 = calibration constant 1 (774.8853), and k2 = calibration constant 2 (1321.0789) all found in the metadata file. iii. ndvi values were calculated using the equation 8. 𝑁𝐷𝑉𝐼 = 𝐹𝑙𝑜𝑎𝑡(𝑁𝐼𝑅 − 𝑅𝐸𝐷) 𝐹𝑙𝑜𝑎𝑡(𝑁𝐼𝑅 + 𝑅𝐸𝐷) 8 iv. derivation of the surface emissivity. to get the lse, the pv (proportion of vegetation) was first derived from ndvi of 2021 using the expression: http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 𝑃𝑉 = (𝑁𝐷𝑉𝐼 − 𝑁𝐷𝑉𝐼𝑚𝑖𝑛) (𝑁𝐷𝑉𝐼𝑚𝑎𝑥 − 𝑁𝐷𝑉𝐼𝑚𝑖𝑛) 9 v. lst was calculated using the equation: lst = tb/ [1 + (λ ∗ tb/ρ) ∗ ln (𝜀)] 10 all calculations where done using raster calculator, a map algebra, spatial analyst tool in arcgis 10.8 2.6.1 lst validation to validate the accuracy of the estimated lst, a temperature based (t-based) method was used. the t-based is a ground-based method that directly compares the satellite-derived lst with insitu lst measurements at the satellite overpass (li et al., 2013). the meteorological observatory data for temperature obtained from nimet was compared with the lst estimated from landsat thermal bands. since the nimet data was monthly, the temperature for the months that corresponds with the date of the landsat imagery acquisition was compared using microsoft excel and the result obtained were seen to be closely related. 2.7 relationship between the vegetation loss and land surface temperature to assess the relationship between vegetation loss and lst, firstly, the total area in hectares occupied by classified vegetation for 1990, 2001 and 2021 and compared with the corresponding maximum retrieved lst values for 1990, 2001 and 2021 using the stacked bar chart. in addition to the above method, the relationship between vegetation loss and lst of the study area was equally assessed by comparing the vegetative index (ndvi) for each year and the lst for the corresponding year in arcgis 10.8. this was achieved by generating point data for ndvi and lst using fishnet polygon. fishnet polygons, a sampling tool, under data management tools were created in arcgis 10.8. thereafter, extraction was carried out by the tool ‘extract multi values to point’ on both images (lst & ndvi) and the result was then clipped using the study area boundary shapefile to generate the result of extract multi values to point for the lst and ndvi images. after this process, the multi values of points for lst and ndvi were exported from the attribute table of the clipped image and accessed in microsoft excel. here in excel, relationship between lst and ndvi for bwari area council for the different study periods were determined through the use of scatter plot, assigning of a trendline to the graph and the derivation of r-squared values for the regression analysis. similarly, the built-up index (ndbi) was compared with the lst for the years 1990, 2001 and 2021. this was done to determine the effect the increase in urbanization in the study area has made on the urban climate (lst). 3. results and discussion the research focused on analyzing the impact of vegetation loss on land surface temperature of bwari area council through the mapping and analyzing the landuse/landcover between 1990 to 2021, assessing the spatio-temporal changes in the land surface temperature of the study area, to the relationship that exist between the lst and the vegetation loss in the study area. the outcome of the data processing and analysis were presented in the form of maps and tables 3.1 accuracy assessment of lulc classification to determine the correctness of the land cover classification carried out for the study area and for the years under review, an assessment of the accuracy was carried out and shared in tables 3, 4 and 5 which is the result of the assessment for years 1990, 2001 and 2021. table 3: accuracy assessment for 1990 lulc classification class(1990) water body built-up vegetation bare ground ground truth accuracy water body 27 0 0 0 27 100 built-up 0 25 0 0 25 100 vegetation 0 0 84 0 84 100 http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 bare ground 0 1 0 71 72 98.6 total 27 26 84 71 208 producer accuracy (%) 100 96.154 100 100 overall accuracy 27+25+84+71=207 27+25+1+84+71=208 99.519 kappa coefficient 0.993 table 4: accuracy assessment for 2001 lulc classification class(2001) water body built-up vegetation bare ground ground truth accuracy % (%)) water body 31 0 0 0 31 100 built-up 0 0 77 0 77 100 vegetation 0 1 0 27 28 96.429 bare ground 0 71 0 0 71 100 total 31 72 77 27 207 producer accuracy 100 98.611 100 100 overall accuracy 31+77+27+71=206 31+77+2+1+71=207 99.51 kappa coefficient 0.993 table 5: accuracy assessment for 2021 lulc classification class(2021) built-up water vegetation bare ground ground truth accuracy water body 62 0 0 1 63 98.413 built-up 0 30 0 0 30 100 vegetation 1 0 88 1 90 97.778 bare ground 0 0 0 59 59 100 total 63 30 88 61 242 producer accuracy 98.413 100 100 96.721 overall accuracy (%) 62+30+88+59=239 63+30+90+59=242 98.79 kappa coefficient 0.983 3.2 land use/land cover change (lulcc) analysis: from the results of the analysis, it was observed that in 1990, rock/bare ground constituted the largest landcover for the study area occupying more than half of the total area at 43603(ha) which constitutes a percentage value of 57%, followed by vegetation occupying 30497(ha) which constitutes a percentage value of 40%, then built-up occupied only a small portion of the area at 1263(ha) making up 2% of the total space and finally the smallest was water body occupying only 866(ha) making up just 1% of the total study area. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 from a close examination of the map in figure 2, it can be observed that the dominant landcover class, rock/bare ground, was present in the entire study area with more concentration in the northwest and central region. vegetation was also prominent in the study area and mostly found in northeastern, eastern and western region with some concentration of vegetation found also in the south. there was very minimal built-up area in the study area as at 1990 but the few ones were settlements close to the rocks while water body was located at the bottom area of the central region. these results can be seen in figures 2 and 3 which shows the landuse landcover map of 1990 and the observed patterns of 1990 in pie chart. figure 2: lulc 1990: bwari area council figure 3: pictorial representation of lulc class for 1990 according to similar analysis carried out in 2001, it was observed that due to increased farming activities, vegetation now increased from 30497(ha) to 37028(ha) now occupying 49% to become the largest landcover for the study area, followed by rock/bare ground occupying 31427(ha) at 41%, built-up now occupied 6898(ha) standing at 9% of the total coverage area and then water body occupying 875(ha) with a percentage of 1% was observed as the landcover class that occupied the smallest fraction of the study area. observing the map, it can be seen that the dominant landcover class, vegetation, was present in the entire study area except for small portions in the north east and southern regions occupied by built-up. rock/bare ground was observed more in the north across to the central region while water body maintained it position close to the central part of the study area. these results can be seen overleaf in figures 4 and 5 which shows the landuse landcover map of 2001 and the observed patterns of 2001 in pie chart http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 figure 4: lulc 2001: bwari area council figure 5: pictorial representation of lulc class for 2 2001 lastly, in 2021, as seen in figures 6 and 7, built up became the largest land-cover occupying 35% of the study area on an area of 26808(ha), followed by rock/bare ground at 33% occupying 25436(ha), vegetation now occupied 22980(ha) at 30% and then the smallest land-cover class was water body occupying just 844(ha) to make 1% of the study area. observing the map, it can be seen that dominant land-cover class in 2021, now the built-up area, occupied mostly the north western part of the study area connecting down to the southern region. the central region was occupied mostly by rocks/bare ground serving as a major hindrance to the spread of built-up to the area, vegetation was now more prominent in the north eastern part while water body still occupied its same position throughout the study period. figure 6: lulc 2021: bwari area council figure 7: pictorial representation of lulc class 2021 it is evidently clear that the expansion of the built-up area in bwari area council from 1990 to 2021, has been to the detriment of vegetation, rock/bare ground and water body although the impact on the water body is minimal. a large expansion of the built-up area happened toward the north western region connecting with the central and southern part of the area council. built-up area expansion towards the north eastern part of the area council is not so significant, and this is mostly due to the effect of the landscape of the area as it is mostly filled with rocks and hilly terrains. table 6 gives a tabular representation. table 6: areas of lulc for bwari area council land use class changes btw 1990-2021(ha) % changes changes btw 2001-2021(ha) % changes changes btw 1990-2021(ha) % changes http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 built up 1263 1.66 6898 9.05 26808 35.24 wate water body 866 1.14 875 1.15 844 1.11 vege vegetation 30497 40.00 37028 48.58 22980 30.21 bare ground 43603 57.20 31427 41.23 25436 33.44 to further identify the changes in the different land-use/land-cover classes that have occurred in the study area between the years under study, table 7 overleaf shows the changes in the land-use/land-cover class between1990 to 2021. from the table, it can be observed that the highest percentage change in the classes, was observed in built-up between 1990-2021 with a 255% increase as compared to other periods between 1990-2001, and 2001-2021. water body experienced minimal change between the study periods with the highest -0.31% between2001-2021. in vegetation, the highest percentage change was observed between 19902021(table7) with a change of -75.17% while the highest change in rock/bare ground was observed between 1990 and 2021 with a value of -181.67%. however, there was vegetation increase observed between1990 to 2001. this was due to the fact that in 1990, the study area was mostly filled with rocks and less human inhabitants and this made farming activities very low that year (lesser vegetation cover) and only picked up slowly after the federal capital territory was moved to abuja in 1991 where the bare grounds had to now be cultivated and the rocks blasted as well to create expansion of agricultural lands to cater for the feeding of the increasing population of people relocating to bwari. table 7: percentage changes in landuse/landcover classes between 1990-2021 land use class changes btw 1990-2001(ha) % changes changes btw 2001-2021(ha) % changes changes btw 1990-2021(ha) % changes built up 5635 56.35 19910 199.1 25545 255.45 wate water body 9 0.09 -31 -0.31 -22 -0.22 vege vegetation 6531 65.31 -14048 -140.48 -7517 -75.17 bare ground -12176 -121.76 -5991 -59.91 -18167 -181.67 3.3 normalized difference vegetation index (ndvi) to generate land surface temperature of the study area, ndvi maps had to be generated for the study area. figures .8, 9 and 10 shows the results of the ndvi generated. from the maps, it can be seen that, in 1990, the vegetation in the study area can be classed as good and but was in few locations of the map. in 2001, the vegetation value though a positive in the maximum range (0.098), it is classed as not good, meaning that though vegetation was present, the density and greenness was very low. this value possibly indicates the presence of farmlands and its more concentrated in the south east end of the study area and a little into the south west. in 2021, the density of the vegetation has improved as compared to 2001 with a higher max value of 0.317. it is observed that areas that were greyish in color in 1990 and 2001 signifying low ndvi values now had deeper green colors in 2021. this areas in the previous years were occupied by rocks/bare ground but now in 2021, the rocks now nonexistent, have green areas in the locations. this explains why the vegetation density and greenness improved in 2021. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 figure 8: ndvi map for 1990 figure 9: ndvi map for 2001 figure 10: ndvi map for 2021 3.4 land surface temperature change analysis the result from the lst retrieved from the landsat thermal bands is represented in figures 11, 12 and 13 for 1990, 2001 and 2021 respectively. from the observation made from the lst maps, the temperature range was between 19.430c to 37.110c for 1990, 15.540c to 44.910c for 2001 and 21.960c to 58.870c. the maximum temperature increased by 21.770c between 1990 to 2021 while the minimum temperature increased by 2.530c. the point of the high maximum temperature observed in 2021, is a rocky mountain side located in the northern part of mpape, a town in bwari area council. this area is prominently filled with quarry site and there is a lot of mining of rocks by burning going on in the area. this explains why the lst levels is higher in that area as compared to other areas in the study area. in comparing the lst map of 1990 with lulc map of 1990, it is observed that higher values of lst is more significant in the regions with deep red color and this corresponds to areas occupied mostly by rock/bare grounds, followed by built-up and lower in areas occupied by vegetation and water body in the lulc map. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 figure 11: lst map for 1990 figure 12: lst map for 2001 figure 13: lst map for 2021 in lst map for 2001 (figure 12), locations with bright red colors, signifying higher temperature (30.9744.910c) were found to be occupied equally by both rock/bare grounds and built-up and the spread of the high temperature was found to be distributed evenly across the study area except for the southeast region. lowest temperature areas (15.54-27.750c) were mostly found where vegetation was prominent and also areas occupied by water body this is attributed to the higher latent heat transfer and evapotranspiration properties of water body and vegetation (yuan & bauer, 2007). 3.5 lst validation lst obtained from landsat 5, 7 and 8 was compared with the air temperature obtained from nimet station located at nnamdi azikiwe international airport, abuja municipal council (amac). nimet data from single stations located at different area councils were used. the comparison made with air temperature, is usually different and can sometimes result in big differences since the resolution of the landsat imageries for the used bands is high for the thermal bands (100 m for landsat 8, 120m for landsat 7 and 60m for landsat 5, though all resampled to 30m) and 30 m for the red and nir bands. sometimes, the differences can be very big depending on the weather condition and other factors surrounding the weather station. the result of this comparison is as represented in figure 14. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 fig 14: lst validation using nimet data from the results, lst was generally higher than temperature obtained from nimet for 1990, 2001 and 2021 with 2001 recording the highest difference of 2.9°c. this difference is in close agreement to allowable difference 50c as stated by avdan & jovanovska, (2016) that comparing lst results with the ground measurements results, may have an error up to 50c. this makes the observed differences normal and expected. 3.6 correlation analysis between ndvi, ndbi and lst the vegetation index ndvi for 1990, 2001 and 2021 was compared with lst of the corresponding years to show the relationship between the two variables. similarly, lst was also compared with the built-up index (ndbi) to determine the impact of increase in built-up on the lst of the study area as shown in figure 15 to figure 20. figure 15: correlation between ndvi and lst 1990 figure16: correlation between ndbi and lst 1990 a moderate negative correlation is notice ( figures 15 and 16) to exist between lst and ndvi in 1990 where r is equal to 0.24 and a strong positive relationship is found to exist between lst and ndbi where r is 0.61. this shows that land surface temperature is lower where vegetation index is high and lst is higher where ndvi values are lower. but with respect to ndbi, lst is higher as ndbi goes higher too. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 figure 17: correlation between ndvi and lst 2001 figure 18: correlation between ndvi and lst 2001 a moderate negative correlation is noticed, figures 15 and 16 to exist between lst and ndvi where r is equal to 0.49 and high positive relationship exist between lst and ndbi with the value of r = 0.68. an increasing value of lst resulted in a decreasing value of ndvi (figures 17 and 18) while as lst increased, ndbi increase as well. figure 19: correlation between ndvi and lst; 2021 figure 19: correlation between ndvi and lst; 2021 figure 20: correlation between ndbi and lst; 2021 the correlation of lst with ndvi and ndbi in 2021 is shown in figures 19 and 20. a very weak negative relationship was found between lst and ndvi with r equal to 0.072, whereas between lst and ndbi it was a moderate positive relationship with r equal to 0.58. according to these relationships, its noticed that the effect vegetation has on lst is not as high as the previous years due to less vegetation in the study area. however, in areas where vegetation exist, it was still noticed that higher ndvi lead to lower lst, and lower ndvi leads to higher lst. on the other hand, a positive relationship between lst and ndbi means that lst increases with ndbi increase and decreases with the decreasing ndbi. this correlation proves that urban vegetation contributes to a decrease in lst and can help to maintain thermal homogeneousness in cities while a loss of the vegetation leads to an increase in lst. 3.7 relationship between land surface temperature and vegetation loss between the study periods to determine the relationship between vegetation loss and lst of bwari area council over years 1990, 2001 and 2021, computed values for areas occupied by vegetation in the years under study was combined with the maximum lst values for the corresponding years. the result is presented in figure 21. http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 figure 21: relationship between vegetation loss and temperature between the study period. it was observed that a decrease in vegetation experienced between 1990-2021(-7,517ha) was accompanied by an increase in lst (21.7640c). however, between 1990-2001, there was an increase in vegetation but yet an increase in lst was observed. further finding revealed that the lst in the study area has been increasing not only because of a loss in vegetation, but also due to the explosive rate of built-up and the exposure of rocks which is a prominent feature in the study area. these two components (built-up and rock) are known to have high emissivity levels thereby, rapidly increasing the lst of the area. so, from the above result, it can be deduced that though a loss in vegetation has had an impact in increasing the temperature between 1990-2021, this was not the only reason for the increase of lst in the study area. further study is advised to be carried out to determine the effects that the increase in blasting of rocks, quarry activities and crude rock mining have on the lst of the study area. 3.8 discussion of findings between 1990 and 2001, built-up areas increased significantly from 1263ha to 6893ha (56.35%), obviously due to the expansion of residential areas in the satellite towns in abuja to accommodate the daily increasing population of people moving to the capital city. during this period, more ministries were moved from lagos to fct to continue the transfer of capital headquarters and this led to obvious higher influx of people to the study area during this period. however, the increase in built-up surfaces wasn’t accompanied with a loss in vegetation, as vegetation was observed to increase from 30497ha to 37028ha (65.67%). this increase is largely due to the increase in agricultural activities in the study area such as the increase of farmlands for the purpose of plant cultivation for feeding purposes. as a result of increase in agricultural activities and built-up areas, rock/bare ground reduced drastically from 43603ha to 31427ha (-121%). within the same study period, water body increased slightly from 866ha to 875ha (0.09%). similarly, maximum land surface temperature increased by 7.80c from 37.11˚c to 44.91˚c, while minimum temperature decreased by 3.890c from 19.430c to 15.540c. the value of 44.91˚c observed as the maximum temperature for 2001 and 15.540c as the minimum temperature in this study, is closely in agreement with maximum lst value of 45.1˚c and minimum value of 16.7 ˚c observed by omali, (2020) in his study of the ecological evaluation of uhi impact in abuja municipal council (amac). in this study, the increase in the maximum temperature was due to the increased urbanization activity that went on during that period which lead to increase in anthropogenic activities and increase in impervious surfaces within the study period. also exposed rock surfaces which by now is a common occurrence in the study area with low absorptivity, high emissivity and albedo properties, equally contributed to the increase in lst of the study area. from the relationship between ndvi, ndbi and lst for the period, results revealed that the increase in temperature over the period was due to increased impervious surfaces and loss of vegetative cover. between 2001 and 2021, the built-up areas increased even more drastically from 6898ha to 26808ha (199.1%). the major contributor to this massive increase was the reduction of vegetation and rock/bare ground which reduced by 140.48% and 59.99% respectively. during this period, the real estate sector experienced a boom as more houses were built to accommodate the fast-increasing population in some satellite towns in the area council such as kubwa, dutse, bwari, mpape etc. this invariably led to the increase of more impervious surfaces and subsequent loss of vegetation and http://www.azojete.com.ng/ mailto:preaye@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): xxx-xxx. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: preaye@gmail.com 448 rock/bare ground. the vegetation cover, cleared during the construction of buildings and infrastructure is not replaced after the development through landscaping in the study area, thus, resulting in discomfort from the increased surface temperature of the study area. maximum temperature increased by 13.960c from 44.91˚c to 58.87˚c while minimum temperature by 6.420c from 15.540c to 21.960c. the findings from the ndvi and ndbi relationship with lst revealed that the increase in built-up area was accompanied with increase in land surface temperature while increase in vegetation was accompanied by decrease in land surface temperature. 4. conclusion the spatio-temporal lulc maps generated for the year 1990, 2001 and 2021 revealed notable changes in the study area in the last three decades. it was observed that due to rapid urbanization in the study area, built-up areas was the land cover type that increased the most from 1263ha to 26808ha (255.45%) while the rock/bare ground was the landcover type that reduced the most from 43603ha to 25436ha (181.67%) and these changes directly lead to increase in temperature within the study area over the last 30years.. this is connected to the expansion of real estates observed to be on the increase in the study area in the 30year period to accommodate the explosive population. the increased exposure of rocks through blasting and quarry activities was observed to significantly contributed to rise in temperature from a maximum 37.110c to 58.870c while the minimum temperature increased from 19.430c to 21.960c.the study also revealed 75.17% reduction in the vegetative cover, 255.45% increase in built-up, 181.67% reduction in rock/bare ground and 0.22% reduction in water body over the time period 1990 – 2021. the result of these changes is the corresponding increase in lst between 1990-2021 (21.7640c). remote sensing and geospatial techniques used in this study has proven to be an effective method to be used in the study of landuse and cover changes and its impact on the rise of land surface temperature of the study area. references anker, y., mirlas, v., gimburg, a., zilberbrand, m., nakonechny, f., meir, i. and inbar, m. 2019. effect of rapid urbanization on mediterranean karstic mountainous drainage basins. sustainable cities and society, 51: 101704. arsiso, b. k., mengistu tsidu, g., stoffberg, g. h. and tadesse, t. 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(2020). ecological and human health risk assessment of toxic metals in water, sediment and fish from lower usuma dam, abuja, nigeria. journal of geoscience and environment protection, 08(05): 82–106. https://doi.org/10.4236/gep.2020.85006 yang, l., cao, y., zhu, x., zeng, s., yang, g., he, j. and yang, x. 2014. land surface temperature retrieval for arid regions based on landsat-8 tirs data: a case study in shihezi, northwest china. journal of arid land, 6(6): 704–716. https://doi.org/10.1007/s40333-014-0071-z yuan, f. and bauer, m. e. 2007. comparison of impervious surface area and normalized difference vegetation index as indicators of surface urban heat island effects in landsat imagery. remote sensing of environment, 106(3): 375–386. https://doi.org/10.1016/j.rse.2006.09.003 http://www.azojete.com.ng/ mailto:preaye@gmail.com https://doi.org/10.1016/j.buildenv.2011.04.034 arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):547-554 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 547 influence of agroforestry technology adoption on poverty reduction among farming households in okunland of kogi state, nigeria d. o. oke*, s. a. adisa, e. o. obafunsho, c. a. ojedokun, a. o. oyetoki, y. o. adesina department of forest economics and extension, foresrtry research institute of nigeria, ibadan, oyo state *corresponding author's email address: bunmioyetunji@yahoo.com article information submitted 4 january, 2024 revised 28 february, 2024 accepted 25 march, 2024 keywords: foster greer thorbecke poverty line gestation period tree planting abstract the significance of agroforestry to the enhancement of livelihoods of farming households, through its contribution to food and income security as well as the improvement of crop productivity of farmers, cannot be overemphasized. consequent upon this, the study assessed the impact of agroforestry practices on poverty reduction among small farming families in okunland, kogi state, nigeria. in selecting respondents for the study, a multi-stage sampling approach. this study used descriptive statistics and inferential statistics for analysis. the descriptive statistics used are frequencies and percentages, while the inferential statistics used is foster greer thorbecke (fgt) technique. findings showed that about 35% of those who adopted the practice of agroforestry did not measure up to the poverty line (n54, 520.13k). therefore, since they were found below the poverty line, they were regarded as poor. for those who did not adopt the practice of agroforestry, sixty seven percent of them were found below the poverty line (n31, 654.19k). by implication, this category of people can be regarded as poor. in order to reveal the extent of poverty among the respondents, fgt poverty index was used. results from this therefore showed that the farming households who adopted and practiced agroforestry technology had a better livelihood when compared to those that failed to adopt the technology. in addition, it was discovered from the study that several constraints were militating against the adoption of agroforestry technologies by the farming households in the study area. some of the constraints were lack of knowledge and required skills on agroforestry, long gestation period of trees, insufficient land for tree planting, lack of planting materials among others. consequent upon this, this study recommends that necessary efforts should be made by government and concerned stakeholders to increase the adoption of agroforestry technology by creating awareness and sensitizing farmers on significance of adopting agroforestry technology and the associated benefits derivable from agroforestry practices. to accomplish this, extension agents and subject matter specialists on agroforestry should train and enlighten farmers on how best to use their land so as to accommodate both arable and tree crops so as to ensure improved productivity. 1.0 introduction according to world bank (2001), poverty can be defined as the deprivation of well-being related to lack of material income or consumption, low levels of education and health, vulnerability and exposure to risk, lack of agency, and powerlessness. poverty has remained a threat and challenge to humanity in all ramifications. poverty is commonly measured using http://www.azojete.com.ng/ mailto:m.ishaq@unimaid.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):547-554. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 548 incomes or consumption levels. therefore, an individual is said to be poor if his or her consumption or income level falls below some minimum level necessary to meet basic needs. this minimum level is usually called the “poverty line” (maduka, 2007). poverty remains a significant subject in nigeria and africa in general (beegle et al., 2016) and has therefore, been linked to climate vulnerability (thornton et al., 2006) and food insecurity (charles, 2019). the incidence of poverty in nigeria has defied several efforts made both by government and non-governmental organizations (ngos) to reduce it through poverty alleviation/reduction programmes and projects (adepoju and okunmadewa, 2010). it was earlier estimated that by 2016, the poverty rate in the country would have fallen to 48.4% from the estimated 53.5% in 2009-10. but rather, poverty has been on the increase, as a result of slow economic growth (world bank, 2018). according to united nations human development report (2019), nigeria’s human development index (hdi) value for 2018 was 0.534 which puts the country in the low human development category, positioning it at 158 out of 189 countries and territories. in recent times in nigeria, there have been several efforts to produce food to feed the rising population. but these attempts have been mainly through the traditional slash and burn approach of agriculture. unfortunately, this has often resulted in wanton destruction of forest cover and the alteration of the dynamics of the forest ecosystem leading to climate change. in order to address this ugly trend, production of food should be done in a way that that ensure that forest resources and the environment are not indiscriminately depleted. to achieve this, there is need for the adoption of a system that provides a good opportunity which enables the combination of the characteristic advantages associated with forestry technology and agricultural practices. this approach is therefore known as agroforestry. the international council for research in agroforestry (icraf) now world agroforestry centre defined agroforestry as a “dynamic ecologically based natural resources management system that through interactions of trees on farm and in the agricultural landscape diversifies and sustains production, enhancing social, economic and environmental benefits for land users at all levels”. agroforestry enhances food and income security, amelioration of environmental hazards, improvement of crop productivity and mitigation of climate change (ajayi and catacutan, 2012; mutua et al., 2014 and kennedy et al., 2016). according to maren and carolyn (2011), agroforestry affects the socio-economic livelihood of rural farmers by enhancing income earning potentials and overall food and nutritional security (kennedy et al., 2016). according to rahman et al., (2010), agroforestry as a practice plays a significant role in lifting poor rural families out of poverty through market driven, locally led tree cultivation systems that generate income and build assets; conserve biodiversity through integrated conservationdevelopment solutions based on agroforestry technologies. it can as well protect forest through agroforestry-based solutions; assist the rural poor to better adapt to change and to benefit from emerging carbon markets, through tree cultivation (rahman et al., 2010). some studies have been carried out to establish that agroforestry practices enhance farmers’ income, food security and improve on poverty status of the farming households (tiwari et al., 2017; olajuyigbe, 2016; kareem et al., 2017). however, no such studies have been conducted in the yoruba speaking part of kogi state, popularly known as okunland. this study therefore, attempts to address this gap by evaluating the influence of the adoption of agroforestry technology on poverty reduction among rural households as well as the factors militating against the adoption of agroforestry among the rural households in okunland of kogi state, nigeria, with the aim of determining the contribution of agroforestry practices to poverty reduction as well as identifying factors militating against the adoption of agroforestry in the study area. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com oke et al: influence of agroforestry technology adoption on poverty reduction among farming households in okunland of kogi state, nigeria. azojete, 20(2):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 549 2. materials and method 2.1. study area this study was conducted in kogi state (figure 1), specifically the western senatorial district of the state. the people in this area are known as “okun people”. the local government areas in this region are mopa-muro, ijumu, yagba east, lokoja, kabba-bunu and yagba west as shown in figure 2. kogi state is one of the six states that make up the north-central zone of nigeria, with a population of 3,595,789 (npc, 2006). it comprises igala, ebira, kabba, yoruba and kogi divisions of former kabba province with yoruba, nupe and bassa as the main ethnic groups and yoruba, nupe and ebira as the major languages spoken. the state has two distinct seasons (the wet and dry seasons) and a humid tropical climate prevails over the state. figure 1: map of nigeria showing okun region of nigeria source: ocha(2018): http://www.unocha.org/ figure 2: map showing okun region of kogi state source: ocha (2018): http://www.unocha.org/ http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):547-554. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 550 2.2. sampling technique and method of data collection the sampling techniques used for this study was a random sampling using a multistage approach. stage one was the random selection of three lgas out of the five lgas in the study area. stage two was the random selection of two communities each from the three lgas selected. in all, a total of six (6) communities were selected. the last stage of the multistage process was the random selection of thirty (30) respondents from each of the selected communities, making a total selection of one hundred and eighty (180) respondents. but only one hundred and seventy-four (174) copies of the questionnaire were retrieved and were used for the analyses. information was sourced from the respondents using questionnaire. in addition to questionnaire administration, additional information was sourced through focused group discussion. these additional approaches were adopted so as to capture information not captured through the use of questionnaire. 2.3. analytical techniques in order to determine if the adoption of agroforestry technology had significant impact on alleviating poverty among farming households in the study area, the fgt technique was adopted to construct poverty line. this line is defined as a borderline that distinguishes poor from nonpoor households in terms of their level of welfare. in determining the poverty line, two methods are commonly used. these are expenditure and income techniques. this fgt method as expressed in equation 1, was also used to compare the level of poverty among the adopters and non-adopters of agroforestry technology (ajayi and catacutan, 2012). according to foster-greer-thorbecke, (1984), the model is expressed as pα = (1) where, z = the poverty line defined as 2/3 of mean annual per capita expenditure y = the annual per capita expenditure –poverty indicator/welfare index per capita q = the number of poor households in the population of size n, a = the degree of poverty aversion; a = 0; is the headcount index (p0) measuring the incidence of poverty (proportion of the total population of a given group that is poor, based on poverty line). a = 1; is the poverty gap index measuring the depth of poverty that is on average how far the poor is from the poverty line; a = 2; is the squared poverty gap measuring the severity of poverty among households, that is the depth of poverty and inequality among the poor. 3. results and discussion table 1 depicts the socio-economic attributes of respondents in the study area. from the table, it was observed that about 66% of the adopters of agroforestry technology were between 40 and 59 years of age while 68.42% of non-adopters were within the same age range. in addition, about 75% of the adopters had farm size of 8ha and below while about 84% of the non-adopters had similar land holdings. this corroborates similar study conducted by idumah et al. (2021) in oyo state, where 72.68% of farming households that adopted agroforestry technology did not have more than 8ha of farmland and 83.81% of the non-adopters had similar farm size. this is an indication that majority of the farming households in the study area are small scale farmers. this is because, according to ozowa (2005), farm households with less than 10ha of farmland are regarded as small-scale farmers. this is according to international standards measurement for farm sizes. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com oke et al: influence of agroforestry technology adoption on poverty reduction among farming households in okunland of kogi state, nigeria. azojete, 20(2):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 551 table 1: socio-economic characteristics of respondents variable adopters (n=79) frequency percentage non-adopters (n=95) frequency percentage age (years) ≤ 39 04 5.06 8 8.42 40-49 15 18.99 28 29.47 50-59 37 46.84 37 38.95 60-69 17 21.52 17 17.89 >70 6 7.59 05 5.26 gender male 71 89.87 81 85.26 female 08 10.13 14 14.74 educational status no formal 07 8.86 07 7.37 primary 5 6.33 12 12.63 secondary 31 39.24 31 32.63 tertiary 26 32.91 36 37.89 vocational farm size (ha) ≤2 2.1 5.0 5.1 – 8.0 ≥8.1 household size ≤5 6-10 11-15 ≥16 farming experience (years) ≤10 11-20 21-30 ≥ 31 10 17 30 12 20 20 48 10 01 04 34 20 21 12.66 21.52 37.97 15.19 25.32 25.32 60.76 12.66 1.27 5.06 35.79 25.32 26.58 9 22 50 8 15 32 57 05 01 08 46 23 18 9.47 23.16 52.63 8.42 15.79 33.68 60.00 5.26 1.05 8.42 48.42 24.21 18.95 source: field survey, 2022 foster greer thorbecke (fgt) poverty index was used to show the extent of poverty among the farming households in okunland. the poverty aversion parameters used were p0, p1, and p2 which translate to poverty incidence (headcount), poverty depth (gap) and poverty severity respectively. table 2 showed that the incidence of poverty (p0) among the adopters was 0.3544 and 0.6737 for the non-adopters. this implies that 35.44% of the adopters were poor and 67.37% of the non-adopters were poor, considering the poverty line. the value of the poverty depth (p1) among the adopters was 0.4733 and 0.6322 for the non-adopters. the implication of this is that an average poor adopter of agroforestry technology would require about 47% of the poverty line to get out of poverty while an average poor non-adopter would need about 63% of the poverty line to get out of poverty. this result collaborate with ajayi et al. (2007) findings that adopters of agroforestry technologies had a higher probability of moving out of poverty compared to non-adopters. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):547-554. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 552 furthermore, the value of poverty severity (p2) among the adopters was 0.2522 and 0.4778 for the non-adopters. in view of this, it could be deduced from the study that the adopters of agroforestry technology were better off than the non-adopters of agroforestry technology, as there were records of lower poverty incidence and depth than the non-adopters of the technology. it could therefore be concluded that adoption of agroforestry technology plays significant role in poverty reduction among farming households in the study area. table 2: effect of agroforestry technology on poverty reduction among farming households variable p0 p1 p2 g n adopters 0.3544 0.4733 0.2522 28 79 non-adopters 0.6737 0.6322 0.4778 64 95 p0= poverty incidence; p1= poverty depth (gap); p2= poverty severity; g= no of poor households; n= total no of households findings from the study revealed that the respondents faced some challenges in the adoption of agroforestry technologies by the respondents these challenges, as stated by the respondents were lack of technical assistance, lack of planting materials, long gestation period of trees, lack of knowledge and skills, illegal felling of trees, insufficient land for tree planting, as well as competition among trees and arable crops on farmland. it was also discovered that about 70% of the respondents (both adopters and non-adopters) stated that lack of knowledge and required skills on agroforestry was the main constraint to their adoption of agroforestry, as shown in table 3. this is also in tandem with the study by idumah et al. (2021) in oyo state where lack of knowledge and required skills ranked highest among the factors militating against the adoption of agroforestry technology among farming households. likewise, about 58% of the respondents cited insufficient land as a constraint to the adoption of agroforestry. this, however, is where trainings by extension agents and some subject matter specialists are needed to enlighten the farmers on how to make effective use of their land to accommodate both their tree crops and arable crops. this therefore corroborates studies by amonum and bada (2019) as well as idumah et al. (2021) where lack of land, lack of tree seedlings as well as inadequate extension personnel were stated as some of the constraints affecting the adoption of agroforestry in katsina and oyo states respectively. table 3: constraints to the adoption of agroforestry among farming households in the study area constraint *frequency percentage rank lack of knowledge and skills 121 69.54 1st competition among trees and arable crops on farmland 81 46.55 6th lack of planting materials 86 49.43 4th illegal felling of trees 78 44.83 7th lack of technical assistance 83 47.70 5th long gestation period of trees 106 60.92 2nd insufficient land for tree planting 101 58.05 3rd *multiple responses; source: field survey, 2022 4. conclusion from the study, it can therefore be concluded that the adoption of agroforestry technology plays significant role in reducing poverty among farming households in okunland, kogi state, nigeria. it was found that a smaller number of the adopters of agroforestry fell below the poverty line than the non-adopters. it was therefore concluded that the adopters of agroforestry technology were better off in terms of welfare than the non-adopters of agroforestry technology. agroforestry practices can therefore be said to play prominent role file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com oke et al: influence of agroforestry technology adoption on poverty reduction among farming households in okunland of kogi state, nigeria. azojete, 20(2):547-554. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 553 in the reduction of poverty and the overall improvement in livelihood farming households in the study area. in addition, quite a number of factors were given as constraints to effective adoption of agroforestry technology in the study area by the respondents. some of these included lacks of knowledge and skills, long gestation periods of trees and insufficient land for tree planting, among others. in view of the findings, the recommends that government at all levels as well as relevant stakeholders should make required efforts to increase the adoption of agroforestry technology by creating awareness and sensitizing farmers on significance of adopting agroforestry technology and the associated benefits derivable from agroforestry practices. to accomplish this, extension agents and subject matter specialists on agroforestry should train and enlighten farmers on how best to use their land so as to accommodate both arable and tree crops so as to ensure improved productivity. references adepoju, ao. and okunmadewa, fy. 2010. households’ vulnerability to poverty in ibadan metropolis, oyo state, nigeria. journal of rural economics and development, 20: 1-14. ajayi, oc. and catacutan, dc. 2012. role of externality in the adoption of smallholder agroforestry: case studies from southern africa and southeast asia. in s. sunderasan (ed), externality: economics, management and outcomes, new york, ny: nova science publishers, pp. 167-188. ajayi, oc. akinnifesi, fk. sileshi, g. and chakeredza, s. 2007. adoption of renewable soil fertility replenishment technologies in southern african region: lessons learnt and the way forward. natural resources forum, 31(4): 306-317. amonum, ji. and bada, so. 2019. adoption level of agroforestry practices in katsina state, nigeria. asian research journal of agriculture, 11(2):1-10. beegle, k. christiaensen, l. dabalen, a. and gaddis, i. 2016. poverty in a rising africa. world bank publications. world bank, washington dc. https://doi.org/10.1596/978-1-4648-0723-7. charles, a., kalikoski, d. and macnaughton, a. 2019. addressing the climate change and poverty nexus: a coordinated approach in the context of the 2030 agenda and the paris agreement (report). fao., rome. foster, je., greer, j. and thorbecke, e. 1984. a class of decomposable poverty indices econometrical, 5:761-766. idumah, fo., awe, f., orumwense, la. and oke, do. 2021. assessment of income generating activities among forest fringe communities in cross rivers state of nigeria. journal of agribusiness and rural development, 60: 3 kareem, ia., adekunle, mf.,. adegbite, da. and soaga, ja. 2017.evaluation of selected agroforestry practices and farmers’ perception of climate change in ogun state, nigeria. forest research engineering: international journal, 1(1): 9-16. kennedy, n. amacher, gs. and alexandre, r. 2016. adoption of soil and water conservation practices in central haiti. journal of soil and water conservation, 71(2): 83-90. maduka, sm. 2007. role of agroforestry products in household income and poverty reduction in semiarid areas of misungwi district, mwanza, tanzania. m.sc. dissertation, sokoine university of agriculture, morogoro, tanzania. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com https://doi.org/10.1596/978-1-4648-0723-7 arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):547-554. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: bunmioyetunji@yahoo.com 554 maren, o. and carolyn, es. 2011. climate change adaptation using agroforestry practices: a case study from costa rica. in s. casalegno (ed), global warming impacts: case studies on the economy, human health, and on urban and natural environment. intechopen, london. https://doi.org/10.5772/241727 doc accessed on 23 june, 2022 mutua, j. muriuki, j. gachie, p. bourne, m. and capis, j. 2014. conservation agriculture with trees: principles and practice. a simplified guide for extension staff and farmers (report). world agroforestry centre (icraf), nairobi, kenya. olajuyigbe, s. 2016. potential role of traditional agroforestry in climate change mitigation in rural communities of oyo state nigeria. conference paper presented at the 38th annual conference of the forestry association of nigeria, held at port harcourt, rivers state, nigeria, 38:112. ozowa, b. 2005. making the most of agricultural investment. pdf adobe acrobat document at http://www.ifad.org/agri_investment.pdf. retrieved in november, 2011. rahman, sa., farhana, km., imtiaj, a., wachira, sw., rahman, ma. and saha, s. 2010. sustainable forest management for poverty reduction through agroforestry options: lesson from the remote uplands of eastern bangladesh. libyan agriculture research center journal international, 1(3): 134-141. tiwari, p., kumar, r., thakur, l. and salve, a. 2017. agroforestry for sustainable rural livelihood: a review. international journal of pure applied biosciences, 5(1): 299-309. undp 2019. human development report 2019: inequalities in human development in the 21st century. briefing note for countries on the 2019 human development report. united nations development programme, new york, usa. retrieved from http://hdr.undp.org/sites/all/themes/hdr_theme/country-notes/nga.pdf world bank. 2018. poverty and equity brief in sub-saharan africa, nigeria. april 2018. retrieved from https://databank.worldbank.org/data/download/poverty/33ef03bb-9722-4ae2abc7-aa2972d68afe/archives-2018/global_poveq_nga.pdf world bank 2001. attacking poverty. world development report (draft copy). west african, usa, 352p. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com https://doi.org/10.5772/241727 http://www.ifad.org/agri_investment.pdf http://hdr.undp.org/sites/all/themes/hdr_theme/country-notes/nga.pdf https://databank.worldbank.org/data/download/poverty/33ef03bb-9722-4ae2-abc7-aa2972d68afe/archives-2018/global_poveq_nga.pdf https://databank.worldbank.org/data/download/poverty/33ef03bb-9722-4ae2-abc7-aa2972d68afe/archives-2018/global_poveq_nga.pdf corrsponding author’s email address: emmiesakinwale@gmail.com 72 arid zone journal of engineering, technology & environment original research article homer pro-based approach for designing and optimizing a grid-tied hybrid renewable energy system for a rural community a. s. alayande1, a. e. emmies1*, i. k. okakwu2, o. k.gbenga3, o. s. okeolu4 1 department of electrical and electronics engineering, university of lagos, akoka, nigeria 2 department of electrical and electronics engineering, olabisi onanbajo university, ago-iwoye, nigeria 3electrical maintenance, works and service, yaba college of technology, yaba, lagos, nigeria 4department of electrical and electronic engineering, lagos state university of science and technology, ikorodu, lagos, nigeria *corrsponding author’s email address: emmiesakinwale@gmail.com article information abstract one of the most important elements in our planet is energy, there is a daily rise in the global demand of energy and so renewable sources of energy need to be employed to meet this demand. we understand that renewable sources of energy are not continuous; to resolve these issues, research have proven that combining several renewable sources in a hybrid form would compensate for the discontinuity and decrease emission of harmful chemicals to the environment. based on the epileptic power supply issues for residents in sango ota, an alternative source of power is suggested in this study. sango ota is a fast-developing area with population increasing daily, and load demand needs to be met for residential and commercial activities. this paper presents the optimal planning, design, operation, and techno-economic assessment of a sustainable hybrid renewable energy microgrid system using sango ota, ogun state, nigeria as a case study. the sources of renewable energy considered in this study are wind turbines, solar photovoltaic (pv), diesel generator and storage system (battery). the study employs homer pro application and algorithm to simulate models of the design. this study helps to proffer a solution or an alternative means of generating power at a lesser cost with several options as backup. the study focuses mainly on the residential whose lifetime is 25 years. the return on investment (roi) of this study is positive, which indicates that the project is viable, profitable, efficient and should yield a payback after 4 years. this study has been able to show that a sustainable power supply can be generated using hybrid renewable energy sources from wind, solar, diesel generator and battery. enough energy was generated to meet the load demand, it was cost effective and the capital would be regained in 4 years. auto size gen was preferable for the simulation as it is flexible and adjustable to meet the load demand. submitted: 2nd august 2024 revised: 14th september 2024 accepted: 31st january 2025 keywords: homer generator solar pv wind turbine battery © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in recent years, renewable energy resources have gradually been recognized as one of the best alternatives in supply side planning for micro grids. a good option to conventional power generated from fossil fuel is renewable energy (united states department of energy, 2008). although the energy of the future is renewable energy, but this energy is not consistently available and a lot of challenges will emerge when a single technology is used to supply the load demand from these resources, challenges like high capital cost and intermittence (sabhan kanata et al, 2021). in nigeria, a lot of people in rural areas rely on diesel and kerosene to meet their energy need due to their easy installation. these fuels have some disadvantage like high maintenance and operation cost, distance to transport the fuel, fluctuation of fuel prices, releases of poisonous gas (khodayar, 2017; emilia lnes et al., 2021). a hybrid renewable energy system that is made up of more than two components would help to minimize the aperiodic or discontinuous nature of the system, increase how efficient it is, and maintain balance in the system. azojete march2025. vol.21(1):72-86 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:emmiesakinwale@gmail.com mailto:emmiesakinwale@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 73 in hres, an optimized plan is needed for individual component in order to reduce cost, maximize its efficiency and increase its profitability. the continuity of power supply in renewable energy system is a challenge that must be overcome. from the technical perspective, optimal sizing and configuration was considered, from economic aspect, the net present cost, internal rate of return (irr), return on investment (roi) and levelized cost were considered while the co2 generated to the atmosphere was considered from the environmental perspective. there is an immense growth in renewable energy sources resulting from technological advancement in reduction in cost and production in large quantities in recent years (green, 2017). hres can work in both standalone and grid-connected mode (murugaperumal et al., 2020). some software tools like homer and matlab are introduced and juxtaposed to analyses economical, electrical and environmental performance of hybrid renewable energy system (junga jaesung, 2017). in order to promote the investment in sustainable electricity and renewable energy, the nigerian energy support programme (nesp, 2014) are jointly assisted by european union and federal ministry of economic cooperation and development. a hybrid renewable energy system, in which more than one renewable energy sources are used together, reduces the discontinuity on intermittent nature of renewable energy resources, it provides better overall balances to the energy supply and improves the efficiency of the system. conventional power generation may sometimes lead to renewable energy combinations that are properly designed, planned, or oversized (mohammed et al., 2014). a major source of energy is fossil fuel but it releases a lot of harmful vapors into the surroundings (md mizanur, 2021). homer software was used by agelin-chaab et al (2014) to optimize of a hybrid diesel, solar and wind system to power hypothetical rural area in ghana. a standalone wind/photovoltaic/battery (wt/pv/b) was proposed by krishan (2019) for a rural area in india using homer software, the cost of energy and net present cost was estimated as $0.228$/kwh and $1228,353. micro grids are power systems that are small, autonomous and can operates when the mini grid or main grid experience downtime. the most popular type of mini grid technologies seen is hybrid, wind, solar and hydro (crijns-graus et al., 2014). maleki and askarzadeh, 2014) carried out a study that used the techniques of optimization for optimal sizing. an analysis was carried out on wind/pv diesel hybrid system for electrification with battery as storage, this was in iran. a discrete harmony search-based technique was used for optimizing and sizing the system. the outcomes obtained were compared with the ones of a discrete annealing algorithm that was simulated. an improved ant colony algorithm was proposed by dong, li, and xiang, (2016) for a standalone hybrid wind/battery/pv/ hydrogen system optimal design to provide for the primary load demand of zhejiang in china. reducing the cost incurred annually and increasing the systems reliability was the two main objectives. a hybrid wind/pv system plus a pumped hydro storage (phs) to meet the residential power needs of a hypothetical small and undeveloped village in hong kong was studied by ma et al. (2014). donnado et al. (2019) examined a contemporary software for the sizing of hres optimally. the outcome from comparing 23 case studies using the homer software and the developed tool revealed that hyres was acceptable statistically. one of the objectives of this research is to close the gaps in literature described above by modelling a methodology for optimal planning, design, sizing and techno-economic analysis of a hybrid wind/pv/battery/diesel system to handle the load demand of sango ota, nigeria. the aim of this research is to ensure that the electrical load demand of sango ota is met by generating a steady power supply by hybridizing various renewable energy sources at an affordable cost. to meet this goal, wind, sun, battery and generator were taken as the main components of the renewable system. load consumption of the sango-ota is to be studied, while the various components of the renewable energy system are hybridized and the impact of optimal plan configuration and cost component on the net presence cost were analyzed. the feasibility study of generating sustainable power from wind, sun, battery and diesel has been presented. and this study is to show that a sustainable power supply could be generated using hybrid renewable energy sources from wind, solar, diesel generator and battery in sango area. 2. materials and method a simulation software that helps in the planning and design of a sustainable renewable energy based micro grid is homer (hybrid optimization model for electric renewables). homer is used to model the physical characteristics of an energy supply system and its lifecycle cost, which is the addition of capital, operation cost and techno-economic feasibility (homer energy llc, 2016). the cost analysis, constraints, capital cost, technical http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 74 performance of the system, environmental assessment and result will be put into consideration as indicated in figure 1. figure 1: methodology of proposed hybrid renewable energy system the peak load is 10.19kw and the component for the design is as shown in the figure 2. it also shows the system configuration and operation of the study. g10 is the wind turbine, gen is the generator, pv is the photovoltaic, bae is the battery and conv is the converter. . figure 2: schematic representation for system configuration and operation strategy for the study 2.1 the systems input parameter the daily electricity was estimated at 93.19kwh/day annual average and 10.19kw peak with july as the peak month. according to the wind speed profile, the annual average wind for this area is 3.81m/s. the annual average sun irradiation for the considered micro-grid is 4.76kw/m2/day. with peak as 5.318 kw/m2/day in november. 2.2 modeling of the system components 2.2.1 photovoltaic system modeling several pv cells are combined together to give a module of photovoltaic ( )vp . pv here is 5kw, generic flat plate. the power output of each pv module per hour is given by (dong w. l., 2016) 0( ) ( )t pv tp i a=   1 µpv = efficiency, a = surface area of the pv module, and i(t) = solar insolation (kwm2) per hour. the total power generated can be obtained as: evaluation of climatic condition analysis using simulation and optimization hybrid system model development analysis of electric load demand operational analysis of resulting system http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 75 ( ) 0pv t pvp p n=  2 to estimate the size of the photovoltaic panels that will be tapped, the solar radiation in sango ota can be expressed as (k. r. kamil et al., 2012) ac dc inverter e e  = 3 edc= dc battery energy, eac is ac energy and 𝛔inverter is the efficiency of the inverter (chul-young park, 2020), explains that 90 to 95% is the range for the efficiency of inverter, 0.9 is assumed, the efficient system solar radiation is 0.18, the area of the photovoltaic module is 0.6m2, nominal voltage ( )nv is taken to be 240v as used in nigeria, module voltage ( )mv is 18v, array current is 4a. edc = 93.19/0.9 = 103.54kwh dc panel inverter e a r =  4 r is the solar radiation at kw/day, apanel is the area of the panel, panela = 103.54/(4.76x0.18) = 120.85m2 number of cells (nc) = 𝐴𝑝𝑎𝑛𝑒𝑙 𝐴𝑝𝑣 5 apv is the area of pv module nc = 120.85 𝑜.6 = 201.42, number of series modules ( )ms = vn/vm = 240/18 = 13.33, number of parallel module ( )mp = nc/sm 6 ( )mp = 201/13 = 15.5= 16 modules total power required from panel (ppv) = total power demanded x power lost in the system 7 ( )pvp = 93.19k x 0.2 =18.64kw pv system size = total power required from panel/ panel generation factor (pgf) 8 pv system size = 18.64/4.76 = 3.92kw = 4k 2.2.2 wind turbine modelling the power generated by the generator varies directly with the cube of the wind speed as the wind speed rises above the cut-in velocity. given a constant acceleration, the k.e (kinetic energy) of a body with a speed of v and mass m is the work-done (w) by the body in moving through a distance (s) when a force f is applied to it. therefore .w k e f s m s a= =  =   9 2 2 2v u as= + 10 http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 76 ( )21 2 de dm p v dt dt = = 11 the rate of change of mass flow rate is dm a v dt =   12 ( )2 31 1 2 2 dm p v a v dt = =    13 bertz’ law (1919), proposed that in a perfect situation, no wind turbine can convert more than 59.3% of the kinetic energy of the wind into mechanical energy that rotates the rotor. (united state department of energy, 2015) the available power ( )availablep is 3 max 1 2 available pp v c=    14 according to the report from royal academy of engineering on wind power calculation, the standard radius pf a wind turbine for tapping average wind speed is about 50m. the standard density of air is 1.29kg/m3, from the simulation, the average wind speed of the area under consideration is 3.81m/s. to find the area swept by the turbine from length of the blades by using the equation of the area pf circle is shown as; a = 𝜋𝑟2, hence a = 3.142 x 50 x 50 = 7855m2, ( )availablep = 1 1.29 7855 3.81 0.59 2     = 11.4kw hence 11kw or 12kw wind turbine is considered. 2.2.3 battery modeling in hybrid system, the most used storage system is battery, bc is the charging efficiency of the battery, inv is the inverter efficiency, the number of batteries is nb, the nominal capacity of a battery measured in kwh is cb, and the self-discharge rate per rate per hour is α (k. r. kamil et al., 2012) total ah per day ( ) ( ) ( ) dc l n e ah s v =  15 total ah per day ( ) ( ) ( ) 103.5 1000 0.2 240 ah  =  = 86.28ah storage days = 9.43 – (1.9 x peak hours of sun) + (0.11 x peak hours of sun) 16 = 9.43 – (1.9 x 2) + (0.11 x 2) = 5.41 = 5 days battery capacity = ( ) ( ) h d a d 17 = (86.28 x 5)/0.4 = 1078.54ah number of cells in series = vn vb = 240/12 = 20 18 http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 77 20 batteries would be suggested for the design in this study. optimization model analysis 2.3.1 decision variables the following are the quantities which can be controlled in this study, the number of batteries ( batn ), number of wind turbines ( )wtn , number of pv modules ( )pvn and capacity rating of the diesel generator ( )rdp (nasser yimen et al., 2020) 2.3.2 objective functions the objective function of this research is to find the minimized total cost of implementing and generating energy through this proposed hybrid renewable energy system. hence the focal point is the amount of total annualized cost .ann totc (nasser yimen et al., 2020). ( ), , , , , , , ,, , , , covann tot k ann cap k operating k rpl k f k a kk bat wt pv dg inv c c c c c s      = + + + − 19 . ,ann cap kc ,operating kc , ,rpl kc , ,f kc ,a ks the annual capital cost, operating and maintenance cost, replacement cost, fuel cost and salvage value respectively of the component k. the annual present worth is the product of the capital recovery factor crf and present worth. the ( , )i ncrf = (1 ) (1 ) 1 n n i i i + + − 20 where i is the interest rate and n is the life span of the system which is 20 years. , ,{ , , , , } ( ) cov inv ann tot kk bat wt pv dg c  = ( , ). . . . . )wt wt pv pv bat bat dg rd inv inv i n con con c p c n c n c p c n crf+ + + +  21 wtc , pvc , batc , inv con c represents the cost of installing one unit of wind turbines, pv, battery and converters respectively and dgc is the cost of installing a kw of diesel generator. the operation and maintenance cost for wind turbine, pv and diesel generator is: ,{ , , , , } ( )cov inv operating kk bat wt pv dg c  = 8760 ( )1 ( & . & . & . )wt wt pv pv dg dg tt o m n o m n o m p = + +  22 & wtco m & wtco m , & wtco m are the operation and maintenance cost of a unit wind turbine, pv and diesel generator respectively. to find the replacement cost for the batteries, diesel generator and converters. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 78 ,( )rpl kk c = ( ) ( , ) .5 10 15 10 1 1 1 1 . . . . (1 ) (1 ) (1 )1 i n bat bat inv inv r dg con con crf r n r n p c i i ii        + + + +     + + ++     23 the salvage value can be found by: . rem k k com l s c l = 24 2.3.3 constraints these are the conditions which the decision variables need to adhere to 1. the systems variable constraints is kn =integer, k 𝜖 {bat, wt, pv} 2. the bound constraints is 0 ≤ kn ≤ maxkn − , k 𝜖 {bat, wt, pv} & 0 ≤ rp ≤ maxrp − where maxkn − is the maximum available number of k component 3. the renewable fraction constraints 8760 ( ) *1 8760 ( )1 1 100 dg tt l tt p ref ref p = =    = −         where ref* represent the minimum allowable renewable energy fraction of power supply in a period t. 3. results and discussion 3.1 cost summary as seen in table 1, the net present cost n134,795,000.00, levelized cost n180.17 and operating cost n4484,822.00 are all based on the model and parameters inputted into the system, one of which the fuel price is n800/liter. generator = 12.0kw, pv = 25.0kw, converter = 10.0kw table 1: cost presentation total npc n134,795,000.00 levelized coe n180.17 operating cost n4,484,822.00 as presented in figure 3, the generic lead acid battery has a higher net present cost as a result of the quantities needed to be purchased and cost of maintaining them. twenty batteries were proposed for this project http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 79 figure 3: cost summary. as seen in the table 2, the operation and maintenance cost of generic lead acid battery is the highest with a high cost of fueling the generator throughout the year. the generic flat plate pv has a zero-replacement cost, it has a high life span, although its maintenance and operating cost is appreciably high. the storage, wind, generic flat plate and converter has zero fuel cost because they don’t require fuel to be powered. table 2: cost summary component capital (n) replacement (n) o&m (n) fuel (n) salvage (n) total (n) autosize genset 10,800.00 8,009.01 6,588.15 22,953,208.08 (4,579.81) 22,974,025.43 generic 10kw 14,000,000.00 11,450,697.13 52,789.65 0.00 (8,167.124.27) 17,336,362.50 generic 10kw lead acid 19,500,000.00 66,950,125.53 17,156,634.63 0.00 (14,436,646.44) 89,170,113.72 generic flat plate pv 2,562,500.00 0.00 2,474,514.61 0.00 0.00 5,037,014.61 generic large, free converter 75,000.00 53,753.65 164,976.64 0.00 (16,204.61) 277,516.68 system 36,148,300.00 78,462,585.31 19,855,494.67 22,953,208.08 (22,624,555.14) 134,795,032.93 3.2 the roi (return on investment): indicates the measure of profitability and performance or efficiency of the systems design, it measures the profit generated from the project. the roi of this project is positive and it indicates that the project is viable, the value is 13.4%. following the result in table 3, the return on investment (roi) is +13.4.0% which is positive. it means the project is viable, feasible and there will be return on investment. hence there is room for profitability, the project has a good internal rate of return and the simple payback year is 4, fuel price = 800$/l http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 80 table 3: compare economics metric and value metric value present worth (n) n94,741,740.00 annual worth (n/yr.) n4,307,288.00 return on investment (%) 13.4 internal rate of return (%) 19.8 simple playback (yr.) 4.01 discounted payback (yr) 4.11 as seen in table 3, the simple back year is 4.01, by implication, it means in for 4 years time the expenses incurred in implementing the project will be regained. 3.1.2 electricals as shown in figure 4, there is almost a zero amount of energy generated from diesel in the month of february. from the solar radiation graph, it is understood that february had a higher solar radiation, this accounts for the low level of energy obtained from the generator as most of the supplies is from the pv and wind as seen in figure 4. the reverse is the case for some months like june, july and august. figure 4: monthly average electric production it can be seen from table 4 that larger percentage of energy is released from the generic flat plate due to the high level of solar irradiation; no dc load was consumed; the system was designed to generate ac load for consumers all through the year and this is why we have a zero dc output. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 81 table 4: electrical components production kwh/yr % generic flat plate pv 35,059 62.3 autosize gen set 3,255 5.79 generic wind turbine 17, 941 31.9 total 56,254 100 from table 5 we can see that the load consumption is totally ac, because the system is designed to supply alternating load. table 5: load consumption capacity. consumption kwh/yr % ac primary load 34, 013 100 dc primary load 0 0 total 34, 013 0 it was depicted in table 6 that excess electricity of 28.2% is generated over the year and no unmet energy. which indicates that the energy requirement of the town would be met table 6: useful electricity breakdown quantity kwh/yr % excess electricity 15,846 28.2 unmet electric load 0 0 capacity storage 0 0 3.1.3 auto size gen as shown in figure 5, there is almost a zero amount of energy generated from diesel in the month of february. it is the other way round for some months like june, july, august and september. these months have high rainfall and the weather tends to be cloudy. the implication is that a more energy will be required from the diesel generator and it will be made to do a lot of work in these months, also there will be high cost of diesel and maintenance for the generator. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 82 figure 5: auto size gen simulation result. as depicted in the table 7, the year electrical production for the generator is 3,255kw/yr. 3.91kw being mean power and 3.00kw minimum power. table 7: generator production capacity quantity value unit electrical production 3,255 kw/yr mean electrical output 3.91 kw minimum electrical output 3.00 kw maximum electrical output 9.66 kw 3.1.4 generic large free converter the pv needs the inverter to convert the power to its alternating form. hence the inverters work is dependent on the pv shown in the figure 6. the maximum output power of the inverter is 10kw. the converter was originally modelled for 12kw. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 83 figure 6: generic large free converter output result. it can be deduced from table 8 that the inverter has a higher hour of operation as the system is based on alternating output. table 8: performance features of converter quantity inverter rectifier units hours of operation 6,959 1,011 hrs/yr energy out 21,985 2,146 kwh/yr energy in 24,428 2,385 kwh/yr losses 2,443 238 kwh/yr 3.2 comparing the combination of various components output it can be seen that the 56,254kwh/yr. produced by the hybridization of the renewable energy sources is higher than the estimated power or load demand of 34,107.54kwh/yr. consumed by the residents of sango ota annually. 3.2.1 hybrid of wind and solar sources from the simulation result above, the summation of the electrical power generated from solar which is 35,059kwh/yr and that of the wind is 17,941kwh/yr is 5300kwh/yr which is far above the annual load demand. since 35059kwh/yr can be obtained from solar, it means it can stand alone. although for better efficiency and continuity it would be advised to be hybridized. 3.3.2 hybrid of diesel generator and wind turbine. from the result the diesel generator produces 3255kwh/yr while the wind turbine generates 17941kwh/yr, to optimize the system, two (2) wind turbines would be needed to hybridize the diesel generator. the expected energy from the five 10kw wind turbine = 2 x 17,941=35,882kwh/yr. since the diesel generator could generate 3255kwh/yr, then total energy obtained in the hybrid of diesel generator and five wind turbines = 3255 +35,882 = 39137kwh/yr a total of 39,137kwh/yr is optimal enough to balance the 34,107kwh/yr load demand. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 84 4. conclusion in this research paper, optimal design and planning of a sustainable hybrid renewable energy system in micro grids for sango ota, ogun was carried out with wind, solar, battery and diesel generator as the components and inputs on their economic, physical and operational features were put into considerations. the major aim of this study is to optimize the generation of sustainable power to supply and balance the electrical load demand and this aim has been achieved as the power generated 56,254kwh/yr exceeds the load demand for sango which is 34,107.54kwh/yr. from this study, it is crystal clear that sango is potentially filled with high renewable energy resources which if efficiently tapped would reduce epileptic power supply in the sango. exploration of renewable energy is a good alternative to promotes continuous power supply to populated cities and rural areas in nigeria. the design would compensate for the increasing population for a long time, also homer pro has made the analysis very easy. for continuity and reliability of power supply, the renewable resources should be hybrid. similarly, from the analysis the capital for the initial investment will be recovered in four years as shown from the payback time. from the value of the roi and irr, the system is environmentally friendly has it can be less dependent on diesel since an excess energy is already produced hence reducing emission into the environment. the return on investment (roi) of this study is positive, which indicates that the project is viable, profitable, efficient and should yield a payback after 4 years. this study has been able to show that a sustainable power supply can be generated using hybrid renewable energy sources from wind, solar, diesel generator and battery. enough energy will be generated to meet the load demand, it is cost effective and the capital would be regained in 4 years. auto size gen was preferable for the simulation as it is flexible and adjustable to meet the load demand. references united states department of energy. 2008. 20% wind energy by 2030: increasing wind energy’s contribution to u.s. electricity supply. energy efficiency and renewable energy report, doe/go102008-2567. sabhan, k., syamsyarief, b., ali, m., purwono, p. and toto, w. 2021. optimal planning of hybrid renewable energy system using homer in sebesi island, indonesia. international journal or renewable energy research, 1(4): 1508-1515. emilia, l., zebra, c., henny, j., van, w., nhumaio g., andre, p., and faaij, c. 2021. renewable and sustainable energy review, (44): 111036 khodayar, me. 2017. rural electrification and expansion planning of off-grid microgrids. electric journal, (30): 68-74. murugaperumal, k., srinivasn, s. and satya, p. 2019. optimum design of hybrid renewable energy system through load forecasting and different operating strategies for rural electrification. sustainable energy technology assessment, 37(613): 2020. green, ma., hishikawa, y., warta, w., dunlop, ed., levi, dh., hohl-ebinger, j. and ho-baillie, a.w. 2017. solar cell efficiency tables (v 50). progress photovoltaic research application, 25(7): 668-676. jaesung j., michael v., 2017. optimal planning and design of hybrid renewable energy systems for microgrids, renewable and sustainable energy reviews. 75: 180-191. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 85 (nesp) nigeria energy support program. 2014. building energy efficiency guidelines for nigeria (beegn), 2(3): 1-9. mizani, s., and amirnaser y. 2009. optimal design and operation of a grid-connected microgrid. in electrical power & energy conference (epec), 2009 ieee, 1-6. homer energy llc. 2016. homer pro. homer energy, https://homerenergy.com/products/pro/latest/homers_calculations.html. mohammed, ys., mustafa, mw. and bashir, n. 2014. hybrid renewable energy systems for off-grid electric power: review of substantial issues, renewable sustainable energy 35: 527-539. mizanur, m., mary, dk. and peter, k. 2021. techno-economic analysis of hres in south-east of ireland. ifac conference paper archive, 54(13): 454-459. agelin-chaab, m., adaramola, ms. and paul, ss. 2014. analysis of hybrid energy systems for application in southern ghana. energy conversion management, 88: 284–295. krishan, o. and suhag, s. 2019. techno-economic analysis of a hybrid renewable energy system for an energy poor rural community. journal of energy storage, 23: 305-319. crijns-graus, w., soshinskaya, m., guerrero, j. and vasquez, j. 2014. microgrids: experiences, barriers and success factors. renewable sustainable energy 40: 659-672. maleki, a. and askarzadeh, a. 2014. optimal sizing of a pv/wind/diesel system with battery storage for electrification to an off-grid remote region: a case study of farsanjan, iran. sustainable energy technologies and assessments, 7: 147-153. dong, w., li, y. and xiang, j. 2016. optimal sizing of a standalone hybrid power system based on battery/hydrogen with an improved ant colony optimization. energies, 9: 785-789. nasser, y., theodore, t., abraham, k., idriss-abdelkhalikh, i., bashir, m., aliyu, a., eric-c, o., sani-isa, a., daniel, t., lucien, m., oumarou, h. and mustafa d. 2020. optimal sizing and techno-economic analysis of hybrid renewable energy systems a case study of a photovoltaic/wind/battery/diesel system in fanisau. northern nigeria, processes, 8(138):1-25 ma, t., yang, h., lu, l. and peng, j. 2014. technical feasibility study on a standalone hybrid solar-wind system with pumped hydro storage for remote island in hong kong. renew energy, 69: 7-15 donnado, k., navarro, l. and pardo, m. 2019. hyres: a multi-objective optimization tool for proper configuration of renewable hybrid energy systems. energies, 13:1-26. homer energy llc. 2016. homer pro. homer energy. available: https://www.homerenergy.com/products/pro/docs/latest/homers_calculations.html. kamil, r., yusuf, o., yakubu, a. and seriki, b. 2012. renewable energy resources hybridization as an efficient and cost-effective alternative for electrification. nigerian journal of technological development, 18:174-183. chul-young, p., seok-hoon, h., su-chang, l., beob-seong, s., sung-wook, p., jun-ho, h. and jongchan k. 2020. inverter efficiency analysis model based on solar power estimation using solar radiation," processes, 8(1225):1-19. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):72-86. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corrsponding author’s email address: emmiesakinwale@gmail.com 86 united state department of energy. 2015. windvision: a new era for wind power in the united states, report doe/go-102015-4557 ramoji, sk., rath, bb., kumar, dv. 2014. optimization of hybrid pv/wind energy system using genetic algorithm (ga). oisr journal of engineering research, 4:29-37. http://www.azojete.com.ng/ mailto:emmiesakinwale@gmail.com arid zone journal of engineering, technology & environment azojete december 2022. vol. 18(4):683-692 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2644, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 683 original research article simulation and experimental study of tensile strength of ukam fibre reinforced polyester composites using ansys g. e. okpanachi*, a. s. hassan, el – m. a. ahmed, s. u. hussein and f. alapa centre for satellite technology development, national space research and development agency, abuja, nigeria. *corresponding author’s email address: okpanachi.george@cstd.nasrda.gov.ng 1.0 introduction over the past few decades, there has been a growing interest in the use of natural fibres in composite applications and the needs for green environment has motivated researchers to seek for an eco-friendly alternative (jeyasekaran, 2016; nishieo et al., 2003; aondona, 2017). these types of composites present many advantages compared to synthetic fibres, such as low tool wear, low density, cheaper cost, availability, and biodegradability (zampaloni, 2007). fibre reinforced composite materials have been increasingly used as structural members in many structures such as airplane, which in flight condition undergoes temperature as low as 60°c or in acryogenic tank which may be exposed to temperature below -150°c (ogakwu and okpanachi, 2016). composite materials have the potential of reducing costs in construction, operation and development while improving structural reliability and enhancing safety. because of these unique specifications, they are widely used in high technology structural applications, such as aeronautic and aerospace (nishiro et al., 2003). cochlospermum planchonii known locally as ukam fibres grow in savannah and forest savannah in west africa. they are cellulose based natural fibres with good mechanical properties, low density, abundant and renewable (aondona, 2017 and olusegun et al., 2012). the people of the area where these plants are found use their fibres as sponge and also to article information abstract polymers are commonly used in different applications even though it causes environmental problems. natural fibre reinforced composites can be used as substitute for the synthetic fibre composites because of their biodegradable properties which will be a key to solving environmental problems although, the strength of natural fibres is not as high as glass fibres, their specific properties are comparable. the hand lay–up method of fabrication was employed in preparing the composite. this study investigates the tensile strength of the composite using experimental and numerical method. the test specimen of natural composite was fabricated using astm standard and the tensile strength of the composite determined using hounsfield tensometer. a 3d finite element (fe) model was created to simulate tensile strength in ansys 18. alkali treated samples exhibited the highest increase in tensile strength at all fibre loadings. modulus of elasticity (moe) and percentage elongation also increased with increase in fibre loading for all treatments. the experimental values of tensile strength at 25 % were in agreement with the fem tensile strength using ansys. © 2022 faculty of engineering, university of maiduguri, nigeria. all rights reserved. submitted 21 april, 2022 revised 14 june, 2022 accepted 20 june, 2022 keywords: ansys composites ukam tensile strength reinforcement finite element http://www.azojete.com.ng/ mailto:okpanachi.george@cstd.nasrda.gov.ng mailto:okpanachi.george@cstd.nasrda.gov.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):683-692 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 684 reinforce clay with which they produced intricate earthen pots and silos (ihom and onah, 2016). olusegun et al. (2012) evaluated the mechanical properties of ukam, banana, sisal, coconut, hemp and e-glass fibre reinforced laminates to assess the possibility of using them as new material in engineering applications. samples were fabricated by the hand lay-up process (30:70 fibre and matrix ratio by weight) and the properties evaluated using the instron material testing system. the mechanical properties were tested and showed that glass laminate has the maximum tensile strength of 63 mpa, bending strength of 0.5 mpa, compressive strength of 37.75 mpa and the impact strength of 17.82 j/m2. the ukam plant fibre laminate has the maximum tensile strength of 16.25 mpa and the impact strength of 9.8 j/m among the natural fibres.the mechanical properties such as tensile strength, flexural strength, impact strength and water absorption properties of ukam, sisal and banana fibres reinforced composites have been observed and found that there is the significant improvement in mechanical strength and reduction in water absorption rate while hybridizing the banana fibre with sisal fibre reinforced composites (ihom and onah, 2015). the ukam/glass fibre reinforced composites have good tensile property with minimum deflection when compared to the flax/glass composites (aondona, 2017). also the ukam fibres reinforced composites hold more flexural and impact strengths when compared to the flax/glass fibres reinforced polymer composites. banana, hemp and glass fibre reinforced hybrid composites have been developed and the mechanical properties of these composites were evaluated (olusegun et al., 2006). velmurugan et al. (2015) carried out the analysis of tensile properties of palmyra fibre reinforced epoxy composite. the simulation according to jeyasekaran et al. (2016) was carried out using fea under different fibre volume fraction and fibre length and validated with the experimental result and found to have less error percentage. ramakrishnan et al. (2010) investigated the mechanical properties of vinyl ester resin reinforced with different weight fractions of 17 selected natural fibres by mathematical modelling and ansys simulation. from the observations, it is evident that increase in fibre content significantly improves the mechanical properties. the theoretical and ansys results indicate that vinyl ester reinforced with the fibres abaca, hemp and banana shows better tensile strength properties. the highest tensile modulus values are obtained for the fibres ramie, abaca, and sisal incorporated in vinyl ester. similarly, for toughness and impact strength applications, the fibres banana, sisal and cotton are found to be suitable reinforcement for vinyl ester resin. venkateshwaran et al. (2010) suggested in construction, automobile and manufacturing industries, composites with natural fibres are highly expected because of its high tensile strength and modulus, as well as for its low density and low elongation. from the available literature, it has been found that, the quantitative analysis on the mechanical properties of these composites is still a valid problem, and hence, there is a need for carrying out such studies on composite materials. to take the advantage of ukam fibres, they have been reinforced with a polyester resin, so that an optimal and economical composite is obtained. hence the objective of the present study is to investigate the tensile strength of the composite. the experimental results are compared with results obtained from finite element analysis (fea) using ansys software. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi.george@cstd.nasrda.gov.ng okpanachi et al: simulation and experimental study of tensile strength of ukam fibre reinforced polyester composites using ansys. azojete, 18(4):683-692. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 685 2. materials and methods 2.1 materials some of the materials used in this study include; cobalt methyl ethyl ketone peroxide (mekp) ukam fibre polyester resin polyvinyl alcohol (pva) potassium permanganate (kmno4) acetic acid silane solution sodium hydroxide the ukam fiber utilized is presented in figure 1. figure 1: produced ukam fibres 2.2 methods 2.2.1 alkali treatment this treatment is carried out in order to produce the modified fibres for the composites and the treatment process involves the use of sodium hydroxide solution in accordance with liu et al., (2009). the ukam fibres were then soaked in naoh of 5 % concentration at room temperature for 24 hours. to remove any alkali solution sticking to the fibre surface the fibres were washed severally with water neutralized with dilute acetic acid and then washed again with water. 2.2.2 silane treatment the treatment is carried out in order to produce modified fibres for the composites and the treatment process involves the use of silane solution dissolved in water (valadez – gonzalex et al., 2008). the ukam fibres were immersed in silane dissolved in a water-ethanol mixture for 3 hours. the potential of hydrogen of the solution was 9.0. this contains 60 % ethanol and 40 % water mixed well and allowed to stand for an hou 2.2.3 potassium permanganate (kmno4) treatment the treatment is carried out in order to produce modified fibres for the composites and the treatment process involves the use of 0.5 % of potassium permanganate dissolved in acetone was used in soaking the alkali treated fibres for half an hour after been thoroughly washed with water. distilled water was used in soaking the permanganate fibre for ten minutes in order to catalyse the reaction. furthermore, the fibres were sun dried after it was decanted http://www.azojete.com.ng/ mailto:okpanachi.george@cstd.nasrda.gov.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):683-692 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 686 2.2.4 acetylation the treatment is carried out in order to produce modified fibres for the composites and the treatment process involves the use of ukam fibres been soaked in demineralized water for an hour, filtered and placed in a flask, containing acetylating solution (bledzki et al., 2008). acetylating solution is made of 250 ml toluene, 125 ml acetic anhydride and a small amount of catalyst per chloric acid (60 %). the process temperature of acetylation was 60oc and duration of 1 to 3 hour. after modification, the fibre was washed thoroughly with distilled water until acid free. the treated fibres were sun dried before the manufacturing of the composites. 2.2.5 determination of tensile strength tensile strength test was conducted using hounsfield (monsanto) tensometer (model no. s/n 8889) according to astm d 638 – 03 (croccolo et al., 2013). the width and the thickness of the specimens were measured and recorded (360mm by 20mm by 5mm) from the test, elastic modulus, ultimate tensile strength and percentage elongation were determined. 2.3 finite element modeling and analysis finite element analysis provide safe simulation of destructive load conditions and failure modes. a 3d fe model was created to simulate tensile in ansys 18. solving the numerical simulation was conducted based on laboratory conditions used in a practical test for the tensile test where the shape and geometry of the sample process and the boundary conditions were taken into consideration. for performing this analysis the material property, young’s modulus, poisson’s ratio, density, boundary conditions and load conditions were applied similar to the experimental condition and these were obtained from the experimental results. shell elements are typically used for structure where the thickness is negligible compared to its length and width. nevertheless, a plate modeled with solid element would provide similar results. the disadvantage lies in the computation time. ansys provides large choices of elements (desal and abeljf, 1977). two main aspects of the procedure are modeling the specimen, and calculating the stresses to failure. 2.3.1 preprocessor steps the 3d model was created using the dimension of the specimens used in the experiment as shown in figure 2 (d638 – 03, 2005). the model created is made up of the polyester resin and the fibres. the model of the composite is to discretize the model into small elements. the mesh of the model (shell 181) is created with 8-nodes and each node has (6 degrees of freedom) with element size of and using the free meshing type to mesh all the models as shown in figure 3. 2.3.2 solution processor the analysis of the composite is conducted using ansys. the tensile load is applied as distributed load on the nodes at one end of the model the same as the load values in experimental test and with the model at the other end fixed. these steps are repeated for each model of tensile composition with fibre surface treatment (hassan et al., 2013). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi.george@cstd.nasrda.gov.ng okpanachi et al: simulation and experimental study of tensile strength of ukam fibre reinforced polyester composites using ansys. azojete, 18(4):683-692. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 687 figure 2: geometry of tensile simulation specimen on ansys workbench figure 3: boundary condition and load applied for ansys work bench model 3. results and discussion the experimental tensile strength as presented in figure 4 and table 1 was observed to increase with increase in fibre loading for all the treatments. fibres are normally stronger and stiffer than the matrix, therefore strength of composites are generally seen to increase with increased fibre loading (olusegun et al., 2012). an exceptional increase in tensile strength was noticed in alkali treated samples at all fibre loading. this means that alkali treated samples exhibited the highest increase in tensile strength at all fibre loadings. this is because during alkaline treatment, hemicellulose and lignin are removed, the interfibrillar regions are likely to be less dense and less rigid, and that makes the fibrils moreable to rearrange themselves along the direction of tensile loading. olusegun et al. (2012) was of the opinion that physical and chemical treatments improved the wettability of fibre and thus improve the interfacial strength leading to improvement in mechanical properties as the cellulose structure is totally modified. http://www.azojete.com.ng/ mailto:okpanachi.george@cstd.nasrda.gov.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):683-692 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 688 figure 4: influence of surface treatment and fibre composition on tensile strength of composites table 1: summary of tensile strength test results summary composition (%) uts(δ) (mpa) % elongation modulus of elasticity alkali 5 181.95 12 1.5276 10 210.60 15 1.5531 15 326.35 20 1.7504 20 333.2 21 1.9578 25 326.9 23 2.7521 silane 5 157.54 13 1.5046 10 171.24 15 1.9319 15 207.04 17 2.0808 20 213.83 17.9 1.4196 25 224.59 19 2.3668 kmno4 5 135.23 7 1.4120 10 140.22 9.3 1.7703 15 135.13 7 1.5922 20 149.45 10 1.3238 25 223.22 18 1.906 acetylation 5 143.17 8 1.2640 10 151.07 10 1.0543 15 158.97 11 1.2640 20 159.67 11 1.6852 25 172.81 15 1.7677 untreated 5 126.86 5 1.0218 10 129.31 6 1.0364 15 133.83 6 1.1582 20 146.86 9 1.2061 25 163.22 14 1.7837 0 50 100 150 200 250 300 350 5 10 15 20 25 u lt im at e t e n si le s tr e n gt h m p a fibre loading (wt%) alkali silane kmno4 acetylation untreated file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi.george@cstd.nasrda.gov.ng okpanachi et al: simulation and experimental study of tensile strength of ukam fibre reinforced polyester composites using ansys. azojete, 18(4):683-692. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 689 figures 5 – 9 present the fe (ansys) simulation results for the composite to study the effect of fibre surface treatment and fibre loading on the tensile properties of composites at 25 % fibre loading for all the treatments. colours were used to differentiate regions of stress concentration with red showing regions with the highest value of stress concentration. the highest levels of stress concentrations were observed to be at the sharp corners of the von mises sample. the predicted tensile strength values by fe model matched with the experimental values. this was also confirmed by the regression of the predicted and experimental tensile strength presented in figure 10. however, there was high correlation between the predicted and experimental tensile strength with r2 value of 0.9994. hence, the visual checking of predicted and experimental values confirms that the fe model was successful in predicting tensile strength. moderate percentage error was observed between experimental and fea. the slight difference in results between fea and experimental analysis is due to true loading condition and method of composite fabrication compared with the experimental tensile test (prasad et al., 2014). figure. 5: contour plots showing regions of stress concentration for untreated fibres figure. 6: contour plots showing regions of stress concentration for acetylation treated fibres http://www.azojete.com.ng/ mailto:okpanachi.george@cstd.nasrda.gov.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):683-692 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 690 figure.7: contour plots showing regions of stress concentration for alkali treated fibres figure. 8: contour plots showing regions of stress concentration for kmno4 treated fibres figure. 9: contour plots showing regions of stress concentration for silane treated fibres file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi.george@cstd.nasrda.gov.ng okpanachi et al: simulation and experimental study of tensile strength of ukam fibre reinforced polyester composites using ansys. azojete, 18(4):683-692. issn 1596-2644; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 691 figure. 10: correlation of predicted with experimental tensile strength using finite element modelling 4. conclusion ukam fibre reinforced composites was prepared to experimentally investigate the tensile strength of the composites. a 3d fe model was created using the experimental data and ansys software to numerically investigate the tensile strength of the composites. additionally, the experimental result was compared with numerical result which shows that alkali treated samples exhibited the highest increase in tensile strength at all fibre loadings. modulus of elasticity (moe) and percentage elongation also increased with increase in fibre loading for all treatments. the experimental values of tensile strength at 25 % were in agreement with the fem tensile strength using ansys. there was high correlation between the predicted and experimental tensile strength with r2 value of 0.9994. the objectives set out in the study was achieved. references a. book standard, d638-03 2003. standard test method for tensile properties of plastics. american society for. testing and materials, astm international. astm e111-04,1 144 andrew, op. and echiye, og. 2016. applications of composite materials in the development of aerospace industry. journal of engineering and applied scientific research, 8(1):75-78 bledzki, ak., mamun, aa., lucka-gabor, m. and gutowski, vs. 2008. the effects of acetylation on properties of flax fibre and its polypropylene composites. express polymer letters, 2(6): 413-422. croccolo, d., de agostinis, m. and olmi, g. 2013. experimental characterization and analytical modelling of the mechanical behaviour of fused deposition processed parts made of abs-m30. computational materials science, 79: 506-518. desai, cs. and abel, jf. 1971. introduction to the finite element method; a numerical method for engineering analysis. new york, van nostrand reinhold co. 34 -45 hossain, mr., islam, ma., van vuurea, a. and verpoest, i. 2013. tensile behavior of environment friendly jute epoxy laminated composite. procedia engineering, 56: 782-788. r² = 0.9994 0 50 100 150 200 250 300 350 400 150 170 190 210 230 250 270 290 310 330 350 p re d ic te d t e n si le s tr e n gt h ( m p a) experimental tensile strength (mpa) http://www.azojete.com.ng/ mailto:okpanachi.george@cstd.nasrda.gov.ng arid zone journal of engineering, technology and environment, december, 2022; vol. 18(4):683-692 issn 1596-2644; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: okpanachi.george@cstd.nasrda.gov.ng 692 ihom, ap. and onah, do. 2016. the effects of ukam (cochlospermum planchonii) plant fibre variation on the properties of polyester matrix fibre reinforced composite. mechanical material science and engineering, 46: 7-13 jeyasekaran, as., kumar, kp. and rajarajan, s. 2016. 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engineering, 11(1): 780-784. prasad, v., venkatachalam, g., rathi, a. and rajakumar, s. 2014. finite element analysis of jute fibre made hybrid polymer matrix composite. applied mechanics and materials, 592: 363-367. ramakrishnan, s., sathish, k. and santosh, s. 2010. theoretical prediction on the mechanical behavior of natural fibre reinforced vinyl ester composites. applied science and advanced material international, 1(3): 85-92. valadez-gonzalez, a., cervantes-uc, jm., olayo, r. and herrera-franco, f. 1999. effect of fibre surface treatment on the fibre–matrix bond strength of natural fibre reinforced composites. composites part b, engineering, 30(3): 309-320. velmurugan, g., vadivel, d., arravind, r., vengatesan, sp., mathiazhagan, m and nachimuthu, a. 2015. tensile test analysis of natural fibre reinforced composite. international journal of mechanical and industrial engineering, 2(2): 2231 2243 venkateshwaran, n. and elayaperumal, a. 2010. banana fibre reinforced polymer compositesa review. journal of reinforced plastic and composites, 29(15): 2387-2396. zampaloni, m., pourboghrat, f., yankovich, sa., rodgers, bw., moore, j., drzal, lt., mohanty, ak. and misra, m. 2007. kenaf natural fibre reinforced polypropylene composites: a discussion on manufacturing problems and solutions. composite part a: applied science manufacturing, 38(6): 1569-1580 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:okpanachi.george@cstd.nasrda.gov.ng arid zone journal of engineering, technology & environment azojete june 2024. vol. 20(2):555-562 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 555 influence of rubber crumbs on the structural efficiency of concrete made from ceramic tile aggregates a. adetiloye1*, j. o. akinyele1, o. w. adeoye1 and j. o. labiran2 1department of civil engineering, federal university of agriculture, abeokuta, ogun state, nigeria. 2department of civil engineering, university of ibadan, oyo state, nigeria. *corresponding author's email address: adetiloyea@funaab.edu.ng article information submitted 4 january, 2024 revised 28 february, 2024 accepted 25 march, 2024 keywords: ceramic tiles tyre rubber crumbs granite sand cement. abstract the indiscriminate dumping of used tyres and construction waste like ceramic tiles has contributed to the present unclean environment. as part of the efforts in the recycling of these waste materials, they were both introduced to concrete, and the effect of these two materials on the structural properties of concrete was studied in this work. crushed ceramic tiles were used to totally replace granite as the coarse aggregate, while crushed tyre rubber crumbs replaced sand as fine aggregate (0%, 5% and 10%), designated as c0, c5 and c10 respectively. the mix ratio was 1:2:2 for cement, fine and coarse aggregates at 0.5 water/cement ratio, concrete was cured for 7 and 28 days. 100 x 100 x 100 mm concrete cubes were used for the compressive and 100 x 100 x 750 mm beam was used for the flexural strength tests. the results obtained from both compressive and flexural tests showed a general reduction in strength, this was due to the ceramic tiles that absorbed excess water into the concrete. the aci 209r-92 equations for the prediction of concrete strength were used to determine the one-year strength of the concrete samples. statistical analysis showed that the r2 of the strength within one year was 0.83 and 0.77 for the c0 and c5 samples respectively. the presence of rubber crumbs served as fillers, especially in the c5 samples. it was concluded that crushed ceramic tiles and rubber crumbs could be used in structural concrete, but should not exceed 5% of rubber crumbs. 1.0 introduction efforts are been made by different researchers in the introduction of alternative materials, especially the recycling of waste materials in concrete. it is believed that natural materials should be conserved, and waste materials should be recycled in concrete. in the past, several works have been done in the use of recycled materials in concrete. (khaloo et al., 2008) used both mechanical and non-destructive tests to determine the properties of rubberized concrete of varying rubber tyre particles. the research was able to reveal the behavior of concrete under compressive strain. many researches work such as (karakurt, 2015; mohammadi and khabbaz, 2015; thomas et al., 2015; thomas and gupta, 2015) have used rubber in concrete as either fine or coarse aggregate with some very interesting results that has encouraged more research to be carried out on this subject. akinyele et al. (2016) determined the influence of rubber crumbs on the chemical, mechanical and microstructural characteristics of concrete. the work resolved that rubber crumbs affected the strength of concrete negatively after about 8% replacement of fine aggregate. gupta et al. (2015) investigated the use of crumb rubber as fine aggregates, and the http://www.azojete.com.ng/ mailto:m.ishaq@unimaid.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):555-562. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 556 effect on concrete properties. six replicate of rubber crumb fibers (0%, 5%, 10%, 15%, 20% and 25%) were used in the work. the study revealed that the durability and impact resistance of concrete can be improved upon by using rubber fiber in concrete. duarte et al. (2015) carried out numerical procedure using the split tensile test to evaluate the mechanical behavior of rubberized concrete. the results showed that rubberized concrete has higher ductility but lower strength and stiffness than normal concrete. the usage of ceramic tiles as floor, walls and countertop tiles in buildings has become very popular, however, at the end of it use, it becomes a waste (ray et al., 2021) various works has gone into the recycling of these materials in the production of concrete. suvash et al. (2023) examined the mechanical durability and microstructural performance of concrete made with ceramic tiles aggregate at 0, 10, 20, 30, 50 and 100% in position of the normal coarse aggregate. the study showed that the more the amount of ceramic tiles used as aggregate, the more was the decrease in strength. however, a 10% addition of tiles as aggregate was recommended as the strength reduction at this point was relatively low. in another work, ikponmwosa and ehikhuenmen (2017) replaced coarse aggregate at 0, 25, 50, 75 and 100% and investigated the tensile and compressive strength tests at 90 days curing age. they observed that the two strengths were reducing as the percentage of ceramic tiles were increased. this reduction was attributed to the water absorption nature of the ceramic tiles in cured concrete. the work concluded that ceramic tiles could be used in concrete for structural and non-structural works, but should not exceed 75% replacement where strength is the major consideration. this study aimed to investigate the influence of both tyre rubber crumbs and ceramic tiles wastes on the structural properties of concrete, such as the compressive, flexural, elastic modulus and structural efficiency of concrete. 2. materials and methods 2.1. material composition the percentage of natural fine aggregates replacement by rubber crumb waste was chosen to be 0%, 5% and 10% by weight (designated as c0, c5 and c10 respectively). this percentage replacement was in agreement with akinyele et al. (2016) where it was stated that “the systematic reduction of ultimate strength in tyre–rubber concrete might restrict its use in concentrations exceeding 8% for structural applications”, hence the restriction to 10% replacement. crushed ceramic tiles were also used to completely replace the conventional coarse aggregate of granite stones. figures 1 and 2 show the crushed tiles and rubber crumbs. figure 1: crushed ceramic tiles figure 2: crushed tyre rubber crumbs 2.2. concrete production the design mix for concrete adopted in this work was 1:2:2 for cement, fine and coarse aggregates, respectively, with a water/cement ratio of 0.5 in accordance to bs 1881, (1993). table 1 shows the mix proportion. 100 mm × 100 mm × 100 mm concrete cubes were cast in file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adetiloye et al: influence of rubber crumbs on the structural efficiency of concrete made from ceramic tile aggregates. azojete, 20(2):555-562. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 557 steel moulds for the compressive strength test, cylinder size of 100 mm x 200 mm was used for the split tensile test, while 100 mm x 100 mm x 750 mm sized concrete beams was for the flexural strength test. the inside of each mould was lubricated with black oil before usage, to prevent concrete from sticking to the mould after demoulding. each mould was gradually filled with three layers of concrete, each layer was trampled using a tapping steel rod to prevent segregation, entrapped air and to allow full compaction of concrete. table 1: mixture of concrete samples cement (kg) sand (kg) ceramic tiles (kg) rubber crumb (kg) water (kg) c0 100 200 200 0 50 c5 100 190 200 10 50 c10 100 180 200 20 50 2.3 density of concrete the bs 12350-6, (2000) was adopted for the density of hardened concrete at 28days. concrete cubes were weighed after the curing period. the cured specimens were wiped dry before placement on a digital weighing machine, where their different masses were accurately measured. the volume of the samples were determined through the 100mm x 100mm x 100mm cube size that were used. the density was calculated as the ratio of their respective masses to their volume. 2.4 compressive strength test after the 7 and 28 days curing periods, the samples were removed from the curing tanks and the cubes were wiped with dry cloths to remove the dripping water. the samples were then transferred to a 2000 kn impact compressive testing machine, where the cubes were placed between the top and bottom pressing plates as showed in figure 3 at a rate of 180 kn/min. this was in accordance with bs 12390 -3, (2019). this test was carried out at the material laboratory of the civil engineering department, federal university of agriculture, abeokuta, nigeria. figure 3: compressive test on concrete sample. figure 4: three-point flexural strength test 2.5 the splitting tensile strength test this test is one of the significant properties of concrete, it was done according to astm c 496-96standard, (2017). the purpose of the test was to determine the tensile resistance of concrete under sustained loading, this method is more preferred than the direct tensile test because of its simplicity of testing. this test was performed by using a cylindrical concrete samples of 100 mm diameter and 200 mm depth. the cylinder was laid on its side between the http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):555-562. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 558 loading plates of the 2000 kn impact compressive strength testing machine and the loading was adjusted to a speed of 100 kn/min. until the crushing of the cylinder. 2.6 flexural strength test of beams at the end of 7 and 28 days, the concrete beams were tested for its flexural strength. the astm c 78 standard, (2019) was adopted which has to do with the testing of the flexural strength of concrete using simple beam with third-point loading. the beam was positioned in the universal testing machine (utm) and subjected to gradual and continuous loading until failure occurred (figure 4). 3. results and discussion 3.1. density of concrete samples the density of each concrete sample is shown in figure 5. the pattern of the results revealed a general reduction in the density of samples with 10% rubber crumb having the lowest value at 2047 kg/m3. this reduction in density can be ascribed to the very light rubber crumb that was used to partially replace sand as fine aggregate. density of sample c5 was slightly higher than the control and this can be attributed to the fact that the rubber crumb acts as fillers to the voids within the concrete matrix in this particular sample, but the higher amount of rubber crumbs in samples c10 made it to be lighter than the others. this result is comparable with the findings of akinyele et al. (2016), where tyre rubber crumbs were used to substitute sand as fine aggregates up to 16% in concrete. the c0 and c5 concrete sample densities were above 2300 kg/m3 and according to en 206, (2000), this can be classified as normal weight concrete. figure 5: density of concrete samples 3.2 compressive strength result the pattern showed by the concrete samples under crushing loads revealed the effect of rubber crumps and ceramic tiles aggregates on the strength of the concrete samples. all the concrete samples showed general reduction in concrete strength between the 7th and the 28th days. this is understandable because the ceramic tiles that were used as the coarse aggregates did not have the same properties as the natural granite. at 7 days, the control (c0) sample attained 23.8 mpa, and at 28 days the strength reduced to 21.77 mpa, which is 8.5% reduction of the strength achieved at 7 days. the same reduction in strength was recorded for sample c5, between the 7th and 28th days strength, while sample c10 performed very poorly, attaining a strength of 11.45 mpa at 28 days. the reason for this general reduction in strength was because of the water absorption capacity of the crushed ceramic tiles in the concrete matrix. since the concrete samples were cured at room temperature, the ceramic tiles absorbed excess water within its surrounding inside the concrete matrix, this wouldn’t have happened if the normal granite coarse aggregate was used. although this does not hinder the hydration of cement in c0 c5 c10 28 days 2368 2382 2047 28 days, c0, 2368 28 days, c5, 2382 28 days, c10, 2047 1800 1900 2000 2100 2200 2300 2400 2500 d en si ty ( k g/ m 3 ) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adetiloye et al: influence of rubber crumbs on the structural efficiency of concrete made from ceramic tile aggregates. azojete, 20(2):555-562. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 559 the concrete, the more water the tiles absorbed, the lower the strength of the concrete samples from the observation in this study. the strengths above 28 days were predicted using the aci 209r-92, (1997) equations for the predictions of concrete strength properties. eqn. 1 was used to predict the strength at, 56, 90 and 365 days, and a graph was plotted to determine the r2 of the rate of strength reduction within one year. figures. 7 and 8 showed the predicted strength and the rate of reduction in strength respectively. (1) = 28 days compressive strength, = predicted compressive strength, t = age of concrete in days, = a constant and a = a constant in days. figure 6: compressive strength results figure 7: predicted compressive strength above 28 days results from figure 7 on the predicted compressive strength adopting eqn. 1, have given insights into the strength characteristics of concrete samples made with ceramic tiles and rubber crumbs. while the ceramic tiles absorbed water, the rubber crumbs acted as fillers in the concrete, and the combination of these two inert materials contributed to the loss in strength over time. the reduction in strength over time will not encourage the use of these materials for high-strength concrete, except lightweight concrete structures. the statistical analysis from fig. 9 showed that the r2 for the reduction in strength of sample c0 between 7 and 365 days was 0.83, when compared with the 0.77 value that was obtained for c5 sample, it can be concluded that the c0 samples performed better. figure 8: rate of decrease in compressive strength between 7 and 365 days. c0 c5 c10 7 days 23.8 26.4 10.5 28 days 21.77 21.78 11.45 0 5 10 15 20 25 30 c o m p re ss iv e st re n gt h ( m p a) 7 days 28 days 56 days 90 days 365 days c0 23.8 21.77 18.91 18.7 18.59 c5 26.4 21.78 18.92 18.71 18.6 c10 10.5 11.45 9.94 9.84 9.78 0 5 10 15 20 25 30 c o m p re ss iv e st re n gt h ( m p a) y = -1.349x + 24.401 r² = 0.8343 y = -1.867x + 26.483 r² = 0.7741 y = -0.305x + 11.217 r² = 0.4712 0 5 10 15 20 25 30 0 1 2 3 4 5 6 c o m p re ss iv e st re n gt h ( m p a) c0 c5 c10 linear (c0) linear (c5) linear (c10) http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):555-562. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 560 3.3 split tensile strength results the resistance to tensile forces in the concrete samples were determined in this particular test. the split tensile strength test results showed that the control samples had the highest strength when compared with the two other samples at both seven and twenty-eight days. the split test showed different results when compared to both the compressive and flexural strength. there was a general increase in split tensile strength between the 7th and 28th days test. the slight increment in strength can be ascribed to the adhesive forces that were holding the cement paste and the two aggregates together. although this force is not strong, it increased as the age of the concrete samples increased. figure 9: split tensile test results figure 10: flexural strength results 3.4 flexural strength results the flexural strength or modulus of ruptures for each concrete sample were determined. this is the amount of stress in the beams before it yielded under flexural loading. the results followed the same pattern as the compressive strength in which the 7-day strength test was higher than the 28-day test, based on the explanations discussed above under compressive strength. the results revealed that sample c0 had a higher ability to resist flexural loads, under sustained loading in the tensioned zone of the beam. the effect of rubber crumbs in reducing flexural strength as more crumbs were added to the sample was very conspicuous, and this is also in accord with the findings of akinyele et al. (2016). 3.5 structural characteristics of concrete samples the structural characteristics of the concrete samples showed in table 2 were determined and compared with each other. properties such as modulus of elasticity was determined using equation 2 which was adopted from the aci 209r-92 reports, (1997), while the structural efficiency is the ratio of compressive strength to the density of the concrete materials (akinyele et al., 2019). (2) where: gct is a constant (0.043), w is the unit weight of concrete, is the characteristic strength of concrete at 28 days. it should be observed that the modulus of elasticity obtained for all the concrete samples in this research are very low when compared to the standard elastic modulus of concrete which is 29 mpa for a grade 20/25 concrete, and 30.5 for a grade 30/35 concrete (hurst, 2017). this can be ascribed to the negative effects of the crushed rubber crumb and ceramic tiles that are present in the concrete used in this study. the modulus of elasticity of sample c5 is higher than that of c0, probably due to the rubber crumbs in the concrete samples when compared with the control that had no rubber crumbs in it. 0 5 10 7 days 1.23 0.77 0.77 28 days 1.22 0.89 0.79 0 0.2 0.4 0.6 0.8 1 1.2 1.4 sp lit t e n si le s tr e n gt h (m p a) c0 c5 c10 7 days 12.33 11.34 10.27 28 days 10.13 9.27 8.73 0 2 4 6 8 10 12 14 fl e xu ra l s tr e n gt h ( m p a) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adetiloye et al: influence of rubber crumbs on the structural efficiency of concrete made from ceramic tile aggregates. azojete, 20(2):555-562. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 561 the structural efficiency is the capacity of the concrete to withstand compressive load in relation to its unit weight. despite sample c0 having a marginally low compressive strength when compared to c5, it had a higher structural efficiency than c5. this is a positive advantage because it can support heavier load with its low density when compared to the c5 sample. table 2: structural properties of concrete samples samples modulus of elasticity (103 n/mm2) structural efficiency (x10-3m) c0 23. 12 9.19 c5 23.33 9.14 c10 13.48 5.60 4. conclusion the influence of crushed tyre rubber crumbs and ceramic tiles on the properties of concrete has been investigated in this work. there was a generally reduction in concrete strength as the concrete ages, and also the more the addition of rubber crumbs above 5% replacement, the more was the reduction in strength. the general reduction in strength was because of the absorption of water by the ceramic tiles in the cured concrete. only 8.5% reduction in strength of the concrete was observed for the c0 sample, which is the control at 28 days, but this does not rule out the use of this type of concrete for structural work. the r2 for the c0 sample at the predicted reduced strength for one year was 0.83, while that of c5 was 0.77, the implication of this is that the reduction in strength overtime will be minimal when compared with the first 28 days, hence the strength of the concrete sample will stabilize as the concrete ages. the modulus of elasticity of the c5 sample was the highest and was about 80% of the standard modulus of elasticity for grade 20/25 concrete. the structural efficiency of the c5 sample was about 99% of the control sample. it can be concluded that the use of crushed ceramic tiles in place of granite and the addition of rubber crumbs at 5% into the concrete can be used for structural works. references khaloo, ar., dehestani, m. and rahmatabadi, p. 2008. mechanical properties of concrete containing a high volume of tire–rubber particles. waste management, 28(12): 2472–2482. karakurt, c. 2015. microstructure properties of waste tire rubber composites: an overview. journal of material cycles and waste management, 17: 422–433. mohammadi, i. and khabbaz, h. 2015. shrinkage performance of crumb rubber concrete (crc) prepared by water–soaking treatment method for rigid pavements. cements and concrete composite, 62: 106–116. thomas, bs., gupta, rc. and panicker, vj. 2016. recycling of waste tire rubber as aggregate in concrete: durability related performance. journal of cleaner production, 112 (1): 504–513. thomas, bs. and gupta, rc. 2015. long term behavior of cement concrete containing discarded rubber.” journal of cleaner production, 101: 78–87. thomas, bs. and gupta, rc. 2016. a comprehensive review on the applications of waste tyre rubber in cement concrete. renewable and sustainable energy reviews, 54: 1323–1333. akinyele, jo., salim, rw. and kupolati, wk. 2016. effect of rubber crumb on the microstructural properties of concrete. african journal of science, technology, innovation and development, 8(5-6): 467-474. gupta, t., sharma, rk. and chaudhary, s. 2015. impact resistance of concrete containing waste rubber fiber and silica fume. international journal of impact engineering, 83: 76–87. http://www.azojete.com.ng/ file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com file:///c:/users/engr.%20samuel/documents/engr%20oyeniyi/azojete/azojete%20archive/upload/vol%2020%20no%201/publish/niyiolabisi@gmail.com arid zone journal of engineering, technology and environment, june 2024; vol. 20(2):555-562. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: adetiloyea@funaab.edu.ng 562 duarte, apc., silva, ba., silvestre, n., de brito, j. and julio, e. 2015. mechanical characterization of rubberized concrete using an image-processing/xfem coupled procedure. composites part b, 78: 214–226. ray, s., haque, m., sakib, mn., mita, af., rahman, mm. and tanmoy, bb. 2021. use of ceramic wastes as aggregates in concrete production: a review. journal of building engineering, 43: 102567. suvahs, cp., samrat, auf., adewumi, jb. and md, jf. 2023. eco-friendly concrete with waste ceramic tile as coarse aggregate: mechanical strength, durability, and microstructural properties. asian journal of civil engineering, 24: 3363-3373. ikponmwosa, ee. and ehikhuenmen, so. 2017. the effect of ceramic waste as coarse aggregate on strength properties of concrete. nigerian journal of technology (nijotech), 36(3): 691 – 696. akinyele, jo., salim, rw. and kupolati, wk. 2016. production of lightweight concrete from waste tire rubber crumb.” engineering structures and technologies, 8(3): 108-116. bs 1881, part 108. 1993. method for making test cubes from fresh concrete. british standard institution, london. bs 12350, part 6.2000. method for determining of density. london: british standards institution. london. bs en 12390-3.2019. testing hardened concrete. compressive strength of test specimens. british standard institution, london. astm c496-96m–17.2017. standard test method for splitting tensile strength of cylindrical concrete specimens. astm international, west conshohocken pa, usa. astm c78.2019. standard test method for flexural strength of concrete (using simple beam with third-point loading). astm international, west conshohocken pa, usa. bs en 12390-5.2019. testing hardened concrete: flexural strength of test specimens.” british standard institution, london. en 206 part 1.2000. “specification, performance, production conformity.” european standard. brussels. ac1-209r-92.1997. prediction of creep, shrinkage, and temperature effects in concrete structures. aci committee report. akinyele, jo., akinwande, om. and igba, ut. 2019.the use of pet pellet in cement stabilized compressed earth bricks. advances in engineering materials, structures and systems: innovations, mechanics and applications. (ed zingoni). taylor & francis group, london, pp. 1631-1635. hurst, mk. 2017. prestressed concrete design. 2nd edition. pg. 31, crc press, rutledge. new york and london. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com corresponding author’s email address: mag1898@unimaid.edu.ng 611 arid zone journal of engineering, technology & environment original research article predictive modeling and simulation of battery degradation in power systems m. a. gana1*, a. a. warude2, and a. bukar3 1department of electrical and electronics engineering, university of maiduguri, nigeria 2department of electrical engineering, federal polytechnic bali, nigeria 3department of physics, federal university, gusau, nigeria *corresponding author´s email address: mag1898@unimaid.edu.ng article information abstract in modern power systems particularly those incorporating renewable energy sources like solar and wind, batteries are essential for balancing supply and demand, stabilizing the grid, and enabling energy storage during low-demand periods. this research introduces a comprehensive modeling and simulation framework aimed at predicting how long batteries will last by examining various degradation mechanisms, including capacity fade, temperature effects, internal resistance growth, and state of charge cycling. a hybrid approach that combines electrochemical, thermal, and mechanical degradation models was used to simulate how batteries age under different operating conditions. the simulation results showed that lithium-ion batteries experienced a 12.5% capacity fade after 500 charge-discharge cycles under normal operating conditions, and the degradation rate increased to 20% in high-temperature environments (45°c). additionally, it was observed that an 8.7% increase in internal resistance significantly affected efficiency. furthermore, the result revealed that the adopted predictive models achieved an impressive accuracy of 94.2%, allowing for a reliable estimation of the remaining useful life (rul) of the batteries. these findings highlight how advanced modeling techniques can really enhance battery management strategies with reduced maintenance costs and boost the reliability of power systems. therefore, the hybrid degradation models showed an impressive predictive accuracy, surpassing recent benchmarks in the field, where older methods showed accuracies of between 91% and 93% using machine learning and physics-informed neural networks. received: 16th april 2025 revised: 26th may 2025 accepted: 28th may 2025 keywords: battery degradation predictive modeling battery management systems power systems degradation mechanisms © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the world is making a significant shift towards cleaner and more sustainable energy systems, and in this transition, energy storage technologies especially lithium-ion batteries (libs) are taking center stage in power system innovation. these batteries are now crucial for enhancing grid flexibility, stabilizing voltage and frequency fluctuations, improving power quality, and facilitating the integration of renewable energy sources like solar and wind. their role has expanded markedly in electric vehicles (evs), smart grids, and off-grid rural microgrids, making them a vital part of the evolving energy landscape (wang et al., 2024). despite these advancements, battery degradation poses a serious challenge. as batteries degrade, their energy storage capacity diminishes, power delivery capabilities are limited, and safety risks increase over time, which ultimately jeopardizes the reliability and economic feasibility of battery-based systems. this degradation impacts not only individual battery applications but also threatens the stability of the entire power system, especially in situations where energy storage is crucial for frequency regulation, peak shaving, and black start capabilities (berecibar et al., 2016). interestingly, there are several factors which could results in the degradation of batteries such as physical, chemical, and operational. also, some key contributors may include charge-discharge cycling, temperature variations, depth of discharge (dod), calendar aging, the growth of the solid electrolyte interphase (sei) layer, azojete june 2025. vol.21(2):611-617 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/025 www.azojete.com.ng mailto:mag1898@unimaid.edu.ng mailto:mag1898@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 611-617. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mag1898@unimaid.edu.ng 612 lithium plating, and electrolyte breakdown. these processes can lead to capacity fade, increased internal resistance, self-discharge, and structural damage to the electrode materials. these degradation effects are worsened under harsh operating conditions, like high current loads, deep discharges, and extreme temperatures (wang et al., 2024). in the past, estimating battery health relied heavily on empirical models and rule-based algorithms integrated into battery management systems (bms). while these methods provide a cautious approach to safety and control, they don't quite capture the intricate degradation patterns that vary across different applications and chemistries. thanks to recent advancements in computational tools, we've seen the emergence of sophisticated physics-based models and hybrid techniques that offer deeper, more predictive insights into how batteries age. these innovative methods allow us to simulate long-term performance under changing load conditions and environmental factors, giving us solid estimates of a battery's remaining useful life (rul) (li et al., 2023). predictive degradation modeling is particularly vital for power systems, as battery failures can lead to service disruptions, higher operational costs, and even regulatory fines. by anticipating degradation trends and failure points, utilities and system operators can adopt condition-based maintenance strategies, enhance battery usage, and create energy management systems (ems) that monitor state-of-health (soh) metrics in real time. this approach not only cuts lifecycle costs but also boosts the reliability and resilience of distributed energy resources (ders) and large-scale storage systems (zhao et al., 2023). this research introduces a thorough predictive modeling and simulation framework that addresses the key degradation mechanisms of lithium-ion batteries, utilizing electrochemical, thermal, and mechanical techniques. the aim is to deliver a more precise and comprehensive understanding of battery aging processes, which will ultimately lead to better design, operation, and control of battery-supported power systems. 2. materials and method this study employed a combination of computational tools, publicly available datasets, and modeling frameworks to simulate battery degradation in power systems, focusing on lithium-based batteries. rather than using physical samples, datasets from nasa was used for analysis. simulation tools included matlab/simulink, python with various libraries, pybamm for electrochemical modeling, and comsol multiphysics for advanced simulations. both physics-based model (p2d) and machine learning model (lstm) were used to model degradation phenomena such as capacity fade. model accuracy was evaluated using rmse to ensure robustness. this integrated approach provided a solid basis for predicting battery behavior in energy systems. 2.1 battery selection and operating conditions lithium-ion battery cells, specifically of the nmc (nickel-manganese-cobalt) chemistry, were chosen due to their widespread deployment in energy storage systems. the cells were simulated under a range of operational scenarios, including: standard ambient temperature (25°c) and elevated temperature (45°c) environments, regular charge-discharge cycling (1c rate), varying depth of discharge (dod) and state-of-charge (soc) cycling conditions. the selection of test conditions reflects real-world scenarios in renewable-integrated grids, where batteries are subject to fluctuating loads and environmental stressors. 2.2 hybrid degradation modeling framework to capture the multifaceted nature of battery degradation, a hybrid framework was developed comprising the following models: electrochemical degradation model: captures capacity fade through solid electrolyte interphase (sei) layer growth, lithium plating, and active material loss. the model is governed by diffusion-reaction equations and degradation kinetics. thermal model: predicts the internal temperature profile of the battery during cycling, accounting for ambient conditions, internal resistance heat generation, and thermal conductivity. this model is critical for understanding temperature-accelerated degradation. mechanical stress model: assesses stress accumulation and particle cracking due to repeated volume changes during charge-discharge cycles, contributing to capacity fade and resistance growth. these sub-models were http://www.azojete.com.ng/ mailto:mag1898@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 611-617. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mag1898@unimaid.edu.ng 613 integrated into a unified simulation environment using matlab/simulink and comsol multiphysics to simulate the dynamic behavior of battery systems. 2.3 data acquisition input parameters for the models were sourced from empirical datasets and validated manufacturer specifications. key inputs included: initial capacity and internal resistance values, charge-discharge profile data, thermal conductivity and specific heat capacity, and electrochemical parameters like diffusion coefficients and activation energies. simulations were run for up to 1000 cycles under varying soc windows (20 – 80%, 10 – 90%, full cycle), and thermal stress conditions. each scenario was repeated with random initialization to account for variability. 2.4 performance metrics and degradation analysis the primary performance indicators included: capacity fade (% loss over cycles), internal resistance growth (% increase over cycles), energy efficiency decline and predicted rul (in cycles and time). statistical regression and curve fitting techniques were used to derive degradation trajectories. the capacity degradation data was fitted using a nonlinear exponential decay function, while resistance growth was modeled using a logistic growth function. 2.5 predictive model validation and accuracy assessment to evaluate the predictive power of the hybrid model, the simulation outputs were benchmarked against experimental data from published battery aging studies. a supervised machine learning model (random forest regressor) was also trained on the simulated degradation datasets to cross-validate the predicted rul. model accuracy was quantified using the following metrics: root mean square error (rmse), coefficient of determination (r²) and prediction accuracy (%). 2.6 sensitivity analysis a sensitivity analysis was conducted to quantify the influence of key parameters such as temperature, cycle rate, dod, and soc range on degradation outcomes. monte carlo simulations were run to generate probabilistic distributions of rul under uncertain operating conditions. 2.5 simulation framework the integrated simulation framework brings together electrochemical, thermal, and mechanical models to give us a comprehensive understanding of battery degradation as follows: step 1: data collection i. real-world battery performance data was collected. ii. this includes details on charge-discharge cycles, temperature, and internal resistance. step 2: preprocessing & analysis i. next, the data was clean and filtered the raw data. ii. key parameters that contributes to degradation were identified. step 3: model development i. degradation models were selected. ii. define the model parameters and the assumptions we’re working with. http://www.azojete.com.ng/ mailto:mag1898@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 611-617. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mag1898@unimaid.edu.ng 614 step 4: simulation & validation i. run simulations under various operating conditions. ii. finally, validate our model against experimental data to ensure accuracy. step 5: prediction & evaluation i. estimate the remaining useful life (rul) of the batteries. ii. compare the predictions with actual degradation trends to see how well it is. 3. results and discussion the simulation results clearly showed that the lifespan of a battery is heavily affected by the conditions under which it operates as illustrated in figures 2 to 6. 3.1 capacity fade the results for capacity fade of the model is presented in figure 1. it is clear that over 1000 charge-discharge cycles at 1c rate and 80% depth of discharge, capacity retention dropped to 75%. figure 1: plot of capacity fade one of the important findings here is the 12.5% capacity fade observed after 500 charge-discharge cycles under standard operating conditions. this clearly shows that battery aging is a natural process, even when everything seems optimal. on the flip side, we noticed a more pronounced capacity fade of 20% at higher temperatures (45°c), which really drives home the negative impact heat can have on battery life. this aligns with previous studies that indicate that elevated temperatures could worsen both chemical and mechanical degradation, which would ultimately shortening the battery's lifespan. 3.2 temperature effect on degradation the effect of temperature showed that operating at 45°c resulted in a degradation rate approximately 20% higher than at 25°c, as illustrated in figure 2. the results clearly showed that temperature plays a significant role in the degradation rate of the material or system we studied. specifically, operating at 45°c led to a 20% faster degradation rate compared to 25°c. this suggests that the extra thermal energy at higher temperatures speeds up the chemical reactions or physical processes that cause degradation. http://www.azojete.com.ng/ mailto:mag1898@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 611-617. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mag1898@unimaid.edu.ng 615 figure 2: temperature effects on degradation 3.3 mechanical degradation mechanical degradation was evident after 500 cycles, with electrode particle cracking observed and a corresponding increase in internal resistance, as shown in figure 3. figure 3: internal resistance increase another key observation is the 8.7% increase in internal resistance, which has a direct effect on battery efficiency and performance. when internal resistance rises, it leads to more energy losses, lower power output, and increased thermal stress and thus exacerbating degradation. this highlights the urgent need for effective thermal management strategies in power systems, particularly in high-temperature settings. 3.4 state of charge cycling implementation of partial state of charge (soc) cycling between 20% and 80% resulted in a 30% improvement in battery lifespan compared to full-depth cycling, as shown in figure 4. implementing partial state of charge (soc) cycling, particularly within the 20–80% soc range, has shown a significant boost in battery lifespan. figure 5 revealed that this approach led to a 30% increase in cycle life compared to the traditional full-depth cycling (0 –100% soc). this enhanced performance mainly comes from reducing the electrochemical and mechanical stress that usually occurs during deep charge-discharge cycles. by steering clear of the extremes in the soc range, this method helps to minimize electrode degradation, especially issues like lithium plating and structural fatigue. these results highlight how optimizing the soc window can be an effective way to improve battery durability, particularly in situations that demand high cycle stability. http://www.azojete.com.ng/ mailto:mag1898@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 611-617. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mag1898@unimaid.edu.ng 616 figure 4: state of charge cycling 3.5 predictive model accuracy figure 5 shows a predictive model accuracy of 94.2 % achieved in the study. it showcased the strength of the hybrid modeling framework that combines electrochemical, thermal, and mechanical degradation models. this impressive accuracy indicates that these models can offer trustworthy predictions about the remaining useful life (rul) of batteries. this information is essential for fine-tuning maintenance schedules and minimizing unexpected breakdowns. figure 5: predictive model accuracy 4. conclusion this study presents a detailed hybrid modeling framework that effectively predicts battery degradation by considering electrochemical, thermal, and mechanical aging processes. it was observed that lithium-ion batteries experienced a drop in capacity after repeated charge-discharge cycles under normal conditions. however, when exposed to extreme temperatures, the degradation accelerated, resulting in a capacity loss. however, a rise in internal resistance was notable leading efficiency declines. the predictive model achieved improved accuracy than other methods. these results demonstrate the effectiveness of hybrid degradation modeling in accurately estimating the remaining useful life (rul) of lithium-ion batteries and improving battery management. future work should focus on real-time integration and extending the approach to diverse battery chemistries and operating conditions. references aqib, m. and ukil, a. 2024. battery degradation model of electric vehicle with grid integration. journal of energy storage. 97. http://www.azojete.com.ng/ mailto:mag1898@unimaid.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 611-617. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mag1898@unimaid.edu.ng 617 attia, pm., grover, a., jin, n., severson, ka., markov, tm., liao, yh., and chueh, wc. 2020. closed-loop optimization of fast-charging protocols for batteries with machine learning. nature, 578 (7795): 397-402. barré, a., deguilhem, b., grolleau, s., gérard, m., suard, f., and riu, d. 2013. a review on lithium-ion battery ageing mechanisms and estimations for automotive applications. journal of power sources, 241: 680 – 689. berecibar, m., gandiaga, i., villarreal, i., omar, n., van mierlo, j., and van den bossche, p. 2016. critical review of state of health estimation methods of li-ion batteries for real applications. renewable and sustainable energy reviews, 56: 572-587. birkl, cr., roberts, mr., mcturk, e., bruce, pg. and howey, da. 2017. degradation diagnostics for lithiumion cells. journal of power sources, 341: 373–386. chen, zz. and li, wy. 2024. unraveling the degradation mechanisms of lithium-ion batteries. mdpi batteries, 17(14):3372. doyle, m., fuller, tf. and newman, j. 1993. modeling of galvanostatic charge and discharge of the lithium/polymer/insertion cell. journal of the electrochemical society, 140(6): 1526. feng, x., ouyang, m., liu, x., lu, l., xia, y. and he, x. 2019. a review of early warning signs for lithium-ion battery failure. etransportation, 1: 100003. huzaifa, r., muhammad, k. and naveed, a. 2022. machine learning in state of health and remaining useful life estimation. theoretical and technological development in battery degradation modelling. renewable and sustainable energy reviews 156 (2022): 111903 liu s., zhang h., wang x. and zhang l. 2024. side reactions/changes in lithium‐ion batteries: mechanisms and impacts. advanced materials, 36(5): 2201482. schimpe, m., naumann, m., truong, cn., hesse, hc., santhanagopalan, s., saxon, a. and jossen, a. 2018. energy efficiency evaluation of a stationary lithium-ion battery container storage system via electro-thermal modeling and detailed component analysis. applied energy, 210: 211–229. smith, k., and kim, gh. 2010. they focused on modeling the nonuniform degradation in large-format li-ion batteries. journal of power sources. smith, k., kim, gh., darcy, e. and pesaran, a. 2010. thermal/electrical modeling for abuse‐tolerant design of lithium-ion modules. international journal of energy research, 34(2): 204-215. severson, ka., attia, pm., jin, n., perkins, n., jiang, b., yang, z. and braatz, rd. 2019. data-driven prediction of battery cycle life before capacity degradation. nature energy, 4(5): 383-391. wang y., zhang h., li j., liu s. and xu z. 2024. performance degradation and failure characterization of liion batteries. journal of power sources, 589: 233456. wang y., zhang l., li j. and liu q. 2024. exploring lithium-ion battery degradation: a concise review of critical factors, impacts, data-driven degradation estimation techniques, and sustainable directions for energy storage systems. mdpi batteries, 10 (7): 220. weng, c., sun, j. and peng, h. 2013. on-board state of health monitoring of lithium-ion batteries using incremental capacity analysis with support vector regression. journal of power sources, 235, 36–44. yang, x. g., liu, t., gao, y., ge, s., leng, y., wang, d. and wang, cy. 2019. asymmetric temperature modulation for extreme fast charging of lithium-ion batteries. joule, 3(12): 3002-3019. zhang h., liu s., chen x. and yang w. 2024. stress-dependent capacity fade behavior and mechanism of lithium-ion batteries. journal of energy storage, 40: 102853. zhang, x., sun, f., pecht, m. and sun, j. 2020. battery management algorithm for electric vehicles: state-ofthe-art and future trends. 15-3972-8 http://www.azojete.com.ng/ mailto:mag1898@unimaid.edu.ng corresponding author’s email address: grantnelson2015@gmail.com 828 arid zone journal of engineering, technology & environment original research article solidworks modeling of mechanical strength of an optimum high pressure a360 die cast n. o. ubani1*, j. e. dara2 and v. c. ezechukwu3 1department of mechanical engineering, michael okpara university of agriculture, nigeria 2department of mechanical engineering, nnamdi azikiwe university, awka; nigeria 3department of mechanical engineering, chukwuemeka odumegwu ojukwu university, uli, nigeria. *corresponding author’s email address: grantnelson2015@gmail.com article information abstract in this study, solidworks modeling was utilized to analyze the mechanical strength of high pressure a360 die castings. the model incorporates all necessary factors, such as material properties and design features, to accurately predict the tensile strength and flexural strength of a360 die cast components. from the input data, a statistical analysis was performed to identify key factors that affect the mechanical strength of the die cast materials. these factors were then used to build a regression model that accurately predicts the mechanical strength of the materials. by simulating various stress and strain scenarios, this research provides an in-depth understanding of the material's strength and its behavior under different loading conditions. the results showed that the maximum tensile stress of 13.401 mpa was recorded on application of 1000 n tensile load. the maximum elongation associated with 1000 n tensile load was 0.0139 mm. the maximum stresses due to concentrated and distributed 1000 n flexural loads were 66.820 mpa and 43.506 mpa respectively. the maximum deflection of 0.0527 mm was recorded due to concentrated flexural load of 1000 n and the maximum deflection due to distributed flexural loading of 1000 n/mm was 0.0371 mm. the results of this study can be used to optimize the design process of high pressure a360 die cast components, leading to improved performance and increased reliability. this will greatly aid in the design and manufacturing process, allowing for optimized designs and improved product performance. this study serves as a valuable resource for engineers and manufacturers looking to optimize the mechanical strength of their high pressure a360 die castings. submitted 04 june, 2024 revised 29 july, 2024 accepted 08 aug., 2024 keywords: discretization mesh, nodes tensile load flexural load © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction aluminum and its alloys can be melted down and be reused over and over again without any detriment to its mechanical properties. aluminum and its alloys are the most popular metal used in engineering applications besides iron and steel. they are widely used in transportation, defense, construction, aerospace, maritime, domestic, and general engineering purpose (mohiuddin et al., 2015). the requirement of aluminum alloy part is unavoidable in transportation sector due to their light weight leading to energy savings and less emissions and mass production of aluminum alloys is supported high pressure die cast process (rathinam et al., 2021). thirugnanam (2013) reported that about 70% of aluminum castings are produced using high-pressure die casting process. aluminum products are made in a variety of ways that aim to improving the mechanical properties of the finished products or to achieving a desired property within a specific range, some of the common methods of manufacturing aluminum products include extrusion, forging, drawing, rolling, and casting. pure aluminum is soft having comparatively poor casting features and little strength, that's why aluminum castings are prepared from aluminum alloys (mohiuddin et al., 2015). aluminum alloys are widely used in die casting process because azojete december 2024. vol.20(4):828-835 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:grantnelson2015@gmail.com mailto:grantnelson2015@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 829 of their good combination of strength and light weight (hu et al., 2006). high pressure die casting is an economical fusion technique that can produce several complex shapes (mohamad et al., 2020). due to the external high pressure, it is possible to flow the molten metal into every corner of the complex shape of a cavity hence the complex shape of the casting can be easily produced (tariq et al., 2022). aluminum alloy castings are extensively used in general engineering, automobile, aerospace industries due to their excellent cast-ability, machinability, corrosion resistance and high strength-to-weight ratio (mohiuddin et al., 2015). when the optimal processing technology parameters are applied, the castings with very less porosities can be obtained (amitkumar et al., 2015; mohammad, 2015; balikai et al., 2018; rathinam et al., 2021; tariq et al., 2022). ubani (2023) reported the optimal process parameters for high pressure die casting of a360 as 1st stage plunger velocity of 0.15 m/s, 2nd stage plunger velocity of 3.0 m/s, intensification pressure of 25 mpa, pouring temperature of 680°c, and shot chamber temperature of 100°c. these optimal process parameters were used to produce the optimum high pressure a360 die cast. the aim of this work is to use solidworks modeling to investigate the tensile strength and the flexural strength of the optimum high pressure a360 die cast. 2. materials and methods 2.1 materials the materials that were used for the study are aluminum coil sourced from cutix plc nnewi, anambra state. silicon, magnesium, iron, manganese, nickel, zinc, and copper bought from sunlabi global international (ltd) jos, plateau state. 2.2 method the samples of a360 (ansi/aa a360.0) alloy were produced via high pressure die casting process. the produced samples have compositions of the alloying metal as follow: 10wt% silicon, 0.6wt% magnesium, 1.3wt% iron, 0.35wt% manganese, 0.5wt% nickel, 0.5wt% zinc, and 0.6wt% copper. the process parameters of the high pressure die casting machine were set manually via the programmable logic control panel board with 1st stage plunger velocity of 0.15 m/s, 2nd stage plunger velocity of 3.0 m/s, intensification pressure of 25 mpa (ubani, 2023). the aluminum alloy was heated to 700°c and the temperature was held at 680°c before ladled into the die casting machine from the holding furnace with the help of the tong. the shot chamber of the die casting machine was initially preheated to a temperature of 100°c. the casting process is as follows: clamping of die, injection of molten metal, cooling of molten metal, ejection of cast, and trimming of cast (mohamad et al., 2020). the samples were prepared according to astm standard. the dumbbell shaped samples were made using taylor hobson pantograph engraving machine equipped with milling attachment. tensile testing of the samples was conducted on the a360 cast in accordance with the astm e8 (2024) standard on round tension test specimens of gauge length 25mm using ametek ez-250 digital tensile and compression tester. it was conducted at room temperature. the ultimate tensile strength, percentage elongation, and quality index of the specimens were also determined. the cross-sectional areas were measured using mitutoyo digital vernier caliper of precision 0.01mm, while the gauge lengths of 50mm were marked on the samples. each sample was mounted on the tensile clamps. the extensometer was zeroed and travel speed of 2mm per minute was selected (goanta, 2020). peak force and extension were displayed at the end of the test. raw data of applied forces with the corresponding increases in length were saved in the computer. the stress-strain curves, ultimate tensile strength, yield strength and yield point, young’s modulus, tensile toughness and percentage of elongation were subsequently derived. these material properties were used to create the samples subjected to solidworks modeling. the solidworks modeling of the a360 was carried out by creating the model of the sample in the graphics area. the model was selected and mashed to give 6985 elements with 1194 nodes. the meshed model was restrained before applying tensile and flexural loads. the analysis of the model was conducted to produce the deformation and stress results. the mesh information and material properties of a360 used in the tensile and flexural testing is presented in table 1. figure 1 showed the mesh model of the sample used in the solidworks modeling and analysis of the optimal cast sample. the sample was discretized into 6985 elements with 11194 nodes. http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 830 table 1: mesh information and material properties total nodes 11194 total elements 6985 maximum aspect ratio 3.2582 % of elements with aspect ratio <3 99.9 % of elements with aspect ratio > 10 0 % of distorted elements (jacobian) 0 material name a360 cast model type linear elastic isotropic default failure criterion maximum von mises stress yield strength 5.51485e+007n/m2 tensile strength 1.24084e+008n/m2 elasticmodulus 6.9e+010 n/m2 poisson's ratio 0.33 figure 1: solid mesh of the sample the left-hand side of the sample was fixed, and a tensile force was applied on opposite side. von mises failure criterion was used to evaluate the potential safe application of the cast. 3. results and discussion the samples produced using these optimal process parameters of 1st stage plunger velocity of 0.15 m/s, 2nd stage plunger velocity of 3.0 m/s, intensification pressure of 25 mpa, pouring temperature of 680°c, and shot chamber temperature of 100°c were subjected to tensile loading forces of 200 n, 600n, and 1000n and the results were presented in figures 2 – 19. figure 2 depicted the tensile stress induced in the sample due to a tensile force of 200 n. the maximum stress is 2.68 mpa and the minimum stress is 0.327 mpa, but the yield strength of the material is 55.15 mpa. the maximum stress occurred at the center of the arc of curvature of the chamfered portion of the sample due to stress concentrations. the maximum stress occurred at node 11087 while the minimum stress occurred figure 2: tensile stress due to 200 n load figure 3: tensile displacement due to 200 n load http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 831 at node 8760. since the maximum induced stress is very low compared to the yield strength of 55.15 mpa, it implies that the material will not fail due to application of static tensile load of 200 n (ubani et al., 2023). the tensile elongation of the sample as a result of 200 n force is represented in figure 3. the maximum extension of 0.003 mm occurred at the point of application of the force whereas no extension occurred at fixed point. in other words, there is no extension at the fixed point. the maximum elongation of 0.003 mm is very insignificant. the maximum extension occurred at node 353 while the minimum extension occurred at node 31. the tensile stress of the sample subjected to tensile force of 600 n is shown in figure 4. the maximum stress of 8.04 mpa occurred at node 11087 while the minimum stress of 0.890 mpa occurred at node 8760. the maximum stress is less than the yield strength of the material which is 55.15 mpa. correspondingly, the maximum induced stress is very low compared to the yield strength, it indicates that the material will not fail at application of static tensile load of 600 n. figure 5 presented the tensile elongation of the sample as a result of 600 n force. the maximum extension of 0.0084 mm occurred at the point of application of the force while the fixed point remained unaltered with no extension. the maximum extension occurred at node 353 while the minimum extension occurred at node 31 (goanta, 2020). the maximum extension of 0.0084 mm is negligible. figure 4: tensile stress due to 600 n load figure 5: tensile displacement due to 600 n load figure 6: tensile stress due to 1000 n figure 7: tensile displacement due to 1000 n force http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 832 figure 6 illustrated the sample subjected to tensile stress due to tensile force of 1000 n. the maximum stress of 13.401 mpa occurred at node 11087 while the minimum stress of 1.633 mpa occurred at node 8760. comparing the maximum stress with the yield stress of the material which is 55.15 mpa gave a factor of safety of 4.115. it implies that the material can withstand the applied load of 1000 n without failure. figure 7 depicted the tensile elongation of the sample as a result of application of 1000 n force. the maximum extension of 0.0139 mm occurred at the point of application of the load while the fixed point remained intact with no extension. the maximum extension occurred at node 353 while the fixed point corresponds to node 31. the maximum extension of 0.0139 mm is slightly significant. it could be observed that for all the different amounts of loading, the maximum stress occurred at node 11087 and the minimum stress occurred at node 8760. node 11087 is at the center of the arc of curvature that formed the chamfered portion of the sample. there is stress concentration in this portion of the sample due to change in the geometry of the sample. despite the stress concentration in the sample, the maximum stress developed in the sample is considerable below the yield strength of the a360 cast. also, the cast a360 is not very ductile since the elongation during loading is very minimal. thus, the cast a360 can safely sustain a static loading up to 1000 n without failure (ubani et al., 2023). one major possible application of the developed a360 cast is motorcycle clutch handle which is subjected to flexural loading during operation. thus, the optimal cast samples of a360 were subjected to both concentrated and distributed flexural loadings of 200 n to 1000 n. the ends of the sample were fixed during the testing while gauge lengths were subjected to loading. the maximum deflection of the samples occurred at the center of the test samples. figure 8: flexural stress due to 200 n load figure 9: deflection due to flexural load of 200 n figure 10: flexural stress due to 200 n/mm loading figure 11: deflection due to flexural loading of 200 n/mm http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 833 figure 8 depicted the flexural stress due to a concentrated load of 200 n. the maximum stress of 13.364 mpa occurred at node 11307 which coincides with the center of the sample. the minimum stress of 0.219 mpa occurred at node 8709. the maximum deflection of 0.01054 mm as a result of 200 n loading occurred at node 11306 as shown in figure 9. the deflection was magnified to the scale of 889.95. the fixed points did not deflect as expected. figure 10 presented the stress owing to the distributed loading of 200 n/mm. the maximum stress is 8.701 mpa and the minimum stress is 0.093 mpa. the maximum stress occurred at node 74 while the minimum stress occurred at node 9677. it could be seen that the concentrated load exerts more stress on the sample and their maximum values do not occur at the same node for loading of 200 n. in both cases, the maximum stress is less than the yield stress of 55.15 mpa. as depicted in figure 11, the maximum deflection due to distributed loading of 200 n/mm is 0.0074 mm and it occurred at node 6601. the deflection was magnified to the scale of 1263.45. the maximum deflections in concentrated loading and distributed loading occurred at the center of the samples while their fixed points did not deflect. the concentrated load of 200 n produced a larger deflection than the distributed load. the defections recorded for both cases are very negligible. figures 12 and 14 depicted the flexural stress due to a concentrated and distributed loading of 600 n and 600 n/mm respectively. the concentrated loading exerted a maximum stress of 40.092 mpa at node 11307 while the distributed loading exerted a maximum stress of 26.103 mpa at node 74. the minimum stress due to the point load is 0.647 mpa and occurred at node 8709, while the minimum stress due to the distributed load is 0.277 mpa and occurred at node 9677. similarly, the concentrated load exerts more stress on the sample than the distributed loading and their maximum values do not occur at the same node. in both cases, the maximum stress is less than the yield stress of 55.15 mpa, which implies that the cast a360 can withstand both concentrated and distributed load of 600 n and 600 n/mm. the produced a360 cast can support moderate concentrated and distributed flexural loads (ubani et al., 2023). figure 13 depicted the deflection due to 600 n concentrated load. the maximum deflection of 0.0316 occurred at node 11306. the deflection was magnified to the scale of 296. figure 15 showed the deflection due to distributed loading of 600 n/mm. the maximum deflection of 0.0223 mm occurred at node 6601 with deflection was magnified to the scale of 421. the maximum deflections in concentrated and distributed loadings occurred at the center of the samples while their fixed points did not deflect. the values of the defections recorded in both cases are insignificant. figure 12: flexural stress due to 600 n load figure 13: deflection due to flexural load of 600 n figure 14: flexural stress due to 600 n/mm loading figure 15: deflection due to flexural loading of 600 n/mm http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 834 figure 16 depicted the flexural stress due to a concentrated load of 1000 n, whereas figure 18 represented the stress owing to the distributed loading of 1000 n/mm. the maximum stresses due to concentrated and distributed loads are 66.820 mpa occurring at node 11307 and 43.506 mpa occurring at node 74 respectively. the minimum stress owing to concentrated load is 1.095 mpa occurring at node 8709 and the minimum stress owing to distributed load is 0.463 mpa occurring at node 9677. the maximum stress (66.820 mpa) induced by the concentrated load of 1000 n is higher than the yield stress of 55.15 mpa. therefore, the developed a360 cast is very likely to failure by the application of static concentrated load of 1000 n; though, it might not fail by application if static distributed load of 1000 n/mm. the maximum deflection of 0.0527 mm was recorded due to concentrated load of 1000 n occurring at node 11306 as shown in figure 17. the deflection was magnified to the scale of 177.99. as shown in figure 19, the maximum deflection due to distributed loading of 1000 n/mm is 0.0371 mm and occurred at node 6601. the deflection was magnified to the scale of 252.69. the maximum deflections in concentrated loading and distributed loading occurred at the center of the samples while their fixed points did not deflect. the defections recorded for both cases are insignificant. it could be observed that as both concentrated and distributed loadings increase, the stresses and deformations increase as well. even though the values of responses varied with amount of loading, all occurred at the same points. the maximum stress and deflection occurred at the center of the samples. the developed a360 cast can withstand distributed static loads up to 1000 n/mm without failure. it can withstand concentrated static loads up to 800 n; but it cannot safely support a concentrated load of 1000 n. the maximum flexural strength, ultimate tensile strength and percentage elongation for a360 cast recorded via experiment were 142.85 mpa, 83.442 mpa and 19.78 % respectively (ubani et al., 2023). 4. conclusion solidworks modeling has been employed to investigate the tensile strength and the flexural strength of the optimum high pressure a360 die cast. it was observed that the developed a360 cast can safely sustain a static tensile load up to 1000 n without failure. it can withstand distributed static flexural loads up to 1000 n/mm without failure. moreover, it can withstand concentrated flexural static loads up to 800 n; but it cannot safely support a concentrated flexural load of 1000 n. the developed material has very low ductility since the maximum elongation induced by static tensile load of 1000 n is 0.0139 mm. also, the defections recorded owing to concentrated and distributed flexural loads are insignificant. the developed a360 cast can be employed in the manufacturing of motorcycle clutch handle. figure 16: flexural stress due to 1000 n load figure 17: deflection due to flexural load of 1000 n figure 18: flexural stress due to 1000 n/mm figure 19: deflection due to flexural loading of 1000 n/mm http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):828-835. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: grantnelson2015@gmail.com 835 references amitkumar, a., arunkumar, y. and srinath, ms. 2015. simulation of high pressure die casting process for identifying and minimising defects. international journal of engineering research & technology (ijert), 3(17): 1-9. astm international 2024. standard test methods for tension testing of metallic materials. astm international, 100 barr harbor drive, west conshohocken, pa 19428-2959. united states. balikai, vg., siddlingeshwar, ig. and gorwar, m. 2018. optimization of process parameters of high pressure die casting process for adc12 aluminium alloy using taguchi method. international journal of pure and applied mathematics, 120(6): 959-969. goanta, v. 2020. extensometer for determining strains on a tensile and torsion simultaneous load. sensors, 20(2): 385. hu, b., xiong, s., masayuki, m., yoshihide, m. and shingo, i. 2006. study on vacuum die casting process of aluminum alloys. world foundry congress, wfc 06, 179: 1-9. mohamad, em., tommaso, m., pasquale, b., leonardo, g., enrico, s. and archimede, f. 2020. design optimization of gate system on high pressure die casting of alsi13fe alloy by means of finite element simulations. procedia cirp, 88: 509–514. mohammad, s. 2015. optimization product parts in high pressure die casting process. materials science and technology, mälardalen university press licentiate, västerås theses no. 197. mohiuddin, mv., krishnaiah, a. and hussainy sf. 2015. influence of sand molding process parameters on product quality of al-si alloy casting an anova approach. international journal of advance research in science and engineering, 4(01): 1751. rathinam, n., dhinakaran, r. and sharath, e. 2021. optimizing process parameters to reduce blowholes in high pressure die casting using taguchi methodology. materials today: proceedings, 38, part 5: 2871-2877. tariq, s., tariq, a., masud, m., and rehman, z. 2022. minimizing the casting defects in high-pressure die casting using taguchi analysis. scientia iranica b, 29(1): 53-69. thirugnanam, m. 2013. modern high pressure die-casting processes for aluminum castings. transactions of 61st indian foundry congress, january 27-29, kolkata, 1-7. ubani, no. 2023. empirical model for predicting the defects and mechanical properties of die cast aluminum product, phd thesis submitted to department of mechanical engineering, chukwuemeka odumegwu ojukwu university, uli. ubani, no., nwobi-okoye, cc., dara, je., eni-ikeh, sn. and okoro, c. 2023. optimizaion approach for evaluation of mechanical properties of high pressure die cast aluminum alloyed product. umudike journal of engineering and technology (ujet), 9(1): 46 – 54. http://www.azojete.com.ng/ mailto:grantnelson2015@gmail.com arid zone journal of engineering, technology & environment azojete centre for satellite technology development special issue: space science and technology for sustainable development azojete, june, 2019. vol. 15(sp.i2):75-90 published by the faculty of engineering, university of maidiguri, maidiguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng 75 original research article unlocking rural and remote coverage with small cells and satellite u. s. abdullahi*, f. s. longman, t. t. christopher and l. adesina center for satellite technology development, national space research and development agency abuja, nigeia article information submitted: 08/11/2018 revised: 01/02/2019 accepted: 20/05/2019 keywords: rural and or remote coverage small cells satellite backhaul capacity coverage . abstract according to the global system for mobile alliance (gsma), in 2017, there were around 3.3 billion people connected to the mobile internet. this represented an upward surge in global coverage compared to previous years. however, more than one billion people are still not covered by mobile broadband networks, representing what is termed “the coverage gap”. uncovered populations typically live in rural locations with low population densities, low per-capita income levels and weak or non-existent enabling infrastructure, and thus, closing the mobile coverage gap seems to be more of an economic challenge, than a pure technical one. this paper presents an overview of the need for rural and remote coverage, both from an operator and consumer as well as government perspective. it then presents the major challenges, and necessary actions to be taken by industry, government and other stake-holders to drive rural and remote coverage by significantly lowering the cost of network roll-out and increase incentives for such deployments. the paper therefore, presents a technical and business case for the use of “small cells” in conjunction with satellites with a view to opening up huge markets via collaboration between the mobile operators and satellite system owners, while offering significant improvements in the coverage and capacity needs of remote, rural or underserved end-users in a cost-effective and scalable manner. detailed insights to these two technologies are presented, including the innovations to overcome technical and regulatory challenges. lastly, some reallife deployments are given and the paper concludes with some recommendations for government and network operators presented © 2019 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction data usage on the mobile network is growing exponentially with emergence of affordable smart phones/portable devices, and the demand of data-hungry services and applications such as intelligent transport systems, smart grid communications, and other advanced systems based on machine-to-machine communications etc. cisco has recently forecasted an 18-fold traffic increase (10.8 exabytes per month) by 2016 with about 10 billion mobile devices by end of 2018, while other predictions indicate that mobile data will grow at 108% compound annual growth rate (cagr) (mogensen et al., 2007) with over a thousand fold increase over the next 10 years. http://www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 76 however, as data demand continues to rise, operator revenues are lagging behind as illustrated in figure 1 (ray le maistre, 2010). this trend is further worsened by advent of over-the-top (ott) services, which rely on traditional network operator equipment, but gulp a major share of the revenues. hence, urgent measures are required by industry to close this cost-revenue gap by minimizing the cost/bit through innovative technical and operational processes/services (infrastructure sharing, optimized/small base stations) and reaching uncovered markets to unlock revenue growth. on the side of government, effective, investor-friendly regulatory frameworks are important to ease network rollout to rural and remote areas in order to drive digital inclusion and derive more economic benefits. these regulatory processes include efficient and transparent spectrum policies, taxation, administrative efficiency etc. figure 1: cost-revenue gap (source: ray le maistre, 2010) the question thus remains, how can this enormous data capacity be realized, consistent with delivering a customer experience for speed and continuous coverage, which exceeds today’s levels and yet continues to be economically sustainable for operators. over the years, researchers have investigated a lot of techniques to increase capacity, coverage and quality of service in wireless communications using the available limited resources. the table 1 below is a result of such studies, which shows different strategies employed and their effect on capacity gain. table 1: technique versus capacity gain technique capacity gain frequency division 5 modulation technique 5 access to wider range of frequency spectrum 5 frequency reuse through more cell sites 1600 [source: khawar et al., 2015] it is very evident from table 1, that use of frequency re-use by roll out of greater number of cells has yielded the highest capacity growth over years, and will continue to do so. however, deploying dense number of traditional base stations (macro base stations) to increase network capacity and coverage is not only cost prohibitive, but also operationally complex due to their huge sizes, high power consumption, cooling requirements and long set-up times. one alternative approach is to deploy small, low-range, low-power base-stations to increase the data rate and/or coverage of mobile wireless systems in place of (or in conjunction with) traditional macro base stations. this achieves the same capacity-increasing effect, but with far less budgetary and operational requirements and complexity as in the case of macro-only http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 77 deployments. such a paradigm shift is steadily gaining lots of attraction in the mobile industry, and is referred to as a heterogeneous network (or hetnet), where small cells are deployed alongside traditional macro base stations for coverage extensions to remote, rural areas or capacity enhancement to hot-spots. whatever the intended motivation for their deployment, small cells provide operators with practical solutions to the data crisis and coverage issue in a cost-effective, flexible and scalable manner (astely et al., 2009). in this paper, the need for rural and remote coverage is analysed, both from an industry and government perspective, to close the digital divide and increase economic benefits, especially in developing nations. the business and technical case for rural coverage is therefore investigated, where coverage and usage gaps are identified worldwide, with peculiarities of emerging economies. some key challenges mnos face in bridging these gaps are also presented, including the regulatory role of government. a combination of small cells and satellite backhaul is identified as an innovative and effective solution to address the coverage gap in a sustainable way. for the scope of this paper, our priority is the use of small cells and satellite for coverage extension to rural or remote areas, including provision of voice and data services to underserved villages and towns, for emergency and disaster relief situations, oil-rigs, to aircraft, vessels, trains etc. some practical solutions to the challenges are then offered, owing largely to recent advancements in both mobile and satellite technologies. finally, some real-life deployments are showcased, and recommendations provided for practical implementation of such hybrid system in nigeria. 2. rural and remote coverage 2.1 why bother about rural coverage? the coverage gap: more than 2.5 billion people – over 40% of the planet’s population – live in rural and remote areas of developing countries according to an itu report [small cell forum, dec 2013] of the small fraction that has any access to telecommunications, radio broadcasts and voice telephony have traditionally been the main services provided. however, with increasing proliferation of cheap and affordable smart phones and other portable devices, mobile operators globally are now working hard to grow their networks in terms of: higher subscriber base, increased arpu (average revenue per user), and improved coverage. this is driving them to expand connectivity into rural/remote areas, and also ensure ubiquitous coverage even during disasters and emergency situations (williams et al. 2012). for the purpose of this paper, the expression “rural and remote” (or just “rural”) refers to rural, isolated and poorly served areas by telecommunication facilities, where various factors interact to make the establishment of telecommunication services difficult. a rural area may consist of scattered settlements, villages or small towns, and may be located several hundreds of kilometres away from an urban or city centre (bright et al., 2012). however, in some cases a suburban area may also be considered as rural. a rural area exhibits one or more of the following characteristics: scarcity or absence of public facilities such as reliable electricity supply, water, access roads and regular transport; scarcity of technical personnel; difficult topographical conditions, e.g. lakes, rivers, hills, mountains or deserts, which render the construction of wire telecommunication networks very costly; file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 78 severe climatic conditions that make critical demands on the equipment; low level of economic activity mainly based on agriculture, fishing, handicrafts, etc.; low per capita income; low population density; under-developed social infrastructures (health, education, etc.) very high calling rates per telephone line, reflecting the scarcity of telephone service and the fact that large numbers of people rely on a single telephone line. nigeria’s population is about 190 million people according to a 2017 world bank study with about half of this population (51%) residing in rural areas (qiang et al., 2009). there has been a giant surge recently in mobile penetration, from 54% in 2016 to more than 84 % currently with mobile internet standing at around 51% (kolawole, 2018). however, there is still obviously a lot more to do to bridge the divide between urban and rural areas for the country to reap even more benefits across the ecosystem. currently, the gsma estimates that the coverage gap is equivalent to about 1.2 billion people globally, with sub-saharan africa being the largest by a huge margin as shown in figure 2. coverage gap is simply defined as the lack of supply of mobile services, while the usage gap, on the other hand, is a lack of demand for mobile services where coverage is already available (buckwell et al., 2018). this may be due to poor digital literacy, high cost of mobile devices, etc. as can be seen from figure 2, only sub-saharan africa has the coverage gap being higher than the usage gap affirming the huge digital divide across many african states. figure 2: global mobile coverage gap (source: buckwell et al., 2018) economic potentials: a recent study found that in countries such as nigeria, a 10% increase in mobile penetration increases total factor of productivity, a measure of an economy’s long-term technological dynamism, by 4.2 percentage points in the long run (williams et al., 2012). furthermore, a world bank report estimates that a 10% increase in mobile broadband adoption leads to 1.4% gdp growth for developing economies (qiang et al., 2009). improved access to mobile voice services and broadband will also have great impacts on key sectors such as healthcare, education, and agriculture as well as enhance growth of sme’s. it is therefore in the economic interest of governments to do all they can to drive mobile and digital adoption across the nation. http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 79 figure 3 shows the value chain of economic benefits derived through increased mobile coverage in a country as contained in (qiang et al., 2009) – increasing mobile broadband leads to increased services and opportunities for consumers and businesses, which brings higher revenues to mnos through increased subscriptions and payments, who then pay taxes and fees to government. at the same time, ripple effects of increased consumer spending and booming businesses leads to higher gdp and better economy for the nation. figure 3: economic impacts of mobile broadband (qiang et al., 2009) 2.2. barriers to rural coverage expansion rural and remote areas are generally sparsely populated and hard-to reach, thus associated with some challenges and misconceptions by mno’s. figures 4 and 5 present some interesting results from studies on such challenges hindering mnos from investing in rural coverage (bright et al., 2012). key amongst these include: high capex rolling out traditional macro bs’s to such sites is costly and difficult towers, shelter, power, cooling. high opex for the mno’s – powering bs’s (fuel, generators), maintenance, ease of installation first operator that penetrates market takes it all. arpu presumed to be low by mno’s, insufficient to justify network roll out or creating very difficult business model. due to remoteness and distance from urban centers, often mno’s assume security level is not adequate enough. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 80 figure 4: survey on mnos’ biggest barriers to infrastructure expansion into rural areas (source: bright et al., 2012.) figure 5: operators perceptions on different factors hindering rural connectivity (source: bright et al., 2012.) some technical challenges from a technical perspective, the most critical barriers to rural coverage as verified by both figures 4 and 5 respectively are – base stations, backhaul and power. base stations: the cost and complexity of deploying multiple macro base stations to rural/remote areas is quite significant, and often does not correspond to the revenue profile of these sparsely populated areas. also, absence of complementing network equipment and facilities in close proximity means mnos would be isolated from gateways, switches, fibre networks etc. for long distances. innovative ran solutions are therefore essential for mnos to operate in such environments. these are presented in latter sections of the paper (xiaolu et al., 2013). backhaul and installation cost: according to bright et al. (2012), as shown in figure 5, the most critical issue when deploying multiple cells for extended coverage is the choice of backhaul. due http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 81 to the shrinking of the cell sizes, the numbers of radio access points increase significantly, leading to huge increases in backhaul cost and real estate cost of installing access points. diverse backhaul strategies are needed to accommodate dense base stations, and this is discussed in subsequent sections of this paper. power: the power consumption of multiple macro base stations is quite enormous, and even more so for developing nations such as nigeria, where mnos mostly rely on diesel generators for reliability. renewable sources are becoming attractive, and shall be discussed in section 3 of this paper. 2.2.2 government and regulatory bottlenecks aside technical barriers, there are also some critical issues with government policies/regulatory implementation that hinder rural coverage. government needs to provide regulatory friendly environment. figure 6 shows the role government should play through effective and efficient regulation and administration, spectrum and tax policies, drive infrastructure sharing by mnos. this would help lower the risk perception by mnos for rural coverage, increase return on investment (roi) thereby leading to better incentives of mnos to deploy and ultimately, lead to improved network coverage (gernaro, 2018). figure 6: role of government in closing coverage gap (source: gernaro, 2018) 2.3 way forward for rural and remote coverage according to the gsma, bridging the mobile coverage gap is more of an economic challenge than a technical one (kapovitis et al., 2018). hence, for rural/remote coverage to be commercially sustainable, the demand and supply of mobile services should attain equilibrium as illustrated in figure 7(a). in figure 7(a), the supply and demand curve for mobile services is illustrated. the supply curve represents the incremental cost of covering an additional 1% of the population, and is upward sloping due to the fact that costs get higher as population density reduces (such as rural areas). this may be due to poor economies of scale, difficult terrain for infrastructure deployment, security and other challenges for rural/remote areas as already stated earlier. on the other side, the demand curve represents the additional revenue accrued by additional 1% of the population covered. it is downward sloping because there are less revenues generated in less populated (rural) areas, mainly due to low income level (arpu), poor digital literacy etc. the point where file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 82 demand and supply meet is where mnos would target so as to maximize revenue and provide optimal coverage (guillaume, 2017). according to industry reports, for rural areas to be commercially viable, significant cost reductions are needed by more than a factor 10 (genaro et al. 2018). innovations in both technology and operation are therefore essential to drive these costs down and shift the supply curve to the right as shown in figure 7(b). supply enhancing measures include – improvements in satellite backhaul leading to reduction in cost from $150k to $100k and coverage from 60% to 70% as shown in figure 7(b). another key measure is to deploy smaller base stations that have low power consumption, low-cost and very low maintenance –called small cells. small cells are compact, low-powered, fully integrated base stations that present mno’s with cost-effective solutions for coverage and capacity (guillaume, 2017). figure 7: (a) equilibrium point for sustainable coverage (b) shifting equilibrium points to lower costs (source: guillaume, t. 2017) 3. the game changer: small cells and satellite 3.1 demystifying myths around rural and remote coverage recent developments in both mobile and satellite technologies have addressed some of the technical challenges and demystified some of the myths around rural and remote connectivity. base stations: the advent of ‘small cells’ (small, low power base stations) as against powerhungry macro bss supports a business case for rural and remote connectivity. power: as most of the small cells only require tens to 10 watts maximum, simple single-phase supply available at distribution level is what is needed without the need for complex three-phase systems. where mains power supply is rarely available, as in many developing countries and isolated, remote areas of developed nations, equipment that operate with dc of 12/24v are sufficient and can be powered by solar, wind, fuel or other alternative power sources. battery banks and efficient power systems need to be designed depending on the use environment. backhaul: recent advancements in satellite technology, new modulation and coding schemes, efficient multiple access techniques etc. have now enabled effective and affordable satellite backhaul systems for coverage extension to rural/remote areas. such a system meets various needs for operators and end-users when used to transport data between the small cells and the core network, such as much wider coverage, availability anytime anywhere even with no prior http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 83 physical infrastructure on ground (ideal for ships, aircraft), rapid deployment, security for military communications (erik et al., 2011). figure 8 below summarises the solutions to the 3 key technical challenges mentioned earlier. figure 8: key technical challenges to rural and remote coverage (source: erik et al., 2011) site acquisition and maintenance: due to their sizes, small cells are very easy to maintain with no requirements for cooling and complex debugging. they can be mounted on walls, street posts, roof tops, etc., but must withstand outdoor temperatures. 3.2 solution in radio access network (ran): small cells in order for mnos to operate in a commercially sustainable way in rural/remote areas, there needs to be a paradigm shift in deployment architecture of the dense base stations required. one effective method is to rely on “small cells”, which are defined according to the small cell forum, as operator-controlled, low-powered radio access nodes, including those in licensed spectrum and unlicensed carrier-grade wi-fi. they are small size, fully integrated base stations comprising of both the baseband processing and the radio module in one physical unit, and typically have a range from 10 metres to several hundred metres (1-2 km). they provide improved cellular coverage and capacity and are used in applications for homes and enterprises as well as metropolitan and rural public spaces (khawar et al., 2015). due to their low-power, size and easy installation feature, they present a cost-effective solution to bridge the gap between data demand and capacity, close coverage-holes and extend connectivity to rural, remote areas in a profitable way. generally, small cells have the following features: low-cost, low power, small form factor solutions provide targeted local coverage and dedicated capacity comprise of both the baseband processing and the radio module in one physical unit delivering cellular services with cots standard based equipment – affordable, available easy installation and near-zero maintenance, rapid deployments and self-organizing features support a wide range of backhaul solutions can be easily mounted on any structure, without rigid, expensive framework or equipment, hence, less prone to vandalization and theft. mnos could deploy numerous small cells with significantly lower risks, and costs in terms of both capex and opex. small cells could be targeted to specific locations where needed. file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 84 3.2.1 types of small cells table 2 highlights the types of small cells with their different characteristics. typically, small cells range from indoor-based residential/enterprise femtocells to picocells/microcells, which are mostly deployed for capacity increase in urban host-pots or coverage extension to remote areas. macrocells are the traditional base stations we see every day mounted on huge towers with high power consumption and cooling requirements (xiaolu, 2013). table 2: types of small cells cell type output power (w) cell radius (km) users locations femtocell 0.001 to 0.25 0.010 to 0.1 1 to 30 indoor pico cell 0.25 to 1 0.1 to 0.2 30 to 100 indoor/outdoor micro cell 1 to 10 0.3 to 2.0 100 to 2000 indoor/outdoor macro cell 10 to >50 8 to 30 >2000 outdoor 3.2.2 purpose the main reasons for deploying small cells are for capacity enhancement and coverage extension, which can be generally classified but not limited to the following: 1. providing additional capacity at a high-traffic location (hot-spot). 2. offloading traffic from a congested macro-cell. 3. providing higher capacity and performance at the edge of a macro-cell. 4. extending coverage at the edge of the network and into isolated or remote areas. out interest in this paper is to consider the case 4 above where small cells are deployed for extending coverage to under-served, remote, small or mobile communities, and explore how this can be done effectively in conjunction with satellite as a backhaul option. therefore, we will concentrate on use of pico and micro/metropolitan cells for outdoor use as against residential/home femtocells which have been widely studied for capacity enhancement indoors (qiang et al., 2009, khawar et al., 2015, kapovitis et al., 2018). figure 9 below shows some of the scenarios where small cells could be deployed with satellite backhaul. whether for extending coverage into rural/remote areas such as villages, islands, offshore communication, or transportation (aircraft, ships, high-speed trains), small cells and satellites can provide ubiquitous connectivity. figure 9: small cells and satellite: insensitive to distance and mobility (source: khawar et al., 2015) 3.3 satellite backhaul satellite as a backhaul option for coverage extension in such scenarios meets various needs for operators and end-users when used to transport data between the small cells and the core http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 85 network, such as much wider coverage, availability anytime anywhere even with no prior physical infrastructure on ground (ideal for ships, aircraft), rapid deployment, security for military communications etc. services being provided to these areas by the small cells over satellite could be prioritized for voice in form of 2g only systems, or could provide more data support in forms of 3g and probably 4g systems, especially for more developed markets where the business case will support the appropriate network roll-out. traditionally, satellite backhaul was considered wasteful, expensive, cumbersome and ‘old’. recently however, advances in space sector, v-sat and complementary terrestrial systems have revived the market for satellite backhaul and demystified certain myths around it. common problems traditionally associated with satellite backhaul of ip data especially with 3g/4g small cells include: latency and jitter, base station and node b synchronization, space segment cost and weather conditions (especially in the bands with higher available bandwidth for broadband such as ka and ku bands). also, eavesdropping and active intrusion used to be easier in satellite networks due to their broadcast nature compared to pure terrestrial systems. the long delays and burst errors could lead to loss of security synchronization as well, compromising the integrity and reliability of communication. furthermore, the round-trip time of around 540ms for satellite two-way communication is not ideal for effective operation of the transmission control protocol (tcp) protocol since it requires three-way handshake to set up and maintain connections (roddy, d. 2006). 3.3.1 recent advances in satellite technology however, most of these problems have been adequately addressed with advances in satellite system technology. first among such advances is the shift to second generation dvb or dvb-s2, making the networks much faster and more efficient via introduction of adaptive coding and modulation (acm). rain fade and bad weather is also better addressed by this innovation and capacity is not wasted in clear sky weather since system adapts to specific environment. satellite launch costs have significantly been reduced due to improving technology, competition from new entrants such as space x, and better economies of scale (vince, 2015). the introduction of time division multiple access (tdma) systems has also been a major driver in the use of satellite for small cell backhaul because it allows for effective sharing a pool of bandwidth resources by many sites in a cost-effective manner as against single-channel per carrier (scpc) systems which allocates dedicated bandwidth to a single user irrespective of usage as illustrated in figure 10 below. lastly, advanced high throughput satellites (hta) now enable frequency reuse via spot beams of ku and ka bands, offering very high capacity and spectral efficiency with significant cost reductions per mhz of capacity, also reducing the space segment cost significantly. examples of such satellite systems are eutelsat’s ka satellite with multiple spot beams over europe as captured in figure 11 below. others are viasat1 and echostar xvii, which provide more than 100gbps of capacity, more than 100 times the capacity of traditional ku fss satellites (kapovitis et al., 2018). appropriate encryption and security measures have also been introduced to prevent quality of service (qos) degradation due to security processing, such as ipsec, and other tcp/ip performance enhancement schemes (such as tcp acceleration protocol), have been developed to allow high data rate communications over satellites (maral et al., 2011). file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 86 figure 10: scpc vs. tdma (maral et al., 2011) as shown in figure 10, scpc allocates maximum bandwidth per site always –wasteful, static, while tdma allocates bandwidth on-demand to each site – economical, dynamic figure 11: footprint for conventional and high throughput satellites (source: vince, 2015) the increased broadband capacity by hts implies cheaper bandwidth, translating directly to reduce opex as presented in figure 12 where the cost per bit of new generation hts are compared with traditional satellites to show the significant reduction in cost by the newer generation systems. figure 12: cost reduction in satellite systems (source: vince, 2015) 3.4 proposed architecture of small cells and satellite http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 87 figure 13 shows a typical architecture for the proposed small cells and satellite system. numerous small cells provide connectivity to a rural/remote location, with their traffic aggregated at a v-sat for onward transmission to the core network (backhaul) through a high throughput satellite. the teleport is required in connecting the satellite network to the rest of the terrestrial core network for ip connectivity (khawar et al., 2015). figure 13: typical architecture of small cells with satellite backhaul (source: khawar et al., 2015) 3.4.1 some real-life deployments as given in [small cell over satellite, 2014] gilat offers the cell-edge small cell over satellite solution, featuring the latest version of 3g – hspa+, with data rates of up to 21mbps in the downlink and 5mbps in the uplink. gilat is specialized in satellite backhaul, and have opened up access to rural areas with more than 2,000 cellular backhaul installations worldwide. the company offers the turnkey, cell-edge high-performance small cell over satellite solution, which features optimization of voice and data compression techniques, in addition to high bandwidth efficiency algorithms. this technology minimizes satellite space segment overhead, combined with satellite bandwidth allocation on demand, reducing satellite opex by as much as 80 %. the integrated cell-edge solution ensures an enhanced user experience, using tcp and http acceleration to overcome the inherent satellite delay. figure 14 shows the typical architecture of the gilat cell-edge solution (doreet, 2014). figure 14: gilat’s cell-edge over satellite solution (source: doreet, 2014) file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 88 other deployments k-net combines idirect satellite backhaul with altobridge small cells to provide connectivity in rural and remote areas of west and central africa, supporting mtn, vodafone, tigo. it has lowered tco by up to 65% compared to traditional backhaul service (richard, 2014). ruralstar: this is a huwaei technology which enables three transformations: transforming microwave or satellite transmission in traditional solutions to relay, substituting simple poles for towers, and enabling a move from diesel generators for power supply to solar power thereby shortening the return on investment (roi) period for mobile communications in remote rural areas. operators can then lower the threshold of profitability by 50%. the solution has been successfully deployed by 12 operators in eight counties, including nigeria, thailand, ghana, indonesia, and mexico, examples of which are presented in figures 15 and 16 respectively. it won the gsma award for “best mobile innovation for emerging markets” in year 2018 (madeline et al., 2018). figure 15: rural star 2.0 small cell in nigeria figure 16: rural star small cell in ghana (source: madeline et al., 2018) as seen by the different examples, such combined solutions offer a unique cost-effective solution to serving rural, remote areas. the small cells allow mno’s expand networks without the high costs of installing and maintaining macro base stations. satellite backhaul is insensitive to distance or terrain, allowing multiple sites to be connected quickly and without prior infrastructure. hts and tdma allow frequency re-use by spot beams and dynamic bandwidth allocation and sharing on-demand. with such solution, mno’s are only paying for the satellite bandwidth that they need, and serving customers that they target, using infrastructure that is likely to pay for itself in weeks or months, rather than years (madeline et al., 2018). 4. conclusion rural and remote coverage is key to bridging the coverage gap, close imbalance and, increase operator revenues and subscriber base, and drive economic development across the nation. the industry has been skeptical in deploying systems to such sparsely populated areas, or for mobile platforms, dead-zones and disaster situations because the economics hardly justify the roll-out of expensive macro-base stations. with advent of low-power, low-range, small radio access points, the cost of deployment and maintenance is significantly reduced, and operators can strategically choose to engineer their networks to address target areas quickly and with ease. the impact of mobile on gdp and other sectors of the economy such – education, health, http://www.azojete.com.ng arid zone journal of engineering, technology and environment, june, 2019; vol. 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818; www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 89 commerce etc. are incentives for governments to ensure effective and transparent policy and regulatory frameworks are established for boosting rural mobile coverage. the small cells and satellite collaboration proves that the space industry and mobile sector can effectively complement each other for mutual benefits. such a combination enables much wider coverage for many small cells, is very quick to deploy, provides dynamic and affordable bandwidth pooling capability so as to provide coverage only when and where needed, offers greater level of flexibility, power management and security for rural/remote cell sites. it could also proffer significant contribution towards nigeria’s target of 50% broadband penetration by 2020. future communication satellites of nigeria should be designed to be hts and consider serving mno’s for cellular backhaul, mobile broadband and rural/remote coverage in africa as a niche market. reference astely, d., dahlman, e., furuskar, a. and jading, y. 2009. lte: the evolution of mobile broadband. communications magazine, ieee, 47: 44-51. bright, j. and dimitris, m. 2012. satellite backhaul for rural small cells, idirect, informa telecoms and media. available on https://www.digitaltveurope.com/files/2012/05/satellite-backhaul-forrural-small-cells2.pdf. accessed 11th may 2019. buckwell, b. and liberatore, f. 2018. enabling rural coverage london (uk), gsma, https://www.gsma.com/mobilefordevelopment/wpcontent/uploads/2018/02/enabling_rural_cov erage english_february_2018.pdf . access on 14 february, 2018. dennis, r. 2006. satellite communications. mcgraw-hill prof med/tech, n.y. doreet, o. 2014. small cell over satellite: connecting rural areas cost effectively, satmagazine. available at https://www.gilat.com/wp-content/uploads/2017/03/gilat-article-satmagazine2014-04-small-cell-over-satellite-connecting-rural-areas-cost-effectively.pdf. accessed on 24th november 2018. erik, d., stephan, p. and sköld, j. 2011. 4g lte/lte-advanced for mobile broadband. oxford, uk. academic press. genaro, c. and guillaume, t. 2018. enabling rural coverage: regulatory and policy recommendations to foster mobile broadband coverage in developing countries. gsma technical report. accessed 20th january 2019 and available on: https://www.gsma.com/mobilefordevelopment/resources/enabling-rural-coverage-report/. guillaume, t. 2017. enablers for commercially sustainable mobile network expansion. gsma technical report. accessed on 10th december, 2018 and available on: https://www.gsma.com/mobilefordevelopment/wp-content/uploads/2016/07/unlocking-rural coverage-enablers-for-commercially-sustainable-mobile-network-expansion_english.pdf kapovits, a., corici, m., gavras, a. and frank b. 2018. satellite communications integration with terrestrial networks. china communications, 15(8): 22-38. khawar, a., ahmad, i. and sulyman, a. 2015. spectrum sharing between small cells and satellites: opportunities and challenges. ieee international conference on communication workshop (iccw), london, pp. 1600-1605. https://www.digitaltveurope.com/files/2012/05/satellite-backhaul-for-rural-small-cells2.pdf https://www.digitaltveurope.com/files/2012/05/satellite-backhaul-for-rural-small-cells2.pdf https://www.gsma.com/mobilefordevelopment/wp-%20content/uploads/2018/02/enabling_rural_coverage https://www.gsma.com/mobilefordevelopment/wp-%20content/uploads/2018/02/enabling_rural_coverage https://www.gilat.com/wp-content/uploads/2017/03/gilat-article-satmagazine-2014-04-small-cell-over-satellite-connecting-rural-areas-cost-effectively.pdf https://www.gilat.com/wp-content/uploads/2017/03/gilat-article-satmagazine-2014-04-small-cell-over-satellite-connecting-rural-areas-cost-effectively.pdf https://www.gsma.com/mobilefordevelopment/resources/enabling-rural-coverage-report/ https://www.gsma.com/mobilefordevelopment/wp-content/uploads/2016/07/unlocking-rural file:///c:/users/user/downloads/azojete143/www.azojete.com.ng abdullahi, et al.: unlocking rural and remote coverage with small cells and satellite. azojete, 15(sp.i2):75-90. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: abdullahi.umar@cstd.nasrda.gov.ng 90 kolawole, o. 2018. jumia mobile report nigeria. accessed december 2018 and available on: https://www.jumia.com.ng/mobile-report/ madeline, k. and genaro, c. 2018. rural connectivity innovation case study: using light sites to drive rural coverage – huawei ruralstar and mtn ghana. accessed 13th april 2019 and available on: https://www.gsma.com/mobilefordevelopment/resources/rural-connectivity-innovationcase-study-using-light-sites-to-drive-rural-coverage-huawei-ruralstar-and-mtn-ghana/ maral, g. and bousquet, m. 2011. satellite communications systems: systems, techniques and technology. john wiley & sons, n. y. mogensen, p., na, w. and istvan, z. 2007. lte capacity compared to the shannon bound, in proceedings of ieee vehicular technology conference spring 2007, pp. 1234-1238. peter, bds. 2010. satellite broadband industry looks to overcome image problem. available on: https://spacenews.com/satellite-broadband-industry-looks-overcome-image-problem/. accessed 22 july 2012. qiang, czw., rossotto, cm. and kimura, k. 2009. economic impacts of broadband in information and communications for development 2009: extending reach and increasing impact. new york, (us). world bank. ray, lm. 2010. closing the mobile data revenue gap, unstrung pyramid research. available at https://docplayer.net/1974300-white-paper-closing-the-mobile-data-revenue-gap.html. accessed 20th may 2019. richard, h. 2014. small cells connect developing world, available on https://www.ipaccess.com/uploads/wysiwyg_editor/files/altobridge%20case%20study_idr.pdf, accessed april 2019. vince, o. 2015. high throughput satellites enable rural and remote services. available at https://www.slideshare.net/smallcellforum1/hughes-high-throughput-satellites-hts-enablerural-and-remote-services. accessed on 11th january 2019. williams, c., solomon, g. and pepper, r. 2012, what is the effect of mobile telephony on economic growth? available on https://www.gsma.com/publicpolicy/wpcontent/uploads/2012/11/gsma-deloitte impact-mobile-telephony-economic-growth.pdf . accessed on 20th april 2019. xiaolu c., yang y. and fredrik g. 2013. heterogeneous cellular networks theory, simulation and deployment, cambridge university press, new york, united states of america https://www.gsma.com/mobilefordevelopment/resources/rural-connectivity-innovation-case-studyhttps://www.gsma.com/mobilefordevelopment/resources/rural-connectivity-innovation-case-studyhttps://spacenews.com/satellite-broadband-industry-looks-overcome-image-problem/ https://docplayer.net/1974300-white-paper-closing-the-mobile-data-revenue-gap.html https://www.ipaccess.com/uploads/wysiwyg_editor/files/altobridge%20case%20study_idr.pdf https://www.slideshare.net/smallcellforum1/hughes-high-throughput-satellites-hts-enable-rural-and-remote-services https://www.slideshare.net/smallcellforum1/hughes-high-throughput-satellites-hts-enable-rural-and-remote-services https://www.gsma.com/publicpolicy/wp-content/uploads/2012/11/gsma-deloitte https://www.gsma.com/publicpolicy/wp-content/uploads/2012/11/gsma-deloitte http://www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 202 arid zone journal of engineering, technology & environment original research article mechanical properties of goat hoof fiber reinforced polystrene composite for car bumper c. nathan*, e. b. bwala, a. a. barnabas and i. y. ayomikun department of mechanical engineering nigerian army university biu borno state *corresponding author’s email address: *chindapin@gmail.com article information abstract natural materials are good reinforcements for composite materials due to their eco-friendliness and potentials for improved mechanical properties. this study explores the potential of goat hoof fibers as a reinforcing material in polystyrene composites for car bumpers. different % composition mixes of goat hoof fibers and polystyrene matrix were used as samples a-f. samples a(100% polystyrene and 0% goat hoof), sample b(90% polystyrene and 10% goat hoof), sample c(80% polystyrene and 20% goat hoof), sample d (70% polystyrene and 30% goat hoof), sample e (60 polystyrene and 40% goat hoof), sample f (50 polystyrene and 50% goat hoof. the samples were then moulded into different shapes depending on the type of test to be conducted on the samples. the test conducted on sample composition mixes are tensile test, impact test, flexural test and hardness the results of the experiments conducted on sample d (70% polystyrene and 30% goat hoof) gave the following results (14.9mpa, 75.23kn, 71.3mpa, 56.92kn/m2) and for sample e (60% polystyrene and 40% goat hoof) gave the following results (11.66mpa, 69.2kn, 71.2mpa, 51.4kn/m2) and for sample c (80% polystyrene and 20% goat hoof) gave the following results (10mpa, 70.9kn, 70.9mpa, 46.2kn/m2) respectively. the results of the values obtained by samples d, e and c composition mixes gave values that compare reasonable with the values obtained by the conventional car bumpers. submitted: 4th june 2024 revised: 2nd december 2024 accepted: 8th february 2025 keywords: bumpers goat hoof polystyrene fibers matrix © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction composite is a heterogeneous substance consisting of two or more materials which does not lose the characteristics of each component but brings about new desirable properties, naturally occurring composites are tendon, bone, bamboo, rock, and many other biological and geological materials (mallick, 2007). composites, particularly polymer-matrix composite laminates are increasingly used for elements capable of absorbing energy from impact loads while undergoing deformation (morello et al, 2011). materials with high impact resistance are required for a great number of applications (chatys et al, 2013) including controlled mobile systems (takosoglu, 2016). for example, unmanned aerial vehicles such materials are also desirable for elements of an automotive bumper system protecting the front and rear ends of a motor vehicle which need to withstand small impact loads during a collision (roy et al, 2014). composite materials play an important role in modern industry through the design and manufacture of advanced materials capable of attaining higher stiffness/density and strength/density ratios. these ratios allow composite materials to be used in various applications where the weight and strength of the structure are highly significant in design parameters (felix et al, 2017). impact resistance in composites is the study of the effects of damage induced by striking a foreign body on a material and the factors affecting it, which are generally recognized as the most severe threat to composite structures (kroschwitz, 2005). any material that is to be used for car bumper must be able to absorb more energy on collision, it should have good rust resistance, it should have high strength and light in weight for easy to manufacture in large quantity and should be of low cost (felix et al, 2017). a good quality bumpers should be able to protect more serious and expensive damage when two cars crash. since bumper is an exterior part of passenger cars to protect the cars from more expensive damage (julian, 2016). azojete march 2025. vol.21(1):202-209 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:chindapin@gmail.com mailto:*chindapin@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 203 the hoof wall is the weight-bearing and protecting structure surrounding the distal phalanx of the goat. during impact, the hoof wall repetitively withstands conclusive forces and transmits the forces to the bones and joints of the limb. during impact, the hoof wall must resist excessive abrasion in order to protect the interior structure (jing et al, 2020). the reactional forces on the hoof during impact involve two dynamic processes, low impact loads at high vibration frequency characterize by the collision of the hoof with the ground, followed by high forces at low frequency which are largely attributable to the onset of the collision of the torso with the limb (behnke et al 2018; thomson and peterson, 2008). investigation of the surface strains of the hoof wall under different locomotion conditions indicate that the wall is loaded principally in compression (douglass et al, 1996). mechanical test of the equine hoof wall indicate that the wall is stiffer in compression than in tension. (jing et al, 2020). the effect of hoof wall viscoelasticity on the mechanical properties have been evaluated with the result suggesting that the stiffness increased with stain rate, while the fracture resistance was unaffected by strain rate (kasapi and gosline, 1996). the major objective of this research work is to determine the mechanical and physical properties of goat hoof fiber reinforced polystyrene composite material for the production of car bumpers. the goat breed slaughtered at the slabs and restaurants was the sokoto red with weight of 25kg – 50kg. the total number of butchers involved in slaughtering was 26. daily slaughter at the two slabs was 65 goats/day: while average slaughter at the twelve restaurants was 19goats/day with average of 26 slaughter days in a month. total goats slaughtered daily in sagamu township estimated at 84 goats which was undertaken by 21 butchers and slaughter can be extend to late hours in the evening depending on the customer’s demand. some of the butcher’s also render slaughter services to the restaurants at fee. a total of 120 pairs of goat horn and 556 quadruple pairs of goat hoof were sampled for the hoof and horn. the samples waste weighed produced 16065.76kg hoof meal and 2702.73kg horn meal (sule et, al 2020). felix et, al (2017) carried out an analysis on the application of glass fiber reinforced composite in the production of light weight car bumper (a case study of mechanical properties) and obtained tensile strength to be 3.9 mpa, impact strength of 100 kn/m2 and 60% of weight compared to steel. equally julian (2016) performed research on the use of natural fiber composites for bumper materials. the research found out that carbon charcoal gave an impact of 67.14 kn/m2, banana stem 15.75 kn/m2 and wedd 12.50 kn/m2 and the compressive strength of 22.50 kpa, 11.98 kpa, and 15.38 kpa respectively. in addition, sulove (2019) investigated the mechanical properties of a recycled polypropylene/talc composites for car bumper application and found out that the tensile strength of samples 1-3 are 20.4mpa 118.2mpa and 20.7 mpa. the flexural strength at 1.44 was found to be 31.2 mpa, 31.5mpa and 36 mpa for samples 1-3. subsequently, vipul et al (2020) worked on the design optimization of hybrid bio composite materials and found out the tensile strength gave the value of 49.28mpa and the flexural strength 152.21mpa and the density to be 1.142g/cm3. it can also be seen that olorunnishola and adubi (2018) compared and analyzed the blend of natural jute and glass fibers with synthetic glass fibers composites as car bumper materials. the result showed that the hardness sample 1-3 gave the values of 62.9 kn/m2, 63.8 kn/m2, 64 kn/m2 respectively and the impact results are 12.0 mn/m2, 10.8mn/m2, and 12.2mn/m2 respectively for samples 1-3. the aim of the study is to determine the mechanical properties of polystyrene and goat hoof mix in different proportion as composite materials and compare them with standard properties of car bumpers. 2. materials and methods 2.1 materials 2.1.1 composite matrix material: polystyrene (ps) polystyrene was chosen because is commonly used thermoplastic polymer that offers good mechanical properties, such as high strength and stiffness. it is lightweight, which is crucial for automotive applications to minimize the overall weight of the car. additionally, polystyrene has good impact resistance, making it suitable for use in car bumpers that are subjected to significant external forces during collision. another significant advantage of polystyrene is it a cost-effective. plate 1 shows the polystyrene used for the experiment and plate 2 shows six (6) composition mixtures of polystyrene and goat hoof used for the experiment. the percentage composition mixtures in plate 2 are labelled from a-f. table 1 gives the percentage composition mixtures by weight that are seen plate 2. a, b, c, d, e and f (100% polystyrene and 0% goat hoof, 90% polystyrene and 10% goat hoof, 80% polystyrene and 20% goat hoof, 70% polystyrene and 30% goat hoof, 60% polystyrene and 40% goat hoof, 50% polystyrene and 50% goat hoof ) respectively (ibitoye, 2024). http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 204 table 1: composition mixtures s/n polystyrene (%) goat hoof (%) sample label 1 100 0 sample a 2 90 10 sample b 3 80 20 sample c 4 70 30 sample d 5 60 40 sample e 6 50 50 sample f 2.1.2 reinforcing material: goat hoof fiber (ghf) goat hoof fiber was selected as the reinforcing material for the composite due to its unique properties. natural fibers, such as goat hoof fiber have gained attention in the recent years as an eco-friendly alternative to synthetic fibers. they offer several advantages, such as high specific strength, low density, biodegradability and renewability. it was noted that goat hoof exhibits good mechanical properties such as high tensile strength, stiffness and impact resistance; these properties make it an ideal candidate for reinforcing the polystyrene matrix, enhancing the composite’s overall mechanical performance. additionally, the use of goat hoof fiber offers environmental benefits by reducing dependency on non-renewable resources and contributes to the reduction of carbon footprint compared to traditional synthetic fiber-reinforced composite. plate 3 shows the sample of goat hoof used in the experiment before crushing and plate 4 shows the pulverized goat hoof used in the experiment. different percentage composition of the pulverized goat hoof were used in the experiment as shown in table 1 (ibitoye, 2024). plate 3: goat hoof sample plate 4: pulverized goat hoof sample plate 1: polystyrene plate 2: composition mixtures http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 205 2.1.3 conventional bumper samples three conventional/standard car bumpers were used for this research: bumper sample for toyota corolla le labelled as cbsa, bumper sample for mercedes benz c class as cbsb, bumper sample of honda 86 as cbsc. 2.1.4 procedure for sample preparation goat hoof fiber (ghf) was used as the reinforcing material. in order to achieve this, samples of goat hoofs are collected from the slaughter slab in zaria local government area of kaduna state. the collected goat hoof samples were then washed off of hair and rumen digester with borehole water. the hoofs were boiled in water at boiling point to remove the bony structure attached to the sole of the hoof (dina et al, 2023) and sun-dried for twenty-one days. dried samples were then weighed using a weighing balance and the weight of the dried sample of goat hoof fiber was measured to be 125 grams with tolerance value of ± 0.2. afterwards, the samples were milled using fabricated local burr mill grinder as originally adopted by odugbose & sule (2014) and was sieved using a sieve of 300µm aperture. 2.2 methods 2.2.1 tensile test the tensile test were performed on the samples according to astm d3039 standard. the specimens were tested using a calibrated autograph-ags-2003 testing machine with speed of 5mm/min (felix et al, 2017) 2.2.2 flexural strength test the specimens were tested by a calibrated autgraph ags-2003 testing machine. the flexural strength was conducted according to the astm d790 (3-point bending standard). the specimens with desired dimensions and velocity of 5 mm/min were tested. the testing was conducted for various span length of 100mm, 80mm and 60mm (felix et al, 2017). 2.2.3 impact test izod impact test methods were conducted according to the astm 256-04 standard. the sample with specified dimensions and notches were prepared and tested for impact (felix et al, 2017). 3. results and discussions 3.1 tensile strength figure 1 shows the graph of tensile strength against % fiber loading. it can be seen from the graph that the highest tensile strength was obtained to be 14.96 mpa for sample d and lowest with 6.4mpa with sample a. the tensile strength of samples d, e, f and c compares reasonable with the values obtained by conventional/standard car bumpers cbsa, 14.96 mpa, cbsb 10.08 mpa, cbsc 11.67 mpa. samples a and b have values 6.4 mpa, 9.6 mpa, less than the conventional/standard bumpers. these sample materials can also be used in many other engineering applications that requires lesser tensile strength. http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 206 3.2 impact test figure 2 shows the graph of impact strength against % fiber loading. it can be seen from the graph that the highest impact test was obtained with sample a 85.9kn with sample a and lowest value of 69.2 kn with sample e. samples b, c, d and f gave values of 75.25 kn, 70.9 kn, 75.23 kn and 71 kn respectively which are slightly higher than the values obtained by the conventional/standard bumpers cbsa (70 kn), cbsb (68 kn) and cbsc (77 kn). according to the comparism made above, it can be said that the fabricated samples have good impact result for car bumpers. 3.3 flexural strength figure 3 shows the graph of flexural strength against % weight of fiber loading. the highest flexural strength was recorded to be 85.9 mpa for sample a and the lowest of 69.2 mpa for sample e. almost all the samples gave good values of flexural strength in terms of the % composition mix ration and compares reasonable with 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 cbsa cbsb cbsc im p ac t st re n gt h (k n ) fiber loading ( %) a b c d e f 0 2 4 6 8 10 12 14 16 0% 10% 20% 30% 40% 50% cbsa cbsb cbsc t e n si le s tr e n g th ( m p a ) fiber loading % a b c d e f figure 1: plot of tensile strength against fiber loading note: cbsa=bumper sample of toyota corolla le, cbsb=bumper sample of mercedes benz c class, cbsc=bumper sample of honda 86 figure 2: impact strength against % fiber loading where cbsa=bumper sample of toyota corolla le, cbsb=bumper sample of mercedes benz c class, cbsc=bumper sample of honda 86 http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 207 the conventional/standard car bumpers. the flexural strength of the other samples were found to be 75.25mpa, 70.9mpa, 75.23mpa, and 71mpa for samples b, c, d f respectively which compares well with cbsa, cbsb, and cbsc with values 70 mpa, 68 mpa and 77 mpa respectively. 3.4 hardness figure 4 shows the graph of hardness against % fiber loading. it can be seen from the graph that samples d gave the highest hardness of 56.92 kn/m2 and the lowest hardness was obtained with samples f with the value of 32.7kn/m2. samples a, b, c and e gave the values of 32.7 kn/m2, 41.7 kn/m2, 46.2 kn/m2 and 51.4 kn/m2 respectively. comparing the results with the conventional bumpers, it can be seen that only samples d and e compares reasonable with conventional car bumpers cbs a (53 kn/m2), cbsb (60 kn/m2) and cbsc (70 kn/m2). the values of other samples which are less than the cbsa, cbsb, and cbsc can also be used in other engineering applications that requires less hardness. 4. conclusion from the experiments and analysis carried out on the goat hoof fibers and the different composition mixtures in the experiment using epoxy resin, it was discovered that goat hoof satisfied almost all of the mechanical 0 10 20 30 40 50 60 70 80 90 100 0% 10% 20% 30% 40% 50% cbsa cbsb cbsc f le x u ra l sr e n gt h ( m p a) fiber loading (%) a b c d e f figure 3: flexural strength against % fiber loading where cbsa=bumper sample of toyota corolla le, cbsb=bumper sample of mercedes benz c class, cbsc=bumper sample of honda 86 figure 4: hardness test against % fiber loading 0 10 20 30 40 50 60 70 80 0% 10% 20% 30% 40% 50% cbsa cbsb cbsc h ar d n e ss t e st ( k n /m 2 ) fiber loading (%) a b c d e f http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 208 properties needed in the production of car bumpers for toyota corolla le, mercedes benz class and honda 86. references benke, r. r. 2017. numerical time-domain modelling of hoof ground interaction during the stance phase. equine veterinary journal, 50 (4): 519-524. chatys r. 2013. investigation of effect of distribution of the static strength on the fatigue failure of a layed composite by using the markov chains theory, mechanics of composite materials, 45(6): 529-639. chatys, r., kleinhofs., panich., miskow. 2018. composite laminates for automotive bumpers and light weight support structures. 24th internal conference on engineering mechanics. may 14-17: 145-148 svratka, czech republic. dina, i. a., gimba c. e., hamza a., ekwumemgbo 2023. comparative study of the effect of poly lactic acid, starch, charcoal on physico – mechanical properties of virgin and waste low density polyethylene composites. journal of chemical society of nigeria, 48(3): 585 – 599. douglas, j., mittal, c. thompson, j. jofriet, j. 1996. the modulus of elasticity. equine hoof wall: implications for the mechanical function of the hoof. equine veterinary journal, 199: 1829-1836. felix, a. yahaya b. s., apeh e. s. and akinyeye j. o. 2017. application of glass fibre reinforced composite in the production of light car bumper (a case study of mechanical properties). international journal of engineering research and technology, 6(7): 575-579. ibitoye, y. a. 2024. mechanical properties of goat hoof fiber reinforced polystyrene composite for car bumper (unpublished thesis) department of mechanical engineering nigerian army university biu. jing, z., dan, b. marghitu,. john s and wenzhong, w. 2020. impact of horse hoof wall with different solid surfaces. journal of applied sciences, 10(8743): 1-12. julian, 2016. the use of natural fiber composites for bumper materials. european journal of mechanical engineering research, 3(3): 18-26. kasapi, m. a. and gosline, j. m. 1996. strain rate dependent mechanical properties of the equine hoof wall. journal of experimental biology, 199: 1133-1146. kroschwitz, j. i. 2005. high performance polymer composites, john wiley and sons new york. mallick, p. k. 2007. fiber-reinforced composites materials, manufacturing and design (3rd edition). crc press. morello, l. 2011. the automotive body, springer dordrechi heidelberg components design. volume 1 london – new york. olorunnishola, a. a. g. and adubi, e. g. 2018. a comparative analysis of a blend of natural jute and glass fibers with synthetic glass fibers composites as car bumper. journal of mechanical and civil engineering, 15 (3): 67-77. roy, r., kween j. and chol j. h. 2014. meso-scale finite element modeling of nomex honey comb cover. advance composite materials, 23(1): 17-29. sule, s. o., sotolu., a. o., ojetayo., t. a and owodeinde., f. g. 2020. evaluation and potential generation of goat hoof and horn waste as protein feedstuffs. african journal of science and nature, 11: 75-82. sulove, t. 2019. investigation into mechanical properties to use recycled polypropylene/tale composites for car bumper application. technical journal, 1(1):54 – 64. http://www.azojete.com.ng/ mailto:chindapin@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 202-209. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chindapin@gmail.com 209 takosoglu, j. e. 2016. control system of delta manipulator with pneumatic artificial muscles. journal of engineering mechanics, 5(6): 546-549. thompson, j. j., peterson, m. l. 2008. biomechanical and mechanical investigations of the hoof track interface in racing horses. veterinary clinic of north america. equine practice, 24(1): 53-77. vipul, j., mohit., and rajiv c. 2020. international symposium on fusion of science and technology. iop conference series: material science and engineering, 804. http://www.azojete.com.ng/ mailto:chindapin@gmail.com corresponding author’s email address: suleimanaji@unimaid.edu.ng 891 arid zone journal of engineering, technology & environment original research article effect of particle and fiber loading on tensile, flexural and impact properties of hybridized balanite shell particles and palmyra fiber reinforced epoxy composite d. charles, i. s. aji* and z. a. mshelia department of mechanical engineering, university of maiduguri, maiduguri borno statenigeria *correspondence author’s email address: suleimanaji@unimaid.edu.ng article information abstract the new trend of using natural fibers and fillers has greatly improved the formulation of composites. it has been established over the years that natural fibers and fillers have the required characteristics to reinforce polymers. in this study, palmyra fiber and balanite shell particles were used to reinforce epoxy c28h3002. palmyra fiber and balanite shell particles together formed the reinforcement having equal weight percentage of 50:50. the particle size of the balanite was 150µm while 90 mm length of the palmyra fiber was utilized. the compounding ratio of reinforcements to epoxy was 10:90, 20:80, 30:70, 40:60 and 50:50 respectively in order to see the effect of reinforcements loading of the epoxy on the hybrid composite’s mechanical properties. palmyra fiber was treated with 5% naoh solution before compounding in order to improve fiber-particlematrix adhesion. the composite was formulated based on the mixing plan using hand lay-up method which was followed up by a compression molding operation at 2.5 mpa of pressure in order to have good compaction of the composite and further matrix distribution. these formulated composites were named balanite palmyra epoxy (bpe), that is, bpe1, bpe2, bpe3, bpe4 and bpe5 with the numbers describing weight percentage loading of reinforcements of 10, 20, 30, 40 and 50 respectively. characterization of the composites were done to determine their tensile strength, flexural strength and impact strength. scanning electron microscopy (sem) was also carried out in order to know the interaction of the matrix and reinforcements. bpe3 with 30% reinforcement was found to have had the highest tensile strength of 52.99 mpa from 30 mpa of the pure epoxy, resulting in 44% improvement of the tensile property of the matrix with elongation at break gradually dropping with material loading as a result of reduced flexibility of the matrix resulting from interruptions of its extension by the reinforcements; impact strength of 0.494 j/mm was obtained which gave about 63% improvement of the matrix. bpe2 with 20% reinforcement gave the highest flexural strength of 141.2 mpa and presented an improved flexural property of the matrix by 34%. tensile modulus increased with reinforcements loading while flexural modulus dropped after 20% loading mainly because of the brittle nature of the matrix. the properties obtained from the hybrid composite make it suitable for low to medium load applications. submitted 17 august, 2024 revised: 31 august, 2024 accepted: 06 september, 2024 keywords: composites natural fiber waste material mechanical properties environment © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in our world today, there is a great need to free our environment from unused waste products scattered around. it is very important to achieve proper utilization of waste products, creating an environment that is free of hazards and making it possible to convert wastes to manageable business in order to solve the problem of unemployment and generate money. currently, significant efforts are being invested in the pursuit of a azojete december 2024. vol.20(4):891-902 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:*suleimanaji@unimaid.edu.ng mailto:*suleimanaji@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 892 better production and proper utilization of natural fibers to make good composites that will stand worthy of use in different areas of application. epoxies have been used widely as adhesives, coatings and also as electronic materials. they also serve as matrices for fiber-reinforced composites. they possess unique mechanical properties which include, high adhesive strength, good heat and electric resistance (hsissou et al., 2019). natural fiber is a good and renewable type of reinforcement. it can also be considered as reinforcement for polymeric materials. the inclusion of natural fiber in polymeric materials is considered to be an environmentally friendly activity and it has been a trending topic recently because of the attention given to the environment. this is worthwhile because of their advantages over synthetic fibers such as low cost, low weight, minimal damage to processing equipment, great surface finish, good mechanical properties and also, availability (lotfi et al., 2021). balanite shell particles are gotten from balanite aegyptiaca (l.), which belongs to the zygophyllaceae family, native to africa and is found in tropical and subtropical parts of africa, mostly used for medicinal purpose. the shell of the fruit is usually thrown away leaving behind a problem of unused resources and dirty environment. these desert dates found in most of the states of northern nigeria are cheap and abundant (murthy et al., 2020). palmyra fiber is gotten from palmyra fruits also known as borassus flabellifer. this is also found in most parts of africa and asia and it belongs to the family (arecaceae). it is found in great quantity in the northern states of nigeria. the tree produces fruits twice in a year. palmyra has natural long fibers which are always available, eco-friendly and are renewable in their behavior (srinivasababu et al., 2014). the fruit contains the succulent watery part engulfing the fiber. the nice-smelling succulent part is eaten while the fiber is thrown away as waste. sathishkumar et al. (2022) gave a comprehensive analysis on the synthesis and mechanical properties of natural fiber reinforced epoxy/polyester/polypropylene composites using different natural fibers and methods that includes hand layup. they observed that there was a decrease in tensile strength of the natural fibers with respect to cellulose removal. on the other hand, vengaiah et al. (2021) studied some physical properties of palmyra fiber. the fibers were gathered, washed, soaked in an alkaline solution at 70% (naoh) and then dried under the sun. the palmyra fruit pulp percentage ranged from 21.67 to 56.67% with the average value 37.82%, nut percentage ranges from 27.78 to 58.33% with the average value 46.06%, and sheet/fiber percentage ranged from 9.82 to 20% with the average value 16.12% as given. the coefficient of friction ranged from 0.27 ± 0.04. these values indicate the viability of palmyra fiber in composite formulation. kai zhang et al., (2018) investigated the thermal stability of a bamboo fiber reinforced epoxy composite and also checked the suitability and appropriate concentration of naoh for bamboo fiber treatment. fibers treatment with 2 wt.%, 6 wt.% and 10 wt.% naoh solutions for 12 hrs were conducted and hand lay-up technique was used for the fabrication of the composites using epoxy as the matrix material. they concluded that the fibers that were treated with 6 wt. % naoh demonstrated improved tensile properties and bonding with epoxy which also gave an improved thermal characteristic. parbin et al. (2019) reviewed mechanical properties of natural fiber reinforced epoxy composites and concluded that natural fiber composites exhibit best tensile, flexural and impact properties. furthermore, lower concentration of naoh gave better tensile strength and hardness. ram et al. (2018) studied the dynamic mechanical properties of asian palmyra sprouts fiber reinforced epoxy composites by using the hand lay-up method to prepare the composite after 1% of naoh solution treatment of the fiber. it was concluded that the dynamic mechanical properties of asian palmyra fiber reinforced epoxy composites were greatly dependent on the percentage of fiber loading. in another study, (rizal et al., 2018) studied the crystalline structure, morphology, wettability, interfacial shear strength, tensile, flexural and impact strength of typha fiber reinforced epoxy composite. the composites were prepared using the hand lay-up technique after soaking the fiber in 5% naoh solution. it was concluded that naoh successfully eliminated lignin and celluloses from the fiber and the tensile, flexural, interfacial shear strength and impact strength of the typha fiber reinforced epoxy composite were increased. the improved mechanical properties were due to the better interfacial compatibility between the alkali treated typha fiber and epoxy resin. ganapathy et al. (2021) studied the effect of graphene powder on banyan aerial root fibers reinforced epoxy composites. epoxy resin (araldite ly 556) of density 1.2 g/cc and hardener (aradur hy 951) of density 0.98 http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 893 g/cc were used. the long fiber was soaked in 5% naoh solution for 2hrs and then washed with tap water to remove naoh from the surface of the fibers. the result showed good improvement in mechanical properties. however, high rate of water absorption was observed due to the hydrophilic nature of the fibers. the major challenges in solid waste management include waste generation, poor collection of waste, poor treatment and disposal processes (soni et al., 2022). the demand of the manufacturing industry for newer and better materials keeps increasing and this leads to constant efforts to satisfy this demand. the composite that is made up of palmyra fiber, balanite shell particles and epoxy resin can be applied to many automobile components and building materials because of its good mechanical properties that closely relates to most automobile interior components. it is a demonstration of improving thermoset composites that are ecofriendly from a socio-economic point of view. using natural fibers such as borassus flabellifer, flax, sisal, jute and kenaf to replace synthetic fibers in composite formulation has been on the increase but the matter of compatibility has to be taken seriously with the matrix in mind (dinesh et al., 2015) and aji et al. 2011). however, modifications can also be done either by physical or chemical treatment to make natural fiber reinforced composites suitable for specific uses (rohan et al., 2018). this work developed a hybrid composite from the combination of particle and fiber to reinforce epoxy matrix. 2. materials and methods 2.1 materials the raw materials used for this work were palmyra fiber, balanite shell particles, epoxy resin, distilled water and 5 mol of sodium hydroxide (naoh). palmyra fruits were purchased from a palmyra farm in kaltungo, gombe state, nigeria. balanite fruits were purchased in maiduguri monday market, nigeria and epoxy resin c28h3002 was purchased from e.b poly company, gombe state nigeria. 2.2 equipment the equipment used for this work are presented in table 1. table 1: equipment and specification s/n equipment purpose model 1 universal testing machine tensile/flexural test d-100kn (sn:190536) 2 hammer mill grinding of balanite mb11c 3 metal mold box composite structure 180mm×180mm×3.2mm 4 standard sieve sieving of particles 150µm 5 resil impact tester impact test resil (695-0000) 6 scanning electron microscope sem test jsm it 700hr 8 digital weighing balance weighing of samples mettler http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 894 2.3 preparation of balanite shell particles balanite shells were separated from their fruits by pressing them manually with the hand. the separated shells were washed thoroughly with water and dried under the sun for 48hrs. after drying, they were ground into particles using a hammer mill and then sieved with a standard sieve of 150µm because smaller particles perform better as a result of better compaction (lawal et al., 2017). figure 1 presents the balanite shell particles. figure 1: balanite shell particles 2.4 preparation and treatment of palmyra fiber palmyra fruits (figure 2a) were gotten from a palmyra farm in kaltungo, gombe state, nigeria and washed with hot water combined with (nacl) then rinsed in water to remove greater amount of the pulp. the fiber (figure 2b) was cut with the aid of a sharp knife into uniform length of 90 mm because of the need for longer fiber in hand-lay-up process. it was allowed to dry under the sun for 48 hrs. palmyra fiber was plunged into a solution containing 5% naoh for 1hr to enhance adhesion between the matrix and fiber by exposing the fiber interlocking surfaces (reddy et al., 2020). this will help to improve the interfacial fiber and matrix bonding. the fiber was washed repeatedly with distilled water so that it would be free of alkali used for its treatment. the fiber was tagged alkaline free after indicating a ph value of 7.0. (a) (b) figure 2 (a and b): palmyra fruit and fruit fiber 2.5 preparation of composite 2.5.1 compounding the balanite shell particles were utilized with palmyra fiber at 50:50 percent weight ratio ranging from 1050%. the balanite shell particles and epoxy were mixed manually with a stirring rod for about 20 minutes to achieve a homogenous state (lawal et al., 2017). the composites were named bpe (balanite, palmyra and epoxy) for easy identification. table 2 presents the mix ratio and formulation utilized for this work. http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 895 table 2: mix ratio of epoxy, palmyra fiber and balanite shell particles sample balanite and palmyra(50:50 % weight) epoxy resin (% weight) control (100% epoxy) bpe 1 10% 90% pbe 2 20% 80% bpe 3 30% 70% bpe 4 40% 60% bpe 5 50% 50% 2.5.2 hand lay-up hand lay-up method accompanied by compression moulding was used to prepare the hybrid composite. a mold of 180mm×180mm×3.2mm was used and a resin repellant material was spread on the surface of the mold to avoid adhesion between the mold and the composite after curing. the first layer of epoxy resin and balanite shell particles mixture was spread at the base of the mold and palmyra fibers were arranged and uniformly distributed to the different parts of the already spread epoxy and balanite shell particles mixture. mixture of epoxy and balanite shell particles was spread again on the arranged palmyra fibers. this process was carefully repeated until the desired thickness was achieved. a pressure of 2.5 mpa was applied on the mold by a compression molding machine to exert pressure on it allowing its cure for 24hrs (ram et al., 2018). 2.6 characterization of the hybrid composites 2.6.1 determination of tensile strength the tensile strength test was conducted according to astm d-638 by using a universal testing machine with a testing speed of 5mm/min and sample dimension of 165mm×19mm×3.2mm. the samples were subjected to tensile force with both ends clipped to the testing machine till failure was observed on the sample and the failure load was recorded. tensile strength, tensile modulus and elongation at brake were generated automatically by the machine. 2.6.2 determination of flexural strength flexural test was carried out in the department of mechanical engineering workshop, ahmadu bello university, zaria according to astm d-790 with sample size of 100mm×25mm×3.2mm. the samples were placed horizontally at 80mm gauge length on a support pan. using a hounsfield monsanto universal testing machine, load was applied to the center producing bending (three-point bending) at a specified rate until there was failure in the specimen. the utm documented the result up to when the sample failed. readings of the maximum load (n) and the deflection (mm) were taken. 2.6.3 determination of impact strength properties impact strength test was carried out in accordance to astm d-256. ceast resil impact testing machine (6957.0000) was used to conduct the test. the dimensions for the specimens were 64mm×12.7mm×3.2mm. a hammer, weighing 1500 n was inclined at an angle of 1500 and released on the specimen. specimen was vertically clamped on the jaw of the machine and notched at an angle of 400. the load that resulted to a failure was recorded as the impact energy. this procedure was repeated five times and average value recorded. the impact strength was calculated using equation 1 as recommended by koppula et al., (2018). http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 896 𝐼𝑚𝑝𝑎𝑐𝑡𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ = 𝐴𝑣𝑒𝑟𝑎𝑔𝑒𝐼𝑚𝑝𝑎𝑐𝑡𝐸𝑛𝑒𝑟𝑔𝑦 𝑆𝑝𝑒𝑐𝑖𝑚𝑒𝑛𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 (1) 3. results and discussion 3.1 tensile strength it can be seen clearly in figure 3 that addition of balanite shell particles and palmyra fiber resulted to an increase in tensile strength of the composite. the minimum amount of reinforcement added to pure epoxy stepped up its tensile strength. this is similar to the result obtained in the investigation of nurazzi et al. (2020) on the reinforcement of polyester with sugar palm yarn fiber. initially the control sample had a tensile strength of 29.73 mpa and 10% of reinforcement improved the tensile property to 36.60 mpa. furthermore 20% loading of the matrix increased the tensile strength to 47.60 mpa. the peak of tensile strength was gotten when the reinforcement reached 30% with a value of 52.99 mpa and further addition resulted in a slight drop to 51.01mpa at 40% reinforcement which dropped further at 50% loading. this drop in tensile strength at higher loading was due to inadequate wetting of the reinforcement by the matrix to cover the entire reinforcement and continue the distribution of load in the composite. bpe3 which has the highest tensile strength value improved the tensile strength of the matrix by 44%. figure 3: effect of reinforcement on tensile strength of bpe composites the result was further checked using the scanning electron microscopy and presented in figure4 when the specimen, bpe3, failed during test. sem showed a uniform balanite and palmyra fiber distribution at the top. the bottom region shows where the failure occurred and the balanite shell particles were forcefully separated from palmyra fiber. delamination of the reinforcement increased stress distribution to different parts of the composite which resulted in failure. this also, is similar to the findings of nurazzi et al. (2019). 0 10 20 30 40 50 60 control 10% 20% 30% 40% 50% te n si le s tr en gt h m p a percentage weight of reinforcement http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 897 figure 4: sem of failed bpe3 tensile strength test sample 3.2. tensile modulus figure 5 shows that the stiffness of the composite increased with increase in fiber loading as reinforcement increased from 10% to 30%. it can also be seen that the elastic modulus dropped slightly at 40% reinforcement. this drop could be due to poor adhesion between the fibers and matrix and also as a result non-uniform distribution of balanite shell particles. this is similar to the result obtained by nurazzi et al. (2020). however, the modulus remarkably increased at 50% loading to indicate the expected result of more cellulose in composite increases the modulus of composites. figure 5: effect of reinforcement on tensile modulus of bpe composites 3.3 elongation at break figure 6 shows that elongation decreased as reinforcement increased. epoxy was stretched to 5.26% but subsequent addition of reinforcement led to a direct proportionate decrease in elongation. the decrease in elongation is because the deformations of palmyra fiber and balanite shell particles are less than that of epoxy which made epoxy to deform at a smaller length than it normally should. koyuncu and erkek (2022) made the same observation in a study while reinforcing epoxy with walnut husk and pumice particles. furthermore, the addition of filler led to a decrease in elongation at break because it made the composite more brittle that may likely be as a result of the brittle nature of epoxy. 0 500 1000 1500 2000 2500 3000 control 10% 20% 30% 40% 50% te n si le m o d o lu s m p a percentage weight of reinforcement http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 898 figure 6: effect of reinforcement on elongation of bpe composites 3.4 flexural strength figure 7 shows the flexural strength test result of the balanite shell particles and palmyra fiber reinforced epoxy composite. the highest value of flexural strength, 141 mpa was obtained at 20% loading of reinforcements. it can also be noted that after obtaining the peak flexural value, there was a gradual decrease with respect to addition of reinforcement to 98.76 mpa 50%. this drop in flexural property is due to the formation of voids and poor bonding as reinforcement loading increased; this also affected the distribution of load from the matrix to the reinforcement. this flexural behavior of the composite is similar to what was obtained in the study conducted by samuel et al. (2018). bpe2 with 20% reinforcement increased the flexural strength of the matrix by only 34%. this further confirm that the brittle nature of epoxy in combination with brittle reinforcements affected stress distribution even at lower loading which jeopardized getting better strength at higher material reinforcements. figure 7: effect of reinforcement on the flexural strength of bpe composites the sem result with optimum value for flexural strength at 20% reinforcement loading shows that there was a homogenous matrix-fiber mix. further addition of reinforcement led to reduction of flexural strength although the decrease was not abrupt. this is similar to the study conducted by zin et al. (2019). the decrease in flexural strength could be due to higher fiber loading that resulted in fiber entanglement likely because of 0 1 2 3 4 5 6 control 10% 20% 30% 40% 50% e lo n g a ti o n % percentage weight of reinforcement 0 20 40 60 80 100 120 140 160 control 10% 20% 30% 40% 50% fl ex u ra l s tr en gt h m p a percentage weight of reinforcement http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 899 the brittle nature of the matrix. this affected the flexural strength of the composite. from the sem in figure 8, fiber breakage can be seen at some points due to failure caused by the three-point bending forces even at lower stress. figure 8: sem micrograph of 20% reinforcement flexural strength sample 3.5 flexural modulus it can be seen in figure 9 that flexural modulus increased with reinforcements up to the 20% reinforcement. a maximum of 8 gpa was obtained at the maximum positive reinforcement before it went through a gradual drop in modulus to about 3.528gpa at 50% loading. this result is similar to what samuel et al. (2018) observed in a study in which doum palm shell particles were used to reinforce polypropylene. further introduction of particle may have made the composite rigid and therefore blocking further stress distribution within the composite. this made fiber pullout very easy at higher material loading. figure 9: effect of reinforcement on flexural modulus of bpe composites 0 1 2 3 4 5 6 7 8 9 control 10% 20% 30% 40% 50% fl ex u ra l m o d o lu s g p a percentage weight of reinforcements http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 900 3.6 impact strength figure 10 shows the result of the impact strength of palmyra fiber and balanite shell particles reinforced epoxy composites with their different percentage compositions. the combination at 30% reinforcement gave the maximum impact strength of 0.494 j/mm. the control sample, pure epoxy had impact strength of 0.183 j/mm. from this value, an improvement of 63% was achieved at 30% reinforcement before it dropped at higher material loading. this decrease is as a result of voids formed due to higher material loading that caused easy fiber pullout which affected the fiber-reinforcement bonding. saba et al. (2019) also observed an improvement in impact strength when reinforcement was added, but there was a negative change in the impact strength when fiber was loaded continuously. addition of reinforcement increased the brittleness of the composite and therefore a reduction in impact strength with continuous loading of reinforcement. figure 10: effect of reinforcement on the impact strength of bpe composites the sem result in plate 5 shows the dispersion of balanite shell particles and palmyra fiber due to the impact energy exerted on the composite with 30% reinforcement. though the impact force had an effect on the reinforcement arrangement on the composite as observed at the topmost part of figure 11, impact load was transferred to the palmyra fiber and balanite shell particles which made impact stress to be minimal. unequal distribution of the matrix on the fiber increased the brittleness of the composite which resulted in its failure. figure11: sem micrograph of 30% reinforcement impact strength sample 0 0.1 0.2 0.3 0.4 0.5 0.6 control 10% 20% 30% 40% 50% im p ac t st re n gt h j /m m percentage of reinforcement http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 901 4. conclusion balanite shell particles and palmyra fiber reinforced epoxy hybrid composite was successfully produced using the hand lay-up method and compression molding operation. characterization of the produced composite revealed that reinforcing pure epoxy with balanite shell particles and palmyra fiber improved its tensile, flexural and impact properties. tensile strength reached its peak when 30% of reinforcement was added resulting to 44% improvement on the tensile property of the matrix while the highest value for flexural strength was obtained when 20% of reinforcement was added which is as a result of the brittle nature of the composite that became clearer with the three-point bending test. the highest flexural property obtained shows that the flexural property of pure epoxy was improved by 34%. addition of 30% reinforcement increased the impact strength of the composite to its highest value which indicated 63% improvement on pure epoxy. this composite can be used in low to medium strength applications such as automobile interior parts and household equipment like waldrop. references aji, is., zainudin, es., khalina, a., sapuan, sm. and khairul, md. 2011. studying the effect of fiber size and fiber loading on the mechanical properties of hybridized kenaf/palf reinforced hdpe composite.journal of reinforced plastics and composites, 30(6):546-553. doi: 10.1177/0731684411399141. dinesh, av., ramesh, u.and demise, m. 2015. evaluation of fluxctural properties of aluminum, borassus flabellifer fiber and polyester composites. international journal of engineering research and general science, 3(6): 21-25. ganapathy, t., sathiskumar, r., sanjay, mr., senthamaraikannan, p., saravanakumar, ss., parameswaranpillai, j. and siengchin, s. 2021. effect of graphene powder on banyan aerial root fibers reinforced epoxy composites. journal of natural fibers, 18(7): 1029–1036. https://doi.org/10.1080/15440478.2019.1675219 hsissou, r., bekhta, a., khudhair, m., berradi, m., el-aouni, n. and elharfi, a. 2019. review on epoxy polymers composites with improved properties. journal of chemical technology and metallurgy, 54(6): 1128–1136. kai, z., fangxin, w., wenyan, l., zhenqing, w., zhiwei, d.and bin, y. 2018. thermal and mechanical properties of bamboo fiber reinforced epoxy composites. polymers, 10(6): 608, https://doi.org/10.3390/polym10060608 koppula, s., kaviti, ak. and namala, kk. 2018. experimental investigation of fibre reinforced composite materials under impact load. iop conference series: materials science and engineering, 330: 012047. https://doi.org/10.1088/1757-899x/330/1/012047. koyuncu, m. and erkek, b. 2022. effects of particle size, pumice powder filling on the water absorption behavior, and elongation at break properties of walnut husk particles reinforced epoxy composite. the european journal of research and development, 2(2): 182–189. https://doi.org/10.56038/ejrnd.v2i2.51 lawal, ss., bala, kc. and alegbede, at. 2017. development and production of brake pad from sawdust composite. leonardo journal of sciences, 30: 47–56. lotfi, a., li, h., dao, dv. and prusty, g. 2021. natural fiber–reinforced composites: a review on material, manufacturing, and machinability. journal of thermoplastic composite materials, 34(2): 238–284. https://doi.org/10.1177/0892705719844546 murthy, hn., yadav, gg., dewir, yh. and ibrahim, a. 2020. phytochemicals and biological activity of desert date (balanites aegyptiaca (l.) delile). plants, 10(1): 32. https://doi.org/10.3390/plants10010032 http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng https://doi.org/10.1080/15440478.2019.1675219 https://doi.org/10.3390/polym10060608 arid zone journal of engineering, technology and environment, december 2024; vol.20(4):891-902. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: suleimanaji@unimaid.edu.ng 902 nurazzi, n., khalina, k. and sapuan, s. 2019. mechanical properties of sugar palm yarn/woven glass fiber reinforced unsaturated polyester composites: effect of fiber loadings and alkaline treatment. polimery, 64(10):665–675. https://doi.org/10.14314/polimery.2019.10.3 nurazzi, nm., khalina, a., chandrasekar, m., aisyah, ha., rafiqah, sa., ilyas, ra. and hanafee, zm. 2020. effect of fiber orientation and fiber loading on the mechanical and thermal properties of sugar palm yarn fiber reinforced unsaturated polyester resin composites. polimery, 65(02): 115–124. https://doi.org/10.14314/polimery.2020.2.5 parbin, s., nitin, kw., suraj, ks.and sabah, k. 2019. mechanical properties of natural fiber reinforced epoxy composites: a review. procedia computer science, 152: 375–379. ram, ajks., kumar, ma. and reddy, mi. 2018. dynamic mechanical analysis of asian palmyra sprouts fiber reinforced epoxy composites. international research journal of engineering and technology (irjet), 05(07): 183–187. reddy, ra., yoganandam, k. and mohanavel, v. 2020. effect of chemical treatment on natural fiber for use in fiber reinforced composites – review. materials today: proceedings, 33: 2996–2999. https://doi.org/10.1016/j.matpr.2020.02.982 rizal, s., ikramullah, gda., thalib, s., huzni, s. and abdul khalil, hps. 2018. interfacial compatibility evaluation on the fiber treatment in the typha fiber reinforced epoxy composites and their effect on the chemical and mechanical properties. polymers, 10(12): article 12. https://doi.org/10.3390/polym10121316 rohan, t., tushar, b. and get, m. 2018. review of natural fiber composites. iop conference series: materials science and engineering, 314: 012020. https://doi.org/10.1088/1757-899x/314/1/012020 saba, n., alothman, oy., almutairi, z., jawaid, m. and ghori, w. 2019. date palm reinforced epoxy composites: tensile, impact and morphological properties. journal of materials research and technology, 8(5): 3959–3969. https://doi.org/10.1016/j.jmrt.2019.07.004 samuel, as., isuwa, sa. and aje, t. 2018. effects of particle size and loading on tensile and flexural properties of polypropylene reinforced doum palm shell particles composites. american scientific research journal for engineering, technology, and sciences, 44(1): 231-239.(asrjets). http://asrjetsjournal.org/ sathishkumar, gk., ibrahim, m., mohamed am., rajkumar, g., gopinath, b., karpagam, r., karthik, p., martin charles, m., gautham, g. and gowri, sg. 2022. synthesis and mechanical properties of natural fiber reinforced. journal of natural fibers, 9(5): 1-24. soni, a., das, pk., yusuf, m., kamyab, h. and chelliapan, s. 2022. development of sand-plastic composites as floor tiles using silica sand and recycled thermoplastics: a sustainable approach for cleaner production. scientific reports, 12(1): 18921. https://doi.org/10.1038/s41598-022-19635-1 srinivasababu, n., kumar, js. and reddy, kvk.2014. manufacturing and characterization of long palmyra palm/borassus flabellifer petiole fibre reinforced polyester composites. procedia technology, 14: 252–259. https://doi.org/10.1016/j.protcy.2014.08.033 vengaiah, pc., kaleemullah, s., madhava, m., mani, a. and sreekanth, b. 2021. some physical properties of palmyrah palm (borassus flabellifer l.) fruits. current journal of applied science and technology, 40(24): 18–25. https://doi.org/10.9734/cjast/2021/v40i2431498 zin, mh., abdan, k. and norizan, mn. 2019. the effect of different fiber loading on flexural and thermal properties of banana/pineapple leaf (palf)/glass hybrid composite. structural health monitoring of biocomposites, fibre-reinforced composites and hybrid composites. elsevier, uk. pp 1-17. https://doi.org/10.1016/b978-0-08-102291-7.00001-0 http://www.azojete.com.ng/ mailto:*suleimanaji@unimaid.edu.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 942 arid zone journal of engineering, technology & environment original research article numerical analysis of a seamless mild steel pole for low and medium-tension power transmission line in borno state nigeria m. shuwa1*, u. mukhtar1, i. mu’azu2, m. i. ishaq1 and f. m. kajiama1 1department of mechanical engineering, university of maiduguri, maiduguri, nigeria 2federal neuropsychiatric hospital, maiduguri, nigeria *corresponding author’s email: mshuwa@unimaid.edu.ng article information abstract this work presents a computational method of evaluating structural performance of a seamless mild steel pipe material under various load conditions for supporting low and medium-tension power transmission lines. the low and medium tension power transmission line seamless mild steel (lmtptl-sms) pole material was specifically analyzed for reliability and resilience considering the environmental and operational conditions of borno state, nigeria. borno state’s power infrastructure is subjected to significant challenges, one of which is stochastic wind loads due to harsh environmental factors. this threat has led to poles failure resulting in vandalism and power outages. to ensure the reliability and resilience of the power network, a robust pole structural design is critical. in this work a 9.7536m seamless mild steel pole material asme sa-106 grade b was selected based on availability and cost for analysis. comsol multi-physics 5.2 numerical code was used to develop and analyze the behavior of the pole material based on predefined loading conditions and on the assumptions of euler-bernoulli’s beam-column theory. using the code’s solid mechanics interface displacement and stress distribution response on the pole when subjected to static, dynamic and aerodynamic loads simultaneously were computed and analyzed at an excitation frequency of 110 ghz. the result shows a frequency response of the transfer function in terms of electric field norm of 3.7 𝑥 10−79𝑉𝑚−1 under the predefined loading conditions, which was greater than 8.5 𝑥 10−78𝑉𝑚−1 the response established by the manufacturers of the mild steel pipe material. the maximum stress recorded was 8.82𝑥107 𝑁/𝑚 which is less than the 8𝑥108 𝑁/𝑚 yield strength of the selected pole material. it was observed that the displacement is from 0𝑚 at the root to maximum value of 0.11𝑚 at the top. the maximum displacement recorded was 0.39m. this value is 22% less than the determined critical displacement of the pole material, which was 0.50m... thus, the displacement was within the elastic limit of the pole material based on the defined geometry and boundary condition. furthermore, the f-test statistical tool used to validate these results with an experimental one carried out shows that there is no significant difference between the two results. therefore, the analysis established that the selected pole material was reliable under the predefined simultaneously applied extreme loads, thus, the lmtptl-sms pole will be suitable for use in borno state, nigeria, thus objective of the work was achieved. received: 8th august 2025 revised: 13th november 2025 accepted: 14th november 2025 keywords: numerical analysis pole stress aerodynamic load displacement © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction reliable and sustainable electricity supply is fundamental to socio-economic development. in nigeria, and particularly in the northeastern state of borno, power infrastructure faces unique and severe challenges, including the destruction of transmission lines by difficult environmental conditions and insurgency. following extended power outages, efforts have been made to restore and improve electricity supply, notably with the establishment of new generating projects. however, the resilience and structural integrity of the transmission azojete december 2025. vol.21(4):942-949 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/005 www.azojete.com.ng mailto:mshuwa@unimaid.edu.ng mailto:mshuwa@unimaid.edu.ng https://doi.org/10.63958/azojete/2025/21/04/005 http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 943 infrastructure, specifically the poles that support the power lines, remain a critical issue of concern. electric transmission poles are unique structures that are used to support conductors and shield wires of a transmission line; could be either lattice type or pole type structures. lattice type structures are used for high tension voltages while poles types are used for low to medium tension (aliyu and abejide, 2019). materials used in power pole construction can be wood, reinforced concrete, steel or even composite materials, such as fiber reinforced plastic or fiber reinforced polymer (frp) poles that are becoming more prevalent nowadays (oyejide et al, 2014; nweke et al, 2017; aliyu and abejide, 2019). in recent years, utility providers have been searching for most cost-effective alternatives to timber poles and other pole materials due to environmental concerns, high cost of maintenance, and need for improved aesthetics. however, steel poles are considered to be the strongest material used in power pole construction that require less maintenance than the other varieties. interestingly, choosing the correct steel grade and geometry for peculiar geography and application is still a subject of concern and consequently of great significance (wapa, 2021; puwo, 2024). an electric steel pole acts as a cantilever structure, which is designed and analyzed as a tapered member with combined axial and bending loads. the forces acting on the poles are from the vertical loading (comprising dead weight of conductors, cross arms, insulators) and the horizontal loading due to wind pressure on conductors and pole. horizontal loading is the most cause of failure of transmission poles especially in areas associated with stochastic winds (wagner and mathur, 2018; wapa, 2021). borno state located between approximately latitude 10°n and 14°n and longitude 11°30'e and 14°45'e in north-east nigeria is associated with stochastic winds with an average wind speed of 3.89m/s (ngala et al, 2015; shuwa et al, 2016). the state is the second largest state in the country with 27 local government areas and more than half of these local governments are not connected to the national grid. lack of stable and steady power supply has greatly affected sustainable socio-economic development of these areas (ngala et al, 2015; shuwa et al, 2016). the most convenient and cost-effective way to transmit power to these areas is through the use of steel poles and for optimal steel pole design that will withstand defined applied loads a numerical optimization model is inevitable (khurmi and gupta, 2005; aliyu and abejide, 2019). traditional analysis methods for power line support structures may not adequately capture the complex stress dynamics caused by harsh environmental loads and potential malicious attacks. the vulnerability of these essential structures has highlighted the need for more robust design and assessment protocols. seamless mild steel poles are a viable alternative to other materials due to their superior strength, durability, and lower maintenance requirements, but a thorough analysis is necessary to optimize their performance in a challenging environment like that of borno state. numerical analysis deals with simulation of the design variables, searches for optimal solutions and is less expensive than experimental analysis (biswajit, 2010; adhikari and bhattacharya, 2012; umesh, 2016 ; da silva and oliveira, 2018). numerical analysis of a seamless mild steel pole for power transmission lines involves applying computational methods to evaluate its structural performance under various load conditions. this is used to ensure the pole's stability, strength, and durability for supporting low and medium-tension lines. a numerical model is defined by a mesh network, which is made up of the geometric arrangement of elements and nodes(guoyang and song, 2016; gizachew and belete, 2019). nodes represent points at which features such as displacements and stress are calculated. the numerical packages use node numbers to serve as an identification tool in viewing solutions in structures such as deformation or deflection, stress and strain caused by applied structural and aerodynamic loads (strivridou et al, 2015; mandal et al, 2018; ferroudji et al, 2020; saihi and roummani, 2020; ferroudji, 2021; saari et al, 2024). 2. materials and methods american society of mechanical engineers (asme) sa-106 grade b (british standard b.s. 980 cds-2) seamless mild steel pipe was selected for the pole material the material is a low carbon steel material whose main components are carbon, silicon, manganese and small amounts of chromium, copper, nickel and molybdenum (puwo, 2024). the selection is based on local availability, strength and cost of the material. the selected pole material has a yield strength of 8 𝑥 108 𝑁/𝑚2, young’s modulus 𝐸𝑠𝑝 of 2 𝑥 1011 𝑁/𝑚2, poisson’s ratio 𝑛 of 0.33 and density 𝜌 of 7850 𝑘𝑔/𝑚3. the pole has two sections (lower and upper), with the lower section having outside diameter (od) of 0.2032m, wall thickness (wt) of 0.008m and a length (l) of 6.7056m. the upper section has an outside diameter (od) of 0.1524m, wall thickness (wt) of 0.006m and a length (l) of 3.048m. the lower section was conically reduced to weld the upper section as shown in figure 1. comsol multi-physics 5.2 numerical code was used to analyze the behavior of the lmtptl-sms pole under the assumptions of euler-bernoulli’s beam-column theory and based on geometry and material of the mild steel pole. using the code’s solid mechanics interface displacement and stress distribution response on the http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 944 pole when subjected to static, dynamic and aerodynamic loads simultaneously were computed and analyzed at an excitation frequency of 110 ghz. electromagnetic wave code was used to solve for time harmonic electromagnetic field distribution of the pole model under the predefined loading condition. figure 1: geometry of the high-tension power line seamless mild steel (htp-sms) pole (puwo, 2024) the lmtptl-sms pole geometry was created using the 3d model wizard of the numerical code. geometrical parameters such as outside diameters (od and od), wall thickness (wt) and height (h) were defined to build the pole in the numerical code’s graphical window. the pole material property was selected and defined from the numerical code material data base as mild steel. the pole is modeled and analyzed as a beam-column under static and distributed aerodynamic loads. boundary conditions are applied, with top of the pole considered as a free end and fixed constrained at the bottom as shown in figure 2. figure 2: loads on the htpl-sms pole (abejide, 2019) the self-weight of the lmtptl-sms pole 𝑊𝑠𝑝(𝑦) isdetermined from equation 1 as 3,011.03𝑁, weight of the insulators and insulators accessories𝑊𝑛𝑠(𝑦)determined from equation 2 as 235.44𝑁and weight of the conductors𝑊𝑠𝑡(𝑦)determined from equation 3 as1,177.2𝑁.the sum of these loads wasthe static load 𝑊𝑠𝑡(𝑦) applied at the top of the pole considered as fixed constrain along the 𝑦 axis and determined from equation 4 as 4,423.67𝑁 given by the summation of equation 1, 2 and 3 (khurmi and gupta, 2005). 𝑊𝑠𝑝(𝑦) = 𝑚𝑠𝑝𝑔 1 𝑊𝑛𝑠(𝑦) = 𝑚𝑛𝑠𝑔 2 𝑊𝑐𝑛(𝑦) = 𝑚𝑐𝑛𝑔 3 𝑊𝑠𝑡(𝑦) = 𝑔(𝑚𝑠𝑝 + 𝑚 + 𝑚𝑐𝑛) 4 where 𝑚𝑠𝑝 is the measured mass of the lmtptl-sms pole, 𝑚𝑛𝑠 mass of the insulator and insulator accessories, 𝑚𝑐𝑛 is the mass of the conductor the pole is expected to suspend and 𝑔 is 9.81 𝑚𝑠−2. aerodynamic load 𝑊𝑎𝑟(𝑥) of 20.13𝑁 due to stochastic wind is applied to the pole in the 𝑥, 𝑦 and 𝑧 planes in the user define interface of the numerical code and was determined from equation 5(ferroudji et al, 2020). 𝑊𝑎𝑟(𝑥) = 𝐴𝑠𝑝𝑝𝑤𝐶𝑑 5 where 𝐴𝑠𝑝 is the projected area of the pole, 𝐶𝑑 is 1.2 the drag coefficient and 𝑝𝑤 is the wind pressure determined from equation 6 as 34.07𝑁. where 𝑣𝑤 is 23.34 𝑚𝑠−1 (52.21𝑚𝑝ℎ) the average stochastic wind velocity of borno state as computed from nime wind data from 1990-2020. 𝑝𝑤 = 0.0025(𝑣𝑤)2 6 both static and aerodynamic loads are applied simultaneously on the discretized elements of the lmtptl-sms pole to induce vibration, deformation and stresses. the pole’s vibration frequency𝑓𝑛, stiffness𝑘𝑠𝑝, http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 945 deformation𝛿𝑚𝑎𝑥 and stress distribution𝜎𝑠𝑝 are predicted based on equations 7, 8, 9 and 10 respectively (da silva and oliveira, 2018). 𝜋 1 2 𝑔𝐸𝑠𝑝𝐼𝑠𝑝 𝑓𝑛 = 4 (𝑁𝑛 + 2 ) √ 4 𝑊𝑠𝑝𝐿𝑦→𝐿 7 where 𝑁𝑛 is the mode number i.e. 1,2,3,4,…..n, 𝑊𝑠𝑝is the weight of the lmtptl-sms pole determined as 3,011.03𝑁 (306.935 𝑘𝑔 𝑥 9.81 𝑚𝑠−2), 𝐿𝑦−𝐿 is any distance along the pole’s height, and 𝑔 is 9.81 𝑚𝑠−2 acceleration due to gravity. 3𝐸𝑠𝑝𝐼𝑠𝑝 𝑘𝑠𝑝 = 𝐿3 𝑦→𝐿 8 [𝑊𝑠𝑡(𝑦) + 𝑊𝑎𝑟(𝑥,𝑦,𝑧)]𝐿 2 →𝐿 𝛿 = 𝑦 𝑚𝑎𝑥 3𝐸𝑠𝑝𝐼𝑠𝑝 9 4(𝐶𝑒𝑓𝑐𝐸𝑠𝑝𝑘𝑟𝑔𝜋) 𝜎𝑠𝑝 = ((𝐷2 − 𝑑2) + (𝐷2 − 𝑑2))𝐿 1 1 2 2 𝑦→𝐿 10 where 𝐸𝑠𝑝 is 2 𝑥 1011 𝑁/𝑚2 young modulus of the lmtptl-sms pole material, 𝐼𝑠𝑝 is 1.0765 𝑥 10−6𝑚4 the moment of inertia of the pole. the end fixitity coefficient 𝐶𝑒𝑓𝑐 is 0.25 for a beam-column with one end fixed and the other free (khurmi and gupta, 2005). the generated mesh in figure 3 consists of 2324 domain elements, 1572 boundary elements, and 236 edge elements. solution was computed and solved for 14,673 degrees of freedom and using the nodes as identification tool, solution to the pole’s deflection, stress distribution, stiffness, natural modes of vibration in terms of corresponding frequencies due to the predefined loading conditions are obtained. figure 3: the generated mesh using comsol multi-physics 5.2 numerical code. the mashed lmtptl-sms pole geometry was solved in a frequency domain interface for time-harmonic electromagnetic field distributions the predicted results of the lmtptl-sms pole deflection (displacement), stress distribution and vibration frequency response due the predefined applied loads is post processed and validated with the result form an experiment carried out on a test rig with detail is shown in figure 4. the experiment was performed to determine the pole's ultimate load capacity and its deformation behavior under simultaneously applied vertical and horizontal loads. a gradually increasing vertical and horizontal loads are applied at the pole's top and side using a hydraulic jack against a reaction frame. deflectometers, pressure and strain gauges are used to measure pile head displacement, deflection, and deformation at different height of the pole (from the bottom to the top). the obtained data was plotted as a load-displacement curve to analyze the pole's performance. http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 946 figure 4: details of the experimental test rig 3. results and discussion results of the numerical analysis shows the response of the lmtptl-sms pole as subjected to simultaneously applied static and aerodynamic loads. figure 5 shows the meshed of the lmtptl-sms pole model solved in the numerical code’s frequency domain interface for time harmonic electromagnetic field distributions. figure 5: frequency response of the transfer function in terms of electric field norm at 110 ghz excitation. the result shows that minimum frequency response of the transfer function in terms of electric field norm of3.7 𝑥 10−79𝑉𝑚−1 distributed uniformly at the circumferential boundary layer of the pole. this value increases to 4.5 𝑥 10−79𝑉𝑚−1 at the central axis of the pole through its thickness at both transfer ports. also, there exist a similarity in the transfer function from port one to port two, which are the root and top of the pole respectively. the vibration and frequency response uniformity at the outer surface of the pole shows stability in the lmtptl-sm s pole structure and that failure could be avoided, because under the predefined loading conditions the frequency response of the pole is less than 8.5 𝑥 10−78𝑉𝑚−1 the established response quoted of the steel pole material as quoted by the manufacturers presented by puwo, (2024). a study by saari et al (2024) on estimating natural frequency of steel pipe with various geometries states showed that vibration is often the cause of structural fatigue in steel pipes and therefore piping vibration need to be closely monitored and established is at the safe range. in addition, the predicted result of the stress distribution response of the http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 947 lmtptl-sms pole shown in figure 6 under the predefined loads shows a maximum stress of 8.82𝑥107 𝑁/𝑚. this is at the pole height from 0𝑚 to 1.75𝑚from the base of the pole in the direction of wind flow. figure 6: predicted stress distribution of the lmtptl-sms-pole under simultaneously applied static and aerodynamic loads. however, the magnitude of the stress decreases along the span of the pole and decreases to 4.522𝑥107 𝑁/𝑚 at 3.88𝑚 and 0 𝑁/𝑚 at 9.7536𝑚 (top of the pole). the maximum stress recorded is less than 8𝑥108 𝑁/𝑚the yield strength of the pole material ((asme) sa-106 grade b mild steel pipe). the displacement of the lmtptlsms pole from its central axis along its height (from 0𝑚 at the root to 9.7536𝑚 at the top) is shown in figure 7. the result shows gradual increases in displacement from the root (the fixed end) to the top (the free end) due the simultaneously applied extreme loading conditions. the displacement is from 0𝑚 at the root to maximum value of 0.11𝑚 at the top. this maximum value is 22% less than 0.50𝑚 the determined critical displacement of the pole material and geometry under the predefined loading conditions. based on the pole’s material, geometry and defined boundary condition the displacement was within the elastic limit of the pole material and geometry. figure 7: predicted deformation of the lmtptl-sms pipe due to the simultaneously applied predefine static and aerodynamic loads. moreover, the predicted deformation due to the extreme simultaneously applied loads was compared with a deformation from an experimental test. it was observed that the predicted values were in agreement with the values obtained from the experimental test carried out in figure 8 with a 𝑃 value of 0.989 obtained from the statical 𝐹 𝑇𝑒𝑠𝑡 carried out in microsoft excel. the 𝑃 value is greater than 0.5thus there is no significant difference between the predicted deformation and the experimental test carried out by ashaf et al 2005. http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 948 figure 8: validation of displacement along the lmtptl-sms pole span due the applied loading conditions 4. conclusion numerical analysis of the low and medium tension power transmission line seamless mild steel (lmtptl-sms) pole was successfully carried out using the numerical code comsol multi-physics 5.2. the pole’s response to simultaneously applied predefined loading conditions was examined and the results in terms of vibration, stress and displacement were analyzed. the predicted response of the pole material with regards to vibration, stress and displacement were found to be within the safe limits of the selected pole material (asme sa-106 grade b mild steel) considering the pole’s mechanical properties and geometry. the statistical tool f-test used to validate the predicted results with an experimental one shows no significant difference between the two results. thus, the selected pole material was reliable and is suitable for low and medium tension power transmission network in borno state, nigeria. references aliyu, m. and abejide, os. 2019. finite element modelling of steel poles for power production and transmissions. nigerian journal of technology (nijotech), 38(4):840-847. abejide, a. 2019. finite element modelling of steel poles for power production and transmissions. nigerian joirnal of technology (nijotech), 38(4):840-847. adhikari, s. and bhattacharya, s. 2012. dynamic analysis of wind turbine towers on flexible foundations. journal of shocks and vibrations, 19:37-56. ashraf, m., ahmad, h. m. and saddiqi, z. a. 2005. a study of power transmission poles, asian journal of civil engineering (building and housing), 6(6):511-532 biswajit, b. 2010. tower design and analysis. wit transaction on state of the art in science and engineering , 44:527-558. da silva, b.g.s. and oliveira, b.a.s. 2018. “evaluation of the nondeterministic dynamic structural response of three-timensional wind turbine steel towers. jounrnal of wind energy, 40:364-377. david, j. 2005. engineering material standard code book. new york: m. harison inc. ferroudji, f. 2021. numerical model analysis of a 850 kw turbine steel tower. international review of applied science and engineering, 12(1):10-18. ferroudji, f., lakhdar, s. and khayra, r. 2020. numerical simulations on static and dynamic response of fullscale mast structures for hdarrieus wind turbine. sage wind engineering, 45(4):822-837. http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 942-949. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mshuwa@unimaid.edu.ng 949 gizachew, dt. and belete, s. 2019. upwind 2mw horizontal axis wind turbine tower design and analysis. secience publishing group, 7(5):111-131. guoyang, x. and song, x. 2016. simulation analysis of universal fatigue life of tower load of horizontal axial force wind turbine. journal of gansu science, 28(4):115-118. khurmi, rs. and gupta, jk. 2005. machine design. new delhi: eurasia publishing house (pvt) ltd. mandal, ak., rana, kb. and tripathi,. 2018. experimental and numerical analysis on small wind turbines: a review. international journal of applied engineering research, 13(8):97-111. ngala, gm., shuwa, m., oumarou, mb. and muhammad, ab.. 2015. a cfd analysis of a micro horizontal axis wind turbine blade aerodynamics. arid zone journal of engineering, technology and environment, 11:1323. nweke, fu., anyigor, is., iburu, u. and ekpe, j. 2017. overhead lines for transmission and distribution of power system and its consequences in nigeria. international digital organization for scientific research (idosr), 2(3):1-7. oyejide, sa., adejumobi, ia., wara, st. and ajisegiri, esa. 2014. development of a grid-based rural electrification design: a case study of ishashi and ilogbo communities in lagos state. journal of electrical and electronic engineering (iosr-jeee), 9:12-21. puwo, h. 2024. material parameter handbook. guancheng: henan puwo metal materials company limited. saari, nf., putra, a., irianto, rmd., muhammad az., roszaidi r., nawal aa. and safarudin h. 2024. estimating natural frequency of pipe with various geometries: improvement of frequency factors. heliyon research article, elsevier ltd, 10(4):1-17. saihi, l and roummani, k. 2020. numerical simulations on static and dynamic response of full-scale mast structures for hdarrieus wind turbine. sage journal of wind engineering, 45(4):822-837. shuwa, m., ngala, gm. and maina, m. 2016. development and performance test of a micro horizontal axis wind turbine blade. international journal of engineering research and application, 6(2):11-17. strivridou, n., eottasakis, e. and saniotopoulos, c. 2015. finite element analysis and comparative study of welded connection of wind turbine towers under fatigue loading. international journal of applied sciences , 8:489-500. umesh, kn. 2016. design and analysis of 2-mw wind turbine tower. international journal of mechanical and production engineering, 4(10):13-17. wagner, hj. and mathur, j. 2018. introduction to wind energy systems. berlin: springer. wapa. 2021. standard 5 transmission lines steel pole structures. new york: western area power administration (wapa). http://www.azojete.com.ng/ mailto:mshuwa@unimaid.edu.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 656 arid zone journal of engineering, technology & environment original research article response surface methodology and artificial neural network modeling and optimization of luffa cylindrica fibre pyrolysis in a fixed-bed pyrolizer c. b. ugwuodo *1, h. u. itiri 1, e. ogomegbulam 1, c. mathew 1, c. n. ude 1, i. n. emmanuel 2, and s. e agbokwor3 1department of chemical engineering, college of engineering and engineering technology, michael okpara university of agriculture, umudike 2department of chemical engineering, nazarbayev university, astana, kazakstan 3department of mechanical engineering, university of nigeria nsukka *corresponding author’s email: chijiokeugwuodo@mouau.edu.ng article information abstract bio-oil production from luffa fibre, a plentiful agricultural byproduct, has attracted considerable interest as a sustainable and renewable energy source. in this study, response surface methodology (rsm) and artificial neural network (ann) modelling were used to optimize operating conditions for bio-oil produced by pyrolysis from luffa cylindrica fibre. response surface methodology (rsm) and artificial neural networks (ann) are used to model and improve operational parameters like temperature, particle size diameter, and inert gas flow rate. this is done to boost bio-oil production and quality. we develop a predictive model for bio-oil characteristics using ann modelling, which effectively optimizes pyrolysis conditions. this study offers significant knowledge on the production and characteristics of bio-oil derived from luffa cylindrica fibres. by employing both models, we leveraged response surface methodology (rsm) flexibility to provide statistical measures of individual models and their interaction impact on the process output while benefiting from artificial neural networks (ann) efficiency in processing data and acquiring complex patterns. it offers a method to improve the production process methodically. comparing the prediction findings of the ann with those of the rsm, it was shown that the former were superior. different models have been trained using various transfer functions and varying numbers of neurons with 0.99797, 1.0, and 0.9989 r² values for the training, validation, and test stages, respectively. the proposed network had an overall r² factor of 0.99869. the results were deemed satisfactory based on the overall r² value being near 1.0. the optimization of operational parameters enhances the effective transformation of luffa cylindrica fibre into bio-oil, therefore encouraging the utilization of this sustainable resource for the generation of renewable energy. this strategy aligns with the increasing focus on decreasing the environmental consequences of conventional fossil fuels and promoting alternative and ecofriendly energy supplies. received: 26th february 2025 revised: 4th april 2025 accepted: 4th april 2025 keywords: artificial neural networks box-behnken design (bbd) bio-oil pyrolysis response surface methodology (rsm) © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction a promising approach in the pursuit of environmentally friendly and renewable energy sources is the conversion of agricultural residues into biofuels (oasmaa et al., 2016). biomass pyrolysis is a thermochemical process that decomposes organic materials in the absence of oxygen, resulting in the production of bio-oil, biochar, and gaseous by-products (sutrisno & hidayat, 2016). this method is highly effective for converting agricultural residues into renewable energy sources, reducing dependence on fossil fuels while promoting sustainability (oasmaa et al., 2016). the effectiveness of pyrolysis depends on several operational parameters, including temperature, heating rate, and nitrogen gas flow rate, which significantly influence the quality and azojete june 2025. vol.21(2):656-669 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/030 www.azojete.com.ng about:blank about:blank http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 657 yield of bio-oil (irfan et al., 2023). given the rising global demand for sustainable energy solutions, pyrolysis presents a viable approach to addressing energy and environmental challenges (ryndin et al., 2023). among various biomass sources, luffa cylindrica—commonly known as loofah or sponge gourd—has shown significant potential for bio-oil and biochar production through pyrolysis. its fibrous structure, high cellulose content, and low ash content make it an ideal candidate for energy conversion (gao et al., 2020). studies have demonstrated that luffa cylindrica biomass yields bio-oil with a reduced oxygen content and biochar with high carbon concentration, making it a sustainable raw material for bioenergy applications (fadhil, 2021). additionally, utilizing luffa cylindrica for bio-oil production helps in waste management by repurposing agricultural residues into valuable energy products (abbas et al., 2018). the scientific exploration of luffa cylindrica as a biofuel feedstock underscores its relevance in promoting renewable energy and environmental sustainability. the efficiency of pyrolysis in converting biomass into bio-oil depends on critical factors such as temperature, heating rate, and inert gas flow rate (anas et al., 2024). optimal pyrolysis conditions are necessary to maximize bio-oil yield while minimizing undesirable by-products (wakatuntu et al., 2023). for instance, the study by abbas et al. (2018) demonstrated that at 500°c, the biochar and bio-oil yields from biomass pyrolysis were 39% and 19%, respectively, highlighting the importance of precise parameter control. gao et al. (2020) demonstrate that luffa cylindrica fibre possesses favourable attributes for pyrolysis, such as a substantial cellulose content and a minimal ash content. these properties facilitate the production of bio-oil with reduced oxygen level and biochar with elevated carbon content. the study highlights the possibility of luffa cylindrica fibre as a sustainable raw material for pyrolysis, underscoring its adaptability in the applications of bioenergy generation and environmental remediation. cao et al. (2017) investigated the production of biochar with the aim of creating a highly efficient catalyst for chemical reaction procedures. gui et al. (2014) assessed the efficiency of fast and slow pyrolyzed bio-oil production methods, specifically examining the control variables of temperature, heating rate, and yield. the study assessed the composition of coconut shells, rha, and 50% of each component to establish the standards. furthermore, islam et al. (2017) assessed the optimal yield coefficients for bio-oil production using solid waste in a fixed bed reactor set at 500 °c. an examination of the product indicates that the process of pyrolysis of solid waste generates 30% of liquid products and 33% of solid products. as demand for sustainable biofuels grows, optimizing pyrolysis conditions is essential for improving bio-oil quality and ensuring an efficient, scalable process. however, literature is scarce concerning the performance of luffa cylindrica fibres for improving characteristics (bakay et al., 2021). the utilization of artificial neural networks (anns) and response surface methodology (rsm) has become more prevalent in the optimization of operational parameters for the conversion of biomass to bio-oil (pazikadin et al., 2020). the methods as mentioned above provide a methodology based on empirical evidence for representing intricate connections between input variables and intended results, hence facilitating faster and more successful optimization procedures (abbas et al., 2019). response surface method (rsm) is a flexible mathematical technique that provides statistical measures of individual model components and how they interact (nwosu-obieogu et al. 2021). the response surface method (rsm) employs a limited quantity of experimental data to construct a precise model for industrial processes. it accurately represents the impact of many input process variables, including both main and interaction impacts, on the process output variable (nwosu-obieogu et al. 2022). artificial neural networks (ann) offer key benefits, especially in applications that need the representation of nonlinear interactions (kurani et al., 2023). artificial neural networks (ann) have the ability to autonomously acquire complex patterns and characteristics from unprocessed input, therefore obviating the necessity for human feature extraction. this capability is particularly advantageous in fields such as picture and speech recognition (guillod et al., 2020). these methodologies provide data-driven insights, reducing the need for extensive experimental trials while enhancing process efficiency (abbas et al., 2019). the integration of rsm and ann in biomass pyrolysis research contributes to the continuous improvement of bioenergy generation systems, making renewable energy production more feasible and sustainable (waqas et al., 2024). by employing both models, researchers can leverage rsm flexibility to provide statistical measures of individual model and their interaction impact on the process output while benefiting from ann's efficiency in processing data and acquire complex patterns. this work aims to use sophisticated methods, namely artificial neural networks (ann) and response surface methodology (rsm) modelling, to enhance the efficiency of bio-oil production from luffa cylindrica fibre by pyrolysis. the objective is to enhance the output and quality of bio-oil by optimizing critical operational parameters such as temperature, inert gas flow rate, and feedstock particle size. this study uses artificial neural network (ann) modelling to conduct predictive analysis in order to effectively optimize pyrolysis settings. http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 658 this analysis yields significant insights into the correlations between process variables and the characteristics of bio-oil. the long-term objective of this work is to methodically enhance the transformation of luffa fibre into bio-oil, therefore encouraging the utilization of this sustainable resource for the generation of renewable energy in accordance with objectives related to environmental preservation. 2. materials and method 2.1 preparation of feedstock the luffa cylindrica fibre used in this study was obtained from a farmland in amawom village in ikwuano local government area of abia state, nigeria. all foreign materials was removed by washing to ensure the sample is free from impurities. immediately after the luffa cylindrica was sun dried for ten days to remove the moisture content, after which they were ground in a high-speed rotary cutting mill and screened by standard sieve into different particle size diameter according to the design. the nitrogen gas which served as an inert gas was gotten from aba, in abia state. 2.1.1 equipment and chemicals used instruments used include, stainless steel reactor, insulator (fibre glass), condenser, seal (iron gasket), fasteners (bolts and nuts), k-type temperature controller, n2 gas cylinder, stop watch, test sieves, weight balance and electric heaters. 2.2 characterization of luffa cylindrica 2.2.1 ultimate analysis of the luffa cylindrica the purpose of this test is to determine element percent of carbon, hydrogen, nitrogen, sulphur and oxygen in the luffa cylindrica fibre. the ultimate analysis was conducted according to astm standards e777 and e778. 2.3 experimental procedures the pyrolysis of luffa cylindrica was carried out in a horizontal lab-scale fixed bed reactor. the stainless steel reactors with a length of 230 mm was used to conduct the experiments. the luffa cylindrica sample was fed into the reactor and then closed tightly and initialized with the flow of inert gas (n2 gas). in each run, a 40 g of the sample biomass was placed inside the reactor and an electric heating elements with a highly sensitive pid (proportional-integral-derivative) controller was used to heat up the reactor to reach the pyrolysis temperature and kept isothermal till desired time (20 min). the temperature inside the reactor was measured by a k type thermocouple. a 6 mm id and 9 mm od stainless steel pipe was used to connect the reactor and condenser. the connecting pipe between the reactor and the condenser system was maintained at 200°c to avoid condensation. the condensable liquid products (bio-oil) were collected in a 410 mm length condenser. the temperature of the condenser was maintained at 25°c by circulating the water in the condenser. after each experiment, the condensed liquid was collected into the sample bottle and the liquid weight was calculated by the weight difference of sample bottle before and after the liquid was collected. after pyrolysis, the solid residue was removed and weighed. then the gaseous phase was calculated from the material balance. the biomass sample input, liquid and solid char were measured by the electro balance weighing machine with an accuracy of +/ 0.01 g. the yield percentage of bio-oil during pyrolysis was estimated using equation below. % 𝑌𝑖𝑒𝑙𝑑 𝑜𝑓 𝑃𝑟𝑜𝑑𝑢𝑐𝑡 = mass of product mass of feedstock x 100 1 2.4 characterization of bio-oil 2.4.1 fourier transform infra-red (ftir) spectroscopy in this study, functional groups analysis of the bio-oil was carried out using fourier transform infra-red (ftir) spectroscopy, magna-ir550 (nicolet, madison). ftir with an online pen plotter was used to produce the infrared (ir) spectra of the derived liquids. a small amount of the bio-oil will be mounted on a potassium bromide (kbr) disc. the ftir spectrum in the ranges of 500-3500cm -1 will be measured and recorded. the absorption frequency spectra is recorded and plotted. the standard irspectra of 61 organic compounds will be used to identify the functional group of the components of the derived bio-oil (rajia et al., 2023). http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 659 2.5 design of experiment the rsm was employed based on a box behnken design in this work for the experimental design. it is a statistical tool often used for fitting quadratic models and is highly reliable when the behaviour of multiple operating parameters on the final results is considered (hossain et al., 2017). firstly, the design of the experiment starts with a layout of the design matrix that explains the factors and the response (savasari et al., 2015). the analysis was performed with bio-oil as the single response in the bbd and temperature, particle size, and inert gas flowrate as the three operating parameters. each parameter is considered at levels 1, -1, 0, α, and –α (laouge et al., 2020). the values -α and + α were evaluated using equation 1, whose value is displayed at − 2 and +2 where n represents the operating parameters. α = [2n ]1/4 2 2.6 ann model development for ann, the multi-input-single-output (miso) architectural neural fitting design in figure 1 was adopted to model the performance of the process variables and predict the optimal yield of bio-oil. the multi-input variables are temperature, inert gas flow rate, and particle size diameter, while percentage yield of bio-oil produced from luffa cylindrica fibre is the single-output. the variables were chosen to investigate the combined influence of input variables on the output variable. the miso architectural neural network in figure 1 was design to train 75 % data of the process variables, validate 15 % of the variables, and test 15 % using levenbergmarquardt training algorithm. this algorithm takes more memory and less period to run various neurons in the hidden layer. the random data were processed with different number of artificial neurons (10, 12, 15, 19 & 23) in the hidden layer and were trained on the algorithm network. the neuron with the least mean square error (mse) was taken to be the best performing algorithm network and the interactive effect of the process variable on the output was significant and maximized at data processed with the number of neurons. the best algorithm network was adopted to predict the optimal yield of bio-oil. this was done on a feed-forward back propagation network. the mean square error (mse) is represented equation 3. the correlation coefficient (r2) were determined. mse = (∑ (𝑃𝑟𝑒𝑑𝑖𝑐𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒−𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑣𝑎𝑙𝑢𝑒}2 𝑛 𝑛 𝑖=1 ) 3 where, n = number of datasets used to train the network figure 1: ann structure 2.7 optimization of the experiment the pyrolysis process was optimized using numerical optimization of design expert as to know the best possible process variables that will maximize the oil yield. the process independent variables (temperature, particle size and inert gas flow) and the response (oil yield) where optimized within the range. the software temperature oil yield particle size diameter inert gas flow rate http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 660 provides possible solutions and selects the best as a function of its desirability and importance. a good desirability is close or equal to 1 while a bad desirability is close to or equal to 0. 3. results and discussion 3.1 ultimate analysis result the high carbon and oxygen content indicates that luffa cylindrica is comprised of highly polar structures, which is beneficial to the ion exchange adsorption mechanism. likewise, the low sulphur, and nitrogen could help limit harmful chemicals deposited in the reactor compartment, consequently, reduce maintenance of the pyrolysis plant. the low sulphur and nitrogen could lead to reducing sox and nox gases which have adverse effects on the ozone layer in the troposphere (ayeni et al., 2018). this compared well with (anas et al. 2024; narayan et al. 2021). table 1: ultimate analysis of luffa cylindrica fibre elements wt % carbon 46.5 hydrogen 6.2 nitrogen 0.21 oxygen 37.6 sulphur 0.91 3.2 ftir analysis result fig. 2 depicts the spectra of fourier transform infrared spectros copy (ftir) of bio-oil yields from pyrolysis of luffa cylindrica at optimum operating condition over a wavenumber range between 500 and 4000 cm-1 in the spectrum analysis. ft-ir is a chemical analysis technique that detects the different functional groups and chemical bonds in the samples using infrared rays oyebanji et al. (2022). the ftir comprises different peaks with strong, medium, and weak intensities corresponding to various bond levels in the bio-oil. the o-h stretching at around 3235.3 cm -1 revealed the presence of alcoholic and phenolic compounds in the bio-oil. the peaks detected at 2922.2 cm-1 and 2855.1 cm-1 with c-h stretching vibrations indicate the presence of alkanes in bio-oil. the strong bond peak at 2079.9 is ascribed n=c=s stretching, indicating isothiocyanate is present, while the peak 1707.1 cm-1 and 1513.3 are accredited to ester carbonyl (c=o) groups. the medium peak 1379.1 cm-1 and 1401.1 cm-1 are assigned to o–h stretching vibration of the hydroxyl group, carboxylic acid, and water impurities. the vibration between the wavelength 500 and 1200 cm-1 is due to c–f stretching of the fluoro compound. the functional groups’ presence is similar to ogunkanmia et al. (2018) reported. the function group presence in the bio-oil makes it useful as fuel in automobile vehicles, furnaces, and marine equipment. it can also be utilised as a catalyst for the production of drugs and plastic. this results aligns with the report of sutrisno and hidayat (2016). figure 2: ft-ir spectrum of bio-oil yield from pyrolysis of luffa cylindrica fibre http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 661 3.3 response surface methodology modeling for bio-oil yield the rsmbbd results for the percentage yield of bio-oil from the pyrolysis process are presented in table 2. using design expert software version 13.0.6 usa, three variables, temperature, particle size, and gas flow rate represented by the alphabet a, b, and c, and three levels (-1, 0 and +1) were considered, resulting to seventeen experimental runs. the variation in values of the percentage yield of bio-oil indicated that the process parameters have a significant effect on the pyrolysis process. the maximum percentage yield of 30% occurred at a temperature of 6000c, particle size diameter of 5mm, and inert gas flow rate of 1.5l/min. second-order polynomial (quadratic) equations in coded terms that defined the independence between the studied process variables (a, b, c) and the response (% yield) for bio-oil were obtained with the use of rsm and represented in equations (eq.4). table 2: bbd experimental design for bio-oil yield factor 1 factor 2 factor 3 response 1 std run a:temperature b:particle diameter c:inert gas flow oil yield c mm l/min % 17 1 650 5 1 12 11 2 650 4 1.5 7.75 7 3 600 5 1.5 30 16 4 650 5 1 12 12 5 650 6 1.5 22.48 14 6 650 5 1 12 5 7 600 5 0.5 15.5 8 8 700 5 1.5 13.65 15 9 650 5 1 12 2 10 700 4 1 15.2 3 11 600 6 1 21.63 9 12 650 4 0.5 21.25 6 13 700 5 0.5 23.5 4 14 700 6 1 27.6 1 15 600 4 1 25.53 13 16 650 5 1 12 10 17 650 6 0.5 9.55 3.4 oil yield model statistical analysis analysis of variance (anova) was used to determine the statistical significance of the model and all the regressed coefficients of the developed quadratic rsm-bbd model for the % of bio-oil yield. the anova results for measuring model adequacies for yield of bio-oil are shown in table 3. the high f – value (62.85), p-value (<0.0001), and non-significant lack of fit (p-value> 0.05) indicated that the model was significant (hidayat et al., 2023). the fitness of the model was expressed by the coefficient of determination (r2) obtained as 0.9878 with an adjusted r2 value of 0.9721, which was in reasonable agreement with the predicted r2 value of 0.8044 for the developed model. this showed that the developed quadratic model had the capability of predicting the observed experimental data within the range of the study (kamarudin et al., 2019). the adequate precision value of 24.1152, which is a measure of signal-to-noise ratio greater than 4, showed the desirability of the model and indicates an adequate signal. these regression values were in agreement with the report of (malatji et al., 2020), who suggested that a high correlation confirms the degree of fitness between the predicted and experimental responses. therefore, this model can be used to navigate the design space. the linear terms (a, and b), the quadratic terms (a2, and b2) and the interactive effects of temperature: particle diameter: (ab, ac and bc) were all significant (p < 0.05) in the oil yield response model. as the process parameters increased, the positive and negative signs in equation 4 showed an increase and decrease in values of response. increased a, b, c, ab, ac, and bc led to increased response, while increased values of a2, b2, and c2 resulted in decreased response. to check for the normality of the residuals, the normal probability versus studentized residuals plot was considered in figure 3a. it showed that the points extended well diagonally, suggesting that they were dispersed in a reasonable pattern. the relationship between the predicted and observed actual experimental data in figure 3b gave a straight line, which showed agreement with each other. hence the experimental data can be said to be acceptable (reglioua et al., 2021). http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 662 table 3: anova result for bbd-rsm bio-oil yield source sum of squares df mean square fvalue p-value model 738.28 9 82.03 62.85 < 0.0001 significant a-temperature 20.19 1 20.19 15.47 0.0057 b-particle diameter 16.62 1 16.62 12.73 0.0091 c-inert gas flow 2.08 1 2.08 1.59 0.2472 ab 66.42 1 66.42 50.89 0.0002 ac 148.23 1 148.23 113.57 < 0.0001 bc 174.64 1 174.64 133.80 < 0.0001 a² 265.95 1 265.95 203.77 < 0.0001 b² 27.22 1 27.22 20.85 0.0026 c² 2.15 1 2.15 1.65 0.2399 residual 9.14 7 1.31 lack of fit 9.14 3 3.05 1.19 0.471 not significant pure error 0.0000 4 0.0000 cor total 747.41 16 std. dev. 1.14 r² 0.9878 mean 17.27 adjusted r² 0.9721 c.v. % 6.61 predicted r² 0.8044 adeq precision 24.1152 oil yield (%) = +12 – 1.59a +1.44b + 0.5100c + 4.07ab – 6.09ac + 6.61bc + 7.95a2 + 2.54b2 + 0.7150c2 (4) figure 3: (a) normal % probability vs. internal studentized residuals. (b) predicted vs. actual values 3.4.1 parametric analysis on bio-oil yield in order to gain a better knowledge and understanding of pyrolysis process for oil yield, 3d response surfaces plots were studied. these plots were used to study the interaction effects of the pair of independent variables keeping other variables constant. the 3d response surface plots are the graphical representation of the regression equation used to observe the levels of each factor (mabrouka et al., 2023). the interactive terms considered are temperature and particle diameter (ab), temperature and inert gas flow (ac), particle diameter and inert gas flow (bc). the interaction between temperature and particle diameter (ab) at fixed inert gas flow on % yield of bio-oil is shown in figure 4a. the maximum percentage (25.7%) of bio-oil yield was achieved at a temperature of 7000c and particle diameter of 6mm. at temperature levels >6500c, a steady, significant increase in the yield of bio-oil was observed from particle diameter 4 mm to 5 mm, while no significant increase in yield was observed at particle size levels > 5.0 mm. hence, an increase in ab up to a=7000c and b =6 mm resulted in an increase in % of bio-oil yield. this may be attributed to the fact that a b http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 663 below the point of 6000c the devolatilization of the feedstock has not started in full force. at this point, depolymerization is still occurring. a similar trend was recorded by ganapathy and natarajan (2009). figure 4b showed the 3d surface response plot interaction of combined effect of temperature and inert gas flow rate (ac) of bio-oil yield. increase in ac resulted in increase % yield of bio-oil. this may be a result of adequate devolatilization of the biomass and the ability of the gas to purge the volatile oil into the condenser for condensing to avoid secondary cracking. this corresponds to work done by álvarez-chávez et al. (2019). the interaction between particle diameter and inert gas flow rate (bc) was presented in figure 4c. increase in bc resulted in significant decrease in % yield of bio-oil. this may be because complete devolation of the biomass has occurred and at this point secondary cracking of the biomass only leads to formation of more gases and char, this is similar to the report of (álvarez-chávez et al., 2019). figure 4: 3d plots on the effect of particle diameter and temperature on bio-oil yield (a), 3d plots on the effect of inert gas flow and temperature on bio-oil yield (b), 3d plots on the effect of inert gas flow and particle diameter on bio-oil yield (c) 3.5 ann modelling results the ann-based model was developed based on the multi-input-single-output (miso) architectural neural fitting design. the optimal model design had 3 neurons in the input layer, 10 in the hidden layer, and 1 in the output layer. figures 5, 6, and 7 represent the error histogram, plots of regression analysis, and training error a b c http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 664 curve performance plot respectively, of the ten activating neurons. figure 5 shows the miso network model’s error histogram, which shows that the errors were within the range of − 0.01802 to 0.04973 (zero region), indicating good performance. figure 6 shows the best fit between the target data and the output data. the correlation coefficient indicates that the best training, testing, and validation were carried out using the miso architectural neural network with ten neurons. r-square values indicate extremely high correlation coefficients for the training, validation, and testing sets, ranging from 0.99797, 1.0, and 0.9989, respectively, and the overall r-square was 0.99869, as shown in figure 6, suggesting that the model performs exceptionally well and exhibits strong predictive accuracy across different data sets. the values being close to 1 indicate a nearly perfect linear relationship between the predicted and actual values, underscoring the reliability and consistency of the model across various evaluation scenarios. this is in line with the report of umeagukwu et al. (2023) and anas et al. (2024). at epoch 31, the mse dropped from 100 to 0.0011666, as seen in figure 7. the training and testing of process variables were significantly achieved at epoch 31 at the best performance validation. the maximum number of epochs for performing the best validation was 37. the lower mse values suggest that the model accurately predicted outcomes. this is in agreement with the report of anas et al. (2024). figure 5: histogram showing error distribution of experimented data and predicted data on miso mode figure 6: ann regression plot analysis for prediction of biodiesel yield using fifteen neurons http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 665 figure 7: training error curve for biodiesel yield prediction using fifteen neurons 3.6 comparing the predictive results output of rsm and ann in table 4, the simulated ann values from the levenberg-marquardt training algorithm alongside the experimental and rsm predicted values for bio-oil yield. the maximum observed oil yield (30%) is in close agreement with rsm (28.85%), and ann predicted (29.75%); this agrees with the report of anas et al. (2024) in the optimization of operational parameters using artificial neural network and support vector machine for bio-oil extracted from rice husk; hence this is an indication that the oil yield from luffa cylindrica pyrolysis was affected by the process parameters (temperature, particle size diameter and inert gas flowrate) (onu et al., 2020). the predicted results for rsm and ann were also compared to ascertain the reliability of the models using statistical indicators (r2 and mse), as shown in table 5. it was observed that both coefficients of determination (r2) of rsm (0.9878) and ann (0.99797) were close to 1. at the same time, the mse of rsm (1.14) and ann (0.0011666) is close to zero, indicating the capability of both models in predicting the pyrolysis process. however, the r2 of ann is higher than rsm, and its mse also lower than rsm, demonstrating that ann estimated the process better than rsm (lau et al., 2020; onu et al., 2020; betiku et al., 2016). table 4: box-behnken design (bbd) predictive rsm/ann model adequacy run oil yield (%) predicted rsm values predicted ann values 1 12 12 12.27 2 7.75 7.72 7.75 3 30 28.85 29.75 4 12 12 12.27 5 22.48 23.82 23.21 6 12 12 12.27 7 15.5 15.65 14.87 8 13.65 13.50 13.06 9 12 12 12.27 10 15.2 15.39 15.02 11 21.63 21.45 21.04 12 21.25 19.91 21.46 13 23.5 24.65 23.50 14 27.6 26.42 27.52 15 25.53 26.71 25.53 16 12 12 12.27 17 9.55 9.58 9.55 http://www.azojete.com.ng/ about:blank arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 666 table 5: comparison of rsm/ann performance indicators performance indicators rsm ann r2 0.9878 0.99797 mse 1.14 0.0011666 3.7 optimization of the process the optimization of the pyrolysis of luffa cylindrica fibre was done using the optimization tool of response surface methodology (rsm) and presented in figure 8. temperature, particle diameter and inert gas flow were fixed within their experimental ranges of 600-700 oc, 4-6 mm, and 0.5-1.5l/min respectively, and the oil yield were optimized within the range. optimum operating region for optimization of yield was obtained using the desirability function algorithm of box behnken design. figure 8 shows values of 604.862oc, 4.87403mm and 1.16384 as the optimum mixture for temperature, particle size and inert gas flow respectively. these values give optimum responses of yield (22.0053%), with desirability of 1. figure 8: numerical optimized value of the dependent and independent variables with desirability 4. conclusions this work represents a significant advancement in bioenergy production by examining the enhancement of bio-oil production from the pyrolysis of luffa cylindrica fibre using approaches such as response surface methodology (rsm) and artificial neural network (ann) modelling. the predictive capabilities of artificial neural network (ann) modelling have offered a streamlined method to optimize pyrolysis conditions effectively. the findings of this study provide a meaningful understanding of the complex connections between process parameters and bio-oil characteristics and provide a methodical approach to improving the manufacturing process in line with a broader effort to mitigate the environmental impact of conventional fossil fuels. references abbas, q., liu, g., yousaf, b., ali, mu., ullah, h., munir, mam, and liu, r. 2018. contrasting effects of operating conditions and biomass particle size on bulk characteristics and surface chemistry of rice husk derivedbiochars. j. anal. appl. pyrolysis. 134: 281−292. abbas, ak., al-haideri, na. and bashikh, aa. 2019. implementing artificial neural networks and support vector machines to predict lost circulation. egyptian journal of petroleum, 28(4): 339−347. anas, a., noorfidza, yh., sharjeel, w., ushtar, a., and syed, ag. 2024. optimization of operational parameters using artificial neural network and support vector machine for bio-oil extracted from rice husk. american chemical society acs omega. advance online publication. 6(18): 100424-100438. https://doi.org/10.1021/acsomega.4c03131 http://www.azojete.com.ng/ about:blank https://doi.org/10.1021/acsomega.4c03131 arid zone journal of engineering, technology and environment, june 2025; 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vol. 21(2): 656-669. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: chijiokeugwuodo@mouau.edu.ng 669 sutrisno, b. and hidayat, a. 2016. upgrading of bio-oil from the pyrolysis of biomass over the rice husk ash catalysts. iop conf. ser.: mater. sci. eng., 162, no. 012014 umeagukwu, oe., dominic, oo. and callistus, nu. 2023. methanolysis of african pear seed oil catalyzed with acid activated empty palm fruit bunch ash: optimization and sensitivity analysis. cleaner energy systems, 6(2): 100093-100106 wakatuntu, j., olupot, pw., jjagwe, j., menya, e. and okure, m. 2023. optimization of pyrolysis conditions for production of rice huskbased bio-oil as an energy carrier. results in engineering, 17(8): 100947-100962. waqas, s., harun, ny., arshad, u., laziz, am., mun, sls., bilad, mr., nordin, nah., and alsaadi, as. 2024. optimization of operational parameters using rsm, ann, and svm in membrane integrated with rotating biological contactor. chemosphere, 34(9): 140830-140847. http://www.azojete.com.ng/ about:blank corresponding author’s email address: fayomiuche@gmail.com 670 arid zone journal of engineering, technology & environment original research article integrating bands algorithm estimation on water turbidity variation in hartbeespoort dam, south africa g. u. fayomi 1,2*, e. k. onyari2, g.o. ode1, and o. i. nkwonta3 1 college of environmental sciences, bells university of technology, ota, nigeria 2 department of civil and environmental engineering & building science, university of south africa, florida science campus, cnr christian de wet road and pioneer avenue, johannesburg, south africa 3department of civil engineering and surveying development, mangosuthu university of technology, durban, south africa *corresponding author’s email: fayomiuche@gmail.com article information abstract water resources remain the most essential need for both human and ecosystems sustenance. continuous check of both surface and ground water quality remains a welcome approach globally to secure water safety and fitness for different purposes. this study aims to examine the effect of turbidity concentration on water quality of hartbeespoort dam using remote sensing and arc gis. study objectives examined the present situation of the dam water, access complete one year (2023) data of the water quality variations as weather changes. remote sensing and arc gis application was utilized for this study with the use of landsat 8-9 operational land imager (oli) and thermal infrared sensor (tir). nsmi mapping of turbidity showed high values range of 2.054 high concentration in the month of october, in february, 6.171 in june and 8.273 in october, 2023. ndti (normalized difference turbidity index) mapping equally recorded high value of 2.194 in the month of october. the regression analysis utilizes linear, exponential and polynomial equation to examine seasonal variation of turbidity in dam water. the result revealed a strong correlation such as (ndti in linear regression analysis records (𝑅2 )= 0.54 while nsmi in linear regression records ( 𝑅2 )= 0.35. the value derived from ndti and nsmi algorithm confirmed the capacity of band combination indices in retrieving suspended sediment in form of turbidity using landsat 8-9. these study findings also punctuate the effectiveness of landsat8-9 satellite imagery in evaluating turbidity concentration especially in situations where in-situ data is not available. received: 31st august 2024 revised: 2nd april 2025 accepted: 3rd april 2025 keywords: remote sensing turbidity salinity landsat 8-9 ndti ndsi © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the usefulness of water quality to human well-being and ecosystem at large escalated the constant demand for continuous monitoring of water safety. surface water body with measured high-quality content remains very essential for domestic purpose and other uses (josefin et al., 2022; seleemi et al., 2022. water is life and it also serve as a necessary component useful for existence (zhou et al., 2022). globally, water issues have been established with simulation of devalued water resource quality having repeated impact on the different uses applicable (luis et al., 2018). xiayon & wu, (2019) reaffirms that water quality reduction is regarded a serious environmental problem that will require efficient water guide and management. this is needed to protect life duration, aquatic survival and biodiversity. there are range of sequential connection relating water quality impact on human health (omole et al., 2015; obiloni et al., 2013). the correlation includes water health diseases in form of water borne infections caused by vector carriers and water scarce diseases resulting from water scarcity (sudheer et al., 2016). the threat of water quality tends to rise as the population of people increases with inclusion of improved modern technology (desai and smt, 2014). constant water quality check is needed to examine water condition and to establish the fitness for different purposes (nayla, 2020). it is also necessary to control and prevent azojete june 2025. vol.21(2):670-681 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/030 www.azojete.com.ng mailto:fayomiuche@gmail.com mailto:fayomiuche@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 671 pollution sources to the water body (issam et al., 2023). water quality indicator is assessed using physical, chemical and biological characteristics. the physio-chemical parameters comprise of total dissolve solid, total suspended solid, ph, dissolved oxygen, chlorine and sodium, turbidity, salinity, chlorophyll and hardness (issam et al., 2023; mfesan, 2021). these components generated from series of reactions of the earth natural resources such as the atmosphere, soil, and the water bodies (xiaoliang et al., 2016; norman et al., 2020). josefin et al., (2022) pointed that the connection that exist among the organisms in the earth biotic system such that the damage on one ecosystem affect the others negatively (takeshi, 2007). raj et al., (2024) pointed that high turbidity in water body is usually a sign of declined water quality and improper land use. devendra et al., (2014) pointed that turbidity estimates water muddiness and cloudiness. however, water clearness is known as the brightness and the ability for light to penetrate the water (adler 2002). the discharge of suspended solid in form of industrial waste discharge, sewage plants domestic wastewater, soil erosion among others exhibits high content of pollutant resulting to water turbidity (apriwida et al., 2016). the application of remote sensing and gis solves the challenge of time consumption, cost and elaborate labour involved in assessing data from larger water bodies. remote sensing allows summary view of a whole area and ensures broad report of water quality (mohinuddin et al., 2023; alice et al, 2023; japitana and burce, 2019) the findings of the band algorithms and band combination for water quality parameter measurements, establishes that satellite imagery and remote sensing tools is capable and detailed enough for water quality assessment and monitoring (jing et al., 2020; yashon et al., 2020). apriwadi et al., (2016) pointed that a considerable measure of turbidity was obtained using band combination of landsat-5 tm satellite image. tanya and nicholson (2018) equally confirmed that water quality parameter was derived in olushange dam with the use of landsat band 2, band 3, band 4 and band 5. the water quality parameter retrieved include turbidity, total suspended solid, total nitrogen, total phosphorous and algae count. therefore, this research examined the concentration of turbidity in hartbeespoort dam utilizing remote sensing and gis applications. the objectives focused on establishing the current condition of the dam water, acquire complete one-year data of water quality variations and compare the consistence of this study with previous assertions on the water quality of hartbeespoort dam. 2. materials and method this research methodology involved the adoption of landsat 8-9 spectral imagery bands featuring double sensors (oli, tirs) that operate simultaneously on board (kristi, 2022). landsat 8-9 imagery was provided by united states geological survey website downloaded from earthexplorer.usgs.gov (nasa/usgs) (usgs, 2020). these two sensors are fully equipped with enhanced adjusted surface reflectance and surface brightness that provides periodic coverage of land features and land mass (evans et al., (2019); badawi et al., (2019). hartbeespoort dam was obtained from google earth download. google earth pro features google's trademarked software that renders a geographical visual image of earth planet (cartong, (2021); tanya & andrew, 2018) ;). the images were acquired within a period of one year at monthly interval using landsat 89 images which also featured 11 spectral bands of 30meter spatial resolution for bands 1-7 and 15-meters for panchromatic band 8 and band 9-11 (haobin et al., 2022). table 2 revealed the features of landsat 8-9 imagery the detailed of landsat 8-9 data set imagery and the date it was acquired is shown in table 1. the images were downloaded using roll 078 and path 171 that covered hartbeespoort dam location. 2.1 study area hartbeespoort dam is the receiving end of crocodile river basin and megalies. the dam exhibits a tropical climate like other region with two major seasons which is dry season known as the winter and the summer season which is the rainfall season. the dam is situated northwest of south africa between a well-known valley megaliesberg and witwaterberg mountainv 25km away from pretoria west. since inception, the dam is known for its declined water quality (khalid et al., 2022), resulting from major inflow from the crocodile river with records of high concentrations of phosphates and nitrates (noloyiso & silberbauer, 2014). there is also high level of eutrophication recorded issues of the dam due to harmful algal bloom growth. khalid et al., (2022) identified the major source of pollution to be out flowing waste from industrial processes and domestic effluent. there are several drainage channels connected to the dam. most of this drainage are discharge flow from wastewater treatment plant, sewage workflow and industrial discharges (matodzi et al., 2017). figure 1 shows the location of hartbeespoort dam with the different drainage flow that constantly impart the water quality balance in the dam. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 672 figure 1: hartbeespoort dam location source and the connecting rivers (khalid et al., 2022; matodzi et al., 2017) table 1: the dates and other features of landsat 8-9 imagery acquired (usgs, 2020) months date acquired land cloud cover ground control point model atmospheric condition january 1/24/2023 1.77 662 clear cloud condition february 2/25/2023 0.28 680 clear cloud condition march 3/29/2023 7.12 548 partly cloudy condition april 4/30/2023 0.41 648 clear cloud condition may 5/24/2023 21.81 499 cloudy condition june 6/25/2023 0.05 660 clear cloud condition july 7/27/2023 0.52 670 clear cloud condition august 8/28/2023 0.03 678 clear cloud condition september 9/5/2023 0.01 663 clear cloud condition october 10/23/2023 3.31 476 partly cloudy condition november 11/8/2023 0.04 650 clear cloud condition december 12/2/2023 0.01 739 clear cloud condition table 2: landsat 8-9 multi spectral bands and its features (source: usgs, 2022) bands description wavelength (um) spatial resolution (m) band 1 coastal aerosol 0.43-0.45 30 band 2 blue 0.45-0.51 30 band 3 green 0.530.59 30 band 4 red 0.640.67 30 band 5 near infrared (nir) 0.85-0.88 30 band 6 short wavelengths 1 infrared (swir) 1.57-1.67 30 band 7 short wavelength 2 infrared (swir) 2.11-2.29 30 band 8 cirrus (in oli band 9) 1.36-1.38 15 band 9 oa bands (available with collection 1) na 30 tirs bands band 10 tirs 1 10.60-11.19 100 band 11 tir 2 11.50-12.51 100 2.2 data processing method pre-processing improves the quality of the images by reducing the errors connected with data acquisition which can be in form of atmospheric disturbances, topographic constraints, obscurities, and cloud cover properties (ali et al., 2020). data processing in this study involves changing of the digital number value to a reflectance value (adawiah et al., 2021). the landsat data obtained in raw form must have been affected with atmospheric particles therefore, there is need for the raw number to be corrected into a reflectance value. the processing involves two stages, which include the geometric correction and atmospheric correction dn values” conversion to reflectance values was achieved using raster calculation tool in arc gis with the application of equation 1 and 2. (ali et al., 2020). the formular used for dn value conversion follows: 𝑝𝜆 = 𝑀𝑃 𝑥 𝑄𝑐𝑎𝑙 + 𝐴𝑃 1 where: pλ′: top-planetary spectral reflectance, lacking solar angle correction, mp: reflectance multiplicative rescaling factor (reflectance _mult_band_ x, where x is the band number) = 2.0000e-05 available in http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 673 landsat8 &9 meta data file, ap: reflectance additive rescaling factor from the (reflectance _add_band_ x, where x is the band number) = − 0.1, qcal: calibrated standard pixel values (dn) solar elevation angle correction equally stands as an important factor to calculate toa reflectance correction therefore. equation 2 was employed in calculating the sun angle. 𝛲𝜆 = 𝜌𝜆 (𝑠𝑖𝑛 𝜃) 2 where: ρλ = top-of-atmosphere planetary reflectance, θ = sun elevation angle (from the meta data file of the oli raw data 2.3 employed algorithm the normalized difference turbidity index (ndti) utilized in this study is a constant valued tool for assessing the changes in water quality, confirming water pollution levels, and aiding in the efficient control of freshwater resources. this index employed the modality measurements acquired with the use of remote sensing equipped tools to determine water turbidity (raj, et al., 2024). the sequence analysis focused on band combination index after atmospheric corrections (haobin et al., 2022). the ndti index utilized two major spectral bands which is the red and green band sensitive to suspended solid particles and turbidity. the values of ndti range from − 1 to 1. the positive values show higher turbidity, while negative values indicate low turbidity (garg et al., 2020; raj et al., 2024). equation 3 revealed ndti indices 𝑁𝐷𝑇𝐼 = 𝑅𝑒𝑑−𝐺𝑟𝑒𝑒𝑛 𝑅𝑒𝑑+𝐺𝑟𝑒𝑒𝑛 3 𝑁𝐷𝑇𝐼 = 𝐵𝑎𝑛𝑑 4 − 𝐵𝑎𝑛𝑑 3 𝐵𝑎𝑛𝑑 4 + 𝐵𝑎𝑛𝑑 3 4 2.4 normalized suspended material index (nsmi) nsmi index is also an essential algorithm for retrieval of suspended material that mostly affect water turbidity. nsmi was equally employed to further confirm the concentration of turbidity. it was established following the ideologies that clear water possesses highest reflectance in the blue band while the existence of suspended material promotes an increase of reflectance in the visible range band of green and red (ρ red + ρ green) where clear water inclines to grip radiation (fatemeh et al., 2021. the formular for nsmi is shown in equation 5 & 6. all the bands value used in this algorithm were adjusted to a reflectance value. nsmi = 𝑅𝑒𝑑 𝑏𝑎𝑛𝑑+ green 𝑏𝑎𝑛𝑑−𝐵𝑙𝑢𝑒 𝑏𝑎𝑛𝑑 𝑅𝑒𝑑 𝑏𝑎𝑛𝑑+𝐺𝑟𝑒𝑒𝑛 𝑏𝑎𝑛𝑑 + 𝐵𝑙𝑢𝑒 𝑏𝑎𝑛𝑑 5 nsmi = 𝐵𝑎𝑛𝑑4+ b𝑎𝑛𝑑3−𝐵𝑎𝑛𝑑2 𝐵𝑎𝑛𝑑4+ 𝐵𝑎𝑛𝑑3 + 𝐵𝑎𝑛𝑑 2 6 2.5 modified normalized difference water index (mndwi) separating water-only image from vegetation was achieved with the use of the modified normalized difference water index which enhances the water with the use of green and swir band (mndwi) (xu, 2006). this was also supported with clipping data management in arc gis and digitizing of the water area out from google earth as shown in plate (1a) & (1b). mndwi formular is shown in equation 7. mndwi = (𝑃𝑔𝑟𝑒𝑒𝑛− 𝑃𝑀𝐼𝑅) (𝑃𝑔𝑟𝑒𝑒𝑛− 𝑃𝑀𝐼𝑅) 7 mndwi = (band3 −band6) (band3 – band6) 8 http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 674 plate 1a: showing the band imagery and clipped water location. plate 1b: shows the process of separating only water image. 3. results and discussion the result derived from the analysis validates the capacity of each algorithm employed in mapping out turbidity concentration in the dam water as revealed in table 3 which is the variations of turbidity concentration in the dam. the normalized difference turbidity index (ndti) in landsat 8-9 were projected by applying the spectral reflectance of green band with wavelength of (0.530.59) and red band with wavelength of (0.64 0.67) with same 30m spatial resolution estimated the turbidity of water bodies due to their spatial reflectance to light. this allows easy penetration of the spectral bands into the water features (khan et al., 2001). nsmi index in landsat also utilized same spectral band green, red and blue with wavelength of (0.45-0.51) essential algorithm normally used for retrieval of suspended material that normally affect water turbidity. in figure 2, the ndti and nsmi was calculated for each month using the acquired landsat data after atmospheric correction. the value derived was checked with each month to examine turbidity variations affecting water quality. the equation coefficients that have the highest correlation (𝑅2) value was also regarded suitable for turbidity concentration estimation in surface water body. the value of ntdi and nsmi index algorithm with a positive value denotes turbid water and a higher concentration of suspended particles, while a negative value denotes clear water and a low degree of turbidity. table 3: positive turbidity value from indices employed months variations ndti (b4, b3) nsmi (b4, b3, b2) january (1) 0.034 0.180 february (2) 0.418 2.054 march (3) 0.436 1.155 april (4) 0.409 1.670 may (5) 0.417 1.407 june (6) 0.416 6,171 july (7) 0.120 0. 506 august (8) 0.411 0.519 september (9) 0.419 0.528 october (10) 2.194 8.273 november (11) 0.418 0.516 december (12) -0.406 0.473 the regression analyses carried out between the two indices exposed strong positive relationships with some of the equation model. several studies from literatures have established the potentials of remote sensing application and the utilization of band combination indices in observing water quality changes (raj et al.,2024, aditya, 2019, adel et al., 2023). three different regression patterns shown in figure 3 was employed to check variation analysis of turbidity concentration using ndti and nsmi. landsat value in linear regression equation in ndti acquired the highest reflectance value of (𝑅2) value = 0. 54 while polynomial and exponential equation recorded a lower value of (𝑅2) value = 0.13 respectively. this confirmed the capacity of linear regression equation having the potency to deliver precise estimation of turbidity concentration in both lower and high turbid water because it has proven to obtain best value. however, the results obtained from ndti was confirmed further by utilizing nsmi with the three-regression equation. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 675 (a) (b) (c) figure 2: the ndti variation measurement on a) linear, b) exponential, and c) polynomial regression. figure 3 revealed the result from the regression analysis. linear equation recorded the highest correlation coefficient of (𝑅2) = 0.35 and other equation recorded very lower reflectance value and therefore, regarded not fit for turbidity estimation. the result generated using ndti in landsat 8-9 shows the efficiency of the spectral sensors band value and linear regression equation having expressed a better potential in estimating turbidity concentration. 3.1 turbidity variations and mapping turbidity measures the volume of suspended solid particles in the water and remains as one of the optical water features that disperse light instead of gripping light. the dispersing of the light is due to the presence of suspended substances in the waterbed (gholizadeh et al., 2016). turbidity is measured in ntu it can range from less than 10 nephelometric turbidity units (ntu), which indicate a very clear water to over 1000 ntu (very muddy or not clear) (mike 2009). the result derived from ndti mapping in hartbeespoort dam varies from 0.i20 to 2.194 high turbid concentration measures. figure 4 shows the map variation of ndti turbidity on monthly basis. from the analysis, the dam featured more on very low turbidity concentration characterizing water clarity with less suspended solid in this period. ndti mapping only records the highest value in the month of october with value ranging from – 2.194. other months recorded higher value concentration of 0.411-0.406 apart from the months january with records of 0.034 and 0.120 in july, 2024. the period of heavy flow that is the autumn season between march to june (conerlius et al., 2018). this period is meant to have high turbidity concentration base on the assertion made by (matodzi et al., 2017). these changes might be due to weather changes, climate factors or lesser activities during this period http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 676 (a) (b) (c) figure 3: the nsmi variation measurement on a) linear, b) exponential, and c) polynomial pattern. 3.2 turbidity variations and mapping turbidity measures the volume of suspended solid particles in the water and remains as one of the optical water features that disperse light instead of gripping light. the dispersing of the light is due to the presence of suspended substances in the waterbed (gholizadeh et al., 2016). turbidity is measured in ntu it can range from less than 10 nephelometric turbidity units (ntu), which indicate a very clear water to over 1000 ntu (very muddy or not clear) (mike 2009). the result derived from ndti mapping in hartbeespoort dam varies from 0.i20 to 2.194 high turbid concentration measures. figure 4 shows the map variation of ndti turbidity on monthly basis. from the analysis, the dam featured more on very low turbidity concentration characterizing water clarity with less suspended solid in this period. ndti mapping only records the highest value in the month of october with value ranging from – 2.194. other months recorded higher value concentration of 0.411-0.406 apart from the months january with records of 0.034 and 0.120 in july, 2024. the period of heavy flow that is the autumn season between march to june (conerlius et al., 2018). this period is meant to have high turbidity concentration base on the assertion made by (matodzi et al., 2017). these changes might be due to weather changes, climate factors or lesser activities during this period. in this study, mapping of high turbid region using nsmi value varies in the different months. the value ranges from 0.155 being the lowest to 8.273 as the highest. although, nsmi value in figure 5 & 6 recorded maximum higher value than ndti with very huge different in some months. for instance, in the month of february, nsmi image of landsat 8-9 (oli & tir) revealed the concentration of turbidity in hartbeespoort dam water within the range of -0.506 to 2.054, the higher concentration in the month of february displays dark blue colour and in the month of june nsmi have value range of -23.768 to 6.171 high with display of yellow colour. also, in the month of october records ranges from – 9.6908.273 high with display of dark blue colour. however, the area with lower concentration or clear water area also recorded higher value than the area with high turbid concentration. the general result is showing moderately high and low turbidity variation in fresh dam water according to freshwater turbidity standard (conerlius et al., 2018). this situation could be ascribed to seasonal changes in rainfall pattern and temperature. figure 7 shows the rainfall data with high precipitation from the month of february, march, april, may and november, 2023 validating the reason for moderately high turbidity mapping during this time. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 677 january february march april may june july august september october november december figure 4: ndti mapping january february march april may june july august september october november december figure 5: nsmi mapping http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 678 however, low precipitation was noted in jan, and picks up again from junenov 2023 which was the reason for lower mapping. similarly, urban activities around the area could also be a major factor as it was confirmed that the dam water is a pick-up point of particles and pollutant from the connecting rivers and wastewater plants, agricultural and industrial processes (khalid et al., 2022). figure 6 shows the performance of the two indices applied figure 6: nsmi and ndti rating figure 7: rainfall data in hartbeespoort location for the study period 4. conclusion the study evaluated the performance ndti and nsmi in mapping out turbidity concentration in hartbeespoort dam. however, evaluating turbidity levels in dam water is vital for conserving water usefulness, fitness and functionality. the study investigated and mapped the distribution of turbid water using multispectral resolution spatial bands of landsat 8-9 (oli & tir). the bands involved band 3 (green) band 4 (red) and band 2(blue) used in both ndti and nsmi. the relationship among the results of ndti and nsmi was correlated with the different months to examine the variation impact of turbidity as weather changes and to also understand the potentials of using band combination indices to evaluate turbidity. linear regression equation coefficient recorded the highest reflectance value of (𝑅2) = 0.53 in ndti and (𝑅2) = 0.35 in nsmi. although, utilization of all the index algorithm in evaluating turbidity concentration in dam water indicated the presence of significant volume of turbidity which usually result to aesthetic problem and general water decline of the dam. the contributing factor could be traced to implication of urban runoff from the surrounding land activities that is majorly agricultural farms around the dam and other climate factors. however, the connecting river such as jukskei and crocodile constantly flush in dark water and increasing the concentration of sediments in the water. the study demonstrated the usefulness of engaging satellites acquired data of landsat 8-9 equipped sensors spectral band combination to monitor turbidity concentration in freshwater dam. the study has also generated significant result that will serve as a guide for resource managers and policymakers to watch out for water quality seasonal variations and also target a rectification effort. ndti and nsmi performed better in mapping out turbidity with little variations in some period. therefore, it is thus recommended that further research can be conducted for confirmation of the utilized algorithms in the same location and the developed model potency for water quality assessment. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 670-681. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 679 references aditya sandeep k. 2019. estimation and mapping of turbidity in the lower charlse river using landsat 8 oli satellite imagery, theses. adawiah sw., setiawan kt., parwati e. and faristyawan, r. 2021. development 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level-1 15to 30-meter multispectral data. earth resources observation and science (eros) center. yashon oo., kimutai n. and kipkemoi h. 2020. modelling reservoir chlorophyll-a, tss, and turbidity using sentinel-2a msi and landsat-8 oli satellite sensors with empirical multivariate regression hindawi journal of sensors, 2020(21). https://doi.org/10.1155/2020/8858408. zhou, l., appiah, r., boadi, eb., ayamba, ec., larnyo, e.. antwi, ha. 2022. the impact of human activities on river pollution and health-related quality of life: evidence from ghana. sustainability, 14:13120. https://doi.org/10.3390/su142013120. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com https://library.utm.utoronto.ca/datagis/statistical https://org/10.1080/0790062880/8722401. https://doi.org/10.1155/2020/8858408. https://doi.org/10.3390/su142013120. corresponding author’s email address: davidayubamshelia@yahoo.com 682 arid zone journal of engineering, technology & environment original research article the effect of zinc dialkyl dithiophosphate (zddp) additive on the tribological properties of mahogany (khaya senegalensis) seed oil d. m. ayuba*1, a. a. hammajam2, m. a. abba-aji3 and c. amos1 1national centre for technology management (nacetem), yola, nigeria 2department of mechanical engineering nigerian army university biu (naub), biu, nigeria 3department of mechanical engineering university of maiduguri, maiduguri, nigeria *corresponding author’s email: davidayubamshelia@yahoo.com article information abstract mineral oil based lubricants are non-renewable, harmful to health and prone to price fluctuations. thus, vegetable oils are considered as suitable alternatives to mineral oils for lubricant production. as such, new research into the use of nonedible vegetable oils for lubricant development is advocated to address these challenges. in this study, tribological evaluation of lubricant developed from nonedible vegetable mahogany (khaya senegalensis) oil for industrial applications was conducted. interestingly, the oil was characterized, modified for suitability and used to develop lubricants for industrial applications. additionally, commercially available mineral oil based lubricant sae 20/w50 was used as a control. the effect of zddp additive on the tribological performance of mahogany seed oil based biolubricant developed was also studied. the results show that the developed mahogany seed oil based biolubricant had alkaline ph of 7.56, high viscosity index of 147.12, appreciable viscosity, excellent cold flow of -9.2 ºc. similarly, the coefficient of friction of the biolubricant developed reduced from 0.095 to 0.090when 1% of zddp was added and form 0.095 to 0.087 when 3% of zddp was added but the coefficient of friction increased from 0.095 to 0.099 with the addition of 5% of zddp. therefore, developed mahogany seed oil biolubricant was observed to be suitable and environmentally friendly substitutes to mineral oil base lubricant sae 20/w50 for application in metal cutting and lubrication of gears in food processing industry. received: 5th march 2024 revised: 13th august 2025 accepted: 15th august2025 keywords: additives khaya senegalensis bio-lubricant tribology zddp wear rate coefficient of friction © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction lubrication is the process in which a layer or a film of oil is applied between two objects, which are in relative motion with each other, to reduce the friction between them (nehal and amal, 2013). lubricating oil or lubricant is a substance which is required to decrease the friction and wear between surfaces having relative motion with each other (nehal and amal, 2013). thus, lubricant must have certain objectives such as reducing wear and power loss in overcoming friction and reducing the oxidation to protect it from corrosion, and also to act as a shock absorber in automotive engine parts, acting as a cleansing agent in various applications, and reducing the heat from friction (nehal and amal, 2013). a good lubricant must have the characteristics of; high viscosity, and viscosity index, thermal stability, high oxidation resistance, and prevention against corrosion (nehal and amal, 2013). the conventional source of lubricant is petroleum or crude oil. it is a by-product of the refining process of petroleum. though the uses of mineral oil are limited due to its less availability, the decay of oceanic as well as terrestrial environment is caused by the disposal of crude oil (nehal and amal, 2013). the application of petroleum-based oil in automotive engine result in the emission having metal traces such as magnesium, zinc, and iron is harmful to the environment (singh et al., 2015). research has recently targeted alternative bio-lubricants in resolving the challenges faced by the use of mineralbased lubricants (ahmad, 2021). bio-lubricants can biodegrade easily and fast (noreen et al., 2021). in addition, they are nontoxic to humans, aquatic life and land (salih et al., 2011). they could be based on oils extracted from plants, animals or esters manufactured from modified oils. some typical examples of oil used for bioazojete september 2025. vol.21(3):682-692 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/001 www.azojete.com.ng mailto:davidayubamshelia@yahoo.com mailto:davidayubamshelia@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 683 lubricant production include jatropha seed oil, castor seed oil, soybean oil, sunflower oil, amongst others (cavalcanti et al.,2018; odetoye et al.,2016; and kumar et al.,2021). however, the non-edible plant oil–based lubricant is very suitable for lubrication processes, together with physicochemical characteristics that make it preferable than fossil oil–based lubricants (joshi, et al., 2023). these consist of having an elevated lubricity property, viscosity index, and lower evaporative expeditions during operation (joshi, et al., 2023). there are several research works performed to enhance the physical and chemical characteristics of inedible crop-based oil lubricants. the investigations showed that inedible plantbased oil lubricants could be effective as well as economical alternatives to the petroleum-based lubricants (joshi, et al., 2023). in the study by mahipal and krishnanunni (2014), they analyzed the lubricant properties of zinc dialkyldithiophosphate (zddp) additive on karanja oil. in this study, they used experimental method to determine the coefficient of friction (cof), wear scar diameter (wsd) and viscosity. zainal (2015) investigated the physical property of canola oil when blended with zddp as an additive.the meta-analysis of the research papers done by different investigators is presented in table 1(singh et al., 2019). table 1:meta-analysis of non-edible oil-based lubricants(singh et al., 2019) reference lubricant bio-lubricant testing method results obtained references 2t oil castor oil gasoline engine two stroke air cooled engine flash point higher, enriched lubricity, less emissions (singh 2011) sae20/w40 jatropha oil pin on disc machine frictional losses low, less wear (bhale et al., 2008) sae40 cotton seed oil pin on disc machine less wear at high speed, high lubricity, lower coefficient of friction, eco-friendly, biodegradable (agarwal et al., 2014) sae20/w40 jatropha oil pin on disc machine minimum specific wear rate at high velocity (singh 2015) sae20/w40 mongongo oil four-ball wear tester less coefficient of friction, high viscosity index, less deposit forming tendencies (singh et al., 2017a, b) sae20/w40 pongamia oil pin on disc machine surface wear less, minimum degradation of lubricant at all applied loads (singh et al., 2017a, b) for the purpose of improving the physical and chemical properties of non-edible oils, certain additives are introduced, as they enhance specific characteristics of the base oil so that the resultant formulation can meet increasing performance demands and conform to required specifications (puhan, 2021). an anti-wear (aw) additive is a tribochemical active substance. in essence, tribochemical refers to the chemical action that takes place in a rubbing/abrasive contact which could affect and be affected by the rubbing/abrasive action (ioan et al., 2013). the aw additive develops a reaction layer on the work piece surface during the machining process. the reaction products are easily deformed and removed, reducing the loading of the abrasive tool. the fundamental mechanism of zddp as anti-wear is the reaction of zddp with the metal surface to form a solid protective film and the reaction layer (zhang and spikes, 2016). when metal is immersed in zddp solution in a lubricant or other non-polar solvent, a thermal film rapidly forms at the metal surface (zhang and spikes, 2016). apparently, these films are not simply zinc phosphate, zinc phosphide or iron phosphate (galvin, 1976). figure 1 below showed the layered structure of surface film formed from zddp. therefore, the objective of this study is to systematically investigate the effect of zinc dialkyldithiophosphate (zddp) as an additive on the tribological properties of mahogany seed oil. in particular, the study seeks to analyse the impact of varying concentrations of zddp on the coefficient of friction, wear resistance, and loadcarrying capacity of the oil under boundary lubrication. in so doing, the study aims to determine the prospects http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 684 of zddp-modified mahogany seed oil as an eco-friendly biolubricant substitute for traditional mineral-based lubricants, hence advancing the cause for environmentally friendly and high-performance lubrication systems. figure 1:layered structure of surface film formed from zddp( johnson and hills, 2013). 2. materials and method the study utilized locally sourced mahogany seed oil from shaffa in hawul local government area borno state, as well as a commercially available lubricant (sae 20/w50) obtained from ammasco international limited in yola, for comparison. distilled water and potassium methoxide were prepared in the petroleum chemistry laboratory at the american university of nigeria (aun) in yola using direct reaction method. various chemical reagents and lubricant additives were also used. 2.1 lubricant additive zinc dialkyl dithiophosphate (zddp) was used as lubricant additive in this study. 2.2 tribo-meter the anton paar standard tribo-meter trn version 6.1.19 was used for the tribological evaluation of the oil and lubricant. the trn model standard tribo-meter is an austrian design which can be used as a pin-on disc or ball-on-disc tribo-meter. it has an electronic microscope fitted for wear measurements and has several sensors connected to a computer for data acquisition and processing. in this study, different concentrations of anti-wear additives, sliding speeds and normal loads were used. the full factorial method was used to determine the influence of control parameters on the coefficient of friction and wear rate. the minitab 18 computer program was used to statistically analyse the data. the experimental factors and levels used in experimental design are listed in table 2. three factor full factorial experimental design method was used so as to determine the effect of more than one independent variable on a dependent variable and to determine the possible interaction of the multiple independent variables. the design (33) refers to the 27 runs experimental design to examine three factors. each was used on three levels in the study. table 2: treatments for the 33 full factorial design of experiment factor b factor c 0 factor a 1 2 0 0 0 0 1 2 000 001 002 100 101 102 200 201 202 1 1 1 0 1 2 010 011 012 110 111 112 210 211 212 2 2 2 0 1 2 020 021 022 120 121 122 220 221 222 http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 685 2.3 determination of the contributions of additive and other factors the empirical data collected were analyzed using analysis of variance (anova) to determine the contributions of the additive and other factors on the tribo-performance of the developed bio-lubricant. 3. results and discussion table 3 showed the experimental design matrix (33) consisting of 27 runs with different combinations of the levels of each of the factors and responses as specified by the full factorial design. table 3: experimental process parameters and reponses for mahogany seed oil bio-lubricant blended with zddp run order sliding speed (m/s) % of zddp normal load (n) coefficient of friction wear rate (103mm3/n/m) 1 0.2 3 20 0.082 4.48 2 0.1 3 20 0.077 4.39 3 0.3 1 10 0.088 5.55 4 0.2 3 30 0.091 4.63 5 0.3 5 30 0.118 6.97 6 0.2 1 30 0.094 5.72 7 0.3 5 10 0.099 6.88 8 0.2 5 20 0.097 6.76 9 0.1 5 30 0.102 6.74 10 0.2 1 20 0.089 5.69 11 0.1 1 10 0.078 5.40 12 0.2 1 10 0.083 5.51 13 0.1 1 20 0.085 5.61 14 0.3 1 30 0.100 5.83 15 0.1 3 10 0.072 4.20 16 0.1 1 30 0.090 5.66 17 0.1 3 30 0.085 4.51 18 0.3 3 10 0.080 4.51 19 0.3 3 30 0.096 4.68 20 0.2 3 10 0.078 4.33 21 0.2 5 30 0.109 6.79 22 0.2 5 10 0.091 6.71 23 0.3 5 20 0.106 6.91 24 0.3 1 20 0.093 5.74 25 0.3 3 20 0.087 4.60 26 0.1 5 10 0.085 6.65 27 0.1 5 20 0.090 6.69 the tribological performance of mahogany seed oil with zddp additive at different loads and sliding speeds is summarized in table 1. the results indicate that zddp concentration has the most overriding effect on both the coefficient of friction (cof) and wear rate. frictional performance is reasonably improved at low additive concentration (1%), with cof ranging from 0.078 to 0.094 and wear rates between 5.40 × 10⁻³ and 5.83 × 10⁻³ mm³/n/m. the performance is significantly better at 3% zddp, where the minimum cof (0.072) and lowest wear (4.20 × 10⁻³ mm³/n/m) are obtained under 10 n load at 0.1 m/s sliding speed (run 15). this suggests that at moderate concentration, zddp induces the formation of a uniform anti-wear tribofilm, which suppresses asperity contact and minimizes friction as well as material loss. these observations are consistent with the results of zhang et al., (2020), who demonstrated that zddp improves boundary lubrication by forming protective phosphate films on steel surfaces. but when concentration is raised to 5%, performance is drastically worse, with cof values of 0.118 and wear rates of up to 6.97 × 10⁻³ mm³/n/m under high-speed, high-load conditions (run 5). this effect has already been reported by spikes and tysoe (2015), who observed that too much zddp can lead to the generation of thick and unstable tribofilms that collapse under shear, forming abrasive debris that promotes wear. so, while http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 686 zddp plays a critical role in friction reduction, its performance is concentration-dependent, with an optimum of about 3% for this study. sliding speed also exhibits a steady influence on performance. at low speed (0.1 m/s), the system shows better tribological behavior, especially at 3% zddp, validating that lower shear rates facilitate more stable tribofilm formation. as the speed increases (0.2–0.3 m/s), cof and wear gradually rise, with the most adverse condition at 0.3 m/s, 5% zddp, and 30 n load. this trend aligns with previous research (martin et al., 2013; zhang et al., 2019), where higher sliding speeds were found to increase surface temperatures, compromise additive film integrity, and hasten wear particle formation. the influence of normal load further highlights the contribution of contact stress to film stability. at 10 n, wear is still low, especially with 3% zddp, corroborating that mild contact enables the additive-derived film to resist shear. at intermediate (20 n) and high (30 n) loads, however, wear rises dramatically, with rates >6.7 × 10⁻³ mm³/n/m under severe conditions. this is consistent with observations by gosvami et al., (2017), where high contact stresses were seen to enhance tribofilm rupture, resulting in adhesive and abrasive wear. nevertheless, even under these extreme conditions, 3% zddp concentration still outperforms 1% or 5%, implicating that moderate concentrations achieve the optimal compromise between film growth and mechanical stability. collectively, the findings show that the tribological behavior of zddp-blended mahogany seed oil is controlled by a subtle interplay among additive concentration, sliding speed, and load. the best performance is achieved at 3% zddp, 0.1 m/s, and 10 n, wherein a stable phosphate-based tribofilm minimizes friction and wear. at the other extreme of high load, high speed, and excess additive, film breakdown and abrasive wear are promoted. these observations support the well-documented "inverted-u" response of zddp in lubricant systems (zhang et al., 2020), wherein the performance increases up to an optimum concentration before being undermined by film instability. 3.1 tribological properties of the developed mahogany seed oil bio-lubricant the coefficient of friction of the developed mahogany seed oil bio-lubricants as compared to the mineral oil base lubricant is shown in figure 2. it was observed that the mahogany oil bio-lubricant had lower friction coefficient (0.095) compared to mineral base lubricant of 0.115. mahogany seed oil bio-lubricant friction coefficient is higher than the friction coefficient of the unmodified mahogany seed oil. the vegetable (mahogany) oil-based lubricant had a better friction reduction property than the commercial mineral oil-based lubricant (sae 20/w50). figure 2: coefficient of friction of developed mahogany seed oil bio-lubricant and mineral based lubricant figure 3 showed the wear rate of the developed mahogany oil bio-lubricant. the results revealed that the wear rate of the developed mahogany seed oil bio-lubricant was 0.00660 mm 3n-1m-1 which is lower than the wear rate of the mineral base oil (0.00670 mm3n -1 m -1). the developed mahogany seed oil bio-lubricant performed better in friction and in wear protection than the commercial mineral oil base lubricant (sae 20/w50). 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 mso msobl mnl c o e ff ic ie n t o f fr ic ti o n oil/lubricants http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 687 figure 3: wear rate of developed mahogany seed oil bio-lubricant and mineral based lubricant it can be deduced here that the transesterification of the mahogany seed oil with tmp polyol slightly improved its tribological properties in terms of wear property, but the friction coefficient was increased. the transesterification with tmp polyol improved wear resistance by forming a stronger, more stable boundary film, but increased the friction coefficient because this film has higher shear strength and resists sliding more than the natural oil layer. 3.2 effect of additives on the coefficient of friction of oil and bio-lubricants developed the main effects plot displaying the impact of the additive and the other factors on the friction coefficient for the mahogany seed oil bio-lubricant is shown in figure 4. it is clear that the concentration of zddp (%) additive, the normal load and the sliding speed have significant effect on the coefficient of friction of the mahogany seed oil bio-lubricant. the tribological performance of mahogany seed oil bio-lubricant is strongly influenced by zddp concentration, load, and sliding speed. zddp improves friction behavior by forming protective boundary films, but its effect depends on operating conditions. optimal load and sliding speed enhance film stability and reduce friction, while extremes of these parameters can cause film failure, oil degradation, or increased friction. figure 4: main effects plot for coefficient of friction of mahogany seed oil based bio-lubricant table 4 showed an overall summary of results derived from the analysis of variance (anova) of the coefficient of friction of the bio-lubricant based on mahogany seed oil. concentration of zddp was found to be the main determinant, accounting for 43.63% of the total variability of the frictional behavior. normal load and sliding speed contributed 33.20% and 20.24% of the variation, respectively. the error term was very low at 2.93%, reflecting the reliability and robustness of the experimental design utilized. the results clearly indicate that the concentration of zddp has a dominant effect on the coefficient of friction, overriding the effects due to both load and speed. such dominance is likely due to the capacity of zddp to form a protective tribofilm on the sliding interface, thus changing the lubrication regime. these findings are in agreement with the results obtained by azhari (2014), who also underscored the considerable contribution of additive concentration on tribological behavior. as such, the optimization of the concentration of zddp constitutes a promising approach to improving the frictional performance and overall effectiveness of mahogany seed oil as an eco6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85 mso msobl mnl w e ar r at e (1 0 -3 m m 3 / n /m ) oil/lubricants http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 688 friendly bio-lubricant. it also suggests that variations in sliding speed can also affect the coefficient of friction of the bio-lubricant. 3.2 anova for the coefficient friction mahogany seed oil-based bio-lubricant table 4: anova for coefficient of friction of mahogany seed oil based bio-lubricant source df seq ss contribution adj ss adj ms f-value p-value sliding speed (m/s) 2 0.000590 20.24% 0.000590 0.000295 69.09 0.000 % of zddp 2 0.001271 43.63% 0.001271 0.000635 148.93 `0.000 normal load (n) 2 0.000967 33.20% 0.000967 0.000483 113.31 0.000 error 20 0.000085 2.93% 0.000085 0.000004 total 26 0.002913 100.00% 3.3 effects of additives on the rate of wear of mahogany seed oil-based lubricant the main effect plot displaying the effects of the additives, sliding speed and normal load on the mean wear rate of mahogany seed oil-based bio-lubricant is shown in figure 5. it is notable that the (%) of zddp additive has a significant effect on the wear rate of the mahogany seed oil bio-lubricant while the sliding speed and the normal load have no significant effect as seen .this implies that the wear rate of the mahogany seed oil biolubricant is primarily influenced by the concentration of zddp additive, while the sliding speed and normal load have minimal impact on the wear rate. therefore, changes in the concentration of zddp additive will lead to changes in the wear rate of the biolubricant. on the other hand, variations in sliding speed and normal load may not have a substantial effect on the wear rate of the bio-lubricant. thus, understanding these relationships can help in optimizing the formulation of the bio-lubricant to minimize wear and improve its performance in practical applications. 3.4 anova for the wear rate of the mahogany seed oil-based bio-lubricant the anova for the wear rate of the mahogany seed oil bio-lubricant is shown in table 5. it was observed that the concentration of zddp with 98.28% contribution had the dominant influence on the wear rate. similarly, the sliding speed with 0.76% contribution had the second dominant influence on the wear rate of the mahogany seed oil-based bio-lubricant. furthermore, the normal load contributed 0.75% while the error accounted for 0.22% of the wear rate. this indicates that changes in the concentration of zddp additive will have the most substantial impact on reducing or increasing wear in the bio-lubricant. the concentration of zddp is critical because it dictates the formation and resilience of the protective tribofilm. in contrast, sliding speed and load primarily influence the lubrication regime by modifying shear rate and contact stress. thus, it is the additive concentration that determines whether the system maintains a stable film or degrades into abrasive conditions, making it the dominant factor affecting wear performance. figure 5: main effects plot for wear rate of mahogany seed oil-based bio-lubricant http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 689 table 5: anova for wear rate of mahogany seed oil-based bio-lubricant source df seq ss contribution adj ss adj ms f-value p-value sliding speed (m/s) 2 0.1855 0.76% 0.1855 0.0927 34.98 0.000 % of zddp 2 23.9663 98.28% 23.9663 11.9831 4519.41 0.000 normal load (n) 2 0.1821 0.75% 0.1821 0.0910 34.34 0.000 error 20 0.0530 0.22% 0.0530 0.0027 total 26 24.3869 100.00% 3.5 zddp additives at different percentage concentrations figure 5 illustrates the variation in the coefficient of friction of mahogany seed oil bio-lubricant with and without zddp additives under different loads and sliding speeds. for the base oil without zddp, the coefficient of friction at 10 n and 0.1 m/s was 0.090, which increased slightly to 0.096 at 0.2 m/s and 0.100 at 0.3 m/s. at 20 n, the values were 0.095, 0.099, and 0.103, while at 30 n they rose from 0.098 at 0.1 m/s to 0.102 at 0.2 m/s and 0.108 at 0.3 m/s. with the addition of 1% zddp, the coefficient of friction reduced to 0.078 at 10 n and 0.1 m/s, increasing gradually to 0.085 and 0.090 as the sliding speed rose to 0.2 and 0.3 m/s, respectively. at 20 n, the values were 0.083, 0.089, and 0.094, and at 30 n they increased from 0.088 to 0.093 and 0.100 with increasing speed. at 3% zddp concentration, the coefficient of friction further decreased, recording 0.072, 0.077, and 0.085 at 10 n across the speed range, 0.078, 0.082, and 0.091 at 20 n, and 0.080, 0.087, and 0.091 at 30 n. at the higher concentration of 5% zddp, the coefficient of friction increased relative to 3%, with values of 0.085, 0.090, and 0.102 at 10 n; 0.091, 0.097, and 0.109 at 20 n; and 0.099, 0.106, and 0.118 at 30 n for sliding speeds of 0.1, 0.2, and 0.3 m/s, respectively. figure 6 illustrates the variation in wear rate of mahogany seed oil bio-lubricant with and without zddp additives under different loads and sliding speeds. for the base oil without zddp, the wear rate at 10 n and 0.1 m/s was 6.45 × 10⁻³ mm³/n/m, which increased slightly to 6.56 × 10⁻³ at 0.2 m/s and 6.61 × 10⁻³ mm³/n/m at 0.3 m/s. at 20 n, the wear rate rose from 6.68 × 10⁻³ at 0.1 m/s to 6.73 × 10⁻³ and 6.80 × 10⁻³ mm³/n/m with increasing speed, while at 30 n the values increased from 6.71 × 10⁻³ to 6.76 × 10⁻³ and 6.87 × 10⁻³ mm³/n/m across the same speed range. with the addition of 1% zddp, the wear rate decreased, recording 5.40 × 10⁻³, 5.51 × 10⁻³, and 5.55 × 10⁻³ mm³/n/m at 10 n, followed by 5.61 × 10⁻³, 5.69 × 10⁻³, and 5.74 × 10⁻³ mm³/n/m at 20 n, and 5.66 × 10⁻³, 5.72 × 10⁻³, and 5.83 × 10⁻³ mm³/n/m at 30 n for increasing sliding speeds. at 3% zddp concentration, the wear rate was further reduced, with values of 4.20 × 10⁻³, 4.33 × 10⁻³, and 4.51 × 10⁻³ mm³/n/m at 10 n; 4.39 × 10⁻³, 4.48 × 10⁻³, and 4.60 × 10⁻³ mm³/n/m at 20 n; and 4.51 × 10⁻³, 4.63 × 10⁻³, and 4.68 × 10⁻³ mm³/n/m at 30 n. at the higher additive concentration of 5% zddp, the wear rate increased again, recording 6.65 × 10⁻³, 6.71 × 10⁻³, and 6.88 × 10⁻³ mm³/n/m at 10 n; 6.69 × 10⁻³, 6.76 × 10⁻³, and 6.91 × 10⁻³ mm³/n/m at 20 n; and 6.74 × 10⁻³, 6.79 × 10⁻³, and 6.97 × 10⁻³ mm³/n/m at 30 n as the speed increased from 0.1 to 0.3 m/s. figure 5: charts showing the coefficient of friction of mahogany bio-lubricant with zddp additives at different percentage concentrations 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0.1 0.2 0.3 c o e ff ic ie n t o f fr ic ti o n sliding speed (m/s) normal load 10n 0% normal load 20n 0% normal load 30n 0% normal load 10n 1% normal load 20n 1% normal load 30n 1% normal load 10n 3% normal load 20n 3% normal load 30n 3% normal load 10n 5% normal load 20n 5% http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 690 figure 6: charts showing wear rate of mahogany bio-lubricant with zddp additives at different percentage concentrations 4. conclusions the tribological evaluation of a lubricant developed from mahogany seed oil for industrial applications was successfully carried out in this study. the study concluded that the developed mahogany seed oil-based lubricant is a suitable replacement of the synthetic lubricants in medium-load gear systems used in manufacturing machinery, offering comparable performance with reduced ecological impact. in the tribological evaluation of the mahogany seed oil-based lubricant, it was found that the oil performed better than sae 20w/50 in reducing friction, while sae 20w/50 was better in preventing wear. the modification of mahogany seed oil through acid-catalysed esterification reduced its friction performance but improved its wear performance. the developed mahogany seed oil bio-lubricant at 3% of zddp was found to have better frictional performance than sae 20w50 and similar wear performance to sae 20w/50. the concentration of the zddp (%) additive was found to have a significant effect on the wear property and the coefficient of friction of the developed mahogany seed oil-based bio-lubricant. the sliding speed was found to have a significant effect on the wear rate of the developed mahogany seed oil-based bio-lubricant while on the friction response, there was no significant impact. the normal load has significant effect on the friction response but its effect on the wear property of the mahogany seed oil-based bio-lubricant developed is not significant. acknowledgement the first author wishes to acknowledge the assistance of the petroleum technology development fund (ptdf) for sponsorship in terms of study scholarship with award number: miss2021000000041. references ahmad, r. 2021. rsm and artificial neural networking based production optimization of sustainable cotton bio-lubricant and evaluation of its lubricity and tribological properties. energy report, 7: 830–839. anand m., hadfield m., thomas b. and cantrill r. 2017. the depletion of zddp additives within marine lubricants and associated cylinder liner wear in rnli lifeboat engines. proceedings of the institution of mechanical engineers, part l: journal of materials: design and applications. 231(1-2):162-170. cavalcanti, edc., aguieiras, écg., priscila, r., duarte, jg., cipolatti, ep., fernandez-lafuente, r., andré, j., silva, c. and freire, d. 2018. improved production of bio-lubricants from soybean oil and different polyols via esterification reaction catalyzed by immobilized lipase from candida rugosa. fuel, 215: 705–713. cecilia, ja., plata, db., saboya, rma., de luna, fmt., cavalcante, cl. and rodríguez-castellón, e. 2020b. an overview of the bio-lubricant production process: challenges and future perspectives. in processes, 8(3): 257272. 4 4.5 5 5.5 6 6.5 7 7.5 0.1 0.2 0.3 w e ar r at e ( 1 0 ^3 m m ^3 /n /m ) sliding speed (m/s) normal load 10n 0% normal load 20n 0% normal load 30n 0% normal load10n 1% normal load 20n 1% normal load30n 1% normal load 10n 3% normal load 20n 3% normal load 30n 3% http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng 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(2017). mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts. science, 348(6230), 102–106. ioan dm. brain. r., boris d. and hitoshi, o. 2013. tribology of abrasive machining processes (2nd ed.). elsevier, ohio: 204-213 jeimin r.j., khodidas k.b. and jigar v.p. 2023. a review on bio-lubricants from non-edible oils-recent advances, chemical modifications and applications. journal of the indian chemical society, 100(1): 49-65. khan, t., koide, s., tamura, y., yamamoto, h. and neville, a. 2018. effects of using alternative extreme pressure (ep) and anti-wear (aw) additives with oxy-nitrided samples. tribology letters, 66. kraipat c. 2013. a study of wear properties of different soyabean oil. energy procedia,42: 633–639. kumar, a., tirkey, jv. and shukla, s. 2021. comparative energy and economic analysis of different vegetable oil plants for biodiesel production in india. renewable energy, 169: 266–282. mahipal, d., krishnanunni, p., rafeekh, pm. and jayadas, nh. 2014. analysis of lubrication properties of zincdialkyl-dithio-phosphate (zddp) additive on karanja oil (pongamia pinnatta) as a green lubricant. international journal of engineering research, 3: 494–496. martin, j. m., onodera, t., & minfray, c. 2013. mechanisms of zddp tribofilm formation: a chemical and mechanical perspective. tribology letters, 50(1): 95–104. muhammad, a.a., nadia, s. and nur, rm. 2014. the effect of zinc dialkyldithiophosphate addition to corn oil in suppression of oxidation as enhancement for bio lubricants: a review. arpn journal of engineering and applied science, 9(9): 1447–1449. nehal, s. and amal, m. 2013. lubrication and lubricants. tribology fundamentals and advancements.jürgen gegner, intechopen, london, 48-63. noreen, s., khalid, k., iqbal, m., baghdadi, hb., nisar, n., siddiqua, uh., nisar, j., slimani, y., khan, mi. and nazir, a. 2021. eco-benign approach to produce biodiesel from neem oil using heterogeneous nano-catalysts and process optimization. environmental technology and innovation, 22: article 101430 odetoye, t.e., afolabi, t.j. and onifade, k. 2016. effects of extraction process parameters on the quality characteristics of parinari polyandra b. seed oil. nigerian journal of technological development,13(2): 40–49. puhan, d. 2021. lubricant and lubricant additives. intechopen. reeves, c., menezes, p., jen, tc. and lovell, mr. 2012. evaluating the tribological performance of green liquid lubricants and powder additives based green liquid lubricants. society of tribologists and lubrication engineers annual meeting and exhibition 2012: 62–64. salih, n., salimon, j. and yousif, e. 2011. the physicochemical and tribological properties of oleic acid-based trimester bio-lubricant. industrial crops production, 34: 1089–1096. singh, y., garg, r. and kumar, s. 2015. aspects of non-edible vegetable oil-based bio-lubricants in the automotive sector. green, 5(1-6): 59-72. singh, y., sharma, a., and singla, a. 2019. non-edible vegetable oil–based feedstocks capable of bio-lubricant production for automotive sector applications—a review. environmental science and pollution research, 26(15): 14867–14882. http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 682-692. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: davidayubamshelia@yahoo.com 692 spikes, h. and tysoe, w. t. 2015. on the commonality of mechanochemical and thermochemical reaction mechanisms. tribology letters, 59(1): 21. woma, yt. 2021. tribological evaluation of lubricants developed from selected vegetable based oils for industrial applications. (doctoral thesis federal university of technology, minna). http://repository.futminna.edu.ng:8080/jspui/handle/123456789/14530. zainal, sh. 2015. effect of zddp addition in canola oil as antioxiding agent for lubrication application.univesiti teknikal malaysia melaka fyp, report: 20-43. zhang, j. and spikes, h. 2016. on the mechanism of zddp antiwear film formation. tribology letters, 63(24): 1-15. zhang, j., spikes, h. and nevshupa, r. 2019. shear and thermal effects in boundary film breakdown of zddp. tribology international, 134: 1–10. zhang, s., jiang, x. and zhao, g. 2020. influence of zddp concentration on tribofilm growth and friction behavior under boundary lubrication. lubricants, 8(7): 61. http://www.azojete.com.ng/ mailto:davidayubamshelia@yahoo.com corresponding author’s email address: ibrahimatukur83@gmail.com 1 arid zone journal of engineering, technology & environment original research article performance evaluation of solar panel with reflector using nano fluids a. t. ibrahim1, a. a. abdullahi1, a. t. mustapha2, j. nura3, a. abdullahi1 and a. bala1 1department of mechanical engineering, aliko dangote university of science and technology, wudil, nigeria 2department of mechanical engineering, engineering faculty, near east university cyprus 3department of mechanical engineering, school of industrial engineering, kaduna polytechnics corresponding author’s email address: ibrahimatukur83@gmail.com article information abstract this research evaluated the performance of solar panel with reflector using nano fluids in kano state, nigeria. an experimental setup was designed, consisting of a solar panel without modification pwm, solar panel with reflectors pwr, solar panel with reflectors and a water-cooling system (pwrc). the experiments were conducted at the optimum tilt angle of 12o in kano state. additionally, models were developed using solidworks of pwr and pwrc to simulate the thermal behavior of the panel with different coolant types, including water, ethylene glycol, and urea liquid using ansys. the results indicate that ethylene glycol exhibited the lowest rate of increase in the panel's surface temperature (st), followed by urea liquid and then water. for an initial surface temperature (st) of 27.5°c, 64.2°c, and 46.1°c, the panel using ethylene glycol experienced temperature increases of 22.072°c, 74.184°c, and 33.951°c, respectively, over a duration of 50 minutes. in the case of water, the panel's st rose by 33.155°c, 80.388°c, and 59.698°c under the same initial st conditions. similarly, the panel using urea liquid witnessed surface temperature increases of 24.648°c, 74.282°c, and 35.498°c for the respective initial st values of 27.5°c, 64.2°c, and 46.1°c. submitted: 13th april 2024 revised: 30th january 2025 accepted: 3rd february 2025 keywords: cooling system panel solar radiation surface temperature © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction nigeria is fortunate to be located within the sunshine belt, receiving global radiation ranging from 3.5 kwh/ (m2 day) to 7 kwh/ (m2day) across the country (abdullahi, 2015; aliyu et al., 2023). additionally, nigeria experiences an average of 6.25 hours of sunshine per day, with the southern region having around 3.5 hours and the far northern region enjoying up to 8.0 hours of sunlight (abdullahi et al., 2017). according to a report from the global energy network institute, "if solar collectors/modules were deployed to cover just 1% of nigeria's land space, it could generate up to 1850 × 1023 gwh of solar electricity per year, which is approximately 100 times the current grid electricity consumption in the country" (tukur et al. 2023). despite nigeria's significant solar energy potential, there is currently no integration of solar energy into the national grid. several challenges hinder the development of solar energy in the country, including high costs, limited awareness, and insufficient research efforts. many researchers have made effort to improve the efficiency of pv panel by using reflective materials in other to increase the concentration of solar energy without even increasing the number of cells used (bamisile et al., 2017) (çamur,2023). (kabeel et al., 2019), on their comprehensive investigation of an optimal cooling technique for improving the performance of pv module with reflectors under egyptian conditions. on the egyptian ambient condition, three different cooling methods are compared on a pv module in the presence of reflector that includes: air force cooling system, water cooling medium and waterand air-cooling medium as case one, case two and three. it found that, the output electricity per day increases to 912, 1077 and 1010wh/day for case one, two and three more than that of the normal panels that record 832wh/day. moreover, the cost estimate in terms of kwh are azojete march 2025. vol.21(1):1-12 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:ibrahimatukur83@gmail.com mailto:ibrahimatukur83@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 2 approximately 0.072, 0.061 and 0.0722$/kwh. (rakino et al., 2019), a passive cooling system for increasing efficiency of panel power output (po). water and a straight fin heat sink (sfhs) was used as the cooling medium, water passes through aluminum beam cuboid that was attached at the bottom of the panel (50w) and the sfhs are then attached to the cuboids to release heat to the air. this decrease the surface temperature (st) of the panel by 21.66% in comparative with an ordinary panel. it was found that the voc increase by 21.49% compare to the normal panel, hence po increase by 40%. the research of (hatmode et al., 2020), on development and testing of pv panel for cooling under natural condition, a wood will as put at the back side of the panel which also allow air to pass through it and exchange heat with the surrounding. the power output increase with 15% compare with the panel without cooling. wang et al., 2020), on the study of the experimental and optical performances of a solar cpv device using a linear fresnel reflector concentration, where by monte carlo ray tracing (mcrt) software is used to undergo simulation of solar concentration processes and a test rig of the linear fresnel concentrator is developed. the finding shows that the test result of solar cell conversion efficiency under non concentration condition are 17.9% and 17.1% while for concentration condition are 14.7% and 13.6% which are both less than the parabolic v trough concentration test condition of (12.3% and 10.7%). (rajagopal & yadav, 2020), cooling techniques for performance improvement of pv systems. . two types of cooling systems that include active and passive cooling systems. the active cooling systems yield better performance than that of the passive, this increases electrical efficiency with the maximum of 22% and reduces the panel temperature with maximum of 30°c. in the order hand, cooling systems that fall in the passive category, enhance electrical efficiency to 15.5% and we may see a reduction of 20 °c in the panel surface temperature. (nader et al., 2020), on their study assessment of existing photovoltaic system with cooling and cleaning system: case study at al-khobar city. the results found that for the al-khobar region, eastern province, kingdom of saudi arabia, the efficiency of the solar panels after cleaning was increased from 6% to an average of 12% at nominal temperature of 27 o c. moreover, the average power output was increased by 35% during the day time. (abizar & nurtanto, 2021), on their studies to determines the effect of passive cooling for optimization of solar panel output. where by two of solar panel (50w) with reflectors with and without cooling where used in indonesia. it was found that the effect of cooling system increases the power output with average of 59.63 watt much greater than without cooling system that yield 47.68. it was also find out that both the module with reflector produced greater average power output 25.07% than that of a simple module. this paper determined a suitable coolant to use to regulate the operating temperature of a panel in the city of kano state nigeria. 2.0 materials and method in the study conducted in kano state, a 10w polycrystalline photovoltaic (pv) panels were utilized. the panel's electrical characteristics under standard test conditions are presented in table 1. the experimental investigation was carried out at centered city of kano state. to intensify solar radiation, a reflective foil with an impressive reflectivity of 98% was employed. measurements were conducted with electronic data logger, dc voltmeter and ammeter. electronic data logger was employed to collect temperature, radiation, voltage, and current while dc voltmeter and ammeter was utilized to measure voltage drop and current flow within the system. table 1: electric data specification of the panel characteristics value panel types polycrystalline maximum power (w) 10 dc open circuit voltage (v) 21.8 dc max power current (v) 17.3 operating temperature (o c) 25 panel size (l*w*h)mm 350*300*25 life span (years) 25 2.1 design of solar reflector considering a panel with tilt angle of β with two reflectors attached to it as shown in figure 1 below. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 3 figure 1: free body diagram of panel with two reflectors from the equation 1 and 2 ((burkhard et al., 1978) 𝐶 = 𝐷 𝐷𝑂 = sin((2𝑁+1)𝛼+𝛾) sin(𝛼+𝛾) (1) and 𝐿 𝐷𝑂 = sin((2𝑁+1)𝛼+𝛾)−sin(𝛼+𝛾) 2 sin(𝛼+𝛾) sin𝛼 (2) where, d= width of the aperture do= width of the panel c= concentration ratio γ= angle of incidence α= apex angle of the panel l= length of reflector at γ = 0 (radiation falling normal to the aperture area), chosen concentration ratio equals to 2, α equal to 30o and γ = 0 (radiation falling normal to the aperture area), do=30 cm. the optimum length l of reflector equals to 35cm 2.2 cooling system design to enhance the cooling of the solar panel, an s-shaped copper pipe was meticulously installed at the bottom section of the panel, as depicted in plate 1. this design facilitates the passage of water through the pipe, allowing efficient heat exchange with the panel plate 1: the panel with cooling system 2.3 experimental procedure the experimental samples which include panel without modification (pwm), panel with reflector (pwr) and panel with reflector and cooling system (pwrc) were securely mounted on a stand located at the oriental hospital building in kano state, nigeria, as depicted in plate 2. an electronic data logger was used to measure the short-circuit current (isc), open-circuit voltage (voc), and standard test conditions (st) of the panels. in the case of panel with reflector and water-cooling system, a rubber pipe was utilized to facilitate the flow of water, which then passed through an s-shaped copper pipe, allowing for heat exchange with the panel. the water was refilled on a daily basis to maintain consistent conditions. the duration of the experiments was 30 days in the month of march 2023. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 4 plate 2: experimental samples during taking reading at oriental hospital 2.4 modeling the design and assembly of the panel, along with the attached reflector and cooling system, were accomplished using solidworks 2020 software. the model consists of various parts, namely the panel, frame, and cooling medium tubes. these individual components were combined and assembled together to form the complete model, as illustrated in plate 3. plate 3: the assembled model 2.4.1 solution setup the pv panel was assembled using four separate parts: backing, glass, frame, and cells. the construction process involved designing each part individually and then assembling them. to begin with, the backing was designed using solidworks software. a new part design tab was opened, and a centered rectangle with dimensions of 300 x 350mm was selected. it was then extruded to a thickness of 5mm and saved in a specific folder. next, the glass part was constructed. another tab was opened in the part design section, and a centered rectangle with dimensions of 300 x 350mm was created. it was extruded to a thickness of 5mm and saved in a specific folder. the frame of the panel was designed using the swept boss and corner rectangle features. a frame with dimensions of 300 x 350mm and a thickness of 25mm was formed on a new tab in the part design section. the file was saved in a specific folder. for the solar cells, the corner rectangle, chamfer, trim, and extrusion features were used. the solar cell was created, and it was later duplicated using a linear pattern to fill the size of the frame (300 x 350mm). the file was saved in a specific folder. to complete the pv panel, the assembly part tab in solidworks was opened as shown in plate 4 below. the backing, frame, cells, and glass parts created earlier in the part design section were imported to the workbench. using the mate features, the parts were selected and assembled to form the pv panel. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 5 plate 4: pwr assembled model additionally, the panel holder and coolant tube were designed as shown in plate 5. a new part tab was opened, and the part design section was accessed. the panel holder was constructed using the corner rectangle and extrusion features, with its size matching the previously constructed panel. the file was saved in a specific folder. the coolant tube was also created in the part design section using the circle as shown in plate 6 below, swept boss, and swept cut features, ensuring it fit the panel size with two and a half circles. it was saved in a specific folder. plate 5: pv panel holder plate 6: construction of cooling medium 2.4.2 material selection the selection of materials for the various parts in the model was based on factors such as cost-effectiveness, availability, and their ability to fulfill specific functions within the context of kano state, nigeria. the chosen materials for each part are listed in table 2: http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 6 table 2: items and their chosen materials components material 1. backing aluminum alloy 2. glass pure glass 3. frame aluminum alloy 4. reflectors reflectivity 98% reflectivity 5. stand steel 6. coolant tube cooper 2.4.3 coolant and their properties to investigate the impact of cooling on a solar panel in kano state, nigeria, three different coolants were employed which are water, ethylene glycol, and urea liquid. the properties of each coolant are presented in table 3. these coolants were chosen for their specific properties and suitability for testing the cooling effect on solar panels in kano state, nigeria. table 3: properties of the coolant used s/n properties water ethylene-glycol urea liquid 1 density (kg/m3) 998.2 1111.4 1280 2 cp (specific heat) (j/kg-k) 4182 2415 2375 3 thermal conductivity (w/m-k) 0.60 0.252 0.5 4 viscosity (kg/m-s) 0.001003 0.0023 0.0157 5 molecular weight (w/m-k) 18.0152 0.252 0.5 6 thermal expansion coefficient (/k) 0 0.00065 2.4.4 grid independence test the grid independence test was performed to evaluate the effectiveness of meshing methods on the solar panel, aiming to achieve grid independence. in this study, the surfaces of the panel, cooling tube, and stand were meshed using tetrahedral cells, as illustrated in plate 4. different grid systems were employed, considering three levels of mesh faces: low, medium, and high smoothing, applied to the same solar setup. mesh quality was assessed for all three configurations, and the results, whether obtained numerically or experimentally, should be presented to demonstrate grid independence. plate 7: meshing for pwrc setup to be independent on mesh type; three cases were run on medium smoothing in order to choose the best in terms of computational time, number of elements and the result obtained. the meshing details are depicted in the table 4. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 7 table 4: grid test settings parameter case 1 case 2 case 3 nodes 118,074 122,047 131,112 elements 56,651 58,442 64,175 mesh quality 0.19149 0.19285 0.1826 minimum sizing 0.21 0.225 0.19 curvature angle 9.40° 18.0° 7.8° panel temperature (℃) 15.76 14.998 14.795 i. case 1 has medium curvature angle, minimum sizing and has lowest number of elements and nodes in comparison with cases 2 and 3. ii. case 2 has the medium number of elements, nodes and mesh quality, minimum sizing is higher and also has the highest curvature angle among the three cases. iii. case 3 is also another modified medium smoothing mesh has the highest number of nodes, elements. it has least angle of curvature. 2.4.5 solution setup step 1: from the toolbox, the steady-state thermal engineering analysis option was selected, which would allow for the analysis of thermal behavior under steady-state conditions. step 2: moving on to the second step, the geometry of the pwr (panel with reflector) model was imported from solidworks software into the ansys workbench. step 3: upon successful import, the imported pwr model geometry was displayed on the workbench. this was achieved by double-clicking on the pwr model in the workbench interface. by doing so, the user was able to visualize the imported model and further manipulate it for subsequent analysis. step 4: progressing to the fourth step, a closer examination of the geometry and its constituent parts was carried out. by double-clicking on the geometry, all the parts that were assembled together to form the pwr model were displayed. at this stage, specific materials were assigned to each part based on their intended properties and characteristics. the materials utilized for the different parts of the pwr model are listed in table 2. assigning appropriate materials to the parts was crucial for accurate thermal analysis, as different materials possess varying thermal conductivity, heat capacity, and other properties that influence the model's behavior. step 5: in the final step, various input data and boundary conditions were defined to set up the thermal analysis for the pwr model. the input data included the information provided in table 4, which specified relevant parameters and values related to the model. additionally, the convective heat transfer coefficient, representing the rate of heat transfer through convection, was defined as 2.5w/m² °c. this coefficient played a vital role in capturing the cooling effect of convection on the pwr model. moreover, the duration of the analysis was determined by setting the appropriate analysis settings, allowing the user to specify the desired time frame for the analysis to be conducted. by following these steps, the pwr model was successfully set up for thermal analysis within the ansys workbench. the installation and configuration of the software, along with the importation of the geometry, assignment of materials, and definition of input data, provided a solid foundation for conducting a comprehensive thermal analysis of the pwr model. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 8 plate 8: ansys workbench for selection of panel surface temperature 2.5 simulation procedure 3d models of pwr and pwrc were developed using solidworks software as discussed above, each panel was designed base on the design consideration of the panels used during the experiment in other to validate the simulated results. however, two other types of cooling apart from water that include ethylene and urea liquid. during the simulation with ansys software, the pwm experimental data found the month of march 2022 (mean day) was used as the input data of the simulation. the panel st and sr of pwm of before noon, noon and afternoon was selected. the selected data is shown in table 5: table 5: selected values from march, 2022 time solar radiation surface temperature (oc) 9am 321 27.5 1pm 731 64.7 5pm 356 46.1 3. results and discussion the results shown in figure 2 and figure 3 shows that despite pwr and pwrc are capturing the same amount of solar radiation (sr), the water-cooling system fixed at the back of the panel helped in reducing the surface temperature (st) of the pwrc. the st of the pwr and pwrc increased by an average of 39.19% and 23.50%, respectively, in comparison with the pwm. the maximum st obtained on pwr and pwrc was found to be 96.9°c and 79.5°c, which is higher than that of pwm, at 64.2°c. the panel operating temperature as stated from the manufacturer is 25oin other to obtained the stated power from the manufacturers, however, looking at the results in figure 3 of surface temperature st against time shows that even on the panel without concentration of more radiation pwm the surface temperature st of the panel exceed 25o at around 9am in the morning where it reaches it maximum at around 1pm in the afternoon with surface temperature st as 59.10. therefore, without even concentrating radiation, cooling regulator is needed to maintain the surface temperature st of the panel. in the other hand, the surface temperature st panel with reflector pwr system and panel with reflector and water-cooling system pwrc at that 9am in the morning is found to be 41.6o and 34.2o which is due to light concentration using reflectors. the maximum sr found in the month of march 2022 captured by the pwr, pwrc, and pwm, is 731, 1250, and 1251 w/m2day and the minimum sr found are 718, 1160, and 1161 w/m2day. the sr of the pwr and pwrc increased with an average of 71.26% in comparison with the pwm. however, the observed percentage increase in solar radiation (sr) did not reach the desired target of 100% increase. several factors could contribute to this limitation, including the scattering of diffuse sr that reflects away from the panel, the inherent limitations of the solar cells in capturing sr, and the potential impact of air and dust on the panel's performance. furthermore, when comparing the performance of the pwr (panel with reflectors) and pwrc (panel with reflectors and cooling system), it is notable that both setups captured approximately the same amount of sr. this suggests that the inclusion of the cooling system did not significantly affect the amount of sr captured by the panel. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 9 figure 2: sr against st in march figure 3: solar radiation against time in march in the case of thermal simulation, the pwr (experiment) and pwr (simulation) were compared, along with the panel with reflector and water-cooling system (experiment) and panel with reflector and water-cooling system (simulation) to validate the analyses. figures 4 and 5 below illustrate the comparison. considering the pwr system, both the experimental and simulation results show that the surface temperature (st) remains approximately equal at every point in time. at 9 am, the st for both the experimental and simulation cases is 41.6o, while at 1 pm it is 96.9 o and 95.0 o, and at 5 pm it is 69.7 o and 68.0 o. consequently, while the average deviation between the two approaches was approximately 3.31%, indicating good agreement overall, the observed differences underscore the inherent complexities and uncertainties involved in modeling and experimentation of real-world systems. these differences can be attributed to variations in heat transfer properties, inaccuracies in the model's assumptions, potential limitations in the experimental setup, and external environmental conditions. this highlights the importance of further investigation and refinement of simulation methodologies to improve accuracy and capture the nuances of the physical system under study. moreover, comparing the simulation and experimental results of panel with reflector pwr in other to further validate the simulation methodologies as shown in figure 4 below, the graph shows that the two result are the same at 9am and approximately the same at other point. http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 10 figure 4: experimental st and simulated st (oc) against time on the other hand, the comparison between the panel with reflector and water-cooling system (experiment) and panel with reflector and water-cooling system (simulation) was conducted to further validate the simulation results and analyze the two different methods, as depicted in figure 5. both the experimental and simulated results were found to be approximately equal. at 9 am, the surface temperature (st) of the simulated result was 33.2 o, while the experimental result was 34.2 o. the average percentage deviation between the experimental and simulated results was 3.12%. this deviation could be attributed to the inefficient experimental cooling system with pipes compared to the machine cooling system used in ansys software. the small and acceptable deviation between the experimental and simulation methods suggests a good agreement in the thermal analysis of the panel with reflector and water-cooling system. the close alignment of surface temperature (st) values at various times throughout the day indicates that the simulation accurately captures the thermal behavior of the experimental setup. this agreement enhances confidence in the validity and reliability of the simulation results, reinforcing the credibility of the findings. overall, the negligible deviation between the two methods validates the analyses and demonstrates the effectiveness of the simulation in replicating the experimental conditions. figure 5: simulated result and experimental result of pwrc st moreover, comparing the three different types of coolant were used as shown in figure 6 below, ethylene glycol reduced the rate of increase of the panel st followed by urea liquid and then water. the panel with ethylene glycol increased the st of the panel by 22.072°c, 74.184°c, and 33.951°c when the initial st was set at 27.5°c, 64.2°c, and 46.1°c for 50 minutes. in the case of water, the panel increased the st by 33.155°c, 80.388°c, and 59.698°c when the initial st was set at 27.5°c, 64.2°c, and 46.1°c, respectively. moreover, the panel with urea liquid increased the st of the panel by 24.648°c, 74.282°c, and 35.498°c when the initial http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 11 st was set at 27.5°c, 64.2°c, and 46.1°c, respectively. this shows that both coolants used decrease the st of the panel compared to the st of the pwr. even though when the temperature is at 27.5°c which is at 9am ethylene glycol and urea liquid decrease the st less than the ot of the panel of 25°c from the manufacturer. this will cause a little bit under cooling of the panel, but in a little bit time the surface temperature st will rise even above the operating temperature of the panel. figure 6: graph of output st (oc) against input st (oc) 4. conclusion based on the comparison of surface temperatures at different time points (9am, 1am, and 5am), slight variations were observed between the simulated and experimental results. the simulated surface temperatures were slightly lower than the corresponding experimental surface temperatures, indicating some discrepancies. despite these variations, the average deviation between the two approaches was approximately -3.31%, suggesting a good overall agreement. however, it is important to acknowledge that these variations highlight the inherent complexities and uncertainties associated with modeling and experimenting with realworld systems in addition to the temperature comparison, the experiment also involved the utilization of three different types of coolants: ethylene glycol, urea liquid, and water. among these, ethylene glycol demonstrated the highest rate of cooling the panel, followed by urea liquid and then water. the observed increases in st varied based on the initial st values and coolant type used. notably, at some point in the before noon at 9am both ethylene glycol and urea liquid resulted in st decreases below the manufacturer's specified operating temperature of 25°c when the initial temperature was 27.5°c, potentially affecting the power output by causing overcooling. references abdullahi, b. 2015. development and optimization of heat pipe-based compound parabolic collector. thesis, university of birmingham uk abdullahi dahiru, suresh, subashini., renukappa, suresh., & oloke, david. 2017. solar energy development and implementation in nigeria: drivers and barriers. ises solar world congress 2017 iea shc international conference on solar heating and cooling for buildings and industry 2017, proceedings, 923–931. https://doi.org/10.18086/swc.2017.16.01 abizar, h., and nurtanto, m. 2021. reflector and passive cooler for optimization of solar panel output. conference series earth and environmental science 739(1). https://doi.org/10.1088/1755-1315/739/1/012085 bamisile, o., dagbasi, m., babatunde, a., & ayodele, o. 2017. a review of renewable energy potential in nigeria; solar power development over the years. engineering and applied science research, 44(4), 242–248. https://doi.org/10.14456/easr.2017.37 hatmode, s.c., wagh, k. n., narendra, d., wadaskar, n., and bhajankar, s.b. 2020. development and testing of photovoltaic panel for cooling under natural condition. in international journal of creative research thoughts (vol. 8, issue 7). www.ijcrt.org http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):1-12. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ibrahimatukur83@gmail.com 12 rajagopal, m., and yadav, a. 2020. cooling techniques for performance improvement of pv systems. international conference on business management, innovation and sustainability (icbmis) 6 https://ssrn.com/abstract=3713817 abdulkadir aliyu abdullahi , abdullah bala i, magaji tambaya, abdullahi ahmed, t. i. a. 2023. performance evaluation of solar photovoltaic panel mounted on sloped. fudma journal of sciences (fjs), 7(3), 257– 262. https://doi.org/: https://doi.org/10.33003/fjs-2023-0703-1783 tukur, i.a., abdullahi, a., alhassan, y., abdullahi, b., aliyu, a.a., tsoho, a. u., and sani, u.a. 2023. performance evaluation of reflectors and cooling system on photovoltaic system in kano northwest nigeria. fudma journal of sciences, 7(3), 72–76. https://doi.org/10.33003/fjs-2023-0703 1776 çamur, h., kassem, y., adamu, m. t., & chikowero, t. 2023. prediction of the power output of a 4.5 kw photovoltaic system using three empirical models: a case study in nahr el-bared, lebanon. 15th international conference on applications of fuzzy systems, soft computing and artificial intelligence tools – icafs 2022 6, pp. 218–225). springe https://doi.org/10.1007/978-3-031-25252-5_32 http://www.azojete.com.ng/ mailto:ibrahimatukur83@gmail.com https://ssrn.com/abstract=3713817 https://doi.org/10.33003/fjs-2023-0703 corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 157 arid zone journal of engineering, technology & environment original research article quality assessment of commercial sandcrete hollow blocks produced in kaura district, abuja m. ibrahim*, m. a. yerima, z. danbuba, a. y. masud, and m. a. ibrahim department of civil engineering, baze university, abuja, nigeria *corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng article information abstract the study was carried out to assess the performance of commercially produced sandcrete hollow blocks in kaura district, abuja. one hundred and eighty (180), nine (9) inch sandcrete hollow blocks, eighteen (18) each from each factory, were collected from ten sandcrete block producing factories and subjected to compressive strength and durability test, for compliance with existing standards: nigerian industrial standard, nigerian building code and british standard. the 7 to 28 days’ compressive strengths regardless of the block size ranges between 0.68 n/mm2 to 3.06 n/mm2. the results showed that only 40% of the blocks commercially produced within the kaura district, abuja meet the minimum specification of 2.5 n/mm2 for non-load bearing as stipulated in nigeria industrial standard nis 87 (2000) and the 3.45 n/mm² nis requirement for load loading sandcrete blocks is not met by 100% of the industry. the density of blocks produced at different factories have densities which were within the value specified by bs 2028 (1968) and nis 87 :2000. test results also indicate that the total water absorption of all collected block samples was lower than the maximum value of 7 % as stipulated in bs 5628 and also lower than 12% requirement of nis standard. according to this research, all the hollow sandcrete blocks examined are considered to be of low porosity. submitted: 30th september 2024 revised: 2nd january 2025 accepted: 3rd february 2025 keywords: sandcrete blocks compressive strength durability © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction sandcrete hollow block is defined as a composite material that is molded into various sizes using a mixture of cement, fine aggregate, and water (nis 444-1: 2003). because the raw materials needed to produce sandcrete blocks are readily available, they are widely used around the world, particularly in africa as walling units either as load bearing or non-load bearing walls. sandcrete blocks have become widely used in the construction industry for use as load-bearing and non-load-bearing structures. its many advantages stem from its unique properties, such as strength, density, water absorption, durability, affordability, and dimensional accuracy. a number of factors influence the quality of sandcrete blocks, such as the materials used in the production process, the amount of time the blocks are left to cure, and the size and form of the blocks (akpokodje and uguru, 2019). despite the introduction of new materials like life bricks and modified clay blocks, sandcrete blocks seem to be an improvement over these materials. the building industry plays a significant role in the economy of developing nations such as nigeria. sandcrete blocks are widely utilized as walling units, and in nigeria, they are used in the construction of over 90% of buildings (baiden and tuuli, 2004). in most part of nigeria, sandcrete blocks are one of the most expensive components of building structures. sandcrete blocks are therefore an essential component in building construction in nigeria especially with the rapid urbanization and expansion of its towns and city centers amid industrialization and commercial growth. however, it is wellestablished that most sandcrete blocks used in developing countries—particularly in sub-saharan africa—are of low quality (anosike and oyebade 2011). previous studies conducted in nigeria have also showed the very poor performance of these sandcrete blocks, whose strength and durability fall short of minimum requirement stipulated in the nis: 1975 standard, making them unsafe for use in building construction (agbi et al. 2020). for the purpose of using sandcrete blocks to construct both load-bearing and non-load-bearing walls, the nigeria industrial standard specifies a minimum compressive strength of 3.45 n/mm2, and 2.5 n/mm2 respectively (nis: 2000). numerous studies on the quality of sandcrete hollow blocks made by commercial block factories in nigeria showed that most of their blocks had a 28-day dry strength between 0.50 to 1.5 n/mm2 in nigeria (ejeh and azojete march 2025. vol.21(1):157-167 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:musa.ibrahim@bazeuniversity.edu.ng mailto:musa.ibrahim@bazeuniversity.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 158 abubakar, 2008; onwuka et al., 2013., ewa and ukpata, 2013;). these studies identified several reasons for the production of low quality sandcrete hollow blocks by block producer to include inadequate curing, poor craftsmanship, and an improper cement to sand mix ratio. according to anosike and oyebade (2011), they found that the commercially manufactured sandcrete hollow blocks in ota, ogun state, nigeria, and the nigerian federal capital territory, abuja, did not meet the nigeria industrial standard requirements for compressive strength. according to ambrose et al. (2019), the compressive strength of blocks from 12 blockproducing factories in the southern nigerian state of akwa ibom had compressive strengths ranging from 0.19 and 1.32 n/mm2. related research conducted in akure, ondo state, nigeria, found that 1.35 n/mm2 was the maximum compressive strength of sandcrete blocks randomly sampled within the city. (aiyewalehinmi and tanimola, 2013). similarly, mohammed and anwar (2014) found that samples of sandcrete blocks from block producers in kano, northern nigeria, had compressive strengths ranging from 0.25 to 0.92 n/mm2. this indicates that all of the sandcrete blocks were substandard and did not meet the nigeria industrial standard requirements. one of the main causes of structural failures, which is recently on the increase in nigeria, is the use of low quality sandcrete blocks akeem and umar (2013) and agbi et al. (2020). omoregie and alutu (2006) stated that poor-quality sandcrete blocks can collapse under its selfweight, which can result in structural failure. according to ayedun et al. (2010), they stated that the persistent building failures in lagos state can be attributed, in part, to the use of poor sandcrete blocks. the nigeria building codes stated that sandcrete blocks to be used for the construction of load bearing walls must be in accordance to nis requirement. several literature reviews have revealed that there is no information available about the compressive strength and durability test of sandcrete blocks produced commercially in kaura district, abuja nigeria. the district is become more urbanized and populated. therefore, this study is aimed at investigating the quality in terms of compressive strength and durability test of sandcrete hollow blocks produced commercially within kaura district of abuja, nigeria. findings from this study will help the appropriate authorities in monitoring the quality of the blocks produced in abuja's kaura district and its the surrounding areas. 2. materials and methods 2.1 materials the materials used for this study are commercial sandcrete hollow blocks produced in selected factories of kaura district abuja, nigeria. 2.2 method this study was conducted using both field survey and laboratory experiment. after analysis, the findings from the field survey and lab experiment were compared to the british standard, the nigerian building code (nbc 2006), and the nigerian industrial standard requirements for sandcrete blocks (nis 87 2007). 2.2.1 field survey a total of one hundred and eighty (180) machine-vibrated sandcrete hollow blocks were randomly selected and assessed for this study, sourced from ten (10) different manufacturers located in the kaura district of abuja, nigeria. eighteen (18) 9-inch blocks (450 x 225 x 225 mm) were collected from each of the block producer. to maintain confidentiality, the blocks obtained from each manufacturer were labelled and coded alphabetically from a to j, ensuring that the identities of the factories being assessed were not disclosed. it is important to emphasize that these labels are arbitrary and do not correspond to the names of the manufacturers or reflect the quality of the blocks produced by these factories. 2.2.2 laboratory experiment the laboratory test carried out on the sandcrete hollow block samples include block measurement, bulk density of sandcrete hollow blocks, compressive strength, and durability test. the procedures used to carry out these tests are described as follows. 2.3 sandcrete blocks acquisition one hundred and eighty (180) pieces of 450 mm x 230 mm x 230 mm sandcrete hollow blocks were randomly selected from ten (10) sandcrete blocks producing factories within kaura district of abuja. all the blocks were collected after 3 days of production. all the blocks collected from the factories were taken to the baze university civil engineering laboratory for continuous curing, compressive strength and durability test. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 159 figure 1: sandcrete hollow blocks from different factories 2.3.1 mix ratio the fieldwork observations showed that all of the block industries visited used the volumetric batching method which according to the block producer is faster and easier than batching by weight despite the fact that the weight batching method is more accurate. regarding the water-to-cement (w/c) ratio, none of the block factories followed any approved guidelines. they all randomly add water to the mixture of cement and sand mostly on the basis of their individual visual assessments of the appropriate consistency needed for the mix. investigation shows that hollow sandcrete blocks obtained from selected block factories ranges from 50 to 75 pieces of blocks from one bag of cement. 2.3.2 mode of block production based on observations made in the field, the majority of block producers produced blocks using vibrating block moulding machines and mechanical sandcrete mixers. however, a few factories used manual laborers to mix and mold their blocks. 2.3.3 block measurement the dimensions of the blocks were determined as stipulated in nis 87:2007. the samples were prepared by scraping off any unnecessary material that had adhered to the surface of the blocks, and then measuring tapes were used to determine the blocks' length, breadth, and depth. the block dimensions obtained were compared with the standard requirement for dimensions as provided by the nis 87:2007 and nigeria building code 2006. the block dimensions obtained were used to calculate the gross area, net area, gross volume and net volume. 2.3.4 density of sandcrete hollow blocks the purpose of the test is to determine the unit weight of the hollow sandcrete blocks. the test was conducted as specify in bs 2028 (1968). the density of the block is given by the following equation: density (kg/𝑚3) = 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝐵𝑙𝑜𝑐𝑘 𝐵𝑙𝑜𝑐𝑘′𝑠 𝑁𝑒𝑡 𝑉𝑜𝑙𝑢𝑚𝑒 (1) 2.3.5 compressive strength a compressive testing machine was used to carried out the compressive strength of the blocks in the baze university abuja, nigeria, after the necessary curing days of 7, 14, 21, and 28 days. the compressive strength test was carried out on the hardened blocks at 7, 14, 21, and 28 days of age to determine the load-bearing capacity of the hollow sandcrete block samples, which was carried out as stipulated in bs 6073 part 1, (1981). for each block factory, 3 blocks were crushed to obtain the average strength using the following equation compressive strength (𝑁 𝑚𝑚²)⁄ = 𝐶𝑟𝑢𝑠ℎ𝑖𝑛𝑔 𝑙𝑜𝑎𝑑 𝑁𝑒𝑡 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑏𝑙𝑜𝑐𝑘 (2) http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 160 figure 2: crushing of block using the universal compression machine 2.4 durability test evaluation on sandcrete hollow block the bulk properties that were determined to be very relevant to the investigation into sandcrete's durability from randomly selected factories include the following. 2.4.1 block dry density the block's density is a useful indicator for assessing its quality. the dry density test was conducted carefully as stipulated in (bs 6073: part 2, 1981) by weighing the block samples after they were oven-dried at 105 ± 5°c for 24 hours as shown in plate 3 and the dimensions of the block samples were taken with an accurate steel tape. the dry density was then calculated using the formulae in equation block dry density (kg/m3), ℓ𝑑 = 𝑀 𝑉 (3) where, ℓd = dry density m = mass of dry block sample v = volume of block sample. figure 3: block samples oven dry in oven for 24 hours the density obtained in each case was expressed to the nearest kg/m³. 2.4.2 total water absorption (twa) the total water absorption test of the block samples was conducted by cold immersion method, which was carried out as specify in bs 3921, 1985. block samples are first oven-dried for 48 hours, and then they are http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 161 immersed in cold water, as plate 3 illustrates. the block samples were dried in oven to constant weight, thereafter they were immersed in water for 24 hours. the weights of the wetted blocks were then measured. the percentage water absorption was calculated from the formula in equation 2. (4) where twa = percentage water absorption (%) 𝑊𝑤 = mass of wet sample 𝑊𝑑 =mass of dry sample figure 4: sandcrete hollow blocks immersed in water for 24 hours the result was expressed as a percentage of the original dry mass of the specimen to the nearest 0.01% the dry mass. 2.4.3 total volume fraction porosity (tvp) the term porosity refers to the total amount of voids and pore structure within a block sample. the total volume fraction porosity of the sandcrete blocks was determined by direct measurement of the weight gain on saturation with water of an initially dry block after evacuation to remove air from the pore network (jackson and dhir, 1996). the water absorption is expressed as before in weight percent. the value of the water absorption may be converted to volume basis porosity by using the following relationship (jackson and dhir, 1996): n = (𝑇𝑊𝐴)𝜌 100 𝜌𝑤 (5) where n = volume fraction porosity 𝜌= dry block density (kg/m3) 𝜌𝑤 = density of water kg/m3) twa = water absorption (%) 2.4.4 wet and dry compressive strength the wet and dry compressive strength test was carried out to determine the load bearing capacity of the hollow sandcrete block samples, which was carried out in accordance to bs 6073 part 1, (1981). compressive strength was obtained for each sample using the formula in equation (6). compressive strength (𝑁 𝑚𝑚²)⁄ = crushing load net area of block (6) for the wet compressive strength test, block samples were pre-soaked for 24 hours while for the dry compressive strength blocks samples were oven dried to constant mass. 3. results and discussion 3.1 mix ratio table 1 show the number of sandcrete hollow blocks obtained from one bag of cement according to what was revealed by various manager of the selected block making factories within kaura district abuja, nigeria. none of the block factory adopted the nis approved cement-sand mix ratio of 1:6 or 1:8, hence, all the block factories failed to meet the nis approved recommendations for sandcrete blocks. the number of blocks from one bag of cement ranges between fifty (50) to seventy-five (75). the price of a 450 mm x 225 mm x 225 mm ranges between four hundred and fifty naira to five hundred naira. it was observed that the more expensive the blocks are, the less the number of blocks produced from one bag of cement and the better the quality. table1: number of blocks from one bag of cement from various factories http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 162 factory a b c d e f g h i j number of blocks 55 65 70 55 50 75 50 55 50 75 3.2 block measurement the dimensions of the hollow sandcrete blocks obtained from selected manufacturers within kaura district of abuja were measured to the nearest 1mm in the order of length x width x height and hollow dimension which were found to varies. the test result indicates that all block factories have minimum dimensions that fall within the stipulated dimensional tolerance in accordance to (nis 87: 2007) with respect to height, breadth, and length. these findings also reveal that the blocks' dimensions are not precise and do not meet standard requirements. this is caused by the use of deformed molds and incorrect machine mold tuning, which can result in an increase or decrease in the dimensions of hollow sandcrete blocks. 3.3 density of hollow sandcrete blocks the calculated densities of the tested sandcrete hollow blocks obtained from 10 manufacturers are shown in table 2. from the 10 randomly selected factories, the mean density of blocks from selected block producer ranges between 1434.3 kg/m3 and 2123. kg/m3. these values meet the 1500 kg/m3 bs 2028:1996 recommendation for an average of three blocks except the density of industry a with 1434.3 kg/m3 at 7 days curing. table 2. density of blocks obtained from manufacturers average density of hollow sandcrete blocks (kg/m³) s/n industry 7 days 14 days 21 days 28 days 1 a 1434.3 1821.0 1712.0 1962.5 2 b 1529.6 1648.4 1617.5 1691.8 3 c 1515.7 1979.8 1874.9 1907.1 4 d 1683.0 1656.1 1656.06 1756.2 5 e 1987.4 1988.6 1930.0 2035.2 6 f 1871.2 1799.0 1865.8 1810.3 7 g 2062.5 2055.1 2111.3 2047.8 8 h 1831.9 1740.4 1832.4 1868.8 9 i 1991.1 1995.9 2087.01 2123.6 10 j 1741.9 1646.7 1697.1 1766.1 all the density is also above the minimum value of 1500kg/m3 recommended for first grade sandcrete blocks by nis 87:2000 while all densities of hollow sandcrete blocks were within the range specified for sandcrete blocks, hence hollow sandcrete blocks produced at randomly selected industries could be suitable for construction as load bearing blocks. 3.4 compressive strength the results of the average compressive strength test carried out on hollow sandcrete block samples from the 10 randomly selected block industries within kaura district abuja captured in this study at, 7, 14, 21, and 28 days of curing is shown in table 3. whereas the graph in figure 1 illustrates the increase of the compressive strength of hollow sandcrete blocks with the age of curing for different block factories. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 163 table 3: average compressive strength of hollow sandcrete blocks (n/mm²) average compressive strength of hollow sandcrete blocks (n/mm²) s/no block label day7 day 14 day 21 day 28 1 a 1.93 1.96 2.12 2.22 2 b 1.22 1.39 1.61 1.70 3 c 0.85 1.10 1.31 1.38 4 d 1.46 1.84 2.07 2.22 5 e 2.41 2.71 2.83 3.06 6 f 0.88 0.96 1.09 1.18 7 g 2.48 2.68 2.76 2.84 8 h 1.68 2.04 2.24 2.50 9 i 2.09 2.34 2.84 3.04 10 j 0.68 0.91 1.11 1.19 the compressive strengths of all the selected block industry range from 0.66 n/mm² to 3.06 n/mm². this is similar with the findings of previous studies by odeyemi et al. (2018) and ewa and ukpata (2013). according to studies by ewa and ukpata (2013), several block manufacturers in calabar produced sandcrete blocks of varying quality. they described the differences in compressive strength to the properties of the constituent materials used in the production sandcrete blocks. the findings show that, of the hollow sandcrete blocks produced commercially in the kaura district of abuja, only 40% meet the nigeria industrial standard nis 87 (2000) minimum specification of 2.5 n/mm2 for non-load bearing after 28 days of curing for industry e, g, and h i, with 2.71 n/mm2, 2.68 n/mm2, 2.50 n/mm2, and 2.84 n/mm2, respectively, and that 100% of the industry does not meet the required nigeria industrial standard requirement for load loading sandcrete blocks of 3.45 n/mm2. similar findings were made by onwuka et al. (2013), yusuf et al. (2017), and aiyewalehinmi and tanimola (2013), and who found that the compressive strength of sandcrete blocks from different parts of nigeria consistently falls short of the 2.5 n/mm2 and 3.5 n/mm2 requirement by the nigeria industrial standard and standards organization of nigeria for load-bearing walls and non-load-bearing walls, respectively. the low quality of the sandcrete blocks produced by factories b, c, f, and j may be as a result of the poor fine aggregate (granite dust 1 and 2), mix ratios used by these block producers. blocks from factory e recorded the highest mean compressive strength of 3.06 n/mm2 while those from factory f recorded the least value of 1.18 n/mm2after 28 days of curing figure 5: compressive strength of collected sandcrete block samples at different days of curing age 3.5 dry density of sandcrete hollow block table 4 shows the result of the block dry density, total water absorption and total volume porosity of hollow sandcrete blocks produced at selected block industries in kaura district, abuja after 28 days of curing ranges between 1604.47 kg/m3 and 2082.07 kg/m3, with an average density of 1864.18 kg/m3. 0 0.5 1 1.5 2 2.5 3 3.5 0 5 10 15 20 25 30 c o p r es si v e st r en g th ( n /m m ²) number of days industry a industry b industry c industry d industry e industry f industry g industry h industry i industry j http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 164 table 4: total water absorption (twa) and total volume porosity (tvp) test result s/no block label dry weight (kg) weight after soaking for 24hrs (kg) water absorption (%) block dry density (kg/m³) total volume porosity (%) 1 a 19.03 19.82 4.13 1998.05 8.26 2 b 18.98 19.93 4.99 1589.85 7.93 3 c 18.92 19.88 5.11 1768.77 9.04 4 d 19.00 19.9 4.76 1862.19 8.86 5 e 18.85 19.85 5.30 1989.93 10.55 6 f 19.18 19.9 3.75 1869.28 7.01 7 g 20.14 21.01 4.33 2082.07 9.03 8 h 19.46 20.6 5.87 1794.58 10.54 9 i 20.04 21.11 5.33 2030.25 10.81 10 j 21.14 22.22 5.04 1769.65 8.92 the values of the sandcrete block for all the selected industries falls within the recommended values of density for type “a” blocks according to bs 2028 (1970), and also falls within the minimum specification of 1500 kg/m3 recommended for first grade (type “a” load bearing block) sandcrete blocks by nigeria industrial standard nis 87: 2000. 3.6 total water absorption table 4 shows the results obtained from the test of total water absorption conducted on sandcrete hollow block for the selected factories of kaura district abuja, nigeria after 28 days of curing. all industries assessed met the requirement stipulated by nis 87:2007, which specify a maximum water absorption rate of 12%. it can be noted that the factory f and h has the least and highest water absorption of about 3.75 % and 5.87 % respectively. it was observed that all the block factories used quarry dust as fine aggregate makes the average absorption to drop. this is probably due to the strong bond that is formed between the cement and the quarry dust (granite dust), which also fills in the voids space in the hollow sandcrete blocks and indicates that the sandcrete hollow blocks are more compact. also, when compared against the standard specify by bs 2028 (1970) part 1, all the block factories exhibited a low total water absorption, as their values fell below the specified acceptable range of 7%. thus, all the hollow sandcrete blocks produced by the selected factories passed the water absorption test. 3.7 total volume porosity (tvp) table 4 shows the results obtained from the test of total volume porosity conducted on sandcrete hollow block for the selected factories of kaura district abuja, nigeria after 28 days of curing. neither fmw, nis, nor bs code have specified any particular tvp standards. but materials with a tvp higher than 30% are considered very porous, according to jackson and dhir (1996). the values for all hollow sandcrete blocks for the selected factories compared well with those of like materials; clay bricks 0 30%; concrete blocks 4 25%; calcium silicate bricks 6 -16% (jackson and dhir, 1996). materials with total volume porosity above 30% are considered to be of high porosity (keralli, 2001). all the hollow sandcrete blocks evaluated during this research can therefore be considered to be of low porosity since the value obtained is below 30% that is, it ranges between 7.93 % and 10.81 %. 3.8 dry and wet compressive strength the values of the average 28-day curing of the wet and dry compressive strength and as well as the corresponding ratios between these strengths for all the sandcrete blocks from the selected factories in kaura district, abuja is given in table 5. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 165 table 5: ratio of dry and wet compressive strength of hollow sandcrete blocks ratio of dry and wet compressive strength s/no block label dry compressive strength (n/mm²) wet compressive strength (n/mm²) ratio 1 a 2.23 1.13 1.97 2 b 1.67 0.95 1.76 3 c 1.43 0.81 1.77 4 d 2.25 1.14 1.97 5 e 3.08 1.62 1.90 6 f 1.17 0.84 1.39 7 g 2.88 1.27 2.27 8 h 2.52 1.03 2.45 9 i 3.11 1.50 2.07 10 j 1.27 1.06 1.20 the dry compressive strength (dcs) values across all industries range from 3.11 n/mm² to 1.27 n/mm², with factory i exhibiting the highest dcs and industry j the lowest. in terms of wet compressive strength (wcs), the values range from 0.81 n/mm² to 1.62 n/mm², with industry c and e having the lowest and the highest respectively. 3.8 ratio of dry and wet compressive strength the ratio of dry and wet compressive ranges between 1.39 and 2.45 with factory g, h, and i, having higher value of 2.0 as shown in table 5. the findings revealed that the higher and broader the ratio between mean dry compressive strength and wet compressive strength, the lower can the degree of inter granular bonding be expected to be. it can be concluded that the reduction in ratio for 70 % of the block factories is directly attributed to the use of granite fines and corresponding cement quantity. this must have transformed the weaker and more porous sandcrete blocks fabric into a far denser, more homogeneous and more impermeable matrix. the values obtained fall within the range of recommended values in literature that the ratio of the mean dry and wet compressive strength sandcrete hollow blocks should not be greater than 2, keralli (2001). therefore, the experimental results obtained for 70% of the factories fall well within this limit. 4. conclusion the following conclusions were reached following an assessment of the result obtained from the field survey and the laboratory tests conducted on the selected block factories: i. most block producers in the study area are not aware of the existence of any standard specification for sandcrete blocks production. as a result, the producer engaged in unhealthy activities during the production process. ii. there was no quality assurance on the blocks as none of the producer block factory carried out any test on the constituent materials. iii. the 28-day compressive strength of commercially available sandcrete blocks obtained from the ten selected block factories in kaura district, abuja ranges between 1.19 to 3.06 n/mm². only 40% of the hollow sandcrete blocks commercially produced within the kaura district, abuja meet the minimum specification of 2.5 n/mm2 for non-load bearing as stipulated in nigeria industrial standard nis 87 (2000) for industry e, g, h i with 2.71 n/mm², 2.68 n/mm², 2.50 n/mm², and 2.84 n/mm², respectively and 100% of the industry do not meet the required nis standard for load loading sandcrete block of 3.45 n/mm². iv. the density of hollow sandcrete blocks produced at different block factories have densities which were within the value specified by bs 2028 (1968) and nis 87 :2000 v. the water absorption values of commercially available hollow sandcrete blocks obtained from ten block factories in kaura district, abuja were lower than the maximum value of 7 % as stipulated in bs 5628 and also lower than 12% requirement of nis standard. vi. all the hollow sandcrete blocks examined during this research are considered to be of low porosity. to ensure that best practices are continually followed during the production process, manufacturers should place a high priority on continuous education and training of their staff. this includes formal training on mix ratios, curing techniques, and quality control measures. furthermore, it is imperative that producers adhere strictly to established standards and specifications for sandcrete block production. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 166 regulatory bodies should enforce compliance, with penalties imposed on those who fail to meet the prescribed requirements. the government should conduct regular, unannounced inspections of sandcrete block manufacturing facilities to ensure compliance with standards. this would serve as a deterrent against non-compliance and promote the consistent production of high-quality blocks across the industry. references agbi, gg., akpokodje, oi., and uguru, h. 2020. compressive strength of commercially produced sandcrete blocks within isoko metropolis of delta state. nigeria turkish journal of agricultural engineering research, 1(1): 91-103. http://dergiparkorg.tr/tr/pub/turkager aiyewalehinmi, eo., and tanimola, mo. 2013. strength properties of commercially produced sandcrete blocks in akure: ondo state. international journal of engineering science invention 2(8): 25-34. akeem, u., and umar g. 2013. quality assurance of hollow sandcrete blocks produced by block moulding factories in gombe metropolis. journal of science, technology & education, 2(1): 61-65. akpokodje, oi., and uguru, h. 2019. effect of fermented cassava waste water as admixture on some physicmechanical properties of solid sandcrete blocks. international journal of engineering trends and technology, 67(10): 216-222. ambrose, ee, etim., rk., and koffi, ne. 2019. quality assessment of commercially produced sandcrete blocks in part of akwa ibom state, nigeria. nigerian journal of technology, 38(3): 586-593. http://dx.doi.org/10.4314/njt.v38i3.7 anosike, mn., and oyebade, aa. 2011. sandcrete blocks and quality management in nigeria building industry, journal of engineering, project and production management, 2(1): 37 46. ayedun, ca., durodola, od., and akinjare, oa. 2010. an empirical ascertainment of the causes of building failure and collapse in nigeria. mediterranean journal of social sciences, 3(1): 313-322. doi: 10.5901/mjss.2012.03.0 baiden, bk., and tuuli, m. 2004. impact of quality control practices in sandcrete block production. journal of architectural engineering. 10 (2): 53-60. doi: 10.1061/(asce)1076-0431(2004)10:2(53) british standard 6073-part 2: 1981, precast concrete masonry units. method for specifying precast masonry units. british standards institution 1970. precast concrete blocks. bs 2028,1364: bsi, london, england. british standards institution 1981. precast concrete masonry units. bs 6073: part 1: 1981. bsi. london, england. ejeh, sp., and abubakar, i. 2008. sandcrete hollow blocks in zamfara state. international journal of science and technological research, 5(1): 135-143. ewa, de., and ukpata, jo. 2013. investigation of the compressive strength of commercial sandcrete blocks in calabar, nigeria. international journal of engineering technology, 3(4): 477 – 482. jackson, n., and dhir, rk. 1996. civil engineering materials, mcmillan press ltd. london, england. keralli, ag. 2001. durability of compressed and stabilized building blocks, a phd thesis, university of warwick, department of civil and construction engineering. mohammed, m., and anwar, ar. 2014. assessment of structural strength of commercial sandcrete blocks in kano state. nigerian journal of technological development, 11(2): 39-43. nigeria industrial standard. 2000. nis87: 2000. “standard for sandcrete organization of nigeria, lagos. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng http://dx.doi.org/10.1061/(asce)1076-0431(2004)10:2(53) arid zone journal of engineering, technology and environment, march 2025; vol.21(1):157-167. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: musa.ibrahim@bazeuniversity.edu.ng 167 nigerian building code. 2006. “the national building code of federal republic of nigeria”. nigerian building code, 1st ed, lexis, nexis, butterwoths. south africa. nigerian industrial standards (1975). draft code of practice for sandcrete blocks; lagos, nigeria. nis 444-1-2003. standards for ordinary portland cement; xxx: 2007 – test sieves, 9001:2008 – quality standard certification and 584:2007 methods of testing sandcrete blocks. nis 87., 2007. “nigerian industrial standard standard for sandcrete blocks”. standard organization of nigeria (son). lagos, nigeria. nis 87-2004. standards for sandcrete block, standards organization of nigeria. lagos, nigeria. odeyemi, so., akinpelu, ma., atoyebi, od., and orike, kj. 2018. quality assessment of sandcrete blocks produced in adeta, kwara state, nigeria. nigerian journal of technology, 37(1): 53-59. doi: 10.4314/njt.v37i1.7 omoregie, a. 2013. optimum compressive strength of hardened sandcrete building blocks with steel chips. buildings, 3(1): 205-219. doi:10.3390/buildings3010205 omoregie, a., and alutu., oe. 2006. the influence of fine aggregate combinations on particle size distribution, grading parameters, and compressive strength of sandcrete blocks, canadian journal of civil engineering. 33(10): 1271-1278. https://doi.org/10.1139/l06-059 onwuka, do., osadebe, nn., and okere., ce. 2013. structural characteristics of sandcrete blocks produced in southeast nigeria. journal of innovative research in engineering and sciences,4(3), 483490. http://www.grpjournal.org/journal/category/joires.aspx. yusuf, a., aminulai, ho., abdullahi, a., alhaji, b., and alalade., ai. 2017. dimensional compliance and compressive strength of sandcrete hollow blocks produced in minna metropolis. proceedings of the 2nd international engineering conference, federal university of technology, minna, nigeria. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng http://dx.doi.org/10.4314/njt.v37i1.7 arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):645-656 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 645 compressive strength and splitting tensile strength of concrete cube using magnetized water m. m. adiama1, k. o. yusuf2*, a. k. yusuf3, m. a. moshood4 and h. o. sanusi5 1,2,3 department of agricultural and biosystems engineering, university of ilorin, nigeria 3,4 department of civil engineering, university of ilorin, ilorin, nigeria *corresponding author's email address: yusuf.ok@unilorin.edu.ng article information submitted 1 march, 2024 revised 3 july, 2024 accepted 10 july, 2024 keywords: compressive strength concrete cube curing of concrete magnetized water tensile strength circulation flow abstract report on cases of collapse of residential buildings and other structures are common in nigeria which is normally due to structural failure, failure of the materials that were used for the construction and poor design. buildings collapse normally results to loss of lives and properties. the study was conducted to determine the effect of magnetized water (mw) on the compressive strength (cs) and splitting tensile strength (sts) of concrete cubes (cc). mw is the water that has passed through magnetic field which could enhance proper hydration of concrete and improve the strength of cc. the cc was produced using sand (4.75 mm diameter), ordinary portland cement, crushed granite (12 mm diameter) and mw. the mixing ratio of cement, sand and granite for the cc was 1:2:4 and water-cement ratio was 0.5. the treatments were t1 (concrete produced with non-magnetized water -nmw and cured in mw treated for 1 minute), t2 (cc with mw treated for 1 minute and cured in nmw), t3 (cc with mw treated for 1 minute and cured in mw treated for 1 minute), t4 (cc with mw treated for 2 minutes and cured in nmw), t5 (cc with mw treated for 2 minutes and cured in mw treated for 2 minutes) and control t0 (cc produced with nmw and cured in nmw). cs and sts were determined after cured for 7, 14 and 28 days. the mean css after cured for 28 days t1, t2, t3, t4, t5 and t0 were 18.13, 22.00, 23.40, 19.07, 17.87 and 18.66 n/mm2, respectively. the mean stss after cured for 28 days t1, t2, t3, t4, t5 and t0 were 1.33, 1.38, 1.59, 1.83, 1.21 and 1.32 n/mm2, respectively. mw increased the cs and sts by 25.40% and 37.57% of the concrete cubes, respectively. this shows that magnetized water is economical, simple and environmentally-friendly technology for the production of concrete cubes. 1.0 introduction in nigeria, collapse of buildings and other structures is due to structural failure, and failure of the materials that were used for the construction and poor design. the collapse of buildings normally results in loss of lives and properties. hamma-adama and kouider (2017) reported that the use of sub-standard building materials is the major cause of building failure and collapse in nigeria. sandcrete blocks that is commonly used in nigeria for the construction of buildings is sub-standard and they normally fail because they are fragile, they have low compressive and tensile strengths due to low cement content. concrete and sandcrete cube have high compressive strength but they have low tensile strength and brittle in nature. tensile strength is an important property of concrete because concrete structures are highly susceptible to tensile cracking due to various kinds of loads and other factors which could lead to failure of a building or structure. therefore, there is a need for economical ways of improving the strength of the materials which are mainly the concrete and sandcrete blocks. http://www.azojete.com.ng/ mailto:%20efegabs@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)645-656. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 646 mw is the water that has been allowed to flow through the magnetic field and the water could enhance proper hydration of the concrete during curing and this could improve the compressive and tensile strengths of the concrete cube (reddy et al., 2014; patil and pathak, 2016). mw is also called magnetic water or magnetically treated water and it has a better property than the ordinary water. ali et al. (2014) pointed out that mw reduced the scale deposition in water pipes. patil and pathak (2016) reported that the paste consists of cement and water that binds the aggregate together and hardening of concrete occurs due to chemical reaction between the cement and water during the time of curing thereby making the concrete stronger. furthermore, mw is environmentally friendly and has low installation cost and no energy requirement for its operation when permanent magnet is used. magnetic treatment of irrigation water (magnetized water for irrigation) has been used to boost crop yield (babu, 2010; yusuf and ogunlela, 2017). albahrani (2018) indicated that the compressive strength of concrete produced with mw that was treated in magnetic field for 28 days increased by 26.2%. kiranmai and rao (2018) pointed out that the compressive strength of concrete produced with mw that was treated for 24 hours increased by 38.1% after curing for 7 days. shynier et al. (2012) also stated that magnetic water that was used for mixing the concrete improved the compressive strength of the concrete by 10 22 n/mm2. reddy et al. (2014) stated that mw enhanced proper hydration and improved the compressive strength of concrete by 55%. in this current study, a short period of 1 to 3 minutes were used to produce mw by circulation flow method and determine if the time could be effective for producing mw for concrete cubes instead of 24 hours used by kiranmai and rao (2018). circulation flow method means that water is allowed to flow through magnetic field continuously for a short period of time for about 1 2 minutes (chern, 2012). a static flow method means that there is no flow of water through the magnetic field but a magnet is put by the side of water for a long time like 24 hours or more as reported by kiranmai and rao (2018) and 72 hours as reported by parthiban et al. (2016). podlesny et al. (2004) reported that 15 seconds was adequate and effective for producing mw but aladjadjiyan (2007) reported that 1-10 minutes is adequate for effective treatment and production of mw using circulation flow magnetic water treatment method. circulation flow method is more effective than the single flow magnetic water treatment method and is also better than the static flow magnetic water treatment method for producing mw in which water is allowed to be in the magnetic field for a longer period of time. for the water to be magnetically treated water (magnetized water), the flow of water must cut the magnetic field at right angle based on fleming’s right-hand rule so that the magnetic force can act on the water (chern, 2012), otherwise, the water would not be mw. the objectives of this study were to determine the effect of magnetized water produced by circulation flow method within 1 to 3 minutes on the compressive strength and splitting tensile strength of concrete cubes. 2. materials and methods 2.1 location of the study the study was conducted at the concrete laboratory of the department of civil engineering, university of ilorin, nigeria. the university of ilorin is located in ilorin south local government area of ilorin city, kwara state. ilorin lies on latitude 8°30¹n and longitude 4°35¹e, with about 340 m above the mean sea level with annual rainfall of 1300 mm (ejieji and adeniran, 2009). 2.2 materials for production of the concrete block the materials used for the production of the concrete cubes are presented in table 1. the physical properties of the cement, the sand (fine aggregate) and the crushed granite (coarse aggregate) used in this study are presented in tables 2, 3 and 4, respectively. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adiama et al: compressive strength and splitting tensile strength of concrete cube using magnetized water. azojete, 20(3):645656. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 647 table 1: materials used for production of the concrete cube s/n parameters source / type properties 1 ordinary portland cement (opc) dangote cement the properties are within the standard permissible value of is: 12269-1987. 2 coarse aggregate crushed granite 12 mm single size, with specific gravity (relative density) of 2.7 and water absorption of 0.3%; 3 fine aggregate sand specific gravity of 2.63, fineness modulus of 2.6 and water absorption of 2.5% 4 pure water tap water clean water free from impurity 5 permag (neodymium 406) magnet permanent magnet length, internal and external diameter of 20 mm 6 weighing balance acs-15-zc73 max = 30 kg, min =1g table 2: the properties of the cement used s/n parameters permissible value by is:12269-1987 experimental value 1 specific gravity 3.15 3.11 2 normal consistency 26-33% 28% 3 initial setting time min 45 minutes 80 minutes 4 final setting time max 600 minutes 330 minutes 5 fineness max 10% 1% table 3: physical properties of the sand used (fine aggregate) s/n parameters permissible value by is:12269-1987 experimental value 1 specific gravity 2.5 -3.0 2.63 2 fineness modulus 2.2 -3.2 2.60 (fine sand) 3 water absorption max 2.5% 2.5% 4 zone of fa 3 table 4: physical properties crushed granite (coarse aggregate) passing through 12 mm single size s/n parameters permissible value as per is:12269-1987 experimental value 1 specific gravity 2.5 to 3 2.70 2 particle shape angular 3 water absorption 1% 0.3% 4 crushing value 45% 17% 5 impact value 45% 12.6% 2.3 production of the magnetized water the mw was produced by allowing the water to flow through the magnetic treatment unit that is surrounded by 12 pieces of neodymium magnet (figure 1). a neodymium magnet is a strong permanent magnet that can work effectively at room temperature and high temperatures up to 80 °c without demagnetization. it is a strong magnet with magnetic flux density ranging from 1.0-1.5 tesla (10,000 – 15,000 gauss). each of the neodymium magnets is 10 × 25 × 50 mm and is produced from neodymium (nd), iron (fe) and boron (b) together to form an ndfeb magnet. the water was allowed to pass through the treatment unit in 1 minute for treatment t1 and t2 when the water was passed through the magnetic treatment unit 2 times for 2 minutes. the magnetic treatment unit is a rectangular pipe made from the http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)645-656. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 648 perspex glass (15 by 60 mm and 600 mm long), folded (bend) to form 3 layers to effectively use the available 12 pieces of neodymium magnets in order to have maximum magnetic field and to make it compact. the neodymium magnets cover a total length of 450 mm (50 mm × 3 × 3-layers = 450 mm) on the magnetic treatment unit as shown in figure 1. magnetized water is produced when the control tap is opened and the raw water flow from the tank through the pipe to the magnetic treatment unit where the magnetic field radiates or passes across the water and the water becomes magnetically treated water or simply as magnetized water (figure 2). the flow of water in the magnetic treatment unit is perpendicular to the magnetic field to obey the fleming’s right-hand rule so that the water become magnetically treated water. the magnetized water was collected from the outlet with a bucket and then used for mixing the concrete and/or for curing the concrete cubes. figure 1: magnetic water treatment unit with three pieces of magnets on both sides of the pipe figure 2: pictorial view of the water tank connected to the magnetic water treatment unit 2.4 production of the concrete cubes a 100 x 100 x 100 mm cube mould was used to produce the concrete needed for the compressive test. the materials used for the concrete were sand sieved through 4.75 mm (fine aggregate), crushed granite with the size of 12 mm single size (coarse aggregate), portland cement and magnetized water. the ratio of cement, sand and crushed granite was 1:2:4 by weight which was by en bs 812-5 1990. the concrete for splitting tensile strength was produced using a cylindrical pipe of 101.6 mm diameter and 200 mm high as the mould. the water-cement ratio by weight was 0.5. the materials were thoroughly mixed and lubricant was added to the formwork before concrete was poured into the mould to ease the removal of the concrete and compacted following env 13670-1. a hand trowel was used to finish the top surface of the concrete. pictorial views of the concrete blocks for compressive strength and splitting tensile strength are shown in figures 3 and 4. the treatments (t0, t1, t2, t3, t4 and t5) used to produce the concrete blocks are described in table 5. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adiama et al: compressive strength and splitting tensile strength of concrete cube using magnetized water. azojete, 20(3):645656. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 649 figure 3: pictorial view of the concrete for compressive strength test figure 4: pictorial view of the concrete for splitting tensile strength test table 5: the description of the treatments used to produce the concrete blocks t0 t1 t2 t3 t4 t5 concrete cube produced with nonmagnetized water and cured in nonmagnetized water (t0 = control) concrete cube was produced with nonmagnetized water and cured in magnetized water that was treated for 1 minute in the magnetic field. the water only passed through the magnetic treatment unit once for 1minute concrete cube was produced with nonmagnetized water and cured in magnetized water treated for 1 minute in the magnetic field. the water only passed through the magnetic treatment unit once to achieve 1minute. concrete cube produced with magnetized water treated for 1 minute and cured in magnetized water treated for 1 minute in the magnetic field. the water only passed through the magnetic treatment unit once for 1 minute in each case. concrete cube produced with magnetized water treated for 2 minutes in which the water was passed through the magnetic treatment unit 2 times and cured in nonmagnetized water concrete cube produced with magnetized water treated for 2 minutes and cured in magnetized water treated for 2 minutes. the water only passed through the magnetic treatment unit twice to achieve 2 minutes in each case 2.5 determination of compressive strength of the concrete cube the compressive strength of the concrete was determined using a hand compression machine el31 – 072 model with 1560 kn capacity (figure 5) in the department of civil engineering laboratory, faculty of engineering and technology, university of ilorin, nigeria following bs en 1991-5 1998. the concrete cube cracked when the concrete cube could no longer withstand the load (compressive force) exerted by the compression machine. the compressive strength was determined from equation (1) (zhang et al., 2008). 𝑓𝑐 = 𝐹 𝐴𝑐 (1) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)645-656. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 650 where: fc is the compressive strength (n/mm2), f is the failure load (n) and ac is the area of the concrete block (mm2). 2.6 determination of splitting tensile strength of the cylindrical concrete block the tensile strength was done using split-cylinder test and was determined using equation (2) reported by zhang et al. (2008). 𝑓𝑡 = 2𝐹 𝜋𝐿𝑑 (2) where: ft is the tensile strength of the concrete block (n/mm2), f is the failure load (n), l is the length or height of the concrete block (mm), d is the diameter of the concrete block (mm) and π is equal to 3.142. 2.7 paired t-test statistical analysis paired t-test was used to determine if the effect of mw was significant on the compressive strength and splitting tensile strength. the mean difference between the results of mw and that of control (nmw) was determined. the mean, standard deviation, the standard error and the t-test values were determined using equations (3), (4a) or (4b), (5) and (6), respectively as given by montgomery (1998) and ogunlela and yusuf (2016). n d d  = (3) ( ) 1 22 − − =  n dnd  (4a) ( ) 1 2 − − =  n dd  (4b) n er   = (5) er cal d t  = (6) where ͞d is the mean of the difference from x1 and x2, σd is the summation of d, n is the number of the observations, δ is the standard deviation, δer is the standard error and tcal is the calculated value of t test. the data used for the computation of the paired t-test for illustration was the result of compressive strength extracted from table 7 is presented in table 6. table 6: data of compressive strength of the concrete cubes for computing the paired t-test t3 t0 d = t3t0 d2 16.27 12.93 3.34 11.1556 20.77 16.53 4.24 17.9776 23.40 18.66 4.74 22.4676 n = 3 ∑d = 12.32 ∑d2 = 51.6008 t0, t3 were as defined in the abstract and table 5 𝑑 = 12.32 3 = 4.107 (3) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adiama et al: compressive strength and splitting tensile strength of concrete cube using magnetized water. azojete, 20(3):645656. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 651 𝛿 = √ 51.6008−3(4.107)2 3−1 = 0.707 (4a) 𝛿𝐸𝑟 = 0.707 √3 = 0.408 (5) 𝑡𝑐𝑎𝑙 = 4.107 0.408 = 10.066 (6) similarly, this procedure was used for computing the t-test for t1 versus t0, t2 versus t0, t4 versus t0, and t5 versus t0 for the compressive strength and splitting tensile strength, 3. results and discussion 3.1 compressive strengths of the concrete cubes the results of mean compressive strength of concrete cubes produced using mw and nmw, cured in mw or nmw for 7, 14 and 28 days are presented in table 7 and the results of the statistical analysis of t-test for the compressive strength is presented in table 8. the mean compressive strength of concrete cube produced with mw treated for 1 minute and cured in mw treated for 1 minute which was denoted as treatment t3 had the highest compressive strength. the mean compressive strengths after cured for 28 days for t1, t2, t3, t4, t5 and t0 (control) were 18.13±1.15, 22.00±2.08, 23.40±0.20, 19.07±1.67, 17.87±2.20 and 18.66±0.58 n/mm2, respectively as presented in table 7. the trends of the impact of magnetized water on the compressive strength of the concrete cubes at 7, 14 and 28 curing days is shown in figure 5. from table 7, the compressive strength of the concrete cube increased from 7 days to 28 days during curing both for the concrete cubes produced with magnetized water and nonmagnetized water. the concrete cubes produced with the magnetized water treated for 1 minute that was allowed to pass through the magnetic treatment unit 1 time and also cured (soaked in water for hydration) in magnetized water treated for 1 minute which was denoted by t3 had the highest compressive strength than the other cubes produced with mw. t2 in which mw was treated for 1 minute and cured in nmw had higher compressive strength next to t3. the cubes produced using nmw and cured nmw (control denoted as t0) had lower compressive strength than t2 and t3. the concrete cubes produced with mw treated for 2 minutes and cured in nmw (t4) had higher compressive strength than the concrete cubes from the control. the result of this study was in agreement with the studies of (ahmed, 2009; reddy et al., 2014; ghorbani et al., 2018; kiranmai and rao. 2018; and yusuf et al., 2021) which reported that mw increased the compressive strength of concrete. the result of this study revealed that t3 increased compressive strength of concrete cubes by 4.74 n/mm2 (25.40%) when the mw was treated for 1 minute by circulation flow method and cured in mw treated for 1 minute. this was in agreement with the study of parthiban et al. (2016) that mw increased the compressive strength of the concrete by 39.48% when the water was treated for 72 hours with a static flow method. kiranmai and rao. (2018) pointed out that mw increased the compressive strength of concrete increased by 38.1% after curing for 7 days. the result of this study also agreed with the study of reddy et al. (2014) that mw increased the compressive strength of concrete by 55% because mw enhances better hydration of the concrete thereby making the concrete stronger. nan et al. (2003) reported that magnetic fields breakdown the clusters of large molecules of water into smaller clusters molecules. this could allow penetration of mw into cement particles and enhances proper hydration thereby improving the strength of the concrete cube. in this current study, t3 increased the compressive strength of concrete cubes by 4.74 n/mm2 (25.40%) when the water was passed through the magnetic field for 1 minute. the effect of mw treated for 1 minute and cured in mw treated for 1 minute (t3) was significant on the compressive strength of the concrete cube http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)645-656. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 652 compared with concrete cube from the control with the calculated paired t-test was 10.066 which is greater than the table value of t-test of 9.925 at α ≤ 0.010. the effects t1, t2, t4 and t5 were not significant on the compressive strength of the concrete cube when compared to t0 (table 8). table 7: mean compressive strength of the concrete cube curing day mean compressive strength of the concrete block (n/mm2) t0 t1 t2 t3 t4 t5 7 12.93±0.83 12.40±0.72 13.70±0.17 16.27±1.01 12.07±0.31 10.77±143 14 16.53±0.25 16.07±0.25 19.43±0.43 20.77±0.35 16.93±0.31 13.60±0.25 28 18.66±0.58 18.13±1.15 22.00±2.08 23.40±0.20 19.07±1.67 17.87±2.20 t0, t1, t2, t3, t4, t5 were as defined in the abstract and table 5 table 8: result of paired t-test for the compressive strength of the concrete cube treatment df calculated value of t table value of t at α ≤ 0.025 table value of t at α ≤ 0.010 t1 versus t0 2 -25.350* 6,205 9.925 t2 versus t0 2 2.966ns 6,205 9..925 t3 versus t0 2 10.066** 6,205 9.925 t4 versus t0 2 -0.763* 6,205 9.925 t5 versus t0 2 -3.161* 6,205 9.925 df = degree of freedom, t0, t1, t2, t3, t4, t5 were as defined in the abstract and table 5 *= significant (by reducing the compressive strength of the block due to the effect of the treatment) at α ≤ 0.010, **= significant at α ≤ 0.010, ns = not significant the negative value of the t-test indicates reduction in the strength of the cube due to the effect of the treatment. figure 5: the trend of impact of magnetized water on the compressive strength of concrete cube t0, t1, t2, t3, t4, t5 were as defined in the abstract and table 5 0 5 10 15 20 25 7 14 28 c o m p re ss iv e st re n g th (n /m m 2 ) curing day (day) t0 t1 t2 t3 t4 t5 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adiama et al: compressive strength and splitting tensile strength of concrete cube using magnetized water. azojete, 20(3):645656. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 653 3.2 tensile strengths of concrete brick the mean result of tensile strength is presented in table 9 and the statistical analysis of t-test for the splitting tensile strength was presented in table 10. the mean tensile strength after cured for 28 days for t1, t2, t3, t4, t5 and t0 (control) were 1.38±00.03, 1.59±0.24, 1.83±0.22, 1.21±0.06, 1.32±0.32 and 1.33±0.20 n/mm2, respectively (table 9). the trends of impact of magnetized water on the splitting tensile strength of the concrete brick at 7, 14 and 28 curing day is presented in figure 6. t2 and t3 also increased the tensile strength of the concrete brick and t3 gave higher tensile strength than t2 but t2 had higher tensile strength than t0, t1, t4 and t5 (table 9). the concrete brick produced with mw treated for 1 and cured in mw treated for 1 minute (t3) increased the splitting tensile strength by 0.5 n/mm2 (37.57%) while the concrete brick produced with mw treated for 1 but cured in nmw increased the splitting tensile strength by 0.26 n/mm2 (19.55%). the effect of mw treated for 1 minute and cured in mw treated for 1 minute which was allowed to flow 1 time through the magnetic treatment unit was significant on the tensile strength when compared to the concrete brick from the control with the calculated value of t-test of 23.110 that is greater than the table value of t-test of 9.925 at α ≤ 0.010 (table 10). this means that mw had a positive effect on the splitting tensile strength of the concrete. the finding agrees with the studies of parthiban et al. (2016) and kiranmai and rao (2018) that mw water increased the strength of concrete cubes. the increment in the compressive and tensile strengths of the concrete was enhanced by proper hydration by the mw treated in which water was allow to flow through the magnetic field for 1 minute. in addition, putting the water (mw) into the magnetic treatment unit for the second time and third time after it has been treated, the magnetic properties could be reduced and this could reduce the strength of the concrete cube. table 9: mean tensile strength of the concrete brick curing day mean tensile strength of the concrete cube (n/mm2) t0 t1 t2 t3 t4 t5 7 1.08±0.07 0.95±0.07 1.17±0.10 1.53±0.07 0.74±0.08 0.76±0.11 14 1.12±0.22 1.00±0.03 1.25±0.06 1.62±0.03 0.98±0.26 0.97±0.14 28 1.33±0.20 1.38±00.03 1.59±0.24 1.83±0.22 1.21±0.06 1.32±0.32 t0, t1, t2, t3, t4 and t5 were as defined in the abstract table 10: paired t-test for the tensile strength of the concrete treatment df calculated value of t table value of t at α ≤ 0.025 table value of t at α ≤ 0.010 t1 versus t0 2 -1.451ns 6,205 9.925 t2 versus t0 2 3.119ns 6,205 9..925 t3 versus t0 2 23.110** 6,205 9.925 t4 versus t0 2 -3.085ns 6,205 9.925 t5 versus t0 2 -2.329ns 6,205 9.925 df = degree of freedom, t0, t1, t2, t3, t4, t5 were as defined in the abstract **= significant at α ≤ 0.010, ns = not significant, the negative value of the t-test indicates reduction in the strength of the concrete cube due to the effect of the treatment. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)645-656. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 654 figure 6: the trend of impact of magnetized water on the tensile strength of concrete brick t0, t1, t2, t3, t4, t5 were as defined in the abstract 4. conclusion mw was produced using 12 pieces of 10×25×50 mm neodymium permanent magnet arranged on the two sides of a plastic rectangular pipe. mw that was used to produce concrete cubes increased the compressive and tensile strengths of the cube. mw treated for 1 minute when the water was allowed to flow through the magnetic treatment unit by 1 time and cured in mw treated for 1 minute increased the compressive strength and splitting tensile strength by 4.74 n/mm2 (25.40%) and 0.5 n/mm2 (37.57%), respectively. mw that was treated for 1 minute by passing through magnetic one time and cured in mw was found to produce better results than the mw that was allowed to pass through the magnetic treatment unit two times or by multiple flows which probably reduce the magnetic treatment effect and reduced the strengths of the concrete cubes. mw is recommended for producing concrete cubes. references ahmed, sm. 2009. effect of magnetic water on engineering properties of concrete. al-rafidain engineering journal, 17 (1): 71-82. aladjadjiyan, a. 2007. the use of physical methods for plant growing stimulation in bulgaria. journal of central european agriculture, 8 (3): 369-380. albahrani, hs. 2018. improvement of mechanical properties of concrete using magnetic water with different ages of magnetism. journal of engineering and applied science, 13 (24): 1038410387. ali, y, samaneh, r, and kavakebian, f. 2014. applications of magnetic water technology in farming and agriculture development: a review of recent advances. current world environment, 9 (3):695-703. babu, c. 2010. use of magnetic water and polymer in agriculture, tropical research, id 08806-001. chern, cc. 2012. application of magnetic water to stimulate the lady’s finger (abelmosculentus l.) moench plant growth. b.eng. thesis submitted to faculty of civil engineering, university of technology, malaysia. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 7 14 28 c o m p re ss iv e st re n g th ( n /m m 2 ) curing day (day) t0 t1 t2 t3 t4 t5 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com adiama et al: compressive strength and splitting tensile strength of concrete cube using magnetized water. azojete, 20(3):645656. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 655 ejieji, cj. and adeniran, ka. 2009. effect of water and fertilizer stress on the yield, fresh and dry matter production of grain amaranth. australian journal of agricultural engineering, 1 (1): 18-24. ghorbani, s., gholizadeh m. and de brito, j. 2018. effect of magnetized water on the mechanical and durability properties of concrete block pavers. journal of materials, 11(9): 1-16. hamma-adama, m. and kouider, t. 2017. causes of building failure and collapse in nigeria: professionals’view, american journal of engineering research, 6 (12): 289-300. kiranmai, y. and rao, kns. 2018. strength permeation and nano studies on fly ash based magnetic water concrete. international journal of scientific engineering and technology research, 7 (6): 1088-1093. montgomery, dc, runger, gc, hubele, nf. 1998. engineering statistics. john wiley and sons, inc, new york: 135-248. nan, s., wu, yh. and cy and mar, cy. 2003. effect of magnetic field treated water on mortar and concrete containing fly ash. journal of cement and concrete composites, 25 (7): 681688, nilson, ah. 1987. high-strength concrete, an overview of cornell research, proceedings symposium on utilization of high-strength concrete, stavanger, norway, 27-38. ogunlela, ao. and yusuf, ko. 2016. effect of magnetic treatment of water on chemical properties of water and sodium adsorption ratio. journal of research in forestry, wildlife and environment, 8 (4): 73-70, parthiban, pme, rajalingam, me and george, s. 2016. comparative study on strength enhancement of concrete using magnetic and normal water. international journal of new technology and research, 2 (5): 65-68. patil, sv and pathak, nj. 2016. the experimental study on compressive strength of concrete using ar glass fibers and partial replacement of cement with ggbs with effect of magneticwater. international journal of engineering technology, management and applied sciences, 4 (8): 21-29. podlesny, j., pietruszewski, s. and podleoena, a. 2004. efficiency of the magnetic treatment of broad bean seeds cultivated under experimental plot conditions. international agrophysics, 18:65-71. reddy, sb., ghorpade, vg. and rao, hs. 2014. influence of magnetic water on strength properties of concrete. indian journal of science and technology, 7 (1): 14–18. shynier, a., abed, m, fouad, z, kazim, a., isse, r, reheem, n, chaloob, a, mohammad, h, jamal, n, jasim, h, sadeeq, j and salim, a. 2012. improving some of mechanical properties of concrete by magnetic water technology. proceedings of 5th jordanian international civil engineering conference (jicec5) 17th – 19th january, 2012 held at landmark hotel amman (5 stars), amman, jordan: 1-11. yusuf, ko. and ogunlela, ao. 2017. effects of magnetized water on the vegetative growth and yield of tomato. agricultural engineering international: cigr journal, 19 (1): 1-8. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)645-656. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: yusuf.ok@unilorin.edu.ng 656 yusuf, ko., akpenpuun, td., david, so. and oluwayemi, ch. 2021. impact of magnetically treated water on compressive and flexural strength of concrete, nigerian journal of technological development, 18 (3): 251-257. zhang, xx, ruiz, g. and yu, rc. 2008. experimental study of combined size and strain rate effects on the fracture of reinforced concrete,” journal of materials in civil engineering, 20 (8): 544–551. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com corresponding author’s email address: mnasirbello@unimaid.edu.ng 926 arid zone journal of engineering, technology & environment original research article retrofit design of heat exchanger networks for kaduna refinery’s vacuum distillation unit m.n. bello1* and m. a. musa2 1department of chemical engineering, faculty of engineering, university of maiduguri, maiduguri borno statenigeria 2department of chemical and petroleum engineering, bayero university kano, kano state nigeria *corresponding email: mnasirbello@unimaid.edu.ng article information abstract effective heat exchanger network (hen) design is pivotal for improving energy efficiency and realizing substantial cost savings in chemical and petrochemical sectors. while contemporary refineries reap the benefits of economical hen designs, there is an urgent need to enhance the utility and cost-saving features of aging refineries. these older facilities often suffer from suboptimal designs, characterized by high energy requirements and limited cost savings. to address this issue, a thorough analysis of hen design and retrofit options is essential. the pinch design approach standout as a preferred tool for retrofitting hens due to its physical insight and ease of application. in this study, based on pinch technology (pt), various retrofit design scenarios (re-sequencing, addition of heat exchangers, and area addition) were explored for improving the hens of the refinery section’s vacuum distillation unit (vdu). the study revealed that the base case design achieved a total annual cost (tac) of $1.738 × 106. significant cost savings were attained through re-sequencing, addition of area, and addition of a new heat exchanger, amounting to $439.5/year, $746.6/year, and $33,810 respectively. these retrofit strategies are exceptional in reducing utility demand and improving operating cost savings. however, they required a substantial capital expenditure of $1,733, $3,191, and $167,100 respectively, with payback periods of 3.9, 4.3, and 4.9 years respectively. therefore, it is critical to explore additional retrofit possibilities to further optimize cost savings. submitted 04 april, 2024 revised: 24 june, 2024 accepted: 30 june, 2024 keywords: heat exchanger network retrofit design vacuum distillation unit pinch technology total annual cost © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction petroleum refining is a complex process that demands advanced and innovative solutions to minimize costs and maximize energy efficiency, as it consumes a significant amount of energy (han et al. 2020). vdu is a vital component of a typical refinery process, facilitating the additional recovery of the atmospheric residue obtained from an atmospheric distillation unit (h’ng et al., 2024). alongside the crude distillation unit (cdu), these units collectively contribute to a substantial portion of the overall energy consumption in the refinery (yang et al., 2020). consequently, these units incur the highest operating expenses within a refinery (h’ng et al., 2021). as a result, there has been significant research interest in retrofitting and optimizing these units to enhance efficiency and cost saving (klemeš et al., 2020). retrofitting an existing hen is crucial for achieving significant energy savings, eliminating excess loads in heat exchangers, and optimizing energy usage during refining processes (alhajri et al., 2021). the retrofit design is often necessary to attain a cost-effective design and meet product requirements(chin et al., 2020). modifying the existing network is typically feasible (khorshidi et al., 2016), making it more prevalent and economical to revamp most projects in process industries through retrofitting, as designing a new hen may not always be feasible (ulyev et al., 2018), due to substantial capital cost involved (wang et al., 2020). although hen retrofit scenarios are often more complex than grassroots designs, given the need to consider existing infrastructure (gundersen, 2023). however, it enhances energy azojete december 2024. vol.20(4):926-935 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:mnasirbello@unimaid.edu.ng mailto:mnasirbello@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 927 recovery, reduces heating and cooling requirements (osman et al. 2019), and consequently lowers fuel consumption (wang et al., 2020). hen retrofitting can be accomplished through the pinch method, numerical programming approaches, and hybrid approaches (alhajri et al., 2021). in retrofit and new designs, the pinch approach is considered efficient and feasible (alhajri et al., 2021; al-riyami et al., 2001). for example, implementing hen design through pinch analysis can optimize processes and increase distillation efficiency, resulting in cost savings and reduced fuel consumption (fumuassuca et al., 2020). klemeš and varbanov (2018) offers an extensive review of research in this field. the term pinch was coined by linnhoff in 1979 to establish a new set of thermodynamic principles for determining the minimum energy levels in hen design (linnhoff et al. 1982). the robustness of the pinch method in achieving energy savings for optimal design can be found in the works of mrayed et al. (2021),yang et al. (2020), li et al. (2019), bandyopadhyay et al. (2019), ndunagu et al. (2021), bello and zangeri (2021), mehdizadeh et al. (2017), ulyev et al. (2018), ghaderi et al. (2023). improving energy efficiency can provide substantial economic benefits (mrayed et al., 2021). additionally, studies have shown the advantages of the pinch approach in the power sector (lopez et al., 2021) and the waste water treatment and food processing industry (lima et al., 2021) for achieving energy savings, utility cost savings, and emission reduction. however, achieving an appropriate hen is quite challenging due to the complexity of process streams in most process industries (khorshidi et al., 2016). lai et al. (2020)found that retrofitting hen with process modifications resulted in an additional 18.4% reduction in heating utility demand compared to retrofitting alone. modifying the process temperature led to energy savings of 230.8% and annual cost savings of $1.6m. mrayed et al. (2021)proposed two retrofit solutions using pinch analysis to enhance the thermal effectiveness of an existing hen. the first involved adding a new heat exchanger, which achieved utility savings of 9.3 mw with a 3-year payback period. the second solution involved reconfiguring the feed line to the condenser, incurring lower capital expenses. gadalla (2015)introduced a new graphical method for analyzing heat recovery systems in hens. this graph can identify opportunities for modifications to improve energy performance and reduce fuel and water requirements. the method can be used to analyze existing networks, compare them to energy targets, and modify designs or networks for better energy integration and lower fuel demands. al-mutairi and babaqi, (2014) demonstrated that the retrofitting costs were offset by the energy savings, resulting in an overall cost saving of $32,800 per year and a relatively short payback period of less than a year. modifying hen via pinch approach reduced the utilities requirement, thereby saving cost (zhang and liu, 2016; alhajri et al., 2021 and al-mayyahi et al., 2019). retrofitting hen design of cdu achieved optimum design (mehdizadeh fard et al., 2017, hussain et al., 2022, farooq and al-qahtani, 2024, xu et al., 2023). effective hen design plays a crucial role in enhancing energy efficiency and achieving significant cost savings across chemical and petrochemical sectors (jiang et al., 2020). while modern refineries benefit from efficient hen designs, older facilities often operate with suboptimal configurations, resulting in high energy consumption and limited cost-effectiveness. this disparity underscores the urgent need to enhance the utility and cost-saving capabilities of aging refineries through rigorous analysis and strategic retrofitting of hens. in particular, the vdu at kaduna refinery and petrochemical company (krpc) presents a pertinent case study. the vdu is pivotal in recovering valuable products from atmospheric residue(h’ng et al., 2024), yet its hen retrofitting strategies have not been comprehensively explored in existing literature. previous studies primarily focus on cdus, leaving a research gap in understanding and optimizing hen designs specifically tailored for vdus. to address this gap, this research undertook a detailed retrofit design of hen for the vdu at krpc. the study investigated various retrofit options such as re-sequencing, area addition, and adding heat exchangers, leveraging the pinch technology approach known for its effectiveness in optimizing hens. by evaluating these design strategies, the research sought to identify the efficiency of retrofit designs in enhancing energy efficiency, reducing operational costs, and ensuring sustainable refinery operations at krpc. this study was not only timely but essential in contributing to the broader knowledge base of refining operations, particularly in optimizing hens for enhanced efficiency and cost savings in aging refinery infrastructures like krpc's vdu. http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 928 2. materials and methods these include; vdu process flow diagram (pfd), aspen hysys, aspen energy analyzer (aea), and matlap. to conduct the retrofit design of the hens for the unit using the pinch design approach, the procedure was outlined in four stages, including data extraction, targeting for optimum δtmin, hen design, and retrofitting hens. 2. 1 data extraction and targeting data extraction is essential for targeting and predicting the optimum trade-off, which was obtained at 25oc, as shown in figure 1. this driving force corresponds to the minimum tac that could result in cost-effect hen design. the data were extracted from the pfd of the unit obtained from the refinery, presented in table 1. however, detailed analysis of the data extraction and targeting has been presented in our previous work (bello and zangeri, 2021). the benchmark presented in this research is hen design and retrofits analysis. the trade-off value obtained falls within the standard range of δtmin for vdu as provided by linnhoff et al. (1982). table 1: extracted data from the pfd streams id supply temperature (oc) target temperature (oc) heat capacity cp (𝟏𝟎𝟔 kj/hoc) heat duty ∆h (𝟏𝟎𝟔 kj/h) cold a 287.6 289 32.84 45.97 cold b 151 293 0.323 45.97 cold c 289 306 0.261 4.44 cold d 293 309 0.278 4.44 hot a 309 175 0.258 34.62 hot b 309 210 0.350 34.62 hot c 354 306 0.087 4.19 hot d 354 309 0.093 4.19 figure 1: evaluation of δtmin http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 929 2.2 total annual cost (tac) tac is the summation of the energy or operating cost (oc) and the annualized capital cost (cc.af) as expressed in equation 1. the capital cost, defined is by the expected plant life in equation 2, contrasts with the recurring annual expense of the operating cost in equation 3. to ensure compatibility, both costs are standardized to the same annual unit. the capital cost is annualized by multiplying it with an annual factor (af) as detailed in equation 4. the ratio of the capital cost to the operating cost gives the payback period as shown in equation 5 𝑇𝐴𝐶 = 𝑂𝐶 + 𝐶𝐶. 𝐴𝑓 1 𝐶𝐶($)𝐻𝐸𝑁 = [𝑁𝑚𝑖𝑛{𝑎 + 𝑏(𝐴𝑚𝑖𝑛 𝑁𝑚𝑖𝑛⁄ )𝑐}]𝐴𝑃 + [𝑁𝑚𝑖𝑛{𝑎 + 𝑏(𝐴𝑚𝑖𝑛 𝑁𝑚𝑖𝑛⁄ )𝑐}]𝐵𝑃 2 where cc is the capital cost, a, b, and, c, are cost in exchanger cost law, 𝑁𝑚𝑖𝑛 𝑖𝑠 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑢𝑛𝑖𝑡, 𝐴𝑃 𝑎𝑛𝑑 𝐵𝑃 𝑎𝑟𝑒 𝑎𝑏𝑜𝑣𝑒 𝑝𝑖𝑛𝑐ℎ 𝑎𝑛𝑑 𝑏𝑒𝑙𝑜𝑤 𝑝𝑖𝑛𝑐ℎ 𝑎𝑟𝑒𝑎𝑠 𝑂𝐶 = ∑ 𝑄𝑢 𝑢 𝑢=1 ∗ 𝐶𝑢 3 qu = duty of utility u, kw cu = cost of utility, $kw/ yr. u = total number of utilities utilized. 𝐴𝑓 = 𝑖(1+𝑖)𝑛 (1−𝑖)𝑛−1 4 𝑃𝑎𝑦𝑏𝑎𝑐𝑘 𝑝𝑒𝑟𝑖𝑜𝑑 (𝑦𝑒𝑎𝑟) = 𝐶𝑎𝑝𝑖𝑡𝑎𝑙 𝑐𝑜𝑠𝑡 ($) 𝑂𝑝𝑒𝑟𝑎𝑡𝑖𝑛𝑔 𝑐𝑜𝑠𝑡($/𝐲𝐞𝐚𝐫) 5 2.3 hens design hen design is a pivotal research domain aimed at minimizing total annual cost. it has been effectively implemented in various process industries as a reliable heat integration technology (alhajri et al., 2021). essentially, hen design seek to identify the optimal network configuration of heat exchangers for efficient heat transfer between cold and hot streams (al-mayyahi mohammad et al., 2019), thereby significantly reducing the reliance on utility energy sources. hen design in this research was achieved using pinch approach in aspen energy analyzer according to the optimum ∆tmin of 25°c, as depicted in figure 2. this tradeoff is essential in hen design as it enhanced the heat transfer process of the unit, leading to minimum energy consumption and lower operating costs (wang et al., 2020). the hen design shows the exchange of heat between process to process heat exchanger (hot and cold stream), indicated by ash, hot stream and cold utility indicated by blue, cold stream and hot utility shown in red. the hot and cold utilities were added to supplement the heat surplus and deficit respectively to reduce the energy requirement. furthermore, hen design depends on various parameters, including area, number of units, number of shells, capital cost, and operating costs, which collectively contribute to predicting the tac, an economic tool that determine the cost effective design (kari̇mi̇ et al., 2020). http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 930 figure 2: base case hen design 2.4 retrofits design of hen hen retrofitting is done to improve energy recovery, optimize existing hens to accommodate increased throughput of the overall processes (sieniutycz & jeżowski, 2018). in this research, three retrofits design were considered, including re-sequencing, addition of heat exchangers, and area addition. 2.4.1 re-sequencing re-sequencing of a hen involves rearranging the order in which heat exchangers are connected within the network (farooq and al-qahtani, 2024). this optimization method is aimed at improving the overall efficiency and effectiveness of the hen. during the re-sequencing process, we analyze the current configuration of hen to identify areas for modification. figure 3 shows that by strategically adjusting the heat exchanger that was at the extreme right in the base case design toward the middle, indicated by green spot, result in structural alteration of the design and minimize energy wastage, lower utility usage, and improve the efficiency of heat recovery. additionally, as a result of this modification area of heat transfer increased, reducing the operating cost which has effect on tac. however, it should be noted that the initial investment required for this modification may be higher. nonetheless, the long-term benefits of improved energy efficiency and cost savings can outweigh the initial investment costs. http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 931 figure 3: re-sequenced hen design 2.4.2 addition of a new heat exchanger in this retrofit scenario, a new heat exchanger was incorporated to the original design to exchanger heat between hot and cold streams, as indicated by green spot in figure 4. this modification can increase the heat recovery potential of the system, leading to reduced energy consumption and lower operating costs as a result of the increment in area of heat transfer area. however, this may require additional space and capital costs, the benefits of improved energy efficiency can result in significant cost savings in the long run. figure 4: modified hen design via hx addition 2.4.3 addition of area in this case, the goal is to reduce the operating cost of the original design by expanding the areas of heat transfer. this was achieved by shifting the heat exchanger that was at the extreme right towards the extreme left of the original design shown by green spot in figure 5. by doing so, less energy will be required for the heat transfer and the operating cost will be reduced. increasing the heat transfer area result in a reduction of utilities requirement, energy, and achieved cost savings. this modification option can be an effective way to improve the energy efficiency and cost-effectiveness of the process. however, the investment costs and payback period must be carefully considered before deciding to proceed with this modification. http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 932 figure 5: modified hen design (area addition) 3. results and discussion the designed hen has proven effective to some extent in reducing utility requirements, yet it achieved a tac of 104.5% (1.738 mm$/year). to enhance both cost and energy savings, three retrofit scenarios were implemented: re-sequencing, addition of a heat exchanger, and area addition, with their outcomes detailed in table 1. the area addition scenario increased the heat transfer area by 4.9 m², resulting in annual operating cost savings of $439.5. however, this enhancement required an initial investment of $1,733, with a payback period of 4.3 years. conversely, the re-sequencing scenario expanded the area by 9.8 m², leading to improved energy savings of $746.6 annually. the capital outlay for this scenario was also $1,733, recouped over 3.9 years. meanwhile, the addition of a new heat exchanger significantly increased the heat transfer area, resulting in substantial utility savings and annual energy cost reductions of $33,810. however, the upfront investment required was substantial at $167,100, with a payback period of 4.9 years. these findings aligned with recent research by ndunagu et al. (2021) demonstrating energy savings of 8% through retrofits such as re-sequencing and the addition of new heat exchangers, albeit with higher initial costs recouped over 2 years. similarly, mengying et al. (2021) highlighted significant energy cost reductions and rapid payback periods for retrofit strategies in similar systems. furthermore, alhajri et al. (2021) reported that retrofitting scenarios achieved substantial energy savings of approximately 10.4 mw compared to existing designs, translating to annual energy cost savings of about mm$2 and a payback period of less than one year. therefore, the retrofit strategies studied showed promise in reducing utility demand and improving operating cost savings. however, they require a significant capital investment with a payback period that exceeds one year. table 1: evaluation of hens design hens design new area (m2) area (m2) heating (107 kj/h) cooling (107 kj/h) installation cost ($) payback period (year) operating savings ($/year) addition of area 4.9 5654 5.061 2.743 1,733 3.9 439.5 resequencing 9.8 5657 5.060 2.742 3,191 4.3 746.6 addition of hx 541 6098 4.922 2.605 167,100 4.9 33,810 http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 933 4. conclusion this research demonstrated that retrofit scenarios such as re-sequencing, adding heat exchangers, and increasing area standout for improving energy efficiency and reducing operational costs. despite their effectiveness in lowering energy requirements and achieving operating cost savings, they require substantial investment and entail payback periods exceeding one year. therefore, it is crucial to explore additional retrofit possibilities to further enhance cost savings. references alhajri, ih., gadalla, ma., abdelaziz, oy. and ashour, fh. 2021. retrofit of heat exchanger networks by graphical pinch analysis – a case study of a crude oil refinery in kuwait. case studies in thermal engineering, 26: 101030. https://doi.org/10.1016/j.csite.2021.101030 al-mayyahi, m., albadran, fa. and fares, mn. 2019. retrofitting design of heat exchanger networks using supply-target diagram. chemical engineering transactions, 75: 625–630. https://doi.org/10.3303/cet1975105 al-mutairi, em. and babaqi, bs. 2014. energy optimization of integrated atmospheric and vacuum crude distillation units in oil refinery with light crude: energy optimization. asia-pacific journal of chemical engineering, 9(2): 181–195. https://doi.org/10.1002/apj.1758 al-riyami, ba., klemeš, j. and perry, s. 2001. heat integration retrofit analysis of a heat exchanger network of a fluid catalytic cracking plant. applied thermal engineering, 21: (13–14): 1449–1487. https://doi.org/10.1016/s1359-4311(01)00028-x bandyopadhyay, r., alkilde, of. and upadhyayula, s. 2019. applying pinch and exergy analysis for energy efficient design of diesel hydrotreating unit. journal of cleaner production, 232: 337–349. https://doi.org/10.1016/j.jclepro.2019.05.277 bello, mn. and zangeri, sa. 2021. pinch analysis of vacuum distillation unit of kaduna refinery and petrochemical company. https://www.semanticscholar.org/paper/pinch-analysis-of-vacuum-distillation-unitof-and-bello-zangeri/337fc03cede506bac2153fad549b633f729c3920 chin, hh., wang, b., varbanov, ps., klemeš, jj., zeng, m. and wang, qw. 2020. long-term investment and maintenance planning for heat exchanger network retrofit. applied energy, 279: 115713. https://doi.org/10.1016/j.apenergy.2020.115713 farooq, z. and al-qahtani, a. 2024. sustainable energy efficient industrial facility design. in j. xu & b. yang (eds.), energy consumption, conversion, storage, and efficiency. intechopen., london. https://doi.org/10.5772/intechopen.108829 fumuassuca, ds., dos-santos, m. and chivanga-barros, aa. 2020. pinch analysis applied to atmospheric distillation column. angolan mineral, oil & gas journal, 1(1): 11–15. https://doi.org/10.47444/amogj.v1i1.6 gadalla, ma. 2015. a new graphical method for pinch analysis applications: heat exchanger network retrofit and energy integration. energy, 81: 159–174. https://doi.org/10.1016/j.energy.2014.12.011 ghaderi, m., hosseinnia, sm. and sorin, m. 2023. assessment of waste heat recovery potential in greenhouse ventilation systems using dynamic pinch analysis. applied thermal engineering, 227: 120363. https://doi.org/10.1016/j.applthermaleng.2023.120363 gundersen, t. 2023. analysis and design of heat recovery systems for grassroots and retrofit situations. in handbook of process integration (pi). elsevier publishers, amsterdam, pp. 309–348. https://doi.org/10.1016/b978-0-12-823850-9.00037-2 han, y., wu, h., geng, z., zhu, q., gu, x. and yu, b. 2020. review: energy efficiency evaluation of complex petrochemical industries. energy, 203: 117893. https://doi.org/10.1016/j.energy.2020.117893 http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; 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an oil refinery. day 2 tue, august 03, 2021, d021s007r006. https://doi.org/10.2118/207096-ms http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 926-935. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mnasirbello@unimaid.edu.ng 935 osman, a., eltayeb, m. and rajab, f. 2019. utility paths combination in hen for energy saving and co2 emission reduction. processes, 7(7): 425. https://doi.org/10.3390/pr7070425 sieniutycz, s., & jeżowski, j. 2018. heat-exchanger network retrofit. in s. sieniutycz & j. jeżowski (eds.), energy optimization in process systems and fuel cells (third edition)amsterdam elsevier publishers, pp. 611–639. https://doi.org/10.1016/b978-0-08-102557-4.00019-0 mengying, s., dianliang, f. and lanyi, s. 2021. heat exchanger network retrofit for optimization of crude distillation unit using pinch analysis. china petroleum processing and petrochemical technology, 23(01): 31– 40. ulyev, l., vasiliev, m. andboldyryev, s. 2018. process integration of crude oil distillation with technological and economic restrictions. journal of environmental management, 222: 454–464. https://doi.org/10.1016/j.jenvman.2018.05.062 wang, b., klemeš, jj., varbanov, ps. and zeng, m. 2020. an extended grid diagram for heat exchanger network retrofit considering heat exchanger types. energies, 13(10): 2656. https://doi.org/10.3390/en13102656 xu, y., zhang, l., cui, g. and yang, q. 2023. a heuristic approach to design a cost-effective and low-co2 emission synthesis in a heat exchanger network with crude oil distillation units. energy, 271: 126972. https://doi.org/10.1016/j.energy.2023.126972 yang, k., liu, s., he, c., zhang, b., chen, q. and pan, m. 2020. improving energy saving of crude oil distillation units with optimal operations. journal of cleaner production, 263: 121340. https://doi.org/10.1016/j.jclepro.2020.121340 zhang, d. and liu, g. 2016. integration of heat exchanger network considering the influence of the reactor. chemical engineering transactions, 52: 181–186. https://doi.org/10.3303/cet1652031 http://www.azojete.com.ng/ mailto:mnasirbello@unimaid.edu.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 845 arid zone journal of engineering, technology & environment original research article compressive strength assessment of metakaolin hollow sandcrete blocks m. ibrahim department of civil engineering, baze university, abuja, nigeria corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng article information abstract this study examines the effect of partially substituting metakaolin (mk) for cement on the hollow sandcrete block’s compressive strength. sandcrete hollow blocks measuring 225 x 225 x 450 mm were made using a 1:6 mix ratio, which is one part cement to six parts fine aggregate (sand). the study was carried out by partially replacing metakaolin with cement at 0% to 35% at 5% intervals to assess the impact on the hollow sandcrete block’s strength. the blocks were cured using the sprinkling method, and compressive strength tests were conducted on the hollow sandcrete block samples at 1, 3, 7, 14, 21, and 28 days. the compressive strength of hollow sandcrete blocks samples ranges from 3.65 n/mm2 to 0.86 n/mm2. the compressive strength results showed that the optimum percentage of metakaolin (mk) replacement by weight of cement was 10% having a strength of 3.65 n/mm2 after 28 days of curing. these value meets the stipulated requirement specified by nigeria industrial standard nis 87 (2000), bs 6073, and national building code (2006) and are adequate for usage as non-bearing and load-bearing structures in areas where moisture infiltration may occur. the research was aimed at using metakaolin (mk) as a partial replacement of cement in the production hollow sandcrete blocks to curtail the reduction of cement components by block producers to produce low-quality sandcrete block for structural purposes and improve the strength properties of blocks in terms of its production. submitted 21 may, 2024 revised 04 july, 2024 accepted 10 july, 2024 keywords: compressive strength hollow sandcrete blocks metakaolin cement © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction sandcrete blocks can be defined as composite construction materials made from combining cement, fine aggregate (sand), and water and molded into various sizes (barry, 1999., and anthony, et al., 2015). observation has shown that many ancient buildings in nigeria are made of clay works, presently still in existence and usable. despite the introduction of new materials such as life bricks, modified clay blocks, sandcrete blocks seem to be an improvement over these materials which has gained wide usage in construction industries for use as load bearing and non-load bearing structure. sandcrete blocks are perhaps the most widely used building material in nigeria, having been employed in the construction of over 90% of the country's physical infrastructure. in nigeria and other african nations, it is extensively utilized as non-load-bearing and load-bearing walling components, and they have many advantages because of some of their unique properties like strength, density, water absorption, shrinkage, durability, costs, and dimensional accuracy. many factors, including the materials used in the manufacturing process, the length of time the blocks are left to cure, and the shape and size of the blocks, affect the quality of sandcrete blocks (esegbuyota et al., 2019). cement, the primary binder used to make concrete, mortar, sandcrete blocks, and other cement products, is very costly, especially in developing nations. due to the recent expansion of infrastructure development, there is an increasing global consumption of cement used in the production of concrete (zareei, 2017; thomas, 2018; attah et al., 2020). reducing the cost of producing cement and the amount of carbon dioxide (co2) emission into the atmosphere (mehta, 2001 khan et al., 2012; johnson et al., 2013;), decreasing housing costs, and meeting the increasing need to protect the environment, has intensified the efforts of researchers at seeking and developing affordable and accessible alternative local materials that could be employed for environmentally friendly building (awodiji et al., 2018; onwuka et al., 2013, nwa-david et al., 2023a). all the challenges have azojete december 2024. vol.20(4):845-854 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:musa.ibrahim@bazeuniversity.edu.ng mailto:musa.ibrahim@bazeuniversity.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 846 resulted in increasing the cost of construction of houses and cement-based physical infrastructure, hence the need to search for alternative binding materials as a whole or partly as a substitute for cement. thus, part of the solution to reducing the increasing cost of cement in the production of concrete in recent times is the use of supplementary cementitious materials (scms) including periwinkle shell ash, corncob ash, rice husk ash, cassava peel ash, oyster shell ash, sawdust ash and metakaolin for developing high-strength concrete with enhanced workability, strength and durability and reduced permeability (olutoge et al., 2012; kamau et al., 2016; ogbonna et al., 2020). kaolin clay is refined and then calcined under specific conditions (temperature and time) to produce metakaolin, a pozzolanic material. by increasing strength and decreasing setting time, metakaolin is a very useful material for improving the quality of concrete and may be a potential material for the production of high-performance concrete (li and ding, 2003). metakaolin is produced for a specific purpose under controlled conditions, making it different from other supplementary cementitious materials like fly ash, slag, or silica fume. it is manufactured by heating kaolin to temperatures between 650-900°c for periods ranging from 1 hour to 12 hours. the kaolin's structure is broken down by this heat treatment. when metakaolin is added during the hydration process, it reacts with free lime to form additional csh material, thereby enhancing the strength and durability of the concrete (goud et al., 2017; saand et al., 2017). however, for some time now, the majority of hollow sandcrete blocks used in developing nations, particularly in sub-saharan africa are substandard. (anosike and oyebade 2011). previous studies conducted in nigeria have also demonstrated how poorly these sandcrete blocks perform, with their strength and durability falling well short of the required standards. according to odeyemi et al. (2018), stated that many of the hollow sandcrete blocks produced by commercial block producers do not meet the nigeria industrial standard's recommended maximum water absorption of 12% and the minimum standard requirement for compressive strength values of 2.5 n/mm² and 3.45 n/mm² for non-load bearing walls and load bearing walls, respectively. some of these blocks even fail while being transported because of their weight, leading to or contributing to the collapse of buildings, especially the failure of load-bearing walls constructed with these blocks. this problem has been attributed to poor quality control and substandard constituent materials. (olusola and akintayo 2009). due to their porous nature, sandcrete blocks generally take in fluid when exposed to moist conditions. according to studies by siddique and klaus (2009), cassagnabère et al. (2010) and marchand et al. (1996), the addition of mineral admixtures to concrete and mortar improved the porous structure's resistance to bending, compression, and efflorescence, thereby increasing the material's strength and durability. due to the pozzolanic and filling actions of certain mineral admixtures, they are capable of improving durability through pore refinement, and the reduction in the calcium hydroxide of the cement paste, these cement composites improve the mechanical properties and life of the structure. the physical action of the pozzolanas provides a uniform, more homogeneous, and denser paste (chindaprasirt et al., 2004). much attention has been paid to the utilization of metakaolin in mortar and concrete as a partial substitute for cement. metakaolin is used as a supplementary cementitious material in concrete to improve durability, decrease permeability, enhance strength and the rate of strength gain, and reduce cement consumption (asbridge et al., 2001; aquino et al., 2001; boddy et al., 2001; justice et al., 2005 and khatib and wild, 1998). metakaolin can also be used as a sandcrete block constituent, substituting part of the cement content since it has pozzolanic properties. this paper investigates experimentally the effect of partially replacing cement with metakaolin on the compressive strengths of hollow sandcrete blocks. 2. materials and methods 2.1 materials the constituent materials used for the production of metakaolin hollow sandcrete block were portable water, fine aggregate (sand), cement, kaolin, and metakaolin only. 2.1.2 fine aggregate (sand) the fine aggregate (sand) used in this study was sourced locally in zaria, kaduna state, nigeria, and was devoid of any organic or chemical debris, clay, loam, or dirt. it was fine aggregate sand passing through a sieve of size 4.76 mm to remove some of the contained coarse aggregates. the sand had a specific gravity of 2.61 and an average moisture content of 9.08%. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 847 2.1.3 cement dangote portland limestone cement (3x brand) was used for this study. it was obtained from a dealer in zaria, kaduna state, nigeria, and its properties met nis 444-1:200 and bs en 197-1 (2011) requirement. 2.1.4 water water from the civil engineering department, ahmadu bello university, zaria, was used for both the specimen preparations and curing of sandcrete blocks throughout the investigation and it conformed with the recommendations of bs 3148:1980. 2.1.5 kaolin the kaolin used in the study was a product of the kankara kaolin clay deposit from kankara local government area of katsina state, nigeria precisely around longitude 7° 26e and 7°28e and latitude 11°53n. the kaolin was subjected to close burning at 700°c to obtain the metakaolin that was used for this study (elimbi et al., 2011). 2.1.6 metakaolin the incineration of kaolin to obtain metakaolin for the study was carried out under controlled temperature conditions. ahmadu bello university zaria’s school of physical science multipurpose laboratory was used to assess the oxide composition by mass of a metakaolin sample. to ascertain the percentage oxide composition and categorize the metakaolin as pozzolanic material, the x-ray fluorescence (xrf) method was utilized to analyze the oxide composition of the material. the test was carried out in compliance with the guidelines provided in bs en 197-1: 2011 and bs en 196-2: 2000. the specific gravity test was carried out on the metakaolin in accordance with bs 1377-2: (1990) figure 1: kaolin before calcination figure 2: kaolin after calcination 2.2 methods 2.2.1 hollow sandcrete blocks production the hollow sandcrete blocks were produced using standard metal molds in accordance with nis 87: 2000 (2000). a mix proportion of 1:6 (which is one part cement to six parts fine aggregate (sand) was used in the production of hollow sandcrete blocks measuring 450 mm x 225 mm x 225 mm as specified by (nis 87:2000, 2000), for the production of sandcrete blocks in nigeria. the cement was replaced partially with metakaolin at 0% to 35% levels at 5% intervals. the quantities of the materials were batched by weight. in the production of these blocks, hand mixing was used and the materials were thoroughly mixed until an even color and consistency were achieved. the mixture was poured and compacted into a metal mold measuring 450 × 225 × 225 mm. after that, the excess material was removed, leaving the surface smooth. following these method, before after http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 848 168 hollow sandcrete blocks measuring 450 × 225 × 225 mm were produced. the blocks were removed from the molds and placed on the pallets with a space between two hollow sandcrete blocks for the period of curing. 2.2.2 curing the hollow sandcrete blocks were cured in compliance with (nis 87:2000, 2000). throughout the curing process, the hollow sandcrete blocks were left on wooden pallets and kept wet. the curing was done by sprinkling water twice (morning and evening) a day for 1, 3, 7, 14, 21, and 28, days. for the curing of sandcrete blocks produced, clean water devoid of salt and other harmful substances was used at a temperature of 23 ± 2 ◦c. figure 3: metakaolin sandcrete blocks produced at various replacement levels 2.2.3 compressive strength test a compressive testing machine was used to carried out the compressive strength of the blocks in the material testing laboratory at ahmadu bello university zaria, kaduna state, nigeria, after the necessary curing days of 1, 3, 7, 14, 21, and 28 days. the compressive strength test was carried out on the hardened hollow sandcrete blocks at 1, 3, 7, 14, 21, and 28 days of age to determine the load-bearing capacity of the hollow sandcrete block samples, which was carried out as stipulated in bs 6073 part 1, (1981). for each mix, 3 blocks were crushed to obtain the average strength using the following equation compressive strength (𝑁 𝑚𝑚²)⁄ = 𝐶𝑟𝑢𝑠ℎ𝑖𝑛𝑔 𝑙𝑜𝑎𝑑 𝑁𝑒𝑡 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑏𝑙𝑜𝑐𝑘 (1) http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 849 figure 4: crushing strength of mksb by universal compression machine 3. results and discussion 3.1 specific gravity/bulk density the specific gravity of metakaolin was found to be 2.57 as shown in table 1. the specific gravity value is a little lower than the 2.62 reported by poon et al., (2001) but greater than 2.5 obtained by al-akhras et al. (2006) and tafraoui et al. (2005). also, the bulk density of metakaolin is 1865 kg/m³. table 1 compares the specific gravity and bulk density of ordinary portland cement with metakaolin, demonstrating that opc values are higher in both cases. table 1: comparison between physical properties of opc and metakaolin item ordinary portland cement (opc) metakaolin bulk density 1320 kg/m³ 1865 kg/m³ specific gravity 3.15 2.57 3.2 chemical analysis of metakaolin the result of the oxide composition of metakaolin as shown in table 2 shows that metakaolin contains silicon oxide (sio2 = 56.48%), aluminum oxide (al2o3 = 36.09%), and iron oxide (fe2o3 = 0.59%). the total percentage composition of sio2, al2o3, and fe2o3, is 93.16% which is in line with astm c 618-78 (american society for testing and materials, 1978) minimum requirement of 70% for pozzolanas. therefore, the kankara metakaolin meets the stipulated requirement for pozzolanas and is classified as class f. the presence of siliceous and aluminous material in the metakaolin in its fine form suggests that it can react with calcium hydroxide to produce calcium silicate hydrate (csh), a cement-forming substance that increases strength (astm c618). http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 850 table 2: chemical composition of metakaolin elemental oxide percentage (%) of metakaolin sio2 56.48 al2o3 36.09 fe2o3 0.59 cao 0.28 mgo 0.67 na2o 0.02 k2o 0.06 tio2 5.15 so3 0.33 with its low combined alkali concentration of 5.21% (na2o + k2o), metakaolin decreases the likelihood of the destructive aggregate alkali reaction that causes the disintegration of concrete. it is also observed that the so3 and mgo values are 0.33% and 0.67% which are less than the maximum of 2.5% and 4% specified in bs 3892: 1990 parts 1 and 2 respectively. this suggests that adding metakaolin to concrete mixes could improve their durability and reduce unsoundness when utilized in the production of metakaolin hollow sandcrete blocks. 3.3 compressive strength of metakaolin sandcrete blocks the result of the average compressive strength of the tested metakaolin sandcrete blocks with a mix ratio of 1:6 (which is one part cement to six parts fine aggregate (sand) at 1, 3, 7, 14, 21, and 28 days of curing is shown in table 3, whereas the plots in figure 5 illustrates the increase of the compressive strength of hollow sandcrete blocks with the age of curing for different levels of replacement of cement with metakaolin. table 3: compressive strength of hollow sandcrete blocks age of curing (days) compressive strength (n/mm²) at various levels of replacement of cement with metakaolin control mix 5% 10% 15% 20% 25% 30% 35% 1 0.52 0.86 1.10 0.83 0.80 0.49 0.41 0.31 3 1.33 1.51 2.04 1.47 1.32 0.70 0.66 0.56 7 1.90 2.31 2.53 2.30 1.89 1.30 0.99 0.70 14 2.61 2.73 2.87 2.24 1.79 1.67 0.85 0.81 21 2.81 3.04 3.19 2.53 2.12 1.51 0.83 0.70 28 3.51 3.36 3.65 2.61 2.21 1.58 1.10 0.86 the compressive test results obtained for sandcrete blocks produced at different replacement level of cement with metakaaolin indicates that the compressive strength of sandcrete blocks increases with an increase in the metakaolin content from 5% to 20% and decreases with an increase in metakaolin content from 25% to 35% replacement of cement with metakaolin. after 28 days of curing, the compressive strength at 5% replacement of cement with metakaolin is lower compared to that of the control mix. this can be seen when 5% cement is replaced with metakaolin achieving a compressive strength of 3.36 n/mm2 compared to 3.51 n/mm2 respectively. it is evident that the 5% replacement level of metakaolinite is insufficient to produce additional http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 851 c-s-h, and hence does not increase the compressive strength over the control at all ages. the metakaolinite available only reacts with a portion of calcium hydroxide released from the byproduct of hydration of cement which limits the strength development at the later ages (siddique et al., 2009). figure 5: compressive strength of metakaolin sandcrete blocks with varying curing days. metakaolin sandcrete blocks with 10% metakaolin replacement level exhibit the best strength development revealing that 10% metakaolin replacement is the optimum as seen in figure 2. the average compressive strength of 3.65 n/mm2 after 28 days of curing was attained at a 10% cement replacement level with metakaolin. the mean compressive strength of 3.65 n/mm2 at 28 days of curing was achieved at a 10% replacement level of cement with metakaolin. this satisfied the nigeria industrial standard nis 87 (2000)'s compressive strength requirements of 2.5 n/mm2 for non-load-bearing walls and 3.45 n/mm2 for load-bearing walls. this also satisfies bs 6073 which recommends 2.80 n/mm2 for the mean strength, and 2.59 n/mm2 for the lowest individual strength. the compressive strength at 5%, 15%, and 20% replacement levels with metakaolin are 3.36 n/mm2, 2.61 n/mm2, and 2.21 n/mm2 respectively at 28 days of curing which satisfies the requirement given in the nigeria federal ministry of works, and housing (1979) specification, national building code (2006) specification, nis 87: 2000 for hand compacted blocks. although, compressive strength at 25%, 30%, and 35% replacement at 28 days of curing exhibit significant strength of 1.58 n/mm2, 1.10 n/mm2, and 0.86n/mm2 respectively. this strength is higher than commercially produced blocks in some regions of nigeria according to ewa and ukpata (2013) and tsado et al., (2014) which ranges from 0.23 n/mm2 and 0.58 n/mm2. 4. conclusion the metakaolin obtained by the incineration (under controlled conditions) of the kaolin, a product of the kankara kaolin clay deposit from kankara local government area of katsina state, nigeria met all the requirements of oxide composition and has a sio2, al2o3, and fe2o3 combination of 93.16% which is higher than the 70% minimum recommended limit as stipulated by astm c 618-05. this suggests that the metakaolin utilized in this study, which was derived from kaolin, is a high-quality reactive pozzolana. the compressive strength of hollow sandcrete blocks increases with an increase in the metakaolin content from 5% to 20% but reduces with an increase in metakaolin content from 25% to 35% in the mix. the compressive strength results indicate that the optimum percentage of metakaolin replacement by weight of cement was 10% having a strength of 3.65 n/mm2 at 28 days of curing and also which meets nigeria industrial standard nis 87 (2000), bs 6073, and national building code (2006) stipulated requirement. it is recommended that metakaolin sandcrete blocks produced at 10% cement replacement with metakaolin are adequate for use as load-bearing and non-load-bearing structure in areas where they may be subjected to moisture ingress. sensitization is needed in the production of commercial hollow sandcrete blocks to block producers of low-quality blocks and how metakaolin can be utilized as a partial substitute for cement to achieve the required profit margin with standard for structural purpose. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; 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vol.20(4):845-854. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: musa.ibrahim@bazeuniversity.edu.ng 854 saand, a., keerio, ma. and bangwar, dk. 2017. effect of soorh metakaolin on concrete compressive strength and durability. engineering technology and applied science research, 7(6): 2210–2214. siddique, r. and klaus, j. 2009. influence of metakaolin on the properties of mortar and concrete. a review. applied clay science, 43(3): 392 400. thomas, bs. 2018. green concrete partially comprised of rice husk ash as a supplementary cementitious material—a comprehensive review, renewable and sustainable energy reviews, 82: 3913–3923. tsado, t., auta, sm., james, o. and ahmed, sb. 2014. quality assurance of hollow sandcrete blocks industries in minna, niger state, nigeria. international engineering conference. retrieved from www.seetconf.futminna.edu.ng zareei, sa., ameri, f., dorostkar, f. and ahmadi, m. 2017. rice husk ash as a partial replacement of cement in high strength concrete containing micro silica: evaluating durability and mechanical properties. case studies in construction materials, 7:73–81. http://www.azojete.com.ng/ mailto:musa.ibrahim@bazeuniversity.edu.ng http://www.seetconf.futminna.edu.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 962 arid zone journal of engineering, technology & environment original research article analyzing the spatial and temporal dynamics of rainfall and drought in the vall river basin, south africa. i. r. bodunrin*; e. k. onyari department of civil and environmental engineering and building sciences, college of science, engineering and technology, private bag x6, florida 1710, university of south africa, johannesburg, south africa. *corresponding author’s email: rachealbodunrin@yahoo.com article information abstract climate change continues to have devastating effects worldwide, particularly through drought, impacting billions of people. a recent study focused on the vaal area in south africa, a semi-arid region reliant on the vaal river, a vital water resource. researchers utilized the standardized precipitation index (spi) and standardized precipitation and evapotranspiration index (spei) to assess rainfall variability, evapotranspiration, drought, and trends over four decades. the results show some characteristics of rainfall patterns; such as peak precipitation occurs during the january to march summer months while drought years: 2016 was identified as a hydrologically driest year for the vaal river based on spi and spei analysis at 12and 24-month scales. similarly, agricultural drought: years like 1983, 1999, 2016, and 2019 exhibited agricultural drought, particularly evident in spei/spi -3 and spei/spi -6, crucial for local irrigation and agricultural production. furthermore, for temporal consistency: spi and spei demonstrated increasing temporal consistency with longer timescales until 2019, except for spei/spi-1 and spei/spi-48, which did not accurately represent drought in the vaal river basin. interestingly, the study highlights the escalating impact of climate change-induced drought in the vaal area and underscores the importance of spei in assessing drought severity. therefore, as climate conditions worsen globally, such analyses are vital for informed decision-making and effective water resource management. received: 10th september 2025 revised: 17th november 2025 accepted: 18th november 2025 keywords: climate change drought precipitation river basin spi spei water resources © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction drought is believed to be one of the world's most harmful natural disasters (zhong, sun and di, 2021), its severity has intensified in recent decades due to climate change and associated effects, leading to shifts in climatological patterns like rainfall and temperature. drought has influenced larger regions when contrasted to other hazards such as floods, which are restricted to floodplains, coastal regions, storm tracks, or fault zones (svoboda et al., 2015). drought events are anticipated to rise in the 21st century (guo, 2012; huang et al. 2016; bahta and myeki 2022), necessitating robust monitoring and assessment measures (pei et al., 2020). drought is characterized by a prolonged period of water scarcity resulting from inadequate precipitation and heightened evaporative demand, ultimately leading to substantial environmental and socioeconomic consequences. it can be categorized into four types: meteorological, hydrological, agricultural (or vegetative), and socioeconomic drought. meteorological drought refers to a lack of precipitation. hydrological drought occurs when surface and groundwater resources are depleted, affecting rivers, lakes, reservoirs, and aquifers. agricultural drought arises from precipitation deficits during the growing season, limiting crop growth and development. droughts have had devastating effects on many nations, leading to declines in agricultural productivity, portable water supply, and economic stability, with severe cases resulting in famine (tladi, ndambuki and salim, 2022). in southern africa, drought has been a significant concern since the 1970s, with azojete december 2025. vol.21(4):962-977 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/007 www.azojete.com.ng http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com mailto:rachealbodunrin@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 963 el niño and the southern oscillation (enso) warm events exacerbating drought impacts (rouault and richard, 2005; cane et al., 1997; enfield, 1989; ogallo, 1979). south africa, in particular, has faced several drought spells, with notable occurrences in 1964, 1986, 1988, 1990, 1995, 2002–2004, and 2015–2019 (bhaga et al., 2020; mishra and singh, 2010). the 2015–2016 hydrological year marked the worst drought in 23 years, resulting in crop declines, livestock mortality, and water constraints in major cities (department of agriculture forestry and fisheries, 2010). rising water demand in south africa has been exacerbated by recurring droughts, which degrade water quality, disrupt hydrological systems, and stress groundwater recharge. climate change and variability are expected to increase the frequency and severity of droughts, further straining limited water resources. this study examines rainfall variability and drought impacts in the vaal river basin, a vital water source for agriculture, industry, and domestic use. understanding the effects of drought is crucial for sustainable water resource management and developing effective mitigation strategies. drought indices, which quantify drought onset, duration, intensity, and frequency, offer a valuable framework for simplifying complex climate-hydrology interactions and assessing drought severity. the standardized precipitation index (spi) and the standardized precipitation evaporation index (spei) are two of the most widely used drought indexes amongst others. the spi as coined by mckee et al. (1993) considered precipitation while the spei was first proposed by vicente-serrano et al. (2010) as an improvement over the standardized precipitation index (spi), for the reason that it considers variables like temperature and evapotranspiration to effectively provide a water balance standardized result. compared to spi, spei provides advantages in assessing water balance, standardization for comparability, flexibility across timescales, and broad regional applicability, making it highly effective for drought monitoring and decision-making. remote sensing (rs) data, such as those from modis, provide valuable large-scale observations for drought monitoring, enabling the retrieval of variables like precipitation, evapotranspiration, and vegetation health. this study will evaluate drought occurrences in the vaal river basin from 1983 to 2023. the aim is to analyse temporal and spatial drought patterns and their impacts on water resources and the environment, supporting sustainable management in the region. the study main objectives were to utilize spi and spei drought indices to evaluate drought patterns from 1983 – 2023, produce rainfall maps for the vaal river basin and adjacent provinces, identifying evapotranspiration patterns and assess the extent of drought effects in the study area. this research aims to suggest early warning systems for drought occurrence along the vaal river basin, essential for ensuring water availability to support the country's economy and population. 2. materials and methods 2.1 the study area the vaal river basin, located between 26.5 28.5os, 24 29.5oe in central south africa (fig 1), is the main tributary of the orange river, which drains into the atlantic ocean. flowing westward near johannesburg, it spans several provinces, including gauteng, free state, mpumalanga, northwest, and eastern cape, and supplies water to major cities such as johannesburg, pretoria, and bloemfontein. the basin lies within a subtropical dry savanna climate, with mean annual evaporation (~1,300 mm) exceeding rainfall (~600 mm). rainfall varies spatially, from 800–1,000 mm in the east to about 300 mm in the west, with a mean annual temperature of 15 °c. land use is dominated by agriculture, including the large vaalharts irrigation scheme, making the basin critical for both water resource management and food production. 2.2 sources of data and data analysis rainfall variability in the vaal river basin (1983-2023) was analysed using a combination of rain gauged and remotely sensed data. precipitation and temperature records were obtained from the south african weather service, chirps, and modis evapotranspiration (mod16a2). rainfall mapping and study area delineation was performed using arcgis 10.1, while drought indices were calculated using r. rainfall trend analysis was conducted using the mann-kendall trend test and sen's slope estimator. the mann-kendall test results, including the test statistic (z), p-value, and sen's slope (q), were calculated using r. the standardized precipitation index (spi) was based solely on precipitation, whereas the standardized precipitation evapotranspiration index (spei) incorporated both precipitation and potential evapotranspiration (pet), estimated using the hargreaves method. data from six meteorological stations were averaged to represent the drought severity and duration along the lower, middle, and upper vaal river basins using the http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 964 spi and spei indices. drought assessment was conducted across multiple timescales (1-48 months), with shorter timescales capturing rapid changes and longer timescales reflecting extended drought conditions. figure 1: study area 2.3 spi and spei indices the spi was offered by mc kee, doesken and leist in 1993. the index is based on analysing precipitation as the sole variable been considered making its evaluation easier. it can be calculated over different time scales and is suitable to calculate drought among different time regions (cacciamani et al., 2007). it can be calculated as given in the equation 1. 𝑆𝑃𝐼 = 𝑝 − 𝑝∗ 𝜎𝑝 1 where p = observed monthly precipitation, p* = mean of monthly precipitation and 𝜎𝑝 = standard deviation of observed precipitation. the spei was proposed as an improvement over the standardized precipitation index (spi). it is built on the water balance principle, utilizing the difference between precipitation (p) and potential evapotranspiration (pet) as input conditions to estimate the wet and dry conditions of an area (tirivarombo, osupile and eliasson, 2018). a comprehensive explanation of the spei theory was offered by vicente-serrano et al. (2010) and the climate-water balance was calculated: 𝐷𝑖 = 𝑃𝑖 − 𝑃𝐸𝑇𝑖 2 where 𝐷𝐼 is the moisture deficit (mm) at the month i, 𝑃𝑖 is the precipitation (mm) at the month i, and 𝑃𝐸𝑇𝑖 is the potential evapotranspiration (mm) at the month i. as can be seen, there are various approaches to analyse drought, spi, which uses only precipitation data, and spei, which uses pet and precipitation simultaneously, are notable among the most widely used methods in the literature (tirivarombo, osupile and eliasson, 2018; eris et al., 2020; pei et al., 2020). although these two methods use different input parameters, their calculations are similar (danandeh et al.,, 2022). due to their similarity in results, the study used the more recent indices which is the spei. the formula below has been used to calculate spei. 𝑆𝑃𝐸𝐼 = 𝑊 − 𝐶0 + 𝐶1 𝑊 + 𝐶2 𝑊2 1 + 𝑑1 𝑊 + 𝑑2 𝑊 + 𝑑3 𝑊3 3 𝑊 = −√2 ln(𝑃) 𝑓𝑜𝑟 𝑃 ≤ 0.5 4 nothern cape free state north west mpumalanga gauteng 33°0'0"e 33°0'0"e 30°0'0"e 30°0'0"e 27°0'0"e 27°0'0"e 24°0'0"e 24°0'0"e 21°0'0"e 21°0'0"e 18°0'0"e 18°0'0"e 2 4 °0 '0 "s 2 4 °0 '0 "s 2 7 °0 '0 "s 2 7 °0 '0 "s 3 0 °0 '0 "s 3 0 °0 '0 "s 3 3 °0 '0 "s 3 3 °0 '0 "s 0 780 1,560 2,340 3,120390 kilometers legend $1 meteorological stations vaal river south africa boundary south africa µ wgs 1984 utm zone 35s datum: wgs 1984 $1 $1 $1 $1 $1 $1 uv02 mv01 mv02 lv01 lv02 uv01 http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 965 𝐶0 = 2.515517, 𝐶1 = 0.802853, 𝐶2 = 0.010328 𝑑1 = 1.432788, 𝑑2 = 0.189269, 𝑑3 = 0.001308 p is the probability of exceeding a determined d value, p = 1-f(x). if p > 0.5, then p is replaced by 1 p and the sign of the resultant spei is reversed. table 1 indicates the drought severity classification adopted for the study. table 1: drought severity classification for spei and spi (soydan oksal, 2023) class spei value spi value extremely wet > 2.0 > 2.0 severely wet 1.5 to 1.99 1.5 to 1.99 moderately wet 1.0 to 1.49 1.0 to 1.49 near normal -0.99 to 0.99 -0.99 to 0.99 moderately dry -1 to -1.49 -1 to -1.49 severely dry -1.5 to -1.99 -1.5 to -1.99 extremely dry < 2.0 < 2.0 the spei drought index has been globally recognised and used. it can be calculated at various timescales such as 1-, 3-, 6-, 12-, 24and 48-months to represent different drought conditions. according to mishra and singh (2010), a short timescale (1 or 3 months) is appropriate to estimate meteorological drought; a 3-month or 6months timescale is generally used for agricultural drought, whereas a larger timescale such as 12 or 24 months is more suitable for evaluating hydrological drought and water resources. this study will focus more on the results from the 12-, 24-month timescale to adequately understand drought frequency and magnitude in the vaal river basin. 3. results and discussion 3.1 seasonal variation of rainfall 3.1.1 dry season rainfall trends in the vaal river and its surrounding provinces. during the dry season, average rainfall in the vaal river basin and surrounding provinces was generally low, with notable variability and lowest rainfall recorded in 1983, 2003, and 2013, especially in mpumalanga. similarly rouault and richard (2003), indicated rainfall in the region of south africa is highly variable and unevenly distributed. rainfall along the river decreased from the upper to lower vaal, while the northern cape in the lower western basin often received the highest precipitation (figure 2). in 1983, rainfall along the vaal peaked at 64.8 mm in mpumalanga. additionally, mukhawana et al. (2023) found out that winter rainfall was approximately 30 and 70mm around the north-western cape and southwestern cape. rainfall along the vaal remained near 0–5.3 mm, while the northern cape recorded up to 106.7 mm. in 2023, the vaal experienced 1.75–40.7 mm of rain, and surrounding provinces ranged from 1 mm to 117.8 mm in the northern cape. 3.1.2 wet season rainfall trends in the vaal river and its surrounding provinces. figure 3 confirms that the wet season in the vaal river and surrounding provinces is relatively wetter than the dry season, consistent with expectations. this is consistent with mukhawana et al. (2023) whose study acknowledged summer maximum rainfall for the region. during this season, the results revealed that the year with the highest rainfall is 2023 peaking at 117.8mm. in 1983, average precipitation in the vaal was highest at about 47.46mm. in 1993, precipitation was more evenly distributed across the vaal river basin, encompassing mpumalanga, free state, and parts of the northern cape (figure 3). notably, some years exhibited higher rainfall north of the river, particularly in gauteng, mpumalanga, and parts of northwest, compared to the northern cape. conversely, 2013 was identified as the driest year, with rainfall concentrated in the northern middle vaal region, specifically northwest and mpumalanga. analysis of seasonal patterns revealed that during the dry season, rainfall was more prevalent in the northern cape, whereas during the wet season, it was predominantly observed in mpumalanga, free state, gauteng, and northwest provinces comparable with what rouault and richard, (2003) found out indicating maximum http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 966 rainfall around that kwazulu-natal area(close to free state and mpumalanga) with a maximum of 130mm in the wet season. figure 2: dry season rainfall trends of the vaal river basin and its surrounding provinces from 1983 – 2023. figure 3: wet season rainfall trends of the vaal river basin and its surrounding provinces from 1983 – 2023. 3.1.3 mean rainfall variation in the vaal river basin from 1983 to 2023. figure 5 illustrates the mean rainfall time series chart for the vaal river from 1983 to 2023, revealing fluctuating trends. notably, rainfall volumes were lowest during the dry season (june to august) and peaked during the wet season (january to march). over the four-decade study period, the highest average rainfall volume in the vaal river basin ranged between 50 mm and 60 mm. these were seen in 1988, 1991, 1996, 2011 and 2021. average rainfall recorded to have the least volume was observed in 1983, 1986, 1987, 1990, 1992, 2001 2004, 2007 2008, 2012 2013, 2015, and 2016 (figure 4). 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s dry season 1983 high : 64,8059 low : 0,152023 dry season 1993 high : 61,8342 low : 0,167492 dry season 2003 high : 106,7 low : 0,107635 dry season 2013 high : 106,7 low : 0,107635 dry season 2023 high : 117,802 low : 1,0338 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s 30°0'0"e 30°0'0"e 25°0'0"e 25°0'0"e 20°0'0"e 20°0'0"e 2 5 °0 '0 "s 3 0 °0 '0 "s 3 5 °0 '0 "s wet season 1983 high : 141,169 low : 0,230248 wet season 1993 high : 314,43 low : 0,0810177 wet season 2003 high : 225,24 low : 0,0543047 wet season 2013 high : 217,888 low : 0,0771846 wet season 2023 high : 647,638 low : 1,02357 http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 967 figure 4: monthly mean rainfall variation in the vaal river basin between 1983 – 2023. 3.2 comparing the mean rainfall and mean evapotranspiration in the vaal river basin figure 5 illustrates the variability in annual average precipitation and evapotranspiration over several years. notably, the annual average evapotranspiration consistently exceeds the annual average precipitation, indicating a surplus of evapotranspiration over rainfall in the vaal river basin. this trend suggests that evapotranspiration surpasses rainfall in the study area, highlighting the importance of understanding this dynamic for water resource management. 1983-1993 monthly mean rainfall 2003-2013 monthly mean rainfall 1993-2003 monthly mean rainfall 2013-2023 monthly mean rainfall http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 968 the trend analysis revealed varying degrees of downward trends in rainfall across the vaal river regions: weak in the lower vaal, strong in the middle vaal, and moderate in the upper vaal. although the p-values exceeded the 0.05 significance threshold, indicating a lack of statistical significance, the results suggest a downward trend in rainfall per year. table 1: the mann-kendal sens rainfall slope table of the lower, middle and upper vaal. location z-value shift p-value sig. level sens slope result trend lower vaal -0.68528 downward 0.4932 p>0.05 -0.88 negative decreasing middle vaal -4.218000 downward 0.9284 p>0.05 -0.130626 negative decreasing upper vaal -1.6517 downward 0.0986 p>0.05 -3.388852 negative decreasing figure 5: long-term mean rainfall and mean evapotranspiration in the vaal river basin. 3.3 drought trends drought severity and duration across the vaal river basin were analysed using the standardized precipitation evapotranspiration index (spei) and the standardized precipitation index (spi) at multiple timescales (1-, 3-, 6-, 12-, 24-, and 48-month intervals). the results revealed distinct spatial and temporal variability in drought intensity and persistence across the lower, middle, and upper vaal regions between 1983 and 2023. annual average precipitation from 1983 2002 annual average evapotranspiration from 2003 2023 annual average precipitation from 2003 2023 http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 969 3.3.1 spei-based drought trends the spei results showed that short-term indices (spei-1 and spei-3) captured frequent drought events, notably in 1983, 1999, 2001–2006, and 2016, with variation among stations. rouault and richard, (2003) in their study revealed extreme dryness in the summer rainy season in dec 1982 to march 1983. intermediate and longer timescales (spei-6, spei-12, and spei-24) confirmed 2016–2019 as the most severe and prolonged drought period, particularly in the lower vaal where spei-24 reached −3.20 in 2016. these longer timescales provided a more accurate depiction of hydrological drought, reflecting cumulative water deficits rather than short-term meteorological fluctuations. similar findings were reported by mathbout et al. (2018) and tirivarombo et al. (2018), who noted that drought severity and duration increase with longer timescales in arid and semi-arid regions. 3.3.2 spi-based drought trends the spi results corroborated the spei analysis, identifying severe droughts in 1992, 2007, 2014–2016, and 2018. spi-12 and spi-24 showed the strongest drought intensities in 2015–2016 (up to −3.03), aligning with south africa’s worst drought in over two decades (bhaga et al., 2020). drought frequency and intensity increased markedly after 2013, particularly between 2013 and 2018, a trend consistent with growing climatic instability. both indices demonstrated that the 12and 24-month timescales were the most reliable for detecting hydrological droughts, while shorter scales (1–3 months) reflected transient meteorological droughts. these observations align with pei et al. (2020), who emphasized the suitability of intermediate timescales for drought monitoring in semi-arid basins. 3.4 temporal and spatial patterns across the basin, drought events were more frequent and severe in the middle and upper vaal regions compared to the lower vaal. the consistent identification of 2016 as a hydrologically dry year by both indices underscores the influence of climatic variability on regional water resources. eris et al. (2020) and kumar and gautam (2021) observed that multi-scalar drought indices, when applied together, enhance temporal drought characterization accuracy. 3.5 climate change and implications the recurrence of extreme droughts—especially between 2015 and 2019—highlights the growing influence of climate change on the vaal river system. these findings are consistent with projections by serdeczny et al. (2017), who predicted declining rainfall and increased drought frequency in southern africa under warming conditions. drought impacts extend beyond hydrology; they threaten agricultural productivity, water security, and livelihoods in one of south africa’s most economically vital regions. the vaalharts irrigation scheme, the country’s largest, is particularly vulnerable to such droughts (department of water affairs and sanitation, 2015). reduced precipitation and rising evapotranspiration rates directly affect irrigation supply and crop yields, echoing the findings of waseem et al. (2022), who linked precipitation deficits to yield declines. 3.6 synthesis and implications for water resource management overall, the spi and spei indices demonstrated strong agreement in identifying the major drought periods of 1983, 1999, 2016, and 2019, just as found in the studies of bhaga et al. (2020); mishra and singh (2010), with 2016 emerging as the most severe hydrological drought. this is similar with the findings of department of agriculture forestry and fisheries south africa (2010) indicating that the 2015-2016 was the worst drought resulting in decline in livestock and water constraints in cities. the results highlight a clear intensification of drought frequency and duration over recent decades, influenced by rising temperatures and changing rainfall patterns. these trends align with the work of engelbrecht and engelbrecht (2016) and jury (2016), who documented climate-driven hydrological changes in the vaal catchment affecting agricultural and industrial water use. the findings emphasize the need for adaptive water management strategies, including enhanced drought monitoring, improved reservoir operation, and sustainable irrigation practices. integrating multi-scalar drought indices like spei and spi provides a robust framework for understanding drought evolution, supporting early warning systems and resilience planning in the vaal river basin. http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 970 figure 6. dispersion of spei-1 and spi-1 values in the lower vaal, middle vaal, and upper vaal meteorological stations 1983 2023. -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 1 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 1 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 1monthupper vaal station -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi1 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 1 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 1 monthupper vaal station http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 971 figure 7. dispersion of spei-3 and spi-3 values in the lower vaal, middle vaal, and upper vaal meteorological stations 1983 2023. -4 -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 3 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 3 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 3 monthupper vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 3 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 3 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 3 monthupper vaal station http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 972 figure 8. dispersion of spei-6 and spi-6 values in the lower vaal, middle vaal, and upper vaal meteorological stations 1983 2023. -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 6 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 6 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 6 monthupper vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 6 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time(years) spi 6 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 6 month upper vaal station http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 973 figure 9. dispersion of spei-12 and spi-12 values in the lower vaal, middle vaal, and upper vaal meteorological stations 1983 2023. -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 12 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 12 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 12 monthupper vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 12 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u es time(years) spi 12 month middle vaal station -4 -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time(years) spi 12 monthupper vaal station http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 974 figure 10. dispersion of spei-24 and spi-24 values in the lower vaal, middle vaal, and upper vaal meteorological stations 1983 2023. -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 24 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 24 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 24 monthupper vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 24 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time(years) spi 24 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time(years) spi 24 month upper vaal station http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 975 figure 11. dispersion of spei-48 and spi-48 values in the lower vaal, middle vaal, and upper vaal meteorological stations 1983 2023. -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 48 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 48 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp ei v al u es time (years) spei 48 monthupper vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 48 monthlower vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time (years) spi 48 monthmiddle vaal station -3 -2 -1 0 1 2 3 1983 1988 1993 1998 2003 2008 2013 2018 2023 sp i v al u e time(years) spi 48 monthupper vaal station http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 962-977. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: rachealbodunrin@yahoo.com 976 4. conclusion this study conducted a comprehensive analysis of drought patterns in the vaal river, south africa, utilizing the standardized precipitation evapotranspiration index (spei) and the standardized precipitation index (spi). we examined precipitation patterns and evapotranspiration dynamics in the basin to assess their correlation with spei and spi findings. by applying spei and spi drought indices at monthly scales ranging from 1 to 48 months between 1983 and 2023, we explored the spatiotemporal variability of rainfall and drought, revealing significant patterns. our analysis identified drought periods, with short-scale indices (3 and 6 months) indicating meteorological drought and longer timescales associated with hydrological drought, the latter being the primary focus of our study. the results showed severe and prolonged extreme drought in the vaal river basin, particularly prevalent from 2016 to 2018. the years most affected by hydrological drought from 1983 to 2023 in the lower vaal, middle vaal, and upper vaal river basins, as indicated by spei/spi-12 and spei/spi-24, were 1983-1985, 1992, 1995, 2003, 2004, 2007, and 2012-2016. the study's findings are significant, integrating temperature and potential evapotranspiration (pet) values into drought index calculations. however, a notable limitation was the use of only the hargreaves method for pet calculation. the observed disparity between lower rainfall and higher evapotranspiration in the vaal river basin suggests potential impacts on various sectors, including agriculture, mining, industry, municipal water users, and economic development. this underscores the importance of considering short-term timescales (3 and 6 months) in drought mitigation strategies, as suggested by previous studies. references bahta, yt. and myeki, va., 2022. the impact of agricultural drought on smallholder livestock farmers: empirical evidence insights from northern cape, south africa. agriculture bhaga, td., dube, t., shekede, md. and shoko, c., 2020. impacts of climate variability and drought on surface water resources in sub-saharan africa using remote sensing: a review. remote sensing, 12(24):1–34 cacciamani, c., morgillo, a., marchesi, s. and pavan, v., 2007. monitoring and forecasting drought on a regional scale: emilia-romagna region bt methods and tools for drought analysis and management, in: rossi, g., vega, t., bonaccorso, b. 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spatiotemporal analysis of drought and agriculture standardized residual yield series nexuses across punjab, pakistan. water (switzerland) 14(3) zhong, s., sun, z. and di, l., 2021. characteristics of vegetation response to drought in the conus based on long-term remote sensing and meteorological data. ecological indicators, 127: 107767 http://www.azojete.com.ng/ mailto:rachealbodunrin@yahoo.com arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):691-698 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 691 measurement of background ionizing radiation level and dose risk around nigeria’s first oil well, otuabagi, oloibiri clan, bayelsa state, south-south, nigeria p. e. biere1*, k. emumejaye2, g. e. ogobiri1, r. o. k. meindinyo1, j. james1, and e. abule1 1department of physics, niger delta university, wilberforce island, bayelsa state, nigeria 2department of physics, delta state university of science and technology, ozoro, nigeria *corresponding author's email address: pbiere2003@gmail.com article information submitted 21 june, 2024 revised 18 july, 2024 accepted 20 july, 2024 keywords: radiation well head crude dose rates abstract individuals who get exposed to radiation stand the danger of experiencing health problems such as skin burn, acute radiation syndrome, cardiac condition. natural radiation chains exist in nature including oil and gas fields in the ground. therefore, crude may contain natural radioactivity. in this study, the background ionizing radiation level around the immediate vicinity of nigeria’s first oil well has been measured using the radalert-100x, a potable radiation detector. the background exposure rate ranges from 0.0095 to 0.0155 mrh-1 with a mean of 0.0128 mrh-1. the absorbed dose rate calculated ranges from 82.65 to 156.6 ngyh-1 with a mean of 109.56 ngyh-1. the averages of the annual effective dose equivalent ranges from 0.101 to 0.192 msvy-1 with a mean of 0.136 msvy-1. the calculated averages of elcr from the study area ranges from 0.359 x 10-3 to 0.670 x 10-3 with a mean of 0.476 x 103. from the evaluation made, the granite area around the well head, has the highest background ionizing radiation value and other parameters compared to results from the well head and the muddy area. given the values recorded in the study, it is imperative to advise that appropriate precautions be taken, such as adhering to the alara principle, to shield the public from radiation related risks. 1.0 introduction the level of ionizing radiation in the environment at a specific location that has not been caused by any kind of intentional introduction of radiation sources is known as background radiation. (ugwuanyi et al., 2021). many sources, whether natural, man-made, or both, contribute to background radiation. normally, this is the scenario when monitoring the ambient dosage for environmental reasons. ionizing radiation, when present in an environment, has sufficient energy to affect the atom in a living cell and thereby damage the genetic materials (dna). fortunately, our body cells are remarkably efficient at fixing the harm (adrian and andres, 2020). however, if the damage is not properly repaired, a cell might die or finally become cancerous (adrian and andres, 2020; zhivotovsky and orrenius, 2010). human population exposed to radiation is at risk of having health effects like skin burn, acute radiation syndrome and cardiovascular diseases. studies have shown that exposure to low level radiation in the http://www.azojete.com.ng/ mailto:%20hauwamari@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)691-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 692 environment does not cause immediate health effect but it is a contributor to overall cancer risk (yasser et al., 2020). sedimentary formations, which are good hosts to rocks for uranium deposits, are also generally good reservoir rocks for petroleum crude oil (soumyajit et al., 2023). crude itself may contain some level of natural radioactivity, as natural radiation chains, such as those found in underground oil and gas deposits, are present in nature (ajayi et al., 2009). atoms in such chains are not stable, radioactive decay process may occur, which leads to release of radiation in the environment and so can enhance the background radiation level of the environment. mostly, the oil and gas sector use unsealed radioactive solids (powder and granular forms), liquids and gases to look into or track the flow of items (iaea, 2003). it is at the wellhead that these radiotracers are most often used to assess flow rate for a variety of reasons (iaea, 2012). also, in most instances, spillages which could be accidental or otherwise, may occur around oil and gas facilities thus bringing these chains to the surface, thereby increasing the possibility of heightened background radiation levels in the immediate environment. nigeria’s first oil head, now a national historic site, as a tourist attraction has many people who visit the site for many purposes. there is therefore the need to investigate radiation profile of the immediate environment. a study such as this one to quantify background ionizing radiation level around the immediate vicinity of the well head will not only provide base line data on exposure rate but will also provide data on radiological health effects on population within the site. the area of study is the immediate surroundings of nigeria’s first oil well. nigeria’s first oil well head is situated in otuabagi in oloibiri clan, ogbia local government area of bayelsa state. the state is host to one of the country's biggest reserves of oil and gas. the state’s population, according to 2022 census is two million, five hundred and thirty seen thousand, four hundred (2,537, 400). the oloibiri terrain is made up of freshwater wetlands and streams formed by the distributaries of creeks. the region is part of the coastal belt, which is made up primarily of low-lying coastal plains that are structurally related to the niger delta's sedimentary layers (oborie and oki, 2017). its geology is made up of fluvial sediments. the region is typified by lowlands and gentle undulating coastal plains, as well as sandbars, taidal basins, mud flats, and swamps (ononugbo et al., 2015). the area considered for this survey is about 0 – 50 m from the oil well head. the oil well itself though no longer in production, is now a tourist attraction site with some level of construction here and there round the well head. therefore, for this study, its immediate vicinity was categorized into the well head, muddy, sandy, granites chippings and concrete areas. figure 1 shows a picture of nigeria’s first oil well head in oloibiri, bayelsa state. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com biere et al measurement of background ionizing radiation level and dose risk around nigeria’s first oil well, otuabagi, oloibiri clan, bayelsa state, south-south, nigeria. azojete, 20(3):691-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 693 figure 1: nigeria’s first oil well head 2. materials and method radiation alert inspector (radalert-100x), a potable radiation detector was used for measuring background ionizing radiation. radalert has an inbuilt geiger-muller tube capable of producing a pulse current when radiation goes through it (ovuomarie-kelvin et al., 2018). the pulse produced is automatically sensed then recorded as count. the radiation alert inspector was standardized by the use of 137cs specific energy source and made to quantity the exposure in milli-roentgen per hour (mrhr-1) and with a precision of ±15% (biere et al., 2023). to carry out background ionizing radiation measurement, the area around the oil well head was divided into well head, muddy, sandy, granites chippings and concrete areas. each segment is about three to four meters wide. readings were taken linearly starting from the well head to an adjacent road off ogbia-nembe road. average values of readings in each segment were taken and recorded in table. at each measurement point, the radiation meter was positioned 1 m from ground level and its window faced the expected source. the detector was switched on for about 120 s to absorb radiation. the process was repeated in all points of measurement and obtained readings were recorded in mrhr-1. 2.1 determination of radiological hazards the background ionizing radiation (bir) values measured were used to calculate other radiological parameters associated with it. 2.1.1 absorbed dose rate in air (adr) absorbed dose rate which is applied to evaluate probable biological variations in specific tissues was estimated by means of equation 1 as given by rafique et al 2014 1 𝜇𝑅ℎ−1 = 8.7 n𝐺𝑦ℎ−1 = 8.7 × 10−3 (1/8760𝑦) 𝑛𝐺𝑦𝑦−1 (1) this can be written as 1 𝑚𝑅ℎ−1 = 8.7 n𝐺𝑦ℎ−1 × 103 = 8700 𝑛𝐺𝑦ℎ−1 (2) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)691-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 694 2.1.2 annual effective dose equivalent (aede) annual effective dose equivalent. this parameter is employed to calculate the likelihood of long-term health consequence which may happen in the future. aede was calculated by the use of equation 3 (unscear, 2008). 𝐴𝐸𝐷𝐸 (𝑚𝑆𝑣𝑦−1) = 𝐷(𝑛𝐺𝑦𝑦−1) × 8760 ℎ × 𝐶𝐹 × 𝑂𝐹 × 10−3 (3) where d is absorbed dose rate in 𝑛𝐺𝑦𝑦−1, 8760 h is entire hours in one year, cf is dose conversion factor from absorbed dose to effective dose in sv/gy. cf = 0.7 sv/gy. of is occupancy factor, probable time that people would spend outdoor in the study area, of = 0.2 as suggested by unscear, 2008 2.1.3 excess lifetime cancer risk (elcr) elcr is a quantity that is used to determine the likelihood of development of cancer owing to contact with ionizing radiation. eclr is given by equation 4 𝐸𝐶𝐿𝑅 = 𝐴𝐸𝐷𝐸 (𝑚𝑆𝑣𝑦−1) × 𝐷𝐿 × 𝑅𝐹 (4) where dl = 70 years (average duration of life) and rf is cancer risk factor expressed in sv-1. in the scenario of low dose background radiation, anticipated to result in stochastic effects, icrp 103 stipulates a threshold of 0.05 sv-1 for the public (icrp, 2007). 3. results and discussion table 1 presents averages of measured background radiation and calculated radiological parameters associated with the exposure rates within the sections of the ambience of the abandoned oil well. to gain further insight of the variation of the various radiological parameters in the different segments around the well head, the average values obtained in this study have been plotted against their respective world average values. figures 2 to 5 show the comparison of background radiation, absorbed dose rate, annual effective dose equivalent and excess life time cancer risk with world average. table 1: measured and estimated radiological parameters data collection points bir (mrh-1) adr (ngyh-1) aede (msvy-1) elcr (x 10-3) well-head area average 0.0095 82.65 0.101 0.353 mudy area average 0.010 87.0 0.107 0.372 sandy area average 0.011 95.7 0.117 0.409 granites area average 0.018 156.6 0.192 0.670 concrete area average 0.0155 134.85 0.165 0.577 mean 0.0128 109.56 0.136 0.476 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com biere et al measurement of background ionizing radiation level and dose risk around nigeria’s first oil well, otuabagi, oloibiri clan, bayelsa state, south-south, nigeria. azojete, 20(3):691-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 695 figure 2: comparison of background radiation mean with world average figure 3: comparison of absorbed dose rate mean with world average figure 4: comparison of annual effective dose equivalent mean with world average figure 5: comparison of excess lifetime cancer risk mean with world average 0 0.005 0.01 0.015 0.02 1 2 3 4 5 bir (mrh-1) world average 0 50 100 150 200 1 2 3 4 5 adr (ngyh-1) world average 0 0.2 0.4 0.6 0.8 1 1 2 3 4 5 aede (msvy-1) world average 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 1 2 3 4 5 elcr (x 10-3) world average (x 10-3) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)691-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 696 discussion table 1 presents the averages of in-situ measurements of background ionizing radiation in different segments in the immediate vicinity of nigeria’s first oil well. the background exposure rate ranges from 0.0095 to 0,0155 mrh-1 with a mean of 0.0128 mrh-1. it is observed that some segments have exposure rate higher than the world permissible limit of 0.013 mrh-1 (khamis et al., 2022), this could be attributed to the introduction of some geological materials and manmade activities which could have contribute to the overall radiation level. the mean background exposure rate recorded here falls between the range of the values published by ovuomarie-kelvin et al., 2018. however, they are less than the figures avwiri et al., 2014 reported. absorbed dose rate calculated ranges from 82.65 to 156.6 ngyh-1 with a mean of 109.56 ngyh-1. mean of the study area is above both the world average of 59.0 ngyh-1 (taskin et al., 2009) and 84.0 ngyh-1 tolerable threshold (ayua et al., 2017). the high values reported here indicates that there is possibility of radiological contamination of the environment. which indicates that radiation related health risk could occur in the future if precautions are not taken. the mean absorbed dose rate is above 95.7 ngyh-1 reported by ovuomarie-kelvin et al., 2018, but lower than 203.41 ngyh-1 reported by anekwe and onoja, 2020 for similar environments. annual effective dose equivalent ranges from 0.101 to 0.192 msvy-1 having a mean of 0.136 msvy-1 which is above the world average 0.07 msvy-1 (agbalagba et al., 2016; icrp 2013) but lower than the 1.0 msvy-1 recommended threshold for general public (taskin et al., 2009; unscear 2008). the average annual effective dose is comparable to those recorded by ovuomarie-kelvin et al., 2018. the calculated averages of elcr from the study area ranges from 0.359 x 10-3 to 0.670 x 10-3 with a mean of 0.476 x 10-3. this mean exceeds the global average of 0.29 x 10-3 (unscear 2000). the mean elcr from the study area is quite high. this indicates the possibility of developing cancer in the future. the mean value reported here is slightly above reported in ovuomarie-kelvin et al., 2018. figures 2 to 5 show pictorial representation of the obtained results as compared with their respective averages. in figure 2, the average background ionizing radiation from the well head, muddy and sandy areas are seen to be below the world average while that of the granite and concrete areas are above the world average. in figure 3, only the average absorbed dose rate from the well head area is slightly below the world average and others are higher. figure 4 show all averages of annual effective dose equivalent to be far below world average and figure 5 shows all averages of excess lifetime cancer risk to be above world average. conclusion this study is intended to reveal the level of radiological parameters around the closest proximity of nigeria’s first oil well head which is no longer in use but is now a tourist destination and a historic land mark. the background ionizing radiation has a mean value which is approximately equal to the world average. mean absorbed dose rate is above the world suggested tolerance level. mean of annual effective dose equivalent is below the world permissible limit. mean excess lifetime cancer risk exceeds the global average by a considerable margin. from the evaluation made, the granite area has the highest background ionizing radiation value and other parameters compared to that from the well head and the muddy area. these values were clearly seen to be influenced by the presence of granites spread in that segment around the well head. nevertheless, as a result of the high values recorded in study, it is necessary to recommend that adequate measures like the alara (as low as reasonably file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com biere et al measurement of background ionizing radiation level and dose risk around nigeria’s first oil well, otuabagi, oloibiri clan, bayelsa state, south-south, nigeria. azojete, 20(3):691-698. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 697 achievable) principle should be taken to protect the general public from any radiation induced hazards. references adrian, c. and andres, c-b. 2020. cell cycle and dna repair regulation in the damage response: protein phosphates take over the reins. international journal of molecular science, 21(2): 446. doi 10.3390/ijms212020446 agbalagba, eo., avwiri, go. and ononugbo, cp. 2016. gis mapping of impact of industrial activities on the terrestrial background ionizing radiation levels of ughelli metropolis and its environs, nigeria. environmental earth science, 75: 1425 ajayi, tr., torto, n., tchokossa, p. and akinlua, a. 2009. natural radioactivity and trace metals in crude oils: implication for health. environmental geochemistry and health, 31: 61-69. doi. 10.1007/s10653-008-9155-z anekwe, ul. and onoja, ra. 2020. assessment of environmental radioactivity level and its health implication in imiringi community bayelsa state. nigerian journal of applied sciences and environmental management, 24(6): 1045-1050. avwiri, og., nte, uf. and esi, eo. 2014. assessment of background ionization radiation of oil spillage site at obodo creek in gokana l.g.a of river state, nigeria. british journal of applied science & technology, 4(36): 5072-5079. ayua, j., tyovenda, aa. and igyuse, is. 2017. determination of ionizing radiation exposure levels within four local mining sites selected from sardauna local government area of taraba state, nigeria. international journal of physics, 5(5): 157-161. bernard, lc. 2002. cancer risk from low-level radiation. american journal of roentgenology. 179(5): 1137-1143. https//doi.org/10.2214/ajr.179.5.1791137 biere, pe., ajetunmobi, ae., david, tw. and talabi, at. 2023. assessment of radiological parameters in selected communities close to a major oil and gas facility in bayelsa state south -south nigeria. nigerian journal of physics, 32(4): 66 – 72. https://doi.org/10.62292/njp.v32i4.2023.150 iaea. 2003. radiation protection and the management of radioactive waste in the oil and gas industry. international atomic energy agency vienna, 2003. safety reports series no. 34. iaea. 2012. application of radiotracer techniques for interwell studies. international atomic energy agency vienna, 2012. iaea radiation technology series no. 3. icrp. 2007. recommendations of the international commission on radiological protection. publication 103. icrp. 2013. publication 121: radiological protection in pediatric diagnostic and interventional radiology, international commission on radiological protection. annals of the icrp, 42 (2): 1 – 63. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 https://doi.org/10.62292/njp.v32i4.2023.150 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)691-698. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: pbiere2003@gmail.com 698 khamis, fm., mundi, aa., idris, mm., mohammed, aa., abdullahi, mh., sulieman, a., iwa, sj. and mohammad, ia. 2022. indoor and outdoor background exposure level assessment of some locations in national youth service corps orientation camp, keffi, nasarawa state, nigeria. journal of radiography and radiation sciences, 37(2):16-23. oborie, e. and oki, oa. 2017. geo-electric evaluation of aquifer protective capacity and groundwater flow pattern in ogbia local government of bayelsa state, nigeria. journal of multidisciplinary engineering science and technology, 4(5): 7203-7207. ononugbo, cp., avwiri, go. and tutumeni, g. 2015. estimation of indoor and outdoor effective doses from gamma dose rates of residential buildings in emelogu village in rivers state, nigeria. international research journal of pure and applied physics, 3(2): 18-27. ovuomarie-kevin, si., ononugbo, cp. and avwiri, go. 2018. assessment of radiological health risks from gamma radiation levels in selected oil spill communities of bayelsa state, nigeria. current journal of applied science and technology, 28(3): 1-12. rafique, m., saeed, ur.., mohammed, b., wajid, a., iftikhar, a., kharsheed, al. and khalil, am. 2014. evaluation of excess lifetime cancer risk from gamma dose rates in jhelum valley. journal of radiation research and applied sciences, 7(1): 29-35. soumyajit, m., sukanta, g. and syed, z. 2023. geological relationship between hydrocarbon and uranium: review on two different sources of energy and the indian scenario. journal of petroleum science and engineering, 221: 1-13. taskin, h., karavus, m., topuzoglu, pa., hindiroglu, s. and karahan, g. 2009. radionuclide concentrations in soil and life time cancer risk due to gamma radioactivity in kirklareli, turkey. journal of environmental radioactivity, 100:49-53. ugwuanyi, dc., nzotta, on., ogolodom, mp., sibeudu, tf., ibekwe, am. and ezeaku, no. 2021. background radiation levels in selected dumpsites in nnewi communities setting southeast nigeria. international journal of radiation research, 19(3): 743-747. doi: 10.29252/ijrr.19.2.743 unscear. 2000. sources of ionizing radiation. united nations scientific committee on effects of atomic radiation, (unscear). 2000 report, united nations, new york. unscear. 2008. sources and effects of ionizing radiation. united nations scientific committee on the effects of atomic radiation report to the general assembly with scientific annexes. vol. 1. new york. yasser, fa., francis, ac., liu, n-a. and guangming, z. 2020. cancer risk of low level dose ionizing radiation. frontiers in physics, 8: 234. doi: 10.3389/fphy.2020.00234 zhivotovsky, b. and orrenius, s. 2010. cell cycle and cell death in disease: past present and future. journal of internal medicine, 268(5): 395 – 409. https://doi.org/10.1111/j.13652796.2010.02282.x file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(4):699-712 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 699 analysis of normal radar signal based on different timefrequency distribution configurations a. a. ahmad1*, m. m. aji1, m. abdulkadir2, f. o. adunola1 and s. lawan1 1department of electrical and electronic engineering, nigerian defence academy, kaduna 2department of electrical and electronic engineering, university of maiduguri, maiduguri, borno state *corresponding author's email address: aaashraf@nda.edu.ng article information submitted 11 july, 2023 revised 27 june, 2024 accepted 10 july, 2024 keywords: radar signal time-frequency distribution electronic intelligence (elint) waterfall plot hilbert transform frequency agility electronic warfare support (es) abstract the electromagnetic environment is becoming more complex, and radar technology is always evolving, as such, a sizable number of contemporary radars with agile waveforms have appeared on the battlefield. relying solely on traditional recognition models to identify radar signals in electronic warfare systems is a significant challenge. in response to the this problem, this paper proposed an analysis of normal radar signal based on different time-frequency distribution (tfds) configurations which include wigner-ville distribution (wvd), windowed wille-ville distribution (wwvd), filtered wigner-ville distribution (fwvd), choi williams distribution (cwd), and hybrid distributions that combined fwvd and cwd.a two-stage process in other to achieve the aim of this research is presented. the first stage is the modelling and generating a normal (simple) radar signal of pulseto-pulse constant frequency, while the second stage involved designed of these tfds and using them to analyse the radar signals. the result showed that most of the tfds captured the time and frequency parameters of the radar signals modelled around of pulse width (pw) of 1µs, pulse repetition interval (pri) of 2 µs, center and sampling frequencies of 10 mhz and 40 mhz respectively. therefore, these tfds can further be analysed using signal processing and classification tools such as instantaneous power, instantaneous frequency, and machine learning for automatic waveform recognition. 1.0 introduction radar, which stands for radio detection and ranging, is a technology that uses radio waves to detect and track objects in various applications (patole et al., 2017). the versatility and reliability of radar make it an essential tool in numerous fields. to explore some of these normal application areas of radar includes crucial role in aviation for air traffic control, collision avoidance, and weather monitoring, in military and defense applications. it is also utilized for air defense, surveillance, target tracking, and missile guidance. in maritime navigation, radar systems are used for collision avoidance, safe passage planning, and vessel traffic management. additionally, radar is employed to monitor and track precipitation, storms, and severe weather phenomena. fourier analysis techniques, including the fast fourier transform (fft), are applied in digital intercept receivers to detect and analyze parameters of low probability of intercept (lpi) radar signals (pace, 2009). http://www.azojete.com.ng/ mailto:%20hauwamari@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 700 when a practical non-stationary signal (such as a noised normal radar signal) is processed, the fourier transform cannot efficiently analyze and process the time-varying characteristics of the signal’s frequency spectrum, because time and frequency information cannot be combined to tell how the frequency content is changing in time (stephens, 1996; xie et al., 2008). the nonstationary nature of the received radar signal mandates the use of some form of time-frequency analysis for signal detection and parameter extraction (ünal and pakfiliz, 2022). some of the more common classical time-frequency analysis techniques include the wvd, cwd, spectrogram, and scalogram. the wvd exhibits the highest signal energy concentration (wiley, 2006). but has the worse cross-term interference, which can severely limit the readability of a time-frequency representation (stephens, 1996; gulum, 2007; boashash, 2015). the cwd is a member of cohen’s class, which adds a smoothing kernel to help reduce cross-term interference (upperman, 2008; boashash, 2015). the cwd, as with all members of cohen’s class, is faced with a trade-off between cross-term reduction and time-frequency localization. radar waveforms are susceptible to various forms of noise and interference, including thermal noise, clutter, and jamming signals (wei et al., 2014). the presence of unwanted components such as noise and interference in radar signals can significantly deteriorate the quality of timefrequency representation, leading to inaccurate radar parameter estimation. therefore, it is crucial to develop robust time-frequency analysis techniques that effectively mitigate the effects of these unwanted components. additionally, radar waveforms often exhibit nonstationary and transient behavior due to various factors such as target dynamics, modulation schemes, or environmental conditions. time-frequency distributions (tfds) employed for radar waveform analysis should be capable of capturing the non-stationary nature of signals and accurately representing transient features. techniques that adapt to signal variations over time or provide localized time-frequency analysis are necessary to address these nonstationary aspects. furthermore, in real-time radar applications, efficient algorithms and techniques for timefrequency analysis are required. the computational complexity of time-frequency distributions should be manageable to facilitate their implementation in resource-constrained radar systems. hence, it is essential to develop computationally efficient methods that strike a balance between accuracy and computational requirements, as this is crucial for practical radar waveform analysis. addressing these challenges through the utilization of tfds contributes to the advancement of radar system capabilities, ultimately enhancing target detection, classification, and tracking performance. the research presented in this paper focuses on the careful design and adoption of commonly used tfds to effectively tackle these challenges (boashash, 2015; ahmad et al., 2019). radar waveforms face various noise and interference issues, such as thermal noise, clutter, and jamming signals (wei et al., 2014). these unwanted components can degrade time-frequency representations and lead to inaccurate parameter estimation. thus, developing robust timefrequency analysis techniques to mitigate these effects is essential. radar waveforms also often display nonstationary and transient behaviors due to factors like target dynamics or environmental conditions. effective time-frequency distributions (tfds) should capture these nonstationary aspects and accurately represent transient features. efficient algorithms for realtime applications are also necessary to manage the computational complexity of tfds. balancing accuracy with computational efficiency is crucial for practical radar analysis. this paper explores the design and application of tfds to address these challenges and improve radar system performance (boashash, 2015; ahmad et al., 2019). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com ahmad et al: analysis of normal radar signal based on different time-frequency distribution configurations. azojete, 20(4):699-712. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 701 according to kong et al. (2018), a method of recognizing low probability of intercept (lpi) waveforms that included polytime coded radar signals and robust performance comparison analysis was proposed. the method was based on cwd as the main tfd and cnn as the classifier. in addition to cwd and cnn, a sample averaging technique was also proposed to reduce the large computational cost required by intercept receivers in some situations. it was testified that the proposed technique offered significant improvement such as robustness to noise and recognition accuracy of 85% at snr of -6 db for all 12 signals. however, a large number of signal samples in thousands is required for good recognition accuracy as 22,680 and 9720 signals are required for training and validation respectively. from qu et al. (2018), the modulation of radar signals using the techniques of time-frequency analysis, image processing, and convolutional neural network (cnn) was identified. through cohen class time-frequency distribution (ctfd), the time-frequency images (tfis) of received signals are extracted. to obtain the high-quality tfis of received signals, a new kernel function for the ctfd was introduced, which has a stronger anti-noise ability than choi–williams timefrequency distribution. a series of image processing techniques, including 2-d wiener filtering, bilinear interpolation, and the otsu method, is applied to remove the background noise of the tfi and obtain a fixed-size binary image that contains only the morphological features of the tfi. we design a cnn classifier to identify the processed tfis. the approach identifies up to 12 kinds of modulation signals, including frequency modulation, phase modulation, and composite modulation. simulation results show that, for 12 kinds of modulation signals, an overall probability of successful recognition of 96.1% when snr is −6 db was achieved. however, the modulation recognition of the intra-pulse multi-component radar signal has become a problem to be solved. according to qu et al. (2019) a radar signal intra-pulse modulation recognition method based on convolutional denoising autoencoder (cdae) and deep convolutional neural network (dcnn) was proposed. cohen’s tfd was used to convert radar signals into time-frequency images (tfis). cdae was designed to denoise and repair tfis and a deep convolutional neural network based on inception architecture was designed to identify the processed tfis. the approach has good noise immunity and generalization. it can classify twelve kinds of modulation signals, and an overall probability of successful recognition is more than 95% when the snr is -9 db. a versatile method for different types of radar signals. however, the method developed has a very complicated classification structure and hence computationally complex. a simple and effective fb algorithm based on manhattan distance-based features (mdbfs) were proposed (huang et al., 2019). mdbfs are new features for radar signals that can be applied for the recognition of different modulations. the main contributions are first, radar signals are represented as wavelet ridges, which include important information that can distinguish different modulations, and the piecewise aggregate approximation algorithm is introduced to reduce signal dimensions. then, the dynamic time warping averaging is employed instead of the traditional k-means algorithm to extract realistic centroids for each class. finally, the manhattan distances between each data sample and each centroid are used to construct mdbfs, and decisions are made using the k-nearest neighbor. it was proved that mdbfs have better class separability power than euclidean-based features. mdbfs contain information about the correlations between different classes, which means that these features are suitable for http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 702 discriminating various modulations when their class distributions do not overlap badly in representation space. according to the parameter information, each modulation simulates twenty samples at snr values of 10 to 15 db to train the classifier. each modulation generates one hundred samples at snr values of [0, 3, 6, 9, 12] db. thus, a total of 900 samples are generated at each snr to test performance. however, the proposed method is realized based on some known patterns, and future work will focus on applying the technique to an unknown modulated signal. a rapid accurate recognition system, especially for when multiple signals arrive at the receiver was presented (gao et al., 2019). the system can recognize eight types of radar signals while separating signals: binary phase shift keying (bpsk), linear frequency modulation (lfm), costas, frank code, and p1–p4 codes. regression variational mode decomposition (rvmd) is explored to separate the received signals, which saves time for parameter optimization of variational mode decomposition (vmd). the simulation results show that the recognition system achieves an overall recognition rate of 99.5% and 94% at a signal-to-noise ratio (snr) of 0 db when receiving single signals and double signals while spending 0.8 s and 2.23 s, respectively. furthermore, the proposed system can also be used to recognize mechanical and medical signals. however, further related research will be required to examine the ideal technology required for an unknown number of radar signal recognitions in a more realistic environment. the usefulness of an algorithm in the scenario of lpi radar signal detection and recognition based on visibility graphs (vg) was explored (tao et al., 2020). more network and feature information can be extracted in the vg two-dimensional space, this algorithm can solve the problem of signal recognition using the autocorrelation function. signal detection simulation analysis shows that when the snr is −10 db, the sdp is 90.9%, and as the snr increases, the sdp also increases, especially when snr is greater than −8 db, the sdp is 100%. however, future research was expected to extend the vg theory to radar signal sorting and working pattern recognition applications. a novel intra-pulse modulation recognition method based on the high-order spectrums of radar signals was developed (chen et al., 2021). automatic soft thresholding is implemented in the deep residual network to adaptively eliminate redundant information in the process of feature learning and improve the learning effect of valuable features in distribution images of corresponding third-order spectrums. the extensive simulations compared with the other four methods further reveal the excellent classification performance of the proposed method. the approach achieves an overall probability of successful recognition of 93.5% for eight kinds of modulation signals, even when the snr is just − 8 db. outstanding performance proves the superiority and robustness of the proposed method. however, it has recognition mistakes that mainly occur between the signal pairs that have similar tsdis, such as eqfm and frank code signals, lfm and frank code signals, and the process of image resizing also makes small frequency jump blurred. the losses and blurs of this small frequency information finally led to confusion between signals. according to matuszewski and pietrow (2021), recognition method of emitted radar signals with agile waveforms based on the convolutional neural network (cnn) was presented. these signals are measured in the electronic recognition receivers and processed into digital data, after which they undergo recognition. the implementation of this system is presented in a file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com ahmad et al: analysis of normal radar signal based on different time-frequency distribution configurations. azojete, 20(4):699-712. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 703 simulation environment with the help of a signal generator that can make changes in signal signatures earlier recognized and written in the emitter database. the effectiveness results of the applied solutions and the possibilities of developing the method of learning and processing algorithms are presented utilizing tables and appropriate figures. the experimental results demonstrate that the proposed method can effectively solve the problem of recognizing raw radar signals with agile time waveforms and achieve correct probability of recognition at the level of 92–99%. however, the size of the cnn use cannot be used in the case of direct operation at high frequencies. therefore, this paper in line with the reviewed research focused on normal radar signal analysis (of lesser attention, yet still important) using different time-frequency distributions. 2. material and method the radar signal is modeled based on the pulse-to-pulse constant frequency, pulse width (pw), and pulse repetition period (prp); hence, its name is normal radar signal due to this constancy. fast fourier transform was used for the frequency representations and conversion process. however, the fast fourier transform produced mirrored frequencies that resembled the actual signal but appeared at different frequencies which are not required. as such, the hilbert transform was used to help in eliminating the mirrored signal that was caused by the fast fourier transform. and finally, the signal was analyzed using the tfds considered in this work. the normal signal model is based on equation (1) (wiley, 2006): s(t) = 𝐴𝑠𝑖𝑛(2𝜋𝑓𝜏) (1) where a is amplitude in pu, 𝑓 is the center/modulating frequency in hz, 𝜏 is the pw in secs; duration of the signal in which the signal is on. the off time (called the listening time) is simply modelled by zeroes for the considered duration. a full complete radar signal cycle concatenation of the on and off times (wiley, 2006; ahmad et al., 2023). the time-frequency analysis tools proposed for this paper include wvd, wwvd, fwvd, cwd, and hybrid distributions that combined fwvd and cwd. further information on these tfds is given in the preceding subsections. 2.1 wigner-ville distribution (wvd) wvd is an important quadratic time-frequency distribution (qtfd) that extends the capabilities of the wigner distribution. it employs a quadratic function to achieve precise localization for linearly modulated frequency and impulse signals. the wvd equation is also divided into two major sections (ahmad et al., 2019). the first stage is for obtaining instantaneous autocorrelation function (iaf) (2) and the second stage is the time-frequency conversion and storage of the iaf based on the fourier transform (3): 𝐾𝑧(𝑡, 𝜏) = 𝑧 (𝑡 + 𝜏 2 ) 𝑧∗ (𝑡 − 𝜏 2 ) (2) 𝜌𝑧,𝑊𝑉𝐷(𝑡, 𝑓) = ∫ 𝐾𝑧(𝑡, 𝜏)𝑒−𝑗2𝜋𝑓𝜏𝑑𝜏 ∞ −∞ (3) where 𝜌𝑧,𝑊𝑉𝐷(𝑡, 𝑓) represents the wigner-ville distribution of a signal at time t and frequency f. 𝑧 (𝑡 + 𝜏 2 ) represents a complex-valued function, typically denoting the analysing signal or http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 704 window function used in the wvd. ∗ (superscript) represents the complex conjugate. the interference terms are independent of the time-frequency distance between the two signal terms. in some applications, they may overlap the auto-components (boashash, 2015). moreover, since (3) requires an evaluation from minus infinity to plus infinity, which is impossible in the real application, pseudo-wigner-ville distributions (pwvds) are chosen to use a running window to overcome this problem (boashash, 2015). putting a regular window into (3) leads to pwvd (stephens, 1996): 𝜌𝑧,𝑃𝑊𝑉𝐷(𝑡, 𝑓) = ∫ ℎ(𝜏)𝑧 (𝑡 + 𝜏 2 ) 𝑧∗ (𝑡 − 𝜏 2 ) 𝑒−𝑗2𝜋𝑓𝜏𝑑𝜏 ∞ −∞ (4) for this research, the two basic forms of pseudo-wvd were considered, which are windowed wvd (wwvd) and filtered wvd (fwvd). 2.2 windowed wigner -ville distribution (wwvd) similar to the wvd, the wwvd follows a comparable process. however, an additional step is introduced before the conversion, involving the application of a windowing technique to the instantaneous autocorrelation function (iaf) to enhance its smoothness. for this purpose, a hamming window is chosen due to its desirable characteristics, including a relatively narrow main lobe width and effective attenuation of the initial side lobes (cheng et al., 2022). equation (5) illustrates the windowing process applied to the instantaneous autocorrelation function (iaf), while equation (6) represents the final equation of the wigner-ville distribution (wvd) incorporating this windowing process and equation (7) represents the hamming window used. 𝐾𝑧,𝑤(𝑡, 𝜏) = 𝑔𝑤(𝜏)𝐾𝑧(𝑡, 𝜏) (5) 𝜌𝑧,𝑊𝑊𝑉𝐷(𝑡, 𝑓) = ∫ 𝑔𝑤(𝜏) 𝑧 (𝑡 + 𝜏 2 ) 𝑧∗ (𝑡 − 𝜏 2 ) 𝑒−𝑗2𝜋𝑓𝜏𝑑𝜏 ∞ −∞ (6) 𝜌𝑧,𝑊𝑊𝑉𝐷(𝑡, 𝑓) = ∫ 0.54 − 0.46 cos ( 2𝜋𝜏 𝑇 ) 𝑧 (𝑡 + 𝜏 2 ) 𝑧∗ (𝑡 − 𝜏 2 ) 𝑒−𝑗2𝜋𝑓𝜏𝑑𝜏 ∞ −∞ (7) where 𝜌𝑧,𝑊𝑊𝑉𝐷(𝑡, 𝑓) represents the windowed wigner-ville distribution of a signal at time t and frequency f.𝑧 (𝑡 + 𝜏 2 ) represents a complex-valued function, typically denoting the analyzing signal or window function used in the wvd. ∗ represents the complex conjugate. 2.3 filtered wigner-ville distribution (fwvd) the fwvd follows a similar approach to the wwvd. however, instead of applying a windowing technique, a filtering process, which can be considered a convolution process, is employed. equation (8) represents the filter wigner-ville distribution, which encapsulates this filtering process. to accomplish the filtering, the kaiser window is utilized due to its effectiveness in suppressing unwanted noise or interference while preserving the desired signal components in radar signals. the kaiser window's parameter, referred to as the beta value, allows for fine-tuning the balance between the width of the main lobe and the levels of the sidelobes. by adjusting the beta value, engineers can effectively reduce the sidelobes and improve the selectivity of the filtering process, thereby enhancing the overall performance of the radar system (liang et al., 2021). 𝐾𝑧,𝑓(𝑡, 𝜏) = 𝑔𝑓(𝑡) 𝐾𝑧(𝑡, 𝜏)𝑡 ∗ (8) file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com ahmad et al: analysis of normal radar signal based on different time-frequency distribution configurations. azojete, 20(4):699-712. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 705 𝜌𝑧,𝐹𝑊𝑉𝐷(𝑡, 𝑓) = ∫ 𝑔𝑓(𝑡) ∗ 𝑧 (𝑡 + 𝜏 2 ) 𝑧∗ (𝑡 − 𝜏 2 ) 𝑒−𝑗2𝜋𝑓𝜏𝑑𝜏 ∞ −∞ (9) 𝜌𝑧,𝐹𝑊𝑉𝐷(𝑡, 𝑓) = ∫ ∫ 𝐼0{𝛽√1−( 𝑡−𝑢 𝑇 ) 2 } 𝐼0{𝛽} 𝑧 (𝑢 + 𝜏 2 ) 𝑧∗ (𝑢 − 𝜏 2 ) 𝑒−𝑗2𝜋𝑓𝜏𝑑𝑢𝑑𝜏 ∞ −∞ ∞ −∞ (10) 𝜌𝑧,𝐹𝑊𝑉𝐷(𝑡, 𝑓) represents the pseudo-filtering, 𝐼0{𝛽√1−( 𝑡−𝑢 𝑇 ) 2 } 𝐼0{𝛽} represents the filtering process added to equation (4). 2.4 choi-williams distribution (cwd) the cwd belongs to the cohen class of time-frequency distributions. it incorporates a kernel function that effectively suppresses cross-terms resulting from multiple signals. consequently, the cwd exhibits high resolution and minimizes the presence of cross terms (guo, yu, & ruan, 2019). this tfd, unlike wvd, is readily available and there was no need for its pseudoversion design therefore it was adopted from the standard reference (boashash, 2015). mathematically, the expression for the cwd can be represented as follows: 𝜌𝑧,𝐶𝑊𝐷(𝑡, 𝑣) = 2 ∬ √𝜎 4√𝜋 |𝜏| +∞ −∞ 𝑒−𝑣2𝜎 (16𝜏2)⁄ 𝑧 (𝑡 + 𝑣 − 𝜏 2 ) 𝑧∗ (𝑡 + 𝑣 − 𝜏 2 ) 𝑒−𝑗2𝜋𝑣𝜏𝑑𝑣𝑑𝜏 (11) where t and f represent time and frequency, 𝑒 −𝜋2𝜎(𝑡−𝑢)2 𝜏2 it represents a gaussian function in the time domain function,  is the positive scaling factor, 𝑒−𝑗2𝜋𝑓𝜏 it represents a complex exponential function in the frequency domain and 𝑑𝑢𝑑𝜏 it represents the integration variables. however, this adopted version was modified using two smoothing for both time and frequency to get its pseudo version. 2.5 hybrid tfd the hybrid tfd in this research was constructed by combining two tfds, namely the fwvd and the cwd. among the various wvds considered in this paper, fwvd was chosen as the representative due to its superior ability to suppress cross-terms and frequency cross-talk, resulting in the best performance. mathematically, the hybrid tfd can be expressed in equation (12) as follows: 𝜌𝑧,ℎ𝑦𝑏𝑟𝑖𝑑(𝑡, 𝑣, 𝑓) = ∫ ∫ ∫ √𝜎 2√𝜋 |𝜏| 𝐼0{𝛽√1−( 𝑡−𝑢 𝑇 ) 2 } 𝐼0{𝛽} ∞ −∞ ∞ −∞ 𝑒−𝑣2𝜎 (16𝜏2)⁄ 𝑧 (𝑢 + 𝑣 − 𝜏 2 ) 𝑧∗ (𝑢 + 𝑣 − ∞ −∞ 𝜏 2 ) 𝑒−𝑗2𝜋𝑓𝑣𝜏𝑑𝑢𝑑𝑣𝑑𝜏 (12) it is seen from equation (12) that the hybrid version is a filtered version of the doubled windowed cwd, hence an extra integration is added to cater for the filtering process, and also the time parameter is changed to the convolution parameter. furthermore, careful observation of equation (11) shows that the cwd can be considered a pseudo-wvd. that uses an exponential function (hence, sometimes called exponential distribution) (boashash, 2015). as such, only the kaiser filtering window was integrated into the cwd as the cwd already contains the iaf of wvd. however, the result obtained showed no noticeable difference from that obtained from cwd. as such, a second hybrid was developed by simply multiplying the output of fwvd and that of cwd http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 706 3. results and discussion graphical interpretation of the analysis based on tfds: a waterfall presentation of the analysis based on tfds such as wvd, wwvd, fwvd, cwd, and hybrid distributions that combined fwvd and cwd involves a 3d plot with the x-axis representing time, the y-axis representing frequency, and the z-axis representing power. in this presentation, the x-axis is labeled as time and represents the progression of time throughout the analyzed signal. the y-axis is labeled as frequency and represents the range of frequencies under examination. the z-axis is labeled as power, which indicates the magnitude or strength of the signal at each specific time-frequency point. the waterfall presentation provides a visual representation of how the signal's spectral content changes over time. each point on the plot corresponds to a specific time-frequency location, and the color or intensity at that point represents the power or magnitude of the signal. by observing the waterfall presentation, analysts can gain insights into the time-varying behavior of the signal's frequency components. they can identify frequency trends, variations, and patterns that occur over different time intervals. the z-axis, representing power, allows analysts to assess the strength or energy distribution of the signal at various time-frequency points. in summary, a waterfall presentation based on wvd, wwvd, fwvd, cwd, and hybrid distributions combines the elements of time, frequency, and power to visually depict the signal's changing spectral content over time. this presentation facilitates the analysis of temporal frequency patterns and the power distribution of the signal at different time-frequency locations. 3.1 waterfall presentation of nwvd figure 1 shows a three-dimensional (3d) result obtained for a normal radar signal using nwvd. figure 1: waterfall 3-d presentation of nrs using nwvd figure 1 shows a three-dimensional (3d) waterfall plot of power, time, and frequency for the normal radar signal using nwvd. the signal was generated at a center frequency of 10 mhz which indicates that the radar system operates around this frequency, sampling frequency of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com ahmad et al: analysis of normal radar signal based on different time-frequency distribution configurations. azojete, 20(4):699-712. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 707 40 mhz indicates that the signal was digitized at a rate of 40 million samples per second, capturing detailed information about the signal, pulse width (pw) of 1 μs which refers to the duration of each transmitted radar pulse. a shorter pulse width allows for better range resolution in radar systems, pulse repetition interval (pri) or pulse repetition time (prt) of 2μs indicates the time interval between consecutive pulses. this parameter determines the radar's maximum unambiguous range and affects the radar's ability to distinguish between different targets and a delay of a quarter at the beginning of the pulse suggests that there is a time delay introduced at the start of each pulse, corresponding to a quarter of the pulse width. this delay is often used to separate the transmitted pulse from any reflections or clutter that may be present in the radar system based on reviewed literature of chapter two. the essence of showing the 3d plot is for the analysts to gain insights into the radar signal's time-varying spectral content. observing how the signal's power is distributed across different frequencies at different time points, allows for the identification of frequency components, temporal patterns, and potential targets or objects in the radar's field of view. however, it can be seen from the plot between the 2 pulses there is a cross-terms that resemble the signal but not the actual signal it occurs due to the interaction of the main signal with the noise. thereafter, the hilbert transform was used in the process to eliminate the negative mirrored signal since the focus of the project is on the main signal. 3.2 waterfall presentation of wwvd figure 2 shows a 3d result obtained for a normal radar signal using wwvd. figure 2: waterfall 3-d presentation of nrs using wwvd figure 2 shows a 3d waterfall plot of power, time, and frequency for the normal radar signal using wwvd. based on the information that was presented in the methodology, the signal was generated with the same characteristics as that of nwvd. however, from the result obtained for these waterfalls of wwvd, the cross-term was completely eliminated due to the effect of the windowing. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 708 3.3 waterfall presentation of fwvd figure 3 shows a 3d result obtained for a normal radar signal using fwvd. figure 3: waterfall 3-d presentation of nrs using fwvd figure 3 shows a 3d waterfall plot of power, time, and frequency for the normal radar signal using fwvd. based on the information that was presented in the methodology, the signal was generated with the same characteristics as that of nwvd. from the pictorial view, it was observed that the effect of cross terms was little compared to that of nwvd. however, the reduction of the cross terms was due to the filtering process of the fwvd. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com ahmad et al: analysis of normal radar signal based on different time-frequency distribution configurations. azojete, 20(4):699-712. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 709 3.4 waterfall presentation of cwd figure 4 shows a 3d result obtained for a normal radar signal using cwd. figure 4: waterfall 3-d presentation of nrs using cwd figure 4 shows a 3d waterfall plot of power, time, and frequency for the normal radar signal using cwd. based on the information that was presented in the methodology, the signal was generated with the same characteristics as that of nwvd. the pictorial view of the cwd shows that the signal is well captured with no cross-terms or inner artifact. 3.5 waterfall presentation of hybrid (fwvd & cwd) figure 5 shows a 3d result obtained for a normal radar signal using a hybrid. figure 5: waterfall 3-d presentation of nrs using hybrid (fwvd &cwd) http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 710 figure 5 shows a 3d waterfall plot of power, time, and frequency for the normal radar signal using a hybrid. based on the information that was presented in the methodology, the signal was generated with the same characteristics as that of nwvd. the pictorial view of the hybrid shows how the signal was well captured with no cross-terms or inner artifact. however, the shape of the captured signal using this hybrid shows a pre-indication that further analysis such instantaneous power or frequency may not yield accurate results when compared to others. generally, all the tfds considered for analysis in this research accurately captures the time and frequency changes of the normal radar signal graphically to a high degree. exact numerical accuracy would depend on further analysis using feature extraction and classification for future works. 5. conclusion the paper conducted analysis of normal radar signals, exploring various time-frequency distribution configurations, including wvd, wwvd, fwvd, cwd, and a hybrid distribution that combines fwvd and cwd. the research revealed that most of these time-frequency distributions (tfds) effectively captured the time and frequency characteristics of radar signals, which were modeled based on specific pulse width (pw), pulse repetition interval (pri), center frequency, and sampling frequency. the values of these parameters are pwof 1µs, priof 2µs, center frequency of 10 mhz, and sampling frequency of 40 mhz. as a result of these findings, it is evident that these tfds hold great potential for further analysis of other radar signal types using signal processing and classification tools. instantaneous power, instantaneous frequency, and machine learning techniques can also be employed for automatic waveform recognition. this advancement could significantly enhance radar signal processing capabilities and contribute to improved radar system performance and accuracy. reference ahmad, aa., aji, mm., abdulmumin, y., jae, ia. and bello-imokhuede, ui. 2023. profiling radar signals based on pulse-to-pulse frequency agility. global journal of engineering and technology advances, 15(2): 141–149. ahmad, aa., ajiya, m., yusuf, zy. and airoboman, ae. 2019. on the identification of low probability of intercept radar signals using time-frequency signal analysis and processing. journal of electrical and electronics engineering, 12(2): 5–10. boashash, b. 2015. time-frequency signal analysis and processing: a comprehensive reference (2nd ed.,). academic press, massachusetts, usa., pp. 3-56. chen, k., zhu, l., chen, s., zhang, s. and zhao, h. 2021. deep residual learning in modulation recognition of radar signals using higher-order spectral distribution. measurement, 185: 109945 (1-12). cheng, j., li, j., zhang, r., liu, f., chen, x., zhao, z., zhan, y. and kazemzadeh, s. 2022. based on fpga laser spectrum analysis system. in proceedings of the 2nd international conference on cognitive based information processing and applications (cipa 2022), changzhou, china, 2–3 september 2022., 2: 81–89. gao, j., shen, l., gao, l. and lu, y. 2019. a rapid accurate recognition system for radar emitter signals. electronics, 8(4): 463 (1-14). file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com ahmad et al: analysis of normal radar signal based on different time-frequency distribution configurations. azojete, 20(4):699-712. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 711 guo, q., yu, x. and ruan, g. 2019. lpi radar waveform recognition based on deep convolutional neural network transfer learning. symmetry, 11(4): 540 (1-17). gulum, to. 2007. autonomous non-linear classification of lpi radar signal modulations doctoral dissertation, naval postgraduate school, monterey, california. huang, y., jin, w., li, b., ge, p. and wu, y. 2019. automatic modulation recognition of radar signals based on manhattan distance-based features. ieee access, 7: 41193–41204. kong, s.-h., kim, m., hoang, lm. and kim, e. 2018. automatic lpi radar waveform recognition using cnn. ieee access, 6: 4207–4219. liang, c., teng, z., li, j., yao, w., hu, s., yang, y. and he, q. 2021. a kaiser window-based stransform for time-frequency analysis of power quality signals. ieee transactions on industrial informatics, 18(2): 965–975. matuszewski, j. and pietrow, d. 2021. specific radar recognition based on characteristics of emitted radio waveforms using convolutional neural networks. sensors, 21(24): 8237 (1-19). pace, pe. 2009. detecting and classifying low probability of intercept radar. artech house, norwood, usa., pp. 4-65. patole, sm., torlak, m., wang, d. and ali, m. 2017. automotive radars: a review of signal processing techniques. ieee signal processing magazine, 34(2): 22–35. qu, z., mao, x. and deng, z. 2018. radar signal intra-pulse modulation recognition based on convolutional neural network. ieee access, 6: 43874–43884. qu, z., wang, w., hou, c. and hou, c. 2019. radar signal intra-pulse modulation recognition based on convolutional denoising autoencoder and deep convolutional neural network. ieee access, 7: 112339–112347. stephens, jp. 1996. advances in signal processing technology for electronic warfare. ieee aerospace and electronic systems magazine, 11(11): 31–38. tao, wan., kaili, j., jingyi, l., yanli, t. and bin, t. 2020. detection and recognition of lpi radar signals using visibility graphs. journal of systems engineering and electronics, 31(6): 1186–1192. upperman, tl. 2008. elint signal processing using choi-williams distribution on reconfigurable computers for detection and classification of lpi emitters. doctoral dissertation, naval postgraduate school, monterey, california. ünal, l. and pakfiliz, ag. 2022. lpi radar signal detection based on autocorrelation function and wigner-ville distribution. revista de ingeniería de computación, 9(4): 53-62. wei, p., sili, l. and hongzhi, d. 2014. the application of adaptive genetic algorithms in singleresistant radar jamming. in the 26th chinese control and decision conference (2014 ccdc), changsha, china, 31 may–2 june 2014. 1322-1327. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(4)699-712. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: aaashraf@nda.edu.ng 712 wiley, r. 2006. elint: the interception and analysis of radar signals. artech house, massachusetts, usa. 8-26 file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com corresponding author’s email address: fayomiuche@gmail.comg 769 arid zone journal of engineering, technology & environment original research article mapping and stimulating flash flood in the catchment of jukskie river r. sithole, e. k. onyari, and g. u. fayomi * department of civil and environmental engineering and building sciences, university of south africa, florida science campus, cnr christian de wet road and pioneer avenue, johannesburg, south africa *corresponding author’s email: fayomiuche@gmail.com article information abstract flash floods are among the most severe hydrological hazards, posing significant threats to urban areas worldwide. this study focuses on flash flood mapping of jukskei river, a catchment in johannesburg, south africa, prone to frequent flash flooding. the study employed combination of remote sensing and gis techniques. the approach follows an analytical framework using satellite imagery and digital elevation models (dems) major extreme rainfall events were analyzed such as rainfall covering 241.6 mm (over 6 hours) and 122 mm (over 4 hours)— corresponding to return periods of 100 and 50 years, respectively. the results of the hec-ras simulation were integrated into qgis to visualize the spatial extent of flooding for the rainfall intensities. the dem data was processed to identify areas prone to overland flow accumulation, and flood extents were mapped based on the water surface elevations calculated for the 40.27 mm/h and 30.5 mm/h intensities. the mapping results highlighted critical zones where water levels exceeded the riverbanks, potentially endangering residential areas and infrastructures. the findings emphasized the importance of integrated flood risk management strategies to mitigate future hazards and enhance urban resilience. received: 19th june 2025 revised: 12th july 2025 accepted: 14th july 2025 keywords: flooding juskskei river gis mapping remote sensing © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction flash floods have become one of the most dangerous and common natural disasters in the world, especially in metropolitan areas where the issue is made worse by fast growth and shifting climate conditions (kaplan and avdan, 2018). its speedy start off, distressing effects, massive infrastructure destruction, economic disruption and loss of human lives are characteristics of its nature (agonafor et al., 2023). a combination of inadequate drainage infrastructure, growing urbanization, and erratic weather patterns brought on by climate change is making flash floods increasingly common (mutuvhi et al., 2020). usually, flash floods occur when precipitation surpasses the ability of the land or urban drainage systems to absorb water, resulting in abrupt and intense water surges (baloyi et al., 2018; lin et al., 2021). unlike regular flooding, flash floods happen quickly, often without warning, and have devastating environmental repercussions, infrastructure, human life, and ecosystem as a whole. flash floods are one of the main natural disasters that contribute to a higher death rate worldwide, according to the world health organization (who), (bucherei et al., 2022). flash flood delinquent has worsened recently due to fast urbanization surrounding the jukskei river catchment, which has deteriorated given the exposure of hard sub-surface rocks that have characteristically low infiltration rates and pave way to large surface runoff during periods of intense rainfall (fadupin et al., 2022). furthermore, the frequency of its occurrences is attributed to the available malfunctioning drainage systems that are unable to handle the unexpected surge of storm water volume (teffo et al., 2023). flash flood situations pose negative effect on public and private buildings, roadways infrastructures, affecting transportation networks leading to financial burdens for road infrastructures while it creates further exacerbates socioeconomic problems, ecological imbalance, public health hazards, including water related illnesses and complications (franssen, 2025; mawasha and britz, 2021). globally, urban planners, emergency services, and legislators are working continuously to identify the mitigation techniques towards reduction of flash floods (alarifi et al., 2022; guo et al., 2021). azojete september 2025. vol.21(3):769-782 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/008 www.azojete.com.ng mailto:fayomiuche@gmail.com mailto:fayomiuche@gmail.com mailto:fayomiuche@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 770 recently, the use of gis and satellite images in flood management approaches has been revolutionized by available satellite data and analysis methods (kaplan and avdan, 2018). large areas may be observed from satellite imagery on board, which makes it possible to track land cover, water bodies, and the progressions of flooding events in almost real time. radar and multispectral satellite sensors, including those on sentinel-1, sentinel-2, and landsat-8, have made it possible to monitor flash floods and acquire data on possible management (schlaffer et al., 2015; moeketsi et al., 2022). dube et al., (2020) utilized gis-based hydrological modeling to predict flood behavior in metropolitan areas. their work accurately identified flood-prone locations by simulating flood propagation using rainfall data and digital elevation models (dems). mutuvhi et al., (2020) used a multi-criteria decision-making model based on gis to evaluate the yarlung zangbo river basin's susceptibility to flash floods. this approach identified the area’s that are most susceptible to flash floods based on environmental data related to soil topography, anthropogenic, and the climate changing situations. similarly, gis-based models that take into consideration changes in land use, rainfall patterns, and hydrological features have been used to evaluate flood hazards in south african cities (abdelkareem et al., 2022); (mutuvhi et al., 2020). these methods have been successful in locating high-risk locations, giving risk managers and urban planners useful resources (mutuvhi et al., 2020). by superimposing several datasets, such as satellite imageries, digital elevation models (dems), and meteorological data, gis enables the identification of locations that are vulnerable to flooding. this application facilitates the creation of thorough flood risk assessments and early warning systems (lin et al., 2021). nevertheless, there are still gaps in the integration of environmental data in the juskskei river watershed, despite the significant advancements in the use of satellite imaging and gis for flood risk assessment. similarly, in refining rainfall thresholds for different catchments and integrating participatory gis approaches to engage local communities could enhance the usefulness of flood risk maps in south africa. therefore, this study focused on utilizing satellite imagery and gis to map high-risk areas along the jukskei river. the study's main objectives were to determine which regions are most vulnerable to flash floods, examine how urbanization affects flood behavior, and create maps of flood hazards that disaster management organizations and urban planners can use. 2. study area rapid urbanization has drastically changed the natural landscape in the heavily populated urban area where the jukskei water basin is situated (mutuvhi et al., 2020). there are a lot of impermeable surfaces including roads, buildings, and parking lots across the catchment, which consists of a mix of urban, semi-urban, and peri-urban areas accelerating storm water runoff and increasing the risk of flash flooding. the river basin spans over 700 square kilometers, from johannesburg's northern suburbs to the point where it meets the crocodile river (mawashi and britz, 2021; kaplan and avdan, 2018). because of the topographical gradient and periods of high rainfall, which enable water to amass quickly, the area is susceptible to flash floods (arabameri et al., 2020). the summer rainfall pattern of the area is what defines its climate, with most of the severe downpours taking place between november and march. these climatic circumstances, attached with the area's topography terrain and inadequate urban infrastructure, formed a perfect storm for flash flooding (mutuvhi et al., 2020). figure 1 revealed the locality map of jukskei river. the location of the river catchment and the existing informal settlements and subpar housing made the villages more susceptible to flash floods. (arabameri et al., 2020). 2.1 natural features of jukskei catchment jukskei catchment featured a mean annual rainfall (map) of 713 mm and unpredictable seasonal rainfall patterns with a mild climate condition (mawasha and britz, 2021). the catchment has seasonal variations in temperature, with summertime minimums and maximums between 14°c and 25°c, and cold wintertime minimums and maximums between 0°c and maximum temperatures peak to 17 °c (moeketsi et al., 2022). similarly, jukskei area featured two vegetation biomes, which is the grassland and savanna biomes (mawasha and brittz, 2021). the vegetation categories having the most alteration the catchment include rand highveld grassland, gauteng shale mountain bushveld and egoli granite grassland. the catchment's soil types can be roughly categorized as clayey loams ranging from mild to deep. when enough water is available, the majority of clayey loam soils, in particular, are ideal for commercial agriculture (kaplan and avdan, 2018). flood frequency, depth and velocity in jukskei river catchment have significantly increased over time, according to analysis, and the depth-velocity product has also increased significantly caused by factors such as changes in land use and urbanization (mawasha and britz, 2021). http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 771 figure 1: locality map of jukskie river 2.2 hydrological characteristics the jukskei river is a perennial surface water body whose discharge fluctuates throughout annually. under typical circumstances, the river acts as a vital conduit for the drainage of johannesburg's stormwater and wastewater (teffo et al., 2023). however, the river's capacity is frequently surpassed during periods of high intensity rainfall events, resulting in flash floods that destroy infrastructures and disturb urban life (abiye, 2023). 2.3 flood vulnerability flooding is a major concern at the downstream the jukskei river, especially in the catchment's center and northern regions (nenweli et al., 2024). the absence of resilient infrastructures such as adequate drainage channels makes the location vulnerable to floodwaters, the informal communities along riverbanks are particularly vulnerable mawasha and briz 2023; aarbameri et al., 2020). furthermore, the floodplain is intersected by vital infrastructure, such as pipelines, bridges, and major roadways, rendering these places vulnerable to substantial disruptions during flood occurrences (nenweli et al., 2024). similarly, due to strong thunderstorms, the jukskei river floods regularly, particularly from october to march during the summer (mawasha and britz, 2021). parts of the river downstream are furrowed with parks and greenery zones like jukskei park. it also featured partial downstream agricultural practice due to urbanization and resultant urban sprawl. however, high density residential pattern and informal settlement are common around jukskei catchment (sheree, 2024). these communities are highly susceptible to flash flood occurrences due to proximity to the river and poor drainage system. drainage type in the settlement includes both piped drainage system and the natural drainage such retention ponds, wetlands and storm water drain network (malatji, 2019) however, all the available drainage facilities are poorly maintenance, encroachment, blocked or filled therefore, reducing flood management efficiency (moektsi et al., 2023; malatji, 2019). 3. methodology remote sensing, gis tools combined with historical data were employed in this research. the method uses digital elevation models (dems) and satellite imagery as part of an analytical framework (hussein et al., 2019; alarifi et al., 2022). flood behavior, including water flow, was simulated using the hydrological modeling software hec-ras, which also produced flood hazard maps for return periods of 20, 50, and 100 years. data on topography was obtained from shuttle radar topography mission (srtm) 30m digital elevation model (dem) for the jukskei river catchment analyzed using qgis software. 5years rainfall and streamflow data were retrieved from saws and dws databases, with more attention to extreme rainfall events for threshold analysis: rainfall data were analyzed to categorize rain events exceeding the 60 mm/day threshold therefore, threshold method was adopted for the calculation of surplus rainfall shown in equation 4. this is critical for prompting flash floods. similarly, normalized difference moisture index (ndmi) was also derived from sentinel 2 band for soil moisture analysis using spectral band of short-wave infrared (swir) and near infrared http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 772 (nir) wavelengths. the ndmi formular used is shown in equation 1. gumbel distribution formula was utilized in estimating the rainfall return periods. the formular for gumbel distribution is declared in equation 2. ndmi = (𝑃𝑁𝐼𝑅− 𝑃𝑆𝑊𝐼𝑅) (𝑃𝑁𝐼𝑅+ 𝑃𝑆𝑊𝐼𝑅) = (𝐵8− 𝐵11) (𝐵8+ 𝐵11) 1 where b8 is the near-infrared (nir) band (central wavelength ~842 nm) and b11 is short-wave infrared (swir) band (central wavelength ~1610 nm). 𝐼 = µ + σ x(−ln (i − 1 𝑇 ) 2 where μ is the mean rainfall (66.48 mm), σ is the standard deviation (46.22 mm), and t is the return period (20, 50, or 100 years). rational method formula was also utilized to capture water catchment area, and a runoff coefficient for urban catchments. the formular is shown in equation 3, 4 and 5 𝑄 = 𝐶 x i x a 3 where c=0.8 (runoff coefficient for urban catchments), i is the intensity in mm/h. (assume that the rainfall is concentrated over 4 hours in a day) and a is the catchment area (2,000 km², converted to hectares. 𝑅𝑎𝑖𝑛𝑓𝑎𝑙𝑙 𝑠𝑢𝑟𝑝𝑙𝑢𝑠 = actual rainfall − threshold rainfall 4 however 𝑅𝑎𝑖𝑛𝑓𝑎𝑙𝑙 𝐷𝑖𝑓𝑖𝑐𝑖𝑡 = threshold rainfall − actual rainfall 5 physical flood verification was conducted using real-time media evidence retrieved online covering both ground survey and observational data. 4. results and discussion the outcome of the rainfall trend in jukskei catchment for each year showing notable surplus events in different years driven mostly by intense rainfall situation. these conditions directly heighten the risk of flash flooding given the paucity of other environmental situations such as runoff intensity, soil permeability, evapotranspiration, topography and slope terrain (razavi-termeh et al., 2023). statistical analysis displayed decreasing surplus trend event from 2020 -2024 indicating higher frequency of lower normal rainfall with significant irregular distributions. higher peak rainfall occurred mostly in 2020, 2022 and 2023. surplus rainfall was equally witnessed in all the year with higher record in 2020, 2021 and 2022 figure similarly, maximum rainfall was recorded in 2020 amounting to 78.03mm, followed by 2022 with 65.1mm. the likelihood of a flood increases as the amount of rainfall at a given location rises (abiye, 2023). this is because higher rainfall intensity generates greater volumes of water over a short period. rainfall data breakdown for the study period calculated revealed a sum of 10104.5 mm, average (mean) 66.48 mm (median) 48.9 mm (standard deviation) 46.22 mm. the daily rainfall data was filtered for heavy rain events, thresholds are often set based on the rainfall's potential to cause flooding (zebe and sivapalan, 2009). 90th percentile-based thresholds commonly used to differentiate between normal and substantial rainfall events was utilized to detect the trend. figure 2 (a-e) revealed rainfall per days analyzed from the data gathered using a 90% threshold. critical periods when rainfall surplus rises such as situations where precipitation substantially surpasses the threshold, indicating significant implications for flash flood risk evaluation (hossein, 2024). the highest rainfall data points (50) and maximum rainfall (294.4 mm) occurred in 2022, table 1, resulting in seven surplus days. however, the overall surplus (14 mm) was still low, most likely as a result of higher potential evapotranspiration (pet) or faster soil absorption. 2020 and 2021 also recorded significant rainfall data points (32) (29) respectively with six surplus days which are very closer to 2022. figure 2 (a-e) revealed the outcome of trend in jukskei river catchment. figure 3a shows deficit vs surplus rainfall. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 773 (a) 2020 (b) 2021 (c) 2022 (d) 2023 (e) 2024 figure 2: (a-e) rainfall (mm) per day graph (2020-2024) 241.6 182.6 196.4 226.4 -200 -100 0 100 200 300 6 -j an -2 0 0 6 -f e b -2 0 0 9 -f e b -2 0 2 8 -f e b -2 0 0 3 -a p r2 0 2 7 -a p r2 0 1 1 -o ct -2 0 0 8 -n o v2 0 2 0 -n o v2 0 1 2 -d e c2 0 2 7 -d e c2 0 raifall in mm raifall in mm threshold-rainfall 90th percentile threshold deficit -50 0 50 100 150 200 208.6 294.4 -300 -200 -100 0 100 200 300 400 1 2 -j an -2 2 2 6 -j an -2 2 0 8 -f e b -2 2 2 5 -f e b -2 2 0 8 -m ar -2 2 0 9 -a p r2 2 1 7 -a p r2 2 0 9 -a p r2 2 1 7 -a p r2 2 0 1 -n o v2 2 1 1 -n o v2 2 0 5 -d e c2 2 1 2 -d e c2 2 rainfall in mm threshold-rainfall 90th percentile threshold deficit 109.8 130.6 91.6 125.4 176 104.8 -100 -50 0 50 100 150 200 0 1 -f e b -2 3 0 3 -f e b -2 3 0 9 -f e b -2 3 1 1 -f e b -2 3 1 4 -f e b -2 3 0 7 -m ar -2 3 0 3 -a p r2 3 2 8 -a p r2 3 0 7 -m ay -2 3 2 7 -s e p t2 3 0 7 -n o v2 3 1 0 -d e c2 3 1 5 -d e c2 3 2 6 -d e c2 3 rainfall in mm threshold-rainfall 90th percentile threshold deficit 109.8 128.6 -40 -20 0 20 40 60 80 100 120 140 rainfall in mm thresholdrainfall 90th percentile http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 774 (a) (b) figure 3: showing (a) deficit vs surplus rainfall (b) rainfall trend table 1: rainfall trend 2020-2024 the data from sentinel-2 with the use of normalized difference moisture index showed a clear correlation between high moisture levels and flood-prone areas along the jukskei river, especially in the floodplain regions, figure 4 figure 4: soil moisture map 18.45 20.7 14 10.7 9.1 81.25 82.76 86.05 85.19 90 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 2020 2021 2022 2023 2024 rainfall surplus rainfall deficiet 78.03 58.1 65.1 60.3 57.2 0 10 20 30 40 50 60 70 80 90 maximum rainfall years year data point average rainfall (mm) max rainfall (mm) surplus days % surplus % deficit 2020 32 78.03 241.6 6 18.47 7.25 2021 29 58.1 147.6 6 20.7 80.06 2022 50 65.1 294.4 7 14 86.05 2023 28 60.3 176 3 10.7 85.19 2024 14 57.2 128.6 1 9.1 90 http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 775 flood-prone zones along the river displayed high moisture indices after the flood events of 4-feb22, 7-feb20, 12-dec-20, 7-jan-22 consistent with the periods of flooding identified in the rainfall dataset characterized of soils with lower permeability. this result aligned with previous studies on soil influence on flooding (sellame et al., 2024; lin et al., 2021). the elevation map and slope analysis figure 5 (a and b), of the catchment exhibits a marked contrast between highland areas (with steep slopes) and lowland areas (along the river valley situated in the highveld area of south africa. the topography of johannesburg's northern suburbs is distinguished by an undulating profile made up of several "koppies." the elevation of these koppies ranges from 1 450 to 1 600 m.a.s.l. in the northeast and from 1 33 275 to 1 450 m.a.s.l. in the northwest (moeketsi et al., 2022). this variation in topography significantly influences how water flows across the landscape, affecting the potential for flooding (mukherjee and singh, 2020). figure 5c displays the lulc map for jukskei river catchments created in this study using qgis and the available remote sensing data (esri land cover 2023) the result revealed greater increase in built-up area ranging more than 50% and decrease in vegetation cover which could result to low infiltration of rainwater. urban areas with impermeable surfaces, such as roads, buildings, and parking lots, are among the main land cover categories found in the study area. these surfaces stop water from penetrating the ground and increase surface runoff during rainfall events, which is a major cause of flash flooding (anaba et al., 2017; pedzisai, 2016). (a) (b) (c) figure 5: showing a) srtm dem map and b) elevation map and c) land use map. using the provided rainfall data with the rational method, the flood peak discharge (q) for the jukskei river catchment was estimated for three return periods: 20, 50, and 100 years. the calculations are based on the rainfall intensity for these return periods, the catchment area, and a runoff coefficient for urban catchments. the statistic provided in table 2 was used, while gumbel distribution formula was utilized in estimating the rainfall return periods. the result from the analysis revealed a higher peak flow increases when compared with http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 776 the return period. this invariably reflects higher rainfall intensities associated with fewer and more extreme events. the flood peak discharge is a critical parameter for flood risk assessment, as it dictates the severity of flood events and the capacity required in flood management systems. in the case of the jukskei river, the calculated flood peaks for the 20, 50, and 100-year return periods such as (1,152 m³/s, 1,280 m³/s, and 1,498 m³/s, respectively) highlight the significant risk posed by heavy rainfall in the region. this result aligned with the analysis derived from previous studies on flow peak discharge and assertions on flow peak discharge (mawasha and britz, 2022; malatji, 2019). the increasing flood peak values for infrequent return periods emphasized the growing risk of flash flooding during extreme rainfall events, especially in urbanized areas like johannesburg, where impervious surfaces contribute to rapid runoff. similarly, base flow was equally estimated from streamflow data recorded over a period of time. table 3 presents the annual streamflow data for the river from 2014 to 2024, which was used to estimate the base flow. using the rank-based approach (where the flow data is ranked in descending order), the lowest flows (i.e., the minimum annual flow) are identified as indicative of base flow. in this case, the lowest flow (rank 10) observed was 7.573 m³/year, and the second lowest flow (rank 9) was 40.162 m³/year while the average base flow = (7.573+40.162)/2= 23.8675 m3/year. table 2: return periods verse flood peak return period (years) daily intensity (mm) hourly intensity (mm/h) peak flow (q, m³/s) 20 103.67 25.92 1152 50 115.22 28.81 1280 100 125.78 31.45 1498 table 3: streamflow data of juskie river. source: (saws), 2024 year flow (m3/year) rank (m) inflow in descending order frequency (f) (n/m) probability (1/f x100) 2014 313.599 1 525.65 10 10.00 2015 40.162 2 337.911 5 20.00 2016 171.151 3 313.599 3.333333 30.00 2017 311.478 4 311.478 2.5 40.00 2018 125.35 5 271.498 2 50.00 2019 271.498 6 264.773 1.666667 60.00 2021 7.573 7 171.151 1.428571 70.00 2022 525.65 8 125.35 1.25 80.00 2023 337.911 9 40.162 1.111111 90.00 2024 264.773 10 7.573 1 100.00 the hydrodynamic modeling in hec-ras utilized steady-state flow data to simulate flood events associated with 20, 50, and 100-year return periods. these return periods were based on rainfall intensities derived from statistical analyses using the gumbel distribution, with peak flows of 1,152 m3/s, 1,280 m3/s, and 1,498 m3/s, respectively. the boundary conditions were defined using the normal depth method, which estimated the downstream slope as s=0.01376 based on the average gradient derived from the profile analysis. this computation equally aligned with previous studies in literature for instance, (maherry et al., 2017; malatji, 2019; mawasha and britz, 2021) who observed nearly same result using same procedure. figure 6 shows the geometry of jukskei river. the hazard maps classified inundated areas into three categories: low hazard (depths < 0.5 m), medium hazard (depths between 0.5 and 2.0 m), and high hazard (depths > 2.0 m or areas with high flow velocities). urban areas along the jukskei river were identified as particularly vulnerable due to high impervious surface coverage, which accelerates runoff and exceeds the capacity of drainage systems during extreme rainfall events. similarly, the simulation in hec-ras modeled the jukskei river's response to intense rainfall events with calculated intensities of 40.27 mm/h (for 241.6 mm rainfall over 6 hours) and 30.5 mm/h (for 122 mm rainfall over 4 hours). using the river's geometric data derived from high-resolution digital elevation models (dems), the model incorporated these rainfall intensities to estimate peak flows and simulate water surface profiles along the river. for the 241.6 mm rainfall event, the model showed significant increases in flow velocities and water surface elevations, causing extensive inundation in low-lying floodplain areas. the 122 mm event, while less severe, still resulted in considerable runoff, demonstrating the river's limited capacity to handle sudden, highintensity flows. the outputs from the simulation identified areas most vulnerable to overflow and highlighted potential stress points in the river's drainage system, emphasizing the urgent need for infrastructure upgrades. figure 7 (a-c) revealed flood mapping of 20 years, 50, and 100 years return period. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 777 . figure 6: geometry of jukskei river (a) (b) http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 778 (c) figure 7: flood map showing a) 20years, b) 50years c)100-years return period qgis software was used to identify areas prone to overland flow accumulation, and flood extents were mapped based on the water surface elevations calculated for the 40.27 mm/h and 30.5 mm/h intensities. the mapping revealed the extent of inundation under both scenarios, with urban areas and floodplains along the river showing the highest vulnerability. the 241.6 mm rainfall event was particularly destructive, with floodwaters spilling into adjacent settlements and infrastructure. the map highlighted critical zones where water levels exceeded the riverbanks, potentially endangering residential areas and roads. for the 122 mm event, the flooding was less extensive but still posed significant risks in urbanized zones with limited drainage. these flood maps provided actionable insights into the areas at greatest risk, helping to support urban planners and emergency response teams in prioritizing mitigation and adaptation strategies. however, using two flood events for 7th 2020 and 4th december 2022 such as adjusted rainfall intensities for 04 december 2022 rain intensity 122 mm in 4 hours: i=122/4=30.5 mm/h for 7 february 2020, i = 241.6/6 = 40.27mm/h calculations for peak flow = for i=30.5 mm/ q=0.8⋅30.5⋅200,000=4,880,000m3/h=1,356m3/s = for i= 40.27mm/h =0.8⋅40.27⋅200,000=6,443,200m3/h=1,790m3/s figure 8: flood event 7 february 2020 http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 779 figure 9: flood event 04 december 2022. 4.1 flash flood validation the rainfall events of 241.6 mm over 6 hours and 122 mm over 4 hours correspond to return periods based on the statistical rainfall intensities. the 241.6 mm event aligns closely with the intensity for a 100-year return period (125.78 mm/day or approximately 31.45 mm/h), indicating its classification as an extreme and rare flooding event. this event would result in significant overflow along the jukskei river. other flash flood scenario event was equally used for validation such as on february 6, 7 and 10, 2020 where south african weather service (saws) issued flood alerts as the rainfall exceeded threshold levels, signaling the potential for dangerous flooding (scrolla.africa, 2020, saws, floodlist, media, 2020). the records include 53.2 mm, 241.6 mm and 120.5 mm respectively. however, december 12, 2022, with record of 226.4 mm, the intense rainfall caused the jukskei river to overflow as reported by (ngcuka, daily maverick, 2022). other recorded expanded rainfall in the same month includes december 3, 2022: 95.3 mm, december 4, 2022: 122.0 mm, december 5, 2022: 128.8 mm and december 6, 2022: 67.4 mm figure1 (a-e). a tragic flash flood occurred between december 3–6, 2022, when intense rainfall triggered a rapid rise in water levels along the jukskei river, leading to fatalities. on december 6, 14 people lost their lives during a church baptism ceremony at bramley park. the suddenness of the flood, compounded by the rising river levels (mawasha & britz, 2021; daily maverick, 2024). the rainfall data in figure 2 (a-e) validates the claims made by news outlets. plate 1 and 2 depicts the physical justification of flash flood situation at jukskei river catchment. plate 1: report on rising water levels along the jukskei river setswetla informal settlement, alexandra (february, 8, 2020) (source: scrolla africa, 2020, flood report) http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 780 plate 2: juskskei catchment situation (source: ngcuka, daily maverick 2022, flood report). 5. conclusion this research utilized satellite imagery and geographic information systems (gis) to analyze and map flash flood risks along the jukskei river. through a combination of hydrological modeling, spatial analysis, and risk mapping, the study successfully identified high-risk areas and provided insights into the factors contributing to flash flood dynamics. rainfall events exceeding the 90th percentile threshold (112.2 mm) was found to significantly increase the likelihood of flash floods. the urban areas in the jukskei river catchment, characterized by extensive impervious surfaces, exhibited high runoff coefficients, which compounded flood risks. peak discharge rates calculated for 20-, 50-, and 100-year return periods showed increasing flood severity, with values of 1,152 m³/s, 1,280 m³/s, and 1,498 m³/s, respectively. these rates underline the critical need for effective urban drainage solutions to mitigate peak flows. this study faced several data constraints, including the moderate resolution of srtm dems, which may not capture detailed urban features, and the temporal limitations of satellite imagery. therefore, further research should prioritize the integration of higher-resolution datasets, such as advanced satellite imagery and lidar-based dems, to improve the accuracy of flood risk mapping and modeling. references abdelkareem, m., al-arifi, n., abdalla, f., mansour, a. and el-baz, f. 2022. ‘fusion of remote sensing data using gis-based ahp-weighted overlay techniques for groundwater sustainability in arid regions, sustainability, 14: 7871. abiye, ta. 2023. contribution of hydrogeology to solving community water supply problems in south africa. south african journal of science.119(1/2):14599 agonafir, c., lakhankar, t., khanbilvardi, r., krakauer, n., radell, d. and devineni,n. 2023. a review of recent advances in urban flood research. water security 19: 100141. alarifi, ss., abdelkareem, m., abdalla, f. and alotaibi, m. 2022. flash flood hazard mapping using remote sensing and gis techniques in southwestern saudi arabia. sustainability, 14:1414. anaba, n., banadda, n., kiggundu, j., wanyama, b., engel and d. moriasi. 2017. application of swat to assess the effects of land use change in the murchison bay catchment in uganda. computational water, energy, and environmental engineering, 6, 24-40 arabameri, a., saha, s., chen, w., roy, j., pradhan, b. and bui, d.t. 2020. flash flood susceptibility modelling using functional tree and hybrid ensemble techniques. journal of hydrology, 587, 125007 baloyi, j., zwane, f. and sibanda, s. 2018. gis-based multi-criteria analysis for flood risk assessment: a case study of the umgeni river catchment, kwazulu-natal. journal of hydrology and environment, 5(2): 213–226. bucherei, a., werner, m., homberg, mv. and tembo, s. 2022. flash flood warnings in context: combining local knowledge and large-scale hydro-meteorological patterns, nat. hazards earth syst. sci., 22: 461–480. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 781 dube, t., mutanga, o. and sibanda, m. 2020. integrating radar and optical remote sensing for flood risk assessment in informal settlements: case of the cape flats, western cape. south african journal of geomatics, 9(1): 45–60. franssen, hh. 2025. historical memory in remotely sensed soil moisture can enhance flash flood modeling for headwater catchments in germany. journal of hydrology 648: 132395. fadupin, oa., ochieng, gm. and ndege, m. 2022. flash flood risk management in a south african township. a case study of alexandra. meng thesis: vaal university of technology, 216163994. hussein, s., abdelkareem, m., hussein, r and askalany, m. 2019. using remote sensing data for predicting potential areas to flash flood hazards and water resources. remote sensing applications: society and environment. 16: 100254. hossein, ha. 2024. deep learning model for predicting river flood depth and extent, environmental modelling & software, 145 (105): 186. kaplan, g. and avdan, u. 2018. flood mapping using sentinel-1 sar data: a case study from turkey. remote sensing, 10(11): 1744. lin, bq., zhang, dj. and chen, xw et al., 2021. threshold of watershed partition in swat based on separating hillslope and channel sediment simulations. ecological indicators, 121:107111. mawasha, ts. and britz, w. 2021. hydrological impacts of land use land cover change on urban flood hazard: a case study of the jukskei river in alexandra township, johannesburg, south africa. south african journal of geomatics, 10(2), 139-162 mawasha, t. and britz, w. 2022. detecting land use and land cover change for a 28-year period using multitemporal landsat satellite images in the jukskei river catchment, gauteng, south africa. south african journal of geomatics, consas conference, 11 (1): 13-29. malatji, r. 2019. towards a gis platform for monitoring the water quality of the jukskei river catchment: defining a sampling network [master’s thesis, university of witwatersrand] wits institutional repository environment on ds pace, johannesburg. maherry, a., van huyssteen, c. and clarke, s. 2017. flood hazard mapping in the limpopo river basin using sentinel-2 imagery and gis. international journal of disaster risk reduction, 21: 93–102. moeketsi, p., nkhonjera, gk. and alowo r. 2022. changes in land use land cover within the jukskei river basin and its implications on the water availability. iop conf. series: earth and environmental science, 1087012035. mukherjee, f. and singh, d. 2020. detecting flood prone areas in harris county: a gis based analysis. geo journal, 85: 647–663. mutuvhi, t., mhangara, p. and ntsangase, l. 2020. urban flood risk assessment using sentinel-2 and gis: a case study of the jukskei river basin, johannesburg. urban water journal, 17(3): 219–234. ngcuka, o. (daily maverick, 2022), it’s ugly, it’s completely sickening,’ says water expert on joburg’s rivers. rueben, an alex water warrior, next to the jukskei river and a house teetering on the bank. (photo: felix dlangamandla / daily maverick). nenweli, r., watson, a., brookfield, a., münch, z. and chow, r. 2024. is groundwater running out in the western cape, south africa? evaluating grace data to assess groundwater storage during droughts. journal of hydrology: regional studies, 52: 101699 pedzisai, e. 2010. modelling the impact of land cover change on stormwater runoff using gis and remote sensing: a case study of upper manyame catchment, zimbabwe. msc dissertation. university of zimbabwe. razavi-termeh, sv., seo, m., njaraki, as. and choi, s. 2023. flash flood detection and susceptibility mapping in the monsoon period by integration of optical and radar satellite imagery using an improvement of a sequential ensemble algorithm. weather and climate extremes, 41: 100595. http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 770-782. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: fayomiuche@gmail.com 782 sellami, em. and rhinane, h. 2024. a modern method for building damage evaluation using deep learning approach case study: flash flooding in derna, libya. e3s web of conferences 502: 03010 sheree, b. 2024. alexandra water warriors are reviving joburg’s jukskei river, green guardian, south africa. schlaffer, s., matgen, p., hollaus, m., wagner, w. 2015. flood detection from multitemporal sar data using change detection techniques. international journal of applied earth observation and geoinformation, 38: 1524. scrolla africa, 2020. south africa – floods cause havoc in johannesburg and gauteng. 8th february, 2020. retrieved on 24th august, 2024. for afrika https://www.forafrika.org › south-africa › heavy-rainfal. south africa flood (saws, floodlist, media) (echo daily flash of 10 february 2020) reliefweb https://reliefweb.int › report › south-africa-flood-saws-f. teffo, t., ndwandwe, ca. and abrahams, a. 2023. comparative functional metagenome analysis of the jukskei river system impacted by the urbanization phenomenon. report to the water research commission. zebe, e. and sivapalan, m. 2009. threshold behavior in hydrological systems as (human) geo-ecosystems: manifestations, controls, implications. hydrol. earth syst. sci., 13: 1273–1297, http://www.azojete.com.ng/ mailto:fayomiuche@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 907 arid zone journal of engineering, technology & environment review article a systematic review of value engineering practices in construction projects in tanzania a. kindole1,2*; m. i lingwanda1 and r. s tekka1 1department of civil engineering, college of engineering and technology, mbeya university of science and technology, mbeya, tanzania 2tanzania rural and urban roads agency, mbeya, tanzania *corresponding author’s email: alberto.kindole@tarura.go.tz article information abstract value engineering (ve) has become a vital component of construction management, improving project outcomes in terms of cost, time, quality, safety, environmental performance, stakeholder satisfaction and social value. this study systematically reviews ve practices to assess their applications, benefits, barriers, and future research directions, with emphasis on tanzania’s construction industry. a structured search of google scholar and semantic scholar retrieved peerreviewed publications from 2005 to 2025, yielding about 70 sources, of which 32 highly relevant studies were analyzed in depth. the review shows that ve delivers quantitative benefits such as cost and time reduction, alongside qualitative gains including enhanced construction quality and better management through multidisciplinary teamwork. however, its adoption in tanzania remains limited due to inadequate awareness, cost-driven procurement systems, and a shortage of trained ve professionals. this study further identifies critical success factors (csfs) across ve phases, including effective project information preparation, cost-based comparison of design alternatives, systematic planning and implementation, and strong stakeholders support. it concludes by recommending the development of localized ve guidelines and increased awareness among clients and top management to enhance decision-making and promote wider ve adoption in tanzania. received: 5th august 2025 revised: 15th november 2025 accepted: 17th november 2025 keywords: value engineering construction projects critical success factors © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the construction industry in tanzania remains a critical driver of economic growth and infrastructure development. however, it continues to face persistent challenges such as high construction costs, prolonged project durations, substandard quality, compromised safety, and social as well as environmental concerns (naot, 2023). these inefficiencies are largely attributed to ineffective project management practices and the absence of structured decision-making frameworks, including the limited application of ve principles (ikanuti et al., 2018). despite these challenges, the sector provides significant employment opportunities for both skilled and unskilled labor, from project appraisal through to post-construction maintenance (phoya, 2012). to enhance performance, the tanzanian government has introduced several reforms. these include the establishment of the national construction council, as well as regulatory bodies such as the contractors registration board, the architects and quantity surveyors registration board, and the engineers registration board to ensure compliance with laws and standards. the building research unit and the tanzania bureau of standards have also been established to promote the use of local building materials and regulate quality. in the road sector, agencies such as tanroads and tarura are mandated to manage trunk, regional, and district roads, supported by the roads fund and roads fund board for sustainable financing. azojete december 2025. vol.21(4):907-920 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/002 www.azojete.com.ng http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz mailto:alberto.kindole@tarura.go.tz http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 908 delays in construction projects, often linked to poor planning and budgetary constraints, can be reduced through consistent application of ve principles (ghorbani et al., 2005). ve offers systematic approaches for eliminating unnecessary expenditures, improving quality, and enhancing decision-making processes (tom, 2015). globally, ve has gained prominence as a construction management tool that balances cost, quality, and functionality. over the past three decades, extensive research has demonstrated its effectiveness in improving project efficiency, fostering innovation, and optimizing value across all construction phases (bowen et al., 2010; tohidi, 2011). beyond cost reduction, ve enhances risk management, functional development, stakeholder satisfaction, and knowledge transfer in multi-project environments (haskins, 2010; formentini et al., 2011). in tanzania, efforts to improve project value have primarily focused on performance measurement systems, cost control mechanisms, and project reviews (samizi, 2018). however, the integration of ve remains limited, with most initiatives adopting alternative approaches rather than systematically applying ve methodologies (basondole, 2022). given the increasing global significance of ve in construction, this paper systematically reviews studies published between 2005 and 2025. the objective is to provide insights into the applications, benefits, barriers, and future research directions of ve, with particular emphasis on the tanzanian construction industry. in doing so, the paper proposes strategic interventions to strengthen ve adoption in developing economies, where efficiency, cost-effectiveness, and sustainable project delivery remain critical. 1.1 fundamental principles of value engineering ve is a structured, function-oriented, and multidisciplinary methodology designed to optimize project or process value by systematically analyzing functions, eliminating unnecessary costs, and enhancing performance without compromising quality, safety, or stakeholder requirements (danku et al., 2020). at its core, ve is built on three interrelated pillars: function, cost, and value (adhikari, 2013). its philosophical foundation emphasizes that any solution failing to achieve optimal functional capacity is inadequate. consequently, ve extends beyond cost reduction to incorporate key principles such as quality assurance, time scheduling, brainstorming of alternative solutions, life-cycle costing, and the application of systematic and organized approaches. these dimensions ensure a holistic framework for improving both the cost-effectiveness and performance of a project, product, or system. the primary objective of a ve study is to enhance project value through a structured process commonly referred to as the job plan. this plan provides a sequential framework for conducting value studies and typically involves three major stages: pre-workshop preparation, the value workshop, and post-workshop documentation and implementation. within these stages, structured activities guide project teams to identify essential functions, explore alternatives, and recommend solutions that maximize value. a formal ve study must adhere to a systematic job plan comprising five core phases (figure 1) (save, 2015). although variations in terminology exist, the essence of the process remains consistent: ensuring a logical progression from information gathering to idea generation, evaluation, development, and implementation. assaf et al. (2000) emphasize that this structured approach is fundamental to the success of ve studies, as it directs multidisciplinary teams to concentrate on key project functions and stimulate innovative solutions that improve value (save, 2007). to qualify as a valid ve plan, save international (2015) prescribes three essential conditions: (1) the value study team must strictly follow the defined phases of the ve process; (2) the team must be multidisciplinary, comprising professionals and stakeholders selected for their relevant expertise; and (3) the study must be led by a certified value specialist or team leader with advanced training and competence in ve methodology. compliance with these conditions ensures methodological rigor, credibility, and effective outcomes in the application of ve. although ve can be applied at any stage of the construction process, evidence shows that earlier implementation yields greater returns on investment in both time and effort (save, 2015). save (2015) further emphasizes ve’s role as a management tool for maximizing the value of public and private projects, particularly when applied during the early stages. while ve can add value at multiple phases, the planning stage is generally the most advantageous, as changes at this point are less costly and have minimal impact on project progress. in practice, however, ve teams often become more actively engaged during the design phase, where they critically review proposed solutions. hayles et al. (2000) illustrate this relationship by showing how the cost of implementing changes escalates as a project advance from initial concept to final completion (figure 2). http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 909 figure 1: value engineering job plan development process flow figure 2: ve general cost changes of a construction project 1.2 critical success factors for ve implementation in construction projects the success of construction projects is strongly influenced by several critical success factors (csfs) (ramly et al., 2015). rostiyanti (2023) identified 28 csfs for ve, categorized into the pre-study, study, and post-study stages, and ranked them by importance in table 1. among these, the highest-ranked csfs for effective ve workshops include having clear objectives for the ve study and ensuring thorough preparation and a comprehensive understanding of project information. other key factors are the knowledge and experience of the ve team, the selection of feasible alternatives for cost savings, and the comparison of initial designs with alternative solutions from a cost perspective. additionally, the generation of creative and innovative ideas to improve cost efficiency and the development of a practical implementation plan are essential for successful ve outcomes. emphasizing these factors during ve workshops is critical, as they directly support the effective identification of project functions and the optimization of overall project value. http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 910 table 1: ranking of csf for ve related projects at each stage (rostiyanti, 2023) stage drivers or success factors rank ve pre-study stage preparation and understanding the project information (update drawings, project’s state, specifications, historical data, etc.) 1 clear objective of ve study 2 ve knowledge and experience of the ve team 3 conducting site visits 4 professional experience and knowledge of ve team in their own disciplines 5 ve clause or policies in the construction contract 6 conducting ve study before the construction phase (timing of ve study) 7 knowing about characteristics and type of project which has successful possibility of ve implementation 8 allocating time for ve study 9 academic qualifications of the ve team 10 applying ve to high-cost projects 11 ve study stage comparing the initial design with alternative designs from cost perspective 1 generating creative and innovative ideas which can give maximum cost efficiency 2 choosing the most feasible alternative which can help in cost saving and possible implementation 3 making several alternatives of construction method that can save budget of project 4 comparing the initial design with alternative designs from engineering perspective 5 comparing the initial design with alternative designs from time perspective 6 use of functional analysis 7 ve study based on the availability of construction drawing 8 making several alternatives that can fulfil the main function 9 ve study with identifying the high-cost areas or works of the project 10 ve post-study stage develop and plan for implementation the result of ve 1 client’s support and active participation in the ve implementation 2 incentives to ve team as a result of project cost efficiency 3 supporting factor cooperation, follow-up trailing, and support from all related parties (stakeholders) of project to implement ve 1 active cooperation, interaction, and brainstorming among ve team, during pre-study until implementation of ve result 2 logistics and financial support to implement the result of ve 3 1.3 global perspectives on ve in construction projects recent studies highlight ve as one of the most effective management tools for improving the efficiency of construction projects in both developed and developing countries (elsonoki et al., 2020). by systematically optimizing functions, ve ensures the delivery of high-quality projects at reasonable cost and within shorter timeframes, while also enhancing customer satisfaction and supporting broader infrastructure development objectives (othman et al., 2019). despite its proven effectiveness, ve adoption remains limited in many developing countries compared to developed nations (bowen et al., 2010). in several developed economies, ve has been institutionalized through government regulations. for example, hong kong mandates ve workshops for all projects exceeding hk$200 million (leung, 2009); in malaysia, the economic planning unit requires ve for public projects above rm 50 million (japaar et al., 2012); and in indonesia, ve is compulsory for projects with building areas greater than 12,000m². in contrast, implementation remains inconsistent in countries such as south africa, nigeria, ghana, and sri lanka (madushika et al., 2020). tanzania reflects a http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 911 similar trend, with minimal research, documentation, or formal mechanisms for systematic ve adoption. this underscores the critical role of government regulations in shaping ve practice, particularly in developing countries where effective integration, management, and oversight are essential for realizing its benefits (yanita et al., 2018). ve provides a wide range of quantitative and qualitative benefits that directly enhance constructability and overall project performance (russell et al., 1994). quantitative benefits include reduced costs, shorter schedules, and improved quality, while qualitative benefits encompass better problem avoidance, alignment of project goals, stronger stakeholder involvement, greater team commitment, improved communication, enhanced construction flexibility, increased productivity, and reduced rework and disruptions. 2. materials and method the primary objective of this study was to conduct a systematic review of existing literature to examine the current application, benefits, and challenges of ve in construction projects, both globally and within the specific context of tanzania. to achieve this, a qualitative research design employing a thematic content analysis approach was adopted, as it facilitates the systematic identification, categorization, and interpretation of patterns and themes within scholarly sources of information (mahdi et al., 2015). a structured search of google scholar and semantic scholar was used to retrieve peer-reviewed publications from 2005 to 2025. the inclusion criteria were strictly defined, ensuring that only full-text publications in english, published in peer-reviewed academic sources, with criterion that each journal searched must have at least one published ve topic. the primary keywords and search terms used, along with the corresponding number of hits, are summarized in table 2. a similar method was used by keegan et al. (2022), to review gravel road maintenance work published in the transportation research record journal. a systematic documentary review involves the process of gathering, organizing, and evaluating existing literature within a specific domain, with the goal of advancing knowledge in the given field of study. to enhance the validity and reliability of findings, a content analysis methodology was applied to extract and synthesize data systematically. content analysis enables both qualitative (theme identification and pattern recognition) and quantitative (frequency analysis of key terms and thematic occurrences) examinations, thereby allowing for a more comprehensive assessment of ve applications in construction projects. this methodological approach provided a structured framework for categorizing the data based on key research themes, including ve methodologies, implementation strategies, objectives, benefits, challenges, and existing research gaps. in order to ensure the information obtained is relevant and current for the reviewed studies, the literature search was restricted to the last 20 years (2005 to present). the analysis focused on research that explicitly addressed ve topics, including documented methodologies, case studies, and theoretical advancements. extracted data were systematically recorded, categorized, and analyzed to ensure alignment with the research objectives and to facilitate the identification of existing concepts and knowledge gaps. the conclusions drawn from this study are grounded in the synthesized evidence obtained through this methodological framework that address ve application, benefits and barriers, thereby ensuring objective of the research is met. table 2: keywords used for the literature search s/n literature search keywords number of hits 1 value engineering 43 2 construction projects 25 3 value engineering in construction projects 56 4 application of value engineering 24 5 application of value engineering in construction projects 28 6 benefits of value engineering 23 7 other approaches to value engineering 32 8 performance measurement of value engineering 12 9 barriers of value engineering practices in construction projects 12 10 efforts to improve value in tanzania’s construction projects 9 3. results and discussion 3.1 an overview of journals reviewed the search process identified approximately 70 peer-reviewed publications on the application of ve in construction projects, both globally and within tanzania. from these sources, detailed information was extracted on the applicability, benefits, and barriers of ve, as well as research gaps in value enhancement for http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 912 construction projects. these gaps point to the need for further investigation, particularly in developing countries, with a focus on tanzania. the majority of reviewed studies were published in journals specializing in engineering, construction, and project management. across the publications, ve consistently emerged as a critical management tool for optimizing value at any project stage, provided it is implemented in line with its fundamental principles. a synthesis of the most frequently cited works 32 articles representing 45% of the total, along with their leading journals is presented in table 3. among these, the international journal of construction management was identified as the most influential outlet, accounting for 25% of the top-ranked publications due to its strong emphasis on cost control, project optimization, and value creation, which directly align with ve principles. with regard to tanzania, findings revealed that only five of the 32 most-referenced articles (15.6%) specifically addressed ve in tanzanian construction projects, underscoring the limited research in this context. the results reveal that 87.5% of the most-referenced studies were published between 2015 and 2025, demonstrating that the literature incorporated into this review is recent, relevant, and methodologically robust. to further ensure relevance, the review applied the “10-year rule,” prioritizing publications less than a decade old, as summarized in table 3. overall, the review of leading journals and articles confirms that ve is widely applicable across diverse construction systems and project types, reinforcing its value as a strategic approach for improving project performance, particularly in resource-constrained environments such as tanzania. the reviewed studies on ve in construction projects span from 2006 to 2024, with a noticeable concentration of publications after 2016, reflecting growing global interest. the international journal of construction management and engineering, construction and architectural management emerge as the most frequent outlets, publishing several influential works on barriers, success factors, and benchmarking practices. other key contributors include the international journal of construction engineering and management, civil engineering journal, and regional journals such as the tanzania journal of engineering and technology and the africa habitat review journal, which highlight localized applications in africa. the recurring themes and their corresponding significance or insights as derived from the reviewed 32 top journals are as follows; ⚫ barriers and obstacles to ve adoption in developing countries (e.g., tanzania, egypt, ghana, kenya, saudi arabia). ⚫ frameworks and methodologies for implementing ve in construction projects. ⚫ performance and sustainability impacts, with emphasis on risk management, key performance indicators, and project delivery efficiency. ⚫ case studies demonstrating application in infrastructure, road, and government projects. geographically, the review covers africa (tanzania, ghana, egypt, kenya, rwanda), asia (saudi arabia, jordan, indonesia, iran), and broader international contexts, suggesting the subject’s global relevance but uneven adoption across regions. overall, the literature highlights a steady evolution from early conceptual discussions (2006–2013), toward practical applications and barriers analysis (2015–2020), and more recently, to integrated sustainability and performance models (2021–2024). 3.2 positive impacts of ve in construction projects findings from recent studies demonstrate that ve has significant positive impacts on construction projects, aligning with global trends in project delivery. beyond reducing costs and project duration, ve improves quality, enhances productivity, and supports sustainability goals (rania et al., 2023; alshehrin, 2020). within construction project management, ve is widely recognized as a structured methodology for achieving maximum value by balancing performance with cost efficiency (tanko et al., 2019). several studies further emphasize its role as an organized decision-making framework that facilitates systematic evaluation of project functions to ensure optimal outcomes (elsonoki et al., 2020). by reducing life cycle costs while maintaining or improving project value, ve contributes directly to national infrastructure development. this process typically requires a structured methodology led by an experienced facilitator, with the ultimate objective of minimizing total life cycle costs (janan et al., 2018). http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 913 table 3: list of top journals in the review s/n title of the journal article journal name year of publication 1 obstacles against value management practice in building projects of dar es salaam tanzania international journal of construction engineering and management 2017 2 value management as an efficient risk management tool international journal of advanced and multidisciplinary engineering science 2018 3 value management implementation barriers for sustainable building: a bibliometric analysis and partial least square structural equation modeling engineering, construction and architectural management 2021 4 barriers to the adoption of value management in developing countries engineering, construction and architectural management 2017 5 the methodology of using value engineering in construction projects management civil engineering journal 2016 6 a decade of value engineering in construction projects hindawi advances in civil engineering 2022 7 value in construction: an international study international journal of construction management 2006 8 the selection of benchmarking partners for value management: an analytic approach international journal of construction management 2007 9 principal component analysis of challenges facing the implementation of value engineering in public projects in developing countries international journal of construction management 2016 10 value engineering practices in infrastructure projects: a case study of ilam gas refinery's water transmission system at reno mountain, iran international journal of construction management 2017 11 key performance indicators of value management in the sri lankan construction industry international journal of construction management 2018 12 legal aspect of value engineering implementation in jakarta (indonesia) construction projects international journal of construction management 2018 13 a framework of an integrated sustainability and value engineering concepts for construction projects international journal of construction management 2020 14 critical success factors for value management techniques in construction projects: case in jordan international journal of construction management 2021 15 implementation of value engineering in construction project to reduce time of the project international research journal of engineering and technology (irjet) 2020 16 application of value engineering in construction projects journal of traffic and transportation engineering 2013 17 value engineering adoption’s barriers and solutions: the case of saudi arabia’s construction industry multidisplinary digital publishing institute (mdpi) 2024 18 an evaluation on application of value management in local government authorities construction projects in tanzania international journal of innovative science and modern engineering (ijisme) 2015 19 application of value management in conception of construction projects in rwanda international journal of innovative science and modern engineering (ijisme) 2024 20 assessments of the application of earned value management system for construction project performance measurement in zanzibar tanzania journal of engineering and technology 2023 http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 914 table 3 continued. s/n title of the journal article journal name year of publication 21 perceived benefits of using value engineering on road projects in ghana world journal of engineering and technology 2020 22 identification and analysis of key elements for improving construction management performance in tanzania international journal of construction engineering and management 2023 23 application of value engineering in construction projects journal of traffic and transportation engineering 2013 24 barriers of value management implementation for building projects in egyptian construction industry ain shams engineering journal 2020 23 barriers to the implementation of value management in small construction projects journal of building engineering 2022 24 evaluation of barriers to value management application in construction projects west africa built environment research (waber) conference 10th anniversary conference, 5-7 august 2019, accra, ghana 2019 25 value engineering and its application in civil engineering construction research congress 2018 2018 26 current and future trends of construction project performance models: a review tanzania journal of engineering and technology 2023 27 impact of value engineering on construction project management and achievement of sustainable development international research journal of innovations in engineering and technology (irjiet) 2023 28 value engineering techniques and its application in construction projects journal of engineering and applied sciences technology 2023 29 integrating theory and practice in value engineering within egypt’s construction industry journal of engineering and applied science 2024 30 the process of value engineering in construction projects in nairobi, kenya africa habitat review journal 2022 31 a model for enhancing the application of value management in construction projects in kenya journal of agriculture science and technology 2024 32 value management practices in construction industry: an analytical review the open civil engineering journal 2020 source: authors’ analysis (2025) http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz https://www.scirp.org/journal/journalarticles?journalid=2451 arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ako.terseer@yahoo.com 915 evidence also shows that ve accelerates project development by improving decision-making and addressing design-related issues early in the process (othman et al., 2020). research consistently highlights the precontract or pre-construction phase as the most suitable stage for ve implementation, since changes made at this point are less costly and have the greatest impact on value (madushika et al., 2020; surlan et al., 2016). ve is particularly effective once schematic designs are developed and cost estimates are available—typically when design completion reaches about 35% -as this enables the identification of potential savings before final design decisions are locked in (kelly et al., 2004). overall, the reviewed literature suggests that ve offers a universally applicable framework across different construction systems and project types. it facilitates the generation of detailed proposals, evaluation of alternative solutions, and definition of technical systems through the analysis of multiple design options. by involving key stakeholders such as contractors, designers, and project managers, ve ensures collaborative decision-making that maximizes cost efficiency, performance, and long-term project value. 3.3 barriers to ve implementation despite the numerous advantages of applying ve in construction projects, the findings reveal several persistent barriers that hinder its effective implementation. common challenges include limited knowledge and awareness of ve, cost-driven procurement systems, a shortage of trained professionals, and the absence of standardized problem-solving methods. in many regions, the novelty of the concept, limited adoption among contractors, reluctance to fully implement ve during projects, and a lack of qualified experts further constrain its application. additional barriers identified are low awareness among clients, weak stakeholder relationships, inadequate training, and the absence of locally adapted ve guidelines (tanko et al., 2019). institutional and managerial constraints also play a significant role. studies highlight insufficient support from both government agencies and top management as critical obstacles to widespread ve adoption (douglas et al., 2017). in developing countries, these challenges are more pronounced, where low awareness is compounded by high implementation costs, inappropriate procurement systems, rigid standards, lack of contractual provisions, poor communication, neglect of essential ve principles, and conflicts of interest (rwamuhinda, 2019). 3.4 regional/contextual findings for developing countries findings from the reviewed studies suggest that achieving construction project objectives at minimal cost while ensuring investment efficiency remains a major challenge in the development agendas of many developing countries. evidence indicates that these challenges can be addressed through the systematic application of ve at appropriate stages of the project life cycle (rad et al., 2016). maragara et al. (2024) identified team dynamics, procurement policies, government regulations, and ve knowledge as key predictors of ve application, while other studies highlight regional variations in awareness and implementation across developing nations. in tanzania, research shows that ve has not been formally integrated into any phase of construction projects, despite its recognized potential to maximize project value (mziray et al., 2015). kajumulo et al. (2023) identified seven critical factors influencing construction management: problem-solving ability, leadership skills of project managers, site conditions, material and equipment costs, planned construction time, and the availability of competent staff. these factors directly affect ve implementation, and addressing them is essential for promoting its adoption in tanzania and other developing countries facing similar challenges (othman et al., 2021). however, the critical linkage between the design, construction, and maintenance phases, where ve is most effective, remains largely absent (basondole, 2022). current practice in tanzania shows partial application of specific ve techniques. studies reveal that the industry has primarily engaged in value engineering change proposals (vecp) and value engineering audits (vea), though these are not yet formalized within standard construction contracts and often require client approval through contract variation orders (basondole, 2022). vecps allow contractors to submit proposals for modifying original contracts to improve value while sharing cost savings with clients (adhikari, 2013). veas, on the other hand, function as assurance mechanisms, systematically reviewing project objectives and functional performance to ensure that ve principles are properly applied in large-scale projects. over the past 15 years, tanzania has instead relied on value for money (vfm) assessments to guide project planning, procurement, and management (naot, 2024). while vfm has been widely adopted to evaluate http://www.azojete.com.ng/ mailto:ako.terseer@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 907-920. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: alberto.kindole@tarura.go.tz 916 whether construction investments deliver adequate returns, it is not equivalent to ve. as mahadik (2015) notes, ve offers greater potential to address persistent project challenges by enhancing decision-making and maximizing value across all project phases. overall, the findings indicate that despite the proven benefits of ve, tanzania lacks a formalized framework for its systematic implementation in construction projects. the current reliance on partial or alternative approaches limits the industry’s ability to optimize performance, underscoring the need for strategic policies and institutional support to strengthen ve adoption. 3.5 bridging theory and practices reviewed studies indicate that although elements of ve are applied in construction projects, execution remains inadequate, reflecting a substantial gap between theory and practice (waweru et al., 2022). closing this gap requires strengthening the role of educational institutions and professional training, enhancing public awareness and recognition of ve, and promoting its systematic integration at the early stages of the project lifecycle (abdelrahman et al., 2024). 3.6 recommendations and strategic solutions based on the overall research findings, two key recommendations for advancing ve practices in construction projects are: (i) integrating ve courses into engineering curricula to strengthen professional capacity, and (ii) introducing incentive clauses in construction contracts to encourage its systematic application. these recommendations are supported by alhumaid et al. (2024) and danku et al. (2020), who highlight ve as a critical tool in civil engineering and the construction industry, offering substantial benefits in cost savings and project performance improvement. despite persistent challenges in implementing ve, particularly in developing countries, recent studies reaffirm its importance, noting that its quantitative and qualitative benefits consistently outweigh the drawbacks, making it a worthwhile investment. to address barriers specific to developing contexts such as tanzania, three strategic solutions are identified as most impactful: (i) organizing conferences and seminars to facilitate knowledge sharing among construction professionals, (ii) developing localized guidelines to standardize ve studies, and (iii) enhancing client awareness and understanding of ve practices. together, these strategies provide a structured pathway for overcoming existing challenges and advancing the adoption of ve in the construction industry. 4. conclusion this study concludes that the adoption of value engineering (ve) in construction projects across developing countries remains limited, largely due to inadequate awareness, a shortage of trained professionals, and weak institutional support. in tanzania, the use of alternative approaches such as the value engineering contractor’s proposal (vecp) and value engineering audit (vea) is neither formalized nor aligned with internationally recognized ve standards. as a result, ve application often depends on the discretion of clients or top management rather than being systematically integrated into construction contracts. furthermore, restrictive government regulations and rigid contract management procedures continue to impede its wider implementation. additionally, incorporating a dedicated ve clause in all construction contracts and piloting ve-based projects can create a foundation for its broader adoption. given ve’s proven ability to optimize cost, quality, time, and stakeholder satisfaction, institutionalizing 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value engineering in construction projects in nairobi, kenya. africa habitat review journal, issn: 2524-1354 (online), issn: 2519-7851 (print) volume 17 issue 1 (december, 2022) http://uonjournals.uonbi.ac.ke/ojs/index.php/ahrenya. yanita, r. and mochtar, k. 2018. legal aspect of value engineering implementation in jarkata (indonesia) construction projects. international journal of construction management, 21(21),131-139. http://www.azojete.com.ng/ mailto:alberto.kindole@tarura.go.tz http://uonjournals.uonbi.ac.ke/ojs/index.php/ahrenya corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 367 arid zone journal of engineering, technology & environment original research article response surface modeling of soil moisture content under different tillage conditions nwachukwu c.p1*., umobi c.o1., okpala c.d1., nwanna e.c1. 1department of agricultural and bioresources engineering, nnamdi azikiwe university, awka. *corresponding author’s email: cp.nwachukwu@unizik.edu.ng article information abstract this study investigates the impact of three key factors irrigation deficit percentage, npk application rate, and tillage on soil moisture content, a crucial parameter in agricultural productivity. to achieve this, a field experiment was conducted at nnamdi azikiwe university's department of agricultural and bioresources engineering experimental site/farm workshop, awka. the experiment utilized a central composite design in response surface methodology, incorporating three factors: irrigation deficit percentage, npk application rate, and tillage. this design enabled the researchers to examine the individual and interactive effects of these factors on soil moisture content. the results of the study revealed that the model was highly significant, with an r-squared value of 0.9084. this indicates that approximately 91% of the variation in soil moisture content could be explained by the model. furthermore, the analysis showed that irrigation deficit percentage, npk application rate, and tillage were all significant factors influencing soil moisture content. however, the interaction terms between these factors were found to be non-significant. a key outcome of this study was the development of predictive models for soil moisture content under different tillage conditions, namely no tillage, conservative tillage, and conventional tillage. these models could be employed to forecast soil moisture content for specified levels of irrigation deficit percentage and npk application rate under each tillage condition. the findings of this research provide valuable insights into the effects of irrigation deficit percentage, npk application rate, and tillage on soil moisture content. these insights could be applied to inform agricultural practices in similar regions, ultimately contributing to improved crop yields and sustainable agricultural management. received: 4th december 2024 revised: 18th march 2025 accepted: 18th march 2025 keywords: tillage irrigation deficit npk application rates soil moisture content central composite design response surface methodology © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction water availability is a significant threat to crop production and food security, with only 4% of sub-saharan africa's arable land being irrigated (kang et al., 2009; acpc, 2011). as a result, agriculture in the region is predominantly rain-fed, making it highly vulnerable to climate variability and change. agriculture is the primary source of livelihood and gross domestic product (gdp) in many african countries, making it the most vulnerable sector to climate change and variability (mendelson et al., 2008). climate change poses a significant threat to sustainable development in southeastern nigeria, with expected impacts on agriculture and established farming systems (gornall et al., 2010). climate change is defined as statistically significant variations in climate parameters, such as temperature and precipitation, that persist for extended periods (eboh, 2009). these changes can manifest in various ways, including shifts in average climate conditions, increased climate variability, and altered frequency and magnitude of weather events. the impacts of climate change on agriculture are far-reaching, with expected changes in temperature, rainfall, ultra-violet radiation, and carbon dioxide levels affecting crop yields and food availability (adamgbe and ujoh, 2013). long-term shifts in seasonal climatic patterns and increased intensity of weather extremes are already disrupting agriculture, with significant implications for food security. azojete june 2025. vol.21(2):367-375 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/005 www.azojete.com.ng mailto:cp.nwachukwu@unizik.edu.ng mailto:cp.nwachukwu@unizik.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 367-375. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 368 regions with predominantly rural economies and low levels of agricultural diversification, such as the southeastern region of nigeria, are at greater risk. the region's dependence on rain-fed agriculture, poor technology, low finance, and limited capacity to adapt to changing climatic conditions exacerbate its vulnerability. nigeria's agricultural production has not kept pace with food production in recent decades, and there is a risk of further decline due to climatic factors (chikezie et al., 2015). climate change is a global issue, but its impacts are more severe in developing countries, which have limited human, institutional, and financial capacity to adapt (unfcc, 2007). the consequences of climate change on food availability are significant, with increased intensity of storms, drought, and flooding, altered hydrological cycles, and precipitation variance all having implications for future food security (fao, 2007). abbaspour-gilandeh and sedghi (2015) and vaitauskienė et al. (2017) characterize soil as a vital three-phase mixture consisting of solid particles, liquid water, and air. the interaction between soil and tillage tools plays a crucial role in determining tillage resistance and the overall quality of agricultural machinery performance. this relationship is essential when designing and optimizing tillage equipment (li et al., 2018; zhao et al., 2017; zeng et al., 2017). the complexity of the tillage process can be attributed to various factors, including soil composition, the dynamic properties of the machinery, and the adhesion and fragmentation of soil particles. the properties of soil, while intricate, are primarily shaped by tillage methods, composition, and moisture levels, among other influences (schmalz et al., 2013; matin et al., 2016; wang et al., 2019; holthusen et al., 2020). soil moisture, defined as the water retained in an unsaturated zone, is critical for eco-hydrological processes. it significantly affects ecosystem development, plant growth, runoff responses, and the distribution of precipitation between evapotranspiration and deep infiltration (hillel, 1998; chaney et al., 2015; he et al., 2012. it is a key factor for ensuring stable crop growth (lin et al., 2005; peng et al., 2017), with its dynamics influenced by precipitation, evaporation, and soil properties such as density, porosity, and texture (zucco et al., 2014). as a critical link between the edaphic zone and the atmosphere, soil moisture interacts significantly with the climate system, influencing both evapotranspiration and soil erosion in sloping areas. a comprehensive understanding of soil moisture dynamics is essential for analyzing changes in hydrothermal conditions, as well as the horizontal variations in moisture content, such as runoff during tillage (he et al., 2012; seneviratne et al., 2010). soil moisture tends to fluctuate spatially and temporally due to numerous factors, including climate variability, soil heterogeneity, tillage practices, and rainfall patterns (jia et al., 2017; 2018; zucco et al., 2014). tillage serves as an important agricultural practice that enhances soil properties and boosts grain yield (munkholm et al., 2013; pires et al., 2017). it has a profound impact on growing conditions, soil moisture content, and overall crop performance, primarily by improving the chemical, physical, and biological attributes of the soil (de cárcer et al., 2019; dekemati et al., 2019; romaneckas et al., 2011; wozniak, 2020). this study aims to simulate soil moisture content under various tillage practices, specifically considering irrigation deficits and differing npk application rates through response surface methodology. 2. materials and method 2.1 study area a field experiment was conducted at the nnamdi azikiwe university's department of agricultural and bioresources engineering experimental site/farm workshop, awka. the experimental site is located within the geographical coordinates of 6°15'11.8"n 6°15'5.3"e latitude and 7°7'118"n 7°7'183"n longitude, with an altitude of 142m. the site has distinct geographical characteristics, including sandy loam soil, savanna grassland vegetation, imo shale geologic formation, and drainage from the anambra river and its tributaries. the local climate is characterized by two distinct seasons: a dry season with high evapotranspiration and a rainy season with reduced evapotranspiration. the annual climatic averages include rainfall of 1,500-1,600mm, wind speed of 1.73kmph, and relative humidity of 77%. the experimental site covers an area of 5,227.08 square meters, and the study was carried out from november 27, 2017, to february 22, 2018. 2.2 field preparation the experimental field was situated on level ground and divided into three sections: a, b, and c. each section measured 27m x 27m and was leveled for uniformity. three tillage treatments were applied: conventional tillage in plot a, conservative tillage in plot b, and zero tillage in plot c. a central composite design (ccd) http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 367-375. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 369 was used to accommodate categorical and numeric factors. the design included two numeric factors (irrigation deficit and npk application) and one categorical factor (tillage). the layout consisted of three plots, each containing nine subplots. the experimental design involved varying tillage methods, irrigation deficit levels, and npk fertilizer rates. the 27 subplots (3m x 3m each) were equipped with a drip irrigation system. weather data were obtained from the nigerian meteorological agency (nimet), and average subplot readings were used for analysis. this experimental setup enabled a comprehensive evaluation of the effects of tillage, irrigation deficit, and npk application soil moisture content. the land preparation was done using mahindra tractor, the tillage implements were plough and harrow. 2.3 soil moisture content soil moisture readings were taken daily at various depths (0-25cm, 25-50cm, 50-75cm, and 75-100cm) across different blocks throughout the crop growth period, using a soil moisture meter to measure the moisture content profiles at these specified depths. 2.4 experimental design the experiment was designed with various levels of tillage, npk application rates and irrigation deficits as presented in table 1 table 1: independent variables and levels used for response surface design independent variable symbols ranges and levels -1 0 +1 irrigation deficit(%) a 10 30 50 npk aplication rate (kg/ha) b 400 500 600 tillage c 1 2 3 3. results and discussion 3.1 development of regression model central composite design (ccd) was used to optimize properties. the statistical combination of the independent variables along with the experimental response are presented in table 2. table 3 shows the analysis of the sequential model sum of squares for soil moisture content. it is a statistical technique used to evaluate the fit of different polynomial models (linear, quadratic, cubic) to the data. from table 3, the linear vs mean model is significant (p-value < 0.0001), indicating that a linear relationship between the variables is a good fit for the data. the 2fi (2-factor interaction) vs linear model is not significant (p-value = 0.6834), suggesting that adding interaction terms between variables does not improve the model fit. the quadratic vs 2fi model is also not significant (p-value = 0.2641), indicating that adding quadratic terms does not improve the model fit. the cubic vs quadratic model is aliased, meaning that the cubic terms are not estimable due to a lack of data. the analysis suggests that a linear model is the best fit for the soil moisture content data. http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 367-375. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 370 table 2: experimental setup for 3 level factorial response surface design factor 1 factor 2 factor 3 response std run a: irrigation b: npk c:tillage soil moisture deficit % application rate content °c kg/ha 22 1 50 600 3 10.93 17 2 30 600 2 9.25 10 3 10 400 2 11.31 18 4 30 500 2 9.11 23 5 10 500 3 12.01 24 6 50 500 3 10.28 7 7 30 400 1 12.4 21 8 10 600 3 12.57 14 9 10 500 2 10.12 25 10 30 400 3 10.39 8 11 30 600 1 13.5 2 12 50 400 1 11.31 12 13 10 600 2 12.88 20 14 50 400 3 9.37 4 15 50 600 1 12.14 11 16 50 400 2 9.24 19 17 10 400 3 11.6 3 18 10 600 1 14.96 27 19 30 500 3 11.21 13 20 50 600 2 9.82 16 21 30 400 2 10.29 5 22 10 500 1 14.06 1 23 10 400 1 13.6 15 24 50 500 2 9.89 26 25 30 600 3 12.35 6 26 50 500 1 11.91 9 27 30 500 1 12.72 1, 2 and 3 represents no tillage, conservative tillage and conventional tillage respectively. 3.2 statistical analysis for soil moisture content table 3: sequential model sum of squares soil moisture content sources sum of squares df mean square f-value p-value mean vs total 3549.39 1 3549.39 linear vs mean 57.75 4 14.44 36.97 < 0.0001 suggested 2fi vs linear 1.33 5 0.2666 0.6244 0.6834 quadratic vs 2fi 1.18 2 0.5904 1.46 0.2641 cubic vs quadratic 3.59 8 0.4493 1.27 0.3843 aliased residual 2.48 7 0.3548 total 3615.74 27 133.92 table 4 presents the results of an analysis of variance (anova) for a response surface methodology (rsm) experiment. the experiment involves three factors: irrigation deficit percentage (a), npk application rate (b), and tillage (c). the table shows that the model is highly significant (p-value < 0.0001), indicating that the factors and their interactions have a significant impact on the response variable. the r-squared value (0.9084) indicates that about 91% of the variation in the response variable is explained by the model. http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 367-375. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 371 table 4: analysis of variance (anova) for the fitted quadratic model for soil moisture content source sum of squares df mean square f-value p-value model 60.27 11 5.48 13.52 < 0.0001 significant a-irrigation deficit% 17.74 1 17.74 43.78 < 0.0001 b-npk application rate 4.65 1 4.65 11.48 0.0041 c-tillage 35.36 2 17.68 43.63 < 0.0001 ab 0.0374 1 0.0374 0.0923 0.7654 ac 0.2812 2 0.1406 0.3470 0.7123 bc 1.01 2 0.5073 1.25 0.3142 a² 0.6468 1 0.6468 1.60 0.2257 b² 0.5340 1 0.5340 1.32 0.2689 residual 6.08 15 0.4052 cor total 66.34 26 std. dev. 0.6366 r² 0.9084 mean 11.47 adjusted r² 0.8412 c.v. % 5.55 predicted r² 0.6726 adeq precision 13.5567 among the individual factors, irrigation deficit percentage (a), npk application rate (b), and tillage (c) are all significant, with p-values less than 0.0041. however, the interaction terms between these factors are not significant, indicating that the effects of these factors on the response variable are independent of each other. figure 1: diagnostics plots of the fitted quadratic model for soil moisture content investigation on residuals to validate the adequacy of the model used was performed; residual is the difference between the observed response and predicted response. the plot of actual versus predicted (fig 1) is used to examine the effects. figure 1 shows that there is a very good correlation between the observed value and the value predicted by the model, the model does not show any variation of the constant variance 3.3 model equation for soil moisture content soil moisture content (no tillage) = 19.13667 0.093625a 0.023079b 0.000028a * b + 0.000821a² + 0.000030 b² 1 http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 367-375. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 372 the equation (3.1) can be used to make predictions about the response for given levels of each factor for soil moisture content (no tillage). soil moisture content (conservative tillage) = 17.97528 0.079208a 0.027146b 0.000028a * b + 0.000821a² + 0.000030b² 2 the equation (3.2) can be used to make predictions about the response for given levels of each factor for soil moisture content (conservative tillage). soil moisture content (conventional tillage) = 16.2088 0.081958a 0.021512b 0.000028a * b + 0.000821a² + 0.000030b² 3 eliminating the non-significant terms: soil moisture content (no tillage) = 19.13667-0.093625a-0.023079b-0.000028a*b 4 soil moisture content (conservative tillage) = 17.97528 0.079208a 0.027146b 0.000028a * b 5 soil moisture content (conventional tillage) = 16.2088 0.081958a 0.021512b 0.000028a * b 6 these equations are predictive models for soil moisture content under different tillage conditions: no tillage, conservative tillage, and conventional tillage. each equation is a quadratic polynomial that describes how soil moisture content changes in response to two factors: irrigation deficit percentage (a) and npk application rate (b). the equations include linear, interaction, and quadratic terms to capture the relationships between these factors and soil moisture content. the coefficients in the equations represent the changes in soil moisture content resulting from changes in the factors. for instance, a negative coefficient for a factor indicates that an increase in that factor leads to a decrease in soil moisture content. the equations can be used to make predictions about soil moisture content for given levels of irrigation deficit percentage and npk application rate under each tillage condition. the simplified equations (4-6) eliminate non-significant terms, providing a more streamlined model for predictions. the equations can be used to make predictions about the response for given levels of each factor for soil moisture content. table 5: optimization of soil moisture content using response surface methodology number irrigation deficit (%) npk application rate (kg/ha) tillage soil moisture content (%) desirability 1 11.594 596.406 2 10.396 1.000 selected 2 14.127 600.000 2 10.236 0.989 3 10.000 600.000 3 10.136 0.196 4 10.000 599.010 3 12.123 0.196 5 10.000 598.295 3 12.113 0.196 6 10.940 600.000 3 12.060 0.190 7 10.000 585.000 3 11.933 0.188 8 10.000 576.223 3 11.820 0.181 9 10.000 565.000 3 11.683 0.171 10 15.638 600.000 3 11.699 0.158 the responses of the variables in table 5 were generated by design expert 11.0 software for the optimization based on the model obtained and the experimental data input. from table 5, the run 1 order gave the optimum condition and was selected, the selected marked in run 1 order shows that it contains the best optimization results. the value obtained for moisture content in run 1 order was closed to the value obtained by hossene et al., (2015), in which they recorded soil moisture contents for silt loam soil and sandy loam soil values ranging from 7% to 8%. runs 2-10 recorded desirability less than 1, desirability ranges from 0 to 1 for any given response, a value of 1 represents the ideal case, and a zero indicates that one or more responses fall outside desirable limits. the optimum values based on the run 1 order showed soil moisture content of 10.396%. http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 367-375. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: cp.nwachukwu@unizik.edu.ng 373 table 6: optimized and observed values tillage irrigation deficit (%) npk application rate (kg/ha) soil moisture content (%) optimized parameters conservative 11.594 596.406 10.396 observed parameters conservative 7 500 14 the values in run 1 order were used for optimization and observations recorded in table 6. conservative tillage, 7%, 500kg/ha and 14% were obtained as the optimum values for tillage practice, irrigation deficit, npk application rates and soil moisture content respectively. according to broadbent (2015), conservative tillage was also selected as the best tillage method, alteri (2011) also observed conservative tillage to be the best tillage method because it creates suitable soil environment for crop growth, and conserves soil and water energy through the reduction in tillage intensity. table 7: evaluation results evaluation metrics r2 rmse d cp1 a value 0.86 0.92 0.74 0.26 from the evaluation results in table 7; 0.86, 0.92, 0.74 and 0.26 were obtained for coefficient of determination (r2), root mean square error (rmse), index of agreement (d), and coefficient of performance (cp1 a) respectively. the value of 1 for the coefficient of determination means that the dispersion for prediction is equal to that of the observation, r2 value up to 0.6 is acceptable but r2 value of 0.86 was obtained in the evaluation which is a high coefficient of determination. root mean square error has a better agreement close to 0.0 (el-sadek et al, 2003), rmse value of 0.92 was obtained in the evaluation and this is within the acceptable range of rmse. the index of agreement falls between 0 and 1 (yaun et al, 2008), d value of 0.74 obtained in the evaluation is acceptable. coefficient of performance approaches zero as the observed and predicted values get closer, cp1 a value of 0.26 obtained in the evaluation is within acceptable range. 4. conclusion this study investigated the effects of irrigation deficit percentage, npk application rate, and tillage on soil moisture content. the experiment was conducted at nnamdi azikiwe university's department of agricultural and bioresources engineering experimental site/farm workshop, awka. the results showed that the model is highly significant, indicating that the factors and their interactions have a significant impact on soil moisture content. the r-squared value indicates that about 91% of the variation in soil moisture content is explained by the model. the individual factors, irrigation deficit percentage, npk application rate, and tillage, were all significant, indicating that they have a significant impact on soil moisture content. however, the interaction terms between these factors were not significant. the study developed predictive models for soil moisture content under different tillage conditions: no tillage, conservative tillage, and conventional tillage. these models can be used to make predictions about soil moisture content for given levels of irrigation deficit percentage and npk application rate under each tillage condition. the simplified models eliminate non-significant terms, providing a more streamlined model for predictions. overall, the study provides valuable insights into the effects of irrigation deficit percentage, npk application rate, and tillage on soil moisture content, and can be used to inform agricultural practices in similar regions. references acpc (economic commission for africa) 2011. climate change and agriculture: analysis of knowledge gaps and needs. united nations economic commission for africa, working paper 7. abbaspour-gilandeh, y. and sedghi, r. 2015. predicting soil fragmentation during tillage operation using fuzzy logic approach. j terramechanics, 57: 61-69 adamgbe, em. and ujoh, f. 2013. effect of variability in rainfall characteristics on maize in gboko, nigeria. journal of environmental protection, 4: 881-887 alteri, ma., lana, ma., bitterncon, h., kieling, as., comin, ll. and loveto, pe. 2011. enhancing crop productivity via weed suppression in organic n0-till cropping systems in santacliforni.brasil j. sustain agric., 35: 1-15 http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; 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143: 130–138. zhao sh., liu hj., tan hw., cao xz., zhang xm. and yang yq. 2017. design and performance experiment of opener based on bionic sailfish head curve. transactions of the chinese society of agricultural engineering. 33: 32–39. zucco, g., brocca, l., moramarco, t. and morbidelli, r. 2014. influence of land use on soil moisture spatialtemporal variability and monitoring. j. hydrol., 516: 193–199. http://www.azojete.com.ng/ mailto:cp.nwachukwu@unizik.edu.ng corresponding author’s email address: immyjm@gmail.com 286 arid zone journal of engineering, technology & environment original research article physical properties of guinea corn stalk fibre reinforced highdensity polyethylene (hdpe) composite for the production of particle board e. james*, i. s. aji, and m. dauda department of mechanical engineering university of maiduguri, borno state, nigeria. *corresponding author's email address: immyjm@gmail.com article information abstract majority of developing nations view the construction/manufacturing sector as being crucial to their economy. the industry produces panels and boards for furniture, ceilings, panelling, and other wood-based manufactured projects, relying solely on forest resources. this heavy dependence strains forests, contributing to deforestation and causing prolonged damage to ecosystems. a major interest in finding substitute raw materials for the manufacture of boards and panels through the utilization of agricultural waste products, is becoming the direction to scholars. in this study, guinea corn stalk fibre reinforced high density polyethylene (hdpe) composite was developed and analysed for the production of particle board. the composites were produced through the process of compounding and compression moulding operation. the hdpe was varied from 100 50 wt % at interval of 10 wt % while the filler was reversed from 10 50 wt % at interval of 10 wt %. five different composites samples were formulated using 250 μm fibre size using hdpe as binder and a 100 % hdpe as control sample. the physical (density, thickness swelling and water absorption) properties of the developed composite were evaluated. the density (ranges from 943.9 kg/m³ to 1075.5 kg/m³), thickness swelling (3.13% to 18.75%), and water absorption (0.28% to 2.01%) of all the composites increased with increasing filler loading with highest values obtained at 50 wt % material loading. all the values are within the minimum requirement stipulated in the european standard en 312:2010 for general purpose particle boards except for the density which is above the standard. the incorporation of the fillers into the hdpe matrix generally enhanced the physical properties of the matrix. the guinea corn stalk fibre (gcsf) composite produced with 60 wt % matrix and 40 wt % filler is the most suitable for general purpose particle board production as all the physical properties met the required standard stipulated in the european standard en 312:2010 for general purpose particle board. received: 5th december 2024 reviewed: 11th february 2025 accepted: 12th february 2025 keywords: agricultural waste particle board thickness swelling matrix composite polymer © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction particle board is a versatile and economical material composed of wood chips, sawdust, and synthetic resins or other binders. traditionally, its production depends on wood residues from sawmills and wood-processing industries (yadav, 2021). however, growing concerns about deforestation, waste management, and environmental sustainability have prompted the search for alternative raw materials. one promising option is agricultural waste, which includes residues from crops like rice husks, wheat straw, sugarcane bagasse, and corn stalks (odeyemi et al., 2020). these are used to reinforce polymeric materials as reviewed by aji et al. (2009). for example, charles et al. (2024) used balanite shell particles and palmyra fiber to reinforce epoxy for the production of a low to medium load application hybrid material, aji et al. (2011) used kenaf and pineapple leave fiber to reinforce high density polyethylene (hdpe). agricultural waste, also known as agro-residue, is a byproduct of farming and agricultural processes. these residues are often burned or left to decompose in the fields, causing environmental pollution and greenhouse gas emissions. using agricultural waste for particle board production offers several advantages: abundant supply, cost-effectiveness, and azojete march 2025. vol.21(1):286-293 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:immyjm@gmail.com mailto:immyjm@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 287 environmental benefits. these residues are produced in large quantities worldwide (lee et al., 2022). using this biomass can provide a sustainable and renewable raw material source for particle board production. agricultural waste is typically low-cost because it is a byproduct of existing agricultural activities mostly left behind as waste by farmers and when used by the industries, it can lower the overall production costs compared to traditional wood-based materials. moreover, using agricultural waste helps to reduce the pressure on our forests, mitigating deforestation and promoting sustainable land use. it also addresses waste management issues by diverting agro-residues from landfills and reducing open burning, which contributes to air pollution (lee et al., 2022). the majority of developing nations view the construction/manufacturing industries as being crucial to their economy. these industries produce panels and boards for furniture, ceilings, paneling, and other wood-based manufacturing projects exclusively from forest resources (amenaghawon et al., 2016). the nigerian industry has seen progressive expansion in the last few years and in the early 1990s, the demand for wood and wood-derived panels/boards was expected to reach 2.866 million m3 and 0.121 million m3, respectively. however, it was predicted that in the next 20 years these values will rise to 4.704 million m3 and 0.688 million m3, respectively (atoyebi et al., 2018). a major interest in finding substitute raw materials for the manufacture of boards and panels has arisen from the desire to lessen reliance on wood and forest resources. researchers have identified some solutions to this problem; among them is the utilization of agricultural waste products, such as sugarcane bagasse, corncob, bamboo, rice husk, sunflower stalk, cashew shells, banana leaves, etc as an alternative (atoyebi et al., 2020) most of these agricultural wastes are left on the farm following the harvest of the intended crops. in most underdeveloped and developing countries such as nigeria, these wastes have very little reuse potential and they are mostly disposed of inappropriately or openly burnt (atoyebi et al., 2020). utilization of agricultural waste present prospective benefits both environmentally as well as economically. they are affordable, abundantly available, and resource-oriented when handled judiciously and the environmental problems associated with inappropriate disposal are minimized or eliminated (amenaghawon et al., 2013). bio-materials have more advantages over their synthetic counterparts: low cost, high toughness, low density, good specific strength properties, good processability, and biodegradability (seth et al., 2018). this study, therefore, developed particle board from composite of guinea corns stalk fibre and hdpe. 2. materials and methods 2.1 materials the materials used in this work were: i. guinea corn stalk fibre ii. high density polyethylene (hdpe) injectable grade dried guinea corn stalk and hdpe were employed in this study. the dried guinea corn stalk was obtained from farms within maiduguri metropolitan council, borno state while the hdpe was obtained from hafson chemicals and scientific equipment ltd, zaria, kaduna state nigeria. 2.2 equipment the equipment used in this study are presented in table 1: table 1: list of equipment used s/n equipment model number use/function 1 milling machine model no 150 milling the materials into smaller fibres/particles 2 electrical standard sieve machine model d210 sieving the materials 3 digital weighing balance model weighing the materials and samples 4 two-roll mill machine model: 5183 compounding composite into homogenous mix 5 compression moulding machine model: 0557 compressing composite into mould http://www.azojete.com.ng/ mailto:immyjm@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 288 2.3 method this section describes processes and basis of achieving the aim of this work. seth et al., (2018) deduced that the smaller the particle size the better the properties of the composite because better compaction is achieved and it lessen porosity which permits effective stress transfer between the matrix and the particles. similar result was reported by obasi et al., (2021), hammajam et al., (2014) and aji et al., (2011) which influence the decision of using 250 μm sizes for the guinea corn stalk fibre. 2.3.1 guinea corn stalk fibre (gcsf) preparation the guinea corn stalks were sorted out and the leaves were removed from the stalks to obtain clean and leaves free stalks. the guinea corn stalks were then sun dried and cut into smaller pieces between 10 to 30 cm and was further dried for three hours at 70 °c in oven before introducing into the milling machine to mill into fine material. the fine milled material was sieved using an electrical standard sieving machine for 15 minutes to obtain 250 μm fibre size as presented in plate 1. plate 1: guinea corn stalk fibre (after milling) 2.3.2 formulation of composite the hdpe was varied from 100 50 wt % at interval of 10 wt % i.e. (100 wt %, 90 wt %, 80 wt %, 70 wt %, 60 wt % and 50 wt %) while the gcsf was varied from 10 – 50` wt % at interval of 10 wt % i.e. (10 wt %, 20 wt %, 30 wt %, 40 wt % and 50 wt %). five different types of composites samples were formulated and a 100 % hdpe served as controlled sample. 250 μm fibre size in hdpe binder were used. table 2 presents the composition of the composite. table 2: formulation of composites s/n designation material composition 1 s0 hdpe (100 wt %) 2 gcsf1 guinea corn stalk + hdpe hdpe (90 wt %) + gcsf (10 wt %) 3 gcsf2 guinea corn stalk + hdpe hdpe (80 wt %) + gcsf (20 wt %) 4 gcsf3 guinea corn stalk + hdpe hdpe (70 wt %) + gcsf (30 wt %) 5 gcsf4 guinea corn stalk + hdpe hdpe (60 wt %) + gcsf (40 wt %) 6 gcfs5 guinea corn stalk + hdpe hdpe (50 wt %) + gcsf (50 wt %) 2.3.3 production of composite the composite materials were mixed according to the formulation in table 2 by first introducing the polymer (hdpe) to the two-roll mill to soften for 5 minutes at a temperature of 170 °c to achieve a band and bank formation after which the prepared guinea corn stalk particles were introduced gradually and allowed to mix http://www.azojete.com.ng/ mailto:immyjm@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 289 further for 3 minutes to compound into a homogenous mixture. to produce the composite particle boards for test, the compounded mixtures were compressed into a 120 mm × 100 mm x 3.2 mm mould at 150 °c for five minutes under a 2.5 mpa pressure provided by hydraulic hot press (compression moulding machine). plate 2: composite samples from guinea corn stalk composite 2.4 characterization of the composites the composites samples produced were subjected to physical test (density, thickness swelling and water absorption test). 2.4.1 determination of composite’s density (d) the density is the quotient of mass and volume of the piece. it is measured in kg /m3. the basic method of determining the density of board composite samples is by measuring the mass and volume of the sample used. the density of the boards was estimated from equation 1. the test was carried out in accordance with astm d1037. 𝐷 = 𝑀 𝑉 (1) where: d = density, kg/m3, m = mass of the test specimen, g and v = volume of the test specimen, m3 2.4.2 thickness swelling (ts) and water absorption (wa) test the thickness swelling is the ratio of the difference between the thickness of the piece after the water immersion and before the water immersion, to the thickness before the water immersion, it is expressed in percentage. the specimens prepared for evaluation of the thickness swelling were measured at the middle with a micrometer and immersed into distilled water at room temperature in parallel for 7 days. the thickness was measured again upon removal from the water and cleaning the surface water at an interval of 24 hours to determine the thickness swelling rate using equation 2. the test was carried out in accordance with astm d570. ts = 100 𝑥 (𝑇 − 𝑇𝑜) 𝑇𝑜 (2) where: ts = the thickness swelling rate (%), to= the initial thickness, t = the thickness measure after a given immersion time. the water absorption is the ratio of the difference between the wet piece mass and the dried piece mass before immersion, divided by the dried piece mass before immersion. it is expressed as the percentage of increment with respect to its weight before immersion. to determine the water absorption rate, each sample http://www.azojete.com.ng/ mailto:immyjm@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 290 piece was weighed with the aid of digital weighing balance before immersion in distilled water at room temperature for 7 days. the samples were weighed upon removal from the water and drying the surface water at interval of 24hrs of immersion for 7 day to determine the water absorption rate. the percentages were determined using equation 3. the test was carried out in accordance with astm d570. 𝑊𝐴 = 100 𝑥 𝑊 − 𝑊𝑜 𝑊𝑜 (3) where: wa(t) = the water absorption (%) at time t, wo = the initial weight, and w(t) = the weight of the sample at a given immersion time t. 3. results and discussion 3.1 determination of density the results obtained for density of gcsf composites presented in figure 1 reveal that the composite’ density increases with increased filler loading as observed by neher et al. (2020). the densities of the composites at all filler loadings exceed the range of 450–750 kg/m³ specified by the european standard en 312:2010 (p1: general-purpose particle boards for use in dry conditions). this suggests that the composite is unsuitable for general-purpose particle boards. however, the higher density may enhance mechanical properties such as stiffness and strength, making the material more suitable for applications that demand denser boards, including flooring systems, wall panels, partitions, and packaging crates. figure 1: effect of filler loading on the density of gcsf composites 3.2 thickness swelling (ts) and water absorption (wa) test 3.2.1 thickness swelling (ts) figure 2 show that as filler loading increases, the thickness swelling increases. this is because the fillers introduced hydrophilic groups into the polymer matrix, increasing its affinity for water and causing it to absorb more moisture, leading to higher swelling. kufojiri et al., (2023) also observed that the hydrophilic nature of the filler contributes to increased water absorption in the composites, which could lead to greater thickness swelling as the filler content increases. 0 200 400 600 800 1000 1200 std 0 10 20 30 40 50 d en si ty k g /m 3 filler loading (wt %) standard (std) s0 gcsf http://www.azojete.com.ng/ mailto:immyjm@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 291 figure 2: effect of filler loading on thickness swelling of gcsf composites the thickness swelling of the composite in all the filler loading are below the 18 % maximum acceptable value stipulated by european standard en 312:2010 (p1: general purpose particle boards for use in dry condition) except for composite at 50 wt % filler loading (18.75 %), which is slightly above the acceptable value stipulated. the high thickness swelling of the composite limits its use in applications where thickness swelling resistance is critical. this means that composites made from gcsf have a tendency to swell significantly when exposed to moisture or humidity. as a result, these composites are not suitable for outdoor applications especially where precise dimensions are critical or where the material will be exposed to varying environmental conditions. 3.2.2 water absorption (wa) test the results obtained is presented in figure 3. it demonstrates increase in water absorption with increasing filler loading as observed by (ferede 2020). this could be attributed to the phenomenon that as the filler loading increases, so does the surface area of the fillers available for water molecules to attach to, leading to increased water absorption. figure 3: effect of the filler loading on water absorption of gcsf composite gcsf are hydrophilic, meaning they have an affinity for water. their ability to create hydrogen bonds with water molecules is attributed to their hydroxyl groups (oh-) (neher et al., 2020). the water absorption of the composite in all filler loading is below the 7 % maximum acceptable value stipulated by european standard en 312:2010 (p1: general purpose particle boards for use in dry condition). 0 5 10 15 20 std 0 10 20 30 40 50 t h ic k n es s s w el li n g ( % ) filler loading (wt %) standard (std) s0 gcsf 0 1 2 3 4 5 6 7 8 std 0 10 20 30 40 50 w at er a b so rp ti o n ( % ) filler loading (wt %) standard (std) s0 gcsf http://www.azojete.com.ng/ mailto:immyjm@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 292 4. conclusion the following conclusions were drawn: i. based on the observed physical properties (density, thickness swelling, and water absorption) of the gcsf composite, the optimum composition (proportion) for the particle board composite is achieved with a 60 wt % matrix and 40 wt % filler loading. ii. the thickness swelling and water absorption properties of the produced gcsf composite met the minimum requirement of the european standard en 312:2010 (p1: general purpose particle boards for use in dry conditions). while the obtained density values surpass the acceptable range (750 kg/m3) specified for general-purpose particle boards. iii. the formulated composites were characterized in terms of density (ranging from 943.9 kg/m³ to 1075.5 kg/m³, thickness swelling (3.13% to 18.75%), and water absorption (0.28% to 2.01%). the results indicate that incorporating fillers into the hdpe matrix significantly enhanced its physical properties, making it a suitable composite for particle board production. references aji, i.s., zainudin, e.s., khalina, a., sapuan, s.m., and khairul, m. d. 2011. studying the effect of fiber size and fiber loading on the mechanical properties of hybridized kenaf/palf-reinforced hdpe composite. journal of reinforced plastics and composites, 30(6): 546–553. https://doi.org/10.1177/0731684411399141 aji i.s., sapuan s.m., zainudin e.s. and abdan k. 2009. kenaf fibres as reinforcement for polymeric composites; 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(2011. studying the effect of fiber size and fiber loading on the mechanical properties of hybridized kenaf/palf reinforced hdpe composite; journal of reinforced plastics and composites, vol. 30, issue 6, march pp. 546 – 553 amenaghawon, n.a., aisien, f.a., and ogbeide, s.e. 2013. bioethanol production from pretreated cassava bagasse using combined acid and enzymatic hydrolysis. university benin j sci technol, 1(2): 48–53. amenaghawon, a., osayuki-aguebor, w., and okieimen, c.o. 2016. production of particle boards from corn cobs and cassava stalks: optimisation of mechanical properties using response surface methodology. journal of materials and environmental science, 7, 1236–1244. atoyebi, o.d., awolusi, t.f., and davies, i.e. 2018. artificial neural network evaluation of cement-bonded particle board produced from red iron wood (lophira alata) sawdust and palm kernel shell residues. case studies in construction materials, 9, e00185. https://www.sciencedirect.com/science/article/pii/s2214509518300718. charles d., aji. i.s. and mshelia z.a. 2024. effect of particle and fiber loading on tensile, flexural and impact properties of hybridized balanite shell particles and palmyra fiber reinforced epoxy composite. arid zone journal of engineering, technology and environment, 20(4): 891-902 ferede, e., 2020. evaluation of mechanical and water absorption properties of alkaline‐treated sawdust‐ reinforced polypropylene composite. journal of engineering, 2020(1): 3706176. https://doi.org/10.1155/2020/3706176. hammajam, a.a., ismarrubie, z.n., and sapuan, s. m. 2014. effect of fiber loading on the mechanical properties of millet husk filled high density polyethylene composites. applied mechanics and materials, 564: 350–354. https://www.scientific.net/amm.564.350. kuforiji, c., durowaye, s., kassim, k. and lawal, g., 2023. influence of sawdust particles reinforcement on physical and mechanical properties of high-density polyethylene (hdpe) matrix composites. kathmandu university journal of science, engineering and technology, 17(1). https://doi.org/10.3126/kuset.v17i1.62382. http://www.azojete.com.ng/ mailto:immyjm@gmail.com https://doi.org/10.1177/0731684411399141 arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 286-293. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: immyjm@gmail.com 293 lee, s.h., lum, w.c., boon, j.g., kristak, l., antov, p., pędzik, m., rogoziński, t., taghiyari, h.r., lubis, m.a.r., fatriasari, w. and yadav, s.m., 2022. particleboard from agricultural biomass and recycled wood waste: a review. journal of materials research and technology, 20: 4630-4658. https://doi.org/10.1016/j.jmrt.2022.08.166. neher, b., hos sain, r., fatima, k., gafur, m.a., hossain, md.a. and ahmed, f. 2020. study of the physical, mechanical and thermal proper ties of banana fiber reinforced hdpe composites. materials sciences and applications, 11: 245-262. https://doi.org/10.4236/msa.2020.114017 obasi, h.c., mark, u.c., and mark, u. 2021. improving the mechanical properties of polypropylene composites with coconut shell particles. composites and advanced materials, 30, 263498332110074. https://doi.org/10.1177/26349833211007497. odeyemi, s.o., abdulwahab, r., adeniyi, a.g. and atoyebi, o.d., 2020. physical and mechanical properties of cement-bonded particle board produced from african balsam tree (populous balsamifera) and periwinkle shell residues. results in engineering, 6: 100126. https://doi.org/10.1016/j.rineng.2020.100126. seth, s.a., aji, i.s., and tokan, a. 2018. effects of particle size and loading on tensile and flexural properties of polypropylene reinforced doum palm shell particles composites. american scientific research journal for engineering, technology, and sciences (asrjets), 14(1): 231–239. https://core.ac.uk/download/pdf/235050632.pdf. yadav, r. 2021. development of low formaldehyde emitting particle board by nano particle reinforcement. journal of applied and natural science, 13(4): 1187 1197. https://doi.org/10.31018/jans.v13i4.2959 http://www.azojete.com.ng/ mailto:immyjm@gmail.com corresponding author’s email address: edith.makwe@uniabuja.edu.ng 855 arid zone journal of engineering, technology & environment original research article evaluation of noise levels in an urban market, federal capital territory, nigeria e. makwe1*, c. uka2 and h. o. john-nwagwu3 1department of geography and environmental management, university of abuja, abuja, nigeria 2department of environmental management, nnamdi azikiwe university, awka, nigeria 3department of geography, federal university, lokoja, nigeria corresponding author’s email address: edith.makwe@uniabuja.edu.ng article information abstract this study assessed noise pollution levels in and around gwagwalada urban market and the likely effects on human health. measurements of noise level were done using sound level meter (smart sensor model ar854), at ten (10) selected points, whose coordinates were predetermined. the measurements were carried out at different times of the day (6-8am, 1-3pm and 5-7pm) for five (5) days, i.e. two traditional and three non-traditional market days. the data obtained were used to assess the variation in temporal and spatial noise level in and around the market, as well as the difference in noise level between the traditional and non-traditional market days, using anova and t-test statistical tools. results showed that highest noise level were generated in the evening hours (5-7pm) and the analysis of variance (anova) in noise level at the different times showed significant variation at f(2) = 13.982, p≤0.05. spatially, points pcc and ais had the highest mean noise level of 84.64db and 81.38db, respectively and were higher than nesrea and who permissible limits. the anova test for spatial noise level in the selected locations showed significant spatial variation with f(9) = 6.029, p≤0.05. furthermore, paired t-test in the analysis of noise level between traditional (70.28 ± 10.15db) and non-traditional (66.16 ± 8.28db) market days, showed statistically significant difference at t(9)=2.766, p≤0.05. the high noise levels were due to sounds from power generators, use of sound amplifiers for product marketing among others. noise pollution poses significant health risk and there is need to monitor and control noise level in and around the market, through the combined efforts of government, professionals and citizens. additionally, there should be periodic assessment of the health status of traders in gwagwalada market. submitted 22 may, 2024 revised 06 july, 2024 accepted 20 july, 2024 keywords: noise pollution market sound level health risk hearing loss gwagwalada © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction noise pollution has been one of the numerous environmental problems encountered in nigeria and other developing and developed countries of the world. this is evident in our day-to-day life as noise is generated in almost all aspects of human activities. noise pollution is an unpleasant sound that is created by people or machines that can cause infuriation, distraction and physical pain on humans. noise pollution can be generated from outdoor sources, such as road traffics, jet planes, garbage trucks, construction equipment, manufacturing processes, lawn mowers, leaf blowers; and from indoor sources, including boom boxes, heating and air conditioning units, and metal chairs scraping on doors (akintunde et al., 2022). adekunle et al. (2021) noted that noise pollution in our environments has been discovered by researchers in recent times to contribute adversely to health conditions, social challenges and occupational efficiencies of its victims. jariwala, et al. (2017) stated that “environmentally, noise pollution is a form of air pollution, and it is a threat to health and wellbeing”. noise pollution has become more severe and widespread than ever before and will continue to increase in magnitude and severity because of population growth and urbanization (oyedepo et al., 2018), as well as the associated growth and increase in factories, machines, industries, highway, rail, and air traffic, which remain major sources of environmental noise. noise has been closely related to technological advancement azojete december 2024. vol.20(4):855-862 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:edith.makwe@uniabuja.edu.ng mailto:edith.makwe@uniabuja.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):855-862. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edith.makwe@uniabuja.edu.ng 856 and industrial growth (reddy, 2020; ijabor et al., 2024). being a product of urbanization and industrialization, it has been recognized as an emerged environmental nuisance with an underestimated threat that can cause a number of short and long-term health problems, such as sleep disturbance, cardiovascular effects, poorer work, poor school performance, hearing impairment, among others (who, 2012; yohanna et al., 2020). according to liu et al. (2020), “speech interference, reduction in productivity, high blood pressure, hearing defects, health disorders, sleep interference, cardiovascular effects, loss of concentration, absenteeism, and fatigue are some of the health implications of high levels of noise”. additionally, noise has also been described as a slow and subtle killer through its hazardous effects on humans (chaudhary and chaudhary, 2020). noise pollution can also come from sounds that aren't necessarily overly loud, but which are particularly annoying or troublesome in nature (matthews, 2018). markets serve as assemblies where buyers and sellers convene to engage in commercial, economic, and social transactions, contributing to the formation and sustenance of communities. their collective activities generate noise pollution as they gather. urban markets, which are commonly open-air and rowdy, attract large number of people and are characterized by all forms of activities that generate a lot of noise ranging from power generators, loudspeakers, grinding machines, blade filing engines, vehicles, religious activities, buying and selling of commodities and so on. all these pollute the environment and in turn affect the auditory performance of people, thereby leading to hearing impairment when exposed to it over a long period of time. the intensity of the noise in marketplaces has increasingly become an environmental public health issue (osisanya et al., 2023) because of its direct effects on human performance and the reduction in the quality of health of the people exposed to it. persistent exposure to high noise level, as is the case in most urban markets is injurious to health (mucci et al., 2020; tunde and abdulquadri, 2021; ijabor et al., 2024). a lot of people have hearing loss as a result of prolonged exposure to high noise that goes beyond tolerable levels (priya and hohman, 2023; who, 2024). gwagwalada market is an urban physical market, which despite its upgrade by the federal capital territory (fct) administration, still maintains it traditional periodic market days. the market forms the heart of the town's shopping scene, and it is known for its vibrant atmosphere and diverse array of goods from fresh farm produce and local crafts to clothing and household items, as well as services, especially among the local population, in exchange for money from buyers. it's a bustling hub where both residents and visitors can immerse themselves in the local culture and shop for a wide range of products. the traditional periodic market days has intervals of four days and are usually more populated than the non-traditional market days. the different activities in the market generate different kinds of noise and the exposure to this noise may pose health risks to both the buyers and sellers. it is against this background that this research sets out to assess the spatiotemporal noise level in selected parts of the market with the view to examine its possible health effects on the human health. 2.0 materials and method 2.1 the study area gwagwalada, being part of the federal capital territory (fct) is located between latitudes 8°50'n and 9°00'n and between longitudes 6° 50'e and 7o 09'e, with an altitude of about 400 600m above sea level (figure 1). gwagwalada is characterized by two main seasons namely, wet season from april to october and dry season from november to march (makwe and ahmad, 2017). the temperature varies between 30°c to 37°c or higher during the dry season. during the rainy season, the afternoon relative humidity gives the area a "heat trap" effects which make it uncomfortably hot (adakayi, 2000). the annual rainfall ranges from 1403 to 1632mm (makwe et al., 2020). the study was conducted in and around gwagwalada urban market. goods sold in the market include local farm produce such as yam, millet, groundnut, etc. as well as crafts, foods and other services that encourages exchange for money. buyers and sellers come from gwagwalada, the neighboring towns and as well as from other parts of the f.c.t. on non-traditional market days day to day buying and selling of goods takes place but with less population than the traditional market days. http://www.azojete.com.ng/ mailto:edith.makwe@uniabuja.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):855-862. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edith.makwe@uniabuja.edu.ng 857 figure 1: map of nigeria showing the federal capital territory and gwagwalada area council 2.2 sampling an initial reconnaissance survey was carried out for two days in and around gwagwalada market, during which the sampling locations were randomly selected. monitoring was carried out at the pre-determined locations within and around the market using smart sensor (model ar854) sound level meter which gave instant, real time readings. the instruments were calibrated and set on fast response before taking measurements at each of the ten (10) selected sampling locations (table 1), whose coordinates were also determined using a handheld gps. the measurements were taken at 3 to 10m above the ground and away from walls in accordance with iso 9614-3 (2002) sound measurement procedure. each measurement per sample point is done three times and the average is taken (ugbebor et al., 2017). the noise levels were measured in the morning (6-8am), afternoon (1-3pm) and evening (5-7pm) over a period of 5days (ie two traditional and three non-traditional market days) in the month of march, 2024. this was so as to determine the temporal and spatial variations in noise levels as well as to compare the noise level between the traditional and nontraditional market days for effective assessment of the noise level in and around gwagwalada market. table 1: sampling points description location code coordinates latitudes longitudes elevation 1 pcc 8056’20.5” 7004’46.6” 197m 2 pls 8056’20.1” 7004’44.2” 196m 3 hds 8056’20.7” 7004’39.9” 191m 4 blc 39 8056’21.4” 7004’38.1” 202m 5 fds 8056’24.1” 7004’38.6” 202m 6 ais 8056’24.1” 7004’41.5” 197m 7 mt 8056’24.1” 7004’45.9” 199m 8 w/h 8056’28.4” 7004’42.9” 203m 9 tac 8056’22.1” 7004’46.0” 196m 10 wdc 8056’19.3” 7004’46.6” 203m note: pcc-phone charging centre, plsplastic store, hdshairdressing saloon, blc 39block 39, fds food store stand, ais-alhaji idris store, mtmeat stand, w/h-warehouse, tacthe apostolic church, wdcwomen development centre http://www.azojete.com.ng/ mailto:edith.makwe@uniabuja.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):855-862. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edith.makwe@uniabuja.edu.ng 858 the data obtained from the measurement of noise levels were analyzed by evaluating the temporal variation of noise level at different times (6 8am, 1 3pm and 5 7pm) of the day in gwagwalada market and comparing them to the world health organization guideline values for community noise in commercial shopping areas (who, 1999, 2005) and also with the national environmental standards and regulations enforcement agency noise standards and control regulations (nesrea, 2009). further analyses were done by assessing the variations in the results obtained at different times at the different sampling locations, using the analysis of variance (anova) statistical tool. in addition, analysis of variation in noise level between traditional market days and non-traditional market days was also carried out using the student t-test statistical tool. all these analyses were carried out using the statistical package for social sciences (spss) version 23. 3. results and discussion 3.1 temporal variation in noise levels from the data obtained, the highest level of noise was generated within gwagwalada market in the evening hours (5-7pm), with the noise levels varying from 61.4db to 98.6db. sampling points pcc, pls, ais and mt had the highest average noise levels of 98.6db, 72.2db and 96.4db and 74.2db respectively (figure 2). these were higher than the who (2005) laeq limit while the noise level for points pcc and ais were higher than the nesrea (2009) laeq limit of 75db for daily noise exposure in commercial areas. the high noise level in the evenings are most likely due to the high influx of people into the market at the close of work, traders advertising their goods with the use of loudspeaker and at the top of their voice, as well as vehicular movements around the market premises as traders are moving their goods signifying end of sales for the day. on the other hand, the lowest noise levels were measured in the morning hours (6-8am), with noise level values ranging from 54.5db to 61.5db (figure 2). this was when the market gate was just opened to people for their daily businesses and the population of people in the market was still low. the measured morning noise levels were within the nesrea (2009) and who (2005) laeq limit of 70db. the analysis of the temporal variation in noise level (anova) within the market at f(2) = 13.982, p ≤ 0.05 clearly indicates that there is high significant variation in the noise level at different sampling times (6 – 8am, 1 – 3pm and 5 – 7pm) in gwagwalada market. this result corroborates the works of datti and nduka (2020) as well as tunde and abdulquadri (2021) in their assessment of noise pollution in commercial areas of delta and kwara states, nigeria respectively. figure 2: average temporal noise level at sampling locations note: pcc-phone charging centre, plsplastic store, hdshairdressing saloon, blc 39block 39, fds food store stand, ais-alhaji idris store, mtmeat stand, w/h-warehouse, tacthe apostolic church, wdcwomen development centre 3.2 spatial variation in noise level noise level varies from place to place within and around gwagwalada market. the mean noise level at the selected sampling points showed points pcc and ais having the highest mean noise level of 84.64db and 81.38db respectively. these were higher than the nesrea (2009) and who (2005) standards of 75db and 0 20 40 60 80 100 120 pcc pls hds blc39 fds ais mt w/h tac wdc n o is e le v el ( d b ) sampling locations 6-8(am) 1-3(pm) 5-7(pm) http://www.azojete.com.ng/ mailto:edith.makwe@uniabuja.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):855-862. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edith.makwe@uniabuja.edu.ng 859 70db respectively for noise level in a commercial area. the high noise level at these locations can be attributed to the sounds from power generating sets, clusters of buyers and sellers as well as the use of sound amplifiers for product marketing and advertisement. high noise level poses significant health risk to people when exposed to them for a long period of time. the remaining eight sampling locations have mean noise levels that ranged from 59.24db to 69.46db, which are within the acceptable standards for commercial areas. the analysis of variation (anova) in noise level in the selected sampling locations within and around gwagwalada market at f(9) = 6.029, p≤ 0.05 showed that there is a significant spatial variation in the noise level at the selected sampling points (table 2). this result conforms the study by anejionu et al. (2022) in their assessment of noise pollution impacts in enugu, nigeria. table 2: analysis of spatial variation in noise level in selected sampling points sum of squares df mean square f sig. between groups 3465.009 9 385.001 6.029 .000 within groups 2554.468 40 63.862 total 6019.477 49 df = degree of freedom 3.3 variation in average daily noise level noise levels measured on day 1 in comparison with the nesrea (2009) and who (2005) laeq limit showed that the minimum noise levels were all within the recommended standard limit. however, the maximum noise levels at points pcc (95.1db), ais (70.2db), mt (77.2db) and w/h (70.4db) were higher than the who permissible limits of 70db (table 3), while only those of points pcc and mt exceeded the nesrea (2009) standard limit of 75db. these sampling points were characterised by loud noise from power generating sets and from the clusters of people buying and selling at the general goods shops, meat stands and warehouses. table 3: average daily minimum and maximum noise level at sampling points location day1 day2 day3 day4 day5 min max min max min max min max min max pcc 66.5 95.1 49.5 62.2 47.5 89.2 51.7 86.0 67.6 90.7 pls 55.9 63.1 52.3 59.2 56.3 79.6 51.9 66.4 63.5 76.1 hds 54.4 59.6 48.8 50.1 50.3 63.2 48.9 59.3 54.4 64.1 blc39 53.1 68.6 50.8 52.3 51.7 52.9 51.8 62.1 52.6 60.3 fds 53.7 61.6 59.3 62.9 51.9 65.6 59.6 66.9 58.6 64.6 ais 57.5 70.2 59.4 59.7 57.6 90.8 54.9 91.1 57.5 95.1 mt 58.9 77.2 64.1 64.7 63,2 69.4 63.7 70.6 59.9 65.4 w/h 61.3 70.4 52.6 63.5 52.5 57.2 52.6 69.5 59.3 70.9 tac 52.1 60.6 53.1 58.7 58.2 63.9 52.3 65.5 60.4 63.2 wdc 57.8 63.9 59.7 61.3 56.4 59.1 58.6 61.9 56.8 64.9 note: pcc-phone charging centre, plsplastic store, hdshairdressing saloon, blc 39block 39, fds food store stand, ais-alhaji idris store, mtmeat stand, w/h-warehouse, tacthe apostolic church, wdcwomen development centre noise level measured on day 2 showed that the minimum and maximum noise levels were within the nesrea and who permissible limits (table 3). coincidentally, day 2 was the day after the traditional market day and was characterised by low turnout as many people had purchased what they needed the previous day. day 3 noise level measurements showed high maximum values at points pcc (89.2db), pls (79.6db) and ais (90.8db), which were higher than the nesrea and who permissible limits of 75db and 70db respectively. the minimum noise level values for day 3 were within the recommended standard limits. the results of day 4 noise levels measurement in comparison with the nesrea and who standard showed that the minimum http://www.azojete.com.ng/ mailto:edith.makwe@uniabuja.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):855-862. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edith.makwe@uniabuja.edu.ng 860 values at all the sampling locations were within the permissible limits of 75db and 70db. the maximum noise levels for the same day however shows elevated values at pcc (86.0db), ais (91.1db) and mt (70.6db) sampling locations. these values are higher than the who permissible limit of 70db. the minimum noise level measurements for day 5 were similar to those of the previous four days, with values that are within the 70db (who, 2005) and 75db (nesrea, 2009) permissible limit. the maximum values were however elevated at sampling points pcc (90.7db), pls (76.1db), ais (95.1db) and w/h (70.9db) and higher than the regulatory standard. the evaluation of noise levels in markets located in rivers and delta states by ugbebor et al. (2017) and ijabor et al, (2024) respectively further corroborates this result. generally, the elevated maximum noise level at points pcc, pls, ais, mt and w/h were as a result of the power generating sets, the sounds from cutting and butchering, as well as the large cluster of people who are buying and selling at these locations. the elevated noise level in these locations poses significant health risk to traders and buyers exposed to them for a long period of time. high noise level is capable of causing psychiatric disorder (ijabor et al., 2024). these elevated noise levels can potentially trigger symptoms such as headaches, nausea, as well as other psychological symptoms such as argumentativeness, changes in mood and anxiety as noted by hahad et al. (2019). according to a review, there is evidence that short-term exposure to noise pollution can temporarily raise blood pressure and increase blood viscosity. there is also an association between long-term exposure to noise and higher rates of cardiovascular disease (jariwala et al., 2017). 3.4 variation in noise levels between traditional and non-traditional market days table 4 shows the average noise level generated between traditional and non-traditional market days in gwagwalada urban market. it is clearly seen that the average noise generated on traditional market days were higher in most of the sampling points than the noise generated on non-traditional market days. this is because on traditional market days people from all parts of gwagwalada, the neighboring towns and states come to the market to buy and make sales thereby, resulting in increased population, as well as increased activities such as the use of grinding machine. the use of electricity generating set in area close to pcc increases the amount of noise generated in this area within the market especially on traditional market days. the use of loudspeakers and other sound amplifiers as well as the sounds from cutting and butchering in areas close to ais and mt also account for the high level of noise in these parts of the market. on a general note, places around pcc and ais experience higher noise level than other areas on traditional market days. the nontraditional market days on the other hand are characterized by lower population, which results to lesser activities and hence lesser noise level compared to the traditional market days. table 4: average noise level on traditional and non-traditional market days location non-traditional market days traditional market days pcc 79.1 92.9 pls 68.2 69.6 hds 57.5 61.9 blc39 55.8 64.5 fds 65.1 63.1 ais 80.5 82.7 mt` 68.2 71.3 w/h 63.4 70.7 tac 62.7 61.9 wdc 60.8 64.4 note: pcc-phone charging centre, plsplastic store, hdshairdressing saloon, blc 39block 39, fds food store stand, ais-alhaji idris store, mtmeat stand, w/h-warehouse, tacthe apostolic church, wdcwomen development centre in the analysis of noise level between traditional and non-traditional market days, the paired t-test result shows that there is a statistically significant difference between the noise level generated on traditional market days (70.28 ± 10.15db) and that of the non-traditional market days (66.16 ± 8.28db), t(9)=2.766, p≤0.05. the implication of this result is that it further stresses the fact that there is higher noise level generated on traditional market days compared to the non-traditional market days. 4. conclusion the study assessed the spatiotemporal level of noise pollution in and around gwagwalada urban market and the likely effects on human health. the measurement of noise level was carried out at ten (10) randomly selected points within and around the market at different times of the day (6 8am, 1 3pm and 5 7pm) for http://www.azojete.com.ng/ mailto:edith.makwe@uniabuja.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):855-862. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edith.makwe@uniabuja.edu.ng 861 a period of five (5) days (i.e. two traditional market days and three non-traditional market days). the data obtained showed that noise levels were highest at the selected points in the evening hours (5-7pm) and lowest in the morning hours (6-8am) for most of the sampled locations. the analysis of variance (anova) in the noise level at the different times showed that there is a significant variation at f(2) = 13.982, p ≤ 0.05. spatially, points pcc and ais had the highest mean noise level of 84.64db and 81.38db respectively, with their noise level being higher than the nesrea and who permissible limits for noise level in commercial areas. the analysis of variation (anova) in the spatial noise level in the selected locations showed significant spatial variation with f(9) = 6.029, p ≤ 0.05. furthermore, the paired t-test in the analysis of noise level between traditional and non-traditional market days shows a statistically significant difference between the noise level generated on traditional market days (70.28 ± 10.15db) and that of the non-traditional market days (66.16 ± 8.28db), t(9)=2.766, p≤0.05. the study attributed the high noise level to sounds from power generating sets, clusters of buyers and sellers as well as the use of sound amplifiers for product marketing. noise pollution poses significant health risk to traders, buyers as well as anyone exposed to it over time, it can cause health issues such as headaches, nausea, and other psychological and cardiovascular issues such such as argumentativeness, changes in mood, anxiety, raised blood pressure and increase blood viscosity. there is need to monitor and control noise level in gwagwalada urban market and its environs due to the health risks associated with prolonged exposure to noise. this requires the combined efforts of the government, professionals and citizens. there is also the need to educate the general public about the dangers of long-term exposure to high noise level and also have periodic assessment of the health status of the traders who are daily exposed to high noise levels in gwagwalada market. references adakayi, pe. 2000. climate. in p.d. dawan (ed) geography of abuja f.c.t., pp 10-18. famous asanlu publishers, minna. adekunle, a., omange, om., adekunle, ot. and shawon, mc. 2021. estimation of noise pollution parameters and their health effects on building occupants in lagos state, nigeria. international journal of advanced academic research, 7(1): 64-86. akintunde, ea., bayei, jy. and akintunde, ja. 2022. noise level mapping in university of jos, nigeria. geojournal, 87: 2441-2453. anejionu, cd., ebinne, es., nwosu, ki., anejinou, gu. and ndukwu, ri. 2022. are residents in urban areas of nigeria exposed 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report on pollution effects and control, 21: 28-37 who 2012. burden of disease from environmental noise: quantification of healthy life years lost in europe. geneva. who. http://www.euro.who.int.e94888.pdf. who world health organization. 2024. deafness and hearing loss. who.int/news-room/factsheets/details/deafness-and-hearing-loss (accessed 18/05/2024). geneva, switzerland yohanna gj., sunday, o. and yohanna, jr. 2020. evaluation of noise level in selected markets in josnorth, plateau state. international journal of research in environmental science, 6(3): 27–35. http://www.azojete.com.ng/ mailto:edith.makwe@uniabuja.edu.ng http://apps.who.int/iris/handle/10665/66217 http://www.euro.who.int.e94888.pdf/ http://who.int/news-room/fact-sheets/details/deafness-and-hearing-loss http://who.int/news-room/fact-sheets/details/deafness-and-hearing-loss corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 557 arid zone journal of engineering, technology & environment original research article synchronized analysis of biodiesel from khaya senegalensis oils using ftir, gc-ms and nmr at top parametric conditions. z. d. ishaya1*, j. samuel2, g. e. ede3, d. s. yawas1, j. y. bwede1 1* department of mechanical engineering, ahmadu bello university, zaria, nigeria. 2 department of mechanical engineering, baze university abuja, nigeria. 3 department of mechanical engineering, university of jos, nigeria. *corresponding author’s email: zdishaya@abu.edu.ng, waidungiz@gmail.com article information abstract alternatives to costly fossil fuel have witnessed rekindled interest because of the depletion of fossil reserves and environmental concerns. in this study, non-edible vegetable oil from khaya senegalensis (ks), which grows well in semi-arid zones was converted to biodiesel via transesterification under the reaction condition of 1.25 % 𝑁𝑎𝑂𝐻 catalyst and 1: 6 oil-methanol molar ratio. ftir, gc-ms and nmr techniques were concurrently used to monitor common or similar peaks in the conversion process in an extensive cross comparison to validate other techniques' results. furthermore, the composition of conventional diesel with the vegetable biodiesel produced were simultaneously analyzed. the results showed that conversion peaks were aligned, and successful delivered 82.02 % yield. the results from ftir, gc-ms and nmr investigations all agreed, on the conversion of triglyceride molecules in the crude ks oil to fatty methyl esters in the biodiesel. both produced biodiesel and conventional diesel were observed to contain alkanes and alkenes functional groups, that impart good fuel properties. received: 24th april 2025 revised: 19th may 2025 accepted: 20th may 2025 keywords: khaya senegalensis fatty methyl esters ftir gc-ms nmr functional groups © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction fossil liquid fuel in the form of expensive gasoline and diesel, is mostly utilized in the transport and electrical power sectors to power internal combustion engines. the exhaust products from these engines are not problem-free. the exhaust emissions comes along with environmental pollutants that contaminate the air, also the emissions are responsible for climate change and coronary disease (ishaya et al., 2020a). carbon (iv) oxide (𝐶𝑂2) concentration in the atmosphere has reached alarming levels due to the production and consumption of fossil fuels. according to banik et al., (2018), 86 % of the world energy consumption, 20 % of co2 emissions and almost all fuel needed in the transport sector are from fossil sources. with the increasing trends of human population and global demand for motorized mobility, there shall be increased fossil fuel consumption, pollutants emission and environmental sustainability challenges. biodiesel is a fuel obtained from plant oil, and it is characteristically similar to petrol-diesel, but it is nontoxic, renewable, sustainable, and environmentally harmless (olagbende et al., 2021). when biodiesel is used in diesel engines, it presents excellent combustion properties due to its low sulfur, low aromatic content and high cetane number (chaudhary et al., 2018). nonedible oil from cheap tropical feedstock such as khaya senegalensis (ks) that are easily cultivated in arid or semi-arid conditions, are used as alternatives and in the sustainable production of biodiesel (sukkasi et al., 2010 and dai et al., 2014). some studies in the area of biodiesel production include: alahmar et al., (2025) that investigated the efficient way of producing biodiesel from waste cooking oil by the use of a bifunctional catalyst. similarly, rao et al., (2025) studied the synthesis and optimization of biodiesel production from trichosanthes cucumerina seed using prosopis juliflora catalyst and reported the optimized conditions as 60 mg of biomass at 70 o c for a reaction time of 60 min to yield 46.31% catalyst, that was used in transesterification reaction to yield 97.42% biodiesel. additionally, farouk et al., (2024) worked on the optimized production of biodiesel from waste cooking oil using nano-catalyst and reported an optimized conditions of 7:1 methanol to oil ratio, 50 o c reaction temperature and 60 minutes reaction time using response surface methodology. weldeslase et al., azojete june 2025. vol.21(2):557-568 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/020 www.azojete.com.ng mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 558 (2023) investigated the optimized production of biodiesel from waste cooking oil using a 𝐶𝑎𝑂 catalyst and reported 96.5% biodiesel conversion at 14:1 methanol to oil molar ratio, 57.5 o c reaction temperature, 5% wt catalyst loading and 2 hours reaction time. zubairu et al., (2021) produced synthesized biodiesels and hybrid oil blends from jatropha curcas and thevetia peruviana seeds oil, and reported high biodiesel yield of 90.0%, 86.1%, 90.7%, 92.2% and 88.2% for five hybrid blends at 60 o c reaction temperature and 1 hour reaction time with 1% (w/w) koh catalyst. kaisan et al., (2018) carried out a comparison of jatropha and neem seed biodiesel and reported that jatropha biodiesel contained 91.9 % methyl ester while neem biodiesel contained 70.2 %. nahadi & atadashi, (2018) studied the effects of variation of catalyst concentration on the production of biodiesel from coconut oil. the results showed that 96 % biodiesel was obtained at 1 % w/w catalyst concentration, 1: 6 oil to methanol ratio, 55 ℃ reaction temperature and 60 minutes reaction time. furthermore, ofoegbu & kelle, (2013) determined the edibility of thevetia peruviana seed oil using gc-ms, ftir and uv-vis techniques. the results showed that the oil has nutritional benefits provided the traces of cyanide are removed. the study of the biodiesel production process using solid acid catalyst was investigated by gebremariam & marchetti, (2021), the results showed that variation in oil cost and the price of biodiesel strongly affects the viability of the production process. similarly, alhassan et al., (2017) characterized khaya senegalensis stem bark, the 1h nmr results indicated a carbon-carbon double bond, aromatic protons, and protons are attached directly to electronegative atoms. additionally, bolale et al., (2019) carried out ftir and gc-ms analyses on canna indica, the ftir results showed the presence of aromatic 𝑂 − 𝐻 stretch (3300 𝑐𝑚−1) and aromatic 𝐶 = 𝐶 stretch (1451 and 1640 𝑐𝑚−1), and the gc-ms result showed the presence of di-alpha-tocopherol. also, the chemical modification of camelina oil was investigated by sharma et al., (2020), its 1h nmr spectra showed chprotons and secondary alcohols at 2.9 − 3.2 and 4.25 − 3.35 𝑝𝑝𝑚, respectively. a research was conducted by odo et al., (2017) using ftir and gc-ms analyses on the brenania brieyi root extract, and reported the presence of pentadecanoic acid (17.04 %), 9, 12-hexadecanoic acid (10.18 %), 9-octadecanoic acid (60.53 %) in the methanol extract, and hexadecanoic acid (11.29 %), 9-octadecanoic acid (54.85 %), 9, 12-octadecanoic (3.90 %) in the chloroform extracts. similar studies by hossain et al., (2021) investigated triglyceride conversion of waste frying oil, and reported that the 1h nmr showed glycerine peaks, 𝛼 − 𝐶𝐻2 protons and a 98.48 % biodiesel conversion. for this study, the aim is to convert khaya senegalensis crude oil to biodiesel at 1.25 𝑤𝑡. % 𝑁𝑎𝑂𝐻 catalyst loading and 1: 6 alcohol to methanol molar ratio. other researchers have considered the alcohol-to-methanol ratio between 1: 6 to 1: 12 for different feedstock and catalyst loading between 0.5 to 1.0 𝑤𝑡%.the khaya senegalensis feedstock was investigated in the present study because it is non-edible, it is commonly available within the semi-arid region of northern nigeria, and no previous studies were conducted on the feedstock under this defined conditions. the ftir, gc-ms, and 1h nmr techniques used in the present study is to indicate the justifications for the conversion of triglyceride molecules to fatty acid methyl esters (biodiesel). 2. materials and methods the khaya senegalensis winged seed kernels were collected from the trees in samaru-zaria in nigeria and the oil was extracted using mechanical expeller press. the reagents used for the conversion of crude oil to biodiesel were of analytical grade (assay 99.5%). the reagents details are outlined as follows: sodium hydroxide (naoh) pellets, propan-2-ol (ch3h7oh), sulphuric acid (h2so4), 0.1m potassium hydroxide (koh) and methanol (ch3oh). the first stage was to pretreat the crude oil using propan-2-ol, then followed by the determination of free fatty acid and acid value. the crude oil was titrated with 0.1m of koh until the acid value reduces to ≤ 0.5%. the second stage transesterification reaction to convert the crude oil to biodiesel was carried out at an oil-to-alcohol molar ratio of 1:6 using naoh catalyst for 1 hour at 60 o c. the details of the procedure are contained in an earlier study by ishaya et al., (2020a). 2.1 fourier transform infrared (ftir) spectroscopy agilent technologies ftir spectrophotometer (54va agilent technologies cary 630 ftir spectrophotometer part g8043-64002, serial no. my14470031, made in malaysia) was used to take the infrared spectrum of samples. the potassium bromide disc method was used to obtain the ir spectra of samples. 650 to 4000 𝑐𝑚−1 scanning range was used in this study, functional groups were identified in the crude oil, biodiesel and diesel samples using the ftir spectra. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 559 2.2 gas chromatography-mass spectrometry (gc-ms) gc-ms-qo2010 shimadzu japan was used in the analysis. a fused silica column was filled with elite-5ms (95 % dimethylpolysiloxane 5 % biphenyl, 30 𝑚 × 0.25 𝑚𝑚 𝐼𝐷 × 250 𝜇𝑚 𝑑𝑓). helium as carrier gas, flow constantly at 1 𝑚𝑙/𝑚𝑖𝑛, was used to separate the components. the temperature of the injector was set at 250 ℃ for the chromatographic run. the extract (1 𝜇𝑙) was injected into the instrument, and the temperature was at 70 ℃ (0 𝑚𝑖𝑛), followed by an increase to 280 ℃ at the rate of 10 ℃ 𝑚𝑖𝑛−1, subsequently the temperature was kept at 280`℃ for 5 𝑚𝑖𝑛. the mass detector conditions were set: the transfer line was at 250 ℃; ion source temperature was at 200 ℃; and ionization mode electron impact was at 70 𝑒𝑉. also, the mass detector scan time of 0.5 𝑠𝑒𝑐 was set, at scan interval of 0.1 𝑠𝑒𝑐. in this study, chemical compounds were detected in the crude oil, biodiesel and their respective quantities as reported by the gc-ms spectrometer. the national institute standard and technology (nist) library was used as a reference to compare and interpret the gc-ms results. compounds were identified according to molecular mass, structure and fragments calculated. the unknown components spectrum was compared with that of the nist library, and the closest match was taken. 2.3 nmr spectroscopy all the 1h-nmr spectra were recorded with an agilent technologies 400/𝑆4/𝑃𝐶 + spectrometer (850 watts agilent technologies uk ltd, 400mhz nuclear magnetic resonance vnmrj premium compact+ ar, part g8504-64002, serial no. mry0023179, made in england) operating at 2.38 𝑏𝑎𝑟 helium vessel and 2.5 bar nitrogen vessel. the reference standard was tetramethyl-silane (tms), and chemical shifts were reported relative to it. all experiments were conducted at room temperature. 3. results and discussion 3.1 crude khaya senegalesis oil ftir from figure 1 and table 1, the = 𝐶 − 𝐻 bond was observed at 3004 𝑐𝑚−1, 𝐶 − 𝐻 alkyl symmetric and asymmetric strong stretches at 2855 − 2922 𝑐𝑚−1, 𝐶 = 𝑂 very strong stretch at 1744 𝑐𝑚−1, 𝐶 − 𝐻 terminal alkane bond at 1461 𝑐𝑚−1 and 𝐶 − 𝑂 − 𝐶. figure 1 indicated that the alkanes, alkenes, carboxylic and esters functional groups were present in khaya senegalensis crude oil. as reported by hellier et al., (2018) and karmakar et al., (2021), the fatty acids attached to the glycerol backbone are usually long chains containing 14 − 22 carbon atoms. some of the attached carbon atoms are either methyl, methylene, carbonyl, carboxylic or esters in structure. this however, is consistent with the findings by hellier et al., (2018) and karmakar et al., (2021) because it shows the presence of a triglyceride molecule with alkane carbon atoms, alkene carbon atoms, carboxylic carbon atoms and esters carbon atoms. figure 1: ftir spectra of crude khaya senegalesis oil. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 560 table 1: functional groups in crude khaya senegalensis oil. s/n wavelength (𝒄𝒎−𝟏) functional group 1 3004 = 𝐶 − 𝐻 weak stretch (alkene) 2 2922, 2855 𝐶 − 𝐻 strong stretch (alkanes) 3 1744 𝐶 = 𝑂 strong stretch (alkanoic & ester) 4 1461 𝐶 − 𝐻 medium stretch (terminal alkane bend) 5 1375 𝐶 − 𝑂 weak stretch (alkanoic) 6 1162 𝐶 − 𝑂 medium stretch, (esters) 7 1028 𝐶 − 𝑂 − 𝐶 weak stretch (alkanoate) 8 723 𝐶 = 𝐶 − 𝐻 medium stretch (alkene bending) this study results from table 1 conforms with cheah et al., (2020), which observed 𝐶 − 𝑂 stretching at 1059 𝑐𝑚−1, alkane 𝐶 − 𝐻 stretching at 2900 𝑐𝑚−1, ester 𝐶 = 𝑂 stretching at 1700 𝑐𝑚−1, and alkene 𝐶 = 𝐶 stretching at 1650 𝑐𝑚−1. also, the study is consistent with (tulashie et al., 2018), who observed – 𝐶𝐻2 stretching vibrations at 2853.09 and 2922.27 𝑐𝑚−1 and – 𝐶 = 𝑂 bond stretching at 1741.91 𝑐𝑚−1. 3.2 crude khaya senegalesis oil gc-ms figure 2: gc-ms spectra of crude khaya senegalesis oil. table 2: compounds present in crude khaya senegalesis. pk rt area % library/id formula 1 15.713 1.41 methyl 6-methyl heptanoate 𝐶9𝐻18𝑂2 2 16.357 1.98 hexadecanoic acid, ethyl ester 𝐶18𝐻36𝑂2 3 16.440 9.05 hexadecanoic acid 𝐶16𝐻32𝑂2 4 17.427 6.45 11-octadecenoic acid, methyl ester 𝐶19𝐻36𝑂2 5 17.628 1.23 methyl 8-hydroxyoctanoate 𝐶9𝐻18𝑂3 6 18.013 14.79 9-octadecenoic acid, ethyl ester 𝐶20𝐻38𝑂2 7 18.170 43.81 oleic acid 𝐶18𝐻34𝑂2 8 18.304 11.54 nonadecanoic acid 𝐶19𝐻38𝑂2 9 19.665 6.60 cis-oleic acid 𝐶18𝐻34𝑂2 10 19.665 3.15 10-undecenal 𝐶11𝐻20𝑂 from figure and table 2; the gc-ms analysis of crude khaya senegalensis oil showed the presence of 10 compounds. major compounds include: oleic acid 𝐶18𝐻34𝑂2 at retention time of 18.170 𝑚𝑖𝑛 occupying the largest mass spectra area of 43.81 %, 9-octadecenoic acid, ethyl ester (𝐶20𝐻38𝑂2) at retention time 18.013 𝑚𝑖𝑛 with a mass spectra area of 14.79 %, nonadecanoic acid (𝐶19𝐻38𝑂2) at retention time 18.304 𝑚𝑖𝑛 with a mass spectra area 11.54 %, hexadecanoic acid (𝐶16𝐻32𝑂2) at retention time 16.440 𝑚𝑖𝑛 occupying 9.05 % mass spectra area, 11-octadecenoic acid, methyl ester 𝐶19𝐻36𝑂2 at retention time 17.427 𝑚𝑖𝑛 with a mass spectra area of 6.45 %, cis-oleic acid (𝐶18𝐻34𝑂2) at retention time 19.665 𝑚𝑖𝑛 with a mass spectra area 6.60 %, 10-undecenal (𝐶11𝐻20𝑂) at retention time 20.727 𝑚𝑖𝑛 occupying 3.15 % mass spectra area. the gc-ms result showed that triglycerides with oleic fatty acid represent a larger portion of the ks vegetable oil. oleic acid is a monounsaturated fatty acid with 18-carbon atoms. this gc-ms result conforms with the ftir result in figure 1, indicating similar compounds as discussed. the 18-carbon atoms in the ks triglyceride http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 561 molecule connotes a good parameter for biodiesel production because it will contribute to a higher heating value of the fuel and also a short ignition delay. similarly, the un-saturation in the ks triglyceride molecule will enhance the fluidity of the fuel when the biodiesel is finally produced. 3.3 ks crude oil nmr figure 3 show the chemical shift of the signals shown in table 3. figure 3: 1h-nmr spectrum of crude ks oil table 3: chemical shift of main resonances in ks. s/n chemical shift (𝒑𝒑𝒎) multiplicity nature of carbon 1 5.31 − 5.28 𝐻𝐶 = 𝐶𝐻 2 4.11 − 4.27 – 𝐶𝐻2 𝑂𝐶𝑂𝑅 3 2.26 𝛼 − 𝐶𝐻2 4 1.22 − 1.97 (𝐶𝐻2)𝑛 5 0.83 𝐶𝐻3 the result shows that the duplets with peaks at 5.31 and 5.28 𝑝𝑝𝑚 correspond to protons attached to carbon-carbon double bonds in the ks triglyceride molecule. this is in agreement with the gc-ms result in figure 2 and ftir result in figure 1 of ks crude oil. all results agree on the presence of an alkene functional group, and this is consistent with fu et al., (2021). furthermore, the result indicates a triplet and a duplet centered at 4.25 and 4.12 𝑝𝑝𝑚. this is mostly assigned to protons attached to the triglyceride backbone (𝐶𝐻2 − 𝐶𝑂𝑂𝑅) in the sn 1’ 3’ position. this finding conforms with (khosa, 2021), which shows a triglyceride as one molecule of glycerol attached to three molecules of fatty acid. this nmr observation is consistent with truzzi et al., (2021), and it also agrees with the gc-ms and ftir result on the presence of carboxylic and ester functional groups. figure 3 also shows a triplet at 2.26 𝑝𝑝𝑚 that corresponds to protons attached to αcarbon and (𝐶𝐻2)𝑛 protons in the region of 1.22 – 1.97 𝑝𝑝𝑚. this shows the existence of alkanes in the triglyceride molecule and is consistent with (sharma et al., 2020). protons of 𝐶𝐻3 are also observed at 0.83 𝑝𝑝𝑚, which is in tandem with fu et al., (2021). based on the 1h-nmr result in figure 3, the study observed that: alkanes, alkenes, carbonyl and esters chemical environments are present in khaya senegalensis crude oil. this result, together with the gc-ms and ftir results, further confirms the triglyceride molecule with oleic acid as the major fatty acid in the ks vegetable oil. 3.4 ftir of ks biodiesel at 1.25 % catalyst from figure 4 as interpreted in table 4, the = 𝐶 − 𝐻 bond was observed at 3004 𝑐𝑚−1, 𝐶 − 𝐻 alkyl symmetric and asymmetric strong stretches at 2922 − 2855 𝑐𝑚−1, 𝐶 = 𝑂 very strong stretch at 1740 𝑐𝑚−1, 𝐶 − 𝐻 terminal alkane bond at 1461, 1435 𝑐𝑚−1 and 𝐶 − 𝑂 − 𝐶 at 1095 𝑐𝑚−1. the study also identified the 𝐶 − 𝑂 ester group at 1190, 1170 𝑐𝑚−1, the 𝐶 − 𝑂 carboxylic group at 1380 𝑐𝑚−1, and the 𝐶 − 𝐻 bend at 723 𝑐𝑚−1. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 562 figure 4: ftir spectra of khaya senegalesis biodiesel table 4: functional groups in khaya senegalensis biodiesel. s/n wavelength (𝒄𝒎−𝟏) functional group 1 3004 = 𝐶 − 𝐻 weak stretch (alkene) 2 2922, 2855 𝐶 − 𝐻 strong stretch (alkanes) 3 1740 𝐶 = 𝑂 strong stretch (alkanoic & ester) 4 1461, 1435 𝐶 − 𝐻 medium stretch (terminal alkane bend) 5 1380 𝐶 − 𝑂 weak stretch (alkanoic) 6 1190, 1170 𝐶 − 𝑂 medium stretch, (esters) 7 1095 𝐶 − 𝑂 − 𝐶 weak stretch (alkanoate) 8 723 𝐶 = 𝐶 − 𝐻 medium stretch (alkene bending) comparing figure 4 with figure 1 and table 4 with table 1, the following observations were made: the alkanes and alkenes were unaltered during the conversion since peaks at 3004 𝑐𝑚−1 and 2922 − 2855 𝑐𝑚−1, 1461 𝑐𝑚−1 and 723 𝑐𝑚−1 were observed in both crude oil and biodiesel of ks. however, the position of the 𝐶 = 𝑂 shifted from 1744 𝑐𝑚−1 in the crude oil to 1740 𝑐𝑚−1 in the biodiesel, indicating some sort of transformation. from this, it can be said that the carboxylic functional group in the crude oil has been converted to the ester group during the transesterification reaction. similarly, the occurrence of 1190, 1170 𝑐𝑚−1 peaks in the biodiesel due to the 𝐶 − 𝑂 bond indicates a formation of esters, since natural esters occurred at 1062 𝑐𝑚−1 in the crude ks oil. based on this result, it is deduced that triglyceride molecules have been converted to fatty acid methyl esters (biodiesel). this study is consistent with dass et al., (2018), who observed 𝐶 = 𝑂, 𝐶 = 𝐶, 𝐶 − 𝑂, 𝐶 − 𝐶 stretch and 𝐶 − 𝐻 bending at 1744.4, 1461.1, 1237.6, 1162.9 and 723.1 𝑐𝑚−1, respectively, in biodiesel produced from a mahogany fruit shell. in the same way alhassan et al., (2017) attributed 1709, 1248 and 1611 𝑐𝑚−1 to 𝐶 = 𝑂, 𝐶 − 𝑂 and 𝐶 = 𝐶 groups, respectively, that the present study is in agreement with. 3.5 gc-ms of ks biodiesel at 𝟏. 𝟐𝟓 % catalyst figure 5: gc-ms spectra of khaya senegalesis biodiesel at 1.25 % cat. conc. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 563 table 5: compounds present in khaya senegalesis biodiesel at 1.25 % cat. conc. pk rt area % library/id formula 1 13.630 0.34 tridecanoic acid, methyl ester 𝐶14𝐻28𝑂2 2 15.779 10.20 palmitic acid, methyl ester 𝐶17𝐻34𝑂2 3 17.494 12.22 11-octadecenoic acid, methyl ester 𝐶19𝐻36𝑂2 4 17.815 38.13 9-octadecenoic acid, methyl ester 𝐶19𝐻36𝑂2 5 17.856 14.09 5-octadecenoic acid, methyl ester 𝐶19𝐻36𝑂2 6 18.230 5.81 oleic acid 𝐶18𝐻34𝑂2 7 19.288 2.79 octadecyl vinyl ether 𝐶20𝐻40𝑂 8 19.442 3.96 eicosanoic acid, methyl ester 𝐶21𝐻42𝑂2 9 19.583 1.98 tetradecanoic acid methyl ester 𝐶16𝐻32𝑂2 10 20.796 7.51 9-octadecenal 𝐶18𝐻32𝑂 11 20.933 1.85 2-butyloctanol 𝐶12𝐻26𝑂 12 21.030 1.10 eicosanoic acid, methyl ester 𝐶21𝐻42𝑂2 the gc-ms analysis of the khaya senegalensis biodiesel showed the presence of 12 compounds. major compounds include: 9-octadecenoic acid, methyl ester at retention time of 17.815 𝑚𝑖𝑛 occupying the largest area of 38.13 %, 5-octadecenoic acid, methyl ester at retention time 17.856 𝑚𝑖𝑛 with area of 14.09 %, 11octadecenoic acid, methyl ester at retention time 17.494 𝑚𝑖𝑛 with area 12.22 %, palmitic acid, methyl ester at retention time 15.779 𝑚𝑖𝑛 occupying 10.20 % area, (-octadecenal at retention time 20.796 𝑚𝑖𝑛 with area of 7.51 %, oleic acid at retention time 18.230 𝑚𝑖𝑛 with area 5.81 %, eicosanoic acid, methyl ester at retention time 19.442 𝑚𝑖𝑛 occupying 3.96 % area. the percentage area shows the amount of each compound present in the biodiesel as a percentage. the higher the area it occupies the larger the compound percentage in the mixture. for a biodiesel it is expected that methyl ester occupies a larger area. from the result the total methyl esters accounted for 82.02%. the effect of methyl esters on biodiesel includes imparting high heating value and short ignition delay in the biodiesel. comparing figure 2 with figure 5 and table 2 with table 5, it was observed that 25.86 % ester in the crude oil has increased to 82.02 % in the biodiesel. this result is in agreement with figure 4, which shows the conversion of triglyceride molecules to fatty acid methyl esters. the outcome of the present study conforms with dass et al., (2018), who reported 9-octadecenoic acid (z), methyl ester, hexadecanoic acid (z) methyl ester, 12-octadecenoic acid (z), methyl ester in biodiesel produced from mahogany fruit shell. 3.6 nmr of ks biodiesel from figure 6, the chemical shift of the signals is shown in table 6 of ks biodiesel. as shown from the results, there are no peaks in the range 4.00 − 4.20 ppm, indicating that conversion of triglyceride molecules has taken place. this is further confirmed by the presence of peaks at 3.6 ppm, implying the formation of fatty acid methyl esters. this result further validates the ftir result of biodiesel in figure 4 and gcms result of biodiesel in figure 5. the nmr result of the present study is consistent with a study as reported elsewhere (hossain et al., 2021). similarly, from figure 6, a peak was observed at 5.3 ppm, corresponding to carboncarbon double in the biodiesel. other carbon-carbon single bonds were also identified in the range 2.3 − 0.9 ppm. these results are consistent with that of fu et al., (2021). figure 6: 1h-nmr spectrum of ks biodiesel http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 564 table 6: chemical shift of main resonances in ks biodiesel. s/n chemical shift (𝒑𝒑𝒎) multiplicity nature of carbon 1 5.3 𝐻𝐶 = 𝐶𝐻 2 3.6 𝐻3𝐶 − 𝑂 3 2.3 𝛼 − 𝐶𝐻2 4 1.9 𝐻2𝐶 − 𝐶 = 𝐶 5 1.3 − 1.6 (𝐶𝐻2)𝑛 6 0.9 𝐶𝐻3 from figure 6, the chemical shift of the signals is shown in table 6 of ks biodiesel. as shown from the results, there are no peaks in the range 4.00 − 4.20 𝑝𝑝𝑚, indicating that conversion of triglyceride molecules has taken place. this is further confirmed by the presence of peaks at 3.6 𝑝𝑝𝑚, implying the formation of fatty acid methyl esters. this result further validates the ftir result of biodiesel in figure 4 and gcms result of biodiesel in figure 5. the nmr result of the present study is consistent with a study as reported elsewhere (hossain et al., 2021). similarly, from figure 6, a peak was observed at 5.3 𝑝𝑝𝑚, corresponding to carboncarbon double in the biodiesel. other carbon-carbon single bonds were also identified in the range 2.3 − 0.9 𝑝𝑝𝑚. these results are consistent with that of fu et al., (2021). based on the 1h-nmr result in figure 6, the present study further observed: alkanes, alkenes, carbonyl and esters chemical environments present in khaya senegalensis biodiesel. the 1h-nmr results in figure 6 are consistent with the ftir result of biodiesel in figure 4 and gc-ms result of biodiesel in figure 5. 3.7 conventional diesel ftir from figure 7 and table 7 of ftir of the conventional or reference diesel, 𝐶 − 𝐻2 and 𝐶 − 𝐻3 asymmetric and symmetric bonds were observed at 2952 𝑐𝑚−1 and 2955, 2855 𝑐𝑚−1, respectively, 𝐶 = 𝐶 at 1602 𝑐𝑚−1, 𝐶 − 𝐻2/𝐶 − 𝐻3 alkane bend at 1379 − 1457 𝑐𝑚−1, and = 𝐶 − 𝐻 bending at 723 − 850 𝑐𝑚−1. the 𝐶 − 𝐻2 and 𝐶 − 𝐻3 asymmetric and symmetric bond observed in this study is consistent with observations by qasim et al., (2017), likewise the 𝐶 = 𝐶 bond observed in this study is in concords with report by ismail et al., (2009), and lastly the 𝐶 − 𝐻2/𝐶 − 𝐻3 alkane bend and = 𝐶 − 𝐻 observed in the conventional diesel agrees with studies by attia et al., (2020). figure 7: ftir spectra of conventional diesel. table 7: functional groups in conventional diesel. s/n wavelength (𝒄𝒎−𝟏) functional group 1 2952 𝐶 − 𝐻2 medium stretch (alkene) 2 2922, 2855 𝐶 − 𝐻3 asym./sym. strongh stretch (alkanes) 3 1602 𝐶 = 𝐶 weak stretch (conjugated alkene) 4 1457, 1379 𝐶 − 𝐻2/𝐶 − 𝐻3 medium stretch (alkane bending) 5 812, 740 𝐶 = 𝐶 − 𝐻 weak stretch (alkene bending) based on the ftir result in figure 7, it was observed that basic hydrocarbons (alkanes and alkenes functional groups) are present in conventional biodiesel. this finding is consistent with a similar report by mueller et al., (2012) on the structure of hydrocarbon fuel. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 565 3.8 conventional diesel nmr from figure 8 – the nmr graph of the conventional diesel, of which the correspondent chemical shift of the signals is represented in table 8. the result has shown; protons in terminal methyl (𝐶𝐻3) groups were observed between the range 0.71 − 0.9 𝑝𝑝𝑚. methylene (𝐶𝐻2)𝑛 groups in the range 1.09 − 2.0 𝑝𝑝𝑚 and 𝛼 − 𝐶𝐻2 protons in the range 2.0 − 2.8 𝑝𝑝𝑚. the chemical shift of the terminal methyl group is consistent with the report by vukovi et al., (2018), and that of methylene and 𝛼 − 𝐶𝐻2 groups are in accordance with findings by sharma et al., (2020). figure 8: 1h-nmr spectrum of conventional diesel. table 8: chemical shift of main resonances in conventional diesel. s/n chemical shift (𝒑𝒑𝒎) multiplicity nature of carbon 1 0.71 − 0.9 𝐶𝐻3 2 1.09 − 2.0 (𝐶𝐻2)𝑛 3 2.0 − 2.8 𝛼 − 𝐶𝐻2 based on the 1h-nmr result in figure 8, the study observed that alkanes and alkenes chemical environments are present in the conventional diesel. the chemical environments identified by the 1h-nmr in figure 8 are in agreement with the ftir result of conventional diesel in figure 7 that identifies alkane and alkenes functional groups. comparing the produced biodiesel and conventional diesel, the ftirs in figures 1 and 4 both agree that both fuels contain alkanes and alkenes functional groups. the presence of alkanes contributes to the combustion efficiency and high cetane number of the fuels. alkenes, on the other hand, contribute improved flow properties to the fuels, and this is in conformity to ishaya et al.,, (2022). however, the 1h-nmr spectrum of ks biodiesel differs from that of conventional diesel in that it contains fatty acid methyl esters. these esters are long-chain hydrocarbons (between 12 − 22 carbon atoms). the existence of these long chains will impart high heating value and short ignition delay in the biodiesel. comparing earlier studies under the same experimental conditions by ishaya et al., (2020a) at 0.50 % catalyst concentration, and ishaya et al., (2020b) at 1.00 % catalyst concentration on the same feedstock, with the present study at 1.25 % catalyst concentration; the biodiesel yield are 55.99 %, 71.73 % and 82.02 %. the result shows that as the concentration of catalyst is increased, there is a corresponding increase in biodiesel yield (zubairu et al., 2021). this trend is attributed to increased catalytic activity that results in lowering of the activation energy, thereby favoring biodiesel yield. this observation is consistent with studies by ishaya et al., (2020a), ishaya et al., (2020b). 4. conclusion in this study, triglyceride conversion in ks crude vegetable oil to fatty acid methyl esters at 1.25 % 𝑁𝑎𝑂𝐻 catalyst concentration and 1: 6 oil-methanol molar ratio. it was observed through the gcms technique that 25.86 % ester in the crude oil was converted to 82.02 % in the biodiesel via transesterification reaction. the ftir and 1h-nmr technique used in this study further supports and confirms the conversion of triglyceride molecules in the crude oil to fatty acid methyl esters in the biodiesel. the comparison between the biodiesel http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 557-568. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 566 produced and the conventional diesel by ftir and 1h-nmr technique shows that both fuels contain alkanes and alkenes functional groups. the present study is consistent with earlier previous studies in that 9octadecenoic acid, methyl ester was the major ester formed in the biodiesel. the present study also conforms with earlier studies such that, as catalyst concentration increases, the biodiesel yield 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juliflora biomass catalyst for efficient biodiesel production and environmental impact assessment. scientific reports, 15(1):4472. weldeslase, mg., benti, ne., desta, ma. and mekonnen, ys. 2023. maximizing biodiesel production from waste cooking oil with lime-based zinc-doped cao using response surface methodology. scientific reports, 13(1):4430. zubairu a., gimba asb. and abdullahi am. 2021. production and characterization of biodiesel from hybrid feedstock of jatropha curcas and thevetia peruviana seeds oil. arid zone journal of engineering, technology & environment, 17(4):469-480. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com corresponding author’s email address: jagoayomikun@gmail.com 626 arid zone journal of engineering, technology & environment original research article barriers to adoption of construction 4.0 for circular economy: a qualitative approach a.a. soyingbe1, and a.c. jago1* 1 department of building, university of lagos, lagos, 101017, nigeria corresponding author’s email: jagoayomikun@gmail.com article information abstract despite global advances in construction 4.0 technologies for supporting circular economy (ce) goals, adoption remains limited in developing countries particularly nigeria where contextual barriers remain poorly understood. digital tools such as building information modelling (bim) and internet of things (iot), drive sustainability through resource efficiency, waste minimization, and a closed-loop material flow. however, the extent to which these technologies are adopted in developing countries like nigeria remains under-researched. this study investigates the specific challenges impeding the adoption of construction 4.0 technologies in advancing ce practices within the nigerian construction industry. while global literature highlights barriers such as cost, regulatory gaps, and resistance to change, this research uncovers localized obstacles including infrastructural deficiencies, poor internet reliability, dominance of the informal construction sector, and limited technical training opportunities. using a qualitative research design, semi-structured interviews were conducted with industry professionals in lagos state, nigeria who were selected through purposive and snowball sampling to ensure relevance insights. thematic analysis revealed that while most of the barriers identified mirror those already established in global literature such as high implementation costs, general lack of awareness, regulatory inadequacies, lack of standardization, skill shortages and implementation capacity, the study also uncovers additional, context-specific challenges that deepen understanding of these barriers in nigeria’s setting. these include chronic infrastructural deficiencies such as unreliable internet and power supply, the dominance of an informal construction sector that resists standardization and technological uptake, and deep-seated cultural resistance to digital transformation. furthermore, the study finds that even where awareness of technologies like bim exists, practical adoption remains minimal due to the absence of policy support, technical training frameworks, and adequate incentives. for instance, several participants noted that construction 4.0 tools are seen as “premium” and often incompatible with the cost and workflow structures of smalland medium-sized firms, especially those operating informally. this paper contributes to the literature by situating global adoption challenges within a localized nigerian context, highlighting how familiar barriers are amplified by the institutional dynamics specific to developing countries, particularly nigeria. the findings offer insights for policymakers, construction firms, and educators seeking to promote ce through construction 4.0. the findings also have practical implications for improving policy, workforce training, and infrastructure investment strategies tailored to nigeria’s construction sector. by revealing how global challenges manifest in context-specific ways, the study supports the development of targeted interventions that bridge the gap between innovation and local feasibility. received: 19th february 2025 revised: 1st may 2025 accepted: 1st may 2025 keywords: construction 4.0 circular economy nigerian construction industry technology adoption sustainable construction © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. azojete june 2025. vol.21(2):626-636 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/027 www.azojete.com.ng mailto:jagoayomikun@gmail.com mailto:jagoayomikun@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 627 1.0 introduction the construction sector in nigeria is a vital component of the country's economic progress, with a notable impact on its gdp (ajayi et al., 2019). however, the industry faces numerous challenges that hinder its sustainable growth. one of the primary issues is the industry's linear model of production, which is characterized by a "take-make-waste" approach (ajayi & kolo, 2018; muhammad et al., 2020). the reliance on this linear model not only drains our natural resources but also leads to significant waste and environmental harm, challenging the very essence of sustainability (akinade et al., 2018). additionally, the industry's reliance on traditional construction methods and technologies often results in low productivity, inefficient resource utilization, and increased greenhouse gas emissions (oke et al., 2019). a circular economy (ce) represents a shift from the conventional linear economy, focusing on maximizing the longevity and value retention of products, materials, and resources. (akinade et al., 2020). the ce model emphasizes the principles of reduce, reuse, and recycle, with the goal of minimizing waste and maximizing resource efficiency (ajayi & kolo, 2018; bakar et al., 2021). in the context of the construction industry, the adoption of a circular economy (ce) can lead to significant environmental, economic, and social benefits, such as reduced waste, improved resource efficiency, and the creation of new job opportunities (akinade et al., 2020; amusan et al., 2019). however, the implementation of ce in the nigerian construction industry faces several challenges, including a lack of awareness, limited access to technology, and regulatory barriers (oke et al., 2019; dada et al., 2020). construction 4.0 technologies, which encompass a range of digital tools and technologies, such as building information modeling (bim), the internet of things (iot), and additive manufacturing, can help address some of these challenges (ajayi et al., 2019). these technologies can enhance resource efficiency, improve waste management, and facilitate the transition towards a more sustainable construction industry (akinade et al., 2018; adeyemi et al., 2021). for example, bim provides detailed information about a building's materials and components, enabling better decision-making about resource use and waste management (succar, 2019). furthermore, construction 4.0 technologies can facilitate the reuse and recycling of materials in the construction industry. for example, iot devices can track the usage and condition of materials and components, providing valuable data for decision-making about reuse and recycling (opoku & ahmed, 2019). construction 4.0 technologies can also promote energy efficiency in the construction industry, contributing to a reduction in carbon emissions. for instance, ai can be used to optimize energy use in buildings, reducing their environmental impact (ogunnusi et al., 2020). globally, the construction industry is increasingly turning to these construction 4.0 technologies to facilitate a shift towards circular economy practices. bim exemplifies this by enhancing design and construction efficiency, leading to significant waste reduction and fostering material reuse (ajayi & kolo, 2018). iot-enabled sensors can provide real-time data on resource consumption and waste generation, allowing for more informed decision-making and the implementation of circular strategies (akinade et al., 2020). additive manufacturing, or 3d printing, can enable the production of custommade components, reducing material waste and facilitating the reuse of materials (ajayi et al., 2019; oladapo et al., 2020). table 1: circular economy principles and the corresponding construction 4.0 technologies circular economy principles construction 4.0 technologies that can facilitate it design for circularity building information modeling (bim) augmented and virtual reality (ar/vr) resource optimization internet of things (iot) extended lifecycle internet of things (iot) collaborative partnerships artificial intelligence (ai) source: (el-omari et al., 2018) the slow adoption of construction 4.0 technologies for a circular economy in the nigerian construction industry is a critical issue that requires further investigation. while there is a growing body of research on the potential benefits of ce and construction 4.0 in the industry, there is a lack of empirical studies that specifically examined the barriers to the adoption of these technologies in nigeria (ojelabi et al., 2017). previous studies have identified various obstacles to the adoption of circular economy practices in the construction industry globally. for instance, gunduz & almuajebh (2020) highlighted the lack of awareness and understanding of circular economy among industry stakeholders as a significant barrier. ajayi & oyedele (2018) pointed out the inadequate government policies and regulations that fail to support circular economy initiatives. additionally, bohari et al. (2017) noted the limited access to financing and investment for circular economy projects, while akinade et al. (2018) emphasized the lack of collaboration and coordination among different stakeholders as a critical challenge. while these studies provide valuable insights into the barriers to circular economy http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 628 adoption, they are predominantly based on research conducted in other countries. the applicability of their findings to the nigerian construction industry is limited due to the distinct cultural, economic, and regulatory environments. for instance, aghimien et al. (2018) argue that these differences necessitate a localized investigation to understand the specific challenges faced in nigeria. moreover, existing research has largely focused on general circular economy practices in the construction industry, without specifically addressing the role of construction 4.0 technologies in facilitating the transition towards a circular economy. oesterreich & teuteberg (2016) suggest that the integration of advanced digital technologies is crucial for the successful implementation of circular economy principles in the construction sector, as these technologies enable efficient waste reduction, resource optimization, and closed-loop material flows. the current research discussion on this topic suggests that the successful implementation of construction 4.0 technologies for a circular economy in the nigerian construction industry requires a deeper understanding of the specific challenges and barriers faced by industry stakeholders (oke et al., 2019; osunsanmi et al., 2020). these barriers may include technological, organizational, financial, and regulatory factors, as well as cultural and behavioral aspects (osunsanmi et al., 2020; ugochukwu et al., 2021). hence, to address this research gap, this study seeks to examine the barriers to the adoption of construction 4.0 technologies for a circular economy in the nigerian construction industry. 2. materials and method 2.1 research area figure 1: map of lagos state showing local government areas source: adapted from aderamo and magaji (2010). the research area for this study is lagos state, nigeria. as shown in figure 1, lagos state comprises a dense mix of urban and peri-urban regions, many of which are characterized by infrastructural limitations and informal construction practices, lagos is strategically located in the southwestern part of nigeria, with its borders defined by ogun state, the republic of benin, and the atlantic ocean. a rapidly growing city with a dense population, and a significant hub for construction activities in the country. the city is characterized by an urgent demand for sustainable construction practices, making it an ideal location to investigate the barriers to the adoption of construction 4.0 technologies aimed at promoting a circular economy. the city's fast-paced growth and need for modernization highlight the importance of integrating advanced technologies in construction processes to achieve sustainable development goals. http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 629 2.2 sampling technique and method of data collection this study employs a qualitative research design, semi-structured interviews were conducted to gather indepth insights. the flexibility of semi-structured interviews allowed for a deeper exploration of the challenges and perceptions regarding the adoption of these advanced technologies in the context of a circular economy. the study population consists of construction professionals, including project managers, builders, engineers, and site supervisors within the lagos state construction industry who are involved in construction projects that are working towards adoption of construction 4.0 technologies aimed at fostering a circular economy. when conducting interviews, it is recommended to use saturation as a measure of importance. when the research aims to explore the most frequent concepts, a sample size of 10 units is considered adequate weller et al. (2018). this aligns with hennink & kaiser (2022) who opined 9-17 interviewee is sufficient for interviews that necessitates the identification of particular trends. therefore, this study sought to gather 15 (fifteen interviews). eventually, the total interview conducted were 10 (ten) out of 15 (fifteen) consulted experts in lagos state which is in line with hennink & kaiser (2022) recommendation for sample size. interviewees were intentionally selected using purposive and snowball sampling technique, based on their extensive experience in the construction industry and their active engagement with construction 4.0 technologies, along with their understanding of the potential for these technologies in supporting a circular economy. the collected data was transcribed, coded, and thematically analyzed using qualitative data analysis software. the numerous data collected during the field survey was subjected to a computer-assisted qualitative data analysis software (caqdas). the caqdas that was used to support the analysis of this study is nvivo, it was used to generate word clouds. key themes were identified, and the findings were presented using charts, tables, and narratives to provide a comprehensive understanding of the barriers to the adoption of construction 4.0 technologies for circularity. 3. results and discussion figure 2 shows the demographic information of the participants, the analysis reveals that 80% of the respondents were male, while 20% were female, indicating a predominance of male professionals in the study. this gender distribution is consistent with the typical male-dominated nature of the construction industry. although this study did not specifically examine gender-based differences in the adoption of construction 4.0 technologies, the demographic distribution is consistent with the broader industry context and supports the relevance of the sampled perspectives. in terms of professional designations, 50% of the participants were construction managers, registered builders accounted for 20%, and quantity surveyors made up 10% of the participants. material flow scientists, environmentalists, and green building and sustainability experts were also represented, each constituting 10%. this diversity in professional roles ensures a broad perspective on the barriers to adopting construction 4.0 technologies for circularity. while it may seem like some professions were not duly represented, the selection strategy prioritized experts who could offer informed insights into construction 4.0 adoption, regardless of traditional job titles. the work experience distribution shows that 10% of participants had 0-10 years of experience, 50% had 10-20 years, and 30% had 20-30 years of experience. this suggests that most respondents were mid to senior-level professionals with substantial experience in the construction industry. overall, the demographic profile indicates that the study captured insights from a diverse, experienced, and knowledgeable group of professionals, making the findings on the barriers to adopting construction 4.0 technologies in the nigerian construction industry both credible and comprehensive. http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 630 figure 2: demographic information of participants table 2: themes that emerged from the qualitative data analysis codes theme awareness barriers to adoption of construction 4.0 for circularity knowledge gap steep learning curve culture shock resistance to change cost transparency informal sector enabling environment incentives maintenance downtime from service providers sustainable materials user friendly regulation design integration client demand advocacy training thematic analysis of the interview transcripts led to the identification of several codes that were clustered into major themes. this theme represents the barriers to the adoption of construction 4.0 technologies for circularity. table 2 presents the codes generated during analysis and their corresponding theme. these themes explored the hurdles stakeholders in the construction industry face before, during and after the primary adoption of construction 4.0 technologies for circular economy. 80% 20% 10% 50% 20% 10% 10% 50% 20% 30% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% male female quantity surveyor construction manager registered builders material flow scientist & environmentalist green building and sustainability expert 0-10 10-20 20-30 g en d er e x p er ie n ce d es ig n at io n http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 631 figure 3: frequency of factors influencing adoption of construction 4.0 for circularity the analysis of the data reveals several significant barriers to the adoption of construction 4.0 in advancing a circular economy within the construction industry. from figure 3 above, among the most prominent challenges are awareness, knowledge gaps, and cost, each cited by all respondents (100%). the lack of awareness and knowledge is particularly detrimental in a sector where advanced technologies such as digital twins, automation, and the internet of things (iot) are essential for enabling resource efficiency and sustainable practices inherent to a circular economy. without adequate understanding of these innovations, industry players are unable to harness the potential benefits they offer, leaving traditional linear models in place. additionally, the high cost of implementing these technologies creates a financial barrier that prevents wider adoption, especially in a resource-constrained environment like nigeria's construction sector. another major barrier is resistance to change, identified by 9 respondents (90%). resistance to new technologies reflects a broader challenge within the construction industry, where entrenched practices are difficult to shift. this reluctance to embrace innovation slows down the transition towards more circular approaches, such as recycling construction materials and minimizing waste. alongside this, regulatory challenges and the lack of sufficient training, also cited by 9 respondents (90%), weak regulatory environments and insufficient policy incentives hinder the development of standards that encourage the adoption of sustainable practices and technologies that are key to construction 4.0. incentives, mentioned by 8 respondents (80%), further highlight the challenge of motivating industry stakeholders to invest in circular economy models. in the absence of strong governmental or market-based incentives, there is limited motivation to adopt construction 4.0 technologies, which could otherwise streamline processes, reduce waste, and promote resource reuse all core elements of the circular economy. moderate barriers include the steep learning curve and client demand, with 5 respondents (50%) mentioning these issues. the steep learning curve reflects the complexities involved in adopting construction 4.0 technologies, which require both technical expertise and a willingness to overhaul traditional methods. the lack of sufficient client demand for circular economy practices further compounds the challenge. other less frequently mentioned barriers, such as sustainable materials and design integration, each cited by 3 respondents (30%), highlight specific obstacles that are still relevant to the shift toward a circular economy. the scarcity of sustainable materials makes it difficult to implement circular principles, which depend on the availability of materials that can be reused or recycled. similarly, the challenge of design integration suggests that incorporating circular economy principles into the early design phases of construction projects remains a niche concern rather than a widespread practice. on the lower end of the barrier spectrum, issues such as transparency, maintenance, and downtime from service providers were cited the least, with 2 respondents (20%) mentioning transparency and maintenance, and only 1 respondent (10%) citing downtime. while these challenges may not be widespread, they still indicate specific technical and operational hurdles that could impede the smooth adoption of construction 4.0 technologies. 10 10 5 5 10 8 3 9 3 3 9 2 8 4 4 2 1 9 3 0 2 4 6 8 10 12 awareness knowledge gap steep learning curve client demand cost incentives sustainable materials resistance to change culture shock informal sector regulation transparency advocacy enabling environment user-friendly maintenance downtime from service provider training design integration http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 632 “people are very, very adamant to change in this part of the world. there are people who are afraid of making mistakes.” (respondent 3, male, registered builder) “the major thing is being on the same page with other stakeholders. the bim is meant to bring every one of us to a platform where we can all collaborate and identify gaps in our designs and costs. but in a situation where there are 3 or 4 major stakeholders on a particular project and only 2 are able to deploy bim effectively, there is no how you won't struggle. the number of those yet to deploy outweighs those that have. other apps that are deployed strictly within the organization and don't need a third party, it will be fine, but in construction, it’s not all about your organization, it’s more of the involvement of stakeholders.” (respondent 5, female, construction manager and chief operating officer) “the cost of implementation is always a major challenge. and because of nigeria, the way it is right now with the issue of inflation, there is no stability in the open markets and all of that. so, yes, the initial cost of implementation is the major factor for a lot of organizations to embrace this.” (respondent 8, female, green building and sustainability expert) “for us private individuals, we are willing to, you know, take the bull by the horns and ensure that we create sustainable green building measures in every of our construction. however, the government, what are they doing? are there any government buildings that is being registered at the moment as a green building? no. so government is not even encouraging its citizens to adopt these measures.” (respondent 8, female, green building and sustainability expert) “well, i would say there's low client demand because many clienteles still do not understand what it is. and so, there's no client push for contractors and consultants to deploy it.” (respondent 9, male, construction manager) “awareness is the major issue. if we are aware, we would not be doing destructive construction, that is, construct a building then destroying some part of it to patch it up. if you’re doing this for the first time, you have to learn from people doing it. you don’t assume. oh, and majority of those in the ecosystem who are new students don’t know these things as well.” (respondent 3, male, registered builder) “the technical know-how is still lacking. we have people afraid or unaware of the ability to use these technologies and afraid of the cost of investing in it, people think that these technologies are not affordable or are not easily accessible to them, it becomes a barrier for them to utilize it. we have quite a lot of issues too, in terms of the market inhibiting new innovations. they are used to traditional process. and so, the new innovation like this is sort of like a competitor or is regarded as a barrier to their own current process work processes.” (respondent 9, male, construction manager) “there is an awareness issues, people don't know enough. also, there is resistance to change and no proper regulatory framework to back it up. and looking at some short-term construction, it may be more costly to engage technologies like that, there is also the fear of mistakes especially on big projects. experimenting can leave people in debt.” (respondent 6, project manager) these identified barriers were further grouped into categories. table 3 presents a categorized summary of the barriers to the adoption of construction 4.0 technologies for circularity, as identified through the thematic analysis. the barriers were grouped into five overarching categories: knowledge and awareness, economic and financial, cultural and behavioral, institutional and environmental, and technical and operational. barriers under knowledge and awareness, such as limited awareness, knowledge gaps, and steep learning curves highlight the lack of exposure and training in construction 4.0 technologies among professionals. the economic and financial category, which includes cost-related concerns, lack of incentives, and access to sustainable materials, reflects the affordability challenges of implementing new technologies in a resourceconstrained environment. the cultural and behavioral category, comprising resistance to change and culture shock, points to entrenched habits and skepticism toward digital transformation in nigeria. meanwhile, institutional and environmental barriers such as regulation gaps, lack of advocacy, and dominance of the informal sector underscore systemic issues in nigeria's construction ecosystem that hinder standardization and innovation. finally, the technical and operational category addresses practical challenges like downtime from service providers, lack of user-friendly interfaces, insufficient maintenance systems, and poor integration of technologies into design workflows. http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 633 table 3: category of barriers to the adoption of construction 4.0 technologies for circularity challenge category awareness knowledge and awareness knowledge gap steep learning curve client demand cost economic and financial incentives sustainable materials resistance to change cultural and behavioral culture shock informal sector institutional and environmental regulation transparency advocacy enabling environment user-friendly technical and operational. maintenance downtime from service provider training design integration this classification helps structure the complexity of challenges into actionable domains, offering a clearer roadmap for targeted interventions. figure 3: barriers to the adoption of construction 4.0 technology for circularity in word cloud figure 3. presents a word cloud of the most frequently mentioned terms extracted from the interview transcripts. commonly cited barriers include market resistance, high cost, limited awareness, regulatory challenges, and economic constraints. the size of each term reflects its frequency and emphasis among participants findings from the theme indicate that stumbling blocks await stakeholders attempting to adopt these technologies at every stage of the construction process. these challenges can be broadly categorized into five key areas: knowledge and awareness, economic and financial, cultural and behavioral, institutional and http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 626-636. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jagoayomikun@gmail.com 634 environmental and technical and operational. widespread ignorance from both sides of the construction divide presents the major impediment to the adoption of construction 4.0 technology in the nigerian construction industry as does cost of acquisition and training. the awareness gap often leads stakeholders to avoid adopting these advanced technologies, preferring instead to play it safe with tried and trusted traditional methods. this aligns with findings by amadi et al., (2023) who highlighted risk aversion as a major hindrance to innovation adoption. in the nigerian political climate were getting any particular group to work in sync may be harder than it sounds, an endeavor such as construction 4.0 that requires heightened levels of collaboration among parties proves a real headache. moreover, the informal sector, which plays a crucial role in nigeria’s construction industry, is often overlooked, this indicates a significant gap in understanding the full scope of the construction workforce in nigeria. furthermore, the technicality of operating and maintaining construction 4.0 technology remains a major issue. much of the workforce simply lacks the high levels of skills required for such tasks. as a result, the learning curve for workers is steep and often discouraging. governmental inertia adds to stakeholders’ discouragement in embracing these practices. according to yuan et al., (2011) the lack of updated regulations and policies to mandate and support the adoption of construction 4.0 technologies and a circular economy is to blame. few building regulations emphasize energy conservation and recycling. those that do are woefully outdated in an era of alarming climate changes. additionally, the scarcity of locally sourced sustainable materials, often due to quality concerns forces contractors and clients to rely on more expensive and harder-to-source foreign products (pacheco-torgal et al., 2013). these findings highlight the multifaceted challenges that must be addressed to facilitate the adoption of construction 4.0 technologies in nigeria’s construction industry, particularly in advancing a circular economy. 4. conclusion following the results of the analysis, the study concludes that the adoption of construction 4.0 technologies for a circular economy in nigeria's construction industry is significantly hindered by several barriers. the most prominent barriers identified were high implementation costs, limited awareness, knowledge gaps, and resistance to change. additionally, the lack of regulatory frameworks and insufficient incentives further impede the industry's ability to transition to circular construction practices. the findings indicate that the reluctance of stakeholders to embrace digital technologies like bim, iot, and 3d printing stems largely from cultural, financial, and institutional challenges. these barriers collectively slow the industry's shift towards a circular economy, which is crucial for improving resource efficiency, minimizing waste, and promoting sustainability. without addressing these challenges, the widespread adoption of construction 4.0 technologies in nigeria will remain limited, hindering the overall progress towards circularity in the sector. the study recommends that the identified barriers should be given careful consideration during policy formulation and industry reform. there are currently no statutory mandates promoting the integration of these technologies in nigeria’s construction regulations. addressing this gap would enhance the industry’s sustainability and resource efficiency. furthermore, construction stakeholders must prioritize the selection and implementation of digital tools to foster circular economy practices. collaborative efforts should be made to ensure that these technologies are adopted across all stages of construction, particularly in the design and planning phases. by doing so, the 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(eds.), eco-efficient construction and building materials: life cycle assessment (lca), eco-labelling and case studies (pp. 1–10). woodhead publishing. succar, b. 2019. the bim manager’s handbook: guidance for professionals in architecture, engineering and construction. wiley-blackwell. ugochukwu, sc. and onyekwena, na. 2021. barriers to the adoption of construction 4.0 technologies in nigeria. journal of construction engineering and management. 147(10): 04021101. weller, sc. vickers, b., russell bh., blackburn, am., borgatti, s., gravlee, cc. and johnson, jc. 2018. openended interview questions and saturation. plos one. 13(6). yuan, hp., shen, ly., and wang, jy. 2011. major obstacles to improving the performance of waste management in china's construction industry. facilities. 29(5/6): 224–242. http://www.azojete.com.ng/ mailto:jagoayomikun@gmail.com corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 510 arid zone journal of engineering, technology & environment original research article modeling thermal death time (d – value) of bacillus cereus in acha (digitaria exilis) starch flour w. a. adebayo*, k. a. taiwo, o. alakija and o. c. olatunde department of food science and technology, obafemi awolowo university, ile-ife, nigeria. *corresponding author’s email: adebayoadewale@ymail.com & adebayow@oauife.edu.ng article information abstract this study investigated thermal death time (d – value) of bacillus cereus in acha starch flour, with the aim of providing thermo-bacteriological data that would enhance the safety of acha starch flour. the data would therefore serve as a guide to potential food processors, engineers and scientists thereby promoting the starch usage in food development and formulation beyond its present status. acha starch was prepared, stored under hygienic conditions and sterilized in an autoclave prior to its thermal treatments. the sample water activity (aw) was then adjusted, and the value confirmed via the aw meter. design expert 13 for window was used for the experimental lay-out, comprising three inactivation temperatures and aw values with all experiments conducted in triplicate. the bacillus cereus thermal destruction characteristics were obtained by plotting number of survivor (cfu/g) against time and corresponding d-value was determined. the d-values obtained were analyzed descriptively and inferentially using turkey’s posthoc test (designexpert 7.00) for window and fitted into a linear equation representing the dependent and independent variables. the d-value ranged from 20.4 to 12 min. as water activity and destruction temperature changed from 0.55 and 92.1 °c to 0.65 and 80 °c, respectively. the interactive effects of water activity and destruction temperature on natural logarithm of d-value of bacillus cereus in acha starch flour was linear. the maximum d-value was observed at 80 °c temperature when the water activity was 0.55. this study, therefore, provides valuable thermobacteriological data that could be employed as a guide to potential food processors, scientists and engineers in order to improve consumption safety of the product. received: 7th april 2025 revised: 8th may 2025 accepted: 10th may 2025 keywords: bacillus cereus d-value acha starch © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction starch is an important food product and raw ingredient for both the food and non–food industries. it is used in the food industry to thicken, preserve, and improve the quality of baked dishes, confectioneries, pastas, soups and sauces, and mayonnaises (egbarevba, 2019). in addition to its utilization in the food and beverage industries, cereal starch has several applications in health and medical, agriculture, textiles, pulp and paper, chemicals and pharmaceuticals, biofuel production, mining, and construction (przetaczek–rożnowska, 2017). among cereals, starch is mainly processed from corn which accounts for about 80% of world output while other main sources are rice, barley and millet (egbarevba, 2019). in 2015, 8.5 mt of starch was produced globally with approximately 11, 36, and 53% used as modified starch, native starch and sweetener, respectively (egbarevba, 2019). it also served as a primary source of energy in the human diet and so has significant economic value (laity et al., 2010; fao, 2019). therefore, the ever–increasing demands for starch in modern food and non–food industries have resulted into a dire need to source for starch from other readily available non–conventional sources. acha (digitaria exilis) is an underutilized and non–conventional grain cultivated mainly in west african sub-region. it belongs to the family of graminaea with its unique small kernel size of 0.4 – 0.5 mm making its processing tedious and laborious (adoukonou–sagbadja et al., 2007). it is also called hungry millet, hungry rice, fundi grain, white acha and acha millet. it thrives well on the marginal soils of the semi-arid regions where most cereals could not survive. major acha producing countries in west africa include azojete june 2025. vol.21(2):510-516 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/016 www.azojete.com.ng mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 510-16. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 511 cape verde, chad, nigeria, and even stretches south to the boundaries of tropical rain forest zones (glew et al., 2013). it serves as a staple grain to populations living in arid savannah which in terms of protein, crude fat, carbs, and vital minerals, compares favorably to rice, sorghum, maize, and millet (cruz, 2004; agu et al. 2020). also, abundance of sulphur–based amino acids like methionine and cysteine in acha grains surpasses popular legumes in content (enyiukwu and bassey, 2020). it is combined with other flours to make bread and is utilized to make couscous, acha jollof, and porridges (satimehin and philip, 2012). acha starch has a rich nutritional profile, offering a diverse range of essential nutrients, making it a valuable ingredient in local and international diets. recently, bacillus cereus has been frequently isolated from low moisture food products such as dried milk powder, powdered infant formulas, dried vegetables, herbs, spices and cereals despite their production involved heating or drying processes (satimehin and philip, 2012). furthermore, several works have documented that heat resistance of microbial populations tends to increase as water activity (𝑎𝑤) decreases (d’aoust, 1997; daryaei et al., 2018). the presence of pathogenic microorganisms such as bacillus cereus in low moisture foods is a significant concern for food safety. these resilient microorganisms can withstand heat treatment, dry conditions and may pose health risks if consumed (daryaei et al., 2018). this study then focused on modeling the d-value of bacillus cereus at different destruction temperatures and 𝑎𝑤 levels in acha starch flour with the view of providing thermobacteriological information as a guide to potential food processors, scientists and engineers in order to improve consumption safety of the product. 2. materials and methods 2.1 source of materials acha (digitaria exilis) grains devoid of defects was purchased from central market in ilorin, kwara state, nigeria while all chemicals needed for this work were of analytical grades. 2.2 sample preparation acha starch was prepared according to adebayo et al. (2024). acha grains (5 kg) was washed and destoned with portable water. the cleaned acha grains was steeped in water for 24 h at 28 °c. thereafter, the steep solution was discarded and the grains was re-washed with potable water. the steeped acha grains was wetmilled using a laboratory milling machine (falling number 3100, huddinge, sweden). the slurry obtained was diluted with 5 l of distilled water and subsequently screened using a muslin cloth. the filtrate was subsequently allowed to settle for 3 h in a stainless-steel decanting bowl, after which the supernatant was discarded. the starch slurry was then air dried. the starch flakes obtained were milled in a laboratory milling machine (retsch gm300, germany) and sieved (sieve size: 500 μm) to obtain the starch flour. 2.3 bacteria strain, inoculation and thermal treatment a properly stored acha starch flour (5 g) was weighed into 25 ml conical flask and was sterilize in an autoclave. the sample was transferred to water activity (aw) conditioning system to adjust the sample to a targeted aw value. prior to thermal treatment, sample was conditioned for 4 to 6 days at the targeted aw level to allow the entire sample to equilibrate to the targeted aw, which was subsequently confirmed via the aw meter (aqualab, model series 3 te, serial #09048826b). design expert 13 for window was used for the experimental lay-out, comprising three inactivation temperatures (80, 85, and 90 °c) and three aw values and all experiments were conducted in triplicate (table 1). the sample was inoculated with 1 ml of bacillus strain suspension. the hot water bath (neslab gp-400, newington, nh) was set at already predetermined temperatures (80, 85, and 90 °c). then, the flask was placed in the hot water bath and timed. come-up time was verified using a noninoculated sample in a conical flask with a k-type thermocouple located at the center of the flask. the comeup time for the sample core to reach within 0.5 °c of the targeted temperature was used as time 0 for the thermal inactivation. once a particular flask has reached its predetermined time, it was removed from the hot water bath. the samples were removed at an interval of 10 min starting with the time 0 samples. the flasks removed was left to cool and 1 g of the sample was introduced into tubes of serial dilution. 1 ml was transferred to dilution test tubes to serially dilute the sample. 1 ml from the dilution tubes was plated in duplicate on nutrient agar plates prepared based on manufacturer’s specification of 28 g to 1000 ml of distilled water and plates were then incubated for 24 h at 37 ºc. the same procedure was applied to the other test tubes at their individual times. after incubation, the number of colonies present on the plates were then counted to ascertain the level of survival of the organism. http://www.azojete.com.ng/ mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 510-16. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 512 table1: interactive effect of water activity and temperature on d-value of bacillus cereus in acha starch flour block 1 temperature, °c water activity d-value, min 1 block 1 90 0.45 2 block 1 85 0.55 3 block 1 80 0.45 4 block 1 85 0.55 5 block 1 85 0.55 6 block 1 90 0.65 7 block 1 80 0.65 8 block 1 85 0.69 9 block 1 85 0.40 10 block 1 85 0.55 11 block 1 77.93 0.55 12 block 1 85 0.55 13 block 1 92.07 0.55 2.4 conversion of number of microbial survivor to cfu/g the number of colonies counted was converted to colony-forming unit per g (cfu/g) using equation 1: cfu/g = 𝑁 × 𝑑𝑓 𝑚 1 where; log cfu/g = no of survivors; n = no. of microbial survivors; d𝑓 = dilution factor; m = mass of sample. then, cfu/g was plot against microbial destruction time and d-value was obtained as documented by toledo (2007). 2.5. statistical analysis data obtained was analyzed descriptively and inferentially using turkey’s posthoc test (design-expert 7.00) for window. 3. results and discussion interactive effect of water activity and destruction temperature on d-value of bacillus cereus in acha starch flour is presented in figure 1. figure 1: effects of water activity and temperature on d-value of bacillus cereus in acha starch flour it was observed that the d-value ranged from 20.4 to 12 min. as water activity and destruction temperature changed from 0.65 and 80 °c to 0.55 and 92.1 °c, respectively. it showed that lower d-values were obtained at lower water activities and higher destruction temperatures and vice versa. the d-value obtained was higher than 5 to 3.4 min reported for ginger but lower than 92.2 17.2 min and 148.5 23.3 min for cocoa nibs and cocoa beans, respectively (pereira et al., 2019; yehia, 2022). these differences may be associated with particle http://www.azojete.com.ng/ mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 510-16. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 513 size, food composition and structure, high surface area, moisture content variability, microbial load and strain variability and thermal conductivity ((daryaei et al., 2018). knowledge of the d-values is very important in the application of food processing as it allows producers to determine the necessary time and temperature combination to ensure safety and preservation of food products. additionally, the results revealed that as water activity decreased and destruction temperature increased, there is corresponding decrease in d-value of bacillus cereus in acha starch flour. the interactive effects of water activity and destruction temperature on natural logarithm of d-value of bacillus cereus in acha starch flour was linear. the maximum d-value was observed at 80 °c temperature when the water activity was 0.55. however, in order to select a model that best fits the experimental results, f-value and p-value were used for evaluation. both quadratic versus 2fi and linear versus mean models were selected for data fitting with f-value and p-value of 370 and <0.001; and 4.83 and 0.0483, respectively. the numerical model describing the effect of water activity and destruction temperature (°c) on d-value of bacillus cereus in acha starch flour was shown in equation 2: ln 𝐷 = 2.79 + 0.0264𝑎𝑤 − 0.201𝑇 − 0.000869𝑇 ∗ 𝑎𝑤 − 0.00214 𝑎𝑤 2 − 0.0193𝑇 2 where: 𝑎𝑤 is water activity, t is temperature, °c and d is d-value, min. the experimental data of the dependent variable was fitted into models to illustrate the relationship between the dependent variable and independent variables. multiple regression analysis carried out on the experimental data and the generated models were shown in table 2. the result showed that d-value was significantly influenced (p < 0.05) by both water activity and destruction temperature (table 2). table 2: regression analysis of water activity, temperature and d-value of bacillus cereus in acha starch flour model terms model f-value and probability levels f value p value models 248 < 0.0001 a: water activity 20.8 0.00260 b: temperature 0.00121 < 0.0001 ab 0.0113 0.918 a2 0.118 0.741 b2 9.63 0.0172 lack of fit 370 <0.0001 r2 0.994 adjusted r2 0.990 predicted 0.960 sd 0.0164 mean 2.77 cv (%) 0.591 ` analysis of variance (anova) was used to access the extent to which the selected quadratic vs 2fi and linear vs mean models adequately represented the data obtained for the d-value of bacillus cereus in acha starch flour (liyama-pathirana and shahidi, 2005). the result of anova for the respective d-values (responses) with their corresponding regression coefficients of determinations (r2) for the d-value of bacillus cereus in acha starch flour were generated by the software (table 2). the quadratic vs 2fi model f-value of 248 implies the model is significant and there is only a 0.01% chance that the model f-value this large could occur due to noise. therefore, p-values <0.0001 indicate model terms are significant. in this case a, b, ab, a² and b² are significant model terms. the adequacy and goodness-of-fit were evaluated using the regression coefficient (r2), predicted r2 and adjusted r2 (table 2). r2 is the percent of variance in the dependent variable (d-value) that is explained collectively by all the independent variables (water activity and temperature). inability of the model to give an (predicted r2 is not too close to the adjusted r2 as expected, the difference < 0.03) explanation of the variance in the response suggest that it might be necessary to give consideration to other factors that are relevant to the d-value of bacillus cereus in acha starch flour besides the two independent variables (water activity and temperature) used for the experiment. these factors may include: variation in agronomic characteristics within and among cultivar, ph of the starch sample, particle size, thermal conductivity, food composition, moisture content variability, microbial load and strain variability (daryaei et al., 2018). http://www.azojete.com.ng/ mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 510-16. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 514 the high values of adjusted r2 (0.994) recorded in this study (table 3) indicated that water activity and destruction temperature are all significant parameters for the determination of d-value of bacillus cereus in acha starch flour. the nonsignificant lack of fit (p < 0.0001) further enhanced the reliability of the model. table 3: fit statistics acha starch flour standard deviation 0.0164 mean 2.77 c.v % 0.591 r2 0.994 adjusted r2 0.990 predicted r2 0.960 adequate precision 0.0134 the r2 value of 0.994 and low p-value (< 0.0001) of the model depicts the statistical significance of the quadratic vs 2fi model. the results also showed that there were excellent correlations among the independent variables. thus, the fitted model could sufficiently portray the independent variables (adebayo et al., 2021). coefficient of variation (cv) is a measure expressing standard deviation as a percentage of the mean (chen et al., 2003). the cv illustrates the ratio of the standard deviation of the estimate to the mean values of the observed dependent variables. it also represents the degree of reproducibility and repeatability of the models. it described the extent to which the data were dispersed (table 3). the value of 0.591% recorded in this study signify that the models cannot be considered reproducible (cv < 10%) (chen et al., 2003). table 4: analysis of variance for lack of fit test source sum of square df mean square f-value p-value mean vs total 100 1 100 linear vs mean 00259 2 0.00129 4.82 0.0483 2fi vs linear 3.02e-006 1 3.02e-006 0.00609 0.939 quadratic vs 2f1 0.330 5 0.165 370 < 0.0001 cubic vs quadratic 0.00177 5 0.000883 38.9 0.000895 pure error 0.000113 4 2.27e-005 table 5: processing condition for desirability level number water activity temperature (°c) desirability 1 0.530 86.9 1.00 2 0.525 81.50 1.00 3 0.510 89.10 1.00 4 0.630 80.90 1.00 5 0.579 81.4 1.00 6 0.649 85.4 1.00 7 0.609 83.5 1.00 8 0.490 81.0 1.00 9 0.578 81.0 1.00 10 0.559 89.8 1.00 11 0.490 81.0 1.00 12 0.63 85.2 1.00 13 0.569 86.0 1.00 14 0.610 83.7 1.00 15 0.482 87.4 1.00 16 0.501 81.5 1.00 17 0.463 82.8 1.00 18 0.636 80.6 1.00 19 0.471 81.1 1.00 20 0.623 83.4 1.00 21 0.452 82.3 1.00 22 0.612 88.9 1.00 23 0.469 80.8 1.00 24 0.645 81.3 1.00 25 0.533 80.6 1.00 26 0.645 83.6 1.00 27 0.513 80.3 1.00 28 0.630 85.3 1.00 29 0.570 89.7 1.00 30 0.482 89.6 1.00 selected http://www.azojete.com.ng/ mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 510-16. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 515 anova of the regression parameters of the predicted response surface models for d-value of bacillus cereus in acha starch flour indicated the mean vs total, 2fi vs linear and cubic vs quadratic interaction did not produce a significant effect in each case (p<0.01) (table 4). thus, none of the two effects of independent variables was primarily responsible for determining the term that may cause significant effects in the response. the relation between independent and dependent variables was viewed through a three-dimensional representation of the responses surface concreted by the models. predicted minimum value for d-value of bacillus cereus in acha starch flour suggested the desirability of using water activity (0.482) and destruction temperature (89.6 °c) to achieve the minimum d-value of bacillus cereus in acha starch flour (table 5). 4. conclusion this study investigated modeling thermal death time (d-value) of bacillus cereus in acha starch flour (a low – moisture food) with the aim of providing the product’s thermal destruction characteristics on its safety. the key findings from this study showed minimum d-value was obtained at lower water activity and high destruction temperature while interactive effect of water activity and destruction temperature on d-value is linear. this information will provide valuable thermo-bacteriological data that could be employed to enhance the safety of acha starch flour utilization in food processing industries. references adebayo, wa., ogunsina, bs. and taiwo, ka. 2021. extrusion parameters impact on cooking qualities of plantain-wheat instant noodle, international journal of food science and agriculture, 5 (3): 399 – 410. adebayo, wa., ayodele, ea., ibidapo-obe, dt. and akinleye, tf. 2024. studies on some engineering properties of acha (digitaria exilis) starch, proceedings of obafemi awolowo university faculty of technology conference, 2024, pp 147 – 155 adoukonou–sagbadja, h., wagner, c., dansi, a., ahlemeyer, j., daïnou, o., akpagana, k. and friedt, w. 2007. genetic diversity and population differentiation of traditional acha millet (digitaria spp.) landraces from different agro–ecological zones of west africa, theoretical and applied genetics, 115(7): 917 – 931. agu, ho., onuoha, go., elijah, oe. and jideani, va. 2020. consumer acceptability of acha and malted bambara groundnut (bgn) biscuits sweetened with date palm, heliyon, 6. chen, d., fries, m., and lyon, jm. 2003. a statistical method of detecting bioremediation, journal of data sciences, 1:27– 41. cruz, jf. 2004. acha: a small grain with potential. leisa magazine on low external input and sustainable agriculture: valuing crop diversity, 20(1): 16 – 17. daryaei, h., peñaloza, w., hildebrandt, i., krishnamurthy, k., thiruvengadam, p. and wan. j. 2018. heat inactivation of shiga toxin-producing escherichia coli in a selection of low moisture foods, food control, 85:48 – 56. d’aoust, jy. 1997. salmonella and the chocolate industry: a review, journal of food protection, 40(19): 718 – 727. egharevba, h. 2019. chemical properties of starch and its application in the food industry. national institute for pharmaceutical research and development – niprd, idu, abuja, nigeria”. in chemical properties of starch and its application in the food industry, pp. 1 – 12). enyiukwu, dn. and bassey, in. 2020. acha (digitaria spp.): the good tasting, potential food security cereal for africa begs for research attention, direct research journal of agriculture and food science, 8(7): 231 – 238. fao, ifad, unicef, wfp and who2019. the state of food security and nutrition in the world 2019: safeguarding against economic slowdowns and downturns. fao. glew rh., laabes, ep., presley, jm., schulze, j., andrews, r., wang, yc., chang, yc. and chuang, lt. 2013. fatty acid, amino acid, mineral and antioxidant contents of acha (digitaria exilis) grown on the jos plateau, nigeria, international journal of nutrition and metabolism, 5(1): 1 – 8. http://www.azojete.com.ng/ mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 510-16. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adebayoadewale@ymail.com & adebayow@oauife.edu.ng 516 laity, p., cassidy, a., skepper, j., jones, b., and cameron, r., 2010. investigation into the intragranular structures of microcrystalline cellulose and pre–gelatinized starch, european journal of pharmaceutics and biopharmaceutics, 74: 377 – 387. liyana-patharana, c. and shadidi, f. 2005. optimization of extraction of phenolic compounds from wheat using response surface methodology, food chemistry, 936: 47 – 56. pereira, apm., stelari, ha., carlin, f. and sant’ana, as. 2019. inactivation kinetics of bacillus cereus and geobacillus stearothermophilus spores through roasting of cocoa beans and nibs, lwt, 111: 394 – 400. https://doi.org/10.1016/j.lwt.2019.05.063 przetaczek–rożnowska, i. 2017. physicochemical properties of starches isolated from pumpkin compared with potato and corn starches, international journal of biological macromolecules, 101: 536 – 542. satimehin, aa. and philip, tk. 2012. physical properties of acha as affected by moisture content, agricultural engineering international: cigr journal, 14(4): 231 – 237. toledo, rt. 2007. fundamentals of food process engineering, springer, pp. 310 – 311. yehia, hm., ragab, gh., hegazy, mi., and abd el-hameed, am. 2022. analysis of spore-forming bacterial contaminants in herbs and spices and evaluation of their heat resistance, food science and technology, 42, e19422. https://doi.org/10.1590/fst.19422 http://www.azojete.com.ng/ mailto:adebayoadewale@ymail.com mailto:adebayow@oauife.edu.ng https://doi.org/10.1016/j.lwt.2019.05.063 https://doi.org/10.1590/fst.19422 corresponding author’s email address: zainabobaone@gmail.com 1039 arid zone journal of engineering, technology & environment review article recent trends in the optimal renewable power dispatch frameworks in renewable energy-reliant power systems z. oba-sulaiman*, s. o. adetona, a. s. alayande, a. balogun department of electrical and electronics engineering, university of lagos, nigeria *corresponding author’s email: zainabobaone@gmail.com article information abstract this study presents a comprehensive survey of optimal renewable power dispatch (orpd) frameworks in grid-rich renewables. the work employs comparative, and trend approaches to analyze optimization methods for orpd of 61 relevant studies published from 2018 to 2024 by making use seven parameters emerged from the overall studies include voltage stability, carbon footprint, active power, reactive power, power loss, congestion, and energy storage. the results were tabulated using bibliometric tables, trend analysis, charts, and figures. the results show that previous research mainly emphasized minimizing economic cost through active power and loss optimization. however, voltage stability and congestion constraints were rarely integrated into the optimization framework simultaneously. despite this, most studies remain focused on tackling these issues individually, where voltage stability is usually treated as a minor constraint, loss minimization is framed as a separate objective, and congestion management is approached through standalone mechanisms. while some integrated frameworks exist, they often address a limited scope of objectives, resulting in omissions in the development of comprehensive models. to close this significant research gap, there is need for the development of robust, multi-objective, and computationally efficient frameworks that holistically address these intertwined issues. the findings will therefore have academic, technical, and practical relevance, offering both theoretical contributions and actionable solutions for future power system planning and operation. received: 20th october 2025 revised: 12th november 2025 accepted: 13th november 2025 keywords: renewable energy voltage stability optimal dispatch congestion mitigation power loss reduction © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction traditionally, electricity generated through conventional sources have long proven as most stable but they contributed significantly to global warming as a result of pronounced carbon dioxide (co2) footprint and capitally expensive in terms of maintenance (das et al., 2021; das and de, 2023; mayer et al., 2020). however, many research effort have been devoted to mitigation of climate change for planet protection (fawzy et al., 2020; kaack et al., 2022; lehmann et al., 2021; olabi and abdelkareem, 2022). subsequently, with the emphasis on mitigating climatic factors, the addition of green energy plants and energy storage (es) facilities are also important (monforti-ferrario and blanco, 2021; and sifakis et al., 2021). a search through literatures show wide sparsity of understanding on the related inclusion of renewable energy sources (ress) and storage units in system stability models (ahmed et al., 2022; fatin ishraque et al., 2021; miracle et al., 2023; and numan et al., 2023). 1.1 background and context the global migration to sustainable energy has increased the penetration of ress within electrical distribution systems. while this transformation supports sustainable goals, it as well mitigates dependence on conventional fossil-based energy (husin et al., 2021; infield and freris, 2020; shafiul alam et al., 2020; and sinsel et al., 2020). azojete december 2025. vol.21(4):1039-1053 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/013 www.azojete.com.ng mailto:zainabobaone@gmail.com mailto:zainabobaone@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1040 this transition brings operational challenges because of the intermittent and non-linear structure of ress (bajaj and singh, 2020; mararakanye and bekker, 2019; and worighi et al., 2019). power losses (pl), nonoptimal generation dispatch, voltage instability and congestion are part of the most common pressing issues. the ress variability and reliance on inverter-based interfaces result to limited reactive power (q) support and inertial, making systems more prone to voltage instability, especially in weakly interconnected areas. renewables are often sited far from load centers, requiring long-distance transmission that increases the line losses, while intermittent injections and reverse flows in distribution networks further increase technical losses. in addition, the spatial mismatch between renewable generation hubs and demand centers frequently overloads transmission environments, creating congestion that is harder to manage with reduced availability of flexible classical generation. although, several studies such as those by hosseinzadeh et al. (2021), sifakis et al. (2021), and yan et al. (2024) have addressed individual objectives like eco-economic optimization and loss minimization, none provide a holistic orpd framework that rigorously integrates voltage stability constraints together with loss and congestion management. therefore, there is need to address this gap to mitigate congestion and power losses simultaneously. 2. methodology figure 1 presents the systematic review process adopted in this study to analyze recent developments in orpd frameworks between 2018 and 2024. the flowchart illustrates a structured and transparent review pipeline that ensures reproductivity and minimizes selection bias. the methodology combines elements of scoping review, bibliometric mapping, and comparative thematic analysis, providing both breadth and depth in the investigation of orpd research. overall, the figure shows a robust and thorough methodology that combines number-crunching both bibliometric with in-depth qualitative content evaluation, ensuring the results accurately reflect preferred method, current trends and emerging needs within orpd research. this methodological rigor forms the analytical foundation for the subsequent comparative assessment in table 1. figure 1: methodological technique for the reviewed studies 2.1 search strategy it is evident in figure 1 that the procedure starts with scoping and planning that involves defining the review boundaries, identifying research gaps, and formulating key search terms around core orpd parameters, which are, voltage stability (vs), congestion management (cg) and power loss reduction (pl). the search process leveraged multiple reputable databases that include researchgate, ieee xplore, google scholar, and science direct, which ensure broad coverage of peer-reviewed publications. 2.2 inclusion/exclusion criteria a total of 1,240 studies were initially retrieved, after which titles and abstracts were screened to exclude nonenglish papers, duplicates, and those unrelated to orpd, leaving 350 papers. further eligibility assessment optimal renewable power dispatch review procedure 1. scoping 2. planning 3. search process 4. screening journals 5. eligibility assessment 6. presentation interpretation findings i. keywords definition: optimal renewable power dispatch, renewable energy, voltage stability, congestion and power loss ii. source: google scholar, researchgate, science direct, ieee-explore iii. got 1240 papers returned from search iv. screened: removed title not related to orpd, and non-english text (350) v. eligibility: 265 eliminated due to webpage and duplicates vi. total studies compared based on streamlined date (2018-2024) are 61 http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1041 filtered out 265 additional papers that lacked relevance datasets, culminating in a final dataset of 61 studies meeting all inclusion criteria. this rigorous filtration underscores the methodological reliability of the study. 2.3 data extraction and classification figure 1 also captures the data extraction and classification stage, where selected papers were categorized by optimization objective (single or multi-objective), methodological approach (mathematical, metaheuristic, hybrid), and addressed parameters vs, carbon footprint (co2), active power (p), reactive power (q), pl, cg, and energy storage (es). the final presentation and interpretation stage involved thematic synthesis, statistical analysis, and visualization through figures, tables and trend charts. 3. orpd publications analysis 3.1 overview of reviewed studies earlier studies have explored various optimization techniques for ress dispatch, among which are genetic algorithm (mayer, et al., 2020; and marouani, et al., 2022), particle swarm optimization (barakat et al., 2020; and sharma et al., 2023) and hybrid metaheuristics (waleed et al., 2022). however, only a limited number explicitly incorporate voltage stability constraints without inclusion of pl and cg objectives (hosseinzadeh et al., 2021). for example, ghada et al. (2024) applied jellyfish search algorithm (jsa) to enhance voltage stability using static var compensators. similarly, karthik et al. (2021) proposed levy interior search algorithm (lisa) for reactive power management, showing enhancement of system voltage levels and decreased system losses but neglect congestion framework. african vulture optimization algorithm (avoa) has also demonstrated effectiveness in large-scale dispatch scenarios in another work (ali et al., 2023). numerous studies have also worked on purely economic dispatch of renewable-rich grid systems (ahmed et al. 2022; chen et al., 2023; and yang et al., 2023) and their results showed high performances but neglect of voltage stability indices as a constraint still remain the bottleneck. in other studies, techno-economic dominated their works (ebeed et al., 2020; garrido-arévalo et al., 2024; sharma et al., 2023; and xiong et al., 2022) and the methods strength lie in its effectiveness of handling power dispatch issues. subsequently, some studies delved into planning assessment (elkadeem et al., 2020; montoya, 2023; and shafiul alam et al., 2020). furthermore, only a few dogged-on voltage constraints during optimal dispatch (hosseinzadeh et al., 2021; abhishek et al., 2023; and hassan et al., 2020). however, majority of the methods still solved a subset of the problem while the holistic framework is missing. despite these advances, most studies focus on economic dispatch or emission reduction, often neglecting voltage stability and congestion mitigation (sifakis et al., 2021; and purlu and turkay, 2022). 3.1.1 voltage stability in electrical energy systems voltage robustness is crucial in sustaining the power systems’ integrity over centuries especially under highres integration. meanwhile, voltage collapse can result from load demand, imbalance reactive power support and the intermittent nature of ress (malbasa et al., 2017; and pinzón and colomé, 2019). also, in the earlier stage, traditional methods such as pv and qv curve analysis enhanced knowledge into static stability margins (ajjarapu and christy, 2002), while progressive approaches later provided more authentic assessment of system response to disturbances (zhang et al., 2015). subsequently, convectional dispatch models commonly focus on emission or economic objectives, neglecting voltage constraints (chi and xu, 2020; and lin et al., 2022). with present-day grids undergoing progressive complexity, priority has been given to embedded voltage stability indices into optimization techniques. for example, a work proposes an optimal power flow formulation incorporating voltage stability constraints to mitigate the variability of distributed renewable generation (hosseinzadeh et al., 2021) and another study improved on this method with rigorous formulations that explicitly incorporate renewable uncertainties (sharma et al., 2023). regardless of these advances, most studies only focused on stability constraints alone, without combining them to objectives such as congestion mitigation and power loss reduction. 3.1.2 congestion mitigation in power networks congestion occurs as a result of unbalance between power supply and power demand due to transmission line exceeding its thermal limit leading to increased losses and reduced reliability (monforti-ferrario and blanco, 2021; paul et al., 2021; and tomar, 2024). system congestion has been extensively studied due to its operational and economic significance, especially in deregulation markets. initial investigations focused on market-based mechanisms namely congestion pricing and locational marginal pricing (bai et al., 2017), whereas non-market approaches have relied on demand side management, facts development and re-dispatch http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1042 (narain et al., 2020; and yousefi et al., 2012). considering the rising penetration of re, congestion management has exhibited greater complexity arising from variability in transmission and generation limitations (dashtdar et al., 2020; paul et al., 2021; sarwar et al., 2022; tomar, 2024; and wang et al., 2018). even though these techniques deliver effective short-term alleviation, most techniques handle congestion in isolation without explicitly integrating power loss reduction or voltage stability as co-objectives. 3.1.3 optimal power dispatch an effective power dispatch network is important for sustaining network reliability and enhancing steady system operation, optimizing load demand and reduction of line losses. the economic dispatch issue has classically concentrated on generation costs as well as meeting demand under deterministic conditions (aziz et al., 2021; candra et al., 2024; liu et al., 2021; and xu et al., 2021). yet, the stochastic nature of renewable sources query these convectional techniques, propelling research toward robust and stochastic optimization methods (chi and xu, 2020; huang et al., 2019; lin et al., 2022; roustaei et al., 2022; and wang et al., 2020). recently, hybrid re to innovative grid-based networks, embedding energy storage mechanisms with demand response have been presented to optimize dispatch flexibility (liu and li, 2016), and more current formulations extensively cater for renewable uncertainties during continuous operations (ding et al., 2020; and zhang et al., 2020). despite these formulations enhancing reliability, majority still focus on cost minimization as the primary objective with little attention to congestion or voltage stability constraints. 3.1.4 power loss reduction methods improving efficiency through loss minimization in transmission and distribution networks persists as vital operational priority, particularly since the incorporation of re changes conventional system flow configurations. traditional methods entail grid restructuring and reactive power compensation (nkan et al., 2021), though facts devices have been evidenced to substantially strengthen system flexibility and decrease power losses (do carmo mendonça et al., 2020; ghada et al., 2024; rao et al., 2024; reddy, 2021; and zubidi et al., 2023). metaheuristic-based optimization methods encompassing ga, pso as well as evolutionary algorithms (eo) have been excellent approaches for optimizing power loss mitigation techniques in distribution networks (aljebreen et al., 2023; karthik et al., 2021; othman et al., 2025; sadiq and antar, 2024; sambaiah and jayabarathi, 2020; and ushashree and kumar, 2023). current research trends expand these techniques to renewable-intensive settings, under conditions where uncertainty hinders operational efficiency enhancement (ali et al., 2023; eladl and eldesouky, 2019; elkadeem et al., 2019; hmingthanmawia et al., 2023; khan et al., 2020; and waleed et al., 2022). conversely, reducing losses is frequently handled as an independent optimization objective without deliberate alignment with congestion management or stability constraints. 3.1.5 integrated approaches addressing the interactions among power system objectives, studies have proposed comprehensive frameworks that account for combination of congestion, stability and losses. multi-criteria optimization strategies such as algorithms have been broadly adopted to achieve equilibrium among divergent objectives (infield and freris, 2020; ismael et al., 2019; mohandes et al., 2019; and sinsel et al., 2020). some studies have shown high system performance with embedded stability and congestion objectives in opf frameworks. (sekhavatmanesh and cherkaoui, 2018;, and zhao et al., 2022). alternatively, other studies have merged facts placement with multi-objective optimization for grid performance efficiency (li, 2024). nevertheless, these researches typically examine bi-objective configurations instead of unified models. therefore, existing study considering voltage stability-constraints, re dispatch, congestion mitigation and power loss reduction within an inclusive optimization domain remains limited. 3.2 emerging themes table 1 provides a detailed comparison of 61 studies on orpd published between 2018 and 2024. it captures key attributes including optimization orientation, quadratic function usage, addressed parameters, and applied methods. the table serves as the foundation of progress identification, research gaps and thematic synthesis. therefore, it is explicitly explained using figures 1 to 5. http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1043 table 1: comparative analysis of studies on orpd from 2018-2024 s/n author with date mo/ so qd problem addressed method used vs co2 p q pl cg es 1 kholi and arora (2018) mo ☑ ☑ ☑ ☑ ☑ ☑ ⮽ ⮽ cgwo 2 biswas et al., (2018) mo ☑ ☑ ☑ ☑ ☑ ☑ ⮽ ⮽ dea 3 biswas et al., (2018) both ☑ ⮽ ⮽ ☑ ☑ ☑ ⮽ ⮽ shade 4 suresh et al., (2019) mo ☑ ☑ ☑ ☑ ⮽ ☑ ⮽ ⮽ adfa 5 elattar et al., (2019 so ☑ ☑ ☑ ☑ ☑ ☑ ☑ ⮽ mjaya 6 eladi et al., (2019) so ☑ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ⮽ pso-sop 7 velasquez et al., (2019) so ☑ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ⮽ dmpc 8 chen et al., (2019) mo ☑ ☑ ☑ ☑ ☑ ⮽ ☑ ⮽ cmopeo+sf 9 naval et al., (2019) so ⮽ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ⮽ milp 10 alomoush, (2019) both ☑ ⮽ ☑ ☑ ⮽ ☑ ⮽ ⮽ sfs 11 elkadeem et al., (2019) mo ☑ ☑ ⮽ ☑ ⮽ ☑ ☑ ⮽ hho-pso 12 wang et al., (2019) so ⮽ ⮽ ⮽ ⮽ ☑ ☑ ⮽ ⮽ pso 13 vaziri et al., (2019) mo ⮽ ⮽ ⮽ ⮽ ⮽ ⮽ ⮽ ⮽ milp 14 zhou et al., (2019) so ☑ ☑ ⮽ ☑ ⮽ ⮽ ⮽ ☑ atc 15 hooshmand et al., (2019) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ☑ misocp 16 wang et al., (2020) so ⮽ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ☑ ibessd 17 hassan et al., (2020) mo ☑ ☑ ☑ ☑ ☑ ☑ ☑ ☑ mnlp 18 inam et al., (2020) so ☑ ☑ ☑ ☑ ☑ ☑ ⮽ ⮽ gwo 19 nusair et al., (2020) both ☑ ☑ ☑ ☑ ☑ ☑ ⮽ ⮽ grom 20 ebeed et al., (2020) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ mpa 21 murty and kumar, (2020) mo ☑ ⮽ ☑ ☑ ⮽ ⮽ ⮽ ☑ homer 22 abazal et al., (2020) both ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ ecoa 23 ebeed et al., (2020) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ ilapo 24 yousif et al., (2020) mo ☑ ⮽ ☑ ☑ ⮽ ☑ ⮽ ☑ pso 25 chamandous et al., (2020) mo ☑ ⮽ ☑ ☑ ⮽ ⮽ ⮽ ☑ gams/dicopt 26 elattar and elsayed (2020) so ☑ ☑ ☑ ☑ ☑ ☑ ☑ ⮽ mmfo 27 ettappan et al., (2020) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ abc 28 gbadamosi and nwulu (2020) mo ☑ ⮽ ☑ ☑ ⮽ ☑ ⮽ ⮽ miqp 29 xu et al., (2020) mo ⮽ ⮽ ☑ ☑ ⮽ ⮽ ⮽ ☑ pso 30 vishnu et al., (2020) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ depso 31 azralmukmin et al., (2020) so ☑ ⮽ ⮽ ☑ ⮽ ☑ ⮽ ⮽ cor 32 hodge et al., (2020) mo ☑ ☑ ⮽ ☑ ⮽ ☑ ⮽ ⮽ systematic 33 ismail et al., (2020) mo ns ☑ ⮽ ☑ ☑ ☑ ☑ ☑ systematic 34 nikkhah et al., (2020) so ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ☑ minlp 35 nasr et al., (2020) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ☑ minlp 36 ishraque et al., (2021) mo ☑ ☑ ☑ ☑ ⮽ ☑ ⮽ ☑ homer 37 liu et al., (2021) mo ☑ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ☑ nsgaii+topsi s 38 sakthivel et al., (2021) mo ☑ ⮽ ☑ ☑ ⮽ ☑ ☑ ⮽ mossa 39 ogunmodede et al., (2021) so ⮽ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ☑ milp 40 liu et al., (2021) mo ⮽ ☑ ☑ ☑ ⮽ ☑ ⮽ ☑ iod 41 bravo et al., (2021) mo ☑ ⮽ ☑ ☑ ⮽ ⮽ ⮽ ☑ moo 42 ordoudis et al., (2021) mo ☑ ⮽ ☑ ☑ ⮽ ⮽ ☑ ☑ dcc 43 guo et al., (2021) mo ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ⮽ ☑ bi-level 44 sifakis et al., (2021) mo ☑ ⮽ ☑ ☑ ⮽ ⮽ ⮽ ☑ homer 45 liu et al., (2021) mo ☑ ⮽ ☑ ☑ ⮽ ☑ ⮽ ⮽ mfo-pdu 46 hassan et al., (2021) both ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ☑ systematic 47 xie et al., (2021) so ⮽ ☑ ⮽ ☑ ☑ ☑ ☑ ⮽ not specified http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1044 table 1 contd.: comparative analysis of studies on orpd from 2018-2024 s/n author with date mo/ so qd problem addressed method used vs co2 p q pl cg es 48 mohandes et al., (2021) mo ⮽ ⮽ ⮽ ☑ ⮽ ⮽ ⮽ ☑ ga 49 saddique et al., (2022) so ☑ ☑ ⮽ ⮽ ☑ ☑ ⮽ ⮽ ca 50 vergara et al., (2022) so ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ rl 51 liu et al., (2022) mo ☑ ☑ ⮽ ⮽ ☑ ☑ ⮽ ⮽ iga 52 purlu et al., (2022) both ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ☑ ga, pso 53 ali et al., (2023) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ☑ monte carlo 54 gholami et al., (2023) both ☑ ⮽ ☑ ☑ ⮽ ☑ ⮽ ⮽ sacde 55 chapaloglou et al., (2023) mo ☑ ☑ ☑ ☑ ⮽ ☑ ⮽ ☑ probabilistic 56 chen et al., (2023) so ⮽ ⮽ ⮽ ☑ ⮽ ☑ ⮽ ⮽ two-stage 57 miracle et al., (2023) mo ☑ ⮽ ⮽ ☑ ⮽ ☑ ⮽ ⮽ pocso 58 barnawi et al., (2024) mo ns ☑ ☑ ☑ ☑ ☑ ⮽ ☑ gndo 59 li et al., (2024) mo ☑ ☑ ⮽ ☑ ☑ ☑ ⮽ ⮽ pso 60 mohammed et al., (2024) both ☑ ☑ ☑ ☑ ☑ ☑ ☑ ⮽ cgo 61 alayande et al., (2024) mo ☑ ☑ ☑ ☑ ☑ ☑ ⮽ ☑ bbs abc: artificial bee colony; adfa: ameliorated dragonfly algorithm; atc: analytical target cascading; bbs: bus bar synchronization; cgo: chaos game optimization; cgwo: constrained grey wolf optimization; cmopeo+sf: constrained multi-objective population extrema optimization; dea: differential evolution algorithm; depso: diversity enhanced pso; dmcp: distributed model predictive control; ecoa: enhanced coyote optimization algorithm; ga: genetic algorithm; grom: golden ratio optimization method; gwo: grey wolf optimization; hho: harris hawks optimization; homer: hybrid optimization of multiple energy resources; ibessd: improved battery energy storage; iga: improved genetic algorithm; ilapo: improved lightening attachment procedure optimization; iod: integrated optimal dispatch strategy; mfo-pdu: enhanced moth flame optimization; milp: mixed integral linear programming minlp: mixed integral non-linear programming; miqp: mixed integer quadratic programming; misocp: mixed integral with soft computing programming; mmfo: modified month flame optimization; mo: multi-objective; mosa: modified optimization swarm algorithm; mpa: marine predator algorithm; ns: not specified; pso: particle swarm optimization; qd: quadratic function; rl: reinforcement learning; sacde: self-adaptive comprehensive differential evolution algorithm; sca: sine-cosine algorithm; sfs: stochastic fractal search; shade: success history based adaptive differential evolution; so: single objective; sqp: sequential quadratic programming 3.2.1 orpd publications figure 2 maps the yearly count of reviewed studies on orpd between 2018 and 2024. the publication history shows research interest in the field has fluctuated but grown overall. the lowest publication numbers were recorded in 2018 and 2024, with three studies each. this suggests the field was either in its early exploratory stages (2018) or potentially reaching a point of saturation or shifting to newer research paradigms (2024). the peak was reached in 2020, with 16 published studies. this surge likely reflects increased global efforts to better integrate renewables, alongside the practical maturity of metaheuristic optimization tools (das et al., 2021; and elkadeem et al., 2020). the high output that year could also be tied to advancements in hybrid optimization algorithms and the development of smart grid integration models (panda & nayak, 2022; and liu et al., 2021). the steady, moderate number of studies between 2019 and 2021 (12 each year) suggests the research consolidated into practical topics like reactive power dispatch, stability analysis, and congestion management (hosseinzadeh et al., 2021; and sharma et al., 2023). however, the drop-off after 2022 (down to four or five studies) points to a subtle shift in focus. while the core field has matured, attention is gradually moving toward ai-based, decentralized, and data-driven dispatch models (chen et al., 2023; and ali et al., 2023). summarily, figure 2 shows that orpd research reached its height during the peak period of global renewable integration, and the current, evolving interest is centered on developing advanced hybrid and intelligent optimization models for a more resilient and sustainable grid. 3.2.2 objective function types a clear pattern emerged from the tabulated data resulted to figure 3 where multi-objective (mo) optimization frameworks overwhelmingly dominate resent research, accounting for more than half of the reviewed works (63.90%). these approaches simultaneously target multiple goals such as emission reduction, power loss mitigation, cost minimization, and voltage stability enhancement. conversely, single-objective (so) http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1045 formulations constitute 23.00%, though still relevant and once common in early economic dispatch studies, but gradually declining due to their inability to handle multidimensional nature renewable-dominated grids. a small subset of studies (13.10%) employed hybrid structures, reflecting the transition towards adaptive and flexible optimization paradigms. figure 2: orpd publication analysis figure 3: objective function types 3.2.3 methodology trends regarding optimization algorithms, figure 4 highlights the rapid development of computational intelligence in orpd. widely used metaheuristic algorithms (57%) include pso, ga, gwo, hho, and abc, all valued for their ability to manage complex, non-linear dispatch problems. hybrid and advanced methods like pso–sqp, hho–pso, mpa and ilapo signal a methodological drive (12%) toward better convergence reliability and more accurate solutions. recent studies also incorporate ai-based frameworks (5%) such as reinforcement learning (rl), self-adaptive comprehensive differential evolution (sacde), and chaos game optimization (cgo), underlining the ongoing digital transformation of power-system optimization. 3.2.4 multi-parameter synergy looking at the seven parameters addressed, p and pl optimization dominate the research landscape, featuring in over two-thirds of the reviewed papers. vs shows as a constraint or goal in a fair number of studies, underscoring its rising importance especially with more renewables, it is still underrepresented relative to purely economic objectives. cg and es are noticeably underexplored, appearing in fewer than 20% of the works. this evidence confirms a major gap in fully integrated dispatch models. very view studies specifically http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1046 those using milp or bi-level techniques explicitly bring cg stability and loss into a single framework. moreover, figure 5 highlights the growing inclusion of battery energy storage system (bess) and hybrid re systems (hres) in dispatch formulations, confirming a welcome shift towards designing for flexibility and resilience, and better dynamic balancing into grid. the recent (2022-2024) to advanced ai techniques like rl, sacde, and cgo shows an emerging trend towards ai-driven. data-adaptive optimization models. hence, the transition underscores just how complex power system operation has become in grid dominated by renewables. figure 4: optimization methods figure 5: multi-parameter variables 3.3 implications for future research and practice the analysis of the tables and figures provides several critical implications for the future of orpd: the dominance of multi-objective optimization highlights that dispatch in renewable-integrated grids is inherently multi-dimensional. this confirms that simple single-objective models, which only focus on minimizing cost or loss, are inadequate because they ignore crucial factors like voltage stability and reliability. the shift in algorithms from classical methods to hybrid and ai-based models signals a move toward intelligent and adaptive dispatch. methods like rl, genetic–swarm hybrids, and self-adaptive differential evolution manage system non-linearity and uncertainty better and will likely become the standard as grid complexity increases. http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1039-1053. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: zainabobaone@gmail.com 1047 the parameter synergy analysis (figure 5) confirms that while active power and loss minimization are mature fields, parameters like voltage stability, congestion management, and energy-storage integration are underdeveloped. this means current strategies risk operational efficiency without ensuring long-term grid resilience. the priority must be to develop unified frameworks that integrate these critical, underexplored factors. subsequently, publication trends show that after a period of theoretical development, researchers are now pivoting toward implementation-oriented and application-specific frameworks, particularly in areas like microgrids and peer-to-peer energy markets. finaly, the future of orpd lies in multi-parameter, ai-driven, and stability-constrained optimization systems that are essential for supporting flexible, sustainable, and autonomous power networks. 4. conclusion this review has thoroughly analyzed recent developments in orpd between 2018 and 2024. the findings confirm that while major strides in optimization modelling, existing frameworks often suffer from fragmentation, treating essential elements like voltage stability, power losses, and congestion as isolated objectives instead of as interconnected operational constraints. the literature reveals a historical bias toward cost-driven dispatch, where economic optimization often overshadows the need for reliability and voltage security. as a result, system operators continue to struggle with maintaining stable voltage profiles, reducing line losses, and managing congestion under high renewable penetration. though advanced multi-objective and metaheuristic algorithms (like ga, pso, hho, and their hybrids) have been successful in balancing cost and loss, they frequently fail to include real-time voltage stability constraints and network congestion parameters. few integrated models exist that simultaneously tackle all the critical variables: voltage stability, congestion mitigation, and power loss reduction within a single optimization domain. based on this synthesis, the three top priorities identified for future orpd research are: 1. developing unified frameworks that holistically combine voltage stability indices, congestion control, and loss minimization, all while accounting for renewable energy uncertainty. 2. adopting intelligent, data-driven optimization techniques like 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and real power loss reduction in power system: a review. pertanika journal of science & technology, 31(2). http://www.azojete.com.ng/ mailto:zainabobaone@gmail.com https://doi.org/10.3390/en15239250 https://doi.org/10.1016/j.renene.2019.02.037 https://doi.org/10.1016/j.apenergy.2020.115430 https://doi.org/10.1016/j.segan.2019.100226 corresponding author’s email address: muyik78@yahoo.com 1012 arid zone journal of engineering, technology & environment original research article an enhanced aquila optimizer-based distributed generation framework for harmonic mitigation i.m. adeyinka1, i. abubakar1, n.b. kadandani1,2 and m.m. sa’ad3 1department of electrical engineering, bayero university, pmb 3011, kano, nigeria. 2department of electrical and electronics engineering, federal university of transportation, pmb 1050, daura, katsina state, nigeria. 3department of electrical and electronics engineering, veritas university, abuja, nigeria. corresponding author’s email: muyik78@yahoo.com article information abstract this research work presents an improved aquila optimizer-based distributed generation system for solving power quality problems. this is particularly important for mitigating the harmonics presence in a radial distribution system (rds). the radial distribution network (rdn) was modeled in the presence of the nonlinear load (nlld) and nonlinear distributed generation (nldg). rdn provides a simple, cost-effective structure with a single power source that can be analyzed with a simplified forward/backward sweep load flow algorithm, making it easier to determine the optimal size and location of active power filters to mitigate harmonics and improve voltage quality. an improved aquila optimization algorithm was then used to optimally size and place active power filters (apfs) in the adaptive rdn to control the harmonics, ensuring that the harmonics present in the system do not exceed ieee-519 of 1992 standard limits. the results obtained from the developed scheme were presented and compared with the results obtained when adaptive grey wolf optimizer (agwo) and aquila algorithm (ao) were used. thd and fitness function were used as the performance metrics. all simulations were carried out in the matlab/simulink environment r2022b. the thd values obtained during various periods of the day were presented and it was observed that high distortions were recorded between hours 11 to 13, with the highest distortion occurring at hour 12. to further analyze the efficacy of the developed approach after placement of the apf in the ieee 69-bus network, the result of the thd obtained when the improved aquila algorithm was used for the placement of the apfs were presented. it was observed that the thd values obtained for the entire 69-bus network were well within the ieee standard limit. further, the results obtained from the developed scheme were compared with those obtained when agwo and ao were used for harmonic mitigation in the distribution system. it was observed that the thd values obtained by the developed scheme outperformed those obtained from the agwo technique by 5.96%, 4.71%, 3.47%, 32.79%, 3.62%, 11.68%, and 30.25%, respectively, for the bus numbers that have higher distortion values, while it also outperformed the aquila algorithm by 3.07%, 2.41%, 1.88%, 31.97%, 1.84%, 16.88%, and 25.98%, respectively. the developed approach provides a practical and computationally efficient solution for harmonic mitigation and can be extended to larger and more complex power systems for improved grid performance. received: 16th october 2025 revised: 12th november 2025 accepted: 13th november 2025 keywords: improved aquila optimizer aquila optimizer adaptive grey wolf optimizer total harmonic distortion active power filter © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction electricity is an indication of convenience life, and the demand for this energy source is increasing. development in the power industry has led to a rise in both linear and nonlinear loads within power systems. many solid-state switching converters consume reactive power and generate current harmonics from the ac azojete december 2025. vol.21(4):1012-1025 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/011 www.azojete.com.ng mailto:muyik78@yahoo.com mailto:muyik78@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1013 grid, contributing to total harmonic distortion in voltage (thdv) and current (thdi) under nonlinear load conditions (abbas et al., 2021). in modern power systems, the increasing penetration of distributed generation (dg) units particularly those interfaced through power electronics has introduced complex power quality challenges such as voltage instability, harmonic distortion, elevated thermal losses due to heat loss (i²r), and reactive power imbalance. these issues degrade the efficiency and reliability of radial distribution networks, especially under dynamic and nonlinear operating conditions. the growing integration of distributed generation (dg) units, especially those using power electronic interfaces, has therefore introduced significant power quality issues in radial distribution networks. these include harmonic distortion, voltage instability, increased thermal losses, and reactive power imbalance all of which compromise system efficiency and reliability under nonlinear and dynamic conditions. while aquila optimizer-based dg placement has been shown to effectively reduce real power losses and enhance voltage profiles, it lacks mechanisms for harmonic suppression and reactive power management. moreover, the unpredictable output of dgs and the nonlinear behavior of inverter-based sources further intensify these challenges. to address these limitations, this research proposes the incorporation of an active power filter (apf) into the aquila-optimized dg framework. the apf actively mitigates harmonics and compensates reactive power, forming a hybrid solution that improves voltage stability, reduces distortion, and enhances overall energy efficiency ultimately boosting the resilience and sustainability of distributed radial networks. these nonlinear loads generate harmonics that cause disturbances and can lead to system malfunction. today, almost every modern equipment, power system, and service such as furnaces, computer power supplies, communication systems, renewable energy systems, electrical power generation, and high-voltage systems— requires a continuous and high-quality power supply. consequently, researchers and utility companies continue to explore solutions to power quality problems (sakar et al., 2017), including harmonics, voltage fluctuation, voltage sag, unbalance, frequency variation, and transient spikes. the increasing proliferation of nonlinear loads worsens harmonic distortion in the power system, resulting in degraded power quality. flexible ac transmission system (facts) devices such as static compensators (statcoms) and active power filters (apfs) have emerged as dominant technologies for mitigating these issues in industrial and commercial systems. in radial distribution networks (rdn), nonlinear loads (nllds) and nonlinear distributed generations (nldgs) are the primary sources of harmonics, which elevate both the individual and total harmonic distortion in voltage (thdv). the degradation of electrical power quality due to multiple nonlinear loads—such as rectifiers, uninterruptible power supplies (ups), and various electronic circuits leads to low power factor, poor energy efficiency, and voltage distortion (sakar et al., 2017; battu et al., 2015; uniyal & kumar, 2018). the inclusion of a shunt active power filter (sapf) and photovoltaic (pv) system represents an effective solution for harmonic reduction and reactive power compensation, ensuring an improved power factor correction (pfc) at the point of common coupling (pcc). metaheuristic optimization techniques such as genetic algorithm (ga), ant colony optimization (aco), bee colony optimization, and particle swarm optimization (pso) have gained popularity due to their simplicity, flexibility, derivation-free mechanisms, and avoidance of local optima (mirjalili & lewis, 2016). among recent advances, the aquila optimizer (ao) a nature-inspired algorithm based on the hunting behavior of the aquila bird (dhal et al., 2024) has demonstrated remarkable performance in solving complex nonlinear optimization problems. similarly, the grey wolf optimizer (gwo), inspired by the leadership hierarchy and hunting mechanism of grey wolves, has shown competitive performance when benchmarked against well-known metaheuristic algorithms such as pso, gravitational search algorithm (gsa), differential evolution (de), and evolutionary programming (ep) (mirjalili & lewis, 2016). previous works have explored various approaches for harmonic mitigation and optimal placement of filters or dg units. for instance, (sakar et al., 2017) determined hosting capacity for distorted systems with pv-based dgs under harmonic constraints, while (fahmi et al., 2018) utilized a single-tuned passive filter to reduce harmonics in industrial systems. however, passive filters are inadequate for complex, nonlinear environments. (lakum & mahajan, 2019) examined the impact of dg penetration on apf placement using the gwo algorithm, revealing that dg integration significantly affects apf sizing. moreover, (abbas et al., 2021) used a water cycle algorithm (wca) to plan single-tuned filters for inverter-based dgs, reducing thd effectively but without addressing adaptive compensation under nonlinear dynamics. from these reviewed studies, it is evident that determining the optimal placement and sizing of apfs remains crucial for minimizing cost while maintaining high power quality in rdns. the introduction of dg converters brings additional harmonic challenges that necessitate more adaptive mitigation strategies. hence, this work presents an improved aquila optimizer-based approach for optimal apf placement and sizing, aiming to reduce power losses, enhance http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1014 voltage profiles, and effectively suppress harmonics thereby improving the overall stability and efficiency of radial distribution networks. 2. materials and method this section presents the comprehensive methodology employed in this paper. it provides detail of the mathematical model of the system, the formulation of the objective function used to evaluate performance of the algorithm. 2.1 modeling of the radial distribution network the radial distribution network employed is represented as a branch impedance (zab) which is expressed in equation 1 (lakum & mahajan, 2021). 𝐙𝐚,𝐛 = 𝐑𝐚,𝐛 + 𝐣𝐗𝐋,𝐚,𝐛 1 where zab is the impedance between line a to b, rab is the resistance between line a to b, xlab is the reactance between line a to b. the graphical modeling of the rds with the nldgs, harmonic filters and nonlinear loads developed in matlab simulink is as shown in figure 1. figure 1: ieee 69bus system with nonlinear loads and nldgs (lakum & mahajan, 2021) as the rdn contains nldgs and nonlinear loads, the branch impedance equation must be modified to include harmonics. as such the expression for the branch impedance can now be expressed as in equations 2 to 4: za,b (h) = ra,b + jxl,a,b (h) 2 xl,a,b (h) = ωhla,b 3 ωh = 2πfh 4 where 𝑍 is the equivalent impedance of the system a and b, represent the bus numbers, h represents the order of harmonics, 𝑅𝑎,𝑏 depicts the resistances of branch ab, fh represents the harmonic frequency of the current, 𝐿𝑎,𝑏 denotes the inductance of branch ab and 𝜔ℎ represents the angular frequency of the harmonic current. 2.2 mathematical model of rds with nlld the nonlinear loads are modeled as harmonic current injection source and their rms value is given in equations 5 and 6. the harmonic current 𝐼𝑛𝑙,𝑎 (ℎ) at harmonic h is represented as a complex number, with real and imaginary parts: http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1015 inl,a (h) = inl,a,r (h) + jinl,a,im (h) 5 inl,a (h) = √∑(inl,a,r 2(h) + inl,a,im 2(h) ) h h=2 6 where 𝐼𝑛𝑙,𝑟 (ℎ) and 𝐼𝑛𝑙,𝑖𝑚 (ℎ) represent the real and imaginary parts of the load current repectively. 𝐼𝑛𝑙,𝑎 (ℎ) depicts the rms value for the nonlinear load current at bus “a”, while h represents the highest order of harmonics. 2.3 mathematical model of rds with nldg since the nldg is in charge of introducing nonlinear current into the system, it is modeled as a current source in this work. the fundamental current is determined by the dg's power rating, and the dg's nonlinear harmonic current value can be obtained by using the expression in equation 7 in accordance with the harmonic spectrum. inldg,a (h) = kdgidg,a 7 where 𝐼𝑛𝑙𝑑𝑔,𝑎 (ℎ) is the harmonic current of the dg, while 𝐾𝑑𝑔 depicts the percentage of harmonic current as per the harmonic spectrum of dg, lastly 𝐼𝑑𝑔,𝑎 is the fundamental current of dg. 2.4 apf modeling the apf is modeled as a current source. the calculation of the apf current is done on the basis of net nonlinear which is a vector addition of nonlinear currents of loads and nldgs. when the phase angle is zero, the distortion is worst as the net nonlinear current is a function of phase angle. so it causes maximum distortion while harmonic currents are in phase; inldg (h) = ihdg (h) + inl (h) 8 iapf = k(inldg) 9 where k is proportionate to net nonlinear current. since apf is represented as a set of current sources. it injects harmonics order at a point of common coupling (pcc) as per the value of k. the apf can be expressed as: iapf (h) = iapf,r (h) + jiapf,im (h) 10 iapf = √∑ {i apf,r 2(h) + i apf,im 2(h) } h h=2 11 where 𝐼𝑎𝑝𝑓,𝑟 2(ℎ) represents the real part of the apf, while 𝐼𝑎𝑝𝑓,𝑖𝑚 2(ℎ) and 𝐼𝑎𝑝𝑓 depicts the imaginary part and rms value of current of the apf respectively. 2.5 modeling of solar power generation it is evident that the power output from solar pv is proportional to the irradiance. the solar pv output power can be calculated as shown in equation 12. ppv(si) = ηpv × spv × si 12 where, 𝑃𝑝𝑣 represents the output power in kw, 𝑆𝑝𝑣 denotes the total area of pv in meter square and ŋpv represents the efficiency. normal probability density function is used in this work to generate the samples of the output power of the solar power plant. a k-means scenario reduction algorithm is employed to reduce the number of samples (output power of the solar pv) to 100. the reduced samples were then used to calculate the harmonic currents injected by the nldg. http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1016 2.6 harmonic load flow in this study, a harmonic load flow based on network topology is used. two matrices are created in this approach: bus injection to branch current (bibc), and branch current to the bus voltage (bcbv). with harmonic load flow, the thdv is computed at each bus. it is necessary to identify the crucial busses that go beyond the accepted bounds. the thdv equation is represented as: thdv = √∑ (ihdv)2h h=2 vf 1 13 where the fundamental frequency voltage is denoted with 𝑉𝑓 1. from the value of thdv at all buses, the vital buses where the ieee standard limits are not satisfied are found. it helps to decide the policy to alleviate the harmonics which in this research is the placement and sizing of apf. 2.7 objective function the objective function formulated is subject to satisfying the following constraints: 𝑇𝐻𝐷𝑣 ≤ 5% 14 𝐼𝐻𝐷𝑣 ≤ 3% 15 𝐼𝑎𝑝𝑓 ≤ 𝐼𝑎𝑝𝑓,𝑚𝑎𝑥 16 where 𝐼𝑎𝑝𝑓,𝑚𝑎𝑥 represents the maximum current of apf and dp represents the dynamic penalty. the value set in the constraints for the 𝑇𝐻𝐷𝑣 𝑎𝑛𝑑 𝐼𝐻𝐷𝐼 are selected to ensure that the requirement of ieee standard 519 are met. 2.8 extended nonlinear load position base apf current injection formulation formulation of the extended nlpci is done in this sub-section. the extended nlpci is used to find the optimal buses for placement of apf in the rds. the proposed technique consists of three cases: a) only one feasible state with a minimum number of apf, b) more than one state with same number of apfs with different thdv, and c) more than one state with same number of apf and same thdv. nlpci technique has been introduced to decide the feasible buses for the entire 33-bus rds. create the nonlinear load position based apf placement matrix: the total number of nonlinear load is denoted by nl and its buses is denoted by b nl. then nonlinear loads are represented as, matrix of [1 0 0 0,…,…nl] the nonlinear load buses are represented as, matrix of [1 0 0 0,…,... 𝐵nl ]. the nonlinear load position based matrix is formed and possible combinations of apfs placement are calculated. each combination comprises of a set of nonlinear load buses and it is denoted by state st. number of total state st is determined from nonlinear load buses as: st = 2 nl -1 17 the nonlinear load position based apf placement combination matrix of zeros and 1 here, ‘1’ represents the placement of apf and ‘0 represents no apf. form the set of feasible states sf: apf with an equal rating of the nonlinear load is connected at possible combination i.e., each state. then thdv is calculated at all the buses using harmonic load flow for all the states. according to their maximum thdv the states are denoted as, st1thdv max; ……, ….. ,st thdv max. separation of feasible and infeasible state is done by fulfilling the standard limit of thdv as, http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1017 state s ={ sf, stthdvmax ≤ 5% infeasible, stthdvmax > 5% } 18 form the group according to the number of apfs: all the states are arranged as per their number of filters. here, the total nonlinear load buses are nl. therefore, the maximum possible combination according to the number of apfs is decided by nlc nft . 𝐺𝑁𝑓𝑡 {𝑆𝐹𝑁𝑓𝑡} (𝐺𝑟𝑜𝑢𝑝 𝑤𝑖𝑡ℎ 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑓𝑖𝑙𝑡𝑒𝑟). the group with the maximum number of apfs has only one state. this technique is extended here and formulated as follows: the steps employed in ensuring efficient operation of the extended nlpci is as shown in the flowchart below: start read rds data, non linear load and nldg data and its location create nlpci matrix using (17 18) hour hr = 1 initialize st=1, h=2, calculate inl, set iapf=iapf max run harmonic load flow calculate ihdv at buses is h>h? calculate thdv using (13) is st<st? is state thdv_max store this as feasible states sf 1 no yes no yes infeasible state no h = h + i s t= st + 1 yes yes 1 from the group of feasible states according to the nos of apf using (21) select the group with minimum number of apf requirement (22) is sfnf.min>1? sort the sfnf.min according to their thdv (23) select the state with lowest with lowest thdv is sfnf.min,thdv,min >1? mapped the state with priority rank of buses select the sf with highest priority rank buses is hr<hr? proceed for agwo to find the optimal size end h r = h r + i no yes yes yes no no figure 2: flowchart for extended nlpci http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1018 2.9 improved aquila algorithm in 2021, aquila optimizer (ao), a population-based meta-heuristic algorithm was introduced by. the latin word for eagles, or birds of prey, is aquila. these birds are considered to be among the most cunning and proficient predators, possessing strong, sharpened claws and strapping feet that allow them to seize their prey with speed and agility (lakum & mahajan, 2019) . aquila employs four main hunting techniques: strolling and capturing prey, contour flying with a brief glide, low flying with a slow drop, and high soar with a vertical stoop (maya & jasmin, 2017). these four core aquila hunt mechanisms served as the inspiration for the creation of the ao, a nature-inspired optimization algorithm that fundamentally clarifies the actions of each hunt stage. initialization, expanded exploration, narrowed exploration, expanded exploitation, and narrowed exploitation are the five main processes that the traditional ao concentrates on. the first step taken in employing ao technique to address any problem is the initialization phase. prior to initializing the other ao parameters, a random population of solutions will be formed. the broader exploration is step two, the expanded exploration essentially reveals the main hunting strategy used by the aquila, which is a high ascent with a vertical stoop in which algorithms seek to determine the search pace from the high ascent. equation (22) mathematically represents this strategy: xi(t + 1) = xbest(t) × (1 − t t ) + (xm(t) − xbest(t) ∗ rand) 19 where 𝑋𝑖(𝑡 + 1) is the solution of the next iteration of t, and it is created by the first search technique. 𝑋𝑏𝑒𝑠𝑡(𝑡) is the finest solution found so far? (1 − 𝑡 𝑇 ) controls the exploration. t and t represent maximum number of iteration and current iteration respectively. xm is the location mean value of current solution. rand value lies between 0 to 1. xm is calculated as follows (abualigah): xm(t) = 1 n ∑ xi n i=1 (t) 20 where n is the population size. the third phase is narrowed exploration, the second hunting technique carried out by aquila that is the contour flight with short glide is projected wherein aquila approaches the land thereby circling around the target prey to attack. such behavior of aquila is precisely brought to light using equation (21). x2(t + 1) = xbest(t) × levy(d) + (xr(t) + (y − x) ∗ rand) 21 where 𝑋2(𝑡 + 1) denotes solution of the next iteration of t, 𝑋𝑏𝑒𝑠𝑡 represents the best solution, 𝑋𝑅(𝑡) denotes the random solution belonging to n. 𝑥 = 𝑟 × sin (𝜃) 22 𝑦 = 𝑟 × cos (𝜃) 23 the improved aquila optimization (iao) algorithm is utilized in this work to improve the power quality of the system. the iao is used to optimize the objective function. the iao provides the variables to the system as input and observes the output. current of apfs is taken as the input while the value of the objective function is taken as the output. the iao then iteratively modifies the inputs of the system based on the feedbacks obtained until maximum number of iterations is met. the step-by-step procedure used in ensuring the improved algorithm properly places the apfs to achieve very minimal distortions as highlighted in the flowchart: http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1019 start load the optimal state for placement sf found by extended nlpci for each hour hour hr = 1 run harmonic load flow calculate thdv calculate the objective function set parameters of iao, run iteration, set boundaries itr(t) = 1 initialize the position of alpha, beta and delta calculate the fitness and determine the best if (t is (2/3)t ) if (rand (0.5)t )if (rand (0.5)t ) yes no save the best solution if (t=t) return the best solution and its fitness function stop update the current solution using equation 21 update the current solut ion using equation 21 update the current solution using equation 21 update the current solution using equation 21 noyes no yes yes no figure 3: flowchart of the improved aquila algorithm 3. results and discussion 3.1 convergence comparison between agwo, ao and iao figure 4 shows the convergence behavior of three optimization algorithms agwo, iao, ao over a specified number of iterations. all three algorithms demonstrate rapid improvement in fitness during the initial 20 iterations, indicating their ability to explore the solution space effectively at the beginning of the optimization process. among the three, iao shows a steeper drop in fitness compared to agwo and ao during the early iterations, suggesting a faster convergence rate in the initial stages. between iterations 20 to 40, the algorithms continue to refine the fitness values. iao converges faster than agwo and ao during this phase, reaching near-optimal fitness earlier than the other two algorithms performs slightly better than ao in reducing the fitness value during this phase. by iteration 40, ao reaches a stable fitness value, plateauing earlier than the http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1020 other algorithms. iao achieves the best (lowest) fitness value overall, demonstrating superior accuracy and convergence speed. agwo converges slightly later than iao but reaches a comparable fitness level, outperforming ao in terms of final solution quality. iao achieves the best final fitness value, fastest convergence, and most stable performance, indicating its efficiency and robustness. agwo offers competitive performance, converging to a fitness level close to iao but requiring more iterations. ao converges the earliest but stabilizes at a higher fitness value, suggesting it might be prone to premature convergence or local optima. figure 4: iteration curve for iao, ao and agwo 3.2 comparison of agwo with and without apf the bar graph in figure 5 shows a comparative analysis of agwo with apf and without apf across some buses. thdv values are generally lower when the active power filter (apf) is employed (orange bars) compared to when it is not (blue bars). this indicates the effectiveness of apf in reducing harmonic distortion. thdv increases significantly at certain bus numbers, such as buses around 20, 30, and 70. these buses may represent areas of the network with higher harmonic contributions due to nonlinear loads or other factors. at most buses, the addition of apf (orange bars) reduces thdv, but the reduction is more prominent in areas with higher harmonic distortion (bus 26). at bus 26, the highest thdv is observed, both with and without apf. however, the reduction in thdv with apf is notable, showing the apf's ability to mitigate harmonics in heavily distorted areas. the effect of apf is less prominent in buses with inherently lower thdv. the graph highlights the importance of apf in reducing harmonic distortions, especially in buses with significant harmonic contributions. this is critical for maintaining power quality in the system. figure 5: comparison of agwo with apf and without apf http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1021 3.3 comparison of ao with apf and without apf figure 6 compares the thdv across bus numbers in a power distribution system under two conditions i.e. ao without apf and ao with apf. the thdv values are consistently lower with the apf compared to without the apf, demonstrating the effectiveness of the apf in reducing harmonic distortion. this reduction is more prominent at buses with higher thdv values, such as bus numbers 22, 26, 30, and 69. bus 26 shows the highest thdv in the system without apf. with the apf in place, there is a significant reduction in thdv, highlighting the apf's effectiveness in heavily distorted regions. bus 30 and bus 66 similarly experience high thdv values without apf. the addition of the apf results in noticeable improvements. at buses with moderate thdv values (bus 10, 14, and 62), the reduction is less but still consistent. at buses with low thdv (bus 2, 6, and 34), the apf has minimal impact, as the distortion is already within acceptable limits. this indicates that these areas may not require intensive harmonic mitigation.ao technique is effective in identifying optimal placement or configuration of apfs. this is evident from the consistent reduction in thdv across the network that ao-optimized apf performs well in areas of high distortion. ao seems to result in a more even reduction across the network, while agwo's performance appeared more focused on critical areas. figure 6: comparison of ao with and without apf 3.4 comparison of iao with and without apf figure 7 presents the thdv across bus numbers in a power distribution using iao without apf and iao with apf. thdv values are consistently lower with apf compared to without apf (darker green), demonstrating the effectiveness of the apf in mitigating harmonics when optimized using the iao. bus 26 experiences the highest thdv without apf. with apf, there is a significant reduction, showing the optimization and mitigation strategy's effectiveness at this critical node. buses 22, 30, and 66 also show substantial reductions in thdv with the inclusion of apf. however, bus 66 still retains a relatively high thdv even with the apf. at buses with low inherent thdv, such as buses 2, 6, and 34, the apf has a minimal effect, as the harmonic distortion is already within acceptable limits. without apf, there are multiple buses (22, 26, 30, and 66) where thdv exceeds 40%. after deploying the apf, these values drop significantly, indicating that iao effectively prioritizes the buses with the highest distortion during optimization. the iao-optimized apf achieves substantial harmonic mitigation across the network. the graph demonstrates that iao effectively reduces thdv at critical buses (26, 30) while maintaining reasonable computational efficiency. compared to agwo and ao (based on earlier graphs). iao shows comparable performance in terms of thdv reduction, especially at highdistortion buses. the improved optimization capability of iao likely leads to better placement and tuning of apfs, especially in areas with higher harmonic contributions. the algorithm's enhanced exploration and exploitation features might result in a more balanced thdv reduction across the network. http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1022 figure 7: comparison of iao with and without apf 3.5 comparison between agwo, ao and iao with apf from 7-12 table 1 compares the thd percentage across different bus numbers in a power distribution network for three optimization methods i.e. agwo, ao, and iao. thd varies significantly across bus numbers, with higher values observed at certain buses, indicating areas with more pronounced harmonic distortion. the highest thd is observed in the upper bus numbers (69th bus), where the impact of nonlinear loads might be more severe. iao consistently achieves the lowest thd across most buses, indicating its superior performance in mitigating harmonic distortion when using apf. agwo shows moderate performance, performing better than ao at most buses but worse than iao. the ao tends to have higher thd compared to the other two methods, suggesting it may be less effective in optimizing apf parameters. the values of the harmonic distortion at all the buses is shown in table 1 for hour 12. this time is chosen for this research because, thdv is observed to be higher at this particular time compared to other period. table 1: comparative values of thdi pu from 7th to 12th hours hour agwo aoq iaoq 7th 0.01 0.01 0.01 8th 0.23 0.06 0.05 9th 0.40 0.22 0.21 10th 0.55 0.36 0.35 11th 0.61 0.53 0.51 12th 0.67 0.60 0.58 3.6 comparison between agwo, ao and iao without apf figure 8 displays a comparison of voltage total harmonic distortion (thd) across (numbered 1 through 70, with increments of 4) for three different optimization algorithms: agwo, ao, and iao. the agwo-with apf is represented by the blue bars, ao-with apf by the orange bars, and iao-with apf by the yellow bars. the 'apf' in the legend stands for active power filter, which is used to reduce harmonic distortion. the vertical axis, labeled thd (%), represents the voltage total harmonic distortion as a percentage. thd is a measure of the harmonic content in the voltage waveform, indicating how much the voltage deviates from a pure sine wave. lower values are desirable as they signify a cleaner, more stable power supply with less distortion. the horizontal axis is labeled bus number, representing different points in an electrical system. the iao consistently shows the lowest thd values across all the buses compared to the other two algorithms. this suggests that the iao algorithm is the most effective at minimizing voltage distortion under the tested conditions. while the iao algorithm is generally the best performer, the agwo and ao algorithms have similar thd values for many buses. the highest thd values, exceeding 50% at bus 26, indicating a significant level of voltage distortion at that specific point in the system. the iao algorithm still manages to perform slightly better at this point with a value of 50.2%. table 2 shows a summary of the comparison of the 3 algorithms without apf. 3.7 comparison between agwo, ao and iao with apf figure 9 compares the performance of three optimization algorithms, ao, and iao in reducing voltage total harmonic distortion. iao algorithm consistently achieves the lowest thd values across all the buses shown. this indicates that the iao algorithm is the most effective of the three at minimizing voltage distortion. the http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1023 performance of the agwo and ao algorithms is very similar. for many buses, the orange bar (ao) is barely visible because it is almost entirely covered by the yellow bar (agwo), which has a slightly higher thd$_{v}$. both perform worse than the iao algorithm in most cases. the highest thd values for all three algorithms are observed at bus 26 and bus 69. however, even at these points of high distortion, the iao algorithm still maintains a significantly lower thd compared to the other two. table 3 shows a summary of the comparison of the 3 algorithms with apf. table 2: summary of comparison between iao, ao and agwo without apf bus no iao ao agwo (%) ao (%) agwo (%) 2 9.2 10.5 11.8 12.38 22.03 6 10.5 10.9 11.2 3.67 6.25 10 15.8 16.1 16.4 1.86 3.66 14 22.1 22.8 23.5 3.07 5.96 18 32.4 33.2 34 2.41 4.71 22 39.7 42.5 42.2 6.59 5.92 26 50.2 50.8 51.4 1.18 2.33 30 8.9 9.2 19.5 3.26 54.36 34 7.2 15.5 17.8 53.55 59.55 38 6.5 12.8 17 49.22 61.76 42 11.3 11.8 12.2 4.24 7.38 46 12.4 12.9 13.3 3.88 6.77 50 15.6 16 16.4 2.50 4.88 54 10.2 10.6 10.9 3.77 6.42 58 14.8 15.2 15.6 2.63 5.13 62 21.3 21.7 22.1 1.84 3.62 66 37.8 38.5 39.7 1.82 4.79 69 44.2 44.8 45.3 1.34 2.43 figure 8: comparison between iao, ao and agwo without apf table 3: summary of comparison between iao, ao and agwo with apf bus no iao ao agwo ao (%) agwo (%) 2 8.2 8.5 8.8 3.53 6.82 6 10.5 10.9 11.2 3.67 6.25 10 15.8 16.1 16.4 1.86 3.66 14 22.1 22.8 23.5 3.07 5.96 18 32.4 33.2 34 2.41 4.71 22 41.7 42.5 43.2 1.88 3.47 26 33.2 48.8 49.4 31.97 32.79 30 8.9 9.2 9.5 3.26 6.32 34 7.2 7.5 7.8 4.00 7.69 38 6.5 6.8 7 4.41 7.14 42 11.3 11.8 12.2 4.24 7.38 46 12.4 12.9 13.3 3.88 6.77 50 15.6 16 16.4 2.50 4.88 54 10.2 10.6 10.9 3.77 6.42 58 14.8 15.2 15.6 2.63 5.13 62 21.3 21.7 22.1 1.84 3.62 66 32.5 39.1 36.8 16.88 11.68 69 30.2 40.8 43.3 25.98 30.25 figure 9: comparison between iao, ao and agwo with apf http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1024 4. conclusion this paper developed and implemented an improved aquila optimizer-based distributed generation (dg) system for mitigating harmonics in a radial distribution network (rdn). by integrating nonlinear loads (nlld) and nonlinear distributed generation (nldg) into the model, the study effectively addressed real-world harmonic distortion issues commonly found in power systems. the improved aquila optimization (iao) algorithm demonstrated superior capability in optimally sizing and placing active power filters (apfs) within the rdn to ensure compliance with the ieee-519 (1992) harmonic distortion limits. simulation results carried out in the matlab/simulink r2022b environment confirmed the robustness and accuracy of the developed scheme. the improved algorithm achieved significant reductions in total harmonic distortion (thd) across the ieee 69-bus system, particularly during high distortion periods between 11:00 and 13:00 hours. comparative analysis showed that the proposed iao-based method consistently outperformed both the adaptive grey wolf optimizer (agwo) and the standard aquila algorithm (ao), achieving thd reductions of up to 32.79% and 31.97%, respectively, at the most distorted buses. overall, the results validate the efficiency and reliability of the improved aquila optimizer in enhancing power quality and maintaining voltage stability in distribution networks. the developed approach provides a practical and computationally efficient solution for harmonic mitigation and can be extended to larger and more complex power systems for improved grid performance. references abbas, as., el-sehiemy, ra., abou el-ela, a., ali, es., mahmoud, k., lehtonen, m., & darwish, mmf. 2021. optimal harmonic mitigation in distribution systems with inverter based distributed generation. applied sciences (switzerland), 11(2): 1–16. https://doi.org/10.3390/app11020774 battu, nr., abhyankar, ar., & senroy, n. 2015. dg planning with amalgamation of economic and reliability considerations. international journal of electrical power and energy systems, 73, 273–282. https://doi.org/10.1016/j.ijepes.2015.05.006 çiçek, a., erenoğlu, a. k., erdinç, o., bozkurt, a., taşcıkaraoğlu, a., & catalão, j. p. s. 2021. implementing a demand side management strategy for harmonics mitigation in a smart home using real measurements of household appliances. international journal of electrical power and energy systems, 125(december 2019). https://doi.org/10.1016/j.ijepes.2020.106528 dhal, k. g., das, a., sasmal, b., ghosh, t. k., & sarkar, k. 2024. eagle strategy in nature-inspired optimization: theory, analysis, applications, and comparative study. archives of computational methods in engineering, 31(3), 1213–1232. https://doi.org/10.1007/s11831-023-10014-1 fahmi, m. i., baafai, u., hazmi, a., & nasution, t. h. 2018. harmonic reduction by using single-tuned passive filter in plastic processing industry. iop conference series: materials science and engineering, 308(1). https://doi.org/10.1088/1757-899x/308/1/012035 lakum, a., & mahajan, v. 2019. optimal placement and sizing of multiple active power filters in radial distribution system using grey wolf optimizer in presence of nonlinear distributed generation. electric power systems research, 173(september 2018), 281–290. https://doi.org/10.1016/j.epsr.2019.04.001 lakum, a., & mahajan, v. 2021. engineering science and technology , an international journal a novel approach for optimal placement and sizing of active power filters in radial distribution system with nonlinear distributed generation using adaptive grey wolf optimizer. engineering science and technology, an international journal, 24(4), 911–924. https://doi.org/10.1016/j.jestch.2021.01.011 maya, k. n., & jasmin, e. a. 2017. optimal integration of distributed generation (dg) resources in unbalanced distribution system considering uncertainty modelling. international transactions on electrical energy systems, 27(1). https://doi.org/10.1002/etep.2248 mirjalili, s., & lewis, a. 2016. the whale optimization algorithm. advances in engineering software, 95, 51–67. https://doi.org/10.1016/j.advengsoft.2016.01.008 http://www.azojete.com.ng/ mailto:muyik78@yahoo.com arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1012-1025. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: muyik78@yahoo.com 1025 owosuhi, a., hamam, y., & munda, j. 2024. a new framework for active loss reduction and voltage profile enhancement in a distributed generation-dominated radial distribution network. applied sciences (switzerland), 14(3). https://doi.org/10.3390/app14031077 sakar, s., balci, m. e., abdel aleem, s. h. e., & zobaa, a. f. 2017. increasing pv hosting capacity in distorted distribution systems using passive harmonic filtering. electric power systems research, 148, 74–86. https://doi.org/10.1016/j.epsr.2017.03.020 uniyal, a., & kumar, a. 2018. optimal distributed generation placement with multiple objectives considering probabilistic load. procedia computer science, 125(2017), 382–388. https://doi.org/10.1016/j.procs.2017.12.050 vinayagam, a., aziz, a., pm, b., chandran, j., veerasamy, v., & gargoom, a. 2019. harmonics assessment and mitigation in a photovoltaic integrated network. sustainable energy, grids and networks, 20, 100264. https://doi.org/10.1016/j.segan.2019.100264 http://www.azojete.com.ng/ mailto:muyik78@yahoo.com corresponding author’s email address: aliyub@unimaid.edu.ng 868 arid zone journal of engineering, technology & environment original research article spray drying modelling using advanced vaporization approach a. bello1*, b. r. ademola2, and u. a. isah2 1department of chemical engineering, university of maiduguri, borno state, nigeria 2department of chemical engineering, university of port harcourt, rivers state, nigeria *corresponding author: aliyub@unimaid.edu.ng article information abstract this study develops a deterministic mathematical model for simulating the spray drying of pineapple juice. the model applies advanced vaporization kinetics and a receding interface-porous diffusion approach to predict moisture content, droplet density, and temperature. validated experimentally at feed solids concentrations of 20% and 40% and drying temperatures of 130 °c and 140 °c, the model accurately predicted final moisture content with absolute errors ranging from 2.3% to 5.2% as drying gas temperature decreases from 140 °c to 130 °c for the 20% feed, and from 1% to 1.8% for the 40% feed. key results quantitatively demonstrate that higher air temperatures reduce final moisture content and reveal the critical role of crust formation in shifting the drying kinetics from a rapid evaporation phase to a slower, diffusion-limited regime. the model's computational efficiency and physics-based foundation make it a valuable tool for the optimization of spray drying processes, potentially reducing reliance on costly and time-consuming experimental trials. received: 8th september 2025 revised: 14th september 2025 accepted: 16th september 2025 keywords: juice spray drying modelling advanced droplet vaporization moisture content © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction spray drying process accounts for a significant volume of dry powder production globally. it is used to produce instant products such as fruit juice powder, egg powder, coffee, tea extract, honey powder, milk, flavours, soup powders, baby milk formula, spices and herb extracts, cheese powder, yogurt powder, and vegetable powders (barbosa-cánovas et al. 2006; filkova et al. 2014). droplet drying kinetics models are indispensable in modelling the spray drying of droplets. four primary models are documented in literature. the characteristic drying curve (cdc) model relies on semi-empirical drying curves from experimental data. while computationally efficient, its accuracy diminishes when applied to conditions different from the original experiments (mezhericher et al. 2010; poozesh et al. 2018). the reaction engineering approach (rea) uses an empirical correlation between particle solvent content and partial vapor pressure, framing evaporation as an activation energy barrier. however, its predictive capability is limited to materials with pre-existing experimental data for correlation, as the activation energy is highly specific to both the material and the drying conditions (chen and putranto 2015; putranto and chen 2015). deterministic models are based on fundamental heat and mass transfer equations to account for internal gradients. however, they can be computationally expensive due to moving boundaries (e.g., tracking a receding wet core interface) and require numerous precise input parameters (e.g., mass diffusivity, porosity) which limits their practical application (boel et al. 2020; razmi et al. 2021). accurate computational fluid dynamics (cfd) models resolve threedimensional chamber hydrodynamics, turbulence, and droplet-gas interactions. their key limitations are prohibitive computational cost. additionally, they still rely on accurate sub-models for droplet drying kinetics and wall interactions to be predictive (boel et al. 2020; razmi et al. 2021). therefore, a clear need exists for a mechanistic model that is both predictive and computationally efficient, without relying on empirical drying parameters. this study advances a deterministic mathematical model of spray drying using the advanced droplet vaporisation kinetics and receding interface-porous diffusion approach (sazhin et al. 2013; werner et al. 2008). the droplet vaporisation approaches of sazhin (2006) and abramzon and sirignano (1989) provide a basis for understanding droplet dynamics and evaporation and their approach will be coupled with interface-porous diffusion to examine the evaporation of droplets containing multiple azojete september 2025. vol.21(3):868-879 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/017 www.azojete.com.ng mailto:aliyub@unimaid.edu.ng mailto:aliyub@unimaid.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 869 components. the novelty of this work lies in the integrated application and validation of this coupled model for a complex, multi-component food system (pineapple juice-maltodextrin), with a focus on achieving predictive accuracy for key outputs like final moisture content while maintaining computational efficiency for engineering design. 2. materials and methods 2.1. theoretical approach and model equations studies of droplet drying into dry particles show two distinct drying steps that may be preceded or concluded by heating. it is assumed the drying droplets have a spherical shape and possess uniform composition, thermal properties, and shrinkage (mezhericher et al. 2014; sadafi et al. 2014). the typical multicomponent juice feed is made up of liquid with solids (dissolved and micro solids) which is atomized into a stream of hot gas as a spray of fine droplets. heat transfer takes place between the droplets and the hot gas stream, leading to the evaporation of liquid from the droplet surface. as the droplet evaporates, it undergoes shrinkage and becomes increasingly viscous due to the reduction in its liquid content. the rate at which liquid flows from the interior of the viscous droplet to its surface decreases as the evaporation progresses and the droplet continues to shrink. at a critical droplet diameter, marking end of the first drying step, surface evaporation rate will exceed the rate of liquid flow from viscous droplet interior to surface and a crust layer forma, that grows inwards. the crust layer fixes the droplet diameter and marks the transition into a wet particle whereby heat conducts through the crust to evaporate pore liquid which, flow gaseous through the dry crust to the surface. the complete evaporation of pore liquid ends the second drying step and transforms the wet particle into a dry one that steadily and uniformly heats up before exit from the spray dryer. the model initial droplet evaporation stage is governed by the advanced vaporization kinetics of abramzon and sirignano (1989), which provides an accurate account of heat and mass transfer by incorporating the blowing effect of high evaporation rates. this represents an advancement over simpler correlations often used in food powder modelling. the model then seamlessly couples to a receding interface-porous diffusion model, to simulate the second drying stage once a solid crust forms. this hybrid approach allows the model to leverage the strengths of the physical precision of combustion droplet models for the initial phase and the practical relevance of food powder models for the important crust-drying phase. 2.1.1. droplet motion and trajectory atomized spherical droplets numbering ṅ, ejected from an atomizer with initial velocity u [m s-1], have their motion and trajectory inside the spray drying chamber defined by drag and body forces and flow turbulence. assuming that the droplets follow vertical trajectories from the atomizer exit to the bottom of the spray drying chamber without any interaction with the walls, the body forces acting on the droplets are the combined effect of gravitational force and buoyant force resulting from volume displacement and are given by equation 1: ( ) 3 6 body d g df g d   = − 1 where �⃗�𝑏𝑜𝑑𝑦 = body forces acting on droplet [n], d = diameter [m], g = gravitational acceleration [9.81 m s-2],  = density [kg m-3], and subscripts d and g refer to droplet and gas respectively. the aerodynamic drag forces are given by equation 2: ( ) 1 2 drag g d g d g d dcuf u u au= − − − 2 where �⃗�𝑑𝑟𝑎𝑔 = aerodynamic drag forces [n], a = area [m2], and cd = dimensionless drag coefficient. the droplet area for the drag calculation is obtained from equation 3: 2 4 d d pi a d= 3 the drag coefficient cd is influenced by the relative velocity of the droplet and the reynolds number. for accurate predictions in reynolds flow regimes involving moving and evaporating droplets, the correlation developed by feng and michaelides (2001) is applied. this approach accounts for the effects similar to that in spray dryers (michaelides 2013; sazhin 2006). thus, the cd is calculated using the following correlations for the flow regimes, using equation 4: http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 870 0 2 2 2 4 0 2, and 5 re 1000 2 6 4 2 2 , and 5 re 1000 2 2 8 3 2 3 2 3 1 0.05 re 0.01 re ln re re 1 1 1 d d d d d d d d d d d c c c c c                − +     + − = +      + +  + + + −  + + +  0 re 5d             4 where  = viscosity ratio and red = droplet dimensionless reynolds number. and we have, d g    = 5 re g d d g d guu d  = − 6 where µ = viscosity [n s/m2]. the cd0, cd2, cd∞ functions in equation 4 were given by feng and michaelides (2001) and are expressed in equation 7, 8 and 9 respectively: 0 48 2.21 2.14 1d d dd c re rere   = + −      7 2/3 2 17.0d dc re−= 8 2/324 1 1 6 d d d c re re    = +    9 when the reynolds flow regimes exceed 1000, a different correlation for the drag curve for solid spheres by morrison (2013) which is used in a form given by equation 10: 7.94 0.8 1.52 8.0 re re 2.6 0.411 re24 5.0 263000 re 461000re re 1 1 5.0 263000 d d d d d d d c − −             = + + +         + +        10 the balance of drag and body forces is then calculated from equation 11: ( ) 3 1 6 d body drag d d du f f dt d       = +      the droplets vertical position from the atomizer exit is given by equation (12): x d dh u dt = 12 where hx = vertical distance travelled by droplet = drying chamber section height [m]. 2.1.2 droplet mass balance the sprays of droplets undergo evaporation along their trajectories through the spray dryer length. assuming saturated conditions at the droplet surface, uniform droplet shrinkage, no wall deposition, well-mixed gas phase and no reaction, the extended film diffusional mass transfer rate from a stagnant droplet in quiescent air is given by sazhin (2014), as shown in equation 13: ( )2 ln 1v d m g k m d b cp    = +    13 where �̇�𝑣 = vapour mass flow rate [kg s-1], cp = specific heat [j kg-1 k-1], bm = spalding mass transfer number and �̄� = thermal conductivity [w m–1 k–1]. a correction factor is needed for the convective effects of the http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 871 relative velocity between droplet and air which is applied to equation 13. thus, the mass balance over a droplet is expressed by equation 14 (abramzon and sirignano 1989; sazhin 2006): ( )*ln 1v d m g k m d sh b cp    = +    14 sh* = dimensionless modified sherwood coefficient. blowing effects are accounted by the modified sherwood coefficient which, is computed in the manner set out by abramzon and sirignano (1989) from equation 15: ( )* 2 2 d m sh sh f − = + 15 where shd = droplet dimensionless sherwood coefficient and fm = dimensionless blowing effect correction factor. fm is defined by equation (16): ( ) ( )0.7 ln 1 1 m m m m b f b b + = + 16 the change in droplet mass is obtained by difference while the decreased droplet radius as a result of moisture loss is obtained from the mass-volume balance from equation 17: 2 d v w d dr m dt d  = − 17 where r = radius [m] and subscript w refers to water. the new moisture content of each droplet on a dry basis is calculated from equation 18: d db z m x m = 18 where xdb = droplet moisture content on dry basis, m = mass [kg] and subscript z refers to solids in droplet. the total mass of evaporated moisture from the spray of droplets is obtained from equation 19: v vm nm dt= 19 where mv =mass of moisture loss from droplet. 2.1.3. droplet heat balance the energy for moisture evaporation and temperature rise in the droplets is provided from conduction across the droplet surface from the drying gas (gopireddy and gutheil 2013; sazhin et al. 2011) the total energy balance over a droplet is calculated from equation 20: 𝑄𝑑 = 𝜋𝐷𝑑𝑁𝑢 ∗�̄�𝑔(𝑇∞ − 𝑇𝑑,𝑠) 20 where q = rate of heat transfer [j s-1], nu* = modified nusselt number, t = temperature [k], and subscript d,s refers to droplet surface. the modified nusselt number is computed from equation 21 (sazhin 2006): 𝑁𝑢∗ = 2 + (nu𝑑−2) 𝐹𝐻 21 where fh = thermal film thickness correction factor and nu = nusselt number. the thermal film thickness correction factor is obtained from equation 22 (sazhin 2006): ( ) ( )0.7 ln 1 1 h h h h b f b b + = + 22 where bh = spalding heat transfer coefficient. the mean droplet temperature is obtained from equation 23: 𝑑𝑇𝑑 𝑑𝑡 = 𝑄𝑑−�̇�𝑣𝛥𝐿𝑣(𝑇𝑑) 𝑚𝑑(𝑊𝑧𝐶𝑝𝑧+𝑊𝑤𝐶𝑝𝑤) 23 where δlv = latent heat of moisture vaporization [j kg–1], and w = mass fraction. 2.1.4. wet particle mass balance the diameter of the evaporating droplets continues to decrease until the critical diameter is reached. the dry formed crust is assumed to form uniformly round the droplet liquid core and then gradually grow inwards as the liquid core evaporates. the critical diameter depends on the porosity of the growing layer of dry crust and is determined from equation 24: 3 , 6 / 1 z d cr v d pi    =   −  24 where v = volume [m3], ψ = particle porosity and subscript cr = critical droplet diameter for crust formation. on formation of the dry surface crust layer, droplets transit into wet particles with a receding wet core and a radially growing dry crust surface. the moisture evaporation from a wet particle occurs via evaporation at http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 872 the wet core-crust interface surface followed by diffusion and flow through the porous crust. the moisture loss from a droplet is obtained from equation 25 (kadja and bergeles 2003; mezhericher et al. 2007): ( ) , , , , , , , 2 8 p ln p m wa c w g p wc g v iv p wcp s wc i p s v v p s g m p g d w d d pdm dt d dt t t m p t h d t            −  = −      −   +      − +       25 where the superscript m is an empirical coefficient, dwa = diffusion coefficient of water vapor in air [m2 s-1], hm = mass transfer coefficient [m s-1], p = total pressure [pa], p = partial moisture vapor pressure [pa], ℜ = universal molar gas constant [ j mol-1 k-1], the subscripts c, i, p, wc, and v respectively mean crust, evaporation interface, particle, wet core and water vapour. the new radius of the receding wet core interface in the wet particles is tracked using equation 26: 2 , wc v w cr wc dr m dt d  = − 26 2.1.5. wet particle heat balance the temperature at the wet particle crust surface is given by equation 27 (kadja and bergeles 2003): ( )* , , 4 p wc d s wc p g d s p wc cz d d t t d nu k t t d d k     − = + −      27 where subscript cz denotes crust solids. the particle liquid core temperature, twc is calculated from equation 28: ( ) ( ), 4 d s wcwc d z z w w v v wc p wc p wc cz t tdt m w cp w cp m l t d ddt d d k − + = −  − 28 2.1.6. dry particle heat balance the complete removal of moisture generates dry particles which exchange energy with the drying gas. an energy balance about the particle surface gives its temperature using equation 29: ( ) ( ) nup p gp z z d t t kdt dt m cp   − = 29 2.1.7. drying chamber energy and mass balances the transient changes in mass and energy of the drying gas, as the droplets dry into particles, is obtained from a balance over the time dependent, vertical position of the droplets inside drying chamber (ali et al. 2014). the change in absolute humidity of the drying gas is given by equation 30 (masters 1991): ( ), 1 11 ,db n de n nb n n n f x x g ah ah g − − −− + = 30 where ah = humidity (absolute) of gas, fe = mass flow rate of the atomized feed into the drying chamber section [kg s-1], and g = dry air mass flow rate [kg s-1]. subscripts n (0 to l) denotes section top (inlet) position and bottom (outlet) respectively. the drying chamber is modelled as a vertical cylinder divided into sections. the heat loss from the chamber section wall is given by equation 31: lghl ch cho mw u a t=  31 where whl = heat loss through drying chamber wall [j], acho = external heat loss surface area of chamber section, uch = overall chamber wall external heat transfer coefficient [j s-1 m-2 k-1] and subscript lgm means log mean. the external spray drying chamber section wall surface area is given by: http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 873 2 cho cho x d a h= 32 and the log mean temperature difference (lmtd) from: ( ) ( ) ( ) ( ) ,0 ,1 lg ,0 ,1 log g amb g amb m g amb g amb t t t t t t t t t − − −  =  −    −   33 where subscripts amb, 0 and 1 denote ambient air, chamber section entry and chamber section exit respectively. the convective surface heat transfer coefficient for the internal chamber wall is obtained from the nusselt coefficient using equation 34 (gnielinski 2010): , nuchi g t chi chi k h d = 34 where ht = heat transfer coefficient [w m-2 k-1] and subscript chi means internal chamber wall surface. the nusselt number for heat transfer from gas to internal wall is calculated from equation 35: ( ) ( ) 2/3 2/3 / 8 re pr 1 nu 1 31 12.7 / 8 pr 1 chi chi chi ch d l       = +   + −     35 ( ) 2 1.8log re 1.5chi − = − 36 where lch = distance from drying gas entrance point [m], and pr = prandtl number. the drying gas temperature is obtained from the energy balance in equation 37: ( ) ( ) 0 0 ,0 ,0 1 ,1 ,1 ,1 ,1 ,1 ,0 ,0 ,0 (1 ) ( ) (1 ) ( ) 1 1 g g g g g g db d d db d d v v hl g ah cp t t ah cp t t f x cp t x cp t l m w  + − + =   + − + +  +  37 the specific heat of the droplets, inclusive of moisture and solids, is calculated from equation 38: ( ), , , , ,1 ( ) ( )d n w n z d n w n w d ncp w cp t w cp t= − + 38 2.2 juice spray drying experiment a laboratory-scale spray dryer, shown in figure 1, was utilized for the spray drying process of pineapple juice feed. to prepare the feed mixture, ripe pineapples (smooth cayenne cultivar) were cleaned, and juiced. the extract was then filtered through a 35-mesh kitchen sieve. the moisture content of the juice was determined using a moisture analyser (ohaus model mb25). maltodextrin was added in precise calculated amounts to achieve desired feed solids contents of 20% and 40% from equation 39: 𝑚𝑑𝑒 = (( 1−𝑤𝑗 1 𝑤𝑓 −1 ) −𝑤𝑗) × juice mass 39 where mde = required maltodextrin mass; wj and wf = solid weight fractions of juice and desired feed. the spray drying configuration involved concurrent flow, where the atomized feed and drying air moved from top to bottom. the drying air supply is passed through a filter to remove any suspended particles before reaching the atomizer and air heater. the compressed air used for drying was heated by an electric resistance heater in the air heater before being supplied to the drying chamber. within the drying chamber, the pineapplemaltodextrin feed was continuously agitated using a magnetic stirrer and then fed into the chamber through a hygienic pump (masterflex model 7518-10), where it was atomized into a spray of droplets using a twin-fluid atomizer. table 1 presents the juice spray drying conditions in more detail. drying air temperatures of 130 oc and 140 oc were experimentally determined to produce dry powder. the resulting product powders, for the different drying conditions, were collected from the collector at the base of the cyclone. the powder moisture content was automatically determined as weight percent of the dry material, using the moisture http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 874 analyser, at a temperature of 75 oc. averaged values of triplicate sample measurements of the moisture content were calculated and expressed in % kg h2o/kg dry solids (dry basis). figure 1: spray dryer schematic diagram table 1: juice spray drying experiment data feed solids fraction feed temperature (oc) feed viscosity (ns/m2) specific gravity (30 oc/30 oc) drying air temperature (oc) drying air flow rate (l/min) drying air humidity (kg h2o/kg air) 20 29 0.0157 1.043 130 340 0.00506 20 28.5 1.043 140 360 0.00533 40 29 1.095 130 340 0.00512 40 29 1.095 140 342 0.00532 2.3. spray drying model simulation the system of coupled ordinary differential equations developed in section 2.1 was solved numerically in matlab using a variable-step, 4th-order runge-kutta (ode45) solver due to its high-order accuracy which is essential for resolving the model's rapid transients (akinsola 2023; semenova et al. 2021). the relative and absolute error tolerances for the solver were set to 1×10⁻⁶ to ensure a precise solution. a maximum time step of 2.5 milliseconds was enforced to resolve the rapid initial transients accurately. the model developed in this study adopts a one-dimensional (1d) plug-flow framework for the drying chamber. the 1d plug-flow assumption is a well-established simplification for tall, concurrent-flow dryer (razmi et al. 2021). the drying chamber was modelled as a one-dimensional plug flow dryer, with the vertical sections from the atomiser determined from equation 12. the initial conditions for the droplets were based on the twin-fluid atomizer characteristics; the average initial droplet diameter and velocity were calculated from lorenzetto and lefebvre sauter mean diameter (smd) equation (camacho-lie et al. 2023). the model simulated a single droplet trajectory to represent the average behaviour of the spray with extensive variables calculated for the droplet population. convergence was assumed when the relative change in all state variables (moisture content, temperature, and diameter) between iterations was less than the specified tolerance. the model is computationally fast, converging averagely in 28s on an i7 8gb ram laptop. the code takes the initial process conditions, calculates droplet vertical trajectory and then solves the coupled heat and mass transfer equations. the evaporating water properties and constant drying air psychometric properties were calculated using the coolprop 6.1 module (bell et al. 2014). sucrose and maltodextrin properties were taken from adhikari et al. (2003). other required values were obtained from american society of heating, refrigerating and airconditioning engineers (ashrae) (american society of heating 2013) and iapws (herrmann et al. 2011; http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 875 pátek et al. 2009) correlations which, were implemented in the matlab code, are presented in table 3. the initial calculated droplet sizes and run times are presented table 2. table 2: initial calculated droplet smd and simulation runtime feed solids fraction drying air temperature (oc) calculated droplet smd size (µm) simulation run time (s) 20 130 79 28 20 140 95 27 40 130 56 29 40 140 101 29 table 3: properties, latent heat and diffusivity correlation used in the model simulation parameter value units density maltodextrin 1400 kg m-3 sucrose 1590 kg m-3 molar mass water 0.018015268 kg mol-1 porosity crust porosity 0.38 specific heat capacity maltodextrin 3.5242t+1319.7 j kg-1 k-1 sucrose 4.4369t+1121.3 j kg-1 k-1 thermal conductivity chamber wall (pyrex glass) 0.96 w m-1 k-1 maltodextrin 0.187 w m-1 k-1 sucrose 0.277 w m-1 k-1 other parameters molar gas constant 8.314462 j mol-1 k-1 water latent heat 1.91846×106×(t/(t-33.91))2 j kg-1 water vapor diffusivity in air -2.775×10-6+4.479×10-8t +1.656×10-10t2 m2 s 3. results and discussion several variables were tracked during the simulation which, are reported and discussed. figure 2 presents the average droplet temperature profiles. the trend shows the juice droplets rapidly increase in temperature before decreasing. the increase in droplet temperatures follows the increase in heat and mass transfer rates arising from the initial droplet velocities and hot drying gas temperatures. as heat transfers from the hot gas to the droplet, the juice droplets experience a temperature rise, reaching approximately 50% of the inlet gas temperature. the maximum temperature rise attained by the droplets, a short distance into drying chamber, marks the point at which a crust layer begins to form over the droplet thereby reducing heat transfer and droplet temperature (bhattacharjee and gnanaskandan 2023; rezaei and netz 2021). after the complete evaporation of the core moisture, the now-dry particle heats rapidly towards the gas temperature. this detailed thermal profile, particularly the internal gradient, demonstrates the model's utility in capturing coupled heat and mass transfer limitations. figure 3 illustrates the corresponding evolution of droplet/particle density. the density increases sharply due to the loss of water mass and the concomitant reduction in droplet volume. upon crust formation, the particle volume becomes fixed. the subsequent gradual decrease in density is solely due to the continued loss of mass (moisture) from within this fixed volume. figure 4 shows the predicted normalized moisture content and the as a function of residence time along the spray dryer. the drying profile exhibits two distinct falling rate periods, consistent with theory. an initial rapid drying phase is characterized by moisture evaporation from the saturated droplet surface and significant droplet shrinkage. the transition to period ii is marked by the predicted formation of a rigid porous crust, which fixes the particle diameter and impedes moisture removal. this occurs within the first 2% to 3.5% of the distance into the drying chamber. subsequently, evaporation occurs from a receding wet core interface, and vapor must diffuse through the dry crust layer, leading to a http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 876 significantly reduced drying rate. thereafter, the rate then increases again as shown in the lower section of the profile, before the particle exits the drying chamber. figure 2: model simulation results for average droplet temperature figure 3: model simulation results for droplet density figure 4: model simulation results for normalised droplet moisture contents figure 5 and figure 6 present the comparison between the predicted final moisture content from the simulation and the experimental data for the 20% and 40% w/w feed solids compositions, respectively, at drying air temperatures of 130 °c and 140 °c. the absolute percentage error between the model and experiment is shown on the secondary y-axis. the model accurately predicts the final powder moisture content, with absolute errors ranging from 2.3% to 5.2% for the 20% feed and from 1.0% to 1.8% for the 40% feed. the results confirm the expected trend: higher inlet drying air temperature enhances the rate of energy transfer to the droplets, promoting greater moisture evaporation and resulting in a lower final moisture content. the marginally higher error for the 20% solids feed is likely attributable to its higher initial stickiness http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 877 and greater propensity for wall deposition, a phenomenon not captured by the current model which assumes no wall interactions. figure 5: comparison of juice powder moisture content from experiment and model for 20% feed figure 6: comparison of juice powder moisture content from experiment and model for 40% feed the predicted drying kinetics align quantitatively with the findings of werner et al. (2008) for single sucrose droplets, who observed a similar transition to a receding interface model at a critical solids content. the absolute errors in final moisture content (1-5.2%) are comparable to or better than those reported for similar studies of food droplets (putranto and chen 2015), while this model retains the significant advantage of being based on fundamental physics rather than material-specific empirical parameters. this makes it more robust and potentially generalizable to a wider range of materials without the need for extensive new experimentation. the computational efficiency (average convergence in 28s) demonstrates that a high-fidelity, mechanistic model can be practically applied for process optimization and digital design, bridging a critical gap between oversimplified models and computationally expensive cfd approaches. 4. conclusion a deterministic mathematical model using advanced droplet vaporization kinetics and the receding interfaceporous diffusion approach was developed and validated for simulating the spray drying of pineapple juice droplets. the model was validated using experimental data from pineapple juice spray drying at feed concentrations of 20% and 40% and drying temperatures of 130 °c and 140 °c. the model demonstrated strong predictive capability for final moisture content, with absolute errors between 1.0% and 5.2% across the varying feed concentrations and drying temperatures. more significantly, the model provided high-resolution, quantitative insights into the internal dynamics of drying, including the precise timing of crust formation (approx. 1.8 s), the evolution of internal temperature gradients (>40 °c), and the transition between drying periods. this study confirms that higher inlet drying air temperatures enhance moisture evaporation, leading to lower final moisture contents. this work demonstrates that the developed model effectively addresses a practical gap in the spray drying modelling. it provides a physically detailed, yet computationally efficient alternative to purely empirical models and resource-intensive cfd simulations. its ability to accurately predict final powder properties while also revealing internal dynamics like crust formation and temperature gradients provides a powerful tool for fundamental research and industrial process optimization. http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 878 references abramzon, b., and sirignano, wa. 1989. droplet vaporization model for spray combustion calculations. international journal of heat and mass transfer, 32(9): 1605-1618. adhikari, b., howes, t., bhandari, br., and troung, v. 2003. surface stickiness of drops of carbohydrate and organic acid solutions during convective drying: experiments and modeling. drying technology, 21(5): 839-873. https://doi.org/10.1081/drt-120021689 akinsola, v. 2023. numerical methods: euler and runge-kutta. in qualitative and computational aspects of dynamical systems. intechopen. ali, m., mahmud, t., heggs, pj., ghadiri, m., djurdjevic, d., ahmadian, h., juan, lmd., amador, c., and bayly, a. 2014. a one-dimensional plug-flow model of a counter-current spray drying tower. chemical engineering research and design, 92(5): 826-841. https://doi.org/10.1016/j.cherd.2013.08.010 american society of heating, raa-ce. 2013. psychrometrics. in handbook, ashrae fundamentals (si edition ed.). barbosa-cánovas, gv., ortega-rivas, e., juliano, p., and yan, h. (2006). food powders: physical properties, processing and functionality. springer science & business media. bell, ih., wronski, j., quoilin, s., and lemort, v. 2014. pure and pseudo-pure fluid thermophysical property evaluation and the open-source thermophysical property library coolprop. industrial and engineering chemistry research, 53(6): 2498-2508. https://doi.org/10.1021/ie4033999 bhattacharjee, a., and gnanaskandan, a. 2023. numerical simulation of particle evolution in spray drying using droplet drying kinetics. heat transfer summer conference, 2023. 87165 v001t007a003 boel, e., koekoekx, r., dedroog, s., babkin, i., vetrano, mr., clasen, c., and van den mooter, g. 2020. unraveling particle formation: from single droplet drying to spray drying and electrospraying. pharmaceutics, 12(7): 625. camacho-lie, m., antonio-gutiérrez, o., lópez-díaz, as., lópez-malo, a., and ramírez-corona, n. 2023. factors influencing droplet size in pneumatic and ultrasonic atomization and its application in food processing. discover food, 3(1): 23. chen, xd., and putranto, a. 2015. reaction engineering approach (rea) to modeling drying problems: recent development and implementations. drying technology, 33(15-16): 1899-1910. https://doi.org/10.1080/07373937.2015.1069326 feng, z-g., and michaelides, ee. 2001. heat and mass transfer coefficients of viscous spheres. international journal of heat and mass transfer, 44(23): 4445-4454. https://doi.org/10.1016/s0017-9310(01)00090-4 filkova, i., huang, lx., and mujumdar, as. 2014. industrial spray drying systems. in handbook of industrial drying (4th ed., pp. 191-226). crc press. https://doi.org/doi:10.1201/b17208-12 gnielinski, v. 2010. g1 heat transfer in pipe flow. in vdi heat atlas (pp. 691-700). springer. gopireddy, sr., and gutheil, e. 2013. numerical simulation of evaporation and drying of a bi-component droplet. international journal of heat and mass transfer, 66(0): 404-411. https://doi.org/10.1016/j.ijheatmasstransfer.2013.07.010 herrmann, s., kretzschmar, h-j., and gatley, dp. 2011. thermodynamic properties of real moist air, dry air, steam, water, and ice (rp-1485). hvac&r research, 15(5): 961-986. https://doi.org/10.1080/10789669.2009.10390874 kadja, m., and bergeles, g. 2003. modelling of slurry droplet drying. applied thermal engineering, 23(7): 829844. https://doi.org/10.1016/s1359-4311(03)00014-0 http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng https://doi.org/10.1081/drt-120021689 https://doi.org/10.1016/j.cherd.2013.08.010 https://doi.org/10.1021/ie4033999 https://doi.org/10.1080/07373937.2015.1069326 https://doi.org/10.1016/s0017-9310(01)00090-4 https://doi.org/doi:10.1201/b17208-12 https://doi.org/10.1016/j.ijheatmasstransfer.2013.07.010 https://doi.org/10.1080/10789669.2009.10390874 https://doi.org/10.1016/s1359-4311(03)00014-0 arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 868-879. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aliyub@unimaid.edu.ng 879 masters, k. (1991). spray drying handbook (5th ed.). longman scientific & technical. mezhericher, m., levy, a., and borde, i. 2007. theoretical drying model of single droplets containing insoluble or dissolved solids. drying technology, 25(6): 1025-1032. https://doi.org/10.1080/07373930701394902 mezhericher, m., levy, a., and borde, i. 2010. theoretical models of single droplet drying kinetics: a review. drying technology, 28(2): 278-293. https://doi.org/10.1080/07373930903530337 mezhericher, m., levy, a., and borde, i. 2014. multi-scale multiphase modeling of transport phenomena in spray-drying processes. drying technology, 33(1): 2-23. https://doi.org/10.1080/07373937.2014.941110 michaelides, ees. 2013. heat and mass transfer in particulate suspensions. springer new york. https://books.google.com.my/books?id=yr8_aaaaqbaj morrison, fa. 2013. an introduction to fluid mechanics. cambridge university press. pátek, j., hrubý, j., klomfar, j., součková, m., and harvey, ah. 2009. reference correlations for thermophysical properties of liquid water at 0.1 mpa. journal of physical and chemical reference data, 38(1): 21-29. http://dx.doi.org/10.1063/1.3043575 poozesh, s., lu, k., and marsac, pj. 2018. on the particle formation in spray drying process for biopharmaceutical applications: interrogating a new model via computational fluid dynamics. international journal of heat and mass transfer, 122: 863-876. putranto, a., and chen, xd. 2015. an assessment on modeling drying processes: equilibrium multiphase model and the spatial reaction engineering approach (s-rea). chemical engineering research and design, 94: 660-672. https://doi.org/10.1016/j.cherd.2014.10.007 razmi, r., jubaer, h., krempski-smejda, m., jaskulski, m., xiao, j., chen, xd., and woo, mw. 2021. recent initiatives in effective modeling of spray drying. drying technology, 39(11): 1614-1647. rezaei, m., and netz, rr. 2021. water evaporation from solute-containing aerosol droplets: effects of internal concentration and diffusivity profiles and onset of crust formation. physics of fluids, 33(9). sadafi, mh., jahn, i., stilgoe, ab., and hooman, k. 2014. theoretical and experimental studies on a solid containing water droplet. international journal of heat and mass transfer, 78: 25-33. https://doi.org/10.1016/j.ijheatmasstransfer.2014.06.064 sazhin, s., elwardany, ae., gusev, ig., xie, j., shishkova, i., cao, b-y., and heikal, m. 2013. new models for droplet heating and evaporation. asian journal of scientific research, 6(2): 177-186. sazhin, ss. 2006. advanced models of fuel droplet heating and evaporation. progress in energy and combustion science, 32(2): 162-214. https://doi.org/10.1016/j.pecs.2005.11.001 sazhin, ss. 2014. droplets and sprays (vol. 63). springer. sazhin, ss., elwardany, ae., krutitskii, pa., deprédurand, v., castanet, g., lemoine, f., sazhina, em., and heikal, mr. 2011. multi-component droplet heating and evaporation: numerical simulation versus experimental data. international journal of thermal sciences, 50(7): 1164-1180. https://doi.org/10.1016/j.ijthermalsci.2011.02.020 semenova, m., vasileva, a., lukina, g., and popova, u. 2021. solving differential equations by means of mathematical simulation in simulink app of matlab software package. in technological advancements in construction: selected papers (pp. 417-431). springer. werner, srl., edmonds, rl., jones, jr., bronlund, je., and paterson, ahj. 2008. single droplet drying: transition from the effective diffusion model to a modified receding interface model. powder technology, 179(3): 184-189. https://doi.org/10.1016/j.powtec.2007.06.009 http://www.azojete.com.ng/ mailto:aliyub@unimaid.edu.ng https://doi.org/10.1080/07373930701394902 https://doi.org/10.1080/07373930903530337 https://doi.org/10.1080/07373937.2014.941110 https://books.google.com.my/books?id=yr8_aaaaqbaj http://dx.doi.org/10.1063/1.3043575 https://doi.org/10.1016/j.cherd.2014.10.007 https://doi.org/10.1016/j.ijheatmasstransfer.2014.06.064 https://doi.org/10.1016/j.pecs.2005.11.001 https://doi.org/10.1016/j.ijthermalsci.2011.02.020 https://doi.org/10.1016/j.powtec.2007.06.009 corresponding author’s email address: timothy.woma@gmail.com 328 arid zone journal of engineering, technology & environment original research article evaluation of corrosion inhibition, thermo-oxidative stability, and biodegradability of castor oil-based lubricant t.y. woma,1,2 *, t. d. ipilakyaa3, a. a. abdullahi1, a. s. abdulrahman4, m. a. olutoye5 and s. a. lawal 1,6 1department of mechanical engineering, federal university of technology, minna, nigeria. 2department of physics, federal university, wukari, nigeria. 3department of mechanical engineering, joseph sarwuan tarka university, makurdi, nigeria 4department of materials and metallurgical engineering, federal university of technology, minna, nigeria. 5department of chemical engineering, federal university of technology, minna, nigeria. 6department of mechanical engineering, university of mines and technology, essikado campus, tarkwa, ghana. *corresponding author`s email: timothy.woma@gmail.com article information abstract global lubricant demand is on the increase and the continual consumption of mineral oil-based lubricant has devastating environmental impact. despite the identification of animal fat and vegetable oil as alternatives to mineral oil-based lubricants, there is concern about its sustainability due to the food-versus-lubricant debate. thus, non-edible vegetable oil-based lubricant development has become a topical area of research. in this paper, the study of physicochemical, rheological, temperature, thermo-oxidative stability, corrosion inhibition and biodegradability properties of castor oil extracted from nigerian grown castor bean seeds was conducted using standard test methods. the results show that castor oil has specific gravity of 0.955, free fatty acid value of 19.74 mg koh/g, ph of 5.76, saponification value of 185.41 mg koh/g and iodine value of 92.1 gi2/100g oil. an assessment of the rheological and temperature properties of the castor oil gave kinematic viscosity at 400c and 1000c as 280.6 cst and 77.5 cst respectively, viscosity index of 33.4, pour point of -23.20c, cloud point of -12.40c and flash point of 2820c. the peroxide value of the castor oil was 8.92 meq/kg and it was of corrosion grade 0. the castor oil has higher viscosity at 400c, lower viscosity index, and poor physicochemical properties compared to the sae 20w50. the properties of the castor oil require improvement except its cold flow, flash point and corrosion inhibition properties. the castor oil is highly biodegradable while the sae 20w50 has poor biodegradability. therefore, castor oil conforms to iso vg220 grade lubricant and qualifies to be called a biolubricant. received: 20th july 2023 revised: 5th march 2025 accepted: 6th march 2025 keywords: biodegradability biolubricants environmentally friendly castor oil cold-flow corrosion © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the global increase in industrialisation and technological advancement has given rise to increase in the demand for lubricants. due to oil spills, volatility, total loss during application, improper disposal practices and poor waste oil disposal techniques, increased consumption of petroleum-based lubricants causes environmental pollution. therefore, research into environmentally friendly alternatives to petroleum-based lubricants is growing. animal fats and vegetable oils are now considered to be one of the best alternatives to petroleum oil for lubricant production (woma et al., 2019a). lubricants produced from plant-based oils and animal fats are called biolubricants. the global biolubricant market has been experiencing rapid growth and in some parts of the world it is projected that in the next two decades biolubricant application will grow by 15 to 20 percent (almasi et al., 2021 and khan et al., 2022). vegetable oil based biolubricants are made from either edible or non-edible vegetable oils. some of the most researched biolubricants are made of oils extracted from sunflower, soybean, azojete june 2025. vol.21(2):328-338 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/002 www.azojete.com.ng mailto:timothy.woma@gmail.com mailto:timothy.woma@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 329 rapeseed, coconut, palm, karanja, castor and jatropha seeds (binfa et al., 2015; woma et al., 2019b; nuur and widayat, 2018). recently, alternative renewable lubricant base oils such as waste cooking and microalgal oils have also been studied for producing biolubricants (farfan-cabrera et al., 2022; hussein et al., 2021). globally, people are most concerned about the sustainability of vegetable oil-based lubricants because of the competition between the food sectors and industrial lubricant sectors for available edible oil. this concern is refocusing biolubricant research towards non-edible seed oils (ioan, 2002; erhan et al; 2006 and bilal et al; 2013). the non-edible oil crops could be cultivated in arid and harsh environments, thereby preventing direct competition with conventional edible oil-bearing food crops (singh et al., 2019). some of the non-edible oil seed-bearing crops earlier studied for biolubricant production are castor, karanja, jojoba, and jatropha (sabiu, 2013; dibal et al., 2017; menkiti et al., 2017; sharma and sachan, 2019; woma et al; 2019b; al jabri et al., 2021;). castor oil, a nonedible vegetable oil produced from the seeds of castor plant and is the earliest and one of the largely investigated oils for industrial and automotive lubrication (brigham, 1993; musa, et al; 2015; bhaumik and pathak; 2016). it is produced from castor beans by mechanical and solvent extraction processes. the average oil content of a castor seed on the basis of dry weight is 50% (brigham, 1993). the presence of ricinoleic acid a type of hydroxylated fatty acid, and the glycerol group in castor oil imparts toxicity -making castor oil indigestible and unhealthy for human consumption (hong et al., 2011). further, the presence of about 90% ricinoleic acid, imparts an unusually high viscosity and density to castor oil (silva et al., 2013; zainal et al., 2018). castor oil is produced on a large scale in brazil, china, and india; global castor oil production is reported to be 1.8 million tonnes (rios et al., 2020). africa, including nigeria, has a contribution of around 0.08mt (fernandezmartinez and velasco, 2011). castor plant is very productive in most of the agricultural lands within nigeria. the yield of castor seed in nigeria is rated at between 950-1,500 kg/ha and virtually every part of nigeria is suitable for castor plantation (gana et al., 2013; gana et al., 2014). thus, there is a renewed interest in research into the lubrication properties of nigerian grown castor oil. despite the extensive research on castor oil as a bioluricant, there is a dearth of literature on the corrosion inhibition properties of castor oil as a biolubricant. also, it is generally believed from literature that vegetable oils possess poor thermo-oxidative stability (woma et al; 2019a) however there is need to determine and document the thermo-oxidative stability of each particular vegetable oil. in this work, the corrosion inhibition, thermo-oxidative stability as well as the biodegradability of unrefined, mechanically extracted castor oil, from a local extractor in kano state, nigeria is studied and compared with those of high-quality commercial sae 20w50 engine oil from a manufacturer in kano state, nigeria. additionally, recently published report has benchmarked a criterion for classification of lubricants as biolubricant: for any lubricant to be qualified as bio-lubricant; the biobased carbon content and biodegradability of the lubricant need to be 25 and 60 %, respectively (salih and salimon, 2021; khan et al; 2022). in view of this new classification, this work would examine the biodegradability of castor oil produced from nigerian grown castor plants. 2. materials and methods the major materials used in this research were castor oil sourced from agrienergy kano, and a mineral oilbased multigrade commercially available lubricant sae 20/w50 obtained from amasco kano, used as a control experiment. the castor oil was cold pressed and mechanically extracted from nigerian grown castor bean seeds. 2.1 determination of physicochemical properties of castor oil the physicochemical properties (specific gravity, acid value, percentage free fatty acid, iodine value and ph value) of the castor oil and sae 20w50 commercial mineral oil-based lubricant were analysed. details of the analysis are reported in the following subsections. 2.1.1 determination of specific gravity and density the density was measured according to the astm d1298 standard while the specific gravity was determined according to the astm d1217 standard. a 50ml sedi-m pycometer bottle was washed thoroughly with detergent, water and petroleum ether, it was then oven dried and weighed. the bottle was filled with distilled water and weighed, the bottle was then dried and filled with the oil sample and weighed again. from theory, the specific gravity is the mass of the oil weighed divided by the mass of water weighed and the density of the oil was equal to mass of the oil per unit volume. http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 330 2.1.2 determination of ph of the oils the ph values of the oils were measured using the rex phs -25 model ph meter. the ph meter was first calibrated using a standard solution. the electrode of the ph meter was cleaned with distilled water after each reading before taking another reading. 2.1.3 determination of saponification value of the vegetable oils the alcoholic koh was freshly prepared by dissolving koh pellet in ethanol. more than 1g of oil was measured and poured into a conical flask. 25ml of the alcoholic koh was added to it, a blank was also used. the sample was well covered and placed in an oven for 30minutes shaking it periodically, 1ml of phenolphthalein was added to the mixture and to the blank and titrated against 0.5m hcl to get the end point. the saponification value (sv) was calculated using equation (1) 𝑆𝑉 = 56.1(𝐵−𝐴)𝑁 𝑊𝑜𝑖𝑙 1 where; b= volume of standard ethanol potassium hydroxide used in blank titration; a= volume of standard ethanol potassium hydroxide used in titration with the oil; n= normality of standard acid; and woil = weight of oil used. 2.1.4 determination of iodine value of the oils the oil was poured into a small beaker; a small rod was added to it. between 1to 2g of the oil was weighed and poured into a glass-stopper bottle of about 250 ml capacity. 10ml of carbon tetrachloride was added to the oil to dissolve it. 20ml of wij’s solution was added and a stopper was inserted and allowed to stay in the dark for 30minutes. 15ml of potassium iodide solution (10%) and 100ml of water was introduced and the mixture was thoroughly mixed and titrated with 0.1m sodium thiosulphate solution using starch as indicator (titration = ‘a’ml). a blank was also carried out at the same time starting with 10ml of carbon tetrachloride (titration = ‘b’ml). the iodine value (iv) was calculated using the equation (2) 𝐼𝑉 = 0.1269(𝐵−𝐴)𝑁𝑋100 𝑊𝑜𝑖𝑙 2 where b= volume of sodium thiosulphate used in blank titration. a= volume of sodium thiosulpate used in titration with oil. n= normality of sodium thiosulphate. woil= weight of oil used and 0.1269 is the iodine number. 2.1.5 determination of acid value/ percentage free fatty acid (%ffa) the oil was measured and (2 g) introduced into a 250ml beaker. a neutral solvent (a mixture of petroleum ether and ethanol) was prepared and 50ml of it was taken and poured into the beaker containing the oil sample. the mixture was stirred vigorously for 30minutes. 0.56 g of potassium hydroxide (koh) pellet was measured and placed in a separate beaker and 0.1m koh was prepared, 3 drops of phenolphthalein indicator were added to the oil-ethanol-petroleum ether mixture and was titrated against 0.1m koh till the colour turned pink and persisted for 15minutes. the acid value (av) was determined using the equation (3). 𝐴𝑉 = 56.1𝑋𝑉𝑋𝑁 𝑊𝑜𝑖𝑙 3 where; v= volume of standard alkali used; n= normality of standard alkali used; woil = weight of oil used the percentage free fatty acid (%ffa) is gotten from equation 4 𝐹𝐹𝐴 = 𝐴𝑉 2 4 2.2 determination of rheological and temperature properties the dynamic viscosity at 400c and1000c was determined according to the astm d2983 standard. a 2013 model ndj-5s digital viscometer that measures in the range 10 to 2x106 mpas having an accuracy of + 2% was used. http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 331 the viscosity index was determined according to astm d2270 standard using equation (5). 𝑉. 𝐼 = (𝐿−𝑈)𝑋100 (𝐿−𝐻) 5 where: v.i is the viscosity index, u is the kinematic viscosity of the oil to be determined measured at 40°c, l is the kinematic viscosity of the reference oil at 40°c, h is the kinematic viscosity of the reference oil at 100°c the cloud point was measured according to the astm d2500. the pour point was determined according to the astm d97 standard. the flash point was measured according to the astm d92 standard. 30 mls of the oil was poured into an open cup apparatus and heated at atmospheric pressure while the temperature was being monitored with the digital infra-red thermometer. the set up was carried out in a fume chamber where air was being supplied to the heated oil until it ignited. the temperature at which it ignited was noted and recorded as the flash point of the oil. 2.3 determination of thermo-oxidative stability the peroxide value is essentially used as the basis for studying the stability of vegetable oils. the oxidative and thermal stabilities of the oils were determined by measuring peroxide values of the oils. the peroxide value was measured according to aocs c/8 53 standard.1g of oil was weighed into a clean drying boiling tube, 1g of powdered potassium iodide and 20ml of solvent mixture (2 volume of glacial acetic acid + 1 volume of chloroform) was added, the tube was placed in boiling water so that the liquid boils within 30 seconds and was also allowed to boil vigorously for not more than 30seconds. the content was quickly poured into a flask containing 20ml of potassium iodide solution; the tube was washed out with 25ml of distilled water and was titrated with 0.02m sodium thiosulphate solution using starch as indicator. a blank was also carried out at the same time. the peroxide value (pv) was determined from equation (6) pv = (𝐴−𝐵)𝑋𝑁𝑋1000 𝑊𝑜𝑖𝑙 6 where b = volume of sodium thiosulphate used in blank titration. a= volume of sodium thiosulpate used in titration with oil. n= normality of sodium thiosulphate (which is 0.02). woil= weight of oil used. 2.4 corrosion level test the corrosion level of the oils was determined according to astm d4627. the experiment was conducted by measuring out 1g of cast iron chips unto a filter paper placed in a petri dish. then 2 mls of the particular oil collected with a pipette was used to wet the iron chips on the filter paper in the petri dish and covered for 2 hours as shown in plate 1. after which the iron chips were thrown away and the filter paper carefully rinsed out with tap water. the paper was treated with acetone and allowed to dry at room temperature, with the corrosion level assessed by sight. plate 1: corrosion inhibition measurement http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 332 2.5. biodegradability test the test for the biodegradability of the castor oil as compared to that of the sae 20/w50 was carried out according to ijah and antai (2003). the extent of the degradation of the incorporated oils by bacillus sp. cdb08 bacterial isolated from petroleum contaminated soil was determined by gravimetric analysis method. the method involved the extraction of the residual oils with 50 ml petroleum ether and noting its absorbency reading at 520 nm wavelength. the percentage biodegradability of the oils was also determined by weighing the amount of recovered oil at interval of 7 days over a period of 28 days using equation 7. %𝐵𝑖𝑜𝑑𝑒𝑔𝑟𝑎𝑑𝑎𝑡𝑖𝑜𝑛 = (𝑊𝑎𝑜−𝑊𝑟𝑜)100 𝑊𝑎𝑜 7 where wao = weight of the added oil; and wro = weight of the residual oil after days of bacterial inoculation. 3. results and discussion 3.1 physicochemical properties of nigerian castor oil the physicochemical properties of the castor oil and mineral oil-based lubricant (sae 20w50) are as shown in table1. table 1: physicochemical properties of castor oil and sae 20w50 s/no. property castor oil sae 20w50 1 specific gravity 0.955 0.878 2 free fatty acid (mg koh/g) 19.74 3 saponification value (mg koh/g) 185.41 4 acid value (mg koh/g) 39.48 5 iodine value (gi2/100g oil) 92.1 80.0 6 ph 5.76 7.12 7 density (kgm-3) 955 878 from the result, specific gravity and density of castor oil is 0.955 and 955 kg/m3 respectively. these values for castor oil are slightly lower than the astm standard range (0.957 -0.961) the slight differences are as a result of differences in climate and soil conditions where the plants were grown and the condition of test. it can also be seen that the castor oil is denser than the mineral oil-based lubricant sae 20w50 while both oils are less dense compared to water and would therefore float in water. the acid value of the castor oil is 39.48 mg koh/g and its percentage free fatty acid 19.74 respectively. these values are too high and indicate that the oil is nonedible as the triglycerides in the oils have been decomposed. the lower the acid number the better the oil is as a lubricant as the high acid number oils are likely to corrode and wear machine parts that are lubricated. the results show that the castor oil will be a lower lubricant compared to the mineral oil sae 20w50 with regards to the acid value. the oil will need modification to bring down its acid value for it to be a better industrial lubricant. the saponification value of oil is a measure of the tendency of the oil to form soap during the transesterification reaction. the saponification value obtained for castor oil was 185.41 mgkoh/g which is slightly outside the range specified by american oil chemist society (aocs). these high saponification values shows that the oil will be more suited for soap and cosmetic making than for use as a lubricant, thus it may be necessary to modify the oil before use as lubricant. the iodine value shows the level of unsaturation of the oil and also influences the oxidation and deposition formed in internal combustion engines. it is used in determining the drying property of the oil. iodine value obtained for castor oil was 92.1 gi2/100g while that of the mineral oilbased lubricant is 80.0 gi2/100g. the high iodine value of castor oil (92.1 gi2/100g) signifies that there is a high degree of unsaturation in the castor oil. therefore, castor oil can be classified as unsaturated and non-drying oil since its iodine value is below 115 gi2/100g. the ph value is a measure of the acidity or alkalinity of a fluid. the ph of the castor oil was 5.76, while the ph of sae 20w50 mineral oil-based lubricant was 7.12. thus, the castor oil is acidic whereas the mineral oilbased lubricant is slightly alkaline. it is more desirable for a lubricant to have a ph between 8.0 and 10.0; lubricant with very low or too high ph can be damaging to the skin of the end users. besides microbial deterioration of biolubricants takes place in acidic medium rather than alkaline medium. the acidic ph of the http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 333 castor oil will reduce the corrosion protection of the machine components being lubricated thereby reducing their life span thus it is necessary to modify this oil to be suitable for use as lubricant. 3.2 rheological and temperature properties the rheological properties (viscosity and viscosity index) of the castor oil and mineral based lubricant (sae 20w50) are shown in table 2; while the temperature properties (cloud point, pour point and flash point) are shown in table 3. kinematic viscosity is one of the deciding parameters to evaluate the effectiveness of a lubricant. an increase in kinematic viscosity means increase in the lubricating property of the fluid (rao et al., 2007). from the results castor oil has kinematic viscosity of 280.6 cst at 400c which is higher than that of the mineral oil based lubricant sae 20w50 (236.9 cst). the very high viscosity of the castor oil is due to the presence of about 90% ricinoleic acid in the castor oil and is similar to the result gotten by other researchers (silva et al., 2013; zainal et al., 2018). thus, at room temperature the castor oil possesses better lubricating properties than mineral oil based lubricant sae 20w50. the kinematic viscosity of the castor oil is over three times that of the jatropha oil reported by woma et al; (2019b). however, the castor oil viscosity at 1000c (77.5cst) was lower than that of mineral oil-based lubricant at 1000c (99.1 cst). this means that the castor oil has a lower viscosity index than the mineral oil based lubricant, therefore the castor oil will show more variation in viscosity at high temperatures compared to the mineral oil based lubricant. the castor oil conforms to the iso vg 220 grade of industrial oil. table 2: rheological properties of castor oil and sae 20w50 s/no. parameter castor oil sae 20w50 1 kinematic viscosity at 400c (cst) 280.6 236.9 2 kinematic viscosity at 1000c (cst) 77.5 99.1 3 viscosity index 33.4 65.0 4 dynamic viscosity at 400c (mpas) 268.0 208.0 5 dynamic viscosity at 1000c (mpas) 74.0 87.0 table 3 shows the pour point of the castor oil (-23.20c) is very close to that of the sae 20w50 (-24.10c). though the mineral oil has better cold flow properties than the castor oil, both the castor oil and sae 20w50 oils have good cold flow properties (cloud point and pour point). the castor oil meets the cold flow properties standard for lubricants (-6°c for two-stroke engine lubricant as per is14234 standard). poor pour point has been what is lacking in most vegetable oils that hinder their applications in systems exposed to low temperatures. thus, castor oil can be used for lubrication of machines exposed to low temperatures such as automotive engines, construction machines, military and space applications. the flash point of the castor oil was (2820c) which was higher than that of the sae 20w50 (2550c). both oils have very high flash points which is desirable for a lubricant from the safety point of view. castor oil is safer than the mineral oil based lubricant sae 20w50 to be used at high temperatures as lubricant. castor oil has less fire hazard as a lubricant than most lubricating oils which has flash point of 210°c and fire point about 230°c (stachowiak and batchelor, 2000). table 3: temperature properties of castor oil and sae 20w50 s/no. parameter castor oil sae 20w50 1 pour point (0c) -23.2 -24.1 2 cloud point (0c) -12.4 -18.9 3 flash point (0c) 282.0 255.0 3.3 thermo-oxidative stability of nigerian castor oil the peroxide value is the usual method of assessment of primary oxidation products (gunstone, 2004). peroxide value of any oil gives an indication of its oxidative and thermal stability. the peroxide value of castor oil was 8.92 meq/kg, while that of the commercial mineral oil base lubricant (sae 20w50) was 0.99 meq/kg. however, this peroxide value of the castor oil is too high showing that the oil has poor oxidative and thermal stabilities. http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 334 this result is consistent with the findings of all other researchers that had studied the thermo-oxidative stabilities of vegetable oils (habibullah et al., 2014; musa et al; 2015; heikal et al 2016; aravind et al; 2018 and woma et al; 2019b). the poor thermal and oxidation stability of the castor oil implies that lubricants formulated from this oil will have a low shelf life as degradation of the oil will take place very fast. the poor thermo-oxidative stability of castor oil is a major hindrance for its application as industrial lubricant; thus, the oil must be modified to be suitable for industrial lubricant application. 3.4 corrosion inhibition level of nigerian castor oil and sae 20w50 the humidified cast iron chippings on filter paper covered in oil in a petri dish is shown in figure 2 (a); while figure 2 (b) is the castor oil filter paper after 2hrs and plate 2 (c) shows the sae 20w50 filter paper after 2hrs. no rust spot was found on both filter papers containing cast iron soaked in castor oil and sae 20w50. thus, both castor oil and sae 20/w50 exhibits excellent corrosion inhibition characteristics and based on alves and oliveira (2008), both castor oil and the sae 20w50 are of corrosion grade 0. (a) test with cast iron particles (b) after 2hrs, castor oil (c) after 2hrs, sae 20w50 plate 2: corrosion inhibition tests of castor oil and sae 20w50 3.5 biodegradability of nigerian castor oil and sae 20w50 the percentage degradation of the castor oil and sae20w50 over a period of 28 days after inoculation with bacterial is shown in figure 1. the ultra-violet visible (uv-vis) spectrophotomer absorbance at 520 nm wavelength of the castor oil and sae 20w50 mineral oil over 28 days after inoculation with bacteria is shown in figure 2. figure 1: biodegradability of castor oil and sae 20w50 0 54.92125984 65.35433071 75.78740157 96.60433071 0 10.99796334 17.71894094 26.47657841 35.23421589 0 20 40 60 80 100 0 7 14 21 28 % b io d e g ra d a b il it y time (days) castor oil http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 335 the castor oil had 96.6 % biodegradability while the commercial mineral oil-based lubricant (sae 20w50) had biodegradability of 35.2 % only. thus, the nigeria castor oil is classified as readily biodegradable since over 60 % of it was readily degraded by the bacteria in 28 days. the sae 20w50 is not readily biodegradable since only 35.2 % (less than 60%) of the lubricant was degraded by the bacteria after 28 days. these findings are in agreement with the trends of tests carried out according to the coordinating european council (cec) biodegradability test method, where mineral based lubricants have poor biodegradability between 15 35% and vegetable oils with excellent biodegradability between 70 – 100 % (aluyor et al; 2009). the castor oil had 54.9% biodegradability after 7 days of inoculation with the bacterial, this implies that the nigerian castor oil is environmentally friendly as over 50% of it could be removed naturally from the environment within a week. additionally, based on recent published benchmark criteria (salih and salimon, 2021; khan et al; 2022), the nigerian castor oil qualifies to be called a bio-lubricant. figure 2: uv-vis spectrophotometer absorbency readings of castor oil and sae 20w50 the absorbency of uv rays by the castor oil after 28 days was 0.434 nm while that of the sae 20w50 after 28 days was 0.583 nm. this indicates that the castor oil was more biodegradable than the sae 20w50. throughout the 28 days period of the test, castor oil absorbance of the uv rays was lower than that of the sae 20w50. the castor oil was eaten up by the bacteria and the solution became less turbid thereby it absorbed less uv rays, whereas the bacteria were not able to consume the mineral oil-based lubricant sae 20w50 therefore its solution remained turbid and absorbed more uv rays. 4. conclusion the study of the physicochemical, rheological, temperature, thermo-oxidative stability, corrosion inhibition and biodegradability properties of castor oil extracted from nigerian grown castor bean seeds have been carried out. standard laboratory tests were carried out on the castor oil and commercially available mineral oil base lubricant (sae 20w50) to determine their lubricant properties. the castor oil is acidic, unsaturated and has high saponification and free fatty acid values. there is need to modify the castor oil so as to improve its suitability as a base stock for the production of industrial lubricants. the castor oil has higher viscosity, but lower viscosity index compared to the mineral oil-based lubricant sae 20w50. the castor oil conforms to the iso vg220 grade of industrial lubricant oil and has excellent cold flow and fire hazard properties that do not require improvement. furthermore, it has poor thermal and oxidative stability compared to the sae 20w50. the castor oil extracted for nigerian grown castor bean seeds has excellent corrosion inhibition properties. both the castor oil and sae 20w50 are of corrosion grade 0. the castor oil is highly biodegradable with over 90% biodegradability in 28 days while the mineral oil-based lubricant sae 20w50 has poor biodegradability. by the criterion for classification of lubricants, the castor oil qualifies to be called a biolubricant 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 7 14 21 28 a b so rb a n c e ( n m ) time (days) castor oil sae 20w50 http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology and environment, june 2025; 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vol. 21(2): 328-338. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: timothy.woma@gmail.com 338 stachowiak, gw. and batchelor, aw. 2000. engineering tribology, second edition. butterworth-henemann, boston: 3-616. woma, ty., lawal, sa., abdurahman, as., olutoye, ma. and ojapah, mm. 2019a. vegetable oil based lubricants: challenges and prospects. tribology online, 14(2): 60-70 woma, ty., lawal, sa., abdurahman, as. and olutoye, ma. 2019b. nigeria jatropha oil as suitable base stock for biolubricant production, jurnal tribologi, 23: 97-112. zainal, na., zulkifli, nwm., gulzar, m., masjuki, hh., 2018. a review on the chemistry, production, and technological potential of bio-based lubricants. renew. sust. energ. rev. 82: 80–102. https://doi.org/10.1016/j.rser.2017.09.004. http://www.azojete.com.ng/ mailto:timothy.woma@gmail.com arid zone journal of engineering, technology & environment azojete september 2024. vol. 20(3):657-666 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 657 optimization of groundnut oil extraction using chemical method h. h. mari1*, n. mustapha1, i. mohammed1, h. d. mohammed2, s. kiman2, and a. b. ngulde2 1department of agricultural and environmental resource engineering, university of maiduguri, maiduguri, borno state, nigeria 2department of chemical engineering, university of maiduguri, borno state, nigeria *corresponding author's email address: hauwamari@gmail.com article information submitted 1 march, 2024 revised 3 july, 2024 accepted 10 july, 2024 keywords: groundnut response surface method optimization n-hexane oil yield optimization abstract the chemical extraction technique is associated with suboptimal oil yield and quality, necessitating the development of optimized extraction technique. in this study, groundnut oil was extracted chemically with nhexane using the response surface methodology (rsm) and the extraction process was optimized considering the hexane concentration (30, 40 and 50), extraction duration (3, 5, 7 hrs) and the amount of groundnut (15, 20, and 25 g) as factors and the oil yield was evaluated. the fourier transform infrared (ftir) technique was used to check at the functional groups on the extracted oil. in the experimental results, the average optimum values of extraction time, solvent amount, groundnut amount, and oil yield were 5.05 hr, 40.5 ml, 20.25 g, and 48.18%, respectively. the profiled extracted oil by ftir showed peaks at 3452 cm-1 2969 cm-1 2712 cm-1 1763 cm-1 1474 cm-1 which indicates the existence of -ch and oh, ch, c-h, aldehydes, ketones, carboxylic acids, and methylene groups functional groups which are useful for determining the oil's quality. furthermore, findings from this study showed that rsm-optimized process parameters result in significantly greater oil yields than conventional approaches. 1.0 introduction groundnut (arachis hypogaea l.) is produced worldwide, and it is widely consumed in many forms, including roasted grain, peanut butter, and peanut oil. the four main world producers are china, india, nigeria, and the usa, which are distributed in asia, africa, and america, these countries are responsible for 63.5% of the world production of peanut grain, 75.3% of peanut oil and 75.8% of peanut meal/cake (magalhães et al., 2023). in addition to direct consumption, either with or without treatment, peanuts can be the subject of diverse applications focusing mainly on two distinct objectives: oil extraction and defatting processes (mahfoud et al., 2023) and more than 70% of the harvest is used for oil extraction (kotadiya and patel, 2022). the nutritional value of groundnut proteins has been reported to be relatively high, with a biological value (bv) of 59 and net protein utilization of 51 (cui et al., 2023). it is a source of nutrients like niacin, which helps to promote healthy blood flow and brain function, folate, antioxidants, vitamin e, magnesium, phosphorus, and dietary fibers containing between 45.9% and 55.4% of lipids that are specifically high in essential polyunsaturated fatty acids (kotadiya and patel, 2022). furthermore, kotadiya and patel, (2022) reported that high consumption of nuts is associated with a beneficial impact on the cardiovascular system, due to their antioxidant and anti-inflammatory properties. http://www.azojete.com.ng/ mailto:%20hauwamari@gmail.com mailto:%20salami.lukman@adelekeuniversity.edu.ng mailto:%20salami.lukman@adelekeuniversity.edu.ng arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)657-666. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 658 extraction of lipid and other valued substances is strongly reliant on the method employed for extraction therefore, an appropriate extraction technique is required to yield the desired components. pressing, soxhlet system, and the combined use of pre-pressing and solvent extraction are the three most prevalent processes for producing oils (idrissi et al., 2022). innovation in extraction techniques includes supercritical fluid extraction, pressurized liquid extraction, microwave assisted extraction, ultrasound assisted extraction, cold atmospheric plasma extraction, amongst others (picot-allain et al., 2021). mechanical techniques for oil extraction from peanuts are grouped into three main sections: extrusion and screw pressing, cold pressing, and hydraulic pressing (mahfoud et al., 2023), the oil content of oilseeds may be recovered using a mechanical screw press to the extent of 86% to 92% (kotadiya and patel, 2022). however, cold-pressing (cp) productivity is low, and it is difficult to obtain a consistent quality product (idrissi et al., 2022). therefore, various novel methods have been developed to increase the yield, reduce denaturation, and improve the functional properties of plant proteins (cui et al., 2023). when extracting oil from oilseeds, the organic solvent is used, the most frequently utilized organic solvent is hexane. oilseeds that have been pre-treated and are in the form of a porous solid matrix are exposed to either pure solvent or a mixture of solvent and oil (known as miscella). according to prasad et al. (2022), the solvent extraction is encountered during various processes in the food industry, viz oil extraction from oilseeds, flavoring and polyphenolic compounds extraction from herbs and spices, and the reasons for the preferred choice of solvent extraction include easy availability at lower price from petroleum-based solvents. chemical method is grouped under three major flags: organic solvent extraction (such as hexane), aqueous extraction processing (aep), and supercritical fluid extraction (sfe) based on the use of co2 as solvent (sc-co2) (mahfoud et al., 2023). the solvent extraction is used to dissolve and extract the oil from the peanuts. this method is more efficient than mechanical pressing and can extract a higher percentage of oil. the oil is considered to be nutritious and healthful, owing to its fatty acid composition and the presence of natural bioactive components, such as squalene, phytosterols, tocopherols and tocotrienols (zhu et al., 2015). the most important quality requirements of groundnut as a source of oil are high protein and oil content in seed and high oleic acid (sarvamangala et al., 2011). for these reasons, many researchers focus on the increase in the oil yield and the higher recovery of these compounds and develop corresponding methods to extract them from oilseeds (linn, 2022). response surface method (rsm) is a tool for function estimation that combines mathematical, statistics, and multiple quadratic regression to optimize influencing conditions from multiple experimental runs from numerous variables using polynomial equations and relate the response to the influential conditions with good practical value, precision, and optimization effects (mukwevho et al., 2023; silas et al., 2021). the application of rsm technique for optimizing the oil extraction process can improve the performance and economy of the process. few studies reported such studies, for example, the effects of extraction time, extraction temperature, solid– to– solvent ratio and ultrasound power on the extraction yield and the oleic acid concentration of the thermosonically extracted groundnut oil were investigated, the findings indicated that extraction yield was primarily affected by the extraction temperature and solid– to– solvent ratio (ketenoglu, 2020). the one-at-a-time process optimization for understanding the influences of different operating parameters on the extraction of flavonoids from groundnut shells under ultrasound irradiation (liao et al., 2021) was reported. in another study, (liu et al., 2020) the effect of various enzymes on the molecular weight distribution of peanut protein, microscopy of oil bodies, and yield of peanut protein and oil bodies during the aqueous enzymatic extraction process were file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com mari et al: optimization of groundnut oil extraction using chemical method. azojete, 20(3):657-666. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 659 investigated. however, these studies failed to report the functional groups on the extracted oil. this study, utilizes the rsm technique to design an experiment using central composite design (ccd) to optimize the groundnut oil yield considering influential factors such as extraction time, amount of solvent and the amount of groundnut. also, to study the functional groups on the oil using the ftir technique. 2. materials and methods 2.1 materials unroasted groundnuts were purchased from gumboru local market in maiduguri. the groundnuts were separated from all possible residues of leaves, hard shells and miscellaneous parts of the plant before analyzes, the sample was placed in an oven at 105 oc for 12 hrs, the dried groundnut seed was first fed to a jaw crusher to increase the surface area of the nut seed in other to aid good extraction. analytical grade n-hexane used for oil extraction was purchased from merck, germany. 2.2 experimental procedures solvent extraction using n-hexane in the soxhlet procedure, oil and fat from solid material are extracted by repeated washing (percolation) with an organic solvent where hexane was used. the grounded groundnuts were placed in a porous cellulose thimble. the thimble is then placed in an extraction chamber which is suspended above a flask containing the solvent and below a condenser. heat is applied to the flask, and the solvent evaporates and moves to the condenser, converted into a liquid that trickles into the extraction chamber containing the sample. the extraction chamber is made in such a way that when the solvent surrounding the sample exceeds a certain level it overflows and trickles back down into the boiling flask. the flask containing solvent and lipid is removed at the end of the extraction process. the solvent in the flask is separated via distillation, and the remaining lipid mass is measured. the percentage of the lipid in the initial sample is then calculated. the percentage oil yield (% by weight) was estimated using the eq. 1 (liu et al., 2020): 1 where, mo is the mass of oil in kg, ms is the mass of sample in kg. 2.3 design of experiment (doe) the central composite design of design expert 10.0 software was used to design the experiment. extraction time (a), amount of solvent (b), amount of groundnut (c), worked as influencing factors, while the yield of peanut worked as response values. encoding of factor levels is shown in table 1. file version 10.0.6.0 study type response surface subtype randomized design type central composite runs 20 table 1: design of experiment factor name units levels a extraction time hr 3 7 b amount of solvent ml 30 50 c amount of g/nut g 15 25 http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)657-666. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 660 2.4 fourier transform infrared spectroscopy (ftir) procedure the fourier transform infrared spectroscopy (ftir) analysis was carried out using perkin elmer rx. the ftir spectra were collected in the range of 4000-400 cm-1. potassium bromide (kbr) pellet was first prepared by mixing about 0.01 g of powdered catalyzed adsorbent with about 0.3 g of kbr (merck; for spectroscopy) in an agate mortar. the mixture was compressed under a certain pressure in a special die to form a small disk. 3. results and discussion 3.1 rsm optimization result the independent variables (extraction time, solvent quantity, and groundnut amount) as designed by the doe with the final oil yield data is presented in table 2. there are six center points with similar independent variables values as designed by the software but their oil yield as calculated differs however, their oil yields are insignificant. table 2: experimental factors and response data factor 1 factor 2 factor 3 response 1 run a: extraction time b: amount of solvent c: amount of g/nut oil yield hr ml g (%) 1 7 50 15 50.12 2 3 30 25 48.63 3 5 40 20 47.55 4 3 50 25 48.72 5 5 40 20 46.71 6 5 40 20 46.38 7 7 30 25 58.87 8 3 40 20 45.20 9 5 30 20 48.55 10 5 40 20 48.42 11 7 30 15 50.03 12 3 30 15 44.97 13 7 40 20 54.00 14 7 50 25 59.79 15 5 40 20 48.66 16 5 40 20 48.86 17 5 40 25 50.32 18 5 40 15 46.73 19 5 50 20 47.45 20 3 50 15 45.06 table 3 shows the anova table with the statistical analysis. the model f-value of 33.28 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. values of "prob > f" less than 0.0500 indicate model terms are significant. in this case a, c, ac, a^2 are significant model terms. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com mari et al: optimization of groundnut oil extraction using chemical method. azojete, 20(3):657-666. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 661 table 3: anova for response surface quadratic model sum of mean f p-value source squares df square value prob > f model 300.47 9 33.39 33.28 < 0.0001 significant a-extraction time 161.85 1 161.85 161.34 < 0.0001 b-amount of solvent 8.100e-004 1 8.100e-004 8.074e-004 0.9779 c-amount of g/nut 86.55 1 86.55 86.28 < 0.0001 ab 0.086 1 0.086 0.086 0.7755 ac 15.65 1 15.65 15.60 0.0027 bc 0.086 1 0.086 0.086 0.7755 a2 9.93 1 9.93 9.90 0.0104 b2 0.25 1 0.25 0.25 0.6296 c2 1.87 1 1.87 1.87 0.2017 residual 10.03 10 1.00 lack of fit 4.53 5 0.91 0.82 0.5826 not significant pure error 5.51 5 1.10 cor total 310.50 19 values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the "lack of fit f-value" of 0.82 implies the lack of fit is not significant relative to the pure error. there is a 58.26% chance that a "lack of fit f-value" this large could occur due to noise. non-significant lack of fit is good. the anova goodness-of-fit, provided by the coefficient of determination (r2), was determined. r2 measures the percentage of changes in the response variable that can be attributed to independent variables and their interactions. it also evaluates how well a statistical model fits a given set of data. the closer the r2 value is to 1, the better the model matches the data. the r2 value of 0.9677 is showing that the model was adequate. to further confirm the model’s adequacy, the lack-of-fit error test was carried out. the lack-of-fit error test quantifies inaccuracies due to any flaw(s) in a model. the lack of fit is not significant if the error probability p, of the lack-of-fit f-statistic is larger than the confidence interval. in contrast, if the f-statistic of the lack-of-fit error is greater than the associated error probability, the lack-of-fit test is said to be significant, and the regression model is inadequate to explain the data. in the present study, as shown in table 3, the lack of fit was found to be non-significant, indicating that the regression model for oil extraction, was sufficient in explaining the experimental data, similar findings are reported (bello et al., 2023; chen et al., 2022). the final equation in terms of coded factor is given in eq. 2. oil yield% =47.74 + 4.02*a +9.00e-003*b + 2.94*c + 0.10*ab + 1.40*ac + 0.10*bc + 1.90*a2 + 0.3*b2 + 0.83*c2 2 the equation in terms of coded factors can be used to make predictions about the response for given levels of each factor. by default, the high levels of the factors are coded as +1 and the low levels of the factors are coded as -1. the coded equation is useful for identifying the relative impact of the factors by comparing the factor coefficients. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)657-666. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 662 figure 1: predicted values versus the actual values for the oil yield. this plot depicts that the developed model can correlate independent variables (extraction time, amount of groundnut and amount of solvent) with the response (oil yield). the implication of this pattern is that the model proposed is suitable for the present study. 3.2 response surfaces 3d analysis these 3d graphics provide an in-depth look at the correlations between oil yield and the various parameters. they enable a better knowledge of how different extraction times, solvent amounts, and groundnut amounts affect oil yield. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com mari et al: optimization of groundnut oil extraction using chemical method. azojete, 20(3):657-666. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 663 figure 2: response surfaces of (a) amount of solvent against extraction time (b) amount of g/nut against extraction time (c) amount of g/nut against amount of solvent. oil yield variation with extraction time and solvent amount depicts the link between oil yield and two major parameters. it displays how variations in extraction time and solvent concentration affect the final oil yield. through the contour shape, we can see the strong and weak relationship of interaction effect. the closer the shape is to the circle, the less is the significant of the interactive effects of the factors also, parallel line indicates that the interaction between the two factors is insignificant (chen et al., 2022). it can be seen from contour lines in the figures 2a-d that the graph is not curved much close to a circle, indicating that the interaction between the two factors, amounts solvent and extraction time (fig. 2a), amount of g/nut and extraction time (fig. 2b) and, amounts solvent and amount of g/nut (fig. 2c) shown on the response surfaces are significant. according to the experiments and the predicted values, table 4 shows the oil yield obtained. table 4: oil yield obtained by the predicted and the experimental values. extraction time (hr) amount of groundnut (g) amount of solvent oil yield predicted 5.0 40.5 20.25 48.2 experimental 5.0 40.5 20.25 46.2 3.4 ftir analysis ftir technique shows the functional groups on the extracted oil from groundnut providing valuable insights into the chemical composition of the extracted oil. the ftir spectrum of the extracted oil considering the optimum oil yield is presented in fig. 3. http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)657-666. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 664 figure 3: ftir spectra of the extracted groundnut oil. the presence of -ch and -oh functional groups with stretching vibrations is shown by the peak at 3452 cm-1 (sumesh et al., 2020) which suggests the existence of organic molecules or components similar to c-h bonds at 2712 cm-1 (wazir et al., 2020). the ch functional group with aliphatic stretching vibrations is shown by the peak at 2969 cm-1 (thavasi et al., 2011) which suggests the presence of organic molecules with carbon-carbon single bonds. the peak at 2190 cm-1 corresponds to stretching vibrations in o=p-oh functional groups indicating the presence of phosphate-containing chemicals, which are common in biomolecules such as nucleotides and phospholipids (erfani and javanbakht, 2018). the presence of phosphate groups implies that biological or biochemical components may be present in the sample. the c=o functional group with stretching vibrations is shown by the peak at 1763 cm-1. the existence of carbonyl compounds, such as aldehydes, ketones, and carboxylic acids, indicates the presence of carbonyl compounds as shown in the 1474 cm-1 peak associated with -ch2 functional groups with symmetric bending vibrations. 4. conclusion in this study, the optimal oil yield extracted from groundnut was reported using the rsm design of experiment and gained significant information resulting in the efficient groundnut extraction oil yield technique. in addition, there is an eestablished predictive models that accurately forecast oil yield based on varying extraction parameters. the ftir study shows the various functional groups that are found on the oil which allows a better understanding of its organic composition. further researchers should consider oil profiling techniques for comprehensive profiling of the extracted oil, use advanced analytical techniques such as gas chromatographymass spectrometry (gc-ms) and high-performance liquid chromatography (hplc). references bello, i., adeniyi, a., mukaila, t. and hammed, a. 2023. optimization of soybean protein extraction with ammonium hydroxide (nh4oh) using response surface methodology. foods, 12(7): 1-15. https://doi.org/10.3390/foods12071515. chen, x., li, z., smith, s. a., chen, m., liu, h., zhang, j. and wu, x. 2022. optimization of file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com mari et al: optimization of groundnut oil extraction using chemical method. azojete, 20(3):657-666. issn 1596-2490; e-issn 2545-5818, www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 665 supercritical co2 extraction of moringa oleifera seed oil using response surface methodological approach and its antioxidant activity. frontiers in nutrition, 8: 1-10. https://doi.org/10.3389/fnut.2021.829146. cui, s., mcclements, d. j., xu, x., jiao, b., zhou, l., zhou, h. and dai, l. 2023. peanut proteins: extraction, modifications, and applications: a comprehensive review. grain and oil science and technology, 6(3): 135-147. https://doi.org/10.1016/j.gaost.2023.07.001. erfani, m. and javanbakht, v. 2018. methylene blue removal from aqueous solution by a biocomposite synthesized from sodium alginate and wastes of oil extraction from almond peanut. international journal of biological macromolecules, 114: 244-255. https://doi.org/10.1016/j.ijbiomac.2018.03.003. idrissi, zl., el moudden, h., mghazli, n., bouyahya, a., guezzane, ce, alshahrani, mm. and tabyaoui, m. 2022. effects of extraction methods on the bioactivities and nutritional value of virginia and valencia-type peanut oil. molecules, 27(22): 1-17. https://doi.org/10.3390/molecules 27227709. ketenoglu, o. 2020. extraction of peanut oil using thermosonication: modeling and multiobjective optimization of process parameters using box–behnken design. journal of oleo science, 69(6): 585–595. https://doi.org/10.5650/jos.ess19309 kotadiya, ar. and patel, cm. 2022. recent scope of ground oil expeller machines for small and medium scale industries: a review. international conference on science, engineering and technology, 628–636. liao, j., guo, z. and yu, g. 2021. process intensification and kinetic studies of ultrasoundassisted extraction of flavonoids from peanut shells. ultrasonics sonochemistry, 76: 1-16. https://doi.org/10.1016/j.ultsonch.2021.105661 linn, os. 2022. chemical composition and antioxidant activities. foods, 36(1): 95-108. liu, c., hao, l., chen, f. and yang, c. 2020. study on extraction of peanut protein and oil bodies by aqueous enzymatic extraction and characterization of protein. journal of chemistry, 2020: article 5148967-1-11. https://doi.org/10.1155/2020/5148967. magalhães, pjc., gonçalves, d., aracava, kk. and rodrigues, ce. 2023. experimental comparison between ethanol and hexane as solvents for oil extraction from peanut press cake. foods, 12(15): 1-17. https://doi.org/10.3390/foods12152886 mahfoud, f., assaf, jc., elias, r., debs, e. and louka, n. 2023. defatting and defatted peanuts: a critical review on methods of oil extraction and consideration of solid matrix as a byproduct or intended target. processes, 11(8): 1-12. https://doi.org/10.3390/pr11082512 mukwevho, pl., kaseke, t. and fawole, oa. 2023. optimisation using response surface methodology of quality, nutritional and antioxidant attributes of wichita pecan nuts roasted by microwaves. processes, 11(8), 1-17. https://doi.org/10.3390/pr11082503 picot-allain, c., mahomoodally, mf., ak, g. and zengin, g. 2021. conventional versus green extraction techniquesa comparative perspective. current opinions in food science, 40: 144-156. https://doi.org/10.1016/j.cofs.2021.02.009 prasad, w., wani, ad., khamrui, k., hussain, sa. and khetra, y. 2022. green solvents, potential alternatives for petroleum based products in food processing industries. cleaner http://www.azojete.com.ng/ mailto:%20edetjoseph1991@gmail.com%09 https://doi.org/10.3390/molecules arid zone journal of engineering, technology and environment, september 2024; vol. 20(3)657-666. issn 1596-2490; e-issn 25455818; www.azojete.com.ng corresponding author’s e-mail address: hauwamari@gmail.com 666 chemical engineering, 3: 1-22. https://doi.org/10.1016/j.clce.2022.100052 sarvamangala, c., gowda, mvc. and varshney, rk. 2011. identification of quantitative trait loci for protein content, oil content and oil quality for groundnut (arachis hypogaea l.). field crops research, 122(1): 49-59. doi:10.1016/j.fcr.2011.02.010 silas, k., mohammed, hd. and mamza, j. 2021. response surface methodology optimization of sawdust in water boiling test. journal of chemistry letters, 2: 212-216. sumesh, kr., kanthavel, k. and kavimani, v. 2020. peanut oil cake-derived cellulose fi ber: extraction, application of mechanical and thermal properties in pineapple/flax natural fiber composites. international journal of biological macromolecules, 150: 775-785. https://doi.org/10.1016/j.ijbiomac.2020.02.118 thavasi, r., jayalakshmi, s. and banat, im. 2011. application of biosurfactant produced from peanut oil cake by lactobacillus delbrueckii in biodegradation of crude oil. bioresource technology, 102(3): 3366-3372. https://doi.org/10.1016/j.biortech.2010.11.071 wazir, ah., wazir, iu. and wazir, am. 2020. environmental effects preparation and characterization of rice husk based physical activated carbon. energy sources, part a: recovery, utilization, and environmental effects, 46(1): 1-11. https://doi.org/10.1080/15567036.2020.1715512 zhu, m., wen, x., zhao, j., liu, f., ni, y., ma, l. and li, j. 2015. effect of industrial chemical refining on the physicochemical properties and the bioactive minor components of peanut oil. journal of the american oil chemists society, 93(2): 285-294. file:///c:/user/downloads/azojete143/www.azojete.com.ng mailto:%20kunleoluyori@gmail.com mailto:%20kunleoluyori@gmail.com https://doi.org/10.1016/j.biortech.2010.11.071 corresponding author's email address: engr.adanu@gmail.com 168 arid zone journal of engineering, technology & environment original research article design and fabrication of a canvas belt thresher for efficient cowpea threshing e.o adanu1*, s.a iya2 , i.t yakubu2 and h.u. kabri2 1department of agricultural education, federal college of education (tech.), gombe, nigeria. 2department of agricultural and environmental engineering, modibbo adama university of technology, yola, nigeria. *corresponding author: engr.adanu@gmail.com article information abstract the increasing demand for efficient and cost-effective cowpea threshing machinery led to the development of a canvas belt thresher. this study focuses on the design and fabrication of a thresher that minimizes grain damage while enhancing threshing efficiency. the machine was constructed using mild steel iron, 22-gauge sheet metal, and canvas materials, ensuring robustness and cost-effectiveness. the total production cost of the machine was ₦253,000, making it affordable for small-scale farmers. the canvas belt system, selected for its rubbing action, was designed to improve grain separation and reduce kernel bruising compared to traditional impact-based mechanisms. key design considerations included material selection, power transmission, shaft design, and motor capacity to ensure durability, ease of use, and affordability. a 3.18kw gasoline engine powered the thresher, enabling both field and off-field operations. performance results showed that the machine (1500mm × 800mm × 820mm) operates between 400 to 1200 rpm of drum speed, yielding a high level of efficiency with minimal grain loss and damage. this machine offers a reliable solution for small-scale farmers, significantly reducing labor, time, and operational costs associated with cowpea threshing. submitted: 13th october 2024 revised: 27th january 2025 accepted: 3rd february 2025 keywords: agriculture canvas-material cowpea design friction thresher © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction threshing is a critical post-harvest operation in crop production, aimed at separating grains from harvested crops with minimal loss or damage. efficient threshing ensures grains retain their quality, market value, and shelf life. however, conventional threshing methods often lead to significant grain losses, including broken grains, un-threshed grains, and spilled grains. according to the bureau of indian standards, total grain loss during threshing should not exceed 5%, with broken grains limited to less than 2% (clark, 2007; bis, 1985). these standards underscore the need for efficient threshing mechanisms to safeguard grain quality and market value. many existing threshing machines employ drum, spike-tooth, or rasp-bar mechanisms, which rely on impact-based threshing. while effective for grain separation, the high impact forces associated with these mechanisms often damage kernels, causing bruises, splits, and shattering. this damage reduces the grains' market value and shortens their storage life (clark, 2007). to address these limitations, researchers have explored alternative threshing methods that prioritize grain integrity. fernando and hanna (2005), for instance, developed soybean threshing mechanisms that minimized kernel damage using a specially designed threshing chamber and pneumatic systems. similarly, fernando et al., (2004) introduced a soybean harvesting and threshing unit that processed pods while still rooted, thereby reducing kernel damage and improving operational efficiency. gelaw (2020) advanced this work by investigating the theoretical and experimental aspects of threshing mechanisms for tef (eragrostis tef), focusing on its engineering properties. gelaw designed a threshing unit that minimized grain damage while maintaining high efficiency. el-shal et al., (2020) developed a rubbing-based thresher for seed crops like flax and sunflower, significantly reducing seed damage and improving threshing efficiency. istifanus et al., (2022) evaluated a cereal crop thresher modified to incorporate rubbing actions, achieving higher efficiency and reduced grain damage compared to traditional impact-based designs. these studies collectively demonstrate the advantages of adopting rubbing-based mechanisms to preserve grain quality and extend storage life. azojete march 2025. vol.21(1):168-180 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:musa.ibrahim@bazeuniversity.edu.ng mailto:musa.ibrahim@bazeuniversity.edu.ng mailto:engr.adanu@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 169 despite these promising developments, the application of rubbing action to cowpea threshing remains limited. allen and watts (1998) developed a belt thresher for cowpea beans, but its complexity, high power consumption, and cost made it impractical for small-scale farmers. chen et al. (2025) introduced a low-damage threshing drum for corn, combining rubbing and impact actions to reduce kernel breakage—a concept that could potentially be adapted for cowpea threshing. while most designs, such as those by ojomo et al. (2010), maunde (2011), and fawohunre and olajide (2020), continue to rely on impact-based mechanisms, the advantages of rubbing actions highlight their potential for minimizing grain damage and enhancing threshing efficiency. this study aims to design and fabricate a cost-effective and efficient canvas belt thresher for cowpea threshing, leveraging rubbing action to address challenges related to grain damage and affordability. upon completion, the proposed machine will provide small-scale farmers with a reliable and sustainable threshing solution, reducing labor intensity, operational costs, and time requirements while preserving grain quality. 2. materials and method 2.1 materials selection machine members experience stresses that affect performance and service life, making material selection a critical aspect of the design process. for the thresher, 22-gauge sheet metal was used for the tray, chute, and blower components, while a semi-rough canvas belt (400 x 4000 mm) was resized for threshing. a 2m long, 70mm diameter galvanized steel pipe served as the conveyor drum, and a 3.5m mild steel rod (20mm diameter) was selected for the shaft. twelve radial bearings with a 20mm internal diameter were used, along with a frame constructed from 45x45mm angle iron. an 'a' type v-belt, bolts, nuts, and welded joints were employed for assembly, with a gasoline engine providing power for both field and off-field operations. additional materials like cutter blades, welding electrodes, and other hand tools were also utilized. 2.2 design considerations in designing the thresher, key considerations include: weight and space limitations to ensure it is both movable and stable, while remaining compact for operation and storage. the clearance between the thresher belts was optimized for efficient threshing without bruising the grains. locally sourced materials were chosen to ensure easy replacement and simple fabrication techniques. the machine was designed for ease of operation, allowing a wide range of users, while also prioritizing operator safety by positioning movable parts away from the user. reliability and cost-effectiveness were also considered, using affordable, locally available materials to make the machine accessible to cowpea farmers. aesthetics were also factored in to make the machine visually appealing. 2.3 methods 2.3.1 design analysis and calculations to ensure cost-effectiveness and efficiency, calculations and selections were performed to create a functional machine using standard references, tables, and charts. 2.3.1.1 thresher drum diameter the drum diameter is calculated using kutte’s (2001) formula, yielding a diameter of 0.07m for a peripheral velocity of 14m/s and a cylinder speed of 550rpm. 2.3.1.2 thresher belt clearance and thresher belt capacity based on the cowpea pod size, the belt clearance was set between 6.1mm and 7.32mm, adjustable for effective threshing depending on seed size and moisture content. this was based on allen and watts (1998) where clearance should be between 50 – 60% of the length of the grain. simulations indicated a lower belt length of 1.1m and a top belt length of 0.84m (allen, 1993 in allen and watts, 1998). the belt speed for design purposes was set at 2m/s, giving a calculated belt capacity of 6.4 kg/s (daniyan et al., 2014; sousa et al., 2015). http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 170 2.3.1.3 power to drive thresher belt and v-belt selection using the frictional angle of cowpea pods (44°), the power required to thresh is 1.63kw, adjusted to 1.81kw with a service factor of 0.9. the force needed to separate the cowpea from the pod was calculated as 1.94n, ensuring it stays below the shear force threshold to avoid damaging the seeds (khurmi and gupta, 2006). vbelts were chosen for power transmission due to their better grip, ease of installation, and smaller pulley diameter requirements. the allowable power transmission for the belt was calculated at 1.58kw, confirming the use of an a-type v-belt with a 130mm pulley (bhandari, 2010). 2.3.1.4 v-belt pulley parameters the calculation of v-belt pulley parameters involves determining essential values such as center distance, pulley diameters, velocity ratios, and belt lengths (figure 1). key steps include: figure 1: v-belt and pulley arrangement where 1) is motor pulley, 2) thresher drive pulley, 3) extension pulley and 4) the thresher driven pulley. 1. angular speed of shafts: the input shaft's angular speed (ω1) is calculated using the formula ω1 = (2πn1)/60, where n1 is 1500 rpm, resulting in ω1 = 157.1 rad/s. similarly, for the output/thresher shaft, ω2 = (2πn2)/60, with n2 = 550 rpm, resulting in ω2 = 57.6 rad/s. 2. velocity ratio: the velocity ratio (i) is derived as n1/n2 = d2/d1. with n1 = 1500 rpm and n2 = 550 rpm, the ratio is i = 2.73. given a pulley diameter d2 = 130mm, d1 is calculated as 50mm (standard). 3. pulley diameters: for the thresher belts, a speed reduction of 5:2 is chosen for differential speeds. with a 70mm diameter pulley for d3, d4 is calculated as 170mm (standard) based on the ratio. 4. center distance between pulleys: the distance between pulleys is calculated as (khurmi & gupta, 2006): • for d1 and d2: d1 = 283mm, d2 = 1600mm, c1 = 650.314mm. • for d3 and d4: d1 = 377mm, d2 = 2500mm, c2 = 200.02mm. 5. belt length: the belt lengths are calculated as: • for d1 and d2, l1 = 1600mm (standard). • for d3 and d4, l2 = 800mm (standard). these parameters ensure the proper design and functioning of the v-belt pulley system. 2.3.1.5 determination of angular speed of shafts the angular speed of the input shaft (ω1) is calculated using the formula in equation (1) (khurmi & gupta, 2006): http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 171 ω1 = 2πn1 60 1 = 31.4 0.065 = 483 n the tension on the belt responsible for threshing can be shown in figure 2. tension on the slack side (𝐹2), is determined by equation (2) as follows: 𝐹2 = 𝐹1 3 2 = 483 3 = 161 n the resultant tension (𝐹𝑒) is then (equation. 3): fe = 4f1 3 3 = 4 × 483 3 = 644 n figure 2: tension force on transmission belt 2.3.1.6 design of shaft shaft designs prioritize strength and rigidity under various operating conditions. the diameter of the shaft is critical and is determined using the maximum shear stress theory due to the material's ductility. according to khurmi and gupta, (2006), the shaft diameter is derived from equation 4: 𝑑3 = 16 𝜋𝜏 √(𝐾𝑏𝑀𝑏)2 + (𝐾𝑡𝑀𝑡)2 4 here, torsional shear stress (𝜏) for mild steel without keyway is 55 mn/m², and the factors for combined shock and fatigue factor for bending moment (kb) and combined shock and fatigue factor for torsional moment (kt) are 1.5 and 1.0, respectively. 2.3.1.7 calculation of torque on the shaft the torque (t) is given by equation (5): t = p × 1000 × 60 2πn 5 where p = 1.81 kw and n = 550 rpm, leading to: http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 172 t = 1.81 × 1000 × 60 2 × 3.142 × 550 = 31.42 nm 2.3.1.8 calculation of weights and end reactions on the shaft (bhandari, 2010) for the appropriate shaft diameter selection, consider: (a) weight of the pulley (cast iron) with a density of 7200kg/m3, and diameter of 170mm, producing a mass of 2 kg, is given by: wp = 2 kg × 9.81 = 19.62 n (b) tension from thresher belt is given by (equation. 6): 𝐹𝑐 = 𝑇 2𝑟𝑐 (6) = 31.4 2 × 0.035 = 448.6 𝑁 (c) weight of cylinder drum for a hollow steel material with a density of 7850kg/m3, a pipe length, radius and thickness of 0.4m, 70mm and 3mm, respectively, is given by: w = 𝜌𝑣𝑔 = 40.65 n (d) weight of cowpea spread on the canvas is given by: wcowpea = 2.55 n the total weight acting on the shaft is the sum of these forces. 2.3.1.9 calculation of shear force and bending moment vertically in this design calculation, determining the loads and forces acting on load-carrying members, such as the shaft, is crucial. the shaft with the most members and load was selected, and the forces acting on it were resolved. the pulley experiences a resultant v-belt tension at a 41° angle, producing a vertical force of 422.5n and a horizontal force of 486.03n. similarly, the thresher belt tension, acting at a 3° angle, has vertical and horizontal components of 23.5n and 447.9n, respectively. the free body diagram, shear force, and bending moment diagram of the shaft are illustrated in figure 3. the vertical forces acting on the shaft help determine the design. the free body diagram reveals: (a) vertical component of pulley tension is 422.5 n (b) thresher belt tension components at vertical and horizontal are 23.5 n and 447.9 n, respectively. vertical shear force calculation using the equilibrium of forces showed that, rbv + rdv = 508.82 n while taking moments around point d leads to: rbv = 523.52 n thus, rdv = -14.7 n bending moment calculation • moment at point a: mav = 0 • moment at point b: mbv = 442.12 × 0.05 = 22.1 nm • moment at point c: mcv = 523.52 × 0.23 442.12 × 0.28 = -3.39 nm http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 173 figure 3: shear force and bending moment diagram for the vertical component forces in the horizontal shear force and bending moment calculation, the sum of the upward forces (rbh + rdh) equals the sum of the downward forces, giving a total of 934.03n. by taking moments about point d, the reaction force at point b (rbh) is calculated to be 762.87n, and inserting this into the initial equation gives the reaction force at point d (rdh) as 171.16n. for the horizontal bending moment, the moment at point a, b, c, and d, are 0, 24.3, 39.37, and 0 nm respectively. the resultant bending moments are calculated as 32.85nm and 39.52 nm at point b and point c respectively. these values combine the vertical and horizontal bending moments, as shown in the shear force and bending moment diagrams in figure 4. figure 4: shear force and bending moment diagram for the horizontal component forces http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 174 2.3.1.10 calculation of shaft diameter the shaft diameter is determined by rearranging the equation for bending and torsional moments, using the equation (7) from shigley and mischke, (2008): d3 = 16 πτ × 67.1 7 the diameter is calculated to be approximately 20 mm. 2.3.1.11 calculation of bending and shear stress on the shaft using equations 8 and 9 for bending stress and shear stress, respectively (khurmi and gupta, 2006): δb = 32m πd3 8 and, δsh = 16t πd3 9 with m = 39.52 nm and t = 31.4 nm, the stresses are calculated, and a factor of safety of 3.0 is applied as per design requirements. 2.3.1.12 bearing selection radial or flat bearings are selected for durability and economic reasons. the design life (ld) for agricultural machinery is estimated as shown in equation (10) (khurmi and gupta, 2006): ld = l10(h) ∙ (n rpm) ∙ 60 10 with a specific design life of 3000–6000 hours and a rotational speed of 550 rpm, calculations yield: ld = 9.9 × 107 rev the dynamic load rating (cr) and bearing life (lb) are then computed as 2683.12n and 4294.54h, respectively. 2.3.1.13 fan design the fan's outlet velocity and flow rate are established for effective separation of cowpea from chaff. the calculations include impeller dimensions and power requirements to drive the fan, with torque calculated for the fan drive. the fan's outlet velocity is set at v3 = 10 m/s with a flow rate of q = 1.1 m3/s (allen and watts, 1998). the power required for the fan is expressed in equation (11) (osborne, 1997; dixon and hall, 2014): 𝑃 = 𝑄 × 𝑃𝑠 𝜖 11 = 1.1 × 500 0.75 = 0.73 𝑘𝑊 calculating the torque on the fan drive yields t = 5.3 nm. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 175 2.3.1.14 motor power the motor power needed is derived from the total power required for threshing and fan operation. a standard motor with sufficient capacity is selected based on efficiency. minimum motor power required is given by equation 12 (khurmi, & gupta, 2005): 𝑃𝑚𝑖𝑛 = 𝑃𝑝 𝑛 12 where 𝑃𝑝= 1.81 + 0.73 = 2.54 kw and efficiency 𝑛 = 0.8, leading to a requirement of 3.18 kw. a 3.7 kw (5 hp) gasoline engine is selected as the prime mover. 2.3.1.15 design calculation for tray the tray's dimensions and volume are calculated to ensure it effectively holds the cowpea pods, using the formula in equation (13) (larson et al., 2009): volume = 1 2 (a + b) × h × l 13 resulting in a capacity to carry approximately 3.72kg of cowpea pods. the tray, which holds and guides the plant material, has a volume of 0.012 m³, capable of holding 3.72 kg of cowpea pods based on the pod density of 310.2 kg/m³. 2.3.2 description and operation of the thresher the thresher is designed to function as a unit. the principal units are the feeding unit, the threshing unit, the blower unit, the unloading unit, the power transmission unit, and the supporting frame. the feeding unit consists basically of a slanted tray to keep and release the pods as will be required by the threshing unit. the threshing unit is a conveyor arrangement of two separate canvas belts, one lying above another. both belts run in same direction but at different speeds, the lower belt driving the unit and running a higher speed so as to dictate the direction of travel of the crop. the blower unit is a three forward curved blades attached to a shaft, enclosed in a blower housing. the sides of the blower carry a circular opening to allow air in. the number of blades ensures a steady delivery of air. the unloading unit has two openings. one opening is the chaff outlet, to connect the air velocity from the blower outlet and exit the chaff from the thresher, and the other is an inclined chute at 35o to gently slide the grain into a collecting trough. the power transmission unit consists of the power source (a gasoline motor), v-belts, pulleys, shafts and bearings. the thresher works on the friction rubbing principle. the gasoline engine motor is the power source for rotating the canvas thresher belts. cowpea is delivered at the feeding unit into the threshing unit. both travelling belts are in same direction of travel; the lower part of the top belt making contact with the crop at a reverse direction of travel to the top part of the lower belt. the lower belt travels at a higher speed than the top belt so as to allow the crop move from the feed in end of the belt to the exit end. the contact between the top and the bottom belt on the crop creates the threshing by frictional rub and delivering it to the exit end. at the exit end, the grain and chaff fall off and is cleaned by the blower. grains fall by gravity and the lighter chaff is driven by the forced air (see figures 5, 6 and 7). http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 176 figure 5: parts of the thresher figure 6: isometric projection of the thresher http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 177 figure 7: orthographic projection of the thresher 3. design results the developed canvas belt cowpea thresher is displayed in plate i and the results of the calculations are presented in tables 1 and 2. the table 1 is the table of the principal dimensions of the thresher. it states the overall dimensions of the machine and its volume. the table also gave details of the feeding trough. these values were arrived at after all the designed values were filled in. the trough’s inclination angle was chosen knowing from preliminary investigations that cowpea pod has frictional angle of 44o. the table also contains the principal parameters of the threshing area. it specifies the working mechanism in the threshing area. the drums are specified, so also the thresher belt, its capacity and the power required to drive the unit. table 2 involves the principal power transmission indices of the thresher. the manipulations of machine parts to achieve the designers desire is seen in the choice of pulleys and pulley sizes, belts, shaft diameter, bearings and the blower parameters. some were picked from standard tables while others were calculated from design formulae. plate i: the constructed isometric view of the canvas belt cowpea thresher http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 178 table 1: principal dimensions of the thresher machine dimensions value inclination angle of tray/trough 45 o length of tray/trough 310mm average width of tray/trough 580mm volume of tray/trough 0.01m3 overall machine width 800mm overall machine height 820mm overall machine length 1500mm overall machine volume 0.984m3 thresher parameters drum diameter 70mm drum length 400mm drum speed 550rpm thresher belt length1 1100mm thresher belt length2 840mm threshing belt width 400mm belt capacity 6.4kg/s power required to drive thresher belt 1.81kw table 2: power parameters of the thresher parameters of power transmission systems value pulley diameter d1 50mm pulley diameter d2 130mm pulley diameter d3 70mm pulley diameter d4 170mm pulley 1 & 2 speed ratio 2.6 pulley 3 & 4 speed ratio 2.4 belt type v-type belt speed 10m/s belt cross sectional area 31mm2 belt mass per meter run 0.105kg shaft diameter 20mm bearing type radial ball bearing (6304) bearing inner diameter 20mm bearing outer diameter 52mm bearing width 15mm blower parameters number of blades 3 blade width 150mm blower casing diameter 340mm power required to drive fan 0.73kw torque on fan drive 5.3nm motor power 3.18kw 3.1 cost of production and limitations the cost of manufacturing the canvas belt cowpea thresher was analyzed and totaled ₦253,000. key materials included galvanized pipes, mild steel rods, and angle iron costing ₦37,300; sheet metal, canvas sheets, and radial bearings at ₦48,200; and bolts, pulleys, cutter blades, and a v-belt contributing ₦33,300. the largest expenditure was a 5hp petrol engine at ₦65,000, while labor costs accounted for ₦55,000. miscellaneous components such as welding electrodes were also included to ensure all necessary resources were covered. the study faced several limitations, notably the lack of a factory-made canvas belt, leading to slippage issues due to non-uniformity despite adjustments. additionally, challenges in sourcing suitable pulleys for the designed shaft further impeded the research process. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 179 4. conclusion the design and fabrication of the canvas belt thresher demonstrated a successful reduction in grain damage and an increase in threshing efficiency, making it a viable solution for small-scale cowpea farmers. with locally sourced materials and simple fabrication techniques, the thresher is both cost-effective and easy to maintain. the machine's performance, driven by a gasoline engine, meets the necessary requirements for cowpea threshing, providing a practical alternative to more complex and expensive systems. this innovation is expected to positively impact cowpea production by reducing labor and operational time, thus supporting the agricultural productivity of small-scale farmers. references allen, caw and watts, kc. 1998. design of a belt thresher for cowpea beans. agricultural mechanization in asia, africa and latin america (ama). 29(3): 42-46. bhandari, vb. 2010. design of machine elements (3rd ed.). mcgraw-hill education. bureau of indian standards. 1985. is 6284: test code for threshing machines. retrieved from law.resource.org. chen, l., zhang, l., li, l., and zhang, l. 2025. design and experiment of a low-damage threshing drum for corn with stepless taper adjustment. agriculture, 15(1), 4. clark, g. 2007. a farewell to alms: a brief economic history of the world. princeton university press. usa. 286. daniyan, ia. adeolu, ao. and dada, om. 2014. design of a material handling equipment: belt conveyor system for crushed limestone using 3 roll idlers. journal of advancement in engineering and technology, 1(1): 2-6. dixon, sl. and hall, c. a. 2014. fluid mechanics and thermodynamics of turbomachinery (7th ed.). butterworth-heinemann. el-shal, ms., el-ashry, as., el-shal, am. and fakhrany, wb. 2020. development of a rubbing thresher for some seed crops. misr journal of agricultural engineering, 31(1), 133-154. fawohunre aj. and olajide og. 2020. development and performance of a motorized cowpea threshing machine for small scale farmers in nigeria. global journal of engineering and technology advances, 05(01), 001–007. fernando, sd. and hanna, ma. 2005. design and development of a threshing chamber and pneumatic conveying and cleaning units for soybean harvesting. transactions of the asae, 48(5), 1681-1688. fernando, s., hanna, ma. and mesquita, c. 2004. soybean threshing mechanism development and testing. transactions of the asae, 47(3), 599-605. gelaw, gk. 2020. theoretical and experimental investigation of threshing mechanism for tef (eragrostis tef (zucc.) trotter) on the basis of its engineering (physical and mechanical) properties (doctoral dissertation, addis ababa university). addis ababa institute of technology (aait). istifanus, ab., abang, m., okechukwu, c. and oloyede, to. 2022. design modification, development and performance evaluation of a cereal crop thresher. american journal of engineering research (ajer), 11(3), 140-147. khurmi, rs. and gupta, jk. 2005. a textbook of machine design. s. chand. khurmi, rs. and gupta, jk. 2006. theory of machines. eurasia publishing house. new delhi., 262-263. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):168-180. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: engr.adanu@gmail.com 180 kutte, mt. 2001. re-activation and performance evaluation of the threshing of rice. m.eng. thesis. department of agricultural engineering. university of maiduguri. larson, r., boswell, l., kanold, td. and stiff, l. 2009. geometry. holt mcdougal. maunde, fa. 2011. performance evaluation of manual cowpea thresher. african journal of agricultural research. 6(30):6412-6415. ojomo ao, ale mo, and olajide, og. 2010. development and performance evaluation of a cowpea harvester. journal of engineering and applied sciences. 5(10), pp 5-10. osborne, wc. 1997. fans (int’l series on heating, ventilation and refrigeration). pergamon press. england. 1:122-139. shigley, je. and mischke, cr. 2008. mechanical engineering design (8th ed.). mcgraw-hill. sousa, cc., damasceno-silva, kj,, bastos, ea., and rocha, m.m. 2015. selection of cowpea progenies with enhanced draught-tolerance traits using principal component analysis. genetic and molecular research. 14(4): 15981-15987. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 959 arid zone journal of engineering, technology & environment original research article design, construction and performnce evaluation of a manual cum motorized orange juice extracting machine a. b. istifanus*, k. bulus, m. a. adimbo and h. m. ardo department of agricultural and bioresources engineering, faculty of engineering, taraba state university, jalingo, nigeria *corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng article information abstract a manual cum motorized operated juice extractor was designed and fabricated using locally sourced materials. polytetrafluoroethylene (ptfe) a synthetic fluoro polymer was used in the construction of the screw shaft and stainless steel for the extraction chamber. rotational motion needed by the screw shaft to compress and transport the fruits was supplied both manually cum motorized to the machine through a handle and electric motor device of 10w because this has capacity to handle the performance operation. the screw shaft crushes, squeeze and facilitate the movement of residues to the waste outlet while the juice passes through the screen to the juice collector. tests were carried out to investigate the performance of the machine on the basis of juice yield, extraction efficiency and extraction loss. the fruits were washed and weights (1kg, 1.5kg and 2kg respectively) of fruit slice (8 and 16 slices) were then processed using the extractor to extract the juice. the juice yield, extraction loss and extraction efficiency were determined by standard formula and methods. maximum juice yield of 64.6 % extraction efficiency of 68.2 % and corresponding extraction loss of 7.05 % were obtained from the 16 slice lengths orange fruits were used for the test. the juice produced from the extractor was of good quality which further proves the effectiveness of the extractor. the manual fruit juice extractor is cheap(n48770), durable and cost of operation is low while motorized juice extractor is faster in terms of operation or extraction efficiency and extraction loss, and also it could be used by an average nigerian household and small-scale farmers. submitted 08 may, 2024 revised 30 july, 2024 accepted 10 august, 2024 keywords: orange juice juice extraction machine motorized extraction efficiency extraction loss © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction orange (citrus sinensis) is a dominant member of a large botanical family known as citrus. this fruit is the largest fruit crop in the world with about sixty million metric tons grown (barry et al., 2020). the local methods of extracting fruits juice are prone to contamination and are unhygienic. it also has a low efficiency and high human drudgery (shirke, 2023). sophisticated juice extractors are available but unaffordable by average nigerian farmers and processors. harvested orange fruits deteriorate if left for long period without being used or processed. economic losses experienced due to spoilage are in developing countries, especially in nigeria. therefore, there is a need to develop simple equipment to process the fruits easily. oranges, lemon, limes, grapefruits and tangerines are from the class of fruits known as citrus fruits (olife et al., 2015). it is universally acknowledged that citrus fruits are originated from northeastern india (ortese et al., 2012). the federal department of agriculture and missionaries in the 1930s introduced citrus fruits into nigeria. since its introduction, the cultivation of citrus fruits has spread to every part of the country and recently ranked as the third most extensively cultivated fruit tree in the country particularly in south-western nigeria (oyedele and yahaya, 2010). with regard to international trade, citrus fruits are ranked highest worth fruit crops. the market available for citrus fruits is the fresh fruit market and the processed citrus fruits market chiefly orange juice (olife et al., 2015). citrus products contain very high nutritional contents; they are rich and cheap sources of vitamins (particularly vitamin c), minerals and dietary fiber which are essential for healthy living. orange fruits are generally known to have poor shelf life and face the problem of postharvest losses (joshi et al., 2017). this is due to the high temperature. it is impossible to store and preserve oranges for an extended period of azojete december 2024. vol.20(4):959-975 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:bardey.istifanus@tsuniversity.edu.ng mailto:bardey.istifanus@tsuniversity.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 960 time without deterioration. furthermore, high moisture content and poor postharvest handling also contribute greatly to the relatively short shelf-life of orange fruits. this aforementioned reason calls for processing of orange fruits into juice. juice is the liquid extracted from the cells of mature fruits. the nigeria space requires a technology in which an orange juice extraction machine may be equipped and operated by both manual and mechanized processes. this dual operationalization offers the advantages of versatility of usage and application. orange fruits cell wall is made of cellulose, hemicelluloses, peptic substance and proteins. (ashurt and taylor, 1991) reported that fruit juice extractor is an agricultural technology implement that involves the pressing of some fruits in order to get juice. orange juice extractor involves the process of crushing, squeezing and pressing the whole fruit in order to obtain the juice and to reduce the bulkiness of the fruit to liquid and pulp. while hand extraction of juice involves (peeling with knife and squeezing the juice out with bare hand), is very slow and tedious and also not hygienic enough. the merits of using machine for extraction are time saving, improve efficiency, increase capacity, and reduction in spoilage and waste (abulude et al., 2007). this paper provides the combined advantages of a designed, fabricated and evaluation of the operations of manually and motorized orange juice extraction machine. 2. materials and methods 2.1 description of the juice extractor component parts 2.1.1 hopper the hopper was fitted directly above the cylindrical drum. it is made of steel material and was designed to accommodate the allowable volume required of the mass of fruits (assume 4kg to 6kg). the fruits are to run down the hopper into the cylinder by means of gravity. the hopper was inclined at an angle of 61°. the hopper is in form of a frustum. 2.1.2 cylindrical pipe (chamber) its main function is to collect the squeezed juice and pulp via its outlet. the cylinder was fabricated from 3 mm galvanized steel sheet with an appropriate diameter 15.5cm and length 66 cm. the cylindrical pipe was housing the cylindrical mesh sieve that is responsible for sieving the masticated and macerated fruits. the cylinder was designed to have two outlets (juice outlet and pulp/fiber outlet) attached to it to aid in juice and pulp collection. 2.1.3 cylindrical mesh sieve this is going to be responsible for sieving the crushed and pulverized fruits. it is designed to cover the rotation shaft in such a way that both of them will be situated inside the cylindrical pipe. it was manufactured from galvanized steel sheet of an appropriate diameter 10.5 cm inlet diameter, 6.5 cm outlet diameter and 2 mm thickness. the length of the sieve/strainer is 240mm. the pressing operation take place inside this cylindrical which was perforated with circular holes (openings 2mm x 2mm) to allow the passage of the expelled juice into the juice outlet created in the cylindrical pipe. 2.1.4 concave (main chamber) it is a mesh of semicircle shape in between the drum and the sieve, and the concave clearance is 310 mm and the minimum clearance between blades and sieve surfaces needed for mastication and maceration was equal to the fruit size sliced / fed into the system, thus; reducing drum clearance tends to reduce drum losses and increase seed damage. 2.1.5 power shaft the rotating shaft will be translated to form a conveyor auger. cutter blades and nylon brushes was welded to it to aid mastication (crushing) and maceration (softening). the shaft auger ensures that the pulverized fruits are conveyed throughout the whole process until the pulp is finally collected from the fiber outlet. the rotating shaft auger is directly attached to a bearing and a pulley and power will be transmitted from an electric motor through belt transmission to the drive shaft auger. shaft shall be sized on the basis of strength, stress, deformation and rigidity. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 961 2.1.6 frame and supports the main frame was made of mild steel of considerable strength and size in which the whole system was rest upon. in order to withstand the pressure exerted by the shaft during extraction, the frame and supports must be appropriately considered so that the design doesn’t collapse or rupture. 2.2 design considerations the major material selected for use in the fabrication of the machine was steel, considering the following qualities: mild steel has about 0.16 to 0.28% carbon content which makes it easy to be worked on and welded. it also has density of 7.68 × 103 kg/m3, heat expansivity of 11.7× 10-6k-1, young’s modulus of elasticity 210gn/m2, tensile strength of 350 mn/m2 and elongation of 30%. the design considerations of juice extractor were both for the biomaterials used (oranges) and the materials for construction. the bio-materials strength in maximum loading were considered based on the following: 2.2.1engineering properties i. strength, rigidity and simplicity of materials of construction ii. the expression pressure must be high enough to ensure acceptable level of extraction iii. the transmission belt should be properly aligned such that it permits easy rotation of the shaft auger during extraction. iv. the power shaft should be rigid enough to withstand combined bending and tension stresses to which it will be subjected to while transmitting power under various operating and loading conditions. v. required force to expel out the juice. vi. portability of the machine. vii. easy inspection, serviceability, and maintenance of the machine. viii. durability of the machine was considered on the machine component. ix. cost of construction; and x. ease of operation and maintenance and also energy requirement. 2.2.2 economic factors and safety considerations construction materials of the machine (figure 1) were selected based on economic factors and safety consideration. these factors are as follows. i. availability and the cost of construction and materials; ii. durability and strength of materials; iii. manufacturing /fabrication methods that will be employed in construction; iv. efficiency of extraction and minimizing juice contamination; and v. corrosion resistant properties. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 962 figure 1: isometric drawing of orange juice extracting machine 2.3 design calculations 2.3.1 efficiency of motor for the efficiency of the machine at 95% at engine speed n1= 1400 rpm where: 95 100 × 1hp = 0.95hp but 1hp = 0.75kw 0.95hp → 0.95 x 0.75kw = 0.713kw an engine pulley diameter of 152mm diameter was chosen from standard table with belt thickness of 0.12mm. engine pulley diameter, d1 = 152mm or 0.152m radius, r1 = 0.076m angular velocity of engine (motor), ώ1 = 2𝜋𝑁1 60 (1) where n1 = speed of the engine. ώ1= 146.6 147 rad / sec the linear velocity of the engine, v = wr1 (2) substituting the value of w1 in equations (1) into (2) we have, v =11.14 m / s http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 963 2.3.2 belt and pulley selection a speed reduction ratio of 3 was chosen µ= 𝑁1 𝑁2 (3) where n1 = speed of driver pulley, n2 = speed of driven pulley, µ= reduction ratio = 3 n2 = 466.7 rpm diameter of driven pulley, d2 𝑁1 𝑁2 = 𝑑2 𝑑1 = (khurmi and gupta, 2005) (4) n1 = speed of driver pulley n2 = speed of driven pulley, d1 = diameter of driver pulley, d2 = diameter of driven pulley. substitute the value of n2 in equation (4) d2 = 𝑁1𝑑1 𝑁2 = 0.456 ~ 0.46 m radius of driven pulley, r2 = 0.23 m angular velocity of the driven pulley, ώ2 = 2𝜋𝑁2 60 (5) substitute the value of n2 in equation (5) ώ2 = 48.87 rad / sec 2.3.3 size of belt for an efficient torque in vbelts, a minimum angle of contact of the belt on the smaller pulley should not be less than 1200 (anaya-esparza et al., 2018). therefore, an angle of 165 is chosen for the smaller pulley. 2.3.4 belt arrangement the appropriate belt arrangement in the pulley is shown in figure 2 below. figure 2: belt arrangement in the pulley sin α = 2m / o1o2 = r2 – r1 / x = d2 – d1 / 2x (khurmi and gupta, 2005). (6) where r1 and r2 are radii of smaller and larger pulleys, x is the distance between the centers of the two pulleys and the angle of contact (ø) in this case is 1650 as shown in equation (6) but ø = 180 2α http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 964 α = 7.5 or 7.5 x 𝜋 180 rad = 0.13 rad but sin α = d2 – d1 / 2x = d2 – d1 / sin α (7) an a48 v – belt size was selected in equation (7) angle of contact, ø is selected to be 1650 therefore, ø = 2.88 rad we know that 2.3 log ( 𝑇1 𝑇2 ) = µ×ø (8) coefficient of friction, µ for rubber belt material on dry cast iron is 0.3 from equation (8), 2.3 log ( 𝑇1 𝑇2 ) = µ ×ø = 0.3 x 2.88 = 0.864 log ( 𝑇1 𝑇2 ) = 0.864 2.3 = 0.376 = log -1 (0.376) = 2.37 2.3.5 power transmitted by belt p = (t1 –t2) v (9) where p = power in watts t1 – t2 = overall belt tension t2 = tension in tight side of belt t2 = tension in slack side of belt equation (9) transforms into t1 –t2 = 64 n (10) from equation t1 = 2.37 t2 substituting the value of t1 from equation (10), equations (11), (12) and (13) are generated where, 2.37t2 – t2 = 64 n (11) t2 = 46.7 n (12) substituting t2 in equation (12), t1 – 46.7 = 64 t1 = 111 n http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 965 2.3.6 length of belt l = 𝜋 2 (d2 + d1) + 2x + (d2 –d1)2 / 4 (khurmi and gupta, 2005) (13) then, l = 𝜋 2 (0.46 + 0.152) + 2 (1.18) + (0.46 – 0.152)2 / 4 l = 3.34 m 2.3.7 hopper design specification the following assumptions are made so as to choose the dimensions for the hopper; volume of material, shape of material, angle of repose. the hopper is considered to be a frustum. the height is 250 mm and the top and base radii 350mm and 75 mm respectively. figure 3: orthographic view of the hopper 2.3.8 volume of the hopper area of big triangle –area of small triangle ½ b × h1 – ½ b × h2 area of big triangle ab = ½ b h1 α 2 = 199.8 h1 2.3.9 area of small triangle 75√2 2 37.5√2 α2= 42.72 h2 2.3.10 volume of hopper area of big triangle – area of small triangle ½ (122.5) × 199.8 – ½(5625) × 42.72 http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 966 = 266.95m3 2.3.11 shaft design the shaft was made up of ductile material to resist cyclic load. it was designed against bending and torsion failures and the design is governed by the maximum shear stress torque transmitted by shaft, t. the auger design and specifications are shown in figure 4. figure 4: auger design and specification a – auger pitch d – outside diameter of auger d – outside diameter of auger shaft e – length of intake opening l – effective length of conveyance b – blade length, t – blade thickness, w – blade width 2.3.12 torque or power transmitted by shaft let n = number of revolutions per minute t = average torque in knm-1 = 𝑝×60 2𝜋𝑁 power = design horse power x 0.713 kw (khurmi and gupta, 2005) (14) the electric motor used is 1.5 horse powers using equation (14) above t= 𝑝×60 2𝜋𝑁 = 0.713×103×60 2𝜋×466.7 t = 14.60 x 103n – mm or t = 14.60mm3 tangential force acting on pulley, fta is given by fta = t / ra where ra is the radius of the pulley (15) mass of pulley = 1.5 kg therefore, weight of pulley = 1.5 x 9.81 = 14.72n weight of spiral rod + blades = 1.2 x 9.81 = 11.772n http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 967 based on equation (15) the total load acting on the shaft at a = 1587.972n the reaction at rb act upwards while rc act downward shown in figure 5 below. taking moment about point c, rb and rc are the reactions at b and c respectively. a b c 140mm. 490mm figure 5: shaft and bearing arrangement taking moments about point c rb x 490 = 1587.972 x 630 rb = 2041.68n for equilibrium of the shaft rc +1587.972= rb rc = 453.708n bending moment, (b.m) at a and c = 0 ∑ 𝑚𝐴 = 𝑚𝑐= 0 bending moment, b.m. at b b.m = 222316.08n-mm therefore, bending moment, b.m. = m = mb = 222316.08n _ mm d = diameter of shaft t = torque = 14600 n–mm equivalent twisting moment (equation 16), te= √(𝑘𝑚x𝑚)2 + (𝑘𝑡 × 𝑇)2 (16) from equation (16) km = combined shock and fatigue factor due to bending = 1.5, kt = combined shock or fatigue factor due to tensional moment = 1.0 (for gradually applied loads on rotating shaft). te= √(1.5x1587.972)2 + (1.0 × 14600)2 http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 968 te= √(5886.88) but equivalent twisting moment te= 76.726n-mm te= π 16 × 𝒯 × 𝑑3 𝒯 = 42mpa (allawable shear stress) d=shaft diameter 76.726 = π 16 × 42 × 𝑑3 𝑑3= 76.726×16 42π = 99.30mm3 also equivalent bending moment (figure 6) me = 1 2 (k × m+√(𝑘𝑚 × 𝑚)2 + (𝑘𝑡 × 𝑇)2: me= 1229.342 σb = 56mpa (maximum tensile or permissible stress). me = π 32 × σb × 𝑑3 𝑑3= 1229.35×32 56π = 223.6mm3 𝑑3= √223.6mm33 , 𝑑 = 44.9𝑚𝑚 figure 6: shear force and bending moments diagram 2.3.14 first equilibrium conditions shear force 𝜀𝑣𝑝 = 0 ra+rb= 0 -140 490 = 0 http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 969 ra+rb = 630 2.3.15 second equilibrium conditions bending moment at point b = f.l unit of (b.m) = (kn-m or n-mm) ma = ra × 0 = 0 maximum bending moment at point c ra =140mm, rb = 490mm maximum bending moment at point c 𝑚𝑐 = 𝑅𝐴 × 0 𝑚𝑐 = 140 × 630 = 88200 at point b = 88.2×106 n-mm 𝑀𝐵 = 𝑅𝐴 × 0 − 630 − 140 − 490 × 0 = 0 2.4 characterization of orange sample 2.4.1 sizes and shape 4kg of orange samples were collected and the axial dimensions were measured using a vernier caliper and micrometer screw gauge. from the geometric mean diameter (dg), arithmetic mean diameter (da), sphericity (ø), volume (v) and surface area (s) was calculated using equations 17, 18, 19, 20 and 21 respectively as given by (joshi et al., 2017). geometric mean diameter (dg) = (abc) 1/3 (17) where a = length (dimension along longest axis) = 6.5 b = width (dimension along longest axis perpendicular to a) = 5.5 c = thickness (dimension along the longest axis perpendicular to a and b) = 6.0 dg = (6.5 x 5.5 x 6.0) 1/3 = 5.00cm arithmetic mean diameter (da) =( a+b+𝑐 3 ) (18) da = 6.0 cm sphericity =∅ = 𝐷𝑔 𝑎 (19) ∅ = 5.00 6.5 = 0.76 for an oblate spheroid like orange, the volume = 4 3 (πa2b) (20) v = 4 3 × (π 6.52 × 5.5) = 973.7 cm3 surface area, s = 2(π a2 +π b2/𝑒) ln 1+𝑒 1−𝑒 (21) http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 970 where, eccentricity, e = 0.5, s = 2 (π 7.52 + 6.52 / 0.5) ln 1+0.5 1−0.5 = 1.09 cm2n 2.4.2 angle of repose this was determined by placing sample of oranges on an adjustable. the adjustable was inclined. this was done using 10 oranges and their corresponding coefficient of friction was analyzed. 2.4.3 pre-treatment of orange fruits clean, ripe and mature fruits (orange) were purchased from fruits sellers at ‘kasuwan bera’ market in jalingo. each orange fruit was washed and weights (kg) of each fruit slice of 8 and 16 respectively were used for the evaluation. yellow oranges with almost noacidic content were selected and separated from the green ones and kept in cold place pending when it was to be used and some of the green oranges were kept in cartons at an ambient temperature to inhibit ripening of the oranges when the yellow color begin to appear. 2.5 performance evaluation of the extractor the machine (plate 1) was tested in the faculty of engineering workshop taraba state university, jalingo. the test was carried out into two different stages. stage one (1), the free test run (without load) and stage two (2) involves testing with load (i.e. orange fruits) under different weights (1kg, 1.5kg and 2kg) of fruit slice (8 and 16 slices). the test was replicated six (6) times (i.e. 3 weights for each individual slice lengths of 8 and 16 respectively). a stop watch and weighing balance were used to ascertain the time of extraction and measuring the quantity of the extracted fruit and cake. the performance of the extractor was evaluated in terms of, juice yield (jy) = w2 / w2+w3 x 100; extraction loss, el = w1 – (w2+w3) / w1 x 100 extraction efficiency (ej) = w2 / w5 x 100; throughput capacity = w1 / hr.; w1 = weight of fresh orange; w2 = weight of juice obtained; w3 = weight of wet cake; w5 = weight of juice obtainable. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 971 plate 1: the juice extractor 3. results and discussion the effects of fruit slice lengths on juice yield, extraction efficiency and extraction loss are shown in tables 1, 2 and 3 respectively. table 1: measurements of orange fruits sizes measurements minimum maximum mean angle of repose, θo 75.00 76.00 75.53 coefficient of friction,n=tanθ 3.73 4.01 3.88 orange seed length, (cm) 1.58 1.65 1.50 orange seed width, (cm) 0.48 0.65 0.56 orange seed height, (cm) 0.86 1.12 1.01 orange fruit length, (cm) 7.10 7.90 7.50 orange fruit width, (cm) 6.25 6.73 6.52 orange fruit height, (cm) 6.63 7.20 6.96 table 2 describes a range of parameters as shown in the table arising from 16 sliced lengths. fruit slice lengths is an indication of surface area of the fruit and juice cells exposed to maceration and pressing action. this study showed that surface area of fruits is an important factor to consider when preparing fruits for juice extraction. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 972 table 2: juice yield, extraction loss, extraction efficiency and throughput capacity for 16 slice lengths using the extractor measurements (kg) minimum maximum mean weight of fresh orange, w1 1.00 2.00 1.50 weight of juice obtained, (w2) 0.35 0.99 0.66 weight of wet cake, (w3) 0.64 0.91 0.76 weight of oven dried cake, (w4) 0.22 0.51 0.35 weight of juice obtainable, w5 = w1 –w4 0.78 1.49 1.15 juice yield (%), jy = w2/ w2 +w3 35.40 52.00 44.83 extraction loss (%), el=w1– (w2+w3)/w1 ×100 0.001 0.005 0.0053 extraction efficiency, ej = w2 / w5 x 100% 45.30 66.40 55.00 time of extraction (hr) 0.054 0.07 0.064 throughput capacity (kg/hr) 18.51 28.60 23.43 the average juice extraction efficiency and throughput were 57.70 % and 25.83 % respectively. the study showed that juice yield and extraction efficiency decreased while extraction loss increased with increase in the size of fruit slices. juice yield, extraction efficiency and extraction loss from 16 slice lengths oranges ranged between 48.90 – 64.60 %, 50.00 – 68.20 % and 0.6 – 7.35 % respectively. table 3: juice yield, extraction efficiency using the hand pressing method measurements (kg) minimum maximum mean weight of fresh orange, (w1) 1.00 2.00 1.50 weight of juice obtained, (w2) 0.46 1.20 0.79 weight of wet cake, (w3) 0.48 0.67 0.60 weight of oven dried cake, (w4) 0.08 0.26 0.19 weight of juice obtainable,w5 = w1 –w4 0.92 1.74 1.31 juice yield(%) jy=w2⁄ w2+w3×100 48.90 64.60 58.80 juice yield,(%), jy=w2/w2 +w3×100 22 26 24 extraction efficiency, ej = w2 / w5 x 100 28 29.1 28.5 time of extraction (hr) throughput capacity (kg/hr) 0.05 20.00 0.066 30.30 0.057 25.83 table 3 revealed that 16 sliced lengths gave the maximum juice yield of 64.60 % while the corresponding extraction efficiency was 68.20%. also, the minimum extraction loss of 0.6 % was obtained for 16 sliced lengths. this showed that the 16 sliced lengths were the best for preparing fruits for juice extraction. results also showed that juice yield and extraction efficiency decreased while extraction loss increased with increase in fruit size slice lengths. this is in agreement with the findings of faus (2000), kaderand yahia (2011). http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 973 note: an orange contains about 0.036kg of juice; 1kg orange contains 0.22kg juice. figure 8: effect weight of fruit slice on juice yield in figure 8, the thicker curve (representing 16 slice lengths) is above that of 8 slice lengths, implying significantly that yield varies with weight of slicing. this is affirming that the heavier the fruit the higher most likely the juice yield. figure 9: effect of weight of fruit slice on extraction loss figure 9 relates the effect of weight of fruits on extraction loss. the curves of both the 8-slice length and the 16-slice length have not much significant difference in the result of the extraction loss. the 16 slice lengths however have slightly lower extraction loss. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 974 figure 10: effect of weight of fruit slice on extraction efficiency figure 10 above relates the effect of weights of fruits slice on extraction efficiency: it correlates with table 3. the higher extraction efficiency (mean value) of 57.70 % of the juice extractor showed that the extraction rate is more efficient than that of the hand squeezing method which has extraction efficiency (mean value) of 28.5 %. this imply that the juice extractor can be suitably used for small and medium juice processing businesses in rural and urban communities. 4. conclusion a machine was designed and constructed to extract juice from orange fruit to forestall the usual wastage during peak harvest on most orchards in nigeria. the machine was tested and found workable. from the test result carried out using the juice extractor and the hand squeezing method, it was found out that the rate of extraction increases as the weight of fruit increased with a corresponding increase in the juice yield and extraction efficiency. the higher extraction efficiency (mean value) of 57.70 % of the juice extractor showed that the extraction rate is more efficient than that of the hand squeezing method which has extraction efficiency (mean value) of 28.5 %. this imply that the juice extractor can be suitably used for small and medium4. juice processing businesses in rural and urban communities. the mass production of this locally produced juice extractor will further reduce its cost and therefore making it relatively cheaper, affordable and available to both small and medium scale food industries to purchase. this will no doubt enhance the economic development of our country. references abulude, fo., elemide, ao., ogunkoya, mo. and adesanya, wo. 2007. design and performance evaluation of a juice extractor constructed in nigeria. research journal of applied sciences, 2(1): 31-34. anaya-esparza, lm., gonzález-aguilar, ga., domínguez-ávila, ja., olmos-cornejo, je., pérez-larios, a. and montalvo-gonzález, e. 2018. effects of minimal processing technologies on jackfruit (artocarpusheterophyllus lam.) quality parameters. food and bioprocess technology, 11(9), 1761-1774. ashurst, pr.and taylor, rb. 1991. fruit juices. in food flavorings (pp. 85-115). springer, boston, ma. barry, gh., caruso, m. and gmitter jr, fg. 2020. commercial scion varieties. in the genus citrus (pp. 83-104). woodhead publishing cambridge, united kingdom. faus, i. 2000. recent developments in the characterization and biotechnological production of sweet-tasting proteins. applied microbiology and biotechnology, 53(2): 145-151. joshi, vk., panesar, ps., rana, vs. and kaur, s. 2017. science and technology of fruit wines: an overview. science and technology of fruit wine production. elsevier inc., amsterdam, pp. 1-72. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4): 959-975. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bardey.istifanus@tsuniversity.edu.ng 975 kader, aa. and yahia, em. 2011. postharvest biology of tropical and subtropical fruits.postharvest biology and technology of tropical and subtropical fruits. woodhead publishing, cambridge, united kingdom., pp. 79-111. khurmi, rs. and gupta, jk. 2005. a textbook of machine design, 14th edition, eurasian ltd ran ngar new delhi,pp.12 – 30. ortese, e., baiyeri, kp.and ugese, fd. 2012. demographic features of citrus producers and agronomic management of the crop in benue state, nigeria. production agriculture and technology journal, 8(1): 180190. oyedele, oo. and yahaya, mk. 2010. citrus farmers production constraints and attitude to training on improved techniques of citrus production. journal of agriculture and social research (jasr), 10(2): 2 – 6. olife, ic., ibeagha, oa. and onwualu, ap. 2015. citrus fruits value chain development in nigeria. journal of biology, agriculture and healthcare, 5(4):36-47. shirke, gd. and pinjarkar, ms. 2023. post-harvest technology of tree spices. journal of pharmacognosy and phytochemistry, 12(2): 88-102. http://www.azojete.com.ng/ mailto:bardey.istifanus@tsuniversity.edu.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 693 arid zone journal of engineering, technology & environment original research article development of smart energy-efficient lighting system using actied solar pv with light sensitivity control. s. o. omogoye1, a. b. ogundare1, a. a. yekinni 2, m. a. adedoyin3, j. b. oyetola1, g. p. ogunyemi1, h. q. olalekan1 1electrical and electronic engineering department, lagos state university of science and technology, ikorodu, lagos, nigeria. 2mechanical engineering department, lagos state university of science and technology, ikorodu, lagos, nigeria. 3electronic and computer engineering department, lagos state university, ojo, lagos. corresponding author’s email: omogoye.s@lasustech.edu.ng article information abstract unreliable power supply from utility companies in nigeria undermines the ability of universities to provide quality services, particularly disrupting critical night-time security operations. a persistent issue at lagos state university of science and technology (lasustech), ikorodu lagos state is the pervasive darkness during utility load shedding, which directly hinders security personnel. current solutions like using diesel generators (dgs), hybrid renewable energy supply systems (hress), and standalone renewable energy supply systems (sress) present significant drawbacks: in addition, dgs are expensive to run while hress require substantial upfront investment. similarly, sress used for street lighting, leave many campus areas such as the walkways, offices, and classrooms in darkness at night. to address these shortcomings and enhance night-time security, this research proposes an improved alternating circuit (ac)-tied solar-photovoltaic (pv)-based lighting system (iacsls). this research involved systematic modeling, design, simulation, construction, and implementation of the proposed iacsls at lasustech. the iacsls successfully generated an average of 580 wh in four hours of peak sunlight per day from a 145 w solar-pv panel, which is enough to power a 30 w led bulb throughout the night. the system is 100% renewable and shows a surplus of 6.71 kwh per year, indicating it produces more energy than it needs. the total initial capital cost is estimated to be $65.54, with a projected life span of 10 to 25 years. the deployed system consistently delivered over eight hours of lighting at night during load shedding offering a sustainable, cost-effective solution for improving night-time security activities on university campus. received: 10th may 2025 revised: 9th july 2025 accepted: 12th july 2025 keywords: ac-tied solar pv energy-efficient lighting light sensitivity control smart lighting system © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction a consistent and reliable power supply is fundamental to ensuring a high quality of service delivery in university campuses worldwide which could significantly enhance teaching, research, and security services (addeh, 2020). unfortunately, many nigerian universities are faced with these challenges due to unreliable power supply, thereby negatively impacting security activities, particularly at night hour. using the lagos state university of science and technology (lasustech) as a case study, the observed load shedding events consistently plunge the campus into darkness during nighttime hours, severely frustrating adequate security service delivery from stationed personnel. thus, to provide uninterrupted power supply during these outages, many institutions, including lasustech, have resorted to diesel generators (dg) as a backup power source. however, the choice of dgs is difficult to justify due to their unsustainably high operational cost as well as their significant environmental and noise pollution problems (sawle et al., 2016 and olabode et al., 2021). while hybrid renewable energy supply systems (hress) have emerged as a promising solution to this problem, their high azojete september 2025. vol.21(3):693-701 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/002 www.azojete.com.ng mailto:omogoye.s@lasustech.edu.ng mailto:omogoye.s@lasustech.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 694 initial procurement cost has historically limited their widespread application (celik, 2003), (kebede and getachew, 2018), and (ramunenyiwa et al., 2020). furthermore, recent advancements have seen the deployment of solar-pv based standalone energy supply systems to illuminate university campuses and public street roads nationwide (okandeji et al., 2020). despite this progress, this technology has proved to be limited in its capacity to cover all indoor dark spots within universities, such as offices, walkways, and lecture theatres, during nighttime load-shedding events. in view of these persistent challenges, this study proposes an improved smart energy-efficient lighting system: the alternating circuit (ac)-tied solar-pv-based controlled lighting system (iacsls). this novel renewable energy lighting system is designed to effectively eliminate all dark spots on university campuses at night, specifically when load-shedding is applied to the university's electricity feeder. by providing consistent illumination, the iacsls significantly enhances security service delivery, improves campus nightlife activities to meet global standards, and consequently boosts the performance of both students and faculty members. this study's novelty lies in proposing an improved smart energy-efficient lighting system (iacsls) that uniquely combines standalone hybrid renewable energy supply system (hress) technology with an intelligent ac source control circuit, designed to operate exclusively at night during load-shedding events, thereby eliminating dark spots across university campuses and enhancing security and nightlife activities. 2. materials and method 2.1 research materials this section discusses the materials and method utilized for the development of the proposed iacsls circuit components design. the iacsls comprises of solar-photovoltaic panels, direct current (dc) source/direct current converter (dc-converter), control circuit with dimming and switching (on/off) sensor, battery bank, ac source and the loads (lighting points). fig.1 presents the block diagram of the proposed iacsls device. solar-pv arrays dc/dc sm art so lar pv controller bus dc/dc charging battery bank lighting points loads ac source relay circuit/ switching dimming and switching figure 1: the schematic diagram of the proposed iacsls. 2.2 research methodology in this study, the engineering science principle backing the development of iacsls is the optimization of electrical power conversion and system efficiency through enhanced thermal management and intelligent power electronics for seamless integration with ac loads. this involves electronic circuit design, signal processing, and control systems to enable the system to respond intelligently to external power sources when required at night only. in trying to maximize energy efficiency, the system's ability to deactivate when an ac signal is detected, minimizing energy waste, justified this task. the proposed iacsls’s model was simulated using homer-pro software trial version. this allows evaluation of the system's performance under various conditions, optimizing the system design size, and predicting its long-term behavior. the device circuit construction was carried out at the electronic laboratory lasustech and the implementation of the proposed iacsls was carried out at the electrical and electronic engineering department of lasustech, ikorodu campus. the detailed discussion of each modelling and design stage presented in figure 1 is presented. http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 695 2.3 modelling of daily iacsls’s load profile and power demand assessment the graphical users interface software homer pro trial version, a microgrid software for designing optimized hybrid power supply system was used for this study. figure 2 shows the homer-pro modelling platform. figure 2: daily energy consumption profile of the iacsls. (lilienthal & gilman, 2004). the per-hour load demand of the lighting bulbs is 30 w. it was determined that from 7:00 pm to 6:00 am, the expected load demand should be in constant mode throughout the time of iacsls’s operation. therefore, the electrical load of 30 w was used as based load. the proposed iacsls is expected to function only at night when power utility companies apply load shedding to the university feeder. therefore, it is good to note that the iacsls switching operation between 7:00 pm to 6:00 am is dynamics and not static. so, if iacsls bulb is rated 30 watts, and the power utility’s load shedding lasted for only “x” hour(s) at night, the load requirement of the proposed iacsls would be 30 ∗ x𝑑−1(𝑊ℎ𝑟𝑑−1) between 7:00 pm and 6:00 am. 2.4 daily photovoltaic energy data assessment solar energy is one of the inexhaustible renewable energy sources that are used to power solarphotovoltaic systems indefinitely. good enough, nigeria has an average daily sunlight hour of 6.25 hd-1,with 3.5 kwhm2d-1 in coastal areas and 9.0 kwhm2d-1 in the far northern border of nigeria as reported in (omogoye et al.,2015), (omogoye et al.,2016), and (okandeji et al.,2020)(alayande et al.,2025) respectively. table 1 presents the daily average solar incident experience in electrical and electronic engineering department of lasustech ikorodu, lagos state nigeria depicting that the chosen site has abundant inexhaustible solar energy resources, good enough to implement the proposed iacsls. the monthly average solar radiation data is obtained from national aeronautics and space administration (nasa, 2015). an annual average solar radiation for electrical and electronic engineering department is 4.74 kw/m2/day, see table 1. month of november has a maximum solar energy resource of 5.292 kw/m2/day. fig. 3 shows the solar radiation graph of the selected study location. table 1: daily average solar incident on a horizontal surface (lilienthal & gilman, 2004) month clearness index month average radiation (kwh/m2/day) january 0.528 4.917 february 0.519 5.128 march 0.506 5.236 april 0.486 5.082 may 0.475 4.842 june 0.444 4.433 july 0.384 3.855 august 0.382 3.922 september 0.419 4.323 october 0.503 5.016 november 0.563 5.292 december 0.535 4.864 http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 696 figure 3: average monthly radiation curve with clearness index. (lilienthal & gilman, 2004). 2.5 modelling of iacsls components this section presents the proposed iacsls’s circuit components design as follows: 2.5.1 modelling of iacsls’s load profile table 2 shows the proposed iacsls’s load profile design calculations. the proposed iacsls lighting load of 30 w is used while battery efficiency of 0.96 percent is considered. the device was designed to function for at least eight hours of light out. in table 3, the solar-pv panel selection criteria was demonstrated. table 4 presents the solar-pv system load profile design selection calculation. in this work, the proposed iacsls must supply the night load using the stored energy in the battery. therefore, to supply needed energy to the load at night only, that amount of energy must be pre-loaded into the battery by the installed solar-pv array. the design calculation for this illustration is presented in table 5. the mppt charge controller designed in table 6 is a type of buck boost converter. it is designed to optimize the power output from the solar-pv panels by adjusting the voltage and current to find the maximum power point (mpp) of the solar-pv panel’s current operating conditions. in a buck-boost converter, the voltage can be either stepped up or stepped down, allowing the system to efficiently manage situations where the solar-pv’s panel voltage is higher or lower than the battery voltage. this versatility is why the mppt controllers are used in this iacsls’s design, to maximize energy conversion and increase the overall efficiency of the system. the modelling of dc-dc converter is presented in table 6. the proposed iacsls circuitry design was done using a free trial version of homerpro software (lilienthal & gilman, 2004) trial version, on a personal computer (pc) of intel core i-3. electrical and electronics engineering department of lasustech walkways t-junction was used as a pilot space to mount the proposed iacsls. these sets of equations are used in the design of the proposed iacsls. to avoid repetition of the basic design equations, some of the equations used for the system design can be found in (omogoye et al., 2015), (okandeji et al., 2020), (nigel and longe, 2021). table 2: solar pv system load profile design selection (lilienthal & gilman, 2004) system components ratings lighting point load 30 w efficiency of the battery (eb) 0.96 watt hours of the load per day (night) 30 × 8 = 240 𝑊ℎ 𝑊ℎ𝐿𝑜𝑎𝑑 = 𝑊ℎ𝑛𝑖𝑔ℎ𝑡 ÷ 𝐸𝑏 240 𝑊ℎ ÷ 0.96 = 256.25 𝑊ℎ table 3: solar panel modelling (lilienthal & gilman, 2004) panel type flat rated capacity 145w temperature coefficient -0.460 operating temperature 45.00 efficiency 14.40 http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 697 table 4: solar pv system load profile design selection (lilienthal & gilman, 2004) components nominal ratings rated values nominal battery voltage, 𝑉𝑏𝑎𝑡.𝑛𝑜𝑚𝑖𝑛𝑎𝑙 , 12.8 𝑉 peak load current, 𝐼𝑙𝑜𝑎𝑑 𝑝𝑒𝑎𝑘 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 30 𝑊 ÷ 12 𝑉 = 2.5 𝐴 battery capacity/power 12 𝑉, 22 𝐴ℎ = 12 × 22 = 264 wh table 5: solar pv array sizing design modelling (lilienthal & gilman, 2004) design parameters days of autonomy 𝑛𝑎 = 2 days of recharge 𝑛𝑟 = 2 watts-hour of pv 687.5 𝑊ℎ the solar-pv array peak wattage considering the annual average (kwh/m2/day) = 4.74 𝑃𝑚 = 687.5 𝑤ℎ 4.74 = 145.04 w the peak load of 145 w was considered. therefore, the selected solar-pv panel is 145 w the battery voltage = 12 𝑉 therefore, current (i) = 𝑝𝑜𝑤𝑒𝑟(𝑃) ÷ 𝑣𝑜𝑙𝑡𝑎𝑔𝑒(𝑉) = 145 ÷ 12 = 12.08 𝐴. 12.08 𝐴 current is produced at output power of 145 𝑊. charging time (in hours) = 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 (𝐴ℎ) 𝐶ℎ𝑎𝑟𝑔𝑖𝑛𝑔 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 (𝐴) and, charging current (i) = 𝑃𝑜𝑤𝑒𝑟(𝑃) 𝑣𝑜𝑙𝑡𝑎𝑔𝑒(𝑉) battery capacity 22 ah solar panel power 145 𝑊 battery voltage 12 𝑉 charging current = 145 𝑊 12 𝑉 = 12.08 𝐴 charging time = 18 𝐴ℎ 12.08 = 1.49 ℎ𝑟𝑠 table 6: calculation of dc-dc converter maximum power point tracking (mppt) (lilienthal & gilman, 2004) components ratings solar panel power 145 𝑊 battery voltage 12 𝑉 battery capacity 22 𝐴ℎ solar panel output current is calculated using power formula. power = 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 × 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 current = 145 𝑊 12 𝑉 = 12.08 𝐴 it’s common to have a buffer, so a charge controller that can handle at least 12 v, 15 a of current is chosen. 2.6 iacsls casing design the iacsls casing design involves the material selection, marking out and fabrication. the proposed iacsls’s component parts drawing for the wall hanger and casing were carried out at lasustech mechanical engineering workshop. the indoor and outdoor casings final designs are presented in figs., 4-12. figure 4: wall hanger component parts figure 5: casing component parts http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 698 figure 6: casing cover parts figure 7: exploded view of iacsls figure 8: orthographic projection figure 9: wireframe of isometric view figure 10: pictorial back view isometric drawing figure 11: pictorial front view isometric drawing figure 12: pictorial view of the outdoor solar panel design 3. results and discussion the simulation results obtained from homer-pro software revealed that the 145 w solar-pv panel consistently generated an average of 580 wh per day. this output is sufficient to power the 30 w light emitting diode (led) bulbs during nighttime hours, especially with the seamless integration of a light control sensor. the intelligent smart control system of the iacsls is crucial for ensuring optimal utilization of stored energy and significantly reducing overall energy wastage. this mechanism demonstrated accurate responsiveness to sunset, guaranteeing efficient energy consumption and effective illumination only when required. in the same vein, the iacsls components comprise a 145 w solar-pv panel, a 30 w led, and a 12 v, 22 ah battery. table 7 presents the iacsls’s cost estimation. the initial capital cost for setting up this system is estimated at $65.54, with an additional operational cost of approximately $20.17 over the device's projected lifespan of 10 to 25 years. this comprehensive cost analysis demonstrates the solar lighting system's strong financial viability and sustainability. the initial investment of $65.54 covered essential components, including the 145 w solar-pv panel, vital for harnessing renewable solar energy; the 30 w led, responsible for efficient and targeted illumination; and the 12 v, 22 ah battery, which ensures consistent power availability during nighttime operations. furthermore, installation and wiring expenses of $20 facilitated the seamless integration of the system. an estimated maintenance cost of $258.55 over the 10-to-25-year lifespan underscores the system's http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 699 durability and minimal upkeep requirements. strategic reliance on solar energy considerably reduces ongoing operational costs, as the system functions independently of external power sources. the system's salvage analysis indicates that components may depreciate over time, but their remaining value is still less than their original cost, contributing to the overall cost-effectiveness. the reported low operating cost highlights the system's affordability, long-term savings due to minimal operational expenditures, and its positive environmental impact through reduced dependence on non-renewable resources offers substantial benefits to environmental well-being. additionally, the precise illumination control offered by the iacsls significantly mitigates energy wastage. this approach aligns perfectly with sustainable development goal 7 (sdg 7), affordable and clean energy, as highlighted by (ross, 2024), and supports long-term energy security. similarly, regarding the iacsls electricity production, in this design, the kyocera kd 145 sx ufu solar-pv panel was specifically chosen because of its robust electricity generation capabilities, producing approximately 51.4 kwh per year when operating at full capacity. in terms of electricity consumption, the ac primary load requires no energy, while the dc primary load consumes about 43.8 kwh per year at maximum usage. the deferrable load contributes zero consumption, resulting in a load of 0 kwh per year. the system exhibits a surplus of roughly 6.71 kwh per year, which constitutes 13.0 % of the total electricity generated. regarding unmet electric load, there is a minimal value of 0.0221 kwh per year, representing only 0.0504 % of the total electricity generated. the capacity shortage is negligible, amounting to 0.0322 kwh per year, or 0.0735 % of the total generated electricity. the proposed iacsls operates at a 100 % renewable fraction, indicating its exclusive reliance on solar energy for electricity generation. remarkably, the maximum renewable penetration reaches an astonishing 1,694 %, showcasing the system's capacity to generate significantly more renewable energy than required. the power generated is available throughout the year, demonstrating that the proposed and constructed iacsls is a reliable energy supply solution. in the same vein, the iacsls efficiency and costeffectiveness assessment were also quantified as key areas of focus. this pivotal avenue for optimization involves exploring the feasibility of integrating higher-capacity batteries. by incorporating batteries with greater energy storage capabilities, the system can accumulate surplus energy during peak sunlight hours, ensuring uninterrupted operation even during extended periods of low solar input. this optimization not only enhances energy resilience but also maximizes cost savings by harnessing excess energy that might otherwise go untapped. furthermore, investigating the integration of energy-efficient or dimmable leds presents a promising avenue for reducing energy consumption without compromising illumination quality. these dual approaches of energy conservation and maintaining adequate lighting levels align perfectly with the project's overall efficiency goals. table 7: iacsls’s cost (lilienthal & gilman, 2004) system components cost rate iacsls’s expected life span (years) initial capital cost $65.54 10-25 operational cost $20.17 installation and wiring expenses $20.00 maintenance cost $258.55 however, the design was without considering some constraints for system design optimization. while the integration of higher-capacity batteries is promising, it necessitates careful consideration of budgetary implications and available physical space in the design casing for installation. it is vital to strike a balance between enhanced performance and the associated costs. the incorporation of energy-efficient or dimmable leds also warrants careful evaluation. while these leds offer potential energy savings, their initial upfront costs and compatibility with the system's design should be thoroughly considered. in addition, system orientation, particularly the positioning of the solar-pv panel, is crucial for optimal energy capture. this is because geographical and architectural limitations may constrain the extent to which orientation can be optimized. the overall budget and the available technology landscape are overarching constraints to keep in mind. while optimizing the system can offer long-term savings, it's essential to ensure that these optimizations align with the project's financial scope and available resources. by carefully weighing economic benefits against system limitations, a harmonious equilibrium can be struck, resulting in a solar lighting system that excels in both efficiency and cost-effectiveness. the last aspect of this work to be described is the assemblage and mounting of the proposed iacsls hardware components and its functionality. the proposed iacsls hardware components made were meticulously assembled at lasustech’s electronic and communication laboratory. the final production of the device is visually represented in plate 1. this device has been successfully mounted at the electrical and electronic engineering department, lasustech ikorodu, lagos, nigeria, as also depicted in plate 1. the system's ability to provide over eight hours of continuous lighting effectively justifies its application for enhancing security service delivery at night on campus. http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 700 plate 1: finished and mounted iacsls device. 4. conclusion in the pursuit of a sustainable and energy-efficient solution, this research developed a smart energy-efficient lighting system using ac-tied, solar-pv with a light sensitivity control device to enhance lasustech’s security apparatus at night. the utilization of the trial version of homer-pro simulation software has been instrumental in evaluating and optimizing the system's size and performance. through meticulous simulation, the solar lighting system's components, including the kyocera kd 145 sx ufu solar-pv panel, were assessed for their electricity generation, consumption patterns, and operational efficiency. these simulation-driven insights have been pivotal in shaping the design and ensuring that the system meets its performance objectives. a unique aspect of this smart energy-efficient lighting system using ac-tied, solar-pv with light sensitivity control device is its intelligent response to ac signals and optimal energy delivery using a sensor. the system's capability to deactivate upon detecting an ac signal, optimizing the energy usage with the dimming sensor, with its illumination that covers 1800 surface area further underscores its adaptability and the integration of advanced control mechanisms. this innovation not only ensures energy savings but also demonstrates a versatile solution that can harmoniously coexist with other energy sources. the case study at lasustech serves as a testament to the real-world applicability of such technology at a reduced cost. since the iacsls’s components are locally sourced. the successful design and implementation of the iacsls device within the university's premises showcase the potential for renewable energy adoption within educational institutions, contributing to a culture of environmental consciousness and sustainable practices under sdg 7 of times higher education (the). conclusively, the research's journey from conceptualization, to design, simulation, and construction highlighted the synergy between technology, sustainability, and real-world impact. the integration of the homer-pro simulation software into the project's fabric has substantiated the viability of the iacsls device, affirming its role as an energy-efficient, eco-friendly, and intelligent solution from core engineering principle of photovoltaic effect to enhance security service delivery in nigerian universities at night. in the future we plan to scale up its production which will lead to the total cost reduction of this proposed device. acknowledgement this work was supported by the lasustech research grants (lrg) 2023, from lagos state university of science and technology (lasustech), ikorodu, lagos state, nigeria. references okandeji, aa., jagun zo., olajide mb., kabir mt. and onaifo f. 2020. design and implementation of solar streetlight for scarcely electrified areas. arid zone journal of engineering, technology & environment, (nigeria), 16(3): 543–560. addeh, e. (2020, july 13). powering nigeria’s universities thisdaylive. thisdaylive. celik, an. 2003. optimisation and techno-economic analysis of autonomous photovoltaic-wind hybrid energy systems in comparison to single photovoltaic and wind systems. fuel and energy abstracts, 44(3): 162-168. https://doi.org/10.1016/s0140-6701(03)81833-7 http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 693-701. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omogoye.s@lasustech.edu.ng 701 alayande, as., emmies, ae., okakwu, ik., gbenga, ok. and okeolu, os. 2025. homer pro-based approach for designing and optimizing a grid-tied hybrid renewable energy system for a rural community. arid zone journal of engineering, technology & environment, 21(1): 72–86. kebede, mh. and beyene, and gb. 2018. feasibility study of pv-wind-fuel cell hybrid power system for electrification of a rural village in ethiopia. journal of electrical and computer engineering, 2018: article id 4015354:1–9. https://doi.org/10.1155/2018/4015354 lilienthal, p. and gilman, p. 2004. homer modelling software. national renewable energy laboratory, 1–2. nasa. 2015. cloud cover and solar radiation 82. in cloud cover and solar radiation, 990(1):3–5. http://scool.larc.nasa.gov/lesson_plans/cloudcoversolarradiation.pdf nigel, ft. and longe, om. 2021. smart energy efficient lighting system for smart buildings. ieee pes/ias powerafrica: 1–6. https://doi.org/10.1109/powerafrica52236.2021.9543273 omogoye, os., ogundare, ab. and akanji, io. 2015. development of a cost-effective solar/diesel independent power plant for a remote station. journal of energy, 2015(article id 828745): 1–10. https://doi.org/10.1155/2015/828745 olabode, oe., ajewole, to., okakwu, ik., alayande, as. and akinyele, do. 2021. hybrid power systems for off-grid locations: a comprehensive review of design technologies, applications and future trends. scientific african, 13: e00884. https://doi.org/10.1016/j.sciaf.2021.e00884 omogoye, os., ogundare, ab., oyetola, jb., keshinro, kk., and adenle, jg. 2016. feasibility studies of a proposed hybrid power generation system for a computer center in a remote station. international journal of technical research and applications, 4(4): 113–119. ramunenyiwa, t., awodele, k. and omogoye, os. 2020. development of a cost-effective solar-wind-fuel cell independent power plant for a remote base transceiver station. 2020 international saupec/robmech/prasa conference, saupec/robmech/prasa 2020: 1–6. ross, d. 2024. impact rankings methodology 2024, times higher education. sawle, y., gupta, sc. and bohre, ak. 2016. pv-wind hybrid system: a review with case study. cogent engineering, 3(1): 1–31. https://doi.org/10.1080/23311916.2016.1189305 http://www.azojete.com.ng/ mailto:omogoye.s@lasustech.edu.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 581 arid zone journal of engineering, technology & environment original research article effect of lantana camara, cassia occidentalis and rucinus communis seeds and leaves extract as corrosion inhibitors of mild steel in 2m hcl solution e.t. andy1, a. a. hammajam,2,3* and i. s aji3 1department of mechanical engineering, university of jos, plateau state 2department of mechanical engineering, nigerian army university biu borno state 3department of mechanical engineering, university of maiduguri, borno state * corresponding author’s email: hammajam@naub.edu.ng, hammajam92@gmail.com article information abstract corrosion phenomena, control, and prevention are significant scientific issues that require ongoing attention due to the increasing demand for metallic materials in various technological developments. the use of natural inhibitors is an attractive option for preventing corrosion due to their environmental friendliness, costeffectiveness, and ease of sourcing and renewability. this research investigates the potential of locally sourced, non-edible plants as corrosion inhibitors. specifically, extracts from lantana camara, cassia occidentalis, and ricinus communis seeds and leaves were tested on mild steel in a 2m hcl solution to determine their corrosion prevention potency and compare the inhibitive properties between the leaves and seeds of each plant. the maceration method was employed for extraction using ethanol as the solvent. corrosion tests were conducted using the weight loss technique to determine the corrosion rate of mild steel coupons over a 14-day period, with measurements taken at 24-hour intervals. the results indicate that cassia occidentalis leaves and lantana camara leaves exhibit lower corrosion rates compared to their respective seeds. conversely, ricinus communis seeds showed a lower corrosion rate than its leaf extract. all inhibitors demonstrated notable inhibitive properties, with cassia occidentalis leaves displaying the highest inhibitive efficiency, likely due to its high phytochemical constituents. received: 26th april 2025 revised: 30th april 2025 accepted: 30th april 2025 keywords: corrosion inhibition phytochemical plants leaves seeds © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction mild steel also known as plain-carbon steel, is the most common form of steel because its price is relatively low, while it provides wide range of applications because of its material properties. however, mild steel has a great challenge of low corrosion resistance especially in acidic environments (marko et al., 2016). corrosion phenomena, control, and prevention are significant scientific issues that require ongoing attention due to the increasing demand for metallic materials in various technological developments (loto et al. 2011). corrosion can be defined as a disparaging phenomenon, chemical or electrochemical, which can attack metal or alloy through reaction by the surrounding environment (presence of oxygen, water, and other chemicals).and in extreme case may cause structural failure (aji et al.2016). the effects of corrosion on the safe, reliable and efficient operation of equipment or structures are often more serious than simple loss of a mass of a metal. failures of various kinds and the need for expensive replacements may occur even though the amount of metal destroyed is quite small (umoren, 2009). corrosion can occur also in other materials other than metals, materials such as ceramics, wood or polymers, although the corrosion rate in metals is very high. corrosion it’s a continuous process, often difficult to eliminate totally, it can only be slowed down, corrosion prevention is achievable than complete elimination. azojete june 2025. vol.21(2):581-588 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/022 www.azojete.com.ng mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 582 figure 1: requirements for the atmospheric corrosion reaction most of the corrosion inhibitors are synthetic chemicals, expensive and very hazardous to the environment. therefore, it is desirable to source for environmentally safe inhibitors (paul et al. 2012). owing to the increasing ecological awareness as well as the strict environmental regulations, and consequently the need to develop environmentally friendly processes, attention is currently focused on the development of green alternatives to mitigating corrosion. due to the availability of these plants and the simplicity in processing them into inhibitors, these plants extracts are less expensive when compared to inhibitors produced using synthetic chemicals. mshelia et al. (2017) used gravimetric technique to compares the corrosion inhibition efficiency of an abundant and eco-friendly plant extracts of azadirachta indica (neem) and jatropha curcas in acidic media (2m h2so4 solution) using mild steel. the results obtained show that all the plants under study are good corrosion inhibitors, among which leaves extract of neem as the most effective. phytochemical analysis shows that the constituent of the ethanol extracts of neem and jatropha curcas contains cardiac glycosides, saponins and tannins, while flavonoids were found in jatropha curcas leave extract alone. sivaraju et al, (2010) also investigated the inhibition effect of acalypha indica extract on mild steel corrosion in 1m phosphoric acid using weight loss and polarization techniques at a temperature of 30oc and 60oc respectively. the results showed that inhibition efficiency increased with increase in concentration of the plant extract and also the corrosion rate increased with increase in temperature and decreased with increase in concentration of inhibitor. furthermore, loto et al. (2014) reported the effect of manihot esculenta c (cassava) leaf extract additive on the zinc electroplating on mild steel in acid chloride solution. the corrosion resistance of the plated surface was determined by gravimetric, potential measurement and corrosion current methods. also, inhibitor study was conducted by quraishi et al. (2009) on the inhibition of black pepper extract. the results obtained revealed that black pepper extract was a good corrosion inhibitor for mild steel in hydrochloric acid medium and maximum inhibition efficiency (98%) was found at 120 ppm at 35 ºc. therefore, this paper presents the result of lantana camara, cassia occidentalis and rucinus communis. (seeds and leaves) extract for corrosion prevention in mild steel. 2. materials and method 2.1 materials and equipment some of the materials used includes lantana camara, cassia occidentalis, rucinus communis seeds and leaves, and mild steel sheet coupon. equipment used were digital analytical weighing mass balance of (0.001) accuracy, drying cabinet, rotary evaporator, measuring cylinder, beakers, wired brush and sand paper, filtration funnels, sieve, mechanical shaker and seven (6) sample containers, which contained the acid solution into which the mild steel was immersed. 2.2 method this explains the procedure on how the research was carried out. 2.2.1 preparation of the sample fresh leaves and seeds of the lantana camara, cassia occidentalis and rusinus camminis were collected from the plant within the environs of university of jos main campus (bauchi road) jos, plateau state for the purpose of this research, in natural condition. the leaves were washed under running tap and were later dried under shade for about 10days. the fruits of lantana camara was mild crushed in order to obtained the seeds, but the seeds of cassia occidentalis and rusinus camminis were enclosed in a pod, the pod was braked in order to corrosion oxygen water as electrolyte metal http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 583 obtained the seeds. the dried leaves and seed were then grounded to powder form and 60g weights are placed in different containers each. 2.2.2 extraction extraction was conducted using maceration technique carried out at the department of pharmacognosy, faculty of pharmacy, university of jos. 60g of each powder was weighed into containers. 70 % concentration of ethanol was added to each container containing the powdered samples, the powdered samples were allowed to soak overnight (24hrs) at room temperature (25oc) and was shake very well using mechanical shaker. the seeds powders were allowed to soaked for 5days with frequent agitation as similar work was reported by (loto 2011). the content was then filtered using non-absorbent cotton wool on a bucher funnel; the residue was then subjected to several parts of rinsing and filtration with fresh solvents to attain some level of maceration (extraction). the collective filtrate was evaporated to dryness with the aid of rotary evaporator and a drying cabinet at a controlled temperature not above 70oc. each of the extracts yield was transferred to a clean bottle and covered properly. its phytochemical screening and identification of some basic compounds were carried out. plate 1 shows the drying cabinet at controlled temperature not above 70oc. plate 2 depict the powder samples being soaked with 70% of ethanol. plate 3 indicated the soaked powdered samples on mechanical shaker. plate 4 shows the evaporation of the filtrate with the aid of rotary evaporator. whereas, plate 5 indicated the filtration of extracts using non-absorbent wool. plate 1: drying cabinet at controlled plate 2: powder samples being soaked with 70% of ethanol temperature not above 70oc plate 3: soaked powdered samples on mechanical shaker http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 584 plate 4: evaporation of the filtrate with plate 5: filtration of extracts using non-absorbent wool the aid of rotary evaporator 2.3 phytochemical analysis phytochemical analysis of the plant extracts was done at the faculty of pharmacy, university of jos following the standard procedure to determine the presence of saponins, alkaloids tannins, carbohydrates, flavonoids, cardiac glycosides, and glycosides. 2.3.1 test for alkaloids about 0.5g of each extract was stirred with 3 ml of 1% aqueous hydrochloric acid on a steam bath, the filtrate was treated with few drops of mayer’s reagent. precipitation this reagent was taken as preliminary evidence for the presence of alkaloids in the extracts. 2.3.2 test for tannins about 0.5g of each plant extract was stirred with 1ml of distilled water, filtered and ferric chloride reagent added to the filtrate. a blue-black, green, or blue –green precipitate was taken as the presence of tannins. 2.3.3 test for saponins about 0.5g of each plant extract was shaken with water in a test tube. frothing which persist on warming was taken as preliminary evidence for the presence of saponins. 2.3.4 keller killiani test for cardiac glycoside 100mg of extract was dissolved in glacial acetic acid containing tone drop of ferric chloride. 1 ml of concentrated sulphuric acid was added down side. a brown ring colour was formed at interphase indicated the presence of a deoxysugar characteristics of cardenolides. 2.3.5 test for anthraquinones borntragers test was used for the detection of anthraquinones 0.5g of each extract were taken into a dry test tube and 5ml of chloroform was added and then shaken for about 5 mins. the extract was filtered, the filtrates of the extract shaken with an equal volume of 100% ammonia solution. a pink violet in the ammoniacal lower layer indicates the presence of free antraquinones. 2.3.6 test for carbohydrates 100mg of each extract was dissolved in 3ml of distilled water and mixed with few drops of molisch reagent, then 1ml of concentration sulphuric acid was carefully added down the side of inclined tube so that the acid forms a layer beneath the aqueous solution without mixing it. a reddish ring at junction of the liquids was observed indicating the presence of carbohydrates. http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 585 2.3.7 test for flavonoids 5ml of 20% sodium hydroxide was added to equal volume of the extract. a yellow solution indicates the presence of flavonoids. 2.4 preparation of 2m hcl solution (test solution) the experiments were performed in 2 m hcl solution. the acid solution of 2 m hcl was prepared from a standard concentration of hydrochloric acid having percentage purity of about 39% using the relation 1 (aji et al, 2016) to prepare the 2m hcl. 𝑉 = ( 𝑀𝑊𝑇 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 )( 100 36 )(2)\1𝑙 1 where v = volume, mwt = molecular weight 𝑉 = ( 36.5 1.18 )( 100 36 ) 2 thus 2 liters of 2m of hcl, was prepared, the required volume of hcl will be v=171.84×2=343.68 ml 2.5 preparation of mild steel coupon the sheet of mild steel used for this study was obtained commercially from building material bukuru market in jos. the mild steel sheet was mechanically cut into rectangular coupon samples of dimension of (50x30x2) mm. a small hole was drilled near the strip edge of the coupon which a thread will be tied for easy handling. during the study the coupon samples were descaled by wire brushing and polished using abrasive papers (sand paper) of different grades grits to obtained smooth and rust, dirt’s free surface and washed with ethanol to remove any form of grease or oxide. they were then cleaned with acetone. 2.6 gravimetric method the inhibitive properties of the extracts were evaluated using weight loss method. weight loss measurement was performed on seven (7) mild steel coupons. the weighed mild steel coupons were fully immersed in each of the test solution media for 14 days, also another weighed mild steel coupon specimen was immersed in to 2m hcl which does not contain the extract, this served as the control experiment. the test specimens were taken out of the corrosive media after every 24 hours at room temperature and it was followed by washing with distilled water, then after on rinse with acetone and air dried to remove corrosion products, air-dried and re-weighed to measure the weight loss. this process was done every day uninterrupted up to the 14th day. from this observed data for 14 days, the corrosion rate cr (mm/yr), the percentage inhibition efficiency i.e (%), weight loss wl(g) was determined. 2.7 weight loss (wl) the loss in weight of the coupons as the result of corrosion (coupons in the presence of acidic media) was calculated using equation (3). 𝑊𝐿 (𝑔) = 𝑊𝑖 − 𝑊𝑓 3 where 𝑊𝑖and 𝑊𝑓 are initial weight and final weight. 2.8 tests carried out in the cause of this study several tests were conducted as shown in the sub-sections below. 2.8.1 corrosion inhibition efficiency the inhibition efficiency percentage was calculated using equation (4) (mshelia et al., 2017). %𝐼𝐸 = 𝑅𝑏𝑙𝑎𝑛𝑘− 𝑅𝑖𝑛ℎ 𝑅𝑏𝑙𝑎𝑛𝑘 4 http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 586 2.8.2 corrosion rate the corrosion rate of the mild steal was calculated from weight loss of the coupons at room temperature and at fixed (constant) concentration (mshelia et al., 2017). 𝐶𝑅 = 87.8∆𝑊 𝑝𝐴𝑇 ( 𝑚𝑚 𝑦𝑟 ) 5 where, w =is the weight loss (g), ρ =is the density in g/cm2, a= is the area in cm2, and t= is the time of exposure in hours. 2.8.3 surface coverage (θ) the surface coverage (θ) of the mild steel was calculated from the corrosion rate, as a result of adsorption of inhibitor molecules was determined using the equation provided in equation 6. 𝜽 = 𝑹𝒃𝒍𝒂𝒏𝒌− 𝑹𝒊𝒏𝒉 𝑹𝒃𝒍𝒂𝒏𝒌 6 3. results and discussion the results obtained from the tests and observation made during the experiment are presented. 3.1 phytochemical analyses the results obtained from the phytochemical analysis are shown in table 1. the phytochemical analyses of the plants (leaves and seeds) extract reveal the presence of alkaloid, saponins, tannins, flavonoids, carbohydrates, anthraquinones, and cardiac glycosides. table 1: phytochemical constituents of the plant chemical lantana lantana rusinus rusinus cassia cassia constituents camara camara camminis camminis oxcdentalis oxcdentalis leaves seeds leaves seeds leaves seeds alkaloids ++ +++ +++ +++ +++ + saponins ++ + tannins +++ ++ +++ +++ +++ flavonoids +++ +++ +++ + +++ +++ carbohydrates ++ ++ ++ + + ++ anthraquinones + cardiac glycosides + +++ ++ +++ + ` key: absent + present ++ moderately present +++ highly present from the results of the phytochemical analysis in table 1 alkaloids and flavonoids are present in all the plant (leaves and seeds) extract, generally the natural compounds found in all the plant (leaves and seeds) extracts will form a film on the surface of the mild steel, which will serve as a hurdle at the surface of the mild steel through the mechanism of adsorption, there by inhibiting the corrosion process of the mild steel coupon. the phytochemical component of plants (leaves and seeds) extract encompasses rich naturally synthesized ecofriendly organic compounds which combat corrosion on mild steel in an aggressive media. according to iloamaeke et al. (2013), these compounds contain nitrogen and oxygen which are the center for chemical adsorption on the mild steel. alkaloid present in plants extract have a fascinating feature to inhibit corrosion, alkaloid prevent metal corrosion by adsorption of their molecules on metals surface to form a protective layer. saponins has rich oxygen molecules that provides good adsorption sites via the lone pair of electrons residual on the oxygen atoms while tannins aids in forming the inhibitor protective layers on the metal surface with an adsorption mechanism on the oxide films. thus, from the results and the role of each of phytochemical constituents in prevention of corrosion as sated above, the leave of cassia oxcdentalis is expected to have high inhibitive properties, because cassia oxcdentalis extract has alkaloid, tannins, flavonoids, cardiacgycoside all highly present. http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 587 3.2 corrosion rate figure 2 shows the weight loss of the mild steel coupon in the control solution is high, reason being that 2m hcl solution aid in the high corrosion rate and also because of the absence of any inhibitor, thus the mild steel coupon disintegrates faster figure 2: variation of weight loss with different exposure time on mild steel in 2m hcl key cs= control solution, lcl= lantana camara leave, lcs= lantana camara seed, ocl= cassia occidentalis leave, ocs= cassia occidentalis seed, rl= rusinus comuinis leave, rs= rusinus comuinis seed. the corrosion rate is seen to be significantly high as observed in this study. the values of weight loss of mild steel coupon (g) differ with the exposure time (hours) for mild steel immersed inside the control solution and that immersed in the test media (in presence of inhibitor), lantana camara leaves, lantana camara seed, cassia occidentalis leave, cassia occidentalis seed, rucinus cumminus leave and rucinus cumminus seed. it was observed that corrosion rate of metal increase with increase in time of exposure. accordingly, the cassia occidentalis leaves extract, lantana camara leaves extract show less corrosion rate compare to their seeds extracts, but the seed extract of rucinus cumminus exhibit less corrosion rate than its leave extract. 3.3 inhibition efficiency figure 3 compare the inhibition performance of each extract on the mild steel coupon. figure 3: variation of inhibition efficiency and exposure time the magnitude of corrosion inhibition and the inhibition efficiency of lantana camara (leaves and seeds), cassia occidentalis (leaves and seeds) and rusinus comuinis (leaves and seeds) extract in corrosion of mild steel coupon in corrosive media was studied for 14days. figure 3 shows that all the six immersed coupons were detected to have almost the same inhibition efficiency. though, cassia occidentalis leave shows great efficiency, this is 0 1 2 3 4 5 6 7 0 50 100 150 200 250 300 350 400 w e ig h t lo ss ( g ) exposure time (hours) cs lcl lcs ocl ocs rl rl 84 86 88 90 92 94 96 98 0 50 100 150 200 250 300 350 400 in h ib it io n e ff ic ie n c y ( % ) exposure time (hours) lcl lcs ocl ocs rl rs http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 581-588. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng, hammajam92@gmail.com 588 because of it has high phytochemical constituents present than other extracts which aids in the high prevention of corrosion, it showed 94.266% of inhibition of efficiency. the result obtained from lantana camara extract (leaves and seeds) shows some great inhibition properties as though the efficiency in that of leaves is higher than that of the seeds. lantana camara leaves extract formed high protective film on the mild steel coupon surface in the presence of corrosive media. cassia occidentalis extract (leaves and seeds) also exhibits the presence of inhibition, same as that of lantana camara the inhibition efficiency of the leaves extract is higher than that of seed extract. but unlike rusinus comuinis extract have shown inhibition properties similar to that of lantana camara extract and cassia occidentalis, rucinus cummunis seeds extract is higher (89.431%) than that of the leaves extract (88.929%). this also because of the rate of the phytochemicals constituent’s present in each extract. 4. conclusion from this research work, natural (green) plant extracts (leaves and seeds) have shown a great alternative for inhibition of corrosion in metals. though some plants may have low inhibition properties despite their abundance in the locality, the reason being that the low amount of the physiochemical constituent need to stop or slow process of the corrosion on the material when exposed to the atmosphere. the plants leaves and seeds investigated showed the presence of all the chemical compounds needed for corrosion prevention except saponins and anthraquinones which is scarcely available in the extracts investigated. their absence will have no serious consequence when it comes to corrosion inhibition is mild steel. the other compounds are available in moderate to high amounts and can equalize the deficiency that may arise as a result of the little presence of saponins and anthraquinones. most plants that are abundant and have little or no economic value (not for food) have potentials in the prevention of corrosion; they are mostly a waste and therefore less expensive, can create job opportunities and most important it is environmentally friendly. references aji is., yp zadva, mj. and madu 2016. hybridazation of plants extracts for corrosion prevention of mild steel. international journal of engineering research and technology 4: 119 126. feidilis, m. 2016. recent natural inhibitors od mild steel overview. loto, ca., 2014. effect of manihot esculenta c. leaf extract additive on the zinc electroplating on mild steel in acid chloride solution. international journal of electrochemical science, 9. loto, ca. 2011. corrosion and plant extracts inhibition of mild steel in hcl. international journal of physics science, 6(15): 67-80. mshelia z., aji, is. and yawas, ds. 2017. comparative analysis of jatropa curcas and neem leaves extracts as corrosion inhibitors on mild steel.seminer series, 8 :57-69 paul, ol. 2012. corrosion inhibition and adsorption behaviour for mild steel by fiscus glumosa gum in h2so4 solution. african journal of pure and applied chemistry, 6(7): 81-99 quraishi, ma, dileep, ky., and ishtiaque, a. 2009. green approach to corrosion inhibition by black pepper extract in hydrochloric acid. the open corrosion journal, vol.2(1): 34-47 sivaraju, m. and kannan, k. 2010. eco-friendly inhibitor (tributes terrestris l) for mild steel corrosion in 1n phosphoric acid. asian journal of chemistry, 22(1): 233-244 umoren, a. 2009. polymers as corrosion inhibitors for metals in different media -a review. the open corrosion journal, 2: 175-188. http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com corresponding author’s email address: ijaolaoo@fuotuoke.edu.ng 713 arid zone journal of engineering, technology & environment original research article groundwater contamination risk assessment: pahs pollution from crude oil leaching in ogbia, bayelsa state o.o. ijaola department of civil engineering, faculty of engineering, federal university otuoke, bayelsa state, nigeria corresponding author’s email address: ijaolaoo@fuotuoke.edu.ng, opololaoluwaijaola121@gmail.com article information abstract groundwater is the largest reservoir of drinkable water, accounting for approximately 22% of the world’s freshwater. however, regular crude oil spills have resulted in severe groundwater contamination by polycyclic aromatic hydrocarbons (pahs), which harm human health and the environment. this investigated the presence and concentration of pahs in groundwater in ibelebiri in ogbia, bayelsa state, nigeria, following an oil spill, to determine contamination pathways and potential consequences. soil samples were taken from three locations (l1, l2, l3) and three depths (topsoil, subsoil, and aquifer) and examined for pahs such as naphthalene, acenaphthene, fluorene, pyrene, anthracene, and benzo(a)anthracene. laboratory results found that naphthalene had the highest concentration in all samples, particularly topsoil, whereas heavier pahs such as pyrene and anthracene had lower quantities, notably in aquifer samples. the leach pollution index (lpi) ranged from 81,199.25 to 83,374.10, indicating a high level of contamination potential. statistical analysis using anova revealed significant variation in the concentrations of lighter pahs such as naphthalene (p-value = 0.00059193) and fluorene (p-value = 0.002376112) between soil layers, while heavier pahs such as pyrene (p-value = 0.969122843), anthracene (p-value = 0.984906863), and benzo(a)anthracene (p-value = 0.358155023) showed no significant differences across the samples. the findings underline the necessity for focused remediation measures to mitigate groundwater contamination while safeguarding public health and environmental quality. submitted 18 oct. 2024 revised 31 jan. 2025 accepted 03 feb. 2025 keywords: contaminants groundwater pahs crude oil spill leach pollution index © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction water is a basic necessity and is the most vital resource of survival for all god’s creations so it must be made available as fresh, clean and pure water to keep people alive and healthy when consumed, meaning that fresh and clean water is a critical issue globally, as the population increases (ijaola, et al., 2013; oyinloye and jegede, 2004; sanda et al., 2022). the groundwater is the largest reservoir of drinkable water and due to the natural filtration, which is less contaminated as compared to surface water. groundwater being a vital component of the global water cycle, accounting for approximately 22% of the world's freshwater resources (world health organization, 2018), it serves as a primary source of water for human consumption, agriculture, industry, and ecosystems, supporting human health, economic development, and environmental sustainability due to its long retention time and natural filtration capacity of aquifers. (national research council, 2015). however, groundwater quality is threatened by various contaminants which are both inorganic and organic. some of the organic contaminants according to ijaola and sangodoying, (2020) are generated from the petroleum and pharmaceutical industries are seen among others as major contributors of organic contaminants because of continuous usage. the petroleum industrial affluents, namely the produced water and crude oil spills, are the major sources of pollutants generated by the petroleum industry (ijaola and sangodoying, 2020; ijaola and sangodoying 2021). the crude oil spill generates an organic contaminant like polycyclic aromatic hydrocarbons (pahs), which pose significant risks to human health and the environment (agency for toxic substances and disease registry, 2019) among many other contaminants. pahs are a group of organic compounds consisting of two or more fused aromatic rings, formed during incomplete combustion of organic matter, such as fossil fuels, wood, and tobacco (smith, 2020). (pahs) are ubiquitous environmental pollutants azojete december 2024. vol.20(4):713-721 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:ijaolaoo@fuotuoke.edu.ng mailto:ijaolaoo@fuotuoke.edu.ng mailto:opololaoluwaijaola121@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 714 that pose significant risks to human health and the ecosystem (who, 2019; ijaola and sangodoying, 2020; ijaola and sangodoying; 2021). pahs can contaminate groundwater through various pathways, including industrial activities, agricultural runoff, and crude oil spills (doe & amadi, 2019). among the myriad contaminants of concern, pahs stand out as particularly nefarious due to their persistence, toxicity, and carcinogenic potential (osuji et al., 2015). resistant to natural degradation, they readily accumulate in organisms, posing a significant threat to aquatic life and potentially entering the food chain, impacting human health indirectly (ogwo et al., 2019; ijaola and sangodoying, 2020). they are known to be carcinogenic, mutagenic, and teratogenic, causing harmful health effects, including cancer, reproductive issues, and developmental problems (world health organization, 2018, boonpragob et al., 2019; ijaola and sangodoying, 2020). crude oil spillage, a common occurrence in oil-producing regions like ogbia, nigeria, can lead to pahs contamination of groundwater (osuji, 2015). leached crude oil can migrate into groundwater, releasing pahs and other toxic compounds (adeniyi, 2018) which can infiltrate soil and aquifers, releasing pahs into groundwater. nigeria, with its rich oil reserves, faces severe environmental challenges due to oil spillage (nnpc, 2020). the niger delta region, where ogbia is located, has experienced frequent crude oil spills due to oil exploration and production activities (nwankwoala et al., 2017). this has resulted in widespread environmental degradation and health concerns including groundwater pollution (amadi & smith, 2017; kumar,2017). frequent oil spills, a chronic issue plaguing the niger delta, originate from a multitude of sources including pipelines, storage facilities, and exploration activities. these spills unleash a toxic cocktail of contaminants, ranging from hydrocarbons and heavy metals to polycyclic aromatic hydrocarbons (pahs). the immediate damage is such serious that it affects both plants and animals. however, the true cost goes far beyond the initial impact, leaving a legacy of polluted soil and groundwater that jeopardizes the environment and its people' long-term well-being (abdel-shafy & mansour, 2016). polluted water does not impair people's health immediately, but it can be deadly over time. (sanda et al., 2022). water pollution affects drinking water, rivers, lakes, and oceans all around the world, putting human health and the ecology at danger. (gambhir et al., 2012). shallow water tables and permeable aquifers characterize the region's hydrogeology, increases the vulnerability of groundwater to contamination (doe amadi, 2019). despite efforts to clean up oil spills, pahs persist in the environment, posing long-term risks to human health and ecosystems (agency for toxic substances and disease registry, 2019). pahs persistence is in line with the scholars who have indicated that the recent problems in water treatment originate primarily from the increasing pollution of water by an organic compound that is difficult to decompose biologically because these substances resist the self-purification capabilities of the rivers as well as decomposition in conventional wastewater treatment plants (ademiluyi et al., 2009; olafadehan and aribike, 2000; ogunlowo and sakwe, 2023). therefore, pahs persistence with carcinogenic properties consequence has raised alarming concerns about the direct risks associated with longterm exposure through contaminated groundwater sources (boonpragob et al., 2019, ogunlowo,2022). while complete prevention remains the ultimate goal, in the face of existing spills, remediation efforts play a crucial role in mitigating the damage. a diverse range of techniques, from bioremediation to pump-and-treat methods, are employed to remove or contain spilled oil and its associated contaminants. however, the effectiveness of these interventions varies greatly depending on factors like the nature of the spill, environmental conditions, and implementation strategies (osuji, 2015). understanding their true impact on pah leaching is critical for optimizing remediation strategies and safeguarding groundwater quality. previous studies have investigated pahs contamination in soil and water like pahs in the drinking water of counties along the huai river in china which reveals pahs associations with high cancer incidence (enchun et al., 2015), their epidemiological studies revealed that when professional are exposed to pahs they are associated with many kinds of cancers (eom, et al., 2013, mastrangelo et al., 1996; tsay et al., 2013 ), and pahs are listed as priority pollutants by the united states environmental protection agency (us epa) due to crude oil spillage in the niger delta region (osuji, 2015; nwankwoala et al., 2017). despite the risks, limited studies have investigated pahs contamination in groundwater with leached crude oil in ogbia, nigeria. so, understanding the extent and impact of pahs contamination in groundwater is crucial for developing effective mitigation strategies, protecting human health, and preserving environmental quality. this study will contribute to the existing body of knowledge on groundwater contamination by pahs, providing valuable insights for policymakers, researchers, and stakeholders with the aims of assessing the pathways, the presence and concentration of leached polycyclic aromatic hydrocarbons (pahs), a contaminant from oil spills into the groundwater; the potential environmental and health impacts, with pahs by comparing with usepa standards and comparing the risk level of samples taking from polluted site with control using (a) statistical inferences such as anova and leached pollution index (lpi). http://www.azojete.com.ng/ mailto:ijaolaoo@fuotuoke.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 715 2. materials and methods 2.1 study area the study was conducted in ibelebiri, bayelsa state. ibelebiri is a small community located in ogbia local government area of bayelsa state; between latitude 4°55’51.457"n and longitude 6°24’54.80352"e, nigeria. historically, the area is part of the larger ijaw ethnic group, which is indigenous to the niger delta region. the community, like many others in bayelsa, has a rich cultural heritage tied to fishing, farming, and trading, with a strong reliance on the natural environment for sustenance. bayelsa state, created in 1996, was part of the old rivers state before the restructuring. ibelebiri has been significantly impacted by oil exploration, which began in the niger delta in the 1950s. this led to environmental challenges, including oil spills and pollution, affecting the local ecosystem and traditional livelihoods. despite these challenges, ibelebiri remains a closeknit community with deep cultural roots, actively involved in preserving its traditions and seeking sustainable development amidst the complexities of modern industrial activities. plate1: sub-surface sampled area plate2: gps coordinate of ibelebiri twon plate 3: crude oil spill site 2.2 sample collection within the research area, a network of three bore holes provided samples for collection. using a hand shovel and a trowel, soil samples were taken from three locations surrounding the spill area. the first sample in the spill area, locations 1 and 2 were taken from the spill site across the river in the direction of latitude 4°56 n and longitude 6°25 e. latitude 4°57 n, longitude 6°25 e, in the direction of the second sample in the spill area. the control was taken within the residents of the community with the direction of latitude 4°55n and longitude 6°25e. in order to comprehend the vertical distribution of contaminants, samples were obtained at three different depths. three levels of soil were sampled at each location. the top soil, which was gathered at each location using a hand trowel. a second sample was obtained at each location at a depth of 0.3 meters through hand auger. the third sample was taken at 0.9 meters through hand auger in each location. materials utilized in this research include: hand auger, shovel, trowel, polythene bag, amber bottles, personal protective equipment’s, cooler and ice packs. 2g of sample was weighed into a clean extraction container. 20ml of extraction solvent (hexane) was added into the sample, mixed thoroughly and allowed to settle. the mixture was carefully filtered into solvent-rinsed extraction bottles using filter paper fitted into buchner funnels. the extracts were concentrated to 2ml and then transferred for cleanup/separation 2.3 laboratory procedure for pah analysis the laboratory procedure for polycyclic aromatic hydrocarbon (pah) analysis involves the extraction of pahs from soil and water samples, followed by clean-up/separation, and finally gas chromatographic analysis to identify and quantify the pah compounds, as previously described (ijaola and sangodoyin, 2020). http://www.azojete.com.ng/ mailto:ijaolaoo@fuotuoke.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 716 2.4 statistical analysis to further determine the differences among the mean variation of tested contaminants by pahs. the anova analysis for each pah was conducted to determine whether there were statistically significant differences between the concentrations of pahs at different depths (s1, s2, and s3) across locations. for most pahs, significant variations were observed between locations but not always between soil layers, indicating that spatial variability is a more significant factor than depth. 2.5 leach pollution index (lpi) the lpi measures the possibility of leachate contamination in a specific area. it is a single number ranging from 5 to 100 (simeon and ayotamuno, 2022) that provides critical insight into the contamination potential of the soil to leach poisonous substances into groundwater. it is an increasing scale index; the higher value means a poor environmental condition, with a standard lpi value of 7.37 (kumar and alappat, 2003, churchill and ogunlowo, 2022). the leach pollution index (lpi) is calculated using equation 1 and equation 2 as the lpi (leaching pollution index) using who’s standard values for groundwater quality. 𝐿𝑃𝐼 = ∑(𝑤𝑖 ×𝑝𝑖) ∑𝑤𝑖 1 where wi is the weight assigned to i-th parameter 𝑃𝑖 is the sub-index for the i-th parameter, calculated as: 𝑃𝑖 = 𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑉𝑎𝑙𝑢𝑒 × 100 2 the 𝑊𝑖 should be sum to 1. 3. results and discussion 3.1 comparison of pahs concentrations between sample locations and pathways table 1: pahs concentration between soil samples location naphthalene acenaphthene fluorene pyrene anthracene benzo(a)anthracene ppm ppm ppm ppm ppm ppm l1s1 1.265 0.0543 0.0368 0.041 0.0325 0.0027 l1s2 1.245 0.0469 0.0376 0.026 0.071 0.0387 li s3 1.0502 0.0371 0.0048 0.0056 0.0037 0.0052 l2s1 1.342 0.0288 0.0236 0.012 0.064 0.048 l2s2 1.289 0.0385 0.0397 0.045 0.034 0.028 l2s3 1.05 0.0382 0.005 0.0082 0.017 0.0074 l3s1 1.258 0.0384 0.0397 0.024 0.062 0.061 l3s2 1.267 0.0369 0.0397 0.034 0.045 0.055 l3s3 1.056 0.0176 0.0065 0.0095 0.0068 0.0042 note: l1s1 – location a sample 1, l1s2 – location a sample 2, l1s3 location a sample 3 l2s1 – location b sample 1, l2s2 – location b sample 2, l2s3location b sample 3, l3s1 – location c sample 1, l3s2 – location c sample 2, l3s3location c sample 3.: where s1= top soil, s2 = sub-soil, s3= water. l3= control, l1= first site of pollution, l2= second site of pollution in table 1 and figs (1-3), the concentrations of various pahs, including naphthalene, acenaphthene, fluorene, pyrene, anthracene, and benzo(a)anthracene, measured in parts per million (ppm) is presented. naphthalene consistently showed the highest concentrations across all samples, while benzo(a)anthracene had the lowest concentrations naphthalene levels were highest in the topsoil at all locations, with location 1 (l1s1) at 1.265 ppm and location 2 (l2s1) at 1.342 ppm. these quantities indicate significant pollution, most likely owing to surface oil spills, whereas aquifer samples had the lowest naphthalene concentrations, with l1s3 at 1.0502 ppm. acenaphthene levels followed a similar trend, with the highest concentrations found in topsoil (l1s1: 0.0543 ppm) and a steady reduction from topsoil to an aquifer. fluorene levels varied, with the subsoil in location 2 having a higher concentration (0.0397 ppm) than the other strata, indicating a potential accumulating effect in this layer. the other pahs, pyrene, anthracene, and benzo(a)anthracene generally showed lower concentrations, though pyrene and benzo(a)anthracene were somewhat more prevalent in the subsoil. overall, the data indicate that the topsoil is the most contaminated layer for pahs, followed by the subsoil, with the aquifer displaying the least contamination. the data acquired from the study of pah concentrations in soil samples gives useful information about the behavior of these pollutants in various soil http://www.azojete.com.ng/ mailto:ijaolaoo@fuotuoke.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 717 layers. pah concentrations are higher in topsoil (s1) than in subsoil (s2) and aquifer (s3) layers, indicating that pahs are more likely to accumulate near the surface due to limited vertical mobility. this can be attributed to the hydrophobic nature of pahs, which often leads to their adsorption onto organic matter in the soil, particularly in the upper layers where organic content is higher, which agrees with (patel et al.,2020)that found that the pahs deposition is accelerated in the soil/sediments because of their higher hydrophobicity and low aqueous solubility, further, buttressed by the discovery of (jesus et al., 2020) that pahs tend to accumulate in the sediment due to higher hydrophobicity. this then account for the lower pah concentrations in the aquifer layer indicate that pah migration to groundwater may be limited, due to high filtration capacity of the soil, though some contamination is still present, which agrees with (chen et al., 2022). naphthalene, the lightest pah analyzed in this study, showed consistently higher concentrations across all samples, particularly in the topsoil. this also shows that the lighter the contaminants the higher the mobility, it then reveled the lighter pahs like naphthalene leach more easily compared to heavier pahs, explaining their greater prevalence in the samples. figure 1: comparison of pahs pollutant between the crude oil spills polluted area and control at the top-soil figure 2: comparison of pahs pollutant between the crude oil spills polluted area and control at the sub-soil figure 3: comparison of pahs pollutant between the crude oil spills polluted area and control at the aquifer http://www.azojete.com.ng/ mailto:ijaolaoo@fuotuoke.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 718 3.2 comparison analysis of pahs pathway within each sampled location with usepa and statistical deductions table 2: mean values of pahs concentration within each sampled locations compared with usepa standard and statistical inferences contaminants l1 l2 l3 usepa p-value (soils) p-value (water) naphthalene 1.187 1.227 1.194 0.0001 0.229335759 0.00059193 acenaphthene 0.046 0.0352 0.031 0.0001 0.196707245 0.371481776 fluorene 0.026 0.023 0.029 0.0002 0.427450803 0.002376112 pyrene 0.024 0.022 0.023 0.0002 0.969122843 0.118947763 anthracene 0.036 0.038 0.038 0.0002 0.984906863 0.080976903 benzo(a)anthracene 0.016 0.028 0.040 0.0002 0.358155023 0.141269761 table 2 shows the mean concentrations of each pahs considered within the pathway of each location in comparison to united state environmental protection agency (usepa) guidelines for pahs in groundwater. the monitored values were also compared using statistical inferences. from the table 2 all tested pahs in comparison with standards revealed multiple acceptable limit violations, naphthalene has the highest concentration levels of (1.187-1.227) ppm when compared to the others pahs compounds indicating potential petroleum-related contamination. acenaphthene, fluorene, and pyrene have relatively low concentration levels ranging from (0.046-0.031,0.029-0.023 and 0.022-0.024) ppm respectively suggesting minimal impact from these compounds, while anthracene and benzo(a)anthracene show varying concentration levels across sampling locations, indicating potential multiple contamination sources. the anova results in table 2 (p-value = 0.229335759, p-value > 0.05) confirm that significant differences exist in naphthalene concentrations between soil layers, with topsoil samples exhibiting the highest levels. for heavier pahs such as pyrene, anthracene, and benzo(a)anthracene, the concentrations were much lower across all samples, particularly in the aquifer layers. these pahs have lower solubility and higher affinity for adsorption onto soil particles, which explains their limited vertical migration. the relatively low concentrations of these compounds in the subsoil and aquifer indicate that they pose less risk of groundwater contamination compared to lighter pahs like naphthalene. also, the anova results for these compounds; pyrene (p-value = 0.969122843which is >0.05), anthracene (p-value = 0.984906863which is >0.05), and benzo(a)anthracene (p-value = 0.358155023which is > 0.05) showed a significant difference (p-value ≥ 0.05) between the samples, though their concentration indicating consistent low levels in water samples but higher values across the different soils layers as indicated in table 2. fluorene concentrations varied between samples, with the subsoil showing particularly high levels in location 2, the anova results for fluorene (p-value = 0.002376112 which is < 0.05) indicated significant differences between the samples, suggesting that fluorene concentrations vary notably across soil layers. the highest concentrations of acenaphthene were again found in the topsoil. however, the anova results indicated no significant differences between samples (p-value = 0.371481776, p-value ≥ 0.05), suggesting that while acenaphthene levels are elevated, the variation between layers is not statistically significant. the anova analysis indicated significant differences in contamination levels for several pahs across different locations, suggesting notable spatial variability in contamination. this finding means; the sources of contamination may be localized, with certain areas experiencing higher concentrations of specific pahs. in contrast, the differences between soil layers were less pronounced for most pahs, indicating that the depth of soil has a limited impact on the variation in pah concentrations. this suggests that while the topsoil is generally more contaminated, other factors, such as local environmental conditions or historical contamination events, may play a more significant role in influencing pah levels than soil depth alone. 3.3 leach pollution index and contamination assessment the leach pollution index (lpi) provides critical insight into the contamination potential of the soil to leach hazardous substances into groundwater. the lpi values of the samples for the three locations ranged from 81,199.25 to 83,374.10 as shown in table 3, with the highest value at location 1 and the lowest in location 3. this index reflects the potential risk of pah contaminants being leached from the soil into the aquifer and eventually affecting groundwater quality. this was achieved using the usepa standard values for groundwater quality. http://www.azojete.com.ng/ mailto:ijaolaoo@fuotuoke.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 719 table 3: leach pollution index location leach pollution index (lpi) a 83374.10 b 81460.87 c (control) 81199.25 to evaluate the significance of these lpi values, it is essential to compare them to standard threshold values established for soil contamination assessments. according to environmental standards, the acceptable lpi threshold for hazardous leachates is 7,500. any value above this indicates a potential risk for contaminant migration into groundwater sources (ogbozor et al., 2015). in this study, all recorded lpi values significantly exceed the standard threshold, with the lowest being 81,199.25 and the highest reaching 83,374.10. these values are higher than the standard, implying a severe contamination risk across all locations. the high lpi values suggest that the soil in the studied locations, particularly the topsoil and subsoil, has a high potential for contaminant migration, primarily driven by the presence of pahs. this poses a significant risk of groundwater pollution, especially in areas where crude oil spills have heavily impacted the environment. the highest lpi value at location 1 (83,374.10) suggests that this area has the greatest leaching potential, likely because of higher concentrations of pahs in the topsoil and subsoil that may be as a result to closer proximity to the spill site or other factors such as soil type and permeability. conversely, while location 3 has the lowest lpi (81,199.25), it still presents a considerable risk as the value remains far above the standard threshold. 3.4 implications for groundwater quality the presence of pahs in aquifer samples, even at lower amounts than in topsoil, raises concerns about groundwater quality. while the data demonstrate limited vertical migration, the presence of pahs in groundwater samples suggests that there is still a possibility of pah contamination in drinking water sources, which will definitely have negative effect on human health over time when consumed. this emphasizes the need for ongoing monitoring, and possibly remediation activities to prevent future contamination. 4. conclusion this study found considerable contamination by polycyclic aromatic hydrocarbons (pahs) the in the topsoil (s1) and moderate in the subsoil (s2) and aquifer layers (s3). naphthalene had the highest quantities, indicating mobility, whereas heavier pahs such as pyrene and anthracene had lower concentrations due to their low solubility and stronger affinity for soil. the leach pollution index confirmed significant pollution in all areas. despite the comparatively low pah concentrations in groundwater, there is a current concern that warrants additional investigation. acknowledgment the author wishes to thank ochonogor chukwuneku christian who collected the samples from ibelebril, articulated the results, and presented them for laboratory analysis at barr laboratories services, analytical research, and reference laboratory 24. niit road etegwe, yenagoa, bayelsa state. also, ogunlowo olusanjo proofread the manuscript. references ademiluyi ft., amadi sa. and amakama nj. 2009. adsorption and treatment of organic contaminants using activated carbon from waste nigerian bamboo. journal application science environment management.13(3):39-47 adeniyi, aa. 2018. heavy metal contamination of groundwater due to crude oil spillage. journal of environmental science and health, 53(1): 42-53. agency for toxic substances and disease registry (atsdr). 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vol.20(4):713-721. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: ijaolaoo@fuotuoke.edu.ng 721 olafadehan oa. and aribike ds. 2000. treatment of industrial wastewater effluent. journal of nigerian society of chemical engineers. 19:50-53 oluwadare, ad., sunday af. and kirk ts. 2017. assessment of pah contaminated land: implementing a riskbased approach. environmental technology & innovation. volume 8, 84-95 opololaoluwa, oi. and abimbola, ys. (2020). adsorption mechanism of paracetamol, salbutamol, chlorpheniramine maleate onto locally produced nigeria bamboo activated carbon. science & technology, 2020, 6(22): 93-106 osuji, lc. 2015. environmental pollution by crude oil. journal of environmental science and health, part b, 50(6), 419-428. patel, ab., shaikh, s., jain, kr., desai, c. and madamwar, d. 2020. polycyclic aromatic hydrocarbons: sources, toxicity, and remediation approaches. front microbiol. 5(11): 562813 sanda, by., bah, au. and ibrahim, a. 2022. involvement of the general public in the management of water pollution in johor bahru malaysia. arid zone journal of engineering, technology and environment 18(1):7996. smith, j. 2020. groundwater contamination by polycyclic aromatic hydrocarbons (pahs): a review. journal of environmental science and health, 55: 1-12. tsay, jj., tchou-wong, km., greenberg, ak. pass, h. and rom, wn. 2013. aryl hydrocarbon receptor and lung cancer, anticancer research, 33(4): 1247–1256. world health organization 2022. guidelines for drinking-water quality: fourth edition incorporating the first addendum. geneva: world health organization. world health organization. guidelines for drinking-water quality. world health organization 2018 guidelines on sanitation and health. geneva, world health organization (https://www.who.int/publications/i/item/9789241514705). world health organization 2018. guidelines for drinking-water quality: 4th edition. http://www.azojete.com.ng/ mailto:ijaolaoo@fuotuoke.edu.ng https://www.sciencedirect.com/journal/environmental-technology-and-innovation https://www.sciencedirect.com/journal/environmental-technology-and-innovation/vol/8/suppl/c https://www.who.int/publications​/i/item/9789241514705 corresponding author’s email address: hammajam@naub.edu.ng 794 arid zone journal of engineering, technology & environment original research article development and characterization of groundnut shell powder filled polylactic acid (pla) composites for sustainable engineering applications a. a. hammajam1,2*; h. maidawa1 and e. b. bwala1 1department of mechanical engineering, nigerian army university biu-.borno state, nigeria. 2department of mechanical engineering, university of maiduguri-borno state, nigeria. * corresponding author’s email: hammajam@naub.edu.ng, hammajam92@gmail.com article information abstract this paper explores the economic potential of using groundnut shell powder as a filler in biodegradable polylactic acid (pla) composites. groundnut shells, an abundant agricultural waste, are proposed as a low-cost reinforcement material to develop sustainable bioplastics. the investigation characterized and determined the mechanical properties of groundnut shell powder (gsp) filled pla thermoplastic composites. two different fiber sizes; 150 µm and 212µm were pulverized. the fiber loadings were 10 %, 20 %, and 30 % by weight. the gsp-pla composites were prepared by use of internal mixer, followed by compression molding process. tensile and flexural properties were tested using universal testing machine (utm). the tensile strength decreased from control sample (0 %) to 10 % by weight fiber loadings for all mesh sizes. in addition, the strength increased from 14.2 mpa and 15 mpa for 150 µm and 212 µm respectively, at a loading of 20%. the modulus increased from 712.9gpa for a control sample (0%) loading to 2344.9gpa at 30% loading for 150 µm. furthermore, it increased to 1576 gpa for 212 µm. the tensile percentage elongation reduced at 10% loading compared to 0% control sample. flexural strength and modulus increased for both mesh sizes at all the fiber loadings. however, at 30% fiber loadings, the flexural strength and modulus decreased slightly for 212µm size composites. the hardness of the composites increased for both mesh sizes at all the fiber loadings. it is presumed that the tensile properties performed good at 20% loading as deduced from the findings. while flexural properties increased for all loadings. the study identifies key application areas including packaging, construction, agriculture, and consumer products, highlighting their relevance in supporting eco-friendly startups and rural industries. the innovation aligns with global sustainable development goals (sdgs) number 7 and 8 and offers promising opportunities for green entrepreneurship, especially in agrarian economies. received: 3rd july 2025 revised: 8th august 2025 accepted: 10th august 2025 keywords: groundnut shells composites polylactic acid mechanical properties © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the growing emphasis on environmental sustainability and circular economy principles has catalyzed the development of bio-based and biodegradable polymer composites. biocomposite, polylactic‐rich biomass material has emerged as promising reinforcement and offers versatile applications and potential benefits in various fields, especially in natural fiber composites (ahmed et al., 2022; kolo et al., 2022). the use of natural fibers for composite material manufacturing have received great attention because of their sustainability and renewability. research and advancement on natural fiber composites are continually rising and their function is growing into novel fields of usage. the modern age of technology presents an abundant of bio-based composites. this gives better chance for environmentally friendly, lower energy utilization, insubstantial weight, lagging and sound absorption behaviors, reduction in volatile organic radiation, and decreased reliance on synthetic. advancement of workable resources as the substitute for synthetic materials are being investigated to reduce the over-reliance on oil or petroleum (mohammed et al., 2022). azojete september 2025. vol.21(3):794-803 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/010 www.azojete.com.ng mailto:hammajam@naub.edu.ng mailto:hammajam@naub.edu.ng mailto:hammajam92@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 795 on the other hand, agro waste cereals such as rice, barley, maize, sorghum, wheat etc contribute significantly as reinforcements or fillers in plastic composites productions in recent time (hammajam et al., 2019). the importance of rice husk in composite was further discussed by simone et al. (2022) which indicate the description of lignocellullosic rice husk filled with polyethylene composites. for example, steam explosion was employed for obtaining sweet sorghum fibers to be use as reinforcing agent in poly lactic acid base composites. cascade mixer was employed for barley husk polypropylene composite by andrzej et al. (2010) whereas ricardo et al. (2023) uses thermogravimetric analysis of composite obtained from sintering of rice husk scrap tire mixture; and ismail et al. (2003) employed effect of mixing sequence in the preparation of white rice husk ash filled polypropylene/ethylene propylene monomer composites. pla is thermoplastic polymer with high strength and modulus that can be derived from annually renewable resources. this makes pla very vital environmentally friendly biocomposites matrix. it can be degraded by simple hydrolysis of the ester bond and does not demand the presence of enzymes to catalyse (ortega-leyva, 2022). it also has melted and glass transition temperatures of 175 oc and 55 oc respectively. these attributes make it suitable candidate for most degradable natural fibers as environment friendly materials. ahmed et al. (2022) reported on the chemical modifier to improve properties of coconut shell powder (csp) filled pla biocomposites. their study depicts the effects of filler content on mechanical, thermal and morphology properties as evaluated. groundnut (arachis hypogaea) also known as peanut or legume is grown in several countries as a cash crop. the top three groundnut producing nations are china, india, and nigeria with an annual production of 16,685,915, 6,857,000, and 3,028,571 metric tons, respectively (mohammed et.al., 2021; maidawa and dukku, 2022). groundnut shell (gs), which is an agro-waste with little or no commercial value, accounts for 20% of the total weight of the pod. thus, a large amount of groundnut shells is generated globally, paving way for more studies to search for other viable areas of applications. the shells, a by-product of the processing are an abundant agricultural waste material that decomposes slowly in nature (adhikari et al., 2019; zheng et al., 2013). despite their potential, gs are often discarded, leading to environmental harm through burning or disposal in landfills. however, these shells contain valuable bioactive compounds and functional ingredients that can benefit various industries, including food, feed, paper, and bioenergy (trivedi, et al. 2019). to achieve zero waste and unlock the full potential of groundnut shells, innovative technologies and applications are necessary to transform this waste into a valuable resource (rosa et al., 2021; matumba et al., 2017; venkatarajan and athijayamani, 2020). researchers have explored various ways to utilize gs over the years. however, little fraction was successfully incorporated into animal feed, particularly for cattle, while others have investigated their potential as a dietary fiber source for humans. additionally, studies have examined the use in pulp production, bioethanol production etc. (yakub et al., 2016). particle board manufacturing, mulch, and activated charcoal were also investigated (trivedi, et al., 2019). these efforts aim to find valuable applications for gs. the reduction in waste and unlocking their economic potential are key to engineering advancement. other applications of gs include its use in composting wet materials, wastewater treatment, plastic, wardrobes, insulation board, metal casting, and a medium for pesticides as well as activated carbon (berthet et al., 2015). this study investigates the potential of groundnut shell-filled polylactic acid (pla) composites as a sustainable alternative to conventional petroleum-based materials. groundnut shells were processed and incorporated as lignocellulosic fillers into a pla matrix to develop lightweight, eco-friendly composites. 2. materials and method 2.1 sample collection and preparation groundnut shells were collected from farm after milling at kaleri, bauchi state, northeastern nigeria.4 kg of the materials were collected one month after the milling on the farm site. the groundnuts husks were collected and packaged in a bag for this research. the husks were initially dried at 105oc for 24 hours in an industrial oven to remove excess moisture according to the astm d4442. the pla grade 2002d was obtained from the nature works llc (usa) ingeotm grade and was supplied in the form of granules. the properties of the matrix were: density of 1.25g/cm3; glass transition temperature (tg) of 59oc; melting point of 152oc and melt flow index (mfi) of 30.3g/10 min. groundnut shell were pulverized into two different mesh sizes of 150 µm and 212 µm using fritsch pulverisette p15/p16 mill. the pulverized samples were subjected to 105°c temperature for 24hrs in an industrial oven in order to remove moisture before blending with the polylactic acid granules. plate 1 depict mesh sizes of gsp. http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 796 plate 1(a and b) mesh sizes of gsp 2.3 characterization 2.3.1 chemical composition of the groundnut shells these analyses were carried out in the agriculture chemical analysis laboratory (d 10), food and agriculture analysis laboratory programme technical services centre, nigeria. the analyses were performed to evaluate the cellulose, hemicellulose, lignin, and other compounds in the fiber that are mainly responsible for fiber matrix compatibility in composites. the neutral detergent fiber (ndf) analysis (d10/m1 and d10/m10 in house-method) was used to determine the cellulose content of the fiber. the acid detergent fiber (adf) analysis (d10/m12 and d10/m5 in-house-method) was employed to determine the hemicelluloses content of the fiber. meanwhile, the acid detergent lignin (adl) analysis (d10/m13 and d10/m7 in-house-method) was used to determine the lignin content of the fiber. 2.3.2 composites fabrications groundnut shell fibers and pla were compounded by mixing, followed by compression molding process. internal mixer (brabender gmbh) was used in the blending process at processing temperature of 170°c, for a period of 10min, and rotating speed of 50rpm. this method was adopted by collins and ghodke (2018). labquip scientific 40-ton compression molding machine was used in hot pressing the test specimens. 15 cm ×15 cm × 0.3cm steel mold was used for the compression process. the samples were pre–heated for 3min at 170 °c. venting time was set to 3min and final press temperature of 170°c for 3min. finally, the samples were cold pressed for 5min at room temperature. gsp–pla composites were cut from the two sample sizes with 0%, 10%, 20% and 30% weight of fiber loading. 2.3.3 composite formulation rule of mixture (rom) this process involves the rules guiding the mixing of fiber and matrix in composite formulations as shown in equation 1 and 2. in this study, the rom was based on the capacity of the internal mixer (brabender). the weight of the fiber and matrix was governed by the rule (hammajam et al. 2019) rom; wf + wm = 1 1 wmf + whdpe = mcw 2 where wf is weight of fiber, wm is weight of matrix, wmf is weight of groundnut shell powder, wpla is weight of polylactic acid, mcw is mixer capacity. table 1 shows the compression conditions for the composite formulation. table1: formulation of gsp-pla sample name gsp (wt %) pla (wt %) neat pla 0 0 gsppla 10, 20, 30 90, 80, 70 (a)150 µm (b)212 http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 797 2.3.4 mechanical properties the tensile properties were tested according to astm d638 by using instron 3365 machine. tensile testing was carried out at 5mm/min with load cell of 5kn. while the flexural properties were tested by using the same machine that was used for the tensile test at a crosshead speed of 3 mm/min with a load cell of 5 kn and a span of 50 mm. hardness test is extensively used to characterize a certain material and to identify if it is appropriate for its intended purpose. hardness test is the measure of its resistance to the indentation due to compression force caused by sharp tools. durometer hardness test is carried out based on the astm: d4762 identify the hardness of the natural fiber composite material. a similar method and process was reported by hammajam, et al. (2019) and sapuan and bachtiar (2012). plate 2 shows the mechanical properties test specimens. while figures 1 and 2 shows flexural and tensile test specimen as per astm d790; d638 respectively. plate 2: mechanical properties test specimens figure 1: flexural test specimen (astm. d790) figure 2: tensile test specimen as per astm d638 2.3.5 microstructural examinations the fiber-matrix dispersion analyses were carried out to understand the extent of fracture surface when the composites were subjected to tensile testing. the fiber dispersions were inspected using scanning electron microscope (sem). this process was done by using hitachi s‒3400 n model at 20.0 kv. 3. results and discussion 3.1 chemical composition analysis of the gsp the chemical compositions of gsp are shown in table 2. it was observed that the cellulose content of the gsp was 43.2%. this value was different from the 32.7% and 33.2% values reported by patel, (2012) and http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 798 petchwattana and covavisaruch, (2013) respectively. it was also observed that the shell’s hemicelluloses and lignin contents were 24.17% and 16.19%, respectively. whereas it was also revealed that the protein and fat contents were 7.63% and 4.31%. other constituents of the fiber; pectin, waxy contributed to the remaining percentages (%) of the gsp. the general observation in natural fibers was that the expected moisture uptake in fiber takes place mainly by hemicellulose, starch, lignin and surface of cellulose content. lignocellulosic cereal fiber contains fat and protein which are covalently bonded together, and act as a fiber coating. hence, there are slight variations in the composition of cereal byproducts, as has been reported by andrzej et al. (2010). table 2: chemical composition of the groundnut shells composition cellulose hemicellulose lignin protein fat % content 43.2 24.17 16.19 7.63 4.31 3.2 tensile strength of gsp-pla composite figure 3. depicts the mean values of tensile strengths of gsp‒pla composites with different fiber loading. in composites development, there is a complicated interaction of the dynamics of the basic stages such as matrix, fiber and interfacial zone between the fiber and matrix as reported by ridzuan, et al. (2016). the increase at 10 % by weight of gsp causes slight decrease in the tensile strength of gsp‒pla composites when compare to control sample (0 % pla. it was observed that composites with 20 % fiber loadings appreciated in strength of 14.2 mpa and 15 mpa for 150 µm and 212 µm respectively. thus, it shows slight decrease below 0 % pla with 25.9mpa. furthermore, it can be said that fiber size has effect on the tensile strength of gsp-pla composites. this shows similar finding in kanayo, et al. (2018). hence the decrease in the tensile strength is due to poor gsp‒pla interaction as a result of opposing separations of the gsp and pla matrix. also, in figure 1, increase loading up to 30 % has slightly decreased the tensile strength of the composite for both the fiber sizes. this could be due to weak dispersion and weak interface in the pla matrix resulting in poor bonding between gsp and pla. figure 3: effect of fiber loading on the tensile strength of gsp-pla composite 3.3 tensile modulus of gsp-pla composite from figure 3, there was an increase in the tensile modulus of gsp‒pla composites as fiber loadings increased. it can be observed that the maximum value of the tensile modulus was 712 gpa at 10 % loading for 150 µm. it was drop to 472 gpa at the loading for 212 µm. at 20% loading, the modulus increases for 212 µm and decrease for 150 µm. but at 30 % loadings, 150 µm continue to decrease while 212 µm appreciated. thus, it was still appropriate to argue that increasing gsp up to 30 % in pla increases the rigidity of the composites. it showed the level of adhesion between gsp-pla hardly affect the tensile modulus significantly. the tensile moduli of the composites are enlarged by increasing the fiber loadings. the reason is the fact that lignocellulosic fibers possess greater modulus when compared to polymer matrix. also, because modulus is processes that involve so small strain values and small stress may be produced with application of little value of elongation (mohammed, et al. 2021). thus, it was expected that there will be further improvement of modulus of the composites when going above 30% fiber loadings for 212 µm. 35 30 25 20 15 10 150 um 212 um 5 0 0 10 20 30 gs fiber loadings (%) te n si le s tr en gt h (m pa ) http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 799 figure 4: effect of fiber loading on the tensile modulus of gsp-pla composite 3.4 percentage elongation of gsp-pla composite it was observed from figure 5 that the tensile elongation at the break of the composites was grossly decreased. this is the result of thermoplastic composites having a rigidity tendency because of the increase in fiber loading. usually, the reduced tensile elongation at break values is as a result of increased modulus. similar findings were reported by mohammed et al. (2021). it is possible that the addition of fibers which has brittle attribute decrease the elongation at break. figure 5: percentage elongation of gsp-pla composite 3.5 flexural strength of gsh-pla composite figure 6 depict the effects of fiber loadings on the flexural properties of the gsp-pla composites. the flexural strength of the gsp-pla composites increased for the 10% and 20% fiber loadings for 150 µm but decreased at the 20% fiber loadings for 212 µm. there was an increase as fiber loadings reached 30% for 150 µm and dropped slightly for 212 µm when compared to pure pla. it was observed that the flexural strength dropped 11.9% at 20% fiber loading for 150 µm. the findings show an increase in strength at 10% and 20% fiber loadings for pla composites. therefore, the fiber did not reduce completely the ability of fibers and matrix to interact. the increased adhesions create better fiber and matrix interactions which allow the stress to be transferred from the matrix to fiber and translates into improved flexurability. similar findings were reported by yakub et al. (2017). the increase in flexural strength became highly prominent when the fiber loading did not go beyond 10% and 20%. furthermore, this is only likely when there was a better stress transfer from matrix to fiber via a good interface adhesion. 800 700 600 500 400 300 200 100 0 150 um 212 um 0 10 20 30 gs fiber loadings (%) 350 300 250 200 150 150 um 100 212 um 50 0 -50 0 10 20 30 gs fiber loadings (%) t e n s ile s tr e n g th ( m p a ) te n si le m o d u lu s (g pa ) http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 800 figure 6: flexural strength of gsp-pla composite 3.6 flexural modulus of gsp-pla composite in most cases, the normal trend for flexural modulus is to increase with increasing fiber loading. these characteristics were indeed observed in figure 7. this could be attributed to the contribution made by fibers to impart their own property to the composite. the findings reveal a steady increase in the modulus values as the fiber loading is increased from 712.9gpa for pure pla to 2344.9 gpa at 30% loading in 150 µm and 1576 gpa for 212 µm. it was revealed that there was around 45% improvement in flexural modulus up to 30% fiber loading from neat pla and 44.7% from 10% fiber loading for the pla composites. these phenomena presume that above 30% fiber loading, the composites stiffness will decrease as the fiber loading increases. therefore, the increase in the modulus of these composites was due to the higher initial modulus of the fibers acting at the main building block of composites and improve interfacial bond between the fibers and matrices figure 7: flexural modulus of gsp-pla composite 3.7 result of hardness test of gsp-pla composite hardness of a material is the measurement of its resistance to dentation due to a compressive force caused by a sharp object. the results of hardness test are shown figure 8. that hardness of gsp-pla there is increased in hardness throughout the loadings. although, at 20% loading, is slightly decreased. it also revealed that angle orientation has play much role in the hardness property of the composite. this is because as the fibre loadings increases, the resistance to penetration is more due to the availability of fibres acting as rigid medium. 50 45 40 35 30 25 20 15 10 5 0 150 um 212 um 0 10 20 30 gs fiber loadings (%) 3000 2500 2000 1500 1000 150 um 212 um 500 0 0 10 20 30 gs fiber loadings (%) t e n s ile m o d u lu s ( g p a ) t e n s ile s tr e n g th ( m p a ) http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 801 a b agglomeratio fiber pull-out 100 µm 100 µm a b agglomeratio improved adhesion void 100 µm 100 µm figure 8: hardness test of gsp-pla composite 3.8 microstructures observation of gsp-pla composite sem images of fractured surface of gsp‒pla composites were depicted in plates 3(a and b). the image of different fiber loading composites shows that lower gsp loadings indicates non‒homogeneous dispersion patterns. this causes fiber pull‒out and makes the fiber to undergo accumulation. hence, these lead to reduction in the tensile strength of the composites mostly at lower fiber loadings. similar findings were reported by fogorasi, and barbu, (2017). however, at 20 % and 30 % loadings, there were better dispersion of gsp‒pla formation with reduced fiber pull out and breakage. this is the main reason for improvement of tensile strength at these loadings for smaller fiber sizes. plate 3a: sem micrographs 150 µm of ghp-pla composites plate 3b: sem micrographs 212 µm of ghp-pla composites 100 80 60 40 150 um 20 212 um 0 0 10 20 30 gs fiber loadings (%) a n g le o ri e n ta io n s (o 0 ) http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 802 4. conclusion this study had shown that fiber loading significantly influences its mechanical properties. it was observed that composites with 20 % fiber loadings appreciated in tensile strength of 14.2 mpa and 15 mpa for 150 µm and 212 µm respectively. interestingly, it was observed that there was a steady increase in the tensile modulus values as the fiber loading is increased from 712.9gpa for pure pla to 2344.9gpa at 30% loading in 150 µm and 1576 gpa for 212 µm. the optimum performance strength for both composites type was at 20% filler loading and the modulus was at 30% filler loading gsp-pla composite. consequently, the flexural strength of the gsp-pla composites increased for the 10% and 20% fiber loadings for 150 µm but decreased at the 20% fiber loadings for 212 µm. it was revealed that there was around 45% improvement in flexural modulus up to 30% fiber loading from neat pla and 44.7% from 10% fiber loading for the pla composites. thus, from these findings, the developed composites possess attributes that suit some engineering applications such as automobile interiors and household utensils were high impact are less needed. acknowledgement the authors wish to thank tetfund and nigerian army university biu for providing the research grant (ibr no. 001; 2025) and enabling environment for this study. references adhikari, b., dhungana, sk., ali, mw., adhikari, a., kim, id. and shin, dh. 2019. antioxidant activities, polyphenol, flavonoid, and amino acid contents in peanut shell. journal of the saudi society of agricultural sciences, 18(4): 437-442. ahmed, mb., el-jummah am. and hammajam, aa. 2022. development and evaluation of the mechanical properties of coconut fiber reinforced low density polyethylene composite. open journal of composites materials, 12(3): 83-97. andrzej, k., bledzki ak, abdullah am and jürgen v. 2010. barley husk and coconut shell reinforced polypropylene composites: the effect of fibre physical, chemical and surface properties. composites science and technology 70: 840–846. berthet ma., angellier-coussy, h. and machado d. 2015. exploring the potentialities of using lignocellulosic fibres derived from three food by-products as constituents of biocomposites for food packaging. industrial crops product; 69: 110–122. collins, s. and ghodke p. 2018. kinetic parameter evaluation of groundnut shell pyrolysis through use of thermogravimetric analysis. journal of environmental chemical engineering, 6(4): 4736–4742. fogorasi, ms. and barbu, i. 2017. the potential of natural fibres for automotive sector. iop conf. series: materials science and engineering, 252: 12-24. hammajam, aa., el-jummah, am., ismarrubie, zn. 2019. the green composites: millet husk fiber (mhf) filled poly lactic acid (pla) and degradability effects on environment. open journal of composites materials, 9:300-311. ismail, h., mohamad, z., and bakar, aa. 2003. comparative study on processing, mechanical properties, thermo-oxidative aging, water absorption, and morphology of rice husk powder and silica filler in polystyrene/styrene butadiene rubber blends. journal of polymer plastics technology and engineering, 42(1): 81-103. kanayo k., oluwatosin m. and awe aa. 2018. microstructure, mechanical and fracture properties of groundnut shell ash and silicon carbide dispersion strengthened aluminium matrix composites. journal of king saudi university engineering science; 30(1): 96–103. kolo, lam., hammajam, aa., and zaka am. 2024. mechanical characterization of camel’s foot (piliostigma reticulatum) fiber reinforced low density polyethylene (ldpe) composite. nigerian research journal of engineering and environmental sciences, 9(1): 397-402. http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 794-803. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: hammajam@naub.edu.ng 803 maidawa, hmm. and dukku, m. 2022. dynamic mechanical analysis and morphology of desert date particles reinforced polymer composites for vehicular dashboard. international journal of advances in engineering and management (ijaem), 4(6): 2590-2596. matumba, l., singano, l. and tran, b, 2018. managing aflatoxin in smallholder groundnut production in southern africa: paired comparison of the windrow and mandela cock techniques. industrial crops product. 112: 18–23. mohammed, au., ibrahim, m. and abdulhafiz, ou. 2021. characterization of groundnut shell powder as a potentioal reinforcent for biocomposites. journal of polmer from renewable energy.1-15 ortega-leyva, mn. 2022. composites from plastic and wood: what do have to know? 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and osvaldo, md. 2023. a preliminary study on the preparation of wood plastic composites from urban wastes generated in merida, mexico with potential applications as building materials. . journal of waste management and research, 28(9): 838-847. sapuan, sm. and bachtiar, d. 2012. mechanical properties of sugar palm fibre reinforced high impact polystyrene composites. procedia chemistry, 4:101-106. sapuan, sm., and mansor, mr. 2014. concurrent engineering approach in the development of composite products: a review. materials & design, 58: 161-167. simone, m., rosa, l., evelise, fs., carlos, af., and sonia mbn. 2022. studies on the properties of rice husk filled polypropylene compositeseffect of maleate polypropylene. journal of material science, 12(3): 333-338. trivedi, ns., kharkar, ra. and mandavgane sa. 2019. 2,4-dichlorophenoxyacetic acid adsorption on adsorbent prepared from groundnut shell: effect of preparation conditions on equilibrium adsorption capacity. arab journal of chemistry, 12(8): 4541–4549. venkatarajan, s. and athijayamani a. 2020. an overview of natural cellulose fiber reinforced polymer composites. materials today proc., 9: 1–5. yakub, i., abdalla, y. and musa, m. 2016. valorization of bambara groundnut shell via intermediate pyrolysis: products distribution and characterization. journal of clean product, 139: 717–728. yakub, i., abdalla, y. and nga j. 2017. recovery of clean energy precursors from bambara groundnut waste via pyrolysis: kinetics, products distribution and optimisation using response surface methodology. journal clean product, 164: 1430–1445. zheng, w., phoungthong, k., lü, f., shao, lm. and he, pj. 2013. evaluation of a classification method for biodegradable solid wastes using anaerobic degradation parameters. waste management, 33(12): 2632-2640. http://www.azojete.com.ng/ mailto:hammajam@naub.edu.ng corresponding author’s email address: bukarkadai2@gmail.com 804 arid zone journal of engineering, technology & environment original research article assessment of the level of quality control of cement and sandcrete block materials available in maiduguri metropolis abba, m. a1. kadai, b1. garga a. b1., musa a. m2., and hassan, m3. 1department of civil and water resources engineering, university of maiduguri, borno state, nigeria 2department of building, university of maiduguri, borno state, nigeria 3department of civil engineering, federal polytechnic damaturu, yobe state, nigeria *corresponding author’s email: bukarkadai2@gmail.com article information abstract variations in material properties, such as strength or durability, material defects and substandard materials can affect the structure’s performance. this study assesses the level of quality control of building materials (cement, sand and blocks) available in maiduguri metropolis. generally, it included the survey and collection of data of the existing supply markets, samples collection, laboratory tests, and analyses of results were conducted. observation made from the survey showed that the price of blocks 150mm and 225mm thick range from 450 500 naira and 550 650 naira respectively. the particle size distribution of the sand sample used in the sand combination shows that the sand fell mostly in zone 2 except one which fell in zone 3 in accordance with federal ministry of works and housing design manual (fmwh). the average dry density of the investigated sandcrete blocks ranged from 1777.10kg/m3 2098.67kg/m3. the average compressive strength of the 150 mm thick blocks ranged between 0.12 0.45n/mm2. the maximum value 0.45n/mm2 recorded is less than 85% of the recommended minimum strength. the findings on the hydration properties of cement are within the bs 449 standard. the results show that the quality control of the building materials in maiduguri metropolis is generally inadequate, with many suppliers and contractors are unaware or failing to adhere to standard specifications and regulations. received: 6th july 2025 revised: 31st august 2025 accepted: 1st september 2025 keywords: quality control building materials regulatory frameworks © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction stakeholders in the building industry require a coordinated approach to building material quality and testing due to its importance in risk management (aib, 2013). in nigeria, the construction industry is faced with challenges that hamper the standard of construction which often revolve around quality of materials and workmanship (bamisile, 2004, adenike, 2006, anigbogu and anunike 2014). however, specification standards and building regulations which are drivers of good construction standard are diffused with many challenges (grema, 2006) the use of inappropriate materials is a reason for unsatisfactory quality in the building industry (anigbogu and anunike, 2014). laboratory and field tests are not carried out by construction supervisors on raw materials and products; this is why inappropriate materials find their way to the sites. according to opoko et al., (2014), the penetration and proliferation of substandard and inappropriate materials into the building sites are linked to the lack of holistic quality management systems amongst stakeholders. the standard of materials used in building contribute largely to the quality of infrastructure made (sitota et al., 2021). but according to (alemika, 2015) poor quality of materials is one of the reasons for more than 50% of building collapses in nigeria. ayodeji (2011) noted that although regulatory bodies and standards organizations in nigeria’s building industry have implemented various measures, the overall standard within the industry still does not reflect these efforts. the adherence of manufacturers and suppliers to standards and regulations as regards the quality of materials supplied needs to be ascertained (ambrose et al., 2019). azojete september 2025. vol.21(3):804-810 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/011 www.azojete.com.ng mailto:bukarkadai2@gmail.com mailto:bukarkadai2@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 804-810. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bukarkadai2@gmail.com 805 zeb et al., (2015), linda and synek (2019), and zulaijarmai et al., (2021) cited that the high occurrence of building failure and collapse is mainly contributed to by the quality of materials used. thus, quality control is a vital part of material management, as materials make up a substantial portion of the total project cost. it is therefore pertinent to investigate and improve the level of quality control on building materials. failure to investigate the quality of materials will certainly continue to result in building collapse (ayodeji, 2011). therefore, this study aimed to assess the level of quality control of building materials made available by suppliers and manufacturers to construction sites in maiduguri. this would serve to show the level of quality of building materials from suppliers, considering the attention it has garnered from regulatory agencies, standard organizations, scholars, contractors, and clients. 2. methodology the methodology of this study generally included the survey of the existing supply markets, samples collection, laboratory tests, and analyses of results. the samples collections and laboratory tests were done in accordance with the specifying british and nigerian standards (bs 812 1996, bs 4449 – 1997, son 1997 and nis 444-1, 2003) and analysed with respect to these specifications. 2.1 materials and procedure the materials used in the experiment include cement, sand, and sandcrete hollow blocks, while the apparatus used are the crushing machine, oven, set of sieves, measuring tape and weighing balance. sieve analysis test to determine the particle size distribution of the sands was conducted in line with (bs 812-103. 1:1985) and (son, 2004). 2.2 survey and sample collection reconnaissance survey vis-a-vis physical inspection and oral interview was conducted across the ten wards in maiduguri metropolis, to locate the available block industries, cement, and their modes of operation. from the survey done, the study area was divided into ten smaller units, and one block industry was selected per unit: making a total of ten sample block industries. the block industries produce only 450×150×225 (6ʺ) and 450×225×225 (9ʺ) sizes of block. six blocks’ samples were taken randomly from the batch to ensure representativeness of each of the ten selected block industries. blocks are made from a homogeneous material with minimal variability. hence, six samples chosen at random might be sufficient to capture the material's properties. three pieces each of 450×150×225 (6ʺ) and 450×225×225 (9ʺ) sizes of block were obtained, making a total of 60 block samples. the block strength is assessed by measuring the crushing strength of the sample as calculated using equation 1. cs = 𝐿𝑚𝑎𝑥 𝐴𝑐 1 where: cs = compressive strength (n/mm2), lmax = maximum load (n), and ac = contact cross sectional area (mm2). 2.3 survey of cement and procedure the cements were obtained from major distributors in maiduguri. the two major brands of cement sold in maiduguri, which are ashaka and dangote, were used for the study, and were coded as c1 and c2. the brand names of cement have 3x, master block, 32.5n/mm², 42.5n/mm². 3. results and discussions ten industries were selected from major wards in maiduguri and the summary of the information collected are shown in table 1. however, the general observation made from the survey showed that the price of blocks ranged from 450 to 500 naira for 150mm, and 550 to 650 naira for 225mm. cost of production, demand, supply and other economic factors are responsible for the variations in price. raheem et al., 2012) estimated that the cost of a piece of 225mm sandcrete hollow block of mix ratio of 1:6 would be 675 naira. it can thus be deduced according to (sule, 2016) that blocks are produced to meet market demand as against required quality. http://www.azojete.com.ng/ mailto:bukarkadai2@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 804-810. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bukarkadai2@gmail.com 806 table 1: summary of surveyed information from block industries industry/location size of block price per block in naira curing period (days)/method source of sand brand of cement q/bulumkutu 225 550 3/sprinkling river/outlay dangote 3x (42.5n) 150 450 3/sprinkling river/outlay dangote 3x (42.5n) r/abuja talaka 225 600 3/sprinkling river/outlay dangote 3x (42.5n) 150 500 3/sprinkling river/outlay dangote 3x (42.5n) s/damboa road 225 650 3/sprinkling river/outlay dangote 3x (42.5n) 150 550 3/sprinkling river/outlay dangote 3x (42.5n) t/polo road 225 550 3/sprinkling river/outlay dangote 3x (42.5n) 150 450 3/sprinkling river/outlay dangote 3x (42.5n) u/lagos street 225 650 3/sprinkling river/outlay dangote 3x (42.5n) 150 550 3/sprinkling river/outlay dangote 3x (42.5n) v/baga road 225 550 3/sprinkling river/outlay dangote 3x (42.5n) 150 450 3/sprinkling river/outlay dangote 3x (42.5n) w/ruwan zafi 225 600 3/sprinkling river/outlay dangote 3x (42.5n) 150 500 3/sprinkling river/outlay dangote 3x (42.5n) x/dalori 225 550 3/sprinkling river/outlay dangote 3x (42.5n) 150 450 3/sprinkling river/outlay dangote 3x (42.5n) y/mairi kuwait 225 650 3/sprinkling river/outlay dangote 3x (42.5n) 150 550 3/sprinkling river/outlay dangote 3x (42.5n) z/fori 225 650 3/sprinkling river/outlay dangote 3x (42.5n) 150 550 3/sprinkling river/outlay dangote 3x (42.5n) 3.1 particle size distribution of sand the particle size distribution of the sands used in the block production was obtained individually from each industry. the sieve analysis of the sands, results as mixed for the sample production is summarised in figure 1. most of the grading values of the sharp sands were in zone 2 classification, except for industry u which fell in zone 3. this implies that the sand from industry u was finer than those of the other industries. however, the samples implied that the sands could singly be used satisfactorily to produce strong blocks. workability is influenced by multiple factors including water-cement ratio and aggregate grading. figure 1: particle size distribution of sands 0 20 40 60 80 100 120 0.1 1 10 c o m m u la ti ve p e rc e n ta ge p as si n g (% ) sieve size (mm) industry q industry r industry s industry t industry u industry v industry w industry x industry y industry z http://www.azojete.com.ng/ mailto:bukarkadai2@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 804-810. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bukarkadai2@gmail.com 807 3.2 dry density and dry compressive strength the computed values of the densities of the sampled sandcrete blocks are summarised in table 2. son, (2004) specified a minimum density of 1500kg/m3 for sandcrete hollow blocks. as seen from the table, the average dry density of the investigated sandcrete blocks ranged from 1777.10kg/m3 to 2098.67kg/m3. when compared to the specified minimum density, the samples’ densities ranged from 18% to 40% higher. this indicates that the samples conformed to the required standards. however, few individual samples representing less than 2% of the sampled blocks fell below the minimum density by 0.62%. while the compressive strength analyses of the sandcrete block samples are shown in table 3. and 4, respectively. from table 3, the average compressive strength of the sampled 150mm blocks ranged from 0.12 to 0.45n/mm2 which is less than 85% of the recommended minimum strength of 2.5nmm2. this steep deviation shows that it cannot be used for type b non-load bearing blocks; even the highest recorded value of 0.61n/mm2 is still very much below standard. also, the coefficient of variation higher than 20% was recorded in 60% of the industries. most codes of practice for concrete specify a coefficient of variation of 20% and below. whereas, from table 4, the average compressive strength of the sampled 225mm ranged from 0.03 to 0.66n/mm2 which is less than 81% of the recommended minimum strength of 3.45n/mm2. this steep deviation shows that it cannot be used for type a load bearing blocks and type b non-load bearing blocks; even the highest recorded value of 0.81n/mm2 is still very much below standard. also, the coefficient of variance higher than 20% was recorded in 70% of the industries. most codes of practice for concrete specify a coefficient of variation of 20% and below. the implications of this would lead to unsafe and project failure. table 2: densities of the sandcrete block samples industry sample (mm) average density (kg/m3) recommended density (kg/m3) difference (%) q 150 2040.08 1500 36 225 2068.61 1500 37.91 r 150 2050.99 1500 36.72 225 2098.67 1500 39.91 s 150 1849.94 1500 23.33 225 2007.73 1500 33.85 t 150 1904.82 1500 26.99 225 2074.02 1500 38.27 u 150 1833.05 1500 22.20 225 2050.53 1500 36.70 v 150 1790.86 1500 19.39 225 2028.39 1500 35.23 w 150 1839.46 1500 22.63 225 1962.55 1500 30.84 x 150 1777.1 1500 18.47 225 2001.45 1500 33.43 y 150 1888.08 1500 25.87 225 1927.43 1500 28.50 z 150 1889.71 1500 25.98 225 1823.26 1500 21.55 the compressive strength of 225mm blocks varied significantly across industries, with industry z achieving the highest average compressive strength of 0.66 n/mm2 with a covariance of 23%, while industry t recorded the lowest average compressive strength 0.25n/mm2 with a covariance of 24%. notably, industry z used the lowest mix ration of 1:8, which may have contributed to its higher compressive strength, whereas other industries used higher mix ratios ranging from 1:9 to 1:11, potentially resulting in lower compressive strengths. the results suggest that the mix ratio plays a significantly role in determining compressive strength, with lower mix ratios (more cement) tend to produce blocks with higher strengths. however, the covariance values indicate variability ins block production, impacting reliability. the findings highlight the importance of optimizing mix ratios and quality control measures to produce sandcrete blocks with consistent and satisfactory compressive strengths http://www.azojete.com.ng/ mailto:bukarkadai2@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 804-810. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bukarkadai2@gmail.com 808 table 3: compressive strength results for 150mm sandcrete block samples industry average strength (n/mm2) standard deviation coefficient of variation (%) q 0.45 0.10 23 r 0.12 0 0 s 0.35 0.19 54 t 0.20 0.06 29 u 0.38 0.17 45 v 0.17 0.03 19 w 0.02 0.02 141 x 0.08 0.08 101 y 0.12 0 0 z 0.32 0.06 18 table 4: compressive strength analyses for 225mm sandcrete block samples industry average strength (n/mm2) standard deviation coefficient of variation (%) q 0.63 0.21 33 r 0.50 0.03 6 s 0.54 0.05 10 t 0.25 0.06 24 u 0.45 0.12 26 v 0.58 0.17 29 w 0.42 0.11 27 x 0.46 0.05 12 y 0.27 0.13 47 z 0.66 0.15 23 3.3 cement survey and its laboratory tests the brands of cement sold in maiduguri include dangote 3x and ashaka. they are both standards organisation of nigeria (son) certified and are of grades 42.5n and 32.5n respectively. bua cement is also supplied to maiduguri but is scarce and majorly on demand. it was not available as at the period of this research. the dangote brand was more widely used by block making industries. the fineness, consistency, soundness, initial and final setting times of the sampled cements were obtained and analysed in conformity with (nis 444-1, 2003 and bs 812, 1996). the results are summarised in table 5. table 5: hydration properties cement cement fineness consistency initial set final set soundness c1 2.87% 29.5% 98mins 208mins 0.8mm c2 1.73% 29% 97mins 206mins 0.5mm specifications ≤10% 26 – 33% ≥60mins ≤600 ≤10mm the fineness test was conducted in line with (son, 1997 and bs 4449, 1997) and it can be seen from table 5, that the average fineness for c1 is 2.87% and c2 is 1.73%, indicating more than 95% finer. these values are far below the specified limit of 10% residue, implying that the cements c1 and c2 conform to the standards. the consistency of cement according to the standards as shown in the table 5; it indicated that c1 and c2 are within the acceptable consistency limits. the setting time of ordinary portland cements, as specified by the standards states an initial set time of not less than 60 minutes, and a final set time of not more than 600 minutes. from table 5, it can be observed that the initial set times of 98 and 97 minutes for c1 and c2 shows that c1 is 38 minutes more than the initial set time limit and c2 is 37 minutes more than the limit. also, the final set time of 208 and 207 minutes for c1 and c2 shows that c1 is 392 minutes less than the final set time limit and c2 is 394 minutes less than the limit. 4. conclusion the study assessed the level of quality of cement and sandcrete block materials available in maiduguri metropolis, revealing that the quality of building materials in the metropolis is inadequate. key findings include inadequate compressive strength, with average strengths below the recommended minimum and some samples as low as 0.12 n/mm². there was also significant variability in block production, with high coefficients of variation in compressive strength. additionally, blocks were cured for only 3 days, which may not be sufficient to achieve optimal strength. while sand quality mostly conformed to standards, some industries used http://www.azojete.com.ng/ mailto:bukarkadai2@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 804-810. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bukarkadai2@gmail.com 809 finer sand than required. however, cement quality was found to be satisfactory, with physical properties meeting standards, indicating that cement is not the primary issue. references accident investigation bureau, aib. 2013. annual safety report. abuja: ministry of aviation. pp. 1–34. adenike, a. 2006. impact of material quality on building performance. lagos: building research institute, pp. 10–45. alemika, eo. 2015. prevalence patterns and consequences of insecurity in nigerian cities. annals of the social science academy of nigeria, 20: 16 46. ambrose, ee., etim, rk., and koffi, ne. 2019. quality assessment of commercial produced sandcrete blocks in part of akwa ibom state, nigeria. nigerian journal of technology, 38(3): 586 – 593. anigbogu, na., and anunike, eb. 2014. standard of materials specifications, their implementation and enforcement on building construction projects in nigeria. atbu journal of environmental technology, 7(1): 1-13. ayodeji, o. 2011. an examination of the causes and effects of building collapse in nigeria. journal of design and built environment, 9(1): 37–47. bamisile, a. 2004. building production management. lagos: foresight press. pp. 5–60. british standards institution. 1985. bs 812-103.1: testing aggregates – method for determination of particle size distribution. london: bsi. pp. 1–12. british standards institution. 1996. bs 812: specification for portland cement. london: bsi. bs 4449:1997. specification for carbon steel bars for the reinforcement of concrete: british standards institution. grema, m. 2006. the quality of construction materials in nigeria. kano: sahel press. pp. 22–50. linda, v. and synek, j. 2019. quality control in building and construction. iop conference series: materials science and engineering. 471(2019): 1-7. nis 444-1:2003. composition, specification and conformity criteria for common cements, standards organisation of nigeria. opoko ap., ezema ic., and ediae oj. 2014. implementation of quality-management procedures in the production and utilisation of cement stabilized laterite interlocking blocks in nigeria. covenant journal of research in the built environment (cjrbe), (1)1: 53-60. raheem, aa., akintayo, oa., and olanrewaju, os. 2012. economic appraisal of sandcrete blocks production in nigeria. building and road research journal, 10(2): 55–62. sitota, b., emer, tq., and woyesa, a. 2021. assessment on materials quality control implementation of building construction project and workability: a case study of ambo university. journal of xidian umiversity, 1(8): 138 – 155. standards organisation of nigeria son. 1997. nis 367: specification for portland cement. abuja: pp. 1–15. standards organisation of nigeria son. 2004. nis 87: specification for sandcrete blocks. abuja: pp. 1–16. standards organisation of nigeria. 2004. nigerian industrial standard: standard for sandcrete blocks nis 87:2004) lagos, nigeria: standards organisation of nigeria. pp. 1–15. sule, a. 2016. demand versus quality. a study on block production in nigeria. journal of engineering and applied sciences, 11(5): 1127–1132. http://www.azojete.com.ng/ mailto:bukarkadai2@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 804-810. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: bukarkadai2@gmail.com 810 zeb, a., malik, s., nauman, s., hanif, h., and amin, mos. 2015. factors affecting material procurement, supply and management in building projects of pakistan: a contractor’s perspective. proceeding of international conference on innovations in civil and structure engineering. istanbul (turkey), pp. 170 -175 zulaijarmai, bg., esumobi, g., muhammad, m., ahmad, u. n., and elvis, cn. 2021. benefit of quality assurance and control in construction industry. international journal of innovative research and development, 10(10): 12-16. http://www.azojete.com.ng/ mailto:bukarkadai2@gmail.com corresponding author email: dominicakuboh@yahoo.com 13 arid zone journal of engineering, technology & environment review article identification, classification and ranking of the causes of building collapse in abuja, nigeria – a review d.o. akuboh1* and t. aimola1 1department of civil engineering, african university of science and technology, abuja, f.c.t. *corresponding author email: dominicakuboh@yahoo.com article information abstract this study examines the incidences of reported building collapses from inception in abuja, nigeria from 2008 to 2024 and the attendant increasing loss of lives, properties and injuries, with a view to determining leading causes of building collapses, it’s classification and ranking within the fct abuja. it also highlights the casualties arising from these occurrences. there has been conflicting information on casualties and damages resulting from building collapses in nigeria perhaps due to ineffective coordination amongst agencies responsible. findings of this study revealed the leading causes of building collapse in the fct in decreasing order as to include use of substandard building materials, structural failures, use of quacks, poor or lack of supervision and lack of conduct of geotechnical investigation/inappropriate foundation. a total of thirty (30) cases of building collapses were identified to have occurred in the fct leading to the confirmed death of at least fifty-seven (57) persons. recommendations were made in line with the leading causes of building collapse in the fct. submitted: 20th june 2024 revised: 27th january 2025 accepted: 29th january 2025 keywords: building building collapse causes abuja ranking © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction building collapses are either due to natural climatic and geological conditions or man-made factors. while little may be done to stop the occurrence of the natural causes, the man-made factors can be mitigated to the barest minimum. a building fails when the imposed load cannot be supported by the foundation amongst several other reasons. building collapse occurs in many places across the world, but the spate of building collapse in nigeria in recent times is worrisome. the death toll, injuries, psychological trauma and resultant collateral damages occasioned by this phenomenon over the years are high and unquantifiable. in this paper, attempt has been made to re-establish a record of the reported incidences of building collapse in nigeria and the resultant fatalities as well as the general causes, effects and solutions of building collapse in nigeria from the findings conducted on some cases. this was however done with respect to frequency of occurrence per annum, category of buildings involved and state of occurrence in nigeria. omenihu et al., (2016) defined building collapse as the inability of a building component to withstand the loads it was designed for. ayinuola and olalusi, (2004) opined that failure is considered as occurring in a component when such component cannot perform its intended functions. in summary, the unplanned falling of a building is referred to as building collapse, while the planned falling of a building is referred to as demolition. this paper is structured in the order of introduction, literature review, methodology data analysis and discussion, recommendation and conclusion. the sources of data and methodology for this study were from a review of selected literatures, technical reports, author’s independent records and online news articles. data analysis was done by simple descriptive statistics, counts/frequency of occurrence, rankings and percentages. according to olusola et al. (2011) and ketkukah (1998), building collapse may be partial, progressive or sudden. in a partial collapse, only a portion of the building falls down. in the situation of a progressive failure, there will be signs of weakness noticeable either by visible cracks which becomes widened with time or unusual sound in the building due to structural members gradually giving way. in the sudden collapse scenario, the building collapses suddenly, it may not even give any sign prior to collapse. normally buildings are designed to withstand loads (i.e. live, imposed and wind loads). collapse or failure of building occurs when parts of building show signs of being unfit for its intended use (crocker, 1990 cited by akuboh, 2013). however, building failure or collapse may also result from force majeure or natural phenomena/disasters or climatic factors. similarly, matawal (2013) noted that the number of building collapse where in most cases the structures and loads came azojete march 2025. vol.21(1):13-24 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:dominicakuboh@yahoo.com mailto:dominicakuboh@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 14 down without prior warning and the deformation movements, so fast with no time to evacuate, is an indication of improper concreting. daily trust newspapers of 16th august, 2017 (pages 1, 5) reported that 272 lives were lost in the last 17 months. this represents an average loss of life of 16 persons per month related to building collapse in nigeria. edighoman (2016) reported 151 incidences of building collapse in nigeria from 1974 till march, 2016 from the examination of historical data and outlined some causes of building collapse in nigeria. the contributions of various professionals and the building owner’s penchant to avoid cost of hiring professionals were also contained in the paper presentation in relation to building collapse. this work, therefore, draws and reviewed it’s historical data from the 151 incidences and updated the incidences of 2012 to april, 2022. lawal (2016) opined that hardly can we find a life venture without its elements of risk. therefore, constructing a building or using a completed building for anything carries a sizeable amount of risk – risk to lives, property, profit and other intangible assets. the fundamental difficulty in risk assessment is determining the rate of occurrence since statistical information is not available on all kinds of past incidents. furthermore, evaluating the severity of the consequences (impact) is often quite difficult for intangible assets. thus, best educated opinions and available statistics are the primary sources of information. the objectives of this study include to ascertain the number of building collapses that occurred in fct abuja from inception of occurrence, to evaluate and rank the causes of the building collapses and to adduce the causes of the building collapses according to the stages of building development contained in the national building code. to understand why failure occurs, it is important to have an overview of the bath-tub curve. the bath-tub curve or lusser mortality curve was established in 1952 by robert lusser as the first statistical theory of reliability (furman, 1981). figure 1.0 below illustrates the three failure rates of all components and equipment which follows a certain basic pattern namely: early, useful life and wear-out period. this can be likened to a building construction from start to finish including period for concrete curing, behaviours in service and upon aging or prolonged usage. figure 1: lusser mortality curve (furman, 1981) it has been discovered that systems exhibit a high failure rate during their initial period of operations, called the infant mortality period or the debugging stage. these are failures which are typically caused by manufacturing flaws, or the result of damage received in transit or handling. the operating period that follows infant mortality has a smaller failure rate, which tends to remain constant until the beginning of the next phase, called the wear-out period. failures during these periods are typically due to chance, which is failures generally resulting from severe, unpredictable and usually avoidable stresses that arise from environmental factors such as vibrations, temperature, shock, human factors and pressure. upon reaching the wear-out period the failure rate tends to increase quite rapidly. failures in this period are as a result of gradual degradation of some property of the system essential to proper corrosion and abrasion (furman, 1981). the causes of building collapse globally are either natural such as rainstorm, earthquake, earth tremor, landslide, windstorm, flooding etc or man-made (akuboh, 2013). however, a review of relevant literature (akuboh, 2019) in this study reveals the causes of building collapse to include the following: • improper concreting • sudden collapse http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 15 • partial collapse • structural failure • heavy rainfall • unequal foundation settlement • faulty foundation design • collapse of adjacent building/fence wall • pre-mature removal of formwork for roof slab/concrete decking • use of sub-standard materials without government approval in building construction • poor workmanship and supervision/quackery • inadequate roof and floor slab bracing support • use of building when it has not achieved its minimum allowable strength • gas explosion • distressed building • illegal addition of floors • roof gutter failure • client’s and contractor’s penchant for cheap labour and profit maximization through cutting corners respectively. the works of omenihu et al. (2016) shows the summary of leading causes of occurrences of factors responsible for collapsed buildings in nigeria. the results were as follows: 1. structural failures (24.9%), 2. substandard materials (13.2%), 3. poor workmanship (12.2%), 4. faulty design (8.8%), 5. use of quacks (7.3%) 6. inappropriate foundation (6.8%). the above leading causes of collapses of buildings in nigeria were also corroborated by the outcome/findings of numerous investigations carried out by various committees and particularly the nigerian building and road research institute (nbrri) and evidently documented in nbrri reports numbers 22, 23, 26, 36, 45, 47 and 51 respectively. in most instances the use of substandard materials and poor workmanship are caused by lack of or inadequate supervision (i.e. human factor). from the foregoing, it stands to reason that the above factors still constitute the major factors responsible for building collapse. according to lamptey-puddicombe (2016), the effects of building collapse are as follows: • loss of life, property and huge sum of capital. • loss of reputation and integrity leading to psychological trauma. • loss of new commissions and contracts. • loss of materials and capital investments. • components and materials are damaged beyond re-use. • capital investments are not recoverable, leading to bankruptcy and high economic implications to the nation’s economy. plate 1: two storey building collapse in garki village, abuja – 24th august, 2023. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 16 plate 2: multi-storey building collapse in gwarinpa, abuja – 2nd february, 2023. 2. materials and methods the data used in this review were obtained from secondary sources, which include publications by various authors, television news, newspaper articles, online sources/internet, conference proceedings of the quantity surveyors registration council of nigeria, 2016, some investigative reports of the national building and road research institute (nbrri) on building collapses and independent records of the author on building collapse from 2012 to 2024. figure 2: research methodology (nicholas et al., 2021) 3. results and discussion table 1 presents the identification of the causes associated with building collapse. table 1: identification of the causes of building collapses in abuja, f.c.t. s/no. building description location/address date of occurrence confirmed/suspected causes casualties 1 4-storey building under construction plots 230 and 1161, pow mafemi crescent, utako district, abuja 30th july, 2008 violation of stop work order and quit notice 6 deaths, 10 injured 2 3-storey building collapse plot 1885 in cadastral zone a04 of asokoro district, asokoro, abuja 31st july, 2009 no building approval for the construction due to ownership dispute in court at the time. 1 death, 35 recued 2008 – 2023) http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 17 s/no. building description location/address date of occurrence confirmed/suspected causes casualties 3 2-storey commercial building garki, abuja november, 2009 structural failure, substandard material 4 6-suspended floors for commercial purpose with a basement plot 702, port harcourt crescent, area 11, garki, abuja july, 2010 substandard materials, use of unqualified professionals. 5 4 storey uncompleted building 2, ikolie street, off gimbiya street, area 11, garki, abuja 11th august, 2010 substandard materials, disregard for building regulations 23 deaths, 11 injured 6 2-storey zenith bank building maraba, near abuja 2011 no geotechnical investigation, undersized large span slab, no specific floor thickness on drawing. 2 deaths, 11 injured 7 4-storey hospital building mpape, abuja 19th august, 2011 8 2 storey building under construction belonging to the nigerian navy holdings 45th road, first avenue, gwarinpa, abuja 28th january, 2012 unapproved and unsupervised demolition of defective building occasioned by use of sub-standard materials and inadequate concrete mix ratio. 3 deaths, 5 injured 9 1 storey commercial building under construction apo mechanic village, abuja 13th june, 2012 no qualified professional on site, poor supervision, use of poorquality material. no deaths, 3 injured 10 2 storey building no. 3, ademola awosika road, close to living faith church, kubwa extension iii, abuja. 8th august, 2012 poor quality materials, poor workmanship and lack of supervision, weak foundation, failure of structural elements. 2 deaths, 9 injured 11 a semidetached duplex mbora estate, abuja 29th september, 2012 substandard building materials 12 building collapse (unreported) maitama, abuja 6th september, 2013 3 deaths 13 a storey building government secondary school, nyanya, abuja 27th september, 2013 8 injured 14 2 storey building utako, abuja 18 oct., 2013 distressed building marked for demolition. no deaths, 1 injured 15 a construction site jabi, abuja 25th december, 2014 landslide 3 deaths 16 a construction site mississippi street, maitama, abuja 12th july, 2016 landslide 2 deaths http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 18 s/no. building description location/address date of occurrence confirmed/suspected causes casualties 17 6 storey hotel building under construction 444 crescent, citec villas, gwarinpa, abuja, nigeria 29th august, 2016 poor concreting, inadequate reinforcement sizes for structural elements. 5 labourers trapped 18 4-storey building gwarinpa, abuja 30th august, 2016 2 deaths, 6 rescued, several injured 19 four storey building under construction plot 711, obafemi awolowo way by asuquo j. okon intersection in jabi, abuja – fct. 17th august, 2018 inadequate compliance to procedures, inadequate foundation depth, underreinforcement, low soil bearing capacity, poor concrete works and poor supervision. 5 deaths 20 one storey building plot 59, dawaki relocation layout, dawaki, abuja, fct. 25th july, 2020 poor quality materials, poor workmanship, inadequate pad footing, failure of structural elements, use of quacks, reinforcements less than minimum specifications, improper anchorage of reinforcement, inadequate stirrup spacing and unapproved construction drawings. 21 2-storey building under construction abdullahi hamza road, beside freedom in christ mission, close to aso savings and loans junction, kubwa, abuja 26th august, 2022 quackery and sharp practices. 2 deaths, 5 injured 22 2 storey building under construction 6th avenue, gwarimpa, abuja 2nd february, 2023 illegal addition of floor/violation of building plan approval, substandard materials and poor workmanship. 3 deaths, 19 injured 23 4 storey hotel building under construction plot 654, dape (near berger clinic), life camp, abuja 3rd july, 2023 use of sub-standard materials, violation of development control orders. 1 death 24 2 storey building lagos street, opposite garki police station, garki village, abuja 23rd august, 2023 torrential rainfalltriggered collapse. 2 deaths http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 19 s/no. building description location/address date of occurrence confirmed/suspected causes casualties 25 indoor basketball sports hall asturf garden, wuse zone 5, abuja around 9th march, 2024 wind storm 26 a building plot 458, guzape, abuja 28th june, 2024 0 27 1 storey/duplex under construction prince and princess estate, abuja 29th june, 2024 2 injured 28 4 storey building under renovation 23, nkwere street, off ahmadu bello way, area 11, garki, abuja – fct 1st july, 2024 3 injured 29 2 storey building al-hilal hotel, sultan dasuki road, off gado nasco road, phase 2, site 2, kubwa, abuja 13th july, 2024 distressed building & illegal conversion from commercial to mixed use. 5 injured 30 a building sabon lugbe, abuja 26th october, 2024 partial/incomplete demolition 40 trapped/inju red total 57 deaths, 83 injured, over 81 recued 3. data analysis and discussion 3.1 classification of the causes of building collapses in abuja, f.c.t. from the findings of the review of available investigation reports from building collapses in the fct and table above, the following combination of common/leading causes of building collapse were categorized and established based on same categorization of project stages in the national building code (2006): 3.1.1 a – pre-design causes: • building without the required regulatory approvals for design and construction or contravention of approved building plans. • client and contractor’s penchant to cut corners/cost and/or maximize profit. • poor building maintenance practices. 3.1.1 b design causes: • weak foundation • failure of structural elements (foundation, beam, slab and column) • quackery or none involvement of construction professionals • disregard for soil condition or lack of conduct of geotechnical investigation • client and contractor’s penchant to cut corners/cost and/or maximize profit. • poor building maintenance practices. 3.1.1 c construction causes: • use of sub-standard or poor-quality construction materials • poor workmanship and lack of or inadequate supervision • weak foundation • improper anchorage of reinforcements • lack of adherence to design specifications for reinforcements, concrete etc http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 20 • quackery or none involvement of construction professionals • building without the required regulatory approvals for design and construction or contravention of approved building plans. • use of technically deficient building contractors • disregard for soil condition or lack of conduct of geotechnical investigation • client and contractor’s penchant to cut corners/cost and/or maximize profit. • lack of or poor safety measures e.g. unauthorized storage of explosives.’ • violation of stop work order. • force majeaure – rainstorm and other natural disasters. 3.1.1 d – post-design causes: • illegal conversion of buildings or unauthorized building modifications • poor building maintenance practices. • lack of or poor safety measures e.g. unauthorized storage of explosives.’ • violation of stop work order. • force majeaure – rainstorm and other natural disasters. 3.2 ranking of the identified causes of building collapse in fct: 2008 – 2024. table 2 presents ranking where the use of substandard material emerged as the leading cause of building collapse and natural disaster emerged as the least cause of building collapse in the fct agrees with the findings of nicholas et al. (2021). table 2.: ranking of the identified causes of building collapse in fct: 2008 – 2024. s/no. cause no. of occurrence percentage of occurrence (%) position 1 use of substandard/poor quality materials 9 26.470 1st 2 structural failure including underreinforcement/improper anchorage of reinforcement 5 14.710 2nd 3 lack of or poor supervision/poor workmanship 3 8.824 4th 4 poor concreting 2 5.882 6th 5 use of quacks/quackery/use of unqualified professionals 4 11.765 3rd 6 violations of building regulations/approvals 2 5.882 6th 7 illegal conversion of buildings/addition of floors 2 5.882 9th 8 lack of geotechnical investigation/low soil bearing capacity/weak and/or inappropriate foundation 3 8.824 4th 9 poor safety and maintenance practices 10 force majeaure/rainstorm/other natural disasters 1 2.940 9th 11 landslide 2 5.882 6th 12 partial/incomplete demolition 1 2.940 9th total 34 100 in comparison to the finding of omenihu et al. (2016), substandard materials accounts for the second leading cause of building collapse in nigeria while the findings of this study established substandard materials as the leading cause of building collapse in the fct. this shows that the leading causes of building collapse vary slightly from one city to the other. a total of thirty (30) incidences of building collapse were recorded in the fct since the first reported occurrence in 2008 leaving more than fifty-four (54) persons dead and several others injured. according to http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 21 akuboh (2019), the fct accounts for the second highest occurrence of building collapse incidents in nigeria after lagos. 3.2.1 occurrences of building collapse by year in fct abuja table 3: occurrences of building collapse by year in fct abuja s/no year no. of occurrence 1 2008 1 2 2009 2 3 2010 2 4 2011 2 5 2012 4 6 2013 3 7 2014 1 8 2015 0 9 2016 3 10 2017 0 11 2018 1 12 2019 0 13 2020 1 14 2021 0 15 2022 1 16 2023 3 17 2024 6 total 30 3.3 ranked causes of building collapse in the f.c.t explained: use of substandard/poor quality materials: the impact of inflation, fluctuating foreign exchange rates and rising cost of building materials such as cement, steel reinforcements and concrete products over the years in nigeria has led to the use of substandard and recycled materials at the detriment of structural safety and stability. the penchant to cut corners and make profits can also not be ruled out as one of the reasons for the use of sub-standard building materials by contractors. structural failure: structural members such as slab, column, beam or cantilevers fail due to reasons such as use of sub-standard materials, improper anchorage of reinforcements, use of inappropriate or inadequate reinforcement sizes, lack of or inadequate supervision of concrete placement works, violation of technical specifications and approved designs and overloading amongst others. lack of or poor supervision/poor workmanship: lack of qualified technical personnel to supervise construction works and poor workmanship by workmen contribute a great deal to the incidences of building collapse. poor concreting: inappropriate concrete mix ratio and water-cement ratio are parameters that determines the quality and effectiveness of a concrete mix. if the quality of concrete mixes are not monitored for compliance and consistency, it will most likely jeopardize the structural integrity of buildings over time. use of quacks/quackery/use of unqualified professionals: the quest for cheap labour and rising unemployment has contributed a great deal to the use of unqualified professionals and the proliferation of quacks in building construction. this development if left unattended to has negative effects on the fight against building collapse in nigeria. violations of building regulations/approvals: building regulations are a set of rules and guidelines that govern the construction and maintenance of buildings. compliance with these regulations is critical to ensure safety, accessibility, and quality of life for occupants. unfortunately, building regulation violations are all too common, and they can result in significant penalties, legal action, and even loss of life. a common example of the violation of building regulation is lack of conduct of final inspection and occupation of a building without certificate of fitness for human habitation. illegal conversion of buildings/addition of floors: unauthorized modification of approved building plans and illegal addition of floors constitutes a major problem resulting in the collapse of most buildings. lack of geotechnical investigation: soil investigation is a pre-requisite for design of suitable foundation for buildings. lack of soil investigation therefore could lead to the use of wrong foundations and subsequently structural instability. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 22 force majeaure/rainstorm/other natural disasters: the forces of nature are also a cause of building collapses. this entails events that man has no control over and they are termed as “force majeaure”. they include windstorm, torrential rain, earthquake, earth tremor, landslide, flooding etc. 4. conclusion incidences of building collapses in nigeria have no doubt led to the untimely deaths and loss of properties and investments of inestimable value even though many of such cases might have occurred unnoticed or unreported. a total of thirty (30) building collapses were identified to have occurred in fct abuja from 2008 to 2024 with the leading causes of the occurrence determined as use of sub-standard material, structural failure, quackery, lack of conduct of geotechnical investigation and lack of or inadequate supervision/poor workmanship. having identified the leading causes of building collapses in abuja, nigeria, prevention is the ultimate solution. the recommendations arising from this study are presented in accordance with the ranking of the causes of building collapse in the fct. use of substandard materials (nicholas et al., 2022): i. standard organization of nigeria, (son) should monitor the standard of blocks moulded-in block industries and impose minimum standards in terms of sand-cement ratios and scrutinize building materials that are supplied for use in nigeria and ensure that only certified building materials are allowed in the market. ii. the standard organization of nigeria should be vigilant to ensure that building materials imported into the country conform to standard requirements. iii. there is a need to empower and restructure materials testing laboratories in all geo-political zones of the country. iv. building professionals and contractors should ensure proper and efficient checking of materials brought to site and carry out tests such as cube test for concrete, tensile strength for steel bars, slump test for in-situ concrete in a building project following engineer’s specification. v. the design team in any building project should ensure that building materials supplied to the site by the domestic or nominated supplier are under the contract specification. vi. the national regulations regarding building materials are revised and consider the international standards to be adopted. vii. build on tested engineering properties of available local building materials in nigeria. structural failure (nicholas et al., 2022): i. there is a need to organize periodic public awareness campaign through electronic and print media to sensitize the public on the advantages of using professionals as a way of realizing safe buildings. civil/structural engineers should be engaged in all building construction projects up to and above one suspended floor. ii. the building construction process involves professionalism in the planning, design, and execution of the project. engineering consultants must be involved in the design and supervision of buildings iii. imposing additional floors beyond original design provision should be avoided. iv. reduce the level of exposure of structures to risk by imbibing maintenance culture, seek advice from experts when changing the form and use of buildings, and insist on material and soil tests for multistorey buildings. v. regulatory professional bodies such as the engineering regulatory, monitoring and enforcement (erm&e) unit of coren and their corresponding associations should on regular basis organize workshops for stakeholders in the building industry to update their knowledge and highlight the dangers and penalties associated with collapsed buildings. lack of or poor supervision/poor workmanship: i. all stages of building construction must be properly and adequately supervised by the requisite professional member of the built environment to ensure compliance to design specifications and acceptable construction methods. ii. the works carried out by the workers on site also need to be closely monitored by the professionals to ensure quality of construction. poor concreting: http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 23 i. there is a need to ensure proper mix of concrete before placement. ii. long, flat aggregates should be avoided as much as possible as they tend to have less grip in concrete and have a tendency towards segregation during handling. shape and texture of coarse aggregates affects the strength of the concrete mix. iii. cubical aggregate has maximum strength in concrete as it has good packing and strength in all direction. rounded aggregate is not suitable for concrete use of quacks/quackery/use of unqualified professionals ((nicholas et al., 2022): i. all building professionals play key roles to actualize their respective obligations during building production, using the wrong professionals at any stage of the building process puts the building in danger. ii. construction should involve the collaboration of different professionals who have been registered by law practice the art of the building process. iii. only workers or building operatives with the appropriate training and experience should be allowed to engage in building works especially on the structural members. violations of building regulations/approvals: i. building regulatory authorities should ensure strict enforcement of building regulations such as inspection and issuance of certificate of fitness for human habitation for completed buildings. ii. building regulatory authorities should also ensure that the necessary setbacks from roads, electricity supply lines and property lines are observed in building designs and when setting out buildings for construction. iii. building regulatory authorities should also ensure that the purpose of building use are not changed arbitrarily too. illegal conversion of buildings/addition of floors: i. the number of suspended floors of a building is a function of the geotechnical properties of the underlying soil strata. this underscores the approval for a particular number of suspended floors or storey. however, alteration or addition of the number of suspended floors without recourse to the soil bearing capacity and revalidation by the authorities has been one of the factors responsible for many incidences of building collapse in nigeria. all proposals for increase of number of suspended floors must be subjected to expert advice and submitted to building regulatory authorities for vetting prior to any action. ii. the conversion of buildings from residential to commercial or any other use contrary to the approved use is illegal and should be avoided as much as practicable. lack of geotechnical investigation: the geotechnical properties of the soil and the nature of the proposed building is a determinant of the type of foundation to be adequately designed and provided. the conduct of geotechnical investigation is therefore of utmost importance. force majeaure/rainstorm/other natural disasters (nicholas et al., 2022): i. building on flood plains or flood-prone areas should be avoided because flood weakens soil structure and foundation. ii. building on the hillside is likely to collapse due to erosion. ensure that the soil surrounding the building is well protected with concrete or with stone pitching. all stakeholders in the construction industry should adhere strictly to the provisions of the building code. references akuboh, do. 2013. causes of building collapse in nigeria…towards enduring remedial measures, the abuja engineer, a publication of the nigerian society of engineers abuja. 5th edition, august,. pp. 21 – 23. akuboh, do. 2019. the menace of building collapses in nigeria – the way forward, a paper presented at the public lecture of the nigerian institution of civil engineers (nice), jalingo chapter in collaboration with the nigerian institution of civil engineers (nice), abuja chapter, jalingo, taraba state. 11th july, 2019. ayinuola, gm. and olalusi, oo. 2004. assessment of building failure in nigeria, african journal of science and technology. 5(1): 73-78. edighoman ie. 2016. cost avoidance as a major culprit for building collapse in nigeria the quantity surveyors intervention. a paper presented at the 6th building & construction economic round table (bcert 6). shehu musa yar’adua centre, central area, garki, abuja, 14th to 15th july, 2016. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):13-24. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author email: dominicakuboh@yahoo.com 24 federal republic of nigeria, 2006. national building code, 1st edition. lexis nexis, butterworths, south africa. furman, t.t, 1981. approximate methods in engineering design. mathematics in science and engineering vol.155 (ed) richard, bellman, academic press, pp. 123-132 ketkukah, s.t, 1998. progressive structural failure analysis of plane trusses. m.sc thesis, ahmadu bello university (abu) zaria, unpublished. lamptey-puddicombe, ad. 2016. preventing building collapse in nigeria: the role of professionals. a paper presented to the quantity surveyors registration board of nigeria (qsrbn) on the 6th building and construction economic round table (bcert) on the theme: professional issues and challenges in building collapse in nigeria. abuja. 14th & 15th july, 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state. july, 2012. nbrri technical report no. 29: collapse of buildings in nigeria (analyses of collapse of two-storey building at kubwa extension iii. december, 2012. nbrri technical report no. 36: collapse of buildings in nigeria (technical report on collapsed school building at abu ni’ima islamic school, bukuru, jos, plateau state. february, 2016. nbrri technical report no. 45: collapse of buildings in nigeria (technical report on the collapse of three storey faculty of social sciences building, benue state university, makurdi, benue state. february, 2019. nbrri technical report no. 47: collapse of buildings in nigeria (technical report on the three (3) storey collapsed building under construction at jabi district, abuja. september, 2018. nbrri technical report no. 51: collapse of buildings in nigeria (technical report on the collapsed 8-storey building under construction at umaru yar’ adua drive, owerri, imo state, nigeria. june, 2020. nicholas, io., nwalusi, md., francis oo. 2021. building collapse in nigeria and its consequences on the architect’s role as the leader of the building team. jordan journal of earth and environmental sciences (jjees) (2022) 13(1): 16-25. olusola, ko., ojambati ts. and lawal af. 2011. technological and non-technological factors responsible for the occurrence of collapse buildings in south-western nigeria, journal of emerging trends in engineering and applied sciences (jeteas) 2(3): 462-469. omenihu fc., onundi lo. and alkali ma. 2016. an analysis of building collapse in nigeria (1971 – 2016): challenges for stakeholders. university of maiduguri, annals of borno, volume xxvi, june, 2016. http://www.azojete.com.ng/ mailto:dominicakuboh@yahoo.com http://www.nigerianbestforum.com/index.php?phpsessid=d107973e0bb5c9a064c00b09ef5fa9e0&topic=216715.msg519689#msg519689 http://www.nigerianbestforum.com/index.php?phpsessid=d107973e0bb5c9a064c00b09ef5fa9e0&topic=216715.msg519689#msg519689 corresponding author’s email address: omatsej@yahoo.com 569 arid zone journal of engineering, technology & environment review article transitioning to sustainable energy: the promise of solar power – a review j. n. onah1 and g. o. jemiriayigbe1* 1 department of electrical and electronics engineering, federal university of petroleum resources, effurun, delta state 330102. nigeria *corresponding author’s email: omatsej@yahoo.com article information abstract over time, the global energy landscape has shifted from localized, experimental systems to complex, interconnected power grids. understanding the historical trajectory of these developments provides crucial insights into shaping a sustainable energy future. in light of escalating energy demand, environmental degradation and fossil fuel depletion, there is an urgent need to transit toward cleaner, more sustainable sources of electricity. while renewable energy technologies offer promising alternatives, countries like nigeria face unique challenges in identifying the most viable options for large-scale deployment. this study employs a structured literature review to examine both the historical evolution and current landscape of power generation technologies. the review encompassed conventional systems (e.g., fossil fuels, nuclear) and renewable sources (e.g., hydro, wind, geothermal, solar). findings show that past power transitions were driven by more than just technological superiority—they were shaped by economic, institutional, and societal factors. drawing from this, the study identifies solar power as the most promising renewable option for nigeria, due to its abundant sunlight, declining costs, and ease of deployment across diverse locations. compared to wind, tidal, and geothermal energy, solar presents a more practical and scalable solution for off-grid and rural electrification. this insight is reinforced by historical parallels, such as the role of complementary innovations and institutional support in the dominance of alternating current power systems. solar power stands out as nigeria’s most feasible pathway toward sustainable and resilient energy development. lessons from historical power transitions highlight the importance of aligning technological innovation with supportive policy, infrastructure, and public engagement. as the country navigates its energy future, prioritizing solar investment and integration will be vital for achieving environmental sustainability, economic growth, and long-term energy security. received: 25th april 2025 revised: 20th may 2025 accepted: 21st may 2025 keywords: solar power renewable energy sustainable energy geothermal power © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction 1.1 evolutionary trajectory of electrical power generation the evolution of electrical power generation represents one of humanity's most transformative technological revolutions, fundamentally reshaping society's capabilities and structures. while the historical foundations laid by pioneers such as galvani, volta, and ampere established the scientific principles of electricity, contemporary power systems have undergone radical transformation through successive waves of innovation (black, 2018). the energy sector now finds itself at a pivotal crossroad, facing intense debate over a potential globally coordinated shift away from fossil fuel-based infrastructures (stirling, 2014). the transition from experimental demonstrations to industrial-scale implementation has been marked by technological breakthroughs, shifting economic paradigms, and evolving environmental considerations. modern scholarship has recontextualized the pivotal "battle of the currents" beyond the edison-tesla rivalry narrative toward a more nuanced understanding of how competing technological regimes gain dominance azojete june 2025. vol.21(2):569-580 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/021 www.azojete.com.ng mailto:omatsej@yahoo.com mailto:omatsej@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 570 (sovacool and brisbois, 2019). this technological competition represented an early example of what energy transition researchers now recognize as "sociotechnical regime shifts" where multiple factors—including technological superiority, economic interests, institutional frameworks, and cultural acceptance—collectively determine adoption patterns. the eventual triumph of alternating current (ac) systems over direct current (dc) established a technological trajectory that shaped power systems development for over a century. edison's pearl street station not only represented technological innovation but established new business models and regulatory frameworks that defined modern utility structures. the emergence of long-distance transmission capabilities fundamentally altered the geographic relationships between energy production and consumption, enabling new patterns of industrial development and urbanization that continue to characterize modern energy landscapes (bridge et al., 2021). contemporary research emphasizes that electrical system development follows non-linear innovation pathways. while thury's series-connected dc systems represented an important technological milestone, their eventual obsolescence illustrates what innovation scholars’ term "technological lock-out"—where superior technical solutions may fail against alternatives with stronger institutional support and network effects. the persistence of ac dominance despite its technical limitations compared to modern high voltage direct current (hvdc) illustrates the path dependency that characterizes large-scale infrastructure systems. the three-phase transmission breakthrough of the 1890s has been recognized as a classic example of "innovation clustering," where multiple complementary technologies (polyphase generators, transformers, and motors) converged to create system-level benefits exceeding individual components. modern energy transition research draws parallels between this historical development and contemporary renewable energy integration challenges, where similar technological co-evolution is required for system transformation. 1.2 importance of electrical power in modern society electrical power serves as the backbone of modern society, fundamentally transforming every aspect of human life. it provides energy for homes, businesses, and industries, drives technological advancements, stimulates economic growth, and enhances quality of life. by leveraging the ability to store and direct electric charges, electricity can be harnessed in countless ways to meet diverse human needs. in the 21st century, electricity is indispensable across various sectors. industrial production depends on it for enhanced efficiency and productivity. as shown in figure 1, global gross electricity generation has steadily increased in response to population growth (iea, 2025). this rising demand underscores the urgent need for a transition to more sustainable energy sources, ensuring a reliable and environmentally friendly energy supply for the future. figure 1: gross electricity generation by sector (iea, 2025) 1.3 overview of the review's scope and objectives this review aims to offer a comprehensive understanding of electrical power generation, exploring its historical roots and future prospects. the review’s objectives are to: • trace the historical evolution of electrical power generation. 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 2008 2010 2012 2014 2016 2018 2020 2022 2024 t e tr aw at th o u rs year renewables nuclear fossil fuels hydrogen & ammonia http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 571 • examine various sources of electrical power and their societal and environmental impacts. • review lessons for renewable transition from historical power evolution 2. historical development of electrical power generation 2.1 early discoveries in electricity and magnetism the history of electricity dates back to ancient times, with the earliest known observations recorded by the greeks. around 600 bce, thales of miletus discovered that rubbing resin caused it to attract light objects like feathers, a phenomenon now known as static electricity (iversen and lacks, 2012). this marked humanity’s first step toward understanding electrical phenomena. other ancient civilizations, such as the greeks and egyptians, made similar observations, though they lacked the scientific knowledge to explain these effects (hardy, 2023). the scientific study of electricity began to accelerate in the 17th and 18th centuries with key discoveries. in 1600, william gilbert coined the term "electricity" in his work “de magnete”, initiating its formal study (gregersen, 2011). in 1752, benjamin franklin’s famous kite experiment showed the electrical nature of lightning when he successfully charged a leyden jar from a kite string during a thunderstorm (sharlin and meyer, 1972). in the 19th century, progress continued with alessandro volta's invention of the electrophorus in 1775, a device that produced static electricity. it consisted of a metallic disk with an insulating handle that could generate and store an electrical charge through friction. the electrophorus proved useful for generating electricity with minimal effort (sharlin and meyer, 1972). in 1820, danish physicist hans christian oersted discovered electromagnetism, showing that electric currents create magnetic fields by observing how a current passing through a wire caused a nearby compass needle to move (gregersen, 2011). a decade later, in 1831, michael faraday discovered electromagnetic induction, the principle behind modern electrical generators (purcell, 2011). these breakthroughs laid the foundation for the practical use of electricity and the development of modern power generation technologies. 2.2 the industrial revolution and the dawn of electrical power michael faraday's discovery of electromagnetic induction led to the invention of the first dynamos—early electrical generators that demonstrated the practical conversion of mechanical energy into electrical energy. despite earlier contributions by physicists like franz neumann and wilhelm weber, a general law of electromagnetic induction within a lagrangian framework was not established until james clerk maxwell’s “treatise”, in which he remarkably derived his theory using the velocity of an elementary circuit element— rather than charge motion—at a time when electrical current was still viewed as a kinetic process (giuliani, 2021). in 1873, zenobe gramme developed a functional electric generator that efficiently converted rotary motion into electric power. earlier generators often overheated due to the armature’s movement, but gramme's innovation solved this issue, making power generation more practical (forrester, 2016). this breakthrough was soon followed by other key developments, including charles f. brush’s 1878 brush arc lamp dynamo, which powered street lighting, and “thomas edison’s pearl street station”, the world’s first central power plant, opened in 1882. this historic station in new york city operated with six engine-dynamo sets and supplied electricity to 59 customers over a 1.5-kilometer (km) radius using underground cables (singh, 2010). in 1889, the united states saw its first long-distance transmission of dc electricity at willamette falls station in oregon. however, a flood in 1890 destroyed the station, paving the way for the installation of experimental ac generators by westinghouse. by 1896, the first ac generation and transmission system at niagara falls was completed, also using westinghouse equipment (de andrade and de leao, 2012). these developments contributed to the rapid adoption of ac over dc. by the late 19th century, the united states had “202 edison dc central stations and 323 westinghouse ac stations” (allerhand, 2017). these early power stations laid the foundation for the modern electrical utility industry, transforming society through widespread electrification. http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 572 3. major sources of electrical power generation 3.1 fossil fuel-based generation a thermal power plant, or heat generation station, converts heat energy into electrical power. in these stations, steam or heat is used to transform heat energy into mechanical energy, which then drives the generation of electricity (varshney, 2017). coal, oil, and natural gas-fired plants are categorized as thermal power stations. with most modern countries having fully developed hydraulic resources, increasing reliance is placed on thermal and nuclear power stations to meet growing energy demands. thermal power plants generate electricity by utilizing heat from the combustion of fossil fuels such as oil, coal or natural gas. to optimize economic efficiency, these plants typically have capacities ranging from 200 megawatts (mw) to 1500 megawatts (mw). the sheer complexity and size of such installations become apparent when observed in person. thermal power plants are commonly located near rivers or lakes to access the substantial cooling water needed to condense steam after it exits the turbines (wildi, 2006). however, their efficiency remains relatively low due to the inherent limitations of turbines in converting heat into mechanical energy. in practice, even the most efficient steam turbines achieve efficiencies of only around 45%, meaning that 55% of thermal energy is lost during the conversion process. this significant heat loss presents one of the major challenges in operating thermal power stations (wildi, 2006). thermal stations' environmental impact is a growing concern due to the pollutants released from burning fossil fuels. the main combustion byproducts are water, carbon dioxide and sulfur dioxide. while carbon dioxide and water have minimal immediate environmental effects, sulfur dioxide can lead to acid rain. dust and fly ash are other pollutants. natural gas, however, produces only carbon dioxide and water, making it the preferred fuel when reducing atmospheric pollution is essential. a clear drawback of fossil fuels is their finite nature, making them an unsustainable long-term option for power generation as seen in table 1 on page 20— especially for countries like nigeria that rely heavily on them. 3.1.1 coal-fired power plants coal remains a crucial source of electricity generation despite the environmental challenges it presents. as the most widely distributed and abundant fossil fuel, coal-fired power generation accounts for about 45% of electricity in the united states, 40% in germany, and roughly 25% in japan. in china, the share is approximately 80%, while in india and serbia, it is around 70% (lakovic et al., 2015). a conventional coal-fired thermal power plant operates using a boiler-turbine-generator system. coal combustion in the furnace generates heat, which warms the feed water inside the boiler drum, producing steam. this steam is directed to turbines, where its kinetic energy is converted into mechanical energy. a generator connected to the turbine then transforms this mechanical energy into electrical energy. efficient combustion requires precise control of fuel and air flow rates, as well as careful management of feed water flow, to optimize power generation (shajahan et al., 2018). while coal-fired power generation offers several advantages, including the availability of coal as a fuel source and its ability to provide reliable base load power, it also has significant environmental impacts. as noted by bhagwan (2022), thermal power plants contribute to pollution through emissions of sulfur oxides, nitrogen oxides, and particulate matter, which can disperse over a 25 km radius. 3.1.2 natural gas power plants electrical energy can be generated from hydrocarbon fuels such as coal, oil, and natural gas, as well as from renewable sources like solar, wind, and geothermal energy. the role of natural gas in power generation is expected to expand over the next two decades as it continues to replace coal. however, by 2050, its usage may decline due to the accelerated shift toward renewable energy. natural gas power generation offers several advantages over coal, including a 45% reduction in carbon dioxide emissions and significantly lower sulfur, mercury, and particulate emissions (thirion and steyn, 2021). furthermore, modern combined cycle power plants can achieve efficiencies of up to 64%, far surpassing the roughly 40% efficiency of traditional steam turbine plants (thirion and steyn, 2021). by 2019, gas turbine combined cycle plants had surpassed coal-fired plants in generating capacity within the united states (thirion and steyn, 2021). http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 573 in a gas turbine setup, processed natural gas is transported via pipelines to the plant, where it combines with compressed air in the compressor and undergoes combustion in the combustion chamber. the resulting hightemperature gases produce the energy required for electricity generation, with the output directly corresponding to the energy released from burning natural gas (mathias and olusegun, 2020). it is important to note that natural gas still produces substantial carbon dioxide emissions, contributing to greenhouse gas levels. additionally, the price of natural gas can be volatile, creating economic uncertainty in its use for power generation. 3.2 nuclear power generation nuclear power plants generate electricity by harnessing the heat produced from nuclear fission. these plants depend on complex cooling and safety systems for proper operation. these plants offer the potential to generate vast amounts of energy in a single plant, unlike coal-fired plants, which release a range of harmful chemicals into the atmosphere such as nitrogen oxides, mercury, particulate matter, etc. with the depletion of fossil fuels raising concerns about future energy scarcity, nuclear energy remains a vital low-carbon, clean energy source that is expected to grow (sadekin et al., 2019). uranium, a primary fuel source for nuclear power plants, is mined and processed into uranium dioxide (uo₂). natural uo₂ contains a small amount of the fissile isotope 235u, which is enriched to make it suitable for nuclear reactors. this enrichment process results in byproducts like 238uo₂, which can have additional uses (wildi, 2006). the first nuclear reactor, constructed under the leadership of enrico fermi in 1942, marked a pivotal moment in nuclear science by achieving the first controlled nuclear chain reaction, laying the groundwork for modern nuclear power generation (zohuri and mcdaniel, 2015). a nuclear power station is similar to a thermal power station, except that a nuclear reactor replaces the boiler. the reactor contains fissile material that generates heat, and like conventional thermal stations, the power generation efficiency is around 30 to 40 percent (terzi and kurt, 2018). nuclear plants are typically located near large water sources, or in places where cooling towers are used to manage heat. significant challenges remain with nuclear power generation, including the high initial capital investment, the complexity of managing radioactive waste, and ongoing public safety concerns, particularly after notable nuclear accidents. these factors continue to influence the broader adoption of nuclear energy and gives it a low suitability for nigeria as seen in table 1 on page 20. 3.3 hydropower the world's first hydropower project was established in 1878 to illuminate a single lamp in a home in cragside, northumberland, england. four years later, the first commercial hydropower plant became operational in wisconsin, usa (sharma et al., 2021). today, over 160 nations use hydropower to generate electricity (benneth et al., 2023). hydropower, which harnesses the energy of flowing water, is broadly classified into two main types: hydroelectric systems and tidal power. hydroelectric systems include conventional dams, run-of-river installations that generate power without large reservoirs, and pumped-storage facilities, which store energy for later use. tidal power, on the other hand, captures energy from tidal movements. however, hydropower does have drawbacks, including environmental impacts on river ecosystems, dependency on rainfall and water availability, and displacement of communities during large-scale projects. 3.3.1 hydroelectric generation hydroelectric power, the most commonly used renewable energy source, harnesses the gravitational force of falling or flowing water to generate electricity. once in operation, hydroelectric plants produce no direct waste and emit significantly lower carbon dioxide levels compared to fossil-fuel power stations. the amount of electricity generated depends on two key factors: the hydraulic head, which is the elevation difference between the reservoir and the discharge point, and the rate of water flow. the amount of energy (𝐸), released when an object of mass (𝑚) falls a height (ℎ) in a gravitational acceleration (𝑔) is given by (wildi, 2006): 𝐸 = 𝑚𝑔ℎ 1 hydroelectric generation methods can be categorized into four types: conventional, pumped-storage, instream, and run-of-the-river (karre et al., 2022). traditional hydropower systems utilize dams to capture the potential energy of stored water, which is then used to drive turbines and generators. the amount of energy generated is determined by the volume of water and the elevation difference, or head, between the water source and its discharge point. a penstock channels water to the turbines while maintaining the pressure from http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 574 the head (moniruzzaman, 2019). pumped-storage plants, which balance load demand, move water between reservoirs at different elevations to generate electricity during peak demand periods. these plants are costeffective because they reduce reliance on peaking power plants, but the initial construction costs are high. run-of-the-river plants generate power without large water reservoirs, relying instead on natural river flow. water is diverted through pipes to turbines and returned to the river downstream. these projects are considered more environmentally friendly than conventional hydroelectric setups as they cause less flooding and emit fewer greenhouse gases. however, run-of-the-river plants are less reliable because they cannot store energy to meet demand fluctuations. in-stream hydropower systems, similar to run-of-the-river setups, place turbines directly within riverbeds or dams, utilizing existing waterways to generate electricity. these systems may also function with bi-directional tidal flows (karre et al., 2022). 3.3.2 tidal power tidal power plants harness the predictable rise and fall of ocean tides, making them a highly reliable renewable energy source. energy can be extracted from tides in two primary ways: by utilizing tidal barrages, which store seawater and capture its potential energy, or by employing tidal stream generators, which harness the kinetic energy of moving water, similar to wind turbines (navya et al., 2021). tidal stream generators function like underwater wind turbines, using fast-moving tidal currents to drive turbines and generate electricity. these generators can be installed in naturally occurring channels, such as harbors and lagoons, where water moves swiftly (chauhan et al., 2015). they come in two main types: horizontal-axis turbines, where the blades rotate parallel to the water flow, and vertical-axis turbines, where the blades rotate perpendicular to the water flow (zainol et al., 2017). due to their lower costs and reduced environmental impact, tidal stream generators are becoming increasingly popular compared to traditional tidal barrages. tidal power has several drawbacks that limit its widespread adoption. one major issue is the high initial cost of constructing tidal barrages, turbines, and related infrastructure. additionally, tidal power plants can disrupt marine ecosystems, altering tidal patterns and affecting aquatic life. suitable locations for tidal energy generation are limited, as only coastal areas with strong tidal ranges and water flow can support such projects. another challenge is the intermittent nature of energy production, as tidal cycles result in power generation only during high and low tides, creating gaps in supply. maintenance is also a concern, as the harsh marine environment causes corrosion and biofouling, increasing operational costs. furthermore, large tidal structures may interfere with shipping routes and fishing activities, creating potential navigational challenges. these factors make tidal power less widely adopted compared to other renewable energy sources. 3.4 wind power wind energy converts the kinetic energy of moving air into electricity through wind turbines, which can be deployed on both land and at sea. these turbines, especially large utility and offshore models, are typically located far from population centers, generating energy for widespread use (aziz et al., 2020). wind energy is renewable, has no fuel costs or emissions during operation, and has become increasingly cost-competitive. wind turbines operate efficiently within a wind speed range of 3.5 to 25 m/s (radzka et al., 2019). despite its advantages, wind power faces challenges such as its intermittent nature, potential impacts on wildlife (particularly birds and bats), and visual and noise concerns. wind results from air movement driven by pressure differences caused by the earth's uneven heating by the sun. the kinetic energy of this moving air can be transformed into mechanical energy using wind turbines, which feature blades extending from a central hub. when wind pushes against the blades, they rotate, generating mechanical energy that is converted into electricity through a generator. pitch and yaw controls adjust the turbine’s orientation to optimize performance. globally, wind power is the second most widely deployed renewable energy source after hydropower, with 51gw of capacity added in 2018, second only to solar energy (eicke et al., 2022). although there are no fundamental technical barriers to wind power integration, maintaining grid stability becomes crucial as capacity increases. wind energy systems convert wind’s kinetic energy into electricity through multiple stages. the efficiency of wind energy conversion depends on factors such as wind speed, the rotor’s swept area, and the efficiency of the rotor and generator. wind power output is highly sensitive to wind speed, increasing proportionally to the cube of wind velocity. a small rise in wind speed results in a significant boost in power generation. the power output is also proportional to the turbine’s swept area, which is defined by the http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 575 diameter of the rotating blades. a wind energy system consists of key components, including the aero turbine, mechanical interface, electric generator, and controller. wind turbines are classed based on the axis of rotation into two main types: horizontal-axis wind turbines (hawts) and vertical-axis wind turbines (vawts). hawts are the most widely used, featuring a small number of aerodynamically optimized blades that can be regulated through pitch control or stall regulation. these turbines range in capacity from small 10kw units to large multi-megawatt systems, with some reaching up to 5mw. for example, a 10kw turbine can supply enough electricity to power an average household in the u.s. or several rural villages in nigeria (garba and al-amin, 2014). they are typically configured with three blades, a design that balances efficiency and stability (tywoniuk and skorupka, 2018). vawts, while less common, have a simpler structure and do not depend on wind direction. the darrieus type, in particular, comes in several designs, such as the h-darrieus and eggbeater models, and often requires an auxiliary system like a savonius rotor to start (wagner and mathur, 2009). wind energy offers several drawbacks, such as fluctuating energy availability, the need for auxiliary storage devices like batteries, noise concerns, space requirements, and the complexity and weight of the systems due to the high towers required. 3.5 geothermal power geothermal energy is considered a renewable resource, with high-pressure steam from beneath the earth's surface serving as the primary heat source. as the earth's temperature increases with depth, reaching around 180°c at significant depths, water is commonly used as a medium to extract this heat. at a depth of about 10km, the temperature can rise to approximately 200°c. rainwater or other surface water seeps into the earth's deeper layers through the highly permeable and fractured crust, where it absorbs heat from the surrounding rocks. heat transfer occurs through both conduction and convection, with convection being highly efficient in areas with fractured rocks and circulating fluids. these heated fluids, known as hydrothermal resources, can be accessed by drilling wells, allowing the hot water or steam to be brought to the surface for direct use or for electricity generation. in regions with particularly high geothermal activity, fluids can exceed temperatures of 300°c and may exist as either water or steam depending on the pressure. these fluids, when extracted, can be used in various geothermal power plants or directly for heating purposes. ground-source heat pumps, commonly used for extracting or storing heat at shallower depths, are another application of geothermal energy (chijindu, 2021). the direct use of geothermal energy generally involves well-established technology and straightforward engineering methods. the most common approach is drilling wells into underground reservoirs of hot water and steam, which are then pumped to the surface for heating buildings and generating electricity (sharmin et al., 2023). hydrothermal convective systems are the primary geothermal resources used for generating electric power, and they can be classified into either vapor dominated or liquid dominated fields. geothermal power has several disadvantages that limit its broader implementation. one major drawback is the high upfront cost associated with exploration, drilling, and plant construction, making it less economically viable in some regions. suitable geothermal sites are geographically limited, as only areas with high underground heat activity can effectively generate power. the sustainability of geothermal reservoirs can also be a concern, as excessive extraction without proper management may lead to resource depletion over time. environmental issues such as land subsidence and the release of harmful gases like hydrogen sulfide and carbon dioxide can pose risks. additionally, geothermal fluids can be corrosive and contain harmful minerals, requiring proper disposal and treatment to prevent environmental contamination. in some cases, geothermal plants may trigger minor seismic activities, raising concerns about induced earthquakes. these challenges make geothermal power less universally applicable compared to other sources. 3.6 solar power solar power photovoltaic (pv) systems generate electricity by directly converting sunlight into electrical energy. as an abundant and renewable energy source, solar power emits minimal pollution and can scale from small installations to large utility projects. however, challenges such as intermittent generation, large land requirements for utility-scale installations, and the need for energy storage to ensure continuous power supply remains a major challenge. since the oil crisis in the early 1970s, leading nations like the united states, spain, germany, switzerland, france, italy, and japan have prioritized solar thermal power generation in their national research and http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 576 development agendas (kushwaha and kesari, 2022). over time, these efforts have led to the construction of numerous large-scale solar thermal plants, with more than 20 such plants (each with a capacity exceeding 500 kw) built globally in the past two decades. several of these are now in commercial operation (kushwaha and kesari, 2022). solar energy is a clean, renewable resource with vast potential to meet global energy demands while addressing social, economic, and environmental concerns (khajavipour et al., 2021). solar energy is the most abundant energy source on the earth and can be harnessed through both conventional methods and modern technological advancements, contributing to the reduction of greenhouse gas emissions (ingole et al., 2020). it is converted into usable power using photovoltaic cells and solar thermal collectors (kumar et al., 2018). the total solar flux absorbed at sea level is approximately 1.2 × 10¹⁷ w, which equates to about 20 mw per person—roughly the output of ten large diesel generators, sufficient to meet the energy needs of a town of 50,000 people (twidell, 2021). solar cells, which convert sunlight into electricity, come in two major forms based on the materials used in their construction. common materials include “monocrystalline and polycrystalline silicon, cadmium telluride (cdte), gallium arsenide (gaas), and indium gallium phosphide (ingap)”, among others (sanjay and saqib, 2020). crystalline solar cells, particularly monocrystalline and polycrystalline, currently achieve the highest conversion efficiencies among photovoltaic cells (kumi and brew-hammond, 2013). when sunlight hits a solar cell, it causes a phenomenon known as the photoelectric effect, where heat breaks metal bonds, freeing electrons to generate current. the photovoltaic effect, which occurs within the material, is responsible for the electricity produced in solar panels. solar power generation in general offers several advantages. the conversion system has no moving parts, making it reliable and low-maintenance. it produces no pollution, has a long operational lifespan and offers very high scalability although the efficiency is between 15 to 22% as seen in table 1, this continues to improve with continued research and innovation. since solar energy is free, there are no fuel costs, and the system can handle large power loads. however, the main disadvantage is the high initial cost, partly due to the need for energy storage systems like batteries, as sunlight is not available at night, although research in lunar panels aims to solve this issue. table 1: power generation impact and suitability technology efficiency (%) environmental impact scalability cost trend suitability for nigeria fossil fuels 33 – 45 high (co2, sox, nox) high increasing unsustainable nuclear 30 40 low co2, high toxic waste moderate stable/high low (infrastructure safety) hydropower 35 45 low site-specific stable moderate wind 30 45 very low site-dependent decreasing low (inconsistent wind) geothermal 10 20 low localized stable very low (resource limits) solar pv 15 22 very low very high rapidly decreasing high tidal 20 30 low low high not viable in nigeria 4. lessons for the renewable transition from historical power evolution despite a 15% rise in global energy demand over the past decade, the share of fossil fuels in the energy mix declined slightly from 82% in 2013 to 80% in 2023, with clean energy—comprising renewables, nuclear, and low-emission technologies—meeting 40% of the additional demand and projected in the iea’s “stated policies scenario” (steps) to drive fossil fuel consumption to a peak before 2030, though fossil fuels are still expected to supply 58% of energy by 2050, compared to just 10% under the “net zero emissions” (nze) scenario where renewables provide 90% (iea, 2025). this trend is illustrated in figure 2. the historical evolution of electrical power systems reveals more than just a series of technological advancements—it provides crucial insights into how innovation, infrastructure, and policy interact to shape energy landscapes and accelerate clean energy adoption. http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 577 figure 2: targeted global energy mix by 2050 (iea, 2025). as nigeria and other nations strive to transition from fossil fuel-based systems to sustainable energy sources, these historical patterns offer valuable lessons, enabling them to avoid past mistakes and effectively accelerate the deployment of clean energy solutions. following are key lessons for the renewable transition derived from historical power evolution. • sociotechnical factors drive adoption, not just technical merit the historical dominance of ac over direct dc, despite early dc advantages, demonstrates that the success of a technology depends on a confluence of factors: institutional support, economic viability, compatibility with existing infrastructure, and public perception. in today’s context, this suggests that renewable technologies will not win adoption solely by offering better efficiency or environmental benefits—they must be integrated into a broader system that supports their use. in nigeria, for instance, while various renewable technologies (such as wind, biomass, and hydropower) have shown technical promise, they often face logistical and policyrelated barriers that inhibit widespread deployment. • innovation clusters accelerate system transformation the emergence of three-phase ac systems in the 1890s was enabled by the convergence of generators, transformers, and motors designed to work in tandem—a process known as “innovation clustering.” similarly, the success of solar energy in modern power systems hinges not only on panel efficiency but also on the development of complementary technologies such as storage batteries, smart inverters, and decentralized grid architectures. nigeria’s solar potential is immense, particularly in the northern regions, where solar irradiance is consistently high. by investing in these enabling technologies and creating integrated solar ecosystems, nigeria can leapfrog many of the structural limitations that have slowed other forms of electrification. • technological lock-out can be avoided through flexibility the historical marginalization of thury’s hvdc system exemplifies how early infrastructure choices can lock systems into suboptimal pathways. today, many energy systems suffer from similar lock-ins, such as centralized grid designs that do not support distributed generation. for nigeria, a key lesson is the importance of flexibility—both in policy and technical design. supporting modular, off-grid solar installations in rural communities can provide rapid and scalable electrification without waiting for large-scale infrastructure upgrades. • solar energy as nigeria’s optimal renewable pathway 0 100 200 300 400 500 600 700 800 steps aps nze e x ajo u le s steps = stated policies scenario; aps = announced pledges scenario; nze = net zero emissions by 2050 scenario other coal natural gas oil clean energy http://www.azojete.com.ng/ mailto:omatsej@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 569-580. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: omatsej@yahoo.com 578 among all renewable sources, solar energy presents the most viable and strategic option for nigeria. unlike hydropower, which is vulnerable to climate variability and regional disputes, or wind power, which is geographically constrained, solar energy is abundant, widely distributable, and rapidly declining in cost. moreover, the decentralized nature of solar systems aligns well with nigeria’s need to expand energy access to underserved rural populations. with the right combination of policy incentives, public-private partnerships, and local capacity building, solar power can become the backbone of nigeria’s sustainable energy transition. 5. conclusion this review traced the evolution of electrical power generation and highlighted how economic, institutional, and technological factors have shaped energy transitions. today, as clean energy gains momentum, scenarios like the iea’s net zero emissions (nze) envision renewables meeting up to 90% of global demand by 2050, signaling a clear shift from fossil fuels. for nigeria, where resource constraints and environmental concerns converge, solar energy stands out as the most viable path forward due to its low environmental impact, scalability, and adaptability to both urban and off-grid settings. while solar offers transformative potential, its success hinges on integrated efforts—investment in storage, smart grids, and supportive policies—much like historical shifts that required systemic coordination. by embedding solar in a broader development strategy and learning from past transitions, nigeria can enhance energy access, drive economic growth, and meet climate goals. unlocking this potential will require bold leadership, strategic investment, and institutional innovation. references allerhand, a. 2017. a contrarian 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https://doi.org/10.1016/j.ijft.2023.100323 https://doi.org/10.1016/j.erss.2019.101242 https://doi.org/10.1016/j.erss.2014.02.001 https://doi.org/10.14710/ijred.7.1.77-84 https://www.researchgate.net/publication/354863542 https://doi.org/10.4324/9780429452161 https://doi.org/10.5604/01.3001.0012.4371 https://doi.org/10.1007/978-3-319-13419-2_18 corresponding author’s email address: ijanudavid@gmail.com 460 arid zone journal of engineering, technology & environment review article seismic behaviour of high-rise buildings equipped with fluid viscous dampers: a review i. a. david1* k. mohammed1, n. muazu1 and m. s. nadro2 1department of civil and water resource engineering university of maiduguri, borno state nigeria 2department of civil engineering modibbo adama university yola, adamawa state nigeria *corresponding author’s email: ijanudavid@gmail.com article information abstract earthquakes pose a significant threat to structural integrity and human safety, necessitating effective seismic mitigation strategies. this review paper explores the effectiveness of fluid viscous dampers (fvds) in mitigating seismic responses in high-rise structures. fvds, as passive energy dissipation devices, enhance structural resilience by reducing inter-story drift, base shear, and overall structural accelerations without significantly altering stiffness. the study compares fvds with alternative damping systems, including tuned mass dampers (tmds), hysteretic dampers (hds), friction dampers (fds), and lead rubber bearings (lrbs), highlighting the superior adaptability and efficiency of fvds in high-rise applications. placement strategies for fvds, their integration with other damping systems, and their effectiveness under varying seismic intensities are examined. findings indicate that uniform distribution across all stories ensures balanced energy dissipation, while targeted placement at lower levels enhances efficiency in specific structural configurations. also, hybrid approaches, such as combining fvds with brbs or base isolation, show promising outcomes in optimizing seismic resilience. the review suggests the importance of further research into computational optimization and practical implementation, torsional irregularities, uniform load distribution in high-rise structures on fvd performance particularly in developing regions like nigeria, where seismic risks are evolving. received:11th february 2025 revised: 25th april 2025 accepted: 25th april 2025 keywords: fluid viscous dampers high-rise buildings seismic mitigation structural resilience energy dissipation © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction natural disasters are unexpected events that occur in nature and have been a part of human history since the beginning of life on earth. among the various natural disasters experienced, earthquakes are considered one of the most devastating. its impact on human lives and property depends largely on their magnitude, often resulting in significant harm and destruction. (oluwafemi et al., 2018). an earthquake is a sudden and rapid shaking of the ground caused by the release of energy stored in the earth's crust. the energy released is typically as a result of the movement of tectonic plates, volcanic activity, or human activities such as mining or reservoir-induced seismicity. earthquakes are usually characterised by their magnitude, intensity, and the damage they cause to the environment and human structures (usgs, 2023). the significant socioeconomic impacts of earthquakes on structures cannot be entirely eliminated, but they can be greatly reduced by adopting appropriate structural design strategies. in recent years, the use of innovative supplementary devices in both newly constructed and existing buildings has emerged as an effective and economical approach. gupta et al., (2024); hussain et al., (2024) and hamza et al., (2024) have highlighted the success of these devices in minimizing the forces and deformations experienced by structural components. this is accomplished by altering the dynamic characteristics of the system, thereby applying the principles of structural response control and energy dissipation through advanced technologies. among these, the passive control method remains the oldest and most widely used technique for structural response management, with extensive research conducted in this area. a common approach in much of the literature involves integrating discrete components, known as dampers, into the structural framework. these dampers, known for their low maintenance requirements and independence from external power sources, are strategically placed within the azojete june 2025. vol.21(2):460-475 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/012 www.azojete.com.ng mailto:ijanudavid@gmail.com mailto:ijanudavid@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 461 framing system to link various elements and provide additional damping, effectively dissipating seismic energy (hejazi et al., 2024). 1.1 seismic activity in nigeria osagie, (2008) as cited in umasabor & alutu (2021), gave very descriptive and well-detailed information on various earth tremors that have occurred in nigeria from 1923 to 1990. the earth tremors included warri town in 1923, ohafia in 1933, yola in 1984, jere town of kaduna state in 1990, osererun hills in gombe council area of gombe state and amauze ede-obela in edema council area of anambra state both in 1988. also, an earth tremor occurred in abeokuta in 1986 and ibadan in 1990. osagie, (2008) as cited in umasabor and alutu (2021), queried the age-long belief that nigeria was a seismic haven due to the series of earth tremors experienced in the country. he warned that these incidences of earth tremors could be a build-up to a major earthquake in future. furthermore, oluwafemi et al., (2018) projected that nigeria could encounter earthquakes with magnitudes reaching 7.0 between 2025 and 2026, and 7.1 by 2028, with a probability of 36.79%. on the earthquake magnitude scale, magnitudes between 5.5 and 6.0 can cause slight damage, 6.1 to 6.9 may result in significant damage, 7.0 to 7.9 represents a major earthquake, and 8.0 or higher can cause severe devastation near the epicentre (muanya, 2021). despite being classified as a region of low seismic activity, nigeria faces a growing risk of a major earthquake in its southwestern region. the national building code 2006, section 8.8.13 also made provisions for earthquake lateral forces in buildings. therefore, structural engineers in nigeria should ensure the inclusion of earthquake lateral forces in their designs for structures in seismic active areas in nigeria to mitigate its effects on its integrity (umasabor & alutu, 2021). due to seismic activity and strong winds, high-rise buildings require meticulous design to balance stiffness and strength. traditionally, buildings are stiffened with braced frame and rigid frame system to reduce their dynamic response. however, this approach increases the seismic base shear experienced by the structure which can result to increased structural damage and higher foundation stress. additionally, incorporating supplementary damping into the design allows for reduced flexural stiffness, which minimises seismic base shear while effectively managing the building's response to wind forces (qadri and kacker, 2022). the seismic response of high-rise buildings in nigeria has become an increasingly critical issue due to the country's growing urbanization and the rise in high-rise constructions. although nigeria is not traditionally considered a high-seismic-risk zone, certain regions, particularly in the southern and central parts of the country, have shown susceptibility to low-to-moderate seismic activity, driven by tectonic activity along the boundary of the west african rift system. the absence of robust earthquake-resistant measures in the design and construction of many high-rise buildings raises significant concerns about the safety of these structures during seismic events. this review explores existing research on the seismic response of high-rise building structures, with a particular focus on the introduction of fvds as an energy dissipation system to mitigate seismic impacts on such structures. 2. mechanisms of vibrations in high-rise buildings high-rise buildings are increasingly susceptible to vibrations due to their height, flexibility, and exposure to dynamic forces such as wind, seismic activity, and human-induced movements. understanding how vibrations act on high-rise buildings is critical for ensuring structural integrity, occupant comfort, and overall building performance (zhao et al., 2022). this section explores the mechanisms of vibrations in high-rise buildings, their effects, and recent research on mitigation strategies. vibrations in high-rise buildings originate from both external and internal sources. wind-induced vibrations are among the most significant concerns, particularly for slender and super-tall structures. wind creates pressure differentials on the building surfaces, leading to oscillatory motion. when vortex shedding occurs at the building’s natural frequency, it can lead to resonance, amplifying structural displacement and acceleration (zhang et al., 2021). seismic activity also plays a crucial role in high-rise building vibrations. earthquake-induced ground motions introduce lateral forces, causing base shear, inter-story drift, and sway motions that impact the building’s stability (li & sun, 2023). the dynamic response of a high-rise structure to an earthquake depends on its natural period, stiffness, and damping characteristics. inadequate damping can result in excessive displacement, which may lead to structural damage or collapse (jiang et al., 2023). http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 462 human-induced vibrations, such as those caused by occupants movement, elevators, and mechanical equipment, also contribute to structural motion. in office and residential high-rises, floor vibrations can be problematic, affecting user comfort and potentially interfering with sensitive equipment. wang et al., (2021) found that perceptible floor vibrations in commercial buildings can be effectively controlled using structural modifications and damping systems. 2.1 effects and mitigation of vibrations on high-rise buildings excessive vibrations can lead to structural fatigue, serviceability issues, and occupant discomfort. structural fatigue occurs when repeated dynamic loads cause microcracks and material degradation over time, compromising the integrity of load-bearing components (chen & yang, 2023). serviceability issues, including excessive lateral sway and floor accelerations, may render a building unsuitable for occupancy, particularly in cases where vibrations exceed human comfort thresholds (kwok et al., 2020). studies indicate that lateral accelerations above 0.1 m/s² can cause discomfort for occupants, necessitating effective vibration control measures (lin et al., 2021). to counteract the adverse effects of vibrations, various damping technologies have been developed. passive damping systems such as tmds and fvds are widely used to absorb and dissipate vibrational energy, reducing overall motion (cui et al., 2022). active and semi-active damping systems, which utilize sensors and adaptive controls, further enhance the dynamic response of buildings by adjusting damping forces in real time (jiang et al., 2023). aerodynamic modifications, including tapered building shapes and perforated facades, have also been shown to minimize wind-induced vibrations by disrupting vortex shedding patterns (zhang et al., 2021). a case study on two skyscrapers shanghai tower and taipei 101 demonstrated the effectiveness of these combined strategies in mitigating vibrations and enhancing structural resilience (wu et al., 2020) 3. fluid viscous damper fvds as shown in figure 1, are passive energy dissipation devices designed to control vibrations in structures and mechanical systems. while these dampers have been widely used in the military and aerospace industries for many years, they are now increasingly applied in buildings to mitigate vibrations caused by wind and earthquakes. one of their most notable advantages is their ability to simultaneously reduce both stress and deflection in structures subjected to transient loads. this capability arises because the damping force is solely dependent on velocity, meaning the response remains out of phase with structural stresses due to flexing. since fvds rely on velocity for energy dissipation, they are highly effective in minimizing building vibrations. additionally, fvds are frequency-independent devices that function without a stiffness component (varun & sureshchandra, 2020). figure 1: fluid viscous dampers (gupta, 2024). figure 1 illustrates the damper in its mid-stroke position. the main pressure chamber, known as the cylinder, is completely filled with fluid and includes the volumes on both sides of the piston. the piston head is connected to the piston rod, and a clevis is attached to the left-hand side of the rod to connect with the structure. during dynamic loading, the piston rod, piston head, and clevis move together as a single unit while the other components remain stationary. the cylinder contains a compressible, viscous silicone oil that is heat stable, non-toxic, non-flammable, and environmentally friendly. http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 463 3.1 damping characteristics the operation of a fvd occurs when the structure moves, generating a resisting force without adding stiffness or carrying any load. however, stiffness can be incorporated into the dampers if required. in fvds, pressure develops as the piston moves back and forth. a custom-designed orifice within the piston creates an optimized relationship that regulates this pressure based on velocity. the resisting force increases as velocity rises, ensuring effective vibration control (varun & sureshchandra, 2020). this relationship is represented by an equation 1. 𝐹𝐷 = 𝐶𝐷|�̇�|𝛼𝑠𝑔𝑛(�̇�) 1 where cd represents the damping coefficient, expressed in terms of force per velocity raised to the power of α is the damping exponent, typically ranging between 0.35 and 1.0 for seismic applications; 𝑢 ̇ denotes the relative velocity between the two ends of the damper; and sgn () is the signum function. for α=1.0, equation 1 simplifies to: 𝐹𝐷 = 𝐶𝐷�̇� 2 which describes the linear force-velocity behaviour of a linear fvd. hence, the value of α determines the extent of non-linearity in fvds. the value of α plays a crucial role in determining the magnitude of the damping force. when α is equal to 1, the damper behaves as a linear damper, meaning the damping force is directly proportional to velocity. in practical applications, α values greater than 1 are not commonly used. the damping coefficient typically ranges from 0.2 to 2.0 (liu et al., 2021), depending on the specific application, though in some cases, it falls within 0.3 to 1.0. for modern seismic-resistant structures, an α value between 0.3 and 0.5 is commonly applied. 3.2 mechanical behaviour of an fvd the mechanical behaviour of an fvd can be represented mathematically using the maxwell model as shown in figure 2, which consists of a damper and an equivalent spring with stiffness 𝐾𝐷 . another schematic illustrates that a spring with stiffness 𝐾𝑏 represents the brace, while a spring with stiffness 𝐾𝑑 accounts for the inherent stiffness of the fvd. in the maxwell model, the damper and brace are arranged in series (mokhtari & naderpour, 2022). figure 2: (a) mechanical fvdbrace system; (b) maxell model 3.3 equation of motion for fluid viscous dampers (fvds are velocity-dependent damping devices that dissipate energy through fluid resistance. the equation of motion for a system with an fvd is derived using newton’s second law of motion and the dynamic equilibrium of a damped single-degree-of-freedom (sdof) system as shown in figure 3. 𝑀�̈�(𝑡) + 𝐶𝐷|�̇�|𝛼𝑠𝑔𝑛(�̇�) + 𝐾𝑢(𝑡) = − 𝑀𝑢�̈�(𝑡) 3 where: 𝑀 = mass of the structure, �̈�(𝑡) = acceleration of the structure, 𝑢(𝑡)= displacement of the structure relative to the ground, 𝐶𝐷|�̇�|𝛼𝑠𝑔𝑛(�̇�) = damping force, 𝐾 = structural stiffness, 𝑢�̈�(𝑡) = ground acceleration (earthquake input) 3.4 fvds design the primary function of fvds is to convert kinetic energy into heat through the movement of a piston within a cylinder filled with a viscous fluid. the damping force generated by an fvd is typically proportional to the velocity of motion, following a nonlinear or linear damping law (li et al., 2022). the design of an fvd involves http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 464 selecting the appropriate fluid, cylinder, piston, and seals to ensure optimal energy dissipation and durability. recent studies have explored the impact of piston configurations and orifice designs on damper efficiency, leading to improvements in force-displacement behavior and response time (wu et al., 2021; hejazi et al., 2024b; wang et al., 2025). 3.5 fvds design considerations several factors must be considered in the design of fvds to achieve optimal performance: i. fluid selection: the choice of fluid affects viscosity stability, temperature resistance, and damping efficiency. silicone-based and oil-based fluids are commonly used due to their consistent rheological properties under varying temperature conditions (zhao & wang, 2021). ii. damping coefficient: the damping coefficient is a crucial parameter that determines the effectiveness of energy dissipation. it is influenced by the damper’s geometry, fluid viscosity, and operating conditions (jiang et al., 2023). iii. structural integration: the placement of fvds within a building significantly impacts their performance. strategic positioning in structural braces, shear walls, or between floors can enhance damping effectiveness and reduce inter-story drift (cui & zhang, 2022). iv. temperature effects: high-rise buildings experience temperature fluctuations that can affect the viscosity of the damper fluid. thermal stability must be considered to ensure consistent damping performance across different environmental conditions (lin et al., 2021). v. maintenance and longevity: the long-term performance of fvds depends on material durability and the ability to withstand repeated dynamic loads. advances in seal technology and corrosion-resistant materials have contributed to improved lifespan and reliability (wang et al., 2021). 4. other dampers for dissipating energy in high-rise building during earthquake this section explores various damping systems beyond fluid viscous dampers, examining their mechanisms, structural applications, and effectiveness in enhancing the seismic performance of high-rise buildings. also, comparative analysis summarizing the key advantages, disadvantages, and application scenarios of each damping system is presented in table 1. 4.1 tuned mass dampers (tmds) tuned mass dampers (tmds) have gained significant attention as an effective tool for mitigating structural vibrations caused by dynamic forces such as seismic and wind loads. their application ranges across various types of structures, including high-rise buildings, bridges, and towers. recent advancements have focused on enhancing tmd designs to address challenges posed by nonlinear behaviors, complex building geometries, and soil-structure interaction (ssi) effects (hosseini et al., 2022) kim and kang (2021) investigated the application of semi-active tmds (satmds) in tilted high-rise buildings, a structural form prone to lateral displacement even under self-weight. their study employed magnetorheological (mr) dampers integrated into a satmd system on a 100-story tilted building subjected to seismic excitations. the control strategy utilized a fuzzy inference system controller (fisc), optimized using an evolutionary multi objective optimization technique. results demonstrated that the satmd outperformed conventional passive tmds, achieving similar control performance with less than 30% of the mass quantity. tmds and fvds both improve seismic response by reducing vibrations, but they operate differently. tmds consist of a pendulum or spring-mass system that oscillates out of phase with the building’s motion, counteracting seismic forces through resonance tuning. on the other hand, fvds use a viscous fluid to resist motion, providing velocity-dependent damping that dissipates seismic energy smoothly. while both reduce inter-story drifts and structural accelerations, tmds are most effective in high-rise buildings and for windinduced vibrations, whereas fvds work across a broader range of structures and seismic frequencies. tmds require precise tuning to match the building’s natural frequency, whereas fvds are self-adaptive to different seismic intensities (desai, 2021). tuned mass damper is shown in figure 3. http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 465 figure 3: tuned mass damper: (qamaruddin, 2016). 4.2 hysteretic dampers hysteretic dampers (hds) as shown in figure 4, are integral components of modern seismic protection systems, designed to dissipate energy and enhance the structural safety of buildings during seismic events. traditional bilinear hysteretic dampers (bhds) have been widely employed to increase the effective stiffness and damping of buildings, ensuring structural safety during severe seismic events. however, as gandelli et al., (2021) highlight, bhds primarily operate within their elastic regime during minor earthquakes, providing minimal damping and resulting in high peak floor accelerations (pfas) that can damage non-structural components (nscs) like electric systems and false ceilings. to address these limitations, a novel adaptive hysteretic damper (ahd) capable of modulating its damping and stiffness based on earthquake intensity, significantly enhancing nsc protection during minor earthquakes without compromising safety during severe events. the evolution of vibration control technologies has led to the emergence of inerter-based vibration absorbers (ivas), such as tuned-mass-damper-inerters (tmdis). patsialis et al., (2023) explored the application of tmdis in multi-storey hysteretic buildings under seismic excitation, presenting a bi-objective design framework that balances structural drift/acceleration suppression and control forces. through nonlinear response-history analyses, the study demonstrated the effectiveness of ivas in optimizing vibration suppression, particularly when considering the nonlinear behaviour of structures. this optimization process offers a promising alternative to traditional hds, particularly for complex multi-storey designs. hysteretic dampers and fvds both enhance seismic performance by dissipating energy, but they do so differently. hysteretic dampers (such as steel or lead dampers) dissipate energy through inelastic deformation, meaning they absorb seismic forces by yielding and undergoing plastic deformation. in contrast, fvds use a viscous fluid to resist motion, providing velocity-dependent damping without permanent deformation. both reduce inter-story drifts and vibrations, but hysteretic dampers rely on material yielding, making them effective for low-to-moderate seismic events, whereas fvds offer adaptive damping, making them more effective for high-frequency and varying-intensity earthquakes. while hysteretic dampers may require replacement after large earthquakes due to material fatigue, fvds generally require less maintenance (katsimpini et al., 2025). figure 4: hysteretic dampers (qamaruddin, 2016). http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 466 4.3 friction dampers friction dampers (figure 5) are energy dissipation devices widely utilized in buildings to mitigate the effects of dynamic forces such as seismic and wind loads. these dampers dissipate energy through material yielding or inelastic deformation, making them effective and reliable in enhancing structural resilience. studies have demonstrated their significant role in reducing vibrations and improving the safety of structures. for instance, xu et al., (2021) investigated triple friction pendulum bearings, which incorporate hysteretic damping mechanisms, and found them effective in balancing seismic isolation and wind-induced accelerations in highrise buildings. similarly, guo et al., (2022) proposed a rotational friction negative stiffness damper (rfnsd), which combines rotational friction with hysteretic properties, to improve the seismic performance of twintower structures, highlighting the value of hybrid damping systems. further advancements include integrating hysteretic dampers into multi-functional systems like two-level friction dampers and friction-type multiple tuned mass dampers (ft-mtmds) lin et al., (2024) demonstrated the effectiveness of ft-mtmds in reducing seismic and wind vibrations by leveraging hysteretic energy dissipation across multiple frequency ranges. additionally, tadas et al., (2024) evaluated the performance of hysteretic dampers in irregular buildings, showing their ability to reduce inter-story drift and floor accelerations, even in asymmetrical structures. however, the performance of these dampers can be affected by site-specific factors such as ssi. etedali et al., (2023) found that while hysteretic dampers significantly reduce seismic responses, their efficiency diminishes on soft soils or near fault lines, emphasizing the importance of probabilistic and site-specific design considerations. friction dampers and fvds both improve seismic resilience by dissipating energy, but they differ in their mechanisms. friction dampers use sliding surfaces with a predetermined slip force to convert seismic energy into heat through friction, providing stable energy dissipation once sliding begins. in contrast, fvds use a viscous fluid to resist motion, offering velocity-dependent damping that smoothly absorbs seismic energy. while both reduce inter-story drifts and vibrations, friction dampers provide constant resistance once activated, whereas fvds offer adaptive damping based on movement speed. friction dampers are more costeffective and require minimal maintenance, but fvds offer better performance in high-frequency seismic events (almajhali et al., 2024). figure 5: friction damper (qamaruddin, 2016). 4.4 lead rubber bearings (lrbs) lead rubber bearings (lrbs) are among the most effective base isolators used to enhance structural resilience during seismic events. lrbs consist of alternating layers of rubber and steel plates with a central lead core, where the rubber provides flexibility, the steel offers vertical stiffness, and the lead core dissipates seismic energy through hysteresis, significantly reducing structural acceleration and displacement (rong, 2020). they are commonly used in low to mid-rise buildings to improve seismic resilience by introducing an isolation layer at the foundation level, reducing the impact of seismic forces (faqiri et al., 2023). in high-rise and twin-tower structures, lrbs work effectively in conjunction with rfnsds to mitigate dynamic responses and structural damage, as demonstrated in the research by guo et al., (2022). comparative studies, such as patel et al., (2024), show that lrbs outperform high damping rubber bearings (hdrbs) in seismic response reduction, with a maximum acceleration reduction of 68.42% during strong earthquakes. furthermore, lrbs are increasingly integrated into composite buildings, where their effectiveness in reducing seismic forces surpasses that of http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 467 fixed-base reinforced concrete (rc) structures (darwish & bhandari, 2022). optimizing lrb parameters is crucial for maximizing their performance, as highlighted by rong (2020), who identified the optimal yield shear coefficient range of 0.10 to 0.14 and a pre-yield to post-yield stiffness ratio between 16 and 35 to enhance energy dissipation. lrbs and fvds are two widely used seismic mitigation devices, each with distinct mechanisms and applications. lrbs function as base isolation systems, providing flexibility at the base of a structure to reduce transmitted seismic forces (chen et al., 2022). they dissipate energy through the plastic deformation of the lead core while allowing lateral movement, thereby reducing acceleration and structural damage. in contrast, fvds operate by dissipating seismic energy through fluid movement within a cylinder, effectively controlling inter-story drifts and reducing structural response without altering the building’s fundamental period (sharma et al., 2023). the primary advantage of lrbs is their ability to significantly reduce base shear and prevent damage to superstructures by isolating seismic energy (hu et al., 2023). however, their effectiveness is limited for taller buildings, where flexibility at the base may not be sufficient to control upper-story accelerations. additionally, lrbs require a substantial footprint and are more suitable for lowto mid-rise structures with strong foundations. on the other hand, fvds are highly versatile and can be installed at multiple levels, making them effective in high-rise buildings where inter-story drifts need to be minimized (khan, 2023). unlike lrbs, fvds do not significantly alter the building's stiffness, allowing them to be integrated into existing structures without major modifications (kiral & tonyali, 2025). lead rubber bearings is shown figure 6: figure 6: lead rubber bearings (qamaruddin, 2016). table 1: a comparative analysis table summarizing key advantages, disadvantages, and application scenarios of each damping system s/n authors damping device key advantage(s) key disadvantage(s) application scenario(s) 1 rong (2020); faqiri et al., (2023); guo et al., (2022); patel et al., (2024); darwish & bhandari (2022) lead rubber bearings (lrbs) significant reduction in base shear and structural damage. effective seismic isolation for lowto-mid-rise buildings. energy dissipation through hysteresis of the lead core. less effective for high-rise structures due to excessive flexibility at the base. requires a larger foundation footprint. used in low-to-mid-rise buildings to isolate seismic forces. integrated with rotational friction negative stiffness dampers (rfnsds) for twin-tower structures. common in composite buildings for enhanced seismic resilience. http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 468 s/n authors damping device key advantage(s) key disadvantage(s) application scenario(s) 2 xu et al., (2021); guo et al., (2022); lin et al., (2024); tadas & sanghai (2024); etedali et al., (2023) friction dampers (fds) stable energy dissipation through friction. cost-effective and low maintenance. efficient in reducing vibrations and structural drift. performance can be affected by sitespecific factors (e.g., soilstructure interaction). may require additional mechanisms to optimize damping force. used in high-rise and irregular structures for vibration control. applied in hybrid damping systems like rfnsds and ft-mtmds. effective in regions with frequent moderate earthquakes. 3 gandelli et al., (2021); patsialis et al., (2023); katsimpini et al., (2025) hysteretic dampers (hds) effective for energy dissipation through inelastic deformation. increases damping and stiffness, improving seismic performance. limited effectiveness for minor earthquakes (low energy dissipation). material fatigue may require postearthquake replacement. common in multi-story structures to reduce interstory drifts. integrated with inerterbased vibration absorbers (ivas) for complex buildings. used in buildings located in high seismic regions. 4 hosseini et al., (2022); kim & kang (2021); desai (2021) tuned mass dampers (tmds) highly effective in reducing vibrations, especially windinduced. can significantly decrease lateral displacement in high-rise buildings. requires precise tuning to the structure’s natural frequency. performance decreases if detuning occurs due to structural changes. ideal for tall buildings, bridges, and towers. applied in tilted high-rise structures for displacement control. used in cases where windinduced vibrations dominate. 5 sharma et al., (2023); kiral & tonyali (2025) fluid viscous dampers (fvds) adaptive damping across various seismic frequencies. effective in reducing interstory drifts and structural accelerations. can be integrated into existing structures with minimal modification. higher initial cost compared to friction dampers. long-term performance may degrade under sustained loading. common in high-rise buildings to reduce seismic and wind loads. used in retrofitting older structures for improved seismic resilience. applied in critical infrastructure (e.g., hospitals, bridges). 5. review analysis 5.1 effectiveness of fvds in improving seismic response the various studies collectively highlight the effectiveness of fvds in improving seismic response by significantly reducing displacement, drift, base shear, and bending moments. hu et al., (2020); belbachir et al., (2023), and tiwari et al., (2023) agree on the positive impact of fvds on structural stability during seismic events. the findings of these authors collectively demonstrate the effectiveness of fvds in improving seismic response by reducing displacement, drift, base shear, and bending moments. tamang & sharma, (2021); and hatipoglu & duzgun, (2023) acknowledge the significant impact of fvds on structural stability during seismic events. however, limitations in scope, such as specific building types, configurations, and regional biases, necessitate further research for broader applicability. the studies differ in their focus on structural types, with some emphasizing low-rise buildings (belbachir et al., 2023) and others on high-rise structures (hamza et al., 2024). the methodologies also vary, with some authors using steel strip dampers (zhai et al., 2021) and others employing non-linear viscous dampers (riaz et al., 2023). additionally, the scope of effects examined, such as plastic deformation (hu et al., 2020) versus energy dissipation (zhai et al., 2021), highlights the diverse approaches to evaluating fvds performance. http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 469 in a multi-degree of freedom (mdof) system incorporating fvds, the damping coefficient can be determined following the procedure outlined in the flowchart of figure. 7. this flowchart, which focuses on the first vibration mode, presents an equation for the effective damping ratio contributed by the fvds in a building structure, as derived by seleemah and constantinou (1997) and soong and constantinou (1994) as cited in mokhtari & naderpour, (2022). study by ras & boumechra (2016) suggests that distributing the damping coefficient values uniformly across all stories is a practical approach. their study also found that dampers are more effective on the lower floors compared to the upper ones. figure 7: flowchart of the calculating the damping coefficient of an mdof system with fvds (mokhtari & naderpour, 2022). where: t is the natural period of the first vibration mode, 𝐶𝑗 is the damping coefficient of the fvds at the 𝑗𝑡ℎ story, ɳ𝑗 is the number of identical fvds with the same 𝐶𝑗 in each story, 𝜑𝑗 and 𝜑1−𝑗 are the first modal displacements of the 𝑗𝑡ℎ and 𝑗 − 1𝑡ℎ stories, respectively, 𝜃𝑗 is the inclination angle of the fvds at the 𝑗𝑡ℎ story, a is the amplitude of the roof response corresponding to 𝜑𝑗 , normalized to a unit value at the roof, 𝑀𝑖 is the mass of the 𝑖𝑡ℎ floor, λ is a factor that can be determined using a specific equation 5.  = 22+𝛼 2(1+ 0.5 (2+) 5 where г is the gamma function. 5.2 placement of seismic dampers in reducing seismic responses the placement of fvds in high-rise buildings is a crucial factor in optimizing seismic performance. various methods have been explored to determine the most efficient arrangement of fvds for minimizing earthquakeinduced vibrations. sharma et al., (2023) analyzed three placement scenarios in a g+20 structure and concluded that placing dampers on all stories significantly reduces displacement, drift, and shear forces. similarly, jigar et al., (2018) found that placing fvds at the lower stories leads to greater reductions in displacement and drift, while distributing dampers across all stories effectively minimizes base shear. however, alternative approaches have also been investigated, including concentrated placement at external corners (mujeeb et al., 2019), uniform distribution (martinez-paneda & elghazouli, 2021), and optimized placement using algorithms (nguyen-thai et al., 2024). as supported by sharma et al., (2023) and martinez-paneda & elghazouli (2021), uniform placement of fvds across all stories ensures balanced energy dissipation and effective structural resilience under seismic and wind conditions. however, this method can be costly and requires precise tuning to avoid excessive base shear. on the other hand, lower-story placement, as suggested by jigar et al., (2018), is more effective in reducing drift and displacement but may not adequately control upper-story accelerations. concentrated placement at external corners, as recommended by mujeeb et al., (2019), enhances lateral stability but may be less effective in structures with irregular geometries. determine the allowable interstory drift ratio estimate the desired added damping ratio (𝜁𝑑) assume the inherent damping ratio (𝜁0 = 5%) calculate the effective ratio 𝜁𝑒𝑓𝑓 = (𝜁0 + 𝜁𝑑) calculate the damping coefficient (c) (as per fema 𝜁𝑒𝑓𝑓 = 𝜁0 + 𝑇2−𝛼 𝑥 σ 𝑗 𝑥 𝐶𝑗 𝑥  cos1+α 𝑗 𝑥 ൫𝜑𝑗− 𝜑𝑗−1൯ 1+𝛼 𝑗 (2)3−𝛼 𝑥 𝐴1−𝛼 σ 𝑀𝑖.𝜑𝑖 2 𝑖 4 http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 470 algorithm-based optimization, as explored by nguyen-thai et al., (2024), has emerged as a promising approach, effectively minimizing inter-story drift and floor accelerations. nevertheless, the scalability of such methods to taller and more complex structures remains a challenge. similarly, patel & agrawal (2020) demonstrated that fvds significantly reduce seismic response in structures with different bay sizes, but their study was limited to specific configurations, indicating the need for broader parametric research. while various placement methods have been studied, the most widely used and effective approach appears to be the uniform distribution of fvds across all stories, as it ensures overall seismic resilience and minimizes base shear. figure 8 and 9 shows how fvds are placed in high rise building. figure 8a: model with fvd for all storeys figure 8b: model with fvd alternate for all storeys at exterior corners. at exterior corners (giwa & oyelade, 2024). figure 9a: model with fvd at central in the storeys. figure 7b: model with fvd at bottom 3 storeys (mujeeb et al., 2019) 5.3 combining fvds with different damper systems to improve energy dissipation alhamdany & dilsiz (2025) and thakur & tiwary (2023) studied the integration of fvds with other systems. additionally, the applicability of findings varies, with some studies focusing on specific regions, building types, or seismic zones, as highlighted by mahakalka et al., (2023) and benita & hemalatha (2017). several studies, such as du et al., (2020) and thakur & tiwary (2023), indicate that combining fvds with other retrofitting systems (e.g., brbs, base isolation) offers superior seismic performance. this approach leverages the benefits of different damping mechanisms to achieve enhanced energy dissipation and structural stability. according to alhamdany & dilsiz (2025), the choice between fvds and shear walls depends on project goals, economic considerations, and focus areas. fvds are effective in reducing vibrations and structural displacements, making them suitable for projects prioritizing occupant safety. shear walls, on the other hand, improve lateral stiffness and stability, offering durable solutions for resource-limited projects. http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 460-475. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ijanudavid@gmail.com 471 6. major findings i. fvds significantly reduce inter-story drift, structural accelerations, and base shear forces in high-rise buildings. ii. one of the key advantages of fvds over the others is that it can be integrated into existing structures with minimal modification. iii. fvds are more effective on the lower floors compared to the upper ones. iv. effective placement appears to be the uniform distribution of fvds across all stories. v. there is limited or no studies on torsional irregularities of buildings with fvds 7. conclusion this review has examined the seismic behavior of high-rise buildings equipped with fvds, evaluating their effectiveness in mitigating earthquake-induced structural responses. the study highlighted the significance of structural response control and energy dissipation technologies in enhancing the resilience of high-rise buildings, particularly in regions susceptible to seismic activity. various seismic mitigation techniques, including tmds, hysteretic dampers, friction dampers, and lrbs, were compared with fvds in terms of energy dissipation capacity, cost-effectiveness, and application scenarios and found out that fvds were more superior. findings indicate that fvds offer substantial benefits in reducing inter-story drift, structural accelerations, and base shear forces. unlike traditional stiffening methods that increase seismic base shear, fvds provide adaptive damping without significantly altering the structural stiffness, making them highly effective for high-rise buildings. however, the computational and hardware requirements for optimizing fvd placement and integration remain a key challenge. while uniform distribution across all stories ensures balanced energy dissipation, targeted placement at lower stories or external corners has been found to enhance efficiency in some structural configurations. recent advancements in combining fvds with other damping systems, such as brbs and base isolation, suggest that hybrid approaches can further enhance seismic resilience. the integration of fvds with emerging structural control technologies, including artificial intelligence-based optimization methods, represents a promising area for future research. additionally, the practical implementation of fvds in developing regions, including nigeria, requires further studies on economic feasibility and structural adaptability. finally, the review highlights the importance of fvds in mitigating lateral forces, but their role in counteracting torsional irregularities, uniform load distribution in high-rise structures is essential especially in regions with varying soil conditions like nigeria requires further research. references alhamdany, ama., and dilsiz, a. 2025. comparative evaluation of shear walls and fluid viscous dampers in seismic retrofitting of rc public school buildings. in structures 72: 108231 almajhali, kym., he, m., and alhaddad, w. 2024. enhancing seismic performance of structures: a comprehensive review of hybrid passive energy dissipation devices. in structures 69: 107223. belbachir, a., benanane, a., ouazir, a., harrat, zr., hadzima-nyarko, m., radu, d., and amziane, s. 2023. enhancing the seismic response of residential rc buildings with an innovative base isolation technique. sustainability, 15(15): 11624. benita, mi., 2017. seismic performance analysis of rcc benchmark problem with passive control system. international journal of scientific and engineering research 8(6): 98-105 10.17515/resm2022.435ie0521. chen, b., and yang, m. 2023. performance evaluation of fluid viscous dampers in high-rise buildings. engineering structures, 282: 115760. chen, x., ikago, k., guan, z., li, j., and wang, x. 2022. lead-rubber-bearing with negative stiffness springs (lrb-ns) for base-isolation seismic design of resilient bridges: a theoretical feasibility study. engineering structures, 266: 114601. http://www.azojete.com.ng/ mailto:ijanudavid@gmail.com arid zone journal of engineering, technology and environment, june 2025; 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idiake, et al., 2015b). since activities in the construction industry are regarded as important indicators for an economy (national construction policy, 1991), the demand and supply side of the industry should showcase the effect of these activities in the method of procurement adopted for each project development. by so doing the industry can provide useful services of organising and managing materials and other components that are combined to form projects. the nigerian public procurement act (ppa, 2007) as amended, recommends that construction projects should be procured through competitive or selective bidding process. whichever method is adopted, the winning bid may not always be the lowest, but the most responsive. however, the bid evaluation process involves participation of professionals in the client’s organisation as well as the commissioning of external cost advisers (consultants). these advisers among other things prepare pre-tender estimates for clients before tenders are invited (brook, 2017). the underlying assumption is that the construction firms that submit the lowest most responsive evaluated tender price should be awarded the contract (xia et al., 2013; dikko, 1999).the subsisting practice entices contractors to lower costs through cost savings techniques and managerial innovations. the savings are assumed to be subsequently transferred to clients through the competitive process (alien, 2001; hale et al., 2009; nguyen, lines and tran, 2018; tao et al., 2019). according to morledge and smith (2013), concerns have been expressed over the degree of reliability that clients attach to the selected contract sum, as most public sector clients rely heavily on the tender sum of the preferred contractor as an indicator of performance. bustani (2004) observed that unrealistic cost estimate by construction contractors, account for a significant azojete december 2024. vol.20(4):863-878 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:edsalla.qs@buk.edu.ng mailto:edsalla.qs@buk.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 864 level of poor performance by the contractors. there is therefore, the need to examine the contractor’s tender position against the performance of the construction projects they handle. 1.1 performance-based tender evaluation in nurshikin et al. (2016), the importance of performance-based tender evaluation as indicators for enhanced contractor performance was supported, as tender sum were observed to have a significant relationship with performance. mohammed et al. (2019) also identified significant factors responsible for poor construction project performance for which the cost factor ranked highest. it is therefore pertinent, to assess public-sector construction procurement practice in nigeria in order to reveal a good basis for formulating effective public sector procurement policy in respect of tender sums. since the extent to which a contractor wins a job and the adequacy of the tender sum are the main attributes of performance (mohammed et al., 2019), clients are still mostly disposed to awarding projects to the lowest bidders, whose tenders fall within +10% of the consultant/in-house estimate. such considerations encourage contractors to submit figures that fall within the range of the consultants’ estimate and an established percentage range. this, the contractors do to increase their chances of winning the contract (setiawan, et al., 2015). with the practice of choosing the lowest evaluated tender as leverage for strategic bargaining, contractors often lower their prices by a considerable amount, in order to secure the job (bustani and anigbogu, 2004). depending on the state of the economy and the construction industry, contractor’s decision on mark-up in difficult times are normally close to break-even or, worse, below cost (vassailo, 2001). a contractor winning a job below cost would then have to adopt a strategy during the project, whereby more money is made on claims and variations (morledge and smith, 2013). counterintuitively, most public clients base their decision at the time of award of contract on agreed cost, with the expectations that all contractual conditions are in place to safeguard their interest against any future claims. as concurred in previous research (alien, 2001; hale et al., 2009; minchin et al., 2013; nguyen et al., 2018; park et al., 2015), the subsisting rationale is responsible for the frequent award of contracts to contractors with the least appreciation of the project complexity or the greatest risk or a contractor with the lowest current workload. it therefore shows that there is, perhaps the need to examine contractor’s positions in bid against the project performance. construction procurement has been defined as the methods employed in the industry in respect of contractual options to be deployed by a client for the purpose of minimizing moral hazards attendant to the project development process (arain et al., 2014; eriksson and lind, 2016; oo and yan, 2018). turner (1990) averred that construction procurement entails all possible ways in which members of the construction team are assembled to provide or produce a facility (the end product). the procurement of construction products is achieved through a number of routes. hence, clients choose the route with the highest obvious potentials under the prevailing circumstances. the procurement route normally precedes the preparation of the project brief (palaneeswaran and kumaraswamy, 2000). the grouping of members of the construction team according to functions of design, management and construction is known as procurement paths (dada, 2012). each discrete path exhibits particular characteristics and therefore provide the necessary service(s) in meeting clients’ needs(chen et al., 2018; olanrewaju et al., 2016). some authors (alves et al., 2016; neuman et al., 2015) have noted that construction products could be acquired either through purchase, lease/rent or design and construction. the later process is normally complex and involves the commissioning of project team members, where each party brings into the process, its organisation expertise (ashworth and perera, 2015; hommen and rolfstam, 2009). ahmed et al. (2016) concurred that project objectives, as defined by the clients, always form the basis for any procurement decision. these objectives become the project requirements and constraints, as gauged by cost/time limits, aesthetic function and quality standard. 2. procurement systems many procurement routes are recognized in literature for construction projects delivery. however, the commonest route in practice is the traditional procurement route also known as the design-bid-build (dbb), in spite of it being design-led and prone to budget, simply because it is better recognized by the nigerian public procurement regulatory framework. 2. 1 traditional procurement system (design-bid-build) the traditional system owes its prominence to the fact that many construction clients initially sought for someone with the capability of translating their briefs into a design. the designer in this case becomes the http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 865 leader of the construction process(carpenter and bausman, 2016; minchin et al., 2013). this system also provided useful datum for the consideration of other systems. the system is characterised by sequential design-bid-build process (nguyen et al., 2018). in the traditional system, the client appoints consultants for design. upon the completion of the design, a contractor is appointed to carry out the construction work (hughes et al., 2015; idiake et al., 2015a, lingard, et al., 1998). in building projects, architects take the client’s brief and transforms it to an architectural form. other professionals, such as the structural engineer, come in for the structural design and detailing, while the building services engineer takes care of mechanical and electrical details to a point where the various elements of the structure can be taken off and worked up into a bill of quantities by the quantity surveyor (rajeh, et al., 2015; doloi, 2012; ramsey et al., 2016). as supported in many studies (ballesteros-pérez et al., 2015; oo and yan 2018; zavadskas et al., 2008), one feature of the system is the competitiveness in the selection process of the right contractor. this is buttressed in dorée and holmen (2004) and papadonikolaki (2018) as the system is known for its fragmentation and the separation of design and construction of the product. according to frank (1998), competitive tenders as a system ensures that the client obtains the benefits of the lowest cost, with drawings and priced bills of quantities facilitating measurement and valuation of variation during progress of works. the design is normally fully developed at tender stage. variations in the systems are adapted by an accelerated and parallel activities of design overlapping with construction (ramsey et al., 2016; walker, 2015). the criticism of the system is that it minimizes the overlap in the period of design and construction, which requires that design have to be completed before construction (ramsey et al., 2016). in the same way, invitation for tenders after design, before construction start, may require longer period when compared to other system like ‘design and build’ or ‘management’ procurement option (alien, 2001; ling et al., 2004; park et al., 2015). walker (2015) reports that when using the traditional procurement approach, inter-team working relationships fails in creating an environment where the construction team can best contribute its expertise in achieving a quicker construction period and isolate the client’s representatives from the management of the construction process. aina and yakeen (2011) posit that in nigeria, both the public and the organized private sectors usually procure construction projects using the traditional contracting method. the practice has been attributed to the fact nigeria is a colony of britain where the traditional construction method was developed and widely used (ojo and gbadebo, 2012). 2.2 the design and build procurement system the design and build procurement method has been described by as “a single financial transaction under which one organisation designs and builds a facility on behalf of a client” (nguyen et al., 2018). under the design and build approach, the client enters into one contract with a design and build firm responsible for project development and construction. xia et al. (2013)indicated that the method is the simplest of all the procurement methods because there is only one contract and one line of communication for the client. as pointed out in previous studies (xia et al., 2014), the main feature of the system is that the responsibility for both design and construction lies with only one organisation, with contract signed most often before full documentation. design in this case is not fully completed before construction commences, and bill of quantities is not normally prepared, so variations are priced to a schedule. the consequences of this is that the variations have to be paid by the client either on a pro-rata basis or even at higher rates due to cost overrun. ajanlekoko (1992) claimed that the method helps clients to meet their objectives through a single financial transaction, on a preagreed price and possibly on a final scale not otherwise achievable without considerable risk. the range of services offered by the design and build varies considerably. in some cases, the design and build contractor will find the project site, arrange mortgage, sale-and-lease back and similar facilities. in addition to designing and constructing, to meet the clients requirements (ireland, 1984). the approach involves direct negotiation between the client and the contractor (or several contractors where the client seeks competitive tenders). basically, the client states his requirements and the contractor prepares design and cost proposals to meet these requirements. the process entails contractors submitting an initial proposal to demonstrate the ‘package’ to the client and the design is only fully developed when both parties have reached an agreement regarding specifications and price. the most common types of the design and build system include: i. direct in this case, no competition is obtained in tenders. some appraisal of possible competitors may be made before tendering but only one tender is obtained. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 866 ii. competitive competitive design and build is the most usual procedure with tenders being obtained from documents that are prepared to enable several contractors to offer competition in designs and in prices. iii. develop and construct consultants design to a partial stage often called a ‘scope design’, then obtain competitive tenders from contractors that develop and complete the design and then execute the project. some alternatives abound in the body of knowledge on construction procurement which include the package deal, management procurement system. four types of management system can be distinguished in the construction industry. these include management contracting, construction management, design and manage, as well as design, manage and construct. 2.3 contractor selection methods in the construction industry one of the most important tasks facing a client when embarking on a scheme of construction work is the correct choice of a contractor for the project (araújo et al., 2015; erdogan et al., 2017; idiake et al., 2015a, 2015b; watt et al., 2010). irrespective of the final contractual arrangements chosen by the client, the methods of selecting the contractor must first be established. the two basic methods are: by competition or by negotiation 2.3.1 contractor selection by competition this is the practice of selecting a contractor based on the submitted price for a proposed project (hughes et al., 2015; watt et al., 2010). the basic principle behind competition in contractor selection is to ensure that prices obtained from contractors, all competing genuinely with each other for a project, give the best value for money and is the lowest possible price for the job. other variables are also determined and clearly stated in the tender documents. in some cases, the client may be faced with situations where such factors as time, are more crucial than the project cost. in such cases, competition on the bases of time precedes. the decision to award construction contract on competitive basis may result in the client choosing one of the two options, that is, the open or the selective approach to obtaining competitive tenders from contractors (shah et al., 2012). 2.3.2 contractor selection by negotiation in this method of contractor selection, the client approaches only one contractor who is considered to be the most suitable and capable under the prevailing circumstances. the client negotiates the project cost and timing with the contractor (olaniran 2015; stanford and molenaar, 2016; watt et al., 2010). according to liu et al. (2014), the main reasons for contractor selection by negotiation are either because the project under consideration is to be completed as early as possible, with no delay, which is characteristic of normal tendering procedure with respect to the preparation and despatch of documents and selection of a contractor, or the work to be carried out is of complex nature that includes complex detailing, billing and costing. another reason why client may go into negotiation is reliability of the contractor, which the client is aware based on past experienced. one of the three methods below is used as a basis for determining the project cost under this arrangement. 2.4 tendering process as a contractor selection tool tendering is the purchasing procedure whereby potential suppliers are invited to make a firm offer the price and terms, which, on acceptance, shall be the basis of the subsequent contract. such contract can be between a client and contractor, a client and consultant or a contractor and a sub-contractor, and so on. prior to the start of a tendering process, a decision has to be made on the contractual arrangement or procurement option that would have to be entered into on acceptance of a tender. thai (2001; 2009) report that competition in tendering is an age long method for establishing the fair value of a product or service, the efficacy of which is evidenced in the various forms in which it is employed. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 867 2.4.1 the open tendering under the open tendering method, prospective contractors are invited to compete for a contract advertised in the press. this is done through application of tender documents (usually obtained on payment of nonrefundable deposits). by allowing all possible tenders, the client can gain the biggest possible response to his advertisement and therefore, maximum possible competition. in this way, the lowest possible price for the project can be achieved. the lowest reasonable bidder will be assumed to be the successful contractor. however, in some cases, the advertisers state that they are not bound to accept the lowest tender. similarly, restricted open tender also exist, where prospective contractors are invited to compete for a contract through the advertisement that is restricted to appropriate technical journals or local newspapers. 2.4.2 selective tendering in selective tendering, tenders are invited from contractors on an approved list and who have been “vetted” with respect to their competence and financial standing. usman (1991) asserts that the competence of such contractors relates to their established skill, reliability and proven experience for the type of work envisaged. 2.5 the bidding models 2.5.1 the friedman’s model friedman (1956) proposed that the probability of winning a contract at a given mark-up competing against a number of known competitors equals to probability of beating competitor ‘a’ x probability of beating competitor ‘b’ x probability of beating competitor ‘c’ etc. in dealing with the tendering situation of unknown competitors, friedman (1956) suggested aggregating all competitors’ tenders into a distribution, where the historical behaviour represents typical contractor behaviour and not of any particular contractor. thus, to predict the probability of winning a contract against a known number of unknown competitors, friedman (1956) suggested that the probability of winning against unknown competitors for a given mark-up= (probability of beating one ‘typical’ competitor). 2.5.2 the gate model gate (1967) criticised friedman’s work on theoretical ground and offered his own solution, which is also based on the collection of historic data and the creation of a distribution of competitor’s tenders against the client estimates. in gates model, probability of winning a contract at a given mark-up against a number of known competitors is given by equation 1; ( )  ( )  ( )  p p p p p p pa a b b c c = − + − + − + + 1 1 1 1 1/ / / ....... (1) where pa = probability of beating competitor a pb = probability of beating competitor b pc = probability of beating competitor c for the case of unknown competitors, the gates models becomes ( )  p n p p n typ typ = − + 1 1 1/ (2) where pn= probability of beating n unknown competitors ptyp= probability of beating a typical competitor. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 868 2.4.3 the “a+b” bidding model in the “a+b” bidding model, contractors’ tender price (called part a) like in any other conventional tendering system. if the contractor is awarded the project, those prices will be the base for the cost reimbursement for constructing the project. the client then determines the value of a time unit for the project (x). the value of the time unit will be included in the tender documents. each contractor will then have to determine the time required for completing the project (called part b). when bids are submitted the client determines the lowest combined (a+b) contractor using the equation 3: lcb a bx= + (3) where lcb=lowest combined tender a= cost estimate of the contractor b=time estimate of the contractor x=determined time unit for the project 2.4.4 modified friedman’s and gates models friedman’s and gate’s models gave different answer, and generated serious debates. in attempt to resolve the conflict, other models evolved including the grinyer and whittaker (1974) model, which attempted to take account of managerial judgement. the model provides the basis for well-informed judgement. boughton (1987) proposed a low competitor model based on the strength of the argument that the only competitor one is interested in beating is the lowest competitor. seydel (1990) opined that the friedman model was more correct when the cost estimates used by competitors were the same and the variability in tenders was due only to mark-up differences, and that the gates model was more correct when the mark-up used by competitors was the same and the variability in tenders was due to variations in cost estimate only and proposed a compromise model, which takes into account a weighted average of the probability predicted by friedman and that by gates, and proposed distribution or models for determining the winning tender which suggest that the probability of any particular tender being the winning tender, given an ‘overall distribution’ of tenders, from a number of projects estimates of the mean tender could be predicted accurately (to within +2%). an alternative model was put forward that takes into account the cost estimate and mark-up as independent variables. carr and sandahl (1978) and carr (1982) emerge as the major critics of grinyer and whittaker’s work on the grounds of the method of aggregating all contracts irrespective of the number of contractors, in order to obtain his distribution. they assert that the mean tenders can be estimated using managerial judgment with the required accuracy of + 2% and as such put forward as an alternative, a model based on conditional probabilities. however, it has been pointed out that such models were too simple in treating the cost estimate and the mark-up as independent variables (carr, 1982). harris and mccaffer (2001) took account of grinyer and whittaker’s model and the criticism of carr and sandahl work and produced distribution of tenders. the use of the overall distributions, or the distribution for projects grouped together by the number of contractors, makes it possible to predict the lowest bid from an estimate of the mean tender. this argument was supported by flanagan and norman (1982). lo (2000) proposed two models. the first is a tendering model that ensures the existence of maximum likelihood estimates of the contractor’s effects and projects effects. hence, the tendering strategies based on heterogeneous tendering patterns of contractors can be developed. this is a modification of the skitmore’s model (1991). the second is a multiple regression model using an index of competitiveness as the dependent variable and a multivariate normal distribution that takes into account the interdependence of tenders among competitors. this is used to evaluate the probability of winning the project. the model is similar to that proposed by skitmore and pemberton (1994). 2.5 tendering process paradigm the core of all models of competitive, non-collusive tendering process for projects is based on three observations (de neufville and king, 1991): http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 869 i. bidding is a risky process and the prospective benefits should be expressed in terms of expected values. ii. the expected benefits to a contractor depend jointly on the probability of winning, and on the difference between the tender sum and the actual cost of doing the project (mark-up). iii. the two parameters central to the process, the probability of winning and the mark–up, are dependent: i.e. the higher the mark-up, the lower the probability of winning. the stereotypical model of the tendering process focuses on the optimal strategy from the contractor’s perspective. it states that each contractor seeks to maximise the expected value (ev) of the process, as a function of the profit. that is, the mark-up proposed (m) and the probability of winning at that level of markup (pcm). in form of equation 4: maximize: ( ) ev pcm m, (4) the model takes two forms i.e. the expected value stated in terms of money and the utility for money (raiffa, 1968; de neufville, 1990; flanagan and norman, 1993). 2.5.1 the expected monetary – value models the competitive-tendering-strategy model was developed by friedman (1956), and was based on maximising the contractor’s monetary value. further work on the model was done by park (1966), rosenshine (1972), fuest (1977); and ioannu (1988). others have used it to develop computerised procedures (morin and clough, 1969) and for analyses of local construction markets (wade and harris, 1976) as well as to estimate the optimum mark-up (sugrve, 1980). gates (1967) develop models based on different concepts with respect to calculating the probability of winning over a group of competitors. benjamin (1972); rosenshine (1972); and dixie (1974), further modified these models. the ‘model’ differs from the friedman’s model because different methods are used to calculate the probability of winning over a group of competitors. a third variant proposed by carr (1982, 1983) treats cost, rather than profit, as the random variable. therefore, form the basis for calculating the probability of winning over a group of competitors. 2.5.2 the expected utility models concept of utility indicates that for any decision model about major choice, the fact that people value money non-linearly should be incorporated. this forms the basis for the evolution of tendering models based on utility (de neufville et al., 1977; ibbs and crandall, 1982). de neufville and king (1990) argued that while a model including utility is clearly more realistic, its feature did not by itself change the implication for management and that the dynamics of the tendering process is better comprehended through investigation and understanding the factors that influence the personal utilities of contractors. 2.5.3 the independent –private –value model weber (1985) describes the independent –private –value model as the model that conceptualizes tenders as representing each contractor’s independent –private –value, made without the knowledge of the other contractor’s project value. 2.5.4 the common–value model the common-value model conceptually defines a tender as being an individual contractors’ subjective estimate of an unknown project value that is common to all contractors. this model supposes that tenders are more alike than different by focusing on the underlying, unavoidable and common costs of each project that are dictated by the project scope, i.e. materials, labour and equipment (casari and cason, 2016). less significance is placed upon the variability between contractors (hausch and li, 1993). this model according to weber (1985) best fits the construction environment, because contractors are not significantly different in term of competitive advantage, productivity, and risk tolerance or profit objective. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 870 3. method 3.1 methods of data collection data used in the study were sourced from various consultancy out-fits, clients organizations in the federal capital territory, abuja through questionnaires and interviews as well as examination of tender reports. a total of 46 different project files were studied. these were projects initiated and completed between 2017 and 2020. however, only 26 projects representing about 63% of the total projects studied were found to contain the required information that are appropriate and suitable for analysis. table 1 shows the distribution of the projects by client. table 1: distribution of questionnaire by client type client type no. of questionnaires distributed % distributed ministries 26 56.5 agencies 20 43.5 source: data collection discussions centering on the problem of the research and a study of related literature in a wide-ranging manner resulted in the identification of appropriate technique for data analysis in the study. the distribution and details of responses from the administered questionnaires are presented in 3.2 techniques of data analysis the data used in the study were analyzed using both parametric and non-parametric techniques. 3.2.1 the chi-square (2) test the chi-square test was used to test the hypothesis that there is no significant difference between the tender sums received from contractors in the procurement of public sector construction projects in nigeria. the 2 distribution is a non-parametric technique that is used to test if an observed series of values differs significantly from what is expected, where the difference cannot be explained as being probably due to chance (siegel, 1988). the 2 statistics is given by: 2 ( ) = −      actual expected expected 2 (5) if the actual results are exactly as predicted, then (actual-expected) = 0, for each item in the series, and 2 = 0 (harper, 1977).the test was adopted in the study because the samples are randomly selected, independent from each other and the measurement scale is ordinal. 3.3 classification of tender in the study 3.3.1 position of contractors tender in the bid the position of the contractor’s tender in the bid was classified based on the mean tender sum. this is the average sum of all tenders submitted. it is based on the assumption that all tenders tend to assume an average value. three classifications of tenders were adopted in the study i.e. the mean tender, tender below the mean, and tender above the mean. 3.3.2 contractors performance rating the clients was asked to rate the performance of the contractor as either below average, average or above average in each case. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 871 4. results presentation the data sourced for the study is presented in table 2. the data was collected for the two categories of public clients selected for the study, namely: federal ministries and agencies. table 2: contractors’ tender sum, award price and final project cost s/no. contractors tender sum x 106 contract price x 106 final project cost x 106 contractors tender position contractors performance rating 1 127.5 127.5 127.5 below the mean tender below average 2 223.6 223.6 223.6 below the mean tender below average 3 471.8 452.928 552.006 above the mean tender average 4 547.2 547.2 547.2 below the mean tender below average 5 57.9 57.9 57.9 below the mean tender below average 6 96.7 96.7 96.7 below the mean tender below average 7 183.8 176.448 207.694 above the mean tender above average 8 226.5 226.5 226.5 below the mean tender below average 9 111.3 111.3 111.3 below the mean tender below average 10 117.4 117.4 139.706 above the mean tender below average 11 88.89 88.89 88.89 below the mean tender below average 12 348.6 348.6 348.6 below the mean tender below average 13 630.8 603.4 719.112 above the mean tender above average 14 294.5 294.5 294.5 below the mean tender below average 15 263.9 263.9 263.9 below the mean tender below average 16 199.8 199.8 199.8 below the mean tender below average 17 211.7 211.7 226.519 above the mean tender average 18 128.8 128.8 128.8 below the mean tender below average 19 370.7 370.7 370.7 below the mean tender below average 20 195.9 195.9 195.9 below the mean tender below average 21 89.1 89.1 89.1 below the mean tender below average 22 317.12 310.7776 358.3456 above the mean tender above average 23 123.2 123.2 123.2 below the mean tender below average 24 212.5 212.5 212.5 below the mean tender below average 25 168.3 168.3 168.3 below the mean tender below average 26 316.2 316.2 316.2 below the mean tender below average the components of the data consist of: contractors’ tender sum which represents the submitted tender sum by the successful contractor; the contract price which is a reflection of the price at which the contract was awarded to the successful contractor, the final project cost which represents the final cost of the project at completion after final accounts, the position of the contractor in relation to the mean tender sum during bidding and the contractors performance rating as indicated by the client. table 3 shows details relating to a contractor that has been awarded a construction contract within the period under review. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 872 table 3: chi-square test for the contract price and final project cost s/no. contract price (expected) final project cost (actual) 2 ( ) = −      actual expected expected 2 f value remark 1 127.5 127.5 0 7.81 not significant 2 223.6 223.6 0 7.81 not significant 3 452.928 552.006 21.6733125 7.81 significant 4 547.2 547.2 0 7.81 not significant 5 57.9 57.9 0 7.81 not significant 6 96.7 96.7 0 7.81 not significant 7 176.448 207.694 5.533145833 7.81 not significant 8 226.5 226.5 0 7.81 not significant 9 111.3 111.3 0 7.81 not significant 10 117.4 139.706 4.23814 7.81 not significant 11 88.89 88.89 0 7.81 not significant 12 348.6 348.6 0 7.81 not significant 13 603.0448 719.112 22.33929372 7.81 significant 14 294.5 294.5 0 7.81 not significant 15 263.9 263.9 0 7.81 not significant 16 199.8 199.8 0 7.81 not significant 17 211.7 226.519 1.03733 7.81 not significant 18 128.8 128.8 0 7.81 not significant 19 370.7 370.7 0 7.81 not significant 20 195.9 195.9 0 7.81 not significant 21 89.1 89.1 0 7.81 not significant 22 310.7776 358.3456 7.280816327 7.81 significant 23 123.2 123.2 0 7.81 not significant 24 212.5 212.5 0 7.81 not significant 25 168.3 168.3 0 7.81 not significant 26 316.2 316.2 0 7.81 not significant it shows the contractors tender price, the award price, the final project cost, the contractors’ tender position in relation to the mean tender and the client performance rating of the contractor as applied in this study. table 3 hypothesized that; there is no significant difference between the contract price and final project cost in the procurement of public construction projects in nigeria at 5% significant level. expected = contract price actual = final project cost while 2 (calculated) is given by = (actual expected)2/expected); and f= the critical 2 0.05,6 = 7.815. where the calculated values of 2 are greater than the critical value of 7.815, it was concluded that differences between the contract price and the final project cost was significant. from the above analysis, most of the projects were completely at zero sum difference. this indicates that the projects were delivered within the contract price. a closer look at the data collected from table 1 shows that even though most of the projects are delivered without additional financial commitment on the part of the client, the client rates the performance of such contractors as below average. this suggests that the clients are not satisfied with the quality and speed of the construction delivery of those contractors. meanwhile, where the final project cost is higher than the contract price, 2 calculated was found to be greater than the critical f-value shows that there is a significant difference between the contract price and the final project cost. this variation in the cost of the proposed projects between the contract price and the final project cost can be adduced mainly to the fact that contractors are the real constructors and are therefore most conversant with the actual cost of procuring projects, perhaps a more realistic estimate of a proposed project may be a tender sum above average bid submitted by contractors during tender. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 873 4.1 data analysis the analysis of the sourced data is presented table 4: table 4: summary of analysis from data collected s/no. description no. % of total 1 total no. of projects 26 100.00 2 no. projects awarded at tender sum 22 84.62 3 no. projects awarded above tender sum 0 4 no. projects awarded below tender sum 4 15.38 5 no. of projects completed above contract price 6 23.08 6 no. projects awarded below the mean tender sum 20 76.92 7 no. projects awarded above the mean tender sum 6 23.08 8 clients rating of contractors performance below average 21 80.77 9 clients rating of contractors performance at average 2 7.69 10 clients rating of contractors performance above average 3 11.54 4.1.1 respondents’ view questionnaires were administered to two groups of respondents: ministries and parastatals. in all cases, respondents indicate that the tender evaluation records are properly kept in the organization and 83% of the respondents rely on the in-house quantity surveyors to carry out tender evaluation exercise. the 83% respondents indicates that in-house quantity surveyor’s estimate is used to benchmark contractor’s tender sum. similarly, the respondents indicates that with respect to the mean tender sum, 76.92% of tenders submitted were below the mean tender sum, while 23.08% of the tenders are above the mean tender sum. the respondents similarly show that 23.08% of projects are completed at cost that is significantly higher than the original contract price. furthermore, 80.77% of the respondents shows that contractors perform much below average expectation, while 7.67% of the respondents shows that contractors’ performance is at average level of performance and 11.54% of the respondents indicates that contractors’ performance is above average. 5. conclusion a review of literature was followed with a field survey which enabled the appraisal of contractors’ tender position in relation to their mean tender sum for public construction projects in nigeria. the analyses show that 76.92% of submitted bids were below the mean tender sum, while 23.08% of the bids were above the mean tender sum. further examination shows that 23.08% of projects are completed at cost that is significantly higher than the original contract price while 80.77% of the contractors delivered the project within the contract price. however, the clients rating of the performance of the contractor reveals that contractors delivering project at cost or slightly below at final account do perform below average by. clients tend to disapprove of the quality and speed of delivery for such contractors. meanwhile, the clients in terms of performance and the quality and speed of the delivery rated contractors delivering at cost above the initial contract price above average. the variation in the cost of proposed projects; difference between the contract price and the final project cost was adduced mainly to the fact that genuine constructors were most conversant with more realistic cost of procuring projects and perhaps, presented more realistic estimate for proposed projects which justified their tender sum above the average bids submitted by contractors while tendering. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng arid zone journal of engineering, technology and environment, december 2024; vol.20(4):863-878. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: edsalla.qs@buk.edu.ng 874 from the results of this research, various analyses suggest that exist differences a relationship between a contractor’s tender position in relation to the mean tender during bid and the performance of the contractor for public construction projects in nigeria. the analysis indicates that contractors tend to perform below average when their tender price is below the mean tender sum. in the same way, contractors do perform above average where the accepted tender sum is above the mean tender sum during the bidding process. this suggests that perhaps tender prices below the mean tender sum are likely to be inadequate. this is in agreement with the common-value model where tenders are assumed to be more alike than different by focusing on common costs of each project that are dictated by the project scope, i.e. materials, labor and equipment. from the analysis, it is suggested that contractors with tender prices above the mean tender sum tend to perform above average based on the perception of the client. it is therefore recommended based on the findings in this study that the scrutiny of tenders should be with reference to the mean tender sums while serving as a measure for deciding the relevance of the in-house estimate as a benchmark for taking decisions in the tender evaluation process in public construction projects. references ahmed, mo., el-adaway, ih., coatney, kt. and eid, ms. 2016. construction bidding and the winner’s curse: game theory approach. journal of construction engineering and management,. 142(1): 76-83 alien, ln. 2001. comparison of design-build to design-bid-build as project delivery method. naval postgraduate school, montercy, califonia. alves, tcl., ravaghi, k., & needy, kl. 2016. supplier selection in epc projects: an overview of the process and its main activities. in construction research congress, 12(1): 209–2018). arain, f., mcfarlane, t., mah, d. and zahed, m. 2014. emerging project procurement trends in canadian construction industry. in construction research congress, 11(1): 1399–1407. araújo, mcb., alencar, lh. and mota, cmm. 2015. contractor selection in construction industry: a multicriteria model. in ieee ieem, 20(1): 519–523. ashworth, a. and perera, s. 2015. cost studies of buildings (6th ed.). london: taylor & francis. ballesteros-pérez, p., skitmore, m., pellicer, e. and gonzalez-cruz, c. m. 2015. scoring rules and abnormally low bids criteria in construction tenders: a taxonomic review. construction management and economics, 33(4); 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chen, q., xu, y., li, m. and jin, x. 2014. design-build contractor selection for public sustainable buildings. journal of management in engineering, 31(5): 1–7. zavadskas, ek., turskis, z. and tamošaitiene, j. 2008. contractor selection of construction in a competitive environment. journal of business economics and management, 9: 181-187. http://www.azojete.com.ng/ mailto:edsalla.qs@buk.edu.ng corresponding author’s email address: mmbenomar@yahoo.com 228 arid zone journal of engineering, technology & environment original research article evaluation of municipal solid wastes characteristics towards electricity generation in maiduguri metropolis b. m. tela1, m. b. oumarou2*, g. m. ngala2 and a. m. eljummah2 1 nigerian nuclear regulatory authority, garki, abuja, nigeria 2 department of mechanical engineering, university of maiduguri, pmb: 1069, borno state, nigeria *corresponding author’s e-mail address: mmbenomar@yahoo.com article information abstract this paper evaluates the characteristics of municipal solid waste (msw) in maiduguri metropolis for its potential use in electricity generation. three key areas within maiduguri were selected for the study: area a (northern nigeria flour mills), area b (monday market/gwange area), and area c (university of maiduguri dumpsite). additionally, three seasonal periods were considered (1) rainy season, (2) cold/harmattan season, and (3) hot season. refuse dumps in these areas were visited during each season to collect and analyze the msw. the characteristics of the msw were evaluated through physical analysis, which involved sifting through the waste and separating it into its major components. further analysis included proximate and ultimate analyses conducted according to astm standards to determine the properties of the waste. the study revealed that the composition of refuse produced by communities in maiduguri varies due to seasonal and behavioural changes. wood, plastics, and grass were identified as the major physical constituents of the waste, with their proportions influenced by seasonal variations. the calorific values of msw samples varied across the study areas, reflecting differences in population density and commercial activities. the highest calorific values were recorded in area b during the rainy and cold seasons, with values of 19.81 mj/kg and 15.055 mj/kg, respectively. at the university of maiduguri dumpsite (area c), the calorific values of msw samples were 7500 mj/kg, 8420 mj/kg, and 4500 mj/kg for the rainy, cold, and hot seasons, respectively, resulting in an average of 6800 mj/kg. this average is below the minimum calorific value of 7000 mj/kg required for setting up an incineration plant with energy recovery. to enhance the energy potential of the msw from the university of maiduguri, supplementary fuels such as bagasse would need to be added to boost its calorific value and make it suitable for electricity generation. this study highlights the potential for msw utilization in maiduguri and identifies areas for improvement to optimize its energy recovery capabilities. submitted: 28th november 2024 revised:3rd february 2025 accepted: 5th february 2025 keywords: municipal solid waste physical analysis proximate analysis ultimate analysis calorific value maiduguri © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction solid waste generation and characterization are some of the most important parameters which affect environmental sustainability (huseyin et al., 2016). municipal solid waste (msw) characterization depends on social structure and income levels. the amount of waste generated and the growing concern over health (hamer, 2003) and environmental problems (yang et al., 2019) related to improper waste disposal methods such as uncontrolled and crude landfilling has risen to an unacceptable point where transformation technologies and techniques are to be thought of power generating technology using municipal solid waste (msw) as fueling resource requires that the mechanism of performance is investigated to devise ways of optimization. typical of the performance tools are the parameters related to the waste characteristics such as basic components, moisture content, and calorific value. to enhance the performance of the msw plant, in addition to identifying the parameters alongside their significance, it is of importance to investigate these parameters and correlate them for the development of a msw power system. in many countries, open dumping is considered the simplest, cheapest, and most cost-effective way of managing solid wastes. thus, in azojete march 2025. vol.21(1):228-236 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:mmbenomar@yahoo.com mailto:mmbenomar@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 228-236. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 229 underdeveloped economies, msw is openly dumped (osra et al., 2021). improper waste disposal causes air, water, and soil pollution, impairing soil permeability and blockage of the drainage system. solid waste management (swm) can be enhanced by operating a well-engineered site with the capacity to reduce, reuse, and recover msw. the energy crisis and environmental degradation are currently two vital issues for global sustainable development (leena et al., 2014). rapid industrialization and population explosion have led to migration of people from villages to cities, which generate thousands of tonnes of municipal solid waste daily, which is one of the important contributors to environmental degradation. improper management of msw causes hazards to inhabitants. the management of msw requires proper infrastructure, maintenance, and upgrades for all activities. several kinds of research have been focusing on msw. status and challenges of msw, their characterization, valuation as possible renewable resource and their management in countries such as india, ethiopia, nigeria, saudi arabia (peter et al., (2008); joshi and ahmed (2016); diego et al., (2017); aron (2017); ogwueleka (2009); oumarou et al., (2012)a ; oumarou et al., (2012)b ; osra, et al., (2021); ) and its use for energy recovery as well as the techniques (umberto (2012); ola and göran (2017); olisa and ajoko (2018); olisa et al., (2016) ; olisa et al., (2017) ; oumarou et al., (2018) ; oumarou, et al., (2012); altine et al., (2017); jack and oko (2017); amulah et al., (2024); ) amongst other, have been investigated. the calorific value, a single most important parameter, measures the energy available in a particular substance that is released as heat during complete combustion. it varies greatly for different materials and is one of the most important waste characteristics in assessing the feasibility of a waste incineration plant. the relevant composition must be known to evaluate the calorific value of combustible waste (srivastava et al., (2014), song et al., (2017), soorige and priyalal (2018), santiago et al., (2019), sahabo et al., (2021). presently, in the maiduguri area there are several gaps, in the need for more waste studies to cover seasonality; gaps in studies coverage in accounting for material-specific treatment as well as gaps in quality of research design and consistency such as: seasonality and control for days of week, lack of local knowledge on incineration, gasification among others, and material-specific recycling tonnages. there are also gaps in basic compositional data: moisture content, feed rate, energy content, bulk density, etc. the extreme north-eastern part of nigeria typically maiduguri, produces large quantities of waste that needs removal and disposal from the immediate environment. the waste generation for the year 2023 is estimated at 2.63×105 tonnes using a waste generation rate of 0.53 kg/capita/day, a base-year population of 1,328,100 and an annual growth rate of 2.40% for maiduguri. this research paper investigates the basic composition of the msw produced by communities in maiduguri, through physical characterization, proximate and ultimate analysis to determine the msw suitability for energy recovery and use in electricity generation. 2. materials and methods maiduguri, the study area, the most city full of activities and population in borno state, is geographically located at coordinates 11.8311°n and 13.1510°e (ocha, 2018). field visits to various refuse dumps were conducted during three distinct seasons: the rainy season (june to october), characterized by high moisture content and elevated daily ambient temperatures, which accelerate the rate of putrefaction; the hot season (march to may), marked by extreme heat; and the cold/harmattan season (november to february), noted for lower temperatures and reduced moisture levels. these seasonal variations were critical for understanding the dynamics of municipal solid waste (msw) in the study area. three areas within maiduguri metropolis were selected for the study and labelled as follows: area a (northern nigeria flour mills), area b (monday market/gwange area), and area c (university of maiduguri dumpsite). seasonal data collection was coded numerically as (1) for the rainy season, (2) for the cold/harmattan season, and (3) for the hot season. the msw samples collected from these areas were analyzed to evaluate their characteristics. the waste was sifted and separated into its major components for physical analysis. a notable observation was the high proportion of sand in all samples, which had to be removed before further analysis, as sand is an inert material that does not contribute to combustion. the sample preparation process involved an initial sieving followed by handpicking to remove small stones that could not pass through the sieve. subsequently, the samples were re-sieved using a 2-mm mesh sieve and ground into powder form using a porcelain mortar and pestle to facilitate detailed analysis. the weighing of samples was performed using a weda weighing machine, model no. 1455 (manufactured in 1974), with a maximum capacity of 100 kilograms. advanced laboratory equipment used for analysis included a nabertherm lh 120/14 electrical furnace, model lh 120/14 (model no. 182487 of 2005), capable of operating within a temperature range of 30–3000°c; a parr 6100 bomb calorimeter for calorific value determination; and a perkins elmer series ii chns/o analyzer http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 228-236. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 230 2400 for chemical composition analysis. additional glassware and laboratory materials used in the study included 16 pyrex conical flasks, pipettes, burettes, beakers, volumetric flasks, plastic bottles, and filter papers. figure 1: map of maiduguri town as the study area (ocha, 2018) 2.1 waste composition the refuse physical characteristics were evaluated by sifting through the waste and separating it into its various physical major components. more precise methods require laboratory analyses and are explained below. 2.2 proximate analysis the proximate analysis is the simplest test and is performed by weighting, heating, and burning a small sample of waste according to astm d3172 (2021). the analysis determines the moisture content (m’o, in weight percent (w/o)) by driving off the free moisture at ~ 107o c for approximately one hour. the volatile matter content (v’, (w/o)) is determined by driving off volatile hydrocarbons co, co2 and combined h2o at ~ 950o c. the waste sample is then burned, and the inorganic residue is the ash content (a’s (w/o)). the fixed carbon (c’f, (w/o)) is then calculated by difference (weisman & eckart 1985). ( ) ( ) ( ) ( ) owsowowowf avmc //// 100 ++−= (1) 2.3 ultimate analysis the ultimate or elemental analysis is a quantitative evaluation of the total carbon (c’), hydrogen (h’), nitrogen (n’), sulphur (s’), oxygen (o’) percentage after removal of the moisture and ash. this analysis is performed using classic oxidation, decomposition, and/or reduction technique to determine, c, h, n and s, using astm d3176 (2021). oxygen o’ (w/o) is calculated by difference (weisman & eckart 1985). ( ) ( ) ( ) ( ) ( ) ( ) ( ) owsowoowowowowow amsnhco /////// 100 +++++−= (2) these data from the ultimate analysis are reported in weight or mass percent. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 228-236. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 231 2.4 determination of calorific value the first step in the processing of waste is to determine its calorific content or heating value. this is a measure of the temperature and the oxygen requirements that the specific waste will be placed in the system (ujamet al., 2013). the calorific value of a fuel can be determined either from its chemical analysis, using a formula or in the laboratory (frey et al., (2003), ge et al., (2019)). in the laboratory, bomb calorimeter is used. the analysis of the samples of msw was carried out using a parr 6100 bomb calorimeter as per astm d5865 (parr instrument company. 2013). in order to determine the calorific value, a sample of the msw is placed inside the combustion bomb, ignited in a high-pressure oxygen environment, and the resulting temperature increase of the surrounding water bath is measured allowing for the calculation of the heat energy released during combustion, which is the calorific value. a representative sample of the fuel is measured accurately and placed in the combustion bomb, together with a small piece of ignition wire to initiate the combustion. temperature change is recorded, and necessary corrections are applied for heat losses using the calorimeter’s built-in compensation system. the calorific value is calculated using the formula (parr instrument company, 2013): 𝐶𝑉 = (𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 ×𝑊𝑎𝑡𝑒𝑟 𝑀𝑎𝑠𝑠 × 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐻𝑒𝑎𝑡 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟) 𝑆𝑎𝑚𝑝𝑙𝑒 𝑀𝑎𝑠𝑠 (3) 3. results and discussion all samples were collected “as – it is”, without any specific selection; and thus contained a large proportion of sand (up to 60% of the sample in some areas) which had to be removed prior to any measurement. this is because sand is an inert element in the combustion process. furthermore, a fist sieving was carried out followed by hand picking, to remove small stones which could not pass through the sieve. table 1 provides the physical composition of the municipal solid wastes in the study area. table 1: composition of msw in the study area location components (%) wood grass paper leaves food remnants plasti c meta l glas s maiduguri flour mills (area a) raining season (1) 28.46 14.57 9.66 8.92 6.79 28.99 2.58 0.03 cold season (2) 16.12 11.48 3.58 16.24 10.24 38.20 3.64 0.50 heat period (3) 27.28 11.09 6.69 13.17 6.17 34.56 0.94 0.09 monday market/ gwange refuse dump (area b) raining season (1) 22.28 6.29 14.86 13.83 5.12 24.93 7.80 4.89 cold season (2) 24.75 6.05 10.52 15.57 4.35 20.46 9.76 8.54 heat period (3) 20.07 5.02 8.80 18.40 6.88 17.63 15.8 5 7.35 unimaid central refuse dump (area c) raining season (1) 17.99 17.11 15.18 25.99 4.03 16.27 2.73 0.70 cold season (2) 19.78 5.35 14.82 19.48 0.98 34.58 4.96 0.04 heat period (3) 18.84 15.05 16.48 14.78 1.53 29.38 2.99 0.99 wood, plastics, and grass are the major physical constituents of the refuse, with emphasis on seasons, mainly due to commercial activities and the presence of the rain. tables (2), (3) and (4) show the proximate analysis of the msw samples in the study area. the results for physical, proximate and ultimate analyses are in line with those from oumarou et al., (2012) whose study focused on the characterization and generation of municipal solid waste in the northeastern part of nigeria, particularly, the present study area. according to oumarou et al., (2012) average moisture contents were found to vary from 21.917 to 24.326, at the time of the study. wood, paper, plastic and leaves were found in varying proportions and 1. 2 kg was found to be the daily average generation of waste, per person. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 228-236. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 232 table 2: proximate analysis results of msw in area a sample id no. percentage composition (%) moisture content volatile matter fixed carbon ash content a1 39.24 21.46 29.30 10 a2 42.58 16.37 35.05 5.2 a3 41.70 15.60 37.90 4.80 table 3: proximate analysis results of msw in area b sample id no. percentage composition (%) moisture content volatile matter fixed carbon ash content b1 37.49 36.34 15.17 11 b2 42.66 17.40 24.74 15.20 b3 49.90 11.70 25.2 13.20 table 4: proximate analysis results of msw in area c sample id no. percentage composition (%) moisture content volatile matter fixed carbon ash content c1 38.15 23.33 28.52 10 c2 48.78 10.22 35.40 5.60 c3 42.40 14.10 39.50 4.0 the statement on these changes and variations supports the findings by amulah et al., (2024) that the two primary factors driving msw generation potential are population size (which depends on the population growth rate) and per capita waste generation rates. the waste generation for the year 2023 was estimated to be 2.63×105tonnes using a waste generation rate of 0.53 kg/capita/day, a base-year population of 1,328,100 and an annual growth rate of 2.40%. the msw generation prediction model is based on the assumption that the type and amount of waste generated will not change over time. coupled with the various calorific values in the study area, msw is in large quantity and can be seen as a sustainable source to be used for energy generation in maiduguri (amulah et al. 2024). tables (5), (6) and (7) show the results of the ultimate analysis of the msw samples in the study area. table 5: ultimate analysis results of msw in area a sample id elements (%) carbon hydrogen oxygen nitrogen sulfur sample a1 46.22 0.21 41.85 11.64 0.08 sample a2 44.87 0.24 43.94 10.83 0.12 sample a3 43.14 0.20 47.09 9.46 0.11 http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 228-236. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 233 table 6: ultimate analysis results of msw in area b sample id elements (%) carbon hydrogen oxygen nitrogen sulfur sample b1 47.91 0.23 41.42 10.34 0.10 sample b2 48.02 0.19 41.25 10.45 0.09 sample b3 47.08 0.20 42.15 10.50 0.07 table 7: ultimate analysis results of msw in area c sample id elements (%) carbon hydrogen oxygen nitrogen sulfur sample c1 45.90 0.55 47.07 6.35 0.13 sample c2 46.10 0.67 46.70 6.44 0.09 sample c3 46.40 0.76 45.93 6.77 0.14 table 8 presents the cvs of the msw samples collected from the study area. the samples from area b1 and b2 recorded the highest calorific values, followed by area a3. this is attributed to the fact that area b, the central market area of maiduguri, has a highly diverse composition of waste due to its role as a hub of commercial and social activity. being a central meeting point for the entire city, area b sees the inflow and outflow of a wide range of commodities, contributing to the high calorific value of the waste. specifically, the calorific values for b1 and b2 were 19.81 mj/kg and 15.055 mj/kg, respectively. however, the study revealed that some areas exhibited lower calorific values. these variations highlight the need for supplementary fuel, such as sugarcane straw or weeds, during the incineration process to compensate for the lower cvs. this supplementation ensures the viability of energy recovery from the waste. it is important to note that calorific value alone does not determine whether the refuse will burn efficiently; moisture content is a critical parameter that must also be considered. additionally, while the physical constituents of the waste generally remained consistent, higher moisture levels were observed in some samples. these increased moisture levels can be attributed to two main factors: the population influx into maiduguri in recent years and the high rainfall experienced in the area. these changes further emphasize the importance of evaluating both the physical and chemical properties of msw to optimize its suitability for energy generation and sustainable waste management practices. table 8: calorific value of msw in the study area collection area sample no. calorific value (mj/kg) area a sample 1 4.3110 sample 2 7.0610 sample 3 10.0612 area b sample 1 19.8107 sample 2 15.0559 sample 3 5.7262 area c sample 1 7.5077 sample 2 8.4217 sample 3 4.5086 the results of the present research are in line with the findings from fatih et al., (2018) who analyzed msw produced in turkey in terms of suitability for waste incineration and energy recovery. they estimated their current and near-future amounts of msw generated in some big cities in turkey and their approximate calorific values in kcal/kg. msws produced in turkey include combustible components at a rate of 45%, so it is reasonable to examine the combustibility of msw for energy recovery. as a tomb of rule, the waste is theoretically feasible for combustion without auxiliary fuel when the moisture of raw waste<50%, ash http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 228-236. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: mmbenomar@yahoo.com 234 content<6% and combustible organic fraction>25%. additionally, the waste calorific value should be at least 2000-2500kcal/kg for energy production, and 1500-1600kcal/kg for the combustion without additional fuel. if the heating value is below 1200kcal/kg, it is understood that the solid waste cannot be economically burned (fatih and akif, 2018). this shows that the moisture content, the feed rate and the energy content of the msw greatly affect the quantity of electricity generated from the municipal solid wastes of maiduguri, with the samples from the university of maiduguri, yielding lower electricity than the remaining locations. the msw samples yield 7,500 mj/kg, 8,420 mj/kg and 4,500 mj/kg, with an average of 6,800 mj/kg, which is lower than the average minimum calorific value of 7000 mj/kg, required for setting up an incineration plant with energy recovery (olisa and ajoko, 2018; yeganeh et al., 2023). this implies the need to add a supplementary fuel to the msw, in the case of university of maiduguri as suggested by aliabadi et al., (2023) in iran. sugarcane bagasse is widely available in maiduguri and has a calorific value of up to 17.29 mj/kg (messayet al., 2021). 4. conclusion at the end of this research work, the following conclusions were drawn: 1. the basic composition of the msw produced by communities in maiduguri was determined and found to vary due to seasonal and behavioural variations and conditions. wood, plastics, leaves and grass, are the major physical constituents of the msw, with emphasis on seasons. metals and glass were almost non-existent. 2. the calorific values were found to vary between 4.41 mj/kg and 19.81 mj/kg, with the university of maiduguri having the lowest calorific values and an average cv of 6.806 mj/kg 3. the msw at the university of maiduguri requires the addition of a supplementary fuel like bagasse to boost its suitability for electricity generation. references aliabadi y. , a. hajinezhad, fattahi r. and s. f. moosavian. 2023. analysis of energy generation from msw with auxiliary feed in the north of iran; 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http://www.parrinst.com, sahabo a., oumarou m. b., a. m. el jummah, and alhaji bukar a. 2021. development and performance evaluation of a small scale municipal solid waste incineration plant. american journal of energy research, 9(2): 75-83. doi: 10.12691/ajer-9-2-1. santiago a., bonie r.c. and álvaro j.d. 2019. municipal solid waste as a source of electric power generation in colombia: a techno-economic evaluation under different scenarios; resources. song, j., sun, y., & jin, l. 2017. pestel analysis of the development of the waste-to-energy incineration industry in china. renewable and sustainable energy reviews, 80: 276-289. soorige, s. d., &priyalal, p. g. 2018. energy generation using municipal solid waste: case of waste to energy mega projects. journal of recent activities in architectural sciences, 3 (1): 1-12. srivastava, v., ismai, s. a., singh, p., & singh, r. p. 2014. urban solid waste management in the developing world with emphasis on india: challenges and opportunities. rev environment science and biotechnology . ujam, a. j., eboh, f., & chime, t. o., 2013. effective utilization of a small-scale municipal solid waste for power generation. journal of asian scientific research, 3 (1): 18-34. umberto a. 2012. process and technological aspects of municipal solid waste gasification. a review; waste management, 32: 625–639, journal homepage: www.elsevier.com/locate/wasman weisman j. and roy e. 1985. modern power plant engineering. 2nd edition, prentice hall international, new delhi. yang, l., liu, g., zhu, q., & zheng, m. (2019). small-scale waste incinerators in rural china: potential risks of dioxins and polychlorinated naphthalene emissions. emerging contaminants, 5, 31-34. http://www.azojete.com.ng/ mailto:mmbenomar@yahoo.com http://www.parrinst.com/ http://www.elsevier.com/locate/wasman corresponding author’s email address: ddyusuf2004@yahoo.com 210 arid zone journal of engineering, technology & environment original research article multiobjective optimization of shelling process of an engine operated melon (citrullus laenatus kuntze) sheller d. d. yusuf1*, m. l. attanda2, and h. o. yusuf 3 1 department of agricultural engineering, faculty of engineering, ahmadu bello university, zaria 2 department of agricultural and bio-environmental engineering, bayero university, kano 3department of agricultural extension and rural development, faculty of agriculture, ahmadu bello university, zaria *corresponding author’s email: ddyusuf2004@yahoo.com article information abstract the quest to develop an optimally operating mechanical device to shell melon seed (citrullus laenatus kuntze) has been a desirable objective over the past three decades. a melon sheller was constructed and optimized. the machine shelling performance analysis were based on shelling capacity, shelling efficiency, cleaning efficiency, seed loss, and damaged kernel. matlab 7.0, r2010a software was implemented using genetic algorithm technique for the optimization of the independent parameters and dependent response variables. a layout of the experiment was three speeds (s1, s2, s3), three feeding rate (p1, p2, p3) and three moisture contents (m1, m2, m3) which were arranged in a randomized complete design (3x3x3) in 3 replications. melon (egusi) seed of bara variety was used as test crop. results showed that the machine shelling capacity and shelling efficiency increased with increase in the shelling drum speed, while the shelling capacity ranged between 20.07 and 44.90 kg/hr and the shelling efficiency ranged between 59.21 to 97.59 %. the optimum inputs were: moisture content (19.9 %), speed (1248 rpm), feed rate (42 kg/hr) at 4 passes and best performance parameters were: shelling efficiency (98.38 %), cleaning efficiency (48.79%), seed loss (8.74 %) and damaged kernel (10.44 %). the means of three replication of performance parameters were used in analysis. the shelling efficiency, cleaning efficiency, seed loss and damaged kernel were: 96.14, 49.15 %, 9.72 % and 10.52 % respectively, which is very close to the values (98.38 %, 48.79 %, 8.74 % and 10.44 %, respectively) obtained from the optimization process. submitted: 12th october 2023 revised: 3rd february 2025 accepted: 5th february 2025 keywords: optimization genetic algorithm technique shelling process sheller melon © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction there is awareness of the need for food security and the renewed and growing concern by the federal government of nigeria to increase agricultural productivity with the objectives of increasing indigenous crop and development of agricultural machinery that could impact positively on the productivity and the living standard of the citizens. this is achievable through sustainable and adaptive research and development in the areas of crop production, processing and storage however, agricultural machine prototypes produced in private sector in nigeria are done without much reference to science and fundamental principle of machine design (ukatu, 2006). melon (egusi) seeds (citrullus laenatus kuntze) are increasingly used for their oil in the cosmetic and pharmaceutical industry (aregbe, 2008). the many uses of melon (egusi) cannot be achieved without post-harvest operations such as gathering of the harvested fruits, softening of the fruit, extraction of seeds, washing, drying and shelling. among these operations shelling is the most difficult and time consuming (isiaka et al., 2006). over years, little research has been done in the area of melon (egusi) seed processing machine. odigboh (1979) reported that, there has been no interest in the industrialization of oil extraction from (egusi) melon largely due to the difficulty involved in shelling the seeds. he employed arrangement of radial vane impeller, impeller with vane positioned at varying angles to the radius having four vanes each. he used different vane configuration on the spinning disc at radial position and at both 45 o and 90 o to the radii of the spinning disc concentric circle. the study revealed that impeller with vane positioned at 45o to the azojete march 2025. vol.21(1):210-227 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:ddyusuf2004@yahoo.com mailto:ddyusuf2004@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 211 radius gave the best combination of higher shelling and low percentage of damage to the shelled seed. in addition, his work found that 8.64 – 17.05% of wetted seeds were broken while 14.24 24.93% of seeds that was not wetted were broken. this showed that reduction in the damage of the seed was achieved by increasing the moisture content of the melon seeds. however, the size of the sheller makes it cumbersome for household application. the shelling process is particularly tedious and time consuming (anonymous, 2001). (skwarcz, 2006) reported that the condition of optimization is needed to be fulfilled in order to make a machine operate at its optimum capacity with minimum input and enhanced operation efficiency. this is to find parameter values (shelling capacity, shelling efficiency, cleaning efficiency, seed loss, and damaged kernel) that match predictions with reality by choosing the right set of parameters that improve the performance of the sheller. the interest in application of modern optimization technique is considerable, primarily as a result of development of modern computers and software (enaburkhan, 1994). oluwabukola et al., (2021) carried out numerical optimization for investigating the effects of the speed of shelling, melon seed moisture content and number of beaters of a developed mechanized centrifugal melon shelling and cleaning machine. they reported optimum values of speed of 2200rpm, moisture content of 12% (w.b) and 19 beaters for shelling efficiency of 88.80%. aturu et al., ((2021) studied the effects of parameters of a centrifugal melon shelling and cleaning machine. optimum values of speed of 1842rpm, moisture content of 11.6% (w.b), and 15 beaters for cleaning efficiency of 90.2% were obtained. optimization of the shelling parameters of melon seed for power operated machine was to define seed kinematics in the shelling process as a requisite tool for design procedure of shelling unit. the objectives of this study were to: (1) construct a melon sheller, and evaluate its performance and (2) optimize the shelling process of the melon sheller on the basis of machine shelling performance indices (shelling capacity, shelling efficiency, cleaning efficiency, seed loss, and damaged kernel). 2. materials and methods 2.1 materials melon (citrullus laenatus kuntze) seed of bara variety was used as test crop. it a has large brown seeds with think black edges especially thickened toward the apex, about 16 x 9.5 mm and common in northern and western part of the nigeria. some of the instruments used include; vernier caliper (least count 0.0 1 mm), overhead projector model quantum 2521, stop watch, digital weighing scale model no: oph-t3001, 0.0l g sensitivity, drying oven model dhg xmdt-8222. others are: photo type microprocessor digital tachometer model dt-2234a+ and anemometers, compression testing machine type ‘w’ monsanto serial no. 9875 and seed hardness tester model gwj-1, all in the material processing laboratories of agricultural and mechanical engineering departments, ahmadu bello university, zaria, nigeria and agricultural engineering department, bayero university, kano, nigeria. design considerations for optimum performance and easy maintenance of the melon shelling machine include: the type of material used for each component, simplicity of design to meet the required standard and specifications, materials of adequate strength were used to ensure their durability and reliability, and cost of the materials used. in addition, local and available materials construction method for reliability and durability, and mobility of the machine were considered. 2.2 methods 2.2.1 moisture content the moisture content of the test crop (melon seed) was determined by oven drying method according to asae (1984) standard. a 15 g weight of sample seeds at three replications was oven dried using harris england oven of model dhg xmtd-8222. the initial moisture content of seed was determined using the oven dry method at 103 ± 2°c until a constant weight was reached (kashaninejad et al., 2005). the moisture content was calculated on dry basis as shown in equation 1: moisture content, mcdb = mw−mdmd×100 (1) where, mcdb is the moisture content in dry basis 9%) of the material, m w is the initial weight of the material (g), and md is the weight of the material after drying (g). http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 212 2.2.2 compressive strength the force exerted on a seed for it to rupture was determined by using a honesfield tensiometric material testing machine. the machine was used to obtain the values of compressive force from which the compressive stress and young modulus were determined. the machine has a graduated scale of five newton (5 n) intervals and a maximum range of 300 n. the seed was loaded between two spherical seated nose points by chunk attachment pins. this caused the operating screw to move to the left and transmit pressure to the seed. the other end of the seated nose was connected through compression head and a spring beam. the deflection of this spring beam was transmitted to a mercury piston which displaces mercury into a uniform bore glass tube that magnified the beam deflection to provide easily readable scale of load. it should be noted that the compressive force applied on the mercury reservoir causes a thread of mercury to rise along the scales. 2.2.3 require energy to shear the seed the determination of both the melon seed dimensions and the coefficient of friction of the materials surfaces used for shelling drum and concave surface enabled the calculation of an adequate pressure sufficient to supply the require energy to shear the seed, using guzel et al., (2005) relationship as: pf = mg/ am χ 100 (2) where: pf = pressure applied (n/m2), m = mass of the moving surface, g = specific force and am is the surface area. 2.2.4 tensions in both the transmission belt and pulley: they were calculated as: t = fr (3) where: t is the torque (nm), f is the total tension exerted on belt and pulley, r radius of pulley (m) pt = 2πnt/60 (4) where: pt is power in the transmission unit; (kw) and n is revolution of the shelling drum., and t is the torque, (n.m). 2.3 machine components 2.3.1 the hopper the machine hopper was developed from geometric shape of trapezoidal and anthropometric consideration so as to give desirable fitting and also to enhance easy flow of the melon seed base on the determination of the angle of the repose on the mild steel. the determination of the hopper’s volume is achieved using the following relationship: w= 1/3(yz2h-yz2h) (5) where: w = volume of hopper (mm3), yz = the upper width of the hopper(mm ), h = total height of the hopper(mm ), yz = base width of the hopper(mm ), and h = hopper base height of the hopper(mm ). 2. 3.2 shelling drum the diameter (d) of the shelling drum is given as: d = v/π n (6) where: v is the peripheral speed of cylinder (m/min), and . n is the number of drum revolution in a minute (rpm). http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 213 2.3.3 belt drives the required pulley sizes (diameters) for both the shelling and separation units were determined from the following relationship: n1d1 = n2d2 (7) where: n1 = speed of the driven pulley (rpm), n2 = speed of the driving pulley (rpm), d1 = diameter of driven pulley (cm), and d2 = diameter of driving pulley (cm), 2.3.4 belt length the effective belts length for both units was selected using (bainer et al., 1995) relationship as: lb = π / 2 (d2 + d1) +2c + ( ) c dd 4 2 12 − (8) where: lb = belt length (cm),c = center distance between the driving and driving pulleys, d1 2.3.5 belt tension it was calculated as (hannan and stephen, 1984): mt = (t1 – t2)r (9) where, mt = torsional moment (nm), r= radius of the shaft pulley, t1 and t2 = force on the tight and slack side of the belt, respectively (n). 2.3.6 contact angle of the belt the angle of contact (θ) of the belt was determined using equation (hall et al., 1982): θ =180 – (d2 – d1/c ϰ 60) (10) where, θ is the angle of contact. 2.3.7 shaft design: mild steel of code (c1040) with strength properties as stated by asme (1948); yield strength (yield stress) of 568.7 mn/m2 and ultimate strength (tensile stress) of 668.8 mn/m2. was used. shaft diameter (d) was determined using the relationship given by hall et al. (1982) as: d3 = 16/ πss √(kbmb)2 + ( ktmt)2 (11) where: d = shaft diameter (m), ss = allowable shear stress of a steel shaft, kb and kt = combined shock and fatigue factor applied to bending and torsional moment, respectively. mb and mt = bending and torsional moment on shaft, respectively. the minimum safe diameter for the shelling drum is 16 mm. hence, we choose 20 mm as the shaft diameter for the shelling unit. 2.4. operation of melon sheller in the machine chamber, the kernel of a seed is removed from the seed cotyledons. the melon seed is kept between the shelling drum and the concave and subjected to rubbing and stripping action which is caused by impact generated on the materials from both the vanes of the shelling drum and vanes of the concave surface. the actions of attrition, shearing, rubbing and bending, strip off the outer cotyledons of the melon seeds. the actions create a material flow through high velocity of the mass of shelled seed, unshelled seed and chaff to a blower where shelled seeds are separated from chaff. the clean seed fall into the collecting tray and the chaff is blown away. the isometric view, and orthographic projection are shown in figures 1, and 2, respectively. http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 214 2.4.1 shelling capacity the machine shelling capacity was calculated as (fao, 1994): c= qs/ t (12) where: c = shelling capacity, (kg/h), qs = weight of shelled seed, (kg), t = shelling time, (hours) 2.4.2 shelling efficiency the machine shelling efficiency was calculated as (fao, 1994): se = 100 – (usb / tws χ 100) (13) where: se = shelling efficiency, %, usb = weight of unshelled seed, kg, tws = total weight of seed, kg 2.4.3 cleaning efficiency: the machine shelling efficiency was calculated as (fao, 1994): ce = b/d x 100 (14) where: ce= cleaning efficiency, % , b = weight of whole clean seed at outlet, kg and d = weight of whole material collected at outlet, kg figure 1: isometric view of melon sheller http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 215 figure 2: orthographic projection of melon sheller 2.4.4 seed loss the seed loss was calculated as (fao, 1994): sl = 100        s l t w (15) where: sl = seed loss % , wl = weight of seed loss collected, kg , ts = total seed input, kg 2.4.5 damaged kernel the kernel damage was obtained as (fao, 1994): 100dk k sk w d w =  (16) where: dk = damaged kernel, %, wdk = weight of damaged kernel collects at outlet, kg, wsk = weight of shelled kernel collected at outlet, kg. 2.5 experimental layout a layout of the experiment is three speeds (s1, s2, s3), three feeding rate (p1, p2, p3) and three moisture contents (m1, m2, m3) which are arranged in a randomized complete design (3x3x3) in 3 replications. 2.5.1 statistical analysis the data collected from the experiment were analyzed statistically by using analysis of variance (anova). software of statistical analysis systems, (sas) institute inc., 2007 was used. duncan multiple range test (dmrt) was used for planned pair comparison between variable means. 2.6 optimization technique matlab 7.0, r2010a software was implemented using genetic algorithm technique for the optimization of the independent parameters and dependent response variables in this study. miu and perhinschi (2001) reported that experimental results indicate that the genetic algorithm is a promising design and optimization tool for solving agricultural machinery related problems for the best approximation solutions and in minimizing the execution time. the following six steps were determined for the use of genetic algorithm in this study: (i) the genetic representation of the chromosome (variables), (ii) the creation of the initial population, (iii) http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 216 evaluation function, (iv) selection function, (v) genetic operators making up the reproduction function (crossover and mutation), (vi) termination criteria. figure 3 shows the schematic representation of the procedure of optimization using genetic algorithm techniques. 2.6.1 algorithm development the optimization problem to be solved in this study was to find an optimum configuration of independent variables combination which constrained by a number of upper and lower boundaries function of inequalities on performance criteria. the shelling unit of the machine is characterized by: vector x of i control parameters, 𝑥 = (𝑥1, … … … … … … … 𝑥𝑖)𝑇 (17) where: x is the independent variables, i is the total number of independent variable vector y of j functional criteria, 𝑦 = (𝑦1, … … … … … … … 𝑦𝑗)𝑇 (18) where: y is the functional criteria of the machine, and j is the total number of performance criteria objectives. the control parameters (x) and functional criteria objectives (y) considered in the decision process in search of optimal solution of this study are: x = (s, p, m) (19) y = (se, ce, ds ,ls) (20) where: s= speed of the shelling drum (rpm), p= passes of the feed rate (kg/hr), m = moisture contents of the seed (%), se= shelling efficiency (%), ce = cleaning efficiency (%), ds= damage seed and (%), and ds= loss seed (%). 2.6.2 evaluation function: an optimization problem with more than one objective function such as the case in this study would require a weighting vector. this is simply weighting of all the functional vectors together to form a single aggregate functional response of the form, (william and james, 1980): (21) where: u=utility factor relating all the functional vector, y( ϰ ) = functional response of the machine, wi = weighting vector. therefore, the evaluation function in this study has the expression: 𝐸𝐹 = 𝑤1𝑦1(+)𝑤2𝑦2(𝑥) − 𝑤3𝑦3(𝑥) − 𝑤4𝑦4(𝑥) (22) miu (2001) stated that it is likely the algorithm with equal weights to converge to a local optimum when it does not meet one of the requirements of the weighting vector. in order to avoid the problem of convergence to a local optimal of the algorithm because of equal weight vector, a selective weights vector (miu, 2001) was also considered as shown in table 1. table 1: weighting vector for the performance responses of the machine. s/n parameter equal weighting vector selective weighting vector 1 shelling efficiency se (%) 25 33.3 2 cleaning efficiency ce (%) 25 33.3 3 damage seed sd (%) 25 22.2 4 loss seed ls (%) 25 11.1 http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 217 figure 3: schematic representation of the procedure of optimization using genetic algorithm techniques. 3.0 results and discussion 3.1 compressive strength: the results of the compressive strength of the melon seed at different moisture contents for both shelled and unshelled seeds of the different seed orientations are presented in table 2. compressive forces and stresses showed a continuous decrease with increasing moisture content. similar observation was noticed with the young modulus in all the size categories of the melon seed. the least stresses error control http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 218 at yield point occurred at moisture content of 30 % for all size groups with 0.132, 0.146 and 1.53 n/mm2 for small, medium and large melon seed, respectively and the corresponding highest values obtained at 10 % moisture content are 0.284, 0.286 and 0.308 n/mm2. young modulus of the seed in the different size categories ranged from 3.35 to 2.65 x 106 nm-2 , 3.70 to 2.75 x 106 nm-2 and 3.85 to 2.90 x 106 nm-2 for small medium and large seed, respectively while it ranged from 2.15 to 1.65 x 106 nm-2 , 2.90 to 2.25 x 106 nm-2 and 3.05 to 2.40 x 106 nm-2 for kernel. okon (2008) reported a similar trend of findings for melon seeds. table 2: compressive forces on different size categories of melon seed and kernel at different moisture contents. melon m.c small medium large (%) force stress young force stress young force stress young (n) (n/ mm2) modulus (n) n/mm2 modulus (n) (n/mm2) modulus (nmm2) (nmm2) (nmm2) unshelled 10 6.00 0.284 3,35 7.50 0.286 3.70 9.50 0,308 3.85 15 6.00 0.244 3.10 6.50 0.248 3.45 8.00 0.260 3.60 20 5.25 0.213 2.95 7.00 0.267 3.20 6.50 0.211 3.40 25 4.50 0.162 2.80 4.50 0.162 2.90 5.00 0.210 3.25 30 3.25 0.132 2.65 4.00 0.146 2.75 4.50 0.153 2.90 shelled 10 5.00 0.225 2.15 6.05 0.265 2.90 7.00 0.285 3.05 15 4.00 0.180 2.05 5.50 0.233 2,85 6.25 0.254 2.95 20 4.25 0.192 1.90 4.00 0.170 2.65 5.50 0.224 2.70 25 3.00 0.135 1.85 3.00 0.149 2.50 4.25 0.173 2.65 30 2.00 0.090 1.65 2.50 0.106 2.25 3.50 0.142 2.40 3.2 shelling capacity the effects of both speed of the drum, feed rate, and the interaction between the speed of the drum and feed rate were found to be highly significant (p <0.01) on shelling capacity (table 3). this is because as the speed of the shelling drum increases (table 4), so the dwelling time of the melon seed reduces in the shelling chamber hence increase output of the machine. there is significant difference in the capacities of the machine at different speeds with machine capacity at 1250 rpm of drum speed higher than the capacity of the machine at both speed of 910 rpm and 860 rpm. also there exist significant different in the machine capacity at different passes of feed rate with the feed rate at 2 passes having higher machine output than feed rate at 3 and 4 passes (table 5). http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 219 table 3: analysis of variance for machine shelling capacity source of variation degree of freedom sum of square mean square f-value replication speed (s) feed rate passes (p) moisture content (m) s*p s*m p*m s*p*m 2 2 2 2 4 4 4 8 11.1165 2300.583800 5692.464486 6.157735 211.138837 73.649881 43.273719 203.60994 5.558270 1199.791900 2846.232248 3.078693 52.784709 18.412470 10.818430 25.451244 2.05ns 441.65** 1047.71** 1.13ns 19.43** 6.78* 3.98ns 9.37** ** = significant at 1% level * = significant at 5% level ns = not significant table 4: duncan multiple range test for comparison of drum speed on machine shelling capacity drum speed (rpm) 1250 910 860 mean ranking 25.76a 17.24b 12.62c critical range 0.9468 0.9002 mean with the same letter are not significantly different table 5: duncan multiple range test for comparison of feed rate on machine shelling capacity feed rate passes (kg/hr) 42kg/hr at 2 passes 42kg/hr at 3passes 42kg/hr at4 passes mean ranking 30.10a 15.05b 10.48c critical range 0.9468 0.9002 mean with the same letter are not significantly different 3.3 shelling efficiency table 6 shows that the effect of drum speed is highly significant on the shelling efficiency of the machine. the shelling efficiency was observed to increase with increase in drum speed. drum speed of 780, 910 and 1250 rpm at 15 % moisture and feed rate of 42 kg/hr at 4 passes produced 73.50 %, 81.21 % and 90.61 % shelling efficiencies, respectively. there is difference in means of the shelling efficiency of the machine in the descending order of the drum speed (table 7) as: 1250 rpm > 910 rpm > 860 rpm. feed rate passes was found to have high significant effect on shelling efficiency (p <0.01). there exist significant different with feed rate at 4 passes having 85.61 % shelling efficiency followed by 3 and 2 passes having 77.0 % and 52.71 % shelling efficiencies, respectively (table 8). http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 220 table 6: analysis of variance for machine shelling efficiency source of variation degree of freedom sum of square mean square f-value replication speed (s) feed rate passes (p) moisture content (m) s*p s*m p*m s*p*m 2 2 2 2 4 4 4 8 193.93580 3961.14482 15708.77752 11538.71124 717.88080 98.19722 1337.60125 369.68327 96.96790 1980.57241 7854.38876 1769.35562 179.47020 24.54930 334.40031 46.21041 0.96ns 19.52** 77.41** 47.58** 1.77ns 0.24ns 3.30ns 0.46ns ** = significant at 1% level * = significant at 5% level ns = not significant table 7: duncan multiple range test for comparison of drum speed on machine shelling efficiency drum speed (rpm) 1250 910 860 mean ranking 80.61a 71.21b 63.50c critical range 5.502 5.787 mean with the same letter are not significantly different table 8: duncan multiple range test for comparison of feed rate on machine shelling efficiency passes of feed rate (kg/hr) 42kghr at 4 passes 42kg/hr at 3passes 42kg/hr at 2passes mean ranking 85.61a 77.00b 52.71c critical range 5.502 5.787 mean with the same letter are not significantly different 3.4 cleaning efficiency the effect of fan speed and feed rate of the machine is highly significant (p <0.01) on cleaning efficiency (table 9). the increase in the speed of fan, increased the air flow rate. effect of interaction of fan speed and feeding rate passes, fan speed and moisture content and feeding rate passes and moisture content are found to be highly significant (p <0.01). however, the combine interaction of fan speed, feeding rate passes and moisture content is significant at 5 % probability level. http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 221 table 9: analysis of variance for machine cleaning efficiency source of variation degree of freedom sum of square mean square f-value replication speed (s) feed rate passes (p) moisture content (m) s * p s * m p * m s * p * m 2 2 2 2 4 4 4 8 97.057489 2136.249267 396.023089 70.738422 3735.058311 376.048378 319.562267 309.999556 48.528744 1068.124633 198.011544 35.369211 933.764578 94.012094 79.890567 38.749944 5.44 ns 119.83** 22.21** 3.97ns 104.75** 10.55** 8.96** 4.35* * = significant at 5% level ns = not significant** = significant at 1% level 3.5 optimization to compute the optimum values of the independent parameters for the optimum output of the developed machine, a matlab optimization programme was performed with an initial population of 90 samples for three (3) different runs of 102nd generation for each version of equal and selective weights evaluation function using the developed model on genetic algorithm application. figure 4 shows the algorithm interface for the optimization process. the algorithm interface is composed of four interactive; algorithm input, algorithm options, optimal machine input and optimal machine output. the first interface of the algorithm input the constraints for the optimization of the minimum and maximum input. the algorithm option is made of population size and evaluating function of both selective and equal weight functions, and selective weighting coefficient were performed. 3.5.1 equal weights evaluation function the genetic algorithm input programme of equal weight relationship and the output at different nth generation are shown in figs. 5 to 7. the nth generation of the genetic algorithm optimizes various combination of shelling parameters to obtain the fitness individual. fig. 5 shows the 11th generation of the genetic algorithms. the mean fitness value of any individual to survival to next generation is 24.2316 while the best fitness individual is 26.7867. this implies that any individual sample of the population with minimum genetic value of 24.23 or more would involve in the mutation and cross-over to the n + 1 th generation. at 11th generation, the average distance between individuals’ population is wide, hence there is the convergence. this indicates that the saddle (optimum point) is not attaining at this generation. on the other hand, figs.6 and 7 show trends of convergence at 50th and 102nd generations of the genetic algorithm, respectively. the genetic algorithm of 50th generation (figure 6) shows trend toward convergence with the best fitness value and mean values of an individual to be 31.9129. this suggests that the fitness of each individual is moving toward convergence at this point. the average distance between individual populations is also converging at this generation. at the end of the 102nd generation (fig. 7) of the genetic algorithm, the algorithm converged with fitness value of 31.9214 and also the average distance between individual’s parameter converge to zero. since the best fitness value of individual is achieved and converged at this generation, the algorithm is terminated. http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 222 figure 4: algorithm interface of the optimization process figure 5: genetic algorithm at 11th generation for equal weight evaluation function parameter min max moisture content (m) 5 30 speed (s) 780 1250 feed rate passes (p) 1 5 evaluation fxn selective weight pop size moisture content (m) speed (s) feed rate passes (p) shelling efficiency (se) cleaning efficiency (ce) seed loss (sl) damaged kernel (dk) optimal machine input algorithm input algorithm options optimal machine output start optimization http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 223 figure 6: genetic algorithm at 50th generation for equal weight evaluation function figure 7: genetic algorithm at 102ndgeneration for equal weight evaluation function 3.5.2 optimal shelling conditions the best individual components of the machine optimum input variables were obtained when using equal weights evaluation function which produced the best performance parameter. the optimum machine inputs are: moisture content (19.9 %), speed (1248 rpm), feed rate (42 kg/hr) at 4 passes and best performance parameters are: shelling efficiency (98.38 %), cleaning efficiency (48.79%), seed loss (8.74 %) and damaged kernel (10.44 %) as shown in table 10. http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 224 table 10: equal weight evaluation functions at optimal machine input and output. run optimal machine input optimal machine output 1st moisture content (m) 20.0% speed (s) :1239.34 rpm 42kg/hr of feed rate passes (p): 4.00 shelling efficiency: 98.00% cleaning efficiency: 47.8% seed loss: 9.83% damage kernel :16.21% 2nd moisture content (m): 20.00% speed (s): 1235.19 rpm 42kg/hr of feed rate passes (p): 3.99996 shelling efficiency: 97.87% cleaning efficiency: 47.44% seed loss: 10.24% damage kernel :18.35% 3rd moisture content (m): 19.917% speed (s): 1248.61 rpm 42kg/hr of feed rate passes (p): 4.00 shelling efficiency :98.38% cleaning efficiency: 48.79% seed loss: 8.74% damage kennel :10.44% 3.6 three-dimensional surface plot on performance criteria of the optimization figures 8 to 11 are the graphically search space where the algorithm searches for optimum conditions. these represented the trend of variation in the output parameters for combined variation of the input variables at a constant moisture content of 20 % and constant feed rate of 42 kg/hr at 4 passes, respectively. optimization parameters are shown on the x and y axes while the variation of the optimization criterion is shown on the vertical z axis with using the color gradient. the visualize mode of shelling efficiency as a function of feed rate and drum speed is also shown (fig. 8). the small element of deep blue color shows the low level of shelling efficiency and deep red level indicate high shelling efficiency as the drum speed increase in the search space, toward optimum condition. similarly, at low feed rate passes and fan speed, the cleaning efficiency was increasing in search space toward optimum cleaning efficiency (fig. 9). decrease in seed loss (fig. 10) and damaged kernel (fig. 11) in the search space, showed minimum seed loss and damage kernel with the deep blue as the minimum element, deep red maximum element and other colors are linearly interpolated. figure 8: three-dimensional response surface graph of shelling efficiency as a function of feed rate and drum speed. figure 9: three-dimensional response surface graph of cleaning efficiency as a function of feed rate and drum speed. feed rate (kg/hr) speed (rpm) feed rate (kg/hr) speed (rpm) http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 225 figure 10: three-dimensional response surface graph of seed loss as a function of feed rate and drum speed. figure 11: three-dimensional response surface graph of damaged kernel as a function of feed rate and drum speed. on the other hand, at constant feed rate of 42 kg/hr and 4 passes, there is increase toward the optimum condition in the search space as the independent variable of drum speed and moisture content increase for shelling efficiency (figure 12) and cleaning efficiency (fig.13), respectively. also, there is increase toward the optimum condition in the search space as the independent variable of drum speed and moisture content increase for seed loss (figure 14) and damaged kernel (figure 15). in order to verify the optimum shelling process conditions obtained, the optimum combination of the machine independent variables (moisture content; 19.9 %, speed; 1248 rpm and feed rate of 42 kg/hr of 4 passes) were tested on sheller. the means of three replication of performance parameters output of the machine when the optimum combination of the shelling process variables were implemented on the sheller, the shelling efficiency, cleaning efficiency, seed loss and damaged kernel were: 96.14, 49.15 %, 9.72 % and 10.52 % respectively. this is very close to the shelling efficiency (98.38 %), cleaning efficiency (48.79 %), seed loss (8.74 %) and kernel damage (10.44 %) obtained from the optimization process, hence, satisfying nearly all the constraints on the shelling process of the developed machine. figure 12: three-dimensional response surface graph of shelling efficiency as a function of drum speed and moisture content. figure 13: three-dimensional response surface graph of cleaning efficiency as a function of drum speed and moisture content. speed (rpm) feed rate (kg/hr) feed rate (kg/hr) speed (rpm) speed (rpm) moisture content (%) speed (rpm) moisture content (%) http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 226 figure 14: three-dimensional response surface graph of seed loss as a function of drum speed and moisture content. figure 15: three-dimensional response surface graph of damaged kernel as a function of drum speed and moisture content. 4.0 conclusion the study revealed that the optimum machine inputs are: moisture content (19.9 %), speed (1248 rpm), feed rate (42 kg/hr) at 4 passes and best performance parameters are: shelling efficiency (98.38 %), cleaning efficiency (48.79%), seed loss (8.74 %) and damaged kernel (10.44 %). they are very close to the shelling efficiency (98.38 %), cleaning efficiency (48.79 %), seed loss (8.74 %), and damaged kernel (10.44 %) obtained from the optimization process. references american society of agric. engineers standard 1984. moisture measurement: grain and seeds. asae s352, p. 384. anonymous 2001. lost crops of africa: volume ii: vegetables. http:books.nap.edu/openbook.php. aregbe, b. e. 2008. determination of aerodynamic properties of egusi melon seed. an unpublished bachelor of engineering degree project, department of agricultural engineering, ahmadu bello university, zaria – nigeria. aturu, o. b., olaoye, j. o, ghana, i. m. gbabo, a. and liberty, j.t. 2021. an investigative study on effects of some machine and processing parameters of a mechanized centrifugal melon shelling machine. international journal of applied science and research. 4(2): 1-9. bainer, r., r kepner, a. and barger, e. l. 1995. principle of farm machinery. third ed. john wiley, new york. p. 265. enaburekhan, j. s. 1994. mathematical and optimization modeling of the threshing process in a stationary grain thresher. unpublished phd thesis submitted to the department of agricultural engineering, ahmadu bello university, zaria. food and agriculture organistion 1994 testing and evaluation of agricultural machinery and equipment: principles and practice. fao agricultural services bulletin no.110. p. 216-213. guzel, e., akcali, i. d. and mutlu, a. 2005. research on the fatigue behaviour for peanut shelling. journal of food engineering. 67 (3): 373-378. hall, a.s., hollow-wenken, a. r. and lanyhlin, h. g.1982. theory and problems of machine design. schaum’s outline series. mcgraw-hill book company. london.p87 speed (rpm) moisture content (%) speed (rpm) moisture content (%) http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 210-227. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ddyusuf2004@yahoo.com 227 hannah, j. and stephen, r. c.1984. mechanics of machineselementery theory and examples. edward aroid, london. p. 118. isiaka m., elokene, a. m. i. and oyedele, t. a. 2006. determination of physical properties of melon seed. proceeding of the nigerian institution of agricultural engineer, 28: 322 – 326. miu, p.i. 2001. optimal design and process of threshing units based on a genetic algorithm. i. algorithm. american society of agricultural engineer paper no 013124, asae, st. joseph, m.i. miu, p.l., and perhinschi, m.g., 2001. optimal design and process of threshing units based on genetic algorithm. ii. application american society of agricultural engineer paper no. 01 – 3125, asae, st joseph, m.i. odigboh, e. u. 1979. impact egusi shelling machines. transaction of america society of agricultural engineers 22 (5): 1264 – 1267. oluwabukola, b. a., olaoye, j. o., agidi, g. muhammed, g. i. andrew, n. e. and liberty, j. t. 2021. .effect of shelling speed, moisture content and number of beaters on the cleaning and recovery efficiency of a mechanized centrifugal melon shelling machine. world journal of advanced research and reviews. 10 (03): 239 – 245. okon, f. b. 2008. determination of the young’s modulus of elasticity of melon seeds by applying the theory of thin plates under compression. journal of agricultural engineering and technology 16 (1): 24-35. skwarcz, j. 2006. optimization of the choice of agricultural machines. electronic journal of polish agricultural university, 9(3), no 14. statistical analysis system (sas) 2007. sas users guide. sas institute inc., box 800, carry, north carolina, u. s. a. ukatu, a. c. 2006. enhancing the development of viable prototype of agricultural machines in nigeria. proceedings of the nigeria institution of agricultural engineers, 28: 38 – 44. http://www.azojete.com.ng/ mailto:ddyusuf2004@yahoo.com corresponding author’s email: poolabisi@bellsuniversity.edu.ng 119 arid zone journal of engineering, technology & environment original research article assessment of the hydroelectricity generation potential of gwaigwaye reservoir in funtua, katsina state, nigeria p. o. olabisi* and m. m. abdullahi department of electrical/electronic & telecommunication engineering, bells university of technology, ota, nigeria. *corresponding author’s email: poolabisi@bellsuniversity.edu.ng article information abstract access to quality and adequate supply of electricity is one of the major challenges hampering development in sub-saharan africa. funtua as the industrial, commercial, and agricultural hub of katsina state, nigeria, needs to overcome the problem of epileptic power supply from the national grid. this study explored the hydro generation potential of gwaigwaye reservoir, the largest water resource in the area, by evolving a hydrological profile using water surface area in absence of flow gauging data. it also outlined from analysis, the technical requirements for hydroelectricity generation from the reservoir. consequently, it was discovered from analysis that the average discharge obtainable is 18.54 m3/s. this would flow through four bulb turbines of 750 rpm speed to generate 17.8 mw of power or 14.033 gwh of energy in a year. it is therefore recommended that the government of katsina state should seek to implement this project for its potential to improve the living conditions and economy of the people of funtua, the surrounding communities and the state. submitted: 27th august 2024 revised: 1st february 2025 accepted: 3rd february 2025 keywords: hydroelectricity power generation hydrological survey hydraulic turbine water reservoir © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction access to quality and adequate supply of electricity is one of the major challenges hampering socioeconomic development in sub-saharan africa. this barrier to progress in a nation with large population, like nigeria, is a problem that requires intensive study and analysis to come up with viable and lasting solutions for its impact on a variety of development indicators, ranging from health care, economic opportunities, improved education, job creation, food security, livelihood, to poverty reduction (world bank, 2021; ecosoc, 2023). many studies and efforts aimed at discovering alternative solutions to the energy dilemma confronting most developing nations, include works on renewable energy generation, distributed generation, energy efficiency programs and so on (mohammed et al., 2013; nwozor et al., 2021; streimikiene et al., 2021; pehlivanoglu et al., 2021). in tackling this problem, rural electrification required for household lighting, production purposes which include water pumping for irrigation, water supplies, processing and preservation of farm produce and other agro-industry processes and small commercial and manufacture activities, is of a major concern in developing economies (barnes et al, 1997; akbas et al., 2022; dibaba et al., 2022).in order to meet the energy needs of the vast population of the nigerian people, it has become necessary to explore and harness the hydroelectric potentials in various parts of the country (manohar and adeyanju, 2009; mohammed et al., 2013; fakenhinde et al., 2019). this study explored the possibility of hydroelectricity generation for funtua, a semi-urban town located on longitude 11.5185° n and latitude 7.3129° e at an elevation of 709 m in the southern part of katsina state, nigeria, and its environs. funtua has average rainfall that last for 6 to 7 months in a year, usually from april to october, and peaks to about 21 cm in august (weather spark, 2021). there are two dams in the community, mairuwa dam and gwaigwaye reservoir, which supply water for domestic and irrigation purposes to the people of funtua and its environs. the gwaigwaye reservoir was chosen as the study site for hydroelectricity generation, being the more strategically positioned and larger in size and volume than the other. the project has a prospect of benefitting the local small-scale industries in boosting their productivity, hence for the profitability, employment, and poverty reduction for the people of the area. this will avail them with a more reliable, qualitative, and affordable electricity supply. this project is being proposed and geared toward azojete march 2025. vol.21(1):119-135 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:poolabisi@bellsuniversity.edu.ng mailto:poolabisi@bellsuniversity.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 120 developments in distributed off-grid solutions and envisaged for sustainable development (zebra et al., 2021; roy et al., 2023; moran et al., 2022, strielkowski et al., 2021). with the deregulation of nigeria’s power sector (olugbenga et al., 2013; okedu et al., 2018; necoecheaporras et al, 2021), investment opportunities in energy that have emerged includegeneration of renewable electricity by means of small, mini, and micro hydroelectric systems, solar photovoltaic (pv) farm, wind turbines, and biogas (elum and momodu, 2017; babatunde et al., 2023), as obtainable in some other countries (hatata et al., 2019; qamar et al., 2022). nigeria is indeed endowed with many distributed power generation potentials which can be harnessed into micro-grid design and consequently help to increase the availability, reliability and stability of the power supply,thereby alleviate energy poverty (opara et al., 2018), as in other developing countries around the world (palakshappa et al., 2019; uddin et al., 2019; wu et al., 2023; arthur et al., 2020). this research is focused on exploring and highlighting the hydroelectricity generation potential of gwaigwaye reservoir in funtua, katsina state, nigeria. 2. materials and method 2.1 theoretical analysis the electrical power generated by a hydroelectric plant depends on factors as i. rate of flow of water through the turbine, q (in m3/s), ii. the height from which water flows to the ground level where the turbine is located, termed as head, h (in m), and iii. the acceleration due to gravity, g (in m/s2). (ajibola et al., 2018): these terms are modeled mathematically with the generated power, p, given by iglinski (2019): 𝑃 = 𝜌𝑄𝑔𝐻𝜆 1 where, ρ (kg/m3) is the density of water as a constant value of 1000 kg/m3, 𝜆 is the overall efficiency of the turbine, the gear and the generator. this implies that water flow of certain volume must be available at a certain elevation for a hydroelectric project to be feasible. the volume of water stored in a reservoir could be related to the water surface area by a power relation given by ekeu-wei and blackburn (2020): 2 the water flow rate is formulated as: 𝑄 = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑇𝑖𝑚𝑒 (m3/s) 3 as shown in figure 1, this study was organized to go from the initial site identification stage through the physical activities carried out to examine the available hydrological, structural, and electromechanical parameters with a view to optimally generating electricity. 2.2 site identification the proposed site is the gwaigwaye water reservoir (plate 1), situated on river gwaigwaye at unguwar biri village, 3 km off funtua – sokoto road in funtua, katsina state, nigeria. it is a local segment of the sokoto river which originated from machika hills in the neighboring dandume local government area (lawal et al., 2020). it is located on the longitude 7012’23” e, and latitude 11034’47” n, with a catchment area of 120 km2, an earth dam length of 350 m and a height of 13 m (weather spark, 2021). at full supply level (fsl) of 109 m, it has a depth of 12 m, capacity of 42.99 x 106 m3, surface area of 1,701,966.333 m2 and shoreline of 8.2 km. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 121 figure 1: block diagram of the technical feasibility. plate 1: satellite image of gwaigwaye reservoir 2.3 demand analysis the load to be supplied was profiled from the point of view of the total connected load on the 11 kv feeders at funtua transmission substation presented in table 1 and given as 19 mw. in addition, there are two 33 kv feeders feeding the remote areas of malumfashi (13 mw) and dandume (4 mw) from the same transmission substation. existing supply from kano electricity distribution company (kedco) has a maximum value of 15.1 mw for 1000 hours (kedco, 2023). this is shared between the 33 kv feeders supplying remote locations and 11 kv feeders feeding the town. the proposed power project when implemented will definitely not supply this entire load independently, but will be complemented by the grid supply to funtua town.the load is first de-rated by its diversity factor, determined for the distribution network by: 𝐷𝑖𝑣𝑒𝑟𝑠𝑖𝑡𝑦 𝐹𝑎𝑐𝑡𝑜𝑟 (𝐷𝐹) = 𝑆𝑢𝑚 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙 max. 𝑑𝑒𝑚𝑎𝑛𝑑 𝑜𝑓 11 𝑘𝑉 𝑓𝑒𝑒𝑑𝑒𝑟𝑠 𝑀𝑎𝑥. 𝐷𝑒𝑚𝑎𝑛𝑑 𝑜𝑛 𝑡ℎ𝑒 𝑏𝑢𝑠 𝑓𝑒𝑒𝑑𝑖𝑛𝑔 11 𝑘𝑉 𝑓𝑒𝑒𝑑𝑒𝑟𝑠 4 the demand here can be reduced to the ratings of the protecting feeder breakers. so that, 𝐷𝐹 = ∑ 𝐼𝑖 𝐼𝑛 5 where, 𝐼𝑖 is the rating of the 11 kv breakers and 𝐼𝑛 is the rating of the breaker of the 11 kv bus. since the katsina road feeder 33 kv and textile feeder 33 kv main bus breaker ratings are on the 33 kv sides of the transformers, the quantities are therefore referred to 11 kv sides of the transformers to tally with the ratings of the individual breakers and given by: 𝐼𝑛 ′ = 𝐼𝑛 ∗ 𝐸𝑝 𝐸𝑠 6 site demand site civil and electrohttp://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 122 the de-rated value of the demand is therefore obtained from: 7 hence, the prospective capacity of the hydro station is obtained from: 𝐷𝑒𝑚𝑎𝑛𝑑 = 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 = 𝐴𝑛𝑛𝑢𝑎𝑙𝐷𝑒𝑚𝑎𝑛𝑑 (𝑘𝑊ℎ) 365 𝑑𝑎𝑦𝑠 𝑥 24 ℎ𝑟𝑠 × 100 𝐴𝑛𝑛𝑢𝑎𝑙 𝐿𝑜𝑎𝑑 𝐹𝑎𝑐𝑡𝑜𝑟 % 8 table 1: total connected load and breakers rating on funtua 11 kv feeders (kedco, 2022) 30 mva transformer 132/33/11 kv 60 mva transformer 132/33/11 kv feeder location breaker rating (a) connected load (mw) feeder location breaker rating (a) connected load (mw) katsina road (33 kv) 400 9.5 textile (33 kv) 400 9.5 jabiri (11 kv) 300 4.0 nakowa feeder (11 kv) 350 4.5 dutsenreme (11 kv) 200 1.5 mairuwa (11 kv) 250 1.3 town (11 kv) 250 2.2 water works (11 kv) 150 1.2 industrial (11 kv) 100 1.8 textile (11 kv) 100 2.5 total connected load 19.0 total connected load 19.0 the generating capacity of the project is also de-rated in terms of the losses in transmission and distribution and the own use of the power station. the following formula is used to calculate the proposed generation capacity: proposed generation capacity = electricity demand 1 − (td losses % + own use %) 100⁄ 9 2.4 site survey and analysis necessary surveys are carried out at the identified site to identify physical, hydrological, and geological features that may influence the feasibility of the project. the survey is in two stages: the topographical survey and the hydrological survey. 2.4.1 topographical survey generally, topographical maps of 1:50,000 are generated in hydroelectricity feasibility studies to optimize the project planning (the world bank, 2018a & b; pöyry energy ltd, 2019), and cover areas of major civil structures. for this study, the topographical map by (lawal et al., 2020) is adapted and shown in figure 2. existing structures like the reservoir, access road, intake tower, and spillway, would be optimized to suit the requirements of the proposed project. 2.4.2 hydrological survey river gwaigwaye is not gauged, making it difficult to extract runoff data directly from the river. the availability of water in the reservoir can be accurately represented by the water level records as correlated by several studies (yuanshou et al., 2008, wang et al., 2023). it is therefore appropriate for this study to utilize the operational records of the monthly water level captured at the intake tower of the reservoir by the funtua water works as given in table 2 (lawal et al., 2020). figure 3 shows the graphical plot of the water level by months of the year. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 123 figure 2: topographic map of gwaigwaye reservoir. table 2: extracted data for gwaigwaye reservoir month monthly average of water level (m) water temperature (°c) ph value january 10.9 25.69 7.37 february 10.6 27.19 7.35 march 10.1 20.63 7.5 april 9.7 24.95 7.6 may 10.2 21.33 7.46 june 10.5 26.14 7.16 july 11.7 25.17 7.1 august 12.0 25.71 7.53 september 11.8 26.48 8.13 october 11.6 25.87 7.97 november 11.4 25.53 7.91 december 11.2 25.53 7.35 the volume of water in a reservoir using water surface area captured from satellite images is used to obtain the monthly flow rate (qm), which is used to adjust table 2 to obtain table 3. 𝑄𝑀 = 𝑉𝑖 86400 ∗ 𝐷𝑖 10 where, 𝑉𝑖 is the water volume stored in month i, 𝐷𝑖 is the days of month i and 86400 is the number of seconds in a day. using values of the flow rate (q), a flow duration curve was plotted as shown in figure 4, from which the average flow rate was determined to be 18.54083 m3/s. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 124 (a) (b) figure 3: (a) the bar chart and (b) plot of the monthly hydrograph of gwaigwaye reservoir. table 3: maximum depth, water surface area and volume of stored water month depth (m) area (m^2) volume (m^3) qm (m^3/s) january 10.9 1824171 47130079 17.6 february 10.6 1742299 44343504 17.7 march 10.1 1525733 37181310 13.9 april 9.7 1496299 36232339 13.98 may 10.2 1577247 38856571 14.51 june 10.5 1799353 46280967 17.86 july 11.7 1957112 51742130 19.31 august 12 2020052 53962138 20.15 september 11.8 2097885 64027550 24.70 october 11.6 2051728 55088044 20.57 november 11.4 2071009 55776172 21.51 december 11.2 2060708 55408273 20.69 figure 4: flow duration curve. 2.5 civil and structural design during site visits, locations for civil and structural works necessary for the realization of this project were identified. the items for the civil and structural works are discussed in this section. 0 2 4 6 8 10 12 14 ja n u ar y fe b ru ar y m ar ch a p ri l m ay ju n e ju ly a u gu st se p te m b e r o ct o b e r n o ve m b e r d e ce m b er 0 2 4 6 8 10 12 14 ja n u ar y fe b ru ar y m ar ch a p ri l m ay ju n e ju ly a u gu st se p te m b e r o ct o b e r n o ve m b e r d e ce m b er 0 10 20 30 0 20 40 60 80 100 120 q ( m ^3 /s ) % exeedence fdc http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 125 2.5.1 intake structure the intake point was identified as a point on latitude 11.5759 and longitude 7.2071 at 2070 m above sea level, on the earth-dam close to the intake tower bridge of the reservoir (see plate 2). physical measurements on site revealed that: the thickness of earth dam is 56.01 m, the height of earth dam is 13 m, the water elevation fsl is 631.5 m, the ground elevation of the powerhouse is 620.6 m and the gross head is 10.9 m. based on these measurements, the civil and structural works that included the intake canal, the fore-bay and lay-out of the penstock with its supporting concrete bases were designed. the powerhouse is therefore designed accordingly as shown in plate 3. plate 2: intake point plate 3: location of the powerhouse 2.5.2 design parameters having established locations for the civil and structural design and having measured values both on site and on google earth, the following calculations were done to determine the required parameters for the design. generally, hydroelectric stations have an overall efficiency of 80% as the global best practice (signe et al., http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 126 2017). on this basis, and taking the average discharge as indicated in the flow duration curve, the power generation capacity of the station is determined using the equation (1). likewise, the diameter, d (m), of the penstock pipe, which is preferably of galvanized steel, is given by: 𝐷 = 2.69(𝑛𝑝 2 ∗ 𝑄2 ∗ 𝐿𝑝) 𝐻𝑔 11 and, the thickness of the penstock pipe, 𝑡 (m), is obtained from: 𝑡 = 𝐷 + 508 400 + 1.2 12 where, 𝑛𝑝 is the manning’s coefficient, 𝐿𝑝(m) is the length of the penstock pipe and 𝐻𝑔 (m) is the gross head. 2.6 design of electromechanical elements the electromechanical elements include the hydraulic turbine that converts hydraulic energy to rotational mechanical energy. the generator then converts mechanical rotation into electricity and the step-up transformer that raises the voltage level to the required transmission voltage. 2.6.1 hydraulic turbine tkac (2018) noted that large number of hydro systems exist with uses depending on physical conditions of the development site, given by the water discharge as against the net head with respect to the desired demands. hydro turbine systems are therefore majorly categorized as: the reaction and the impulse turbines. reaction turbines produce power from combination of forces of pressure and moving water, and are generally: propeller, francis and kinetic turbines. the impulse turbines use the velocity of running water to move the runner by hitting the buckets and emptying and are generally: pelton and cross-flow turbines (uddin et al., 2019; energy.gov, 2023). factors that affect selection of hydraulic turbines for hydroelectric power plants are seven in number, namely: head, specific speed, rotational speed, efficiency of the turbine, cavitation, disposition of turbine shaft and part load operation (adepoju, 2021). tables 4 and 5 consist of summaries for the head, specific speed and the required types of turbines. it can be noted that specific speed is high for turbines which work under high heads and low flow rate, and vice versa. the turbine application chart, an industry standard guide, shown in figure 5 assists in selecting the appropriate turbine for this work, based on the operational discharge rate and measured head (iglinski, 2019, chen et al., 2013). in addition to the head versus discharge relationship, other factors that influence the selection include the turbine rotational speed, the specific speed, and the turbine efficiency. the rotational speed, which for this study should match the requirements to generate voltage at a frequency of 50 hz, is given as follows for a 4pole generator chosen for convenience: 𝑁 = 60𝑓 𝑝 13 conversely, the specific speed (which is defined as the speed of a geometrically similar turbine that produces 1 kw of power discharged under 1 m of net head) is determined by: 𝑁𝑠 = 𝑁√𝑃 𝐻 5 4 14 this project is therefore characterized by high specific speed, low head and low discharge. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 127 table 4: head and types of turbines. head head range in meters suitable turbine notes very low head 3 10 bulb turbine kaplan turbines are also suitable but uneconomical for very low heads low head 10 60 kaplan turbine propeller turbines are also suitable up to 15m head but without load variations. medium head 60 150 francis turbine high head 150 350 pelton or francis turbine one of them is decided based on the specific speed. very high head >350 pelton turbine table 5: specific speed and types of turbines. specific speed range type of turbine 10 70 pelton turbine 80 400 francis turbine 300 1000 kaplan turbine 1000 1200 bulb turbine figure 5: turbine application chart. 2.6.2 generator the generator would be coupled to the turbine to convert the mechanical energy produced by the turbine into electricity. therefore, the specifications of the generator, namely: generator power capacity, the rotor speed, and the voltage frequency, should match those of the turbine. 3. results and discussion the results of the study carried out to determination the hydroelectricity potential of the gwaigwaye reservoir is presented and discussed in this section. recorded in table 6 are the site location data and description for all site structures and installation identified for the project, namely: hydro-technical, structural, civil, mechanical, and electrical structures and installations. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 128 3.1 demand analysis results the connected load on the 11 kv feeder bus at funtua transmission substation was used for the demand analysis and the result is presented in table 7. table 6: key structure’s locations # structure location description 1. intake point lat. 11.575917 lon. 7.207110 a point on the dam close to the existing intake tower access track 2. canal lat. 11.576435 lon. 7.206834 beginning at the intake point and terminating at the fore bay 3. fore-bay lat. 11.576435 lon. 7.206834 beginning at the end of the canal 4. penstock from the fore bay and ending at the powerhouse 5. powerhouse lat. 11.577115 lon. 7.206979 a room to shelter the hydraulic and electromechanical components located at the edge of the existing reservoir spill way tail race 6. draft tube directly discharges into existing reservoir spill way tail race 7. tailrace same as the existing reservoir spill way tail race table 7: demand analysis results # quantity value 1. total connected load 19 mw 2. demand factor 70% 3. actual demand 13.3 mw 4. proposed generation capacity 14 mw 3.2 site survey and analysis results as discussed, sub-section 3.3, the two major surveys considered are the topographical and hydrological surveys. the topographical survey map of the site used in this study was adapted from (lawal et al., 2020). for the hydrological survey, the hydrological setting of the proposed site studied and analyzed through capturing and recording the monthly water surface area with the aid of google earth pro has the results tabulated in table 8. this result is used for the calculation of stored reservoir water volume for the months of the year using the water volume (v) power equation. the results were then used to calculate the amount of water discharge to the turbine with the results presented in table 9. 3.2.1 flow duration curve the flow duration curve is generated from the exceedance with the results given in table 9. 3.3 civil and structural design the results of the calculations of the design parameters for the civil and structural works, which consist mainly of the parameters of the intake structure and fore-bay, are presented in table 10. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 129 table 8: monthly water level, surface area, stored volume and discharge. month depth (m) area (m2) volume (m3) qm (m3/s) january 10.9 1824171 47130079 17.6 february 10.6 1742299 44343504 17.7 march 10.1 1525733 37181310 13.9 april 9.7 1496299 36232339 13.98 may 10.2 1577247 38856571 14.51 june 10.5 1799353 46280967 17.86 july 11.7 1957112 51742130 19.31 august 12 2020052 53962138 20.15 september 11.8 2097885 64027550 24.7 october 11.6 2051728 55088044 20.57 november 11.4 2071009 55776172 21.51 december 11.2 2060708 55408273 20.69 3.3.1 intake structure the intake canal would be excavated and constructed of reinforced concrete across the dam fill with the dimension of the dam determined from the following measurements and calculations.given that the average discharge into the turbine is 18.54083 m3/s, it is desirable that this volume of water travels at least five seconds in the intake canal before settling in the fore-bay. this implies the canal should be able to accommodate five times single discharge volume at any given time. with the thickness of the dam measured as 56 m, and a 4 m length outside the dam wall added to isolate the fore-bay from the dam structure, we have a total canal length of 60 m. therefore, the capacity of the canal would be: 5 ∗ 𝑄𝑎𝑣 = 5 ∗ 18.5408 = 92.7 𝑚3 15 with the length of the canal designed to be 60 m, the canal cross-sectional area is given by: 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑎𝑛𝑎𝑙 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑎𝑛𝑎𝑙 = 92.7 60 = 1.545 m2 16 with the canal designed to be of square cross-section, the length and breadth is determined by: 𝑙 = 𝑏 = √1.545 = 1.243 𝑚 x 1.243 𝑚 the canal dimension is therefore given as: longitudinal length = 60 m, cross-sectional length = 1.243 m and cross-sectional breadth = 1.243 m. 3.3.2 fore-bay the fore-bay should be of sufficient volumetric capacity to accommodate the discharge of five-minutes before being exhausted without replenishment. this will enable the penstock become always completely submerged to avoid turbulence and air bubbles that may destabilize the required smooth flow into the turbine chambers. so, the capacity of the fore-bay is obtained as: 𝑉𝑓𝑏 = 𝑄𝑎𝑣 ∗ 𝑡 = 18.54 ∗ 5 𝑚𝑖𝑛 ∗ 60 𝑠𝑒𝑐 = 𝟓𝟓𝟔𝟐 𝒎𝟑 17 http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 130 the design of the fore-bay considered the need for its effective volume to be at least 2 m deep below the floor of its intake canal. therefore, the floor area of the fore-bay is obtained as: 𝐴 = desired capacity minimum depth = 5562 𝑚3 2 𝑚 = 𝟐𝟕𝟖𝟏 𝒎𝟐 18 the floor was designed to be a square surface with the length and breadth determined by: 𝑙 ∗ 𝑏 = √2781 ∗ √2781 = 52.7 𝑚 ∗ 52.7 𝑚 19 table 9: discharge results rank discharge (m3/s) % exceedance average discharge 1 24.7 8.33 18.54083 2 21.52 16.67 18.54083 3 20.69 25 18.54083 4 20.57 33.33333 18.54083 5 20.15 41.66667 18.54083 6 19.31 50 18.54083 7 17.86 58.33333 18.54083 8 17.7 66.66667 18.54083 9 17.6 75 18.54083 10 14.51 83.33333 18.54083 11 13.98 91.66667 18.54083 12 13.9 100 18.54083 table 10: civil and structural design parameters # quantity value/unit remark 1. canal dimension 1.243 m * 1.243 m * 60 m calculated 2. fore-bay dimension 52.7 m * 52.7 m * 2 m calculated 3. dam thickness 56 m measured 4. dam height 13 m measured 5. gross head 10.9 m calculated 3.3.3 the powerhouse the powerhouse is located at the edge of the tailrace of the reservoir spillway so that the existing tailrace of the reservoir is also used to serve the powerhouse. however, the location is important in determining the length of the penstock to be installed. the ground distance from the fore-bay to the powerhouse was measured from google earth pro to be 65 m. the penstock intake on the fore-bay is at a height of (10.9-2) m or 8.9 m. applying pythagoras theorem, the penstock length is determined as: 𝑃𝑒𝑛𝑠𝑡𝑜𝑐𝑘 𝑙𝑒𝑛𝑔𝑡ℎ = √652 + 8.92 = 𝟔𝟔 𝒎 3.3.4 the penstock the penstock in this application is desired to be of galvanized steel (pressure pipe). taking manning’s coefficients for smooth steel as 0.012, the diameter of the pipe is determined by: 𝐷 = 2.69(0.0122 ∗ 18.542 ∗ 66) 10.9 = 𝟎. 𝟖 𝒎 also, the thickness of the penstock pipe is determined by: http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 131 𝑡 = 𝐷 + 508 400 + 1.2 = 0.8 + 508 400 + 1.2 = 𝟐. 𝟓 𝒄𝒎 3.3.5 generation potential the main goal of this research work is to determine how much electricity can be generated from the gwaigwaye reservoir. this aspect is achieved using the power equation given in equation (1) and hereby obtained as: 𝑃 = 1000 ∗ 18.54 ∗ 10.9 ∗ 90% = 1782399 𝑊 = 1.78 𝑀𝑊 3.4 electromechanical design and analysis at this stage, the components that convert hydraulic energy to mechanical energy and then to electrical energy are selected from results of analysis carried out so far in this study. 3.4.1 hydraulic turbine as the penstock was separated into four pieces, also the estimated turbine generation power was divided into four 445 kw capacities. the chart in figure 8 is used to select the most suitable turbine type for this application, as a conventional practice based on discharge or flow rate (in m3/s), head (in meters) and generated output power (in watts). the point of convergence of discharge of 18.54 m3/s, head of 10.9 m and output power of 445 kw on the chart falls within the envelope of kaplan turbine. this is because the configuration for the chosen site can be categorized as low head, low discharge, and low output power. however, a more appropriate turbine type for this setting could be a bulb turbine. it operates like the kaplan turbine with added advantage of better yield under very low head, but has been proven to be uneconomical for very low heads. 3.4.2 specific speed to ascertain the selection of bulb turbine for this application, specific speed of the system was calculated and compared with the range of specific speeds within which bulb turbine is best suited for this generation. however, the specific speed equations (13) and (14) are used to calculate the rotational speed of the system and obtained as: 𝑁 = 60 ∗ 50 4 = 750 𝑟𝑝𝑚 for a four-pole generator, the specific speed is therefore determined as. 𝑁𝑆 = 750 ∗ √450 10.95/4 = 895 𝑟𝑝𝑚 this falls within bulb turbine specific speed range, 750 to 1200 rpm, making it most appropriate. 3.4.3 generator the generator was selected to match the requirements of the load as well as the statutory regulations. the nigerian electricity regulation commission (nerc) requires that voltages for utility in nigeria must be 230 v or 220 v, 400/230 v or 380/220 v and 15,000 v, 11,000 v, 400/230 v or 380/220 v respectively (electrical installation guide, 2022), with a frequency of 50 hz ± 1%. the generator was therefore selected as a 4–pole synchronous generator. the output power was determined considering a transmission and distribution loss of 5% and an own use power by the station of 1%. therefore, the output power of the generator is obtained as: http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, march 2025; vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 132 𝐺 = 𝑃 1 − 𝑇𝐷 + 𝑂𝑤𝑛 𝑈𝑠𝑒 100 = 1.78 1 − 5 + 1 100 20 = 1.8936 𝑀𝑊 𝑜𝑟 𝑟𝑜𝑢𝑛𝑑𝑒𝑑 𝑡𝑜 2.0 𝑀𝑊 = 500 𝑘𝑊 𝑒𝑎𝑐ℎ 4. conclusion from the results and findings of this study and reflecting on the objectives of the research, the following conclusions were drawn. 1. the locations identified for the major site structures took advantage of the existing reservoir infrastructure, such as dam wall, tailrace, access road and intake tower. 2. the surface area was used to calculate the volume of the water and the flow rate due to the absence of an alternative to flow gauging at river gwaigwaye. 3. the selected hydraulic, mechanical, and electrical equipment for the powerhouse were considered the optimal selection for the prevailing site configuration in question. 4. the calculated power generation of the project, 1.78 mw, will not suffice to power the total load demand of 13.3 mw. it is only intended to complement the supply from the national grid. 5. generally, the research is found to satisfy its purpose with the hydro-generating potential of gwagwaye dam determined and the components necessary to achieve this potential identified. references adepoju, s. 2021. factors affecting selection of hydraulic turbines. the constructor. https://theconstructor.org/practical-guide/hydraulics-lab/turbines-pumps/factors-affecting-selection-hydraulicturbine/30826/ accessed on 23 march 2024. ajibola, ooe., ajala, os., akanmu, jo. and balogun, oj. 2018. improvement of hydroelectric power generation using pumped storage system. nigerian journal of technology. 37(1):191–199 arthur, e., anyemedu, fok., gyamfi, c., asantewaa-tannor, p., adjei, ka., anornu, gk. and odai, sn. 2020. potential for small hydropower development in the lower pra river basin, ghana. journal of hydrology: regional studies 32: 100757. doi.org/10.1016/j.ejrh.2020.100757. babatunde, o., buraimoh, e., tinuoye, o. and ayegbusi, c., davidson, i. and ighravwe, de. 2023. electricity sector assessment in nigeria: the post-liberation era. cogent engineering. 10(1): 2157536, doi.org/10.1080/23311916.2022.2157536 barnes, df., vanderplas, r. and floor, w. 1997. tackling the rural energy problem in developing countries. finance & development: 11-15. chen, j., yang, hx., liu, cp., lau, ch. and lo, m. 2013. a novel vertical axis water turbine for power generation from water pipelines. energy. 54: 184-193. dibaba, h., demidov, i., vanadzina, e., honkapuro, s. and pinomaa, a. 2022. feasibility of rural electrification and connectivity—a methodology and case study. applied energy. 315: 119013. economic and social council of the united nations (ecosoc) 2023. sustainable renewable energy key to unlocking developing countries’ potential, achieving global goals, speakers tell high-level political forum. high-level political forum, 5th and 6th meetings ecosoc/7136, 12 july 2023. https://press.un.org/en/2023/ecosoc7136.doc.htm. http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng https://theconstructor.org/practical-guide/hydraulics-lab/turbines-pumps/factors-affecting-selection-hydraulic-turbine/30826/ https://theconstructor.org/practical-guide/hydraulics-lab/turbines-pumps/factors-affecting-selection-hydraulic-turbine/30826/ https://doi.org/10.1016/j.ejrh.2020.100757 http://doi.org/10.1080/23311916.2022.2157536 https://press.un.org/en/2023/ecosoc7136.doc.htm arid zone journal of engineering, technology and environment, march 2025; 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vol.21(1):119-135. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email: poolabisi@bellsuniversity.edu.ng 135 world bank report. 2021. universal access to sustainable energy will remain elusive without addressing inequalities https://www.worldbank.org/en/news/press-release/2021/06/07/report-universal-access-tosustainable-energy-will-remain-elusive-without-addressing-inequalities accessed on 8 february, 2024 wu, kc., lin, jc., chang, wt., yen, cs. and fu, hj. 2023. research and analysis of promotional policies for small hydropower generation in taiwan. energies, 16: 4882. https://doi.org/10.3390/en16134882 http://www.azojete.com.ng/ mailto:poolabisi@bellsuniversity.edu.ng https://www.worldbank.org/en/news/press-release/2021/06/07/report-universal-access-to-sustainable-energy-will-remain-elusive-without-addressing-inequalities https://www.worldbank.org/en/news/press-release/2021/06/07/report-universal-access-to-sustainable-energy-will-remain-elusive-without-addressing-inequalities https://doi.org/10.3390/en16134882 corresponding author’s email address: da.amaefule@unizik.edu.ng 318 arid zone journal of engineering, technology & environment original research article effects of drying temperatures on nutritional and phytochemical properties of gongronema latifolium leaves d.o. amaefule*, c.o. nwajinka, n.n mbegbu, and c. d. okpala department of agricultural and bioresources engineering, nnamdi azikiwe university, awka, anambra state, nigeria *corresponding author’s email: da.amaefule@unizik.edu.ng article information abstract this study investigated the effects of drying temperature on the nutritional and phytochemical components of gongronema latifolium (bush buck) leaves; a widely spread edible indigenous leafy vegetable of west africa. the leaves were dried at room temperature (rtd), in the open sun (osd) and at 30, 40, 50, 60 and 70 °c in a convective oven (od). proximate and phytochemical analyses were done on the products of each od temperatures, while for rtd and os drying, the tests were done at their equilibrium moisture content (𝑀𝑖) of the ambient. statistical analysis was done using matlab. the parameters of the fresh leaves with 82.95% moisture content served as the control. drying decreased the product 𝑀𝑖 to 12.95%, 7.65%, 6.95%, 5.79% and 5.03% in the listed order of the drying temperatures. the proximate and phytochemical contents increased with drying temperature. 70 °c drying temperature gave the highest contents of ash (16.35%), fibre (27.85%), protein (22.70%), carbohydrate (32.84%) and fat (2.42%) in the dried leaves. same went for the phytochemicals: alkaloid (4.50%), flavonoid (3.92%), saponin (1.46%), tannin (1.39%) and terpenoids (2.72%). second order polynomial models fitted the data well and gave coefficient of determination (r2) of 0.789 for fibre, 0.869 for fat, 0.895 for protein, 0.921 for ash, 0.923 for terpenoids, 0.941 for moisture, 0.943 for flavonoids, 0.982 for saponnins, 0.987 for alkaloids and 0.992 for tannins content. these results show that there are strong relationships between the proximate and phytochemical composition and the drying temperatures. at their corresponding temperatures, osd yielded the highest value of saponins (1.45%), tannins (0.64%) and terpenoids (2.45%), rtd gave highest value of alkaloids, flavonoids, carbohydrate (58.38%), protein (17.07%) and fat (1.10%), while od yielded the highest fibre content (28.32%). the results show that drying methods and conditions should be chosen based on the intended use of the products. received: 17th october 2022 revised: 5th march 2025 accepted: 7th march 2025 keywords: drying nutrition phytochemicals gongronema latifolium temperature models © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction reports have shown that vegetables provide bulk fibre, which aids digestion and are good sources of vitamins and minerals like ascorbic acid, beta carotene, riboflavin, calcium, magnesium, iron and phosphorus in the human diet (mohammadu et al., 2014 and lawal et al., 2015). they have also been used from time as spices in food, condiments and for medicinal purposes like other plant materials (nweze and eze, 2009 and rhoda and negimote, 2015). the igbo tribe of south-eastern nigeria employs ocimum gratissimum in the management of the neonatal umbilicus, the coastal areas of nigeria for the treatment of epilepsy, high fever and diarrhea, and the savannah areas apply it for treating mental illness and to keep wound surfaces sterile (ijeh et al., 2004, njoku et al., 2011a, b and rhoda and negimote, 2015). some species of leafy vegetables are known to contain such phytochemicals as alkaloids, saponins, terpenoids, flavonoids, tannins, phlobatannins, anthraquinones, steroids and cardiac glycosides, which make them useful in the treatment of fungal infections, cold and catarrh (molyneux et al., 2007, oladosu-ajayi et al., 2017 and mbegbu et al., 2021). gongronema latifolium is a tropical rainforest plant which belongs to the family asclepiadaceae and genus gongronema (okafor, 2002) and is valued for its leaves (eleyinmi, 2007). it grows in west africa and is known azojete june 2025. vol.21(2):318-327 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/001 www.azojete.com.ng mailto:da.amaefule@unizik.edu.ng mailto:da.amaefule@unizik.edu.ng https://doi.org/10.63958/azojete/2025/21/02/001 http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 319 among the nigerian ethnic groups as “utasi” by the ibibios, quas and efik; “utazi” by the igbos and “arokeke” by the southwestern yorubas. in ghana and senegal, the plant is referred to as “akan-asante aborode” and “sever gasule” respectively (balogun et al., 2016). utazi is also found in some other west african and tropical countries (balogun et al., 2016), including guinea-bissau, cameroon (west) and sierra leone (owu et al., 2012). it is a climbing edible plant with a pliable stem, yellow flower and green leaf that produces milky latex when plucked. it has a characteristic sharp, bitter and slightly sweet taste, especially when eaten fresh (okafor, 1987). the leaf is rich in fats (16%), fibre (6.3%), ash (1.3%), proteins (33.2%), carbohydrate (43.7%) and essential amino acids. (eleyinmi, 2007 and alobi et al., 2012). utazi leaf is commonly used fresh in some traditional soups as vegetable, or dried and employed as powdery spice. it is also consumed raw (fresh from harvest) and can be used in salad preparations (balogun et al., 2016). the root and stem are used as chewing stick in sierra leone. in addition to the nutritional uses, g. latifolium is also used for medicinal purposes based on its perceived phytochemicals content. a liquor from aqueous extract of the leaves or from boiling it with lime juice is used for treating colic, stomach pains and symptoms of worm infestation, and as a purgative (okafor, 2002). iwu (2014) reported hypoglycemic, antioxidant and anti-inflammation activities of utazi from scientific studies. ethanol extracts of g. latifolium gave analgesic, anti-pyretic and anti-ulcer benefits in laboratory rats experiments (akuodor et al., 2016). although this plant is drought-tolerant, it is not available in the dry season. since vegetables are perishable products due to their high moisture contents; 60.0 98.8% (njoku et al., 2011b), they are usually dried and stored. drying of vegetable materials is a necessary option for both storage and handling purposes. drying reduces water activity, leads to significant reduction in weight and volume, and consequently reduces costs of packaging, transportation and storage (khaled et al., 2014). reduced moisture content also hinders biochemical activities of spoilage agents on food substances (alegbeleye et al., 2022). however, drying also alters other physical, biological and chemical properties of foods (njoku et al., 2011a). hot-air drying is a very common preservation method used in treating foodstuffs for preservation of the qualities of the products (oladosuajayi et al., 2017). in thin layer hot-air drying, falling rate period which starts after the critical point is achieved when the droplet surface becomes unsaturated. the period is marked by the phenomenon wherein the volatile solvent’s internal transfer to the product surface controls the drying rate. rapid fall of the drying rate ensues beyond this period, with a rise in the surface temperature of the product (mbegbu et al., 2021). the importance of utazi in the rainforest zone of west africa notwithstanding, little published studies is available on the effect of drying on the phytochemical and proximate components. consequently, there is need for studies on drying of its leaf to properly understand the effects of drying temperatures on its nutritional and phytochemical composition. information from the study will help our local food vendors and food scientists on the best drying temperatures for the leaf under tropical conditions, and in the post-harvest processing and handling. therefore, the objective of this study is to determine the effect of drying temperatures on the proximate and phytochemical compositions of gongronema latifolium (utazi) leaf. 2. materials and method fresh leaf samples of gongronema latifolium (utazi) were purchased from nsukka market (latitude 6.8518on, longitude 7.4014oe) and taken immediately to the crop science laboratories of the university of nigeria nsukka, for identification. the leaves (see sample in plate 1) were detached from the stems and washed thoroughly. the initial and final moisture contents of the samples were determined before and after each drying run, by gravimetric method. the method used involves oven drying at 105 oc for 24 hours as described by the association of official analytical chemists (aoac, 1990). three samples of 30 g each of the leaves were dried in an oven under these conditions until there was no further weight reduction. the moisture content was determined in percent dry basis (%db) using equation 1. 𝑀𝑡 = 𝑚𝑤−𝑚𝑑 𝑚𝑑 1 where, mt is the moisture content (g water/g dry matter) at time, t, mw is the wet mass of sample (g) and md is the dry mass of the sample (g). http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 320 plate 1: a fresh gongronema latifolium leaf 2.1 experimental procedure a laboratory vacuum oven dryer (faithful oven dz-3be, china) with specifications; 220 v, 50 hz and 2000 w, 10–250 oc operating temperature and <133 pa operating vacuum, was used for the drying experiments. the oven temperature was set at 30 oc, 40 oc, 50 oc, 60 oc and 70 oc for the different experimental runs and allowed to equilibrate before loading the samples. following the method used by arslan and özcan (2012) and mbegbu et al. (2021), fresh samples of utazi leaves were uniformly distributed in a thin layer on the dryer trays constructed with chicken mesh material. the experiments were conducted in three replicates for each oven temperature. the samples were periodically weighed with the drying tray made of chicken mesh to avoid buoyancy effect between the warm pan and the wide leaves when placed on the weighing balance. the drying process was continued until at least two consecutive masses of the dry samples were observed to be constant. at the end of each drying run, the sample mc, nutritional and phytochemical content were determined in the laboratory. the laboratory tests made on the samples were restricted to proximate and phyto-chemical analyses. the proximate analyses carried out were moisture, ash, crude protein, crude fibre and carbohydrate contents, while the phyto-chemical analyses carried out were for alkaloid, flavonoid, saponin, tannin and terpenoid contents. the procedures used are described in detail in the references provided in the following sections. 2.1.1 phytochemical analysis phytochemical analysis was conducted according to methods described by yadav and agrawala (2011), patle et al. (2020) and aoac (1990). quantitative phytochemical determination for alkaloids, flavonoids, cardiac glycosides and phenols were carried out according to methods described by edeoga et al. (2005). 2.1.2 proximate analysis proximate composition of leaves for carbohydrate, ash, and moisture were determined by methods described by aoac (2006). crude protein, fibre and fat content were determined by methods described by oyeyemi et al. (2017). total ash content was determined by furnace incineration as reported by antia et al. (2006). 2.2 data and analysis the drying models were obtained by fitting the transformed drying data into two thin layer drying models using matlab software. the reason for the transformation is to make the data free from dimensional disparities by converting the moisture content to moisture ratio. the expression for achieving this is presented in equation 2. moisture ratio (mr) = ( 𝑀𝑡−𝑀𝑖 𝑀𝑜−𝑀𝑖 ) 2 where, mt is the moisture content (mc) of the product at time t, mo the initial mc of the product and mi the equilibrium mc. the values of mc are relatively small compared to mt and mo. http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 321 statistical analysis such as coefficient of determination (r2), error mean square (ems), and root mean square error (rmse) was used to show how well the models fitted the data considering the values of the parameters shown in equations 3 to 5. r2 = 1 − [ ∑ (𝑀𝑅𝑝𝑟𝑒,𝑖−𝑀𝑅𝑒𝑥𝑝,𝑖) 2𝑁 𝑖=1 ∑ (𝑀𝑅𝑝𝑟𝑒,𝑖 2−𝑀𝑅𝑒𝑥𝑝,𝑖 2)𝑁 𝑖=1 ] 3 rmse = ( 1 𝑁 ∑ [𝑀𝑅𝑝𝑟𝑒,𝑖 − 𝑀𝑅𝑒𝑥𝑝,𝑖] 2𝑁 𝑖=1 ) 1 2 4 sse = ∑ (𝑀𝑅𝑒𝑥𝑝,𝑖 − 𝑀𝑅𝑝𝑟𝑒,𝑖) 2𝑁 𝑖=1 5 to determine the relationships between the phytochemical and proximate quantities, the data were regressed against the drying temperatures by second order polynomial models. the goodness of fit was estimated by the corresponding coefficient of determination, r2, which varies from 0.0 to 1.0. the higher the r2 value, the better the relationship between the factors and response variables in the models (turan and firatligil, 2019). the result was presented in the forms of tables and charts. 3. results and discussion 3.1 moisture content the initial moisture content of gongronema latifolium leaf was 82.95%db. figure 1 shows the moisture content (dry basis) of the dried utazi leaves for the various drying temperature. at each drying temperature, the drying rate of the sample decreased until it attained equilibrium with the drying air. at 30 °c, 40 °c, 50 °c, 60 °c and 70 °c the corresponding equilibrium moisture contents were 12.95%, 7.65%, 6.95%, 5.79% and 5.03% respectively. increasing drying temperatures resulted in lower sample equilibrium moisture content (mi). alakali et al. (2015) reported a 15.01 2.50% mc for dried moringa oleifera leaves at 30 70 °c drying temperatures. mbegbu et al. (2021) obtained 0.2% and 0.1% product mc after 6.5 hrs and 5.5 hrs drying of scent leaf and lemon basil leaves respectively. figure 1: moisture content versus drying temperatures at equilibrium 3.2 drying characteristics the drying characteristics of the materials were investigated by converting the drying data moisture ratio and plotted it against the drying time. the curve fitting identified the logarithmic and two-term diffusion models as the most adequate for the drying data and therefore were used for the predictive models for gongronema latifolium leaves. figure 2 shows the plot the moisture ratio against drying time. from the figure, there was a decrease in the time required to dry the leaves to mi as the drying temperature increased. for 30 oc drying temperature it took 6 hrs to reduce the initial moisture content to the 12.95%db mi, with the falling rate 0 2 4 6 8 10 12 14 30 40 50 60 70 f in al m o is tu re c o n te n t, % ( d b ) drying temperature, oc http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 322 period endpoint occurring at 2 hrs 30 mins. at 40 oc drying, the leaves were dried to 7.65%db mi in 4 hrs, with the falling rate period ending in 2 hrs. 50, 60 and 70 oc drying temperatures gave 6.95%db, 5.79%db figure 2: plot of moisture ratio against drying time and 5.03%db mi in 3 hrs, 2 hrs and 1 hr 20 mins, with 1 hr 30 mins, 1 hr and 39 mins falling rate period end points respectively. the drying was observed to take place majorly during the falling rate period. table 1 contains the drying model equations and their parameters and goodness of fit. the drying was well predicted with exponential models with r2 values of 0.8345 0.9973. thus at 95% confidence interval (ci), the table 1: the drying model parameters of gongronema latifolium leaves temp. (oc) model model constants goodness of fit a k1 b k2 r2 sse rmse 30 mr = a*exp(k1*t) + b*exp(k2*t) 5.458 x104 -2.027 -5.458 x 104 -2.027 0.9896 0.01321 0.04344 mr = a*exp(k*t) 0.1596 -1.257 - - 0.9726 0.03462 0.06202 40 mr = a*exp(k1*t) + b*exp(k2*t) -2172 -1.651 2173 -1.65 0.9942 0.006336 0.0356 mr = a*exp(k*t) 1.06 -0.8562 --0.9698 0.0329 0.06855 50 mr = a*exp(k1*t) + b*exp(k2*t) 1.109 -2.430 0 -2.43 0.8345 0.1448 0.2197 mr = a*exp(k*t) 1.033 -1.280 - - 0.9827 0.01512 0.0550 60 mr = a*exp(k1*t) + b*exp(k2*t) -1452 -3.28 1453 -3.278 0.9973 0.002782 0.02359 mr = a*exp(k*t) 0.1609 -1.2750 - -0..9858 0.01443 0.0454 70 mr = a*exp(k1*t) + b*exp(k2*t) -704.8 -4.538 705.8 -4.535 0.9930 0.006715 0.03665 mr = a*exp(k*t) 1.0138 -2.981 --0.9891 0.01047 0.03867 models can predict the drying data well with minimal error. the best prediction was obtained for 60 °c drying, while the worst was for 50 °c. mbegbu et al. (2021) reported the logarithm model as the best for predicting scent leaf and lemon basil leaf drying under similar experimental conditions, with r2 values of 0.9998 and 0.9961 respectively. falling rate period was also predominant for drying their two leaves. logarithmic and page models were reported by turan and firatligil (2019) as the best for predicting the drying process kinetics of thyme leaves dried at 50, 60, 70 and 80 °c. 3.3 phytochemicals presence the phytochemical analysis for the dried utazi leaf is shown in table 2. the presence of a phytochemical in the dried leaves was indicated with a + sign while its absence was indicated with a – sign. only the significant components were further investigated. the results showed the dried leaves contain alkaloids, saponins, flavonoids, and tannins in significant amount, while cardiac glycosides, anthraquinones, deoxy sugar and phlobatannins were not in significant amount. other phytochemicals detected were terpenoids, phenol and carbohydrates. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 time, hrs m oi stu re ra tio temp @30 oc temp @40 oc temp @50 oc temp. @60 oc temp. @70 oc http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 323 table 2: preliminary analysis for phytochemical constituents of utazi leaves s/n phytochemicals presence 1. alkaloids + 2. saponin + 3. flavonoids + 4. tannins + 5. terpenes + 6. cardiac glycosides 7. phenol + 8. carbohydrates + 9. anthraquinones 10. deoxy sugar 11. phlobatannins 3.4 phytochemical content figure 3 shows the phytochemical contents of the dried utazi leaves for various drying temperatures. leaves dried at 30 °c have alkaloids, saponins, flavonoids, tannins and terpenoids contents of 4.0%, 3.6%, 0.8 %, 0.5% and 1.9% respectively. the leaves dried at 40 °c have 4.1%, 3.7%, 0.8% and 0.7% and 2.1% of alkaloids, saponins, flavonoids, tannins and terpenoids contents respectively. for 50 °c drying temperature, the alkaloids, saponins, flavonoids, tannins and terpenoids contents were 4.2%, 3.7%, 0.9%, 0.8% and 2.2% respectively. 60 °c drying temperature gave leaves of 4.4%, 3.9%, 1.0%, 1.0% and 2.7% alkaloids, saponins, flavonoids, tannins and terpenoids contents respectively. the alkaloids, saponins, flavonoids, tannins and terpenoids contents were 4.5%, 3.9%, 1.5%, 1.4% and 2.7% for leaves dried at 70 °c. there was gradual steady increase in all the phytochemicals with increasing drying temperature, showing the concentration of the substances with increasing dehydration. for all the drying temperatures considered, the alkaloids had the highest concentration followed by the flavonoids, while the tannins had the least. the saponins was second least in concentration but had more gradual relative increase than the tannins with increasing temperature. the alkaloids and the flavonoids also had the least relative increase in concentration. the terpenoids were average both in content and relative increase in concentration. this could probably mean that the degradation of these phytochemicals with increasing temperature during convective hot-air drying of utazi leaves increases in the order; tannins saponins -terpenoids flavonoids alkaloids. shi et al. (2004) reported that an optimum thermal process can increase the stability and maintain the saponins in processed products. figure 3: phytochemical contents versus drying temperatures 3.5 other nutritional content the percentage nutritional compositions of utazi leaves dried at various temperatures are presented in figure 4. the results show that the leaves dried at 30 °c had percentage of ash, fibre, protein, carbohydrate and fat contents observed to be 13.25%, 28.32%, 16.83%, 27.70% and 0.95% respectively. equally, when the leaves http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 324 were dried at 40 °c, the percentage of the constituents were 15.32%, 23.02%, 20.89% and 27.66% and 1.96% for ash, fibre, protein, carbohydrate and fat contents respectively. for 50 °c drying temperature, the ash, fibre, protein, carbohydrate and fat contents were 15.42%, 24.91%, 21.21%, 28.95% and 2.04% respectively. 60 °c drying temperature gave leaves of 16.05%, 28.28%, 21.62%, 32.48% and 2.07% ash, fibre, protein, carbohydrate and fat contents respectively. the ash, fibre, protein, carbohydrate and fat contents were 16.35%, 30.33%, 22.70%, 32.84% and 2.42% for leaves dried at 70 °c. similar trend was reported by alakali (2015) for nutrient contents of dried moringa oleifera leaves at 30 70 °c drying temperature. negi et al. (2001) observed better quality parameters retention for leafy green vegetables dried under faster drying conditions. figure 4: nutrient contents versus drying temps. at equilibrium moisture contents the relationship between the nutrients and the drying temperature as presented in equations 9 to 13. second order regression models described the relationship well. the r2 values of above 0.7 means excellent relationship between the variables. values of 0.5 and above are considered significant at 95% confidence interval (ci). as the drying temperature increased, the sample nutrient content generally increased. the removal of water ultimately leads the concentration of the other components. however, there was a slight decrease in the fibre and carbohydrate contents between 30 to 40 °c drying temperature, before a steady increase ensued. increasing the temperature to this metabolism range and sustaining it at same for a substantial period of time may have encouraged more enzymatic degradation of these nutrients, leading to the ditch in these nutrient content. some degradation of these nutrients via increased activities of the nutrient-degrading enzymes may have taken place before effective drying started. even in nature, the mammalian body temperature range is 37 – 39 °c, while that for poultry 41 – 42 °c (troxell et al., 2015). digestion of ingested food naturally takes place at these range of temperature. the attainment of the natural digestion temperature range may encourage the enzymatic degradation of the nutrients under artificial condition. 3.6 phytochemicals and nutritional – temperature models the phytochemical and proximate quantities of the dried bush buck leaves were established by curve fitting and expressed mathematically as a function of the drying temperatures by second order polynomial models. the goodness of fit were also shown by the respective r2 values. the close-to-1.0 values meant very good relationships between the variables. r2 values of 0.5 and above are considered significant at 95 % confidence interval (ci). the results of the regression models are shown in equations 6 to 16. their coefficients of determination were also found to show strong relationships. 𝑇𝑒𝑟𝑝𝑒𝑛𝑜𝑖𝑑𝑠 % = 0.003𝑇2 + 0.242𝑇 + 1.65; (𝑅2 = 0.923) 6 𝐴𝑙𝑘𝑎𝑙𝑜𝑖𝑑𝑠 % = 0.009𝑇2 + 0.073𝑇 + 3.914; (𝑅2 = 0.987) 7 𝐹𝑙𝑎𝑣𝑜𝑛𝑜𝑖𝑑𝑠 % = 0.001𝑇2 + 0.092𝑇 + 3.508; (𝑅2 = 0.943) 8 𝑆𝑎𝑝𝑜𝑛𝑛𝑖𝑛𝑠 % = 0.057𝑇2 − 0.188𝑇 + 0.952; (𝑅2 = 0.982) 9 𝑇𝑎𝑛𝑛𝑖𝑛𝑠 % = 0.027𝑇2 + 0.055𝑇 + 0.418; (𝑅2 = 0.992) 10 𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒 %𝑤𝑏 = 0.006𝑇2 − 0.792𝑇 + 30.68; (𝑅2 = 0.941) 11 http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 325 𝐴𝑠ℎ. % = −0.217𝑇2 + 1.992𝑇 + 11.69; (𝑅2 = 0.921) 12 𝐹𝑖𝑏𝑒𝑟. % = 1.155𝑇2 − 6.006𝑇 + 32.27; (𝑅2 = 0.789) 13 𝑃𝑟𝑜𝑡𝑖𝑒𝑛. % = −0.419𝑇2 + 3.762𝑇 + 13.97; (𝑅2 = 0.895) 14 𝐹𝑎𝑡. % = −0.097𝑇2 + 0.892𝑇 + 0.288; (𝑅2 = 0.869) 15 𝐶𝑎𝑟𝑏𝑜ℎ𝑦𝑑𝑟𝑎𝑡𝑒. % = 0.217𝑇2 + 0.207𝑇 + 26.91; (𝑅2 = 0.900) 16 in equations 6 to 16, 𝑇 is the oven temperature at which the utazi leaves were dried. results of the data analysis show that there are strong relationships between the test variables (proximate and phytochemicals) and the process (drying temperatures) variables in the range of 30 oc to 70 oc. this is supported by the values of the coefficient of determination (r2) which ranges from 0.789 for fibre to 0.992 for tannin. time taken to reduce the mc of the bush buck leaves to an equilibrium mc also varied with the drying temperature and decreased with increasing drying temperature. the same trend was observed for the elapsed drying period up to the end of the falling rate period. 3.4 effects of drying methods on phytochemical and nutrient contents room temperature (rtd) yielded the highest value of alkaloid (6.90%) followed by convective oven drying (od) (4.00%) and open sun drying (osd) (3.25%). rtd yielded the highest value of flavonoid (6.80%) followed by osd (3.75%) and od (3.60%). osd yielded the highest value of saponin (1.45%) followed by od (0.80) and rtd (0.80%). osd yielded the highest value of tannin (0.64%) followed by od (0.48%) and rtd (0.29%). osd yielded the highest value of terpenoids (2.45%) followed by rtd (4.00%) and od (1.90%). rtd yielded the highest value of ash (13.25%) followed by rtd (13.07%) and osd (12.22%). rtd yielded the highest value of fat (1.10%) followed by od (0.95%) and osd (0.68%). od yielded the highest value of fibre (28.32%) followed by osd (7.23%) and rtd (5.08%). rtd yielded the highest value of protein (17.07%) followed by od (16.83%) and osd (16.64%). rtd yielded the highest value of carbohydrate (58.38%) followed by osd (54.87%) and od (27.70%). for the temperature range of 30 oc to 70 oc, the values of alkaloid range from 4.0 to 4.5 %, from 3.60 to 3.92 % for flavonoids, from 0.80 to 1.46 % for saponins, from 0.48% to 1.39% for tannins and from 1.90 to 2.72% for terpenoids. in the same range of temperature (30 oc to 70 oc), the ash content ranged from 13.25 to 16.35%, fat content from 0.95 to 3.94%, fibre from 28.32 to 30.33%, protein from 16.83 to 22.70% and carbohydrate from 27.70 to 32.84%. 4. conclusion this paper reports the results of the investigation of the effects of drying temperatures on the proximate and phytochemical components of gongronema latifolium (utazi) leaves. the equilibrium moisture contents and drying times were in decreasing order of the drying temperatures, and varied from 12.95% for 30 oc to 5.03% for 70 oc drying temperatures. increased nutritional and phytochemical contents correlated with higher drying temperatures. the study showed that drying temperature has influence on the dry matter content and nutritional contents of the dried product. the results also showed that drying methods affect the proximate and phytochemical contents of the dried leaves. highest values of saponins, tannins and terpenoids were obtained from sun drying while alkaloids, flavonoids, carbohydrate, protein and fat were highest from room temperature drying and higher fibre values from oven drying in the dried leaves. the intended use of the dried leaves should therefore be considered in choosing the drying methods and conditions. references akuodor, gc., idris-usman, ms., mbah, cc., megwas, ua., akpan, jl., ugwu, tc., okoroafor, do. and osunkwo, ua. 2010. studies on anti-ulcer, analgesic and antipyretic properties of the ethanolic leaf extract of gongronema latifolium in rodents. african journal of biotechnology, 9(5): 2316-2321. alakali, js., kucha, ct., and rabiu, ia. 2015. effect of drying temperature on the nutritional quality of moringa oleifera leaves. food science, 9(7): 395-399. alegbeleye, o., odeyemi, oa., strateva, m. and stratev, d. 2022. microbial spoilage of vegetables, fruits and cereals. applied food research, 2(1): 100122. alobi, no., ikpeme, em., okoi, ai., etim, kd. and eja, me. 2012. phytochemical and nutritional profile of lasianthera africana, heinsia crinata and gongronema latifolium. new york science journal, 5(3): 45-48. http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 326 aoac 2006. official methods of analysis. 18th edn., the william byrd press, richmond, va., usa. aoac 1990. official methods of analysis of the association of chemists. analysis of the association of chemists, washington, dc. 223-225: 992-995. antia, bs., akpan, ej., okon, pa. and umoren, iu. 2006. nutritive and anti-nutritive evaluation of sweet potatoes (ipomea batatas) leaves. pakistan journal of nutrition 5: 166-168. arslan, d. and özcan, mm. 2012. evaluation of drying methods with respect to drying kinetics, mineral content, and color characteristics of savory leaves. food bioprocess technology 5: 983–991. balogun, me., besong, ee., obimma, jn., mbamalu, os. and djobossie, sfa. 2016. gongronema latifolium: a phytochemical, nutritional and pharmacology review journal of physiology and pharmacology advances. 6(1): 811-824. edeoga, ho., okwu, de. and mbaebie, bo. 2005. phytochemical of some nigerian medicinal plants. african journal of biotechnology, 4(7): 685-688. eleyinmi, af. 2007. chemical composition and antibacterial activity of gongronema latifolium. journal of zhejiang university, 8(5): 352-358. doi :10.1631/jzus.2007.b0352 ijeh, ii., njoku, ou. and ekenza, ec. 2004. medicinal evaluation of xylopiaaethiopica and ocimum gratissimum. journal of medical aromatic science, 2: 45-46 iwu, mc. 2014. pharmacognostical profile of selected medicinal plants. in iwu (ed), handbook of african medicinal plants. routledge handbooks online. crc press. illinois wesleyan, usa. doi:10.1201/b16292-4 khaled, my. and sayed, mm. 2014. effect of drying methods on the antioxidant capacity, color, and phytochemicals of portulacaoleracea l. leaves. journal of nutrition and food sciences, 4(6): 1000322 lawal, oo., essien, nc., essien, nm. and ochalla, f. 2015. vitamin c content of some processed green leafy vegetables. european journal of experimental biology, 5(2): 110-112. mbegbu, nn., nwajinka, co. and amaefule, do. 2021. thin layer drying models and characteristics of scent leaves (ocimum gratissimum) and lemon basil leaves (ocimum africanum). heyliyon, 7(2021): e05945. doi:10.1016/j.heyliyon.2021.e05945 molyneux, rj., lee, st., gardner, dr., panter, ke. and james, lf. 2007. phytochemicals: the good, the bad and the ugly. phytochemistry, 68(22-24): 2973-2985. doi:10.1016/j.phytochem.2007.09.004 mohammadu, gl., abdullahi, as., lawal, am. and umar, kj. 2014. effects of three drying techniques on mineral composition of some leafy garden vegetables. journal of applied chemistry. 2(1): 38-42. negi, ps. and roy, sk. 2001. effect of drying conditions on quality of green leaves during long term storage. food research international, 34(4): 283-287. doi:10.1016/s0963-9969(00)00165-4 njoku, ou., joshua, pe., agu, cv. and dim, nc. 2011. antioxidant properties of ocimum gratissimum (scent leaf). new york science journal, 4(5):98 -102. njoku, vo., obi, c. and onyema, om. 2011. phytochemical constituents of some selected medicinal plants. african journal of biotechnology 10(66) doi: 10.5897/ajb11.1948. nweze, ei. and eze, ee. 2009. justification for the use of o. gratissimum l in herbal medicine and its interaction with disc antibiotics bmc. complementary and alternative medicine, 9: 37. okafor, jc. 1987. identification and conservation of plants used in traditional medicine. proceedings of the international workshop on evaluation of traditional medicines, university of nigeria, nsukka, nigeria march 11-14 1987: 62-68. http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 318-327. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: da.amaefule@unizik.edu.ng 327 okafor, jc. 2002. tropical 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(family: lamiaceae) and bitter leaf vernonia amygdalina del. (family: asteraceae) extracts. advances in zoology and botany 5(4): 50-54, http://www.hrpub.org .doi: 10.13189/azb.2017.050403 owu, du., nwokocha, cr., obembe, ao., essien, ad., ikpi, de. and osim, ee. 2012. effect of g. latifolium ethanol leaf extract on gastric acid secretion and cytoprotection in streptozotocin-induced diabetic rats. west indian medical journal, 6(9): 853-860. oyeyemi, sm., adeniran, bm., owoade, lr. akerele oo. and tijani, sa. 2023. effect of 300gy gamma (𝛾) radiation dose on nigerian onion: a proximate composition. african journal of food science 17(12): 268-272. patle, tr., shrivas, k., kurrey, r., upadhyay, s., jangde, r. and chauhan, r. 2020. phytochemical screening and determination of phenolics and flavonoids in dillenia pentagyna using uv-vis and ftir spectroscopy. spectrochimica acta part a: molecular and biomolecular spectroscopy, 242(2020): 118717. doi: 10.1016/j.saa.2020. 118717 rhoda, hg. and negimote, b. 2015. drying characteristics and kinetics of bitter leaf (vernonia amygdalina) and scent leaf (ocimum gratissimum). chemical and process engineering research, 32: 1-11. shi, j., arunasalam, k., yeung, d., kakuda, y., mittal, g. and jiang, y. 2004. saponins from edible legumes: chemistry, processing, and health benefits. journal of medicinal food, 7(1): 67-78. doi: 10.1089/109662004322984734 troxell, b., petri, n., daron, c., pereira, r., mendoza, m., hassan, hm. and koci, md. 2015. poultry body temperature contributes to invasion control through reduced expression of salmonella pathogenicity island 1 genes in salmonella enterica serovars typhimurrium and enteritidis. applied and environmental microbiology, 81(23): 8192-8201. doi: 10.1128/aem.02622-15 turan, oy. and firatligil, fe. 2019. modeling and characteristics of thin layer convective air-drying of thyme (thymus vulgaris) leaves. czech journal of food sciences, 37: 128-134. yadav, rns. and agrawala, m. 2011. phytochemical analysis of some medicinal plants. journal of phytology 3(12): 10-14. http://www.azojete.com.ng/ mailto:da.amaefule@unizik.edu.ng corresponding author’s email address: ruqaiyaa70@gmail.com 261 arid zone journal of engineering, technology & environment original research article hardness, density and water absorption properties of doum palm shell particles and sugarcane bagasse reinforced polypropylene hybrid composite k. r. kyari*, i. s. aji and m. dauda department of mechanical engineering, faculty of engineering, university of maiduguri, p. m. b. 1069, maiduguri. *corresponding author’s e-mail address: ruqaiyaa70@gmail.com article information abstract agricultural waste issues have been a subject of discussion mainly on its conversion to wealth because of some environmental problems associated with it. the use of natural fibers and agricultural wastes for the formulation of composites materials has therefore continue to receive great attention. this work is focused on the utilization of doum palm shell particles and sugarcane bagasse to reinforce polypropylene (pp) in the production of a hybrid composite. the influence of material loading on the hardness, density and water absorption properties of the composite was studied. the composites were set by compounding pp and doum palm shell particles using compression moulding technique. the particulate size of the filler materials considered was 150 μm. the different material loading to matrix mixture were 10:90,20:80, 30:70, 40:60 and 50:50 respectively, after which the composites were characterized. sem analysis was also carried out in order to know the level of interaction between the matrix and materials loaded. analyses of variance (anova) were employed for optimization of the results. hardness of neat pp was 65hv but gradually decreased with material loading to a value of 42.3hv at 50wt% loading of the pp. water absorption showed a direct proportionality with exposure time and fiber loading up to 8.49% after 14days of soaking. material loading ensured increased density proportionally to 0.468g/cm3 at 50 wt%. the optimization result showed significant difference in most of the results obtained. it is concluded that doum palm shell and sugarcane bagasse hybrid composites have potential for industrial application. received april 2024 reviewed june 2024 accepted june 2024 keywords: characterization compression moulding reinforcement formulation material loading © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the biodegradable and environmentally friendly properties of natural fiber/filler composites, together with their high strength and stiffness, make them a promising option for reinforcing materials in polymer matrix composites (okeke et al., 2020). the increased interest in composites have been prompted by growing demand for environmentally friendly resources, mounting prices for petroleum-based polymers, and imposing environmental limitations (samuel et al., 2019). researchers have also made efforts to utilize thermoset polymers such as epoxy for composite formulation (charles et al. 2024). polymer composites are made up of polymers as the matrix and one or more fillers or fibers added to fulfill certain requirements such as acceptable mechanical and physical qualities, enhanced thermal qualities, reduced weight and resistance to wear. composites used in vehicle and aircraft applications, for example, must have strong thermal and mechanical qualities. historically, glass or carbon-based synthetic fibers were utilized as composites' reinforcement and have the ability to create superior qualities. nevertheless, with rising global environmental concerns, its delayed biodegradability is a drawback. as a result, researchers are discovering more workable methods to improve polymeric composites' biodegradability. natural fibers and fillers have good potential as polymer reinforcements because of these required properties as reviewed by aji et al. (2009). the key benefits of utilizing natural fibers are mainly because of their low cost, low weight, nonabrasiveness and non-hazardous properties. it has been determined that in comparison to the use of metals, composite materials have the potential to greatly lower the weight and cost of vehicles. reducing vehicle azojete march 2025. vol.21(1):261-269 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:ruqaiyaa70@gmail.com mailto:ruqaiyaa70@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 262 weight to conserve fuel is one of the primary goal for developing novel materials for automotive applications (getu et al., 2020). particulate reinforcement of polymers is vital for enhancing their physical and mechanical characteristics; attributes include hardness, impact strength, resistance to abrasive wear, etc., making them more suitable for use in applications in engineering. particles incorporated into the polymer matrix can regulate a polymer's mechanical properties. fillers have an impact on many other aspects of composite materials, including solidity, density, and cost reduction. the mechanical behaviour of composites made of polymers is significantly impacted by the effects of particle/filler loading, fiber length and fiber orientation (obasi et al., 2021; aji et al. 2011). doum palm (hyphaenethebaica) are desert palm trees that are mostly found in the nile valley. it bears edible, egg-shaped fruit. in nigeria's north, it produces exceptionally well as "goruba" in hausa and it is widely recognized. reportedly, it is among the world's most advantageous plants. the doum palm's leaves can be eaten, and their stem can be used to build structures. the leaves are also used to make mats, ropes, baskets, and hats(hossam et.al.,2018). bagasse is the excess of 30% that remains after the crushing of the sweet cane stalk in sugar or alcohol mills. bagasse is obtained from several parts of the cane stalk, such as the outer rind and the crushed inner pith (dan-asabe et al.,2018). polypropylene (pp) is a polymer synthesized catalytically from propylene and has the lowest density among commodity plastics. pp has a high resistance to chemicals and may be changed using a number of techniques, such as extrusion and injection molding. it is also utilized for several parts of an automobile, i.e. dashboards, batteries casing, air conditioning ducts, doors, and quarter panels (adediran et al., 2022). 2. materials and methods 2.1 materials materials utilized for this experiment were: i. sugarcane bagasse and doum palm shell particles sourced from baga road and gamboru (custom) market in maiduguri nigeria. ii. polypropylene with density 0.905g/cm3, melt flow index of 12g/10min and melting temperature of 135-1710c was purchased in hafason chemicals and scientific equipment ltd, 53, sokoto road, samaru zaria, kaduna state nigeria. iii. distilled water. iv. sodium hydro-oxide (naoh) for treatment of the bagasse fiber. v. ph paper for testing the alkalinity and basicity of the fiber 2.2 equipment the equipment used in this work were: • two roll mill, north bergen, u.s.a(model: 5183) for compounding the composite • microhardness tester, vicker hardness tester (model no mv 1-pc) • digital weighing balance, mettler instruments ltd (model no: ae200) • standard set of sieves (150μm size required) 2.3 methods 2.3.1 extraction, treatment and preparation of fiber the bagasse fibers were collected from baga road market in maiduguri, weighed to 500.50grams.it was cut to the length of 3mm and chemically treated by submerging it in alkaline solution with 10% naoh solution for 3 hours (putra & anggono, 2020). it was filtered, washed with distilled water severally until the colour of http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 263 the filtrate became clear and the ph of the filtrate to approximately 7.0.the cleaned bagasse was dried under the sun for 48hrsas reported by (abedom et al., 2021). the dried fibers were pulverized into particulate using laboratory milling machine (mekinsagro products ltd model no 150) as depicted in figure 1(a-c) and then sieved separately using astm sieve size 150μm because smaller particle size tend to undergo better compaction and therefore provides the composite with reduced porosity which gives effective stress transfer between matrix and particles (samuel et al., 2018). (a) sugar cane (b) bagasse (c) pulverized bagasse figure 1(a-c): pulverized bagasse from sugarcane 2.3.2 doum palm shell particle extraction and preparation weighed 500:50rms of doum palm shell was collected from gamboru (custom) market maiduguri. the edible part of the fruit and the seed were removed. the shell was weighed and dried under the sun for 24 hours until the residual moisture was ensured to have greatly reduced when it showed a constant weight after each measurement. the dried doum palm shell was shredded to smaller pieces and milled into particulate form using laboratory milling machine (mekins agro products ltd model no 150) as shown in figure 2(a-c).the powdered doum palm shell were sieved separately using astm sieve size 150μm, which was the required size (adebisi et al., 2021). (a) doum palm fruit (b) doum palm shell c) doum palm particles figure 2(a-c): doum palm shell particles preparation from doum palm fruits 2.3.3 composite preparation the sugarcane bagasse and doum palm shell particles and polypropylene were blended together in a two-roll mill. first, polypropylene was melted to allow for adequate flow of the molten polymer before pouring the sugarcane bagasse and the doum palm shell particles as reinforcing materials. the composites samples were produced by a melt mixing process involving the introduction of the pp pellet while the rolls of the two rolls mill machine were in counter clockwise motion and soften for a period of 5 minutes at a temperature of 180 °c and rotational speed 45rpm. the bagasse were utilized with doum palm shell at a ratio of 50:50 percent by weight ranging from 10-50% of the total weight while pp were varied in the composite till a suitable mixture was obtained. the composite obtained from the mixing process was placed into a metal mould of dimensions 140 mm x 120 mm x 3.2 mm and was placed on the hydraulic hot press (compression moulding machine) at a temperature of 160oc and pressure of 2.5 mpa for 5 mins. it was allowed to cool at room temperature, removed from the mould and labelled accordingly. five specimens for each sample were tested for hardness, http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 264 density and water absorption and the composites were named dps/scb (doum palm shell/ sugarcane bagasse) for easy identification. figure 3 describes the flow chart of the production process while table 1 shows the formulation processes. doum palm particles pulverized bagasse polypropylene melt-mixing and compression moulding hybrid composite sheet figure 3: flow chart for the production of hybrid composite table 1: formulation table 2.4 characterization of the composites upon production of the hybrid composites, their properties were characterized. 2.4.1 determination of hardness properties hardness is the resistance of a solid to local deformation. the hardness test characterizes the indentation hardness of materials by measuring the depth of penetration of the indenter point. a hard indenter was placed onto the surface of a material and then pressed into the material. indentation test for composite samples were carried out in accordance with astm d2240 on a micro vicker hardness tester as depicted in figure 4. five samples were used to determine the hardness and was recorded directly by the machine through a computer monitor attached to the hardness tester. sample bagasse (scb) and doum palm shell (dps) polypropylene (% weight) (50:50% weight) control 0 100(500.50 grms) dps/scb a 10 90 dps/scb b 20 80 dps/scb c 30 70 dps/scb d 40 60 dps/scb e 50 50 http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 265 figure 4: micro vicker hardness tester 2.4.2 investigation of its water absorption behaviour this test was carried out in accordance with astm d-570 with sample size of 70mm × 25mm × 3.2mm. the weights of the samples were taken on a digital weighing machine and soaked in water as depicted in figure 5. after every 24 hours for 14 days, the samples were removed, dried with a tissue paper gently and weighed again. the expression in equation 1 by kumar et al. (2019) was used to determine the water absorption of the samples. (1) where m1 is the mass of the sample (g) before water immersion and m2 is the mass of sample after every 24 hours water immersion. figure 5: sample specimen of water absorption 2.4.3 determination of density the samples were weighed on a digital weighing machine and the volumes were determined by liquid displacement method. the samples were placed in water and the volume of water displaced was same as the volume of the samples. this test was carried out in accordance with astm d-792. the expression of density was calculated using equation 2 (agbo et al., 2020). density, (2) where m is the mass, of the sample (g), v is the volume of the sample (cm3) and p is density. http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 266 2.4.4 micro-structural analysis the internal morphology of the composites produced were studied by microscopic analysis using pro: x: phenom world (model no. 800-07334). the microscopic features of the sample were viewed and a particular area of the microscopic feature was magnified under electron microscopy at 300x magnifications and 15kv until clear electron features of the samples were viewed and recorded accordingly. 3. results and discussion 3.1 hardness of the composite figure 6 shows the influence of the fiber and particles loading on the hardness property of pp reinforced with sugarcane bagasse and doum-palm shell particles. it shows a gradual drop in hardness of the composite with material loading. a drop of 35% of the composite hardness was observed from the initial 65hv value for neat pp at 50wt% loading of pp. increased in material loading softened the composite (ismail et al., 2018).the addition of doum palm shell particles and sugarcane bagasse decrease the matrix surface resistance to the indentation (ali et al., 2020). figure 6: effect of material loading on hardness of dps/scb/ pp hybrid composite plate 1 shows the scanning electron microscopy test result of hardness at 50wt% fiber loading. it indicates image of inadequate mixing of composites. cracks of matrix surface was observed leading to poor interfacial bonding. 65 63.2 62 58.5 45.6 42.3 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 h ar d n es s (h v) dps/scb hybrid filler loading (%) http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 267 plate 1: sem micrograph of 50wt% for hardness 3.2 water absorption behaviour of the composite figure 7 shows the result of water absorption behaviour of pp reinforced sugarcane and doum palm shell particles composite. the water absorption increased from 1.61% for neat pp to maximum of 8.49% at 50wt%. the water absorption property of the composites increases with exposure time and fiber-particle loading of the matrix for all the formulation. it can be seen that the composites with higher filler loading showed tendency for more water absorption. this is because sugarcane bagasse and doum palm shell particles contains polar hydroxyl group which result in water absorption of the composite the hydrophilic nature of particles and the greater interfacial area between the particles and the matrix resulted in an increase in water uptake as the particles content increases in the matrix (jacob et al., 2018).the water absorption was high at 8.49% at 14 days exposure. 0 2 4 6 8 10 12 14 16 0 1 2 3 4 5 6 7 8 9 wa te r a bs or pt io n ( % ) experimental time (days) 0.0 wt% 10 wt% 20 wt% 30 wt% 40 wt% 50 wt% figure 7: percentage water absorption of dps/scb composites 3.3 density test figure 8 shows the density test of the composite which showed increase with increase in material loading of pp. the fiber and particles loading made the composite denser than the neat pp. the density increases from 0.115g/cm3 for neat pp to maximum 0.468g/cm3 at 50wt%, it is about 75 % increase when compared with the neat pp. the densities of the material loading were higher than that of pp which increased the overall density of the formulated hybrid composite. this is not an advantage when weight is a critical factor in material http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 268 selection for the production industry. except for some automobile components, example, the conventional headliner which varies from 0.3g/cm3 to 0.5g/cm3(ibraheem et al., 2015). it has shown that the density result was found to be in standard range of honda accord headliner 0.5 g/cm3 (savic and hector, 2011). figure 8: density of dps/scb composites 4. conclusion doum palm shell particle and sugarcane bagasse reinforced pp was successfully produced using melt-mixing and compression moulding method. the study showed that hardness of composites decreased gradually with increase in material loading of pp. the density and water absorption behaviour showed increase with increase in material loading. the density of the particles used influenced the overall density of the hybrid composite produced. when these physical properties are a critical factor in industrial production of certain products, such materials must be selected with carefulness. references abedom, f., sakthivel, s., asfaw, d., melese, b., solomon, e., & kumar, ss. 2021. development of natural fibre hybrid composites using sugarcane bagasse and bamboo charcoal for automotive thermal insulation materials. advances in materials science and engineering, 2021, article id 2508840 10 pages. https://doi.org/10.11/2021/2508840 adebisi, aa., mojisola, t., shehu, u., & adam, ms. 2021. in-situ synthesis and property evaluation of highdensity polyethylene reinforced groundnut shell particulate composite. international journal of engineering materials and manufacture, 6(4): 305–311. https://doi.org/10.26776/ijemm.06.04.2021.06 adediran, aa., akinwande, aa., balogun, oa., & bello, os. 2022. mechanical and optimization studies of polypropylene hybrid bio composites. scientific reports, 2022(12): 24688, 1–18. https://doi.org/10.1038/s41598-022-06304-6 agbo, cj., okorie, ba., & idu, hk. 2020. study of the structural and mechanical properties of recycled high density polyethylene / palm kernel shell ash bio-composite. chemical and process engineering research, 62(2020): 28–36. aji i.s., sapuan s.m., zainudin e.s. and abdan k. 2009. kenaf fibres as reinforcement for polymeric composites; a review; international journal of mechanical and materials engineering, vol. 4, no. 3, university of malaya, selangor, malaysia aji i.s., zainudin e.s., khalina a., sapuan s.m. and khairul m.d. (2011. studying the effect of fiber size and fiber loading on the mechanical properties of hybridized kenaf/palf reinforced hdpe composite; journal of reinforced plastics and composites, vol. 30, issue 6, march pp. 546 – 553 0.115 0.148 0.275 0.359 0.402 0.468 0.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0 10 20 30 40 50 automobile headliner (savic and hector, 2011) d en si ty (g /c m 3 ) dps/scb hybrid filler loading(%) http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com https://doi.org/10.26776/ijemm.06.04.2021.06 https://doi.org/10.1038/s41598-022-06304-6 arid zone journal of engineering, technology and environment, march 2025; vol. 21(1): 261-269. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ruqaiyaa70@gmail.com 269 ali, j. b., musa, ab., danladi, a., & bukhari, mm. 2020. physico-mechanical properties of unsaturated polyester resin reinforced maize cob and jute fibre composites. journal of natural fibres, 00(00): 1–13. https://doi.org/10.1080/15440478.2020.1841062 charles d., aji. i.s. and mshelia z.a. 2024. effect of particle and fiber loading on tensile, flexural and impact properties of hybridized balanite shell particles and palmyra fiber reinforced epoxy composite. arid zone journal of engineering, technology and environment, 20(4): 891-902 dan-asabe, b., yaro, sa. & yawas, ds. 2018. micro-structural and mechanical characterization of doum-palm leaves particulate reinforced pvc composite as piping materials. alexandria engineering journal, 57(4): 2929– 2937. https://doi.org/10.1016/j.aej.2018.07.007 getu, d., babu, r., masresha, m., & kishan, s. 2020. materials today: proceedings production and characterization of bamboo and sisal fibre reinforced hybrid composite for interior automotive body application. materials today: proceedings, https://doi.org/10.1016/j.matpr.2020.08.780 hossam, s. el-beltagi, heba i. mohamed, hny. and emf. 2018. biological activities of the doum palm (hyphaene thebaica l.) extract and its bioactive components. antioxidants in food and its applications. https://doi.org/http://dx.doi.org/10.5772/intechopen.74772 ibraheem, a.,samotu,mohammed duda, fo, anafi and do obada 2015. suitability of recycleyed polyethelene/palm kernel shell-iron fillings composites for automobile application, tribology in industry, 37(2): 142-153. ismail, mm, faisal, a., kuar, o., nason 2018. the investigation on the physio-mechanical properties of jute fiber reinforced unsaturated (ufr) composites. chemical science international journal 22(1): 1-4. http://doi/10.9734/csji/2018/40021 jacob.j, mamza, ahmed, as yaro. 2018. effect of groundnut shell powder on the viscoelastic. bayero journal of pure and applied sciences, 11(1): 139–144. http://dx.doi.org/10.4314/bajopas.v11i.23s kumar, d., pagar, dd., kumar, r., & pruncu, ci. 2019. recent progress of reinforcement materials : a comprehensive overview of composite materials. journal of material science and technology, 8(6): 63546374. https://doi.org/10.1016/j.jmrt.2019.09.068 obasi, hc., mark, uc., & mark, u. 2021. improving the mechanical properties of polypropylene composites with coconut shell particles. journal of compiosites and advanced materials, 30:1-10. https://doi.org/10.1177/26349833211007497 okeke, pe., atuanya, cu., & umembamalu, jc. 2020. optimization of processing parameters and its effect on the mechanical properties of recycled low density polyethylene composite reinforced with tetracarpidiumconophorum shell particulates materials research express, 7(2): 025305. https://doi.org/10.1088/2053-1591/ab6d30. savic, v., & hector, l. g. (2011). effects of thickness on headliner material properties. sae technical paper 2011-01-0463 2011 .pg5. https://doi.org/10.4271/2011-01-0463 seth sa., aji is, tokan a. 2018. effects of particle size and loading on tensile and flexural properties of polypropylene reinforced doum palm shell particles composites. american scientific research journal of engineering technology & science, 44(1): 231-239. seth sa., aji is., tokan a. 2019. investigation of the impact, hardness, density and water absorption of polypropylene filled doum palm shell particles composite. journal of information engineering and applications https://doi.org/10.7176/jiea putra bu and anggono, j. 2020. reinforcement of polypropylene with alkali-treated sugarcane bagasse fibres : mechanism and consequences .comosites science and technology 200(2020): 108428 https://doi.org/10.1016/j.compscitech.2020.108428 http://www.azojete.com.ng/ mailto:ruqaiyaa70@gmail.com https://doi.org/10.1080/15440478.2020.1841062 https://doi.org/http:/dx.doi.org/10.5772/intechopen.74772 https://doi.org/10.1088/2053-1591/ab6d30 https://doi.org/10.7176/jiea corresponding author: engr.adanu@gmail.com 181 arid zone journal of engineering, technology & environment original research article performance evaluation and optimization of a canvas belt cowpea thresher for small-scale farming applications 1*e.o adanu, 2s.a iya, 2i.t yakubu and 2h.u. kabri 1department of agricultural education, federal college of education (tech.), gombe, nigeria. 2department of agricultural and environmental engineering, modibbo adama university of technology, yola, nigeria. *corresponding author: engr.adanu@gmail.com article information abstract this study evaluates the performance of a canvas belt thresher designed specifically for cowpea, addressing post-harvest challenges in threshing efficiency, seed damage, and grain loss. traditional threshers often lack precision for cowpea, leading to reduced yield and high labour demands. the constructed canvas belt thresher was tested at various drum speeds (200–1200 rpm) and moisture contents (10–14%) to determine its impact on threshing recovery, efficiency, cleaning ability, and seed integrity. comparative performance was also assessed against a spike-tooth thresher, revealing the canvas belt thresher’s enhanced threshing efficiency (93.98%) and lower unthreshed grain percentage (6.02%) at optimal conditions. while the canvas belt thresher showed reduced throughput (91.33 kg/h) compared to the spike-tooth (181.89 kg/h), it minimized grain damage (3.83% vs. 11.54%) and achieved a higher threshing recovery rate (89.62%). overall, the canvas belt thresher demonstrated effective threshing and cleaning for cowpea, although certain design refinements, such as covering the belt edges to reduce seed loss, could further enhance its efficiency and yield. this study highlights the potential of a canvas belt thresher for cowpea to support post-harvest processing, reduce losses, and improve yield quality in regions reliant on cowpea as a staple crop. future research could investigate adjustments in belt configuration and speed control for further optimization. submitted: 13th october 2024 revised: 27th january 2025 accepted: 3rd february 2025 keywords: canvas-material cowpea-threshing efficiency performance recovery © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction cowpea (vigna unguiculata) is a vital legume crop, particularly for smallholder farmers in africa and asia, providing a critical source of protein, income, and soil-enriching nitrogen (omoigui et al., 2018). despite its significance, traditional cowpea post-harvest processing remains labour-intensive, especially threshing, which is predominantly done manually. manual threshing often results in inconsistent threshing, higher labour costs, seed breakage, and inefficiency, directly impacting farmers’ income and market access (fao, 2004). in addressing these challenges, effective mechanical threshing methods can enhance productivity, reduce postharvest losses, and provide a more consistent product. existing threshing machines, designed for cereals like wheat and maize, are unsuitable for cowpea due to the legume’s fragile structure and sensitivity to damage. cowpea seeds are more delicate than cereal grains, and conventional threshers often cause excessive seed breakage and loss, diminishing their market and nutritional value (fernández et al., 2022; kamara et al., 2020). cowpea’s low hardness and tendency to crack require gentler processing (refaay et al., 2023). standard threshers also overlook cowpea’s unique aerodynamic properties, with spike-tooth types causing damage due to high-impact forces (dessye and fetene, 2021; bello, 2020). the limitations of current threshing machines underscore the need for a cowpea-specific solution that balances efficiency with the gentleness required to preserve cowpea seeds. advances in agricultural engineering have led to threshers designed with lower impact forces and controlled environments, such as a cowpea thresher with a canvas belt mechanism that shows promise in reducing seed damage while achieving high efficiency (olajide et al., 2022). performance evaluations indicate that these specialized threshers can significantly reduce damage, achieving up to 96.75% efficiency with minimal seed loss, a notable improvement over conventional azojete march 2025. vol.21(1):181-191 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:engr.adanu@gmail.com mailto:engr.adanu@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 182 machines, which often damage over 10% of seeds (appah, 2017). by focusing on low-impact designs tailored to cowpea’s unique properties, these innovations support the crop's economic and sustainable production (bello, 2020; dessye and fetene, 2021). this study evaluates the performance and optimization of a canvas belt cowpea thresher developed to address the limitations of traditional threshing machinery in cowpea processing. by leveraging the friction-rubbing principle, the thresher employs controlled belt speed and positioning to gently separate seeds from pods, aiming to minimize grain damage, reduce losses, and enhance recovery (mohsenin, 1970; mohsenin, 1986; nowosad et al., 2023). through rigorous testing under varying drum speeds and moisture levels, the study assesses its efficiency, grain damage, seed loss, and recovery, with a comparison to spike-tooth threshers revealing unique operational strengths (ozguven and kubilay, 2004). comparative analysis with spike-tooth threshers highlights the unique advantages of the canvas belt system, supporting advancements in agricultural mechanization to enhance productivity, food security, and economic stability. the research supports agricultural mechanization with implications for food security and economic stability (pwc nigeria, 2021; sasu, 2024; voice of nigeria, 2022; zhang et al., 2021). 2. materials and methods 2.1 description of the canvas belt cowpea thresher the thresher (plate 1) was constructed at the centre for industrial studies (cis), abubakar tafawa balewa university (atbu), bauchi, leveraging available tools and equipment. components such as angle irons, shafts, and sheet metal were cut to specification, joined by welding or bolting, and assembled with belts and pulleys to complete the design. key units include the feeding, threshing, blower, unloading, power transmission, and support frame. the thresher operates on a friction-rubbing principle. powered by a gasoline engine, it uses two conveyor belts with varying speeds to thresh cowpea pods. contact between belts causes threshing, with a blower separating chaff from grain; grains are collected in a trough while chaff exits via an airflow outlet. plate 1: the canvas belt cowpea thresher (l): test operation and setting of the thresher prior to testing (r) 2.2 methods 2.2.1 performance test of the canvas belt cowpea thresher performance tests were conducted on the thresher to evaluate its feed rate, threshing recovery, threshing efficiency, cleaning efficiency, percentage grain damage, and grain loss. a total of 100 kg of unthreshed cowpea (kanannado variety) was used for the tests. the cowpea was sundried for 24 hours, and its moisture content was determined using a g-7 grain moisture meter. the cowpea was then conditioned to three levels of moisture content. the rewetting method described by singh and goswami (1996) was adopted, and shown in equation (1) to estimate the amount of water needed for each moisture level (appendix 1). for each test, 1 kg of unthreshed cowpea was used at moisture contents of 10.0%, 12.0%, and 14.0%, with the machine operating at five different speeds: 200 rpm, 400 rpm, 600 rpm, 900 rpm, and 1200 rpm. the speed was measured using a hand-held digital laser tachometer (model: dt-209x, accuracy: ±1 rpm) (appendix 2). the http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 183 time required to process 1 kg was recorded from the start to when the last grain exited the threshing unit. grains from all outlets were collected and weighed separately. q = wi(mf−mi) 100−mf (1) where; q is the mass of water to be added in g; wi is the initial mass of sample to be conditioned in g; mf is the final or desired moisture content (%) and mi is the initial moisture content (%). the following parameters and performance metrics were evaluated: a: total grain input per unit time, where a = b + c + d. b: weight of threshed grain at the main outlet. c: threshed grain weight at other outlets. d: unthreshed grain weight at all outlets. performance parameters (niae, 2023): 1. damaged grain, % = e a × 100% (e: damaged grain at all outlets) 2. blown grain, % = f a × 100% (f: whole grain at chaff outlet) 3. grain loss, %= g a × 100% (g: all grain losses) 4. unthreshed grain % = h a × 100% (h: unthreshed grain) 5. threshing efficiency = 100 unthreshed grain % 6. cleaning efficiency, % = i j × 100% (i: whole grain at main outlet; j: total material at main outlet) 7. threshing recovery, % = b a × 100% 2.2.2 comparative performance evaluation with a commonly used cowpea thresher a spike-tooth multi-crop thresher was evaluated alongside the canvas belt cowpea thresher to compare their performance. the spike-tooth thresher consists of several key units: the feeding unit, threshing unit, delivery unit, power transmission unit, and the frame (plate 2). the machines were tested at moisture contents of 10% and 14%, operating at a speed of 600 rpm. for each test, 1.3 kg of cowpea was fed into the machine, and the duration of the threshing process was recorded from the start until the last grain exited the thresher. the threshed material was then separated into whole seeds, unthreshed pods, broken seeds, chaff, and loss materials. these data were used to calculate key performance metrics, including feed rate, performance efficiency, percentage of unthreshed pods, threshing efficiency, percentage grain damage, threshing recovery, and seed loss. the results are summarized in table 4. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 184 plate 2: the spike tooth multi-crop thresher 2.3 experimental design the experiment was laid on a factorial design, where 2 independent variables (drum speed and moisture content) were combined at levels of 3 and 5 to obtain 15 treatments replicated thrice in a complete randomized design (crd). descriptive statistics, regression analysis and the mean analysis of variance (anova) were statistical tools used to analyse the results and how it affects the dependent variables of threshing recovery, performance efficiency, threshing efficiency, percentage unthreshed, cleaning efficiency, grain damage, seed loss, blown away seeds, material capacity and throughput capacity. 3.0 results and discussions 3.1 canvas belt cowpea thresher test the testing of the constructed canvas belt cowpea thresher was conducted with three replications, and the results are summarized in tables 1a, 1b, and 2. tables 1a and 1b presents the mean performance of the thresher at drum speeds of 200 rpm, 400 rpm, 600 rpm, 900 rpm, and 1200 rpm, alongside moisture content levels of 10.0%, 12.0%, and 14.0%. this table includes the grand mean, standard deviation, and least significant difference of the parameters assessed as influenced by drum speeds and moisture contents. the summarized results provide a comprehensive overview of the performance across the various conditions tested. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 185 table 1a: mean values and least significant difference of parameters as influenced by the effects of drum speeds at 10%, 12% and 14% moisture contents drum speed, rpm % moisture content lsd grand mean standard deviation 10 12 14 percentage unthreshed, % 200 7.14 7.21 7.53 400 6.33 6.38 6.71 600 6.21 6.23 6.366 900 6.02 6.02 6.07 mc=0.052 1200 6.33 6.46 6.65 ds=0.067 6.5096 0.457 threshing efficiency, % 200 92.86 92.79 92.47 400 93.67 93.62 93.29 600 93.79 93.77 93.63 900 93.98 93.98 93.93 mc=0.052 1200 93.67 93.54 93.35 ds=0.067 93.4904 0.457 cleaning efficiency, % 200 64.17 63.00 62.49 400 62.13 63.21 62.69 600 72.41 71.47 74.65 900 92.21 92.42 90.58 mc=0.33 1200 85.74 85.71 85.52 ds=0.43 75.2259 12.175 grain break, % 200 4.46 4.406 4.32 400 4.074 4.04 3.972 600 4.18 4.054 3.926 900 4.074 4.02 3.834 mc=0.054 1200 3.834 3.814 3.734 ds=0.069 4.0495 0.217 blown away seed, % 200 0.37 0.33 0.33 400 0.37 0.4 0.37 600 0.8 0.83 0.86 900 1.58 1.43 1.51 mc=0.053 1200 2.88 2.27 2.45 ds=0.681 1.1187 0.860 seed loss, % 200 2.1 2.022 1.962 400 2.262 2.22 2.178 600 2.934 2.916 2.838 900 3.714 3.774 3.474 mc=0.05 1200 3.822 3.9 4.122 ds=0.064 2.949 0.791 mc = moisture content (%); ds = drum speed (rpm) http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 186 table 1b: mean values and least significant difference of parameters as influenced by the effects of drum speeds at 10.0%, 12.0% and 14.0% moisture contents. cont’d drum speed, rpm % moisture content lsd grand mean std dev. 10.0 12.0 14.0 throughput capacity, kg/hr 200 52.22 50.56 49.50 400 59.38 56.06 55.49 600 72.36 72.2 69.44 900 91.33 87.44 86.82 mc=0.065 1200 105.28 103.87 100.13 ds= 0.084 74.14 9.76 performance eff, % 200 96.87 96.97 97.03 400 96.63 96.70 96.70 600 96.16 95.94 96.18 900 95.62 95.15 95.73 mc=0.099 1200 96.26 95.94 95.35 ds= 0.127 96.21 0.620 material capacity, kg/hr 200 14.4 14.19 13.88 400 19.67 18.7 18.44 600 24.02 24.67 23.61 900 32.54 31.28 31.58 mc=0.057 1200 34.78 34.24 32.71 ds= 0.073 24.58 7.589 mc = moisture content (%); ds = drum speed (rpm) table 2 details the analysis of variance (anova) for the thresher's performance. the optimal throughput capacity was achieved at a moisture content of 10.0% and a drum speed of 1200 rpm, attributed to the increased speed of the thresher belt that facilitates quicker product processing, as well as the lower moisture content allowing for smoother flow. the anova results indicate that drum speed, moisture content, and their interaction significantly affected the feed rate at a 5% significance level. the thresher achieved a percentage of unthreshed grain of 6.02% at a drum speed of 900 rpm and moisture contents of 10.0% and 12.0%, demonstrating a decrease in unthreshed grain with increasing drum speed until 900 rpm, after which it began to increase table 2: anova of the canvas belt cowpea thresher performance f-cal df percentage unthreshed threshing efficiency cleaning efficiency grain breakage bas seed loss throughput capacity performance efficiency material capacity replica 2 drum speed (a) 4 18.23*** 15.67*** 22.89*** 12.34** 30.67*** 19.45*** 44.78*** 13.56** 27.89*** moisture content (b) 2 5.67* 4.54* 8.03** 3.88 9.23** 6.12* 11.56** 4.78* 10.12** (a*b) 8 2.34 3.22 5.41* 1.45 6.78** 4.01* 7.22** 2.98 5.67** error 30 total 44 * for p<0.05 (significant); ** for p<0.01 (highly sig.); *** for p<0.001 (very highly sig.) the thresher exhibited a threshing efficiency of 93.98% at 900 rpm and moisture contents of 10.0% and 12.0%. this efficiency aligns with previous studies, with ahaneku et al. (2003) and irtwange (2009) reporting efficiencies of 99% and 96.39%, respectively, for cowpea. the anova showed significant differences in all tested parameters affecting threshing efficiency. the data indicated that threshing efficiency improved with increased drum speed, peaking at 900 rpm, before declining with higher moisture content. this observation http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 187 supports zaalouk (2009), but contrasts with umogbai et al. (2014), who found that increased moisture content solely affected efficiency. cleaning efficiency reached its highest performance at 92.42% when operating at 900 rpm and 12.0% moisture content. the analysis highlighted that the interaction between moisture content and drum speed significantly influenced cleaning efficiency, although drum speed alone had no effect at a 5% significance level. additionally, the testing indicated that the lowest percentage of grain damage occurred at 1200 rpm and 14.0% moisture content, revealing that moisture content significantly impacts grain damage more than speed. the test for blown-away seeds revealed an optimal result of 0.33% at 200 rpm and 14.0% moisture content, demonstrating that thresher drum speed correlates with fan speed, which can increase blown-away seeds. the seed loss recorded a minimal figure of 1.96% at 200 rpm and 14.0% moisture, better than the findings of ahaneku et al. (2003) and irtwange (2009). overall, the machine achieved an optimal threshing recovery of 89.62% at a drum speed of 900 rpm and moisture content of 10.0%, with the analysis of variance confirming significant effects of both parameters on recovery. more of the trend can be visualized in the figure 1. the regression model and coefficient of determination for the thresher parameters, shown in table 3, indicate high predictability for throughput capacity (r² = 99.14%) and less predictability for grain breakage (r² = 93.75%). table 3: regression model showing the interaction between drum speed and moisture content on the threshing parameters s/n parameter linear model r2 1 percentage unthreshed 0.0035*ds + 0.1535*mc + 5.9635 0.9789 2 threshing efficiency -0.0011*ds 0.0412*mc + 94.0385 0.9641 3 cleaning efficiency 0.0119*ds 0.0462*mc + 62.0817 0.9563 4 grain breakage -0.0007*ds 0.0325*mc + 4.6705 0.9375 5 blown away seed 0.0019*ds + 0.0003*mc + 0.0083 0.9876 6 seed loss 0.0017*ds + 0.0281*mc + 1.6595 0.9721 7 performance efficiency -0.0001*ds 0.0286*mc + 96.8389 0.9234 8 material capacity 0.0135*ds 0.1827*mc + 11.9485 0.9897 9 throughput capacity 0.0545*ds 0.9595*mc + 49.6513 0.9914 ds = drum speed (rpm); mc = moisture content (%) http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 188 figure 1. canvas belt cowpea thresher parameter results at combine drum speed and moisture content settings for percentage unthreshed (%), threshing efficiency (%), cleaning efficiency (%), grain break (%), blown away seed (%), seed loss (%), throughput capacity (kg/hr), performance efficiency (%), and material capacity (kg/hr). 3.2 spike tooth multi-crop thresher test table 4 is the mean results of the canvas belt cowpea thresher performance at drum speed of 600rpm and moisture content levels of 10.0%, and 14.0%. it also comprises, the grand mean and the standard deviation of the parameters assessed as influenced by drum speeds and moisture contents. the results presented in table 4 showed that whole seeds collected and the seed loss were not affected by change in moisture content. it further showed that there was a decrease in performance with respect to threshing efficiency, grain damage, threshing recovery, material capacity, performance efficiency and throughput capacity as moisture content increased from 10.0% to 14.0%. meanwhile, the percentage unthreshed increased at increasing moisture content of the crop. the machines throughput capacity at 10.0% moisture content which was 181.89kg/hr is better compared to the 110.86kg/hr by irtwange (2009). the machine has a performance efficiency of 98.46%, that is to say it is more effective when compared to the 81.21% performance efficiency by ojo et al. (2010) at almost the same moisture content of cowpea tested. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 189 table 4: mean values of spike-tooth multi-crop thresher performance parameters as influenced by levels of moisture content at drum speed of 600rpm. performance parameter % moisture content grand mean sd 10.0 14.0 throughput capacity, kg/hr 181.89 177.05 179.47 1.56 unthreshed, % 24.62 26.15 25.39 0.87 threshing efficiency, % 75.38 73.85 74.62 0.87 grain damage, % 13.08 11.54 12.31 0.88 seed loss, % 1.54 1.54 1.54 0 threshing recovery, % 59.23 57.7 58.47 0.87 material capacity, kg/hr 83.95 82.35 83.15 0.89 performance efficiency, % 98.46 97.69 98.08 0.62 3.3 comparison of the prototype canvas belt and the spike-tooth thresher the canvas belt cowpea thresher was compared with a spike-tooth multi-crop thresher, using the same engine power and cowpea variety, as shown in tables 1 and 4. tests used optimal settings: 600 rpm for the spiketooth and 900 rpm for the canvas belt. the spike-tooth thresher achieved higher throughput (181.89 kg/h at 10% mc) than the canvas belt (91.33 kg/h). increasing the speed beyond 900 rpm caused stability issues in the canvas belt. the canvas belt thresher showed a lower unthreshed percentage (6.02%) compared to 24.62% for the spike-tooth. threshing efficiency was higher for the canvas belt (93.98%) than the spike-tooth (75.38%). grain damage was 3.83% for the canvas belt and 11.54% for the spike-tooth at 14% mc. seed loss was higher for the canvas belt (3.47% at 14% mc) than for the spike-tooth (1.54% at 10% mc). threshing recovery differ, with 89.62% for the canvas belt and 59.23% for the spike-tooth, although wear and tear on the spike-tooth caused several openings. the spike-tooth showed better overall efficiency (98.46% vs. 95.73% for the canvas belt). however, improvements to the canvas belt, such as covering the sides to reduce seed spillage, could enhance performance. additionally, the canvas belt's integrated cleaning mechanism, absent in the spike-tooth, makes its threshing process more complete. 4. conclusion the study evaluated the canvas belt cowpea thresher's performance and compared it with a spike-tooth thresher. the results indicate that the canvas belt thresher, with optimal performance at 900 rpm and 10% moisture content, achieved higher threshing efficiency (93.98%) and lower unthreshed percentage (6.02%) compared to the spike-tooth thresher. however, its throughput was lower, and seed loss was slightly higher at higher moisture levels. suggested improvements to reduce seed spillage, combined with its effective cleaning mechanism, could enhance its suitability for smallholder cowpea farmers, offering a viable alternative to conventional methods. based on the findings, future studies should consider to: 1. test alternative belt materials that are durable and friction-effective to enhance belt efficiency and lifespan. 2. optimize belt design and speed by adjusting parameters such as speeds, widths, and textures to improve seed handling, reduce spillage, and increase throughput. 3. enhance the blower airflow design to improve the separation of chaff and grain, particularly in higher moisture conditions. http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 190 references ahaneku, ie., kamal, ar. and ogunjirin, oa. 2003. design, construction, and performance evaluation of a multipurpose crop thresher. journal of agricultural engineering and technology, 11: 17–23. appah, s. 2017. effect of open-air drying duration on seed moisture and the threshing quality of cowpea. journal of advances in agriculture. bello, rs. 2020. design, construction, and performance evaluation of cowpea thresher. journal of multidisciplinary engineering science and technology (jmest), 3(2). dessye, b. and fetene, m. 2021. the effect of moisture content on the performance of melkassa multicrop thresher in some cereal crops. journal of agricultural science and technology. fernández, ja., messina, cd., salinas, a., prasad, pvv., nippert, jb. and ciampitti, ia. 2022. kernel weight contribution to yield genetic gain of maize: a global review and us case studies. journal of experimental botany, 73(11): 3597–3609. food and agriculture organization of the united nations (fao). 2004. post-harvest compendium: cowpeas. retrieved from https://www.fao.org/fileadmin/user_upload/inpho/docs/post_harvest_compendium__cowpeas.pdf irtwange, sv. 2009. design, fabrication, and performance of a motorized cowpea thresher for nigerian smallscale farmers. african journal of agricultural research, 4(12): 1383–1391. kamara, ay., kamai, n., omoigui, lo., togola, a., ekeleme, f. and onyibe, j. e. 2020. guide to maize production in northern nigeria. ibadan, nigeria: international institute of tropical agriculture. mohsenin, nn. 1970. physical properties of plant and animal materials. new york: gordon and breach science publishers. mohsenin, nn. 1986. physical properties of plant and animal materials. new york: garden and breach science publishers. nigerian institution of agricultural engineers (niae). 2023. codes and standards booklet: 2023 2nd edition. retrieved from https://niae.net/1/wp-content/uploads/2023/11/codes-and-standards-booklet-2023-2ndedition_064713.pdf nowosad, k., bocianowski, j., kianersi, f. and pour-aboughadareh, a. 2023. analysis of linkage on interaction of main aspects (genotype by environment interaction, stability, and genetic parameters) of 1000 kernels in maize (zea mays l.). agriculture, 13(10): 2005. ojo, mo., ale, mo. and olajide, og. 2010. development and performance evaluation of a cowpea harvester. journal of engineering and applied sciences, 5(10): 5–10. olajide, og., oladimeji, ao. and ale, mo. 2022. development and performance evaluation of a cowpea threshing machine. global journal of engineering and technology advances, 13(1): 22-26. omoigui, lo., kamara, ay., batieno, j., iorlamen, t., kouyate, z., yirzagla, j., diallo, s. and garba, u. 2018. guide to cowpea production in west africa. ibadan, nigeria: international institute of tropical agriculture. ozguven, f. and kubilay, v. 2004. some physical, mechanical, and aerodynamic properties of pine (pinus pinea) nuts. journal of food engineering, 68, 191–196. pwc nigeria. 2021, september. positioning nigeria as africa’s leader in maize production for afcfta. retrieved november 2, 2024, from https://www.pwc.com/ng/en/assets/pdf/positioning-nigeria-as-africaleader-in-maize-production-for-afcfta.pdf http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com https://niae.net/1/wp-content/uploads/2023/11/codes-and-standards-booklet-2023-2nd-edition_064713.pdf https://niae.net/1/wp-content/uploads/2023/11/codes-and-standards-booklet-2023-2nd-edition_064713.pdf arid zone journal of engineering, technology and environment, march 2025; vol.21(1):181-191. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author: engr.adanu@gmail.com 191 refaay, mms., el-sayed, as. and awad, mca. 2023. development of a cowpea threshing machine. turkish journal of agricultural engineering research, 4(1): 46–60. sasu, dd. 2024, september 30. production of maize in nigeria from 2010 to 2021. statista. retrieved november 2, 2024, from https://www.statista.com/statistics/1300743/production-volume-of-maize-in-nigeria/ singh, kk. and goswami, tk. 1996. physical properties of cumin seed. journal of agricultural engineering research, 6(4): 93–98. umogbai, vi., fulani, au. and obetta, se. 2014. development and evaluation of a powered cowpea thresher. international journal of engineering science and technology (ijest), 6(6): 359–369. voice of nigeria. 2022, march 15. nigeria’s maize production at highest level since independence – usda. retrieved november 2, 2024, from https://von.gov.ng/nigerias-maize-production-at-highest-level-sinceindependence-usda/ zaalouk, ak. 2009. evaluation of local machine performance for threshing bean. misrata journal of agricultural engineering, 26(4): 1696–1709. zhang, h., lu, y. and ma, y. (2021). genetic and molecular control of grain yield in maize. molecular breeding, 41(18). http://www.azojete.com.ng/ mailto:engr.adanu@gmail.com corresponding author's email address: deborah2james@yahoo.com 722 arid zone journal of engineering, technology & environment original research article characterisation of rice husk and wood ash as constituents for production of phosphorus and potassium d. j. malgwi1*, a. n. jones2 and m. a. musa2 1 department of civil engineering technology, ramat polytechnic, maiduguri, borno state, nigeria 2 department of civil and water resources engineering, university of maiduguri, maiduguri, borno state, nigeria *corresponding author’s email address: deborah2james@yahoo.com article information abstract this study investigated the potentials of rice husk and wood ashes from various species (mahogany, iroko and mghelina) as sustainable sources of phosphorus (p) and potassium (k). the raw rice husk sample was obtained from dala rice mill while different wood species such as mahogany, iroko and mghelina, were obtained from baga road timber shade both in maiduguri, borno state. both raw materials were carbonized at different temperatures ranging between 350-750°c respectively. the laboratory analysis of the ash samples was conducted using atomic absorption spectrophotometer (aas) to determine the presences of k, and p. the result shows that rice husk ash contains a mean value in terms of mg/100g of k2o (3.593) and p2o5(1.382). also, mahogany wood ash contains 4.48mg of k and 0.55 mg of p. similarly, iroko wood ash was found to consist of 5.14g of k and 0.56g of p. in addition to mghelina wood ash(beech wood), it was found that compounds present has a mean values in terms of g/100g of k (10.4) and p (0.96). it is noteworthy that p was highest in wood ash (mghelina) amongst the materials tested. therefore, the presence of these compounds in wood and rice husk ashes could be a potential low-cost resource for the production of inorganic fertilizer. submitted 26 november, 2023 revised 02 may, 2024 accepted 24 may, 2024 keywords: phosphorus potassium carbonization extraction © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction growing concerns about global environmental degradation and energy insecurity has intensified the quest for sustainable alternatives. biomass resources, particularly forestry and agricultural wastes like rice husk and wood ash, have emerged as promising renewable energy sources. characterizing these waste materials as constituents for producing phosphorus and potassium offers a compelling solution. rice husk and wood ash with their abundant availability and have low operating costs, can be harnessed to generate essential nutrients for agricultural applications, unlocking their eco-friendly fertilizers, minimizing waste disposal issues while supporting sustainable development (yin et al., 2008). however, one major issue arising from the use of forestry and timber biomass is the generation of ash as a by-product and its monumental environmental and health concern which could be challenging and highly expensive to curtail (who, 2015). additionally, majority of biomass ash generated in thermal plants which includes materials such as wood, rice husk, bagasse and agricultural waste are burned to generate electricity or heat and the end products either disposed of in landfill or uncontrolled agricultural fields. however, due to scarcity of waste disposal or management facilities, growing environmental concerns, and increasing volume of ash generated from various sources poses significant environmental and management challenges in recent years (prakash et al., 2007). the burning of the biomass releases carbon monoxide to the atmosphere (which is poisonous) with resultant consequential and undesirable atmospheric pollution. however, in maiduguri, the population relies heavily on limited alternative energy sources, rapid urbanization, climate changes and insufficient waste management facilities. there are three main categories of nutrients required by plants which includes macronutrients, micronutrients and heavy metals (priyadharshini et al.,2009). macronutrients include elements such as phosphorus, potassium, calcium and magnesium while micronutrients include iron, sodium, manganese and copper (masso et al., 2017). the contents of macroand micronutrients also indicate that the ash is a valuable fertiliser, but the content of heavy metals precludes use in circumstances where these substances might enter the human food chain (masso et al., 2017). the potential negative impact azojete december 2024. vol.20(4):722-726 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:deborah2james@yahoo.com mailto:deborah2james@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deborah2james@yahoo.com 723 on the forest ecosystem and the surrounding environment due to an increased utilization of biomass for energy needs should be mitigated (wang et al., 2013). to obtain a more sustainable utilisation of biomass fuels, the ash obtained from the combustion of the biofuel could be recycled back to the soil for amendments as valuable forest and tree/shrub fertiliser (wang et al., 2013). this paper characterised carbonized rice husk and some wood species under control environment (pyrolysis) for extraction of p and k as constituents for the production of inorganic fertilizer. 2. materials and methods 2.1 materials in this study, the materials and equipment used for the processing of rice husk and wood ashes includes the following. the materials included raw rice husk, mahogany, iroko and mghelina samples (grinded), while the equipment used included fabricated oven, thermometer, sieve and digital scale. 2.1.1 sample preparation the raw materials were collected manually and spread to dry prior carbonization. 20g of rice husk and 150g of woodchips were placed into the fabricated kiln under low oxygen supply which was ignited and burnt into ashes at varying temperature ranges of 350-750°c for rice husk and wood respectively. the burnt ashes were allowed to cool before collection. the ash samples were collected and labeled in plastic containers prior to use and then transported to chemistry department, yobe state university for laboratory analysis. the buck scientific 210vgp atomic absorption spectrophotometer (aas), uk 2005 was then used to analyze the ash samples. the elements analyzed were sodium (na), potassium (k), magnesium (mg), manganese (mn), calcium (ca), zinc (z), phosphorus (p), silicon (s), iron (fe) and aluminum (al). 2.1.2 rice husk preparation approximately, 20g of rice husk was placed in a prefabricated kiln and fired at a temperature of 500 to750°c to avoid environmental pollution as reported by rao et al. (1992). cremation time was 15hours after carbonization was reached, the rice husk ashes were allowed to cool in the kiln. combustion was then recorded visually by opening the oven and collecting the rice husk ash in an airtight polyethylene bag. the samples were analyzed in the laboratory to determine the elemental composition of rice husk ashes. 2.1.3 wood ash preparation the wood ash formulation uses three species of wood samples such as mahogany, iroko and mghelina. approximately 150g of woodchips were pyrolyzed in a prefabricated kiln by heating to 500°c. at the end of degassing, the lid of the vessel was removed and the remaining char burnt at 350°c. it took 5-8hours to burn completely at this low temperature. the low temperature ash formed by the above process was used for laboratory analysis. samples were allowed to heat at the required temperature to ensure adequate heating time and complete any conversion that may have been initiated at the sample holding temperature. 2.2 determination of elemental composition 2.2.1 digestion method the ash samples were digested prior to analysis. the ash samples were moisturized with few drops of distilled water. thereafter, it was mixed with 2ml concentrated hydrochloric acid (80%hcl), and then dried on hot plate at 100°c. furthermore, it was mixed with 5ml nitric acid (20%) and filtered using whatman filter paper of size 10µm into volumetric flask of 100ml.the extract was then ready for analysis using the analytical machine. they were determine using the buck scientific 210vgp atomic absorption spectrophotometer (aas), uk 2005.the procedure was as follows: you press and hold on button until the spectrophometer turns on. then, you scroll up and select all tests from the testing menu. scroll and then select the tests to be conducted chloride, nitrate, sulphate, phosphate, dissolved oxygen and others, from the menu depending on parameters to be tested and select programmed tests then rinse a clean tube with sample water and fill it to the l0th line with the sample. then you insert the filled tube into the chamber and close the lid after which you will select scan blank after that you remove it from the spectrophometer and add the content of one packet or tablet of reagent that is chloride – tt, nitrate reducing reagent, sulphate reagent, phosphate acid reagent, then reinsert the cap and shake until the powder dissolves completely. wait for 5 minutes for full colour development. then at the end of 5 min waiting period mix and insert tube into chamber. close lid, select scan sample and record result. press off button to turn spectrophotometer off or press exist button to exit to a previous menu or make another menu selection. the procedures were repeated three times and their mean values obtained. http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deborah2james@yahoo.com 724 3. results and discussion 3.1 elemental composition of rice husk ash the results from the characterization of rice husk ash are shown in table 1. the results show that the various compounds present in the samples have mean, standard deviation and individual values in terms of mg/100g.the results shows that rha is the primarily composed of silicon dioxide (sio2) accounting for approximately 79.757% of the total elemental components. the mean value of 3.593 k2o ,1.382 p2o5, 1.025 cao, 0.626 mgo, 0.069 mno, 0.045 zno, 0.367 fe2o3 and 0.558 al2o3. this is consistent with previous studies. the major elements in this study p and k compared with research by iara et al. (2016) revealed similarity in compounds present with 0.23% p2o5 and 0.69% k2o which are lower than those obtained in the present work. table 1: elemental composition of rice husk ash in oxide s/no. elements (mg/100g) sample1 sample 2 sample 3 mean sd 1 na2o 0.174 0.174 0.174 0.174 0.000 2 k2o 3.775 3.107 3.898 3.593 0.426 3 mgo 0.456 0.715 0.708 0.626 0.148 4 mno 0.069 0.069 0.069 0.069 0.000 5 cao 0.989 1.143 0.943 1.025 0.105 6 zno 0.011 0.08 0.045 0.045 0.035 7 p2o5 1.238 1.192 1.716 1.382 0.290 8 sio2 79.85 78.805 80.616 79.757 0.909 9 fe2o3 0.396 0.383 0.323 0.367 0.039 10 al 2o3 0.699 0.617 0.358 0.558 0.178 3.2 elemental composition of mahogany wood ash the results from the characterization of mahogany wood ash as presented in table 2 below shows significant amounts in mean, standard deviation and individual values in terms of g/100g with 5.90 calcium ,8.16 silicon ,4.48 potassium,0.55 phosphorus ,1.67 zinc ,2.07 iron and 0.50 manganese it was observed that compounds of interest p and k are 4.48 and 0.55 respectively. the findings correlate with the results reported by ngassam et al. (2021) in their study on mahogany bark. table 2: elemental composition of mahogany wood ash s/no. elements (g/100g) sample 1 sample 2 sample 3 mean sd 1 sodium 0.19 0.21 0.18 0.19 0.02 2 potassium 4.57 4.43 4.45 4.48 0.07 3 magnesium 0.30 0.32 0.31 0.31 0.01 4 manganese 0.51 0.49 0.51 0.50 0.01 5 calcium 5.90 5.61 6.20 5.90 0.29 6 zinc 1.60 1.74 1.68 1.67 0.07 7 phosphorus 0.48 0.50 0.69 0.55 0.11 8 silicon 8.20 8.28 8.01 8.16 0.14 9 iron 2.17 2.00 2.04 2.07 0.09 10 aluminum 1.48 1.48 1.52 1.50 0.02 3.3 elemental composition of iroko wood ash table 3 presents the results from the characterization of iroko wood ash shows significant amounts in mean, standard deviation and individual values in terms of g/100g with 15.30 calcium, 0.58 silicon, 5.14 potassium, 0.56 phosphorus, 1.67 zinc, 2.54 iron and 0.83 manganese. http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deborah2james@yahoo.com 725 table 3: elemental composition of iroko wood ash s/no. elements (g/100g) sample 1 sample 2 sample 3 mean sd 1 sodium 1.93 1.97 1.75 1.88 0.12 2 potassium 5.06 5.08 5.26 5.14 0.11 3 magnesium 1.30 1.30 1.27 1.29 0.02 4 manganese 0.85 0.84 0.81 0.83 0.02 5 calcium 15.15 15.33 15.43 15.30 0.14 6 zinc 2.65 2.36 2.61 2.54 0.16 7 phosphorus 0.57 0.58 0.53 0.56 0.02 8 silicon 0.57 0.59 0.58 0.58 0.01 9 iron 0.30 0.33 0.35 0.33 0.03 10 aluminum 0.14 0.14 0.15 0.14 0.00 3.4 elemental composition of mghelina wood ash (beech wood) the results from the characterization of mghelina wood ash (beech wood) are shown in table 4. shows significant amounts in mean, standard deviation and individual values in terms of g/100g with 36.91 calcium, 7.93 silicon, 10.40 potassium, 0.96 phosphorus, 0.47 zinc, 1.23 iron and 0.09 manganese. it was observed that the compounds present of interest p and k are 0.96 and 10.40 respectively. annune et al. (2020) validates these findings. table 4: elemental composition of gmelina wood ash (beech wood) s/no. elements (g/100g) sample 1 sample 2 sample 3 mean sd 1 sodium 2.52 2.54 2.52 2.53 0.01 2 potassium 10.38 10.42 10.42 10.40 0.02 3 magnesium 0.72 0.78 0.68 0.73 0.05 4 manganese 0.09 0.09 0.09 0.09 0.00 5 calcium 39.95 32.77 38.01 36.91 3.72 6 zinc 0.47 0.47 0.47 0.47 0.00 7 phosphorus 0.96 0.97 0.96 0.96 0.00 8 silicon 7.95 7.96 7.87 7.93 0.05 9 iron 1.25 1.11 1.33 1.23 0.11 10 aluminum 1.51 1.47 1.49 1.49 0.02 3.5 mean value of p and k from rice husk and wood ashes table 5 presents the mean values of phosphorus (p) and potassium (k) in rha and three types of wa: mahogany, iroko and mghelina. it was found that the ashes have reasonable content. the p and k content found in the rice husk ash was 1.38 mg/100g and 3.59 mg/100g, whereas p and k of wood ash for mahogany were 0.55g/100g and 4.48g/100g, iroko were 0.56g/100g and 5.14g/100g and mghelina (beech) were 0.96g/100g and 10.40 g/100g respectively. in comparison of p values mghelina ˃ iroko ˃mahogany ˃rice husk indicting that wa has higher content of p, while k values mghelina ˃ iroko ˃mahogany ˃rice husk indicting that mghelina wa has higher content of k. table 5: mean value of phosphorus (p) and potassium (k) from rice husk and wood ashes s/no. elements rha(mg1 00g) mahogany wa (g/100g) iroko mghelina 1 2 phosphorus potassium 1.38 3.59 0.55 4.48 0.56 5.14 0.96 10.40 4. conclusion the analysis of the result indicates that the concentration of p and k are highly significant with p˂ 0.01. the presence of high contents of p from wood ash(mghelina), 10.4 g/100g and k from rice husk, 3.59 mg/100g signifies its potential for npk blend. http://www.azojete.com.ng/ mailto:deborah2james@yahoo.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4):722-726. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author's email address: deborah2james@yahoo.com 726 references 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mailto:deborah2james@yahoo.com https://iris.who.int/handle/10665/186463 corresponding author’s email address: yahabeebeeh@gmail.com 811 arid zone journal of engineering, technology & environment original research article modeling and simulation of a solar farm using homer pro software for university of maiduguri senate complex m. m. hamidu*, a. m. el-jummah, m. shuwa department of mechanical engineering, university of maiduguri, borno state, nigeria *corresponding author’s email: yahabeebeeh@gmail.com article information abstract the current state of energy insecurity in maiduguri calls for immediate action to explore and implement alternative energy sources, especially off-grid sources such as solar power, wind power etc. which could provide reliable, cost-effective, and sustainable energy solutions to the town and neighbourhoods. the university of maiduguri is not an exception, equally faced with electricity disruptions that almost ground down the academic and administrative activities. this study aims at modeling and simulation of a solar farm using homer pro software for university of maiduguri senate complex to enhance power supply. it involves conducting an energy audit to determine the complex's electrical energy consumption, prediction of future energy demand using homer pro software, designing a solar farm model based on the energy audit and the predicted energy demand of the senate complex using same software. data collected were analysed and optimised for system sizing. based on the optimization results, model 1682 canadian solar max power cs6u-340m, 340 w per panels, 144 lead acid generic batteries rated at 1kw each (totalling 4603ah) and 2 inverters with a combined capacity of 318kw were designed, which met the annual load demand of the complex (1.03 gwh). this study, if implemented will address the power challenges faced by the senate complex building, thereby reducing the administrative and academic bottle neck faced by the university. received: 6th august 2025 revised: 3rd september 2025 accepted: 4th september 2025 keywords: homer pro energy modeling senate complex university of maiduguri solar farm © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction electricity supply in maiduguri, the capital of borno state, nigeria, has been severely hindered due vandalization because of security challenges, inadequate infrastructure and with recent high cost of electricity bills, many areas were in darkness (edomah et al., 2021). these disruptions have caused significant interruptions in socioeconomic activities, administrative and academic in higher institutions of learning across the state. thus, the need to look for more alternative energy, most especially upgrade for better, sustainable and uninterrupted supply. solar power in particular, presents a promising solution for regions like maiduguri, which experience high levels of solar radiation. solar energy technologies, such as photovoltaic (pv) systems that directly convert sunlight into electricity, and concentrated solar power (csp) systems, offers significant potential to meet the region's energy needs (lewis et al., 2010). despite their advantages, solar power systems face challenges, such as intermittency, energy storage, and system integration, which must be addressed to ensure reliability (nguyen et al., 2022). optimization tools, such as the hybrid optimization model have been instrumental in overcoming these challenges by simulating various renewable energy configurations and enabling effective system design (nrel, 2008). in nigeria, the privatization of the power sector in 2013 left many areas, particularly maiduguri, with an unreliable electricity supply, as the privatized grid infrastructure remains inadequate and vulnerable (nerc, 2015). this instability directly impacts critical institutions, such as the university of maiduguri, where facilities like the senate complex regularly experience power shortages that disrupt academic and administrative functions. this calls for immediate action to explore and implement alternative energy sources, such as solar power which could provide reliable, cost-effective, and sustainable energy solutions for these institutions. this study aims to design and model a solar farm to meet the energy of the senate complex at the university of maiduguri using homer pro software with the objective of optimizing the system for energy reliability, sustainability, and cost-effectiveness. the research will begin with azojete september 2025. vol.21(3):811-819 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/012 www.azojete.com.ng mailto:yahabeebeeh@gmail.com mailto:yahabeebeeh@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 812 an energy audit of the senate complex to assess its current and future energy requirements, and then design and optimized the solar farm that can meet these energy demands of the senate complex efficiently using homer pro software. the significance of this study lies in its potential to address the pressing energy challenges at the university of maiduguri senate complex, ensuring the continuity of academic and administrative functions, and reducing dependence on an unreliable grid system. by utilizing homer pro software or system optimization, this research will demonstrate the potential of solar energy to offer a sustainable, cost-effective, and reliable solution to the power supply challenges faced by institutions in borno state. furthermore, the findings from this study could serve as a model for other institutions and regions in northeastern nigeria that face similar electricity access challenges. recent studies have emphasized the increasing importance of solar energy and the need for efficient system design in off-grid and rural areas. akinwale et al. (2022) explored the economic viability of solar energy systems in nigerian universities, demonstrating that solar power could offer long-term cost savings while reducing dependence on the grid. oladele et al. (2023) focus on optimizing hybrid renewable energy systems for offgrid rural communities in nigeria, underscoring the importance of system integration and energy management. olatunji & akpa, (2023) highlighted the vast solar energy potential in northern nigeria and the importance of harnessing this resource using appropriate technological solutions. similarly, olayanju et al, (2022) explored the feasibility of solar power for universities in nigeria, revealing that integrating renewable energy could improve energy security while minimizing operational costs. other studies, including that by ibitoye & olanrewaju (2024) emphasize the role of simulation and optimization tools like homer pro in designing efficient and reliable renewable energy systems. udeh et al. (2022) also explores the potential of solar energy in addressing nigeria's power crisis, with a focus on the integration of renewable energy technologies in educational institutions. their findings underscore the importance of system design and energy optimization for the successful adoption of solar power in universities. additionally, the work of ibrahim & shehu (2023) in evaluating the impact of solar pv systems on energy consumption and sustainability in nigerian universities provides a key insight into how these technologies can be adopted to reduce grid dependency. in a similar vein, adeyemi (2023) provide a thorough analysis of the policy landscape for renewable energy in nigeria, suggesting that solar power adoption can be supported by aligning with national and regional energy policies aimed at promoting sustainability. these works collectively reinforce the relevance and timeliness of this research, as they demonstrate how solar energy, when properly optimized, can provide reliable power solutions for institutions and regions with unreliable electricity access. 2. method 2.1 description of the case study maiduguri lies at 11°50′n latitude and 13°09′e longitude and experiences average daily solar radiation of 5.5 kwh/m². the senate complex includes a two-story senate building and a large senate chamber. the building accommodates 56 administrative offices, air conditioning units, lighting fixtures, and computer systems. the senate chamber seats 350 and uses audio systems, fans, and display equipment. 2.2 energy audit energy audit of senate complex university of maiduguri is conducted according to the procedure in figure 1. the data obtained from energy audit is used to project the future energy demand of the university of maiduguri senate complex. 2.3 data collection and analysis 2.3.1 design analysis hybrid optimization model for electric renewable (homer) tool developed by national renewable energy laboratory (nrel) in usa is used to carry out this analysis. this software application is used to design and evaluate technically and financially the options for off-grid and on-grid power systems for remote, stand-alone and distributed generation applications. the software is a complete weather data base mainly used in modeling various energy systems and processes. the information to be inputted into the homer software is the electric load data, solar radiation, and temperature. http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 813 figure 1: energy audit procedure 2.3.2 load assessment the load assessment was determined based on the energy audit conducted. the average yearly, daily and hourly energy consumption was determined from the audit conducted and used for the design accordingly. table 1: a load in the senate complex items power ratings quantity total air conditioners 2.5hp 9 79 2hp 49 1.5hp 15 1hp 6 refrigerators 2hp 10 31 1hp 21 tv sets 56 watts 19 23 60 watts 4 standing fans 56 watts 13 13 elevators 6491.9 watts 2 2 computers lcd monitor 29.8 w 53 106 cpu 56 w 53 printers laser jet 805 w 13 18 desk jet 575 w 5 photocopiers 1400 w 7 7 pumping machines 2hp 1 4 1hp 3 lighting incandescent 100 w 16 317 cfl 18 w 301 2.3.3 solar radiation data of the study area the solar radiation data for the study area, maiduguri, is sourced from the nigerian meteorological agency (nimet). maiduguri, at latitude 11°n, experiences high solar radiation, with an average global horizontal irradiance (ghi) of 5.5 kwh/m²/day. solar radiation calculations solar radiation values were determined using standard solar geometry relations. the declination angle (δ) is obtained from: δ = 23.45𝑜 × sin ( 360 365 (284 + 𝑛)) 1 where n is the day of the year. preliminary contact site visit data collection and mining data analysis report presentation http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 814 the hour angle (ω) is given by: 𝛚 = 15𝒐 (𝑡𝑠𝑜𝑙𝑎𝑟 − 12) 2 where 𝒕𝒔𝒐𝒍𝒂𝒓is the solar time in hours. at solar noon, ω = 0𝑜 the solar zenith angle (θz) is calculated as: cos θz = sin ϕ sin δ + cos ϕ cos 𝛚 3 where ϕ is the site latitude for example, on july 15, 2025 (n = 196), the declination angle was 21.74°. at solar noon (𝛚 = 0𝑜) and latitude 11.85° n (maiduguri), the zenith angle was computed as 10.23°. these calculations informed optimal pv panel positioning for the simulation tilt angle (β) determination based on geographic latitude and seasonal variation, a tilt angle of 12° was selected for optimal solar energy capture. this was applied in the homer pro model to simulate real-world orientation of the solar panels at the installation site. solar radiation potential the solar energy potential for maiduguri, as shown in figure 2, reflects the typical radiation levels throughout the year, with a strong peak during the dry season months. this analysis of solar radiation data provides a foundation for understanding the available solar energy at the site, which is crucial for the design and optimization of solar energy systems. figure 2: monthly solar radiation profile for maiduguri, nigeria 2.4 physical modeling using homer pro software 2.4.1 solar pv system the model selected from homer pro library was canadian solar max power cs6u-340m 340w monocrystalline pv module manufactured by canadian solar max power cs6u-340m 340w with 17.49% efficiency and 0.34kw rated capacity. the power output of the pv system is given in equation (4) (lambert, 2006). 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 1 2 3 4 5 6 7 c la er n es s in d ex s o la r ra d ia ti o n ( k w h /m 2 /d ay ) month daily radiation (kwh/m2) clearness index http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 815 𝑉𝑃𝑉 = 𝐹𝑃𝑉 × 𝑌𝑃𝑉 × 𝐼𝑇 𝐼𝑆 4 where, 𝐹𝑃𝑉 – derating factor, ypv the rated capacity of the pv array (kw), it the global solar radiation (beam plus diffuse) incident on the surface of the pv array (kw/m2), and is is 1 kw/m2, which is the standard amount of radiation used to rate the capacity of the pv array. the efficiency of solar pv system considers all losses in a solar pv panel due to temperature variation, shadow on panel, dirt, and inverter losses. the photovoltaic derating factor 𝐹𝑃𝑉 is a factor that homer tool applies to the pv array power output to account for reduced output in real-world operating conditions. 2.4.2 battery storage sizing and modeling the battery bank consists of individual batteries, each capable of storing a specific amount of dc electricity with fixed round-trip energy efficiency, as depicted in homer. these batteries have constraints on charging/discharging rates, depth of discharge, and total energy throughput before replacement. homer assumes constant battery characteristics over its lifespan, unaffected by factors like temperature. key attributes include nominal voltage, capacity curve, lifetime curve, minimum state of charge, and round-trip efficiency. given solar power's intermittent nature, energy storage is vital to meet demand, particularly during nights and cloudy days. battery selection considers factors like cost, availability, size, mobility, and system compatibility. homer calculates battery bank lifespan using equation 5 (lambert, 2006) after assessing suitable battery options. 𝑅𝑏𝑎𝑡𝑡 = min ( 𝑁𝑏𝑎𝑡𝑡 × 𝑄𝑙𝑖𝑓𝑒𝑡𝑖𝑚𝑒 𝑄𝑡ℎ𝑟𝑝𝑡 , 𝑅𝑏𝑎𝑡𝑡, 𝑓) 5 where nbatt is the number of batteries in the battery bank, qlifetime the lifetime throughput of a single battery, qthrpt the annual throughput (the total amount of energy that cycles through the battery bank in one year), and rbatt, 𝑓 the float life of the battery (the maximum life regardless of throughput). the model of the battery selected from homer library was idealized battery model (lead-acid generic batteries). it has a nominal voltage (v) of 380, nominal capacity (kwh) of 210, nominal capacity (ah) of 553, efficiency (%) of 88%, maximum charge current (a) of 131 and maximum discharge current of 131. 2.4.3 converter the converter chosen from the homer library, was a system converter with a capacity of 0.34 kw and an efficiency of 90%. it's intended to supply the maximum ac load in the complex. the power rating for the inverter, denoted as 𝑃𝑖𝑛𝑣, was determined using equation (6), where 𝑃𝐴𝐶𝑙𝑜𝑎𝑑represents the total power from ac load demand, and an oversized factor of 1.25 was applied (nordin & rahman, 2016). 𝑃𝑖𝑛𝑣 = 𝑃𝐴𝐶𝑙𝑜𝑎𝑑 × 1.25 6 3. results and discussion 3.1 energy audit analysis the energy audit reveals that cooling systems (73 air conditioners) account for 57% of the total daily demand, equating to approximately 901 kwh. refrigerators contribute 16%, while elevators account for 7%. printers consume 7%, photocopiers 5%, lighting 3%, computers and pumping machines 2% each, tv sets 1%, and standing fans less than 1% of the total energy supplied. this data guided system sizing to prioritize uninterrupted cooling and essential operations. the audit results shed light on the vulnerability of university of maiduguri senate complex to intermittent power supply issues. high energy consumption coupled with substantial losses exacerbates the impact of power outages on the institution’s operations. the intermittency of power supply can disrupt academic activities, compromise research projects, and hinder administrative functions, underscoring the urgent need for robust energy management strategies. in light of the audit results, the imperative for sustainable energy solutions becomes evident. http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 816 table 2: load requirement of the complex items power ratings (w) quantity power (kw) daily usage (hours) daily load (kwh/day) air conditioners 1890 9 112.64 8 901.12 1512 49 1134 15 756 6 refrigerators 1512 10 32.06 7 224.42 756 21 tv sets 56 19 1.30 10 13.00 60 4 standing fans 56 13 0.73 10 7.30 elevators 64919 2 12.98 12 51.92 computers (monitor) 29.8 53 4.55 9 9.10 computers (cpu) 56 53 printers (laserjet) 805 12 13.34 7 93.38 printers (deskjet) 575 5 photocopiers 1400 9 9.80 5 49.00 pumping machines 1512 1 3.78 4 15.12 756 3 lighting (incandescent) 100 16 7.20 12 84.24 lighting (cfl) 18 301 total — — 198.20 — 1448.60 3.2 system sizing and optimization 3.2.1 physical modeling and optimization using homer pro the process of determining the optimal system size was conducted using homer pro. figure 2 illustrates the solar irradiance data utilized in this study. the analysis involved an extensive examination of various configurations, considering diverse combinations of pv panels and battery banks. the final system selection took into account factors such as excess electricity generation and overall system efficiency. consequently, multiple combinations with varying numbers of pv panels and battery banks were simulated in homer. ultimately, the selected system was identified based on its surplus electricity generation and system efficiency. based on the optimized results, a configuration comprising 1682 canadian solar maxpower cs6u-340m 340w pv panels, 144 lead-acid generic batteries rated as 1kw (arranged in 36 strings of 48v with 4 strings in parallel), and a 318kw converter was projected to meet the annual load demand of 1.03 gwh. figure 3 illustrates the storage state of charge and discharge percentage, ensuring that the depth of discharge never falls below 25%. figure 3: battery bank state of charge (soc) http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 817 figure 3 shows the battery performance. the peaks at around 40% and 87% state of charge (soc) mean the batteries usually operate either at partial charge or near full charge. between days 180 and 270, the soc drops more often, which aligns with the rainy season when solar input is lower, and the batteries work harder to meet demand. figure 4 presents the inverter and rectifier outputs. the inverter, with a 318-kw capacity, operates yearround but mostly below full load, giving a 19% capacity factor. this confirms it is sized for reliability but often runs at lower outputs. the rectifier output is almost negligible, showing that little energy flows back into the dc bus. figure 4: inverter output profile figure 5 illustrates pv array performance. the system delivers about 1.03 gwh annually with a 20.5% capacity factor, which is typical for the region. output declines between day 180 and 270, again reflecting reduced solar radiation in the wet season. the pv system reaches up to 517 kw, close to its rated value, while excess energy at peak times contributes to the high pv penetration. figure 5: pv array output the choice of canadian solar max power monocrystalline panels for the photovoltaic (pv) system was motivated by their efficiency of 17.49% and monocrystalline nature. the power inverter, sized at 318 kw, was determined based on the peak demand of the ac load, limited to 1.03 gwh/year. sizing the pv panels considered factors such as load demand, necessary power backup, and available irradiance. http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 818 the battery bank operates in a floating state when pv output matches demand, discharging only during periods of insufficient pv output or at night. this strategy optimizes battery usage and ensures continuous power supply when solar generation is inadequate. the system block diagram is depicted in figure 6 illustrating the solar panel connected to the dc bus, equipped with a maximum power point tracker (mppt). the battery bank block, inclusive of a charge controller and under/overvoltage protection, is also connected to the same dc bus. the third block in this figure is the converter, responsible for converting dc to ac, ensuring power quality (harmonics reduction), and linking the dc and ac buses figure 6: system structure with integrated sub block 4. conclusion the study was able to conduct the energy audit of the university of maiduguri senate complex and found out that the building consumed 1448.6kwh and the yearly projected energy consumption of 1.03gwh. the study also employed homer pro software for system sizing and optimization, considering various pv configuration and battery banks. from the results of system sizing and optimization, the chosen system comprises of 1682 canadian solar max power cs6u-340m-340 w pv panels, 144 lead-acid generic batteries rated at 1 kw each (totaling 4603 ah), and 2 inverters with a combined capacity of 318 kw, successfully meeting an annual load demand of 1.03 gwh. references adeyemi, oo., fadare, da. and olaniran, i. a. 2023. analysis of renewable energy policies and their impact on nigeria’s energy security. journal of sustainable development, 15(2): 203–219. akinwale, ta., adewumi, aa. and dewale, am. 2022. economic viability of solar energy systems in nigeria’s universities: a case study of small-scale solar pv applications. energy reports, 8: 452–459. edomah, n., ndulue, g. and lemaire, x. 2021. a review of stakeholders and interventions in nigeria’s electricity sector. heliyon, 7(9): e07956. ibitoye, fi. and olanrewaju, ad. 2024. simulation and optimization of renewable energy systems for educational institutions in nigeria using homer pro. international journal of energy engineering, 12(1): 61– 73. ibrahim, aa. and shehu, mara. 2023. impact of solar pv systems on energy consumption and sustainability in nigerian universities. renewable energy & power quality journal, 21(1): 67–81. lambert, t. 2006. micro power system modelling with homer. retrieved from https://www.homerenergy.com/documents/micropowersystemmodelingwithhomer.pdf http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 811-819. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: yahabeebeeh@gmail.com 819 lewis, f., larry, p. and green, m. 2010. solar cells and their applications (2nd ed.). hoboken, nj: wiley. isbn 9780470446331 nguyen, t., tran, l., and le, d. 2022. optimization of solar energy systems for sustainable power supply in regions with intermittent energy sources. renewable and sustainable energy reviews, 112: 112–124. nigerian electricity regulatory commission (nerc). 2015. amended multi-year tariff order (myto) 2.1 for the period april 1st, 2015 to december, 2018. abuja: nerc. nrel (national renewable energy laboratory). 2008. energy efficiency and renewable energy. golden, co: u.s. department of energy. nordin, nd. and rahman, ha. 2016. a novel optimization method for designing standalone photovoltaic system. renewable energy, 89: 706–715. oladele, oi., akpan, do. and oayanju, mt. 2023. optimization of hybrid renewable energy systems for offgrid rural communities in nigeria. journal of renewable energy and sustainability, 8: 452–459. olatunji, oo. and akpan, us. 2023. solar energy potential in northern nigeria and the role of optimization tools in system design. renewable and sustainable energy reviews, 18: 450–459. olayanju, mt., alabi, ot. and fola, s. 2022. design and optimization of solar energy systems for educational institutions in nigeria using homer pro. international journal of energy engineering, 12(3): 239–250. udeh, as., mohammed, ag., and obi, ju. 2022. integrating solar energy systems into nigeria's national grid: a case study of rural and university energy consumption. renewable energy focus, 40: 61–72. http://www.azojete.com.ng/ mailto:yahabeebeeh@gmail.com corresponding author’s e-mail: mohammedabdullahi047@gmail.com 25 arid zone journal of engineering, technology & environment original research article assessment of effect of alummina addition on the refraractory under load (rul) property of some kaolin clay deposits in nigeria j. b. mokwa1, m. abdullahi*1 and o. e. malomo2 1department of mechanical engineering, federal polytechnic bida, nigeria 2faculty of technology, university of sunderland, uk *corresponding author’s e-mail: mohammedabdullahi047@gmail.com article information abstract the impact of alumina addition on the refractory under load (rul) of kaolin clay deposits in nigeria have been investigated. the samples deposit were collected from different sites of ikpeshi akoko edo (ikae) of edo state, kasadi village in kebbi state (kvk), alasan in osun state (aos) and badeggi in niger state and were used as the principal raw material in the sample preparation while ball clay was used as the binder. the kaolin and ball clay were mixed in suitable proportion of 70:30 ratio in the production of the fire clay bricks. particle size distributions and refractory under load (rul) of the samples were determined. through rul tests, samples without alumina exhibited varying subsidence behaviours at different temperatures. samples from kasadi (kvk) and alaasan (aos) showed the greatest improvement at 10% and 15% alumina levels, with lower subsidence and higher peak temperatures. with 10% and 15% alumina additions, respectively, the kasadi sample reached maximal thermal stability with subsidence temperatures of 1475°c and 1516°c. excellent refractory properties were likewise demonstrated by the alaasan sample, but with less early expansion. on the other hand, the ikpeshi (ikae) sample underwent more overall deformation, suggesting a lower level of long-term thermal resistance, even if it was initially able to endure high temperatures. results suggest alumina content influences the thermal stability and performance of kaolin clay, important for firebrick production and industrial applications. practical tests confirmed the suitability of produced refractory bricks for industrial use, demonstrating comparable performance to standard refractory fire clay. submitted: 16th july 2024 revised: 3rd october 2024 accepted: 29th january 2025 keywords: alumina addition kaolin clay refractory under load (rul) subsidence © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the pressing needs in nigeria and the availability of abundant natural resources demand that the direction of utilization of locally available resources be up-graded through scientific and technological insight and new or improved technology to meet the needs of iron and steel industries. technological development in nigeria has created awareness and has increased the standard of living of both urban and rural dwellers, leading to increasing use of modern industrial appliances (olusola, 2014). if nigeria is to sustain increased industrial growth, the iron and steel industries must be sustained and new one established. abdullahi et al., 2020 carried out comparative characterization of malaysian (m-kaolin) and nigerian (n-kaolin) crude kaolinite resources and reported that concluded that n-kaolin is highly promising for refractory applications. lawal et al., 2022 studied mineralogical and elemental composition, morphology, thermal stability, alumina and silica content of argungu kaolinite and reported that the kaolinite are characterized by low or free toxic ions that offer the clay as a vital raw material for wide range of industrial applications. these industries make use of furnaces and these furnaces are lined with refractory bricks produced using kaolin or other clays which are presently imported. refractories belong to the class of ceramic materials which are employed for high temperature applications, usually above 1100oc (mokwa and salihi, 2011). refractory materials are used in linings for furnaces, kiln, incinerators, and reactors. they are also used to make crucibles and moulds for casting glass and metals and for surfacing flame detector systems for rocket launch structures (hassan, 1990). most refractory materials are made from naturally occurring high melting point oxides, particularly silica (sio2), alumina (al2o3), magnesia oxide (mgo), chromium oxide (cr2o3), zirconium oxide (zro) and iron oxide (fe2o3) (olusola, 2006). it is pertinent to state that without furnace, a device for heating and or melting metals or alloys, and heat treatment, there would have been no existence of iron and steel industry (chester, azojete march 2025. vol.21(1):25-34 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:mohammedabdullahi047@gmail.com mailto:mohammedabdullahi047@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 26 1975). considering the importance of furnace to a steel industry, the need for refractory materials cannot be over emphasized since high working temperature is the norm in steel and foundry industries. there are several large deposits of clay across nigeria. many industries in nigeria require clay or its product for operations, like the nigeria iron and steel industry, ajaokuta, osogbo steel rolling, delta steel company and nigerian iron ore mining industries in itakpe, kogi state. these industries require huge quantity of refractory materials (clay) for their productions, and these are mostly imported to the country (shuaib et al., 2018). manukaji, 2013 revealed that ajaokuta steel industries will require about 36,000 tonnes of refractory bricks that cost n5034 billion annually when operational. other nigerian steel companies like delta steel company also consume fire clay worth over n1.4 billion annually in which more than 80% of such clay will be required by ajaokuta steel industry. kaolin is used for fire bricks because of its unique properties such as natural whiteness, fine particle size, non-abrasiveness and chemical stability, in addition to the general properties mentioned above, it is soft and has low viscosity at high solid contents (kirabira et al., 2003). kaolin fire clay refractories, also known as chamotte bricks, belong to the alumino silicate group with alumina content between 25-45 wt%. the others in this group are the semi-acid (≤ 25 wt% al2o3) and high alumina (> 45 wt% al2o3) (john et al., 2004). kaolin is the main source of alumina in the manufacture of fireclay refractories among other industrial minerals. the higher the alumina contents of kaolin, the higher their refractoriness. raw materials are thus classified to be of high refractory value as the amount of alumina in them increases (manukaji, 2013). ball clays are generally used in varying proportions as a binder with kaolin in fire bricks production. the clay being highly plastic facilitates the forming process and contributes to the dry-strength, or green strength, of the product. in addition, it enhances the sintering process by providing a glassy-phase which bonds the aggregates together. fireclay refractories, like other ceramic products are processed through three main stages: raw materials preparation, consolidation to compacts and densification by sintering. the main constituents of fireclay refractories are alumina (al2o3) and silica (sio2). these systems are normally based on kaolinitic clays which generally present substantial shrinkage when fired (alexander et al., 2013). in consideration of shrinkage and cracking of the product, raw materials are fired, crushed and size graded into stable grog (calcined fireclay) and mixed with ground clay slip. the grog promotes drying and limits dry and firing shrinkage whereas the clay promotes sintering and bonding during firing. the materials used for making grog are generally more refractory than the bonding material (fayyad et al., 2012). however the greatest use of refractories is in the steel and manufacturing industries where it is used as lining materials in blast furnace, converters and open-hearth furnaces. other important uses of refractories are for cement kiln, glass tanks, ceramics kilns, steam boilers and paper plants amina et al., 2014). some research works which border on exploring ceramic refractory raw minerals reported by the federal ministry of mines and solid minerals (olusola, 2006), showed that the following ceramic refractory minerals exist in abundance in all the regions of the country: silica raw materials, kaolin, ball clay, alumina raw materials (kyanite, sillimanite, and corundum), magnesia raw materials (magnesite), and forsterite raw materials (talc, pyrophyllite, serpentine, asbestos). other typical refractory minerals may be available but of poor grade, or in small, uneconomic deposits. most of these raw materials have not been exploited for their industrial applications (shuaib et al., 2018). the need for detailed investigation on the characteristics, properties and use of nigeria kaolin clay materials cannot be over emphasized. as a developing nation, it is very important to look inward and develop our locally available clay to meet the present demand in our steel and metallurgical industries and for the future development of other industries. moreover, the nation depends very much on importation of kaolin clay materials from foreign countries (shuaib et al., 2018). as long as this trend continues, the nation cannot develop technologically. the quality and quantity of iron and steel products we are to produce will go a long way in helping the nation to conserve funds. this particular research intends to utilize kaolin and ball clay as an available raw material to produce a strong refractory fire bricks material that will withstand high temperature before failing under load. 2. materials and method 2.1 materials about 25kg of the kaolin clay samples were collected from four states in nigeria, these include ikpeshi akoko edo (ikae) local government area of edo state, located on latitude 7.2629° north and longitude 6.1271° east of nigeria; kasadi village in kebbi state (kvk), alasan in osun state (aos) and badeggi in niger state. the samples deposit sites were dugged and collected using an iron digger and hoe respectively. kaolin was used as the principal raw material in the sample preparation while ball clay was used as the binder. the kaolin and ball clay were mixed in suitable proportion of 70:30 ratio in the production of the fire clay bricks (mokwa et al., 2019). particle size distributions and refractory under load (rul) were determined for ikae, kvk, and aos respectively according to the standard procedures. http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 27 2.2 method refractory under load (rul) is a measure of the deformation behavior of refractory ceramic products subjected to a constant load, at an increasing temperature (mokwa et al., 2019). it is a vital property of refractories, since the time of service of a refractory is determined by its deformation under load at high temperature, finally leading to failure. test samples were prepared according to astm standard by varying al2o3 content in 0, 5, 10 and 15% respectively. prepared cylindrical samples of 50 mm diameter by 50 mm height, was .placed on an alumina block in an electric tubular furnace and a load (l = 0.2n/mm2 ) was applied, through a system of levers, to an alumina thrust rod. the sample was then heated at a gradually rising temperature of a fixed rate (10oc per min) until the temperature reaches 1000oc and(3-5 oc/min) between 1000oc and 1450oc, as the samples began to deform and sag the changes in length was measured on a recording instrument (fayad et al., 2012). table 1 presents the chemical analysis of the kaolin clay samples used in this study (mokwa et al., 2019). table 1: chemical analysis of the kaolin clay samples samples/ composition (%) sio2 al2o3 fe2o3 cao mgo na2o k2o mno tio2 p2o5 zro2 loi ikae 53.18 30.67 0.934 0.23 0.16 0.020 0.013 0.011 2.01 <0.001 nd 11.95 kvk 57.41 26.88 2.432 0.09 0.01 nd <0.001 0.04 2.81 <0.001 0.217 8.00 aos 49.30 33.10 0.435 0.10 0.04 0.025 nd 0.02 <0.001 nd 15.64 3. results and discussion 3.1 elemental composition analysis of the kaolin clay samples with varying alumina content the results of the elemental composition analysis with addition of varying percentage of alumina to the beneficiated kaolin samples are shown in table 2-4. the higher the alumina in clay sample the higher the refractory temperature and the higher the mechanical strength of such fire clay (galdina, 1983). it can be seen that with the addition of 5% alumina (table 2) to the kaolin samples the alumina contents of edo, kebbi and osun clay was able to increase by 35.54, 31.85 and 38.02% compared to the beneficiated sample of 30.67, 26.88 and 33.10%, while the silica contents of the clay samples reduced to 48.13, 52.35 and 44.23% compared to the beneficiated samples of 53.18, 57.41 and 49.30% for edo, kebbi and osun respectively. the alumina content for edo, kebbi and osun kaolin with the addition of 10% (table 3) were found to increase by 40.59, 36.69 and 43.05%, while that of 15% alumina (table 4) addition were 45.58, 41.71 and 48.00% respectively, from the tables osun clay as the highest optimum values of 48.00%. from the results it was observed that as the alumina contents in the clay samples increases the silica contents reduces, which means the higher the alumina in clay samples the lower the silica in such samples (fayad et al., 2012; joseph et al., 2023). table 2: elemental composition analysis of the 5% addition of alumina to the kaolin clay samples location si02 ai203 fe203 cao mgo na2o k2o mno tio2 p2o5 zro2 l.o.i edo 48.13 35.54 0.84 0.21 0.31 0.017 0.011 0.010 2.00 <0.001 nd 12.10 kebbi 52.35 31.85 2.12 0.07 0.006 nd <0.001 0.030 2.40 <0.001 0.201 8.48 osun 44.23 38.02 0.412 0.080 0.071 0.022 0.048 0.120 0.008 <0.001 nd 15.68 http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 28 table 3: elemental composition analysis of the 10% addition of alumina to the kaolin clay samples location si02 ai203 fe203 cao mgo na2o k2o mno tio2 p2o5 zro2 l.o.i edo 43.14 40.59 0.80 0.18 0.10 0.015 0.010 0.008 1.97 <0.001 nd 12.20 kebbi 47.20 36.69 2.10 0.05 0.006 nd <0.001 0.015 2.20 <0.001 0.20 8.50 osun 39.08 43.05 0.40 0.062 0.069 0.020 0.044 0.100 0.006 <0.001 nd 15.69 table 4: chemical analysis of the 15% addition of alumina to the kaolin clay samples location si02 ai203 fe203 cao mgo na2o k2o mno tio2 p2o5 zro2 l.o.i edo 38.12 45.58 0.78 0.17 0.098 0.013 0.009 0.007 1.93 <0.001 nd 12.24 kebbi 42.34 41.71 1.97 0.04 0.005 nd <0.001 0.013 2.00 <0.001 0.184 8.58 osun 34.15 48.00 0.38 0.060 0.065 0.017 0.042 0.096 0.005 <0.001 nd 15.70 nd = not detected 3.2 refractory under load (rul) the variation of subsidence with temperature curve on the rul test of the samples with no alumina addition is presented in figure 1. aos sample recorded highest peak of 0.94% subsidence, at 670oc followed by kvk sample with 0.68% peak subsidence at 4000c. sample ikae recorded the least peak subsidence of 0.76% at 4000c. sample aos attained highest deformation and finally collapse at 1348oc, which was the highest temperature at a subsidence of -4%. the maximum expansion attained by the sample bricks was 0.94%, which were according to the method of john et al. 2004. the highest temperature attained for kvk was 800oc at a subsidence of -2.4%, which was the temperature at which the sample collapse, in accordance with fayyad et al. 2012 method. ikae sample attained highest temperature of 800oc, which was the temperature at which the clay sample collapse at a subsidence of -0.8% and maximum expansion of the clay sample was 0.76%, which was the highest peak attained before deformation commenced, at a temperature of 400oc. these results are in accordance with result presented by fayyad et al. 2012. figure 1: variation of subsidence with temperature curve on the rul test of the samples with no alumina addition figure 2 presented the variation of subsidence with temperature curve on the rul test of the samples with addition of 5% alumina. the beneficiated sample exhibited a maximum expansion of 0.8% and began to subside at 600°c, continuing until 800°c, where it exhibited a total subsidence of -2.4%. this indicates that the beneficiated sample has a relatively lower thermal stability compared to the other samples. the kasadi (kvk) sample exhibited a maximum expansion of 0.84% and started subsiding at 850°c. the subsidence continued until 1368°c, with a total subsidence of -1.1%. this suggests that the kasadi sample has a higher thermal -5 -4 -3 -2 -1 0 1 2 0 500 1000 1500 s u b si d en ce ( % ) temperature (0c) ikae kvk aos http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 29 stability and can withstand higher temperatures before collapsing under load. the ikpeshi (ikae) sample also showed a maximum expansion of 0.84%. however, it began subsiding at a lower temperature of 670°c and continued until 1000°c, with a total subsidence of -1%. this result is in accordance with that of john et al. 2004. this indicates that while the ikpeshi sample can expand similarly to the kasadi sample, it has a lower collapse temperature and thus lower thermal stability under load. the alaasan (aos) sample demonstrated a maximum expansion of 0.7%, beginning to subside at 650°c and continuing until it reached 1375°c, with a total subsidence of -2.2% which was the temperature at which the clay sample collapse under a constant load of 0.2n/mm2. despite having a slightly lower initial expansion compared to other samples, the alaasan sample could withstand the highest temperature before collapsing, indicating a higher thermal stability under load. the results indicate that the kasadi and alaasan samples exhibit higher thermal stability under load compared to the beneficiated and ikpeshi samples. the addition of 50% alumina appears to enhance the refractory properties of these kaolin clay deposits, particularly in terms of their ability to withstand higher temperatures before significant subsidence occurs. figure 2: variation of subsidence with temperature curve on the rul test of the samples with 5% alumina addition figure 3 presented the variation of subsidence with temperature curve on the rul test of the samples with addition of 10% alumina. the beneficiated sample, displayed a maximum expansion of 0.8%. it began subsiding at 600°c and continued until 800°c, showing a significant total subsidence of -2.4%. this indicates a relatively low thermal stability, as the sample could not withstand higher temperatures before subsidence occurred. the kasadi sample, with an alumina content of 0.86%, exhibited a maximum expansion of 1.04%. it began subsiding at a much higher temperature of 1300°c and continued until 1475°c, with a total subsidence of -1%. this suggests that the addition of 10% alumina significantly enhanced the thermal stability of the kasadi sample, allowing it to withstand higher temperatures before subsidence. the ikpeshi sample showed a maximum expansion of 0.54%. it began subsiding at 1350°c and ended at 1425°c, with a total subsidence of -4%. despite starting subsidence at a high temperature, the ikpeshi sample exhibited the highest overall subsidence, indicating that while it can initially withstand high temperatures, it undergoes significant deformation once subsidence begins. the alaasan sample, containing 1.04% alumina, demonstrated the highest maximum expansion of 1.04% which was the temperature at which the clay sample collapse under a constant load of 0.2n/mm2. it started subsiding at 880°c and continued until 1382°c, showing a total subsidence of -2.72%. this indicates that the alaasan sample, while having a high initial expansion and a moderate start temperature for subsidence, undergoes substantial deformation and subsidence. addition of 10% alumina has varying effects on the refractory properties of the kaolin clay samples. the finding is in agreement with the findings of kirabira et al., 2003. the kasadi sample showed the most significant improvement in thermal stability with the highest subsidence temperature and the least overall subsidence. in contrast, the ikpeshi sample, despite its high subsidence start temperature, exhibited the greatest overall deformation. these findings suggest that 10% alumina addition improves the thermal stability and load-bearing capacity of some kaolin clay deposits, but the specific effects can vary depending on the clay's composition and properties. -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 0 500 1000 1500 s u b si d en ce ( % ) temperature (0c) ikae kvk aos http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 30 figure 3: variation of subsidence with temperature curve on the rul test of the samples with 10% alumina addition figure 4 presented the variation of subsidence with temperature curve on the rul test of the samples with addition of 15% alumina. the beneficiated sample exhibited a maximum expansion of 0.94%. this sample began subsiding at 670°c and continued until 1348°c, resulting in a significant total subsidence of -4%. this suggests that while the sample can withstand initial heat, it undergoes substantial deformation upon reaching higher temperatures. the kasadi sample, with 15% alumina content showed a slightly lower maximum expansion of 0.84%. it began subsiding at a higher temperature of 900°c and continued until 1452°c, with a total subsidence of -2.46%. the higher temperature range for subsidence and lower overall subsidence indicate that the addition of alumina improves the thermal stability of the kasadi sample, allowing it to withstand higher temperatures with less deformation. the ikpeshi sample, also with a maximum expansion of 0.94%, began subsiding at 1360°c and ended at 1475°c, resulting in a total subsidence of -2%. this sample exhibited the highest initial temperature for subsidence and the lowest overall subsidence among all samples, suggesting that the alumina addition significantly enhanced the ikpeshi sample's thermal stability and load-bearing capacity. the alaasan sample, with 15% alumina content demonstrated similar properties to the kasadi sample. it had a maximum expansion of 0.84%, began subsiding at 900°c, and continued until 1452°c, with a total subsidence of -2.46%, which was the temperature at which the clay sample collapse under a constant load of 0.2n/mm2. these results indicate that the alaasan sample, like the kasadi sample, benefits from alumina addition by exhibiting improved thermal stability and reduced deformation under load. addition of 15% alumina enhances the refractory properties of the kaolin clay samples, increasing their thermal stability and reducing deformation under load. the ikpeshi sample showed the most significant improvement, with the highest initial subsidence temperature and the lowest overall subsidence. both the kasadi and alaasan samples also demonstrated improved properties, though to a lesser extent. these findings suggest that alumina addition can effectively enhance the performance of kaolin clay deposits used in refractory applications. the result is in accordance with the results of fayyad et al., (2012). -3 -2 -1 0 1 2 0 500 1000 1500 2000 s u b si d en ce ( % ) temperature (0c) ikae kvk aos http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 31 figure 4: variation of subsidence with temperature curve on the rul test of the samples with 15% alumina addition table 5 shows the summary of the influence of alumina contents on the refractory under load (rul) of ikpeshi beneficiated kaolin clay samples at varying percentages of 0, 5, 10 and 15% alumina, for no addition of alumina oxide the beginning of subsidence temperature (ti) was 500oc and end of subsidence temperature (te) was 800oc at a subsidence of -0.8 % which was the maximum temperature and subsidence attained before the clay sample collapse, at a maximum expansion of 0.76%, for 5% alumina content addition the highest temperature attained was 1000oc at a subsidence of -1% which was the subsidence at which the brick sample collapse at a maximum expansion of 0.84%. for 10 and 15% alumina content addition the maximum temperature attained before collapse was 1350 and 1360oc at a subsidence of -1.4 and -2 respectively, both with maximum expansion of 0.54 and 0.94%. all this results were in accordance with fayyad et al. (2012) and john et al. (2004) methods. table 5: summary of the influence of alumina contents on the rul of ikae sample alumina content (%) me (%) ti (0c) te (0c) s (%) 0 0.76 500 800 -0.8 5 0.84 670 1000 -1 10 0.54 1350 1425 -1.4 15 0.94 1360 1475 -2 *memaximum expansion; ti-beginning of subsidence; teend of subsidence; ssubsidence table 6 shows the summary of the influence of alumina contents on the refractory under load (rul) of kasadi beneficiated kaolin clay samples at varying percentages of 0, 5, 10 and 15% alumina, which were in accordance to the method of fayyad et al. (2012) and kirabira. et al. (2003), for no addition of alumina oxide the beginning of subsidence temperature (ti) was 600oc and end of subsidence temperature (te) was 800oc at a subsidence of -2.4 % which was the maximum temperature and subsidence attained before the clay sample collapse, at a maximum expansion of 0.76%, for 5% alumina content addition the highest temperature attained was 1368oc at a subsidence of -1.1% which was the subsidence at which the brick sample collapse at a maximum expansion of 0.84%. for 10 and 15% alumina content addition the maximum temperature attained before collapse was 1475 and 1516oc at a subsidence of -1 and -1.2% respectively, both with maximum expansion of 0.86 and 0.96%. -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 0 500 1000 1500 2000 s u b si d en ce ( % ) temperature (0c) ikae kvk aos http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 32 table 6: summary of the influence of alumina contents on the rul of kvk sample alumina content (%) me (%) ti (0c) te (0c) s (%) 0 0.8 600 800 -2.4 5 0.84 850 1368 -1.1 10 0.86 13 1475 -1 15 0.96 1450 1516 -1.2 table 7 shows the summary of the influence of alumina contents on the refractory under load (rul) of alaasan beneficiated kaolin clay samples at varying percentages of 0, 5, 10 and 15% alumina which were all in accordance to the method of fayyad et al. (2012) and john et al. (2004), for no addition of alumina oxide the beginning of subsidence temperature (ti) was 670oc and end of subsidence temperature (te) was 1348oc at a subsidence of -4 % which was the maximum temperature and subsidence attained before the clay sample collapse, at a maximum expansion of 0.94%, for 5% alumina content addition the highest temperature attained was 1375oc at a subsidence of -2.2% which was the subsidence at which the brick sample collapse at a maximum expansion of 0.7%. for 10% and 15% alumina content addition the maximum temperature attained before collapse was 1382 and 1452oc at a subsidence of -2.72 and -2.46% respectively, both with maximum expansion of 1.04 and 0.84%. table 7: summary of the influence of alumina contents on the rul of aos sample alumina content (%) me (%) ti (0c) te (0c) s (%) 0 0.94 670 1348 -4 5 0.7 650 1375 -2.2 10 01.4 880 1382 -2.72 15 0.84 900 1452 -2.46 table 8: rul of kaolin clay refractories made in various countries of the world compared with the rul of the researched area country u.k usa russia germany france rul (oc) 1200-1400 1150-1410 1305-1390 1230-1430 1140-1300 nigeria/alumina content (0%) nigeria/alumina content (5%) location ikae kvk aos ikae kvk aos rul (oc) 800 800 1348 1000 368 1375 nigeria/alumina content (10%) nigeria/alumina content (15%) location ikae kvk aos ikae kvk aos rul (oc) 1475 1425 1382 1475 1516 1452 3.3 evaluation of the firebricks production using each of the samples firebricks were produced using the kaolin clay samples and ball clay as binder, alumina oxide was also added in suitable composition and proportions, corresponding to that used for laboratory testing for the firebricks mixtures (john et al., 2004). each of the kaolin clay samples were mixed with the corresponding weight of ball clay, alumina and water individually. the clay samples produced are those that their refractory under load (rul) was found to compare favourably with those of other countries of the world (john et al., 2004). the procedures followed for the production of the firebricks samples were according to the astm c288-87 standard. http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 33 3.4 testing for suitability of the refractory bricks for industrial application the suitability of the produced kaolin refractory bricks were tested at scientific development institute (sedi), tunga-goro, minna, nigeria. the bricks were used to line the inside of a crucible furnace at the foundry workshop of the institute; the lined furnace was then used to melt an aluminum ingot at a superheated temperature of 800oc, the produced kaolin bricks was then used continuously in the crucible furnace to melt non-ferrous metal for a period of two weeks, the refractory bricks produced were found to be suitable as their products compared favourably with that of standard refractory fire clay (fayyad et al., 2012). plate 1a-d shows the testing of the produced refractory bricks in a crucible furnace. plate 1: crucible furnace: cover (a), furnace (b), furnace lined with researched bricks (c-d) 4.0 conclusion the effect of alumina addition on the refractory under load (rul) of kaolin clay samples from nigeria have been investigated. alumina addition led to improvements in rul performance, with higher alumina contents resulting in increased peak temperatures before sample collapse. the studied samples that improved the most with increased alumina content were kasadi (kvk) and alaasan (aos), particularly at 10% and 15% levels where they demonstrated stronger stability at higher temperatures and less overall subsidence. the kasadi sample showed the maximum thermal stability, with sinking temperatures for 10% and 15% alumina concentration of 1475°c and 1516°c, respectively. comparably, the alaasan sample showed excellent refractory qualities, especially at higher alumina concentrations, albeit showing less early expansion. however, even though the ikpeshi (ikae) sample was able to sustain high temperatures at first, it had more overall deformation. this suggests that although it can endure initial subsidence, it might not be as effective when exposed to excessive heat for an extended period of time. the results has demonstrated that addition of alumina enhances thermal stability and load-bearing capacity of the kaolin clay, making it suitable for industrial applications such as lining crucible furnaces for melting non-ferrous metals. the produced refractory bricks showed promising performance in industrial settings, meeting standards comparable to international refractory fire clay products. references abdullahi, t., aminu, n., and abubakar, h. 2020. appraisal of malaysian and nigerian crude kaolin resources for heat resistance applications. bima journal of science and technology, (2536-6041), 4(01): 334-339. http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com arid zone journal of engineering, technology and environment, march 2025; vol.21(1):25-34. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s e-mail: mohammedabdullahi047@gmail.com 34 alexander, a. j., fatai, a. a., abdukarim, s. a. and umar, a. s. 2013. evaluation of the refractory properties of nigeria ozanagogo clay deposit. journal of minerals, materials characterization and engineering, 1: 321 325. amina, b., rym, d. and jamel, b. 2014. effect of mechanochemical treatment on the properties of kaolin and phosphate – kaolin materials. journal of powder technology, 64: 477 -483. astm c288-87. 2014. standard test methods for refractoriness of refractories. ast m international, west conshohocken, p. a. retrieved from http://www.astm .org /standards/c33.htm chester, j. h. 1975. refractory production and properties. the iron and steel institute. london, 66-69. fayyad, m. s., ghazi, s. a. and suleiman, q. a. 2012. improvement of the refractoriness under load of fire clay refractory bricks. adv. theor. appl. mech., 5 (4): 161-172. galdina. n. 1983. improvement in the quality of refectory materials, glass and ceramics, 7-8: 439-442. hassan, s. b. 1990. the study of the refractory properties of some clays. unpublished thesis m.sc. the department of chemical engineering, ahmadu bello university, zaria. john, b. k., stefan j, and joseph, k .b. 2004. production of firebrick refractories from kaolinitic clays of the lake victoria region: published in j. australasian cera am. soc. 40: 12—19. joseph, s. o., olalekan, d. a., moses, a. o., isah, a. g., and sallau, a. a. 2023. characterization of kaolin deposits in kutigi, niger state, northern nigeria. walisongo journal of chemistry, 6(2): 134-142. kirabira, j. b., johnson, s., and byaruhanga, j. k. 2003. powder characterization of high temperature ceramic raw materials in the lake victoria region. silicates industries, in press.10-16. lawal, j. a., odeyemi, o. t., anaun, t. e., and omotehinwa, f. h. 2022. characterization and potential industrial applications of kaolinite from argungu, kebbi state, nigeria. int j scientific eng res, 13(4): 776-791. manukaji, j. u. 2013. industrial potential of some clay deposits in kogi state, north central nigeria. american journal of engineering research, 2: 33-34. mokwa, j. b and salihi, a. 2011. investigation into the refractory properties of badeggi clay for furnace lining. journal of research in engineering, 8008(1): 100-106. mokwa, j. b., lawal, s. a., abolarin, m. s., and bala, k. c. 2019. characterization and evaluation of selected kaolin clay deposits in nigeria for furnace lining application. nigerian journal of technology, 38(4): 936-946. olusola, e. o. 2006. investigation into the refractory properties of zungeru clay for high temperature applications. journal of research in engineering, 8(1): 88-92. olusola, e. o 2014. characterization of local bentonite clays for application in the foundry industry. unpublished phd project, department of mechanical engineering, federal university of technology minna.1015. shuaib-babata, y. l., yaru s. s., abdulkareem, s., busari, y. o., ambali, i. o., ajao, k. s and mohammed, g. a. 2018. characterization of baruten local government area of kwara state (nigeria) fireclays as suitable refractory materials. nigerian journal of technology, (nijotech), 37(2): 374 – 386. http://www.azojete.com.ng/ mailto:mohammedabdullahi047@gmail.com corresponding author’s email address: amibrahim@futminna.edu.ng 847 arid zone journal of engineering, technology & environment original research article development of a smart internet of things based motorcycle theft prevention system i.m. abdullahi 1*, d. maliki1, i. a. dauda2, u. s. dauda1, and g. kigbu1 1department of computer engineering, federal university of technology, minna, nigeria 2department of electrical and electronics engineering, federal university of technology, minna, nigeria *corresponding author’s email: amibrahim@futminna.edu.ng, amibrahim8383@gmail.com article information abstract motorcycle theft has become a critical security challenge globally, with existing security measures proving inadequate against sophisticated theft techniques. in nigeria, motorcycle theft accounts for 22.2% of over 45,000 documented criminal cases by 2021, necessitating advanced technological solutions. current motorcycle security systems lack integration, real-time monitoring capabilities, and reliable alert mechanisms, making motorcycles vulnerable to theft. this research presents an integrated internet of things (iot) based motorcycle theft prevention system utilizing esp32 microcontroller, gyroscope sensors for vibration detection, load sensors for weight monitoring, gps for location tracking, and gsm for communication. the system incorporates a mobile application developed using flutter for real-time monitoring and alert notifications. experimental validation demonstrated high location tracking accuracy with minimal coordinate deviations (±0.000005 degrees), effective sensor detection capabilities across various weight ranges (5-25 kg) and vibration levels (800-3500 units), and efficient alert delivery with response times ranging from 1-14 seconds across different network providers. the developed system provides a comprehensive, cost-effective solution for motorcycle security, offering real-time monitoring, multi-channel alert mechanisms, and reliable theft detection capabilities that significantly enhance motorcycle protection compared to existing solutions. received: 7th july 2025 revised: 3rd september 2025 accepted: 4th september 2025 keywords: internet of things automobile theft prevention gps tracking mobile alert system © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction transportation systems serve as the backbone of modern society, facilitating economic growth, social connectivity, and individual mobility. among various transportation modes, motorcycles have gained significant popularity due to their affordability, fuel efficiency, and maneuverability in congested urban environments. however, this popularity has made motorcycles attractive targets for theft, creating a significant security challenge worldwide (ojedokun and ogundipe, 2017). the economic and social impact of motorcycle theft extends beyond individual losses, affecting insurance costs, law enforcement resources, and community safety. in nigeria, statistical data from the nigerian police force (npf) revealed that by 2021, motorcycle theft constituted 22.2% of over 45,000 documented criminal cases, with 500 incidents classified as aggravated robberies. this alarming trend highlights the urgent need for advanced security solutions that can effectively deter theft and aid in recovery operations. current motorcycle security solutions encompass various approaches, including mechanical locks, alarm systems, immobilizers, and basic gps tracking devices. while these technologies provide some level of protection, they suffer from significant limitations including vulnerability to tampering, lack of real-time monitoring, poor integration capabilities, and limited user interaction interfaces. recent advances in internet of things (iot) technology, sensor systems, and mobile communications present unprecedented opportunities to develop more sophisticated and effective security solutions. despite the availability of various security technologies, existing motorcycle theft prevention systems exhibit several critical gaps: azojete september 2025. vol.21(3):847-856 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/015 www.azojete.com.ng mailto:amibrahim@futminna.edu.ng mailto:amibrahim@futminna.edu.ng mailto:amibrahim8383@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 848 i. limited integration: most current systems operate as standalone solutions without comprehensive integration of multiple security technologies. ii. inadequate real-time monitoring: existing systems lack effective real-time monitoring and immediate alert capabilities. iii. poor user interface: limited user-friendly interfaces for system monitoring and control. iv. single point of failure: reliance on single communication channels or detection methods. v. insufficient detection sensitivity: poor ability to distinguish between authorized and unauthorized access or movement. the key objective of this paper is to develop an integrated iot-based motorcycle theft prevention system that combines multiple sensor technologies, real-time communication, and user-friendly interfaces for enhanced motorcycle security. the project involves designing and implementing a multi-sensor detection mechanism that combines gyroscope-based vibration detection and load sensors to provide comprehensive theft detection, alongside developing real-time tracking capabilities using gps technology integrated with wireless communication systems. a mobile application interface is created for system monitoring, control, and alert reception, ensuring users can manage the system conveniently. the system’s performance is evaluated in terms of detection accuracy, response time, and reliability under various operational conditions to ensure robustness. key contributions include the novel integration of gyroscope and load sensors for enhanced theft detection, a multi-channel communication system employing sms, wi-fi, and cloud-based notifications for redundant and reliable alert delivery, the development of a comprehensive mobile app for real-time monitoring and control, and a systematic evaluation of system performance across multiple metrics and network environments. the remainder of this paper is organized as follows: section 2 presents a comprehensive review of related works and gap analysis. section 3 details the system design and methodology. section 4 presents the implementation and testing procedures. section 5 discusses the experimental results and performance analysis. section 6 addresses system limitations and challenges. section 7 concludes the paper and outlines future research directions. kigambiroha (2023) developed a motorcycle theft prevention system integrating rfid, gsm, and gps technologies. the system featured motion detection, alarm mechanisms, rfid-based access control, and real-time gps tracking. however, the system's heavy dependence on rfid technology created vulnerabilities including susceptibility to rfid cloning attacks, limited range of operation, and potential system failures due to rfid card loss or damage. similarly, ananda and amin (2023) designed an rfid-based ignition control system utilizing rfid cards and ktp verification for unauthorized access prevention. while innovative, the system's reliance on rc522 modules and ktp components raised concerns about system robustness and scalability in diverse operational environments. kumar et al. (2023) proposed an iot-based vehicle theft prevention system combining gps and gsm technologies for remote tracking and security enhancement. the system demonstrated effective real-time location monitoring capabilities. however, critical limitations included heavy dependence on gsm connectivity, vulnerability to signal interruptions in remote areas, and lack of multi-sensor integration for comprehensive threat detection. agarwal (2021) developed a vehicle theft prevention system emphasizing ease of installation, user-friendly interfaces, and cost-effectiveness. despite these advantages, the system faced challenges including gps accuracy limitations in urban environments, constrained battery life, signal interference issues, and extended data processing times affecting real-time response capabilities. wenda (2022) implemented a motorcycle theft prevention system using arduino uno with ultrasonic and pir sensors for intrusion detection. while the research provided valuable insights into sensor effectiveness, limitations included narrow sensor technology evaluation, insufficient consideration of real-world deployment challenges, and lack of comprehensive integration testing. fernandez et al. (2022) developed twamats, a comprehensive device-based system incorporating alarms, fingerprint sensors, wi-fi modules, various sensors, gps, and microcontrollers. the system included a mobile application for image viewing and location history management. however, concerns arose regarding wi-fi dependency, potential data security vulnerabilities, and system complexity affecting reliability. jauhari et al. (2022) introduced a motorcycle security system combining touch key functionality with voice commands for engine ignition control. while demonstrating innovation in user interface design, the system required extensive testing for bluetooth module reliability and voice recognition accuracy under varying environmental conditions. jajuli et al. (2021) designed a system integrating voice commands, fingerprint verification, smartphone monitoring, and iot technology. despite comprehensive feature integration, the system's dependence on internet connectivity and potential susceptibility to environmental interference raised questions about operational reliability. syahputra and zachary (2021) utilized fuzzy logic and iot technologies for realtime theft prevention through sensor-based http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 849 alarm activation and telegram notifications. while innovative in analytical approach, the system's complexity and platform dependency on telegram limited its broader applicability and user adoption potential. based on this comprehensive analysis, the identified gaps that our research addresses include: (1) lack of robust multi-sensor integration combining vibration and load detection, (2) absence of redundant communication channels for reliable alert delivery, (3) limited real-world performance validation across diverse network conditions, (4) insufficient user interface development for practical system management, and (5) inadequate consideration of power management and system scalability issues. table 1 summarizes the research gap. table 1: summary of research gap research technology used strengths limitations gap addressed kigambiroha (2023) rfid, gsm, gps multi-technology integration rfid vulnerability, single point failure sensor redundancy needed kumar et al. (2023) iot, gps, gsm real-time tracking gsm dependency, limited sensors multi-sensor integration fernandez et al. (2022) multiple sensors, gps comprehensive features wi-fi dependency, security concerns robust communication channels agarwal (2021) gps, basic tracking cost-effective, userfriendly limited accuracy, battery constraints enhanced power management wenda (2022) arduino, pir, ultrasonic sensor integration insights limited scope, deployment gaps real-world validation needed 2. materials and methods the proposed iot-based motorcycle theft prevention system employs a multilayered architecture comprising sensing, processing, communication, and user interface layers. the system architecture ensures redundancy, reliability, and scalability while maintaining cost-effectiveness and user-friendliness. 2.1 sensing subsystem the sensing unit contains sensors used to detect and track motion, weight changes and direction. 2.1.1 gyroscope sensor the gyroscope serves as the primary vibration detection mechanism, capable of detecting orientation changes and movement patterns indicative of theft attempts. the sensor is calibrated to establish baseline readings during normal motorcycle stationary states and programmed to trigger alerts when deviations exceed predefined thresholds. calibration procedures include setting sensitivity parameters to distinguish between environmental vibrations (wind, nearby traffic) and suspicious activities (unauthorized movement, lifting attempts). 2.1.2 load sensor the load cell detects weight variations on the motorcycle seat, providing secondary confirmation of unauthorized access. the sensor is strategically positioned to monitor seat occupancy and can differentiate between authorized users (based on weight profiles) and potential theft scenarios (sudden weight removal or abnormal loading patterns). 2.1.3 gps module the global positioning system module provides continuous location tracking with high accuracy. the module is configured for periodic location updates and emergency tracking modes, ensuring minimal power consumption during normal operation while maintaining rapid response capabilities during theft events. http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 850 figure 1: block diagram of the system. 2.2 processing unit the esp32 serves as the central processing unit, coordinating all system components through its highperformance dual-core processor and integrated wireless capabilities. key features utilized include: (1) dualcore architecture enabling parallel processing of sensor data and communication tasks, (2) built-in wi-fi and bluetooth capabilities for local connectivity, (3) multiple gpio pins for sensor interfacing, (4) low-power modes for extended battery operation, and (5) robust security features for data protection. 2.3 communication subsystem the gsm communication module provides cellular connectivity for sms alerts and cloud data transmission. the module supports multiple network bands ensuring compatibility across different regions and network providers. features include automatic network selection, signal strength monitoring, and failover capabilities. integrated esp32 wi-fi capabilities enable local area network connectivity for configuration updates, data synchronization, and high-speed data transmission when within range of known networks. 2.4 power management the power subsystem utilizes high-capacity lithium-ion batteries selected for their superior energy density, low self-discharge characteristics, and extended operational lifespan. the power management circuit includes: (1) battery monitoring and protection circuits, (2) intelligent charging controllers, (3) power optimization algorithms, and (4) emergency power modes for extended operation during theft events. 2.5 embedded software the esp32 software, built with the arduino ide, is designed with a modular structure to ensure it is easy to maintain and expand over time. it brings together four key parts: the sensor management module, which takes care of setting up sensors, cleaning up the data, and filtering out noise; the decision engine, which interprets that data, adjusts intelligently with machine learning, and decides when to raise alerts; the communication handler, which ensures smooth and reliable connections through gsm, wi-fi, and the cloud; and power management, which keeps an eye on battery health, saves energy when possible, and extends operating time. altogether, these modules make the system smart, adaptable, and efficient. 2.6 mobile application design the mobile application is built with flutter to ensure smooth performance on both android and ios, following the model-view-controller (mvc) design pattern for clean and scalable development. it offers user-friendly features such as real-time gps tracking with interactive maps, instant security alerts via push notifications, historical route tracking, system calibration tools, battery monitoring, and strong authentication for secure access. on the backend, firebase firestore powers a reliable and scalable cloud infrastructure, with cloud functions managing data processing, notifications, and analytics. system integration is carried out in structured http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 851 phases. starting from individual component testing, then subsystem integration, parallel software development, full system assembly, and finally, rigorous field testing in real-world conditions. to ensure accuracy and reliability, the system undergoes careful calibration: gyroscopes are tuned for theft detection sensitivity, load sensors are adjusted for weight thresholds and environmental factors, and gps accuracy is verified against reference points while balancing power efficiency. figure 2 shows the mobile application interface of a message received. figure 2: whatsapp notification of the system. 2.7 implementation and testing 2.7.1 prototype development the system prototype was developed following the architectural specifications outlined in section 3. the implementation process involved careful selection of commercial-grade components, custom pcb design for sensor integration, and robust enclosure design for environmental protection. the prototype incorporates all specified hardware components within a compact, weatherproof housing suitable for motorcycle installation. 2.7.2 testing procedures and protocols location tracking experiments were conducted systematically throughout multiple days to evaluate gps accuracy under various conditions. testing involved collecting coordinates at predetermined locations and comparing measured values against established google maps references. the comprehensive approach included multiple time points across different environmental conditions, ensuring thorough evaluation of realtime location capture capabilities. load sensor testing employed systematic weight application procedures using calibrated weights ranging from 5kg to 25kg. each weight increment was applied systematically, and corresponding detection status was recorded to verify system sensitivity and threshold accuracy. vibration detection testing exposed the system to controlled vibration inputs across a range from 800 to 3500 units, measuring system responsiveness and detection consistency. tests were conducted under controlled laboratory conditions to establish baseline performance metrics. communication system performance was evaluated across multiple network providers (mtn, airtel, glo, 9mobile) under varying network conditions. testing protocols measured delivery times for sms alerts, whatsapp notifications, and mobile application push notifications. network speed measurements were recorded in kilobytes per second, with corresponding delivery times documented for comprehensive performance analysis. 3. results and discussion 3.1 location tracking performance analysis the location tracking system demonstrated exceptional accuracy with minimal coordinate deviations as shown in table 2. analysis of gps performance revealed consistent accuracy levels with average deviations of http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 852 ±0.000005 degrees in both latitude and longitude measurements compared to google maps reference coordinates. table 2: location tracking accuracy results time instance measured longitude measured latitude reference longitude reference latitude deviation (degrees) 12:00:05 6.452168 9.531246 6.452173 9.531251 0.000007 12:02:12 6.452399 9.531568 6.452404 9.531573 0.000007 12:02:44 6.452519 9.531343 6.452524 9.531348 0.000007 12:03:05 6.452632 9.531216 6.452637 9.531221 0.000008 12:04:30 6.452763 9.530988 6.452768 9.530995 0.000009 the location tracking results demonstrate exceptional accuracy suitable for real-world theft prevention applications. the minimal deviations (less than 1 meter in practical distance) ensure reliable location identification for recovery operations. consistency across multiple time instances indicates robust gps module performance and effective signal processing algorithms. figure 3: location tracking interface screenshot 3.2 load sensor detection performance load sensor testing confirmed reliable detection capabilities across the entire tested weight range as shown in table 3. the system successfully detected all applied weights from 5kg to 25kg, demonstrating appropriate sensitivity for motorcycle security applications. load sensor performance exceeded expectations with 100% detection success rate and rapid response times under 120 milliseconds. the increasing detection confidence with higher weights demonstrates proper calibration and sensor sensitivity. these results confirm the sensor's capability to reliably detect unauthorized seat occupancy changes indicative of theft attempts. http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 853 table 3: load sensor detection results applied weight (kg) detection status response time (ms) detection confidence (%) 5 detected 120 98.5 10 detected 115 99.2 15 detected 110 99.8 20 detected 108 99.9 25 detected 105 99.9 3.3 vibration detection analysis vibration detection testing revealed consistent performance across diverse vibration intensity levels, confirming the system's capability to detect unauthorized movement attempts as shown in table 4. table 4: vibration detection performance results test instance vibration reading (units) detection status false positive rate (%) sensitivity level 1 800 detected 2.1 high 2 1200 detected 1.8 high 3 1500 detected 1.5 optimal 4 2500 detected 0.8 optimal 5 3500 detected 0.3 maximum vibration detection results demonstrate excellent sensitivity with 100% detection success and decreasing false positive rates at higher vibration levels. the optimal sensitivity range (1500-2500 units) provides the best balance between detection reliability and false alarm minimization, making it ideal for real-world deployment scenarios. 3.4 communication system performance communication performance testing across multiple network providers revealed variable response times influenced by network infrastructure and signal strength conditions as shown in table 5. table 5: multi-network communication performance analysis network provider average speed (kb/s) sms delivery time (s) app notification time (s) whatsapp delivery time (s) reliability score (%) mtn 675 3 2 4 96.8 airtel 550 8 7 9 94.2 glo 750 1 2 3 98.1 9mobile 425 10 8 12 91.5 communication performance analysis reveals significant variation across network providers, with glo demonstrating superior performance in terms of delivery speed and reliability, while 9mobile showed the longest delivery times. the multi-channel approach ensures redundant communication pathways, with at least http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 854 one channel achieving delivery within 10 seconds across all tested scenarios. this redundancy is crucial for reliable alert delivery during theft events. figure shows the bar chart of the multi-network communication performance analysis. the graph shows that glo network has the highest speed compared to others followed by mtn network. 3.5 system integration performance comprehensive system testing demonstrated successful integration of all components with coordinated operation under various scenarios. the system achieved 98.7% overall reliability with mean time between failures (mtbf) exceeding 720 hours during continuous operation testing. this is shown in figure 5 where the mobile application showing the bike status displayed. it shows when the bike is in danger and the time stamp. figure 4: multi-network communication performance analysis figure 5: mobile application interface screenshots http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 855 the prototype of the system was designed and implemented according to the required specifications, with all hardware needed, the system was successful and performed as expected. plate 1 shows the protype of the developed system. plate 1: prototype of the system. 3.6 implementation challenges the system faces several limitations and challenges across technical, environmental, implementation, and security domains. technically, gps accuracy can degrade in dense urban or indoor settings, battery life drops with intensive use, and balancing sensor sensitivity against false alarms remains difficult. environmentally, extreme weather and dense urban electromagnetic interference threaten sensor accuracy and communication quality, while network coverage gaps impede alert delivery. implementation challenges include installation complexity requiring expertise, unit costs limiting affordability, and scalability concerns with server capacity and communication costs. security and privacy issues arise from the risk of sophisticated cyberattacks on iot devices and sensitive gps data handling subject to regulatory compliance. future mitigation plans involve advancing sensor fusion, power management, weatherproofing, cost reduction via volume manufacturing, and expanding connectivity through lora, satellite, and 5g to enhance coverage and reliability. 4. conclusion this research successfully developed and validated a comprehensive iot-based motorcycle theft prevention system that integrates multiple sensor technologies such as; gyroscope-based vibration detection, load sensing, and gps tracking. also, a multi-channel communication for robust theft detection and alerting were embedded. the system demonstrated exceptional performance with highly accurate location tracking (±0.000005 degrees), perfect sensor detection success (100%), and reliable communication (98.7%). a user-friendly mobile application enables real-time monitoring and control, while redundant communication channels ensure alert delivery across varying network conditions. the solution provides scalable, cost-effective, and superior security compared to single-technology systems, laying a solid foundation for future research and commercial deployment in iot-based motorcycle security. looking ahead, future work will focus on making the system smarter, more reliable, and widely deployable. advanced machine learning, including neural networks and deep learning, will be integrated to predict threats more accurately and adapt thresholds in real time, reducing false alarms while keeping security strong. the sensor suite will be expanded with biometrics, advanced motion detectors, and environmental monitoring to provide richer, more precise data. a cloud-based analytics platform will enable predictive maintenance, community-driven security insights, and proactive threat prevention using big data and ai. integration with smart city infrastructure such as; traffic systems, law enforcement, and surveillance networks will allow coordinated responses and support broader urban safety goals. communication will also be strengthened through emerging technologies like 5g, lora, and satellite links, ensuring reliable performance even in remote areas. http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 847-856. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: amibrahim@futminna.edu.ng 856 acknowledgements the authors sincerely appreciate the support provided by the tertiary education trust fund (tetfund) institution-based research intervention (ibri), federal university of technology, minna, nigeria, for sponsoring this research titled " development of a smart automobile theft prevention and tracking system" (grant no. tetfund/futminna/2024/056). references agarwal, v., sharma, s. and agarwal, p. 2021. iot based smart transport management and vehicle-to-vehicle communication system. in proceedings, 709–716. ananda, r. and amin, m. 2023. use of ktp to activate start motorcycle engine with module rc-522. jurteksi (jurnal teknologi dan sistem informasi), 9(3): 515–520. fernandez, rb., theodore, d. and seroje, r. 2022. two-way motorcycle authentication with alerting and tracking system using mobile application. international research journal of advanced engineering and science, 7(3): 246–255. jajuli, e., effendi, mr., kamelia, l., mardiati, r., miharja, d. and zaki hamidi, ea. 2021. the implementation of motorcycle security system using voice commands and fingerprint sensors. proceeding of 15th international conference on telecommunication systems, services, and applications, tssa 2021. jauhari, mf., maryati, rs. and raihan, r. 2022. design of touch key-voice command based vehicle additional security system. proceedings of the 5th first t1 t2 2021 international conference (first-t1-t2 2021), 9: 255–259. kigambiroha, m. 2023. motor cycle theft control system using rfid, gsm and gps technology. busitema university institutional repository. kumar, jmsvr., shahi, a., aytha, r., varri, g. and brundavanam, d. 2023. vehicle theft prevention system using iot. aip conference proceedings, 2492(1). ojedokun, oa. and ogundipe, aa. 2017. motor vehicle theft in nigeria: socio-economic implications and the way forward. international journal of criminal justice sciences, 12(2): 274-290. syahputra, z. and zachary, mf. 2021. application of fuzzy logic in motorcycle security systems based on internet of things (iot). infokum, 10(1): 595–603. wenda, a. 2022. a new approach to motorcycle theft prevention system based on arduino uno. sinkron : jurnal dan penelitian teknik informatika, 7(4): 2317–2328. http://www.azojete.com.ng/ mailto:amibrahim@futminna.edu.ng corresponding author’s email address: gambo.anthony@yahoo.com 637 arid zone journal of engineering, technology & environment original research article drone equipment and configuration for detecting theft in telecommunication infrastructure c. o.njoku1, a. v.gambo2*, and y. bello3 1department of mechanical engineering, air force institute of technology, kaduna 2department of mechanical engineering, ahmadu bello university, zaria 3department of mechatronics engineering, air force institute of technology, kaduna *corresponding authors’ email: gambo.anthony@yahoo.com article information abstract drone aircrafts, also known as an unmanned aerial vehicle (uav) or unmanned aircraft systems (uas) has gained more importance in environmental monitoring as well as in telecommunication infrastructure theft response around the world. the study aims at identifying the type of sensors that can be mounted on drones for effective telecommunication infrastructure theft detection and prevention. the various parts of drone and configuration were tested. sensors capable of detecting telecommunication infrastructures in the visible, infra-red, near infra-red, laser fluoro-sensor were all evaluated. the ability of the uav to continuously and successfully patrol along or beside telecommunication infrastructure reveals that it takes about 5 minutes for the uav to complete a programmed 150m autonomous patrol. during power test, result showed that for every 150m programmed patrol, 15 minutes of solar charging is required to restore the battery back to its initial voltage. it was concluded that a drone can properly be used for telecommunication infrastructure theft response operations. appropriate sensors mounted on the drone can detect telecommunication infrastructure theft and can also access locations which are not readily accessible and other aerial patrol platform. the limitation of drones is the payload capability and its inability to operate well in windy weather since data collection with drone are faster, cheaper and easier during telecommunication infrastructure theft response operations. it is highly recommended to mount the suitable sensor capable of detecting telecommunication theft and vandalization even during nighttime operations. received: 19th february 2025 revised: 31st april 2025 accepted: 1st may 2025 keywords: uav drones telecommunication infrastructuresensor © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction a drone can be defined as “a land, sea or air vehicle that is remotely or automatically controlled (domaille and campion, 2018). drone aircrafts, also known as an unmanned aerial vehicle (uav) or unmanned aircraft systems (uas) has gained more importance in environmental monitoring as well as in telecommunication infrastructure theft response around the world. the operations that require the use of a drone are both for simple freight transport and for dealing with natural disasters such as an earth quake, fires, floods, tsunamis and similar emergencies (michail et al., 2019). drone aircrafts have the potential to deliver information quickly and economically in areas with access difficulties and have the ability to fill an important gap in surveillance capability (joshi, 2019). uav are able to fly with high altitudes above clouds which minimizes the cloud effects in imaging and targeted object appreciation. they are able to overcome some of the limitations encountered by other means of aerial and in situ observations. for instance, satellite observations can be constrained by the sensor’s spatial and spectral resolutions, atmospheric conditions, revisit time and cost (domaille and campion, 2018). for the drone to achieve this there are some auxiliary equipment and configuration needed to ensure it has the capability of performing the effective function of surveillance and detection. azojete june 2025. vol.21(2):637-645 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/028 www.azojete.com.ng mailto:gambo.anthony@yahoo.com mailto:gambo.anthony@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 638 the incorporation of infra-red/night vision technology can aid in its visibility in unlit areas or at night. such human surveillance activities have been performed for some time by the military and by civilian police forces and the technology is now crossing over into commercial use. according to guarnera (2023), applications such as “drone in a box” are becoming available (where surveillance drones are flown and charged autonomously as an alternative to patrolling sites). drone technology is already in limited use with many network operators and tower owners although its applications are far from ubiquitous (passifiume, 2017). to date, the use of drones in telecommunication industries has focused on the “drone technology” itself. focus is now being shifted to how the output from drone surveillance can be better utilized in telecomm infrastructure theft detection. this is so because drones have now become more accurate, reliable, self-aware (in respect of their surroundings) and better at capturing images (bleiberg, 2014). such drones can be used to obtain reliable and real time information by triggering signals about physical objects through the process of recording, measuring and interpreting photographic images. both drone technology and photogrammetric software modeling technology have evolved sufficiently which has made it possible to create accurate representations of three dimensional structures (such as towers, communication masts) from the image and positioning data collected by drones. the images are post processed (usually as a service-triggering alarm) and the output is then made available to decision makers (chris, 2023). the telecommunications industry plays a vital role in keeping us connected, and the integration of drones into this field is revolutionizing how we maintain and expand these networks. as drones in telecommunications industry become increasingly prevalent, they are transforming the way companies approach tower inspections, network expansions and emergency response time. with benefits such as efficient tower inspections, improved network planning and cost savings, the use of drones in the telecommunications industry has grown rapidly. according to rejeb (2023), the use of drones with smart intrusion detection and alarm systems to curb theft and vandalism of telecomm infrastructures has helped to eliminate the following challenges associated with the traditional human-based methods: i. cost savings: drones offer significant cost savings in the telecommunications industry by reducing the need for manual labour and expensive equipment. they can quickly perform tasks that would otherwise require specialized equipment or teams of technicians, such as tower inspections, mapping and network planning. additionally, drones can minimize downtime by identifying issues before they cause network outages thereby reducing maintenance costs, ii. improved safety: the use of drones in telecommunications greatly enhances worker safety. climbing towers for inspections and maintenance can be dangerous and accidents can result in injuries or even fatalities. drones eliminate the need for technicians to climb towers in many cases, reducing the risk of accident and promoting a safer work environment, iii. increased efficiency: drones can perform tasks more quickly and accurately than humans, increasing efficiency in the telecommunications industry. they can inspect towers, map terrain and test signal strength in a fraction of the time it would take a team of technicians. this improved efficiency allows companies to better allocate resources and focus on other critical aspects of their operations, iv. better data collection: drones equipped with advanced sensors and cameras can collect valuable data that can be used to optimize networks, monitor infrastructure and plan future expansions. highresolution imagery, 3d models and signal strength data provide companies with the information they need to make data-driven decisions and improve their operations. the disabling of critical communications networks due to vandalism and theft has a significant impact on essential public services like emergency response, health care, energy grids and public transportation which can lead to broader societal costs and potential risks to public safety. the vandalization of these public infrastructures can lead to service disruptions, increased service charges, revenue decline, increased expenditure on security measures and erosion of public trust (schwung, 2022). 2. materials and method 2.1 materials the materials used for this research includes: http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 639 2.1.1 uav system uavs are particularly useful in areas where landing and take-off runs are impossible and they are also portable. the high power consumption for hovering flights relatesto their flight durations (typically to one hour based on electric motors and rechargeable batteries), although the largest platforms can accommodate larger fuel capacity. control is typically via line-of-sight and for a quick analysis. they are readily deployable using a one or two-man crew for the programmed intrusion/vandalism detection mission. the modeled and dimensioned 3-d structure of the uav system is as shown in figure 1. figure 1: 3-d modeling and dimensioning of the uav system 2.1.2 development board the development board used in the uav system to perform autonomous intrusion/vandalism detection was the arduino uno rev. 2.1.3 global positioning system the arduino gps shield is a gps module breakout board designed for global positioning system tracking as shown in plate 1. it requires a supply voltage of 5v and operates at a baud rate of 38,400 bps. it has an onboard sd card slit for data storage and often stacked on top of the arduino board placed on the uav system. plate 1: gps shield and antenna mounted on arduino uno rev 2.1.4 xbee a pair of xbee pro 900 hp wireless modules is used to establish wireless communication between the uav unit and the host pc at the remote base station. the basic parameters of the module are shown in table 1. http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 640 table 1: relevant parameters of the xbee pro hp module parameters specifications rf band rate 900mhz rf data rate 10 kpbs 0r 200 kbps indoor urban range (2.1 db antenna) 10 kpbs up to 2,000 ft (610 m) 200 kpbs up to 1,000 ft (305m) outdoor los range (2.1 db antenna) 10 kpbs up to 9 miles (15.5km) 200 kpbs up to 4 miles (6.5km) supply voltage 2.1v – 3.6v transmit voltage 215ma receive voltage 29ma 2.1.5 motor shield a mega motor shield for arduino was used to connect the 12v motors to the 12v lead acid battery. the motor shield draws its power supply from the 12v lead acid battery and feeds that to motors ‘a’ and ‘b’ of the uav system depending on the logic signal it receives from the program uploaded into the arduino uno rev as shown in plate 2. plate 2: connections for mega motor shield and mega motor shield stacked on arduino uno rev 2.1.6 magnetometer plate 3 depicts a magnetometer which used to ensure an accurate 180 degrees turn in the opposite direction after the completion of the patrol so that the uav system can patrol in the opposite direction. plate 3: magnetometer 2.1.7 ultrasound sensor the hc-sr04 as depicted in plates 4(a) and 4(b) are ultrasound sensors which are capable of transmitting and receiving ultrasound waves. during patrol, using the hc-sr04 sensor, if the uav system detects an obstacle http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 641 less than 35cm in front of it, it takes a detour route to avoid the object before continuing along its patrol route. plate 4: hc-sr04 sensor 2.1.8 camera the ls-y201-infrared camera as shown in plates 5(a) and 5(b) captures high resolution pictures using serial port. the infrared feature has a built-in sensor to sense the ambient light and will automatically turn on infrared leds when light intensity is low. it requires a power supply of 3.3v or 5v, a current consumption rate of 80 – 200ma and a serial baud rate of 38,400 bps and the image resolution is set to 320×240 pixels (yin, 2013). plate 5: ls-y201-infrared camera 2.1.9 solar panel in other to maintain continuous power supply to the uav system, a solar panel was incorporated into the system. the solar panel has an output power of 8w, an output voltage of over 18v and an output current of 450 ma. it is made from polycrystalline cell and keeps batteries charged for optimum performance. 2.2 method the schedule of the research methodology for this research work ranged from the feasibility study on drone surveillance application, uav configuration, sensor integration and testing procedures. 2.2.1 uav system requirements the hierarchical decomposition of the uav system which ranges from power, propulsion, structures, guidance, navigation and control (gnc), payload, battery, inertial measurement unit (imu), flight computer, radar, motors, global positioning system (gps), body, arms and landing gear is as outlined in figure 2. http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 642 fig. 2: hierarchical decomposition of the uav system 2.2.2 technical specifications the set of key performance indicators which are capable of describing the performance competence of the uav system is as outlined below in table 2. table 2: design specifications of the uav system specifications values dimensions 405mm x 371mm x 70mm weight 1000g power 200w rotors 4 propellers 10” x 4.5” (10” in diameter and 4.5” in pitch) battery 3300mah (c) 3s lipo 35c (max) controller arduino uno rev 3 payload mass 150g diagonal size (propellers excluded) 520mm motors (for medium size uav of 500mm) a2212 brushless out runner dc motor, 1000kv. no load current @ 10v:0.5a. thrust @ 3s with 1045 propeller 800gms approx.. current capacity 12a/60s motor dimensions 27.5 x 30mm esc specification 18a (30a recommended) propellers rpm 7536 rpm input voltage 11.1v pitch speed 32.1 mph (51kmh) efficiency 80% weight to be lifted by the uav 2kg or more flight time up to 15 minutes 2.2.3 flight dynamics figure 3 depicts the uav flight dynamics that was taken into cognizance as defined by the inertial frame. uav’s position with respect to the ground along with the gravity pointing in the negative z-direction and the body frame which was defined by the uav’s different orientations. we also considered six degrees of freedom which described any time space motion of a rigid body in motion. it was made up of three translational motions that made the uav move longitudinally (forward and backward), vertically (upward and downward) and laterally (right and left). in addition, there were three rotational motions along three axes which made the uav move rotationally among each axis to produce roll, pitch and yaw movements. http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 643 figure 3: the relative orientation between inertial frame and body frame of a uav in 3d space 2.2.4 testing procedures the experimentation was carried out in accordance with the procedures of dmitryet al., (2018). as the uav system moves towards the telecommunication intrusion/vandalized site, it simultaneously checks for any intrusion using the hc-sr04 sensor mounted in front of the uav. on detection of any intrusion/vandalism, it stops and takes pictures of such intrusion/vandalism via the ls-y201-infrared camera which captures high resolution pictures using serial port. images and gps location of the intrusion site are sent wirelessly to the host pc at the base station via the xbee modules and such intrusion can be verified from the acquired images. similarly, during patrol, the unit constantly checks to ensure that it was travelling in the correct direction using the onboard magnetometer and if the unit drifts away from its original direction, a path adjustment algorithm was employed to return it to the correct direction. furthermore, the uav system was programmed to autonomously detect and avoid obstacles along its surveillance path using hc-sr04 sensor. in the event of obstacle detection less than 35cm away from the uav system, it takes a detour route to go around the obstacle before resuming its patrol. upon arriving at the end location, the uav system turns 180 degrees using information provided by the onboard magnetometer. after turning, the system waits at a preset time interval of 30minutesbefore patrolling the intrusion site again on a return mission. the gps data for the end and start locations were interchanged so that the unit can patrol in the opposite direction. in every one hour, the uav system patrolled the 150m stretch of the intrusion site for approximately 5 minutes. the uav system will be able to detect any intrusion/vandalism, capture 320 × 240 pixel images of the intrusion/vandalism site and transmits the intrusion/vandalism gps location and images to a pc at a remote base station, 100m away from the intrusion/vandalism site within 10 seconds. the gps latitude of the surveillance route ranges from 5.53986o–5.53977o. when the uav system detects an intrusion or physical tampering of the infrastructure, its gps longitude may range from 5.82597o–5.82525o. the variation from its pre-set range signals an intrusion or physical tampering will automatically make the uav system to wirelessly issue an alarm message to the host pc at the remote base station, signaling the surveillance team that an intrusion or physical tampering has been detected. after alerting the surveillance team to the presence of an intrusion, the uav system will continue its patrol of assigned surveillance route. in addition to the gps location of the intrusion, the system will also capture 320 × 240-pixel image of the intrusion and then transmit a picture of the vandalization or intrusion taken by its onboard camera module within the 10 seconds. so not only does the surveillance team know that an intrusion has occurred and its location, they are also to visually see the vandalized or intruded section of the infrastructure. the base station was located approximately 100m away from the surveillance route and the remote pc with the receiving xbee module was at the base station. the decision-making model of the uav system that can be commercialized is shown in figure 4. when the uav system is initialized, it obtains its current location using global positioning system (gps). it also obtains the gps location of the start and end points of the intrusion/vandalization it is assigned to detect as well as its orientation using the onboard magnetometer. north, south, east and west orientation information was also acquired by magnetometer, which assures that the uav system is travelling in the correct direction. http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 644 figure 4: decision-making model of the uav 3. results and discussions the ability of the uav system to proffer short-, mediumand long-term solutions was evaluated under the following criteria: 3.1 surveillance patrol the ability of the uav to continuously and successfully patrol along or beside telecommunication infrastructure reveals that it takes about 5 minutes for the uav to complete a programmed 150m autonomous patrol. this result is in agreement with the works ofjoshi (2019) in their study they stated that once the unit completes its surveillance patrol, it stops and turns 180 degrees to face the opposite direction within 5 minutes. 3.2 power test the 12v battery of the uav system was measured before and after the completion of the 150m patrol. during time intervals between patrols, an 18v solar panel will charge the 12v battery to ensure continuous availability of power supply between patrols. for every 150m programmed patrol, 15 minutes of solar charging is required to restore the battery back to its initial voltage as stated elsewhere (bleiberg, 2014). table 2 gives the result of the battery test for the uav during the surveillance patrol. table 2: battery test for uav system during and in-between surveillance patrol initial battery voltage (v) patrol time (m) patrol distance (m) battery voltage after patrol solar charging time (m) final battery voltage (v) 12.92 5 150 12.65 15 12.92 12.92 5 150 12.65 30 12.98 3.3 obstacle avoidance the hc-sr04 ultrasonic sensor on the uav system was programmed to automatically alert the unit in case of an obstacle in front of it. a detour route to avoid the obstacle was taken by the uav when the sensor detects any obstacle less than 35cm in front of the uav system. this is in agreement with previous works by stewart, (2018). 4. conclusion the research has delved into the many ways drones are revolutionizing the telecommunication industry. a survey of current drone detection and classification techniques indicates a fast-expanding area characterized by considerable technological advances and novel approaches. the fast development in the usage of uavs has prompted serious issues about privacy, security and safety. as a result, developing effective uav detection algorithms has become critical. the paper has offered an overview of several uav detection approaches, such as radar-based, acoustic-based, rf-based and visual-based approaches. however, the discussion also emphasized the inherent challenges that persist. the size and speed diversity of drones, their dynamic behavior http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 637-645. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: gambo.anthony@yahoo.com 645 and similarity to other flying objects and their limited battery life make the detection task more challenging. additionally, different interference factors in real-world scenarios, including adverse weather and lighting conditions, urban locations with plenty of obstructions such as buildings and trees, ambient and background noise, wind, the presence of wireless communication signals from wi-fi and bluetooth sources, bird echoes, etc, present unique challenges for each detection modality. it is believed that this review article will be a helpful resource for academics, engineers and policymakers working in uav detection and classification. references bleiberg, j. 2014. new innovations that could change the world. availability in https://www.brookings.edu/blog/techtank/2014/06/10/10-new-innovations-that-could-change-the-world/ accessed on 30 october, 2024. chris g. 2023. connecting the world: how drones are revolutionizing the telecommunications industry. https://www.bluefalconaerial.com/home/contact/. accessed on 5 may, 2023. dmitry y. tyugin, aa. kurkin, vd. kuzin, dv. zeziulin, vs. and makarov, rv. 2018. the exploration of autonomous mobile robot movement”: characteristics in difficult off-road conditions of a coastal zone. international journal of imaging and robotics, 18(1). domaille, s. and campion, d. 2018: droning on: a review of uav use in recent surveillance attended by itopf and considerations for the future.available in https://www.itopf.org accessed on 20 january, 2025. guarnera, f. 2023: drone in a box: an overview of use and applications of uav for telecommunications infrastructure surveillance patrol.international journal of imaging and robotics, 11(4). joshi, d. 2019. drone technology: uses and applications for commercial, industrial and military drones in 2020 and the future. availability in https://www.businessinsider.com/drone-technology-uses-applications accessed on 30 october, 2024. michail, p., avraam, c. and dimitrios, p. 2019. uav flight control based on arduino board implementations.international journal of engineering applied sciences and technology, (4)5: 438-443. passifiume, b. 2017. university of calgary professor developing new drone technology. availability inhttps://calgaryherald.com/technology/science/vision-based-navigation-is-just-like-in-humans-calgaryprofessor-developing-new-drone-technologyaccessed on 7 january, 2025. rejeb, a., rejeb, k., simske, s.j. and treiblmaier, h. 2023. drones for supply chain management and logistics: a review and research agenda. int, j. logist. res. appl. 26: 708 – 731 schwung, m., lunze, j. 2022. cooperative control of uavs over an unreliable communication network. ieee aerosp. electron. syst. mag. 37: 20 -34 stewart, d. 2018. the use of drones in telecoms. availability in befutureready@techmahindra.comaccessed on 17 november, 2024. yin mm. 2013. development of process control with obstacle avoidance behavior in autonomous mobile model. international journal of imaging and robotics, 10(2). http://www.azojete.com.ng/ mailto:gambo.anthony@yahoo.com https://www.brookings.edu/blog/techtank/2014/06/10/10-new-innovations-that-could-change-the-world/ https://www.bluefalconaerial.com/home/contact/ https://www.itopf.org/ https://www.businessinsider.com/drone-technology-uses-applications https://calgaryherald.com/technology/science/vision-based-navigation-is-just-like-in-humans-calgary-professor-developing-new-drone-technology https://calgaryherald.com/technology/science/vision-based-navigation-is-just-like-in-humans-calgary-professor-developing-new-drone-technology mailto:befutureready@techmahindra.com corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 389 arid zone journal of engineering, technology & environment original research article energy storage: the key to reliable renewable energy grids s. n. ukagu1, m. o. atu1 and i. a. onyegbadue1* 1electrical and computer engineering department, college of engineering, igbinedion university, okada, edo state. *corresponding author’s email: onyegbadue.ikenna@iuokada.edu.ng article information abstract integrating intermittent renewable energy sources into the power grid poses significant challenges to grid stability and reliability. this study examines the integration of energy storage systems (ess) into power grids to enhance stability and performance. a simulation framework was developed to analyze the technical and economic viability of battery energy storage systems (bess) and pumped hydro storage (phs) systems. the results demonstrate the effectiveness of ess in alleviating voltage fluctuations, frequency deviations, and grid disturbances. a diversified energy storage portfolio with optimized siting and innovative market mechanisms maximizes the benefits of ess integration. the study reveals that bess excel in rapid response times and scalability, while phs systems offer superior economic benefits. this study pioneers a comprehensive simulation framework integrating technical, economic, and regulatory aspects to optimize energy storage systems (ess) integration, providing novel insights into maximizing grid stability and performance amidst escalating renewable energy integration. the findings provide valuable insights for policymakers, industry stakeholders, and researchers seeking to optimize energy storage strategies for resilient, sustainable, and efficient power systems. received: 23rd february 2025 revised: 9th april 2025 accepted: 29th may 2025 keywords: energy storage systems (ess) battery energy storage systems (bess) pumped hydro storage (phs) power flow analysis dynamic simulation © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the modern power grid is confronting an array of unprecedented challenges, largely stemming from the escalating integration of intermittent renewable energy sources, fluctuations in energy demand, and the urgent need for improved grid stability and reliability (hossain et al. 2018; das et al. 2024; shao et al. 2024; liu et al. 2023). these challenges have illuminated the critical need for innovative and efficient solutions capable of tackling the complexities inherent in contemporary power grid operations (zheng et al. 2024; zaidi et al. 2023; o’dwyer et al. 2019). among these solutions, energy storage systems (ess) have emerged as a pivotal element, providing a versatile tool for achieving grid balance, managing peak electricity demand, and enhancing overall grid stability (rana et al. 2023; onyegbadue et al. 2024; yekini et al. 2024). recent research has significantly underscored the importance of ess in mitigating various forms of grid instability that can arise from integrating renewable energy sources (gwon et al. 2022; baghayipour et al. 2018; wang et al. 2022; ostrowska et al. 2022). these studies have investigated how ess can effectively manage peak demand periods, thereby ensuring that the energy supply meets consumer needs during times of high usage (tushar et al. 2018; oskouei et al. 2022). through the development of simulation models, researchers have been able to analyze the effects of different types of ess on grid performance, exploring both the technical and economic feasibility of deploying lithium-ion batteries for grid-scale energy storage (sati et al. 2024; chen and chen 2018; farrokhabadi et al. 2018). furthermore, optimization models have been crafted to examine the role of ess in enabling better grid balancing and addressing peak demand, while also assessing the economic viability of incorporating these systems into existing power grid infrastructures (strielkowski et al. 2019; sarker et al. 2021; madueme and onyegbadue 2018). the integration of renewable energy sources, such as solar and wind power, into the grid presents new challenges, including issues of intermittency and variability (liang 2016; kalakotla and korra 2024; liang 2017). azojete june 2025. vol.21(2):389-400 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/007 www.azojete.com.ng mailto:onyegbadue.ikenna@iuokada.edu.ng mailto:onyegbadue.ikenna@iuokada.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 390 these challenges can lead to destabilization of the grid, diminished power quality, and heightened greenhouse gas emissions (gowda et al. 2018; mascarella et al. 2015; pawar and bavdhane 2022; sharma et al. 2023; almohaimeed and abdel‐akher 2020). ess can serve as a critical buffer against these fluctuations, stabilizing energy supply and demand dynamics by storing excess energy during low-demand periods and releasing it during peak usage times (saldarini et al. 2023). the multifaceted potential of ess to enhance grid stability and performance has been recognized by both researchers and industry stakeholders (bahloul et al. 2024). the benefits offered by ess include but are not limited to, peak demand reduction, load-shifting capabilities, and overall grid stabilization (katsanevakis et al. 2017). nevertheless, the integration of ess into power grids does not come without challenges—technical, economic, and regulatory hurdles persist that must be addressed to facilitate successful implementation (de rosa et al. 2018; neubauer et al. 2015; liu et al. 2020; onyegbadue et al. 2022). despite the progress made in this field, considerable gaps remain in current research. for instance, relatively few studies have developed comprehensive models that encompass the diverse range of ess technologies available. additionally, there is a pressing need for refined control strategies that optimize the operation of ess in the context of grid balancing and peak demand management. detailed economic analyses are also lacking, which are essential for evaluating the economic viability of ess in various grid scenarios. moreover, comparative studies examining the strengths and weaknesses of different ess technologies are necessary to guide future advancements. to navigate these challenges, it is essential to cultivate a comprehensive understanding of ess technologies, their myriad benefits, and their inherent limitations. this effort necessitates a multidisciplinary approach that combines technical insights, economic assessments, and regulatory considerations. by advancing understanding in these areas, researchers and industry stakeholders can identify avenues for innovation and develop effective strategies for seamlessly integrating ess into power grids. this study intends to contribute significantly to the body of knowledge surrounding ess by simulating and critically analyzing the impact of these systems on grid stability and overall performance. the specific objectives of this research include modelling various types of ess—such as batteries and pumped hydro systems—to analyze their technical characteristics and performance under different scenarios, investigating how ess can play a crucial role in grid balancing and managing peak demand to uncover optimization opportunities, and assessing the economic feasibility of integrating ess into power grids to delineate the cost-benefit tradeoffs associated with their adoption. a pioneering simulation framework is introduced in this study, integrating technical, economic, and regulatory aspects to optimize energy storage systems (ess) integration and provide new insights into achieving maximum grid stability and performance amidst growing renewable energy capacity. the findings from this research will contribute to the formulation of more effective ess integration strategies, ultimately enhancing the stability and performance of the electrical grid in a rapidly evolving energy landscape. 2. materials and method this study utilized a comprehensive modelling approach to assess the integration of energy storage systems within power grids. specifically, battery energy storage systems (bess) and pumped hydro storage (phs) systems were modelled to capture their fundamental dynamics. the bess model incorporated equations for the state of charge and voltage dynamics, while the phs model included equations that describe the changes in potential and kinetic energy during both pumping and generation processes. these models were subsequently integrated into the power flow analysis to simulate their effects on the grid, considering the power output from energy storage systems within the power flow equations. a dynamic simulation was employed to evaluate the system's response to temporal changes, utilizing the solution of differential equations that characterize the dynamic behavior of the grid and the energy storage systems. additionally, a cost-benefit analysis was conducted to assess the economic viability of integrating energy storage, accounting for initial investments, operational and maintenance costs, as well as the economic lifespan of the energy storage systems. the study leveraged a variety of data sources, including power grid databases and historical grid operation data from the transmission company of nigeria, meteorological databases from nasa resources, and renewable energy plant data from existing renewable energy facilities in nigeria. furthermore, manufacturer specifications, along with research papers and technical literature, http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 391 were employed to gather parameters for the energy storage systems. the effectiveness of energy storage integration was evaluated through several performance metrics, including the voltage stability index (vsi), frequency deviation, round-trip efficiency, state of charge (soc) management, return on investment (roi), and the levelized cost of storage (lcos). the simulation methodology integrated power flow analysis, dynamic simulation, economic feasibility analysis, and sensitivity analysis, creating a comprehensive framework for evaluating the integration of energy storage into power grids, while considering both technical and economic dimensions. the simulation flow chat is contained in figure 1. figure 1: simulation flow chat the simulation flowchart, depicted in figure 1, is comprised of the following steps: i. initialization the program begins by initializing the necessary models, including the battery storage model and pumped hydro model. relevant data, such as grid and renewable generation data, is also loaded to initialize the energy storage simulation. ii. simulation of grid integration the simulation commences with the integration of grid data, marking the beginning of the energy storage simulation. iii. energy storage system simulation this step involves a time-step loop and the following processes were executed: a. battery simulation: the battery storage model is simulated and encompasses charging and discharging processes. b. pumped hydro simulation: the pumped hydro model is simulated, including pumping water and generating power. c. update grid power balance: the grid power balance is updated based on the simulation results. d. save state metrics: key state metrics, such as battery state of charge and reservoir level, are saved for future reference. http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 392 iv. economic analysis and results processing the economic metrics for both battery and pumped hydro systems are calculated. the computed economic metrics are then saved to csv files for further analysis. v. results of visualization various results are plotted to provide insights into the simulation, including: a. grid power balance b. battery state c. reservoir level d. grid stability metrics e. disturbance response vi. conclusion the simulation process concludes, marking the end of the program. 2.1 mathematical formulation the following equations illustrate a simplified model for a generic battery: a. state of charge (soc) dynamics: 𝑑𝑆𝑜𝐶(𝑡) 𝑑𝑡 = 𝑃𝑖𝑛(𝑡) − 𝑃𝑜𝑢𝑡(𝑡) 𝐶𝑏𝑎𝑡 where: soc(t) is the state of charge at time t, pin(t) is the power input to the battery at time t, pout(t) is the power output from the battery at time t, cbat is the battery capacity. the voltage dynamic equation can be modelled thus; 𝑉(𝑡) = 𝑉𝑛𝑜𝑚 − 𝑅𝑖𝑛𝑡 . 𝐼(𝑡) where: v(t) is the battery voltage at time t, vnom is the nominal voltage of the battery, rint is the internal resistance of the battery, i(t) is the current flowing through the battery at time t. these equations are derived based on principles of electrical engineering and battery dynamics. pumped hydro storage systems involve the elevation and release of water to generate electricity. the model includes equations describing the potential and kinetic energy changes during the pumping and generation processes. a. potential energy change: ∆𝑃𝐸 = 𝑚. 𝑔. ∆ℎ where: δpe is the change in potential energy, m is the mass of water, g is the acceleration due to gravity, δ h is the change in height. b. kinetic energy change: ∆𝐾𝐸 = 1 2 . 𝑚. (∆𝑣)2 where: δke is the change in kinetic energy, δv is the change in velocity. c. power output during generation: 𝑃𝑜𝑢𝑡(𝑡) = 𝜂𝑔𝑒𝑛 . 𝜌. 𝑔. 𝑄(𝑡). 𝜂𝑚𝑒𝑐ℎ where: pout(t) is the power output during generation, ηgen is the generator efficiency, ρ is the water density, g is the acceleration due to gravity, q(t) is the water flow rate at time t, ηmech is the mechanical efficiency. http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 393 these equations are derived based on principles of physics and fluid dynamics. 2.2 input parameters the input parameters for both the pumped hydro and battery storage systems for 100 mw capacity are given thus; table 1: input parameters for both systems parameter pumped hydro battery storage voltage in (v) 400 400 voltage out (v) 380 390 frequency in (hz) 50 50 frequency out (hz) 49.95 49.99 energy in (kwh/yr) 365,000,000 365,000,000 energy out (kwh/yr) 277,400,000 299,245,250 investment cost ($) 262,300,000 355,800,000 operational cost ($) 3,040,000 1,204,000 operational years 80 12 3. results and discussion the simulation results provide valuable insights into the effective integration of energy storage systems, encompassing both battery and pumped hydro technologies, within the power grid. these outcomes are derived from a simulation framework that exactly examines grid integration, system dynamics, and economic viability over a simulated period of 350 days. figure 2 presents a graphical representation of the simulated grid power balance throughout the simulation period. this plot showcases the intricate dynamics between renewable energy generation, grid demand, and the operation of energy storage systems. the fluctuations in the grid power balance, characterized by peaks and troughs, underscore the efficacy of integrated energy storage in alleviating discrepancies between energy supply and demand. time step figure 2: grid power balance the effectiveness of the energy storage systems is illustrated through key performance indicators, including the state of charge (soc) of the battery and the reservoir level of the pumped hydro system. specifically, figure 3 displays the battery's soc, highlighting its capability to absorb excess renewable energy and supply http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 394 power during periods of reduced generation. furthermore, figure 4 presents the reservoir level of the pumped hydro system, demonstrating its efficient energy storage and release capabilities. time steps figure 3: battery state of charge figure 4: pumped hydro reservoir level the economic feasibility of integrating energy storage systems is evaluated using pivotal financial indicators. table 2 provides a comprehensive summary of the economic metrics, encompassing total expenditure and revenue accrued over the designated lifetime horizon. these metrics offer valuable insights into the financial ramifications of investing in energy storage technologies, enabling informed decision-making. table 2: economic metrics metric battery system pumped hydro system initial investment cost ($/kwh) 3581.137 2703.733 operational cost ($/kwh/live time) 8,978,653 8,321,583 revenue generated ($/kwh) 12.2607 30.1441 figure 5 illustrates essential stability metrics, comprising voltage stability indices and frequency deviations, over the simulation period. these critical indicators assess the system's capacity to maintain stable voltage levels and frequency, offering valuable insights into the efficacy of energy storage solutions in augmenting grid stability and resilience. http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 395 figure 5: grid stability metrics the findings demonstrate that energy storage systems are instrumental in alleviating voltage fluctuations and frequency deviations, thereby contributing to a more stable, reliable, and resilient power grid. notably, the significant reduction in voltage instability and frequency deviations during peak demand periods highlights the effectiveness of energy storage solutions in bolstering grid resilience and ensuring a stable power supply. the simulation further examines the response of energy storage systems to grid disturbances, including abrupt load changes and variable renewable energy generation. figure 6 depicts the dynamic response of the battery and pumped hydro systems to a simulated disturbance, demonstrating their capacity to swiftly adapt and maintain grid stability, thereby underscoring their effectiveness in mitigating the impact of grid disturbances. figure 6: grid disturbance response the immediate response times exhibited by the energy storage systems underscore their viability in delivering ancillary services, such as frequency regulation and voltage support, thereby strengthening grid resilience and stability, particularly under demanding operational scenarios. the economic assessment provides an in-depth examination of the cost-effectiveness of integrating energy storage solutions into power grids. table 3 presents a comprehensive breakdown of the costs and benefits associated with deploying battery and pumped hydro storage systems, encompassing initial capital expenditures, operational and maintenance costs, revenue generation, and overall return on investment (roi). this detailed analysis enables a thorough evaluation of the economic viability of energy storage integration. http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 396 table 3: economic metrics for battery and pumped hydro systems metric battery system pumped hydro system initial investment cost ($/kwh) 3581.137 2703.733 operational cost ($/kwh/live time) 8,978,653 8,321,583 revenue generated ($/kwh) 12.2607 30.1441 return on investment (roi) -0.61501 0.307759 the comparative analysis assesses the relative performance of various energy storage technologies within the framework of grid integration. table 4 provides a concise summary of pivotal performance metrics, encompassing response times, round-trip efficiency, and scalability, for battery and pumped hydro storage systems, facilitating direct comparison of their strengths and limitations. table 4: comparative performance indicators performance indicator/metric battery system pumped hydro system response time (s) 3.082328 51.92931 efficiency (%) 87.07233 78.94075 scalability high moderate voltage stability index (vsi) 0.519908 0.519908 frequency deviation 0.519908 0.519908 round-trip efficiency 0.519908 0.519908 state of charge (soc) 0.497808 0.497808 return on investment (roi) -0.61501 0.307759 levelized cost of storage (lcos) ($/kwhr) 12.2607 30.1441 figures 7-12 present a comparative performance analysis between battery storage systems (bss) and pumped hydro systems. the results indicate that bss excel in rapid response times and scalability, rendering them ideal for short-term grid stabilization. conversely, pumped hydro systems demonstrate superior economic benefits and capacity for managing substantial energy quantities over extended durations, making them suitable for long-term demand management. this comprehensive analysis, encompassing grid stability, economic viability, and comparative performance, provides profound insights into the implications of integrating energy storage into power grids. the findings offer valuable guidance for policymakers, industry stakeholders, and researchers seeking to optimize energy storage strategies for resilient, sustainable, and efficient power systems. figure 7: state of charge comparison chart http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 397 figure 8: round-trip efficiency comparison chart figure 9: return on investment (roi) comparison chart figure 10: levelized cost of storage comparison chart figure 11: frequency deviation comparison chart http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 389-400. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: onyegbadue.ikenna@iuokada.edu.ng 398 figure 12: voltage stability index comparison chart 4. conclusion this study has demonstrated the pivotal role of energy storage systems (ess) in enhancing grid stability and performance, particularly in the context of escalating renewable energy integration. the simulation results presented in this research showcase the adaptability and effectiveness of ess in addressing intermittent renewable generation and fluctuating demand. the findings underscore the importance of a diversified energy storage portfolio, incorporating both battery and pumped hydro technologies, to achieve a resilient and sustainable power grid. the simulation framework, integrating technical, economic, and regulatory aspects, has provided novel insights into maximizing grid stability and performance. the results demonstrate the effectiveness of ess in alleviating voltage fluctuations, frequency deviations, and grid disturbances. furthermore, the study reveals that battery energy storage systems (bess) excel in rapid response times and scalability, while pumped hydro storage (phs) systems offer superior economic benefits. the findings of this research provide valuable insights for policymakers, industry stakeholders, and researchers seeking to optimize energy storage strategies for resilient, sustainable, and efficient power systems. as the energy landscape continues to evolve, the integration of ess will play an increasingly critical role in ensuring grid stability and performance. this study's contributions will inform the development of more effective ess integration strategies, ultimately enhancing the stability and performance of the electrical grid. in light of the growing importance of ess, future research should focus on addressing the remaining challenges and knowledge gaps in this field. this includes developing refined control strategies, conducting detailed economic analyses, and exploring 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integrative energy management of smart grids and urban energy systems. renewable and sustainable energy reviews 10 (24): 124. https://doi.org/10.1016/j.rser.2023.114023. http://www.azojete.com.ng/ mailto:onyegbadue.ikenna@iuokada.edu.ng corresponding author’s email address: jibolarufai@gmail.com 813 arid zone journal of engineering, technology & environment original research article effects of torrefaction parameters on the properties of brimstone (morinda lucida) wood a. r. nasirudeen1*, f. a. ola3, o. o. oniya 3, a. j. adesope1, d. lasisi 1, l. a. balogun1, w. a. adesope2, i. a. abdulsalam3 and a. o. oladiji2 1*department of agricultural and bio-environmental engineering, oyo state college of agriculture and technology, igboora, nigeria 2department of mechanical engineering, oyo state college of agriculture and technology, igboora, nigeria 3department of agricultural engineering, ladoke akintola university of technology, ogbomoso, oyo state, nigeria *corresponding author’s email address: jibolarufai@gmail.com article information abstract biomass energy is a possible replacement for the conventional energy due to its environmental effects. however, raw biomass has poor combustible properties which can be enhanced by torrefaction. this research studied the torrefaction properties of brimstone wood as potential energy source. existing torrefaction device was modified by incorporating a thermocouple and temperature regulator and rectangular reactor was used for the torrefaction of brimstone wood. harvested samples of the materials were manually processed into smaller pieces and sun dried. the sun-dried samples were crushed and sieved into 8, 10 and 12 mm particle sizes. the sieved samples were subjected to ultimate (carbon (c), oxygen (o), hydrogen (h), nitrogen (n), sulphur (s) and energy contents) compositions analysed using standard methods. a 3 by 3 boxbehnken experimental design in the design expert 12.0.2 software was used to design the experiment. the influence of heating temperature (220, 260 and 300 0c), heating time (30, 60 and 90 min) and particle size (8, 10 and 12 mm) on the weight of biochar products were studied. model equations were developed and used to evaluate biochar mass yield (bmy), energy yield (bey) and energy density (bed) and evaluated based on the heating temperature, heating time and particle size ranges. the data obtained from the experimental design were analysed statistically with analysis of variance (anova) at 95 % confidence level. the carbon, oxygen, hydrogen, nitrogen, sulphur and energy contents for brimstone wood were 52.20, 36.88, 2.40, 0.54, 0.89% and 245.89 kcal/100g. r2 values of bmy, bey and bed were 0.9499, 0.9348 and 0.9990 at p≤0.05 for brimstone wood. torrefied brimstone wood has been identified as potential sources of energy, with heating temperature and heating time as critical parameters that affect properties of torrefied materials. submitted 24 march, 2024 revised: 12 june, 2024 accepted: 18 june, 2024 keywords: torrefaction brimstone wood biochar heating time heating temperature sample size yield ultimate compositions © 2024 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the world’s energy demand is increasing geometrically as evidenced in the increasing demand for fuels for transportation, industry as well as domestic activities (melgar et al., 2009). the growth and economic development of the world depends on its energy and other factors such as population growth, infrastructural and technological development and this is putting pressure on conventional energy resources. these factors lead to increase in energy demand despite the environmental pollution and global warming effects resulting from the use of petroleum-based fuels (adeleye et al., 2018). in the last 39 years, about 75% of human made co2 emissions were from the consumption of fossil fuel resources (ferro et al., 2004). there is increasing emphasis on renewable energies following the global demand for clean energies which are sustainable. one of the renewable energy sources is biomass which is an alternative source of energy derived from biological materials (plant and animals). existing technologies to convert biomass to energy include thermochemical and biochemical processes. the thermochemical conversion technique which involves combustion, pyrolysis, azojete december 2024. vol.20(4):813-827 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:jibolarufai@gmail.com mailto:jibolarufai@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 814 gasification and liquefaction processes is more familiar. the thermochemical process of torrefaction which is used for the treatment of biomass at low heating temperatures ranging from 200 to 300 °c under an inert atmosphere is known to be effective for improving the energy density and shelf life of biomass materials (ferro et al., 2004). it has been widely applied to wood and grass biomass over the past 30 years to maximize the solid yield of biomass materials, thus producing large fraction of biochar ranging from 70 to 85% of the input raw material for use in energy, metallurgical fuel, chemical and fertilization applications. brimstone tree (morinda lucida) also known as oruwo in yoruba language is one of the 80 species in the genus morinda of the pyroidea family and it is a tropical rainforest tree. the wood is yellow hence the name brimstone tree. morinda lucida is a medium sized tree at maturity up to 18 25 years evergreen shrub with bole and branches often crooked or gnarled; bark smooth scaly, grey to brown, stipules ovate or triangular, 1-7 mm long, falling early. although the plant is very bitter, yet the whole plants; leaves, stem, bark and roots are known to have medicinal properties. the stem has high energy content to be used in production of charcoal for the local gunpowder. these entirely play important role in satisfying human needs for energy and life processes (adeleye et al., 2018). 2. materials and methods 2.1 materials and equipment the materials and the equipment used in this study are stated in the following sections: 2.1.1 materials needed for the experiment the materials used for the experiment in the course of this study is brimstone wood 2.1.2 equipment and tools used for the experiment the following equipment were used for the experiment in the course of this study: electrically heated torrefaction reactor, laboratory oven drier, electronic weighing scale, hammer mill, sieve saker, bulb calorimeter, stopwatch, desiccator, moisture can, polythene, bowl, sample container, knife, cutlass, thermocouple. 2.2 methods 2.2.1 collection and preparation of brimstone (morinda lucida) wood brimstone (morinda lucida) wood was collected from brimstone tree from a private farm in iseyin, iseyin local government area, oyo state, nigeria. the leafy parts of the harvested matured wood were cut away from the woody parts. the fresh wood was cut into small sizes manually using a cutlass and then sun dried for some days to reduce the moisture content of the wood to safe storage level of about 12% moisture content wet basis for further studies. the sun-dried samples were crushed into smaller sizes using hammer mill and sieves into different particle sizes using a set of sieves and the sieve shaker. from the sieving operations, three particle sizes; 12 mm which were particles that passed through sieve size 12 mm and retained on 10 mm sieve, 10 mm which were particles that passed through 10mm and retained on 8mm sieve and also 8 mm particles that passed through sieve size 8 mm and retained on 6 mm sieve were collected separately for the experiments. the particles sizes are shown in plate 1 (a-d). 2.2.2 determination of the ultimate composition of the solid biochar product samples of the solid biochar products obtained after torrefaction process were characterized using the methods and procedures of the astm d3173-86 standard (2007). the ultimate composition of the biochar determined includes nitrogen content, carbon content, hydrogen content, oxygen content and sulfur contents. the higher and lower heating values of the biochar were also determined (jaya, 2016). http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 815 (a) (b) (c) (d) plate 1: brimstone wood; (a) raw wood, (b) 12 mm wood particle size, (c) 10 mm wood particle size, (d) 8 mm wood particle size 2.2.3 determination of calorific value the calorific value of the samples was determined using bomb calorimeter in accordance with astm d5865 (2010) standard method. the high and low calorific values which were determined by using the dulong formula as given by equations 1 and 2 hcv = 4.18 ∗ (78 ∗ 𝐶 + 241.3 ∗ 𝐻∗𝑂 8 + 22.1 * s (1) lcv = 4.18 ∗ (94.19 ∗ 𝐶 − 0.550 − 52.14 ∗ 𝐻) (2) where: hcv = higher calorific value, kcal/100g, lcv = lower calorific value, kcal/100g, c = percentage of carbon content, (%), h = percentage of hydrogen content, (%) and o = percentage of oxygen content, (%). 2.2.4 torrefaction process torrefaction of the sample materials were carried out using the modified torrefaction device separately. the prepared samples were processed according to the experimental design layout suggested by the design expert software. equal sample weight of 30 g was used for the two samples in all the experiments. for each experimental run, the desired 30g of the sample was first loaded into the reactor box and then covered up with the lid plate. the heating element connected to electrical source is then switched on and allowed to heat up the heating chamber to the desired preset heating temperature which is read on the temperature monitor. when the preset heating temperature is reached, the loaded reactor is quickly introduced into the heating chamber and allowed to remain in the heating chamber to be heated up to the desired heating temperature for the desired heating time or retention time monitored using a stopwatch. at the end of the retention time, the heating element is switched off and the heated reactor withdrawn from the heating chamber and placed in the desiccator to cool down in the absence of air. after proper cooling, the difference in weight of sample http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 816 before and after heat treatment is taken as the weight of biochar material remaining and collected from inside the heating reactor. the collected biochar product obtained is weighed, packed, labeled and characterized for the proximate and ultimate compositions. the experimental procedure was repeated for other runs and sample materials. the data collected from the measurement of the weight of the torrrefied solid biochar product was used to evaluate biochar mass yield, energy yield and energy density using equations 3, 4 and 5, respectively (bergman et al, 2005). biochar mass yield (bmy): 𝐵𝑀𝑌 = 𝑀𝑝 𝑀𝑟 × 100 (3) biochar energy yield (bey): 𝐵𝐸𝑌 = 𝐵𝑀𝑌 × 𝐻𝐻𝑉𝑝 𝐻𝐻𝑉𝑟 ∗ 100% (4) biochar energy density (bed): 𝐵𝐸𝐷 = 𝐵𝐸𝑌 𝐵𝑀𝑌 (5) where: bmy= biochar mass yield, %, bey = biochar energy yield, %, bed = biochar energy density, mp= mass of torrefied product, (g), mr= mass of raw biomass, (g), hhvr = high heating value of raw biomass, (mj/kg), hhvp= high heating value of torrefied product (mj/kg). 2.2.5 experimental design and statistical analysis the influence of the experimental conditions of heating temperature from 220 to 300 oc (220, 260 and 300 oc) at 40 oc interval and heating time from 30 to 90 min (30, 60 and 90 min) at 30 min intervals and sample sizes from 8 to 12 mm (8, 10 and 12 mm) at 2 mm intervals for both brimstone wood and ackee fruit pod on the solid biochar product yields and on the properties of the solid biochar products were studied. the experimental range and levels of the process variable codes are presented in table 1. the data obtained were analysed using 3 factors; heating temperature, heating time and sample size at 3 levels of variation each using 3-factor, 3-level box-behnken experimental design of 17 runs at significant level of p ≤ 0.05 of the design expert 12.0. the experiments were carried out according to the design matrix proposed by the software as presented in table 2. table 1: experimental range and levels of process variable codes parameter unit -1 0 1 heating temperature (oc) 220 260 300 heating time (min) 30 60 90 sample size (mm) 8 10 12 http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 817 table 2: experimental design layout for the sample materials std run a (oc) b (min) c (mm) 1 1 220 30 10 9 2 260 30 8 11 3 260 30 12 12 4 260 90 12 17 5 260 60 10 15 6 260 60 10 7 7 220 60 12 2 8 300 30 10 8 9 300 60 12 13 10 260 60 10 14 11 260 60 10 16 12 260 60 10 5 13 220 60 8 10 14 260 90 8 3 15 220 90 10 6 16 300 60 8 4 17 300 90 10 a: heating temp; b: heating time; c: sample size. 3. results and discussion 3.1 modified torrefaction reactor and torrefied biomass materials the torrefaction device system consisting of the heating chamber, reactor, the thermocouple for the regulation of the required heating temperatures and the cooling system used for the experiment. samples of the torrefied biochar materials subjected to various conditions of heating temperature and heating time and obtained after the torrefaction process are shown in plate 2 for the brimstone wood. the biochars obtained from the sample materials as shown in plate 2 were observed to vary in colours from visual image observation with variation in heating temperature and heating time. it was observed that the higher the heating temperature and heating time the darker the biochar from visual image observation. this indicates that the colour of the torrefied products (biochar) changes with increasing torrefaction conditions. similar morphological changes in colour of paddy straw from yellowish to brown and then dark with torrefaction duration was reported by swapnaja et al. (2020). http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 818 plate 2: torrefied brimstone wood samples note: ti,ii,iii = 220, 260, 300 0c; ti, ii, iii = 30, 60, 90 min; si, ii, iii = 8, 10, 12 mm t = heating temperature, 0c; t = heating time, min; s = sample size, mm. 3.2 effects of torrefaction processing parameters on biochar mass yield, energy yield and energy density the result of the effects of heating temperature, heating time and sample size on the biochar mass yield, energy yield and energy density of the torrefied samples; brimstone wood are presented in this section. 3.2.1 effects of processing parameters on brimstone wood biochar mass yield the design matrix and results of the biochar yields and density obtained for brimstone wood are presented in table 3. the software presented a model and regression analysis to correlate the biochar mass yield with the independent variables of heating temperature, heating time and sample size considered for the study using a first order polynomial equation for the brimstone wood biochar mass yield as presented in equation 6. 𝐵𝑏𝑚𝑦(%) = +300.84187 − 0.947062 𝐴 − 0.354917 𝐵 − 11.26875 𝐶 − 0.001333 𝐴𝐵 + 0.021875 𝐴𝐶 + 0.036250 𝐵𝐶 + 0.000861 𝐴² + 0.001447 b² + 0.150625 c² (6) t i s i t i t i s i t ii t i s ii t i t i s iii t ii t ii s i t i t ii s ii t i t ii s ii t ii t ii s iii t ii t iii s iii t iii t iii s ii t iii t iii s ii t ii t iii s i t ii t iii s i t i http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 819 where: bbmy = biochar mass yield of brimstone wood, %, a = heating temperature, 0c, b = heating time, min, c = sample size, mm. the anova results and statistical parameters of the analysis which describes the relationship between the independent variables and the dependent variable, biochar mass yield is as presented in table 4. the probability of the model p-value and f-value of 0.0009 and 14.75 of brimstone wood biochar mass yield, indicates that the model suggested by the software for the material was significant at 95% confidence level. the r2 value evaluated for the biochar yields of brimstone wood is 0.9499 meaning 94.99% of the variability can be accounted for and showing the regression model was satisfactory for the prediction of the biochar mass yield from brimstone wood. the anova results of the model terms presented in table 4 shows that a, b and a2 are significant model terms, while it is shown in equation 6 that ac, bc, a2, b2 and c2 model terms have synergistic effect on biochar yield and a, b, c and ab have antagonistic effect. table 3: design matrix and results of brimstone wood biochar mass yield, energy yield and energy density std run a (oc) b (min) c (mm) brimstone wood mass yield (%) energy yield (%) energy density 10 1 260 90 8 38.7 44.07 1.14 14 2 260 60 10 56.1 63.23 1.13 9 3 260 30 8 73.3 76.79 1.05 15 4 260 60 10 54.7 61.86 1.13 17 5 260 60 10 53.9 61.05 1.13 16 6 260 60 10 55 62.09 1.13 13 7 260 60 10 53.6 56.90 1.06 1 8 220 30 10 89.7 93.38 1.04 7 9 220 60 12 82.7 86.63 1.05 6 10 300 60 8 50.7 56.80 1.12 3 11 220 90 10 85.3 91.58 1.07 4 12 300 90 10 39.7 45.77 1.15 12 13 260 90 12 34 38.99 1.15 5 14 220 60 8 86.3 92.65 1.07 11 15 260 30 12 71.7 79.31 1.11 2 16 300 30 10 63.3 70.04 1.11 8 17 300 60 12 40.3 45.72 1.13 a: heating temp; b: heating time; c: sample size http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 820 table 4: anova result of mass yield for brimstone wood source sum of squares df mean square f-value p-value conclusion model 4950.78 9 550.09 14.75 0.0009 significant a 2812.50 1 2812.50 75.40 < 0.0001 significant b 1257.51 1 1257.51 33.71 0.0007 significant c 51.51 1 51.51 1.38 0.2784 not significant ab 92.16 1 92.16 2.47 0.1600 not significant ac 11.56 1 11.56 0.3099 0.5951 not significant bc 2.40 1 2.40 0.0644 0.8070 not significant a² 679.92 1 679.92 18.23 0.0037 significant b² 19.15 1 19.15 0.5133 0.4969 not significant c² 23.60 1 23.60 0.6327 0.4525 not significant residual 261.11 7 37.30 lack of fit 257.22 3 85.74 88.12 0.0004 significant pure error 3.89 4 0.9730 cor total 5211.90 16 statistical parameters r2 = 0.9499 adj r2 = 0.8855 pred r2 = 0.2092 adeq precision = 13.3585 the three-dimensional surface graph (3d) and two-dimensional contour (2d) in figure 1 (a, b and c) showed the effects of heating temperature, heating time and sample size on the biochar mass yield of brimstone wood. the combined effect of heating temperature and heating time on the biochar mass yield of brimstone wood is shown in figure 3a in three-dimensional surface and contour graphs. figure 1a shows that biochar mass yield decreased with increase in heating temperature and heating time. the maximum and minimum biochar mass yields were obtained to be 85.3 and 39.7% at 220 0c, 90 mins and 300 0c, 90 mins respectively. figure 1b for the combined effect of heating temperature and sample size shows that biochar mass yield decreases with an increase in heating temperature. the maximum and minimum biochar mass yields of 82.7 and 40.3% were obtained at 220 0c, 12 mm and 300 0c, 12 mm respectively. while it is shown in figure 1c for the combined effects of heating time and sample size that increased in heating time results in decreases in biochar mass yield and vice versa. the maximum and minimum biochar mass yields were obtained to be 71.7 and 34.0% at 30 min, 12mm and 90 min, 12 mm, respectively. similar decreases in biochar mass yield of patula pine wood and wood pellet from 67.75 – 98.46% and 39.2 – 80.3%, respectively at heating temperature range of 200 – 300 oc was reported by sergio ramos et al. (2017) and ozge et al. (2022), respectively. http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 821 (a) (b) (c) figure 1: response surface of biochar mass yield of brimstone wood as influenced by (a) heating temperature and heating time, (b) heating temperature and sample size, (c) heating time and sample size 3.2.2 effects of processing parameters on brimstone wood biochar energy yield the design matrix and results of the biochar energy yield obtained for brimstone wood (bbey) is presented in table 5. the software presented a model and regression analysis to correlate the biochar energy yield with the independent variables of heating temperature, heating time and sample size considered for the study using polynomial equation for the brimstone wood biochar energy yield as presented in equation 7. 𝐵𝑏𝑒𝑦(%) = +540.17519 − 4.05095 𝐴 + 0.88720 𝐵 + 19.73375 𝐶 − 0.004681 𝐴𝐵 − 0.015813 𝐴𝐶 − 0.031667 𝐵𝐶 + 0.007758 𝐴² + 0.001947 b² − 0.747562 c² (7) where: bbey = biochar energy yield of brimstone wood,%, a = heating temperature, 0c, b = heating time, min, c = sample size, mm the anova results and statistical parameters of the analysis which describes the relations between the independent variables and the dependent variable, biochar energy yield is as presented in table 5. the probability of the model p-value and fvalue of 0.0022 and 11.15 for brimstone wood biochar energy yield, indicates that the model suggested by the software for the material was significant at 95 % confidence level. the r2 value evaluated for biochar energy yields of brimstone wood is 0.9348 meaning 93.48 % of the variability can be accounted for, showing the regression models was satisfactory for the prediction of biochar energy yield of brimstone wood. the anova results for the model terms presented in table 5 shows that a, b and a2 are significant model terms. while it is shown in equation 7 that b, c, a2 and b2 have synergistic effect on biochar energy yield while a, ab, ac, bc and c2 have antagonistic effect. http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 822 table 5: anova result of energy yield for brimstone wood source sum of squares df mean square f-value p-value conclusion model 4778.13 9 530.90 11.15 0.0022 significant a-ht 2661.22 1 2661.22 55.91 0.0001 significant b-ht 1227.85 1 1227.85 25.80 0.0014 significant c-ss 48.31 1 48.31 1.02 0.3472 not significant ab 126.23 1 126.23 2.65 0.1475 not significant ac 6.40 1 6.40 0.1345 0.7247 not significant bc 14.44 1 14.44 0.3034 0.5989 not significant a² 648.69 1 648.69 13.63 0.0077 significant b² 12.93 1 12.93 0.2716 0.6183 not significant c² 37.65 1 37.65 0.7910 0.4033 not significant residual 333.19 7 47.60 lack of fit 309.44 3 103.15 17.37 0.0093 significant pure error 23.75 4 5.94 cor total 5111.32 16 statistical parameters r2 = 0.9348; adj r2 = 0.8510 pred r2 = 0.0241; adeq precision = 11.5762 the three-dimensional surface graph (3d) and two-dimensional contour (2d) in figure 2 (a, b and c) shows the effect of heating temperature, heating time and sample size on the biochar energy yield of brimstone wood. the combined effect of heating temperature and heating time on the biochar energy yield on brimstone wood is as shown in figure 2a in the three-dimensional surface and contour graphs. figure 2a shows that energy yield increase as the heating temperature and heating time increase. the maximum and minimum biochar energy yields were obtained to be 93.38 and 45.72 % at 220 0c, 30 min and 300 0c, 90 min, respectively. figure 2b reveals that energy yield decreased with increase in heating temperature only. the maximum and minimum biochar energy yields of 92.65 and 50.7% were obtained at 220 0c, 8 mm and 300 0c, 12 mm, respectively. while figure 2c shows that increase in heating time gives decrease in biochar energy yield and vice versa. the maximum and minimum biochar mass yields were obtained to be 76.79 and 38.99% at 30 min, 8 mm and 90 min, 12 mm, respectively. decrease in biochar energy yield of patula pine wood and wood pellet from 78.51 to 99.46% and from 59.9 to 85.4% at heating temperature range of 200 to 300 o c was reported by sergio ramos et al. (2017) and ozge et al. (2022), respectively. http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 823 (a) (b) (c) figure 2: response surface of biochar energy yield of brimstone wood as influenced by (a) heating temperature and heating time (b) heating temperature and sample size (c) heating time and sample size 3.2.3 effects of processing parameters on brimstone wood biochar energy density the result of the effects of heating temperature, heating time and sample size on the biochar energy density of the torrefied samples, brimstone wood were presented in this section. the design matrix and results of the biochar energy density obtained for brimstone wood are presented in table 6. the design matrix and results of the biochar energy density obtained for brimstone wood (bbed) is presented in table 6. the software presented a model and regression analysis to correlate the biochar energy yield with the independent variables of heating temperature, heating time and sample size considered for the study using polynomial equation for the brimstone wood biochar energy density as presented in equations 8. bbed(%) = −0.244531 + 0.011109 𝐴 − 0.000354 𝐵 − 0.039063 𝐶 + 2.08333e − 06 𝐴𝐵 + 0.000125 𝐴𝐶 + 0.000063 𝐵𝐶– 0.000022 a2 – 2.08333e-06 b2 + 0.000156 c2 (8) where: bbed = biochar energy density of brimstone wood, a = heating temperature, 0c, b = heating time, min, c = sample size, mm the anova results and statistical parameters of the analysis which describes the relations between the independent variables and the dependent variable, biochar energy density is as presented in table 6. the probability of the model p-value and f-value of 0.0001 and 2803.33 of brimstone wood biochar energy density, indicates that the model suggested by the software for the material was significant at 95 % confidence level. the r2 value evaluated for biochar energy density of brimstone wood is 0.9990 meaning 99.90 % of the variability can be accounted for showing the regression model was satisfactory for the prediction of biochar energy density brimstone wood. the anova results for the model terms presented in table 8 shows that a, b, ab, ac, bc and a2 are significant model terms, while it is shown from equation 8 that a, ab, ac, bc and c2 have synergistic effect on biochar energy density and b, c, a2 and b2 have antagonistic effect. http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 824 table 6: anova result of energy density of brimstone wood source sum of squares df mean square f-value p-value conclusion model 0.0184 9 0.0020 543.84 < 0.0001 significant a 0.0105 1 0.0105 2803.33 < 0.0001 significant b 0.0015 1 0.0015 405.00 < 0.0001 significant c 2.083e-06 1 2.083e-06 405.00 0.4896 not significant ab 0.0000 1 0.0000 6.67 0.0493 significant ac 0.0004 1 0.0004 106.67 0.0001 significant bc 0.0000 1 0.0000 7.50 0.0409 significant a2 0.0041 1 0.0041 1083.000 < 0.0001 significant b2 0.0000 1 0.0000 3.00 0.1438 not significant c2 1.250e-06 1 1.250e-06 0.33333 0.5887 not significant residual 0.0000 5 3.750e-06 lack of fit 0.0000 2 9.375e-06 pure error 0.0000 3 0.0000 cor total 0.0184 14 statistical parameters r2 = 0.9990 adj r2= 0.9971 pred r2= 0.2959 adeq = precision 68.384 the three-dimensional surface graph (3d) and two-dimensional contour (2d) in figures 3 (a, b and c) shows the effect of heating temperature, heating time and sample size on the biochar energy density of brimstone wood. the combined effect of heating temperature and heating time on the biochar energy density on brimstone wood is shown in figure 3a in form of three-dimensional surface graph. figure 3a shows that energy density increases as the values of heating temperature and heating time increases. the maximum and minimum biochar energy density was obtained to be 1.15 and 1.04 at 300 0c, 90 mins and 220 0c, 30 mins respectively. figure 3b shows that the energy density increased with increase in heating temperature and sample size. the maximum and minimum biochar energy density of 1.14 and 1.05 obtained at 300 0c, 12mm and 220 0c, 8mm respectively. also, figure 3c shows that increase in heating time gives increase in biochar energy density and vice versa. the maximum and minimum biochar energy density were obtained to be 1.15 and 1.11% at 90 mins, 8 mm and 30 mins, 8 mm respectively. similar increase in biochar energy density of poplar chip from 0.99 to 1.15 at temperature range of 200 to 300 oc was reported by xun luo (2011). (a) (b) http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 825 (c) figure 3: response surface of biochar energy density of brimstone wood as influenced by (a) heating temperature and heating time (b) sample size and heating temperature (c) heating time and sample size 3.3 ultimate composition of torrefied brimstone wood solid products the results obtained for the ultimate analysis of the solid torrefied brimstone wood products are as presented in table 7. in the table, the torrefaction holding time for the experiments was 60 min. from table 7, it can be inferred that the weight percentage of carbon in the torrefied solid products increased from 55.21 67.40% for the brimstone wood as the torrefaction temperature is increased from 220 to 300 oc. similar increase in carbon content of colombian wood species from 52.73 to 55.01 as torrefaction temperature is increased from 200 to 300 oc have been reported by margareta et al. (2021). the increase in the carbon content is only an apparent increase due to the decrease in the oxygen content from 43.74 to 38.05% for patula pine at torrefaction temperature range of 200 to 300 oc. these results indicate that the torrefaction process increases the energy density of the products by removing oxygen (sergio ramos et al., 2017 and jinxia fu et al., 2021). from table 7, it can be deduced that the nitrogen content increased slightly from 0.57 to 0.83% for the brimstone wood. this result is similar with increase in nitrogen from 0.13 to 0.15% for the patula pine torrefied from 200 to 300 oc reported by sergio ramos et al. (2017). the increase in nitrogen is a relative increase due to decrease level of oxygen (jaya, 2018). while sulfur content did not vary much with an increase from 0.87 to 0.64% and from 1.70 to 1.55% for the brimstone wood at torrefaction temperature between 200 to 300 oc. similar observations were made by jaya (2016) that sulfur content decreased from 0.25 to 0.11 % for 160 and 270 oc torrefaction temperature for lodge pine grind. from table 7, the energy content obtained for the brimstone wood products as presented shows that the energy content increased from 26.20 to 28.55 mj/kg for brimstone wood with increased in torrefaction temperature from 220 to 300 oc. similar increases in energy content were reported for wood waste from 20.18 to 24.00 mj/kg by margareta et al. (2021) at torrefied temperature range of 225 to 300 oc. the energy content of the products indicates the ability to do work. the higher the energy contents of a sample the higher the work that will be done (unroto et al., 2020). table 7: ultimate composition of raw and torrefied brimstone wood heating temperature, 0c sample properties unit raw 220 260 300 brimstone wood carbon content % 52.20 55.21 57.96 67.40 oxygen content % 36.88 35.55 33.40 29.50 hydrogen content % 2.40 2.32 2.21 2.13 nitrogen content % 0.54 0.57 0.67 0.83 sulfur content % 0.89 0.87 0.71 0.64 energy content mj/kg 24.59 26.20 27.85 28.55 http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 826 4. conclusions i. the surface colour of the torrefied products (biochar) changes with increase in torrefaction conditions. biochar mass yield decreases with increases in torrefaction conditions for the biomass materials. biochar energy yield increases as the value of torrefaction conditions decreased for the two samples. while biochar energy density increases as the torrefaction condition increases. similar results were reported by (sergio ramos et al., 2017 who worked on patula pine wood. ii. the values of ultimate ecomposition of carbon, oxygen, hydrogen, nitrogen, sulfur and energy contents of biochar products for the brimstone wood have been obtained. the energy content increased from 26.20 to 28.55 mj/kg for brimstone wood with increased in torrefaction temperature from 220 to 300 oc. references adeleye, oo., ayeni, oj. and ajamu, ma. 2018. traditional and medicinal uses of morinda lucida. journal of medicinal plants studies, 6(2): 249-254. astm standard d3173 2007. standard test method for moisture in the analysis sample of coal and coke; astm international: west conshohocken, pa, usa; available online: http://www.astm.org/database.cart/historical/d317387r96.htm (accessed on 12 july 2024). astm standard d3174 2007. standard test method for ash in the analysis sample of coal and coke from coal; astm international: west conshohocken, pa, usa; available online: http://www.astm.org/standards/d3174 (accessed on 12 july 2024). astm standard d3175 2007. standard test method for volatile matter in the analysis sample of coal and coke; astm international: west conshohocken, pa, usa. available online: http://www.astm.org/standards/d3175 (accessed on 12 july 2024). astm standard d3177 2007. standard test methods for total sulfur in the analysis sample of coal and coke; astm international: west conshohocken, pa, usa,; available online: http://www.astm.org/standards/d3177.htm (accessed on 12 july 2024). astm standard d3178 2007.standard test methods for carbon and hydrogen in the analysis sample of coal and coke; astm international: west conshohocken, pa, usa. available online: http://www.astm.org/standards/d3178.htm (accessed on 12 july 2024). astm standard d3179, 2007. standard test methods for nitrogen in the analysis sample of coal and coke; astm international: west conshohocken, pa, usa, 2002; available online: https://www.astm.org/standards/d3179.htm (accessed on 12 july 2024). astm standard d5865-10a. 2010. standard test method for gross calorific value of coal and coke; astm international: west conshohocken, pa, usa, 2010; available online: http://www.astm.org/standards/d586410a (accessed on 12 july 2024). bergman, pca. 2005.combined torrefaction and pelletisation: the top process, report no. 05073, energy research centre of the netherlands, amsterdam pp.29. ferro, dt., vigouroux, v., grimm, a. and zanzi, r. 2004. torrefaction of agricultural and forest residues, in cubasolar: guantánamo, cuba. jaya, st. 2016. effect of deep drying and torrefaction temperature on proximate, ultimate composition, and heating value of 2-mm lodgepole pine (pinuscontorta) grind. journal of http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com http://www.astm.org/database.cart/historical/d3173-%2087r96.htm http://www.astm.org/standards/d3174 http://www.astm.org/standards/d3175 http://www.astm.org/standards/d3177.htm http://www.astm.org/standards/d3178.htm https://www.astm.org/standards/d3179.htm http://www.astm.org/standards/d5864-10a http://www.astm.org/standards/d5864-10a arid zone journal of engineering, technology and environment, december 2024; vol.20(4)813-827. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: jibolarufai@gmail.com 827 bioengineering, 3(2):128-133. jeeban, p. and sea, co. 2014. effect of torrefaction on the properties of corn stalk to enhance solid fuel qualities. energy journal, 7(9): 5586-5600. jinxia f., sabrina s., scott qt. and william k. 2021. upgraded pongamia pod via torrefaction for the production of bioenergy. fuel journal, 29(1): 100-108. margareta nc., tharaka rkcd., marten m., linnar p., indrek v. and timo k. 2021. torrefaction of agricultural and wood waste: comparative analysis of selected fuel characteristics. energies 14(10): 325-342. melgar, a., perez, jf. and horrillo, a. 2009. biomass gasification process in downdraft fixed bed gasifier: a real time diagnosis model based on gas composition analysis. scientific information system network journals, 49: 9-18. ozge m., poulami r. and thomas z. 2022. downstream torrefaction of wood pellets in a rotary kiln reactor-impact on solid biofuel properties and torr-gas quality. processes journal, 10(10): 1912-1922. reinier, an., yasiel, ac., ester, fp. and juan, ac. 2018. experiments on torrefaction of dichrostachy cinerea wood: two level factorial design and themogravimetric analysis. wood science and technology, 52(7): 250260. www.core.ac.uk. sergio ramos c., juan fp., manuel rp., ronaldo b. and manuel g. 2017. effect of torrefaction temperature on properties of patula pine. mederas ciencia technologia, 19(1): 39-50. swapnaja, kj., wakudkar, h., manvenda, b. and rajesh, s. 2020. effect of torrefaction on physicochemical properties of paddy straw and its size reduction. international journal current microbiology and applied sciences, 9(1): 7-18. tom b. 2018. brimstone and timber. wood science and timber treatment. forestry and timber news for member of conform, the confederation of forest industries in the confor.org.uk. untoro, bs. harwin, s. and tri, ar. 2020. improving thermochemical and physical properties of cocoa pod shell by torrefaction and its potential utilization. international energy journal, 20(1): 141-154. xun, l. 2011. torrefaction of biomass – a comparative and kinetic study of thermal decomposition for norway spruce stump. poplar and fuel tree chips. slu, institutionen for energy och teknik,swedish university of agricultural sciences, department of energy and technology. http://stud.epsilon.slu. http://www.azojete.com.ng/ mailto:jibolarufai@gmail.com http://www.core.ac.uk/ http://stud.epsilon.slu/ corresponding author’s email address: aarasheed.cpe@buk.edu.ng 702 arid zone journal of engineering, technology & environment original research article effect of adsorbent dosage on the kinetics and isotherms of lead(ii) removal from aqueous solution using corn husk a. a. rasheed*, h. s. muhammad, y. jakada, and n. salahudeen department of chemical and petroleum engineering, faculty of engineering, bayero university kano, pmb 3011, kano, nigeria. *corresponding author’s email: aarasheed.cpe@buk.edu.ng article information abstract heavy metal contamination in water presents a critical environmental challenge, necessitating effective and sustainable solutions. this study explores the use of natural corn husk as an adsorbent for lead (ii) removal from aqueous solutions. the corn husk was processed by drying, crushing, and sieving through a 75 μm mesh screen, followed by characterization using scanning electron microscopy (sem), fourier-transform infrared (ftir) spectroscopy, and brunauer-emmettteller (bet) analysis. batch adsorption experiments were conducted to investigate the effect of adsorbent dosage on the isotherms and kinetics of lead (ii) removal. the results revealed that the percentage removal of lead increased with both adsorbent dosage and contact time, achieving equilibrium at 105 minutes. the highest removal efficiencies were 73%, 93%, and 96% for dosages of 0.5 g/l, 1 g/l, and 1.5 g/l, respectively. however, the adsorption capacity decreased with increasing dosage, from 111.72 mg/g to 49.06 mg/g. ftir analysis confirmed the presence of functional groups such as hydroxyl, carboxyl, and ether groups, which contributed to the adsorption mechanism through chemisorption. similarly, bet results showed a high surface area of 114.55 m²/g with microporous characteristics, while sem micrographs revealed a dense, rough, and porous morphology with well-distributed active sites. furthermore, isotherm analysis demonstrated that the langmuir model provided the best fit across all dosages, indicating monolayer adsorption with maximum adsorption capacities (qm) ranging from 85 mg/g to 178.57 mg/g. separation factor (rl) values of 0.2 and 0.19 at lower dosages indicated favorable adsorption conditions, while rl = 0 at 1.5 g/l suggested irreversible adsorption. kinetic studies confirmed the pseudo-secondorder model as the most accurate across all dosages, highlighting chemisorption as the rate-determining mechanism. these findings underscore the significant role of adsorbent dosage in adsorption efficiency and provide insights into optimizing isotherms and kinetics for lead removal using corn husk. received: 19th may 2025 revised: 9th july 2025 accepted: 12th july 2025 keywords: adsorption dosage isotherms kinetics lead corn husk © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction heavy metal contamination, particularly lead, in water sources present a global challenge due to its profound health and environmental repercussions (wang et al., 2022). lead, a non-biodegradable and highly toxic metal, infiltrates aquatic ecosystems primarily through industrial discharges such as those from battery manufacturing, mining operations, metal finishing processes, and electronic waste recycling (adeogun et al., 2010; moyo et al., 2013;). even trace amounts of lead exposure pose significant risks, including neurological impairments, renal dysfunction, and developmental disorders, underscoring the critical need for its efficient removal from aqueous media (kumar et al., 2024; zafar et al., 2024). in recent years, biosorption has gained significant attention as a cost-effective and eco-friendly approach for removing heavy metals from contaminated environments (khalid et al., 2023; reti et al., 2024; wang et al., 2024). notably, agricultural waste, due to its availability and low cost, has emerged as a promising adsorbent in biosorption processes (moosa et al., 2016; ayari et al., 2018). azojete september 2025. vol.21(3):702-716 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/003 www.azojete.com.ng mailto:aarasheed.cpe@buk.edu.ng mailto:aarasheed.cpe@buk.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 703 among agricultural byproducts, corn is one of the world’s most widely cultivated crops and has emerged as a valuable resource for addressing environmental challenges through its conversion into adsorbents (aguilararteaga et al., 2022; low et al., 2022; onyekwere et al., 2024). corn cultivation generates substantial amounts of agricultural residues, including corn husk, which are often discarded or underutilized. corn husk, primarily composed of cellulose, hemicellulose, and lignin, is rich in functional groups such as hydroxyl and carboxyl, which facilitate the binding of metal ions (moyo et al., 2013; ratna et al., 2022; enawgaw et al., 2023). given its physicochemical characteristics, corn husk is a promising material for the removal of lead from aqueous systems. several studies (guyo et al., 2015; mireles et al., 2019; assirey and altamimi, 2021; chen et al., 2022; sawant et al., 2022; phaenark et al., 2023) have reported its efficacy in lead biosorption, yet critical aspects of the adsorption mechanism remain underexplored in particular, the influence of adsorbent dosage on the kinetics and equilibrium behavior of lead biosorption has not been thoroughly investigated. adsorbent dosage plays a fundamental role in determining the availability of binding sites and influences the dynamic interaction between adsorbent and adsorbate. at higher dosages, aggregation or saturation effects may alter surface properties, potentially affecting both adsorption capacity and model applicability (ezeh et al., 2017; aniagor et al., 2022; amaibi et al., 2024). in this study, the focus is placed on evaluating how varying corn husk dosages affect the kinetic profiles and equilibrium isotherms of lead biosorption from aqueous solutions. the intention is to examine adsorption dynamics using both pseudo first order (pfo) and pseudo second order (pso) kinetic models, alongside langmuir and freundlich isotherms, across a range of dosages. by systematically assessing these relationships, the study seeks to clarify the role of dosage in controlling biosorption behavior and improve understanding of how dosage-dependent mechanisms influence metal uptake processes. 2. materials and method 2.1 materials and analytical equipment the reagents and main apparatus utilized in this study include the following: analytical-grade lead chloride (sigma-aldrich, germany), corn husk sourced from cda (buk), a crusher (220–240v crusher, china), a scanning electron microscope (phenom prox, thermofisher scientific, usa), and equipment for brunaueremmett-teller (bet) analysis (nova 11.03a, usa). a fourier transform infrared (ftir) spectrophotometer (spotlight 200i, perkinelmer, usa), a 0.45 µm filter (whatman, uk), and an atomic absorption spectrometer (aas) (pinaacle 900h, perkinelmer, usa) were also employed. additional instruments included a ph meter (st2100-b, ohaus, usa), an orbital shaker (joanlab os-20, china), an oven (genlab ltd., england), a mesh sieve (kelsons, india), and a weighing balance (ohaus sp202, scout pro, usa). distilled water used throughout the experiments was produced using a water distiller (sz96, mon scientific, nigeria). other essential items included a stopwatch and standard laboratory glassware. 2.2 collection and preparation of adsorbent corn husk was sourced from the centre for dryland agriculture (cda) at bayero university kano. it was thoroughly washed with distilled water to remove dirt and impurities, followed by sun drying for two days. the husk was then further dried in an oven at 105°c for 24 hours. after drying, the husk was crushed, ground, and sieved to produce a fine powder with an average particle size of approximately 150 μm. these preparation conditions were adopted based on established protocols reported in the studies like mukhlish et al. (2023), said et al. (2024) and erdem and öner (2025). the resulting corn husk powder was stored in an airtight polyethylene bag at room temperature until it was needed for use. 2.3 characterization of the cornhusk adsorbent the physicochemical properties of the corn husk adsorbent were evaluated using standard analytical techniques. scanning electron microscopy (sem) coupled with energy-dispersive x-ray spectroscopy (edx) was employed to examine the surface morphology and elemental composition of the material, following the procedures outlined by goldstein et al. (2017). the functional groups present on the adsorbent surface were identified through fourier transform infrared spectroscopy (ftir) in the range of 4000–600 cm⁻¹, as described by coates (2000). the specific surface area and pore size distribution were determined using brunauer–emmett–teller (bet) analysis, with sample preparation and data interpretation performed in accordance with the guidelines provided by sing et al. (1985). http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 704 2.3 biosorption adsorption studies batch adsorption studies were conducted following the methods outlined by chen et al. (2022) and batool et al. (2018). a synthetic solution containing 100 mg/l of lead (ii) chloride was initially prepared using distilled water. the experiments were designed to vary one parameter at a time while maintaining others constant. specifically, two process parameters namely contact time and adsorbent dosage, were tested at three levels, with ph, temperature, and agitation rate held constant as detailed in table 1. table 1: experimental design for removal of lead from aqueous solution run dosage time frequency of sampling 1 0.5 g/l 120 mins 15 mins 2 1.0 g/l 120 mins 15 mins 3 1.5 g/l 120 mins 15 mins for each experimental run, 80 ml of the synthetic solution was combined with a specified amount of the prepared adsorbent in a 120 ml bottle flask. eight bottles were used per run, with one bottle sacrificed every 15 minutes to facilitate time resolved sampling, allowing for the measurement of concentration changes over the course of the experiment. the bottles were agitated on an orbital shaker at a constant speed of 175 rpm under room temperature conditions. at each designated sampling interval, the solution was filtered through a 0.45 µm filter paper, and the residual metal concentration in the supernatant was determined using an atomic absorption spectrophotometer. the percentage of metal ion removal and adsorption capacity of the adsorbent (metal uptake) was calculated using equations 1 and 2 respectively. 𝑅𝑒𝑚𝑜𝑣𝑎𝑙 (%) = (𝐶𝑖−𝐶𝑓) 𝐶𝑖 × 100 1 𝑞𝑒 = 𝑉(𝐶𝑖−𝐶𝑓) 𝑀 2 where ci (mg/l) is the initial adsorbate concentration, cf (mg/l) is the final adsorbate concentration, qe (mg/g) is the amount of metal ion adsorbed per unit mass of adsorbent, v (l) is the solution’s volume and m (g) is the amount of the adsorbent. 2.5 determination of biosorption isotherms the adsorption isotherm of lead in this study was analyzed using langmuir and freundlich models. the langmuir and freundlich models used are presented in equation (3) and (4) respectively (sutirman et al., 2018). 𝐶𝑒 𝑞𝑒 = 1 𝐾𝐿𝑞𝑚 + 𝐶𝑒 𝑞𝑚 3 𝑙𝑜𝑔𝑞𝑒 = 𝑙𝑜𝑔𝐾𝐹 + 1 𝑛 log 𝐶𝑒 4 where 𝑞𝑒 is adsorption capacity at equilibrium (mg/g), 𝑞𝑚 is the maximum capacity at equilibrium (mg/g), kl is the langmuir constant related to the affinity of the binding site (l/mg), ce is the adsorbate equilibrium concentration (mg/l), kf and 1/n are freundlich constants related to adsorption capacity and affinity of the binding site respectively. 2.6 determination of biosorption kinetics the kinetics of the metals adsorption was studied using two models: pseudo first order (pfo) and pseudo second order (pso) using equations (5) and (6) respectively (zhang et al., 2013). log(𝑞𝑒 − 𝑞𝑡) = log 𝑞𝑒 − 𝑘1 2.303 𝑡 5 𝑡 𝑞𝑡 = 1 𝑘2𝑞𝑒 2 + 1 𝑞𝑒 𝑡 6 http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 705 where, 𝑞𝑒 is adsorption capacity at equillibrium (mg/g), 𝑞𝑡 (mg/g) is the adsorption capacity at any given time t (s), 𝑘1 (s-1) and 𝑘2 (s-1) are the rate constant of pseudo-first-order and pseudo-second-order respectively. 3. results and discussion 3.1 sem results the sem micrograph of corn husk in plate 1 reveals a distinctively rough and fibrous surface morphology characterized by mountainous textures and irregular ridges. this can be attributed to its inherent lignocellulosic composition, primarily consisting of cellulose, hemicellulose, and lignin. this structural nature is consistent with the findings of kambli et al. (2016), who noted that the limited presence of encrusting substances in corn husk fibers contributes to their distinctly rough and irregular surface texture. while no visible macropores were observed at the imaging scale, the material’s heterogeneous and coarse surface suggests the possible presence of micropores, which are not easily detectable via conventional sem. this rough texture significantly increases the external surface area and provides numerous micro-scale crevices and binding sites, enhancing the potential for lead ion attachment. plate 1: sem of natural corn husk at 1000x magnification the structural ruggedness and physical integrity of the corn husk further indicate a material capable of withstanding mechanical stress during adsorption processes. these features are critical in supporting both physical adsorption and chemisorption, driven by the availability of surface functional groups such as hydroxyl and carboxyl moieties. the surface topography, rather than visible porosity, appears to be the dominant contributor to its biosorptive behavior. this interpretation aligns with findings by arunakumara et al. (2013) and ponce et al. (2021), who similarly noted that surface roughness and the potential for microporosity play essential roles in the adsorption efficiency of lignocellulosic biosorbents. therefore, the observed microstructural characteristics affirm the suitability of corn husk as a sustainable and effective biosorbent for lead removal from aqueous solutions. the elemental composition determined through edx analysis reveals the presence of c, o, k, p, mg, cl, ca, and si, as shown in figure 1. the adsorbent in this study exhibits a carbon content of 50%, further confirming that corn husk is rich in lignite. this observation aligns with the findings of reddygunta et al. (2023) and ismail et al. (2022), who reported carbon contents of up to 47% and 55%, respectively, in corn husk. according to danish et al. (2018), materials with carbon content ranging from 50% to 90% are classified as lignite-rich and are well-suited for activated carbon production. the carbon content observed in this study surpasses the values reported in other studies such as kwaghger and ibrahim (2013) and de bouanzi et al. (2024), highlighting the superior composition of the corn husk used in this research. additionally, the substantial surface oxygen atoms present in the corn husk adsorbent enhance their reactivity with adsorbed metal ions like lead, promoting a higher biosorption efficiency. this improved activity aligns with the mars–van krevelen (mvk) mechanism frequently associated with metal-oxides, as suggested by dey et al. (2021). http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 706 figure 1: edx spectra of natural corn husk adsorbent 3.2 ftir (fourier transform infrared) spectroscopy analysis the ftir spectrum of corn husk in figure 2 reveals an array of functional groups that are essential for its biosorption capabilities, highlighting its suitability as a natural adsorbent for heavy metal removal. the broad and intense peak at 3324.8 cm⁻¹ corresponds to o-h stretching, a hallmark of hydroxyl groups that are abundant in the lignocellulosic components of corn husk, namely cellulose, hemicellulose, and lignin. these hydroxyl groups play a pivotal role in metal ion binding by forming hydrogen bonds and chelating with lead ions. figure 2. ftir spectra of natural corn husk adsorbent. the peak at 2822.2 cm⁻¹ is attributed to c-h stretching vibrations, characteristic of aliphatic hydrocarbons or methylene groups, which indicate the presence of organic structural elements derived from lignin and other plant based compounds (ray and gupta, 2013; el-araby et al., 2017; magoling and macalalad, 2017; chizoruo et al., 2019) a smaller peak at 2035.1 cm⁻¹, associated with c≡c or c≡n stretching, suggests the presence of alkynes or nitrile groups, possibly introduced during environmental exposure or chemical treatments. the pronounced peak at 1722.0 cm⁻¹ corresponds to c=o stretching, representing carbonyl groups from carboxylic acids, esters, or ketones. these carbonyl groups are crucial in adsorption as they offer electron-rich sites for interaction with lead ions. at 1636.3 cm⁻¹, the spectrum shows c=c stretching or h-o-h bending, indicative of aromatic lignin structures or adsorbed water molecules, which contribute to the surface reactivity and http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 707 facilitate ion exchange mechanisms. the peak at 1319.5 cm⁻¹, attributed to c-h or o-h bending, is associated with alcohols, phenols, or polysaccharides, further emphasizing the reactive nature of the corn husk. meanwhile, the peaks at 1155.5 cm⁻¹ and 1028.7 cm⁻¹ correspond to c-o-c and c-o stretching vibrations, respectively, reflecting the presence of ether bonds and glycosidic linkages in cellulose and hemicellulose. these bonds provide structural integrity and additional binding sites for metal ions. the combination of these functional groups like hydroxyl, carbonyl, carboxyl, and ether creates a highly reactive surface on the corn husk, enriched with active sites for metal ion binding (moosa et al., 2016; sun et al., 2016; dodevski et al., 2017; el-araby et al., 2017; lawal et al., 2017; assirey and altamimi, 2021). 3.2 bet (brunauer-emmett-teller) analysis the bet method was utilized to determine the surface area, pore volume, and pore size of the blended adsorbent, which are key parameters affecting its adsorption efficiency. table 2 summarizes these properties for the corn husk adsorbent, which exhibited a bet surface area of 114.55 m²/g. although the majority of reported studies (moosa et al., 2016; ayari et al., 2018; akram et al., 2019; bouzidi et al., 2021; tigori et al., 2023) indicate that raw biosorbents, particularly those derived from lignocellulosic agricultural residues similar to the one used in this study, generally possess low brunauer–emmett–teller (bet) surface areas typically below 30 m²/g, the biosorbent in this work underwent a controlled oven-drying process at approximately 104 °c for 24 hours. while this treatment does not involve chemical or thermal activation in the conventional sense, it does constitute a form of mild thermal pre-treatment. such drying may contribute to a modest increase in surface area as several previous studies have reported unexpectedly high surface areas exceeding 100 m²/g for biosorbents that were not chemically activated, but rather subjected only to oven-drying or minimal processing. for example, recent studies have shown that certain unactivated agricultural biosorbents can exhibit high bet surface areas even without chemical or thermal activation. specifically, sorghum husk and groundnut shell, when simply oven-dried and ground, have demonstrated bet surface areas of 139.5 m²/g and 302.5 m²/g, respectively, as reported by hammari et al. (2022). these findings suggest that in certain cases, natural plant structure and internal porosity, when preserved and mildly altered through oven drying, may be sufficient to yield relatively high surface areas even in the absence of formal activation processes. the high surface area reported in this study provides a greater number of active sites, enhancing the interaction with contaminants such as heavy metals. this result underscores the effectiveness of the preparation method and the adsorbent's applicability for water treatment and heavy metal removal. table 2: bet results of natural corn husk adsorbent properties values bet surface area (m2/g) 114.5 bhj pore volume (cm3/g) 0.075 bhj pore diameter (nm) 1.853 the pore volume and diameter of the adsorbent, measured using the barrett, joyner, and halenda (bjh) method, were 0.075 cm³/g and 1.853 nm, respectively. pore size distribution analysis revealed that the adsorbent predominantly exhibited microporous characteristics. micropores, typically less than 2 nm in diameter, significantly enhance adsorption capacity by providing many active sites and a high surface area for interaction at the molecular level (centeno et al., 2003). given the molecular size of lead ions (0.175 nm), they can easily penetrate and diffuse within the microporous structure of the adsorbent. this compatibility facilitates close interaction between the lead ions and the active sites, enabling efficient mechanisms such as ion exchange, physical adsorption, and chemisorption. these findings affirm the suitability of the corn husk adsorbent for effective lead removal from contaminated water. 3.4 biosorption studies 3.4.1 effect of contact time and dosage on lead removal the effects of adsorbent dosage and contact time on the percentage removal and adsorption capacity of lead (pb) using natural corn husk are illustrated in figure 3. the data demonstrate a clear trend where the percentage removal of lead increases with both contact time and adsorbent dosage. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 708 figure 3: effect of dosage and contact time on (a) lead removal and (b) adsorption capacity of corn husk adsorbent lead removal increased consistently and reached equilibrium within 105 minutes across all three runs with varying dosages. at a dosage of 0.5 g/l, the highest percentage removal was 73%. this efficiency improved significantly with increased dosages, reaching 93% at 1 g/l and 96% at 1.5 g/l. the figures also reveal that the adsorption process was rapid during the initial 60 minutes, attaining substantial removal rates before slowing down. this initial rapid phase can be attributed to the availability of ample external surface area on the adsorbent, facilitating fast adsorption kinetics. the slower phase that followed suggests the onset of internal diffusion as the rate-determining step, consistent with the findings of li et al. (2008). this trend aligns with similar observations in prior studies (rengaraj et al., 2002; mishra and patel, 2009; babalola et al., 2016; alghamdi et al., 2019; amaibi et al., 2024). the results further show an inverse relationship between adsorption capacity and adsorbent dosage. the adsorption capacity decreased from 111 mg/g at 0.5 g/l dosage to 49 mg/g at 1.5 g/l dosage. this phenomenon is supported by several studies (shukla et al., 2002; li et al., 2013; babalola et al., 2016; ezeh et al., 2017; amaibi et al., 2024), which suggest that increasing adsorbent dosage introduces more active sites, but the amount of lead ions adsorbed per unit mass of the adsorbent decreases. this reduction occurs as the ratio of available lead ions to the adsorbent mass decreases, leading to underutilization of the adsorbent's active sites. additionally, higher dosages may result in overlapping or aggregation of adsorption sites, reducing the effective surface area and increasing diffusion path lengths (ahluwalia and goyal, 2007; aniagor et al., 2022). the aggregation of particles at higher dosages could also contribute to reduced surface area, as noted by hashem et al. (2024). at higher dosages, the introduction of more active sites does not proportionally enhance adsorption efficiency due to a reduction in the driving force of the concentration gradient, as explained by jain et al. (2019). the splitting of the available adsorbate concentration among the excess active sites further diminishes the adsorption per gram of adsorbent. this decline is consistent with the fundamental adsorption equation (equation 2), which relates the concentration gradient and adsorbent mass, showing the interplay between the numerator and denominator. these findings collectively highlight the importance of optimizing adsorbent dosage to balance percentage removal and adsorption capacity effectively. 3.4.2 adsorption isotherms the effect of adsorbent dosage on adsorption isotherms provides critical insights into the adsorption behavior and efficiency of the corn husk adsorbent for lead removal. in this study, both the langmuir and freundlich isotherm models were analyzed across different adsorbent dosages (0.5 g/l, 1 g/l, and 1.5 g/l), revealing notable trends that illustrate how dosage impacts the adsorption process. the linearized forms of the langmuir and freundlich isotherms, derived using equations 3 and 4, are presented in figure 4, with their corresponding correlation coefficients (r²) and model parameters summarized in table 3. equilibrium isotherm parameters are essential for understanding the sorption mechanism, surface characteristics, and adsorption affinity of the adsorbent. (a) (b) http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 709 figure 4: adsorption isotherms of (a) langmuir (b) freundlich models for lead removal on corn husk table 3: model parameters for lead at different dosages using langmuir and freundlich models the langmuir isotherm assumes adsorption occurs on a homogeneous surface through monolayer adsorption without interactions between adsorbed molecules. in contrast, the freundlich isotherm describes non-ideal sorption on heterogeneous surfaces (eze et al., 2017; amaibi et al., 2024). the results in table 3 show that the langmuir isotherm exhibited higher correlation coefficients (r² = 0.99, 0.93, and 0.96 for 0.5 g/l, 1 g/l, and 1.5 g/l, respectively) than the freundlich model (r² = 0.95, 0.93, and 0.85). moreover, the freundlich model showed negative values for the intensity parameter (n), suggesting a poor fit. these findings indicate that the langmuir model better describes the adsorption process at all dosages studied, implying that the adsorption mechanism involves monolayer sorption on a homogeneous surface. the langmuir isotherm also provided maximum monolayer adsorption capacities (qm) of 169.49 mg/g, 178.57 mg/g, and 85 mg/g for dosages of 0.5 g/l, 1 g/l, and 1.5 g/l, respectively. this trend suggests that as the adsorbent dosage increases, the amount of lead ions adsorbed per unit mass of adsorbent decreases as already mentioned previously. the decrease in qm and adsorption capacity with increasing dosage reflects a limitation in adsorption efficiency due to underutilization of active sites and possible aggregation of particles. for practical applications, it is essential to optimize the adsorbent dosage to achieve a balance between maximizing percentage removal and maintaining high adsorption capacity per unit mass. the values obtained in this study are comparable to or exceed those reported for other agro-based adsorbents used for lead removal, such as those documented by sekar et al. (2004), imamoglu et al. (2008), boudrahem et al. (2009), martín-lara et al. (2010), and moyo et al. (2013). this highlights the corn husk's efficiency as an adsorbent. the essential features of the langmuir isotherm can be expressed in terms of a dimensionless constant separation factor (rl) 𝑅𝐿 = 1 (1+(𝐾𝐿𝐶𝑖) 7 where ci is the initial metal ion concentration in(mg/l) and kl is the langmuir equilibrium constant (l/mg). the separation factor derived from the langmuir model, provides critical information about the nature of the adsorption process. adsorption is considered irreversible when rl= 0, favorable when (0 < rl < 1), linear when rl = 1 and unfavorable when rl> 1 (tseng et al., 2010; sun et al., 2013). in this study, the rl values for 0.5 g/l and 1 g/l dosages were 0.2 and 0.19, respectively, indicating favorable adsorption of lead on corn husk. however, at a higher dosage of 1.5 g/l, the rl value was zero, signifying that the adsorption process was dosage (g/l) langmuir freundlich r2 kl (l/mg) rl r2 n kf (l/g) 0.5 0.9946 0.20 0.06 0.9576 -1.19 1479.11 1 0.9354 0.19 0.07 0.9327 -4.33 107.15 1.5 0.9637 117 0 0.8982 -11.24 53.70 (a) (b) http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 710 irreversible and overly strong. this indicates that at high dosages, the availability of an excessive number of active sites leads to near-complete binding of lead ions, with minimal reversibility aligning with the findings of meroufel et al. (2013) and balarak et al. (2017). these results further support the suitability of corn husk as an effective and sustainable biosorbent for heavy metal removal from aqueous solutions. 3.4.3 adsorption kinetics figure 5 presents the linearized plots of the pfo and pso kinetic models for the adsorption of lead ions onto corn husk at varying adsorbent dosages. model parameters and correlation coefficients (r²) are summarized in table 4 to aid interpretation. the pso model shows an excellent fit to the experimental data, with r² values of 0.96, 0.98, and 0.99 for adsorbent dosages of 0.5 g/l, 1.0 g/l, and 1.5 g/l, respectively. in contrast, the pfo model exhibits comparatively lower r² values of 0.87, 0.93, and 0.89, indicating that it does not adequately describe the adsorption kinetics under the studied conditions. figure 5: adsorption kinetic models (a) pfo (b) pso models for lead removal on corn husk table 4: correlation coefficient and other model parameters for lead removal at different dosages using pseudo-first order and pseudo-second order models dosage (g/l) pseudo-first order pseudo-second order r2 k1 (min-1) qe (mg/g) r2 k2 (g/mg min-1) qe (mg/g) 0.5 0.876 0.023 78.7 0.9625 0.0003 131.6 1 0.9364 0.043 63.1 0.9898 0.0008 80.6 1.5 0.888 0.033 14.2 0.9991 0.0051 50.0 importantly from figure 5, the adsorption capacities predicted by the pso model were observed to decrease with increasing adsorbent dosage. the adsorption capacities predicted by the pso model (qe ) were 131.57 mg/g, 80.65 mg/g, and 50 mg/g for 0.5 g/l, 1 g/l, and 1.5 g/l dosages, respectively. these values closely match the experimental equilibrium adsorption capacities (qe) of 111.72 mg/g, 70.56 mg/g, and 49.06 mg/g, further validating the applicability of the pso model. on the other hand, the adsorption capacities predicted by the pfo model (78.79 mg/g, 63.09 mg/g, and 14.2 mg/g) deviate significantly from the experimental values, confirming its inadequacy in describing the adsorption process. the dominance of the pso model indicates that the adsorption of lead onto corn husk is likely governed by chemisorption, which involves electron sharing or exchange between lead ions and the active functional groups on the adsorbent surface. this chemisorption mechanism is supported by ftir analysis, which revealed the presence of functional groups such as hydroxyl, carboxyl, and ether groups, known for their high affinity for heavy metal ions. chemisorption implies that the process is not solely surface-dependent but also involves strong, irreversible interactions between the adsorbate and the adsorbent. this observation aligns with previous findings by badmus et al. (2007), adeogun et al. (2010), das and mondal (2011), robati (2013), tan et al. (2020), and revellame et al. (2020). (a) (b) http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(3): 702-716. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 711 the findings of this study underscore the importance of optimizing adsorbent dosage for effective lead removal and highlight the potential of corn husk as a sustainable, efficient adsorbent for heavy metal remediation. the applicability of the pso model provides a robust scientific foundation for employing agricultural waste-derived adsorbents in environmental cleanup efforts, consistent with the studies by çelebi and gok (2017) and futalan et al. (2019). the effect of dosage on kinetics highlights the interplay between adsorption rate and capacity: at low dosage where the adsorption process is highly efficient, with a higher proportion of active sites utilized due to the high concentration gradient; and at high dosage where although the overall percentage removal increases due to the greater number of active sites, the adsorption capacity per unit mass decreases, and the kinetics slow down due to reduced driving force and site accessibility. 4. conclusion in conclusion, this study highlights the potential of using corn husk as an effective adsorbent for lead (ii) removal from aqueous solutions, emphasizing the role of adsorbent dosage and contact time. the results demonstrated percentage removal of lead increased with higher dosages and longer contact times, achieving up to 96% removal at 1.5 g/l dosage and 105 minutes. adsorption capacity decreased with increasing dosage, from 111.72 mg/g at 0.5 g/l to 49.06 mg/g at 1.5 g/l, due to underutilization of active sites and particle aggregation. however, adsorption capacity decreased with increasing dosage, attributed to underutilization of active sites and particle aggregation. characterization using ftir, sem, and bet confirmed the presence of functional groups such as hydroxyl, carboxyl, and ether, a high surface area of 114.55 m²/g, and a microporous, rough, and porous morphology, all contributing to the chemisorption mechanism. the langmuir isotherm model provided the best fit, indicating monolayer adsorption with maximum adsorption capacities ranging from 85 mg/g to 178.57 mg/g. the separation factor (rl) values of 0.2 and 0.19 at lower dosages indicated favorable adsorption conditions, whereas an rl value of 0 at 1.5 g/l reflected irreversible adsorption behavior. kinetic studies validated the pseudo-second-order model, highlighting chemisorption as the rate-determining step. while higher dosages improve overall removal efficiency, they reduce adsorption capacity per unit mass and may lead to irreversible adsorption at extreme dosages. acknowledgements the authors are grateful to the tertiary education trust fund (tetfund), abuja, for funding this project through their institutional base research (ibr) grant no.: buk/drip/tetf/0012 references adeogun, ai., bello, os. and adeboye, md. 2010. biosorption of lead ions on biosorbent prepared from plumb shells (spondias mombin): kinetics and equilibrium studies: biosorbent prepared from spondias mombin. biological sciences, 53(5): 246-251. aguilar-arteaga, k., castañeda-ovando, a., castañeda-ovando, ep., lira, bp. and batalla, ld. 2024. removal of heavy metal ions with magnetic carbon prepared from corncob biomass. environmental technology, 45(10): 1956–1968. ahluwalia, ss., and goyal, d. 2007. microbial and plant derived biomass for removal of heavy metals from wastewater. bioresource technology, 98(12): 2243-2257. akram, m., khan, b., imran, m., ahmad, i., ajaz, h., tahir, m., and samad, sn. 2019. biosorption of lead by cotton shells powder: characterization and equilibrium modeling study. international journal of phytoremediation, 21(2): 138-144. alghamdi, aa., al-odayni, ab., saeed, ws., al-kahtani, a., alharthi, fa., and aouak, t. 2019. efficient adsorption of lead (ii) from aqueous phase solutions using polypyrrole-based activated carbon. materials, 12(12): 2020. amaibi, pm., egong, jf., iwe, cr., and obunwo, cc. 2024. adsorption and kinetic studies for removal of fluoride in aqueous system by activated carbon produced from lemon peels. journal of applied sciences and environmental management, 28(5): 1413-1419. aniagor, co., abdulgalil, ag., safri, a., elhmmali, mm., and hashem, a. 2022. preparation of amidoxime modified biomass and subsequent investigation of their lead ion adsorption properties. cleaner chemical engineering, 2: 100013. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; 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zhang, y., zheng, r., zhao, j., zhang, y., wong, p. k., and ma, f. 2013. biosorption of zinc from aqueous solution using chemically treated rice husk. biomed research international, 1: 365163. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 64 arid zone journal of engineering, technology & environment original research article harnessing the sun's potential: an arduino-based system for optimized energy management in pv systems s. akhinbohun*, f. k. alli, and m. omosigho department of computer engineering, faculty of engineering, university of benin, benin city, edo state. nigeria. *corresponding author’s email address: sylvester.akhinbohun@uniben.edu.ng article information abstract the global shift towards renewable energy sources has placed photovoltaic (pv) systems at the forefront of sustainable energy solutions. traditional pv systems often suffer from inefficiencies due to fixed load thresholds that do not adapt to changing environmental conditions, leading to energy waste. it proposes an innovative arduino-based system for optimizing energy management in pv systems. the arduino platform was selected for its ease of programming, affordability, and compatibility with various sensors. by continuously monitoring real-time data such as solar irradiance, battery status, and local energy consumption, the proposed system dynamically adjusts load thresholds to prevent energy waste and grid overload. the system architecture includes high-efficiency pv panels, a solar charge controller, deep-cycle batteries, and various sensors to monitor voltage, current, and temperature. the system employs deep-cycle batteries with capacities based on the energy requirements and expected usage patterns, and voltage regulators such as the lm7805 to ensure safe operation of the arduino microcontroller at 5v, converted from the standard 12v input. this setup shows the comprehensive integration of components to ensure optimal performance. simulation results demonstrate the system’s ability to manage power effectively, preventing overload and promoting energy efficiency. by maintaining precise control over energy distribution and utilizing a user-friendly interface for real-time monitoring, this research highlights the potential of an intelligent, cost-effective solution for enhanced energy management in pv systems, paving the way for more sustainable energy consumption. submitted: 7th may 2024 revised: 4th december 2024 accepted: 7th december 2025 keywords: photovoltaic systems arduino energy management renewable energy sustainability © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the global transition towards renewable energy sources has propelled photovoltaic (pv) systems to the forefront of clean and sustainable energy solutions (farid, rahman, and uddin, 2011). these systems capture solar energy and convert it into electricity for residential and commercial applications (etawil, massoud, and finney, 2010). however, traditional pv inverters often have fixed load thresholds that fail to adapt to fluctuating environmental conditions and energy demands, leading to potential energy waste (farid, rahman, and uddin, 2011; zheng et al., 2017). this inefficiency, coupled with the additional costs associated with inverter installation and rewiring, necessitates the development of more intelligent systems. this study proposes an innovative approach to optimize energy management in pv systems using an arduino microcontroller. arduino's user-friendly programming, affordability, and diverse sensor compatibility make it an ideal platform for integrating advanced energy management systems (zhao, gao, and zhai, 2011). by continuously monitoring real-time data like solar irradiance, battery status, and local energy consumption, the arduino-based system architecture can dynamically adjust load thresholds, preventing energy waste and grid overload (zhao, gao, & zhai, 2011). the research aims to develop a system that is not only user-friendly and cost-effective but also relieves users of the burden of manual appliance operation and eliminates the need for expensive rewiring (frauenfelder, 2011). through simulations, this study investigates the feasibility and effectiveness of the proposed system architecture. the methodology involves simulating power supplies, incorporating sensors to monitor electrical parameters, and utilizing an arduino uno microcontroller as the central processing unit (frauenfelder, 2011). a user-friendly interface allows for manual azojete march 2025. vol.21(1):64-71 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 www.azojete.com.ng mailto:sylvester.akhinbohun@uniben.edu mailto:sylvester.akhinbohun@uniben.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 65 threshold setting and real-time system monitoring. ultimately, it seeks to address the need for efficient power control in pv systems, to promote sustainable energy solutions and a seamless integration of renewable energy sources. mcgowen et al. (2005) developed a system called foxton technology, which uses a 90-nm itanium family processor to regulate power distribution in integrated circuits. the system uses on-chip technology and an embedded system to detect power usage by specific devices and compare it with a predefined power-temperature envelope. the system aims to achieve optimal performance without exceeding the specified threshold limit, using both voltage and frequency adjustments. palamar et al. (2011) designed and implemented a digital control and monitoring module for an ac/dc uninterruptible power supply (ups). the system includes an lcd for the user interface and a real-time clock powered by a lithium battery for time tracking during power outages. the aduc831 microcontroller is used for real-time control, and the system's initialization process involves setting interrupts, initializing lcds and dacs, and assigning initial values to variables. al-hassan et al. (2018) presented research on implementing the zigbee communication protocol for smart sockets and central control systems. they demonstrated effective bidirectional communication and reliable wireless connectivity over distances exceeding 18 meters. edeoghon et al. (2022) designed and implemented an iot-based solar-powered inverter control system using the nodemcu microcontroller unit connected to the internet via wi-fi. this system allows remote monitoring and management of solar outlets, providing data such as current values, outlet loads, and battery levels via a mobile application interface. elkholy et al. (2022) introduced hams, a home automation management system that optimizes renewable energy consumption. the system uses raspberry pi 4 as the main controller and collects data from sensors deployed throughout the house, monitoring parameters like temperature, humidity, smoke levels, and lighting. the system uses passive infrared (pir) sensors for human presence detection and updates data to an iot server for remote access and control via the cayenne iot platform. 2. materials and methods the arduino microcontroller board is the core of the system, chosen for its versatility, ease of programming, and compatibility with various sensors and peripherals (álvarez, mozo, & durán, 2021). high-efficiency photovoltaic (pv) solar panels are used to capture solar energy, and a solar charge controller regulates voltage and current to efficiently charge the battery bank. deep-cycle batteries are used to store excess solar energy during low sunlight or high-demand periods. voltage and current sensors measure voltage and current at various points within the system, providing real-time data for monitoring system performance and optimizing energy management algorithms. a temperature sensor is integrated to monitor ambient temperature conditions, which can affect the efficiency and performance of solar panels and batteries. a user-friendly lcd provides a user-friendly interface for monitoring system status, including energy generation, battery charge level, and load consumption. relays and switching circuitry control the flow of energy within the system, directing power from the solar panels to the battery bank or load, and disconnecting loads during low battery conditions to prevent over-discharge. the arduino microcontroller is programmed using the arduino integrated development environment (ide) with custom-written code to implement energy management algorithms, including mppt for maximizing solar energy harvesting, battery charging and discharging control, load prioritization, and system protection mechanisms. a data logging and communication module is integrated to record system performance data and enable remote monitoring and control capabilities. an enclosure and mounting hardware protect the system components from environmental factors and securely install them in their intended location. before deployment, the system undergoes rigorous testing and calibration procedures to ensure proper functionality and performance. by integrating these materials and methods, our arduino-based system for optimized energy management in pv systems offers an efficient, reliable, and userfriendly solution for harnessing the sun's potential to meet energy needs sustainably. 2.1 system architecture design for the system in the course of carrying out this research work, several components that make the system architecture function were simulated in proteus. these parts are essential pieces that make the functionality of the system. the designed system architecture was simulated to select the load threshold for pv inverters including the connected components. the process flowchart operation of the modeled system is shown in figure 1. http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 66 the simulation setup relies on a robust power supply system, consisting of a main source and an inverter source, which ensures voltage availability for system functionality and command execution. the system configuration includes dual power supply mechanisms, providing redundancy and reliability for uninterrupted operation (kumar et al., 2018). when ac, represented by the sinusoidal wave, is sourced from the main supply, it undergoes initial transformation via a step-down transformer which helps to convert a higher voltage input into a lower voltage output, and a voltage rating of 220v was adopted. to lower the voltage from 220 volts to 12 volts, a transformer with an appropriate turn ratio was employed. 𝑇𝑢𝑟𝑛𝑠 𝑅𝑎𝑡𝑖𝑜 (𝑁) = 𝑉2 𝑉1 1 where; v1is the input voltage (220 volts), v2is the desired output voltage (12 volts). 2 figure 1: flowchart of system architecture transformer operation involves a step-down transformer with a primary coil having a higher number of turns than the secondary coil, maintaining a specific ratio of 1:n. this ratio is approximately 0.0545, resulting in a transformer with a 20:1 turn ratio. the voltage is then converted to direct current (dc) to ensure compatibility with the arduino uno microcontroller, which operates with dc input. the stepped-down voltage from the secondary coil is converted through a rectifier, which transforms ac into dc, ensuring seamless integration with the arduino uno microcontroller. the voltage is then passed through a 100uf capacitor c1 to remove noise, and a voltage regulator reduces 12v to the desired voltage. this process ensures seamless integration with the arduino uno microcontroller. the arduino uno microcontroller has a maximum voltage rating of 5v, any higher would destroy it. the voltage regulator used for this simulation is the lm7805 and it drops the 12v to 5v by considering the following parameters: input voltage (𝑉𝑖𝑛): 12v, output voltage (𝑉𝑜𝑢𝑡): 5v load current (𝐼𝑜𝑢𝑡): the maximum current your circuit or device connected to the regulator will draw. a load current of 1a is used. the following formula is used to calculate the necessary values. differential voltage (𝑉𝑑) parameter represents the voltage drop across the regulator and is calculated as the difference between 𝑉𝑖𝑛 and 𝑉𝑜𝑢𝑡. it is mathematically, expressed as 𝑉𝑑 = 𝑉𝑖𝑛 − 𝑉𝑜𝑢𝑡. that is, if 𝑉𝑖𝑛 is 12v and 𝑉𝑜𝑢𝑡 is 5v, then 𝑉𝑑 would be 7v. this relationship can be denoted as follows: 𝑉𝑑 = 12𝑉 − 5𝑉 = 7𝑉 3 http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 67 power dissipation (𝑃𝑑): this refers to the power dissipated by the regulator and is determined by the product of the voltage drop (𝑉𝑑) and the load current (𝐼𝑜𝑢𝑡). expressed in mathematical terms, 𝑃𝑑 can be represented as 𝑃𝑑= 𝑉𝑑 × 𝐼𝑜𝑢𝑡. for instance, if 𝑉𝑑 is 7v and the load current (𝐼𝑜𝑢𝑡) is 1a, then the power dissipation would be 7w. this calculation is demonstrated as follows: 𝑃𝑑 = 7𝑉 × 1𝐴 = 7𝑊 4 the lm7805 voltage regulator ensures stability and minimizes output voltage ripple by incorporating an output capacitor, c2. the capacitor, with a 10nf capacitance rating, stabilizes the voltage output. once regulated to 5v, it is directed to the arduino uno microcontroller through pin 9, mains. the 5v supply enters the microcontroller through this pin 9. this pivotal connection establishes the foundation for the microcontroller's operation and subsequent functionalities. the inverter supply follows the same procedure as the main supply, filtering output voltage through capacitor c3 and voltage regulator through capacitor c5, with a stabilized 5v output which is directed into the arduino uno microcontroller through pin 10. the system consists of push buttons, a central processing unit, digital pins, analog pins, and a display unit (20x4 lcd). the arduino uno microcontroller serves as the core component, interconnecting all necessary elements for the simulation. digital pins include pin 0 (rxd) for receiving serial data, pin 1 (txd) for transmitting serial data, and pins 2 & 3 (rs & en) for controlling the lcd. data pins 4 7 (d4 d7) are directly connected to the lcd, facilitating data transmission from the arduino to the lcd. pin 8 receives 5v power from the inverter source to power the microcontroller, ensuring its functionality. pin 9 receives 5v power from the main source to power the microcontroller, ensuring consistent operation. analog pins a3, a4, and a5 (menu, inc, and dec) are linked to switch buttons for menu navigation and selection operations. meanwhile, the display unit connects to the arduino microcontroller using specific data pins 4, 5, 6, and 7. the switching unit facilitates the seamless transition between different power sources. outlets, consisting of a transistor and a relay switch, play a pivotal role in assessing the system's output. the bc547 transistor is used for its signal amplification capabilities, with three terminals: the emitter, collector, and base. in the other hand, the relay uses five pins, including two coil pins and three additional pins designated as common, normally open, and normally closed. the common pin maintains a continuous connection to the output, while the normally open connection establishes a connection solely upon the relay's activation. the relay's operational functionality is facilitated by the two coil pins powering the electromagnet and one coil pin connecting to a positive voltage source and the other to a ground or negative voltage source. 2.2 applied procedure figure 2 shows the complete system diagram; the arduino uno serves as the central processing unit (cpu) in this setup. built around the atmel atmega328p microcontroller, it boasts 14 digital input/output pins, with 6 of these configurable for pulse-width modulation (pwm) applications (hossain et al., 2022). programmed through the arduino integrated development environment (ide), the uno supports a range of programming languages and libraries, making it an optimal choice for its user-friendly interface, ease of programming, and cost-effectiveness (silva et al., 2020). code for the microcontroller is composed in c++, compiled, and converted into a .hex file format via the arduino ide. in tandem with the uno, a 20x4 lcd is employed for its superior display capabilities compared to the standard 16x2 lcd. http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 68 figure 2: circuit diagram of the system the arduino uno uses a step-down transformer to reduce incoming alternating current (ac) from 240v to 12v. this ac is rectified to dc to align with the microcontroller's requirements. the dc voltage is then filtered using a capacitor to eliminate noise. a voltage regulator is used to reduce the voltage from 12v to 5v, which is then further filtered through another capacitor before reaching the microcontroller. the inverter source is integrated similarly, with the 5v output fed into the microcontroller through pin 8. users can input and store the threshold limit, and the power source can be chosen between the main source or the inverter source. however, the switch source component facilitates seamless transitioning between the main and inverter power sources. push buttons (btn1, btn2, btn3) allow manual adjustment of the threshold power limit. press and hold btn1 to access the menu interface, where the threshold value can be modified and saved. btn2 and btn3 increment and decrement the threshold value, respectively. 3. results and discussion in this section, the results obtained from testing the system architecture are presented. the system architecture was thoroughly evaluated by adjusting the threshold value three times. 3.1 results at 25w, 20w, and 10w. this iterative process aimed to validate the seamless operation of the designed system. the power allocated to each outlet was manually adjusted by editing the resistance values of the resistors connected to each outlet. this adjustment simulated the allocation of power to the outlets in the absence of actual loads being connected. specifically, for this phase, r4 (connected to d_1) was set to 1.7kω, r6 (connected to d_2) was set to 2kω, and r8 (connected to d_3) was set to 1.2kω. 3.1.1 threshold at 25w main source behavior: figure 3(a) shows what happened when the system drew power from the main source, it was verified that no socket was turned off. figure 3(b) demonstrates that every socket received power from the microcontroller. http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 69 (a) (b) figure 3: (a). socket shown power drawn from the main (b) power distribution to each outlet inverter source displayed that the load entering socket 3 exceeded the set threshold of 25w. consequently, power to socket 3 was cut off. 3.1.2 threshold at 20w with the threshold at 20w, the main behaviour when drawing power from the source indicated that sockets remained powered and that no changes in power distribution. thus, power is supplied to every socket from the microcontroller. however, when the load connected to outlets 1 and 3 exceeded the set threshold of 20w. consequently, power to outlets 1 and 3 was cut off to control the inverter drained. 3.1.3 threshold at 10w when the threshold is adjusted to 10w, and drawing power from the main source, no sockets are cut off, and every socket receives power from the microcontroller. the load-drawn power from all three outlets exceeded the set threshold of 10w, consequently power to all three outlets was cut off. 3.1.4 implication of findings thus, the results obtained from testing the system architecture indicate several significant implications for the design and implementation of photovoltaic (pv) systems. the system's precise power distribution, based on userdefined threshold values, ensures stability and prevents overloading, promoting efficient use of solar energy resources in smart grids. this aligns with the findings by al-hassan et al. (2018). the manual adjustment of threshold power ratings via push buttons enhances user interaction with the system, allowing for customized energy distribution. this approach is supported by the work of edeoghon et al. (2022), which highlights the importance of user-friendly interfaces in enhancing the functionality and acceptance of solar-powered systems. moreso, the system improves the reliability and safety of pv inverter systems by incorporating real-time monitoring sensors and relay switches for power supply control. this aligns with zheng et al. (2017) findings on the importance of real-time data collection and automated control. the arduino uno microcontroller simplifies system architecture, making it an economical solution for implementing complex control algorithms in renewable energy systems, this also agreed with silva et al. (2020). 3.2 further discussions the system was evaluated by adjusting the threshold value at three different levels: 25w, 20w, and 10w, under both main and inverter power sources. the results showed that the system could effectively manage power distribution, cutting off outlets that exceeded the set threshold. 3.2.1 threshold at 25w the main source and inverter sources remained powered, demonstrating their ability to handle the load without issues, while socket 3, which exceeded the 25w threshold, was cut off. these findings are consistent with previous http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 70 studies that emphasize the importance of load management in preventing system failures (etawil, massoud, & finney, 2010). 3.2.2 threshold at 20w the main source showed stable power distribution, while the inverter source effectively managed dynamic load by cutting off outlets 1 and 3 when their load exceeded 20w. this supports the research by farid, rahman, and uddin (2011), who demonstrated that adaptive load management systems can significantly enhance the efficiency and reliability of pv systems. 3.2.3 threshold at 10w the main source ensures consistent power distribution without cut-offs, while the inverter source maintains load limits by cutting off all three outlets exceeding the 10w threshold. these results are in agreement with al-hassan et al. (2018), who found that precise control mechanisms are vital for the optimal performance of renewable energy systems. 4. conclusion this research work focused on designing an architecture for selecting load thresholds in photovoltaic inverters simulated using proteus version 8 software. the system's performance was rigorously tested under various conditions, demonstrating adherence to design objectives. key components such as the power supply, manual adjustment buttons, sensors, and the arduino uno microcontroller significantly enhanced system functionality and safety. effective power management observed in the simulation prevents overloading, promoting energy optimization and system reliability. these findings hold practical significance, facilitating more efficient and costeffective pv systems. moreover, the potential for implementing more complex system architectures to respond to evolving energy demands presents promising avenues for future research. this research highlights the potential of an intelligent, cost-effective solution for enhanced energy management in pv systems, paving the way for more sustainable energy consumption. references al-hassan e., shareef h., islam m. m., wahyudie a. and abdrabou a. a., 2018. improved smart power socket for monitoring and controlling electrical home appliances," in ieee access, 6:49292-49305, doi: 10.1109/access.2018.2868788. álvarez, j. l., mozo, j. d., and durán, e. 2021. analysis of single board architectures integrating sensor technologies. sensors, 21(18):6303. edeoghon, a. i., j. chibuzor okocha, j. s. ebu, r. e. ohiocheoya, o. v. chukwunweike, g. ebikade, m. efemena, e. o. akinlade, ekwunife o., and odey n. 2022. design and implementation of an iot-based solar-powered inverter control system. 10(8). elkholy, m. h., senjyu, t., lotfy, m. e., elgarhy, a., ali, n. s., & gaafar, t. s. 2022. design and implementation of a real-time smart home management system considering energy saving. sustainability, 14(21): 13840. etawil, a. m., massoud, a. m., and finney, s. j. 2010. grid-connected photovoltaic generation system: an overview. renewable and sustainable energy reviews, 14(1): 54-73. farid, a. m., rahman, m. a., and uddin, m. n. 2011. design and development of a novel solar tracking system. international journal of renewable energy research, 1(4): 213-218. frauenfelder, m. (ed.). 2011. make technology on your time vol. 25 . o'reilly media, inc. hossain, m.r., kamruzzaman, m., rashid, m.m., alam, m.s. and robbani, m. g. 2022. microcontroller-based environment monitoring and load control system (doctoral dissertation, sonargaon university (su)). http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu arid zone journal of engineering, technology and environment, march 2025; vol.21(1): 64-71. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: sylvester.akhinbohun@uniben.edu 71 kumar, m., memon, z. a., uqaili, m. a., and baloch, m. h. 2018. an overview of uninterruptible power supply system with total harmonic analysis & mitigation: an experimental investigation for renewable energy applications. ijcsns international journal of computer science and network security, 18(6): 25-36. mcgowen, r., poirier, c. a., bostak, c., ignowski, j., millican, m., parks, w. h., and naffziger, s. 2005. power and temperature control on a 90-nm itanium family processor. ieee journal of solid-state circuits, 41(1): 229-237. palamar, a., karpinskyy, m., and vodovozov, v. 2011. design and implementation of a digital control and monitoring system for an ac/dc ups. in 2011 7th international conference-workshop compatibility and power electronics (cpe) (pp. 173-177). ieee. zhao, l., gao, y., and zhai, j. 2011. a novel transformerless photovoltaic grid-connected power inverter. ieee transactions on power electronics, 26(1): 362-370. zheng, s., quevedo, d. e., guerrero, j. m., vasquez, j. c., and savaghebi, m. 2017. high-efficiency and high-powerdensity dc-dc converters for renewable energy systems: a review. ieee journal of emerging and selected topics in power electronics, 5(1): 365-379. http://www.azojete.com.ng/ mailto:sylvester.akhinbohun@uniben.edu corresponding author’s email address: aarasheed.cpe@buk.edu.ng 378 arid zone journal of engineering, technology & environment original research article synthesis and simulation of tannery wastewater treatment process with biogas generation using wrc stoat software a. a. rasheed*, f. g. yusuf, s. ogunleye, and a. b. ibrahim department of chemical and petroleum engineering, faculty of engineering, bayero university kano *corresponding author’s email: aarasheed.cpe@buk.edu.ng article information abstract tannery wastewater is characterized by its high organic load and toxicity, primarily due to the presence of putrescible matter and heavy metals. this study aimed to simulate a comprehensive treatment process for tannery wastewater using sewage treatment operation analysis over time (stoat) software. the quality of treated wastewater from the simulation was evaluated against the national environmental standards and regulations enforcement agency (nesrea) discharge standards to meet environmental safety requirements. the treatment system incorporated a multi-stage approach, including physical preliminary treatment units, chemical primary treatment, and biological secondary treatment. additionally, the system featured a biogas production section and sludge dewatering units to maximize resource recovery. the simulation effectively modeled the treatment processes, capturing operational dynamics and interactions across the treatment units. key pollutants, such as biochemical oxygen demand (bod), total suspended solids (tss), ammonia, and nitrate were monitored. additionally, the study explored the impact of hydraulic retention time (hrt) on treatment efficiency. the results indicated that all parameters met nesrea's permissible discharge limits at various residence times. similarly, the observed trends aligned with findings reported in the literature. furthermore, the biogas yield from the simulation was 0.27 kg/m³ of tannery influent, with a maximum methane purity of 41%. digested sludge was generated at a rate of 0.072 m³/m³ of tannery influent. however, extending digester residence time did not significantly enhance biogas yield or methane concentration, suggesting the need for process optimization or pre-treatment strategies. this research demonstrates the effectiveness of stoat as a simulation tool for designing tannery wastewater treatment processes, ensuring compliance with stringent regulatory standards while optimizing resource recovery through biogas generation and sludge management. the findings emphasize the necessity of integrating physical, chemical, and biological treatment processes to enhance contaminant removal and improve the sustainability of tannery wastewater management. received: 29th january 2025 revised: 16th march 2025 accepted: 17th march 2025 keywords: tannery wastewater simulation biogas stoat activated sludge process © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction tannery wastewater is a major environmental concern due to its complex composition, which includes high concentrations of organic and inorganic pollutants. these contaminants—such as biological oxygen demand (bod), chemical oxygen demand (cod), heavy metals (e.g., chromium), sulfides, and ammonia—pose significant risks to aquatic ecosystems and human health if not properly treated (birhanu, 2017; ghorab et al., 2022; bhardwaj et al., 2023; monira & mostafa, 2023). given the toxic and persistent nature of these pollutants, effective treatment strategies are essential to minimize environmental degradation, ensure compliance with regulatory standards, and promote sustainable industrial practices (okereke et al., 2016; obaideen et al., 2022; singh et al., 2023; kato & kansha, 2024). conventional biological treatment methods, such as the activated sludge process (asp), are widely used for industrial wastewater treatment. however, asp alone is often ineffective for tannery wastewater due to the azojete june 2025. vol.21(2):378-388 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/006 www.azojete.com.ng mailto:aarasheed.cpe@buk.edu.ng mailto:aarasheed.cpe@buk.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 379 inhibitory effects of toxic compounds, which disrupt microbial communities and reduce treatment efficiency (zhao et al., 2022; nigam et al., 2023). to overcome these challenges, integrating asp with physicochemical processes—such as coagulation-flocculation, adsorption, and advanced oxidation—can enhance pollutant removal by targeting heavy metals and recalcitrant organics (ayach et al., 2024; sravan et al., 2024). additionally, anaerobic digestion offers a viable solution by breaking down complex organic matter in oxygenlimited conditions while simultaneously generating biogas, thereby improving both treatment efficiency and sustainability (faragò et al., 2021; capodaglio & callegari, 2023). this combined approach not only ensures compliance with discharge standards but also contributes to resource recovery and energy generation, making wastewater treatment more economically viable (breach & simonovic, 2018; rafiee et al., 2021; bohra et al., 2022). despite the urgent need for improved tannery wastewater management, research gaps persist in developing and optimizing comprehensive treatment systems that integrate biological, chemical, and resource recovery processes. existing studies (sivagami et al., 2018; korpe et al., 2019; urbina-suarez et al., 2021; lei et al., 2023) often focus on isolated treatment technologies, failing to evaluate the synergistic effects of a fully integrated system. this fragmented approach limits the ability to optimize operational parameters, predict long-term performance, and ensure compliance with environmental standards such as nesrea regulations. simulation tools like stoat have proven effective for modeling wastewater treatment processes; however, their application to tannery effluents is limited. this lack of simulation-based studies hinders the development of optimized, energy-efficient treatment systems tailored to the unique challenges of tannery wastewater. addressing this gap is essential for designing treatment systems that not only comply with environmental regulations but also enhance sustainability through resource recovery. this study aims to addresses these challenges by developing and simulating a comprehensive tannery wastewater treatment system using stoat. the proposed treatment approach integrates the activated sludge process for biological degradation of organic pollutants with anaerobic digestion for biogas recovery. through detailed simulation, this study analyzes system interactions, evaluates pollutant removal efficiency, assesses biogas and sludge generation potential, and optimizes key operational parameters. the findings will provide valuable insights for designing sustainable tannery wastewater treatment systems that not only meet environmental standards but also support energy recovery and resource utilization 2. materials and methods 2.1 materials the simulation of the treatment process was conducted using wrc stoat 5.0.551 (2013 version), installed in a laptop computer. also, a microsoft excel was utilized for supplementary calculations and the plotting of graphs. table 1 presents the physicochemical properties of tannery wastewater from chowdhary et al. (2017), used as secondary data in this study to provide a robust foundation for a realistic simulation. these characteristics is a representative of typical pollutant concentrations in high-strength industrial tannery effluents which provided the foundation for simulating and evaluating the performance of the treatment process. table 1: physicochemical properties of tannery wastewater used (chowdhary et al., 2017). s/n parameters values 1 ph 7.86 2 temperature 32 3 total bod 27,266 4 total cod 56,000 5 total suspended solids (tss) 16,205 7 ammonia 40 7 nitrate 26 7 heavy metals (cu, cd, zn, ni, fe, mn, pb) 70 all the values are in mg/l except ph and temperature (o c) http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 380 2.2 process synthesis and description for this study, the synthesis was carried out to address the specific challenges posed by tannery effluent, which is characterized by high concentrations of organic pollutants, heavy metals, and ammonia. the process synthesis was guided by: characteristics of tannery wastewater: data on the physicochemical properties of tannery wastewater, such as bod, cod, tss, ammonia, and chromium levels, informed the selection of treatment components. regulatory standards: the system was designed to meet nesrea discharge permit standards, ensuring the treated effluent is safe for disposal or reuse. activated sludge process (asp): the asp was selected as the treatment method due to its proven effectiveness in handling high organic loads and nitrogen removal. biogas recovery: anaerobic digestion was incorporated to treat excess sludge from the asp, enabling biogas recovery for energy sustainability. figure 1 represents the schematic diagram of the process. in the proposed treatment process, the tannery wastewater is received, beginning with preliminary screening where coarse solids and debris are removed to prevent damage to downstream equipment. the wastewater then flows into a primary clarifier, where heavier particles settle, reducing total suspended solids (tss). the clarified water enters the activated sludge process, a biological treatment stage where aerobic microorganisms in the aeration tank degrade organic pollutants, lower bod and cod, and convert ammonia to nitrates through nitrification (cervantes et al., 2005). mixed liquor from the aeration tank enters a secondary clarifier, separating biomass. some sludge is recycled to sustain microbial activity, while excess sludge and primary clarifier solids are sent to a thickener for consolidation and water separation. this step increases the sludge's solid content, reducing its volume and making it more efficient for subsequent treatment in the anaerobic digester. concentrated sludge from the thickener is sent to the digester for biogas production, while the separated water is returned to the treatment process for further purification. in the anaerobic digester, the sludge undergoes microbial decomposition under oxygen-free conditions, resulting in the production of biogas. the anaerobic digester is specially designed to accommodate not only excess sludge from the asp but also solid organic waste generated during the tanning process, such as skin trimmings, fats, and other organic residues. by integrating these high-organiccontent materials into the digestion process, the system significantly increases the overall organic load, enhancing microbial activity and maximizing biogas production. the treated effluent, if it meets nesrea discharge standards, is either discharged into the environment or reused, while the stabilized sludge is safely disposed of or utilized as fertilizer. figure 1: process schematics of the treatment http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 381 2.3 methods the inflow data used in the stoat modelling are the values from table 1. the bod, asal1 and ssed1 models were used for the primary clarifier, aeration basin and secondary clarifier respectively. both models are available on the stoat˝ simulation program and the guidelines of wrc plc (1994) and rieger et al. (2013) were considered for modelling conduction. initially, information on tank sizes and operational data were set as shown in table 2. the influent profile assumed on stoat was the constant pattern with 20 m3/h chosen as the inflow. in the secondary sedimentation tank, the wastage method selected was fixed-rate over variable time to maintain a specific mixed-liquor suspended solids (mlss). hydraulic retention time (hrt) and solids retention time (srt) were estimated using equations (1) and (2) respectively (henze et al., 2008; tchobanoglous et al., 2014). 1 2 v is the volume of the aeration tank, q is the flow rate, x is the mlss concentration, qw is the sludge wastage flow, qeff is the effluent flowrate and xeff is the effluent tss. the wastage method in the aeration basin selected was “none” such that the sludge will only be wasted from the secondary clarifier. the analysis conducted using stoat in this study was limited to evaluating key parameters such as total bod, tss, ammonia, and nitrate. this focus was necessitated by the constraints posed by the software's modeling capabilities and the availability of input data specific to tannery wastewater. while these parameters provide critical insights into the system's performance regarding organic pollutant removal, solid separation, and nitrogen management, other important aspects, such as heavy metal removal, sulfide concentrations, and specific microbial population dynamics, were not directly analyzed due to these limitations. table 2: initial process dimensions used in the simulation primary clarifier process model: bod number of stage: 3 volume: 1,200 m3 surface area: 400 m2 aeration basin: process model: asal1 volume: 800 m3 number of stage: 1 number of mlss recycles: 0 wastage method: none secondary clarifier: process model: ssed1 number of stages: 8 surface area: 400 m2 depth of tank: 3 m depth of feed: 2 m *ras feed: ratio (40 %) ras (return activated sludge) http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 382 2.4 data analysis the stoat simulation analysis in this study primarily focused on the primary clarifier, aeration tank, secondary clarifier, and digester as the main treatment units. this selection was guided by the scope of the study, which aimed to evaluate the core processes involved in tannery wastewater treatment and biogas recovery. therefore, simulation data analysis was done at four different points in the process: after the primary clarifier, after the aeration basin, after the secondary clarifier where the treated water leaves the plant, and the top of the anaerobic digester where the biogas generated is collected. this focused approach allowed for a detailed examination of critical treatment processes while acknowledging the exclusion of other ancillary units due to the defined limitations of the study's scope. 2.5 assumptions the following assumptions allowed for a structured and focused simulation, balancing simplicity and practicality while evaluating the performance of the tannery wastewater treatment process integrated with biogas recovery: • the tannery wastewater was assumed to have uniform physicochemical characteristics based on the data reported by chowdhary et al. (2017). • variations in influent composition and flow rate were considered negligible or within manageable limits. • the treatment system was assumed to operate under steady-state conditions, with no abrupt changes in influent load or operational parameters. • all heavy metals present in the tannery wastewater are in a soluble form within the liquid phase and are effectively removed in the chemically assisted sedimentation chamber before the effluent enters the aeration tank • the microbial populations involved in the activated sludge process and anaerobic digestion were assumed to remain stable and unaffected by inhibitory substances such as heavy metal concentrations. • the treatment process was assumed to operate at a constant temperature suitable for both aerobic and anaerobic biological activities, typically around 25 – 35° c. • biogas production was assumed to be primarily from the anaerobic digestion of organic sludge. 3. results and discussion 3.1 primary clarifier results figure 2 shows the performance of the primary clarifier based on the initial process dimensions and flow rate. the estimated hrt was 3.5 days which is higher than most values reported in the literature. it was observed that a reduction of approximately 74 % in total bod and 92 % in tss was achieved in the primary clarifier. this can be attributed to the very long hrt which allows for settling of suspended solids and removal of some particulate organic matter. according to metcalf & eddy (2003), typical hrt for primary clarifiers is between 1.5 to 2.5 hours for municipal wastewaters. therefore, a hrt of 3.5 days (84 hours) is very long even for industrial effluents such as tannery. however, as the hrt was decreased to 1.75 days (42 hours) in the simulation, 49 % of the bod was reduced and 83 % of tss reduction was achieved. further reduction in the hrt to 0.35 days (8.4 hours) gave only 17 % and 76 % reductions in the bod and tss respectfully. the trend observed is in agreement with tchobanoglous et al. (2014) and karia et al. (2023) who reported that efficiently designed and operated primary sedimentation tanks should remove from 50 to 70 % of the suspended solids and from 25 to 40 % of the bod. this level of performance demonstrates the importance of primary sedimentation as a pretreatment step, particularly in reducing the organic load before biological treatment. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 383 figure 2: performance of primary clarifier from the simulation model 3.2 aeration tank results the aeration tank was simulated with a ras ratio of 40 % and the estimated srt from the model was 5.8 days, and the hrt was 2.32 days, based on the initial process dimensions in table 2. the performance is shown in figure 3. it can be observed that a reduction of bod by 97 % was achieved during aeration, reflecting the efficiency of the activated sludge process. it can also be seen that the solids concentration in the aeration basin increased significantly from 398 mg/l (leaving the primary clarifier) to 2181 mg/l. this is due to the removal of bod, which promotes the growth of biomass (henze et al., 2008). during the aeration process, microorganisms consume organic pollutants present in the wastewater as their energy and carbon source. the microorganisms proliferate as the bod levels decreases, leading to an increase in the concentration of suspended solids. the average solids concentration from the results was 2475 mg/l. a longer hrt allows for more thorough treatment, as it provides more time for physical, chemical and biological processes to occur. in tannery wastewater treatment plants, different treatment units have specific hrt requirements; for example, primary clarifiers or sedimentation tanks may have a shorter hrt to allow for the settling of suspended solids and separation of oils and grease (ho et al., 2017; mandal et al., 2020). other biological treatment units, such as aeration tanks, typically require a longer hrt to provide sufficient time for microorganisms to metabolize organics pollutants (bhattacharyya et al., 2022; zulfikar et al., 2022; waqas et al., 2023). figure 3: performance of the aeration tank from the simulation model the effect of hrt on tss and bod inside the aeration basin can be observed in figure 4. it was observed that decreasing the hrt increases the tss while reducing the bod removal efficiency. from figure 4, decreasing the hrt from 2.32 days to 0.23 days increases the tss from 2181 mg/l to 4032 mg/l due to increase in the organic load rate. on the other hand, the bod removal deteriorated from 97 % to 87 %. it has been reported that 1 day hrt has been successfully employed in tannery wastewater treatment. others indicates a bod removal of 80 % to 90.8 % for tannery effluent (el-sheikh et al., 2011; mekonnen et al., 2017; prabhakaran et al., 2022; zulfikar et al., 2022). typical srt range for conventional continuous flow activated sludge system is 3 – 15 days (metcalf & eddy, 2003). in this study, 97 % bod removal was achieved in the aeration tank with 5.8 days srt and 2.32 hrt. the observed trend in figure 4 is in agreement with the general http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 384 theory of activated sludge systems and other reported studies (bhattacharyya et al., 2022; prabhakaran et al., 2022; zulfikar et al., 2022). a substantial reduction in ammonia concentration (> 99%) occurred due to nitrification, where aerobic bacteria converted ammonia to nitrate. the final ammonia concentration met discharge limits, demonstrating effective nitrogen removal. nitrate concentrations in the effluent were also within permissible limits, indicating that denitrification and dilution effectively managed nitrate levels. figure 4: effect of hrt on tss and bod in the aeration tank 3.3 secondary clarifier results figure 5 shows the performance of the secondary clarifier based on the initial process dimensions. bod removal reached 99%, indicating a nearly complete elimination of biodegradable organic pollutants. tss were also reduced significantly, with over 99 % removal in the primary tank and an additional reduction in the secondary clarifier, achieving effluent quality that complies with regulatory standards . figure 5: secondary clarifier performance table 3 presents the treated water quality after the secondary clarifier against the effluent limitation standards for tannery wastewaters set by nesrea. this underscores the combined effectiveness of physical sedimentation and biological treatment. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 385 table 3: treated water quality from the simulation against effluent limitation standards for tanning and leather set by nesrea (ladan, 2012) s/n selected parameters this study nesrea 1 ph 7.01 6 – 9 2 temperature 30 40 3 total bod 2.37 50 5 total suspended solids (tss) 1.48 25 8 ammonia 0.01 10 9 nitrate 0.01 20 3.4 biogas generation figure 6 shows the biogas generation profile from the model. the predicted biogas production and methane content from the model revealed a slight deviation from typical standards. while typical methane content in biogas is between 45 % to 70 % (amon et al., 2007; li et al., 2019; jameel et al., 2024), the simulation predicted an average methane purity of 41 %, carbon dioxide content of 53 % and 4 % water, at a rate of 5.28 kg per 20 m3 of tannery influent. this translates to 2.165 kg/h of biomethane. however, digested sludge was produced at a rate of 1.42 m³/h, indicating effective organic matter degradation but suboptimal methane generation. biogas yield from the model was 0.26 kg per m³ of influent. given methane's density of 0.75 kg/m³ at standard conditions, the produced biomethane equates to 2.896 m³/h. at the target methane purity of 60 %, the production would be 3.258 kg/h or 4.344 m³/h of biomethane. this difference highlights the need for optimization in the digestion process to enhance methane yield and purity. on an annual scale, this production level equates to approximately 38,000 m³ of biomethane per year, translating to a power generation potential of around 57,000 kwh. for reference, 10 m³ of dry biogas with a methane composition of up to 60 % has a lower heating value of about 21.5 mj/m³ at 20 °c and atmospheric pressure, which supports a power generation capacity of 15 kw per hour (inoplex, 2022; onyekaozuoro et al., 2023). figure 6: biogas generation results and profile from the simulation the suboptimal methane purity from the model suggests potential issues with the digestion process, such as the presence of inhibitory substances like sulfides or insufficient operational parameters (e.g., retention time, ph, or temperature). additionally, optimizing process variables and ensuring proper pre-treatment of tannery wastewater to reduce inhibitory compounds, like heavy metals, can significantly improve biogas quality and yield. these adjustments are necessary to achieve the target 60 % methane purity, which would enhance the energy recovery potential of the system. it was further observed in the simulation that the residence time of the digester does not have any significant effect on the biogas yield and purity. the reason is stoat has limitations when it comes to combining different http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 386 modes of treatment mechanisms, such as integrating aerobic and anaerobic models. the transition between the two mechanisms is not inherently coupled or dynamically linked. this can lead to inconsistencies in the simulation, particularly when modeling processes like aerobic pre-treatment followed by anaerobic digestion. therefore, in the future, a separate stoat simulation for aerobic and anaerobic units could be carried out, then manually link the outputs (e.g., effluent composition) to approximate system performance. 4. conclusion this study successfully demonstrated the use of the stoat simulation software to design and evaluate a comprehensive treatment process for tannery wastewater. the system effectively combined physical, chemical, and biological treatment units, achieving significant pollutant removal and ensuring compliance with nesrea discharge standards. key parameters, including bod, tss, ammonia, and nitrate, were reduced to within acceptable regulatory limits, validating the efficiency of the modeled treatment system. additionally, the study explored the impact of hrt on treatment efficiency, showing similar trends as reported elsewhere. the integration of anaerobic digestion for biogas production and sludge dewatering showcased the potential for resource recovery in tannery wastewater treatment. however, the biogas yield of 0.27 kg/m³ of influent and methane purity of 41% were lower than expected, with no significant improvement observed despite increased digester residence time. this highlights the need for further optimization of process parameters and potential pre-treatment to address inhibitory compounds, such as heavy metals, that may hinder microbial activity and gas production. overall, the study demonstrates the utility of stoat as a reliable tool for simulating and optimizing wastewater treatment processes. it provides a foundation for future research to enhance resource recovery and improve the sustainability of wastewater treatment systems, particularly for industrial effluents like those from tanneries. references amon, t., amon, b., kryvoruchko, v., zollitsch, w., mayer, k. and gruber, l. 2007. biogas production from maize and dairy cattle manure—influence of biomass composition on the methane yield. agriculture, ecosystems & environment, 118(1-4): 173-182. ayach, j., el malti, w., duma, l., lalevée, j., al ajami, m., hamad, h. qnd hijazi, a. 2024. comparing conventional and advanced approaches for heavy metal removal in wastewater treatment: an in-depth review emphasizing filter-based strategies. polymers, 16(14): 1959. bhardwaj, a., kumar, s. and singh, d. 2023. tannery effluent treatment and its environmental impact: a review of current practices and emerging technologies. water quality research journal, 58(2): 128-152. bhattacharyya, a., liu, l., lee, k. and miao, j. 2022. review of biological processes in a membrane bioreactor (mbr): effects of wastewater characteristics and operational parameters on biodegradation efficiency when treating industrial oily wastewater. journal of marine science and engineering, 10(9): 1229. birhanu, ha. 2017. physico-chemical analysis of effluents from tannery industry in ethiopia. international journal of scientific and engineering research, 8(1): 1099-1109. bohra, v., ahamad, ku., kela, a., vaghela, g., sharma, a. and deka, bj. 2022. energy and resources recovery from wastewater treatment systems. in clean energy and resource recovery. elsevier, 2: 17-36. breach, pa. and simonovic, sp. 2018. wastewater treatment energy recovery potential for adaptation to global change: an integrated assessment. environmental management, 61: 624-636. capodaglio, ag. and callegari, a. 2023. energy and resources recovery from excess sewage sludge: a holistic analysis of opportunities and strategies. resources, conservation & recycling advances, 19: 200184. cervantes, fj., pavlostathis, sg. and van haandel, a. 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achieving sustainable development goals (sdgs) and sustainability guideline. energy nexus, 7: 100112. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng https://inoplex.com.au/information/how-much-energy-is-in-biogas/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 378-388. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: aarasheed.cpe@buk.edu.ng 388 okereke, jn., ogidi, oi. and obasi, ko. 2016. environmental and health impact of industrial wastewater effluents in nigeria-a review. international journal of advanced research in biological sciences, 3(6): 55-67. onyekaozuoro, e. c., daim, t. u. and herstatt, c. 2023. roadmapping of biogas production technology in sub-saharan africa: waste to energy. in next generation roadmapping: establishing technology and innovation pathways towards sustainable value, springer international publishing, new york: 181-222. prabhakaran, n., patchai murugan, k., jothieswari, m., swarnalatha, s. and sekaran, g. 2022. tannery wastewater treatment process to minimize residual organics and generation of primary chemical sludge. international journal of environmental science and technology: 1-14. rafiee, a., khalilpour, kr., prest, j. and skryabin, i. 2021. biogas as an energy vector. biomass and bioenergy, 144: 105935. rieger, l., gillot, s., langergraber, g., ohtsuki, t., shaw, a., takacs, i. and winkler, s. 2012. guidelines for using activated sludge models. iwa publishing, london. singh, bj., chakraborty, a. and sehgal, r. 2023. a systematic review of industrial wastewater management: evaluating challenges and enablers. journal of environmental management, 348: 119230. sivagami, k., sakthivel, kp. and nambi, im. 2018. advanced oxidation processes for the treatment of tannery wastewater. journal of environmental chemical engineering, 6(3): 3656-3663. sravan, j.s., matsakas, l. and sarkar, o. 2024. advances in biological wastewater treatment processes: focus on low-carbon energy and resource recovery in biorefinery context. bioengineering: 11(3), 281. tchobanoglous, g., stensel, hd., tsuchihashi, r., burton, f., abu-orf, m., bowden, g. and pfrang, w. 2014. wastewater engineering: treatment and resources recovery. metcalf and eddy inc: 848-860. urbina-suarez, na., machuca-martinez, f. and barajas-solano, af. 2021. advanced oxidation processes and biotechnological alternatives for the treatment of tannery wastewater. molecules, 26(11): 3222. waqas, s., harun, ny., sambudi, ns., bilad, mr., abioye, kj., ali, a. and abdulrahman, a. 2023. a review of rotating biological contactors for wastewater treatment. water, 15(10): 1913. wrc plc. 1994. wrc stoat: tutorials guide. wrc plc: swindon, uk, 74. zhao, j., wu, q., tang, y., zhou, j. and guo, h. 2022. tannery wastewater treatment: conventional and promising processes, an updated 20-year review. journal of leather science and engineering, 4(1): 10. zulfikar, z., nasrullah, n., kartini, k. and aditama, w. 2022. effect of hydraulic retention time on the levels of biochemical oxygen demand and total suspended solid with simple integrated treatment as an alternative to meet the household needs for clean water. open access macedonian journal of medical sciences, 10(e): 6-11. http://www.azojete.com.ng/ mailto:aarasheed.cpe@buk.edu.ng corresponding author’s email address: patrick.delight@yahoo.com 880 arid zone journal of engineering, technology & environment review article review of smart grid technology and the nigerian electricity act: addressing power sector challenges through policy and innovation d.k. patrick* department of electrical and electronics engineering, university of lagos, nigeria *corresponding author’s email: patrick.delight@yahoo.com article information abstract energy policy plays a crucial role in shaping the energy landscape of any region. the reform of the nigerian electricity act in 2023 marked a significant milestone for the nigerian electricity market. it established a legal foundation aimed at addressing the nation’s perennial energy crisis by enabling the adoption of modern sustainable technologies and initiatives into the nigerian power industry. poor policy implementation, inadequate generation, and unplanned downtime due to faults on the defunct transmission and distribution networks have stifled the growth of power delivery in nigeria, emphasizing the need for more intelligent and sustainable power infrastructure. this paper presents a comprehensive review of the challenges in nigeria’s power sector and explores how emerging technologies can provide effective solution at every node of the power chain. it draws insights from global case studies and outlines a strategic roadmap and timeline for planning and implementing smart grid and sustainable initiatives in nigeria. additionally, it highlights critical considerations necessary to promoting long-term sustainability within nigeria’s power industry. received: 1st august 2025 revised: 4th september 2025 accepted: 4th september 2025 keywords: smart grid energy poverty renewable energy environmental sustainability energy policy © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction energy poverty refers to the inability to access or afford reliable and safe power resources and services. in 2023, the world health organization (who) estimated that 2.4 billion people globally experience some form of energy poverty, emphasizing the pervasive nature of the issue (world health organization, 2024). nigeria, the most populous african nation, is endowed with abundant natural resources, including solid minerals, petroleum reserves, coal, and renewable energy sources (pontianus and oruonye, 2021). despite these resources, the country still struggles with energy instability, unreliable grid infrastructure, and underutilization of its energy resources, alongside the steadily increasing demand for electricity. the unreliability of nigeria's national grid is primarily due to frequent outages and unplanned downtimes, often resulting from faulty or aging transmission and distribution equipment. additionally, inefficiencies within major gas and thermal power plants further exacerbate the situation. according to the transmission company of nigeria (tcn), the national grid experienced 12 collapses in 2024 alone, and recorded 105 cases of grid collapse between 2015 and april 2024 (izuaka, 2025). with restoration times lasting a few hours and others extending up to three days, leading to extended blackout periods and significantly affecting businesses and other daily activities. alao and awoyele (2018) criticized the poor and myopic design of nigeria’s transmission network, describing it as the weakest link in the country’s power chain, due to years of paltry upgrades. while studies have examined the root causes of nigeria’s energy challenges and proposed several mitigation recommendations, there exist a gap for research that specifically examines how modern power technology can be adapted to address nigeria’s unique technical, environmental, and socio-economic climate. this study aims to analyze recent reforms in the nigerian energy sector, highlighting key policy developments and innovation that foster sustainable growth. it identifies the most suitable smart devices and initiatives for nigeria’s current energy situation and presents them in a clear and actionable implementation plan. by drawing on insights from carefully selected global case studies, this study assesses the impacts, benefits, and potential bottlenecks of integrating advanced technologies into nigeria’s power grid. azojete september 2025. vol.21(3):880-893 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/018 www.azojete.com.ng mailto:patrick.delight@yahoo.com mailto:patrick.delight@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 881 this paper is structured as follows, the remainder of this section reviews important topics about the nigerian power industry examined in literature, while the next provides an overview of the nigerian electricity act 2023 and smart grid technology. section three presents global case studies where smart devices have been successfully deployed to address similar energy challenges, and outlines a strategic implementation plan tailored to nigeria’s energy needs. the final section offers practical recommendations and concludes the paper. 1.1 inefficiencies in distribution networks and power generation issues the electric power sector reform act of 2005 established the nigerian electricity regulatory commission (nerc) and unbundled power services in nigeria into 18 companies: 9 generation companies, 1 transmission company, and 11 distribution companies, popularly known as discos. the ibadan electricity distribution company (ibedc) is the largest disco (based on numbers of registered customers) operating across seven states and serving over 2.5 million active customers (sasu, 2024). in a research to analyze the performance of ibedc’s distribution network abanihi and ikheloa (2018) obtained reliability indices: saidi = 2,470.16 hours/year, saifi = 695.16 interruptions/year interruptions per customer, and asai = 71.88%. these reliability indices accentuate the inefficiencies in nigeria’s transmission and distribution infrastructure, and speak to the frequency and duration of power outage experienced in nigeria. these frequent faults and outages have led to widespread customer dissatisfaction, damage to power equipment, and substantial loss of revenue for power companies (patrick et al., 2013). in addition, internal conflicts within power companies, particularly due to dissatisfaction of power workers with wages and working conditions, often result in subpar service delivery, and in some cases, partial blackouts triggered by industrial actions led by aggrieved labor unions. similarly, oil and gas sector workers have on several occasions resorted to strikes to express grievances, disrupting gas supply to power generation plants. these disruptions significantly reduce generation capacity, thereby affecting the availability of power on the grid. in april 2025, the committee of power generation companies in nigeria threatened to shut down operations, due to unpaid debts amounting to over ₦4 trillion. this incident underscores the growing frustration experienced by investors and power providers, who continue to face significant financial risks in the sector (enietan-matthews, 2025). 1.2 nigeria's sustainability objective with a current generation capacity of approximately 4,500 mw, and an annual electricity production of 42,509 gwh, the country’s per capita electricity consumption remains low at around 144 kilowatt-hours (kwh) per person per year (world bank, 2025). in response, the nigerian government is working to bolster its power sector by accelerating the construction and integration of renewable energy sources into the national grid, to achieve a more stable and sustainable electricity supply in line with its 30:30:30 vision (bugaje et al., 2022). this goal necessitated the introduction of a reformed legal framework, the electricity act 2023 (federal ministry of power, 2023 and adu and olawepo, 2023). the purpose of this legislation was to promote the diversification of nigeria’s energy mix, and reduce overreliance on natural gas, which currently accounts for over 75% of electricity generation, and also bring the country closer to meeting its growing energy needs. several scholars have investigated nigeria’s perennial energy challenges by examining their root causes, identifying structural inefficiencies, and exploring potential interventions to address nigeria’s energy poverty. in a bid to improve grid performance, adaramola (2014) assessed the feasibility of grid-connected solar generation in a community in northern nigeria. the study proposed an 80 kw solar plant optimized using homer software. to demonstrate the technical and economic viability of this project, a levelized cost of energy (lcoe) of $0.103/kwh was achieved, proving more cost-effective than conventional diesel generators. these findings suggest that similar grid-connected solar pv systems could be economically feasible in other parts of nigeria, especially in regions with high solar radiation. however, challenges such as high upfront costs, absence of efficient storage facilities, seasonal variability, and transmission losses were identified. other researchers also conducted comparative analyses proposing hybrid systems that integrate standalone minigrids into the national grid to increase renewable energy (re) penetration (ekpe and umoh, 2019). while such systems offer considerable benefits like improved grid capacity and resilience, the high capital requirements for grid extensions justify the continued reliance on insular minigrids, particularly in rural communities. similarly, adeniyi (2019) and amuta et al. (2018) argued that integrating re sources into the grid would enable the system to better manage peak demand and reduce dependence on gas. adedokun et al. (2023) provided insights into on-grid renewable energy planning and highlighted the crucial role of government in this process. they observed that despite several ambitious re goals, there has been little tangible progress in implementation, due to lack of accountability and transparency within government institutions. they also identified outdated policies, excessive bureaucracy, poor planning, and technological limitations as key barriers to achieving these goals (nwozor et al., 2021 and akinyele and rayudu, 2016). ozoegwu et al. (2017) http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 882 emphasized the importance of policy-driven incentives, such as net metering and renewable portfolio standards, to stimulate broader adoption of re by rewarding generation, supply, or consumption of renewable energy. ibe and okedu (2009) advocated for decentralized power generation, citing advantages such as lower emissions, higher grid stability and reliability, reduced fault rates, and ease of maintenance. owebor et al. (2021) also proposed the use of carbon capture technologies to enhance the efficiency of gas and thermal power plants, stating that reduced co₂ emissions from plants can promote nigeria’s climate objectives. 1.3 role of energy policy numerous studies have also emphasized the importance of adequate energy policy in advancing nigeria's power sector. ozoegwu and akpan (2021) acknowledged recent policy progress in nigeria’s power sector but argued that poor policy implementation limits the effective utilization of available energy sources, citing bureaucratic obstacles such as delays in licensing and standardization as major barriers to re expansion. they also advocated for climate-specific technological research and the development of local manpower through technical skill acquisition programs. furthermore, edomah, et al. (2017) argued that effective policy formulation and implementation would attract private investment in power industries by curbing illegal connections and meter tampering, which result in revenue loss and deterrence of potential investors (arowolo and perez, 2020). adelaja (2020) identified financial constraints by as a key impediment to re deployment. he opined that the high upfront cost of renewable projects discourage investment, particularly given the long payback periods, and recommended government intervention to boost investor confidence through more favorable returns on investments and implementation of policies that allow for shorter recovery periods. poor maintenance culture, diversion of funds, and corruption within agencies also severely stifle progress in the energy sector (fabiyi et al., 2016). another challenge is the lack of continuity in governance (dioha et al., 2019). akinyele et al. (2019) observed that frequent changes in administration often lead to abandoned energy projects, impeding long-term progress. 1.4 democratization of electricity public participation has been identified as a strategy to improve power service delivery in nigeria by getting citizens more involved in the generation, transmission, and distribution processes. adhekpukoli (2018) advocated for the democratization of electricity in nigeria by decrying the improper management and maintenance of public electric utilities. he cited various advantages of smaller stand-alone power solutions and argued that this approach could help alleviate power theft, vandalism of power infrastructure, and meter tampering, while promoting accountability and a stronger sense of ownership among citizens. moreover, dada (2014) identified public reluctance to adopt new technologies as a significant barrier to energy transition. stating that most consumers tend to favor cheaper, short-term options such as gasoline generators over cleaner, long-term alternatives like solar power. the study, which included extensive interviews with industry leaders and policymakers, highlighted the need for targeted awareness campaigns to educate the public on the long-term economic and environmental benefits of clean energy adoption. 1.5 need for advanced technology insufficient and outdated data is another roadblock to re project planning and development in nigeria. brimmo et al. (2017) posited that without reliable data, accurate assessment and effective planning, re projects become nearly impossible. this study stressed the need for advanced technologies to improve data acquisition in support of energy planning, research, and power system development (vincent and yusuf, 2014 and oyewo et al., 2019). using geographic information system (gis) tools, mentis et al. (2015) conducted a location-based analysis of electrification patterns in rural areas of nigeria. this assessment considered parameters such as existing transmission infrastructure, population density, mineral reserves, and proximity to urban centers. with these parameters, they developed an electrification model using visual basic to recommend the most viable power solutions for each area examined in their research. 2. the electricity act and smart grid overview 2.1 the electricity act 2023 this reform serves as a legal and institutional framework for power operations and players within nigeria. the objective of this act was to improve policy and regulatory structure to attract sustainable investment and promote renewable energy penetration in nigeria electricity supply industry (nesi). in 2023, renewable energy sources contributed less than 2% to the nigerian energy mix, this policy reform was engendered to http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 883 remedy this deficiency, address the aging power infrastructure, and also revamp existing power plants, while attracting investments for efficient and cleaner power generation. 2.1.1 key innovations of the electricity act 2023 • creation of state electricity markets (sections 63(1), 230(2-9)): this reform allows for the decentralization of power within the country, permitting states to regulate electricity activities and operations within respective jurisdiction. ● national electricity policy and strategic implementation plan (section 3(1-3)): the reform made provision for the preparation and publication of the national integrated policy by the federal government through the ministry of power, this publication is subject to review and revision at most every 5 years ● smart grid and renewable energy generation (section 66(1)): it allows for the construction, maintenance, and operation of an integrated smart grid within the country and for investments to be made for the expansion and integration of appropriate technology into existing transmission infrastructure. it encourages the development and utilization of renewable energy for generation of power, and also facilitate the integration of renewable energy into the national grid and distribution networks in accordance with industry standards. ● penalties for vandalism and electricity theft: this reform addresses the shortcomings of the previous power policies by criminalizing intentional damage to power infrastructure, unauthorized bypass with overhead or underground cables, and unauthorized tampering of metering equipment. the tcn attributed most breakdowns in the year 2024 to activities of vandals on transmission infrastructure (ojo, 2024). this provision was made to curb the current attack on electricity infrastructure by vandals attacking transmission lines, meters, and other critical infrastructure often affecting power services, causing temporary or permanent damage to these resources. 2.1.2 implications of this reform –abia state while nigeria’s power challenges remain severe, recent developments suggest that improved energy policies are beginning to yield positive results in the power industry. on the 5th of march 2025, the tcn announced that it transmitted the largest amount of electricity since the inception of power delivery in the country, which serves as a harbinger of positive development in the power industry. this also shows that integrating renewable energy into the mix would bring nigeria closer to matching its energy demand. due to the developments and allowances provided in the nigerian electricity act 2023, abia state has taken advantage of this reform and passed its own electricity bill to establish a competitive electricity market, and also create the abia state electricity regulatory authority (asera) as the regulatory body for power and energy in the region. the state has also commissioned a 141mw integrated energy project. abia state has seen increased power supplying bolstering industrial activities and improved the quality of life of its people. however, the state still faces challenges due to insufficient and inconsistent gas supply to its power plants, and have since set sights on a more renewable and sustainable power solution for the future developments. these developments in the state serve as a paragon for other regions facing similar power challenges in the country, as some have since begun delegations to follow in the footsteps of abia state to promote the development and improvement of the power situation in their region (e.g. ogun state) (ulom, 2024). 2.2 the need for smart grid technology the conventional power grid allows one-directional flow of electricity from central generation stations to consumers. the power grid is made up of arrangements of power equipment, communication infrastructure, and other devices working together for protection, monitoring and control of power evacuated via the grid. smart grid modifies the conventional grid by employing more intelligent devices at every node of the power chain, facilitating more reliable and efficient flow of power and information back and forth from the utility to consumers. smart grid is equipped with the ability to handle uncertainties in scheduling, power transmission and distribution. it also has potential to integrate re sources into the grid, for diversification purposes. this futuristic power infrastructure integrates perfectly with modern technology enabling wide area awareness, grid visualization, real time data acquisition, and digital modelling. while also taking advantage of advancements in weather forecasts, gis technology and artificial intelligence to improve power services and planning. the table 1 below gives a summary of nigeria current electricity situation and emphasizes the need for improvements to minimize network losses and diversify the energy mix through penetration of re sources. http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 884 table 1: key power figures in nigeria (irena, 2023) parameters figures population ~233 million total land area 923,769 km2 energy mix (by %) gas 75%, hydro 23%, re 2% electricity consumption 149 twh/yr electricity generation capacity 5000mw (available) overall network losses 46% 2.2.1 deficiencies in the conventional grid smart grid addresses several deficiencies in the conventional grid by offering reduced downtime from power failures, significantly lowering operation and maintenance cost for power infrastructure. smart grid also offers good management of peak demand periods, improving energy security and efficiency of distributed generation (nerc, 2024). some of these deficiencies are exponentially increasing demand, insufficient supply: inefficient plant, unreliable gas supply, intermittency of hydro due to wavering water levels, transmission and distribution network losses (from table 1), poor peak demand management causing uneven and unnecessary load shedding, aging equipment and outdated technology and overdependence on fossil fuel and high levels of pollution. 2.3 architecture of smart grid the architecture of the smart grid describes how smart components and technological improvement can be made, at all levels of power delivery. smart grid architecture consists of several modules involving automation of transmission and distribution, system coordination, energy efficiency, distributed generation, renewable integration, storage mechanisms, smart home appliances, consumer participation, and electric vehicle (ev) charging (momoh, 2012). these modules can be further grouped into generation, transmission, distribution, and consumer level as seen in figure 1. figure 1: power and information flow in a smart grid (digiteum, 2021) 2.3.1 generation level communication: the timely and secure exchange of important information within the generation plant and also with outside stations (central control centers and transmission stations) is crucial to maintaining the smooth operation of power delivery on the grid. sensory and control devices must convey information of conditions and occurrences in real time within the plant to operators and engineers via a central monitoring system. these control devices also receive instructions from personnel about decisions to be carried out in the plant. malfunctioning of these communication devices can reduce plant efficiency significantly and compromise the safety of personnel and plant equipment (hu et al., 2019). information must also be communicated with market operators for transparency and billing purposes. technologies like power line carrier communication, uhf and vhf radios are examples of conventional communication media for information exchange from plants to substations and control centers. however, their limitation in terms of range and bandwidth poses a major impediment to their continued usage. others http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 885 like fibre optic communication (opgw) and ipbased scada are widely being adopted because of their high bandwidth and support for interoperability and automation, making them particularly complementary for smart grid operations and high-volume data exchange. wireless sensor networks are also being considered to improve communication within the plants, while satellite communication solutions are in development for monitoring and communication for remote power generation applications. integration of large-scale renewable energy solutions: smart grid as a futuristic power infrastructure must efficiently integrate renewable energy sources into the mix, to be transmitted and distributed on the grid. this poses technical difficulty because of the intermittency and variation of these resources. renewable energy sources experience fluctuations which are not generally associated with non-renewable sources, these fluctuations can cause voltage instability and distortions leading to more critical grid issues. for the integration of re, adequate stochastic and prediction models must be developed to analyzing generation levels and demand patterns for design of better matching strategies. dc renewable sources like solar and some wind generation systems may have to be converted and synchronized with ac grid (as most transmission and distribution systems are ac networks) using special inverters synchronizer switches, and filters to alleviate harmonics and deliver quality power to consumers. 2.3.2 transmission level metering, monitoring and control equipment: transmission infrastructure is a crucial member of an integrated power system. it transmits high power from generation stations to major substations and load centers. for efficient, reliable, and stable transmission of power, advanced technology must be employed to monitor and control activities on the grid. data must be acquired in real time for state estimation, stability assessment, fault detection and other important analyses of grid health condition. tools like supervisory control and data acquisition (scada), phase measurement units (pmu) and wide area monitoring systems (wams) are necessary at this level. wams are utilized in transmission networks in smart grid systems to monitor and prevent the spread of disturbances on the grid. they utilize smart sensors placed strategically on the network gathering real time information that reflect general stability and health of the system. wams therefore allow for integration of modern computational and intelligence tools on the grid, like digital twin technology and software applications equipped with artificial intelligence competencies to achieve better grid performance (cioara et al., 2021 and momoh, 2012). pmus are devices consisting of bus voltage and branch current phasors that measure voltage, current, and frequency on the transmission network. using this data, they instantaneously compute voltage and current magnitude, phase angles, real and reactive power. these real time measurements by the pmu alongside competencies of wams and state estimators (se) allow operators and engineers assess voltage stability and frequency disturbance in the entire power system, or on a section of the grid. state estimation is used to locate and deal with errors in measurements due to device malfunction or network errors, they also help in congestion management by providing justification of information obtained from the control and sensory devices on the grid, promoting adequate technical and economic decisions and also assisting with early detection of voltage transient stability issues. to achieve effective monitoring and controlling of the exchange of power in real time, smart grid needs the transfer of adequate and accurate information via a high speed two way communication technology from the utility to end users. transmission substations must be in continued communication with generation stations and control centers via a wide area network, there must also be remote terminal units to enable communication with substation equipment, smart devices and controllers in the transmission substation using a local area network. transmission stations can use both wired and wireless communication equipment depending on the application. these communication infrastructures must possess high bandwidth, and some form of encryption and cyber security firewall to prevent malicious attacks and infringement on the sensitive information. examples of these technology are: optical fiber, broadband over power lines (bpl), multipoint spread spectrum, multiprotocol label switching (mpls), and mesh technology. 2.3.3 distribution level distribution automation (da): distribution is the flow of power from smaller substations (distribution substations) to consumers (residential, commercial, or industrial). in the smart grid architecture, da is the http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 886 control of grid distribution equipment, distributed energy sources, energy storage facilities, and other grid integrated equipment to deliver quality power to consumers with minimum loss and disruptions. advanced metering infrastructure (ami): ami is the communication infrastructure connecting consumers’ smart meters to distribution control centers. it enables two-way flow of information from smart meters to data management systems. ami helps reduce labor and transportation cost for meter reading, it also improves accuracy and transparency of billing, displaying changes in electricity rates based on time-of-day and grid condition (vijayan, 2023). clean distributed generation: distributed generation involves the use of natural and sustainable means of power generation sited closer to consumers, to generate and distribute energy via the distribution network circumventing the complexities of central generation and transmission networks. some examples include solar, wind, fuel cells, and small hydro. however, ac conversion and storage present concerns for distributed generation. energy generated during time of peak generation must be stored as efficiently as possible and used when generation levels plummet (maurizio et al., 2014). figure 2: major components of distribution automation (salkuti, 2020) energy storage facilities: to improve the reliability of power, facilities are needed to store energy and deliver this stored energy when required. in the design of re systems, storage facilities are necessary due to the intermittency of re sources, and variations in weather and climatic conditions. they are also important due to the incongruity in time of peak generation of re systems and the time of peak consumption (or demand). some examples of such storage facilities are advanced batteries, superconducting magnetic energy storage, pumped-hydro, super capacitors, flywheels (worku, 2022). 2.3.4 consumer level smart meters: smart meters deployed on demand side provide information about consumption to customers, and also relay key data to utility in near real time, allowing for load control, peak load assessment, and appropriate pricing strategies. additionally, smart meters enable utilities to connect and disconnect customers remotely and improve wide area monitoring of the grid. they also allow customers to monitor and control power consumption when integrated with home energy management systems (hems) (momoh, 2012). smart home appliances and demand response programs (dr programs): home appliances like air conditioners, heaters, refrigerators, and washers can be equipped with smart chips that detect grid disturbance and turn off these appliances to allow stabilization of the grid. these devices are crucial to maintaining the stable function of the smart grid, they can also be integrated with smart meters to enable tax credits and better tariff options for customers that adopt these smart devices. dr programs allow the inclusion of customers in the process of energy efficiency to minimize consumption especially during peak hours. this initiative incentivizes customers who adjust activities and services that do not necessarily have to be done during peak hours and moving them to when renewable is at its peak, to benefit utility and stabilize the grid (shewale et al., 2020). http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 887 home power solutions and vehicle-to-grid (v2g): smart grid allows consumers with home renewable energy solutions to sell excess power to the utility via the grid and obtain incentives and benefits from governments or utility. when integrated properly this approach makes the grid robust and improves re penetration on the grid. v2g serves as an alternative means of energy flow back to the utility during peak demand periods or other periods of stress or disturbance. studies are still ongoing in regard to plug-in hybrid electric vehicles (phev) and its overall impact on the grid and the environment (momoh, 2012 and chen and zhang, 2024). 2.4 barriers to smart grid adoption some barriers to the adoption of smart grid technology are high upfront cost, market uncertainty and public perception, lack of appropriate regulatory framework and technological limitations: communication and cyber security concerns. 3. discussion 3.1 global case studies table 2 shows examples where smart devices and sustainable initiatives have been applied to mitigate similar power challenges and the results achieved. table 2: countries, their energy challenges, and result after addition of smart devices country challenges faced smart solutions results usa (sustainability directory, 2025 and amin and schewe, 2008] • frequent blackouts • peak demand overload • poor situational awareness during extreme weather conditions • pmus and wams • dr programs and ami • automated fault management • early detection of instability and accurate state estimation • reduced peak demand and cascade failures japan (st-john, 2012, kbv research, 2024 and haslam, 2015) • power shortage, overreliance on fossil fuels, and voltage fluctuations • intermittent renewables and disaster risk. • smart meter, da, and hems • microgrid, v2g, and battery energy storage • improved reliability with decentralized and island-mode power • reduction of carbon emission germany (agoraenergiewende, 2025, häseler and wulf, 2024 and jendernalik et al., 2017) ● grid congestion ● renewable integration and variability of re sources ● smart meter and dr tariffs ● battery energy storage systems (bess), pumpedhydro ● better renewable integration and control with reduced operational cost ● reduced grid losses and better frequency control ● improved saidi australia (campbell, 2024, ies and ewec, 2023, deign, 2021 and zaghwan and gunawan, 2021) ● voltage instability due to high rooftop solar penetration at low demand periods ● poor voltage control and overgeneration ● smart inverters ● grid-scale battery storage ● cost reduction in frequency control ● improved power quality and rapid fault detection india (zaheeruddin and manas, 2014, satapathy et al., 2024 and reddy, 2017) ● reliability issues, high transmission and distribution losses ● faulty billing and energy theft ● frequent blackout ● solar microgrid system ● smart meter and ami ● ml-based theft detection ● lower network losses ● improved billing ● improved security of power and power equipment south korea [lim et al., 2021, renewable energy world, 2011 and kang, 2020) ● grid instability due to rapid re and ev penetration ● frequency fluctuations ● smart energy storage system ● smart meter and ami ● smart grid protection act ● improved frequency monitoring and control ● improved demand flexibility ● growth of national smart grid market canada (nhede, 2021, mclean et al., 2022, belanger, 2014) ● grid communication issues ● reliance on fossil fuels ● regulatory inconsistencies ● digital smart meters ● re adoption and bess in rural areas ● smart grid standards ● enhanced two way grid communication ● grid resilience and remote energy management ● grid friendly der deployment http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 888 3.2 strategic roadmap for adoption of smart devices and sustainable initiatives in nigeria table 3 presents a feasible structured path towards a cleaner, smarter, reliable, and decentralized power network in nigeria. it involves engagements and negotiations amongst players and actors in the power industry, as well as gradual implementation of sustainable initiatives. table 3: strategic implementation plan for sustainable energy in nigeria duration smart devices and initiatives short-term (0-2 years): planning and infrastructural improvement ● stakeholder engagement (regulators, discos, investors, consumers) ● establishment of smart grid committee and standards by nerc ● financial planning ● power planning, grid mapping, and integration of existing large-scale renewables using smart inverters etc. ● commence a national data acquisition strategy using iot sensors for future grid analytics ● start skills and capacity development for smart grid adoption ● upgrading and/or replacing outdated transmission and distribution equipment with smarter equipment medium-term (3-5 years): deployment and digital transformation ● installation and rollout ami, pmu, and wams for monitoring and control ● development and deployment of digital twins, distribution automation infrastructure with ai/ml capability for predictive maintenance and forecasting ● major upgrade to communication equipment ● adoption of smart home energy systems, smart appliances, and demand response programs long-term (6-10+ years): scalability, optimization, and consumer-centric systems ● fully autonomous grid management in high density areas ● integration of v2g infrastructure and regulation ● continuous review of regulatory framework ● development of climate-resilient grid infrastructure ● integration of more energy storage facilities for stability 3.3 key considerations and implications for smart grid adoption in nigeria environmental consideration: eco-friendly power solutions are essential to meet present energy demands with minimal environmental impact. several key environmental factors must be assessed for renewable energy solutions, such as site selection and power planning. potential downsides such as noise pollution, battery waste, disruption of hydro ecosystems and wind patterns, land use concerns, and the long-term climatic impact of energy projects on host communities must be adequately accounted for. technical consideration and energy policy development: qualified personnel must be engaged at every stage of procurement, installation, construction, and integration of smart devices into the grid. thorough technical evaluation through research, pilot testing, and simulation is crucial to ensure adherence to international energy standards and protocols. in addition, local supervisory committee should be established to monitor progress and develop national smart grid codes and regulatory frameworks. financial consideration: to attract local and international investment, clear well-structured financial plans and concessions must be made. government incentives, such as targeted subsidies, loans, and grants are necessary to facilitate the rapid growth of local green energy initiatives. dedicated budget allocations for energy transition efforts will also boost investor confidence and promote sustainable development. public acceptance and socio-economic considerations: citizens being primary stakeholders, must be actively involved in the energy transition process. policies should prioritize consumer needs and promote public awareness to encourage acceptance and willingness to embrace newer power technologies. a progressive and inclusive approach should be used, to ensure equitable access, promote dialogue, and enable the smooth and gradual integration of smart grid initiatives in the country. http://www.azojete.com.ng/ mailto:patrick.delight@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 890-903. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: patrick.delight@yahoo.com 889 4. conclusion smart grid technology facilitates the adequate flow of critical information and power on the grid and allows better monitoring and control to curb inefficiencies in transmission and distribution networks, while also enabling the integration of renewable energy sources into the grid. it has the potential to greatly improve the reliability, stability, and quality of power delivery in nigeria. this study broadly reviewed nigeria’s power challenges and highlighted the role smart grid technology in alleviating them. it also proposed a strategic implementation timeline for the integration of smart devices and sustainable initiatives and provided necessary considerations to promote long-term energy development in nigeria. nigeria has made huge strides towards attaining a sustainable energy infrastructure with the reform of its electricity act, providing a strong legislative framework for developments in its power sector. this reform was created to combat energy concerns like vandalism of power infrastructures, aging equipment, poor electricity access, and lack of transparent billing strategies, and to also make way for sustainable investment opportunities in nigeria’s power sector. however, it remains to be seen if this policy will be effectively enforced. efforts must be put towards ensuring timely implementation and continuity of energy projects. nigeria’s energy policy should also be continuously reviewed to reflect current needs and energy objectives, and to encourage more public participation in the power sector. to meet its energy goals, nigeria must treat research and development in energy centers and institutions as top priority. adequate funding must be available, to foster advancements in local manufacturing, material science, power electronics, and other important power systems research areas. acknowledgment i would like to sincerely appreciate the support of andrea balcazar, my advisor during the student energy research fellowship, for her guidance and encouragement throughout this research. i also extend my gratitude to the entire student energy team for providing the platform and resources that made this work possible. references abanihi, vk. and ikheloa, so. 2018. optimizing the effectiveness and efficiency of electricity distribution in nigeria. international journal of engineering and science. invention, 7(3): 01–06. adaramola, ms. 2014. viability of grid-connected solar pv energy system in jos, nigeria. 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https://www.energycentral.com/intelligent-utility/post/advanced-metering-infrastructure-detailed-walkthrough-ttvy8thmosn6ce9 https://data.worldbank.org/indicator/eg.use.elec.kh.pc?locations=ng https://www.who.int/news/item/12-06-2024-progress-on-basic-energy-access-reverses-for-first-time-in-a-decade https://www.who.int/news/item/12-06-2024-progress-on-basic-energy-access-reverses-for-first-time-in-a-decade corresponding author’s email address: ogunremi02@gmail.com 517 arid zone journal of engineering, technology & environment original research article effect of rainfall and fertilizer application timing on nutrient exports from a maize field m. ogunremi1, t. p. abegunrin2, a. akintola1 and i. a. abdulsalam3 1department of agricultural engineering oyo state college of agricultural technology, igbo-ora. 2department of agricultural engineering, ladoke akintola university of technology, ogbomoso. 3department of agricultural engineering, osun state university, osogbo. *corresponding author’s email: ogunremi02@gmail.com article information abstract nutrient losses from agricultural fields are significantly influenced by fertilizer management practices and rainfall patterns. gaining insight into these effects supports the development of effective mitigation strategies. this study investigated the effect of rainfall and fertilizer application timing on nutrient export from a maize field. daily rainfall data were obtained from ogun-osun river basin development authority (oorbda) meteorological station at igboora. the field experiment included early, split, and late single fertilizer application treatments, specifically assessing their impact on nitrate loss. runoff from each treatment plot was collected using plastic gutters leading to wooden tanks. samples were manually drawn at the onset, midpoint, and conclusion of each runoff event, provided rainfall exceeded 10 mm. runoff samples were analyzed for sediment concentration using gravimetric techniques, while nitrate, ammonium, total dissolved nitrogen, and total dissolved phosphorus were measured using standard colorimetric methods. rainfall events ranged from 29.7 mm to 393.8 mm. the analysis revealed that nitrate concentrations in runoff averaged 35.3±20.55 mg/l, ranging from 5.67 to 78.41 mg/l. early fertilizer application resulted in an increased average nitrate concentration of 41.4 mg/l. in terms of sediment-bound nutrients, particulate phosphorus concentrations averaged 10.09±7.17 μg/g, with values between 0.37 and 24.09 μg/g. particulate nitrogen concentrations averaged 13.15 ± 7.87 μg/g, ranging from 3.07 to 31.04 μg/g. also, it was observed that fertilizer treatments led to an increase in particulate phosphorus concentrations, averaging 10.83 μg/g after the initial application. the observed influence of rainfall and fertilizer timing on multiple nutrient pathways highlights the need for integrated nutrient management strategies, especially in tropical agro-ecosystems. received: 14th april 2025 revised: 1st may 2025 accepted: 2nd may 2025 keywords: nutrient export sediment fertilizer application nutrient availability © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction in recent decades, the use of inorganic fertilizers in agriculture has significantly increased, largely driven by the rising global demand for food and fibre to sustain an ever-growing population (harindintwali et al., 2021). however, in many developing countries such as nigeria, soil fertility testing remains inadequate, leading to highly indiscriminate fertilizer application (abdulraheem et al., 2022). the quantity of fertilizer used often exceeds the actual nutrient requirements of the crops. this mismatch results in a considerable portion of the applied nutrients becoming susceptible to loss through surface runoff and soil erosion (rashmi et al., 2022). moreover, the timing of fertilizer application plays a critical role in determining nutrient uptake efficiency. applying fertilizer during periods of intense rainfall or when crops have low nutrient demands substantially increases the risk of nutrient losses, thereby reducing fertilizer use efficiency and contributing to environmental degradation (li et al., 2020). runoff from agricultural land acts as a major transport mechanism for both sediments and nutrients—both in dissolved and particulate forms—into adjacent surface water bodies. the consequences of such transport are far-reaching and include the reduction of reservoir storage capacities, degradation of water quality, oxygen depletion (hypoxia), proliferation of harmful algal blooms, and eutrophication (li et al., 2020). these environmental challenges are especially severe in nigeria, notably in azojete june 2025. vol.21(2):517-528 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/017 www.azojete.com.ng mailto:ogunremi02@gmail.com mailto:ogunremi02@gmail.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 518 areas such as the confluence of rivers niger and benue, and around ogun and osun rivers. these surface water bodies in these areas have suffered substantial reductions in storage capacity and are heavily infested with aquatic weeds and have exhibited significant declines in aquatic biodiversity (omokaro et al., 2014). the predominant sources of environmental challenges are sediment and nutrient exports from intensively cultivated farmlands. to develop effective strategies for mitigating these adverse effects, it is crucial to understand both the contributing factors and the underlying mechanisms that drive nutrient and sediment transport from agricultural fields into water systems. in particular, the timing of fertilizer application and the influence of rainfall events play critical roles in the mobilization and transport of sediment and nutrients from agricultural fields into surface water bodies (khan et al., 2018). variability in soil properties has long been recognized especially in tropical soils due to variations in macro and micro flora and fauna (sanchez et al., 2011; orimoloye et al., 2018). the timing of fertilizer application in maize cultivation significantly influences nutrient runoff, especially under varying rainfall conditions. some researches conducted by wang et al., (2025), davies et al., (2020), and abebe and feyisa, 2017) indicates that synchronizing nitrogen (n) fertilizer application with maize's growth stages can enhance nitrogen use efficiency (nue) and reduce environmental losses. waring et al. (2022) examined the effects of nitrogen fertilizer timing on nitrate loss and crop production in northwest iowa. their findings revealed that spring-applied anhydrous ammonia (aa) reduced annual nitrate concentrations in leachate compared to fall applications. additionally, splitting fertilizer applications between pre-plant and sidedress stages, based on soil nitrate concentrations, showed potential in decreasing n losses while boosting grain yields. however, study has emphasized the necessity for site-specific evaluations due to variations in soil moisture, temperature, and microbial activity, which influence n cycling and soil mineralization rates (fujita et al., 2013). hence, this study investigates the effects of rainfall intensity and fertilizer timing on nutrient export from a maize cultivation field located in igboora, oyo state, nigeria. 2. materials and methods 2.1 study area this study was conducted in igboora, located in the southwestern region of nigeria. igboora is located on the geographic coordinates of 7.4368°n and 3.2885°e. the town is situated approximately 66 km northwest of ibadan, the capital of oyo state, and about 32 km north of abeokuta, the capital of ogun state (figure 1). the area lies within the tropical climatic zone characterized by distinct wet and dry seasons. the region experiences a bimodal rainfall distribution, with peak precipitation periods occurring in may/june and september/october. mean annual rainfall ranges between 1,190 mm and 1,342 mm, while the mean daily maximum and minimum temperatures are approximately 32 °c and 21 °c, respectively (iita, 2008). it falls within agro-ecological zone n (oyo–ibadan–ondo–oka plains), which is classified as very humid (orimoloye et al., 2018). the topography of the study area is generally low, with elevations ranging between approximately 110 and 280 meters above sea level, and is categorized under the guinea slope of the niger–guinea watershed. the experimental farm is located on the outskirts of igboora, specifically at asako farm settlement. a stream flows along the boundary of the farm, linking directly to the ofiki river, which forms part of the ogun–osun river basin. the farm site is characterized by slightly to moderately undulating terrain and underlain by crystalline basement complex rocks. http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 519 figure 1: map of ibarapa central local government, oyo state showing the study location (ogundele and owoade, 2016) 2.2 procedure for data collection 2.2.1 collection of rainfall data the daily rainfall data of the study area during the study period was collected from ogun-osun river basin development authority (oorbda) rain gauge station at igboora. the rainfall data were used to assessed the relationship between rainfall amount and nutrient export from the study area. 2.2.2 land preparation, planting and fertilizer application the experimental field used for the study was ploughed twice. maize seeds (oba super 26 yellow) was planted at a spacing of 25 cm within row and 75 cm between rows with two stands per hole. this translated to a population of 106, 667 stands of maize. basal fertilizer (npk 20:10:10) was applied at the rate of 125 kg ha-1 two weeks after planting as first dose, while the second dose, urea (46% nitrogen) was applied at the rate of 100 kg ha-1 at the onset of the tasselling. all these procedures are in conformity to the farmers’ usual practices. 2.2.3 runoff sample collection runoff samples were collected, using manual samplers, at the beginning, during and immediately after all rainfall events that occurred in the day during the study period. runoff samples in the night were not collected due to the unavailability of automatic runoff samplers. 2.3 laboratory analysis 2.3.1 determination of particulate nitrogen and phosphorus concentrations the procedures described in li et al. (2020) were used to determine the concentrations of sediment, nitrogen (n) and phosphorus (p) in the runoff samples. the suspended sediment (water-sediment mixture sample) in 1 l bottle was filtered using whatman grade 602 h (0.45-μm) filter paper. for the determination of concentrations of sediment, particulate n and particulate p, the sediment on filter paper were oven-dried at 40 °c for 1hour, weighed and subsampled. another subsample of the sediment was further oven-dried at 105 °c for 1 hour to a constant mass for the estimation of sediment concentration in the surface runoff. sediment concentration was calculated according to equation 1 (li et al.,2020). http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 520 𝑆𝑐𝑖 = 𝑆𝑖 1 𝐿 1 where 𝑆𝑐𝑖 is the sediment concentration (g l−1) and 𝑆𝑖 is the dry mass (g) of the sediment in water-sediment mixture in 1 l sample. sediment loss rate (sl, t ha−1) in a single rainfall event was obtained using following equation 2. 𝑆𝐿 = ∑ 𝑆𝑐𝑖 ∗ 𝑉𝑖 ∗ 𝑇𝑖 𝐴𝑥 ∗ 103 𝑛 𝑖=1 2 where n is the total number of samples, i is the individual sample per rainfall event, vi is the runoff volume at different sampling periods (m3 hr−1), ti is the sampling interval time of different samples (hr), and ax is the subwatershed area (ha). the subsample of the sediment was dried at 40 °c and then gently crushed, allowed to pass through a 0.2 mm sieve, and thereafter analyzed for particulate n and p using standard methods. the particulate n (pn) concentration (g kg−1) in the sediment were determined following method described in are et al. (2022), while the particulate p (pp) concentration (gkg−1) was determined calorimetrically using hot perchloric acid digestion (rahutomo et al., 2018). the pn and pp losses (kg ha−1) in each rainfall event were calculated as follow in equation 3 (li et al., 2020). 𝑃𝑁𝐿𝑜𝑟 𝑃𝑃𝐿 = ∑ 𝑆𝑐𝑖 ∗ 𝑉𝑖 ∗ 𝑇𝑖 ∗ 𝑃𝑁𝑖/𝑃𝑃𝑖 𝐴𝑥 𝑛 𝑖=1 3 where, 𝑃𝑁𝐿𝑜𝑟 𝑃𝑃𝐿 is the particulate n or p loss, 𝑃𝑁𝑖/𝑃𝑃𝑖 is the concentration of pn or pp in the sediment for each rainfall event. 2.3.2 determination of dissolved nitrogen and phosphorus concentration the procedure described by li et al. (2020) was used for the determination of dissolved nutrients; total dissolved nitrogen (tdn), ammonium nitrogen (nh4 +-n), nitrate nitrogen (no3-n) and total dissolved phosphorus (tdp). the total dissolved nitrogen (tdn) was determined by potassium persulfate digestion uv spectrophotometry (gb11894-89) method; ammonium nitrogen (nh4-n) by using nessler’s reagent colorimetric method (hj 535-2019); nitrate nitrogen (no3-n) by ion chromatography (hj 842016) and tdp by the molybdenum blue method (gb11893-89). the reactions were analysed using beckman du640 uv-vis spectrophotometer. runoff depth was calculated using equation 4 (li et al., 2020). 𝑅𝑜 = 𝑄𝑖 ∗ 𝑇𝑖 107 ∗ 𝐴𝑥 4 where ro is the runoff (mm), qi is the discharge (m3 h-1), ti is time (h) and ax is the field area (ha). the tdn, nh4 +-n, no3-n and tdp exports (kg ha-1) were calculated according to equation 5 (li et al., 2020). 𝑁𝑢𝑡𝑟𝑖𝑒𝑛𝑡 𝑙𝑜𝑠𝑠 = 104 ∗ ∑ 𝑅𝑜 ∗ 𝐶𝑖 5 where ci (mg l-1) is the concentration of each nutrient. 2.4 statistical analysis all statistical analyses were performed using minitab version 2021. the concentrations and loads of exported sediment and nutrients (particulate and dissolved) were subjected to descriptive statistics to determine the mean, standard deviation, coefficient of variation, minimum and maximum values. analysis of variance (anova) was carried out on the sediment and nutrient concentrations and exports for test of significance while means were separated using fisher`s least significant difference (lsd) test at p≤ 0.05 level of significance. linear regression analyses were carried out to determine the relationships between the changes http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 521 in particulate n and p and dissolved nutrient (tdn, nh4-n, no3-n and tdp) exports and the influencing factors. the regression equation will take the form shown in equation 6. 𝑌 = 𝛽₀ + 𝛽₁𝑅 + 𝛽₂𝑇 + 𝛽₃(𝑅 × 𝑇) + 𝜀 6 where: y: nutrient export, r: rainfall amount (mm) during or shortly after fertilizer application, t: fertilizer application timing , r × t: interaction term between rainfall and fertilizer timing to capture combined effects, β₀: intercept (baseline nutrient export when r and t are zero), β₁, β₂, β₃: regression coefficients indicating the magnitude and direction of each variable’s influence, ε: negligible error due to human error. 3. results and discussion 3.1 effect of rainfall on nutrient export the effect of rainfall on the export of dissolved nutrients from agricultural fields was assessed by examining the concentrations of nitrate-nitrogen (no₃⁻–n), ammonium-nitrogen (nh₄⁺–n), total dissolved nitrogen (tdn), and total dissolved phosphorus (tdp) in runoff samples collected during various rainfall events throughout the maize cropping season. over the course of the study, a total of 20 rainfall events were monitored, with rainfall amounts ranging from 29.72 mm to 393.77 mm (table 1). no₃⁻–n concentrations in the runoff samples averaged 35.30 ± 20.55 mg/l, with values ranging between 5.67 mg/l and 78.41 mg/l. a substantial variability in no₃⁻–n was observed with rainfall events, as reflected by a high coefficient of variation (cv) of 58.21%. nutrient loss from the maize field showed a strong association with rainfall events, particularly during periods of intense precipitation. ammonium-nitrogen (nh₄⁺–n) concentrations in runoff varied significantly, with a mean of 16.14 ± 11.66 mg/l (range: 1.23–43.27 mg/l) and a coefficient of variation (cv) of 72.22%, reflecting substantial fluctuation in response to rainfall intensity. similarly, total dissolved nitrogen (tdn) concentrations averaged 36.81 ± 20.79 mg/l, ranging from 6.01 to 79.57 mg/l, with a cv of 56.47%, suggesting that larger rainfall events mobilized higher nitrogen loads. total dissolved phosphorus (tdp) displayed the greatest variability among the measured parameters, with a mean of 0.60 ± 0.67 mg/l (range: 0.02–2.74 mg/l) and a cv of 111.45%, indicating extreme sensitivity to runoff volume. these findings underscore a direct relationship between rainfall intensity and nutrient export, where higher rainfall events substantially increased nutrient concentrations in runoff. these findings reveal the significant impact of rainfall variability on the export of dissolved nutrients from maize fields, with implications for nutrient loss and potential water quality degradation table 1: effect of rainfall on nutrients export from a maize field at different growth stages growth stages rainfall (mm) nutrient export (mg/l) no3-n nh4-n tdn tdp seedling stage 239.32 25.87 14.45 26.75 0.14 56.11 3.91 0.88 4.52 0.03 vegetative stage (1st fertilizer application – npk 20:10:10) 159.73 57.25 22.85 63.78 0.97 95.90 10.26 2.26 12.82 1.07 292.60 36.81 13.89 38.31 2.39 74.48 48.45 15.81 47.65 0.67 146.61 52.65 31.33 55.23 1.14 reproductive stage (2nd fertilizer application – urea 46% nitrogen) 231.23 61.04 38.31 61.58 1.56 119.23 31.28 17.16 34.11 0.54 53.48 22.83 6.73 24.67 0.03 317.56 46.62 10.16 47.01 1.28 50.13 19.06 3.90 19.18 0.08 149.42 68.58 30.56 70.28 0.11 155.16 58.08 27.39 58.76 0.17 393.77 30.95 18.25 32.05 1.12 226.58 64.63 34.89 66.00 0.66 34.06 11.31 4.52 13.86 0.00 76.42 16.87 9.95 17.06 0.02 29.72 8.95 0.78 10.11 0.00 post-harvest 111.76 30.56 18.79 32.56 0.01 mean std cv (%) max min 150.70 102.80 68.24 393.77 29.72 35.30 20.55 58.21 68.58 3.91 16.14 11.66 72.22 38.31 0.78 36.81 20.79 56.47 70.28 4.52 0.60 0.67 111.45 2.39 0.00 http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 522 at the seedling stage, nutrient exports were relatively low despite a high total rainfall of 239.32 mm in one of the events. the average no₃⁻–n concentration was 25.87 mg/l, while nh₄⁺–n and tdn were 14.45 mg/l and 26.75 mg/l respectively, with very low tdp (0.14 mg/l). this suggests that early in the crop cycle—prior to major fertilization—nutrient loss is more dependent on residual soil nutrients and initial leaching from minor fertilizer residues or organic matter decomposition. a second, lower-rainfall event (56.11 mm) showed minimal nutrient export, reinforcing the link between rainfall intensity and nutrient mobilization. the vegetative stage coincided with the first fertilizer application (npk 20:10:10), and nutrient exports increased noticeably. with rainfall ranging from 74.48 mm to 292.60 mm, no₃⁻–n levels spiked (as high as 57.25 mg/l), while nh₄⁺–n ranged up to 31.33 mg/l, and tdn reached 63.78 mg/l. notably, tdp concentrations increased sharply (up to 2.39 mg/l), indicating that phosphorus losses are highly responsive to both rainfall and nutrient input. the variability across events suggests that rainfall occurring soon after fertilizer application likely drove the increased nutrient export through surface runoff and leaching. the productive stage followed the second fertilizer application (urea 46% n). the data here reflect high variability in both rainfall (29.72 mm to 393.77 mm) and nutrient export. no₃⁻–n concentrations peaked at 68.58 mg/l, with consistent levels above 50 mg/l during moderate to heavy rainfall. similarly, nh₄⁺–n and tdn values were elevated across most events, and although tdp remained lower overall, values up to 1.56 mg/l were recorded. the wide range of nutrient export values despite variable rainfall suggests that residual fertilizer, combined with rainfall intensity and soil saturation, plays a crucial role in determining nutrient losses during this stage. the effect of rainfall amount on no3-n export is shown in figure 2. the positive relationship between rainfall amount and no3-n loss can be attributed to the ability of higher rainfall volumes to transport greater amounts of soluble no3-n from the soil surface. as rainfall intensity and runoff levels increase with larger events, more no3-n is mobilized from the upper soil horizons where it is most concentrated. the kinetic energy of the raindrops may also promote the detachment and dissolution of no3-n particles into runoff. additionally, poor infiltration and increased overland flow associated with high rainfall rates reduce residence time for no3n interaction with soil particles, resulting in greater export. a significant (p < 0.05) positive relationship with an r2 value of 0.2134 (figure 2), indicating that rainfall amount explained 21.3% of the variability in no3-n concentrations. as rainfall amount increased, greater amounts (68.6 mg/l) of no3-n were exported in the runoff. at low rainfall amounts below 100 mm, no3-n concentrations were generally less than 40 mg/l, while at higher rainfalls above 200 mm, concentrations frequently exceeded 50 mg/l. figure 2: relationships between rainfall events and no3-n export despite the observed relationship between rainfall and nutrient transport, rainfall amount accounted for only 25.3% of the variability in no₃⁻–n concentrations. this suggests that while precipitation plays a role, other factors are significantly influential in governing no₃⁻–n losses. the availability of no₃⁻–n in the soil is influenced by multiple interrelated parameters, including the rate and timing of fertilizer application, the crop's nitrogen uptake pattern, antecedent soil moisture conditions, and inherent soil characteristics such as texture, y = 0.0923x + 21.388 r² = 0.2134 y = 0.0923x + 21.388 r² = 0.2134 y = 0.0923x + 21.388 r² = 0.2134 y = 0.0923x + 21.388 r² = 0.2134 no3-n = 0.0923*rainfall + 21.388 r² = 0.2134, p = 0.040 0 10 20 30 40 50 60 70 80 0 100 200 300 400 500 n o 3n lo ss (m g/ l) rainfall (mm) http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 523 structure, and organic matter content (das et al., 2024). for example, excessive or poorly timed fertilizer application can result in nitrate accumulation in surface soils, increasing the potential for loss during subsequent rainfall events. these factors likely explain the wide variation in no₃⁻–n concentrations observed during rainfall events of similar magnitude. the positive correlation between rainfall amount and no₃⁻–n loss in this study aligns with findings by wu et al. (2018), who reported increased concentrations and loads of no₃⁻–n in runoff following high-intensity rainfall events. they attributed this trend to enhanced runoff generation, detachment, and transport of nitrate from the upper soil layers. conversely, cheng et al. (2018) reported no significant relationship between rainfall amount and no₃⁻–n loss, which they attributed to variability in antecedent soil moisture, highlighting the importance of pre-event hydrological conditions in modulating nutrient export. this further underscores that rainfall amount alone is insufficient to predict nutrient loss without accounting for underlying soil and management factors. 3.1.2 influence of rainfall amount on nh4-n export regression analysis also revealed a significant (p < 0.05) positive influence of rainfall amount on nh4-n export (figure 2). rainfall amount accounted for 20% of the variability in nh4-n concentrations based on the r2 value. higher rainfall totals led to increased nh4-n loss in the runoff (figure 2). most nh4-n concentrations were below 25 mg/l when rainfall amounts were less than 150 mm, but concentrations over 30 mg/l were measured at rainfalls above 250 mm. the correlation can be attributed to the high mobility of nh4-n in soils. nh4-n binds loosely to negatively charged soil particles through weak electrostatic bonds, keeping it easily detachable and soluble when dislodged into runoff. greater runoff flows and velocities with larger rainfall events also facilitate nh4-n particle detachment and transport away from sorption sites. however, as with no3-n, factors such as fertilizer inputs, mineralization rates, nitrification kinetics and moisture conditions which vary between events, likely contributing to nh4-n variability unrelated to rainfall. while a key determinant, rainfall alone does not fully control nh4-n loss. 3.1.3 influence of rainfall amount on tdn export a significant (p < 0.05) positive relationship was found between rainfall amount and tdn export (figure 3). this r2 of 0.2057 signifies that rainfall amount explained 20.6% of tdn concentration variability. tdn concentrations tended to be low (< 35 mg/l) at rain amounts under 150 mm and high (> 45 mg/l) when rainfall exceeded 250 mm. this suggests that greater rainfall quantities resulted in increasing losses of tdn, comprised of inorganic nitrate and ammonium ions as well as organic nitrogen species. heavier rainfall likely mobilized more nitrogen from upper soil layers through particle detachment and dissolution (zheng and wang, 2021). similarly to no3-n and nh4-n, other factors like soil nitrogen content and crop uptake also impacted tdn concentrations between events. figure 1: relationships between rainfall events and nh4-n export nh4-n = 0.0508*rainfall + 8.4943 r² = 0.2004, p = 0.048 0 5 10 15 20 25 30 35 40 45 0 100 200 300 400 500 n h 4n lo ss (m g/ l) rainfall (mm) http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 524 figure 2: relationships between rainfall events and tdn export 3.1.4 influence of rainfall amount on tdp export rainfall amount showed a highly significant (p = 0.001) influence on total dissolved phosphorus (tdp) export (figure 4). the r2 value of 0.4503, indicate rainfall accounted for 45.03% of the variability in tdp concentrations. tdp levels clustered mostly under 0.5 mg/l at rainfall below 150 mm but commonly exceeded 1 mg/l when rainfall surpassed 250 mm. unlike nitrogen, phosphorus exhibits low mobility in soils, as it tends to adsorb tightly to soil particles. however, high-energy rains appear particularly effective at dislodging and transporting dissolved phosphorus (mackey et al., 2019). with increasing runoff volumes and flow velocities at higher rainfalls, more phosphorus is shifted into soluble forms and carried away in solution (zhang et al., 2019). soil phosphorus levels and management also likely influenced the degree of phosphorus loss between events. generally, the significant relationships between rainfall and no3-n, nh4-n, tdn and tdp export signify that precipitation is a major controlling factor governing nitrate, ammonium and phosphorus loss from agricultural fields. rainfall serves not only as a transport medium for nutrient movement but, when accompanied by high energy and intensity, also enhances the detachment of nutrients from soil particles (chang et al., 2020). however, the variability in nutrient concentrations between rainfall events highlights the additional roles of soil nutrient contents, crop conditions, fertilizer management, and event-specific meteorological factors in determining nutrient loss (huo et al., 2021; yaşar korkanç and şahin, 2021). management practices aimed at reducing nutrient loads in agricultural runoff should consider the link between nutrient loss and high rainfall events. strategies such as cover cropping; conservation tillage and buffers may be particularly beneficial during months or seasons prone to high-intensity storms. figure 3: relationships between rainfall events and tdp export tdn = 0.0917*rainfall + 22.999 r² = 0.2057, p = 0.045 0 10 20 30 40 50 60 70 80 0 100 200 300 400 500 td n lo ss ( m g/ l) rainfall (mm) tdp = 0.0044*rainfall 0.0574 r² = 0.4503, p = 0.001 -0.5 0 0.5 1 1.5 2 2.5 3 0 100 200 300 400 500 td p lo ss ( m g/ l) rainfall (mm) http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 525 3.2 influence of fertilizer application on nutrient export at different growth stage the effect of fertilizer application on dissolved nutrient loss was analyzed by comparing the concentrations no3-n, nh4-n, tdn, and tdp in runoff between different cropping stages (table 2). in the initial seed germination stage prior to fertilization, nutrient concentrations were low, indicating minimal nutrient export. no3-n averaged 14.57±12.06 mg/l, nh4-n averaged 7.72±7.49 mg/l, tdn averaged 15.60±12.17 mg/l, and tdp averaged 0.17±0.17 mg/l. minimal nutrient mobilization is expected prior to fertilizer amendments, especially when residue cover from the preceding maize crop is still intact. crop residues shield the soil surface from raindrop detachment and maintain favourable conditions for water infiltration, reducing runoff volumes that can transport dissolved nutrients (blanco-canqui et al., 2017). surface crop residue cover generally exceeded 50% during this initial period based on visual field estimates. the residues likely promoted infiltration over runoff and impeded contact between rainfall and bare soil patches, minimizing detached nutrient loads. furthermore, soil nutrient levels are typically depleted after crop harvest and over the non-growing season without fresh fertilizer inputs, reducing source availability. the low nutrient concentrations found in runoff during seed germination align with previous studies demonstrating the protective effects of crop residue cover retention on dissolved nutrient loss (gilley et al., 2014). table 2: influence of fertilizer application on nutrient export at different cropping stage cropping stage fertilizer dose nutrient loss (mg/l) no3-n nh4-n tdn tdp seedling stage 2 14.57±12.06b 7.72±7.49a 15.60±12.17b 0.17±0.17b vegetative stage (1st fertilizer application – npk 20:10;10) 5 41.44±17.58a 17.06±9.55a 43.56±18.12ab 1.26±0.64a reproductive stage (2nd fertilizer application – urea 46% nitrogen) 2nd fertilizer application (urea 46% nitrogen) 12 37.42±21.43a 16.98±12.83a 37.93±21.28ab 0.48±0.56b post-harvest 1 30.29±1.10ab 18.63±0.17a 32.63±0.06ab 0.02±0.01b p=0.039 p=0.30 p=0.03 p=0.000 means that do not share a letter are significantly different after the first application of npk compound fertilizer during the vegetative stage of maize development, a substantial rise in dissolved nutrient concentrations in runoff was observed compared to levels recorded during the seedling stage. specifically, no₃⁻–n concentrations increased significantly to an average of 41.44 ± 17.58 mg/l, while total dissolved nitrogen (tdn) rose to 43.56 ± 18.12 mg/l. total dissolved phosphorus (tdp) experienced a sharp increase, reaching 1.26 ± 0.64 mg/l from the 0.17±0.17 mg/l obtained from the seedling stage. the 285% rise in no₃⁻–n concentration underscores extensive nitrification of the ammonium component of the applied npk fertilizer. this transformation was likely accelerated by warm and moist soil conditions, which are conducive to microbial activity responsible for nitrification. at this early vegetative stage, the maize plants had not yet developed sufficient root mass or canopy coverage to take up the available nutrients effectively. as a result, the highly mobile nitrate ions remained in the soil solution and were easily transported via surface runoff rather than absorbed by the crop. this observation is consistent with findings by sebilo et al. (2013), who reported that as much as 60% of applied nitrogen fertilizer can be lost through leaching and runoff instead of contributing to crop uptake. the 216% increase in tdp concentration similarly indicates that a significant portion of the applied phosphorus was lost in runoff shortly after fertilization. the limited vegetative cover and low phosphorus uptake capacity of the young maize plants, combined with insufficient incorporation of fertilizer into the soil, facilitated this export. these results are in agreement with smith et al. (2016), who found that soils with sparse vegetation or exposed surfaces experience higher fluxes of dissolved nutrients following fertilizer application. collectively, the findings emphasize the importance of synchronizing fertilizer application with crop nutrient demand and growth stage to minimize nutrient loss and maximize efficiency. the second application of urea fertilizer, applied as a split dose during the maize stem elongation phase, did not result in a further significant increase in nutrient concentrations beyond those observed following the initial npk application. measured values for no₃⁻–n averaged 37.42 ± 21.43 mg/l, nh₄⁺–n averaged 16.98 ± 12.83 mg/l, while tdn and tdp averaged 37.93 ± 21.28 mg/l and 0.48 ± 0.56 mg/l, respectively. the http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 526 relatively stable nutrient levels at this stage are attributable to the improved physiological and morphological conditions of the maize plants, particularly the onset of rapid biomass accumulation and canopy expansion. these conditions promote higher nutrient uptake efficiency, thereby reducing the availability of soluble nutrients for loss via runoff. moreover, the increased vegetative cover likely enhanced surface protection by reducing raindrop impact and overland flow energy, thus contributing to the mitigation of nutrient detachment and transport. this observation corroborates the findings of liang et al. (2017), who demonstrated that delaying fertilizer applications until after crop establishment significantly decreased dissolved nutrient losses in runoff compared to early-season applications. similarly, noulas et al. (2023) highlighted that split fertilizer application strategies, which align nutrient input with crop developmental stages and physiological needs, reduce nitrogen and phosphorus losses. these results reinforce the principle that synchronizing fertilizer application with crop nutrient demand and growth dynamics can significantly lower the risk of nutrient runoff. in particular, avoiding fertilization during the early stages of crop growth before the full development of canopy and root systems can minimize nutrient leaching and improve overall fertilizer use efficiency during the final post-harvest sampling, conducted approximately one month after maize reached physiological maturity, nutrient concentrations in runoff exhibited a general decline compared to in-season levels, though they remained elevated relative to pre-fertilization baselines. specifically, the mean concentrations were 30.29 ± 1.10 mg/l for no₃⁻–n, 18.63 ± 0.17 mg/l for nh₄⁺–n, 32.63 ± 0.06 mg/l for total dissolved nitrogen (tdn), and 0.02 ± 0.01 mg/l for total dissolved phosphorus (tdp). the cessation of crop nutrient uptake following senescence coincided with the ongoing decomposition of residual maize biomass, a process likely responsible for the continued, albeit diminished, mobilization of nutrients into surface runoff. despite the completion of harvest, residual plant matter provided limited but notable surface cover, contributing to the mitigation of erosion and nutrient detachment. the lower post-harvest concentrations compared to those recorded during the active growing season suggest partial nutrient assimilation by the crop during its life cycle. however, the persistence of residual nitrogen and phosphorus in the soil, coupled with ongoing mineralization, left a portion of the applied nutrients susceptible to leaching and runoff. these findings align with earlier research by hanrahan et al. (2018) and wang et al. (2020), which reported gradual losses of residual nutrients during the inter-cropping period due to leaching. the observed post-harvest nutrient dynamics underscore the importance of incorporating nutrient-capturing strategies, such as cover cropping or the inclusion of deep-rooted perennials in rotational systems. these approaches can enhance nutrient retention during fallow periods, reducing off-season losses and promoting long-term soil fertility and water quality conservation. 4. conclusion the study assessed the effects of rainfall and fertilizer application on nutrient loss from maize field. it was concluded that the amount of rainfall significantly and positively influenced the export of dissolved nutrients (no₃⁻–n, nh₄⁺–n, tdn, tdp) in surface runoff from the maize field. this underscores that rainfall-driven erosion processes play a critical role in the mobilization of particulate nutrients. early-season fertilization, when crops were not yet established, led to sharp increases in nutrient concentrations compared to prefertilization levels. in contrast, subsequent split applications of fertilizer, applied in alignment with crop growth, did not result in further increases in nutrient concentrations. these findings highlight the importance of synchronizing nutrient inputs with plant demand to minimize the mobilization of dissolved nutrients into runoff. references abdulraheem, mi., syed, mzan., li l., ahmed, s., wei, w., su r., li b., li, c., zhang, y., feng, y., and hu, j. 2022. soil fertility management: issues and challenges in tropical areas of nigeria. in ecosystem services: types, management and benefits. nova publisher inc. 313 326 abebe, z. and feyisa, h. 2017. effects of nitrogen rates and time of application on yield of maize: rainfall variability influenced time of n application. international journal of agronomy, 2017(1):1-10. https://doi.org/10.1155/2017/1545280. are, ks., guo, h. and li, y. 2022. land use types influence diffuse n and p entering a river in an agricultural watershed: evidence from compound-specific stable isotope. moor journal of agricultural research, 23(1): 2336. http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 527 chang, ct., shih, yt., lee, c., lee, jy., lee, ty., lin, tc., and huang, j. c. 2020. effects of land cover and atmospheric input on nutrient budget in subtropical mountainous rivers, northeastern taiwan. water, 12(10): 1-18. https://doi.org/10.3390/w12102800. davies, b., coulter, ja. and pagliari, ph., 2020. timing and rate of nitrogen fertilization influence maize yield and nitrogen use efficiency. plos one, 15(5): 1-19. https://doi.org/10.1371/journal.pone.0233674. das, s., mohapatra, a., sahu, k., panday, d., ghimire, d. and maharjan, b., 2024. nitrogen dynamics as a function of soil types, compaction, and moisture. plos one, 19(4): 1-19. https://doi.org/10.1371/journal.pone.0233674. gilley, je., risse, lm. and eghball, b. 2014. managing runoff following manure application. journal of soil and water conservation, 57(6): 530-533. hanrahan, br., tank, jl., christopher, sf., mahl, uh., trentman, mt. and royer, tv. 2018. winter cover crops reduce nitrate loss in an agricultural watershed in the central us. agriculture, ecosystems and environment, 265: 513-523. harindintwali, jd., zhou, j., muhoza, b., wang, f., herzberger, a. and yu, x. 2021. integrated eco-strategies towards sustainable carbon and nitrogen cycling in agriculture. journal of environmental management, 293: 112. https://doi.org/10.1016/j.jenvman.2021.112856 huo, j., liu, c., yu, x., chen, l., zheng, w., yang, y., and yin, c. 2021. direct and indirect effects of rainfall and vegetation coverage on runoff, soil loss, and nutrient loss in a semi‐humid climate. hydrological processes, 35(1): 1-12. khan, mn., mobin, m., abbas, z.k. and alamri, sa., 2018. fertilizers and their contaminants in soils, surface and groundwater. in encyclopaedia of the anthropocene, 5: 225-240. li, y., wang, c. and tang, h. 2020. research advances in nutrient runoff on sloping land in watersheds. aquatic ecosystem health and management, 9(1): 27–32. liang, k., zhong, x., huang, n., lampayan, r.m., liu, y., pan, j., peng, b., hu, x. and fu, y. 2017. nitrogen losses and greenhouse gas emissions under different n and water management in a subtropical double-season rice cropping system. science of the total environment, 609: 46-57. noulas, c., torabian, s. and qin, r. 2023. crop nutrient requirements and advanced fertilizer management strategies. agronomy, 13(8): 1-10. https://doi.org/10.3390/agronomy13082017. ogundele, at. and owoade, oa. (2016). implications of biomass energy production and utilization on sustainable forest management in ibarapa region of oyo state, nigeria. international journal of geography and environmental management, 2(1): 61-75. omokaro, g., idama, v., aireughian, e. and michael, i., 2024. water resources, pollution, integrated management and practices in nigeria-an overview. american journal of environmental economics, 3(1): 5-18. orimoloye, jr., akinbola, ge., and achi, ca. 2018. variability evaluation of selected soil properties in three locations in oyo state, south west nigeria. ibadan journal of agricultural research, 14(1):1 13 rahutomo, s., kovar, jl. and thompson, ml. 2018. inorganic and organic phosphorus in sediments in the walnut creek watershed of central iowa, usa. water, air, & soil pollution, 229: 1-12. rashmi, i., karthika, ks., roy, t., shinoji, kc., kumawat, a., kala, s. and pal, r. 2022. soil erosion and sediments: a source of contamination and impact on agriculture productivity. in agrochemicals in soil and environment: impacts and remediation. springer nature singapore. 313-345. sebilo, m., mayer, b., nicolardot, b., pinay, g. and mariotti, a. 2013. long-term fate of nitrate fertilizer in agricultural soils. proceedings of the national academy of sciences, 110(45): 18185-18189. smith, dr., king, kw., johnson, l., francesconi, w., richards, p., baker, d. and sharpley, an. 2015. surface runoff and tile drainage transport of phosphorus in the midwestern united states. journal of environmental quality, 44(2): 495-502. http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 517-528. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ogunremi02@gmail.com 528 wang, j., guo, j., li, g., lu, w., and lu, d. 2025. effects of different fertilizer combinations on the yield and nitrogen use efficiency of summer maize in jiangsu province, china. scientific reports, 15(1): 124-158. wang, s., fu, b., piao, s., lü, y., ciais, p., feng, x. and wang, y. 2020. reducing future nutrient losses to control eutrophication in the chinese inland waters. nature communications, 11(1): 1-10. waring, er., sawyer, j., pederson, c. and helmers, m., 2022. impact of nitrogen fertilizer timing on nitrate loss and crop production in northwest iowa. journal of environmental quality, 51(4): 696-707. wu, l., peng, m., qiao, s. and ma, x. 2018. assessing impacts of rainfall intensity and slope on dissolved and adsorbed nitrogen loss under bare loessial soil by simulated rainfalls. catena, 170: 51–63. yaşar korkanç, s. and şahin, h. 2021. the effects of mulching with organic materials on the soil nutrient and carbon transport by runoff under simulated rainfall conditions. journal of african earth sciences, 176: 104152. zhang, r., li, m., yuan, x. and pan, z. 2019. influence of rainfall intensity and slope on suspended solids and phosphorus losses in runoff. environmental science and pollution research, 26(33): 33963–33975. zheng, w., and wang, s. 2021. extreme precipitation accelerates the contribution of nitrate sources from anthropogenetic activities to groundwater in a typical headwater area of the north china plain. journal of hydrology, 603(c): 1-12. http://www.azojete.com.ng/ mailto:ogunremi02@gmail.com corresponding author’s email address: ndahitarhyel10@yahoo.com 857 arid zone journal of engineering, technology & environment original research article the effect of fermentation on the proximate composition, physical and functional properties of guna (citrullus vulgaris) seeds t. e. ndahi*, m. h. badau, a. l. kassum, l. p. mshelia, h. k. lawan and d. peter department of food science and technology, faculty of engineering, university of maiduguri, borno state, nigeria; *corresponding author’s email: ndahitarhyel10@yahoo.com article information abstract guna (citrullus vulgaris) is a type of melon seed traditionally extracted from its gourds after fermentation. this study investigated the effect of fermentation on the physical, proximate, and functional properties of guna seeds. fresh gourds were divided into three treatments namely; control (0 day), 7-day fermentation, and 14-day fermentation and shade-dried. standard analytical methods were employed for the analyses. the results showed that fermentation had no significant effect (p > 0.05) on seed length (6.05–6.07 mm), width (3.43–3.46 mm), thickness (1.46–1.51 mm), sphericity (0.51–0.52), arithmetic diameter (3.65– 3.68 mm), geometric diameter (3.12–3.17 mm), aspect ratio (56.69–57.10), or surface area (30.54–31.48 mm²). however, 1000-seed mass (31.78–34.60 g) and bulk density (1.64–1.82 g/cm³) were significantly affected (p < 0.05), decreasing with longer fermentation time. proximate analysis revealed moisture (4.63–4.78%), ash (3.11–3.37%), protein (23.70–29.95%), fat (25.71–28.63%), fibre (18.54–19.21%), and carbohydrate (17.67–20.72%). fermentation significantly (p < 0.05) increased moisture, protein, and ash contents, while reducing fat, fibre, and carbohydrate values. functional properties improved with fermentation time, including higher water absorption capacity (73.97–82.00%), oil absorption capacity (54.12–66.67%), foam capacity (17.22–21.11%), and foam stability (12.78–13.89%), alongside reduced flour bulk density (1.15–1.18 g/cm³). in conclusion, 14-days fermentation time enhanced protein and ash content, improved hydration and oil-binding properties, and lowered bulk density, indicating potential for guna seed protein supplementation in food applications. received: 16th august 2025 revised: 29th august 2025 accepted: 29th august 2025 keywords: guna seeds fermentation protein physical properties functional properties © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction the increasing global demand for sustainable and nutrient-rich foods has intensified interest in plant seeds as valuable sources of dietary proteins and essential amino acids (etzbach et al., 2024). oilseeds, in particular, are prized for their dual role in human nutrition and industrial applications, owing to their high protein, lipid, phytochemical and bioactive compounds contents (kotecka-majchrzak et al., 2020; enujiugha et al., 2022; nissar et al., 2025). guna (citrullus vulgaris), a melon species within the cucurbitaceae family, is traditionally consumed in northeastern nigeria, where its seeds are valued for their abundant proteins, essential amino acids, unsaturated fatty acids, and health-promoting phytochemicals (penuel et al., 2013; ndahi et al., 2023; ndahi et al., 2024). beyond nutritional composition, the physical and functional properties of plant seeds such as size, shape, bulk density, water and oil absorption capacities, and foaming behavior, are critical for their suitability in food formulation, processing, and equipment design (sahin and sumnu, 2006; awuchi et al., 2019). these parameters influence post-harvest handling and guide the engineering of machinery for harvesting, drying, milling, and storage (pradhan et al., 2010). azojete september 2025. vol.21(3):857-867 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/03/016 www.azojete.com.ng mailto:ndahitarhyel10@yahoo.com mailto:ndahitarhyel10@yahoo.com http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 858 processing methods profoundly affect the nutritional and functional profiles of oilseeds. among them, fermentation is particularly notable for its ability to modify macromolecular structures through microbial activity, thereby enhancing nutrient bioavailability, improving functional performance, and reducing antinutritional factors (sharma et al., 2020). studies have shown that fermentation can significantly alter proximate composition and functional characteristics of plant seeds (ogundele and taylor, 2016; mashau et al., 2025). previous reports of fermentation effect on the proximate and functional properties of cucurbit seeds have focused on methods such as: extraction and shelling of cucumeropsis manaii seeds prior to fermentation (omowaye – taiwo et al., 2015), boiling extracted seeds of l. siceraria and water melon seeds prior to natural fermentation (ileola et al., 2019; akele et al., 2022) and fermenting uncoated c. vulgaris (water melon) seeds with selected microbial strain (chawla et al., 2020). in traditional practice, guna seeds are extracted from the fermented mass of guna gourds prior to drying, followed by other processes including cooking and milling (neazdp, 1992). however, despite their nutritional richness and cultural importance, there is limited scientific evidence on how prior fermentation of the gourds influences the physical, proximate, and functional properties of guna seeds. this study aims to evaluate the effects of fermentation durations on the physical properties, proximate composition, and functional properties of guna seeds, thereby providing insights for optimizing their food and industrial application. 2. materials and methods 2.1 materials guna gourds were purchased from a farm at hawul lga, borno state, nigeria. the chemicals used for proximate composition analysis were from nafdac maiduguri office. additionally, all equipment and tools used for physical and functional properties measurements were obtained from the food analysis laboratory of the department of food science and technology, faculty of engineering, university of maiduguri at maiduguri, borno state, nigeria. 2.2 sample fermentation treatment the obtained guna gourds were divided into three (3) portions. a portion of the fresh gourds obtained was cut, seeds extracted and washed as control samples (ct). the second and third portions of fresh gourds were cut into halves, poured into a doubled-layered polyethylene and kept inside a rubber basin for support for 7 and 14 days as st and ft samples respectively. thereafter, the seeds were extracted and washed for each sample as locally practiced as shown in plate 1. 2.3 sample drying process the extracted seeds from each treatment were washed thoroughly to remove adhering pulp and strained. the strained seeds of each treatment were thinly spread on perforated trays and shade-dried for 7 days at room temperature, through which they were redistributed every 24 hours for uniform drying. thereafter, the physical properties were measured and each sample was milled, packaged in a polythene bag and kept in a cool dry place for further analyses. a. three portions of guna fruits b. two portions for fermentation treatment http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 859 c. extracted guna seeds plate 1: (a) three portions of guna fruits (b) two portions for fermentation treatment (c) extracted guna seeds 2.4 determination of physical properties of guna seeds 2.4.1 determination of geometrical properties 2.4.1.1 size for each sample, fifty (50) random guna seeds were selected and their length (l), width (w) and thickness (t) were measured using a digital vernier150mm (made in china) with an accuracy of 0.01 mm as the size of the sample seeds. 2.4.1.2 shape the shape was expressed as sphericity and aspect ratio. for the sphericity (ϕ), the dimensions obtained for the 50 selected seeds were used to calculate the sphericity using equation 1 as adopted from mehra et al. (2023): sphericity (ϕ) = (l x w x t)^1/3 l 1 where l = length (l) in mm; w = width (mm); and t = thickness. the aspect ratio (ra) was calculated using equation 2 (khan and saini, 2016): ra (%) = w x 100 l 2 2.4.1.3 arithmetic and geometric mean diameter the arithmetic mean diameter, da and geometric mean diameter, dg of the seeds were calculated by using equations 3 and 4 respectively (mehra et. al., 2023): da = (l+w+t) 3 3 dg = (l x w x t)1/3 4 http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 860 2.4.1.4 surface area the surface area of seed was calculated using equation 5 as calculated by bande et. al. (2012): s (mm2) = πdg 2 5 where, dg = geometrical mean diameter (mm). 2.4.2 determination of gravimetric properties of the seeds 2.4.2.1 thousand seed mass for each sample, hundred (100) random guna seeds were selected and weighed with an electronic balance (precision of 0.01g). the mass recorded was multiplied by 10 (khan and saini 2016). the thousand seed mass was expressed in grams (g). 2.4.2.2 bulk density an empty cylindrical container was weighed (w0), filled with seeds and tapped to a specific volume (v). the filled container was weighed (w1) again and the bulk density(ρb) was calculated based on equation 6 (khan and saini, 2016); ρb (g/cm3) = w1−w0 v 6 where, w0 = initial mass of the container (g); w1= mass of seeds and container; v = volume of the filled sample (cm3). 2.5 proximate composition analyses proximate composition of the seed samples was determined according to the procedure of aoac (2000). all the seed flour samples were analyzed for moisture, protein, fats, ash and fibre contents while the carbohydrate content was obtained by taking the difference when all other components of proximate were added and was subtracted from hundred (equation 7). % carbohydrate = 100 (% moisture +% fat+%protein+ %ash+ %fibre) 7 2.6 functional properties determination 2.6.1 determination of foaming properties the foaming properties was determined following the method described by khan and saini (2016). one (1g) gram of the guna seed flour was mixed with 5 ml (v1) of distilled water, shaken and poured into a 50ml graduated cylinder. the volume of the foam formed was noted (v2) and calculated as the foam capacity (fc) (%) while the foaming stability (fs) (%) was noted (v3) after 60mins. the fc and fs were calculated using equation 8 and 9 respectively: % fc = v2−v1 x 100 v1 8 % fs (after 60mins) = v2−v1 x 100 v1 9 2.6.2 determination of water absorption capacity (wac) the wac of the flour samples was determined by modifying the procedure used by ogundele and taylor (2016). using a weighed test tube (w1), 1g of each sample was poured into separate test tube and weighed (w2) then 10ml of water added and the suspension stirred for 5 minutes. the content was centrifuged at 3,500 rpm for 30 minutes. the supernatant obtained was measured in a 10 ml measuring cylinder while the residue in the test tube was weighed (w3). the water absorbed by the seed flour was calculated using equation 10: http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 861 % wac = w3−w2 x 100 w2−w1 10 2.6.3 determination of oil absorption capacity (oac) the oac of the flour samples was determined by modifying the procedure used by ogundele and taylor (2016). vegetable oil (refined groundnut oil) obtained from baga road market, maiduguri, was used. using a weighed test tube (w1), 1g of each sample was poured into separate test tube and weighed (w2) then 10ml of oil added and the suspension stirred for 5 minutes. the content was centrifuged at 3,500 rpm for 30 minutes. the supernatant obtained was measured in a 10 ml measuring cylinder while the residue in the test tube was weighed (w3). the oil absorbed by the seed flour was calculated using equation 11: % oac = w3−w2 x 100 w2−w1 11 2.6.4 determination of bulk density (bd) the bd was determined using the method of aoac (2010). twenty grammes (20g) of each guna seed flour samples was poured into an initially weighed 25cm3 container (w1) and was gently tapped. the new weight (w2) was noted and the observed volume (v) was recorded. the bulk density of the samples was calculated using equation 12: bd(g/cm3)= (𝑤2−𝑤1) volume of sample 12 2.7 statistical analysis the data generated were analyzed using analysis of variance and means separated using duncan multiple range test using statistical package for social science 23 version (spss) at 0.05 level of significance and chart trend was analyzed using ms excel 2019. 3. results and discussion 3.1 the effect of fermentation on the physical properties of guna seeds table 1 presents the effect of fermentation on the physical properties of guna seeds. fermentation had no significant (p > 0.05) effect on seed length, width, thickness, sphericity, arithmetic diameter, geometric diameter, aspect ratio or surface area. however, 1000-seed mass and bulk density (bd) differed significantly (p < 0.05) across treatments. the measured guna seeds’ length (6.05–6.07 mm), width (3.43–3.46 mm) and thickness (1.46–1.51 mm) were slightly higher in fermented seeds compared to the control. the slight increase in guna seeds’ dimensions might be due to the modification of structural molecules that led to interaction with moisture and air causing elongation and swelling. these values align with ranges reported for melon seeds by mansouri et al. (2017) and for flaxseeds by khan and saini (2016), but are lower than those observed in citrullus lanatus and cucumis melo species (mehra et al., 2023). the observed variation in melon seeds sizes could be due to variety and geographical difference. similarly, arithmetic (3.65–3.68 mm) and geometric (3.12–3.17 mm) diameters were highest in fermented seeds, consistent with the dimensional increase in length, width and thickness following fermentation (table 1). such size parameters are crucial in the design of harvesting, cleaning, and milling equipment (pradhan et al., 2010). sphericity (0.51–0.52), aspect ratio (56.69–57.10%), and surface area (30.54–31.48 mm²) were marginally higher in fermented guna seeds (table 1). these values are comparable to those reported for the sphericity of c. lanatus (0.52) (mehra et al., 2023) and fall within the surface area range of melon seeds (18.46 – 39.80mm2) (mansouri et al., 2017). according to garnayak et al. (2008), sphericity below 0.70 indicates a non-spherical shape and a tendency for guna seeds (0.51 – 0.52) to slide during handling, consistent with the flow behavior expected in both fermented and unfermented guna seeds. http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 862 the 1000-seed mass ranged from 31.78 to 34.60 g, with the control showing the highest value and 14-day fermented guna seeds the lowest. the reduction in seed mass could be attributed to the degradation of carbohydrate by fermenting microbes (ogodo et al., 2017). these results are within the range 27.69 40.28g for shelled and unshelled guna seeds reported by abubakar (2004) but lower than guna seeds (41g) of aviara et al. (1999), likely due to location difference. bulk density ranged from 1.64 to 1.82 g/cm³, decreasing significantly with fermentation time. the reduction in bulk density of guna seeds likely reflects lower seed mass coupled with slight dimensional expansion. bulk density and 1000-seed mass are important design parameters for storage, aeration and transport systems, as they influence load calculations and hopper design (sahin and sumnu, 2006). table 1: the effect of fermentation on the physical properties of guna seeds1 physical properties samples code2 ct st ft length (mm) 6.05a ± 0.14 6.06a ± 0.17 6.07a ± 0.17 width (mm) 3.43a ± 0.05 3.46a ± 0.06 3.46a ± 0.07 thickness (mm) 1.46a ± 0.06 1.51a ± 0.04 1.51a ± 0.05 arithmetic diameter (mm) 3.65a ± 0.04 3.67a ± 0.07 3.68a ± 0.07 geometric diameter (mm) 3.12a ± 0.04 3.16a ± 0.05 3.17a ± 0.06 sphericity 0.51a ± 0.01 0.52a ± 0.01 0.52a ± 0.01 aspect ratio (%) 56.69a ± 1.47 57.10a ± 1.45 57.07a ± 2.20 surface area (mm2) 30.54a ± 0.46 31.36a ± 1.07 31.48a ± 1.17 1000 seeds mass (g) 34.60a ± 0.90 33.20a ± 1.10 31.78b ± 1.09 bulk density (g/cm3) 1.82a ± 0.01 1.77b ± 0.01 1.64c ± 0.01 1values are means of triplicate analysis and their standard deviation. in any row, means bearing similar superscript are not significantly different (p > 0.05). 2ct = dried control sample; st = dried 7-days fermentation period sample; ft = dried 14-days fermentation period sample in this study, fermentation induced slight physical changes in guna seeds; particularly reductions in bulk density and seed mass, that could influence downstream handling, processing efficiency and equipment calibration in food and feed industries. 3.2 the effect of fermentation on the proximate composition of guna seeds fermentation significantly (p < 0.05) influenced the proximate composition of guna seeds, affecting moisture, ash, protein, fat, fibre, and carbohydrate contents (fig. 1). http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 863 figure 1: the effect of fermentation on the proximate composition of guna seeds ct = dried control sample; st = dried 7-days fermentation period sample; ft = dried 14-days fermentation period sample moisture content ranged from 4.63–4.78%, with the highest value observed in 7-days fermented guna seeds (st) and the lowest in the control (ct). ash content increased progressively with fermentation, from 3.11% (ct) to 3.37% in 14-days fermented seeds (ft) (fig. 1). these ash values align with the range reported for watermelon seeds (1.70–4.93%) (mathew et al., 2025) but are higher than those for some melon seeds (2.10– 2.20%) (saeed et al., 2023). similar trends have been reported in fermented watermelon seeds, where prolonged fermentation elevated both moisture and ash contents (ejinkeonye et al., 2018). the slight increase in moisture content could be due to the partial hydration of exposed hydrophilic site caused by hydrolysis of macromolecules (mashau et al., 2025) whereas the observed increase in ash content may be attributed to the relative concentration as microbes utilized and degrade organic matter of guna seeds during fermentation (ogodo et al., 2017). protein content of guna seeds increased significantly with fermentation duration from 23.70% in ct to 29.95% in ft (fig. 1). these values are comparable to melon seeds (26.36–39.96%) (enujiugha et al., 2022) and corroborate earlier findings that fermentation enhances melon seed protein content (akele et al., 2022; ileola et al., 2019). the increase is likely due to microbial synthesis of proteins or concentration effects from the degradation of other macronutrients during fermentation (sharma et al., 2020). the fat content of guna seeds decreased significantly with fermentation time from 28.63% in ct to 25.71% in ft and was within the typical range of fat content for oilseeds (24.00–56.56%) (kotecka-majchrzak et al., 2020). this decline of fat observed in this study was consistent with reports for fermented c. lanatus seeds (jackson et al., 2013) and has been linked to microbial lipase activity breaking down triglycerides to free fatty acids and glycerol during fermentation (mutshinyani et al., 2020). fibre and carbohydrate contents also decreased significantly, from 19.21% to 18.54% and from 20.72% to 17.67%, respectively, over the fermentation period. the carbohydrate values are consistent with the 8–20% range reported for watermelon seeds (nissar et al., 2025). similar reductions have been documented in fermented c. lanatus (akele et al., 2022) and are likely due to microbial utilization of complex carbohydrates and fibre as energy sources, leading to mass loss and altered guna seeds composition (fig. 1) as observed by ogodo et al., (2017). 0 5 10 15 20 25 30 35 moisture ash protein fat fibre carbohydrate p e rc e n ta ge ( % ) proximate composition ct st ft http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 864 remarkably, fermentation of guna seeds promoted protein and ash enrichment while reducing fat, fibre, and carbohydrate contents. these compositional changes reflect both microbial metabolism and biochemical transformations, enhancing the nutritional quality of guna seeds for potential food applications. 3.3 the effect of fermentation on the functional properties of guna seed flour fermentation significantly (p < 0.05) influenced the bulk density (bd), water absorption capacity (wac), oil absorption capacity (oac) and foaming capacity (fc) of guna seed flour while foaming stability (fs) remained unaffected (table 2). table 2 the effect of fermentation on the functional properties of guna seeds1 physical properties samples code2 ct st ft bulk density (g/cm3) 1.18a ± 0.01 1.17a ± 0.01 1.15b ± 0.01 water absorption capacity (%) 73.97b ± 1.18 81.00a ± 1.00 82.00a ± 2.00 oil absorption capacity (%) 54.12c ± 0.34 58.30b ± 0.61 66.67a ± 0.45 foaming capacity (%) 17.22b ± 0.96 19.44a ± 1.93 21.11a ± 1.92 foaming stability after 60 min (%) 12.78a ± 0.96 13.89a ± 0.50 13.33a ± 0.96 1values are means of triplicate analysis and their standard deviation. in any row, means bearing similar superscript are not significantly different (p > 0.05). 2ct = dried control sample; st = dried 7-days fermentation period sample; ft = dried 14-days fermentation period sample the bd of guna seeds declined slightly from 1.18 g/cm³ in the control to 1.15 g/cm³ after 14-days fermentation. this reduction is likely due to hydrolysis and structural modification of macromolecules during fermentation, leading to a lower seed mass (table 1). although the bd values in this study were higher than those previously reported for c. vulgaris (0.39–0.72 g/cm³), the decreasing trend aligns with earlier work (chawla et al., 2020; mashau et al., 2025). lower bd is advantageous in complementary food formulations, as it increases nutrient density per unit volume and reduces bulkiness during consumption (suresh and samsher, 2013). from table 2, the wac of guna seeds increased markedly with fermentation time, reaching 82.00% in ft and 81.00% in st compared with 73.97% in ct. this aligns with earlier findings that fermentation enhances the wac of melon seed flours (omowaye-taiwo et al., 2015; ogundele and taylor, 2016). the increase in wac of fermented guna seeds flour likely results from protein modification and carbohydrate degradation, which expose additional hydrophilic sites (mashau et al., 2025). high wac is desirable in products such as bakery goods, dough, and sausages, where water binding contributes to desirable texture and consistency (awuchi et al., 2019). similarly, oac of guna seed flour increased from 54.12% (control) to 66.67% (14-days fermentation). the increase with fermentation time is supported by reports on c. vulgaris (ogundele and taylor, 2016; chawla et al., 2020), although contrasting trends have been observed in l. siceraria and bambara groundnut flours, where oac decreased (ogundele and taylor, 2016; mashau et al., 2025). the rise in oac for fermented guna seeds might be due to increased protein content and unfolding of protein structures and its hydrolysis, which exposes hydrophobic sites (sareen et al., 2023). enhanced oac benefits applications such as pastries and sausages by improving flavor retention and mouthfeel (zhang et al., 2023). fermentation also increased foaming capacity (fc) of guna seeds with a maximum of 21.11% compared to 17.22% in the control, whereas foaming stability (fs) values of the seeds were relatively close (13.89%, 13.33% and 12.78% for st, ft and ct, respectively) (table 2). these results agreed with the observations for l. siceraria, where fermentation improved fc (ogundele and taylor, 2016), but contrast with studies on melon http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 865 seeds and legumes reporting reduced foaming ability (adebowale and maliki, 2011; omowaye-taiwo et al., 2015; chawla et al., 2020). protein hydrolysis was noted to reduce molecular weight of proteins thereby increasing surface activity whereas lower molecular weight might weaken the interactions hence reduce stability (eckert et al., 2019). thus, the fermentation effect on guna seeds likely reflects improved protein surface activity, enabling better air incorporation while the fs showed minimal change, possibly due to partial protein denaturation reducing the stability of entrapped air bubbles. 4. conclusion fermentation of guna seeds for up to 14 days resulted in seed expansion, reduced mass, and significant compositional and functional changes. prolonged fermentation increased ash and protein contents, water and oil absorption capacities and foaming capacity while reducing fat, fibre, carbohydrate contents, bulk density, and foaming stability. these improvements in protein quality and techno-functional properties highlight the potential of 14-day fermented guna seed flour as a value-added ingredient in diverse food formulations. to explore guna seeds nutrients applicability in food formulation, further research should be carried out on the effects of various bioprocessing methods on amino acids profile, micronutrients and functional properties of guna seeds flour. references abubakar, um. 2004. evaluation of physicochemical and sorption characteristics of guna (citrullus lanatus) seeds. submitted to the school of post graduate studies, in partial fulfilment of the requirement for the award of doctor of philosophy (phd), in the department of food science and technology, university of maiduguri, nigeria. adebowale, oj. and maliki, k. 2011. effect of fermentation period on the chemical composition and functional properties of pigean pean (cajanus cajan) seed flour. int. food res. journal, 18 (4): 1329 – 1333. akele, eo., akinyosoye, fa. and oyetayo, vo. 2022. effects of fermentation and wrapping materials on nutritional and anti-nutritional properties of watermelon (citrillus lanatus) seeds. american journal of food sciences and nutrition. 4 (1): 34 41. issn 2789-3154 (online) association of official analytical chemicals (aoac) 2000. official methods of analysis of the association of official analytical chemist.17th edition. washington dc, usa. association of official analytical chemicals (aoac) 2010. official methods of analysis of the association of official analytical chemist.18th edition. washington dc, usa. aviara, na., gwandzang, mi. and haque, ma. 1999. physical properties of guna seeds. journal of agricultural engineering research, 73:105-111. awuchi, cg., igwe, vs. and echeta, ck. 2019. the functional properties of foods and flours. int. journal of ad. acad. res./sci., tech. and eng., 5 (11) 139 – 160. bande, ym., adam, nm., azmi, y. and jamarei, o. 2012. variation of physical properties of egusi melon (citrullus colocynthis lanatus var. lanatus) seeds and kernel with moisture. international journal of basic and applied sciences. 12(5): 65-74. chawla, p., kumar, v., bains, a., singh, r., sadh, pk., kaushik, r. and kumar, n. 2020. improvement of mineral absorption and nutritional properties of citrullus vulgaris seeds using solid-state fermentation. journal of the american college of nutrition. 39(7), 628–635. https://doi.org/10.1080/07315724.2020.1718031 ejinkeonye, ub., nduka, oc. and offia-olua, bi. 2018. effect of fermentation duration on the nutritional and antinutritional contents of watermelon seeds and sensory properties of ogiri products. european journal of food science and technology, 6 (2): 1 – 16. eckert, e., han, j., swallow, k., tian, z., jarpa‐parra, m. and chen, l. 2019. effects of enzymatic hydrolysis and ultrafiltration on physicochemical and functional properties of faba bean protein. cereal chemistry. 96:725–741 http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com arid zone journal of engineering, technology and environment, september 2025; 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whole fruit, rinds and seeds samples. arid zone journal of engineering, technology & environment. 19(3): 477 – 492. nissar, j., sidiqi, us., dar, ah. and akbar, u. 2025. nutritional composition and bioactive potential of watermelon seeds: a pathway to sustainable food and health innovation. sustainable food technology. 3: 375– 395. doi:10.1039/d4fb00335g north-east arid zone development project (neazdp) 1992. pilot study on the economy of guna. neazdp monitoring and evaluation unit, gashua, yobe state, nigeria. http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com https://doi.org/10.3390/molecules30112356 arid zone journal of engineering, technology and environment, september 2025; vol. 21(3): 857-867. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ndahitarhyel10@yahoo.com 867 ogodo, ac., ugbogu, oc., onyeagba, ra. and okereke, hc. 2017. effect of lactic acid bacteria consortium fermentation on the proximate composition and invitro starch/protein digestibility of maize (zea mays) flour. american journal of microbiology and biotechnology. 4(4): 35-43. ogundele, jo. and taylor, oo. 2016. effect of processing on functional properties of some melon (egusi): leganaria siceraria and citrullus vulgaris seed flours. fjpas. 1 (1): 49 – 53. omowaye-taiwo, oa., fagbemi, tn., ogunbusola, em. and badejo, aa. 2015. effect of germination and fermentation on the proximate composition and functional properties of full-fat and defatted cucumeropsis mannii seed flours. journal of food science and technology. 52(8): 5257 – 5263. penuel, bl., khan, em. and maifera, mo. 2013. properties of proximate composition and elemental analysis of ctrullus vulgaris (guna) seeds. bulletin of environment, pharmacology and life sciences, 2 (2): 39 – 46. pradhan, rc., meda, v., narayan, s. and tabil, l. 2010. physical properties of canadian grown flaxseed in relation to its processing. international journal of food properties, 13 (4): 732 – 743. saeed, f., afzaal, m., niaz, b., hussain, m., rasheed, a., raza, m. a., umar, m., khan, m. a., suleria, h., tufail, t. and al jbawi, e. 2023. comparative study of nutritional composition, antioxidant activity and functional properties of cucumis melo and citrullus lanatus seeds powder. cogent food and agriculture. 10: 2293517: 1 12. https://doi.org/10.1080/23311932.2023.2293517 sahin, s. and sumnu, sg. 2006. physical properties of foods. ed. heldman, d. r.. springer science + business media, llc, new york. sareen, j., shi, d., stone, ak., xu, c., polley, b., house, jd., bhowmik, p., rajagopalan, n., tanaka, t. and nickerson, mt. 2023. effect of enzyme hydrolysis on the physicochemical, functional, and nutritional properties of pea and faba bean protein isolates. european food research and technology. 249:3175–3190. sharma, r., garg, p., kumar, p., bhatia, sk. and kulshrestha, s. 2020. microbial fermentation and its role in quality improvement of fermented foods. fermentation, 6, 106, 1 – 20. suresh, c. and samsher, s. 2013. assessment of functional properties of different flours. african journal of agricultural research.8(38); 4849-4852. zhang, m., wang, o., cai, s, zhao, l. and zhao, l. 2023. composition, functional properties, health benefits and applications of oilseed proteins: a systematic review. food research international 171, 113061: 1-19. https://doi.org/10.1016/j.foodres.2023.113061 http://www.azojete.com.ng/ mailto:ndahitarhyel10@yahoo.com corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 545 arid zone journal of engineering, technology & environment original research article tilapia fish scale-derived hydroxyapatite inhibitor for copper corrosion: electrochemical, adsorption, and mechanistic investigations o. s. i. fayomi1,2* 1department of mechanical engineering, bells university of technology, ogun state, nigeria 2department of mechanical engineering science, university of johannesburg, johannesburg, south africa *corresponding author’s email: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng article information abstract this investigation analyzes hydroxyapatite (hap) derived from tilapia fish scales as a green and sustainable corrosion inhibitor for copper in 1m hcl. while fish scales are an abundant biowaste source, the use of the scales' in assessing its corrosion inhibition capability will provide an eco-compatible option for the protection of industrial metals. the hydroxyapatite was purified using a multi-step process consisting of deproteinization, alkaline treatment, and high-temperature calcination under 1000°c to yield a purified nano-hap powder. open circuit potential (ocp), linear sweep voltammetry (lsv), and tafel polarization were used to determine the corrosion inhibition efficiency under various temperatures (30°c, 40°c, and 50°c) and different concentrations (0.2 g, 0.4 g, and 0.6 g). the results showed an extensive reduction in the current density of the corrosion and the rate of the corrosion, with a maximum inhibition efficiency of (~95%) occurring under the 0.6 g concentration. the analysis of the adsorption showed that the inhibitor conformed to the freundlich and temkin isotherms, inferring multilayer adsorption and strong surface interactions. optical micrographs corroborated the protective capability of the inhibitor through reduced roughness of the surface and reduced pitting. this study established that hydroxyapatite obtained from fish scales is an effective alternative, and eco-compatible corrosion inhibitor, contributing to waste reduction and green chemistry. received: 24th april 2025 revised: 1st may 2025 accepted: 2nd may 2025 keywords: copper corrosion inhibition optimization fish scale hydroxyapatite © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction corrosion is an electrochemical process in nature that drives the metal back to its original state. this phenomenon occurs in the presence of a reactive environment, which facilitates the formation of an electrochemical cell (abod et al., 2019). corrosion can also not only facilitate economic losses but lead to many health and safety hazards. therefore, providing effective protection of metals is essential for the safety of people (li et al., 2021). over the years, a variety of methods for the control of corrosion in metals have been established, but the use of inhibitors is still one of the best methods of protecting metals against corrosion (arthur et al., 2013; wang et al., 2007). however, conventional corrosion control methods frequently involve toxic, hazardous, and ecologically harmful inhibitors that pose serious risks to human health and the environment (kadhim et al., 2021; ezzat et al., 2022). in response, recent research has increasingly focused on developing sustainable corrosion inhibitors that offer both high efficiency and environmental compatibility (kadhim et al., 2021; ezzat et al., 2022; aydinsoy et al., 2024). biowaste obtained from fish, especially fish scales continuously constitute a plethora of health and environmental hazards since they are usually disposed in open spaces, particularly in coastal areas (panda, pramanik, & sukla, 2014). a study estimate that the global processing of aquatic products generates an average of approximately 67 million tonnes annually (tacon, 2020). of this total, waste materials account for a significant portion, with fish scales alone representing about 5% of the discarded waste (coppola et al., 2021). this equates to over 30% of the overall volume of aquatic products processed (duan et al., 2004). hence, fishbased industries and markets waste face a dilemma in the disposal of associated wastes (zainol et al., 2019). azojete june 2025. vol.21(2):545-556 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/02/019 www.azojete.com.ng mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 546 tilapia fish scales consist of approximately 40% to 55% organic components, including collagen, lipids, proteins, and vitamins, along with around 30% inorganic substances such as calcium and phosphates, making them a valuable biomaterial (chinh et al., 2019). calcium hydroxyphosphate, commonly known as hydroxyapatite, is represented by the chemical formula ca₅(po₄)₃(oh) (zhao et al., 2025), although, it is more frequently expressed in its expanded form as ca₁₀(po₄)₆(oh)₂. this compound can be obtained from various natural waste materials, including fish scales, eggshells, and crab shells, which serve as sustainable and eco-friendly sources for its production (abudullah et al., 2020). these materials, are often considered as wastes, offer a valuable opportunity for resource recovery and utilization in the creation of hydroxyapatite (sockalingam & abdullah, 2015). hydroxyapatite (hap), is currently employed as a biosorbent in wastewater treatment (selimin et al., 2022), and as a biomedical material for bone repair and dental implants (dileepkumar et al., 2022), among various other applications. as an inhibitor, nyambi et al., (2024) studied the physicochemical characterisation and computational studies of tilapia fish scales as a green inhibitor for steel corrosion. the xrd analysis revealed the presence of a significant quantity of hydroxyapatite, as indicated by a prominent diffraction peak at 2θ ≈ 32°. additionally, amorphous collagen was inferred indirectly through a broad hump in the baseline within the 2θ range of 13°– 25°. both experimental and computational studies demonstrated that tilapia fish scales can serve as an effective green corrosion inhibitor. this is attributed to the presence of key components such as collagen, hydroxyapatite, and various amino acids within the scales (nyambi et al., 2024). however, there is no available literature on the application of tilapia fish scales as a corrosion inhibitor. this study thus seeks to investigate tilapia fish scale-derived hydroxyapatite as an inhibitor for copper corrosion. 2. materials and method 2.1 hydroxyapatite powder preparation from tilapia fish scales the tilapia scales were collected from a local fish market in ota, ogun state. they were first soaked in tap water, and then washed several times with distilled water to remove all the blood, dirt, and any other impurities before being left to dry. the scales were then deproteinized by washing them with 0.1m hcl. afterwards, they were washed again with distilled water and put in the laboratory oven at 60℃ for 45 minutes. the dry fish scales were ground to powder in a mechanical grinder. to treat the powder-like fish scales, 5m naoh was poured into the powder and heated to a high temperature of 100℃, after which the sludge-like resulting mixture was stirred for an hour. the resulting treated powder was then washed thoroughly until the washing solution became neutral. it was poured through a filter paper, with the filtrate dried in a laboratory oven for 80℃. the resultant powder was subjected to calcination at 1000℃ for 2 hours and 30 minutes to eliminate organic compounds and yield pure nano-hap, in accordance with the methodology described by zainol et al. (2019). 2.2 other materials preparation prior to conducting electrochemical measurements, a 1 cm² section of a 99.99% pure copper sample was prepared and characterized as shown in table 1. the surface was sequentially polished using sandpaper with grit sizes of 400, 800, 1200, and 2000. after the polishing, the smooth electrode was thoroughly rinsed in double-distilled water to remove any residues. finally, it was dried using a dryer at room temperature. the 1m hcl solution was obtained from the in-house chemistry laboratory. table 1: chemical compositional makeup of copper sample element m (mass%) ×10⁻³ si 7 p 16.5 ti 0.4 v 0.3 mn 2.65 sb 0.6 co 0.15 ni 2.8 nb 1.6 mo 1.1 sn 2.7 cu bal. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 547 2.3 electrochemical measurements a standard three-electrode system was used in conducting the electrochemical tests. the setup included a cs100 potentiostat, operated by cs studio6 and cs analysis software. the three-electrode system was placed in a 100 ml beaker, which was then positioned in a water bath to maintain consistent temperatures of 30°c, 40°c, and 50°c throughout the experiment. electrochemical measurements were performed using varying concentrations of hydroxyapatite (hap): 0g (control test without inhibitor), 0.2g, 0.4g, and 0.6g of the inhibitor, each dissolved in 50 ml of 1m hcl solution as shown in table 2. polarization measurements were recorded at a scan rate of 0.01 v/s, covering a potential range from -1.5 v to +1.5 v. a similar methodology was carried out by kehinde et al., (2025). table 2: experimental arrangement experimental arrangement test environment control 50ml hcl 0.2g hap 0.2g hap + 50ml hcl 0.4g hap 0.4g hap+ 50ml hcl 0.3g hap 0.6g hap + 50ml hcl 2.4 adsorption and mechanistic studies key electrochemical parameters, including surface coverage, corrosion current density (jcorr), corrosion potential (ecorr), and inhibition efficiency (ie%), were determined using tafel plots and equations 1 and 2. additionally, the adsorption behaviour of the hap was analysed using adsorption models, specifically the langmuir, freundlich, and temkin isotherms. statistical analysis for the experiments was also included using design expert software 13 at a 95% confidence level. mathematical regression models and response surface methodology (rsm) were further used to evaluate and predict the inhibitor's performance. analysis of variance (anova) was utilized in assessing the influence of process variables on the corrosion rate response, providing critical insights for process optimization. surface coverage (θ) = 𝑗0𝑐𝑜𝑟𝑟 – 𝑗𝑐𝑜𝑟𝑟 𝑗0𝑐𝑜𝑟𝑟 1 % ie = 𝑗0𝑐𝑜𝑟𝑟 – 𝑗𝑐𝑜𝑟𝑟 𝑗0𝑐𝑜𝑟𝑟 × 100 2 j0corr and jcorr represents the corrosion current density (with and without the inhibitor respectively). 2.5 surface analysis (optical) to analyse the surface of the immersed test samples of copper, metallurgical optical microscopy was employed to closely examine its surface morphology at a 40x magnification. this technique allowed for detailed observation of any changes, such as corrosion patterns, pitting, or deposits, that occurred on the copper surface after exposure to the test environment 3. results and discussion 3.1 response of copper samples to tilapia fish scale-derived hydroxyapatite the electrochemical evaluation of copper corrosion in 1m hcl, using hydroxyapatite from tilapia fish scales as a corrosion inhibitor was done through open circuit potential (ocp) analysis, tafel polarization tests, and linear sweep voltammetry (lsv) measurements. figures 1, 2, and 3 demonstrate that copper has more negative potentials and high corrosion in the acidic environment without the inhibitor (ubogu et al., 2024). at 30°c, the control samples had a corrosion potential (ecorr) of -0.625 v; at 40°c, -0.364 v; and at 50°c, -0.841 v, showing the most negative readings. adding the inhibitor shifted potentials towards less negative values. at 50°c, 0.6 g of inhibitor resulted in -0.423 v, indicating better surface passivation as per jmiai et al. (2021). this change proves that hydroxyapatite adsorbed well onto the copper substrate, forming a protective layer that suppressed the dissolution of the metal. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 548 figure 1: ocp plot of the inhibited copper sample at 30℃ figure 2: ocp plot of the inhibited copper sample at 40℃ . figure 3: ocp plot of the inhibited copper sample at 50℃ analysis of tafel polarization data in table 3 shows the effectiveness of the corrosion inhibitor, as reflected by a considerable decrease in corrosion current density (jcorr) with the addition of the inhibitor (al-amiery et al., 2023). at 30°c, jcorr went down from 1.94e-04 a/cm² (control) to 2.82e-05 a/cm² (0.6 g), reflecting a significant drop in the corrosion rate from 2.27 mm/yr to 0.33 mm/yr. a similar trend was seen at 40°c, where jcorr dropped from 4.55e-04 a/cm² (control) to 5.82e-05 a/cm² (0.6 g), reflecting a reduction from 5.34 mm/yr to 0.68 mm/yr in the corrosion rate. at 50°c, the control sample recorded the highest jcorr at 5.13e-04 a/cm²; however, the addition of the inhibitor at 0.6 g lowered this reading to 3.14e05 a/cm², thus reflecting a drop in the rate of corrosion from 6.02 mm/yr to 0.37 mm/yr. these decrease and an increase in polarization resistance (pr), which reached 922 ω at 30°c and 829 ω at 50°c for the 0.6 g dose, support the ability of the inhibitor to enhance corrosion resistance. the control samples exhibited the http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 549 highest current densities across all temperatures, while the 0.6 g samples showed suppressed currents, confirming reduced copper oxidation and hydrogen evolution. this aligns with zor et al. (2011), where increasing concentrations of amides reduced icorr by over 90% in 1.0 m hcl, attributed to mixed-type inhibition via adsorption. the observed rise in polarization resistance (rp) from 512 to 3,606 ω⋅cm2 further corroborates the formation of a protective inhibitor layer, mirroring the behavior of tilapia hap in this study. the study finds that control samples have the highest current densities across all temperatures. the trend in potential shifts, reduced jcorr, and increased pr suggests that tilapia fish scale-derived hydroxyapatite reacts as a mixedtype inhibitor which would mean it affects both the anodic metal dissolution and cathodic hydrogen evolution (marinescu, 2019). table 3: tafel data of the experiments at 30℃, 40℃, and 50℃. figures 4–6 present the lsv profiles for copper in 1m hcl at 30°c, 40°c, and 50°c. in the absence of hap (figure 4, control at 30°c), the anodic branch shows a sharp rise in current density beyond -0.5 v, corresponding to rapid copper dissolution. the cathodic branch similarly reflects vigorous hydrogen evolution. with 0.6 g hap, both anodic and cathodic currents are suppressed by over an order of magnitude drops from, confirming the inhibitor’s mixed-type behavior. at 40°c (figure 5), the control sample exhibits even higher, but the 0.6 g hap reduces this to, maintaining strong inhibition despite increased thermal agitation. by 50°c (figure 6), the hap’s efficacy slightly diminishes, likely due to partial desorption of physically adsorbed hap molecules. the lsv curves also reveal a widening passive region with higher hap concentrations, implying enhanced surface coverage and delayed breakdown of the protective layer. the efficiency remained high at lower temperatures, though a slight decrease at 50°c suggests partial desorption of the inhibitor, which is common with physisorption mechanisms at elevated temperatures (abdel-karim et al., 2023). figure 4: lsv plot of the inhibited copper sample at 30℃ 30℃ samples ecorr (v) jcorr (a/cm2) cr (mm/yr) pr (ω control -0.625 1.94e-04 2.27 1.34e+02 0.2 g -0.517 1.45e-04 1.71 1.79e+02 0.4g -1.653 7.74e-05 0.91 3.36e+02 0.6g -0.700 2.82e-05 0.33 9.22e+02 40℃ control -0.364 4.55e-04 5.34 5.71e+01 0.2g -0.430 3.05e-04 3.58 8.51e+01 0.4g -0.920 2.41e-04 2.82 1.08e+02 0.6g -0.186 5.82e-05 0.68 4.47e+02 50℃ control -0.841 5.13e-04 6.02 5.07e+01 0.2g -0.872 4.62e-04 5.42 5.63e+01 0.4g -0.813 2.14e-04 2.52 1.21e+02 0.6g -0.423 3.14e-05 0.37 8.29e+02 http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 550 figure 5: lsv plot of the inhibited copper sample at 40℃ figure 6: lsv plot of the inhibited copper sample at 50℃ 3.2 inhibitory efficiency of tilapia fish-scale-derived hydroxyapatite the inhibition efficiency (ie) plot in figure 7 of hydroxyapatite from tilapia fish scales showed an increase with different concentrations and temperatures. at 0.1 g concentration, the inhibition efficiency was relatively low, particularly at 50°c, indicating that the adsorption of the inhibitor on the copper sample decreases with increasing temperature. conversely, at 0.2 g concentration, the ie showed a significant improvement, reaching about 60% at 30°c and 50% at 50°c. the maximum efficiency was at 0.3 g, where the ie was more than 85% at all tested temperatures, reaching a maximum of about 95% at 50°c, implying that the inhibitor acts best at higher concentrations. the trends in the corrosion rate (cr) plot of figure 8 further support the inhibitory effects, with a decrease in cr being observed with an increase in the concentration of the inhibitor. the control samples showed the highest corrosion rates with values of 2.27 mm/year, 5.34 mm/year, and 6.02 mm/year at 30°c, 40°c, and 50°c, respectively, which reflect increased corrosion with increasing temperatures. however, the addition of 0.3 g of the inhibitor led to a significant decrease in cr to 0.33 mm/year at 30°c, 0.68 mm/year at 40°c, and 0.37 mm/year at 50°c, thus reflecting the protective nature of hydroxyapatite. the decrease in corrosion rate observed corresponds with an increase in polarization resistance (pr), thus supporting the hypothesis of inhibitor adsorption on the copper surface, which creates a barrier that reduces the corrosion rate, aligning with a study by arukalam et al., (2025) that investigated the inhibitive property of hydroxypropyl methylcellulose (hpc) on copper corrosion in 1.0 m hcl and 0.5 m h2so4 and the results showed that the corrosion rate decreased significantly in the presence of hpc, and the polarization resistance (pr) increased, indicating effective adsorption of the inhibitor on the copper surface and the formation of a protective barrier. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 551 figure 7: inhibitor efficiency of tilapia fish scale-derived hydroxyapatite figure 8: corrosion rate of the copper samples 3.3 adsorption response of copper samples the tilapia fish scale-derived hydroxyapatite adsorption behaviour on the copper surface in 1m hcl was analyzed using langmuir, freundlich, and temkin isotherms. the langmuir isotherm assumes monolayer adsorption on a homogeneous surface and its adsorption parameters in table 4 gave low correlation coefficientsr2=0.529, 0.108, and 0.777 at 30°c, 40°c, and 50°c, respectively, which indicates a poor fit. the adsorption equilibrium constant kads values of 1.197, 1.579, and 0.403 mol-1 suggest weaker adsorption at 50°c, implying that desorption occurs at elevated temperatures, reducing the inhibitor's effectiveness (sharma et al., 2019). the poor adherence to the langmuir model suggests that adsorption is not strictly monolayer but involves interactions between adsorbed molecules and the surface. the freundlich isotherm, which accounts for multilayer adsorption on different types of heterogeneous surfaces (vigdorowitsch et al., 2021), showed a high correlation as indicated by r2 values in table 4 of 0.991, 0.912, and 0.972 at temperatures of 30°c, 40°c, and 50°c, respectively. the rise in the adsorption constant kads from 1.602 to 3.159 mol-1 with increasing temperature shows that the extent of adsorption increases at higher temperatures. this is in agreement with the postulation that inhibitor molecules interact with different active sites on the copper surface, leading to a heterogeneous distribution (vogler, 2013). the good fit with the freundlich isotherm suggests that the phenomenon of adsorption goes beyond a single layer, involving multilayer adsorption, which increases efficacy at higher concentrations. table 4: adsorption parameters from langmuir and freundlich isotherm. temperature (℃) kads(mol-1) r2 langmuir adsorption isotherm 30 1.196945161 0.529261967 40 1.579126492 0.108487207 50 0.40343823 0.776681035 freundlich adsorption isotherm 30 1.602157754 0.991497689 40 1.21075642 0.912338532 50 3.159289871 0.971582724 http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 552 the temkin isotherm shown in table 5 provided high correlation coefficients (r2 = 0.997, 0.835, and 0.9960), validating the presence of lateral interactions among adsorbed molecules, correlating with a study by chiter et al (2021). the free energy of adsorption (δgads) values of -15.27, -16.22, and -15.42 kj/mol indicate a spontaneous adsorption process dominated by physisorption, as the values fall within the range of physical adsorption (<−20 kj/mol) just as in a study by husaini, (2021) that investigates the effect of benzaldehyde on aluminium corrosion inhibition in a solution of sulfuric acid. the experimental values of gibbs free energy (δgads) were between -17.94 to -18.27 kj/mol, indicating a spontaneous adsorption process dominated by physisorption. the increasing adsorption constant kads up to 40°c suggests an optimal adsorption temperature, while a slight decline at 50°c implies a minor desorption effect. the adsorption behavior of tilapia fish scalederived hydroxyapatite (hap) on copper in 1m hcl was further analyzed using the temkin isotherm, which accounts for interactions between adsorbed molecules and heterogeneous surface sites. figure 9 plots surface coverage (θ) against the natural logarithm of inhibitor concentration (ln c) at 30°c, 40°c, and 50°c. the linear relationships (r² = 0.996–0.997) validate the temkin model, with slopes (b) of 0.5485, 0.4632, and 0.7562 at 30°c, 40°c, and 50°c, respectively. based on the findings obtained, tilapia fish scale-derived hydroxyapatite acts as a mixed-type inhibitor that affects the anodic and cathodic processes related to copper corrosion. table 5: adsorption parameters from temkin adsorption isotherm. temperature (ᵒc) kads(mol-1) δgads (kjmol-1) r2 ln(kads) 1/t δgads/t b= slope 30 7.7332 -15.2736 0.9966 2.0455 0.0033 -0.0504 0.5485 40 9.1793 -16.2238 0.8351 2.2169 0.0032 -0.0518 0.4632 50 5.6188 -15.4238 0.9958 1.7261 0.0031 -0.0478 0.7562 figure 9: a graph of θ against ln c. the adsorption is predominantly physical, as confirmed by the δgads values and better fit to the freundlich and temkin models. the increase in adsorption with temperature suggests that molecular interactions and surface coverage enhance inhibition efficiency, making the extract more effective at higher concentrations. the hap inhibitor forms a protective multilayer film-like cover on the surface of the copper, preventing direct acid attack and reducing corrosion rates effectively. 3.4 optical micrographs of the test copper samples optical micrographs of the test samples exposed to corrosive environments, both with and without the addition of hydroxyapatite as a corrosion inhibitor, are shown in plate 1(a-d) at 40x magnification. without the particulate inhibitor (plate 1a), the copper samples indicate corrosion disturbance indicative of high corrosive activity. on the other hand, plate 1(b-c) show that the surface morphology shows minimal evidence of corrosion in samples treated with different additional concentrations of the hydroxyapatite inhibitor. plate 1(d) has similar surface features; however, slight pitting is observed on the surface of the sample that has the highest particle concentration. these microscopic findings align with the findings obtained from electrochemical measurements. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 553 (a) (b) (c) (d) plate 1 (a-d): optical micrographs of the test copper samples (control, 0.2g, 0.4g, 0.6g). 3.5 empirical optimization the inhibition efficiency (ie) from the doe data in table 6 of hydroxyapatite from tilapia fish scales (tfshap) was found to increase in effectiveness as the concentrations increased. at temperatures of 30°c, 40°c, and 50°c, the inhibitor performance was directly related to the increase in temperature, indicating increased surface coverage and probable chemical interaction between the inhibitor and copper. the corrosion rate (cr) analysis showed a significant reduction from 6.02 mm/year without the inhibitor to 0.37 mm/year at 50°c with 0.6 g of the inhibitor, thus proving the efficiency of tfs-hap as a corrosion inhibitor. likewise, at 40°c, cr reduced from 5.34 mm/year to 0.68 mm/year, and at 30°c, it reduced from 2.27 mm/year to 0.33 mm/year. these data suggest that the inhibitor performs best under conditions of increased concentrations and increased temperatures. table 6:design of experiment (doe) data factor a: temperature (ᵒc) factor b: concentration (g) response 1: cr (mm/yr) 0 30 2.27 0.2 30 1.71 0.4 30 0.91 0.6 30 0.33 0 40 5.34 0.2 40 3.58 0.4 40 2.82 0.6 40 0.68 0 50 6.02 0.2 50 5.42 0.4 50 2.52 0.6 50 0.37 the findings from the anova analysis in table 7 further supports the statistical significance of the inhibition process, as indicated by a model f-value of 46.30 and a p-value that os lower than 0.0001, reflecting a strong http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 554 relationship between concentration, temperature, and corrosion inhibition. factor a (concentration) had the most significant effect (f = 147.12, p < 0.0001), thus confirming that the inhibitor dosage is critical for effective corrosion control. factor b (temperature) also reflected a significant influence (f = 53.92, p = 0.0003), emphasizing the effect of temperature variations on the adsorption properties and effectiveness of the inhibitor. the interaction term (ab) also reflected statistical significance (f = 22.74, p = 0.0031), suggesting a synergistic effect between concentration and temperature. the model reliability was supported by a high r² value of 97.24%, in addition to an adjusted r² of 95.37% and a predicted r² of 87.70%, collectively reflecting that the model is a good representation of the experimental data. furthermore, the coefficient of variation (cv%) of 16.46% further supports the validity of the findings. to enhance the effectiveness of the inhibitor, a central composite design (ccd) method was employed resulting in the development of a quadratic regression model that best predicts the relationship between concentration and temperature on the corrosion rate, as expressed in equation 3. upon optimization, it was established that the optimal inhibitor concentration is 0.471 g, coupled with a suitable temperature of 46.54°c, yielding a cr of 2.105 mm/year. the fisher test was carried out to analyse the statistical validity of the model by way of comparing the mean square values from the model and the residual mean squares which confirms the sensitivity and reproducibility of the model, as shown in figure 10. cr = 3.31 − 2.06a + 1.14b − 0.9922ab − 0.3656𝐴2 − 0.6612𝐵2 (3) table 7: anova results showing copper-optimised response to tilapia fish scale-derived hydroxyapatite inhibition source ss df ms f-value p-value remark model 44.540 5.000 8.910 46.300 0.000 sig a-conc. 28.300 1.0000 28.3 147.12 < 0.0001 b-temp. 10.370 1.0000 10.37 53.92 0.0003 ab 4.380 1.0000 4.38 22.74 0.0031 a² 0.317 1.0000 0.3169 1.65 0.2467 b² 1.170 1.0000 1.17 6.06 0.049 residual 1.150 6.0000 0.1924 cor total 45.690 11.0000 r2 = 97.24%; adjusted r2 = 95.37%; predicted r2 = 87.70%; cv%= 16.46 ** sssum of square; dfdegree of freedom; msmean square; sig.significant** figure 10: tilapia fish scale-derived hydroxyapatite inhibition correlation with temperature and concentration 4. conclusion tilapia fish scales, often discarded as waste, contain hydroxyapatite, a biocompatible material with potential applications in corrosion inhibition. this study evaluates hydroxyapatite extracted from fish scales as a green alternative to synthetic corrosion inhibitors for copper in acidic environments. the hydroxyapatite was obtained through a series of chemical and thermal treatments and then tested for its inhibition performance 30 35 40 45 50 0 0.1 0.2 0.3 0.4 0.5 0.6 0 1 2 3 4 5 6 7 c r ( m m /y r) a: conc. (ml)b: temp. (c) 2.098692.098692.09869 3d surface factor coding: actual cr (mm/yr) design points: above surface below surface 0.33 6.02 x1 = a x2 = b http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 555 in 1m hcl. electrochemical results showed that increasing the hydroxyapatite concentration significantly reduced the corrosion rate, with a maximum inhibition efficiency of 95% at 0.6 g. the inhibitor formed a stable multilayer protective film on the copper surface, preventing metal dissolution. adsorption studies confirmed a strong adherence of the inhibitor molecules to the metal surface, with the freundlich and temkin models best describing the adsorption behavior. microscopic analysis further validated the protective effect, showing reduced surface roughness and fewer corrosion pits in treated samples. statistical optimization identified 0.471 g of hydroxyapatite at 46.54°c as the optimal conditions for maximum inhibition. these findings highlight the potential of fish scale-derived hydroxyapatite as a sustainable and effective corrosion inhibitor, addressing both environmental concerns and industrial corrosion challenges. acknowledgements bells university of technology is gratefully acknowledged for its support during the research study. references abdel-karim, am., ahmed, ym. and el-masry, mm. 2023. ag-cuo/epoxy hybrid nanocomposites as anticorrosive coating and self-cleaning on copper substrate. scientific reports 13(1): 19248–19251. abdullah, nh., mohamed noor, aa., mat-rasat, ms., mamat, s., mohamed, m., mohd shohaimi, na. and mohd amin, mf. 2020. preparation and characterization of calcium hydroxyphosphate (hydroxyapatite) from tilapia fish bones and scales via calcination method. materials science forum 1010(1): 596–601. abod, bm., al-alawy, rm., khadom, aa. and kamar, fh. 2019. experimental and theoretical studies for tobacco leaf extract as an eco-friendly inhibitor for steel in saline water. journal of bioand tribo-corrosion 5(3): 75–78. al-amiery, a., isahak, wnrw. and al-azzawi, wk. 2023. multi-method evaluation of a 2-(1,3,4-thiadiazole2-yl) pyrrolidine corrosion inhibitor for mild steel in hcl. scientific reports 13(1): 9770–9773. arthur, de., jonathan, a., ameh, po. and anya, c. 2013. a review on the assessment of polymeric materials used as corrosion inhibitor of metals and alloys. international journal of industrial chemistry 4(1): 1–4. arukalam, io., uzochukwu, in., uche, r., udunwa, di., egole, cp. and ndukwe, ai. 2025. inhibitive property of hydroxypropyl methylcellulose on acid corrosion of copper: experimental and computational simulation. bulletin of materials science 48(1): 40–43. aydinsoy, ea., aghamaliyev, zz., aghamaliyeva, db. and abbasov, vb. 2024. a systematic review of corrosion inhibitors in marine environments: insights from the last 5 years. processing of petrochemistry and oil refining 25(3): 1–4. chinh, nt., manh, vq., trung, vq., lam, td., huynh, md., tung, nq. and hoang, t. 2019. characterization of collagen derived from tropical freshwater carp fish scale wastes and its amino acid sequence. natural product communications 14(7): 1–4. chiter, f., costa, d., maurice, v. and marcus, p. 2021. corrosion inhibition of locally de-passivated surfaces: dft study of 2-mercaptobenzothiazole on copper. npj materials degradation 5(1): 52–55. coppola, d., lauritano, c., palma esposito, f., riccio, g., rizzo, c. and de pascale, d. 2021. fish waste: from problem to valuable resource. marine drugs 19(2): 116–119. dileepkumar, vg., et al. 2022. a review on the synthesis and properties of hydroxyapatite for biomedical applications. journal of biomaterials science, polymer edition 33(2): 229–232. duan, r., ying, l. and zhang, y. 2004. monitoring the decalcifying process of fish scale by titration. journal of huaihai institute of technology (natural science edition) 13(1): 54–57. ezzat, a., motaal, sma., ahmed, as., sallam, hb., el-hossiany, a. and fouda, a. 2022. corrosion inhibition of carbon steel in 2.0 m hcl solution using novel extract (pulicaria undulata). biointerface research in applied chemistry 12(5): 6415–6418. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng arid zone journal of engineering, technology and environment, june 2025; vol. 21(2): 545-556. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: ojosundayfayomi3@gmail.com, osfayomi@bellsuniversity.edu.ng 556 husaini, m. 2021. corrosion inhibition effect of benzaldehyde (methoxybenzene) for aluminium in sulphuric acid solution. algerian journal of engineering and technology 4(1): 74–77. jmiai, a., tara, a., el issami, s., hilali, m., jbara, o. and bazzi, l. 2021. a new trend in corrosion protection of copper in acidic medium using jujube shell extract: experimental, quantum chemistry and monte carlo study. journal of molecular liquids 322(1): 114509–114512. kadhim, a., al-amiery, aa., alazawi, r., al-ghezi, mks. and abass, rh. 2021. corrosion inhibitors: a review. international journal of corrosion and scale inhibition 10(1): 54–57. kehinde, ei., fayomi, os. and atiba, jo. 2025. corrosion behaviour of aa6063 alloy in acidic chloride conditions: inhibition by pennisetum glaucum extract. journal of bioand tribo-corrosion 11(2): 1–4. li, h., zhang, s. and qiang, y. 2021. corrosion retardation effect of a green cauliflower extract on copper in h₂so₄ solution: electrochemical and theoretical explorations. journal of molecular liquids 321(1): 114–117. marinescu, m. 2019. recent advances in the use of benzimidazoles as corrosion inhibitors. bmc chemistry 13(1): 136–139. nyambi, nf., premlall, k. and govender, kk. 2024. the physicochemical characterisation and computational studies of tilapia fish scales as a green inhibitor for steel corrosion. engineering proceedings 67(1): 1–4. panda, nn., pramanik, k. and sukla, lb. 2014. extraction and characterization of biocompatible hydroxyapatite from freshwater fish scales for tissue engineering scaffold. bioprocess and biosystems engineering 37(1): 433– 436. selimin, ma., latif, afa., lee, cw., muhamad, ms., basri, h. and lee, tc. 2022. adsorption efficiency of hydroxyapatite synthesised from black tilapia fish scales for chromium (vi) removal. materials today: proceedings 57(1): 1142–1145. sharma, s., ko, x., kurapati, y., singh, h. and nešić, s. 2019. adsorption behavior of organic corrosion inhibitors on metal surfaces: some new insights from molecular simulations. corrosion 75(1): 90–93. sockalingam, k. and abdullah, hz. 2015. extraction and characterization of gelatin biopolymer from black tilapia (oreochromis mossambicus) scales. aip conference proceedings 1669(1): 101–104. tacon, ag. 2020. trends in global aquaculture and aquafeed production: 2000–2017. reviews in fisheries science & aquaculture 28(1): 43–46. ubogu, ae., fayomi, os. and atiba, jo. 2024. microstructural and anti-corrosion responses of copper in naclfishbone ash environment. 2024 ieee 5th international conference on electro-computing technologies for humanity (nigercon) 1(1): 1–4. vigdorowitsch, m., pchelintsev, a., tsygankova, l. and tanygina, e. 2021. freundlich isotherm: an adsorption model complete framework. applied sciences 11(17): 8078–8081. vogler, ea. 2013. surface modification for biocompatibility. in: lakhtakia, a., & martín-palma, rj. (eds.), engineered biomimicry. boston: elsevier, 189–192. wang, h., wang, x., wang, h., wang, l. and liu, a. 2007. dft study of new bipyrazole derivatives and their potential activity as corrosion inhibitors. journal of molecular modeling 13(1): 147–150. zainol, i., adenan, nh., rahim, na. and jaafar, cna. 2019. extraction of natural hydroxyapatite from tilapia fish scales using alkaline treatment. materials today: proceedings 16(1): 1942–1945. zhao, z., sun, m., xia, j., xu, h. and wu, y. 2025. a specific calcium silicate hydrate (pc/sp/ca-h) for simultaneous removal of phosphate and fluoride from low concentration water: feasible and mechanisms research. journal of water process engineering 71(1): 107312–107315. zor, s., saracoglu, m., kandemirli, f. and arslan, t. 2011. inhibition effects of amides on the corrosion of copper in 1.0 m hcl: theoretical and experimental studies. corrosion journal of science and engineering 67(12): 125001–125004. http://www.azojete.com.ng/ mailto:ojosundayfayomi3@gmail.com mailto:osfayomi@bellsuniversity.edu.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1054 arid zone journal of engineering, technology & environment original research article development of an automatic door access control system using fingerprint and passcode verification technology d. c. uguru-okorie 1, a. a. aribisala, *, a. m. adebimpe1, o. o. fagbohun1 and k. ojaomo2 1department of mechatronics engineering, federal university oye-ekiti, oye-ekiti, nigeria 2department of mechatronics engineering, federal polytechnic, ado-ekiti, nigeria *corresponding author’s email: adetoye.aribisala@fuoye.edu.ng article information abstract access control systems are essential in modern security architecture, yet traditional methods such as mechanical locks and single-factor authentication remain vulnerable to duplication, spoofing, and environmental limitations. to address these challenges, this paper presents the development of an automatic door access control system that integrates fingerprint biometrics with passcode verification on an arduino platform. the major contribution of this work lies in its dual-factor authentication design, which enhances security while maintaining affordability, scalability, and ease of use. the system was implemented using an as606 fingerprint sensor for biometric enrollment and verification, complemented by a keypad for passcode input and an intruder alarm for intrusion response. experimental results demonstrated that the fingerprint scanner reliably captured and matched minutiae with confidence scores ranging from 0 to 255, and that thumbprints provided higher accuracy rates than index fingers, with a maximum accuracy of 70%. the integration of a secondary passcode layer and an intruder alarm further improved the robustness of the system compared to existing singlemode solutions. future work will explore the integration of additional biometric modalities and iot-based monitoring to expand functionality. overall, this study demonstrates that dual-factor authentication on an open-source platform offers a practical, secure, and cost-effective solution for modern access control. received: 9th september 2025 revised: 2nd december 2025 accepted: 4th december 2025 keywords: control system fingerprint biometrics dual-factor authentication intruder detection android-based security © 2025 faculty of engineering, university of maiduguri, nigeria. all rights reserved. 1.0 introduction access control remains a central concern in the design of secure buildings and homes, especially as traditional systems based on mechanical locks and keys continue to show vulnerabilities (chukwuemeka and kasim, 2025). keys can be duplicated or destroyed, locks can be forced open, and the overall reliability of such systems is often poor in contexts where security is paramount. to address these shortcomings, recent innovations have shifted toward electronic and biometric solutions that provide higher levels of accuracy and user verification (hemant et al., 2022), (zainuddin et al., 2024). in particular, fingerprint recognition has emerged as a dominant biometric modality because of its universality, uniqueness, and relative immunity to environmental variations compared to alternatives such as facial or voice recognition. at the same time, the use of low-cost microcontroller platforms such as arduino has opened opportunities for building affordable and adaptable access control systems that can be deployed in diverse contexts (hardyan et al., 2023; cookey et al., 2024). several studies over the last decade have explored the efficiency and robustness of these systems. for example, hardyan et al. (2023) developed an arduino-based smart home security system that integrated fingerprint recognition with intrusion detection, achieving high levels of accuracy but showing sensitivity to environmental conditions such as dust interference. similarly, cookey et al. (2024) implemented a fingerprint identification device on arduino uno, confirming the ability of low-cost microcontrollers to handle biometric verification reliably. however, their design relied on single-factor authentication, leaving it vulnerable if the fingerprint azojete december 2025. vol.21(4):1054-1062 published by the faculty of engineering, university of maiduguri, maiduguri, nigeria. print issn: 1596-2490, electronic issn: 2545-5818 https://doi.org/10.63958/azojete/2025/21/04/014 www.azojete.com.ng mailto:adetoye.aribisala@fuoye.edu.ng mailto:adetoye.aribisala@fuoye.edu.ng http://www.azojete.com.ng/ arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1055 sensor failed or was spoofed. more advanced multi-modal approaches have also been proposed. barfield et al. (2025) introduced an iot-enabled smart lock that combined fingerprint and facial recognition with real-time cloud connectivity, but its reliance on continuous internet access and higher hardware costs limited its suitability for low-resource environments. kumar et al. (2020) designed a hybrid rfid–biometric system, which worked well in controlled conditions but suffered delays and bottlenecks when scaled to multiple users. alternatives such as facial and voice recognition have also been investigated. olaniyi et al. (2019) presented a raspberry pi–based facial recognition door system that performed adequately in ideal lighting but failed under poor illumination. shafique et al. (2021) applied voice recognition to smart locks, but performance was hindered by background noise and variations in speech. these limitations reinforce the practicality of fingerprint-based systems, which offer higher stability and faster authentication across diverse conditions. a common thread in these works is the tension between security and practicality. single-mode systems are simple and cost-effective but prone to spoofing or device failure, while multimodal iot-heavy systems improve robustness but introduce concerns about scalability, privacy, and cost. this gap highlights the need for access control solutions that can strengthen authentication without becoming prohibitively expensive or technically complex. the present study addresses this challenge by developing an automatic door access control system that combines fingerprint biometrics with passcode verification on an arduino platform. therefore, the major contribution of our study is the dual-factor authentication design i.e., the system must be authenticated by both fingerprint and passcode verification. by integrating these two modes of authentication, the system avoids the shortcomings of single-factor designs while steering clear of the complexity and resource demands of cloud-dependent solutions. the use of arduino further ensures that the design remains affordable, opensource, and upgradeable. in this way, the study contributes to the field of electronic security by demonstrating a balanced, dual-authentication approach that is practical for both residential and institutional applications while remaining adaptable to future enhancements. this paper is structured into five main sections. section 2 presents the system design, including both the hardware and software components, as well as the operational workflow. section 3 details the experimental results obtained from the implementation, while section 4 provides a critical discussion of these findings in relation to existing studies. finally, section 5 concludes the paper and outlines potential directions for future work. 2. system design 2.1 hardware components five hardware components were utilized in this work. table 1 presents the list of these components along with their respective functions, while plates 1 to 3 provide the physical representations of the arduino uno board, as606 fingerprint scanner and the solenoid lock respectively. a more detailed explanation of the roles and operation of each component within the system is provided in the subsequent sections. table 1: hardware components s/no hardware component function 1 universal serial bus (usb) cable connects the arduino board to computer for uploading purposes 2 arduino uno board serves as the main microcontroller for testing and interfacing all system components 3 as606 fingerprint scanner scan the user’s thumbprint 4 solenoid lock to lock and unlock the door 5 light emitting diode (led) indicator to indicate when the door is unlocked 2.2 software components 2.2.1 arduino programming arduino is an open-source microcontroller platform widely used for prototyping embedded systems. programming for arduino is carried out in its integrated development environment (ide), which employs a simplified version of c/c++ and allows users to easily write, edit, and upload code to the board via a usb http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1056 interface. one of the key advantages of arduino is the presence of an inbuilt bootloader that enables programs to run directly on the hardware without requiring external programming devices (widhalm et al., 2021). the decision to adopt arduino in this work is based on its flexibility, affordability, and ease of use when compared to alternative microcontrollers such as pic (perjaru et al., 2023). in particular, the arduino board incorporates the atmega2560 microcontroller, which allows programs to be stored, modified, and re-uploaded for maintenance or system upgrades. the general workflow of the arduino ide follows a straightforward cycle of writing code, compiling it, uploading to the board, and executing the program. this simplicity makes it suitable for rapid development and iterative testing of system features. plate 1: arduino uno board plate 2: as606 fingerprint scanner plate 3: solenoid lock 2.2.2 fritzing to complement the arduino environment, the project also employed fritzing software. fritzing is a design tool that provides libraries of electronic components, including sensors, displays, and microcontrollers, to facilitate the creation of circuit diagrams in a virtual environment. it supports visualization of circuit layouts before physical implementation, reducing the likelihood of errors during construction (faíña, 2022). the circuit schematic for this work, designed using fritzing, is presented in figure 1. figure 1: circuit diagram 2.2.3 fingerprint sensor software the as606 fingerprint sensor is a biometric module designed to authenticate individuals based on the unique ridge patterns and minutiae of their fingerprints. widely adopted in security applications such as mobile devices, laptops, and smart locks, the sensor ensures that access is granted only to authorized users (yin et al., 2022). in operation, the as606 captures a high-resolution image of a fingerprint and processes it to extract distinctive features. these features are converted into a digital template that is stored in the device’s memory for subsequent comparison. during verification, the newly scanned fingerprint is matched against the stored templates to determine the degree of similarity. the sensor uses capacitive scanning technology, which detects variations in capacitance across the ridges and valleys of the finger, making it more resistant to errors and environmental disturbances than purely optical methods. the software that supports the as606 sensor is responsible for handling these biometric processes. it manages image acquisition, feature extraction, and template storage, while also implementing the matching algorithms that verify identity. in addition, the software provides functions for enrolling new users, deleting templates, and managing access levels, ensuring flexibility in security applications. when integrated into a larger access control system, this capability allows seamless authentication of multiple users with high reliability. for this work, integration of the as606 with arduino was achieved through the adafruit fingerprint library, a widely used arduino library that provides functions for communicating with fingerprint modules over serial connections. the library simplifies tasks such as enrolling users, verifying fingerprints, retrieving template ids, and handling errors. by leveraging these pre-defined functions, the development process becomes faster and less error-prone, while still allowing modifications where needed. combined with the arduino ide, the library ensures that the as606 sensor works in harmony http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1057 with other components such as the keypad and solenoid lock, forming a cohesive dual-authentication access control system. the block diagram in figure 2 illustrates the overall methodology adopted in developing the automatic door access control system using fingerprint and passcode verification. the process begins with hardware identification and component interfacing, followed by circuit design, programming, and prototype implementation. figure 2: methodology block diagram 2.2.4 system operation workflow before obtaining experimental results, the system was designed to follow a structured process flow that governs user authentication and door access. the sequence begins with the user entering a pre-set password or passcode through the keypad interface. if the input matches the stored password, the user is permitted to proceed to the next stage of verification. however, if an incorrect password is entered, the system allows a maximum of three attempts. after the third unsuccessful attempt, access is denied and the door remains locked. following successful password entry, the second level of authentication requires the user to place a finger on the fingerprint scanner. the fingerprint module first undergoes an enrolment process during system setup, where each authorized user’s fingerprint is captured, the minutiae features are extracted, and the resulting digital template is stored in memory alongside the user’s id. during actual operation, the scanner captures the presented fingerprint and compares the extracted minutiae with the stored templates. if a match is found, the system identifies the user as authorized, and the solenoid lock is disengaged to allow entry. if no match is detected, access is denied, ensuring that only individuals with both the correct passcode and a registered fingerprint can successfully open the door. the overall authentication workflow is illustrated in the process flow chart shown in figure 6. the chart depicts the sequence from passcode entry, verification, and conditional branching (correct/incorrect password attempts), through to fingerprint scanning, matching, and the final access decision. this visual representation highlights the dual-layer security mechanism and the logical progression of system operations prior to testing. figure 3 shows the pictorial view of the developed system showing the internal components. identify features/ hardware to be used design circuit and identify i/o pins to arduino board construct circuit in preparations for testing stage test by ‘load and run’ program for each feature using arduino obtain results construct circuit to be used in the prototype build prototype http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1058 figure 3: system authentication process flow plate 4: pictorial view of developed system showing the internal components 3. results and discussion 3.1 fingerprint enrollment results for the system to maintain a database of users, each individual must first undergo a fingerprint enrollment process. during this stage, the arduino communicates with the fingerprint scanner to initialize user registration. the user is prompted to input an identification (id) number, which is then linked to the corresponding fingerprint template. as illustrated in figure 4, the fingerprint minutiae of a user were successfully captured and stored with the assigned id:2. the extracted features are saved within the onboard flash memory of the fingerprint sensor, ensuring that the template can later be retrieved and matched during the authentication phase. this confirms the system’s ability to reliably enroll and store unique biometric identifiers for future verification. 3.2 fingerprint verification results the fingerprint verification process was carried out to evaluate the accuracy and reliability of the developed access control system. during testing, the system correctly identified the enrolled user by comparing the newly scanned fingerprint with the stored template. the fingerprint scanner generated a confidence score on a scale of 0 to 255, where higher values indicated stronger matches and greater authentication reliability. the http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1059 outputs were monitored both on the arduino serial monitor and the lcd display, while the intruder alarm functionality was tested to confirm its responsiveness to unauthorized access attempts. table 2 presents the summary of the fingerprint verification and the system’s response. figure 4: fingerprint enrollment table 2: fingerprint verification and system response test stage observed output system response / action remarks fingerprint enrollment user prompted to enter id. fingerprint captured and stored in onboard memory with id: 2. template successfully created and stored for future comparison. enrollment successful; memory storage validated. fingerprint verification (serial monitor) system detected stored fingerprint with id: 2. displayed a confidence score between 0–255, indicating accuracy of match. fingerprint verified successfully; access granted. high reliability of identification. fingerprint verification (lcd display) lcd displayed user id: 2 after successful match between current scan and stored template. access authorized; solenoid lock disengaged. confirms integration of lcd with control logic. intruder detection (incorrect attempts) multiple incorrect password or unregistered fingerprint inputs. intruder alarm activated to alert security personnel. system responded correctly to unauthorized access. the results in table 2 demonstrate that the developed access control system performed effectively in recognizing authorized users and rejecting unauthorized access. the fingerprint sensor successfully enrolled users by capturing and storing unique fingerprint minutiae, and the verification tests confirmed the accuracy of template matching. the use of a confidence score (0–255) allowed quantifiable evaluation of match precision, which enhances system transparency and diagnostic capability. the consistency between the serial monitor and lcd display outputs validates the robustness of the communication between the arduino microcontroller and the peripheral components. the system’s ability to http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1060 correctly identify the stored fingerprint (id: 2) with a high confidence level confirms the dependability of the as606 fingerprint module when integrated into a dual-authentication framework. the intruder alarm feature also performed as expected, triggering alerts during repeated failed login attempts or unregistered fingerprint scans. this functionality significantly improves system reliability, addressing one of the major weaknesses in earlier single-mode authentication systems. a similar observation was made by hardyan et al. (2023), who reported that incorporating responsive security alerts enhances real-time system integrity in arduino-based smart home designs. likewise, the findings align with cookey et al. (2024), who emphasized the need for multi-layer verification to minimize spoofing and improve resilience. the integration of fingerprint and passcode authentication, supported by responsive alarm feedback provides a balanced combination of security, reliability, and operational simplicity. the tabulated verification outcomes confirm that the system performs consistently across both biometric and behavioural authentication stages, offering a scalable and cost-effective approach for modern access control applications. the process flow for detecting and responding to an intruder is illustrated in figure 5. this flow highlights the sequence of events from the point of detection to the activation of the alarm system, ensuring that any security breach is immediately communicated to relevant personnel for timely intervention. figure 5: process flow on intruder detection 3.3 fingerprint scanner accuracy test to evaluate the reliability of the fingerprint scanner, an accuracy test was conducted to assess its performance across different fingers. the test involved five individuals, named as a, b, c, d and e, each providing four fingerprints: the left and right thumbs, as well as the left and right index fingers. the scanner’s confidence level, ranging from 0 to 255, was used as the basis for determining accuracy. as illustrated in figure 6, the results revealed notable variations in performance depending on the finger used. the left thumbprint produced the highest accuracy, achieving a recognition rate of 70%, followed by the right thumbprint at 67.2%. in contrast, the right index finger and left index finger yielded lower accuracies of 41.4% and 30%, respectively. these findings suggest that thumbprints offer more reliable biometric features for enrollment and verification compared to index fingers, thereby reinforcing their suitability for access control applications. figure 6: scanner accuracy test although the system achieved a maximum fingerprint accuracy of 70%, this performance must be understood in relation to the capabilities of the as606 optical fingerprint sensor employed in the design. optical scanners capture images using reflected light, which makes them sensitive to finger dryness, smudges, and variations in http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; vol. 21(4): 1054-1062. issn 1596-2490; e-issn2545-5818; www.azojete.com.ng corresponding author’s email address: adetoye.aribisala@fuoye.edu.ng 1061 finger placement (mohamed abdul cader et al., 2023). these factors often reduce matching consistency when compared with capacitive or ultrasonic scanners. the choice of an optical sensor was intentional, as optical modules are more resilient to electrostatic discharge and physical degradation; however, this robustness comes with the trade-off of lower feature resolution accuracy (yu et al., 2023). therefore, the 70% accuracy observed reflects the inherent limitations of the sensor technology rather than shortcomings in the dual-factor authentication framework itself. future work may improve accuracy by integrating higher-resolution optical modules or transitioning to capacitive or ultrasonic sensors. the integration of an intruder alarm provides an additional safeguard by addressing unauthorized access attempts. this design choice responds to criticisms of earlier systems that failed to account for intrusion scenarios. for instance, hardyan et al. (2023) developed an arduino-based smart home security system with high accuracy but noted susceptibility to environmental interference. unlike their system, the present work incorporates both dual authentication and alarm response mechanisms, thereby enhancing reliability under real-world conditions. our findings demonstrate that the dual-factor design successfully addresses the limitations of single-mode biometric systems while avoiding the complexity of resource-intensive multimodal or iot-heavy approaches. therefore, a dual-factor system on a low-cost platform effectively mitigates the weaknesses of single-factor systems without incurring the high cost of complex multimodal systems. the system developed represents a balanced and scalable solution for residential and institutional applications, with the potential for future integration of additional biometric modalities or wireless monitoring without compromising its affordability and accessibility. in comparison with related works, the present system demonstrates clear improvements in both security and adaptability. whereas cookey et al. (2024) relied solely on fingerprint authentication, leaving their design exposed to single-point failures, our dual-factor approach ensures resilience through layered verification. similarly, while hardyan et al. (2023) achieved promising results with sensor-based smart home security, their system lacked a responsive intrusion-handling mechanism, which our alarm integration successfully addresses. taken together, these enhancements underscore the contribution of this study as a practical advancement in the development of robust, low-cost, and user-friendly access control systems. 4. conclusions this study presented the design and implementation of an automatic door access control system that integrates fingerprint biometrics with passcode verification on an arduino platform. the system was developed to address the limitations of traditional lock-and-key mechanisms and single-mode authentication systems, which are often vulnerable to duplication, spoofing, and environmental interference. by combining two layers of authentication, the developed system enhances security while maintaining low cost, simplicity, and adaptability. the experimental results demonstrated that the as606 fingerprint sensor successfully enrolled and verified users’ fingerprints with measurable confidence scores, and that thumbprints yielded about 92.17% higher accuracy rates than the index-fingers. this difference is because of the larger surface area covered by the thumb. the inclusion of a passcode verification step further strengthened system reliability, ensuring that even if one authentication method were compromised, access would still remain restricted. additionally, the integration of an intruder alarm introduced a responsive mechanism for handling unauthorized access attempts, thereby reinforcing the system’s suitability for real-world applications. compared to related works, the system offers improvements in resilience and practicality. unlike single-factor arduino-based solutions that rely solely on fingerprint authentication, the proposed system reduces vulnerability by incorporating dual-factor verification. it also addresses a critical limitation in earlier studies by providing a built-in intrusion response. these contributions position the system as a balanced solution that combines robustness with economic feasibility, making it suitable for deployment in residential, institutional, and small-scale commercial environments. future research would focus on incorporating additional biometric modalities, such as facial recognition or iris scanning, to further strengthen security. integration with iot platforms could also allow for remote monitoring and control, although careful consideration must be given to privacy and connectivity challenges. overall, the system demonstrates that layered authentication on a flexible and open-source platform like arduino can deliver a reliable and cost-effective approach to modern access control. references barfield, a., mendoza, j. and patel, r. 2025. advanced smart lock system: enhancing door security with biometric authentication and advanced technology features. proceedings of the international institute of http://www.azojete.com.ng/ mailto:adetoye.aribisala@fuoye.edu.ng arid zone journal of engineering, technology and environment, december 2025; 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